Hydrothermal Synthesis Of Rutile TiO₂ Nanomaterials Based On Assistance Of Imidazolium-type Ionic Liquids

Titania, as a kind of semiconductor materials, has exhibited promising application in catalysis, sensing, optics, DSC, and Li battens mainly due to its unique physicochemical properties, such as wide band gap, good optical stability and nontoxicity, etc. Preparation of titania nanomaterials with well-difined size, morphology, dimensionality and diversity through novel synthesis approaches and investigations of its formation mechamism should be a key precondition to reveal the relations between the structures and the real applications. Moreover, ionic liquids have been attracted more attention to prepare iorganic nanomaterials as a new type solvent. In this dissertation, valuable explorations have been carried out on preparation of rutile nanomaterials by assistance of simple imidozalium-type ionic liquids under hydrothermal conditions. The purposes are to develop the new synthetic method of TiO₂ and explore the new functions of ionic liquid. This dissertation consists of six chapters.In Chapter 1, the concept and characteristics of nanomaterials were briefly reviewed, and the structural characterization and properties of titania, mainly including rutile, were introduced. Synthetic strategies of rutile were also reviewed. Simultaneously, the properties of ionic liquid and use in nanostructure materials were introduced. Based on the above concept, the background, contents of this study were put forword, and the characterization methods in this paper were also listed.In Chapter 2, rutile films consisting of rectangular rnanorods were facilely deposited on glass substrates from strongly acid solution of TiCl₄. The highly ordered arrays of nanorods was realized in presence of ionic liquid (IL) of [Bmim]Br by following a hydrothermal process. In this process, Degussa P25 nanoparticles served as seeds that were pre-deposited on the substrates to facilitate the array of rutile nanorods. A mechanism related with surface adsorption of imidazole salts on TiO₂ surface was proposed to explain the influence of imidazolize salts on formation of the rutile and anatase crystlas phase. It was considered that theÏ€-Ï€interaction between imidazole cations adsorped on rutile surface was the main cause of rutile formation and elongate the size of rutile rods.In Chapter 3, Morphology evolution of rutile particles from nanorods to microcones, again microspheres were realized with the increasing amount of TiCl₄ via self-assembly under hydrothermal condition. A kind of ionic liquids, 1-octyl-3-methylimidazole bromide ([C₈mim]Br) was used to assist the fabrication of rutile nanostructures in the system. The presence of [Cgmim]Br apparently resulted in the aggregation of rutile particles via self-assembly, till porous structures was formed on the surface of microspheres. The corresponding mechanism of self-assembly was proposed to explain the effect of [C₈mim]Br on fabrication of these rutile nanostructures.In Chapter 4, rutile nanocrystals with low dimension, including nanorods and nanocubes, were prepared in presence of ionic liquid of 1-dodecyl-3-methylimidazole chloride ([C₁₂mim]Cl) under hydrothermal condition. The conditions, mainly including concentration of IL and Ti source, were ranged widely to investigate the formation of rutile crystals. Furthermore, the role of Cl^- anions played in the system was discussed.In Chapter 5, Barium titanate and strontium titanate nanoparticles were both prepared by following a nanaqueous route when n-butylamine was used as solvent. In this process, the growth of particles was controlled via controllably releasing water of crystallization of reactants, and the corresponding mechanism so-called as "release-hydrolysis" was put forward and discussed.The last charper, the innovative conclusions were summarized.