L-lysine-assisted hydrothermal synthesis of β-NaGdF4:Eu3+ microcrystals: Morphology evolution, luminescence and magnetic properties

Abstract Eu3+ doped β-NaGdF4 microcrystals were prepared by using an L-lysine-assisted hydrothermal synthetic method and the morphology evolution was successfully controlled. Hierarchical β-NaGdF4:Eu3+ microcrystals with different morphologies were obtained by changing the moles of L-lysine and the volume of H2O, respectively. The photoluminescence properties of the β-NaGdF4:Eu3+ samples with different morphology were comparatively discussed, in which the hollow hexagonal tube-like β-NaGdF4:Eu3+ exhibited the strongest fluorescence emission intensity owing to the high crystallinity. The characteristic luminescence properties of Tb3+-single doped, Yb3+/Er3+-, and Yb3+/Tm3+-codoped NaGdF4 microcrystals obtained in the presence of L-lysine under hydrothermal condition were also investigated. The superparamagnetic performance of β-NaGdF4:Eu3+ samples at 3 K were characterized in comparison to their paramagnetic property at 300 K, and the results indicated that all samples are paramagnetic at room temperature and the hollow tube-like β-NaGdF4:Eu3+ microcrystals exhibits best saturation magnetization values of 111.11 emu/g at 3 K. The results imply that the morphology-tunable β-NaGdF4:Eu3+ microcrystals are expected to have promising applications for micro/nano optical/magnetic functional devices.