Quwei Ni,Zhibin Mei,Chunxia Li,Jieying Li,Jiachun Liu,Wanqiang Liu,Jiansheng Huo,Qianming Wang
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 Bi3+-activated Sr3–xGdxGaO4+xF1–x phosphor with tunable color has been constructed by a cooperative cation–anion substitution strategy with to the replacement of [Sr2+–F–] by [Gd3+–O2–]. When x = 0, the sample Sr3GaO4F/Bi3+ possesses a peak wavelength at 438 nm, and this value will shift to 470 nm if x is equal to 1 (Sr2GdGaO5/Bi3+). In addition, photoluminescence tuning from blue to red has been realized successfully by an efficient Bi3+ → Eu3+ energy migration model in Sr2.6Gd0.4GaO4.4F0.6 samples. The specific Bi3+ → Eu3+ 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 Bi3+ and a red signal from Eu3+) 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 Bi3+, and the multi-phonon de-excitation mode leads to the thermal quenching of Eu3+. At room temperature (298 K), the determined maximum relative sensitivity (Sr) is 1.27% K–1. Moreover, the absolute sensitivity (Sa) 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.
The self-activated mechanoluminescence (ML) of oxysulfides MZnOS (M = Ca, Sr, Ba) is very weak, and bright ML from these hosts is usually achieved with activator-doping strategy. Herein, a promising alkaline-earth-metal-ion blending strategy, instead of activator doping, is proposed to achieve intense and self-activated ML from MZnOS. Upon partially substituting the Ca 2+ of CaZnOS with Ba 2+ and vice versa, intense and eye-visible ML is achieved via exerting a small mechanical stimulus of 2 N onto the obtained Ca 1-x Ba x ZnOS (0 < x < 1). The luminescence center for ML of Ca 1-x Ba x ZnOS is intrinsic oxygen vacancy, so that Ca 1-x Ba x ZnOS can give off efficient and self-activated ML. Under optimum conditions, the maximum ML emission of Ca 0.84 Ba 0.16 ZnOS is about 50-folds and 170-folds to that of CaZnOS and BaZnOS, respectively. Promisingly, Bi 3+ can be incorporated into the lattice of Ca 1-x Ba x ZnOS, transferring ML center from the oxygen defects of Ca 1-x Ba x ZnOS to the activator of Ca 0.96-x Ba x ZnOS:Bi 0.04 , and eventually enable further enhanced ML by about twofolds. This alkaline-earth-metal-ion blending strategy can also enhance Bi 3+ -activated ML from M 0.96 ZnOS:Bi 0.04 , the maximum emission for ML of Ca 0.80 Ba 0.16 ZnOS:Bi 0.04 is 36-folds and 38 folds to that of Ca 0.96 ZnOS:Bi 0.04 and Ba 0.96 ZnOS:Bi 0.04 , respectively. This work opens an avenue to develop new ML hosts and luminophores with efficient emission.
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