Controllable synthesis and crystal structure determined upconversion luminescence properties of Tm3+ (Er3+) ions doped YbF3 and NaYbF4 crystals

Graphical abstract: - Highlights: • The synthesis of YbF3 and NaYbF4 crystals was successfully fulfilled by hydrothermal method. • The phase and morphology of products were adjusted by changing the hydrothermal conditions. • Relatively enhanced ultraviolet upconversion emissions were observed in YbF3 nanocrystals. • The crystalline phase impact on the upconversion luminescence was systematically studied. - Abstract: The synthesis of YbF3 and NaYbF4 crystals was successfully fulfilled by a facial hydrothermal method. The phase and morphology of the products were adjusted by changing the surfactant additive and fluorine source and tuning the pH value of the initial solution. The products with various morphologies range from octahedral nanoparticles, corn-like nanobundles, nanospheres, microrods, and hollow microprisms were prepared at different conditions. The growth mechanism of these products has been systematically studied. Impressively, relatively enhanced high order ultraviolet (UV) upconversion (UC) luminescence was observed in Tm3+ (Er3+) ions doped YbF3 nanocrystals (NCs) compared with NaYbF4 microcrystals under the excitation of 980 nm infrared laser. The investigation results reveal that the crystal symmetry of matrix has significant effect on the spectra and lifetimes of the doping lanthanide ions. The simply synthesized water soluble YbF3 NCs with efficient UV UC luminescence may find potential application in biochemistry