Fluorescence resonance energy transfer quenching at the surface of graphene quantum dots for ultrasensitive detection of TNT

This paper for the first time reports a chemical method to prepare graphene quantum dots (GQDs) from GO. Water soluble and surface unmodified GQDs, serving as a novel, effective and simple fluorescent sensing platform for ultrasensitive detection of 2,4,6-trinitrotoluene (TNT) in solution by fluorescence resonance energy transfer (FRET) quenching. The fluorescent GQDs can specifically bind TNT species by the π-π stacking interaction between GQDs and aromatic rings. The resultant TNT bound at the GQDs surface can strongly suppress the fluorescence emission by the FRET from GQDs donor to the irradiative TNT acceptor through intermolecular polar-polar interactions at spatial proximity. The unmodified GQDs can sensitively detect down to ∼0.495 ppm (2.2 μM) TNT with the use of only 1 mL of GQDs solution. The simple FRET-based GQDs reported here exhibit high and stable fluorescence. Eliminating further treatment or modification, this method simplifies and shortens the experimental process. It possesses good assembly flexibility and can thus find many applications in the detection of ultratrace analytes.