Reduced graphene oxide-graphene quantum dots-Fe3O4 nanocomposite modified electrode for determination of dopamine

In the present work, carbon paste electrode was modified by reduced graphene oxide-graphene quantum dots-Fe3O4 (RGO/GQDs/Fe3O4) nanocomposite and employed for dopamine detection. The characterization of the RGO nano-sheets, RGO/GQDs and RGO/GQDs/Fe3O4 nanocomposites was performed by field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM/EDX) and transmission electron microscopy (TEM). The electrochemical behavior of the electrodes was investigated by cyclic voltammetry that the results showed a significant increase in peak current for RGO/GQDs/Fe3O4/CPE. Under the optimized empirical conditions, efficiency of the RGO/GQDs/Fe3O4/CPE sensor for dopamine determination was examined using cyclic voltammetry and differential pulse voltammetry methods. A linear relationship between dopamine concentration and the peak current was discovered for modified electrode over a wide range from 5 to 150 mu M with the limit of detection of 3.43 mu M and 5-160 mu M with the limit of detection of 1.43 mu M in CV and DPV methods, respectively. Based on chronoamperometry studies, it was determined that the oxidation process of dopamine on the surface of the modified electrode is controlled by its diffusion from inside the solution to the surface of the electrode. The obtained values of diffusion coefficient and rate constant for dopamine using the chronoamperometry method were 1.3 x 10(-8) cm(2) s(-1) and 22.9 x 10(8) cm(3) mol(-1) s(-1), respectively. The good applicability of the proposed sensor for dopamine analysis in real samples was reported by obtaining suitable recovery values in the range of 96.5-103%.