Determining the Self-Assembling and Redox Process of a Viologen Monolayer by Electrochemical Quartz Crystal Microbalance

Abstract

Electrochemical and quartz crystal microbalance (EQCM) methods are used to probe the redox behavior of self-assembled monolayers of viologen derivatives with long alkyl chains and disulfide or thiol groups that provide for attachment to gold electrodes. The EQCM measurements revealed that cations exit and enter the viologen monolayer during reduction and oxidation, respectively. In this study, the self-assembly process of viologen was monitored using resonant frequency (ΔF) and resonant resistance (ΔR). The QCM measurements indicated a mass adsorption for viologen assembling on the gold surface with a frequency change of approximately 135 Hz and calculated its surface coverage (Γ) to be 3.5273×10-9 mol/cm2. Also, a reversible redox process was observed and analyzed with an ionic interaction at the viologen/solution interface using ΔF.

A Study on the Surface Characteristic of the Viologen Self-Assembled Monolayers Using Qca and STM

“…In this case, the frequency decreased rapidly at first, and then the decrease was getting slow. The assembling process of the VC 8 …”

The roles of anion and solvent transport during the redox switching process at a poly(butyl viologen) film studied by an EQCM

“…It is generally accepted that the reaction of the first redox couple for a polyviologen film is limited by the diffusioncontrolled process [16], so the charge compensation from the counterions, i.e., anions, should be the dominant species during the electrochemical reaction for such polycationic films. In addition, Ock et al also inferred that cations might not easily diffuse into the viologen monolayer because of its alkyl chain [10]. Since PBV molecule also has a butyl group, it is reasonable to neglect the effect of cations but to consider that of anions only.…”

“…By employing resonance on a quartz crystal, it is practicable to obtain small mass changes at the thin-film from the changes in the resonant frequency of the resonator [6]. These techniques had been used to study the redox behavior of viologen monolayers formed by the self-assembly process [7][8][9][10].…”

Modeling the response of a quartz crystal microbalance under the specific adsorption of microbubbles

“…Moreover, the QCM is also used as a biosensor (e.g., DNA or, enzyme sensor). [13][14][15] Some researchers attempt to obtain a higher sensitivity by adopting a wireless-electrodeless QCM. [16][17][18] In these cases, loaded substances are represented as a thin film or viscoelastic body.…”