38
O. Farinre et al.
Fig. 9. Raman spectra of pristine and functionalized graphene nanoplatelets: (a) Carboxyl-GnPs,
(b) Fluorocarbon-GnPs, (c) Nitrogen-GnPs, (d) Ammonia-GnPs, (e) Oxygen-GnPs, (f) ArgonGnPs, and (g) Pristine-GnPs.
GnPs reflects a smaller crystallite size and our XRD experimental data support this result.
Table 4 shows that the 2D peak of GnPs functionalized with 35 wt% carboxyl shifts to a
lower frequency when compared to the 2D peak of pristine GnPs, because the carboxyl
(-COOH) group behaves as an electron donor (n-type dopant). The wavenumber of the
2D band is expected to shift to lower values upon n-type doping in graphene, as reported
in earlier studies [21].
Fig. 10. (Left) Raman spectra of GnPs functionalized with 7 wt% of carboxyl, with inset clearly
showing the D’ peak near the G peak; (Right) Raman spectra of GnPs functionalized with 35 wt%
of carboxyl showing the D + D’ feature.
The XRD spectra of pristine and functionalized GnPs are shown in Fig. 11, where the
diffraction peaks (002), (100) and (110) are clearly observed in the spectra. The interlayer
spacings (d 002 ) of pristine and functionalized GnPs have been calculated using Bragg’s
formula shown in Eq. (5), while the crystallite sizes (out-of-plane (D c ) and in-plane (D a ))
are calculated using the Scherrer Eq. (6). The constants 0.89 and 1.84 are the Scherrer
constants, FWHM (002) and FWHM (100) are the full width half maximum of the
diffraction peaks (002) and (100), respectively, and θ is the Bragg angle corresponding to
O. Farinre et al.
Fig. 9. Raman spectra of pristine and functionalized graphene nanoplatelets: (a) Carboxyl-GnPs,
(b) Fluorocarbon-GnPs, (c) Nitrogen-GnPs, (d) Ammonia-GnPs, (e) Oxygen-GnPs, (f) ArgonGnPs, and (g) Pristine-GnPs.
GnPs reflects a smaller crystallite size and our XRD experimental data support this result.
Table 4 shows that the 2D peak of GnPs functionalized with 35 wt% carboxyl shifts to a
lower frequency when compared to the 2D peak of pristine GnPs, because the carboxyl
(-COOH) group behaves as an electron donor (n-type dopant). The wavenumber of the
2D band is expected to shift to lower values upon n-type doping in graphene, as reported
in earlier studies [21].
Fig. 10. (Left) Raman spectra of GnPs functionalized with 7 wt% of carboxyl, with inset clearly
showing the D’ peak near the G peak; (Right) Raman spectra of GnPs functionalized with 35 wt%
of carboxyl showing the D + D’ feature.
The XRD spectra of pristine and functionalized GnPs are shown in Fig. 11, where the
diffraction peaks (002), (100) and (110) are clearly observed in the spectra. The interlayer
spacings (d 002 ) of pristine and functionalized GnPs have been calculated using Bragg’s
formula shown in Eq. (5), while the crystallite sizes (out-of-plane (D c ) and in-plane (D a ))
are calculated using the Scherrer Eq. (6). The constants 0.89 and 1.84 are the Scherrer
constants, FWHM (002) and FWHM (100) are the full width half maximum of the
diffraction peaks (002) and (100), respectively, and θ is the Bragg angle corresponding to