Effect of visible light on the water contact angles on illuminated oxide semiconductors other than TiO2

Wide band gap semiconductor oxides such as TiO2, Ta2O5, ZnO, indium–tin oxide, InTaO4 or In2O3 are materials with water contact angles in dark between 60° and 130°. The present investigation shows that thin films of these oxides become hydrophilic when they are irradiated with ultraviolet light. This finding indicates that the transformation of the wetting properties of illuminated wide band gap oxides is a common phenomenon not restricted to TiO2. An additional evidence found for ZnO and InTaO4 is that the water contact angle decreases by 30°/40° when they are irradiated with visible light.