Developing scintillators with high light yield (LY), superior irradiation stability, and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence (XEOL) imaging. Lanthanide doped fluoride nanoparticles possess low toxicity, superior environmental stability, facial fabrication process, and tunable emissions, which are appropriate candidates for the next generation nanoscintillators (NSs). However, the low LY and strong positive hysteresis greatly restrict their practical application. Here, we propose an effective strategy that engineers energy gap to significantly enhance the LY. Our results verify that the tetragonal LiLuF₄ host benefits the crystal level splitting of Tb³⁺ ions, which greatly promotes the electrons population on the Tb³⁺:⁵D₄ level followed by the enhanced LY. The LY of LiLuF₄:Tb@LiLuF₄ NSs is calculated to be ~ 31,169 photons/MeV, which is much higher than the lead halide perovskite colloidal CsPbBr₃ (~ 21,000 photons/MeV) and LuAG:Ce (~ 22,000 photons/MeV) scintillators. Moreover, the positive hysteresis is remarkably restricted after coating a thin shell. The X-ray detection limit and spatial resolution are measured to be ~ 21.27 nGy/s and ~ 7.2 lp/mm, respectively. We further verify that this core/shell NS can be employed as scintillating screen to realize XEOL imaging under the low dose rate of 13.86 μGy/s. Our results provide an effective route to develop high performance NSs, which will promote great opportunities for the development of low-dose high-resolution XEOL imaging devices.

Natural sunlight activated persistent luminescence (PeL) is ideal candidate for optical information display in outdoors without the requirement of electric supply. Except the brightness and duration, the stability especially water resistance of the PeL materials is of significant importance for practical application, which remains a great obstacle up to date. Herein, we report a new sunlight activated PeL glass ceramic containing hexagonal Sr₁₃Al₂₂Si₁₀O₆₆:Eu²⁺ crystals, which exhibits strong blue PeL and can last more than 200 h. The PeL can be charged by the full wavelengths located in AM 1.5G due to the broad distribution of traps in the crystal structure. The PeL is clearly observed by the naked eye even after 24 h upon sunlight irradiation irrespective of the weather, and the photoluminescence intensity only decreased ~3.3% after storing in water for 365 d. We demonstrate its potential application for thermal and stress responsive display as well as long-term continuous security indication upon sunlight irradiation, which not only save vast energy and reduce environment pollution, but also are appropriate for outdoor usage.