Stable Dispersion of Graphene in Water, Promoted by High-Yield, Scalable Exfoliation of Graphite in Natural Aqueous Extracts: The Role of Hydrophobic Organic Molecules
Apostolos Koutsioukis, Georgios Florakis, Elias Sakellis, Vasilios Georgakilas
Abstract
The van der Waals interactions between graphene nanosheets and hydrophobic molecules derived from natural aqueous extracts are indicated as the driving force for high-yield exfoliation of graphite and effective dispersion of graphene produced in pure water. Although it seems paradoxical, the absorption of small hydrophobic organic molecules on large graphene surfaces decreases the hydrophobic character of graphene nanosheets, resulting in significant improvement of graphene dispersibility in water. This fact reveals a totally novel mechanism to produce high-quality graphene nanosheets by liquid exfoliation of graphite in natural aqueous extracts and their dispersion in water at relatively high concentrations. This method is easily scalable, environmentally friendly, and low cost and showed remarkable yields. More importantly, the role of van der Waals interactions in preventing the hydrophobic effect is an unexplored area that could open new pathways for the development of two-dimensional materials or the stabilization of colloidal systems such as polymers, proteins, or other biomolecules.