Realization of an Optical Thermometer via Structural Confinement and Energy Transfer.

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-activated SrGdGaOF phosphor with tunable color has been constructed by a cooperative cation-anion substitution strategy with to the replacement of [Sr-F] by [Gd-O]. When = 0, the sample SrGaOF/Bi possesses a peak wavelength at 438 nm, and this value will shift to 470 nm if is equal to 1 (SrGdGaO/Bi). In addition, photoluminescence tuning from blue to red has been realized successfully by an efficient Bi → Eu energy migration model in SrGdGaOF samples. The specific Bi → Eu 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 and a red signal from Eu) 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, and the multi-phonon de-excitation mode leads to the thermal quenching of Eu. At room temperature (298 K), the determined maximum relative sensitivity () is 1.27% K. Moreover, the absolute sensitivity () is 0.067 K since the temperature is elevated to 523 K. The collected results are superior to most of the reported optical thermometry materials.