Photocatalytic activity and luminescence properties of RE3+-TiO2 nanocrystals prepared by sol-gel and hydrothermal methods

A series of Y3+, Pr3+, Er3+ and Eu3+ modified TiO2 photocatalysts were obtained via sol-gel (SG) and hydrothermal (HT) methods. Samples prepared this way were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission microscopy (STEM), BET surface area method and luminescence spectroscopy. The photocatalytic activity of the synthesized samples was evaluated by the degradation of phenol in aqueous solution under visible and ultraviolet light irradiations. Phenol in aqueous solutions was successfully decomposed under visible light (lambda > 420 nm) using TiO2 modified with RE ions. Luminescence properties of the samples as well as XRD and XPS analyses, indicate that RE are rather in the form of their oxides than in the form of cations in the crystal structure of TiO2. Photocatalysts prepared by SG method possessed higher amount of RE2O3, fewer of OH- groups and Ti3+ species on the surface layer than powders obtained by HT method. Action spectra analysis showed that Pr3+-modified TiO2 could be excited under visible light in the 420-250 nm range. Furthermore, photocatalysts obtained by HT method showed higher photocatalytic activity and lower intensity of luminescence emission than photocatalyst prepared by SG method. (C) 2015 Elsevier B.V. All rights reserved.