Pr³⁺-Doped β-NaYF₄ for temperature sensing with fluorescence intensity ratio technique

Pure β-NaYF₄:0.8%Pr³⁺ powder sample was synthesized by the hydrothermal method. The temperature dependence of the fluorescence intensity ratio (FIR) of emission bands corresponding to the 3P1-3H5 and 3P0-3H5 transitions was measured in the temperature range of 120 K to 300 K excited by a 473 nm continuous wave (CW) laser. The dependence of the FIR on temperature is well fitted with an exponential function and the effective energy difference obtained is 457 cm^-1, which gives further an absolute temperature sensitivity of 0.01352 K^-1 at 300 K. The monotonous increase of FIR with temperature and high absolute temperature sensitivity demonstrate that this material can be used as temperature sensor. In addition, mono-dispersed NaYF₄:1%Pr³⁺ nanoparticles were also synthesized.