Synthesis and upconversion luminescence properties study of NaYbF4:Tm3+ crystals with different dopant concentration

Up-Conversion Luminescence Processes in NaLaF4 Doped with Tm3+ and Yb3+ and Dependence on Tm3+ Concentration and Temperature

In this work, luminescence processes in polycrystalline NaLaF₄:Tm³⁺ and NaLaF₄:Tm³⁺,Yb³⁺ materials were studied. Luminescence spectra and decay kinetics measurements were performed for NaLaF₄ doped with various Tm³⁺ concentrations (0.01, 0.1, 0.5, 1, and 2 mol%) under direct excitation to ³P₀, ¹D₂, ¹G₄, and ³H₄ states. It was found that some of the Tm³⁺ excited states are more affected by Tm³⁺ concentration than other states. Under infrared excitation of Yb³⁺, energy transfer to Tm³⁺ occurred and intensive ultraviolet and blue up-conversion luminescence was observed. Possible up-conversion mechanisms are discussed. Spectroscopic measurements show that long-duration excitation radiation reduces ultraviolet up-conversion luminescence intensity, and this intensity reduction is related to sample heating due to high excitation radiation density and a poor heat sink from samples. It was found that sample configuration for spectroscopic measurements is crucial to correctly describe measured up-conversion luminescence spectra.

Near-infrared excited ultraviolet emitting upconverting phosphors as an internal light source in dry chemistry test strips for glucose sensing

UV-emitting upconverting nanophosphors can be used as an internal light source in test strips for glucose measurement.