Trap Energy Upconversion‐Like Near‐Infrared to Near‐Infrared Light Rejuvenateable Persistent Luminescence

Abstract Persistent‐luminescence phosphors (PLPs) have a wide variety of applications in the fields of photonics and biophotonics due to their ultralong afterglow lifetime. However, the existing PLPs are charged and recharged with short‐wavelength high‐energy photons or inconvenient and potentially risky X‐ray beams. To date, deep tissue penetrable NIR light has mainly been used for photostimulated afterglow emission, which continues to decay and weaken after each cycle, Herein, a new paradigm of trap energy upconversion‐like near‐infrared (NIR) to near‐infrared light rejuvenateable persistent luminescence in bismuth‐doped calcium stannate phosphors and nanoparticles is reported. In contrast to the existing PLPs and persistent‐luminescence nanoparticles, the materials enable the occurrence of a reversed transition of the carriers from a deep‐level energy trap to a shallow‐level trap upon excitation by low‐energy NIR photons. Thus these new materials can be charged circularly via deep‐tissue penetrable NIR photons, which is unable to be done for existing PLPs, and emit afterglow signals. This conceptual work will lay the foundation to design new categories of NIR‐absorptive–NIR‐emissive PLPs and nanoparticles featuring physically harmless and deep tissue penetrable NIR light renewability and sets the stage for numerous biological applications, which have been limited by current materials.