Upconversion luminescence and optical temperature-sensing properties of LiNbO3:Yb3+/Er3+ nanoparticles

Abstract

LiNbO₃:Yb³⁺/Er³⁺ nanocubes with an average diameter of approximately 500 nm were applied in non-invasive optical temperature sensors for the first time. With increasing annealing temperature, a two orders of magnitude enhancement of green and red upconversion emissions arose from a combined effect of the decreased surface quenching centers and the increased concentration of Yb³⁺ and Er³⁺ ions in the interior of the crystal lattice. Based on the fluorescence intensity ratio technique, the LiNbO₃:Yb³⁺/Er³⁺ nanocubes showed an excellent maximum sensitivity of approximately 0.0094 K⁻¹ at 340 K, which signifies their potential application in optical thermometry.