Application of graphene quantum dots in the detection of Hg2+ and ClO− and analysis of detection mechanism

Graphene quantum dots (GQDs) are a new type of carbon material that have received widespread attention in recent years. However, due to their complex structure, it is difficult to explore their fluorescence emission mechanism and application mechanism. In this work, GQDs with simple structure were prepared using citric acid as a single precursor. The fluorescence properties and structure of GQDs were characterized, and the results confirmed that their luminescence originated from the n → π* electronic transition produced by the oxygen-containing functional groups in the edge state. Significantly, GQDs can be used as excellent probes to detect Hg 2+ and ClO − in aqueous solution. Hg 2+ combines with the carboxyl groups of the edge states of GQDs to form a complex, and then reduces the fluorescence emission through non-radiative electron transfer . ClO − can oxidize the hydroxyl groups in the edge states of GQDs to make them positively charged, which prevents electron transfer related to the luminescent center and reduces fluorescence emission.