Enhancing X‐Ray Excited Persistent Luminescence in Lanthanide‐Doped Fluoride Nanoparticles via a Versatile Acid Pickling Strategy

Abstract X‐ray excited persistent luminescence (XEPL) of lanthanide‐doped fluoride nanoparticles (NPs) holds promise for applications in back‐ground free bio‐medicine and flexible 3D imaging. However, it remains a daunting challenge to develop a universal and convenient route to greatly improve the XEPL performance of most fluoride nanosystems. Herein, for the first time, a versatile acid pickling strategy is proposed to greatly enhance the XEPL intensity of lanthanide‐doped fluoride NPs with different chemical compositions and activator types. Especially, after treatment with diluted HCl, the XEPL intensity of the NaYF 4 : Tb NPs with a mean particle size of ≈ 7 nm is enhanced ≈17.4 times. Mechanistic studies indicate the trap density in the NPs upon X‐ray irradiation is greatly enhanced after HCl treatment, contributing to the enhanced XEPL intensity. By integrating the HCl‐treated NPs into a scintillation film, the X‐ray image resolution is significantly increased from 6.3 to 11 lp mm −1 , and the quality of delayed X‐ray images improved, particularly at low‐dose irradiation rates. These findings are expected to advance the development of high‐performance X‐ray‐activated persistent fluoride NPs and their applications for low‐dose high‐resolution X‐ray imaging.