Molecular junctions electrochemical

Keywords Charge transport Electrochemical molecular junctions Electron tunnelling Electron hopping Molecular electronics Photoactive molecular junctions... 

Second, in designing new molecule-based electronic devices, one of the major goals is the precise control of the current flowing between the terminals. Electrochemical molecular junctions allow for control of the potentials of the electrodes with respect to the redox potential of incorporated redox-active molecules with well-defined, accessible, tunable energy states. These junctions represent unique systems able to predict precisely at which applied potential the current flow will take off. Even though the presence of a liquid electrolyte represents a detriment towards possible applications, they provide the concepts for designing molecular devices that mimic electronic functions and control electrical responses. 

Tian J-H, Yang Y, Zhou X-S, Schollhom B, Maisonhaute E, Chen Z-B, Yang F-Z, Chen Y, Amatore C, Mao B-W, Tian Z-Q (2010) Electrochemically assisted fabrication of metal atomic wires and molecular junctions by MCBJ and STM-BJ methods. ChemPhysChem 11 (13) 2745-2755... 

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Electrochemically Gate-Controlled Charge Transport in Redox-Active Molecular Junctions... 

STM measurements on molecular junctions in solution have been realized by groups in Miami [66], Lyngby [34] and Liverpool [33, 67]. Performing the STM experiments in a liquid environment provides a way to combine well-established electrochemical techniques with in situ electronic STM characterization of a single or a small number of molecules. One particular advantage of this approach is the option to use an electrochemical reference electrode as a third electrode (gate) in the setup in addition to the tip and substrate electrodes (source and drain). Such a setup closely resembles a (three-terminal) transistor setup, as the third electrode can be used to manipulate the transmission properties of the junction molecules by applying a potential between the substrate and the reference electrode. 

An electrochemically assisted jump-to-contact process has also been applied in the development of a modified STM-BJ approach by fhe present author s group [70]. This technique has the advantage that it allows the construction of chemically well-defined, atomic-size contacts, and is possible with both chemically active and/or soft metals. The metal contacts created in this way have been confirmed as having a well-defined structure, suitable for studying the mechanical properties of the nanocontacts [62, 71]. As in the conventional STM-BJ approach, the pair of metal electrodes created after breaking the contact provides the electrodes to construct metal-molecule-metal molecular junctions. These improvements have extended the capability of conventional STM-BJ to create a variety of metal nanocontacts and single-molecule junctions beyond the Au-molecule-Au junctions. 

Zhou, X.S., Liang, J.H., Chen, Z.B. and Mao, B.W. (2011) An electrochemical jump-to-contact STM-break junction approach to construct single molecular junctions with different metallic electrodes. Electrochemistry Communications, 13, 407-410. 

In the following we will present results of a single-junction conductance study with 44-BP under electrochemical potential control, enabling the precise tuning of the molecular orientation, relative to the substrate, upon application of an adjustable gate voltage [290] in a well-controlled environment [86, 302]. 

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