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A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

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A) Effect of applied bias potential on the photocurrent of MtrC/RuP-TiO2 (+MtrC) and RuP-TiO2 only (−MtrC) measured with EDTA (+ EDTA) and without EDTA (−EDTA). The response was measured by linear sweep voltammetry (LSV) at 5 mV s−1. B) Normalized photocurrent (the difference between photocurrent generalized with and without the sacrificial electron donor EDTA). The gray bars represent the times during with the photoanodes are illuminated.
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fig07: A) Effect of applied bias potential on the photocurrent of MtrC/RuP-TiO2 (+MtrC) and RuP-TiO2 only (−MtrC) measured with EDTA (+ EDTA) and without EDTA (−EDTA). The response was measured by linear sweep voltammetry (LSV) at 5 mV s−1. B) Normalized photocurrent (the difference between photocurrent generalized with and without the sacrificial electron donor EDTA). The gray bars represent the times during with the photoanodes are illuminated.

Mentions: Since MtrC is a redox protein that exists in oxidized and reduced states, it can also operate as an electrical diode or on/off switch for photocurrent. When MtrC is reduced at potentials below −0.3 V, no oxidative photocurrents are observed and the system behaves the same as without the sacrificial electron donor EDTA (Figure7A). This switch is clearly distinct from the behavior of RuP-TiO2 without MtrC (when TiO2 is directly adsorbed on the SAM-modified electrode). In Figure 7B, differences in photocurrent with and without EDTA are plotted, where the switch in oxidative photocurrent is more clearly visible upon reduction of MtrC. When MtrC is reduced (i.e., at potentials below 0 V), the electron transfer from RuP-TiO2 to MtrC is impaired, explaining the observed switch in photocurrent. The switch thus provides direct proof that for the MtrC/TiO2 hybrid system the majority of electron transfer proceeds via MtrC and that the densely packed monolayer of MtrC prevents direct interaction between the gold electrode and the RuP-TiO2 layer, confirming the formation of the layered structure schematically depicted in Figure8.


A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

A) Effect of applied bias potential on the photocurrent of MtrC/RuP-TiO2 (+MtrC) and RuP-TiO2 only (−MtrC) measured with EDTA (+ EDTA) and without EDTA (−EDTA). The response was measured by linear sweep voltammetry (LSV) at 5 mV s−1. B) Normalized photocurrent (the difference between photocurrent generalized with and without the sacrificial electron donor EDTA). The gray bars represent the times during with the photoanodes are illuminated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493899&req=5

fig07: A) Effect of applied bias potential on the photocurrent of MtrC/RuP-TiO2 (+MtrC) and RuP-TiO2 only (−MtrC) measured with EDTA (+ EDTA) and without EDTA (−EDTA). The response was measured by linear sweep voltammetry (LSV) at 5 mV s−1. B) Normalized photocurrent (the difference between photocurrent generalized with and without the sacrificial electron donor EDTA). The gray bars represent the times during with the photoanodes are illuminated.
Mentions: Since MtrC is a redox protein that exists in oxidized and reduced states, it can also operate as an electrical diode or on/off switch for photocurrent. When MtrC is reduced at potentials below −0.3 V, no oxidative photocurrents are observed and the system behaves the same as without the sacrificial electron donor EDTA (Figure7A). This switch is clearly distinct from the behavior of RuP-TiO2 without MtrC (when TiO2 is directly adsorbed on the SAM-modified electrode). In Figure 7B, differences in photocurrent with and without EDTA are plotted, where the switch in oxidative photocurrent is more clearly visible upon reduction of MtrC. When MtrC is reduced (i.e., at potentials below 0 V), the electron transfer from RuP-TiO2 to MtrC is impaired, explaining the observed switch in photocurrent. The switch thus provides direct proof that for the MtrC/TiO2 hybrid system the majority of electron transfer proceeds via MtrC and that the densely packed monolayer of MtrC prevents direct interaction between the gold electrode and the RuP-TiO2 layer, confirming the formation of the layered structure schematically depicted in Figure8.

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

No MeSH data available.


Related in: MedlinePlus