Zirconia Nanotube Coatings - UV-Resistant Superhydrophobic Surfaces

Surface modifications influence material interactions such as wettability, imparting hydrophobicity or hydrophilicity. Mainstream research focused on enhancing product shelf-life, directs attention towards superhydrophobic surfaces (SHS). SHS offer several benefits for outdoor applications such as self-cleaning, anti-soiling, anti-mist etc. In this manuscript, we explore the possibility of combining structural and chemical modifications to metal substrates in order to create superhydrophobic metal oxide surfaces. ZrO2-nanotubes are evaluated with regard to their application as transparent UV-stable superhydrophobic coatings. Nanostructured oxide surfaces are created via single-step electrochemical anodization. The absence of HF acid-based pre-etching steps offer a safe and alternatively a green synthesis route. Anodized oxides are modified using octadecylphosphonic acid self-assembled monolayers, demonstrate superhydrophobicity and are evaluated for their mechanical stability under a jet of water, chemical stability under indirect sunlight irradiation in air/water and direct UV exposure. Zirconia nanotubular films were evaluated for optical transparency using light microscopy and surface wettability of the different zirconia-composites was compared to the model system-titania. Structural and compositional differences of the SAM layer upon time dependent decay were analyzed with X-ray photoelectron spectroscopy.