Graphene in Ionic Liquids: Collective van der Waals Interaction and Hindrance of Self-Assembly Pathway

Over the past decade, there has been
much controversy regarding
the microscopic mechanism by which the π-electron-rich carbon
nanomaterials such as graphene and carbon nanotubes can be dispersed
in ionic liquids. Through a combination of a quantum mechanical calculation
on the level of density functional theory, an extensive molecular
dynamics study on the time scale of microseconds, and a kinetic analysis
at the experimental time scale, we have demonstrated that collective
van der Waals forces between ionic liquids and graphene are able to
describe both the short-ranged cation−π interaction and
the long-ranged dispersion interaction and this microscopic interaction
drives two graphene plates trapped in their metastable state while
two graphene plates easily self-assemble into graphite in water.