Enhancement of upconversion luminescence in NaBiF4: Er3+/Yb3+/Lu3+ for temperature detection

Abstract

Optical thermometer has got lots of attention by virtue of non-contact, fast response speed, high sensitivity, anti-interference ability, which is less affected by the environment. However, most fluorescent thermometers still suffer from low sensitivity. Here, an optical thermometer based on NaBiF: Er/Yb/Lu with enhanced upconversion luminescence is reported. The sample emits strong green light of Er under 980 nm laser excitation and with the increase of Lu, the whole luminescence intensity of NaBiF: 2 % Er/20 % Yb/ 2.5 % Lu is enhanced by about 3 times, which due to local crystal field distortion. Meanwhile, the lifetime of Er is prolonged and the temperature detection performance is also improved with the substitution of Lu. The relative sensitivity reaches a maximum of 0.841 % K at 301 K. The results suggest that it is an optical nanothermometer with great potential.