A graphene quantum dot-based method for the highly sensitive and selective fluorescence turn on detection of...

A facile assay method for the highly sensitive and selective sensing of biothiols based on graphene quantum dots (GQDs) has been developed. GQDs emitted strong blue fluorescence in an aqueous buffer solution. It was observed that mercury(II) ions could efficiently bind and quench the fluorescence of the GQDs. When a biothiol compound (glutathione, cysteine, or homocysteine) was added to the assay mixture of GQDs and mercury(II), it bound to mercury(II) ions. Hg(2+)-GQD complex dissociated, and a fluorescence turn-on signal was detected. The emission intensity changes of the GQDs could be directly related to the amount of biothiol added to the assay solution. The assay is highly sensitive, the limits of detection (LOD) for GSH, Cys and Hcy were 5 nM, 2.5 nM and 5 nM, respectively. The assay is also highly selective, a number of amino acids and proteins were tested, and little interference was observed. In addition, GSH standard recovery in serum samples was also demonstrated. We envision that our assay method could facilitate the biothiol quantification related biological and biomedical research.