An X-ray Photoelectron Spectroscopic Study of Multilayers of an Electroactive Ferrocene Derivative Attached to Platinum and Gold Electrodes

Pretreated (anodized) Pi and Au electrode surfaces derivatized with (1,1'-ferrocenediyl)dichlorosilane have been analyzed by X-ray photoelectron spectroscopy (XPES). The derivatized surfaces exhibit Fe 2p_3/2 bands with binding energies consistent with ferrocene iron and with large companion satellite peaks. Using a layer model, relative Fe 2p_3/2 and electrode substrate intensities (Au or Pt) can be correlated with ferrocene coverage measured by cyclic voltammetry. The results indicate that electrochemical charge transfer can occur through ferrocene/silane layers of thicknesses exceeding 100 Å. XPES data indicate that the attached electroactive material contains less than the expected 1:1 ratio of Fe:Si, indicating some ferrocene degradation in the attachment procedure. These surface analyses accord well with elemental analyses of hydrolyzed material resulting from reaction of H₂0 with (1,1'-ferrocenediyl)dichlorosilane which also shows less than a 1:1 Fe:Si ratio.