White‐Light‐Excitable Deep‐Red/NIR Organic Afterglow Nanoparticles for High‐Contrast In Vivo Imaging

Abstract

ABSTRACT Near‐infrared (NIR) organic afterglow probes are attractive for deep‐tissue, high‐contrast bioimaging, yet simultaneously achieving white‐light excitation, long‐lived NIR phosphorescence, and uniform nanoparticle fabrication remains challenging. Herein, we develop a bottom‐up route to lattice‐matched host–guest nanocrystals by incorporating a rigid phenylcarbazole host (BMC) with scaffold‐matched, extended‐conjugation guests (PyC or BPC). The resulting doped crystals show guest‐dominated deep‐red/NIR afterglow, with the longest‐wavelength vibronic band reaching 762 nm and can be activated by visible light up to 475 nm, delivering an ultralong lifetime of 126.1 ms and a phosphorescence quantum yield of up to 2.7%. Importantly, the intrinsic homogeneity of the lattice‐matched incorporation enables direct formation of monodisperse phosphorescent nanoparticles via simple bottom‐up nanoprecipitation, avoiding the size heterogeneity and material loss typically associated with top‐down crystal fragmentation. These nanoparticles exhibit negligible cytotoxicity and deliver bright, persistent deep‐red/NIR emission under white‐light excitation for high‐contrast in vivo imaging.