Luminescence mechanism of Eu3+ ions doped NaYF4 nanocrystals via in situ time-resolved spectroscopy

In this paper, we fabricated NaYF4: Eu3+ nanocrystals via a facile hydrothermal approach. By a technique of in situ optical spectroscopy, the luminescence kinetics of the NaYF4: Eu3+ nanocrystals were real-time monitored by a confocal optical microscopy system. It is discovered that the most intense emission peak of Eu3+ ions is at 615 nm (D-5(0) -> F-7(2)) that belongs to the electric dipole (ED) transition and its intensity is sensitive to the crystal environment. The D-5(0) -> F-7(2) emission band could appear obvious stark-splitting phenomenon during the heat process of the nanocrystals at 1000 degrees C. The luminescence mechanism of NaYF4: Eu3+ nanocrystals is analyzed by Judd-Ofelt theory. The special spectroscopic properties of NaYF4: Eu3+ nanocrystals at high temperature could have an impact on the optical properties of trivalent lanthanide ion doped fluoride materials and associated applications. Furthermore, this finding may serve as a promising and powerful technique to better investigate the PL mechanism.