Oxidized Graphite and Graphene

Graphite surface (in particular, EG surface) contains a lot of structural imperfections, such as oxidized groups and residual molecules of oxidizers (Morimoto and Miura 1985). They can be involved in formation of H-bonded complexes with water-type molecules. Active protons in such associations should be subjected to a deshielding effect of electron-donating atoms, and, besides, in this case, one could expect the appearance of H NMR signals with down-field shift relative to the corresponding resonance lines for a condensed phase. As no such peaks were found in the spectra, and, in addition, experimentally determined chemical shifts for water are close to calculated values, it may be concluded that the concentration of these sites in EG is low in comparison with hydrophobic adsorption sites on basal graphite planes of a carbon surface. 

FIGURE 3.48 H NMR spectra for water in a frozen aqueons snspension of oxidized graphite. (According to Karpenko, G.A. et al., Teoret. Eksperim. Khim., 26, 102, 1990b.) 

Nuclear Magnetic Resonance Studies of Interfacial Phenomena 

When interacting with such inclusions, water molecules are subjected to a shielding effect of ring currents in aromatic systems similar to the effect observed in EG. The value of g-factor that is close to g-factor for free electrons provides evidence for the validity of our argument. 

The effect of electron-donor agents on the hydration of GO colloidal particles was studied using H NMR (Turov et al. 1991a-c). The water/GO dispersion (1.4 wt% of solid phase) was examined 

---