2.4. Optical Characterization
The UV–vis spectra of doped and undoped TiO2 and ZnO were
obtained by using Cary 50 UV–vis spectrophotometer. The diffuse
reflectance spectra were obtained using a Shimadzu 2450 UV–vis
spectrophotometer with an ISR-240A integrating sphere attachment
with barium sulfate as the standard.