Voltammetry of Self-Assembled Ferrocene Octanethiol Monolayers on Metal-CoatedHigh Temperature Superconductor Electrodes at Sub-T(sub c) Temperatures

摘要

A scheme is described for measuring electron transfer kinetics between a surface-immobilized redox monolayer and a high temperature superconductor (HTSC) electrode at temperatures above and below the superconductor transition temperature T(sub c). The scheme depends on coating the HTSC electrode with an ultrathin metal film (Au, Ag) onto which redox monolayers of ferroceneoctanethiol with octanethiol diluent are co-chemisorbed by self-assembly. The ferrocene redox moiety is separated from the metal film/HTSC by an alkane chain tunneling barrier. Cyclic voltammetry and potential electron transfer rate measurements are given for monolayer coated HTSC/Au film and SC/Ag film electrodes at tme temperatures above and below the 119 K T(sub c) of the Tl2Ba2CaCu2O8 (Tl2212) superconductor employed as the HTSC/metal electrode. The ferrocene monolayers display well-defined voltammetry down to 105 K. While the electron transfer rate measurements are estimates only, the voltammetry and rate measurements are the first of their kind for a molecular monolayer on an electrode in the superconducting state. The results will guide adjustment of the alkane chain tunneling barrier to a length appropriate for slower and more accurate electron transfer rate measurements, even at applied overpotentials large enough to reduce the electron transfer barrier to values smaller than the electron-pairing energy. jg.