Photo-induced hydrophilicity of polycrystalline SrTiO3 thin films

In the current work, we investigate the photo-induced hydrophilicity of SrTiO3 thin films prepared by the sol-gel process. The SrTiO3 thin films were prepared with different grain sizes but the same crystalline phase, almost the same crystallinity and band gap. With increasing heated temperature, the grain sizes on the film surfaces increased and became more heterogeneous microstructure. Fraction of methylene blue (MB) decomposed on the films was almost the same under UV-A or UV-B light irradiation. Although the films did not show highly photo-induced hydrophilic conversion under UV-A light irradiation, they exhibited the photo-induced hydrophilicity under UV-B light irradiation. The films with smaller grains were highly hydrophilic and higher hydrophilicizing rate than those with larger grains. These results indicate that the SrTiO3 films exhibited the photo-induced hydrophilicity, and it was affected by the surface microstructure.