Manipulation of Coupled X‐Ray‐Excited Persistent Luminescence and Upconversion in Er3+ Doped Fluoride Nanoparticles for Multifaceted Applications

Abstract Lanthanide doped nanoparticles (NPs) exhibit tunable X‐ray‐excited optical luminescence and X‐ray‐excited persistent luminescence (XEPL), holding broad prospects for applications in display/anti‐counterfeiting and X‐ray imaging. The development of effective strategies for multi‐dimensional applications based on lanthanide‐doped fluoride NPs are a constant challenge. Here, core–shell structured fluoride NPs, in which the heavy metal fluoride shell effectively suppresses the non‐radiative relaxation and simultaneously improve the X‐ray absorption of the shell are designed and fabricated. Under X‐ray irradiation, the developed NPs exhibit an increased number of secondary electrons which migrate to Er 3+ centers at the interface and greatly improve the XEPL intensity. Additionally, the introduction of Mn 2+ further enhances the XEPL intensity and offers an effective route to control the red‐green ratio of the upconversion spectrum. The NPs co‐doped with Mn 2+ exhibit a bright green XEPL under X‐ray irradiation and a red emission under 1532 nm laser excitation. It is further validated that these NPs can be utilized for advanced anti‐counterfeiting and high‐resolution delayed imaging based on a film containing NPs as a scintillation screen. These findings suggest a new strategy of designing Er 3+ doped NPs for multi‐dimensional applications.