Wetting transparency of supported graphene is regulated by polarities of liquids and substrates

Abstract

Graphene has to be supported on a substrate in a variety of applications. The underlying substrate can exert a remarkable impact on the wettability of graphene, but the inherent mechanism remains elusive. By quantifying the static contact angles of water (polar liquid) and diiodomethane (nonpolar liquid) droplets on graphene supported on different kinds of substrate, we found that the apparent wetting transparency of the supported graphene with airborne hydrocarbon adsorption depends essentially on polarities of both the liquids and the underlying substrates, and that, in most cases, the supported graphene exhibits wetting translucency. With the Owens-Wendt theory, we then identified the specific components of the surface energy, which indicated that inserting graphene does not introduce a polar interaction and that the apparent transmitted polar energy of one layer of graphene is ∼20% for the investigated substrates. The apparent polarity of supported graphene can potentially be tuned by the underlying substrate. Practically, the wettability of graphene can be determined by investigating the competitive relationship between the reduced dispersive and polar interaction of the substrate and the increased dispersive one introduced via inserting the graphene layers. Our findings may have significant implications in designing functional nanostructures through tuning the surface properties of graphene by its surroundings.