Mohammad Hadi Ghatee - Department of Chemistry, Shiraz University, Shiraz 71946, Iran
Ramin Eradeh - Department of Chemistry, Shiraz University, Shiraz 71946, Iran

Demand in graphene preparation is due to its central role in fabrication of a variety of microelectronic devices. We synthesized graphene nano-sheets by liquid phase exfoliation of graphite flakes, using five quaternary ammonium-based ionic liquids as solvent. Ionic liquids with different alkyl chain lengths were selected to study the role of liquid nature, particularly the surface thermodynamic properties, on the extent and efficiency of exfoliation. Well stabilized dispersed graphenes in ionic liquids are produced by exfoliation of graphite using a tip ultrasonicator. Graphenes were characterized quantitatively by dispersion value and qualitatively by Scanning Electron Microscopy, X-Ray Diffraction, as well as by Ultraviolet-Visible and Fourier Transform InfraRed spectroscopic methods. As a result, dispersion value of graphene is decreased (from 1.8 to 1.05 mg/ml) with alkyl chain length, while the quality of exfoliatedgraphene is increased. Kinetic study was involved the stability assessment of dispersion in different ionic liquids over time, where triethyl(octyl)ammonium bis(trifluoromethylsulfonyl) imide found to produce themost stable dispersion. Hence, a balance between repulsive Coulombic and attractive van der Waals forces warrant the stability. These observations on dispersion values can be fundamentally related to the solubility properties of solvent and solute in terms of their known surface thermodynamic properties

Graphene, Quaternary Ammonium-Based Ionic Liquids, Liquid Phase Exfoliation,Surface Thermodynamic Properties