Redox reactions on TCNQ-modified self-assembled monomolecular films

Suitably modified mono- and bimolecular films, including bilayer lipid membranes (BLMs), o er 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 (similar to 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. (C) 1998 John Wiley & Sons, Ltd.