Synthesis of UV/NIR photocatalysts by coating TiO2 shell on peanut-like YF3:Yb,Tm upconversion nanocrystals

We have developed a facile method to synthesize upconversion YF3:Yb,Tm nanocrystals in ethylene glycol. These nanocrystals exhibit an assembly structure with a peanut-like appearance. A layer of TiO2 shell can be facilely coated on the YF3:Yb,Tm nanocrystals via a sol–gel process and crystallized through annealing. The developed YF3:Tb,Tm@TiO2 particles show good photocatalytic activity under the UV band and work better in the UV/NIR band of a Xe lamp, as the core particles can efficiently upconvert NIR light into UV one.