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 (Cu 8 (PO 3 OH) 2 (PO 4 ) 4 • 7H 2 O) 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. Compared with the surface modified with ODT, the PDES-modified surface has lower contact angle hysteresis (CAH) for water droplets. It should provide new insight to prepare novel multifunctional materials with potential industrial applications such as corrosion prevention, drag reduction, self-cleaning, and so forth.

Preparation and Characterisation of Super‐Hydrophobic Surfaces

“…Experiments carried out on copper, in which surface oxidation followed by functionalisation gave rise to super-hydrophobic copper surfaces, promise corrosion prevention. [134] This technology could be applied to other forms of surface protection from water. Hydrophobic surfaces not only repel water droplets but show resistance to humidity.…”

Theoretical Explanation of the Lotus Effect: Superhydrophobic Property Changes by Removal of Nanostructures from the Surface of a Lotus Leaf

“…On a lotus leaf, water is prevented from penetrating the air pockets of the leaf by the nano-micro structure (Cassie state). Therefore, theoretical analysis of the lotus effects originated with the application of certain equations and the related studies could be categorized into three types: (1) experimental and theoretical studies on the wetting transition between the Wenzel and Cassie states, [21][22][23][24][25][26][27][28][29][30][31][32][33][34] (2) theoretical studies on the Cassie state's ability to maintain the lotus effect, [37][38][39][40][41] and (3) quantitative and semi-quantitative analyses of various physical factors such as adhesion force. 42,43 However, only a few studies on the lotus effect have considered sliding phenomena.…”

Fabrication of Superhydrophobic Copper Surface on Various Substrates for Roll-off, Self-Cleaning, and Water/Oil Separation

“…For examples, superhydrophobic s ilver film on copper substrate, 35 superhydrophobic CuO film, 36 honeycomb-like three-dimensional porous structures of superhydrophobic hydroxy cupric phosphate heptahydrate fabricated copper surface, 37 etc. have been described.…”