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Embedding and Photoactivating Photosystem I in Unique Organic-inorganic Matrices

出版	University of Tennessee, Knoxville, 2019
URL	http://books.google.com.hk/books?id=lOMS0AEACAAJ&hl=&source=gbs_api

註釋The transmembrane photosynthetic protein complex Photosystem I (PSI) possesses remarkable photoactive electrochemical properties which make it highly sought after for incorporation into biohybrid photovoltaic devices. In the pursuit of all such endeavors, three main factors must always be kept in view: understanding the direct redox transfer steps, threedimensional coordination and stabilization of PSI aggregates, and interfacial connectivity with conductive pathways. This thesis presents steps taken to further these three concepts, contributing to the research community what may help utilize the great potential of PSI. First is presented detailed electrochemical investigations into the role of dissolved O2 as a catalyst for methyl viologen (MV) to scavenge photoactivated electrons from PSI monolayers. These measurements, apart from demonstrating the ability of dissolved O2 in the electrolyte medium to act as a direct electron scavenger, also reveal that the dissolved O2 forms a complex intermediate species with MV which plays the essential role in mediating redox pathways for unidirectional electron transfer processes. Second, a novel 3D architecture is described to organize and stabilize PSI in the myriad of harsh conditions in which it needs to function. PSI is encapsulated in a highly stable nanoporous metal-organic framework, ZIF-8, denoted here as PSI@ZIF-8. The ZIF-8 framework provides a unique scaffold with a robust confining environment for PSI while protecting its precisely coordinated chlorophyll networks from denaturing agents. Pump-probe spectroscopy confirms the photoactivity of the PSI@ZIF-8 composites even after exposure to denaturing agents and organic solvents. This work provides greater fundamental understanding of confinement effects on pigment networks, while significantly broadening the potential working environments for PSIintegrated bio-hybrid materials. Finally, inspired by our successful encapsulation of PSI@ZIF-8, cations from this precursor are used to form charge transfer complexes with the extremely strong organic electron acceptor TCNQ. This PSI-Zn-H2mim-TCNQ charge transfer salt complex was dropcast on ITO as dense films. Through voltammetric cycling and the exchange of Zn2+ and H2mim+ cations, electrochemical annealing of the film increases electrical connectivity and electron conductivity that enabled PSI embedded charge transfer film to generate an order of magnitude greater photocurrents.