scholarly journals The Effect of Anchor Group on the Phonon Thermal Conductance of Single Molecule Junctions

2021 ◽  
Vol 11 (3) ◽  
pp. 1066
Author(s):  
Mohammed D. Noori ◽  
Sara Sangtarash ◽  
Hatef Sadeghi
Keyword(s):  
Single Molecule ◽  
Thermoelectric Materials ◽  
Quantum Interference ◽  
High Performance ◽  
Waste Heat ◽  
Thermal Conductance ◽  
Phenylene Ethynylene ◽  
Anchor Group ◽  
Single Molecule Junctions ◽  
Phonon Thermal Conductance

There is a worldwide race to convert waste heat to useful energy using thermoelectric materials. Molecules are attractive candidates for thermoelectricity because they can be synthesised with the atomic precision, and intriguing properties due to quantum effects such as quantum interference can be induced at room temperature. Molecules are also expected to show a low thermal conductance that is needed to enhance the performance of thermoelectric materials. Recently, the technological challenge of measuring the thermal conductance of single molecules was overcome. Therefore, it is timely to develop strategies to reduce their thermal conductance for high performance thermoelectricity. In this paper and for the first time, we exploit systematically the effect of anchor groups on the phonon thermal conductance of oligo (phenylene ethynylene) (OPE3) molecules connected to gold electrodes via pyridyl, thiol, methyl sulphide and carbodithioate anchor groups. We show that thermal conductance is affected significantly by the choice of anchor group. The lowest and highest thermal conductances were obtained in the OPE3 with methyl sulphide and carbodithioate anchor groups, respectively. The thermal conductance of OPE3 with thiol anchor was higher than that with methyl sulphide but lower than the OPE3 with pyridyl anchor group.

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 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.

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

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.

Structure Design for High Performance n-Type Polymer Thermoelectric Materials

2021 ◽  
Author(s):  
Qi Zhang ◽  
Hengda Sun ◽  
Meifang Zhu
Keyword(s):  
Conjugated Polymers ◽  
Thermoelectric Materials ◽  
High Performance ◽  
Waste Heat ◽  
Building Blocks ◽  
Structure Design ◽  
Potential Candidate ◽  
Polymer Backbone ◽  
P Type ◽  
Polymer Thermoelectric

Abstract Organic thermoelectric (OTE) materials have been regarded as a potential candidate to harvest waste heat from complex, low temperature surfaces of objects and convert it into electricity. Recently, n-type conjugated polymers as organic thermoelectric materials have aroused intensive research in order to improve their performance to match up with their p-type counterpart. In this review, we discuss aspects that affect the performance of n-type OTEs, and further focus on the effect of planarity of backbone on doping efficiency and eventually the TE performance. We then summarize strategies such as implementing rigid n-type polymer backbone or modifying conventional polymer building blocks for more planar conformation. In the outlook part, we conclude forementioned devotions and point out new possibility that may promote the future development of this field.

Quantum Interference Enhanced Thermoelectricity in Ferrocene Based Molecular Junctions

2019 ◽  
Vol 19 (11) ◽  
pp. 7452-7455
Author(s):  
Ashkan Vakilipour Takaloo ◽  
Hatef Sadeghi
Keyword(s):  
Seebeck Coefficient ◽  
Single Molecule ◽  
Power Factor ◽  
Quantum Interference ◽  
Room Temperature ◽  
Thermoelectric Power Factor ◽  
Molecular Scale ◽  
Single Molecule Junctions ◽  
Path Structure ◽  
Single Path

Recent experimental indications of room-temperature quantum interference in the sub-nanometer single molecules suggest that such effects could be utilized to engineer thermoelectric properties of organic single molecule junctions. In this paper, we show that the thermoelectric power factor is significantly enhanced in double path ferrocene cycles compared to the single path counterpart. Due to quantum interference in the double path structure, the Seebeck coefficient is significantly enhanced while the conductance is less affected compared to single path structure. The power factor of the ferrocene cycles are 1–2 orders of magnitude higher than the best organic material reported today. This opens new avenues for future molecular scale organometallic thermoelectricity.

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