A highly sensitive ratiometric fluorescent sensor for copper ions and cadmium ions in scallops based on nitrogen doped graphene quantum dots cooperating with gold nanoclusters

[Display omitted] •GQDs-AuNCs ratiometric fluorescent sensor was prepared by electrostatic interaction.•The sensor was used to detect Cu2+ and Cd2+ in scallops.•The paper-based sensor can be used for semi-quantitative detection of Cu2+ and Cd2+.•The detection limits are 4.12 nM for Cu2+ and and 943 nM for Cd2+, respectively. Based on the electrostatic interaction, we constructed a ratiometric fluorescence nanomixture of graphene quantum dots-gold nanoclusters (GQDs-AuNCs) for the quantitative detection of Cu2+ and Cd2+. When Cu2+ or Cd2+ was added into the reaction system, the fluorescence of GSH-AuNCs at 565 nm can be quenched by Cu2+ and enhanced by Cd2+ while the intensity of N-GQDs at 403 nm stayed constant. Under the optimized conditions, the fluorescence intensity ratio (I565/I403) of the GQDs-AuNCs system was proportional to the concentration of Cu2+ and Cd2+ in the range of 8×10−8 mol/L-6×10−6 mol/L and 1×10−6 mol/L-4×10−5 mol/L, respectively, with detection limits of 4.12×10−9 mol/L and 9.43×10−7 mol/L, respectively. In the presence of Cu2+ and Cd2+, the paper-based vision sensor would produce visible fluorescent color changes, which can be used for rapid detection on site. The method has been successfully applied to the determination of Cu2+ and Cd2+ in scallops with satisfactory results.