We report a simple, facile, and reproducible
method for the fabrication
of electrochemically reduced graphene oxide (ERGO) films on glassy
carbon electrode (GCE) by the self-assembly method. The graphene precursor,
graphene oxide (GO), was self-assembled on GCE through a diamine linker
which was preassembled on GCE by electrostatic interaction between
the positively charged amine and the negatively charged layers of
graphene oxide (GO). The oxygen functional groups present on the surface
of GO were electrochemically reduced to retain the aromatic backbone
of graphene. The attachment of GO followed by its electrochemical
reduction was confirmed by ATR-FT-IR spectroscopy, Raman spectroscopy,
X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic
force microscopy (AFM), and scanning electron microscopy (SEM). Raman
spectra show that the intensity ratio of D and G bands was increased
after the electrochemical reduction of GO. XPS results reveal that
the carbon-to-oxygen ratio was increased after the electrochemical
reduction of electrostatically assembled GO. Further, Raman and XPS
results confirm the removal of oxygen functional groups present on
the surface of GO after electrochemical reduction. Impedance spectral
studies show that the electron transfer reaction was facile at ERGO
modified GCE. Finally, the electrocatalytic activity of ERGO was examined
by studying the oxidations of ascorbic acid (AA), dopamine (DA), and
uric acid (UA). It enhanced the oxidation currents of AA, DA, and
UA when compared to bare GCE. The electrocatalytic activity of the
present modified electrode was highly stable.
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.
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