Green Room-Temperature Phosphorescent Carbon Dots with a Lifetime of around 1 s

Organic ultralong room-temperature phosphorescence (RTP) has attracted extensive attention and has been a sparklingly heated topic due to its promising applications in bioimaging, encryption, and optoelectronic devices. However, the synthesis procedures for these materials are always cumbersome, costly, and involve toxic substances as well. Herein, a facile, low-cost, and hypotoxic strategy has been developed to achieve green RTP by the hydrothermal reaction of carbon source together with boric acid, resulting in the in situ rigidification of carbon dots into the B2O3 matrix. The designed green RTP carbon dots (CDs@B2O3) exhibited an ultralong lifetime of 905.5 ms, lasting more than 8 s. This excellent performance was mainly due to the restricted vibration and rotation of CDs by the covalent bond formation and the suppressed nonradiative recombination of triplet excitons via B2O3 matrix rigidification. Moreover, we demonstrated the practical applications of the prepared CDs for bioimaging, anti-counterfeiting, and information encryption. This work provides design principles to construct metal-free RTP materials with ultralong lifetime and high stability for promising remarkable applications.