Rational Design of Oxygen-Enriched Carbon Dots with Efficient Room-Temperature Phosphorescent Properties and High-Tech Security Protection Application

Room-temperature phosphorescent (RTP) carbon dots (CDs) have been fascinated by a lot of scholars because of their stable triplet excited states and environmental friendliness. Herein, novel fluorescent oxygen-enriched CDs were synthesized by a simple one-step solvothermal approach, which can be applied in cell imaging directly as a nontoxic fluorescent probe. When mixing the CDs with polyvinyl alcohol, the composite exhibits excellent RTP performance, which has the exciting prospect of applications in security protection. The observed RTP is attributed to the lone pair electrons provided by oxygen-rich functional groups of CDs. Benefitting from the n → π* transition and triplet exciton filling, the C–O–C groups of CDs play a significant role in their ultralong RTP performance. Our finding creates an avenue for advanced security protection technology based on metal-free RTP carbon nanomaterials.