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07ACS-National Meeting论文Abstract_Inorganic(有Nano的)
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INOR 21 Synthesis and characterization of covalently attached polyethyleneimine functionalized single-wall carbon nanotubes Christopher A. Crouse, Eoghan Dillon, Ramon Colorado Jr., and Andrew R. Barron, Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX 77005, crous1ca@rice.edu The solubility of single-wall carbon nanotubes (SWNTs) in aqueous and organic solvents is a difficult barrier that must be overcome to allow for potential applications in the biomedical and material sciences. Previous work involving the addition of polymers towards the dissolution of SWNTs has focused on the covalent attachment of polymers to the carboxylic acid moieties found at the open ends of SWNTs or the physical adsorption of polymers or surfactants on the sidewalls. In this work the reaction between branched-polyethyleneimine (PEI) and uncut, fluorinated-SWNTs (F-SWNTs) was performed yielding the covalent attachment of the polymer to the sidewalls of the nanotubes. These results were confirmed through solid state NMR, Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy and thermal gravimetric analysis studies. The resulting PEI functionalized SWNTs (PEI-SWNTs) are shown to have an increased solubility in aqueous media of up to 0.4 mg/mL. The synthesis, characterization, and possible biomedical applications of the newly formed PEI-SWNTs will be discussed. INOR 22 Synthesis of aligned single-walled carbon nanotube networks Chris Papadopoulos and Badr Omrane, Department of Electrical and Computer Engineering, University of Victoria, Victoria, BC V8W 3P6, Canada, papadop@uvic.ca With their excellent combination of mechanical, thermal, chemical and electrical properties, single-walled carbon nanotubes (SWNTs) have emerged as one of the most important materials in nanoscale science and technology. However, the controlled synthesis of SWNTs remains a key challenge for their practical implementation. In particular, controlling the type, size, positioning and orientation of nanotubes will be crucial for translating their fundamental properties into useful structures. Here we employ catalytic chemical vapor deposition coupled with precise nanoscale patterning to promote the alignment of lateral SWNT networks grown on silicon wafers. Results of growth trials and characterization of the networks via electron microscopy and scanning probe methods will be presented. The electronic properties and potential applications of the aligned SWNT networks will also be discussed. INOR 23 Substrate effects on the growth of single-walled carbon nanotubes (SWNTs) from iron complexes, clusters, and colloids on surfaces Ramon Colorado Jr., Christopher A. Crouse, Clayton C. Gallaway, Alvin Orbaek, and Andrew R. Barron, Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, TX 77005, colorado@rice.edu Our investigations of the vapor-solid-liquid (VLS) growth of single-walled carbon nanotubes (SWNTs) from metallic catalysts on solid substrates (e.g. iron nanoparticles on silicon wafers) have suggested that there is a correlation between the nature of the substrate and the activity of the growth catalyst. An understanding of potential catalyst activation and deactivation pathways is essential in developing methods for increasing the total yield of grown SWNTs from catalyst precursors. To this end, we have studied the VLS growth of SWNTs from iron oxide catalyst precursors on various substrates (Si, Spin-on-glass, HOPG, Al2O3) under different growth conditions (i.e. varying growth temperatures and gases). In addition, we have examined how changes in the roughness and morphology of the substrates affect nanotube growth with respect to both the catalyst activity and the orientation of the grown nanotubes. Characterization of the SWNTs by AFM, SEM, and Raman spectroscopy will be presented. INOR 26 Synthesis of small diameter carbon nanotubes by catalytic decomposition of methane Xiang-ju Xu and Shao-ming Huang, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, China, daisyxxj2003@yahoo.com.cn Small diameter carbon nanotubes(CNTs) have been synthesized over Fe/Mo/MgO catalyst by catalytic decomposition of methane at 1000°C. The produced carbon material primarily consists of a CNTs bundle with a small amount of individual CNTs. The diameter of an individual CNTs is in the range of 5-10 nm. The as-synthesized CNTs have a yield of over 100% relative to the weight of supplied catalyst. Critical issues for synthesis of small diameter CNTs were further discussed in terms of procedure of catalyst preparation, growth time, and temperature. Our results show that methane can be a very ideal carbon source for the synthesis of small diameter CNTs. We suggest that catalytic decomposition of methane over Fe/Mo/MgO catalyst can promise a large-scale production of small diameter CNTs. INOR 27 “Green” approach for fabrication of conducting polymer nanocomposite: The catalytic role of carbon nanotubes Yufeng Ma, Pui Lam Chiu, Arnaldo Serrano, Alex Chen, and Huixin He, Chemistry Department, Rutgers University, 73 Warren Street, Newark, NJ 07102, Fax: 973-353-1264, huixinhe@newark.rutgers.edu The catalytic behavior of carbon nanotubes (CNTs) just aroused a hot debate. For a long time people believed that the electrocatalytic properties of CNTs can be exploited for a wide variety of applications. However, very recently, Compton and coworkers challenged these general beliefs and demonstrated that the origin of the electrocatalytic behavior of CNTs observed previously is the metal catalyst residues, such as iron oxide particles, that remain in the batch after the fabrication of nanotube and the purification process. In this report, we will present the intrinsic catalytic capability of the single-walled carbon nanotubes (SWNTs). This catalytic capability is not only chirally selective, but also depends on the dispersion methods and dispersion agents used to disperse them into aqueous solutions. Due to the remarkable catalytic capability of the SWNTs, conducting polymer nanocomposites are fabricated by a “greener” process. INOR 28 Photocatalytic nanofibers and nanotubes made by atomic layer deposition Markku Leskela, Marianna Kemell, Viljami Pore, Eero Santala, and Mikko Ritala, Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FIN-00014, Finland, Fax: +358 9 191 50198, markku.leskela@helsinki.fi Because of the self-limiting growth principle Atomic Layer Deposition (ALD) suits very well for depositing thin films on nonplanar surfaces. Neither the size of the substrates nor the size of the structural features has any clear threshold value in ALD. ALD suits very well for making and modifying of nanomaterials. In this presentation the use of ALD for depositing conformal TiO2 films on nonplanar nanostructured surfaces is exemplified by three ways: deposition of thin films on porous alumina, deposition of films on nanofibers made with a porous alumina template, deposition of thin films on nanofibers either on natural fibers like cellulose or electrospun polymer nanofibers. The oxide nanotubes are obtained by annealing in air the TiO2 coated nanofibers and thereby removing the carbohydrate kernel. Photocatalytic activity of the nanomaterials were studied by decomposing methylene blue. The photocatalytic activity could be enhanced by coating the material with noble metal nanoparticles. Reusable magnetic nanofibers were obtained by coating electrospun iron acetate composite fibers with ALD TiO2. INOR 29 Carbon dioxide as a carbon source for synthesis of carbon nanotubes by chemical vapor deposition Xiang-ju Xu, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, China, daisyxxj2003@yahoo.com.cn Carbon dioxide was successfully used as carbon source in synthesis of carbon nanotubes(CNTs) by chemical vapour deposition(CVD) over Fe/CaO catalyst. The influence of some reaction parameters, including carbon source, furnace temperature, and types of support media is discussed in this paper. The product was evaluated using both Transmission electron microscopy(TEM) and Raman spectroscopy. Straight, crooked and branching structures of multi-walled carbon nanotubes(MCNTs) were discovered from the TEM micrographs of product. Their average diameters are about 50 nm. Raman spectrum results show that the nanotubes grew perfectly. The formation mechanism of MCNTs in this process was also studied. INOR 308 Thiol group sidewall functionalization of single walled carbon nanotubes Heather L. Rhoads1, Christopher N. Brammer2, Donna J. Nelson1, and Ruibo Li1. (1) Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019, Fax: 405-325-6111, hrhoads@ou.edu, (2) Department of Chemical, Biological, and Materials Engineering, University of Oklahoma Since their discovery, there has been an intense effort to characterize single walled carbon nanotubes (SWNTs) and to understand their properties. This information will allow researchers to develop SWNTs for applications intended to improve all aspects of life from medical to electrical and mechanical technology. Several characterization techniques, such as Raman, near-IR, UV-Vis, and TGA have been employed for years to characterize SWNTs, but more recently, NMR was found to be useful for determining both type and degree of functionalization. Such information will enable more direct syntheses for precise control of nanomaterial applications. To our knowledge, we report the first NMR spectra demonstrating thiol group sidewall functionalization; NMR data are analyzed in conjunction with Raman, FTIR, UV-Vis, and TGA data. In addition, a brief discussion of planned applications for our product's photoelectric properties will be presented. INOR 339 Potassium intercalation of graphitic nanofibers Jason A. Michel and Charles M. Lukehart, Department of Chemistry, Vanderbilt University, 1822 VU Station B, Nashville, TN 37212, Fax: 615-343-1234, j.michel@vanderbilt.edu Graphitic nanofibers (GNFs), grown by catalytic decomposition of carbonaceous gases, were reacted with potassium metal to form intercalation compounds. Three types of graphitic nanofiber were employed, namely platelet, herringbone, and narrow tubular herringbone, each with unique morphology. The air-sensitive stage 1 and stage 2 intercalation compounds were characterized by powder XRD. Thermionic electron energy distributions (TEED) show that the stage 1 intercalation compound has a work function of φ=2.2 eV, as compared to φ=4.7 eV for pristine GNFs, a reduction of 2.5 eV. The intercalation compounds have also been shown to initiate the polymerization of olefins such as isoprene and styrene to form GNF-polymer composites. INOR 350 Palladium nanoclusters on carbon nanotubes for flexible hydrogen sensors Yugang Sun, Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, ygsun@anl.gov, H. Hau Wang, Materials Science Division, Argonne National Laboratory, Qing Cao, Department of Chemistry, University of Illinois at Urbana-Champaign, and John A. Rogers, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign Hydrogen sensing represents an important technique in a wide range of applications for ‘hydrogen economy' such as industrial processing, fuel cells, hydrogen storage and separation, etc. Conventional hydrogen sensors are fabricated, in general, on rigid substrates (e.g., glass, quartz, silicon wafers) by using continuous as well as discontinuous palladium films (or wires) with lateral dimensions on the nanometer scales. The rigidity (and/or fragility) of these devices somehow limits their application in systems with curvilinear surfaces that require conformal lamination and mechanical shock-resistance. In contrast, hydrogen sensing devices fabricated on flexible polymeric substrates can find applications complementary to that of the conventional sensors on rigid substrates. We have recently found that nanoclusters of palladium deposited on the support of networks of single-walled carbon nanotubes significantly change the transport property of carbon nanotubes when the composites are exposed to hydrogen. Printing thin films of the Pd/nanotube composites on poly(ethylene terephthalate) (PET) sheets generates light-weight, shock-resistive, flexible hydrogen sensors. The as-fabricated devices have excellent performance which is comparable (even higher) to the conventional sensors. For example, these sensors can detect hydrogen with concentration as low as 30 ppm in air. The response time is as short as 7.5 second when the devices are exposed to 0.1% hydrogen in air at room temperature. [ Last edited by lingyun79 on 2007-3-25 at 14:26 ] |
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INOR 368 Synthesis of colloidal II-VI and IV-VI metal sulfide semiconductor nanowires by the solution-liquid-solid growth mechanism Jianwei Sun and William E. Buhro, Department of Chemistry, Washington University, 1 Brookings Dr, Campus Box 1134, Saint Louis, MO 63130, jsuna@artsci.wustl.edu High-quality monodisperse crystalline semiconductor nanowires (NWs) are of both scientific and technological interest due to their wide range of optical and electrical properties. Here we demonstrate the synthesis of colloidal II-VI and IV-VI metal sulfide semiconductor NWs via the solution-liquid-solid (SLS) growth mechanism developed by our group. The NWs are grown by using single-source metal diethyldithiocarbamate precursors and Bi nanoparticles serving as the catalyst in trioctylphosphine oxide (TOPO) solvent. The structure of the NWs is determined by XRD and TEM studies. The absorption and the photoluminescence properties are also studied, which demonstrate quantum-confinement effects. INOR 369 Synthesis of silicon carbide nanotubes by chemical vapor deposition Nongyue He, State Key Laboratory of Bioelectronics, Southeast University, 210096 Nanjing, China, Fax: 86-25-83790885, nyhe1958@163.com, Deliang Tao, Hunan Key Laboratory of Green-Packaging and Application of Biological Nanotechnology, Hunan University of Technology, Zhengfang Xie, State Key Lab of Advanced Ceramic Fibers & Composites, National University of Defense Technology, and Song Li, Hunan Key Laboratory of Green Packaging and Application of Biological Nanotechnology, Zhuzhou Institute of Technology, Wenhua Lu, Zhuzhou 412008, China, Fax: 86-733-2182097, solisong@163.com Silicon carbide (SiC), a typical non-oxide ceramic compound with excellent oxidization resistance, outstanding corrosion resistance, high thermal conductivity with low thermal expansion coefficient, high hardness and abrasion resistance, has been paid great attention. Silicon carbide nanotubes (SiCNTs) were directly synthesized here by chemical vapor deposition (CVD). Methyltrichlorosilane was selected as SiC gaseous source, ferrocence and thiophene as the catalyst and the cocatalyst, respectively. The influences of reaction temperature, contents of catalyst and cocatalyst, and content of gaseous source on morphologies of the products were investigated, respectively. The products were identified by high-resolution transmission electron microscopy, scanning electron microscopy, x-ray diffraction and energy-dispersive x-ray, respectively. The synthesis of SiCNTs by CVD is a condition-dependent process. SiCNTs with 20~80 nm in outer diameter and 15~35 nm in inner diameter were observed. The wall structure similar to that of carbon nanotubes was not found for the SiCNTs. INOR 370 Nanoparticle size and self-assembly within nanoclay hybrid films Michael Nolan Jr. and Michael E. Hagerman, Department of Chemistry, Union College, Schenectady, NY 12308, nolanm2@union.edu Comparisons of the inclusion chemistry of Laponite and other synthetic hectorite films offer routes to examine the influence of nanoparticle size and interlamellar cations on organic guest entrapment and host-guest interactions that mediate self-assembly. We have used various cationic rhodamine dyes included within these nanoclay hybrid films as photoprobes of organic-inorganic interfaces and film nanoarchitectures. Detailed optical analyses including electronic absorption and fluorescence spectroscopy have afforded study of how the fluorescence properties of rhodamine changes with respect to concentration and nanoscaffold binding location. Spectral red shifts in both absorption and emission indicated that the chromophores formed J-aggregated dimers with maximum luminescence at very low guest concentrations. H-aggregation and higher order aggregates with reduced luminescence were observed at higher guest loadings. These studies offer synthetic routes for selective tuning of organic-silica interfaces with important implications for future work on optoelectronic devices and gas sensors. INOR 371 Naturally occurring fluorescent (NOF) mineral inspired luminescent colloidal nanocrystals Timothy N. Lambert1, Bernadette A. Hernandez-Sanchez1, Timothy J. Boyle1, Harry D. Pratt III1, Nicholas L. Andrews2, Diane S. Lidke2, Janet M. Oliver2, and Bridget S Wilson2. (1) Advanced Materials Laboratory, Sandia National Laboratories, 1001 University Blvd SE, Albuquerque, NM 87106, Fax: (505)-272-7304, tnlambe@sandia.gov, (2) Department of Pathology, The University of New Mexico Health Sciences Center In an effort to develop new non-cytotoxic luminescent colloidal nanocrystals (NCs) for live cell imaging, we have initiated a NIH-funded program to prepare and evaluate new nanoprobes based on naturally occurring fluorescent (NOF) minerals and lanthanide-doped ceramic oxides. The major goals are to develop new probes that are highly fluorescent, bio-compatible, non-toxic, and tunable. With this in mind we have prepared sphalerite [(Fe/Zn)S], scheelite [Ca(WO4)], manganoan [(Mn/Ca)CO3] and perovskite (CaTiO3) inspired nanomaterials and lanthanide (Dy, Nd, Eu, Tb, Er) doped ceramic oxides, utilizing solution precipitation and solvothermal methods. Surface capping with functionalized poly(ethyleneglycol) molecules/lipids has yielded water soluble NCs that are currently being evaluated for their luminescent properties, as well as their non-toxicity and ability to report on cell-signaling events with various cell lines. The synthesis, materials characterization, water-solubilization methods, biocompatibility and cell-signaling efforts to date will be presented. This work supported by the Department of Energy, Office of Basic Energy Sciences and the United States Department of Energy under contract number DE-AC04-94AL85000. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the United States Department of Energy. INOR 372 Synthesis and characterization of mono and multi-element (Nb,Ru)-MSU molecular sieves Izabela Nowak1, Agnieszka Feliczak1, and Mietek Jaroniec2. (1) Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland, Fax: +48-61-8658008, nowakiza@amu.edu.pl, (2) Department of Chemistry, Kent State University Mesoporous (Nb,Ru)MSU-X materials have been successfully prepared for the first time by using tetraethyl orthosilicate, ammonium trisoxalate complex of niobium(V), chloropentaamineruthenium(III) chloride and fatty alcohol polyoxyethylenepolyoxypropylene ether as the sources of silicone, niobium and mesostructure-directing agent, respectively, at different pH values of the synthesis gel. The use of p-octyl phenyl derivatives having different number of PO groups, i.e., 7 or 14, led to the formation of samples of different pore sizes. All the (Ru,Nb)-MSU samples showed diffraction patterns typical for mesostructured materials with a worm-like ordering. The resulting materials featured high surface area (500-1000 sq. m/g), large porosity (mesopore volume up to 0.8 cu. cm/g) and uniform pore size (pore width range: 2.5–6 nm). It appears that ruthenium and niobium were incorporated into the pore walls of these materials. INOR 373 Effect of synthesis method on the physical and catalytic property of nanosized NiO Feng Yang, Ying Wu, Tinghua Wu, and Huilin Wan, Institute of Physical Chemistry, Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, Zhejiang Normal University, Jinhua 321004, China, ying-wu@zjnu.cn, ying-wu@zjnu.cn In recent years there has been an increasing interest in the synthesis of nanosized crystalline metal oxides. The physicochemical property of nanoparticles has intimate connection with the preparation technique. Nanosized NiO material was prepared by different methods. It's obvious that synthesis techniques influence the size, shapes and distribution of NiO nanoparticls. Therein NiO prepared by sol-gel and reverse micro-emulsion method has the larger special surface area and better particle distribution, compared with solid-state milling and precipitation method. The special surface area of NiO nanoparticles influences the adsorptive property, which has intimate connection with their catalytic behavior. The undecomposed surfactant covering the partial surface of NiO prepared by micro-emulsion method and calcinated at low temperature restrained its adsorption. Thus, NiO nanoparticles prepared by sol-gel method have good adsorptive property and best catalytic behavior for oxidation dehydrogenation of ethane reaction at lower reaction temperature. INOR 374 Effects of solvent on properties of TiO2 porous films prepared by a sol-gel method from the system containing PEG Jinfei Luo and Xiaoxin Liu, School of Chemical Engineering & Technology, Tianjin University, Weijin road 92, Tianjin 300072, China, Fax: 86-22-87401961, luojinfei@tju.edu.cn Four different solvents were used to prepare porous TiO2 films by the sol-gel method from the system containing tetrabutylorthotitanate as starting material and PEG as a template. The comparison of effects of the four solvents on the porous structure, film thickness, crystallization behavior from amorphous to anatase and optical properties of the resultant TiO2 porous films are discussed. The maximum thickness of the film prepared by one-run dip-coating reaches over 1.17 ìm when 1-decanol is used as the solvent. The mechanism for formation of the porous structure is interpreted based on the phase separation and self-assembly of PEG in the sol systems. |
12楼2007-03-25 14:19:37
lingyun79
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INOR 351 Palladium nanoparticles supported on polyaniline nanofibers as catalysts for the formation of C-C bonds Benjamin Gallon1, Robert W. Kojima2, Richard B. Kaner2, and Paula L. Diaconescu1. (1) Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, CA 90095, bgallon@gmail.com, (2) Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles Palladium nanoparticles supported by polyaniline nanofibers generate systems that are stable, work in water and air and, besides the ease and reproducibility of their synthesis, combine a redox active metal with a redox active support. Such a combination may provide unique characteristics, which could prove beneficial in catalytic cycles since most of them involve redox processes. Our studies on C-C bond forming reactions show that we are in the possession of very active catalysts for the Suzuki coupling of aryl halides and boronic acids in water. The role of the polyaniline support is investigated and certain reactions indicate that it can function as an electron reservoir and regenerate catalytically active species. INOR 357 Carbon nanotube contrast agents for MRI and CT Valerie C. Moore1, Pratixa Joshi1, and Jodie L. Conyers2. (1) Department of Internal Medicine, University of Texas Health Science Center at Houston, 6770 Bertner Avenue THI C964A, Houston, TX 77030, Fax: 832-355-9368, Valerie.Moore@uth.tmc.edu, (2) The University of Texas Health Science Center at Houston Nanoparticles hold great promise for medical imaging. Our lab is investigating the use of single walled carbon nanotubes as a container for CT and MR active atoms. Two filling methods have been utilized, sublimation and liquid intercalation, to encapsulate a variety of atoms - iodine, gadolinium, erbium, barium, iron, chromium, and manganese. With subsequent PEG functionalization, the filled nanotubes are biocompatible as determined through a variety of in vitro assays. This poster will describe theoretical calculations regarding contrast efficacy, comparisons of different filling and subsequent functionalization methods, and the current results from in vitro and in vivo biocompatibility studies. INOR 364 One-step synthesis of core-shell mesoporous carbon nanofibers using anodic alumina membranes as template Mingbo Zheng, Jieming Cao, Xingfei Ke, Guangbin Ji, Yongping Chen, and Jie Tao, Nanomaterials Research Institute,College of Materials Science & Technology, Nanjing University of Aeronautics & Astronautics, 29 Yudao Street, Nanjing 210016, China, Fax: 0086-25-84895289, zheng329@yahoo.com.cn, jmcao@nuaa.edu.cn One-dimensional mesoporous carbon materials possess the specialities of the one-dimensional nanomaterials as well as the properties of mesoporous carbon materials. In this work, we synthesized new core-shell mesoporous carbon nanofibers using pluronic F127 (EO106PO70EO106)/resol mixture solution as the precursor solution and the anodic alumina membranes (AAM) with different diameter sizes (80 nm and 300 nm) as the templates. The as-synthesized samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and nitrogen adsorption-desorption methods. The results of SEM and TEM revealed the core-shell structure of the nanofibers. Parallel mesopores, which were produced from the removal of pluronic F127, were observed in the shells of the nanofibers. The core of the sample synthesized from the AAM with 300 nm diameter had the circular mesopore architecture. Nitrogen adsorption-desorption characterizations indicate that these materials had large BET surface area and pore volume. The formation mechanism of these new materials was studied. INOR 376 Growth of carbon nanotubes from nanoparticulate catalysts generated by in situ laser ablation of metal targets Bradley D. Fahlman and Leontios A. Nezeritis, Department of Chemistry, Central Michigan University, Dow Science 357, Mount Pleasant, MI 48859, Fax: 989-774-3883, fahlm1b@cmich.edu A variety of metallic nanoparticles have been used to catalyze the growth of carbonaceous nanostructures (e.g., nanotubes, nanofibers, etc.). The most heavily used compositions include Fe, FexOy, Co, Ni, Ni/Y, and Co/Ni species. Carbon nanotubes are thought to grow from these catalysts via a vapor-liquid-solid (VLS) mechanism, which was first postulated ca. 30 years ago for the growth of semiconductor wires. We recently discovered a method to generate carbonaceous nanostructures via a surface-nucleation mechanism, whereby growth occurs at room temperature – far below the melting point of the catalyst seed. Whereas this method employed iron oxide nanoparticles encapsulated within a dendritic macromolecular host, we wish to simplify the nature of the catalyst through in situ generation of nanoparticles via laser ablation of metal targets with a Nd:YAG laser (1064 nm) within our reaction flask. The carbon source for nanostructural growth will be tetrachloroethylene, which will be dechlorinated through interaction with potassium metal within an organic solvent. The resultant product will be characterized by FESEM and TEM/EDS/EELS. INOR 531 The effect of physical characteristics on biocompatibility and cellular internalization of carbon nanotubes Valerie C. Moore1, Ashley Leonard2, Brandi K. Price2, Jodie L. Conyers3, and James M. Tour4. (1) Department of Internal Medicine, University of Texas Health Science Center at Houston, 6770 Bertner Avenue THI C964A, Houston, TX 77030, Fax: 832-355-9368, Valerie.Moore@uth.tmc.edu, (2) Rice University, (3) The University of Texas Health Science Center at Houston, (4) Departments of Chemistry, Mechanical Engineering and Materials Science, Rice University Single walled carbon nanotubes are being investigated as nanovector platforms because of their unique near infrared absorption and fluorescence spectra and their size and shape. We have investigated the effect of length, surface functionalization, and purity on biocompatibility and cellular internalization. The surface functionalization, not length or purity, is the predominant property that determines biocompatibility. PEG functionalization renders nanotubes with average lengths for 30 nm to 300 nm nontoxic while PEI wrapping exhibits some toxicity. Additionally, the cellular distribution for the two functionalizations is different, PEG distributes relatively evenly throughout the cytoplasm, while the PEI distributes in vacuoles and in some cases appears to associate with the nucleus. Biocompatibility was assessed by AnnexinV/PI and viability assays with both chronic and acute exposures. Cellular uptake was monitored and quantified with fluorescence and co-localization staining. Studies with longer nanotube (> 1 micron) are underway, final results will be presented at the meeting. INOR 536 Impact of carbon nanomaterial size regimes on smooth muscle cell growth Pavan M. V. Raja1, Jennifer Connolley2, Gopal P. Ganesan3, Lijie Ci4, Pulickel M. Ajayan5, Omkaram Nalamasu6, and Deanna M. Thompson2. (1) Chemical and Biological Engineering, Rensselaer Polytechnic Institute, CII 9015 - CIE, 110 8th Street, Troy, NY 12180, rajap@rpi.edu, (2) Biomedical Engineering, Rensselaer Polytechnic Institute, (3) Center for Integrated Electronics, Rensselaer Polytechnic Institute, (4) Department of Material Science and Engineering, Rensselaer Polytechnic Institute, (5) Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, (6) Center for Integrated Electronics and Department of Materials Science and Engineering, Rensselaer Polytechnic Institute Carbon nanotubes (CNTs) are unique carbon nanomaterials (CNMs) possessing diverse application potential ranging from electronic devices to therapeutic constructs. However, their potential impact on human health requires careful evaluation, prior to their commercialization. CNT - mammalian cell interaction studies could help understand this impact, on an in vitro basis. CNTs typically form polydisperse aggregates in cell culture medium. Smaller size regimes of non-aggregated CNTs and associated amorphous and graphitic carbon may also be present, which can be isolated by centrifugation and/or filtration of the medium. Our work addresses the impact of these size regimes in purified singlewalled carbon nanotubes (SWNTs), on the growth kinetics of rat aortic smooth muscle cells (SMCs). Our initial trends show that finely dispersed SWNT-related nanomaterials could significantly affect the SMC growth behavior. We further extend this study to compare the effects of the SWNTs with other sister CNMs, such as activated carbon, and carbon black. [ Last edited by lingyun79 on 2007-3-25 at 14:13 ] |
2楼2007-03-25 13:05:30
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INOR 676 Optical sensors for DNA-drug interactions: An application of single-walled carbon nanotubes Daniel A. Heller1, Dhaval Patel2, Brittany M. Martinez2, Jong Hyun Choi2, and Michael S. Strano2. (1) Department of Chemistry, University of Illinois at Urbana-Champaign, RAL Box 93-5 MC-712, 600 S Mathews Ave, Urbana, IL 61801, dheller1@uiuc.edu, (2) Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign Complexes of DNA-encapsulated carbon nanotubes serve as sensitive markers for the activity of chemotherapeutic drugs which alkylate DNA. The intrinsic fluorescence of single-walled carbon nanotubes, which exhibits environmental sensitivity, is employed for optical transduction of drug binding events to the DNA-nanotube complex. The emission, between 800 and 1600 nm, is photostable under continuous excitation and penetrates biological media which normally absorbs or scatters light at visible wavelengths. The complexes exhibit a concentration-dependent red-shift in emission energy of up to 6 meV upon binding to alkylating agents such as nitrogen mustards and platinum compounds. Within single cells, the nanotubes detect alkylating activity and transmit real-time information about the activity of the drugs. The sensors will be employed to investigate drug degradation as well as multi-drug resistance in cancer therapy. INOR 669 Synthesis of graphite nanorods by CVD method Xiang-ju Xu, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, China, daisyxxj2003@yahoo.com.cn Graphite nanorods were prepared by chemical vapor deposition(CVD) of methane at temperature 865°C to 930°C. X-ray Diffraction(XRD) and Raman spectroscopy results indicate that the product has graphite structure with high purity. Transmission Electron Microscopy(TEM) confirmed that the product has the shape of rods. The average diameters of the product is about 16.3 nm and lengths of up to 800 nm. INOR 716 Solubilization of single-walled carbon nanotubes for nanostructure solar cells Tingying Zeng and Jianxin Geng, Chemistry, Western Kentucky University, 1906 College Heights Blvd-11079, Bowling Green, KY 42101-1079, Fax: 270-745-5361, tingying.zeng@wku.edu SWCNT has high electrical conductivity, mechanical strength and Young's modules, as well as good thermal conductivities. The high metallic property of SWCNTs offers amazing possibilities to create nanoelectronic/nanoscale optoelectronic devices. If attached by photoactive conjugated polymer, SWCNT would lead to a strong electrical field formed to dissociate excitons, which results from the interaction of SWCNTs through its graphitic layer with conjugated polymer. The high electrical conductivity will increase the polymer thin film conductivity by increasing the charge carrier mobilities. All these advantages would significantly improve the power conversion efficiency and mechanical properties of carbon nanotube-modified polymer photovoltaics. Here we report our preliminary research on the solubilization of SWNTs using poly(3-hexylthiophene) (P3HT) and the corresponding nanoarchitecture property characterizations for nanostructured solar cells. INOR 85 The use of single walled carbon nanotubes for detection of DNA hybridization: Kinetics, thermodynamics, and applications Esther S Jeng, Department of Chemical and Biomolecular Engineering / Strano Research Group, University of Illinois Urbana-Champaign, 600 S. Mathews Ave., Urbana, IL 61801, ejeng@uiuc.edu, and Michael S. Strano, Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign Single-walled carbon nanotubes (SWNT) can be used for studies with biological materials. When individually dispersed, semiconducting SWNT exhibit band-gap photoluminescence at near-infrared (nIR) wavelengths. The nIR region is critical in many biological detection schemes, as interference from cell autofluorescence and light absorption of whole blood and tissue are low at these wavelengths. The addition of complementary DNA to nanotubes with pre-adsorbed probe DNA causes a modulation in nIR photoluminescence. DNA-SWNT therefore allow for label-free nanoscale detection of hybridization. We studied the kinetics and thermodynamics of this process on the nanotube, and investigate further applications for this sensor. INOR 30 Controlling the anatase/brookite ratio in sol-gel synthesized titanium dioxide nanoparticles Sara L. Isley and R. Lee Penn, Department of Chemistry, University of Minnesota, 139 Smith Hall, 207 Pleasant St. S.E, Minneapolis, MN 55455, Fax: 612-626-7541, isley@chem.umn.edu Titanium dioxide nanoparticles with different anatase/brookite ratios have been prepared via sol-gel syntheses. Rietveld refinements of X-ray diffraction patterns are used to quantitatively track the brookite content and particle sizes as functions of synthetic and hydrothermal aging variables. Results demonstrate that both brookite content and anatase particle sizes decrease with decreasing Ti/H2O ratio. The presence of chloride has the most influence over the brookite content during the sol-gel synthesis and not during hydrothermal aging. Increasing ionic strength during synthesis and hydrothermal aging influences the final anatase/brookite ratio and the particle size. Substantial control over the anatase and brookite contents can be achieved by modifying synthetic and hydrothermal aging variables. INOR 31 Characterization of porous catalysts by N2 sorption and small angle neutron scattering (SANS) studies Sharath R Kirumakki1, Houston P. Perry2, Abraham Clearfield3, Sai Venkatesh Pingali4, and P. Thiyagarajan4. (1) Chemistry Department, Texas A&M University, College Station, TX 778432, skirumakki@mail.chem.tamu.edu, (2) Department of Chemistry, Texas A&M University, (3) Department of Chemistry, Texas A & M University, (4) Intense Pulsed Neutron Source, Argonne National Laboratory There is great technological interest in the design of multifunctional porous materials. We have synthesized families of porous potential catalysts including layered zirconium phosphonates1 and porous NiO-Al2O3-SiO2 systems2 with high surface areas ranging from 250 m2/g-600 m2/g. N2 sorption studies were carried out to determine the pore sizes of these materials. Gas adsorption methods have long been employed for this purpose but their interpretation has been a subject of ongoing debate. The Small Angle Neutron Scattering (SANS) data will be utilized to complement and validate the pore sizes determined. Contrast matched SANS will help differentiate between open pores and closed pores in the materials. Pore connectivity can also be determined by this method. The pore sizes in the layered materials are greater than their interlayer distance and therefore it is very important for us to understand the nature of these pores. Based on the N2 sorption and SANS techniques we will try to describe the pore structure of our materials. Ref: 1. A. Clearfield, Z. Wang, J. Chem. Soc., Dalton Trans, 2002, 2937 – 2947. 2. S.R. Kirumakki, B.G. Shpeizer, G.V. Sagar, K. V.R. Chary, A. Clearfield, Journal of Catalysis, 242, 319-331 (2006) INOR 32 Synthesis and structures of bis(2-dimethylaminoethyl)amine adducts of strontium bis(2,2,6,6-tetramethylheptane-3,5-dionate) and their use in the chemical vapor deposition of cubic strontium-doped hafnium dioxides Wayne L. Gladfelter1, Bing Luo1, Dan Yu2, Benjamin E. Kucera1, and Stephen A. Campbell2. (1) Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, gladfelt@chem.umn.edu, (2) Department of Electrical and Computer Engineering, University of Minnesota Monomeric, eight-coordinate Sr(tmhd)2[HN(CH2CH2NMe2)2](EtOH) (1), where tmhd is 2,2,6,6-tetramethylheptane-3,5-dionato, was synthesized from the reactions of HN(CH2CH2NMe2)2, H-tmhd and Sr(OEt)2(EtOH)4. Heating compound 1 at 130 °C dissociated EtOH to form monomeric, seven-coordinate Sr(tmhd)2[HN(CH2CH2NMe2)2](2). In a cold-wall, low-pressure chemical vapor deposition reactor, 2 was used as a liquid precursor at 115 to 175 °C to deposit high-κ dielectric strontium hafnium oxide films in combination with the use of Hf(OtBu)4. The Sr/(Sr + Hf) atomic ratios of the films ranged from 0 to 0.83. XRD showed that films with low Sr doping, e.g. ≤ 0.15, exhibited a crystalline phase consistent with Sr-stabilized cubic hafnia while films with higher Sr contents were amorphous. The dielectric constants of the films increased as the proportion of the cubic phase increased. A maximum value of 25 was obtained for the film with a Sr/(Sr + Hf) ratio of 0.07. INOR 35 Hybrid silica-polymer composites for radiation detection applications Banu Kesanli and Sheng Dai, Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831-6201, kesanlib@ornl.gov Optically transparent, flexible silica-polymer composites were prepared through sol-gel processing. Sol-gel precursors tetraethyl orthosilicate (TEOS) and 1,4-bis(triethoxysilyl)benzene, (BzTEOS) were hydrolyzed in the presence of HCl in THF and commercially available poly[styrene-b-(styrene-co-butadiene)-b-styrene] triblock copolymer, Styroflex, yielding transparent monoliths. The samples were characterized with TGA and 29Si NMR techniques. Studies revealed that these crack-free, transparent hybrid materials are also efficient matrices to be explored as plastic scintillators for radiation detection applications. The hybrid composites were doped with organic scintillator and lithium-6 which is the neutron absorber. Their alpha particle and neutron detection performances were evaluated. The samples revealed emissions at 421 nm upon doping with PPO/POPOP organic scintillator solution. Hybrid silica polymer samples doped with 3.5 wt% 6Li+ showed high scintillation efficiencies for thermal neutrons. INOR 36 Bifunctional mesoporous nanocatalysts by solvent-assisted postgrafting synthesis Tewodros Asefa and Krishna K. Sharma, Department of Chemistry, Syracuse University, 111 College Place, 1-048 Ceneter for Science and Technology, Syracuse, NY 13244, Fax: 315-443-4070, tasefa@syr.edu The design, synthesis and self-assembly of inorganic, organic and organometallic molecules into solid state nanoscale structures is important for the development nanostructured materials for various electronics, catalytic, sensing, separation, biological and medical applications. For instance, by supramolecular self-assembly of alkoxysilanes, mesoporous solid-state silica materials, which are important host materials for a variety of catalytic groups, results. Subsequent postgrafting on the surface silanols of these materials with aminororganosilanes produces solid base catalysts for a number of reactions. In this talk, I will discuss a one-step method we have recently discovered for postfunctionalization synthesis of efficient, bifunctional acid-base mesoporous solid catalysts containing high surface areas and tunable pore sizes at the nanometer scale. By judicious choices of solvents, control over their structures and catalytic properties has also possible. The synthesis, structures and compositions as well as the catalytic properties of the materials towards a Henry reaction (nitroaldol condensation) will also be discussed. INOR 37 From platinum and [Ge2Se6]4- and [GeSe4]4- precursors to hexagonal mesostructured chalcogenides: Detailed investigation of the solution behavior Santanu Bag and Mercouri G. Kanatzidis, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, s-bag@northwestern.edu Mesostructured chalcogenide materials have the potential to be promising candidates for novel semiconducting devices. Using Zintl anions and linking metals in suitable solvents and templating surfactants can lead to porous chalcogenides. We will present the surfactant templated synthesis of mesostructured materials based on [Ge2Se6]4- and [GeSe4]4- and Pt2+ as linking metal. Both surfactant head group and chain length can be varied systematically to study their effect on the long range order of the final mesostructures. These materials show sharp band gap transitions in the range of 1.3-1.7 eV. The solvent dependence of these building blocks is of great interest because it affects the nature of the structures. The solution behavior and interspecies equilibria were investigated in detail with variable temperature NMR spectroscopy. Reaction chemistry was employed to shift the exchange equilibria and prevent the formation of undesired species. INOR 41 Triplet valence states and atomic-scale p-n junctions in manganese perovskite oxides from hydrothermal systems Shouhua Feng, Hongming Yuan, Zhan Shi, Yan Chen, Keke Huang, Guangsheng Pang, Jixue Li, and Ying Hou, College of Chemistry, Jilin University, 1788 Linyuan Road, Changchun 130012, China, Fax: +86-431-5168624, shfeng@mail.jlu.edu.cn Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search for nano-scale and/or atomic-scale devices with particular properties by specific preparations in the same systems has been extensively conducted. We present here the triplet valence states (three oxidation states) of manganese (Mn3+, Mn4+, Mn5+) in the perovskite oxide, La0.66Ca0.29K0.05MnO3, which most interestingly show the rectifying effect as atomic-scale p-n junctions of single crystals. The family of cubic perovskite oxides was synthesized by the so-called hydrothermal disproportionation reaction of MnO2 under the condition of strong alkali media. The new concept of the atomic-scale p-n junctions, based on the ideal I-V curves for the p-n junctions in the single crystal, basically originates from the structural linkages of [Mn3+-O-Mn 4+-O-Mn5+], where Mn3+(t2g 3eg 1) and Mn5+(t2g 2eg0) in octahedral symmetry serve as a donor and an acceptor, respectively, corresponding to the localized Mn4+(t2g3eg 0). [ Last edited by lingyun79 on 2007-3-25 at 14:13 ] |
3楼2007-03-25 13:06:30
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INOR 42 Direct synthesis of monolayer-proctected silver nanocrystals: Effect of capping molecules Kwi Jong Lee, Young Il Lee, In Keun Shim, Byung Ho Jun, and Jaewoo Joung, eMD Lab, Central R&D Institute, Samsung Electro-Mechanics, 314, Maetan3-Dong, Yeongtong-Gu, Suwon, Gyunggi-Do, South Korea, Fax: 82-31-300-7900(4553), kwijong.lee@samsung.com In this study, we attempted to present a direct synthesis of narrowly dispersed silver nanoparticles in highly concentrated organic phase (> 2 M) without use of a size-selection process. The fully organic phase system contains silver nitrate as a silver precursor, n-butylamine as a media dissolving silver salt, toluene as a media, and NaBH4 as a reducing reagent. Variable types of fatty acids were used as a capping molecule. Even using only generic chemicals, monodispersed silver nanocrystals with size of 7 nm were easily synthesized at 100 gram-scale in 1 liter reactor. In addition, systematic studies revealed that the silver nanocrystals synthesized through in situ ligand exchange were stabilized through bidentate bridging of carboxyl group. INOR 94 Nanoporous semiconductors for photocatalytic applications Pingyun Feng, Department of Chemistry, University of California at Riverside, Pierce Hall, Riverside, CA 92521, Fax: 951-827-4713, pingyun.feng@ucr.edu Semiconductor-based heterogeneous systems for photocatalytic production of hydrogen from water is one of the simplest and most economical methods for solar energy utilization. However, the low conversion efficiency of the current materials limits their practical application. Crystalline nanoporous semiconductors offer promise as efficient photocatalysts because they uniquely integrate semiconductivity, crystallinity, high surface area, and uniform porosity. Here, we describe synthesis, structure, and photocatalytic properties of a family of porous semiconducting materials, many of which are built from nanosized clusters. Furthermore, these open-framework semiconductors can function as host to accommodate optically active species with complementary properties, which provides an additional level of control over photocatalytic properties in these materials. INOR 95 Development of H2 evolution sites for overall water splitting on particulate photocatalysts Kazunari Domen, School of Engineering, The University of Tokyo, 7-3-1,Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, Fax: +81-3-5841-8838, domen@chemsys.t.u-tokyo.ac.jp Nanoparticles of various transition-metal oxides are studied as cocatalysts for H2 evolution in overall water splitting. We present on two types of new cocatalysts: (1) mixed-oxides consisting of Cr and another transition-metal and (2) noble-metal/Cr2O3 (core/shell) nanoparticles. These cocatalysts are loaded on particulate photocatalysts (e.g. GaN:ZnO solid solution) by an impregnation or an in-situ photodeposition method. When GaN:ZnO is used as a base photocatalyst, loading Rh2-yCryO3 nanoparticles results in the largest improvement in the activity. Rh2-yCryO3-loaded GaN:ZnO functions as an active and stable photocatalyst for overall water splitting under visible light irradiation (> 400 nm), achieving the quantum efficiency of 2-3% at 420-440 nm. In this presentation, the structures and photocatalytic properties of such cocatalysts will be presented in detail. INOR 106 Surface chemistry of gold nanostructures deposited on oxides: Oxide-specific O2 interactions with supported gold Suljo Linic and Siris Laursen, Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, linic@umich.edu Oxide-supported Au nanostructures are promising low-temperature oxidation catalysts. It is generally observed that Au supported on reducible oxides is more active than the Au supported on irreducible oxides. Recent studies also suggest that cationic Au+ is responsible for the unique Au/oxide catalytic activity. This observation is contrary to the conventional perception that oxide supports donate electronic charge to Au. We have utilized DFT calculations and ab initio thermodynamic studies to investigate the oxidation state of Au nanostructures deposited on reducible and irreducible supports. We find that there are fundamental differences in the electronic structure of Au deposited on the different oxides. We propose a simple model, grounded in the first principles calculations, which attempts to explain the oxide-specific catalytic activity of Au nanostructures and which can account for the presence and the role of cationic Au+. INOR 108 How do we achieve nanocatalysis by design? Anne M. Chaka, Physical and Chemical Properties Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8380, Gaithersburg, MD 20899-8380, Fax: 301-869-4020 Nanocatalysis by design is highly desirable but remains elusive for many reasons, such as limited data on well-characterized systems, and the challenges of bridging the ideal conditions of single crystal UHV surface science and computational models with realistic industrial processes. Questions of how to design a catalyst are complicated by the fact that materials with identical chemical compositions can have very different reactivity depending upon processing conditions for synthesis, plus the size and morphology of the resultant particles. This presentation will discuss how we can develop a synergy between experiment, theory, and modeling to delineate the essential chemistry and physics required for quantitative predictions and transferability of models to novel systems to enable design. Examples will be presented from metal oxide catalysts for oxidation, and gold-palladium nanoclusters. INOR 114 Monodisperse, mesoporous silica spheres as a sensor substrate Thomas A. Schmedake, Ronald B. Soriano, and Adam M. Jakob, Department of Chemistry, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223-0001, Fax: 704-687-3151, tschmeda@email.uncc.edu Mesoporous, monodisperse silica spheres are a versatile substrate for gas phase and solution phase sensing applications. The synthesis of monodisperse colloidal silica with diameters much less than 1,000 nm and with ordered mesoporosity is possible by the hydrolysis of a tetraalkoxysilane in the presence of an alkylamine surfactant under basic conditions. Mesoporous spheres were grown through a sol-gel self-assembly process which utilized cetyltrimethylammonium bromide as a porogen. The procedure produces highly monodisperse sub-micron spheres with hexagonally arrayed pores. The ~ 2.5 nanometer pores enable analyte specific fluorescent dyes to be incorporated into the spheres following surfactant removal. A common fluorescent dye for determining oxygen concentration, Ru(bipy)32+, could be incorporated up to loading levels of 2% by weight. The resulting dye filled spheres were evaluated as sensors for oxygen. The small size of the spheres results in very rapid response times of a few seconds. The monodispersity also provides opportunities to assemble spheres into colloidal arrays for additional functionality. INOR 115 Incorporation of niobium into cage-like silica mesostructures Izabela Nowak, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland, Fax: +48-61-8658008, nowakiza@amu.edu.pl, and Mietek Jaroniec, Department of Chemistry, Kent State University Cage-like ordered mesoporous silicas with incorporated niobium, NbSBA-16, were obtained by direct insertion of metal ions during one-pot synthesis using two different recipes. It was shown that NbSBA-16 materials have the BET specific surface of about 800-1000 sq. m/g and mesopore pore volume of about 1.0 cu. cm/g, similar to those observed for purely siliceous SBA-16. As expected for SBA-16 silicas, 20-50% of the total pore volume in the NbSBA-16 samples studied belongs to the complementary pores (micropores and interconnecting cage apertures) depending on the synthesis temperature. The mesopore diameters were about 7.0-11.0 nm. The samples obtained by both recipes contained niobium located in the framework as well as an extra-framework niobia deposited on the pore walls. The aforementioned synthesis recipes allowed us to synthesize three-dimensional NbSBA-16 structures of various morphology and different contributions of complementary, ordered and textural pores, which is of great importance from catalysis viewpoint. INOR 116 Ratiometric quantum dot chemosensors based on modulation of Fluorescence Resonance Energy Transfer Rebecca C. Somers, Preston T. Snee, Andrew B. Greytak, Moungi G Bawendi, and Daniel G. Nocera, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Rm 2-209, Cambridge, MA 02139, rsomers@mit.edu A reversible and ratiometric nanocrystal pH sensor was synthesized by tethering CdSe/ZnS (also known as quantum dots, QDs) to fluorescent sensing dyes. The construct combines the advantages offered by the QDs such as broad excitation profiles and high quantum yields, with the specific sensing ability of the dye. Fluorescence Resonant Energy Transfer (FRET) between donor QDs and acceptor dyes in the sensing construct is modulated by analyte concentration. The presence of an isosbestic point between the two emission maxima allows the sensor to be self-calibrating. The pH-sensing construct is the first example of a CdSe nanocrystal based sensor that is both reversible and ratiometric. The synthetic approach utilized in our constructs is general and can be exploited for sensing other analytes both reversibly and ratiometrically. Applications in biological studies incorporating the QD sensors will also be discussed. INOR 117 Optical properties of nanoparticles with hollow structures: A single nanoparticle spectroscopy study Min Hu1, Jingyi Chen1, Younan Xia1, Gregory V. Hartland2, and Manuel Marquez3. (1) Department of Chemistry, University of Washington, Seattle, Seattle, WA 98195, Fax: 206-685-8665, mhu2@u.washington.edu, (2) Department of Chemistry and Biochemistry, University of Notre Dame, (3) INEST Group, Research Center, Philip Morris USA, Inc The optical properties of hollow structured nanoparticles (Au-Ag nanoboxes and nanocages) were investigated by performing Rayleigh scattering spectroscopy measurements on single nanoparticles, whose morphology and composition had been analyzed by Scanning Electron Microscopy (SEM). This single nanoparticle spectroscopy study removed the inhomogeneous broadening effect and enables us to precisely determine how the homogeneous line widths depend on the dimensions and morphology of the particles. The results show that both radiation damping and electron surface scattering make significant contributions to the linewidth. The electronic dephasing times for these systems was determined to be ca. 4 fs. The sensitivity of the plasmon resonance with respect to the local environment has also studied for these nanoparticles. The results suggest that both the inner and outer surfaces of hollow nanoparticles determine the spectral line shift with respect to the local environment change. INOR 118 Long-range electronic energy transfer in quantum dot nanocomposites: Toward lowering the optical gain threshold of quantum dots Mahmoud Emara, Scott Burya, and P. Gregory Van Patten, Department of Chemistry and Biochemistry, Ohio University, Clippinger Laboratories, Athens, OH 45701, me217103@ohio.edu Antenna-like clusters of nanocrystals have been assembled and studied in colloidal suspension. These clusters contained a single CdTe nanocrystal surrounded by a group of smaller CdTe nanocrystals and/or multiple Au nanocrystals. Controlled assembly was achieved through the use of complementary ligands on the different nanocrystals that formed clusters either through electrostatic assembly or through covalent bonding of the ligands. These clusters are designed to enhance excitation probability at the central acceptor nanocrystal through Förster Resonance Energy Transfer or via plasmon-assisted absorption. The clusters have been characterized by dynamic light scattering and TEM imaging, as well as steady-state and time-resolved absorption and photoluminescence spectroscopies. The enhanced production of excitons at the central nanocrystal is proposed as a means to reduce the optical gain threshold of colloidal semiconductor nanocrystals. INOR 119 High-efficiency carrier multiplication and ultrafast charge separation in semiconductor nanocrystals Richard D. Schaller, Milan Sykora, Sohee Jeong, and Victor I. Klimov, Chemistry Division, Los Alamos National Laboratory, MS-J567, Los Alamos, NM 87545, Fax: 505-667-0440, rdsx@lanl.gov We demonstrate novel methods for the study of multiple exciton generation from a single photon absorption event in semiconductor nanocrystals that are complementary to our previously reported transient absorption method. By monitoring the time-dependence of photoluminescence from nanocrystals via time-resolved emission, we find that carrier multiplication is observable due to the Auger decay of biexcitons. Additionally, we observe spectral signatures of multiple excitons produced from the absorption of a single photon. Photoluminescence spectra at short times following excitation with high-energy photons are red-shifted compared to the single-exciton emission band, which is consistent with previous observations of significant exciton-exciton interactions in nanocrystals. We then show that charge transfer between a nanocrystal and a Ru-based catalyst model compound takes place on a timescale that is faster than Auger recombination, which points toward a possible design of donor-acceptor assemblies that can be utilized to take advantage of carrier multiplication. [ Last edited by lingyun79 on 2007-3-25 at 14:14 ] |
4楼2007-03-25 13:07:37