Construction Of Graphene Quantum Dots-gold Nanoclusters Ratiometric Fluorescence Sensor And Its Application In Aquatic Products Detection

Graphene quantum dots(GQDs)and gold nanoclusters(AuNCs)have attracted much attention due to their low cytotoxicity,high biocompatibility and unique optical properties.They are often used to construct ratiometric fluorescence sensors.Compared with the single emission wavelength fluorescence sensors,the ratiometric fluorescence sensor has the advantages of avoiding environmental interference,improving sensitivity and obvious color changes.Therefore,it can be used for visual quantitative detection.In this paper,N-GQDs were synthesized by hydrothermal method.Gold nanoclusters were synthesized by glutathione(GSH)as template.N-GQDs and GSH-AuNCs were assembled by electrostatic interaction to made GQDs-AuNCs ratiometric fluorescence sensor,which was applied to the safety detection of aquatic products.The main contents of this paper are as follows:1.Using graphene oxide as raw material,nitrogen doped GQDs(N-GQDs)were synthesized by hydrothermal method.AuNCs were synthesized using GSH as template.N-GQDs and GSH-AuNCs were connected by electrostatic interaction to form GQDs-AuNCs ratiometric fluorescent sensor for the detection of Cu²⁺and Cd²⁺.When Cu²⁺or Cd²⁺was added into the reaction system,the fluorescence of GSH-AuNCs was quenched by Cu²⁺at 565 nm or enhanced by Cd²⁺,while the fluorescence intensity of N-GQDs remained unchanged at 403 nm.Under the optimal conditions,when the concentration of Cu²⁺was 8.00×10^-8 mol/L-6.00×10^-6 mol/L,the fluorescence intensity ratio(I₅₆₅/I₄₀₃)of GQDs-AuNCs system was linearly correlated with the concentration of Cu²⁺and the detection limit was 4.12×10^-9 mol/L.When the concentration of Cd²⁺was 1.00×10^-6 mol/L-4.00×10^-5 mol/L,the fluorescence intensity ratio(I₅₆₅/I₄₀₃)of GQDs-AuNCs system was linearly correlated with the concentration of Cd²⁺and the detection limit was 9.43×10^-7 mol/L.In the presence of Cu²⁺and Cd²⁺,the paper-based vision sensor can produce fluorescent color changes easily observed by eyes.The paper-based vision sensor can be used for rapid detection of Cu²⁺and Cd²⁺in the field.Interference experiments showed that the ratiometric fluorescence sensor had strong selectivity and had been successfully applied to the determination of Cu²⁺and Cd²⁺in scallops with good results.2.N-GQDs and GSH-AuNCs were connected to form GQDs-AuNCs dual-mode fluorescence colorimetric sensor for the detection of NO₂^-.Under acidic conditions,3-aminophenol can react with NO₂^-to form azo compounds with UV absorption peak at440 nm,which increased with the increase of the concentration of NO₂^-.Because the fluorescence peak of N-GQDs overlaped with the UV absorption peak of azo compounds at 420 nm,the fluorescence intensity of N-GQDs decreased with the increase of the concentration of NO₂^-,while the fluorescence intensity of GSH-AuNCs remained unchanged at 565 nm.When the concentration of NO₂^-was 4.00×10^-6 mol/L-6.00×10^-5 mol/L,the concentration of NO₂^-was linearly correlated with the fluorescence intensity ratio(I₄₂₀/I₅₆₅)of GQDs-AuNCs sensor and the detection limit was 1.30×10^-7 mol/L.At the same time,the color changes in the detection process can be directly observed by eyes and quantitatively detected by UV-Vis spectrum.When the concentration of NO₂^-was 1.20×10^-5 mol/L-1.20×10^-4 mol/L,there was a linear correlation between the concentration of NO₂^-and the UV peak intensity ratio(A/A₀)of GQDs-AuNCs sensor and the detection limit was 5.77×10^-6 mol/L.Interference studies showed that GQDs-AuNCs sensor had strong selectivity.The method was applied to the determination of NO₂^-in canned fish.The results of fluorescence and colorimetry were consistent and the experimental results were good.