Nitrogen-doped carbon dots with excitation-dependent room temperature phosphorescence for multi-level anti-counterfeiting applications

In recent years, carbon dots (CDs) have received widespread attention due to their superior photoluminescence effect, high chemical stability and other characteristics. This research aims to explore a new multi-level anti-counterfeiting technology, which achieves efficient anti-counterfeiting of products by introducing the characteristics of Nitrogen-doped CDs (N-CDs) to excite room-temperature phosphorescence (RTP). Firstly, N-CDs were successfully prepared through a simple and effective synthesis method. The obtained N-CDs exhibited excellent RTP properties that lasted for 4 s, providing a feasible fluorescence (FL) label for multi-level anti-counterfeiting. Secondly, through the mixture of N-CDs and NaOH, a unique optical effect can be formed and the lifetime of FL can last for 8 ns, which improved the anti-counterfeiting capability and accuracy. Finally, further research found that the unique properties of N-CDs not only have broad application potential in the field of product anti-counterfeiting, but also can promote the development of anti-counterfeiting technology. This technique has the advantage of being easy to operate and low cost, as well as allowing RTP emission. Therefore, the multi-level anti-counterfeiting technology based on N-CDs proposed in this study provides an innovative and feasible solution to improve product security, and provides a solid foundation for research and application in related fields. •The N-CDs@NaOH sample exhibited blue FL emissions of 406 nm and 465 nm under excitation at 254 nm and 365 nm, respectively.•And there was blue-green RTP emission of 471 nm and 510 nm after excitation at 254 nm, with a lifetime of 0.82 ms (visible to the naked eye for 3 s).•But after excitation at 365 nm, it only exhibited green RTP emission of 514 nm, with a lifetime of 1.56 ms (visible to the naked eye for 4 s).•An anti-counterfeiting mark was designed using N-CDs@NaOH to exhibit different FL and RTP effects at different excitation wavelengths.