Redox reactions on TCNQ-modified self-assembled monomolecular films

Abstract

Suitably modified mono- and bimolecular films, including bilayer lipid membranes (BLMs), offer exceptionally good opportunities for probing electric field effects on charge transfer and redox reactions in biosensor and molecular electronics research and development. This work presents the redox reactions of tetracyano-p-quinodimethane (TCNQ) molecules incorporated in a self-assembled octadecanethiol monolayer (SAM) on polycrystalline gold electrodes, depending upon the type of supporting electrolyte cations and their concentration. Our results show that TCNQ-modified Au–SAM electrodes exhibit selectivity versus alkali metal cations in aqueous supporting electrolyte (∽10 kJ mol−1 difference between K+ and Li+ and between Cs+ and K+). The slope of the ‘calibration curves’ for Li+ and K+ is about 59 mV per decade of concentration of the analyte. The explanation of this behaviour is based on the Donnan potential model; however, an ion-pairing effect can also be involved. Our preliminary results show also that the TCNQ molecules within the octadecanethiol monolayer may act as a molecular redox device. © 1998 John Wiley & Sons, Ltd.