Controllable Synthesis Of Titania Nanospheres With Hierarchical Structures And Research On Their Performances

The synthesis of titania nanomaterials with controlled shape is an important goal of advanced materials chemistry, due to their superior performances in many fields, such as photocatalysis, dye-sensitized solar cells (DSSCs), biomedicine and so on. Therefore, the research on titania nanomaterials has attracted much attention.Titania nanocrystallines of various morphology have been synthesized, such as nanowires, nanorods, nanotubes, diamond, different polyhedron, etc. But in recent years, the synthesis of TiO2 nanocrystalline with hierarchical structures has become hot spots of research in the worldwide. Because the structures are built with smaller nanoparticles, this endows them more advantages, such as large specific surface area and rich mesopores. These advantages make them possess potential application prospect in the fields of photocatalysis, DSSCs and biomedicine. Therefore, the developing of research on TiO2 nanomaterials with hierarchical structures is very significant, and has a broad application space.In this thesis , there are several major work as follows:(1) A combined sol–gel and solvothermal process was introduced to fabricate the titania microspheres by using lauryl alcohol , aminobenzene and nonanoic acid as the structure-directing agent respectively. The three kinds of TiO2 microspheres were investigated through various characterization methods such as SEM, HRTEM, XRD,BET and so on. Results show that their diameters are between 500nm and 700nm, and they are composed of smaller nanoparticles with about 13nm size in diameter.They are anatase and their crystallinity are very good. Moreover, they possess large specific surface area and rich mesoporous, in which the biggest specific surface area is 101m2 /g and the average pore diameter is about 9.2 nm.(2) The photocatalysis and DSSCs properties of the three kinds of TiO2 microspheres were studied .They exhibited the higher photocatalytic and photovoltaic properties compared with commercial Degussa P25 powder. Among them, the titania microspheres fabricated by using nonanoic acid as the structure-directing agent have the best photocatalytic effect, it only needs 5mg sample to make 25ml of 20ppm Rhodmine B auqeous solution degradated completely in 40min. The titania microspheres fabricated by using aminobenzene as the structure-directing agent also have the best photovoltaic performance. Its photoelectric conversion efficiency reaches 6.55%. We make use of dyes adsorption capacity, diffuse reflection spectrum and impedance diagram to analyze the reasons on the differences among their performances from specific surface area, optical properties and charge transports.(3) First, polystyrene (PS) spheres with different particle sizes were synthesized by using emulsion polymerization and dispersion polymerization. And using the sulphonated PS spheres as templates, TiO2 @ PS nuclear-hull composites with different sizes have been successfully synthesized. Then after toluene dissolution processing and high temperature firing, we got TiO2 hollow spheres with different particle sizes. The TiO2 hollow spheres were investigated through various characterization methods such as TEM, XRD and so on. The results show that they are anatase, and their shells are made up of smaller titania nanopaticles.Through the experimental results, we indeed find that TiO2 nanomaterials with hierarchical structure have better photocatalytic and photovoltaic performances. It provides reference for the synthesis of new TiO2 nanomaterials with high photocatalytic activity and photoelectric conversion efficiency in future. Moreover, these nanospheres with hierarchical structures may have very good application prospects in biomedical domain according to the test results.