Mesoscopic siumulation of sodium dodecyl sulfate aggregates on graphene nanosheets

Abstract

Sodium dodecyl sulfate (SDS) aggregates on graphene sheets (GS) and graphene nanoribbons (GN) were studied using dissipative particle dynamics (DPD) simulations. The effects of GS size and GN width on aggregate morphology were investigated, as well as that of surfactant coverage. The SDS aggregates were studied on 3x3 nm², 6x6 nm², and 12x12 nm² GS and on 3 nm, 6 nm, and 12 nm wide GN, at ambient conditions. Our results suggest that the SDS aggregate shape depends on the size of the GS and GN. The quantification of the results was in the form of SDS contact angles, order parameter, and density profiles. Both GS and GN were modified with functionalized edges to mimic graphene oxide. A reduction in adsorbed surfactant was observed on both GS and GN upon functionalization. To understand the effect of the surfactants on stabilization of GS dispersion, two GS of different sizes and covered by different amounts of surfactant were allowed to diffuse in an aqueous system. As the simulations progressed, some of the graphene nanosheets aggregated. The results were quantified using snapshots, and by quantifying the simulation time required for the GS to agglomerate. The mechanism of agglomeration was discussed qualitatively. Increasing the amount of surfactant decreased the likelihood of GS aggregation and also affected the GS agglomeration mechanism.