Modulation of thulium upconversion in potassium tetraphosphate (KLaP4O12) nanocrystals by co-doping with Yb3+ ions

Abstract

The influence of sensitizer concentration on the up-conversion properties of KLa_0.99−xTm_0.01Yb_xP₄O₁₂ nanocrystals was investigated in a wide range of Yb³⁺ concentrations (x = 0.05–0.5). This impact was manifested by Yb³⁺ concentration dependent variation of up-conversion emission spectra, blue to NIR emission ratio variation, luminescence decay times as well as on the order of upconversion processes. The observed processes of energy transfer between Yb³⁺ and Tm³⁺ were discussed in terms of reduction of the average distance between dopants, Tm³⁺ → Yb³⁺ back energy transfer and energy migration to surface quenchers over a Yb³⁺ sublattice.