Role of Temperature on the Phase Modification of TiO₂ Nanoparticles Synthesized by the Precipitation Method

Nanostructured TiO₂ samples have been synthesized successfully by a simple precipitation method. The prepared samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), photoluminescence (PL) spectroscopy, ultra violet (UV) spectroscopy and Raman spectroscopy respectively. The as-prepared TiO₂ nanoparticls appear to be a single anatase phase with average crystalline size 37.68 nm at 150 ^∘C and found to be transformed from anatase to rutile phase during the annealing of samples in the temperature range from 150 ^∘C to 600 ^∘C. The TEM images indicate the particle sizes are in the range between 12 and 25 nm for anatase phase TiO₂ at 400 ^∘C and 30–45 nm for rutile phase TiO₂ at 600 ^∘C. The luminescence property of the TiO2 nanoparticles studied by the emission properties confirms the presence of defect levels caused by the oxygen vacancies. Raman spectroscopy was used to identify and quantity the amorphous and crystalline TiO₂ phases. FTIR studies reveal weak complex vibrations between the titanium and oxygen species and also additional unsaturated sites (Ti³⁺) through incorporation of (OH) groups, not otherwise seen in bulk TiO₂.