Long-term stable solid concentrated graphene dispersion assisted by a highly aromatic ionic liquid

Hypothesis: The sonochemical exfoliation of graphite in solution has been demonstrated as a promising and easy technique for producing graphene dispersions. This is usually done in organic solvents and leads to unstable dispersions with very low graphene concentration. Ionic liquids (ILs) represent a versatile and safe alternative to traditional organic solvents. A few recent studies reported the use of commercial ILs with bulky anions, such as bis(trifluoromethylsulfonyl)imide, and aromatic cations, such as imidazolium, which favour the exfoliation of graphite through 7C -7C and cation -7C interactions. Although recently inves-tigated, the role of aromatic groups on imidazolium cations is still controversial and systematic studies are still necessary. Besides, these studies were limited to liquid dispersions at room temperature.Experiments: Herein, we prepared four highly aromatic imidazolium-based ILs, including the newly reported 1-(naphthylmethyl)-3-benzylimidazolium bis(trifluoromethanesulfonyl)imide, [(Np)(Bn)im] [NTf2]. These ILs were used for the sonochemical exfoliation of graphite and compared with a commercial benchmark, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][NTf2].Findings: Interestingly, [(Np)(Bn)im][NTf2] allowed reaching solid dispersions at room temperature con-taining thin few layer graphene sheets with long-term stability (up to 2 years) and high concentration (3.6 mg/mL). Such graphene dispersion combines long-term stability in the solid-state and high process -ability in the liquid state, by a simple heating above 60 degrees C.(c) 2023 Elsevier Inc. All rights reserved.