Fog-harvesting performance of hydrophobic zinc oxide nanorods combined with nanoscale roughness on the topmost surface

Zinc oxide nanorods (ZnO-NRs) were prepared on a Si wafer by hydrothermal processing (single-roughness ZnO-NRs). Subsequently, some samples were treated using hydrothermal processing again under an alkaline condition to produce nanoscale roughness on the topmost surface ({0001}) of the rod (double-roughness ZnO-NRs). The obtained samples possessed the expected structure and were coated with a hydrophobic fluoroalkyl silane. These samples consequently became highly hydrophobic. The double-roughness ZnO-NRs exhibited higher sliding angles than the single-roughness ZnO-NRs. The double-roughness ZnO-NRs fog-harvesting performance was better than that of the smooth FAS9 coating or the single-roughness ZnO-NRs. The time dependence of the entire harvested water amount corresponds to the theoretical calculation. The droplet overlapping is expected to affect the results obtained for the double-roughness ZnO-NRs.