Nitrogen and sulfur co-doped carbon quantum dots as fluorescence sensor for detection of lead ion

A fluorescent carbon quantum dots (N-S CQDs) doped with nitrogen (N) and sulfur (S) with tunable wavelength was successfully prepared by one-step hydrothermal reaction for sensitive detection of Pb2+. The doping of N and S narrows the band gap of the CQDs and makes the wavelength red shift, so that the carbon quantum dots displayed maximum emission peak at 540 nm under 460 nm excitation. The addition of Pb2+ quenched the fluorescence due to the specific combination of Pb2+ with the carboxyl and sulfhydryl on the surface of the CQDs, forming a coordination structure. Under optimal conditions, the CQDs revealed outstanding anti-interference capability and a favorable linear relation was obtained in the scope of 0.2-12 mu M and 40-200 mu M with the limit of detection of 0.097 mu M and 5.624 mu M for Pb2+. Besides, the CQDs had been successfully used for monitoring Pb2+ in river water with good accuracy and recovery.