Liquid-phase exfoliation of expanded graphites into graphene nanoplatelets using amphiphilic organic molecules

[Display omitted] •A simple method to fabricate the graphene nanoplatelets (GNPs) is demonstrated.•The GNPs are exfoliated from expanded graphites by amphiphilic molecules in solvents.•The quality of graphitic structure for GNPs is largely preserved after exfoliation process.•Exfoliated GNP solutions are stably maintained for 9months without surfactants. Graphenes with a two-dimensional lattice of carbons have been widely employed in diverse applications owing to their excellent electrical, thermal, mechanical, and gas-barrier properties. However, the frequently-used reduced graphene oxide (rGO), which is synthesized from natural graphites by strong oxidation and subsequent reduction via highly toxic components, exhibits imperfect characteristics because of remaining defect sites on its basal planes. Therefore, in this work, we present a convenient way to prepare graphene nanoplatelets (GNPs) with minimized defect sites on their basal planes employing liquid-phase exfoliation of edge-functionalized expanded graphites (EGs) with amphiphilic organic molecules. Exfoliated GNPs revealed approximately sub-7-nm-thickness and showed stable dispersibility in an organic media during 9months. Furthermore, spray-coated GNP films presented homogeneously stacked morphologies without noticeable agglomerations.