Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces

Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self-cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water-oil separation. An aqueous ink based on three-dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso- to the macroscale. The surface wettability of a Gr-coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr-coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr-based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity-driven oil-water separation.