Abstract
The sol-gel method was successfully used to prepare a series of TiO2-SiO2 and rare earth (RE) (La3+, Nd3+, Sm3+, Gd3+)-doped TiO2-SiO2 nanoparticles at a doping level of 3 atomic percent. The structural features of parent TiO2-SiO2 and RE-TiO2-SiO2 fired at 550 degrees C have been investigated by XRD, UV-diffuse reflection, SEM and nitrogen adsorption measurements at -196 degrees C. XRD data verified the formation of typical characteristic anatase form in all the prepared RE-doped TiO2-SiO2 samples. In comparison with the pure TiO2-SiO2 samples (ca. 35 nm in diameter), the RE-TiO2-SiO2 samples have relatively small particle size indicating that the doping with RE metal ions can improve the particle morphology, and retard the grain growth of TiO2-SiO2 during heat treatment. The results indicated that Gd3+ doped TiO2-SiO2 has the lowest bandgap and particle size compared with pure TiO2-SiO2 and other nanoparticles of RE-doped TiO2-SiO2. The highest surface area (S-BET) and pore volume (V-p) values were recorded for Gd-TiO2-SiO2 as well. The effect of doping on the photoactivity was evaluated by the photocatalytic degradation of EDTA as a probe reaction. Among all the pure and RE-doped TiO2-SiO2, Gd3+-TiO2-SiO2 performed the highest catalytic activity towards the tested reaction. That might be due to its special characteristics of particle size, surface texture and bandgap properties. Details of the synthesis procedure and results of the characterization studies of the produced RE-TiO2-SiO2 are presented in this paper. (C) 2010 Elsevier B.V. All rights reserved.