Multiple ratiometric nanothermometry operating with Stark thermally and non-thermally-coupled levels in upconverting Y2-xMoO6:xEr3+ nanoparticles

Contactless optical nanothermometers of high thermal sensitivity are in great demand in various fields. In this work, we applied a facile sol-gel method to synthesize a series of Y2-xMoO6:xEr(3+) upconverting nanoparticles (UCNPs), capable of acting as luminescence nanothermometers. Upon 980 nm laser light irradiation, with increasing Er3+ content, the prepared samples show a color-tunable upconversion emission, from green to yellow. Comparison of the thermometric properties determined by the Stark thermally coupled levels (TCLs) with those determined by the Stark non-thermally coupled levels (non-TCLs) showed that the superior thermal sensitivity (maximal S-r = 2.063%K-1 at 303 K) is achieved for the non-TCLs F-4(9/2)(1())/S-4(3/2)(1()). Moreover, a higher content of Er3+ in UCNPs (Y1.88MoO6:0.12Er(3+) UCNPs) has been found to lead to a significant increase of S-r (S-r MAX = 2.460%K-1 at 303 K). Y2-xMoO6:xEr(3+) UCNPs are promising materials for contactless nanothermometers of high sensitivity. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study synthesized a series of Y2-xMoO6:xEr(3+) upconverting nanoparticles using a sol-gel method, showing high thermal sensitivity. Comparing the thermometric properties determined by thermally coupled and non-thermally coupled levels, the optimal conditions for achieving superior thermal sensitivity were identified, with Er3+ content found to significantly impact the thermal sensitivity.