Hydrophilicity of anatase TiO_2/Cr-doped TiO_2 thin films with different band gaps

摘要

Based on the concept that the electron-hole separation effect caused by a different band-gap structure would improve its hydrophilicity, anatase-TiO_2/Cr-doped TiO_2 thin films were synthesized by DC magnetron sput tering. The optical band gaps of TiO_2 thin films decreased from 3.23 to 2.95 eV with increasing Cr-doping con tent Multilayer TiO_2 thin films with different band gaps exhibited a superhydrophilicity under UV illumination. In particular, in anatase TiO_2 (3.23 eV)/4.8% Cr-doped TiO_2 (2.95 eV), the hydrophilicity, which indicated a contact angle of less than 20°, lasted for 48 h in the dark after UV illumination was discon tinued. This outstanding result has rarely been reported for TiO_2 thin films, which confirmed that the prom inent superhydrophilicity of anatase TiO_2/Cr-doped TiO_2/glass could be attributed to the retardation of electron-hole recombination caused by the band-gap difference.