A general strategy to enhance surface hydrophobicity through modifying a rough-textured surface with weakly hydrophilic elemental sulfur

Abstract

Lotus leaves usually get the superhydrophobicity from the presence of epicuticular wax on its multilevel micro- and nano-structured surface. It is known that the epicuticular wax is weakly hydrophilic with a contact angle of ∼ 74°, and inorganic elemental sulfur also has a weak hydrophilicity similar to the wax. Inspired by the waxy feature, here we first attempt a superhydrophobicity-harvested strategy by modifying a rough surface with weakly hydrophilic elemental sulfur. The superhydrophobicity of a series of materials including metal hydroxides, oxides, sulfides and chlorides, metals, and even hydrophilic organics, can be achieved by prefabricating their topographic textures combined with elemental sulfur surface modification. DFT calculation suggests that the presence of V_S defects on the elemental sulfur coatings can make their rough surfaces have a stronger affinity for O₂^2– than for H₂O, which allows for the formation of O₂^2–-adsorbed layer on their surface, and thus imbues the hydrophobicity or superhydrophobicity. Our study offers a new and general approach to enhance the surface hydrophobicity via inorganic rather than low surface-energy organic modification.