NIR to intense UV-Blue photon transition by upconverting LuF3: Yb3+, Tm3+@BiOCl core@shell composite for pollutant degradation

Abstract

Combining lanthanide ion (Ln3+)-doped upconversion luminescent materials with photocatalysts is an effective strategy to develop near-infrared (NIR)-responsive photocatalysts. Herein, a novel core-shell structured upconversion photocatalyst LuF3: Yb3+, Tm3+@BiOCl (LYT@BiOCl) was synthesized by hydrothermal/solvothermal method. The core is constituted of LuF3: Yb3+, Tm3+ (LYT) upconversion nanoparticles (UCNPs). A BiOCl shell with relatively narrow band-gap was coated on LYT core via a solvothermal process. Solar NIR photons were successfully converted to UV-Blue photons by LYT, which activated the BiOCl shell to produce electron-hole pairs. The excellent core-shell structure of LYT@BiOCl was confirmed by a series of test characterizations, which provides the necessary conditions for efficient energy transfer between LYT and BiOCl. The fluorescence lifetime decay of the 1G4 levels of Tm3+ in LYT@BiOCl further demonstrates the existence of an efficient Förster resonance energy transfer (FRET) channel between LYT and BiOCl. Moreover, photocurrent and EIS tests illustrated LYT(10)@BiOCl has greater photocurrent response and smaller interface transfer resistance. As a result, under the light irradiation of λ > 800 nm and λ > 400 nm (300 W Xenon lamp with a filter), the photocatalytic performance of LYT@BiOCl was always higher than pure BiOCl. Especially, a great enhancement of + 42% and + 64% on the MB degradation efficiency was achieved in LYT(10)@BiOCl compared with pure BiOCl, respectively. This work might provide a useful reference for the rational design of highly efficient NIR-responsive photocatalysts.