Facile synthesis, formation mechanism and tunable upconversion luminescence of nanocrystals co-doped by Yb3+/Tm3+

摘要

The well-defined lanthanide co-doped upconversion nanoparticles(UCNPs) had been synthesized using a simple solvothermal route at 150 degrees C, which was lower than previous reports. The shuttle-like and spherical UCNPs co-doped by Yb3+/Tm3+ had been prepared, respectively. The morphology, crystal phase and size distribution of various UCNPs could be easily controlled. The growth mechanism and morphology transition of UCNPs had been deduced by schematic diagram. UC luminescence could be tuned by employing different host lattices (GdF3, YF3, NaGdF4 and NaYF4). NaGdF4:Yb3+/Tm3+ displayed the strongest UC luminescence at 475 nm among four kinds of UCNPs, and its emission intensity was almost 10 times higher than that of NaYF4:Yb3+/Tm3+. UC mechanism had been determined by energy level diagrams. It's revealed that the accumulation and energy transfer of Gd3+ could be demonstrated in polycrystalline structure. The work provided a simple method for preparation of UCNPs with tunable UC luminescence. (C) 2016 Elsevier Ltd. All rights reserved.