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Quasi One-dimensional Nanomaterials: Chemical Solution Synthesis, Characterization and Application

Author: ZhangHui
Tutor: ZuoDuanZuo;YangDeRen
School: Zhejiang University
Course: Materials Physics and Chemistry
Keywords: TGA assisted hydrothermal process Sonochemistry CdS ZnO Se Quasi one-dimensional nanostructures core-shell nanostructures
CLC: TB383
Type: PhD thesis
Year: 2005
Downloads: 2232
Quote: 2
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Abstract


Since the discovery of carbon nanotubes in early 1990’s, quasi one-dimensional nanomaterials have received intensive interests due to their novel physical, chemical, and biological properties as well as the potential applications in nanodevices. Large-scale, cost-effective, simple and practical synthesis and assembly of one-dimensional nanomaterials is of importance for the fundamental research and application.In the dissertation, the quasi one-dimensional nanostructures of a variety of functional materials have been synthesized by chemical solution routes. The effects of synthetic conditions on the morphology, size, structure and properties of the nanomaterials have been systematically investigated. Moreover, the formation mechanisms of the as synthesized nanostructures have been elucidated. Finally, the application of ZnO nanostructures has been preliminarily addressed. The significant results achieved in this dissertation are given as below:(1) The quasi one-dimensional nanomaterials of sulfides have been fabricated by a novel thioglycolic acid (TGA) assisted hydrothermal method. Compared to previous method, it has simple, practical, cost-effective, large-scale and environment-friendly advantages. The quasi one-dimensional nanostructures of sulfides prepared by this method include: single crystalline hexagonal CdS nanorods and polycrystalline nanorod bundles; polycrystalline monoclinic CdS nanobelts, nanotubes and nanfibers; single crystalline tetragonal Bi2S3 ultra-long nanowires and nanoflowers; single crystalline tetragonal FeS nanorods; single crystalline hexagonal SnS2 nanobelts and single crystalline cubic PbS nanorods. It has been well proved that the TGA-assisted hydrothermal method is extensively applicable in the synthesis of one-dimensional nanomaterials of sulfides.The effects of synthetic conditions of the TGA-assisted hydrothermal process including the time, constituents of precursor solution, temperature, TGA, temperature ramping rate, sulfur source and organic additive, etc. on the morphology, size and structure of the one-dimensional sulfide nanomaterials have been investigated. The investigation of optical properties of CdS nanorods prepared by the TGA-assisted hydrothermal process indicates that there are three photoluminescence (PL) bands of CdS nanorods at 398, 485, and 580 nm, respectively. Among them, the PL band at 398 nm originates from the emission of the complex of CdS nanorods, and the PL band at 485 nm arises from the band to band emission, which is blueshifted in comparison to that of the bulk CdS, while the PL band at 580 nm is resulted from the deep-level withinthe bandgap of CdS. The superimposition of the above-mentioned three bands leads to a wide band at 440nm, which accounts for the reason that the peak wavelength of PL emission band is shorter than that of absorption band is not quantum size effect but the existence of the complex clusters in the surface of CdS nanorods.(2) A new sub-phase of CdS has been fabricated. The monoclinic CdS has been derived by the TGA-assisted hydrothermal process at low temperatures of 100-160 ℃ . Preliminary study of X-ray diffraction (XRD) pattern results in their crystallographic parameters. The further study indicates that the monoclinic phase of CdS can firstly be transformed into the cubic phase and then into the hexagonal phase when annealed at temperatures larger than 350℃. The ultra-violet absorption spectra (UV-vis) reveal that the bandgap of the monoclinic CdS is about 2.7eV.(3) A novel route to the synthesis of sulfide nanotubes and oxide/ sulfide core-shell nanostructures derive from one-dimensional oxide nanomaterials by the sulfuration reaction during the TGA-assisted hydrothermal process and the subsequent acid or alkali treatment has been presented. Compared to previous methods, it has simple, practical, cost-effective, large-scale and extensively applicable advantages. Based on this route, ZnS nanotubes, ZnO/ZnS core-shell nanostructures, SnS2 nanotubes, SnO2/SnS2 core-shell nanostructures, and MnO2/MnS

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