Self-cleaning efficiency of titanium dioxide surface under simultaneous UV irradiation of various intensities and water flow

We investigated the self-cleaning efficiencies of titanium dioxide (TiO₂) surface under ultraviolet (UV) irradiation in combination with a water flow (UV/water) condition using oleic acid as the model surface contaminant. UV light intensities were varied from a typical indoor intensity level to a representative outdoor intensity level in Japan. The combined UV/water treatment exhibited a much higher self-cleaning efficiency than either condition alone. This suggests that the self-cleaning effect occurred at nanometersized photo-induced superhydrophilic domains of the TiO2 film surface located at the interface of the TiO₂ surface, oleic acid, and air.