Near-infrared emitting Nd3+-Yb3+ codoped Y2O3 nanocrystals for highly sensitive optical thermometry

Rare earth ions activated nanomaterials have been extensively considered as promising candidates for optical thermometry due to their unique photoluminescence characteristics. Nevertheless, thermally coupled levels-based thermometers are suffering from low sensitivity because of the restriction of small energy gap. Herein, the phonon-assisted energy transfer from Yb3+ to Nd3+ in Y2O3 nanoparticles, which makes the near infrared emissions of Nd(3+ )and Yb3+ ions respond to temperature inversely, is utilized to achieve sensitive temperature measurement via the ratiometric method. When pumped by 980 nm continuous wave laser, the multizone thermometry is performed owing to the different dependence of energy transfer on the temperature. The maximum relative sensitivities achieved in the temperature ranges of 423-773 K and 303-333 K are both approximately 2.3% K-1, which are superior to most previously reported luminescence-based temperature sensors. In addition, it is found that the measurement sensitivity is significantly influenced by the laser-induced heating effect especially at relatively low temperatures. Under the excitation of 980 nm square wave laser, the relative sensitivity is enhanced from 2.3% to 2.9% K-1 in the physiological temperature region. These findings can provide an effective pathway to improving the thermometric behavior and expanding the application of luminescence temperature sensing in various fields. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Rare earth ions activated nanomaterials show promise for optical thermometry due to their unique photoluminescence characteristics. By utilizing phonon-assisted energy transfer, sensitive temperature measurement has been achieved with maximum relative sensitivities of approximately 2.3% K-1 in specific temperature ranges. Laser-induced heating effect significantly influences measurement sensitivity, but can be enhanced by utilizing square wave laser excitation in physiological temperature region.