Investigations of potential-dependent fluxes of ionic permeates in gold nanotubule membranes prepared via the template method

We have been exploring the transport properties of gold nanotubule membranes prepared by electrolessly plating Au within the pores of a microporous polycarbonate filter. We have previously shown that when a potential that is negative of the potential of zero charge (pzc) of the membrane is applied, these membranes are cation permselective, and at potentials positive of the pzc, these membranes are anion permselective. A potentiometric method was used to demonstrate this potential-dependent ion permselectivity. Transport experiments showing how the fluxes of anionic and cationic permeate species change as a function of potential applied to the membrane were not done. Such transport experiments would provide a better indication of the ability of these membranes to separate cations from anions in a potential-dependent membrane-based separation process. For this reason, we have conducted a series of fundamental investigations aimed at determining how the fluxes of cations and anions change as a function of potential applied to the Au nanotubule membranes. Fluxes of two cationic and two anionic permeate species were investigated in membranes containing nanotubules with two different inside diameters. The anionic permeates showed high fluxes at positive applied potentials and low fluxes at negative applied potentials. The opposite trend was observed for the cationic permeates.