Symposium Organizers
Norman Wagner University of Delaware
Gerald G. Fuller Stanford University
Jennifer Lewis University of Illinois, Urbana-Champaign
Ko Higashitani Kyoto University-Katsura
W1: Self-Assembly of Colloidal Crystals I
Session Chairs
Monday PM, April 17, 2006
Room 2001 (Moscone West)
9:00 AM - **W1.1
On-chip Manipulation by Electric Fields: From Self-Assembling Particles to Self-Propelling Devices
Orlin Velev 1 , Suk Tai Chang 1 , Vesselin Paunov 2
1 Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Department of Chemistry, University of Hull, Hull United Kingdom
Show AbstractWe have demonstrated previously how dielectrophoresis, particle interaction with external AC fields, can be used to manipulate and assemble colloidal particles on any size scale, from nanometer gold particles, to submicron sized latex, to millimeter sized droplets. The structures that can be assembled by these methods include, for example, microwires, switchable photonic crystals, and complex anisotropic supraparticles. We will demonstrate here that an additional level of complexity can be engineered to turn the particles into prototypes of self-propelling micromachines. We show how various types of miniature semiconductor diodes floating in water can propel themselves when an uniform alternating electric field is applied across the container. The millimeter-sized diodes generate electroosmotic force, which propels them in the direction of either the cathode or the anode depending on the surface charge of the particles. The electroosmotic velocity depends on the electrolyte concentration and pH of the solutions. The velocity of the particles, however, does not depend strongly on their size; the electrokinetic mobility could, in principle, be used to propel particles or devices on the microscale. The diode motility can be used to power rotating "gears" and can be controlled by light. Thus, diodes propelling in electric fields suggest rudimentary solutions to problems facing self-propelling microdevices, including harvesting power from external sources, internally controlled movement, and potential for a range of additional functions.
9:30 AM - W1.2
Utilizing the Electronic Industry's Tricks for Transistor Fabrication for Development of New Delivery Colloidal Vehicles for Nanomedicine Applications
Larken Euliss 1 4 , Christopher Welch 2 , Stephanie Gratton 1 4 , Benjamin Maynor 1 4 , Klaus Hahn 2 4 , Rudy Juliano 2 4 , Joseph DeSimone 1 3 4
1 Chemistry, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, United States, 4 Lineberger Comprehensive Cancer Center, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, United States, 2 Pharmocology, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, United States, 3 Chemical Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe delivery of therapeutic, detection and imaging agents for the diagnosis and treatment of cancer patients has improved dramatically over the years with the development of nano-carriers such as liposomes, micelles, dendrimers, biomolecules, polymer particles, and colloidal precipitates. While many of these carriers have been used with great success in vitro and in vivo, each suffers from serious drawbacks with regard to stability, flexibility, or functionality. To date, there has been no general particle fabrication method available that afforded rigorous control over particle size, shape, composition, cargo and chemical structure. By utilizing the method we has designed referred to as Particle Replication In Non-wetting Templates, or PRINT, we can fabricate monodisperse colloidal particles with simultaneous control over structure (i.e. shape, size, composition) and function (i.e. cargo, surface structure). Unlike other particle fabrication techniques, PRINT is delicate and general enough to be compatible with a variety of important next-generation cancer therapeutic, detection and imaging agents, including various cargos (e.g. DNA, proteins, chemotherapy drugs, biosensor dyes, radio-markers, contrast agents), targeting ligands (e.g. antibodies, cell targeting peptides) and functional matrix materials (e.g. bioabsorbable polymers or stimuli responsive matrices). PRINT makes this possible by utilizing low-surface energy, chemically resistant fluoropolymers as molding materials and patterned substrates to produce functional, harvestable, monodisperse polymeric particles.To demonstrate the potential and compatibility of PRINT for introducing “soft” molecular recognition moieties and/or valuable therapeutic agents into functional particles, we have encapsulated oligonucleotide and protein cargos within them to generate monodisperse “particle devices.” We have incorporated fragile biological cargos and recognition agents, i.e. DNA, proteins (fluorescently-labeled avidin (MW 68 kDa)), and small anti-cancer agents (doxorubicin) into PEG nanoparticles using the simple, mild and general PRINT technique. We have arguably generated DNA delivery vectors that are themselves first generation “synthetic viruses” (monodisperse populations of shape-specific particles containing DNA). Furthermore, these biomolecule-containing particles could be used as nanoscale, shape-specific biosensors or next-generation therapeutic agents. We were able to confirm the encapsulation of the oligonucleotides by observing fluorescence from monodisperse particles using confocal microscopy.PRINT has several distinct advantages over other vector fabrication techniques in that the particles are monodisperse and shape specific. In addition, no surfactants condensation agents, etc. are required.
9:45 AM - W1.3
Structure and Dynamics of Bbiphasic Colloidal Suspensions.
Ali Mohraz 1 , Eric Weeks 2 , Jennifer Lewis 1
1 Materials Science and Engineering, Univeristy of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Physics, Emory University, Atlanta, Georgia, United States
Show AbstractWe investigate the structure and dynamics of concentrated biphasic mixtures comprised of attractive and repulsive silica microspheres using confocal laser scanning microscopy. One population of colloids is rendered hydrophobic by chemically modifying their surface. These species flocculate when suspended in an index-matching (water-DMSO) solvent, while their unmodified (charge-stabilized) counterparts remain individually dispersed.By labeling the two microsphere populations with different fluorescent dyes, we can directly image the flocculated and dispersed phases independently. The structural and dynamical parameters salient to the mixture’s rheology are quantified as a function of total colloid volume fraction and different ratios of the two phases. These results will provide new insights into the development of concentrated colloidal inks for direct-write assembly of complex 3D structures.
10:00 AM - W1.4
Coulomb Blockade at Room Temperature in Nanoparticle Arrays Aligned on DNA Scaffolds
Gregory Kearns 1 2 , James Hutchison 1 2
1 Chemistry, University of Oregon, Eugene, Oregon, United States, 2 Materials Science Institute, University of Oregon, Eugene, Oregon, United States
Show AbstractNanoparticles are of great interest as components in new materials and devices due to their size dependent optical and electronic properties. Two significant challenges in developing nanoparticle-based devices are assembling nanoparticles in a useful way and bridging nanoscale assemblies to microscale electronics. We have developed methods to form linear arrays of 1.5 nm particles that can be easily integrated with the microscale in order to exploit the properties of the nanoscale components while allowing access to the devices through microscale contacts. Metal nanoparticles with core diameters of less than 2 nm exhibit Coulomb blockade at room temperature, which can be used to develop new electronic devices such as single electron transistors (SET). These devices offer several advantages over semiconductor-based transistors—(i) they are 1-2 orders of magnitude smaller than current state-of-the-art transistors, (ii) SETs are not hindered by electron tunneling that can lead to device heating and/or failure in semiconductor based transistors, and (iii) it is possible to use a greener, bottom-up assembly approach to develop complex structures.We have developed a convenient synthetic route to monodisperse 1.5 nm gold nanoparticles that can be functionalized with a wide range of ligand shells. Using these particles, we have shown that, in solution, nanoparticles can be organized into linear arrays using electrostatic interactions between the negatively charged backbone of DNA and the positively charged ligand shell of functionalized nanoparticles. These interactions result in extended linear chains of close-packed nanoparticles. Close-packing of the nanoparticles on the DNA scaffold allows precise control over interparticle spacing by the appropriate choice of ligand shell. In order to make useful devices of these arrays, we have been working to align DNA on surfaces prior to coating with nanoparticles in order to obtain parallel, linear arrays of nanoparticles. Using specially fabricated TEM grids composed of a silicon grid with thermally grown, electron transparent SiO2 windows, we have shown that we can make long-range (tens of microns) parallel arrays of nanoparticles on thermal SiO2 in a three step assembly process involving (i) silanization of the SiO2 surface, which promotes molecular combing of DNA and limits nonspecific adsorption of positively charged nanoparticles, (ii) molecular combing of DNA on the silanized surface, and (iii) nanoparticle assembly on the linear arrays of DNA. TEM analysis of these arrays shows that the arrays are parallel over the entire substrate and that high purity nanoparticles maintain their core size and spacing as determined by the thickness of the ligand shell. With these arrays we have developed electronic test structures that exhibit Coulomb blockade at room temperature.
10:15 AM - W1.5
Dewetting Induced Formation of Nanoparticle Stripe Patterns.
Jiaxing Huang 1 2 , Franklin Kim 1 2 , Andrea Tao 1 2 , Stephen Connor 1 2 , Peidong Yang 1 2
1 Department of Chemistry, UC-Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract10:30 AM - W1.6
Generalized Rule for Order Formation by Colloidal Nanoparticles Adsorbed on a Substrate.
Minoru Miyahara 1 , Satoshi Watanabe 1
1 Chemical Enginering, Kyoto University, Kyoto Japan
Show Abstract Ordered arrays of particles have been attracting much attention recently because of their unique functions especially as optical devices. We performed Brownian dynamics simulations of adsorption of electrostatically stabilized colloidal particles and their spontaneous order formation on a planar surface with countercharge, in which the particle–particle and particle–substrate interactions are modeled based on the DLVO theory. The results obtained are: (1) A hexagonally ordered array by adsorbed particles is found to form only if a controlling factor, the “average force” acting between adsorbed particles, exceeds a limiting value that is common to various ionic strengths; (2) A general concept extended from the Alder transition is proposed to give a comprehensive understanding of the characteristics of the “average force”, with which the controlling factor and resultant ordered structure can be predicted a priori for any combination of temperature, ionic strength and particle size. Further, large-scale simulations were performed to observe time-evolution of ordered domains and their merging processes, which exhibited two types of different behaviors depending upon the Debye lengths or ionic strengths: one type with easily merging domains and the other one with prevailing domain structures. The origin of the difference will be discussed in connection with the "average force" and the characteristics of the particle-substrate interactions.
10:45 AM - W1.7
Regulation of Atomic Alignment in Superlattices of Au and Ag Nanoparticles.
Keisaku Kimura 1 , Yang Yang 1 , Suhua Wang 2 , Seiichi Sato 1 , Hiroshi Yao 1
1 Graduate School of Science, University of Hyogo, Hyogo Japan, 2 Department of Chemistry, National University of Singapore, Singapore Singapore
Show AbstractIntense research interest is focusing on the nano-sized substances such as surface modified gold and silver nanoparticles, nanodiscs and nanowires due to their notable electronic and optical properties based on the quantum size effect. Fabrication of macroscopic architecture using these nano-sized materials as a constructing block will be a next target in the coming nanotechnology era. There are many reports on the construction of two and three-dimensional superlattices made by metallic nanoparticles, because it will provide a peculiar performance based on collective electronic behaviors resulting from interparticle interactions between neighboring ordered particles. In order to accomplish an ultimate collective motion of electrons or excitation energy moving this ordered structure, we need atomic orientational as well as translational alignment in the superlattice. While regular lattices made of nanoparticles are prepared by spontaneous evaporation of organic solvent in most cases, we have developed a new class of superlattice at an air/water interface by virtue of the ionic or hydrogen bonding interactions under an equilibrium condition [1]. It was found that water cluster exist interstitially in the superlattice spacing observed by FTIR at room temperature [2]. At the same time, some arc patterns in the diffraction from atoms superimposed with the diffraction from superlattice were observed in the transmission electron diffraction (TED), suggesting atomic orientational arrangements to some extent in this small crystal. We will present more complete TED pattern that shows coexistence of atomic and superlattice orientational alignment in the crystal.Two metallic nanoparticles, gold and silver, were used to construct nanoparticle assemblies. For a typical preparation of gold nanoparticles at thiol to gold ratio = 3, 0.5 mmol of HAuCl4 aqueous solution was mixed with 1.5 mmol of MSA in 100-mL methanol. A freshly prepared 0.2 M ice-cold aqueous NaBH4 solution (25 mL) was then added under vigorous stirring. After further stirring for 1h, the precipitate was gathered by decantation and centrifugation. The precipitate was washed with water/methanol solution and then with pure methanol and ethanol. Finally, the sample was obtained as a solid powder by freeze-drying. The mean particle diameter was typically 3.5 nm (fwhm: 0.4 nm). The crystallization took place at an air/water interface in 4-10 days in the presence of an appropriate amount of hydrochloric acid in a sealed vial giving numerous micrometer-sized nanoparticle crystals with clear crystal habit [1,2]. The TED and TEM images were taken by a Hitachi H8100 transmission electron microscope. Samples were set on the amorphous carbon film on the Cu grid. The observed TED pattern is discussed along with the sample preparation treatment.[1]. K.Kimura, S.Sato and H.Yao, Chem.Lett., 2001, 372-373.[2]. S.Wang, H.Yao, S.Sato and K.KimuraJ.Amer.Chem.Soc. 126(24)(2004)7438-7439.
11:30 AM - **W1.8
Functionalised Interfacial Particulate Coatings from Block Copolymer Micelles.
Simon Biggs 1 , Grant Webber 1 , Kenichi Sakai 1 , Steven Armes 2
1 Institute of Particle Science and Engineering, University of Leeds, Leeds United Kingdom, 2 Chemistry, University of Sheffield, Sheffield United Kingdom
Show AbstractThe facile production of highly functional particle coatings has many potential benefits across a wide range of established products in sectors such as pharmaceuticals, personal care, household and agricultural products. The key challenge is to produce a coating easily and at low cost. This provides significant challenges to both technology and manufacturing. In this paper, I will describe recent research into the production of novel particle coatings that potentially have a high degree of functionality but which can be produced very easily allowing for scale-up and manufacture. These coatings are based upon simple stimulus-responsive polymer materials that, themselves, have a high degree of potential variety. Allied to this is the possibility of 'tuning' the quality of the coating providing a wide variety of coating options.Results of recent research we have undertaken to characterise particulates coated by multilayers of stimulus responsive copolymer micelles will be described. These layers have been characterised by a combination of techniques including AFM, QCM-D, optical reflectometry, and zeta potential measurements.We will also discuss the potential applications of materials such as these in areas such as delivery agents, rheology modifiers, and capsule manufacture.
12:00 PM - W1.9
Patterning Colloidal Films via Evaporative Lithography.
Daniel Harris 1 2 , Angel Chan 1 2 , Jennifer Lewis 1 2
1 Materials Science, University of Illinois, Urbana, Illinois, United States, 2 Materials Research Laboratory, University of Illinois, Urbana, Illinois, United States
Show AbstractWe investigate evaporative lithography as a route for creating patterned colloidal films during drying. Specifically, films comprised of silica microsphere and polystyrene nanoparticle mixtures are patterned by placing a mask above the film surface to induce periodic variations between regions of free and hindered evaporation. Fluorescence and confocal microscopy coupled with surface profilometry measurements reveal that particles segregate laterally within the drying film, as fluid and entrained particles migrate towards regions of high evaporative flux. Such films exhibit remarkable pattern formation that can be regulated by carefully tuning initial film composition, mask geometry, and the separation distance between the mask and underlying film.
12:15 PM - W1.10
Directed Self-assembly of Virus Particles at Chemical Templates.
Sung-Wook Chung 1 , Chin Cheung 2 1 , Anju Chatterji 3 , Tianwei Lin 3 , John Johnson 3 , James DeYoreo 1
1 Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemistry, University of Nebraska, Lincoln, Nebraska, United States, 3 Department of Molecular Biology, Scripps Research Institute, La Jolla, California, United States
Show AbstractIcosahedral viruses in solution are colloidal systems in which inter-particle potentials can be modulated by both site-directed mutagenesis and variation of solvent composition. Because individual surface sites can be engineered to bind specifically to self-assembled monolayers (SAMs), their assembly at surfaces can be directed by chemical templates. As a result, the physics of directed colloidal assembly can be explored in a system where the governing interactions are variable. Moreover, because other sites on viruses can be engineered to present catalytic, electronic, or optically active moieties, control over virus organization defines a route to nanoscale device fabrication. Here we report results using scanned probe nanolithography (SPN) to direct organization of viruses into 1D and 2D patterns and in situ AFM imaging to investigate the dynamics of organization as pattern geometry, inter-viral potential, virus flux, and virus-pattern interaction are systematically varied.As a model system, we chose Cowpea Mosaic Virus genetically engineered to present either cysteine (Cys) or histidine (His) tags at specific sites on the capsid surface. Atomically-flat gold substrates coated with SAMs of polyethylene glycol (PEG) terminated alkyl thiols were patterned with either maleimide (MA) or nickel-chelating nitrilotriacetic acid (Ni-NTA) terminated alkyl thiols using SPN. Template features had sizes ranging from 10-100nm and were separated by 50 to 1000nm. Virus attachment occurred either through a metal coordination complex between His-tags and Ni-NTA, or through a covalent bond between Cys and MA groups. AFM was then used to investigate the degree of ordering, packing geometry, assembly kinetics, and cluster-size distribution both on the templates as well as the surrounding PEG-terminated regions.We show that the degree of ordering depends on all parameters chosen: surface chemistry, virus concentration, PEG concentration, and feature size and separation. For example, as the solution PEG concentration is increased, which increases virus-virus attraction through hydrophobic effects, 2D arrays of viruses evolve from poorly-ordered, to well-ordered rhombohedral, and then hexagonally close packed assemblies and 1D patterns increase from one multiple rows of viruses in width. Disordered clusters form on PEG functionalized regions, but cluster growth dynamics is altered. Taking cues from previous work on both epitaxial and colloidal systems, we present a physical picture of virus assembly at templates in which the dominant factors are the ratio of virus flux to surface mobility and the strength of the virus-virus interaction, the latter being modulated by hydrophobic interactions and or/covalent bonds.This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
12:30 PM - W1.11
Directed Adsorption of Polyelectrolyte- and Nucleic Base-Functionalized Colloids
Marianne Terrot 1 , Paula Hammond 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe selective adsorption behavior of macromolecules, colloidal particles, and polyelectrolyte multilayers is of great importance to the production of nano and micro-scale features within organic thin films. We have previously demonstrated the ability of chemical surface templates to direct the deposition of polyelectrolyte multilayers; recently, this approach has been extended to polyelectrolyte-functionalized colloids, making possible the assembly of multi-component colloidal arrays via selective adsorption. Unlike lateral arrays of multilayer films, these colloidal assemblies can be efficiently and faithfully transferred from the original surface template directing their assembly to a new matrix better suited to the final application. In order to design more complex arrays of three or more components, we have sought to broaden the range of interactions used to guide adsorption and specifically, to seek out species capable of specific recognition. For this, we took our inspiration from nature and explored the ability of nucleotide base pairing to direct assembly; multiple hydrogen bonding such as that existing between adenine and uracil and cytosine and guanine is ideally suited to our work as the interaction is both highly specific and readily modulated via temperature and pH. RNA homopolymers were used both for functionalization of polystyrene latex colloids and for chemical patterning of surfaces; we have also synthesized base-terminated silanes for more robust functionalization of silicon surfaces and colloids. Finally, we explore the self-assembly in solution of microspheres asymmetrically functionalized with complementary bases.
W2: Self-Assembly of Colloidal Crystals II
Session Chairs
Monday PM, April 17, 2006
Room 2001 (Moscone West)
2:30 PM - **W2.1
Adding Optical Functionality to 3D Self-Assembled Colloidal Crystals: Waveguides, Cavities, and Emitters
Paul Braun 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractThree-dimensional photonic crystals have been postulated to exhibit a number of unique properties which may enable new paradigms for controlling light. However, photonic crystals formed through colloidal crystallization have limited application due to their lack of refractive index contrast and inherently periodic structure. New physics and new applications such as efficient light generation, negative refractive index properties, lasers, waveguides, and optical cavities require the incorporation of new materials and aperiodic defect structures within the colloidal crystal. I will present our results on the use of multiphoton writing, electrochemistry, and chemical vapor deposition to create highly functional 3D colloidal crystal based optical devices including 3-D waveguides with sharp bends, embedded optical cavities, and light emitters.
3:00 PM - W2.2
Tunable Stopgap in Photonic Crystals Based on Homogeneous & Core-shell ZnS Colloids.
Ian Hosein 1 , Chekesha Liddell 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show Abstract3:15 PM - W2.3
Integration of Self-assembled Three-dimensional Photonic Crystals onto Structured Silicon Wafer.
Rudolf Zentel 1 , Jianghui Ye 1 , Sanna Arpianen 2 , Jouni Ahopelto 2 , Sergei Romanov 3 , Clivia Sotomayor Torres 3
1 Chemistry, University Mainz, Mainz Germany, 2 , VTT Centre for Microelectronics, VTT Finland, 3 Tyndall National Institute, University College Cork, Cork Ireland
Show Abstract Advanced photonic circuits will need complex architectures, which can be achieved using functional platforms for positioning, shaping and coupling of high-quality two- and three-dimensional (2D and 3D) PhCs. In contrast to 2D PhCs, which can be built-in directly to, for example, SOI platforms by means of well-developed 2D nanolithography, integration of 3D PhCs poses a great challenge. Assembling 3D PhCs through wafer bonding was proved complicated and costly procedure, with no straightforward prospect of further integration. Alternative 3D nanolithography, which imply in-situ 3D patterning of polymer template followed by its infiltration by high refractive index semiconductor and completed by nanocomposite inversion, look more efficient but remains a costly process and requires sophisticated equipment. In our opinion, self-assembly of monodisperse microspheres into opal structures remains the favourite route towards templates for platform-integrated photonic materials, owing to its simplicity, flexibility and low cost. In particular, the preparation of a silicon-inverted PhC on a silicon platform for the telecommunication frequency range is practically important target. Accomplishing this task requires, first of all, realization of perfectly crystalline low refractive index 3D templates. The quality of colloidal crystal on structured silicon wafer will depend on the method of opal assembly, commensurability of opal lattice constant and pattern dimensions and spatial selectivity of opal growth. So far, opals have been crystallized in channel structures, whereby the deposition of opal on top of the wafer surface was mostly prevented by covering it with a slide or by making this surface hydrophobic. These methods are difficult to apply if the opal should be assembled on micrometer-size isolated areas. Combination of directed evaporation-induced self-assembly (DEISA) process and slowly stirring solution to keep the spheres in a levitated state (ADEISA), subsequently, suggested as a solution for assembling large spheres in channels.In this paper, we report the growth of high quality colloidal crystals from very large SiO2 spheres of 890 nm diameter in a drawing apparatus. The choice of sphere size is dictated by the need to match the telecommunication wavelength range and the high-order photonic bandgaps of the inverted Si-opal. Crystallization in moving meniscus allows easy managing of opal parameters by changing the withdrawal speed comparing to evaporation temperature control and can be implemented to growth of high quality opals onto complex structured silicon wafers. We focus on optimizing the opal crystallization conditions in confined geometries of complex topology and obtained silica opals with excellent quality, which is confirmed by optical and microscope studies.
3:30 PM - W2: SA co II
BREAK
4:00 PM - **W2.4
Fabrication Techniques for Photonic Crystals
Pierre Wiltzius 1
1 MS&E Department and Physics Department, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractPhotonic crystals are materials that allow the manipulation of light in new and unexpected ways. Colloidal self-assembly and multi-beam interference lithography are great tools to build crystals with interesting optical properties. Recent progress on making large area single crystals using colloidal self-assembly and holographic multi-beam interference techniques will be discussed. In addition, optical characterization and some device applications using photonic crystals will be presented.
4:30 PM - W2.5
Tuning the Optical Properties of Colloidal Thin Films Using Dual-frequency Liquid Crystal.
Elton Graugnard 1 , Jeffrey King 1 , Swati Jain 1 , Yana Zhang-Williams 2 , Iam-Choon Khoo 2 , Christopher Summers 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractPatterned 3D optical structures based on colloidal thin films, such as opals and inverse opals, offer unprecedented control over the propagation of light within materials, enabling effects such as slow light, negative refraction, and photonic band gaps. Inverse opals have been studied extensively due to the ability to form a complete photonic band gap for a high refractive index backbone. Concurrently, several groups have studied optical tuning by infiltrating inverse opals with non-linear optical materials, such as liquid crystals. To fully exploit the potential optical properties, devices whose optical properties can be dynamically controlled are necessary. Here, we report the combination of a high refractive inorganic backbone with a dual-frequency liquid crystal to create a hybrid film whose Bragg reflectance peak can be tuned over a large range, exhibiting both blue and red shifts about a central wavelength.Polymer colloidal thin films were formed by directed self-assembly of polystyrene spheres from 329 to 820 nm in diameter, and then sintered to increase the diameter of the contact points between neighboring spheres. The sintered films were infiltrated with amorphous titania, (refractive index 2.31 at 800 nm) using low temperature atomic layer deposition (ALD). The infiltrated films were ion-milled to expose the polystyrene spheres, which were then etched by immersing the films in toluene, creating lattices of air spheres within a dielectric backbone. These sintered inverse films were infiltrated at 60C with MLC2048, which is a multi-component liquid crystal (LC) with a frequency dependent polarization. By varying the frequency of an applied electric field, the Bragg peak position could be both blue and red shifted by controlling the orientation of the infiltrated LC, which dynamically controlled the refractive index contrast within the hybrid structure. The details of the fabrication process and the results of the optical tuning will be discussed, along with potential applications of these results.
4:45 PM - W2.6
Emission of TRITC Dye Encapsulated Silica-Nanoparticles in Non-Closepacked Photonic Crystals
Poorna Rajendran 1 , Erik Herz 1 , Ulrich Wiesner 1 , Chekesha Liddell 1
1 Materials Science and Engineering, Cornell University, ithaca, New York, United States
Show AbstractThe development of high performance light sources including low threshold microlasers and efficient light-emitting diodes has been one of the most promising applications of photonic crystals. Realizing such devices requires a spatially extended light source integrated into a periodic dielectric structure (photonic crystal) for effective photon confinement and control of spontaneous emission. Due to their broadband emission, which is easily made to coincide with the photonic crystal stopband, dyes are attractive probes of photonic bandgap effects (spectral redistribution, spatial filtering, amplified spontaneous emission, band-edge lasing) on the emission of optically active materials. Here, we investigate the modification of tetramethylrhodamine isothiocyanate (TRITC) dye emission characteristics due to changes in the local density of photon states within a photonic crystal. High-brightness, photostable core-shell nanoparticles (Cornell Dots ~30 nm in diameter) consisting of the TRITC dye encapsulated in a silica shell were co-assembled with polystyrene beads into photonic crystals using a convective approach. Dye incorporation through this hierarchical self-assembly process overcomes common problems in dye-opal composite systems such as fluorescence quenching at high dye concentration, reduced excited state lifetime and fluorescence quantum yield due to uncontrollable intermolecular interactions between the dye and its chemical environment, incomplete infiltration of interstitial pore space, and limited control of volume filling fraction in close-packed systems. The spectral position of the photonic crystal stopband was tuned, by varying the PS template bead size as well as the relative concentration of PS beads to dye incorporated nanoparticles. Large excesses of the fluorescent nanoparticles led to ordered non-closepacked morphologies as determined by scanning electron microscopy. Photoluminescence, transmission and reflectance measurements revealed inhibited spontaneous emission due to the existence of a photonic stopband with wavelength range comparable to that of the emission wavelength of the fluorescent nanoparticles. In addition, the refractive index contrast was enhanced to promote stronger light-matter interactions by removing the polymer sphere template using a plasma etch.
5:00 PM - W2.7
Plasmon-coupling in Self-assembled Colloidal Metal Nanoparticle Arrays.
R. de Waele 1 , A.F. Koenderink 1 , J.T. van Wijngaarden 1 , A. van Blaaderen 2 , A. Polman 1
1 Center for Nanophotonics, FOM-institute AMOLF, Amsterdam Netherlands, 2 Soft Condensed Matter, Utrecht University, Utrecht Netherlands
Show Abstract5:15 PM - W2.8
Capillary Force Indexing of Colloidal Nanoparticles.
Michael Gordon 1 , David Peyrade 1
1 Laboratoire des Technologies de la Microelectronique, LTM-CNRS, Grenoble France
Show Abstract Going beyond the microelectronics-only frontier is quickly becoming a necessary mindset in the fabrication and large-scale implementation of nano-objects into useful devices and structures. For example, colloidal synthesis techniques can now provide a wealth of different nanoscale materials with well controlled shape and size dispersion (2-100 nm). However, large-scale assembly and precise localization of many nano-objects at the same time is still rather challenging. In this work, we use capillary forces to direct the self-assembly of Au nanoparticles (NPs) into lithographic patterns during colloidal solution evaporation (single droplets and large baths). Particle indexation was studied in real-time using dark-field optical microscopy of evaporating droplets to understand how NP flow within the drop, particle congregation at the tri-phase contact line, and intermittent contact line pinning affect the organization process. This visualization demonstrated that good pattern filling requires a large NP flux from the liquid interior toward the drop edge and that the contact line must advance smoothly over the pattern as the colloidal solution de-wets. As such, indexation was seen to be extremely sensitive to the template material (photoresist, SiO2), surface treatment (controlling the contact angle), and evaporation speed/direction. By optimizing the evaporation process, NPs from 10-200 nm were organized into a wide variety of lithographic features such as holes (round/square/triangular), trenches, and large open areas. Furthermore, it was possible to control pattern filling at the single particle level over extended areas (100x100 μm^2). Careful adjustment of the hole size and shape allowed well-organized arrays (50x50 matrix) of 1, 2, 3, or 4 (non-touching) particle groups within one hole to be created. The lithographic template layer was also removable after indexation by plasma treatment without damaging NP organization - opening up a new route to particle arrays for application to nanowire growth (templates) or optical detection of single molecules. This talk will discuss particulars of the evaporation process, indexation, and plasmon spectroscopy conducted on individual groups of 1-4 spherical Au NPs sitting on Si/SiO2, to demonstrate that the number of particles/hole (1, 2, 3, or 4 NPs) can be distinguished in far-field.
5:30 PM - **W2.9
Ionic Colloidal Crystals from Oppositely Charged Particles.
Alfons van Blaaderen 1
1 Physics, Utrecht University, Utrecht Netherlands
Show AbstractConcentrated dispersions of monodisperse colloidal particles are both interesting as model system to study fundamental condensed matter questions like freezing and melting and because their self-organization can be used to make regular 3D (metallo-)dielectric structures that can be used in advanced (photonic) applications. Moreover, the process of colloidal crystallization into 3D periodic lattices can be manipulated relatively easily by using external fields and studied quantitative on a single particle level with light microscopy. In this talk we will show how colloidal crystals can be grown from binary dispersions of oppositely charged spheres and manipulated with external fields. Previously, it was considered not possible to grow equilibrium phases from such systems because of heteroaggregation. Our new findings make it possible to grow large (binary) crystals of large particles (e.g., 2 micron), which is interesting for photonic applications. Moreover, ionic crystallization and glass formation can now be modelled with colloids, if the Debye screening length is made to be sufficiently large. However, the fact that the interparticle interactions are screened Coulomb also gives interesting new opportunities that are not possible with atomic salts. The fact that the colloids together with their double layer are charge-neutral relieves the strong restrictions on stoichiometry that need to be met for ionic crystals. Thus, we have observed CsCl type crystals of 2 micron sized particles that were not equally charged (e.g., + 125e, -75e). For applications it is important that CsCl crystals could also be obtained from mixtures of oppositely charged micron sized PMMA and silica spheres, despite the large density difference. For a size ratio between large (L) and small (S) spheres of 0.31 we have in addition seen: LS6, LS8, NaCl and NiAs type crystals. Some of the crystal types we observed have, as far as we know, never been seen before. We investigated the stability of the different crystal types also by Madelung calculations and computer simulations. Finally, we show that relatively small external electric fields can be used to melt the ionic colloidal crystals. At low volume fractions of the oppositely charged spheres an interesting out-of-equilibrium phase transition takes place whereby the particles that move in the same direction organize themselves in ‘lanes’ that are oriented in the field direction. At higher volume fractions the particles get jammed into structures that resemble wavy patterns perpendicular to the field direction.
Symposium Organizers
Norman Wagner University of Delaware
Gerald G. Fuller Stanford University
Jennifer Lewis University of Illinois, Urbana-Champaign
Ko Higashitani Kyoto University-Katsura
W3: Pickering Emulsions & Colloids at Interfaces
Session Chairs
Tuesday AM, April 18, 2006
Room 2001 (Moscone West)
9:30 AM - **W3.1
Exploring the Fundamentals and Applications of Pickering Emulsions.
Lenore Dai 1
1 Chemical Engineering, Texas Tech University, Lubbock, Texas, United States
Show Abstract10:00 AM - W3.3
Coalescence and Buckling of Particle-Laden Droplets
Gerald Fuller 1 , Hui Xu 1 , John Kirkwood 1
1 , Stanford University, Stanford, California, United States
Show AbstractThe addition of colloidal particles to the interface between oil and water can stabilize droplets against both coalescence and volume reduction. This is accomplished through a number of mechanisms including "drop-to-drop" bridging of the particles across the continuous phase and liquid-to-solid phase transitions of the interface as particle concentration is increased. These phenomena are examined in detail. The bridging of particles causes droplets in an emulsion to adhere to each other through an aggregate of such particles. Such aggregates are observed to grow with time in a power law response having an exponent of 0.33. This power law dependence can be predicted with a simple model where capillary forces balance hydrodynamic forces. The liquid-to-solid transition of particle-laden interfaces was studed by measuring the internal pressure of droplets as their contents are withdrawn. It is shown that the pressure-droplet volume curves can be used to extract the interfacial mechanical properties of the droplets. In particular, the Youngs modulas and bending modulus are reported.
10:15 AM - W3.4
Colloidosomes as Polymerization Vessels.
Stefan Bon 1 , Patrick Colver 1
1 Chemistry, University of Warwick, Coventry, West Midlands, United Kingdom
Show Abstract10:30 AM - W3.5
Advanced Metal Foams Stabilized by Novel Nano and Colloidal Particles.
Robert Pugh 1 , Martin Andersson 1
1 Chemistry, Institute for Surface Chemistry, Stockholm Sweden
Show Abstract10:45 AM - W3: interfaces
BREAK
11:15 AM - **W3.6
Stimuli-responsive Emulsions Stabilized by Nanocomposite Microgel Particles Alone.
Bernard Binks 1 , Ryo Murakami 1 , Steven Armes 2 , Syuji Fujii 2
1 Chemistry, University of Hull, Hull United Kingdom, 2 Chemistry, University of Sheffield, Sheffield United Kingdom
Show AbstractAqueous dispersions of lightly cross-linked poly(4-vinylpyridine)/silica nanocomposite microgel particles are used as sole emulsifiers of methyl myristate and water (1:1) at various pH and at 20 °C. The particles swell with decreasing pH of the aqueous dispersion (hydrodynamic diameter increases from 248 nm at pH = 8.0 to 513 nm at pH = 3.6). For batch emulsions prepared above pH = 3.4, oil-in-water emulsions form which are stable to coalescence but exhibit creaming. However below pH = 3.3, oil-in-water emulsions are very unstable to coalescence and phase separation occurs just after homogenization. The pH for 50 % ionization of the particles in bulk solution (pKa) was determined to be 3.4. Thus the charged swollen particles no longer adsorb at the oil-water interface. For continuous emulsions (emulsion prepared at pH = 7.5 and pH decreased progressively), demulsification takes place rapidly below pH = 3.3, implying that particles adsorbed at the oil-water interfaces can be charged and detached from the interfaces in situ. Furthermore, at a fixed pH (4.0), addition of sodium chloride into the aqueous dispersion increases the degree of ionisation of the particles and batch emulsions are significantly unstable to coalescence at salt concentrations above 0.2 M. Therefore, the degree of ionization of such microgel particles is a dominant factor in controlling the coalescence stability of oil-in-water emulsions.S. Fujii, E.S. Read, B.P. Binks and S.P. Armes, Adv. Mater., 17 (2005), 1014.
11:45 AM - **W3.7
Observations of the Behavior of Solid Particles at Oil-Water Interfaces
Janet Elliott 1 , Raymond Chiang 1 , Samuel Asekomhe 1 , Jacob Masliyah 1
1 Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractNanometer sized solid particles are known to play a role in stabilizing emulsions. However, detailed study of the behavior of such particles at interfaces is difficult because the position of the particles at the interface cannot be directly optically observed. A number of interesting phenomena have been observed in oil-water emulsion systems containing naturally occurring and experimentally introduced nanometer scale solid particles. For example, the presence of naturally occurring solids in particular size ranges is known to contribute to the stability of water-in-diluted-bitumen emulsions that confound the extraction of this heavy oil from oil sands. Observations have been made of the crumpling “skins” that can be seen when water is removed from a water-in-crude-oil drop at specific conditions; however, the nanoscale structure of the skin and its direct relation to emulsion stability are unknown. In other experiments with model systems, the phase in which introduced nano-particles first reside affects whether stable oil-in-water or water-in-oil emulsions are formed. We have constructed a macroscopic model consisting of 10-100 micrometer diameter glass beads attached at oil-water interfaces, the position of which can be directly observed. While such a system does not exhibit all of the colloidal scale behavior of real solid-particle-stabilized emulsion droplets, the role of particle position at the interface on the observed drop behavior can be directly studied. Our model system behaves similarly to colloidal scale systems in that particles protruding from a droplet surface can prevent coalescence. Using the reduced gravity environment of a parabolic flight aircraft, we have been able to observe the movement of solid particles during coalescence. In this environment, the particles are large enough to observe directly but have diminished effects of gravity – gravity would normally play a role in an enlarged system but would not be significant in the nanoscale system of industrial interest. In order to understand some of the behavior observed in reduced gravity, we have performed further ground-based experiments, studying the role of the initial phase of the particles on their behavior at oil-water interfaces. The behavior observed in the model system helps explain some previously published nanoscale solid-particle-stabilized emulsion results and is consistent with the location of particles at interfaces being influenced by hydrophobicity, starting phase, the presence of energy barriers (such as those caused by line tension) and van der Waals attraction. Finally, area contraction of droplets with particles attached at the interface shows that the attachment of hydrophobic beads of intermediate contact angles is sufficient to cause interface crumpling. The crumpling is similar to that observed for water drops in crude oil or bitumen subjected to interfacial area retraction.This research was funded by the Canadian Space Agency and NSERC.
12:15 PM - W3.8
Measurements of Static and Hydrodynamic Interaction Forces between Pluronic Stabilized Oil Droplets
Raymond Dagastine 1 , Tam Chau 1 , Derek Chan 3 , Geoff Stevens 1 , Franz Grieser 2
1 Chemical and Biomolecular Engineering, University of Melbourne, Melbourne, Victoria, Australia, 3 Mathematics and Statistics , University of Melbourne, Melbourne, Victoria, Australia, 2 School of Chemistry, University of Melbourne, Melbourne, Victoria, Australia
Show AbstractPluronics, (PEO-PPO-PEO) tri-block co-polymers, are commonly used in a wide range of applications ranging from emulsion stabilization to drug delivery due to their low toxicity and price. Understanding the behaviour of adsorbed Pluronics layers at oil-water interface and their effect on interactions on the nanometer scale is crucial in controlling emulsion stability, hence improving process efficiency and prolongs product shelf life. However, measurements of interfacial forces at deformable interfaces are uncommon due experimental challenges. In this work, we have employed a recently developed method using atomic force microscopy (AFM) to study the static and hydrodynamic interactions between oil droplets in aqueous solution stabilized by a series of Pluronic co-polymers. Both electrostatic double layer and steric forces were observed in combination with pronounced hydrodynamic drainage forces. The effect of stabilizer length on both surface forces and hydrodynamic drainage will be discussed.
12:30 PM - W3.9
pH-Responsive Diblock Copolymer Micelles: Self-Assembly at Solid/Aqueous Solution Interfaces and the Application.
Kenichi Sakai 1 , Erica Wanless 2 , Steven Armes 3 , Simon Biggs 1
1 School of Process, Environmental and Materials Engineering, University of Leeds, Leeds United Kingdom, 2 School of Environmental and Life Science, The University of Newcastle, Callaghan, New South Wales, Australia, 3 Department of Chemistry, The University of Sheffield, Sheffield United Kingdom
Show AbstractA diblock copolymer poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethyl amino)ethyl methacrylate) (PDMA-PDEA) can form pH-responsive micelles reversibly in aqueous solution: PDMA-PDEA exists as unimers under an acid condition, while in alkaline solution it forms core-shell micelles with the hydrophobic PDEA chains located in the cores and the hydrophilic PDMA chains forming the micelle coronas. When adsorption is investigated from the micellar solutions, the adsorbed layer structure at either a mica/aqueous solution or silica/aqueous solution interface shows an adsorbed layer of micelles. Interestingly, however, titration to a lower pH is not seen to completely degrade this layer even when the bulk structures would be completely disaggregated. Rather, we see that: (i) the adsorbed micelles seen at high pH are observed to “open” at low pH (due to protonation of the hydrophobic PDEA core chains); and, (ii) the original core-shell adsorbed micelles appear to be reformed on returning to high pH. In this presentation, we report evidence for the self-assembly of PDMA-PDEA micelles at a silica/aqueous solution interface as a function of polymer concentration and elapsed time, respectively. In addition, the effects of repeated exposure to acidic/alkaline water on the adsorbed micelle structures are presented. The possible applications of such adsorbed polymer films will also be discussed and the results of some preliminary investigations will be presented. For example, this new type of ‘smart’ surface coating may provide a novel route to encapsulate a wide range of hydrophobic molecules (into the PDEA cores) and then to facilitate their release in response to an external stimulus. Based on this possibility, we have been studying the required conditions to develop controlled capture and release applications. Secondly, such a core-shell micelle may act as a nanoreactor for preparing nano-ordered materials. In particular, it is accepted that the development of organic/inorganic hybrid materials using a self-assembled molecular layer is an exciting prospect. Thus, in our work, we have been preparing metal nanoparticles encapsulated by a zwitterionic diblock copolymer poly(2-diethylamino) ethyl methacrylate-block-poly(methacrylic acid) (PDEA-PMAA) in order to organise the particles at solid/aqueous solution interfaces.
W4: Colloid Synthesis I
Session Chairs
Tuesday PM, April 18, 2006
Room 2001 (Moscone West)
2:30 PM - **W4.1
Development of Thermoresponsive Magnetic Nanoparticles and their Application to Biotechnology and Medicine.
Akihiko Kondo 1 2 , Noriyuki Ohnishi 2
1 Chemical Science and Engineering, Kobe University, Kobe, Hyogo, Japan, 2 , Magnabeat Inc., Goi, Chiba, Japan
Show Abstract3:00 PM - W4.2
Preparation and Characterization of Self-Assembled Nanoparticles from Cello-Oligosaccharide-Pendant Polymers
Takao Satoh 1 , Shoji Nagaoka 2 , Makoto Takafuji 1 , Hirotaka Ihara 1
1 , Kumamoto University, Kumamoto Japan, 2 , Kumamoto Industrial Research Institute, Kumamoto Japan
Show AbstractRecently, cellulose spherical particles have received much attention as functional materials, possessing potential applications including drug delivery, enzyme encapsulation and catalysis.However it is not easy to prepare nano-sized cellulose particles because cellulose shows poor workability due to its low solubility both in water and common organic solvents.If we succeed to prepare nano-sized cellulose particles, various important applications like nano-carrier, nano-catalysis and probe will be expected. In this paper, we introduce nano-sized particles derived from cello-oligosaccharide-pendant polymers as analogues of cellulose. The nano-sized particles were prepared through the following procedure: (1) Synthesis of saccharide pendant vinyl monomer from constitutional units of cellulose such as glucose (C1), cellobiose (C2) and cellotriose (C3). (2) Polymerization of the obtained saccharide-pendant vinyl monomer in aqueous solutions using ammonium peroxydisulfate as an initiator and N,N,N',N'-tetraethylethylenediamine as an accelerator.The molecular size of the obtained saccharide-pendant polymers were determined by SEC with an exclusion molecular weight value of 2.0 x 107. When water was used as an eluent, the elution time was almost around Mlim of the column. However, when LiBr was added to the eluent, the elution time was remarkably delayed. These results indicate that the obtained polymer behaves as huge aggregates caused by intermolecular hydrogen bondings. In addition, we observed these huge aggregates by transmission electron microscopy (TEM). TEM images indicated that the shape was spherical particles and the average diameter of poly(C1), poly(C2) and poly(C3) were 24 nm, 36 nm and 76 nm, respectively.In conclusions, we could prepare nanoparticles spontaneously with novel saccharide-pendant polymers.
3:15 PM - W4.3
A Novel Simple Route to Synthesize Aqueous Niobium and Tantalum Precursors for Ferroelectric and Photocatalytic Applications.
Ai-Dong Li 1 2 , Jin-Bo Cheng 1 2 , Qi-Yue Shao 1 2 , Di Wu 1 2 , Yue-Feng Tang 1 2 , Nai-Ben Ming 2 3
1 Materials Science and Engineering Department, Nanjing University, Nanjing, Jiangsu, China, 2 National Laboratory of Solid State Microstructures , Nanjing University, Nanjing, Jiangsu, China, 3 Physics Department, Nanjing University, Nanjing, Jiangsu, China
Show AbstractDue to the great potentials of tantalate and niobate materials in ferroelectric and photocatalytic fields, development of proper tantalum or niobium precursors is urgently need. In wet chemical synthesis of Ta-based or Nb-based oxide such as sol-gel and metalorganic decomposition, alkoxides of tantalum and niobium are most frequently used as starting sources. However, certain inherent problems are associated with Ta or Nb alkoxides, including relatively high cost and great sensitivity to moisture. Recently a simple polymerizable complex (PC) route, known originally as the Pechini method, has been developed to solve these problems. However, air-stable water-soluble tantalum and niobium precursors are still not easily available. In this paper, a simple novel route to synthesize aqueous tantalum and niobium precursors has been developed using cheap and stable Nb2O5 or Ta2O5 as starting source, based on the basic flux technique. Various analytical techniques have been employed to characterize the formation mechanism, purity, and thermal decomposition features of the precursors. The synthesis processing has been optimized. These Ta or Nb precursor solutions have higher Ta or Nb ion purity over 99.5% among detectable positive ions with long shelf life. IR analyses confirms that the element Ta or Nb exists in the precursor solution as the group of COO-Ta (Nb)-O. Using home-made Ta and Nb precursors, several ferroelectric and photocatalytic nanopowders such as LiTaO3, Sr0.75Ba0.25Nb2O6, SrBi2Ta2O9, and Sr2Nb2O7, have been prepared at lower processing temperature (500-850 oC) by a modified PC method. They have pure crystalline phases with uniform sizes of 20-100nm and larger specific surface area in the range of 9-20 m2/g, compared to conventional solid phase reaction at 1000-1300 oC. The related ferroelectric and photocatalytical properties have also been characterized. All these results demonstrate that this is an attractive and flexible approach for fabrication of tantalate and niobate functional materials.
4:00 PM - **W4.4
Underlying Mechanisms of Size Control of Uniform Nanoparticles.
Tadao Sugimoto 1
1 , Tohoku University (Prof. Emer.), Sendai Japan
Show AbstractInsights are given into underlying mechanisms for size control of uniform nanoparticles in liquid phases. At the outset, a fundamental equation of the nucleation of monodispersed particles for their size control is derived, and the applicability of the equation is discussed. Then, a reverse micelle system and a gel-sol system are chosen to characterize the nucleation and size control of uniform nanoparticles in the individual systems, as typically applicable and inapplicable cases, respectively.The fundamental formula of nucleation, leading to the final number of particles in a monodisperse system, is derived on assumption of the LaMer mechanism, in which the nucleation stage is automatically terminated by the lowered supersaturation with the increasing consumption of monomer for the growth of the generated stable nuclei under a constant supply of monomer. The formula tells us that the final particle number is proportional to the supply rate of monomer and inversely proportional to the volume growth rate of a generated nucleus. Since the supply rate of monomer is assumed to be constant in the mass balance between the monomer supply and its consumption for nucleation and growth of the nuclei, this formula is not necessarily applicable to every monodisperse system. For example, it may apply to open systems, in which monomer is constantly furnished from outside, and closed systems for the formation of metal oxide particles by slow hydrolysis of alkoxides in sol-gel systems or by forced hydrolysis of transition metal ion at a low pH. However, it is inapplicable to some other closed systems, in which the supply rate of monomer is increased in accordance with the increasing consumption rate of the monomer for the growth of the generated nuclei, such as gel-sol systems for particle formation by the dissolution of precursor gel.As an example of applicable systems, we shed light on a reverse micelle system for the formation of uniform AgCl nanoparticles, which has recently provided conclusive counterevidence against the conventional explanation of the formation mechanism of uniform nanoparticles in reverse micelle systems, in terms of the reaction in individual water pools as nanoreactors or nanotemplates. As an example of inapplicable systems, we bring into focus the nucleation and size control of anatase TiO2 nanoparticles in a gel-sol system based on the dissolution of Ti(OH)4 gel, in which the solute concentration is kept constant at a high level in equilibrium with the gel, and thus the nucleation stage is terminated only by the lowered solubility of the gel itself with the development of the hydrogen bonding of the gel network. The nucleation rate and the final particle number are determined by the pH-dependent concentration of a specific precursor complex of titanium ion in equilibrium with the gel.
4:30 PM - W4.5
Intermetallic Nanoparticles for Fuel Cell Applications: Synthesis and Characterization Studies.
Chandrani Roychowdhury 1 , Francis DiSalvo 1
1 Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States
Show AbstractIn the quest for improved anode electrocatalysts for direct fuel cells (e.g. DMFC), several platinum containing ordered intermetallic systems have been investigated, focusing on attempts to synthesize nanoparticles of pure phases of such compounds. Various synthetic techniques have been attempted, and this has led to the formation of many intermetallic compounds with varying domain and particle sizes. We present here our results from many novel synthetic techniques that have successfully achieved this goal to make intermetallic nanoparticles. The Polyol process has used to produce 20 nm sized PtBi particles. PtPb has been synthesized by reduction of the corresponding metal salts with hydrazine. The mean particle size has been of the order of 10 nm and this can be controlled by use of different surfactants. PtBi and PtPb have been synthesized by using alcohols as the solvent and NaBH4 as the reducing agent. Carbon supported intermetallic nanoparticles have also been synthesized by chemical co-reduction of novel metal precursors. Results from the characterization studies of these nanoparticles using pXRD, SEM, UHV-STEM, EDX, electron diffraction, XPS, BET surface area measurements and light scattering analyses, are discussed. Finally, electrocatalytic activity of these compounds towards the oxidation of many fuels, for future application in PEM fuel cells, is discussed.
4:45 PM - W4.6
Molecular Mechanism for the Synthesis of Colloidal CdSe Semiconductor Nanocrystals by Thermal Decomposition of Organometallic Precursors.
Haitao Liu 1 2 , A. Alivisatos 1 2
1 Department of Chemistry , University of California, Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory , Berkeley, California, United States
Show AbstractThe synthesis of CdSe nanocrystals was investigated using 1H and 31P NMR spectroscopy. We have found that water significantly changed the reaction products and kinetics. In the absence of water, the reaction products were CdSe, phosphine oxide, and polyphosphonic acid. In the presence of water, phosphonic acid instead of polyphosphonic acid was produced. A reaction mechanism was proposed, in which the key step was the decomposition of phosphine selenide via a SN2 pathway. The mechanism was believed to be applicable to the synthesis of other group II-VI materials. It was successfully used to explain a number of experimental observations, including the dependence of reaction rate on substrates and the acceleration effect of water on the reaction. The application of the mechansim in the synthesis of group II-VI nanocrystals were demostrated.
5:00 PM - W4.7
Synthesis and Shape Separation of Gold Nanoparticles
Mohan Srinivasarao 1 2 , Kyoungweon Park 1 , Vivek Sharma 1
1 School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, Altanta, Georgia, United States, 2 School of Chemistry and Biochemistry , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe shape and size of the gold nanoparticles greatly affect many physical properties and hence the applications depend on the shape and size. There have been tremendous efforts to develop methods which can yield nanoparticles with good control over the particle shape and size. Among the many methods to produce gold nanoparticles of various sizes and shapes, wet chemical routes are considered to be versatile, economical and easy to perform procedure. The chemical principle is the reduction of an aqueous solution of gold (III) derivatives - chloroaurate (AuCl4-) in most cases. Reduced gold atoms start to precipitate in the form of small sub-nanometer particles (nucleation). The gold atoms that appear later stick to the existing particles (growth).In the wet chemical method, the most common observation is as follows: Trimethylammonium surfactant is a prerequisite as a stabilizer for the successful formation of anisotropic shape of gold nanoparticles. The concentration of surfactant should be above its crictial micelle concentration (CMC), and hexadecyltrimethylammonium bromide (CTAB) has been shown to be most effective to produce nanorods in a larger fraction, while maintaining mild conditions for the reduction. In attempting to provide a mechanism for the synthesis of gold nanorods the key issue is why the particle grows faster in one direction in comparison to the other direction. The role of CTAB in the synthesis of nanorods has been discussed extensively and the consensus is that CTAB adsorbs preferentially on to the specific crystal facet of the gold nanoparticles, thus confining the growth direction. Then the adsorption and reduction kinetics should greatly affect the morphology of NR, as has been found in the literature. Then in order to control the growth of nanoparticles, one should be able to manipulate the adsorption and reduction kinetics so that the gold particles grows slowly, while the stabilizing agent can exert control over the growth direction. In this talk we focus on the parameters which we believe exert control over the rate of reduction and adsorption. Once the nanoparticles have been made, the particles need to be separtated by their shape and size. The shape separation of gold nanorods from a mixture of rods and spheres is accomplished using centrifugation. We elucidate the hydrodynamic behavior of nanoparticles of various shapes to identify the parameters to achieve efficient separation. The particles undergo Brownian motion under the presence of external field, and at short times, develop Gaussian concentration profiles with peaks that move with different sedimentation velocities dictated by their Svdberg coefficients. This effects a separation of particles, presenting viability of centrifugation to separate nanoparticles.
5:15 PM - W4.8
Controlled Synthesis of Zinc Selenide Nanostructures using Oil-Water-Amphiphilic Block Copolymer Liquid Crystals
Georgios Karanikolos 1 2 , Paschalis Alexandridis 1 , T Mountziaris 3 1
1 Chemical and Biological Engineering, State University of New York, Buffalo, New York, United States, 2 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 3 Chemical Engineering, University of Massachusetts, Amherst, Massachusetts, United States
Show AbstractA technique for simultaneous size and shape control of compound semiconductor nanostructures using lyotropic liquid crystals as templates is presented. The liquid crystals are formed by self-assembly of a poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) block copolymer in the presence of a polar and a non-polar solvent. PEO-PPO-PEO block copolymers, due to their amphiphilic character, exhibit very rich structural polymorphism when dissolved in selective solvents of different polarity, and can attain a number of microstructures such as spheres, cylinders, and lamellae. In our previous work, luminescent ZnSe quantum dots* and single-crystalline nanorods** with average diameters below 10 nm were synthesized in oil-in-water microemulsions and lyotropic liquid crystals respectively, using the PEO-PPO-PEO/heptane/formamide self-assembled system and a reaction between diethylzinc dissolved in heptane with hydrogen selenide. In this work, the PEO-PPO-PEO/water/p-xylene system was used as template to study nanocrystal synthesis in the dispersed water phase. Luminescent quantum dots of ZnSe were grown in the spherical domains of reverse (water-in-oil) cubic liquid crystals by reacting zinc acetate with hydrogen selenide. Hollow nanospheres and hollow nanotubes were grown around the dispersed spherical and cylindrical oil nanodomains of the normal (oil-in-water) cubic and hexagonal phases, respectively. Free-standing quantum wells (nanoplates or nanolaminates) were grown in the lamellar liquid crystals. The zinc selenide nuclei are formed by a spontaneous and irreversible reaction between zinc acetate and hydrogen selenide,that is either bubbled through the microemulsion or allowed to diffuse into the liquid crystalline templates. The nuclei grow by surface reactions with unreacted precursors and by cluster-cluster coalescence to yield nanocrystals that acquire the shape and morphology of the self-assembled liquid crystalline domains. The nanostructures were characterized by HR-TEM, XRD, EDX and optical spectroscopy. The shape of the nanocrystals can be controlled by selecting the structure of the templating phase and the phase where the zinc precursor is dissolved. The size of the nanocrystals can be controlled by the size of the nanodomains and the concentration of the zinc precursor in them. Extensions of this work to other II-VI systems, such as CdSe and (Zn,Mn)Se will be discussed.* G.N. Karanikolos, et al., Langmuir, 20(3), 550 (2004).** G.N. Karanikolos, et al., Nanotechnology, 16(10), 2372 (2005).
5:30 PM - W4.9
Structural studies of surfaces and interfaces in core-shell CdSe-ZnS nanorods
Deborah Aruguete 1 , Benjamin Boussert 1 , Matthew Marcus 2 , Sirine Fakra 2 , Bryce Sadtler 1 , A. Paul Alivisatos 1
1 Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 , Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractWe present a structural study of core-shell CdSe-ZnS nanorods (3 × 20 nm cores), with ZnS shells of varying thickness (0.5-1 nm), using Zn, Se, Cd, and S X-ray absorption spectroscopy (XAS). We find that the Zn-S bond distances contract by up to 0.021(+0.005, -0.006)Å with respect to bulk ZnS, even though the ZnS has been grown on CdSe, which has a larger lattice constant. We observe the presence of Cd-Se and Cd-S bonds, but no Zn-Se bonds, confirming that there is an intermediate layer of CdS between the ZnS shell and the CdSe core. We also discuss the significance of our findings for understanding photoannealing-induced changes in core-shell nanorod optical properties.
5:45 PM - W4.10
Electronic Structure Studies of CdSe Nanocrystals Using Synchrotron Radiation
Robert Meulenberg 1 , Jonathan Lee 1 , Louis Terminello 1 , Tony van Buuren 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractWe have examined band edge shifts in colloidal CdSe nanocrystals using synchrotron radiation. In particular, Cd s states located at the conduction band minimum (CBM) show drastic size dependencies while the Cd d levels located a few electron volts up from the CBM show more localized behavior. This was not expected based on effective mass theories, although more sophisticated calculations are shown to agree better with experiment. Changing the surface ligand has very little effect on the shift of the band edges, but does affect the local bonding significantly. In addition, we find that the electronic structure can further be tuned by the incorporation of dopant atoms. Our experimental findings will be compared with recent theory to help resolve the nature of quantum confinement in CdSe nanocrystals. This work was supported by the Division of Materials Sciences, Office of Basic Energy Science, and performed under the auspices of the U.S. DOE by LLNL under contract No. W-7405-ENG-48.
Symposium Organizers
Norman Wagner University of Delaware
Gerald G. Fuller Stanford University
Jennifer Lewis University of Illinois, Urbana-Champaign
Ko Higashitani Kyoto University-Katsura
W5: Synthesis and Assembly I
Session Chairs
Wednesday AM, April 19, 2006
Room 2001 (Moscone West)
9:00 AM - **W5.1
Colloids with Directional Interactions.
David Pine 1 , Dana Breed 2 , Vinothan Manoharan 3 , Raymond Thibault 4 , Craig Hawker 4
1 Physics, New York University, New York, New York, United States, 2 Department of Chemical Engineering, University of California, Santa Barbara, California, United States, 3 Physics Department, Harvard University, Cambridge, Massachusetts, United States, 4 Materials Department, University of California, Santa Barbara, California, United States
Show AbstractA method for synthesizing a versatile new class of nearly spherical colloidal particles that interact with well-defined non-spherical symmetries is described. These particles are typically several hundreds of nanometers in diameter and have attractive interaction potentials with twofold, threefold, fourfold, or higher symmetries. For example, a colloidal suspension of particles with attractive potentials possessing twofold symmetry forms chains while a suspension of particles possessing fourfold symmetry forms aggregates with local tetrahedral symmetry. Thus, these particles have a well-defined “valence” analogous to atoms: the particles with twofold and fourfold attractive interactive potentials are analogous to sulfur and carbon, respectively, for example. Exotic higher symmetry particles are also available, particles with 7-fold or 12-fold icosahedral symmetries can be made.
9:30 AM - W5.2
Synthesis & Assembly of Nonspherical Iron Oxide-Silica Colloidal Building Blocks.
Stephanie Lee 1 , Mark Buckley 2 , Ian Hosein 1 , Itai Cohen 2 , Chekesha Liddell 1
1 Department of Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Physics, Cornell University, Ithaca, New York, United States
Show AbstractAnisotropic colloidal building blocks of controlled size and shape are of fundamental importance since they have been predicted not only to form new phases and exhibit novel colloidal behavior, but also to enable advances in emerging technology fields. For example, calculations have shown that nonspherical colloids in a face-centered cubic packing arrangement produce complete photonic bandgaps by lifting symmetry induced degeneracies in the band structure of photonic crystals. The resulting bandgaps are more tolerant to disorder arising from self-assembly processes than those associated with crystals composed of spherical building blocks. While research on spherical colloids with narrow size distribution has matured, methods resulting in monodispersed nonspherical particles appropriate in size for photonic crystal applications are relatively scarce and assembly is just beginning to be explored. In the present work, monodispersed hematite Fe2O3 particles of various morphology (peanuts, rods, and ellipsoids) are synthesized from condensed ferric hydroxide gel and coated with a shell of fluorescent silica. A sonochemical approach was employed to control the silica shell thickness. The core was subsequently converted to magnetite Fe3O4 by heat treatment in a reducing atmosphere. Ordered structures were obtained using magnetic field-directed assembly parallel and perpendicular to the substrate. Hollow, fluorescent silica shells were formed by selectively etching the core-shell particles with concentrated hydrochloric acid. Using confocal microscopy, the shear-induced ordering of the hollow anisotropic shells in confined colloidal solutions was also investigated. Colloidal phases were determined as a function of major parameters (i.e., shear rate and volume fraction) for each particle morphology system. The potential of these systems as photonic crystals with active, nonspherical bases will be discussed.
9:45 AM - W5.3
Synthesis of Surface-anisotropic Polystyrene Particles
Ilona Kretzschmar 1
1 Chemical Engineering, City College of New York, New York, New York, United States
Show AbstractThe increasing need for smaller, cheaper, and faster electronic circuitry has led to intensive research in the area of directed three-dimensional self-assembly. As a result the need for particles with anisotropic surfaces to aid such directed assembly has become apparent because most synthetic methods known to date yield particles with highly isotropic surfaces. Subsequent modification of these particles by chemical means usually leads to non-directional growth or shrinkage of the particles. Colloidal assembly of surface-isotropic particles results in formation of opal-like crystalline mono- and/or multilayers, which find their applications in areas such as photonics unless a mold is applied as a shape-directing agent. The ability to partially functionalize particle surfaces has crystallized as the key step towards directed assembly in three dimensions.
Very few groups1-3 have reported successful anisotropic decoration of particles. The surface modification is usually achieved by either employing shadowing effects or templating methods. Here we report our recent results on the modification of silver micro- and nanometer-sized, spherical particles by electrochemical means. The method presented consists of three subsequent steps; (i) assembly of a particle monolayer, (ii) partial embedment of the particle monolayer into a polymer film, and (iii) particle modification by electroless silver deposition onto the templated particles. Our method uses sulfonated polystyrene particles in the range from 100 nm to 2.4 μm. The first step involves the convective assembly of these particles into large area monolayers with domain sizes of ca. 6000 particles. In the second step, we embed the monolayers into polydimethylsiloxane (PDMS). Utilization of the effect of curing on the viscosity of PDMS as well as the effect of the pressure applied to the stamp enables us to control the embedment depths of the particles in the stamp. Subsequent exposure of the exposed particle surfaces to the electroless deposition environment yields particles with different sizes of silver caps. The paper will discuss the influence of stirring rate, exposure time, salt concentration, and amount of reducing agent on the structure and quality of the deposited film. Further, the stability of the deposited films during sonication and mechanical stress is discussed. (1)Lu, Y.; Xiong, H.; Jiang, X.; Xia, Y.; Prentiss, M.; Whitesides, G. M. J. Am. Chem. Soc. 2003, 125, 12724 - 12725. (2)Choi, J.; Zhao, Y.; Zhang, D.; Chien, S.; Lo, Y.-H. Nano Lett. 2003, 3, 995 - 1000. (3)Paunov, V. N.; Cayre, O. J. Adv. Mat. 2004, 16, 788-791.
10:00 AM - **W5.4
Homogeneously Nucleated and Epitaxial Growth of Colloidal Crystals
William Russel 1 , Matthew Sullivan 2 1 , Wesley Kopacka 1 , Paul Chaikin 3 1
1 Chemical Engineering, Princeton University, Princeton , New Jersey, United States, 2 , Schlumberger Inc, Boston, Massachusetts, United States, 3 Physics, New York University, New York City, New York, United States
Show AbstractColloidal dispersions offer ideal models for exploring experimentally the fundamental aspects of nucleation and growth through suppression of heterogeneous nucleation and time-resolved measurement in either Fourier or real space. Furthermore, advances in colloid synthesis and soft lithography enable the formulation of simple model systems and convenient templates for epitaxial growth. Recent and ongoing experiments with density and indexed matched dispersions of hard spheres probed via classical light scattering and confocal microscopy confront a variety of fundamental issues: functional dependence of rates of nucleation and growth, effects of curvature and surface tension, dendritic instabilities, polymorphism due to alternate stackings of hexagonal layers, and the mechanics and dynamics of equilibrium crystals.
10:30 AM - W5.5
Nanostructured Thin Films From Block Copolymer Micelles: Expanding the Scope of Possible Morphologies from Diblock Copolymers
Thomas Hermans 1 , Bas Lohmeijer 1 , Russell Pratt 1 , Ho-Cheol Kim 1 , Jeongsoo Choi 1 , Geraud Dubois 1 , Robert Waymouth 2 , James Hedrick 1
1 k17, IBM research, San Jose, California, United States, 2 Chemistry Department, Stanford University, Stanford, California, United States
Show AbstractBlock copolymers are remarkable self-assembling systems that can assume a wide variety of morphologies including lamellar, hexagonal-packed cylindrical and body-centered cubic sherical structures, depending on the relative volume fractions of the blocks. The use of amphiphilic block copolymers to direct the organization of polymerizing silica has been shown to produce well-ordered hexagonal mesoporous silica with pore sizes of 75 to 300A. Unlike conventional surfactants, block copolymers offer the possibility of fine-tuning the polymer/solvent phase behavior by adjusting molecular weight, composition, monomer types and deposition solvent. Here we describe the use of solvent selectivity to create self-assembled structures from diblock copolymers that template organosilicate vitrificate into a wide range of nanostructures with sizes ranging from lithographically achievable features down to features only possible from a “bottom-up” approach. Poly(lactide-b-dimethylacrylamide) diblock copolymers are shown to form micelles and inverse micelles depending on the solvent selection, and since polydimethylacrylamide is miscible with organosilicate oligomers, the micelles can selectively sequester the organosilicate into the either the corona or core of the micelle. Following vitrification of the organosilicate and thermal decomposition of the diblock copolymer a wide range of porous morphologies were achieved.
10:45 AM - W5.6
Self-assembly of Block Copolymer–Experiment, Simulation and Applications.
Yeng Ming Lam 1 , Lixin Song 1
1 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore
Show Abstract11:30 AM - **W5.7
Surfactant-Induced Dewetting and its Use in Crystallization.
Patrick Spicer 1
1 Complex Fluids Research, Procter and Gamble Co., West Chester, Ohio, United States
Show AbstractLiquid emulsion droplets can violently dewet their own solid crystals during crystallization as a result of surfactant adsorption. The crystal shape formed is a function of the relative rates of dewetting and crystallization as controlled by surfactant adsorption, cooling rate, and liquid purity. For negligible dewetting rates, crystals nucleate and grow within the droplet. At similar crystallization and dewetting rates, the droplet is propelled around the continuous phase on a crystalline “comet tail” much larger than the original droplet. Rapid dewetting causes the ejection of small discrete crystals across the droplet’s oil-water interface. The phenomenon has been investigated for its use in purification and templating of materials.
12:00 PM - W5.8
Preparation of Completely Dispersed Magnetite Nanoparticles by Surfactant Assisted Method in Organic Solvents.
Motoyuki Iijima 1 , Mayumi Tsukada 1 , Hidehiro Kamiya 1
1 Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan
Show Abstract12:15 PM - W5.9
DNAzyme- and Aptamer-directed Assembly of Nanoparticles and Their Applications as Colorimetric Sensors
Yi Lu 1 , Juewen Liu 1
1 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractLargely due to the high extinction coefficients and distance-dependent optical properties, metallic nanoparticles have been shown to be very attractive in DNA-related colorimetric assays. We have previously reported the use of DNAzymes for directed assembly of gold nanoparticles and its application as colorimetric sensors for metal ions such as lead (1-4). We are interested in expanding this methodology to even broader range of molecules. Aptamers (nucleic acid-based binding molecules obtained through systematic evolution of ligands by exponential enrichment (SELEX)) may provide such a platform. Preferably, the assembly and sensing should be simple to design, easy to operate and give fast color change with minimal materials consumption. We herein communicate a general sensor design method that can meet all the above criteria (5). To demonstrate the generality, sensors for adenosine and cocaine have been designed, both of which can produce color changes in seconds and at room temperature. Since no special feature on the aptamers is required, the design should be able to be used for any molecule of choice. 1. Juewen Liu and Yi Lu, J. Am. Chem. Soc. 125, 6642-6643 (2003); 2. Juewen Liu and Yi Lu, Anal. Chem. 76, 1627-32 (2004); 3. Juewen Liu and Yi Lu, J. Am. Chem. Soc. 126, 12298-12305 (2004); 4. Juewen Liu and Yi Lu, J. Am. Chem. Soc. 127, 12677 - 12683 (2005); 5. Juewen Liu and Yi Lu, Angew. Chem., Int. Ed. (in press).
12:30 PM - W5.10
Exploring the Optical Properties of Shape-controlled Silver Nanocrystals and their Assemblies.
Andrea Tao 1 , Peidong Yang 1 2
1 Chemistry, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract12:45 PM - W5.11
Nanoscale Artificial Molecular Receptors for Use in Suspensions, Coatings or Membranes - Molecularly Imprinted Polymer Nanospheres
Guenter Tovar 1 2 , Carmen Gruber-Traub 1 , Marc Herold 1 , Achim Weber 1 , Melanie Dettling 2 , Saygun Sezgin 2 , Herwig Brunner 1 2
1 Biomimetic Surfaces, Fraunhofer IGB, Stuttgart Germany, 2 Institute for Interfacial Engineering, University of Stuttgart, Stuttgart Germany
Show AbstractMolecular imprinting is a template polymerization which produces artificial binding sites in polymers. Their specific cavities can be used for molecular recognition reactions mimicking the antibody-antigen interaction, but now with a completely synthetic system. A major drawback for a broad exploitation of the imprinting technology as specific polymer material was its preparation method. Molecularly imprinted polymers (MIP’s) were usually synthesized as polymer monoliths, ground, sieved and a portion of about 20 % of useful particles was selected for further use. Such particles are intrinsically irregularly shaped and have typical dimensions in the range 10 – 20 µm. MIP’s prepared in this way, however, proofed to be highly effective and selective as stationary phase in HPLC. Nowadays MIP’s with a more defined morphology and of smaller size open new applications for these artificial receptor material. In a new approach, we synthesized MIP’s as nanoscopic spheres. [1] A variety of highly crosslinked copolymer networks, e.g. poly(methacrylic acid)-co-(ethylene glycol dimethacrylate) nanoparticles were prepared by miniemulsion polymerization in presence of a molecular template (e.g. amino acid derivatives L- or D-boc-phenylalaninanilid) with a yield of 98 % 2.[2] Coagulate-free and stable latexes were obtained. The prepared polymer colloids are in the size range of 50 – 300 nm. The efficiency of the imprinting process was quantified by ligand binding experiments using UV/Vis and HPLC. [3] The nanoscopic molecularly imprinted polymers (MIP’s) allowed for the first time for an examination of the non-covalent interaction between the synthetic receptor and various ligands by microcalorimetry. [4] The two-phase preparation method introduced here now opens the way to imprinting mor complex templates such as peptides or proteins. The preparation and the use of the colloidal MIP’s, e.g. as the surface coating of an optical waveguide sensor, and as the specifier in a selective composite membrane are presented. [5][1] Tovar, G. E. M., Kräuter, I., Gruber, C., Top. Curr. Chem. 2003, 227, 125-144.[2] D. Vaihinger, K. Landfester, I. Kräuter, H. Brunner, G. E. M. Tovar, Macromol. Chem. Phys. 2002, 203, 1965.[3] Lehmann, M., Brunner, H., Tovar, G. E. M., J. Chromatogr. B 2004, 808, 43-50.[4] A. Weber, M. Dettling, H. Brunner, G. E. M. Tovar, Macromol. Rapid Commun. 2002, 23, 824.[5] M. Lehmann, H. Brunner, G. E. M. Tovar, Desalination 2002, 149, 315.
W6: Synthesis and Assembly II
Session Chairs
Wednesday PM, April 19, 2006
Room 2001 (Moscone West)
2:30 PM - **W6.1
Field and Shape Effects on the Assembly of Ordered Structures from Micron-size Particles.
Michael Solomon 1
1 , University of Michigan, Ann Arbor, Michigan, United States
Show Abstract3:00 PM - **W6.2
Generalized and Large-scale Synthesis of Monodisperse Nanocrystals without a Size Selection Process.
Taeghwan Hyeon 1 2 , Jongnam Park 1 2 , Jin Joo 1 , Kwangjin An 1 2 , Sang-Hyun Choi 1 2
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 National Creative Research Initiative Center for Oxide Nanocrystalline Materials , Seoul National University, Seoul Korea (the Republic of)
Show AbstractWe developed a generalized synthetic procedure to produce monodisperse nanocrystals of many transition metals, metal oxides, and metal sulfides without a size selection process. Highly-crystalline and monodisperse nanocrystals were synthesized from the thermal decomposition of metal-surfactant complexes. These synthesized nanocrystals include metals (Fe, Cr, Cu, Ni, and Pd), metal oxides (gamma-Fe2O3, Fe3O4, CoFe2O4, MnFe2O4, NiO, and MnO) metal sulfides (CdS, ZnS, PbS, and MnS) and core/shell nanocrystals of Ni/Pd and Cu/CuO. We report the ultra-large-scale synthesis of monodisperse nanocrystals by the thermolysis of metal-oleate complexes, prepared from the reaction of metal salts and sodium oleate. We synthesized as much as 40 grams of monodisperse ferrite nanocrystals using 500 mL of solvent. Using a seed-mediated growth process, monodisperse magnetite nanocrystals with continuous size spectrum of 6, 7, 8, 9, 10, 11, 12, 13, 14 nm were synthesized. We synthesized various oxide nanocrystals with various shapes were synthesized via non-hydrolytic sol-gel reactions. We synthesized uniform and highly-crystalline zirconia with high-temperature tetragonal crystal phase, uniform ZnO nanocrystals with cone, hexagonal cone, and rod shapes, and anatase TiO2 nanorods with uniform diameter of 3.4 nm using non-hydrolytic sol-gel reactions. The synthesis and the growth mechanism will be discussed in the current presentation.
W7: Synthesis II
Session Chairs
Wednesday PM, April 19, 2006
Room 2001 (Moscone West)
4:00 PM - **W7.1
Template Preparation of Porous Polymer-Based Materials via Sequential Self-Assembly
Frank Caruso 1 , Yajun Wang 1
1 Department of Chemical & Biomolecular Engineering, University of Melbourne, Melbourne, Victoria, Australia
Show AbstractTemplating techniques have been widely employed to generate materials with tailored properties. Mesoporous silica (MS) has been commonly used in template synthesis, largely due to its high surface area and tunable pore size (typically between 2-50 nm). For example, metal, metal oxide, carbon, and polymer replicas have been prepared by using MS templates. However, the preparation of such materials has involved the infiltration of low molecular weight species into the templates followed by chemical reactions and template removal to generate porous materials. Herein, we report the template synthesis of a range of nanoporous materials of diverse morphology, composition and function via the sequential solution assembly of preformed polyelectrolytes (PEs) and/or (bio)macromolecules in MS matrixes. This approach offers a general and versatile method to prepare nanoporous materials with tailored properties. We demonstrate that this method is applicable to a broad range of polyelectrolytes (e.g., synthetic and natural polyelectrolytes) and biomacromolecules, and that it is suitable for MSs of different shapes (spheres, fibers etc.) and sizes, enabling the generation of a suite of porous polymer-based materials. Such materials are expected to find application in biosensing, enzyme catalysis, and controlled drug delivery.
4:30 PM - W7.2
Surface Engineering of Micro and Nanoparticles.
Kenneth Lau 1 , Karen Gleason 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThere are currently many approaches to accomplish surface functionalization and modification of particles with polymers. Liquid phase methods include spray drying of polymer solutions, surface initiated polymerization, coacervation and layer-by-layer assembly. Dry methods include physical and chemical vapor deposition. Liquid methods such as spray drying suffer from particle agglomeration during coating especially for particles below 100 µm in size due to strong liquid surface tension forces from liquid bridges which form between the particles during solvent evaporation. Dry methods such as plasma enhanced chemical vapor deposition result in polymers with a high degree of crosslinking and lack of chemical specificity.We present an all-dry encapsulation process, initiated chemical vapor deposition (iCVD), to produce stoichiometric polymer coatings on fine particles without agglomeration. iCVD can be viewed as a liquid phase radical polymerization sans the solvent. Monomer and initiator are introduced in the vapor phase. The initiator is thermally decomposed by a series of heated filament wires to form primary radicals. These radicals together with the monomer are adsorbed onto a cold surface where polymerization events (initiation, propagation and termination) take place.Surface engineering will be demonstrated on micro and nanoparticles either by layering a polymer with the requisite functionality on the surface or by subsequent modification of the polymer to obtain the desired functionality. Spectroscopic data demonstrate that well-defined, stoichiometric, linear chain polymers can be formed in a CVD environment. Microscopy data show that particles remain unagglomerated after particle encapsulation. By incorporating methacrylic acid functionality directly in the polymer coating, a pH-dependent release of core material (e.g., pharmaceutics, dyes) can be achieved. By binding amine-containing molecules to a glycidyl functional polymer coating, surface active particles can be achieved. Kinetic modeling reveals a gas-to-surface radical polymerization that is similar to liquid phase polymerization, yielding tools for new materials design and scale-up rules for surface engineering.
4:45 PM - W7.3
Synthesis and Tunable Phase Transition Behavior of Thermo-Responsive Nanogels Based on N,N -Diethylacrylamide/N,N-Dimethylacrylamide Copolymers
Xihua Lu 1 , Cheuk-Wai Kan 1 , Erin Doherty 1 , Annelise Barron 1
1 Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract5:00 PM - W7.4
Creating Air-Stable Tethered Lipid Bilayers as Cell Membrane Mimics
Luis Cascao-Pereira 1 , Mark Gebert 1 , William Throndset 1 , Matt Flynn 1 , Meredith Fujdala 1 , Vicky Huynh 1 , Todd Becker 1
1 , Genencor , Palo Alto, California, United States
Show AbstractLipid bilayers on solid substrates have shown great promise as cell membrane mimics. Potential applications include drug discovery, biocompatible surfaces and biosensors. To date, the fragile nature of biomimetic lipid bilayers have precluded their incorporation into practical devices, such as biosensors, due to their lack of stability. Attempts to increase the stability of artificial lipid bilayers include the use of polymer cushions [1] and chemical tethering to the solid substrate [2]. In this paper, we report on tethered lipid bilayers (t-BLM) that were made stable against exposure to an air interface when dried for long-term storage. Upon rehydration the t-BLM regains nearly all of its functionality. We will discuss the role of drying process parameters, formulations and provide some mechanistic insights. Our t-BLM is made of phytanyl lipids and is linked to a gold substrate via disulphide bonds. Moreover, the t-BLM possesses an ionic reservoir made of hydrophilic ester linkers suitable for the incorporation of membrane proteins, especially ion-channels [2, 3]. We characterize our lipid bilayers at different processing stages by electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), fluorescence microscopy, fluorescence recovery after photobleaching (FRAP), and the ability to incorporate membrane proteins, in our case the ion channel gramicidin-A. Bilayers stored wet lose physical integrity and functionality within a few weeks. EIS measurements indicate loss of electrical seal due to increased leakage conductance. Tapping AFM reveals lipid bilayer rearrangement leading to desorption and the appearance of bilayer-free defect patches. In contrast, rehydrated bilayers remain insulating even after prolonged dry storage. Further incorporation of gramicidin allows dimer formation and rise in conductance levels. FRAP studies show that fluidity (percent recovery) and mobility (in-plane diffusion constant) of rehydrated bilayers remain comparable to the fresh, never dried, state. This approach enables long-term storage in the dry state, while taking advantage of the self-assembly nature of lipids in their fluid, wet state for device manufacture.1. Sinner, E.K. and W. Knoll, Functional tethered membranes. Current Opinion in Chemical Biology, 2001. 5(6): p. 705-711.2. Cornell, B.A., et al., A biosensor that uses ion-channel switches. Nature, 1997. 387(6633): p. 580-583.3. Sang-Kyu Lee, L.G.Cascao-Pereira., Rafael F. Sala, Susan P. Holmes, Kevin J. Ryan and Todd Becker, Ion channel switch array: A biosensor for detecting multiple pathogens. Industrial Biotechnology, 2005. 1(1): p. 26-31.
5:15 PM - W7.5
On the Principle of Fabrication of Hierarchical meso- and macropore Architectures by Liquid- crystalline and Polymer Colloid Templating.
Ozlem Sel 1 , Daibin Kuang 1 , Matthias Thommes 2 , Bernd Smarsly 1
1 Colloids Department, Max planck Institute of Colloids and Interfaces Am Muhlenberg 1, Golm Potsdam Germany, 2 , Quantachrome Instruments, 1900 Corporate Drive, Boyton Beach FL 33426, Florida, United States
Show AbstractHierarchical porous materials are of interest both in fundamental research and for applications such as catalysis, adsorption, chromatography or electrode materials. In this context, we define a hierarchical pore architecture as a 3D arrangement of well-defined pores of different sizes, the smaller ones being located in the walls between the larger pores, establishing the connectivity. So far in literature, there are not many reports on truly hierarchical porous materials probably due to lack of suitable templates. This study concentrates on the generation of porous silica with hierarchically organized bimodal mesoporosity of adjustable size and well-defined shape by using surfactant mixtures and the nanocasting procedure. Ideally for the build-up of hierarchical mesoporosity, two types of micelles should self-assemble to an organized “alloy” phase, with the small surfactant being located in the interstitial sites of the BC mesostructure. A systematic study of combinations of various BCs (F127, KLE, SE) with smaller surfactants (P123, C16mimCl, CTAB) revealed that hierarchical bimodal mesopore architectures could only be obtained by the usage of BCs with a strong hydrophilic-hydrophobic contrast such as KLE (H(CH2CH2CH2(CH)CH2CH3)x(OCH2CH2)yOH) and SE (poly(styrene)-(poly(ethylene oxide)) giving rise to pores between 6-22 nm. Furthermore, the ionic liquid (IL) (1-hexadecyl-3-methylimidazolium-chloride) C16mimCl appeared to have advantageous templating properties, resulting in 2-3 nm pores being located between the spherical BC mesopores, while phase separation was observed for Pluronics and CTAB as small templates. Thereby, the study provided general insights into the mixing and co-self-assembly behavior of BCs and ionic surfactants in water and confirmed the special templating properties of ILs, as recently proposed [1]. Moreover bimodal silica (KLE/IL) materials were used as model systems to verify a novel NLDFT (non-local density functional theory) approach that enables the determination of the spherical mesopore size accurately which is not possible with BJH method. On top of the bimodal mesoporosity, additional tunable macroporosity was created by the presence of polymer spheres, leading to the desired well-defined trimodal hierarchical pore architectures. As a major improvement, due to the pore hierarchy these large-pore materials showed relatively high surface area and pore volume, and the size of densely packed macropores could be even decreased down to 90 nm [2]. The same approach was also used to obtain bimodal meso- macroporous silica films and is also applicable to obtain hierarcy in the pore structure of metal oxides such as CeO2 or TiO2. The materials were characterized by electron microscopy, small-angle x-ray scattering, Hg- porosimetry and N2 sorption using NLDFT approach.References[1] Kuang et al. J. Am. Chem. Soc., 2004, 126, 10534-10535.[2] Smarsly et al. Langmuir, accepted.
5:30 PM - W7.6
Ionic Liquids as Templates for the Fabrication of Nanostructured Materials.
Helena Kaper 1 , Bernd Smarsly 1 , Markus Antonietti 1
1 Colloid department, Max-Planck-Institute of Colloids and Interfaces, Potsdam, Brandenburg, Germany
Show AbstractIonic liquids as templates for the fabrication of nanostructured materialsRecently, ionic liquids (IL) have gained a lot of attention. ILs are organic salts with low melting points, in fact many are liquid at room temperature. Their peculiar characteristics include negligible vapour pressure, thermal stability, high ionic conductivity and a large electrochemical window. These features make them interesting for industrial applications such as environmentally friendly solvents, electrochemical devices and for separation techniques.As shown recently1,2, aside from these classical applications ionic liquids, can be used as templates to generate inorganic mesoporous materials, showing structural building blocks on the nanometer scale. Such materials are of interest for catalysis, new types of solar cells, separation, etc. The basis for these new applications of ILs is their general phase behavior, and, in particular, the liquid-crystalline behavior observed for certain ILs. The main objective of the current study is the elucidation of the relationship between the role of ionic liquids as templates and their chemical composition. In contrast to other conventional surfactants like CTAB (cetyltrimethylammoniumbromide), certain ionic liquids show thermotropic and lyotropic phase behavior. Thus, the phase behavior of C16mimCl (1-hexadecyl-3-methylimidazolium chloride) was investigated in detail. The thermotropic behavior of C16mimCl is quite complex. DSC (differential scanning calorimetry) and in-situ temperature dependent WAXS (wide angle x-ray scattering) experiments reveal up to three crystal modifications and strong supercooling effects. The lyotropic phase behavior of C16mimCl in water exhibits three phases: micellar, hexagonal and lamellar. At very low water content, a miscibility gap is observed.In the present study, the ability of ionic liquids to act as template was used for the synthesis of crystalline mesoporous titanium oxide. Here they take over the role as solvent and template at the same time, allowing a low-temperature synthesis (even smaller than 100 °C) of crystalline TiO2 (anatase) with significant porosity up to 200 m2/g, mesopores of the size 2-10 nm and nanocrystals 5-10 nm in size. It is worthy to note that the process is performed without additional solvents and with only low water content. Ionic liquids with different cations (imidazolium, pyrrolidinium and phosphonium based), various alkyl chain lengths and diverse anions were examined in order to study the relationship between the chemical structure the templating properties. The mesostructure, crystallinity and porosity of the mesoporous titania was studied in detail by various techniques such as SAXS (small angle x-ray scattering), WAXS (wide angle x-ray scattering), TGA (thermal gravity analysis) and nitrogen adsorption. 1. Y.Zhou et al. J. Am. Chem. Soc. 2003, 125, 14960.2. M. Antonietti et al. Yong, Angew. Chem. Intern. Ed. 2004, 43, 4988.
5:45 PM - W7.7
Controlling the Growth of Biomolecular Mesoporous Microcrystals.
Joshua Falkner 1 , Achala Talati 1 , Ali Al-Somali 1 , Stephanie Adrianse 1 , Anju Chatterji 2 , John Johnson 2 , Tianwei Lin 2 , Vicki Colvin 1
1 Chemistry, Rice University, Houston, Texas, United States, 2 Molecular Biology , Scripps Research Institute, La Jolla , California, United States
Show AbstractProtein and virus crystals offer some unique properties in that they are mesoporous materials (2 - 20 nm) that consist of chemically heterogeneous pore walls. These pores are tunable in size depending on the crystal structure and occupy 30-70% of the total crystal volume. It has been demonstrated that these crystals are useful for a variety of applications such as catalyst or as a stationary phase for chromatography. However the performance of these applications could be enhanced by using smaller crystals which will allow greater mass transport within the crystalline material. Here we discuss methods for controlling biomolecular crystal growth to achieve uniform sub-micron biomolecular crystals of a specific size, shape, and the desired crystal morphology.
W8: Poster Session: Colloid I
Session Chairs
Thursday AM, April 20, 2006
Salons 8-15 (Marriott)
9:00 PM - W8.1
Nanostructured Biomaterials for Implantation with Reduced Bacterial Adhesion
Faith Coldren 1 , Nicole Levi 1 , David Carroll 1 , Mark Welker 4 , Elizabeth Palavecino 2 , William Wagner 2 , Holly Tyler 3 , Barnaby Dedmond 3 , Beth Smith 3 , Thomas Smith 3 , Lawrence Webb 3
1 Physics, Center for Nanotechnology and Molecular Materials, Wake Forest University, Winston-Salem, North Carolina, United States, 4 Chemistry, Wake Forest University, Winston-Salem, North Carolina, United States, 2 Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States, 3 Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States
Show AbstractApproximately 112,000 orthopaedic device-related infections occur per year in the United States, at an approximate hospital cost of $15,000-70,000 per incident. Implant related infections may lead to multiple problems for patients such as wound breakdown, failure of bone healing, and chronic osteomyelitis. As many as 80% of these infections are caused by Staphylococcus aureus. S. aureus has been shown to adhere to extracellular matrix and plasma proteins as well as to implants. This adhesive growth, which is pivotal in the development of osteomyelitis, is facilitated by the bacterium’s elaboration of an exopolysaccharide layer which functions to enable adherence of the bacteria to inert surfaces such as an orthopaedic implant or sequestrum while also conferring some resistance to antibiotics. The goal of this study was to investigate the effects of fullerene species on the adherence and bioactivity of S. aureus to standard implant materials. PLLA constructs impregnated with fullerene species and stainless steel (Kirschner wire) coated with various fullerene species were studied. Using scanning electron microscopy we observed altered growth morphology between the coated Kirschner wire and S. aureus. Standard adhesive analysis revealed a reduced adhesion of the bacteria to coated Kirschner wire. Additionally, atomic force microscopy was used to elucidate the microscopic origins of adhesion between the bacteria and fullerene species and PLLA constructs. The results of our adhesion studies for the nanostructured biomaterials that we investigated will ultimately be used to design more inert surfaces for implantation.
9:00 PM - W8.10
Low Temperature Synthesis of Ag Nanowires.
Sung Yang 1
1 Chemistry, Kyung Hee Univ., Yongin Korea (the Republic of)
Show AbstractSilver nanoparticles and nanowire were synthesized by reducing silver nitrate with hydrazine in the presence of tetrabutylammonium bromide. The temperature has played important roles in determining the shape of the nanocrystals. The aspect ratio could be controlled over a wide range, from 1 to 70 by varying the reaction time. Transmission electron microscopy studies indicate that the ends of the nanowire are terminated by four {111} facets arranged radially to the <100> direction of elongation and side walls of the nanowires along the length is surrounded by {110} facets. The very selective Ag ions diffusion onto the highly reactive {111} facets is supposed to result the anisotropic growth.
9:00 PM - W8.11
In situ Nanoparticle Synthesis on Monolayer Templates
Krisanu Bandyopadhyay 1
1 Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan, United States
Show Abstract9:00 PM - W8.12
The Properties of Colloidal Layered Double Hydroxides
Elizabeth Gardner 1 , Sandra Blough 1 , Jennifer Gursky 1 , Luis Bonilla 1
1 Chemistry, University of Texas at El Paso, El Paso, Texas, United States
Show AbstractLayered double hydroxides (LDHs) are an important class of synthetic materials with applications in catalysis, environmental remediation, pharmacology, protective coatings and composite materials. Recent advancements such as colloidal-LDHs and LDH-organic hybrids have led to enhanced physiochemical properties that increase the potential applications of LDHs in areas such as nanocomposites, biomaterials, photonic crystals membranes, and sensors. The physiochemical properties of the colloidal-LDHs are being studied through a combination of experimental and theoretical calculations. The effect of solvent on the particle size and morphology is being investigated with powder X ray diffraction, FTIR, and TEM. The relative energies of various M2+/M3+ ratios and structures is being modeled using Gaussian 03W with periodic boundary conditions by building the unit cell in incremental steps.
9:00 PM - W8.13
Thermo- and pH-Sensitive Enzymatically Synthesized Polyaniline Colloidal Particles
Rodolfo Cruz-Silva 1 2 , Jorge Romero-Garcia 2 , Layza Arizmendi 2 , Eduardo Arias-Marin 2 , Ivana Moggio 2
1 Laboratorio de Polimeros, Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Cuernavaca, Morelos, Mexico, 2 Departamento de Materiales Avanzados, Centro de Investigacion y Quimica Aplicada, Saltillo, Coahuila, Mexico
Show AbstractPolyaniline colloidal particles were prepared by enzymatic polymerization of aniline using different environmentally sensitive water-soluble polymers as steric stabilizers. The progress of the reaction was monitored by UV-Vis spectroscopy, conductometry and open-circuit potential measurements, indicating that enzymatic polymerization is fast and occurs without pernigraniline formation during the oxidation stage. Fourier transform infrared spectroscopy showed the formation of the emeraldine salt form of polyaniline during the reaction. Morphology of the polyaniline colloids were observed by transmission electron microscopy. The synthesized particles were studied by X-ray photoelectron spectroscopy, indicating that the steric stabilizers were attached to the surface. Colloidal particles stabilized with poly(N-isopropyl acrylamide) underwent rapid flocculation when the temperature of the dispersion exceeded the lower critical solution temperature of this thermosensitive polymer. This behavior was reversible by cooling the solution under agitation, and this process could be repeated many times without apparent change in the colloid stability. In an analogous behavior, the dispersions of chitosan stabilized polyaniline particles were stable under acidic conditions, but when a dilute solution of ammonium hydroxide was added, the particles started to flocculate, and a clear transition was observed at a pH of 6.5, close to that where chitosan becomes insoluble. Different applications of this environmentally responsive polyaniline colloids, such as polyaniline films selective deposition, separation technologies and thermochromic windows will be discussed.
9:00 PM - W8.14
Novel Porous Silica Nanoparticles for Mercury Removal in Flue Gas
Tingying Zeng 1 , Jainxin Geng 1 , Wei-ping Pan 1
1 Chemistry, Western Kentucky University, Bowling Green, Kentucky, United States
Show Abstract9:00 PM - W8.15
Phase Behavior of Membrane Coated Colloids for Bioanalytical Applications
Nathan Clack 1 , Michael Baksh 1 , Jay Groves 1 2
1 Biophysics, University of California, Berkeley, California, United States, 2 Chemistry, University of California, Berkeley, California, United States
Show AbstractMembrane proteins are of substantial pharmacological significance because proteins, such as G-protein coupled receptors, are the starting points for many of the signaling cascades implicated in cancer and immune disorders. Recently, we developed an assay using cell-sized lipid coated beads displaying membrane bound receptors to detect subtle molecular interactions on the membrane surface via traditional microscopy methods without implementing sophisticated or complicated experimental protocols. These membrane modified beads self assemble into two-dimensional dispersions via biological recognition events exhibiting collective behaviors while enabling direct imaging of many interacting particles and providing a statistical readout of the colloidal structure. Binding of proteins to the membrane causes a colloidal phase transition that can be harnessed as a detection strategy. However, the mechanisms effecting colloidal aggregation and dispersion remain elusive. Even in an aggregated state, these like-charged beads are typically separated by hundreds of nanometers, suggesting changes in long-range electrostatic interactions govern observed structural transitions. To explore this seemingly anomalous behavior, we observe how changes in electrostatic parameters, such as ionic strength and bead surface potential, effect bead pair-interaction potentials estimated using high-resolution statistical imaging of low-density colloidal monolayers. These potentials are used as input to a Monte Carlo integration in order to predict resulting phase behavior. By comparing simulated and observed colloidal structures, we aim to establish whether pair interactions are sufficient to describe observed behavior. In addition, the same methodology is applied to study how protein binding changes effective pair interactions and, in turn, colloidal structure. Understanding the nature of these interactions will facilitate the design of future colloid based strategies for detecting ligand-receptor interactions.
9:00 PM - W8.16
Modification of Citrate-Stabilized Gold Nanoparticles with Functionalized Thiols Containing Charged Pendant Groups
Jennifer Dahl 1 2 , James Hutchison 1 2
1 Chemistry, University of Oregon, Eugene, Oregon, United States, 2 Materials Science Institute, University of Oregon, Eugene, Oregon, United States
Show AbstractCitrate stabilized gold nanoparticles have garnered the interest of nanomaterials researchers in recent years due to their unique size-dependent optical and electronic properties, as well as their ease of preparation. However, successful organization of these particles into useful structures has been limited to labor intensive manipulations using microscopy probes or electron-beam lithography. Here, new functionalization chemistry is presented where the complex, electrostatically bound citrate ion stabilization shell is replaced with a covalently bound ligand shell composed of thiols bearing either positive, negative, or neutral pendant functional groups. These ligand shells provide a new means of nanoscale manipulation of the particles, as well as improved stability in a wide range of environments.
9:00 PM - W8.17
CdSe Quantum Dots: Improving Synthesis and Photoluminescence.
John Mayo 1 , William Yu 1 , Joshua Falkner 1 , Vicki Colvin 1
1 Chemistry, Rice University, Houston, Texas, United States
Show AbstractMany synthetic methods are in existence for CdSe Quantum Dots, but some improvements are necessary. A cleaner synthesis, limiting toxic or other dangerous reagents and solvents, is the first area of improvement that will be discussed. Increasing the Photoluminescence Quantum Yield through synthetic methods is the next area of improvement that will be discussed. Other improvements will be mentioned in other Quantum Dot systems such as the near-IR emitter, PbSe.
9:00 PM - W8.18
Low-Temperature Size-Controlled Synthesis Of CoFe2O4 Nanoparticles For Data Storage Applications.
Eric Calderon-Ortiz 1 , Oscar Perales-Perez 1 , Carlos Rinaldi 1
1 , University of Puerto Rico, Mayaguez, Puerto Rico, United States
Show Abstract9:00 PM - W8.19
A "Polymerization" approach to Explain the Oriented Attachment Mechanism in Anisotropic Nanocrystals
Caue Ribeiro 1 , Eduardo Lee 1 , Elson Longo 2 , Edson Leite 1
1 Chemistry, Universidade Federal de Sao Carlos, Sao Carlos, SP, Brazil, 2 Chemistry, Universidade Estadual Paulista, Araraquara, Sao Paulo, Brazil
Show AbstractTailoring the shape and properties of nanostructures is one of today’s major challenges that must be overcome to allow for the large-scale use of nanotechnology. The controlled preparation of nanocrystals colloids with specific size and shape has been recently investigated extensively in studies involving the synthesis of nanoparticles and methods for growing anisotropic crystals such as nanowires, nanoribbons and nanorods among others. However, this is still a very active field strongly motivated for the preparation of nanostructures with tailored morphologies using nanoparticles as building blocks. In this sense, investigations into growth and coarsening mechanisms in colloidal suspensions of nanoparticles are fundamental to clearly understand how anisotropic nanostructures are formed. In this way, the kinetic model of stepwise polymerization is revisited, with some adaptations intended for its application in the kinetics of the oriented attachment of nanoparticles in colloidal suspensions, which result in the formation of anisotropic particles (nanowires). The kinetic equations obtained predicts a non-linear behavior of the nanowire lenght to time, i.e., a equation of the type l = -C.1/ln(t/1+t), where l is the particle lenght, C a constant and t the time. The general shape of the equation shows a strong logaritmic behavior for very small particles, and a almost linear in larger wires. A comparison with experimental data from SnO2 and TiO2-anatase reported in the literature shows good agreement with the model and supports comparisons with other systems.
9:00 PM - W8.2
Equilibrium Particle Aggregates In Attractive Colloidal Suspensions.
Simona Sennato 1 2 , Federico Bordi 1 2 , Cesare Cametti 1 2
1 Physics, University La Sapienza, Roma, Italia, Italy, 2 , Istituto Nazionale di Fisica della Materia INFM, CRS-SOFT, Unita' Roma1, Roma Italy
Show Abstract9:00 PM - W8.21
Low-Temperature Synthesis and Magnetic Characterization on TM-doped ZnS Nanostructures
Sandra Dussan 1 , melissa Morales 3 , Cesar Echevarria 1 , Oscar Perales-Perez 2 , M.S Tomar 1
1 Physics Department, University of Puerto Rico Mayaguez campus, Mayaguez, Puerto Rico, United States, 3 Industrial Biotechnology, University of Puerto Rico Mayaguez campus, Mayaguez, Puerto Rico, United States, 2 General Engineering-Materials Science and Engineering, University of Puerto Rico Mayaguez campus, Mayaguez, Puerto Rico, United States
Show Abstract9:00 PM - W8.22
PVP Micellar Nanoreactors for Blue-Luminescent ZnO Quantum Dots
Cleva Ow-Yang 1 , Ani Kamer 1 , Fatma Uyar 1 , Emine Begum Gulsoy 1 , Hasan Kurt 1 , Cem Ozturk 1
1 Faculty of Engineering & Natural Sciences, Sabanci University, Istanbul Turkey
Show AbstractWednesday, April 19New Presenter AuthorPoster W8.22PVP Micellar Nanoreactors for Blue-Luminescent ZnO Quantum Dots. Fatma Uyar
9:00 PM - W8.23
Block Copolymer Brush-Ag Hybrid Thin Films by Surface-Initiated Polymerization for Antimicrobial and Antifouling Surfaces.
Xiaowu Fan 1 , Daniel Sherman 1 , Simonida Grubjesic 1 , Haeshin Lee 1 , Phillip Messersmith 1
1 Biomedical Engineering, Northwestern University, Evanston , Illinois, United States
Show AbstractAg colloids have been widely used as antimicrobial materials due to their bactericidal characteristic and non-toxic nature. Poly(ethylene glycol) (PEG)-based polymer coatings are well known for their resistance to fouling by proteins and cells. In this study, we combine the properties of these two materials by creating block copolymer-Ag hybrid thin films. Our synthetic strategy involves grafting diblock copolymer brushes from a Ti substrate using surface-initiated polymerization (SIP) and subsequent in situ formation of silver nanoparticle within the polymer coating. First, we designed and synthesized a biomimetic bifunctional initiator containing a catechol for adsorption to metal surfaces and an alkyl bromine to initiate atom transfer radical polymerization (ATRP). The initiator was immobilized onto Ti substrates by chemisorption from aqueous solution, after which surface-initiated ATRP (SI-ATRP) was performed using a new methacrylamide monomer containing a catechol side chain. Both initiator and monomer were inspired by the catecholic amino acid 3,4-dihydroxyl-L-phenylalanine (DOPA), a key component of water-resistant mussel adhesive proteins. The catechol moiety of DOPA is believed to form strong surface complexes with metal oxides and to participate in redox reactions leading to crosslinking of the mussel protein glue. After SI-ATRP of the catechol based monomer formed a poly(DOPA) (P(DOPA)) block, the living nature of ATRP was exploited to form a second block by addition of a PEG-methacrylate monomer. Subsequently, the P(DOPA)-co-PEG diblock copolymer coated substrates were then submerged in AgNO3 to form metallic Ag by redox reaction with the catechol side chains of the P(DOPA) block. The formation of diblock copolymer and subsequent metallization was confirmed by x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Antifouling tests were performed by culturing 3T3-Swiss albino fibroblast cells on grafted and unmodified surfaces. In our preliminary short-term (4 hours) cell adhesion experiments, P(DOPA) and P(DOPA)-Ag surfaces showed comparable level of cell attachment with unmodified Ti while P(DOPA)-PEG-Ag hybrid thin film surface demonstrated nearly 99% reduction in cell adhesion. Staphylococcus epidermidis RP62A was cultured on bare Ti and grafted substrates at a density of 1x105 CFU/mL for 2 hours and the bacterial adhesion densities were quantified to assess the antimicrobial performance. As compared to bare Ti, a control pure PEG surface (prepared by SI-ATRP directly from initiator modified substrate) demonstrated approximately 80% less in bacterial adhesion whereas the P(DOPA)-PEG-Ag hybrid coating sample exhibited approximately 95% less bacterial adhesion.
9:00 PM - W8.24
A Novel Approach for the Preparation of InP Nanocrystals
Zhaoyong Sun 1 , Jun Zhang 1 , Ming Zhang 1 , Jiye Fang 1
1 Dept. of Chemistry & AMRI, Univ. of New Orleans, New Orleans, Louisiana, United States
Show AbstractIII-V semiconductor quantum dots are of considerable interest due to their extensive applications in the optoelectronic and biomedical fields. In order to meet the practical use, the convenient and scalable production of III-V monodisperse nanoparticles is inspiring. We report an efficient and rapid method of preparing highly monodisperse InP quantum dots using a wet-chemical redox synthetic approach with a noncoordinating solvent, employing organic reducing agent LiBH(CH2CH3)3 and yellow phosphor. As advantages of this approach, reaction temperature is relatively low (80°C-120°C) and reaction time is less than 2 hours. Moreover, capping ligand TOP and stabilizing agent oleic acid play important roles in the formation of InP nanocrystals in polar or non-polar solvents. Without oleic acid, the produced InP nanocrystals are soluble in ethanol. Our characterization shows that the photoluminescence properties of InP nanocrystals are highly dependent on the particle size.
9:00 PM - W8.25
Wet-chemical Synthesis of ZnTe Quantum Dots
Jun Zhang 1 , Zhaoyong Sun 1 , Jiye Fang 1
1 Dept. of Chemistry & AMRI, Univ. of New Orleans, New Orleans, Louisiana, United States
Show AbstractZnTe quantum dots (QDs) have been attractive very much because of their potential applications in optoelectronic devices of operation in the blue-green region. This report describes a convenient one-step synthesis, producing high-quality ZnTe nanocrystals with high yield using a high-temperature organic solution approach. Anhydrous zinc chloride was dissolved in phenyl ether under argon protection and oleylamine was added as a capping agent. Pre-prepared solution of metallic tellurium in trioctylphosphine (TOP) was rapidly injected into the hot reaction mixture as the source of tellurium, and the system was vigorously agitated at certain temperature for several min. The crystalline growth was subsequently terminated by quickly removing the heating source. The resulting nanocrystals were isolated by centrifugation and were re-dispersed in Hexane. The obtained spherical ZnTe nanocrystals are highly monodispersed and their sizes can be controlled simply by tuning the growth time. The morphology and phase structure were investigated using TEM and XRD. The adoption of a dynamic injection technique significantly improved the morphology. Photoluminescence (PL) spectra were also studied, indicating that quantum-size-confinement effect could be observed when the size is less than 10 nm.
9:00 PM - W8.26
Preparation of Cellulose/TiO2/CoO-Al2O3 Hybrid Spherical Microbeads for Color Materials with Photo-catalytic Activity
Shoji Nagaoka 1 , Kenji Arinaga 2 , Shigenori Hamaoka 3 , Makoto Takafuji 2 , Hirotaka Ihara 2
1 Materials Development Department, Kumamoto Industrial Research Institute, Kumamoto, Kumamoto, Japan, 2 Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University, Kumamoto, Kumamoto, Japan, 3 , Kyushu Inoac Co. Ltd., Fukuoka, Fukuoka, Japan
Show AbstractThis paper introduces a new method for preparation of blue-colored photo-catalytic materials supported on cellulose spherical microbeads, in order to develop environmental-friendly color materials. These microbeads were prepared by the modified phase separation method using a cellulose xanthate (viscose) and a polyacrylate aqueous solution as reported previously[1]. TiO2 nano-particles (21 nm) were used as photo-catalyts, and CoO-Al2O3 sub-micron-particles (700 nm) were used as inorganic pigments. Interestingly, the distributions of TiO2 and CoO-Al2O3 particles in the obtained microbeads remarkably depended on the preparation condition. For example, when TiO2 were homogeneously mixed with CoO-Al2O3 by a dry-milling method, these inorganic moiety were preferentially concentrated on the surface of the obtained microbead. In order to evaluate photo-catalytic activities for decomposition of acetaldehyde, a gas-bag A method was carried out. The hybrid microbeads showed much higher photo-catalytic activity compared with the corresponding hybrid microbeads prepared by mechano fusing method in which TiO2 were dispersed. We also describe that yellow, red and green-colored photo-catalysts can be prepared according to the present method using TiO2-Sb2O3-NiO, Fe2O3 and TiO2-CoO-NiO-ZnO as inorganic pigment. [1] S. Nagaoka, K. Arinaga, H. Kubo, S. Hamaoka, T. Sakurai, M. Takafuji and H. Ihara, Polymer. J., 37, 186 (2005).
9:00 PM - W8.27
Surface Plasmon Resonances of Metal Polyhedral Nanoparticles
Cecilia Noguez 1 , Ana Gonzalez 1
1 Instituto de Fisica, UNAM, Mexico D. F. Mexico
Show Abstract9:00 PM - W8.28
New Generation of Two-in-One Magnetic-Fluorescent Nanocomposite Materials for Biomedical Applications.
Serena Corr 1 , Yurii Gun'ko 1 , Aisling Byrne 1 , Swapankumar Ghosh 2 , Dermot Brougham 2
1 Chemistry, Trinity College Dublin, Dublin Ireland, 2 Chemical Sciences, Dublin City University, Dublin Ireland
Show AbstractResearch on magnetic nanoparticles is of great importance and interest because of their applications in magnetic recording devices and biomedicine. In particular, the use of magnetic fluids of magnetite (Fe3O4) and iron oxide (Fe2O3), as both diagnostic tools in the form of magnetic resonance imaging (MRI) contrast agents and as a method of hyperthermic cancer treatment, is one of the fastest growing areas of nanobiomedical research. The main aim of this work is to prepare a new generation of materials which exhibit both magnetic and fluorescent properties. These novel materials represent an exciting prospect in bionanotechnology because they may be used for both visualisation of intercellular components and mechanical manipulation using an external magnetic field. This new material is extremely water stable, opening up the possibility of a new generation of magnetic fluids with fluorescent markers.Here we present our research on the preparation of new magnetic nanocomposites, employing a siloxane coating on magnetite nanoparticles, followed by treatment with fluorescent dyes such as porphyrins. These new nanomaterials have been studied using different techniques such as TEM, SEM, IR, UV-vis, Photoluminescence, Confocal and Mössbauer spectroscopy and magnetisation measurements and NMR dispersion techniques. Properties and potential uses of this material for biomedical research will be discussed.
9:00 PM - W8.29
Sintered Nanoparticles for High Temperature Interconnect Joints
A Murray 1 2 , P Jaroenapibal 3 , B Koene 4 , S Evoy 1 2
1 Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, 2 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 3 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 4 , Luna Innovations, Blacksburg, Virginia, United States
Show AbstractOil field, automotive, aerospace and military instrumentation operate in extreme environments ranging from 200°C to over 500°C. Combined with rapid thermal fluctuations inherent in high power semiconductor devices, these elevated temperatures render conventional lead based soldering techniques inadequate. Alternate bonding processes are therefore required to sustain such applications. Synthesis costs of Ag nanoparticles have recently dropped dramatically enabling their widespread application in the microelectronic industry. Current research shows that sintered Ag colloids have previously been used to form a die-attach at temperatures less than 300°C and pressures of 40 MPa[1]. We here report the development of a metallic colloid sintering process that would enable the creation of bonding layers at such moderate temperatures as well as pressures lower than 10MPa. Sintering processes, using 50% by weight n-propyl acetate dispersion of an Ag colloid, were studied. The colloidal solution exhibited bimodal size distribution averaging at 16.2nm and 103.7nm. Sintering was performed at temperatures ranging from 100°C to 300°C while subjected to pressures ranging up to 1 MPa. The inclusion of a polymer was also investigated as a way to promote efficient sintering under such moderate conditions. Its relatively low decomposition temperature made it an excellent additive that increased the integrity of the colloidal film during processing. Bond formation was characterized through the combined use of shear delamination tests, conductivity measurements, and SEM/EDX characterization. Significant particle coagulation was observed when the Ag nanoparticles were sintered at 300°C, resulting in initial shear strengths of approximately 2.4MPa. Although the addition of polymer increases the lifetime of a cast (rather than sintered) film, tests have shown this addition also decreased conductivity as well as shear strength of the sintered interconnect joint. Further development of this research will include evaluation of the eutectic alloying of additional metallic nanoparticles. Electrical and mechanical resilience testing under environmental conditions including climatic, thermal, and structural dynamics will be a major component in assessing the viability of the outlined approach. The application of such colloid sintering dimple-array interconnects will also be discussed.References:1. Zhiye (Zach) Zhang and Guo-Quan Lu, IEEE transactions on electronics packaging manufacturing, vol. 25, No. 4, p 279-283, Oct. 2002
9:00 PM - W8.3
Nanoscale Indentation of Polymer and Composite Nanoparticles by Atomic Force Microscopy.
Silvia Armini 1 2 , Ivan Vakarelski 3 , Caroline Whelan 1 , Karen Maex 2 1 , Ko Higashitani 3
1 , IMEC, Leuven Belgium, 2 Department of Electrical Engineering, Katholieke Universiteit Leuven, Leuven Belgium, 3 Department of Chemical Engineering, Kyoto University, Kyoto Japan
Show AbstractAtomic Force Microscopy (AFM) was employed to probe the mechanical properties of surface-charged polymethylmethacrylate (PMMA)-based terpolymer and composite terpolymer core-silica shell nanospheres in air and water media. The composite particles were achieved using two different approaches: tuning the pH of the reaction in order to have attractive electrostatic interactions between the terpolymer core and the smaller silica particles forming a continuous shell (composite B), and using silane-coupling agents as an interface between the core and the shell (composite A). On the basis of Hertz’s theory of contact mechanics, Young’s modulus (E) of 4,4, 10,3 and 11,1 GPa were measured in air for the PMMA-based terpolymer, the composite B and the composite A respectively, by analysis of force-displacement curves. In water, E decreases to 1,6 GPa for the terpolymer, to 3,6 GPa for composite B, while it remains constant at 11,1 GPa for composite A. This trend is related to the swelling of the polymer in water confirmed by Dynamic Light Scattering. The observation that E increases with the silica diameter, confirms that the size of the core and the thickness of the shell impact the composite mechanical properties. Close correlation is found between absolute values of elastic moduli determined by nanoindentation and known values for bulk materials. Since these composite materials exhibit properties of the organic polymer cores, such as toughness and elasticity, and/or that of ceramic shells, such as chemical stability and hardness, they are particularly interesting for potential applications in reducing defectivity during the process of Chemical Mechanical Planarization.
9:00 PM - W8.30
Phase Transformation Kinetics of Ag-doped FePt Magnetic Nanoparticles.
Ki-Eun Kim 1 , Min-Seok Kim 1 , Ji-Hyung Moon 1 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show AbstractFePt magnetic nanoparticles have been very actively studied for high-density magnetic recording application since they have high crystalline anisotropy when they are in face-centered tetragonal (FCT) structure. However, the annealing temperature to obtain FCT structure must be low enough to prevent sintering of FePt nanoparticles. Some alloying elements such as Ag and Cu have been introduced to reduce the phase transformation from disordered FCC to ordered FCT structure. Vacancy mechanism was suggested as a possible mechanism for the reduced phase transformation temperatures. In this study FePt nanoparticles doped with different content of Ag were synthesized using polyole method and as prepared nanoparticles were identified in disordered FCC structure using x-ray diffraction (XRD). The phase transformation kinetics study was performed by heating the nanoparticles at different temperatures for different time periods. The degree of FCC-to-FCT phase transformation was obtained using quantitative x-ray diffraction (Q-XRD). The variation in relative XRD integrated peak intensities was monitored. The degree of phase transformation at a specific temperature and time period was applied to Johnson-Mehl-Avrami (JMA) isothermal kinetic analysis. The Avrami exponent and activation energy values were determined using the JMA plots for FePt nanoparticles and those containing different content of Ag. The activation energy for the phase transformation decreased with increase of Ag content in FePt nanoparticles most possibly due to the increased vacancy concentration and thus high-Ag content FePt nanoparticles showed enhanced phase transformation kinetics. However, the saturation magnetization (Ms) decreased above certain Ag content.The kinetics experiments were also performed non-isothermally using differential scanning calorimetry (DSC) and DSC results were applied to the modified Kissinger kinetic analysis. The accuracy of the activation for the phase transformation obtained from Q-XRD and JMA analysis was confirmed.
9:00 PM - W8.31
Porous, Hollow, and Ball-in-ball Type Metal Oxide Microspheres
Won Hyuk Suh 1 , Ah Ram Jang 2 , Yoo-Hun Suh 2 , Kenneth Suslick 1
1 School of Chemical Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Dept. of Pharmacology, College of Medicine, Neuroscience Research Institute, MRC, National Creative Research Initiative Center for Alzheimer's Disease, Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe synthesis and control of materials in the submicron regime has seen an explosion of effort over the past decade. Various examples of metal and semiconductor nanoparticles are a focus of world-wide research. The availability of simple and scalable synthetic methods, however, often remains a limiting factor. We have now developed ultrasonic spray pyrolysis (USP) for the facile preparation of porous, hollow, or ball-in-ball nano-sized oxide materials. Anatase titania nanoparticles and silica composites were synthesized using an inexpensive ultrasonic generator (household humidifier); morphology and pore size were controlled by the silica to Ti(IV) ratio and silica particle size. With the introduction of transition metal ions, we were able to generate core-shell type structures in a single-pot synthesis. Products were characterized by SEM, (S)TEM, EDS, XRD, and confocal microscopy. With the growing concern of health effects of nanoparticles, we also investigated the endocytosis and cytotoxicity of these nanomaterials on mammalian cell lines. These nanoparticles are rapidly taken up into the cytoplasm (but not the nucleus) of macrophages and show very little cell toxicity.
9:00 PM - W8.32
Morphology of Random Poly(styrene-co-methacrylic acid ) Copolymers Neutralized with NaOH and Cast from DMF Solution
Jae-Jin Park 1 , Yu-Ri Park 1 , Youn-Jeong Cho 2 , Jeong-A Yu 3 , Joon-Seop Kim 1
1 Dept. of Polym. Sci. & Engr., Chosun University, Gwangju Korea (the Republic of), 2 Dept. of Chemistry, Chosun University, Gwangju Korea (the Republic of), 3 Dept. of Science Education, Chosun University, Gwangju Korea (the Republic of)
Show AbstractPoly(styrene-co-methacrylic acid) copolymer containing 6 mol% of acid units was neutralized with NaOH in different levels and their morphology was studied using SEM and TEM techniques. It was observed that the acid sample formed spherical particles, whose diameters were in the range of 50-400 nm. When 3 % of the acid groups were neutralized, however, the distribution of the particle sizes was found to become narrower, and the spherical particles started forming networks. At 20 % of neutralization level, the ionomer samples formed a layer consisting of very compactly packed spheres. As expected, the increasing degree of neutralization to 100 % made the size voids between nano-sized particles smaller. When the ion content of the ionomer increased to 9 mol% ionomer, one found only the smooth ionomer surface, no voids, at 100 % neutralization.
9:00 PM - W8.33
One-step One-phase Synthesis of Metallic Nanoclusters/Nanoparticles and their Properties.
Nanfeng Zheng 1 , Galen Stucky 1
1 Department of Chemistry and Biochemistry , University of California, Santa Barbara, California, United States
Show AbstractSyntheses of nanoclusters and nanoparticles with size less than 10nm have been widely dominated by Brust method, a two-phase reduction method. We present here a rather facile one-step one-phase synthesis of metallic nanoclusters and nanoparticles. This one-phase synthetic method can afford a wide range of metallic particles with narrow size distribution, which allows the easy formation of superlattices or even single crystals. Together with their syntheses, the unique optical, electrical and chemical properties of different nanoparticles will be also discussed.
9:00 PM - W8.34
Growth Kinetics of Mn-doped CdS Dilute Magnetic Nanocrystal Quantum Dots.
Ji-Hyung Moon 1 , Min-Seok Kim 2 , Yun-Mo Sung 2
1 Mater. Sci. & Eng., Daejin Univ, Pochun Korea (the Republic of), 2 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show AbstractDue to size-dependent light emitting characteristics II-VI semiconductor colloidal nanocrystals have been investigated for cell tagging applications through the formation of bioconjugates with suitable proteins. By adding magnetic properties to the nanocrystals more precise cell tracing using magnetic resonance imaging (MRI) and the fast drug delivery systems using magnetic field gradient can be realized. In this study Mn-doped CdS nanocrystals were synthesized using two-pot wet chemistry. The electron paramagnetic resonance (EPR) spectra of Mn-doped CdS showed the hyperfine splitting at 83x10-4 cm–1. With the increase in Mn content the decrease in lattice constants of Cd1-xMnxS was confirmed by X-ray diffraction (XRD) analyses. Also, when Mn content (x) increases in Cd1-xMnxS it is observed that the photoluminescence (PL) peaks slightly red shift since the small size Mn doping could induce tensile strain to the CdS lattices. The growth kinetics of Mn-doped CdS nanocrystals has been investigated and the amount of doping was changed. The size variation was monitored using full width at a half maximum (FWHM) of XRD peaks, shifts in PL peaks, and high-resolution transmission electron microscopy (HRTEM) analyses. It is found that the growth kinetics reasonably follows the Lifshitz-Slyozov-Wagner (LSW) theory for Ostwald ripening. We confirmed that the Ostwald ripening kinetics of Cd1-xMnxS decreases with Mn composition (x) at constant temperature. From the reaction rate constant (K) in LSW equation the diffusion constant values were determined with temperature. Arrhenius plots were created using the diffusion constant values for each Cd1-xMnxS nanocrystal with different Mn content (x) and activation energy values were determined for the ripening. This kinetics difference was discussed based upon the difference in the ionic field strength, which can be determined by the ratio of an ionic valence to an ionic radius. Since the ionic radius of Mn2+ is smaller than that of Cd2+ the ionic field strength of Mn-S is higher than that of Cd-S ions, and thus Cd1-xMnxS nanocrystals with high Mn content show higher activation energy for the growth. Thus, it can be concluded that the diffusion of Mn2+ ions is the mechanism determining Ostwald ripening kinetics in Cd1-xMnxS nanocrystals.
9:00 PM - W8.35
Nanocomposite Membranes Based on Doped Polyantimonic Acid.
Alexander Popov 1 , Dmitry Zakharyevich 1
1 Condensed Matter Physics, Chelyabinsk State University, Chelyabinsk Russian Federation
Show Abstract9:00 PM - W8.36
On the Structural and Optical Properties of ZnO Nanoparticles formed in Silica by Ion Implantation.
Maria Tagliente 1 , Marcello Massaro 1 , Giovanni Mattei 2 , Paolo Mazzoldi 2 , Giovanni Pellegrini 2
1 New Technologies and Materials Unit, ENEA, Brindisi Italy, 2 Dipartimento di Fisica, Universita' di Padova, Padova Italy
Show AbstractZinc Oxide (ZnO) is a II-VI semiconductor material with a wide direct band-gap of 3.37 eV at room temperature (RT). In the past decades, the material has been used for a variety of applications such as gas sensors, surface acoustic wave devices, or transparent contacts. Recently, ZnO has gained a new substantial interest primarily because to its potentialities for optoelectronic and spintronic applications. The renewed interest has been fueled by the availability of high-quality bulk substrates, reports of p-type conduction and theoretical predictions of its ferromagnetic behavior at room temperature when doped with transition metals. In the domain of optoelectronics, its main applications include devices emitting in the blue and UV regions by exploiting its wide band-gap such as light-emitting and laser diodes. With respect to several wide band-gap semiconductor materials, ZnO has the advantage of a larger exciton binding energy (about 60 meV) which paves the way for an intense near-band-edge excitonic emission at room and higher temperatures. On the other hand, a band gap engineering can be also achieved by the incorporation of Cadmium and Magnesium atoms into the ZnO lattice. Many techniques have been used to prepare ZnO in various forms, such as single crystals, powders and films. In the past few years, the great attention toward materials with nanometric size have motivated a number of studies on the synthesis of ZnO nanocrystals. Ion implantation is one of the most effective and versatile technique to obtain nanoparticles. ZnO particles embedded in silica matrix have been successfully prepared by ion implantation followed by thermal oxidation.In this work, we report on a detailed structural and optical characterization of the ZnO-silica nanocomposites by using several complementary techniques; in particular, Glancing Incidence X-ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS), linear Optical Absorption (OA) in the UV-near IR spectrum and Photo-Luminescence (PL). The ZnO nanoparticles embedded in SiO2 matrix were prepared by implanting the substrates with 130 keV Zn+ ions at doses of 1, 1.5 and 2*1017 ions/cm2. Subsequently, the implanted samples were annealed for 1h in a furnace at a temperature between 500 and 800°C under flowing O2 gas. X-ray diffraction results indicate the formation of Zn and ZnO nanoparticles in the as-implanted and annealed samples, respectively. Moreover, the ZnO nanocrystals embedded in the SiO2 matrix have a (002) preferred orientation. After the oxidation, the optical absorption spectra show an absorption edge at about 374 nm by confirming the presence of the ZnO particles. A relatively strong exciton photoluminescence peak was observed at room temperature under pulsed N2 laser excitation at λ=337nm. The results obtained, peculiarly related to the implantation doses and annealing temperature, are discussed.
9:00 PM - W8.37
Chemical Reactions of Inorganic Nanocrystals
Yadong Yin 1 , Can Erdonmez 2 , Andreu Cabot 2 , Paul Alivisatos 1 2
1 The Molecular Foundry, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Chemistry, University of California, Berkeley, California, United States
Show AbstractColloidal inorganic nanocrystals are promising building blocks for developing novel functional materials due to their ease of fabrication and processing, and the combination of strongly size- and shape-dependent physical properties. Great efforts have been devoted to synthesizing nanocrystals with morphologies of higher complexity in order to uncover greater potential of nanotechnology. In this presentation, we will summarize our recent studies on the production of nanostructures with new morphologies and/or compositions through chemical reactions of pre-formed colloidal inorganic nanocrystals. Hollow nanocrystals of metals, semiconductors, and insulators, and heterogeneous bimetallic dimers will be used as examples to illustrate the process of transformations.
9:00 PM - W8.38
Artificial Opals are Non-close-packed fcc Structures.
Florencio Garcia-Santamaria 1 , Paul Braun 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractWednesday, April 19thTransfer oral (W13.9) to poster (W8.38)Artificial Opals are Non-close-packed fcc Structures.Florencio Garcia-Santamaria
9:00 PM - W8.4
Development of Nano-structured Conductive Polymer Composites for Vapour Sensing: Self Structuring of Gold Nanoparticles in Thin Layers by Spin-coating.
Audrey Bouvree 1
1 , Lorient University , Lorient France
Show Abstract9:00 PM - W8.5
Spontaneous Crystallographic Ordering in Multilayered Cobalt Nanoparticle Assemblies.
Deborah Aruguete 1 , Can Erdonmez 1 , Tamara Radetic 2 , Joel Moore 3 , A. Paul Alivisatos 1
1 Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 , National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Physics, University of California, Berkeley, California, United States
Show AbstractMonodisperse Co particles with an average diameter of 9.0 nm are synthesized and assembled into ~1 μm diameter terraced structures. These structures display strong texture in the diffraction patterns, a previously observed, but relatively rare, phenomenon seen in packing of faceted nanoparticles. The unique crystallography of the particles allows us to conclude that three-fold symmetry of the pattern arises purely from presence of three distinct alignments adopted by the particles in the assembly. Dark field images suggest that these alignments segregate, to a degree varying from aggregate to aggregate, into domains that sometimes span a large fraction of the total extent of the aggregates. The potential roles of particle faceting, shape and interparticle dipolar interactions in determining thevarious levels of observed organization are discussed.
9:00 PM - W8.6
Fabrication of Three Dimensional Nanofluidic Mixer for Microfluidic Devices Using Inverse Opal Structure
Jau-Ye Shiu 1 , Peilin Chen 1
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Show AbstractEffective mixing is one the most important issues in the microfluidics, especially for microfluidic systems used in the chemical and biological applications. Most of today’s microfluidic mixer designs are two-dimensional, which may not provide efficient mixing for three-dimensional microchannel system. Here we describe a simple approach to fabricate three-dimensional nanofluidic mixer in the microchannels. To construct nanofluidic mixers, well-ordered colloidal crystal was first grown in the microchannels using monodispersed polystyrene nanoparticles by evaporation assisted self-assembly process. The size of polystyrene nanoparticles was in the range of 200-400 nm. Inverse opal structures can be obtained by filling the void space among nanoparticles with sol-gel and subsequent removal of polystyrene nanoparticles by dichloromethane. When the inverse opal structure was integrated into the microfluidic system, it worked as an efficient nanofluidic mixer. Our experimental result indicated that such nanofluidic mixer can effective mix two streams of non-interacting flows within seconds.
9:00 PM - W8.7
Aging Process of Cobalt Nanoparticles
Cindi Dennis 2 , Guangjun Cheng 1 , Angela Hight Walker 1 , Robert Shull 2
2 Materials Science and Engineering Laboratory, NIST, Gaithersburg, Maryland, United States, 1 Physics, NIST, Gaithersburg, Maryland, United States
Show AbstractWith recent advances in the chemical synthesis of magnetic nanoparticles with controllable size and shape, magnetic nanoparticles are finding applications in a variety of fields, ranging from Coulomb blockade in single electron devices to hyperthermia for cancer treatments. However, for all of these applications, the environments of these nanoparticles and variations in their composition affect their magnetic behavior and change their effective lifetime. Therefore, it is necessary to track how their composition and resulting magnetic behavior varies as a function of time. Here, 9nm cobalt nanoparticles synthesized using thermo-decomposition in 1,2-dicholorbenenze (DCB) are used to study the aging process. Observations of these particles in a variety of solvents, including dichlorobenzene and toluene, as well as dispersed in epoxy have shown the onset of a purple-tinge over the course of several months when the sample is exposed to air. Hysteresis loops and zero-field-cooled/field-cooled (ZFC/FC) measurements are carried out to study their magnetic properties associated with this aging process. The apparent leaching of cobalt ions from cobalt nanoparticles is confirmed through the magnetic response of the particles over the same time period. The saturation magnetization as well as the coercivity of the cobalt nanoparticles are found to decrease with time, in a manner that can be directly correlated with the loss of cobalt into the surrounding solvents or epoxy. Transmission electron microscopy (TEM) is used to characterize the evolution of the size and shape of these nanoparticles.
9:00 PM - W8.8
Interaction Forces Between Thermoresponsive Surface and Colloidal Particle in Aqueous Solution Studied Using Atomic Force Microscopy.
Naoyuki Ishida 1 , Mikio Kobayashi 1
1 Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Show Abstract
Symposium Organizers
Norman Wagner University of Delaware
Gerald G. Fuller Stanford University
Jennifer Lewis University of Illinois, Urbana-Champaign
Ko Higashitani Kyoto University-Katsura
W9: Microstructure & Rheology
Session Chairs
Thursday AM, April 20, 2006
Room 2001 (Moscone West)
9:00 AM - **W9.1
Bending Colloidal Aggregates with Light: The Micromechanics of Particulate Gels.
Eric Furst 1
1 Department of Chemical Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractThe micromanipulation and dynametrical capabilities of laser tweezers provide the ability to probe the mechanics and interactions of colloidal materials on nanometer to micrometer lengthscales. I will present a recent application of laser tweezers to investigate the mechanical properties and microrheology of particulate gels. Our approach focuses on the micromechanics of aggregates that mimic the stress-bearing backbone in gels. Using time-shared optical traps, backbone mimics are directly assembled in salt solutions into precisely-controlled geometries. The aggregate bending rigidity is then measured. Aggregates behave elastically up to a critical bending moment, after which they exhibit small stick-slip rearrangements. The bending rigidity is found to be sensitive to the particle surface chemistry, ionic species and ionic strength. The bending rigidity between individual particles agrees with the JKR model of particle adhesion, providing a direct link between the micromechanics and the interfacial adhesion energy of the particles. Overall, these experiments enable us to bridge macroscopic rheology of colloidal gels to the underlying microstructural response. Furthermore, the new insight we have gained provides useful strategies for controlling gel behavior by manipulating the nanoscale near-contact interactions between Brownian particles.
9:30 AM - **W9.2
Glass Transition Seen in Confined Colloidal Suspensions.
Eric Weeks 1 , Carolyn Nugent 1
1 Physics, Emory University, Atlanta, Georgia, United States
Show AbstractWe study concentrated colloidal suspensions, a model systemwhich has a glass transition. These are suspensions of smallsolid particles in a liquid, and exhibit glassy behaviorwhen the particle concentration is high; the particles areroughly analogous to individual molecules in a traditionalglass. We view the motion of these colloidal particles inthree dimensions by using an optical confocal microscope.This allows us to directly study the microscopic behaviorresponsible for the macroscopic viscosity divergence of glasses.In particular, we study how confinement changes the particledynamics. We confine a colloidal suspension betweentwo parallel walls, and find that in thin sample chambers theparticle motion is greatly slowed. This suggests thatconfinement causes the onset of the glass transition to happen"sooner", at particle concentrations which are not normallyglassy. Particle motion perpendicular to the walls issignificantly slower than motion parallel to the walls.
10:00 AM - W9.3
Short-range Attraction and Long-range Repulsion in the Formation of Cluster Phases and Low-density Arrested Disordered States in Colloidal Systems.
Stefano Mossa 1
1 , European Synchrotron Radiation Facility, Grenoble France
Show Abstract10:15 AM - W9.4
Length Scale Dependent Relaxation in a Colloidal Gel.
Emanuela Del Gado 1 2 , Walter Kob 3
1 Dipartimento di Scienze Fisiche, Universita di Napoli "Federico II", Napoli Italy, 2 , CNISM, Napoli Italy, 3 Laboratoire de Colloides, Verres et Nanomateriaux, Universite Montpellier II, Montpellier France
Show Abstract10:30 AM - W9.5
Cluster Phase and Gel Formation in Colloidal Systems
Emanuela Zaccarelli 1 , Stefano Mossa 3 , Francesco Sciortino 1 , Piero Tartaglia 2
1 , Dipartimento di Fisica and CNR-INFM-SOFT, Universita' La Sapienza , Rome Italy, 3 , ESRF, Grenoble France, 2 Dipartimento di Fisica, CNR-INFM-SMC, Universita' La Sapienza, Roma Italy
Show AbstractWe study gelation processes in charged colloid-polymer mixtures using Molecular and Brownian Dynamics simulations.Colloidal particles interact with competing short-range depletion attraction and long-range screened electrostatic repulsion.When repulsion is capable of effectivelly contrast the attraction, phase separation at low densities is inhibitedand we find evidence of an equilibrium cluster phase,in agreement with experiments.Changing the repulsion parameters, cluster shape crosses from spherical to elongated[1]. In the former case,we find gelation as a Wigner glass transition of clusters[2], while in the latter, arrest is observed when such spiral-like clusters branch and percolate[3].[1] S. Mossa, F. Sciortino, P. Tartaglia and E. ZaccarelliGround state clusters for short-range attractive and long range repulsive potentials Langmuir 20, 10756, 2004[2] F. Sciortino, S. Mossa, E. Zaccarelli and P. TartagliaEquilibrium cluster phases and low density arrested disordered states: The role o short-range attraction and long range repulsion Phys. Rev. Lett. 93, 055701, 2004[3] F. Sciortino, P. Tartaglia and E. ZaccarelliOne-dimensional cluster growth and branching gels in colloidal systems with short-range depletion attraction and screened electrostatic repulsion J. Phys. Chem. B in press 2005.
10:45 AM - W9.6
Effects of Electrolytes and Solution pH on Silica Nanotribology.
Bogdan Donose 1 , Elena Taran 1 , Ivan Vakarelski 1 , Ko Higashitani 1
1 Chemical Engineering, Kyoto University, Kyoto Japan
Show Abstract Lateral force measurements between a polished silica wafer and a colloidal silica particle in various electrolytes solutions were performed using an Atomic Force Microscope (AFM).In the case of monovalent cations, at high electrolyte concentrations, a significant lowering of the frictional coefficient occurs. An another important finding was that the degree of lubrication can be related to the hydration enthalpy of the cations adsorbed on surfaces; the smaller and more hydrated the cations are, the stronger the lubrication is. It is also found that the friction coefficient decreases with the concentration increase of barium and strontium salts, but this effect is reversed in the case of magnesium salts. These results imply that the tribological properties of silica in electrolyte solutions are the outcome of a combined effect of anions, cations and their hydration properties. The pH effect on the friction forces between silica surfaces was also investigated. The tribological properties of silica were studied in a wide range of pH, between 3.6 and 10.6. For values of pH between 3.6 and 8.6, there are no significant changes in the frictional behavior. At pH values of 9.6 and 10.6, strong lubrication effects were observed, where the friction coefficient becomes approximately ten times lower than in the case of solutions of pH 3.6-8.6. This friction reduction is possibly explained by a softening in the upper layer of the silica surface due to silica-increased dissolution in a high pH. The models for these phenomena will be proposed.
11:30 AM - **W9.7
Strict Simulations of Motion of Colloidal Particles and Host Medium.
Ryoichi Yamamoto 1 2 , Yasuya Nakayama 1 2 , Kang Kim 1 2
1 Department of Chemical Engineering, Kyoto University, Kyoto Japan, 2 PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
Show AbstractWe have been proposed a direct numerical simulation scheme for colloidal dispersions [Phys.Rev.E 71, 036707 (2005)]. We improved the previous scheme and formulated a full explicit time-marching, called the ''Smoothed Profile (SP) method''. The SP method as a direct numerical simulation of particulate flow provides a way to couple continuum fluid dynamics with rigid-body dynamics through smoothed profile of colloidal particle. Moreover, the SP method is extended to multi-component fluids, such systems as charged colloids in electrolyte solutions. Dynamics of colloidal dispersions is solved as much computational cost as required for solving non-particulate flows. Numerical results which assess hydrodynamic interactions of colloidal dispersions are presented to validate the SP method. The SP method is not restricted to any constitutive model of the host fluids. Henceforth, it can be applicable to colloidal dispersions in complex fluids.We compute the fluid velocity and the electrostatics potential by solving both Navier-Stokes and Poisson equations directly. The time evolutions of the colloidal particles and the density of counter ions are then determined by solving Newton's equation of motion and advection-diffusion equation, respectively, in a consistent manner so that the electro-hydrodynamic coupling can be fully taken into account. The electrophoretic mobility of spherical colloidal particles is calculated in several situations including those in concentrated dispersions. The comparisons with theories show excellent quantitative agreements.
12:00 PM - **W9.8
Microstructure and Rheology of Anisotropic Particles
Charles Zukoski 1 , Eric Mock 1
1 Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois, United States
Show AbstractUniform anisotropic particles with characteristic sizes of 200-300nm are synthesized using a seeded emulsion polymerization technique. The particles are sufficiently uniform that when dispersed in water or a polar solvent at high concentrations they order. Here we explore the role of anisotropy in the order/disorder transition, the microstructure of the ordered phases and the flow properties of dense suspensions. This work is motivated by a desire to produce colloidal crystals with packing that is not cubic. Our initial work focuses on shape anisotropy and methods of synthesizing large quantities of uniform anisotropic particles.
12:30 PM - W9.9
STF-ArmorNovel Energy Adsorbing Composites Containing Colloidal & Nanoparticle Dispersions
Norman Wagner 1
1 Chemical Engineering, Univ. Delaware, Newark, Delaware, United States
Show AbstractNovel ballistic resistant composite materials are formulated from colloidal & nanoparticle dispersions. Through ballistic testing, the mechanism of energy adsorption at ballistic rates is demonstrated to result from reversible shear thickening in the colloidal dispersion. As a basis for the rational design of ballistic resistant materials, we report a rheological and microstructural investigation of dispersions particles of varying size, shape (prolate and oblate aspect ratio), and surface modification. Rheology-Small Angle Neutron Scattering studies (RHEO-SANS) of the particle organization and alignment during shear thickening provide structure- property relations that connect the shear thickening transition with the enhanced energy absorption. These results are predicted by micromechanical models to elucidate the mechanism of shear thickening in suspensions of anisotropic particles. The application of these dispersions in formulating novel energy absorbing materials is discussed.
12:45 PM - W9.10
Relaxation of Aggregates in a Jamming Colloidal Suspension After Shear Cessation.
Francesca Ianni 1 2 , David Lasne 2 3 , Regis Sarcia 2 , Pascal Hebraud 2 4
1 , SOFT-INFM-CNR c/o Dipartimento di Fisica "La Sapienza" di Roma, Rome Italy, 2 , P.P.M.D. UMR 7615 ESPCI, Paris France, 3 , C.P.M.O.H. UMR 5798, Talence France, 4 , IPCMS UMR 7504, Strasbourg France
Show AbstractW10: Synthesis III
Session Chairs
Thursday PM, April 20, 2006
Room 2001 (Moscone West)
2:30 PM - W10.1
Superparamagnetic Nanoparticles in Flexible EM Shields and Galvanic Isolators
Douglas Schulz 1 , Anthony Caruso 1 , Pamela Jeppson 1 , Rob Sailer 1 , Eric Jarabek 1 , Joe Sandstrom 1 , Peter Eames 2 , Mark Tondra 2 , Douglas Chrisey 1
1 Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota, United States, 2 , NVE, Eden Prairie, Minnesota, United States
Show AbstractWe have isolated Co-ferrite superparamagnetic nanoparticles that exhibit extremely high saturization magnetization (Ms) values exceeding 130 emu/g and coercive fields (Hc) less than 80 Oe using a micelle synthetic approach. Given superior properties, these materials are poised to replace Fe-Ni permalloy (Ms 90 emu/g) in a number of applications. Nanoparticles have been dispersed into polymer systems and applied in thin film form to yield flexible, insulating nanocomposites. These materials are high-performance nanocomposites whereby magnetic properties exceed any bulk material purely as a consequence of reduced particle size and its effect on exchange. Co-ferrite nanocomposites have been tested for device application where coatings that provide both magnetic flux isolation and concentration are used to optimize magnetic field sensors by reducing 1/f noise and providing a means of controlling internal and/or external magnetic fields in galvanic isolators. Device performance and nanoparticle characterization will be presented.
2:45 PM - W10.2
Perfect Dispersion and Programmed Assembly of Metal Oxide Nanoparticles via in-situ Surface Modification during Supercritical Hydrothermal Synthesis
Tadafumi Adschiri 1
1 , Tohoku university, Sendai Japan
Show AbstractNanoparticles have attracted considerable interest for their use in various applications to nano hybrid materials (polymer-metal oxide etc.). However, because of the extremely high surface energy, nanoparticles significantly aggregated, and this is the main reason for the difficulty in the application of nanoparticles for producing nano hybrid materials. We have proposed and developed a method of supercritical hydrothermal synthesis of metal oxide nanoparticles. Recently, we modified this new method to synthesize organic-inorganic-bio-molecule fused materials. By introducing organic species (aminoacids, carboxylic acids, amines, alcohols, aldehydes etc.) during supercritical hydrothermal synthesis, nanoparticles whose surface was modified with organic materials were synthesized, which was probably due to the homogeneous phase formation in supercritical conditions. We succeed in synthesizing surface modified metal oxide nanoparticles (several to 20 nm), which cannot be synthesized by the other methods. Modification of bio-materials including amino acids or peptides is also possible. This type of surface modification allows the designer to incorporate unique characteristics of the nanoparticles into their products, including perfect dispersion of inorganic nanoparticles in aqueous solutions, organic solvents or in polymers. This can be used for nanohybrid polymers, nano-ink, or nano-paints. Furthermore, bio-modification of nanoparticles leads to form nanobiohybrid materials.Once the surface is covered with the organic chemicn the abse, as shown in this figure, In high tem fluids provide various possibilities for nanotechnology ssembly of nanoparticles for the fabrication of IT devices.
3:00 PM - W10.3
Real Time Electron Tunneling to Gold Monolayer Protected Clusters by Scanning Probe Microscopy.
Ning Zheng 1 , GangLi Wang 2 , Ezra Bussmann 1 , Clayton Williams 1
1 Physics, University of Utah, Salt Lake City, Utah, United States, 2 Chemistry, University of Utah, Salt Lake City, Utah, United States
Show AbstractReal time electron tunneling to individual gold monolayer protected clusters (MPC) on a 10 nanometer silicon dioxide film has been performed by single electron tunneling force measurements [1,2]. The Au140 clusters are protected by a shell of hexane-thiol ligands. The gold MPCs have a diameter of ~ 3 nm, as measured by contact Atomic Force Microscopy (AFM). After locating the MPCs with the AFM, the voltage biased probe tip is placed several nanometers above the nano-particles and is scanned vertically toward the surface, while recording the frequency shift of the oscillating cantilever. We typically observe several abrupt steps in the smooth frequency shift curve as the tip approaches. These steps correspond to electron tunneling events to the MPC. Such tunneling measurements may potentially be used in the determination of the electronic structure and charging energy of the individual gold MPCs. The technique will be described and the electron tunneling results will be presented. [1] E. Bussmann, Dong Jun Kim, and C.C. Williams, Appl. Phys. Lett. 85, 2538 (2004) [2] E. Bussmann, N. Zheng, and C. C. Williams, Appl. Phys. Lett. 86, 163109 (2005)
3:15 PM - W10.4
Cryo-Microscopy of Magnetic Dispersions and Coatings.
Hui Luo 1 , Lorraine Francis 1 , L. Scriven 1
1 Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThe stability and microstructure of magnetic dispersions play a crucial role in the production of particulate magnetic tapes. Magnetic interaction, van der Waals attraction and steric repulsion determine the dispersion stability and structure. Here we report results from the direct visualization of microstructures of commercial magnetic dispersions by cryogenic scanning electron microscopy (cryo-SEM). Magnetic dispersions were prepared by dispersing magnetic nanoparticles of iron, acicular in shape, in an organic solvent mixture (methyl ethyl ketone, toluene, cyclohexanone) containing dissolved polymer binders (polyvinyl chloride and polyurethane). Dispersions were pipetted into closed containers (diameter: 3mm, depth: 300μm), frozen by plunging into liquid ethane at its normal freezing point, and then prepared in the frozen state for cryo-SEM. Specimens were freeze-fractured to reveal internal structures, sublimed to enhance contrast, and coated with about 5 nm platinum to avoid charging. They were then examined in the cryo-SEM with secondary electron and backscattered electron imaging. The images of frozen magnetic dispersions showed individual iron particles randomly oriented and embedded in organic solvent/polymer matrix. Cryo-TEM and the electron diffraction pattern established that the organic solvent mixture vitrified during the freezing process. The evolution of coating microstructure during drying was explored by using identically prepared coatings frozen after different times of drying. Implications of these results for the production of magnetic tapes with high degrees of particulate orientation were considered.
4:00 PM - W10.5
Combining Self Assembly with Lithography to Fabricate Photonic Devices.
George Zhao 1 , Qingfeng Yan 1 , Zuocheng Zhou 1
1 Chemical & Biomolecular Engineering, National Uni of Singapore, Singapore Singapore
Show Abstract4:15 PM - W10.6
Tailor-Made Nano Composite Materials for Optics.
Frederic Rocco 1 , Thierry Cardinal 1 , Mona Treguer 1
1 chemistry, ICMCB, PESSAC France
Show AbstractThe possibilities of designing and mastering the new physical and chemical properties of nano-structured materials have been at the center of the large interest they have received in the academic and industrial domains. Confinement effects and the enhanced role of the interface are key parameters. Designing composite materials with controlled nanometric interfacing of different materials is offering new possibilities for developing new structures. Proper design allows to control interaction of the composite material components to create new properties to meet technological requirements. A particular emphasis has been given to the enhancement of the optical response of hybrid metal based nanomaterials. Two main composite systems have been elaborated via ionizing radiation : colloidal Agn / Ag42+ clusters and Agn /CdSn semiconductor.For the Agn/Ag42+ system, a strong amplification of the fluorescence intensity of the charged oligomeric clusters has been observed. The Ag42+ clusters luminescence is enhanced by the local electric field effect associated to the metal (surface plasmon resonance). A parallel of the luminescence properties of Ag42+ isolated entities and silver colloidal particles oxidized afterwards has also be done. The optical properties of CdSn/Agn system have also been investigated. Again a strong amplification of the luminescence of the semiconductor is observed. This system also exhibits enhanced non linearity. In addition, a significant change in THG signal and the appearance of SERS effect is observed. For both systems, the interest focus on understanding the chemical nature of the interaction and its effect on the electronic properties as well as their evolution from bulk to nanoscale materials. Those both nanomaterials developments offer applications in optics and biophotonics. The Agn/Ag42+ may offer alternative from organic dye molecule for dynamic study of biological entities. The problem of photobleaching of the current used dye molecule is limiting their use. The other composite will allow to developp new optronic composants since it exhibits non linear index modification with application of small electric tension.
4:30 PM - W10.7
The Nature of Detonation Nanodiamond Aggregates and Nanodiamond Fractioning
Vladimir Kuznetsov 1 , Yuriy Butenko 1 , Ilya Mazov 1 , Sergey Moseenkov 1 , Olga Shenderova 2 , Darin Thomas 2 , Irina Larionova 3 , Alexander Frolov 3
1 , Boreskov Institute of Catalysis, Novosibirsk Russian Federation, 2 , International Technology Center , Raleigh, North Carolina, United States, 3 , Federal Research and Development Center ALTAY, Biysk Russian Federation
Show Abstract4:45 PM - W10.8
Effective Transfection of Cells with Multi-shell Calcium Phosphate-DNA Nanoparticles.
Viktoriya Sokolova 1 , Wolfgang Meyer-Zaika 1 , Ina Radtke 2 , Rolf Heumann 2 , Matthias Epple 1
1 Institute for Inorganic Chemistry, University of Duisburg-Essen, Essen Germany, 2 Chair of Biochemistry, Molecular Neurobiochemistry, University of Bochum, Bochum Germany
Show Abstract5:00 PM - W10.9
Bimodal Size Distributions in Zinc Oxide Aerosols Produced by Laser Evaporation
Masashi Matsumura 1 , Renato Camata 1
1 Dept of Physics, University of Alabama at Birmingham, Birmingham, Alabama, United States
Show AbstractNanoparticle formation during laser ablation is a widely observed phenomenon. When performed in background gases, this process leads to gas-suspended nanoparticle populations in a complex environment where nanoparticle nucleation, gas-phase reactions, evaporation/condensation, Brownian coagulation, and coalescence may take place over similar time scales. One very distinct feature of nanoparticle populations produced during pulsed laser ablation is the bimodal character of their size distributions. This has been observed in numerous materials systems and it can often be explained by the simultaneous operation of more than one mechanism of nanoparticle generation. In some cases, however, bimodal size distributions arise even when a single process of particle formation is at work. This is the case for nanoparticles formed during KrF pulsed laser ablation of zinc oxide (ZnO), an important direct-gap semiconductor with potential applications in light emitting devices, sensors, and actuators. In this work we combine direct size distributions measurements of gas-suspended ZnO nanoparticles with a particle dynamics model to explain the origin of the bimodal size distributions in this system. We have measured the ZnO nanoparticle size distributions using a differential mobility nanoparticle spectrometer. This method was used to perform in-situ particle spectrometry in the 1-60 nm size range and observe the gas-phase dynamics of nanoparticles formed during KrF laser ablation of ZnO targets in inert gas atmosphere with background pressures in 70-760 Torr range using laser fluences of 0.25-6.25 J/cm2. During ablation at low laser fluences (<2 J/cm2), the gas-suspended nanoparticle populations consistently exhibited bimodal size distributions. For the lowest fluence investigated (0.25 J/cm2) and pulse energy of 2.5 mJ, the bimodal distribution was found to consist of a superposition of two log-normal distributions with geometric mean diameters of 14 nm and 39 nm, and geometric standard deviations of 1.55 and 1.65, respectively. As the laser pulse energy increases in the 2.5-6.3 mJ range, the mode centered at 14 nm experiences a monotonic shift toward smaller diameters while the mode at 39 nm remains unchanged. Measurements are analyzed in light of the approximate size distributions calculated using a simple particle dynamics model, which accounts for simultaneous nucleation, coagulation, and coalescence of non-spherical particles. The model consists of a set of population balance equations that also tracks variations in particle surface area. It allows for the formation of two monodisperse particle dynamic modes: a laser generated particle nucleation mode and a coagulation and coalescence or accumulation mode. We discuss the results of our in-situ size distribution measurements in relationship to the predictions of this simplified model, with emphasis on the physical processes that lead to the appearance and evolution of the ZnO bimodal size distributions.
5:15 PM - W10.10
Universal, Wireless, Nano-optical Voltmeters for Measuring Electric Fields Throughout Cells.
Katherine Tyner 1 , Raoul Kopelman 2 , James Miller 1 , Stephanie Runkle 1 , Martin Philbert 1
1 Toxicology Program, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemistry Department, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract5:30 PM - W10.11
Angle-dependent optical extinction of anisotropic metal-shell colloids
Joan Penninkhof 1 , Albert Polman 1 , Christina Graf 2 , Alexander Moroz 2 , Alfons van Blaaderen 2 , Luke Sweatlock 3 , Harry Atwater 3
1 Center for Nanophotonics, FOM-Institute AMOLF, Amsterdam Netherlands, 2 Debye Institute, Utrecht University, Utrecht Netherlands, 3 Applied Physics, Caltech, Pasadena, California, United States
Show AbstractMetallo-dielectric colloids may be used to create electromagnetic field enhancements that lead to fluorescence enhancements or ultra-sensitive (bio)sensing. Silica-core metal-shell colloids have the advantage above bulk metal particles that the plasmon resonance frequency can be tuned by varying the ratio of core radius and shell thickness. Here, we present a new method to tune the anisotropy of metallo-dielectric core-shell colloids by MeV ion irradiation. Oblate ellipsoids are formed, with an aspect ratio that can be accurately controlled by the ion irradiation fluence. We study the details of the ion beam deformation process with the aim to achieve control over particle size and shape, using silica colloids with a 300-600 nm diameter, covered with a 20-60 nm thick Au shell [1]. Size aspect ratios up to a factor 3 are achieved, depending on the ion fluence, the size of the silica core and the thickness of the metal shell. Ion irradiation is a directional technique: all shape-deformed particles are aligned on a substrate. This enables ensemble-averaged studies of the anisotropy-dependent optical properties. We observe that the optical extinction of anistropic silica-Au core-shell particles is strongly angle-dependent, with peak shifts well into the infrared for the transverse mode. This (counter-intuitive) observation is supported by finite difference time domain simulations. Detailed studies of the electromagnetic field distribution are made to identify the physical origin of the resonance shift.The effect of electromagnetic field enhancement near the highly curved metal surfaces can be systematically studied by a thin additional silica coating on the metal shell colloids as a spacer layer. Dye molecules and quantum dots can be incorporated in the sillica or attached to the surface. The experimental data can be compared with results from FDTD and T-matrix calculations.[1] Penninkhof et al, Adv. Mater. 17 (2005) 1484-1488
5:45 PM - W10.12
Surface Passivation of Gold Nanoparticles in MALDI Mass Spectrometry.
Kate Stumpo 1 , David Russell 1
1 Chemistry, Texas A&M University, College Station, Texas, United States
Show AbstractThe optical and electronic properties of nanoparticles, esp. gold nanoparticles (AuNPs), have been extensively investigated in recent years, and many applications are emerging in the fields of chemical physics and chemical biology. Importantly, these physical properties can be tuned as desired, as they are based on NP size, shape, composition, and surface derivitazation. Recently, we have demonstrated the utility of AuNPs as matrices for matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS).[1] Using 2, 5, and 10 nm AuNPs we have successfully ionized a number of peptides and small proteins and observed abundant ion signals in positive- and negative-mode UV MALDI. These alternative substrates offer a number of advantages over conventional MALDI matrices (e.g. small organic acids): (i) greater flexibility in sample deposition conditions (e.g. pH, solvents, etc.), (ii) relatively uncomplicated spectra in the matrix region (low mass range), (iii) Au-cluster species as internal standards for mass calibration, and (iv) AuNPs afford a very high shot-to-shot and spot-to-spot reproducibility (<10 % RSD). We present here further research to better understand fundamental nanoparticle chemistry and physics. Specifically, we have investigated how surface chemistry affects the MALDI ionization event. Surface association of species in solution (e.g. analytes, ions) and the solvent structure around these species have an effect on analyte interactions with the AuNPs, thus leading to changes in ionization efficiency. NPs prepared by the citrate reduction method have residual ions in solution (i.e. citrate) that adsorb to the NP surface and serve as electrostatic stabilizers. Citrate can be displaced by other anions (e.g. halides or oxyanions) as demonstrated here, and by others.[2] Better understanding of how surface chemistry affects MALDI will allow for the design of matrices towards specific applications, i.e. selective concentration of analytes prior to MS analysis or matrix incorporation into tissue samples, providing for in vivo imaging.[1] J. McLean, K. Stumpo, and D. Russell, J. Am. Chem. Soc. 2005, 127, 5304-5305.[2] (a) M. Wanner, D. Gerthsen, S. Jester, B. Sarkar, and B. Schwederski, Colloid Polym. Sci. 2005, 283, 783-792; (b) S. Cumberland and G. Strouse, Langmuir, 2002, 18, 269-276.
W11: Poster Session: Colloid II
Session Chairs
Friday AM, April 21, 2006
Salons 8-15 (Marriott)
9:00 PM - W11..37
Production of Onion-like Carbon Aggregates of Controllable Size.
Vladimir Kuznetsov 1 , Yuriy Butenko 1 , Ilya Mazov 1 , Sergey Moseenkov 1 , Olga Shenderova 2 , Alexander Okotrub 3 , Lubov Bulusheva 3 , Anatolii Romanenko 3
1 , Boreskov Institute of Catalysis, Novosibirsk Russian Federation, 2 , International Technology Center , Raleigh, North Carolina, United States, 3 , Nikolaev Institute of Inorganic Chemistry , Novosibirsk Russian Federation
Show Abstract9:00 PM - W11.1
Gd- and Sm-doped Ceria Powder Synthesis by Carbonate Coprecipitation.
Kil Soon Park 1 , Nam Soo Chae 1 , In sang Yoo 1 , Young Soo Yoon 2 , Hyung Wook Choi 1 , Hyon Hee Yoon 1
1 Chemical Engineering, Kyungwon University, Sungnam Korea (the Republic of), 2 Advanced Technology Fusion , Konkuk University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - W11.10
Nonspherical Engineering of Polymer Colloids.
Jinwoong Kim 1 , Ryan Larsen 1 , David Weitz 1
1 Div. of Engineering and Applied Sciences / Dept. of Physics, Harvard University, Cambridge, Massachusetts, United States
Show AbstractIn this presenataion, we introduce a method for synthesizing a variety of nonspherical polymer particles of uniform size and morphology. Our particular interest is to control the geometry and phase property of individual nonspherical particles. Basically, the method consists of first swelling cross-linked polystyrene particles with styrene monomers and initiators in aqueous media. Upon heating to polymerization temperatures, the elastic-retractile force in the swollen cross-linked particle induces a phase separation between the cross-linked particle and the monomer phase. The polymerization of the monomer phase gives rise to doublet particles comprised of two spheres tightly joined together by an interpenetrating network. An interesting observation is that repeating the procedure gives rise to triple particles that have either triangle or rod-shaped morphologies depending on the degree of cross-linking in the seed particles. Also, by varying the synthesis procedure we can produce several varieties of particles, including dumbbell, rod-like, triangles, diamonds, cones, and janus particles. We expect these particles to be useful as building blocks for hierarchical self-assembly, as material probes in microrheology, and as a model system for studying the effect of particle shape on the rheology of dense colloidal suspensions.
9:00 PM - W11.11
Spherical Silica Epoxy Nanocomposites.
Chenggang Chen 1 2 , David Anderson 1 2 , Baur Jeffery 2 , Ryan Justice 3 , Dale Schaefer 3
1 Nonmetallic Division, University of Dayton Research Institute, Dayton, Ohio, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States, 3 Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractSilica is a very common filler for polymeric materials. Spherical silica nanoparticles as a new type of nanofiller in polymeric materials has drawn much interest in academia and industry. The control of the morphology of the nanocomposite is critical in the development of new and better materials. In this presentation, studies on the spherical silica epoxy nanocomposite with different morphologies will be reported. The spherical silica can be dispersed homogeneously in the epoxy matrix. The homogeneous dispersion can include an individual silica nanoparticle (~13 nm) throughout the whole epoxy matrix or it can be in the aggregated state (~100 nm). The characterization by transmission electron microscopy (TEM) at low and high magnification verifies these morphologies of the spherical silica epoxy nanocomposites. The ultra-small-angle x-ray scattering studies show consistent results with the TEM results. The mechanical properties of the nanocomposite with individually-dispersed morphology are significantly improved.
9:00 PM - W11.12
Close-Packed Hemispherical Microlens Array from Two-Dimensional Ordered Polymeric Microspheres.
Hye Jin Nam 1 , Jong Hyeon Lee 1 , Ju Won Yoon 1 , Duk Young Jung 1
1 Chemistry, SungKyunKwan University, Suwon, Kynuggi-do, Korea (the Republic of)
Show AbstractThis paper describes facile, reproducible soft-lithographic technique for fabricating hexagonally close-packed microlens arrays using ordered polymeric microspheres. Close-packed monolayers of monodispersed polystyrene microspheres were deposited on flat cleaned glass substrate using spin-casting technique. The relief structure of highly ordered microspheres successfully generated their negative replica of PDMS elastomers with hexagonal arrays of honeycomb structures. Closely packed hemispherical microlens arrays were fabricated by dispensing a liquid photopolymer into the negative PDMS replica and then curing with UV irradiation through the glass substrate. Sub-micrometer scaled microlens with uniform, cleaned surface morphology was easily prepared by using two molds, PDMS and photopolymer, without using patterned template fabricated by complicated engineering. This technique provides reliable route to produce embossed thin layers with surface structure from nanometer to micrometer by controlling particle size of polymer microsphere on the flat substrates of centimeter-scale.
9:00 PM - W11.13
In Situ One-Pot Synthesis of 1-Dimensional Transition Metal Oxide Nanocrystals.
Jung-wook Seo 1 , Young-wook Jun 1 , Seung Jin Ko 1 , Jinwoo Cheon 1
1 chemistry, yonsei university, Seoul Korea (the Republic of)
Show AbstractOne-dimensional colloidal metal oxide nanocrystals are of great importance in materials chemistry, but reports on these materials are rare due to lack of well-defined synthetic protocols. Here we present a highly effective one-pot synthetic protocol to produce 1-dimensional nanostructures of transition metal oxide (e.g. W18O49, TiO2, and Mn3O4) through high temperature colloidal reactions of metal chloride and surfactants. The nanocrystals obtained have high crystallinity and narrow size distribution. Anisotropic rod shapes are preferentially grown along the surface with higher energy. The method developed here is versatile, reproducible, and simple and therefore it can be used as a generalized protocol for a variety of 1-D metal oxide nanocrystals.
9:00 PM - W11.14
Grain-size Control of a Colloidal Crystal by using a Centrifugal Sedimentation Method.
Yoshihisa Suzuki 1 , Tsutomu Sawada 2 , Atsushi Mori 3 , Katsuhiro Tamura 1
1 Department of Chemical Science and Technology, The University of Tokushima , Tokushima Japan, 2 , National Institute for Materials Science, Tsukuba Japan, 3 Department of Optical Science and Technology, The University of Tokushima, Tokushima Japan
Show AbstractHighly concentrated (volume fraction φ = 0.61) and relatively large (2 mm X 5 mm max. in a pillar-like shape) grains of a colloidal crystal were grown by centrifugal sedimentation of polystyrene particles (diameter d = 0.34 μm) dispersed in a concentrated KCl aqueous solution (8 X 10-3 molkg-1). The crystal grew one-directionally along the direction normal to the substrate at the bottom of the crystal growth cell. The grains had face-centered-cubic structure and all the (111) planes of the grains oriented parallel to the side wall of the cell. The obtained structure of the grains showed the “geometrical selection” of the pillar-like grains. The structure looked similar to the solidification structure (columnar texture) of metal alloys. Through the geometrical selection, the farther the growth front of the crystal was from the substrate, the smaller the number of its constituent grains (in other words, the larger the size of the grains) was and the closer was the maximum growth rate direction to the normal to the substrate. Thus the geometrical selection indeed led to the pillar-like structure of the relatively large grains. The average grain size also increased with decreasing sedimentation rate, since the decrease resulted in the decrease in the number of the nuclei on the substrate. The final grain size after the geometrical selection depended solely on the number of the nuclei. In fact, an increase in the centrifugal acceleration (at the bottom substrate) from 8 to 21 G several hours after the nucleation did not inhibit the continuous growth of the pillar-like grains. Larger acceleration (> 84 G), however, stopped the continuous growth, and resulted in the nucleation and sedimentation of randomly oriented small grains on the top of the growth front. Thus the slow nucleation rate by the slow sedimentation at the bottom substrate and the appropriate increase in the sedimentation rate after the nucleation allow the efficient production of the large colloidal crystal grains.
9:00 PM - W11.16
Using Click Chemistry to Functionalize the Surface of Iron Oxide Nanocrystals.
Meghann Brown 1 , Jeremiah Johnson 1 , Nicholas Turro 1 2 , Jeffrey Koberstein 2
1 Department of Chemistry, Columbia University, New York, New York, United States, 2 Department of Chemical Engineering, Columbia University, New York, New York, United States
Show AbstractWe have synthesized iron oxide nanocrystals by pyrolysis in trioctyl amine using oleic acid as the ligand. We further modified the surface of the iron oxide nanocrystals by attaching “click” functional groups to the surface through ligand exchange. We have successfully employed click chemistry to functionalize the surface of the iron oxide nanocrystals, creating either hydrophyllic or hydrophobic surfaces. The click chemistry strategy allows us to modify the iron oxide surface by covalently attaching either small molecules that have been previously synthesized by conventional methods, or click-functional polymers which have been synthesized by ATRP. We have characterized the modified nanocrystals using Transmission Electron Microscopy, Infrared Spectroscopy, X-Ray Diffraction, and Thermogravimetric Analysis.
9:00 PM - W11.17
Photoluminescence Dynamics of Colloidal CdS Quantum Dots.
DaeGwi Kim 1 , Masaaki Nakayama 1
1 Depertment of Applied Physics, Osaka City University, Osaka Japan
Show AbstractThe size dependence of excitonic states and interactions between elementary excitations in semiconductor quantum dots (QDs) has been extensively investigated so far. Since optical properties of the QDs depend on the size, the preparation of the QDs with a narrow size distribution is essential in studies of QDs. Furthermore, surface structures of QDs strongly affect excitonic relaxation processes because of a high value of the surface to volume ratio. Thus, the control of the surface structure is important to control photoluminescence (PL) properties of QDs. However, owing to considerable difficulty of controlling size distributions and surface structures, there have been few systematic studies of the temperature dependence of absorption, PL, and PL-decay profiles. In the present work, we have investigated exciton dynamics in surface-modified CdS QDs prepared by a colloidal method. The CdS QDs were prepared by injecting H2S gas into aqueous solutions containing Cd(ClO4)2 and sodium hexametaphosphate (HMP). The size distribution of QDs was controlled using a size-selective photoetching: The size-distribution width was reduced to ~5% after the photoetching. The QD surface was modified by the addition of Cd(ClO4)2 after adjusting pH of solutions to alkaline region: This process leads to formation of a Cd(OH)2 layer on the surface of QDs. The sample solution was mixed with polyvinyl alcohol (PVA) aqueous solutions. The final solution was spread on a glass, and the excess water was evaporated by heating at 80 degree for 2 hours. This process produces film samples, that is, CdS QDs dispersed in PVA films. In the PL spectrum, the band-edge emission is clearly observed as a main PL band. We note that the surface modification remarkably enhances the band-edge emission by 10^4 times. Thus, we have succeeded preparing the size- and surface-controlled CdS quantum dots. The decay profiles exhibit unusual temperature dependence: The decay time becomes longer as the temperature is increased. The temperature dependence of the profiles can be explained in terms of a three-level model: a ground state and two excited states of a lower-lying bound state and a higher-lying dark-exciton state.
9:00 PM - W11.18
High Quality Blue Fluorescent CdSe/ZnS Nanocrystals.
Marco Zanella 1 , Stefan Kudera 1 , James Lin 2 , Wolfgang Parak 1 , Liberato Manna 3
1 Biophysics, LMU Muenchen, Muenchen Germany, 2 , Chung-Yuan Christian University , Taipei Taiwan, 3 , National Nanotecnology Laboratory, Lecce Italy
Show AbstractCdSe nanocrystals (NCs) have been exploited extensively in applications in which they serve as fluorophores, because of the tunability in the visible range of the light emitted from them. Depending on the NCs size, the emission color extend from the blue to the red region of the spectrum, and the quantum yield and stability of the NCs is increased if a shell of higher band gap material (usually ZnS) is grown around the original CdSe cores. While the preparation in high yields of strongly luminescent, core/shell NCs emitting from green to red colors is an easy task, there have been so far few viable approches that yield significantly large amounts of extremely small, blue emitting core/ shell NCs based on CdSe cores, because of the difficulties with the synthesis, the isolation and the stabilisation of NCs having such small sizes.The preparation of small CdSe NCs containing only a few atoms is not new.Soloviev and coworkers have synthesized an homologous series of CdSe cluster molecules [1-2] capped by selenophenol ligands and have investigated their optical properties. This series has been recentely enriched by the synthesis of larger CdSSe cluster molecules[3]. These cluster molecules are important for assessing the detailed structural parameters of extremely small NCs and for understanding the concept of magic size in semiconductor clusters. Unfortunately, they are not particularly suited for practical applications because their synthesis is not so straightforward, they do not show strong band edge emission and in addition the peculiar nature of their surface ligands should make them labile to additional treatments, such as surface ligand exchange or shell growth.Here we present a simple route to magic size CdSe NCs based on the modification of traditional organometallic approaches designed for the synthesis of CdSe NCs of larger sizes and demonstrate the possibility to grow a ZnS shell on them. [1] Soloviev, V.; Eichofer, A.; Fenske, D.; Banin, U. J. Am. Chem. Soc. 2000, 122, 2673.[2] Soloviev, V.; Eichofer, A.; Fenske, D.; Banin, U. J. Am. Chem. Soc. 2001, 123, 2354.[3] Zheng, N.; Bu, X.; Lu, H.; Zhang, Q.; Feng ,P. J. Am. Chem. Soc. 2005, 34, 11963.
9:00 PM - W11.19
Flow Behavior of Colloidal Fluids and Gels by Micro-Particle Imaging Velocimetry.
Mark Roberts 1 , Ali Mohraz 2 , Kenneth Christensen 4 , Jennifer Lewis 2 3
1 Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractThe flow behavior of colloidal fluids and gels in microchannels is investigated by micro-particle imaging velocimetry (μ-PIV). Hydrophilic and hydrophobic silica particles (φ = 0.15-0.33) are suspended in an index matched fluid (water/DMSO) to allow for imaging in straight square microchannels under pressure driven flow. Stress viscometry measurements are carried out to allow comparison of flow properties to velocity profiles obtained by μ-PIV.
9:00 PM - W11.2
Fabrication of ZnO Nanoparticles with Visible Photoluminescence Using Pulsed Laser Ablation in Aqueous Media
Chun He 1 , Takeshi Sasaki 1 , Hiroyuki Usui 1 , Yoshiki Shimizu 1 , Naoto Koshizaki 1
1 Nanoarchitectonics Research Center , National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
Show AbstractZnO has been receiving much attention as an advantageous luminescent material due to its relative high efficiency as a promising low-voltage phosphor and can be used in the green range for vacuum fluorescent displays and field emission displays. Despite of the progress in the studies on the nature of the green luminescence from ZnO, there are still unresolved issues as to what are the relevant native defects of this oxide. By far, most of the well-defined ZnO crystals have been synthesized by traditional method based on high temperature solid-state method or chemical solution rout. Usually, these methods are involved calcination process of ZnO in a reducing or oxidizing atmosphere, in this way, the number of oxygen vacancies or other vacancies can be varied, which is then related to changed defect in the visible intensity. In this work, ZnO nanoparticles with green photoluminescence have been fabricated by pulsed laser ablation (PLA) of a zinc target in aqueous solutions with controlled surface chemistry. The phase structure and particles size were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface chemistry effects on photoluminescence of ZnO nanoparticles were also investigated. The conspicuously stable well-defined ZnO nanocrystals with very narrow size distribution were obtained by ablation Zn target under the acidic or basic condition due to the electrostatic repulsion, leading to a significant reduction of their size, simultaneously, the intensity of the green emission of smaller nanoparticles increased while that of the exciton emission decreased. The increase of the green light emission intensity as the particle size decreases suggests that there is a greater fraction of oxygen vacancies in the ZnO due to higher surface area to volume ratio for smaller nanoparticles. However, the green emission can be partly suppressed by post-coating the nanoparticles with amphoteric surfactant (lauryl dimethylaminoacetic acid betaine), indicating that this emission originated from part of surface defect of ZnO. This method is proved to be a simple method for the fabrication of bare ZnO nanoparticles with the enhanced green emission in an aqueous media. This study was partially supported by Industrial Technology Research Grant Program ’05 from New Energy and Industrial Technology Development Organization (NEDO) of Japan.
9:00 PM - W11.20
Synthesis and Self-assembly of Nanomaterials Using Genetically Engineered Viruses For Medical and Semiconductor Applications.
Seung-Wuk Lee 1 2
1 Bioengineering , University of California, Berkeley, Berkeley, California, United States, 2 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States
Show Abstract9:00 PM - W11.21
Unexpected Self-assembly of Silver Nanoparticles Separated by Size-selective Polyacrylamide Gel Electrophoresis Method.
Yang Yang 1 , Yuko Shimizu 1 , Hiroshi Yao 1 , Keisaku Kimura 1
1 Graduate School of Science, University of Hyogo, Hyogo Japan
Show AbstractSilver nanoparticles with unique plasmon band in the visible region are promising materials for the future electronic and optical device fabrication. Despite many well-established synthetic routes for silver nanoparticles, it is necessary to develop advantageous techniques to control their size, to tailor their shape and further to organize their arrangement for the formation of different nanoarchitectures. In this study, the technique of a wide-ranged polyacrylamide gel electrophoresis (PAGE) is used to separate hydrophilic mercaptosuccinic acid (MSA) -modified Ag nanoparticles. It is found that MSA-modified silver nanoparticles could be isolated in a series of fractions with respect to their size by using PAGE method, which leads to different distinct sizes with significantly narrowed size distribution in each fraction. The particle migration rate determined by the mass of Ag nanoparticles and the charge at the surface under electric field allow an effective separation of the particles depending on their size. After extraction of sols in the gel into organic solvent by cetyltrimethylammonium bromide (CTAB) based on anion-cation electrostatic interaction, the Ag nanoparticles of each fraction can be further assembled into ordered superlattice structure due to their uniform size. It is interesting to find that in some fraction separated by PAGE method, monodisperse nanoparticles of two different sizes coexist, where two or three -dimensional superlattice composed of either big nanoparticles or small nanoparticles are found by TEM observation. Besides, monodisperse nanoparticles of two different sizes are also mixed in some area, in which a special superlattice composed of both big and small nanoparticles is obtained. This kind of 3D superlattice possesses the crystal structure of the intermetallic compound CaCu5 (AB5) type. A possible mechanism for the coexistence of dual-sized Ag nanoparticles in some fraction as well as the importance of their practical application is discussed.
9:00 PM - W11.22
Thin Film Assemblies of Carbon Black with Tunable Transparency and Electrical Conductivity.
Jaime Grunlan 1 2 3 , Jason Jan 1 2 , Matthew Walton 1 2 , Ethan McConnell 1 2 , Woo Sik Jang 1 2
1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Polymer Technology Center, Texas A&M University, College Station, Texas, United States, 3 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractElectrically conductive polymer composites filled with carbon black have been studied for decades in a variety of sensor and shielding applications. Despite significant advances, these systems remain plagued by high processing viscosity and brittle mechanical behavior due to the high carbon black loading required for sufficient electrical conductivity. The present work demonstrates highly conductive carbon black-filled thin films. Using layer-by-layer (LbL) assembly from low viscosity aqueous mixtures containing carbon black and polyelectrolytes, dense composite films containing 45 wt% CB are produced that are less than one micron thick and exhibit electrical conductivity of more than 2 S/cm. Even with such a high concentration of carbon black these films remain very flexible. The LbL deposition process is a route to creating low-cost conductive films that may be used in a variety of sensing and shielding applications. These films can be made optically transparent by changing the pH of the deposition mixtures, which could be exploited for a variety of filter applications.
9:00 PM - W11.23
Facile Preparation of Ru Nanoparticles-Cellulose Fibers and Ag Nanoparticles-Nylon Fibers Composites.
Victor Sanchez 1 , Pablo Garcia-Tobon 1 , Sergio Reyes-Vega 1 , Raul Morales-Luckie 1 , Jesus Arenas-Alatorre 2
1 Chemistry, Universidad Autonoma del Estado de Mexico, Toluca Mexico, 2 Physics, Universidad Nacional Autonoma de Mexico, Mexico, D.F., Mexico
Show AbstractSilver nanoparticles were prepared in nylon fibers, by means of a simple reduction reaction at ambient conditions. Particles of less than 10 nm were obtained using the nylon fibers as nanoreactors. The porous nylon fibers, observed by scanning electron microscopy (SEM), along to the oxygen and nitrogen density from the amide moiety, provide effective sites for in situ reduction of silver ions, using a NaBH4 aqueous solution, and for the formation and stabilization of the nanoparticles. The same synthetic method was utilized for preparation of ruthenium nanoparticles-cellulose fibers composites. Ru nanoparticles of less than 10 nm were also obtained. Ultraviolet-visible (UV-Vis) absorption spectra revealed peaks from the surface plasmon resonance of the silver nanoparticles at around 400 nm. Transmision electron microscopy (TEM and HRTEM) study showed that Ag and Ru nanoparticles were homogeneously dispersed in the nylon and cellulose templates, respectively. X-ray photoelectronic spectroscopy (XPS) was also used to characterize the Ag nanoparticles-nylon fibers and Ru nanoparticles-cellulose fibers composites.
9:00 PM - W11.24
Synthesis of BaTiO3 Nanocrystals and Nanocrystal Thin Film Ferroelectrics.
Zhuoying Chen 1 3 4 , Limin Huang 1 3 4 , James Wilson 1 3 4 , Sarbajit Banerjee 1 3 4 , Richard Robinson 1 3 4 , Irving Herman 1 3 4 , Robert Laibowitz 1 2 3 , Stephen O'brien 1 3 4
1 Applied Physics and Applied Math, Columbia University, New York, New York, United States, 3 Columbia Materials Research Science and Engineering Center (MRSEC) , Columbia University, New York, New York, United States, 4 Columbia Nanocenter (NSEC), Columbia University, New York, New York, United States, 2 Electrical Engineering, Columbia University, New York, New York, United States
Show AbstractThe family of complex oxide pervoskites (including BaTiO3, Pb(Zr,Ti)O3 and (Ba,Sr)TiO3) possessing the ferroelectric property have far reaching applications in the electronics industry. The investigation of micron to nanoscale ferroelectric materials (thin films and particles) has prompted a desire for a deeper understanding of how size effects polarization and ferroelectric order. We report the synthesis and processing of nano-structured thin films of barium titanate (BaTiO3) built from uniform nanoparticles. The nanoparticles were prepared by a chemical processing, based on thermal decomposition of a bimetallic barium titanium molecular precursor Barium Titanium Glycolate (BaTi(C2H4O2)34C2H6O2 H2O) in the presence of oleic acid (a capping group), followed by high-temperature crystallization of this nucleation-controlled intermediate. The method offers a versatile means of preparing uniform and monodisperse BaTiO3 nanocrystals, which can be used as a basis for micropatterned or continuous BaTiO3 nanocrystal thin films. We observe the BaTiO3 nanocrystals crystallize with evidence of tetragonality. We investigated the preparation of well-isolated BaTiO3 nanocrystals smaller than 10 nm with control over aggregation and crystal densities on various substrates such as Si, Si/SiO2, Si3N4/Si and Pt-coated Si substrates. BaTiO3 nanocrystal thin films were then prepared, resulting in films with a uniform nanocrystalline grain texture. Electric field dependent polarization measurements show spontaneous polarization and hysteresis, indicating ferroelectric behavior for the BaTiO3 nanocrystalline films with grain sizes in the range 10-30 nm.
9:00 PM - W11.25
Synthesis of Asymmetric Silver-decorated Polystyrene Spheres by Electroless Deposition.
Jingqin Cui 1 , Ilona Kretzschmar 1
1 Chemical Engineering, The City College of New York, City University of New York, New York, New York, United States
Show AbstractComposite nano-structures have many unusual optical, magnetic and electronic properties. Furthermore, asymmetric particles present novel orientation dependent synthetic and chemical functionality, which enables them to act as ideal structures for fundamental research and application. Most of the currently used methods to modify particles such as chemical and physical vapor deposition or beam epitaxy onto templates require elevated temperatures as well as vacuum conditions. It is desirable to develop techniques with milder conditions to fabricate surface-asymmetric micro- and nanoparticles. In our work we investigate the electroless deposition of silver, an economical, controllable process usually performed under mild conditions, for partial modification of spherical particles with micrometer dimensions. Our recent results on combining partial embedment of spheres with electroless deposition enabling the partial modification of microspheres are presented here. In our experiments we employ a monolayer assembly of micrometer-sized spheres to create a template for partial modification of the spheres. An assembly of sulfate polystyrene (PS) spheres composed of well-packed hexagonal pattern and a small amount of square lattices domains is prepared with medium temperature convective assemble. The whole particle layer is removed from the silicon wafer by stamping with a partially cured poly(dimethylsiloxane) (PDMS) film. Pre-curing of the PDMS is employed to control the viscosity and stiffness of PDMS during stamping. Upon application of the stamp most spheres are partially embedded in the PDMS film and the particle layer is completely peeled off from the silicon wafer after curing. Scanning electron microscope (SEM) images show successful silver nanoparticle (NP) deposition onto the exposed surfaces of the PS spheres via electroless deposition. Most NPs deposited are between 50~150 nm in size for a 2.40±0.12 μm sphere diameter. Both the pre-curing time and the applied pressure on the PDMS film during stamping affect embedment depth, i.e., the resulting exposed portion of sphere surface, significantly. We investigated the effect of stirring rate during the reaction on the size and the uniformity of the deposited NPs. Further, the influence of the polystyrene sphere size on the silver NP diameter is determined.Our work shows that the electroless method developed in our laboratory can be used for the partial modification of symmetric particles leading to particles with anisotropic surfaces. Such particles can be used for the controlled and directed assembly of particles into desired three-dimensional structures.1. C. Charnay, A. Lee, S. Man, C. E. Moran, C. Radloff, R. K. Bradley, and N. J. Halas, Reduced symmetry metallodielectric nanoparticles: Chemical synthesis and plasmonic properties. J. Phys. Chem. B 2003, 107, 7327-7333
9:00 PM - W11.26
Synthesis of Novel Bimetallic Core-shell Nanoparticle via Thermal Decomposition Method.
In-Keun Shim 1 , Kwi Jong Lee 1 , Jaewoo Joung 1
1 Central R&D Institute, Samsung Electro-Mechanics, Suwon-Si, kyungki-do, Korea (the Republic of)
Show AbstractCopper nanoparticles coated with a noble metal were prepared by continuous thermolysis of metal complexes. These nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The results showed that these nanoparticles exhibit monodispersed core-shell shape with a dense core and a lightly coated shell. The electrical and oxidation behavior of these particles are reported and discussed. It is found that the presence of thin noble metal coating plays an important role in preventing oxidation of the copper nanoparticles.
9:00 PM - W11.27
Controlled Release of Drug and Bio-molecules from an Organically Modified 2:1 Trioctahedral Magnesium Phyllosilicate Matrix.
Stewart Holmstrom 1 , Avinash Patil 1 , Stephen Mann 1
1 School of Chemistry, University of Bristol, Bristol United Kingdom
Show AbstractAn inorganic-organic hybrid layered material based on a 2:1 trioctahedral phyllosilicate framework with covalently linked aminopropyl (AMP) functionalities was synthesised using a one-step direct method. The resulting magnesium (organo)phyllosilicate was characterised using a variety of physico-chemical techniques. The feasibility of an AMP-functionalised clay as a host matrix was explored by protonation of the amino groups in aqueous solution, which resulted in delamination of the layered sheets, followed by intercalation of anionic guest species, such as drug molecules, biomolecules and polymers during restacking. Successful intercalation of ibuprofen, poly(styrene sulphonate) (PSS), Polymethyl acrylamido propane sulphonic acid (PMAPSA) and poly(acrylic acid) (PAA) was confirmed by PXRD, which showed in each case an increase in the basal (d001) spacing. Potential applications of the ibuprofen-AMP composites were explored by investigating the release of drug molecules from the clay galleries using UV-Vis spectroscopy. The results showed a controlled and delayed release profile. As the drug release rates could in principle be influenced by co-intercalation of auxiliary molecules, organoclay materials containing drug molecules sequestered in association with intercalated polymers were also prepared and investigated.
9:00 PM - W11.28
Patterning of Cell Attachment to Biocompatible Glassy Polymeric Carbon by Silver Ion Implantation.
Robert Zimmerman 1 , Ismet Gurhan 2 , Claudiu Muntele 1 , Daryush Ila 1 , F. Ozdal-Kurt 3 , B. Sen 4
1 Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama, United States, 2 Ege University , Faculty of Engineering, Ismir Turkey, 3 CBU , Faculty of Science, Manisa, Turkey, 4 EU , Faculty of Dentistry, Ismir Turkey
Show Abstract9:00 PM - W11.29
Identification of Hydroxy Apatite Binding Peptides Depending on Various pH.
Anna Merzlyak 1 , Seung-Wuk Lee 1 2
1 Bioengineering , University of California, Berkeley, Berkeley, California, United States, 2 Physical Bioscience Division, Lawrence Berkeley National Lab, Berkeley, California, United States
Show Abstract9:00 PM - W11.3
Synthesis of Small ZnO Nanocrystals by Pulsed Laser Ablation (PLA) in Aqueous Media with the Presence of Surfactant and Their Self-Assembly Towards Spindle-like ZnO Aggregates.
Chun He 1 , Takeshi Sasaki 1 , Yoshiki Shimizu 1 , Yoshie Ishikawa 1 , Naoto Koshizaki 1
1 Nanoarchitectonics Research Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Show Abstract9:00 PM - W11.30
In-situ Polymerization of Poly (methyl methacrylate)/MgAl Layer Double Hydroxides Nanocomposites with Highly Dispersion and Enhanced Physics Properties.
Tsung-Yen Tsai 1 , Shau-Wen Lu 1 , Fu-Shou Li 1
1 Department of Chemistry & Center for Nanotechnology, Chung Yuan Christian University, Chung Li City, Taoyuan, Taiwan
Show AbstractPoly (methyl methacrylate)/MgAl Layer Double Hydroxides (PMMA/ MgAl LDH) nanocomposites were synthesized by in situ free radical polymerization with the organic modified MgAl-K2 LDH in the methyl methacrylate monomer and initiator of benzoyl peroxide. Two-dimensional host materials of MgAl-K2 LDH were prepared by the hydrothermal reaction with the basal spacing of 18.3 nm, determined by X-ray diffraction measurement. However, PMMA/Mg-Al-K2 LDH nanocomposites do not come out the first diffraction peak of MgAl-K2 LDH because polymerization takes place in the Mg-Al-K2 LDH galleries. The ordinary of laminar structure is broken apart while the polymerization occurred between the layered galleries. The TEM images indicate that there are two types of nanocomposites. One is intercalated PMMA/ Mg-Al-K2 LDH nanocomposites and the other is exfoliated one. Therefore, the PMMA/Mg-Al-K2 LDH nanocomposites do not only have well dispersion in PMMA system, but also the thermal and mechanical properties have enhanced as compared to the pure PMMA resin.
9:00 PM - W11.31
Preparation of High Surface area Ni-SDC Cermets Using a Surfactant-assisted Co-precipitation Method.
Sang Joon Park 1 , Tae-Wook Eom 1 , Jae-Eun Oh 1 , Hae-Kwang Yang 1 , Kyung Hwan Kim 2
1 Chemical and Bio Engineering, Kyungwon University, Seongnam City Korea (the Republic of), 2 Electrical Engineering, Kyungwon University, Seongnam City Korea (the Republic of)
Show Abstract9:00 PM - W11.32
Nanofabrication of Pattern and Parts by the Wet Approach(II): Fabrication of Shape-designed Nano Sheets Composed of Metal Oxides.
Rie Takaki 1 2 , Shigenori Fujikawa 1 2 , Toyoki Kunitake 2 1
1 Innovative Nanopatterning Lab., RIKEN, Wako, Saitama, Japan, 2 Topochemical Design Lab., RIKEN, Wako, Saitama, Japan
Show AbstractPreparation of ultrathin film is an indispensable technology in nanotechnology. Especially in nanometer precision the shapes of nano architectures play important role in producing new phenomena, functions and properties and the shape design is, thus, extremely important. Therefore next target in nanofilm technology is to design the film shape freely. In this study, we report the preparation of the shape-designed self-supporting nanofilms composed of ultrathin metal oxide layers. Lithographically-fabricated line and hole patterns on polymer-coated silicone wafer were employed as a template. Its surface was covered with ultrathin metal oxide by the surface sol-gel process. The surface sol-gel process is based on the stepwise chemisorption of metal alkoxides from solution onto substrate surfaces and subsequent hydrolysis of the alkoxide moiety to give nanometer-thick oxide films. In this process, the film thickness is controllable with 1nm precision by adjusting the number of dipping cycles. Titanium butoxide [Ti(OnBu)4] and isocyanate silane [Si(NCO)4] were employed as a precursor molecule in the sol-gel reaction. After 30 cycles of the surface so-gel process, the film thickness of the metal oxide layer on the template surface is about 20 nm. In the case of SiO2 coating, the smooth ultrathin films were obtained, though titania coating gave rugged surface. The substrate was then subjected to reactive ion etching (RIE) to remove the top and bottom side of the metal oxide layer, leaving behind side wall part of the coating layer. Next, the substrate was immersed into the organic solvent to dissolve the resist pattern, and the side wall was peeled off from the substrate into solvent. In the case of titania, the self-supporting titania film having wide area was not obtained, due to the film was very fragile. On the other hand, flexible and smooth ultrathin nanotapes were obtained from the silica-coated substrate, and its width corresponded to the height of the template patterns. Even in the silica film prepared from the 5cycles of the surface sol-gel process, it maintained the self-supporting property and the tape shape. Our approach is basically nanocoating-based fabrication process to replicate the sub-micrometer-sized template structures into film shape. This approach can extract the structural information of the template into film materials at nanometer region, and provides new aspects to fabricate shape-designed nanomaterials.
9:00 PM - W11.33
Controlled Hierarchical Assembly of Magnetic Microspheres.
Brandon McKenna 1 , Muhammet Toprak 1 , J. Waite 1 2 , Galen Stucky 1 3
1 Department of Chemistry and Biochemistry, University of California- Santa Barbara, Santa Barbara, California, United States, 2 Department of Molecular, Cellular Developmental Biology, University Of California, Santa Barbara, California, United States, 3 Materials Department, University Of California, Santa Barbara, California, United States
Show AbstractThe ability to assemble materials that are organized over different length scales has a recognized importance for the development of new functional materials. In particular, the potential for application of emerging nanoscale objects can often be realized only by arranging such components into larger scale assemblies. Complex coacervation is one phenomenon that presents new opportunities for single-step syntheses of ordered micron-scale objects that are composed of predefined nanoscale objects. Coacervation is a spontaneous aqueous phase separation that often produces microspheres from oppositely-charged chemical entities. We have previously studied such assemblies made from organic ions, metallic nanoparticles, or quantum dots, and we have utilized the coacervates' chemical properties to form inorganic shell structures. We have sought to extend the variability of assembly components, to in turn extend the variety of potential uses.In this work, we demonstrate the first example of coacervation that uses superparamagnetic nanoparticles as assembling components. The resulting objects retain the original magnetic properties, and are unusually robust under various conditions. We show the ability of these new assemblies to effect mineralization of inorganic shells, and we demonstrate the potential use of these hybrid assemblies for biomedical applications.
9:00 PM - W11.34
The Effects of Surfactants on the Morphology of Colloidal Crystals in Self-assembly.
Zuocheng Zhou 1 , Qin Li 1 , Xiusong Zhao 2 , Victor Rudolph 3
1 Department of Chemical Engineering, Curtin University of Technology, Perth, Western Australia, Australia, 2 Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore, 3 Division of Chemical Engineering, The University of Queensland, Brisbane, Queensland, Australia
Show Abstract9:00 PM - W11.35
Effects of Ionization Level on the Morphology of P(MMA-co-MAA) Ionomers Cast onto Si Wafer
Youn-Jeong Cho 1 , Beom-Gyu Lee 1 , Jae-Jin Park 2 , Joon-Seop Kim 2 , Jeong-A Yu 3
1 Dept. of Chemistry, Chosun University, Gwangju Korea (the Republic of), 2 Dept. of Polym. Sci. & Engr., Chosun University, Gwangju Korea (the Republic of), 3 Dept. of Science Education, Chosun University, Gwangju Korea (the Republic of)
Show AbstractThe morphology of P(MMA-co-MAA) ionomers, neutralized with NaOH partly and fully, cast onto Si wafer from 2×10-3g/mL THF solution, was investigated using SEM and TEM techniques. It was found that the acid form PMMA copolymer formed spherical particles of 60-400 nm. In addition, as the solution concentration decreased, the size of spherical particles decreased to 70-210 nm, with decreasing its size distribution. When the acid groups of P(MMA-co-MAA) copolymer were neutralized with NaOH, the size and size distribution of the spherical particles also decreased. When the ionization level became 20 %, the ionomer exhibited network features. As the ionization level increased further, the ionomer started forming rough coats. It was also found that the surface of the coats became smoother with increasing degree of neutralization.
9:00 PM - W11.38
Characterization of Montmorillonite Binding Peptides Identified using Phage Display.
Sharon Jones 1 , Lawrence Drummy 1 , Richard Vaia 1 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractMontmorillonite (Na+-MMT) can be used to improve the durability and temperature resistance of polymeric materials, and we have attempted to determine the potential interactions between MMT and biological molecules, such as peptides. To this end, we have performed phage-display on Na+-MMT, MMT modified with a primary ammonium surfactant, and MMT modified with a quaternary ammonium surfactant. We have identified several strongly binding peptide sequences, as well as one peptide sequence (designated S2) that specifically binds to all three forms of clay. In examining the S2 sequence, we have verified phage binding to MMT by Low Voltage Transmission Electron Microscopy (LVTEM). We have also discovered that the peptide will bind to and intercalate between the MMT sheets in aqueous suspensions, affecting the inter-sheet spacing of the dried out powders, as measured by by X-ray diffraction. Future work includes determining the binding affinities of the various peptides to MMT, as well as studying of the nature of the MMT-peptide interaction.
9:00 PM - W11.39
Patterning Biomolecules Using Switchable Superhydrophobic Surfaces
Jau-Ye Shiu 1 , Chiung Wen Kuo 1 , Peilin Chen 1
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Show AbstractSuperhydrophobic surfaces, with a water contact angle larger than 150 degree, have attracted a lot of research attentions recently. The study of superhydrophobic surfaces dose not only allow investigating the influence of surface nanostructures on the water-repellent behavior similar to those observed in many living organs, but it may also lead to new industrial applications such as self-cleaning, anti-adhesion and oxidation resistant coating. It has been shown that the surface nanostructures amplify both hydrophobic and hydrophilic effect. Based on this observation, we have designed a switchable superhydrophobic surface using electrowetting effect. To fabricate switchable superhydrophobic surfaces, thin films of Teflon were spin-coated on the ITO glass and treated by oxygen plasma. Superhydrophobic surfaces with water contact angle up to 170 degree were obtained by this approach. When applying voltage, the water contact angle can be tuned systematically from 167 degree to less than 10degree and switched from the superhydrophobic state to the superhydrophilic state within a few tens of seconds. Using such switchable superhydrophobic surface, we are able to pattern biomolecules such as IgG on the superhydrophobic surface. Our result indicated the biomolecules patterned by such method remain active can be used to conjugate to antigen such as anti-IgG.
9:00 PM - W11.4
Repeat Sequence Proteins as Matrices for Nanocomposites
Lawrence Drummy 1 , Hilmar Koerner 2 , David Phillips 1 , Joseph McAuliffe 3 , Manoj Kumar 3 , B. Farmer 1 , Richard Vaia 1 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 2 , University of Dayton Research Institute, Dayton, Ohio, United States, 3 Biomaterials Group, Genencor International, Palo Alto, California, United States
Show AbstractRecombinant protein-inorganic nanocomposites comprised of highly exfoliated and well dispersed Na+ montmorillonite (MMT) in a recombinant protein matrix based on silk-like and elastin-like amino acid motifs (silk elastin like protein (SELP)) were formed via a solution blending process. An exfoliated microstructure was found to be controllably produced by the favorable interaction of positively charged residues along the protein backbone with the negatively charged montmorillonite layers. We have characterized the zeta potential, or surface charge, of MMT suspensions in water with increasing SELP concentration. These measurements revealed the amount of adsorbed SELP protein necessary to completely neutralize the MMT surface charge. To illustrate the effect of charge on dispersion, zeta potential measurements were compared with measurements from a negatively charged succinylated version of the SELP molecule, and its complexes with MMT. Transmission electron microscopy was used to compare dispersion of the MMT in both the positively and negatively charged proteins. Charged residues along the protein backbone were shown to dominate long-range interactions, whereas the SELP repeat sequence, which is similar in both proteins, lead to local protein/MMT compatibility. Up to a 50% increase in room temperature modulus and a comparable decrease in high temperature coefficient of thermal expansion occurred for cast films of SELP/MMT containing 2-10 wt% MMT.
9:00 PM - W11.40
Direct-Write Templated Assembly of 3D Silicon Hollow-Woodpile Photonic Crystals
Gregory Gratson 1 , Florencio Garcia-Santamaria 1 , Mingjie Xu 2 , Virginie Lousse 3 , Shanhui Fan 3 , Jennifer Lewis 1 2 , Paul Braun 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractImpressive developments in silicon (Si) micro-fabrication are enabling new applications in photonics, micro-electromechanical systems (MEMS), and biotechnology. Yet conventional Si microfabrication techniques require expensive masks and time-consuming procedures, including multiple planarization or bonding steps, to generate three-dimensional (3D) structures. In contrast, direct-write approaches, such as laser scanning and ink deposition, provide rapid flexible routes for fabricating 3D micro-periodic structures. However, these approaches are currently limited to polymeric structures that lack the high refractive index contrast and mechanical integrity required for many applications. To fully take advantage of these rapid, flexible assembly techniques, we have developed a replication (or templating) scheme that allows their structural conversion within the temperature constraints imposed by both the organic and inorganic components of the system. Here, we present this novel route for creating 3D Si hollow-woodpile structures that couples direct-write assembly of concentrated polyelectrolyte inks with a sequential silica/Si chemical vapor deposition (CVD) process. The optical properties of the 3D micro-periodic woodpiles are characterized after each fabrication step. These interconnected, hollow structures may find potential application as photonic materials, low-cost MEMS, microfluidic networks for heat dissipation, and biological devices.
9:00 PM - W11.6
High Performance CdSe and CdSe/ZnS Quantum-Rod/Sol-Gel Nanocomposites
Nanguo Liu 1 , Jagjit Nanda 1 , Victor Klimov 1 , Melissa Petruska 1
1 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractIn the burgeoning field of nanoscience, semiconductor nanocrystal quantum dots and quantum rods receive considerable attention because of their potential applicability in telecommunications, remote sensing, photovoltaics, solid-state lighting, and biomedical imaging. Unlike quantum dots, quantum rods exhibit linearly polarized emission and enhanced optical gain, which are of interest for polarized light emission and polarized lasing. Despite recent achievements in the syntheses of quantum rods, photochemical instability hinders their use in real-world applications. In an effort to stabilize semiconductor quantum rods, robust sol-gel matrices were exploited to enhance the mechanical, chemical, thermal, and photochemical properties of the particles. CdSe and CdSe/ZnS core/shell quantum rods are encapsulated in silica, titania, and zirconia nanocomposite films. The resulting materials display improved optical stability over quantum rods not contained in a matrix material, have high quantum rod volume loadings and refractive indices, and demonstrate room temperature amplified spontaneous emission.
9:00 PM - W11.8
Nanofabrication of Pattern and Parts by the Wet Approach (I): Fabrication of Metal Oxide Nanoline Array with Dimensions of sub-30 nm.
Shigenori Fujikawa 1 2 , Rie Takaki 1 2 , Toyoki Kunitake 2 1
1 Innovative Nanopatterning Lab., RIKEN, Wako, Saitama, Japan, 2 Topochemical Design Lab., RIKEN, Wako, Saitama, Japan
Show Abstract Fabrication of nanopatterns with dimensions of sub-30 nm has been actively studied, especially in semiconductor industry. Although photolithography-based fabrication is the most process-friendly approach, it requires very high cost for processing equipments and large space. This approach is now getting close to technical and process limitation, and alternative methods are, thus, strongly desired for sub-30-nm fabrication. Recently, size reduction lithography was reported1), and is based on surface coating of line templates and anisotropic etching of the coating layer to leave the side wall of the coating layer as a size-reduced line pattern. Unfortunately, chemical vapor deposition was employed as surface coating process to form silicon-based layers on templates, and thus, coating materials are limited to vaporizable compounds. We herein report fabrication of metal oxide nanolines with sub-30 nm widths by size reduction lithography combined with the surface sol-gel process. Organic nanoline structures fabricated by photo-lithography technique were covered with ultrathin metal oxide layers with thicknesses of a few tens nm by the surface sol-gel process. Titanium alkoxide and silicon tetraisocyanate were employed as precursor molecules. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) results show that uniform silica layers were formed on the template surface after the surface sol-gel process. The top-side of the coating layer on the template was selectively removed by a CF4 plasma etching, and then the organic moieties were removed by oxygen plasma. Only the side walls were left behind on the solid substrate, and its width and heights were about 20 nm and 360 nm, respectively. The high aspect ratio (height/width= about 18) is noteworthy. Titania lines were also fabricated by the same approach. In the surface sol-gel process, the film thickness is controllable with 1 nm precision by adjusting the number of the adsorption cycle. The width of the current lines corresponds to the film thickness of the metal oxide on the template, since the line was a part of the film before etching. Therefore, the line width is controllable with 1 nm precision. In addition, the surface sol-gel process provides material variety in surface coating, and composite nanofilms of organic/inorganic and hetero-inorganic combinations can be employed. The current approach provides a new methodology to fabricate nano-architectures in the sub 30-nm regime.1) Y.-K. Choi, J. Zhu, J. Grunes, J. Bokor, and G. A. Somorjai, J. Phys. Chem. B 2003, 107, 3340-3343
9:00 PM - W11.9
Self-Assembly of Nanoparticles Provides Sustained Release of Compounds from the Surfaces of Implantable Devices.
Catherine Lo 1 , Paul Van Tassel 2 , W. Mark Saltzman 1
1 Biomedical Engineering, Yale University, New Haven, Connecticut, United States, 2 Chemical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractBiocompatibility of implantable devices can affect their functional integrity in chronic implantation. Therefore, long-term local delivery of compounds to improve the biocompatibility of these devices is of great interest. A novel method is presented here for sustained release of compounds from a layer of biodegradable nanoparticles adhered onto the device surface. Silicon substrate was initially modified by deposition of cationic poly-L-lysine polyelectrolyte, followed by immersion in an aqueous suspension of negative charged poly(lactide-co-glycolide) nanoparticles. The particles are driven by electrostatic interaction to self-assemble onto the device surface. The assembly thus creates a well organized thin-film coating of particles on the implantable device, with the versatility to provide simultaneous release of multiple compounds. Furthermore, the extent of nanoparticle adsorption can be controlled through altering the pH and ionic strength of the particle suspension. Specifically in this report, rhodamine-B encapsulated nanoparticles were used to visualize the particle adsorption on the test substrates. Successful performance of the delivery system was evaluated from the fluorescence release profile.
Symposium Organizers
Norman Wagner University of Delaware
Gerald G. Fuller Stanford University
Jennifer Lewis University of Illinois, Urbana-Champaign
Ko Higashitani Kyoto University-Katsura
W12: Synthesis IV
Session Chairs
Friday AM, April 21, 2006
Room 2001 (Moscone West)
9:00 AM - **W12.1
Exploiting Anisotropy for Building Block Assembly of Shape Amphiphiles.
Sharon Glotzer 1
1 Dept of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe unique anisotropy of today’s new nanoparticle and colloidal building blocks starkly contrasts with the isotropic, spherical colloids that have been the focus of particle assembly for nearly a generation. As the materials community gains further control over the design and fabrication of these new particles, they are poised to become the “atoms” and “molecules” of tomorrow’s materials and devices, with applications including sensors, alternative energy, photonics, nanoelectronics and nanocomputing, imaging, drug delivery, and more. In this talk, we present results of computer simulations of patchy particle [1] and polymer-tethered nanoparticle [2] “shape amphiphiles” undergoing self assembly. We show how various measures of anisotropy, including building block shape, patterning, functionalization and interaction selectivity, can be combined and exploited to achieve complex mesoscale one-, two- and three-dimensional structures such as wires, sheets, shells, and helices through self assembly [3,4]. We also discuss the formation of diamond arrays from tetrahedrally patched particles [5], 2-D “S-layer”-like sheets from CdTe nanoparticles [6], and convex structures from conical and spherical particles [7].References1.Z.L. Zhang and S.C. Glotzer, “Self-assembly of patchy particles,” Nano Lett. 4(8), 1407 (2004). 2.Z.L. Zhang, M.A. Horsch, M.H. Lamm and S.C. Glotzer, “Tethered nano building blocks: Towards a conceptual framework for nanoparticle self-assembly,” Nano Lett. 3(10): 1341 (2003)3.Mark A. Horsch, Zhenli Zhang, and Sharon C. Glotzer, "Self-assembly of polymer tethered nanorods", PRL 95, 056105 (2005).4.Iacovella CR, Horsch MA, Zhang Z-L, Glotzer SC, "Phase diagrams of self-assembled mono-tethered nanospheres from molecular simulation and comparison to surfactants," Langmuir, 21(21); 9488 (2005).5.Zhenli Zhang, Aaron Keys, Ting Chen and Sharon C. Glotzer, "Self-assembly of patchy particles into diamond structures from molecular mimicry", Langmuir, ASAP, 2005.6.Zhiyong Tang, Zhenli Zhang, Ying Wang, Sharon C. Glotzer, and Nicholas A. Kotov,, preprint.7.Ting Chen, Zhenli Zhang and Sharon C. Glotzer, preprint.
9:30 AM - W12.2
Microstructure as Liquid-ordered Phase and Rigidity of Frozen Catanionic Bilayers.
Thomas Zemb 1
1 laboratoire Claude Frejacques, CEA, Gif sur Yvette France
Show Abstract9:45 AM - W12.3
Cu2O Nanoparticles – Synthesis, Characterization, and Catalytic Behavior in CO Oxidation.
Brian White 1 2 , Ming Yin 2 3 , Stephen O'Brien 2 3 , Nicholas Turro 1
1 Chemistry, Columbia University, New York, New York, United States, 2 Materials Science & Engineering, Columbia University, New York, New York, United States, 3 Applied Physics & Applied Mathematics, Columbia University, New York, New York, United States
Show Abstract10:00 AM - W12.4
Magneto-optical Characterization of Mn Doped II-VI Semiconductor Nanoparticles.
Donny Magana 1 , Geoffrey Strouse 1
1 Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States
Show AbstractMetal doped semiconductors have been an area of interest for their use in spin related devices. The observed strong s-d and p-d exchange interations between the dopant ion and the lattice gives rise to unique mangnetic and optical properties that are of great interest, because of the ability to observe emission from the manganese 4T2-6A1 transition. For this, different sized MnCdSe nanoparticles were synthesized and temperature dependent photoluminescence and absorption were taken in the presence and obsences of an applied magnetic field. The observation of Mn(II) emission was evident at different temperatures dependent on the size of the nanoparticle. Insight into the spin orbit energy is gathered when comparing the energy difference between states of an undoped CdSe and MnCdSe. A model is proposed for the observation in the reduction of the spin orbit energy when CdSe is doped with Mn.
10:15 AM - W12.5
Functionalized Luminescent Oxide Nanoparticles for Biological Probes.
Domitille Giaume 1 , Didier Casanova 2 , Khalid Lahlil 1 , Martin-Pierre Sauviat 2 , Antigoni Alexandrou 2 , Thierry Gacoin 1 , Jean-Pierre Boilot 1
1 Laboratory of Condensed Matter Physics, CNRS, Palaiseau France, 2 Laboratory for Optics and Biosciences, CNRS-INSERM, Palaiseau France
Show AbstractRare earth doped oxide as bulk materials are well known for their numerous applications in light emitting devices. Emission properties of nanoparticles, in association with their small size, allow to look for new applications such as the elaboration of transparent luminescent devices or new biological labels. The key issue for such applications is the surface functionalization of the particles, in order to preserve their dispersion state and/or ensure strong interactions towards specific target sites.We will describe our work concerning the synthesis and the functionalization of rare earth doped yttrium vanadate particles, mainly aiming biological applications. YVO4:Eu particles (50 nm in diameter) are obtained as a stable suspension through a simple coprecipitation of precursors salts in water, as described previously.1 This suspension exhibits a strong red emission with a quantum yield of about 20 % and an emission lifetime of 0.7 ms.The process of surface functionalization of the particles relies on their encapsulation with an organically functionalized silica shell. A primary layer of silicate is grafted at the surface of the nanoparticles, followed by the growth of a shell of condensed alkoxysilane bearing an epoxy function. This function was chosen in order to allow further versatile grafting reaction with organic groups of interest. Special care is taken for the characterization of the obtained functionalized shell, using 29Si and 13C solid MAS NMR, thermogravimetric analysis and Infra-red spectroscopy.Concerning biological applications, the epoxy-functionalized particles are reacted with guanidinium groups, in order to study the localization of Na+ channels on live cardiac myocytes. Specific interactions between these guanidinium groups and Na+ channels are expected, since they are the active part of complex toxins known for their specific blocking effect. Electrophysiological experiments indeed confirm that the functionalized nanoparticles mimic the toxin and thus present a strong interaction with the Na+ channels.The particles are then observed directly on live cardiac myocyte by fluorescence microscopy. The high specificity of the interaction between nanoparticles and the sodium channels is evidenced,2 so that the distribution of emission spots can be taken as representative of the Na+ channels spatial distribution.1 A. Huignard et al., Chem. Mat. 12, 1090 (2000) ; A. Huignard et al., Chem. Mat. 14, 2264 (2002).2 E. Beaurepaire et al., Nanoletters 4, 11, 2079 (2004).
10:30 AM - W12.6
Nonaqueous and Halide-free Synthesis of Crystalline Indium Tin Oxide (ITO) Nanoparticles with High Electronic Conductivity.
Jianhua Ba 1 , Markus Niederberger 1 , Dina Fattakhova 2
1 , Max Planck Institute of Colloids and Interfaces, Potsdam-Golm Germany, 2 Physical and electrochemical department, Hannover University, Hannover Germany
Show AbstractIndium tin oxide (ITO) is well known as one of the most important transparent conductive oxides (TCOs). It has been broadly used in the fabrication of optoelectronic devices, electrochemical devices, window coatings or gas sensors. due to its outstanding electro-optical properties and thermal-mechanical stability. Although many techniques, such as reactive electron vaporation, DC and rf magnetron sputtering, reactive thermal deposition, coprecipitation method or sol-gel process, have been developed to produce ITO films and powders, the realization of the synthesis of highly crystalline ITO nanoparticles with narrow size distribution still keeps very challenging. Herein, we report a novel and straightforward method to synthesize ITO nanoparticles with high crystallinity, uniform particle morphology and narrow particle size distribution (around 10 nm). All the procedures were performed in nonaqueous media without any halogen precursors involved. By following the benzyl alcohol route [1,2], the ITO nanoparticles were obtained after solvothermal reaction at relatively low temperature (200°C) and proven to be highly conductive. The unique features of this approach to synthesize ITO nanoparticles exhibit great potentials to produce advanced conductive coatings, gas sensors and other electronic devices. In this presentation, we will give a detailed synthesis procedure of the ITO nanoparticles and their characterization including TEM, HRTEM, EDX, XRD and XPS. Furthermore, we will present conductivity measurements of ITO samples with various SnO2 doping contents in the range of 2-20wt%, use of these nanopraticles for film fabrication and investigation of the gas sensing properties. [1]. Pinna, N.; Neri, G.; Antonietti, M.; Niederberger, M. Angew. Chem. Int. Ed. 2004, 43, 4345.[2]. Niederberger, M; Garnweitner, G; Pinna, N; Antonietti, M. J. Am. Chem. Soc. 2004, 126, 9120.
10:45 AM - W12.7
Monitoring the Evolution of Magnetic Nanoparticles in Spherical Protein Cages Using EMR
Michael Klem 1 2 , Hongyan Li 3 2 , Keith Gilmore 3 2 , David Singel 1 2 , Mark Young 4 2 , Yves Idzerda 3 2 , Trevor Douglas 1 2
1 Chemistry & Biochemistry, Montana State University, Bozeman, Montana, United States, 2 Center for Bioinspired Nanomaterials, Montana State University, Bozeman, Montana, United States, 3 Physics, Montana State University, Bozeman, Montana, United States, 4 Plant Sciences, Montana State University, Bozeman, Montana, United States
Show AbstractThe development of materials on the nanometer scale are of considerable interest because of the novel magnetic, catalytic, and optical properties they posses arising from the large surface areas and quantum size effects characteristic to these materials. Spherical protein cages, like the Fe storage protein ferritin was used as a constrained reaction environment for the mineralization of magnetic Fe oxide nanoparticles. The ferritin proteins were chemically loaded with Fe3O4 and/or γ-Fe2O3 nanoparticles where the core size was determined by TEM. Electron Magnetic Resonance (EMR) was used to monitor the particle growth and give insight into the mineralization pathway. Simulation of the EMR lineshapes give insight into the magnetic moment and particle size distributions. The EMR lineshapes are comprised of two components, a broad component for the nanoparticle, and a sharp component corresponding to the initial nucleation of the nanoparticle. As the particle grows, the narrow component is reduced and the broad component becomes dominant. The ability to monitor the magnetic behavior of nanoparticles during synthesis affords one the potential to tune the magnetic properties of the nanoparticles as they are being formed.
11:30 AM - W12.8
Synthesis and Cation Exchange of CdSe Nanocrystals in Nanoliter Reactors.
Emory Chan 1 2 , Matthew Marcus 3 , Richard Mathies 1 , Paul Alivisatos 1 2
1 Department of Chemistry, UC-Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract11:45 AM - W12.9
Self Assembly of Responsive Core/Shell Nanostructured Particles.
Xingmao Jiang 1 , C. Jeffrey Brinker 1 2
1 Department of Chemical and Nuclear Engineering/Center for Micro-Engineered Materials, University of New Mexico , Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractWell controlled structure and surface chemistry of self-assembled nanoporous silica materials make them of interest for ‘smart’ fillers that could impart to coatings and paints long term corrosion inhibition properties through controlled release. In this talk we describe aerosol-assisted evaporation induced self assembly as a means to prepare nanoporous core shell particles in which a Ce corrosion inhibitor is encapsulated within an ordered nanoporous silica shell. The release can be controlled effectively over a wide range by the pore size, the pore surface hydrophobicity, the salt solubility, and the pH value of the release medium. The nanostructured particles and superhydrophobic coating layer of the particles have shown excellent protection for aluminum alloys. Functionalization of the pore surface improves the hydrothermal stability and delays the release. Azobenzene modified particles show a photoresponsive release. NaCl is selected as a model salt to investigate transport during both self assembly and controlled release. Ordered core-shell particles with a cubic single crystal NaCl core have been prepared. A mathematical model has been developed to evaluate the release behavior and acquire the effective diffusion coefficients for the ions. A simulation approach has also been established to quantitatively describe the transient coupled heat and mass transfer with moving boundaries for the evaporation induced self-assembly process. The simulation agrees well with experimental data on the evolution in droplet size, temperature and compositions for evaporating ethanol-water droplets. It is demonstrated that for evaporating ethanol-water-NaCl droplets the first oversaturation, nucleation and crystallization of NaCl happen at the droplet center instead of the surface as a result of quicker diffusion of NaCl than ethanol and depressed NaCl solubility by ethanol. For diffusion controlled NaCl crystallization, there is only one single crystal NaCl formed for each droplet smaller than a critical size, which is determined by aerosol generation conditions. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.
12:00 PM - W12.10
Protein-stabilized Colloidal Particles
Maurice Mehagnoul 1 , Leonard Flendrig 1 , Ingrid Winter 1 , Peter Versluis 1 , Johan Hazekamp 2 , Eli Roijers 2 , Ruud den Adel 2 , Gert-Jan Goudappel 2 , Krassimir Velikov 1
1 FSD, UFHRI, Unilever R&D Vlaardingen, Vlaardingen Netherlands, 2 AMI, UFHRI, Unilever R&D Vlaardingen, Vlaardingen Netherlands
Show AbstractColloidal particles find many applications in the formulation of paints, agricultural and home & personal care products, in drug delivery, foods, and as a precursor for advanced nanostructured materials. Preparation and stabilisation of colloidal particles in complex systems is a challenging task. To increase the stability of colloidal particles very often surfactants or polymers are used to absorb on the particle surface. As being surface active, proteins are another large class of molecules that can provide stabilisation effect in colloidal dispersions. Here we present initial results on the use of globular proteins for stabilisation of colloidal particles from low soluble minerals prepared by homogeneous precipitation.
12:15 PM - W12.11
A Hydrodynamic Focusing-Based Nanoreactor for Preparation of Morphology-Controlled and Mono-Dispersed Nanoparticles
Karla Coti 2 , Yanju Wang 3 , Weixing Lu 1 , Hsian-Rong Tseng 1
2 Chemistry and Biochemistry, UCLA, Los Angeles, California, United States, 3 Chemistry and Biochemistry, Calstate LA, Los Angeles, California, United States, 1 Molecular & Medical Pharmacology, UCLA, Los Angeles, California, United States
Show AbstractIt remains a great challenge to prepare nanoparticles with precise and simultaneous control of their morphologies, sizes and polydispersities by conventional synthetic protocols utilizing macroscopic reactors. The problems are (i) poor mixing efficiency which leads to heterogeneous reaction conditions (e.g., concentration and temperature) and (ii) lack of control upon nucleation and growth processes during the formation of nanoparticles. In this presentation, we will describe the development of a hydrodynamic focusing beam-based nanoreactor, in which an ultra-fast mixing and continuous reaction at sub-micron scale have been achieved. Such an open dynamic system provides solutions to generate homogeneous reaction conditions and to realize a distinct separation between the nucleation and growth processes. By performing hydrodynamic mixing in this nanoreactor, a proof-of-concept study was demonstrated to produce mono-dispersed conducting polymer nanoparticles with tunable and uniform dimensionalities ranging from 20 to 200 nm. We believe that this newly developed nanoreactor can be generalized and diversified for productions of a wide range of mono-dispersed nanoparticles.
12:30 PM - W12.12
Tandem Chain Walking Polymerization and ATRP for Efficient Synthesis of Dendritic Nanoparticles for Bioconjugation
Zhibin Guan 1 , Guanghui Chen 1
1 Department of Chemistry, University of California, Irvine, Irvine, California, United States
Show AbstractAmphiphilic organic nanoparticles and their biomolecule conjugates are important for many nanobiotechnology applications including catalysis, sensors, bioanalysis, drug delivery, and bioelectronics. The development of efficient synthesis of nanoparticle bioconjugates is important for these endeavors. In this study, we combined two powerful transition-metal catalyzed polymerization methods: chain walking polymerization (CWP) followed by atom transfer radical polymerization (ATRP), to efficiently synthesize dendritic nanoparticles with tunable sizes and reactive surface functionalities. Using the chain walking palladium-alpha-diimine catalyst, dendritic polymers bearing multiple initiation sites were synthesized and used as macro-initiators for subsequent Cu(I)-mediated ATRP. Control of molecular weight and size of the water soluble core-shell polymeric nanoparticles was achieved by tuning reaction conditions. Addition of N-acryloyloxysuccinamide (NAS) monomer at the end of the ATRP afforded NHS activated polymer nanoparticles. Conjugation with both small dye molecule and protein (ovalbumin) yielded nanoparticle conjugates with high dye or protein per particle ratio. With the efficient synthesis and good biocompatibility, these nanoparticles can have many potential applications in bioconjugation.
12:45 PM - W12.13
Organometallic Synthesis and Spectroscopic Properties of Colloidal ZnS:Cu,Pb Nanocrystals.
Andres Osvet 1 , Oliver Ehlert 2 , Miroslaw Batentschuk 1 , Martina Weidner 1 , Isabel Brauer 1 , Thomas Nann 2 , Albrecht Winnacker 1
1 Department of Materials Sciences 6, University of Erlangen-Nuremberg, Erlangen Germany, 2 , Freiburg Materials Research Center, Freiburg Germany
Show AbstractNanosized phosphors are increasingly interesting materials for various applications including biological markers and lighting devices. Studying the electronic properties of impurities and defects that serve as activators and traps is necessary for the applications, and is important for the understanding of the fundamental physics of these materials. In this work we have prepared and characterized ZnS nanoparticles with Cu and Pb doping using a novel organometallic synthesis approach. In macroscopic form, the material is a well-known phosphor which shows long afterglow and may be used as an infrared-stimulable storage phosphor.Transmission electron microscopy, x-ray diffraction and energy-dispersive x-ray analysis were used to study the morphology of the synthesised nanoparticles. The particles have an average diameter of approx. 5 nm with a fairly narrow size distribution. Their crystal structure is cubic.The spectroscopic properties of the luminescent centres were studied by photoluminescence (PL) and PL-excitation spectroscopy between 10 K and room temperature. The PL spectra of the particles contain blue, green, and red bands, depending on the preparation details which lead to the presence of different dopant-related defect centres. The green luminescence with a maximum at 520 nm arises from Cu-related centres, the red luminescence is tentatively ascribed to the Pb-related centres.Due to the small dimensions, the impurity and defect properties are strongly affected by the nearby surface and surface states.Photoluminescence decay measurements were used to study the thermal quenching and revealed temperature-dependent energy transfer between the luminescent centres. Effects of thermal treatment of the samples on their spectroscopic properties, and photodegradation under UV excitation in solution as well as in air will be discussed.
W13: Synthesis V
Session Chairs
Friday PM, April 21, 2006
Room 2001 (Moscone West)
2:30 PM - W13.1
Microbial Synthesis of Noble Metal Nanoparticles using Metal-reducing Bacteria
Yasuhiro Konishi 1 , Kaori Ohno 1 , Norizoh Saitoh 1 , Toshiyuki Nomura 1 , Shinsuke Nagamine 1
1 Chemical Engineering, Osaka Prefecture University, Sakai Japan
Show AbstractNoble metals nanoparticles can be applied to a wide range of functions such as catalysis, optics and biosensing. Although chemical and physical synthetic routes to noble metal nanoparticles have been extensively developed, another possibility is synthesis by bioreduction of noble metal ions using microorganism. For microbial synthesis of noble metal nanoparticles, we focused on the metal-reducing bacterium Shewanella algae. Intracellular synthesis of gold nanoparticles was achieved at 25°C and pH 7 using S. algae with hydrogen gas as the electron donor. The reductive deposition of gold by S. algae was a fast process: 1 mol/m3 AuCl4- ions were completely reduced to insoluble gold within 30 min. Speciation of gold in bacterial cultures of S. algae by X-ray Absorption Near-Edge Spectroscopy (XANES) showed that the trivalent gold ions were rapidly reduced to gold metal in the bacterial cells. Transmission electron microscopy (TEM) of thin sections of S. algae cells revealed that the biogenic gold nanoparticles of 10-20 nm were located in the periplasm. When the pH of the HAuCl4 solution was decreased from 7 to 1, many of the biogenic gold particles were synthesized extracellularly. The gold particles synthesized at pH 1 were typically 50 nm and 500 nm, and some were angular in shape and single crystal. This suggests that at pH 1, a gold-reducing enzyme is released from the periplasmic space into the aqueous solution, and the enzyme catalyzes the reduction of gold ions in the aqueous solution. We can therefore conclude that the solution pH is an important factor in controlling the morphology of biogenic gold particles and location of particle formation. Microbial synthesis of platinum nanoparticles was achieved at 25°C and pH 7 using S. algae with lactate as the electron donor. The microbial reduction of 1 mol/m3 PtCl62- ions was so fast that there was a 90% decrease in the aqueous platinum concentration within 60 min. High magnification TEM image shows aggregates of biogenic platinum nanoparticles, in which individual, discrete nanoparticles had a diameter of about 5 nm. We strongly believe that the microbial synthesis of noble metal nanoparticles is potentially attractive as an environmentally friendly alternative to conventional methods.
2:45 PM - W13.2
Biomimetic Synthesis and XAS Characterization of TiO2 Nanoparticles Synthesized in the Protein Cage Ferritin
Michael Klem 1 2 , Keith Gilmore 3 2 , Jesse Mosolf 1 2 , Ryan Boysen 1 2 , Robert Szilagyi 1 2 , Yves Idzerda 3 2 , Mark Young 4 2 , Trevor Douglas 1 2
1 Chemistry & Biochemistry, Montana State University, Bozeman, Montana, United States, 2 Center for Bioinspired Nanomaterials, Montana State University, Bozeman, Montana, United States, 3 Physics, Montana State University, Bozeman, Montana, United States, 4 Plant Sciences, Montana State University, Bozeman, Montana, United States
Show AbstractThe development of materials on the nanometer scale present an opportunity to study emergent properties of a material as they transition from molecular to extended solid behavior. Toward this goal, protein encapsulated TiO2 nanoparticles were synthesized by photoreduction of a Ti(IV) citrate precursor in the presence of the protein cage ferritin. Ferritin is a 24 subunit protein that self-assembles into a 12 nm spherical cage with an interior diameter of approximately 8 nm that has been exploited extensively in biomimetic materials synthesis. The resulting TiO2 nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, electron diffraction, and x-ray absorption spectroscopy. The x-ray absorption spectra at both the Ti L- and K- edge show some departure from the absorption spectra of the bulk phase (rutile). Using theoretical methods, a cluster based model has been developed that accurately describes the measured absorption spectra in terms of deviation from the ideal TiO6 octahedra. This cluster based theoretical approach provides an elegant framework to bridge the nano and macro scale lengths.
3:00 PM - W13.3
Developing New Nanoprobes From CdSe/ZnS Semiconductor Nanocrystals
Aihua Fu 1 , Weiwei Gu 2 , Kai Zhang 1 , Frank Chen 4 , Haw Yang 1 2 , Carolyn Larabell 2 , A. Paul Alivisatos 1 3
1 Department of Chemistry, University of California Berkeley, Berkeley, California, United States, 2 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractSemiconductor nanocrystals, also called quantum dots, are a new class of fluorescent biological labels. Recent advances in synthesis, surface chemistry and optical property characterization of quantum dots have resulted in a variety of applications in biological imaging and detection schemes. To create new nanoprobes from semiconductor nanocrystals with an even wider range of applications, we developed two strategies. In one, we assembled quantum dots and Au nanoparticles into discrete nanostructures using biological molecules; in the other, we developed water-soluble rod shaped semiconductor nanocrystals (quantum rods) for biological imaging. The preparation, optical property characterization and bio-applications of these new nanoprobes are addressed.
3:15 PM - W13.4
Surface Engineered Metallic Nanoparticles and Their Utilization in Surface Enhanced Raman Scattering (SERS).
Blake Simmons 1 , Alec Talin 1 , Eric Majzoub 1 , Gene Lucadamo 1
1 Nanoscale Science and Technology Department, Sandia National Laboratories, Livermore, California, United States
Show AbstractSurface enhanced Raman scattering (SERS) is a powerful technique that holds great promise in the development of highly sensitive, portable, and fully autonomous remote sensors and devices. One of the crucial components to this approach is the presence of spatially ordered metallic nanoparticles in a rational fashion. We present here the synthesis and utilization of metallic nanoparticles with engineered surfaces that possess unique morphologies and spectroscopic characteristics that enhance this SERS response. The metallic nanoparticles were synthesized in a mixed surfactant system containing equimolar amounts of dioctyl sulfosuccinate and phosphatidylcholine. These surfactant mixtures can form a high viscosity mesophase after the addition of a proscribed amount of water to form a bicontinuous microemulsion. These dynamic bicontinuous networks of water and oil separated by an amphiphilic barrier dispersed throughout a given system volume are ideal candidate templates for producing nanoparticles with unique characteristics and novel surface morphologies. The resultant nanoparticles are highly polycrystalline and possess a distinct roughened morphology on length scales ideal for SERS. These nanoparticles were then shown to have an amplified SERS response, when compared to analogous spherical nanoparticles, in the presence of Rhodamine 6G.
4:00 PM - W13.5
Synthesis and Catalytic Activity of Bimetallic Clusters Using Peptides.
Joseph Slocik 1 , Morley Stone 1 , Rajesh Naik 1
1 Materials and Manufacturing Directorate, Air Force Research Lab, Wright-Patterson AFB, Ohio, United States
Show AbstractPalladium nanoparticles have proven to be effective and efficient catalysts for dehalogenation, reduction, and hydrogenation reactions. Approaches to their synthesis have involved the use of dendrimers, supercritical fluids, palladium-surfactant complexes, and ferritin protein cages. For example, PAMAM dendrimers of different generations have yielded monodisperse palladium nanoparticles encapsulated within the dendrimer host for the hydrogenation of unsaturated alcohols, while ferritin cages were used to mineralize catalytically active palladium particles in situ. Alternatively, we describe the synthesis of gold-palladium nanoparticle structures via gold-peptide interfaces displaying an affinity for palladium and its associated catalytic activity.
4:15 PM - W13.6
Protein-Functionalized Core-Shell Nanoparticles for Cellmimetic Signalling
Guenter Tovar 1 2 , Peter Scheurich 3 , Herwig Brunner 1 2 , Susanne Bryde 3 , Klaus Pfizenmaier 3 , Ingo Grunwald 3 , Thomas Schiestel 1
1 Biomimetic Surfaces, Fraunhofer IGB, Stuttgart Germany, 2 Institute for Interfacial Engineering, University of Stuttgart, Stuttgart Germany, 3 Institute for cell biology and immunology, University of Stuttgart, Stuttgart Germany
Show AbstractCytokines play a key role in cell-cell communication. Usually they are investigated in a soluble form or (over)expressed at the surface of a cell line. Both ways are often erroneous in biomedical research as the first is an improper simplification whereas the latter usually leads to a complex response pattern due to multiple cell-cell interactions. Objectives of this work is the built-up of synthetic-bionic hybrid systems consisting of organically modified silica nanoparticles and the cytokine Tumor Necrosis Factor-α (TNF) to create a defined system for the investigation of membrane-TNF signaling. Silica particles with a size of 100 nm are synthesized and fluorescence markers are incorporated into the particles. We modify the nanoparticles with different functional shells to provide protein binding groups at their surface. Suitable anchor groups are introduced into the N-terminus of TNF by recombinant methods. This approach leads to a covalent and site-directed coupling of the protein. The resulting hybrid particles are characterized by physico-chemical and biological methods.The particles initiate cellular responses otherwise only seen for cellmembrane-bound TNF. Thus, the hybrid Nanoparticles are clearly showing new and cell analogous properties. These particles are thus referred to as NANOCYTES and may become a valuable tool for biomedical research, diagnosis and in future therapy with high potential as a new anti-cancer drug.[1] T. Schiestel, H. Brunner, G. E. M. Tovar; Controlled Surface Functionalization of Silica Nanospheres by Covalent Conjugation Reactions and Preparation of High Density Streptavidin Nanoparticles. Journal of Nanoscience and Nanotechnology 2004, 4, 504-511.[2] S. Bryde, I. Grunwald, A. Hammer, A. Krippner-Heidenreich, T. Schiestel, H. Brunner, G. E. M. Tovar, K. Pfizenmaier, P. Scheurich; Tumor Necrosis Factor (TNF)-Functionalized Nanostructured Particles for the Stimulation of Membrane TNF-Specific Cell Responses. Bioconjugate Chemistry in press.
4:30 PM - W13.7
Fabrication of Magnetic and Fluorescent Nanocarriers and Their Solution Dynamics
Yudhisthira Sahoo 1 , Edward Furlani 1 , Tymish Ohulchanskyy 1 , Ludmila Cinteza 1 , Earl Bergey 1 , Paras Prasad 1
1 Chemistry, Institute for Lasers, Photonics and Biophotonics, SUNY at Buffalo, Buffalo, New York, United States
Show AbstractNanosized superparamagnetic particles are routinely used in various biomedical applications including diagnostic imaging (MRI), bioseparation (magnetic labeling), and therapeutic drug delivery. Among the metallic, alloy, and ferrite nanoparticles, iron ferrite magnetite has been investigated most extensively. In this presentation, different synthetic routes for magnetite will be discussed, with particular emphasis on controlling the surface structure using either chemical modifications or micellar encapsulation, yielding in both cases a stable aqueous ferrofluid of the nanocarriers. In the first case, citric acid is attached to the surface of magnetite, and the terminal carboxylate group is bound to a fluorophore dyes rhodamine 110 or 4',6-diamidino-2-phenylindole, dihydrochloride (DAPI). In the second approach, magnetite organosol is co-encapsulated with a fluorescent drug 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) within a diacylphospholipid polymeric micelle. In both cases, magnetophoretic control on the confocal fluorescence images of the nanocarriers has been observed. The magnetophoretic control of these functionalized nanocarriers will be discussed in the context of practical microfluidic systems for bioapplications.
4:45 PM - W13.8
Synthesis of Gold Nanorods with Precisely Controlled Surface Plasmon Resonance Wavelengths.
Frank Tsung 2 , Jianfang Wang 1 , Galen Stucky 2
2 Chemistry and Biochemistry, University of California Santa Barbara, Goleta, California, United States, 1 Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong China
Show Abstract5:00 PM - W13.9
Colloidal Synthesis of Antimonide Quantum Dots.
Chris Evans 1 , Stephanie Castro 2 , Brian Landi 1 , Sheila Bailey 3 , Ryne Raffaelle 1
1 NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, New York, United States, 2 , Ohio Aerospace Institute, Brookpark, Ohio, United States, 3 , NASA Glenn Research Center , Cleveland, Ohio, United States
Show AbstractFriday, April 21Presentation Time and Paper Number Change W13.10 to W13.94:00 PM Colloidal Synthesis of Antimonide Quantum Dots. Chris M. Evans
5:15 PM - W13.10
Tethering Polydiacetylene Colloids to Glass Fiber Filters for Fluorescence-based Biosensing Applications.
Mary Reppy 1 , Bradford Pindzola 1 , Emily Cleveland 1
1 , Analytical Biological Services Inc., Wilmington, Delaware, United States
Show AbstractFriday, April 21Presentation Time and Paper Number Change W13.11 to W13.104:15 PM Tethering Polydiacetylene Colloids to Glass Fiber Filters for Fluorescence-based Biosensing Applications. Mary Reppy
5:30 PM - W13.11
Designing Hot Spots: Anisotropic Metal-Silica Hybrid Assemblies For Surface Enhanced Raman Spectroscopy
Martin Schierhorn 1 , SeungJoon Lee 1 , Galen Stucky 1 , Martin Moskovits 1
1 Chemistry and Biochemistry, UCSB, Goleta, California, United States
Show AbstractFriday, April 21Presentation Time and Paper Number Change W13.12 to W13.114:30 PM Designing Hot Spots: Anisotropic Metal-Silica Hybrid Assemblies For Surface Enhanced Raman Spectroscopy. Martin Schierhorn