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.