Temperature-Dependent Upconversion Luminescence Multicolor Tuning And Temperature Sensing Of Multifunctional Beta-Nayf4:Yb/Er@Beta-Nayf4:Yb/Tm Microcrystals

Temperature is one of the physical parameters that affects the emission luminescence properties of upconversion (UC) materials. Temperature-dependent emission color tuning and good temperature sensitivity in multifunctional beta-NaYF4:Yb/Er@beta-NaYF4:Yb/Tm microcrystals were achieved under 980 nm excitation. Based on the different emission bands (blue, green and red bands) and spectral sensitivities of the core-shell structured microcrystals to temperature, intense white-light emission was obtained at room temperature and a real-time naked-eye recognizable emission color change from white to the purplish-pink region was realized with the temperature increasing from 300 to 500 K. Furthermore, optical temperature sensing properties of the sample with good sensitivity (from 0.0034 to 0.0044 K-1) were investigated by using a fluorescence intensity ratio between 521 nm (H-2(11/2) -> I-4(15/2) transition) and 540 nm (S-4(3/2) -> I-4(15/2) transition) in the temperature range from 300 to 500 K. The results indicate that the sample has high sensitivity in a relatively wide range of temperature intervals, especially in the low temperature region. We believe that the multifunctional core-shell structured microcrystals exhibit promising applications in white-light emitting diodes, the anti-counterfeiting field, and temperature sensing.