Influence of annealing on the structural, optical and photoluminescence properties of TiO2 nanoparticles

TiO2 nanoparticles were synthesized by co-precipitation method and annealed at 500 degrees C and 700 degrees C in air.The samples were characterized by powder X-ray diffractometry (XRD), Raman, UV-Vis-NIR and Photoluminescence spectroscopic measurements.XRD and Raman analysis confirmed that both the samples possess single phase anatase type tetragonal structure. The average crystallite size of the 500 degrees C and 700 degrees C annealed TiO2 nanoparticles were estimated to be 10 3 and 14 4 nm respectively. Optical absorption study showedthat in both the samples maximum photo absorption take place below 400 nm and the band gap energy were found to be 2.87 (0.2) eV and 2.37 (0.3) eV for 500 degrees C and 700 degrees C respectively.Photoluminescence spectrums of the two samples displayed strong emission in the visible hand with multiple electronic transitions in the 400-850nm range, which suggests presence of various types of lattice defects in the TiO2 matrix. Increase in annealing temperature leads to red shifting of the visible hand and reduction of hand gap energy. Computed values of CCT were found to he 1992K and 1980K for 500 degrees C and 700 degrees Crespectively, which makes them suitable material for the light harvesting optoelectronic devices.