A simple route to transform normal hydrophilic cloth into a superhydrophobic–superhydrophilic hybrid surface

Abstract

Metal nanoparticles are known as extremely hydrophilic substances due to their high surface energy. Hydrophobic properties of the metal nanoparticles can be realized only if the nanoparticles are pretreated with low-surface-energy chemicals. In this paper, two adjacent transition metals, i.e. Fe and Co, were selected and coated on a commercially available fabric via a facile in situ growth method. n-Octadecyl thiol, which possesses low surface energy, was selected as the modifier to obtain a superhydrophobic–superhydrophilic hybrid fabric depending on the thiol's selective modification to Fe and Co nanoparticles on the fabric. The surface Co nanoparticles can be modified by n-octadecyl thiol and transform to hydrophobic nanoparticles; however, the surface Fe nanoparticles could not be modified by n-octadecyl thiol in our experimental condition; thus, they retained the hydrophilic property. An as-prepared fabric with these two kinds of nanoparticles evenly distributed on the surface is termed as a superhydrophobic–superhydrophilic hybrid fabric because it shows superhydrophobic property and possesses many superhydrophilic spots. This material is expected to realize water harvesting similar to the desert beetle that collects micro droplets of water from the morning fog without using any external energy source.