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Alotaibi T, Alshahrani M, Alshammari M, Alotaibi M, Taha TAM, Al-Jobory AA, Ismael A. Orientational Effects and Molecular-Scale Thermoelectricity Control. ACS OMEGA 2024; 9:29537-29543. [PMID: 39005829 PMCID: PMC11238236 DOI: 10.1021/acsomega.4c02141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 07/16/2024]
Abstract
The orientational effect concept in a molecular-scale junction is established for asymmetric junctions, which requires the fulfillment of two conditions: (1) design of an asymmetric molecule with strong distinct terminal end groups and (2) construction of a doubly asymmetric junction by placing an asymmetric molecule in an asymmetric junction to form a multicomponent system such as Au/Zn-TPP+M/Au. Here, we demonstrate that molecular-scale junctions that satisfy the conditions of these effects can manifest Seebeck coefficients whose sign fluctuates depending on the orientation of the molecule within the asymmetric junction in a complete theoretical investigation. Three anthracene-based compounds are investigated in three different scenarios, one of which displays a bithermoelectric behavior due to the presence of strong anchor groups, including pyridyl and thioacetate. This bithermoelectricity demonstration implies that if molecules with alternating orientations can be placed between an asymmetric source and drain, they can be potentially utilized for increasing the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).
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Affiliation(s)
- Turki Alotaibi
- Department
of Physics, College of Science, Jouf University, Sakaka 72388, Saudi Arabia
| | - Maryam Alshahrani
- Department
of Physics, College of Science, University
of Bisha, P.O. Box 551, Bisha 61922, Saudi Arabia
| | - Majed Alshammari
- Department
of Physics, College of Science, Jouf University, Sakaka 72388, Saudi Arabia
| | - Moteb Alotaibi
- Department
of Physics, College of Science and Humanities in Al-Kharj, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Taha Abdel Mohaymen Taha
- Physics
and Engineering Mathematics Department, Faculty of Electronic Engineering, Menoufia University, Menouf 32952, Egypt
| | - Alaa A. Al-Jobory
- Department
of Physics, College of Science, University
of Anbar, Anbar 31001, Iraq
| | - Ali Ismael
- Department
of Physics, Lancaster University, Lancaster LA1 4YB, U.K.
- Department
of Physics, College of Education for Pure Science, Tikrit University, Tikrit 3400, Iraq
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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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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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Alshehab A, Ismael AK. Impact of the terminal end-group on the electrical conductance in alkane linear chains. RSC Adv 2023; 13:5869-5873. [PMID: 36816091 PMCID: PMC9936266 DOI: 10.1039/d3ra00019b] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 02/13/2023] [Indexed: 02/19/2023] Open
Abstract
This research presents comprehensive theoretical investigations of a series of alkane-based chains using four different terminal end groups including amine -NH2, thiomethyl -SMe, thiol -SH and direct carbon contact -C. It is widely known that the electrical conductance of single molecules can be tuned and boosted by chemically varying their terminal groups to metal electrodes. Here, we demonstrate how different terminal groups affect alkane molecules' electrical conductance. In general, alkane chain conductance decreases exponentially with length, regardless of the anchor group types. In these simulations the molecular length varies from 3 to 8 -CH2 units, with 4 different linker groups; these simulations suggest that the conductances follow the order G C > G SH > G SMe > G NH2 . The DFT prediction order of the 4 anchors is well supported by STM measurements. This work demonstrates an excellent correlation between our simulations and experimental measurements, namely: the percent difference ΔG, exponential decay slopes, A constants and β factors at different molecular alkane chain lengths.
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Affiliation(s)
- Abdullah Alshehab
- Physics Department, College of Science, King Faisal UniversityAl AhsaSaudi Arabia
| | - Ali K. Ismael
- Department of Physics, Lancaster UniversityLancaster LA1 4YBUK
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