Green and efficient synthesis of carbon quantum dots and their luminescent properties

Using citric acid as the carbon source and glutathione as nitrogen and sulfur donor, carbon quantum dots co-doped with N and S (N/S-CQDs) were successfully synthesized with a fast (within 1 h) and clean microwave-assisted oil bath method. The quantum yield reached as high as 76.5% at 350 nm excitation light. Simultaneously, we found that the N/S-CQDs were featured with good anti-photobleaching properties and sodium chloride concentration had little effect on the fluorescence intensity of N/S-CQDs, which were of great significance for the application of fluorescent N/S-CQDs in real environment such as sensing and imaging. Moreover, N/S-CQDs coped gold nanoparticles (AuNPs) performed fluorescence resonance energy transfer (FRET) from N/S-CQDs to AuNPs, building a complex fluorescent probe for the detection of drug methimazole.