Hydrophilic and photocatalytic performances of lanthanum doped titanium dioxide thin films

Pure and La-doped TiO2 thin films were prepared on glass by sol-gel method using tetrabutyl titanate as Ti precursors. Their chemical composition, structure and properties were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV-Visible spectrophotometer and optical contact angle measuring instrument, respectively. The results showed that the content of La was the key factor for hydrophilic and photocatalytic activity. LaTiO3 could be formed in La-doped TiO2 thin films, which caused the TiO2 lattice distortion and restrained the transition from anatase to rutile. By adding 0.3 wt.% La to the TiO2 thin films, the optimal hydrophilic character could be obtained and the contact angle was only 9.6°. La-doped TiO2 thin films could expand the wavelength response range of TiO2, and thus increase the speed of the photocatalytic reaction. 92.02% of methylene blue was finally degraded when the concentration of La was 0.3 wt.%. The expressions of ln(CA0/CA) as functions of photocatalytic time were deduced which were well consistent with the experimental results.