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

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.