UV–visible light photocatalytic properties of NaYF4:(Gd, Si)/TiO2 composites

Abstract

In this study, a new novel composite photocatalystof NaYF4:(Gd, Si)/TiO2phosphor has been synthesized by two step method of solution combustion and sol-gel. The photocatalyst powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. Raman spectroscopy confirmed theanataseTiO2 phase which remarkably increased with existence of yttrium silicate compounds between 800 cm−1and 900 cm−1.Double-addition of Gd3+-Si4+ions in NaYF4 host introduced sub-energy band levels with intense absorption in the ultraviolet (UV) light region.Photocatalytic activity was examined by exposing methylene blue (MB) solutions mixed withphotocatalystpowders to 254 nm UV-C fluorescent lamp and 200 W visible lights. The UV and visible photocatalytic reactivity of the NaYF4:(Gd, 1% Si)/TiO2phosphor composites showed enhanced MB degradation efficiency. The coating ofNaYF4:(Gd, 1% Si)phosphor with TiO2 nanoparticles creates energy band bending at the phosphor/TiO2 interfaces. Thus, these composites exhibited enhanced absorption of UV/visible light and the separation of electron and hole pairs for efficientphotocatalysis.