Improving photocatalytic activity by combining upconversion nanocrystals and Mo-doping: a case study on β-NaLuF4:Gd,Yb,Tm@SiO2@TiO2:Mo

Abstract

A novel double-shell-structured β-NaLuF₄:Gd,Yb,Tm@SiO₂@TiO₂:Mo nanocomposite photocatalyst has been developed for the first time. The nanocomposite consists of uniform β-NaLuF₄:Gd,Yb,Tm upconversion nanocrystals as the core, a media shell of SiO₂, and a lot of small sized anatase TiO₂ nanoparticles as the outer shell. The TiO₂ shell is modified by Mo-doping, which can narrow the band-gap of TiO₂ and act as an electron trap, resulting in enhancement of light absorption and reduction of the recombination rate of the photogenerated carriers. The upconversion nanocrystals can convert NIR into UV and visible light which is overall absorbed by the modified TiO₂ shell. The photocatalytic activities of the prepared products are evaluated through photocatalytic degradation of RhB under the irradiation of simulated solar and NIR light. The results show that the as-prepared nanocomposite displays a high photocatalytic activity which is significantly higher than that of commercial P25 and pure TiO₂. This work provides new insights into the fabrication of TiO₂-based composites as high performance photocatalysts and facilitates their application in environmental protection issues using solar light.