Electrochemistry of redox-active self-assembled monolayers

Abstract

Redox-active self-assembled monolayers (SAMs) provide an excellent platform for investigating electron transfer kinetics. Using a well-defined bridge, a redox center can be positioned at a fixed distance from the electrode and electron transfer kinetics probed using a variety of electrochemical techniques. Cyclic voltammetry, AC voltammetry, electrochemical impedance spectroscopy, and chronoamperometry are most commonly used to determine the rate of electron transfer of redoxactivated SAMs. A variety of redox species have been attached to SAMs, and include transition metal complexes (e.g., ferrocene, ruthenium pentaammine, osmium bisbipyridine, metal clusters) and organic molecules (e.g., galvinol, C 60 ). SAMs offer an ideal environment to study the outer-sphere interactions of redox species. The composition and integrity of the monolayer and the electrode material influence the electron transfer kinetics and can be investigated using electrochemical methods. Theoretical models have been developed for investigating SAM structure. This review discusses methods and monolayer compositions for electrochemical measurements of redox-active SAMs.

Electronic Properties of Mono‐Substituted Tetraferrocenyl Porphyrins in Solution and on a Gold Surface: Assessment of the Influencing Factors for Photoelectrochemical Applications

“…Therefore, k ET was estimated assuming the ideal situation in which a = 0.5, that is, symmetric energy barriers for the redox reactions were considered. [25] Under these simplifications, the electron transfer rate constant was determined as the intercept of the straight line obtained by the plot of DE p vs log(u s ) according to the equation: [37] …”

“…Instead, for an ideal electrochemical behavior of adsorbed species, the separation between the peaks (DE p = E pa ÀE pc ) is required to be zero at low scan rates because diffusion does not take place. [25] The large size of B(C 6 F 5 ) 4 À makes the approach and the removal to the redox sites hard, as the monolayer has to reorganize to accommodate and release the anions. As a consequence, peaks move in the opposite directions; that is, oxidation and reduction processes are more difficult as the scan rate increases.…”

Molecular interactions of β-cyclodextrins with monolayers containing adamantane and anthraquinone guest groups

“…The experimental Tafel plot was fitted to theoretical line of the Butler-Volmer equations for low overpotentials region [19]:…”

“…The experimental Tafel plot was fitted to theoretical line of the Butler-Volmer equations for low overpotentials region [19]: In case of adamantane -β-cyclodextrin complexes both the host and the guest are nonelectroactive and a different method should be used for monitoring the complexation reaction. Our approach was to "decorate" β-CD with a side -group which is electroactive.…”

Cucurbit[8]uril‐Regulated Nanopatterning of Binary Polymer Brushes via Colloidal Templating

“…The CB[8]‐functionalized gold electrode is redox‐responsive as indicated by the black curve in Figure 6, the current ( i p ) decreased from 90 to 31 μA (a reduction of 66%) after assembly of the Azo‐Si colloids on the electrode (blue curve) 45. As i p is directly proportional to A sur under constant scan rate, this significant decrease in i p can be attributed to the fact that the well‐ordered Azo‐Si colloidal crystal blocks the electron‐transfer event thereby reducing A sur 46. A further decrease in i p to only 3 μA (90% overall decrease in current) was observed (red curve) after the assembly of Np‐PEG 2 k brushes; the electrochemically inactive PEG polymer brushes cover the remaining, accessible gold surface, further reducing A sur .…”