Near-infrared persistent phosphors: Synthesis, design, and applications

Long persistent phosphors (LPPs) can maintain luminescence for an appreciable time after terminating the excitation light, which can be compared to an optical battery. This intriguing optical phenomenon has attracted a lot of attention in numerous areas, such as safety display, biomedicine and data-storage technologies. Owing to the efficient elimination of autofluorescence interference from biological samples and the ultra-long near-infrared (NIR) afterglow emission, NIR LPPs show deeper tissue penetration depth offering a bright prospect for various bioapplications, such as in vivo biosensing, bioimaging, and imaging-guided therapy. In this review, we focus on the recent developments in the aspect of synthesis procedures, design and applications of NIR LPPs and highlight the rational design of various kinds of transition metal and rare earth ions-doped NIR LPPs in the first to third tissue transparency window. Moreover, some remaining challenges and further efforts towards this rapidly expanding area are also envisioned at the end of this review.