Advanced Security Printing Enabled by Biomass-Derived Multicolor Anti-Counterfeiting Fluorescent Carbon Dot Ink with Multimodal Applications

One of the most pressing challenges in fluorescence-based anti-counterfeiting technology is the development of multi-color fluorescent materials that simultaneously satisfy the stringent requirements of high security, cost-effectiveness, and environmental sustainability. Biomass-derived fluorescent carbon dots (CDs) are characterized by their low cost, non-toxicity, and tunable multicolor fluorescence, making them ideal candidates for developing multicolor fluorescent inks with multi-level anti-counterfeiting capabilities. In this study, N-doped tricolor CDs were synthesized via a solvothermal method using orange juice, lemon juice, and banana leaves as biomass precursors. These CDs exhibited distinct blue, green, and blue-red dual-emission fluorescence, with their structure-property relationships and luminescence mechanisms systematically investigated through comprehensive characterization techniques. A glycerol-based tricolor fluorescent ink system was developed, enabling multilayered information encryption under UV/visible light dual-mode through integrated processes such as handwriting, screen printing, and stamping. Furthermore, flexible sensing films were fabricated by incorporating CDs into polyvinyl alcohol (PVA) matrices. Remarkably, the CDs-embedded films exhibited significantly enhanced electrical signal responses during mechanical sensing. This work not only provides a novel strategy for high-value utilization of biomass resources but also opens innovative pathways for developing intelligent anti-counterfeiting materials and flexible electronic devices.