Preparation and characterization of upconversion luminescent LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals

LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals were successfully synthesized using solvothermal method. The crystal structure, morphology and photoluminescence properties of as-prepared nanocrystals were investigated in detail. XRD patterns show that the obtained LaF3:Yb3+,Er3+ core and LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals exhibit hexagonal structure. The average particle size is about 9.3 nm and 11.4 nm for core and core/shell nanocrystals, respectively. Compared with LaF3:Yb3+,Er3+ nanocrystals, both the upconversion emission intensity and the lifetime increase in LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals. The enhancement can be attributed to the LaF3 shell which can eliminate the nonradiative centers on the surface of LaF3:Yb3+,Er3+ nanocrystals.