Influence of cobalt doping on the structural, optical and luminescence properties of sol-gel derived TiO2 nanoparticles

We have investigated the structural and optical properties of sol-gel derived cobalt-doped Titanium dioxide (TiO2) nanoparticles. X-ray diffraction patterns exhibit that Co-doped TiO2 forms in anatase phase without any formation of secondary phases. SEM images reveal that the as-grown nanoparticles are almost spherical in size with average particle size in the range of 35-50 nm. Raman spectra recorded at room temperature show that Co doping cancels the rutile phase that was present in the pure TiO2 sample. The energy band gap calculated using UV/Vis spectra and Tauc's relation is found to be of direct bandgap nature and its value decreases with the doping concentration of cobalt. Our photoluminescence results indicate that a photoluminescence emission is found to be centred around 380 nm in the ultraviolet and around 680 nm in the visible range of spectrum.