Elucidating the role of methyl viologen as a scavenger of photoactivated electrons from photosystem I under aerobic and anaerobic conditions

Abstract

We present detailed electrochemical investigations into the role of dissolved O2 in electrolyte solutions in scavenging photoactivated electrons from a uniform photosystem I (PS I) monolayer assembled on alkanethiolate SAM (self-assembled monolayer)/Au surfaces while using methyl viologen (MV(2+)) as the redox mediator. To this end, we report results for direct measurements of light induced photocurrent from uniform monolayer assemblies of PS I on C9 alkanethiolate SAM/Au surfaces. These measurements, apart from demonstrating the ability of dissolved O2 in the electrolyte medium to act as an electron scavenger, also reveal its essential role in driving the solution-phase methyl viologen to initiate light-induced directional electron transfer from an electron donor surface (Au) via surface assembled PS I trimers. Specifically, our systematic electrochemical measurements have revealed that the dissolved O2 in aqueous electrolyte solutions form a complex intermediate species with MV that plays the essential role in mediating redox pathways for unidirectional electron transfer processes. This critical insight into the redox-mediated electron transfer pathways allows for rational design of electron scavengers through systematic tuning of mediator combinations that promote such intermediate formation. Our current findings facilitate the incorporation of PS I-based bio-hybrid constructs as photo-anodes in future photoelectrochemical cells and bio-electronic devices.

Construction of photobiocathodes using multi-walled carbon nanotubes and photosystem I

“…The generation of the photocurrent can be limited by different factors, such as inefficient connection between PSI and electrode, limited availability and/or hampered diffusion of the acceptor compound as well as slow reaction kinetics of the acceptor (e.g., O 2 ) under the chosen experimental conditions. As the reaction with molecular oxygen is rather slow and diffusion of oxygen represents a limiting factor in the process of electron scavenging from the F B ‐cluster we investigated the photocurrent behavior upon addition of the methyl viologen (MV 2+ ) since it is known that MV 2+ can enhance the rate of electron withdrawal from the reduced F B ‐cluster .…”

Jolly green MOF: confinement and photoactivation of photosystem I in a metal–organic framework

“…Past studies have extensively investigated the photoelectrochemical activities of PSI layers attached to conducting surfaces such as gold electrodes, [3][4][5][6][7] carbon nanotubes, 8-10 metal oxide nanowires, 11 or plasmonic nanostructures. [12][13][14] However, a signicant hurdle in these studies has been the weak optical absorption of a single PSI monolayer (only 0.34% of incident light at 680 nm).…”

Tuning the photocurrent generations from photosystem I assembled in tailored biotic-abiotic interfaces

“…[4,6,7] Our past works have also demonstrated photocurrent generations from PSI monolayer immobilized on self-assembled monolayer (SAM)/Au substrates from colloidal suspensions using detergent-mediated chemistry and electric field-assisted assembly. [8][9][10][11] But, our efforts in depositing dense monolayers of PSI with preferential orientation of PSI and efficient photocurrent generation has only yielded limited success. To further enhance the efficiency of energy conversions in PSI/ SAM-based assemblies, we have been targeting biomimetic confinements and plasmon-induced electric field enhancement strategies.…”