Realization of an Optical Thermometer via Structural Confinement and Energy Transfer

This is the authors' abstract. We don't add key points for this paper.

The influence of temperature on a variety of physiological or chemical processes has generated considerable interest, and recently noninvasive lanthanide-incorporated optical thermometers have been considered as promising candidates for monitoring its changes at different scales. Herein, a novel Bi 3+ -activated Sr 3– x Gd x GaO 4+ x F 1– x phosphor with tunable color has been constructed by a cooperative cation–anion substitution strategy with to the replacement of [Sr 2+ –F – ] by [Gd 3+ –O 2– ]. When x = 0, the sample Sr 3 GaO 4 F/Bi 3+ possesses a peak wavelength at 438 nm, and this value will shift to 470 nm if x is equal to 1 (Sr 2 GdGaO 5 /Bi 3+ ). In addition, photoluminescence tuning from blue to red has been realized successfully by an efficient Bi 3+ → Eu 3+ energy migration model in Sr 2.6 Gd 0.4 GaO 4.4 F 0.6 samples. The specific Bi 3+ → Eu 3+ energy transfer has been explained by dipole–dipole interactions derived from a model of the Dexter pathway. Intriguingly, the two dopants (a blue signal from Bi 3+ and a red signal from Eu 3+ ) possess different thermal responses to increasing temperature. Accordingly, the intensity ratio values are sensitive to the temperature changes. The energy level cross relaxation causes the quenching effect of Bi 3+, and the multi-phonon de-excitation mode leads to the thermal quenching of Eu 3+ . At room temperature (298 K), the determined maximum relative sensitivity ( S r ) is 1.27% K –1 . Moreover, the absolute sensitivity ( S a ) is 0.067 K –1 since the temperature is elevated to 523 K. The collected results are superior to most of the reported optical thermometry materials.