Nanostructured superhydrophobic silver surfaces

Inspired by "lotus-effect", a superhydrophobic surface, in general, is prepared via two steps: (i) creating a surface roughness and then (ii) lowering the surface energy via a self-assembly of organic molecules or via low surface energy coatings. Superhydrophobicity cannot result if one of these two essential factors does not coexist. In the present work, it has been shown that superhydrophobic properties can be achieved on silver surfaces both via two-steps and a novel and simple one-step process. In the two step-processes a fractal-structured silver film deposited on copper surface by galvanic exchange reactions was passivated using stearic acid organic molecules to reduce the surface energy resulting in the superhydrophobicity. In the one-step process, however, the copper substrates were simply immersed in the silver nitrate solution containing fluoroalkylsilane (FAS-17) molecules resulting in superhydrophobicity. The silver films prepared both via two-steps and one-step processes were found to be highly water repellant with the water drops rolling off those surfaces. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were utilized to understand the morphology, molecular bonding, and chemical properties of the superhydrophobic silver surfaces.