Temperature-dependent optical properties of TiO2 nanoparticles: a study of band gap evolution

In this study, we present the first comprehensive investigation of the temperature-dependent band gap energy of anatase TiO2 nanoparticles, utilizing transmission measurements in the range of 10–300 K. X-ray diffraction pattern exhibited nine peaks related to tetragonal crystal structure. Scanning electron microscope image showed that the nanoparticles with the dimensions of 25–50 nm were found as micrometer sized agglomerated. When the spectrum obtained as a result of the transmission measurements was analyzed, it was seen that the band gap energy decreased from 3.29(5) to 3.26(6) eV as the temperature was increased from 10 to 300 K. Temperature-band gap dependence was analyzed using Varshni and O’Donnell-Chen optical models and optical parameters of the TiO2 nanoparticles like absolute zero band gap energy, rate of change of band gap with temperature and average phonon energy were reported.