Preparation And Photocatalytic Properties Of Super-hydrophilic And Transparent TiO₂ Thin Films

In this thesis, TiO2 thin films were prepared by a facile modified dip coating method. The properties of the films including crystal structures, thickness, surface morphology and optical properties were studied using X-ray diffraction (XRD), ellipsometry, scanning electron microscopy (SEM), UV-Vis spectroscopy (UV-Vis) and atomic force microscopy (AFM). Post-annealing temperatures and thickness of the TiO2 films were evaluated based on their effects on photocatalysis and superhydrophilicy of the films. Brief results were showed as followed.(1) A facile modified dip coating method has been developed to fabricate ultra-smooth, transparent and superhydrophilic TiO2 thin films on glass substrates. Posting-annealing at 400℃ in dry air resulted in anatase T1O2 structures. The TiO2-lfilm possessed an RMS roughness of 2.6±0.7 nm, a thickness of 76nm and an average transmittance of 87% at the visible region, respectively.(2) The factors including annealing temperatures and film thickness were examined with their effects on hydrophilicity of TiO2 thin films prepared by modified dip coating method. The equilibrium water contact angle of the films decreased with increasing post-annealing temperatures. A water contact angle of 0° was obtained on TiO2 films annealed over 400℃ in dry air, i.e. a super-hydrophilic surface was achieved. Obvious effect of the times of dip coating was not showed on superhydrophilicy of TiO2 thin films. The TiO2 film remained super-hydrophilic with an equilibrium water contact angle less than 5° within 15 days. The TiO2 film on glass substrate also displayed excellent antifogging performance.(3) The post-annealing temperatures, film thickness and initial concentration of methylene blue were investigated with their effects on the photocatalysis of TiO2 thin films prepared with modified dip coating method. Photocatalytic performance of the TiO2 films annealed below 400℃ in dry air was weakened with increasing film thickness. That of the TiO2 films annealed over 400℃ was enhanced with increasing film thickness with dip coating times less than 3. However, with dip coating times over 3, the photocatalytic performance of the films was weakened. The photocatalytic performance of the films was enhanced with increasing the initial concentration of methylene blue solution when the concentration is less than a certain value, while it showed an inverse trend with the concentration over that value. The degradation within the same period was achieved with a low ratio.