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Multifunctional Free-Standing Membrane from the Self-assembly of Ultralong MnO2 Nanowires

Lan, Bang, Yu, Lin, Lin, Ting, Cheng, Gao, Sun, Ming, Ye, Fei, Sun, Qingfeng, He, Jun
ACS Applied Materials & Interfaces 2013 v.5 no.15 pp. 7458-7464
asymmetric membranes, filtration, hydrophilicity, hydrophobicity, industry, magnetism, manganese dioxide, nanoparticles, nanowires, scanning electron microscopy, silane, wettability
In this work, we report the preparation of a free-standing membrane with strong mechanical stability and flexibility through a facile vacuum filtration approach. A field-emission scanning electron microscopy image demonstrates that the membrane composed of MnO₂ nanowires is 50 nm in width and up to 100 μm long and the nanowires are assembled in parallel into bundles. A possible formation mechanism for the ultralong nanowires and the free-standing membrane has been proposed. Meanwhile, the properties of the membrane could be controlled by incorporating different materials to achieve composite membranes. In order to demonstrate the broad applicability of the MnO₂ membrane, we fabricate a variety of composite membranes exhibiting various novel properties including magnetism and reversibly switchable wettability between hydrophilicity and hydrophobicity through various material modification, including CoFe₂O₄ nanoparticles and organic triethoxy(octyl)silane. Furthermore, the free-standing membrane could also simultaneously be functionalized with two materials, which reveal multiple properties. The synthesis method of a free-standing MnO₂ membrane is simple and environmentally friendly, and it is easily scalable for industry. These composite membranes constitute a significant contribution to advanced technology.