Color-tunable luminescence, energy transfer and temperature sensing behavior of hexagonal NaYF4:Ce3+/Tb3+/Eu3+ microcrystals

In this paper, a series of color-tunable phosphors from green to yellow and eventually to red have been successfully synthesized with efficient Ce3+ -> Tb3+ -> Eu3+ energy transfer in hexagonal NaYF4 host. The energy transfer processes from Ce3+ to Tb3+ and from Tb3+ to Eu3+ and the corresponding energy transfer efficiencies are carefully investigated by the photoluminescence excitation spectra, emission spectra and the decay curves. Impressively, the Ce3+ -> Tb3+ -> Eu3+ energy transfer mechanism has been proposed and can be attributed to the strong absorption of ultraviolet light by sensitizers (Ce3+), followed by energy migration to Tb3+ ions, from which the energy is finally transferred to activators (Eu3+). Furthermore, the temperature sensing behavior of beta-NaYF4:Ce3+/Tb3+/Eu3+ under 248 nm ultraviolet light excitation is also studied to explore the possible application of the as-synthesized sample in optical thermometry. Evidently, the results suggest that the investigated beta-NaYF4: Ce3+/Tb3+/Eu3+ sample may be a promising candidate for optical temperature sensor. (C) 2016 Elsevier B.V. All rights reserved.