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Organized one dimensional nanomaterials : from preparations to applications

Authors Wen, Xiaogang
Issue Date 2005
Summary This thesis is mainly concerned with the development of organized one dimensional (1D) nanomaterials and their applications. We have synthesized Ag2S, Cu2S nanowires, Fe2O3 nanobelt and nanowire arrays and ZnO nanobelt arrays from corresponding metal substrate respectively via gas solid reaction methods under different growth conditions. The effect of various parameters including temperature, reaction time, composition of gas, surface pre-oxidation, size of source materials etc. on the growth of metal oxide/sulfide 1D nanostructure have been studied systemically. The size and morphology of these 1D nanomaterials could be rationally controlled by adjusting the growth conditions. A tip growth mechanism has been confirmed based our results. The properties including PL, Raman, field effect transistors, and field emission of these materials have been measured. Cu(OH)2 nanoribbons have been synthesized by a solution solid reaction method using Cu and Cu2S nanowires as precursors. Cu(OH)2 nanoribbons can form well-aligned arrays on Cu substrate. Low temperature facilitate the formation of CU(OH)2 nanoribbon arrays. Reaction conditions affect the morphology, crystal structure, even composition of the products much. CuO nanorod arrays of several nm in diameter could be synthesis in changed condition. Cu(OH)2 nanoribbon arrays are good sacrifice template for synthesizing other Cu-based 1D nanomaterials. It has been converted to CuO, Cu2O, Cu8S9, Cu etc. 1D nanostructure through different physical and chemical reaction process. Au/Cu2S core/sheath nanowires have been synthesized in solution phase via a simple template-induced redox deposition process, after removing the Cu2S template, Au nanotubes have been formed. The photoelectrochemistry (PEC) properties of it have been studied. Ag dendritic nanostructures have been prepared via solution reaction. We have revealed that the stem, branch, and sub-branch grow along <100>, <111> and <100> directions, respectively. Such a preferential growth pattern along <100> and <111> alternately lead to the formation of the Ag nanodendrites. In another development, we have synthesized unltrathin Zn nanowires (<5nm) by a vapor transport method. Small molecules are induced into the gas phase as capping reagents. In this process, the small molecules serve as capping reagents or templates to confine the lateral growth and facilitate the formation of ultrathin 1D nanostructures . We also extended our studies to the application of various 1D nanomaterials we synthesized. The results demonstrated that the ZnO nanobelt arrays show good NH3 sensitivity at room temperature. Fe2O3 nanobelt arrays are sensitive to humidity in high relative humidity (RH) range. The SERS studies of Cu nanowires and Ag nanodendrites indicated that Cu & Ag 1D nanostructures demonstrate much higher signal than their corresponding bulk metal electrodes, The Ag nanodendrites have also been used in biosensor. Our studies indicate the Ag nanodendrites with high surface area can facilitate the electron transport and improve the sensitivity of biosensor significantly.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005
Language English
Format Thesis
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