Electron Transfer and Electronic Conduction through an Intervening Medium

Edwards, Peter P.; Gray, Harry B.; Lodge, Matthew T. J.; Williams, R. J. P.

doi:10.1002/anie.200703177

Cited by 115 publications

(142 citation statements)

References 40 publications

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“…27 These values far exceed the distances of <2 nm required for electron hoping/tunneling 42,43 as the rate of electron exchange (k ex ) decreases exponentially with the distance (d) between the donor and acceptor molecule. The rate is given as:…”

Section: 30mentioning

confidence: 99%

Lack of cytochrome involvement in long-range electron transport through conductive biofilms and nanowires of Geobacter sulfurreducens

Malvankar

Tuominen

Lovley

2012

Energy Environ. Sci.

193

166

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Two competing models for long-range electron transport through the conductive biofilms and nanowires of Geobacter sulfurreducens exist. In one model electrons are transported via pili that possess delocalized electronic states to function as protein wires with metallic-like conductivity. In the other model electrons are transported by more traditional electron transfer via electron hopping/tunneling between the c-type cytochromes in G. sulfurreducens biofilms and pili. The cytochrome hypothesis was further examined. Quantifying c-type cytochromes in G. sulfurreducens biofilms and pili indicated that there are insufficient cytochromes to account for electron transport through the bulk of the biofilm or pili and demonstrated that there is a negative correlation between cytochrome abundance and biofilm conductivity. Direct imaging using atomic force microscopy revealed that cytochromes were not packed close enough on pili to permit electron hopping/tunneling along the pili. Inactivating cytochromes had no impact on biofilm conductivity. The results of electrochemical gating studies were inconsistent with electron transport via cytochromes. Theoretical considerations suggest that a cytochrome model cannot explain the previously reported response of biofilm conductivity to temperature changes. These multiple lines of evidence, which rely on approaches with different sets of assumptions, demonstrate that the hypothesis that long-range electron transport through G. sulfurreducens biofilms and nanowires can be attributed to electron hopping/tunneling between c-type cytochromes is incorrect. In contrast, these multiple lines of evidence are consistent with long-range electron transport through the biofilms via networks of pili that possess metallic-like conductivity.

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Section: 30mentioning

confidence: 99%

Lack of cytochrome involvement in long-range electron transport through conductive biofilms and nanowires of Geobacter sulfurreducens

Malvankar

Tuominen

Lovley

2012

Energy Environ. Sci.

193

166

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“…1,2 Marcus theory provides a powerful theoretical framework for electron transfer. 3 It estimates the rate of nonadiabatic electron transfer by the equation…”

Section: Introductionmentioning

confidence: 99%

Reorganization Energy for Internal Electron Transfer in Multicopper Oxidases

Farrokhnia

Heimdal

et al. 2011

J. Phys. Chem. B

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We have calculated the reorganisation energy for the intramolecular electron transfer between the reduced type 1 copper site and the peroxy intermediate of the trinuclear cluster in the multicopper oxidase CueO. The calculations are performed at the combined quantum mechanics and molecular mechanics (QM/MM) level, based on molecular dynamics simulations with tailored potentials for the two copper sites. We obtain a reorganisation energy of 91-133 kJ/mol, depending on the theoretical treatment. The two Cu sites contribute by 12 and 22 kJ/mol to this energy, whereas the solvent contribution is 34 kJ/mol. The rest comes from the protein, involving small contributions from many residues. We have also estimated the energy difference between the two electron-transfer states and show that the reduction of the peroxy intermediate is exergonic by 43-87 kJ/mol, depending on the theoretical method. Both the solvent and the protein contribute to this energy difference, especially charged residues close to the two Cu sites. We compare these estimates with energies obtained from QM/MM optimisations and QM calculations in vacuum, and discuss differences between the results obtained at various levels of theory.

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“…[61] The parameter β is the exponential decay constant for tunnelling and measures the magnitude of current lost per unit length of the molecular wire, which can vary from approximately 0 Å -1 (metal) to 3.5 Å -1 (close to vacuum). [62,63] The β value used in the present work was 0.6033 Å -1 and was calculated using value of 0.57 Å -1…”

Section: Sams On Pt Electrodesmentioning

confidence: 99%

Modification of Electrode Surfaces by Self‐Assembled Monolayers of Thiol‐Terminated Oligo(Phenyleneethynylene)s

et al. 2013

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The wire‐like properties of four S‐(4‐{2‐[4‐(2‐phenylethynyl)phenyl]ethynyl}phenyl) thioacetate derivatives, PhC≡CC6H4C≡CC6H4SAc (1), H2NC6H4C≡CC6H4C≡CC6H4SAc (2), PhC≡CC6H2(OMe)2C≡CC6H4SAc (3) and AcSC6H4C≡CC6H4C≡CC6H4SAc (4) (Figure 1), all of which possess a high degree of conjugation along the oligo(phenyleneethynylene) (OPE) backbone, were investigated as self‐assembled monolayers (SAMs) on gold and platinum electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The redox probe [Fe(CN)6]4− was used in both the CV and impedance experiments. The results indicate that the thiolates derived from thioacetate‐protected precursor molecules 1 and 2 form well‐ordered monolayers on a gold electrode, whereas SAMs derived from 3 and 4 exhibit randomly distributed pinholes. The electron tunnelling resistance and fractional coverage of SAMs of all four compounds were examined using electron tunnelling theory. The analysis of the results reveal that the well‐ordered SAMs of 1 and 2 exhibit higher charge‐transfer resistance in comparison to the defect‐ridden SAMs of 3 and 4. The additional steric bulk offered by the methoxy groups in 3 is likely to prevent efficient packing within the SAM, leading to a microelectrode behaviour, when assembled on a gold electrode surface. The protected dithiol derivative 4 probably binds to the surface through both terminal groups which prevents dense packing and leads to the formation of a monolayer with randomly distributed pinholes. Atomic force microscopy (AFM) was used to examine the morphology of the monolayers, and height images gave root‐mean‐square (RMS) roughness′s which are in agreement with the proposed SAM structures.

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Electron Transfer and Electronic Conduction through an Intervening Medium

Cited by 115 publications

References 40 publications

Lack of cytochrome involvement in long-range electron transport through conductive biofilms and nanowires of Geobacter sulfurreducens

Lack of cytochrome involvement in long-range electron transport through conductive biofilms and nanowires of Geobacter sulfurreducens

Reorganization Energy for Internal Electron Transfer in Multicopper Oxidases

Modification of Electrode Surfaces by Self‐Assembled Monolayers of Thiol‐Terminated Oligo(Phenyleneethynylene)s

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