The characterisation of commercial 2D carbons: graphene, graphene oxide and reduced graphene oxide

In this work we have comprehensively characterised 13 products from commercial suppliers that are claimed to be 2D materials: graphene, graphene oxide and reduced graphene oxide. The techniques used have investigated the materials from the macroscale to the atomic scale. The results are consistent across all length scales: none of the products meet the ISO definition of “a single layer of carbon atoms”. Rather, they are largely nanographite with a small percentage of single layer material present. One of the techniques used was inelastic neutron scattering (INS) spectroscopy. INS enables the materials to be examined in the C–H/O–H stretch region without the complications of electrical anharmonicity that bedevil infrared spectroscopy. The spectra clearly show that most of the hydrogen is present as sp² C–H; sp³ C–H is either absent or present as a minority species. This provides strong support for the Lerf and Klinowski model of graphene oxide. The spectra also show that the number of hydroxyls present is small, indicating that most of the oxygen is present as epoxides or carbonyls.