Self-Assembly of Surfactant Mixtures on GrapheneNanosheets: Insights from Molecular Dynamic Simulation

Because of two-dimensional structure, large surface area and unique mechanical, thermal, opticaland electrical properties of graphene, it has attracted much attention for promising applications,such as in energy, composites, biotechnology and electronics [1]. However, these applicationsrely on the mass production of high-quality and low-cost graphene. Owing to thehydrophobic nature of graphene nanosheets, their non-covalent functionalization with surfactantsis an effective method for the production of graphene stable aqueous suspensions [2].Computer simulation has been a powerful tool for gathering information at molecular-levelabout the process of adsorption and assembly of different molecules on nanomaterials [3]. Inthis study, large-scale and all-atomistic molecular dynamic simulations were used to study theeffect of mixing two surfactants on micelle assemblies structure formed on graphene. For examinationof the structural assemblies’ characteristics formed from surfactants on graphene,the density profiles of the head and tail groups of surfactant were plotted as a function of the zdistance perpendicular to graphene (Fig. 1). The simulations showed thatthe random adsorptionmodel first changes to the monolayer model and then the hemispherical model with anincreased surfactant concentration. (***) Fig. 1 The simulated density profiles of the head groups (a and c) and the tail groups (b and d) as a functionof the distance from the z-axis of the graphene for two cationic-rich and anionic-rich mixtures with three differentsurface coverages including low surface coverage (blue line), medium surface coverage (red line) andhigh surface coverage (green line).