Yadong Yin University of California-Riverside
Yugang Sun Argonne National Laboratory
Dmitri Talapin University of Chicago
Hong Yang University of Rochester
Y1: Nanocrystalline Building Blocks
Tuesday PM, April 14, 2009
Room 3006 (Moscone West)
9:00 AM - **Y1.1
Nanocomposite Engineering of Nanocrystalline Materials
Jackie Ying 1 Show Abstract
1 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Nanocrystalline materials are of interest for a variety of applications. This talk describes the design and functionalization of nanocomposite materials for biological and chemical applications. Specifically, we have generated metallic, metal oxide and semiconducting nanocrystals for bioimaging, biolabeling, bioseparation, biosensing and catalysis. These nanocrystals are ≤ 10 nm in size, and are surface modified to provide for high dispersion, biocompatibility, and water solubility. They are used as building block to create multifunctional nanocomposite particles. For example, magnetic quantum dots can be tailored in both fluorescence and magnetic properties by manipulating their structure, composition and particle size.
9:30 AM - **Y1.2
Functional Nanoparticles: Synthesis and Potential Applications.
Shouheng Sun 1 Show Abstract
1 Department of Chemistry, Brown University, Providence, Rhode Island, United States
The talk focuses on the synthesis and applications of monodisperse transition metal nanoparticles. Using organic solution phase reactions, we have produced a series of monodisperse nanoparticles of Fe, Fe/Fe3O4, Fe3O4, hollow Fe3O4, and dumbbell-like M-Fe3O4 (M = Au, Pt) with controlled sizes and shapes. Once functionalized with a special antibody, peptide and an antitumor agent, these nanoparticles can be made target-specific and are promising for medical diagnostics and therapeutics. In contrast, upon the removal of the surfactant, the Pt- or Au-based nanoparticles become highly active catalysts for oxygen reduction and CO oxidation and are important for fuel cell applications.
10:00 AM - **Y1.3
Two Dimensional (2-D) Nanocrystals via Chemical Synthesis.
Jinwoo Cheon 1 Show Abstract
1 Chemistry, Yonsei University , Seoul Korea (the Republic of)
Two dimensional (2-D) crystals, that possess nanoscale dimension only in the c-axis and have infinite length in the plane, have been emerging as important new materials due to their unique properties and potential applications in areas ranging from energy storage, electronics, to catalysis. In this talk, I will describe a new concept for the fabrication of 2-D nanosheet crystals by using a “shape transformation” route. Our surfactant-assisted low-temperature solution process is critical in stabilizing 2-D nanosheet structures as opposed to conventional high-temperature gas-solid route which yield only 0-D or 1-D shapes. These 2-D crystals now exhibit unique nanoscale characteristics as demonstrated in their highly enhanced charge capacity as electrode materials of lithium ion batteries.
10:30 AM - Y1.4
Design of Functional Nanocrystals Solids.
Dmitri Talapin 1 , Maryna Bodnarchuk 1 , Sara Rupich 1 , Jong-Soo Lee 1 , Maksym Kovalenko 1 Show Abstract
1 Department of Chemistry, The University of Chicago, Chicago, Illinois, United States
Colloidal nanocrystals are considered promising building blocks for electronic and optoelectronic devices. Potentially, they can combine the advantages of crystalline inorganic semiconductors with size-tunable electronic structure and inexpensive solution-based device fabrication. However, several fundamental problems have to be solved before these materials will compare favorably to the competitive approaches, e.g. organic electronic materials. The electronic properties of nanocrystal solids are determined by concentration of mobile carriers and electronic communication between individual nanocrystals. We developed several approaches to electronic doping of nanocrystal solids based on the formation of inter- and intra-nanocrystal charge transfer complexes. For example, hydrazine molecules adsorbed at the nanocrystal surface behave as n-type charge-transfer dopant whereas Au-PbS core-shell nanocrystals show stable p-type doping due to electron transfer from PbS shell into the Au core. The bulky and insulating nature of conventional organic capping ligands typically results in poor electronic coupling in the nanocrystal solids. To address this problem we demonstrate that molecular metal chalcogenide complexes can serve as versatile ligands for a broad range of colloidal nanocrystals. This new class of nanocrystal colloids provides a set of advantages such as all-inorganic design, small (<0.5 nm) interparticle spacing, easy thermal ligand-to-semiconductor conversion, and diverse compositional tunability for both nanocrystal and ligand constituents. As the model systems, we show electron mobility of ~3×10-2 cm2/Vs in arrays of CdSe nanocrystals and very high (~200 S/cm) conductivity in 5 nm gold nanocrystal solids capped with [Sn2S6]4- Zintl ions.
10:45 AM - Y1.5
Structural Control of Anisotropic Nanocrystal Heterostructures
Hunter McDaniel 1 , Moonsub Shim 1 Show Abstract
1 MatSE, UIUC, Champaign, Illinois, United States
Anisotropic nanocrystal heterostructures (NCHs) provide opportunities to synergistically combine the unique properties of two or more materials potentially leading to entirely new properties. Due to electronic and optical properties that are strongly dependent on size and shape, and furthermore, due to the necessity for physically and chemically accessing both components of the heterostructure (which may be achieved via enhancing anisotropy), the key step towards functional multi-component systems is the ability to control not only the size and shape but also spatial orientation of each component with respect to each other. In order to better understand growth mechanism leading to enhanced anisotropy in NCHs synthesized from nearly spherical seeds, we have examined various factors that contribute to structural diversification in Fe3O4/CdS system. Pseudo-separation of nucleation and growth allows us to quantify how the number of heterojunctions formed varies with concentration and the size of the seed nanocrystals. A careful examination of the size dependence of the maximum number of CdS particles that can be nucleated per seed nanocrystal suggests strain induced limitations. By increasing the growth rate, we observe evolution of dots-on-dot structures to rods-on-dot structures without the need for rod promoting capping molecules. Crystallographic details allow us to identify three distinct morphologies that can arise in rods-on-dot heterostructures. Although the junction planes contain identical or nearly identical coincidence sites in all cases, diversity in structure arises due to zinc blende/wurtzite polytypism in CdS. Further enhancement in structural control can be achieved with the addition or dilution of capping ligands prior to the growth of the second material. This technique can be extended to achieve more complex NCHs beyond the two-component systems.
11:30 AM - **Y1.6
III-V Semiconductor Nanocrystals: Optical Quality Control in Synthesis and Surface Modification.
Xiaogang Peng 1 Show Abstract
1 , Univ of Arkansas, Fayetteville, Arkansas, United States
Synthetic chemistry of III-V semiconductor nanocrystals has been considered as a significant challenge in the field of colloidal nanocrystals. The synthetic chemistry seems to be quite different from that of their II-VI counterparts, such as CdSe ones. This talk will discuss the recent development along this direction. The main focus will be on controlled growth of plain core InP and InAs nanocrystals, their corresponding core/shells, and the surface modification of the nanocrystals with hydrophilic organic ligands.
12:00 PM - **Y1.7
Periodic Superlattices Self-assembled from Nanoparticles.
Elena Shevchenko 1 Show Abstract
1 Argonne National Laboratory, Center for Nanoscale Materials, Argonne, Illinois, United States
Periodic structures of nanoparticles is considered to be promising materials for a number of applications such as solar cells, field emission transistors, catalysts, etc. Nanoparticles of different size, shape, composition can assemble into periodic structures isostructural with atomic and ionic compounds as well as into quiasicrystals. Different types of interactions (Coulombic interactions, dipolar, van der Waals, etc) occur between nanoparticlesduring crystallization that challenge the control over the type of crystal and size of ordered domain. Self-assembly of multicomponent nanoparticles (core-shells, dumbbells, etc) greatly extends the variety of the periodic superlattices. We will demostrate the examples of single component and multicomponents superlattices and quasicrystals assembled from nanoparticles and overview the contribution of particle-particle interactions. Typically, crystallization happens randomly on the substrate. We will discuss our strategies directed on the localization of the crystallization process and designof periodic structures with potentially interesting properties. Also we will discuss the possibility of the post-preparative manipulation of the structure of self-assembled superlattices.
12:30 PM - Y1.8
Towards Making n-type Quantum Dots: Tin and Indium Doped CdSe Quantum Dots.
Santanu Roy 1 , Christopher Tunenga 1 , Pinar Dagtepe 1 , Jacek Jasinski 2 , Viktor Chikan 1 Show Abstract
1 Deaptment of Chemistry, Kansas State University, Manhattan, Kansas, United States, 2 Institute for Advanced Materials and Renewable Energy, University of Louisville, Louisville, Kentucky, United States
Controlling conductivity of semiconductor is one of the next frontiers of quantum dot research. In this report, doping of CdSe quantum dots with indium of tin are explored using a relatively low temperature synthetic approach. The high resolution nanoprobing shows that indium significantly fluctuates from particle to particle. The tin doped CdSe samples show preferential adsorption of tine into the CdSe quantum dots during synthesis. The photoluminescence of doped samples exhibit steeper temperature dependence compared to undoped CdSe quantum dots, which is expected due to the n-type of character of the quantum dots. The Polarized time-resolved photoluminescence shows that indium and tin doping significantly enhances the carrier relaxation in the quantum dots resulting increased polarized emission. Both terahertz–time domain spectroscopy data and the time-resolved PL data suggests that the dopant distribution is random in the indium doped CdSe and somewhat clustered in the tin doped CdSe samples.Reference: 1) Christopher Tuinenga, Jacek Jasinski, Takeo Iwamoto, Viktor Chikan, ACS nano, 2008, vol 2, no 7, 1411-1421
12:45 PM - Y1.9
Surface Chemistry of Colloidal PbSe Nanocrystals.
Iwan Moreels 1 , Bernd Fritzinger 2 , Jose Martins 2 , Zeger Hens 1 Show Abstract
1 Inorganic and Physical Chemistry, Ghent University, Gent Belgium, 2 NMR and Structure Analysis Unit, Ghent University, Gent Belgium
The organic ligands of colloidal semiconductor nanocrystals serve many purposes. During synthesis, they determine the particle size and shape. After synthesis in organic media, they may be exchanged for hydrophilic ligands rendering the particles water soluble, and more recently, they have proven to be essential in providing the nanocrystal with an adequate charge to produce binary superlattices of various compositions. Despite their importance, in literature one finds only few studies on the organic ligands and the corresponding nanocrystal surface chemistry.In this contribution, we present the composition of Q-PbSe nanocrystal core and ligand shell.[3,4] The Pb:Se ratio of the nanocrystals is determined with inductively coupled plasma mass spectrometry (ICP-MS). Although they are synthesized in presence of an excess of Se, we find that the nanocrystals contain an excess of Pb atoms, which can be interpreted as a Pb surface excess. Detailed structural modeling shows that Q-PbSe consist of a stoichiometric PbSe core, terminated by a pure Pb surface shell. The ligands are studied with nuclear magnetic resonance spectroscopy (NMR). Detailed analysis using different NMR techniques (diffusion ordered spectroscopy, heteronuclear single quantum coherence spectroscopy) allows us to distinguish the nanocrystal ligands from unbound molecules and permits identification of the ligands. We find that the ligand shell is composed almost entirely of oleic acid (OA). Tri-n-octylphosphine is also used during synthesis, yet it represents less than 5% of the nanocrystal ligands. A procedure is derived to determine the number of ligands per nanocrystal from quantitative NMR data. We find an OA grafting density of 4.2 ligands per nm^2. This value corresponds almost exactly to the number of excess Pb atoms added to the nanocrystal surface.Although the results presented are focussed on a single system (oleic acid capped PbSe nanocrystals), the methods used are general and therefore applicable to a wide range of materials of various shapes and sizes. We therefore believe that these results are of great value in, for instance, directing and understanding the formation of complex nanocrystal superstructures. E. Shevchenko et al., Structural diversity in binary nanoparticle superlattices, Nature 2006, 439, 55-59. Y. Yin et al., Colloidal nanocrystal synthesis and the organic-inorganic interface, Nature 2005, 437, 664-670. I. Moreels et al., Composition and size-dependent extinction coefficient of colloidal PbSe quantum dots, Chem. Mater. 2007, 19, 6101-6106. I. Moreels et al., Surface chemistry of colloidal PbSe nanocrystals, DOI: 10.1021/ja803994m.
Y3: Poster Session
Tuesday PM, April 14, 2009
Exhibition Hall (Moscone West)
6:00 PM - Y3.1
Purification of High Aspect Ratio Gold Nanorods: Complete Removal of Platelets.
Bishnu Khanal 1 , Eugene Zubarev 1 Show Abstract
1 Chemistry, Rice University, Houston, Texas, United States
Because physical and chemical properties of nanostructures strongly depend on their shape, it is of great importance to find either synthetic or separation techniques that can produce objects of a particular shape in a pure state. This presentation will describe a solution to a long standing problem of separating 2D platelets from 1D nanorods. The key aspect of our approach relies on the partial dissolution of faceted platelets with Au(III)/CTAB complex that transforms them into smaller nanodisks. Because of the reduction in size, the 2D structures become fully soluble in water and can be separated from the nanorods that undergo slow precipitation. In addition, the isolated nanodisks can be converted back into initial faceted platelets upon treatment with Au(I)/ascorbic acid mixture. As a result of these simple procedures, a seemingly inseparable mixture of rods, platelets, and spheres is converted into nearly pure individual components.
6:00 PM - Y3.10
Synthesis and Transformation of Se-based Colloidal Chalcogenide Materials.
Geon Dae Moon 1 , Sungwook Ko 1 , Unyong Jeong 1 Show Abstract
1 Materials Science and Engineering, Yonsei Univ., Seoul Korea (the Republic of)
This talk will provide a number of ways to fabricate these Se-based nanostructured materials and their transformation into other types of structures. Selenium is an interesting material due to its electronic and photonic properties enabling a range of applications such as photocopying machine, pressure sensor, and electrical rectifier. Of all characteristic properties of Se, the high reactivity with other chemical reagents can make selenium transform into other functional materials. The transformed structures from Se colloids can be used to obtain unconventional nanostructures by utilizing the various different solubility of Se in various solvents. Furthermore, Amorphous Se colloids as a starting material can be applied to synthesize trigonal selenium nanowires. Se has a unique property that it can grow in one-dimensional direction anisotropically, which makes t-Se NW networked on the substrate by controlling the interfacial energy between Se and substrate.
6:00 PM - Y3.11
Evaluating the Affinity of Capping Molecules for Nanoparticles in Suspension by DOSY NMR.
Francois Ribot 1 , Francois Guillemot 1 , Benoit Dubertret 2 , Luk van Lokeren 3 , Rudolph Willem 3 Show Abstract
1 CMCP - UMR7574, UPMC / CNRS, Paris France, 2 LPEM - UPR5, CNRS, Paris France, 3 HNMR Centre, Vrije Universiteit Brussel, Brussel Belgium
During the synthesis, handling, processing or assembling of nanoparticles (NPs), the capping molecules, which cover their surface, play a key role, and accordingly, a detailed knowledge of the surface chemistry of NPs is highly desirable to understand and improve their syntheses as well as to rationalize their application. In particular, measuring, in suspension, the affinity of organic molecules for NPs is of prime importance. However, evaluating this affinity in situ is not a simple task, especially when the capping molecules are involved in a dynamic equilibrium between a free and a grafted form.In the last years, DOSY (Diffusion Ordered Spectroscopy) NMR has appeared as an efficient tool to monitor, in suspension, the interaction between organic molecules and NPs. Indeed, on top of the classical solution NMR parameters (chemical shifts and scalar coupling constants), this technique gives access to diffusion coefficients. Species can thus be differentiated on the basis of their translational mobility and sorted according to their size, without the need of a physical separation. As a consequence, capping molecules interacting with NPs can be distinguished from the free ones as they diffuse more slowly.The possibilities offered by DOSY NMR in the field of nanoparticles will be illustrated with three examples: cerium dioxide nanoparticles functionalized with long chain carboxylic acids , titanium dioxide nanoparticles prepared by hydrolysis-condensation of titanium butoxide in the presence of acetylacetone and p-toluene sulfonic acid  and CdSe quantum dots covered by trioctylphosphine oxide (TOPO). In the last example, emphasis will be placed on the dynamic between adsorbed and free TOPO molecules. In toluene, a lifetime of 0.7 s has been estimated for TOPO molecules interacting with CdSe QDs.1. F. Ribot, V. Escax, C. Roiland, C. Sanchez, J. C. Martins, M. Biesemans, I. Verbruggen, R. Willem, Chem. Commun., 2005, 1019.2. L. Van Lokeren, G. Maheut, F. Ribot, V. Escax, I. Verbruggen, C. Sanchez, J.C. Martins, M. Biesemans, R. Willem, Chem. Eur. J., 2007, 13, 6957.
6:00 PM - Y3.12
Enhancement of Fluorescence in Colloidal CuInS2 Nanocrystals by Introduction of Crystal Defect
Masato Uehara 1 , Kosuke Watanabe 2 , Yasuyuki Tajiri 2 , Hiroyuki Nakamura 1 , Hideaki Maeda 1 2 3 Show Abstract
1 Micro- & Nano-space Chemistry Group, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tosu, Saga Japan, 2 Department of Molecular and Material Sciences, Interdiscplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka Japan, 3 CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama Japan
We obtained a low toxic fluorescent Cu-In-S nanocrystal with a concept; improvement of fluorescence by introduction of crystal defect. In addition, our structural analyses reveal that the nanocrystals have many crystal defects without phase separation, which are different from bulk materials.Semiconductor nanocrystals such as CdSe have been attractive candidates for bio-tag and luminescence device due to the optical properties. Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronic Equipment (WEEE) have however, been issued in Europe for restricting using some elements such as Cd, Pb, Hg and so on, resulting alternative materials have been studied. We focused a material CuInS2 chalcopyrite semiconductor as alternatives of CdSe. CuInS2 is a direct transition semiconductor. The band gap energy of bulk CuInS2 is 1.5 eV and is expected to show the fluorescence in the visible range to near-infrared range by the quantum effect such as CdSe NCs. We tried to improve the quantum yield of this low toxic material which is an alternative for CdSe fluorescent. Although this nanocrystal shows the luminescence at the ambient temperature, the luminescent is attributed to not excitonic recombination as reported by some groups. The reported CuInS2 nanocrystals have high colloidal stability and well-defined particle size distribution. The fluorescence, however originates not from the band exciton recombination but from the donor-acceptor (D-A) transition, which are related to crystal defects, and the quantum yield was not high compared to CdSe fluorescent. Some reports in the relevant literature describe that a defect pair of copper vacancy and indium substitute for copper has low formation energy and that it readily exists in materials. In this study, we intentionally introduced the crystal defect in nanocrystal with the prospect that the fluorescence intensity would be increased. We tried to introduce and control the defect structure of nanocrystals. The stoichiometric CuInS2 nanocrystals were synthesized facilely by heating a solution of metal complexes and dodecanethiol. The fluorescence would be originated from the crystal defect. We introduced the crystal defect in nanocrystal by the alteration of the elemental ratio in the ram material solution. Consequently, the synthesized nanocrystal have many crystal defects related to Cu deficiency without the formation of secondary phase as reported in CuInS2 bulk materials according to our structural analyses. In the Raman analyses, the A1 vibration peak was shifted with alteration of cation ratio. The vibration wavenumbers are close to theoretical values of Matsushita et al, and it indicated that the nancrystals have homogeneous structure without phase separation. The fluorescence quantum yield of nanocrystal having many defects reached to 5%. Furthermore, by ZnS-coating the quantum yield was increased to 15% which is promising for application.
6:00 PM - Y3.13
Photon Induced Effects in Functionalized Carbon Nanotubes.
Harsh Chaturvedi 1 , Jordan Poler 2 Show Abstract
1 Physics and Optical Sc, UNC-Charlotte, Charlotte, North Carolina, United States, 2 Chemistry, UNC, Charlotte, North Carolina, United States
Single Walled Carbon Nanotubes (SWNT) are important for devices and sensors based on nanotechnology. Future optoelectronic devices can be made from the assemblies of diverse nanostructure materials and SWNTs, providing enhanced functionality. Molecular assembly by bottom up approach requires directed self assembly of rigid molecular components. Rigid ruthenium complexes have very strong absorbance in the visible spectrum and charge transfer properties; whereas SWNTs have exceptional electron accepting and charge transport properties. We have shown specific binding of these complexes with the end of SWNTs. Samples have been characterized using atomic force microscopy, and scanning electron microscopy. Absorption and Raman spectroscopy shows charge transfer and diameter selective binding of these metallodendrimers onto SWNTs. Photon enhanced aggregation properties of SWNT due to these ruthenium complexes are demonstrated. Ruthenium centered phenanthroline complexes exhibit a strong metal to ligand charge transfer. We believe that the nanotube quenches charge from the ligand after the complex has been optically excited. This results in optically altering the carrier density, and therefore the transport properties of the nanotubes. Field effect transistors (FET) have been fabricated using e-beam and conventional lithography. Photon induced affects on the charge transport are shown. Principles of optical gating where the current between drain and source can be significantly control by the light intensity will be presented.
6:00 PM - Y3.14
Synthesis and Structural Characterization of Ba0.7Sr0.3TiO3 Nanofibers.
Frank Mendoza 1 , Ricardo Martinez 1 , Gerardo Morell 1 , Ram Katiyar 1 Show Abstract
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
This work describes the fabrication of barium strontium titanate Ba0.7Sr0.3TiO3 (BST30) nanofibers in two steps, by means of hot filament chemical vapor deposition (HFCVD) and pulsed laser deposition (PLD). The ferroelectric material was deposited at films of bamboo like carbon nanotubes on top of a copper substrate (BCNT/Cu). XRD study confirmed the phase perovskite structure of BST30 coating at BCNTs/Cu. TEM analysis confirmed that BCNTs are the base of the BST30 nanofibers.
6:00 PM - Y3.15
Ag-Au-Ag Heterometallic Nanorods Formed Through Directed Anisotropic Growth.
Daeha Seo 1 , Jongwook Jung 1 , Hyunjoon Song 1 Show Abstract
1 chemistry, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Heterostructured nanocrystals containing multiple components are attracting attention due to not only their multifunctional properties but also new features arising from the effective coupling of different domains. Numerous semiconducting heterostructures have been synthesized by gas phase deposition, and are being for the miniaturization of electronic and photonic circuits. Metallic heterostructures, in contrast, are generally grown on hard templates such as anodic aluminum oxides by electrochemical deposition. Synthesis without templates is relatively difficult owing to distinct reduction rates and lattice mismatch of the different components. Even when selecting materials with similar lattice constants, precise tuning of the reaction conditions is strictly required for the formation of multimetallic nanostructures. Xu et al. successfully generated heterodimer particles at a micelle liquid-liquid interface, and Yang et al. utilized polyhedral Pt nanocrystals to induce either isotropic growth of Pd nanopolyhedrons epitaxially or anisotropic growth of Au nanowires heterogeneously. There have been few reports of synthesis of multisegmented metallic nanostructures without hard templates despite this approach is advantageous in terms of structural variety and controllability.We have recently demonstrated that single-crystalline polyhedral gold could be readily formed by the preferential overgrowth of spherical particles. Using a similar strategy, we promoted anisotropic growth from multiply twinned particles (MTPs). In the present work, we report the synthesis of Ag-Au-Ag heterometallic nanorods through directed overgrowth from gold decahedrons and rods by adding silver ions and poly(vinyl pyrrolidone) (PVP). The silver component was readily converted to Ag2S by reaction with Na2S to generate a semiconductor - metal - semiconductor heterojunction on the nanorods. Furthermore, Ag domains could be converted to metal hollow structure by galvanic replacement reaction.
6:00 PM - Y3.16
SiGe Nanorings: Growth, Characterization, and Photoluminescence Properties
Chih Ho 1 , Cheng-Ying Chen 1 , Jr-Hau He 1 Show Abstract
1 , National Taiwan University , Taipei Taiwan
Currently nanorings (NRs), artificial nanoscale clusters, are attractive because there is a great deal of interest in nanostructures from theoretical, experimental, and device perspectives. The feasible NR fabrication is demanded in the field of electronic and optoelectronic devices at the nanoscale. In addition, NRs exhibit novel physical and chemical properties resulting from quantum size effects. For example, with the presence of Coulomb correlation, the Aharonov-Bohm effect of excitons exists in a finite but small width of NR. When the width of the ring becomes large, the non-simply-connected geometry of NR is destroyed and in turn yields the suppression of Aharonov-Bohm effect. Accordingly, NRs need to scale down to exhibit the size effects. Many studies have focused on the optical property of the self-assembled Si1-xGex nanostructures. To our knowledge, the photoluminescence (PL) analysis from previous studies showed that only type-II band alignment of Si1-xGex NR, resulted from indirect non-phonon-assisted recombination between the holes confined in the Si1-xGex and the electrons confined at the interface between the strained Si and the Si1-xGex, has been fabricated. Although the type-I band alignment of Si1-xGex quantum wells (QWs) and NDs have been observed under controlled conditions,[3-4] it is demanded to obtain the type-I NRs which confine both electrons and holes with the NRs for its potential applications, such as single electron transistor and quantum computer.In the present study, we demonstrated a novel self-assembly technique for the fabrication of large-scale, uniform and ultra-small Si1-xGex NRs with the capability in control of composition and sizes without any special equipment. The formation of NRs is mediated by Au NDs. Si1-xGex NRs exhibit the enhancement of PL intensity over conventional Si1-xGex thin film due to quantum size effects. The luminescence efficiency as a function of the composition and size of Si1-xGex NR has been investigated. Power-dependent PL demonstrates that the NR mediated by Au NDs is type-I band alignment. The process promising the availability of a wide range of concentrations and size of type-I Si1-xGex NRs can serve as a useful platform for the fundamental understanding and future practical applications of NRs.References(1)Hu, H.; Zhu, J. L.; Li, D. J.; Xiong, J. J. Aharonov-Bohm effect of excitons in nanorings. Phys. Rev. B 2001, 63, 195307. (2)Li, F. H.; Tao, Z. S.; Qin, J.; Wu, Y. Q.; Zou, J.; Lu, F.; Fan, Y. L.; Yang, X. J.; Jiang, Z. M. Nanotechnology 2007, 18, 115708.(3)Wan, J.; Luo, Y. H.; Jiang, Z. M.; Jin, G.; Liu, J. L.; Wang, K. L.; Liao, X. Z.; Zou, J. Appl. Phys. Lett. 2001, 79, 1980.(4)Fukatsu, S.; Shiraki, Y. Appl. Phys. Lett. 1993, 63, 2378.
6:00 PM - Y3.18
Synthesis of Monodisperse Au, Au-Fe3O4 Composite Nanoparticles and Their Applications.
Youngmin Lee 1 , Sheng Peng 1 , Chao Wang 1 , Chenjie Xu 1 , Shouheng Sun 1 Show Abstract
1 Chemistry, Brown University, Providence, Rhode Island, United States
Au-Fe3O4 composite nanoparticles are synthesized by epitaxial growth of Fe3O4 on Au seeds. First, Au particles are synthesized by a burst of nucleation with the injection of a reducing agent to Au salt in organic solution phase. Then, Fe3O4 nanoparticles are grown on the seeds by thermal decomposition of Fe(CO)5 in organic solvent followed by air oxidation. These composite nanoparticles show both surface plasmon absorption of noble metal and magnetic properties of Fe3O4. Moreover, they show enhanced catalytic properties compared to their individual components. The novel properties of these composite particles can be further used for biological and catalytic applications. For biomedical applications, Au-Fe3O4 particles can be functionalized on each end with different moieties making it possible to target cancer cells and release drugs for treatment. Also, optical property of noble metal and magnetic property of Fe3O4 make it possible to trace the particles. For catalytic applications, nano-scale Au particles show catalytic activities toward many reactions which are not catalyzed with bulk gold. Oxidation of CO, selective oxidation of alcohols are the examples of such reactions. Especially, when Au-Fe3O4 composite nanoparticles are used, Au may show enhanced catalytic properties due to the strongly attached oxide support.
6:00 PM - Y3.19
Chemical Synthesis of Shape-Controlled Indium and Germanium Nanoparticles via Control of Reduction Kinetics at Room Temperature
Nam Hawn Chou 1 , Raymond Schaak 1 Show Abstract
1 Chemistry, Penn State University, University Park, Pennsylvania, United States
Metal precursors that have negative reduction potential vs standard hydrogen electrode have been synthesized with a variety of chemical approaches. Reduction of these metal precursors generally require harsh reaction conditions (e.g., high reaction temperatures and strong reducing agents), which can be inadequate for yielding precisely shape-controlled nanoparticles. To overcome these obstacles, as well as obtain shape-controlled nanoparticles, facile chemical approaches are necessary. Here we present a simple and robust kinetically controlled borohydride reduction process for synthesizing shape-controlled In and Ge nanocrystals at room temperature. By controlling the reduction rate via the rate of addition of sodium borohydride in tetraethylene glycol to an alcohol solution of InCl3 or GeCl4 in the presence of poly(vinyl pyrrolidone), indium nanoparticles are formed with shapes of high aspect ratio nanowries, uniform octahedra, and truncated octahedra, and germanium nanoparticles with sphere and cube shapes.
6:00 PM - Y3.2
Facile Synthesis Route To Ultra-Thin Hematite And Goethite-Hematite Core-Shell Nanorods.
Sara Cavaliere-Jaricot 1 , Arnaud Brioude 1 , Philippe Miele 1 Show Abstract
1 , LMI-University of Lyon, Villeurbanne France
Hematite (α-Fe2O3) is an environmentally friendly, low cost, high resistant to corrosion and versatile material with n-type semiconducting and magnetic properties. Due to such stability and electronic properties, this oxide has various applications in several fields as catalyst, photocatalyst, photoelectrode, battery electrode, gas sensor, pigment and magnetic material. Considerable interest has been devoted toward hematite nanostructures of various morphologies because of the novel size- and shape-dependent chemical and physical properties appearing at the nanoscale. A variety of physical and chemical strategies have been developed for the synthesis of size-controlled hematite 1D nanostructures: pulsed laser deposition(PLD), metal-organic chemical vapor deposition (MOCVD), hydrothermal synthesis, microwave assisted hydrothermal synthesis, sol-gel process, template-assisted synthesis, iron-water vapor reaction, forced hydrolysis, and micellar synthesis [1-4]. Such synthesis routes involved the introduction of surfactants or shape control ions, high temperatures, precursor calcination steps, and are often time-consuming. Furthermore, it still remains a challenge to develop simple and mild routes to synthesize nanorods with ultra-thin diameters. One-dimensional hematite (α-Fe2O3) nanorods with very small diameter of about 10 nm and length between 100 to 200 nm were synthesized in aqueous solution at low temperature with a simple and rapid method based on the oxidation of Fe3O4 nanoparticles at acidic pH, without using surfactants . HRTEM (High Resolution Transmission Electron Microscopy) also showed the presence of core-shell structures. The core phase is goethite (α-FeOOH) with the typical d(110)=4.18Å (JCPDS n°81-0464) interplanar distance and the shell is composed of hematite layers with the typical d(104)=2.703 Å interplanar distance (JCPDS n°33-0664). It is likely to think that the formation mechanism of the core-shell structures involves the heterogeneous nucleation of hematite on initially precipitated goethite cores. For thinner nanorods, we can assume that the goethite phase has been totally transformed into hematite one. Further characterization of such 1D nanostructures was performed by Raman and UV-vis spectroscopy and will be discussed in more detail. 1. Zhong, Z.; Ho, J.; Theo, J.; Shen, S.; Gedanken, A. Chem. Mater. 2007, 19, 4776.2. Zhang, X.; Li, Q. Mater. Lett. 2008, 62, 988.3. Wu, J.-J.; Lee, Y.-L.; Chiang, H.-H.; Wong, D.K.-P. J. Phys. Chem. B 2006, 110, 18108.4. Zhou, W.; Tang, K.; Zeng, S.; Qi, Y. Nanotechnology 2008, 19, 065602.5.Cavaliere-Jaricot, S.; Brioude, A.; Miele, P. Langmuir, submitted.
6:00 PM - Y3.21
Synthesis and Characterization of Submicron-Sized and Monodisperse Liquid Crystal Capsules
Yi-Chun Liu 1 , Sheng-Wen Lin 1 , Hui-Lung Kuo 1 Show Abstract
1 , ITRI/MCL, Hsinchu Taiwan
The optically anisotropic colloidal particles enable many new studies of both technological and scientific interests in recent years. Especially birefringent colloids from liquid crystal are usually spherical and have tunable optical properties when exposed to external electric/magnetic field. They are therefore believed to be a good candidate for making intriguing optical devices. However, it is challenging to make submicron-sized liquid crystal particles with very low polydispersity using standard emulsion techniques.Here we developed a new method to prepare the liquid crystal particles by first synthesizing the monodisperse hollow inorganic spheres and then allowing the liquid crystals to infiltrate into the hollow spheres. The resulting liquid crystal colloidal particles have adjustable diameters ranging from 200~500nm with a low polydispersity of 0.05. The inorganic shells can prevent liquid crystals inside from leaking out and also hold the spherical shape of colloidal particles after the evaporation of the dispersant. The good chemical resistance of inorganic materials to liquid crystals was also crucial for long-term reliability. The fill-in ratio of liquid crystals was determined by small angle x-ray scattering and the director configuration of liquid crystals confined in the shell was studied by confocal microscopy. A thin film assembled by the liquid crystal colloidal particles was sandwiched between two glass slides coated with a thin transparent layer of indium doped tin oxide (ITO) and an electric field which is perpendicular to the sample plane was applied over the sample. The isotropic-anisotropic transition induced by the alignment of liquid crystals can be observed, indicating that liquid crystals confined in the inorganic shells can still be driven by external electric field. We believed that the submicron-sized liquid crystal capsules have great potential for making optically tunable devices.
6:00 PM - Y3.22
Mechanistic Study of Deposited Hydroxyapatite(HAp) on Biocompatible TiO2 Nanotubes.
Yu-Jeong Cho 1 , Won Hee Lee 1 , Tea Ju Kang 1 Show Abstract
1 Advanced Materials Engineering, Sejong University, Seoul, 98 GunJa-Dong,Gwangjin-Gu, Korea (the Republic of)
In this study, a vertically aligned nanotubes array of titanium oxide was fabricated on cpTi(commercial pure titanium) substrate by anodic oxidation method at 20V from 1hr to 4hrs in 0.5MNH4H2PO4+0.12M NH4F. The phase of self-organized nanotubes which turn into rutile in anatase is transformed by increasing time at fixed voltage. The internal diameter of nanotubes that was observed to under about 100nm more than about 50nm was controlled by adjusting pH(2~7) of the electrolyte. To promote bioactivity, HAp(sigma Aldrich) nano powders were deposited on the surface of TiO2 nanotubes with various phase(anatase or rutile) by using a electrophoretic deposition method at 100V from 10s to 5min. The coated HAp layer on the surface of TiO2 nanotubes is affected by applied potential and time. The nanotubes that HAP was coated were hydrothermally treated to increase adhesion at 80° for 5hrs in the distilled water. XRD measurements reveal that hydrothermal treated nanotubes increase crystalinity. As a result of XPS analysis, adhesion of coated HAp on the surface of TiO2 nanotubes is intensified with increasing of electrophoretic deposition time. The self-organized nanotubes are expected to be a good precursor system for the osseointegration of dental implants.
6:00 PM - Y3.23
Morphology and Crystallization Control During Nonaqueous Synthesis of Crystalline Cuprous Oxide Nanocubes.
Dorota Koziej 1 , Markus Niederberger 1 Show Abstract
1 Department of Materials, ETH Zürich, Zürich Switzerland
Nonaqueous solution routes to metal oxide nanoparticles offer a beneficial alternative to the aqueous approach. So far, metal oxides containing cations that are sensitive towards reduction to the respective metals by alcohols (such as copper or lead) were believed to be not accessible by the benzyl alcohol route. In contrast to this, we report on the synthesis of highly crystalline Cu2O nanocubes by reacting copper (II) alkoxide in a mixture of aromatic ketone and alcohol. Time evolution XRD, FTIR, SEM and HR-TEM measurements show that the resulting cubes form via a stepwise process. At first, amorphous, few μm long and 200 nm thick fiber bundles are formed. In the course of the reaction they continuously transform to single phase almost perfectly cube shaped Cu2O nanoparticles. The FTIR measurements shows a correlation between a broad band at 450 cm-1 attributed to the Cu(II)-O and a band at 620 cm-1 of Cu(I)-O band of Cu2O. The assignment of the Cu(II)-O to a certain compound is ambiguous. However, we could exclude CuO, Cu(OH)2, as well as the precursor. Thus, this band has to belong to Cu(II)-O vibration of the amorphous intermediate compound. Decrease of this band with increasing of the Cu(I)-O band points to the reduction of the Cu(II) to Cu(I) during the re-crystallization step. It is worth to note that if the reaction is run only in alcohol besides Cu2O, also CuO is formed. The variation of the reaction time gives a hint about the nanoparticles crystallization mechanism. If the reaction is stopped early enough, cupric oxide is crystallizing out of minute amount of precursor. SEM measurements show the as prepared CuO particles embedded in the amorphous matrix. Afterwards the amorphous matrix is transformed into the amorphous fiber bundles; and only then, the crystalline Cu2O cubes are formed. It turns out that the fiber formation is a prerequisite condition for obtaining Cu2O nanocubes. Interestingly, the transformation rate from the intermediate phase to Cu2O depends on the alcohol concentration in the reaction mixture. In the absence of alcohol the precursor reacts with ketone to produce amorphous fiber bundles. Almost at the same time the nucleation of 5 nm small Cu2O cubes takes place. In the consecutive process, the amorphous fiber bundles are instantly dissolved in ketone, and delivering the monomers for the ripening of the Cu2O cubes. However, their size distribution even after 24 hours is much broader (3-200 nm) than from the reaction in the mixed solvents (30-40 nm). Obviously, the alcohol influences not only the nucleation but also the growth of nanocubes. The results clearly prove that the nonaqueous approach involving alcohols can be extended to Cu2O. Furthermore, changing the mixture of organic solvent gives the possibility to control the morphology and the kinetics of a dissolution and re-crystallization of nanoparticles.  M. Niederberger, G. Garnweitner, Chem. Eur. J. 2006, 12, 7282-7302
6:00 PM - Y3.24
Preferred Orientations of electrodeposited Nanorod Metals
Insoo Kim 1 , Bobomurod Hamrakulov 1 , Byung Hyun Park 2 Show Abstract
1 advanced materials and science, kumoh national institute of technology, Gumi, Gyung Buk Korea (the Republic of), 2 , Smart Applications Co. LTD, Cheonan, Chungnam Korea (the Republic of)
Anodic aluminum oxide (AAO) was used as a template to prepare highly ordered Ni metal nanowire arrays. This AAO template was fabricated with two-step anodizing method, using dissimilar solutions. The metal nanowire was prepared in this porous anodic aluminum oxide templates from Watt solution and additives by a DC electrodeposition.The diameters of metals were about 40~80 nm and the lengths were about 20 um with the aspect ratio of about 25-50. The ordered metal nanowire arrays were characterized by X-ray diffractometer(XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Vibrating Sample Magnetometer (VSM). The ordered metal nanowire had different preferred orientation (or texture) with the electrodeposition conditions. In addition, the ordered metal nanowire showed different magnetization properties with the electrodeposition conditions and preferred orientations.
6:00 PM - Y3.25
Nano Structured Carbon Materials with Spheres, Hollow Spheres and Layered Structures
Ji-Eun Park 1 , Ekaterina Grayfer 1 , Yeongri Jung 1 , Jung Hoon Hong 1 , Sung-Jin Kim 1 Show Abstract
1 Department of Chemistry.Nano Science, Ewha Womans University, Seoul Korea (the Republic of)
A new methodology for the synthesis of luminescent graphene oxide spheres via low temperature soft chemical route including generation of carbonaceous precursors by the condensation of glucose molecules at 180 °C was developed. Carbon balls and hollow carbon spheres were produced and their luminescent properties were studied. First, carbon balls were synthesized by hydrothermal method from glucose precursor at temperature of 170 0C using varying glucose concentration and reaction time. It was found that low glucose content (0.5M) lead to large amorphous carbon particles growing with prolonged reaction times to reach the size of 50-1000 nm, while high glucose concentration (2.5M) produced carbon balls of two sizes – 200 nm amorphous particles and 5-10 nm crystalline particles. The materials were investigated by means of TEM, SAED, XRD, IR, Raman and PL-spectroscopy. IR spectra revealed the presence of oxygen functional groups on the surface (hydroxyl, carbonyl, carboxyl groups). The PL studies have shown that carbon balls exhibited weak luminescent properties. Second, hollow graphene oxide spheres were prepared by a new approach using silica coated magnetite-template in size controllable route. The synthetic methodology combined with Kirkendall process of miniaturized Bunsen Cell allowed to obtain 25 nm graphene oxide hollow spheres. Studies on graphene oxide hollow spheres by TEM, Raman, and PL spectroscopy have revealed that the resulting materials consist of semiconducting graphene oxides. They displayed very strong luminescent properties. In our presentation we will discuss about the origin of luminescence of there nano structured materials base on solid-state MAS (magic angle spinning) 13C/29Si NMR spectroscopy.
6:00 PM - Y3.26
PbSe/PbS Binary Nanocrystal Superlattice for Infrared Photodetectors.
Don-Hyung Ha 1 , Christopher Murray 1 2 Show Abstract
1 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Due to the solution processibility of nanocrystals, photodetectors based on nanocrystals provide a low cost, easily processed opportunity for photodetection on flexible substrates. Another strong motivation for developing nanocrystal photodetectors is the potential to selectively tune the wavelength of the photodetectors by varying the size of the nanocrystals. Especially for the near-infrared (NIR) region, PbS and PbSe nanocrystals are good candidates since their absorption fall between wavelengths of 900-1500nm and 1400-2500nm, respectively, covering a wide range of the IR region. Binary nanocrystal superlattice is adopted for detection by a wide wavelength range on a single chip. This presentation reports the synthesis, structural characterization, and the self assembly of binary superlattices as well as photocurrent measurements. For binary nanocrystal superlattices, a large area of a few μm was obtained by assembly of 5nm PbS and 11nm PbSe nanocrystals. The binary superlattice is cuboctahedral AB13 type (A=PbSe nanocrystal, B=PbS nanocrystal ), confirmed by TEM and XRD. We compare the photocurrent of single component with that of binary superlattice. Photocurrent and normalized detectivity are measured from the binary nanocrystal superlattice photodiode under the illumination of NIR light by the wavelength range of 800 to 2500 nm and under dark conditions.
6:00 PM - Y3.27
Solvothermal Transformation of Biphasic Cu2S-CuInS2 Nanoparticles to Monophasic CuInS2 Nanorods.
Stephen Connor 1 , Ching-Mei Hsu 2 , Ben Weil 2 , Yi Cui 2 Show Abstract
1 Chemistry, Stanford University, Stanford, California, United States, 2 Materials Science and Engineering, Stanford University, Stanford, California, United States
Ternary I-III-VI2 semiconductors have garnered great interest due to their promise for photovoltaic applications. The I-III-VI2 class of materials has myriad benefits, including large absorption coefficients, good stability under solar radiation, and a tunable Fermi energy upon the addition of dopants. Recently, colloidal nanocrystals of these solar absorber materials have attracted much attention. Nanocrystal syntheses can utilize lower processing temperatures than bulk synthesis methods, and device fabrication with nanocrystals can benefit from roll to roll processing and solution-phase processing such as printing. In addition, chemically synthesized nanostructures can generally provide well-defined domains for understanding complex phase behaviors such as vacancy ordering and Cu(I) ion diffusion, which are particularly important in I-III-VI2 semiconductors. To better understand and control this materials system, we have synthesized wurtzite CuInS2 nanorods and Cu2S-CuInS2 nanoparticles by a low temperature, solution-phase growth. We observe the chemical transformation of biphasic Cu2S-CuInS2 heterostructured nanocrystals into monophasic CuInS2 during growth. This transformation is facile for two reasons. The sharing of the sulfur sub-lattice by the hexagonal chalcocite Cu2S and wurtzite CuInS2 makes the lattice distortion small. Also, Cu2S is possibly in a superionic conducting state at the growth temperature of 250○C wherein the copper ions move fluidly. Our results provide valuable insight into the controlled solution growth of ternary chalcogenide nanoparticles and will aid in the development of solar cells using ternary I-III-VI2 semiconductors.
6:00 PM - Y3.28
Nanotubular J-Aggregates as Organic Templates for Silver Nanostructures.
Doerthe Eisele 1 , Anna Burmistrova 1 , Hans v.Berlepsch 2 , Christoph Boettcher 2 , Constans Weber 1 , Stefan Kirstein 1 , Keith Stevenson 3 , David Vanden Bout 3 , Juergen Rabe 1 Show Abstract
1 Department of Physics, Humboldt University Berlin, Berlin Germany, 2 Research Centre for Electron Microscopy, Free University Berlin, Berlin Germany, 3 Department of Biochemistry and Chemistry, University of Texas at Austin, Austin/TX, Texas, United States
Organic/inorganic quasi one-dimensional nanocomposites can be made by a number of synthetic routes. Template driven schemes offer a specific approach to control the size and shape of the desired synthetic product given by the template’s size and shape. In contrast to other established methods, the self-assembly based approach presented here has two key features, which allow the controlled bottom-up assembly of complex nanostructured materials: First, the nanoscopic template self-assembles in solution allowing both, directed assembly and facile isolation of nanostructures.Second, the template functions as localized chemical reducing agent, thus the template itself acts as precursor. This aspect reduces the common mass transport issues.We used J-aggregates from an amphiphilic cyanine dye as a nanotubular template for silver nanostructure growth. The dye molecules self-assemble in polar solvents into weakly coupled double-walled nanotubules with an outer diameter of 13 nm and lengths up to several microns. We show that Ag+ can be reduced into various Ag nanostructures by oxidizing the tubular J aggregates. The Ag nanostructures grow directly on the tubules, and under certain conditions also inside the tubules. The nanostructures within the tubules are polycrystalline and were observed only after illumination with visible light. The template can be removed from the nanostructures by rinsing the solution with appropriate solvents.
6:00 PM - Y3.29
Surface Energy-Controlled in-Plane Growth of t-Se Nanowires Transformed from a-Se Colloids and Array NWs in Polymer Thin Films
Sungwook Ko 1 , Geon Dae Moon 1 , Unyong Jeong 1 Show Abstract
1 , Yonsei Uni., Seoul Korea (the Republic of)
One-dimensional nanostructures have been the subject of intensive researches due to their potential uses as active components or interconnects in fabricating nanoscale electronic or electromechanical devices. In-situ parallel growth of NWs on the surface of solid substrates may be advantageous over handling the pre-made NWs due to its simpler process. This presentation suggests in-situ parallel growth of NWs on the surface of solid substrates and a novel approach to fabricate arrayed NWs on the pretreated PDMS pattern in polymer thin film. The in-plane growth of the nanowires along the substrates made possible the creation of a chemically interconnected nanowire network. The t-Se nanowire can be further converted to a variety of other chalcogenide semiconductor nanowires with high carrier mobility. Since the process is solution-based and the production scale is readily enlarged, we expect the approach may find immediate industrial applications.
6:00 PM - Y3.32
Ordered Nano-scale Size Structures on Surface of Doped Oxides after Plasma Treatment.
Nicolay Kulagin 1 Show Abstract
1 Physics, Kharkov National University for Radio electronics, Kharkov Ukraine
Results of the experimental and theoretical study of electronic and crystalligraphic structure and spectral properties of micro- and nano-scale sized crystals and clusters on surface of separate oxides, such as sapphire, garnets and perovskite doped with iron and lanthan groups elements before and after plasma treatment are presented this report. Change of the crystallographic structure, optical and luminescence spectra, ESR, and X ray spectra of the samples was studied after hydrogen and helium middle temperature plasma treatment. The main pecularities of the appearence of the self-ordering nano-scale structures on the oxide surface were investigated, too. The main rules of design of micro- and nano-scale sized self-organization structures on surface of the oxides are proposed as basis of high effective luminescence materials, novel laser materials and ECD elements.
6:00 PM - Y3.4
Synthesis of the TiO2 Multi-branched Nanostructure under Electron Beam Irradiation for Dye-sensitized Solar Cells.
Jang Yong-oon 1 , Jeong Yong Lee 1 , Jung Ho Jin 1 , Hyunjung Shin 2 , Changdeuck Bae 2 , Youngjin Yoon 2 , Hyunchul Kim 2 , Byung Cheol Lee 3 , Young Hwan Han 3 , Ji Hyun Park 3 Show Abstract
1 , KAIST, Daejeon Korea (the Republic of), 2 , Kook-min university, Seoul Korea (the Republic of), 3 , Korea Atomic Energy Research Institute (KAERI), Deajeon Korea (the Republic of)
Microstructural research has been much studied about dye-sensitized solar cells (DSSC) due to its high theoretical solar-to-electrical conversion efficiency (about 33%) and low manufacturing cost. Especially, the nano-crystal material and the dye directly related to the electron transportation and the electron – hole generation in DSSC have been main research subjects. Recently, TiO2 which is the nano-crystal material for DSSC has been studied in the microstructural aspect to increase the conversion efficiency, such as making variable architecture for increasing the dye absorption contents, coating the TiO2 nano-tube with the quantum dots which have higher band gap materials than this, etc. Herein, we proceed with making new TiO2 nano-structure using electron beam irradiationThe metal alkoxide composed of the 1 mol of titanium iso-propoxide [Ti(OiPr)4] and the 1 mol of acetylaceton reacted with water in propylene glycol methyl ether acetate (PGMEA) solvent. After this process which made the bonding among Ti, O and other organics, the polymer solution was deposited on a  silicon substrate and a TEM copper mesh grid. The electron beam irradiation was progressed with the linear electron accelerator facility in Korea Atomic Energy Research Institute, and the shape, microstructure and chemical composition of the irradiated polymers were characterized using TEM, XRD, SEM and EDX. At the same irradiation condition, the solution on silicon did not generate specific structure due to smooth surface of the substrate. It meant that nucleation site which was needed to make branch was insufficient and that site was a point that surface energy was high. The phase of TiO2 branch and cluster changed from amorphous to crystal as irradiation time was increased.
6:00 PM - Y3.5
Fabrication and Characterization of CdSe/ZnS/CdSe/ZnS Quantum Dot Quantum Well Structures.
Soon Il Jung 1 , Joo In Lee 1 , Il Ki Han 2 Show Abstract
1 Advanced Industrial Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon Korea (the Republic of), 2 Nano Devices Research Center, Korea Institute of Science and Technology (KIST), Seoul Korea (the Republic of)
We investigated the effects of different growth conditions and surface passivation on the growth of CdSe QDs. Moreover, we studied the formation and optical properties of CdSe/ZnS/CdSe/ZnS quantum dot quantum well (QDQW) heterostructures. The synthesis of CdSe QDs by pyrolysis of organometallic reagents was performed by using the hot-matrix method. In addition, synthesized CdSe QDs were studied to evaluate the structural and optical properties using atomic force microscope, UV-absorption, and photoluminescence (PL) measurement.In this QDQW system, the narrow band-gap CdSe QDs acts as a well and wide band-gap ZnS QDs acts as a barrier. The intensity of the luminescence of CdSe/ZnS/CdSe/ZnS QDQW structure was almost two orders of magnitude higher than that of the CdSe/ZnS core/shell structure. This result implies that the ZnS barrier system improves the charge confinement in the well. At the same time ZnS passivation resulted in an enhancement of the emission due to a decrease of surface trap emissions such as vacancies, local lattice mismatches, or dangling bonds at the surface.
6:00 PM - Y3.7
Oxide Nanocrystals Modeling: Combined HRTEM and ab initio Calculation Approach.
Daniel Stroppa 1 , Luciano Montoro 1 , Armando Beltran 3 , Tiago Conti 2 , Rafael Silva 2 , Juan Andres 3 , Edson Leite 2 , Antonio Ramirez 1 Show Abstract
1 LME, LNLS, Campinas, SP, Brazil, 3 , Universitat Jaume I, Castelló Spain, 2 LIEC, UFSCar, São Carlos, SP, Brazil
Nanocrystals modeling turns into a unique tool given that the development of reliable nanostructured devices is dependent of the ability of synthesize and characterize materials at the atomic scale. Among the most significant challenges on nanostructures characterization is the accurate evaluation of crystal growth mechanism and its dependence with nanoparticles shape and doping elements distribution. This work presents a new approach for nanocrystals modeling by the combined application of HRTEM characterization, image simulation and ab initio calculation on surface energy distribution and further correlation by Wulff shape theorem. In addition to the technological interest for optoelectronic devices, such as transparent conductive oxide (TCO) application, Sb:SnO2 (ATO) nanocrystals obtained by a nonaqueous route were chosen as model materials for the proposed methodology due to inapplicability of the most common dopants localization techniques given the nanoscrystals dimension and the atomic number similarity between Sn and Sb. Our results showed that the Wulff construction can not only describe ATO nanocrystals shape as function of surface energy distribution but also retrieve dopants localization information by the dimensional analysis of nanoparticles shape and provide the oriented attachment growth mechanism evaluation by a three-dimensional nanocrystals modeling. The  and  directions were identified as preferential oriented attachment directions and Sb enrichment was identified on  and  nanocrystals facets. Obtained results illustrated the potential of HRTEM characterization and ab initio calculations combined use for describing the oriented attachment growth mechanism and identifying dopants segregation on nanostructured particles.
6:00 PM - Y3.9
A General Strategy for High Surface Area Mesoporous Nanocrystalline Nonoxide Spheres by Aerosol Process.
Qiangfeng Xiao 1 , Hiesang Sohn 1 , Yunfeng Lu 1 2 Show Abstract
1 , ucla, Los Angeles, California, United States, 2 , Tulane university, New Orleans, Louisiana, United States
The study on mesoporous materials has been expanding during the past decade. Based on the interaction between organic–inorganic species, several synthesis pathways, such as direct surfactant–inorganic interaction (S+I–, S–I+, S0I0), mediated interaction (S+X–I+, S–X+I–), have been intensively implemented to prepare for mesoporous materials. However they are limited by the need for fabrication of mesoporous nonoxides such as metals, metal alloys, semiconductors. Here we propose an alternative simple and versatile strategy that integrates aerosol process and liquid phase nanotechnology. In the spherical aerosol reactor, the process involves rapid solvent evaporation into concentrated precursors followed by the formation of nanoparticles at high temperature which later agglomerate to create mesoporous spheres. The success of the strategy depends on appropriate precursor activity and ligand binding capability. Its versatility is demonstrated by the fabrication of mesoporous metals (Ni, Pt), metal alloys (NixPt1-x), and semiconductors CdS, CdSe, CdTe,Bi2Te3.The above prepared materials coupled with magnetic, electronic, thermoelectric, luminescence properties and high internal surface area promise new types of multifunctional nanomaterials with the potential applications in catalysts, drug delivery, sensors, hydrogen storage, supercapacitors, thermoelectric etc.
Yadong Yin University of California-Riverside
Yugang Sun Argonne National Laboratory
Dmitri Talapin University of Chicago
Hong Yang University of Rochester
Y4: Complex Structures by Assembly I
Wednesday AM, April 15, 2009
Room 3006 (Moscone West)
9:30 AM - **Y4.1
Synthesis and Self-Assembly of Silver Nanocrystals.
Younan Xia 1 Show Abstract
1 Biomedical Engineering, Washington University, St. Louis, Missouri, United States
Firstly, I will discuss the synthesis and self-assembly of silver nanocubes into specific structures by modifying their side faces with hydrophobic or hydrophilic monolayers. In terms of monodispersity and availability, silver nanocubes are unrivaled as a new class of building blocks for self-assembly. The cube itself has a non-spherical shape and the anisotropy attribute of this system can be enhanced by selectively functionalizing the specific faces of a cube with an alkanethiolate monolayer. This surface functionalization gives the silver nanocubes directionality with respect to their interactions. The resultant assemblies have been found to have structures and shapes that can be pre-designed by functionalizing the six faces of a cube with hydrophobic and hydrophilic monolayers in different schemes. The second part of my talk will be focused on the synthesis and self-assembly of silver nanospheres into dimers in a solution phase to generate well-controlled hot spots for surface-enhanced Raman scattering
10:00 AM - **Y4.2
Anisotropic Shortening and Overgrowth of Gold Nanorods and Their Assembly
Jianfang Wang 1 Show Abstract
1 Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China
Methods have been developed for tailoring the plasmonic properties of gold nanorods, including the longitudinal surface plasmon resonance wavelength (LSPRW), absorption and scattering cross sections. Specifically, anisotropic oxidation has been developed for gradually shortening Au nanorods (J. Am. Chem. Soc. 2006, 128, 5352). During the shortening process, the nanorod diameter remains unchanged while the nanorod length becomes smaller. Transverse overgrowth has been realized by selectively bonding small thiol molecules to the ends of Au nanorods (J. Am. Chem. Soc. 2007, 129, 6402). The presence of thiol molecules at the ends of Au nanorods blocks the overgrowth along the length direction, resulting in the preferential growth on the side faces of Au nanorods. As a result, the nanorod length remains unchanged and the nanorod diameter gradually increases as more Au precursor is added. A combination of these two methods allows for the growth of Au nanorods with desired scattering and absorption cross sections (ACS Nano 2008, 2, 677). Finite-difference time-domain (FDTD) calculations further show that the ratio of scattering to extinction cross sections increases linearly as a function of the diameter for nanorods with a fixed aspect ratio. Au nanorods with tunable scattering and absorption cross sections will be highly desired for biotechnological applications, where absorption-dominant nanorods will be beneficial for photothermal therapy and scattering-dominant nanorods will be advantageous for scattering-based bio-imaging.Organic dyes have been adsorbed on Au nanorods to make free-standing hybrid nanostructures and the coupling between molecular and plasmonic resonances has been investigated (J. Am. Chem. Soc. 2008, 130, 6692). The coupling strength can be tuned by using nanorods with LSPRWs ranging from 570 to 870 nm. The maximum coupling-induced plasmon shift is observed to be up to 140 nm. The plasmon shift is found to decay rapidly with increasing spacing between the dye and nanorod.We have demonstrated the assembly of Au nanorods in either end-to-end or side-by-side fashions by bonding thiol molecules to Au nanorods (Chem. Commun. 2007, 1816; Small 2008, 4, 1287). The assembly and disassembly can be reversibly controlled. FDTD calculations have been performed on assembled Au nanorods at varying gap distances to obtain the dependence of the plasmonic shift on the gap distance. The calculated relationship has been employed to estimate the gap distances between assembled Au nanorods. We have further demonstrated the formation of large-area, 3D ordered assemblies of Au nanorods by droplet evaporation (Angew. Chem. Int. Ed. 2008, accepted). The reversibly controlled assembly and disassembly of Au nanorods will be useful in bio-sensing and bio-imaging and the formation of large-scale ordered assemblies of Au nanorods will have potential for optical applications.
10:45 AM - Y4.4
Divalent Metal Nanoparticles
Francesco Stellacci 1 , Jin Young Kim 1 Show Abstract
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
It is know that specific molecules can spontaneously arrange on various surfaces forming two-dimensional poly-crystalline mono-molecular layers called self-assembled monolayers (SAMs). These organic coatings are used to impart targeted optical, electronic and biological properties to surfaces. Very often SAMs composed of more than one type of molecule (mixed-SAMs) are used to simultaneously impart multiple properties. Scanning tunneling microscopy (STM) studies have shown that, in mixed SAMs, molecules phase-separate in domains of random shape and size. We will show that when mixed SAMs are formed on surfaces with a radius of curvature smaller than 20 nm they spontaneously phase-separate in highly ordered phases of unprecedented size. The reason for this supramolecular phenomenon is also topological and can be rationalized through the “hairy ball theorem”. In the specific case of mixed SAMs formed on the surface of gold nanoparticles, the molecular ligands separate into approx. 0.6 nm wide phases of alternating composition that encircle or spiral around the particle metallic core. The result is the formation of nanoparticles with two point defects in diametrically opposed positons that can be selectively functionalized. The resulting particles can be used to assemble chains and other newer forms of nanoparticles assemblies.
11:30 AM - **Y4.5
Quantum Dots for Photovoltaics and Bioapplications
Horst Weller 1 2 Show Abstract
1 , Center of Applied Nanotechnology, Hamburg Germany, 2 , University of Hamburg, Hamburg Germany
This talk describes recent developments in the synthesis and characterization of semiconductor nanoparticles (quantum dots) including size, shape and surface control. We will present results on the standardized fabrication using a preparative flow system, which allows an outstanding reproducibility of the samples. We report on the non-covalent attachment of quantum dots to carbon nanotubes and shape transformations induced by the attachment. Preliminary studies show interesting perspectives using these nanocomposites for photovoltaic applications.We discuss the use of nanoparticles for biological and medical applications which includes a robust coating with biocompatible polymers and embedding nanoparticles in polymer vesicles. We also present experiments on the toxicity of nanoparticles using advanced optical microscopy for in-vitro cell culture studies. Examples on the improvement of magnetic resonance imaging using tailored superparamagnetic nanoparticles are given.
12:00 PM - **Y4.6
Self-assembled Hybrid Nanofibers Confer a Supramolecular Magnetorheological Material.
Zhimou Yang 1 , Bei Zhang 1 , Jinhao Gao 1 , Xixiang Zhang 1 , Bing Xu 1 2 Show Abstract
1 Chemistry, Brandeis University, Waltham, Massachusetts, United States, 2 Chemistry, The Hong Kong University of Science and Technology, Hong Kong China
Most magnetorheological materials, composed of magnetic microparticles in a liquid, require significant amounts of magnetic particles and a large magnetic field to achieve the desired effects. Here, we report on a new type of magnetorheological materials consisting of small amounts of magnetic nanoparticles (0.8 wt%) but exhibiting large rheological change (i.e., a gel-sol transition) upon the application of a small magnetic field. We use self-assembly to create hybrid nanofibers, which consist of supramolecular hydrogelators and magnetic nanoparticles, as the matrices of the hydrogel. Localized in the nanofibers at a distance of 1-2 nm, the magnetic nanoparticles occupy a small volume fraction of the hydrogel, significantly enhancing the magnetic dipole interactions between them, which results in the large magnetoresponse. This strategy generates a hierarchical nanostructure and eliminates several drawbacks of the simple mixture of polymers with nanoparticles, and thus provides a new methodology that uses magnetic force to control the nanostructures and properties of soft materials.
12:30 PM - Y4.7
Self-Assembly of Magnetically Hard-Soft FePt Nanochains inside 1-D channels of Mesoporous Silica.
Van Le 1 , Sarah Tolbert 1 Show Abstract
1 , UCLA, Los Angeles, California, United States
Hierarchical organization of magnetic nanocrystals is a powerful method for tuning magnetic interactions. In this work, hard (ferromagnetic) and soft (superparamagnetic) FePt nanocrystals are stacked inside 1-D arrays of a mesoporous silica host matrix in order to induce constructive dipole coupling between particles to form nanochain superstructures. By imparting the host anisotropy upon these particle chains, we can tune the magnetic properties of the stacked particles. Through SQUID magnetometry, we show that the hard nanocrystal chains have higher magnetic energy compared to random agglomeration of nanoparticles due to constructive dipole coupling encouraged by the nanoscale geometry. Furthermore, we show that by creating a stack of mixed hard and soft nanocrystal inside the chain, we gain the highest magnetic energy of all. By examining the magnetic properties of both pure and mixed hard and soft FePt nanostacks, we can determine how the magnetization reversal barrier can be enhanced through both enthalpic and entropic components as a function of magnetic stack composition. In addition, we can create fused yet single nanorods by simple insitu annealing inside the pores.We are able to show that unfused particle stacks follow a well-known fanning mode magnetization reversal while the nanorods show a coherent reversal mode during spin flipping.
Y6: Poster Session
Thursday AM, April 16, 2009
Salon Level (Marriott)
9:00 PM - Y6.1
Hollow, Solid, and Amorphous Nickel Phosphide Nanoparticles.
Junwei Wang 1 , Aaron Johnson-Peck 1 , Joseph Tracy 1 Show Abstract
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Nickel phosphide (Ni2P) is an n-type semiconductor with a bulk band gap of 1.0 eV. Ni2P nanoparticles (NPs) have potential applications in photoelectrochemical solar cells and catalysis. Recently, trioctylphosphine (TOP) has been used as a phosphorus precursor for the solution-phase preparation of Ni2P NPs. Both hollow and solid Ni2P NPs have been reported, but the conditions that determine whether the Ni2P core is hollow, solid, or amorphous remain substantially unexplored. Here, we report control over the formation of Ni2P NPs with crystalline-hollow, amorphous-solid, and crystalline-solid structures by adjusting the P:Ni ratio of the reactants and exploring different temperature ramp sequences. For low P:Ni ratios, crystalline-solid Ni NPs formed at 220-240 oC are converted into crystalline-hollow Ni2P NPs via the Kinkendall effect. Increasing the P:Ni ratio initially causes a decrease in the total NP diameter while maintaining hollow cores, but for higher P:Ni ratios, amorphous-solid Ni2P NPs form at 240 oC. Upon heating to 300 oC, the amorphous cores become crystalline and remain solid, as verified by HRTEM and electron diffraction measurements. These results suggest a possible general principle for controlling the structures of phosphide, oxide, sulfide, and selenide NPs amenable to the Kirkendall effect: Adjusting the precursor ratio can modify the nucleation and growth behaviors, thus enabling the formation of different kinds of NP structures.
9:00 PM - Y6.10
Self-Organized Regular Arrays of Anodic Valve Metal Oxide Nanotubes.
Yeonmi Shin 1 , Seonghoon Lee 1 Show Abstract
1 Chemistry, Seoul National University, Seoul Korea (the Republic of)
Al, Hf, Zr, Ta, Nb, Ti and W are classified as valve metals because their oxides have rectifying prorerties. Self-organized regular oxide nanotubes formed by the electrochemical anodization of valve metals have attracted much attention due to their unique geometrical structures (i.e., a narrow pore size distribution and a high aspect ratio), facile fabrication process, economic feasibility, and their versatile potential applications. Particularly, titanium oxide nanotubes (TiO2) has been extensively investigated under appropriate anodizing conditions and has found a wide range of applications (e.g., dielectric mirrors, photocatalysis, biocompatible dental or bone implants, dye-sensitized solar cells (DSSCs), and supercapacitors and hydrogen generator). Zirconium oxide (ZrO2) (for instance, thermal stability, high ionic conductivity, and low electronic conductivity at high temperature) are used as an oxygen sensor or as a solid-electrolyte for fuel cell. Here, we report a simple approach for fabrication of self-organized regular arrays of anodic valve metal oxide nanotubes by a two-step anodization with electropolishing pretreatment of metal. The preparation of an essential flat metal surface was achieved by electropolishing of bare metal foil prior to an anodization. This smooth surface ensures an equivalent electric field distribution on the metal surface during the first anodization, which leads uniform and regular growth of nanotubes in the entire surface. After this flattening process, concaves on the textured metal surface allow the electric field to be focused on their centers, and thus focused electric field leads homogeneous growth of nanotubes through the second anodization. This technique can be easily adapted and extended to prepare regular arrays of self-organized other valve metal oxide nanotubes.
9:00 PM - Y6.11
Assemblies of Nanocrystal Quantum Dots on Single-walled Carbon Nanotubes: Efficient Charge Transfer.
Sohee Jeong 1 , Hyung Cheoul Shim 2 , Soohyun Kim 2 , Chang-Soo Han 1 Show Abstract
1 Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon Korea (the Republic of), 2 Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
The ability to transport extracted carriers from the nanocrystal quantum dots (NQDs) is essential for the development of NQD based photovoltaic applications and optoelectronic sensors. Coupling of NQDs to one-dimensional nanostructures such as single wall carbon nanotubes (SWNTs) or various types of nanowires is expected to produce a composite material which facilitates selective wavelength absorption, charge transfer to 1-D nanostructures, and efficient electron transport. We assembled prepared CdSe (core and core/shell with ZnS) semiconductor nanocrystal quantum dots on single walled carbon nanotubes via non-covalent attachment using pyridine molecule followed by FET formation using dielectrophoresis (DEP), to demonstrate the efficient charge transfer. By monitoring electrical signatures from NQD decorated SWNTs upon photoexcitation, we were able to characterize the charge transfer from photoexcited NQDs to SWNTs.
9:00 PM - Y6.12
Nano -periodic Structures Observed from Novel Hybrid Glasses Generating Large Acoustic Wave.
Kyung Choi 1 , Kenneth Shea 1 Show Abstract
1 , University of California, Irvine, California, United States
A family of Cr/CrOx-doped hybrid glasses has been molecularly designed by inserting alkylene spacers between inorganic oxides then synthesized by sol-gel copolymerization. The morphology of the sol-gel glass reveals substantial regions of dark contrast, highly organized nano-periodic structures in TEM images. We believe that the novel nano-periodic structures observed from the hybrid glass based on hexylene-bridge xerogel are sustained over substantial domains and appears to arise from organically modified glassy lattice fringes. In electron diffraction pattern, it also shows the circled diffraction patterns arise from crystalline Cr metal and a set of diffractions near the center of the beam corresponded to the nano-fringe structures observed in TEM images. From the diffraction pattern corresponded to the nano-fringes, a lattice space of the nano-periodic patterns was calculated about 50 Å from a distance between two diffraction spots in two sets of diffraction patterns. In laser experiments, the hybrid glass shows a new optical property, generation of a huge acoustic wave; the diffraction efficiency (45 %) of the glass is higher than that of methanol (25 %), which means the compressibility of the hybrid glass is as effective as the liquid. When the laser beam goes through a solid media, the density wave is usually linear. The hybrid glass showed a strong ‘acoustic response’, which was as strong as liquid for specific applications, for example, novel diffraction beam modulators.
9:00 PM - Y6.14
Unique Anisotropic Polyhedral Self-Assembly of Carbon Nanotubes and Ag Nanoparticles.
Zhenquan Tan 1 , Hiroya Abe 1 , Makio Naito 1 , Satoshi Ohara 1 Show Abstract
1 , Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka, Japan
We report a unique self-assembling behavior of Ag nanoparticles (NPs) supported CNTs nanocomposites. At first, Ag NPs were precipitated homogeneously on the walls of SDS-coated CNTs by chemical reduction with NaBH4, directly in aqueous solution. Afterward, a certain amount of AgNO3 aqueous solution was dropped into the Ag-CNT dispersion and was reduced by hydroxylamine at a weak alkaline condition. This subsequent treatment resulted in anisotropic polyhedral self-assembly of Ag-CNT nanocomposites. We also attempted to control the morphology of the self-assembly by adjusting the molar ratio of the reactants and the reducing reagent. This unique self-assembly behavior based of CNTs and Ag nanoparticles is really interesting, and never reported previously in our knowledge. The novel self-assembly is expected to some applications in catalyst and photoelectronic materials.
9:00 PM - Y6.15
c-Axis Oriented L10-FePt Nano-rods on TiN Underlayers for High Density Perpendicular Magnetic Recording Media.
Yoshiko Tsuji 1 , Naoya Nishimura 1 , Shinichi Nakamura 2 , Suguru Noda 1 Show Abstract
1 Chemical System Engineering, The University of Tokyo, Tokyo Japan, 2 Center for Instrumental Analysis, Aoyama Gakuin University, Kanagawa Japan
L10-FePt attracts attention for high-density perpendicular recording media due to their high magnetic anisotropy. The easy magnetization axis, which corresponds to the c-axis of the L10-FePt particles, should be aligned perpendicular to the film plane, and particle size and inter-particle spacing should be controlled as well. For practical applications, we have reported that c-axis oriented L10-FePt nanoparticles are formed on (200)-oriented polycrystalline TiN underlayers by conventional sputtering method  and that their nanostructures and magnetic properties are determined by the nanostructures of TiN underlayer such as crystallite size and the degree of (200) orientation . Because recording stability is determined by the volume of each FePt nanoparticle, it is important to increase each crystallite volume with keeping the crystallographic structure and the number density. In this study, two approaches of making FePt nano-rods are introduced. One is to make multi-epitaxial (FePt/TiN)n columns, and the other is to isolate FePt grains of columnar structured FePt thin film by changing its grain boundary into non-magnetic phase. Nanostructures of FePt nano-rods were revealed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of nanostructures on magnetic properties of FePt nano-rods will be discussed. S. Noda, Y. Tsuji, A. Sugiyama, A. Kikitsu, F. Okada, and H. Komiyama, Jpn. J. Appl. Phys. 44 (11), 7957-7961 (2005).  Y. Tsuji, S. Noda, and Y. Yamaguchi, MRS spring meeting, J5.11 (2007).
9:00 PM - Y6.16
Self-organizing Dimer Formation of Silver Nanocubes through Face Selective Functionalization and Surface Plasmon Coupling at Its Fractal Junction
Shuhei Uchida 1 , Nobuyuki Zettsu 1 , Munehisa Mitani 1 , Taro Ichimura 2 , Atsushi Taguchi 3 , Satoshi Kawata 2 3 Show Abstract
1 Research Center for Ultra-precision Science and Technology, Osaka University, Suita, Osaka, Japan, 2 Department of Applied Physics, Osaka University, Osaka Japan, 3 Nanophotonics Laboratory, RIKEN, Saitama Japan
Very recently, a number of research groups have been demonstrated that organized nanostructures could be designed through the stepwise integration of various nanometer-scale building blocks. Theoretical approaches have been utilized for understanding electromagnetic interaction in lithographically organized spherical nanoparticles as nanochains by varying their diameter and interparticles distances, symmetry, and polarization direction. In contrast to such physically fabricated nanoparticles array, the possibility of designing chemically fabricated one-dimensional nanostructures has been limited. We have demonstrated self-organizing dimer formation of the partially hydrophobized Ag nanocubes by face selective functionalization approaches. The procedure for making the homogenous Ag nanocube dimers is easy and straightforward, where contains of three steps as followings: i) preparation of Ag nanocubes monolayer films through controllable fluidic self-assembly. ii) face selective functionalization applying to the upper surface on the Ag nanocubes monolayer with hydrophobic self-assembled monolayer (SAM) by using micro contact printing. iii) spontaneous self-aggregation of Ag nanocube into the dimeric structure driven by hydrophilic-hydrophilic interaction under aqueous environment. Quiet similar approach has been individually demonstrated by Xia group. Pre-functionalized Ag nanocubes with self assembled monolayer of dodecanethiol aggregated into dimers driven by hydrophobic-hydrophobic interparticle interactions to reduce solvation free energy. Both experimental and theoretical studies revealed that the dimers exhibited two plasmon peaks in visible and near infra-red regions where contributed to transverse and longitudinal plasmon resonances, respectively. Furthermore, applying electrodynamic calculation based on FDTD method clearly showed that greater enhancement of local field appeared with the average amplitude of electric field to be 1.0x1015 at the fractal space between the aggregated Ag nanocubes when the dimer was illuminated under longitudinally polarized light. These fascinate optical properties is potentially available for use as a new type of NIR contrast agent for the detection of boil-medical events.
9:00 PM - Y6.17
Temperature-sensitive Microgels with Stable Photoluminescence Based on Covalently Bonded Quantum Dots.
Kang Sun 1 , Weihai Yang 1 , Hongjing Dou 1 , Wanwan Li 1 , Ke Tao 1 Show Abstract
1 , State key lab of metal matrix composites, Shanghai China
The loading of fluorescent quantum dots in environment-sensitive microgels should provide a new generation of fluorescence marker and can be used in wide biomedical fields, such as drug and biomolecules delivery and tracing, or biological assay. This work presents a novel multifunctional system of temperature-responsible microgel loaded with quantum dots covalently. The resultant microgels display stable photoluminescence, which is not obviously corresponding to the precursor microgels, with their thermo-responsibility keeping. In this research, cross-linked hydroxypropyl cellulose-polyacrylic acid (HPC-PAA) microgels which are temperature-sensitive and rich in -COOH were synthesized at first, exhibiting a lower critical solution temperature (LCST) at about 45 °C. Because of the hydrophilic-hydrophobic transformation of HPC, the as-prepared microgels show obvious size change at the LCST, indicating swelling below this temperature and shrinking above it. After that, diethyl carbodiimide (EDC), a commonly used coupling agent for connecting –COOH with –NH2, was used to activate the HPC-PAA microgel, providing the position for further covalent connection with quantum dots. Then, previously prepared CdTe nanocrystals stabilized by cysteamine were mixed with microgel under mild and green conditions. After separating and purification, the resultant microgels were found covalently connected to CdTe nanocrystals from inside to periphery, with bright photoluminescence.Comparing with reported literatures, microgels prepared in current work possess stable fluorescence without influence of LCST, that is, the fluorescent intensity varied with the increment of temperature as same manner as pure CdTe, without any fluorescent quenching or sharp decrease. More importantly, the fluorescence intensity of microgels is reversible. Although the fluorescent intensity gradually decreases with temperature increasing, which is similar to pure quantum dots, when temperature decreases from above LCST back to room temperature, the intensity would increase back to their as-prepared state. Stable photoluminescence combining with temperature-sensitive swelling behavior makes the microgels suitable for some applications which require bright and stable photoluminescence without significant temperature dependence.
9:00 PM - Y6.18
Low-density, Semi-ordered Nanoparticle Arrays as Templates for Single-Molecule Imaging.
Randall Stoltenberg 1 , Jerrod Schwartz 3 4 , Stefan Mannsfeld 2 , Stephen Quake 3 4 , Zhenan Bao 2 Show Abstract
1 Chemistry, Stanford University, Stanford, California, United States, 3 Bioengineering, Stanford University, Stanford, California, United States, 4 , Howard Hughes Medical Institute, Stanford, California, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States
The high-density limit of block copolymer-templated nanoparticle arrays has been well-studied. Such ordered nanoscale features have already been employed in the semiconductor industry to form Si nanocrystals for flash memory and to template insulating layers for back-end interconnects. We report that block copolymers can also be used to template low-density, semi-ordered nanoparticle arrays of varying materials. These arrays have interparticle spacings within the resolution of optical microscopy making them promising platforms for single-molecule fluorescence microscopy.
9:00 PM - Y6.19
The MOD Route to Oxide Nanostructure and Nanocomposite Films. Spectroscopic and Thermal Analysis.
Susagna Ricart 1 , Anna Llordes 1 , Teresa Puig 1 , Xavier Obradors 1 , Marlies Van Bael 2 , An Hardy 2 , Jordi Farjas 3 , Pere Roura 3 Show Abstract
1 ICMAB, CSIC, Bellaterra Spain, 2 Laboratory of Inorganic and Physical Chemistry, Universiteit Hasselt, Diepenbeek Belgium, 3 Grup de Recerca en Materials i Termodinàmica, Universitat de Girona, Girona Spain
Physical and chemical properties of substances can be considerably altered when they are exhibited on a nanoscopic scale, and this phenomenon opens up a completely new perspective for materials design that benefits from the introduction of particle size as a new, powerful parameter. In particular, oxide nanostructures and nanocomposite thin films represent new class of materials which exhibit special mechanical, electronic, magnetic and optical properties due to their size-dependent phenomena. Use of the chemical route for the preparation of oxide nanostructures and nanocomposites is a very effective and low cost approach. In this way, different oxide nanostructures, as BaZrO3, Y2O3, doped-CeO2 and LaO2 have been studied. MOD precursors of some of these phases have been used to grow nanostructures on single crystal substrates by means of self-organized strain induced processes. On the other hand, YBa2Cu3O7 oxide nanocomposites have been grown by using a suspension of oxide nanoparticles in a YBCO solution (ex-situ approach) or by using an in-situ approach from mixed metaloorganic precursors .The different strategies require the proper selection of appropriate inorganic or metaloorganic salts, use of additives, initial chemical analysis and study of the stability of the precursor solutions, and analysis of thermal stability and crystallization process. Understanding of the overall process should lead to determine the mechanisms involved and predict processing conditions. Consequently, we have used in-situ characterization techniques of general validity to analyze the decomposition and crystallization of the oxide nanostructures. The decomposition path has been studied by analyzing the released gaseous products (evolved gas analysis, EGA), and this has been done by coupling thermogravimetric analysis with FTIR spectroscopy (TGA-FTIR) and mass spectroscopy (TGA-MS). These methods have enabled us to continuously examine the reaction products and detect the main part of the volatile compounds obtained in the decomposition step. On the other hand, thermo-analytical techniques coupled with MS have also provided us with a simple and rapid way to extract the crystallization kinetics of the oxide nanostructures starting from MOD precursors. These analysis have enabled us to determine the thermodynamic and kinetic parameters of the crystallization process for each oxide phase , and define the thermal treatments suitable to achieve a particular nanostructure.
9:00 PM - Y6.2
Synthesis of Silver Nanosquares Through Self Assembly of Silver Nanoparticles.
Sonal Padalkar 1 2 , John Hulleman 3 , Seung Min Kim 1 2 , Jean-Cristophe Rochet 3 , Eric Stach 1 2 , Lia Stanciu 1 2 Show Abstract
1 Material Science and Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 3 Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States
A growing interest in nanostructured materials is due their proposed applications in a variety of fields such as catalysis, sensing and as storage devices. Nanocubes and nanosquares are particularly fascinating structures since they can be used not only as storage devices but also for sensing purposes. In the present work, Ag nanosquares have been fabricated in the presence of poly-L-lysine. The Ag nanosquares have pores in the range of ~10-~20nm. The size of the Ag nanosquares was ~200nm. The size of the squares can be successfully altered by varying the process variable. The nanosquares were characterized by UV-Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, electron energy loss spectroscopy and high resolution transmission electron microscopy
9:00 PM - Y6.20
Self-Assembly of Copper Oxalate Nanocrystals Using Additives Raman Spectroscopy of The Coated Nanostructures.
Julien Romann 1 2 , Virginie Chevallier 1 2 , Alexandre Merlen 1 2 , Jean-Christophe Valmalette 1 2 Show Abstract
1 , IM2NP - UMR CNRS 6242, La Garde France, 2 , Université du Sud Toulon Var, La Garde France
A promising “bottom-up” way to design nanostructures by simple experimental methods is being explored through copper oxalate (CuC2O4), a nanocrystalline material featuring particular self-organization properties (1). Copper oxalate µm-sized nanostructures with several shapes (lenses, cushions, drilled cushions, and square rods) have been obtained by aqueous precipitation using additives. The removal of the additives from the nanostructures without damaging their morphology has been successfully achieved through a laser induced photo-bleaching process (2) characterized in situ by Raman spectroscopy.Copper oxalate was precipitated using copper nitrate dihydrate and sodium oxalate aqueous solutions. The precipitation was realized without additive (CuOx-R), with 125 g/L of glycerol (CuOx-G), with 30 g/L of PEG (CuOx-P), and with 10 g/L of HPMC (CuOx-H). Copper oxalate nanostructures were observed by scanning electron microscopy. FTIR and Raman spectroscopy were then performed. Photo-bleaching experiments were carried out using the Raman laser source (514.5 nm) with a 10X objective at a power of 3.2 mW.The nanostructures elaborated without and with each of the three additives show distinctive morphologies. A kinetic study processed during the CuOx-R (cushions) synthesis reveals a four steps self-assembly mechanism of copper oxalate nanocrystals. This mechanism can be applied to all of the studied samples and explains the specific influence of each additive on the final morphologies. It appears that both glycerol and HPMC modify the shape of copper oxalate nanostructures (lenses and square rods respectively) through kinetic effects. The role of PEG is still discussed, but the obtained shape (drilled cushions) seems to reveal a core-shell structure that is confirmed by previous works (3) and by the proposed mechanism.The FTIR spectra show the copper oxalate vibration modes including carboxylate stretching, which is shifted from one sample to another. The presence of adsorbed additives for CuOx-G, -P and -H is confirmed as vibration modes of each additive can be observed.The Raman spectra strongly differ concerning the baseline, which features strong fluorescence interference for the samples with additives. A decrease of the baseline followed by the copper oxalate degradation is observed for all samples during the laser exposition. The baseline decrease is consistent with a photo-bleaching phenomenon where the additives are gradually eliminated from the nanostructures due to the laser exposition. By stopping the laser exposition before the final degradation, nanostructures without adsorbed additives and with preserved morphologies are successfully obtained.(1) N.Jongen, P.Bowen, J.Lemaître, J.-C.Valmalette, H.Hofmann, J. Colloïd Interface Sci. 226, 189-198 (2000)(2) J.F.Kauffman, M.Dellibovi, C.R.Cunningham, J. Pharm. Biomed. Anal. 43, 39-48 (2007)(3) L.C.Soare, P.Bowen, J.Lemaître, H.Hofmann, J. Phys. Chem. B 110, 17763-17771 (2006)
9:00 PM - Y6.21
Synthesis of One-dimensional Titanium Dioxide Nanostructures.
Ben Cottam 1 , Alexander Bismarck 2 , Milo Shaffer 1 Show Abstract
1 Dept of Chemistry, Imperial College London, London United Kingdom, 2 Chemical Engineering, Imperial College London, London United Kingdom
Finely structured titanium dioxide is a technological material of long-standing importance for many applications including pigments and catalysis. There is growing interest in smaller, truly nano-sized titanium dioxide particles with well-defined crystallinity and a range of geometries from spheres to rods and tubes, that are relevant to applications in composites, photovoltaics, sensors, and catalysis. High aspect ratios, in particular, introduce high surface to volume ratios, network forming abilities, and opportunities to control anisotropic properties. Here we report a number of different synthetic strategies for producing high aspect ratio titanium dioxide nanostructures.Ttitanium dioxide is commonly obtained via hydrolysis of metal alkoxides or halides; however, enhanced control over the reaction can be achieved in non-hydrous conditions. A comparison will be made between nanorods synthesised via hydrolytic and non-hydrolytic routes, using different structure directing agents. Typical products are small, single crystal nanorods of anatase (~ 3 × 25 nm), although aging reactions under suitable conditions yield single crystal rutile nanorods (15 x 135 nm). The hydrolytic synthesis can be dramatically accelerated when performed on a microfluidic chip, as compared to a conventional bulk reaction. One powerful alternative strategy is based on high temperature templating reactions on carbon nanotubes; the nanotubes are first converted to titanium carbide and them to titanium oxide (either rutile or anatase as preferred). The diameter and orientation of the resulting titania nanowires reflects the structure of the original carbon nanotube material. By leveraging the versatility of current carbon nanotube synthesis, aligned titania nanowire arrays can be generated with controlled dimensions. Preliminary composite and device application data will be provided.
9:00 PM - Y6.22
How Static is the Nanoparticle Ligand Shell? An Answer Based on 1H NMR NOE Spectroscopy.
Bernd Fritzinger 1 , Richard Capek 2 , Iwan Moreels 2 , Rolf Koole 3 , Jose Martins 1 , Zeger Hens 2 Show Abstract
1 NMR and structural analysis, Ghent University, Gent Belgium, 2 Physics and chemistry of nanostructures, Ghent University, Gent Belgium, 3 Condensed matter and interfaces, Utrecht University, Utrecht Netherlands
Most colloidal nanoparticles sols are stabilized by steric hindrance, where each nanoparticle is covered by a shell of ligands that prevent aggregation. Apart from stabilizing the sol, these ligands play a crucial role during the nanoparticle synthesis and in the formation of functional superstructures based on the controlled assembly of nanoparticles . Fundamental questions regarding their role concern the strength of the ligand-nanoparticle interaction and the adsorption/desorption characteristics of particular ligands .In this contribution, we present two examples to show that solution state 1H NMR NOE spectroscopy – which exploits the transfer of spin polarization between neighboring protons in nanometer sized objects based on the nuclear Overhauser effect – gives a unique view on the dynamics of the ligands in the nanoparticle ligand shell. With dodecyl amine (DDA) capped CdTe nanoparticles, we find that the DDA resonances have all the features of free ligands in a regular NMR study using 1D 1H, DOSY and 1H-13C HSQC. However, in contrast to free DDA, the Q-CdTe|DDA resonances develop strong negative NOEs. From this, we conclude that DDA is a loosely bound ligand, adsorbing and desorbing at a rate of at least 100 s-1. With oleic acid capped CdSe, no evidence of ligand adsorption/desorption is observed, until free oleic acid is added to the Q-CdSe|OA sol. We observe strong, negative NOEs between free oleic acid molecules and we obtain the adsorption/desorption rate constant from the NOE cross peak build up. Depending on the concentration of free OA, values in the range 2-6 s-1 are found. The adsorption/desorption rate is related to the strength of the ligand/nanocrystal interaction. Therefore, these results yield a first basis to compare calculations on this interaction  with experimental data and provide a starting point for the rational functionalization of nanoparticle with specific ligands of choice. Y. Yin, A.P. Alivisatos, Nature 437, 664-670 (2005). I. Moreels, J.C. Martins, Z. Hens, ChemPhysChem 7, 1028-1031 (2006). L. Manna, L.W. Wang, R. Cingolani, A.P. Alivisatos, J. Phys. Chem. B 109, 6183-6192 (2005).
9:00 PM - Y6.23
Selective Assembly of Colloidal Nanoparticles into Nanopatterned Templates by Dip-Coating Process and Its Applications
Il Seo 1 , Chang-Woo Kwon 2 , Hyun Ho Lee 3 , Du Yeol Ryu 4 , Yong-Sang Kim 1 , Ki-Bum Kim 2 , Tae-Sik Yoon 1 Show Abstract
1 Nano Science & Engineering, Myongji University, Yongin, Gyeonggi, Korea (the Republic of), 2 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 3 Chemical Engineering, Myongji University, Yongin, Gyeonggi, Korea (the Republic of), 4 Chemical Engineering, Yonsei University, Seoul Korea (the Republic of)
Selective assembly of various colloidal nanoparticles, such as surfactant stabilized iron oxide (Fe2O3), FePt, CdSe, and Au nanoparticles, on preformed nanopatterns by dip-coating process is investigated. Hexagonally ordered nanopatterns with a size in the range between 30 to 100 nm are prepared by using self-assembled diblock copolymer of polystyrene and poly(methyl methacrylate) (PS-b-PMMA) on Si substrate, and by using nanoporous anodic alumina oxide (AAO) templates. For the selective assembly of particles, the nanopatterned substrates are dipped into colloidal solutions and pulled out with various speeds. The dipping and pulling out substrates are also repeated for completely filling all the patterns. It is experimentally observed that the particles are assembled selectively inside AAO patterns driven by the capillary force upon drying the solvent after pulling out the substrate from the solution. In addition, the particles are successfully integrated selectively inside the diblock copolymer patterns. The number of particles inside the patterns increases by repeating dip-coating. The parameters in dip-coating process affecting the selective assembly into nanopatterns are investigated such as particle concentration and excess surfactant concentration in the solution, dip-coating speed, number of dipping, etc. Finally the properties and applications of selectively assembled nanoparticles in nanopatterns will be discussed, for example, magnetic properties for patterned magnetic media, seeds for carbon nanotube growth, electrical properties for non-volatile memory devices, and so on.
9:00 PM - Y6.24
``Hard enough? We want it harder!” SmCo-based Nanomagnets.
Sheng Peng 1 , Hongwang Zhang 1 , Shouheng Sun 1 Show Abstract
1 Chemistry, Brown University, Providence, Rhode Island, United States
Among all hard magnetic materials, SmCo-based alloy system has attracted very intensive research interests because of its superior properties (large coercivity, high moment and high Curie temperature) and potential applications such as high-performance permanent magnets and high-density data storage media. Due to extreme chemical instability, the fabrication of size and composition controlled SmCo-magnets has remained a great challenge. In our group, we aim to fabricate hard nanomagnets of SmCo for high temperature and high energy applications. Through high-temperature reductive annealing of binary-assembled CoO-Sm2O3 nanoparticles, we have achieved composition control and partial size control in making SmCo-based hard magnets with sub-micron sized magnetic grains. The structure and magnetic property of the resulted SmCo product have been characterized using XRD, VSM and SQUID. We have achieved about 52kOe coercivity of SmCo5 at 5K. We believe SmCo permanent magnet with high energy product will be readily fabricated by warm compaction.
9:00 PM - Y6.25
Modulating the Current of a Nanodevice by a Living Cell: A Biotransistor.
Jennifer Kane 1 , Jason Ong 1 , Ravi Saraf 1 Show Abstract
1 , University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Isolated single nanoparticles and array of nanoparticles act as switching devices sensitive to charging by a single electron. For a typical 5 nm Au particle, the switching barrier energy due to Coulomb blockade from a single electron charging is ~100 meV, making room temperature switching difficult and very noisy. In an array, the switching energy can be a few eV (at cryogenic temperatures), but unlike a single nanoparticle, the energy barrier reduces linearly and vanishes at room temperature. We have developed a “reactive self-assembly” method to make a network of one-dimensional necklaces of nanoparticles that behaves as a single-electron device at room temperature. Furthermore, upon cementing the particles with an inorganic semiconductor, the switching behavior at room temperature is significantly improved. To demonstrate an interesting application of room temperature single-electron switching, we couple the network to a living microorganism to modulate the device current by regulating the cell’s metabolic activity. In the talk we will describe fabrication of the necklace and biotransistor device.
9:00 PM - Y6.27
Multicolored Light-Emitting Diodes Based on All-Quantum Dot Multilayer Films Preapred by the Layer-by-Layer Deposition
Wan Ki Bae 1 2 , Jeonghun Kwak 2 , Jaehoon Lim 1 , Seonghoon Lee 3 , Changhee Lee 2 , Kookheon Char 1 Show Abstract
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 School of Electrical Engineering and Computer Science, Seoul National University, Seoul Korea (the Republic of), 3 School of Chemistry, Seoul National University, Seoul Korea (the Republic of)
The layer-by-layer assembly is one of the most prominent and practical methods to deposit well-defined thin films containing functional nano-objects such as polymers, nanoparticles, nanotubes, or nanosheets onto various substrates. Since the layer-by-layer method mainly relies on specific interaction forces such as electrostatic interactions, hydrogen bonding, and covalent bonds between each layer, it usually provides homogeneity and uniformity of prepared films in large area along with tolerable compatibility with other patterning techniques. In this presentation, we demonstrate QLEDs in large area based on all-QD multilayer films prepared by the layer-by-layer deposition of QDs, showing the device performance with a turn-on voltage of 4.5 V, an external quantum efficiency of 0.3 % with a brightness of 450 cd/m2 at current density of 50 mA/cm2, and the maximum brightness up to 1,000 cd/m2. Multicolored QLEDs were also realized based on the systematic analysis on the exciton recombination zone within all-QD multilayer films and the controlled arrangement of different QDs with different emission in the exciton recombination zone by patterning techniques such as ink-jetting or contact printing.
9:00 PM - Y6.28
Amorphous Indium Gallium Zinc Oxide(a-IGZO) Thin Film Transistors Fabrication using Self-assembled Source/drain Electrodes.
Hyunho Kim 1 , Youngje Cho 2 , Jaegab Lee 1 , Duckkyun Choi 2 Show Abstract
1 School of Advanced Materials Engineering, Kookmin University, Seoul, Seoul /SungBuk-gu, Korea (the Republic of), 2 Division of Materials Science and Engineering, Hanyang university, Seoul, Seoul /SeongDong-Gu, Korea (the Republic of)
a-IGZO was pre-patterned with n-octadecyltrichlorosilane (OTS) molecules by using μ-contact printing methods followed by cobalt deposition using metal oxide chemical vapor deposition(MOCVD) method. As OTS surface was low energy, cobalt was selectively deposited on IGZO surface. The contact angle measurement was carried out to confirm whether OTS was formed. The selective deposition of cobalt electrodes were confirmed by atomic force Microscopy (AFM) and optical image. a-IGZO based TFT was simply fabricated using cobalt electrode as source/drain. a-IGZO films were protected from other contaminants by surrounding OTS. We measured the electrical characteristics before and after annealing without removing OTS. The fabricated a-IZGO TFT showed the mobility 0.34 cm2/Vs and threshold voltage 3.08 V, subthreshold slope 0.27 V/decade, on/off ratio 3.6 x 105.
9:00 PM - Y6.3
Thermoelectric Power and Electronic Transport in Binary Nanocrystal Composite Solids.
Dong-Kyun Ko 1 , Don-Hyung Ha 1 , Christopher Murray 1 2 Show Abstract
1 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
The promise of semiconductor nanostructures, as a technological material, depends critically on doping to tailor their electronic behavior. Especially for thermoelectric applications, precise control over doping is a crucial step in maximizing thermoelectric efficiency of power generation. In this presentation, we study the modular assembly of binary composite nanocrystals, as an effective bottom-up design tool, to create a new family of artificial solids with a prescribed set of doping levels. Silver telluride nanocrystals (Ag2Te), which can act as dopants, are introduced in lead telluride (PbTe) nanocrystal assemblies in order to modify the carrier concentration until an optimum power factor is realized. Using nanocrystals as a fundamental building block, this strategy enables us to design and engineer high-efficiency thermoelectric material system that maximizes thermoelectric power factor and in turn the figure of merit which may exceed the current state-of-the-art bulk counterpart. This presentation reports the synthesis and structural characterization of lead telluride (PbTe) and silver telluride (Ag2Te) nanocrystals as well as electronic and thermoelectric characterization of their binary composite solid. Hall measurement and field effect transistor characteristics were studied in order to identify the carrier type, mobility, and concentration. Temperature dependence of low-bias conductivity was also characterized to gain a better understanding on electronic conduction. Finally, Seebeck voltage was measured with varying PbTe to Ag2Te nanocrystal concentration ratio in order to investigate the Seebeck coefficient as a function of carrier concentration.
9:00 PM - Y6.30
Microwave-Assisted Synthesis of Magnetic, Crystalline, Nickel Nanoparticles via Chemical Transformation of Nickel Salts.
Keith Donegan 1 2 , Joseph Tobin 1 2 , Jeffrey Godsell 2 , Terrence O Donnell 2 , Saibal Roy 2 , Michael Morris 1 3 , David Otway 1 , Justin Holmes 1 3 Show Abstract
1 Chemistry, University College Cork, Cork Ireland, 2 Microsystems Centre, Tyndall , Cork Ireland, 3 CRANN, Trinity College Dublin, Dublin Ireland
Nanostructured materials represent the transition between individual molecules and bulk solids. They present unique and enhanced properties when compared to their bulk material analogues such as catalytic, non-linear optic, semiconductive and magnetic properties. The physical and chemical properties of these nanoparticles are very much dependant on their size and shape. The use of microwave technology for the synthesis of nanomaterials has received growing interest in recent years due to the reduction in manufacturing costs due to energy savings, shorter reaction times and excellent reproducibility with high levels of yields. The principle of microwave heating stems from polar molecules attempting to orientate with the electric field in the microwave frequency range. Thus, polar solvents such as ethylene glycol, alcohols and DMF which have high dielectric losses are therefore ideal solvents for microwave heating. Solvent choice, along with careful control of the metal precursor, the length of time of reaction and the choice of wrapping ligand have led to the synthesis of metal nanoparticles with various morphologies and sizes. Using a novel microwave synthesis, we have prepared faceted nanocrystalline with spherical, trigonal, hexagonal, cubic and diamond morphologies, with various sizes and small size distributions. Nickel nanoparticles, with average diameters of 25, 33 and 40 nm have been produced after hold times of 1, 10 and 60 mins, respectively. The morphologies of the nanoparticles have also shown to be dependant on reaction time with highly facetted, single-crystalline Ni nanoparticles being produced after a reaction time of 10 mins. SQUID measurements on each of these particles, taken from temperatures ranging from 300K down to 5K, indicate that they are ferromagnetic in nature, while the reaction times affects the coercivity and saturation magnetization. The coercivity and saturation magnetization values of all of these samples were shown to decrease with increasing temperatures. The coercivity values have shown to decrease as the particle size decreases as expected. Values of 130 Oe and saturation magnetization values of 47.4 emu g-1 have been observed at room temperature for single-crystalline nickel nanoparticles. The saturation magnetisation has been observed to increase to 51.3 emu g-1 at 5K, while the coercivity decreases to below 100 Oe with decreasing particle size. The particles have been characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX) and UV-visible adsorption spectroscopy. (1)P.J. Reynolds (Ed.), On Cluster and Clustering, Elsevier Science Publisher, Amsterdam, 1993(2)Microwave-Enhanced Chemistry: Fundamentals, Sample Preparation, Applications (Eds.: H.M. Kingston, S.J. Haswell), American Chemical Society, Washington DC, 1997
9:00 PM - Y6.31
Novel Inorganic Nanocomposites Based on Anisotropic Nanostructures Synthesized in Solid State Nanoreactors.
Andre Eliseev 1 , Irina Kolesnik 1 , Kirill Napolsky 1 , Nina Sapoletova 1 , Alexandr Vyacheslavov 1 , Alexey Lukashin 1 , Yuri Tretyakov 1 , Peter Goernert 2 , Natalia Grigorieva 4 , Sergey Grigoriev 3 , Helmut Eckerlebe 5 Show Abstract
1 Dept. of Materials Science, Moscow State University, Moscow Russian Federation, 2 , INNOVENT e.V., Jena Germany, 4 , St-Petersburg Nuclear Physics Institute, Gatchina Russian Federation, 3 Dept. of Physics, St-Petersburg State University, St.-Petersbourg Russian Federation, 5 , GKSS Forschungszentrum, Geesthacht Germany
The preparation of nanostructures with controlled dimensions and properties is one of the most important challenges in materials science today. Nanowires appear to be the most promising nanosystems owing to highest anisotropy factors, which could certainly increase functional properties of nanomaterials. However, the use of nanostructures is restricted because of their low stability. The optimal approach to this problem is the preparation of nanocomposite materials. Thus, the main goal of this work is considered as elaboration of basic principles for preparation of nanoparticles with controlled physical properties in one-dimensional solid state nanoreactors. The study represents the formation of magnetic, semiconductor and catalytic composites based on the metallic (Fe, Ni, Ag, Fe-Co, Fe-Pt alloys) and metal oxide (alfa-Fe2O3, gamma-Fe2O3, Fe3O4, etc.) nanowires in a variety of 1D nanoreactors such as single-wall carbon nanotubes (inner diameter of 1-1.4 nm), zeolites (D=0,5-2 nm), mesoporous silica or aluminosilicates (D=2-20 nm) and anodic alumina (D=20-80 nm). It is shown that particles shape and size are in good agreement with that of the pores, while an average length of nanowires could be varied in a vide range. Thus, our approach leads to functional materials with nanosized active elements, which could find an application in various fields of engineering and technology. This work is supported by RFBR (06-03-33052, 06-03-33136, 04-02-17509) and FASI (203.01.02.001).
9:00 PM - Y6.32
Actinide Epitaxial Thin Films Grown by Polymer-assisted Deposition.
Eve Bauer 1 , Thomas McCleskey 1 , Anthony Burrell 1 , Quanxi Jia 1 , Piyush Shukla 2 Show Abstract
1 Materials Physics Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 New Concepts Team, Milliken, Spartanburg, South Carolina, United States
Many thin film deposition techniques such as chemical vapor deposition (CVD) involve volatile precursors, which poses a safety concern when depositing actinide thin films. We will report here on the use of a water based solution technique known as polymer assisted deposition (PAD) for the formation of epitaxial actinide thin films. We have used this process to make stable, epitaxial uranium films in multiple oxidation states. UO2 films are obtained on a lanthanum aluminum oxide substrate and expitaxial U3O8 films on a single crystal c-plane Al2O3 substrate. The oxidation states of uranium can be “pinned down” simply by matching the substrate lattice to the film crystal lattice. The oxidation state of actinides plays a key role in the chemistry that can occur during the storage of radioactive materials. Studies on the surface chemistry of high quality thin films can provide fundamental information for modeling the complex issues in storage. For instance, the oxidation of UO2 generates a powder-like U3O8, which can cause the splitting of the storage sheath, impacting the safety of long term storage of actinides. PAD can be used to make other films such as nitrides by simply changing the atmosphere under which the films are annealed. Annealing a uranium solution under a mixture of N2/H2 has produced a black, semi-conducting UN2 film. Uranium nitrides are of particular interest because UN is a good candidate for the nuclear fuel of fast breeder reactors and accelerator-driven sub critical reactors. We are also looking at Np oxide and nitride films using this process.
9:00 PM - Y6.33
Spatially-extended Excitons in (ZnSe/CdS)/CdS Heterostructured Nanocrystals.
Mikhail Zamkov 1 , Nishshanka Hewa-Kasakarage 1 , Maria Kirsanova 1 , Alexander Nemchinov 1 , Nickolas Schmall 1 , Patrick El-Khoury 1 Show Abstract
1 , Bowling Green State University, Bowling Green , Ohio, United States
We report on organometallic synthesis of luminescent (ZnSe/CdS)/CdS semiconductor heterostructured nanorods that produce an efficient spatial separation of carriers along the main axis of the structure (type II carrier localization). Nanorods were fabricated using a seeded-type approach by nucleating the growth of 20-100 nm CdS extensions at [000±1] facets of wurtzite ZnSe/CdS core/shell nanocrystals. The difference in growth rates of CdS in each of the two directions ensures that the position of ZnSe/CdS seeds in the final structure is offset from the center of the rod, resulting in a spatially asymmetric distribution of carrier wave functions along a hetero-nanocrystal. Present work demonstrates a number of unique properties of (ZnSe/CdS)/CdS NCs, including enhanced magnitude of quantum confined Stark effect, and subnanosecond switching of absorption energies that can find practical applications in electroabsorption switches and ultrasensitive charge detectors.
9:00 PM - Y6.4
Synthesis of 1D Crystals in the Channels of Single-walled Carbon Nanotubes.
A. Eliseev 1 , M. Chernysheva 1 , N. Verbitskii 1 , A. Lukashin 1 , Yu. Tretyakov 1 , N. Kiselev 2 , O. Zhigalina 2 , A. Kumskov 2 , A. Krestinin 3 , J. Hutchison 4 Show Abstract
1 Department of Material Science, Moscow State University, Moscow Russian Federation, 2 , Institute of Crystallography, Moscow Russian Federation, 3 , Institute of Problems of Chemical Physics, Chernogolovka Russian Federation, 4 Department of Materials, University of Oxford, Oxford United Kingdom
Single-walled carbon nanotubes (SWNTs) nowadays draw close attention of scientific community worldwide due to their unique electronic and structural properties accompanied by extraordinary mechanical behavior depending on the diameter and conformation of tubes. The filling of SWNTs with favourable conductive, optical or magnetic materials impulses the development of novel class of nanotube architectures and nanoscale materials applicable as active elements of electronic devices and circuits. The present study is focused on the controllable growth of nanocrystals in channels of single-walled carbon nanotubes with inner diameter 1-1.4 nm and investigation of their effect on electronic properties of obtained nanostructures. SWNTs were obtained by catalytical arc-discharge method followed by purification and oxidation at 500°C in dry air for 0,5 hour. The filling of SWNTs by Mhaln (M=Ag, Cu, Fe, Co, Ni; Hal = Cl, Br, I) was performed using capillary technique via impregnation of pre-opened nanotubes by molten salts at temperatures 100°C above melting point of corresponding compound in vacuum (0.01 mbar) with subsequent slow crystallization of nanoparticles (up to 0,02°C/min). The synthesis of nanocomposites MHalc@SWNT (M=Cd, Pb, Zn; Halc=S,Se, Te) was carried out by two-step molten media method consisting in treatment of carbon nanotubes with molten MI2 in vacuum (0.01 mbar) and then – by molten halcogene with the proceeding of reaction and the formation of CdS particles (or PbS, respectively).The obtained samples were characterized by HRTEM imaging, EDX analysis, impedance and Raman spectroscopy. HRTEM data showed the formation of 1D nanocrystals in nanotubes channels with clearly defined ordered structure. The Raman spectra of obtained samples proved that the incorporation of compounds directly affect the electronic structure of SWNT resulting in shifts of characteristic RBM- and G-lines.
9:00 PM - Y6.5
Pore Collapse in Nanoporous Palladium and Platinum Induced by Thermal and Hydrogen Treatments.
Markus Ong 1 , Ilke Arslan 1 , Matthew Klein 1 , David Robinson 1 Show Abstract
1 Energy Systems, Sandia National Laboratories, Livermore, California, United States
Nanoporous materials are of interest for hydrogen and energy storage due to their high surface area. Recent work by Robinson, et al. has demonstrated new routes of synthesizing nanoporous palladium and platinum nanoparticles that achieve both high pore density and scalability. This present study assesses the ability of these materials to resist structural modifications such as pore collapse and particle sintering when subjected to extreme thermal or hydrogen environments. Quantitative analysis by porosimetry indicates minimal change in pore size and specific area of these materials when heated in vacuum to 150 °C. However, in hydrogen environments, significant degradation of the morphology of palladium can occur at even at room temperature if the miscibility gap in the Pd-H phase diagram is crossed. Complementary qualitative analysis by transmission electron microscopy show that pore collapse in palladium can occur dramatically on very short time scales around 400 °C during in situ heating. The platinum was not significantly affected by the hydrogen exposures and could be heated as high as 600 °C without significant pore collapse or particle sintering.
9:00 PM - Y6.6
Formation Mechanisms of Zn Nanocrystals in Heterointerfaces Between ZnO Thin Films and n-Si (001) Substrates Due to Thermal Treatment.
Jongmin Yuk 1 , Jeong Yong Lee 1 , Young Su No 2 , Tae Whan Kim 2 , Won Kuk Choi 3 Show Abstract
1 Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 373-1 Guseong-Dong, Yuseong-Gu, Korea (the Republic of), 2 Advanced Semiconductor Research Center, Division of Electronics and Computer Engineering, Hanyang University, Seoul, 17 Haengdang-dong, Korea (the Republic of), 3 Thin Film Material Research Center, Korea Institute of Science and Technology, Seoul, 136-701, Korea (the Republic of)
Nanocomposites containing nanoparticles have attracted significant attentions because of both fundamental physical properties and potential applications in electronic and optoelectronic devices operating with lower currents at higher temperatures . Among these devices, nonvolatile flash memories with nanoscale floating gates containing nanocrystals have been particularly interested since memory devices can be fabricated with low-power and ultrahigh-density elements. The prospects of potential applications of memory devices utilizing nanoparticles have driven extensive efforts to form various kinds of nanoparticles on semiconductor substrates. Recently, inorganic nanocomposites based on three-dimensionally-confined nanocrystals embedded in insulating layers have been extensively investigated for their promising applications in nonvolatile memory devices with nano-floating gates . In this study, the formation of Zn nanocrystals was investigated in heterointerfaces between ZnO thin films and n-Si (001) substrates, which were fabricated by using molecular beam epitaxy. After fabricating the ZnO thin films, thermal annealing was sequentially applied in a nitrogen atmosphere with a tungsten-halogen lamp as the thermal source for 5 min at 900oC. Then, the annealed thin films were observed by transmission electron microscopy (TEM). The bright-field TEM image of the annealed ZnO/Si heterostructures shows that one layer of metallic Zn nanocrystals with an average diameter of 5 nm was formed in the amorphous 10 nm SiO2 layer between the ZnO thin film and the Si substrate. From energy dispersive X-ray spectroscopy (EDS) analysis, Zn, O, and Si were detected together with C in the heterointerface between ZnO film and Si substrate. The metallic Zn nanoparticles were confirmed by high-resolution TEM imaging in comparison with the crystallographic lattice spacings and the angles of metal Zn. In addition, these nanoparticles are individually single crystals. This result indicates that the formation of Zn nanocrystals originates from the diffusion of Si atoms from the Si substrate. Because the SiO2 layer existing between the ZnO thin film and the Si substrate is thermodynamically much more stable than the ZnO layer, the Zn nanocrystals are formed in the SiO2 layer. The possible formation mechanisms of Zn nanocrystals in heterointerfaces between ZnO thin films and n-Si (001) substrates due to thermal treatment can be described on the basis of the TEM, HRTEM, and EDS measurements.AcknowledgementThis work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (No. R0A-2007-000-20044-0).1. N. J. Craig, J. M. Tayler, E. A. Lester, C. M. Marcus, M. P. Hanson, and A. C. Gossard, Science 304, 565 (2004).2. M. Kanoun, A.Souifi, T. Baron, and F. Mazon, Appl. Phys. Lett. 84, 5079 (2004).
9:00 PM - Y6.7
Mesoporous Silica as Templates for Crystalline Palladium and Gold Nanostructures: Synthesis and Catalytic Activity
Ben Estes 1 , Hanging Chen 1 4 , Sami Chanaa 1 , Andrew Lupini 3 , John Larese 1 2 Show Abstract
1 Chemistry, University of Tennessee, Knoxville, Tennessee, United States, 4 College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China, 3 Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge , Tennessee, United States
The use of mesoporous silica spheres as templating agents for crystalline palladium nanoparticles has been studied. Monodispersed, nanocrystalline palladium particles with narrow size distribution of ~2 nm in diameter have been synthesized within the confines of two different mesoporous silica substrates and studied for activity as heterogeneous catalysts. Catalytic reactions to be presented include hydrogen peroxide formation, Heck coupling reactions, and selective hydrogenation. In addition, a novel synthetic route to gold and palladium nanowires is described using SBA-15 as a template. Using the bio-polymer Chitosan as a chelating agent, it was found that a simple thermal treatment could be used to produce nanocrystalline wires of 200 to 500 nm and ~7 nm in diameter within the silica pore channels. Characterization of the materials is performed by high resolution TEM, adsorption/desorption isotherms, FTIR, XPS and SAXS.This work is supported by the Division of Materials Science, Office of Science, Basic Energy Sciences under contract DE-AC05-00OR22725 and the NSF under DMR-0412231.
9:00 PM - Y6.8
Compositional Tuning of ALD deposited Yttrium-stabilized Hafnium Oxide Films to Improve Dielectric Properties.
Qian Tao 1 , Prodyut Majumder 1 , Gregory Jursich 1 , Manish Singh 1 , Christos Takoudis 2 Show Abstract
1 Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois, United States, 2 Departments of Chemical Engineering and Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States
Hafnium oxide (k~20) has been heralded as the new high dielectric constant material for the gate dielectric layer in the future transistors and capacitive memory cells. However, further device scaling necessary for maintaining the Moore’s law would require dielectric materials with even higher permittivity. Interestingly, the cubic and tetragonal polymorphs of hafnium oxide hold promise because of their higher permittivities (k~29 and k~70, respectively) based on theoretical calculations. Typically, these polymorphs are stable only at very high temperatures (T>1750 0C and T>2700 0C, respectively). Recent results have shown that the incorporation of other metal oxides, such as yttrium oxide, into hafnium oxide films may allow a pathway to obtain these high permittivity polymorphs at lower temperatures. This could make hafnium oxide based films a long term solution for the high-k dielectric problem.A detailed structure-property investigation needs to be done for the doped HfO2 thin films in order to understand the stabilization mechanism of the cubic structure and the effect of varying composition on the dielectric properties. Such a study requires a deposition process that is robust and provides strong control of the composition. Compared to pulsed laser deposition, sputtering and chemical vapor deposition, sub-monolayer control of the deposition process makes atomic layer deposition (ALD) the ideal technique for this study and future commercialization of doped-HfO2 films. In this work, Atomic Layer Deposition (ALD) has been used to deposit nano-laminated yttrium-doped hafnium (YDH) oxide films with varying content of yttrium using a new yttrium precursor (tris(ethylcyclopentadienyl) yttrium) and tetrakis(diethylamino) hafnium, with water vapor as the oxidizer. The as-deposited films and films subjected to rapid thermal annealing at 600 0C and 800 0C for 5 min were analyzed. The film composition and changes in crystalline structure were investigated using x-ray photoelectron spectroscopy (XPS) and grazing incidence x-ray diffraction (GIXRD), respectively. YDH films were grown around 25 nm for C-V and I-V measurements to characterize the dielectric behavior. Cross-sectional TEM studies revealed the conformation of the laminated nanostructure. A coconcentration effect was observed in the composites which showed dielectric constant that was higher compared to pure HfO2 or Y2O3 films.
9:00 PM - Y6.9
Polymer-Nanoparticle Composites: Self-Assembly and Improved Functionalities.
Matthias Zorn 1 , Wan Ki Bae 2 , Nawaz Mohammed Tahir 3 , Wolfgang Tremel 3 , Kookheon Char 2 , Rudolf Zentel 1 Show Abstract
1 Institute of Organic Chemistry, University of Mainz, Mainz Germany, 2 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 3 Institute of Inorganic Chemistry, University of Mainz, Mainz Germany
Polymer-nanoparticle composites combine unique functions of inorganic nano-objects with useful properties derived from polymers. Polymers, for example, can provide solubility, processability, stimuli-responsiveness and semiconducting properties to the nanocomposites.We synthesized well-defined block copolymers via RAFT polymerisation containing a soluble block and an anchoring block, which can be covalently jointed through reactive ester chemistry. The soluble block can offer functions such as solubility and processability. If the block copolymers are bound to nanorods of oxidic semiconductors through the anchoring blocks, the nanocomposites thus prepared are soluble in solvents, leading to good dispersion in polymer matrices of the same chemical structure. Due to the anisotropy of rod-shaped particles, liquid crystalline phases can be obtained, demonstrating the clearing temperature as well as recrystallization due to self- assembling nature of such nanorods. We also encapsulated CdSe@ZnS quantum dots with polystyrene (PS) and semiconducting triphenylamine (TPA) polymer brushes. After the surface modification of quantum dots (QDs) with PS brushes, those QDs maintain 80 % of the initial photoluminescence before the surface modification and the surface-modified QDs showed the enhanced stability under UV irradiation. QDs with TPA brushes were also tested for LED devices, showing enhanced device performance (i.e., external quantum efficiency increased three-fold) when compared with unmodified QDs.References: M. Zorn, S.Meuer, Y. Khalavka, M.N. Tahir, C. Sönnichsen, W. Tremel, R. Zentel, J. Mater. Chem., 2008, 18, 3050. M. Zorn, R. Zentel, Macromol. Rapid Commun., 2008, 29, 922.