▎ 摘　　要

The development of near-infrared (NIR) light-driven photocatalysts is needed to utilize the large portion of NIR energy in sunlight. In this work, a new strategy to fabricate advanced upconversion-based NIR-driven photocatalysts was developed by integrating core-shell nanostructure of alpha-NaYF4:Yb,Tm@TiO2 with reduced graphene oxide (RGO) nanosheets. This new alpha-NaYF4:Yb,Tm@TiO2/RGO composite was synthesized by a facile wet chemical method. The product exhibited significantly enhanced photocatalytic activity than bare alpha-NaYF4:Yb,Tm@TiO2 and alpha-NaYF4:Yb,Tm/TiO2/RGO physical mixture for the degradation of various organic pollutants, including methylene blue (MB), methyl orange (MO) and phenol, under NIR (980 nm laser) irradiation. Highly reactive hydroxyl radicals ((OH)-O-center dot) were found to be the major reactive species. It was revealed that the core-shell structure of alpha-NaYF4:Yb,Tm@TiO2 improved the upconverison UV energy transfer, while the incorporation of RGO facilitated the photo-generated e(-)-h(+) separation after excited by the upconversion energy. Our discovery highlights the potential of developing NIR-driven photocatalysts by taking advantage of the synergic effects of core-shell upconversion materials combined with graphene for environmental and energy-related applications. (C) 2015 Elsevier B.V. All rights reserved.