Nanoperovskite doped with Yb3+ and Tm3+ ions used as an optical upconversion temperature sensor

The temperature variation of the emission bands of the YAlO3:Yb3+/Tm3+ nanoperovskite has been analysed under 975 nm excitation to test its performance as a temperature sensor. The emission bands, originating from 3F2,3 → 3H6 and 3H4→ 3H6 transitions, are located at 700 and 800 nm respectively (first biological window of the human tissue), and were measured from room temperature until 470 K. The calibration of the optical sensor has been made by two different methods. In the first one, based on the fluorescence intensity ratio technique, the areas under the two emission bands were used. In the second procedure the ratio of the intensities at two different wavelengths is estimated. The results showed a higher sensitivity in the biophysical temperature range for the fluorescence intensity ratio method, while a better sensitivity was obtained with the second method for temperatures above 340 K. Once the calibration is made, it is possible to monitor the temperature of the nanoperovskite in the aforementioned range while the sample is heated with the laser.