Self-assembled monolayers on mercury probed in a modified surface force apparatus

Area of Science:

• Electrochemistry
• Surface Science
• Materials Science

Background:

• Self-assembled monolayers (SAMs) are ordered molecular assemblies on surfaces.
• Understanding SAMs on mercury is crucial for electrochemical applications.
• Mercury interfaces are model systems for studying interfacial phenomena.

Purpose of the Study:

• To investigate the properties of SAMs formed by three different thiol compounds on mercury.
• To analyze the impact of terminal functional groups on the mercury/aqueous interface.
• To elucidate the electrical double-layer characteristics at these interfaces.

Main Methods:

• Cyclic voltammetry and electrocapillary curves were employed.
• A novel surface force apparatus measured electrical double-layer properties.
• Optical interference determined mica-mercury separation under applied potential.

Main Results:

• 11-mercapto-1-undecanoic acid SAMs introduced negative charge via carboxylic acid dissociation.
• 11-mercapto-1-undecanol and 1-undecanethiol SAMs modified the interface dipole potential.
• A 90 mV difference in dipole potential change was observed between the alcohol and alkyl SAMs.

Conclusions:

• Terminal groups of SAMs significantly influence mercury/aqueous interface dipole potential.
• The study demonstrates the utility of the modified surface force apparatus for interfacial studies.
• SAMs offer tunable control over electrochemical interface properties.