Ionic liquid-mediated functionalization of graphene-based materials for versatile applications: a review

Industrial applications of the graphene (G) and graphene oxide (GO) can be further explored by making them more dispersible in the aqueous and organic environments. Several attempts have been performed to enhance the dispersity of the G and GO in which surface functionalization is one of the most effective methods. Recently, surface functionalization of G and GO using ionic liquids is gaining particular emphasis because of their high thermal and chemical stability, low volatility, very high ability to dissolve a wide range of compounds and more importantly their environmental-friendly behaviour. The covalent functionalization of G and GO is mostly being achieved by acylation, esterification, isocyanate formation, nucleophilic ring opening, amide formation, and diazotization and cycloaddition reactions. Non-covalent functionalization mostly involves electrostatic forces, hydrogen bonding, π–πinteractions, van der Waals interaction and donor–acceptor interactions. Because of their high dipolar nature, ionic liquids strongly interact with the sp2-hydrodized carbon networks of G and GO sheets and make them more dispersible as compared to their native networks. In the present review article, we described the collection of reports available on covalent and non-covalent functionalization of G and GO using ionic liquids and their industrial applications. The ionic liquid-functionalized graphene (G-IL) and graphene oxide (GO-IL) are extensively used in pollutants decontamination, sensing and bio-sensing, lubrication, catalysis, and carbon dioxide capturing and hydrogen production. The G-IL and GO-IL represent an essential class of materials for versatile future applications.