Role of the Supporting Electrolyte Ions and Additives on the Electron Transport Properties of Electrografted Films Bearing Ferrocenyl Moieties

The electrochemical oxidation of 6-ferrocenylheptanoate was used to modify the surface of glassy carbon electrodes with thin films bearing ferrocene molecules. These films grow layer by layer and behave as surface redox catalyst during the electrografting. The electrografted films have a structure with pinholes or channels, whose existence was deduced from the redox behavior of the film in acetonitrile solution containing different supporting electrolytes and organic additives. The electron transport through this film requires the presence of the electrolyte anions in the film channels. However, the voltametric feature of the grafted films is sensitive to the electrolyte cation size. The supporting electrolyte anions inside the film channels stabilize the ferrocenium species during the film oxidation. However, the presence of the cations is required to keep the inner charge balance. The inclusion of both anions and cations inside the grafted film determines the surface coverage obtained from the voltammetric experiments.