Direct exfoliation of graphene in ionic liquids with aromatic groups

• Imidazolium ionic liquids with phenyl groups disperse graphene noncovalently without stabilizers.
• The graphene concentration is higher in diphenyl than in monophenyl substituted ionic liquids.
• DFT calculations show phenyl-graphene π–π interactions help stabilize graphene–IL dispersions.

Novel ionic liquids (ILs) were designed and synthesized to contain aromatic groups on the imidazolium cation that non-covalently interact with graphene surfaces. This route enables the dispersion of pristine graphene without covalent functionalization or an additive stabilizer; such dispersions are stable against aggregation and display high concentration values. We find that ILs without these aromatic groups are less effective in graphene dispersion, and the dispersed graphene concentration increases with increasing interaction between the cation and graphene surface. Density functional theory (DFT-D3) calculations support the experimental observations and provide a foundation for predictive modeling of IL design for optimal graphene dispersions.

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