Electrochemical Impedance Spectroscopy for Investigation on Ion Permeation in Thioctic Acid Self-Assembled Monolayer

Abstract

Electrochemical impedance spectroscopy was employed to investigate the permeation of electrolyte ions in thioctic acid self-assembled monolayer when its structure was changed by the interaction of copper ions. The ion permeation was evaluated by using relatively low excitation frequencies, 0.2 Hz to 1000 Hz, and quantified by an extra resistive component in the equivalent circuit (RSAM). The extent of ion permeation affected by the electrode potentials and the electrolyte concentration were investigated. The experimental results verified that RSAM decreased ~70% by interaction with copper ions and that RSAM increased ~2 - 3 times when the electrolyte concentration was decreased by 10 times. This analysis can be performed without addition of redox species.