Electrochemically controlled rectification in symmetric single-molecule junctions.
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Single-molecule electrochemical science has advanced over the past decades and now extends well beyond molecular imaging, to molecular electronics functions such as rectification and amplification. Rectification is conceptually the simplest but has involved mostly challenging chemical synthesis of asymmetric molecular structures or asymmetric materials and geometry of the two enclosing electrodes. Here we propose an experimental and theoretical strategy for building and tuning in situ (in operando) rectification in two symmetric molecular structures in electrochemical environment. The molecules were designed to conduct electronically via either their lowest unoccupied molecular orbital (LUMO; electron transfer) or highest occupied molecular orbital (HOMO; "hole transfer"). We used a bipotentiostat to control separately the electrochemical potential of the tip and substrate electrodes of an electrochemical scanning tunneling microscope (EC-STM), which leads to independent energy alignment of the STM tip, the molecule, and the STM substrate. By creating an asymmetric energy alignment, we observed single-molecule rectification of each molecule within a voltage range of ±0.5 V. By varying both the dominating charge transporting LUMO or HOMO energy and the electrolyte concentration, we achieved tuning of the polarity as well as the amplitude of the rectification. We have extended an earlier proposed theory that predicts electrolyte-controlled rectification to rationalize all the observed in situ rectification features and found excellent agreement between theory and experiments. Our study thus offers a way toward building controllable single-molecule rectifying devices without involving asymmetric molecular structures.
Date Issued
2022-09-27
Date Acceptance
2022-09-01
Citation
Proceedings of the National Academy of Sciences of USA, 2022, 119 (39), pp.1-9
ISSN
0027-8424
Publisher
National Academy of Sciences
Start Page
1
End Page
9
Journal / Book Title
Proceedings of the National Academy of Sciences of USA
Volume
119
Issue
39
Copyright Statement
© 2022 the Author(s). Published by PNAS.This article is distributed underCreative CommonsAttribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/36136968
Subjects
bipotential control
electrolytic control
symmetric single-molecule junctions
tunneling current rectification
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2022-09-22