Impact of Gd ions from the lattice of TiO2 nanoparticles on the formation of reactive oxygen species during the degradation of RhB under visible light irradiation

Gd doped TiO2 nanoparticles with different dopant concentration were prepared by sol-gel method. The crystalline structure of all samples corresponds to the tetragonal anatase phase. Gd3+ doping inhibit the grain size and increase the micro-strains. The decrease of the nanoparticles size by doping was evidenced by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Specific bands of brookite phase appear in Raman spectra. Electron Spin Resonance (ESR) spectroscopy and high resolution transmission electron microscopy (HRTEM) proved the presence of Gd3+ ions substitutionally incorporated at Ti4+ sites of TiO2 lattice. All the samples show photocatalytic activity against RhB and the best performance was obtained using 0.3% Gd-doped TiO2 nanoparticles. The presence of hydroxyl radical at the solid–liquid interface was evidenced using ESR experiment coupled with spin-trapping technique and their influence on photocatalytic activity of the samples was highlighted. With increasing Gd doping level a little increase of the optical band gap was determined.