spectroscopy. Figure 2a, b show AFM and TEM images of the GO sheets. The
thickness, correspond to AFM image (Fig. 2a), is found to be 1.2 nm, which
indicates the formation of double-layered GO nanosheets (Fig. 2c). The UV-visible
spectra of GO and rGO were shown in Fig. 2d. There are two prominent peaks
observed at 230 nm and 300 nm, due to n-p* and p-p* transition of C=C and C=O,
respectively [35].
Raman spectroscopy is regarded as one of the most useful tools for analysis of
defect and disorder present in the crystal structure. Generally, this technique is used
to characterize graphitic derivatives. The ratio of G band to the D band (I D /I G )
calculates the disorder in the graphitic structure. Figure 3 represents the Raman
spectra of GO and rGO sheets. The D band is observed at 1365, 1364 cm
−1 and
corresponding G band are observed at 1597, 1607, for GO, and rGO, respectively.
The origin of G band (sp
2 carbon) arises from C-C bond stretch, and first-order
Raman scattering. The shifting of G band to a higher wave number is may be due to
the oxygenated moieties presence in graphite after oxidation. The D band also
broadened in case of GO due to defects, distortions, size reduction of the sp
2
domains after oxidation. The I D /I G shifted from 0.96 (GO) to 1.0 (rGO) confirms
the attachment of oxygenated moieties to graphene sheets.
Figure 4a depicts the survey XPS of GO demonstrates the presence of C and O
atoms in GO. The high-resolution C1 s XPS spectra (Fig. 4b), representing the
peaks corresponding to four functional groups C–C/C=C, C–O, HO–C=O, C=O,
suggests the successful oxidation to GO [37, 38]. The peaks at binding energy of
284.64 eV, 285.34 eV, 287.28 eV and 289.07 eV correspond to C=C, the C in
C–OH, C(C=O) and (HO–C=O) (carboxyl-C) respectively. Again, O1s
high-resolution XPS spectra are also recorded in Fig. 4c which composed of two
KMnO + 3 H2SO4
4
→ K
+
+ MnO3
+
+ H3O
+
+ 3 HSO4
−
(1)
MnO3
+
+ MnO4 → Mn2O7 (2)
C
O
O
Graphene oxide(Exfoliated)
OH
OH
Graphite
OxidaƟon
C
Fig. 1 Schematic representation of the synthesis of graphene oxide from graphite
Plasmonic Nanoparticles Decorated Graphene Sheets for Detection …
83
thickness, correspond to AFM image (Fig. 2a), is found to be 1.2 nm, which
indicates the formation of double-layered GO nanosheets (Fig. 2c). The UV-visible
spectra of GO and rGO were shown in Fig. 2d. There are two prominent peaks
observed at 230 nm and 300 nm, due to n-p* and p-p* transition of C=C and C=O,
respectively [35].
Raman spectroscopy is regarded as one of the most useful tools for analysis of
defect and disorder present in the crystal structure. Generally, this technique is used
to characterize graphitic derivatives. The ratio of G band to the D band (I D /I G )
calculates the disorder in the graphitic structure. Figure 3 represents the Raman
spectra of GO and rGO sheets. The D band is observed at 1365, 1364 cm
−1 and
corresponding G band are observed at 1597, 1607, for GO, and rGO, respectively.
The origin of G band (sp
2 carbon) arises from C-C bond stretch, and first-order
Raman scattering. The shifting of G band to a higher wave number is may be due to
the oxygenated moieties presence in graphite after oxidation. The D band also
broadened in case of GO due to defects, distortions, size reduction of the sp
2
domains after oxidation. The I D /I G shifted from 0.96 (GO) to 1.0 (rGO) confirms
the attachment of oxygenated moieties to graphene sheets.
Figure 4a depicts the survey XPS of GO demonstrates the presence of C and O
atoms in GO. The high-resolution C1 s XPS spectra (Fig. 4b), representing the
peaks corresponding to four functional groups C–C/C=C, C–O, HO–C=O, C=O,
suggests the successful oxidation to GO [37, 38]. The peaks at binding energy of
284.64 eV, 285.34 eV, 287.28 eV and 289.07 eV correspond to C=C, the C in
C–OH, C(C=O) and (HO–C=O) (carboxyl-C) respectively. Again, O1s
high-resolution XPS spectra are also recorded in Fig. 4c which composed of two
KMnO + 3 H2SO4
4
→ K
+
+ MnO3
+
+ H3O
+
+ 3 HSO4
−
(1)
MnO3
+
+ MnO4 → Mn2O7 (2)
C
O
O
Graphene oxide(Exfoliated)
OH
OH
Graphite
OxidaƟon
C
Fig. 1 Schematic representation of the synthesis of graphene oxide from graphite
Plasmonic Nanoparticles Decorated Graphene Sheets for Detection …
83