Symposium OrganizersCarlos J. Martinez, Purdue University
Zhiqun Lin, Iowa State University
Dong Ha Kim, Ewha Womans University College of National Sciences
Symposium Support 3M Company
National Science Foundation
AAA2: Synthesis and Assembly of Nanoparticles
Tuesday PM, April 10, 2012
Marriott, Yerba Buena, Salons 1-2
2:30 AM - *AAA2.1
Multicompartment/Multicomponent Micelles with Block Copolymer Blending through Kinetic Control of Solution Assembly
Darrin Pochan 1
1University of Delaware Newark USAShow Abstract
The combination of charged block copolymer architecture with the kinetic control of solvent processing offers great flexibility for the creation of new assembled morphologies in solution and outstanding ability to control and manipulate those morphologies. When charged, acidic blocks are present, assembled structures are tunable in a well-defined way via co-assembly of organic bases with adjustable chain structure and control of the solution assembly pathway. A rich variety of polymeric nanostructures have been made such as toroids, disks, and helical cylinders from poly(acrylic acid)-containing diblock and triblock copolymers in THF/water mixtures with multiamines to complex with the PAA. Both the type and amount of multiamine were found to be critical for formation of specific micelles. Kinetic pathways and temporal stabilities of different micelles and nanoscale aggregates have also been studied. Due to low chain exchange dynamics between block copolymeric micelles in solution, global thermodynamic equilibrium is extremely difficult, if not impossible, to achieve. In our block copolymer/THF/water/multiamine quaternary systems, thermodynamics and kinetics of morphological evolution are governed by three important factors, including chain length of hydrophobic blocks, ratio of THF to water, and the interaction of multiamine with hydrophilic PAA block in the corona. Slow kinetics associated with these factors in solution greatly hinders the system from reaching a global equilibrium. However, by taking advantage of slow kinetics behavior of polymeric micelles in solution, one can purposely produce multicompartment micelles and mulitgeometry micelles by now mixing different PAA-containing block copolymers together but forcing them to ultimately reside in the same nanoscale structure through kinetic processing. While kinetically trapped in common nanostructures, local phase separation can occur producing compartments. This compartmentalization can be used within common micelle geometries to make complex spheres and cylinders or can be used to make new nanostructures such as multigeometry aggregates (e.g. hybrid cylinder-sphere aggregates). All is possible through the kinetic control of the assembly process. Cryo transmission electron microscopy (cryoTEM), transmission electron microscopy (TEM), and small angle neutron or x-ray scattering are the primary tools used to characterize the above described nanostructures.
3:00 AM - AAA2.2
Thermoresponsive Assembly and Disassembly of Charged Gold Nanoparticles
Yiding Liu 1 Xiaogang Han 2 Yadong Yin 1 2
1University of California Riverside USA2University of California Riverside USAShow Abstract
Charged gold nanoparticles can be assembled into aggregated structures at low temperature, and disassembled at high temperature with addition of salt in agarose hydrogel. The reversibility and stability of the system are studied by temperature controllable UV-vis absorption spectroscopy based on the different plasmonic profiles during the transition between assembly and disassembly processes. A semi-quantitative theoretical model has been proposed based on both thermodynamic and kinetic considerations. The role of salt concentration and gold nanoparticle concentration are also investigated which qualitatively agree with the theoretic model. The effect of agarose was also studied and can be concluded that it can enhance the stability of the system at high salt concentration.
3:15 AM - AAA2.3
Building and Tailoring Ionic Nanoparticle Networks
Marie-Alexandra Neouze 1
1Vienna University of Technology Vienna AustriaShow Abstract
Recently ionic nanoparticle networks (INN) were reported in the frame of the remarkable development of new inorganic-organic hybrid materials based on nanoparticle assembly. The original method we developed to synthesize 3-D networks is based on the functionalization of metal oxide nanoparticles with ionic linkers, the bridging ligands containing imidazolium units. Recent publications pointed out the powerful synergy of ionic species with nanoparticles. Such synergy makes those new inorganic-organic hybrid materials promising candidates for many applications such as catalysis or electrolytes. The length and rigidity of the imidazolium bridging units was varied. The short-range order of the network was investigated via small-angle X-ray scattering. This short-range order was interpreted as originating from self-organization of the aromatic rings of the ligands bridging the nanoparticles by means of ?-stacking. This hypothesis was validated by luminescence investigations on the hybrid materials. Anion metathesis reactions were performed on ionic silica networks based on imidazolium chloride bridging units. The investigated salts were NaBF4, KPF6 and LiN(SO2CF3)2. X-ray diffraction experiments and Nuclear Magnetic Resonance analysis allowed following the anion metathesis. Small-angle X-ray scattering experiments confirmed that the anion metathesis only very slightly affected the short-range order of the network and did not influence the luminescence properties. The yield of the metathesis reaction was evaluated by energy dispersive X-ray spectroscopy. The anion metathesis reaction provides a tailoring tool for the hybrid material hydrophilicity. Additionally the methodology was extended towards the formation of hybrid material thin films using a layer-by-layer deposition method for the formation of imidazolium-based assemblies of photocatalytic titania nanoparticles. This provides a new route for the controlled processing of this promising class of materials.
3:30 AM - AAA2.4
Direct Assembly of Hydrophobic Nanoparticles to Multifunctional Structures
Zhenda Lu 1 Yadong Yin 1
1University of California, Riverside Riverside USAShow Abstract
Multifunctional particles in the micrometer or sub-micrometer scale that exhibit two or more different properties are highly desirable for many important technological applications, ranging from catalysis and energy to multimodal imaging, detection, and simultaneous diagnosis and therapy. Here, we present a general process that allows convenient production of multifunctional colloidal particles by direct self-assembly of hydrophobic nanoparticles on host particles containing thiolated silica surfaces. By starting with host particles containing a high density of surface thiol groups, hydrophobic nanocrystals of various compositions and combinations can be directly assembled onto the host surface. The assemblies will be further overcoated with a layer of normal silica to stabilize the assemblies and render them highly dispersible in water. Mercapto-silica can also be coated onto nonspherical objects to form new types of hosts that can immobilize nanoparticles and produce multifunctional nanorods, nanodisks, and nanowires. On the other hand, by forming another layer of mercapto-silica coating on the normal silica surface, nanoparticles of different compositions and properties can be introduced onto the host particle surface in a layer-by-layer (LbL) manner. Such assembly approach will provide the research community a highly versatile, configurable, scalable, and reproducible process to prepare various multifunctional structures.
3:45 AM - AAA2.5
Directed Placement of Gold Nanorods Using a Removable Template for Guided Assembly
Armin W Knoll 1 Felix Holzner 1 2 Cyril Kuemin 1 2 Philip Paul 1 James L Hedrick 3 Heiko Wolf 1 Nicholas D Spencer 2 Urs Duerig 1
1IBM Research - Zurich Rueschlikon Switzerland2ETH Zurich Zurich Switzerland3IBM Research - Almaden Almaden USAShow Abstract
The integration of bottom-up synthesized nanoparticles into functional devices is a promising strategy to achieve new functionality at low cost. However, in order to utilize the full range of unique nanoparticle properties, precise control of position and orientation on a target substrate is needed. Several top-down methods have been used to generate guiding fields or structures in order to guide the precise placement and orientation of nanoparticles. To achieve both constraints simultaneously is challenging, in particular for particle dimensions below 100 nm. Here, we present a new placement strategy using a temperature sensitive polymer film as a removable template to position and align gold nanorods onto an underlying target substrate . Guiding structures for the assembly of gold nanorods were written by thermal scanning probe lithography (tSPL) using polyphthalaldehyde (PPA) as a resist . Shape matching groove-structures were produced to capture and align gold nanorods of size 80nm × 25nm. Capillary assembly was used to assemble the nanorods into the PPA guiding structures. After particle assembly the PPA layer was removed cleanly by heating the sample to 215°C for 10s. The smooth decomposition and evaporation process of the PPA leads to a transfer of the nanorods to the underlying substrate without affecting their integrity and placement accuracy. The standard deviation of the angular misalignment and the position error were 25.2° and 10.3 nm, respectively. Residual free removal of the PPA was confirmed by ToF-SIMS and conductive AFM measurements. For future applications, our scanning probe-based method enables high resolution imaging and accurate detection of features on the target substrate prior to the patterning process using the same tip. Applying the presented removable template strategy, this opens up novel perspectives to register the guiding structures to precise locations of functional elements on the target substrate. Meeting a requirement for e.g. advanced photonic applications, the direct integration of asymmetric nanoparticles into devices with a high degree of control over particle position and orientation, thus becomes feasible.  F. Holzner, C. Kuemin, P. Paul, J. L. Hedrick, H. Wolf, N. D. Spencer, U. Duerig and A. W. Knoll, Nano Lett. 11, 3957 (2011)  A. W. Knoll, D. Pires, O. Coulembier, P. Dubois, J. L. Hedrick, J. Frommer, U. Duerig, Adv. Mater. 22, 3361 (2010)
4:30 AM - *AAA2.6
Electrochemical Synthesis of Conducting Polymer and Metal-Conducting Polymer Composite Nanospheres
Yongju Jung 1 Nikhilendra Singh 1 John Roylance 1 Kyoung-Shin Choi 1
1Purdue University West Lafayette USAShow Abstract
An electrochemical method that enables cathodic preparation of conducting polymer (e.g. polypyrrole and Poly(3,4-ethylenedioxythiophene)) nanospheres is developed. This method is based on in situ cathodic generation of an oxidizing agent that can oxidatively polymerize conducting polymers at the cathodic surface. The mechanism of cathodic polymerization, which couples electrochemical reduction and chemical oxidation, is quite different from that of conventional anodic polymerization, and results in the production of conducting polymers with new morphologies not accessible by anodic polymerization. In addition, it makes it possible to assemble metal-conducting polymer hybrid electrodes via one-step cathodic deposition. In this presentation, we will first examine the synthesis conditions and the mechanism of cathodic polymerization and show the morphologies of the resulting polymer electrodes composed of nanospheres creating a three-dimensional porous network. Then we will demonstrate one-step assembly of various metal-conducting polymer composite electrodes retaining the nanosphere morphologies and discuss their applications. This method will provide a simple and versatile route to combine a broad range of conducting polymers and metals with new nanoscale composite architectures that can be used for electrocatalysis, energy storage/conversion, and sensing applications.
5:00 AM - AAA2.7
Electrode-dependent Resistive Switching Characteristics of Maghemite (gamma;-Fe2O3) Nanoparticle Assembly on Flexible Substrate
Jaewoo Yoo 1 Quanli Hu 1 Yoon-Jae Baek 2 Chi Jung Kang 1 3 Hyun Ho Lee 4 Tae-Sik Yoon 1 2
1Myongji University Yongin Republic of Korea2Myongji University Yongin Republic of Korea3Myongji University Yongin Republic of Korea4Myongji University Yongin Republic of KoreaShow Abstract
Resistive switching characteristics of maghemite (?-Fe2O3) nanoparticles (NPs) dependent on electrodes were investigated with the structures of top-electrode(Al,Pt)/?-Fe2O3-NPs/bottom-electrode(Al,Pt)/polyethersulfone(PES). The 30 nm thick ?-Fe2O3 NPs layer coupled with Al electrodes showed both the unipolar and bipolar switchings with abrupt change of resistance. The HRS/LRS ratio was higher than ~102. The abrupt resistance switching with multilevel resistances is thought to be associated with the formation and sequential rupture of multiple filaments. The microstructure and composition analyses verified that the interfacial reaction between NPs and Al electrodes enriching the Fe concentration in NP layer occurred, which facilitated the filament formation. On the other hand, the resistance of NPs layer coupled with the inert Pt electrodes changed gradually with respect to the applied voltage. In addition, the current-voltage characteristics are in accordance with the memristive switching, presenting the gradually changed and retained resistance values determined by the previous bias conditions. The interfacial reaction was not observed with inert Pt electrodes. Thus the internal state of NP layer such as fraction of low and high resistive regions might be modulated and lead to memristive switching of NP layer. These results of switching characteristics, microstructure and compositional analyses verified the electrode-dependent resistance switching mechanism of ?-Fe2O3 NPs assembly, which pave the way to apply the colloidal metal oxide NPs to either nonvolatile memory or memristive devices from the electrode-dependent resistive switching characteristics.
5:15 AM - AAA2.8
Optical Forces vs Thermal Effects in Dense Metal Nanoparticle Ensembles
Eun Sohl Koh 1 Bogdan Dragnea 1
1Indiana University Bloomington USAShow Abstract
Manipulating nanoparticles into highly ordered structure requires an understanding of interparticle forces and role of external field and interfacial properties in thermodynamic equilibrium. Despite the technological importance, however, there is lack of direct experimental data concerning the effective pair potentials of small particles interacting in a solvent medium. Several theoretical papers have addressed the problem of optically induced dipole interaction between metal nanoparticles illuminated by a focused laser beam (L. Novotny and coll. 2008, L. Brus and coll. 2006). Interactions should be strong enough to overcome the Brownian motion at reasonable intensities and result in reversible particle association. These optical forces could be used to finely tune chemical equilibrium in solutions close to suprasaturation, thus controlling crystallization of metallodielectric materials. Moreover, having an adjustable optical force between nanoparticles could help to determine the interparticle chemical forces. Based on this idea, we attempted to determine whether optical forces between nanoparticles can be reliably measured free of thermal artifacts, preferably with a simple setup that probes an ensemble of particles, and whether the optical interaction can be used to reveal the differences in the surface treatments. Using a simple bright-field microscope setup, we experimentally observed that at surface plasmon resonance, a focused laser induces reversible concentration of the gold nanoparticles around the laser focus. Moreover, the profile of the nanoparticle distribution in the medium depends on the surface chemistry.
5:30 AM - AAA2.9
Critical Role of Surface Treatment in Mediating Crystal Domain Size of Nanoparticle Monolayers
Mostafa Bedewy 1 Jingjie Hu 1 A. John Hart 1
1University of Michigan Ann Arbor USAShow Abstract
Defect formation during particle self-assembly is not completely understood, and is a roadblock towards achieving large single-domain crystals that are required for many applications, ranging from optical devices to solar cells. Although, many methods of convective self-assembly of micro- and nanoparticles, such as drop-casting, dip-coating, and blade casting, have been studied to achieve large-area assembly of 2D crystals of particle monolayers, they all result in polycrystalline morphology with inherent inter-crystal boundaries and intra-crystal defects. Despite the apparent differences in all these methods, process-independent particle-particle interactions, as well as particle-surface interactions are primarily responsible for the resultant size of single-crystal domains, as they dictate the nucleation and growth dynamics. We have found that substrate surface charge is a determining factor for the crystal size in polycrystalline monolayers made by blade casting. This was informed by systematically varying the surface properties of glass substrates, after optimizing process parameters for blade casting such as casting speed, blade angle, and blade-surface gap. We utilize substrate treatment in air plasma as a means of tailoring the surface potential of glass substrates used for assembling 500 nm polystyrene spheres by blade casting, and correlate these measurements with crystal size distribution in monolayers. We show that higher negative surface potential leads to larger crystal domains for negatively-charged particles, and explain that based on lowering the energy barrier required for healing defects that randomly originate during crystallization. Our results provide insights into scalable production of a continuously growing macroscopic single crystal of functional particles in a roll-to-roll compatible process.
5:45 AM - AAA2.10
A Precise Understanding of Nanoparticle Size and Density Distributions with 2D Analytical Ultracentrifugation
Osman M Bakr 1 Randy P Carney 2 Jin Young Kim 3 Huifeng Qian 4 Rongchao Jin 4 Hakim Mehenni 1 Francesco Stellacci 2
1King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia2Ecole Polytechnique Federale de Lausanne (EPFL) Lausanne Switzerland3Massachusetts Institute of Technology Cambridge USA4Carnegie Melon University Pittsburgh USAShow Abstract
Nanoparticles (NPs) are finding many research and industrial applications, yet their characterization remains a challenge. Arguably, NP characterization and polydispersity have become rate-limiting steps, hindering the development and prospective uses of these promising materials. NPs' cores - often polydisperse - are coated by a stabilizing shell - generally varying in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Recent advances in sedimentation velocity analytical ultracentrifugation (SV-AUC) allow for the extraction of the sedimentation (s) and diffusion coefficients (D), and the relative concentration of the species present in solution during an experiment. Here we show a novel approach to transform the s and D distributions for NPs in solution into precise molecular weight (M), density (?), and particle diameter (dp) distributions. Studying samples of varying polydispersity and heterogeneity, and in various solvents, we demonstrate the ability to obtain M, ?, and dp distributions on NP samples of various sizes with unparalleled accuracy, achieving density information that would not be achievable otherwise, particularly for particles <10 nm. A single experimental SV-AUC run is sufficient for full NP characterization, without the need for standards or other auxiliary measurements. We provide a simple rule to estimate the particle composition.
AAA1: Nanoparticle and Capsule Synthesis for Drug Delivery and Nanoassembly
Tuesday AM, April 10, 2012
Marriott, Yerba Buena, Salons 1-2
10:00 AM - *AAA1.1
Smart Capsules for Controlled Release
Younan Xia 1
1Georgia Institute of Technology Atlanta USAShow Abstract
In this talk, I will discuss a number of smart systems that can be used for controled release applications. One of the systems is based on phase-change materials(PCMs)that undergo phase transition between solid and liquid states at a temperature slightly higher than the body temeprature. When temperature was below the melting point of the PCM, there was no release of drug due to the hydrophobic nature of the PCM. As the temperature was increased beyond the melting point, the PCM began to melt, and the drug was released at a controllable rate. By using colloidal particles made of gelatin, chitosan, and poly(D, L-lactide-co-glycolide) that have different solubility in water, we could manipulate the release pattern of the drug. We also demonstrated a dual temperature-regulated drug release system by incorporating the two different PCMs into the same device. As an attractive feature, we could easily alter the initiation temperature and release pattern of drugs by judiciously selecting different combinations of PCMs and materials for the colloidal particles.
10:30 AM - AAA1.2
Graft Copolymer Polyelectrolyte Complexes for Delivery of Cationic Peptides
Krista L Niece 1 Asa D Vaughan 1 Johnathan Abercrombie 1 Kai P Leung 1 David I Devore 1
1United States Army Institute of Surgical Research Fort Sam Houston USAShow Abstract
We are developing functional nanoparticles for biomedical applications that are comprised of polyelectrolyte complexes between novel anionic graft copolymers and cationic peptides. The graft copolymers are synthesized with amphiphilic pendent chains designed to stabilize the particles in solution and overcome extra- and intracellular barriers that limit effective drug delivery. Here we present the synthesis of the graft copolymers, their fabrication into self-assembled nanoparticle complexes with cationic peptides, the physico-chemical characterization of these nanoparticle complexes and a demonstration of their biological activity. Peptide-based therapeutics promise to revolutionize treatment for multi-drug resistant microbial infections, cancer and other diseases, but peptide susceptibility to enzymatic hydrolysis in vivo has limited their clinical use. For example, a number of cationic peptides such as Polymyxin B and KSL-W are known to have antimicrobial properties, but degrade within a few hours in vivo. For clinical translation, an effective delivery vehicle for these peptides is required that is structurally and synthetically simple and forms uniform, soluble complexes with a variety of peptide drugs to protect them from degradation and enhance their biological activity. Graft copolymers with synthetically tunable chemical properties have the potential to fulfill these requirements. Our laboratory has synthesized novel copolymers of anionic poly(alkylacrylic acid) backbones grafted with amphiphilic poly(ether amine) side chains using carbodiimide coupling. The extent of grafting, molecular weight, molecular dimensions and electrostatic properties of the copolymers and complexes are characterized by NMR and FT-IR spectrometry, GPC, light scattering and zeta potentials. The side chains are found to promote self-assembly into nanoparticles in aqueous solutions and influence the critical aggregation concentrations. Nanoparticle surface charges and size distributions for polyelectrolyte complexes of the graft copolymers with cationic peptides Polymyxin B and KSL-W and the cationic antibiotic gentamicin, are found to be dependent upon the component cationic:anionic charge ratios. We also demonstrate the effects of graft density and charge ratio on the degradation rates of the peptide-graft copolymer complexes using HPLC analysis. To demonstrate retention of the biological activity of the peptides in the graft copolymer complexes, we measure the minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentrations (MBEC) for planktonic and biofilm Staphylococcus aureus, respectively. We show that copolymer complexation does not inhibit drug activity and in some cases may enhance it. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.
10:45 AM - AAA1.3
Nanostructured Thin Film Devices for Controlled Ocular Drug Delivery
Daniel A Bernards 1 Kevin D Lance 1 Natalie A Ciaccio 1 Elliot Chan 2 Robert B Bhisitkul 2 Tejal A Desai 1
1University of California, San Francisco San Francisco USA2University of California, San Francisco San Francisco USAShow Abstract
As the development of protein-based therapeutics gains momentum, a current challenge for ocular therapies is highly efficacious delivery of protein-based therapeutics over the course of weeks to months. Contemporary delivery routes, such as injections, are hampered by patient compliance, discomfort, risk, and inconvenience, along with limited bioavailability and frequent administration. Consequently, a device capable of a constant rate of drug release is attractive to circumvent these obstacles to therapy. An attractive technology for such a device is the use of nanoporous materials. In porous materials, constant-rate diffusion is possible when the therapeutic of interest is comparable to the material pore size. Often described as "single-file" diffusion, this situation can lead to zero-order kinetics and a constant release rate. For most protein-based therapeutics, pores on the order of a few tens of nanometers are required. To this end, nanoporous polymers have been fabricated for delivery of protein therapeutics within the eye. By combining transport-controlling nanostructures and structural microstructures, the thin film devices fabricated in this effort are physically robust while maintaining functionality. Use of the biodegradable polymer polycaprolactone (PCL) enables a unique approach to degradable devices: because PCL maintains its structural integrity throughout the majority of its degradation time course, structural degradation can be engineered to follow the therapeutic lifetime of the device. As a benchmark for device performance, both antibodies and current ocular therapeutics like Lucentis have been tested. These devices have been investigated in vitro to develop desired release kinetics, payload stability, and polymer degradation. Further in vivo studies have been performed in rabbits to establish long-term biocompatibility, structural integrity, and functionality of these devices.
11:30 AM - *AAA1.4
RBC Membrane-camouflaged Nanoparticles as a Biomimetic Delivery Platform
Liangfang Zhang 1
1University of California San Diego La Jolla USAShow Abstract
Efforts to extend nanoparticle residence time in vivo have inspired many strategies in particle surface modifications to bypass macrophage uptake and systemic clearance. Herein I report a top-down biomimetic approach in particle functionalization by coating biodegradable polymeric nanoparticles with natural red blood cell (RBC) membranes including both membrane lipids and associated membrane proteins for long-circulating cargo delivery. This approach aims to camouflage the nanoparticle surface with the erythrocyte exterior for long circulation while retaining the applicability of the polymeric core. In vivo results revealed superior pharmacokinetics and biodistribution by the RBC-mimicking nanoparticles as compared to control particles coated with the state-of-the-art synthetic stealth materials. I will also report several new strategies for nanoparticle-based combination chemotherapy by concurrently incorporating two different types of drugs into a single polymeric nanoparticle with ratiometric control over the loading of the two drugs. The cytotoxicity of these dual-drug carrying nanoparticles was compared with their cocktail mixtures of single-drug loaded nanoparticles and showed superior therapeutic effect.
12:00 PM - AAA1.5
Fabrication of Polymer Brush Pattern through Colloidal Lithography
Aurore Olivier 1 Rodica Morarescu 1 Julie Pilate 1 Pascal Damman 1
1UMONS Mons BelgiumShow Abstract
During the last few years, the fabrication of patterned polymer surfaces emerged as promising materials for application in the field of surface technologies such as bio/chemical sensor, microfluidic devices, drug delivery etc. [1,2]. The manipulation and control of the surface properties of materials are essential to develop new application. In this respect, polymer brushes are largely used in patterning surface due to their high mechanical/chemical robustness and their ability to modify surface properties . Most of the methods used to develop pattern at nanometer scale require very costly instrumentation, which limits their practical applications. An inexpensive alternative to conventional lithography is the colloidal lithography. This method consists to deposit monodisperse colloidal particles onto various substrates and results in the self-assembly into 2-D hexagonal arrays . In the present work, the regular assembly of particles has been used as a patterning mask. The chemical vapor deposition of polymerization initiator in the particle interstices gave the possibility to enhance polymer growth in this specific area of the substrate. The polymer is formed directly at the surface of glass substrate by Atom Transfer Radical Polymerization (ATRP) of dimethylamino ethyl methacrylate (DMAEMA) initiated from a silane-based monolayer bearing bromoisobutyrate functionalities . The combination of colloidal lithography and surface-initiated radical polymerization formed a honeycomb pattern of thin PDMAEMA brushes. We proved the well control of the pattern dimension using different colloidal particle dimensions.  M. Welch, A. Rastogi and C. Ober, Soft Matter, 2011, 7, 297-302  H-Y Chen and J. Lahann, Anal. Chem., 2005, 77, 6909-6914  A. Olivier, F. Meyer, J-M Raquez, P. Damman, Ph. Dubois, progress in polym sci, 2012, doi:10.1016/j.progpolymsci.2011.06.002  N. J. Trujillo, S.H. Baxamusa, K. K. Gleason, Chem. Mater., 2009, 21, 742-750  A. Olivier, F. Meyer, S. Desbief, P. Verge, J-M Raquez, R. Lazzaroni, P. Damman and Ph. Dubois, Chem. Com., 2011, 47, 1163-1165
12:15 PM - AAA1.6
Hydrothermal Synthesis of Morphologically Controlled Barium Zirconate Fine Particles
Yuki Seino 1 Kiyoshi Kanie 1 Atsushi Muramatsu 1
1IMRAM, Tohoku University Sendai JapanShow Abstract
Multi-elemental perovskite have recently been noticed as a considerable interest because of their highly functional properties. In general, perovskite materials were prepared by solid phase method. Recently, the particles in size and shape control have been studied increasingly by liquid phase reaction to control the domain in the materials. However, it is difficult to control the morphology of the particles because of the difficulty of the dissolution-precipitation process of multi-elemental precursor. In the present study, barium zirconate fine particles precisely controlled in size and shape have been successfully prepared by the hydrothermal method by using barium hydroxide and zirconium complex as precursors. Tetra-i-propoxy zirconium was well mixed and aged with triethanolamine so that complexes stable against hydrolysis were formed. Decarbonated water was added to them, then the solution was well mixed with barium and sodium hydroxide at 60 °C. Then the resultant solution was thermally treated in an autoclave. The morphology of all the particles prepared by the precursor of [Ba] = 0.50 M, [Zr] = 0.25 M, [NaOH] = 0 - 2.0 M was spherical. Meanwhile, the particle mean size was decreased by addition of NaOH into the precursor solutions, since the nucleation is generally promoted by increase in pH. On the other hand, the particle morphology was also controlled to spherical and truncated dodecahedral by decrease in [Ba] and [Zr] concentration with fixing molar ratio Ba/Zr = 2.0. Particles were preferentially grown along (110) face in dilute precursor system. As the concentration became further lower, the edge growth of dodecahedral shape in a particle was essential.These preferential growth was caused by the change in the rate of the metal ion supply. Fluorescence property of doped barium zirconate fine particle will be expected to promoted because of the thorough control in size and shape for them.
12:30 PM - AAA1.7
A Theoretical Study of Embedded Nanoparticles Formation by Ion Irradiation
Kun-Dar Li 1
1National Univeristy of Tainan Tainan TaiwanShow Abstract
A number of materials containing nanoparticles have been extensively studied during the past decades, due to the wide range of their potential applications. In this study, a three-dimensional model was established to investigate the formation of embedded nanoparticles by ion implantation. The nucleation and growth process of nanoparticles, including Ostwald ripening, were described by a phase field model. The effects of implanted ion energy, ion flux and temperature, on the morphology of nanostructures were also studied by considering various distribution profiles of implanted ions along the depth of an irradiated martix, calculated from Monte-Carlo Transport of Ions in Matter (TRIM) code. According the numerical calculations, no precipitates or particles formed in the early stage of implantation due to a low ion fluence and insufficient time for ion diffusion. With increasing ion fluence, immiscible impurity atoms started to segregate as dispersed nanoparticles. For a very high ion fluence, a buried layer of implanted species developed via coalescence. These simulation results were fully consistent with many experimental observations. Our theoretical model gives a possible insight into the mechanism of embedded nanoparticles formation through ion-implantation technology.
Symposium OrganizersCarlos J. Martinez, Purdue University
Zhiqun Lin, Iowa State University
Dong Ha Kim, Ewha Womans University College of National Sciences
Symposium Support 3M Company
National Science Foundation
AAA4: Electric Field-assisted Particle Assembly/Microfluidic Generation of Particles and Capsules
Wednesday PM, April 11, 2012
Marriott, Yerba Buena, Salons 1-2
2:30 AM - *AAA4.1
Electric Field Assembly and Manipulation of Janus, Patchy and Microcircuit Particles
Orlin D Velev 1
1NC State University Raleigh USAShow Abstract
We will discuss how external AC fields could be used to directionally assemble and manipulate complex engineered particles of any size and complexity. One class of objects of specific interest for field-driven assembly includes Janus and "patchy" metallodielectic particles. We will discuss the origins of the directional polarization interactions leading to their assembly in complex anisotropic structures, ways to simulate the dynamics of the process and the effect of particle size and conductivity on the type of structure obtained. We will report how Janus particles consisting of a dielectric hemisphere and a conductive one could be driven by dielectrophoresis with planar electrodes into new types of staggered chains and anisotropic metallodielectric crystals. Patchy metallodielectric particles in AC fields form new types of networks and crystals of unusual symmetry by pre-programmed quadrupolar and hexapolar interactions. Finally, we will discuss how an additional level of complexity can be engineered to turn miniature semiconductor diode "particles" into prototypes of self-propelling micromachines and micropumps. The diodes suspended in water propel themselves electroosmotically when a uniform AC electric field is applied across the container. The direction of motion of these motile particles can be controlled by the signal parameters and they present rudimentary examples of self-propelling "microbots," that could be powered remotely from external sources.
3:00 AM - AAA4.2
Designing Magnetically Controllable Phoretic Swimmers
Alireza Sadeghi 1 Jonathan R Howse 1 Stephen J Ebbens 1 Matthew T Bryan 2
1University of Sheffield Sheffield United Kingdom2University of Sheffield Sheffield United KingdomShow Abstract
Moving nano and micron scale particles in fluids via in-situ conversion of chemical energy into propulsion has provoked great interest in recent years because of its potential in cargo delivery, fluidic transport and self-assembly. These Janus particles take advantage of the concentration gradient created by asymmetrical decomposition of hydrogen peroxide into oxygen and water on their surface to create propulsion. As a result of the Brownian motion on these length scales, directing these highly propulsive particles to a desired target is challenging. Although controlling metallic nano-rods by an external magnetic field have been previously achieved by other research groups, controlling polymeric nanoswimmers using this method has the advantage of boosting the potential of these particles in being employed in drug delivery systems because of their biocompatibility and their size response to the environment. Here, we present the progress we have made towards navigating polymeric phoretic swimmers via controlling the orientation of the particle using an external magnetic field. We introduce different types of propulsive magnetic particles fabricated through methods such as evaporating nickel onto one half of the particles' surface, distributing iron oxide crystals within the polymer matrix and covering polymeric microspheres with chromium dioxide nanoparticles. Next, we study the response of these magnetic Janus particles to a uniform magnetic field in different concentrations of hydrogen peroxide fuel. To accomplish this, the trajectories of propulsive particles have been recorded in a constant fuel concentration in the presence and the absence of a uniform magnetic field to determine the effects of the magnetic field on the direction and velocity of the particles. We report the quantitative values obtained by tracking the particles and this data facilitates the procedure of identifying the most responsive magnetic swimmers and the optimal field strength for directing them. Further steps of this study consist of utilizing the magnetic control technique in directed self-assembly to fabricate multi-particle nanoswimmer configurations with controlled trajectories such as rotational and transitional movements for particular applications.
3:15 AM - AAA4.3
Golidlocks Swimmers: Designing Optimum Devices for Drug Delivery and Microfluidic Transport
Stephen Ebbens 1 Jonathan Howse 1 Ramin Golestanian 2 Gavin Buxton 3 Alireza Sadeghi 1
1Sheffield University Sheffield United Kingdom2Oxford University Oxford United Kingdom3Robert Morris University Moon Township USAShow Abstract
Micron and nano-scale synthetic catalytic devices are able to produce propulsion in fluid environments, and can consequently be used to transport drug delivery systems and cells. To date, transport task demonstrations have used micron sized thrust producing components containing magnetic segments to prevent stochastic rotations off-course. However, little attention has been given to considering the optimum scale for these devices, and the relevant propulsion velocity scaling laws have not been theoretically or experimentally investigated. Furthermore, the potential to optimise and modulate unconstrained device size for autonomous, field-free transport tasks has not been adequately explored. To address these issues, we experimentally determine the velocity scaling law for spherical catalytic swimming devices, demonstrating significant enhancement in intrinsic propulsion velocity is possible by miniaturization to sub-micron scales. This advantage can be straightforwardly used to speed up existing magnetically controlled transport systems, and allow larger cargoes to be transported. Theoretical scaling predictions are derived from the self-diffusiophoresis model for propulsion and shown to be consistent with the experimental data, and used to estimate the limiting size for velocity enhancement. The intrinsic velocity scaling law is used as the basis for a model to predict catalytic swimmer transport rate as a function of size, allowing for Brownian phenomena. This shows that for a given transport distance there is a Golidlocks device size for fastest transport, and that this optimum size increases for longer distance transport tasks. This interplay reflects the inverse cubic relationship between device size and rotational randomization rate, resulting in intrinsically rapid smaller devices having rapidly randomized trajectories in the absence of external control. In fact we show that larger scale, intrinsically slower devices exhibit the fastest statistical transport rates over useful millimetre mescopic scales and can cover these distances within their characteristic rotational time, producing directed motion without the use of magnetic guidance. Exploiting this size-dependent transport behavior also provides a method to autonomously navigate synthetic swimming devices using size/shape changing materials such as responsive hydrogels. We use numerical simulations to demonstrate active chemotaxis in response to pH gradients, based on swelling data for responsive hydrogels suitable for incorporation into swimming devices. In summary, new scaling phenomena for synthetic self-motile materials are presented which suggest faster velocity and increased cargo pulling power for field constrained devices by further miniaturization. Whereas larger devices appear optimal for longer distance, directed autonomous transport. We also show the potential to use this scaling behavior to produce active chemotaxis.
3:30 AM - AAA4.4
Electric Field Assembled Anisotropic Composite for Thermal Dissipation Applications
Myong Jae Yoo 1 Ho-sun Lim 1 Seong dae Park 1 Woo sung Lee 1 Hyeung Gyu Lee 1
1Korea Electronics Technology Institute Seong Nam Republic of KoreaShow Abstract
The current trend in microelectronic components requires thermally conductive but electrically insulating materials. A candidate of such material is composite type material. Composite material is generally fabricated with ceramic particles to obtain thermally conductive property while polymer resins are used as matrix. Most known commercial types of composite materials are utilized as thermal pads, greases or as metal cladded printed circuit board devices. In this study, thermal conductivity of aluminum oxide (Al2O3) reinforced polymer composites was investigated. Aluminum oxide is a well-known thermal conductive material with good electrical insulation properties while meeting low cost. In order to enhance thermal conductivity of the composite, flake-like Al2O3 particles in the polymer matrix were electrically aligned to the direction parallel to the heat flow by application of DC electric fields. Also aluminum oxide particles with spherical morphology were used to fabricate microstructures. The effects of filler content, filler morphology, applied electric field on the microstructure and thermal conductivity of the composite were examined. As the electric field was applied, the occurrence of the microstructural changes, which is anisotropic alignment of Al2O3 particles in the matrix, this assemble of particles in anisotropic connectivity contributed to improvement of thermal conductivity of the composites by increasing thermal conducting path through the composite. Thermal conductivity of up to 1.3W/mK was obtained with filler loading of only 40vol% which is sufficiently higher thermal conductivity compared with other types of composites with similar filler loading amount.
3:45 AM - AAA4.5
Probing the Stability of Surface Chemistry Modifications to Gold Nanoparticles
Idah Pekcevik 1 Maryam Mahmoudi 1 Michael Paul 1 Byron D Gates 1
1Simon Fraser University Burnaby CanadaShow Abstract
Plasmonic gold nanoparticles have been widely used in sensing, drug delivery, tissue and cell imaging, photothermal and photodynamic therapies. Their surfaces can be modified with a wide variety of functional ligands that both impart stability as well as allowing these nanoparticles to be used for specific applications. Our aim is to enhance the stability of gold nanoparticles when suspended in biological media by selectively modifying the surfaces of these nanoparticles. This stability is desirable for applications that utilize the small size of the particles and their optical properties to deliver and release small molecules. One approach used to modify the surface chemistry of gold nanoparticles is through the self-assembly of alkanethiolates. We are interested in understanding the uniformity and robustness of the self-assembled monolayers of alkanethiolates on gold nanoparticles. This understanding is important for reproducibility of experiments when using these nanoparticles in applications relevant to both materials and biological sciences. sThe thermal and colloidal stabilities of these particles are, however, important for applications that include controlled molecular release and stable transport within biological systems. We followed the changes in the properties of the nanoparticles as a function of time to identify the stability of the surface coating within physiological conditions for periods of up to at least one month. Shifts in the plasmon resonances of these particles indicated instability of the particle shape, size and surface chemistry. These changes in shape and size were confirmed by the electron microscopy and particle size analyses. Alterations to the surface chemistry were tracked by monitoring changes in the surface charge. The stability of the decorated nanoparticles was assessed for a wide range of surface chemistries and solution compositions, including additives to destabilize the nanoparticles through competitive interactions with exposed surfaces. Some nanoparticle instability was only observed after long periods of analyses. This study provides important insight into the assessment of instabilities in the surface chemistry that depend on solution composition, temperature, and quality of the self-assembled monolayers.
4:30 AM - *AAA4.6
Functional Microparticles Fabricated from Compound Microfluidic Droplets
Takasi Nisisako 1 2
1Tokyo Institute of Technology Yokohama Japan2University of California, Los Angeles Los Angeles USAShow Abstract
We present microfluidic emulsion-generating systems for producing emulsion droplets with multiple internal compartments and report their applications to the fabrication of functional polymer particles. The width and depth of our microfluidic channels were typically 10-100 um, and the micro-grooves were fabricated primarily by deep reactive ion etching on a planar glass substrate. By infusing two differently colored (e.g., black and white) acrylic monomers as to-be-dispersed phases into the microfabricated channels on a chip, for example, we could prepare monodisperse Janus droplets with two miscible halves, each of which had a distinct color. Subsequent off-chip thermally induced polymerization yielded monodisperse Janus microspheres that had two differently charged halves, with CVs that were typically around 2%. The Janus particles can be used in twisting-ball displays. As another example of the application of compound droplets to particle synthesis, Janus or triphasic droplets consisting of mutually immiscible compartments can be used for synthesizing non-spherical particles. We produced such compound droplets by infusing a photo-curable acrylate monomer and a non-curable silicone oil as to-be-dispersed phases into the channels. The shape of the interfaces in these droplets is determined by the minimization of interfacial energies, and the interface can form snowman-like shapes at equilibrium. In the subsequent polymerization process, a non-curable segment acted as a fluid template. Thus, we could produce concave-convex acrylic particles. We demonstrated capillary-assisted photopolymerization of triphasic droplets and photopolymerization of alternately segmented liquid strings for producing uniformly shaped biconcave particles. These convex-concave particles functioned as optical microlenses. We also report how the production throughput of the abovementioned droplets and particles can be scaled up for industrial applications.
5:00 AM - *AAA4.7
Polymer Microgels: Microenvironments for Cell Studies
Eugenia Kumacheva 1
1University of Toronto Toronto CanadaShow Abstract
Polymer microgels with dimensions in the micrometer size range and precisely controlled size, composition and structure can be readily synthesized or fabricated using microfluidic methods. This presentation demonstrates several microfluidic approaches to producing hydrogel beads from biological polymers. The method exploits microfluidic emulsification of the precursor solution of the biopolymer and gelation of precursor droplets using ionic crosslinking or thermosetting. Furthermore, I will demonstrate new applications of these polymer microgels. One of the applications includes high-throughput generation of vast combinatorial libraries of cellular microenvironments with different compositions and mechanical properties. We show the effect of the properties of these microenvironments on cancer and stem cell fate. Another application exploits polymer microgels with varying dimensions and elastic properties as model cells to study their flow under confinement.
5:30 AM - AAA4.8
``Designer'' Droplet Templating for the Scalable Assembly of Nanostructured Colloidal Aggregates
Volodymyr Lobaz 1 Robin N Klupp Taylor 1 Wolfgang Peukert 1
1FAU Erlangen-Nuremberg Erlangen GermanyShow Abstract
The controlled assembly of nanoparticles into structured aggregates is realized by emulsification of non-polar nanoparticle dispersions with aqueous surfactant solutions and subsequent evaporation. The nanoparticles, deliberately functionalized with hydrophobic moieties, stay trapped within an emulsion droplet, and subsequent slow evaporation of the oil phase leads to the formation of dense, spherical colloidal aggregates in size range 50-250 nm. The dependence of the nanoparticle hydrophobicity on the amount of chemisorbed and physisorbed stabilizer as well as on the controllable transfer of particles from oil to aqueous phase was studied. A detailed study of the influence of the process parameters on the droplet and corresponding aggregate size distributions was carried out. Firstly the mean diameter of colloidal aggregates was found to be proportional to the oil volume fraction and inversely proportional to emulsifier concentration, factors which define the emulsion with coalescence dependent droplet size distribution. It was demonstrated that only coalescence during emulsification influences the droplet size distribution, whereas after emulsification the droplets remain stable. In general the concentrations of the surfactants used were two orders higher than is necessary for saturation of the water/oil interface required for complete transfer of nanoparticles from oil to aqueous phase. This confirms the droplet stabilization kinetics being the key parameter for the formation of the colloidal nanoparticle aggregates. We further studied the influence of the emulsifier (surfactant) on the colloidal aggregate formation. In particular, a narrowed size distribution was observed for polymer emulsifiers compared to low molecular weight ones. Although the former emulsifiers also act as thickeners, adding the shear thinning behavior to the continuous phase, we confirmed that the influence of polymers on the size distribution of colloidal aggregates was due to fast stabilization kinetics compared to the case of low molecular weight stabilizers. After evaporation of the droplet solvent, surfactant molecules remain on the colloidal aggregate surface and determine its charge and functionality. We demonstrate that from a judicious choice of mixtures of ionic and non-ionic surfactants the control over surface properties of aggregates was achieved, opening up numerous opportunities for the systematic design and fabrication of functional nanostructured materials.
5:45 AM - AAA4.9
Microfluidic Microfiber Synthesis - An Emphasis on Fiber Length Control
Janine Nunes 1 Krzysztof Sadlej 1 2 Jee I Tam 1 Howard A Stone 1
1Princeton University Princeton USA2Polish Academy of Sciences Warsaw PolandShow Abstract
Flexible high aspect ratio microparticles, such as microfibers, are of considerable interest for potential rheological and life science applications. This research is focused on the development of a simple microfluidic method for the synthesis of polymeric microfibers of controlled length. Using microfluidics, a stable jet of photopolymerizable monomer solution, surrounded by a non-reactive oil phase, can be formed and polymerized with ultraviolet (UV) light to form a solid microfiber. We explored the use of valve actuation and UV light modulation to control the length of the microfibers. In particular, the valve approach was developed to synthesize fibers with tunable lengths, which has not previously been demonstrated. We observed good, reproducible control of microfiber length as a function of the valve actuation frequency. Cross-linked poly(ethylene glycol) diacrylate microfibers with aspect ratios ranging from 9-140 were generated from a single device by changing only the frequency. Current efforts are focused on adding complexity to the fiber composition (hollow and core-shell microfibers) and fiber geometry (folded and helical microfibers).
AAA5: Poster Session
Wednesday PM, April 11, 2012
Marriott, Yerba Buena, Salons 8-9
9:00 AM - AAA5.1
Interfacial Features of Monodisperse Poly (methacryloyl phosphatidyl choline) Hydrogel Microspheres Fabricated in Micro-capillary Devices
Soyoun An 1 Min Kyung Kim 1 Jonghee Park 1 Youngsun Kim 1 Jin Woong Kim 1
1Hanyang University Ansan Republic of KoreaShow Abstract
Hydrogels are used extensively in many different industrial fields, including medicine, pharmacy, food, and also the basic sciences. One application, is their use as synthetic extracellular matrices for cell encapsulation and transplantation. In this application, hydrogel beads, whose sizes are usually in millimeter ranges, provide a three-dimensional hydrated structure that augments the mechanical integrity of the immobilized cells while simultaneously permitting the facile diffusion of nutrients and metabolites to and from the cells. The immobilized cells can act as micro-factories that produce hormones, such as insulin and growth factors. For this kind of applications, precision control over both hydrogel formation and cell density is needed. Moreover, the process must be biocompatible. These requirements represent a challenge to both the medical and engineering communities. This study introduces a flexible and straightforward method for generating monodisperse suspensions of hydrogel microspheres by using a microcapillary device-based microfluidic technique. The use of microfluidic approach enables tight control over the size and monodispersity of droplets as well as the interfacial property of monomer drop structures, which is essential for not only determining the loading level of encapsulated materials, but also regulating their transport kinetics. We show that fine-tuning of fluids that flow through a geometrically controlled tiny channel allows us to generate a wide variety of novel interfacila structures. This study fabricates a new type of hydrogel microsphers mainly consisting of poly (methacryloyl phosphatidyl choline) (PMPC). It has been reported that this polymer displays a highly enhanced biocompatibility due to the biological affinity of phosphatidyl choline moieties. By taking advantages of this, we try to enlarge biological applicability of PMPC hydrogel microspheres. Basically, we tune the architectures of aqueous monomer drops by changing flow properties as well as interfacial tension of injecting fluids. Then, the complex monomer drops suspending in oil are polymerized by UV irradiation, thus producing monodisperse PMPC hydrogel particles. We characterize not only how their surface affects the cell viability but also how encapsulated molecules behave through the internal structure of the hydrogel phase. We also hybridize inorganic nanoparticles, such as TiO2 and ZnO, with PMPC hydrogel microspheres, in order to experimentally demonstrate that the model inorganic nanoparticles are well immobilized in the molecular mesh of PMPC and reversibly display their original functions with no decays. The robustness and versatility of our microfluidic approach are expected to generate more complex hydrogel systems, thus creating new possibilities to engineer the key functions that are suitable for many advanced biological applications.
9:00 AM - AAA5.12
Characterization of Iron Disilicide Nanocrystals Synthesized from Gas Phase
Andras Kovacs 1 Robert Imlau 1 Martina Luysberg 1 Ervin Mehmedovic 2 Hartmut Wiggers 2
1Research Centre Juelich Juelich Germany2University of Duisburg-Essen Duisburg GermanyShow Abstract
Beta-iron-disilicide (?-FeSi2) is a promising thermoelectric material, because of its chemical stability and low cost. Fabrication of ?-FeSi2 nanostructures, however, is challenging due to its complex structure and narrow compositional range of single phase formation. In this work we report the first results of structural and chemical characterization ?-FeSi2 nanocrystals synthesized from gas-phase. ?-FeSi2 nanocrystals were fabricated by thermal decomposition of silane (SiH4) and iron pentacarbonyl (Fe(CO)5) in a gas phase reactor. The experimental conditions were optimized in order to fabricate the single phase of ?-FeSi2 nanocrystals. Structure of the samples was confirmed by X-ray diffraction measurements. The detailed structure and chemical composition of the ?-FeSi2 nanocrystals were studied using various transmission electron microscopy (TEM) techniques including aberration-corrected TEM and scanning TEM (STEM). The nanocrystals were prepared on lacey C-layer covered Cu microgrid directly from the powder and from organic solvents such as acetone, ethanol, toluol, isopropanol and distilled water. The bright-field (BF) TEM images revealed the formation of agglomerated nanocrystals with grain size of 20 to 40 nm. The crystallographic structure of the nanocrystal was studied using conventional and nano-beam electron diffraction The space group and lattice parameters showed a good match with the bulk parameters of ?-FeSi2 phase. High-resolution aberration-corrected TEM images revealed a formation of an amorphous shell on the surface of ?-FeSi2 nanocrystals. The shell composition was determined using electron energy-loss spectroscopy and energy dispersive X-ray spectroscopy measurements combined with STEM. The shell composition was found to be rich in oxygen and reduced quickly decomposes under the electron beam irradiation.
9:00 AM - AAA5.13
Preparation of Thickness and Composition Controlled Hollow Metal Oxide Spheres from Silica-templated Coordination Polymers
Hee Jung Lee 1 Juhee Son 1 Shin Ae Park 1 Moonhyun Oh 1
1Yonsei University Seoul Republic of KoreaShow Abstract
Hollow micro- and nanostructures have received significant attention due to their applications such as catalysts, chemical sensors, photonic devices, energy storage, chemical reactors, and drug delivery. Even though several methods are available for the fabrication of hollow structures, templating methods are very useful for the construction of products with narrow size distributions and clear-cut structural features. However, there are inherent drawbacks to immobilizing the desired materials on template surfaces, due to potential incompatibilities between materials. Here we report a novel facile method for the preparation of uniform hollow metal oxide particles through calcination and etching processes on starting materials of novel silica@coordination polymer core-shell structures, where a coordination-induced approach allows the immobilization of organic and metal building blocks onto silica templates as a form of coordination polymer. A calcination process transforms coordination polymers into metal oxides to induce the formation of silica@metal oxide and an etching process for the removal of silica templates results in the hollow metal oxides. The compositions of the resulting hollow metal oxides were easily tuned by preparing coordination polymer shell parts using different metal sources during synthesis of silica@coordination polymer core-shell precursors. This novel method may provide a viable general approach for the fabrication of hollow metal oxides with a variety of compositions, sizes, and layer thicknesses. Such oxides could be utilized in practical applications such as catalysts, chemical reactors, and drug delivery, because the compositions and properties of metal oxides can be changed by altering the compositions of the coordination polymer shell.
9:00 AM - AAA5.14
Controlled Synthesis of Fluorapatite Nanorods for Directed Self Assembly by Electrophoretic Deposition
Tammy Yuko Olson 1 Christine A Orme 1 T. Yong-Jin Han 1 Andrew J Pascall 1 Marcus A Worsley 1 Joe H Satcher 1 Joshua D Kuntz 1
1Lawrence Livermore National Laboratory Livermore USAShow Abstract
The optical properties of fluorapatite (FAP) make them promising candidates for laser applications. Recent advancement in laser ceramic manufacturing has shown FAP nanoparticles slip cast and manipulated in a magnetic field to create optically transparent, laser grade ceramics due to alignment of their crystal orientation. Electrophoretic depsition (EPD) offers a much more simple and less expensive alternative. We report the controlled synthesis and characterization of single crystal FAP nanorods for alignment and deposition by EPD. A surfactant was utilized to stabilize the FAP nanorods which resulted in a high zetapotential for increased mobility during EPD. Layers of aligned FAP were then created by an AC and DC field in a EPD cell, which will eventually be sintered to transparency. Controlled synthesis of FAP have a number of other implications in a wide range of fields and the EPD technique for manufacturing device assembly will be discussed in greater detail. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
9:00 AM - AAA5.15
Template-free Preparation of Size-controlled Hollow Polyimide Microspheres via Electrospraying Process
Jin Young Park 1 Kyung Ok Oh 1 Jong Chan Won 1 Haksoo Han 2 Yong Seok Kim 1
1Korea Research Institute of Chemical Technology Daejeon Republic of Korea2Yonsei University Seoul Republic of KoreaShow Abstract
The template-free fabrication of hollow polyimide (HPI) microsphere was carried out by the electrospraying process (ESP). Spherical polyimide (PI) particle can be controlled to have the hollow structure by tailoring the spraying mode during the ESP. Electrospray apparatus was designed to collect HPI microsphere using heat-resistance silicone oil acting as thermal imidization medium. The mean diameters of the hollow microspheres were controlled in the range from 10 up to 100 um by the polymer concentration, the flow rate. The results demonstrate that this method provides the simple template-free fabrication for HPI particles, which retains a hollow shape without the collapse of the shell even at high temperature, have great potential for various applications due to high thermal stability, low density, and low dielectric constant.
9:00 AM - AAA5.16
Facile Fabrication for Polyimide Nanosphere Containing Monodisperse Copper
Jin Young Park 1 Jong Chan Won 1 No Kyun Park 1 Kyung Ok Oh 1 Haksoo Han 2 Yong Seok Kim 1
1Korea Research Institute of Chemical Technology Daejeon Republic of Korea2Yonsei University Seoul Republic of KoreaShow Abstract
A spherical polyimide (PI) particles containing monodisperse copper nanoparticles were simply prepared from the solutions of Cu(acac)2 and poly(amic acid) (PAA) precursor using ultrasonic spray pyrolysis (USP) method without any reducing agent. Copper-containing PAA were synthesized using direct ion-exchange self-metallization process. The copper-containing PAA droplets prepared by USP method undergo the heat treatment for the imidization and the reduction of copper ion. We observed the variation of oxidation state of copper particles according to heating temperature and the molar ratio of copper precursor. Particles were characterized by FT-IR, ICP, XRD, SEM and TEM. Our approach is possible to obtain polyimide particles with high loading of metal without the aggregation. And these particles have potential for various applications such as catalyst, gas separation, and high dielectric material.
9:00 AM - AAA5.17
Nano Lanthanum Silicate as a Potential Solid Oxide Fuel Material
Jessica N Taylor 1 2 Collette Chorney 1 2 Michael T Klem 1 2 Rajendra Kasinath 3 2
1Montana Tech University of the University of Montana Butte USA2Montana Tech of the University of Montana Butte USA3Montana Tech of the University of Montana Butte USAShow Abstract
The synthesis of functional nano-materials for potential applications, such for MRI contrast agents, hyperthermia, and solid oxide fuel systems have recently produced significant and consistent breakthroughs. The control of unwanted toxicity, agglomeration, under mild "green" synthetic conditions are some of the areas that have seen considerable attention. There exist, however, unresolved problems including complex chemistry involving non-aqueous solvents, relatively harsh synthetic conditions, difficulty in obtaining stable particulate suspensions, and control over final particle size and morphology. This work focuses on the use of nanoscale lanthanum silicate oxyapatites as a potential zirconia replacement as a high ionic conductor in a solid oxide fuel cell. These nanoscale lanthanum silicate oxyapatites (nLSO) were synthesized using an aqueous based synthetic method under mild conditions of pH and temperature. The physical properties of these nLSOs were characterized by a variety of techniques including TEM, dynamic light scattering, and XPS. Further work has been carried out using varying dopants to control the ionic conductivity of the final material. The resulting materials were spin coated onto various substrates and tested under fuel cell conditions to evaluate their performance to relevant standards.
9:00 AM - AAA5.18
Synthesis of Hollow Ellipsoidal Silica Nanostructures Using a Wet-chemical Etching Approach
Henan Zhang 1 2 Daniel Akins 1
1The City College of The City University of New York New York USA2The City University of New York, The Graduate School New York USAShow Abstract
We have utilized wet-chemical etching of ellipsoidal silica nanoparticles to form silica nanoshells of a range of elliptical morphologies, with the thicknesses of the silica ellipsoidal nanoshells controlled through variation of synthesis conditions. A mechanism has been proposal to explain how the nanoshells are formed, and we have demonstrated that the porosity of the silica ellipsoid plays a role in the deposition-regrowth process. We have also, through appropriate functionalization of the silica surface, coated the ellipsoidal nanoshells with Au nanoparticles.
9:00 AM - AAA5.19
Study on Synthesis of PVA Stabilized Silver Nanoparticles Using Green Synthesis and Their Application for Biomaterial
JaYoung Cheon 1 Won Ho Park 1
1Chungnam National University Daejen Republic of KoreaShow Abstract
Nanoparticles (NPs) are extensively investigated in recent years because of their potentials in catalysis, optical, mechanical and electronic devices. For these NPs, the catalytic activity as well as their electrical, thermodynamic and chemical properties are dependent on their size and shape. The control over their morphology and size is thus an important aim. Specific control of shape and size are often difficult. Generally, this is achieved by varying the synthesis method, reducing agent, stabilizer, temperature and pH in the reaction system. Usually, metal NPs was prepared by chemical reducing method using organic solvents and toxic reducing agent. However, the environmental and biological hazards are usually caused due to the use of noxious reducing and/or stabilizing agents in the synthesis procedures, like N,N-dimethylformamide (DMF), Hydroxylamine(NH2), hydrazine (N2H4) and sodium borohydride (NaBH4), etc. With the increasing awareness of environmental protection, people are inclined to focus on the 'green chemistry'. So, in the past decade, synthesis of silver NPs have been studied using the hyaluronan, gelatin, starch, chitosan and water-soluble polymer, etc. as reducing and/or stabilizing agents instead of harmful material. Poly(vinyl alcohol) (PVA) is a water-soluble, non-toxic, biocompatible and biodegradable synthetic polymer. Based on these features, PVA has attracted considerable in the biomedical, plastics, and textile fields. In this study, silver NPs are prepared using poly(vinyl alcohol) (PVA) and maltose as stabilizing and reducing agents, respectively. And silver NPs precursor is silver nitrate. We tried to confirm the effect of temperature and pH on the formation of silver NPs. The size distribution and diameter of PVA stabilized Ag NPs were observed by Transmission electron microscopy (TEM) and the reaction rate were characterized UV-vis spectrophotometer. And we investigated the effect of PVA stabilized silver NPs on in-vitro burn wound healing ability.
9:00 AM - AAA5.2
Anisotropic Interactions between Plasmonic Patchy Particles Synthesized via a Template-free, Single Phase Wet Chemical Route
Huixin Bao 1 Dina Ibragimova 2 Andreas Hirsch 2 Robin N Klupp Taylor 1
1Institute of Particles Technology, University Erlangen-Nuremberg Erlangen Germany2Institute of Organic Chemistry LS II, University of Erlangenmdash;Nuremberg Erlangen GermanyShow Abstract
The study of colloidal particles with anisotropy in size, shape and chemical functionality has been a major research interest due to their unique properties and wide range of prospective applications. Among various classes of anisotropic particles, those having heterogeneous distributed surface properties i.e. patchy particles, have received much attention. Theoretical studies of the self- and directed-organization of patchy particles predict various possible arrangements, due to the particles' ability to experience anisotropic interactions with other particles and physical fields. As reported in the literature, methods for making patchy particles with strongly directional interactions are limited. Physical vapour deposition is the most common technique used to synthesize metallic patchy particles, by depositing metal onto a close-packed colloidal monolayer or multilayer. The number and geometry of patches can be somewhat influenced by the angle of evaporation and the orientation of colloidal layers. These techniques are however poorly scalable. In order to exploit the potential for patchy particles to organize into hierarchical functional structures with application potential it is necessary to develop highly scalable and reproducible techniques for their fabrication, storage and triggered assembly. In the present contribution we describe the optimization of facile, scalable and tunable fabrication procedures for the formation of metal patches on silica spheres and the hydrophobization of either the metal or exposed silica. We show that while gold patches can be readily formed on bare silica, these are easily removed from the core particles by the introduction of alkanethiols as well as novel bifunctional dendrimer molecules. To prevent this from occurring we use silica particles that have been partially functionalized with thiol groups to anchor the gold patch in place. Complementary approaches show that the exposed silica can be functionalized without damage to the gold patches. To study the effect of the number and size of patches on the interactions between the patchy particles we consider the electromagnetic interactions between the gold patches when the particles' stability is compromised e.g. by pH changes. The latter could be studied by optical techniques including UV/VIS/NIR spectrophotometry and spectroscopic magnetobirefringence measurements. In the latter case, we include a superparamagnetic core with the aim to show that this facilitates a directed interaction between the plasmon resonant patches.
9:00 AM - AAA5.20
Superhydrophobic Oleophobic Low Moisture Permeation Transparent Nanocomposite Film
Chieh-Ming Tsai 1 Yuan-Ling Chang 1 Sheng-Hao Hsu 2 Yu-Chieh Tu 1 Wei-Fang Su 1 2
1National Taiwan University Taipei Taiwan2National Taiwan University Taipei TaiwanShow Abstract
This research focused on the development of superhydrophobic oleophobic low moisture permeation transparent nanocomposite films. We utilized a three-step process to fabricate the films. The first step involved the synthesis of hybrid resins and fabrication of nanocomposite films. The resins contained a mixture of two different size SiO2 nanoparticles, tricyclodecane dimethanol diacrylate (TCDDA) and a photo-inititor (1-Hydroxy-cyclohexyl-phenyl-ketone, Irg184). The SiO2 nanoparticles were surface-modified by 3-(Trimethoxysilyl) propyl methacrylate (MPS) and then dispersed into TCDDA homogeneously with a 50 wt% of nanoparticles. Dense hybrid films of 60-200 ?m were prepared by casting the resins and photo-curing. In the second step, we treated the nanocomposite films with oxygen plasma for several minutes. Thus, the surfaces could be roughened and SiO2 nanoparticles could be exposed on the surfaces. Surface roughness was controlled by varying weight ratios of different-sized SiO2 in nanocomposites and the condition of oxygen plasma treatment. The final step was to introduce a 1H,1H,2H,2H-perfluorodecyl trimethoxysilane (PFDTMES) coating onto the surfaces the oxygen plasma-treated films by dip-coating of PFDTMES ethanol solution(2wt%). The wet nanocomposite films were then dried at 80°C for 10 minutes. The best-performance nanocomposite film is made from the resin containing 40wt% 70-100 nm SiO2, 10 wt% 20-30 nm SiO2 and 50 wt% TCDDA. It exhibits both superhydrophobicity and highly oleophobicity with a water contact angle of 161° and an n-1-octadecene contact angle of 131°, respectively. It also shows low moisture permeation of 1.44 g*mm/m2*day and good transparency of 80% in visible region for a 60 ?m film. This novel nanocomposite film has potential applications in the encapsulation of optoelectronics and self-cleaning surfaces.
9:00 AM - AAA5.21
Perfect Orientation-controlled Growths of Pure Silica MFI and BEA Zeolite Films on Substrates
Tung Cao Thanh Pham 1 Hyun Sung Kim 1 Ji Yoon Lee 1 Kyung Byung Yoon 1
1Sogang University Seoul Republic of KoreaShow Abstract
Zeolite films bear great potentials to be used in various fields. Dramatic improvements in their performances and large advances in zeolite science can be made if methods to grow them on substrates with the channel directions perfectly aligned in the vertical direction regardless of the thickness. However, despite three-decade long efforts, perfect orientation-controlled zeolite film growths have not been achieved. We now report facile methods to grow silicalite-1 films and pure silica BEA films on substrates with the straight or sinusoidal channels positioning perfectly upright regardless of the thickness. We also report the crucial condition to grow perfectly aligned zeolite films and the interesting properties of the perfectly orientation-controlled zeolite films and the dramatic improvements during their nonlinear optical and molecular sieve applications.
9:00 AM - AAA5.22
Compression and Aggregation-resistant Particles of Crumpled Soft Sheets
Jiayan Luo 1 Hee Dong Jang 1 Jiaxing Huang 1
1Northwestern University Evanston USAShow Abstract
Unlike flat sheets, crumpled paper balls have both high free volume and high compressive strength, and can tightly pack without significantly reducing the area of accessible surface. Such properties would be highly desirable for sheet-like materials such as graphene, since they tend to aggregate in solution and restack in solid state, making their properties highly dependent on the material processing history. Here we report the synthesis of crumpled graphene balls by capillary compression in rapidly evaporating aerosol droplets of graphene oxide. The average size of the crumpled, near spherical particles is in sub-micron range and can be tuned by the concentration of the starting graphene oxide. The crumpled particles are stabilized by locally folded, ?-? stacked ridges as a result of plastic deformation, and do not unfold or collapse during common processing steps. The crumpled particles exhibits strain-hardening behaviors, thus making them remarkable resistant to aggregation in either solution or solid state, and remain largely intact and re-dispersible after chemical treatments, wet processing, annealing and even pelletizing at high pressure. Compared to the regular, flat sheets processed under the same conditions, the crumpled particles consistently have higher surface areas. In addition, the surface area of crumpled particles is more robust, and much less sensitive to material processing history. The dimensional transition associated with the mechanical deformation effectively solves the aggregation problem of graphene without the need for any modification to material composition or surface properties. This should greatly benefit applications using bulk quantities of graphene, such as in energy storage or conversion devices. As a proof of concept, we demonstrate that microbial fuel electrodes modified by the crumpled particles indeed outperform those modified with their flat counterparts. Compared to common particulate materials, particles of crumpled sheets have an alternative set of rules governing their synthesis, structure and properties. Therefore, they could also serve a model system to explore a new set of processing-structure-properties relationship of ultrafine particles.
9:00 AM - AAA5.23
Extended Infrared Absorption on Metal Nano Particles
Jae Hong Park 1 Chi Won Ahn 1 Jun Yong Park 2 Seok Woo Jeon 2 Moon Seop Hyun 1 Hee Yeoun Kim 1
1Korea National NanoFab Center Deajeon Republic of Korea2Korea Advanced Institute of Science and Technology Deajeon Republic of KoreaShow Abstract
The intensification of infrared-active vibrational modes of molecules in close proximity to nanometer-thick metal films, commonly known as surface-enhanced infrared absorption (SEIRA), is receiving increased attention from both a phenomenological and practical viewpoint. The resonant excitation of Plasmon in metallic nanostructures can provide large field enhancements on the surfaces of metals, which in turn provide dramatic increases in the detected spectroscopic signals for molecules adsorbed on their surfaces. The most widely used surface enhanced spectroscopy (SES) is surface enhanced raman scattering (SERS), where the electromagnetic enhancement factor is proportional to the fourth power of the field incident on the molecule. Recently there has been a resurgence of interest in another type of SES, surface enhanced infrared absorption. It has been widely applied to surface trace analysis, bio-sensing, electro sorption, and electro catalysis because of its significant amplification of surface signal and simple surface selection rule. The surface enhanced infrared absorption can be observed easily on metal island films prepared by vacuum evaporation or sputtering and electrochemical or electroless deposition. Metal colloids also support the enhancement. Like surface-enhanced Raman scattering (SERS), SEIRA is chiefly of electromagnetic origin, that is, due to an increase in the local optical field exciting the adjacent molecule. Metal nano clusters much smaller than the wavelength of light facilitate the interaction of the infrared radiation with the metal and adsorbed molecules, resulting in the enhancement. It was explained that the enhancement is greatly affected by the size, and planer density of metal nano clusters compared with metal nano films. Phenomenological and theoretical difference of infrared absorption in broad ranges of wave length including near field to far field infrared rays between metal nano clusters and metal nano films. Especially, metal nano clusters exhibit much higher infrared absorption than metal nano films on broad ranges of wave length. The phenomenon of infrared absorption in the range of near infrared wave length was different from that of far infrared wave length. This different phenomenon involves shift of resonant peaks and absorption intensities on them. Also the planar density of the metal nano clusters suggests a mechanism to explain the phenomenon.
9:00 AM - AAA5.24
Formation of Hollow Au and Ni Silicide Nanospheres
Huang-Yen Lai 1 Chun-Wei Huang 1 Jui-Yuan Chen 1 Wen-Wei Wu 1
1National Chiao Tung University Hsinchu TaiwanShow Abstract
In this work, we demonstrate the solid state reaction of Au/Si and Ni/Si core/shell nanoparticels to form hollow Au and Ni silicide nanospheres. The fabrication of hollow Au and Ni silicide nanospheres has been investigated by ultrahigh vacuum transmission electron microscopy (UHV-TEM). Au and Ni nanoparticles were first synthesized by electron gun deposited Au and Ni on the SiO2 film, followed by annealing to form Au and Ni nanoparticles, and then the Si film was deposited to cover them. When the Au/Si and Ni/Si core/shell nanoparticels were annealed above 700°C, the non-equilibrium counter-diffusion of two species through an interface, the Au and Ni silicide nanoscale spherical shells were formed by Kirkendall effect. In addition, the effects of the thickness of Si shell and annealing temperature for solid state reactions were discussed. Owing to the unique structure and physical properties, the hollow nanospheres should be expected to be applied such as new functional materials in high efficiency catalysis, sensing, and drug delivery agents.
9:00 AM - AAA5.3
Silver-PPy Core-Shell Nanoparticles: Green Synthesis, Characterization and Application
Mincheol Chang 1 Elsa Reichmanis 1
1Georgia Institute of Technology Atlanta USAShow Abstract
Silver-polypyrrole (PPy) core-shell nanoparticles have been fabricated by a facile one-step green synthesis using silver nitrate as an oxidant and soluble starch as an environmentally benign stabilizer and a co-reducing agent. The morphologies of the silver-PPy core-shell nanoparticles prepared here were evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They were further compared with the morphology of bare silver nanoparticles (~50 nm) commercially available from Nanostructured & Amorphous Materials, Inc. An SEM image of the silver nanoparticles obtained after drying from deionized water showed that the particles underwent considerable aggregation. On the other hand, the SEM image of the silver-PPy core-shell nanoparticles prepared via the synthetic approach reported here, showed a relatively uniform, monodisperse film of spherical particles. These results clearly demonstrate that the PPy shells covering the silver nanoparticle surfaces efficiently prevented aggregation of the particles. The size distributions of the core and shell were controlled by injecting different amounts of pyrrole monomer. The diameter of the silver core ranged from 10 to 80 nm and the PPy shell ranged from 10 to 80 nm. In addition, the morphology of the particles was significantly affected by the reaction temperature, changing from snake like core-shell nanomaterials to spherical core-shell nanoparticles. To investigate the colloidal and chemical stability of silver-PPy core-shell nanoparticles, UV-vis absorption analysis was conducted in various solvents including acids, bases, ionic and organic solvents. As a result, it was demonstrated that the PPy shell enhances the colloidal and chemical stability of the silver nanoparticles. Finally, the core-shell materials exhibited high catalytic activity in the reduction of methylene blue dye with NaBH4. The approach we report here could provide for simple, cost effective, and enviromentally benign processes for the "green" fabrication of various metal-conjugated organic polymer core-shell nanoparticles and may have great potential for diverse applications.
9:00 AM - AAA5.4
Composition-tunable Multi Ball-in-Ball Hybrid Metal Oxides
Sora Choi 1 Dongwook Jung 1 Won Cho 1 Moonhyun Oh 1
1Yonsei University Seoul Republic of KoreaShow Abstract
Many examples of micro- and nano-scale particles made from atomic or molecular building blocks are known, with these systems having been extensively explored due to their useful properties. Currently, efforts are ongoing to manipulate the composition, as well as its size and morphology, of particles as part of systematic attempts to alter their chemical and physical properties. Within this context, chemical transformation has emerged a useful method for tuning the composition. Here we report a straightforward strategy for the synthesis of composition-tunable hybrid metal oxide particles with a unique multi ball-in-ball structure consisting of up to four continuous balls. To obtain these new products, we have taken advantage of the coordination polymer particle's (CPP's) unique nature in terms of reactivity and thermal behavior; this has allowed us to produce a broad range of spherical multi ball-in-ball hybrid metal oxides with tunable compositions. Our systems were logically formulated and prepared using the following processes; 1) CPP was prepared using a precipitation method, 2) a cation exchange reaction was used to effect composition transformation, and 3) a final calcination process was use to decompose the CPPs and to obtain the metal oxides. This work provides a way to access a variety of multi-compositional hybrid metal oxides, something that should facilitate their eventual use in practical applications.
9:00 AM - AAA5.5
Formulation and Characterization of Chitosan and Glycol Chitosan Nanoparticles for Pulmonary Administration of Low Molecular Weight Heparin
A. Trapani 1 M. Conese 2 S. Digioia 2 N. Ditaranto 3 Nicola Cioffi 3 L. Sabbatini 3 G. Trapani 1
1University of Bari Bari Italy2University of Foggia Foggia Italy3Universitagrave; degli Studi di Bari Bari ItalyShow Abstract
Low molecular weight heparin (LMWH) is a linear anionic polysaccharide used mainly as anticoagulant for prevention and treatment of deep vein thrombosis, pulmonary embolism and other thromboembolic disorders . However, LMWH exhibits poor oral bioavailability and consequently has to be administered via parenteral route. Due to poor patient compliance associated with injections, alternative routes for LMWH administration have been explored. Thus, it has been found that LMWH pulmonary delivery provides potentially therapeutic useful amounts of this clinically relevant anticoagulant . It is well known, indeed, that the pulmonary route is one of the most convenient and comfortable means of administering high molecular weight drugs via mucoadhesive micro- and nano-particles (NPs). Herein, the mucoadhesive Chitosan (CS)- and Glycol Chitosan (GCS)-based nanoparticles were explored as new delivery systems for LMWH administration to the lung. The particles were formulated in aqueous solution as already described  and a high LMWH content was detected. The chemical characterization of the LMWH-containing NPs was carried out by means of several techniques. In particular, X-ray photoelectron spectroscopy (XPS) was used in conventional mode to study the surface chemical composition of different types of NPs. Depth-profiling XPS analyses were performed as well, and they provided information on the NP surface chemical composition at various depths. As a result, the distribution profile of LMWH into the outer 80 nm of the CS and GCS NPs was reconstructed. Finally, selected NP formulations were administered to rats and the results were compared to the corresponding ones obtained by subcutaneous injection of the anticoagulant. References  R.I.Schulman, Pharm. Ther. 87, 1-9 (2000).  Y Qi et al. PNAS 101, 9867-9872 (2004)  A. Trapani, et al., Int. J. Pharm. Sci. 375, 97-10 (2009).
9:00 AM - AAA5.6
Synthesis of Mondisperse Nanocrystalline Magnetic Metal Oxides by Thermal Decomposition of Metal-organics
Joshua Hill 1 Ling Fei 1 Hongmei Luo 1 Shuguang Deng 1
1New Mexico State University Las Cruces USAShow Abstract
Iron oxide and cobalt oxide nanoparticles have a large number of uses in various fields of biomedicine, and engineering due to their small tunable size and magnetic properties. For example, these nanocrystalline metal oxides have proven useful for improvement of magnetic resonance imaging of cancerous tumors and environmental cleanup of carbon tetrachloride. Monodisperse colloidal suspensions of nanocrystalline iron oxide and cobalt oxide have been synthesized using thermal decomposition of metal-organic precursors with a surfactant which self-assembles to form metal-ligand complexes. It has been noted that the size of the metal oxide nanoparticles can be controlled by variation of synthesis time, and temperature. Transmission electron microscopy was performed to investigate the particle size and agglomeration with various ratios and species of capping ligands. Additionally electron diffraction, dark field imaging and x-ray diffraction were performed to confirm and investigate crystallinity of the colloidal suspensions.
9:00 AM - AAA5.7
Graphene-titanium Dioxide Composite for a Glucose Biosensor
HeeDong Jang 1 Sun Kyung Kim 1 2 Hankwon Chang 1 Jeong-Woo Choi 2
1Korea Institute of Geoscience amp; Mineral Resources Daejeon Republic of Korea2Sogang University Seoul Republic of KoreaShow Abstract
A glucose biosensor is of great concern because of its importance in the monitor of blood glucose for the treatment of diabetes.We investigated the synthesis of graphene (GR)-titanium dioxide (TiO2) composite for an enhanced glucose biosensor. The composite was prepared from evaporating droplets of a colloidal mixture of TiO2 nanparticles and graphene oxide by aerosol self assembly. Effect of GR-TiO2 concentration on the composite property was investigated. The morphological, structural and specific surface area of as-prepared composite were characterized by a field emission-scanning electron microscopy (FE-SEM), an X-ray diffraction (XRD), and N2 adsorption-desorption isotherms (BET), respectively. The GR-TiO2 composite was measured for the glucose biosensor through cyclic voltammetry measurements. Morphology of the as-prepared GR-TiO2 composite was spherical in shape. It was also observed that micron sized porous TiO2 particles were covered by GR. At higher concentration of GR-TiO2 in the colloidal precursor solution, larger size and higher specific surface area of composite were measured. The GR-TiO2 composite showed better catalytic performance for glucose redox than GR biosensor.
9:00 AM - AAA5.8
Study on Synthesis of Chitosan Stabilized Silver Nanoparticles Using Green Chemistry and Their Burn Wound Healing Effects
Yun Ok Kang 1 Won Ho Park 2
1Chungnam National University Daejeon Republic of Korea2Chungnam National University Daejeon Republic of KoreaShow Abstract
Over the past decade there has been increased emphasis on the topic of green chemistry. These efforts aim at the total elimination or at least the minimization of generated waste during chemical reaction. Utilization of nontoxic chemical, environmentally benign solvents and renewable materials are some of the key issues the merit important consideration in the green synthesis. Recently, since silver-based compound has been known for its antimicrobial, antifungal, and anti-inflammatory properties, it has been used for years in the medical field for antimicrobial applications. And also, water-soluble chitosan oligomer (CHI) is obtained by the hydrolysis of chitosan. Until now, many researchers have examined CHI as a promising material for biomedical applications on account of its good biocompatibility, biodegradability, antimicrobial and wound healing effects. Usually, chemical method was used to prepare metal nanoparticles. However, chemical method using chemical reducing agents and solvent are not too suitable to have application to medicine and medical area because they should have associated environmental toxicity or biological hazards. Development of adoption of sustainable processes through green chemistry is attractive about the elimination or minimization of chemical waste. In this study, the concept is how could get a more effective and environmental substitution of 1% silver sulfadiazine cream for burn wound dressing. The final goal is expecting to suggest new medicine that can accelerate the rate of burn wound healing using synergic effect of CHI-Ag NPs prepared by environmental green chemistry. Therefore, we tried to use simple technique, green chemistry for the preparation of silver-based nanoparticles using chitosan oligomer as both the reducing and stabilizing agent, and water as environmentally friendly solvent. And also, depend on reaction condition, the formation including reaction rate, activation energy of chitosan oligomer stabilized Ag nanoparticles (CHI-Ag NPs) were monitored by using UV-vis spectrophotometer, and also the spherical shape CHI-Ag nanoparticles were confirmed using transmission electron microscopy, moreover the structure and crystallinity were characterized. And, the effect of CHI-Ag NPs on in-vitro burn wound healing behavior was investigated.
9:00 AM - AAA5.9
Synthesis of Nanostructured Oxidizers for Controlling the Explosive Reactivity of Nanoenergetic Materials
Soo H. Kim 1 2 Ji Young Ahn 2
1Pusan National University Busan Republic of Korea2Pusan National University Busan Republic of KoreaShow Abstract
In this study, we demonstrate a simple and viable method for controlling the energy release rate and pressurization rate of nanoenergetic materials by controlling the relative elemental compositions of oxidizers. First, bimetallic oxide nanoparticles (NPs) with a homogeneous distribution of two different oxidizer components (CuO and Fe2O3) were generated by a conventional spray pyrolysis method. Next, the Al NPs employed as a fuel were mixed with CuO-Fe2O3 bimetallic oxide NPs by an ultrasonication process in ethanol solution. Finally, after the removal of ethanol by a drying process, the NPs were converted into energetic materials (EMs). The effects of the mass fraction of CuO in the CuO-Fe2O3 bimetallic oxide NPs on the explosive reactivity of the resulting EMs were examined by using a differential scanning calorimeter and pressure cell tester (PCT) systems. The results clearly indicate that the energy release rate and pressurization rate of EMs increased linearly as the mass fraction of CuO in the CuO-Fe2O3 bimetallic oxide NPs increased. This suggests that the precise control of the stoichiometric proportions of the strong oxidizer (CuO) and mild oxidizer (Fe2O3) components in the bimetallic oxide NPs is a key factor in tuning the explosive reactivity of EMs.
AAA3: Particle Assembly at Interfaces: Colloidosomes, Bubbles and Patterned Films
Wednesday AM, April 11, 2012
Marriott, Yerba Buena, Salons 1-2
9:45 AM - *AAA3.1
Physical Chemistry of Lipid/Lipopolymer Shelled Models of Medical Microbubbles
Marjorie L Longo 1
1University of California Davis Davis USAShow Abstract
In this talk, I will reflect upon my group's investigation of the richness of physical chemical behavior in microbubble shells resembling the lipid shells of certain medical microbubbles. These findings will then be related to our most recent work attempting to understand and engineer the performance of microbubbles. We found that a decrease in the permeability of the shell to air took place with increasing saturated acyl chain length and decreased disordered domain boundary density, as could be described by a modified energy barrier theory that incorporated a simple accessible area model. The morphology of microbubble shell collapse structures and shed particles depended upon both reduced temperature and area compression rate, a consequence of time-temperature superposition. Shell monolayer phase behavior and phase diagrams were strongly dependent upon saturated acyl chain length of the major component and number of chains in the minor emulsifier component (mono-acyl vs. di-acyl) and included discovery of a stabilised condensed stoichiometric complex (diC14PC3DSPE-PEG20001). Similarly, the bi-acyl emulsifier (lipopolymer) conferred on the shells 10X higher resistance to gas permeability, a consequence of the reduced disordered boundary density in the presence of this condensed component. These results should shed light upon formulation and performance of lipid-shelled medical microbubbles.
10:15 AM - AAA3.2
Covalently Cross-linked Colloidosomes
Kate L Thompson 1 Steven P Armes 1 David W York 2
1University of Sheffield Sheffield United Kingdom2Newcastle Technical Centre Longbenton United KingdomShow Abstract
Model poly(glycerol monomethacrylate)-based macromonomers have been used to prepare sterically-stabilized polystyrene latexes by either aqueous emulsion or alcoholic dispersion polymerization, affording mean latex diameters of approximately 107 nm or 1188 nm respectively as judged by dynamic light scattering (see K. L. Thompson et al., Macromolecules, 2010, 43, 2169). Such latexes have appropriate surface wettability to stabilize 25-250 ?m oil-in-water Pickering emulsions, depending on the latex concentration and oil type. Colloidosomes are formed by covalent cross-linking of the hydroxyl-functional stabilizer chains from within the oil droplets using a polymeric diisocyanate (tolylene 2,4-diisocyanate-terminated poly(propylene glycol). This oil-soluble cross-linker is confined within the oil droplets, allowing colloidosomes to be prepared at 50 vol % solids without any aggregation (see K. L. Thompson et al., Macromolecules, 2010, 43, 10466). Unlike the non-cross-linked Pickering emulsion precursor, the resulting microcapsules survive removal of the internal oil phase using excess alcohol. This confirms the robust nature of these colloidosomes. A method for controlling their permeability by exploiting the solvent properties of binary oil mixtures has also been evaluated. Microcapsule permeability has been assessed via dye release experiments. Less permeable microcapsules can be obtained by deposition of polypyrrole onto the colloidosome exterior. Finally, Pickering emulsions and colloidosomes can be prepared with the same latex particles using a membrane emulsification cell (see K. L. Thompson et al., Langmuir, 2011, 27, 2357). Careful optimization of the emulsification conditions enables a coefficient of variation (CV) as low as 25 % to be achieved. This is a significant improvement over conventional homogenization techniques, which typically give a CV of more than 50 %.
10:30 AM - AAA3.3
pH-responsive Pickering Emulsions Based on Poly[2-Diethylaminoethyl Methacrylate] Latexes
Andrew John Morse 1 Damien Dupin 1 3 Steve Armes 1 Kate Thompson 1 Keltoum Ouzineb 2 Peter Mills 2 Ron Swart 2
1University of Sheffield Sheffield United Kingdom2CYTEC Drogenbos Belgium3CIDITEK IK4 San Sebastian SpainShow Abstract
Emulsion copolymerisation of 2-(diethylamino)ethyl methacrylate in the presence of divinylbenzene (DVB) cross-linker and a hydrophilic macromonomer, monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA), at pH 9 and 70 °C afforded near-monodisperse, sterically-stabilised latexes at approximately 10% solids. Near-monodisperse particles were produced with a hydrodynamic diameter of 200-220 nm, (measured using dynamic light scattering (DLS)) and showed little dependence on the initial PEGMA stabiliser concentration. These lightly cross-linked latexes acquired cationic microgel character upon lowering the solution pH below the pKa of the cross-linked polymer (6.9). Increasing the degree of crosslinking leads to a systematic reduction in the latex pKa from 7.3 (homopolymer) to 6.9. Protonation of the latex produced a swollen microgel with a hydrodynamic diameter of 700 nm. DLS was used to monitor the latex-to-microgel transition, with the particle hydrodynamic diameter increasing by a factor of 3 upon protonation. Minimal hysteresis of the latex hydrodynamic diameter and zeta potential was observed when subjected to 20 latex-to-microgel transitions. The poly(2-diethylamino)ethyl methacryate (PDEA) latex was found to be an effective Pickering emulsifier at pH 10, forming stable oil-in-water Pickering emulsions when homogenised (12 000 rpm, 2 mins) with four model oils, namely n-dodecane and sunflower oil, isononyl isononate and isopropyl myristate. In contrast, homogenisation of the microgel at pH 3 with n-dodecane and sunflower oil did not produce a stable Pickering emulsion. Lowering the solution pH of a stable Pickering emulsion from 10.5 to 3 resulted in demulsification, which was monitored visually, and using in situ using laser diffraction. Six successive demulsification/emulsification cycles were performed on these PDEA-stabilised Pickering emulsions, with the oil droplet diameter showing no significant change for n-dodecane, isononyl isononate and isopropyl myristate. However, the sunflower oil droplet diameter decreased after each successive cycle from 65 µm down to 22 µm. The oil droplet diameter was also affected by the initial latex concentration. Decreasing the initial latex concentration produced larger oil droplets when using a 220 nm PEGMA-PDEA latex and n-dodecane as the oil phase.
10:45 AM - AAA3.4
Preparation of Spherical, Ordered Colloidal Aggregates Using Inkjet Printing
Enrico Sowade 1 Thomas Blaudeck 1 2 Reinhard R Baumann 1 3
1Chemnitz University of Technology Chemnitz Germany2Chemnitz University of Technology Chemnitz Germany3Fraunhofer Institute for Electronic Nanosystems (ENAS) Chemnitz GermanyShow Abstract
Bottom-up approaches such as self-assembly have attracted growing interest to generate three-dimensional micro and nanostructures with complex shapes. Such structures are interesting for collective functionalities, aiming for e.g. applications in photonics or medicine. In literature, there are a variety of conventional preparation methods such as sedimentation or vertical deposition. However, routes for an efficient manufacture of ordered aggregates with highly symmetrical shape independent of the substrate surface are rare. In this contribution, we present an approach to combine inkjet printing and self-assembly for the manufacturing of three dimensional, spherical aggregates . The aggregates consist of nanospheres arranged as stable ball-shaped structures and exhibit a high degree of symmetry. These aggregates, also called supraballs, are described in literature as photonic balls due to their large number of highly ordered particles, which gives them photonic properties. The properties are less determined by the material of their constituents but rather by their size, surface functionalities and mutual arrangement. By applying inkjet printing with an adapted control signal, small droplets of a water-based ink formulation containing monodisperse polystyrene nanoparticles are ejected out of the inkjet nozzles. The ejected droplets can serve as a confined geometry for the nanospheres in the carrier liquid during evaporation. As a result, the particles can form stable ball-shaped aggregates with hexagonal order, rendering this method suitable for any solid surface in dry environment. Due to evaporation-induced forces during the flight of the droplets, the ball-shaped aggregates can be deposited in appropriate patterns. Our results show, that it is possible to employ inkjet printing technology as a scalable manufacturing method for the preparation of three dimensional and highly ordered spherical aggregates independent of surface properties. The fabrication of these three dimensional nanostructures by combining digital printing technique and self-assembly processes could be a key step towards industrial scale production and industrial applications.  E. Sowade et al., Adv. Eng. Mater. 2011 (accepted) doi: 10.1002/adem.201100245
11:30 AM - *AAA3.5
Uniform Hydrogel Shell Particles; Fabrication, Shell Permeation, and Optical Responsiveness
Jin Woong Kim 1
1Hanyang University Ansan Republic of KoreaShow Abstract
Encapsulation techniques have gained great interests in a variety of fundamental researches as well as industrial applications in fields; they have provided efficient systems for protection and controlled release of encapsulated materials. Typical systems include micelles, liposomes, polymersomes, colloidosomes, polyelectrolyte microcapsules, hydrogel capsules, and polymeric micro- or nano-particles. Among them, there have been considerable studies on hydrogel-based capsules due to the bio-friendly process, high loading capacity, tunable permeability, and controllable phase properties by using external triggers. These advantages of hydrogel capsule systems can allow us to explore new substrates for biochemical processes and probing materials for diagnostics; there have been efforts to develop new types of capsules, which are suitable for these applications, by using sophisticated techniques, such as layer-by-layer assembly or microfluidics. However, to make them more widely useful, it is essential to develop techniques that enable fabrication of hydrogel capsules with controllable morphologies as well as uniform sizes, since these are critical to fine-tuning over the release kinetics of encapsulates. Moreover, they should be produced by using a simple process, thus making them more practical in ultimate applications. In this talk, we introduce a facile method for synthesizing monodisperse hydrogel shells, which are hollow-structured microcapsules. Our studies have demonstrated that poly(vinylamine) (PVAm) hydrogel shell particles can be fabricated by means of in situ hydrolysis and crosslinking reactions. The procedure, carried out using precursor polymer particles dispersed in a strong basic solution, is based on in-situ hydrolysis and subsequent creation of covalent bonds between the hydrolyzed polymer chains. The technique that is essential in our approach is to use polymer chains that are both hydrolyzable and disconnectable and to covalently crosslink the hydrolyzed polymer chains to each other. Here it is truly important to notice that the additional crosslinks are not homogeneously distributed in the hydrogel particles but is instead concentrated at the periphery. Selective removing the core part in the hydrogel particles enable us to generate uniform hydrogel shells. The controllability of shell permeation was investigated by testing species with various molecular weights. We also modified the surface of the shell with an oppositely charged biopolymer and evaluated its permeability. Our hydrogel particles are unique in that the shell phase, which consists of a PVAm network with many primary amine groups, can undergo strong interactions with other species. To demonstrate the applicability of this hydrogel shell system, the shell is hybridized with Au nanoparticles and its response to laser irradiation is investigated.
12:00 PM - AAA3.6
Block Copolymer Nanoparticles as Pickering Emulsifiers: Spheres, Worms and Vesicles
Steven Peter Armes 1
1Sheffield University Sheffield United KingdomShow Abstract
Methacrylic AB diblock copolymers are readily prepared using reversible addition-fragmentation chain transfer (RAFT) chemistry to polymerize a water-soluble monomer, 2-hydroxypropyl methacrylate [HPMA], at 70oC using a highly hydrophilic poly(glycerol monomethacrylate) [PGMA] as a macromolecular chain-transfer agent. As the PHPMA chains grow, they become hydrophobic, which drives the in situ self-assembly of the copolymer chains. This versatile aqueous dispersion polymerization formulation allows the synthesis of sterically-stabilized spherical nanoparticles of 25 to 100 nm diameter with excellent size control at around 10 % solids (Y. T. Li and S. P. Armes, Angewandte Chem., 2010, 49, 4042). Varying just two synthesis parameters enables the final diblock copolymer morphology to be varied systematically from spheres to worms to vesicles. If block copolymer vesicles are targeted, the block copolymer morphology evolves during the growth of the PHPMA block, passing from spheres to worms to vesicles. Transmission electron microscopy studies of the sampled reaction solution reveal fascinating intermediate nano-structures that provide useful insights regarding the evolution of the copolymer morphology, particularly for the worm to vesicle transition. (A. Blanazs, S. P. Armes et al, JACS, 2011, 133, 16581). A detailed phase diagram has been elucidated for one particular formulation, which allows the reproducible synthesis of nanoparticles with predictable morphologies. We have examined the use of these new spheres, worms and vesicles as Pickering emulsifiers for non-polar oils. In each case, stable oil-in-water emulsions are obtained, as judged by conductivity measurements. Emulsion droplet size distributions were characterized by optical microscopy and laser diffraction studies. Moreover, the hydroxyl groups on the PGMA chains allows cross-linking of these nanoparticles at the oil/water interface using an oil-soluble polymeric diisocyanate cross-linker, leading to novel colloidosomes.
12:15 PM - AAA3.7
Mark Williams 1 Steven P Armes 1 David W York 2
1Sheffield University Sheffield United Kingdom2Pamp;G Newcastle United KingdomShow Abstract
Poly(ethylene imine) (PEI) has been adsorbed onto the surface of Laponite clay nanoparticles from aqueous solution at pH 9 in order to produce an effective Pickering emulsifier. This protocol allows formation of stable oil-in-water Pickering emulsions via homogenization of sunflower oil at 12 000 rpm for 2 min at 20 °C. The effect of varying the extent of PEI adsorption on the Pickering emulsifier performance of the surface-modified Laponite is investigated using aqueous electrophoresis, thermogravimetric analysis and laser diffraction studies. A minimum volume-average emulsion droplet diameter of around 60 µm was achieved at a Laponite concentration of 0.50 % by mass when utilizing a PEI/Laponite mass ratio of 0.50. Such emulsions proved to be very stable towards droplet coalescence over time scales of months, although creaming is observed on standing within days due to the relatively large droplet size. These conditions correspond to submonolayer coverage of the Laponite particles by the PEI, which should ensure that there is little or no excess PEI remaining in the aqueous continuous phase. This situation is confirmed by visual inspection of the underlying aqueous phase of the creamed emulsion when using fluorescently-labelled PEI. Finally, these emulsions are converted into colloidosomes via cross-linking of the primary and/or secondary amine groups on the PEI chains adsorbed at the Laponite surface using two commercially available reagents, namely, oil-soluble poly(propylene glycol) diglycidyl ether (PPG-DGE), and water-soluble poly(ethylene glycol) diglycidyl ether (PEG-DGE). These colloidosomes were sufficiently robust to survive the removal of the internal oil phase after washing with excess alcohol, as judged by optical and fluorescence microscopy.
12:30 PM - AAA3.8
Synthesis of Rigid Core/Soft Shell Submicrospheres and the Application of Opal Films
Yu-Cheng Kuo 1 Chen Hui 1
1National central university Zhongli TaiwanShow Abstract
Soap-free emulsion polymerization has been chosen to fabricate monodisperse core-shell P(St-co-MAA)/P(St-co-BMA) spheres by adding BMA monomer during the PS polymerization at boiling state. The ratio of P(St-co-MAA) to P(St-co-BMA) were effected by the adding timing of BMA monomer. The DSC result indicated that core-shell structure could be observed when the BMA adding timing was higher than 40% of PS conversion, and the glass transition temperature of P(St-co-BMA) could be controled the range of temperature between 41.9 oC and 56.7oC. These core shell structure spheres were used for fabrication the colloidal crystal film, and the photonic band gap can be shifted from 455 to 631 nm by using different size of core-shell spheres. All sample can form a film at 30, 50, and 80oC, but the pencil hardness of photonic crystal film can efficiently increased from lower than 6B (normal spheres) to HB(core-shell spheres), These results made the colloidal crystal useful in bioassay, photonic paper, and so on.
12:45 PM - AAA3.9
Deposition of Nano-sized Noble Metals onto the Surface of Carbon Nanocapsules
Boris Bokhonov 1
1Institute of Solid State Chemistry, Siberian Branch, Russian Academy of Sciences Novosibirsk Russian FederationShow Abstract
New carbon nanomaterials of different morphologies (nanotubes, fullerenes, graphene) are among the most popular nano-objects under intense investigation during the recent decades. However, in our opinion, not only search for and discovery of the new forms of carbon may be rather interesting from the scientific and practical points of view. Investigation of the physical and chemical properties of already known carbon nanostructures like metal core - carbon nanocapsule shell may turn out to be useful, too. Low pressure dc arc discharge was used to produce the carbon nanocapsules-metal (Ni, Fe, Mg, Cu and Bi) samples. The deposited materials consisted of metal nanoparticles coated by spherical carbon nanocapsules. The deposition of the nanoparticles of noble metals (platinum, gold, silver) onto the outer surface of carbon capsules was performed using the galvanic replacement reaction which is widely used to obtain hollow metal nanostructures. In this case, unlike for the widespread methods of metal deposition on carbon surface, no additional surface modification was required. Aqueous suspensions of the powder containing metal nanoparticles encapsulated in amorphous carbon shells were treated with the solutions of hydrochloroauric or hydrochloroplatinic acids or with silver nitrate solution. The formation of the nanoparticles of noble metals in the galvanic replacement reaction was detected on the basis of the appearance of X-ray reflections of metals in the diffraction patterns of the solid products of treatment of carbon-encapsulated metal and on the basis of the presence metals (Ni2+, Fe3+, Mg2+, Cu+, Bi3+) ions in the solution and solid depositions. Electron microscopic studies showed that for the short time of treatment with the solutions of HAuCl4, H2PtCl6 or AgNO3, respectively, the nanoparticles of metal gold, platinum and silver several nanometers in size are deposited on the outer surface of carbon capsules of the encapsulated metal particles. With an increase in the time of treatment of encapsulated metal nanoparticles, the formation a layers of noble metal nanoparticles on the surface of carbon capsules and almost complete dissolution of the metal core were observed. To confirm that the main contribution into the reduction of noble metals is made by metal nanoparticles, we treated hollow carbon nanocapsules containing no metal, which were prepared by treatment of encapsulated metal particles with the solution of hydrochloric acid. It was established that the treatment of thus obtained hollow capsules with the solutions of HAuCl4, H2PtCl6 or AgNO3 does not lead to the deposition of noble metals The obtained results show the possibility to use the galvanic replacement reaction for surface modification of carbon nanocapsules with the nanoparticles of noble metals; this opens rather broad outlooks for the direct preparation and design of composite carbon-based nanomaterials of different composition for practical applications.
Symposium OrganizersCarlos J. Martinez, Purdue University
Zhiqun Lin, Iowa State University
Dong Ha Kim, Ewha Womans University College of National Sciences
Symposium Support 3M Company
National Science Foundation
AAA6: Particles for Chemical and Biological Sensing/Particles for Photonic Assemblies
Thursday AM, April 12, 2012
Marriott, Yerba Buena, Salons 1-2
9:30 AM - *AAA6.1
High-performance Chemical Sensing Materials from Template-directed Synthesis
Kurt D. Benkstein 1 Phillip H Rogers 1 Carlos J Martinez 2 Baranidharan Raman 3 Steve Semancik 1
1National Institute of Standards amp; Technology Gaithersburg USA2Purdue University West Lafayette USA3Washington University St. Louis USAShow Abstract
High-performance materials based upon nanostructured building blocks are finding applications in diverse application areas. The microsensor research team at the National Institute of Standards and Technology is interested in using materials based upon nanoparticle structures for developing chemical sensors with advanced measurement capabilities. These sensing devices are built upon micrometer-scale MEMS platforms that enable dynamic high-performance, low-power operations. The new sensing materials enhance the performance characteristics of our chemiresistive devices by increasing signal strength and/or decreasing response time. Furthermore, multiple advanced materials could be combined in multi-element arrays to improve the analytical orthogonality and selectivity of chemical microsensors. In this presentation, we will give an overview of the template-directed materials used in our gas-phase sensing studies, and how they impact the results of those studies. We will focus on sensing materials that employ shells of metal oxide nanoparticles built around sacrificial polystyrene microspheres and discuss how they perform in two challenging applications. First, in simulated breath analysis tests with a dynamic background environment, the microshell materials provide key, trace-analyte detection capabilities in the microsensor array. Second, in simulated planetary exploration scenarios, the metal oxide microshells demonstrate responses to trace biogenic gases in a carbon-dioxide-rich chemical background. We will also describe the use of anodic alumina templates to prepare poly-crystalline metal oxide structures as quasi-1-dimensional sensing materials. Examples of these materials include metal oxide nanowires that are released from the templates for use as sensing materials, and nanotubes that use the template as a support structure in multi-pathway parallel nanotube assemblies. These materials have been examined analyzed as part of a morphologically diverse sensor array or as assemblies of parallel structures. In each case, the materials provide enhancement to the information acquired from the chemical sensor.
10:00 AM - AAA6.2
High-sensitivity Gas-sensor with Inverse-opal Nano-fractal Structure in Trenches Fabricated by Hybrid-particles Suspension Coating
Minoru Abasaki 1 2 Shinichi Souma 2 Nobuyuki Moronuki 3 1 Masakazu Sugiyama 4 1
1BEANS Project Tokyo Japan2Fuji Electric Co., Ltd Tokyo Japan3Tokyo Metropolitan University Tokyo Japan4The University of Tokyo Tokyo JapanShow Abstract
10:30 AM - AAA6.4
Silver ``Catalyzed'' Formation of Gold Patchy Particles
Huixin Bao 1 Benjamin Butz 2 Erdmann Spiecker 2 Robin N Klupp Taylor 1
1Institute of Particle Technology, University Erlangen-Nuremberg Erlangen Germany2Center for Nanoanalysis and Electron Microscopy (CENEM), University Erlangen-Nuremberg Erlangen GermanyShow Abstract
The successful exploitation of functional patchy particles i.e. those having heterogeneous surface properties is reliant on the development of suitable techniques for their scalable and tunable fabrication. Despite this, most reported approaches require the use of phase boundaries, masking or templating structures or mixed liquid and gas phase treatments. In the effort to find new approaches which overcome these issues, a facile one-pot method in aqueous solution to synthesize silver patchy particles with tunable morphology and plasmon resonance has been developed by us. In this approach, silver ions accumulated around silica particles by electrostatic forces are reduced and patches are formed by heterogeneous nucleation and surface growth. A limitation to further application of these particles in e.g. self-organized structures and devices, is their poor morphological instability. To obtain similar plasmonic properties with a more stable structure it would be desirable to produce patchy coatings from gold. However, our process cannot produce gold patches directly since the interactions of ions such as [AuClx(OH)4-x] - with silica are somewhat different than those of Ag+. Furthermore, a simple galvanic replacement of silver by gold leads to detached and defective gold caps. In the present contribution we show that highly stable gold patchy particles can be synthesized via a silver "catalyzed" route. Firstly, small silver patches on the silica surface are formed, with excess reducing agent being used. Subsequently added gold precursor leads to the formation of surface conformal, thin gold patches. In addition to studies of the process parameters and functional properties, in-depth morphological characterization of the patchy particles will be described. HAADF-STEM and EDX studies strongly support our proposed mechanism that silver acts as not only the starting point of patches but also as "catalyst". In this role, silver ions released by the galvanic reaction are deposited again at the edge of the patch due to the reducing agent present. This newly deposited silver can be involved in the galvanic reaction again, the resulting cycles of silver oxidation and reduction leading to the development of conformal gold patches. We show that the size of the obtained gold patches can be tuned and that the materials have superior stability compared to the equivalent silver patches.
11:15 AM - *AAA6.5
Shear-based Orientation of Nanocellulose Films of High Strength and Stiffness
Jeffrey P Youngblood 1 Robert J Moon 2 1 Alexander B Reising 1 Jen-Chieh Liu 1
1Purdue University Crawfordsville USA2US Forest Service Madison USAShow Abstract
Cellulose nanocrystals (CNC's) and nanofibrillated cellulose (NFC) are gaining interest as "green" nanoparticles used as reinforcement phases in lightweight, inexpensive, high-strength composites materials. The high surface area and strong inter-particle hydrogen bonds in CNC's and NFC allow the formation of high-strength network structures. Additionally, the small particle size combined with the smaller void sizes within the network structures allows for optical transparency. Network-structured composites with CNC's and/or NFC being the dominant phase (i.e. greater than 50 vol. %) have been fabricated. Shear-based methods to cast films produced alignment of the CNC's and NFC. Solid, free-standing, transparent films of 100% CNC's and NFC were made using shear-based methods. These films are shown to have high orientation. This orientation is shown to increase strength and stiffness through mechanical testing.
11:45 AM - AAA6.6
Exploiting Mixed Self-Assembled Monolayers for Design and Fabrication of Patchy Particles
Ines Cristina Pons-Siepermann 1 Sharon C Glotzer 1
1University of Michigan Ann Arbor USAShow Abstract
Previous computational studies  explained the formation of patterns (Janus, stripes and 2D micelles) in binary mixtures of immiscible hydrophobic and hydrophilic surfactants adsorbed on gold nanoparticles . As an extension of those studies, we performed atomistic and mesoscale simulations of ternary and quaternary mixed self-assembled monolayers (SAMs) on nanoparticle surfaces. Here we present predictions for new and unexpected patterns for patchy particles that could be synthesized through judicious choice of surfactant architecture, nanoparticle geometry, and SAM stoichiometry.  C. Singh et al. Physical Review Letters 99, 226106 (2007)  A.M. Jackson et al. Nature Materials, 3, 330-336 (2004)
12:00 PM - AAA6.7
Optical Characterization of Slab Photonic Crystals with Asymmetric Dimer Bases
Erin Riley 1 Chekesha Liddell Watson 1
1Cornell University Ithaca USAShow Abstract
The promise of integrated optical devices capable of electromagnetic field localization, switching, spontaneous emission suppression and negative refraction through engineered design has long inspired research on photonic crystals. However, the structural variability through colloidal self-assembly of spherical particles has been limited primarily to high symmetry 2- and 3-dimensional lattices. For finite height 2D slab structures (e.g., based on circular crosssection pillars), light is confined in the third dimension through index guiding. Restrictions in gap polarization and/or bandgap width have been reported. Stronger light-matter interactions have been predicted for more complex geometries. Recently, advances in the synthesis of monodisperse nonspherical colloids such as micron-sized dimers along with their controlled assembly in wedge cell confinement geometry have accessed new centered rectangular and unconventional plastic or rotator phases, among others. Here, the photonic bandgaps in the guided modes for direct and inverted monolayer slabs with in-plane aligned dimer building blocks will be reported. The impact of dielectric filling fraction, lobe asymmetry, degree of fusion between lobes and dielectric contrast on the optical properties will be discussed. Simulations indicate significant band gaps between the fifth and sixth, sixth and seventh, and seventh and eighth bands. The characteristic refraction as a function of structural parameters will also be presented.
12:15 PM - AAA6.8
Photonic Inks Based on One-dimensional Photonic Nanostructures
Mingsheng Wang 1 Yadong Yin 1 Le He 1
1University of California, Riverside Riverside USAShow Abstract
Photonic inks with fast response and bistability have been developed by using one-dimensional fixed photonic nanochains as building blocks. These nanochains have periodically arrangements of magnetite nanoparticles along their long axis and are able to strongly diffract the incident light. Magnetic fields can be used to tune the orientations of nanochains and to establish "On" and "Off" states for their photonic responses. When they are aligned parallel to the viewing direction, their structural color can be observed; otherwise people can only see the native brownish color of magnetite. Bistability can be created for these photonic inks by restricting the rotational Brownian motion of nanochains. A magnetic stimulus is only needed when the inks need to switch from an "Off" state to an "On" state or oppositely, afterwards the inks can be maintained at that state for a long time in the absence of magnetic fields. This makes our photonic inks super energy-saving and great candidates for applications such as e-book readers and advertisement billboards.
12:30 PM - AAA6.9
Characterization of a Self-healing Poly(methyl methacrylate) Bone Cement Containing Encapsulated 2-Octylcyanoacrylate
Alice B.W. Brochu 1 2 William J Chyan 1 William M Reichert 1 2
1Duke University Durham USA2Duke University Durham USAShow Abstract
Self-healing materials are a rapidly emerging class of composites designed primarily for civil, mechanical, electrical, and aerospace applications. These materials hold the potential for extending functional lifetimes by preventing and repairing material failure caused by accumulated microcrack formation. One design concept utilizes a matrix co-embedded with a catalyst and an encapsulated healing agent. Microcracks propagate through the material, rupturing the microcapsules and releasing their contents into the crack plane. Polymerization of the contents by exposed catalyst within the damage site serves to halt and repair crack propagation and maintain material strength. Here we present the characterization of the first self-healing biomaterial system: a poly(methyl methacrylate) (PMMA) matrix embedded with polyurethane capsules containing a water-reactive liquid tissue adhesive, 2-octylcyanoacrylate (OCA). In this research, OCA was encapsulated via emulsion interfacial polymerization of a toluene diisocyanate-based polyurethane prepolymer with a small diol chain extender. Spherical, smooth-shelled microcapsules with average diameters ranging from 75-220 µm were fabricated by adjusting the agitation rate from 350-1100 rpm. A consistent shell thickness to diameter ratio of 0.02 was observed across capsules made at all rates. Analysis of the thermal degradation behaviors of the capsules determined the core content was greater than 52% at all agitation rates. Loss of core contents was less than 7 wt% following 56 days dry storage and was primarily attributed to diffusion and subsequent evaporation of encapsulated solvent. The agitation rate used during fabrication also dictated the compressive strength of the capsules; those made at slower rates possessed thicker shell walls capable of withstanding maximum loads approaching 500 mN. Tensile tests of pure PMMA specimens and specimens containing up to 25 wt% capsules were performed to study the effects of the amount and average size of the capsules on the mechanical properties of the bone cement. In the future, tapered double cantilever beam testing will be used to assess the healing efficiency of this biocompatible self-healing formulation.
12:45 PM - AAA6.10
Self-assembly of Colloidal Photonic Crystals and Magnetically Induced Phase Transition
Le He 1 Yadong Yin 1
1UC Riverside Riverside USAShow Abstract
Self-assembly of uniform colloidal particles has been studied extensively as model systems to mimic the behavior of simple atomic liquids and solids and to fabricate photonic crystals. However, the main challenge in the area remains to traverse the rich phase diagrams in a single sample. The introduction of an additional interparticle dipolar interaction, in nature anisotropic, represents the powerful way to enable more complex phase transitions controlled by external fields. Here, we study the self-assembly of submicrometer colloidal particles to into photonic crystals in different solvents that strongly diffract visible light. Since the interparticle interactions can be dynamically tuned in the magnetic field, we observe rich phase-transitions along with the change of their structural colors. Moreover, our observation indicates the unstable bulk hcp state, which has been predicted, can be created by the application of the external magnetic fields.