Size-Dependent Interfacial Assembly of Graphene Oxide at Water-Oil Interfaces.

The interfacial assembly of graphene oxide (GO) at the water/oil interface was investigated using pendant drop tensiometry as a function of the pH, GO size and concentration, and molecular weight of the polymer ligands. It was found that the smaller the lateral dimension of the GO sheets, the more rapidly the interfacial tension decreased, and the lower was the interfacial tension between the oil and water. The differences in the rates at which the interfacial tension decreased are related to the diffusion of the GO to the interface, the presentation of the GO at the interface, the degree of functionalization relative to the surface area, and the in-plane motion of the GO to accommodate the arrival of more GO at the interface to effectively cover the interface. The solidlike film formed at the interface had a modulus that increased with decreasing lateral GO dimensions.