The Synthesis And Properties Of Zinc-based Nanostructures

Semiconductor nanomaterials show great potential in many applications such as luminescence devices, bio-imaging fluorophores and solar cells due to their outstanding optical and electronical properties. The synthesis route may modify surface state, morphology and intrinsic structure of the obtained nanomaterials and finally control their properties. With the development of nanotechnology, controllable synthesis and performance improvement have become a core objective of modern research on nanomaterials.The present work is focused on the controllable synthesis of zinc-based nanomaterials such as zinc oxide (ZnO), zinc sulfur (ZnS) and zinc hydroxide carbonate (ZHC). ZnO nanostructures with different morphologies were fabricated through an inverse micromicelle method, an Ostwald ripennig of ZnO nanodots, and a anneal treatment of ZHC. Their optical property and applications in the photoelectric conversion field are comprehensively investigated.Uniform ZnO nanorods and ZnO tetrahetrons were obtained through hot mixing of inverse micro-micelles. ZnO nanorods showed a green emission while ZnO tetrahetrons emitted blue light under UV excitation. The inner crystal structure of ZnO nanostructures, template effect of inverse micelle and the modification effect of AOT were combined to determine the final morphology. The fluorescence mechanism of ZnO nanorods and ZnO tetrahetrons are also discussed separately based on experimental results.Uniform and well dispersed ZnO nanodots were prepared through modified sol-gel route and then they are transformed into different nanostructures via a Ostwald ripening mechanism. It was found that the addition of modifiers played an important role on the final morphology of ZnO nanostructures. Such a controllable ripening process could also be expanded to other materials such as CdS.Mn doping of ZnS nanocrystals was carried out by a LSS route. The modification of oleic acid ensured the farbrication of high quality of ZnS nanocrystals and was beneficial for the doping of Mn in ZnS. Mn-doped ZnS can be successfully transferred into the water solution through ligand exchange with mercaptoacetic acid, which was essential for further application.ZHC flowers/ZnO nanorods dual layer structure could be obtained with a modified hydrothermal method. The gradual hydrolysis of HMT under high reaction temperature was determined as the key factor on the formation of the dual-layer structure. Under the excitation of ultraviolet light, ZHC nanoflowers exhibited strong blue emission. By annealing treatment, ZHC nanoflowers were transformed into porous ZnO nanocrystals with inherited morphology, such a structure possessed the advantages of the large area of porous materials and excellent electron transport of monocrystal material. It exhibitted unique advantages when used as photoanode in dye-sensitized solar cells.A series of experiments are designed for understanding the luminescent mechanism of ZHC, which was supposed to be related to structural defects in ZHC. Magnesium (Mg) and aluminum (Al) doped ZnO have been obtained by annealing of Mg or Al doped ZHC, and the photoelectric conversion efficiency of the doped ZnO was investigated.