Microwave-driven green synthesis of carbon quantum dots for fluorescent anti-counterfeiting films: mechanism and application

Abstract

Carbon quantum dots (CQDs) possess exceptional luminescence properties, and the fluorescent films derived from them exhibit significant potential for application in anti-counterfeiting technology. In this study, CQDs were synthesized via a microwave-assisted method using urea and citric acid as precursors. Their fluorescence quenching effect and concentration-dependent behavior were comprehensively investigated. By modulating the content of different solvents (ethanol, PVA), it was found that the fluorescence intensity of CQDs increased with more solvents. Characterization of the samples using Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible absorption spectroscopy (UV-Vis) confirmed that the prepared CQDs contained abundant hydroxyl, carboxyl, and other functional groups on their surfaces. These CQDs demonstrated prominent absorption peaks at 410 nm and exhibited distinct single-peak fluorescence emission spectra with peak wavelengths of 436 nm and 524 nm under 365 nm excitation. The CQDs-PVA composite film was successfully fabricated through parameter optimization. This film exhibits bright blue fluorescence under ultraviolet illumination and demonstrates near-transparency under natural light, thereby establishing a theoretical foundation and offering technical support for the advancement of novel fluorescent functional materials.