Studies On Photo-induced Superhydrophilicity Of TiO₂ Thin Films

The effect of doped SiO₂ and V₂O₅ on the super-hydrophilicity and sensitivity of nano TiO₂ thin films were studied in this dissertation. First, the research and application of nanocompsites and nano TiO₂ were reviewed and the author introduced the preparation methods of nanocomposites in response to the dissertation. The author generalized the effect factor principles, characteristics and applications of the thin film. And several kinds of methods of improving the super-hydrophilicity and sensitivity were represented detailed. And at last, on base of it the investigated orientation of this dissertation was presented.In this research, TiO₂ thin film, SiO₂-TiO₂ and V₂O₅-TiO₂ nanocomposite thin films and nanocomposite powder were prepared on glass substrates by sol-gel processing and dip-coating technique. The films as well as the dried powder of bulk gel were characterized by different techniques, such as X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), atomic force microscope (AFM) and thermogravimetry-differential thermal analysis (TG-DTA).The author designed a series of experiment against the new system by the research on the literatures. On the research of SiO₂-TiO₂ thin film, it was found that the addition of SiO₂ could suppress the structural phase transition and crystal growth of TiO₂ crystal. And the relationship between crystalline size and hydrophilicity under sunlight was investigated in this dissertation. Secondly, the results of the research on V₂O₅-TiO₂ films were similar to SiO₂-TiO₂ films-the introduction of V₂O₅ could suppress the structural phase transition and crystal growth of TiO₂ crystal too. What's more important is that the dopant of V₂O₅ on TiO₂ thin films could produce a visible-light response to the films, the water contact angles decreased from 35° before irradiation to 8° after being illuminated by sunlight for 40 minutes while the those of pure TiO₂ thin films remained unchanged after irradiation. And the contact angles decreased as a whole with increasing the amount of V₂O₅ content. Finally, accordingto the results of the research on sensitivity mechanism, the visible response character was attributed to the 3d energy level of V element. Meanwhile, the V2O5 is a narrowband semi-conductor. When it combined with a wideband semi-conductor, TiO2, it could improve the efficiency of charge separation and expand the spectral response of T1O2.At last, the work in dissertation was generalized and the problems which were unsolved in paper were represented base of this. The orientation of research in future was pointed out.