Controlled growth, intense upconversion emissions and concentration induced luminescence switching of bifunctional Tm3+ doped hexagonal NaYb0.55Gd0.45F4 nanorods

Abstract Bifunctional hexagonal Tm 3+ doped NaYb 0.55 Gd 0.45 F 4 nanorods with tunable size are prepared via in situ cation-exchange reaction using hydrothermal method. The measured field dependence of magnetization of the NaYb 0.55 Gd 0.45 F 4 nanorods shows typical paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of rare-earth ions. When excited by a 980 nm laser, these nanorods exhibit intense multi-color up-conversion (UC) emissions in infrared, red, blue and especially ultraviolet. In addition, luminescent switching between different UC emission wavelengths of 480 nm and 450 nm is observed by adjusting Tm 3+ doping concentration. Based on power-dependent spectral analyses, it is found that with the increase of Tm 3+ doping concentration, due to the suppressed saturation effect, the dominative UC process redistribute the populations at 1 G 4 and 1 D 2 (Tm 3+ ) states of Tm 3+ ion resulting in the above luminescent switching. Our results indicate that bifunctional hexagonal NaYb 1− x Gd x F 4 nanocrystals have potential applications in miniaturized solid-state light sources, optical processing sensors and fluorescent biolabels.