Flexible X‑ray\nImaging and Stable Information\nStorage of SrF<sub>2</sub>:Eu Based on Radio-Photoluminescence

X-ray imaging has garnered widespread interest in biomedical\ndiagnosis\nand nondestructive detection. The exploration of radio-photoluminescence\nhas hastened the advancement of X-ray information storage. However,\nsignificant challenges persist in achieving the prolonged imaging\nof curved objects without attenuation. Here, europium-doped strontium\nfluoride (SrF<sub>2</sub>:Eu) is meticulously created to exhibit a\nlinear response to an extensive range of X-ray doses (maximum dose\n> 5000 Gy), showcasing excellent X-ray information reading/erasing\nreusability properties (10 cycles). This is accompanied by a red-to-blue\nemission transition under UV excitation, sustaining for 150 days without\nattenuation. To elucidate the phenomena of irradiated photoluminescent\ndiscoloration and the reversible X-ray storage of SrF<sub>2</sub>:Eu,\nwe propose an electron-vacancy trap (valence conversion) mechanism,\ninformation stably retained by the SrF<sub>2</sub>:Eu-based device\nunder ambient conditions due to high energy barriers. The time-lapse\nreadout capability is further demonstrated for three-dimensional imaging\nof curved objects (10 lp mm<sup>–1</sup>) based on SrF<sub>2</sub>:Eu embedded within a polydimethylsiloxane (SrF<sub>2</sub>:Eu@PDMS). The SrF<sub>2</sub>:Eu demonstrates time-lapse imaging,\nreversible radio-photoluminescence, and recoverable X-ray storage,\noffering a promising avenue for optical information encryption and\nanticounterfeiting applications.