Hydrophilicity of anatase TiO2/Cr-doped TiO2 thin films with different band gaps

► TiO2 thin films with different band gaps exhibited a superhydrophilicity. ► Anatase TiO2/4.8% Cr-doped TiO2 showed a contact angle of less than 20°. ► The superhydrophilicity lasted for 48 h in the dark after stopping UV illumination.