Mediated Electron Transfer at Redox Active Monolayers. Part 3: Bimolecular Outer-Sphere, First Order Koutecky-Levich and Adduct Formation Mechanisms

Abstract

A number of theoretical models describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers (such as self assembled alkane thiols containing a ferrocene group) is presented. These models are : simple bimolecular outer-sphere, generalized Koutecky-Levich, and substrate binding/ adduct formation . For each model a general expression for the steady state reaction flux is derived. Simplified analytical expressions for the net reaction flux under steady state conditions, are derived for experimentally reasonable situations, and kinetic case diagrams are constructed outlining the relationships between the various approximate solutions. The theory developed enables simple diagnostic plots to be constructed which can be used to analyse experimental data.

NADH Electrooxidation Using Bis(1,10-phenanthroline-5,6-dione)(2,2′-bipyridine)ruthenium(II)-Exchanged Zirconium Phosphate Modified Carbon Paste Electrodes

“…The formation of a complex between NADH and the surface is modeled as a Michaelis -Menten-like mechanism. This approach was introduced by Gorton and coworkers but criticized by Lyons [60]. Lyons indicated that this approach is only valid if the current is much less than the mass transport value.…”

“…Koutecky-Levich has developed an equation where we can determine the reaction rate by studying the reciprocal current as a function of the reciprocal square root of the angular frequency of rotation of the electrode [13][14][15]38,45,60,61]: (3) where Γ is the surface coverage in mol/cm 2 , F is the Faraday constant in C/equiv, A is the area of the electrode in cm 2 , D NADH is the NADH diffusion coefficient in cm 2 /s, v is the hydrodynamic viscosity of the medium (0.010 cm 2 /s) and ω is the angular frequency of rotation of the electrode in s −1 .…”

Mediated Electron Transfer at Redox Active Monolayers. Part 4: Kinetics of Redox Enzymes Coupled With Electron Mediators

“…We will develop the kinetic model in the context of the steady state approximation and so the analysis will be especially pertinent to rotating disc electrode voltammetry. Our method of analysis and mode of approach to the problem will be similar to that described in previous papers in this series [19][20][21].…”

“…This analysis procedure of course is valid , but it must be stated that the direct analytical solution of the cubic equation really does not confer any real physical insight into the nature of the system. Instead it is preferable to adopt a different strategy which has been used in our previous papers of this series [19,21].…”

Interfaces e dispositivos baseados em porfirinas supramoleculares

“…Eletrocatálises de reações de eletrodos modificados [247,248] envolvem a participação direta do material adsorvido. No lugar da transferência eletrônica entre o nível de Fermi do eletrodo metálico e uma substância eletroativa em solução, a reação de transferência eletrônica é promovida pelo filme mediador.…”