Surfactant-Enhanced Adsorption of Graphene Oxide for Improved Emulsification of Oil in Water

Graphene oxide (GO) can be enriched at the air–water interface by the adsorption of surfactant molecules to the surfaces of the GO sheets. The synergism between the surfactant and GO is shown to be responsible for the improved interfacial performance of the composite through a subtle balance of surface charge and surface activity. The use of a photoaddressable surfactant provides a unique probe for investigating the fundamental mechanisms that control adsorption, by inducing spatiotemporal modulation of the surfactant properties by irradiation with light of certain wavelengths. Tensiometry measurements uncover the interfacial activity of the materials, whereas X-ray reflectivity serves to independently determine the interfacial structure and composition. The ratio between the surfactant and GO appears to be the key factor controlling adsorption, with pH and salt offering additional finer control of interfacial properties. This synergism between GO sheets and a surface active small molecule surfactant is utilized to stabilize oil-in-water emulsions with unprecedented effectiveness.