Energy transfer efficiency in YF_3 nanocrystals: Quantifying the Yb~(3+) to Tm~(3+) infrared dynamics

摘要

In this work, we report on the determination of the infrared Yb~(3+) → Tm~(3+) energy transfer efficiency in YF_3:Yb~(3+)/Tm~(3+) nanocrystals through the study of Yb~(3+) dynamics. The obtained results are compared to those previously reported in macrocrystals to analyze possible changes related to size reduction. Luminescence lifetimes are much shorter in the nanoparticles than in bulk samples, a behavior that can be related to Yb~(3+) → Yb~(3+) migration and the enhanced surface/volume ratio of the nanoparticles. On the other hand, Yb~(3+) → Tm~(3+) energy transfer macroparameter remains unaltered, demonstrating that spectroscopic intrinsic parameters such as radiative and nonrradiative probabilities are not affected by size reduction. Finally, a formula that describes Yb~(3+) lifetime dependence with Yb~(3+) and Tm~(3+) concentration is proposed, considering both the effects produced by migration between Yb~(3+) ions and energy transfer from Yb~(3+) to Tm~(3+) ions.