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

► Monodisperse LaF3:Yb3+, Er3+/LaF3 core/shell nanocrystals were prepared. ► Upconversion emission intensity and lifetime enhanced after coating with LaF3 shell. ► Core/shell structure is an efficient way for improving upconversion luminescence.