Highly sensitive and near-infrared excitable optical thermometer based on CaGdAl3O7: Tm3+, Yb3+, Zn2+

Abstract

Optical thermometers have important applications in many fields due to their high sensitivity, high spatial resolution, fast reaction time and non-contact. For the past few years, up-conversion luminescent material temperature sensors have shown great advantages especially the larger penetration depth, which makes it have great application potential in the medical field. However, the popular fluoride-based upconversion luminescent materials have poor thermal and chemical stability. Herein, we report one highly sensitive and near-infrared excitable optical thermometer based on CaGdAl3O7: Tm3+, Yb3+ with better stability for the first time. Upon 980 nm laser excitation, the samples exhibit both intense blue and near-infrared emission bands of Tm3+ ions centered at 475 and 800 nm, respectively. When the doping ratio of Tm3+ and Yb3+ is 1:40, the upconversion luminescence intensity of the sample is the strongest. Obvious luminescence enhancement was achieved by introducing Zn2+, which could be attributed to the distortion of Tm3+ local crystal field. More importantly, the optimized sample has excellent temperature sensing characteristics in 303–503 K and the maximum relative sensitivity is up to 0.026 K−1 at 303 K. The results suggest that CaGdAl3O7:Tm3+, Yb3+, Zn2+ have great potential as thermomoter in extreme condition.