Direct Growth of Hydroxy Cupric Phosphate Heptahydrate Monocrystal with Honeycomb-Like Porous Structures on Copper Surface Mimicking Lotus Leaf

Abstract

Superhydrophobic surfaces were prepared on copper foils via a facile assistant surface oxidation technology and subsequent chemical modification with low free energy materials. The three-dimensional (3D) honeycomb-like porous structures made up of nanoslices of hydroxy cupric phosphate heptahydrate (Cu8(PO3OH)2(PO4)4·7H2O) single crystals were constructed by immersing copper foil in an aqueous solution of phosphoric acid and hydrogen peroxide. The pore size of the 3D structure ranges from hundreds of nanometers to two micrometers, and the thickness of the two-dimensional (2D) nanoslices is about 50−100 nm. The wettability of the porous surfaces was transformed from superhydrophilic to superhydrophobic by chemical modification with octadecanethiol (ODT) or 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDES). It was found that the 3D porous structures of the surfaces helped to amplify the wettability. The resulting static contact angles (CAs) for water were larger than 160° on both of the modified surfaces. Co...