NIR Laser-Treatment, Anti-Oxidation Upconversion Nanoparticles for Optical Temperature Sensing

Rare earth ions doped upconversion nanoparticles have a good potential in optical temperature sensing. Herein, a series of ZnO : Yb/Tm/Ga are prepared, which realize the last sensitization. ZnO semiconductor host is sensitized under 980 nm excitation at power 0.6 W. The upconversion luminescence (UCL) intensity of sample increase about similar to 15 times compared with pre-sensitization. The colors of UCL change from blue to yellow with the excitation powers from 0.20 W to 1.05 W, realizing the multi-color turning. Temperature-sensing properties based on Stark levels and non-thermally coupled energy levels (NTECLs) of Tm3+ are analyzed. The maximum relative sensitivity (S-r) of temperature sensor reaches 44.37 %K-1 at 693 K, which originated from (1)G(4) (652 nm) and F-3(2,3) (700 nm) of Tm3+. The energy gap between the energy level (1)G(4) and F-3(2,3) of Tm3+ is about similar to 1217 cm(-1), which suggest that they are thermally coupled. Moreover, ZnO : Yb/Tm/Ga@SiO2 have no damage to the liver, indicating that UCNPs has a low biological toxicity. The ZnO : Yb/Tm/Ga@SiO2 core/shell upconversion nanoparticles can be used in temperature sensors and biological temperature sensing.