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Molecular electronics is moving forwards with a central vision to create devices with functional molecular components that readily provide unique sensor properties. Proteins are attractive for these purposes due to their specific physical (e.g., optical, electrical) and chemical (e.g., selective binding, self-assembly) functions that offer a large possibility for (bio)chemical applications. We focus on proteins as potential building blocks for future optoelectronic devices following the demonstration of efficient electronic conduction across protein monolayers. Our research addresses several questions: “How general is the electron transport behavior across proteins? What mechanisms enable efficient conduction across large bio-molecules?” We have partially answered these questions following micro- and nanoscopic electronic transport studies with Azurin, Halorhodopsin and Bacteriorhodopsin proteins, considering the influence of cofactors on electronic transport and optoelectronic properties respectively. Our findings indicate that conduction across proteins increases in the presence of intramolecular cofactors (redox-active or conjugated systems), and optoelectronic properties mostly regulated by photo-activated conformation of cofactor. Temperature dependent transport studies across proteins monolayers reveals a super-exchange mediated tunneling below < 200 K temperature range and thermally activated electron transport i.e. hopping at higher temperature. Finally, these details understanding of electron transport across proteins may aid in design of de novo protein mutants for (bio) optoelectronics applications.
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