Long-lived room-temperature phosphorescent complex of B, N, P co-doped carbon dots and silica for afterglow imaging

Room temperature phosphorescent (RTP) materials based on carbon dots (CDs) have attracted abundant attention in bioimaging owing to their long lifetimes and wide Stokes shift, which can reduce the autofluorescence and light scattering in tissue. Although solid-state RTP CDs have been widely reported at present, long-lived RTP CDs in aqueous solutions still remain a challenge because they are usually quenched by oxygen in water. This work develops a heteroatom doping strategy to synthesize long-lived matrix-free phosphorescent B, N, P co-doped CDs (B, N, P-CDs) with cross-linked structure and rich hydrogen bonding network. B, N, P-CDs have an ultralong phosphorescence lifetime of 1.89 s. Subsequently, the complex of B, N, P co-doped CDs and silica (B, N, P-CDs@SiO2) was further obtained by coating the surfaces of B, N, P-CDs with silica by sol-gel method to further confine their molecular vibrations and rotations, which shows an excellent RTP property in aqueous solution with a phosphorescent lifetime of 1.97 s. In addition, the complex displays good biocompatibility, low cytotoxicity, and ability of phosphorescent labeling cells and organism. All these results extend a potential application of the B, N, P-CDs@SiO2 complex as phosphorescent bioimaging probe.