1
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Xu X, Gao C, Emusani R, Jia C, Xiang D. Toward Practical Single-Molecule/Atom Switches. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2400877. [PMID: 38810145 DOI: 10.1002/advs.202400877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 04/29/2024] [Indexed: 05/31/2024]
Abstract
Electronic switches have been considered to be one of the most important components of contemporary electronic circuits for processing and storing digital information. Fabricating functional devices with building blocks of atomic/molecular switches can greatly promote the minimization of the devices and meet the requirement of high integration. This review highlights key developments in the fabrication and application of molecular switching devices. This overview offers valuable insights into the switching mechanisms under various stimuli, emphasizing structural and energy state changes in the core molecules. Beyond the molecular switches, typical individual metal atomic switches are further introduced. A critical discussion of the main challenges for realizing and developing practical molecular/atomic switches is provided. These analyses and summaries will contribute to a comprehensive understanding of the switch mechanisms, providing guidance for the rational design of functional nanoswitch devices toward practical applications.
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Affiliation(s)
- Xiaona Xu
- Institute of Modern Optics and Center of Single Molecule Sciences, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, 300350, China
| | - Chunyan Gao
- Institute of Modern Optics and Center of Single Molecule Sciences, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, 300350, China
| | - Ramya Emusani
- Institute of Modern Optics and Center of Single Molecule Sciences, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, 300350, China
| | - Chuancheng Jia
- Institute of Modern Optics and Center of Single Molecule Sciences, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, 300350, China
| | - Dong Xiang
- Institute of Modern Optics and Center of Single Molecule Sciences, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, 300350, China
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2
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Ripoll C, Del Campo-Balguerías A, Alonso-Moreno C, Herrera-Ochoa D, Ocaña A, Martín C, Garzón-Ruíz A, Bravo I. Fluorescence lifetime nanothermometer based on the equilibrium formation of anthracene AIE-excimers in living cells. J Colloid Interface Sci 2024; 674:186-193. [PMID: 38925064 DOI: 10.1016/j.jcis.2024.06.157] [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: 04/02/2024] [Revised: 06/14/2024] [Accepted: 06/22/2024] [Indexed: 06/28/2024]
Abstract
The effective measurement of temperature in living systems at the nano and microscopic scales continues to be a challenge to this day. Here, we study the use of 2-(anthracen-2-yl)-1,3-diisopropylguanidine, 1, as a nanothermometer based on fluorescence lifetime measurements and its bioimaging applications. In aqueous solution, 1 is shown in aggregated form and the equilibrium between the two main aggregate types (T-shaped and π-π) is highly sensitive to the temperature. The heating of the medium shifts the equilibrium toward the formation of highly emissive T-shaped aggregates. This species shows a high fluorescence emission and a long lifetime in comparison with the π-π aggregates and the freé monomer. A linear relationship between the fluorescence lifetime and the temperature both in aqueous solution and in a synthetic intracellular buffer was found. Fluorescence lifetime imaging microscopy (FLIM) also showed a linear relationship between lifetime and temperature with an excellent sensitivity in MCF7 breast cancer cells, which opens the door for its potential use as FLIM nanothermometer in the biomedical field.
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Affiliation(s)
- Consuelo Ripoll
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química-Física, Grupo FOTOAIR, 02008 Albacete, Spain
| | - Almudena Del Campo-Balguerías
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química Orgánica, Inorgánica Y Bioquímica, Grupo ORCAST, 02008 Albacete, Spain
| | - Carlos Alonso-Moreno
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química Orgánica, Inorgánica Y Bioquímica, Grupo ORCAST, 02008 Albacete, Spain; Centro de Innovación En Química Avanzada (ORFEO-CINQA), Universidad de Castilla-La Mancha. 02008 Albacete, Spain
| | - Diego Herrera-Ochoa
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química-Física, Grupo FOTOAIR, 02008 Albacete, Spain
| | - Alberto Ocaña
- Experimental Therapeutics Unit, Hospital Clínico San Carlos, IdISSC and CIBERONC, Madrid, Spain; START Phase I Unit, Hospital Fundación Jiménez Díaz, Madrid
| | - Cristina Martín
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química-Física, Grupo FOTOAIR, 02008 Albacete, Spain
| | - Andrés Garzón-Ruíz
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química-Física, Grupo FOTOAIR, 02008 Albacete, Spain.
| | - Iván Bravo
- Universidad de Castilla-La Mancha, Unidad nanoDrug. Facultad de Farmacia, Albacete-02008, Spain; Universidad de Castilla-La Mancha, Departamento de Química-Física, Grupo FOTOAIR, 02008 Albacete, Spain.
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3
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Hurtado-Gallego J, van der Poel S, Blaschke M, Gallego A, Hsu C, López-Nebreda R, Mayor M, Pauly F, Agraït N, van der Zant HSJ. Benchmarking break-junction techniques: electric and thermoelectric characterization of naphthalenophanes. NANOSCALE 2024; 16:10751-10759. [PMID: 38747099 PMCID: PMC11154865 DOI: 10.1039/d4nr00704b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 04/15/2024] [Indexed: 06/07/2024]
Abstract
Break-junction techniques provide the possibility to study electric and thermoelectric properties of single-molecule junctions in great detail. These techniques rely on the same principle of controllably breaking metallic contacts in order to create single-molecule junctions, whilst keeping track of the junction's conductance. Here, we compare results from mechanically controllable break junction (MCBJ) and scanning tunneling microscope (STM) methods, while characterizing conductance properties of the same novel mechanosensitive para- and meta-connected naphtalenophane compounds. In addition, thermopower measurements are carried out for both compounds using the STM break junction (STM-BJ) technique. For the conductance experiments, the same data processing using a clustering analysis is performed. We obtain to a large extent similar results for both methods, although values of conductance and stretching lengths for the STM-BJ technique are slightly larger in comparison with the MCBJ. STM-BJ thermopower experiments show similar Seebeck coefficients for both compounds. An increase in the Seebeck coefficient is revealed, whilst the conductance decreases, after which it saturates at around 10 μV K-1. This phenomenon is studied theoretically using a tight binding model. It shows that changes of molecule-electrode electronic couplings combined with shifts of the resonance energies explain the correlated behavior of conductance and Seebeck coefficient.
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Affiliation(s)
- Juan Hurtado-Gallego
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
| | - Sebastiaan van der Poel
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
| | - Matthias Blaschke
- Institute of Physics and Center for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany.
| | - Almudena Gallego
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
| | - Chunwei Hsu
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
| | - Rubén López-Nebreda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
| | - Marcel Mayor
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
- Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), P. O. Box 3640, 76021 Karlsruhe, Germany
- Lehn Institute of Functional Materials, School of Chemistry, Sun Yat-Sen University, Guangzhou 510274, P. R. China
| | - Fabian Pauly
- Institute of Physics and Center for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany.
| | - Nicolás Agraït
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
- Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales 'Nicolás Cabrera' (INC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Herre S J van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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4
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Blankevoort N, Bastante P, Davidson RJ, Salthouse RJ, Daaoub AHS, Cea P, Solans SM, Batsanov AS, Sangtarash S, Bryce MR, Agrait N, Sadeghi H. Exploring the Impact of the HOMO-LUMO Gap on Molecular Thermoelectric Properties: A Comparative Study of Conjugated Aromatic, Quinoidal, and Donor-Acceptor Core Systems. ACS OMEGA 2024; 9:8471-8477. [PMID: 38405513 PMCID: PMC10882689 DOI: 10.1021/acsomega.3c09760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/22/2024] [Accepted: 01/29/2024] [Indexed: 02/27/2024]
Abstract
Thermoelectric materials have garnered significant interest for their potential to efficiently convert waste heat into electrical energy at room temperature without moving parts or harmful emissions. This study investigated the impact of the HOMO-LUMO (H-L) gap on the thermoelectric properties of three distinct classes of organic compounds: conjugated aromatics (isoindigos (IIGs)), quinoidal molecules (benzodipyrrolidones (BDPs)), and donor-acceptor systems (bis(pyrrol-2-yl)squaraines (BPSs)). These compounds were chosen for their structural simplicity and linear π-conjugated conductance paths, which promote high electrical conductance and minimize complications from quantum interference. Single-molecule thermoelectric measurements revealed that despite their low H-L gaps, the Seebeck coefficients of these compounds remain low. The alignment of the frontier orbitals relative to the Fermi energy was found to play a crucial role in determining the Seebeck coefficients, as exemplified by the BDP compounds. Theoretical calculations support these findings and suggest that anchor group selection could further enhance the thermoelectric behavior of these types of molecules.
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Affiliation(s)
- Nickel Blankevoort
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Pablo Bastante
- Departamento
de Física de la Materia Condensada C-III, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Ross J. Davidson
- Department
of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | | | - Abdalghani H. S. Daaoub
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Pilar Cea
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC−Universidad de Zaragoza, 50009 Zaragoza, Spain
- Departamento
de Química Física, Universidad
de Zaragoza, 50009 Zaragoza, Spain
- Laboratorio
de Microscopias Avanzadas (LMA), Universidad
de Zaragoza, 50018 Zaragoza, Spain
| | - Santiago Martin Solans
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC−Universidad de Zaragoza, 50009 Zaragoza, Spain
- Departamento
de Química Física, Universidad
de Zaragoza, 50009 Zaragoza, Spain
- Laboratorio
de Microscopias Avanzadas (LMA), Universidad
de Zaragoza, 50018 Zaragoza, Spain
| | | | - Sara Sangtarash
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Martin R. Bryce
- Department
of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Nicolas Agrait
- Departamento
de Física de la Materia Condensada C-III, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia
de Materiales “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Hatef Sadeghi
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
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5
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Escorihuela E, Del Barrio J, Davidson RJ, Beeby A, Low PJ, Prez-Murano F, Cea P, Martin S. Large area arrays of discrete single-molecule junctions derived from host-guest complexes. NANOSCALE 2024; 16:1238-1246. [PMID: 38116590 DOI: 10.1039/d3nr05122f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The desire to continually reduce the lower limits of semiconductor integrated circuit (IC) fabrication methods continues to inspire interest in unimolecular electronics as a platform technology for the realization of future (opto)electronic devices. However, despite successes in developing methods for the construction and measurement of single-molecule and large-area molecular junctions, exercising control over the precise junction geometry remains a significant challenge. Here, host-guest complexes of the wire-like viologen derivative 1,1'-bis(4-(methylthio)-phenyl)-[4,4'-bipyridine]-1,1'-diium chloride ([1][Cl]2) and cucurbit[7]uril (CB[7]) have been self-assembled in a regular pattern over a gold substrate. Subsequently, ligandless gold nanoparticles (AuNPs) synthesized in situ are deposited over the host-guest array. The agreement between the conductance of individual mono-molecular junctions, appropriately chosen as a function of the AuNP diameter, within this array determined by conductive probe atomic force microscope (c-AFM) and true single-molecule measurements for a closely similar host-guest complex within a scanning tunneling microscope break-junction (STM-BJ) indicates the formation of molecular junctions derived from these host-guest complexes without deleterious intermolecular coupling effects.
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Affiliation(s)
- Enrique Escorihuela
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain.
- Departamento de Química Física, Universidad de Zaragoza, 50009, Zaragoza, Spain
| | - Jesús Del Barrio
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain.
- Departamento de Química Orgánica, Universidad de Zaragoza, 50009, Zaragoza, Spain
| | - Ross J Davidson
- Department of Chemistry, Durham University, South Rd, Durham, DH1 3LE, UK
| | - Andrew Beeby
- Department of Chemistry, Durham University, South Rd, Durham, DH1 3LE, UK
| | - Paul J Low
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, 6009, Western Australia, Australia
| | - Francesc Prez-Murano
- Institute of Microelectronics of Barcelona (IMB-CNM, CSIC), 08193, Bellaterra, Spain
| | - Pilar Cea
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain.
- Departamento de Química Física, Universidad de Zaragoza, 50009, Zaragoza, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - Santiago Martin
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain.
- Departamento de Química Física, Universidad de Zaragoza, 50009, Zaragoza, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Universidad de Zaragoza, 50018, Zaragoza, Spain
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6
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Salthouse R, Hurtado-Gallego J, Grace IM, Davidson R, Alshammari O, Agraït N, Lambert CJ, Bryce MR. Electronic Conductance and Thermopower of Cross-Conjugated and Skipped-Conjugated Molecules in Single-Molecule Junctions. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:13751-13758. [PMID: 37528901 PMCID: PMC10389811 DOI: 10.1021/acs.jpcc.3c00742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 06/21/2023] [Indexed: 08/03/2023]
Abstract
We report a combined experimental and theoretical study of a series of thiomethyl (SMe) anchored cross-conjugated molecules featuring an acyclic central bridging ketone and their analogous skipped-conjugated alcohol derivatives. Studies of these molecules in a gold|single-molecule|gold junction using scanning tunneling microscopy-break junction techniques reveal a similar conductance (G) value for both the cross-conjugated molecules and their skipped-conjugated partners. Theoretical studies based on density functional theory of the molecules in their optimum geometries in the junction reveal the reason for this similarity in conductance, as the predicted conductance for the alcohol series of compounds varies more with the tilt angle. Thermopower measurements reveal a higher Seebeck coefficient (S) for the cross-conjugated ketone molecules relative to the alcohol derivatives, with a particularly high S for the biphenyl derivative 3a (-15.6 μV/K), an increase of threefold compared to its alcohol analog. The predicted behavior of the quantum interference (QI) in this series of cross-conjugated molecules is found to be constructive, though the appearance of a destructive QI feature for 3a is due to the degeneracy of the HOMO orbital and may explain the enhancement of the value of S for this molecule.
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Affiliation(s)
| | - Juan Hurtado-Gallego
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049, Spain
| | - Iain M. Grace
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Ross Davidson
- Department
of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Ohud Alshammari
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Nicolás Agraït
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049, Spain
- Condensed
Matter Physics Center (IFIMAC) and Instituto Universitatio de Ciencia
de Materiales “Nicolás Cabrera” (INC), Universidad Autónoma de Madrid, Madrid E-28049, Spain
- Instituto
Madrileño de Estudios Avanzados en Nanociencia IMDEA-Nanociencia, Madrid E-28049, Spain
| | - Colin J. Lambert
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Martin R. Bryce
- Department
of Chemistry, Durham University, Durham DH1 3LE, U.K.
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7
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Ismael AK. 20-State Molecular Switch in a Li@C 60 Complex. ACS OMEGA 2023; 8:19767-19771. [PMID: 37305247 PMCID: PMC10249121 DOI: 10.1021/acsomega.3c01455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/16/2023] [Indexed: 06/13/2023]
Abstract
A substantial potential advantage of industrial electric and thermoelectric devices utilizing endohedral metallofullerenes (EMFs) is their ability to accommodate metallic moieties inside their empty cavities. Experimental and theoretical studies have elucidated the merit of this extraordinary feature with respect to developing electrical conductance and thermopower. Published research studies have demonstrated multiple state molecular switches initiated with 4, 6, and 14 distinguished switching states. Through comprehensive theoretical investigations involving electronic structure and electric transport, we report 20 molecular switching states that can be statistically recognized employing the endohedral fullerene Li@C60 complex. We propose a switching technique that counts on the location of the alkali metal that encapsulates inside a fullerene cage. The 20 switching states correspond to the 20 hexagonal rings that the Li cation energetically prefers to reside close to. We demonstrate that the multiswitching feature of such molecular complexes can be controlled by taking advantage of the off-center displacement and charge transfer from the alkali metal to the C60 cage. The most energetically favorable optimization suggests 1.2-1.4 Å off-center displacement, and Mulliken, Hirshfeld, and Voronoi simulations articulate that the charge migrates from the Li cation to C60 fullerene; however, the amount of the charge transferred depends on the nature and location of the cation within the complex. We believe that the proposed work suggests a relevant step toward the practical application of molecular switches in organic materials.
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Affiliation(s)
- Ali K. Ismael
- Department
of Physics, Lancaster University, Lancaster LA1 4YB, U.K.
- Department
of Physics, College of Education for Pure Science, Tikrit University, Salahuddin, Al-Qadissiya street 34001, Tikrit, Iraq
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8
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Hamill JM, Ismael A, Al-Jobory A, Bennett TLR, Alshahrani M, Wang X, Akers-Douglas M, Wilkinson LA, Robinson BJ, Long NJ, Lambert C, Albrecht T. Quantum Interference and Contact Effects in the Thermoelectric Performance of Anthracene-Based Molecules. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:7484-7491. [PMID: 37113454 PMCID: PMC10123663 DOI: 10.1021/acs.jpcc.3c00069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/30/2023] [Indexed: 06/19/2023]
Abstract
We report on the single-molecule electronic and thermoelectric properties of strategically chosen anthracene-based molecules with anchor groups capable of binding to noble metal substrates, such as gold and platinum. Specifically, we study the effect of different anchor groups, as well as quantum interference, on the electric conductance and the thermopower of gold/single-molecule/gold junctions and generally find good agreement between theory and experiments. All molecular junctions display transport characteristics consistent with coherent transport and a Fermi alignment approximately in the middle of the highest occupied molecular orbital/lowest unoccupied molecular orbital gap. Single-molecule results are in agreement with previously reported thin-film data, further supporting the notion that molecular design considerations may be translated from the single- to many-molecule devices. For combinations of anchor groups where one binds significantly more strongly to the electrodes than the other, the stronger anchor group appears to dominate the thermoelectric behavior of the molecular junction. For other combinations, the choice of electrode material can determine the sign and magnitude of the thermopower. This finding has important implications for the design of thermoelectric generator devices, where both n- and p-type conductors are required for thermoelectric current generation.
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Affiliation(s)
- Joseph M. Hamill
- School
of Chemistry, University of Birmingham, Edgbaston Campus, Birmingham B15 2TT, U.K.
| | - Ali Ismael
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Alaa Al-Jobory
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
- Department
of Physics, College of Science, University
of Anbar, Ramadi 31001, Anbar, Iraq
| | - Troy L. R. Bennett
- Department
of Chemistry, Imperial College London, MSRH, White City, London W12 0BZ, U.K.
| | - Maryam Alshahrani
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
- Physics
Department, College of Science, University
of Bisha, P.O. Box 344, Bisha 61922, Kingdom of Saudi Arabia
| | - Xintai Wang
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
- School
of
Information Science and Technology, Dalian
Maritime University, Dalian 116026, China
| | - Maxwell Akers-Douglas
- Department
of Chemistry, Imperial College London, MSRH, White City, London W12 0BZ, U.K.
| | - Luke A. Wilkinson
- Department
of Chemistry, Imperial College London, MSRH, White City, London W12 0BZ, U.K.
| | | | - Nicholas J. Long
- Department
of Chemistry, Imperial College London, MSRH, White City, London W12 0BZ, U.K.
| | - Colin Lambert
- Physics
Department, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Tim Albrecht
- School
of Chemistry, University of Birmingham, Edgbaston Campus, Birmingham B15 2TT, U.K.
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9
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Signatures of Room-Temperature Quantum Interference in Molecular Junctions. Acc Chem Res 2023; 56:322-331. [PMID: 36693627 PMCID: PMC9910048 DOI: 10.1021/acs.accounts.2c00726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
ConspectusDuring the past decade or so, research groups around the globe have sought to answer the question: "How does electricity flow through single molecules?" In seeking the answer to this question, a series of joint theory and experimental studies have demonstrated that electrons passing through single-molecule junctions exhibit exquisite quantum interference (QI) effects, which have no classical analogues in conventional circuits. These signatures of QI appear even at room temperature and can be described by simple quantum circuit rules and a rather intuitive magic ratio theory. The latter describes the effect of varying the connectivity of electrodes to a molecular core and how electrical conductance can be controlled by the addition of heteroatoms to molecular cores. The former describes how individual moieties contribute to the overall conductance of a molecule and how the overall conductance can change when the connectivities between different moieties are varied. Related circuit rules have been derived and demonstrated, which describe the effects of connectivity on Seebeck coefficients of organic molecules. This simplicity arises because when a molecule is placed between two electrodes, charge transfer between the molecule and electrodes causes the molecular energy levels to adjust, such that the Fermi energy (EF) of the electrodes lies within the energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital. Consequently, when electrons of energy EF pass through a molecule, their phase is protected and transport takes place via phase-coherent tunneling. Remarkably, these effects have been scaled up to self-assembled monolayers of molecules, thereby creating two-dimensional materials, whose room temperature transport properties are controlled by QI. This leads to new molecular design strategies for increasing the on/off conductance ratio of molecular switches and to improving the performance of organic thermoelectric materials. In particular, destructive quantum interference has been shown to improve the Seebeck coefficient of organic molecules and increase their on/off ratio under the influence of electrochemical gating. The aim of this Account is to introduce the novice reader to these signatures of QI in molecules, many of which have been identified in joint studies involving our theory group in Lancaster University and experimental group in Bern University.
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10
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Alshammari M, Al-Jobory AA, Alotaibi T, Lambert CJ, Ismael A. Orientational control of molecular scale thermoelectricity. NANOSCALE ADVANCES 2022; 4:4635-4638. [PMID: 36341305 PMCID: PMC9595198 DOI: 10.1039/d2na00515h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/03/2022] [Indexed: 06/13/2023]
Abstract
Through a comprehensive theoretical study, we demonstrate that single-molecule junctions formed from asymmetric molecules with different terminal groups can exhibit Seebeck coefficients, whose sign depends on the orientation of the molecule within the junction. Three anthracene-based molecules are studied, one of which exhibits this bi-thermoelectric behaviour, due to the presence of a thioacetate terminal group at one end and a pyridyl terminal group at the other. A pre-requisite for obtaining this behaviour is the use of junction electrodes formed from different materials. In our case, we use gold as the bottom electrode and graphene-coated gold as the top electrode. This demonstration of bi-thermoelecricity means that if molecules with alternating orientations can be deposited on a substrate, then they form a basis for boosting the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).
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Affiliation(s)
- Majed Alshammari
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Sakaka Saudi Arabia
| | - Alaa A Al-Jobory
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | - Turki Alotaibi
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Sakaka Saudi Arabia
| | - Colin J Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
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11
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Wang X, Ismael A, Ning S, Althobaiti H, Al-Jobory A, Girovsky J, Astier HPAG, O'Driscoll LJ, Bryce MR, Lambert CJ, Ford CJB. Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives. NANOSCALE HORIZONS 2022; 7:1201-1209. [PMID: 35913108 DOI: 10.1039/d2nh00241h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Understanding and controlling the orbital alignment of molecules placed between electrodes is essential in the design of practically-applicable molecular and nanoscale electronic devices. The orbital alignment is highly determined by the molecule-electrode interface. Dependence of orbital alignment on the molecular anchor group for single molecular junctions has been intensively studied; however, when scaling-up single molecules to large parallel molecular arrays (like self-assembled monolayers (SAMs)), two challenges need to be addressed: 1. Most desired anchor groups do not form high quality SAMs. 2. It is much harder to tune the frontier molecular orbitals via a gate voltage in SAM junctions than in single molecular junctions. In this work, we studied the effect of the molecule-electrode interface in SAMs with a micro-pore device, using a recently developed tetrapodal anchor to overcome challenge 1, and the combination of a single layered graphene top electrode with an ionic liquid gate to solve challenge 2. The zero-bias orbital alignment of different molecules was signalled by a shift in conductance minimum vs. gate voltage for molecules with different anchoring groups. Molecules with the same backbone, but a different molecule-electrode interface, were shown experimentally to have conductances that differ by a factor of 5 near zero bias. Theoretical calculations using density functional theory support the trends observed in the experimental data. This work sheds light on how to control electron transport within the HOMO-LUMO energy gap in molecular junctions and will be applicable in scaling up molecular electronic systems for future device applications.
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Affiliation(s)
- Xintai Wang
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
- School of Information Science and Technology, Dalian Maritime University, Dalian, China
| | - Ali Ismael
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Iraq
| | - Shanglong Ning
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Hanan Althobaiti
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Science, Taif-University, Taif, Saudi Arabia
| | - Alaa Al-Jobory
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Science, University of Anbar, Anbar, Iraq
| | - Jan Girovsky
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Hippolyte P A G Astier
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Luke J O'Driscoll
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK
| | - Martin R Bryce
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK
| | - Colin J Lambert
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
| | - Christopher J B Ford
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
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12
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Ismael AK, Rincón-García L, Evangeli C, Dallas P, Alotaibi T, Al-Jobory AA, Rubio-Bollinger G, Porfyrakis K, Agraït N, Lambert CJ. Exploring seebeck-coefficient fluctuations in endohedral-fullerene, single-molecule junctions. NANOSCALE HORIZONS 2022; 7:616-625. [PMID: 35439804 DOI: 10.1039/d1nh00527h] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For the purpose of creating single-molecule junctions, which can convert a temperature difference ΔT into a voltage ΔV via the Seebeck effect, it is of interest to screen molecules for their potential to deliver high values of the Seebeck coefficient S = -ΔV/ΔT. Here we demonstrate that insight into molecular-scale thermoelectricity can be obtained by examining the widths and extreme values of Seebeck histograms. Using a combination of experimental scanning-tunnelling-microscopy-based transport measurements and density-functional-theory-based transport calculations, we study the electrical conductance and Seebeck coefficient of three endohedral metallofullerenes (EMFs) Sc3N@C80, Sc3C2@C80, and Er3N@C80, which based on their structures, are selected to exhibit different degrees of charge inhomogeneity and geometrical disorder within a junction. We demonstrate that standard deviations in the Seebeck coefficient σS of EMF-based junctions are correlated with the geometric standard deviation σ and the charge inhomogeneity σq. We benchmark these molecules against C60 and demonstrate that both σq, σS are the largest for Sc3C2@C80, both are the smallest for C60 and for the other EMFs, they follow the order Sc3C2@C80 > Sc3N@C80 > Er3N@C80 > C60. A large value of σS is a sign that a molecule can exhibit a wide range of Seebeck coefficients, which means that if orientations corresponding to high values can be selected and controlled, then the molecule has the potential to exhibit high-performance thermoelectricity. For the EMFs studied here, large values of σS are associated with distributions of Seebeck coefficients containing both positive and negative signs, which reveals that all these EMFs are bi-thermoelectric materials.
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Affiliation(s)
- Ali K Ismael
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Iraq
| | - Laura Rincón-García
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | | | - Panagiotis Dallas
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 15310 Athens, Greece
- Department of Materials, University of Oxford, OX1 3PH, UK
| | - Turki Alotaibi
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Science, Jouf University, Sakaka, Saudi Arabia
| | - Alaa A Al-Jobory
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Science, University of Anbar, Anbar, Iraq
| | - Gabino Rubio-Bollinger
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales "Nicolás Cabrera" (INC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Kyriakos Porfyrakis
- Department of Materials, University of Oxford, OX1 3PH, UK
- Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, ME4 4TB, UK
| | - Nicolás Agraït
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales "Nicolás Cabrera" (INC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Fundación IMDEA Nanociencia, Calle Faraday 9, Campus Universitario de Cantoblanco, E-28049 Madrid, Spain
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Naher M, Gorenskaia E, Moggach SA, Becker T, Nichols RJ, Lambert CJ, Low PJ. A one-pot synthesis of oligo(arylene–ethynylene)-molecular wires and their use in the further verification of molecular circuit laws†. Aust J Chem 2022. [DOI: 10.1071/ch21235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Wilkinson LA, Bennett TLR, Grace IM, Hamill J, Wang X, Au-Yong S, Ismael A, Jarvis SP, Hou S, Albrecht T, Cohen LF, Lambert C, Robinson BJ, Long NJ. Assembly, structure and thermoelectric properties of 1,1′-dialkynylferrocene ‘hinges’. Chem Sci 2022; 13:8380-8387. [PMID: 35919728 PMCID: PMC9297386 DOI: 10.1039/d2sc00861k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/24/2022] [Indexed: 11/21/2022] Open
Abstract
Dialkynylferrocenes exhibit attractive electronic and rotational features that make them ideal candidates for use in molecular electronic applications. However previous works have primarily focussed on single-molecule studies, with limited opportunities to translate these features into devices. In this report, we utilise a variety of techniques to examine both the geometric and electronic structure of a range of 1,1′-dialkynylferrocene molecules, as either single-molecules, or as self-assembled monolayers. Previous single molecule studies have shown that similar molecules can adopt an ‘open’ conformation. However, in this work, DFT calculations, STM-BJ experiments and AFM imaging reveal that these molecules prefer to occupy a ‘hairpin’ conformation, where both alkynes point towards the metal surface. Interestingly we find that only one of the terminal anchor groups binds to the surface, though both the presence and nature of the second alkyne affect the thermoelectric properties of these systems. First, the secondary alkyne acts to affect the position of the frontier molecular orbitals, leading to increases in the Seebeck coefficient. Secondly, theoretical calculations suggested that rotating the secondary alkyne away from the surface acts to modulate thermoelectric properties. This work represents the first of its kind to examine the assembly of dialkynylferrocenes, providing valuable information about both their structure and electronic properties, as well as unveiling new ways in which both of these properties can be controlled. Dialkynylferrocenes are interesting candidates for molecular electronics. Herein, numerous experiments are applied to probe their properties both as single-molecules and in monolayers, demonstrating unique geometric and thermoelectric properties.![]()
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Affiliation(s)
- Luke A. Wilkinson
- Department of Chemistry, Imperial College London, MSRH, White City, London, W12 0BZ, UK
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Troy L. R. Bennett
- Department of Chemistry, Imperial College London, MSRH, White City, London, W12 0BZ, UK
| | - Iain M. Grace
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | - Joseph Hamill
- Department of Chemistry, Birmingham University, Edgbaston, Birmingham, B15 2TT, UK
| | - Xintai Wang
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Sophie Au-Yong
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | - Ali Ismael
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | - Samuel P. Jarvis
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | - Songjun Hou
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | - Tim Albrecht
- Department of Chemistry, Birmingham University, Edgbaston, Birmingham, B15 2TT, UK
| | - Lesley F. Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Colin Lambert
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
| | | | - Nicholas J. Long
- Department of Chemistry, Imperial College London, MSRH, White City, London, W12 0BZ, UK
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15
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Bennett TLR, Alshammari M, Au-Yong S, Almutlg A, Wang X, Wilkinson LA, Albrecht T, Jarvis SP, Cohen LF, Ismael A, Lambert CJ, Robinson BJ, Long NJ. Multi-Component Self-Assembled Molecular-Electronic Films: Towards New High-Performance Thermoelectric Systems. Chem Sci 2022; 13:5176-5185. [PMID: 35655580 PMCID: PMC9093172 DOI: 10.1039/d2sc00078d] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/14/2022] [Indexed: 12/02/2022] Open
Abstract
The thermoelectric properties of parallel arrays of organic molecules on a surface offer the potential for large-area, flexible, solution processed, energy harvesting thin-films, whose room-temperature transport properties are controlled by quantum interference (QI). Recently, it has been demonstrated that constructive QI (CQI) can be translated from single molecules to self-assembled monolayers (SAMs), boosting both electrical conductivities and Seebeck coefficients. However, these CQI-enhanced systems are limited by rigid coupling of the component molecules to metallic electrodes, preventing the introduction of additional layers which would be advantageous for their further development. These rigid couplings also limit our ability to suppress the transport of phonons through these systems, which could act to boost their thermoelectric output, without comprising on their impressive electronic features. Here, through a combined experimental and theoretical study, we show that cross-plane thermoelectricity in SAMs can be enhanced by incorporating extra molecular layers. We utilize a bottom-up approach to assemble multi-component thin-films that combine a rigid, highly conductive ‘sticky’-linker, formed from alkynyl-functionalised anthracenes, and a ‘slippery’-linker consisting of a functionalized metalloporphyrin. Starting from an anthracene-based SAM, we demonstrate that subsequent addition of either a porphyrin layer or a graphene layer increases the Seebeck coefficient, and addition of both porphyrin and graphene leads to a further boost in their Seebeck coefficients. This demonstration of Seebeck-enhanced multi-component SAMs is the first of its kind and presents a new strategy towards the design of thin-film thermoelectric materials. Through an experimental and theoretical study, cross-plane thermoelectricity in Self-Assembled Monolayers (SAMs) was enhanced by adding extra molecular layers, presenting a new strategy towards the design of high thermoelectric materials.![]()
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Affiliation(s)
- Troy L R Bennett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Majed Alshammari
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Skaka Saudi Arabia
| | - Sophie Au-Yong
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Ahmad Almutlg
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Mathematics, College of Science, Qassim University Almethnab Saudi Arabia
| | - Xintai Wang
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Luke A Wilkinson
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Tim Albrecht
- Department of Chemistry, Birmingham University Edgbaston Birmingham B15 2TT UK
| | - Samuel P Jarvis
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Colin J Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | | | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
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16
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O'Driscoll LJ, Bryce MR. A review of oligo(arylene ethynylene) derivatives in molecular junctions. NANOSCALE 2021; 13:10668-10711. [PMID: 34110337 DOI: 10.1039/d1nr02023d] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Oligo(arylene ethynylene) (OAE) derivatives are the "workhorse" molecules of molecular electronics. Their ease of synthesis and flexibility of functionalisation mean that a diverse array of OAE molecular wires have been designed, synthesised and studied theoretically and experimentally in molecular junctions using both single-molecule and ensemble methods. This review summarises the breadth of molecular designs that have been investigated with emphasis on structure-property relationships with respect to the electronic conductance of OAEs. The factors considered include molecular length, connectivity, conjugation, (anti)aromaticity, heteroatom effects and quantum interference (QI). Growing interest in the thermoelectric properties of OAE derivatives, which are expected to be at the forefront of research into organic thermoelectric devices, is also explored.
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Affiliation(s)
- Luke J O'Driscoll
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, UKDH1 3LE.
| | - Martin R Bryce
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, UKDH1 3LE.
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17
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Wang X, Ismael A, Almutlg A, Alshammari M, Al-Jobory A, Alshehab A, Bennett TLR, Wilkinson LA, Cohen LF, Long NJ, Robinson BJ, Lambert C. Optimised power harvesting by controlling the pressure applied to molecular junctions. Chem Sci 2021; 12:5230-5235. [PMID: 34163759 PMCID: PMC8179551 DOI: 10.1039/d1sc00672j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 02/22/2021] [Indexed: 11/21/2022] Open
Abstract
A major potential advantage of creating thermoelectric devices using self-assembled molecular layers is their mechanical flexibility. Previous reports have discussed the advantage of this flexibility from the perspective of facile skin attachment and the ability to avoid mechanical deformation. In this work, we demonstrate that the thermoelectric properties of such molecular devices can be controlled by taking advantage of their mechanical flexibility. The thermoelectric properties of self-assembled monolayers (SAMs) fabricated from thiol terminated molecules were measured with a modified AFM system, and the conformation of the SAMs was controlled by regulating the loading force between the organic thin film and the probe, which changes the tilt angle at the metal-molecule interface. We tracked the thermopower shift vs. the tilt angle of the SAM and showed that changes in both the electrical conductivity and Seebeck coefficient combine to optimize the power factor at a specific angle. This optimization of thermoelectric performance via applied pressure is confirmed through the use of theoretical calculations and is expected to be a general method for optimising the power factor of SAMs.
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Affiliation(s)
- Xintai Wang
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Ahmad Almutlg
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | | | - Alaa Al-Jobory
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | | | - Troy L R Bennett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Luke A Wilkinson
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | | | - Colin Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
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18
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Almughathawi R, Hou S, Wu Q, Liu Z, Hong W, Lambert C. Conformation and Quantum-Interference-Enhanced Thermoelectric Properties of Diphenyl Diketopyrrolopyrrole Derivatives. ACS Sens 2021; 6:470-476. [PMID: 33382942 PMCID: PMC8021221 DOI: 10.1021/acssensors.0c02043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Manipulating the connectivity of external electrodes to central rings of carbon-based molecules in single molecule junctions is an effective route to tune their thermoelectrical properties. Here we investigate the connectivity dependence of the thermoelectric properties of a series of thiophene-diketopyrrolopyrrole (DPP) derivative molecules using density functional theory and tight-binding modeling, combined with quantum transport theory. We find a significant dependence of electrical conductance on the connectivity of the two thiophene rings attached to the DPP core. Interestingly, for connectivities corresponding to constructive quantum interference (CQI), different isomers obtained by rotating the thiophene rings possess the same electrical conductance while those corresponding to destructive quantum interference (DQI) show huge conductance variations upon ring rotation. Furthermore, we find that DQI connectivity leads to enhanced Seebeck coefficients, which can reach 500-700 μV/K. After including the contribution to the thermal conductance from phonons, the full figure of merit (ZT) for the CQI molecules could reach 1.5 at room temperature and it would further increase to 2 when temperature elevates to 400 K. Finally, we demonstrate that doping with tetracyanoquinodimethane can change the sign of the Seebeck coefficients by forming a charge-transfer system with the DPP.
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Affiliation(s)
- Renad Almughathawi
- Physics Department, Lancaster University, LA1 4YB Lancaster, United Kingdom
| | - Songjun Hou
- Physics Department, Lancaster University, LA1 4YB Lancaster, United Kingdom
| | - Qingqing Wu
- Physics Department, Lancaster University, LA1 4YB Lancaster, United Kingdom
| | - Zitong Liu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, NEL, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Colin Lambert
- Physics Department, Lancaster University, LA1 4YB Lancaster, United Kingdom
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19
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Wang Y, Gu Z, Deng X, Zhang B. Ultraviolet-light-triggered isomerization of Rydberg-excited propanal: Real-time capture of ultrafast structural evolution and dynamics investigation. J Chem Phys 2021; 154:054301. [PMID: 33557549 DOI: 10.1063/5.0039802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Structure rearrangement processes, such as isomerization, are attracting extensive interest as a potential carrier in molecular scale electronics design. UV-light-triggered isomerization of Rydberg-excited propanal with two UV photons has been investigated with time-resolved photoelectron spectroscopy. By following the photoionization from 3s Rydberg states in the time domain, the ultrafast structural evolution and the corresponding photoisomerization dynamics are observed and tracked in real-time. The conversion barrier for isomerization from cis-propanal to gauche isomer is estimated to be about 1500 ± 100 cm-1 experimentally. Both the photoisomerization yield and the conversion rate have shown strong dependence on the excitation energy. It is observed that whether vibration modes are selectively excited or not, cis-to-gauche photoisomerization of propanal in 3s Rydberg state occurs once the excitation energy is higher than the conversion barrier without any vibrational excitation specificity. This yields a powerful approach to studying structural evolution dynamics in large molecules, which may have applications in molecular devices.
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Affiliation(s)
- Yanmei Wang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Zhenfei Gu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Xulan Deng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Bing Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
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20
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Ismael A, Al-Jobory A, Wang X, Alshehab A, Almutlg A, Alshammari M, Grace I, Benett TLR, Wilkinson LA, Robinson BJ, Long NJ, Lambert C. Molecular-scale thermoelectricity: as simple as 'ABC'. NANOSCALE ADVANCES 2020; 2:5329-5334. [PMID: 36132050 PMCID: PMC9417915 DOI: 10.1039/d0na00772b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 01/11/2021] [Accepted: 10/06/2020] [Indexed: 05/08/2023]
Abstract
If the Seebeck coefficient of single molecules or self-assembled monolayers (SAMs) could be predicted from measurements of their conductance-voltage (G-V) characteristics alone, then the experimentally more difficult task of creating a set-up to measure their thermoelectric properties could be avoided. This article highlights a novel strategy for predicting an upper bound to the Seebeck coefficient of single molecules or SAMs, from measurements of their G-V characteristics. The theory begins by making a fit to measured G-V curves using three fitting parameters, denoted a, b, c. This 'ABC' theory then predicts a maximum value for the magnitude of the corresponding Seebeck coefficient. This is a useful material parameter, because if the predicted upper bound is large, then the material would warrant further investigation using a full Seebeck-measurement setup. On the other hand, if the upper bound is small, then the material would not be promising and this much more technically demanding set of measurements would be avoided. Histograms of predicted Seebeck coefficients are compared with histograms of measured Seebeck coefficients for six different SAMs, formed from anthracene-based molecules with different anchor groups and are shown to be in excellent agreement.
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Affiliation(s)
- Ali Ismael
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Alaa Al-Jobory
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | - Xintai Wang
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | | | - Ahmad Almutlg
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Majed Alshammari
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Iain Grace
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Troy L R Benett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Luke A Wilkinson
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | | | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Colin Lambert
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
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Nanofabrication Techniques in Large-Area Molecular Electronic Devices. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10176064] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.
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