Controllable Synthesis And Applications Of TiO₂ And ZnS Based Functional Nano-structure Materials

The application of nanomaterials is increasing rapidly in recent years. More importantly, the application in catalysis and photoelectricscience has been receiving greater attention and has now become an important research field. Titanium dioxide (TiO2) and zinc sulfide (ZnS) are widely studied because of their attractive physical, chemical and biological properties.As a semiconductor photocatalyst, TiO2 has some advantages such as low cost, low toxicity and high catalytic activity, which is widely used in photocatalytic synthesis, hydrogen production and degradation of organic pollutants. ZnS also has a large number of applications in catalysis, photoelectric materials, and infrared window materials.In this study, we focous on the synthesis and application of TiO2 and ZnS based nanocomposite. Firstly, we demonstrated the application of photocatalytic surface-initiated polymerization on TiO2 toward well-defined composite nanostructures. Secondly, carbon doped TiO2 hollow shells with controllable crystallinity were synthesized by an self-assmlby method. We also discussed the application of TiO2 hollow shells as photocatalysts in dye degragation. Thirdly, the colloidal photonic crystals based on monodispersed ZnS nanospheres was studied.The main contents of dissertation include three parts:1. Photocatalytic surface-initiated polymerization on TiO2 toward well-defined nanostructuresTiO2 nanospheres were employed as typical photoinitiator, which was believed to be extendable to many other substrates. The excitation of TiO2 by UV light irradiation produces electrons and holes which drive the free radical polymerization near the nanosphere surface, producing TiO2/Polymer nanocomposite. We explored the possibility to generalize this synthesis strategy to many other core materials and polymer coatings.2. An assembly route to TiO2 nanoshells for enhanced photocatalytic activity.Mesoporous nanoshells of C-doped TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the preparation of TiO2/Polystyrene nanocomposite, coating of these nanocomposites with a RF layer and thermal treatment. With the help of the RF coating, the nanoshells not only maintain their small grain size but also form the shell structure with high surface area after calcination at high temperature. The obtained C-doped TiO2 nanoshells show excellent catalytic performance in the decomposition of organic molecules under UV and visible illumination.3. Colloidal photonic crystals based on monodispersed ZnS nanospheres.A co-precipitation method has been developed to synthesize monodispersed and uniform ZnS colloidal nanospheres. The size of nanospheres could be tuned precisely from about 40 to about 200 nm. With a simple SiO2 protected calcination and partially etching, highly charge ZnS@SiO2 with 5% carbon load colloidal spheres were obtained. With the help of sonic, ZnS@SiO2 nanospheres could self-assembled to be a 3D colloidal photonic crystals with different colors and high reflectance.The above research is done in University of California, Riverside. In addition, we studied light emitting property of 6,12-diphenylindolo[3,2-b]carbazole for organic light emitting devices. The compound showed good thermal stability and hole-transporting behavior. Multilayered devices by using DPICZ both as hole transporting material and light emitting material have been prepared, and the results show that the color of the device has less dependence of the operating voltages.