Fabrication of L-Cysteine functionalized Graphene quantum dots as a fluorescent nanosensing probe for determination of mercury

Abstract

Abstract A highly sensitive and selective nanosensing probe for mercury ion is reported. Herein highly luminescent cysteine(cys) functionalized Graphene quantum dots(GQDs) were fabricated through facile one-step pyrolysis method by using ethylene glycol and cysteine. The coating of cysteine not only increases quantum yield to 41% but also enhances selective detection of ppb level of mercury ion in the waste water. The fluorescence intensity of Cys-GQDs was sequentially quenched by different concentrations of mercury ion via forming non-luminescent complexes of Cys-GQDs-Hg(II). HR-TEM study clearly shows a monodisperse Cys-GQDs of sizes 2-5 nm with a spherical shape. Raman spectra of Cys-GQDs display the D and G bands at 1350 cm−1 and 1580 cm−1 respectively. Optimum pH is 8 for mercury detection. The minimum limit for accurate detection of mercury is 0.64 ppb