Synthesis of LiErF4 and LiGdF4 Core-Shell Nanocrystals and Tunable Upconversion Emission from Red to Green

摘要

In this study, LiErF4 and related LiGdF4 core-shell nanocrystals were synthesized via thermal decomposition, and the upcon-version luminescence under an excitation of 980 nm was investigated. The phase of LiErF4 was not changed by a low content of Gd~(3+) dopant, whereas orthorhombic GdF3 formed as an impurity when the amount of Gd~(3+) was increased. The upconversion luminescence intensity of LiErF4 was enhanced by a suitable Gd~(3+) content. Considering the enhanced upconversion emission of LiErF4 and synthesis of pure tetragonal phase LiGdF4, a core-shell structure of LiErF4@LiGdF4:Yb,Er was designed, characterized, and compared to LiYF4@LiGdF4:Yb,Er. LiErF4@LiGdF4:Yb,Er had a yellow upconversion emission output, which was attributed to the combination of the upconversions in the core and shell. Additionally, a series of relevant derivatives of LiErF4@LiGdF4:Yb,Er were prepared for further investigation of their luminescence performance, and red-to-green tunable upconversion luminescence was obtained for these core-shell nanocrystals.