High‐Confidentiality X‐Ray Imaging Encryption Using Prolonged Imperceptible Radioluminescence Memory Scintillators

Abstract X‐ray imaging plays an increasingly crucial role in clinical radiography, industrial inspection, and military applications. However, current X‐ray imaging technologies have difficulty in protecting against information leakage caused by brute force attacks via trial‐and‐error. Here high‐confidentiality X‐ray imaging encryption by fabricating ultralong radioluminescence memory films composed of lanthanide‐activated nanoscintillators (NaLuF 4 : Gd 3+ or Ce 3+ ) with imperceptible purely‐ultraviolet (UV) emission is reported. Mechanistic investigations unveil that ultralong X‐ray memory is attributed to the long‐lived trapping of thermalized charge carriers within Frenkel defect states and subsequent slow release in the form of imperceptible radioluminescence. The encrypted X‐ray imaging can be securely stored in the memory film for more than 7 days and optically decoded by perovskite nanocrystal. Importantly, this encryption strategy can protect X‐ray imaging information against brute force trial‐and‐error attacks through the perception of lifetime change in the persistent radioluminescence. It is further demonstrated that the as‐fabricated flexible memory film enables achieving of 3D X‐ray imaging encryption of curved objects with a high spatial resolution of 20 lp/mm and excellent recyclability. This study provides valuable insights into the fundamental understanding of X‐ray‐to‐UV conversion in nanocrystal lattices and opens up a new avenue toward the development of high‐confidential 3D X‐ray imaging encryption technologies.