Tunable Energy Barrier for Intercalation of a Carbon Nanotube into Graphene Nanosheets: A Molecular Dynamics Study of a Hybrid Self-Assembly

Molecular dynamics (MD) simulations were utilized to explore the energetics of formation of a graphene-carbon nanotube (CNT) hybrid in an aqueous environment, resulting from the intercalation of a single-walled CNT into a gallery defined by two parallel graphene sheets. It was found that the formation of a graphene-CNT hybrid can be decomposed into three processes involving, (a) exfoliation of graphene sheets by repulsive interactions, (b) intercalation of a CNT into the graphene gallery associated with an activation energy barrier, and (c) spontaneous self-assembly/ association of constituent CNT and graphene sheets driven by hydrophobic interactions or electrostatic attraction, leading to the formation of a three-dimensional hybrid. In contrast with pristine graphene sheets, ionic functionalization makes graphene sheets more hydrophilic and enhances their exfoliation in water, resulting in a significant lowering of the CNT intercalation barrier by nearly 150 kcal/mol. The simulations predict that the lo...