Multiscale molecular thermodynamics of graphene-oxide liquid-phase exfoliation

Liquid-phase exfoliation is one of the most feasible methods for mass-production of two-dimensional (2D) nanomaterials such as graphene, graphene-oxide (GO), etc. Assessing requirements for successful exfoliation necessitates molecular-level thermodynamic analysis that can provide quantitative measures such as free energy changes. Here we explain this methodology and apply it to the production of GO that is used as a precursor for graphene synthesis and as an ultrathin substrate for many applications. Three different routes to GO exfoliation are studied, namely parallel and perpendicular to the GO surface as well as exfoliation via edge bending, using multi-scale combination of density functional, force field, and continuum approaches. Detailed analysis of free energy variations reveals relative feasibility of different exfoliation mechanisms and their dependence on system size and surface coverage. The methodology is general and can be applied to liquid-phase exfoliation of other 2D nanomaterials.