Graphene quantum dots decorated with Fe3O4 nanoparticles/functionalized multiwalled carbon nanotubes as a new sensing platform for electrochemical determination of L-DOPA in agricultural products

This paper describes the development and utilization of a new nanocomposite consisting of graphene quantum dots, magnetic nanoparticles and carboxylated multiwalled carbon nanotubes for glassy carbon electrode surface modification. The graphene quantum dots were synthesized via pyrolysis of citric acid. The nanocomposite was characterised by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The modified electrode was used for electrochemical determination of L-DOPA in some agricultural samples. Using differential pulse voltammetry, the prepared sensor showed good sensitivity and selectivity with low overpotential for the determination of L-DOPA in the range from 3.0 to 400 mu mol L-1, with a detection limit of 14.3 nmol L-1. Electrochemical studies suggested that the modified electrode provided a synergistic augmentation on the voltammetric behaviour of electrochemical oxidation of L-DOPA. The amount of L-DOPA in sunflower seed, sesame seed, pumpkin seed and fava bean seed was evaluated with the proposed sensor.