The facile synthesis of nitrogen and sulfur co-doped carbon dots for developing a powerful on-off-on fluorescence probe to detect glutathione in vegetables

To determine the glutathione (GSH) content in vegetables, an on-off-on fluorescence probe was developed by a synthesis of nitrogen and sulfur co-doped carbon dots (N,S-CDs) using the microwave pyrolysis considering citric acid and L-cysteine as precursors. The fluorescence of N,S-CDs was quenched by adding Cu2+ at a concentration of 20-200 mu mol/L due to the inner filter effect. The quenched fluorescence of N,S-CDs@Cu2+ system was recovered by adding the GSH at a concentration of 10-150 mu mol/L due to the sulfhydryl-metal compound mechanism. By observing the GSH concentrations measured by our N,S-CDs@Cu2+ system vs. a traditional fluorescent chelating method, the two measurements provided the GSH data with a good consistence by showing the RSD range of 1.86%-2.27%. This indicates the validation and novelty of our N,S-CDs@Cu2+ system as being a powerful fluorescent probe for effectively and efficiently determining the GSH in vegetables.

Automated summary

A novel fluorescence probe N,S-CDs@Cu2+ system was developed for determining glutathione (GSH) content in vegetables, showing good consistency and stability compared to traditional methods. The probe effectively and efficiently recovers quenched fluorescence in the presence of GSH, demonstrating its validation and novelty for GSH detection in vegetables.