Luminescence probe for temperature sensor based on fluorescence intensity ratio

The β-NaLuF4: Yb3+/Ho3+ nanocrystals have been synthesized via a solvothermal method, which were protected in a SiO2 capillary tube. Upon 980 nm continuous laser excitation, the micro-tube waveguide characteristic was studied. Additionally, the upconversion emissions from the 5F4, 5S2→5I8 (~545 nm), 5F5→5I8 (~650 nm) and 5F4, 5S2→5I7 (~750 nm) transitions of Ho3+ ions in the micro-tube were obtained and studied as a function of temperature in the range of 300~500 K. The maximum sensitivities derived from the fluorescence intensity ratio technique are 1.53% K−1 (I750/I650) and 0.09% K−1 (I545/I650) at 300 K. The result demonstrated that the near infrared-red absolute sensitivity is more sensitive as a thermometer than the green-red at the whole temperature range. The device is a promising candidate for high resolution luminescent thermometers operating under temperature of 300~500 K.