Synthesis And Properties Of Novel Titania Nanostructured Materials

As an important wide band gap semiconductor, TiO2(titania) nanostructure materials have extensive applications in many fields especially in photocatalysis, gas sensors, solar cells. In recent years, many studies have been carried out on the synthesis and application of titania nanomaterials. Titania properties not only depend on the crystalline form and particle size but also on the morphology and microstructure.The main goal of the dissertation is to synthesize novel nano-strucrured TiO2materials, characterize the materials by various techniques and estimate the properties. In the paper, we synthesized size-controlled TiO2hollow spheres, silkworm cocoon-like mesoporous anatase nanostructure titania and Ni-doping TiO2nanofibers. The sizes, structures and morphology of the prepared TiO2can be well controlled. The formation mechanism of the products is discussed. A preliminary analysis was done on the relationship between the structure and its properties. The present work is beneficial to fundamental investigations and providing useful information for the nano-structured TiO2materials investigations. The detailed information of the dissertation is listed as follows:1. Template-Free Fabrication and Photocatalytic Properties of TiO2Hollow SpheresHerein, the sub-micrometer-sized anatase TiO2hollow spheres were solvothermally synthesized using TiCl4as raw material and the mixture of alcohols-acetone as solvent, and the control of the hollow spheres'size was achieved by adjusting the component of the solvent. The factors including the solvothermal reaction conditions and the components of the reaction system affecting the structures and morphologies of the products were investigated and the formation mechanism of the TiO2hollow spheres was also discussed. The as-prepared TiO2hollow structures exhibited a good photocatalytic activity for the degradation of phenol.Based on the analysis of experiment results, it is proposed that the formation of the TiO2hollow spheres goes through the formation of the poor crystallized solid spheres and the transformation of the solid spheres to hollow ones based on the Ostwald ripening process. During the transformation to the hollow spheres, the inner part of the solid spheres gradually dissolved and recrystallized on the shell of the spheres and formed hollow spheres finally.It can be seen that water plays a critical role in the formation of the hollow spheres, which mainly comes from the etherification of ethanol in the typical system. Because different alcohols would exhibit different etherification reaction rate in the system, which would affect the formation and aggregation of primary TiO2nanocrystals, as well as the Ostwald ripening process of the solid spheres. Therefore, alcohols were adjusted in the present experiment in order to adjust the product size and microstructure.2. Synthesis and Photocatalytic properties of Silkworm Cocoon-like Mesoporous Anatase Titania nanostructureMesoporous silkworm cocoon-like anatase titania nanostructures were synthesized by a simple one-step template-free solvothermal route with water, ethyl ether, ammonium sulfate and titanium(IV) sulfate as starting materials. The coordination between ethyl ether and titanium ions regulated the hydrolysis process, while the ammonium and sulfate ions played vital roles in the anisotropic growth and oriented aggregation of titania primary particles. The synergistic effect of ether and ammonium sulfate lead to the formation of silkworm cocoon-like mesoporous anatase titania nanostructure. Further studies showed that the products exhibited good photocatalytic activity for the degradation of phenol in aqueous solution. The photocatalytic activity is closely related to the sintered temperature and the amount of sulfate species on TiO2.3. Preparation, characterization, and gas-sensing properties of Ni-doped TiO2 nanofibers by electrospinningNanostructured pure and Ni-doped TiO2fibers(diameter ca.100nm) were synthesized by combined sol-gel method and electrospinning techniques, in which titanium tetraisopropoxide as raw material, polyoxyethlene pyrrolidone K90as spinnable aids, Ni(CH3COO)2.4H2O as an additive, acetic acid as a stabilizing agent, ethanol as solvent. The Ni-doping of TiO2inhibit effectively the phase transformation from anatase to rutile and the grain growth of anatase titania. The doping with a suitable amount Ni improve the sensitivity of the TiO2nanofibers sensing of ethanol and acetone vapor. The work not only enriches the synthsis of one-dimensional titania nano-structured materials but also provide a theoretical basis and technical support for the development of high performance gas sensors...