The effect of redox site concentration on the rate of electron transport in a redox copolymer film

Abstract

This paper describes the dependency of the rate of electron transport between Os(III/II) complex redox sites as a function of their concentration, in a redox copolymer film prepared from the monomers1 [Os(2,2'-bpy)2(4-pyNHCOCH=CHPh)2]2+ (I) and [Ru(2,2'-bpy)2(4-pyNHCOCH=CHPh)2]2+ (II). The copolymer film is prepared on Pt electrodes by an established electroreductive polymerization method2 using solution mixtures of I and II. Illustrative cyclic voltammetry of two copolymer films3 is shown in Figure 1. The mole fraction, X^, of osmium sites observed in the film5 is identical with the mole fraction of I in the solution monomer mixture; I and II individually electroreductively homopolymerize to form films at nearly identical rates,2f and angular resolved XPS detects no systematic variation of the Os/Ru ratio over the first few outer copolymer layers. These facts, documented elsewhere,6 plus the great structural similarity of I and II, lead us to propose that the Os redox sites are randomly dispersed in a structurally isomorphous sea of copolymer Ru sites.Such an ideal, variable-composition redox copolymer has not been described heretofore.Electrons are transported through redox polymers7 by hopping between redox sites. The overall transport rate is measurable8 as a diffusion constant, Da, but the detailed electron-transport rate-limiting factors remain poorly understood despite much discussion.8,9 Central to this issue is determining how Da depends

Interpretation of electron diffusion coefficient in organic and inorganic semiconductors with broad distributions of states

“…12,13,19,139 The effect of percolation features prominently in the electron transport through redox centers in a solid matrix where the center concentration can be readily varied. 7,36,[140][141][142] However, in these systems the redox centers undergo displacement to a certain extent, from bounded motion around fixed positions, to long range diffusion. The electron transport is a combination of redox center mobility and electron hopping between centers.…”

Polyallylammonium Ferrocyanide Films for Trace Water Detection in Halogenated Solvents

“…It is then possible that the two effects would cancel out. Similar arguments have been used by Facci and Murray, who have observed three different behaviors for the charge-transport diffusion coefficient as a function of redox site concentration [59]. The simplicity of this method, the low detection limits and ability to extend this to continuous processing warrant further investigation into the mechanisms of conduction and applications to nonideal systems.…”

Fabrication and Characterization of DNA/QPVP‐Os Redox‐Active Multilayer Film

“…It indicates that the Os center in the multilayer film has some effect on the electron transfer. Usually, the electroactive center in the electrode coating can be used as electron mediator to enhance the electron transfer rate by electron shuttling between electroactive center and the electrode surface [43,44]. It results in the larger cathodic currents compared to the anodic ones.…”