1-01
Nanostructured Materials Based on Polyelectrolyte Complexes
MARTIEN COHEN STUART, Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB, Wageningen, The Netherlands, martien.cohenstuart@wur.nl
Self-assembly processes in water are often driven by hydrophobic attraction; well known examples are common surfactant micelles and lipid bilayer vesicles. Other binding mechanisms can be very relevant, too, like metal coordination or electrostatic interaction. We discuss in this contribution polymer micelles consisting of oppositely charged polyelectrolytes, at least one of which is a diblock copolymer with a neutral, water soluble block. The core of these micelles consists of an insoluble complex coacervate formed by the ionic chains, and a corona made up of the neutral hydrophilic chains. Typical features of these micelles are that they (i) are formed only within a window of compositions around charge stoichiometry, and (ii) that they are fully reversible with respect to changes in polymer composition, pH and ionic strength in the solution. We have characterized micelles of this kind with a variety of techniques and using various polymers. In addition, we have studied their behaviour on solid surfaces.
1-02
Multifunctional
and Responsive Behavior of ABC Terpolymers with Amphoteric Blocks
C. TSITSILIANIS 1, I . Katsampas1, Y. Roiter2, S. Minko2, 1Department of Chemical Engineering, University of Patras 26504, Patras, Greece and Institute of Chemical Engineering and High Temperature Chemical Processes, ICE-FORTH, 2Department of Chemistry, Clarkson University, Potsdam, NY, ct@chemeng.upatras.gr
ABC block terpolymers constituted of three different polymer blocks demonstrate numerous possibilities of self organization in the bulk, at interfaces and in solutions. This behavior has attracted great interest and caused recent rapid development of the ABC block copolymer synthesis and investigations. The ABC terpolymers exhibit a wide variety of tunable self-assembled morphologies with potential applications in nanotechnology and biomedicine. Here we report on a double hydrophilic stimuli responsive ABC terpolymer poly(2-vinyl pyridine)-b-poly(acrylic acid)-b-poly(n-butyl methacrylate) (P2VP-PAA-PnBMA) which exhibits a rich polymorphism and multifunctionality in aqueous media (multiple response). The properties of the copolymer aqueous solutions depend strongly on pH. At low pH three-compartment spherical micelles with positively charged outer corona are formed. The micelles are thermo-responsive around the upper critical solution temperature (UCST) of the PAA blocks. As pH increases the micelles are transformed to other micellar structures due to the progressive deprotonation of P2VP blocks and the neutralization of PAA blocks. At pH 6 a three-dimensional physical network is formed constituted of hydrophobic domains of P2VP and/or PnBMA blocks interconnected by negatively charged bridging PAA blocks. This physical hydrogel is sensitive to ionic strength which induces a closed loop Sol-Gel-Sol transition. The so formed gel exhibits the characteristic behavior of Telechelic Associative Polyelectrolytes [Macromolecules, 2005, 38, 1307].
1-03
Design of Self Assembled Surfactant
Nanostructures at Interfaces: Effects
of Regio-isomeric and Stereo-isomeric Chemical Structure Changes
RAMESH VARADARAJ, ExxonMobil Research and Engineering Company,
The influence of regio-isomeric and stereo-isomeric changes in surfactant chemical structure on interfacial properties was studied using two sets of alkyl aromatic sulfonate surfactants . Two regio-isomeric sodium n-dodecyl xylene sulfonates : ortho and para isomers, and two stereo-isomeric sodium n‑decyl stilbene sulfonates: dl and meso isomers were synthesized and their interfacial properties determined at the air‑water, hydrocarbon‑water and solid‑water interfaces. For the regio-isomeric xylene sulfonates, the para-isomer exhibited a lower critical aggregation concentration and higher efficiency of interfacial tension reduction at the air‑water, decane‑water and solid -water interfaces. The dynamic interfacial properties i.e., rate of interfacial tension reduction and dynamic wetting were higher for the ortho isomer compared to the para isomer. Differences in molecular packing of the para isomer compared to the ortho isomer is key to account for the observed differences in interfacial properties. For the stereo-isomeric stilbene sulfonates, while the interfacial properties were not significantly different in water, in 0.1N NaCl solution differences in properties between the meso and dl isomers were observed. The meso isomer exhibited a lower critical aggregation concentration and higher efficiency of interfacial tension reduction at the air‑water and decane‑water interfaces. The dl isomer exhibited a higher rate of surface tension reduction at the air‑water interface and marginally better dynamic wetting properties at the Teflon‑water and Parafilm‑water interfaces. Alteration of molecular packing at the interface accounts for these observations. This study demonstrates how subtle differences in molecular packing at interfaces due to regiochemical and stereochemical structural changes can impart significant interfacial property changes in self-assembling molecules. These findings impact the design of self-assembled surfactant nanostructures at interfaces and control of performance attributes such as foaming, emulsification and surface wetting.
1-04
Self-recognising Fluid Monolayers of DNA-based Surfactants:
Properties and Applications
VESSELIN N. PAUNOV, Chun Xu,
Pietro Taylor, Paul D. I. Fletcher, Surfactant & Colloid Group, Department
of Chemistry, University of Hull, Hull, UK, V.N.Paunov@hull.ac.uk
We have designed novel DNA-surfactants prepared by covalent attachment of a hydrophobic anchoring group to the (3’- or 5’-) end of short DNA oligonucleotides. This anchoring group turns these DNA-strands into amphiphilic molecules. Such DNA-surfactants can adsorb at air-water and oil-water surfaces which orients them with respect to the liquid surface and can promote programmable interaction based on Watson-Crick pairing. We show that these materials are surface-active at various fluid surfaces, including air-water and oil-water interfaces, as well as lipid bilayers. We demonstrate that once adsorbed the DNA-surfactants used remain on the liquid surface upon hybridisation with a complementary DNA chain. Complementary DNA-surfactants are used to functionalise fluid surfaces and to program the interactions between them based on Watson-Crick pairing. By selecting the appropriate DNA base sequences the interaction between the fluid surfaces functionalised with DNA-surfactants can be programmed with the level of specificity as the enzyme-substrate interaction. We studied the adsorption of DNA surfactants at the oil-water interface by Drop Shape Analysis and demonstrated that the interfacial tension isotherm at the oil-water interface depends strongly on the number of bases as well as the base sequence in the DNA surfactant. DNA hybridization at the oil/water interface was studied by measuring the interfacial tension of DNA surfactant during temperature jump across the melting point of complementary DNA-surfactants. Complementary sequences and non complementary sequence of DNA surfactant show clear difference during the temperature jump process. We also found that DNA surfactants can be immobilised on hydrophobic solid surfaces by hydrophobic interactions which allowed us to design a novel method for fabrication of DNA arrays based on microcontact printing of aqueous ‘‘inks’’ containing DNA surfactants on solid substrates. Novel type of aqueous inks based on DNA-functionalised small liposomes for micropatterning of solid surfaces with DNA by a microcontact printing technique has been used. We illustrate the capabilities of this technique by specific deposition of complementary DNA-functionalised liposomes onto DNA-micropatterned solid surfaces. Special attention is paid to the wetting properties of the ink with respect to the stamp and the solid substrates. The method allows for efficient attachment of DNA strands to solid surfaces and hybridisation with complementary fluorescently-tagged oligonucleotides. This new technology could be utilised for rapid preparation of DNA-assays and genetic biochips.
1-05
Triggered
Morphological Transformations in Block Copolymer Aggregates in Solution
S. Burke, A. Choucair, F. Liu, L. Luo, H. Shen, A. EISENBERG, Department of Chemistry, McGill University, 801 Sherbrooke Str. West, Montreal, QC, Canada, adi.eisenberg@mcgill.ca
Ever since it was
shown that block copolymer micelles can self-assemble in solution to give
aggregates of a wide range of morphologies, interest in applications of such
structures has grown considerably. For some applications, e.g. delivery of
specific agents out of vesicles, it is useful to understand the factors which
trigger morphological changes, as well as the mechanisms of such changes. In
this presentation, several such mechanisms are reviewed, i.e. rod-to-vesicle and
sphere-to-rod as well as the reverse transitions, in addition to the mechanism
of size changes in vesicles. All these transitions can be induced, in the
vicinity of phase boundaries, by small changes in one of the “morphogenic”
factors, most conveniently the composition of the solvent. The rod-to-vesicle
transition involves a progressive flattening and shortening of the rod, with a
simultaneous generation of curvature in the flattened part (to a structure
resembling a Chinese wok), the enlargement of the curved or bowl-like section
at the expense of the rod, and finally closure of the bowl. Easily accessible
relaxation times are of the order of tens to hundreds of seconds. The reverse
transition involves a very rapid collapse of the vesicle. The sphere to rod
transition involves initially the formation of a “bead necklace” like
structure, and subsequent smoothing of the bumps, while the reverse transition
involves bulb formation and the splitting-off of spherical micelles from the
ends. Finally, vesicle enlargement involves contact and adhesion, coalescence
and formation of a center wall, destabilization of the wall, asymmetric
detachment of the wall at some point, retraction into the outer wall, and
smoothing into a spherical shape. Vesicle fission involves elongation, internal
waist formation, narrowing of the external waist, and complete separation. The
mechanisms are reminiscent of some biological processes, and are usually
subject to two relaxation times.
1-06
Synthesis and
Self-organization of Multiple Stimuli Responsive Amphiphilic Polymers in
Aqueous Media
A. Laschewsky, S. Garnier, M. Mertoglu, K. Skrabania, J.
Storsberg, University
of Potsdam, Germany, and Fraunhofer Institute for Polymer Research, D-14476
Potsdam-Golm, Germany, laschews@rz.uni-potsdam.de
Amphiphilic block copolymers undergo efficient self-organization in bulk and in solution. They form supramolecular aggregates, in particular in aqueous solution. In order to develop dynamic systems instead of purely static ones where the properties are defined once forever by the chemical structure, stimuli-sensitive polymers have been developed. They are generally aimed at changing the character of functional groups reversibly from hydrophilic to hydrophobic, or vice versa, in order to switch the system between an amphiphilic and non-amphiphilic state. In this context, a series of water-soluble AB-diblock and ABC-triblock polymers was synthesized by us via reversible addition fragmentation chain transfer polymerization (RAFT). This method is a powerful method to prepare functional polymers of complex structure. The new block copolymers were investigated concerning their aggregation in water, in dependence on external stimuli. In particular, the possibility of multiple switchable systems is explored for copolymers containing two stimuli-sensitive hydrophilic blocks. Orthogonal switching the hydrophilicity of a single or of several blocks by changing the pH, the temperature or the salt content demonstrates the variability of the various molecular designs, and exemplifies the concept of multiple-sensitive systems.
1-07
Nanostructured
Materials Formulation and Synthesis via Self-Assembly and Directed Assembly of
Amphiphilic Block Copolymers
P. ALEXANDRIDIS, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY, palexand@eng.buffalo.edu
The interplay between (a) self-assembly properties of amphiphilic block copolymers (ABCs) and (b) synthesis and colloidal stabilization of nanoparticles (NPs) in liquid media containing ABCs is a central theme in our research. When dissolved in selective solvent, ABCs can provide nanoscale environments of varying and tunable dimensions and shape, local polarity, concentration, mobility, affinity to surfaces, and reactivity [Macromolecules 1995, 28, 8604; 1998, 31, 6935; 2000, 33, 5574; 2001, 34, 5979; 2002, 35, 4064; 2004, 37, 912]. ABCs can thus initiate NP formation, facilitate NP growth, control NP size and shape, modify NP surfaces for dispersibility in solution or a solid matrix, alter NP optical and electronic properties, and promote long-range NP organization. The relationship between ABC characteristics and NP structure is beneficial for several applications. Examples will be presented from our work on ABC-structured pharmaceutical and coating formulations [J. Colloid Interface Sci. 2002, 252, 226; 2002, 255, 1; J. Phys. Chem. B 2002, 106, 10834], and ABC-templated synthesis of metal nanoparticles [Langmuir 2004, 20, 8426; J. Phys. Chem. B 2005, 109, jp046221z; Nanotechnology 2005, 16, S344].
1-08
Ordering and Interactions in Electrorheological fluids
J. PERSELLO1, B. Cabane2,
G. Bossis3, R. Schweins4, 1LCMI, Université de
Franche-Comté, 16 route de Gray; 25030 Besançon, France, 2PMMH, CNRS
UMR 7636, ESPCI, 10 rue Vauquelin, 75231 Paris cedex 05, France, 3LPMC,
Université de Nice, Parc Valrose, 06108 Nice Cedex 2, France, 4ILL,
BP 156, 38042 Grenoble cedex 9, France, jacques.persello@univ-fcomte.fr
Some fluids can respond to an
applied electric fluid, switching from a disordered structure with a fluid-like
response to an ordered structure with a solid-like response. More research on
these fluids is performed in order to use them as hydraulic actuators in
micro-devices or as electro-optical devices, e.g. sensors, switches,
narrow-band filters, and wave guides. A critical feature in the performance of
such fluids is the control of interparticle interactions. Indeed, the particles
must repel each other at short distances, otherwise the field-induced
aggregation is not fully reversible and the device cannot be switched
repeatedly. In the present work, we combine numerical calculation and
Small-Angle Neutron Scattering experiments to study the phase transitions in
the structure of a fluid made of surface modified silica particles dispersed in
silicone oil. We shall be using the Neutron small angle scattering instrument
as a Surface Force Apparatus. When an electrical field was applied, a
two-dimensional set of diffraction spots was obtained, located in the direction
of chain alignment. The spacing of these diffraction spots yields the average
interparticle distance, which is found to vary, from a complex way, with the
electrical field, the field frequency and the surface chemistry of the silica
particles.
1-09
Nanostructured, Smart Hydrogel Layers
Dirk Kuckling, Katja Kretschmer, Cathrin Corten, Pradeep Pareek, Institut für Makromolekulare Chemie und Textilchemie, TU Dresden,
D-01062 Dresden, Germany, dirk.kuckling@chemie.tu-dresden.de
Photo cross-linkable hydrogels are of
considerable interest as materials in microsystems (e. g. microactuators) and
biotechnology, in which the gel sizes are reduced to the µm-range (gel
thickness and gel extension). Both temperature and pH-responsive hydrogels have been applied for flow
control in microfluidic devices requiring no external power supply. However,
controlling interactions of hydrogels with biomolecules is still a challenge.
For this purpose hydrogel layer assemblies have been investigated.
Novel PNIPAAm block copolymers have been prepared by using controlled radical polymerization. Due to the radical character of the polymerization a random copolymer block of NIPAAm and a chromphore could be attached to the macroinitiator. The volume phase transition of constrained hydrogel layers was studied by a combination of surface plasmon resonance (SPR) spectroscopy and optical waveguide spectroscopy (OWS) as a function of cross-linking density, and composition. This technique has been applied previously for random copolymers, and is now extended to photo cross-linkable block copolymers and hydrogel layer assemblies. The swelling behavior was affected by the macroinitiator content as well as the cross-linking density of the PNIPAAm phase.
1-10
Nanofabrication via Block Copolymer Templates: From Nanoparticle Arrays to
Optical Waveguides
D. H. KIM, Xue Li, King Hang Aaron Lau, Thomas. P. Russell, Jin Kon Kim, W. Knoll, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany, kimdh@mpip-mainz.mpg.de
We present latest developments on the use of self-assembled block copolymer (BCP) thin films as templates and scaffolds for nanostructured materials. First, various simple routes to fabricate hexagonally patterned nanoparticle arrays are discussed. Asymmetric diblock copolymers of poly(styrene-co-ethylene oxide) (PS-b-PEO), poly(styrene-co-2-vinyl pyridine) (PS-b-P2VP), poly(styrene-co-methyl methacrylate) (PS-b-PMMA) with cylindrical microdomains were employed to generate arrays of gold (Au), titania (TiO2), and composite Au/TiO2 by chemical vapor deposition and sol-gel process, and photophysical properties of the resulting hybrid nanostructures are discussed. Second, the potential application of block copolymer thin films as planar optical waveguides is considered. PS-b-PMMA thin films with cylindrical PMMA microdomains oriented normal to the substrate surface were used to couple optical modes in the Kretschmann configuration and their waveguiding properties are investigated. The methodology provides a significant advance over other conventional analytical tools to monitor the nanofabrication processes occurring in the BCPs in terms of the simplicity and high-sensitivity.
1-11
Nanomolecular
Valve Effect of Cu Complex
Hiroshi Noguchi1, Atsushi Kondo1, Hiroshi Kajiro2, Yoshiyuki Hattori3, HIROFUMI KANOH1, Katsumi Kaneko1, 1Chiba University, 1-33 Yayoi-cho, Inage, Chiba, Japan, 2Nippon Steel Corporation, Futtsu, Japan, 3IRI, Takada, Kashiwa, Japan, kanoh@pchem2.s.chiba-u.ac.jp
Adsorption of supercritical gases such as H2, or CH4 on microporus solids has gathered much attention with respect to energy or environmental technologies. A microporous metal organic solid has a great advantage for designing and construction of the porous framework appropriate for selective adsorption of the target molecules. Although general metal organic solids available for adsorption have open channels in the crystals, Cu complex-assembled microcrystal [Cu(bpy)(BF4)2(H2O)2(bpy)]n (bpy = 4,4’-bipyridine) has no open channels. However, Li and Kaneko found a remarkably specific adsorption behavior of high reproducibility for CO2 in Cu complex-assembled microcrystal [Cu(bpy)(BF4)2(H2O)2(bpy)]n (bpy = 4,4’-bipyridine) irrespective of no open channels. Thus, this Cu complex solid is denoted a latent porous copper crystal (LPC). CO2 is vertically adsorbed and desorbed at specific pressures at 273K. The mechanism of such a nanomolecular valve effect has not been clear because the crystal structure was not understood after pretreatment for removal of water molecules from LPC. Recently we have constructed a model structure of LPC from the experimental data from in-situ FTIR, elementary analysis, TG, XRD, and so on. In the present paper, the mechanism of the nanomolecular valve effect will be presented based on the model structure.
1-12
Microcalorimetry and
Scattering in Binary and Ternary PNIPA Systems near the Volume Phase Transition
K. Laszlo1, K. Kosik1, E. Wilk1, E. Geissler2, 1Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest 1521, Hungary, 2Laboratoire de Spectrométrie Physique CNRS UMR5588, Université J. Fourier de Grenoble, B.P.87, 38402 St Martin d'Hères cedex, France, klaszlo@mail.bme.hu
Poly(N-isopropylacrylamide) gels swollen in pure water exhibit a volume phase transition (VPT) at 34ºC, above which the solvent is expelled. Data from isothermal and scanning microcalorimetry and small angle X-ray scattering (SAXS) observations confirmed that the gel collapse involves two stages. The first is prompt microphase separation in which the polymer chains form a foam-like structure: water bubbles several hundred nm in diameter are separated by 10 nm thick polymer film clusters. The second stage involves slow relaxation, with a mutual diffusion coefficient of about 10-17 cm2/s, characteristic of glassy materials. In contact with aqueous phenol solutions, these gels display a VPT already at 20 °C at aromatic acid concentrations that depend on the number of OH-substitutions. Dynamic light scattering measurements, in which light from the thermodynamic fluctuations is heterodyned by that from the large-scale network heterogeneities, show that DcRdyn/f (Dc and Rdyn are the collective diffusion coefficient and the Rayleigh ratio, respectively, f is the polymer volume fraction) is independent of the aromatic concentration. Thus, the friction coefficient of the polymer chains is not modified in the presence of the binary solvent and below the VPT concentration the phenols are not directly in contact with the polymer chain.
1-13
A Novel Method for Controlling the Size
and Spatial Patterning of Defect Domains in a Smectic A Liquid Crystal
S. SHOJAEIZADEH, S. L. Anna, Department of
Mechanical Engineering,
Controlling the size and spatial ordering of defects in liquid
crystals offers new possibilities for exploiting their unique optical and
rheological properties. Recently, confinement of liquid crystals in silicon
microchannels has been shown to create ordered defect patterns [PNAS, 2004, 101, 17340]. However, silicon micromachining is costly and time
consuming. We present an alternate, rapid, and inexpensive method for
controlling defect patterns in smectic liquid crystals on PDMS films. We first
show that as-prepared and
1-14
Pore
Expansion in Fluorinated Surfactant Templated Porous Silica Thin Films through
Supercritical Carbon Dioxide Processing
KAUSTAV GHOSH1, Hans-Joachim Lehmler2, Stephen E. Rankin1, Barbara L. Knutson1, 1Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY, 2Department of Occupational and Environmental Health, University of Iowa, 100 Oakdale Campus #124 IREH, Iowa City, IA, kghos2@uky.edu
The effect of processing mesoporous silica thin films with supercritical CO2 immediately after casting is investigated, with a goal of using the penetration of CO2 molecules in the tails of CO2-philic cationic fluorinated surfactant templates to tailor the final pore size. Well-ordered thin films with 2D hexagonal close-packed pore structure are synthesized through the liquid phase co-assembly of a homologous series of perfluoroalkylpyridinium chloride surfactants and an inorganic silica precursor. Hexagonal mesopore structures are obtained for both unprocessed films and after processing the cast films in CO2 at constant pressure (69-172 bar) and temperature (25oC to 45oC) for 72 hours, followed by surfactant extraction. XRD and TEM analysis reveal controlled and significant increases in pore size for all CO2 treated thin films relative to the unprocessed sample with increase of CO2 pressure. The degree of pore expansion achieved is directly dependent on the length of the fluorinated tail throughout the homologous series of surfactants. These results demonstrate that combining the tunable solvent strength of compressed and supercritical CO2 with the ‘CO2-philic’ nature of fluorinated tails allows one to control the pore size in ordered mesoporous silica thin films through CO2 processing.
1-15
Dynamic Manipulation of
Proteins and Colloidal Scale Objects with Smart NanoTextured Surfaces
A. Toscano, N. Kozlova, M.
M. Santore, Department of Polymer Science and Engineering, University of
Massachusettes Amherst, 120 Governors Drive, Clarkson University, Amherst, MA, santore@mail.pse.umass.edu
Using planar surfaces with 10-nm scale regions of controlled surface chemistry, we are able to manipulate the adhesion dynamics of a variety of objects, ranging from small proteins (3-4 nm in size) to micron-scale colloidal particles. The surfaces exert both selectivity and tunability in the adhesion dynamics. The key to these behaviors is that the surface chemistries making up the nanopatterns exert substantially different forces on the approaching objects / molecules, setting up lateral competition between attractions and repulsions. In the case of protein adsorption, we demonstrate the ability of small adhesive islands to capture individual fibrinogen molecules, or to hold up to 4 lysozyme molecules in relatively close proximity. Surfaces of similar chemistry are shown to give controlled adhesion rates of micron-scale colloidal particles, from a flowing suspension. In the case of the colloidal particles, the adhesion rates depend on the spacing on the attractive islands on the opposing surfaces. The observations suggest a dynamic pattern-recognition mechanism where lengthscales set up by the particle and ionic strength (through fluctuations) mate with those of the surface at the threshold conditions for adhesion.
1-16
Stimuli-Responsive
Polymeric Films from Colloidal Dispersions
MAREK W. URBAN, NSF Materials Research
Science and Engineering Center at USM, The University of Southern Mississippi,
Hattiesburg, MS, marek.urban@usm.edu
Colloidal dispersions have been of
interest for a long time, and recent advances in phospholipid (PL) chemistry
combined with traditional monomer polymerization or crystallization in the
presence of PL resulted in the development of a new generation of colloidal
films that exhibit unique film formation properties. This presentation will
focus on the developments of non-spherical colloidal particles and the effect
of particle morphologies on film formation and stratification near the film-air
(F-A) and film-substrate (F-S) interfaces. Using biologically active PLs it is
possible to induce the formation of surface localized clusters (SLICs) that may
serve as rafts for other applications.
1-17
Stimuli-Responsive Layer-by-Layer Polymeric Films and Capsules
S. SUKHISHVILI, Department of Chemistry
and Chemical Biology, Stevens Institute of Technology,
We discuss the role of hydrogen bonding and electrostatic interactions in pH- and temperature-responsive multilayer films and capsules, which contain a weak polyelectrolyte as one of the multilayer components. We will contrast fundamental differences between electrostatic and hydrogen bonding layer-by-layer polymer self-assembly, including charge regulation and charge imbalance within the film. Along with the systems where hydrogen-bonded and electrostatically adhered polymers are incorporated into different stacks of hybrid films, we introduce copolymers that combine centers for electrostatic and hydrogen bonding in one molecule, such as polybetaines containing carboxylate groups and quaternized derivatives of poly-4-vinylpyridine with pyrrolidone moieties. Such copolymers can be self-assembled via electrostatic mechanism at neutral pH values, but they also yield robust multilayers with polycarboxylic acids at low pH in salt solutions where the films are stabilized by hydrogen bonding. Temperature responsiveness can also be imparted to films by introducing poly(vinyl methyl ether). Strategies to stabilize films at high pH values by introducing covalent cross-links will also be discussed. The permeability of self-assembled layers and capsules to small molecules is strongly pH- and/or temperature-dependent, showing potential for controlled release applications.
1-18
Patterning
of Polymeric and Biomolecular Nanostructures: Approaches and Challenges
STEFAN ZAUSCHER, Department of Mechanical Engineering and Materials Science, Center for Biologically Inspired Materials and Materials Systems, Duke University, 144 Hudson Hall, Durham, NC, zauscher@duke.edu
Fabricating stimulus-responsive, smart polymeric and biomolecular structures on surfaces and the control of their architecture on the nanometer length scale is important for applications in biosensors, proteomic chips and nanofluidic devices. Here we present methods that we have developed that allow for molecular-level control in the fabrication of polymeric and biomolecular nanostructures. First we describe the fabrication and characterization of stimulus responsive, elastin-like polypeptide (ELP) nanostructures grafted onto functionalized thiolates patterned onto gold surfaces with dip-pen nanolithography (DPN). ELPs undergo a reversible, hydrophilic-hydrophobic phase transition in response to external stimuli, such as a change in temperature or ionic strength. This phase transition behavior was exploited to reversibly immobilize a thioredoxin-ELP (Trx-ELP) fusion protein onto the ELP nanopattern above the lower critical solution temperature (LCST) demonstrating the potential for ELP nanoarrays in reusable lab-on-chip devices for protein purification or nanoscale analysis. Next we describe the fabrication of stimulus-responsive, poly(N-isopropylacrylamide) (pNIPAAM) brush nanopatterns in a “grafting-from” approach that combines scanning probe lithography and e-beam lift-off lithography, with surface initiated polymerization using atom transfer radical polymerization (ATRP). We demonstrate the reversible, stimulus-responsive conformational height change of these nanopatterned polymer brushes by inverse transition cycling in water, and water-methanol mixtures. Our nanofabrication approaches are generic and can likely be extended to a wide range of vinyl monomers. Finally we discuss surface-initiated ring-opening metathesis polymerization (ROMP) of cyclic monomers on silicon oxide nanopatterns fabricated by atomic force microscope (AFM) anodization lithography. The combination of anodization lithography and surface-initiated ROMP allows us to fabricate small, nanoscale features on silicon surfaces either by solution or vapor phase introduction of the monomer. We will describe our results characterizing these sample surfaces using TappingMode and potential gradient AFM imaging.
1-19
Nanoscale
Functionalization and Site-Specific Assembly of Colloids by Particle
Lithography
CHARLES E. SNYDER, Allison M. Yake, Jason D. Feick, Darrell Velegol, Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, ces988@psu.edu
The production of a simple localized and nanoscale charge distribution on the surfaces of individual colloidal microspheres is realized here using our technique of “particle lithography”. In this technique, parts of the microspheres are masked off, while polyelectrolytes (or other molecules) cover the remaining portions of the microspheres. The result is a microsphere with a functionalized patch of controlled size. The effectiveness of this process is demonstrated by the accurate and reproducible production of colloidal heterodoublets composed of oppositely-charged microspheres. The particle lithography technique is advantageous since it is not limited by the resolution of photolithography or by functionalizing chemistries, and the technique opens the door for complex site-specific functionalization of particles. The size of the functionalized patch may be tailored through the use of polyelectrolytes (or any masking agents) of different sizes, or by adjusting the salt concentration (i.e. adjusting the Debye layer thickness). The particle lithography process and it’s degree of accuracy will be better understood through modeling.
1-20
Xerogel from Silica and
Naphthanediimide, an Efficient Photoredox Agent
Nelcy D.
A nanohybrid xerogel composed of N, N´-bis(2-phosphonoethyl)-1, 4,
5, 8-naphtalenodiimide (DPN) with silica was obtained by doping the sol-gel
with DPN during the TEOS condensation reaction. Physical and chemical aspects
of the xerogel were obtained by FTIR, TA and BET. Morphological analyses reveal
that DPN are located inside the particle pores. Photochemical studies in the
presence of Trpytophan (Trp) showed that the xerogel is efficiently promoting
the photosensitization of Trp radical formation. Photophysical studies
demonstrated the presence of J-aggregates of DPN. The splitting model of
exciton theory was used to determine the distance between DPN molecules (~7Å).
The silica sterical hindrance and the DPN geometry inside the silica particles
are main factors for the good photosensitizing efficiency of the xerogel.
Sponsors: FAPESP, CNPQ and
1-21
Synthesis and
Rearrangement of Block Copolymer Brushes
WILLIAM J. BRITTAIN, Department
of Polymer Science, The University of Akron,
The synthesis of
tethered block copolymer brushes via
the use of controlled/‘living’ free radical polymerization techniques presents
many significant advantages over traditional free radical polymerization
techniques. In our group, we have found that the most versatile
controlled/‘living’ free radical polymerization techniques are atom transfer
radical polymerization (ATRP) and reversible addition fragmentation transfer
(RAFT) polymerization. Both diblock and
1-22
Ultrahydrophobic Surfaces through Surface-attached Ultrathin Polymer
Films
J. S. D. Jeyaprakash Samuel; I. J. Park, J. RÜHE, Chemistry and Physics of Interfaces, Institute for Microsystems Engineering (IMTEK), University of Freiburg, Georges Köhler-Allee 103, D79110 Freiburg, Germany, ruehe@imtek.de
The leaf of the lotus plant has, like a variety of other plant surfaces, strongly ultrahydrophobic surface properties due to a series of micro- and nanostructures spanning a wide spectrum of length scales. Water cannot wet the surfaces, even upon impact, and rolls easily off the surface, collecting dust and other particles along the way. The study of these unusual wetting properties of such natural surfaces has suggested to introduce such a concept into a variety of different engineering applications. The transfer of this concept into artificial materials, however, had only somewhat limited success so far. After having very good initial properties, the ultra¬hydrophobicity of such surfaces usually deteriorates rather quickly. One of the major problem has been that artificial surfaces, unlike plant surfaces, do not have a possibility to regenerate after physical damage of the micro- or nanostructures and once the surface is mechanically damaged, the surface properties are changed irreversibly. We present new techniques to obtain ultrahydrophobic surfaces through a combination of surface-attachment of fluorinated polymers and microstructure generation. The polymer molecules are either grown on the surface of the substrate through surface-initiated polymerization or become attached through a photochemical process.
1-23
Binary Polymer Brushes:
Structured Surface with Reversiby Tunable Wetting Properties
MARCUS MUELLER, Department of Physics,
Grafting of two incompatible polymers onto a substrate one prevents
macroscopic phase separation and the laterally self-assembled thin film
structures exhibit reversibly tunable wetting properties. Self-consistent field
calculations utilizing the Gaussian chain model and a virial expansion for the
interactions predict a rich phase diagram of laterally periodic morphologies as
a function of solvent quality, composition of the brush, incompatibility of the
two polymer species and grafting density, however, the structures observed in
experiments lack long-range periodic order. We employ
1-24
Mixed Polyelectrolyte Brushes: Adaptive and Responsive Polymer
Surfaces
M. STAMM1, N. Houbenov1, D. Usov2, S. Minko3, 1Leibniz Institute of Polymer Research Dresden, Germany, 2University Ghent, Belgium, 3Clarkson University, Potsdam, NY, stamm@ipfdd.de
We have shown in the past that different binary polymer brush layers at solid surfaces reveal responsive and switching behavior. This can also be shown for polyelectrolyte brushes which are sensitive on pH. Mixed polyelectrolyte - non polyelectrolyte and mixed oppositely charged polyelectrolyte brushes were synthesized by "grafting to" and "grafting from" approaches on solid substrates (Si-wafers and polymer films). The mixed brushes exhibits responsive properties via exposure to organic solvents and water of different pH resulting in switching of the brush morphology, surface energetic state, wettability, and thickness. From AFM investigations different nanostructures are distinguished.
1-25
Nanoprobing of Switchable
Polymer Surfaces
VLADIMIR V. TSUKRUK, Department of Materials Science and Engineering, Iowa State University, 3155 Gilman Hall, Ames, IA, vladimir@iastate.edu
An overview of recent author's results on atomic force microscopy (AFM) probing of nanomechanical and tribological properties is presented and discussed for a wide range of switchable surfaces. We focus on mono- and binary polymer brushes (grafted to, grafted from, and Y-shaped) studied under various conditions (in air, in fluid, and at elevated temperatures), patterned surface films, and photochromic monodendrons of different generations.
1-26
Synthesis
of Segregated Binary Polymer Brushes
IGOR LUZINOV, Yong Liu, Viktor Klep,
School of Materials Science & Engineering Clemson University, 161 Sirrine
Hall, Clemson, SC, luzinov@clemson.edu
Communication is focused on synthesis
of binary polymer brushes with phase-segregated morphology. Namely, polystyrene/polyethylene
glycol methyl ether methacrylate (PEGMA) brushes were fabricated by combination
of “grafting to” and “grafting from” techniques of the polymer anchoring. A ultrathin film consisting of carboxyl-terminated
polystyrene (PS) and poly (methyl methacrylate) (PMMA) blend was first
deposited on a substrate modified with poly(glycidyl methacrylate) and annealed
at 120 oC. As a result
of the grafting islands of PS brushes were created. To complete formation of the segregated
binary brushes, surface initiated polymerization (ATRP) of PEGMA was carried
out. Surface rearrangements of the
segregated brushes were studied by contacting them with selective solvents.
1-27
Synthesis
of Mixed Homopolymer Brushes on Silica Nanoparticles by Living Radical
Polymerization Techniques
Dejin Li, Xia Sheng, BIN ZHAO, Department of Chemistry, University of Tennessee, Knoxville, TN, zhao@novell.chem.utk.edu
By using two different living radical polymerization techniques, atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP), we successfully synthesized mixed poly(t-butyl acrylate) (PtBA)/polystyrene (PS) brushes on silica nanoparticles. Silica particles were prepared by the Stöber process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated ATRP of t-butyl acrylate was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by NMRP of styrene from PtBA particles. The Mn of the grafted PS was found to be the same as that of the free PS formed from the free initiator. Amphiphilic mixed poly(acrylic acid) (PAA)/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and 1H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl3, a selective solvent for PS, and also in CH3OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.
1-28
Novel Smart Core-Shell
Microgels: Synthesis and Characterization
Man Fai Leung1, Junmin Zhu1, Frank W. Harris2, PEI LI1, 1Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China, 2Maurice Morton Institute of Polymer Science, The University of Akron, OH, bcpeili@polyu.edu.hk
Colloidal microgels that are able to alter their volume and properties in response to environmental stimuli, such as pH, temperature and ionic strength are attractive candidates for many potential applications. Recently, microgels with more complex structures, such as a multi-responsive core-shell, have received increasing attention due to the tuneable properties of the individual responsive components. In this presentation, a new method to prepare smart microgels that consist of well-defined temperature-sensitive cores with pH-sensitive shells will be described. The microgels were obtained directly from an aqueous graft copolymerization of N-isopropylacrylamide and N, N-methylenebisacrylamide from water-soluble polymers containing amino groups such as poly(ethyleneimine) and chitosan. The microgel diameters ranged from 300 to 400 nm with narrow size distribution. The unique core-shell nanostructures exhibited tuneable responses to pH and temperature.
1-29
Collapse of Polyelectrolyte Brushes Driven by Ion Pairing
Interactions
OMAR AZZARONI1, Sergio Moya2, Andrew A. Brown1, Tamer Farhan1, Wilhelm T. S. Huck1,2, 1Melville Laboratory for Polymer Synthesis, Department of Chemistry, 2The Nanoscience Centre, University of Cambridge, CB2 1EW, United Kingdom, oa219@cam.ac.uk
Polyelectrolyte brushes are ideal building blocks for soft nanotechnology and the engineering of responsive surfaces. Changes in ionic strength, pH and solvent properties lead to markedly difference on surface properties due to transitions in the polymer brushes between stretched and collapsed states. The traditional framework in polyelectrolyte brushes describes collapse as the result of a significant screening of the charges of the pendants groups. However, a much richer behaviour should be expected when the specific chemical interactions between anions and cations are explicitly studied. The introduction of chemical triggers of collapse (rather than merely relying on ionic strength) will allow the development of surfaces which show responsive behaviour that can be exploited as sensors, as well as actuating mechanisms in fluidic devices. In this work we have investigated the critical role of ion–pairing interactions on the collapse of cationic 2–(methacryloyloxy)ethyl–trimethylammonium chloride (METAC) polyelectrolyte brushes. We observed that in the presence of ion–pairing interactions, the chemical nature of the electrically neutral polymer can be sharply switched from hydrophilic to hydrophobic. This chemical change of the monomer units leads to a collapse driven by hydrophobic interactions with the surrounding water. As a consequence, ion–paired collapsed polyelectrolyte brushes show very compact stiff structures markedly different from similar brushes whose collapse are driven by Coulombic screening.
1-30
Thermally Responsive
Polymer Brushes with High Protein-Binding Affinity
Andy Kusumo1, Lindsay Bombalski2, Qiao Lin3, Krzysztof Matyjaszewski2, Tomek Kowalewski2, James W. Schneider1, ROBERT D. TILTON1,4, Departments of 1Chemical Engineering, 2Chemistry, 3Mechanical Engineering, and 4Biomedical Engineering, 1Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA, tilton+@andrew.cmu.edu
Polymer brushes with tunable protein affinities can be useful for protein chromatography or adsorptive pre-fractionation of crude cell lysate samples. Well controlled brushes of poly(dimethylaminoethylmethacrylate) (PDMAEMA) are grown from thiol-linked initiators on gold surfaces using atom transfer radical polymerization (ATRP). The lower critical solution temperature (LCST) of the brushes is controlled by statistical copolymerization with methylmethacrylate (MMA). The polymer grafting density is controlled by varying the relative amounts of initiator and inert thiol in solution during the initial gold surface modification and is quantified by surface plasmon resonance (SPR). At lower grafting densities, SPR measurements indicate that these brushes have an unexpectedly high affinity for proteins, adsorbing the equivalent of 10-15 monolayers of serum albumin within the brush, under good solvent conditions. Above the LCST, the extent of adsorption increases slightly, but the adsorption rate increases approximately ten-fold. In spite of the greater hydrophobicity of PDMAEMA-co-PMMA compared to PDMAEMA, the protein adsorption is approximately 40-fold slower for the copolymer brushes. This effect is tentatively attributed to a reduction in protein accessible volume within the copolymer brush. The effects of temperature, protein hydrophobicity, brush composition and grafting density on protein binding capacity will be discussed.
1-31
Strong Polyelectrolyte Brush at the Air/Water Interface
PLOYSAI KAEWSAIHA, Kozo Matsumoto, Hideki
Matsuoka, Department of Polymer Chemistry, Kyoto University, Katsura, Nishikyo,
Kyoto, Japan, ploysai@star.polym.kyoto-u.ac.jp
We synthesized an ionic amphiphilic
diblock copolymer having strong acid group; poly(hydroganated
isoprene)-b-poly(styrenesulfonic acid) (PIp-h2-b-PSS) by living
anionic polymerization, and the nanostructure of its spread monolayer on the
water surface was directly investigated by in situ X-ray reflectivity (XR)
technique. The monolayer of a diblock copolymer on a water surface had a smooth
hydrophobic PIp-h2 layer on water and hydrophilic layer consists of
a dense ‘carpet layer’ just beneath the hydrophobic layer and ‘brush-like
layer’ stretching into water. The surface pressure and PSS chain length
dependence of its hydrophobic layer thickness and the brush nanostructure were
quantitatively studied. Furthermore, the effect of salt concentration in the
subphase was also investigated. The thickness of the PSS brush layer decreased
at salt concentrations above 0.2M while no nanostructure change was detected
below 0.2M. This critical salt concentration corresponds to be that of free
counterions inside the brush layer. However almost all of counterions in the
carpet layer might be condensed so that the carpet layer structure is hardly
changed by compression, or salt addition.
1-32
Stimuli-Responsive Polymer Based Composite Microcapsules
C. Déjugnat, T. Mauser, D. Haložan, K. Köhler, D. G. Shchukin, A. Skirtach, G. B. SUKHORUKOV, Max Planck Institute of Colloids and Interfaces, Potsdam/Golm, Germany and IRC at Biomedical Materials, Queen Mary University of London, London, UK, gleb@mpikg-golm.mpg.de
Polyelectrolyte capsules representing a novel type of nano-engineered multifunctional materials are made by layer-by-layer adsorption of oppositely charged polyelectrolytes on the surface of colloidal template particles of 0.05-20 mm diameter. A great variety of materials including synthetic and natural polyelectrolytes, proteins, multivalent ions, organic nanoparticles, lipids were used to build walls of hollow capsules. Many of them were functionalized to provide special surface properties of technical or biological relevance. The possibility of tailoring different functionalities, impregnating inorganic and organic substances both inside capsule volume and in polyelectrolyte shell, controlled release of encapsulated material provided continuous scientific and industrial interest for employing capsules as microcontainers and microreactors. Inorganic nanoparticles incorporated to polyelectrolyte shell makes possible the remote activated release. Smart polymers involved in capsule build-up exhibit reversible sensitivity to environmental conditions, i.e. capable of undergoing sharp physical or chemical modifications in response to external stimuli such as temperature, pH, ions, etc. Here we present the results obtained with hollow and filled capsules prepared with stimuli-responsive polymers and capsules filled with different polymers responsive to ions, pH and temperature. The possibilities for practical applications of such capsules are illustrated.
1-33
Connecting the Wetting and Rheological Behaviors of PDMS-Grafted
Nanospheres in PDMS Melts
DAVID GREEN1, Jan Mewis2, 1Department of Chemical Engineering, University of Virginia, 102 Engineers’ Way, Charlottesville, VA, 2Department of Chemical Engineering, Katholieke Universiteit Leuven, 46 Willem de Croylaan, 3001 Heverlee, Belgium, dlgreen@virginia.edu
Engineered nanocomposites are often formulated by grafting polymer brushes to the surfaces of colloids to optimally disperse them into viscous polymer matrices. In spite of the ubiquity of these filled materials, the essential mechanisms in producing an optimal dispersion have not been well quantified. To this end, rheological and light scattering measurements are made to connect the static wetting and dynamic flow properties of polydimethylsiloxane (PDMS)-grafted silica nanospheres in PDMS melts. By controlling the brush grafting density and the matrix chain length of these model systems, results indicate that the wetting and the flow behaviors can be quantifiably linked. Overall, these studies represent new ways of quantifying the factors that control the dispersion of polymer-grafted nanoparticles in viscous melts.
1-34
Counterion Condensation and Complex Formation on Polyelectrolytes
ULRICH SCHELER,
Leibniz Institute of Polymer Research, Hohe Strasse 6, 01069
The effective charge of polyelectrolytes in solution is significantly lower than the nominal charge, since a considerable fraction of the conterions is not free to move away from the polymer, they are condensed on the polymer. Electrophoresis NMR combined with diffusion NMR permits the direct determination of the charge of molecules and complexes. The effective charge of poly(styrene sulfonate) is decreasing with increasing ionic strength of the solvent. For low molecular weight the effective charge equals the nominal charge. With increasing molecular weight the hydrodynamic friction increases, resulting a reduced diffusion coefficient, while the electrophoretic mobility is constant after only an initial increase. From the combination of both effects an increasing fraction of condensed counterions is concluded. Amino acids can bind to macromolecules through electrostatic interaction. Glutamic acid in solution exhibits a negative electrophoretic mobility, that is increasing by value with pH. The lower magnitude of the electrophoretic mobility in the solution containing the polycation is due to exchange between bound and free acid on the time scale of the experiment. At high pH the acid is fully dissociated and strongly binds to PDADMAC resulting in an electrophoretic mobility close to that of the polycation.
1-35
Polymer-Capped Monodisperse
Magnetic Nanoparticles
M. LATTUADA, T. A. Hatton, Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge MA, lattuada@mit.edu
We have prepared monodisperse magnetic nanoparticles following the organic route proposed by Sun et al. [JACS, 2004, 126, 273]. The particles are stabilized by oleic moieties, and in order to undergo further functionalization a surface ligand exchange reaction is performed by means of which the oleic moieties are replaced by ricinoleic moieties. The additional hydroxyl group of ricinoleic acid enables further reactions to take place. In particular the reaction with acid halides bearing halogen atoms allows one turn the nanoparticles into macroinitiators for Atom Transfer Radical Polymerization (ATRP). ATRP allows one to polymerize a large variety of monomers in controlled conditions, which can impart to the so obtained polymer-capped nanoparticles a wide range of properties. For example, by polymerizing PH or temperature sensitive monomers, one can obtain water soluble monodisperse magnetic nanoparticles showing PH or temperature induced reversible self-assembly. We have grown poly(meth)acrylic acid brushes from the nanoparticle surface through polymerization of trimethylsilyl (meth)acrylate, followed by hydrolysis to yield the PH responsive poly(meth)acrylic acid. The nanoparticles properties can be further tailored by making use of amidation chemistry to attach a variety of molecules and biomolecules to the carboxyl groups.
1-36
Improving Fuel
Cell Performance by Controlling Polymer Membrane Architecture; Nanoparticles
for Enhanced Proton Conduction
Theo B. J. Blijdenstein, Norman J. Wagner, Center for Molecular and Engineering Thermodynamics, Department of Chemical Engineering, University of Delaware, Newark, DE, wagner@che.udel.edu
A key limiting factor for the performance of proton-exchange
membrane fuel cells (PEMFC) is the reduction in proton conductance, and hence,
power output at “high” temperatures (100-150 °C). For standard Nafion™ based systems, this is primarily due
to the loss of water. Hydration of the membrane is necessary for the
percolation of self-assembled proton conduction channels in the ionomeric
membrane. It has been hypothesized that incorporation of nanoparticles has
proved to be beneficial for proton conduction at high temperatures/low
humidity. In the work presented,
select NafionTM composite membranes were prepared by recasting from
dispersions in which particles with known size and surface charge were
incorporated. We investigated how colloidal NafionTM/silica-interactions
in solution determine the structure of both the dispersions and the resulting
membranes. Techniques include rheology, light- and X-ray scattering, light
microscopy and scanning electron microscopy, altogether covering a wide range
of length scales. The performance of the composite membrane regarding proton
conductivity and half-cell activity will be presented and discussed in terms of
the membrane microstructure and the water holding capacity of the membranes.
1-37
Vapor Sensors Based on Gold Nanoparticle Interlinked
with p-Oligophenyldithiols
Y. JOSEPH, B. Guse, A. Yasuda, T. Vossmeyer, Materials Science Laboratory, Sony Deutschland GmbH, Hedelfinger Str. 61, D-70327 Stuttgart, Germany, joseph@sony.de
Recent efforts to control the
physical and chemical properties of nanostructured materials through a
molecular level design have generated enormous interest in thin films comprised
of organically crosslinked metal nanoparticles. Here, we investigate films
prepared by layer-by-layer self-assembly using solutions of
dodecylamine-stabilised 4 nm Au-nanoparticles and oligophenyldithiols of
different lengths. The resulting films are 7 to 30 nm thick, as determined by
AFM and the dodecylamine ligands are exchanged by the crosslinking dithiols
during film assembly as revealed by XPS. Additionally, two main sulfur signals
(S-Au, S-H) are observed indicating that p-p interaction may be important for assembly. All films show linear
current-voltage characteristics and conductivities independent from the length
of the linking molecule. Conductivity measurements at variable temperature are
consistent with an Arrhenius-type activation of charge transport. For
investigating the vapor sensing properties, coated chemiresistors and quarz
micro balances are dosed with vapours of toluene, 1-propanol,
4-methyl-2-pentanone and water. Their resistances increase only slightly
whereas the mass uptake is significant in case of hydrophobic vapors. All
results are compared with results from films interlinked with alkanedithiols of
similar lengths (C6, C9, C12).
1-38
Magnetic-field-guided Growth of
Ferromagnetic Core-Shell Nanomaterials
Liyan Zhao, Karan Sukhija, Nina Heinig, Xiaojing Zhou, TONG LEUNG, WATLabs and Department of Chemistry, University of Waterloo, Waterloo, ON, Canada, tong@uwaterloo.ca
Our recent work on metal nanoparticles (Cu, Ni, Co)
electrochemically deposited on an ultrathin polypyrrole film grown on a
gold-coated silicon electrode shows that the morphology (size, shape, density
and distribution) of these nanostructured materials can be easily controlled by
varying the wet deposition conditions (pH, electrolyte concentration,
deposition potential, charge, and current density), and the thickness and
morphology of the polypyrrole film.
Using similar electrochemical techniques, we have recently obtained
mono-sized, uniformly distributed Fe core-shell nanoparticles with two
different morphologies: quantum dots of 4-10 nm in diameter and 20´110 nm “nano-surfboards”
(<5 nm thick). These
nanoparticles are found to primarily consist of a Fe metallic core and a mixed
Fe oxides shell (2-3 nm thick). In
the present work, we report the first evidence of morphological changes induced
by an external magnetic field during growth. Implications of constructing patterned
nanostructured materials using this technique will also be discussed.
1-39
Advanced
Nanostructured Materials from Block Copolymer – Nanoparticle Assemblies
ULRICH WIESNER, Department for
Material Science and Engineering, Cornell University, 329 Bard Hall, Ithaca, NY,
ubw1@cornell.edu
The study of polymer based
co-assembly (“bottom-up”) approaches to multifunctional polymer-inorganic
hybrid materials is an exciting emerging research area interfacing solid state
and soft materials and offering enormous scientific and technological promise.
By choice of the appropriate synthetic polymers as well as nanoparticle
precursors unprecedented morphology control down to the nanoscale is obtained.
Tailoring of the polymer–inorganic interface is of key importance. The
structures generated on the nanoscale are a result of a fine balance of
competing interactions, a typical feature of complex biological systems. The
potential for new multifunctional materials lies in the versatility of the
polymer chemistry as well as that of the inorganic (nanoparticle) chemistry
that can be exploited in the materials synthesis. In the present contribution
the synthesis and characterization of advanced nanostructured hybrid materials
will be presented with potential applications ranging from microelectronics to
nanobiotechnology. In all cases cooperative self-assembly of organic and
inorganic species is induced by amphiphilic macromolecules. Besides amorphous
and crystalline oxide materials novel systems toward high temperature SiCN and
SiC structures are introduced. Examples will include the preparation of
mesoporous materials and superparamagnetic mesoporous materials with pore sizes
ranging from 5-50 nm for separation technology and catalysis, solid hybrid
polymer electrolytes for battery applications, the synthesis of nanoparticles
with controlled shape, size, and composition for applications in the life
sciences, as well as thin film materials with potential applications in
microelectronics and nanobiotechnology.
1-40
Electric Field Directed Assembly of
Colloidal Particles into Nanostructured Thin Films and Composites
J-C. Lin, D. Liu, M. Z. YATES, Department of Chemical Engineering and Laboratory for Laser Energetics, University of Rochester, Rochester, NY, myates@che.rochester.edu
When an electric field is applied to a colloidal suspension, particles can exhibit a variety of electrokinetic responses that may be exploited to manipulate particles and control their assembly. For example, charged particles move to an oppositely charged electrode by electrophoresis, particles migrate in an electric field gradient by dielectrophoresis, or field induced dipoles on particles cause particles to aggregate in linear chains. Rod-shaped particles can be aligned by an electric field with the longest axis parallel to the applied field. Here we report the fabrication of thin films and composites containing aligned rod-shaped particles through a novel electric-field driven process. The alignment direction of rod-shaped particles in the composite material is controlled by the electrode geometry. Functional particles are selected that give the composite material anisotropic optical and transport properties that are dependent on the alignment direction. The films may find application in membranes and optical materials. The electric field-driven process is applicable to the directed assembly of a variety of types of rod or plate shaped particles to create advanced materials with controlled nanostructure.
1-41
Inversion of Emulsions Stabilised Solely by Ionisable Nanoparticles
B. P. BINKS, J. A. Rodrigues, Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull,United Kingdom, b.p.binks@hull.ac.uk
Certain solid nanoparticles act as excellent emulsifiers of oil and water in the absence of any surface-active agent and, since particles are strongly attached to interfaces, coalescence tends to be absent. However, different types of particles are needed to prepare either oil-in-water (o/w) or water-in-oil (w/o) emulsions in mixtures containing equal volumes of the two liquids. Here we describe a new class of solid particle emulsifier capable of stabilising both emulsion types efficiently. The spherical nanoparticles are those of polystyrene whose surfaces contain ionisable carboxylic acid groups. Inversion of the emulsion type is simply effected by either an increase in pH or salt concentration, both driving the inversion from w/o to o/w. The emulsions are studied using conductivity, optical microscopy and stability measurements. The origin of inversion is due to the change in the wettability of the particles at the interface, brought about by increasing the degree of dissociation of acid groups, rendering particles more hydrophilic as a result.
1-42
A New AC Electrokinetic Technique for Collection and Manipulation of
Particles on Patterned Electrodes
KETAN H. BHATT1, Orlin D. Velev1, Sonia Grego2, 1Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 2MCNC Research and Development Institute, Research Triangle Park, NC, khbhatt@unity.ncsu.edu
We report a new type of microfluidic chip that collects and concentrates colloidal particles from bulk liquid medium using AC electrokinetics. The alternating electric fields were applied to dilute suspensions of latex microspheres enclosed between a patterned silicon wafer and an ITO-coated glass slide. The latex particles entrained by a liquid flow were collected in the center of the conductive "corral" patterns. The particle collection efficiency and speed depended only on the frequency and strength of the applied field and were independent of the material properties of the particles or the electrodes. The leading effect in the particle collection process is AC electrohydrodynamics (EHD). We discuss how the EHD flows emerge from the spatially non-uniform field and interpret the experimental results by means of electrostatic and hydrodynamic simulations. We demonstrate on-chip collection of latex particles, yeast cells and microbes. The technique allows three-dimensional microfluidic pumping and transport by use of two-dimensional patterns.
1-43
Temperature-Induced
Phase Inversion of Emulsions Stabilized by Latex Particles Alone
B. P. Binks1, R. MURAKAMI1,
S. P. Armes2, S. Fujii2, 1Surfactant & Colloid Group, Department
of Chemistry, University of Hull, Hull, United Kingdom,
2Department of Chemistry, University
of Sheffield, Sheffield, S3 7HF, United Kingdom, r.murakami@hull.ac.uk
Aqueous dispersions of poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] (PDMA-PMMA)-stabilized polystyrene latex particles (diameter = 150 nm) were synthesised and used as sole emulsifiers of hexadecane and water (1:1) at various temperatures. At low temperatures (≤ 50 °C) oil-in-water emulsions form which are stable to coalescence but exhibit creaming. At high temperatures (≥ 65 °C) water-in-oil emulsions form which are unstable to coalescence. At intermediate temperatures (55-65 °C), emulsions could be of either type. Thus transitional inversion takes place in the same direction as that occurring in nonionic surfactant-stabilised emulsions. Microscopy observations of the aqueous dispersions indicate flocculation of the particles with increasing temperature. Furthermore, the contact angles of a water drop under hexadecane on a glass substrate coated by PDMA homopolymer increase with increasing temperature, implying an increase in system hydrophobicity. A mechanism to understand this inversion involves consideration of changes in the hydration and ionization of the exterior amino groups on particle surfaces with increasing temperature.
1-44
The Synthesis of FePt Nanoparticles by Two-Liquid Mixing Method
2-01
Nanosize Particles as Building
Blocks for Uniform Colloids of Different Morphologies
EGON MATIJEVIĆ, Center for Advanced Materials Processing,
This talk will address the problems involved in the formation of uniform colloids of different particle shapes. Specifically, the focus will be on the mechanisms by which such particles are generated by aggregation of nanosized precursors. Both chemical and physical aspects of the involved phenomena will be illustrated.
2-02
Applications of Light Scattering Techniques for Determining Doublet Formation Rate of Colloidal Systems
M. Lattuada, Z.
Jia, H. WU, A. Vaccaro, J. Sefcik, M. Morbidelli, Swiss Federal Institute of Technology Zurich,
ETHZ, Institut für Chemie-und Bioingenieurwissenschaften, ETH-Hönggerberg/HCI,
CH-8093 Zürich, Switzerland, hua.wu@chem.ethz.ch
The formation rate of a doublet from two primary particles is one of the fundamental characteristics of a colloidal system. It gives direct estimate of the Fuchs stability ratio W, which can be used to estimate the effective surface charge and is also a prerequisite in the simulations of aggregation kinetics using the population balance equations. Among the available techniques in the literature, those based on light scatterings are most commonly used, because they are noninvasive and supported by sound scattering theories. However, those relying on the dynamic light scattering have ignored the effect of the rotational motion on the measured hydrodynamic radius of the doublets. In the present work, we analyze and show that this effect is significant for a doublet, in the cases of qRp>1 (q is the scattering wavevector and Rp is the radius of primary particles). Thus, before such an effect can be quantified, care must be taken in the applications of the dynamic light scattering to determine the doublet formation rate. Therefore, we have proposed a technique that is based only on the static light scattering (SLS) experiments to determine the doublet formation rate. In particular, this technique monitors the very initial stage of the aggregation, where the system is dominated by only primary particles and doublets. It first determines the conversions of the primary particles to doublets x at different aggregation times by reconstructing the average structure factors of the aggregating system obtained from the SLS experiments. Then, considering the second-order kinetics of the doublet formation, we can obtain the doublet formation rate from the time-dependence of the conversion x, which in turn gives the estimate of the Fuchs stability ratio W. Several aggregation experiments have been carried out to demonstrate the applicability of the proposed technique.
2-03
Destabilization of silica nanoparticles suspensions with Al13 polycations
C. PARNEIX1, B. Cabane2, J. Persello1, 1Laboratoire de Chimie des Matériaux et Interfaces, Université de Franche-Comté –16 route de Gray, 25030 Besançon Cedex, France, 2Laboratoire PMMH, ESPCI - 10 rue Vauquelin, 75231 Paris Cedex 05, France, caroline.parneix@univ-fcomte.fr
Although Al13 polycations (Al12VI(OH)24AlIVO4(H2O)127+) are widely used as coagulants in the water treatment industry, the mechanisms by which they interact with colloidal particles suspended in water and induce their aggregation are not fully understood. We study here how silica sols with different particle sizes in the range 10-25 nm and with pH adjusted to 5 or 9 are destabilized with addition of Al13 polycations. After turbidimetric determination of the aggregation kinetics, the interactions between silica and Al13 as well as those between nanoparticles in presence of Al13 are characterized. The aluminum species present both at the surface of particles and in the dispersion medium are identified using 27Al NMR spectroscopy, whereas osmotic pressure measurements allow us to investigate the modification of interactions between particles with the rate of added coagulant and pH of the dispersion. Small angle neutron scattering experiments provide us additional information about interactions between particles but also about the structure of the aggregates formed. Beside the differences revealed in the aggregation kinetics and the amount of Al13 required for aggregation at pH 5 and 9, suggesting different destabilization mechanisms, the variation of the aggregation conditions appears as a mean to control the morphology of the silica aggregates.
2-04
Heteroflocculation induced
by montmorillonite plates acting as bridging agents
Alois Vanerek, Bob Alince, THEO G. M. VAN DE
VEN, Pulp and Paper Research Centre and Department of Chemistry, McGill
University, 3420 University Street, Montreal, QC, Canada, theo.vandeven@mcgill.ca
In papermaking, a microparticulate retention aid system consisting of bentonite and high molecular weight cationic polymer is commonly used to incorporate mineral pigments in the fiber web. It is believed that the mechanism by which bentonite operates is based on the ability of montmorillonite (its main component) to form a bridge between polymer-covered fibers and colloidal particles, resulting in heteroflocculation. Its performance appears to be related to its ability to delaminate montmorillonite. A common way to promote montmorillonite delamination is treating it with sodium-rich solutions. A novel way of enhancing montmorillonite delamination is to break-up aggregates of fibers held together by montmorillonite stacks. The extent of montmorillonite delamination was evaluated by measuring the deposition of calcium carbonate pigments on fibers coated with cationic polyacrylamide suspended in water. The results show that the flocculation efficiency of montmorillonite strongly depends on its ability to delaminate. Montmorillonite is most effective when it is completely delaminated, in which case single plates form strong bridges between polymer-coated particles.
2-04
Controlling porosity within colloidal heteroaggregates
D. R. E. SNOSWELL, T. Rogers, B. Vincent, School of Chemistry, Bristol University, Bristol, United Kingdom, David.Snoswell@Bristol.ac.uk
Heteroaggregates of cationic poly(2-vinylpyridine) microgels,
anionic polystyrene latex and anionic silica particles have been made by mixing
dilute, aqueous suspensions. The
resulting heteroaggregate flocs were then concentrated by vacuum filtration,
freeze dried, and characterized by mercury porosimetry, SEM and TEM imaging
techniques. Control of the pore
volumes within the dried filter cakes is demonstrated by two techniques. In the first technique,
heteroaggregation at a constant KCl concentration was stopped or ‘arrested’ by
the subsequent addition of silica particles, thereby limiting the size of the
flocs. Pore volume was shown to
increase as the aggregation time prior to ‘arrest’ was increased. In the second technique, the aggregation
time prior to arrest was maintained constant while the KCl concentration was
varied. The pore volume of the
aggregates decreased as the electrolyte concentration increased. The method of arresting the
heteroaggregation potentially allows high volume fractions of flocs to be made
without the formation of a gel which is difficult to process, thereby providing
a method of manufacturing materials with controllable porosity. In addition, incorporation of swellable
microgels in a porous structure offers potential for creating novel structures
suitable for controlled release applications.
2-06
Aggregation Kinetics of Alginate-Coated Hematite
Colloids in Divalent Electrolytes
KAI LOON CHEN1, Steven E. Mylon2, Menachem
Elimelech1, 1Department of Chemical Engineering,
Environmental Engineering Program, Yale University, New Haven, CT, 2Department
of Chemistry, Lafayette College, Easton, PA, kailoon.chen@yale.edu
Aggregation kinetics of alginate-coated hematite colloids is measured in the presence of divalent electrolytes (CaCl2 and MgCl2) by dynamic light scattering. It is shown that alginate undergoes inter-polymer binding in presence of calcium ions, but not with magnesium ions. The aggregation kinetics of the alginate-coated hematite colloids in the presence of the divalent cations is compared with the kinetics in monovalent electrolyte (NaCl). We find that the alginate-coated hematite colloids undergo aggregation by electrostatic destabilization with sodium or magnesium ions, while the aggregate growth rate is much higher with calcium ions. In the case of aggregation with calcium ions, transmission electron microscopy (TEM) reveals hematite colloids enmeshed within clusters of alginate network. We propose that the enhanced aggregation with calcium ions is due to the formation of extended alginate cross-links around the alginate-coated colloids, which greatly increases their collision radii. It is also found that the presence of sodium as a background electrolyte is detrimental to this calcium-induced enhanced aggregation.
2-07
Light driven aggregation of core-shell
chromophoric colloids
MARTIN
PIECH, Nelson S. Bell, Sandia National Laboratories, Chemical Synthesis and
A photo-controlled aggregation in non-polar solvents has been achieved using spirobenzopyran methylmethacrylate (SP-MMA) polymer layers grafted from silica particles. The chromophoric molecules incorporated into these core-shell architectures can be switched from a non-polar closed form (spirobezopyran) to the open, zwitterionic form (merocyanine) through exposure to ultraviolet (UV) irradiation (l ~360 nm). Subsequent visible light irradiation (l ~540 nm) or heat treatment reverses this process. Here, this molecular isomerization reaction was employed to drive colloidal aggregation in border-line solvents. The process is reversible, with the requirement of agitation to redisperse the particles following agglomeration. System fatigue is minimal yielding reproducible results even after a large number of cycles. Dependence of sedimentation behavior on solvent polarity and chromophore content within the SP-MMA layers, system rheological response, and particle adsorption behavior onto optically patterned surfaces are discussed.
2-08
Crystalloluminescence in the
Synthesis of Nanosized Particles
Terry A. RING, Department of Chemical
Engineering, University of Utah, Salt Lake City, UT, T.Ring@m.cc.utah.edu
A new nucleation theory will be presented which allows the prediction of the particle size distribution of atomic clusters. This theory accounts for the collisions of atoms with clusters and clusters with other clusters according to the free energy driving force for their collision and the frequency of their collision by various mixing methods. The frequency of their collision can be predicted by either diffusion or shear induced or turbulence induced models. The free energy for these collisions is a function of the bonding geometry of the initial cluster(s) and resulting cluster. This free energy information is available in a limited number of alkali metal systems from quantum mechanics. The resulting partial differential integral equations are solved for limiting cases, which are used to predict the cluster size distribution. Another benefit of this theory of nucleation is an explanation of crystalloluminescence - light produced during nucleation, which can be used to control the nanosynthesis process so that a very narrow range of clusters is produced.
2-09
Fabrication
of novel types of colloidosomes and liposomes with gelled cores
Paul Noble1, Olivier Cayre1, Rossitza Alargova2, Orlin Velev2, VESSELIN N. PAUNOV1, 1Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull, United Kingdom, 2Department of Chemical Engineering, North Carolina State University, Raleigh, NC, V.N.Paunov@hull.ac.uk
Colloidosomes
and liposomes are core-shell structures that consist of an aqueous core and a
shell formed by fused colloidal particles or lipid bilayers. Recently, it has
been recognised that such microcapsules offer a great potential in controlling
the permeability of entrapped species in pharmaceutical, cosmetic and food
products.
Here we report a versatile fabrication method of novel colloidosomes microcapsules which is based on the following 3 stages: (i) Hot aqueous solution of gelling hydrocolloid is emulsified in a suitable oil in the presence of solid polymer particles dispersed in the aqueous phase to produce a water-in-oil emulsion stabilised by the solid particles and the system is cooled off to set the gel. (ii) The produced suspension of aqueous gel microcapsules coated with a particle monolayer is separated by filtration to remove the oil phase. (iii) The microcapsules are washed and collected into water. This methodology allows us to produce colloidosome microcapsules of diameters varying between several tens of micrometers to several hundreds of micrometers. The function of the gel cores was to support the particle shell around them and to give the microcapsules enough stiffness to be separated from the oil phase by filtration.
Following this technique we have been able produce three different types of colloidosome microcapsules. (a) By combining monodisperse amino-latex microparticles and an oil which swells the latex we have fabricated integral colloidosomes of porous membrane where the pore size is controlled by the degree of swelling. (b) By using monodisperse amino-latex particles and cross-linking agent we were successful in producing colloidosomes of spherical particle monolayers, where the membrane pores are defined by the particle size. (c) By using polymer micro-rod particles as emulsifiers we have synthesized for the first time “hairy” colloidosomes which shells consists of randomly assembled rod-like particles.
We also report the fabrication of novel hybrid giant liposomes with cores of an aqueous gel based on an extension of the Pautot technique. It involves the following three steps: (i) A lipid-stabilised water-in-oil emulsion is prepared in the presence of a gelling hydrocolloid in the aqueous phase. (ii) The water drops, coated with a lipid monolayer are gelled at lower temperature to produce gel beads. (iii) The gelled beads are transferred from the oil phase through the planar oil-water interface where they pick up a second lipid monolayer and convert into giant liposomes of gelled aqueous cores. We maintain a saturated lipid monolayer at the planar oil-water interface by injecting lipid solution in a spreading solvent. These novel microcapsules have higher stability and mechanical strength than conventional liposomes and may find applications as drug delivery vehicles and for controlled release of proteins, vacines, cosmetic and food supplements.
2-10
Aggregation, cluster formation and gelation in colloidal suspensions: From photonic liquids to equilibrium clusters and gels
PETER SCHURTENBERGER, Department of Physics,
With the equilibrium behavior of colloidal systems seemingly well-understood, attention recently turned to non-equilibrium phenomena. In particular the influence of attractive interactions of variable strength and range has been investigated intensively, and it has been demonstrated that the presence of a short ranged attraction can lead to fascinating phenomena that include metastable liquid-liquid phase separation and dynamically arrested states such as attractive and repulsive glasses as well as transient gels. These issues of interparticle interaction, aggregation, cluster and crystal formation and dynamical arrest are of central importance to a variety of topics ranging from cluster formation in various diseases to the production of photonic crystals.
In my lecture I shall outline the various aggregation phenomena that can be observed upon combining short or long range attraction with either a hard and/or soft repulsion. I shall in particular aim at demonstrating the generality of the emerging description on the phase behaviour of a wide range of colloidal suspensions.
2-11
Direct Imaging of Phase
Behavior and Structure of a Strongly Adsorbing Microsphere-Nanoparticle System
JAMES F. GILCHRIST1, Angel T. Chan2, Eric R. Weeks3, Jennifer A. Lewis2, 1Department of Chemical Engineering, Lehigh University, 111 Research Dr., Bethlehem, PA, 2Department of Materials Science and Engineering, University of Illinois, 105 South Goodwin, Urbana, IL, 3Department of Physics, Mail stop 1131/002/1AB, 400 Dowman Dr., Emory University, Atlanta GA, gilchrist@lehigh.edu
We have investigated the phase behavior and 3D structure of a model microsphere-nanoparticle system possessing high charge and size asymmetry in which polystyrene nanoparticles (D = 21 nm) strongly adsorb to silica microspheres (D = 1.18 mm). By varying the nanoparticle:microsphere ratio, we can tailor the transitions between stable fluid and attractive gel phases. Using confocal fluorescence scanning microscopy, we directly observe their 3D structure of as a function of varying composition. In the absence of nanoparticle additions, the electrostatically charged microspheres reside in a stable fluid phase that crystallizes upon sedimentation. As the nanoparticle concentration is initially increased, strong gelation occurs via nanoparticle bridging between colloidal microspheres. At higher nanoparticle concentrations, nanoparticle-coated microspheres are again stabilized by electrostatic interactions. We demonstrate how this fluid-gel-fluid transition can be utilized to control the morphology of both colloidal crystals and gels formed under gravity-driven sedimentation.
2-12
Direct visualization of the coupled aggregation and sedimentation of
weakly interacting colloid-polymer mixtures
MYUNG HAN LEE, Eric M. Furst, Department of Chemical Engineering,
University of Delaware, 150 Academy
St., Colburn Lab., Newark, DE, lee@che.udel.edu,
furst@che.udel.edu
Particle aggregation is of great interest not only due to its occurrence in biological systems, paints and coatings, and numerous foods, but also due to its fundamental role as a simple model system for growth under non-equilibrium conditions. In the past decade, most work has focused on the cluster geometry and growth kinetics in the absence of sedimentation. However, many real aggregation phenomena are influenced by sedimentation. The knowledge of colloidal aggregation in a gravitational field will help to create a thorough understanding of processes occurring in real aggregating systems. Through the use of confocal microscopy, we investigate the coupled aggregation and sedimentation of colloidal particles in polymer solutions as a function of the strength of attraction between particles. We discover that strong coupling between aggregation and sedimentation occurs which limits the growth of clusters depending on the magnitude of attractive forces, resulting in structures of various degrees of compaction. Lastly, we examine the aging of the sediments. Internal restructuring due to gravitational stresses drives the compaction and rearrangement of the gel with time. At high polymer concentration, the particle-particle bonds are not easily broken and the flocs cannot freely reorganize to form compact structures due to the high magnitude of the interaction at contact.
2-13
Aggregation Time Required
for the Bottom-Up Assembly of Colloids
ALLISON M. YAKE, Darrell Velegol, Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, amy151@psu.edu
Numerous studies have demonstrated the bottom-up assembly of complex structures such as colloidal crystals, close-packed aggregates, and even rings and tetramers. We show the production of a simple localized and nanoscale charge distribution on the surfaces of individual colloidal microspheres using our technique of “particle lithography”. In this technique, parts of the microspheres are masked off, while polyelectrolytes cover the remaining portions of the microspheres. The effectiveness of this process is demonstrated by the accurate and reproducible production of colloidal heterodoublets composed of oppositely-charged microspheres. The particle lithography technique is advantageous since it is not limited by the resolution of photolithography or by functionalizing chemistries. A key challenge for the processing of heterodoublets and more complex aggregates is knowing the time required for the assembly to occur. A model has been developed that relates the aggregation times of the colloidal microspheres to their size and concentration in the assembly suspension. This model investigates the Brownian rotation of the microspheres and gives predictions about the experimental times required for the particle lithography technique. Results are presented for the formation of heterodoublets and the aggregations times of microspheres with varying particle suspension conditions.
2-14
Film Formation and Gelation Process Studied by Multispeckle DWS
A. BRUN1, L. Brunel1,
P. Snabre2, 1Formulaction, 10 Impasse Borde Basse, 31240
L’Union, France, 2 Centre de Recherche Paul Pascal, Avenue Albert
Schweitzer, 33600 Pessac, France, brun@formulaction.com
We present
in this work a new optical technique to study film or gel formation from
colloidal systems. Our technology is based on diffusing wave spectroscopy
(DWS), an extension of classical dynamic light scattering (DLS) to concentrated
and opaque media. This new, non-invasive and very simple technique allows
monitoring of the “media movement speed” from all kind of dispersed systems
such as latexes, emulsions, or solvent-born suspensions. Using a laser source
and a video camera as receptor, we have developed an original multi-speckle DWS
technique using a simple and direct processing of the light backscattered from
the system. The kinetics of bulk aggregation is displayed in real time by
specific software.
Different film forming products have
been investigated (e.g., water-based, solvent and solvent-free paints, inks,
adhesives, varnishes, coatings) on various types of substrates (e.g., metal,
plastic, glass, PMMA) and at different thickness from few microns to hundreds
of microns. Preliminary experiments on gelation of yoghurt and gelatine have
also been performed. From the kinetics, a wide range of information can be
extracted such as objective gelation or drying times (e.g., dust-free,
touch-dry, dry-hard), mechanism taking place (e.g., solvent evaporation,
coalescence, cross-linking), thereby offering new possibilities to investigate
these complex colloidal systems.
2-15
Role
of Electrostatic Interactions in Bacterial Deposition
MENACHEM ELIMELECH, Sharon L. Walker, Alexis
J. de Kerchove, Department of Chemical Engineering, Environmental Engineering
Program, Yale University, New Haven, CT, menachem.elimelech@yale.edu
The influence of bacterial electrokinetic properties and surface
bound lipopolysaccharides (LPS) on cell deposition (adhesion) are examined
using three mutants of Escherichia coli
K12 with well-characterized LPS of different lengths and molecular
composition. Two experimental
techniques, a packed bed column and a radial stagnation point flow system, are
employed to investigate bacterial adhesion kinetics onto quartz surfaces over a
wide range of solution ionic strengths.
Although the two systems capture distinct deposition (adhesion)
mechanisms because of their different hydrodynamics, similar deposition
kinetics trends are observed for each bacterial strain. Bacterial deposition rates are directly
related to the electrostatic double layer interaction between the bacteria and
quartz surfaces, in qualitative agreement with classic DLVO theory. However, DLVO theory does not fully
explain the deposition behavior for the bacterial strain with the lengthy,
uncharged O-antigen portion of the LPS.
Neither the length nor the charge characteristics of the LPS molecule
directly correlated to deposition kinetics, suggesting a complex combination of
cell surface charge heterogeneity and LPS composition controls the bacterial
adhesive characteristics. It is
further suggested that bacterial deposition behavior is determined by the
combined influence of DLVO interactions, LPS-associated chemical interactions,
and the hydrodynamics of the deposition system.
2-16
Study of Correlation of Adsorption and Interaction of Ceria
Nanoparticles with Silica Surface
IGOR SOKOLOV1, Quy K. Ong1, Nina Chechik2, David James2, 1Physics Department, Clarkson University, Postdam, NY, 2Rohm and Haas Electronic Materials, Newark, DE, isokolov@clarkson.edu
Using light scattering technique, we developed a new method for detection of the adsorption of ~50 nm ceria particles on silica wafers. Adsorption of the particles was studied in aqueous solutions of different acidity, pH 4,5,6,7,8, and 9. It is of fundamental interest to compare these data with the forces between individual particles and silica surfaces. We use the atomic force microscopy (AFM) to measure such forces directly. We report a new method to modify the AFM probe to get a single nanoparticle on the probe apex. Using this method, we are able to study the interaction between individual ceria particles and silica surface, both long-range and contact (adhesion) forces in aqueous solutions of the same acidity as above. The obtained data and correlation between the measured adsorption and forces are discussed.
2-17
Marangoni effect reverses coffee-ring depositions
HUA HU1, Ronald G Larson2, 1Polymer Division National, Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 2Department of Chemical Engineering, University of Michigan, MI, huhuadce@engin.umich.edu
We report here that Marangoni effect reverses coffee-ring depositions. Most of particles deposit at the center of the droplet, rather than the edge, due to a Marangoni flow induced during droplet evaporation. We develop a full analytical solution to the temperature and velocity fields in the drying droplet to analyze the particle deposition process. The measurement of the fluid flow in the drying droplet confirms our theoretical analysis. Combining the analytical solution for the flow field with Brownian dynamics simulations, we are able to compare our experimental results for particle deposition with predictions. The good consistent between experiment and theory is obtained.
2-18
Controlled
Deposition and Modification of Conductive and Antireflective Nanoparticle
Coatings
Brian G. Prevo, Yeon Hwang, ORLIN D. VELEV,
Department of Chemical and
The convective assembly method for particle deposition was originally designed for assembling colloidal crystals from monodisperse particles for photonic applications. However, we will demonstrate that the method allows facile controlled fabrication of nanoparticle coatings with a range of other useful properties. Two types of nanocoatings that will be presented are conductive metallic films from gold nanoparticles, and antireflective (AR) films from silica microspheres. Uniform nanocoatings were deposited in minutes directly from aqueous suspensions by convective assembly at high volume fraction. Operational ‘phase’ diagrams were constructed, relating the crystal layer thickness and packing symmetry to the process parameters. The deposition process allows control over the coating thickness, number of layers, optical properties, and the electric conductance of the films (in the case of the gold nanocoatings). By varying the deposition speed of the AR silica coatings, the band of optimal transmission could be tuned across the breadth of the visible spectrum (from 450 to 650 nm). The AR coatings were further optimized by the use of particle mixtures, which reduced the reflectance loss on glass by up to 89%. The nanocoatings developed could be used in applications ranging from nanoelectronics to energy efficient windows and solar cells.
2-19
Faradaic Reactions as the
Source of Net Interparticle Motion Driven by ~100 Hz Alternating Electric
Fields
JEFFREY A. FAGAN, Dennis C. Prieve, Paul J. Sides, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, jfagan@andrew.cmu.edu
Over the past decade, observations of net interparticle motion above a planar electrode due to alternating electric fields have been explained by multiple different force mechanisms. While past results indicate that multiple mechanisms are dominant over different frequency ranges, at frequencies for which electrode reactions are important, new results suggest that these reactions are the root cause of both net lateral and vertical particle motion. This talk details the connection between the vertical forces induced by the application of an alternating field in the 30 Hz to 250 Hz frequency range, and new predictions of electrolyte dependent lateral motion that closely match published experiments.
2-20
Galvanic
Cell Mediated Colloidal Crystallization
PENG JIANG,
Dudley A. Saville Ilhan A. Aksay, Department of Chemical Engineering,
We report a novel method for assembling micropatterned colloidal
crystals using in-situ, spontaneous,
galvanic action whereby crystalline arrays can be created by a “galvanography”
technique. For example, by confining particles to shallow trenches,
two-dimensional (2D) ordered single crystals were formed. We observed a sort of
repulsion of silica particles from oppositely charged galvanic electrodes and
crystallization on those with the same polarity. These are counterintuitive
based on electrostatic considerations and appear to result from a bulk
electroosmotic fluid flow (EOF) associated with galvanic process. To our
knowledge, this is the first report of electrokinetics in the context of the
centuries-old galvanic cell concept. This technique has applications in the
construction of electrophoretic microchips for the separation of particles with
different surface charges. In addition to the activity of a bimetallic galvanic
cell, a single polycrystalline metal will also induce preferential colloidal
crystallization via galvanic processes.
2-21
In Situ Layer-by-Layer Film Formation Kinetics under an Applied Voltage
Measured by Optical Waveguide Lightmode Spectroscopy
A. PASCAL NGANKAM, Paul R. Van Tassel, Department of Chemical Engineering, Yale University, New Haven, CT, andre.ngankam@yale.edu
Layer-by-Layer (LbL) thin film assembly occurs via the alternate adsorption of positively and negatively charged macromolecular species. We investigate here the control of LbL film growth through the electric potential of the underlying substrate. We employ optical waveguide lightmode spectroscopy (OWLS) to obtain in situ kinetic measurements of poly(allylamine hydrochloride)/poly(sodium 4- styrenesulfonate) (PAH/PSS) and poly(L-lysine)/dextran sulfate (PLL/DXS) multilayer film formation in the presence of an applied voltage difference (DV) between the adsorbing substrate, an indium tin oxide (ITO) coated waveguiding sensor chip, and a parallel platinum counter electrode. We find initial layer adsorption to be significantly enhanced by an applied potential for both polyelectrolyte systems: the mass and thickness of (positively charged) PAH and PLL layers on ITO are about 60% and 500% larger, respectively, at DV = 2 V than at open circuit potential (OCP), in apparent violation of electrostatics. A kinetic analysis reveals the initial attachment rate constant to decrease with voltage, in agreement with electrostatics. To reconcile these results, we propose a more coiled and loosely bound adsorbed polymer conformation at higher applied potential. Following 10 adsorption steps, the mass and thickness of a PAH/PSS film grown under DV = 2 V are about 15% less than those of a comparable film grown under OCP, reflecting a lower degree of complexation between adsorbing polyanions and more highly coiled adsorbed polycations. Following 14 adsorption steps, the mass and thickness of a PLL/DXS film grown under DV = 2 V are about 70% greater than those of a comparable film grown under OCP, reflecting the increased charge overcompensation in the initial layer. We find the scaling of film mass (M) with the number of adsorption steps (n) to be linear in the PAH/PSS system and exponential in the PLL/DXS system, irrespective of applied voltage. The formation kinetics of PLL/DXS, but not PAH/PSS, change qualitatively under voltage: PLL adsorption is slow to reach a plateau, possibly due to the formation of secondary structure, and a decrease in film mass occurs toward the end of each DXS adsorption step, suggesting a spontaneous removal of some PLL/DXS complexes from the film.
2-22
Secondary Energy Minima
and Surface Charge Heterogeneities Cause Breakdown of Classical Filtration
Theory
NATHALIE TUFENKJI, Department of Chemical Engineering, McGill University, Montreal, QC, Canada, nathalie.tufenkji@mcgill.ca
The mechanisms
and causes of deviation from the classical colloid filtration theory (CFT) in
the presence of repulsive DLVO interactions were investigated. The deposition behavior of uniform
polystyrene latex colloids in columns packed with spherical soda-lime glass
beads was systematically examined over a broad range of physicochemical
conditions, whereby both the fluid-phase effluent particle concentration and
the profile of retained particles were measured. Experiments conducted with three different-sized
particles in a simple (1:1) electrolyte solution reveal the controlling
influence of secondary minimum deposition on the deviation from CFT. To verify the validity of CFT in the
absence of surface charge heterogeneities, two additional sets of experiments
were conducted using solutions of high pH or containing anionic surfactant
(sodium dodecyl sulfate). The
results indicate that both secondary minimum deposition and surface charge
heterogeneities contribute significantly to the deviation from CFT generally
observed in colloid deposition studies.
2-23
Particle Deposition onto Micro-patterned Charge Heterogeneous
Substrates
N. NAZEMIFARD1, S.
Bhattacharjee1, J.H. Masliyah 2, 1Department
of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada, 2Department
of Chemical & Materials Engineering, University of Alberta, Edmonton, AB,
Canada, neda.nazemifard@ualberta.ca, Subir.B@ualberta.ca
The
effect of collector surface charge heterogeneity on particle deposition
efficiency is theoretically investigated near a micro-patterned charged
substrate under radial impinging jet flow conditions. The surface charge
heterogeneity on the collector is modeled as concentric bands of positive and
negative charges having specified width and pitch, providing alternating
favorable and unfavorable deposition sites for the particles. The fluid
velocity distribution for radial impinging jet flow is obtained numerically.
Using this velocity distribution, particle trajectories, concentration
distributions, deposition fluxes, and collector efficiencies are obtained. The
periodic charge heterogeneity on the substrate engenders an oscillating
particle trajectory near the collector. Due to the coupled effects of
hydrodynamic and colloidal forces, a region at the leading edge of each
favorable band on the collector becomes inaccessible for particle deposition,
implying that the actual favorable area fraction of the collector is less than
its nominal value. Utilizing the actual favorable area fraction of the
collector, one can modify the patchwise charge heterogeneity model to calculate
the collector deposition efficiency in impinging jet flow geometry. The results
indicate that the particle trajectories and deposition efficiencies are
increasingly affected by surface charge heterogeneity as one moves radially
away from the stagnation point.
2-24
Capturing the Essence of Deposition Phenomena: Random Sequential
Adsorption and Related Models
JULIAN TALBOT, Department of Chemistry and Biochemistry,
Although it is often the first thing that comes
to mind in describing adsorption and deposition phenomena, the Langmuir model
usually provides a poor description of the deposition of macromolecules and
colloidal particles on solid surfaces. The deposition process in these cases is
often irreversible and, in order to obtain an accurate description, it is
necessary to account for surface exclusion effects and the transport mechanism
of the depositing particles to the interfacial region. It is the purpose of
this talk to review the rather remarkable progress that has been made during
the last fifteen years towards the goal of a quantitative description of
adsorption/deposition processes on solid surfaces.
The paradigm for the recent advances is,
unquestionably, the Random Sequential Adsorption (RSA) model. Originally
conceived to describe the packing of coal, this model accurately describes the
blocking effects of the pre-deposited particles in an irreversible deposition
process. The structure of the deposited particle configuration differs
fundamentally from an adsorbed equilibrium fluid, although the difference can
be negligible at low to medium densities. The basic model and its predictions
for a single component, mixtures, non-spherical particles and macromolecules
undergoing post-adsorption conformational changes will be reviewed. We also show
how it can describe adsorption on a heterogeneous surface (the Random Site
Model). In view of its rather simplistic representation of the transport
process, RSA describes a variety of experimental data with surprising accuracy.
The reasons for this fortuitous result will be discussed.
Larger particles may be strongly influenced by gravity as they deposit and in this case a different model is required. For situations in which gravity plays a dominant role and the particle trajectories are deterministic, the Ballistic Deposition (BD) model is appropriate. A new feature that emerges in this model is the presence of connected clusters of particles, even at low surface coverages. Processes that are intermediate between BD and RSA, which may be characterized by a single parameter, can also be described.
2-25
Embedding of phospholipid
vesicles into exponentially growing polyelectrolyte multilayers: A new way to
surface immobilized nanoreservoirs and nanoreactors
Marc Michel1,2, Guillaume
Fleith2, Jean-Claude Voegel1, Pierre Schaaf2, VINCENT
BALL1, 1Institut national de la Santé et de la Recherche
Médicale, Unité 595, Faculté de Médecine, 11 rue Humann, 67085 Strasbourg
Cédex, France, 2Centre national de la Recherche scientifique,
Institut Charles Sadron, 6 rue Boussingault, 67085 Strasbourg Cédex, France, vincent.ball@medecine.u-strasbg.fr
Polyelectrolyte multilayers (PEMs) appear more and more as versatile tools to functionalize solid liquid-interfaces. Indeed, proteins with their native conformation, DNA, and quantum dots have been embedded in such films. An other functionalization strategy consists in adsorbing covalently modified polyelectrolytes and also stimuli responsive and hydrolysable polyelectrolytes. In this communication we present a method to embed intact (polyelectrolyte stabilized) phospholipid vesicles into PEMs. Two ways of deposition will be described : either by the dipping method or by spray pulverisation. The build up of the architectures was characterized by means of quartz crystal microbalance with dissipation, atomic force microscopy and ellipsometry. The molecular integrity of the vesicles was studied by encapsulation of Fe(CN)64- into the vesicles before embedding and monitoring of the ferrocyanide release from the functionalized PEM by means of cyclic voltametry on the surface of gold electrodes. The spray pulverisation method offers the advantage of faster and easier deposition. We will also present the embedding of two stages of vesicles into the PEMs containing two kinds of encapsulated molecules.
2-26
Preparation of self-assembled
nanostructures using colloidal chemistry
FREDERIC JUILLERAT, Paul Bowen, Heinrich Hofmann, Powder Technology Laboratory, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne (Swiss Federal Institute of Technology), EPFL, CH-1015 Lausanne, Switzerland, frederic.juillerat@epfl.ch
Nanomaterials offer a wide ranging novel applications encompassing electronics, materials sciences, medical sciences and engineering. However, many of these applications require an organization of such materials into various ordered structures. Self-assembly processes that are driven mainly by competing molecular interactions like hydrophobic versus hydrophilic components, gravitational, van der Waals or coulombic interactions, amongst others, have been shown to have the potential of achieving complex structures, from 0D to 3D. For that aim, basic contributions to the self-assembly phenomenon, such as particles-particles and particles-substrate interactions, capillary forces, particle diffusion, must be understood and controlled.
In the present work, silica and gold particles smaller than 100nm
have been assembled in various ordered structures. Three-dimension colloidal crystals with
ordering lengths of tens of mm have been obtained by drying highly
concentrated silica suspensions on flat substrates or by using dip-coating.
Two-dimensional ordered monolayers of nanoparticles have also been produced by
evaporating the solvent of suspensions of adapted pH, ionic strength and
particle concentration. Dip-coating furthermore allowed the production of
micrometers-long chains of particles with diameters between 50 and 15nm using
topographically nanopatterned substrates, prepared by X-ray Interference
Lithography which guides the assembly process. Substrates patterned with holes
combined with dip-coating can lead to ordered arrays of single dots over tens of mm. The forces involved during both
self-assembly and guided-assembly
processes arise notably from dispersion, capillary and adhesion forces.
Theoretical analyses based on existing models have been performed for each
assembled system to establish the relative importance of these contributions as
a function of the most relevant experimental parameters.
2-27
Interpretation
of the stability of water-in-oil emulsions based on adsorption phenomena at
oil/water interface
L. GOUAL, G. Horvath-Szabo, J. H. Masliyah, University of Alberta, Department of Chemical and Materials Engineering, Edmonton, AB, Canada, lgoual@ualberta.ca
Adsorption of bituminous components from
heptane/toluene mixtures at oil/water and oil/gold interfaces was measured in
situ by a Quartz Crystal Microbalance. The adsorption kinetics follows two
distinct regimes depending on bitumen concentration. At low concentration
(<1.5wt%), an unsteady irreversible adsorption at oil/water interface
manifests in the form of a slow and continuous build-up of asphaltenes with
minor resins into multi-layers. At high concentration, a steady adsorption with
limited reversibility is measured where saturation is reached after formation
of a monolayer composed of asphaltenes with major resins. The concentration
regimes are determined by the resin-to-asphaltene ratio in the bulk phase. The
rigidity of oil-water interface at low bitumen concentration is related to the
rigid network formed by sterically non-stabilized asphaltenes. In this regime,
formation of asphaltene bridges between water drops destabilize the emulsions
against flocculation, thus dewatering of bitumen froth is easy. However at high
bitumen concentration, in the steady regime, water-in-oil emulsions are
kinetically stabilized against flocculation by sterically stabilized asphaltene
layers, and dewatering of bitumen froth becomes difficult.
2-28
Anisotropic Adsorption of Molecular
Assemblies on Inorganic Surfaces
J. CHUN1, J.-L. Li2,
R. Car2,
Oriented adsorption of rod-like molecular
assemblies on inorganic surfaces is analyzed in terms of anisotropic van der
Waals interactions between an assembly and the substrate.
The van der Waals interaction is
calculated using a Lifshitz methodology using the anisotropic properties of the
crystalline substrate derived from a first principles computation of the
dielectric response function for graphite. It is shown that, provided the
assembly is sufficiently large, a small amount of substrate anisotropy provides
torque that overcomes rotational Brownian motion near the surface. The
probability of a particular orientation is computed by solving a Smoluchowski
equation that describes the balance between torque and Brownian forces. The
results show that the torque aligns both cylindrical micelles and protein
fibrils. In the systems studied here, the interaction energy is a minimum when
the assembly lies perpendicular to a symmetry axis of a crystalline substrate.
These results agree with experiments with both cylindrical and hemi-cylindrical
micelles and proteins adsorbed on crystalline graphite.
2-29
Monoparticle films of gold
nanorods formed at a liquid-liquid interface
Y. Niidome, M. Yamaguchi, S. Yamada, Department of Applied Chemistry, Kyushu University, Fukuoka, Japan, ynidotcm@mbox.nc.kyushu-u.ac.jp
We have found that a monoparticle-film
of gold nanorod (NRs) could be formed at a liquid-liquid interface of hexane
and water. In this study, we
characterized the optical properties of the monoparticle-films of NRs that were
transferred onto glass substrates. In a
phase-separated solution, 20
mL of the NRs solution and 10 mL of hexane, acetonitrile (5 mL) was vigorously
injected. A monoparticle-film formed at the liquid-liquid interface was
transferred onto a glass plate that was vertically lifted up through the
interface.
Scanning electron microscopic images of the monoparticle-film of NRs
showed that there are few stacked particles in the film. It is known that a NRs solution shows
two clear absorption peaks in visible (~520 nm) and near-IR (~800 nm) regions;
however, the spectra of the deposited films show no clear absorption peaks. The
peak profiles of deposited films prepared from different concentrations of NR solutions
were almost independent of the
concentration of NRs. This indicates that the deposited NRs form
two-dimensional aggregates on the substrates. Degree of the aggregation was
changed by additional amphiphilic molecules, for example, phosphatidylcholine
in acetonitrile.
3A-01
Brownian
motion in the presence of temperature gradients: An extension of Einstein’s
theory on the 100th anniversary of its formulation
HOWARD BRENNER, Department of Chemical Engineering, MIT, Cambridge , MA
Einstein’s theory of Brownian motion,
which addresses only isothermal fluids, is here extended to situations in which
the fluid is subject to an externally-imposed temperature gradient. This
extension involves adding a temperature-gradient animated “drift velocity” U to
the usual diffusive Brownian contribution appearing in the Fokker-Planck
equation governing the particle’s conditional probability density. Remarkably,
this drift velocity, tending to cause the particle to move towards colder
regions of the fluid, is an innate molecular property solely of the solvent in
which the Brownian particle is dispersed. Explicitly, U is independent of the
Brownian particle’s size and shape, as well as of its physicochemical properties.
As such, the drift velocity is exactly the same for a macroscopic particle as
it is for a molecule of the solvent itself. The underlying theory is supported
by experimental thermophoresis data. The ansatz underlying our theory is
derived by elementary sedimentation-equilibrium-type arguments of the type
invoked by Einstein in his 1905 paper. Here, however, instead of an external
force-animated chemical potential gradient causing the Brownian particle’s
drift, the animation is now caused by the temperature gradient. Consequences of
our theory, involving fundamental modifications of the Navier-Stokes and energy
equations for nonisothermal fluids, are discussed. (200 words, exactly)
3A-02
Molecular dynamics simulations of nanodrop motion on uniform and non-uniform
surfaces
SP. S. SARAVANAN, J. B. McLaughlin, R. S. Subramanian, Department of
Chemical Engineering and Center for Advanced Materials Processing,
Results for the motion of nanodrops on solid surfaces will be presented. The results were obtained from molecular dynamics (MD) simulations of drops moving on crystalline solid surfaces. Two driving forces were considered: body forces and wettability gradients. The results indicate that hydrodynamic drag is negligible compared to contact line resistance for drops in the size range considered. A modification of the Blake-Haynes theory was used to model the results of the MD simulations. To obtain values for the Blake-Haynes contact line friction coefficient, MD simulations of drops spreading on uniform surfaces were performed for uniform surfaces having a broad range of wettabilities. In addition, results for the friction coefficient were obtained for receding contact lines. It was found that the friction coefficient for a receding contact line is significantly larger than the friction coefficient for an advancing contact line. The discrepancy between the friction coefficients for advancing and receding contact lines increases rapidly as the surface wettability increases. Since the Blake-Haynes theory makes no distinction between advancing and receding contact lines, a modification of the theory is needed. The modified theory agrees well with the MD results for drop motion on both uniform surfaces and surfaces with wettability gradients.
3A-03
Effects of extreme confinement and field
history on the self-assembly of magnetorheological fluid colloids
R. HAGHGOOIE, P. Doyle, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA , rhaghgoo@mit.edu
The characteristic length scales found in microfluidic devices have been shrinking drastically over the past several years. As a result it is becoming increasingly important to study the effects of this tight confinement. We have used the Brownian Dynamics simulation technique to study the self-assembly of magnetorheological (MR) colloids under confinement. We have examined the effects of extreme confinement (on the order of the size of the MR colloids) and observed that the confinement can induce some very interesting structural properties that deviate from those observed in systems with much less confinement. These deviations manifest themselves in the size of clusters that form as well as the average spacing between the clusters. Additionally we have determined the effects of field history upon the self-assembly of the MR colloids. We have shown that the manner in which the magnetic field is applied can have a significant impact upon the structure as well.
3A-04
Self-Organization
of Amphiphilic Copolymers in Aqueous Media
F. M. WINNIK, Department of Chemistry and
Faculty of Pharmacy, Université de Montreal, Pavillon J. A. Bombardier, CP 6128
Succursale Centre Ville, Montreal, QC, Canada, francoise.winnik@umontreal.ca
The assembly of polymers in water is controlled by various extrinsic factors, such as solution temperature, pH, ionic strength and the presence of additives, but it depends primarily on the chemical composition of the polymer and on the sequence of monomer units. Means to direct the assembly of amphiphilic polymers in water will be demonstrated using as examples various copolymers N-isopropylacrylamide (NIPAM). Of particular interest are telechelic PNIPAM samples of narrow polydispersity prepared by controlled free radical polymerization (RAFT). These polymers assemble in various modes depending on solution concentration and temperature. Their properties in water in the dilute regime were examined by microcalorimetry, light scattering, fluorescence spectroscopy and rheological measurements The properties of telechelic PNIPAMs will be compared to those of sample bearing a few hydrophobes in the middle of the chain, rather than at the chain ends, and to those of telechelic poly(ethylene oxides) of similar sizes.
3A-05
Structure of Microparticles
and Nanoparticles in Solid-Stabilized Emulsions
Sowmitri Tarimala,*
Chihyuan Wu,* Renu Sharma**, LENORE L. DAI*, Department of Chemical
Engineering,
Emulsions of oil and water
stabilized by adsorbed solid particles are known as solid-stabilized emulsions
(often referred to as
3A-06
Creating Polymeric Nanostructured
Networks Through Nucleation and Growth Strategy
JUN-YING XIONG1, Xiang-Yang Liu2, Da-Wei Li2,
Janaky Narayanan2, Shing Bor Chen1, Tai-Shung Chung1, 1Department of Chemical
and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge
Crescent, Singapore 119260, Singapore. 2Department of Physics,
National University of Singapore,
The new season of the material science is beginning. For material scientists, the task of reassembling basic elements now is shifting focus from as-synthesized nanoparticles (first generation) and their single-component assemblies to particles derived from the first-generation ones and supracrystals of different particles. However, nucleation and growth approach, which serves as one of the key strategies to achieve this goal, still remains more like an art than a science. It is the purpose of this study to make a step-forward progress in the quantitative understanding of complex nucleation and growth systems and to use the new knowledge obtained to shed some light on how to use nucleation and growth strategy to fabricate desired nanostructured materials. In this presentation, agarose gelation is used as the typical example. Agarose is a repetitive, essentially uncharged, marine polysaccharide. In the sol state gyration radius of agarose molecules can be as large as ~ 50 nm and behave like typical colloidal particles. In the presentation, kinetics as well as the evolution of the agarose gel topology is elucidated, and the agarose gelation mechanism is identified. It is found that the gelation process can be clearly divided into three stages: induction stage, gelation stage, and pseudo-equilibrium stage. The induction stage of the gelation mechanism is identified using an advanced rheological expansion system (ARES, Rheometric Scientific). It was found that gelation turns out to occur through a nucleation and growth mechanism with a well-defined induction time. The relationship between the induction time and the driving force (supersaturation) follows the 3D nucleation model. A schematic representation of the three stages of the gelation mechanism is given based on in situ turbidity and rheological measurements. Further analysis of the kinetics data using 3D nucleation theory indicates that supersaturation driven mismatching between agarose fibrils plays a crucial role in promoting branching, which is extremely important in the network formation. Molecular simulation is employed to support and visualize the proposed interpretation. Based on the knowledge obtained, some comments for building the second-generation nanostructured materials are given.
3A-07
Preparation and Small Angle Neutrons Scattering Characterization of
Polysiloxane – silica Nanocomposites
M. MEYER1, C. Parneix1
J. Persello1, B. Cabane 2, R. Schweins 3, 1 LCMI, Université de Franche-Comté, 16
route de Gray; 25030 Besançon, France. 2
PMMH, CNRS UMR 7636, ESPCI, 10 rue
Vauquelin, 75231
The incorporation of filler into elastomers imparts many interesting and useful properties to the particle filled composite material. It is well known that the properties mainly depends on the dispersion condition of filler particles and their principal relevant properties : particle size, surface area, filler surface chemistry and on rubber filler interactions.
In the present work, we used Small-Angle Neutron Scattering (SANS) experiments to study the phase transitions in the structure of a composite material made of surface modified silica nanoparticles dispersed in silicone rubber. Self assembling concepts are used in order to explain the role of the silica-rubber and silica-silica interactions on the positioning of silica nanoparticles in three dimensional structures. The phases of interest are the disordered "silica domain" and the long range correlated "fractal silica network".
We investigate again by SANS, whether the fractal network undergoes deformation, reorganization, or breaks at large strains, and correlate the scattering patterns to the mechanical properties of the filled rubber.
From a practical point of view, this presentation is concerned with investigations using model polysiloxane elastomers and silica nanoparticles systems to experimentally elucidate the role of the silica size and surface modification on the long range structure of the silica network.
3A-08
Continuous Polyelectrolyte Nanofilm Growth under an Applied Electric Potential
A. PASCAL NGANKAM, Paul R. Van Tassel, Dept. of Chemical
Engineering,
Polymer nanofilms offer facile control over the physical, chemical, and biological character of a material surface. Adsorption from solution is a simple means of fabrication, but control over film thickness is limited due to rapid saturation. Thicker, multilayer films are possible, but only through many alternate exposures to solutions of complementary species. We show here that a modest electric potential applied between an adsorbing substrate and a counter-electrode, in the presence of a polyelectrolyte solution, can lead to nanofilm growth that is continuous, without apparent saturation; films of arbitrary and controllable thickness may thereby be realized in a single step. We observe this behavior for poly-L-lysine onto indium tin oxide, at substrate potentials exceeding a threshold (Vth), where 0.5 V < Vth < 0.6 V (relative to a standard hydrogen electrode), using optical waveguide lightmode spectroscopy (OWLS). Film growth kinetics are initially very rapid and subsequently become linear with time. Linear growth may even be re-established following interruption by placement of a protein layer, suggesting possible applications in biosensing and bioelectronics. Films grown under an applied electric potential exhibit very modest desorption, but are somewhat unstable to removal of the potential. Chemically cross-linking films using the EDC/NHS method results in greatly improved stability. Atomic force microscopy images reveal films to be particulate, with the particle size slightly exceeding the polymer's hydrodynamic diameter. We find no evidence of electrochemical oxidation at the adsorbing surface, and suspect that secondary structure formation may play a role in the observed behavior.
3A-09
Structure and dynamics of
fluorinated fatty acid SAMs by solid-state NMR
ANDREW O’DONNELL and Linda Reven,
The bonding and chain dynamics of fatty acid monolayers on metal oxides have been previously characterized in detail by solid-state NMR techniques. This current study investigates the structure and molecular dynamics of monolayers of both perfluorinated and semi-fluorinated fatty acids, self-assembled on powdered ZrO2 surfaces. Self-assembled monolayers (SAMS) have been prepared of perfluorinated fatty acids on ZrO2 nanoparticles, with chain-lengths ranging from 8 to 18 carbons. The series of semi-fluorinated alkanoic acids F(CF2)m(CH2)nCOOH, with m = 5, 7, 9 and n = 10, 16, 22 have been synthesized and the monolayers on ZrO2 prepared. All SAMS have been studied by 19F-MAS NMR and 13C-CPMAS using variable temperature and relaxation techniques. PAS-IR spectra have also been collected for comparison with the NMR data.
3A-10
Dynamic NMR Investigation of Lipid-Hydrotrope Interaction in a Homogeneous System
NICOLE HELDT, Fadwa Odeh, Yuzhuo Li* Department of Chemistry and
Center for Advanced Materials Processing,
It has been reported in our previous study that a
homogeneous phase (L1) can be obtained by mixing an appropriate ratio of
hydrotrope and lipids. This microemulsion region can be used to prepare
unilamellar vesicles by dilution with an aqueous media. It has also been shown
that vesicle size is proportional to the lipid/hydrotrope ratio, where the
addition of hydrotrope to these systems affects the curvature of the vesicles
that form. The nature of lipid/hydrotrope interaction in the L1 phase is
important to understanding the vesicle formation mechanism, so as to facilitate
the control of the physical and chemical properties of synthesized vesicles
In this study, the L1 phases for lipid/hydrotope/water
systems were systematically investigated using dynamic NMR method. More specifically, NMR T1 relaxation
times are measured for the L1 systems made of various hydrotropes with
lipid/hydrotrope molar ratios.
Among the hydrotropes studied, the discussion will be focused on sodium
xylene sulfonate (SXS), sodium cumene sulfonate (SCS), and sodium toluene
sulfonate (STS). Due to their
structural difference, it is anticipated that the degree of interaction between
the hydrotrope and lipid varies.
Furthermore, it is hypothesized that subtle differences in
lipid-hydrotrope interactions stem from structural variations in the hydrotopes
and their ability to solubilize various lipids. This in turn influences
physical and chemical properties of the vesicles.
In this talk, some background information on the use
of the L1 phase to prepare vesicles will be presented first. The experimental results obtained using
dynamic NMR methods including spin-latice relaxation time measurement will be
discussed, especially the correlation between the hydrotrope structure and the
lipid-hydrotrope association within the L1 phase. The potential implication of
such variance in lipid-hydrotrope interaction on the vesicle formation
mechanism will be speculated.
3A-11
NanoLab: a Hands-On
Introduction to Nanoscience for Scientists and Engineers
M. B. Johnson, L. A. BumM, Center for Semiconductor
Physics in Nanostructures, Department of Physics and Astronomy, University of
Oklahoma, Norman, OK, bumm@nhn.ou.edu
We have developed a sophomore level laboratory course in nanotechnology. We have taken this hands-on approach to introduce students to the concepts used in nanotechnology much earlier than they would see them in them in the standard curriculum. Although sophomore level students do not generally have the background to understand the full theoretical explanation of all the phenomena, they do take with them a basic understanding that can serve as a framework for appreciating the broader issues when they encounter them in later courses. Topics we have covered are: crystal structure, x-ray diffraction, electron microscopy, electron microprobe, spectrophotometry, extinction, light scattering (Rayliegh & Mie), microfluidics, scanned probe microscopy, and thin-film growth. A report of our experience will be presented.
3A-12
Porous Photopolymer
Photonic Bandgap Structures: Fabrication and Applications
ALEXANDER N. CARTWRIGHT,
Significant research efforts have been focused on the development of effective means for detecting organic molecules optically using porous one-dimensional photonic bandgap structures. To date, most such work has been based on porous silicon microstructures, which are typically created using a controlled electrochemical etching process in a hydrofluoric acid solution. Generally, these sensors rely on changes in the optical resonance that occurs when the porous structure is occupied by the analyte species, allowing for simple and effective optical detection schemes. Here, we present a simple method for the production of polymeric Bragg reflection gratings containing periodic porous layers, and we demonstrate optical detection of organic solvent vapors using these structures. To create the structures, a pre-polymer syrup containing a monomer, a photoinitiator, a co-initiator, liquid crystals (LC), and non-reactive solvent (acetone or toluene) is sandwiched between two pieces of glass, and the periodic structure is then formed by applying an optical interference pattern generated using a simple one-beam setup. We demonstrate that a few different vapors can penetrate the porous structure and effects a change in the effective refractive index of these gratings, inducing a shift in the reflection wavelength. This shift is pronounced, and can easily be observed by eye, or detected by optical means. We also demonstrate that this shift depends on the vapor concentration, and can be used to reversibly and repeatedly detect the vapor’s presence. In addition, we show that the addition of aminosilane to the pre-polymer syrup improves the stability of the resulting gratings, suggesting that this photopolymer fabrication technique could be used to create structures suitable for biological applications in aqueous environments.
3A-13
Design and Study of
Structured Polymer Microspheres
G. Gao, M. Srivastava, N. Burke, R. Takekoh, A.P. Hitchcock, H.D.H. STOVER, Department of Chemistry, McMaster University, Hamilton, ON, Canad, stoverh@mcmaster.ca
Multi-layer microspheres may be formed by controlled thermal or chemical imprinting during the particle formation. Specifically, thermal oscillations imposed on precipitation polymerizations of divinylbenzene can be made to produce matching radial density profiles within the microspheres. In this way, onion-type microspheres having up to 20 nested layers may be produced. Similarly, chemical doping of the growing microspheres with suitable comonomers results in distinct layers enriched in functional comonomer. Phenylmaleimide and itaconic anhydride are examples of reactive comonomers that tend towards alternating incorporation and hence form well-defined shells. These comonomers can be used for subsequent shell-specific chemical functionalization of these spheres. The chemical composition of the resulting onion-type microspheres are quantitatively mapped using Scanning Transmission X-ray Microspectroscopy (STXM). Possible applications of these structured polymer microspheres with controlled porosity and functionality as building blocks for 3D photonic band gap devices, and catalyst supports will be discussed.
3A-14
Aggregation in
thermosensitive copolymers and related applications
X. X. ZHU, M. Nichifor, H.Y. Liu, D.
Avoce, Département de chimie, Université de Montréal, C. P. 6128, succursale
Centre-ville, Montréal, QC, Canada, Julian.Zhu@umontreal.ca
Some water-soluble natural and synthetic polymers can form hydrophobic aggregates and phase-separate when the temperature is raised. This change can occur at a sharp temperature, known as the lower critical solution temperature (LCST), or over a range of temperatures, depending on their chemical structures and composition. We have found that thermosensitive polymers incorporating natural amphiphilic compounds such as bile acids can even manifest a two-stage aggregation behavior. This can be very useful because of its rheological and technological implications and potential biomedical and industrial applications. We have made several series of copolymers with comonomers such as N-substituted acrylamides, bile acid derivatives and even styrene. We found that a small amount of styrene can lower significantly the LCST of the copolymers. A stable emulsion can be formed for such polymers, and they are useful as reversible flocculants and dispersants. The aggregation of the acrylamide copolymers can be facilitated by the presence of the bile acid residues, which can also form micelles with added surfactants. Thermosensitive copolymers are also used as solid support and scavengers in organic synthesis, making the separation process easier.
3A-15
One-pot Synthesis of Block
Copolymer Coated Cobalt Nanocrystals
GUOJUN LIU, Xiaohu Yan, Zhihua Lu, Scott A. Curda, Jyotsana Lal, Department of Chemistry, Queen’s University, 90 Bader Lane, Kingston, ON, Canada, gliu@chem.queensu.ca
Reported in this paper is the preparation of e-Co nanocrystals coated by a monolayer of poly(acrylic acid)-block-polystyrene or PAA-PS. This method, characterized by its convenience and potential to yield particles with narrow size distributions, is adopted from one using oleic acid as the surfactant. The replacement of oleic acid by PAA-PS as the surfactant during Co nanoparticle preparation yields Co/PAA-PS particles that can be solvent-cast to yield mechanically robust bulk films or 2-d ordered Co particle arrays. For the multi-dentate nature of the PAA binding block, the PAA-PS coating is resistant towards solvent rinsing. The thickness of the coating can be increased by increasing the length of the PS block. Such Co nanoparticles may have many potential applications.
3-16
Passivating Quantum Dots using Polymers
T. E. Dykstra, J. K. Oh,, X.-S. Wang, M. A. Winnik, G. D. SCHOLES, Department of Chemistry, University of Toronto, Toronto, ON, Canada, gscholes@chem.utoronto.ca
The molecules at the surface of a semiconductor nanocrystal must fulfil a dual role. In addition to passivating the surface, they must provide an interface compatible with processing and integration steps in manufacturing. For example, water-soluble surface ligands are needed for biological labeling; an electrically conductive layer would be ideal for solar cells; and a polymerizable surface is needed to make photoluminescent polymer composites. A current strategy for meeting these objectives is to replace the ligands introduced during quantum dot synthesis with new ligands, i.e., ligand exchange. We will describe a new approach: use of a multidentate polymer ligand, such as polydimethylaminoethylmethacrylate (PDMAEMA), to modify the surface of CdSe and CdSe/ZnS core-shell colloidal quantum dots. We have found that adsorption of PDMAEMA is accompanied by release of troctylphosphine oxide surface ligands, the process is free of agglomeration, and the modified nanocrystals become soluble in methanol. The photoluminescence properties are well preserved in either toluene or methanol. The polymeric ligands have the following advantages: (a) As-prepared QDs can lose colloidal stability via loss of small molecule ligands that provide only a single binding group (monodentate ligands) to the particle surface. Polymers with many binding groups (multidentate ligands) such as PDMAEMA are significantly more stable to dissociation. (b) The polymer replaces a surface-bound monodentate ligand in dilute solution with high efficacy. (c) The polymer can be functionalized so as to modify the colloidal properties of the QDs.
3A-17
New
approach to reflective type electrochromic display and the effect of particle
size on the color efficiency and switching time
JEE-HYUN RYU, Kyung-Do
Suh, Division of Chemical Engineering,
Reflective type electrochromic display (R-ECD) based on the
viologen-modified polymeric microspheres was proposed, and the influence of
particle size on the electro-optical characteristics was investigated. At
first, the functionalized polymeric microspheres were produced through the
seeded polymerization, and then viologen moieties were refluxed on the surface
in toluene. In order to control the diameter of viologen-modified polymeric
microspheres, the size of polystyrene seed particles was altered using the
solvency of medium during the dispersion polymerization. It was confirmed that
the color efficiency and switching time of R-ECD were depended largely on the
size of polymeric microspheres due to their specific surface area. The particle
size and morphology were monitored utilizing an optical microscope (
3A-18
Molecular stars with a three-fold or a six-fold rotation symmetry:
Self-assembly and Luminescence
SUNING WANG, Wen-Li Jia, Corey Seward, Qinde Liu, Department of Chemistry, Queen’s University, Kingston, ON, Canada
Two classes of molecule star molecules have been synthesized and investigated by our group. The first class has an approximate C3 symmetry with three substituent groups attached to either a benzene, a triazine, or a three-coordinate boron central core. The second class has an approximate C6 symmetry with six substituent groups attached to a central benzene core. The substituent group in both classes is functionalized by either 2,2’-dipyridylamino, 7-azaindolyl, or 2-(2’-pyridyl)benzimidazolyl, which allows further functionalization of the star molecules by metal ions. These two classes of molecules display diverse structures in solution and the solid state. Nanowires formed by self-assembly of some of the 6-fold star molecules have been observed on a graphite surface. The luminescent properties of these molecules are highly dependent on the nature of the functional group and the metal ions present. Some of these molecules have been found to be useful as luminescent sensors for a certain organic analytes. The details of syntheses, structures, luminescent properties of the star molecules and their applications will be presented.
3A-19
Routes of Molecular Energy
Transfer over Self-Assembled Surfactant Interfaces
T.D. Sechler, J.C. DEAK, Department of Chemistry, University of Scranton, Scranton, PA, deakj2@scranton.edu, Y. Pang, Z. Wang, and D.D. Dlott, Department of Chemistry, University of Illinois, Urbana, IL
The intermolecular contacts by which molecular energy is transported across a surfactant interface are observed via IR-Raman spectroscopy. In this technique, an IR light pulse is used to initiate a specific molecular vibration near the interface, e.g. the O-H stretch of a water molecule in a reverse micelle. Following this nascent excitation, time delayed anti-Stokes Raman spectroscopy is used to follow the transfer of the vibrational energy across the surfactant interface as it is passed from water to the surfactant polar group, to the tail region, and lastly to the nonpolar fluid. Data is presented on CCl4/AOT/H2O reverse micelles following independent excitation of water O-H stretch or surfactant C-H stretch. OH excitation reveals energy relaxation of multiple water structures near the interface. Subsequent OH relaxation is strongly coupled to sulfonate vibrational modes of the surfactant head group. The relaxation continues with the sequential movement of energy through the surfactant tail and then into the nonpolar phase. Following CH excitation energy is quickly redistributed among the surfactant head and tail vibrations before it is eventually transferred to the nonpolar phase.
3A-20
Microwave synthesis and applications of semiconductor, metallic and
magnetic nanoparticles
FARID BENSEBAAa, Andrea Firtha, Natasha
Patritoa, Chrisitna Bock, Yvon Le Page, Pascal L’Ecuyer, Dashan
Wang, Florin Zavalicheb, Teodor Veresb, aInstitute
of Chemical Process and environmental Technology, National Research Council of
Canada, 1200 Montreal Rd, M-12, Ottawa, ON K1A 0R6 Canada, bIndustrial
Materials Institute, National Research Council of Canada, 75 de Mortagne Blvd.,
Boucherville, Canada, farid.bensebaa@nrc-cnrc.gc.ca
For numerous reasons, there is a growing interest in using alternative and scalable approaches for the synthesis of nanoparticles. Among these approaches, microwave synthesis has received a growing interest lately. Microwave synthesis has been shown not only to enhance the rate of chemical reactions, but also to give better yields in some cases. Our group has recently applied this approach to prepare semiconductor, metallic and magnetic nanoparticles for specific applications [1-3]. Two specific cases will be discussed. First we will discuss the synthesis and characterisation of alloyed Pt-Ru nanoparticles. The integration of these nanoparticles in a polymeric matrix and their catalytical properties for DMFC (Direct Methanol Fuel Cell) applications will be also presented. In the second case, semiconductor nanoparticle preparation and characterisation will be shown. Their utilization for photovoltaic applications will be also discussed.
3A-21
Direct Laser Micro-Patterning of Self Assembled
Monolayers
M. Reza Shadnam, ALIDAD AMIRFAZLI, Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada, a.amirfazli@ualberta.ca
The ability to engineer surface properties (e.g. wettability, adhesion) at micoscopic scale is the key to the emerging technologically important areas such as biosensors, tissue engineering, MEMS, and controlled delivery of liquids in microfluidics. A “Direct Laser Patterning” (DLP) methodology has been developed to manipulate surface wetting properties using a chemisorbed self assembeled monolayer (SAM) on gold film (alkenethiol type). This talk will provide an overview of the DLP methodology. It will also report on kinetics of SAM desorption using curve fitting of experimentally measured SAM coverage data at different temperatures to Eyring equation. Activation energy of SAM desorption is calculated to be 30 kcal/mol in air. This information is used in a recently developed thermokinetics model, which describes laser induced desorption of SAMs through combining SAM desorption kinetics equation with heat propagation equations in DLP methodology. It was found that contrast plots of experimental scanning electron microscopy (SEM) images, which is correlated to surface coverage of SAMs desorbed after laser irradiation, agreed with the theoretically predicted surface composition of SAMs. The surface composition of SAM was then interpreted in terms of the wetting property of the resulting surface. The effect of incident laser beam power and size on final spatial coverage of SAMs on the surface and feature sizes was investigated both experimentally and by modeling. Considering the correlation of the theoretical and experimental results we concluded that the feature sizes are controllable in a predictable way (using the presented thermal-kinetics model) through varying laser beam power and beam size.
3A-22
Preparation of refined Gold nanorods :
synthesis, shape separation and optical properties
KYOUNGWEON
PARK1, Vivek Sharma1, Mostafa A. El-sayed2,3,
Mohan Srinivasarao1,2, 1School of Polymer, Textile and
Fiber Engineering, 2School of Chemistry and Biochemistry, 3Laser
Dynamics Lab, School of Chemistry and Biochemistry, Georgia Institute of
Technology, Atlanta, GA
Nanoparticle synthesis is characterized by
a polydispersity in the shape and size of particles. Since the shape and size
determine the properties and applications of nanoparticles, the synthesis of
uniformly shaped particles and the separation of desired shape and size from a
mixture of different shapes and sizes are necessary. We describe improved seed
mediated synthesis of gold nanorods producing a high yield of nanorods with low
polydispersity. By understanding
the hydrodynamics of nanorods and nanospheres undergoing centrifugation, the
efficient separation of gold nanorods from mixture of shapes was achieved. The
optical properties of resulting refined gold nanorods are compared to
predictions of existing theories, and the main parameters affecting them such
as particle size and shape or the dielectric properties of the environment are
discussed.
3A-23
Lattice Boltzmann
simulations of drop migration on surface with wettability gradient
XINLI JIA1, J. B. McLaughlin1, Goodarz Ahmadi2, 1Department of Chemical Engineering, 2Department of Mechanical and Aeronautical Engineering and Center for Advanced Materials Processing, Clarkson University, Potsdam NY, jiax@clarkson.edu
This talk will present results for drop migration on solid surfaces
with wettability gradient and chemical roughness. The simulation results were
obtained with the
3A-24
Surface
Properties of Contact Lenses
M. J. Stachowski, G. Friends, D. Seelye,
J.Kunzler, S. Rastogi, Research Development and Engineering, Bausch & Lomb
Inc.,
Hydrogel polymers can be used as biomaterials, and specifically in ocular applications where specific bulk properties are needed for transparency and oxygen permeability. There is difficulty in controlling these complex formulations as to what species move from the gel matrix toward the surface so as to inhibit or enhance surface interactions, such as encountered with a contact lens in a tear film. Specific surface properties are needed for such complex interactions within aqueous pool of mucin, lipids and proteins. These needs depend highly on the patient’s and their wear modality. Additionally in silicone hydrogel polymers, a surface must be rendered hydrophilic, without compromising the surface properties necessary for such deposition resistance. One method commonly used is plasma treatment, which can be used to form surfaces from the bulks’ surface moieties or from new surfaces formed from new monomeric moieties. This functions clinically to impart comfort, wettability, deposition resistance and/or a lubricous nature. Selection of the plasma gas / monomer and the process conditions are specific to the substrate being modified. Vastly different surface properties can be imparted which can change the surface morphology, deposition uptake and surface chemistry, as detected by atomic force microscopy (AFM), scanning electron microscopy (SEM), gas chromatography – mass spectroscopy (GC/MS) and X-ray photoelectron spectroscopy (XPS). Characterization of the surfaces’ elemental composition using XPS can show less pronounced differences, despite significant changes in morphology and deposition uptake, but such subtle differences play a significant role. Hence, surface properties can be controlled and / or enhanced through the surface plasma chemistry controlled by the gas and process conditions, specific to a substrate chemistry, in an attempt to impart these surface property modifications. A general overview background of the technology and examples will be given.
3A-25
Verification of the
Langmuir Isotherm for the Adsorption of Proteins to Polymer Surfaces
Jeong-Yeol Yoon, Marika Klappert, LONNIE J. LUCAS, Department of Agricultural and Biosystems Engineering, The University of Arizona, Tucson, AZ, jyyoon@email.arizona.edu
The Langmuir isotherm has been the best fit for the adsorption of proteins to polymer surfaces, which assumes 1:1 binding of an active site on both the protein and surface. This has long been debated since proteins are large enough to make multivalent attachments to surfaces, where n:1 binding seems likely. To explain this discrepancy, we estimated the contact area (Ac) for a single protein molecule anchored to the surface of a polymer by comparing the Gibbs free energy change of adsorption (–ΔGads, kJ/mol) with the work of adsorption (Wads, mJ/m2). –ΔGads was calculated as 20–28 kJ/mol, from the equilibrium constant (K) obtained from isotherm data of albumin/hemoglobin adsorption on plain/carboxylated/sulfonated polystyrene submicron particles. Wads was calculated as 20–70 mJ/m2, based on the surface tensions of water, proteins and polymer particles obtained from contact angle data of five solvents on their thin films. Both –ΔGads and Wads decreased as the surfaces became more hydrophilic. Dividing –ΔGads by Wads provided Ac = 0.6–1.4 nm2/molecule, which is much smaller than the cross-sectional areas of albumin/hemoglobin (28–40 nm2/molecule). This indicates that only a very small portion of the protein surface is in direct contact with the polymer surface.
3A-26
Fibronectin / Polyelectrolyte Multilayer
Assemblies: Film Formation and Cell Attachment Studies
CORINNE R. WITTMER, Paul R. Van Tassel, Dept. of
Chemical Engineering, Yale University, New Haven, CT, corinne.wittmer@yale.edu
Electrostatically driven layer-by-layer (LbL) self-assembly is a simple and robust method for realizing structurally tailored biomaterial coatings, of thickness ca. 10 nanometers, containing biofunctional ligands. We investigate the placement of fibronectin – a matrix protein useful in tissue engineering applications – onto multilayer films formed by the alternate deposition of poly-L-lysine (PLL) and dextran sulfate (DXS). We use optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation (QCM-D) to characterize film formation in situ. We find fibronectin adsorption to a film terminated with PLL to exhibit rapid kinetics and a large saturation, and to be essentially irreversible. In contrast, fibronectin adsorption to a film terminated with DXS is characterized by slower kinetics and a more modest saturation, and is partially reversible. We find no evidence of fibronectin penetrating the multilayer film. We use optical microscopy to determine the influence of fibronectin/polyelectrolyte multilayer assemblies on human umbilical endothelial cell (HUVEC) behavior. We observe the addition of fibronectin to DXS terminated assemblies to result in drastically increased HUVEC spreading and circularity. In contrast, the addition of fibronectin to PLL terminated assemblies leads to only subtle changes in the HUVEC response. We discuss this key difference in terms of the structure of the adsorbed fibronectin layer as well as the charge and hydration of the multilayer film.
3A-27
Surface Assembly of Protein in
Correlation to Protein Crystallization
Y. W. Jia, X. Y. LIU, Department of Physics, National University of Singapore, Singapore. phyliuxy@nus.edu.sg
The assembly of lysozyme (hen egg white) at the surface of aqueous solution follows the same behaviors as amphiphilic molecules. The critical assembly concentration appearing in the protein solutions is found to coincide with the equilibrium concentration of protein crystals under given conditions. The crystallization of protein regarded as a typical case of protein self-assembly in three dimensions has been discussed. The result reveals also the correlation between protein crystallization and the two-dimensional self-assembly at the surface of substrates. It follows that the protein crystallization conditions can be determined without protein crystals.
3A-28
Surface Treatment with Polymers for Biofouling Retardation
XIAONONG CHEN, Rovert Pelton, Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, chenxi@mcmaster.ca, peltonrh@mcmaster.ca
Polystyrene (PS), polyethylene (PE), polypropylene (PP), glass, and stainless steel were exposed to aqueous solutions of a series amphiphilic polymers at room temperature, including poly(N-isopropylacrylamide) (PNIPAM), polypropylene oxide (PPO)-polyethylene oxide(PEO) block copolymers and PEO. Dynamic contact angle measurements of the material surfaces before and after the treatment indicated that: (1) almost no adsorption of PEO on PS, PE, and PP surfaces; (2) PPO-PEO copolymers adsorbs only minimally on PE and PP surfaces; (3) PNIPAM adsorbs on both hydrophobic and hydrophilic surfaces. The surface morphologies of the materials before and after polymer adsorption were investigated by profilometry. Protein adsorption on PNIPAM pre-adsorbed surfaces was investigated by dual polarisation interferometry (DPI) and profilometry using lysozyme as the model protein. The results obtained indicate that PNIPAM can significantly improve the bio-deposition resistance of artificial surfaces, making PNIPAM treatment attractive for preventing biofouling of protein separation membranes and biomedical devices.
3A-29
Atomic Force Microscopy
Studies of Langmuir-Blodgett Films: Storage Protein from Aleurone Cells of Barley and Lipid Associations
M. T MOAIA-COTISEL*, G. Tomoaia**, T.
Yupsanis***, A.-I. Balea*, A. Mocanu*, *Babes-Bolyai,
University of Cluj-Napoca, Physical Chemistry and Biophysics Department, **Iuliu
Hatieganu, University of Medicine, Department of Orthopaedic Surgery, 3400
Cluj-Napoca, Romania, and ***Aristotle University of Thessaloniki,
Biochemistry Department, Greece, mcotisel@yahoo.com
The adsorption of
storage globulin protein from aleurone cells of barley (Hordeum vulgare L.) on lipid films (e.g. dipalmitoyl phosphatidyl
choline: DPPC or stearic acid: SA) at the air/water interface was studied by
Langmuir-Blodgett technique (LBT) and tapping mode atomic force microscopy
(AFM). The behavior of protein is complex generating large colloidal particles
which appear to strongly adsorb on the lipid monolayers. The obtained results
indicate a long range order within protein, protein:DPPC and protein:SA layers,
as well as electrostatic effects, and lipid surface and protein attraction. The protein layer shows a unique structural pattern in its adsorbed
state that might laid down during grain development and it can generate complex
supramolecular structures involving various classes of biological molecules,
e.g., lipids, natural pigments or combination of those. Due to the high
stability of protein layers, the storage protein might fulfill the key requirement as building blocks
for the production of novel supramolecular materials as required in molecular
nanobiotechnology and biomimetics.
3B-01
How Do
Hydrated Ions Act as the Lubricant between
Silica Surfaces in Solutions?; A Nanotribology Study in Aqueous Solutions by AFM
B. C. Donose, E. Taran,
Understanding of nanotribological phenomena has a critical
importance for the fast development of existing and emerging technologies, such
as chemical mechanical planarization and microelectromechanical systems. Using
Lateral Force Microscopy, we have
investigated the frictional interaction between a micron-size silica particle and a silica wafer in solutions under the conditions
characteristic for these technologies. It was found the friction force was related with two
types of mechanisms: one of them was
related to the microstructure of the layer of surface adsorbed cations, the kind of cations and water molecules, and the other one to the microscopic properties of the
silica surfaces contacting water.
At high electrolyte concentrations, the hydrated cations adsorbed on the surfaces were found to act as
efficient boundary lubricants. The smaller in size and more hydrated cations were, the more frictionless and lubricated
two surfaces were. With respect to the pH of solutions, no significant change in the frictional force was found between pH 3 and pH 8. But at pH > 9, the friction force is extremely small in
the region of low normal loading force, but it increases exponentially in the region of high loading force. It is suggested that the microscopic property of
the silica surface was changed at high pH. The detailed mechanism will be
discussed in the presentation.
3B-02
Interaction between polymer, surfactant and colloid studied by a novel force measurement technique
JOHN PHILIP, Department of Chemistry,
Using a new force measurement approach,1 we investigate the role of associative
polymers on colloidal forces and its implications on long term stability of the
emulsions. This experimental tool has been very effective to obtain insight
into the very early stages of polymer-surfactant interaction. It has been found that the interaction
between polymer, surfactant and colloid can lead to three distinct scenarios,
depending on the sequence of adsorption of polymer and surfactant onto the
colloidal interface. In the first two cases, where the colloidal interface
is adsorbed with or without
surfactant molecules, polymer-surfactant complexation occurs in the bulk phase
but without being adsorbed at the
interface. Under the above condition, the repulsive force between
colloidal droplets is not significantly altered by polymer-surfactant
complexes. In the third case, where
the polymer is pre-adsorbed at the colloidal interface, polymer-surfactant
interaction leads to dramatic changes in repulsive forces (10-13-10-11N)
and onset of repulsion (upto 100nm) due to conformational changes of polymers
at the interface, enhancing the stability of the colloid considerably.
3B-03
Investigation of the Role
of Geometry and Fluid Structure in the Description of Depletion Forces via
Scaled Particle Theory-based Integral Equations for Hard Sphere Fluids
D. W. SIDERIUS, D. S. Corti, School of Chemical Engineering, Purdue University, West Lafayette, IN, dsideriu@purdue.edu, dscorti@purdue.edu
The ability of colloidal particles to self-organize suggests that colloids could generate complex microstructures for use as templates for advanced materials. Precise control of colloidal dispersions, however, rests on our understanding of the forces between colloids and between colloids and surfaces. Depletion forces, which arise solely due to entropic considerations, are a class of forces which play an important role in colloidal aggregation. Depletion forces are typically modeled with excluded volume arguments, although these arguments usually fail to fully capture all entropic effects. To gain further insight into the origin of depletion forces, we examine the fluid structure of hard sphere colloids near surfaces via a newly derived integral equation based on the scaled particle theory of confined hard sphere fluids. Exact solution of the integral equation, along with simulation results, predicts the appearance of a local density enhancement near the colloid-surface interface. These results suggest that the excluded volume argument is not totally adequate for describing depletion forces and instead the geometry of and the fluid structure near the colloid-surface interface must be considered. Overall, the integral equation lends new insights into the nature of depletion forces and highlights the importance of fluid structure in the understanding depletion interactions.
3B-04
Aggregation Modeling using Sinc Methods
TERRY A. RING, Dept. Chemical Engineering, University of Utah, Salt Lake City, UT, T.Ring@m.cc.utah.edu
Aggregation and breakage processes are modeled the population balance equation, which accounts for the particles in the system. The population balance is an integro-partial differential equation that is coupled to the mass, heat and momentum balance equations that are simply partial differential equations. The population balance can be written in various forms, e.g. discrete or cumulative number as well as discrete or cumulative mass, with various bases, e.g. particle size or particle volume, as the internal coordinate. The population balance in all of these forms and bases is still an integro-partial differential equation. This paper solves the cumulative mass population balance in Steigles integral form using Sinc collocation, a finite element method, for several problems including deaggregation of fractal aggregates, aggregation of polystyrene latex particles and the combination of aggregation and breakage of NaCl crystals.
3B-05
The Role of Ultrasonic Analysis in Colloid Characterization
TÕNIS OJA, Gabriel DosRamos, Robert W. Reed, Matec Applied Sciences
Most colloid particle characterization has been typically carried out in severely diluted systems employing primarily light-scattering methods. In recent years, ultrasonic analysis has been steadily developed into a viable and attractive option. Ultrasonic analysis permits colloid characterization at native concentrations, without the need for sample dilution. This presentation provides a review, including recent developments, of the various applications of ultrasonic attenuation, sound speed, acoustic impedance and electroacoustic measurements to colloid characterization.
3B-06
Measurement of the Zeta
Potential of Planar Solid Surfaces by Means of a Rotating Disk
J. D. HOGGARD, P. J. Sides, D. C. Prieve, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, jhoggard@andrew.cmu.edu
A method of measuring the zeta potential of disks is described. Combing the hydrodynamic properties of a
rotating disk, the solution of
3B-07
Structuring of Nanoparticles and Micelles Confined between Surfaces
A. TULPAR, B. Fazelabdolabadi, P. Van Tassel, J. Y. Walz, Department of
Chemical Engineering, Yale University, New Haven, CT
The aim of this work is to
investigate the structuring of charged spherical particles between two surfaces
as a function of bulk particle concentration. The structuring behavior of the
particles can be deduced from the force profiles between two surfaces. In this
work, we measure the force between a silica particle and a silica plate in
aqueous solutions of particles by atomic force microscopy. We use two types of
spherical particles: nanoparticles and micelles. The nanoparticles are Ludox
silica, and the micelles are composed of sodium dodecylsulfate. In both of the systems, the force
profiles are oscillatory and the wavelength of these forces follows the spacing
between the particles in the bulk ((bulk number density)–1/3), not
the effective size of the particles. At high concentrations of nanoparticles
(above 10% by volume) in low ionic strength solutions, the wavelengths of the
forces are smaller than the bulk spacing. Addition of salt to these solutions
brings the wavelengths back to the bulk spacing. We also perform
3B-08
Charge Instability Induced
Breakups of Droplets Containing Ionic Solutes and Suspended Nanoparticles
KUO-YEN LI and Asit K. Ray,
Department of Chemical Engineering, University of Kentucky, Lexington, K, kli2@uky.edu
We have examined the charge stability limits of single evaporating microdroplets containing ionic solutes and nanoparticles. Droplets were suspended in an electrodynamic balance, and a high precision light scattering technique based on optical resonances was used to determine the size and the size change of a droplet at a charge instability induced breakup. The charge level and the charge loss at a breakup were obtained from the dc voltages required to gravitationally balance the droplet prior to and following the breakup. We have examined diethylene glycol (DEG) and triethylene glycol (TEG) droplets containing lithium chloride (LiCl) as well as suspended polystyrene nanoparticles at varying concentrations. While results on pure droplets of DEG and TEG show that breakups due to the charge instability occur at the Rayleigh limit, droplets containing LiCl solute explode at significantly higher charge levels than the Rayleigh limit. Similar results were observed in droplets containing nanoparticles, that is, a droplet can remain stable at a charge density level greater than three times the Rayleigh limit. The results indicate that the charge stability limit depends on the concentration of solute or nanoparticles as well as the size of nanoparticles in the droplet.
3B-09
The use of the QCM-D
technique as a versatile transducer technology for Biosensor applications
Patrik Bjöörn**, Fredrik Höök*, Ralf Richter***, *Department of Solid State Physics, LTH, Sweden, **Q-Sense Inc, 1200 Quail Street, Newport Beach, CA, *** Laboratoire d’Imagerie Moléculaire et Nano-Bio-Technologie, IECB, Université Bordeaux I, 16 Avenue Pey Berland, 33607 Pessac Cedex, France, patrik.bjoorn@q-sense.com
Recent years have seen various biosensor concepts taking the step from the lab into industrial applications. The advance of the quartz crystal microbalance with dissipation (QCM‑D) monitoring offers increased information content and flexible routes in the surface chemistry design. In addition, the QCM-D technique is based on an electro-mechanical principle, thus offering label-free and real-time measurements on surface reactions occulting on any solid surface (metal, metal oxide, polymer) in highly viscous and non-transparent liquids. As a consequence, the QCM-D technique offers unique information for designing novel surface chemistries for a large variety of applications, ranging from corrosion studies, via unspecific adsorption of polymers and biomolecules, to specific biorecognition studies. By measuring not only changes in frequency, related to adsorbed mass, simultaneous recording the crystal damping (energy dissipation), theoretical models can be used to deduce structural changes within thin adsorbed layers.
Recent progress nicely illustrates the use of the QCM-D technique as a biosensor platform compatible with diverse surface chemistry architectures, including lipid bilayers,[1] thiol and silane based functionalized self assembled monolayers,[2] functionalized PLL-PEGs,[3] PEI-CMC hydrogels[4] etc. In particular, these surface architectures have been used to immobilize specific detector molecules (i.e antibodies, [4] DNA, [1] coagulation factors, [5] lipid vesicles [1],). In this presentation, the wide-ranging possibilities offered by the QCM-D principle will be
reviewed, with particular focus on different means to immobilize probe molecules for specific bio recognition reactions.
3B-10
Quartz Crystal Microbalance Based on
Impedance Analysis – Modeling of Interfacial Layer Properties
TAPANI VIITALA1, Jorma Vuorinen1, Piotr Kujawa2, Francoise Winnik2, 1KSV Instruments Ltd, Höyläämötie 7, 00380 Helsinki, Finland, 2Université de Montréal, Faculté de Pharmacie, Pavillon Roger-Gaudry 2900, boul. Édouard-Montpetit, Montréal, QC, Canada, tviitala@ksvltd.fi.
The quartz crystal microbalance (QCM)
technique with its many variants is rather mature technique nowadays and it is
routinely used to provide information about a range of interfacial processes
either in gas or liquid environments. It is widely known that in case of rigid
films the QCM works very well as an accurate gravimetric instrument. However,
the situation changes dramatically when the QCM is used in certain liquid
environments or for studies of thick and soft interfacial layers such as
polymers. In such cases the overlayer is often not rigidly coupled to the
quartz crystal surface and the response of the QCM also depends on the
visco-elastic properties of the overlayer.
We present here how the QCM based on impedance analysis can be utilized to give information on the deviations from rigidity of surface-bound films, and how the measured data can be used for modeling the visco-elastic properties and thickness of the overlayers. We have chosen as model systems one Newtonian liquid, one thick polymer layer in air and a layer-by-layer build-up process of polyelectrolytes in liquid. The modeling used is based on a lumped element approximation of the Transmission Line Model.
3B-11
Multi-Layer Adsorption of
Sodium Alginate on Quartz Surfaces: A QCM-D Study of Adsorbed Layer Properties
ALEXIS J. DE KERCHOVE, Menachem Elimelech, Department of Chemical
Engineering, Environmental Engineering Program, Yale University, P.O. Box
208286, New Haven, CT, alexis.dekerchove@yale.edu
Understanding the adsorption of alginates onto solid surfaces is of paramount importance in a wide range of industrial and natural processes. A quartz crystal microbalance with dissipation (QCM-D) is used to study the multi-layer adsorption of alginate as a function of the polysaccharide concentration and ionic strength. Monitoring the rate of energy dissipation with the QCM-D provides insights into the viscoelastic properties of the adsorbed layer of the alginate polyelectrolyte along with the associated ions and water molecules. We show that for alginate concentrations of 0.1 and 1 g/L, the frequency, or adsorbed mass, increases with increasing ionic strength. The variation of the dissipation with the frequency suggests a linear relationship between the mass shift and the dissipation of the adsorbed layer. The normalization of the dissipation by the frequency change due to alginate adsorption demonstrates that the viscoelastic properties of the layer vary as a function of the ionic strength and alginate concentration. The results are discussed in terms of the variations in molecular configuration and compressibility of the adsorbed layer as a consequence of shielding of the polyelectrolyte charges with increasing ionic strength.
3B-12
Surface Interactions of
PGMA-DETA Polymeric Adsorbent in Copper Ion Removal
CHANGKUN LIU, Renbi Bai*, Department of
Chemical and Biomolecular Engineering, National University of Singapore, 10
Kent Ridge Crescent, 119260, Singapore, chebairb@nus.edu.sg
Adsorption has gained increasing importance in environmental engineering as a purification method to remove various pollutants, such as heavy metal ions. Surface interactions play a crucial role in the effectiveness of the process. In this study, novel polymeric adsorbent was developed from PGMA (poly-glycidyl methacrylate) and were surface-functionalized with diethylenetriamine (DETA). The resultant PGMA-DETA adsorbent was examined for the removal of copper ions from aqueous solutions. Infrared Microspectroscopy (IR-Microscope) was used to study the surface functional groups and chemical changes with copper ion adsorption. X-ray Photoelectron Spectroscopy (XPS) was utilized to reveal the various surface interactions in the adsorption. It was found that the adsorbent was very effective in copper ion adsorption in pH 4 and 5. In addition to the electrostatic interaction, the IR and XPS results show that surface complexation of the nitrogen and possibly the oxygen atoms with copper ions played an important role in the adsorption of copper ions from aqueous solutions.
3B-13
Effects of an Electric Field on Surface Tension of Conducting
Liquids
A. Bateni†, S. Laughton†, A. AMIRFAZLI‡, A.W. Neumann†, †Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON, Canada, ‡Department of Mechanical Engineering, University of Alberta, 4-9 Mechanical Engineering Building, Edmonton, AB, Canada
Understanding the influence of an electric field on interfacial properties of liquids is of importance from both fundamental and practical standpoints. Charged or electrified liquids currently play a key role in various applications, ranging from microfluidic devices to agricultural treatments. Nevertheless, the effects of the electric field on liquid surface properties are not well-understood, mainly due to the lack of reliable tools and methodologies to measure such effects. A novel methodology, called Axisymmetric Drop Shape Analysis for Electric Fields (ADSA-EF), is developed to measure the effect of the electric field on the surface tension of conducting drops. ADSA-EF matches numerically generated drop profiles with the shape of electrified drops observed in an experiment, taking the surface tension as an adjustable parameter. The best match between numerical and experimental profiles corresponds to the true value of surface tension in the electric field. ADSA-EF detected an increase of the order of one percent in the surface tension of conducting liquids, as well as a second-order correlation between liquid surface tension and the applied electric potential. Details of the methodology along with the experimental results will be presented at the conference.
3B-14
Enhancement of Adhesion to Heterogeneously Patterned Substrates
DANIEL A. RAMRUS and John C. Berg, Department of Chemical Engineering, University of Washington, Seattle, WA
Organofunctional silanes have long been used as promoters of adhesion between polymers and mineral oxide surfaces. The present work reports adhesion results obtained using binary combinations of adhesion-promoting and non-adhesion promoting silanes patterned onto an oxide adherend surface. The effects of pattern shape, texture (feature size) and the fractional coverage of the adhesion-promoter are explored for the bonding of poly(vinyl butyral) (PVB) to aluminum (oxide) surfaces using combinations of -aminopropyl triethoxysilane (APS), an adhesion promoter, and octadecyl trichlorosilane (ODTS), a non-adhesion promoter for this system. Climbing drum peel tests reveal that adhesion depends on feature size, shape and area ratio of the silanes, in many cases resulting in a reduction of adhesion compared with that for a pure APS film, but in other cases producing enhancements of as much as 80%. Among the conditions examined thus far, the greatest adhesion was achieved using square islands, 12 x 12 mm in size, surrounded by 1.5-mm wide borders of non-adhesive. Adhesion enhancement is attributed to arrest and confinement of crack propagation. As the crack propagates through a heterogeneous surface it will blunt at the end of an adhesive patch, and must re-nucleate at the start of the next adhesive domain.
3B-15
Two Hundred Years of Contact Angle
Research (1805-2005)
ALIDAD AMIRFAZLI, Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada, a.amirfazli@ualberta.ca
This paper provides an overview of contact angle research in the past 200 years starting with the pioneering work of Thomas Young at 1805. It discusses the current thinking in contact angle research and points to the future areas of interest from a technological as well as fundamental point of view. The presentation mainly will center around solid-liquid-fluid systems, but it will also touch on liquid-liquid-fluid systems. Various interpretations of contact angles in terms of solid surface energetics, line tension, and adhesion among other issues will be discussed. Topics of current interest such as superhydrophobicity (ultrahydrophobicity) and contact angle hysteresis will be discussed from theoretical as well as experimental perspectives. Finally, merits of various techniques used in measuring or determining contact angles from ordinary solid surfaces to micro- and nano-spheres will be discussed briefly.
3B-16
Determination of Surface Tension of Fluoropolymers from Contact
Angles and the Role of Liquid and Polymer Molecular Properties
H. TAVANA, A. W. Neumann, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON, Canada, tavana@mie.utoronto.ca, neumann@mie.utoronto.ca
Contact angle data for liquids with bulky, inert molecules on smooth, inert polymer surfaces fall on a smooth curve when plotted as a function of liquid surface tension. If one or more of these conditions is not met, deviations of typically ~1-3 degrees occur. The existence of such deviations introduces an element of uncertainty in the determination of accurate surface tension of solids. This problem is addressed through contact angle measurements with a large number of liquids of different molecular properties on four different fluoropolymers, i.e. Teflon AF 1600, poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate),oly(octadecene-alt-N-(n-(Rf)butyl)maleimide), and poly(ethene-alt-N-(n-(Rf)butyl)maleimide). It is shown that the deviations are not an artifact of experimental procedures such as film preparation techniques but have physical causes. Several mechanisms are identified as the possible cause for the deviations: vapor adsorption onto the polymer film, an alignment of liquid molecules in the vicinity of the solid surface, and reorientation of the polymer chains upon contact with the test liquids. It is shown that shape, size, chemical composition, and the molecular configuration of liquid molecules as well as of the polymer chains all play a role. In the light of the results obtained, requirements for the determination of accurate surface tension of fluoropolymer films especially with respect to the probe liquids will be presented.
3B-17
A
Methodology for Surface Tension Measurement from the Analysis of Liquid Bridges
Shapes
M. G. CABEZAS, J.M. Montanero, Dpto.
Electrónica e Ingeniería Electromecánica, Universidad of Extremadura, 06071
Surface
tension is widely measured using ADSA techniques. These techniques are
versatile and accurate in many situations. However, ADSA measurements present a
lack of accuracy for small values of the capillary constant, that is, when
working with two liquids of similar densities or when gravity is low. In these
situations, the drop shape is not sufficiently sensitive to variations of the
surface tension, and ADSA can not measure this quantity accurately. In this
work the sensitivity of drops and liquid bridges to surface tension has been
studied numerically. Results show that liquid bridges are more sensitive with
less volume, so they can provide more accurate surface tension measurements
when ADSA fails. The main goal of this contribution is to propose a methodology
that uses liquid bridges instead of drops to measure the surface tension value.
The principle of this methodology is the same as that of ADSA: the surface
tension is measured by comparing the theoretical prediction of the liquid
bridge shape to the experimental one. This new methodology has been validated
by comparing the results with those given by ADSA in situations when ADSA is
reliable.
3B-18
Do Polysaccharides Such as Dextran and Their
Monomers Really Increase the Surface Tension of Water?
M. HOORFAR, M. Kurz, Z. Policova, M. Hair, A. W. Neumann, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON, Canada, hoorfar@mie.utoronto.ca
It has been reported in the literature that polysaccharides and
their monomers increase the surface tension of water. The effect was
interpreted as a depletion of the solute molecules from the water-air
interface. This paper presents accurate measurements of surface tension of
different concentrations of dextrose solution as well as its polymer (i.e.
dextran). An automated drop shape technique called Axisymmetric Drop Shape
Analysis (ADSA) was used for the surface tension determination. The accuracy of
the results was evaluated using a shape parameter, 
, which has been used to quantify the range of the
applicability of ADSA. The results of the above study show that dextrose
solutions decrease the surface tension of water in contradiction to the results
in the literature. Surface tension decreases continuously with increasing
concentration. A similar effect was observed for the dextran solutions.
It is well known that electrolyte solutions, e.g. sodium chloride, increase the surface tension of water. To verify that the setup and the methodology are capable of measuring increases in surface tension, a similar experiment was conducted with a sodium chloride solution. The results obtained from ADSA show that the sodium chloride increases the surface tension of water. It is concluded that dextrose and dextran decrease the surface tension of water. Thus, there is no evidence of depletion.
3B-19
The Interfacial
Tension of Spherical and Aspherical Colloidal Dispersions
DUANE JOHNSON, Lichun Dong, Department of Chemical & Biological Engineering,
The University of Alabama,
The adsorption energy of spherical and aspherical particles onto a liquid-fluid interface and the effect of the line tension are investigated. The results show that without line tension, aspherical particles always prefer to lie flat in the plane of the interface. However, line tension plays a significant role in determining the adsorption of an aspherical particle. First, the line tension creates an energy barrier for the adsorption of particles onto an interface. The planar configuration has a larger energy barrier due to the longer contact line. Therefore, the particles prefer to enter the interface in a homeotropic configuration and then rearrange to a planar configuration or an oblique configuration with a small tilt angle. Second, for prolate particles, an energy maximum occurs at some tilt angles when the line tension is large. Therefore, once the prolate particle is adsorbed on the interface in a homeotropic configuration or with a larger tilt angle, it must conquer an energy barrier to rearrange to a planar configuration. For cylindrical particles, when the line tension is higher, the planar configuration will not be the most energy favorable configuration. The cylindrical particles prefer to stay in the interface with a small tilt angle.
3B-20
Measurement of Line
Tension in Liquid-Liquid Systems
Z. TAVASSOLI, A. Bateni, A. W. Neumann, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON ,Canada, satav@mie.utoronto.ca
A new methodology is presented for line tension measurement in liquid-liquid systems.
Line tension may be an important parameter for the interpretation of the contact angles of small drops and may play a key role in various technologies such as oil-water emulsion in rocks, stability of foams, micro-fluidic circuits, and microbial systems. Although line tension is a well-defined thermodynamic quantity, controversy regarding both the order of magnitude and the sign of this quantity persists.
The methodology is based on a novel procedure of contact angle determination for a lens of one liquid floating on the other liquid. Line tension is highly sensitive to the measured value of this contact angle. Hence a sophisticated technique (Polynomial Fitting for Line Tension) was developed for high accuracy measurement of contact angles. The proposed system is free from contact angle hyteresis and hence of more immediate thermodynamic relevance than similar work with solid/liquid systems.
The design is able to provide relatively stable and reproducible line tension measurements. Preliminary results using a lens of dodecane at an air-water interface suggests an order of magnitude of 10-6 J/m with a negative sign for the line tension. Details and implications will be discussed.
3B-21
Critical Evaluation of the Surface Complexation Model for Metal
Oxide Aqueous Interface based on Measurements of Surface Potential
NIKOLA KALLAY, Tajana Preocanin, Ana Cop, Laboratory of Physical Chemistry, Faculty of Science, University of Zagreb, Marulicev trg 19, 10000 Zagreb, Croatia. nkallay@chem.pmf.hr
Ionic equilibria at metal oxide aqueous interface is commonly interpreted on the basis of the Surface Complexation Model that takes into account mechanism of specific interfacial reactions, their equilibrium constants, and the structure of electrical interfacial layer. Several variations of the basic model were used for interpretation of experimental data. The common experimental techniques are acid base titrations of suspension providing surface charge density in the inner plane, counter ion adsorption measurements and electrokinetics. It was found that these experimental data may be successfully interpreted by several different variations of the model so that one needs to introduce a new experimental technique that might help in solving the problem. There were several attempts to measure surface potential at the inner plane by metal electrodes covered by layer of a metal oxide. However, due to the porosity of oxide layer the data were not reliable. Recently, we have constructed an electrode made of monocrystaline hematite enabling the reliable measurements. These data, together with other data obtained by classical methods, enables evaluation of all parameters characterizing the interface and critical test of the assumptions involved in the application of the Surface Complexation Model.
3B-22
Investigating the Aqueous
Surface Chemistry of TiO2 Pigments using ATR-IR Spectroscopy
SCOTT DICKIE, Jim McQuillan, Department of Chemistry,
TiO2 is the most widely used white pigment in the paint and ceramic industries due to its opacity and light scattering, which impart high levels of whiteness and brightness. However the end performance of paint films in categories such as opacity, gloss and colour distribution is directly related to the stability achieved in the pigment dispersion. The stability of the pigment dispersion can be improved by the addition of surfactants, which to date have been chosen based largely on information obtained from empirical methods and without any fundamental knowledge of the surface chemistry involved.
Typical TiO2 pigments are made up of a particle of rutile between 200 and 300 nm in diameter which is then coated with silica followed by alumina. Pseudoboehmite has been used as a model for the surface of TiO2 pigments and its aqueous surface chemistry has been investigated using attenuated total reflection infrared (ATR-IR) spectroscopy. The identification of a ligand system that will provide more permanent attachment of a surfactant to the pigment surface has been targeted. The talk will outline the aqueous surface chemistry of pseudoboehmite and TiO2 pigments.
3B-23
Effects of Charge and Size on Condensation of Supersaturated Water/n-Butanol
Vapor on Nanoparticles of SiO2, TiO2, d-Mannose, and Rhamonose
CHIN-CHENG CHEN, Yu-An Shen, Hsiu-Chin Cheng, Chia-Te Lin, Department
of Chemical Engineering,
The effects of size and charge on the condensation of a supersaturated water/n-butanol vapor on monodisperse nanoparticles of SiO2, TiO2, D-Mannose and Rhamonose were investigated in a flow cloud chamber (FCC). The dependence of the critical supersaturation, Scr, on particle size of a diameter 5 to 30 nm as well as on charge and charge polarity are determined experimentally. A novel electrospray aerosol generator was developed to generate a high concentration of nanoparticles of less than 10 nm by electrospraying precursors or solution followed by the thermally decomposition or drying. For neutral particles, the experimental Scr decreases with increasing particle size at a rate in a reasonable agreement with the predictions of the Fletcher’s version of Volmer’s theory of heterogeneous nucleation. For charged particles, the nucleation occurs at a Scr lower than that on neutral particles and the charge effect fades away as particle size increases. In addition, a sign preference is detected, e.g., water vapor condenses more readily on negative charge particle, a trend consistent with those observed on ions. However, both effects of charge and charge polarity on Scr are stronger than that predicted by Volmer’s theory for ion-induced nucleation.
3B-24
Preparation temperature dependence of size
and polydispersity of thiol-coated gold nanoparticles determined by SAXS
KURT ERLACHER1, Jørgen M. Jørgensen2,
Jan S. Pedersen2, Kurt V. Gothelf2, 1Bruker-AXS Inc., 5465
East Cheryl Parkway, Madison, WI, 2University of Aarhus, Department
of Chemistry, Langelandsgade 140, DK-8000 Aarhus C, Denmark, kurt.erlacher@bruker-axs.com
For the present study monolayer protected gold colloids were
synthesized by the Schiffrin procedure, with fixed amounts of the reactants but
at various temperatures.
The main purpose was to investigate the relation between the preparation
temperature and the size of the colloids and their corresponding size distribution.
To eliminate possible influences on the mixing procedure of the reductant
different series of synthesis were prepared. The water solvated reductant was
either added slowly over 30 seconds or added at once to obtain fast reaction.
It was expected that the colloids become bigger at elevated preparation
temperatures. In order to extend the temperature range in which the colloids
can be synthesized, three different methods of synthesizing the colloids in the
absence of water were carried out. The first of these methods was to directly
add the reductant in its pure form to the reaction mixture, at the second
attempt another solvent for the reductant was found and the third one was to
try to transfer the reductant to the organic phase with a phase transfer
catalyst. The presence and the sizes of the colloids can be ideally analyzed
using the method of small-angle x-ray scattering (SAXS). A laboratory SAXS
system (NanoSTAR SSS) consisting of Goebel Mirrors, three pinhole collimation
and a 2 Dimensional single photon detector (Bruker AXS Inc.) was used for these
experiments. A clear trend towards bigger colloid sizes at elevated
temperatures was obtained.
3B-25
Size control of nanoparticles
during precipitation the BNG way
I.H. LEUBNER, Crystallization Consulting,
Size control of nanoparticles I achieved by controlling nucleation during precipitation and crystal growth after nucleation. The number of crystals formed and the amount of crystalline mass formed determine the crystal size. The balanced nucleation and growth (BNG) model quantitatively correlates crystal nucleation to addition rate, time of reactant addition, solubility, temperature, and presence of growth restrainers. Experimental results of precision crystallizations will be presented for size control of nano-particles.
3B-26
Synthesis of Platinum
Multipods: Control of Anisotropic Growth
XIAOWEI TENG, Hong Yang+*, +Department of Chemical
Engineering and Laboratory for *Laser Energetics,
Synthesis of nanostructure with
well-controlled morphology has been drawn a great attention recently for its
application for tailoring the electronic, optical, magnetic and catalytic
properties of advanced materials.
Here we report a highly effective synthesis of platinum multipods from
platinum 2,4- pentanedionate in organic solvents by Polyol process. A trace
amount of silver acetylacetonate is used to trigger the nucleation and the
anisotropic growth of Pt nanocrystals.
Pt nanoparticles in forms of I- and V-shaped bipods, various types of
tripods, and planar and three-dimensional (3D) tetrapods have been successfully
synthesized by controlling the reaction temperature, precursor concentration
and by using Ag(acac). Transition
from multipods to spheres of Pt particles is observed and discussed. High resolution transmission electron
microscopy (HRTEM), X-ray diffraction (XRD), nanoelectron diffraction and
energy dispersed X-ray (EDX) are used to characterize the structures of Pt
multipod nanocrystals. A model of formation based on the induced kinetically
controlled growth will be discussed.
3B-27
Transport in polymer gels with charged spherical inclusions
REGHAN J. HILL, Department of Chemical Engineering, McGill University, Montreal, QC Canada, reghan.hill@mcgill.ca
Transport of ions in fluid-saturated polymer gels (e.g., polyacrylamide) with immobile charged inclusions (e.g., silica or latex micro-spheres) is examined under conditions where perturbations to a uniform equilibrium state are driven by (weak) macroscopic gradients of electrostatic potential, pressure or electrolyte concentration.
Electro-migrative, diffusive and convective contributions to the ion fluxes are provided for a wide range of electrolyte concentrations, (inclusion) zeta potentials and (polymer) hydrodynamic permeabilities. The theory, which is not limited by the diffuse double-layer thickness or zeta potential, provides a first step toward a quantitative interpretation of experiments. With the application of an electric field, for example, the particle contribution to the bulk electrical conductivity is obtained. Also of interest, for its influence on micro-mixing and enhanced transport, is the strength of the electric-field-induced flow.
3B-28
Study of Surface Tension of Lung
Surfactant: Influence of Humidity on the Properties of the Surface Film
R. GITIAFROZ1,2, E. Acosta2, Z. Policova1, H. Tavana1, A. W. Neumann1, 1Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON, Canada, 2Department of Chemical Engineering and Applied Chemistry, 200 College St., Toronto, ON, Canada, roya@mie.utoronto.ca
The surface tension of a lung surfactant, i.e. BLES (Bovine Lipid Extract Surfactant), is investigated using a constrained sessile drop methodology. Preliminary work revealed some irregularities, e.g. certain instabilities of the surface film upon compression. It is shown that moisture plays an important role. At low concentrations of BLES solution (0.5 mg/ml) and in the presence of humidity, the surface films are unstable regardless of the extent of compression, i.e. 5%, 10%, 20%, or 30%. This means that when the film is kept compressed at a surface tension lower than the equilibrium value of ~24 (mJ/m2), it cannot sustain the pressure and the surface tension increases towards equilibrium. However, the film is more stable in a dry atmosphere. Apparently, in dry conditions, dehydration of the surface film increases the liquid-crystalline phase transition temperature of phospholipids that are present in the interface. On the other hand in a humid environment, the film is fully hydrated. Hydration of the film decreases the transition temperature of phospholipids and makes them more fluid. Details and implications will be discussed.
3B-29
Binary Colloidal Alloys at Liquid Interfaces – from Super Lattices
to Stoichiometric Clusters
T. S. Horozov, R. Aveyard, B. P. Binks, J. H. Clint, Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull,United Kingdom, t.s.horozov@hull.ac.uk
The behaviour of monodisperse silica particles at oil/water interfaces has been studied by microscope observations. Particles of different sizes and/or hydrophobicity and their mixtures have been spread at the liquid interface to give one- or two-component particle monolayers. Strong long range repulsion through the oil between very hydrophobic particles in one-component monolayers has been observed. The particles in these monolayers have been well ordered in triangular lattices at very large interparticle distances (up to ~20 particle diameters). In contrast, a weak repulsion between hydrophilic particles has been found. The repulsion is mediated mainly through the water and one-component hydrophilic particle monolayers were disordered and aggregated.
Binary mixtures of large (L) and small (S) very hydrophobic particles have formed two-dimensional super lattices of LS2 or LS5/LS6 type depending on the composition. An interesting selective attraction between very hydrophobic and hydrophilic particles with the same or different sizes has been observed in their mixed monolayers. This resulted in formation of mixed clusters containing one hydrophobic and several hydrophilic particles whose stoichiometry depends on the composition of the mixture. The possible reasons for the selective attraction between very hydrophobic and hydrophilic particles observed at the oil/water interface are discussed.
3B-30
Characterization of Dry Adhesion
Between Carboxymethyl Cellulose and Glassine Paper
ZHINAN FENG, Robert Pelton, Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, Canada. fengz@mcmaster.ca
A T-peel technique was developed in this study for characterizing dry adhesion between polymer and paper. Several carboxymethyl celluloses (CMC) samples and glassine paper were examined. It was found that this delamination technique was simple, fast, reliable, repeatable, and cost-effective. The modes of interfacial failure and paper failure were observed depending on CMC characteristics and dosage. T-peel force was not affected by the change in peel rate within the range studied. However, the glassine paper showed significant two-sidedness in adhesion to CMC. The results clearly indicated that the adhesion increased with molecular weight of CMC but decreased with degree of substitution of CMC.
3B-31
A molecular dynamics study of the role of conventional and silicon
surfactants in the wetting of hydrophobic substrates by aqueous solutions
JONATHAN D. HALVERSON1,
J. Koplik2, A. Couzis1, C. M. Maldarelli1, 1Department
of Chemical Engineering, 2Department of Physics, The Benjamin Levich
Institute for Physico-chemical Hydrodynamics, City College of the City
University of New York, New York, NY
Many industrial processes rely on
conventional surfactants to increase the wetting of hydrophobic substrates by
aqueous solutions. For instance, organic surfactants are added to herbicide
solutions in order to achieve a larger wetted area when the solution is applied
to the leaf of a plant, which due to the Epicuticular wax is a difficult-to-wet
surface. For over three decades it has been known that trisiloxane alkoxylate
surfactants or superspreaders are far more effective than conventional
surfactants. However, superspreaders are photosensitive, toxic, and relatively
expensive. Classical molecular dynamics simulations are being conducted to
determine the mechanism by which organic and silicon surfactants increase the
spreading of aqueous droplets on hydrophobic surfaces. Sessile water drops
containing either low-molecular-weight alcohols or polyoxyethylene surfactant
molecules have been simulated at 298 K on an atomistic graphite lattice. During
the course of the simulation surfactant molecules tend to the three-phase
contact line where the headgroups are found to interact strongly with water and
the tailgroups are directed radially outward and displaced from the droplet. An
implementation of the fast multipole algorithm is used for the rapid evaluation
of long-range electrostatic forces. Complementary sessile drop wetting
experiments are being conducted by our research group.
3B-32
Bovine Serum Albumin (BSA) as an adhesive for wet cellulose
SHUNXING SU, Robert Pelton, Department of Chemical Engineering, McMaster University, Hamilton, ON, Canada, peltonrh@mcmaster.ca
Bovine Serum Albumin (BSA) was investigated as an adhesive for wet cellulose by 90º peeling of regenerated cellulose membranes laminated with BSA as the adhesive. Drying and curing at elevated temperature (120ºC) was required for strong adhesion. Ionic strength of the re-wetting water almost had no effect on wet adhesion. Oxidization of the cellulose membranes to introduce more carboxyl groups onto their surfaces increased the wet peel strength by 60%. Implying the peel failures happened at the protein/cellulose interface. The re-wetting pH of the laminated specimens prepared with oxidized membranes determined the ultimate peel strength while the initial pH of the BSA solution had little effect. The pH dependent wet strength might be good for the pulp recycling.
3B-33
Motion of liquid drops on a horizontal surface with a wettability gradient
NADJOUA MOUMEN, R. Shankar Subramanian, John B. McLaughlin, Center for Advanced Materials Processing and Department of
Chemical Engineering, Clarkson University, Potsdam, NY, moumenn@clarkson.edu
Results from experiments performed on the motion of drops of tetraethylene glycol in a wettability gradient present on a silicon surface are reported and compared with predictions from a theoretical model. The gradient in wettability was formed by exposing strips cut from a silicon wafer to the vapors from an alkylchlorosilane. Video images of the drops captured during the experiments were subsequently analyzed for drop size and velocity as functions of time and position along the gradient. In separate experiments on the same strips, the static contact angle formed by small drops was measured and used to obtain the local wettability gradient to which a drop is subjected. The Reynolds, capillary, and Bond numbers in the experiments were relatively small. Even though the velocity of a given drop varied with position on the gradient surface, it is shown that a quasi-steady theoretical model that accounts approximately for the hydrodynamic resistance and the local driving force adequately describes the observed behavior of the velocity of the drops. Also, it is shown that the instantaneous velocity at a given location in the gradient scales linearly with the planform radius of the drop, as predicted by theory.
3B-34
Adhesion between
Precipitated Calcium Carbonate and Cellulose Fibre
Y. XU, R. Pelton, McMaster center for Pulp and Paper Research, Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, xuy2@mcmaster.ca
The adhesion between Precipitated Calcium Carbonate (PCC) particles and Softwood Bleached Kraft (SBK) Pulp fibres was investigated with a 90 degree peel test of two-ply laminated handsheets. A sparse layer of PCC particles was laid at ply/ply interface and the delamination force was found exponentially reduced with the PCC content as a result of stronger fibre-fibre bonds readily replaced by weak PCC-fibre bonds. The strength of 1.7mm scalenohedral PCC-fibre laminates was approximately 1.4N/m compared to 20N/m for filler-free laminates.
Surface coated with carboxylmethyl cellulose (CMC) of PCC particles can significantly improve PCC-fibre laminates strength (2.7N/m). However, polyvinylamine (PVAm) can only promote fibre-fibre laminates strength (38N/m) but has no notable effect on PCC-fibre laminates strength. Phosphate containing copolymers with polyacrylamide (PAMVP) and polyvinyl alcohol (PVAP) can also strengthen PCC-fibre bonds with the fact that PVAP is more effective than PAMVP.
4-01
Expanding the Utility and
Understanding of Room Temperature Ionic Liquids: Including Micelle Formation
and Interactions with Gold Nano-particles
DANIEL W. ARMSTRONG, Department of Chemistry, Iowa State University, Ames, IA, sec4dwa@iastate.edu
Room temperature ionic liquids (RTILs) cannot be adequately characterized on the basis of polarity or any single parameter scale. RTILs are complex entities compared to the relatively simple molecular solvents used in most chemical processes.[1] They are capable of a wider range of intermolecular interactions than most other solvents. This includes: dispersive, n-p, p-p, dipolar, hydrogen bonding, hydrophobic, and ionic interactions. A multi-parameter scale, that takes into account the many different possible solvent properties, can be used to properly characterize RTILs as well as other solvents.[1] Their unique properties appear to induce the formation of solvophobic normal micelles when surfactants are dissolved in RTILs.[2] Also, gold nano-particles are more easily formed and dispersed in RTILs than in normal solvents.[3] We can now understand why RTILs behave differently than single solvents for organic reactions, and which ones are most promising as MALDI matrixes,[4] for extractions and as chromatographic stationary phases.[5,6] Chiral ionic liquids and their use will be discussed as well.[7]
4-02
Development of a Universal
Method for the Determination of Enantiomeric Compositions of Pharmaceutical
Products
CHIEU D. TRAN, Victor I. Grishko, Daniel Oliveira, Department of
Chemistry, Marquette University, P. O. Box 1881, Milwaukee, WI, chieu.tran@marquette.edu
A new method has been developed for the determination of enantiomeric compositions of a variety of drugs including propranolol, atenolol, and ibuprofen. The method is based on the use of the near-infrared (NIR) technique to measure diastereomeric interactions between an added carbohydrate compound with both enantiomeric forms of an analyte followed by partial least square analysis of the data. The fact that the method works well with all three macrocyclic carbohydrates with different cavity size (i.e., a-, b- and g- cyclodextrin) as well as with sucrose, which is a linear carbohydrate, clearly demonstrates that it is not necessary to have inclusion complex formation in order to produce effective diastereomeric interactions. Rather a simple adsorption of the analyte onto a carbohydrate is sufficient. Since inclusion complex formation is not a requisite, this method is not limited to the amino acids studies here but is rather universal and sensitive as it can, in principle, be used to determine enantiomeric compositions for all types of compounds with only microgram concentration and enantiomeric excess as low as 1.5 %, in water or in a mixture of water and organic solvent. Furthermore, it does not rely on the use of rather expensive carbohydrates such as cyclodextrins but is equally as effective even with a simple and inexpensive carbohydrate such as sucrose.
4-03
Determination of
Environmentally Important Metal Ions by Fluorescence Quenching in Micellar
Solutions
F. Nome, H. D. FIEDLER, E. Sapelli, G. C. Bedendo, R. S. Mello, L. V. Vargas, Departamento de Quimica, Universidade Federal de Santa Catarina, Caixa Postal 476, Florianopolis, SC, 88049-970, Brazil, fiedler@qmc.ufsc.br
This work describes the determination of environmentally important metal ions by fluorescence spectroscopy in micellar solutions. Several metal ions have been used as quenchers of the fluorescence of naphthalene, in aqueous micellar sodium dodecyl sulfate (SDS). The quenching by the metal ions can be described by the Stern-Volmer equation and the detection limits are improved with low SDS concentrations. Apparent Stern-Volmer constants decrease in the order: Fe3+ > Cu 2+ > Cr3+ > Ni2+ > Pb2+ and reflect the sensitivity of the method. Similarly, using the cationic chelating agent 8-hydroxyquinoline (8-HQ), allows the simple, rapid and sensitive assay of Zn2+ in aqueous micellar solutions of cetyl trimethyl ammonium bromide (CTABr). In the absence of CTABr, the complex formed between 8-HQ and Zn2+ is insoluble. Micelle-enhanced fluorescence spectroscopy and fluorescence quenching can be used as analytical methods of general application and is an interesting area of research to improve the detection limit of several analytical methods.
4-04
Solid-Phase Microextraction: a Link between Micellar Extraction and Gas
Chromatography
VERÓNICA PINO, Francisco J.
Conde, Juan H. Ayala, Ana M. Afonso, Venerando González. Department of Analytical Chemistry,
Nutrition and Food Sciences,
The Micellar Solid-Phase Microextraction
(MSPME) is a new technique for sample treatment. MSPME intends to combine the
advantages of the micellar extraction with the advantages of the
gas-chromatography by means of the solid-phase microextraction (SPME). The
present work shows not only the use of MSPME to quantify solutes in solid
matrixes but also its ability to determine partition coefficients of solutes
between micellar media and aqueous phases.
In the first case, the PAHs
contained in a reference marine sediment have been extracted with surfactants.
Afterwards, these compounds are removed from the micellar media by using the
adequate SPME fiber, and determined by GC-MS. This step is accomplished just
desorbing the SPME fiber in the injector of the GC, without needing to remove
the surfactant prior to injection. With this new method, the previous
treatments in the analysis of any non-polar compound contained in solid samples
could be reduced to a stage of solubilization of the same ones in a micellar
medium followed by a separation using SPME-GC.
In the second case, the partition
coefficients of 16 PAHs and 29 Phenols between ionic and non-ionic micellar
media and aqueous phases have been established using MSPME. The obtained
results show that this technique is especially adequate by its simplicity and
by leaving the binding equilibrium undisturbed.
4-05
Development of
Functionalized Admicelles in Separation Science
T. SAITOH, M. Hiraide, Graduate School of Engineering, Department of Molecular Design and Engineering, Nagoya University, Chikusa, Nagoya, Aichi, Japan, saitoh@numse.nagoya-u.ac.jp
Surfactant molecules cooperatively sorb on solid surfaces and form aggregates namely hemi-micelles or admicelles in the aqueous solution. Through mixing of surfactants, porous solid materials, and hydrophobic chelating agents or surfactant-conjugated substrates (affinity ligand) in the aqueous solution led to the formation of media for the collection of metal ions or proteins. Different from conventional separation media having chemically bound ligand, the functionalized admicelles have degree of freedom in the preparation. Furthermore, dynamic property and high water permeability of the admicelles can facilitate the interaction of ligand with an objective compound. An admicelle composing of Triton X-100, porous polystyrene-divinylbenzene (Amberlite XAD-4), and Triton X-100-conjugated Cibabron blue 3GA (affinity ligand) was found to be useful for purifying lysozyme from egg white, but was ineffective for the collection of alcohol dehydrogenase (ADH). The uses of octadecylsilyl-silica gel instead of XAD-4 and an affinity ligand having a longer polyoxyethylene moiety were effective for the separation of ADH from bakers’ yeast.
4-06
Powerful
Preconcentration Method for Ultra Trace Amounts of Polycyclic Aromatic
Hydrocarbons and its Application to the Environmental Analysis
Shukuro Igarashi1, YOSHITAKA TAKAGAI2, 1Department of Biomolecular Functional Engineering, Faculty of Engineering, Ibaraki University, Nakanarusawa 4-12-1, Hitachi, Ibaraki, Japan, 2Laboratory of Physical and Chemical Science, Cluster of Science and Technology, Fukushima University, Kanayagawa 1, Fukushima, Japan, igarashi@hcs.ibraki.ac.jp, takagai@sss.fukushima-u.ac.jp
A preconcentration procedure is one of the most important techniques for the environmental analysis. In this study, lower ppt levels of polycyclic aromatic hydrocarbons (PAHs) in environmental water can be determined by the proposed powerful preconcentration method with high performance liquid chromatography using fluorescence detection (FL/HPLC). The preconcentration method consists of the combination of the blue cotton method (solid-phase extraction) and the homogeneous liquid-liquid extraction. In the case of the homogeneous liquid-liquid extraction, PAHs in the eluate of solid-phase extraction were extracted into micro volume of sedimented phase. The proposed method could completely concentrate 1 liter to 20 microliter within one hour and the 20 microliter of sedimented phase is directly injected into FL/HPLC. The entire preconcentration factor was 50,000-fold. Six kinds of PAHs were determined in the range of 3.0 × 10-18 ~ 4.5 × 10-11 mol L-1. These chemicals were also satisfactorily separated. By changing the combination of various preconcentration methods or instrumental analysis, the various samples could be analyzed.
4-07
Cloud Point Extraction as
a Preconcentration Step for the Analysis of Metals in Environmental and
Biological Samples
M. F. Silva, R. A. Olsina, L. FERNÁNDEZ,
Área de Química Analítica, Departamento de Química, Facultad de Química,
Bioquímica y Farmacia, Universidad Nacional de San Luis, 5700 – San Luis,
Argentina, lfernand@unsl.edu.ar
Cloud point extraction (CPE) is a
powerful separation method with a
pronounced capability to preconcentrate trace and ultra-trace metals in
diluted samples of diverse origin such as environmental, biological and
industrial concern. This procedure have advantages over
those currently available including low cost, safety, feasibility for injection
of the surfactant-rich phase into any hydrodynamic analytical system and high
capacity to concentrate a wide variety of analytes of widely varying nature
with high recoveries and very high concentration factors. CPE has been employed for the
preconcentration of metal complexes such as mercury, aluminium and rare-earth
elements prior to inductively coupled plasma atomic optical emission
spectrometry (ICP-OES) and Absorciometry UV-Vis coupled to flow injection (FI).
On the other hand, the possibility to preconcentrate lead and aluminium without
added chelating agents has been demonstrated. Indeed, the
coupling of CPE to Capillary Electrophoresis (CE)
was successfully performed to preconcentrate and simultaneously
determine lead, platinum/palladium, and
iron/dysprosium. The samples under analysis include different water
samples, human saliva, urine and industrial samples.
4-08
Enhanced Organic Photovoltaic Performance from Nanoparticle
– Polymer Blends
Marisol Reyes-Reyes1, Kyung Kim1,
DAVID L. CARROLL1, Seamus Curran2, 1The Center
for Nanotechnology and Molecular Materials, Department of Physics, Wake Forest
University, Winston-Salem NC, 2Department
of Physics, New Mexico State University, Las Crucis NM, carroldl@wfu.edu
Blends of single walled carbon nanotubes (SWNTs), semiconducting nanostructures, nano-metals (Ag, Au), and/or fullerene derivatives with conjugated polymers (MEH-PPV, PFO, PEDOT, P3OT, P3HT), have been of great interest recently as a mechanism to raise the overall performance efficiency of organically-based, flexible, devices such as photovoltaics, organic light emitting diodes, and more. We have recently developed novel methods for controlling both the electronic properties of the nano-phase and the long range “meso-structure” of the blend. Through the use of selective doping (boron and nitrogen dopants) in carbon nano-structures we have demonstrated control over the donor-acceptor role of the nano-phase in the host, allowing for tailoring of the specific trapping levels introduced. Thus, as we show with time-of-flight, we are able to introduce donor or acceptor states within the HOMO-LUMO gap of the host, and control the relative positions of these states. Secondly, we have demonstrated that an order can be created within the nano-phase, with controlled placement and orientation of the nano-particles. These ordered nano-blends of conjugated systems exhibit a number of exciting properties including: modified carrier mobilities, optical absorption, and exciton separation dynamics. In this work we integrate this meta-functional nano-phase blend into a standard flexible organic photovoltaic device. Using commodity polymers, surprisingly high efficiencies can be obtained.
4-09
Morphological Control and Spectrometric Applications of Gold
Nanorods
S. YAMADA,
Department of Applied Chemistry, Graduate School of Engineering,
Gold nanorods (NRs), rod-like nanoparticles, show characteristic two plasmon bands based on a longitudinal oscillation mode along the long axis (far-red/near-infrared region) and a transverse mode perpendicular to the long axis (visible region). Thus, the NR shows a distinct dichroic property. Quite recently, we developed a novel and simple method for the preparation of gold NRs, by the combination of chemical reduction and subsequent photoirradiation. We have first succeeded in well-dispersed fixing of the gold NRs onto a glass substrate by the layer-by-layer approach. When the NR-modified plate was immersed into the solvent, the longitudinal plasmon band showed substantial red shift, while the transverse SP band showed no substantial shift. The degree of peak shift was roughly correlated with the order of refractive index (dielectric constant) of the solvent. The monoparticle layer film of gold NRs was also prepared at the liquid-liquid interface. The NR film showed distinctly larger Raman scattering signals than the corresponding nanospheres film. We also prepared the aggregate of phosphatidylcholine-modified NRs and DNA. Controlled release of DNA from the aggregates was possible by pulsed irradiation of near-infrared laser light.
4-10
Luminescent Nanoparticles as Labels for Biological Molecules
Thomas Nann, Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg, Germany, thomas.nann@fmf.uni-freiburg.de
Luminescent nanoparticles such as
semiconductor nanocrystals (so called Quantum Dots [QDs]) or rare earth doped
nanoparticles gained increasing interest over the past several years. Compared
with organic fluorophores, such particles possess substantial optical
advantages: For example they don’t bleach under excitation, possess a narrow –
often tuneable – spectral linewidth and make new detection techniques possible
e.g. upconversion luminescence or lifetime multiplexing.
The application of these particles
in bioanalytics is promising, but a pre-requisite is, that they are colloidally
stable in biological buffers and can be coupled to appropriate biomolecules.
Since high-quality (monodisperse) nanoparticles are usually synthesised in
non-polar media as for example trioctylphosphinoxide (TOPO) or high-boiling
alkanes, the particle surface must be derivatised in such a way that on the one
hand the phase-transfer is possible and on the other hand biomolecules such as
proteins or nucleotides can be coupled selectively.
First an overview of luminescent
nanoparticles, which are used in bioanalytic applications, is given.
Preparation methods regarding those applications are discussed. Furthermore,
different possibilities for non-polar/polar phase-transfers are presented.
Thereby the encapsulation of single nanoparticles with silica layers will be a
special emphasis (cf. figure 1). Moreover, possibilities for the coupling of
nanoparticles to biomolecules are discussed. Finally, some examples for the
imaging of biological systems with luminescent nanoparticles are presented.
4-11
Nanostructure-Assisted Laser
Desorption Ionization Mass Spectrometry in Bioanalysis
Nancy
H. Finkel, Zhong Guo, Amel Ganawi, LIN HE, Department of Chemistry,
Surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) has drawn considerable attention for its efficiency in detection of species in the low-mass region. Nevertheless, the correlation of the surface property of roughened inorganic substrate with its desorption ionization efficiency remains unclear. We report herein a new nanofabrication method to generate well-controlled surface features and systematically vary the surface geometry with the aim of seeking a fundamental understanding of the SALDI mechanism. Specifically, convective self-assembly is used to generate close-packed 2-D nanoparticle arrays on a flat Si surface. This hexagonal-packed nanoparticle array is then used as a mask in nanosphere lithography to selectively remove portions of Si surfaces in reactive ion etching (RIE) and generates triangle-shaped nanocavities in periodic patterns with pre-defined feature parameters. Mass spectrometry detection of small molecules and peptides on such substrates shows good sensitivity with little fragmentation and minimal background interference. Ordered feature size, shape, and surface density are tailored by varying fabrication conditions. The impacts of surface geometries on MS performance are correlated. The thermal properties of the substrates are investigated. The use of the substrates in metabolite profiling and quantitation of Arabidopsis thaliana extracts is also presented.
4-12
Gold Nanoparticle Matrices
for Bioanalysis using Matrix-Assisted Laser Desorption Ionization
KATHERINE A. STUMPO, John A. McLean, David H. Russell, Laboratory for Biological Mass Spectrometry, Department of Chemistry, Texas A&M University, College Station, TX, kstumpo@mail.chem.tamu.edu
Nanoparticles, esp. gold nanoparticles (AuNPs), have found wide application in chemical biology and biochemical applications. Importantly, the optical and electronic properties of NPs depend on size, shape, composition, and derivatization. Thus, NPs can be tailored to specific applications, e.g. using functionalized AuNPs for selective isolation of target analytes. We present here the utility of AuNPs and surface derivatized AuNPs as potential matrices for matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). These alternative substrates offer a number of advantages over conventional MALDI matrices (e.g. small organic acids): (i) greater flexibility in sample deposition conditions (e.g. pH, solvents, etc.), (ii) relatively uncomplicated spectra in the matrix region (low mass range), (iii) Au-cluster species as internal standards for mass calibration, and (iv) AuNPs afford a very high shot-to-shot and spot-to-spot reproducibility (<10 % RSD). Furthermore, the surface chemistry of AuNPs also plays an important role in the ionization process, and has been investigated. Surface association of ions and the solvent structure around these species in solution have an effect on analyte interactions with the AuNPs, thus leading to changes in ionization efficiency. These studies present many interesting avenues that can be pursed in various chemical biology systems.
4-13
Chemical
Separations Using Nanoparticles
LUIS A. COLON, Jason A. Anspach,
Hector Colón, Glorimar Vicente, Melissa N. Dunkle, Department of Chemistry,
University at Buffalo, The State University of New York, Buffalo, NY, lacolon@buffalo.edu
The use of chromatographic columns packed with small particle diameters allows the exploration of the theoretical limits in liquid chromatography, as theory predicts that a reduction in particle diameter would provide an increase in separation efficiency with a concomitant reduction in analysis time. Our research group has been exploring such predictions by first synthesizing organosilica particles with diameters in the nanometer range and using them for capillary electrochromatography (CEC) and ultrahigh pressure liquid chromatography (UHPLC). Although a gain is noticeable when using particle diameters below 1 µm, the actual gain combined with practical considerations are factors to consider in the separation formats studied. Using another nanoparticle technology and the nanoscale separation technique of capillary electrophoresis, we also explore the use of fluorescent nanoparticles as “labeling” tags to enhance detection of biomolecules. We will discuss our recent findings as we implement these new technologies in chemical analysis.
4-14
Gold Nanoparticles in Open-Tubular Capillary
Electrochromatography and Supercritical Fluid Extraction
JEREMY D. GLENNON, Elizabeth Guihen, Li Yang, Norma M. Scully, Anne M. O'Keeffe, Niamh M. J. Curran, Jean-Marie Prat, Gerard P. O'Sullivan, Department of Chemistry, Analytical & Biological Research Facility (ABCRF), and Supercritical Fluid Center, University College Cork, Cork, Ireland, j.glennon@ucc.ie
Nanoparticles exhibit unique size-dependent optical, catalytic, magnetic, and electronic properties compared to their bulk counterparts and can enhance a variety of technologies including chemical processing, medical, electronic, environmental, separation and sensing applications. Gold nanoparticles in particular, are among the most stable metal nanoparticles, and are viewed as key materials and building blocks, with emerging applications in biology, catalysis and nanotechnology.
To-date, very little research has
been devoted to the application of nanoparticles in separation science. The significant advances, which have been
made in electrophoresis and microchip separations, show the promise to enhance
separation performance by using nanoparticles. For example, latex nanoparticles have been used to coat a micromachined channel on-chip,
and on-chip ion chromatography of inorganic anions, nitrate, nitrite, and
iodide, has been achieved.
In this paper, important new roles
for gold nanoparticles in open-tubular electrochromatography (OTCEC), and in
the extraction of this precious metal using supercritical carbon dioxide will
be highlighted. Specifically, the
use of alkylthiolgold nanoparticles in OTCEC to improve the efficiency of
separation and the selectivity between selected solutes will be demonstrated,
in particular, for hydrophobic test solutes and for selected polycyclic
aromatic hydrocarbons (PAHs).
4-15
Development, Evaluation
and Application of Nanoparticles as Stationary Phases for
Gas Chromatography
ROBERT E. SYNOVEC,a Gwen M. Gross,a Jay W.
Grate,b (a) Center for
Process Analytical Chemistry, Department of Chemistry, Box 351700, University
of Washington, Seattle, WA 98195. (b) Pacific Northwest National Laboratory,
We are exploring using a thin film of gold-centered monolayer protected nanoparticles (MPNs) as a stationary phase for open-tubular gas chromatography (GC). The MPN films have thermodynamic and mass transfer properties that serve them well, providing good chemical selectivity and high separation efficiencies (high N). High surface area-to-volume ratios of MPNs provide ample sample loading capacity. A majority of our work has been with dodecanethiol MPNs, with a dodecanethiol monolayer linked to a gold nanoparticle. Films of dodecanthiol MPNs ranging from 10 to 60 nm provided efficient separations with various capillary dimensions. The MPNs have a nominal diameter of about 3 nm, so film depths are only a few nanoparticle diameters. High-speed separations with dodecanethiol MPNs in a film depth of ~ 15 nm in a square channeled capillary have been achieved and these results hold considerable promise for the development of “high performance” microfabricated GC. We are also investigating MPN columns for ultra high-speed GC, where separations of several analytes in a fraction of a second are achieved, engendering the notion that GC can function like a chemical sensor. Current development of polar stationary phases utilizing 4-chlorobenzenethiol MPNs and 4-(trifluoromethyl)benzenethiol MPNs will also be discussed.
4-16
Non-Cross-Linking Aggregation of DNA-Carrying Nanoparticles for
Single-Base Substitution Assay
MIZUO MAEDA, Kazuo Hosokawa, Kae Sato, Bioengineering Laboratory, RIKEN, 2-1, Hirosawa, Wako, Japan, mizuo@riken.go.jp
The graft copolymer consisting of poly(N-isopropylacrylamide) (PNIPAAm) and single-stranded DNA was prepared as a DNA-conjugated material. Interestingly, the DNA-conjugate was found to form nanoparticles above physiological temperature (Langmuir, 20, 313-319 (2004)). We found that non-cross linking aggregation of the nanoparticles was induced by the hybridization of the surface-bound DNA with the full-match complementary DNA, but not with one-base mismatch. The results demonstrated that the non-cross linking aggregation of DNA-carrying nanoparticles is useful for analyzing various SNPs. The core material is not restricted to PNIPAAm; DNA-functionalized gold nanoparticle (15 nm diameter) was found to show a similar aggregation phenomenon induced only by the fully-complementary DNA, resulting in rapid color change within 3 min at ambient temperature (J. Am. Chem. Soc., 125, 8102-8103 (2003)). This methodology is general in principle and applicable for wide variety of clinical diagnosis.
4-17
Enzymatic
Amplification of Chemical Signals Inspired by Biological Signal Transduction
J. KIKUCHI,
Y. Sasaki, Graduate School of Materials Science, Nara Institute of Science and
Technology, Ikoma, Nara, Japan, jkikuchi@ms.naist.jp
Intermolecular communication between a receptor and an effector on the biomembrane surface plays a pivotal role of the information processing in biological system. We have recently developed an artificial intermolecular communication system on colloidal lipid vesicles, as a molecular device, inspired by the biological signal transduction. The system is constituted in combinations of an artificial ditopic receptor, an enzyme as an effector, and a bilayer-forming synthetic lipid. The cationic bilayer membrane formed with the synthetic peptide lipids or the Cerasome-forming lipids was an effective platform for self-assembling of such functional molecules. On the membrane surface, the enzymatic activity was effectively synchronized with ditopic recognition of the receptor toward an external signal and a mediator species between the receptor and the effector. Marked signal selectivity which is characteristic to the aqueous colloidal interface was observed. The signal transduction efficiency was sensitively tuned with gel to liquid-crystalline phase transition of the matrix membrane. The present molecular device acts as a unique sensing system, in which the information on the molecular recognition of various biologically important species by the receptor is transmitted to the enzyme and amplified chemically as the catalytic reaction.
4-18
Gold
Nanoparticles in Bioanalytical Assays
T. K. T. Nguyen1, ZEEV
ROSENZWEIG2, 1School of Biological Science and Department
of Chemistry, University of Liverpool, Liverpool, United Kingdom, 2Department
of Chemistry, University of New Orleans, New Orleans, LA, zrosenzw@uno.edu
The presentation will focus on the synthesis, functionalization and application of gold nanoparticles in biological assays and as pH sensors in biological samples. Gold nanoparticles were synthesized at different sizes and characterized for their structural characteristics by electronic microscopy and by UV-VIS spectrometry for their optical properties. High quality particles were highly dispersed in aqueous solution, exhibited narrow size distribution and showed a characteristic plasmon resonance absorption peak at around 520 nm. Once aggregated the absorption signal broadened considerably and the color of the solution changed from red to purple. This color change was used to monitor the aggregation of antibody coated gold nanoparticles in their presence of their corresponding antigens. A compact laser-based detection system was constructed and used to monitor the aggregation of the particles using a diode laser at 620 nm and signal and reference photodiodes to monitor the absorption of the analyte solutions. The study concluded that aggregation-based assays of antibody coated gold nanoparticles could be used to quantitatively determine the presence of antigens or antibodies in biological fluids.
4-19
Analytical Measurements Using Polymeric Surfactants
ISIAH MANUEL WARNER, Department of Chemistry, Louisiana State University, Baton Rouge, LA, iwarner@lsu.edu
Over the past several years, we have employed polymeric surfactants as analytical reagents, particularly as mobile phase additives for separations in capillary electrophoresis. We have shown that our polymeric surfactants are broadly applicable to the separation of a variety of analytes, including the separation of chiral compounds by use of chiral polymeric surfactants. More recently, applications for the development of novel nanomaterials in the presence of polymeric surfactants have been explored. Our studies have shown that these polymers are more suitable than conventional micelles for both separations and spectroscopic applications. In this talk, I will focus on the use of polymeric surfactants as separation reagents and for the development of spectroscopic probes. The advantages of these reagents in comparison to regular micelles will also be discussed, particularly with regard to the wide variety of applications. A comparison of the use of polymeric surfactants for separations and spectroscopy will also be made directly to separations and spectroscopy by use of conventional (unpolymerized) micelles.
4-20
Liposome Enhanced Firefly Bioluminescent Assay of ATP in the Presence of Surfactants
HIROFUMI TANI, Tamio Kamidate, Division of Biotechnology and Macromolecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo, JAPAN. tani@eng.hokudai.ac.jp
The firefly bioluminescence (BL) assay has been widely used for the determination of ATP in living cells. In this assay, the ATP extractants such as surfactants are required for the release of ATP from cells, but they often inhibit the BL enzyme, luciferase. On the other hand, surfactants are known to incorporate into liposomes composed of vesicular lipid bilayers. In addition, cationic liposomes were found to enhance the BL intensity. Thus, a cationic surfactant being used as an extractant, liposomes can eliminate the inhibitory extractant and can transform into the BL-enhancer, cationic liposomes, by incorporating cationic surfactants. In this study, we exploited such a double advantage of liposomes for the BL assay of ATP in the presence of cationic surfactants. Liposomes consist of phosphatidylcholine and cholesterol were prepared by the extrusion method using a polycarbonate filter. Benzalkonium chloride (BAC) was used as an ATP extractant. The detection limit for ATP in the mixtures containing 0.06% BAC was 25pM in the absence of liposomes. On the other hand, the BL intensity was remarkably increased by the addition of liposomes into the assay mixture, resulting in the enhancement of the sensitivity for ATP. The detection limit was improved to be 400fM.
4-21
Structure and Dynamics of
Cationic and Nonionic Micelles:
Neutron Scattering Studies
L. J. Magid1, W.-R. CHEN1, P. D. Butler2, D. Bossev3, 1Department of Chemistry, University of Tennessee, Knoxville, TN, 2NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 3Physics Dept., Indiana University, Bloomington, IN, lmagid@nsf.gov, wrchen@ion.chem.utk.edu
Micellar morphology in aqueous micellar solutions of cationic surfactants such as CTAX and CPyX can be manipulated by changing the counterion. Organic counterions that penetrate the micellar interface, such as salicylate and tosylate, produce very large, semi-flexible wormlike micelles. Flexibility depends on the surfactant’s head group, the counterion, and the concentration of added salts. Increasing concentrations of NaSal or NaTos cause the micelles to undergo size reversion back to globules; the salt concentration at which this occurs is counterion-dependent. SANS data that allow micellar contour lengths, persistence lengths and cross-sectional radii to be determined will be presented, and size reversion will be found to correlate with the unfavorable energetics of decreasing radii. Our fitting protocol incorporates changes to the widely-used Pedersen-Schurtenberger scattering functions.
Neutron spin-echo studies on the local dynamics of linear and branched wormlike cationic and nonionic micelles will also be presented, as well as of saturated micellar networks.
4-22
Studies of Reversible
Guanosine Gels
LINDA B. MCGOWN1, Victoria A. Dowling2, Lawrence W. Dick2, 1Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 118 Cogswell, Troy, NY, 2Department of Chemistry, Duke University, Gross Chemical Laboratory, Durham, NC, mcgowl@rpi.edu
Guanosine gels (G-gels) are self-assembled networks of hydrogen-bonded guanine tetrads formed by guanosine nucleosides and nucleotides. G-gels combine desirable properties, such as reversibility, tunability, aqueous solubility, and biocompatibility, with the unique ability to non-covalently and reversibly introduce functionality directly into the G-tetrad network of the gel via hydrogen bonding. Their degree of organization and viscosity are dependent upon monomer concentration, temperature, pH and cation content, providing a variety of parameters that can be used to control their formation/disassembly and to reversibly modulate their properties. This talk will present results of experiments in which G-gels are used for chiral separations in capillary gel chromatography and molecular probe studies of these gel phases related to their performance in chiral separations. Results will also be presented for gels that are under investigation for bioencapsulation.
4-23
Hydrogen Bonded Molecular
Macrocluster Formation at the Solid - Liquid Interface
KAZUE KURIHARA,
Liquid molecules at the solid-liquid interfaces often exhibit different properties from those in the bulk, which is attributed to the surface-induced structuring of liquids. Elucidation of these properties is important in nanoscience and nanotechnology. We recently have found that liquid molecules with the hydrogen bonding functionalities (alcohol, carboxylic acid, and amide) form a hydrogen bonded organized structure, which we call “molecular macrocluster”, on the silica (glass and oxidized silicon) surface when they are adsorbed from their mixtures with non-polar solvents. The surface silanol groups are essential for this structure formation. FTIR-ATR spectroscopy demonstrates the hydrogen bonding interactions between the surface silanol groups and adsorbed molecules in addition to those between adsorbed molecules. Surface forces measurement reveals the long ranged attraction (e.g. extending to 30 ~ 40 nm for normal monohydric alcohol in cyclohexane) due to the contact of the opposed adsorption layers. Half the attraction range is close to the adsorbed layer thickness, which is extraordinarily long range. Interesting differences are observed in the mode of adsorption depending on the chemical groups. Dynamic properties of adsorbed molecules, ethanol on glass in cyclohexane, are studied by NMR spectroscopy. We utilize this molecular macrocluster for preparing polymer thin-films on solid surface.
4-24
Distribution of tert-Butylhydroquinone in Food-Like Emulsions
Stabilized by C12E6
K. GUNASEELAN, Laurence S. Romsted, Rutgers, The State University of
New Jersey, Department of Chemistry and Chemical Biology, Wright-Rieman
Laboratories,
We have developed a new approach for estimating the distributions of antioxidants in opaque, surfactant based, macroemulsions based on the pseudophase model for homogenous microemulsions. The distribution of t-butylhydroquinone, TBHQ, in emulsions composed of tributyrin, C12E6, and acidic water is described by two partition constants between the oil and interfacial, POI, and the water and interfacial, PWI, regions. To estimate values for POI and PWI requires fitting two independent data sets with two independent mathematical relations and solving two equations simultaneously. One data set was obtained by electrochemical determination of the observed rate constant, kobs, for reaction of TBHQ with an arenediazonium ion probe as a function of C12E6 volume fraction. The second data set was obtained by determining the partition constant, POW, of TBHQ between tributyrin and water in the absence of surfactant by UV-Visible spectrometry, POW = 0.015. The values of the partition constants in the emulsion are: POI = 11 and PWI = 7.11 x 102. Application of this approach to a variety of antioxidants in emulsions containing different food oils and emulsifiers should provide new insight into the factors controlling antioxidant distributions and may lead to a development of a new scale of antioxidant efficiency.
4-25
Partitioning of Polar
Aromatic Compounds to Organogels and Application for their Extractive Removal
from Organic Solvents
Melissa M. Stouffer, Julianne M. Braun, Dai Fang, WILLIE L. HINZE, Department of Chemistry, Wake Forest University, PO Box 7486, Winston-Salem, NC, hinze@wfu.edu
Organogels are formed by the addition of gelatin to Aerosol OT [bis(2-ethylhexyl) sodium sulfosuccinate] reverse micelle solutions at elevated temperatures followed by cooling. The “solid” organogels have been shown to retain many of the general properties exhibited by traditional reverse micelle solutions. Some of the general features and characteristics of these materials will be described. Results regarding the stability of organogels in a variety of organic solvents and aqueous mixtures will be presented. Partitioning data for the interaction of polar aromatic compounds (such as substituted anilines, phenols, naphthols) with the AOT organogels will be presented and compared to the partitioning observed for the same interaction with solution AOT inverted micelles. The use of organogels to remove (extract) and/or concentrate organic solutes from organic solvents will be discussed and the relevant extraction parameters summarized. In addition, the use of such an approach as a preconcentration technique prior to spectroscopic chemiluminescent determinations will be illustrated. Preliminary data obtained using CTAB [hexadecyltrimethylammonium bromide] based organogels will also be presented.
4-26
Analytical Applications of
Metal Nanoparticles
O. A. SADIK, M. Omole, D. Andreescu, A. Wanekaya, State University of New York at Binghamton, Chemistry Department, Binghamton, NY, osadik@binghamton.edu
Palladium nanoparticles are of particular interest as catalyst for the synthesis of specialty chemicals, nuclear waste and environmental applications. The objective of this work was to develop a reliable experimental procedure for the synthesis and analytical applications of Pd-based nanoparticle. In designing advanced materials for nanosensors and environmental remediation, nanomaterial synthesis procedures are increasingly required to control the shape and size. Consequently, we have synthesized palladium nanoparticles through the reduction of Pd (II) acetate using polyamic acid (PAA) as a reducing agent in an organic medium at room temperature. The approach is based on subsequent capping and stabilization of the resulting palladium nanoparticles by the PAA. The Pd-based nanostructured materials were characterized using UV/Vis spectroscopy, scanning electron microscopy and transmission electron microscopy (TEM). TEM image analysis showed the synthesized PAA-metal hybrid as well dispersed particle of different shapes (Spherical, pyramidal and octahedral). The particle sizes were in the range of 8.3-13.0 nm. In this presentation, we will show that palladium nanoparticles of variable shape may be synthesized using a simple one step procedure involving the reduction of a palladium salt by polyamic acid at room temperature. The possibility of fabricating a PAA-metal hybrid material for environmental remediation and biosensing would be presented.
4-27
Colloidal CdSe Quantum Dots as Novel Luminescent Probes for Selective
and Sensitive Analytical Determination of Trace Amounts of Ions in Water
Samples
J. M. COSTA-FERNANDEZ, M. T.
Fernández-Argüelles, W. J. Jin, R. Pereiro, A. Sanz-Medel, Department of Physical
and Analytical Chemistry, University of Oviedo, 33006 Oviedo, Spain, jcostafe@uniovi.es
Recent developments are stressing
the importance of adequate surface chemistry in the development of highly
luminescent, water-soluble and biocompatible quantum dots (QDs) for
applications in bioanalysis and diagnostics [1, 2]. Moreover, analytical
chemists have also started to explore these nanomaterials for the development
of a new generation of luminescence optical probes.
Luminescence of QDs is very
sensitive to their surface states; therefore, it is reasonable to expect that
eventual chemical or physical interactions between a target chemical species
with the surface of the nanoparticles would result in changes on their surface
charge affecting the efficiency of the core electron-hole recombination.
Following this approach,
water-soluble surface-modified CdSe QDs have been synthesized and evaluated as
optical probes for selective and sensitive determination of trace amounts of
small ions (free cyanide and copper (II)) in aqueous solutions based on
fluorescence quenching measurements.
After QDs synthesis, a
photostimulation was necessary in order to obtain a stabilized emission profile
resulting in reliable responses to the presence of the analytes. Moreover, the
addition of surfactant agents to the measured aqueous solution was found to
greatly stabilize the colloidal QDs and the fluorescent signals, resulting in a
very high sensitivity for analyte detection (detection limits in the low ng ml-1
range are obtained) [3].
4-28
Synthesis of Semiconductor
Nanoparticles as Probe to Detect Supersaturated Dissolved Oxygen
YONGXIA ZHANG, Duane T. Johnson, Chemical & Biological Engineering Department, University of Alabama, Tuscaloosa, AL, djohnson@coe.eng.ua.edu
High-quality ZnS nanocrystrals are synthesized with a coordinating solvent (i.e. high boiling-point long chain amine) using zinc stearate and elemental sulfur as the precursors. Spherical ZnS nanoparticles (~2nm) were obtained and characterized using several different techniques (XRD, SEM, TEM and UV-Vis). Fluorescence intensity and decay rate of ZnS were acquired using a fluorometer. The ZnS nanoparticles have a good fluorescence at 400 nm and a long decay time (~2.5ms). The fluorescence intensity and decay time are inversely proportional to the dissolved oxygen concentration. Calibrating this relationship allows one to determine the concentration of dissolved oxygen by measuring the fluorescence intensity and/or the fluorescence decay rate. The slow decay rates and bright fluorescence make ZnS nanoparticles potential probes for measuring supersaturated dissolved oxygen, which is difficult to obtain using other techniques.
4-29
Hybridization of DNA Functionalized Silver and Gold Nanoparticles in
Aqueous Dispersions and on Gold Films
Iryna Tokareva, ELIZA HUTTER, Department of Chemistry, Clarkson University, Box 5814, Potsdam, NY, huttere@clarkson.edu
Silver and gold nanoparticles were successfully functionalized by 12mer oligonucleotides and hybridized onto gold nanoparticles in dispersions. The optical and hybridization properties of DNA linked gold-silver ,silver-silver and gold-gold colloidal nanoparticles are described. In addition, the self-assembly of homo-oligonucleotides on gold films and their hybridization with their complementary pairs, unlabeled or labeled by gold and silver nanoparticles, were detected by Polarization Modulated Fourier Transform Infrared Reflection Absorption Spectroscopy (PM-FTIRRAS). PM-FTIRRAS was found to be capable to detect the base pairing between DNA strands and distinguish between the types of oligonucleotides (adenine or thymine) attached to the nanoparticles.
4-30
Novel Evaluation Method of
Nanoparticle Dispersibility in Nanocomposites
by TEM-Computerized
Tomography and 3D Image Analysis
H. SASAKURA1, H. Yoden2,
S. Noda3, Y. Yamaguchi3, 1Japan Chemical
Innovation Institute, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo
113-8656, Japan, 2Japan Chemical Innovation Institute, Hiroshima
University, 1-4-1 Kagamiyama, Higashihiroshima, Japan, 3Department
of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-Ku, Tokyo, Japan, sasakura@chemsys.t.u-tokyo.ac.jp
We propose a novel evaluation
method to characterize three-dimensional (3D) structures
of nanoparticles in nanocomposites by using 3D images obtained from a
transmission electron microscopy assisted by computerized tomography (TEM-CT).
Since physical properties such as transparency,
dimensional stability and thermal durability depend
on
the dispersibility of nanoparticles in a nanocomposite, it is crucial to
reveal the 3D structures of nanocomposites.
The silica nanoparticle/epoxy nanocomposite evaluated is a model
material to figure out our proposed method. First, the nanocomposite 3D images
are reconstructed by TEM-CT. Second, the nanoparticle images are separated from
the nanocomposite by binarization. Third, the summation of the shortest
distances between each separated particle is normalized by an ideal distance
between two particles under fcc structure, which is defined as Universal Factor
(UF) as an index of the particle dispersibility to quantitatively evaluate the
3D structure of nanoparticles. It is found that silica nanoparticles in the
nanocomposite are well dispersed because the UF of the nanocomposite is 0.85.
We also show the simple analytical validation in order to estimate the
error of the length subject to the novel evaluation method.
4-31
Systems Based on Polymeric
Surfactant – Polyvinylpyrrolidone and Organic Reagents: Properties
and Utilization in Analysis
O.V. MIKULENKO, F.A. Chmilenko,
Department of Analytical Chemistry, Dnepropetrovsk National University, Dnepropetrovsk,
Ukraine, analyt@ff.dsu.dp.ua
The influence of polymeric surfactant - polyvinylpyrrolidone (PVP) for various molecular masses (8×103 - 360×103) on spectroscopic, protolytical and complex formation properties of organic reagents (dyes of different classes) is established with the methods of UV-, visual and IR-spectroscopy. It is shown that addition PVP in solution of azo-, triphenylmethane and trioxyfluorone dyes leads to shift of absorption strips maximum of reagents, displacement of reagent dissociation. One can use PVP to modify complex formation of organic reagents with ions of metals: it is shown in increase of contrast and sensitivity of analytical reactions. On the basis of PVP adducts with organic reagents we propose manufacturing of electrochemical sensors for direct determination of polymer content in solution. The conditions of sensors work are established in model and real solutions of medicine. The complex techniques of spectroscopy and electrochemical determination of PVP concentration in medicine, bioobjects, waste water, spectrophotometry techniques of determination of average molecular mass of PVP in substation and metal ion content in different objects are developed.
5-01
Block Copolymer Directed
Self-Assembly of Drug Nanoparticles
Jessica L. Anacker1, Christopher W. Macosko2, ROBERT K. PRUDHOMME3, Thomas R. Hoye4, Walid S. Saad3, 1Ecolab Research Center, Ecolab, 655 Lone Oak Drive, Eagan, MN, 2Departments of Chemical Engineering and Materials Science, University of Minnesota, 3Department of Chemical Engineering, Princeton University, 4Department of Chemistry, University of Minnesota, prudhomm@princeton.edu
Nanoparticle formulations of drugs, printing inks, sun screens, and other hydrophobic organic compounds have distinct advantages in bioavailability, color intensity, and aesthetics, for example. Common requirements of these applications are control of particle size and surface functionality. Commonly used techniques for the production of nanoparticles include salting out, solvent-evaporation, and emulsification-based methods. However, these methods have serious limitations, including long processing times, process scale-up, low nanoparticle drug loading, and lack of controlled nanoparticle size. In order to overcome these limitations, we describe, an easily scalable Flash Nano Precipitation process to produce stable, high concentration, and high drug loading nanoparticles using amphiphilic diblock copolymers. Uniform particles with tunable sizes from 50-500 nm can be prepared. The rules controlling particle formation will be presented using block copolymers as the structure-directing species. The process requires control of three time scales: micromixing times to initiate nucleation, nucleation and growth times for the drug compound, and block copolymer micellization times.
5-02
Enzymatic Cleavage of
Surface-Immobilized Substrates: Effect of Substrate Adsorbed-Layer Age
T. F. Svitova, H.W. Blanch, C.J.RADKE. Chemical Engineering
Department,
Proteolytic enzymes are common components of automatic dishwashing and laundry formulations used to remove protein stains. However, understanding is lacking of their adsorption and kinetic behavior at surface-bound proteins. Using optical waveguide lightmode spectroscopy (OWLS), we study the proteolysis kinetics of subtilisin on surface-immobilized protein substrates including ovalbumin, BSA and beta-casein. We focus specifically on the age of the surface-immobilized protein by measuring the transient protein-layer mass and thickness after 4 and 22 hours of protein adsorption. The rate of proteolysis increases linearly with enzyme concentration for both the 4- and 22-hr adsorbed protein substrate. Surface cleavage rates are compared to the corresponding bulk proteolysis rates, as gauged by fluorometry with FITC-labeled proteins. We argue that structure changes of the proteins upon adsorption influence the proteolysis rates. Longer aging times permit continuing protein unfolding and interfacial rearrangement that further decreases the cleavage rate. This hypothesis is supported by companion interfacial-elasticity measurements for the same proteins adsorbed at the air/water interface as a function of aging time. A simple Langmuir-Michaelis-Menton kinetic model is proposed to describe the kinetics of the simultaneous enzyme adsorption and substrate cleavage of the surface-immobilized protein layers.
5-03
Liquid Core - Polymer Shell Particles
Rob Atkin, Peter Dowding, Andrew Loxley, BRIAN VINCENT, David York*, School of Chemistry, University of Bristol, Bristol, United Kingdom, * P&G Technical Center, Newcastle-on-Tyne, United Kingdom, brian.vincent@bris.ac.uk
Core-shell particles (microcapsules), dispersed in water, with liquid cores and polymer shells of controlled thickness and morphology, are excellent candidates for the controlled release of "active" molecules, such as pharmaceuticals, agrochemicals, perfumes, flavors, dyes, inks, etc. Various methodologies have been reported for making such capsules. In this paper we will discuss a novel method for the preparation and characterization of a variety of different microcapsules, including ones with oil cores and others with aqueous cores, depending on the nature of the active material to be released. The general method used for their preparation is based on internal phase separation of the polymer wall from the droplets of either an oil/water emulsion or a water/oil emulsion depending on the nature of the internal phase required. For the aqueous core particles, the external oil phase is replaced (after shell formation) by an aqueous phase. Control of the various interfacial tensions is critical in obtaining particles with a shell (rather than an “acorn” structure”). The size of the microcapsules, and the polymer wall thickness and permeability can be readily controlled using this method. Characterization of the microcapsules is mainly based on light scattering, optical microscopy and SEM (of the broken microcapsules).
Some data will be presented for release rates and amounts of model active materials, and how this is affected by changes in the various system parameters, such as the size of the liquid core, the polymer shell thickness, and the nature of the polymer shell.
5-04
Effects of Surface Properties on Droplet Formation Inside a Microfluidic
Device
Benjamin Steinhaus1, AMY
SHEN2, Patrick Spicer3, 1Dept. of Mechanical
Engineering,
Micro-fluidic devices offer a
unique method of creating and controlling droplets on small length scales. A
microfluidic device is used to study the effects of surface properties on
droplet formation of a 2-phase flow system. Four phase diagrams are generated
to compare the dynamics of the 2 immiscible fluid system (silicone oil and water)
inside microchannels with different surface properties. Results show that the
channel surface plays an important role in determining the flow patterns and
the droplet formation of the 2-phase fluid system. The surface effect on the
droplet deposition inside microchannels will also be discussed.
5-05
Delivery of Food
Antimicrobials in Micellar Surfactant Systems
JOCHEN WEISS, Food Biophysics Laboratory, Department of Food Science, University of Massachusetts, Chenoweth Lab 234, 100 Holdsworth Way, Amherst, MA, jweiss1@foodsci.umass.edu
Foodborne illness continues to be a problem in the
5-06
Formation Mechanism and Properties of Colloidal Nanoparticles used in Lubricant Additive Formulations
PETER J. DOWDING, Christopher J. Adams1, Brian H. Robinson, David C. Steytler2, 1Infineum UK Ltd., Milton Hill Business & Technology Centre, P.O. Box 1, Abingdon, United Kingdom, 2School of Chemical Sciences, University of East Anglia, Norwich, Norfolk, United Kingdom, Peter.Dowding@Infineum.com
Additives are used in lubricant systems to minimise destructive processes in the engine (e.g. wear and corrosion) and to confer beneficial properties (e.g. more uniformed viscosity with temperature and improved fuel economy). Overbased detergents are an integral element of such additive systems, and consist of surfactant stabilised inorganic nanoparticles (comprising calcium carbonate). Such “overbased” additives represent “model” hard-sphere systems with narrow polydispersity and mean core radius in the range 2 – 5 nm. They have been characterised by a range of techniques including small-angle neutron scattering (SANS). Overbased detergents are used in lubrication packages to neutralise acid species introduced into the lubricant through acidic blow-by gases. In addition, the detergent helps maintain piston cleanliness.
The production of stable nanoparticles (with tailored properties) is an area of current research interest, with potential for a wide range of future applications. For many such systems, a major challenge is the production of particles with consistent quality (and low polydispersity) on a large scale. Overbased detergents are produced on a multi-tonne scale, with a constant particle size and low degree of polydispersity. The mechanism by which such nanoparticles are formed has recently been investigated by small angle neutron scattering and evidence will be presented that suggests the particle formation mechanism is via nucleation-growth (and not the previously reported micellar route). A similar synthesis mechanism may have potential for other inorganic nanoparticles.
In addition, characterisation of the properties of such detergent particles (e.g. core and surfactant shell sizes by SANS) will also be presented.
5-07
The Synthesis of FePt
Nanoparticles by Two-Liquid Mixing Method
TORU IWAKI,
Kanae Yuasa*, Kikuo Okuyama**, *Dept. Chem.
FePt nanoparticles have been synthesized continuously by mixing two precursor liquids: ferric acetylacetonate, Fe(acac)3 , and platinum acetylacetonate, Pt(acac)2 in ethyleneglycol solution with dispersing agents. The reduction reaction of the mixed Fe and Pt ions to the FePt metal alloys in the reaction cell at a high temperature were aided by irradiating the high power of ultrasound continuously. The obtained FePt particle size was found by TEM photograph to be around 3~ 4 nm showing monodisperse and nonagglomerating. The rate of production of the FePt nanoparticles was more than 30g per hour. The composition of Fe and Pt elements in FePt nanoparticles determined by ICP analysis was changed arbitrarily by controlling the flow rate of two precursor liquids. The ferromagnetic property of FePt nanoparticles was obtained by the annealing because as grown sample shows the nature of super-paramagnetic properties. The annealing condition was to keep the FePt nanoparticles at a high temperature for 30 min in an atmosphere of 15% of H2 and 85% of Ar. The magnetic hysteresis loops of FePt nanoparticles were obtained by SQUID measurements. The highest room temperature coercivity ~up to 10 kOe was observed in Fe53Pt47 sample.
The addition of Ag atoms to FePt nanoparticles in the nanoparticles synthesis lowered the annealing temperature of the sample as low as below 350°C. The magnetic properties of the FePtAg and FePt nanoparticles were compared by the measurements of SQUID and XMCD.
5-08
Mesoscale Simulation of Colloids and Surfactants in Consumer Products
FIONA CASE, Case Scientific
Many soft or fluid consumer products, such as foods, paint, detergents, personal care products, and cosmetics, contain nanometer to micron size fluid structures. These structures (such as micelles, vesicles, emulsions and lamella) are formed by the spontaneous self-assembly of natural or synthetic surfactants or block copolymers. In many cases complex mixtures of different surfactants and polymers are required to create the desired structure and performance.
These complex materials are challenging to characterize. Even with the latest developments in light microscopy the fluid structures can be orders of magnitude too small to be observed. Illumination with smaller wavelength radiation (such as x-rays or neutrons) solves the size problem, but results can only be interpreted unambiguously for simplified model systems. Adding to this challenge is the fact that product performance depends not on the static or equilibrium structure of the material, but on its dynamic behavior. When detergent cleans, or soap foams, or a fragrance releases, or margarine spreads, it is the way that the nanometer to micron sized fluid structures change in response to external stimuli that determines performance.
How can we predict the dynamic nanometer to micron scale structure of a particular mixture of surfactants, polymers, oils and additives – of a particular formula? And how can we predict its response to external stimuli - agitation, dilution, or the introduction of a dirty surface? If we could do this, and we could also identify the link between physical properties and consumer perceivable performance (another significant challenge!), we could prescribe the perfect formula for any application.
Computer simulation may provide part of the solution by predicting
the structure and dynamic behavior of materials. There are a number of
different types of simulation. Atomistic scale simulation methods are quite
well established. They can reliably predict the shape of individual molecules
or relatively small clusters of molecules. Using a super-computer, such as
IBM’s Blue Gene/L prototype, the structures of lipid membranes and membrane proteins
can even be predicted. These methods can provide insight into part of the
problem (the behavior of small fluid structures, over the short periods of
time). The much larger scale mixing and flow of materials can be predicted
using methods such as computational fluid dynamics, this is another part of the
solution. But CFD alone cannot predict the effects of varying molecular
structure on the performance of a material (for example of changing the type of
surfactants in a complex mixture). Mesoscale modeling techniques, such as
dissipative particle dynamics and mean-field theories, have proved capable of
modeling a critical length scale for complex fluids – capable of predicting the
self assembly of structures from nanometers to microns in size. This presentation
will provide an overview of different computational approaches, focusing on
mesoscale modeling and its potential application to predict properties of
personal care products such as liquid soaps and detergents. We will also look
to the future, and to the development of new approaches that combine the
different length scales in one simulation. These new methods may finally allow
us to predict the behavior of the fascinating, complex, dynamic materials that
are modern consumer products.
5-09
Fluorescent Silica Colloids for Detection of Absorption of Various Skin
Care Products
S. Iyer, Ya. Kievesky, I. SOKOLOV,
Recently we have synthesized a
new type of very bright nanoporous silica colloids. Organic lasing dye is
encapsulated inside of closed pores, which prevents its leakage. Silica
particles are chemically inert and rather biocompatible. It makes them a good
candidate for tracing of various substances, in particular, skin-care products.
To demonstrate this, we mix the silica particles with two types of moisturizers
broadly used in cosmetics, Vaseline and glycerin. We demonstrate that the
amount and location of the moisturizers on human skin can now be easily
detected with UV light source. The absolute radiance measurements show a good
correlation with amount of the moisturizers measured by
collecting-by-scratching tests. The presented method can be effectively used
for a fast non-contact detection of location of the skin-care products, its spread
with time, and absorption by skin.
5-10
Colloidal Nanoparticles in
Consumer Products
Krassimir P. Velikov, Tim Foster, Clive Marshman, Eddie Pelan, Food Research Center, Unilever Research & Development, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands, Krassimir.Velikov@Unilever.com
Colloidal
nanoparticles have found many applications in a broad range of technologies and
in the processing of various materials including foods, cosmetics, paints, and
drug delivery systems. In addition, due to their ability to assemble in bulk
and at interfaces they are widely used as a precursor for advanced
nanostructured materials. In consumer products, colloidal nanoparticles are
either naturally present, formed during the processing, or intentionally added
to tailor certain functional properties of the product. In this presentation,
we will discuss the fundamental approaches to control product functionality
like composition, structure, stability, taste and appearance.
6-1
Polymerized Colloidal
Array Photonic Crystal Chemical Sensors
We have developed a novel class of smart optical materials based on soft materials which are responsive to their environment and which can be actuated chemically or photonically. Highly charged, monodisperse colloidal particles will self assemble in water into crystalline colloidal arrays (CCA), which are either body centered or face centered cubic structures. We have developed smart materials from these self-assembled structures, which utilize the highly efficient Bragg diffraction of light from the CCA periodicity. We polymerized these CCA into acrylamide hydrogels. These CCA-embedded hydrogels show the rich volume phase transition phenomena characteristic of these soft materials. These materials act as frequency agile optical filters. We have functionalized these hydrogels with dyes and photochromic molecules, as well as with molecular recognition agents which cause the hydrogel to change volume in response to either photons, or the presence of specific analytes (eg Pb2+, glucose etc). The resulting volume changes alter the array spacing, which causes the diffracted light wavelength to shift, or causes the diffraction efficiency to change. We will discuss the volume phase transition properties of these arrays and also describe the use of these arrays and also describe the use of these arrays as chemical sensors, novel ns optical switching materials as well as optical memory devices.
6-2
Lyotropic Liquid Crystal Templating of Mesoporous Hollow Spheres: A
New Route to Materials for Controlled Release and Encapsulation?
A. Wolosiuk, P. V. BRAUN, Department of Materials Science and Engineering, Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, pbraun@uiuc.edu
Hollow spheres (500 nm diameter) containing a periodic array of 3 nm pores in a hexagonal lattice in the shell wall were created through liquid crystal templating of the growth of ZnS on polystyrene and silica colloidal particles, followed by dissolution of the colloidal particle. The colloidal particles were first dispersed into a lyotropic liquid crystal formed from a nonionic surfactant and water that also contained thioacetemide and zinc acetate. Then, ZnS, formed from the reaction of thioacetemide and zinc acetate, heterogeneously deposited in a superlattice structure as defined by the liquid crystal on the surface of the colloidal particles. The mineralized colloidal particles were separated from the liquid crystal, and the colloidal particles were dissolved, resulting in a hollow sphere perforated with a periodic array of nanoholes. Both silica and polystyrene colloidal particles could be used as templates; silica particles are removed with fluoride ions, while polystyrene particles are removed with organic solvents. Initial experiments which demonstrate the sequestering of macromolecules within the mesoporous hollow spheres while permitting the passage of smaller molecules will be described.
6-3
Rippled Metal
Nanoparticles: A New Protein Resistant Material
ALICIA JACKSON, Francesco Stellacci, Department of Materials Science
and Engineering, MIT,
Here we present a new family of mixed ligand nanoparticles that shows sub-nanometer patterns (e.g. ridges) on their ligand shell. This unique sub-nano-structuring of their ligand shell provides new properties to the particles. In particular, we focus on silver and gold particles that have ridges composed of hydrophilic valleys and hydrophobic peaks. We will show the ability to control the supramolecular ordering of the ligands on the nanoparticle surfaces. Indeed, by systematically varying the mixture of ligands introduced during nanoparticle synthesis, one can control the resulting surface properties of the nanoparticles. Scanning tunneling microscopy images show ridges 3 Å deep and 6 Å wide on the ligand shell of nanoparticles. Control of both these parameters is provided by the choice of the ligands and of their molar ratio respectively. We also demonstrate that the nanoparticle ligands interact so as to align the stripes of neighboring nanoparticles over large length scales. The synthetic mechanism that leads to the formation of this supramolecular ordering will be discussed. These particles show unique and unexpected wettability, solubility, self-assembly and surface chemistry properties. They, also, show a remarkable resistance to protein nonspecific adsorption, one order of magnitude better than state of the art antifouling materials.
6-4
Fluorescent Nanoparticles in Cellular Differentiation
B. DUBERTRET, CNRS, Laboratoire d’Optique
Physique, ESPCI 10 rue Vauquelin, 75005, Paris, France, benoit.dubertret@espci.fr
We encapsulate individual nanocrystals in phospholipid block-copolymer micelles, and demonstrate both in vitro and in vivo imaging. When conjugated to DNA, the nanocrystal-micelles act as in vitro fluorescent probes to hybridize to specific complementary sequences. More importantly, when injected into Xenopus embryos, the nanocrystal-micelles are stable, non-toxic (<5x109 nanocrystals per cell), cell autonomous, and slow to photobleach. Nanocrystal fluorescence can be followed to the tadpole stage, allowing lineage tracing experiments in embryogenesis. We show that nanocrytal size is a crucial parameter that determines the particle localization during the embryo development.
6-5
Nano-Pumps in Hydrogels: Electroosmotic Mass Transport Control
Marvi A. Matos1, Robert D. Tilton1,2, Lee
R. White1, Center for Complex Fluids Engineering, 1Department of Chemical Engineering, 2Department of
Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, mmatos@andrew.cmu.edu
Gels are a common matrix for biosensors. Hindered transport through the polymeric matrix slows down the response rate in such sensors. As the number of diagnostic and analytical applications for gel-based sensor devices increases, so does the necessity of new pumping mechanisms for faster response. The network and mechanical properties of the gel make mechanical mixing schemes inappropriate. We are investigating novel internal pumping strategies based on electrically driven convection as a way to accelerate mass transfer in polyacrylamide gels. The gels are doped with charged silica colloids that drive local electroosmotic flow in response to externally applied electric fields. The uniformity of the particle dispersion throughout the gels is investigated by small angle neutron scattering. We use fluorescence spectroscopy to measure the mass transport of a fluorescent dye, amino-methylcoumarin, in these gels as a function of particle loading and applied field strength. Studies of silica particles with different sizes show that the electroosmotic mass transport enhancement is strongest when using nanoscale silica particles. We are also investigating the effects of electrolyte concentration on the electroosmotic pumping effect.
6-6
Highly Luminescent Nanoparticles for in Vivo Cancer
Imaging and Detection
Wei Chen, Nomadics Inc., 1024 South Innovation Way , Stillwater , OK
Deep-tissue optical imaging is of particular interest, as the equipment
costs are lower than for competing technologies such as magnetic resonance imaging. For this purpose, the development of
novel contrast agents with near-infrared (NIR) fluorescence is especially
important. We report on the use of
NIR and upconversion semiconductor nanoparticles in deep-tissue in vivo
optical imaging. Semiconductor nanocrystals of CdMnTe/Hg were grown in aqueous
solution and then coated with bovine serum albumin (BSA). The nanocrystals were approximately 5 nm
in diameter and have a broad fluorescence peak in the NIR (770nm). Nanocrystals were injected either subcutaneously
or intravenously into athymic mice and then excited with a spatially broad 633
nm source; the resulting fluorescence was captured with a sensitive CCD
camera. We have demonstrated that
the nanocrystals are a useful angiographic contrast agent for vessels
surrounding and penetrating a murine squamous cell carcinoma in a C3H mouse.
Preliminary assessment of the depth of penetration for excitation and emission
was done by imaging a beating mouse heart, both through an intact thorax and
after a thoracotomy. The temporal
resolution associated with imaging the nanocrystals in circulation has been
addressed, and the blood clearance for this contrast agent has also been
measured. There was no significant
photobleaching or degradation of the nanocrystals after an hour of continuous
excitation. The stability of the
nanocrystals together with the time resolution of the optical detection makes
them particularly attractive candidates for pharmacokinetic imaging studies.
The author would like to thank the supports by NIH and Army Medical for grants
and his NIH partners for collaborations.
6-7
Harnessing Nanoparticles
for Glycobiology
THANH K. T. NGUYEN, David G. Fernig, Centre for Nanoscale Sciences, School of Biological Sciences and Department of Chemistry, University of Liverpool, BioSciences Building, Crown Street, Liverpool, United Kingdom, ntkthanh@liv.ac.uk
In this paper, we would like to present a new method to stabilise and functionalise nanomaterials (Au nanoparticles, semiconductor Q-dots, and magnetic nanoparticles Co using a “peptide toolbox”. The peptides play three important roles during synthesis: (i) control of the nucleation and growth processes to produce the desired morphology and internal structure; (ii) protect the nanoparticle/cluster cores from chemical degradation and maintain their physical stability (dispersion) in aqueous and biological environments; (iii) to allow functionalisation. For ligand exchange only (ii) and (iii) apply. The ability to tune the properties of the peptides (by varying the length, and sequence of amino acids makes them a unique class of ligands for combinatorial nanomaterial synthesis.
Heparan sulfate proteoglycans (HSPGs), which are strategically located on the surface of mammalian cells, act as regulators of most aspects of cell behaviour and function are involved in the pathology of many disease. The regulatory properties of HSPGs are thought to depend upon the fine structure of the HS glycosaminoglycan chain. Analysis of the structure and function of HS is hampered by the fact that their synthesis is not template driven. There is no amplification step, which would allow analysis of single structures produced by a biologically defined unit such as a cell or group of cells. Consequently, only abundant sources of material representing an average of structures may be analysed.
Nanoparticles offer the possibility of single particle detection that permits the analysis of polysaccharide chains at a hitherto unachievable sensitivity, which will open up new experimental approaches in glycobiology.
6-8
Semiconductor Nanocrystals and Their Practical
Applications
L. BROGAN, Evident Technologies, Inc.
Semiconductor nanocrystals have been the subject of research for decades. Recently, we have witnessed the advent, prototyping and commercialization of quantum dot based products. Since quantum dots represent a tunable band gap semiconductor material, they have inherent advantages over traditional semiconductors with fixed bandgaps. Quantum confinement allows us to tune the electronic structure based on size of the crystal as long as the physical size is less than the exciton Bohr radius. Many people are capitializing on this quantum mechanical feature and fashioning these quantum dots into products from in vivo diagnostics to thermoelectrics, night vision pigments to wear indicators, LEDs to sunscreens. The compelling features of tunable electronic and optical properties along with their colloidally grown form factor makes them an enabling material for many new markets. For diagnostic applications in the life sciences, quantum dots are a natural as they give unlimited emission wavelengths, legendary photostability, broad excitation, and are “relatively” simple in that they are sold as a colloidal suspension. The tunable emission wavelengths allows thing like deep tissue imaging since NIR emission wavelengths are possible, which transport through tissue without scattering. The photostability is called upon in live and fixed cell imaging applications that require extended interrogation under illumination. Broad excitation and emission color variety enable color multiplexing for higher throughput screening. These are no longer research materials since they are commercially available today. The potential for these materials has yet to be fully realized. We are at the headwaters of the development of nanocrystal products.
6-9
Quartz Crystal Microbalance Detection of Peptide Epitope Protected Nanoclusters Using Antibody Recognition
A. E. Gerdon, D. E. Cliffel, D.W. WRIGHT, Department of Chemistry Vanderbilt University, Nashville, TN, david.wright@vanderbilt.edu
A quartz crystal microbalance (QCM) sensor was developed for the quantitative detection of peptide epitope-protected nanoclusters. We have addressed challenges in the area of QCM mass sensing through experimental correlation between damping resistance and frequency change for a reliable mass measurement. Electrode functionalization was optimized with the use of Protein A to immobilize and present polyclonal IgG for antigen binding. This method was developed for the detection of glutathione (antigen) protected clusters of nanometer size with high surface area and thiolate valency. Quantitation of glutathione-nanocluster binding to immobilized polyclonal antibody provides equilibrium constants (Ka = 3.6 + 0.2 x 105 M-1) and kinetic rate constants (kf = 5.4 + 0.7 x 101 M-1s-1 and kr = 1.5 + 0.4 x 10-4 s-1) comparable to literature reports. Additional studies using conformational or linear peptide epitopes from the protective antigen (PA) of B. anthracis presented on the surface of monolayer protected clusters to produce functional nanostructures identified one monoclonal anti-PA antibodies to be specific for the conformational loop structure PA680B. Quantitative studies using a quartz crystal microbalance immunosensor confirmed specificity. These results demonstrate an ability to map monoclonal antibody recognition to specific epitope structures on nanoparticles.
6-10
Tumor-targeted Gadolinium Nanoparticles for Neutron Capture Therapy
and for MRI Contrast Enhancement
MICHAEL JAY, Donghua Zhu, Moses Oyewumi, Russell J. Mumper, Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY, jay@email.uky.edu
Gadolinium can be used in neutron
capture therapy (NCT) in which Gd, if directed to tumors in sufficiently high
concentrations, can capture thermal neutrons resulting in the emission of
tumor-destructive electrons. Gd is
also an effective contrast agent in Magnetic Resonance Imaging. Nanoparticles containing Gd in the core
or bound to the surface were engineered from oil-in-water microemulsion
templates. A folic acid ligand
chemically linked to distearoylphosphatidylethanolamine via a PEG spacer was
used to obtain tumor-targeted folate-coated nanoparticles. These were characterized based on size
distribution, morphology, biocompatibility and tumor cell uptake. The Gd nanoparticles did not aggregate
platelets or activate neutrophils. These nanoparticles were shown to have enhanced retention in the
circulation as well as increased tumor uptake in tumor-bearing athymic mice, thus exhibiting
potential of enhancing the therapeutic success of NCT. Nanoparticles in which Gd was bound to
the surface via DTPA moieties were shown to greatly enhance the contrast of T2-weighted, spin echo images.
These particles have potential for use in MRI blood pool imaging as well as in the imaging of tumors via the Enhanced
Permeation and Retention mechanism.
6-11
Strategies for On-Chip
Assembly of Sensors and Biomaterials from Live Cells
O. D. VELEV, S. Gupta, R. G. Alargova, L. B. Jerrim, P. K. Kilpatrick, Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, odvelev@unity.ncsu.edu
New techniques of assembly of biosensors, nanostructures and nanodevices from live cells will be presented. They are based on principles for nanoparticle assembly into well defined 2D and 3D structures that we have developed earlier. We demonstrate how on-chip dielectrophoresis can be used to co-assemble yeast cells and synthetic micro- and nanoparticles. Depending on the frequency of the field and relative polarizability of the cells and particles, one and two dimensional arrays can be obtained. These arrays can be bound into permanent biocomposites by using molecular recognition. Such cell-nanoparticle chains and membranes can form the basis of sensors, microscopic bioreactors and artificial tissue. We also present a method for assembling and immobilizing large-scale coatings from yeast cells. The coating method is based on convective assembly and deposition in a moving meniscus to make dense two-dimensional arrays. A robust technique for rapid deposition of monolayer cell coatings was designed on the basis of this method. One immediate application of these structures is in biosensors and test beds for toxicity and drug action. The coassembly of live cells and synthetic nanoparticles also yields new biomaterials, in which the functionality of the cells is coupled to the functionality of the nanoparticles.
6-12
Custom BeadChip Technology for Molecular Diagnostics
SUKANTA BANERJEE, BioArray Solutions, Warren , NJ
BioArray Solutions (BAS) has developed unique, proprietary technologies for the rapid and flexible analysis of DNA, proteins and cells on semiconductor chips. Our diagnostic platform combines semiconductor physics, extensive bead chemistry and molecular biology to bring unparalleled flexibility and performance to quantitative DNA, protein and cellular analysis. BAS’ proprietary array manufacturing process includes an evolutionary, two-track manufacturing process that combines wafer-scale assembly with custom bead array production to provide "last-second" customization for maximum flexibility at the lowest possible cost. Thousands of arrays can be produced simultaneously. By arranging large numbers of particles into small areas of the substrate, hundreds to thousands of binding events may be monitored simultaneously. In one standard assay format, a standard CCD camera, in conjunction with an optical microscope, in a single snapshot records 4,000 binding events. With its BeadChipTM assays for genomics and proteomics, BioArray Solutions addresses the challenge of high performance accuracy in multiplexed assays, high patient sample volume and rapid response time.
6-13
Multi-Responsive
Microgels: Morphology Control for Optimized Applications
TODD HOARE, Robert Pelton, Department of Chemical Engineering, McMaster University, Hamilton, ON, Canada, hoaretr@mcmaster.ca; peltonrh@mcmaster.ca
Carboxylic acid-functionalized poly(N-isopropylacrylamide) (PNIPAM) microgels exhibit “smart”, rapid, and reversible responses to changes in temperature, pH and ionic strength. To achieve a targeted set of environmental responses and optimize microgel morphologies for particular applications, one must control not only the bulk content but also the radial and intrachain distributions of functional groups within the microgel matrix, distributions which we have shown to play integral roles in regulating the properties of functionalized microgels. We have developed methods of controlling functional group distributions in carboxylic acid-functionalized PNIPAM-based microgels by tuning the hydrophobicity and copolymerization kinetics of the functional comonomer. The resulting functionalized microgels are extensively characterized, both directly via electron microscopy and indirectly using electrophoresis, titration, calorimetry, light scattering, and rheological techniques. Novel dimensionless plotting strategies allow us to directly compare the microscale and macroscale development of both the thermal and pH-induced transitions, giving insight into both the functional group distributions within the microgels and the underlying mechanisms of microgel swelling. The key influence of the radial and intrachain functional group distributions in the application performance of carboxylic acid-containing microgels is also specifically illustrated by testing the utility of the microgels as drug uptake/delivery vehicles and bioactive molecular conjugation supports.
6-14
Design
of Quantum Dot-Protein Bioconjugates for Use in FRET-Based Assays
A.R. Clapp, I.L. Medintz, E.R. Goldman, H. MATTOUSSI, U.S. Naval Research Laboratory, Division of Optical Sciences and Center for Bio/Molecular Science and Engineering, Washington, DC, hedimat@ccs.nrl.navy.mil
The unique spectroscopic
properties of luminescent quantum dots (QDs), including broad absorption and
size-tunable photoluminescence (PL) spectra ranging from the UV to IR and
exceptional resistance to chemical and photo-degradation, are appealing for use
in developing a variety of bio-inspired applications, ranging from molecular
assays to in vivo cellular imaging. We have developed several
approaches based on non-covalent self-assembly to conjugate biomolecules to
CdSe-ZnS core-shell QDs that were rendered water-soluble using multidentate
surface capping ligands. Antibodies were conjugated to these QDs either
directly or via a bridging adaptor protein. QDs conjugated to proteins
and antibodies prepared using our approaches were found to exhibit high
specificity and stability in solution-based Förster resonance energy transfer
(FRET) assays. In addition, we found that the readily tunable QD emission
permitted effective tuning of the spectral overlap between the QD donor and dye
acceptor, thus allowing excellent control over the FRET efficiency in these
complexes. These findings were further exploited to design FRET-based
nanoscale sensing assemblies for the specific detection of target molecules in
solution. Combined with the advantages of CdSe-ZnS QDs, these hybrid
bioinorganic conjugates represent a very promising tool for use in several
biotechnological applications.
6-15
Up-Converting Phosphorescent Probes for Rapid Diagnostic Assays
SHANG LI, George Giannaras, Ronelito Perez, Mark Fischl, Bonnie
Martinez, Keith Kardos, OraSure Technologies, Inc.,
Recent applications of Up-Converting Phosphor Technology (UPTTM) have demonstrated that up-converting phosphors conjugated to biological-recognizing molecules (such as nucleic acids, peptides, or antibodies) can be used as alternatives to conventional fluorescent probes for high-sensitivity bioassays. In contrast to fluorescent dyes, these phosphorescent probes are excited by infrared lasers and emit intense phosphorescence in the visible range. Because no biological matrix possesses this unusual property, autofluorescence is completely absent in the up-converting phosphorescent assays, which makes UPTTM an ideal choice for detecting biomolecules from complex matrices. A systematic approach for the construction and characterization of Y2O2S up-converting phosphorescent probes for rapid diagnostic assays will be presented. Uniform 200 nm Y2O2S particles are synthesized using the homogenous precipitation method followed by a fluidized bed sulfurization technique. The prepared Y2O2S powders are chemically stable in the dried form, but degrade slowly in common buffers. The surface chemistry of Y2O2S can be controlled by encapsulation of particles with a sol-gel silica coating. Functionalized phosphors particles are made by grafting carboxyl silanes or polyelectrolytes on the silica surface and subsequently characterized using XPS, zeta-potential, and spectroscopic methods. Stability and reproducibility of bioconjugated up-converting phosphorescent probes prepared using carbodiimide chemistry are evaluated in bioassays.
6-16
Block
Ionomer Complexes as Novel Nanomaterials
T.K. BRONICH, A.V. Kabanov, Center for Drug Delivery and Nanomedicine, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE, tbronich@unmc.edu
The block ionomer complexes are spontaneously formed by reacting the
block (or graft) copolymers containing non-ionic and ionic polymeric segments
(“block ionomers”) with oppositely charged species, such as polyions, proteins,
surfactant ions, or metal ions. These complexes belong to the special classes
of nanostructured materials combining the properties of cooperative
polyelectrolyte complexes and amphiphilic block copolymers. These materials
exhibit unique self-assembly behavior: they can spontaneously form either
colloidal dispersions (vesicles, micelles, nanoparticles) or nanocomposite bulk
materials. If the nonionic block in the block ionomer is hydrophilic (e.g.
poly(ethylene oxide)), the resulting complexes are water-dispersed. A variety
of polymer and surfactant components can be used in these composites allowing
adjustment of the materials to respond to environmental changes in broad
ranges, including pH, ionic strength, solvents and temperature variations. If
the nonionic block is hydrophobic (e.g. polystyrene), the self-assembly with
oppositely charged polyions leads to formation of multilayer polyion complex micelles in aqueous
dispersion while interaction with surfactant ions results in formation of block
ionomers complexes dispersed in organic solvents. These
materials are promising in addressing various theoretical and practical problems,
particularly, in pharmaceutics, where block copolymers and polyelectrolyte
complexes are already being intensively investigated as drug and gene delivery
systems.
6-17
Generation of Functionalized Colloidal Gold Nanoparticles Using Bi-Functional Reducing Agents
G. F. PACIOTTI, L.D.
Myer, V. Silin, L. Tamarkin, CytImmune Sciences, Inc. 9640
Our laboratory is using colloidal gold nanoparticles to develop tumor-targeting nanotherapeutics. Our first drug uses thiol groups present on the drug’s key components to bind them to the nanoparticle surface. Yet, we recognize the thiol chemistry alone may limit the types of therapeutics that can be developed on the platform. To address this question we generated functionalized colloidal gold nanoparticles that contain a variety of functional groups present on their surface. Our approach uses bi-functional reducing agents (BFRA) that generate the gold particle, by reducing gold chloride under reflux, and embed/add functional group(s) on the particles’ surface. The BFRAs consist of core polymer containing both free thiol groups and secondary reactive groups. The free thiol groups serve to reduce chloroauric acid into gold nanoparticles, while the secondary reactive groups present on the polymer are used to bind drugs. Two chemically distinct classes of BFRAs were used to manufacture the gold particles. The first type consisted of a 10kD branched-chain polymer of PEG having four thiol groups. The second reducing agent was synthesized on a polylysine core polymer which was thiolated using 2iminothiolane. The particle size, shape, and drug binding characteristics for various preparations are described.
6-18
Integration of
Biocompatible Surface Chemistries in the BARC Biosensor System
S. P. MULVANEY, C. C. Cole, M. Malito, J. C. Rife, C. R. Tamanaha,
L. J. Whitman, Naval Research Laboratory,
We are developing a highly sensitive and selective biosensor system
that uses giant magnetoresistive sensors arrayed in a Bead ARray Counter
(BARC™) microchip to directly detect magnetic microbead labels. The beads are used both to label
biorecognition events and as transduction elements to reduce background through
a patent-pending process known as fluidic force discrimination (FFD). FFD is a controlled bead removal
procedure that leverages the strength of biomolecular recognition against
fluidic forces to selectively remove non-specifically bound bead labels. A number of surface chemistries have
been explored to functionalize the BARC chips, with the best results achieved
on Si3N4 terminated chips. Neutravidin is covalently attached to Si3N4
via glutaraldehyde, and biotinylated capture probes are then employed for
biosensing. Highly sensitive DNA
hybridization assays (10 fM) have been performed and the magnetic sensor signal
confirmed with optical bead counting.
Application of the BARC platform for the multiplexed detection of four
biowarfare agents without PCR, in 30 minutes, and at room temperature, will be
described, as will preliminary results using similar chemistry for sandwich
immunoassays. This work was
supported by ONR, TSWG, and DTRA.
SM, CC, and MM are employees of Nova Research, Inc.,
6-19
Quantification of the
Field Interaction Parameter and the Binding Constants of Several
Antibody-magnetic Nanoparticle Conjugates
J.J. Chalmers, H. Zhang, M. Zborowski, Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, and Department of Biomedical Engineering, The Cleveland Clinic Foundation, Chalmers@chbmeng.ohio-state.edu
It has been previously reported that the magnetophoretic mobility of
labeled cells show a saturation type phenomenon as a function of the
concentration of the free antibody-tag conjugate. Starting with the standard
antibody-antigen relationship, a model was developed which takes into
consideration multi-valence interactions and various attributes of flow
cytometry and cell tracking velocimetry, CTV, measurements to determine both
the apparent dissociation constant and the antibody binding capacity of a
cell. This model, combined with
experimentally obtained data of the field interaction parameter of specific
types of magnetic nanoparticles, was then evaluated on peripheral blood
lymphocytes labeled with anti CD3 antibodies conjugated to
6-20
Preparation
of Organic Nanoparticles Using Microemulsions. – Their Potential Use in Transdermal Delivery
C. Destrée, J. B.NAGY, Laboratoire de RMN, Facultés Universitaires Notre-Dame de la Paix, 61 Rue de Bruxelles, B-5000 Namur, Belgium, Janos.bnagy@fundp.ac.be
Organic
nanoparticles of cholesterol and retinol have been synthesized in various
microemulsions (AOT/heptane/water; CTABr/hexanol/water; Triton X-100/decanol/water)
by direct precipitation of the active principle in the aqueous cores of the
microemulsion. The nanoparticles are observed by transmission electron
microscope using the adsorption of contrasting agents such as iodine vapor,
osmium tetroxide or uranyl acetate. The size of the nanoparticles can be
influenced, in principle, by the concentration of the organic molecules and the
diameter of the water cores which is related to the ratio R=[H2O]/[Surfactant].
The particles remain stable for several months. The average diameter of
cholesterol nanoparticles is comprised between 5.0 and 7.0 nm, while that of
retinol is smaller, being ca. 2.5 nm. The average size of the cholesterol
nanoparticles does not change much either as a function of the ratio R or of the
concentration of cholesterol. The constant size of the nanoparticles can be
explained by the thermodynamic stabilization of a preferential size of the
particles. Different solvents are used to carry the active principle into the
aqueous cores and they do not influence the precipitation reaction in a
significant way.
6-21
Fluorescent Silica Beads
for Detection of Cervical Cancer
,
We present the use of self-assembled fluorescent
silica (glass) beads for detection of cervical cancer. The cells from three
different individuals (3 normal and 3 tumor) were tested for affinity by using
the beads, a few microns glass nanoporous particles which contain fluorescent
dyes sealed inside the pores. Using atomic force microscopy, we studied forces
acting between the silica particles and the cells in-vitro. Using those data,
we developed two different methods for detecting the affinity between silica
and cells in-vitro. In one method we use a simple precipitation of the beads
onto the cells, and with subsequent washing, the unbounded beads are removed.
The second method involves using centrifugation for the removal of the unbounded
beads. Both methods show unambiguous identification between the normal and
tumor cells.
6-22
Fluorescence
Analysis of Polymersome and Filomicelle Delivery
D.E. Discher, F. Ahmed, P. Dalhaimer, Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, discher@seas.upenn.edu
PEG-polyester block copolymers can be made of the right proportion to assemble into controlled release vesicles and cylinder micelles, or polymersomes and 'filomicelles', respectively. Comparisons of these two morphologies, in terms of how they interact with cells and how they behave in vivo, bring new meaning to 'bio-nano'. We make extensive use of fluorescence microscopy to characterize the degradation and release processes as well as cell entry pathways in vitro. We also use such methods in vivo to track their fates, allowing us to identify super-long circulating filomicelles. Emerging tumor studies will be described.
6-23
Superparamagnetic
Nanoparticle-bound Chlorotoxin for Brain Tumor Imaging
Miqin Zhang,
A multifunctional nanoprobe capable of targeting glioma cells, detectable by both magnetic resonance imaging and fluorescence microscopy was developed. The nanoprobe was synthesized by coating iron oxide nanoparticles with covalently-bound bifunctional polyethylene glycol (PEG) which were subsequently functionalized with chlorotoxin, a glioma tumor targeting peptide, and the near infrared fluorescing molecule, Cy5.5. Both MR imaging and fluorescence microscopy showed significantly preferential uptake of the nanoparticle conjugates by glioma cells. Such a nanoprobe can potentially be used to image resections of glioma brain tumors in real time and to correlate preoperative diagnostic images with intraoperative pathology at cellular-level resolution.
6-24
Novel Magnetic Nanosensors
to Probe for Molecular Interactions in High Throughput using NMR and MRI
J. M. PEREZ, L. Josephson, R.Weissleder, MGH-Harvard Medical School, Center for Molecular Imaging Research, 139, 13th Street, 5404, Charlestown MA, jperez@hms.harvard.edu
Designing activatable imaging agents to sense molecular markers and molecular interactions associated with disease would result in the development of more sensitive diagnostic agents and the development of target-specific probes for in vivo molecular imaging applications. Toward this goal, we have developed an assay to sense molecular targets using magnetic nanosensors and nuclear magnetic resonance (NMR) in high-throughput. These magnetic nanosensors consists of biocompatible magnetic nanoparticles capable of detecting a molecular target by changes in the NMR signal of the solution as the nanoparticles self-assemble in the presence of the target. Using four different types of molecular interactions (DNA-DNA, protein-protein, protein-small molecule, and enzymatic reactions) as model systems, we have shown that these magnetic nanosensors can detect these molecular interactions with high sensitivity and selectivity using standard NMR or MRI instrumentation. The target-induced change in NMR signal is detectable in turbid media or whole-cell lysate and is proportional to the amount of target present. The assay is performed in solution, does not require isolation or purification of the samples and could potentially be used for in vivo imaging. We will present data showing the utility of the technique to detect molecular targets related to cancer, atherosclerosis, inflammation and infection. The technology is versatile enough to sense the mRNA, protein and enzymatic activity of a molecular target. Finally, we have been able to detect specific viruses in solution, allowing for sensitive and selective detection of low numbers of viral particles.
6-25
Selectively Moving Biopolymers Through Functionalized Nanotube
Membranes
PUNIT KOHLI1, Charles
R. Martin2, 1Department of Chemistry and Biochemistry,
Southern Illinois University, Carbondale,
IL, 2Department of Chemistry and Center for Research at the
Bio/Nano Interface, University of Florida, Gainesville, FL, pkohli@chem.siu.edu, crmartin@chem.ufl.edu
The ability to regulate transport
across cellular boundaries is essential to the cell’s existence as an open
system. There is a steady traffic
of ions, molecules, polymers and other species across the plasma membrane. For example, sugars, amino acids, and
other nutrients enter the cell; waste products of metabolism leave. The cell takes in oxygen for cellular
respiration and expels carbon dioxide.
It also regulates its concentrations of inorganic ions, such as Na+,
K+, Ca2+, and Cl-, by shuttling them one way
or the other across the plasma membrane.
Mother Nature has created natural channels that are highly selective;
they allow certain molecules and ions to pass more easily than others or they
reject them altogether.
Understanding and mimicking of the transport processes in cells is both
challenging and rewarding from scientific and technological points of
views. We have prepared highly
selective template-synthesized abiotic nanotube membranes that can be used as
model systems for better understanding of transport processes in natural
systems and also mimicking natural ion- and protein-channels. Our nanotubes have diameters of the same
order (1-100 nm) as those found in the natural protein channels. We have designed these nanotube
membranes to selectively recognize and transport nucleic acid oligomers by
modifying the inner surface of nanotubes with complementary nucleic acid
“transporters”. We show that these
membranes can facilitate the transport of the complementary DNA strands
relative to DNA strands that are not complementary to the transporters. Under optimum conditions, single-base
mismatch transport selectivity is obtained. The second part of my talk consists of
fabrication of single-conical gold nanotube membranes functionalized with DNA
that mimics voltage-gated potassium channel. These DNA-immobilized single-conical
nanotubes exhibit “on-off” characteristics with external applied
potential. These bio-functionalized
nanotube membranes may find many potential applications in bioseparations, bio-
and chemical-sensing, drug-detoxifications, and other biomedical and
biotechnological applications.
6-26
Functionalizing FePt Nanoparticle
Surfaces with Silane Chemistry
H. G. BAGARIA, D.
The preparation of monodisperse FePt nanoparticles was first reported by Sun et al. Though the initial motivation for developing these particles was for ultra high density hard drives, these have also found their way into biological applications owing to their high magnetization values. There are reports in the literature where FePt has been used for cell separation and protein tagging applications. The FePt prepared by the procedure developed by Sun et al. uses oleic acid and oleyl amine ligands for stabilizing FePt in non-polar solvents. To make these particles suitable for biological applications 1) they should be made hydrophilic and 2) they should have functional groups on their surface to bind to biological entities. Towards this aim, our XPS studies consistently show that a layer of iron oxide exists on the FePt nanoparticles. This motivated us to study alkoxy silane based ligands as a means to introduce the desired functionality. Studies with magnetite nanoparticles have shown the affinity of alkoxysilane ligands for the iron oxide surface. The present work studies the binding of various silanes on the FePt surface by conducting FTIR and XPS studies.
6-27
Biomaterials from Nanocolloids: Applications for Neurons
NICHOLAS A. KOTOV, Departments of Chemical Engineering, Biomedical Engineering and Materials Science, University of Michigan, Ann Arbor, MI, kotov@umich.edu
The presentation will review the recent advances in the use of nanocolloids to add new functionalities to biomaterials. Layer-by-layer assembly (LBL) affords preparation of ordered layered structures from virtually unlimited palette of nanocolloids. Various functionalities of nanocolloids afford preparation of targeted composites for evaluation of different neuronal functions. Four examples will be discussed. Multilayers from TiO2 nanoshells afford selective determination of neurotransmitters due to ion-sieving effect. Strong, flexible and electroconductive implants can be made from SWNT LBL multilayers. Stringent testing of biocompatibility of these composites was undertaken and it was demonstrated that they are suitable for long-term contacts with tissues. Stimulations of neurons through these films was demonstrated. Nanoparticles with silver nanocolloids can be used to suppress inflammation processes due to infection – one of the most important problems with implantable devices. Photoactive multilayer from semiconductor particles were used to NG108*15 neuron precursor cells on them. It was found that light adsorbed in the nanoparticle layers results in the electrical excitation of the neurons making this system a functional analog of retina. Assemblies of clay-polymer systems demonstrated exceptional toughness similar to that observed in bones. Layered nanocomposites represent an exceptionally versatile tool for production of biomaterials with novel applications derived from unique properties of nanostructured matter.
6-28
Strategies for the Design and Readout of Ultrahigh Density Immunodiagnostic
Platforms
H.-Y. Park, J. Driskell, K. Kwarta, B. Yakes, J. Uhlenkamp, R. Millen, N. Pekas, J. Nordling, R. J. Lipert, M. D. PORTER, Departments of Chemistry and Chemical Engineering, Institute for Combinatorial Discovery, and Ames Laboratory-USDOE, Iowa State University, Ames IA, mporter@porter1.ameslab.gov
The drive for early disease detection, the growing threat of bioterrorism, and a vast range of challenges more generally in biotechnology has markedly amplified the demand for ultrasensitive, high-speed diagnostic tests. This presentation describes efforts to develop platforms and readout methodologies that potentially address demands in this arena through a coupling of nanometric labeling with surface enhanced Raman spectroscopic, micromagnetic, and scanning probe microscopic and readout concepts. Strategies will be described for both the fabrication and read-out of chip-scale platforms that can be used with each novel readout modality. Examples will focus on the use of protein arrays as platforms targeted for immunoassays in early disease diagnosis and the rapid, ultralow level detection of cancer markers and viral pathogens. Each example will also discuss challenges related to sensitivity and nonspecific adsorption and to fluid manipulation at micrometer length scales.
6-29
Design of Multidentate Surface Ligands
for Biocompatible Quantum Dots
H.T. Uyeda, K.M. Hanif, A.R. CLAPP, H. Mattoussi, Division of Optical Sciences, Code 5611, U.S. Naval Research Laboratory, Washington, DC, hedimat@ccs.nrl.navy.mil
The utility of stable water-soluble luminescent quantum dots (QDs) has been demonstrated in biosensing and cellular imaging applications. However, due to the nature of the inorganic QD core, the native surface properties limit their compatibility with aqueous environments. We have designed a series of organic poly-ethylene glycol based surface capping ligands that allow for QD manipulation in aqueous media over a wide pH range. We utilized readily available thioctic acid and various oligo- and poly-ethylene glycols (PEG) in simple esterification schemes, followed by reduction of the dithiolane to produce multi-gram quantities of capping ligand (DHLA-PEG). This strategy was further applied to prepare biotin-terminated DHLA-PEG capping ligands. To form water-soluble QD assemblies, native trioctylphosphine and trioctylphosphine oxide (TOP/TOPO) capped nanocrystals were mixed with an excess of the desired surface ligand and incubated for a few hours to displace the TOP/TOPO molecules. This permitted us to obtain homogeneous dispersions of QDs that were stable over wide pH ranges and extended periods of time. We also prepared QDs having mixed surfaces of dihydrolipoic acid (DHLA) and DHLA-PEG (or DHLA-PEG-biotin). This design and conjugation strategy may facilitate the development of a new generation of QD-bioconjugates for use in a variety of biological applications.
6-30
Nucleic Acid Sequence and
Protein Identification using Gold Nanoparticle Probes and the VerigeneTM
System
J. J. STORHOFF, Y. P. Bao, S. S. Marla, M. Huber, T-F Wei, A.D. Lucas, S. Hagenow, V. Garimella, W. Buckingham, T. Patno, W. Cork and U.R. Müller, Nanosphere, Inc., Department of Applied Science, 4088 Commercial Avenue, Northbrook, IL, jstorhoff@nanosphere.us
Nucleic acid sequence identification is widely used for detection of
viruses, bacterial pathogens, and genetic diseas
6-31
Surface Functionalization of
Semiconductor Quantum Dots for Applications in Biological Sensing
MEGAN A. HAHN, Todd D. Krauss1, Joel S. Tabb2, 1Department of Chemistry, University of Rochester, Rochester, NY, 2Agave BioSystems, Ithaca, NY, mahn@mail.rochester.edu
Having diameters of only a few nanometers, colloidal CdSe semiconductor quantum dots (QDs) are highly emissive, spherical, inorganic particles that exhibit size-tunable physical properties due to the effects of quantum confinement. Typically, these materials are synthesized with relatively inert hydrocarbon surface-groups that must first be modified if they are to be compatible with biological systems. To that end, a variety of strategies have been established to make these hydrophobic surfaces of CdSe QDs applicable for use in biology. We have demonstrated that CdSe/ZnS core/shell QDs functionalized with streptavidin bind specifically to pathogenic Escherichia coli O157:H7 cells labeled with biotinylated antibodies. Using fluorescence microscopy of individual bacterial cells and standard fluorimetry of bacterial cell solutions, we will also present results comparing E. coli O157:H7 cells labeled with QDs to cells similarly labeled with a standard dye, fluorescein isothiocyanate (FITC). The particular biochemical interactions and surface functionalization incorporated in these methods can easily be generalized to allow for the rapid and selective detection of other common pathogens.
6-32
Combining Gold Nanoparticles
with the Quartz Crystal Microbalance to Improve the Sensitivity of DNA Detection
T. Liu, J. A. Tang, L. Jiang, Key Laboratory of Colloid and Interface, Center of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Zhong Guan Cun, Beijing, ROC, taoliu@iccas.ac.cn, leotao1974@yahoo.com
Investigation indicates that the appearance of the malignant tumor is highly correlative with the DNA mutation. It has become an important topic of the cancer study to detect the gene mutation and look for the relation between mutation and pathological change at the molecular level. Rapid detection for trace gene mutation can provide basic data for diagnose disease. Therefore, looking for a rapid and simple method used for detecting trace mutation is important and pressing. QCM is a simple, rapid and real-time measurement of DNA binding and hybridization at the sub-nanogram level. The nanogold particle has many special properties, for example high density, simple operation, and easy size-controlled. Combining these two techniques, i. e., nanoparticle modification of QCM surface and the application of gold narnoparticle amplifier, we improved the detection limit of DNA. This method makes it possible to detect single base mutation less than 10-16 mol / L.
6-33
Effects of Surfactants and Surface Charge on the Performance
of Latex Immunoagglutination Assays in Vitro and in a Microfluidic Device
LONNIE J. LUCAS, Jin Hee Han, Jeong-Yeol Yoon, Department of Agricultural and Biosystems Engineering, The University of Arizona, Tucson, AZ, jyyoon@email.arizona.edu
The latex immunoagglutination assay is a relatively easy, rapid technique for detecting biomolecules. However, improvements in reliability and sensitivity are still required. The main issues involve colloidal stability of the antibody-latex complex and non-specific binding of antigens. To address these issues, we investigated the influence of surfactants and surface charge of particles toward its performance. To examine the effects of surfactants, we used the ionic SDS and the non-ionic Tween 80 with submicron polystyrene (PS) particles. To examine the effects of surface charge we compared plain PS with highly carboxylated PS. All latex particles were conjugated with anti-mouse IgG (developed in goat). The antigen was mouse IgG (positive control) or rabbit IgG (negative control). Immunoagglutination was monitored turbidimetrically using a spectrophotometer. We found that plain PS with either no surfactant or ionic SDS produced many false-positives and false-negatives. Results were substantially improved when non-ionic Tween 80 was mixed with plain PS. When carboxylated PS was used with no surfactant, the results were also very accurate and reliable. We also demonstrated these effects in a Y-channel microfluidic device. Immunoagglutination occurred faster and in greater quantity near the Y-junction, when Tween 80 surfactant was used rather than no surfactant.
7-01
Synthesis and Processing
of Nanoparticles for Bioengineering Applications
JACKIE Y.YING, Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, #04-01,
Singapore, jyying@ibn.a-star.edu.sg
Nanostructured materials are of
interest for a variety of applications.
This talk describes the synthesis and properties of nanostructured
materials that are made up of crystallites or particles of ~10 nm. They may be generated by various
physical and chemical approaches with ultrahigh surface reactivity. Through controlled synthesis in reverse
microemulsions, my laboratory has achieved polymeric nanoparticles for the
glucose-sensitive delivery of insulin.
These stimuli-responsive materials allow for the appropriate insulin
delivery to diabetic patients only when their blood sugar levels are high,
without the need for external blood sugar monitoring. We have also developed apatite-polymer
nanocomposite particles for the sustained, zero-order delivery of protein
therapeutics. By adsorbing valuable
bone morphogenetic proteins on carbonated apatite nanocrystals that were then
encapsulated within biodegradable polymeric microparticles, we are able to
achieve controlled release of this growth factor for the bone healing process
over an extended period of time.
Lastly, we have generated fluorescent semiconductor quantum dots for bioimaging and biolabeling applications. These nanoparticles were surface modified to provide for high colloidal stability, efficient fluorescence, low cytotoxicity and excellent water solubility. They were biocompatible and biofunctionalized for target-specific recognition, and could be used for biosensing and targeted drug delivery applications.
7-02
Nanoparticles as Detection
Labels for Bioaffinity Assays in Point of Care Testing
MICHAEL PUGIA, Bayer HealthCare LLC, Diagnostics Division,
Nano-particles are commonly used in Point-of-Care Testing (POCT) as
detection labels. These small low
cost clinical analyzers use particles as detection labels.Optical signals
generated by latex agglutination, colored latex particles, and colloidal gold
commonly provide little interference and picomolar detection limits (10-12
mol/L). Miniaturization to nL
specimen volumes and lower analyte concentrations resulting from proteomics
discoveries are challenging these limits. Flourimetric, luminescence and
enzyme-linked particles offer more sensitivity at the expense of
complexity. Simple nano-particle
electrochemical methods have recently shown sensitivity to single molecule
limits.
Nano-particles also impact recognition and separation steps in POCT. Immunological recognition of
antigens with antibodies greatly enabled POCT. Particles attached to antibodies are separated when antibodies reacts to antigens
captured on solid phases. Particle variations impact the ability of recognition
components to separate after binding the target substance. The CLINITEK Status analyzer
demonstrates the impact of particles on chromatography separations using incubation, capture and separation zones.
Immunoassay of a new maker for inflammation demonstrates the complexity of
recognition components. Another
fluidic approach is shown in the HbA1c immunoassay on the DCA 2000+
analyzer, while examples of micro-fluidic chips show the impact of future
miniaturized on bio-affinity separations in POCT.
7-03
Cellular Probes Using Amplified Light Scattering
O. Siiman, S. LEDIS Advanced Technology Center, Beckman Coulter,
Inc.,
Silver/gold nanoparticle-aminodextran
(Amdex)-coated polystyrene (PS) beads offer their use either as elastic or
inelastic light scattering probes for diagnostic biological assays. Amplified Mie scattering from CD4/CD8
antibody conjugates of these beads has allowed their use in enumerating the
targeted white blood cells in whole blood by flow cytometry. Recent observations of SERS
(surface-enhanced Raman scattering) from the same beads hold the promise of
using Raman in similar diagnostic tests.
Citrate/Amdex SERS bands were detected from beads either as singlets or
small clusters. However, citrate on
individual silver nanoparticles or on gold nanoparticle-Amdex-PS beads were not
detected with 633nm excitation.
SERS of dyes such as rhodamine 6G were readily observed on individual
silver particles or on gold beads.
Three distinct modes of citrate/aminodextran binding to the silver nanoparticle-Amdex-PS beads were characterized: (1) exchangeable citrate bound through one or more carboxylate group(s)---citrate could be washed away with H2O or D2O; displaced by successively greater concentrations of R6G; or squeezed out mechanically by applying the pressure of a second coverslip on top of a droplet of bead suspension; (2) non-exchangeable citrate/Amdex bound via an alkoxide of a deprotonated alcohol of citrate/Amdex; (3) non-exchangeable citrate/Amdex bound via carboxylate group(s) but with H/D exchangeable alcohol hydrogen atom. The 3 modes of binding provide flexibility in selecting intrinsic, fixed SERS probes as well as the opportunity to add selected, variable probes to the beads for multiple diagnostic targets. Such probes could be used in micro-Raman imaging and, potentially, in a Raman-activated flow cytometer.
7-04
Determination of
Dissolution Rates of Colloidal Dispersion Prepared From Poorly Water Soluble
Drugs Using a Light Scattering Technique
N. P. RYDE, J. D. Pruitt, Elan NanoSystems,
Classic theory predicts that the diffusion limited rate of dissolution of fine particles increases as the particle size becomes smaller. This has been demonstrated in numerous pharmaceutical formulations incorporating NanoCrystal technology. The threshold where the rate limiting transport step changes from dissolution limited to permeation limited oral absorption defines a size below which no further kinetic benefits to absorption are theoretically observed. Pharmacokinetic results suggest a smaller particle size threshold than classic theory (Noyes-Whitney).
A light scattering method was used to determine the in-vitro rate of dissolution for drug dispersions in the absence of solubilizing agents. The experimental results were compared with two different theories, a classic Noyes-Whitney and a modified Noyes-Whitney type equation constrained by a surface mass transfer rate. The new theory treats the surface mass transfer step and diffusion step as two consecutive reactions. The overall dependence on particle size is 1/r for very small particles and 1/r 2 for larger particles (both limits assuming a time dependent boundary layer h = r). Experimental results revealed dissolution rates much smaller than ones predicted from classic theory. The corresponding surface mass transfer coefficient could be extracted from such experiments.
7-05
PFG-NMR Investigation of Liposome Systems Containing Hydrotrope
FADWA ODEH, Nicole Heldt, Michele Gauger, Gregory Slack§,
Yuzhuo Li*, Department of Chemistry,
Particle size is crucially important in
determining the usefulness of a liposome system. This is particularly true for drug
delivery applications. Until now, the particle size of a liposome is typically
determined using a light scattering method. Although the NMR pulsed field gradient
(PFG) experiments are known to yield self-diffusion coefficient for micelles
and other particulate matters, the application of this technique to vesicle
systems has been limited due to the rigid nature of the lipid bilayer which
usually does not give well-defined NMR signals for PFG experiments. This study shows that the polyethylene
oxide chains on a pegylated lipid could serve as an excellent tracer to measure
the self-diffusion coefficient via PFG method. In addition, liposomes containing a
hydrotrope also give adequate signal from the lipid for PFG experiments due to
the increased flexibility of the lipid molecules. In addition to particle size,
PFG-NMR is also used to determine the extent of association of a hydrotrope
with the liposome bilayer.
7-06
Fabrication of
Supraparticles, Janus Microparticles and Microlens Arrays by a Gel Trapping
Technique
VESSELIN N. PAUNOV, Olivier J. Cayre, Physical Chemistry Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull, United Kingdom, V.N.Paunov@hull.ac.uk
Particles with asymmetric shapes that can be used to make crystals with novel optical properties have attracted much attention in recent years. We have shown that the Gel Trapping Technique (GTT) can be used to asymmetrically coat colloidal monolayers creating so-called 'Janus' particles, after the two-faced Roman god of doors. Partially embedded monolayers of monodisperse polystyrene microparticles in polydimethylsiloxane (PDMS) were used to coat the exposed particle surface with gold, resulting in particles with two 'faces'. The technique is relatively simple and could easily be used to make a variety of Janus particles. Monodisperse polystyrene microparticles are spread at a water-oil interface and super long range repulsion between particles adsorbed at the interface leads to a near perfect hexagonal lattice. The water contains the gelling polysaccharide gellan which, on cooling, forms a gel that traps the monolayer and the oil layer may then be removed without disturbing the particles. Pouring liquid PDMS over the gel followed by curing leads to the formation of a partially embedded monolayer trapped within the PDMS resin which can be peeled away from the gel. To make the Janus particles the trapped polystyrene particles were 'half-coated' with gold. Use of particles of different contact angles allows the creation of monolayers with varying degrees of entrapment of the polystyrene particles within the gel and thus to different degrees of coverage on their surface. At certain conditions we have successfully molded the particle monolayer together with its gelled meniscus around the particles which produced 'flying saucer particles' where the polystyrene particles are surrounded by a ring of gellan.
Stretching the PDMS releases the trapped particles and the PDMS films produced, with an ordered array of microholes, could have interesting potential applications as filters or antireflective coatings. By further replicating the microhole array with a photopolymer we produced hexagonally ordered microlens arrays where the lattice constant is fixed by the amount of particles spread at the initial liquid surface.
We also used the same Gel Trapping Technique as a novel method for determining the contact angle of particles adsorbed at air-water and oil-water interfaces. The trapped particles have been imaged on the surface of the PDMS replica with SEM. The particles position with respect to the air-water interface or the oil-water interface has been determined from the SEM images of the PDMS replica which gives information for the particle contact angle at the liquid interface. Particle samples of different size and surface chemistry have been examined. We present results for the particles contact angles at air-water and decane-water interface obtained for sulfate latex particles, hydrophobized silica particles, gold particles and polymer microrods.
7-07
Bone Tissue Engineering:
Towards a Better Understanding of Interfacial Biology
D. LICKORISH, Bone Interface Group, Institute for Biomaterials and Biomedical Engineering, University of Toronto, 170 College Street, Toronto, ON, Canada, d.lickorish@utoronto.ca
Approximately 1 million bone grafts are performed annually in the
7-08
Surface Modification of Mineral Fillers for Dental Composites and
Acrylic Bone Cement
O.SHAFRANSKA1,
A.Kokott1, V.Tokarev2, S.Voronov, G.Ziegler1, 1Friedrich-Baur
Research Institute for Biomaterials, Bayreuth University,
Ludwig-Thoma-Str.,36c, 95447, Bayreuth, Germany, 2National
University “Lviv Polytechnic”, Lviv, Ukraine, olena.shafranska@fbi-biomaterialien.de
The surface modification of mineral fillers for acrylic composites is very promising in bone cement and dental applications. Using surface modified mineral fillers, such as silica and zirconia, in polymer composite materials allowed us to improve substantially the filler – matrix adhesion and the mechanical properties of the composite. In the present work the surface of the mineral filler was modified by adsorption of peroxide copolymer (5-methyl-5-tert-butylperoxy-2-hexen-3-in and maleic anhydride) as well as by the covalent immobilization of methacryloxy- and styryl groups due to interaction with styrylethyl-trimethoxysilane and methacryloxypropyl trimethoxysilane. The peroxide groups were used to initiate the graft polymerization of acrylic monomers. Methacryloxy- and styryl groups interacted with (macro)radicals and formed the covalently attached polymer layers.
The
efficiency of the grafting was studied on the model smooth SiO2
substrate. The amount of the grafted polymer layers was measured by
ellipsometry. We found that the most efficient grafting was approached for the
poly(methyl methacrylate) on the surface modified by the
7-09
Amphiphilic Core-Shell
Nanoparticles with Poly(ethylenimine) Shells as Potential Gene Delivery Carriers
Junmin Zhu,1 Angie Tang, 1 Lai Pang
Law,1 Min Feng1, Kin Man Ho1, Daniel K. L. Lee1,
Frank W. Harris,2 PEI LI, Department of Applied Biology and
Chemical Technology, and Open Laboratory of Chirotechnology of the Institute of
Molecular Technology for Drug Discovery and Synthesis, The Hong Kong Polytechnic University,
Hung Hom, Kowloon, P. R. China, 2Maurice
Morton Institute of Polymer Science, University of Akron, Akron, OH, bcpeili@polyu.edu.hk
Spherical, well-defined core-shell nanoparticles that
consist of poly(methyl methacrylate) (PMMA) cores and branched
poly(ethylenimine) shells (
7-10
Microencapsulation of
Pharmaceuticals into Biodegradable Colloids Using Supercritical Carbon Dioxide
H. Liu, N. Finn, M.Z.YATES, Department of Chemical Engineering and
Laboratory for Laser Energetics, University of Rochester, Rochester, NY, myates@che.rochester.edu
The microencapsulation of pharmaceuticals into biodegradable polymer colloids can be utilized for controlled, extended, and targeted drug delivery. We have developed a solvent-free alternative microencapsulation process that utilizes liquid or supercritical carbon dioxide in place of organic solvents. Here we demonstrate that compressed carbon dioxide may be used to facilitate the transport of pharmaceuticals into aqueous biodegradable polymer colloids. The “nano-precipitation” method was used to form stable aqueous colloids of several types of biodegradable polymers including poly(lactic acid), poly(lactide-co-glycolide), and poly(lactic acid)-block-poly(ethylene glycol). In all cases, particle formation conditions yield particles less than 200 nm in diameter. Liquid or supercritical carbon dioxide was emulsified into the aqueous biodegradable latex in the presence of a lipophillic drug such as indomethacin and progesterone. The carbon dioxide plasticizes the polymers and greatly enhances the transport of drug into the particles. The carbon dioxide process has also been coupled with traditional microencapsulation approaches to minimize solvent usage and to extract residual solvent from polymers.
7-11
Development of a
Three-Dimensional Magnetic Navigation and Magnetically Targeted Drug Delivery
System
S.TAKEDA, Fumihito Mishima, Shigehiro Nishijima, Department of
Sustainable Energy and Environmental Engineering, Graduate School of
Engineering, Osaka University, Japan, stakeda@nucl.eng.osaka-u.ac.jp
One of the key problems associated with drug administration is the difficulty to target specific areas or sites in the body, like cancerous tumors. Typically in these cases, exceedingly large doses of a drug are needed to ensure that some of the drug reaches a specific site, which unavoidably impose substantial toxic side effects at non-targeted organs. In the present study, development of a three dimensional magnetic navigation and magnetically targeted drug delivery system was tried in order to deliver the drug to target specific areas in the body by utilizing magnetic particles and strong magnet. Earnshaw’s theorem states that there is no stable and static configuration of levitating ferromagnetic particle by a combination of a fixed magnetic field and gravitational force. However, the magnetic particle could be levitated in a limited area using by the feedback system. In this paper, designing of the electromagnet was tried to control the movement of particles through the experimental and the computer simulation. The surface modification of the magnetic particles was also discussed in order to control the interaction between the particles and wall of the blood cell.
7-12
Reversible Assembly/Disassembly between Two Different Micelle
Morphologies Comprised of Cyclodextrin and Ferrocene/Ferrocenium Derivatized
Surfactants
Kejun Cheng,YanMei Lan, YAN-YEUNG LUK, Department of
Chemistry; Department of Biomedical & Chemical Engineering, Syracuse
University, Syracuse, NY, yluk@syr.edu
We report the reversible switching between two different micelle morphologies via the disassembly and re-assembly of redox-active surfactants by electrochemical means. The redox-active surfactant is comprised of an aliphatic chain tethered to a ferrocene group covalently caged in the annular void of beta-cyclodextrin (bCD). While beta-cyclodextrin by itself has a water solubility too low for consideration as a hydrophilic head group, our covalent modification renders this molecule amphiphilic, and thus surface active. Using bCD as the hydrophilic head group, this surfactant is bio-friendly in that protein denaturation is minimal or non-existent. Employing a wide range of characterization techniques such as 2-dimensional NMR spectroscopy, circular dichroism and electrochemistry, we demonstrated that accompanying the oxidation of ferrocene to ferrocenium, the surfactant undergoes a large conformational change that results in the disassembly of the micelle formed and re-assembly of a new micelle morphology. We will discuss/present its potential applications in sequestering membrane proteins and controlled drug release.
7-13
Smart Polymer Core-Shell Nanoparticles for Targeted Drug Delivery
Y. Y. YANG, S. Q. Liu, L. H. Liu, R.
Powell, Y. WangInstitute
of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore, yyyang@ibn.a-star.edu.sg
Drug delivery is as important as the development of new drug entities. The main goal of drug delivery is to transport drugs to diseased sites using a therapeutic dosage. A number of nanocarriers have been proposed based on natural and synthetic materials to achieve such a goal. However, the method of delivering drugs to specific cells and cell compartments remains a challenge. The aim of our study is to develop polymer core-shell nanoparticles for transporting drugs/genes to specific tissues, thereby alleviating or eliminating the side effects associated with the use of conventional delivery systems and improving the efficacy of drug or gene therapy. In this talk, pH-triggered temperature-sensitive core-shell nanoparticles will be introduced. The structure of these nanoparticles is stable in the normal physiological environment (pH 7.4), but deforms and releases the enclosed drug molecules in an acidic environment. A signal that recognizes tumor cells is conjugated to the shell of the nanoparticles, making them capable of targeting a drug to tumor cells and then releasing it intracellularly for more efficient and safer cancer therapy. Cellular uptake of the nanoparticles loaded with doxorubicin is higher than free doxorubicin because folate-receptor mediated cell uptake is more specific. Therefore, the nanoparticles loaded with doxorubicin kill cancer cells and suppress cancer growth more efficiently as compared to free doxorubicin.
7-14
Labled Block Copolymer Micelles in the Study of Cellular Internalization
P. Lim-Soo1,
The Possibilty of developing drug delivery systems for specific
subcellular organelles has triggered an interest in the subcellular
localization of specific delivery vehicles such as block copolymer (BC)
micelles. Two micellar systems are described which can be used for this purpose
at different levels of resolution. One involves a micelle consisting of a
hydrophilic poly (ethylene oxide) corona surrounding a hydrophobic core, which
envelops an electron dense gold prarticle. The internalization can be followed
by isolating and sectioning, the cells at specific times after exposure, and
investigating them by electron microscopy. While the technique is somewhat
labor-intensive, the resolution is excellent, and limited essentially by the
size of the gold particle. The other micellar system is based on the attachment
of a flurescent label to the hydrophobic chains, e.g. in micelles consisting of
a diblock copolymer of polycaprolactone and poly (ethylene oxide). Localization
is now studied by confocal fluorescent microscopy, and can be aided by the
labeling, with a different dye, of specific subcellular organelles.
Co-localization is evidenced by color superposition. The technique is simpler
than electron microscopy, but the resolution is typical of optical microscopy.
The two micellar systems thus constitute complementary methods of studying
subcellular localization by techniques with very different resolution
capabilities, giving information over regions of very different sizes.
7-15
Synergy of Drug and Gene
Delivery Using Cationic Polymer Core-Shell Nanoparticles
Y. WANG, S. J. Gao, Y. Y. Yang Institute of Bioengineering and
Nanotechnology, 31 Biopolis Way, The Nanos, #04-01, Singapore, ywang@ibn.a-star.edu.sg
In cancer therapy, two or three agents are often combined to achieve a synergic effect for better killing of cancer cells. For example, p53-encoded gene can be combined with cisplatin to achieve more promising therapeutic results. Co-delivery of cyclosporin A and paclitaxel can improve gene transfection efficiency. To achieve the synergy of drug and gene therapies, we believe that it is necessary to deliver the drug and gene to the same cells. However, up to date, no single nanosized carrier has been reported to deliver a drug and gene simultaneously. In this study, unique polymer core-shell nanoparticles are developed, which can carry a drug and gene simultaneously. For examples, expression levels of luciferase and eGFP genes in 4T1 mouse breast cancer cells are increased by 10 times using the paclitaxel-loaded nanoparticles as compared to the blank nanoparticles. The in vivo studies are conducted in mice bearing subcutaneous 4T1 tumors. Luciferase activity in the tumors, which is transfected by the paclitaxel-loaded nanoparticles/luciferase-encoded plasmid complexes, is 10 times higher when compared to the blank nanoparticles/luciferase-encoded plasmid complexes. Moreover, cyclosporin A has also proved to enhance luciferase gene expression in MB-31-MA cells (a drug resistant cell line). In conclusion, these unique cationic core-shell nanoparticles would provide a promising carrier for co-delivery of drugs and genes.
7-16
Controlled Release of Plasmid DNA from Gold Nanorods Modified with
Phosphatidylcholine Induced by Pulsed Near-Infrared Light
H. Takahashi, Y. Niidome, T. NIIDOME, S. Yamada, Department of
Materials Physics and Chemistry, Graduate School of Engineering, Kyushu
University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, Japan,
thirotcm@mbox.nc.kyushu-u.ac.jp
Gold nanorods (NRs) are rod-like nanoparticles that
have unique optical properties depending on their shape. In order to use NRs for biochemical
applications, we have first partially modified them with phosphatidylcholine
(PC). Partial modification of NRs
with PC has been successful by extraction with chloroform containing PC. The resultant PC-modified NRs (PC-NRs)
could form complexes with plasmid DNA by electrostatic interactions, denoted as
PC-NR/DNA. Pulsed laser irradiation
of NRs induces shape changes into spherical nanoparticles. Irradiation of pulsed 1064-nm laser light
(250 mJ/pulse, 2 min) to PC-NR/DNA complexes induced shape changes of PC-NRs
and at the same time plasmid DNA were released from the complexes as confirmed
from gel electrophoresis. Thus, it
is clear that the shape changes of PC-NRs trigger the release of DNA from the
complexes. It was also found that
the plasmid DNA was released without any damage by laser irradiation. Thus, the near-IR laser irradiation onto
the PC-NR/DNA complexes has realized the selective release of the plasmid DNA
without appreciable structural changes.
7-17
Towards the Development of HFA-based pMDIs for the
Delivery of Hydrophilic Drugs: Combined Chemical Force Microscopy, In-Situ
High-Pressure Tensiometry and Atomistic Computer Simulations
R. P. S. Peguin, P. Selvam, L. Wu, S. R. P. DA ROCHA, Department of
Chemical Engineering and Materials Science, Wayne State University, Detroit, MI,
sdr@eng.wayne.edu
Aerosol inhalation therapy is an alternative to oral and parenteral approaches for the delivery of systemically active drugs. Pressurized metered dose inhalers (pMDIs) are the least expensive aerosol therapy devices available, and have been suggested as potential candidates for the delivery of pharmaceutically relevant biomolecules. However, there have been several challenges in the design of pMDIs as CFCs are being replaced with more environmentally friendly alternatives, such as hydrofluoroalkanes (HFAs). In spite of the fact that the operation of pMDIs with HFAs is similar to those with CFCs, previous formulations are not compatible due to the significantly different properties between these two classes of fluids. Lack of fundamental knowledge on the interfacial properties of volatile propellant mixtures is preventing us from extending the applicability of reliable and simple formulations such as pMDIs for the delivery of polar drugs. Thermodynamic and microstructural properties of the neat and surfactant-modified HFA|Water interface were obtained using a combined experimental and computational approach, including chemical force microscopy, in-situ high-pressure tensiometry and atomistic computer simulations. These studies are relevant not only for the development of aqueous reverse microemulsion-based pMDI formulations, but all HFA-related pMDIs where amphiphilic excipients are generally required.
7-18
Hydrogen-bonded Self-assembled Films and Capsules of
Thermoresponsive Polymers
E. KHARLAMPIEVA, V.Kozlovskaya, S. A. Sukhishvili,
Department of Chemistry and Chemical Biology, Stevens Institute of Technology,
Hoboken, NJ, ekharlam@stevens.edu
Temperature responsive polymers, poly(vinyl methyl ether) (PVME) and poly(N-vinyl caprolactam) (PVCL), were assembled in alternation with polymethacrylic acid (PMAA) at acidic pH via hydrogen bonding using a layer-by-layer technique. The construction of PVME/PMAA and PVC/PMAA films and capsules was confirmed by ellipsometry, in situ ATR-FTIR, and Fluorescence Optical Microscopy. The film thickness and pH-stability were shown to be highly dependent on hydrogen bond strength and the critical ionization of PMAA within the films. The permeability of Thymol Blue dye through films deposited onto alumina supporting membranes was investigated at acidic pH as a function of temperature and revealed striking differences between the two polymer systems. While PVCL/PMAA films did not show any significant effect of temperature on dye permeability in the range of temperatures from 20 to 40oC, permeation through PVME/PMAA films showed drastic increase at temperatures higher than 32̊C. We explain the observed difference by stronger hydrogen bonding between PVCL and PMAA components of the film, which resulted in suppression of film temperature response. However, weakly bound PVME/PMAA systems allowed dehydration of PVME chains at temperatures above its LCST which caused an increase in dye permeability.
7-19
Development of Redox-Active Surfaces and
Micelles for Biocompatible Systems: Caging Ferrocene in Cyclic Oligosaccharides
YAN-MEI LAN, Kejun Cheng, Yan-Yeung Luk, Department of
Chemistry; Department of Biomedical & Chemical Engineering, Syracuse
University, Syracuse, NY, yluk@syr.edu
We report the development of a redox-active surface that is stable under biological conditions. Our system is based on self-assembled monolayers (SAMs) that present a molecularly caged ferrocene. The oxidized form of ferrocene – ferrocenium ion – is not stable in the present of small anions as simple as chloride. Caging the ferrocenium ion in a cyclic oligosaccharide – -cyclodextrin ( CD) renders it stable in biological buffers such as cell culture medium, which contain large concentration of chlorides. We also present a novel micelle system based on the same strategy that covalently cages ferrocene in the annular void of CD. Using OL98\f"Symbol"\s12CD as the hydrophilic head group, this surfactant is bio-friendly in that protein denaturation is minimal or non-existent. Employing a wide range of characterization techniques such as 2-dimensional NMR spectroscopy, circular dichroism and electrochemistry, we demonstrate that accompanying the oxidation of ferrocene to ferrocenium, the surfactant undergoes a large conformational change that results in the disassembly of the micelle formed and re-assembly of a new micelle morphology. We will present its potential application in sequestering membrane proteins and controlled drug release.
7-20
Self-Assembly of Nanoporous Silica Shapes: Synthesis, Morphogenesis,
and Applications
YA.YU. KIEVSKY,
We study the process of self-assembly of nano(meso)porous silica particles via surfactant templating. Process of formation of the mesoporous silica includes growth of the liquid crystalline template and solidification of this template via polymerization of silica precursor. Material obtained as a result of such synthesis (MCM-41) features highly uniform porosity, a large variety of shapes and their sizes. To control the assembly of the desired shapes, we study their morphogenesis. New conditions of self-assembly are found to form monoshaped nanoporous fibers. Recently suggested Origami-type mechanism for synthesizing a rich family of nanoporous silica shapes (cones, tubes, and hollow helixes) is examined. Shape details and their evolution are analyzed by means of XRD, SEM, TEM, AFM, and optical microscopy techniques.
The shapes can possibly serve as templates for various electronic and optical applications. Nanoporous shapes are the prospective hosts for lasing dyes (sealing laser dye molecules inside the silica pores saves them from oxidation and prevents their dimerization). Diffusion from the nanoporous shapes can be used for a control drug release. Another application of mesoporous silica is the coating of optical fibers by uniform low refractive index film with a good adhesion – a possible host for laser dyes or quantum dots.
7-21
Particle Engineering
Technologies for Enhancing Dissolution and Bioavailability
MICHAEL J. JOHNSON, Edmund J. Elder, James E. Hitt, Jonathan C. Evans,
True L. Rogers, The Dow Chemical Company, Dowpharma,
Reports indicate that more than 40% of newly discovered drugs have little or no water solubility. As a result, the development of many exciting new molecular entities is stopped before their potential is realized or confirmed because conducting rigorous preclinical and clinical studies on a molecule that would not have a reasonable pharmacokinetic profile due to poor water solubility is not economical. Further reports indicate that approximately 16% of marketed drugs have less-than-optimal performance specifically because of poor solubility and low bioavailability. Pharmaceutical companies have been able to overcome difficulties with very slightly soluble drugs; however, those with aqueous solubility of less than 0.1 mg/mL present some unique challenges. These drugs are particularly good candidates for advanced particle engineering technologies. Unique nanostructured particles, with enhanced performance attributes, can be obtained through the control of particle size, particle surface area and particle morphology. Enhanced dissolution rates (>80% dissolved in 2 min.), improved bioavailability (>2x) and scale-up (to multi-kilo quantities) has been demonstrated with a portfolio of technologies including controlled precipitation, emulsions and cryogenic approaches. Particle engineering technologies produce stabilized particles with enhanced performance characteristics.
7-22
Molecular Configuration of
ATP in the Interlayer of Hydrotalcite
H. TAMURA, J. Chiba, M. Ito, T. Takeda, S. Kikkawa; Graduate School
of Engineering, Hokkaido University, Sapporo, Japan, h-tamura@eng.hokudai.ac.jp
Hydrotalcite (HT), a layered double hydroxide of magnesium and aluminum, exchanges its interlayer anions with those in external solutions, and has been considered to be a potential vector for anionic medical substances in drug delivery systems. The preparation of well crystallized pure hydrotalcite with nitrate ions in the interlayer (HT-NO3) and the intercalation of adenosine triphosphate (ATP) were studied as a model system. It was found that interlayer nitrate ions were completely exchanged with ATP anions and the average electric charge of the intercalated ATP was evaluated to be -3.6 from the electric neutrality of the intercalate. The intercalation of ATP resulted in a doubling of the interlayer distance and the ATP molecules in the interlayer support a free distance of about 1nm. This distance could be explained by calculations of the molecular configuration of ATP. The triphosphate group is attached to the layer of positive charges and the organic molecule group bends owing to its bond angles and projects to the interlayer with a height of 0.903 nm. The attraction between the organic molecule groups of ATP stretching between the two opposing layer surfaces is considered to sustain the layer structure.
7-23
Modulation of
the Binding Dynamics of Guests with Bile Salt Aggregates with the Addition of
Co-solvents
Chang Yihwa, CORNELIA
BOHNE, Department of Chemistry, University of Victoria, PO Box 3065, Victoria,
BC, Canada, bohne@uvic.ca
Bile salts such as sodium cholate (NaCH) and sodium deoxycholate (NaDC) form aggregates in aqueous solutions with two different binding sites. Primary aggregates, formed at low bile salt concentrations and have a binding site that is hydrophobic. The association and dissociation processes for binding of guests to the primary sites are slow. As the concentration of bile salt is increased the primary aggregates agglomerate into secondary aggregates, where the binding dynamics is fast.
Guest molecules, which are known to bind exclusive to each site, were used to study the effect on the binding dynamics by changing the solvent polarity with the addition of acetonitirile or by changing the viscosity with the addition of ethylene glycol. Addition of ethylene glycol did not significantly affect the binding dynamics to either binding site. The residence time of guests in the primary site could be enhanced with the addition of acetonitrile, or decreased by changing the bile salt from NaCH to the more hydrophobic NaDC. The modulation of the residence time of guests in each binding site will be employed to explore intra-aggregate reactivity with these systems.
7-24
Single Surfactant Non-ionic
Microemulsions
N. NAOULI, H. L.
Rosano, The City College and the Graduate Center of the City University of New
York, 138th Street and Convent Avenue, New York, NY, nnaouli@sci.ccny.cuny.edu
A series of
microemulsions, both W/O and O/W were prepared using the point method and
investigated for insight into formation. Two essential characteristics of the
interfacial surfactant film were identified: equal solubility in the oil and
water phases (“borderline solubility”), and positive interfacial tension at the
W/O interface. Measurement of surfactant(s) transmittance in the two phases
demonstrates that microemulsification occurs when the surfactant interfacial
film is equally soluble in the oil and water phases. Interfacial and surface
tension measurements show that zero interfacial tension is not necessary for
microemulsion formation; further, at the equilibrium, the interfacial tension
must be positive in order to cause the curling of the interface that enables
droplet formation. Calculations of the surfactant molar composition at the
interface allowed us to formulate microemulsions with one single surfactant.
This finding allows us to formulate Lemon oil in water microemulsion with one
single emulsifier. Our results suggest that the structure of the interface is
crucial for microemulsion formation and stability.
7-25
The Use of Pluronic Microemulsions for Drug Detoxification: Investigation of the Interaction Mechanism by NMR Spectroscopy.
M. Varshney1,5, T.E. Morey1,5, E.G. POWELL, M. James2,5, D.O. Shah1,2,5, B.M. Moudgil3,5, R. Partch6, D.M. Dennis1,4,5, 1Departments of Anesthesiology, 2Chemical Engineering, 3Materials Science and Engineering, 4Pharmacology & Experimental Therapeutics, 5Particle Engineering Research Center, University of Florida, Gainesville, FL, 6Clarkson University, Potsdam, NY, DDennis@ufl.edu
Various Microemulsions (MEs) have been developed to address the problem of the lethal effects of overdosed drugs. Pluronic MEs efficiently abate the induced cardiotoxicity in living animals. However, the exact mechanism and important physico-chemical phenomena by which the drug binds to the ME are not clearly understood and need to be investigated on the molecular level to improve ME design and further enhance the efficacy of the ME. Pulse NMR spectroscopy is an expedient technique for elucidating the structural and dynamic interactions between drug and ME. Investigations were carried out using 1H chemical shift, 13C NMR relaxation and self-diffusion measurements to determine the ME-drug interaction mechanism. Results indicate that at low concentrations molecules of the antidepressant, amitriptyline, initially bind with the hydrophobic portion of the Pluronic but bind to sodium caprylate, with increasing concentration. A steep increase in the slope of sodium caprylate chemical shift on increasing amitriptyline concentration compared to the slope of Pluronic indicates that, in addition to the Pluronic molecules, sodium caprylate molecules in ME617 enhance the amitriptyline binding significantly. Additionally, self-diffusion studies indicate that amitriptyline binding stabilize the self-assembly structure of ME617 and show that amitriptyline preferentially binds to the Pluronic and sodium caprylate molecules than to the ethyl butyrate in the microemulsion.
7-26
Evaluation of AFM for
Determining Complexation Forces Between Toxins and Antidote Molecules
A. BENSON, E. Powell, R. Partch, I. Sokolov, Center for Advanced Materials Processing and Department of Chemistry, Clarkson University, Potsdam, NY, bensonam@clarkson.edu
Atomic Force Microscopy (AFM) has become a popular instrument over the years for analyzing the topography of a surface as well as measuring forces between molecules. The sensitivity of the instrument allows researchers to determine forces between a tip that can be modified as well as a substrate. This project involves the use and modification of colloid probes to analyze forces between toxins and antidote molecules. Hydrophobic and - complexation forces between molecules were measured in both polar and non-polar solvents. Modification of the colloid probe and substrate will be presented as well as the AFM results.
7-27
Covalent Attachment of Biotin to TiO2 Nanoparticles
LU YE1, Robert Pelton1, Michael Brook2,
1McMaster Centre for Pulp and Paper Research, Department of Chemical
Engineering, 2Department of Chemistry, McMaster University,
Hamilton, ON, Canada, peltonrh@mcmaster.ca
Biotinylated TiO2 nanoparticles (50~150nm) were obtained by treating TiO2 nanoparticles with 3-aminopropyltriethoxysilane (APTES) in an anhydrous DMSO followed by reaction with N-hydroxysuccinimido-biotin. The biotinylated TiO2 was characterized with 13C and 29Si CP-MAS NMR and FT-IR. The amount of biotinyltriethoxysilane on TiO2 particles was measured by TGA. The dispersion properties and the mean size of TiO2 particles in different solvents were studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The specific surface area (SSA) of TiO2 particles was measured by nitrogen adsorption before and after the two-step modification. The results demonstrated that the biotinyltriethoxysilane was covalently bonded to the TiO2 particle surfaces and the mass percent of biotinyltriethoxysilane is about 1~2.5%. However, the colloidal stability of TiO2 particles was deteriorated. Anhydrous DMSO was superior to anhydrous toluene in the silanization because TiO2 colloidal stability was superior in DMSO.
7-28
Characterization of the Complexes between Polyvinylamine and
Carboxymethyl Cellulose
X. FENG, R. Pelton, Department of Chemical Engineering, McMaster
University, Hamilton, ON, Canada, fengx2@mcmaster.ca
The complexation of poly (vinylamine) (PVAm) and sodium carboxymethyl cellulose (CMC) was studied by dynamic light scattering, electrophoretic light scattering, isothermal titration calorimetry, circular dichroism, and FT-IR spectroscopy. The phase diagram for the complexes as function of polymer concentration showed that either soluble complexes, colloidal complexes or precipitated complexes formed depending upon the ratio of the polymers. Dynamic light scattering indicated that the complexes exhibit a maximum size at 1 mol/L NaCl, suggesting a strongest interaction at this ionic strength. Moreover, complex molecular weight and density are dependent on pH and polymer ratio. Electrophoretic light scattering revealed that the colloidal particles have excess component absorbing on the surface, thus possessing high stability due to electrostatic repulsion. Isothermal titration calorimetry measurements showed that the complexation is endothermic at pH > 7 and exothermic at pH 4 whether in addition of PVAm into CMC or addition of CMC into PVAm. We propose that the complexation of PVAm and CMC is dominated by electrostatic and hydrogen bonding interactions which vary with pH. Finally, circular dichroism was used to demonstrate the conformational change of polymer during complexation.
7-29
Latex Composite
Membranes: Structure, Properties,
and Applications
CHARLES J. MCDONALD, Dow Chemical Company,
We have examined the properties of a new class of microfiltration and ultrafiltration membranes that are fabricated by assembling particles onto the surface of a microporous substrate and stabilizing the resulting porous array into a composite. The particle array contains interstitial voids having a narrow size distribution that serve as channels for size sieving. This aqueous based technology has advantages relative to other membrane fabrication methods in terms of highly controlled asymmetry, the facile adjustment of pore sizes, and the ability to easily modify pore surfaces during the synthesis of particles. In this work we study the properties of the membranes (gas and water permeabilities) fabricated from different size particles and of varying thickness on a number of different supports. The experimental data is then analyzed with a standard model, Carman Kozeny, to develop guidelines for the design of such membranes. For all of the composites, the volume porosity was found to be approximately 0.3, close to what would be expected for hexagonal closest packed array which corresponds to the visual appearance from electron micrographs. In this study, membranes with narrow pore size distributions from 0.038 mm to 0.122 mm were fabricated with fluxes 3-4 times higher than the commercial membranes of similar pore size manufactured by phase inversion processes. This fabrication method also allows the incorporation of colloidal porous polymer particles for the adsorption of proteins based on size. This added dimension to the separations carried out with these membraens are being developed for medical separations such as hemofiltration.
7-30
Development of Supported
Lipid Bilayer Cell Membrane Mimics
J.M. TUCKER, R.D. Tilton, T.M. Przybycien, Departments of Chemical
Engineering and Biomedical Engineering,
The role of the extracellular matrix (ECM) as a diffusive barrier for proteins approaching the cell surface is not well understood. Our goal is to quantify this effect using supported lipid bilayer cell membrane mimics that include ECM mimics. Lipid vesicle adsorption was used to construct supported lipid bilayers on silica surfaces. Vesicles were formed by an extrusion method and consisted of egg phosphatidylcholine (egg PC), dinitrophenyl tagged phosphatidylethanolamine (dNP-PE), and biotinylated lipids. Adsorption to a silica surface was monitored using quartz crystal microgravimetry with dissipation (QCM-D), and a bilayer conformation was confirmed. There was negligible nonspecific adsorption of immunoglobulin G (IgG) but significant specific adsorption of anti-dNP IgG to this bilayer. Thus, an intact lipid bilayer was constructed, and some dNP is accessible for antibody binding. Hydrophobically-modified hydroxyethyl cellulose (hm-HEC) or biotinylated hyaluronic acid were anchored to the bilayer and evaluated as ECM mimics. The effect of ionic strength on the swelling and transport properties of these mimics will be presented.
7-31
Properties of Monolayers of the
Parkinson’s Disease-Related Protein Alpha-Synuclein at the Air-Water Interface
Daryl A. Bosco, Audra Davis, Jeffery W. Kelly, EVAN T. POWERS, Department of Chemistry, The Scripps Research Institute, La Jolla, CA
The histological hallmark of Parkinson’s disease is the presence of intracellular inclusions called Lewy bodies in neurons of the substantia nigra, a region of the brain that controls voluntary movement. The principle component of Lewy bodies is fibrillar aggregates of the 140-residue protein alpha-synuclein. Alpha-synuclein is disordered in solution; however, it is highly amphiphilic, and is known to bind to lipid membranes. Upon membrane binding, it acquires an ordered, helix-rich structure. Both the natural function of alpha-synuclein and its relationship to disease are likely to be linked to its amphiphilicity. We have therefore examined the properties of monolayers of alpha-synuclein at the air-water interface, an environment that is often used to mimic membranes. We have found that alpha-synuclein self-assembles at the air-water interface, forming monolayers that appear striated when deposited onto mica substrates and examined by atomic force microscopy. The factors governing this self-assembly process will be discussed.
7-32
Arraying of Intact
Liposomes on
NIKHIL D. KALYANKAR1, Manoj Sharma1, Charles Maldarelli1,3, David Calhoun2, Lane Gilchrist1, Alexander Couzis1, 1Department of Chemical Engineering, 2Department of Chemistry, 3Levich Institute, Graduate Center and The City College of The City University of New York, NY
We are developing protocols to array individual, intact small unilamellar vesicles(liposomes) onto surfaces with potential application as biosensor probes. In the ongoing research, the surfaces prepared by Micro-contact Printing (MCP) of islands of microscale and sub-microscale dimensions using silanes with ‘amine’ (positively charged) terminal groups onto smooth Silica substrates. Typically the silane used in this step is 3-Aminopropyltrimethoxysilane (APS). These amine islands are biotinylated using NHS-PEO4-Biotin. The background phase is then put down using sequential adsorption of Polyethylene glycol (PEG) terminated silanes from solution using a proper solvent. PEG terminated SAMs are resistant to protein/liposome adsorption. Next step is to attach Streptavidin to the Biotin islands to form patterned Streptavidin arrays capable of binding more Biotin. Low Tg Lipid formulations containing 5% Biotinylated lipids are used to prepare liposomes of 1 micron diameter using extrusion technique. The patterned Streptavidin grid is then exposed to the Liposome solution, which results in attachment of intact liposomes onto islands by ‘Biotin-Streptavidin’ interaction specifically onto the Streptavidin grid. The size of liposomes is matched with the island size so that only one liposome gets attached to each island. Various steps involved in the protocol are confirmed using Fluorescence microscopy, Confocal microscopy and Atomic Force Microscopy.
7-33
The Effect of Humidity on the Adsorption Kinetics of Lung Surfactant
at Air-water Interfaces
YI Y. ZUO, Roya Gitiafroz, Edgar Acosta, Zdenka Policova, Peter N. Cox, Michael L. Hair, A. Wilhelm Neumann, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada, yzuo@mie.utoronto.ca
The in vitro adsorption kinetics of lung surfactant at air-water interfaces is affected by both the composition of the surfactant preparations and the conditions under which the assessment is conducted. Relevant experimental conditions are surfactant concentration, temperature, subphase pH, electrolyte concentration, humidity and gas composition of the atmosphere exposed to the interface. The effect of humidity on the adsorption kinetics of a therapeutic lung surfactant preparation, Bovine Lipid Extract Surfactant (BLES), was studied by measuring the dynamic surface tension (DST). Axisymmetric Drop Shape Analysis (ADSA) was used in conjunction with three different experimental methodologies, i.e. captive bubble (CB), pendant drop (PD), and constrained sessile drop (CSD), to measure the DST. The experimental results obtained from these three methodologies show that for 100% relative humidity (RH) at 37 oC the rate of adsorption of BLES at an air-water interface is substantially slower than for low humidity. These experimental results agree well with an adsorption model that considers the combined effects of entropic force, electrostatic interaction, and gravity. These findings have implications for the development and evaluation of new formulations for surfactant replacement therapy.
7-34
Flow
and Particle Transport in a Human Nasal System
PARSA ZAMANKHAN,1,3Goodarz Ahmadi,1,3 Philip K. Hopke,2,3, Sung-Yung Cheng4, 1Department of Mechanical and Aeronautical Engineering, 2Department of Chemical Engineering, 3Center for Air Resources Engineering and Science, Clarkson University, Potsdam, NY, 4Lovelace Respiratory Research Institute, Albuquerque, NM
In this paper a 3D computational model for studying the flow and nano-size particle transport and deposition in a human nasal passage was developed. The nose cavity was constructed using a series of pictures of coronal sections of a nose of a human subject. For several breathing rates associated with low or moderate activities, the steady state flows in the nasal passage were simulated numerically. The airflow simulation results were compared favorably with the available experimental data for the nasal passages.
Deposition and transport of ultra fine 1 to 100 nm particles in the cavity for different breathing rates was also simulated. The simulation results for the nasal capture efficiency were found to be in reasonable agreement with the available experimental data for a number of human subjects despite anatomical differences. The computational results for the nasal capture efficiency for nanoparticles of different sizes and various breathing rate in a laminar regime were found to correlate with the ratio of particle diffusivity to the breathing rate, or the nose Peclet number. An improved empirical model for the nose capture efficiency was proposed.
7-35
Particle Deposition in 3-D Asymmetric Human Lung Bifurcations
L. TIAN1,3, G. Ahmadi1,3, A. Mazaheri1,3,
Philip K. Hopke2,3, Sung-Yung Cheng4, 1Aeronautical
and Mechanical Engineering Department, 2Chemical Engineering
Department, 3Center for
Air Resources Engineering and Science, Clarkson University, Potsdam, NY, 4Lovelace
Respiratory Research Institute, Albuquerque, NM, tianl@clarkson.edu
Accurate
predication of micro-scale particle behavior in human upper airway is one of
the prerequisites for effective design of inhalation drug delivery
devices. It also could provide
insight into the deposition of contaminants in human respiratory tracks and the
nature of personal exposure. In the past very few works employed 3-D asymmetric
model to study the airflow through human lung, although natural
tracheobronchial branching is generally asymmetric, and such an asymmetry has
profound effect on the subsequent flow fields. Also limited work was devoted to
the study of particle depositions in upper airways where the effect of
turbulence on particle depositions is important. This work approaches three of the
underlying components to provide a realistic computational model for lung
deposition. The new study include: a realistic 3-D asymmetric bifurcation
representation of human upper trachea-bronchial tree; simulation of airflow
field characterizing the inspiratory flow conditions in these branches with
turbulence Reynolds stress transport model; and lastly a particle transport
model for identifying particle deposition pattern as well as deposition
mechanism in the upper tracheobronchial tree.
8-1
Polymer-Supported Iron
Nanoparticles and Microparticles as Remediants for Subsurface Contaminants
Bianca W. Hydutsky1, Bettina Schrick1, Benjamin Beckerman1, Elizabeth Mack1, THOMAS E. MALLOUK1, Kaiti Liao2, Kiran Gill2, Christopher Nelson2, Harch Gill2, 1Department of Chemistry, The Pennsylvania State University, University Park PA, 2PARS Environmental, Inc., Robbinsville, NJ, tom@chem.psu.edu
Soil and groundwater contain a legacy of chemical substances -
including halogenated organics and toxic metal ions - from industrial and
agricultural processes. A decade
ago, scientists at the
8-2
Targeted Delivery of Nanoiron to the NAPL-water Interface
N. B. Saleh, K.
Sirk, T. Sarbu, G. V. Lowry, R. D. Tilton, K. Matyjaszewski,
G. Redden, Department of Civil and Environmental Engineering, Department
of Chemical Engineering, Department of Biomedical Engineering, Carnegie Mellon
University, Pittsburgh, PA, Geoscience Research, Idaho National Laboratory, glowry@andrew.cmu.edu
NAPL source area remediation can decrease mass flux from the site and can expedite remediation. Nanoiron can rapidly degrade NAPL (e.g. TCE) to non-toxic products in situ, but methods to deliver it to the NAPL-water interface are needed for efficient use of the iron. Delivery requires the ability to transport through water-saturated porous media without being filtered out, and the ability to locate the iron at the NAPL-water interface where it can degrade NAPL. The approach developed to provide surface functionality to the nanoiron is similar to targeted drug delivery and may be used to target other specific locations in the subsurface. We demonstrate here the ability to functionalize the reactive nanoiron particle surface for providing efficient transport through the subsurface and preferential partitioning to the NAPL-water interface. Surface modification by amphiphilic block copolymers with highly controllable properties was used to manipulate the electrostatic repulsive forces of the nanoiron, and to increase the iron’s affinity for the NAPL/water interface. The results presented here will show the success of the surface modification in terms of transportability and targeting. Transport of the nanoiron modified by commercially available conventional surfactants and block co-polymers was also examined, and results are presented to demonstrate the relative effectiveness of the synthesized polymer compared to the other modifications. Emulsification of trichloroethylene using synthesized polymer modified particles will demonstrate the ability of the particles to localize at NAPL-water interface.
8-3
Synthesis of Magnetite
Nanoparticles from Reclaimed Acid Mine Drainage
Roger C. Viadero, Jr., XINCHAO WEI, Department of Civil and Environmental Engineering, West Virginia University, Morgantown, WV, Roger.Viadero@mail.wvu.edu
The synthesis of magnetite nanoparticles has been the focus of numerous recent research efforts. In each case, magnetite nanoparticles were formed from reagent-grade chemicals. It is known that acid mine drainage (AMD) produced through coal mining in the Mid Appalachian region can produce waters low in pH and high in dissolved metals, of which iron is most abundant. In this study, Fe was recovered as a ferric hydroxide solid from an AMD water collected from an abandoned coal mine. After solid-liquid separation, the AMD was neutralized to remove other dissolved metals. The resulting supernatant met National Pollutant Discharge Elimination System (NPDES) requirements for discharge. The Fe precipitate was the resolublized and used for magnetite nanoparticle synthesis via coprecipitation at room temperature under nitrogen atmosphere. Based on transmission electron microscope (TEM) and scanning electron microscopy (SEM) observations, most of the magnetite particles ranged from 10 to 15 nm and were spheroidical in shape. Thus, the synthesis of magnetite nanoparticles with the iron recovered from AMD was feasible. Consequently, it is possible to address the need for raw feed stocks in nanoparticle manufacturing, while simultaneously reducing AMD sludge disposal liabilities.
8-4
Bridging the Gap between
Macroscopic and Spectroscopic Studies of Metal Ion Sorption at the Oxide/Water
Interface
L. E. KATZ, C.-C. Chen, M. L. Coleman, A. D. Wiesner, Department of Environmental Engineering, University of Texas, Austin, TX, lynnkatz@mail.utexas.edu
Metal sorption mechanisms were investigated for strontium, cobalt, and lead sorption onto quartz and gibbsite using sodium chloride, nitrate, or perchlorate as background electrolytes. Spectroscopic analyses of concentrated sorption samples were evaluated for their ability to provide insight into the controlling sorption process for more dilute systems. For strontium, outer-sphere complexes identified using x-ray absorption spectroscopy (XAS) of concentrated samples were consistent with macroscopic sorption data collected in more dilute systems. XAS results indicated that cobalt formed new solid phases with dissolved silica or aluminum on oxide surfaces. Macroscopic experiments of cobalt sorption supported the spectroscopic data for total cobalt concentrations of 10-5 M. At lower total cobalt concentrations, adsorption appeared to be the prevailing mechanism of cobalt removal. Spectroscopic and macroscopic results suggested that lead adsorbed as an inner-sphere complex on oxides and that the presence of chloride affected the extent of sorption, respectively. This result was attributed to competition with aqueous lead-chloride complexes based on thermodynamic calculations. The overriding theme of the analysis of these data is that neither spectroscopic analysis nor trends in macroscopic data alone can completely explain the sorption behavior observed in oxide/water systems. The extrapolation of conclusions drawn from data collected at relatively high surface concentrations to more dilute systems must be analyzed in conjunction with aqueous phase thermodynamic data.
8-5
Surface Characterization of a Novel Material for Arsenic Removal
Andy Baker1, Katrin Przyuski1, Arthur D. Kney1, STEVEN E. MYLON2, 1Department of Environmental Engineering, Lafayette College, Easton, PA, 2Department of Chemistry, Lafayette College, Easton, PA, mylons@lafayette.edu
A selective sorption
material composed of iron hydroxide and activated
alumina, designated iron-enhanced activated alumina (IEAA) has proven to
successfully remove arsenic to below the MCL of 10 ppb. In
contrast to many other materials developed for the same purpose, IEAA has the
ability to remove both ionic forms of arsenic, (As(III) and As(V)). While the mechanism for removal of As(V)
may be trivial, that for the removal of As(III) is unknown and requires
study. Extended X-ray Absorption
Fine Structures (EXAFS) and X-ray Near Edge Spectroscopy (XANES) have been used
for surface characterization of this material in the presence of
As(III). Results from these studies
will provide detailed information concerning the coordination environment of
the adsorbed arsenic species on the surface of the IEAA. From this we will can develop a better
understanding of the mechanism for removal of As(III), and hence move to a more
efficient design and synthesis of this IEAA. We will present data from column experiments demonstrating the
efficient removal of As(III) as well as the results from spectroscopic studies
of this material loaded with different forms of Arsenic.
8-6
Novel Nanostructured
Anatase Assemblies from Algae as Strong Catalysts for the Hydrolysis of
Organophosphorous Esters
C.-H. HUANGa, S. Leea,
S. Shianb, K. H. Sandhageb, aSchool of Civil and Environmental Engineering, bSchool of Materials
Science and Engineering, Georgia Institute of Technology, Atlanta, GA, ching-hua.huang@ce.gatech.edu, ken.sandhage@mse.gatech.edu
Novel nanocrystalline anatase (TiO2) assemblies were produced from biologically self-assembled SiO2-based diatom microshells (frustules) via a unique reactive conversion technique. This conversion involves a halide gas (TiF4)/solid displacement reaction that allows for the complete conversion of SiO2 to TiO2 while preserving the starting bioclastic structure. The resulting nanostructured anatase frustules were found to strongly catalyze the hydrolysis of methyl paraoxon and methyl parathion under mild conditions (pH 4.5-9, 25° C), with catalytic effects of 5-25 times greater than that of other commercial anatase nanoparticles. Characterization of these anatase nanomaterials revealed isoelectric points in the range of 2.5 to 4.5, which were lower than for typical anatase (pHIEP of 5.2-6.0), indicating stronger surface acidity. Quantitative fluorine analysis after the conversion reaction indicated that the amount of residual fluorine in the nanocrystalline anatase played a significant role in the surface acidity and in the catalytic effect on the hydrolysis of the two organophosphorous esters.
8-7
Comparison of Surface
Complexation Models for Predicting Bi-Solute Metal Ion Sorption onto Iron
Oxides
A. R.VIEIRA, S. N. Stokes, C.-C. Chen, L.E. Katz, Department of Environmental Engineering, University of Texas, Austin, TX, adriano@mali.utexas.edu
Surface Complexation Models (SCMs) hold significant promise as a tool for predicting the fate and transport of metal ion contaminants. The reliability of SCMs is dependent on the selection of appropriate surface complexation reactions and accurate estimation of the model parameters. The past decade has seen significant improvements in model reliability due to increased use of spectroscopic data for guiding the selection of surface reactions. Yet, many of the intrinsic SCM parameters are correlated with each other and a wide range of parameter sets can still be used to fit single-solute adsorption data equally well. One parameter that contributes to data uncertainty and is required in all SCMs is the surface site density of the adsorbent that is often determined by fitting experimental data. The estimation of the surface site density using an independent technique can limit the resulting set of parameters that fit the adsorption data. In our research, we have shown that site densities estimated using the tritium exchange technique provide better triple layer model SCM predictions of bi-solute metal ion sorption. In this paper, we extend this work to provide a comparison of two SCMs, the diffuse layer model and the triple layer model, for predicting competition of metal ion sorption onto iron oxides over a wide range of experimental conditions that include adsorption and surface precipitation as the predominant sorption process.
8-8
Mechanisms
Controlling the Release of Trace Elements from Clean-Coal Technology
By-product: Effect of Proton and Organic Ligands
Chin-Min
Cheng1, J. Bigham2, H. Walker1, 1Department of Civil and
Environmental Engineering and Geodetic Science and 2School of
Natural Resources, The Ohio State University,
Despite numerous studies aimed at increasing
the utilization of fixated flue gas desulfurization (FGD)
by-products, concern about the leaching of hazardous constituents has limited the
beneficial re-use of these materials. Furthermore, there is a
lack of understanding regarding kinetic processes that control the leaching of
trace elements. In this study, the
release of trace elements from fixated FGD material was investigated by
considering bulk diffusion, pore diffusion, and surface chemical reactions as
possible rate controlling steps. A
flow-through rotating disk system and shrinking core
model (SCM) were used to determine the rate-limiting process. Experimental results and modeling
indicated that the leaching process was controlled by
surface chemical reactions. As a result, the leaching rate can be described by
a combination of an intrinsic hydration reaction and a proton-promoted
dissolution reaction. The effects
of organic ligands, i.e., citric acid, oxalic acid, and humic acid, on leaching
kinetics were also investigated under both acidic and near neutral conditions. A ligand-promoted effect was only
observed with citric acid. In the
case of oxalic acid, formation of calcium oxalate on the surface significantly
inhibited the leaching process. The
adsorption of humic acid selectively inhibited the leaching of Fe with no
significant effect on the leaching of other elements.
8-9
Absorption and
Adsorption of Hydrophobic Organic Contaminants to Black Carbon Soots
THANH H. NGUYEN1, Laura A. Langley2, D. Howard Fairbrother2, William P. Ball1, 1Department of Geography and Environmental Engineering, 2Department of Chemistry, Johns Hopkins University, 3400 N. Charles street, MD
Single solute sorption isotherms from aqueous solution were obtained
for diesel soots and hexane soots using phenanthrene and 1,2,4-trichlorobenzene
as sorbates. Substantial isotherm nonlinearity was observed in all cases.
Compared to sorption with diesel soot SRM 2975, sorption with diesel soot SRM
1650b was lower at low concentrations but higher at high concentrations. Pore
size distribution and BET surface area (BETSA) were calculated using nitrogen
adsorption data. Comparison between pore size distribution-normalized and
BETSA-normalized uptakes for the studied sorbents and those for activated
carbon was used to show the relative importance of surface adsorption to overall uptake. Adsorption
dominates for three soots (SRM 2975, hexane soot, and oxidized hexane soot) at
all concentrations and for the fourth soot (SRM 1650b) only at low
concentrations. For SRM 1650b, a dual domain model is required for description
of the total sorption isotherm of both sorbates studied, with absorption
dominating uptake at higher sorbate concentrations.
8-10
Colloids Partitioning
between Organic and Aqueous Phase Cause the Low Interfacial Tension of DNAPL
S.E. Powers, W. DOU, Department of Civil and Environmental
Engineering,
Many low Interfacial tensions (IFT) have been observed
between some field Dense Non-aqueous phase liquid (DNAPL) and water comparing
to the original organic compounds.
But little study has been done to study the mechanisms lower the
IFTs. A DNAPL sample recovered from
Savannah River Site (SRS) of Department of Energy (DOE) also showed an extreme
low interfacial tension (IFT), which is less than 2 Dynes/cm. The main composition of the DNAPL was
analyzed to be about 80% PCE and 20% TCE, which have IFTs of about 45 Dynes/cm
and 35 Dynes/cm respectively. When
we equilibrated the DNAPL with water, white fine precipitates are observed to
accumulate on the interface. And
the further study of the IFT between the SRS DNAPL and water over time using a
picture pendent drop goinometer showed that the precipitates could account for
the substantially lower IFT.
The formation of the precipitates can be reasoned by the partitioning of
the co-disposed chemicals accumulating on the interface when the DNAPL contacts
aqueous phase. Research works has
been done with a chelating agent EDTA and tin, which was analyzed to be present
in DNAPL to examine the influence of its presence on the IFT. While no evidence showed that the tin
itself can account for the substantial low IFT of SRS DNAPL.
8-11
Application
of ac Electrokinetics in Membrane Filtration Processes
S. H.
Molla, S. BHATTACHARJEE, Department of Mechanical Engineering,
A novel combination of ac dielectrophoresis with crossflow membrane filtration is proposed for separation of the components of aqueous and non-aqueous colloidal systems. The dielectrophoretic forces experienced by a colloidal entity can be attractive or repulsive depending on the dielectric properties of the solvent and the dispersed phases and the frequency of the applied ac signal. Embedding an array of electrodes on a semi-permeable membrane and actuating them with an appropriate ac signal allows manipulation and separation of the constituents of a colloidal suspension or microemulsion. The attractive forces can be employed to preferentially separate the dispersed phase in an emulsion. In contrast, the repulsive dielectrophoretic forces can be utilized to prevent deposition of colloidal particles on the membrane. An analysis of the pertinent transport processes during dielectrophoretic membrane filtration is presented. The simulation results from the trajectory analysis of particles in presence of dielectrophoretic and hydrodynamic forces indicate: (a) attractive dielectrophoretic forces can result in a significant enhancement in the transport of the dispersed phase toward the membrane and (b) repulsive dielectrophoretic forces can prevent colloid deposition onto the membrane and, hence, membrane fouling, in an entirely physical manner.
8-12
JIM C. CHEN2, Menachem Elimelech1, Albert S.
Kim2, 1Department of Chemical Engineering, Environmental
Engineering Program,
The principal issues involved in developing a
8-13
Humic Acid Removal with Aminated PGMA Beads
CHANGKUN LIU, Renbi Bai, Department of Chemical and Biomolecular
Engineering, National University of Singapore, 10 Kent Ridge Crescent,
Singapore, chebairb@nus.edu.sg
Humic substances are ubiquitous in natural waters and can cause various environmental and potential health problems. Adsorption has been one of the methods to minimize the presence of humic substances in water supply. In this study, novel PGMA (poly-glycidyl methacrylate) beads were prepared and aminated with ethylenediamine (EDA) as an adsorbent to remove humic acid from aqueous solutions. Zeta-potential analysis was conducted to examine the surface electrostatic properties, and atomic force microscope (AFM) was used to examine the surface morphologies of the adsorbent (PGMA-EDA) with and without humic acid adsorption. Fourier transform infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were utilized to reveal the surface interactions in humic acid adsorption. It was found that the PGMA-EDA adsorbent is very effective in humic acid adsorption and the amine groups play an important role in interacting with humic acid to be adsorbed. Model fitting study showed that the adsorption follows a pseudo-second-order (PSO) kinetics.
8-14
Colloids in Subsurface Environments: Aggregation, Deposition, and Facilitated
Transport.
MICHAL BORKOVEC, Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland, michal.borkovec@unige.ch
Many transport processes in natural aqueous environments are
dictated by colloids and their interactions. Prominent examples include
formation of a river delta or colloid facilitated transport of contaminants in
the subsurface. Mutual interaction between particles and interactions between
particles and surfaces bear many similarities. For example, homoaggregation
processes between identical particles are of relevance in ripening or pore
clogging phenomena, while heteroaggregation processes between unequal particles
bear close analogies to particle deposition. The lecture will discuss several
recent techniques and developments allowing us to study such aggregation and
deposition processes experimentally, and the possibility to quantify those
processes with the theory of Derjaguin, Landau, Verwey and Overbeek (DLVO).
As an application of these findings, it will be illustrated how colloid
facilitated transport can be understood on a quantitative basis within a
natural soil environment.
8-15
Influence of Alginate and
Ionic Composition on the Stability of Hematite Colloids
KAI LOON CHEN1, Steven E. Mylon2, Menachem Elimelech1, 1Department of Chemical Engineering, Environmental Engineering Program, Yale University, New Haven, CT, 2Department of Chemistry, Lafayette College, Easton, PA, kailoon.chen@yale.edu
Alginate is a polysaccharide ubiquitous in natural aquatic environments and engineered systems. It is very likely that alginate absorbs onto colloidal and particulate matter, influencing the fate and transport of colloids and associated pollutants in aquatic systems. An important characteristic of alginate is the formation of a cross-linked gel matrix in the presence of calcium cations. In this study, we characterize the alginate by potentiometric and complexometric titrations to determine its carboxylic acidity and availability of calcium binding sites, respectively. We then pre-adsorb synthesized hematite colloids with alginate under favorable pH conditions. The aggregation kinetics of the alginate-coated hematite colloids is determined by dynamic light scattering in the presence of monovalent (NaCl) and divalent (CaCl2) electrolytes, and is compared with the kinetics of the bare hematite colloids. The absolute aggregation rate constants for both the bare and coated colloids under favorable conditions at high NaCl concentrations are similar, indicating that they share similar aggregation mechanism of electrostatic destabilization. In the presence of calcium ions, the growth of the alginate-coated hematite aggregates is much faster than in sodium ions, implying that the aggregation mechanisms are different. A discussion of the mechanisms involving the role of alginate will be presented.
8-16
Effect of Monovalent and
Divalent Electrolytes on the Adsorption of Polysaccharides on Solid Surfaces in
Aquatic Systems
ALEXIS J. DE KERCHOVE, Menachem Elimelech, Department of Chemical Engineering, Environmental Engineering Program, Yale University, P.O. Box 208286, New Haven, CT, alexis.dekerchove@yale.edu
Polysaccharides play an important role in the fouling of surfaces in natural and engineered aquatic systems due to their strong adsorptive properties. These highly charged polyelectrolytes adsorb in compact layers, rendering cleaning of the fouled devices difficult and expensive. In this study, adsorption of two model polysaccharides, polygalacturonic acid (PGA) and sodium alginate, was examined as a function of ionic strength and calcium ion concentration utilizing quartz crystal microbalance with dissipation (QCM-D). The variation of frequency, which corresponds to the adsorbed polyelectrolyte mass, was analyzed following incremental increases in the ionic strength and consecutive additions of polysaccharides. PGA had very similar adsorption patterns as alginate in absence of divalent cations. In presence of calcium, both polysaccharides demonstrated significant complexation with calcium ions, showing 20 and 10 times greater initial adsorption of PGA and alginate, respectively, than scenarios without calcium. In most cases, the increase of ionic strength above 100 mM caused a decrease in the adsorbed mass, suggesting compaction or destruction of the adsorbed polyelectrolyte layer. The observed adsorption behaviors are discussed in terms of the structure and chemical properties of the two polysaccharides.
8-17
Effect of Chemical and Hydrodynamic Parameters on Interfacial
Retention of Colloids in Unsaturated Micromodel Channel
V. LAZOUSKAYA, Y. Jin, Department of Plant and Soil Sciences, University of Delaware, Newark, DE, volha@udel.edu
Transport of colloids and colloid-facilitated transport of contaminants in soil and groundwater aquifers have been widely acknowledged in the literature. Mineral-grain attachment, air-water interface and contact line retention are the major mechanisms determining the extent of colloidal transport in unsaturated porous media. Although unsaturated colloidal transport has been extensively studied in past years, its complete understanding is pending. The present study investigates the parameters that affect the behavior of colloids on air-water interface and contact line. The principal elements of the employed experimental system include a glass channel micromodel and laser scanning confocal microscope, which allows the visualization of colloidal systems at the pore scale. The study includes both dynamic (flow) and static experiments. The flow experiments showed strong influence of hydrodynamic conditions both on air-water interface and contact line retention whereas the static experiments reflected the effect of solution chemistry. Applying to natural dynamic systems, the combined effect of chemical and hydrodynamic conditions on colloidal retention in soil is expected.
8-18
Direct observation of
Colloid Deposition at Grain-Grain Contacts in Porous Media Using X-ray
Microtomography
XIQING LI1, C. L. Lin2, Jan D. Miller2, William P. Johnson1, 1Department of Geology and Geophysics, 2Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT, li@earth.utah.edu
Colloid deposition at grain-grain contacts is potentially important in porous media. However, common approaches used to examine colloid deposition (e.g. column experiments) do not differentiate environments of deposition in porous media. In this work, direction observation of the environment of deposition was performed using x-ray microtomography (XMT), a technique that yields exact 3-D representation of the pore domain with a spatial resolution down to 5 micrometers. Near neutrally buoyant microspheres “visible” to x-rays were prepared. Microsphere suspensions (2.0´103 particle-mL-1) were injected into a small column packed with glass beads (average diameter 800 m). Following injection, XMT images were obtained and deposited microspheres were directly characterized. The extent of deposition at grain-grain contacts was examined with changes in fluid velocity and microsphere size. The maximum number of microspheres deposited at grain-grain contacts was located increasingly down-gradient of the column inlet with increasing flow velocity, indicating the reversibility of deposition at grain-grain contacts.
8-19
Secondary Minimum Sorption of Microorganisms: Unexpected Prevalence, Implications and Modeling
L. L. LANDKAMER1, R. A. AbuDalo2, R.W. Harvey1,
D.W. Metge1 & J.N. Ryan2, 1U.S. Geological
Survey, Boulder, CO, 2University of Colorado, Boulder, CO
When colloidal particles and collector surfaces have the same charge, deposition is termed “unfavorable” due to large electrostatic energy barriers inhibiting sorption in the primary minimum. DLVO calculations often reveal the presence of a secondary minimum (Φ2-min) that can trap colloids, but Φ2-min sorption is considered unlikely at low ionic strengths. However, we observed reversible Φ2-min sorption of Cryptosporidium parvum oocysts to clean silica sand at ≤ 0.0001 M NaCl. Φ2-min sorption may explain (1) unexpected removal previously attributed to phenomena such as surface heterogeneities, straining, steric interactions or hydrophobic forces, and (2) unexpected release of colloids that occur in the presence of slight chemistry changes or mechanical inputs of energy. The latter may occur because the energy well at the secondary minimum can be quite shallow (e.g., ≤ 1-2 kBT). A new conceptual model for understanding colloid filtration in unfavorable conditions was developed by expanding on the work of Hahn and O’Melia (2004) relating the depth of the Φ2-min and the Maxwell distribution of colloid energies to detachment probability. Rather than calculating a collision efficiency, all collisions were assumed to result in attachment and a distribution of detachment rates was used to simulate colloid transport in porous media.
8-20
Force Interactions Profiles between Cryptosporidium parvum Oocysts and Silica Surfaces
T. L. BYRD, J. Y. Walz, Department of Chemical Engineering, Yale
University, New Haven, CT, tonya.byrd@yale.edu
The interaction force profile between single Cryptosporidium parvum oocysts and silica particles were measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized during the measurements by entrapment in a Millipore polycarbonate membrane with 3 mm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 to mM. For both electrolytes, the decay length of the repulsive force profile, obtained via the slope of a plot of the logarithm of the interaction force versus oocyst/substrate separation, was found to be essentially independent of the ionic strength and always much larger than the expected Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are strictly steric in nature. The only apparent difference between experiments in the two electrolytes was that strong adhesive forces were frequently observed in the calcium solutions. Comparisons of these results with recent particle deposition studies will also be made.
8-21
Role of Surface Proteins
in the Deposition Kinetics of Cryptosporidium
parvum Oocysts
ZACHARY A. KUZNAR,
Menachem Elimelech, Department of
Chemical Engineering, Environmental Engineering Program, Yale University, P.O.
Box 208286, New Haven, CT, zachary.Kuznar@yale.edu
A radial stagnation point flow system was used to investigate the influence of Cryptosporidium parvum surface properties on oocyst deposition kinetics onto an ultra pure quartz surface. In order to determine the role of oocyst surface-bound proteins in adhesion, the deposition kinetics of viable oocysts were compared with the deposition kinetics of oocysts treated with either heat or formalin. Low deposition rates and corresponding attachment efficiencies were observed with viable oocysts over the entire range of solution conditions investigated, even where DLVO theory predicts the absence of an electrostatic energy barrier. An “electrosteric” repulsion between viable Cryptosporidium and the quartz substrate, attributed to the proteins on the oocyst surface, is surmised to cause this low deposition rate. Treatment of the oocysts with either heat or formalin was found to alter the structure of the surface proteins and reduce steric repulsion with the quartz substrate. Oocyst surface proteins were then removed with a digestive enzyme (Proteinase K), and their overall effect on the oocyst electrokinetic properties, and oocyst deposition rate were determined.
8-22
Profiles of Retained Cryptosporidium Oocysts in Porous Media
– Evidence for Dual Mode Deposition
NATHALIE TUFENKJI, Department of Chemical Engineering, McGill University, Montreal, PQ, Canada, nathalie.tufenkji@mcgill.ca
Spatial distributions of Cryptosporidium parvum oocysts in columns packed with uniform glass-bead collectors were measured over a broad range of physicochemical conditions. Comparison of oocyst retention with results obtained using polystyrene latex particles of similar size suggest that mechanisms controlling particle deposition are the same in both systems, that is, “fast” deposition in secondary energy minima and on favorably charged surface heterogeneities, and “slow” deposition over electrostatic energy barriers. A dual deposition mode model is applied which considers the combined influence of “fast” and “slow” oocyst deposition due to the concurrent existence of favorable and unfavorable colloidal interactions. Model predictions of retained oocyst profiles and suspended oocyst concentration at the column effluent are in good agreement with experimental data. Because classic colloid filtration theory does not account for the effect of dual mode deposition (i.e., simultaneous “fast” and “slow” oocyst deposition), these observations have important implications for predictions of oocyst transport in subsurface environments, where repulsive electrostatic interactions predominate.
8-23
Influence of Nutrient Condition on the Adhesion Kinetics of Burkholderia cepacia G4g and ENV435g
D. Nilasari, S.L. WALKER, Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA, swalker@engr.ucr.edu
The sensitivity of Burkholderia
cepacia G4g and ENV435g adhesion kinetics to nutrient condition has been
observed. The kinetics of
cell adhesion was investigated in a radial stagnation point flow
8-24
Bio-Colloid Facilitated Metal Transport in
Geologic Media: Observations and Surface Complexation Modeling
L.L. LANDKAMER1, R.W. Harvey1,
D.W. Metge1, J. N.
Ryan2,1U.S. Geological Survey, Boulder, CO, 2University
of Colorado, Boulder, CO
Bench-scale experiments demonstrated enhanced Zn(II) and Pb(II)
transport in flow-though columns packed with either iron/aluminum-oxide coated
sand or limestone chips when bacteria were injected with the metal, relative to
experiments performed without bacteria. In a column packed with limestone
chips, the effluent concentration of zinc injected in the presence of bacteria
(Pseudomonas stutzeri, 8.5 × 107 cells/ml) was 8-fold higher than
when no bacteria were injected. The transport of zinc in a column packed with
sand was enhanced 13-fold in the presence of 1.1 × 108 cells/ml. The
bacteria were pre-starved and no carbon source was present, so it is assumed
that the bacteria sorbed and transported the metal independently of cellular
metabolism. The pH dependence of the enhanced transport was modeled using
surface complexation chemistry coupled with a transport model. The surface
complexation model simulates the competition for the metal between the organic
functional groups on the bacterial surfaces and the inorganic functional groups
on the geologic media surfaces. The specific sorption reactions used to model
the metal sorption to the bacteria and the geologic media will be discussed
along with the strategy used to model bacterial transport in the framework of
the contaminant transport model.
8-25
Deposition and Re-entrainment Dynamics of Microbes and
Non-Biological Colloids during Non-Perturbed Transport in Porous Media in the
Presence of an Energy Barrier to Deposition
W.P. JOHNSON, X. Li, M. Tong, S. Assemi, Department of Geology &
Geophysics, University of Utah, Salt Lake City, UT, wjohnson@mines.utah.edu
This presentation examines the non-perturbed deposition and
re-entrainment dynamics of biological and non-biological colloids in porous
media in the presence of an energy barrier to deposition at the grain
surface. Deposition and re-entrainment
rate coefficients were determined from numerical simulation of
breakthrough-elution behavior and the profiles of retained colloids. Results are
presented for non-biological and biological colloids of sizes ranging from 0.25
m to 5 m for transport within porous media of different angularity and
roughness, under a variety of ionic strength and fluid velocity
conditions. In the presence of an
energy barrier, deposition efficiencies decreased with increasing fluid
velocity for all colloids and conditions examined. In the presence of an energy barrier,
re-entrainment rate coefficients increased with increasing fluid velocity. These
results demonstrate that in the presence of an energy barrier to deposition,
hydrodynamic drag mitigates deposition and drives re-entrainment of both
biological and non-biological colloids.
The possibility of colloid association with the primary energy minimum
is considered via a balance of hydrodynamic and adhesive torques. The possibility of colloid association
with the secondary energy minimum is considered via reversibility of
deposition; and via parallel experiments in porous media and simple shear flow
systems.
8-26
Real-time Observation of Colloid Transport in Porous Media at
Mesoscales Using Epi-fluorescence Imaging
Y. Wang and P. ZHANG, Department of Earth and Atmospheric Sciences, City College of New York, New York, NY, pzhang@sci.ccny.cuny.edu
The lack of direct, continuous observation of the movement of colloids in porous media limits our knowledge of the processes that control colloid transport and immobilization in these media. Here we developed a non-evasive, epi-fluorescent imaging technique to quantify the distribution of fluorescent microspheres in translucent sand at mesoscales (maximum view area of 20 cm by 20 cm). Carboxylated latex microspheres were injected into a flow cell (20 cm long by 10 cm wide by 1 cm thick) packed with clean quartz sand at various flow rates and ionic strengths, and then eluted with microsphere-free solution of identical chemistry. Nonmonotonic colloid distribution profiles were observed in all transport experiments under unfavorable deposition conditions. Direct observation and comparison of the 1-D distribution profiles at different elution times (up to 6 pore volumes) clearly showed a down-gradient movement of microspheres during elution, suggesting that the nonmonotonic distribution profiles observed in this particular study was due to the detachment of retained microspheres.
8-27
Role of Zones of Low Hydrodynamic Drag in Colloid Deposition and
Re-entrainment in Porous Media
MEIPING TONG, W.P. Johnson, Department of Geology & Geophysics,
University of Utah, Salt Lake City, UT, tong@earth.utah.edu
Existing colloid deposition models assume that attached colloids are not subject to hydrodynamic drag, whereas recent experiments demonstrate that in the presence of electrostatic repulsion hydrodynamic drag mitigates colloid deposition and drives colloid re-entrainment. The deposition and re-entrainment behaviors of three different-sized carboxylate modified polystyrene latex microspheres were systematically examined in packed porous media and impinging jet systems under various fluid velocity conditions. Deposition efficiencies were compared between the porous media and impinging jet systems to determine the influence of zones of low hydrodynamic drag on colloid deposition. At the end of the experiments, the porous media and the impinging jet experiments were eluted with pure water to deepen the barrier to detachment from primary energy minima, and to eliminate secondary energy minima. The extent of release of retained colloids upon elution with pure water indicated the significance of primary and secondary energy minima to colloid deposition. The results indicate the importance of grain surface angularity in the generation of zones of low hydrodynamic drag that enhance colloid deposition in porous media.
8-28
Deposition and
Characterization of Nanoparticulate
TANYA J. GALLEGOS1, Kim F. Hayes2, Linda M.
Abriola3, 1Department of Civil and Environmental
Engineering, 181 EWRE, 1351 Beal Avenue, Ann Arbor, MI, 2Department
of Civil and Environmental Engineering, 181 EWRE, 1351 Beal Avenue, Ann Arbor,
MI, 3Tufts University, 105 Anderson Hall, Medford, MA, tgallego@umich.edu, ford@umich.edu,
Linda.Abriola@tufts.edu
Nanoscale synthetic
8-29
Homogeneous Nucleation in the Ambient Atmosphere
PHILIP K. HOPKE,
Center for Air Resources Engineering and Science and Department of Chemical
Engineering,
One of the important recent findings has
been that homogenous nucleation in the atmosphere is a much more common event
that had been previously been recognized.
Initially these events were observed in remote areas such as
8-30
Direct Force Measurements between Carboxylate-Modified Latex
Microspheres and a Glass Surface Using Atomic Force Microscopy
SHOELEH
ASSEMI1, Jakub Nalaskowski2, William Paul Johnson1,
1 Department of Geology and Geophysics, 2 Department of
Metallurgical Engineering,
Interaction and adhesion forces
between 1.0-m carboxylate-modified polystyrene latex microspheres and a glass
surface were measured directly with an atomic force microscope using the
colloidal probe technique. Measurements were conducted as a function of ionic
strength in two different electrolytes, NaCl and MOPS (3-(N-morpholino)-propanesulfonic acid) buffer, at pH
6.8-6.9. AFM approach curves were
fitted to theoretical DLVO force curves by varying the surface potential of the
microspheres. The depths of the primary minima of the fitted theoretical DLVO
curves were used to estimate theoretical adhesion forces, and were compared to
the pull-off forces measured by AFM. Pull-off forces measured by AFM in both
electrolytes were consistently a factor of 5 to 10 lower than the pull-off
forces estimated from theoretical adhesion forces obtained from DLVO curves.
AFM-measured pull-off forces decreased with increasing the ionic strength in
both electrolytes, whereas the adhesion forces calculated from DLVO showed
either no change or an increase with increasing the ionic strength. These observations indicate that
the DLVO-based approach for determining adhesion force severely overestimates
the actual adhesion force.
8-31
Development and Use of a Bioluminescent Biosensor for Assessing the Bioavailability of Organic Pollutants in Surfactant
Micelles
Angela Keane1, Peter C.K. Lau2, SUBHASIS GHOSHAL1,
1Department of Civil Engineering, McGill University, Montreal, PQ,
Canada, 2Biotechnology Research Institute, National Research
Council, Montreal, PQ, Canada, subhasis.ghoshal@mcgill.ca
A direct measurement technique for microbial bioavailability was
developed using a whole-cell bioluminescent biosensor, PpF1G4. To create PpF1G4,
bioluminescent reporter genes (lux)
were placed under the control of the promoter region of the solvent efflux pump
genes (sep) in Pseudomonas putida F1. Biosensor PpF1G4 produces a bioluminescent response to a wide range of
aromatic compounds. PpF1G4 was used to evaluate how three
nonionic surfactants (Triton X-100, Brij 30 and Brij 35) influence the
bioavailability of three different organic pollutants (toluene, naphthalene,
and phenanthrene) present as individual compounds in solution in excess of
solubility as well as the bioavailability of multiple solutes partitioned from
non-aqueous phase liquid multi-component mixtures such as coal tar and
creosote. The increased bioluminescent response of PpF1G4 in micellar solutions of Triton X-100 and Brij 35 indicated
higher intra-cellular concentrations of the test compounds, toluene,
naphthalene and phenanthrene, compared to control systems with no surfactants
present. The above results and
transmission electron microscope images of PpF1G4
in micellar surfactant solutions suggest that nonionic surfactants may enhance
bioavailability and biodegradation rates by increasing the mass flux of
substrates present in the micellar pseudophase to the cells through mechanisms
that do not involve visible changes to membrane permeability.
8-32
Mixed-Order Modeling of Simultaneous Particle
and Dissolved Substrate Removal by Aerobic Biological Film Wastewater Treatment
Systems
J. P. BOLTZ1, C. H. La Motta2, 1M. CH2M HILL , Inc., Montgomery, AL, 2Urban Environmental Systems Center and University of New Orleans, New Orleans, LA, jpboltz@uno.edu
Several mechanistic models have been developed to describe the
kinetics of dissolved substrate utilization by biological films, or
biofilms. These models, however,
have limited application when the primary
constituent of chemical oxygen demand in domestic wastewaters is organic
particles. Recent research has
demonstrated that frequently a small fraction of the total chemical oxygen
demand (TCOD) in raw sewage and primary effluents is dissolved. Therefore, there is a need to develop a mathematical
expression capable of describing the removal of simultaneous particulate and
dissolved organic matter from wastewaters.
The primary objective of this
research project is to study the kinetics of particulate COD (PCOD) removal
from wastewaters by biological films and apply the respective kinetic
expression to a model that includes phenomena such as diffusion and reaction of
dissolved substrate inside the biofilm, and the simultaneous flocculation of
organic particles at the external film surface. The resulting mixed-order model
is validated using a laboratory scale completely mixed biofilm reactor.
8-33
High
Performance Carbon Honeycomb for Air Separation
K. LASZLO1,
G. Onyestyák2, E. Geissler3,
1Department of
Physical Chemistry, Budapest University of Technology and Economics, Budapest
1521, Hungary, 2Institute of Surface Chemistry and Catalysis,
Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest 3Laboratoire
de Spectrométrie Physique CNRS UMR5588, Université J. Fourier de Grenoble,
B.P.87, 38402 St Martin d'Hères cedex, France, klaszlo@mail.bme.hu
Carbon adsorbent materials are of paramount importance
in environmental technology, from gas purification and separation to gas
storage or catalyst supports. These processes rely on specific pore size
distributions that contribute to selective adsorption via size exclusion. Low temperature nitrogen adsorption, small
angle X-ray scattering (SAXS) and frequency response (FR) measurements are
reported for carbon prepared by heating wood from scotch fir (Pinus sylvestris) in an inert atmosphere
to temperatures in the range 600°C ≤ T
≤ 1000°C. The honeycomb structure, conserved from the original wood, provides
easy access for gas adsorption and air separation applications. The surface
area measured by gas adsorption, SBET,
and the microporosity both increase with increasing T, while significant mesoporosity develops at 1000°C. Although the
samples are highly anisotropic at distance scales greater than 10 nm, the
specific surface area SX
derived from SAXS is isotropic within experimental error. FR measurements of
the adsorption rate of nitrogen and oxygen reveal strong selectivity in favour
of oxygen for the 700°C sample, whose characteristic slit width is
approximately 0.33 nm. For T=1000°C,
the slit width doubles and the selectivity disappears.
9-01
Methanol Oxidation to
Methyl Formate and Dimethoxymethane on Supported RuOx and H3PVxMo12-xO40
Clusters
Haichao Liu, ENRIQUE IGLESIA, Department of Chemical Engineering, University of California at Berkeley and E.O. Lawrence Berkeley National Laboratory, Berkeley, CA, iglesia@cchem.berkeley.edu
RuOx and H3PVxMo12-xO40 clusters catalyze CH3OH oxidation to methyl formate (MF) and dimethoxymethane (DMM) at near ambient temperatures. DMM synthesis involve bifunctional redox-acid pathways favored by acidic supports. The concurrent formation of dimethylether can be inhibited by titration of acid sites with organic bases to form stable pyridine-polyoxometallate (POM) composite catalysts with high DMM selectivity. Reaction pathways involve catalytic redox cycles using lattice oxygen atoms on active oxides to form primary formaldehyde products and secondary reactions of methoxymethanol or hemiacetal intermediates to form MF on supports containing dehydrogenation functions (ZrO2, SnO2) and DMM on acidic supports (Al2O3, SiO2). Kinetic and isotopic studies showed that initial HCHO synthesis is limited by C-H bond activation on lattice oxygens on both RuOx and POM clusters.
9-02
Chemistry-Aided Design of
Future Clean Fuels
EDWARD L. SUGHRUE, Uday
T. Turaga, Bartlesville Technology Center, ConocoPhillips Company,
Clean fuels are the result of a continuum of changes in the chemical composition of gasoline and diesel. The removal of lead from gasoline in the 1970s, the addition of oxygenates in the 1990s, and the current removal of sulfur each impacted the chemical composition of fuels. Understanding the interaction between fuel composition and process chemistry enables not only optimal application of current refining processes but also development of new approaches to produce clean fuels. For example, utilizing detailed analyses of the distribution of sulfur-containing molecules in refinery streams, reactor models are now used to both design new hydrodesulfurization units and integrate them with existing units. Similarly, molecular analyses of gasoline streams suggest methods to minimize octane loss during the production of ultra-low sulfur gasoline. These and other examples will be used to discuss the impact of future clean fuel requirements on fuel composition and processing.
9-03
The Role of Liquid
Products in Catalyst Pores for Influencing Product Olefin Readsorption and
Hydrocarbon Chain Initiation in Fischer-Tropsch Synthesis
R. J. MADON1, E. Iglesia2, 1Engelhard Corporation,
Iselin, NJ, 2Department of Chemical Engineering, University of
California, Berkeley, CA, Rostam.Madon@Engelhard.com
During Fischer-Tropsch synthesis, catalyst pores are filled with
waxy liquid product hydrocarbons.
This liquid phase helps to increase the overall reaction rates for the
readsorption of product -olefins which in turn increase hydrocarbon chain
initiation. This results in
non-linear Flory product distribution and the formation of a heavier more
paraffinic product slate. We use
transition state theory to show that higher olefin readsorption rates of larger
olefins are not the result of higher solubility of olefins in the liquid
phase. Increasing olefin solubility
is either unimportant for olefin readsorption, or, under certain circumstances,
would actually increase the tendency of adsorbed olefins to desorb rather than
of solvated olefins to readsorb.
Thus the olefin solubility – physisorption model is inconsistent with
transition state theory and with experimental observations. Instead, the liquid hydrocarbon phase
within catalyst pores introduces an intraparticle transport limitation on the
olefin products as they exit these pores.
These intraparticle diffusion limitations induce fugacity gradients that
lead to the observed enhanced olefin adsorption as olefin size increases within
catalyst pores.
9-04
C-H Bond Activation by
Platinum
GABOR A. SOMORJAI, Department of Chemistry and
C-H bond activation for several alkenes (ethylene, propylene, isobutene, cyclohexene, and 1-hexene) and alkanes (methane, ethane, n-hexane, 2-methylpentane, and 3-methylpentane) has been studied on the (111) crystal face of platinum as a function of temperature at low (< 10-6 Torr) and high (1 Torr) pressures in the absence and presence of hydrogen pressures (10 Torr). Sum frequency generation (SFG) vibrational spectroscopy has been used to characterize the adsorbate structures and high pressure scanning tunneling microscopy (HP-STM) has been used to monitor their surface mobility under reaction conditions during hydrogenation, dehydrogenation, and CO poisoning. C-H bond dissociation occurs at low temperatures ~250 K, for all of these molecules, although only at high pressures for the weakly bound alkanes because of their low desorption temperatures. Bond dissociation is known to be surface structure sensitive and we find that it is also accompanied by the restructuring of the metal surface. The presence of hydrogen slows down dehydrogenation and for some of the molecules it influences the molecular rearrangement, thus altering reaction selectivity. Surface mobility of adsorbates is essential to produce catalytic activity. When surface diffusion is inhibited by CO adsorption, ordered surface structures form and the reaction is poisoned. Ethylene hydrogenation is surface structure insensitive, while cyclohexene hydrogenation/dehydrogenation are structure sensitive. n-Hexane and other C6 alkanes form either upright or flat lying molecules on the platinum surface that react to produce branced isomers or benzene, respectively.
9-05
Parameter Estimation in
Nonlinear Models when the Estimates Really Matter
S. Aydogan, J. Caruthers, N. Delgass, S.-H. Hsu, F. Ribeiro, V.
Venkatasubramanian, G.BLAU, S.Orcun Department of Chemical Engineering and
Discovery Park, Purdue University, West Lafayette, IN, blau@ecn.purdue.edu
Classical Nonlinear Design of Experiments and Analysis Strategies are available for discriminating rival kinetic models for catalytic reaction systems and for generating minimum variance parameter estimates for the model selected. These methods are rarely used because of the lack of understanding of their statistical underpinnings by the modeling community, the convenience of linear statistical methods and companion hostility of nonlinear estimation procedures, and finally, the lack of importance of high quality parameter estimates. The ushering in of the era of design informatics has changed this paradigm. It is now critical to estimate high quality microkinetic rate constants and use them as response variables to characterize other physiochemical properties of the catalyst. The power and storage capabilities of the high speed computers are now making it possible to realize design and analysis capabilities which permit the relaxing of questionable assumptions in classical methods while simultaneously providing a more user friendly environment. In this talk we will define and illustrate the need and consequence of applying Markov Chain/MonteCarlo procedures to Bayesian estimation to generate high quality parameter for a simple reaction system. A novel adaptive gridding technique developed to address the computation challenges will also be presented. Finally, generalization of the procedures introduced to more complex system will be discussed.
9-06
Mobility of Catalytic
Nanoparticles
ABHAYA K. DATYE1*, Thomas Hansen1, Mangesh Bore1, Qing Xu1, Ron Goeke1, Lani Miyoshi Sanders1, Brian Swartzentruber2, 1University of New Mexico, Albuquerque, NM, 2Sandia National Laboratories, Albuquerque, NM
Sintering of catalysts is
an important mechanism for catalyst deactivation. The active phase in these catalysts
consists of nanosized metal particles, which can transform at elevated
temperatures into particles as large as few hundreds of nanometers leading to
loss of activity and selectivity.
One of the proposed mechanisms involves the migration and coalescence of
nanoparticles. Models for catalyst
sintering assume that the diffusion of nanoparticles on surfaces scales with
(particle diameter)n,
where the exponent n can vary from -4 to -7. Such models imply that as
particles grow in size, the rates of migration and coalescence will slow
down. In this work, we will report
systematic studies of the migration of nanoparticles on oxide surfaces at sizes
ranging from a few atoms to several tens of nanometers. We have used a variety of techniques,
ranging from scanning tunneling microscopy, scanning electron microscopy as
well as transmission electron microscopy.
We also performed
9-07
Scanning Transmission Electron Tomography and Supported Nanoparticle Catalysts
JOHN MEURIG THOMAS*, Paul A. Midgley, Dept. of Materials Science, University of Cambridge, Cambridge, United Kingdom, Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21, Albemarle St., London,United Kingdom
It is desirable to develop non-destructive methods of determining the distribution of sub-nanometer metallic and bimetallic catalysts supported on highly porous oxides. In particular, the location of nanoparticle Pt-Ru catalysts, which exhibit high activities and selectivities in the hydrogenation of polyenes and other organic compounds, needs to be precisely determined when the siliceous support is composed of non-ordered nanopores of average diameter ca 6 nm. The advantage of doing so using dark-field (rather than bright-field) annular scanning electron microscopy, which can also be adapted to retrieve the elemental composition of individual particles weighing as little as a few zeptograms (10-21g), will be outlined.
9-08
A New Approach to Obtain
Highly-Dispersed Supported Ru/SiO2 Catalysts
S. SOLED, A. Malek, S. Miseo, J. Baumgartner, C. Kliewer, M.
Afeworki, P. A. Stevens, ExxonMobil Research and Engineering Company,
Preparation of metal catalysts is an old field with few new directions discussed in either the academic or patent literature. Most supported metal catalysts are prepared from the corresponding supported metal oxides, classically by incipient wetness impregnation of solutions containing metal salts, followed by drying and then calcination to form the oxides. By changing the preparation method, the interaction between the supported oxide and the support changes, which in turn modifies reducibility and dispersion of the supported metal. Here we report a new approach specifically for preparing well-dispersed supported Ru catalysts on silica. We show that partially oxidizing a Ru- triethanolamine impregnate on silica forms a strongly interacting precursor, which bonds to and spreads on the support. This precursor avoids the necessity of using rigorous anaerobic conditions or esoteric precursors to form supported organometallic complexes. Reduction of this Ru-precursor creates tiny metal crystallites homogeneously distributed on silica, in sharp contrast to what occurs via traditional impregnation routes. This homogeneous distribution also leads to enhanced resistance to reductive sintering, which we clearly demonstrate by chemisorption and TEM techniques. We present preparation, characterization and aromatic hydrogenation data to illustrate this new technique of preparing supported Ru catalysts.
9-09
Poisoning and Deactivation of Cobalt-based
Fischer-Tropsch Catalysts By ppm And Sub-ppm Level Reactive Nitrogen Compounds
S. C. LEVINESS, H. J.
Robota, X. Zhan, J. Engman, Syntroleum Corporation,
Sulfur poisoning of cobalt Fischer-Tropsch catalysts has been known since the earliest days of the technology, and is the subject of numerous scientific publications, including a number by Prof. Bartholomew in the 1980s. More recently extensive work has been conducted in the area of cobalt FT catalyst deactivation due to surface oxidation and/or spinel formation due to high water concentrations and/or water-to-hydrogen ratios. Part per million levels of reactive nitrogen compounds – mainly ammonia, with smaller amounts of hydrogen cyanide and possibly nitrogen oxides – are typically formed in synthesis gas generation processes. The patent literature contains numerous claims for the need, and methods, to remove these compounds from FT synthesis gas feeds but to date very little/no published information exists regarding the actual details of nitrogen compound induced poisoning/deactivation.
We have investigated the effects of NH3, HCN, and NOx both when added to laboratory fixed bed and slurry autoclave synthesis gas feeds and when present in real autothermal reformer/catalytic partial oxidation synthesis gas in a pilot plant scale slurry bubble column reactor. The results of these studies indicate markedly different effects from nitrogen than from sulfur or water induced deactivation mechanisms. The presence of reactive nitrogen compounds initially causes a rapid, though limited, loss of activity. In this regime the deactivation rate is directly proportional to the nitrogen compound feed space velocity. During this phase, the number of impacted sites appears larger than the number of nitrogen atoms involved, but is limited to suppressing activity by only about 35%. Continued operation yields much lower further deactivation rates that are only weakly dependent on the nitrogen compound concentration and space velocity. Nitrogen poisoned catalysts operated with clean synthesis gas feeds show a very slow reactivation, but essentially 100% activity can be easily restored through a relatively mild in-situ hydrogen treatment.
9-10
Spectroscopic
Identification of Carbonaceous Species on Silica-Supported, and
Platinum-Promoted Iron Fischer-Tropsch Catalysts
CALVIN H. BARTHOLOMEW, Jian Xu, Catalysis Laboratory and Department of Chemical Engineering, Brigham Young University, Provo, UT, bartc@byu.edu
Carbonaceous surface species and bulk iron carbides formed under commercially-relevant Fischer-Tropsch synthesis (FTS) conditions on moderately dispersed, high-activity silica-supported iron catalysts (Fe/SiO2, FePt/SiO2 and FePtK/SiO2) were spectroscopically characterized. Bulk iron phase compositions were determined by Mössbauer spectroscopy, and phase transformations of carbonaceous species during pretreatment with CO, H2, or H2/CO and following reaction were characterized using temperature-programmed hydrogenation (TPH). Isothermal transient rates of FTS were also measured for catalysts after different pretreatments.
Six surface and bulk carbonaceous species were quantitatively identified from combined TPH and high-pressure Mössbauer spectra of the FePtK catalyst; They include, in order of decreasing reactivity: (a) adsorbed, atomic carbon (C); (b) amorphous, lightly poly-merized hydrocarbon or carbon surface species (C); (c) bulk ´ and carbides (Fe2.2C and Fe2.5C); and (d) disordered and moderately-ordered graphitic surface carbons. The distribution of active and inactive carbon species varies with pretreatment and time-on-stream. A correlation between the amount of reactive α-carbon (Cα) and initial catalytic activity after different pretreatments was observed. The method of Li et al.1 for deter-mining irreversible chemisorption of CO does not measure active site densities on silica-supported iron quantitatively. Nevertheless, specific activity based on H2 chemisorption after reaction may be proportional to active site density. Models, based on this and pre-vious work, are proposed for iron phase and carbon phase transformations in silica-supported iron during pretreatment, FTS, and post-reaction passivation/oxidation.
9-11
Structure-function
Relationships in Pd-Au Catalysts
D. WAYNE GOODMAN, Department of Chemistry,
Model mixed-metal catalysts consisting of Pd alloyed with Au as bulk films on refractory metal single crystals and as nanoparticles supported on oxides have been characterized using an array of surface techniques including X-ray photoemission spectroscopy (XPS), low energy ion scattering spectroscopy (LEIS), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), infrared reflection absorption spectroscopy (IRAS), metastable impact electron spectroscopy (MIES), scanning tunneling microscopy (STM), temperature programmed desorption (TPD), and reaction kinetics. The surface sensitivity of LEIS and IRAS has been exploited for elucidating atomic composition of the outermost surface layer. Of special interest is the composition of the surface compared to the overall composition, particularly in transitioning from planar surfaces to nanoparticles, in the presence and absence of adsorbates. The mechanistic details of the vinyl acetate synthesis reaction, used to probe the structure-function relationship of these alloy surfaces, will also be discussed.
9-12
The Nature of the Active
Sites in Au/TS-1 Catalysts for Propene Epoxidation by Oxygen and Hydrogen
B. Taylor, L. Cumaranatunge, A. M. Joshi, K.T. Thomson, W. N. DELGASS, School of Chemical Engineering, Purdue University, West Lafayette, IN, delgass@ecn.purdue.edu
Partial oxidation of propylene to propylene oxide (PO) by H2
+ O2 over Au/TS-1 as a function of TS-1 particle size showed the
number of active sites to be limited and that reaction may occur within the
TS-1 crystallites. Catalysts
prepared with low titanium and low gold loadings confirmed the presence of a
small number of very active Au/Ti sites, formed more efficiently at low
loadings. A catalyst consisting of
0.01 wt % Au on TS-1 with a Si/Ti = 500 was found to have the highest activity
per gold atom yet reported (350 gPO hr-1 gAu-1
at 200°C). These catalysts were
also shown to have an inherent gold uptake that, when exceeded, produced
inferior
9-13
Poisoning, and Fouling of V2O5/TiO2
SCR Catalysts by Ash from Coal- and Biomass-Fired Boilers
WILLIAM
C. HECKER, Xiaoyu Guo, Aaron Nackos, John Ashton, Calvin H. Bartholomew, Larry
L. Baxter, Brigham Young University, Provo, UT
A comprehensive study of deactivation of V2O5/TiO2 SCR catalysts by ash minerals from coal- and biomass-fired boilers was undertaken at laboratory and small pilot plant scales. Laboratory activity tests to determine effects of poisoning by basic ash components were conducted on commercially-relevant 1% V2O5/9% WO3/ TiO2 catalysts pre-impregnated with various levels of soluble Na and Ca compounds. These experiments simulate possible poisoning of “dusted” SCR catalysts during exposure to flue gas below the dew point. Significant losses of activity with increasing Na or Ca concentrations are observed, although at Na/V and Ca/V ratios greater than one, activity level approaches a constant low value which is nevertheless still measurable. Loss of activity is significantly greater for Na relative to Ca compounds. These results suggest that substantial loss of activity is associated with adsorption of basic cations on the acid sites of V2O5/TiO2, although poisoning of sites is not complete at saturation coverage by the poison.
Surface sulfation by SO2 of 1-5% V2O5/TiO2 catalysts during reaction, on the other hand, increases catalytic activity. In situ FTIR spectroscopy and XPS analyses indicate that SO2 is not adsorbed as a sulfite or sulfate on vanadia sites but rather on titania sites. Sulfation by SO2 also enhances NH3 adsorption on Brønsted acid site but not on Lewis acid sites; this suggest that sulfation may occur on sites at the interface of vanadia surface species and TiO2. NO reduction activity of both fresh and sulfated vanadia catalysts increases due to an increase in the number of active sites without changing activation energy.
Five commercial vanadia-based catalysts and a monolith catalyst prepared at BYU were tested over several thousand hours in a small pilot plant reactor using slipstreams from commercial boilers in which coal and biomass-coal blends served as fuels. Post mortem, laboratory activity studies of the monolith catalysts after various exposure times indicate that fouling and plugging rather than poisoning are the main deactivation mechanisms for vanadia catalysts under commercial operation.
9-14
Renewable Liquid Alkanes
from Aqueous-Phase Processing of Biomass-Derived Carbohydrates
G. W. HUBER, J. N. Chheda, C. J. Barrett, J. A. Dumesic, Department
of Chemical Engineering, University
of Wisconsin, Madison, WI, dumesic@engr.wisc.edu
Concerns about global warming, national security and the diminishing supply of fossil fuels are causing our society to search for new renewable sources of transportation fuels. Domestically available biomass has been proposed as part of the solution to our dependence on fossil fuels. In this respect, we have recently developed catalytic processes to convert biomass derived molecules to liquid alkanes, which could be used as transportation fuel. Alkanes ranging from C1 to C6 can be produced by aqueous phase dehydration/hydrogenation (APD/H) of sorbitol (hydrogenated glucose) by a bi-functional pathway. Sorbitol is repeatedly dehydrated by a solid acid (SiO2-Al2O3) or a mineral acid (HCl) catalyst and then hydrogenated on a metal catalyst (Pt or Pd). Larger liquid alkanes ranging from C7-C15 can be produced by APD/H of larger carbohydrate-derived molecules. The biorefining of sugars to alkanes plus CO2 and water is an exothermic process in which the products retain approximately 95 % of the heating value and only 30 % of the mass of the reactant.
9-16
Recyclable
Polymerization Catalysts – Silica-Tethered CuBr-Bipyridine Atom Transfer
Radical Polymerization Catalysts
C. W. JONES, J. V. Nguyen, School of
Chemical& Biomolecular Engineering, Georgia Institute of Technology,
Atlanta, GA, cjones@chbe.gatech.edu
It is well-known that most chemical products made on a moderate to large scale are produced in a process that utilizes solid catalysts, as the use of solid catalysts facilitates easy product recovery and repeated catalyst use. However, a notable exception to this trend exists in the area of polymerization catalysis, where most catalysts are single-use entities. For this reason, they are engineered to give extremely high productivities to achieve low residual catalyst content in the final polymers.
Nonetheless, there are many emerging polymerization technologies that produce unique new polymers from old monomers that are commercially very attractive. However, many of them, like atom transfer radical polymerization (ATRP), require a large amount of catalyst that must be effectively recovered and ideally recycled to facilitate potential commercial application. Indeed, ATRP is an attractive technology because it allows for the preparation of well-defined polymers such as block copolymers due to the quasi-living/”controlled” nature of the polymerization. Unfortunately, ATRP requires a relatively high catalyst loading that results in significant metal residue in the final polymer. Thus, a recoverable, recyclable catalyst would be a useful advance.
The construction of solid catalysts for polymerization requires different design rules than catalysts for small molecule transformations. In particular, the role of porosity, or a lack thereof, plays a critical role. Here we report our recent studies into the design of recoverable, recyclable ATRP catalysts based on silica supported CuBr complexes of bipyridine and pyridylmethanimine. The roles of synthetic method, catalyst porosity, and ligand structure are evaluated in the catalytic polymerization of methyl methacrylate. Additionally, a new catalyst regeneration method is introduced and an effective, recyclable system for the controlled polymerization of methacrylate monomers is achieved.
9-17
Naturally Chiral Surfaces
Andrew J. Gellman, Joshua D. Horvath, A. Koritnik, D. RAMPULLA, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA
Single crystalline surfaces terminated in
structures with kinked steps have inherent chirality. The enantioselective properties of these
surfaces have been explored using both temperature programmed desorption (TPD)
and Fourier Transform - Infrared Reflection Absorption Spectroscopy (FT-IRAS)
measurements. The adsorption of
R-3-methylcyclohexanone (R-3-MCHO) has been shown to be enantioselective on the
several different kinked Cu surfaces.
TPD measurements show distinct, resolvable features associated with
desorption from the terraces, steps, and kinks on the surface. The desorption kinetics from the kinks
depend on the relative handedness of the adsorbate and the surface. The decomposition of chiral alkyl groups
including 2-butyl and 2-methyl-butyl have been studeied on the Cu(531) and
Cu(643) surfaces. Their
decomposition by β-hydride elimination yields a number of products and the
product yields have been shown to depend on the relative handedness of the
alkyl groups and the Cu surfaces.
These results suggest that naturally chiral surfaecs can be used for
enantioselective chemical processes such as hetergeneous catalysis or
separations.
9-18
NO Oxidation Reaction Kinetics on Pt/Al2O3
Catalyst
S.S. Mulla, N. Chen, W. N. Delgass, W. S. Epling†, F. H. RIBEIRO,
School of Chemical Engineering, Purdue University, West Lafayette, IN, †Cummins,
Inc., 1900 McKinley Ave, Columbus, IN, fabio@purdue.edu
The oxidation of NO to NO2 over a supported noble metal
component is an important step involved in NOx abatement techniques, e.g.,
selective catalytic reduction (SCR) and NOx storage/reduction (NSR) processes
being developed for lean-burn diesel engines to limit their NOx emission. We
demonstrate here the kinetics of NO oxidation reaction on a Pt/Al2O3
catalyst. The rate equation for the reaction was determined to be 
, with k as the rate constant. Thus, the product NO2
inhibits the forward rate and this makes it imperative to include the influence
of NO2 concentration in any analysis of the kinetics of this
reaction. The apparent activation energy was 82 kJ mol-1 ± 9 kJ mol-1.
We also propose a reaction mechanism consisting of elementary reaction steps
that attempts to explain the observed kinetics. We will also discuss our
attempts to understand the effects of Pt particle size on this reaction. Our
experimental results indicate that the Pt particle size affects the NO
oxidation turnover rate (TOR) significantly, with larger Pt particles giving a
higher TOR. These findings are crucial to optimize the oxidation of NO to NO2,
and hence the overall NSR process.
9-19
Surface Properties of Supported Gold and Alloy
Nanoparticle Catalysts
Jin Luo+, Mathew M. Maye+, Nancy Kariuki+,
Lingyan Wang+, Peter Njoki+, Derrick Mott+,
Yan Lin+, Mark Schadt+, Stephanie I-Im Lim+,
Vivian W. Jones+, CHUAN-JIAN
ZHONG*, Department of Chemistry, State University of New York at
Binghamton, Binghamton, NY, +3M Corporation, cjzhong@binghamton.edu
We have recently been investigating core-shell assembled gold and alloy nanoparticle catalysts for electrocatalytic oxidation of carbon monooxide and methanol and reduction of oxygen, which are of interest to the development of fuel cell catalysts. The exploitation of the catalytic activity of such materials requires the ability to manipulate the interparticle spatial and surface access properties in controllable ways. This ability is inherently linked to the controllable activation of the nanostructure in terms of size and surface properties. This paper reports recent findings of our investigations in probing the structural and morphological evolution of molecularly-capped metal nanoparticles on different support materials under thermal treatment using atomic force microscopy (AFM), infrared spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The results demonstrate that the nanocrystal size and surface binding sites can be controlled by a combination of factors including adhesion, mobility, composition, activation energy and surface tension. These findings have important implications to the design and processing of advanced nanostructured catalysts.
9-20
Electro-catalytically
Performance Improvement of La1-xSrxCo1-yFeyO3
(LSCF) Cathodes Formed Using the Sol-Gel Method
LOUISE J.B. LIU, Viola V. Birss, Dept. of
Chemistry, University of Calgary, Calgary, AB, Canada, jlouise@clarkson.edu
La1-xSrxCo1-yFeyO3 (LSCF) perovskite cathodes display significantly better performance than LaxSr1-xMnO3 (LSM) because of their high catalytic activity for O2 reduction, and their very good ionic and electronic conductivity. The sol-gel (SG) method, combined with low processing temperatures, has become increasingly popular for the preparation of metal oxides, due to its advantages of producing materials with high porosity, high surface areas, and homogeneity on the molecular scale. In the present work, SG methods have been employed to synthesize LSCF cathode and 2 mol% samaria-doped ceria electrolyte. The structure phase, morphology, particle size and elemental composition of the SG-LSCF cathodes was obtained using XRD, HRTEM, SEM and WDS. Electrochemistry was carried out in a 3-electrode half-cell configuration, exposed to air. The cathode so-prepared is found to be primarily composed of the LSCF tetragonal phase and its crystallite size ranges between 20-30 nm. SEM showed that the SG-LSCF cathode layer is ca. 30 mm thick and has highly structured channels with thin walls and pores on the order of a micron or less in diameter. HRTEM images of a typical particle indicate the presence of a highly crystalline plane (101) with a few stacked faults. In terms of the cathode’s electrochemical performance, the specific area resistance of the cathode at 700 oC averaged to ca. 0.30 W·cm2, which was substantially better than that obtained by the traditional synthesis technology.
9-21
Liquid-Phase Reductive
Deposition as Novel Preparation Method of
Hybrid Nano-particulate Catalysts
ATSUSHI MURAMATSU, Yoji Sunagawa, Sarantuya Myagmarjav, Hideyuki Takahashi, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai, Japan
Nanoparticles have been received much attention and been widely studied, since its property can change only by the size because of quantum effect when the size is reduced to nanometer level. The decrease of the size is also expected to enhance the catalytic activity, because the decrease in size results in the increase of the total surface area and active sites with unsaturated bonding. Among various methods to synthesize the nanometer-sized particles, the liquid-phase reduction method is one of the easiest procedures, since nanoparticles can be directly obtained from various precursor compounds soluble in a specific solvent. We have taken Ni as an example of target nano-material and then reported that Ni and Ni-Zn nanoparticles with a diameter from 5 to 10nm and an amorphous-like structure were synthesized by using liquid-phase reduction method and that Zn addition to Ni nanoparticles promote the catalytic activity for 1-octene hydrogenation. However, unsupported particles finally lost their activity due to tremendous aggregation because of its high surface activity. In order to solve this problem, we have been developing the selective deposition method onto TiO2 nanoparticles, named as the liquid-phase selective-deposition method, where TiO2 plays a role of formation center of Ni nanoparticles as well as protection from aggregation and growth of the particles. In this paper, I will focus on the concept of this method and the detailed formation mechanism of Ni-Zn/ TiO2 nanocomposite. Nanoparticles synthesized was dispersed and stabilized by the selective deposition onto TiO2 surface. The particle size was decreased with increasing the amount of Zn added, thus the catalytically active Ni surface area was increased. The selective deposition onto TiO2 surface and addition of Zn to the nanoparticle promoted the catalytic activity of Ni-Zn nanoparticle, e.g. the catalytic activity of Ni-Zn/TiO2 was ca. 10 times higher than that of the unsupported Ni nanoparticles. Ni in the nanocomposite was assigned as metallic, although their surface was oxidized under the atmospheric condition, but Zn and B were deposited as their oxide.
9-22
Active
Media Effect on Strength and Durability of Catalysts
E. D. SHCHUKIN1,2,3, A. I.
Bessonov1, L. N. Sokolova1, S. I. Kontorovich1,
L. N. Burenkova2, B. V. Romanovsky2, 1Institute
for Physical Chemistry of the Russian Acad. Sc., Moscow 117915, Russia; 2Moscow
State University, Moscow, Russia; 3Johns Hopkins University,
Baltimore, MD, shchukin@jhu.edu
The mechanical wear facilitated by the medium influence can be a principal cause of catalyst losses in many heterogeneous catalytic processes. The direct experiments with MgO, Co-Mo, Ca-Ni-P, Al-Cr-K and other catalysts show that both their strength and durability decrease significantly, sometimes dramatically during catalysis with respect to identical tests in the inert media. The effect has been explained as the thermodynamically predicted result of the mutual influence of solid phase and medium in catalytic process: new bonds arising between them may cause bonds weakening and rupture both in adsorbed molecules and in solid surface (i.e., Rehbinder effect manifestation). In this aspect, catalyst is a victim of its destination. However, the resistance of catalyst granules to wear can be essentially improved by perfecting their technology: selection of optimal size grading of the granule forming particles and strengthening contacts between these particles, using nano-disperse inactive fillers and hydration hardened mineral binders, reducing residual internal stresses, etc. Catalysis assisted rupture of surface bonds may result also in creating new surface adatoms and, correspondingly, in accelerating the surface selfdiffusion and particles sintering, i.e., in the increase in strength, or achieving the same interparticle contacts development and strength at lower sintering temperatures (Catalysis Enhanced Sintering - CES). This has been recently shown both for metals (Fe, Ni) and ceramics (alumina, zirconia, yttria) powder samples.
9-23
Synthesis of Nanosized TiO2-SiO2 Complex Particles and Their Photocatalytic Activity
G. W. ZHOU1, Y. Y. Wang1, Z. Y. Shao1,
G. Y. Xu2, G. Z. LI2, 1School of Light
Chemical and Environmental Engineering, Shandong Institute of Light Industry,
Jinan, China; 2Key Laboratory for Colloid and Interface of Ministry
of Education of China, Shandong University, Jinan, China, guoweizhou@hotmail.com
Titania-silica (TiO2-SiO2) nanoparticles were prepared by sol-gel procedure with mix up hydrolyzed titania-sol(TBOT as a titanium precursor) and silica-sol (TEOS as a silica precursor). These nanoparticles were then characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM)-energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-Vis) spectroscopy, Raman spectroscopy and thermogravimetric/differential thermal analysis (TGA/DTA). The analytical results demonstrated that the complex of SiO2 with TiO2 can increase the phase transformation temperature of TiO2 and enhance the thermal stability of TiO2 structure, no rutile phase was observed for the TiO2-SiO2 particles up to 800 0C. The micrographs of TEM and SEM showed that the TiO2-SiO2 particles had a spherical and a narrow size distribution 60~80 nm. The Raman spectra indicated that the nanoparticles showed highly broadened with the blue shift of the anatase features at lower temperature and the peaks sharpened as the temperature increased. In addition, TiO2-SiO2 particles showed high photocatalytic activity on the photocatalytic decomposition of phenol and its derivatives.
10-01
Evaluation
of Decoherence for Quantum Control and Computing
V. PRIVMAN, Center for Quantum Device Technology,
Different approaches in quantifying environment
induced decoherence are considered. We identify a measure of decoherence,
derived from the reduced density matrix of the system, that quantifies the
environmentally induced error, i.e., deviation from the ideal isolated-system
dynamics. This measure can be shown to have several useful features. Its
behavior as a function of time has no dependence on the initial conditions, and
is expected to be insensitive to the internal dynamical time scales of the
system, thus only probing the decoherence-related time dependence. For a
spin-boson model—a prototype of a qubit interacting with environment—we also
demonstrate the property of additivity: in the regime of the onset of decoherence,
the sum of the individual qubit error measures provides an estimate of the
error for a several-qubit system, even if the qubits are entangled, which is
important in quantum-computing applications. This makes it possible to estimate
decoherence for several-qubit quantum computer gate designs.
10-02
Spins
in Semiconductors for Storing and Processing Quantum Information
H. W. JIANG, Department of Physics and
Astronomy,
Spins in semiconductors have many desirable
properties for quantum information processing. Recent key experimental demonstrations
by several groups have considerably improved the prospects of physical implementation
of a semiconductor based processor. In this talk, I will highlight the recent
progress of the UCLA group. The
results of an experiment to manipulate single spin with microwave pulses and to
detect its magnetic resonance and spin orientation will be reported. Effort on the fabrication and
characterize long-coherent-time qubits on epitaxial SiGe heterostructures will
be described. The first
demonstration of trapping, storing, and detecting single photoelectrons in a
controllable electrostatic quantum dot will also be presented.
10-03
Efficient
Wave-Induced Switching & Quantum-NOT Operation in Coupled Quantum Wires
A. Ramamoorthy,1 J. P. BIRD,2,
1Nanostructures Research Group, Department of Electrical
Engineering, Arizona State University, Tempe, AZ, 2Department of
Electrical Engineering, University at Buffalo, the State University of New
York, Buffalo, NY, jbird@buffalo.edu
Coupled quantum wires have been proposed as a
means to realize a scalable solid-state based qubit for quantum computing Both
Gaussian-wave-packet, and plane-wave, based implementations of this approach
have been explored theoretically, along with schemes for entanglement and the
realization of multi-qubit networks. In spite of this interest, however, there
has been little experimental progress on this problem to date. In this
presentation, we present the results of a first practical step towards the
implementation of this approach, providing evidence for the successful
demonstration of a single qubit structure
comprised of two coupled GaAs
quantum wires. Our experimental results reveal extremely efficient switching of
the electron wavefunction (by nearly 100%) between the two waveguides of this
structure, and also show evidence for the proposed quantum-NOT operation in
which an incoming electron wave is switched effectively from one waveguide to
the other. This behavior is observed to temperatures as high as 35 K,
suggesting the considerable potential of this approach. In our presentation we
also speculate on the possibility of extending our results to achieve
entanglement of coupled qubits based on this system.
10-04
Transmission
Coefficient for an Electron Through a Quantum Point Contact in an Electric and
Magnetic Field
M.L. GLASSER1, N.J.M. Horing2,
K. Sabeeh3, Department of Physics and Center for Quantum Device
Technology, 1Clarkson University, Potsdam, NY, 2Department
of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken,
NJ, 3Department of Physics, Quaid-i-Azam University, Islamabad,
Pakistan, laryg@clarkson.edu
Electron transmission through a quantum point
contact (QPC) in the presence of an electric and magnetic field is examined.
The QPC is modeled as a saddle potential. The relevant Green function is
derived using Schwinger’s operator equation of motion method and used to obtain
the transmission coefficient. For vanishing electric field the result reduces
to Fertig and Halperin’s result.
10-05
Mesoscopic
and Microscopic Spin Injection, Spin Precession, Spin Diffusion and Spin
Transport in Semiconductor Nanostructures
M. W. WU, Hefei National Laboratory for Physical
Sciences at Microscale University of Science and Technology of China Department
of Physics, University of Science and Technology of China Hefei, Anhui, China, mwwu@ustc.edu.cn
In this talk we are going to present our
theoretical investigations on spin kinetics of semiconductor nanostructures
based on many-body, single particle and mesoscopic approaches under various
conditions. Both transient and steady-state transports are addressed. In
addition to the cases near the equilibrium, spin kinetics far away from the
equilibrium such as electrons of high spin polarization and/or electrons with
strong electric field (hot electrons) is also discussed in detail. Many novel
effects are predicted.
10-06
Irreversible
Deposition of Particles on Pre-Treated Surfaces
A.
CADILHE, N. Araújo, GCEP-Centro de Física, Universidade do
Minho, 4710-057 Braga, Portugal, cadilhe@fisica.uminho.pt
We present a
10-07
Synthesis
and Applications of Monofunctional Gold Nanoparticles
J. G. Worden, Q. Dai, X, Liu, Q. HUO, Department of Coatings and Polymeric
Materials, North Dakota State University, Fargo, ND, qun.huo@ndsu.edu
In the bottom-up
approach towards nanomaterial development, there are two most important aspects
to be addressed: one is the
synthesis of nanobuilding blocks and the
other one is how to assemble the nanobuilding blocks together into
materials or devices with precisely controlled structures, properties and
functions. Recently our group developed a unique solid phase technique to
synthesize gold nanoparticles with a single functional group attached to the
surface. Using the monofunctional
gold nanoparticles as molecular
nanobuilding blocks, we further demonstrated the synthesis of covalently
bonded nanoparticle/polymer hybrid materials by chemical reactions. This
research provides a promising tool in the precise positioning of nanoparticles
to a particular location of a substrate or scaffold material, and its
applications in quantum computing and quantum devices will be discussed in the
presentation.
10-08
Decoherence
of a Quantum System and Dynamics of a Heat
S. SAIKIN, Center for Quantum Device Technology,
Department of Electrical and Computer Engineering,
The traditional approach to evaluate dissipation
processes in a classical system interacting with an external reservoir is based
on the Markov approximation. In this case evolution of a system possesses a
semi-group property and is local in time. It was shown that for a quantum
system this approximation is valid only on timescales larger than the thermal
time, 
.
In most non-markovian models for evolution of
open quantum systems the bath is described by a set of non-interacting
oscillators. I will consider how an internal interaction between modes of a
thermal bath affects semi-group property and characteristic timescales of
irreversible dynamics of a quantum system.
10-09
Collective
Decoherence of Nuclear Spin Clusters
A. FEDOROV, Center for Quantum Device
Technology, Department of Physics and Department of Electrical and Computer Engineering,
The problem of dipole-dipole decoherence of
nuclear spins is considered for strongly entangled spin cluster. Our results
show that its dynamics can be described as the decoherence due to interaction
with a composite bath consisting of fully correlated and uncorrelated parts.
The correlated term causes the slower decay of coherence at larger times. The
decoherence rate scales up as a square root of the number of spins giving the
linear scaling of the resulting error. Our theory is consistent with recent
experiment reported in decoherence of correlated spin clusters.
10-10
Loss of Coherence in Gate-Controlled Qubit
Systems
D. SOLENOV, Center for Quantum Device Technology,
Department of Physics and Department of Electrical and Computer Engineering,
Clarkson University, Potsdam, NY, solenovd@clarkson.edu
Studies of decoherence for quantum computing has
been based on investigation of an idling qubit system described by a
time-independent Hamiltonian. We present an approach that allows investigating
the influence of essentially time-dependent gate controls on coherence of qubit
system. The approximation to the reduced density matrix is obtained to the
leading order in system-to-environment interaction. In the case of an adiabatic
settings the approximation is shown to give decoherence behavior of the exact
solution. The approach is analyzed on the example of a qubit in the rotating
wave field.
10-11
Single-Photon
Optical Detectors Based on Superconducting Nanostructures
R. SOBOLEWSKI, Department of Electrical and Computer
Engineering and the Laboratory for Laser Energetics, University of Rochester,
Rochester NY, roman.sobolewski@rochester.edu
We review the current state-of-the-art in the
development of superconducting single-photon detectors and demonstrate their
advantages over conventional semiconductor avalanche photodiodes, in terms
ultrafast and very efficient counting capabilities of both visible-light and
infrared photons. Superconducting single-photon detectors (SSPDs) are quantum
photon counters. Their detection mechanism is based on photon-induced
generation of a picosecond voltage transient across a nanostructured, 10´10-mm2-area
NbN meander (4-nm-thick and ~100-nm-wide stripe). Our best devices operate at 2
K and exhibit quantum efficiency of ~30% in the visible to 1.55 m wavelength
range, 2-GHz photon counting rate, timing jitter of <18 ps, and dark counts
<0.01 per second. The SSPDs have already been applied in testers for debugging of
VLSI CMOS circuits and are currently being implemented for free-space optical
communications and in fiber-based quantum key distribution (cryptography)
systems. Transition edge sensors
(TESs) are superconducting nanobolometers and they act as super-sensitive
thermometers. TES devices reach quantum efficiency of >80%, have negligible dark
counts, and possess photon number resolving capability. They are excellent
x-ray detectors with ~1-eV energy resolution and are expected to find
applications in linear optical quantum computation.
10-12
Decoherence and Loss of Entanglement
D. TOLKUNOV and V.
Privman, Center for
Quantum Device Technology, Department of Physics, Clarkson University, Potsdam,
NY, tolkunov@clarkson.edu
We review our recent work establishing by an
explicit many-body calculation for an open quantum-mechanical system of two
qubits subject to independent noise modeled by bosonic baths, a new connection
between two important issues in the studies of entanglement and decoherence. We
demonstrate that the decay of entanglement is governed by the product of the
suppression factors describing decoherence of the subsystems (qubits). This
result is the first detailed model calculation proving an important and
intuitively natural physical property that separated open quantum systems can
evolve coherently, quantum mechanically on time scales larger than the times
for which they remain entangled.
Our result also suggests avenues for future
work. Specifically, for multiqubit systems, it is expected that similar
arguments should apply “by induction.” This will stimulate research to develop
appropriate quantitative measures of entanglement, and attempts to quantify
entanglement and decoherence in a unified way.
10-13
Frequency
Study of the Microwave Induced Resistance Oscillations of a High Mobility
Two-Dimensional Electron Gas
S. A. STUDENIKIN1, M.
Byszewski2, D.K. Maude2, M. Potemski2, A.
Sachrajda1, M. Hilke3, L. N. Pfeiffer4,
K. W. West4, 1Institute for Microstructural Sciences,
National Research Council of Canada, Ottawa, ON, Canada, 2Grenoble
High Magnetic Field Laboratory, MPI/FKF and CNRS, BP 166, 38042 Grenoble, Cedex
9, France, 3Department Of Physics, McGill University, Montreal, QC,
Canada,4Bell Laboratories, Lucent Technologies, Murray Hill, NJ, sergei.studenikin@nrc.ca
Microwave induced resistance oscillations
(MIROs) detected on high mobility samples have attracted much interest
recently. Under certain conditions a zero-resistance state is
observed. We have investigated the evolution of MIROs on a GaAlAs/GaAs
heterostructure (μ~107cm2/Vs) over a very wide frequency
range from ~50 GHz up to ~4 THz, from quasi-classical to the quantum Hall
regime. At low frequencies regular MIROs were observed, with a
periodicity determined by the ratio of microwave to cyclotron
frequencies. For frequencies below 150 GHz the MIROs waveform vs magnetic
field is well described by the existing theoretical models that can be used for
deducing the Landau levels width.
At higher frequencies the weak MIROs were still
observed on a background of relatively strong Shubnikov de Haas oscillations.
The MIROs progressively vanished at higher frequencies, around 400 GHz.
This sets an upper frequency limit for the observation of MIROs.
However, microwave induced resistance changes are still observed at
frequencies above 400 GHz in the form of sharp peaks at the cyclotron resonance
and its second harmonic. The observed resistance changes in the quantum
Hall regime could be qualitatively understood in terms of a bolometric-type
response.
10-14
The
Influence of Weak Measurement on Electron Transport in Quantum Dots Chains
L. FEDICHKIN, D. Solenov, Center
for Quantum Device Technology, Department of Electrical and Computer
Engineering, Department of Physics and Department of Mathematics and Computer
Science, Clarkson University, Potsdam, NY,
leonid@clarkson.edu
We consider the chain of semiconductor quantum
dots with neighboring dots coupled by tunnel barriers with one electron
coherently hopping from one dot to another. The corresponding quantum walk
behavior of electron transport is strongly affected by measurement via quantum
point contacts placed nearby each dot. We derive the evolution of electron
density matrix and analyze the transition from coherent quantum oscillatory
dynamics to diffusive classical motion.
10-15
On
Quantum Walks on Graphs
C. TAMON,Department of Mathematics and Computer
Science, Clarkson University, Box 5815, Potsdam, NY, tino@clarkson.edu
Random walk on graphs is a valuable algorithmic
technique in computer science. The recent interest in quantum walks on graphs
is fueled in part by the positive impact of the classical paradigm, but also in
part by the possibility of exploiting natural physical processes for an
implementation of a quantum model of computation. To date, there are two known
models of quantum walks, discrete and continuous-time, with their respective
algorithmic potential. We outline some recently proven structural properties
about quantum walks on some well-known graphs, along with some preliminary work
on analyzing mixing and decoherence.
10-16
Ballistic
Electro Photonics
V. NARAYANAMURTI, Division of Engineering and
Applied Sciences and Department of Physics, Harvard University, Cambridge,
MA, venky@harvard.edu
The ballistic transport of hot electrons in semiconductors
has long been a subject of interest. In this talk, I will present several
exciting new results which have broad implications for the study of new
semiconductor nanostructures including the transport of spin. These are:
Ballistic Electron Emission Luminescence which
allows the simultaneous monitoring of electron transport and luminescence for
quantum dot structures placed below the surface.
Demonstration of several new types of hot
electron based devices involving the monitoring of spin transport. Examples
include luminescent spin valve transistors and spin valve photodiodes.
Transport and luminescence studies of
semiconductor nanowires such as ZnO.
10-17
Ab
Initio Analysis of Electron-Phonon Coupling in Molecular Devices
H. GUO, Center for the Physics of Materials and
Department of Physics,
We report first principles analysis of
electron-phonon coupling in molecular devices under external bias voltage and
during current flow. Our theory and computational framework are based carrying
out density functional theory within the Keldysh nonequilibrium Green's
function formalism. We analyze which molecular vibrational modes are most
relevant to charge transport under nonequilibrium conditions. For a molecular
tunnel junction of a 1,4-benzenedithiolate molecule contacted by two leads, the
low-lying modes of the vibration are found to be most important. As a function
of bias voltage, the electron-phonon coupling strength can change drastically
while the vibrational spectrum changes at a few percent level.
10-18
Spin-polarized
Injection and Transport in a Schottky Diode
M. SHEN, S. Saikin
and M.-C. Cheng, Center for
Quantum Device Technology, Department of Physics and Department of Electrical
and Computer Engineering, Clarkson University, Potsdam, NY, shenm@clarkson.edu
Using the
10-19
Indirect
Interaction of Localized Magnetic Moments in Luttinger Liquids
D. Mozyrsky1, A. DEMENTSOV2,
D. Tolkunov2, 1Los Alamos National Laboratory, Los
Alamos, NM 87545, 2Center for Quantum Device Technology, Department
of Physics, Clarkson University, Potsdam, NY, dementav@clarkson.edu
Indirect interaction between localized spins in
Luttinger liquid is investigated. We show that spin-spin interaction is an
oscillatory function of distance between localized spins 
with amplitude
decaying asymptotically as 
where 
for attractive
and 
for repulsive
interactions. We also derive effective dynamics for the system of two spins
indirectly coupled via Luttinger liquid in nonequlibrium regime.
11-01
Ionic
Liquid Emulsions Stabilised Solely by Nanoparticles
B.P. BINKS, A.K.F. Dyab, P.D.I. Fletcher, Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull, United Kingdom, P.D.Fletcher@hull.ac.uk
When colloidal particles are partially wetted by both oil and water they adsorb very strongly to the oil-water interface and can serve as excellent emulsion stabilisers. The emulsion type, i.e. water-continuous or oil-continuous and the emulsion stability can be tuned by control of the particle surface’s affinity for the two solvents which can be expressed in terms of the contact angle between the oil-water interface and the particle surface. In this presentation, we describe the formation of both simple and multiple emulsions containing an ionic liquid with either water, an oil or both stabilised solely by silica nanoparticles. We show how emulsion type and stability can be optimised and emulsion phase inversion can be effected by varying the surface coating of the silica nanoparticles. Using different combinations of mutually immiscible mixtures of water, an ionic liquid and an oil we have successfully prepared many different types of simple and multiple emulsions (e.g. “water-in-ionic liquid-in-oil”) which show excellent stability. The emulsion results are correlated with liquid-liquid contact angle measurements on coated silica surfaces.
11-02
Molecularly-Engineered
Nanoparticles and Assemblies for Analytical/Bioanalytical Applications
C. J. Zhong, Jin Luo, Mathew Maye, Stephanie I-Im Lim, Lingyan Wang, Nancy Kariuki, Peter Njoki, Mark Schadt, Derrick Mott, Elizabeth Crew, Yan Lin, Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, cjzhong@binghamton.edu
We have been exploring a general bottom-up
pathway towards processing and assembling metal and alloy nanoparticles for
analytical/bioanalytical applications.
This pathway entails molecularly-engineered processing of particle size,
shape, composition and surface properties and molecularly-mediated assembly via
fine-tunable interparticle interactions including van der Waals forces, covalent
bonding, hydrogen-bonding, or ligand coordination. The
advanced materials present new opportunities in a wide range of technological
applications, including fuel cell catalysis, chemical or biological
sensing, and medical diagnostics or treatments. The unique electronic,
interparticle spacing, chemical specificity, framework binding, molecular
channeling, and catalytic properties of the nanostructured materials provide fine-tunable chemical/biological
sensing interfaces. Recent results of our investigations
will be discussed.
11-03
Some
Phase Diagrams of Fruit Acids and the Consequences in their Application
for Skin Lotions
ABEER AL BAWAB, Chemistry Department, Faculty of Science,
The difference from a formulation point of view
between a di-carboxylic acid and its two related hydroxy acids with one and two
hydroxy groups was investigated by comparing the structure of their emulsions
with a simple non-ionic surfactant as stabilizer and the changes taking place
during evaporation.
The results showed the introduction of a hydroxy group into the structures to have a radical impact on the structure of the emulsion and, especially the changes during evaporation.
An evaluation of the volume fraction of vesicles in the emulsion showed these to occupy a larger volume than is intuitively assumed.
The phase diagrams were determined of lactic and isohexanoic hydroxy- acids as well as salicylic acid with water, a nonionic surfactant and a paraffinic oil to outline the influence of the hydroxy-acids on the structure in a model for a skin lotion.
The results showed the influence of the acid to be similar to that of the oil, but that the difference in chain length between the two alpha acids had only insignificant influence.
The results are discussed from two aspects; the structures involved in the lotion as applied and the action of the lotion residue on the skin after the evaporation of the water
11-04
A Novel Method for the Computer Simulation of
Surfactant Self-Assembly
H. SHINTO, S. Morisada, K. Higashitani,
Department of Chemical Engineering, Kyoto University, Kyoto, Japan, shinto@cheme.kyoto-u.ac.jp
With
the help of increasing computational power, Molecular Dynamics (MD) and Monte Carlo (MC) simulations are very useful
for investigating the microscopic features of matter and material. To investigate the molecular-level features of the
surfactant solutions, several researchers have implemented the MD and MC
simulations of surfactant systems. However, it is still difficult to
simulate the self-assembly of surfactants using the atomistic models,
because long-time simulations of the large-scale systems are required to
examine the surfactant self-assembly. A common alternative
is the use of coarse-grained models to mimic the oil/water/surfactant systems.
The coarse-grained model simulations, however, provide only the qualitative
results, which are sufficiently suggestive but are not quantitatively
comparable with the experimental results.
In this talk, we present an implicit solvent model for the simulation of surfactant molecules in aqueous
solutions, where no water molecules of the
solvent are treated explicitly, but the effects
are incorporated using the solvent-averaged interactions between the surfactant segments in water. This model has been applied to the MD
simulations of (i) the
self-assembly of n-decyltrimethylammonium chloride surfactants
at different concentrations and (ii) the single micelles of different sizes.
The results will be compared with those from experiments and atomistic model
simulations.
11-05
Transformation
of Organized Assemblies in Surfactant Solutions
J. B. HUANG, College of
Chemistry, Peking University, Beijing 100871, P. R. China, JBHuang@.pku.edu.cn
By the variation of molecular structure and physichemical
conditions, the formation and transformation of amphiphilic molecular organized
assemblies such as: micelle, vesicle, were studied.
Transition of surfactant aggregates by adding non-polar organic compounds was investigated in the cationic-anionic surfactant systems. The two-phase systems were transformed into homogenous solutions with the octane addition. The results of DLS demonstrate the decrease of vesicles and the increase of spherical micelles upon octane addition. Such transformation of the surfactant aggregates was also corroborated by the results of time-resolved fluorescence quenching and viscometry.
Surfactant aggregates were also studied in the mixed systems bolaform amphiphiles and opposite charged conventional surfactant. Superior high temperature stability of vesicles was found in some mixed systems. DSC, VT-IR and Fluorescence probe results all revealed that vesicles in C20Na2/DEAB mixed systems can keep stable even at 80.
Temperature-induced micelle—vesicle transformation was also found in the mixed cationic-anionic surfactant systems. Cylindrical micelle to vesicle transition upon the increase of temperature was demonstrated in the system of SDS/DEAB. Notable transition occurred during 30-50oC and such transition was remarkably influenced by surfactant mixing molar ratio and total surfactant concentration.
11-06
Thermodynamics
and Dynamics of Diblock Copolymers at Polymer/Polymer Interfaces
B. J. Reynolds, M. L. Ruegg, N. P. Balsara, C.J. RADKE, Department
of Chemical Engineering, University of Californai, Berkeley, CA, radke@cchem.berkeley.edu
The efficacy of diblock copolymers for stabilizing interfaces between immiscible polymers depends on both thermodynamic and dynamic factors. We study the equilibrium and dynamic concentration profiles of an AB diblock co-polymer (i.e., the surfactant) at an A polymer/ B polymer interface. We create thin polymer films containing two surfactant-bearing polymeric interfaces and follow the transient concentration profiles of the diblock copolymer by dynamic secondary-ion mass spectroscopy (SIMS). For well-equilibrated films, the measured concentration profiles and the adsorption isotherms are in good agreement with self-consistent field theory (SCFT), where all necessary parameters were determined independently from SANS and gel-permeation-chromatography measurements. For the nonequilibrated films, transport of the diblock copolymer depends on the two binary Fickian diffusion coefficients and on the depth of the thermodynamic potential wells that hold the surfactant molecules at the interface. Diffusion coefficients of our system were measured in independent SIMS experiments. We again find excellent agreement between the measured transport rates of the AB surfactant across the film interfaces and those calculated using a SCFT free-energy profile and diffusion in a potential field. Fascinatingly, no kinetic barriers to adsorption/desorption are found. For the first time, surfactant adsorption dynamics at a polymer/polymer interface is addressed.
11-7
The Linker Effect in
Microemulsion Systems
EDGAR J. ACOSTA1, David A. Sabatini2, Jeffrey
H. Harwell3, 1University of
The surfactant-water and surfactant-oil interactions control the overall thermodynamic equilibrium of microemulsion systems. Intuitively, by enhancing these molecular interactions, more oil and water can be co-solubilized in microemulsion systems. One way to enhance these interactions is by introducing lipophilic and hydrophilic linkers in the formulation. Lipophilic linkers such as long chain alcohols (with more than eight carbons), fatty acids, and low HLB non-ionic surfactants tend to segregate near the tails of the surfactants, serving as an extension of these molecules into the oil phase. Hydrophilic linkers, on the other hand, are surfactant-like molecules with short hydrophobe (between six to nine carbons) that co-adsorb at the oil/water interface, increasing the interfacial area. The combination of lipophilic and hydrophilic linkers produce self-assembled pseudo-surfactants at the interface that produce efficient microemulsions with a wide range of oils, without using toxic medium chain alcohols, or high electrolyte concentrations. The use of linker formulations in cleaning applications, environmental remediation, and drug delivery systems will be discussed. The partition / segregation of linkers will be discussed using the “zipper” self-assembly hypothesis that has been proposed to explain the combined linker effect.
11-08
Experimental Observations of Dynamic Surface Tension
atHighly Curved Microfluidic Interfaces
HANS C. MAYER, Shelley L. Anna, Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA
In microfluidic devices, interfaces between two liquid phases are constrained by system geometry to have high curvature. Recent scaling arguments report a new timescale relevant to curved interfaces and predict a shift in the mechanism of surfactant mass transport from diffusion controlled to kinetic controlled based on geometry alone. We have developed a microtensiometer to measure the dynamic surface tension using a highly curved interface formed at the tip of a glass micropipette, immersed in a reservoir of surfactant solution. We show microtensiometer measurements for air-liquid interfaces using aqueous solutions of well characterized poly-ethoxylated surfactants. Our data indicate that the dynamic surface tension equilibrates earlier at more highly curved interfaces, validating the prediction of a shift at microfluidic length scales. Characterizing the dynamics of surfactants at microfluidic length scales will enable better control over the deformation and breakup of drops in microfluidic devices as well as a greater understanding of the role of surfactants in these dynamical processes.
11-09
Processing of Phospholipid Vesicles Using
Supercritical and Compressed Fluids
G.D. Bothun, BARBARA KNUTSON, Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY, bknutson@engr.uky.edu
Emerging applications of supercritical fluids to bioprocessing exploit the interaction of CO2 with phospholipid vesicles. This work examines the influence of CO2 on the bilayer fluidity of liposomes, which are representative of model cellular membranes, at the elevated pressures (up to 13.9 MPa) associated with CO2-based processing of liposomes and microbial sterilization. Fluidization of aqueous dipalmitoylphosphatidylcholine (DPPC) liposomes by pressurized CO2 (present as an excess phase) was studied by steady-state fluorescence anisotropy using the membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Reversible, pressure-dependent fluidization of the phospholipid vesicles was observed in both the gel and fluid phase states of the DPPC bilayer (DPPC, Tm ~ 315 K). These experiments demonstrated substantial melting point depression (ΔTm = -4.8 to -18.5 K) and a large broadening of the gel-fluid phase transition region, which was interpreted using conventional theories of melting point depression. The pressure-dependent surface activity of the of aqueous DPPC liposomes at the CO2 interface was determined using high pressure interfacial tension measurements. This technique provided complementary information on the influence of the CO2 interface on the adsorption and disruption of phospholipids vesicles.
11-10
Synergistic Interactions Between
Linear Polyethylene Oxide Surfactants and the Effect on Surface Tension, Phase
Behavior and Wetting
MAKONNEN M. PAYNE, Alexander Couzis, Charles Maldarelli, Department of Chemical Engineering Graduate Center – CUNY, The City College of New York, Convent Avenue at 138th Street; New York, NY, payne@che-mail.engr.ccny.cuny.edu
In this paper we report findings in synergistic interactions with respect to air-liquid interfacial tension reduction, lyotropic phase behavior and wetting. We have previously reported that combinations of 1-dodecanol with the polyethyleneglycol n-alkyl ether surfactants are able to reduce the air-liquid interfacial tension to values on the order of 20 mN/m when the total surfactant loading is on the order of 0.05% by weight. The mechanism for such significant interfacial tension reduction is not yet completely understood, but we have been able to draw correlations between the tension reduction and the presence of lyotropic phase, in the surfactant solution. In order to gain insight as to what surfactant aggregate structures exist in our mixtures, we employ cross-polarized microscopy and depolarized light scattering, where anisotropy of the aggregated structures gives rise to characteristic patterns that can be observed using a digital camera. We also report here, the ability for some of these surfactant systems to wet a model hydrophobic surface and offer possible implications that can be made about the role of the lyotropic phases and wetting. The model hydrophobic surface used is an octadecyltrichlorosilane self-assembled monolayer on bare silicon.
11-11
On the Self Assembly of
Asphaltenes to Form Nanoscale Aggregates
KEITH L. GAWRYS*, Vinnie Verruto#, Peter K. Kilpatrick#,
*Nalco Company, Energy Services Division, 7705 Highway 90-A, Sugarland, TX, #Department
of Chemical and Biomolecular Engineering, NC State University, Raleigh, NC, peter-k@ncsu.edu
Asphaltenes are the n-heptane insoluble and toluene soluble fraction of petroleum fluids. This solubility definition leads to a heterodisperse mixture of molecules that contain fused aromatic rings, a significant percentage of N, S, O heteroatoms (2-10%, w/w), and an aliphatic periphery and aliphatic connectors of aromatic moieties. This unusual molecular architecture leads to the characteristic colloid-forming properties of asphaltenes: colloidal instability during pressure and temperature reductions, deposition during transportation and processing, self assembly in solution, and adsorption onto solid-liquid, liquid-liquid, and liquid-vapor interfaces. Here, we report a comprehensive study of the self assembly properties of asphaltenes, primarily as probed by small angle neutron scattering (SANS) in organic solutions of heptane, toluene, methyl naphthalene, methanol, and their mixtures. We have systematically explored the fitting of a variety of geometric form factor models to our data and concluded that an oblate cylindrical model with polydispersity in the radial dimension best fits a large dataset of independent experiments. Such a fit, which agrees well with unbiased Guinier analyses of radii of gyration and data extrapolation to obtain zero-Q scattering intensities, enables the evaluation of mean aggregate volume and moments of the aggregate volume distribution. This in turn enables a number of very important conclusions to be drawn about the physical properties of asphaltenic aggregates. First, it is clear from our analysis that asphaltenes entrain a significant fraction of solvent, as much as 50% (v/v), within the interior of the aggregates. Second, this entrained solvent appears to rapidly exchange with solvent in the bulk. Third, the apparent fractal dimension of these aggregates varies over a broad range from 2.2-3.0 and would seem to suggest that asphaltenic aggregates, at least in the nanoscale range (1 nm < Rg < 15 nm), would seem to be better characterized as globular aggregates with roughened surfaces, rather than as mass fractals as many investigators have suggested. We have also been able to probe the flocculation of nanoscale aggregates into larger microscale aggregates. Finally, we report on the interactions of these nanoscale aggregates with each other by evaluating second virial coefficients and by exploring the role of selective solvating agents, such as resins, acids, and polymeric additives.
11-12
Interfacial Alignment of
Micelles in Surfactant-silica Aggregates as a General Approach to Materials
with Oriented Mesopores
B. Tan, S. E. RANKIN, Chemical and Materials Engineering Department,
When silica and a cationic surfactant are precipitated from an ethanol/water/ammonia solution, nearly monodisperse spherical particles with uniform, radially oriented channels result. This structure is ideal for catalysis, adsorption, and chromatrography because it combines low tortuosity with high accessibility. We investigate the formation mechanism of this structure during precipitation of tetraethoxysilane with CTAB. Using TEM to observe samples extracted early in the process and rapidly cooled, thinned and dried, we show that small disordered CTAB-silica aggregates initially form. These aggregate into large spheres, and then CTAB micelles elongate and orient normal to the particle interface, even in arbitrarily shaped particles. The micelles continuously rearrange normal to the particle interface even as the particles aggregate and reorganize into spheres. This alignment implies that there is no preference for polar or nonpolar parts of the silica-surfactant mesophase at the particle-solution interface. This mechanism - precipitating soft silica-organic aggregates followed by nucleation of an ordered structure - can be generalized to other surfactant-templated systems and possibly zeolites. For instance, in layered particles formed using a cationic fluorinated surfactant, the particles elongate perpendicular to the layers. This is consistent with silica-surfactant aggregates initially acting like dispersed soft liquid crystals.
11-14
The Application of Surfactant Phase Behavior in
Developing Oilfield Product
JIANG YANG, Valdimir
Jovancicevic, Baker Petrolite,
Phase behavior was very important for many areas of applications from drilling fluid to enhance oil recovery in petroleum industry. Drag reducing surfactant was developed with studying the phase behavior of the surfactants. The mixture of surfactants and co-surfactants reduce the gel phase of hexagonal liquid crystal, and make faster transition to drag reducing wormlike micelle phase during the dilution.
11-15
Origin of the Sphere-to-Rod
Transition in Micellar Solutions:
Specific Ion Hydration Matters
Yan Geng, LAURENCE S. ROMSTED, Department of Chemistry and Chemical
Biology, Wright-Rieman Laboratories, Rutgers, The State University of New
Jersey, New Brunswick, NJ, romsted@rutchem.rutgers.edu
Understanding the relationships between surfactant structure and aggregate morphology should permit “tuning” of bulk properties of soft materials, which have important applications as thickeners, drag reducers, and hard surface cleaners. Micelle formation and the transition from spherical to rodlike, wormlike and threadlike micelles depend not only on surfactant tail structure, but also surfactant headgroup structure and counterion type (e.g., Hofmeister series) and concentration. However, the balance of forces determining such transitions are not fully understood.
The chemical trapping method based on the heterolytic chemistry of arenediazonium ions is providing new information on the concentrations of weakly basic nucleophiles such as water, halide ions, alcohols and urea within the interfacial regions of association colloids. Recent results show that of the 12-n-12 2Br (n = 2-4) series of gemini surfactants, only the gemini surfactant with n = 2 shows a marked increase in interfacial Br– with a concomitant decrease in interfacial water concentration with increasing surfactant concentration. Published cyro-TEM results show that only 12-2-12 form rods under these conditions. This and other chemical trapping results support a model in which sphere-to-rod transitions are governed by specific ion dependent dehydration of interfacial head groups and counterions to form hydrated ion pairs.
11-16
DNA-copolymer Vesicles for Gene Delivery
A.V. Korobko1, C. Backendorf1, J. R. C. VAN DER MAAREL2, 1Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, the Netherlands, 2National University of Singapore, Department of Physics, 2 Science Drive 3, Singapore
We report the design, structural characterization, and transfection ability of cationic diblock copolymer vesicles loaded with cloning vector DNA. Encapsulation was achieved with a single emulsion technique. For this purpose, an aqueous plasmid solution is emulsified in an organic solvent and stabilized by an amphiphilic diblock copolymer. The neutral block forms an interfacial brush, whereas the cationic attachment complexes with DNA. A subsequent change of the quality of the organic solvent results in the collapse of the brush and the formation of a capsule. The capsules are subsequently dispersed in aqueous medium to form vesicles and stabilized with an osmotic agent in the external phase. Inside the vesicles, the plasmid is compacted in a liquid-crystalline fashion as shown by the appearance of birefringent textures under crossed polarizers and the increase in fluorescence intensity of labeled DNA. The compaction efficiency and the size distribution of the vesicles were determined by light and scanning electron microscopy, and the integrity of the DNA after encapsulation and subsequent release was confirmed by gel electrophoresis. We demonstrate the gene transfer ability of this new model carrier system by the transfection of encapsulated pEGFP-N1 plasmid into HeLa cancer cells through the fluorescence of the expressed GFP protein.
11-17
Controlled Synthesis and
Hierarchical Assembly of One-Dimensional Inorganic Nanostructures in Micellar
Systems
LIMIN QI,* Hongtao Shi, Yurong Ma, Jiming
Ma, State Key Laboratory for
Structural Chemistry of Unstable and Stable Species, College of
Chemistry, Peking University, Beijing, P.R. China, liminqi@pku.edu.cn
Both reverse and normal micelles are used as nanostructured media for synthesizing various one-dimensional (1D) inorganic nanostructures such as nanowires, nanobelts, and nanotubes. Unique catanionic reverse micelles formed by mixed cationic-anionic surfactants are employed for the controlled synthesis and hierarchical assembly of 1D BaXO4 (X = Cr, Mo, W) nanostructures. The effects of various factors, such as the mixing ratio between the anionic and cationic surfactants, the temperature, and the polymeric additives, on the formation of 1D BaXO4 nanostructures and the architectural control of their complex superstructures are examined. A plausible two-stage growth mechanism has been proposed for the formation of the penniform BaXO4 nanowire/nanobelt superstructures. On the other hand, normal micelles of nonionic surfactants are employed for the controlled synthesis of single-crystalline nanotubes, nanowires, and nanobelts of trigonal selenium (t-Se). In particular, well-defined t-Se nanotubes are fabricated in micellar solutions of the nonionic surfactant C12EO23. It is revealed that the nonionic micelles play an important role in controlling the distribution and diffusion of amorphous Se in the solution and hence exert delicate control over the morphology of the 1D t-Se nanostructures. These results demonstrate the great potential of micellar systems in synthesizing and assembling 1D nanostructures in solution.
11-18
Droplet
Breakup in Shear and Elongation Dominated Flows in Microfluidic Devices
A. J. Greiner, J. A. Taylor, G. F. Christopher, S.
L. ANNA, Department of Mechanical Engineering, Carnegie Mellon University,
Pittsburgh, PA, sanna@cmu.edu
Microfluidic devices have recently been
demonstrated as an effective platform for generating monodisperse drops and
bubbles on a drop-by-drop basis. Precise control over droplet size has the
potential to impact a wide range of applications from emulsification to drug
delivery and lab on a chip. In this talk we compare drop formation mechanisms
in microfluidic devices in which flows can be either predominantly shear flows,
or predominantly elongational flows. In either case, drops of an aqueous liquid
form due to viscous stresses imposed by a second oil phase. However, we show
that the two different flow types lead to dramatically different ability to
control droplet sizes. We characterize the drop formation mechanism and the
resulting drop size over a large number of experiments by varying capillary
number, volume fraction, and viscosity ratio. We observe several distinct modes
of breakup that depend on these three dimensionless parameters, as well as the
flow type and microfluidic design.
11-19
Sulfolane Microemulsions as Possible Inert Reaction Media
THOMAS WIELPÜTZ, Thomas Sottmann
and Reinhard Strey, Institute for Physical
Chemistry, University Cologne, D-50939 Cologne, Germany, twielpuetz@uni-koeln.de, tsottma@uni-koeln.de, rstrey@uni-koeln.de
Very recently, it turned out that nano-structured reaction media containing highly inert solvents as tetrahydrothiophen-1,1-dioxid (sulfolane) are needed in strongly oxidizing or reductive reactions. Due to their ability of solubilizing polar and nonpolar solvents with a large nano-structured interface in particular microemulsions provide such interesting reaction media. Starting from the pseudo-ternary microemulsion H2O-n-octane-C12E4/C12E5 (polyoxyethylene n‑alkylether) water was successively replaced by the highly inert tetrahydrothiophen-1,1-dioxid (sulfolane). It is found that an increasing sulfolane content drives the system beyond the tricritical point. Replacing the already long chain surfactants C12E4 and C12E5 by a mixture of the really long chain surfactants C18E6 and C18E8 a sulfolane-microemulsion was prepared for the first time. In a second step the phase behavior of the hydrophilic sulfolane - n‑octane -C18E8 system was tuned at constant temperature (reaction condition) by adding the hydrophobic cosurfactant 1-octanol. Thereby, the size of reverse micelles were investigated by DLS exhibiting radii varying from at least 8 nm to 20 nm.
11-20
Stabilization of Water-in-Oil Emulsions by Silica
Nanoparticles and Surfactant
B.P. BINKS, J. Philip, Surfactant & Colloid Group, Department of Chemistry, University of Hull, Hull,United Kingdom, j.philip@hull.ac.uk
Emulsions are metastable due to the excess energy associated with the large interfacial area. Electrostatic stabilization by surfactants and steric stabilization by macromolecules are quite well understood and the focus is now on solid particle- stabilized systems. Some of the unanswered issues in the area of mixed particle-surfactant systems are the following: What happens when solid nanoparticles and surface-active molecules are used in water-in-oil emulsions? Do particles or surfactant or both go to the interface or is there a preference for one to be at the interface over the other? What happens if solid particles and surfactant form complexes in bulk or at the interface? Do particles and surfactant act synergistically to enhance the long term stability of the emulsions? What are the implications of complexation on the rheology of the emulsion? In this paper, we answer these intriguing questions from systematic studies using water-in-silicone oil emulsions prepared with silica nanoparticles and a polymeric surfactant. These emulsions are characterised by light scattering, optical microscopy, freeze fracture electron microscopy and rheology.
11-21
Photo-Surfactants
J. EASTOE1,M. Sanchez Dominguez1, P. Wyatt1, A. Beeby2, R. K Heenan3, 1School of Chemistry, University of Bristol, Bristol, United Kingdom., 2Department of Chemistry, University of Durham, South Road, Durham, United Kingdom, 3ISIS-CLRC, Rutherford Appleton Laboratory, Chilton, Oxon, United Kingdom, julian.eastoe@bristol.ac.uk
For surfactants containing a suitable chromophore, light can be used to trigger changes in aggregation and adsorption. The advantage of this approach is it eliminates, or minimizes, the need for composition or temperature changes. New photosurfactants have been synthesized, and photoreactions in water, water-in-oil microemulsions, interfacial properties and changes in aggregation characterized [1]. As such changes in activity under wide range of colloidally relevant situations has been demonstrated: airwater, oil-water and solid-liquid interfaces, as well as aggregation in aqueous and microemulsion dispersions. These results highlight the importance of molecular design for generating effective and efficient photosurfactants.
11-22
Controlled Polymerization of Acrylates by
Macromolecular Design via Interchange of Xanthates in Microemulsions
JENNIFER O’DONNELL, Eric W. Kaler, Department of Chemical Engineering, University of Delaware, Newark, DE, odonnejm@che.udel.edu
The ability to produce stable latex nanoparticles of monodisperse polymer chains is desired for many applications. Reversible addition-fragmentation chain transfer (RAFT) has proven to be a successful method of controlled polymerization for many monomers and reaction conditions. However, the polymerization mechanism is not well understood. Implementing RAFT in microemulsion polymerization provides a model system in which to study the RAFT mechanism because microemulsion polymerization eliminates biradical termination by segregating the propagating polymer chains into surfactant stabilized polymer particles.
In this work we have implemented the RAFT process of Macromolecular Design via Interchange of Xanthates (MADIX) in the microemulsion polymerizations of butyl acrylate and 2-ethylhexyl acrylate. The kinetic rates, polymer molecular weights and latex particle sizes have been measured for several MADIX agent to micelle ratios at two initiator concentrations. The results of these experiments provide insight into the mechanism of RAFT polymerizations.
11-23
Ultrasound
for Characterizing Soft colloids
A. DUKHIN, P. Goetz Dispersion Technology Inc., 364 Adams Street , Bedford
Hills , NY
We present experimental data and its interpretation regarding characterization of various emulsions, mini- and micro-emulsions using ultrasound. Characterization includes droplet size distribution and z-potential for both, water-in-oil and oil-in-water systems. This characterization allowed us to establish a link between electric properties and evolution of these systems.
11-24
Flow-induced Phenomena in Solutions of Wormlike
Micelles
Matthew
Liberatore, Florian Nettesheim, Eric Kaler, NORMAN WAGNER,
Surfactant molecules in solution can self-assemble into wormlike micelles. Micellar solutions are common in the cosmetic, detergent and food industries. Solutions of these wormlike micelles have behavior similar to that of polymers, but are also able to reversibly break and recombine. Current work probing two viscoelastic micellar solutions of identical surfactant concentration has found the concentration of incorporated salt to critically influence solution behavior. While the two samples are quite similar in viscosity across a range of shear rates, only one sample exhibits shear-induced phase separation (SIPS). The important length scales of the two micellar networks are investigated via dynamic rheology, rheo-optics and small-angle neutron scattering (SANS). The mesh size and entanglement length of the micelles that exhibit SIPS are smaller than the other sample. Therefore, the solution that phase separates under flow forms a more densely entangled network. Additional investigation into the nonlinear rheology of these samples is completed using particle tracking velocimetry (PTV) and flow-SANS in the 1-2 plane. PTV finds shear banding for the sample exhibiting SIPS while the other sample behaves like a power law fluid. The appearance and growth of the shear bands for the sample exhibiting SIPS will be explored in detail.
11-25
Effect of Oil on Emulsion Characteristics:
Manipulating the Interfacial Domain
H. EGGER1,
E.-H. Liu2, K. M. McGrath1, 1School of Chemical and Physical Sciences, Victoria University of
Wellington, P.O. Box 600, Wellington,
New Zealand, 2Department
of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand, holger.egger@vuw.ac.nz
The ternary systems (water, triton X-100 and n-alkane) were investigated using freezefracture TEM, rheology, laser diffraction particle sizing, and PFG-NMR. The stability of the oil-in- ater dispersed droplet emulsions significantly increased with both the surfactant concentration and the chain length of the oil component. The PFG-NMR experiments monitored a superposition of the restricted diffusion of the oil in the droplets and free and restricted diffusion of the droplets themselves, and were correlated with the TEM images and the particle sizing data. Moreover, the present investigations were compared with earlier investigations where toluene was used as the oil. The change from the aromatic oil to an alkane-based oil dramatically changed the characteristics of the interfacial domain. The concentration range for the formation of emulsions and the variety of microstructures realized were severely restricted, but the interfacial film was much more stable leading to an extremely reduced rate of droplet coalescence. Additionally, concerning the destabilisation mechanisms, the alkane systems followed a much more complicated process compared with the toluene system. It was found that the principal destabilisation process was the same for all alkanes, whereupon the time constant of this process can be adjusted by using the appropriate chain length of the oil.
11-27
Liquid Crystalline
Silicate/Surfactant Mesophase in Nanoscale Confinement
DONGHAI WANG, Rong Kou, Yunfeng Lu, Department of Chemical &
Biomolecular Engineering, Tulane University, New Orleans, LA, ylu@tulane.edu
Cooperative assembly of silicate/surfactant replicates liquid crystalline mesophase of surfactant resulting in highly ordered mesostructures of inorganic/organic composite (e.g. cubic, hexagonal, lamellar structure). The self-assembly process can be altered readily by interfacial, geometric and other boundary conditions due to its weak non-covalent driving forces. In this presentation, we will show self-assembly behavior of liquid crystalline silicate/surfactant mesophase within nanoscale cylindrical pores of anodized alumina membranes. Morphology of the liquid crystalline silicate/surfactant composite was studied using XRD, TEM and SEM. We observed the transition from hexagonal to lamellar mesostructure of the liquid crystalline mesophase within the nanoscale confinement when surfactant concentration is increased. The hexagonal silicate/surfactant mesophase in nanoscale cylindrical pores prefers to orient along long axis of alumina pores, which is distinct from circular hexagonal mesostructure prepared by evaporation induced self-assembly process[1]. Lamellar silicate/surfactant layers grow along curved pore wall surface resulting in oriented concentric lamellar mesophase. The corresponding mesoporous silica wires with oriented hexagonal tubular and concentric lamellar pore channels were obtained after removal of surfactants. The novel structured mesophase and corresponding mesoporous silica/alumina composite are expected in membrane based application such as separation, templating synthesis, etc. This work also will bring the insight of nanoscale confiment effect on self-assembly process.
11-28
Microstructure of
Bicontinuous Nanoporous Materials Prepared from Methyl
Methacrylate/Hydroxyethyl Methacrylate Microemulsions Formulated with
Biocompatible Surfactant
F. Ye, R.T. Vickerman, S. Lopina, H. M. CHEUNG, E. von Meerwall, Department of Chemical Engineering and Department of Chemistry, Physics and Polymer Science, University of Akron, Akron, OH, fy2@uakron.edu
The biocompatible surfactant Ryoto Sugar L-1695 stabilizes transparent microemulsion precursors from the monomers of methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA). Polymerized bicontinuous microemulsions showed nanoporous structure under scanning electronic microscopy (SEM). The pore size distribution of the polymeric materials was determined from freezing point depression (PFD) of water which was characterized by two different methods: differential scanning calorimeter (DSC) and pulsed gradient spin-echo (PGSE) NMR. Results from both DSC and PGSE-NMR indicated that the aqueous content in microemulsion precursor influenced the microstructure of the polymer formed whereby. Increased pore size was observed when increasing aqueous content.
11-29
Transition
from Unilamellar to Bilamellar Vesicles Upon the Addition of an Associating
Biopolymer
Jae-Ho Lee1, Gregory F. Payne2, Vivek Agarwal3, Arijit Bose3, SRINIVASA R. RAGHAVAN1, 1Department of Chemical Engineering, University of Maryland, College Park, MD, 2Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, MD, 3Department of Chemical Engineering, University of Rhode Island, Kingston, RI, sraghava@eng.umd.edu
The effect of adding a hydrophobically-modified chitosan to unilamellar surfactant vesicles is studied using SANS and cryo-TEM. The hydrophobes on the polymer have a tendency to become embedded in vesicle bilayers. This leads to changes in the size and ultimately in the morphology of the vesicles. At low amounts, the addition of polymer decreases the unilamellar vesicle size. At higher polymer concentrations, high-q peaks emerge in the SANS spectra which imply the co-existence of multilamellar vesicles together with the unilamellar ones. Detailed modeling of the SANS data suggests that most of the multilamellar vesicles have exactly two concentric bilayers (i.e., they are bilamellar). This intriguing prediction is confirmed by cryo-TEM images. The origin of the changes in vesicle morphology will be explored in this presentation.
11-31
Synthesis
and Chiral discrimination of Chiral
Sensor with Self-Assembled Monolayers of Functionalized b-Cyclodextrins
Siu-Choon Ng, WEI-GUANG ZHANG, Tong Sun, Chan-Ghua Xu, and Hardy S.O. Chan, Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, Singapore, chmzwg@nus.edu.sg or chmcsoh@nus.edu.sg
Three chiral sensors were
synthesised and studied by using a quartz crystal microbalance (QCM) coated
with self-assembled mercaptyl functionalized b-cyclodextrin
(b-CD) derivatives. which are (6A-w-mercapto-ethylureado-6A-deoxy)heptakis(2,3-di-O-benzoyl)-6B,
6C, 6D, 6E, 6F, 6G-hexa-O-benzoyl-b-cyclodextrin (Ph-b-CDS), (6A-w-mercapto-hexanureado-6A-deoxy)heptakis(2,3-di-O-benzoyl)-6B,
6C, 6D, 6E, 6F, 6G-hexa-O-benzoyl-b-cyclodextrin (Ph-b-CDM) and (6A-w-mercapto-undecanylureado-6A-deoxy)heptakis(2,3-di-O-benzoyl)-6B,
6C, 6D, 6E, 6F, 6G-hexa-O-benzoyl-b-cyclodextrin (Ph-b-CDL). The preferential binding
of the chiral analytes at these b-CD monolayers in comparison with
that on the reference coating suggested the formation of inclusion complexes.
Improved chiral discrimination was achieved by the b-CD
monolayers modified QCM sensors in comparison with GC and HPLC separation
performance. Furthermore on-line dertermination of enantiomeric composition in
the samples by these QCM sensors was described. We also
studied the specific host-guest interactions between enantiomeric analytes and
the self-assembled b-CD
monolayers on QCM under gaseous atmosphere and liquid phase. Thermodynamic parameters about these chiral
discriminatory processes were obtained in gas and liquid phase from the linear
curves of temperature-dependant chiral discrimination factors of the three b-CD monolayers, which revealed the existence
of excellent compensatory enantioselective enthalpy-entropy relationship from
the linear curve of DR,SDH
vs.
12-01
The Rheology of Anisometric Particle Dispersions and "Liquid Armor"
NORMAN J. WAGNER, Center for Molecular & Engineering
Thermodynamics, Dept. of Chemical Engineering,
Novel ballistic resistant composite materials are formulated from colloidal dispersions of anisometric particles. Through ballistic testing, the mechanism of energy adsorption at ballistic rates is demonstrated to result from reversible shear thickening in the colloidal dispersion. As a basis for the rational design of ballistic resistant materials, we report a rheological and microstructural investigation of dispersions of stabilized, acicular precipitated calcium carbonate (PCC) particles of varying aspect ratio. The effects of particle shape on the low shear viscosity, shear thinning behavior, and onset of shear thickening is explored. Rheology-Small Angle Neutron Scattering studies (RHEO-SANS) demonstrate particle alignment with the flow and debunks previously hypothesized mechanisms for shear thickening in anisometric particles. The experimental results demonstrate that increasing particle aspect ratio leads to enhanced shear thickening at much lower particle concentrations than observed in comparable suspensions of spherical colloidal particles. These results are predicted by micromechanical models to elucidate the mechanism of shear thickening in suspensions of anisotropic particles. The application of these dispersions in formulating novel energy absorbing materials is discussed.
12-02
Rheological Behavior of Bauxite Residue and Bauxite Residue Derivatives
E. M. HUMISTON, G. Ahmadi, G. Campbell, Clarkson University, Potsdam, NY, notoem@clarkson.edu
Over 70 million metric tonnes of bauxite residue is produced annually as a by-product of aluminum production. Currently the residue is being landfilled and will continue to be stored in various locations requiring ongoing management because of the caustic nature of the residue. The objective of this research is to provide an understanding of the rheological behavior of bauxite residue and bauxite residue derivatives. Rheological measurements were carried out using a rotational rheometer for shear rates between 0 and 400 s-1 in a range of pH values and various solid concentrations. Two dissimilar shear-thinning regimes are evident within each data set. As pH is reduced the corresponding viscosity curve is shifted to a lower viscosity. A practical rheological model for bauxite residue including the effect of change in pH (via CO2 gas diffusion), solids concentration, while monitoring particle size distribution is described. The goal is to provide the aluminum industry with sufficient information to predict the flow behavior of bauxite residue and bauxite residue derivatives so that engineering processes for their disposal and/or conversion to commercial products can be designed.
12-03
Active
and Nonlinear Microrheology
JOHN F. BRADY, Division of Chemistry and
Chemical Engineering, California Institute of Technology,
Over
the last decade a set of experimental techniques collectively known as ‘microrheology’
has emerged as an alternative to traditional ‘macrorheology’, with the ability
to probe the viscoelastic properties of soft heterogeneous materials (e.g.
polymer solutions, colloidal dispersions, biomaterials, etc.) at the micrometer
(and smaller) scale. In microrheology, elastic and viscous moduli are obtained
from measurements of the fluctuating thermal motion of embedded colloidal probes. In such experiments, the probe motion is
passive and reflects the near-equilibrium (linear response) properties of the
surrounding medium. By actively
pulling the probe through the material, further information about nonlinear
material properties can be obtained, analogous to large amplitude measurements
in macrorheology. We consider
a simple model of such systems: a
colloidal probe pulled through a suspension of neutrally buoyant bath
colloids. The non-equilibrium
spatio-temporal configuration or microstructure of particles induced by the
motion of the probe is calculated analytically and via Brownian Dynamics
simulations and used to infer the dispersion's 'effective microviscosity'. The
computed effective viscosities compare well with analogous macrorheology
studies of sheared colloidal dispersions, suggesting that active tracking
microrheology can be a valuable tool with which to explore the rich nonlinear
behavior of complex materials.
12-04
Microrheology
of a Colloidal Suspension Using Laser Tweezers
A. MEYER, M. H. Lee,
E. M. Furst, Department
of Chemical Engineering, University of Delaware, Newark, DE
The microrheology of a colloidal suspension is measured using laser tweezers and the structure is visualized with confocal microscopy. Suspensions of index-matched silica and fluorinated ethylene propylene (FEP) are seeded with index-mismatched melamine and polystyrene probe particles, respectively. The probes are trapped with laser tweezers and subjected to a uniform flow enabling measurements of the suspension microrheology. Good agreement is found between the microviscosities of FEP measured with laser tweezers and bulk viscosities using a couette cell. As the probe size approaches the suspension particle size, non-linear behavior similar to shear thinning is observed at higher suspension concentrations. This is consistent with the formation of a ``wake'' in the non-equilibrium pair distribution function between the probe and bath particles [Squires and Brady, 2005], which is demonstrated by confocal images of probe experiments in fluorescent silica suspensions.
12-05
Rheological Behavior of
Nano-Dendrimers / Silica Suspensions
GANG LI, Stanley Hirschi, Leela Rakesh, James Falender, Chemistry, Physics, & Mathematics Departments, Central Michigan University, Mount Pleasant, MI
The electrorheological behavior of dendrimers/silica/silicone oil suspensions has been investigated. A surprisingly strong correlation of the electrorheological response with the level of maximum shear stress during steady flow measurements has been noted. The experimental results may be explained by polar or polarizable particles lining up in an external electric field. The drive toward alignment must overpower the Brownian motion and/or mechanical perturbation. Dielectric properties of the suspended particles will favor alignment – but the resistivity of the suspended particles must be high enough to avoid excessive current flow.
12-06
Melting in Temperature Sensitive Colloidal Suspensions
ARJUN G. YODH, Department of Physics & Astronomy,
I will talk about recent experiments from my lab wherein we use temperature-sensitive NIPA polymer and NIPA microgel particles to drive melting transitions. In colloidal crystal experiments we observe premelting at grain boundaries and dislocations. In colloidal rod experiments we observe melting of lamellar phases into nematic phases.
12-07
The Effect of
Nanoparticles on the Structure and Rheology of Clay Suspensions
J. BAIRD, J. Y. Walz, Department of Chemical Engineering, Yale
University, New Haven, CT, jason.baird@yale.edu
Suspensions of clay particles (kaolinite) combined with silica nanospheres undergo a dramatic stabilization process, which increases suspension viscosity as well as elasticity to the point where the suspensions can support their own mass as well as be sectioned. The suspensions develop a significant yield stress, which can be overcome by vigorous shaking, making the process completely reversible. These transitions are observed for kaolinite concentrations of 14 percent by volume (v/o), and nanosphere concentrations as small as 3 percent. Decreasing the nanosphere size at constant volume fraction results in higher yield stresses, significant elasticity, and shorter time scales for gel development. SEM micrographs obtained by cryogenic fracturing of the samples indicate that the added nanoparticles produce a more ordered, 'honeycomb-like' structure, possibly arising from a very localized phase separation. In some of the nanoparticle solutions, ordering of the clay platelets into dense stacks is also observed.
12-08
Evaporation-Induced
Particle Microseparations inside Freely Floating Droplets
SUK TAI CHANG, Orlin D. Velev, Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, odvelev@unity.ncsu.edu
We study colloid particle transport inside single microdroplets of water floating on the surface of inert fluorinated oil. This is done on a new type of microfluidic chips, where the droplets are manipulated with alternating electric fields applied to arrays of electrodes below the oil. The particles collect at the top region of the floating droplets and phase-separate in layers based on their size and density. These remarkable microseparation processes can be used for on-chip synthesis of advanced particles, microscale separations without other integrated components and innovative microbioassays. We report experimental results and theoretical simulations that explain the microsepration as a result of series of processes driven by mass and heat transfer. During the evaporation, a surface tension gradient on top of the droplet occurs as a result of a non-uniform temperature distribution. This interfacial tension gradient generates an internal convective Marangoni flow. The colloidal particles transported by the convective flow collect on the top of the droplets by the hydrodynamic flux compensating for the evaporation. The internal flow pattern and temperature distribution within the evaporating droplet were simulated using finite element calculations. The simulation was consistent with experiments using tracer particles.
12-09
Mobility and In-situ Aggregation of Charged Microparticles at Oil-Water Interfaces
Sowmitri Tarimala, Chihyuan Wu, LENORE L. DAI, Department of Chemical Engineering, Texas Tech University, MS 3121, Lubbock, TX
Particle mobility, aggregate structure, and the mechanism of
aggregate growth at the two-dimensional level have been of long-standing
interest. Here we use
12-10
Crystalline Junctions in Associative Gels: PLA-PEO-PLA Triblocks
with Tunable Rheology
S. K. Agrawal1, N. Sanabria-DeLong2, G. N. Tew2,
S. R. BHATIA1, 1Department of Chemical Engineering and 2Department
of Polymer Science and Engineering,
Soft biomaterials derived from amphiphilic polymers have received considerable attention in the last decade. The ability to tune the modulus of implantable materials to match that of native tissue is crucial for scaffolding applications; unfortunately, a significant limitation of current polymeric biomaterials is a lack of mechanical robustness and a low elastic modulus. We address these issues using hydrogels of poly(lactic acid)-poly(ethylene oxide)-poly(lactic acid) (PLA-PEO-PLA) triblock copolymers, which form associative network gels with the PLA domains serving as network junctions. Our work distinguishes itself from previous studies through controlled crystallinity of the junction points. We can create nanoscale crystalline junctions through use of copolymers in which the PLA block is poly(L-lactic acid) (PLLA), or amorphous junctions through copolymers in which the PLA blocks contain D-lactic acid and L-lactic acid (PDLLA). The crystalline junctions in the PLLA-based gels cause a significant increase in the elastic modulus over the PDLLA gels, allowing us to create biocompatible gels with elastic moduli that are an order of magnitude higher than previously reported with biocompatible associative gels. The modulus is also very sensitive to PLA block length and can be easily tuned through to match the moduli of native tissue for a variety of applications. These crystalline junction points may be considered a new mode of association in polymer gels and a novel method for tuning the rheological properties.
12-11
Microstructural and
Microrheological Properties of Novel Self-assembled Hydrogels
CECILE VEERMAN*, Karthikan Rajagopal#, Joel P. Schneider#, Eric M. Furst*, *Department of Chemical Engineering, University of Delaware, Newark, DE, #Department of Chemistry and Biochemistry, University of Delaware, Newark, DE
Hydrogels are an important class of materials that have extensive uses in tissue engineering and drug delivery applications. Recently, a short 20 amino acid β-hairpin peptide has been designed for the preparation of novel hydrogels, that reversibly folds and gel by a process of hierarchical self-assembly. Little is known of the gelation kinetics and microstructure of these complex materials. A better understanding on a microscopic level is necessary because we expect that for these hydrogels the microscopic structure and heterogeneity will impact the cellular response to the material. In this study the gelation kinetics and microstructure of the self-assembled hydrogels was investigated with the use of multiple particle tracking. An increasing gelation time with decreasing peptide concentration was found. The self-part of the van Hove correlation function and a non-Gaussian parameter were used to obtain insight into the heterogeneity of the microenvironment of the hydrogel. Microrheological techniques enable us to understand the mechanical properties of hydrogels at a microscopic level, enabling the design of novel peptides that will lead to the ultimate microstructural and microrheological properties necessary for tissue engineering and drug delivery applications.
12-12
The Role of Bile Salt in Inducing
Threadlike Reverse Micelles of Lecithin in Organic Solvents
Shih-Huang Tung, Yi-En Huang, SRINIVASA R. RAGHAVAN, Department of Chemical Engineering, University of Maryland, College Park, MD, sraghava@eng.umd.edu
Threadlike or wormlike micelles are formed by charged surfactants in water upon the addition of salt. Here, we report a similar phenomenon in organic solvents, i.e., the formation of reverse wormlike micelles by the phospholipid, lecithin upon the addition of a bile salt. Bile salts are biological amphiphiles having a planar, “facially-amphiphilic” structure. Adding a few mM of the bile salt, sodium deoxycholate (SDC) to a semidilute solution of lecithin in cyclohexane, is enough to induce the growth of reverse micelles from spheres to long, cylindrical threads. In the process, the sample is transformed from a low-viscosity fluid into a highly viscoelastic and flow-birefringent fluid. Similar results are observed in a range of nonpolar organic liquids. We will present data from rheology and small-angle neutron scattering (SANS) on these micellar fluids. A tentative model for the reverse micelle structure will be proposed in an attempt to clarify the role played by the bile salt in inducing micellar growth.
12-13
Dynamics of Brownian
particles in Concentrated Wormlike Micelle Solutions
FLORIAN NETTESHEIM, Matthew Liberatore, Eric W.
Kaler, Norman J. Wagner, Department
of Chemical Engineering, University of Delaware, Newark, DE, netteshe@che.udel.edu
Brownian motion in complex fluids is of scientific interest as the particle motion couples to the underlying dynamics of the suspending media, as well of industrial interest in the consumer products, paints, detergents, and food industries for example, as such formulations often contain colloids and emulsions. Brownian particles are also used as probes of local linear viscoelasticity in complex fluids and biological materials, a technique known as micro-rheology. Here, we investigate the Brownian motion of model colloidal particles dispersed in an entangled wormlike micellar mesh and the associated mixture rheology and microstructure. This regime, where particle size and relaxation times are comparable to the length and relaxation time scales of the suspending medium, is poorly understood. Results of rheological investigations, small-angle neutron scattering, and dynamic and static light scattering are reported. The properties of the wormlike micellar solution and particles are systematically varied to explore the coupling between particle and self-assembled aggregate dynamics and microstructure. Significant effects are observed upon addition of Brownian particles on the relaxation spectra of the micellar fluid. Further, the self-assembled surfactant aggregates are observed to strongly influence the short-time particle dynamics. The results are interpreted with a microstructural model for particle self-assembled surfactant mixture.
12-14
Interfacial Rheology of
Globular and Flexible Proteins at the Hexadecane/Water Interface: Comparison of
Shear and Dilatation Deformation
E. M. Freer, K.S. Yim, G.G. Fuller, C.J. RADKE, Chemical Engineering
Departments, University of California, Berkeley, CA, Stanford University,
Stanford, CA, radke@cchem.berkeley.edu
After long-time exposure, protein adsorption at fluid/fluid interfaces produces interfacial gel-like networks. We utilize interfacial shear and dilatational rheology to probe the structure of a globular protein, lysozyme, and a disordered protein, -casein, at the hexadecane/water interface. For lysozyme, the shear moduli grow with interface age indicating a transition from fluid-like behavior at early times to solid-like network formation at later times. Conversely, the interfacial shear moduli of -casein change very little with interface age. The strong protein intramolecular interactions that stabilize the native conformation of lysozyme act as kinetic barriers to conformational change and later become strong intermolecular interactions that result in aggregation at the interface. The interfacial dilatational storage modulus is comprised of a static response and a dynamic response. The dynamic contribution corresponds to rearrangement and reconfiguration of the protein molecules within the interface and gives a measure of the strength of interprotein linkages. Globular lysozyme, once adsorbed, resists compression giving a high dilatational storage modulus. Contrastingly, -casein exhibits only a small interfacial dilatational storage modulus. For the first time, we establish that surface shear and dilatational moduli measure quite different but complementary molecular characteristics of adsorbed proteins at fluid/fluid interfaces.
12-15
Influence of Non-Newtonian
Behavior on the Dynamic Interface Shapes of Polymer Melts, Solutions and Boger
Fluids
GITA SEEVARATNAM*, Stephen Garoff**, Lynn M. Walker*, Center for
Complex Fluids Engineering, Department of *Chemical Engineering and **Physics,
In this work, we characterize the liquid-vapor interface shape during forced wetting to quantify the effect of fluid elasticity on interface shape. The fluid mechanics near the three phase (solid-liquid-vapor) are complex and the impact of elasticity on this inherently confined geometry is poorly understood. We find that two polymer melts, polyisobutylene (PIB) and polystyrene (PS) exhibit dynamic wetting characteristics of a weakly elastic fluid. We study dynamic wetting by observing the liquid-vapor interface formed on the outside of a silica surface forced into a bath of the test fluid at controlled rates. The results show that the interface shapes of these fluids deviate from the prediction of models that include only Newtonian flow behavior. Using standard rotational rheometry, we examine the shear rates needed to cause non-Newtonian behavior in these fluids and ask where such shear rates arise near the contact line. Experiments on xanthan gum solutions have shown that an increase in shear thinning in the high shear region near the contact line decreases the curvature of the interface near a moving contact line. However, fluids with some level of elasticity and minimal shear thinning show an increase in curvature near the contact line. Differences in these fluid behaviors and ramifications on interface shape will be discussed.
12-16
The Effect of Nonadsorbing
Macromolecules on the Particle Dynamics Near an Interface
R. J. OETAMA, J.Y. Walz, Department of Chemical Engineering, Yale University, New Haven, CT, ratna.oetama@yale.edu
The optical technique of total internal reflection microscopy (TIRM) was used to study the normal Brownian motion of a single colloidal particle near an interface. Using our data analysis method, the particle’s spatially-varying diffusion coefficient can be determined without any knowledge of the forces acting on the particle. Experiments were performed in solution containing small silica nanospheres, polyacrylic acid, and clay platelets to investigate the effect of nonadsorbing species on the dynamics of near-contact particle motion. This talk will focus on the dynamic particle behavior near a solid wall in dilute colloidal suspensions of synthetic clay particles (laponite) that are slowly thickening. Measurements of the equilibrium potential energy profile were also obtained which indicate the development of structures in the laponite solution over time.
12-17
Dramatic Increase in Viscosity with
Temperature as a Result of a Thermoreversible Vesicle-to-Micelle
Transition
Tanner S. Davies, SRINIVASA R. RAGHAVAN, Department of Chemical Engineering, University of Maryland, College Park, MD, sraghava@eng.umd.edu
Complex fluids based on surfactants usually show a decrease in their viscosity upon heating. We report an example of the opposite effect, where the viscosity sharply rises upon heating as a result of a microstructural transformation. This phenomenon is observed in mixtures of the cationic surfactant, cetyl trimethylammonium bromide (CTAB) and a methyl-substituted salicylic acid. Such mixtures self-assemble in aqueous solution to form unilamellar vesicles at room temperature. Upon heating, the vesicles are transformed into long, cylindrical micelles and consequently, the sample changes from a low-viscosity, Newtonian fluid to a viscoelastic, shear-thinning fluid. The zero-shear viscosity increases by a factor of 1000 or more with increasing temperature. The ensuing microstructural changes as a function of temperature are confirmed by small-angle neutron scattering (SANS) measurements. We will discuss and correlate the rheology and SANS data for various sample compositions.
12-18
Structure
and Mechanical Properties of Nanocomposites: Proteins and Nanoparticles
Templated in Self-Assembled PEO-PPO-PEO Mesophases
DANILO C. POZZO, Lynn M. Walker, Center for Complex Fluids
Engineering, Department of Chemical Engineering, Carnegie Mellon University,
Pittsburgh, PA, lwalker@andrew.cmu.edu, dpozzo@andrew.cmu.edu
Highly ordered self-assembled block copolymer mesophases present an attractive way of transferring their structure to otherwise disorganized nanometer sols (proteins or inorganic nanoparticles). Unlike other “bottom-up” nanoparticle organization methods, the tunable structure of the ordered block-copolymer phase provides increased control over the structure of the templated nanoparticle arrays. This method allows us to organize large numbers of particles (1020/L) into controllable three-dimensional structures. Additionally, the use of thermoreversible polymer mesophases permits the stable dispersion of pre-made nanoparticles or globular proteins. In this study, we use rheology to thoroughly evaluate the mechanical properties of these nanocomposites and find that mechanical properties are strongly altered when the concentration of dispersed nanoparticles approaches and exceeds the number of available template sites. Small-angle neutron scattering (SANS) is used to evaluate the coupling between matrix and nanoparticle order. By using solvents containing isotope mixtures in SANS we are able to separately study the structure of the organic and inorganic phases through the variation of the neutron scattering contrast. It is found that the nanoparticles are templated by the polymer gel and that the level of organization is dependent on a number of controllable variables. We quantify the influence of relative concentration, relative dimensions and temperature on both the nanoscale structure and macroscopic composite properties.
12-19
Physical Gelation and
Rheological Properties of Cationic Telechelic Polyelectrolytes
G. Gotzamanis1, F. Bossard2, R.
Lupytsky3, T. Aubry2,
Telechelic polyelectrolytes (TP) are a novel class of Associative Polymers (AP) constituted from a long polyelectrolyte chain end-capped by hydrophobic short polymeric chains. The main feature that makes TP, distinguished from the conventional telechelic APs (non ionic hydrophylic part) is that the chain conformation of the soluble part can be controlled by external conditions such as pH and ionic strength. At a certain pH (depending of the polyelectrolyte nature) and at free salt conditions the central chain adopts a stretched conformation, which has fundamental consequences on the TP association and rheological properties. In this work cationic TP constituted of a long PDMAEMA end-capped by short PMMA blocks have been synthesized end explored in aqueous media. The motivation of this work was to combine the excellent properties of telechelic polyelectrolyte physical gels with the benefits of biocompatibility and capability of cationic macromolecules to be complexed with DNA. Above cgel (0.1 wt%) a transient physical network is formed through an open association mechanism, macroscopically observed by a rapid increase of the solution viscosity. This pronounced concentration dependence is marked, up to a polymer concentration of about 1%wt. Above this critical polymer concentration, a stiff hydrogel is formed for which rheological properties are not significantly strengthened by polymer concentration enhancement. In this higher polymer concentration regime, the physical hydrogel exhibits a peculiar rheological behavior characterized by a Newtonian plateau at low shear stresses followed by a viscosity drop of about five decades, attributed to apparent yield stress behavior, a second Newtonian plateau at intermediate shear stresses and a shear thinning at high stresses.
12-20
Numerical Simulation of
Methane Hydrate in Sandstone Cores
KAMBIZ NAZRIDOUST, Goodarz Ahmadi, Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY, ahmadi@clarkson.edu
Production of methane gas from hydrate dissociation in a core is studied. It is assumed that the core is porous with the pores being partially saturated with hydrate. Using the Fluent™ code with appropriate user defined functions, an axisymmetric model of the core is developed and solved for multiphase fluid flow during the hydrate dissociation. The model contains three separate phases of hydrate (solid/heavily viscous fluid), methane (gas), and water (liquid). The hydrate zone is stationary but water and gas can move freely. For different core temperatures and various production valve pressures, time evolutions of gas and water during hydrate dissociation are evaluated and variations of temperature and pressure are simulated. Variations of relative permeability of the core are included using Corey’s model for porous media. Porosity of the core also changes with saturation of hydrate. It is shown that to maintain a constant natural gas production rate, the production valve pressure must be decreased with time. The simulation results show that the process of natural gas production is a sensitive function of reservoir temperature and hydrate zone permeability.
12-21
A Study of Three-Phase Liquid-Gas-Solid Flows in Microgravity
XINYU ZHANG, Goodarz Ahmadi, Department of Mechanical and
Aeronautical Engineering,
An Eulerian-Lagrangian computational model for simulations of gas-liquid-solid flows in microgravity was developed. In this study, the liquid phase was modeled by a volume-averaged system of Eulerian governing equations, whereas motions of particles and bubbles were evaluated using Lagrangian trajectory analysis approach. It was assumed that the bubbles remained spherical and their shape variations were neglected. The two-way interactions between particle-liquid and bubble-liquid were accounted for in the study. The discrete phase equations used included drag, lift, buoyancy, and virtual mass forces. Interactions between particle-particle and bubble-bubble were accounted for by the hard sphere model. The bubble coalescence was also included in the model. The predicted results under normal gravity condition were compared with the available experimental data in earlier simulations, and good agreement was obtained. The transient flow characteristics of the three-phase flow were studied and the effects of gravity, inlet bubble size, bubble number density and bubble superficial velocity on variation of flow characteristics were discussed. The simulations for low gravity showed that most bubbles are aggregated in the inlet region, and due to the longer residence time and bubble coalescence, and the Sauter mean bubble diameter becomes rather large which can be more than10 mm.
12-22
A New Friction Factor Correlation for Laminar and Single-Phase Fluid Flow through Fractured Rocks
KAMBIZ NAZRIDOUST1, Goodarz Ahmadi1 and Duane
H. Smith2, 1Engineering, Clarkson University, Potsdam, NY, 2National
Energy Technology Laboratory, U.S. Department of Energy, Morgantown, WV, ahmadi@clarkson.edu
Single- and multi-phase flow through fractured media occurs in various situations, such as transport of dissolved contaminants through geological strata, sequestration of carbon dioxide in brine-saturated reservoirs, and in enhanced oil recovery from depleted field. In the present study fluid flows through individual fractures were simulated. A post-processing code was developed and used to generate the three-dimensional fracture inside AutoCAD package from the CT scan data. Several sections along the fracture were considered and GambitTM code was used to generate unstructured grid for flow simulation. Single-phase flows through the fracture section with different flow rate were studied. It was shown that the pressure drop was dominated by the lowest height passages of the fracture. For geological reservoir simulations, the parallel plate model has often been used for estimating flows through fractures. It was shown that the parallel plate flow model with inclusion of the tortuosity effects was in reasonable agreement with the presented CFD simulation results. Based on the simulation data, a new expression for the friction factor for flows through fractures was developed and the model predictions were compared with the simulation results and favorable agreement was achieved.
13-1
The Role of Phase Science in Colloid Science
ROBERT G. LAUGHLIN, Clarkson University, Potsdam, NY, Rua Barão de Ipanema 130/202, Copacabana, Rio de Janeiro/RJ Cep 22050-030, Brasil, rglaughlin@hotmail.com
Those systems of historic interest in the development of colloid science do not display discontinuous changes of state over the range of temperatures studied, and the solvent is not incorporated into the dispersed phase. The dispersed phases of water-insoluble surfactants, however, do incorporate solvent water – lots of it. They also undergo discontinuous phase changes near ambient temperatures. The incorporation of solvent has a profound effect on the ratio of coexisting phases, and all those properties associated with phase ratios. Incorporation as crystal hydrates may introduce complex and interesting colloid chemistry when these are heated past peritectic temperatures.
In biological cell membranes, temperature changes which pass the chain melting temperature should affect not only the membrane structure, but also its water composition. Such changes are predicted to affect the water content of the cytoplasm, and thereby the thermodynamic activity of every water-soluble component in the cytoplasm. The impact of these changes has been neglected, but may extend far beyond the structural perturbations that have been the focus of interest to date.
13-2
What’s New with The Gibbs Adsorption Equation?
B. WIDOM, Department of Chemistry, Baker Laboratory, Cornell
University, Ithaca, NY, bw24@cornell.edu
The Gibbs adsorption equation and some of its implications will be recalled. What had for a quarter century been thought to be the analog of the Gibbs adsorption equation for the line of three-phase contact was recently discovered to be incorrect. A brief account of that problem, and of the related question of how adsorptions at the line of three-phase contact behave as a transition to complete wetting is approached, will be presented.
13-3
Some Applications of
Surfactant Phase Diagrams
STIG E FRIBERG, Chemistry Department,
A series of examples are presented for which the phase diagrams of the systems were either necessary or helpful to solve problems within emulsions , microemulsions and foams.
The examples vary from the stability of foams from non-polar solvents to formulation of microemulsons to the action of hydrotropes to the structural changes in simple emulsions during evaporation. Finally the advantage of applying analytical geometry to such systems is exemplified.
13-4
“Stained Glasses”, Thin
Liquid Films and Lamellar Liquid Crystals
Jan Czarnecki1, Jacob Masliyah2, Nikolay
Panchev2,3, Shawn Taylor2,4, 1Syncrude Canada
Ltd., Edmonton Research Centre, 2Department of Chemical Material
Eng., University of Alberta, 3Visiting student from Institute of
Physical Chemistry, Bulgarian Academy of Science, 4Current
affiliation: Schlumberger Reservoir Fluids Center, Edmonton, AB, Canada, czarnecki.jan@syncrude.com
Foam films drawn from aqueous solutions of sodium naphthenates and
Aerosol OT, at concentrations close to or just above the lamellar liquid
crystal (LLC) phase boundary, contain domains of uniform color (thus of uniform
thickness) with sharp boundaries, resembling 'stained glasses'. To be colored,
the domains must be thicker than half of the visible light wavelength. Analysis
of
13-5
Emulsion Structure and
Stability: Role of Depletion and Structural Forces
DARSH WASAN, Alex Nikolov, Illinois Institute of Technology, 10 West 33rd Street, Chicago, IL, wasan@iit.edu
In this paper, we will review the recent work performed in our
laboratory in the areas of structure and stability of emulsions and foams. We will particularly highlight the role
of long-range oscillatory forces, including attractive depletion and
structural, in controlling dispersion stability. We have developed a novel hybrid surface
force apparatus referred to as the capillary force balance in conjunction with
a differential interference microscopy method to investigate surfactant micelle
or nanoparticle structuring phenomenon inside thinning liquid films confined
between droplets or foam bubbles in concentrated colloidal dispersions. In addition, we have used a
nondestructive Kossel diffraction technique to obtain the structure factors,
and the advanced optical imaging method to obtain the emulsion radial
distribution function to determine the effective inter-droplet
interactions. We have used these
techniques to investigate the effects of surfactant type (i.e., water soluble
and oil soluble), proteins, gums, fat substitute, temperature and shear rate on
emulsion structure and stability.
We have carried out theoretical calculations using the Ornstein-Zernike
equation of statistical mechanics and
13-6
Phase Diagrams of Ternary Lipid Bilayer Mixtures Containing Cholesterol
GERALD W. FEIGENSON, Field of Biophysics, Cornell University, 201
Biotechnology Building, Ithaca, NY, gwf3@cornell.edu
Determination of the phase diagram for a 3-component bilayer mixture of lipids requires use of several different methods in order to resolve ambiguities in the phase boundaries. We employed fluorescence spectroscopy and microscopy, ESR spectroscopy, x-ray and neutron diffraction, and light scattering. Mixtures containing cholesterol that model the outer leaflet of animal cell membranes show rich phase behavior. DSPC/DOPC/cholesterol (distearoyl-PC/dioleoyl-PC/cholesterol) is one such mixture, with a large region of macroscopic separation of L + Lo phases. In contrast, DPPC/DLPC/chol (dipalmitoyl-PC/dilauroyl-PC/cholesterol) shows a much smaller region of separation of L + Lo phases, and the phases are “nanoscopic”. Sphingomyelin/DOPC/chol shows “nanoscopic” coexistence of L + L phases, but macroscopic separation of L + Lo phases.
13-7
Phase Behavior and
Structure in Mixtures of Surfactants and Hydrotropes
ERIC W. KALER, Yamaira Gonzalez, Department of Chemical Engineering,
Colburn Laboratory, University of Delaware, Newark, DE, kaler@udel.edu
Hydrotropes are amphiphilic molecules with hydrophobic portions too small to form micelles. Hydrotropes bind strongly to the surface of micelles and can facilitate the formation of interesting microstructures such as elongated micelles and vesicles. We have investigated the formation and polymerization of worm-like micelles and vesicles made of polymerizable surfactants. The use of water-soluble di-azo free radical initiators for these studies led to the discovery of the spontaneous formation of vesicles from simply mixing the initiator with surfactant alone, without polymerization. The characterization of these mixtures indicated that initiators behave as hydrotropes. Basic amino acids have similar molecular functionality and show a similar hydrotropic behavior, including the formation of gels. This work reveals the power of hydrotropic molecules in driving structural changes in surfactant solutions.
13-8
A New Approach to Dilute and Concentrated Lamellar Phases in Phase
Diagrams of Nonionic Surfactants
COSIMA STUBENRAUCH, Department of
Chemical and Biochemical Engineering, University College Dublin, Belfield,
Dublin 4, Ireland, cosima.stubenrauch@ucd.ie
The present contribution is about
new results on two peculiar features in connection with the lamellar phases (L)
in binary aqueous solutions of nonionic surfactants. The first striking feature
is the formation of highly dilute L phases down to 1 wt.-% of
surfactant, which has been observed for a small number of nonionic surfactants
which are all of the alkyl polyglycol ether (CiEj)
type. So far, in binary H2O - CiEj systems
either the absence or the presence of a dilute L phase has been
reported. In the latter case, the dilute and the concentrated L
phase are always connected continuously. However, for one particular silane
surfactant, namely (CH3)3Si(CH2)6(OCH2CH2)5OCH3, two disconnected L phases were observed. Systematic
investigations of the phase
behaviour of the binary system H2O - C10E4 as
well as of the pseudobinary systems H2O - C10E4/C10E5
enabled us to answer adequately the following questions: (a) Is the
disconnected L phase a peculiarity of the silane surfactant or a
general feature of nonionic surfactants? (b) Are there any structural
differences between the connected and the disconnected L
phases? (c) What is the
process which leads to the disconnection of the L phase?
13-9
Spontaneous Emulsification
and its Relationship to Phase Behavior: Review and Recent Developments
CLARENCE A. MILLER, Department of Chemical Engineering, Rice University, Houston, TX, camill@rice.edu
The relationship of spontaneous emulsification to phase behavior is reviewed with emphasis on results obtained in recent years. Several studies have provided insight on the mechanism of self-emulsification of oils to form oil-in-water emulsions consisting of small droplets. In particular, diffusion and/or chemical reaction can cause changes in composition and hence in spontaneous curvature of surfactant films, which promote inversion from an oil-continuous to a water-continuous microemulsion. Since the latter is not able to solubilize all of the oil present, local supersaturation and subsequent nucleation of oil droplets occurs. Under suitable conditions the lamellar liquid crystalline phase is formed during the inversion process and coats the small droplets, thereby hindering coalescence and reducing the surfactant concentration required to form small droplets. Self-emulsification can also occur without large changes in spontaneous curvature when the surfactant films are initially near the balanced state of zero spontaneous curvature. Formation of the lamellar phase during this process appears to be essential for obtaining small droplets. “Nanoemulsions” with drop sizes of order 100 nm or less have been produced by self-emulsification processes which involve spontaneous emulsification accompanied by gentle stirring. When polymer is dissolved in the droplets, removal of the solvent yields small polymer nanoparticles, which are of interest in applications such as drug delivery. The results of these studies demonstrate that knowledge of equilibrium phase behavior is important in choosing suitable systems and conditions for self-emulsification.
13-10
Water-in-Crude Oil Emulsions – Stability Mechanisms and Environmental
Aspects
JOHAN SJÖBLOM, Pål V. Hemmingsen, Gisle Øye, Andreas Hannisdal,
Marit-Helen Ese, Øystein Brandal, Maria Häger, Ugelstad Laboratory, Department of Chemical
Engineering, NTNU, N-7491 Trondheim, Norway, johsj@chemeng.ntnu.no.
The keynote lecture is going to view
the chemistry of heavy crude oil components and their interaction forms. After
this the formation, stabilization and destabilization of water-in-crude oil
emulsions is viewed. The stabilizing role of the heavy components in the crude
oil is discussed together with ageing effects.
Particle-stabilization is viewed
from three different aspects. The impact of the association of asphaltenes to
form organic nanoparticles is well-known from previous studies. In addition the
role of inorganic fines and small metalnaphthenate particles is discussed. Inorganic fines, mostly oxides from the
formation, will have a natural tendency to accumulate at w/o interfaces
depending on their contact angle. However, what is highly changing the
behaviour of these fines is the adsorption of components from the crude oil
onto their surface. These components are mainly resins and asphaltenes. Another
route to form fines is the reaction between organic naphthenic acids and
divalent cations. It is shown by means of dynamic interfacial tensions that
reactions over w/o interfaces are important in this respect.
It becomes more and more important
to understand the underlying stabililization mechanisms of the dispersed
material due to the tougher regulations on discharges by the state authorities.
Normally the discharges include emulsions (o/w), dispersed particles (with and
without coating) and dissolved components. However, since the dissolved
components will include both naphthenic acids and polar components the
possibility of finding dispersed lyotropic liquid crystals should be profound.
In this study we report for the first time on the results from phase diagram
studies based on model components representing naphthenic acids and polar
phenols in water.
13-11
The Role of Colloid Science and Electrokinetics in Oil Sands
Processing
JACOB MASLIYAH, Zhenghe Xu, Department of Chemical Engineering,
University of Alberta, Edmonton, AB, Canada, Jacob.masliyah@ualberta.ca
Canadian bitumen recovery from oil sands will continue to increase
in the next decades. The present oil sands development in
The presentation deals with research efforts at the
13-12
Relations
Between the Molecular and Nanocolloidal Structure of Asphaltenes
OLIVER C. MULLINS, Schlumberger-Doll Research (SDR),
The science of asphaltenes, the most aromatic fraction of crude oil, has advanced significantly in recent years. Asphaltene molecular weight has recently been elucidated after decades of controversy; time resolved fluorescence depolarization results yielded critical results. Asphaltene molecular architecture has also largely been resolved; x-ray Raman spectroscopy delineated fused aromatic ring geometry. These findings will be reviewed. The Critical Nanoaggregate Concentration (CNAC) of asphaltenes has also recently been delineated for example by high-Q ultrasonic spectroscopy; a decade of literature was misinterpreted (Professor Friberg played a central role in correcting the problem). The governing physics of nanoaggregate formation is evident in asphaltene molecular structure; function follows structure. These precepts which are largely 'freshman chemistry' are shown essentially to define the identity of asphaltenes.
13-13
Liquid Crystallinity and
Emulsion Formation in Ternary Oil-Water-Acid/Soap Systems Comprised of Model
Naphthenic Acids and Their Mixtures with Asphaltenes from Petroleum Fluids
Marit-Helen Ese, M. Lupe Marques, PETER K. KILPATRICK, Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, peter-k@ncsu.edu
In an effort to better understand the role of naphthenic acids and soaps in stabilizing water-in-oil emulsions, we conducted a study of emulsion type and stability in model ternary systems comprised of oil, water, and aromatic and alicyclic ringed acids as functions of pH and acid/soap concentration. The acids selected for study were b-cholanic acid, deoxycholic acid, heptyl benzoic acid and pentane cyclohexanoic acid. The pH of the aqueous phase was systematically varied from 5-13 and the concentration of acid/soap was varied from 0.5-10% (w/w). All of these model systems clearly indicated a transition from oil-in-water emulsions at low pH, to water-in-oil emulsions at higher pH (which varied with the architecture of the hydrophobic group on the acid). At sufficiently high pH, some of the systems reverted back to o/w emulsions. These results are consistent with the interfacial film of acid/soap molecules adopting a lamellar structure when the balance among effective head group size due to electrostatic repulsion and the steric repulsion of cyclic hydrophobic moieties confers a molecular packing parameter close to unity on the system. Under these conditions of balance, there is clear evidence from optical polarizing microscopy that the interfacial films are liquid crystalline. This appears to be a universal phenomenon with monomerically pure acid/soaps. We have also explored the interaction of asphaltenes and model naphthenic acid/soaps as a function of aqueous phase pH and concentration of acid/soap. Under appropriate conditions of pH and using model naphthenic acids with appropriate hydrophobic groups, the presence of the acid/soap can dramatically destabilize w/o emulsion, even at extremely low concentrations (0.05% (w/w)). Interestingly, when the hydrophobic moiety of the acid is sufficiently aromatic or fused ringed aromatic, the addition of the acid/soap can dramatically stabilize w/o asphaltene emulsions. The results suggest judicious ways of minimizing w/o emulsion challenges during the production and refining of petroleum fluids.
13-14
Studies on Properties of
Interfacial Active Fractions from Crude and Its Effect on Stability of Crude
Emulsions
MINGYUAN LI, Jixiang Guo, Meiqin Lin, Zhaoliang Wu, EOR Research Center, University of Petroleum Beijing, Beijing, P.R. China, myli@public3.bta.net.cn
The influence of indigenous interfacial active fractions from crude on the interfacial property between water and crude and its effect on stability of crude emulsions was studied.
It was found that the fatty acid and carboxyl acids in the fractions of asphaltene from Gudong 1#, Gudong 4# crude and of resin from Daqing crude are responsible for decreasing the interfacial tension between the crude oils and water. These acids have smaller relatively molecule mass, more branch chain more oxygen but they were not able to stabilize emulsion formed by model oil and water. It was the acids with lager relatively molecule mass are responsible for stabilizing the emulsions. For model oil and alkali solution system the soap formed by fast reaction of the acid, ester with smaller relatively molecule mass and alkali is responsible for decreasing the interfacial tension between crude oil and water. The soap formed by slow reaction of the acid, ester with lager relatively molecule mass and alkali is responsible for stabilizing crude oil emulsions.
13-15
Phase
Equilibria and Separation of Amphiphilic Extractives from Wood
PER STENIUS1, Esa Pirttinen1, Kari Kovasin2,
1Laboratory of Forest Products Chemistry, Helsinki University of Technology,
Espoo, Findland, 2SciTech-Service Ltd, Rauma, Findland, Per.Stenius@hut.fi
Phase equilibria, particle size and kinetics of phase separation in aqueous sodium alkanoate/sodium rosinate acid systems containing solubilizates representative of water-insoluble compounds in wood (sterols, long-chain alkanols) was investigated by light transmission and backscattering measurements using TurbiScan analyzers. Solution conditions corresponded to those obtaining during cooking and washing of softwood pulp (“black liquor”) and separation of crude tall oil. Creaming rates of the lyotropic phases were highly dependent on the ratio alkanoate/rosinate and the amount of solubilizate. Two-phase regions were found in which lamellar phase was in equilibrium with very dilute solutions, and separation was very efficient. This was utilized to develop method of improving the separation of soaps from dilute systems by addition of non-polar solubilizates. The method was applied successfully, in laboratory scale and mill trials, to the separation of soaps by adding non-polar solubilizates isolated from wood. The amounts of residual dissolved alkanoates and resinates could be reduced by 70-80 %, depending on the amount of “auxiliary” solubilizate added.
13-16
Building an Institute to
Serve Industry with Innovations from Surface Chemistry Research
BRUCE LYNE, Institute for Surface Chemistry (YKI),
The Institute for Surface Chemistry (Ytkemiska Institutet, or YKI
for short) was created to promote research in interfacial science that had
relevance to industry. YKI started
as a laboratory under the auspices of the
Today, YKI remains strongly linked to academe in
13-17
PATRICK T. SPICER1, Richard W. Hartel2, 1Complex Fluids Research, Procter & Gamble Co., 8256 Union Centre Blvd., West Chester, OH, USA, 2Department of Food Science, University of Wisconsin-Madison, Madison, WI, spicer.pt@pg.com
Liquid oil emulsion droplets can violently dewet their own solid crystals during crystallization as a result of surfactant adsorption. The crystal shape formed is a function of the relative rates of dewetting and crystallization as controlled by surfactant adsorption, cooling rate, and lipid purity. For negligible dewetting rates, crystals nucleate and grow within the droplet. At similar crystallization and dewetting rates, the droplet is propelled around the continuous phase on a crystalline “comet tail” much larger than the original droplet. Rapid dewetting causes the ejection of small discrete crystals across the droplet’s oil-water interface. It is shown that the crystallization behavior can be controlled by tuning the molecular packing geometry of the surfactant.
13-18
Dispersions of Glyceryl
Monooleate with PEO-Copolymers Bearing Lipid-Mimetic Hydrophobic Blocks in
Water.
S. Rangelov, M. ALMGREN, Department of Physical Chemistry, Uppsala University, Box 579, SE-751 23, Uppsala, Sweden, almgren@fki.uu.se
Stable dispersions of the cubic phase of glyceryl monooleate (GMO) in water were first obtained by K. Larsson and suggested to require the presence of a three phase area, involving the lamellar phase in addition to the cubic and water. Using suitable stabilizing agents such as poloxamers, it was later shown that stable cubic particles can be obtained also within the two phase area. Furthermore, GMO and sodium cholate form a L3 phase in brine; dilution of this phase in excess brine results in coexisting L3 and cubic particles with some stability.
We have prepared copolymers with PEO as hydrophilic block and blocks containing two to eight dodecyl chains as hydrophobic anchors, in both di- and triblock versions. Dispersing a polymer-GMO mixture in glycerol, and adding this dispersion to excess water, results in the formation of small particles with a broad variation of morphologies depending on the amount and type of copolymer. The particles have been studied by cryoTEM imaging, and their morhophologies will be rationalised from packing and phase behavior.
13-19
Worm-like Micelles and
Microemulsions
HIRONOBU KUNIEDA, Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya, Yokohama, Japan, kunieda@ynu.ac.jp
Wormlike micelles form visco-elastic solutions in which long-flexible micelles are entangled. CTAB is a well-known cationic surfactant, which produces such a visco-elastic system in the presence of some inorganic and/or organic salts. Wormlike micelles are also produced by combining hydrophilic surfactant with cosurfactant in ionic and nonionic surfactant systems. Upon addition of oil to the viscoelastic systems, the considerable reduction in viscosity takes places in some oil systems whereas it is also possible to maintain the viscosity in other oil systems. These systems are also able to call microemulsions. Phase behavior of wormlike micelles and their microemulsions in the mixed surfactant systems will be reported as well as their visco-elastic behavior and structures.
13-20
Friberg Correlations in
Oil Recovery
GEZA HORVATH-SZABO, Lamia Goual, Alejandro Magual, Jacob H. Masliyah,
Department of Chemical and Materials Engineering,
University of Alberta, Edmonton, AB, Canada, ghszabo@usa.net
In the presence of liquid crystal phase (LC-phase), the stability of emulsions increases dramatically. Consequently, the phase behavior of oil/organic-solvent/water systems has an effect on the efficiency of separation of emulsified water. Since LC-phase was identified in bitumen/toluene/water system under alkaline conditions, the phase behavior of sodium-naphthenates/organic-solvents/water was investigated in detail revealing the presence of lamellar LC, microemulsion and high viscosity gel phases. In this system the emulsion stability has a strong correlation with the phase behavior. The LC-phase is located between the dispersed aqueous droplets and organic medium.
In crude oil systems having low surfactant concentration, the volume of the interfacial LC-phase becomes so small that it cannot be identified easily by polarization microscopy. For this case quartz crystal microbalance (QCM) and electroacoustic spectroscopy (EAS) were introduced for the characterization of the adsorbed surface-active materials at the oil-water interface in bitumen-toluene systems. EAS revealed a time dependent relaxation of the surface charge of water-in-oil emulsions. Depending on the bitumen concentration, two distinct adsorption regimes were discovered by QCM. The threshold concentration between these adsorption regimes is in agreement with the critical bitumen concentration corresponding to the rigid-to-flexible transition of the o/w interface.
13-21
Phase Behaviour in
Confinement Studied with a Surface Force Apparatus
HUGO K. CHRISTENSON,
The free energy of a surface has a major influence on phase behaviour in systems where the area-to-volume ratio is large. These include finely dispersed solids and liquids as well as substances confined to meso- and microporous solids. In a surface force apparatus mica surfaces at or close to contact form a single model pore in which surface energy effects on phase behaviour may be conveniently studied. Capillary condensation of liquid from undersaturated vapour is the most familiar example of a surface-induced shift of bulk phase behaviour. I will describe experimental studies of capillary condensation and related phenomena such as melting-point depression in a pore, direct condensation of solid from vapour and capillary evaporation.
13-22
A Magneto-Optical Apparatus for
Boundary Localization of Ternary Phase Diagrams
Knowledge of the phase diagram of
any complex fluid, either colloidal dispersions, surfactant solutions, polymers
or lipids, is the first step needed for efficient formulation in industry or to
investigate molecular interaction.
An optical apparatus designed for
the mapping of binary or ternary phase diagrams will be described. A
polychromatic polarized light illuminates a sample and the rotation of its
polarization is measured with a spectrometer for various magnetic fields. The
measured parameters are the natural and magnetic rotatory power of the sample
which allows the concentration retrieval of every compound to be done. Results
show that the apparatus is suitable for correct positioning of single phase
boundary on the ternary water - n-dodecyl-β-d maltoside - sodium chloride
system.
13-24
Surface Chemical Aspects
of Treatments with Dental Implants
PER-OLOF J. GLANTZ, Department of Prosthetic Dentistry, Faculty of Odontology, S- 214
21 Malrmo,
Reviews of factors influencing the outcome of restorative treatments with dental implants have demonstrated that lack of proper control of implant surface chemistry is one of the most like reasons for the frequent reported failures of such treatments prior to the introduction of so-called osseointegrated Ti-implants in the 1980-ies. Thus, with earlier implant systems surface contamination was often present as the results of poor mechanical finishing and/or sterilization procedures. Such contamination prevents the establishment of initial key contacts between living cells and the actual implant surface. On a long term basis this led to the formation of connective tissue capsules around implants in stead of direct implant-bone contacts that now are known to be essential for successful long term functional control of implant loading and prevention of implant-tissue infections.
This paper present an overview of these problems as well as recent data supporting the view that the establishment of undisturbed, initial contacts between living cells and implant materials with defined surface chemical characteristics is an absolute prerequisite for long term clinical success with modern dental implant systems. It will also point on certain surface chemical problems associated with the efficacy of in situ hygiene procedures for patients wearing dental implants.
13-26
Studies on the Stability of the Choramphenicol in the Microemulsion-based Ocular Drug Delivery Systems
LIQIANG ZHENG, Key Laboratory of Colloid and Interface Chemistry,
Shandong University, Ministry of
Education, Jinan, P. R. China. lqzheng@sdu.edu.cn
Two microemulsion systems which were composed of Span20+Tween20＋isopropyl palmitate+H2O and Span20/80+Tween20/80＋n-butanol＋H2O＋isopropyl palmitate /isopropyl myristate were investigated as potential drug delivery systems for eye drops. Effects of choramphenicol, normal saline, sodium hyaluronate and various oils on the phase behavior were studied. The phase transition was investigated using the electrical conductivity measurements. The choramphenicol is used to treat the eye diseases such as trachoma and keratitis. However, this drug in the common eye drops hydrolyzes very easily. The main product of the hydrolysis is glycol. Here, the choramphenicol was trapped into the oil-in-water microemulsions, its stability was investigated by HPLC assays in the accelerated experiments of three months. The location of the choramphenicol molecules in the microemulsion formulations was determined by means of 1H NMR spectroscopy and dynamic light scattering (DLS). The results of HPLC revealed that the content of the glycols in the microemulsion formulation was much lower than that in the commercial eye drops at the end of the accelerated experiments. It implied that the stability of the choramphenicol in the microemulsion formulations is increased remarkably. The results of NMR and DLS confirmed that the choramphenicol molecules should be trapped into the hydrophilic shell of the microemulsion drops, which were composed of many oxyethylene groups. It was this reason that enabled the choramphenicol molecules in the microemulsions to be screened from the bulk water and its stability to be increased remarkably.
13-27
Application of Phase
Studies for the Formulation of High Ionic Strength Antiperspirant Products
ZHUNING MA, Richard Brucks, Unilever HPC-USA, 3100 Golf Road, Rolling Meadows, IL, zhuning.ma@unilever.com
Antiperspirant products are a very large personal care category, 90% of the American population use antiperspirants every day. The products on the markets are in different forms, such as solid sticks, soft solids, gels, sprays, aerosols, creams and roll-ons. From a colloid chemistry point of view, formulations can be emulsions, microemulsions, co-solvent systems or solid particle suspensions with or without structurants or polymers.
Aluminum salts are the main active ingredients in antiperspirant formulations. When a high salt concentration is involved in making a formulation, the phase behavior of the systems is highly impacted. In this presentation, we will introduce basic knowledge concerning antiperspirant products and how to use phase studies to reach desirable formulation for consumer products.
13-28
Salicylic Acid Vesicle Solutions, Emulsions and their Combinations.
ABEER AL BAWAB1, Stig E. Friberg2, 1Chemistry Department,
Faculty of Science, University of Jordan, Amman 11942, Jordan, 2Chemistry Department,
University of Virginia, Charlottesville,VA, drabeer@ju.edu.jo.
The phase diagrams were determined of salicylic acid as beta hydroxy
acid and to be compared with series of hydroxy acids such as lactic acid,
isohexanoic hydroxy acid and some water soluble acids such as malic, tartaric and citric acid. The acids were
combined with water, a nonionic surfactant and a paraffinic oil to
outline the influence of the hydroxyl acids on the structure in a model for a
skin lotion. The colloidal structures of beta
carboxylic acid topical formulations were determined and the changes during
evaporation after applications were estimated from phase diagrams.
The results showed that; the influence of the acid to be similar to that of the oil, but that the difference in chain length between the alpha acids had only insignificant influence, the significant difference between salicylic acid on one hand and three water soluble acids; malic, tartaric and citric acid, on the other, the water soluble acids showed an increase in the acid concentration in the water to levels that must be considered definitely harmful, while salicylic acid showed no increase in concentration in the individual phases.
13-29
Theoretical Study on
Synergisms of Surfactant Mixtures
ZHENG-WU WANG1,2, Zhong-Ni Wang2, Jun Xu2,
and Ganzuo Li2, 1School
of Chemical and Material Engineering, Southern Yangtze University, 170 Huihe
Rd, Wuxi, P.R. China, and 2Key Lab of Colloid and Interface
Chemistry for State Education Ministry, Shandong University, Jinan, P.R. CHINA,
wangz.w.@263.net
By appointing the ideal mixture system of surfactants as the standard of comparison, synergisms in surface tension reduction efficiency and in mixed micelle formation of binary surfactant mixtures in aqueous solution have been redefined. The conditions and the corresponding optimum point values of these two kinds of synergism also have been deduced on the bases of the regular solution theory and the ideal solution theory. The conclusions have enlarged reasonably the scope of synergism theory proposed by Rosen and his coworkers.
13-30
Colloid and Surface
Science in Consumer Product Development
FRAN E. LOCKWOOD, Z. George Zhang, The Valvoline Company, P.O. Box 14000, Lexington, KY, felockwood@ashland.com
Colloid and surface science plays a key role in product development at many Consumer Products companies. This talk will focus on the consumer products designed for the automotive aftermarket: lubricants, chemicals, and appearance products. These products have evolved dramatically due to empirical and scientific advances in the field. Lubricants today are engine tested under conditions where suspended soot and particulates may exceed 8 % by weight. Appearance products, such as car wash, automotive waxes, tire shines and wheel cleaners, etc., have benefited from an array of advances in detergency, emulsion and microemulsion technology, and colloidal dispersion technology. Automotive chemicals, e.g. fuel system cleaners, have benefited from new detergent technology as well. The impact of colloid and surface science on these consumer products is explained, pointing out some of the key advances.
13-31
X-ray Studies of Mixed Surfactant Ordering and Phases at the Water-Oil Interface
Sai Venkatesh Pingali1, Takanori
Takiue4, Guangming Luo1, Aleksey M. Tikhonov3,
Norihiro Ikeda5, Makoto Aratono4, MARK L. SCHLOSSMAN1,2,
Departments of 1Physics and 2Chemistry, University of
Illinois at Chicago, 845 West Taylor St, Chicago, IL, 3Center for
Advanced Radiation Sources, University of Chicago, and Brookhaven National
Laboratory, National Synchrotron Light Source, Beamline X19C, Upton, NY4Department
of Chemistry, Faculty of Sciences, Kyushu University, Fukuok, Japan, 5Department
of Environment Science, Faculty of Human Environmental Science, Fukuoka Women’s
University, Fukuoka, Japan. schloss@uic.edu
X-ray reflectivity is used to study ordering on the Angstrom scale of a monolayer of surfactants self-assembled at the liquid-liquid interface between bulk water and hexane. This technique determines the electron density as a function of depth through the interface. Studies of the interface between water and single surfactant hexane solutions of either CH3(CH2)19OH or CF3(CF2)7(CH2)2OH demonstrate the liquid order of the hydrocarbon monolayer or the solid order of the fluorocarbon layer, as well as phase changes with temperature. Interfacial tension and x-ray studies of the interface between water and mixed solutions of these surfactants in hexane determine the phase diagram, and the molecular ordering of the phases, as a function of temperature for four different surfactant compositions. An unusual feature is the phase change from a liquid to a solid monolayer that occurs with increasing temperature. A simple model predicts the interfacial coverage as a function of temperature for the mixed surfactant system from the behavior of the single surfactant systems.
13-32
Monolayer
Phase Morphology Induced by Bulk Flow
A. H. HIRSA1, Jonathan J.F. Leung1, M. J. Vogel2, and J. M. Lopez3, 1Mechanical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 2Chemical and Bimolecular Engineering, Cornell University, Ithaca, NY, 3Mathematics, Arizona State University, Tempe, AZ, hirsaa@rpi.edu
Effects of bulk flow on Langmuir monolayers are examined in open flow systems (rectangular cavities and cylinders) driven by the motion of the floor. The air/water interface covered by an insoluble monolayer (vitamin K1) is studied using a Brewster angle microscope (BAM) system that utilizes a pulsed laser to image the coexisting phase domains on the fast-moving surface. The flow field is measured using a digital particle image velocimetry system. A range of flow conditions is considered where the Reynolds number is large (large flow inertia) yet the flow is essentially two-dimensional (planar or axisymmetric). Macroscale flows can induce various mesoscale phase behaviors, such as fragmentation of phase domains. Recent results from this and other groups show that coexisting phase domains, observed over a wide range of monolayer states, have profound effects on the (macroscopic) response of monolayers to flow. We examine the effects of shearing and dilating flows on the coexisting phase domains with the aid of numerical results obtained using the Navier-Stokes equations with Boussinesq-Scriven surface model. We show that the response of coexisting phases to flow and the resulting morphological transitions from one phase to another needs to be accounted for when interfacial hydrodynamics drives the system far from equilibrium.
13-33
Mixed Cationic and
Glycoside Surfactants: Investigation of Ternary Phase Diagram and Predictive
Mesoporous Materials Synthesis
R. Xing, S. E. RANKIN, Chemical and Materials Engineering
Department,
Mixed surfactant systems have the potential to impart controlled
combinations of functionality and pore structure in mesoporous ceramics. In this instance, we combine a
functional glycoside surfactant with a cationic surfactant that more readily
forms liquid crystalline mesophases.
The phase diagram for the ternary system CTAB/H2O/n-Octylβ-D-glucopyranoside (C8G1) at 50 °C is
investigated using polarized optical microscopy. At this temperature, the
binary C8G1/H2O system forms micellar
solutions up to over >70 wt% C8G1, and there is no
hexagonal phase. With the addition of CTAB, we identify a large area of
hexagonal phase, as well as cubic, lamellar
and solid surfactant phases. The ternary phase diagram is used to predict the
synthesis of thick mesoporous silica films via a direct liquid crystal
templating technique. By changing the relative concentrations of mixed
surfactants as well as inorganic precursor species, mesoporous silica films can
be synthesized with variable glycoside content, and with 2D hexagonal, cubic
and lamellar structures. The domains over which different pore structures are
prepared correspond well with those of the analogous mesophases in the ternary
phase diagram if the hydrophilic inorganic species is assumed to act as an
equivalent volume of water.
13-34
Nano-Emulsion Formation by
Low-Energy Emulsification Methods and Phase Behavior
C. SOLANS, P. Izquierdo, D. Morales, N.
Sadurní, J. Esquena, N. Azemar, M. J. Garcia-Celma, Institut d’Investigacions
Químiques i Ambientals de Barcelona (IIQAB), Consejo Superior de
Investigaciones Científicas (CSIC), Barcelona, Spain, csmqci@cid.csic.es
Emulsions with droplet size in the
nanometer scale (typically in the range 20-200 nm) are know as nano-emulsions,
miniemulsions, submicron emulsions, etc. Due to the extremely small droplet
size, nano-emulsions appear transparent or translucent to the naked eye
(resembling microemulsions) and possess stability against sedimentation or
creaming. These properties make nano-emulsions of interest for fundamental
studies and for practical applications. In this communication, our recent work
on the formation of nano-emulsions in water/polyethoxylated nonionic
surfactant/oil systems by low-energy emulsification methods will be reported.
O/W nano-emulsions with droplet sizes as low as 20 nm and high kinetic
stability have been obtained either by the PIT method or at constant
temperature (by changing the composition). It has been inferred from phase
behavior studies that a requirement for the formation of minimum droplet size
is to achieve a complete solubilization of the oil phase in a bicontinuous
microemulsion, independent of whether the initial phase equilibrium is single
or multiphase.
14-01
Growth of Hierarchical
Nanostructured Materials via Soft Solution Routes
NELSON S. BELL, Jun Liu, Jim A. Voigt, Julia Hsu, Tom Sounart, Eric
Sporke, Sandia National Laboratories, P.O. Box 5800-1411,
Nanostructured films have numerous applications including wetting, microfluidics, photonics, and other opto-electronic properties. Solution phase syntheses of nanostructured films provide the potential for cost effective, large scale manufacturing. In this talk, we will review recent progress at Sandia National Laboratories in using solution based, bottom-up approaches to synthesize oriented nanostructured films and complex nanostructures. First, the principles and applications of heterogeneous nucleation and growth will be highlighted. Next, a hierarchical growth method we recently developed to control structural ordering in a step wise manner will be discussed. Large arrays of complex, oriented and ordered architectures have been produced. Growth directing factors that influence crystalline morphologies will be discussed. Finally, we will demonstrate the wide applicability of the methods we developed in different systems.
14-02
Rare Earth Doped Nanocomposites for Photonic Applications
JOHN BALLATO†, Dennis Smith‡, Richard E. Riman*, Chun-Wei Chen*, G. Ajith Kumar*, Center for Optical Materials Science and Engineering Technologies, †School of Materials Science and Engineering, ‡Department of Chemistry, Clemson University, Anderson, SC, *Center for Ceramic Research, Rutgers, The State University of New Jersey, Piscataway NJ, john.ballato@ces.clemson.edu
The proliferation of optical systems for communications, defense, entertainment, automotive, and display applications has manifested the need for devices that can perform a greater number of tasks while being increasingly robust, take up less space, and use less power to operate. These increasingly more stringent requirements continue to spur international research efforts on materials that exhibit multiple optical functionalities. This talk will focus on approaches to achieving greater functionality and efficiency through the use of fluoropolymer nanocomposites. More specifically, theoretical and experimental studies on transparent rare-earth doped halide nanoparticles in unique fluoropolymer matrices will be presented as will potential applications.
14-03
Preparation of Nanoporous Silica and Sodium Fluoride from
Hexafluorosilicic Acid and Sodium Silicate
JONG-KIL KIM, Jin-Soo Kim, Jin-Koo Park and Ho-Kun Kim, Department of Applied Chemistry, Hanyang University 2-304, Science and Technology Building 1, 1271 Sa 1 dong, Ansan, Kyunggi-do, South Korea, pradipsarawade@yahoo.co.in
A process for the preparation of nanoporous silica and recovery of sodium fluoride from hexafluorosilicic acid and sodium silicate at the different molar ratios was studied. In order to prepare the appropriate solutions of initial compounds the 25% hexafluorosilicic acid solution and the 18% sodium silicate solution were used. Obtained nanoporous silica and sodium fluoride have been investigated by XRD, BET, TGA, EDX and SEM methods
14-04
Top-Down
or Bottom-Up: New Approaches for the Fabrication of (Functional)
Three-Dimensional Photonic
Crystals
G. VON FREYMANN1, S.
Wong, M. Deubel1, M. Hermatschweiler1, D. C. Meisel1,
M. Wegener1, N. Tétreault2, E. Vekris2, V.
Kitaev2, G. A. Ozin2, 1Institut für
Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany, 2Department
of Chemistry, University of Toronto, ON, Canada, S. John, Department of Physics, University of Toronto, ON, Canada, freymann@int.fzk.de
Bottom-up self-assembly of colloidal sub-micron size spheres as well as top-down holographic laser lithography in photoresists are reliable tools for the inexpensive, large-scale fabrication of three-dimensional Photonic Crystals. To add functionality to these Photonic Crystals we follow different approaches: A lithographic method allows for reliable waveguide fabrication inside colloidal Photonic Crystals, while Direct Laser Writing (DLW) is the method of choice for holographically fabricated samples.
The crucial step for both methods is the final conversion into high index materials, e.g., silicon. As conventional silicon chemical-vapor deposition (CVD) can be used for bottom-up templates, no such technique is available for photoresist-based samples. Here we demonstrate the successful double-inversion of direct-laser written templates, combining silica and silicon CVD techniques.
Finally, a novel approach for the direct fabrication of three-dimensional Photonic Crystals will be presented, namely DLW in high index of refraction chalcogenide glasses with subsequent wet etching of the unexposed areas.
14-05
Colloidal Crystal
PAUL V. BRAUN, Assistant Professor, Materials Science and
Engineering, University of Illinois at Urbana-Champaign, IL, pbraun@uiuc.edu
Colloidal materials offer interesting opportunities for scientific exploration and formation of functional materials and structures. After a brief introduction to the optical properties of colloidal crystals and photonic band gap materials, I will present our results on synthetic opal based devices. Device fabrication begins with the self-assembly of silica or polystyrene colloidal particles into a colloidal crystal, this colloidal crystal is then used to template a periodic 3-D structure into an optically active material. Colloidal crystals inherently have interesting optical properties, however by inverting the structure into a functional material, the optical behavior can be significantly enhanced. Using such an approach, we have created hydrogel inverse opal chemical and biological sensors. These sensors show rapid (~1 minute) diffusion limited responses to small changes in pH and glucose concentration, and were designed to have an optical diffraction based response that is detectable with the naked eye. The mechanical behavior of these structures turned out to be rather interesting. As the polymer swelled, the inverse opal transformed from fcc to L11 due to the strain field in the hydrogel inverse opal, and antiphase boundaries were observed to form. In contrast to photonic based sensors, which only require periodic structures, for a number of applications, incorporating aperiodic defects on the wavelength of light into an otherwise periodic structure will be critical. For example, a 3-D waveguide with a bend radius on the order of the wavelength of light could be created by embedding a waveguide structure inside of a photonic band gap material. We have been developing multiphoton polymerization of three-dimensional structures to do exactly this, and have demonstrated the writing of waveguide structures within colloidal crystals. A number of issues still must be dealt with to create an optical device, and I will highlight our latest results in this area.
14-06
Novel Types of Optical
Gain Media Based on Photonic
G.R. MASKALY, M.A. Petruska, J. Nanda, I.V. Bezel, N. Liu, R.D.
Schaller, H. Htoon, J.M. Pietryga, V.I. Klimov, Softmatter Nanotechnology and
Advanced Spectroscopy Team, C-PCS, Los Alamos National Laboratory, Los Alamos,
NM , maskaly@lanl.gov
The periodic variations of the dielectric constant in photonic crystals (PCs) give rise to photonic band structures analogous to those for electrons in semiconductors. Near the edges of the photonic band, the photonic density of states and group velocities are modified. In some cases, near zero group velocities are obtained leading to very large optical gains. Since PC properties are wavelength tunable through size variations, their properties can be tailored to match semiconductor nanocrystals (NCs) emissions, which are tunable across a wide spectral range through compositional and size variations. Here, we demonstrate NC incorporation into a variety of PC structures. In one example, we utilize self-assembled opals as a host for NC/sol-gel (NC/SG) nanocomposites. Despite an order-of-magnitude reduction in the NC volume fraction versus NC/SG films, we observe a two-fold reduction in the amplified spontaneous emission (ASE) threshold and an optical gain increase evidenced by the observation of ASE with a 30-m excitation spot. We also discuss the impact of one-dimensional PC structures on the optical properties of NC/SG composites. Here, we incorporate the NC/SG material directly into a one-dimensional PC. The results presented here are steps toward low-threshold NC lasers that can be excited by a continuous wave source.
14-07
The Rate-controlled Synthesis
of Doped Ferroelectric Nanoparticles under
Conditions of
Micro/Nanoreactors.
A.V. RAGULYA, A.V. Polotai, Frantsevich Institute for Problems in
Materials Science NAS of
Synthesis of nanoparticulate materials in micro/nanoscale reactors is widely used as a powerful and precise technique. One of the possible small-scale reactors is particulate intermediate product originating from thermal decomposition of unstable precursors. Scaling relationship between size of reactor and size of the specified nanoparticles is not well-understood one. The recently developed process, so called rate-controlled synthesis, is considered useful in manufacturing of nanosized powders from unstable precursors. The reaction rate-controlled processes (RCP) strongly differ from the conventional synthesis and sintering due to feedback established between transformation value and instantaneous temperature. During RCP, the transformation value is the dependent parameter whereas the temperature is the independent parameter, contrary to conventional processes. The chemical synthesis proceeds through the competition between new phase nucleation and nuclei growth. Both nucleation and growth have different thermal activation energies and, therefore, different rate, which is a function of temperature and heating rate. The competition of mechanisms results in possibility of particle size control. The rate-controlled mode allows flexible temperature-time regime and refinement of particles compared to conventional ramp-and-hold regimes. For instance, the rate-controlled decomposition of unstable precursors of barium titanate, zirconia and lanthanum-strontium manganate resulted in 1.2-2.0 times decrease of particle size compared to linear heating rate regimes. The nanosized barium titanate powders, both pure and doped, have been prepared through the modified Pechini process. The intermediate product of oxalate decomposition was impregnated with soluble precursors of dopants such as niobia, calcia, yttria and subsequently co-decomposed until synthesis of doped barium titanate. The morphological transformations within intermediate resin-like products have been studied by combination of FTIR, RAMAN and Kawazoe methods. The understanding of internal structure of nanoreactors allowed us to clarify features of rate-controlled non-linear heating rate synthesis compared with conventional process of ramp-and-hold.
14-08
Barium Titanate Based Nanocrystalline Ceramics: Preparation and Properties
ANTON V. POLOTAI, Andrey V. Ragulya, Clive A. Randall, Institute of Materials Science Problems NAS of Ukraine, Kiev, Ukraine, Pennsylvania State University, University Park, PA, avp10@psu.edu
Barium titanate is the most widely used dielectric material in surface mount components and is presently under development for the mass production of submicron grain size ceramics. Over the next ten years, these dimensions will become nanoscale if present trends continue. With this view, most of the earlier research has focused on the dielectric properties of BaTiO3 and considered these properties to enhance volumetric efficiency in multilayer ceramic capacitors. One of the major unknowns in these materials is the influence that nanosized grains may have on the reliability of future devices, which is typically controlled by the ionic migration of point defects under a direct bias. The production of fully dense nanocrystalline barium titanate ceramics is a difficult task due to enhanced grain growth during the final stage of sintering. To win this competition between densification and grain growth, the right combination of different factors should exist, such as powder particle size and pore size distribution in green body, sintering schedule and sintering atmosphere, and dopant type and dopant distribution. This work presents results of rate-controlled synthesis and sintering of doped barium titanate, as well as the size effect and its relation to reliability and dielectric properties. It is shown that rate-controlled synthesis by decomposition of thermal unstable precursors gives weakly agglomerated powder with an average particle size around 20 nm, which can be easily doped by modified sol-gel technique. Combining pressureless rate-controlled sintering with controlled atmosphere treatments and effective dopant concentrations yields a nano-grained fully dense ceramic with a grain size of less than 100 nm, with a 4÷5 factor of grain growth, which is 3÷5 times less than in traditional sintering modes. The lifetime and dielectric properties are studied based on grain size and dopant concentration. The prospects of using these results in multilayer ceramic capacitor technologies are discussed.
14-09
Nanoparticles as Functional Building Blocks: Size, Shape and Composition Control and
Property
Xiaowei Teng, Yong Wang, Xinyi Liang, Justin Galloway, HONG YANG,
Department of Chemical Engineering, University of Rochester, Gavett Hall 206,
Rochester, NY, ongyang@che.rochester.edu
Size, size distribution, shape and composition control of sphere, rod and multipods nanocrystals is pivotal in the development of new multifunctional nanomaterials. In this presentation, I will discuss our recent progress in the following areas: 1) size, shape (including monodisperse nanorods, cubes and multipods) and composition control of metals, metal alloys and metal oxides in both conventional solvents and ionic liquids; 2) composition and property of FePt and other alloy-containing magnetic nanocomposites made from core-shell nanoparticles; and 3) the electrode catalytic property of Pt-containing nanoparticles. This talk will cover several classes of nanomaterials including Pt, Ag, PtM (M=Co, Fe and Ni), Fe2O3 and a variety of magnetic core-shell nanoparticles. The emphases are on our understanding and the strategies on the controlled growth of colloidal nanocrystals, and the design of functional materials from nanoparticle building blocks, which possess interesting magnetic and electro-catalytic properties.
14-10
Alkaline Modified Calcium
Doped Lead Titanate Film Humidity Sensor Formed Using Sol-Gel Method
LOUISE J.B. LIU, Zhi-Min Wang, College of Chemistry and Chemical Engineering, Heilongjiang University, Harbin, P. R. China, jlouise@clarkson.edu
This research encompassed the
fabrication, microstructural characterization, and moisture sensitivity of an
alkaline modified, calcium doped, lead titanate thin film humidity sensing
device. The active component for
the humidity sensor is based on a LiyCaxPb1-xTiO3
(Li-CPT) ceramic (x = 0.35 to 0.50, y = 0.005 to 0.01). Films of Li-CPT were prepared by a
sol-gel, spin-coating technique, and then followed by sintering at 550 to 900 oC
for one hour. The films were
structurally characterized by x-ray powder diffraction (PXRD), scanning
electron microscopy (SEM), transmission electron microscopy (TEM), magnetic
resonance force microscopy (MFM), and Raman spectroscopy (RS). Characterization
results indicated the synthesized films were composed of a single perovskite
phase with crystallite particles on the order of 30 – 50 nm. Humidity sensing measurement had been
performed for Li-CPT using resistance measurements at different relative
humidity (j) range of 8% to 93%RH at room
temperature. The variations of resistance values (R) were higher than three
orders of magnitude over the working relative humidity range. The curves of Log
R versus j displayed excellent linearity, high
sensitivity, minimal hysteresis and rapid response to the humidity change.
14-11
Dynamics of the
Electrohydrodynamic Patterning of Thin Polymer Films
NING WU, William B. Russel, Department of Chemical Engineering,
Princeton University, Princeton, NJ, nwu@princeton.edu
We perform one and two-dimensional simulations of an electrohydrodynamic patterning process for a mask-air gap-polymer-substrate sandwich, which is a newly discovered patterning phenomenon. The simulations help us identify the intrinsic pattern resulting from nonlinear interactions to be hexagonal when the mask is unpatterned, consistent with experimental observations. The size of microstructures, periodicity and time for formation agree well with the experimental data. The dynamic evolution of the thin polymer layer under a patterned mask shows that the pillars start to form from corners, propagate along edges and then grow inwards. This growth sequence, identical to experimental observations, creates a square pattern under a square mask, a hexagonal pattern under a triangular mask, etc. Besides the hexagonal pattern, simulations indicate the conditions under which various different patterns that have been observed in experiments should form. The dynamic simulations are very helpful in understanding of the nonlinear dynamics of the patterning process, predicting the final pattern formation under different conditions, and providing insights for future experimental design.
14-12
Shape-Controlled Synthesis of Metallic NanostructuresYOUNAN XIA, Benjamin Wiley, Jingyi Chen and Yujie Xiong, Department of Chemistry, University of Washington, Seattle, WA , E-mail : xia@chem.washington.edu
Future nanotechnology applications, either in electronics, photonics, catalysis, or medicine, require nanostructure building blocks. I will present a solution phase synthesis that produces large quantities of silver, gold, platinum, and palladium nanostructures with controlled size, shape, monodispersity, and crystallinity. Some example nanostructures include silver nanowires and nanocubes, hollow gold nanotubes and nanocages, platinum nanowires and multipods, and palladium nanocubes and nanocages. By controlling nanostructure size and shape, one can tailor the photonic, plasmonic, electronic, and catalytic properties of metallic nanostructures for a given application.
14-13
Dynamic Tuning of Photoluminescent Dyes in
Crystalline Colloidal Arrays
Justin R.
Lawrence, Goo Hwan Shim, Ping Jiang, Moon Gyu Han, Yurong Ying, STEPHEN H.
FOULGER, School of Materials Science & Engineering, Clemson University, foulger@clemson.edu
A number of people in the group have been working on approaches to
dynamically (i.e. in real time) tune the photoluminescent spectrum of dyes
localized on crystalline colloidal arrays. Though a number of experimental
studies have studied the suppression of the spontaneous emission of
photoluminescent (PL) materials at frequencies inside the photonic bandgap of
ordered dielectric structures, the majority of these experimental efforts have
focused on sterically packed colloidal crystals composed of dye-labeled
particles. Though these systems have offered a number of insights into this
class of materials and have established that the emission spectrum of a dye may
be controlled by the photonic lattice parameter, this control is usually
exercised by fabricating samples of different particle diameters to alter the
rejection wavelength.
The ability to dynamically (i.e., in real time) tune the emission
characteristics of the dye through an in-situ modification of the rejection
wavelength has not been previously demonstrated in colloidally-based crystals.
To this end, we focus on the exploitation of mechanochromic tuning to
modify the emission spectra of hydrogel-encapsulated crystalline colloidal
arrays composed of electrostatically self-assembled monodisperse polystyrene
particles coated with the photoluminescent dye Rhodamine-B. The broad rejection
wavelength tuning range, relatively narrow bandwidths, and non-hysteretic
nature of the mechanochromism of these electrostatically based colloidal
crystals suggest that these systems can be exploited to tune the emission
characteristics of an PL dye coupled to a photonic crystal in a slew of
optical/photonic based applications. The variation in the PL spectra of the
system is presented in the adjacent graph as a stop band is mechanochromically
tuned through the emission range; the approximate position of the rejection
wavelength is indicated with the arrows.
14-14
Driving Tomorrow’s Functional Electronics and Optics With Designer
Nanopowders and Nanostructures
R. E. RIMAN, G.A. Rossetti, Rutgers, The State University of New Jersey, Department of Ceramic and Materials Engineering, 607 Taylor Road, Piscataway, NJ, riman@rci.rutgers.edu
Recent progress in the chemical synthesis of nanomaterials has created new opportunities for the application of ceramics in advanced structures and devices. Our laboratory is focused on developing low-cost and robust methods for the synthesis and processing of nanomaterials and on establishing structure-property relationships at the nanometer length scale. Hydrothermal crystallization is known to be a highly flexible process to prepare nanopowders and nanostructured films. Methods for engineering hydrothermal crystallization processes are being developed using traditional fundamental approaches based on thermodynamic and kinetic principles. However, the non-classical mechanism of hydrothermal crystallization has brought forward the importance of non-thermodynamic variables such as fluid hydrodynamics and precursor characteristics. These variables provide additional degrees of freedom for controlling the physical and chemical characteristics of designer particulates. Efforts are being dedicated towards understanding crystallization mechanisms and applying that knowledge to design and construct unique reactor systems. The availability of designer particulates enables new classes of functional materials not accessible with conventional commercial ceramic powder processes. For instance, various families of infrared optics based on transparent halide nanocomposites would not be possible without the availability of nanoparticles that can be dispersed at length scales below 100-nm. Dielectric materials based on titania or barium titanate at the 1-µm length scale require particle sizes less than 200-nm. However, the production of uniform and dispersible powders alone is insufficient to enable the fabrication of functional materials. Appropriate mixing and particle assembly methods are needed and being developed to address the homogeneity length scale requirements, with an emphasis on continuous processing. The ability to create advanced materials with controlled nanostructure has generated a technology pull for computational design of materials. Examples illustrating the steps along the path from particle synthesis to functional materials will be presented for the specific case of new dielectric and optical nanocomposites.
14-15
Engineering the Forces Between Nanocolloids: Challenges and Opportunities
DARRELL VELEGOL, Department of Chemical Engineering, The Pennsylvania State University, 111 Fenske Lab., University Park, PAy, velego@psu.edu
Bottom-up assembly of nanocolloids depends in large part on the forces
between particles. Some forces –
like the use of DNA as a “selective glue” – cause a desirable “directed”
motion. But other forces –
especially the van der Waaals (VDW) forces – cause a random and nonspecific
aggregation of particles. A
critical goal then is to minimize these nonspecific forces between particles so
that aggregation occurs only by design.
Traditional methods for calculating and measuring VDW forces between
particles are not applicable to nanocolloids. In this talk we describe how we use
Axilrod-Teller-Muto theory to help us calculate VDW forces between
nanocolloids, and we will discuss our current approaches (e.g., particle force
light scattering) to measuring interparticle forces for polystyrene and silica
nanocolloids. The focus of the talk
will be on bottlenecks to predicting nanocolloidal forces, possibilities for
better models, and opportunities for bottom-up assembly.
14-16
Preparation and Properties of “Raspberry”-Type Colloidal Building
Blocks of ZnS and Fluorescent Core-Shell Silica Nanoparticles
STEPHANIE H. LEE*, Ian D. Hosein*, Valerie L. Anderson+, Victoria D. Crockett||, Watt W. Webb+, Ulrich B. Wiesner*, Chekesha M. Liddell*, *Department of Materials Science and Engineering, Cornell University, Ithaca, NY, +School of Applied and Engineering Physics, Cornell University, Ithaca, NY, ||Department of Chemistry, Tougaloo College, Tougaloo, MS, cliddell@ccmr.cornell.edu
A synthetic route to incorporate high-brightness core-shell silica nanoparticles (CU Dots 20-30nm) onto high-refractive index (n) ZnS colloids in a “raspberry” configuration is demonstrated. Motivation for this work lies in the promise of phenomena such as enhanced non-linear optical properties leading to ultrafast switching in 3-D photonic crystals with active light-emitting sources. Previous approaches involved either infiltration of a low-n colloidal template with quantum dots or surface modification of such colloids with dye molecules. In the former case tunability at the single particle level is lost, while in the latter, the index contrast is insufficient to promote bandgaps. For the present work, CU Dots and a thin layer of ZnS are co-condensed onto ZnS colloids via the thermal decomposition of thioacetamide in the presence of metal salt. The fluorescent high-n building blocks (200nm-2mm) exhibit complete and uniform “monolayer” coverage without a decrease in monodispersity, and are suitable for assembly into 3-D structures. Incorporating nanoparticles in the raspberry configuration also provides potential for brightness enhancement by avoiding quenching of neighboring dye molecules. The preparation and characterization of these colloids will be highlighted along with preliminary optical measurements of their assembly, including fluorescence microscopy, excitation-emission fluorescence spectroscopy and transmission spectroscopy.
11-17
High-Resolution, High-Sensitivity Particle Size Analysis of
Concentrated CMP Slurries and other Nanoparticle Systems using the New
Techniques of Focused Light Extinction and Scattering
D.F. NICOLI, P. Toumbas, Y.J. Chang, J.S. Wu, K. Hasapidis, Particle Sizing Systems Inc., Santa Barbara, CA, dave@pssnicomp.com
The technique of single-particle optical sensing
(SPOS) is effective for assessing the quality of oxide “CMP” slurries used for
semiconductor processing, ink-jet toners/pigments and a variety of other
nanoparticle-based dispersions and suspensions. The large-diameter “tail” of the
particle size distribution (PSD) can be measured effectively by combining the
methods of light extinction (LE) and scattering (LS), called “LE+LS” (Pat.). However, this approach requires
extensive sample dilution to achieve high sensitivity (> 0.5-um) and avoid
PSD artifacts due to particle coincidences and background scattering. New techniques, called focused
extinction (FX) and scattering (FS), have recently been developed (Pat.), which
utilize a much smaller active sensing zone and novel signal processing
methods. The resulting FX sensor
requires much less sample dilution (often none), while still achieving
excellent small-particle sensitivity not possible using conventional LE
technology. The companion LS sensor
produces PSD results of unprecedented resolution and sensitivity for particles
as small as 0.1-um and concentrations exceeding 10 million/ml. The combined FX and FS capabilities
permit accurate particle size measurement of many submicron systems that are
poorly characterized using laser diffraction and other ensemble techniques.
14-18
Colloidal Self-Assembly, Multibeam Holography and Photonic Crystals
PIERRE WILTZIUS, Beckman Institute for Advanced Science and Technology, Materials Science and Engineering Department and Physics Department University of Illinois at Urbana-Champaign, 405 North Mathews, Urbana, IL, wiltzius@uiuc.edu
Photonic crystals are materials that allow the manipulation of light in new and unexpected ways. Semiconducting materials played a tremendous role in microelectronics and we expect photonic crystals to revolutionize the world of microphotonics in a similar way. Colloidal self-assembly and multi-beam interference lithography are great tools to build crystals with interesting optical properties. I will review some recent progress towards constructing photonic band-gap materials.
14-19
Synthesis and
Characterization of Polymer Encapsulated Nanoparticles for Microelectronic
Applications
PRASHANT MESHRAM, Richard Partch, Center for Advanced Materials
Processing and Department of Chemistry,
rpartch@clarkson.edu; meshraps@clarkson.edu
There are two well-researched methods for constructing the core-shell morphology of particles. The shell can be produced by adsorption of preformed macromolecules onto core surfaces by electrostatic or by non-solvent deposition methods. An alternate method involves mixing core particles with monomers and then initiating polymerization. This procedure is more favorable for obtaining a uniform coating of each particle because of the substantially higher accessibility of t
he active surface of cores for molecules of a monomer compared to the corresponding macromolecules. However, the formation of an organic shell on extremely small silica nanoparticles (~ 20 nm) by the same method has received little attention. In the present work; we demonstrate a process of coating of such small colloidal silica particles with polymers in two layers; the first layer is PDVB (polydivinylbenzene) and the second layer is PHEMA (poly2-hydroxyethylmetha-crylate). Results of several time based adsorption experiments are presented to verify the hypothesis of monomer adsorption on inorganic core with and without initiator. The presence of polymer encapsulating the silica surface was determined by FTIR spectroscopy, transmission electron microscopy(TEM) and ALV particle sizing instruments; while the amount of coated polymer on silica surface was assessed by thermogravimetric analysis(TGA). These polymer coated particles can be used as soft abrasives in CMP application to minimize defects.
14-20
Enlargement of Dye-sensitized Solar Cell by Using High Performance Transparent Electrode and Nano-porous TiO2 Film
SHOJI KANEKO,
Masayuki Okuya*, G.R. Asoka Kumara*, SPD Laboratory, Innovative
Joint Research
Center and *Department of Materials
Science and Technology, Shizuoka University , Johoku, Hamamatsu , Japan
Dye-sensitized photoelectrochemical cell based on nano-porous semiconductor materials are gaining much attention as a promising solar energy conversion system. We have successfully developed a spray pyrolysis deposition technique to prepare high transparent conducting oxide and nano-structured TiO2 films for the fabrication of large-area dye-sensitized solar cell. Transparent conducting oxide film, in which tin-doped indium oxide (ITO) inner layer was covered with fluorine-doped tin oxide (FTO) outer layer, gave low resistivity 1.3 x 10-4 W cm and high optical transmittance about 80 %. TiO2 film, which is formed mainly from a mixed solution of Ti-containing compound and TiO2 sol, has much higher light-scattering properties and dye adsorption porosities. A solar cell consisted of dye-impregnated TiO2 porous film of an about 12 mm thickness and of a 7 x 4 cm2 active area, Pt counter electrode, and redox electrolyte. This solar cell showed short-circuit photocurrent (Isc) 9.89 mA cm-2, open-circuit voltage (Voc) 735 mV in AM-1.5 simulated sunlight (100 mW cm-2) with an efficiency of 5.08%.
14-21
Atomically-Flat Nanosurfaces:
Flat Gold Nanoparticles as a Novel Substrate for STM and Photonic
Studies
D. H. Dahanayaka, J. X. Wang, S.
Hosain, W. D. Tennyson, D. W. Kelle, D. J. Wasielewski, G. D. Lian, L. A. BumM, Center for Semiconductor
Physics in Nanostructures, Department of Physics and Astronomy, University of
Oklahoma, Norman, OK, bumm@nhn.ou.edu
Flat gold nanoparticles (FGNPs) can be used as atomically-flat gold substrates for STM studies. When supported on indium tin oxide (ITO) coated glass the FGNPs can also be used as atomically-flat photonic substrates. Transmission electron microscopy (TEM) shows that FGNPs can be prepared 100–500 nm across with shapes that range from triangular to hexagonal with thicknesses of 15-25 nm. Dark-field optical microscopy is a convenient method for evaluating the FGNP arrays because the FGNPs and spherical gold nanoparticles are distinguished easily by their plasmon resonance spectra. Scanning tunneling microscopy (STM) reveals atomically flat terraces on the large {111} FGNP facets, which are flat to a few atomic layers over entire surface. No stepping (rounding) of the facet is observed even near the edges. STM images demonstrate that well-ordered alkanethiol self-assembled monolayers (SAMs) form on the FGNP/ITO substrates, thus they are excellent substrates for molecularly resolved STM imaging. Our results indicate that our FGNPs grow as single crystals, rather than by aggregation of smaller nanoparticles. An optimized method for growing the FGNPs and for depositing them on ITO coated glass with a high particle density is presented.
14-22
14-23
Two Dimensional
Arrangement of Gold Particles Less Than 10nm
LONG JIANG, Institute of Chemistry ,
Chinese Academy
of Sciences, Beijing
Monodisperse nanogold particles 2-5nm in diameter with standard deviation less than 0.4 have been prepared by using different methods. Many approaches to produce a homogeneous 2D arrangement have been attempted. A well ordered packing domain with area more than 1 mm2 has been achieved on liquid and solid substrates by capillary force. Compare with the result which we obtained before, the area free from voids and quality of packing is much improved. The controlled factors and possible mechanism have been examined and discussed.
14-23
Computer Simulation Study
on Behaviors of Surfactants at the Liquid/Liquid Interface
YING LI*, Feng-Lan Dong, Xiu-Juan He, Key
Lab for Colloid and Interface Chemistry of State Education Ministry, Shandong
University, Jinan 250100, P. R.China, yingli@sdu.edu.cn
Behaviors of surfactants at the interface play an important role in the industrial application, such as oil extraction, deterging process and material preparation. However, the detail information of interfacial region on a molecular level is scarce. Recently, computer simulation has become an effective tool for the study of complex interfacial systems on a detail molecular level, such as molecular dynamics (MD) simulations. However, the time and length scales accessible to ordinary MD simulations are not large enough to study some phenomena in surfactant system. Therefore, a mesoscopic level simulation named dissipative particle dynamics (DPD) is used to investigate the behaviors of surfactants at the water/oil interface.
Dissipative particle dynamics simulation bridges the gap between atomistic and mesoscopic simulations. The simulation strategy is to regard clusters of atoms as fluid particles or beads, some of which are connected by harmonic spring. Soft spherical beads interact through an effective pairwise interaction potential obtained from detailed atomistic molecular dynamics simulations, and thermally equilibrate through hydrodynamics.
The orientation of sodium dodecylsulfonate (DDS) and sodium
dodecylsulfate (SDS) adsorbed at the water/carbon tetrachloride interface has
been studied by considering the variation of root
mean square (RMS) end-to-end distances of surfactants. An increase in the interface concentration of surfactants
results in the increase in the orientation of
surfactants before reaching a full monolayer. Strong hydrophilic head groups
are beneficial to form a well-ordered configuration and appropriate salts make
surfactant molecules more stretched and ordered, which may be interpreted as a
reduction on gauche defects for them.
The synergistic effects
of mixed surfactants sodium dodecylbenzene sulphonate (SDBS) and Triton X-100
(TX-100) at the oil/water interface has also been investingated. With the
decrease in 
and 
, SDBS and TX-100 are driven to adsorb more at the interface
and can decrease sharply the interfacial tension of the mixed system. Also we
have observed that some cavities between SDBS clusters at the interface can be
filled with TX-100 clusters. The inhomogeneous distribution helps to understand
the mechanism of the synergism interaction and the decrease in the interfacial
tension.
Therefore, computer simulation method might be an attractive method to provide effective information about behaviors of surfactants on a mesoscopic level.
14-24
14-25
High Dielectric Properties Ofnm‑sized Barium Titanate Crystallites
and its Origin
S. WADA, T. Hoshina, H.
Yasuno, S.‑M. Nam, H. Kakemoto, M. Yashima, T. Tsurumi, Tokyo Institute of
Technology, Department of Metallurgy and Ceramic Science, 2‑12‑1 Ookayama,
Meguro‑ku, Tokyo, Japan, swada@ceram.titech.ac.jp
BaTiO3 crystallites with various particle sizes from 20 to 1000 nm were prepared by the modified 2‑step thermal decomposition method of barium titanyl oxalate. Investigation of impurity in these particles using both TG‑DTAand FT‑IR measurements revealed that no impurity was detected in the BaTiO3 lattice while hydroxyl and carbonate groups were detected only on the surface. Moreover, their relative densities werealways above 99%. The dielectric constants of these powders were measured using suspensions by a modified powder dielectric measurement method. As a result, the dielectric constant of BaTiO3 particles with a size of around 140 nm exhibited a maximum of around 6,000. Thus, we discussed the origin of high dielectric constant around 6,000 for BaTiO3 particles with a size of around 140nm. The crystal structure of the BaTiO3 particles with sizes below 100 nm was always assigned to cubic m‑3m by a conventional X‑ray diffraction measurement because of significant line broadening. Thus, using a synchrotron radiation X‑ray powder experiment with imaging plate, the crystal structure of the BaTiO3 particles with sizes below 100 nm was investigate from 25? to 300?. As a result, in the BaTiO3 particles with sizes over 40 nm, itwas confirmed that their crystal structure at 25? was assigned to 4mm. This means that the c/a ratio decreased with decreasing particle sizes from 1000 nm to 40 nm. On the other hand, the local and dynamic crystal structure of the BaTiO3 particles with sizes below 1000 nm was assigned to tetragonal 4mm by a Raman scattering measurement. It should be noted that in the particlesize with a maximum dielectric constant of 6,000, its c/a ratio wassmaller than 1.011 as the same as single crystal value. Finally, to explain the origin of high dielectric constant, the model related to superparaelectric behavior was proposed.
14-26
Atomic Layer Deposition on
Submicron ZrO2 and BaTiO3 Particles
BEAU B.
University of Colorado, Boulder, CO, Beau.Burton@colorado.edu
BaTiO3
is a ferroelectric material with a large dielectric constant that is critical
in the fabrication of multilayer ceramic capacitors (MLCs). Because of the ultrathin thickness of
the dielectric layers in MLCs, submicron BaTiO3 particles are used
to fabricate the dielectric layers.
In the past, BaTiO3 particles could be mixed with other
impurity particles to improve the properties of the dielectric layer. This approach is becoming increasingly
difficult because the dielectric layer thickness is approaching the size of the
individual particles. One solution
is to coat the BaTiO3 particles uniformly with ultrathin films to
achieve homogeneous behavior in the thin dielectric layer.
Thin
films can be deposited on particles using atomic layer deposition (ALD)
techniques. ALD is performed using
sequential, self-limiting surface reactions. ALD can achieve atomic layer controlled
and conformal film growth. Our
recent work has shown that ALD techniques can deposit conformal and atomic
layer controlled films on various particles. Our examples in the literature are Al2O3
ALD on BN particles, SiO2 ALD on BN particles and BN ALD on ZrO2
particles. We have also recently
demonstrated catalytic SiO2 ALD on ZrO2 and BaTiO3
particles and ZnO ALD on ZrO2 and BaTiO3 particles. Our current research has focused on
improving SiO2 ALD on ZrO2 and BaTiO3
particles and developing new surface chemistry for Y2O3
ALD on ZrO2 and BaTiO3 particles. ZrO2 particles are employed
as model particles and yield excellent transmission electron microscopy (TEM)
images.
The atomic layer deposition (ALD) of SiO2 is very challenging. SiO2 ALD can be accomplished using SiCl4 and H2O reactants at 600-800 K with large exposures of ~109 L or using TEOS and H2O reactants at room temperature employing NH3 as a catalyst with large reactant exposures of ~109 L. Recently, we have observed much more efficient SiO2 ALD with HSi[N(CH3)2]3 and H2O2 reactant exposures. HSi[N(CH3)2]3 is tris-dimethylaminosilane (Tris-DMAS). SiO2 ALD was studied using Fourier transform infrared (FTIR) spectroscopy to monitor the surface chemistry. The exposures required for the Tris-DMAS and H2O2 reactions were ~106L and ~107L, respectively. The SiO2 thin films were deposited at temperatures ranging from 525-825 K. The maximum growth rate of 1.9 Å/cycle at 825 K was determined by measuring the SiO2 film thickness by TEM. This talk will discuss our results for SiO2 ALD and new results for Y2O3 ALD on ZrO2 and BaTiO3 particles.
14-27
Preparation and Characterization of the Cobalt Titanate CoTiO3 Nanoparticles by Evaporation-Induced Self-Assembly
G. W. ZHOU1, Y. S. Kang2, 1.
The nanostructured photocatalyst of cobalt titanate, CoTiO3 has been prepared by oxidation of Co(OH)2 using titanium dioxide TiO2 powder (P-25) as base material in cetyltrimethylammonium bromide (CTAB) micelle solutions, then followed the calcinations of the produced powders. These nanoparticles were investigated with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and thermogravimetric/differential thermal analysis (TGA/DTA) to determine the crystallite size and the phase composition. The spectroscopic characterizations of these nanoparticles were also down with UV-Vis spectroscopy and FT-Raman spectroscopy. XRD patterns show that CoTiO3 phase was formed at calcinations temperature above 600 0C. The UV-Vis results showed that the CoTiO3 nanoparticles have significant red shift to the visible region (400-700 nm). The new absorption peaks in FT-Raman also show the formation of Ti-O-Co bonds at above 600 0C and just not the mixtures of titanium dioxide with cobalt oxides.
14-28
Shrinking Composite Core-Shell
Nanoparticles for Chemical Mechanical Planarization
SILVIA
ARMINI*†,‡,
The rate at which material is removed during Chemical Mechanical Planarization (CMP) and the degree of defectivity induced by this process are determined by the size, shape, concentration and hardness of the abrasives used in the polishing slurry. The tunable properties of polymer nanospheres, in particular size and hardness modulation, through synthesis design, make them particularly promising as cores in composite organic core/inorganic shell structures for application in CMP. In this work, monodisperse PMMA-based terpolymer particles were synthesized by suspension polymerization. Significant reaction parameters were varied in an effort to prepare particles with a wide and controllable range of size and polymer content. With the aim of understanding the effects of the amount of main monomer, MMA, we found that the average particle size increased within the range 250 to 550 nm with increasing amount in the feed as expected. The particle size distributions obtained were narrow, with a variation of ± 14 nm. The reaction temperature, varied in the range 60-80 °C, showed a significant impact on the polymerization rate and the final particle size and shape. Finally, the influence of the concentration of the initiator, 2,2’-Azobis(2-methylpropionamidine) dihydrochloride, is surprisingly less pronounced and the trend in the particle size behavior is ill-defined.
14-29
Synthesis and characterization of
spirobenzopyran based photoactive polymeric coatings grafted onto flat surfaces
and colloidal particles
MARTIN
PIECH, Nelson S. Bell, Sandia National Laboratories, Chemical Synthesis and
To prepare robust photoactive coatings, the grafting of spirobenzopyran methyl methacrylate-co-methyl methacrylate copolymers from flat silica surfaces and colloidal particles has been performed applying the atom trasfer radical polymerization (ATRP) method. The reaction conditions were optimized with respect to the kind and concentration of surface bound initiator, the type of halide and ligand used in the catalytic complex, presence/absence of untethered initiator and inhibitor, solvent, and temperature. This approach facilitated controlled synthesis of very uniform coatings up to 80 ± 3 nm thick. The content of spirobenzopyran chromophore in the polymer matrix was systematically varied to produce the surfaces and particles with varying characteristics. Exposure of these coatings to alternating UV and visible light irradiation produced reversible wettability changes on surfaces and control of colloidal dispersion stability in particulate suspensions. In this talk, the synthesis and characterization of these photoactive materials will be described in detail with a brief summary of photophysical effects.
15-01
Non Classical Crystallization
HELMUT CÖLFEN, Max-Planck-Institute of Colloids and Interfaces,
Colloid Chemistry, Am Mühlenberg, D-14424
In recent years, increasing evidence is reported that many crystallization events do not obey the laws of classical crystallization i.e. an ion or molecule attachment to a critical crystal nucleus. Starting from the consideration of biominerals with their often complex forms and several levels of hierarchy, a view of particle mediated crystallization events is developed, often starting with amorphous precursor nanoparticles. These precursor particles undergo mesoscopic transformation to nanocrystals and assembly processes to superstructures with complex shape. Some of such intermediates called mesocrystals are shown, which could explain the inclusion of macromolecules in single crystalline biominerals. Subsequent crystallographic fusion of mesocrystals can lead to single crystals with preserved shape. Direct nanoparticle fusion according to the mechanism of oriented attachment can directly lead to single crystals, which will be demonstrated. Also, Polymer Induced Liquid Precursors (PILP's) will be shown as precursor species in non-classical crystallization events leading to complex morphologies for the case of amino acid crystals.
15-02
Principles of Biominerals Architecture: Nucleation Mediated Self-Assembly Of Biomineral Crystals
XIANG Y. LIU, Department of
Physics, Faculty of Sci., National University of Singapore, 2 Science Drive Singapore
Bones and teeth are biocomposites which are self
assembled in a certain manner that require controlled mineral deposition during
their self-assembly to form tissues with unique mechanical properties. Various biomolecules play a pivotal
role during the formation biomineral nano crystallite assembly. However, the
mechanisms of biomolecule-mediated mineral initiation are far from understood.
In this contribution, I will present that the formation of the well-aligned
hydroxyapatite nano crystallite assembly is controlled by the so-called self
(homo)-epitaxial nucleation mediated assembly (SENMA) mechanism, which
unfortunately will be demolished at
high supersaturations due to the unflavored kinetics (supersaturation driven
structural mismatch). It is identified for the first time that biomolecules, e.g. chondroitin sulfate,
facilitate the formation of a well-aligned HAP assembly by suppressing the
supersaturation driven structural mismatch rather than by “cementing” HAP
crystallites.
15-03
Noncovalent
Functionalization of Carbon Nanotubes Using Designed Peptides
G. R. DIECKMANN, Department of Chemistry and NanoTech Institute, The
University of Texas at Dallas, Richardson, TX , dieckgr@utdallas.edu
To fully realize the potential utility of carbon nanotubes, strategies for the effective solubilization, separation and organization of these materials must be devised. In this presentation the use of designed amphiphilic peptides to achieve these goals will be described, with a focus placed on the peptide design, as well as the characterization of the resulting peptide/nanotube composites. Results from circular dichroism, Raman, UV/Vis/NIR, SEM and TEM studies will be discussed which demonstrate that designed amphiphilic peptides are effective at solubilizing carbon nanotubes in aqueous solution, debundling the nanotubes yielding long individual nanotubes, and organizing them into different macromolecular architectures depending on solution conditions. The ability to control nanotube organization by utilizing the self-assembly properties of the peptides provides a facile and versatile method for the manipulation of carbon nanotubes for future applications.
15-04
Manufacturing
with Micro-organisms: Merging
Biological Self-Assembly with Synthetic Chemistry to Yield Functional 3-D
Nanoparticle Structures
Kenneth H. Sandhage1,2,
Shawn M. Allan1, Samuel Shian1, Michael R. Weatherspoon1,
Christopher S. Gaddis1, Phillip D. Graham1, Ye Cai1,
Michael Haluska1, Gul Ahmad1, Benjamin Church1,
Robert L. Snyder1, Dori Landry3, Mark Hildebrand3,
Brian P. Palenik3 1School
of Materials Science & Engineering, Georgia Institute of Technology,
Atlanta, GA, 2Institute for Bioengineering and Biosciences, Georgia
Institute of Technology, Atlanta, GA, 3Marine Biology Research
Division, University of California at San Diego, San Diego, CA, ken.sandhage@mse.gatech.edu
Appreciable global effort is
underway to develop new routes to three-dimensional (3-D) nanostructured
devices. To enable widespread
commercialization, such processes must be capable of: i) precise 3-D
fabrication on a fine scale and ii) mass production on a large scale. These often-conflicting requirements can
be addressed with a revolutionary new paradigm that merges biological
self-assembly with synthetic chemistry: Bioclastic and Shape-preserving
Inorganic Conversion (BaSIC). Nature provides spectacular examples of
micro-organisms (diatoms, coccolithophorids, etc.) that assemble intricate
bioclastic 3-D structures. For
example, tens of thousands of diatom species currently exist, with each species
assembling silica nanoparticles into a microshell with a distinct 3-D shape and
pattern of fine features. Through
sustained biological reproduction, diatoms can generate enormous numbers of 3-D
micro/nanostructures with identical morphologies. Such massive parallelism and
species-specific (genetically-controlled) precision are highly attractive for
device manufacturing. However,
natural bioclastic chemistries are rather limited. With BaSIC, synthetic approaches have
been developed to convert biogenic assemblies into non-natural chemistries
(e.g., TiO2, ZrO2, MgO, BaTiO3, polymers,
etc.), while preserving the 3-D shapes and fine (nanoscale) features. Future research on the genetic
engineering of biomineralizing micro-organisms may be coupled with BaSIC to
yield low-cost nanostructured devices with tailored shapes and tailored
chemistries.
15-05
Preparation of Small
Materials by Interface Selective Reactions Using Biological Materials as
Templates
Y. B. KIM, Department of Nano-Polymeric Systems, PaiChai University,
Daejon, South Korea, ybkim@mail.pcu.ac.kr
Hydrolysis and condensation reactions of water soluble precursors of titania, alumina, silica, silsesquioxane and iron oxide were examined in the presence of interfaces of oil and water or gas and water. Hydrolyzed products from some of these precursors showed interface selectivity as inorganic materials formed selectively at the interfaces. Oil drops and air bubbles coated with silica, titania, alumina, or iron oxide were successfully prepared at room temperature. This type of reaction was applied to coat biological templates that had regular structures such as lipid tubes, hairs, gills of mushrooms, fungi, fibroblasts, and bacteria. The biological materials coated with silica, alumina and titania formed smaller and more rigid replicas of their original shapes than uncoated ones. The sizes of replicas were usually 1/10 to 1/20 of the original materials. Results indicated that most biological materials would be useful as templates to prepare regularly shaped smaller structures made of different inorganic materials.
15-06
Morphosynthesis of Complex
Inorganic Forms Using Pollen Grain Templates
SIMON R. HALL*, Helen Bolger, Vicky Swinerd, Stephen Mann, School of
Chemistry, University of Bristol, Bristol, United Kingdom, s.hall@bristol.ac.uk
Biological structures are distinguished by the extremely high precision of their self-assembly, replication and functionality, and as such provide novel platforms and templates on which to construct and organize chemical processes.
In this work, we describe an exceedingly facile method for replicating the complex surface morphology of flower and tree pollen grains, which in the case of silica produces complex colloidal materials with surface areas higher than 800m2/g. Pollen is a ubiquitous and inexpensive material with a high degree of species-specific morphological complexity. The tough outer shell (exine) of pollen grains is amenable to inorganic mineralization without consequent loss of fine structure, either as a result of geological processes, or as described here through synthetic methods. We show that high-fidelity hollow inorganic replicas of pollen grains can be achieved with both amorphous (silica) or crystalline (calcium carbonate, calcium phosphate) minerals, and demonstrate their potential applicability by post-synthetic functionalization with magnetic or metallic nanoparticles. As proof-of-concept, we also show that the biocompatible replicas can be loaded with the anti-inflammatory drug, ibuprofen, the anti-histamine, chlorpheniramine, and used as a potential drug delivery system with controlled release properties.
15-07
From Organic
Supramolecular Architectures to Inorganic Nanotubes
J. H. JUNG, Nano Material Team, Korea Basic Science Institute (KBSI), 52 Yeoeun-dong, Yusung-ku, Daejeon, 305-333, S.
Korea , jonghwa@kbsi.re.kr
A diversity of supramolecular structures can
be created, not only in nature but also in artificial systems, by self-assembly
of designed “organic” building blocks. In contrast, creation of such diverse
supramolecular structures from “inorganic” materials seems to be very difficult
or nearly impossible. We have studied
self-assembled superstructures of crown-appended cholesterol,
cyclohexane-based, and sugar-integrated gelators in
organic solvents and water. They acted as
versatile gelators of organic fluids such as alcoholic and polar solvents.
Crown-appended cholesterol gels showed lamellar, multi-layered vesicular,
helical and nano-tubular structures. On the other
15-08
GEPI: Genetically
Engineered Polypeptides for Inorganics as Molecular Erectors in Nano- and
Nanobio-technology
C. Tamerler,1 D. T. Schwartz,2 R. Samudrala,3
F. Baneyx,2, MEHMET SARIKAYA,1,2, 1Materials
Science and Engineering, 3Microbiology, and 2Chemical
Engineering, University of Washington, Seattle, WA, sarikaya@u.washington.edu
Physical and chemical functions of
single celled and multi-cellular organisms are carried out through recognition
and sensing by a very large number (billions) of proteins through predictable
and self-sustaining molecular interactions. These functions include ion or
charge exchange or transport, chemical recognition and control via enzymatic
reactions, material synthesis, nucleation, growth and formation. Using biology
as a guide, we design, synthesize, genetically tailor and utilize short
polypeptides for potential molecular erectors, linkers, bracers, and spacers,
or simply as molecular sensors, in recognition, self-assembly, ordered
organization, and fabrication of nanoinorganic materials and molecularly hybrid
systems in nanotechnology (molecular electronics and photonics) and
nanobiotechnology (bio-sensors, -assays, and -materials). Based on the
fundamental principles of molecular biomimetics, i.e., molecular recognition,
self-assembly, and genetic-based fabrication, and adapting combinatorial
biology protocols, we can now genetically engineer polypeptides to specifically
recognize inorganic surfaces and synthetic functional molecules. Once
combinatorially selected and their binding experimentally characterized,
combining the bioinformatics and biophysical approaches, these GEPIs can be
post-selection genetic engineered to further tailor their functions to create
molecular functional constructs, versatile fundamental molecular recognition
elements. This presentation will review the latest developments in this rapidly
developing polydisciplinary field and demonstrate practical utilizations.
15-09
Biomimicking
Drug Transport Systems
A. J. KHOPADE,
Sun Pharma Advanced Research Centre, Tandalja,
Vadodara-390 020,
The indigenous nutrient transport systems (Biovectors) of the body such as, circulating lipoproteins, red blood cells and protein coacervates are inspiring for the synthesis of nanomaterials for delivering bioactives because of the unique surface characteristics that render them a very high biological half-life. Some of the bioinspired drug delivery systems are described as follows: Lipoprotein mimicking biovectors (LMBVs) are nanoemulsions or solid lipid nanoparticles made up of lipoprotein components or their synthetic counterparts. LMBVs are useful in delivering/targeting lipid soluble drugs. Supramolecular biovectors (SMBVs) are synthetic analogues of lipoproteins designed to deliver hydrophilic drugs. SMBVs consist of a hydrophilic nanoparticle core (for drug loading), surface-grafted with lipid and surrounded by a phospholipid monolayer. Ultrathin microcapsules prepared using layer-by-layer technique are cell-mimicking biovectors (CMBVs), which display the typical characteristics of the cell membranes such as nanometer thickness and elasticity. Different types such as pseudo-vesicles and ultrathin capsule-liposome hybrid are possible variations of CMBVs. Globular proteins are water rich structures that can be used for delivery of protein binding drugs. Globular protein mimicking biovectors (GMBVs) are nano coacervates or nanogels that are water-rich, water-insoluble bodies due to lot of water associated with them. Biomineralized spherical inorganic nano-calcium phosphate covered with water-associated sugars, called aquasomes, are used for protein delivery. The experimental experience regarding their synthesis and pharmaceutical use shall be discussed in the presentation.
15-10
Biomimetic Polymer
Networks as Functional Components in Diagnostic and Therapeutic Microdevices
J. ZACH HILT, Department of Chemical and Materials Engineering,
University of Kentucky, Lexington, KY, hilt@engr.uky.edu
Biomimetic polymer networks with tailored affinities and transport
properties for a target molecule have been developed, and these networks have
been demonstrated as functional components in micro- and nanoscale diagnostic
and therapeutic devices. For
controlled drug delivery, these polymers can enhance control over the transport
properties of therapeutic molecule and the corresponding release profile. In biosensors, these polymers are
advantageous alternatives since they do not incorporate any biological
components but mimic biological recognition pathways, while being more robust
and cost effective. Specifically,
glucose responsive copolymer networks containing poly(ethylene glycol) n
dimethacrylate (where n is the number of EG repeat units) at various
crosslinking percentages and acrylamide as a functional monomer were
synthesized in polar, aprotic solvent (dimethyl sulfoxide). Of particular interest, methods were
developed to micropattern these polymer networks with controlled
thicknesses. The equilibrium
binding characteristics and the kinetic binding and release characteristics of
a fluorescent glucose analogue was analyzed using fluorescent microscopy
techniques. Methods were developed
to integrate these networks with substrates at the micro-/nanoscale, enabling
the fabrication of microdevice platforms that are based on silicon
technologies.
15-11
Polymorphism
of DNA-Anionic Liposome Complexes Reveals Hierarchy of Ion-Mediated
Interactions
GERARD C. L. WONG* *Department of
Materials Science & Engineering, Department of Physics, Department of
Bioengineering, University of Illinois at Urbana-Champaign, IL, †Laboratory of
Physical and Structural Biology, National Institute of Child Health and Human
Development, NIH, Bethesda, MD, gclwong@uiuc.edu
Self-assembled DNA delivery systems based on anionic lipids complexed with DNA using divalent cations have been recently introduced as an alternative to cationic lipid-DNA complexes due to their low cytotoxicity. We investigate anionic lipid-DNA (AL-DNA) complexes induced by different cations using synchrotron Small Angle X-ray Scattering (SAXS) and confocal microscopy to show how different ion-mediated interactions are expressed in the self-assembled structures and phase behavior of AL-DNA complexes. Divalent ions can mediate not just DNA-membrane attractions, but also inter-membrane and inter-DNA attractions, both absent in cationic lipid-DNA complexes. Moreover, divalent cations can coordinate non-electrostatically with lipids and modify the resultant membrane structure. We find that at low membrane charge densities, AL-DNA complexes organize into a lamellar structure of alternating DNA and membrane layers crosslinked by ions. At high membrane charge densities, a new phase with no analog in cationic lipid-DNA systems is observed: DNA is expelled from the complex, and a lamellar stack of membranes and intercalated ions is formed. For a subset of the ionic species, high ion concentrations generate an inverted hexagonal phase comprised of DNA strands wrapped by ion-coated lipid tubes. A simple theoretical model shows that this transition is consistent with an ion-induced change in the membrane spontaneous curvature.
15-12
Directed Cell
Migration via Chemoattractants Released from Degradable Microspheres
XIAOJUN ZHAOa,b,1, Siddhartha
Jainb1, H. Benjamin Larmana, Sandra Gonzaleza, Darrell John Irvineab,
aDepartment of Materials Science & Engineering, Massachusetts
Institute of Technology, Cambridge, MA, bBiological Engineering
Division, Massachusetts Institute of Technology, Cambridge, MA, djirvine@mit.edu
Chemotaxis, cell migration directed by
spatial concentration gradients of chemoattractant molecules, is critical for
proper function of the immune system. Materials capable of generating defined
chemoattractant gradients via controlled release may be useful for the design
of improved vaccines and immunotherapies that draw specific cells to an
immunization site. To this end, we encapsulated formyl-Nle-Leu-Phe-Nle-Tyr-Lys
(fN’LFN’YK) peptides or macrophage inflammatory protein-3a (MIP-3a or CCL20) in
degradable poly (lactide-co-glycolide) microspheres that provided sustained
release for more than 2 weeks in vitro.
fN’LFN’YK and MIP-3a chemoattract dendritic
cells (DCs), the key antigen-presenting cells involved in generation of
primarimmune responses, and their precursors, monocytes. Using an in vitro
videomicroscopy migration assay, we detected strong chemotaxis of human
monocytes and monocyte-derived DCs through 3D collagen gels toward microspheres
releasing fN’LFN’YK. Similarly, microparticles releasing MIP-3a were able to
attract mouse bone marrow-derived dendritic cells. Strikingly, prolonged
attraction of DCs from distances up to 500 mm from the source to the point of
contact with individual microspheres was observed. Such microspheres could be
of general interest for the design of vaccines that promote adaptive immunity
and as a platform for studying the biology of chemotaxis in vitro and in vivo.
15-13
Biomimetic Processing
through a Polymer-Induced Liquid-Precursor (PILP) Process
Matthew J. Olszta, Yi-Yeoun Kim, Xingguo Cheng, Lijun Dai, LAURIE B.
GOWER, Department of Materials Science & Engineering, University of
Florida, Gainesville, FL, lgowe@mse.ufl.edu
Studies by the biomineralization community are finding that some of the classic examples of biominerals are formed by an amorphous precursor phase. It seems reasonable to assume that this is one of the primary functions of the acidic proteins associated with biominerals because this can provide a relatively simple means of “molding” elaborate crystal morphologies, the hallmark of biominerals. However, Meldrum and coworkers have demonstrated that elaborate single-crystalline morphologies can also be molded simply by proper selection of the “mold” and crystallization conditions. If this is the case, then one must wonder why Mother Nature has apparently chosen to use the amorphous precursor route? This talk will attempt to address this question through examples taken from our in vitro model system, which demonstrates that the fluidity of the amorphous phase may be critical for achieving some of the morphological features found in biominerals, such as mineral fiber formation via a solution-precursor-solid (SPS) mechanism, templating single crystals via deposition of colloidal droplets, and intrafibrillar mineralization of collagen. Therefore, our focus is not only on determining how the polymer stabilizes the amorphous phase, but also on how it entraps sufficient hydration waters to impart the amorphous precursor with fluidic character.
15-14
Aragonite Growth on Carbonate-Free Single Crystal
BOAZ POKROY, Emil Zolotoyabko,
Department of Materials Engineering, Technion – Israel Institute of Technology,
Haifa , Israel
Although biogenic crystals are grown under standard pressure and temperature, they often exist as metastable polymorphs. A good example is aragonite formation in seashells. Among different factors influencing the biomineralization process, much work had been done in understanding the function of impurity atoms and macromolecules. Special attention has been given to the role of lattice mismatch and stereochemistry. In this research, we tried to determine the net mismatch effect on aragonite growth, eliminating as far as possible the stereochemical contribution. For this purpose, we used several commercially available wafers free of carbonate groups, namely rhombohedral sapphire and lithium niobate, trigonal quartz and cubic silicon. All wafers were cut perpendicular to the threefold axis in order to obtain a trigonal symmetry of cations in the surface plane, which is similar to the local symmetry of Ca ions in the (001) plane of calcite and aragonite.
Experimental results [1] clearly show that aragonite can nucleate and grow c-oriented at mismatches up to 11%. It appears, that up to this value, the reduction of interfacial energy allowing aragonite formation prevails over the increase in the mismatch-induced strain energy. Note that we did not completely suppress the formation of calcite, but facilitated the concurrent nucleation of aragonite crystals. These findings could shed an additional light on the metastable polymorph growth in biogenic crystals.
15-15
Morphological Control of
Inorganic
F. C. MELDRUM, N. Hetherington, A. N. Kulak, E.Loste, R.J. Park, W.
Yue, School of Chemistry, University of Bristol, Bristol, United Kingdom, Fiona.Meldrum@bristol.ac.uk
One of the most immediately striking features of many biominerals is their remarkable morphologies. While many biominerals exhibiting unusual shapes and curved surfaces are amorphous in structure and therefore without a preferred morphology, many biogenic single crystals also exhibit overall morphologies which do not reflect the internal crystal structure, such as the sponge-like calcite skeletal plates of echinoderms. The research described here adopts a biomimetic approach to investigate morphological control of inorganic single crystals. Calcium carbonate has been precipitated within the confines of the regular cylindrical pores of track etch membranes, and the role of an amorphous calcium carbonate (ACC) precursor in morphological control of the product crystals was investigated. A more dramatic demonstration of the control of single crystal morphology was obtained on precipitation of a range of crystals in polymer membranes with sponge-like morphologies. Under a specific range of reagent concentrations, single crystals with sponge-like morphologies were precipitated, as dictated by the confines of the polymer membrane. These experiments demonstrate that simple shape-constraint is sufficient to produce single crystals with non-crystallographic morphologies. Patterning of the surfaces of single crystals has also been produced by precipitation of inorganic crystals on arrays of close-packed silica or polystyrene spheres.
15-16
Preparation, Characterization and Properties of Nanocrystalline
Apatites: Significance for Bone Mineral and Biomaterials
D. Eichert,
Biological poorly crystalline apatites are the main constituent of
mineralized tissues (bone and dentine) but despite their widespread occurrence,
the structure, properties and mode of formation of the apatite nanocrystals are
still the subject of discussion. Synthetic nanocrystalline apatites can be
easily prepared in aqueous media under ambient conditions. One of the most
interesting characteristics of the nanocrystals, revealed by spectroscopic
methods (FTIR, NMR), is the existence of a hydrated surface layer, exhibiting a
very fragile structure irreversibly altered on drying,
that is well developed in freshly formed precipitates. This surface layer
contains labile ionic species which can be easily and rapidly exchanged with
ions from the surrounding fluids. The ion mobility in the hydrated layer can be
related to processes of regulation of the mineral ion
concentration in body fluids and also to “crystal fusion”, often observed in bone and
tooth enamel, by allowing direct crystal-crystal bonding. This process could occur in self-setting biomimetic calcium
phosphate cements. Although the precise structure of the hydrated surface layer
is not yet precisely known, we can take advantage of apatite nanocrystal
surface reactivity to prepare biomaterials (ceramics, coatings, composites) at
low temperature with preserved and adaptable bioactivity.
15-17
From Amorphous Calcium Phosphate
to Artificial Implants
H.
FÜREDI-MILHOFER, Casali Institute of Applied Chemistry, the Hebrew University
of Jerusalem , Jerusalem , Israel
Osteointegration of artificial implants for bone and tooth replacement or repair is facilitated by coating the surfaces of bioinert materials (metals, polymers) with calcium phosphates. In recent years there is growing interest in biologically inspired methods in which calcium phosphate deposition is initiated at room or physiological temperature from low concentration aqueous solutions containing inorganic ions present in human blood plasma (simulated body fluid, SBF). In order to facilitate crystal growth from these solutions, the implant surface is being modified by introducing functional groups or by first depositing amorphous calcium phosphate, ACP, which then serves as a template for subsequent crystal growth. Another important issue is the inclusion of bioactive macromolecules (drugs, growth hormones, etc.) into the coatings, which has so far been attempted by coprecipitation with the inorganic phase. However macromolecules, if present in a crystallizing solution, profoundly influence the crystallization kinetics and properties of the nascent of inorganic salts. Consequently, although coprecipitation of macromolecules is possible, the properties of the calcium phosphate coatings may be profoundly affected in the process. Apparently understanding the fundamental problems associated with nucleation and growth of calcium phosphate crystals in the presence of macromolecules is of high relevance.
In the first part of this paper we
shall address this problem in a review of our recent findings on the influence
of polyelectrolytes, PEs, on nucleation and growth of calcium phosphate
crystals, with specific attention to ACP – crystalline phase transformation and
to the properties of the nascent precipitates. It will be shown that most PEs
exhibit a dual effect, i.e. any particular macromolecule may inhibit or induce
crystallization, the type and intensity of the effect depending on the type,
charge and solution concentration of the macromolecule.
In the second part of the lecture a new, generalized method for the production of coatings of bioinert implant materials will be described, which allows one to avoid the problem of coprecipitation altogether. The method is based on initial deposition of an organic matrix in the form of a polyelectrolyte multilayer, PE ML, and subsequent deposition of ACP particles from an aqueous suspension. The procedure is repeated several times until an organic – inorganic multilayer coating of required thickness is obtained, which is then immersed into a metastable calcifying solution to initiate “in situ” crystal growth within the organic matrix. Novel organic-inorganic nanocomposite coatings, consisting of positively or negatively charged PLL – PGA multilayers (where PLL is poly-L-lysine, PGA is poly-L-glutamic acid), and calcium phosphate deposited in the amorphous form, or crystallized “in situ” upon and/or within the multilayers have been prepared and characterized. Adhesion and proliferation of human osteoblast cells on selected coatings has also been determined. Mechanical and biological tests have shown that composite coatings containing “in situ” grown poorly crystalline apatite and final PLL-PGA-layers possess appropriate biomechanical stability with well adapted adhesion sites for cell adhesion, sufficient cell growth and cell differentiation.
The
advantages of the described coatings for bioinert implant materials are
obvious. The coating procedure is relatively simple and can be automatized.
Both the organic matrix and the mineral phase are prepared "in
situ" and the growth kinetics and properties of the inorganic phase
can be controlled by strict control of the experimental conditions. The coating
process is not sensitive to the nature, size and topology of the substrate.
Bioactive proteins (drugs, growth hormones, etc.) can be incorporated within
the organic matrix without loosing their bioactivity. Since the organic matrix
is laid down independently of the deposition of the inorganic material, the
influence of the added macromolecules on the properties of the inorganic phase
can be minimized.
15-18
Exploiting Oriented
Aggregation to Control Nanocrystal Size and Shape
R. LEE PENN, Anthony
Ratkovich, David J. Burleson, Department of Chemistry,
Oriented aggregation
of nanocrystals is an important mechanism of particle growth in the
solution-phase synthesis of oxide nanoparticles. Oriented aggregation is a
special case of aggregation in which primary nanocrystals are aligned with
respect to one another, resulting in the formation of new single crystals,
often with unique morphologies. Nanocrystal growth by oriented aggregation is
highly dependent on solution chemistry and may provide a means by which
intricate nanostructured objects can be produced. Furthermore, surfactants can
dramatically change the rate of oriented aggregation. Results from zinc oxide and iron oxide
experiments will be presented.
15-19
Unusual Particle Shapes and Assembly Structures
from Mineralized Hydrolgel Microspheres – a
DAYANG WANG, Min Kuang, Gang Zhang, Helmuth
Möhwald, Max Planck Institute of Colloids and Interfaces, D-14424,
Hydrogel microspheres are spherical hydrophilic polymer networks,
swelling or shrinking in response to environmental variables such as pH and
temperature. Thanks to their excellent biocompatibility, aqueous inner interior
environment, and facility of conjugation with bio-macromolecules, hydrogel
microspheres provide appealing analogues of biological organism, such as single
cell compartments. This presentation will be focused on mineralization of CaCO3
within hydrogel microspheres, creating inorganic/organic composite
particles with unusual shapes. Various nanoparticles were incorporated into the
hydrogel spheres based on their stimulus-sensitive swelling behavior. The
introduction of nanoparticles enables not only adding diverse functions into
the composite particles obtained but controlling their shapes also. After
dip-coating on substrates, intriguingly, CaCO3-loaded hydrogel
microspheres are organized in a two-dimensional (2D) hexagonal non-close
packing array, rather different from conventional 2D colloidal crystals. The
separation distance of the neighboring particles can be tuned in a controlled
fashion. Reminiscent to the corneas structure of moth eyes, the resulting 2D
non-close packing structures render the substrates anti-reflective, suppressing
the reflection of light. Owing to their similarity to lithographic patterns,
they were further recruited as templates for self-assembly of other particles.
The resulting binary structures can be easily manipulated by the surface
wettability.
15-20
Dendrimers and Diatoms:
Bio-Inspired Routes to Functional Metal Oxides.
S.L. Sewell, K.C. Halfpenny, D.W. WRIGHT, Department of Chemistry
Vanderbilt University, Nashville, TN,
david.wright@vanderbilt.edu
Unicellular plankton known as
diatoms are able to produce ornate nanostructures of silica at ambient
conditions. In contrast, current materials approaches require extremes of
temperature and pH. Diatoms are able to biomineralize the silica using species
specific peptides known as silaffins that possess lysine residues heavily
post-translationally modified with polyamines. Herein, we report the use of
amine-terminated dendrimers as mimetic templates for silica condensation. Further, the unique host-guest
capabilities of the dendrimer may be used to create novel functional silica
nanospheres with applications in supported heterogeneous catalysis,
biocatalysts, and as biological probes.
15-21
Bioinspired
Nanomaterials Synthesis
MURALI SASTRY,Absar Ahmad, Nanoscience Group, Materials Chemistry
Division, National Chemical Laboratory, Pune – 411 008,
The study of the synthesis, exotic
properties, assembly/packaging and potential commercial application of
nanomaterials is an extremely important topic of research that is expected to
have far-reaching impact global impact.
The focus of my talk will be on an emerging branch of nanotechnology
that derives its inspiration from biology. Recognizing that some of the most
exquisite and highly functional nanomaterials are grown by biological systems
(examples include silica by diatoms and magnetic nanoparticles by magnetotactic
bacteria), many researchers have focused attention on understanding how
inorganic materials are made by biological systems and attempting to replicate
such processes in the lab. In my laboratory, we have investigated the use of
plant organisms such as fungi in the synthesis of nanomaterials over a range of
chemical compositions that include metals, metal sulfides and oxides. An
exciting recent development is the use of plant extracts in nanoparticle
synthesis wherein large concentrations of gold nanotriangles have been obtained
that have potential application in cancer hyperthermia. Organisms such as fungi
are not normally exposed to metal precursor stresses – that they should be
capable of a broad range of biochemical transformations to negate these
stresses is useful in materials chemistry and throws up exciting possibilities.
15-22
Bionanotechnology
Approach in Material Synthesis and Device Fabrication by Applying
Peptide/Protein Assemblies
HIROSHI MATSUI, Department of Chemistry, City
University of New York, the Graduate Center and Hunter College, New York, NY, hmatsui@hunter.cuny.edu
Non-lithographic fabrications of devices such as electronics and sensor have been studied extensively by assembling nanometer-sized building blocks into the device configurations. While various nanocomponents have been applied as building blocks to construct nanodevices, the more reproducible methods to assemble them onto precise positions are desirable. We have been fabricating peptide-based nanotubes (antibody) and functionalizing them with various recognition components (antigen), and our strategy is to use those functionalized peptide nanotubes, which can recognize and selectively bind a well-defined region on patterned substrates, as building blocks to assemble three-dimensional nanoscale architectures at uniquely defined positions and then decorate the nanotubes with various materials such as metals and quantum dots for electronics and sensor applications. This coating was obtained by incorporating certain peptide sequences into peptide nanotubes that can selectively grow specific nanocrystals on nanotubes via biomineralization. By controlling the peptide conformation on the nanotubes, the nanocrystal size, packing density, and shape were controlled. This sequence peptide-incorporated nanotube is expected to become a conductivity-tunable building block for nanodevices.
In Nature, proteins and peptides mineralize various types of metal/semiconductor nanocrystals at room temperature in ambient pressure, which are difficult to achieve in synthetic manner. For future material syntheses, the production of monodisperse nanocrystals at an ambient condition is an important technology to develop. We mimic natural biomineralization systems, and we are succeeded to grow unusual nanocrystals at room temperature in ambient pressure in doughnut-shaped peptide assemblies. The peptide nano-doughnuts were self-assembled from peptides and organic salts. Nanocrystals grown inside the peptide nano-doughnuts were extracted by destroying the doughnut templates via long UV irradiation. The size of nano-doughnut can be control by pH, and therefore the size of nanocrystals can also be controlled. These nano-doughnuts can be self-assembled on specific locations of substrates patterned by AFM-based nano-lithography. Since the size and the interval between nanocrystals are controllable, these nano-doughnut assemblies can be applied to photonics and optics.
15-23
Self-Assembled Nanofibers
and Tubes from Biobased Synthetic Amphiphiles
GEORGE JOHN, Department of Chemistry, City College of the City
University of New York, Convent Avenue at 138th Street, NY, john@sci.ccny.cuny.edu
The self-assembly of low molecular weight building blocks into nanoscale molecular objects has recently attracted considerable interest in terms of the bottom-up fabrication of nanomaterials The building blocks currently used in supramolecular chemistry are synthesized mainly from petroleum-based starting materials. However, biobased organic synthesis presents distinct advantages for the generation of new building blocks since they are obtainable from renewable resources. This study is an effort to combine the philosophies of green chemistry and supramolecular chemistry, making use of renewable plant-derived resources as the starting materials (an alternate feedstock) for the noncovalent synthesis of meso- and nanoscale structures. The use of cardanol (obtained from Anacardium occidentale L, a renewable resource and by-product of cashew industry) and its derivatives for various applications is well known. However its use in the synthesis of aryl glycolipids and their self-assembled nanostructures are new to the literature. The glycolipids are self-assembled to form a variety of well-defined nanostructures including liquid crystalline phases, nanofibers, low-molecular weight gelators and nanotubes under suitable conditions, which could be of use in material applications. Also address the synthetic strategy for new amphiphiles and advances that have led to the understanding of chiral behaviour and the subsequent ability to control the structure of glycolipid nanostructures and the resulting impact of this on future material applications.
15-24
Thermally Responsive Silica-Living
Polypeptide Composite Particles.
S. Turksen, P. S. RUSSO, B. Fong, J. Qiu, E. Soto-Cantu, Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, LA, chruss@LSU.edu
Core-shell composite particles have been prepared, each consisting of a
silica-coated cobalt center to which a homopolypeptide shell, either poly
(-carbobenzyloxy-L-lysine) or poly (-benzyl-L-glutamate), is attached
covalently. Core particles were
coated with a mixture of amino and passivating moieties through silylation
reactions. The amino groups
initiated the polymerization, with attachment, of N-carboxyanhydride
monomers, resulting in a homopolypeptide shell. Characterization by dynamic light
scattering confirmed the helix-coil transition of the polypeptide shell,
reminiscent of the coat proteins of certain viruses, through repeated heating
and cooling cycles in an organic solvent.
The living nature of the polypeptide shell has also been confirmed. The particles have a size and uniformity
that leads to formation of colloidal crystals. Magnetometer measurements suggest the
particles are superparamagnetic.
Supported by NSF.
15-25
Active Transport and
Assembly Using Motor Proteins
B. C. BUNKER, G. D. Bachand, A. K. Boal, S. B. Rivera, R. P.
Manginell, J. M. Bauer, A. M. Bouchard, G. C. Osbourn, E. D. Spoerke, Sandia
National Laboratories, Albuquerque, NM,
H. Hess, University of Washington, Seattle, WA, V. Vogel, Swiss Institute of Technology,
ETH, Zurich, Switzerland, bcbunke@sandia.gov
Energy-consuming proteins including the motor protein kinesin and the microtubule-forming protein tubulin participate in a wide range of materials transport and assembly functions in living systems. Using such “nano-robots”, organisms can create and reconfigure materials via active processes that are not limited by the diffusion and energy constraints encountered in classical self-assembly processes. We are exploring the extent to which these active proteins can be exploited in artificial microfluidic systems to transport and assemble objects ranging in size from molecules to micron-sized objects. Our ultimate goal is to mimic biological processes such as the assembly of diatom skeletons and the reconfiguration of particulate arrays in the color-changing system of the chameleon. This talk will summarize progress made to date towards achieving this goal, including stabilization of proteins for use in artificial environments, guiding of transport, cargo manipulations (particle loading and unloading), and the generation of artificial microtubule organizing centers as scaffolds for particle manipulations.
15-26
Biomaterials from Nanocolloids: Applications for Neurons
NICHOLAS A. KOTOV, Departments of Chemical Engineering, Biomedical
Engineering and Materials Science, University of Michigan, Ann Arbor, MI, kotov@umich.edu
The presentation will review the recent advances in the use of nanocolloids to add new functionalities to biomaterials. Layer-by-layer assembly (LBL) affords preparation of ordered layered structures from virtually unlimited palette of nanocolloids. Various functionalities of nanocolloids afford preparation of targeted composites for evaluation of different neuronal functions. Four examples will be discussed. Multilayers from TiO2 nanoshells afford selective determination of neurotransmitters due to ion-sieving effect. Strong, flexible and electroconductive implants can be made from SWNT LBL multilayers. Stringent testing of biocompatibility of these composites was undertaken and it was demonstrated that they are suitable for long-term contacts with tissues. Stimulations of neurons through these films was demonstrated. Nanoparticles with silver nanocolloids can be used to suppress inflammation processes due to infection – one of the most important problems with implantable devices. Photoactive multilayer from semiconductor particles were used to NG108*15 neuron precursor cells on them. It was found that light adsorbed in the nanoparticle layers results in the electrical excitation of the neurons making this system a functional analog of retina. Assemblies of clay-polymer systems demonstrated exceptional toughness similar to that observed in bones. Layered nanocomposites represent an exceptionally versatile tool for production of biomaterials with novel applications derived from unique properties of nanostructured matter.
15-27
Electronic Nanodevice Piggyback on Live Bacteria
RAVI F. SARAF, Vikas
Berry, Department of Chemical Engineering, University of Nebraska- Lincoln,
Lincoln, NE, rsaraf@unlnotes.unl.edu
Biological motifs ranging from single biomolecule (i.e. DNA, proteins) and biomolecular monolayers (i.e., S-layer), to single-cell (bacteria, viruses, diatoms) and multi-cellular microorganisms (i.e., yeast), are shown to be highly versatile scaffolds for high density, self-assembly of nanoparticles. Leveraging the multi-scale organization in microorganism to fabricate hybrid structure with ‘physical’ nanoscale devices can open doors to fabricate highly functional (integrated) micro-systems. The key to exploiting the hierarchical structure of the microorganism to fabricate electronic micro-system remains in obtaining physiologically well-integrated biophysical hybrid structure interconnected to power and signal ports. We will discuss a fabrication method of using the membrane nanostructure of bacteria to form micron-scale (monolayer) percolating network of Au nanoparticles self-connected to power/signal ports. Using the humidity-induced actuation characteristics of the bacterium to modulate the (single) electron tunneling characteristics of the nanoparticle monolayer we demonstrate, a reversible and robust, humidity-sensing device. A critical aspect that attributes to a successful device is that the bacteria are alive during the entire device fabrication process. In contrast to most impedance based microelectronic humidity sensors, the sensitivity of this device is best at low humidity (relative humidity <20%).
15-28
Spontaneous Assembly of Macroporous Titania
A. Collins, D.C. Martin, S. DAVIS, S. Mann, School of Chemistry,
University of Bristol, Bristol BS8 1TS, United Kingdom, s.a.davis@bristol.ac.uk
Titania is a multifunctional material with a wide variety of potential uses in diverse areas such as photocatalysis and bioactivity. There is considerable interest in the template-directed synthesis of porous titania as the increased surface area and chemical accessibility of such materials offers distinct advantages. Typically, porogens with well defined size and architecture, such as emulsion droplets and colloidal crystals have been used in combination with preformed nanoparticles or in-situ precipitation reactions to prepare macroporous ceramics. In this work, we demonstrate the spontaneous formation of ordered macroporous titania from base catalysed sol-gel reactions and describe the photocatalytic properties of these materials.
15-29
Biotechnology and
Biomimetics Opens New Routes to the Fabrication of Silica and Metal Oxide
Semiconductors
DAVID J. KISAILUS1,2,3,Mark Najarian1,2,3, James
C. Weaver1,2,3, Yosuke Amemiya2,3, Joon Hwan Choi1,
Wenjun Yang2,3, Jan L. Sumerel2,3, Youli Li1;Daniel
E. Morse1,2,3,4, 1Materials Research Laboratory, UC Santa
Barbara, Santa Barbara, CA, 2 California NanoSystems Institute, Santa
Barbara, CA, 3Institute
for Collaborative Biotechnologies, UC Santa Barbara, Santa Barbara. CA, 4
Dept. of Molecular, Cellular, and Developmental Biology,
Working with silica needles produced by marine sponges, our laboratory discovered that the proteins we named “silicateins” catalyze and structurally direct the hydrolysis and polycondensation of silica, titania, gallia and zinc oxide from alkoxide precursors at neutral pH and low temperature. The silicateins are true enzymes, closely related to a well-known family of hydrolases. These are the first reported examples of enzyme-catalyzed, nanostructure-directed synthesis of these materials – and the first such syntheses at low temperature and neutral pH. Interaction with the template-like protein surface is capable of stabilizing polymorphs of these materials that otherwise are not normally observed at low temperatures. A preferential alignment of the resulting nanocrystallites of gallia to the protein was recognized, suggesting an epitaxial-like relationship.
Biomimickry is currently being used to catalyze and template the growth of various metal oxides. We are incorporating analogs of the critical amino acid residues found in silicatein’s catalytic active site, anchoring these functional groups (via self-assembled monolayers on gold) adjacent to one another to facilitate catalytic activity by the same mechanism exhibited by the enzyme. Results have shown that biomimetics of the active site in silicatein are capable of producing silica and metal oxides from alkoxide precursors at neutral pH.
15-30
Surface Patterning of
Silica Nanostructures Using Bio-Inspired Templates and Directed Synthesis
M. J. DOKTYCZ, E. A. Coffman, J. D. Fowlkes, A. V. Melechko, D. P.
Allison, M. L. Simpson, Life Sciences Division and Condensed Matter Sciences
Division, Oak Ridge National Laboratory, Oak Ridge, TN, doktyczmj@ornl.gov
Natural systems excel in directing the synthesis of inorganic materials for various functional purposes. One of the best-studied systems is silica synthesis. Various biological and synthetic polymers have been shown to template and catalyze silica formation from silicic acid precursors. We will describe the use of poly-L-lysine to promote the synthesis of silica in neutral, aqueous solution and when immobilized onto a silicon support structure under similar conditions. Either reagent jetting or conventional photolithography techniques can be used to pattern the templating polymer. Highly interconnected laminate structures are created after exposure to dilute solutions of silicic acid. Photolithographic patterning of (3-aminopropyl) trimethoxysilane, a reagent that mimics the lysine functional group, led to similar silica coatings. The described surface patterning techniques offer a route to integrate conventional silicon patterning technologies with biologically based material synthesis. Such combined fabrication techniques enable controlled assembly over multiple length scales and an approach to understanding interfacial silica synthesis as occurs in natural systems.
15-31
Biomaterials with Hierarchically
Defined Micro- and Nano-Scale Structure
JIAN
TAN1 and W. Mark Saltzman1, 2, 1 School of
Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 2
Department of Biomedical Engineering, Yale University, New Haven, CT, Jt75@cornell.edu
Biomaterials are becoming increasingly important in biomedical practice, particularly as the population ages. Materials that are organized on multiple length scales bear a closer resemblance to biological matrices than those with single scale features and materials with multi-scale organization should be more advantageous in biomedical applications. Many studies have shown that both the micrometer- and nanometer-scale features of materials could significantly influence cellular responses, however, synthesis of organized structures with both length scales for direct biomedical applications has been lacking. Nature has presented us numerous clues on how to produce complex, organized structures. Using a hierarchical approach that mimics natural material formation processes, we developed a method to produce materials with controlled physical structures at both the micrometer and nanometer scale. Our method is based upon a pre-organized micropatterned template and conformal transformation of the architecture with nano-structured minerals, namely hydroxyapatite. The newly developed materials were biocompatible with bone cells, induced a range of desirable cellular responses, and may therefore have direct application in bone tissue engineering. In addition, the design principles employed in this study can be extrapolated to other classes of biomedical materials, including polymers, metals, ceramics or hybrid combinations.
POSTER SESSIONS
ADVANCED NANOSTRUCTURED MATERIALS: SMART COLLOIDS AND NANOPARTICLES.
RESPONSIVE SURFACES AND THIN FILMS
P1-01
Polymeric Nanotubes and Nanorods Made from Poly(Styrene alt. Maleic Anhydride) and Poly(pyrrole)
Cécile Malardier-Jugroot, M.A. Whitehead, THEO G.M. VAN DE VEN, Pulp and Paper Research Centre and Department of Chemistry, McGill University, 3420 University Street, Montreal, QC, Canada, theo.vandeven@mcgill.ca
We recently discovered that it is possible to make nanotubes from alternating copolymers by self-association. An example is poly(styrene-alt-maleic anhydride) (SMA). These polymers consist of hydrophobic styrene groups, alternating with hydrophilic anhydride groups, which hydrolyze in water into two carboxylic groups, which depending on pH, can be both protonated (at low pH), both dissociated (at high pH), or one can be protonated and one dissociated (at neutral pH). At neutral pH an internal H-bond stiffens the molecule. At low and high pH, SMA is flexible and the conformation depends on the chirality of the chain, preventing self-association, whereas for neutral pH the conformation is linear, irregardless of chirality, allowing for a regular association between the chains. This association at pH 7 has been confirmed by dynamic light scattering, Cryo-TEM and SANS. Molecular modeling has shown that the most stable association complex is a nanotube in which 8 SMA chains make up one twist of a helix. The outer diameter of the tube is about 4 nm and the inner diameter 3 nm. The tubes can grow to a length of several microns. The tubes can also associate with themselves, forming sheets, which can stack upon each other. Cryo-TEM and SANS confirm these structures. Filling the nanotubes by monomers and polymerizing them, results in nanorods, which were imaged by AFM.
P1-02
The Role of Substrate
Priming in Hydrogen-Bonded Polymer Self-Assembly of Capsules and Films
V. KOZLOVSKAYA, Sukhishvili, Department of Chemistry and Chemical
Biology, Stevens Institute of Technology,
Growth of hydrogen-bonded multilayers is affected by substrate shape
and charge as well as by deposition conditions of a polycation precursor layer.
The growth of strongly-bound poly(N-vinylpyrrolidone)/poly(methacrylic
acid)(PVPON/PMAA) and weakly-bound poly(ethylene oxide))/poly(methacrylic
acid)(PEO/PMAA) systems is contrasted when these multilayers are deposited onto
bare or poly(ethylene imine) (
P1-03
Responsive Layers from
Heteroarm Star Copolymer
R. LUPITSKYY, S. Minko1, C. Tsitsilianis2, 1Department of Chemistry, Clarkson University, 8 Clarkson Avenue, Potsdam, NY, 2Department of Chemical Engineering, University of Patras, Patras, Greece
A grafted layer from poly(2-vinylpyridine)-star-poly(styrene) was prepared and its responsive behavior and phase segregation has been studied using Atomic Force Microscopy, water contact angle measurements, and X-ray Photoelectron Spectroscopy. The heteroarm star copolymer consists of 7 polystyrene and 7 poly(2-vinylpyridine)-arms (PS7-P2VP7) emanating from one core made of polymerized divinylbenzene. AFM studies revealed that single molecules of PS7-P2VP7 respond to solvent quality by changing there conformation and, therefore, act as spherical mixed polymer brushes. Grafted layers of PS7-P2VP7 exhibit very pronounced phase segregation. It was shown that surface composition, morphology, and wettability of such layers reversibly change in response to external stimuli such as solvents of different quality.
P1-04
pH-Sensitive Membranes from Polyelectrolyte Gels
M. ORLOV, S. Minko, I. Tokarev, Chemistry Department,
Cross-linked polymers were used to obtain pH-sensitive membranes. The properties of the membranes were further investigated. Membranes were prepared according to the principles of phase separation in polymer blends. Depending on the composition of the blend, pores’ sizes could be changed from hundreds of nanometers to several micrometers. The pore-size of the membranes can be regulated by the change of the pH and ionic strength since they are formed from polyelectrolytes. Membranes could be applied for controllable water transport or selective filtration.
P1-05
Surface Plasmon Resonance Spectroscopy Study of the Adsorption of Surfactants to Electroactive Interfaces
L. L. NORMAN, Antonella Badia, Department of Chemistry and the Centre of Self-Assembled Structures, University of Montreal, Montreal, QC, Canada, lana.norman@umontreal.ca
Well-defined electroactive monolayer films have been prepared by the self-assembly of ferrocenylalkanethiols on gold surfaces. These self-assembled monolayers (SAMs) allow one to electrochemically modulate surface interactions such as adhesion and wetting, as well as induce bulk orientation changes in liquid crystals through potential induced changes in the surface charge density. In the present study a combination of electrochemical characterization and surface plasmon resonance (EC-SPR) was employed to investigate the association of anionic surfactants to an electroactive self-assembled monolayer as the redox active monolayer is oxidized. SPR was used to quantify the thickness and the refractive index changes resulting from ion pairing between the ferrocenium cation and the counter ion in the solution. We show that the introduction of charges at an electroactive SAMs/solution interface can be used to influence the surface assembly of ionic surfactants and control the molecular organization of surfactants at SAM/solution interfaces.
P1-06
The Use of Self-Patterned Phospholipid Films for Directed Enzyme
Lithography
N.Y.-W. TANG, A. Badia, FQRNT Centre for
Self-Assembled Chemical Structures and Department of Chemistry, University of
Montreal, Montreal, QC, nathalie.tang@umontreal.ca
A novel method based on
Langmuir-Blodgett deposition was developed for creating patterned monolayer and
bilayer films of phospholipids. Regular stripe patterns with dimensions of few
hundreds of nanometers over several square centimetre areas have been
generated. Atomic force microscopy (AFM) imaging demonstrated that the stripe
patterns are composed of two phospholipids in different phases (solid and
fluid). These stripes are easily controlled in terms of lipid composition,
surface pressure, and film deposition conditions. In this poster, I will
present the mechanism of stripe formation and how the patterned dimensions can
be controlled by using lineactants and a combination of different lipids. Preliminary results on selective phospholipid degradation using
lipolytic enzymes will be discussed. This work expands the repertoire of template composition and pattern
form usable for the fabrication of lipid based surface patterns and
nanostrutures which could serve to spatially direct enzyme action and enzymatic
lithography, and design biomimetic membrane architectures.
P1-07
Fabrication and Study of
Responsive Nanoparticles and Colloids
MIKHAIL MOTORNOV, S. Minko, Department of Chemistry, Clarkson University, Potsdam, NY, mmotorno@clarkson.edu
We report the design and fabrication of smart particles and colloids capable for reversible switching between hydrophilic and hydrophobic states upon external stimuli. Smart nanoparticles are silica nanoparticles with specially designed responsive coating–mixed polymer brush. The mixed brush consists of two unlikely polymers grafted to silica nanoparticles. Two different polymers (A and B) in the mixed brush segregate to avoid unfavorable interactions. The mechanism of phase segregation depends strongly on outside conditions. This adaptive behavior of the mixed polymer brush can be used for engineering surfaces of smart nanoparticles. Polymer A is a water soluble hydrophilic polymer, and the second polymer is a hydrophobic polymer B. In aqueous medium the mixed brush will segregate. Polymer B will segregate to the core, while chains of polymer A will be exposed to the outside. However, in nonpolar organic solvent polymer B will segregate to the core and polymer A will form the outer shell of the particle. In an intermediate case (nonselective solvent for both polymers), the lateral segregation takes place resulting in semi spheres constituted from different polymers. The latter morphology will appear if the particles are introduced into the interface between two immiscible liquids. The goal of this research is to design smart spherical mixed brushes (nanoparticles) which will change the surface characteristics of different materials due to the responsive behavior of the mixed brushes.
P1-08
Modification of Gold Nanostructures by Using Temperature-Sensitive Core-Shell Microgel as a Template.
D. SUZUKI, H. Kawaguchi, Graduate School of Science & Technology, Keio University, Yokohama, Japan, dai95@orion.ocn.ne.jp
We demonstrate the novel thermo-sensitive hybrid core-shell microgels via in situ synthesis of gold nanoparticles using thermo-sensitive core-shell microgel as a template. The template core-shell microgels whose core were mainly composed of poly(glycidyl methacrylate) (GMA) and shell mainly (or fully) composed of poly(N-isopropylacrylamide) (PNIPAM) were synthesized in aqueous medium, and then they were incorporated with functional groups such as thiol, or amino groups. By designing the template structures, we could obtain two types of hybrid microgels. One is hybrid particles with gold nanoparticles localized around the core, and the other is the particles with gold nanoparticles immobilized in the shell. They showed thermo-sensitive properties, especially, in the latter case, the hybrid particles exhibited a reversible color change from red to purple originated from surface plasmon resonance of gold nanoparticles depending on temperature between 25 and 40 degrees. In addition to the thermo-sensitive property, the hybrid particles exhibited unique character of regularly arrangement on solid substrate. The particles obtained by this approach have potential uses for thermo-sensitive applications such as sensor, photonic or electronic devices.
P1-09
Fabrication of Metal Nanostructures Using Self-Assembled Polymer
Layers as Templates
I. TOKAREV, S. Minko, Department of Chemistry, Clarkson University, Potsdam, NY,
itokarev@clarkson.edu
Thin film templates with diverse nanopatterns were designed using the principles of phase separation in polymer blends and block copolymers. The special feature of our approach is the application of low molar mass additives which are easily extracted from the polymer films leaving either nanochannels or nanotrenches. Sputter-deposition and electrochemical deposition were used to fill the templates’ cavities with various metals. An additional control over the metal deposition was achieved by an appropriate combination of polar and nonpolar polymer components of the templates.
P1-10
Organization of Gold Nanoparticles on PS-PMMA Block Copolymer Monolayers
C. LEMAY, A. Ritcey, CERSIM,
Department of Chemistry, Laval University, Quebec, QC, Canada, cynthia.lemay@chm.ulaval.ca
Ordered arrays of metal
nanoparticles exhibit unique properties that may lead to important applications
in the fields of optics and catalysis.
The formation of periodic, ordered structures by block copolymers is
well known. Phase separation in
block copolymers spread at the air-water interface offers an interesting route
to the preparation of patterned surfaces.
For example, polystyrene-b-poly(methyl methacrylate) forms ordered
arrays of well-defined surface micelles when spread at the air-water interface.
These structures are conserved during monolayer transfer to solid substrates by
the Langmuir-Blodgett technique.
Our current research focuses on the subsequent organization of metallic
nanoparticles on these ordered copolymer surfaces. Several strategies are being
investigated. One approach involves
the organization of amine capped gold particles on sulfonated polystyrene
domains of the PS-b-PMMA monolayers.
Water-soluble gold nanoparticles are prepared by the phase transfer
method with two ligands. Gold is reduced by NaBH4 in the presence of
(3-mercaptopropyl)-trimethoxysilane and the particles thus formed are observed
to pass into the organic phase. An
amine terminated ligand is then introduced and reacts via siloxane binding to
produce water-soluble particles. A
second strategy involves the direct spreading of polystyrene capped gold
particles with PS-PMMA at the air-water interface. The ordered arrays are characterized by
AFM and TEM.
P1-11
Composite Films Prepared by
Single Wall Carbon Nanotubes Coated Monodisperse Polymeric Microspheres.
YUN-HO LEE†, Bumsu Kim‡, Jee-Hyun Ryu†, Kyung-Do Suh†, †Division of Chemical Engineering, College of Engineering, Hanyang University, Seoul, Republic of Korea, ‡Div. of Inorganic Chemistry Exam, Bureau of Chemistry & Biotechnology Exam, Korean Intellectual Property Office (KIPO), Daejeon, Republic of Korea, kdsuh@hanyang.ac.kr
Functionalized monodisperse micron-sized polymeric particles were coated with functionalized single-walled nanotubes (SWCNTs). To coat functionalized SWCNTs on the surfaces of particles, polymeric microspheres (poly (styrene-co-acrylamide)) having the amine group on surfaces were synthesized by dispersion polymerization. SWCNTs were functionalized by chemical oxidation, also. The composite films of SWCNTs coated microspheres were obtained by using hot press at temperature over the Tg of microspheres. The morphology and the properties of the SWCNTs coated microsphere were investigated by a scanning electron microscope, infrared spectroscope, thermal analysis (differential scanning calorimetry, thermogravimetric analysis) and zeta potential analysis. In addition, the conductivity, the hydrophobicity and the morphology of composite films were investigated. The small amount of SWCNTs (the weight of ratio polymer : SWCNTs = 500 : 1) coated on microspheres strongly affects the physical properties of microspheres and composite films.
P1-12
Controlled
Alignment of Single-Walled Carbon Nanotubes Using the Langmuir-Blodgett
Technique
Chul Youm, Sang-Keun Oh, SUNG-WOOK CHOI, Jae-Ho Kim*, Department of Molecular Science and Technology, Ajou University, San 5, Wonchun-dong, Yeongtong-gu, 9, South Korea, jhkim@ajou.ac.kr
The
use of single-walled carbon nanotubes (SWNTs) as key building blocks for
carbon-based electronics has, in recent years, been demonstrated for a variety
of applications such as field-effect transistors, field-emission materials and
sensors. Many of these applications
require the integration of SWNTs into ordered macroscopic structures in a
controlled way. Despite of
extensive efforts, however, it is still a challenge to fabricate large scale,
highly organized SWNTs onto solid substrates. Here we describe a method for generating
aligned, patterned SWNT structures over large areas using the Langmuir-Blodgett
(LB) technique. We synthesized
thiophenol-modified SWNTs (SWNT-SHs) through the conventional method based on
amidation of oxidized SWNTs. The
resulting SWNT-SHs were found to be soluble in organic solvents including
chloroform, which allowed the nanotubes to form a stable monolayer at the
water/air interface. We found that
the compression of SWNT-SHs on a LB trough leaded to a uniform SWNT-SH film,
where SWNT-SHs were aligned parallel to the trough barrier. Moreover the
SWNT-SH Langmuir films can be subsequently transferred
onto either homogeneous or pre-patterned solid substrates to form aligned SWNT
films. Importantly, the electrical
conductivity of the resulting SWNT-SH films parallel to
the tube axis was found to be ~15 times higher than that perpendicular to the
axis, reflecting anisotropic electrical properties due to the uniaxial
alignment of individual SWNT bundles.
P1-13
Opportunities Brought by
Cationic Fluorinated Surfactants in Tuning the Mesoporous Silica Particle
Architecture
BING TAN1, Stephen E. Rankin1, Sandhya M. Vyas2, Hans-Joachim Lehmler2, Barbara L. Knutson1; 1Chemical & Materials Engineering, University of Kentucky, Lexington, KY, 2Department of Occupational and Environmental Health, University of Iowa, Iowa City, IA
Fluorinated surfactants are special due to the hydrophobic and lipophobic fluorinated chains. These surfactants tend to assemble into aggregates and form novel “intermediate” mesophases more easily than hydrocarbon surfactants. These properties should allow co-assembly with ceramic precursors to create materials with a wider range of pore size and shapes than are available from hydrocarbon surfactants. Fluorinated surfactants also possess processing advantages for organic functionalization and supercritical carbon dioxide processing. We report a comprehensive investigation of the use of cationic fluorinated surfactants as templates for ordered nanoporous silica. A homologous series of cationic fluorinated surfactants with tail lengths between 4 and 12 carbons is synthesized. Using these surfactants, materials are synthesized either in aqueous solution or in water/ethanol solution. Silica powder with pore size as small as 1.6 nm was obtained by using the C4 cationic fluorinated surfactant. This pore size is the smallest among all pore sizes obtained from a surfactant templating process. Silicas with hexagonal pore structure as well as random mesh phase and vesicles were synthesized. The random mesh phase structure and the vesicle structure with mesoporous shells are the first time to be reported. The variety of pore architectures found in this study is much greater than would be found for a homologous series of hydrocarbon surfactants. We relate this structure variety to the known variety of micelle aggregates and mesophases formed by fluorinated surfactants.
P1-14
Synthesis of Fluorocarbon
Functionalized Mesoporous Silica Using Fluorinated Surfactant Templates
GIFTY OSEI-PREMPEH1, Barbara L Knutson1, Stephen E Rankin1, Hans-Joachim Lehmler2, 1University of Kentucky, Chemical and Materials Engineering, 177 Anderson Hall, Lexington, KY, 2University of Iowa, 222 IREH, Department of Occupational and Environmental Health, Iowa City, IA, bknutson@engr.uky.edu, gosei2@uky.edu
Cationic
fluorinated surfactants have been successfully used as templates in the
synthesis of ordered porous silica materials by our group. This work explores
the direct synthesis of organic functionalized silica materials through fluorinated
surfactant templating. The general templating mechanism, in which the organic
functional groups of the silica precursor are incorporated into the micelle
core, is favored by the surfactant and the organic functional group being of
like chemical nature. Therefore, in the case of fluorinated surfactant
templating, a fluorocarbon functional group may be well aligned within the
silica pores. Investigation of direct synthesis of C6F13C2H4-,
C8F17C2H4- and C10H21-
(for comparison) functionalized porous silica materials has been performed. The
materials were synthesized using cationic fluorinated surfactants, C6F13C2H4NC5H5Cl
and C8F17C2H4NC5H5Cl,
and cetyltrimethylammonium bromide (C16H33N(CH3)3Br-)
as templates.
Fourier transform infrared spectroscopy (FTIR) analysis and TGA confirm the incorporation of the functional groups in the materials after surfactant extraction. Powder X-ray diffraction, transmission electron microscopy (TEM) and nitrogen adsorption analysis are used to characterize the textural properties of the materials obtained from the four different combinations of functional group and surfactant.
P1-15
Self-Assembly of Nanoporous Silica Shapes: Synthesis, Morphogenesis,
and Applications
YA. YU. KIEVSKY,
We study the process of self-assembly of nano(meso)porous silica particles via surfactant templating. Process of formation of the mesoporous silica includes growth of the liquid crystalline template and solidification of this template via polymerization of silica precursor. Material obtained as a result of such synthesis (MCM-41) features highly uniform porosity, a large variety of shapes and their sizes. To control the assembly of the desired shapes, we study their morphogenesis. New conditions of self-assembly are found to form monoshaped nanoporous fibers. Recently suggested Origami-type mechanism for synthesizing a rich family of nanoporous silica shapes (cones, tubes, and hollow helixes) is examined. Shape details and their evolution are analyzed by means of XRD, SEM, TEM, AFM, and optical microscopy techniques.
The shapes can possibly serve as templates for various electronic and optical applications. Nanoporous shapes are the prospective hosts for lasing dyes (sealing laser dye molecules inside the silica pores saves them from oxidation and prevents their dimerization). Diffusion from the nanoporous shapes can be used for a control drug release. Another application of mesoporous silica is the coating of optical fibers by uniform low refractive index film with a good adhesion – a possible host for laser dyes or quantum dots.
P1-16
Fabrication
and Stabilization of Chain Structures from Fe3O4
Nanoparticles in the Magnetic Field
ROMAN SHEPAROVYCH1, Yudhisthira Sahoo3, Mikhail Motornov1, I. Sokolov2, Paras N. Prasad3, Sergiy Minko1, 1Department of Chemistry, Clarkson University, 8 Clarkson Ave., Potsdam, NY, 2Department of Physics, Clarkson University, 8 Clarkson Ave., Potsdam, NY, 3Institute of Lasers, Photonics and Biophotonics, University at Buffalo, The State University of New York, Buffalo, NY
A simple method of a magnetically induced formation of chain-like structures from magnetite nanoparticles and a polyelectrolyte in aqueous solution was developed. Massart's co-precipitation method was used for preparing of the aqueous solution of superparamagnetite (Fe3O4) nanoparticles stabilized with citric acid. Chain structures were fabricated from the magnetite nanoparticles in the applied magnetic field. The wires were stabilized with polyelectrolyte molecules so that the structures conserve the shape upon dilution, centrifugation, and deposition onto solid substrates. The stabilized magnetic wires were used to fabricate aligned structures by applying external magnetic field. We demonstrate that this strategy could be used for the fabrication of complex hierarchical structures.
P1-17
ESR Study on Nanomolecular Valve Effect of Cu Complex
Koji Nakabayashi1, Hiroshi Noguchi1, Atsushi Kondo1, Aya Tohdoh3, Hiroshi Kajiro2, HIROFUMI KANOH1, Katsumi Kaneko1, 1Chiba University, 1-33 Yayoi-cho, Inage, Chiba, JAPAN, 2Nippon Steel Corporation, Futtsu, JAPAN, 3IRI, Takada, Kashiwa, JAPAN, kanoh@pchem2.s.chiba-u.ac.jp
A microporous metal organic solid has a great advantage for designing and construction of the porous framework appropriate for selective adsorption. Li and Kaneko found a remarkably specific adsorption behavior of high reproducibility for CO2 in Cu complex-assembled microcrystal [Cu(bpy)(BF4)2(H2O)2(bpy)]n (bpy = 4,4’-bipyridine) irrespective of no open channels. CO2 is vertically adsorbed and desorbed at specific pressures at 273 K. Thus, this Cu complex solid is denoted a latent porous copper crystal (LPC). Although the mechanism has not been clear, the mechanism of the nanomolecular valve effect will be presented based on the model structure in another paper in this symposium.
In the present study, the mechanism of the nanomolecular valve effect was examined by the ESR measurement on Cu2+ of LPC before and after the gate adsorption of CO2. The ESR data show the characteristics for monomeric species with axial symmetry before the gate adsorption. The distances between atoms along z-axis are elongated longer than those between atoms in the xy plane because of the Jahn-Teller effect. After the gate adsorption, LPC seems to change to a more isotropic octahedral structure, probably accompanied by the shrinkage of the bond distance along z-axis.
AGGREGATION AND DEPOSITION OF
COLLOIDAL PARTICLES
P2-01
Influence of Anions on
Formation of -FeOOH Particles
T. ISHIKAWA1, S. Miyamoto1, K. Kandori1 and
T. Nakayama2, 1School
of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara,
Osaka, Japan, 2Materials Research Laboratory, Kobe Steel, LTD., 5-5
Takatsukadai 1-chome, Nishi-ku, Kobe, Hyogo, Japan, ishikawa@cc.osaka-kyoiku.ac.jp
Steel rusts contain -FeOOH particles in environments containing of Cl- such as marine and coastal districts where steels are easily corroded. Besides Cl- ions, various anions such as SO42- and NO3- result from SOx and NOx in the atmosphere and SiO32- exists in soils, and also PO43- is contained in surface treatment agents of steels. In this study, -FeOOH particles were synthesized by oxidation of FeCl2 and hydrolysis of FeCl3 in solutions containing different anions. The resulting particles were characterized by various techniques. The crystallite sizes obtained by XRD steeply decreased with the addition of SO42- and HPO42- in Fe(II)-oxidation and Fe(III)-hydrolysis. The particle morphology turned from rod to irregular shape on adding SO42- and the addition of SiO32- increased the particle size. The presence of HPO42- also increased the particle size in Fe(II)-oxidation but decreased it in Fe(III)-hydrolysis. The pore size distribution obtained by N2 adsorption showed that the products with SO42- in Fe(II)-oxidation were microporous but those in Fe(III)-hydrolysis were mesoporous.
P2-02
Synthesis of Lanthanide Fluoride Nanoparticles of Varying Shape and Size
Jean-Luc Lemyre, Anna M. Ritcey, Département
de chimie and CERSIM, Université Laval, QC, Canada, lemyre@chm.ulaval.ca
Recent scientific literature
demonstrates a growing interest in new methods of nanoparticle synthesis,
driven primarily by an ever increasing awareness of the unique properties and
technological importance of nanostructured materials. Major issues associated with nanoparticle
preparation include the control of particle size and internal structure. We have explored
several synthetic routes for the preparation of nanoparticles containing rare
earth elements. The fabrication of nanoparticles
within reverse microemulsions has been shown to be a convenient
route to monodisperse particles of controllable size. Yttrium fluoride nanoparticles of
varying crystallinity, shape and size are prepared by precipitation in reverse
microemulsions of water in cyclohexane stabilized with polyoxyethylene
isooctylphenyl ether. YF3 particles obtained by the classical
microemulsion method are found to be monodisperse amorphous spheres, with
controllable diameters between 6 and 50 nm. Furthermore, particles of the same
material obtained by a relatively minor variation of this method are found to
be monodisperse single crystals of octahedral and triangular shapes. The size of the crystalline particles
can be varied between about 25 and 350 nm.
The formation of single crystals can be attributed to the slower
incorporation of the precipitant into the micelles when introduced in this
fashion.
P2-03
Synthesis of Copper (I)
Oxide and Metallic Copper Particles in Polyols
A.Anžlovar, Z. CRNJAK OREL, M.
Žigon, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia, zorica.crnjak.orel@ki.si
Polyol-mediated synthesis was used for the conversion Cu (II) in to Cu (I) oxide and metallic Cu. Cu acetate (0.001-0.04 mol/l) either in di(ethylene glycol) (DEG) or in 1,2-propane diol (PD) was heated close to the boiling temperature of polyols for different periods of time. The chemical composition, average particle size, and morphology were studied (SEM microscopy, X-ray diffraction and FT- IR spectroscopy) in dependence of the temperature, the polyol used and the concentration of precursor. In DEG copper (I) oxide forms nanorod consisted spheres, that collapse into individual nanorods and they decompose and form irregular shaped metallic Cu particles (30 – 200 nm). In PD copper (I) oxide intermediate forms particles (100-300 nm) composed of small units (10-20 nm). With further heating particles become hollow and Cu particles (100 – 700 nm) are formed. The occurrence of hollow structures in DEG and in PD may indicate that transformation of Cu (I) oxide to Cu involves dissolution of the oxide structure (1). The band at 620 cm-1 due to optically active lattice vibrations in oxide was obtained only when the reduction temperature was lower than195 oC in DEG and 175 oC in PD.
P2-04
Coprecipitation of
Composite Colloidal Compounds Copper and Zinc Basic Carbonates
ZORICA CRNJAK OREL1, Jadran
Maček2, Marjan Marinšek2 Stane Pejovnik2, Egon
Matijević3, 1National Chemical Institute, Ljubljana, Slovenia , 2University
of Ljubljana, Faculty of Chemistry and Chemical Technology, 3Clarkson
University, Potsdam, NY, zorica.crnjak.orel@ki.si
Previously it was shown that uniform colloidal spheres of mixed metal oxides could be prepared by coprecipitation in solution of metal salts, but the resulting particles were internally inhomogeneous.
This study describes the formation of composite copper/zinc basic carbonates by decomposition of urea in solutions of two metal nitrates in different molar ratios. This system is of particular interest because the copper compound yields spherical and zinc rod-like particles when formed individually under the same conditions. It was found that in the majority of cases by using solutions of both metal salts and ageing them for 90 minutes, the resulting particles are spherical with only a small fraction (1-3%) being zinc base carbonate. Only when zinc nitrate was at least in four fold excess, the obtained solids appear as spherical assemblies formed from nanoribbons. In these instances the selected area diffraction shows that such particles contain up to 80% of the zinc compound.
The particle size increases with the reaction time, most likely by the Ostwald ripening. At still longer aging times (180 minutes) spherical shapes consisting of nanoribbons (zinc base carbonate) are formed.
P2-05
Preparation of the Au
Nanoparticles Using NaHCO3 as a Reducing Agent
YOUNG-HO LEE, Dae-wook Kim, Seong-geun Oh, Division of Chemical Engineering and Center for Ultramicrochemical Process System (CUPS), Hanyang University, Seoul, Korea, nanoyh@ihanyang.ac.kr
In this paper, the Au nanoparticles were synthesized by polyol process with NaHCO3 (sodium hydrogen carbonate) as a reducing agent. Utilizing NaHCO3 in polyol process achieved the low reaction temperature and the short reduction time. Decomposition of NaHCO3 serves carbonate ions (CO32-) and a small amount of H2O which dissolves the carbonate ions in. Carbonate ions increase pH of the mixtures and accelerate the reduction rate of AuCl4-. In our experiments, the effects of the NaHCO3/Au weight ratio and the PVP concentration on the reduction rate of AuCl4- and the particle size of the Au nanoparticles were investigated. The NaHCO3/Au weight ratio was varied to 10, 5, 3, 1 and 1/5. The reduction rate of AuCl4- was observed by the speeds of the color changes of the mixtures. UV-vis spectra and TEM images indicated that the size of the Au nanoparticles was controlled by the NaHCO3/Au weight ratio and the PVP concentration.
P2-06
Synthesis of Nanocrystals in Ionic Liquids
YONG WANG, Hong Yang, Department of Chemical Engineering and Laboratory for Laser Energetics, 206 Gavett Hall, University of Rochester, Rochester, NY, hongyang@che.rochester.edu
Ionic liquids (ILs) were used in the synthesis of nanostructured CoPt alloys with different compositions and shapes ranging from nanorods, to hyperbranched nanorods and to spherical nanoparticles. The 1-butyl-3-methylimidazolium bis(triflymethyl-sulfonly) imide ionic liquid, [BMIM][Tf2N] was employed as the solvent and the reaction was typically conducted at 350 °C under the protection of argon. Platinum acetylacetonate (Pt(acac)2) and cobalt acetylacetonate (Co(acac)3) were used as the precursors. The morphology, composition and crystal phase of the resulting CoPt alloy nanocrystals could be controlled by changing the concentration and molar ratio of the platinum and cobalt precursors. The rods synthesized were found having a composition of CoPt using powder X-ray diffraction (PXRD) and energy dispersive X-ray (EDX) spectroscopy. The nanoparticles were found to be CoPt3. PXRD, EDX, HR-TEM and micro-electron diffraction (ED) were also used in the characterizations of these nanocrystals.
P2-07
Uniform Ag and AgPd
Nanoparticles for Ultra-Thin Conductive Metallic Layers
B. P. FARRELL, D. V.
Goia, Center for Advanced Materials Processing and Department of Chemistry,
Clarkson University, Potsdam, NYgoiadanv@clarkson.edu
The aggressive reduction in materials costs and the relentless drive to increase the specific volumetric capacitance are two of the most important trends that characterize multi-layer ceramic capacitor technology. Here we present a novel precipitation process capable of generating highly dispersed Ag and AgPd, core-shell, nanoparticles that can be used to construct ultra-thin (150-200 nm) uniform conductive layers and could pave the way for capacitors with a very high number of electrodes and, therefore, high volume capacitances. Characterization of the particles by Field Emission SEM, X-ray Diffraction, TGA and Laser Diffraction Particle Size Analysis confirms the high purity of the metallic phase and reveals the high degree of uniformity and dispersion of the resulting particles. The precipitation process developed allows for the deposition of Pd shells representing 2-30 wt%, and is suitable for large scale manufacturing. A novel deposition technique that can be integrated along with these materials in the existing MLCC manufacturing lines with minimal disruption and in a cost effective manner, is also proposed.
P2-08
Multi-Layer Microfluidic Device to Assemble Uniform Colloidal Clusters
and Double Emulsions
HUA HU, Steven D. Hudson, Polymers Division, National Institute of
Standards and Technology,
We fabricated a novel multi-layer PDMS microfluidic device, which integrates a valve and a Coulter counter, to prepare uniform colloidal assemblies and double emulsions. First, bonding techniques, such as oxygen plasma and a chemical bonding method, and their effects on the bonding strength between two PDMS layers were investigated systematically by monitoring fracture pressure. Second, in this multi-layer device, we developed a novel valve that can stop flow in a microchannel with arbitrary width and depth. The efficiency and the response of the valve are reported. The in-line Coulter counter signals actuation of the valve to prepare controlled-size colloidal assemblies or double emulsions that contain a uniform number of particles or droplets. These advanced structures are expected to have broad applications and significant impact in optical materials and biomaterials.
P2-09
Heteroaggregation Rates and Light Scattering Form Factors of
Asymmetric Particle Doublets by Multi-angle Static and Dynamic Light Scattering
W. LIN, P. Galletto, M. Borkovec,
Laboratory of Colloid Surface Chemistry, Department of Inorganic, Analytical,
and Applied Chemistry, University of Geneva, Sciences II, 30 Quai
Ernest-Ansermet, 1211 Geneva 4, Switzerland, wei.lin@unige.ch
Heteroaggregation denotes aggregation processes in which particle charge and/or size are different. Such phenomena are of greater relevance in applications and natural environments than the analogous processes with identical particles (i.e., homoaggregation). In spite of their relevance, however, heteroaggregation has not been studied much. In this work, the heteroaggregation of two oppositely charged polystyrene latex particles is followed by time-resolved simultaneous static and dynamic light scattering (SSDLS), and from its initial time dependence we can obtain absolute aggregation rates and extract the form factor of the doublets. The heteroaggregation rates are obtained by analyzing the SSDLS data without the need to invoke the optical form factors for the doublets. The experimental form factors are compared with independent calculations based on the T-matrix method and the Rayleigh-Debye-Gans (RDG) approximation. While the RDG approximation is found to be reliable only up to particle diameters of about 250 nm, the superposition T-matrix method is very accurate for all types of doublets investigated, which shows clearly the appropriateness of the T-matrix method to estimate the optical properties of colloidal particles in the micrometer range reliably.
P2-10
Colloid-Colloid and Colloid-Surface Mass Transport Relaxational
Kinetics
A. CADILHE, N. Araújo, GCEP-Centro de Física, Universidade do Minho, 4710-057 Braga, Portugal, cadilhe@fisica.uminho.pt
We present preliminary results of a
P2-11
Measuring
Heteroaggregation Rate Constant of Binary Particle Suspension in the Presence
of Homoaggregation
WEILI YU1, M. Borkovec2, 1Pfizer Groton Laboratories, Pfizer Inc., Groton, CT, 2Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland, yuw@groton.pfizer.com, michal.borkovec@unige.ch
Heteroaggregation between particles of different sizes and properties plays an important role in various applications, such as medicine, ceramics, filtration, flotation, and water purification. In this study, the time-resolved multiangle simultaneous static and dynamic light scattering is used to measure absolute heteroaggregation rate constants in aqueous binary colloidal particles mixtures despite the simultaneous occurrence of homoaggregation. The differences in the form factor of asymmetric dimmers were exploited by using particles of unequal sizes in the range of 100-200 nm, where the Rayleigh-Gans-Debye approximation is accurate. The formation aggregation rate constant for the asymmetric dimmers as a function of the ionic strength was studied up to 300mM.
P2-12
A Coupled Coagulation
Model with Arsenic Sorption Kinetics and Equilibrium
on Fractal Colloids of Hydrous Ferric Oxide (HFO)
JIN-WOOK KIM, Timothy A. Kramer*, Department of Civil Engineering,
In recent years, numerous studies have attempted to solve the continuous population balance equations (continuous integro-particle differential equations). To obtain numerical solutions of the continuous population balance equations, extensive computation time and hardware are required. A realistic maximum size used in coagulation modeling would therefore produce an unmanageable number of simultaneous equations to solve. To overcome this computational non-efficiency of the uniform discrete model, various non-uniform discrete schemes have been introduced.
An improved discretized population balance equation (PBE) is proposed in this study. This improved discretized population balance equation has new probability distribution functions for aggregates produced in non-uniform discrete coagulation modeling. In this study, this model was found to be a substantial improvement in terms of numerical accuracy, stability, and computational efficiency over the continuous model. Further, this model was able to simulate the particle aggregation and breakup with fractal dimensions lower than 3. Moreover, comparisons were made using the fractal aggregate collision mechanisms of orthokinetic coagulation with the inclusion of flow induced breakup. This new algorithm makes it possible to solve fractal particle aggregation and breakup problems with high accuracy, perfect mass conservation and exceptional computational efficiency, thus the new model can be used to develop predictive simulation techniques for the coupled coagulation using computational fluid dynamics (CFD) and chemical reaction modeling.
In this study, this improved coagulation model developed was coupled
with arsenic sorption equilibrium and kinetics on fractal colloids of hydrous
ferric oxide (HFO). The model coupling was achieved by using the colloid
stability factor of 
and/or particle
collision efficiency 
as one component
of the aggregation rate constant (
) and a main function for coupling coagulation model with
chemical reactions such as arsenic sorption. The study reviewed the collision
efficiency studies for perikientic and orthokientic mechanisms and provided the
numerical algorithms to calculate collision efficiency for two different
transport mechanisms, depending on two colliding particle geometric sizes and
surface potentials or surface charges. Finally, unified model that is coupled
coagulation modeling with arsenic sorption kinetics consisting of a sorption
diffusion transport model and surface complexation model was developed. Using
the coupled model developed in this study, it was possible to predict arsenic
sorption (equilibrium and kinetics) and colloid particle collision (surface
potential time evolution, coagulation kinetics and particle size distributions)
during the arsenic sorption and coagulation, simultaneously.
P2-13
Shape Controlled Growth of
Colloid Particles: Numerical Simulation
Dan V. Goia1, V. Gorshkov2, S. Libert2,
E.Matijevic1, V.Privman2,
In this study we proposed a combinational mechanism
of the shape control particle growth. We assume that the aggregation consists of two main processes:
deposition, and rearrangement. Numerical
simulation analysis was used to study the parameters of the shape maintained
growth of the initial particles. The Gaussian
distribution function (GDF) was proposed as the main deposition rule for the
arriving building blocks. Uniform distribution function (UDF) was suggested as the main mechanism for the rearrangement. Two main parameters:
the standard deviation σ and the ratio of
deposition ρ have been chosen for the shape maintained growth
manipulation. The simulation showed that the
combination of parameters σ = 0.5 and ρ = 0.2 gives adequate
results
up to 20,000 deposited building blocks; this corresponds to
the growth of the initial particle twice in volume. Additional
rules for further study are proposed.
P2-14
Preparation Methods and
Infrared Attenuation Capabilities of Highly Conductive Anisotropic Metallic
Particles
D. LE, C. Goia, D.V. Goia, Center for Advanced Materials Processing, Clarkson University, Potsdam, NY, goiadanv@clarkson.edu
In the present work we have prepared highly conductive anisotropic metallic particles and investigated the ability of their aerosols to scatter and absorb infrared radiation. Copper and silver flakes of high aspect ratio were produced by milling spherical particles of the respective metals. Additional treatments, such as silver coating by conventional galvanic displacement, have been applied to the copper flakes to enhance their dispersion, chemical stability, and attenuating properties. It has been found that during the silver deposition by electro-displacement with metallic copper, silver fibers can form. The formation of these fibers occurs through the growth of the silver clusters at the expense of the copper substrate, their properties being strongly affected by the size and shape of the latter. Mass extinction values for the metallic platelets and fibers were calculated from transmittance measurements acquired by Fourier transform infrared spectroscopy.
P2-15
Control of Micro-Spheroid Silica
Structure and Organic Functionalization via a Sol-Gel Method in W/O Emulsion
Y. G. LEE, C. Oh, S. G. Oh, Department of Chemical Engineering, Hanyang University, 17 Haengdang-Dong, Seongdong-gu, Seoul, seongoh@hanyang.ac.kr
A controlled fabrication of silica materials with micro-spheroid type of structure containing a layer of organic functional groups outside the surfaces by using a sol-gel method in W/O emulsion was designed. The presence of Pluronic P123 and surfactants during the acid-catalyzed condensation greatly influenced the final particle morphology.
When Pluronic P123 copolymer was used in the W/O emulsion under the low pH condition, 2 or 3 of water droplets were linearly arranged and inter-condensation of hydrolyzed TEOS molecules occurred. Depending on the surfactants such as non-ionic (Span 80 or AOT), anionic (SDS), cationic (CTAB), used in the aqueous phase, the particle morphology was changed because of the interaction between silica sols and surfactants, including rod-type or egg-type structure. To combine thiol or amine group with the surface of silica particles, 3-mercaptopropyl trimethoxysilane (MPTMS) or 3-aminopropyl trimethoxysilane (APTMS) were used. All samples exhibited characteristic Type II BET isotherms, consistent with non-porous materials. The structure and functionality of these materials were characterized by field-emission scanning electron microscopy, fourier transform infrared spectroscopy, nitrogen adsorption and desorption, optical microscopy, and Energy-dispersive X-ray.
GENERAL PAPERS IN
COLLOIDS AND SURFACE SCIENCE
P3-01
Hydrophobically
Modified Polyvinylamine and Poly (ethylene oxide)-Poly (propylene oxide)-Poly
(ethylene oxide) Complexes
YI WANG, Xiaonong Chen, Robert Pelton, Centre for Pulp and Paper Research, McMaster University, Hamilton, ON, Canada, wangyi@mcmaster.ca
Aqueous solution properties of hydrophobically modified polyvinylamine (HMPVAm) and the formation mechanism of HMPVAM / poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) triblock copolymer complex were studied by dynamic light scattering and fluorescence. The HMPVAm was synthesized by the reaction of polyvinylamine (PVAm) with alkyl bromides. The solution properties of HMPVAm were explained in terms of the balance of hydrophobic interactions and electrostatic repulsion. The influences of the HMPVAm degree of substitution (DS) and solution pH on HMPVAm conformation were significant. Higher DS and pH resulted in a more compact structure. HMPVAm / PEO-PPO-PEO complex solutions were further investigated by dynamic light scattering and fluorescence spectroscopy. Significant changes of light scattering intensity, polymer equivalent size and fluorescence intensity ratio (I1/I3) were observed. These results suggested that the HMPVAm and PEO-PPO-PEO complex formation was driven by hydrophobic interactions.
P3-02
Surface modification of
EPDM rubber by plasma treatment
K.F. GRYTHE, F.K. Hansen, Department of Chemistry, University of Oslo, P.O.Box 1033 Blindern, 0315 Oslo, Norway, k.f.grythe@kjemi.uio.no
The effect of plasma treatment of thin, solvent cast EPDM films has been investigated by means of AFM, XPS and Surface Energy Measurements. Argon, oxygen and nitrogen plasma was used, and the changes in the surfaces were observed as function of treatment conditions and storage times. A modified surface is normally stable, but some treatment conditions also can lead to unstable surfaces. Surface energies were calculated from advancing contact angle measurements by different methods. Plasma treatment lead to changes in the surface energy from 25 up to 70 mN/m, but the absolute values for the surface energies depended on the method used for calculations.
XPS analyses of the modified surfaces revealed that up to 20wt% oxygen can be easily incorporated in the surfaces, and that variations on the order of 5wt% can be controlled by the plasma conditions. Oxygen was mainly found as hydroxyl groups, but also carbonyl- and carboxyl oxygen functionalities were seen.
AFM measurements revealed different surface structures with the three gases that were used. The surface roughness increased generally with treatment time, and dramatic changes could be observed at longer times. At short times, however, surface energy changes were much faster that the changes in surface structure, showing that plasma treatment conditions can be utilized to tailor both surface energies and surface structure of EPDM rubber.
P3-03
AFM Visualization of Polyelectrolyte
Single Molecules under Aqueous Media
YU. ROITER,
S. Minko, Department of Chemistry, Clarkson University, Potsdam, NY, sminko@clarkson.edu
We report on in situ AFM experiments for the visualization of single polyelectrolyte molecules adsorbed on the mica substrate under aqueous environment at different pH and ionic strength. In this experiments we study a weak polyelectrolyte poly(2-vinyl pyridine) when the conformation is affected by the charge density on the polyelectrolyte molecule. The charge density is tuned by change of pH of the aqueous solution and ionic strength (regulated by salt). The experiments allows for the in tact study of the polyelectrolyte conformation introduced by the environment as well dynamic changes of the conformation upon tuned environmental conditions. We compare the conformations obtained in the in situ experiments and the conformations of the molecules in a dry state upon solvent evaporation.
P3-04
Antifreeze Protein: from
Interfacial Structure to Antifreeze Effect
NING DU, Xiang
Y. Liu, Choy L.
Hew, Biophysics
& Micro/nanostructures Lab, Department of Physics, National University of
Singapore, 10 Kent Ridge Crescent, Singapore, phydn@nus.edu.sg
Antifreeze Proteins (AFPs), occurring in some polar animals and plants, are capable of inhibiting ice freezing at subzero temperatures. The antifreeze effect of Antifreeze Proteins on ice nucleation, which was neglected in most studies, was examined based on a “micro-sized ice nucleation” technique in this study. It follows from our experiments antifreeze proteins can inhibit the ice nucleation process by adsorbing onto both the surface of ice nuclei and dust particles, which leads to an increase of the ice nucleation barrier and the desolvation kink kinetics barrier, respectively. It was found that the antifreeze activity of AFPs can be enhanced either by their aggregation at higher concentration or by adding electrolyte into AFPs solutions. This promotion in antifreeze activity is attributed to the rise of surface activity for AFPs aggregates compared to AFPs monomers, and the screening effect of electrolyte to the surface charge of AFPs molecules, respectively. This study enables us to obtain a comprehensive understanding on the antifreeze mechanism of AFPs for the first time.
P3-05
Influence of Ammonia Vapor Post-Treatment on the Porosity
of Mesoporous Silica Prepared with Mixed Cationic and Glycoside Surfactant via
Nanocasting
R. XING, S. E. Rankin, Chemical and Materials Engineering
Department,
2D-hexagonal structured mesoporous silica samples with variable pore
size are synthesized via an acid-catalyzed nanocasting technique using mixtures
of cationic and glycoside surfactants, CTAB and n-Octylβ-D-glucopyranoside (C8G1). The pore diameter
can be tuned by post-treatment of the as-made materials using NH3
vapor at a mild temperature of 50 °C. Without ammonia treatment, the pore size
distribution of silica materials remain almost the same, independent of the
ratio of C8G1 to CTAB. XRD and TEM indicate only a slight
decrease in long-range order.
However, the composition of C8G1 greatly affects
the pore size distribution and degree of long-range order of the materials when
the as-made materials are treated by exposing them to vaporized aqueous
ammonia. To study the influence
of ammonia vapor post-synthesis on the porosity in these samples, two key factors
are varied: the amount of silica
precursor and the amount of NH3
vapor. Based on the
results, we propose that the results cannot be explained entirely by a
difference in the interaction between silica and cationic or nonionic
surfactants at elevated pH.
Instead, we propose that the Maillard reaction takes place during
ammonia treatment, leading to an increase in pore size but also to a loss of
long-range order.
P3-06
ATR-FTIR Study of Adsorption and Structural Arrangement of an Anionic Fluorinated Surfactant at
Germanium/Water Interface
R. XING, S. E. Rankin, Chemical and Materials Engineering
Department,
Adsorption
of anionic fluorinated surfactants, tetraethylammonium perfluorooctylsulfonate
(TEA-FOS) onto hydroxylated germanium from aqueous solution is studied in situ using polarized attenuated total
reflection FTIR spectroscopy. At pH
6.0, slow and extensive adsorption leading to multilayer formation is observed
for a series of bulk solution concentrations spanning from 10% of the critical
micelle concentration (1.0 mM) to well above the cmc. Three kinetic stages, with an
autoaccelerating last stage, are observed by monitoring the intensity of the
fluorocarbon bands. Circular
dichroism measurements of CF2 stretching bands indicate a slight
orientation of the fluorocarbon director normal to the surface as adsorption
proceeds, but not perfect close-packed layer formation. Further studies indicate that both pH
and salt concentrations have significant effect on the adsorption kinetics as
well as structural arrangement. With increase of pH, the final surface coverage
decrease. However, at even pH ~10, far above the IEP of germanium, the
adsorption of anionic surfactant onto negatively-charged surface still can be
observed, which indicates that the tetraethylammonium ions mediates
the interactions between the surfactant head groups and the surface. The
presence of salt increases the initial adsorption rate and change the sequence
of steps leading to multilayer formation.
P3-07
Direct Study of
Interaction of a Single Nanoparticle with Surfaces by the AFM
QUY K. ONG, Igor Sokolov, Physics Department,
Study of interactions of nanoparticles with various surfaces is of great interest for modern nanotechnology. For the first time, we present a new method to measure such interactions directly. By immobilizing nanosized particles onto the tip of atomic force microscopy (AFM), we are able to carry out direct measurements of the particle interaction with various surfaces. Interactions of ceria nanoparticles and either silica or polyurethane surfaces are demonstrated. The results are applicable to Chemical-Mechanical planarization (CMP). The fundamental issue of interaction between silica nanoparticles and silica plane wafer is addressed by connection of adhesion and long-range forces. We measure both types of forces by means of the AFM in aqueous solutions of various acidities.
P3-08
A Simple and Convenient
Method for the Measurement of Electrokinetic Mobility Using a Moving Boundary
Method
MASATAKA OZAKI,1,2* Teppei Ishikawa2, Dashdondog Bayarama2, 1Department of Environmental Science and 2Graduate School of Integrated Science, Yokohama City University,Kanazawa-ku, Yokohama, Japan, ozaki@yokohama-cu.ac.jp
Zeta potential is essential for the study of the stability of
hydrophobic colloids, and a variety of methods are used for the measurement of
the potential. Among them electrophoresis is frequently used. Although many
apparatuses for the measurement of the potential are commercially available,
most of them are not only expensive but also some of them are not available for
small particles in nano-scale. We developed a simple and convenient apparatus
for the measurement of electrokinetic mobility using moving boundary method. In
this method, a sharp boundary could be created automatically under a flat metal
plate or a semi-permeable membrane. This method is not only convenient for the
measurement of electrokinetic mobility but also applicable to dispersions of
nano-scale particles.
P3-09
A New Approach to Investigate the Deposition of Submicronic Particles by Laser Reflection
C. Pignolet, F. Membrey, C. Filiâtre, M. Euvrard, C.PARNEIX, A. Foissy, Laboratoire de Chimie des Matériaux et des Interfaces, Université de Franche-Comté, Besançon, France, celine.pignolet@univ-fcomte.fr
The electrophoretic deposition of
micrometer to nanometer size range colloidal particles onto an electrode in
aqueous media can result in an ordered array of particles. Such structures are
very attractive in a large range of applications: coatings, optical devices,
biosensors… In a former investigation, electrodeposition of micronic
polystyrene particles on a nickel electrode in a dc electric field was studied.
The deposition was observed in situ in a laminar flow cell using optical
microscopy. The purpose of the present work is to extend these investigations
to the submicronic range of particle size. For that purpose we have developed
an experimental setup based on the reflection of a laser beam on the electrode
surface. In order to validate the procedure, preliminary experiments were
performed using micrometric particles, which could be simultaneously observed
with both the regular microscope and the reflection apparatus. A correlation
between the two techniques was experimentally and theoretically established,
leading to the calibration of the system. This new approach allows in situ
investigations of the electrodeposition of nanometric particles (in the range
of a few hundred nanometers).
P3-10
Millisecond Time Resolved
Neutron Reflection Studies of Electrochemical and Surfactant Systems.
J.M. Cooper, R. Cubitt, R.M. DALGLIESH, N. Gadegaard, A. Glidle,
A.R. Hillman, Y.G.J. Lau, E.A. Mas, R.J. Mortimer, R.M. Richardson, D.J. Riley,
K.S. Ryder, E.L. Smith, ISIS, Rutherford Appleton Laboratory, Chilton, Didcot,
Oxfordshire,United Kingdom, r.m.dalgliesh@rl.ac.uk
By synchronizing data collection on a pulsed or chopped neutron source with the application of an external stimulus to a sample it has now become possible to study neutron reflection on time scales from milliseconds to tens of seconds. Recent measurements performed on the CRISP reflectometer at ISIS and the D17 reflectometer at the ILL have investigated the dynamics of the oxidation and reduction of polyvinylferrocene (PVF), the adsorption and desorption of Sodium dodecylsulfate (SDS) at a gold interface and the switching of a nematic liquid crystal phase. Unlike many other surface sensitive techniques neutron reflection has revealed information about the internal dynamics of PVF at an in-situ solvated interface. The use of isotopic substitution (H2O/D2O) allows a unique determination of the solvent and polymer depth profiles and has revealed rate dependent effects in the solvation and desolvation of the polymer film. The continuing development of this neutron reflection technique will add significantly to the information which may be obtained from electrochemical systems as it may be used to probe the relationship between the individual components.
NANOPARTICLES AND COLLOIDS IN
ANALYSIS
P4-01
Modeling and Laboratory Column Study of Transport of Polydisperse
Colloids through Saturated Porous Media
S. PEDDIREDDY, J. Ren, Department of Environmental and Civil
Engineering, Texas A&M University-Kingsville,
Colloid transport through saturated porous media has been studied by many researchers due to its importance in facilitating the transport of highly adsorbing contaminants in subsurface. However, much of the work has assumed monodisperse colloids. It is well known that natural colloidal particles are normally highly polydisperse. Recent studies have also shown the importance of the advances in understanding the transport of polydisperse colloidal suspensions on the analysis of contaminant transport in streams and pore waters. In this work, we conducted both laboratory column experiments and numerical simulations to study the transport of polydisperse colloids through saturated porous media. Both colloid concentration and particle size distribution of effluent samples collected at the end of the column were measured continuously over time. A polydisperse colloid transport model was developed to simulate the effluent colloid concentration and temporal particle size evolution by considering processes including advection, dispersion, and dynamic colloid filtration. The preliminary experiment results clearly showed a decreasing of particle size over time and a significant higher colloid deposition when background electrolyte concentration was high. The polydisperse colloid transport model was used to simulate both the effluent particle concentration and particle size distribution.
P4-02
Surface Immobilization of Individual Ag Nanoparticles for SERS-based Chem/Bio Sensing
S. TAN, D.Pristinski, M. Erol, H. Du, S. Sukhishvili, Department of Chemical, Biomedical and Material Engineering; Stevens Institute of Technology, Hoboken, 1 Castle Point on Hudson, NJ, stan@stevens.edu
We report a study on polymer-mediated immobilization of non-aggregated Ag nanoparticles on planar glass substrates and the resultant surface-enhance Raman scattering (SERS) activity using Rhodamin 6G (Rh6G) as a model molecule. Ag colloidal solution with an average particle diameter of 70 nm was prepared by citrate reduction of AgNO3 using Lee-Meisel method and subsequent fractionation. Self-assembled polyallylamine hydrochloride (PAH) monolayer was employed as the intermediate polymer layer. We have shown that the coverage density of Ag nanoparticles on the glass substrates correlates with the amount of adsorbed PAH. This parameter can be easily controlled by varying the pH and ionic strength during polymer deposition, with pH 9.0 and 0.25 M NaCl in the buffer solution yielding the highest coverage density. The glass substrates immobilized with non-aggregated SERS-active Ag nanoparticles exhibited in-situ detection sensitivity of Rh6G at sub-ppt level, even under highly acidic or basic conditions. The SERS-active substrates could be regenerated by removing the adsorbed Rh6G in a dilute hydrogen-peroxide solution. The effect of salt addition in the analyte solution on the SERS activity of the glass substrates will be discussed.
04-03
The Growing Usage and
Importance of Near Infrared Technology
AMANDA UPTON,
The recent research involving the use of Near Infrared (NIR) has shown to be valuable to the university. NIR is a close resemblance of Infrared (IR) because of its’ ability to pick out functional groups that are contained within a substance. This is a fairly new spectroscopic technique that has been able to improve upon the current way an IR sample can be taken. This is a time efficient and a non-destructive way of analyzing substances of all sorts. NIR has many practical applications in numerous analytical fields including both pharmaceutical and forensics. These fields are able to use NIR technology to build a library containing various samples in order to perform both qualitative and quantitative analysis. Once the library has been built, it becomes possible to use new samples and compare them to the library that has been created to determine if the sample meets the company’s needs.
NANOPARTICLES, COLLOIDS AND
INTERFACES IN
CONSUMER PRODUCTS
P5-01
Smart Plant Protein Inside Microdevices
AMY SHEN1, William Pickard1, Michael Knoblauch2,
Winfried Peters1, 1Department of Mechanical and Aerospace Engineering, Washington
University, St. Louis, MO, 2Fraunhofer Institute for Molecular
Biology and Applied Ecology, Germany, aqshen@me.wustl.edu
With the
discovery of the plant protein forisome, a novel, smart non-living,
ATP-independent biological material became available to the designer of smart
materials for advanced actuating and sensing. The in vitro studies show that
forisomes (1-3 micron wide and 10-30 micron long) can be repeatedly stimulated
to contract and expand anisotropically by shifting either the ambient pH or the
ambient calcium ion concentration. We probe the forisome's conformation
change inside a microfluidic device with the pH modulation. We demonstrate that
the surface properties of the channel wall and the flow condition can influence
the anisotropic shape change of forisomes, and their actuation kinetics
significantly. This study provides insights for multifunctional microvalve
fabrication.
P5-02
The Synthesis of
Polyvinylamine Microgels and Their Effect on Paper Strength
CHUANWEI MIAO, Robert Pelton, McMaster Centre for Pulp and Paper
Research, Department of Chemical Engineering, McMaster University, Hamilton, ON,
Canada, peltonrh@mcmaster.ca
Polyvinylamine (PVAm) microgels were synthesized by post-polymerization crosslinking. In this method, linear PVAm aqueous solution was induced to separate phase by adding salt and adjusting pH, followed by the addition of glutaraldehyde which reacted with amine groups on PVAm chains to crosslink the formed polymer aggregations. Three PVAm microgel samples with different mean size were prepared and their contributions to paper strength were tested and the results were compared with those of linear PVAm. Handsheets containing these polymers were made and their dry tensile, wet tensile and internal bond strengths were measured. The results demonstrated that PVAm microgels can improve strength compared to linear PVAm when the polymer dosage is higher than 0.2 wt % based on the weight of dry pulp. The size of microgels does not have significant effect. Two mechanisms of the better performance of microgels were postulated. Firstly, microgels can achieve higher retention due to their bulk volume; secondly, the deformation of microgels during drying process can fill the voids between rough fibre surfaces to increase the bonding area.
P5-03
Effect of Porosity and
Carbazole Concentration on the Reflective Electrochromic Display Prepared by
Monodisperse Carbazole-Modified Polymeric Microspheres
JUNG-HUN LEE, Jee-Hyun Ryu, Kyung-Do Suh, Division of Chemical Engineering, College of Engineering, Hanyang University, Seoul, Republic of Korea, kdsuh@hanyang.ac.kr
Polycarbazole and its
copolymer are the well-known electrochromic materials, which show a dark green
color at the applied potential. Reflective electrochromic display (R-ECD) based
on polymeric microspheres containing carbazoyl pendants were prepared using the
seeded swelling and polymerization method, then synthesized bicarbazole were
refluxed with the chloro-functional groups. The porosity and content of
carbazole groups were diversified by controlling the amount of toluene and
chloropropene in the 2nd monomer mixture, respectively. Response
time of R-ECD was considerably affected by the specific surface area of
microspheres, and the concentration of carbazole incorporated. The swelling
procedure and morphology of polymeric microspheres were monitored utilizing an optical
microscopy and SEM, respectively. Reflectance changes were measured by
spectrophotometer. Response time and color efficiency of R-ECD were measured by
electro-optic spectrometer.
P5-04
Novel Use of Surfactants
in Copper Chemical Mechanical Polishing
YOUNGKI HONG, Udaya B. Patri, Suresh Ramakrishnan, and S.V. Babu, Interdisciplinary Engineering Science, Department of Chemical Engineering, Center for Advanced Materials Processing, Clarkson University, Potsdam, NY, hongy@clarkson.edu
Surfactants have been used as one of the components of CMP slurries to mainly stabilize the slurries. However, ionic surfactants can interact with material surfaces and change the property of its surface. In this study, Sodium Dodecyl Sulfate (SDS), one of the conventional anionic surfactants was examined as an inhibiting agent of copper dissolution in chemical mechanical planarization (CMP) slurry. SDS showed superior performance on the inhibition of copper dissolution to Benzotriazole (BTA) at acidic condition. SDS of 1mM effectively shut downed the dissolution of copper film as low as ~0nm/min. and the loss of polishing rate was comparable to that of BTA in the case of typical slurry system of glycine and hydrogen peroxide. According to the contact angle measurement result that can determine the hydrophilicity of material surface, SDS turned the hydrophilic surface of copper film into hydrophobic.
SDS and a positively charged copper-film surface at acidic and neutral pHs (IEP = 9~10) develop electrostatic attraction between them. This electrostatic attraction could introduce a surfactant layer onto the copper-film surface and develop a hydrophobic layer of surfactant. This hydrophobic layer could protect the copper-film surface from the slurry chemicals that could dissolve the copper surface. And this hydrophobic layer can be removed by the physical forces. So this aspect can maximize the planarization efficiency of copper CMP and minimize the dishing of copper wire.
P5-05
Selective Polysilicon
Chemical-Mechanical Planarization (CMP) during Fabrication of
Micro-Electro-Mechanical-Systems (MEMS) Devices using Surface-Modified
Aabrasives
ANITA
NATARAJAN1, Sharath Hegde1, S. V. Babu1, 2, 1Department
of Chemical Engineering, 2Center for Advanced Materials Processing,
Clarkson University, Potsdam, NY
An important step in micro-electro-mechanical system (MEMS) device fabrication is deposition and etching of few microns thick layers of polysilicon and silicon dioxide. To minimize the processing difficulties in subsequent processes like patterning, deposition and etching, it is desirable to planarize each deposited polysilicon layer using CMP. In one of the several polishing steps during the device fabrication sequence, selective polishing of the polysilicon top layer over the underlying silicon dioxide/nitride layer is required. Hence, a polishing slurry that selectively removes polysilicon over underlying silicon dioxide or silicon nitride is critical to prevent erosion of either silicon dioxide/nitride, which would be detrimental to the subsequent fabrication steps.
Colloidal silica (~50nm) and
calcined ceria (~250 nm) based slurries were used to achieve high polysilicon polish rates (250-500 nm/min) and high selectivity
of polysilicon over silicon dioxide and silicon nitride (> 75:1). The
surface characteristics of the abrasive and wafer surface were modified in the
presence of several additives. The additive role in the suppression of silicon
dioxide and silicon nitride removal rates by adsorption to the abrasive and
wafer surface was confirmed through Fourier transform infra- red (FTIR)
spectroscopy and zeta potential measurements.
P5-06
Role of Complexing/Chelating Agents in Copper CMP Slurries
U. B. PATRI, S. Pandija, S. V. Babu, Center for Advanced Materials
Processing and Department of Chemical Engineering,
Typically copper CMP slurries are composed of an oxidizer, the most preferred one being hydrogen peroxide (H2O2), a corrosion inhibitor like benzotriazole (BTA), a complexing/chelating agent and other additives along with abrasives like silica or alumina. Glycine, citric acid, ethylene diamine, ethylene diamine tetra acetic acid are some of the many complexing/chelating agents that have been investigated in Cu CMP slurries. However, there has been no definitive elucidation of the role of the molecular structure of the complexing agents - different functional groups (eg: -NH2 vs. -COOH), their relative positions, the length of the carbon chain, etc., - in interacting with copper surface and controlling the material removal rates. In this study, several complexing agents containing amine and/or carboxyl groups (acetic acid, succinic acid, ethylene diamine, glycine, alanine, amino butyric acid and others) have been studied to understand better the role of the molecular structure in determining copper removal rates. The results are consistent with the known activity of –COOH groups at acidic conditions and that of –NH2 groups in an alkaline environment. In comparison with glycine, it was also observed that an increase in the carbon chain length increased the removal rates at acidic pH values and decreased the removal rates at alkaline pH values. Also, Cu removal rates decreased with an increase in the distance between the –NH2 and –COOH groups in an amino acid at all pH values except at 4.
P5-07
Influence of Particle
Surface Charge with Charged Oxidizing Agents for Cu CMP
Kenneth Rushing, Yuzhuo Li, Department of Chemistry and Center for Advanced Materials Processing, Clarkson University, Potsdam, NY, yuzhuoli@clarkson.edu
Hydrogen peroxide has played a vital role in many of the copper CMP systems involved in the manufacturing of IC chips. Recent studies on the use of hydrogen peroxide have suggested mechanisms for the formation of hydroxyl radicals (*OH) as the key component in modifying the copper surface. These hydroxyl radicals are highly reactive intermediates bearing no formal charge leading to very little or no interaction among the charged abrasive particles within a CMP slurry.
Substituting potassium persulfate for hydrogen peroxide in a traditional system has shown promise in the removal and planarization of the overburden copper. Knowledge of potassium persulfate suggests a mechanism, through single-electron transfer and the presence of water, in which there is a production of sulfate radical anions and hydroxyl radicals. These sulfate radical anions carry a formal charge of -1 allowing for interaction among charged abrasive species.
This presentation will demonstrate how the charge of a particle will influence the removal and planarization of copper using anionic oxidizing agents. The particles being studied will possess no surface charge, negative surface charge or positive surface charge within the aqueous slurry.
P5-08
Effect of total surface
area of solids on material removal rate in metal polishing
S. Ramakrishnan, S. B.
Janjam, E. Matijević, S. V. Babu, Chemical Engineering department and Center
for Advanced Materials Processing,
The properties of abrasive particles play a significant role in chemical mechanical planarization (CMP) of metal films. The effect of particle size (silica) on the material removal rates of copper and tantalum in hydrogen peroxide based slurries containing glycine as a complexing agent was investigated earliera. It was shown that the total surface area of the solids in the slurry controlled the material removal rates for both Cu and Ta. The present work extends these studies to other complexing agents: citric acid, maleic acid and acetic acid.
P5-09
Role of Oxalic acid in
Slurry for Copper CMP
S. PANDIJA, D.
Roy, S. V. Babu, Department of Chemical Engineering and Center for Advanced
Materials Processing,
Copper (Cu) disks were polished using oxalic acid and H2O2, with and without abrasives (3 wt % colloidal silica – 50 nm), at different values of the solution pH. Cu polish rates with and without abrasives were similar, indicating that oxalic acid is an effective complexing agent in abrasive-free slurries. At pH ~ 1.5, dissolution rates of Cu in slurry containing oxalic acid and H2O2 were low and the rates increase with an increase in the pH till pH = 3.0. A similar trend was observed with the polish rates of Cu. At pH = 3.0, when the concentration of H2O2 was increased from 0 wt % to 5 wt % in the slurry, the dissolution rates increased, becoming almost constant thereafter till 8 wt % H2O2 and then decrease with a continued increase in the H2O2 concentration. Electrochemical and UV/Visible spectroscopic measurements were performed in order to understand the observed trends of Cu polish rates and formation of Cu-oxalic acid complex.
NANOPARTICLES, COLLOIDS AND
INTERFACES IN MEDICAL/BIOMEDICAL DIAGNOSTIC APPLICATIONS
P6-01
Controlled Release of Plasmid DNA from Gold Nanorods Irradiated by
Pulsed Near-Infrared Light
H. TAKAHASHI, Y. Niidome, T. Niidome, S. Yamada, Department of Materials Physics and Chemistry, Graduate School of Engineering, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, Japan, thirotcm@mbox.nc.kyushu-u.ac.jp
Gold nanorods
(NRs) are rod-like nanoparticles that have unique optical properties depending
on their shape. In order to use NRs for biochemical
applications, we have first partially modified them with phosphatidylcholine
(PC). Partial modification of NRs with PC has been successful by extraction with chloroform containing PC. The resultant PC-modified NRs (PC-NRs)
could form complexes with plasmid DNA by electrostatic interactions, denoted as
PC-NR/DNA. Pulsed laser irradiation
of NRs induces shape changes into spherical nanoparticles. Irradiation of pulsed 1064-nm laser
light (250 mJ/pulse, 2 min) to PC-NR/DNA complexes induced shape changes of
PC-NRs and at the same time plasmid DNA were released from the complexes as
confirmed from gel electrophoresis.
Thus, it is clear that the shape
changes of PC-NRs trigger the release of DNA from the complexes. It was also found that the plasmid DNA was released without any damage by laser
irradiation. Thus, the near-IR laser
irradiation onto the PC-NR/DNA complexes
has realized the selective release of the plasmid
DNA without appreciable structural changes.
P6-02
Preparation and Characterization of Genistein-Modified PLGA Nanocapsules by Introducing the Cationic Moiety
JEONG-BEOM NAM1, Jee-Hyun Ryu1, Jin-woong Kim2, Kyung-Do Suh1, 1Division of Chemical Engineering, College of Engineering, Hanyang University, Seoul, Republic of Korea, 2Div. of Engineering & Applied Sciences, Harvard University, Cambridge, MA, kdsuh@hanyang.ac.kr
Nanocapsules, which formulated from the biodegradable polymers such as poly(D,L-lactide-co-glycoide) (PLGA), poly(D,L-lactide) (PLA), are being extensively investigated as drug release vehicle, or specific carriers for gene delivery. Genistein, extracted from soybeans, is one of the good anti-oxidant agents, therefore, it was chosen a model drug in this study. A cationic moiety, amine structure, was incorporated to the PLGA to capsulate the genistein more efficiently. The modified PLGA-genistein nanocapsules were prepared by using a emulsion-evaporation method. At first, the modified PLGA and genistein in acetone solvent were poured into the Tween 60 aqueous solution with a mechanical stirring. Encapsulation of genistein was achieved by means of the ionic interaction between anionic hydroxyl groups of genistein and cationic amine groups of modified PLGA in the micelles. The content of genistein in nanocapsules and antioxidant activity of capsules were examined utilizing an high performance liquid chromatograph (HPLC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, respectively. Depending on the concentration of cationic moiety in the modified PLGA, the in vitro release profiles of genistein was also investigated.
P6-03
Patterns of the Salt Effects on Protein-Protein Interactions and
Their Implications for Protein Crystallization
A. C. DUMETZ, E. W. Kaler, A. M. Lenhoff, Department of Chemical
Engineering, University of Delaware, Newark, DE, dumetz@che.udel.edu
Proteins have a typical size of few nanometers, and so are in the lower range of the colloidal domain. In order to map out the main patterns of protein-protein interactions, the second osmotic virial coefficient (B22) has been measured using self interaction chromatography (SIC) for seven different proteins (ovalbumin, ribonuclease A, myoglobin, α-lactalbumin, BSA, catalase, cytochrome C) under different conditions of salt and pH. At low salt concentrations the protein interactions can be either attractive or repulsive. At higher salt concentrations, when electrostatic interactions are completely screened, the trends depend of the type of salt. In sodium chloride, for all the proteins studied the B22 remains unaffected, whereas in ammonium sulfate B22 drops steeply at different salt concentrations for each protein. These last trends emphasize the importance of non-DLVO forces on protein interactions and are mainly interpreted in terms of an hydration effect.
NANOPARTICLES, COLLOIDS AND
INTERFACES IN MEDICAL/BIOMEDICAL DIAGNOSTIC APPLICATIONS
P7-01
Thermodynamic Study of the Effects of Procaine on Phospholipid Monolayers
M. Tomoaia-Cotisel1, A. Mocanu1, P.T. Frangopol1, D. A. Cadenhead2, 1 “Babes-Bolyai” University of Cluj-Napoca, Physical Chemistry and Biophysics Department, 3400 Cluj-Napoca, Romania, and 2State University of New York at Buffalo, NY, mcotisel@yahoo.com
The influence of the local anesthetic procaine (PR) on 1,2 – dipalmitolyl-sn-glycero-3- phosphocholine (DPPC) monolayers was investigated at the air/water interface by Langmuir technique. Compression isotherms were investigated as function of concentrations of procaine hydrochloride in aqueous solutions in the range from 10-6 to 10-2 M. The amount of PR penetrating into the DPPC monolayers was derived from the surface pressure increase with increasing procaine concentrations recorded at constant molecular area of DPPC by using the Gibbs’ adsorption equation adapted to interfacial penetration phenomena. The findings show that the presence of DPPC monolayers produces an enhanced adsorption of PR at the air/water interface. At the monolayer collapse an exclusion of PR molecules from the DPPC monolayers is evidenced by atomic force microscope observations on Langmuir-Blodgett films transferred on solid substrates. The pressure dependence of the penetration of the local anesthetic procaine into the phospholipid monolayers may be of relevance in the phenomenon of pressure reversal in anesthesia.
NANOPARTICLES, COLLOIDS AND
INTERFACES IN THE ENVIRONMENT
P8-01
Colloid Retention and Transport
in Porous Media with Mixed Wettability
JIE HAN, Yan Jin, Department of Plant and Soil Sciences,
Migration of colloids can facilitate transport of bacteria, virus,
metal, and radionuclide in the subsurface environment. In this study, saturated
and unsaturated column experiments were conducted to examine the behavior of
latex particles with diameter of 19 nm in 300 to
P8-02
Design Criteria for
Laboratory Reactors Used to Evaluate the Deposition of Colloidal Particulates
on the Surface of Steady State Aerobic Biological Films of Any Thickness
J. P. BOLTZ,1, E. J. La Motta,2, 1CH2M HILL, Inc., Montgomery, AL, 2University of New Orleans, New Orleans, LA, , jboltz@ch2m.com
Generally, a substantial effort is put forth in the design of a bench-scale experimental apparatus when evaluating fixed-film biological wastewater treatment systems. During kinetic investigations, steady state conditions with respect to effluent particle concentration are desirable because they allow for the most simplistic model development and verification. The steady state conditions in an ideal biofilm reactor include evenly distributed biofilm with constant values of film thickness, pH, colloidal particulate concentration remaining in the effluent, DO level, and negligible suspended growth. Realistically, these variables will fluctuate slightly. However, the laboratory reactor must minimize this variation in order to obtain a quasi-steady state with respect to effluent particle concentration. There is a paucity of information in the literature detailing the design criteria for such a reactor. This presentation details the experimental setup including: nutrient solutions necessary for film development and maintenance, commercially available colloids (organic and inorganic), construction material, motor integration, and sampling. Additionally, appropriate inoculation sources as they pertain to experimental objectives are addressed. A presentation of recent research that demonstrates particle removal by aerobic biological films is governed by a physical surface dependent process, namely bioflocculation, indicates colloid analyses can be conducted on films of any thickness.
P8-03
Kinetic Study of Cell
Proliferation of Saccharomyces cerevisiae Strains by Sedimentation/Steric Field
Flow Fractionation in Situ
J. Kapolos1, L. Farmakis2, G. Karaiskakis2, A. KOLIADIMA2, 1Department of Agricultural Products Technology, T.E.I. of Kalamata, 24100 Kalamata, Greece, 2Department of Chemistry, University of Patras, Patras, Greece, akoliadima@chemistry.upatras.gr
The Sedimentation/Steric Field Flow Fractionation (Sd/StFFF) technique is applied to the kinetic study of cells proliferation of Saccharomyces cerevisiae (S. cerevisiae) strains. The size distribution and the mass ratio of the yeast cells were determined as a function of the time from the preparation of the yeast sample dispersion in the culture medium. The results were combined with the growth of the yeast cells and their life cycle and compared with those obtained by scanning electron microscopy (SEM) and those found in the literature. Useful conclusions concerning the budding and the fission of these yeast cells were also extracted.
P8-04
Diffusion Coefficients and Partition Coefficients of SO2
in Water – Air Interface at Different pH Values in the Presence or Absence of
Surfactants.
J. Kapolos1, L. Farmakis2, G. Karaiskakis2, A. KOLIADIMA2, 1Department of Agricultural Products Technology, T.E.I. of Kalamata, Kalamata, Greece, 2Department of Chemistry, University of Patras, Patras, Greece, akoliadima@chemistry.upatras.gr
The physical and chemical phenomena controlling the exchange of gas pollutants between atmospheric and water environment are of great significant in environmental chemistry. Research in this area requires working at scales far smaller than those normally associated with the bulk processes on either side of interface, and requires new experimental and theoretical approaches.
In this work the relatively new technique of reversed flow gas
chromatography (RF-GC) has been applied for measuring the diffusion
coefficients of one of the most common pollutant, SO2, in water at
different pH. Also their partition coefficients in water-air interface were
calculated giving information not only on phase equilibria but also on
interface transport across the air – water boundaries.
Finally the effect of surfactants (FL-70 and Triton) on the transfer of SO2 into water was studied.
P8-05
Influence of dissolved
organic matter and pH on the transport of Cryptosporidium
parvum oocysts in a geochemically heterogeneous saturated porous medium
R. A. ABUDALO1, J. N. Ryan1, R.W. Harvey2, D.
W. Metge2, 1University
of Colorado at Boulder, Department of Civil, Environmental, and
Architectural Engineering, University of Colorado, 428 UCB Boulder, CO, 2U.S. Geological Survey, Water Resources
Division, 3215 Marine Street, Boulder, CO, rula.abudalo@colorado.edu
Dissolved organic matter (DOM) may affect the
attachment of Cryptosporidium parvum
oocysts (a pathogenic protozoan pathogen) in aquifer sediments by altering the
surface characteristics of the oocysts and the grains. To test the effect of DOM on oocyst
transport in geochemically heterogeneous porous media, we measured removal of
oocysts in flow-through sand columns in the presence of a well-characterized
fulvic acid (FA) from the Florida Everglades (0 to 20 mg L-1)
under low pH (pH 5.6-5.8) and ionic strength (10-4 M)
conditions. The columns were
packed with a mixture of quartz sand (96%) and ferric oxyhydroxide-coated
quartz sand (4%). Deposition of
oocysts within the sand columns decreased with increasing FA
concentration. Collision
efficiencies (a) decreased from 0.25 to 0.12 as the FA concentration
increased. To test the effect of pH
on oocyst transport in similar geochemically heterogeneous porous media, a
second set of flow-through sand columns were conducted over a pH range of 5.7
to 10.0 at low ionic strength (10-4 M NaCl). Results of these
experiments demonstrated that the magnitude of oocysts breakthrough was
sensitive to pH; the increase in pH from 5.7 to 10.0 decreased α by 50%.
NANOPARTICLES, COLLOIDS, AND
SURFACES IN ADVANCED CATALYTIC MATERIALS
P9-01
Characterization
of Ni-Zn/TiO2 nanoparticles synthesized by liquid phase
selective-deposition method
Yoji Sunagawa1, Katsutoshi Yamamoto2, Sarantuya Myagmarjav1, Hideyuki Takahashi2, Kiyoshi Kanie2, Nobuaki Sato2, Atsushi Muramatsu2, 1Graduate School of Environmental Studies, Tohoku University, Sendai, Japan, 2Institute for Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
Liquid phase reduction method is among various methods to synthesize nanometer-size metallic particles as catalyst. It has been reported that nickel and nickel-zinc nanoparticles synthesized by liquid-phase reduction method had amorphous-like structure with a diameter from 5 to 10 nm. Additionally, the catalytic activity was promoted for 1-octene hydrogenation by adding Zn to Ni nanoparticles. However, unsupported nanoparticles lost their high catalytic activity due to aggregation. In order to solve this problem, we have been reported that Ni nanoparticles were selectively deposited onto support materials such as TiO2. In the present study, the addition of Zn proved to decrease the nanoparticles size, leading to the increase in the total area of catalytically active Ni surface. In addition, nanoparticles were highly stabilized by the deposition on TiO2, so that the catalytic activity of Zn-added TiO2-supported Ni nanoparticles (Ni-Zn/TiO2) in the 1-octene hydrogenation was ca. 10 times higher than that of unsupported Ni nanoparticles.
NANOSTRUCTURES FOR QUANTUM DEVICE
TECHNOLOGY
P10-01
Material Properties
Optimization for
L. Fedichkin1, A. FEDOROV1, V. Privman1 and M. Yanchenko2, 1Center for Quantum Device Technology, Department of Physics and Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY, 2Russian Academy of Sciences, 34, Nakhimovsky prosp., Moscow, Russia, fedorov@clarkson.edu
Different approaches in quantifying environmentally-induced decoherence are considered. We identify a measure of decoherence, derived from the density matrix of the system of interest, that quantifies the environmentally induced error, i.e., deviation from the ideal isolated-system dynamics. This measure can be shown to have several features useful for optimization of a particular quantum computer design which includes selection of the suitable materials and regimes for coherent control. As a representative example, decoherence of an electron in double quantum dot due to the interaction with acoustic phonons is considered for different experimentally accessible materials.
P10-02
Quantum Dynamics of Electron in a Cycle of Coupled Quantum Dots
L. FEDICHKIN, D. Solenov, C. Tamon, V. Privman, Center for Quantum Device
Technology, Department of Electrical and Computer Engineering, Department of
Physics and Department of Mathematics
and Computer Science, Clarkson University, Potsdam, NY, leonid@clarkson.edu
We derive the set of dynamical equations describing quantum evolution of electron in the array of semiconductor quantum dots forming circle. In the limit of week decoherence the asymptotically exact analytical solution of these equations is obtained. The effect of decoherence on particle dynamics at stronger decoherence rates obtained numerically is also presented. Results show non-trivial dependence of hitting and mixing times upon the decoherence rate.
P10-03
Loss of Coherence in a Qubit Subject to Time-Dependent Gates
D. SOLENOV, V. Privman, Center for Quantum Device Technology, Department of Physics and Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY, solenovd@clarkson.edu
We present the results of the investigation on decoherence processes in qubit systems manipulated by external gates. Different types of time-dependence for the gate functions are considered. We utilize Magnus unitarity-preserving expansion to formulate the approximation for the evolution operator suitable to handle essentially time-dependent gates. Estimates to decoherence of a qubit controlled by the external rotating wave are obtained.
P10-04
Decoherence and Loss of Entanglement
D. TOLKUNOV, V. Privman, Center for Quantum Device Technology, Department of Physics, Clarkson University, Potsdam, NY, tolkunov@clarkson.edu
We review our recent work establishing by an explicit many-body calculation for an open quantum-mechanical system of two qubits subject to independent noise modeled by bosonic baths, a new connection between two important issues in the studies of entanglement and decoherence. We demonstrate that the decay of entanglement is governed by the product of the suppression factors describing decoherence of the subsystems (qubits). This result is the first detailed model calculation proving an important and intuitively natural physical property that separated open quantum systems can evolve coherently, quantum mechanically on time scales larger than the times for which they remain entangled.
Our result also suggests avenues for future work. Specifically, for multiqubit systems, it is expected that similar arguments should apply “by induction.” This will stimulate research to develop appropriate quantitative measures of entanglement, and attempts to quantify entanglement and decoherence in a unified way.
P10-05
Qubit Decoherence due to
Interaction with Non-Ideal Phonon
S. SAIKIN1,2, V. Privman1, 1Center
for Quantum Device Technology, Department of Physics and Department of
Electrical and Computer Engineering,
Most recent studies of non-markovian evolution of a two-level quantum system due to interaction with a bath are based on a spin-boson model, where a thermal bath is represented by a set of non-interacting oscillators. However, in realistic systems the later assumption of non-interacting modes of a bath is not valid. We study how internal dynamics of a phonon bath due to phonon-phonon interactions and isotope scattering affects irreversible evolution of a qubit.
P10-06
M. SHEN, S. Saikin, M.-C. Cheng, V. Privman, Center for Quantum Device Technology, Department of Physics and Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY, shenm@clarkson.edu
Spin-polarized injection in an Fe(100)/GaAs(100) Schottky diode is
investigated by
P10-07
RKKY Interaction in 1D
Electron Systems
ALEX DEMENTSOV, Dima Mozyrsky, Denis Tolkunov, Center for Quantum
Device Technology, Department of Physics,
The indirect interaction between localized spins in 1D electron systems is considered within the frameworks of Luttinger model. It is shown that interaction between conduction electrons serving as carriers of indirect interaction between localized spins plays a significant role.
PREPARATION AND APPLICATIONS OF SOFT COLLOIDS (MICELLES, MICROEMULSIONS,
EMULSIONS AND RELATED SYSTEMS)
P11-01
Thermodynamic Approach on
Specific Interactions in Mixed Lipid and Carotenoid Monolayers
A. MOCANU1, G. Tomoaia2, Cs. Racz1, M. Tomoaia-Cotisel1, 1“Babes-Bolyai” University of Cluj-Napoca, Department of Physical Chemistry and Biophysics, and 2”Iuliu Hatieganu” University of Medicine, Department of Orthopaedic Surgery, 3400 Cluj-Napoca, Romania, amocanu@chem.ubbcluj.ro
Mixed lipid and carotenoid monolayers spread at the air/water interface, namely (1) egg lecithin : β-cryptoxanthin; (2) egg lecithin : β-cryptoxanthin palmitate; (3) egg lecithin : zeaxanthin monopalmitate; (4) distearoyl lecithin : zeaxanthin; (5) distearoyl lecithin : astaxanthin; and (6) distearoyl digalactosyl glycerol : astaxanthin have been investigated. The curves of surface collapse pressure versus monolayer composition are discussed in terms of surface mixture thermodynamics. It has been found that the system (1) presents a perfect behaviour throughout the entire range of composition, while systems (2) and (3) can be satisfactorily described by the regular solution theory. For systems (4) - (6) a new approximation is proposed, considering the formation of supramolecular associations in monolayers. The stability constants of the supramolecular complexes in monolayers are calculated and correlated to the specific interactions that can occur in these mixed monolayers in substantial agreement with the molecular structures of the investigated biocompounds.
P11-02
Formation of Nanolatices within Phase Segregated Micelles
S. ROGERS, J. Eastoe,
The growth of polymer nano-lattices in novel microemulsions has been studied. The systems used exploited the natural incompatibility of fluorocarbon and hydrocarbon materials to drive local phase segregation inside the microemulsion droplets. This was achieved by using a matrix of systems comprising of fluorocarbon and hydrocarbon surfactants and monomers.
Both thermal and UV initiated polymerizations have been carried out and the effect this has on the final lattices studied. These polymerizations have been followed via 1H NMR and SANS/SAXS and the final products imaged via TEM. Results will be reviewed and future prospects presented.
P11-03
Thermal and Rheological
Properties of Carbon nanotube-in-oil Dispersions
YING YANG1, George Z. Zhang2, Eric Grulke1, Gefei Wu2 , 1Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY, 2The Valvoline Company, P.O. Box 14000, Lexington, KY, yyang7@uky.edu
Prior work on asymmetric thermally conducting nanoparticles in dispersions with low thermal conductivity liquids has shown that it is possible to tailor fluids with higher thermal conductivities than the base fluid at modest volume fractions of nanoparticles. Stable and reproducible nanotubes dispersions require careful control of the dispersant chemistry as well as an understanding of their response to shear and temperature changes. This paper addresses the effects of dispersant concentration, energy per unit volume for dispersion, and nanoparticle loading on thermal conductivity and steady shear viscosity of nanotube in oil nanofluids. The thermal conductivities and viscosities of these dispersion correlate to each other, and vary with the size of large scale agglomerates, or clustered nanoparticles, in the fluids. Fluids with large scale agglomerates have high thermal conductivities. Dispersion energy such as sonication can decrease agglomerate size, but also breaks the nanotubes, decreasing both the thermal conductivity and viscosity of nanofluids. Developing high thermal conductivity nanoparticle dispersions may require a balance between the high thermal conductivity of agglomerate structures and the high viscosity of these fluids.
P11-04
Selective Aggregation of Morin in Different TritonX-100 micelles
Weiya Liu, Rong Guo, Yangzhou, University, 27 Wenhua Rd.,
Yangzhou, Suzhou, P. R. China, liuweiya@hotmail.com
Morin (3,2’,4’,5,7-pentahydroxyflavone) is one of the effective antioxidant substances from natural plants and vegetables which can occur dimerization in the solution. The interaction between morin and the TritonX-100 micelles are studied by electronic absorption, fluorescence emission, ATR-FTIR spectra, FF-TEM (Freeze-fracture TEM), and the ab initio quantum calculation. Some interesting results are found.
Morin
can be solubilized in the TritonX-100 spherical micelle mainly in the form of
the dimer and the hydrophobic force is the main driving force. The morphology
of the micelle is changed from
spherical to rock-like and the size of the single spherical micelle is
increased with the solubilization of the morin. Morin cannot be located inside
the TritonX-100 rod-like micelles because of the compact structure and limited solubilization
space of the rod-like micelles, but morin can exist in the form of the monomer
and link the rod-like micelle by forming H-bonding with TritonX-100 to form a
kind of network structure. The ab initio quantum chemical calculations of morin show that
the stable structure of morin is not planar with the phenyl (B-ring) connected
to the C-ring by a single C-C bond around which rotation can occur, and the
B-ring deviates with 38.98 o from the planarity. No matter morin interacts
with TritonX-100 micelle in the form of
monomer or dimer, the active site involves in the interaction is always the phenyl group in the molecule, which leads
to the limitation of the rotation of B-ring and the increased planarity of the
whole morin molecule. The
structure of morin dimer is determined by the nanoscale solubilization space of
the spherical TritonX-100micelle.The two B-rings (deviating with 38.98 o from the planarity of the morin molecule) are
linked by the H-bonding in a face to face mode making the two morin molecules pile up into dimer and the two piled up
phenyls are whole located in the TritonX-100 spherical micelle.
RHEOLOGY AND DYNAMICS OF COMPLEX FLUIDS
P12-01
Evaluating the Intrinsic Bending Force in Chiral Bilayer
Membranes by Molecular Dynamics Simulations
N. GOUTEV, Shimizu,
CREST, Japan Science and Technology Agency, Nanoarchitectonics Research Center,
National Institute of Advanced Industrial Science and Technology, Tsukuba
Central 4-4, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan, nikolay.v.goutev@aist.go.jp
Bilayer membranes made of certain lipids can form twisted or
helical ribbons as well as tubules with chiral molecular packing. According to
a current continuum elasticity theory, such chiral supramolecular structures
originate from an intrinsic bending force that appears in bilayer membranes
with broken chiral symmetry. All variants of the continuum theory developed so
far start by assuming a functional for the elastic energy of the bilayer
membranes and end up expressing the optimal dimensions of the supramolecular
structures in terms of several elasticity moduli. On the example of two
glucolipids, which form tubules and twisted ribbons, respectively, we show here
that instead of being assumed the relevant functional and elasticity moduli can
be derived by molecular dynamics simulations of model bilayer membranes with an
all-atom force field like CHARMM. The results of the simulations support
directly the concept of an intrinsic bending force in chiral bilayer membranes.
P12-02
Atomic Force Microscopy
Studies of Langmuir-Blodgett Films: Phase Transitions in Phospholipid
Monolayers
G. Tomoaia1, M. Tomoaia-Cotisel2, A. Mocanu2, C.-R. Ispas2, A. Dumitru2,I. Halaciuga3, 1”Iuliu Hatieganu” University of Medicine, Orthopedic Surgery, and “Babeş-Bolyai” University of Cluj-Napoca, 2Physical Chemistry and Biophysics Department and 3Physics Department, 3400 Cluj-Napoca, Romania, cispas@chem.ubbcluj.ro
Phase behavior and surface structure of dipalmitoyl phosphatidyl choline (DPPC) spread as Langmuir monolayers at the air/water interface in the absence and in the presence of two drugs in the aqueous phase, such as procaine (PR) or deferoxamine (DFO), at a drug concentration of 10-3 and 10-6 mole dm-3, respectively, have been investigated using Langmuir-Blodgett (LB) technique and atomic force microscopy (AFM). The LB films were transferred on solid substrates, like glass optically polished and mica, at different controlled surface pressures by using vertical transfer and horizontal deposition method. Depending on the lateral surface pressure, highly ordered structures and less organized features have been directly evidenced. In addition these observations reveal some specific molecular interactions between these biologically relevant biocompounds. The data also indicate that both procaine and deferoxamine can penetrate and interact with phospholipid monolayers stabilizing the membrane lipids at both internal and external membrane interfaces.
P12-03
The Rheology and Shear-Induced Microstructure of Nanoaggregate, Fumed Silica Dispersions
C. H. NAM, J. Wagner, Department of Chemical Engineering, University of Delaware, Newark, DE, wagnernj@udel.edu
The rheology of polymeric suspensions of fumed silica particles of varying volume fraction, sizes, and surface modifications are examined. Fumed silica particles are often described as aggregated, fractal-like structures. These fractal aggregate suspensions shear thicken at much lower particle loadings than suspensions of hard, spherical particles. For example, discontinuous shear thickening was observed for a suspension (fumed silica in polyethylene glycol) with a particle loading of only 7% by vol. In this work we explore the mechanism and underlying structure of fumed silica particle dispersions by rheology, microscopy, and light scattering. Thixotropy of the suspensions is also explored with rheological experiments. The results are compared to previous results for shear thickening in near hard sphere suspensions.
P12-04
Numerical Simulation of Particle-Surface
Interaction in a Turbulent Channel Flow
H. NASR1, M.D. Emami2, Ahmadi1, 1Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY, 2Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
This study presents a computational model for Lagrangian simulation of particle transport, dispersion, and deposition including the possibility of rebound from the wall in a turbulent channel flow. An empirical mean velocity profile for the fluid velocity and experimental data for turbulent intensities are used in the analysis. The instantaneous fluctuating velocities are simulated by a continuous Gaussian random field model. The particle equation of motion takes into account the Stokes drag, the Saffman lift, the Brownian motion, and the gravitational forces. The Brownian diffusion is simulated as a white noise process. Starting with an initially uniform concentration near the wall, an ensemble of particle trajectories is generated and statistically analyzed. Several simulations for deposition of aerosol particles of various sizes are performed and the corresponding deposition velocities are evaluated. The computational model predictions for particle deposition velocity are compared with the existing experimental data and earlier simulation results and favorable agreements are observed.
P12-05
Gas-Liquid Dynamic
Behavior in a Bubble Column Reactor
W. CHEN, G. Ahmadi, Department of Mechanical
and Aeronautical Engineering, Clarkson University, Potsdam NY, chenw@clarkson.edu
Bubble coalescence and breakup-up are
important processes that control the bubble size distribution in bubble column
reactors. An experimental and
computational study of the effect of gas superficial velocity on the bubble
size distribution in a (200×10×1000 mm3) rectangular bubble column was
performed. Bubble size distributions were measured using a high speed digital
CCD camera and analyzed by LabVIEW image process system. Dispersed gas-liquid flow in bubble
column was simulated by a population balance model Eulerian multiphase flow
approach within the FLUENT code. The mechanisms of bubble breakup by the
turbulence eddy and bubble coalescence were included in the analysis. It is seen that a central
wave-like bubble plume appears with two staggered rows of vortices which
control the roughly chaotic oscillation characteristics of the bubble
column. The relations between the
bubble size distributions in horizontal and vertical direction were studied.
The model predictions were found to agree well with the experimental data.
P12-06
The Use of Spin-Echo NMR
Experiments for the Investigation of the Dynamics in a Model Slurry System for
CMP Containing Silica Particles
FADWA ODEH, Yuzhuo Li, Department of Chemistry, Clarkson University, Potsdam, NY, odehfm@clarkson.edu
With continuous increase in the complexity of current microelectronic devices and integration of Cu as interconnect, it is required that CMP provides a good surface planarity with minimal surface defectivity. One of the prominent roles of the abrasive particles is its ability to interact with chemical components found in the slurry. Surface adsorption of chemical components on to the abrasive particles can alter the intended chemical and mechanical balance of the slurry. Slurries consisting of abrasive particles of similar characteristics but different surface adsorption characteristic may perform differently in a CMP process. Furthermore, the introduction of copper ions during copper CMP may exacerbate the complexity. These copper ions could interact with the chemical components in the slurry to form copper complexes and also could change the adsorption characteristic of the abrasive particles. The formation of the copper complex and the change in the adsorption characteristic of the particles could have a great impact on the copper CMP performance. Performance will be exemplified with silica based slurry.
The longitudinal relaxation times (T1) of the different components of CMP slurries were measured using Spin Echo-NMR (SE-NMR) at a constant temperature. The fact that NMR is non-invasive and gives information on the molecular level gives more advantage to the technique. The model CMP slurry was prepared in D2O to enable monitoring of T1 for the various components' protons. SE-NMR provide a very powerful tool to study the various interactions and adsorption processes that take place in a model CMP silica based slurry which contains BTA and/or glycine and/or Cu+2 ions, it was found that BTA is very competitive towards complexation with Cu+2 ions and BTA-Cu complex adsorbs on silica surface.
P12-06
Competitive surface
adsorption of key chemicals on abrasive particles in copper CMP slurry
SURESH KUMAR GOVINDASWAMY1, Fadwa Odeh2, Sameer Dhane2, Yuzhuo Li2, 1Department of Chemical Engineering, 2Department of Chemistry andCenter for Advanced Material Processing, Clarkson University, Potsdam, NY
Chemical mechanical planarization (CMP) is an enabling technology for the production of advanced semiconductor devices. It is used for producing global planar semiconductor wafer surface. One of the important constituent of CMP process is the CMP slurry. Slurry is a heterogeneous system consists of solid abrasive particles and reactive chemicals. Choosing appropriate slurry for the process will yield a better Cu CMP performance with less defects and high yield. To achieve this, it is important to understand the interactions among various components in the slurry. One of the prominent roles of the abrasive particles is its ability to interact with key chemical components found in the slurry due to its high surface area. During the CMP process the chemical components in the slurry undergo surface adsorption onto the abrasive particles. Surface adsorption of chemical components on to the abrasive particles can alter the intended chemical and mechanical balance of the slurry. It is equally critical to realize that such a surface adsorption characteristic is unique to each type of particles and the chemical profile of the surface. Slurries consisting of abrasive particles of similar characteristics but different surface adsorption characteristic perform differently in a CMP process. The difference in the surface adsorption characteristic between the abrasive particles results in variation in the interaction between the particles and the chemical constituent in the slurry.
In this talk, competitive surface adsorption of key chemicals on abrasive particles in copper CMP slurry will be discussed. The experimental techniques used in this study will be described. Some potential implications and applications will be discussed.
P12-07
A New Passivating System
for Copper CMP
Yuzhuo Li1,2, Junzi Zhao1,2, DEENESH BUNDI2,3, KRISHNAYYA CHEEMALPATI2,3, VIVEK DUVVURU2,3, 1Department of Chemistry, 2Center for Advanced Materials Processing (CAMP), 3Dept of Mechanical & Aeronautical Engineering, Clarkson University, Potsdam, NY, bundidk@clarkson.edu, cheemalk@clarkson.edu, duvvurvr@clarkson.edu
In today’s slurry for Chemical Mechanical Polishing (CMP) of copper interconnect during wafer processing for advanced microelectronic manufacturing, the commonly used passivating mechanism is based on the formation of a thin layer of water insoluble copper complex. The low solubility of such a complex film prevents the dissolution of copper which protects the lower lying area from chemical attack. One of the most commonly used compounds for such a purpose is benzotriazole (BTA). Although BTA has been widely used in commercially available CMP slurries and other corrosion prevention formulations, it also yielded many challenges such as post CMP clean, over sized particle formation during CMP, and batch to batch consistency.
This poster presents a study in which an alternative mechanism for passivating metal surface is suggested. More specifically, a surfactant system was used to replace molecules such as BTA to form an adsorption layer on the surface of copper. It is found that the strength of the passivation effect is a function of pH, surfactant structure, surfactant concentration, and counter ions.
In this poster presentation, some background information on CMP slurry requirement and working principles will be first introduced. A set of comparative experimental results based on BTA and a surfactant system will be described. The feasibility of using such a surfactant system for copper CMP slurry formulation, especially in the acidic region such as pH = 5, will be analyzed. An even broader implication of using such a concept in other anti-corrosion applications will be further speculated.
ROLE
OF PHASE SCIENCE IN COLLOID AND SURFACE SCIENCE
P13-01
Investigations of Emulsion Films using Electrochemical Methodology.
J. Czarnecki1, D. Exerowa2, K. Khristov2,
J. Masliyah3, E. Musiał3 and N. Panchev2,3, 1Syncrude
Canada Ltd., Edmonton Research Centre; 2Inst. Phys. Chem., Bulgarian
Acad. Sci., 3Dept. Chemical Material Eng., University of Alberta, czarnecki.jan@syncrude.com
A new method for studying properties of thin liquid emulsion films
has been developed. The Exerowa-Scheludko thin liquid film cell was modified by
inserting a pair of electrodes into the water containing compartments. DC
voltage applied across the film allowed measurements of a critical voltage at
which the film breaks. A small AC signal was used to measure the film
capacitance. Measurements were conducted for water –
P13-02
Stratification and “Stained Glass” Behaviour in Foam Films from Complex
Aerosol-OT Solutions.
Jan Czarnecki1, Jacob Masliyah2, Nikolay Panchev2,3,
1Syncrude Canada Ltd., Edmonton Research Centre, 2Dept.
Chemical Material Eng., University of Alberta, 3Inst. Phys. Chem.,
Bulgarian Acad. Sci., czarnecki.jan@syncrude.com
Stratification of foam films drawn from aqueous Aerosol-OT solutions at concentrations well below lamellar liquid crystal (LLC) phase boundary is due to layers of ordered micelles. However, at higher concentrations, where LLC coexists with normal micellar solution in bulk, film stratification is due to stacked bilayers of surfactant molecules. The distance between the ordered bilayers, i.e., d-spacing, in the film is smaller than that for the bulk LLC phase. As the Aerosol-OT concentration increases, the thickness at which the first stratification step occurs increases and the final equilibrium film thickness decreases. Contrary to popular believe the first stratification step can occur well above 60-70 nm. Indeed, for films showing LLC-like structure, film stratification was observed in films several micrometers thick. Here, the film is composed of a number of domains of uniform color (thus of uniform thickness) with sharp boundaries, resembling 'stained glass'. Those thick domains may coexist with black film domains, 18 nm thick, in a single film specimen.
P13-03
Capillary Forces between Surfaces in a Liquid Crystal
near its Isotropic-to-Nematic Phase Transition Temperature
H. SHINTO, K. Kobayashi, T. Hyodo, K.
Higashitani, Department of
Chemical Engineering, Kyoto University, Kyoto, Japan, shinto@cheme.kyoto-u.ac.jp
The interaction forces between the particle and plate in 8CB liquid crystal near its isotropic-to-nematic transition temperature have been measured in-situ using an atomic force microscope (AFM) with temperature controllers. As a result, we found that 8CB molecules orient perpendicular to the DMOAP-coated glass surfaces (i.e., homeotropic orientation), whereas they orient parallel to the graphite and the carbon surfaces (i.e., homogeneous orientation). When two surfaces were of the same kind, attractive forces were observed between them. These attractive forces are attributed to the confinement-induced phase separation of the liquid crystal. On the other hand, only repulsive forces were observed between two surfaces of the different kind.
P13-04
An ATR-FTIR Study of Dicarboxylic Acids
at the Hematite/Water Interface
YU SIK HWANG, John J. Lenhart, Department of Civil and Environmental Engineering and Geodetic
Science, The Ohio State University, Columbus, OH, hwang.156@osu.edu
The focus of the present study is on a molecular-level understanding of the bonding
mode and structure of simple carboxylic acids at the hematite/water
interface. We present results for
four simple dicarboxylic acids (phthalic,
maleic, fumaric, succinic acid) and investigate how surface complex structures
and modes are affected by small differences in the molecular structures of the organic
acids. Applying attenuated
total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and batch
adsorption experiments, we characterized the adsorption of these organic acids to
hematite as a function of pH, ionic strength, and surface loading. Our macroscopic results show that the pH
for maximum adsorption is closely related to the pKa2 of these
organic acids. In the circum-neutral
pH range the highest adsorption density is found for phthalic acid and maleic
acid, followed by succinic acid.
Fumaric acid shows the weakest adsorption. The IR spectra for adsorbed acids are similar
to the spectra for phthalate, maleate, fumarate, and succinate ion in solution,
exhibiting only small variations with pH, ionic strength, and surface
loading. We interpret these IR
results to indicate the presence of single dominant fully depronated outer-sphere
complex (i.e., FeOH2+X2-) for all of the dicarboxylic
acids in the study.
P13-05
IR-Raman Investigation of
the Structure and Energy Transfer Dynamics of a Reverse Micelle Surfactant
Layer
T.D. SECHLER1, J.C. Deak1, Y. Pang2, Z. Wang2, D.D. Dlott2, 1Department of Chemistry, University of Scranton, Scranton, PA, 2Department of Chemistry, University of Illinois, Urbana, IL, sechlert2@uofs.edu
IR-Raman spectroscopy is used to analyze the structure and energy transfer dynamics of a reverse micelle surfactant layer. This technique uses a femtosecond infrared laser pulse to excite a specific vibrational motion in the system while subsequently monitoring the anti-Stokes Raman signal with a second laser pulse at varied delay times. The movement of vibrational energy in the system can then be determined by analyzing the changes in the Raman signal. Also, the emulsions used in this experiment were formulated such that each structural domain of the system gave a unique response in the vibrational spectrum of the system allowing for a correlation between spectral and spatial resolution. Both the rate and mechanism of vibrational energy transfer across the interfacial region were then measured. The rate of vibrational energy transfer to the nonpolar continuum is shown to be dependent on where the energy was deposited into the system.
SYNTHESIS AND CHARACTERIZATION OF NANOMATERIALS FOR ADVANCED MICROELECTRONIC AND PHOTONIC APPLICATIONS
P14-01
New Liquid Mirrors from Silver Nanoparticles: Optimization of
Reflectivity by Controlling Nanoparticle Size
N. CARUFEL, E.F. Borra, A.M. Ritcey,
Center for Optics, Photonics and Lasers (COPL) and Department of Chemistry,
Laval University, QC, Canada, nancy.carufel.1@ulaval.ca
We have been investigating thin reflective surface films of silver nanoparticles at the air-water
interface. Such films represent a new class of liquid mirrors that constitute
an excellent alternative to mercury mirrors because of their low density and
low toxicity. The optical properties of the surface films clearly depend on
certain characteristics of the silver nanoparticles employed in their
fabrication. In particular, we have demonstrated that reflectivity depends on
the size and shape of the constituent particles. Larger nanoparticles (80-120 nm) form better
liquid mirrors than do smaller nanoparticles (20-50 nm). For this reason we have investigated the influence on particle size
of various experimental parameters related to the preparation of the silver
colloid. The suspensions of silver
nanoparticles are prepared by the citrate reduction of silver nitrate (AgNO3) in aqueous
solution. The concentrations of both silver and citrate ion are found to
influence nanoparticle size in an important way. The exact way in which citrate
is introduced (all at once or stepwise) also has an important effect on
nanoparticle formation. Finally, preliminary results involving the use of small
silver particles as precursor seeds suggest that this procedure has much
promise for the control of particle size through the number of germs
introduced. The particles are characterized by transmission electron
microscopy. The optical properties of the surface films are determined with a
UV-visible spectrophotometer equipped with a reflectivity accessory. Future
work will include experiments to establish the relationship between
nanoparticle size and surface film thickness.
P14-02
Nanoparticles of
Conjugated Polymer and Well-Organized Nanoporous TiO2 Shell
Kwang-Suk Jang, Jae Hyun Jeong,
Sung-Ho Cho, JONG-DUK KIM*, Department of Chemical &
Biomolecular Engineering, and the Center for Ultramicrochemical Process
Systems, Korea Advanced Institute of Science and Technology, Daejeon, Republic
of Korea, jdkim@kaist.ac.kr
Synthesis of conjugated polymer-TiO2 nanocomposites has been attracted for their useful applications in optoelectronic devices, such as solar cells, electrochromic devices, light-emitting diodes, and charge-storage devices, which make a heterojunction between organic and inorganic semiconductors where charge transfer occurs. A conjugated polymer-TiO2 core-shell nanocomposite could be obtained by synthesizing polymethineimine and nanoporous TiO2 shell simultaneously. Polymethineimine was synthesized by the ring opening polymerization of s-triazine as a complex with metal halide, such as ZnCl2, SnCl4, and TiCl4. In addition, an ordered array of nanoporous TiO2 was synthesized with frameworks of supramolecular assemblies. Recently, highly organized nanoporous TiO2 was prepared by hydrolysis of TiCl4 in the presence of surfactants or amphiphilic block copolymers. In this study, the core-shell nanoparticles of polymethineimine-nanoporous TiO2 were synthesized within a short time by adding s-triazine to the mother solution of nanoporous TiO2. The mixture of two triblock copolymers was used as a template material for nanoporous inorganic shell, and TiCl4 was used as a catalyst for the ring-opening polymerization of polymethineimine and as a precursor of TiO2.
P14-03
Synthesis and
Characterization of Polymer Encapsulated Nanoparticles for Microelectronic
Applications
PRASHANT MESHRAM, Richard Partch, Center for Advanced Materials Processing and Department of Chemistry, Clarkson University, Potsdam, NY, rpartch@clarkson.edu, meshraps@clarkson.edu
There are two well-researched methods for constructing the core-shell morphology of particles. The shell can be produced by adsorption of preformed macromolecules onto core surfaces by electrostatic or by non-solvent deposition methods. An alternate method involves mixing core particles with monomers and then initiating polymerization. This procedure is more favorable for obtaining a uniform coating of each particle because of the substantially higher accessibility of the active surface of cores for molecules of a monomer compared to the corresponding macromolecules. However, the formation of an organic shell on extremely small silica nanoparticles (~ 20 nm) by the same method has received little attention. In the present work; we demonstrate a process of coating of such small colloidal silica particles with polymers in two layers; the first layer is PDVB (polydivinylbenzene) and the second layer is PHEMA (poly2-hydroxyethylmetha-crylate). Results of several time based adsorption experiments are presented to verify the hypothesis of monomer adsorption on inorganic core with and without initiator. The presence of polymer encapsulating the silica surface was determined by FTIR spectroscopy, transmission electron microscopy (TEM) and ALV particle sizing instruments; while the amount of coated polymer on silica surface was assessed by thermogravimetric analysis (TGA). These polymer coated particles can be used as soft abrasives in CMP application to minimize defects.
SYNTHESIS, CHARACTERIZATION AND APPLICATIONS OF BIOINSPIRED NANOMATERIALS
P15-01
Formation and properties of polysaccharide-based polyelectrolyte
complexes
RODOLPHE OBEID, Piotr Kujawa, Françoise M.
Winnik, Department of Chemistry and Faculty of
Pharmacy, University of Montreal, CP 6128 Succursale Centre Ville, Montréal, QC, Canada
So far the formation of polyelectrolyte complexes has been mainly studied for synthetic polyelectrolytes. Here we describe the complexation between two charged polysaccharides, polycationic chitosan and negatively charged hyaluronic acid. Dynamic light scattering shows that upon mixing these two polymers form submicrometer particles with the hydrodynamic radius depending on polymer concentration, molar ratio as well as molecular weight of two complexing polyelectrolytes. Chain length of chitosan is the major parameter affecting the dimensions of the complexes, i.e. an increase in the molecular weight of chitosan results in the formation of larger particles. The complexes were additionally characterized by atomic force microscopy, which shows the granular morphology and the size similar to that determined from light scattering data. Finally, the thermodynamics of interaction between chitosan and hyaluronic acid was studied using isothermal titration calorimetry.
P15-02
Enzymatic Synthesis of a
Skin Scaffold
Krishna Balantrapu1, Monisha Madalaywala2, Anja Mueller1*, 1Department of Chemistry, Box 5810, Clarkson University, Potsdam, NY, 2Department of Chemistry, Carnegie Mellon University, Department of Chemistry, 5000 Forbes Avenue, Pittsburgh, PA
The objective of skin substitutes is to restore the anatomy and the function of the normal skin after healing of the wound. Artificial skin grafts heal with extensive scarring and loss of some of the skin functions.
We are developing a polymeric scaffold based on a cross-linked polysaccharide. Horse Radish Peroxidase is being used as a catalyst in the synthesis. All the materials synthesized are based on the Poly(glucuronic acid). Several copolymers and cross-linked polymers will be presented. Degradation studies of the polymers and the surface characterization will also be included in the presentation.
15-03
Development and Characterization of Biomimetic Interfaces Using
Lipid Bilayer Arrays on Patterned Polyelectrolyte Templates
Neeraj Kohli, Sachin Vaidya, Robert Y. Ofoli, Robert M. Worden, Ilsoon Lee, Department of Chemical Engineering and Materials Science, Michgan State University, E. Lansing, MI, ofoli@egr.msu.edu
We present novel and robust methods to produce arrays of lipid bilayers on patterned polyelectrolyte multilayers. Such arrays may be useful for high-throughput screening of compounds that interact with cell membranes, and for probing, and possibly controlling, interactions between living cells and synthetic membranes. Liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphate (monosodium salt) (DOPA) were found to adsorb preferentially on poly(dimethyldiallylammonium chloride) (PDAC) and poly(allylamine hydrochloride) (PAH) surfaces. On the other hand, liposome adsorption on sulfonated poly(styrene) (SPS) surfaces was minimal, due to electrostatic repulsion between the negatively charged liposomes and the SPS-coated surface. Poly(ethylene glycol) (m-dPEG acid)-coated surfaces were also found to resist liposome adsorption, as liposomes appear to only bind loosely to these surfaces. These results were exploited to create arrays of lipid bilayers by exposing PDAC, PAH and m-dPEG patterned substrates to DOPA/DOPC vesicles of various compositions. The patterned substrates were created by stamping PDAC (or PAH) on SPS-topped multilayers and m-dPEG acid on PDAC-topped multilayers, respectively. We characterized the resulting interfaces by total internal reflection fluorescence microscopy (TIRFM) along with fluorescence recovery after pattern photobleaching (FRAPP), quartz crystal microbalance (QCM), and fluorescence microscopy, to assess the feasibility of this approach. The results suggest that such biomimetic interfaces can be functionalized for potential applications as biosensors and in biocatalysis.