Electron transfer into self-assembling monolayers on gold electrodes

Abstract

Electron transfer through a nonconjugated hydrocarbon film was studied. 1-Methyl-1{prime}-(10-(octadecylthio)decyl)-4,4{prime}-bipyridinium dibromide, 1-(7-(octadecylthio)heptyl)-1{prime}-propyl-4,4{prime}-bipyridinium dibromide, and 1-hexyl-1{prime}-(5-(octadecylthio)pentyl)-4,4{prime}-bipyridinium dibromide were synthesized and were separately self-assembled with octadecyl mercaptan onto Au electrodes. The sulfide attached to the gold, and the hydrocarbon chains oriented such that the resulting monolayer films had the electroactive group fixed a distance of 5, 7, or 10 CH{sub 2} groups from the surface, which was about 7-12 {angstrom}, depending on the angle of the chains to the surface. The films were characterized by cyclic voltammetry, FTIR, and ellipsometry. Electron transfer depended on the distance of the electroactive group from the surface and was facile in all cases.