Study On Preparations Uniformed TiO₂ Films And Deposited CdS

In reeent years, Periodic mesoporous materials with uniform pore diameters and high specific surface area have been widely used as catalysts, catalyst supports, chemical sensors, electrical and optical devices, and shape/size selective adsorbents for environmentally hazardous chemicals. Although the synthesis and application of ordered microporous solids have been well established , uumerous attempts to obtain geometrically regular mesoporous materials were unsuccessful until in the early 1990s. For mesoporous materials, the investigation focus on the preparing, function, and application. Among these, the large pore meso-nc-TiO2 materials present good host porous structure to form novel heterojunction through growing a variety of wide hand-gap semiconductors and assembling functional polymers, noble metals, carbon nanotubes, and other components in the large mesopore channels, which could be useful for the development of improved efficiency in photocatalysis, photoelectric conversion, and hydrophilic coating materials applications.Wormhole-like mesoporous titania and uniformed nanocrystalline titania have been successfully synthesized through evaporate-induced self-assembly (EISA) method. The obtained samples were characterized in detail by TG-DSC, XRD, Raman, AFM, SEM and TEM. As for wormhole-like mesoporous TiO₂, the template can be removed completely and ordered wormhole-like mesoporous titania structure was formed after being calcinated at 350℃. As for uniformed nanocrystalline titania thin film, uniformed and spheric titania structure was formed after being calcinated at 400℃. The photocatalytic activity experiments of TiO₂ powders with different calcination temperatures were also presented in this thesis. The highest photoactivity of wormhole-like mesoporous titania and uniformed nanocrystalline titania were presented at 400℃and 500℃, respectively. The hydrophilicity of wormhole-like mesoporous titania thin film was higher than that of uniformed nanocrystalline titania thin film, which can be ascribed to the structure of its porous nature. Both obtained samples presented higher hydrophilicity after being irradiated by high press Hg lamp. Furthermore, the wormhole-like mesoporous titania thin film produced photo-induced super hydrophilicity because of its porous structure and large surface area. CdS was deposited on the wormhole-like mesoporous titania thin film electrode through electrodeposition method. The photocurrent action spectra of ITO/TiO₂/CdS composites thin film demonstrated that CdS was successfully deposited on the surface and in the hole of mesoporous titania thin film. Furthermore, the range of photoelectricity response extended to visible light region and photocurrent increased obviously. The absorption intensity of ITO/TiO₂/CdS composites thin film increased and the absorption edge showed red shift obviously, the results demonstrated the formation of TiO₂-CdS heterojunction. In conclusion, the exciting wavelength was extended to visible light region and the utilization efficiency of sun light was enhanced.