La2O2S:Er3+/Yb3+ nanoparticles synthesized by the optimized furnace combustion technique and their high-resolution temperature sensing

Abstract

Nanoparticles of less than 100 nm of La2O2S co-doped with Er3+ and Yb3+ in 2% and 12% concentrations, respectively, were synthesized by the improved furnace combustion technique that limits the precursor usage and without the hazardous chemicals. The lanthanum oxysulfide was identified in hexagonal crystal phase. Under 980 nm excitation the sample exhibits a typical upconversion photoluminescence for Yb3+/Er3+. Due to the high concentration of Yb3+, the red emission of Er3+ is of high intensity due to the energy back-transfer. The red emission is less pronounced in downshifting spectrum. Chromaticity analysis shows high color purities of emissions. La2O2S:Er3+/Yb3+ nanoparticle performances as a luminescent temperature sensor were first predicted by the Judd-Ofelt theory and then compared with the conventional experimental thermometry by Luminescence intensity ratio method, with an excellent match in all parameters. The relative sensitivity at 300 K is 1.14 K−1 and it remains relatively high at the physiologically relevant range. The obtained temperature resolution was 0.17 K at 300 K.