Spontaneous dissolution of graphene in super acids investigated using mean field theory
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Graphene and other allotropes of carbon, such as carbon nanotubes, cannot be dissolved in common solvents such as water or alcohols. Dispersion is possible with the use of surfactants, but this requires sonication. It was experimentally found that spontaneous dissolution is possible however in super acids, such as chlorosulfonic acid. From Raman spectroscopy measurements it is concluded that hydrogen ions, formed by the autodissociation of the acid, bind to Carbon atoms in graphene and carbon nanotubes and, by Coulombic repulsion cause a disjoining pressure that explains the dissolution. To validate this claim, we set up a mean-field theory using charge regulation to describe the disjoining pressure between platelets of graphene due to electric double layer interactions. We consider several complicating factors such as the image charge effect and the finite thickness of the graphene platelets. Our final conclusion is that, within the limitations of our model, double layer repulsions cannot explain the spontaneous dissolution of graphene in chlorosulfonic acid.