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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.

No MeSH data available.


Related in: MedlinePlus

AFM height images of A) template stripped gold modified with a SAM, B) MtrC film, and C) MtrC/TiO2 system on the SAM-modified gold electrode. All images are 1 μm × 1 μm and displayed on a A) 5 or B,C) 10 nm z-scale. All surfaces were modified with SAM consisting of 8-OH/8-NH3+ (ratio of 80/20).
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fig06: AFM height images of A) template stripped gold modified with a SAM, B) MtrC film, and C) MtrC/TiO2 system on the SAM-modified gold electrode. All images are 1 μm × 1 μm and displayed on a A) 5 or B,C) 10 nm z-scale. All surfaces were modified with SAM consisting of 8-OH/8-NH3+ (ratio of 80/20).

Mentions: Comparing the electroactive coverage from CV (0.56 ± 0.11 pmol cm−2) with the total coverage from QCM-D, it is clear that only ≈15% of the adsorbed protein is electroactive. Presumably, the majority of the MtrC is adsorbed on the surface in a configuration that does not allow fast interfacial electron transfer. We note that the formation of a close-packed mono­layer of MtrC is required to prevent RuP-TiO2 from binding directly to the underlying gold electrode and thus for the formation of the biohybrid system. We thus complemented the CV and QCM-D studies with atomic force microscopy (AFM) to visualize the MtrC film. Figure6B shows typical AFM images of MtrC on the SAM surface, which indicate a dense mono­layer of MtrC. A few areas or spots are visible with heights above 4 nm, which seem to be consistent with the deposition of agglomerates of MtrC. Further analysis shows that these areas cover less than 5% of the surface. Further analysis also shows that the measured average height of the MtrC monolayer is 1.8 nm, about half the expected height (3.5 nm) for the prone orientation. This difference is consistent with a pressure-induced compression of the MtrC molecules, commonly observed with AFM.[38]


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)

AFM height images of A) template stripped gold modified with a SAM, B) MtrC film, and C) MtrC/TiO2 system on the SAM-modified gold electrode. All images are 1 μm × 1 μm and displayed on a A) 5 or B,C) 10 nm z-scale. All surfaces were modified with SAM consisting of 8-OH/8-NH3+ (ratio of 80/20).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig06: AFM height images of A) template stripped gold modified with a SAM, B) MtrC film, and C) MtrC/TiO2 system on the SAM-modified gold electrode. All images are 1 μm × 1 μm and displayed on a A) 5 or B,C) 10 nm z-scale. All surfaces were modified with SAM consisting of 8-OH/8-NH3+ (ratio of 80/20).
Mentions: Comparing the electroactive coverage from CV (0.56 ± 0.11 pmol cm−2) with the total coverage from QCM-D, it is clear that only ≈15% of the adsorbed protein is electroactive. Presumably, the majority of the MtrC is adsorbed on the surface in a configuration that does not allow fast interfacial electron transfer. We note that the formation of a close-packed mono­layer of MtrC is required to prevent RuP-TiO2 from binding directly to the underlying gold electrode and thus for the formation of the biohybrid system. We thus complemented the CV and QCM-D studies with atomic force microscopy (AFM) to visualize the MtrC film. Figure6B shows typical AFM images of MtrC on the SAM surface, which indicate a dense mono­layer of MtrC. A few areas or spots are visible with heights above 4 nm, which seem to be consistent with the deposition of agglomerates of MtrC. Further analysis shows that these areas cover less than 5% of the surface. Further analysis also shows that the measured average height of the MtrC monolayer is 1.8 nm, about half the expected height (3.5 nm) for the prone orientation. This difference is consistent with a pressure-induced compression of the MtrC molecules, commonly observed with AFM.[38]

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