Nitrogen-Doped Graphene as a Robust Scaffold for the Homogeneous Deposition of Copper Nanostructures: A Nonenzymatic Disposable Glucose Sensor

The attachment of nitrogen-doped graphene (NG) on glassy carbon electrode (GCE) followed by electrodeposition of copper nanostructures (CuNSs) is described in this paper. Nitrogen-doped graphene oxide (N-GO) was prepared by intercalating melamine into graphene oxide (GO) by sonication. The doping of nitrogen was confirmed from the characteristic peaks at 285.3 and 399 eV in the XPS corresponding to the C–N bond and nitrogen, respectively. The presence of amine groups on the N-GO was exploited to attach them on GCE via Michael’s reaction. Subsequently, N-GO was electrochemically reduced to form NG by reducing the oxygen functionalities present on the N-GO. Then, the CuNSs on the NG modified electrode was prepared by electrodeposition at various applied potentials with different deposition times. The homogeneous deposition of cubic, spherical, quasidendritic, and dendritic NS at the applied potentials of 0, −0.10, −0.30, and −0.40 V, respectively, was evidenced from scanning electron microscopy (SEM) studies. The surface energy of the system can be reduced by the intercalated nitrogen in the graphene layer via doping. Hence, the NG layers with large surface area act as a robust scaffold for the homogeneous deposition of CuNSs. Further, the electrocatalytic activity of the NG-CuNSs modified GCE toward glucose oxidation was studied. In a comparison with NG and CuNSs, the NG-CuNSs exhibited 2-fold higher oxidation current. Further, it was found that the electrocatalytic activity of the composite electrode depends on the shape of the CuNSs. Among the different CuNSs, the NG-dendritic CuNSs electrode exhibited higher electrocatalytic activity. Finally, the practical applicability of the present sensor was demonstrated by fabricating NG-dendritic CuNSs on screen printed carbon electrode for the determination of glucose in human blood serum and urine samples.