scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

Electric Field-induced switching among multiple conductance pathways in single-molecule junctions

2021 ◽  
Author(s):  
Tengyang Gao ◽  
Zhichao Pan ◽  
Zhuanyun Cai ◽  
Jueting Zheng ◽  
Chun Tang ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Scanning Tunneling Microscope ◽  
Binding Sites ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Field Increase ◽  
Electric Field Increase ◽  
Single Molecule Junctions

Here, we report the switching among multiple conductance pathways achieved by sliding the scanning tunneling microscope tip among different binding sites under different electric fields. With the electric field increase,...

Mechanically-Tunable Quantum Interference in Ferrocene-Based Single-Molecule Junctions

2020 ◽  
Author(s):  
María Camarasa-Gómez ◽  
Daniel Hernangómez-Pérez ◽  
Michael S. Inkpen ◽  
Giacomo Lovat ◽  
E-Dean Fung ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Degrees Of Freedom ◽  
Building Blocks ◽  
Ferrocene Derivative ◽  
Single Molecule Junctions ◽  
Molecule Junction ◽  
Single Molecule Junction ◽  
The Impact ◽  
D Orbitals

Ferrocenes are ubiquitous organometallic building blocks that comprise a Fe atom sandwiched between two cyclopentadienyl (Cp) rings that rotate freely at room temperature. Of widespread interest in fundamental studies and real-world applications, they have also attracted<br>some interest as functional elements of molecular-scale devices. Here we investigate the impact of<br>the configurational degrees of freedom of a ferrocene derivative on its single-molecule junction<br>conductance. Measurements indicate that the conductance of the ferrocene derivative, which is<br>suppressed by two orders of magnitude as compared to a fully conjugated analog, can be modulated<br>by altering the junction configuration. Ab initio transport calculations show that the low conductance is a consequence of destructive quantum interference effects that arise from the hybridization of metal-based d-orbitals and the ligand-based π-system. By rotating the Cp rings, the hybridization, and thus the quantum interference, can be mechanically controlled, resulting in a conductance modulation that is seen experimentally.<br>

Charge Transfer Complexation Boosts Molecular Conductance Through Fermi Level Pinning

2018 ◽  
Author(s):  
Kun Wang ◽  
Andrea Vezzoli ◽  
Iain Grace ◽  
Maeve McLaughlin ◽  
Richard Nichols ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Single Molecule ◽  
Quantum Interference ◽  
Transmission Function ◽  
Scanning Tunneling ◽  
Charge Transfer Complexes ◽  
Tunneling Microscopy ◽  
Quantum Interference Effect ◽  
Single Molecule Junctions ◽  
Charge Transfer Complexation

We have used scanning tunneling microscopy to create and study single molecule junctions with thioether-terminated oligothiophene molecules. We find that the conductance of these junctions increases upon formation of charge transfer complexes of the molecules with tetracyanoethene, and that the extent of the conductance increase is greater the longer is the oligothiophene, i.e. the lower is the conductance of the uncomplexed molecule in the junction. We use non-equilibrium Green's function transport calculations to explore the reasons for this theoretically, and find that new resonances appear in the transmission function, pinned close to the Fermi energy of the contacts, as a consequence of the charge transfer interaction. This is an example of a room temperature quantum interference effect, which in this case boosts junction conductance in contrast to earlier observations of QI that result in diminished conductance.<br>

Dissecting Contact Mechanics from Quantum Interference in Single-Molecule Junctions of Stilbene Derivatives

Nano Letters ◽  
2012 ◽  
Vol 12 (3) ◽  
pp. 1643-1647 ◽  
Author(s):  
Sriharsha V. Aradhya ◽  
Jeffrey S. Meisner ◽  
Markrete Krikorian ◽  
Seokhoon Ahn ◽  
Radha Parameswaran ◽  
...  
Keyword(s):  
Contact Mechanics ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Junctions ◽  
Stilbene Derivatives

scholarly journals Voltammetry and molecular assembly of G-quadruplex DNAzyme on single-crystal Au(111)-electrode surfaces – hemin as an electrochemical intercalator

2016 ◽  
Vol 193 ◽  
pp. 99-112 ◽  
Author(s):  
Ling Zhang ◽  
Jens Ulstrup ◽  
Jingdong Zhang
Keyword(s):  
Single Crystal ◽  
Single Molecule ◽  
Electrode Surface ◽  
Molecular Assembly ◽  
Electrode Surfaces ◽  
Potential Control ◽  
G Quadruplex ◽  
Tunnelling Microscopy ◽  
Dna Quadruplexes

DNA quadruplexes (qs) are a class of “non-canonical” oligonucleotides (OGNs) composed of stacked guanine (G) quartets stabilized by specific cations. Metal porphyrins selectively bind to G-qs complexes to form what is known as DNAzyme, which can exhibit peroxidase and other catalytic activity similar to heme group metalloenzymes. In the present study we investigate the electrochemical properties and the structure of DNAzyme monolayers on single-crystal Au(111)-electrode surfaces using cyclic voltammetry and scanning tunnelling microscopy under electrochemical potential control (in situ STM). The target DNAzyme is formed from a single-strand OGN with 12 guanines and iron(iii) porphyrin IX (hemin), and assembles on Au(111) through a mercapto alkyl linker. The DNAzyme monolayers exhibit a strong pair of redox peaks at 0.0 V (NHE) at pH 7 in acetate buffer, shifted positively by about 50 mV compared to free hemin weakly physisorbed on the Au(111)-electrode surface. The voltammetric hemin signal of DNAzyme is enhanced 15 times compared with that of hemin adsorbed directly on the Au(111)-electrode surface. This is indicative of both the formation of a close to dense DNAzyme monolayer and that hemin is strongly bound to the immobilized 12G-qs in well-defined orientation favorable for interfacial ET with a rate constant of 6.0 ± 0.4 s−1. This is supported by in situ STM which discloses single-molecule G-quartet structures with a size of 1.6 ± 0.2 nm.

The Relation between Structure and Quantum Interference in Single Molecule Junctions

Nano Letters ◽  
2010 ◽  
Vol 10 (10) ◽  
pp. 4260-4265 ◽  
Author(s):  
Troels Markussen ◽  
Robert Stadler ◽  
Kristian S. Thygesen
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Junctions

Substitution Pattern Controlled Charge Transport in BN-Embedded Aromatics-Based Single-Molecule Junctions

2021 ◽  
Author(s):  
Hongxiang Li ◽  
Rui Wang ◽  
Kai Song ◽  
Caiyun Wei ◽  
Wenjing Hong ◽  
...  
Keyword(s):  
Charge Transport ◽  
Single Molecule ◽  
Molecular Devices ◽  
Substitution Pattern ◽  
Single Molecule Level ◽  
Single Molecule Junctions ◽  
Molecular Conductance

The understanding of charge transport at single-molecule level is a pre-requisite for the fabrication of molecular devices. Here, we systematically investigate the relation among molecular conductance, substitution pattern and stimuli...

scholarly journals Protonation tuning of quantum interference in azulene-type single-molecule junctions

2017 ◽  
Vol 8 (11) ◽  
pp. 7505-7509 ◽  
Author(s):  
Guogang Yang ◽  
Sara Sangtarash ◽  
Zitong Liu ◽  
Xiaohui Li ◽  
Hatef Sadeghi ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Junctions

The protonation of azulene cores offers significant conductance tuning in single-molecule junctions with quantum interference.

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