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A molecular simulation of interactions between graphene nanosheets and supercritical CO₂

Wu, Bin, Yang, Xiaoning
Journal of colloid and interface science 2011 v.361 no.1 pp. 1-8
carbon dioxide, energy, graphene, molecular dynamics, nanosheets, solubilization, solvents, temperature
The colloidal dispersion stability of nano-sized graphene sheets in supercritical fluid (SCF) media is very important for developing SCF-based exfoliation and dispersion technologies for stabilization and solubilization of graphenes. We carried out molecular dynamics simulations to elucidate the stability mechanism of graphene in supercritical CO₂ (scCO₂). The potential of mean force (PMF) between two graphene nanosheets in scCO₂ was simulated, and the effect of scCO₂ density and temperature on the PMF behavior has been investigated. The simulation results demonstrate that there exists a free energy barrier between graphenes in the scCO₂ fluid, possibly obstructing the aggregation of graphenes. The single-layer confined CO₂ molecules between the graphene sheets can induce a dominating repulsion interaction between graphene sheets. At higher scCO₂ fluid density, there are more confined CO₂ molecules within the interplate regions, resulting in a stronger repulsive free energy barrier. The effect of temperature on the PMF is relatively minor. The scCO₂ solvent structure shows layered confined arrangement in the interfacial region near the graphene nanosheets, which is correlated well with the PMF profile curve.