Utilizing diametrically opposite thermal quenching luminescence to achieve highly sensitive temperature measurement and anti-counterfeiting

The rational design and development of effective optical thermometers based on luminescent materials have received considerable attention over decades due to their unique advantages of fast response, contactless operation and simplicity, to name a few. However, exploring optical thermometers with ultra-high sensitivity is still a challenge. In this work, by taking advantage of the anti-thermal quenching luminescence of Eu3+ ions induced by the thermal redshift of charge transfer bands and the thermal quenching luminescence of Eu2+ and Tb3+ ions, we demonstrate the thermometric potential of CaYGaO4 (CYGO):Eu2+/Eu3+ and CYGO:Eu3+/Tb3+ phosphors. Benefiting from the opposite thermal quenching luminescence of Eu3+ and Eu2+/Tb3+, the maximum relative sensitivity can reach 3.68% K-1 (CYGO:Eu2+/Eu3+) and 5.51% K-1 (CYGO:Eu3+/Tb3+), respectively. Under the irradiation of a single beam of light, the luminous color of the obtained samples undergoes a significant change visible to the naked eye as the temperature increases, which further enhances the temperature sensitivity. In addition to the application of thermometers, considering the strong dependence of luminous intensity and color on excitation wavelength and temperature, we combined these two phosphors to perform a series of demonstration experiments and acquired some fascinating results, which unequivocally confirmed that these phosphors have a bright future in the field of anti-counterfeiting and security labeling. An ultra-sensitive LIR thermometer was constructed based on diametrically opposite thermal quenching luminescence.