Intramolecular charge transfer mediated dual-emission in multi-doped graphene quantum dots for anti-counterfeiting via liquid secret key

Multiple emission GQDs have always been the focus of researchers due to the unique emission characteristics and high-level application capabilities. Nevertheless, the most of GQDs with double emissions are formed by different chemical reactions, and the realization of double emission by adjusting the solvent environment is rarely re-ported. Here, the multi-doped and double-peak emissive GQDs (MD-GQDs) have been synthesized via one pot hydrothermal synthesis and re-dispersed in solvents with different polarity. Systematic characterizations of optical property indicate that the solvent polarity related double-peak emission photoluminescence is ascribed to the existence of multi-emissive centers in MD-GQDs from aromatic C--O bond and surface/edge state (C-N/C-F). Furthermore, the double emission fluorescent mechanism of MD-GQDs has been proposed due to the electrostatic interaction between MD-GQDs and solvent molecules, which induces intramolecular charge transfer (ICT) effect in MD-GQDs. Finally, based on the unique solvent-induced discoloration behavior of MD-GQDs, a multi-mode anti-counterfeiting application based on organic solution as the secret key with easy operation and high visual effect is developed.