Electrodes modified with Nafion films incorporating amphiphilic ferrocene derivatives

The electrochemical behavior of electrodes modified with Nation^® films containing several ferrocene derivatives was investigated by cyclic voltammetry. The derivatives used were alkyldimethyl (methylferrocene) ammonium salts, where the alkyl group was methyl (1), heptyl (2), or hexadecyl (3). The rate of charge propagation across the Nafion film was found to decrease as the length of the alkyl chain increased. This finding was confirmed by rotating disk electrode experiments in which the Nafion-bound ferrocene derivatives mediated the oxidation of ferrocyanide ions in solution. On the other hand, the longer chain derivatives 2 and 3 were retained inside Nafion films more strongly (or for longer times than the methyl derivative 1. Therefore, 2 and 3are suited for use as electrochemical probes to monitor microenvironmental changes in the polyelectrolyte matrix resulting from the incorporation of other species. This was demonstrated using 3 as the probe and tetrabutylammonium ions as microenvironment modifiers.