Fabrication of modified glassy carbon electrode using graphene quantum dot, gold nanoparticles and 4-(((4-mercaptophenyl)imino)methyl) benzene-1,2-diol by self-assembly method and investigation of their electrocatalytic activities

Results of this paper related to fabrication of a simple, reproducible, stable and sensitive glassy carbon electrode (GCE) modified by assembly of graphene quantum dot (GQDs), gold nanoparticles (AuNPs) and 4-(((4-mercaptophenyl)imino)methyl)benzene-1,2-diol (MIB). The GQDs were electrostatically assembled on GCE and electrochemically reduced in 0.1 M phosphate buffer solution (pH = 7.0) with the cyclic voltammetry method at the scan rate of 50 mV s(-1) for 15 cycles in order to reduce the oxygen functional groups. These results lead to the formation of electrochemically reduced graphene quantum dots film on GCE (ERGQD/GCE). In the next step, electrodeposition of gold nanoparticles was successfully performed at constant potential of -0.2 V (vs. SCE) for 40 s on ERGQDs/GCE. The constructed Au/ERGQPs/GCE was characterized with scanning electron microscopy (SEM) and electrochemical techniques. Furthermore, to improve electrocatalytic activity and charge injection, a self-assembled monolayer of functionalized molecules was grafted on the electrode surface by immersion of Au/ERGQD/GCE in aqueous solution (1.0 mM) of MIB. Finally, the electrocatalytic activity of MIB/Au/ERGQD/GCE was investigated by the simultaneous determination of glutathione (GSH), uric acid (UA) and tryptophan (Trp) using differential pulse voltammetry (DPV). This modified electrode enhanced the oxidation currents of GSH, UA, and Trp compared to bare GCE. Under the optimum conditions, the calibration curve of GSH was linear in the range of 0.03-40.0 mu M and 40.0-1300.0 mu M and the detection limit of 9 nM was obtained. According to the results obtained in this study, the electrocatalytic activity of the present modified electrode was highly reproducible and stable. (C) 2014 Elsevier B.V. All rights reserved.