Evidence of graphitic AB stacking order of graphite oxides

Graphite oxide (GO) samples were prepared by a simplified Brodie method. Hydroxyl, epoxide, carboxyl, and some alkyl functional groups are present in the GO, as identified by solid-state C-13 NMR, Fourier-transform infrared spectroscopy, and X-ray photoemission spectroscopy. Starting with pyrolytic graphite (interlayer separation 3.36 angstrom), the average interlayer distance after 1 h of reaction, as determined by X-ray diffraction, increased to 5.62 angstrom and then increased with further oxidation to 7.37 angstrom after 24 h. A smaller signal in C-13 CPMAS NMR compared to that in C-13 NMR suggests that carboxyl and alkyl groups are at the edges of the flakes of graphite oxide. Other aspects of the chemical bonding were assessed from the NMR and XPS data and are discussed. AB stacking of the layers in the GO was inferred from an electron diffraction study. The elemental composition of GO prepared using this simplified Brodie method is further discussed.