Christian Nijhuis: "Electrochemistry" inside Molecular Tunnel Junctions
|When:||Fr 17-05-2019 14:00 - 15:00|
Speaker: Prof. Dr. Christian A. Nijhuis
Address: National University of Singapore
Title: “Electrochemistry” inside Molecular Tunnel Junctions
Date: Friday, May 17th, 2019 Time: 14.00 hrs
Place: Room 5115.0020, Nijenborgh 4, Groningen
Host: Ryan Chiechi
Tel.: +31 50 36 37664 / 38750 (secr)
ABSTRACT Charge transport phenomena across solid-state molecular tunnel junctions are usually assumed to proceed via activationless coherent tunnelling processes which can be described by the Landauer theory . On the other extreme, thermally-activated charge transfer processes frequently encountered in wet electrochemical environments are incoherent and can be described by the Marcus theory . In redox- active molecular junctions, the mechanism of charge transport may be in between these two extremes . We have been studying the mechanisms of charge transport across molecular diodes inside EGaIn junctions based on self-assembled monolayers of with redox-active ferrocenyl (Fc) groups . This system has been well-characterized and yields molecular diodes with exceptionally large rectification ratios . We used this system to demonstrate experimentally the transition from the Marcus to the inverted Marcus region via intra-molecular orbital gating . In the inverted Marcus region, charge transport is incoherent yet virtually independent of temperature; these findings fit well to a theoretical model that combines Landauer and Marcus theories . Recently, we have been studying other types of redox-groups which show interesting phenome including molecular memory. As a group, these findings demonstrate that molecular junctions can operate in the grey zone in between pure electrochemical and tunnelling extremes which can be used in the future design of molecular junctions.
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