Switch-on Fluorescence Sensing of Glutathione in Food Samples Based on a Graphitic Carbon Nitride Quantum Dot (g-CNQD)–Hg2+ Chemosensor

Fluorescence sensing of specific biological molecules by artificial chemosensors is a versatile technique. In the present work, a switch-on fluorescence sensor for rapid, sensitive, and selective sensing of glutathione (GSH) in food samples was developed. This method was based on the g-CNQDs-Hg(2+) system, in which the initial fluorescence from g-CNQDs was quenched by Hg(2+) with an electron transfer process. In the presence of GSH, the fluorescence sensor was switched to the "on" state, which was attributed to a competitive affinity of Hg(2+) to GSH and the functional groups on the surface of g-CNQDs. Under the optimal conditions, the limit of detection (LOD) of 37 nM for GSH was achieved with a wide range of 0.16-16 μM. The repeatability was better than 5.3% for GSH in both standard and food samples (n = 3). Finally, this fluorescence sensor was successfully employed for the determination of GSH in various kinds of food samples with excellent recoveries. Furthermore, this application may pave a new way for fluorescence sensing of other substances in food samples.