Fletcher Benjamin L, Retterer Scott T, McKnight Timothy E, Melechko Anatoli V, Fowlkes Jason D, Simpson Michael L, Doktycz Mitchel J
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
ACS Nano. 2008 Feb;2(2):247-54. doi: 10.1021/nn700212k.
Nanoporous membranes are applicable to a variety of research fields due to their ability to selectively separate molecules with high efficiency. Of particular interest are methods for controlling membrane selectivity through externally applied stimuli and integrating such membrane structures within multiscale systems. Membranes comprised of deterministically grown, vertically aligned carbon nanofibers (VACNFs) are compatible with these needs. VACNF membranes can regulate molecular transport by physically selecting species as they pass between the fibers. Defined interfiber spacing allows for nanoscale control of membrane pore structure and resultant size selectivity. Subsequent physical or chemical modification of VACNF structures enables the tuning of physical pore size and chemical specificity allowing further control of membrane permeability. In this work, the dynamic physical modulation of membrane permeability that results when VACNFs are coated with an electrically actuatable polymer, polypyrrole, is demonstrated. Electrochemical reduction of polypyrrole on the VACNFs results in controlled swelling of the diameter of the nanofibers that in turn decreases the pore size. Dynamic control of membrane pore size enables selective transport and gating of nanoscale pores.
纳米多孔膜由于能够高效地选择性分离分子，因而适用于各种研究领域。特别令人感兴趣的是通过外部施加刺激来控制膜选择性以及将这种膜结构集成到多尺度系统中的方法。由确定性生长的垂直排列碳纳米纤维（VACNFs）组成的膜符合这些需求。VACNF膜可以通过在分子通过纤维之间时进行物理筛选来调节分子传输。确定的纤维间距允许对膜孔结构进行纳米级控制以及由此产生的尺寸选择性。随后对VACNF结构进行物理或化学修饰能够调节物理孔径和化学特异性，从而进一步控制膜的渗透性。在这项工作中，展示了当VACNFs涂覆有可电驱动聚合物聚吡咯时所导致的膜渗透性的动态物理调制。聚吡咯在VACNFs上的电化学还原导致纳米纤维直径的可控膨胀，进而减小孔径。膜孔径的动态控制实现了纳米级孔的选择性传输和门控。
