Surfactant-assisted And Shape-controlled Synthesis Of Anatase Titania Nanocrystals And Their Shape-dependent Photocatalytic Activity

The work is focused on the investigation of shape-controlled synthesis and photocatalytic properties based on TiO2nanocrystals. The main contents of dissertaton include two parts:1. Shape-controlled synthesis of TiO2nanocrystals and the mechanism of tailoring morphology:(1)We choose solvothermal method to prepare TiO2nanocrystals, with a trace amout of water and oleic acid、organic amine as hydrolysis agent and capping surfactant, respecively. By varing the ratio of OAc to organic amine and the type of organic amine, we tailor the shape of TiO2nanocrystals, e.g., rhombs, truncated rhombs, elongated rhombs, small nanodots and quasi-spheres. By adding a certain amout of water, the reaction rate was accelerated. OAc and OAm was used as capping agents because they have different binding strengths to control the growth of the TiO2NCs. Apart from the function of capping ligands, the surfactants OAc and OAm also act as the acid-base pair catalyst to accelerate the condensation reaction without influencing the hydrolysis reaction.(2)Alkylamine with different chain length is cruicail on tailoring the shape of TiO2nanocrystals, because of the different binding strengths and steric hindrance to TiO2.2.Shape-depended photocatalytic activity:(1) The surfactants of the surface of the as-obtained TiO2nanocrystals can be removed and dispersed well in aqueous solution through adsorption of tetramethyl-ammonium hydroxide (TMAH), and the morphology and structure of the obtained TiO2is unchanged.Then we measured the degradation performance of RhB under UV light using these different-shaped TiO2nanocrystals. After25minutes, the photocatalytic degration activity is obviously different of different-shapd TiO2, and the degration rate of truncated rhomb is the best, reaching92%. Besides, we measured the producing hydrogen performance of TiO2under UV light, and the result shows that the rate of producing H2of quasi-spheres is the highest.(2)The reason why photocatalytic activities have different order between degradation organic dye and hydrogen producing is that the two photocatalytic reaction is effected by different face of TiO2. TiO2is acted as oxidation and reduction site in photocatalytic degradation and hydrogen producing, respectively. Under the UV, the photoinduced electrons transfer to{101} facets with the holes to{001} facets, resulting in reduction and oxidation, respectively.