Hydrothermal synthesis and enhanced photoluminescence of Tb3+ in Ce3+/Tb3+ doped KGdF4 nanocrystals

Abstract

RE³⁺ (RE³⁺ = Ce³⁺, Tb³⁺) doped and undoped KGdF₄ nanocrystals have been synthesized by a citric acid assisted hydrothermal method. The nanocrystals crystallize in cubic phase with spherical morphology and an average diameter of 100 nm. The optical properties of Ce³⁺ and/or Tb³⁺ doped KGdF₄ nanocrystals were characterized. The results reveal that the existence of Ce³⁺ (sensitizer) can dramatically enhance the photoluminescence emission intensity of Tb³⁺ (activator) in the co-doped samples due to an efficient energy transfer from Ce³⁺ to Tb³⁺. The energy transfer efficiency of Ce³⁺–Tb³⁺ was evaluated. The critical energy transfer distance between Ce³⁺ and Tb³⁺ was calculated by methods of concentration quenching and spectral overlapping. Experimental analysis and theoretical calculations reveal that the dipole–quadrupole interaction should be the dominant mechanism for the Ce³⁺–Tb³⁺ energy transfer.