Single-Molecule Junction Formation in Deep Eutectic Solvents with Highly Effective Gate Coupling

Qiao, Xiaohang; Vezzoli, Andrea; Smith, Shaun; Higgins, Simon J.; Davidson, Ross J.; Beeby, Andrew; Nichols, Richard J.

Abstract

The environment surrounding a molecular junction affects its charge-transport properties and, therefore, must be chosen with care. In the case of measurements in liquid media, the solvent must provide good solvation, grant junction stability, and, in the case of electrolyte gating experiments, allow efficient electrical coupling to the gate electrodes through control of the electrical double layer. We evaluated in this study the deep eutectic solvent mixture (DES) ethaline, which is a mixture of choline chloride and ethylene glycol (1:2), for single-molecule junction fabrication with break-junction techniques. In ethaline, we were able to (i) measure challenging and poorly soluble molecular wires, exploiting the improved solvation capabilities offered by DESs, and (ii) efficiently apply an electrostatic gate able to modulate the conductance of the junction by approximately an order of magnitude within a ∼1 V potential window. The electrochemical gating results on a Au–VDP–Au junction follow exceptionally well the single-level modeling with strong gate coupling (where VDP is 1,2-di(pyridine-4-yl)ethene). Ethaline is also an ideal solvent for the measurement of very short molecular junctions, as it grants a greatly reduced snapback distance of the metallic electrodes upon point-contact rupture. Our work demonstrates that DESs are viable alternatives to often relatively expensive ionic liquids, offering good versatility for single-molecule electrical measurements.

Citation

Qiao, X., Vezzoli, A., Smith, S., Higgins, S. J., Davidson, R. J., Beeby, A., & Nichols, R. J. (2023). Single-Molecule Junction Formation in Deep Eutectic Solvents with Highly Effective Gate Coupling. Journal of Physical Chemistry C, 127(26), 12802-12810. https://doi.org/10.1021/acs.jpcc.3c03129

• Journal Article Type: Article
• Acceptance Date: May 11, 2023
• Online Publication Date: Jun 27, 2023
• Publication Date: Jul 6, 2023
• Deposit Date: Nov 8, 2023
• Publicly Available Date: Nov 8, 2023
• Journal: The Journal of Physical Chemistry C
• Print ISSN: 1932-7447
• Electronic ISSN: 1932-7455
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 127
• Issue: 26
• Pages: 12802-12810
• DOI: https://doi.org/10.1021/acs.jpcc.3c03129
• Keywords: Surfaces, Coatings and Films; Physical and Theoretical Chemistry; General Energy; Electronic, Optical and Magnetic Materials
• Public URL: https://durham-repository.worktribe.com/output/1901620