Metal Nanotubule Membranes with Electrochemically Switchable Ion-TransportSelectivity

摘要

Membranes that contain cylindrical metal nanotubules that span the completethickness of the membrane are described. The inside radius of the nanotubules can be varied at will; nanotubule radii as small as 0.8 nm are reported here. These metal nanotubule membranes show selective ion transport analogous to that observed in ion-exchange polymers. Ion permselectivity is observed because excess charge density can be present on the inner walls of the metal tubules. The membranes reject ions of the same sign, and transport ions of the opposite sign as this excess charge. Because the sign of the excess charge on the tubule can be changed potentiostatically, a metal nanotubule membrane can be either cation selective or anion selective, depending on the potential applied to the membrane. jg.