Synthesis of Gd-doped TiO2 nanoparticles under mild condition and their photocatalytic activity

Gadolinium (Gd)-doped titania nanoparticles were synthesized under mild condition (low temperature (< 100 °C) and ambient pressure) by a modified sol–gel method. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy (TEM), diffuse reflectance spectra (DRS) and photoluminescence (PL) analysis. The photocatalytic activity was evaluated by degradation of dyes (Reactive Brilliant Red X-3B and rhodamine B) in aqueous solution under visible light and UV irradiation. Results showed that highly crystalline anatase Gd-doped titania was obtained without further heat post-treatment. All Gd-doped samples showed a significant shift in the onset absorption towards the longer wavelength. Appropriate amount of Gd doping could slow the radiative recombination process of photogenerated electrons and holes in TiO2. Furthermore, it exhibited a significant improvement in photocatalytic activity. The trend of the apparent rate constant under visible light was as follows, 0.5 at% Gd-doped TiO2 > 0.3 at% Gd-doped TiO2 > 0.7 at% Gd-doped TiO2 > pure titania > P25 (a commercial titania).