(581d) Electrochemical Characterization of Photosystem I (PS I)/Self-Assembled Monolayer (SAM)/Au Substrates: The Critical Bottle-Necks in Electron Transfer
AIChE Annual Meeting
2014
2014 AIChE Annual Meeting
Nanomaterials for Energy Applications
Nanomaterials for Photovoltaics III
Wednesday, November 19, 2014 - 4:30pm to 4:55pm
Photosystem I (PS I), a supra-molecular protein complex, functions as a biological photodiode
that charge separates upon exposure to light and is responsible for driving natural photosynthesis.
The highly efficient photo-electrochemical activities of PSI (100% quantum efficiency
over 54% of the solar spectrum) make it an ideal candidate for next-generation bio-hybrid
electronic devices. Our specific interest in using PS I for future hybrid photovoltaic (PV)
device fabrications requires optimal encapsulation of these proteins onto chemically grafted
SAM substrates. Our previous results indicate that various experimental parameters alter the
surface attachment dynamics of PS I, deposited from colloidal aqueous buffer suspensions
onto OH-terminated alkanethiolate/Au SAM substrates, thereby resulting in complex structural
arrangements which affect the electron transfer and capture pathway of PSI. We present surface
topographical and electrochemical characterizations of PS I/Au SAM substrates to elucidate
photo-activated electronic activities of PS I monolayer. Specifically, light induced directional
electron transfer by surface immobilized PS I is demonstrated via direct electrochemistry
measurements from PS I complexes assembled on alkanethiolate SAM/Au surfaces prepared
with varying thiol chain lengths (C2, C4, C6, C8). The results reveal the effect of interfacial
thiol brush density and chain length on limiting the electron transfer rate at the donor side
from Au surface to oxidized P700+ reaction center in PS I, due to non-optimal packing and/or,
large tunneling distance through the SAM. On the other hand, at the acceptor side, the electron
donation rates from reduced FB- sites into the solution is significantly increased with the addition
of a soluble electron acceptor, Methyl Viologen (MV2+
previous work shone light on the critical role of oxygen in the electron uptake process, both via
direct mediation from FB-
O2. To this end, the present work takes a step towards detailed electrochemical characterizations
that elucidate and optimize the true bottleneck of electron mediation through PS I monolayer by
separately analyzing the interfacial electron transfer from SAM substrate to P700+ and from FB-
to the solution.
) in the presence of dissolved oxygen. Our
to O2 and through a secondary complex formation between MV2+ and