Stability of r-GO/oil coating on metal. (a) Photos showing a drop of dyed silicone oil (viscosity: around 0.02 Pa·s) flowing down a tilted Al foil in only 10 seconds. (b) In contrast, a drop of r-GO/oil is firmly pinned. (c) Photos showing coatings of r-GO/oil (top) and a high-molecular-weight silicone oil (bottom) of even higher viscosity (around 100 Pa·s), which is dyed red for the convenience of observation. Both coatings are initially stable in air, but when placed under water, the silicone oil film dewets and shrinks within 60 minutes. In contrast, the r-GO/oil coating remains stable. (d) The r-GO/oil coating on a copper wire (1.02 mm diameter) remains stable in a vigorously stirred water bath for days. The inset indicates the position of the wire in the bath.