Voltammetric study on the electron transport through a bilayer lipid membrane containing neutral or ionic redox molecules

Voltammograms for the electron transport through a bilayer lipid membrane, BLM, from one aqueous phase, W1, to another, W2, were recorded with the BLM containing 7,7,8,8-tetracyanoquinodimethane, TCNQ, or decamethyl ferrocene, DMFc, exposed to W1 containing [Fe(CN)6]4− and W2 containing [Fe(CN)6]3−. The formation of an anion radical of TCNQ or a cation of DMFc in the BLM followed by the interfacial redox reactions at both W1 ∣ BLM and BLM ∣ W2 interfaces were demonstrated experimentally, based on the comparison with voltammograms observed using a liquid membrane. The BLM containing TCNQ gave a large current for the electron transport controlled by the electron exchange in the BLM, although the BLM containing DMFc gave a small peak current for the electron transport controlled by mass transfer in the BLM. Such two mechanisms were also observed with BLMs containing other ionic redox species in the BLM. It was found that the electron transport through the BLM requires the proximity between the redox potential of redox species in the BLM and that in aqueous phases as well as the existence of both the oxidized and reduced form in the BLM.