China-US Workshop on Materials Science Abstract 01 RECENT DEVELOPMENTS IN HYBRID INORGANIC-ORGANIC FRAMEWORK MATERIALS

China-US Workshop on Materials Science 02 POROUS FRAMEWORKS BASED ON INDIUM AND ORGANIC LIGANDS Maochun Hong Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences, China May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 2 China-US Workshop on Materials Science Abstract 03 METAL-ORGANIC FRAMEWORKS AND POLYHEDRA (MOFS AND MOPS): NEW MATERIALS DESIGNED FOR H2/CH4 STORAGE Omar M. Yaghi Department of Chemistry, University of Michigan, Ann Arbor, MI 48103, USA An outstanding challenge in the synthesis of crystalline solid-state materials is to alter chemical composition, functionality, and molecular dimensions systematically, that is, without changing the underlying topology. The insolubility of extended solids necessitates that their assembly be accomplished in only a single step. Thus, in order to design a target extended structure with the same precision practiced in organic synthesis, (i) the starting building blocks should have the relevant attributes necessary to assemble into the skeleton of the desired structure, (ii) the synthesis has to be adaptable to using derivatives of those building blocks to produce structures with the same skeleton but different functionalities and dimensions, and (iii) the products should be highly crystalline to facilitate their characterization by X-ray diffraction (XRD) techniques. We have developed the assembly of extended structures of metalorganic frameworks (MOFs) from molecular building blocks. In particular, in MOF-5, octahedral Zn-O-C clusters are linked by benzene struts to reticulate a primitive cubic structure (1) and produce an exceptionally rigid and highly porous structure. We report the systematic design and construction of a series of frameworks having structures based on the skeleton of MOF-5, wherein the pore functionality and size have been varied without changing the original cubic topology. We will also report the synthesis of a new class of truncated tetrahedra (MOP-50-54, shown below) that form molecular crystals capable of gas storage. The exceptionally high surface area (up to 5,000 m2/g) and pore volumes observed for MOFs and MOPs coupled with their appropriately designed aperture make them ideal candidate for methane and hydrogen storage. Indeed, the methane sorption isotherm was measured in the pressure range 0 to 45 atm and room temperature, and found to have an uptake of 240 cm (STP)/g (155 cm/cm) at 36 atm. The H2 isotherm for MOFs show that up to 5 % wt/wt could be stored at 78 K, and up to 2 % wt/wt at room temperature and 10 bar. The presentation will discuss synthesis of these compounds and their use for gas storage including the use of H2 for fueling of cellular phones, laptops, and, in the case of methane, automobiles. Email: [email protected]; tel: 734-615-2146; Fax: 734-615-9751 May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 3 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 04 INORGANIC NANOMATERIALS FOR HYDROGEN AND LITHIUM STORAGE Jun Chen Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, P.R.China Increasing awareness of environmental factors and limited energy resources have led to the urgency of developing clean, affordable, and efficient energies. Hydrogen is considered as one of the best alternative fuels due to its abundance, high-energy containing and non-polluting nature when used in fuel cells. R&D; of hydrogen energy involves hydrogen production, hydrogen storage and transport, and hydrogen utilization. However, the hydrogen storage and transport on more safe and efficient ways for stationary or mobile applications is the “bottleneck” of hydrogen-energy field. For on-board energy storage, vehicles need compact, light, safe and affordable containment. A modern, commercially available car optimized for mobility and not prestige with a range of 400 km burns about 24 kg of petrol in a combustion engine; to cover the same range, 8 kg hydrogen are needed for the combustion engine version or 4 kg hydrogen for an electric car with a fuel cell. At room temperature and atmospheric pressure, hydrogen is a molecular gas and 4 kg of hydrogen occupies a volume of 45 m3. It is obvious that such a volume should be compressed. Thus, a rversible 5-6.5 wt% hydrogen storage less than 100 C is targeted with the same weight and volume of the container in a petrol vehicle. One of the potential classes of materials for hydrogen storage is nanostructured composites, which may open the window to hydrogen storage with the overall consideration of capacity, decomposition temperature, cycling stability, low cost, and safety. Carbon nanotubes continue to be studied for the hydrogen-storage mechanism. However, recent interest has shifted. The main focus is on nanocrystalline complex hydrides, inorganic nanotubes such as boron nitride (BN), titanium disulfide (TiS2), lithium nitride (Li3N), metal-organic frameworks (MOFs), and metals/alloys (Ag/Pd). Supported by NSFC (No. 20325102, 90406001) Email: [email protected]; Tel: 022-23506808; Fax: 022-23509118 May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 4 China-US Workshop on Materials Science Abstract 05 MANIPULATING CARBON NANOTUBES AND USES OF SOL-GEL CHEMISTRY Mark Harmer DuPont CR&D;, Experimental Station, P.O. Box 80328, Wilmington, DE 19880 USA In this talk we will describe the use of DNA and also sol-gel to manipulate carbon nanotubes. In one case the DNA shows a strong affinity for the tubes which opens up a number of applications. In the case of sol-gel, materials can be designed that control the conductivity of the carbon nanotubes for device applications. We will also briefly highlight the use of sol-gel in another area, solid acid catalysis. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 5 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 06 SOME RECENT RESEARCH PROGRESS IN CARBON NANOTUBES AND ONE-DIMENSIONAL AIN NANOSTRUCTURED MATERIALS Zheng Hu Department of Chemistry, Laboratory of Mesoscopic Materials and Chemistry, National Laboratory of Solid State Microstructure, Nanjing University, China May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 6 China-US Workshop on Materials Science Abstract 07 LARGE SIZE LITHIUM ION BATTERIE AND ITS KEY MATERIALS Xuejie Huang *, Hong Li, and Liquan Chen Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China The development of new electrode materials leads to Li-ion batteries with improved performance, higher safety, and lower cost. LiMn2O4 with Al2O3 coating layer in thickness of nanometers shows higher charge/discharge rate capability, better cycling performance at 55 C, and much improved stability. 15Ah Hi-power type Li-ion cells based on this material have power density of 1500W/Kg and high safety. Even Larger size cells can be made based on LiFePO4 cathode. Theoretical calculation predicted that the electronic conductivity of LiFePO4 can be obviously enhanced by small quantity of Cr doping on Li site. It was then confirmed by experiments that its electronic conductivity can be increased up to 8 orders of magnitude. Again, theoretical calculation predicted that the electronic conductivity of LiFePO4 can be much improved by introducing oxygen vacancies. New LiFePO4 sample prepared based on this concept shows satisfied electrochemical performance and could be used in high power batteries. Hard carbon shows superior performance compared with graphite as anode material in the case of EV and HEV batteries. Its nanopores behave as the storing unit of lithium and HCS has reversible capacity over 400mAh/g and with improved cycling performance. Corresponding Author: [email protected],cn Presentation Author: Xuejie Huang May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 7 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 08 NEW THERMOELECTRIC MATERIALS FOR POWER GENERATION AND COOLING APPLICATIONS Tao He DuPont CR&D;, Experimental Station, P.O. Box 80328, Wilmington, DE 19880 USA In recent years, there has been a resurgence of interest in the field of thermoelectrics (TE) driven by the need for more efficient materials for cooling and power generation. TE devices are highly reliable, environmentally benign and maintenance-free, but the use of TE devices is limited to niche applications due to their low efficiencies. The efficiency of a TE device is directly related to the “Figure of Merit” (ZT), which is primarily determined by the crystal structure, composition and band structure of the material used in the device. Recent advances in synthesis, theory and understanding of structure/property relationships of materials have increased the possibility of finding higher efficiency thermoelectrics. Here we will show our efforts at DuPont in designing and developing new inorganic TE materials with enhanced ZT, including oxides, mixed-valence Kondo intermetallics, and skutterudites, etc.. Other research activities related to energy conversion will also be briefly discussed. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 8 China-US Workshop on Materials Science Abstract 09 HYDROTHERMAL SYNTHESIS OF PEROVSKITE MANGANITE OXIDES Shouhua Feng Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Department of Chemistry, Jilin University, Changchun May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 9 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 10 SOLUTION ROUTES TO EPITAXIAL ZNO THIN FILMS F. F. Lange and David Andeen Materials Department, University of California, Santa Barbara, CA, 93106 Several solution routes exist to produce epitaxial thin films [1]. Oxides, nitrides, sulfides, etc, powders can be directly synthesized in a liquid.[1-5] Epitaxy can be achieved by placing a single crystal substrate in such a solution. Nucleation and growth on a single crystal substrate produces an epitaxial thin film. The epitaxial deposition of ZnO on (111) MgAl2O4 (spinel) by hydrothermal deposition at 90oC using an aqueous solution of zinc nitrate and ammonium hydroxide at pH levels ranging from 7 to 11 will be used to illustrate this method. X-ray diffraction indicates that the films are c-plane oriented with zinc faced (001) polarity and the close packed directions in the film and substrate do not coincide, but are rotated by 30o. A crystal chemistry reason shows that this relation not only reduces the coincidence lattice mismatch form 13.6% to -1.6%, but also allows the ZnO tetrahedrons in the ZnO structure to replace both the MgO tetrahedrons and the AlO octahedrons on the (111) plane of the spinel substrate.[5] Because epitaxy occurs at low temperatures, the substrate can be patterned with a polymer via Channel Stamping [6] to lower the dislocation density of the film via a phenomenon know lateral epitaxy overgrowth, where the fast growth direction is inhibited by adsorbed ions, to allow lateral overgrowth. 1 F. F. Lange "Chemical Solution Routes to Single-Crsytal Thin Films," Science, 273 [5277] 903-9 (1996). 2. G.K.L. Goh, C.G. Levi, F.F. Lange, “Hydrothermal Epitaxy of KTaO3 Thin Films,” J. Mat. Res. 17 [11] 2852-2858 (2002). 3. AT Chien, X Xu, JH Kim, J Sachleben, JS Speck, FF Lange, Electrical characterization of BaTiO3 heteroepitaxial thin films by hydrothermal synthesis.” J. Mat. Res 14 (8): 3330-3339 (1999) 4. L. Loeffler, FF Lange, “Hydrothermal synthesis of undoped and Mn-doped ZnGa2O4 powders and thin films.” J. Mat. Res. 19 [3] 902-12 (2004) 5. David Andeen, Lars Loeffler, Nitin Padture and F. F. Lange, Crystal chemistry of epitaxial ZnO on (111)MgAl2 O4 produced by hydrothermal synthesis, Journal of Crystal Growth 259, 103 –109 (2003). 6. P.M. Moran and F.F. Lange, “Microscale Lithography via Channel Stamping: Relationships between Capillarity, Channel Filling and Debonding,” APL 74 [9] 1332-1334 (1999). May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 10 China-US Workshop on Materials Science Abstract 11 SELF-ASSEMBLY OF ORGANIC MOLECULAR NANOSTRUCTURES Chen WANG National Center for Nanoscience and Technology, Beijing, 100080, China Continued efforts have been seen in achieving the goal of assembling organic molecules on solid surfaces in a controllable way. This practice requires fine-tuning of the thermodynamic equilibrium of the molecular assembles, with various interactions, ranging from van der Waals, hydrogen bonds, electro-static, steric interaction etc. The assembled structure could lead to the possibility of artifically designing of molecular nanostructures, possessing rich physical and chemical functions. We will illustrate in this report the efforts with a series of molecular nanostructures that could be adapted as nanometer dimensioned templates for guest molecule inclusion and adsorption, or possible molecular devices. The potential of functional groups inclusions could lead to novel molecular devices. The studies can be performed at single molecule level under ambient conditions and solvents. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 11 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 12 IN-SITU NANOMEASUREMENT INSIDE TEM Xuedong Bai and Enge Wang Beijing National Laboratory for Condensed Matter Physics International Center for Quantum Structures Institute of Physics, Chinese Academy of Sciences Due to the highly size and structure selectivity of nanomaterials, the properties of nanomaterials could be quite diverse. To maintain and utilize the basic and technological advantages offered by the size specificity and selectivity of nanomaterials, it is imperative to study the properties of individual nanostructures, providing a one-to-one correspondence in structure-property characterization. The method based on in-situ measurements in TEM is powerful in a way that it can directly correlate the atomic-level microstructure of the nanomaterials with their physical properties for the same nanoscale sample. In addition, the small size of the nanostructures makes their manipulation rather difficult, the in-situ TEM method provides an appropriate tool for manipulation to quantify the properties of individual nanostructures. In this talk, I will report that the mechanical properties of the individual nanobelts and the dynamic elastics of nanosprings by using the system, which is built by integrating a scanning tunneling microscope (STM) with a high-resolution transmission electron microscope (TEM). And the dynamic field emission properties of carbon nanotubes have also been studied. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 12 China-US Workshop on Materials Science Abstract 13 ONE-DIMENSIONAL NANOSTRUCTURES AS SUBWAVELENGTH OPTICAL ELEMENTS FOR PHOTONICS INTEGRATION Peidong Yang Department of Chemistry, University of California, Berkeley, CA 94720 The manipulation of optical energy in structures smaller than the wavelength of light is key to the development of integrated photonic devices for computing, communications and sensing. Wide band gap semiconductor nanostructures with near-cylindrical geometry and large dielectric constants exhibit two-dimensional ultraviolet and visible photonic confinement (i.e. waveguiding). Combined with optical gain, the waveguiding behavior facilitates highly directional lasing at room temperature in controlled-growth nanowires with suitable resonant feedback. The nanowire optical emission has been studied in detail using high-resolution optical microscopy. This concept of using well-cleaved nanowires as natural optical cavities may be extendable to many other different semiconductor systems. We have further explored the properties and functions of individual ultralong crystalline oxide nanoribbons that act as subwavelength optical waveguides and assess their applicability as nanoscale photonic elements. The length, flexibility and strength of these structures enable their manipulation on surfaces, including the optical linking of nanoribbon waveguides and other nanowire elements to form networks and device components. We have demonstrated the assembly of ribbon waveguides with nanowire light sources and detectors as a first step toward building nanowire photonic circuitry. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 13 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 14 ONE-DIMENSIONAL SEMICONDUCTING AND PIEZOELECTRIC NANOSTRUCTURES SYNTHESIS, GROWTH MECHANISMS AND PROPERTIES Zhong Lin Wang School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta 30332-0245 Nanowire and nanotube based materials have been demonstrated as building blocks for nanocircuits, nanosystems and nano-optoelectronics. Quasi-one-dimensional nanostructures (so called nanobelts or nanoribbons) have been successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium and gallium, by simply evaporating the desired commercial metal oxide powders at high temperatures [1]. The belt-like morphology appears to be a unique and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. Using the technique demonstrated for measuring the mechanical properties of carbon nanotubes based on in-situ transmission electron microscopy [2,3], the bending modulus of the oxide nanobelts, the workfunction at the tip have been measured. Field effect transistors [4] and ultra-sensitive nano-size gas sensors [5], nanoresonators and nanocantilevers [6] have also been fabricated based on individual nanobelts. Thermal conductivity of a nanobelt has also been measured. Very recently, nanobelts, nanorings and nanosprings that exhibit piezoelectric properties have been synthesized, which are potential candidates for nano-scale traducers, actuators and sensors [7, 8, 9, 10]. This presentation will focus on our recent progress in the controlled growth, nano-scale property measurements and nano-size device fabrication using oxide nanostructures that are semiconducting and piezoelectric. [1] Z.W. Pan, Z.R. Dai and Z.L. Wang, Science, 209 (2001) 1947. [2] P. Poncharal, Z.L. Wang, D. Ugarte and W.A. de Heer, Science, 283 (1999) 1513; Electron Microscopy of Nanotubes, ed. Z.L. Wang and C. Hui, Kluwer Academic Publisher (2003). [3] R.P. Gao, Z.L. Wang, Z.G. Bai, W. de Heer, L. Dai and M. Gao, Phys. Rev. Letts., 85 (2000) 622; Z.L. Wang, P. Poncharal and W.A. De Heer, Pure Appl. Chem. Vol. 72 (2000) 209. [4] M. Arnold, P. Avouris, Z.L. Wang,. Phys. Chem. B, 107 (2002) 659. [5] E. Comini, G. Faglia, G. Sberveglieri, Zhengwei Pan, Z. L. Wang Appl. Phys. Letts., 81 (2002) 1869. [6] W. Hughes and Z.L. Wang, Appl. Phys. Letts., 82 (2003) 2886. [7] X.Y. Kong and Z.L. Wang, Nano Letters, 2 (2003) 1625 + cover. [8] Z.L. Wang, X.Y. Kong and J.M. Zuo, Phys. Rev. Letts. 91 (2003) 185502. [9] " Nanowires and Nanobelts – materials, properties and devices; Vol. I: Metal and Semiconductor Nanowires”, Vol. II: Nanowires and Nanobelts of Functional Materials” edited by Z.L. Wang, Kluwer Academic Publisher (2003). [10] X.Y. Kong, Y. Ding, R.S. Yang, Z.L. Wang, Science, 303 (2004) 1348. [11] For details: http://www.nanoscience.gatech.edu/zlwang/ Research sponsored by NSF, NASA and DARPA. Email: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 14 China-US Workshop on Materials Science Abstract 15 STRUCTURE, GROWTH AND MODIFICATION OF NANOSTRUCTURES MADE FROM LAYERED METAL OXIDES L. M. Peng, Q. Chen, S. Zhang, X. Ding and X.G. Xu Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China Nanostructures of lamellar oxides, especially inorganic fullerene-like nanostructures and inorganic nanotubes [1] are important due to their great potential for applications in, e.g. solid lubrication, catalyst, hydrogen storage, anode materials in rechargeable lithium batteries and water splitting, which could be a source of clean energy. These nanostructures may be synthesized using the hydrothermal method at relatively low temperature (typically 100 degree). Extensive investigation has been carried out in our group for the structure and growth of titanate nanotubes [2-3], potassium hexaniobate nanotubes [4,5], KTiNbO5 nanosheets [6] and potassium titanate nanowires [7-9]. We will briefly discuss the common structural aspects of these nanostructures, their formation mechanism [10,11] and modification of their structures and properties via intercalation and exfoliation methods [12]. References: 1. R. Tenne, L. Margulis, M. Genut, and G. Hodes, Nature 360 (1992) 444 2. Preparation and structure analysis of titanium oxide nanotubes, by G.H. Du, Q. Chen, R.C. Che, Z.Y. Yuan and L.-M. Peng, Appl. Phys. Lett. 22 (2001) 3702 3. Trititanate nanotubes made from a single alkali treatment, by Q. Chen, W. Zhou, G.H. Du and L.-M. Peng, Adv. Mater. 14 (2002) 1208 4. Imaging helical potassium hexaniobate nanotubes, by G.H. Du, L.-M. Peng, Q. Chen, S. Zhang and W.Z. Zhou, Appl. Phys. Lett. 83 (2003) 1638 5. Synthesis, modification and characterization of K4Nb6O17-type nanotubes, G.H. Du, Q. Chen, Y. Yu, S. Zhang, W.Z. Zhou and L.-M. Peng, J. Mater. Chem., 14 (2004) 1437-1442 6. Exfoliating KTiNbO5 particles into nanosheets, by G.H. Du, Y. Yu, Q. Chen, R.H. Wang, W.Z. Zhou and L.-M. Peng, Chem. Phys. Lett. 377 (2003) 445-448 7. Potassium titanate nanowires: structure, growth and optical property, by G.H. Du, Q. Chen, P.D. Han, Y. Yu and L.-M. Peng, Phys. Rev. B67 (2003) 035323 8. Synthesis and characterization of K2Ti6O13 nanowires, by B. L. Wang, Q. Chen, R. H. Wang , L. -M. Peng, Chem. Phys. Lett. 376/5-6 (2003) 726-731 9. Strain-induced formation of K2Ti6O13 nanowires via ion exchange, by R. H. Wang, Q. Chen, B. L. Wang, S. Zhang, and L.-M. Peng, Appl. Phys. Lett. 86, (2005) 133101 10. Formation mechanism of H2Ti3O7 nanotubes, by S. Zhang, L.-M. Peng, Q. Chen, G.H. Du, G. Dawson and W.Z. Zhou, Phys. Rev. Lett. 91 (2003) 256103-1:4 11. Structure and formation of H2Ti3O7 nanotubes in an alkali environment, by S. Zhang, Q. Chen, and L.-M. Peng, Phys. Rev. B 71 (2005) 014104 12. This work was supported by the NSF of China, Peking University and the National Center for Nanoscience and Technology. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 15 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 16 COLLOIDAL SEMICONDUCTOR QUANTUM WIRES: SYNTHESIS, SPECTROSCOPY, AND CONFINEMENT EFFECTS William E. Buhro Department of Chemistry, Washington University, St. Louis, MO 63130-4899 The recent availability of soluble III-V and II-VI quantum wires having diameters in the range of 3 – 20 nm has afforded new opportunities to experimentally determine how quantum confinement is influenced by the geometric dimensionality of confinement. Quantum wires are ideal 2D-confinement systems, the properties of which may be compared to those of the analogous 3D-confined dots, 1D-confined wells, and anisotropically 3D-confined rods. The synthesis and spectroscopic behavior of several sets of quantum wires, grown by the solution-liquid-solid mechanism, will be described. The absorption and emission spectra of the wires are used to analyze the band gaps and photoluminescence quantum yields, which are compared to theory and to experimental data from wells, rods, and dots. The results confirm 2D quantum confinement in the wires, and establish quantitatively how the confinement in dots, rods, wires, and wells should differ. We have observed weak room-temperature photoluminescence from the colloidal quantum wires. Our studies show that the photoluminescence quantum yields are influenced by factors previously known to influence quantum yields in quantum dots. These factors include preparative conditions, use of long-chain primary amine surfactants, post-synthesis photo-etching and photo-annealing, and introduction of wider-band-gap inorganic shells. We are also determining how single-nanowire spectroscopic behavior compares to the ensemble spectroscopic measurements. These and related studies will be described. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 16 China-US Workshop on Materials Science Abstract 17 SYNTHESES OF ORDERED NON-SILICA MESOPOROUS MATERIALS Dongyuan Zhao Department of Chemistry, Fudan University, Shanghai, 200433, P. R. China Supramolecular templated mesoporous materials have drawn more and more attention since the discovery of ordered silica or aluminosilicate mesoporous materials one decade ago. Subsequently, the strategy was extended to the synthesis of non-siliceous mesoporous materials that exhibit marvelous properties for catalytic, electronic and magnetic applications. Here we bring forward an "acid-base pairs" concept and report the successful syntheses of a wide variety of highly ordered, large pore, homogeneous, stable mesostructured solids, including various metal oxides (TiO2, Nb2O5), mixed metal oxides (ZrW2Ox, CeTi3Ox), metal phosphates (TiPO, AlPO, NbPO, LiTi2(PO4)3), silico-aluminophosphates (SAPO), and metal borates (AlBO, TiBO) mesostructured phases, and various mixed metal oxides. The composition can be predictively designed and tuned as long as proper inorganic sources are chosen, based on the acid-base characters of the precursors. Highly ordered periodicity and different symmetry mesostructures are accessible. e.g. 2D hexagonal (P6m), 3D body-centerd cubic, Im3m, 3D bicontinuous cubic, Ia3d and lamellar, L. The mesoporous metal oxides have remarkable thermal stabilities (up to 900C), BET surface areas of 100-300 m/g, mesopore sizes of 4-15 nm, and pore volumes of 0.2-0.6 cm/g. Highly ordered mesoporous bioactive glasses (MBGs) with CaO-P2O5-SiO2 compositions have also been synthesized by block copolymer EO20PO70EO20 templating and shown superior in vitro bone-forming bioactivities. The calcined MBG shows a well-ordered 2D hexagonal (P6mm) mesostructure with a cell parameter (a) of 8.50 nm and have uniform mesopores size 4.5-8 nm, high surface area (up to 500 mg) and pore volume (0.5 cmg). Highly ordered, high surface area, soft mesoporous polymers have successfully been synthesized by using surfactant-templating approach. XRD pattern shows mesoporous soft polymers can be a well-ordered 2D hexagonal (p6mm) or/and 3D cubic (Im3m) or/and lamellar mesostructures. We employ microwave digested mesoporous materials to direct the various metal oxide nanowire or nanosphere superlattice formation. The obtained mesostructured metal nanowires are ordered arrays and perfect replica of mesoporous silica host and have single crystalline nature in the domain. By using this general approach, we are able to synthesize well ordered Co3O4, Cr2O3, MnxOy, Fe2O3, NiO, CuO, In2O3, CeO2, ITO, MnNiOx and LaMnO3 patterned nanostructures. Those nanoarrays show high BET surface areas (50-150 m/g), high thermal stabilities (generally above 300C) and uniform Nanopores (inter-crystalline voids). Ordered metal oxide nanopatterns are generally prepared guided by the direct "host-guest inclusion chemistry". The mesostructures can be hexagonal nanowire arrays or cubic nanosphere arrays, depending on their "host" topologies. References: (1) B. Tian, X. Liu, B. Tu, C. Yu, J. Fan, S. Xie, D. Zhao, Nature Materials 2003, 2, 159-163. (2) H. Yang, Q. Shi, B. Tian, Q. Lu, F. Gao, S. Xie, D. Zhao, J. Am. Chem. Soc., 2003, 125, 4724. (3) B. Tian, X. Liu, C. Yu, F. Gao, Q. Luo, S. Xie, B. Tu, D. Zhao, Adv. Mater. 2003, 15, 1286. (4) F. Cao, Q. Lu, D. Zhao, Adv. Maters., 2003, 15, 739. (5) X. Yan, C. Yu, X. Zhou, J. Tang, D. Zhao, Angew. Chem. Int. Ed., 2004, 43, 5980-5984. (6) B. Tian, X. Liu, L. A. Solovyov, Z. Liu, H. Yang, Z. Zhang, S. Xie, F. Zhang, B. Tu, C. Yu, O. Terasaki, D. Zhao, J. Am. Chem. Soc. 2004, 126 , 865-875. (7) H. Yang, Y. Yan, Y. Liu, F. Zhang, R. Zhang, Y. Meng, M. Li, S. Xie, T. Tu, D. Zhao, J. Phys. Chem. B., 2004, 108, 17320-17328. Email: [email protected]; Tel: 86-21-6564-2036, Fax: 86-21-6564-1740 May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 17 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 18 NANOCRYSTALS AND NANOWIRES: FROM FUNDAMENTAL SCIENCE TO APPLICATIONS Yi Cui Department of Chemistry, University of California, Berkeley Semiconductor quantum dots and nanowires represent critical building blocks for nanotechnologies, since their size, shape, composition and properties can be precisely defined. Herein, I present results addressing key aspects of the synthesis, structures, electronic properties, self-assembly and device applications of these nanostructures. For quantum dots, the size and shape are controlled during solution phase synthesis exploiting the hot surfactants. They show spherical, rod and tetrapod-like shapes depending on the growth conditions. Colloidal nanocrystals represent an important type of nanomaterials for electronics, photonics and energy conversion. Understanding the electronic coupling characteristics of self-assembled nanocrystal materials is essential for these applications. I present my recent research in studying coupling in different forms of self-assembled nanocrystal systems. First, semiconductor nanotetrapods are unique self-assembled systems of quantum dots and rods. I have demonstrated by single electron transistor measurements that either ionic or covalent bonding-type of coupling can exist when the interaction between the quantum dot at the junction and the arm rods is weak or strong, respectively. Second, I have developed a facile fluidic method for organizing nanocrystals into large-scale device arrays, which incorporates a controlled number of nanocrystals at lithographically precise locations on a chip and within a circuit. The method provides interesting systems for studying chemically-tunable coupling phenomena. For semiconductor nanowires, the properties of nanowires, such as diameter, length, dopant type (p and n-type) and doping concentration could be precisely controlled during gas-phase synthesis. The n-type and p-type nanowires also have been assembled into key functional nanoelectronic devices such as nanoscale field effect transistors, cross pn junctions, bipolar tranisistors and inverters. The large sensitivity of precisely doped nanowires to gate-voltage in solid state devices suggests that molecular gating could be utilized to create ultra-sensitive chemical and biological sensors. Therefore, I describe a nanowire based sensor that enables label-free, highly-sensitive real-time electrical detection of a wide range of chemical and biological species. The detection of pH, metal ions, protein and DNA are demonstrated. In addition, the application of nanowire sensors for ultrasensitive cancer diagnostics and stochastic single molecule detection will be discussed. These results also imply that nanowires have the great potential for super high integration, enabling high density electronics and sensors for simultaneous multispecies detection and revolutionizing genomics and proteomics. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 18 China-US Workshop on Materials Science Abstract 19 CARBON NANOTUBES AND NANO-CLUSTERS UNDER HYDROSTATIC PRESSURE X. G. Gong Department of Physics, Fudan University, Shanghai-200433, China Pressure is usually used as a useful tool to study the physical properties of materials at meta-stable phases. Nano-materials, due to their “surface effect” and “size effect”, can have rich properties of the meta-stable phase. In this talk, after briefly introduced the constant pressure method specially developed for the nano-system, we will present our simulated results for the pressure-induced hard-soft structural transition for isolated carbon nanotube, bundles of the carbon nanotubes. We will also show the results of the pressure-induced fcc-Ih transition for the Ni nano-particles. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 19 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 20 SOME CHALLENGES IN THE INTEGRATION OF SEMICONDUCTOR MICROPROCESSING TECHNOLOGY AND MOLECULAR ASSEMBLY Galen D. Stucky Department of Materials, Department of Chemistry & Biochemistry, University of California, Santa Barbara, CA 93106 The organization and integration of multiple functional components into integrated device systems can currently be carried out, through the use of current semiconductor microfabrication techniques, with high precision and, most importantly, with inter-component interface integrity that enables efficient information transfer. This technology becomes less practical when one approaches the 20-100 nm length scale and the limits of the compositional and organization flexibility inherent in the two-dimensional assembly procedures that are used. An alternative approach is the use of molecular assembly to combine synthesis, 3-D nanoscale assembly, and processing of function to create macroscopic material systems. A fascinating aspect of this route is the use of nonlinear molecular assembly to create complex emergent or gradient materials with different functionality on the 100-nm length scale or smaller. However, this also has its challenges, particularly with respect to creating multiple interfaces with efficient and well-defined electron and photon transport. A promising strategy might be to combine the precision, reproducibility, and massive parallel processing of semiconductor device microfabrication with the generality and flexibility of molecular self-assembly chemistry. A primary challenge of such a combination is to demonstrate constructive interfacing of different functionalities made by both molecular assembly and semiconductor microprocessing. As an example, the coupling of externally emitted photons generated within a matrix generated by 3-D molecular assembly integrated with an MBE-generated semiconductor microdisk resonator will be described. We will discuss the external coupling behavior and efficiency in terms of spatial position of the emitter, properties of the silica host matrix, and microdisk dimensions. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 20 China-US Workshop on Materials Science Abstract 21 MONODISPERSE NANOCRYSTALS AND NANOSPHERES Xun Wang, Qing Peng, Yadong Li Department of Chemistry, Tsinghua University, Beijing, China Monodisperse nanocrystals/nanospheres with well-designed compositions, crystal structures, sizes and surface properties are appealing to a wide range of research areas including catalysis, optics, biological label and nanodevices fields, because of their potentials in the understanding of magnetic, dielectric and transport properties in nanometer regime as well as their size-dependent properties. In this presentation, we will demonstrate the general synthesis of a broad range of nanocrystals and nanospheres, based on which, the underlying principle in size and shape control in nanoscale will be discussed. A bubble mechanism has been demonstrated to guide the growth of monodisperse ZnSe nano/micro spheres with controllable sizes, with which as templates various oxides, sulfide and selenide semiconductors nanospheres and/or core-shell structures with tunable band gap could be readily obtained through a facile chemical conversion way. Due to their controllable optoelectric properties and self-assembly characteristics, these nanospheres may serve as ideal candidates for applications in solar cell and optoelectric nanodevices. A green synthetic strategy has been developed to obtain natural polymer nanopsheres with biocompatible surfaces, and with these monodisperse nanoshperes as sacrificing templates, various hollow spheres of oxides or nitride semiconductors were successfully prepared. These nanospheres also show their amazing ability in embedding noble metal and/or magnetic nanocrystals to form functional core-shell structures, which have shown some interesting SERS properties and may find applications in biological fields. A general model to get monodisperse nanocrystals has been presented to show the whole picture of the growth of functional nanocrystals with diverse crystal structures and compositions, including noble metal, semiconductors, magnetic/dielectric and fluorescence nanocrystals. The general principles in size control will be discussed. With these monodisperse nanocrystals as functional building blocks, some more unique and exciting applications could be driven from the bottom-up approach to nanoscience and nanotechnology fields. Despite the diversity in crystals structures and properties, we have succeeded in preparing nearly all the functional nanocrystals / nanospheres with controllable size and surface properties, which show the possibilities of the final establishment of a general methodology to low-dimensionality nanostructures and will certainly arouse some new opportunities to nano-related fields. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 21 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 22 TUNING INTERMOLECULAR INTERACTIONS TO CREATE ONE-DIMENTIONAL ORGANIC SEMICONDUCTING NANOSTRUCTURES T.-Q. Nguyen Department of chemistry and Biochemistry, University of California, Santa Barbara, CA, USA Figure 1: Chemical structure of hexa-substituted aromatic compound and dipolar stacks of these molecules to form columnar structures/fibers. Understanding the self-assembly process and molecular arrangement and the ability to control the self-assembly direction are crucial for fundamental and applied research in nanoscience. In our search for one-dimensional (1D) molecular semiconductors, we explore in detail the assembly process of hexa-substituted aromatic compounds in order to find the conditions favoring strong molecular interaction and perhaps molecular conduction. These molecules contain specific functional groups designed to promote self-assembly into molecular wires/fibers via strong intermolecular interactions such as hydrogen bonds, donor-acceptor, or π-π interactions (see Fig. 1). They compose of a conducting core made of a -intermolecular system and an outer insulating layer (alkyl groups). These molecules have the tendency to pack in columnar structures due to the strong π-π interactions and hydrogen bonds (Fig. 2). They are easily synthesized and highly soluble in common organic solvent. Depending on the side-groups and processing conditions, the molecules can either form long wires parallel to the surface (edge-on orientation) or columnar stacks perpendicular to the substrate (face-on orientation). Figure 2 shows the atomic force microscopy (AFM) images (A, B, and C) of the hexa-substituted aromatic compounds. Electrostatic Force Microscopy (EFM) was used to further confirm the orientation of the molecules on surfaces by measuring the surface charge density of these thin films. 800 nm 300 nm 400 nm A B C D E Figure 2: AFM images (A, B, and C) and STM images (D and E) of hexa-substituted aromatics with different side chains. Scanning tunneling microscopy (STM) studies show different molecular packing and spacing between monomers as the side chains are altered (Fig. 2 D and E). Using a larger the π-core and smaller the functional group, the distance between the molecules within a columnar stack can be reduced. We also found that the molecules self-assemble in solution prior to deposit onto a substrate; therefore, solvent and concentration can be used to control the self-assembly process. Additionally, due to a strong permanent dipole moment present in each molecule, electric field is used to direct the self-assembly across a pair of electrodes. The self-assembly of hexa-substituted aromatics into columnar structures on surface offers a unique possibility for 1D charge transport along the stacking direction. Email: [email protected] Tel: (805) 893-4851, Fax: (805) 893-4120 May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 22 China-US Workshop on Materials Science Abstract 23 EQUILIBRIUM SELF-ASSEMBLY OF CONJUGATED BLOCK COPOLYMERS Rachel Segalman Chemical Engineerin, UC Berkeley The synthetic chemistry and device physics of organic optoelectronics are rapidly bringing lightweight, inexpensive, flexible light emitting diode and solar cells closer to reality. While the collective knowledge of electrical properties of these materials is growing rapidly, relatively little is known about their thermodynamic or mechanical properties. Most conductive polymers are fully π-conjugated so that the bonds along the backbones are not freely rotating joints, but rather the molecules behave as rigid rods and do not tend to coil or entangle in a manner similar to classical polymers. Recent breakthroughs in the device physics of these materials have also demonstrated that the morphology of interfaces between two conducting organics of different work function play an integral role in the separation of electrons and holes to generate light in a photovoltaic cell or conversely in the recombination necessary to generate light. Moreover, it is the thermodynamic properties that control this crucial nanometer scale morphology of the active layer. Studies of conductive polymer thermodynamics are made more complicated because these polymers do not follow classical predictions. Furthermore, most rod-coil block copolymer systems are highly segregated resulting in kinetic trapping of non-equilibrium phases and inaccessible order-disorder transitions. We have synthesized a model rod-coil block copolymer consisting of a conjugated rod block with regularly spaced flexible sidechains similar in composition to the coil (see figure below). We demonstrate that by careful tuning of sidechain chemistry and block interactions, we can gain insight into the complex self-assembly of these materials. In this model system, the sidechains protect the rod from enthalpic interactions with the coil while maximum conformational asymmetry is maintained and we observe lamellae, a phasemixed nematic phase and finally an isotropic, mixed phase as temperature is increased. In this talk, I will discuss the effects of molecular conformation (conjugation) on self-assembly and describe the experimental phase diagram of a new weakly segregated rod-coil block copolymer. I will also discuss our observations of the effect of packing on the Flory-Huggins parameter and compare our results to simulations of rod-coil block copolymer phase separation. I will also discuss possible applications of this unique system. Self-Assembling conjugated rod-coil block copolymer. This symmetric block copolymer forms lamellae with a spacing of ~20nm. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 23 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 24 CHALCOGENIDE TETRAHEDRAL CLUSTERS AND THEIR SUPERLATTICES Pingyun Feng Department of Chemistry, University of California, Riverside, California 92521 Chalcogenide tetrahedral clusters and their superlattices represent an interesting class of materials that combines uniform porosity with high electrical conductivity and tunable optical properties. They consist of single-sized tetrahedral clusters that act as molecular building blocks in the formation of well-ordered superlattices from zero to three dimensions. Tetrahedral clusters can be joined directly to produce purely inorganic frameworks or by multidentate organic ligands to form inorganic-organic hybrid frameworks. A number of main-group and transition metals have been incorporated into clusters to allow the modification of structural and physical properties. The structural analysis based on single crystals reveals detailed information that could help the structural elucidation of larger colloidal nanostructures. The synthesis, structures, and various properties such as porosity, photoluminescence, photocatalytic property, and fast ion conductivity will be discussed. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 24 China-US Workshop on Materials Science Abstract 25 DIRECTED ASSEMBLY OF METAL-CYANIDE CLUSTER MAGNETS Hye Jin Choi, Jennifer J. Sokol, Matthew P. Shores, and Jeffrey R. Long Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA General strategies will be presented for the synthesis of metal-cyanide coordination clusters, primarily intended for study as single-molecule magnets. Such cluster magnets are of widespread current interest for their potential applications in high-density information storage and quantum computing, as well as for the investigation of new physical phenomena such as quantum tunneling of magnetization. We contend that the relative simplicity of the structures and magnetic exchange pathways in metal-cyanide cluster systems (as evinced by analogies with Prussian blue type solids) renders them significantly more amenable to the design of single-molecule magnets with higher energy barriers to spin reversal. Figure 1. Structure of the trigonal prismatic cluster [(Me3tacn)6MnMo6(CN)18]. The ability to utilize organic blocking ligands in directing the formation of specific metal-cyanide cluster geometries has been demonstrated with the synthesis, for example, of simple cubic [(tacn)8Co8(CN)12] and face-centered cubic [(Me3tacn)8Cr8Ni6(CN)24]12+ clusters. A variety of unexpected cluster geometries have also been encountered, including double face-centered cubic [(Me3tacn)14Cr14Ni13(CN)48]20+, the largest metal-cyanide cluster yet reported. The substitution of appropriate paramagnetic metal ions into these clusters has led to ground states of up to S = 18, and new species with spins as high as S = 32 are within reach. Incorporation of metal ions possessing a large axial zero-field splitting into such structures is being pursued similarly as a means of generating the axial magnetic anisotropy requisite of a single-molecule magnet. Indeed, the efficacy of this strategy has already been demonstrated with the substitution of Mo for Cr to afford trigonal prismatic [(Me3tacn)6MnMo6(CN)18]2+ (see Figure 1) the first cyano-bridged single-molecule magnet. The viability of our overall approach has been validated recently with the synthesis of [(cyclen)4(H2O)2Mn4Mo2(CN)14], a cluster exhibiting a record spin reversal barrier of 62 cm. Selected Reference (1) “Directed Assembly of Metal-Cyanide Cluster Magnets” Beltran, L. M. C.; Long, J. R. Acc. Chem. Res. 2005, 38, ASAP. Email: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 25 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 26 LOW DIMENSIONAL AZIDO-BRIDGED MOLECULAR MAGNETS: ORDER OR DISORDER Song Gao, Haoling Sun, Yuanzhu Zhang, Xinyi Wang, Zheming Wang State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R.China As a versatile bridging ligand, the azido ion has shown the ability to link two or more metal ions in various modes, μ-1,1 (end-on, EO), μ-1,3 (end-to-end, EE), μ-1,1,1, μ-1,1,3 etc., giving rise to a variety of zeroto three-dimensional polynuclear complexes, which show colorful magnetic behaviors. Recently we focus our attention on low dimensional magnetism of azido-bridged complexes, especially the Co(II)-containing 0D to 2D systems, to obtain new molecular nanomagnets including “single-molecule-magnets” and “single-chain-magnets”. The magnetic ordering and slow magnetic relaxation are investigated for these low dimensional materials. A few typical compounds prepared in our laboratory are depicted below. Email: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 26 China-US Workshop on Materials Science Abstract 27 ELECTRONIC STRUCTURE AND TRANSPORT PROPERTIES OF SINGLE MOLECULES AND NANOPARTICLES Jianquo Hou Hefei National Laboratory for Physical Sciences at Microscale, USTC, Hefei, Anhui Province, China May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 27 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 28 NANOCALORIMETRY: USING SI-MICROMACHINED DEVICES FOR THERMODYNAMIC MEASUREMENTS OF THIN FILMS AND TINY CRYSTALS Francis Hellman Department of Physics and Materials Science and Engineering, University of California, Berkeley, CA 94720-7300 We have used Si micromachining techniques to fabricate membrane-based calorimeters for measuring thermodynamic properties of microgram-quantity samples over a temperature range presently from 1.7 to 550K in magnetic fields to 8T. Prototype scaled down devices have been made which allow precise measurements of nanogram quantities. Different types of thermometers are used for different purposes and in different temperature ranges. Current development efforts are extending the temperature range to 0.3K and 800K, and we are collaborating with the US national high magnetic field lab to extend the field range to 65T in pulsed magnets. These devices are particularly useful for specific heat measurements of thin film samples (typically 100-400 nm thick at present) deposited directly onto the membrane through a Si micromachined evaporation mask. They have also been used for small bulk samples attached by conducting grease, Ga or In, and for powder samples dissolved in a solvent and dropped onto devices. The measurement technique used (relaxation method) is particularly suited to high field measurements because the thermal conductance can be measured once in zero field and is field independent, while the time constant of the relaxation does not depend on thermometer calibration. The devices also have been used with very little modification for thermal conductivity and thermopower measurements, and are also well suited to measurements of calorimetric signals such as those occurring at phase transitions or under irreversible thermal behavior. I will discuss device fabrication and thermal analysis which allow us to precisely identify heat flow in the devices and consequent limits on the absolute accuracy, as well as possible future directions for device development. I will also briefly discuss examples of thermodynamic measurements on several materials of current interest: 1) amorphous SiNX and amorphous RE-doped Si alloys, 2) high precision critical temperature studies of single crystal ferromagnetic SrRuO3, La1-xSrxMnO3 and La1-xCaxMnO3, 3) antiferromagnetic CoO nanoparticles and thin layers, 4) Fe/Cr giant magnetoresistance multilayers. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 28 China-US Workshop on Materials Science Abstract 29 POSITIONING DISSECTION, ISOLATION AND SEQUENCING OF SINGLE DNA MOLECULES BASED ON NANOMANIPULATION AND SINGLE MOLECULE PCR Junhong Lü , Haikuo Li , Hongjie An , Guohua Wang , Ying Wang , Minqian Li , Yi Zhang, Jun Hu a b a Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China; b Bio-X Life Science Research Center, Shanghai JiaoTong University, Shanghai 200030, China Recently, the isolation and biochemical analysis of DNA at the single-molecule level has been recognized very important for genetic research and clinical analysis. A unique technique for the positioning dissection and isolation of single DNA molecules by using atomic force microscopy (AFM) has been demonstrated. Full-length genome DNA molecules were firstly deposited and stretched by a modified “Molecular Combing” technique onto a 3-aminopropyl triethoxysilane-coated mica substrate. Single DNA fragment was dissected from one of that genome DNA strands with the AFM tip at the desired position, and then isolated (or picked up) after a special operation called “kneading”. All the operations including imaging, dissection and isolation could be carried out with one tip. The isolated DNA fragment on the AFM tip could be successfully amplified by single molecule PCR. Sequencing results showed that the isolation and amplification process did not change the sequences of the single DNA fragments. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 29 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 30 DISCOVERING COMPLEX DEFECT ARCHITECTURES VIA SINGLE-CRYSTAL DIFFUSE SCATTERING Branton Campbell Department of Physics & Astronomy, Brigham Young University, Provo, UT 84602, USA The presence of short and intermediate-range structural correlations, even in small volume concentrations, can dramatically alter macroscopic material properties. X-ray and neutron single-crystal diffuse scattering (SCDS) methods are ideally suited to the structural characterization of these subtle and sometimes transient features. Due to marked improvements in source brightness, detector capability, and computational power, it is now possible to probe complex local structures with unprecedented speed, range, and sensitivity. In this seminar, we will examine recent successes including the discovery of superstructural lattice distortions in the high-TC cuprates, polaronic charge-density waves in the colossal magnetoresistive manganites and linear fault defects in a zeolite catalyst. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 30 China-US Workshop on Materials Science Abstract 31 IN-SITU TRANSMISSION ELECTRON MICROSCOPY STUDIES OF THE DEFORMATION RESPONSE OF NANOCRYSTALLINE METALS Eric. A. Stach, Zhiwei Shan , Miao Jin , A. Minor , Scott X. Mao , Joerg M.K. Wiezorek, David M. Follstaedt , John Knapp 6 and J.W. Morris, Jr. 3 1 School of Materials Engineering, Purdue University, West Lafayette, In 47907 2 Department of Mechanical Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA 3 Department of Materials Science and Engineering, University of California, Berkeley, USA 94720 4 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 5 Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA 6 Physical and Chemical Science Center, Sandia National Laboratories, Albuquerque, NM 87185, USA It is has long been known that the grain size of a material has a substantial effect on its mechanical strength, through the well-established Hall-Petch relationship. In the past decade or so, there has been a resurgence of interest in this topic resulting from the ability to create metals with grain sizes in the deep sub-micron to nanocrystalline scale via a variety of processing techniques. In these materials, it has been conjectured that it may no longer be possible to deform individual grains via simple unit dislocation processes, and other mechanisms may be required to achieve plastic flow. Here we utilize the technique of in-situ transmission electron microscopy to directly image how deformation proceeds in materials with grains sizes in the sub-micron and deep nanocrystalline regime. In the first portion of the presentation, we will review our work in the area of in-situ nanoindentation of sub-micron and nanocrystalline evaporated aluminum, while in the second portion, we will compare these results with in-situ uniaxial straining of pulsed-laser deposited (PLD) nickel. We have constructed a unique sample holder for transmission electron microscopy that allows us to perform localized nanoindentation into the edge of an electron transparent material. This permits us to dynamically observe the processes by which mechanical deformation proceeds. During the nanoindentation of sub-micron grains, we find that deformation induces grain growth, resulting from grain boundary migration, grain rotation and grain coalescence. In-situ studies of nanograined films suggest that the same mechanisms are operative, though the difficulty of these nanosized grains makes the evidence less clear (Jin, et al. Acat Mat, 2004). Uniaxial straining experiments of PLD nickel provide additional strong evidence of grain rotation and grain agglomeration. Through the use of dark-field imaging, we have conclusively demonstrated that that when the grain size is on the order of 10 nm grain rotation can become a prominent deformation response. However, even at these small grain sizes, we find that dislocations are trapped within the grains, indicating that dislocation processes are still active. (Shan, et al. Science, 2004) May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 31 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 32 CONTROLLED SYNTHESIS OF NANOWIRE AND NANOTUBE ARRAYS Kai Liu, Shuaiping Ge, Peng Li, Kaili Jiang, Shoushan Fan Department of Physics & Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, P. R. China Assembling carbon nanotubes (CNTs) into macroscopic structures is of great importance to their applications. Since the discovery of the CNT, much progress has been made in vertically aligning CNTs into arrays on substrates, which has found use in field emission display. However, little work has been done on laterally aligning CNTs into continuous CNT yarns or ropes. Here we show a new finding that CNTs can be self-assembled into yarns simply by being pulled out from super-aligned CNT arrays. In this process, the CNT array served as a cocoon. The pure CNT yarn is made of well-aligned CNT segments that are end to end jointed by van der Waals interaction. The CNT polarizer extending to ultraviolet (UV) region was implemented by parallel aligning a large multitude of yarns. The yarns were also used as filaments of a light bulb, which emitted incandescent light with small power consumption. Moreover, the strength and the conductivity of the CNT yarns can be considerably enhanced by high temperature treatment, which may further lead to a variety uses of the yarns at macroscopic level. Silicon nanowire arrays were synthesized by a catalytic chemical vapor deposition (CCVD) method on (100), (110) and (111) silicon substrates. The as synthesized SiNWs were single crystalline with axial direction along [111]. Further more, almost each SiNW naturally oriented perpendicularly to one set of the {111} planes of the substrate. As a result, the orientation of the SiNW array can be fully controlled by the crystal orientation of the substrate. These well-aligned SiNW arrays form regular networks on the substrate, and their orthographic projections on (100), (111) and (110) substrates form rectangular networks, triangular networks and parallel straight-lines respectively. These regular nanowire networks are of great importance in constructing nanoscale electronic and photonic devices. Corresponding author: [email protected] Presentation author: Kaili Jiang May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 32 China-US Workshop on Materials Science Abstract 33 FIELD ELECTRON EMISSION OF QUASI ONE-DIMENSIONAL MATERIALS OF SEMICONDUCTORS OF WIDE ENERGY BAND GAPS Zhibing Li, Shaozhi Deng, Jun Chen, Junchong She and Ningsheng Xu The State Key Laboratory of Optoelectronic Materials and Technologies, Department of Physics, Zhongshan University, Guangzhou, 510275, China Quasi one-dimensional materials have attracted great interest because of their unusual electronic and mechanical properties. Since the discovery of carbon nanotubes, nanorods and nanowires of many materials have been synthesized. We will present our recent results about the synthesis and field emission of nanorods and nanowires of varying semiconductors, including silicon carbide, cupric oxide, copper sulphide materials, zinc oxide, and tungsten oxides. The wide energy band gap materials are mostly concerned since these materials offer the potential to develop a new generation of microand nano-electronic devices that can operate at high power levels, high temperatures, and in harsh environment. They are attractive also because they usually have large thermal conductivity and high saturation drift velocity. To our surprise, it is observed that the nanowires and nanorods of wide energy band gap can also have good properties of field electron emission. For instance, the SiC nanorods exhibit high electron field emission with high stability, in particular, under the lowest turn-on and threshold fields so far reported for nanorods. However, the physical mechanism responsible for field emission from quasi one-dimensional wide band gap semiconductor materials is not clear. Very recently we propose a two-current model for explaining such a phenomenon. The nanorod is assumed to have a thin surface layer containing a large number of localized states originating from defects. We demonstrate in first time that a part of a nanorod exhibits an insulator to semimetal transition under high enough fields with direction parallel to its axis, so that field emission occurs at the apex of the metal-like tip. Electron supply is mainly through conduction band in the metal-like part while through hopping between localized states in another part of the nanorod nearing substrate. Our theoretical model is consistent qualitatively with the experimental observations of field emission from nanorods of SiC and ZnO. The potential application of these novel type of field emitter and further theoretical development will also discussed. Corresponding author: [email protected]; [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 33 Abstract China-US Workshop on Materials ScienceChina-US Workshop on Materials Science 34 SURFACTANT ACTION IN SURFACE-BASED NANOSTRUCTURE FORMATION E. G. Wang * Institute of Physics, Chinese Academy of Sciences, Beijing, China In today’s drive for novel materials, it is often highly desirable to fabricate nanostructures with well controlled shape. Such materials are typically unstable from thermodynamic equilibrium considerations, but can be synthesized using non-equilibrium growth techniques such as molecular beam epitaxy (MBE). In this talk, I will show that, when a surfactant layer is used to mediate the growth, a counter-intuitive fractal-to-compact island shape transition can be induced by increasing deposition flux or decreasing growth temperature. Specifically, I introduce a reaction limited aggregation (RLA) theory, where the physical process controlling the island shape transition is the shielding effect of adatoms stuck to stable islands on incoming adatoms. Also discussed are the origin of a transition from triangular to hexagonal then to inverted triangular observed by experiments. Based on our theory, for clean growth, only triangular islands of a fixed orientation are obtained within a wide range of growth temperatures. This novel picture is further corroborated by growth predictions in the presence of CO, whose preferential decoration of one type of the island edges reverses the intrinsic rate disparity for atom supply, thereby inverting the island orientation. Furthermore, I will show that a low dose of Mn on Ge(100) initiates in a novel subsurface growth mode, characterized by easy access to, and strong preference for, interstitial sites located between the two topmost Ge layers. Strikingly, such a “subsurfactant action” is preserved even during epitaxial growth of additional Ge layers. In contrast, along the (111) orientation, Mn can easily diffuse into the bulk via interstitial sites. *In collaboration with Wenguang Zhu, Jing Wu, B.G. Liu, H. H. Weitering, E. Kaxiras, and Z.Y. Zhang. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 34 China-US Workshop on Materials Science Abstract 35 “DO WE KNOW HOW TO THINK ABOUT SURFACE CHEMISTRY? ELECTRONICALLY NON-ADIABATIC INTERACTIONS IN MOLECULE METAL-SURFACE SCATTERING” Alec Wodtke Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106 When molecules with low levels of vibrational excitation collide with metal surfaces, vibrational inducedexcitation of the metal’s electrons is not strong unless incidence energies are high. Furthermore,theoretical studies suggest that elementary steps in surface reactions, like trapping, diffusion anddesorption are not strongly influenced by coupling between adsorbate nuclear motion and metallicelectrons, i.e the Born-Oppenheimer approximation is valid. There have been only a limited number ofstudies that attempt to test the importance of electronically non-adiabatic influences for large amplitudeintramolecular adsorbate motion characteristic of passing through a chemical transition state. Thesestudies provide accumulating evidence that during transition state traversal, electronically non-adiabaticcoupling can be quite strong. Recently, we observed electron emission for a solid metal surface whenhighly vibrationally excited nitric oxide molecules are scattered from a low work function metal surface.These results give direct evidence that interactions between a metal surface and molecules undergoinglarge amplitude intramolecular nuclear motion can promote strong non-adiabatic coupling to excitedelectronic states of the metal. These results suggest that theoretical approaches relying on theBorn-Oppenheimer approximation may not accurately reflect the nature of transition-state traversal inreactions at metal surfaces and point to the need to account for strong electronically non-adiabaticinfluences in theories of heterogeneous catalysis. Related References(1) Chen, J.; Matsiev, D.; White, J. D.; Murphy, M.; Wodtke, A. M. Chem. Phys. (Netherlands) 2004,301, 161.(2) Wodtke, A. M.; Huang, Y.; Auerbach, D. J. J. Chem. Phys. 2003, 118, 8033.(3) Matsiev, D.; Chen, J.; Murphy, M.; Wodtke, A. M. J. Chem. Phys. 2003, 118, 9477.(4) Silva, M.; Jongma, R.; Field, R. W.; Wodtke, A. M. Ann. Rev. Phys. Chem. 2001, 52, 811.(5) Huang, Y.; Wodtke, A. M.; Hou, H.; Rettner, C. T.; Auerbach, D. J. Phys. Rev. Lett. 2000, 84, 2985.(6) Huang, Y. H.; Rettner, C. T.; Auerbach, D. J.; Wodtke, A. M. Science 2000, 290, 111.(7) J. White, J. Chen, D. Matsiev, D.J. Auerbach and A.M. Wodtke, Nature 433(7025),503-505, (2005). May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 35 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 36MOLECULAR DESIGN AND SYNTHESIS OF NEW MATERIALS AND HETEROGENEOUSCATALYSTS T. Don TilleyDepartment of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 This lecture will describe a non-aqueous precursor method for the preparation of mixed-element oxides,which allows molecular-level control over the elemental composition, homogeneity, and nanostructure ofthe resulting materials. This approach, referred to as the thermolytic molecular precursor method,provides heterogeneous catalysts that possess superior properties relative to catalysts with the samecomposition, but prepared by traditional impregnation methods. It has also been found that certainmolecular precursors are useful for introduction of well-defined, surface-attached catalytic species. Withuse of appropriate templates, this synthetic protocol also affords mixed oxides with a homogeneousdispersion of metal atoms throughout the inorganic framework walls of a mesoporous material. Studieson the influence of nanostructures on catalytic behavior will also be described. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA36 China-US Workshop on Materials ScienceAbstract 37AN HISTORICAL PERSPECTIVE ON CATALYSIS AND POLYMERS: THECORNERSTONE OF GE’S ADVANCED MATERIALS BUSINESS Judith SteinGE Global Research, Niskayuna, NY 12309 Catalysts are employed in many important industrial reactions. In the silicones industry, catalysts are usedin both the synthesis of monomers and in polymerizations. Copper is used as a catalyst for the formationof the primary silicon building block, dimethylchlorosilane, which is produced from the heterogeneousreaction of methylchloride and silicon. Although the mechanism is not completely understood, it iswidely accepted that the reaction proceeds through silylenes on the surface of an intermetalliccopper-silicon species. Promoters, such as phosphorus or tin are employed to control the productselectivity.Hydrosilylation is also an industrially important reaction for the formation of carbon-silicon bonds.Platinum catalysts are generally used. The catalytic cycle involves steps similar to those inhydrogenationoxidative additions, migratory insertion and reductive elimination.Commercial applications for silicones include caulks, sealants, rubbers, paper release coatings andadhesives. All of these products are crosslinkedsilicones. Silicones may be crosslinked viahydrosilylation reactions, Lewis acid catalyzedcondensation reactions or side group polymerizationssuch as cationic cures of epoxysilicones. New productsprepared via these reactions will be discussed. May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 37 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 38SUPER-HYDROPHOBIC SURFACES: FROM NATURAL TO ARTIFICIAL Lei JiangCenter of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080,China The wettability of solid surfaces is a very important property, and is governed by both the chemicalcomposition and geometrical microstructure of the surface. Currently, super-hydrophobic surfaces withwater CA higher than 150 are arousing much interest because they will bring great convenience in dailylife as well as in many industrial processes. Various phenomena, such as snow sticking, contamination oroxidation, and current conduction, are expected to be inhibited on such a surface. Conventionally,super-hydrophobic surfaces have been produced mainly in two ways. One is to create a rough structure ona hydrophobic surface, and the other is to modify a rough surface by materials with low surface freeenergy. While the water CA has commonly been used as a criterion for the evaluation of hydrophobicity ofa solid surface, this alone is insufficient to assess the sliding properties of water droplets on the surface. Afully super-hydrophobic surface should exhibit both high CA and low sliding angle.Our recent studies on lotus and rice leaves reveal that a super-hydrophobic surface with both a large CAand small sliding angle needs the cooperation of microand nanostructures, and the arrangement of themicrostructures on this surface can influence the way a water droplet tends to move. These results from thenatural world provide a guide for constructing artificial super-hydrophobic surfaces and designing surfaceswith controllable wettability. Accordingly, super-hydrophobic surfaces of aligned carbon nanotube films,aligned polymer nanofibers and differently patterned aligned carbon nanotube films have been fabricated.The large scale fabrications of super-hydrophobic polymer surfaces have been developed by modificationof the traditional template method, the adoption of one-step coatings and electrohydrodynamics,respectively. The super-hydrophobic surface is also realized in all pH range, which extends its applicationsnot only to pure water, but to acid and base solution as well. By combining the two factors ofsuper-hydrophobic and super-oleoliphilic, the water-oil separation mesh has been built successfully.Considering the arrangement of the microand nanostructures, the surface structures of the water-strider’slegs were studied in detail, indicating the relationships between super-hydrophobicity and orientation ofthe microand nano-scale composite structures, which will guide us to fabricate micro-fluid devicesartificially in the near future. We also studied the wettability of butterfly’s wing, and found that thearrangement of the micro/nano structure influence the flowing direction of water droplet. In further, thecooperation between surface microand nanostructures and surface modification of poly(N-isopropylacrylamide) gave reversible switching between superhydrophilicity and superhydrophobicityin a narrow temperature range of about 10 °C. The transition can be enhanced by depositing the polymeronto patterned silicon substrates. Additionally, UV light stimulated switcher of superhydrophobic andsuperhydrophilic transition by aligned ZnO film are successfully obtained. These two kinds of switchermaterials are intrigue great interest in the world and were reported as Nature News and Science EditorChoice. Email: [email protected]; Tel: 010-82621396 Fax: 010-82627566 May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA38 China-US Workshop on Materials ScienceAbstract 39BONDING CONFIGURATIONS OF GE ATOMS ADSORBED ON SI(111)-7X7 SURFACES* Hongjun GaoNanoscale Physics & Devices Laboratory, Institute of Physics, Chinese Academy of Sciences, P.O. Box603, Beijing 100080, China The invention of the scanning tunneling microscopy (STM), the determination of the Si(111)-7x7 atomicreconstruction, and the Ge atom adsorption on Si(111) 7x7 surface at the initial stage are the importantevents in the history of surface science and Si technology. However, for over 20 years, despite acountless number of studies on the Si surface, no one has produced any STM images of the Si(111)-7x7that would be even near the calculated charge distributions: either only the twelve adatom-spots were seenregardless, to a large extent, of the bias, or the rest atoms alone were seen at biases at which the adatomswere not seen, and no one has clarified the bonding configuration of the Ge adatom adsorbed onSi(111)7x7. Here we report on the scanning tunneling microscopy experiment and first-principles totalenergy calculation which are combined to determine the “ultimate” STM images for Si(111)-7x7 toresolve the longtime discrepancy between theory and experiment and the Ge adsorption on the Si(111)7x7at the initial stage. For the first time, simultaneously clearly resolved rest and adatom spots are seen,with the rest atom spots almost as bright as those of central adatoms in the unfaulted-half of the unit cells.We demonstrate that Ge atoms replace so-called Si adatoms. Initially, the replacements are random, butdistinct patterns emerge and evolve with increasing coverage, until small islands begin to form. Thecalculated results are in remarkable agreement with experiments. We believe that this work will furtherinvoke significant research interests in design and fabrication of the SPM tip, its applications to exploremore detailed information of nanostructures and their deeper physical properties of nano-systems, andunderstyandinmg and controlling the Ge growth on the Si(111)7x7 surface.. * In collaboration with Y.L. Wang1, H.M. Guo1, H.W. Liu1, D.X. Shi1, S.B. Zhang2, S.W. Wang, andS.T. Pantelides, 1IOPCAS, Beijing, China; 2NREL, Colorado, USA; 3Dept. Physics, Vanderbilt U.,Nashiville, USA. References:1. Y.L. Wang et al., Phys. Rev. B 70, 073312(2004).2. Y.L. Wang et al., Phys. Rev. Lett. 94, 106101(2005) Email: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 39 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 40NOVEL PROPERTIES OF THIN FILMS MODULATED BY QUANTUM SIZE EFFECTS Qikun Xue, Jinfeng Jia, and Xucun MaState Key Laboratory for Surface Physics, Institute of Physics, The Chinese Academy of Sciences, Beijing100080, China It is well-known that the electrons confined in a perfectly uniform thin film are quantized into discreteenergy levels in the vertical direction, forming standing-wave like eigenstates, or quantum well states(QWS). This has been proven to modulate the electronic distribution near the Fermi level (EF), and thussignificantly affect the physical and chemical properties of a thin film material. We have successfullyfabricated ultra-thin Pb films on Si substrates with atomic-scale control of the thickness over amacroscopic area, and investigated the quantum size effect induced special growth behavior, as well as theelectronic structure of the Pb thin films by the angle resolved photoemission spectroscopy (ARPES) andscanning tunnelling microscopy/spectroscopy (STM/STS) [1]. Oscillatory superconducting transitiontemperature, local work function, thermal expansion and chemical reaction were observed when the film isincreased by one atomic layer at a time. The oscillating superconductivity behavior is shown to be directlyrelated with the formation of the QWSs, which modulate the electron density of states near the Fermi leveland electron-phonon coupling, the two factors controlling superconductivity transition [2]. Our workclearly demonstrates the possibility of modifying superconductivity and other physical properties of a thinfilm by exploiting well-controlled and thickness-dependent quantum size effects. References:[1] Yan-Feng Zhang, Yang Guo, Tie-Zhu Han, Zhe Tang, Quan-Tong Shen, Zi-Qiang Qiu, Jin-Feng Jia,Qi-Kun Xue, Phys. Rev. Lett. (submitted).[2] Yang Guo, Yan-Feng Zhang, Xin-Yu Bao et al., Science 306, 1915 (2004). In collaboration with, Yan-Feng Zhang, Yang Guo, Xin-Yu Bao, E. G. Wang, Zhong-Xian Zhao (IOP),Qian Niu (UT Austin), and Z. Q. Qiu (UC Berkeley). May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA40 China-US Workshop on Materials ScienceAbstract 41MONODISPERSE MAGNETIC SINGLE CRYSTAL FERRITE MICROSPHERES Hong Deng, Xiao Lin Li, Qing Peng, Xun Wang, Jin Ping Chen and Yadong LiDepartment of Chemistry Tsinghua University, Beijing, 100084, P. R. China; National Center forNanoscience and Nanotechnology; Beijing, 100081, P. R. China Spinel ferrites (MFe2O4, M = Fe, Mn, Zn, Co) are a kind of the most important magnetic materials andhave been widely used in electronic devices, information storage, magnetic resonance imaging (MRI), anddrug delivery technology. Recently, magnetite(Fe3O4) has been considered as an ideal candidate forbiological applications both as tags in sensing and imaging and as activity agents in tumors therapy. [1]As is well acknowledged, in order to achieve the high performance in function-specific biologicalapplication, magnetic particles are required to have spherical shape, smooth surface, narrow particle sizedistribution, large surface area to bind with many proteins or enzymes, high magnetic saturation ( s) to provide maximum signal, and good dispersity in liquid media. Based on the solvothermal reducingmethod, a series of ferriteMFe2O4 (M = Fe, Mn, Co, Zn) microspheres have been successfullysynthesized. With the size of the ferrite microspheres tunable ranging from ~200 nm to ~800 nm, thisapproach provides a one-step, simple, general and cheap method to prepare monodisperse, magnetic ferritemicrospheres.We believe that these hydrophobic and biocompatible magnetic ferrite microspheres will have animportant application not only in advanced magnetic materials and ferrofluid technology, but also inbiomedical fields such as separation of various chemical and biological entities, target-drug delivery,cancer diagnosis and treatment as well as magnetic resonance imaging. 1. H. Deng, X. L. Li, Q. Peng, X. Wang, J. P. Chen, Y. D. Li, Angew. Chem. Int. Ed. 2005, 44,2782-2785. Corresponding author: [email protected] author: Hong Deng May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 41 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 42GROWTH OF STRAIGHT AND ISOLATED SINGLE-WALLED CARBONNANOTUBES(SWNTS) THROUGH FLOATING CATALYST CHEMICAL VAPORDEPOSITION(FCCVD) METHOD X.Y. Dou, Z.P. Zhou, L. Song, L.F. Liu, S.D.Luo, X.W. Zhao, D.F. Liu, J.X. Wang, Z.X.Zhang, Y.J.Xiang, Y.Gao, L.F.Sun, P.Jiang, J.J.Zhou, G.Wang, C.Y.Wang, W.Y.Zhou, S.S. XieInstitute of Physics, Chinese Academy of Sciences, Beijing, 100080, P. R. ChinaGraduate School of the Chinese Academy of Sciences, Beijing 100080, P. R. China In this paper, we prepared straight and isolated single-walled carbon nanotubes (SWNTs) through floatingcatalyst chemical vapor deposition (CVD) method with the assistance of water vapor. The gas mixture ofargon and the carbon source acetylene were firstly put through a gas washing bottle. We compared theconfigurations of SWNTs grown before and after the water vapor was added into the CVD system. Thegrown SWNTs or their bundles were typically long, straight and isolated on the substrates under theassistance of water vapor. The catalysts particles were also discrete along the SWNTs. We acted theelectric fields on at the same time to learn the behavior of aligned SWNTs grown under thewater-assistance. SWNTs were mostly polarized and aligned along the external fields. Raman scatteringwas also carried out to find out the diameter distribution of grown SWNTs. The RBM peaks after watervapor was added were at 162 cm,186 cm,246 cm. The corresponding diameters of the SWNTs were1.53 nm,1.33 nm,1.00 nm. The peaks before water vapor was added were at 170 cm, 154 cm, 145 cmand 108 cm. The corresponding diameters of the SWNTs were 1.45 nm, 1.60 nm, 1.70 nm, 2.30 nm,respectively. From the diameter distribution of the SWNTs above we conclude that when the water vaporwas added, SWNTs with small diameters could be more easily formed through floating catalyst chemicalvapor deposition method. The SEM configurations and Raman scattering spectroscopy of SWNTs suggestthat the water vapor could affect the size of the catalysts and extend their lifetime during the SWNTsgrowth, which lead to the growth of straight and isolated single-walled carbon nanotubes. Corresponding author: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA42 China-US Workshop on Materials ScienceAbstract 43A GENERAL APCVD ROUTE TO METAL SULFIDES ONE-DIMENSIONALNANOSTRUCTURES Jianping Ge, Jin Wang, Xiaolin Li, Yadong LiDepartment of Chemistry, The Key Laboratory of Atomic and Molecular Nanoscience (Ministry ofEducation), Tsinghua University, National Center for Nanoscience and Nanotechnology, Beijing 100084,China During the past decades, transition metal sulfides have attracted great interest due to their physical andchemical properties. For instance, CdS is widely used for photoelectric conversion in solar cells and forlight-emitting diodes in flat-panel displayers; ZnS is a famous luminescence material with variousluminescence properties, etc.Here, we reported a general atmospheric pressure chemical vapor deposition (APCVD) synthesis of metalsulfides one-dimensional (1-D) nanostructures. The growth process can be well explained by the VLS andVS mechanism.Chlorides (MClx) are chosen as the metal source, because they are proper precursors and have alreadybeen widely used to prepare many useful thin films. Sulfur powder is selected as the S source, for it is lesstoxic than the H2S gas, which is commonly used to prepare sulfides thin film.MClx + S = MSy + S2Cl2In summary, this novel one-step route has been developed to fabricate a group of metal sulfides 1-Dnanostructures on a Si substrate, which might provide abundant resources to the research of mesoscopicphysics and fabrication of nanoscale devices. 1. Ge JP, Li YD, Chem. Commun. 2003, 24982. Ge JP, Li YD, Adv. Funct. Mater. 2004, 14, 1573. Ge JP, Wang J, Zhang HX, et al. Chem. Eur. J. 2004, 10, 35254. Li XL, Ge JP, Li YD, Chem. Eur. J. 2004, 10, 6163.5. Ge JP, Wang J, Zhang HX et al. Chem. Eur. J. 2005, 11, 18896. Ge JP, Wang J, Zhang HX et al. Adv. Funct. Mater. 2005, 15, 3037. Ge JP, Wang J, Zhang HX et al. Sens. Actuator B-Chem., 2005, (in press) Corresponding author: [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 43 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 44FUNCTIONAL NANOWIRE DEVICES Joshua Goldberger, Peidong YangDepartment of Chemistry, University of California, Berkeley, CA 94720 Silicon nanowires have received considerable attention for their application in transistor devices due totheir excellent transport properties and compact size. After nanowire synthesis, fabrication of such devicestypically requires placing wires onto a horizontal substrate with either a top or back gate. However, theamount of energy which this assembly requires, as well as the limitations of the horizontal devicegeometry have hindered nanowire-based electronics from realizing their full potential. Here wedemonstrate the ability to grow epitaxial Si nanowires perpendicular to the Si (111) substrate, withmonodisperse lengths and diameters, and with well-controlled positioning using nanoparticle catalysts.These nanowires are easily integrated into vertical field effect transistors with a surround-gate devicegeometry using standard VLSI processing. Finally, these vertical nanowire field effect transistors(VNFET) possess excellent transport properties, suggesting that optimization of the device structure maymake them competitive with FINFET and MOSFET transistors. Email: [email protected]; [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA44 China-US Workshop on Materials ScienceAbstract 45ELECTROSTATIC INTERACTIONS OF NONPOLAR COLLOIDS ENABLED BY REVERSEMICELLES Ming Hsu, Judith SteinGE Global Research, Niskayuna, NY 12309 While the important role of electrostatic interactions in aqueous colloidal suspensions is widely known andreasonably well-understood, the relevance of charge in nonpolar suspensions remains mysterious. Wedemonstrate that colloidal particles can have surprisingly strong electrostatic interactions inlow-dielectric-constant environments when ions are solubilized by reverse micelles. A simplethermodynamic model, relating the structure of the micelles to the equilibrium ionic strength, is in goodagreement with both conductivity and interaction measurements. Since dissociated ions are soluilized byreverse micelles, the entropic incentive to charge a particle surface is qualitatively changed, and surfaceentropy plays an important role. Email: [email protected]; [email protected] May 23 – 25, 2005, Institute of Physics, Chinese Academy of Sciences, BEIJING, CHINA 45 AbstractChina-US Workshop on Materials ScienceChina-US Workshop on Materials Science 46SYNTHESIS OF SOME ONE-DIMENSIONAL NANOSTRUCTURES BY EXTENDEDVAPOR-LIQUID-SOLID GROWTH K. F. Huo, J. J. Fu, Y. Pan, Z. Hu,* and Y. ChenKey Laboratory of Mesoscopic Chemistry of MOE and Jiangsu Provincial Lab for Nanotechnology,Department of Chemistry, Nanjing University, Nanjing 210093, China As known, vapor-liquid-solid (VLS) growth is one of the most classical and effective methods in thepreparation of one-dimensional nanostructures.1-3 This mechanism functions at the elevated temperatureat which the catalyst exists in liquid phase. Precursors in the vapor phase decompose preferentially at thevapor-liquid (catalyst) interface, depositing the constituent component(s) into the liquid-flux catalystdroplets. Supersaturation then supports whisker-like growth at the liquid-solid interface in such a mannermaking the interface energy the lowest. It is seen that, in the VLS growth, liquid catalyst acts as a mediumto transport component(s) from vapor precursor(s) to whisker-like solid product. Very recently, we haveextended this traditional VLS growth via introducing alloy particles as ‘catalyst’. Some one-dimensionalnanomaterials such as BN nanowires, nanotubes, AlN nanowires and Si3N4nanobelts have beensynthesized by simply nitriding Fe-B, Ni-Al and Fe-Si alloy particles at high temperature withNH3/N2,respectively.4-7 In the extended VLS mechanism, the alloy ‘catalyst’ not only acts as the medium forcomponent transport from vapor to solid as the case in the traditional VLS growth, but also supplies partialcomponent for the final solid product. In other words, a chemical reaction between the component(s) fromthe vapor precursor(s) and ‘catalyst’ itself respectively takes place within the liquid ‘catalyst’, and theresulting product species precipitated in whisker-like morphology when supersaturation is reached. Strictlyspeaking, the alloy particle here is not a ‘catalyst’ rather a reactant, because partial component in the alloyis consumed after the chemical reaction. This extension of VLS growth mechanism provides some newpossibility for the preparation of compound nanostructures.