Abstract
Graphene quantum dots (GQDs) are nano-sized materials having unique properties like the quantum confinement effect and edge effect which has led to its emergence in fluorescence-based applications. The low toxicity, high solubility, chemically inertness, and stable luminescent properties of GQDs must be explored further for its application in sensors and bio imaging studies. A one-pot synthesis of GQDs based on the bottom-up approach has been developed in this study with citric acid and amino acids（glycine、cysteine） precursors to successfully achieve two N-doped Graphene Quantum Dots (N-GQD). In this reaction, amino acid plays dual role of donating both carbon and nitrogen atom. These as-prepared N-GQDs have a high quantum yield of 14（glycine） and 58%（cysteine） as compared to previously reported GQDs. The final product has been characterized using FT-IR, PL, TEM, UV-Vis, XPS, and AFM, which shows successful nitrogen doping as GQDs. These highly fluorescent N-GQDs have been used for faster sensing of tetracycline in honey, making this, a green method as it does not involve the use of any toxic reagent. The detection is based on the on-off mechanism and fluorescent control of N-GQDs. The sensing is primarily based on a π-π stacking interaction between N-GQD and tetracycline by quenching the fluorescence of N-GQDs. Detection of honey has been carried out using a standard addition method. A detection limit of 4 μg·L−1, recovery of 77-112%, and a relative standard deviation of 14.5% is a proof to a highly sensitive detection. Further, rapid detection of 21 commercial honey samples has been carried out, of which, four samples have been found with the presence of tetracyclin.