An Electrochemiluminescent Biosensor Based on Interactions between a Graphene Quantum Dot-Sulfite Co-reactant System and Hydrogen Peroxide

Graphene quantum dots (GQDs) are recently emerging carbon nanomaterials. GQDs have been recognized as attractive electrochemiluminescence (ECL) luminophores, owing to their environmental friendliness, facile preparation, easy labeling, and high ECL activity. However, in terms of the co-reactant of GQDs ECL, only strongly oxidative S2O82- has been well studied and applied in GQD-based ECL sensing, which seriously limits the application of GQD ECL sensors. In the present work, we found that the commonly used reducing reagent, sulfite (SO32-), could serve as a new type of co-reactant of GQD ECL. Moreover, GQDs exhibited much higher ECL activity than spherical carbon quantum dots when using SO32- as the co-reactant, owing to more abundant surface states of GQDs. Further investigation showed that GQD/SO32- ECL could be sensitively quenched by H2O2 at physiological pH. On this basis, new, green, and simple ECL chemical and biological sensors have been proposed for the detection of H2O2 and biologically interesting molecules such as glucose. Additionally, the ECL reaction and sensing mechanisms have also been studied and discussed.