Protein Electronics: Chemical Modulation of Contacts Control Energy Level Alignment in Gold-Azurin-Gold Junctions

Jerry A. Fereiro, Gilad Porat, Tatyana Bendikov, Israel Pecht, Mordechai Sheves, David Cahen

Research output: Contribution to journalArticlepeer-review

52 Scopus citations

Abstract

Making biomolecular electronics a reality will require control over charge transport across biomolecules. Here we show that chemical modulation of the coupling between one of the electronic contacts and the biomolecules in a solid-state junction allows controlling electron transport (ETp) across the junction. Employing the protein azurin (Az), we achieve such modulation as follows: Az is covalently bound by Au-S bonding to a lithographically prepared Au electrode (Au-Az). Au nanowires (AuNW) onto which linker molecules, with free carboxylic group, are bound via Au-S bonds serve as top electrode. Current-voltage plots of AuNW-linkerCOOH//Az-Au junctions have been shown earlier to exhibit step-like features, due to resonant tunneling through discrete Az energy levels. Forming an amide bond between the free carboxylic group of the AuNW-bound linker and Az yields AuNW-linkerCO-NH-Az-Au junctions. This Az-linker bond switches the ETp mechanism from resonant to off-resonant tunneling. By varying the extent of this amide bonding, the current-voltage dependence can be controlled between these two mechanisms, thus providing a platform for altering and controlling the ETp mechanism purely by chemical modification in a two-terminal device, i.e., without a gate electrode. Using results from conductance, including the energy barrier and electrode-molecule coupling parameters extracted from current-voltage fitting and normalized differential conductance analysis and from inelastic-electron-tunneling and photoelectron spectroscopies, we determine the Az frontier orbital energies, with respect to the Au Fermi level, for four junction configurations, differing only in electrode-protein coupling. Our approach and findings open the way to both qualitative and quantitative control of biomolecular electronic junctions.

Original languageEnglish
Pages (from-to)13317-13326
Number of pages10
JournalJournal of the American Chemical Society
Volume140
Issue number41
DOIs
StatePublished - 17 Oct 2018
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

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