Fluorescent N, S co-doped carbon dots for tartrazine sensing and mechanistic perception of their radical scavenging activity

•N, S co-doped Carbon Dots were synthesized using tartaric acid and thiourea.•NSCDs are sensitive and selective to detect tartrazine.•NSCDs have shown potential antioxidant properties against various reactive oxygen species.•Mechanistic insight of DPPH free radical scavenging in acidic and basic medium.