Homogenized redox behavior of electroactive self-assembled monolayers on gold in the organic phase

Abstract

The redox properties of electroactive self-assembled monolayers (SAMs) on gold in the organic phase were investigated by using the thin-film voltammetry approach, i.e., imposing a thin layer of nitrobenzene between the electrode and the bulk aqueous electrolyte. It was discovered that the structures of binary Fc(CH2)11S-/CH3(CH2)10S-Au SAMs became more homogeneous than in aqueous medium, as indicated by the appearance of a single pair of redox peaks even at high ferrocenylalkanethiolate surface densities. Intermolecular interactions became much weaker and eventually negligible (at low Fc surface density) as confirmed by simulating the experimental cyclic voltammograms (CVs) based on theoretical i-E relationship upon considering a Frumkin isotherm. The formation constant of iFc+⋅ClO4−on pairs in the organic phase was found to be much larger than that in aqueous medium, which reaffirms the predominant influence of the microenvironment around the redox centers (organic medium vs. aqueous electrolyte).