Near-Infrared-to-Near-Infrared Optical Thermometer BaY2O4:Yb3+/Nd3+Assembled with Photothermal Conversion Performance

Nowadays, the construction of photothermal therapy (PTT) agents integrated withreal-time thermometry for cancer treatment in deep tissues has become a research hotspot. Herein,an excellent photothermal conversion material, BaY2O4:Yb3+/Nd3+, assembled with real-time opticalthermometry is developed successfully. Ultrasensitive temperature sensing is implemented throughthefluorescence intensity ratio of thermally coupled Nd3+:4Fj(j= 7/2, 5/2, and 3/2) with a maximalabsolute and relative sensitivity of 68.88 and 3.29% K-1, respectively, which surpass theoverwhelming majority of the same type of thermometers. Especially, a thermally enhanced Nd3+luminescence with a factor of 180 is detected with irradiation at 980 nm, resulting from theimprovement in phonon-assisted energy transfer efficiency. Meanwhile, the photothermal conversionperformance of the sample is excellent enough to destroy the pathological tissues, of which the temperature can be raised to 319.3 Kafter 180 s of near-infrared (NIR) irradiation with an invariable power density of 13.74 mW/mm2. Besides, the NIR emission ofNd3+can reach a depth of 7 mm in the biological tissues, as determined by an ex vivo experiment. All the results show the potentialapplication of BaY2O4:Yb3+/Nd3+as a deep-tissue PTT agent simultaneously equipped with photothermal conversion and temperature sensing function

Automated summary

This study successfully developed BaY2O4:Yb3+/Nd3+ as a photothermal therapy agent with real-time temperature sensing capability. The agent exhibits excellent photothermal conversion performance and can be used to destroy pathological tissues.