Abstract
Based on the concept that the electron–hole separation effect caused by a different band-gap structure would improve its hydrophilicity, anatase-TiO2/Cr-doped TiO2 thin films were synthesized by DC magnetron sputtering. The optical band gaps of TiO2 thin films decreased from 3.23 to 2.95eV with increasing Cr-doping content. Multilayer TiO2 thin films with different band gaps exhibited a superhydrophilicity under UV illumination. In particular, in anatase TiO2 (3.23eV)/4.8% Cr-doped TiO2 (2.95eV), the hydrophilicity, which indicated a contact angle of less than 20°, lasted for 48h in the dark after UV illumination was discontinued. This outstanding result has rarely been reported for TiO2 thin films, which confirmed that the prominent superhydrophilicity of anatase TiO2/Cr-doped TiO2/glass could be attributed to the retardation of electron–hole recombination caused by the band-gap difference.
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