Highly efficient and wide range low temperature sensing of upconversion luminescence of NaYF4: Er3+ nanoparticles: Effects of concentration of active or sensitive ions, excitation power and particle size on temperature sensing sensitivity

In this article, NaYF4: Er3+ nanoparticles (NPs) with/without codoping Yb3+ ions were successfully synthesized by the co-precipitation method. The temperature sensing performance of upconversion luminescence of beta-NaYF4: Er3+ under 980 nm excitation was investigated based on the fluorescence intensity ratio (FIR) technology in the temperature range from 113 K to 443 K. The maximum absolute and relative temperature sensitivity were calculated to be 0.0075 K-1 at 443 K and 2.96 %K(-1)at 183 K, respectively. Moreover, the relative sensitivity was over 2.0 %K-1 in the temperature range from 148 K to 248 K. The effects of excitation power, size and structure of particles and concentration of codoping Yb3+ ions on temperature sensitivity were investigated, respectively. The optimum temperature sensing performance of NaYF4: Er3+ was achieved at low excitation power of 0.542 W. While increasing the particle size, coating a NaYF4 layer or codoping Yb3+ ions is harmful to temperature sensing performance. The results indicate that NaYF4: Er3+ NPs have great application prospect in low temperature nanothermometer and present a great reference for future study of optical nanothermometer.