Preparation, Characterization And Properties Of TiO₂、Cu₂O And Cu_2-x Se Micro-And Nano-Materials

Ti O2, Cu2 O and Copper selenide have been extensively applied in many fields because of its excellent properties in catalysis, photoelectric conversion, magnetism and gas sensitivity. Due to the properties of the materials are influenced by morphology, structure, crystal structure and the size of micro/nano materials, designing and controlled synthesis of Ti O2, Cu2 O and Copper selenide materials with novel morphology and structure are of significance from both theoretical and practical application point of view. In this thesis, Ti O2, Cu2 O and Copper selenide were synthesized by solvothermal method, hydrothermal method and sacrificial template method, respectively. The morphology, structure and optical properties of the synthesized Ti O2, Cu2 O and Copper selenide nanomaterials were studied by SEM, TEM, XRD, TG-DTA, UV-Vis and PL etc. The effects of various reaction conditions on the morphologies of the prepared nanomaterials were discussed. The formation mechanisms of Ti O2 nanostructures were proposed. The main content of this thesis is as follows:1. Anatase Ti O2 hollow nanospheres were prepared by solvothermal method, using polyethyleneimine(PEI) as an auxiliary agent, followed by calcination at 400 °C, 500 °C and 700 °C, respectively. The samples were characterized by XRD, SEM, TEM, HRTEM, thermal gravimetric-differential thermal analysis(TG-DTA) and N2 adsorption-desorption isotherm. The optical properties and photocatalytic reaction mechanism were investigated by means of UV-Vis diffuse reflectance spectra and fluorescent technique. The effect of the PEI quantity on morphologies of the products and the formation mechanism of the Ti O2 nanospheres were explored on the basis of series of control experiments. The photocatalytic activities of the samples were evaluated by degradation of rhodamine B(Rh B) solutions and compared with that of the commercial Ti O2(P25). The results clearly show that the Ti O2 hollow nanospheres were formed via the Kirkendall effect. For the first time we find that the morphologies of the products change dramatically with slightly increasing the PEI quantity. The photocatalytic activity of the Ti O2 nanospheres calcined at 500 °C is higher than those of the other two samples and P25. The active species for the photocatalytic reactions is not ×OH.2. The hydrothermal method was used to prepare Cu2 O, using copper nitrate and copper acetate as copper source and appropriate reducing agent was applied. Optimal conditions were obtained by changing the experimental conditions: temperature, time, concentration and surfactant. The samples were characterized by XRD and SEM. The optical properties and photocatalytic reaction mechanism were investigated by means of UV-Vis diffuse reflectance spectra and fluorescent technique.3. The copper selenides nanomaterials were prepared by sacrificial template method from spherical Cu O and Cu2 O precursors, which were prepared using copper chloride, copper nitrate, copper sulphate, potassium carbonate as raw materials, sodium dodecylbenzene sulfonate as a surfactant, and ascorbic acid as a reducing agent. The samples were characterized by XRD and SEM. The optical properties was investigated by means of FT-IR and fluorescent technique. The effects of reducing agent, concentration of the reactants and the amount of reaction solution on the copper selenide morphology and structure were studied. XRD analysis shows that the samples are not pure copper selenide phase, but contain Cu O and Cu2 O precursors. Copper selenide was the shell and the copper oxide / cuprous oxide was core. Because diameter of the sphere is too large, and the shell is too thin, it is easily broken. The FT-IR spectrum shows that the sample has characteristic vibration absorption peak of copper selenide. Analysis of the fluorescence spectra displays that the sample has fluorescence emission at 350~500 nm with a maximum fluorescence peak at 391 nm. It can emit purple-blue light.