1
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Sil A, Alsaqer M, Spano CE, Larbi A, Higgins SJ, Robertson CM, Graziano M, Sangtarash S, Nichols RJ, Sadeghi H, Vezzoli A. Mechanical Manipulation of Quantum Interference in Single-Molecule Junctions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308865. [PMID: 38221684 DOI: 10.1002/smll.202308865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/07/2023] [Indexed: 01/16/2024]
Abstract
Mechanosensitive molecular junctions, where conductance is sensitive to an applied stress such as force or displacement, are a class of nanoelectromechanical systems unique for their ability to exploit quantum mechanical phenomena. Most studies so far relied on reconfiguration of the molecule-electrode interface to impart mechanosensitivity, but this approach is limited and, generally, poorly reproducible. Alternatively, devices that exploit conformational flexibility of molecular wires have been recently proposed. The mechanosensitive properties of molecular wires containing the 1,1'-dinaphthyl moiety are presented here. Rotation along the chemical bond between the two naphthyl units is possible, giving rise to two conformers (transoid and cisoid) that have distinctive transport properties. When assembled as single-molecule junctions, it is possible to mechanically trigger the transoid to cisoid transition, resulting in an exquisitely sensitive mechanical switch with high switching ratio (> 102). Theoretical modeling shows that charge reconfiguration upon transoid to cisoid transition is responsible for the observed behavior, with generation and subsequent lifting of quantum interference features. These findings expand the experimental toolbox of molecular electronics with a novel chemical structure with outstanding electromechanical properties, further demonstrating the importance of subtle changes in charge delocalization on the transport properties of single-molecule devices.
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Affiliation(s)
- Amit Sil
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Munirah Alsaqer
- Device Modelling Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Chiara E Spano
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
- Department of Electronics and Telecommunications, Politecnico di Torino, Corso Duca degli Abruzzi, Torino, 10129, Italy
| | - Adam Larbi
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Simon J Higgins
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Craig M Robertson
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Mariagrazia Graziano
- Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi, Torino, 10129, Italy
| | - Sara Sangtarash
- Device Modelling Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Richard J Nichols
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Hatef Sadeghi
- Device Modelling Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Andrea Vezzoli
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
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2
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Qiao X, Sil A, Sangtarash S, Smith SM, Wu C, Robertson CM, Nichols RJ, Higgins SJ, Sadeghi H, Vezzoli A. Nuclear Magnetic Resonance Chemical Shift as a Probe for Single-Molecule Charge Transport. Angew Chem Int Ed Engl 2024; 63:e202402413. [PMID: 38478719 DOI: 10.1002/anie.202402413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Indexed: 04/05/2024]
Abstract
Existing modelling tools, developed to aid the design of efficient molecular wires and to better understand their charge-transport behaviour and mechanism, have limitations in accuracy and computational cost. Further research is required to develop faster and more precise methods that can yield information on how charge transport properties are impacted by changes in the chemical structure of a molecular wire. In this study, we report a clear semilogarithmic correlation between charge transport efficiency and nuclear magnetic resonance chemical shifts in multiple series of molecular wires, also accounting for the presence of chemical substituents. The NMR data was used to inform a simple tight-binding model that accurately captures the experimental single-molecule conductance values, especially useful in this case as more sophisticated density functional theory calculations fail due to inherent limitations. Our study demonstrates the potential of NMR spectroscopy as a valuable tool for characterising, rationalising, and gaining additional insights on the charge transport properties of single-molecule junctions.
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Affiliation(s)
- X Qiao
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - A Sil
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - S Sangtarash
- Device Modelling Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - S M Smith
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - C Wu
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
- Institute of Optoelectronic Materials and Devices, Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou, 341000, China
| | - C M Robertson
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - R J Nichols
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - S J Higgins
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - H Sadeghi
- Device Modelling Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - A Vezzoli
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
- Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street, Liverpool, L69 7ZF, United Kingdom
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3
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Yang C, Chen Z, Yu C, Cao J, Ke G, Zhu W, Liang W, Huang J, Cai W, Saha C, Sabuj MA, Rai N, Li X, Yang J, Li Y, Huang F, Guo X. Regulation of quantum spin conversions in a single molecular radical. NATURE NANOTECHNOLOGY 2024:10.1038/s41565-024-01632-2. [PMID: 38448520 DOI: 10.1038/s41565-024-01632-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Accepted: 02/13/2024] [Indexed: 03/08/2024]
Abstract
Free radicals, generally formed through the cleavage of covalent electron-pair bonds, play an important role in diverse fields ranging from synthetic chemistry to spintronics and nonlinear optics. However, the characterization and regulation of the radical state at a single-molecule level face formidable challenges. Here we present the detection and sophisticated tuning of the open-shell character of individual diradicals with a donor-acceptor structure via a sensitive single-molecule electrical approach. The radical is sandwiched between nanogapped graphene electrodes via covalent amide bonds to construct stable graphene-molecule-graphene single-molecule junctions. We measure the electrical conductance as a function of temperature and track the evolution of the closed-shell and open-shell electronic structures in real time, the open-shell triplet state being stabilized with increasing temperature. Furthermore, we tune the spin states by external stimuli, such as electrical and magnetic fields, and extract thermodynamic and kinetic parameters of the transition between closed-shell and open-shell states. Our findings provide insights into the evolution of single-molecule radicals under external stimuli, which may proof instrumental for the development of functional quantum spin-based molecular devices.
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Affiliation(s)
- Caiyao Yang
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Centre, College of Chemistry and Molecular Engineering, Peking University, Beijing, P. R. China
- School of Materials Science and Engineering, Peking University, Beijing, P. R. China
| | - Zhongxin Chen
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Cuiju Yu
- Department of Chemical Physics, University of Science and Technology of China, Hefei, P. R. China
| | - Jiawen Cao
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Centre, College of Chemistry and Molecular Engineering, Peking University, Beijing, P. R. China
| | - Guojun Ke
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Weiya Zhu
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Weixuan Liang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Jiaxing Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Wanqing Cai
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China
| | - Chinmoy Saha
- Dave C. Swalm School of Chemical Engineering and Centre for Advanced Vehicular Systems, Mississippi State University, Mississippi State, MS, USA
| | - Md Abdus Sabuj
- Dave C. Swalm School of Chemical Engineering and Centre for Advanced Vehicular Systems, Mississippi State University, Mississippi State, MS, USA
| | - Neeraj Rai
- Dave C. Swalm School of Chemical Engineering and Centre for Advanced Vehicular Systems, Mississippi State University, Mississippi State, MS, USA
| | - Xingxing Li
- Department of Chemical Physics, University of Science and Technology of China, Hefei, P. R. China.
| | - Jinlong Yang
- Department of Chemical Physics, University of Science and Technology of China, Hefei, P. R. China
| | - Yuan Li
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China.
| | - Fei Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China.
| | - Xuefeng Guo
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Centre, College of Chemistry and Molecular Engineering, Peking University, Beijing, P. R. China.
- Centre of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Centre for New Organic Matter, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, P. R. China.
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4
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Jago D, Liu C, Daaoub AHS, Gaschk E, Walkey MC, Pulbrook T, Qiao X, Sobolev AN, Moggach SA, Costa-Milan D, Higgins SJ, Piggott MJ, Sadeghi H, Nichols RJ, Sangtarash S, Vezzoli A, Koutsantonis GA. An Orthogonal Conductance Pathway in Spiropyrans for Well-Defined Electrosteric Switching Single-Molecule Junctions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2306334. [PMID: 37817372 DOI: 10.1002/smll.202306334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Indexed: 10/12/2023]
Abstract
While a multitude of studies have appeared touting the use of molecules as electronic components, the design of molecular switches is crucial for the next steps in molecular electronics. In this work, single-molecule devices incorporating spiropyrans, made using break junction techniques, are described. Linear spiropyrans with electrode-contacting groups linked by alkynyl spacers to both the indoline and chromenone moieties have previously provided very low conductance values, and removing the alkynyl spacer has resulted in a total loss of conductance. An orthogonal T-shaped approach to single-molecule junctions incorporating spiropyran moieties in which the conducting pathway lies orthogonal to the molecule backbone is described and characterized. This approach has provided singlemolecule conductance features with good correlation to molecular length. Additional higher conducting states are accessible using switching induced by UV light or protonation. Theoretical modeling demonstrates that upon (photo)chemical isomerization to the merocyanine, two cooperating phenomena increase conductance: release of steric hindrance allows the conductance pathway to become more planar (raising the mid-bandgap transmission) and a bound state introduces sharp interference near the Fermi level of the electrodes similarly responding to the change in state. This design step paves the way for future use of spiropyrans in single-molecule devices and electrosteric switches.
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Affiliation(s)
- David Jago
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Chongguang Liu
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | | | - Emma Gaschk
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Mark C Walkey
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Thea Pulbrook
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Xiaohang Qiao
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - Alexandre N Sobolev
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Stephen A Moggach
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - David Costa-Milan
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - Simon J Higgins
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - Matthew J Piggott
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Hatef Sadeghi
- School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Richard J Nichols
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - Sara Sangtarash
- School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Andrea Vezzoli
- Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - George A Koutsantonis
- School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
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5
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Alsaqer M, Daaoub AH, Sangtarash S, Sadeghi H. Large Mechanosensitive Thermoelectric Enhancement in Metallo-Organic Magnetic Molecules. NANO LETTERS 2023; 23:10719-10724. [PMID: 37988562 PMCID: PMC10722535 DOI: 10.1021/acs.nanolett.3c02569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/15/2023] [Accepted: 11/15/2023] [Indexed: 11/23/2023]
Abstract
Organic materials are promising candidates for thermoelectric cooling and energy harvesting at room temperature. However, their electrical conductance (G) and Seebeck coefficient (S) need to be improved to make them technologically competitive. Therefore, radically new strategies need to be developed to tune their thermoelectric properties. Here, we demonstrate that G and S can be tuned mechanically in paramagnetic metallocenes, and their thermoelectric properties can be significantly enhanced by the application of mechanical forces. With a 2% junction compression, the full thermoelectric figure of merit is enhanced by more than 200 times. We demonstrate that this is because spin transport resonances in paramagnetic metallocenes are strongly sensitive to the interaction between organic ligands and the metal center, which is not the case in their diamagnetic analogue. These results open a new avenue for the development of organic thermoelectric materials for cooling future quantum computers and generating electricity from low-grade energy sources.
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Affiliation(s)
- Munirah Alsaqer
- Device Modelling Group, School
of Engineering, University of Warwick, CV4 7AL Coventry, United Kingdom
| | - Abdalghani H.S. Daaoub
- Device Modelling Group, School
of Engineering, University of Warwick, CV4 7AL Coventry, United Kingdom
| | - Sara Sangtarash
- Device Modelling Group, School
of Engineering, University of Warwick, CV4 7AL Coventry, United Kingdom
| | - Hatef Sadeghi
- Device Modelling Group, School
of Engineering, University of Warwick, CV4 7AL Coventry, United Kingdom
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6
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Li L, Prindle CR, Shi W, Nuckolls C, Venkataraman L. Radical Single-Molecule Junctions. J Am Chem Soc 2023; 145:18182-18204. [PMID: 37555594 DOI: 10.1021/jacs.3c04487] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Radicals are unique molecular systems for applications in electronic devices due to their open-shell electronic structures. Radicals can function as good electrical conductors and switches in molecular circuits while also holding great promise in the field of molecular spintronics. However, it is both challenging to create stable, persistent radicals and to understand their properties in molecular junctions. The goal of this Perspective is to address this dual challenge by providing design principles for the synthesis of stable radicals relevant to molecular junctions, as well as offering current insight into the electronic properties of radicals in single-molecule devices. By exploring both the chemical and physical properties of established radical systems, we will facilitate increased exploration and development of radical-based molecular systems.
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Affiliation(s)
- Liang Li
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Claudia R Prindle
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Wanzhuo Shi
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Latha Venkataraman
- Department of Chemistry, Columbia University, New York, New York 10027, United States
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
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7
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Tan Y, Li J, Li S, Yang H, Chi T, Shiring SB, Liu K, Savoie BM, Boudouris BW, Schroeder CM. Enhanced Electron Transport in Nonconjugated Radical Oligomers Occurs by Tunneling. NANO LETTERS 2023. [PMID: 37384632 DOI: 10.1021/acs.nanolett.3c00978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
Incorporating temperature- and air-stable organic radical species into molecular designs is a potentially advantageous means of controlling the properties of electronic materials. However, we still lack a complete understanding of the structure-property relationships of organic radical species at the molecular level. In this work, the charge transport properties of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) radical-containing nonconjugated molecules are studied using single-molecule charge transport experiments and molecular modeling. Importantly, the TEMPO pendant groups promote temperature-independent molecular charge transport in the tunneling region relative to the quenched and closed-shell phenyl pendant groups. Results from molecular modeling show that the TEMPO radicals interact with the gold metal electrodes near the interface to facilitate a high-conductance conformation. Overall, the large enhancement of charge transport by incorporation of open-shell species into a single nonconjugated molecular component opens exciting avenues for implementing molecular engineering in the development of next-generation electronic devices based on novel nonconjugated radical materials.
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Affiliation(s)
- Ying Tan
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Jialing Li
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Joint Center for Energy Storage Research, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Songsong Li
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Joint Center for Energy Storage Research, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Hao Yang
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Teng Chi
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Stephen B Shiring
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Kangying Liu
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Brett M Savoie
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Bryan W Boudouris
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Charles M Schroeder
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Joint Center for Energy Storage Research, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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8
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Daaoub A, Morris JMF, Béland VA, Demay‐Drouhard P, Hussein A, Higgins SJ, Sadeghi H, Nichols RJ, Vezzoli A, Baumgartner T, Sangtarash S. Not So Innocent After All: Interfacial Chemistry Determines Charge-Transport Efficiency in Single-Molecule Junctions. Angew Chem Int Ed Engl 2023; 62:e202302150. [PMID: 37029093 PMCID: PMC10953449 DOI: 10.1002/anie.202302150] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/24/2023] [Accepted: 04/06/2023] [Indexed: 04/09/2023]
Abstract
Most studies in molecular electronics focus on altering the molecular wire backbone to tune the electrical properties of the whole junction. However, it is often overlooked that the chemical structure of the groups anchoring the molecule to the metallic electrodes influences the electronic structure of the whole system and, therefore, its conductance. We synthesised electron-accepting dithienophosphole oxide derivatives and fabricated their single-molecule junctions. We found that the anchor group has a dramatic effect on charge-transport efficiency: in our case, electron-deficient 4-pyridyl contacts suppress conductance, while electron-rich 4-thioanisole termini promote efficient transport. Our calculations show that this is due to minute changes in charge distribution, probed at the electrode interface. Our findings provide a framework for efficient molecular junction design, especially valuable for compounds with strong electron withdrawing/donating backbones.
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Affiliation(s)
- Abdalghani Daaoub
- Device Modelling GroupSchool of EngineeringUniversity of WarwickCoventryCV4 7ALUK
| | - James M. F. Morris
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Vanessa A. Béland
- Department of ChemistryYork University4700 Keele StreetTorontoON, M3J 1P3Canada
| | - Paul Demay‐Drouhard
- Department of ChemistryYork University4700 Keele StreetTorontoON, M3J 1P3Canada
| | - Amaar Hussein
- Department of ChemistryYork University4700 Keele StreetTorontoON, M3J 1P3Canada
| | - Simon J. Higgins
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Hatef Sadeghi
- Device Modelling GroupSchool of EngineeringUniversity of WarwickCoventryCV4 7ALUK
| | - Richard J. Nichols
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Andrea Vezzoli
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Thomas Baumgartner
- Department of ChemistryYork University4700 Keele StreetTorontoON, M3J 1P3Canada
| | - Sara Sangtarash
- Device Modelling GroupSchool of EngineeringUniversity of WarwickCoventryCV4 7ALUK
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9
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Chelli Y, Sandhu S, Daaoub AHS, Sangtarash S, Sadeghi H. Controlling Spin Interference in Single Radical Molecules. NANO LETTERS 2023; 23:3748-3753. [PMID: 37071608 PMCID: PMC10176569 DOI: 10.1021/acs.nanolett.2c05068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 04/13/2023] [Indexed: 05/11/2023]
Abstract
Quantum interference (QI) dominates the electronic properties of single molecules even at room temperature and can lead to a large change in their electrical conductance. To take advantage of this for nanoelectronic applications, a mechanism to electronically control QI in single molecules needs to be developed. In this paper, we demonstrate that controlling the quantum interference of each spin in a stable open-shell organic radical with a large π-system is possible by changing the spin state of the radical. We show that the counterintuitive constructive spin interference in a meta-connected radical changes to destructive interference by changing the spin state of the radical from a doublet to a singlet. This results in a significant change in the room temperature electrical conductance by several orders of magnitude, opening up new possibilities for spin interference based molecular switches for energy storage and conversion applications.
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Affiliation(s)
- Yahia Chelli
- Device Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Serena Sandhu
- Device Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Abdalghani H. S. Daaoub
- Device Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Sara Sangtarash
- Device Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Hatef Sadeghi
- Device Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
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10
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Yang X, Hou S, Su M, Zhan Q, Zhang H, Quintero SM, Liu X, Liu J, Hong W, Casado J, Wu Q, Lambert CJ, Zheng Y. Quasi-Free Electron States Responsible for Single-Molecule Conductance Enhancement in Stable Radical. J Phys Chem Lett 2023; 14:4004-4010. [PMID: 37083476 DOI: 10.1021/acs.jpclett.3c00536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Stable organic radicals, which possess half-filled orbitals in the vicinity of the Fermi energy, are promising candidates for electronic devices. In this Letter, using a combination of scanning-tunneling-microscopy-based break junction (STM-BJ) experiments and quantum transport theory, a stable fluorene-based radical is investigated. We demonstrate that the transport properties of a series of fluorene derivatives can be tuned by controlling the degree of localization of certain orbitals. More specifically, radical 36-FR has a delocalized half-filled orbital resulting in Breit-Wigner resonances, leading to an unprecedented conductance enhancement of 2 orders of magnitude larger than the neutral nonradical counterpart (36-FOH). In other words, conversion from a closed-shell fluorene derivative to the free radical in 36-FR opens an electron transport path which massively enhances the conductance. This new understanding of the role of radicals in single-molecule junctions opens up a novel design strategy for single-molecule-based spintronic devices.
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Affiliation(s)
- Xingzhou Yang
- Department of Pharmacy, Sichuan Provincial People's Hospital, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610072, People's Republic of China
| | - Songjun Hou
- Department of Physics, Lancaster University, Lancaster LA1 4YB, U.K
| | - Meiling Su
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xia-men University, Xiamen 361005, People's Republic of China
| | - Qian Zhan
- Department of Pharmacy, Sichuan Provincial People's Hospital, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610072, People's Republic of China
| | - Hanjun Zhang
- Department of Pharmacy, Sichuan Provincial People's Hospital, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610072, People's Republic of China
| | - Sergio M Quintero
- Department of Physical Chemistry, University of Málaga, Andalucia-Tech Campus de Teatinos s/n, Málaga 29071, Spain
| | - Xiaodong Liu
- Department of Pharmacy, Sichuan Provincial People's Hospital, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610072, People's Republic of China
| | - Junyang Liu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xia-men University, Xiamen 361005, People's Republic of China
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xia-men University, Xiamen 361005, People's Republic of China
| | - Juan Casado
- Department of Physical Chemistry, University of Málaga, Andalucia-Tech Campus de Teatinos s/n, Málaga 29071, Spain
| | - Qingqing Wu
- Department of Physics, Lancaster University, Lancaster LA1 4YB, U.K
| | - Colin J Lambert
- Department of Physics, Lancaster University, Lancaster LA1 4YB, U.K
| | - Yonghao Zheng
- Department of Pharmacy, Sichuan Provincial People's Hospital, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610072, People's Republic of China
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11
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Gu MW, Chen CH. Effects of Electrode Materials on Electron Transport for Single-Molecule Junctions. Int J Mol Sci 2023; 24:ijms24087277. [PMID: 37108439 PMCID: PMC10139062 DOI: 10.3390/ijms24087277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/11/2023] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
The contact at the molecule-electrode interface is a key component for a range of molecule-based devices involving electron transport. An electrode-molecule-electrode configuration is a prototypical testbed for quantitatively studying the underlying physical chemistry. Rather than the molecular side of the interface, this review focuses on examples of electrode materials in the literature. The basic concepts and relevant experimental techniques are introduced.
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Affiliation(s)
- Mong-Wen Gu
- Department of Chemistry and Center for Emerging Materials and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan
| | - Chun-Hsien Chen
- Department of Chemistry and Center for Emerging Materials and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan
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12
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Tang A, Li Y, Wang R, Yang J, Ma C, Li Z, Zou Q, Li H. Charge transport of F4TCNQ with different electronic states in single-molecule junctions. Chem Commun (Camb) 2023; 59:1305-1308. [PMID: 36633258 DOI: 10.1039/d2cc06341g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The molecular conductance of 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyano-quinodimethane (F4TCNQ) with different electronic states (neutral, radical anion, and dianion) was investigated by the scanning tunneling microscope break junction (STM-BJ) technique. These electronic states have distinct conductance, and the conductance decreases in the order of neutral > radical anion > dianion. Surprisingly, the molecular conductance of the neutral F4TCNQ junction reaches 10-1.17G0, attributed to its LUMO energy level being close to the Fermi level of the gold electrode. Moreover, we found that neutral F4TCNQ can be gradually reduced to radical anions under a relatively low bias voltage of 100 mV. These results will advance the development of organic optoelectronic devices and molecule electronics.
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Affiliation(s)
- Ajun Tang
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Yunpeng Li
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Rui Wang
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Jiawei Yang
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Chaoqi Ma
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Zhi Li
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Qi Zou
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
| | - Hongxiang Li
- Key Laboratory for Advanced Materials, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
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13
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Single-Molecule Chemical Reactions Unveiled in Molecular Junctions. Processes (Basel) 2022. [DOI: 10.3390/pr10122574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022] Open
Abstract
Understanding chemical processes at the single-molecule scale represents the ultimate limit of analytical chemistry. Single-molecule detection techniques allow one to reveal the detailed dynamics and kinetics of a chemical reaction with unprecedented accuracy. It has also enabled the discoveries of new reaction pathways or intermediates/transition states that are inaccessible in conventional ensemble experiments, which is critical to elucidating their intrinsic mechanisms. Thanks to the rapid development of single-molecule junction (SMJ) techniques, detecting chemical reactions via monitoring the electrical current through single molecules has received an increasing amount of attention and has witnessed tremendous advances in recent years. Research efforts in this direction have opened a new route for probing chemical and physical processes with single-molecule precision. This review presents detailed advancements in probing single-molecule chemical reactions using SMJ techniques. We specifically highlight recent progress in investigating electric-field-driven reactions, reaction dynamics and kinetics, host–guest interactions, and redox reactions of different molecular systems. Finally, we discuss the potential of single-molecule detection using SMJs across various future applications.
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14
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Huez C, Guérin D, Lenfant S, Volatron F, Calame M, Perrin ML, Proust A, Vuillaume D. Redox-controlled conductance of polyoxometalate molecular junctions. NANOSCALE 2022; 14:13790-13800. [PMID: 36102689 DOI: 10.1039/d2nr03457c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We demonstrate the reversible in situ photoreduction of molecular junctions of a phosphomolybdate [PMo12O40]3- monolayer self-assembled on flat gold electrodes, connected by the tip of a conductive atomic force microscope. The conductance of the one electron reduced [PMo12O40]4- molecular junction is increased by ∼10, and this open-shell state is stable in the junction in air at room temperature. The analysis of a large current-voltage dataset by unsupervised machine learning and clustering algorithms reveals that the electron transport in the pristine phosphomolybdate junctions leads to symmetric current-voltage curves, controlled by the lowest unoccupied molecular orbital (LUMO) at 0.6-0.7 eV above the Fermi energy with ∼25% of the junctions having a better electronic coupling to the electrodes than the main part of the dataset. This analysis also shows that a small fraction (∼18% of the dataset) of the molecules is already reduced. The UV light in situ photoreduced phosphomolybdate junctions systematically feature slightly asymmetric current-voltage behaviors, which is ascribed to the electron transport mediated by the single occupied molecular orbital (SOMO) nearly at resonance with the Fermi energy of the electrodes and by a closely located single unoccupied molecular orbital (SUMO) at ∼0.3 eV above the SOMO with a weak electronic coupling to the electrodes (∼50% of the dataset) or at ∼0.4 eV but with a better electrode coupling (∼50% of the dataset). These results shed light on the electronic properties of reversible switchable redox polyoxometalates, a key point for potential applications in nanoelectronic devices.
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Affiliation(s)
- Cécile Huez
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, Villeneuve d'Ascq, France.
| | - David Guérin
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, Villeneuve d'Ascq, France.
| | - Stéphane Lenfant
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, Villeneuve d'Ascq, France.
| | - Florence Volatron
- Institut Parisien de Chimie Moléculaire (IPCM), CNRS, Sorbonne Université, 4 Place Jussieu, F-75005 Paris, France
| | - Michel Calame
- EMPA, Transport at the Nanoscale Laboratory, 8600 Dübendorf, Switzerland
- Dept. of Physics and Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Mickael L Perrin
- EMPA, Transport at the Nanoscale Laboratory, 8600 Dübendorf, Switzerland
- Department of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Anna Proust
- Institut Parisien de Chimie Moléculaire (IPCM), CNRS, Sorbonne Université, 4 Place Jussieu, F-75005 Paris, France
| | - Dominique Vuillaume
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, Villeneuve d'Ascq, France.
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15
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Naghibi S, Sangtarash S, Kumar VJ, Wu J, Judd MM, Qiao X, Gorenskaia E, Higgins SJ, Cox N, Nichols RJ, Sadeghi H, Low PJ, Vezzoli A. Redox-Addressable Single-Molecule Junctions Incorporating a Persistent Organic Radical. Angew Chem Int Ed Engl 2022; 61:e202116985. [PMID: 35289977 PMCID: PMC9322687 DOI: 10.1002/anie.202116985] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Indexed: 12/14/2022]
Abstract
Integrating radical (open-shell) species into non-cryogenic nanodevices is key to unlocking the potential of molecular electronics. While many efforts have been devoted to this issue, in the absence of a chemical/electrochemical potential the open-shell character is generally lost in contact with the metallic electrodes. Herein, single-molecule devices incorporating a 6-oxo-verdazyl persistent radical have been fabricated using break-junction techniques. The open-shell character is retained at room temperature, and electrochemical gating permits in situ reduction to a closed-shell anionic state in a single-molecule transistor configuration. Furthermore, electronically driven rectification arises from bias-dependent alignment of the open-shell resonances. The integration of radical character, transistor-like switching, and rectification in a single molecular component paves the way to further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.
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Affiliation(s)
- Saman Naghibi
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | | | - Varshini J. Kumar
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Jian‐Zhong Wu
- School of ChemistrySouth China Normal UniversityGuangzhou510006P.R. China
| | - Martyna M. Judd
- Research School of ChemistryAustralian National UniversityCanberraATC 2601Australia
| | - Xiaohang Qiao
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Elena Gorenskaia
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Simon J. Higgins
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Nicholas Cox
- Research School of ChemistryAustralian National UniversityCanberraATC 2601Australia
| | - Richard J. Nichols
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Hatef Sadeghi
- School of EngineeringUniversity of WarwickCoventryCV4 7ALUK
| | - Paul J. Low
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Andrea Vezzoli
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
- Stephenson Institute for Renewable EnergyUniversity of LiverpoolPeach StreetLiverpoolL69 7ZFUK
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