pH-Responsive Sponges Fabricated by Ag-S Ligands Possess Smart Double-Transformed Superhydrophilic-Superhydrophobic-Superhydrophilic Wettability for Oil-Water Separation

Advanced applications of surfaces with smart wettability offer great perspectives to design novel materials. pH-responsive smart sponges with double transformation are fabricated via in situ decoration of Ag nanoparticles through an oxidation-reduction reaction and followed by modification with a mixed thiol-ethanol solution containing HS-(CH2)(11)CH3, HS(CH2)(10)COOH, and HS(CH2)(11)OH. The wettability of sponges with optimal thiol proportions can switch reversibly between superhydrophilicity-superhydrophobicity-superhydrophilicity under different pH conditions. In addition, the as-prepared sponges have excellent absorption capacity and high oil-water separation efficiency (99.1%). This report provides a simple approach to prepare smart sponges with switchable wettability which can be further applied to many practical applications, such as marine purification and an oil-water on-off switch.