Characterization of optical response properties for a nanosized TiO2 with visible-light response

Nanosize-TiO2 podwers with visible-light response and photocatalytic capability were synthesized by hydrothermal process with organics as solvents. Results of diffuse reflectance spectra (DRS) for solid TiO2 powders show that the visible light response properties of present nanosize-TiO2 are similar to that of modified TiO2, which have strong visible-light response in visible-light region. On the other hand, UV-Vis absorption spectra of TiO2 suspensions show that the optical properties of present nanosize-TiO2 are similar to that of intrinsic TiO2, and no obvious visible light absorption detected. Such difference in optical properties via DRS and UV-Vis spectra for present nanosize-TiO2 is attributed to the difference status of nanosize-TiO2 existing as solid powder or dilute suspensions. Under the conditions of extreme dilute suspensions, photon induced electron transition accompanied by phonon excitation may be degenerated while it is not the case for solid powders. For present photocatalyst with high activity under visible light irradiation, it is necessary to combine two methods to evaluate the accurate information of the absorption edge and optical response properties.