Characterization of ferrocene-modified electrode using electrochemical surface forces apparatus

Area of Science:

• Electrochemistry
• Surface Science
• Materials Science

Background:

• Self-assembled monolayers (SAMs) are crucial for modifying electrode surfaces.
• Ferrocene derivatives are widely used in electrochemical applications.
• Understanding interfacial forces is key to designing electrochemical devices.

Purpose of the Study:

• To quantify interfacial forces between ferrocene-modified gold electrodes.
• To investigate the influence of counteranions on ferrocenium cation surface charge.
• To determine the degree of dissociation between ferrocenium cations and counteranions.

Main Methods:

• Utilized an electrochemical surface forces apparatus (EC-SFA).
• Measured double-layer repulsion forces between gold electrodes modified with ferrocene alkyl thiol (Fc-SAM) and oxidized ferrocene (Fc(+)-SAM).
• Analyzed surface charge density (σ) and degree of dissociation (αd) in aqueous electrolytes.

Main Results:

• Observed double-layer repulsion for both Fc-SAM and Fc(+)-SAM electrodes.
• Fc(+)-SAM electrodes exhibited a 2.5 times greater surface charge density than Fc-SAM electrodes.
• Determined varying degrees of dissociation (αd) for different counteranions (CF3SO3(-) > SO4(2-) > NO3(-) > ClO4(-)) with Fc(+)-SAM.

Conclusions:

• The surface charge of ferrocenium-modified electrodes is significantly influenced by counteranions.
• Most positive charges on ferrocenium cations are compensated by ion pairing with counteranions.
• Results provide insights into interfacial electrochemistry and SAM-electrode interactions.