Graphene oxide (GO) nanosheets as oil-in-water emulsion stabilizers: influence of oil phase polarity

Hypothesis: Two-dimensional nanoparticles such as graphene oxide (GO) can serve as emulsion stabilizers due their ability to adsorb at oil–water (o/w) interfaces with high atom efficiency. The ability for GO to act as a surfactant is hypothesized to be highly dependent on the nature (i.e. polarity) of the oil phase, which has not considered previously.
Modelling and experiments: The stabilization energy associated with adsorption of GO sheets at an o/w interface was modelled as a function of the polarity of the oil phase using surface tension contributions terms and Hansen solubility parameters (HSPs). Oil-in-water (o/w) miniemulsions were prepared via ultrasonication in the presence of GO for a variety of different oil phases, and were studied using dynamic light scattering (DLS).
Findings: The stabilization energy associated with GO adsorption was greater for non-polar oil phases compared to more polar oils. This behaviour is driven by the significant reduction in the oil–water interfacial tension as the polarity of the oil increases, to the point where GO adsorption is no longer thermodynamically favourable. This was verified by DLS measurements experiments, as GO-stabilized emulsion were successfully prepared for hydrophobic and aromatic oil phases (e.g. styrene), but not for polar oil phases such as methyl methacrylate.