Synthesis and characterization of Yb 3+,Tm 3+:Ba 2YF 7 nanocrystalline with efficient upconversion fluorescence

Abstract

A novel upconversion luminescence nanocrystals Yb 3+,Tm 3+:Ba 2YF 7 were synthesized via the hydrothermal method. They have uniform morphology with a mean size of 30 nm even if annealed at 600 °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 Tm 3+ ions. After post-annealing at 600 °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 Ba 2YF 7 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 Tm 3+ ions.