Band-gap energy estimation from diffuse reflectance measurements on sol-gel and commercial TiO2: a comparative study

摘要

A comparison of the band gap energy estimated from UV-vis reflectance spectra of TiO2 powders prepared by sol-gel route versus commercial TiO2 powders, nano-powder, bulkpowder and P25 is reported. The experimental results obtained from the optical absorption spectra were reported for all the TiO2 samples. Graphic representations were used to calculate E_g: absorbance versus λ.; F(R) versus E; (F(R) hv)~n versus E, with n = 1/2 for an indirect allowed transition and n = 2 for a direct allowed transition. From the results, it could be seen that E_g strongly varied according to the equation used for the graphic representation. Differences in E_g up to 0.5 eV for the same semiconductor depending on the transition chosen were observed. Accurate E_g estimation in the four semiconductors studied was obtained by using the general equation α (hv) ≈ B (hv — E_g)~n (where α ～ F(R)) and indirect allowed transition.