Synthesis Of Titanium Dioxide Microspheres And Self-Assembly

TiO2 materials are one of the best potential candidates to fabricate photonic crystals due to its high refractive index and low absorption in the visible and near-infrared regions. Because the monodispersity and Zeta potential of assembly unit are very important for preparing photonic crystal, so control the synthesis of monodisperse TiO2 nanospheres with high Zeta potential has moved into focus in the field of photonic crystal in recent years. Nevertheless, it is still challenging to produce uniform titanium spheres because of the high hydrolysis reaction activity of titanium alkoxides, which leads to the infeasibility of separating seed formation and growth stages and results in the poor size distribution. To solve this problem, more and more efforts has been made to obtain the TiO2 spheres with narrow size distribution. Herein, the synthesis of TiO2 prepared by sol-gel method with different kinds of ligands as well as sefl-assembly phenomenon of the as-prepared monodispersped TiO2 nanospheres have been researched systematically.In the sol-gel reaction, we often need to add the ligand to slow the hydrolysis reaction activity of titanium alkoxides. In monobasic saturated fatty acid system, the TBT can react with carboxy group to generate the carboxylate. In comparison to precursor such as TBT, the carboxylate derivatives displays much lower hydrolysis rate, which is beneficial to the formation of fine particles with a narrower size distribution. In monobasic saturated fatty acid system, the morphology and size of TiO2 can be tuned by changing the length of carbon chain acid, the consumption of water and reaction temperature.However, the TiO2 particles synthesised in monobasic saturated fatty acid systems exhibited high hydrophobicity due to the presence of the long carbon chain in chelating ligands and there are no surface charges. For preparing the hydrophilic TiO2 particles, we further opted the thioglycolic acid as the ligand. In thioglycolic acid ligand system, when the amount of thioglycolic acid ligand used in the system unchanged, in a proper amount range of water, the size of the as-prepared monodispersed TiO2 nanospheres could be increased from 180 nm to 280 nm. As same as mentioned above, with the ratio of water increasing, the size of monodispersed TiO2 nanospheres experienced a gradual decrease. What' more, the ligand TGA also has a sulfhydryl group, which supply the particles with enough surface charges by changing the pH which is favor to the preparation of photonic crystal.In this thesis, we study the effect of different kinds of monobasic saturated fatty acids on the morphology and size. A series of TiO2 nanospheres with varieties of sizes have been synthesized by choosing the monobasic acid with different length of carbon chain. In addition, we introduced thioglycolic acid intothe controlled synthesised of monodispersed TiO2 nanospheres by sol-gel method for the first time. Then the Zeta potentials of the TiO2 colloidal solution at different pH have beem measured.The self-assemble of monodispersed TiO2 nanospheres synthesised by sol-gel method with different ligands has been studied by a varieties of methods, such as water/air interface and oil/water interface method. It has been found that water/air interface method is a pratical method to realize the self-assemble of the monodispersed TiO2 nanospheres syhthesised by thioglycolic acid.