Interactions of superhydrophobic carbon soot coatings with short alkyl chain alcohols and fluorocarbon solutions

Carbon soot is a nanomaterial, whose extreme water repellency determines its potential industrial applicability in anti-fouling coatings, anti-icing systems, chemical sensors and drag reducing surfaces. The wettability and mechanical durability of the soot can be adjusted through an appropriate chemical treatment, but the underlying mechanism is yet unknown. In this paper, we provide new insights regarding the missing link between the fundamentals of soot-alcohol-fluorocarbon interactions and the derivative physicochemical features/properties of the coating. This is achieved by immersion of three types of superhydrophobic soot coatings in aqueous solutions of methanol, ethanol and isopropanol with variable concentration, and subsequent functionalization with fluorocarbon emulsion. The detailed structural and chemical analysis using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, reveals that the thickness, porosity and ratio of chemical bonds in the soot alter proportionally to the quantity of oxygen functional groups and point defects in the coating, as well as the alkyl chain length of alcohols. Moreover, the chemical treatment with fluorocarbon causes the formation of a thin fluoropolymer film on top of the soot that reinstates its superhydrophobicity and imparts oleophobicity of the surface. These findings are fundamental for further synthesis of soot coatings with controllable surface properties.