Synthesis and characterization of Yb3+,Tm3+:Ba2YF7 nanocrystalline with efficient upconversion fluorescence

A novel upconversion luminescence nanocrystals Yb3+,Tm3+:Ba2YF7 were synthesized via the hydrothermal method. They have uniform morphology with a mean size of 30 nm even if annealed at 600 degrees C. Pumped by 980 nm laser diode the as-synthesized powers emit ultraviolet/blue light, which is in the range of the specific upconversion luminescent spectra of Tm3+ ions. After post-annealing at 600 degrees C in an argon atmosphere for 2 h, their upconversion luminescence intensity is 5 multiple improved and the ultraviolet/blue light can even be seen by the naked eyes under a low excitation power of 20 mW. This indicates that Ba2YF7 is a very effective luminescent host material. Excitation power dependences of individual upconversion emission intensity are plotted, which partly uncover the upconversion luminescence mechanism of Tm3+ ions. (C) 2011 Elsevier B.V. All rights reserved.