Double Emissions in Boron-Doped Carbon Dots for Anticounterfeiting Applications

Carbon dots (C-dots) have excellent optical properties and serve as optical building blocks for various potential applications. However, the origin of the double emission in C-dots is still unclear. It is highly desirable to understand deeply the exciton dynamics in double-emission C-dots on the picosecond time scale. Herein, for the first time, double-emission boron-doped carbon dots (B–C-dots) are synthesized with a quantum yield as high as 41.1%. The B–C-dots have an excitation-dependent quantum yield and photoluminescent spectrum. Compared to one dominant energy state in undoped C-dots, B–C-dots exhibited multiple energy states, as proved by femtosecond transient absorption spectroscopy. The controllable double emissions advance the design of a high-level anticounterfeiting code. As a proof-of-concept, by the combination of single-emission and double-emission C-dots, we produced a highly bright excitation-dependent photoluminescence code, showing the great potential for anticounterfeiting systems.