6. Protobind 1000- Fe2O3 graphene oxide:
XPS analysis6
Composition of Protobind 1000-Fe2O3-graphene :C(76.4 at%), O(23.3
at%) and Fe(0.3 at%)
XPS: survey spectra for sample without purification
Si2p
~103eV
O1s
~533eV
C1s
~285eV
Fe 2p (700-745 eV)
7. Protobind 1000- Fe2O3 graphene oxide:
XPS analysis, (cont.)
7
Core level O1s spectrum Core level C1s spectrum
Comparing the peak shape, carbon present is sp2 in graphene1
1 .Anon. 2013. Available at: http://xpssimplified.com/elements/carbon.php.
8. Protobind 1000- Fe2O3 graphene oxide:
TEM-EDS analysis
8
Before purification
Element Composition (%)
C 89.4 ± 0.2
O 3.3 ± 0.1
Fe 4.9 ± 0.1
Other 2.5
After HNO3 purification
Element Composition (%)
C 93.0 ± 0.4
O 5.6 ± 0.4
Fe 0.8 ± 0.1
Other 0.6
9. Lignosulfonate- Fe2O3 graphene oxide:
TEM analysis
9
Before purification
Element Composition (%)
C 68.0 ± 0.2
O 2.1 ± 0.1
Fe 13.9 ± 0.1
Other 16
After HNO3 purification
Element Composition (%)
C 67.1± 0.3
O 4.9 ± 0.2
Fe 7.6 ± 0.1
Other 20.4
Editor's Notes
The typical binding energies for graphene, sp2C (C=C) and diamond, sp3C (C-C) is ~284eV and 285eV respectively. A carbon with sp2 bond will have a broad asymmetric tail towards higher binding energies and sp3 have a more symmetric peak. Therefore, by comparing the peak shape, it could be noted that the carbon present here is graphene (sp2).
The C1s spectra can be fitted to two main groups, non-oxygenated carbon (C-C/C=C) at 284.6eV; and carbon oxygen single bond (C-O) at 286.1eV. As the number of oxygen bonded to carbon increases, the binding energy also increases because oxygen is more electronegative than carbon and thus it pull the electrons away from carbon98. The possibility of forming Fe-C bonds is ignored because no dominant peak is present at 283.3 eV95. The typical binding energies for graphene, sp2C (C=C) and diamond, sp3C (C-C) is ~284eV and 285eV respectively. A carbon with sp2 bond will have a broad asymmetric tail towards higher binding energies and sp3 have a more symmetric peak. Therefore, by comparing the peak shape, it could be noted that the carbon present here is graphene (sp2). The other more accurate method to confirm this is to check the peak position. It is of no use in here since the reference material involved also carbon. The charge compensation and shift in peaks will avoid extracting the necessary information from the spectrum. However, the reference graphene nano-sheet sample GNP showed the same peak shape and peak position with the rest of the graphene produced. Therefore, the possibility of graphene present in sample is much higher compares to rest of the carbon derived materials.
