A turn-on fluorescent sensor based on coffee-ground carbon dots for the detection of sodium cyclamate

Carbon quantum dots (CQDs) were synthesized by coffee grounds as the carbon source under hydrothermal carbonization treatment for the first time. The obtained turn-on CQDs showed a strong emission at the wavelength of 460 nm, with an optimum excitation of 370 nm, and enrichment of the surface functional groups (–OH, –NH 2 ). Sodium cyclamate in an aqueous solution and the turn-on CQDs could form a core–shell structure by hydrogen bonding and van der waals bonding to enhance the fluorescent emission. With such a design, turn-on CQD-based fluorescence detection techniques towards sodium cyclamate could be realized. Under optimal conditions, a linear relationship was found in the range of 2.8–56 µmol/L sodium cyclamate with the detection limit (3 δ/k ) of 3.16 µmol/L which is lower than the national standard detection limit of 49.7 µmol/L. The sensitive method has a great application prospect in detection of sodium cyclamate in real samples owing to its low detection limit, simplicity and rapidity.