Study On The Hydrophilicity Of TiO₂Thin Films And Photocatalysis Of Ag/TiO₂Composite Films

Titanium dioxide thin films have two kinds of superior properties:photocatalysis and photo-induced hydrophilicity. However, they can’t get practical applications in present stage. The reason is that TiO2only absorbs UV light while there is less than4%UV in the visible sunlight. In this paper, we made TiO2thin films and Ag nanoparticles. The hydrophilicity of TiO2thin films was improved by the plasma treatment and the photocatalysis was enhanced by doping AgNPs. The mechanisms were explored.Firstly, the TiO2thin films were prepared by DC magnetron sputtering and followed by annealing. The films were characterized by XRD and SEM. The hydrophilicity was tested and the correlation between hydrophilicity and preparation parameters was established to obtain the best parameters. Then the TiO2thin films under these parameters were detected, the results showed that the thin films with good surface morphology were anatase.Secondly, TiO2thin films were treated by O2and N2plasma irradiation. The influence of parmeters such as pressure, time and power on hydrophilicity was explored. XPS was took for the samples stored in dark for1h treated by O2and N2plasma irradiation. The results showed that the super hydrophilicity of TiO2thin films after O2plasma treatment is not proportional to the concentration of oxygen vacancies, which suggested that the adsorbed oxygen atom in Ti5c position might play an important role.Finally, Ag nanoparticles were deposited onto the surface of TiO2thin films by thermal evaporation to get nano-Ag/TiO2composite films. R6G and methylene blue were chosen as the probe molecules to study the photocatalysis of Ag/TiO2films. The improvement of photocatalysis of nano-Ag/TiO2composite films was explored by means of UV-Vis spectroscopy and the mechanism was investigated by SEM images. The nano-Ag/TiO2composite films after annealing had the best photocatalysis under UV and visible light. AgNPs played different roles for the cases under the UV and visible light irradiation.