Carbon quantum dots derived from lignin nanoparticles for dual UV-excited fluorescent anti-counterfeiting materials

Carbon quantum dots are widely used as fluorescent materials due to their excellent photostability and low toxicity. However, the majority of carbon quantum dots were limited by a single anti-counterfeiting effect excited by ultraviolet A (UVA, 320-400 nm) light. Herein, carbon quantum dots (CQDs) derived from lignin were developed through the doping of nitrogen, phosphorus, or boron using a one-pot hydrothermal method. These CQDs could show yellow (Y-CQDs) and blue-violet (B-CQDs) fluorescent colors under UVA and ultraviolet C (UVC, 100-280 nm) stimulations, respectively. Via mixing these two types of carbon quantum dots, the mixed dispersion could be used as a printing paste or prepared a film with polyvinyl alcohol. Benefiting from the synergistic effect of two carbon quantum dots, the resultant products could emit blue-purple and yellow-green fluorescence colors under 254 nm and 365 nm UV irradiations, respectively, thereby exhibiting dual anticounterfeiting capabilities. This work paves a new path for developing lignin-based carbon quantum dots that show a promising application for anti-counterfeiting capabilities.