Controllable pore size of three dimensional self-assembled foam-like graphene and its wettability

We propose an effective method for making three-dimensional self-assembled foam-like graphene (SFG) with controllable pore size using a nucleate boiling method. We fabricated different SFGs using nucleate boiling in reduced graphene oxide (RGO) colloid at heat fluxes of 800, 900, 1000, 1100, 1200, and 1300 kW/m2 with tunable pore size, by controlling the heat flux. The resulting pore size showed good agreement with the active nucleation cavity size theory of Hsu, and we determined that the pore size of the SFGs had a bigger effect than the thickness of SFGs on the electrical conductivity. Contact angle measurements, droplet impact, and environmental scanning electron microscopy (E-SEM) analyses were used to characterize both static and dynamic wettability. The resulting sufficiently formed SFG layer had both hydrophobic properties and highly adhesive properties, similar to petal leaves. We postulate that these hydrophobic and hydrophilic properties were caused by hydrophobic RGO planes exposed to the surface and carboxylic groups buried in the structures, resulting from self-assembly; the E-SEM analysis supported these wetting characteristics.