Synthesis of rhombic hierarchical YF3nanocrystals and their use as upconversion photocatalysts after TiO2 coating

Abstract

A facile method has been developed to synthesize uniform nanoscale YF₃ architectures. Interestingly, the unique YF₃ nanostructure exhibits a flat and rhombic appearance which is formulated through the hierarchical assembly of YF₃ nanocrystals along a specific crystalline orientation. Investigations on the formation process suggest that an assembly disassembly process is responsible for the construction of this novel structure. Enabled by doping with different lanthanides ions, the products can exhibit various down- or up-conversion luminescences, showing their potentials in serving as versatile host matrixes. The tunable luminescent properties allow designing effective upconversion photocatalysts when the doped YF₃ nanostructures are coated with a TiO₂ shell on their surface. In particular, the YF₃@TiO₂ hybrid structures have the porous nature that is partially inherited from the YF₃ architectures, whose high surface-to-volume ratio facilitates their use as photocatalysts. In this article, we have demonstrated that the YF₃:Yb,Tm@TiO₂ structures exhibit satisfactory photocatalytic activities under the irradiation of both UV and near IR light. As compared with the conventional TiO₂ catalysts, the hybrid structures here offer better performance in photocatalysis in the full solar spectrum. It is anticipated that this work provides a new approach to designing photocatalysts with responses to a broader spectral range.