An Environmentally Benign Green Approach for the Reduction of Graphene …
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Fig. 4 UV–Vis spectra of a GO and b MRGO
3.4 UV–Visible Spectroscopy
Figure 4a, b shows the UV–vis spectra of the dispersions of GO and RGO in
aqueous medium. The GO spectra revealed two characteristic features: the first a
broad shoulder at 300 nm has been assigned to the n-π* plasmon transition due to
the presence of epoxide and acid groups. The second characteristic was the peak at
230 nm due to the π-π* transition of the C=C bonds which is similar to the values
reported in literature (Mei et al. 2010). After reduction, the plasmon peak at 230 nm
has been red-shifted to 263 nm corroborating an increase in π-electron density or in
other words the electronic conjugation in MRGO nanosheets was restored to some
extent. The results were in line with previously reported results concerning the reduction of GO by ascorbic acid (Zhang et al. 2010) and Hibiscus sabdariffa L. (Chu et al.
2014).
3.5 X-ray Photoelectron Spectroscopy (XPS)
To further exemplify the reduction, the binding energy was characterized using XPS
to examine the removal of the oxygenated functional groups. FWHMs of GO and
MRGO were shown in Fig. 5a, b, respectively. The reduction in peak intensity of
O-1s in the XPS spectrum of MRGO (Fig. 5b) as compared to the FWHS spectrum of GO (Fig. 5a) suggests the successful reduction employing apple extract.
Figure 5c, d shows the deconvoluted C-1s XPS patterns of GO and MRGO, respectively (Chu et al. 2014). The deconvoluted spectrum of GO contains four major peaks
centered at 284.2, 286.2, 288.0, and 289.1 eV corresponding to the C–C/C=C bond
in the aromatic rings, C–O, C=O, and O=C–OH bonds, respectively. However, upon
reduction with apple extract, the slight shifting of the peak positions along with the
noteworthy reduction in the peak intensities can clearly be attributed to the removal
of oxygen moieties. Moreover, the peak at 289.1 eV, due to the presence of –COOH
group, has been observed to diminish completely after reduction.
379
Fig. 4 UV–Vis spectra of a GO and b MRGO
3.4 UV–Visible Spectroscopy
Figure 4a, b shows the UV–vis spectra of the dispersions of GO and RGO in
aqueous medium. The GO spectra revealed two characteristic features: the first a
broad shoulder at 300 nm has been assigned to the n-π* plasmon transition due to
the presence of epoxide and acid groups. The second characteristic was the peak at
230 nm due to the π-π* transition of the C=C bonds which is similar to the values
reported in literature (Mei et al. 2010). After reduction, the plasmon peak at 230 nm
has been red-shifted to 263 nm corroborating an increase in π-electron density or in
other words the electronic conjugation in MRGO nanosheets was restored to some
extent. The results were in line with previously reported results concerning the reduction of GO by ascorbic acid (Zhang et al. 2010) and Hibiscus sabdariffa L. (Chu et al.
2014).
3.5 X-ray Photoelectron Spectroscopy (XPS)
To further exemplify the reduction, the binding energy was characterized using XPS
to examine the removal of the oxygenated functional groups. FWHMs of GO and
MRGO were shown in Fig. 5a, b, respectively. The reduction in peak intensity of
O-1s in the XPS spectrum of MRGO (Fig. 5b) as compared to the FWHS spectrum of GO (Fig. 5a) suggests the successful reduction employing apple extract.
Figure 5c, d shows the deconvoluted C-1s XPS patterns of GO and MRGO, respectively (Chu et al. 2014). The deconvoluted spectrum of GO contains four major peaks
centered at 284.2, 286.2, 288.0, and 289.1 eV corresponding to the C–C/C=C bond
in the aromatic rings, C–O, C=O, and O=C–OH bonds, respectively. However, upon
reduction with apple extract, the slight shifting of the peak positions along with the
noteworthy reduction in the peak intensities can clearly be attributed to the removal
of oxygen moieties. Moreover, the peak at 289.1 eV, due to the presence of –COOH
group, has been observed to diminish completely after reduction.