Near infrared ray to ultraviolet up-conversion luminescence of Tm3+–Yb3+ co-doped (CaY)F2 nanocrystals

Abstract

Near Infrared Ray (NIR)-ultraviolet (UV) up-conversion luminescence (UCL) materials have potential application in many fields of biological science, including cells and tissue labeling for bio-imaging, bio-detection, therapy or multiplexed analysis. Tm3+/Yb3+ co-doped (CaY)F2 nanocrystals have been successfully synthetized through the hydrothermal method, and the effect of different synthesis conditions on the morphology and luminescence property of (CaY)F2 phosphors have been discussed. When the molar concentration of Tm3+ and Yb3+ were 0.4 and 20%, respectively, the obtained (CaY)F2 nanocrystals have excellence density, crystallinity, single particle dispersion, uniform particle size (55.5 nm), and high up-conversion luminescence efficiency with the hydrothermal conditions of 180° C and 12 h and calcined temperature of 500° C. Specifically, the synthesized nanocrystals could be stably excited by a 980 nm pump light, converted to 360 nm UV. In addition, the cytotoxicity of (CaY)F2 nanocrystals has also be explored, which shows low cytotoxicity examined by the L929 murine fibroblast cells. With this biocompatibility and excellent up-conversion luminescence properties, the obtained (CaY)F2 nanocrystals have a high potential as biomaterials for photodynamic therapy assisted by TiO2.