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

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.