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

Abstract

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 divided 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 lowest intercalation barriers would arise for cases where both the energetic cost for graphene exfoliation and steric repulsions between the incoming CNT and graphene sheets are the lowest. Once the CNT moves past the barrier, its further incorporation into the graphene gallery is spontaneous and is assisted by strong hydrophobic interactions between the CNT and graphene surfaces. The most stable hybrid complex was observed when the CNT and graphenes are functionalized with oppositely charged ionic groups.

Interfacial interactions of humic acids with polystyrene nano-plastics in aqueous/ionic environments: a molecular dynamics exploration

“…4). The observed inferences are consistent with the idea of screening of surface charge with enhanced condensation of Na + ions, 35,38,39 and consequently a decrease in Debye screening length. A similar trend is observed for the surface potentials calculated for PS-slab at pH-4 and pH-7 at 0 M and 0.5 M NaCl.…”

“…This significant reduction in the negative potential is due to the screening of its surface charge by Na + ions that are adsorbed onto the interface of PS-Slab (Figure 4). The observed inferences are consistent with the idea of screening of surface charge with enhanced condensation of Na + ions 35,38,39 and consequently a decrease in Debye screening length. A similar trend is observed for the surface potentials calculated for PS-Slab at pH-4 and pH-7 at 0M and 0.5M NaCl.…”

Mechanical properties of graphene-CNT van der Waals heterostructures: a molecular dynamics study

“…These structures are of interest since they approximate heterostructures that have been synthesized experimentally [10,11,18]. There has also been a recent computational study exploring synthesis environments that promote CNT intercalation between graphene sheets and selfassembly to generate such vdW heterostructures [19]. Given their relative ease of synthesis and their promising applications as nanodevices, it is worthwhile to quantify their mechanical properties.…”