Figure 6: Raman spectra of (a) undoped, (b) Ga-doped TiO2 nanoparticles. Peaks indexed as “A” are originating from vibrations associated with anatase TiO2, whereas the peak indexed as “B” in the doped sample is from Ga2O3. (c) UV-Vis-NIR diffuse reflectance spectra of undoped and Ga-doped TiO2 nanoparticles. Inset (i) represents the visible part of reflectance spectrum, and inset (ii) represents the direct bandgap calculations of undoped and Ga-doped TiO2 nanoparticles, (d) approximate energy level diagram of doped TiO2 showing the defect level generation for improved photoactivity and the photocatalytic degradation mechanism (the diagram is not to the scale).