1
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Jang J, Jo JW, Ohto T, Yoon HJ. Seebeck Effect in Molecular Wires Facilitating Long-Range Transport. J Am Chem Soc 2024; 146:4922-4929. [PMID: 38324711 DOI: 10.1021/jacs.3c14012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The study of molecular wires facilitating long-range charge transport is of fundamental interest for the development of various technologies in (bio)organic and molecular electronics. Defining the nature of long-range charge transport is challenging as electrical characterization does not offer the ability to distinguish a tunneling mechanism from the other. Here, we show that investigation of the Seebeck effect provides the ability. We examine the length dependence of the Seebeck coefficient in electrografted bis-terpyridine Ru(II) complex films. The Seebeck coefficient ranges from 307 to 1027 μV/K, with an increasing rate of 95.7 μV/(K nm) as the film thickness increases to 10 nm. Quantum-chemical calculations unveil that the nearly overlapped molecular-orbital energy level of the Ru complex with the Fermi level accounts for the giant thermopower. Landauer-Büttiker probe simulations indicate that the significant length dependence evinces the Seebeck effect dominated by coherent near-resonant tunneling rather than thermal hopping. This study enhances our comprehension of long-range charge transport, paving the way for efficient electronic and thermoelectric materials.
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Affiliation(s)
- Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jeong Woo Jo
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Tatsuhiko Ohto
- Department of Materials Design Innovation Engineering, Nagoya University, Furo-cho, Chikusa-ku, Aichi 464-8603, Japan
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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2
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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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3
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He P, Daaoub AHS, Sangtarash S, Sadeghi H, Yoon HJ. Thermopower in Underpotential Deposition-Based Molecular Junctions. NANO LETTERS 2024; 24:1988-1995. [PMID: 38270106 PMCID: PMC10870761 DOI: 10.1021/acs.nanolett.3c04438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/18/2024] [Accepted: 01/18/2024] [Indexed: 01/26/2024]
Abstract
Underpotential deposition (UPD) is an intriguing means for tailoring the interfacial electronic structure of an adsorbate at a substrate. Here we investigate the impact of UPD on thermoelectricity occurring in molecular tunnel junctions based on alkyl self-assembled monolayers (SAMs). We observed noticeable enhancements in the Seebeck coefficient of alkanoic acid and alkanethiol monolayers, by up to 2- and 4-fold, respectively, upon replacement of a conventional Au electrode with an analogous bimetallic electrode, Cu UPD on Au. Quantum transport calculations indicated that the increased Seebeck coefficients are due to the UPD-induced changes in the shape or position of transmission resonances corresponding to gateway orbitals, which depend on the choice of the anchor group. Our work unveils UPD as a potent means for altering the shape of the tunneling energy barrier at the molecule-electrode contact of alkyl SAM-based junctions and hence enhancing thermoelectric performance.
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Affiliation(s)
- Peng He
- Department
of Chemistry, Korea University, Seoul 02841, Korea
| | - Abdalghani H. S. Daaoub
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Sara Sangtarash
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Hatef Sadeghi
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Hyo Jae Yoon
- Department
of Chemistry, Korea University, Seoul 02841, Korea
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4
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Lee J, Kim E, Cho J, Seok H, Woo G, Yu D, Jung G, Hwangbo H, Na J, Im I, Kim T. Remote-Controllable Interfacial Electron Tunneling at Heterogeneous Molecular Junctions via Tip-Induced Optoelectrical Engineering. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2305512. [PMID: 38057140 PMCID: PMC10837351 DOI: 10.1002/advs.202305512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/31/2023] [Indexed: 12/08/2023]
Abstract
Molecular electronics enables functional electronic behavior via single molecules or molecular self-assembled monolayers, providing versatile opportunities for hybrid molecular-scale electronic devices. Although various molecular junction structures are constructed to investigate charge transfer dynamics, significant challenges remain in terms of interfacial charging effects and far-field background signals, which dominantly block the optoelectrical observation of interfacial charge transfer dynamics. Here, tip-induced optoelectrical engineering is presented that synergistically correlates photo-induced force microscopy and Kelvin probe force microscopy to remotely control and probe the interfacial charge transfer dynamics with sub-10 nm spatial resolution. Based on this approach, the optoelectrical origin of metal-molecule interfaces is clearly revealed by the nanoscale heterogeneity of the tip-sample interaction and optoelectrical reactivity, which theoretically aligned with density functional theory calculations. For a practical device-scale demonstration of tip-induced optoelectrical engineering, interfacial tunneling is remotely controlled at a 4-inch wafer-scale metal-insulator-metal capacitor, facilitating a 5.211-fold current amplification with the tip-induced electrical field. In conclusion, tip-induced optoelectrical engineering provides a novel strategy to comprehensively understand interfacial charge transfer dynamics and a non-destructive tunneling control platform that enables real-time and real-space investigation of ultrathin hybrid molecular systems.
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Affiliation(s)
- Jinhyoung Lee
- School of Mechanical Engineering, Sungkyunkwan University (SKKU), Suwon-si, Gyeonggi-do, 16419, Republic of Korea
| | - Eungchul Kim
- AVP process development team, Samsung Electronics, Cheonan-si, Chungcheongnam-do, 31086, South Korea
| | - Jinill Cho
- School of Mechanical Engineering, Sungkyunkwan University (SKKU), Suwon-si, Gyeonggi-do, 16419, Republic of Korea
| | - Hyunho Seok
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Nano Science and Technology, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Gunhoo Woo
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Nano Science and Technology, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Dayoung Yu
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Nano Science and Technology, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Gooeun Jung
- Park Systems Corp, R&D Center, Suwon, 16229, Republic of Korea
| | - Hyeon Hwangbo
- Park Systems Corp, R&D Center, Suwon, 16229, Republic of Korea
| | - Jinyoung Na
- Park Systems Corp, R&D Center, Suwon, 16229, Republic of Korea
| | - Inseob Im
- Park Systems Corp, R&D Center, Suwon, 16229, Republic of Korea
| | - Taesung Kim
- School of Mechanical Engineering, Sungkyunkwan University (SKKU), Suwon-si, Gyeonggi-do, 16419, Republic of Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Nano Science and Technology, Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Nano Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
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5
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Frank T, Shmueli S, Cohen Jungerman M, Shekhter P, Selzer Y. Large Seebeck Values in Metal-Molecule-Semimetal Junctions Attained by a Gateless Level-Alignment Method. NANO LETTERS 2023; 23:10473-10479. [PMID: 37930154 DOI: 10.1021/acs.nanolett.3c03188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Molecular junctions are potentially highly efficient devices for thermal energy harvesting since their transmission properties can be tailored to break electron-hole transport symmetry and consequently yield high Seebeck and Peltier coefficients. Full harnessing of this potential requires, however, a capability to precisely position their Fermi level within the transmission landscape. Currently, with the lack of such a "knob" for two-lead junctions, their thermoelectric performance is too low for applications. Here we report that the requested capability can be realized by using junctions with a semimetal lead and molecules with a tailored effect of their monolayers on the work function of the semimetal. The approach is demonstrated by junctions with monolayers of alkanethiols on bismuth (Bi). Fermi-level tuning enables in this case increasing the Seebeck coefficient by more than 2 orders of magnitude. The underlying mechanism of this capability is discussed, as well as its general applicability.
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Affiliation(s)
- Tamar Frank
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shachar Shmueli
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Pini Shekhter
- The Tel Aviv Center for Nanoscience and Nanotechnology, Tel Aviv 69978, Israel
| | - Yoram Selzer
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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6
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Abstract
ConspectusUnderstanding the thermoelectric effects that convert energy between heat and electricity on a molecular scale is of great interest to the nanoscience community. As electronic devices continue to be miniaturized to nanometer scales, thermoregulation on such devices becomes increasingly critical. In addition, the study of molecular thermoelectricity provides information that cannot be accessed through conventional electrical conductance measurements. The field of molecular thermoelectrics aims to explore thermoelectric effects in electrode-molecule-electrode tunnel junctions and draw inferences on how the (supra)molecular structure of active molecules is associated with their thermopower. In this Account, we introduce a convenient and useful junction technique that enables thermovoltage measurements of one molecule thick films, self-assembled monolayers (SAMs), with reliability, and discuss the atomic-detailed structure-thermopower relations established by the technique. The technique relies on a microelectrode composed of non-Newtonian liquid metal, eutectic gallium-indium (EGaIn) covered with a native gallium oxide layer. The EGaIn electrode makes it possible to form thermoelectric contacts with the delicate structure of SAMs in a noninvasive fashion. A defined interface between SAM and the EGaIn electrode allows time-effective collection of large amounts of thermovoltage data, with great reproducibility, efficiency, and reliable interpretation and statistical analysis of the data. We also highlight recent efforts to utilize the EGaIn technique for probing molecular thermoelectricity and structure-thermopower relations. Using the technique, it was possible to unravel quantum-chemical mechanisms of thermoelectric functions, based on the Mott formula, in SAM-based large-area junctions, which in turn led us to set various hypotheses to boost the Seebeck coefficient. By validating the hypotheses again with the EGaIn technique, we revealed that the thermopower of junction increases through the reduction of the energy offset between accessible molecular orbital energy level and Fermi level or the tuning of broadening of the orbital energy level. Such alterations in the shape of energy topography of junction could be achieved through structural modifications in anchoring group and molecular backbone of SAM, and the bottom electrode. Molecular thermoelectrics offers a unique opportunity to build a well-defined nanoscale system and isolate an effect of interest from others, advancing fundamental understanding of charge transport across individual molecules and molecule-electrode interfaces. In the Account, we showed our recent work involving carefully designed molecular system that are relevant to answering the question of how thermopower differs between the tunneling and thermal-hopping regimes. The field of molecular thermoelectrics needs to address practical application-related issues, particularly molecular degradation in thermal environments. In this regard, we summarized the results highlighting the thermal instability of SAM-based junctions based on a traditional thiol anchor group and how to circumvent this problem. We also discussed the power factor (PF)─a practical parameter representing the efficiency for converting heat into electricity─of SAMs, evaluated using the EGaIn technique. In the Conclusion section of this Account, we present future challenges and perspectives.
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Affiliation(s)
- Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Peng He
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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7
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Eryilmaz IH, Chen YF, Mattana G, Orgiu E. Organic thermoelectric generators: working principles, materials, and fabrication techniques. Chem Commun (Camb) 2023; 59:3160-3174. [PMID: 36805573 DOI: 10.1039/d2cc04205c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Organic thermoelectricity is a blooming field of research that employs organic (semi)conductors to recycle waste heat through its partial conversion to electrical power. Such a conversion occurs by means of organic thermoelectric generator (OTEG) devices. The recent process on the synthesis of novel materials and on the understanding of doping mechanisms to increase conductivity has tremendously narrowed the gap between laboratory research and their application in actual applications. This Feature Article intends to highlight the impressive progress in materials and fabrication techniques for OTEGs made in recent years.
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Affiliation(s)
- Ilknur Hatice Eryilmaz
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
| | - Yan-Fang Chen
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
| | - Giorgio Mattana
- Université Paris Cité, ITODYS, CNRS, UMR 7086, 15 rue J.-A. de Baïf, F-75013 Paris, France.
| | - Emanuele Orgiu
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
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8
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Park S, Kim E, Choi Y, Jang J, Kwak K, Cho M, Yoon HJ. Thermoresponse of Odd-Even Effect in n-Alkanethiolate Self-Assembled Monolayers on Gold Substrates. Chemistry 2023; 29:e202203536. [PMID: 36548089 DOI: 10.1002/chem.202203536] [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: 11/14/2022] [Revised: 12/22/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
This study examines thermoresponse of odd-even effect in self-assembled monolayers (SAMs) of n-alkanethiolates (SCn , n=3-18) formed on template-stripped gold (AuTS ) using macro- and microscopic analytical techniques, contact angle goniometry (CAG) and vibrational sum frequency generation (VSFG) spectroscopy, respectively. Both CAG and VSFG analyses showed that the odd-even effect in liquid-like SAMs (n=3-9) disappeared upon heating at 50-70 °C, indicating that the heating led to increased structural disorder regardless of odd and even carbon numbers. In contrast, the opposite thermoresponse was observed for odd and even SCn molecules in wax- and solid-like SAMs (n=10-18). Namely, temperature-dependent orientational change of terminal CH3 relative to the surface normal was opposite for the odd and even molecules, thereby leading to mitigated odd-even effect. Our work offers important insights into thermoresponse of supramolecular structure in condensed organic matter.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
| | - Eunchan Kim
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Youngjin Choi
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
| | - Kyungwon Kwak
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Minhaeng Cho
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
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9
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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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10
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Fan X, Wang R, Li M, Tang X, Xu C, Hao Q, Qiu T. High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects. NANOSCALE HORIZONS 2023; 8:195-201. [PMID: 36468209 DOI: 10.1039/d2nh00450j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Optical whispering-gallery-mode (WGM) cavities have gained considerable interest because of their unique properties of enhanced light-matter interactions. Conventional WGM sensing is based on the mechanisms of mode shift, mode broadening, or mode splitting, which requires a small mode volume and an ultrahigh Q-factor. Besides, WGM sensing suffers from a lack of specificity in identifying substances, and additional chemical functionalization or incorporation of plasmonic materials is required for achieving good specificity. Herein, we propose a new sensing method based on an individual WGM cavity to achieve ultrasensitive and high-specificity molecular sensing, which combines the features of enhanced light-matter interactions on the WGM cavity and the "fingerprint spectrum" of surface-enhanced Raman scattering (SERS). This method identifies the substance by monitoring the Raman signal enhanced by the WGM cavity rather than monitoring the variation of the WGM itself. Therefore, ultrasensitive and high-specificity molecular sensing can be accomplished even on a low-Q cavity. The working principles of the proposed sensing method were also systematically investigated in terms of photoinduced charge transfer, Purcell effect, and optical resonance coupling. This work provides a new WGM sensing approach as well as a strategy for the design of a high-performance SERS substrate by creating an optical resonance mode.
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Affiliation(s)
- Xingce Fan
- School of Physics, Southeast University, Nanjing 211189, China.
| | - Ru Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China.
| | - Mingze Li
- School of Physics, Southeast University, Nanjing 211189, China.
| | - Xiao Tang
- School of Physics, Southeast University, Nanjing 211189, China.
| | - Chunxiang Xu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China.
| | - Qi Hao
- School of Physics, Southeast University, Nanjing 211189, China.
| | - Teng Qiu
- School of Physics, Southeast University, Nanjing 211189, China.
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11
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Li Y, Root SE, Belding L, Park J, Yoon HJ, Huang C, Baghbanzadeh M, Whitesides GM. Charge Transport Measured Using the EGaIn Junction through Self-Assembled Monolayers Immersed in Organic Liquids. J Phys Chem B 2023; 127:407-424. [PMID: 36580625 DOI: 10.1021/acs.jpcb.2c07901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This paper describes measurements of charge transport by tunneling through molecular junctions comprising a self-assembled monolayer (SAM) supported by a template-stripped metal bottom electrode (MTS), which has been immersed in an organic liquid and contacted by a conical Ga2O3/EGaIn top electrode. These junctions formed in organic liquids are robust; they show stabilities and yields similar to those formed in air. We formed junctions under seven external environments: (I) air, (II) perfluorocarbons, (III) linear hydrocarbons, (IV) cyclic hydrocarbons, (V) aromatic compounds, (VI) large, irregularly shaped hydrocarbons, and (VII) dimethyl siloxanes. Several different lengths of SAMs of n-alkanethiolates, S(CH2)n-1CH3 with n = 4-18, and two different kinds of bottom electrodes (AgTS or AuTS) are employed to assess the mechanism underlying the observed changes in tunneling currents. Measurements of current density through junctions immersed in perfluorocarbons (II) are comparable to junctions measured in air. Junctions immersed in other organic liquids show reductions in the values of current density, compared to the values in air, ranging from 1 (III) to 5 orders of magnitude (IV). We interpret the most plausible mechanism for these reductions in current densities to be an increase in the length of the tunneling pathway, reflecting the formation of thin (0.5-1.5 nm) liquid films at the interface between the SAM and the Ga2O3/EGaIn electrode. Remarkably, the thickness of the liquid film─estimated by the simplified Simmons model, measurements of electrical breakdown of the junction, and simulations of molecular dynamics─is consistent with the existing observations of structured liquid layers that form between two flat interfaces from measurements obtained by the surface force apparatus. These results suggest the use of the EGaIn junction and measurements of charge transport by tunneling as a new form of surface analysis, with the applications in the study of near-surface, weak, molecular interactions and the behavior of liquid films adjacent to non-polar interfaces.
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Affiliation(s)
- Yuan Li
- Department of Chemistry, Tsinghua University, Beijing100086, China.,Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
| | - Samuel E Root
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
| | - Lee Belding
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
| | - Junwoo Park
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States.,Department of Chemistry, Sogang University, Seoul04107, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul02841, Korea
| | - Cancan Huang
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
| | - Mostafa Baghbanzadeh
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
| | - George M Whitesides
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts02138, United States
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12
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Park S, Jang J, Tanaka Y, Yoon HJ. High Seebeck Coefficient Achieved by Multinuclear Organometallic Molecular Junctions. NANO LETTERS 2022; 22:9693-9699. [PMID: 36441166 DOI: 10.1021/acs.nanolett.2c03974] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
This paper describes the thermoelectric properties of molecular junctions incorporating multinuclear ruthenium alkynyl complexes that comprise Ru(dppe)2 [dppe = 1,2-bis(diphenylphosphino)ethane] fragments and diethylnyl aromatic bridging ligands with thioether anchors. Using the liquid metal technique, the Seebeck coefficient was examined as a function of metal nuclearity, oxidation state, and substituent on the organic ligand backbone. High Seebeck coefficients up to 73 μV/K and appreciable thermal stability with thermovoltage up to ∼3.3 mV at a heating temperature of 423 K were observed. An unusually high proximity of the highest occupied molecular orbital (HOMO) energy level to the Fermi level was revealed to give the remarkable thermoelectric performance as suggested by combined experiments and calculations. This work offers important insights into the development of molecular-scale devices for efficient thermoregulation and heat-to-electricity conversion.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Yuya Tanaka
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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13
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Estimating the Number of Molecules in Molecular Junctions Merely Based on the Low Bias Tunneling Conductance at Variable Temperature. Int J Mol Sci 2022; 23:ijms232314985. [PMID: 36499309 PMCID: PMC9737784 DOI: 10.3390/ijms232314985] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 11/23/2022] [Accepted: 11/25/2022] [Indexed: 12/05/2022] Open
Abstract
Temperature (T) dependent conductance G=G(T) data measured in molecular junctions are routinely taken as evidence for a two-step hopping mechanism. The present paper emphasizes that this is not necessarily the case. A curve of lnG versus 1/T decreasing almost linearly (Arrhenius-like regime) and eventually switching to a nearly horizontal plateau (Sommerfeld regime), or possessing a slope gradually decreasing with increasing 1/T is fully compatible with a single-step tunneling mechanism. The results for the dependence of G on T presented include both analytical exact and accurate approximate formulas and numerical simulations. These theoretical results are general, also in the sense that they are not limited, e.g., to the (single molecule electromigrated (SET) or large area EGaIn) fabrication platforms, which are chosen for exemplification merely in view of the available experimental data needed for analysis. To be specific, we examine in detail transport measurements for molecular junctions based on ferrocene (Fc). As a particularly important finding, we show how the present analytic formulas for G=G(T) can be utilized to compute the ratio f=Aeff/An between the effective and nominal areas of large area Fc-based junctions with an EGaIn top electrode. Our estimate of f≈0.6×10-4 is comparable with previously reported values based on completely different methods for related large area molecular junctions.
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14
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Park S, Jo JW, Jang J, Ohto T, Tada H, Yoon HJ. Thermopower in Transition from Tunneling to Hopping. NANO LETTERS 2022; 22:7682-7689. [PMID: 36067367 DOI: 10.1021/acs.nanolett.2c03083] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The Seebeck effect of a molecular junction in a hopping regime or tunneling-to-hopping transition remains uncertain. This paper describes the Seebeck effect in molecular epitaxy films (OPIn where n = 1-9) based on imine condensation between an aryl amine and aldehyde and investigates how the Seebeck coefficient (S, μV/K) varies at the crossover region. The S value of OPIn linearly increased with increasing the molecular length (d, nm), ranging from 7.2 to 38.0 μV/K. The increasing rate changed from 0.99 to 0.38 μV·K-1 Å-1 at d = 3.4 nm (OPI4). Combined experimental and theoretical studies indicated that such a change stems from a tunneling-to-hopping transition, and the small but detectable length-dependence of thermopower in the long molecules originates from the gradual reduction of the tunneling contribution to the broadening of molecular orbital energy level, rather than its relative position to the Fermi level. Our work helps to bridge the gap between bulk and nanoscale thermoelectric systems.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jeong Woo Jo
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Tatsuhiko Ohto
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Hirokazu Tada
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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15
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Duan L, Zhang Y, Zhao J, Zhang J, Li Q, Lu Q, Fu L, Liu J, Liu Q. Unique Surface Fluorescence Induced from the Core-Shell Structure of Gallium-Based Liquid Metals Prepared by Thermal Oxidation Processing. ACS APPLIED MATERIALS & INTERFACES 2022; 14:39654-39664. [PMID: 35979950 DOI: 10.1021/acsami.2c12420] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Liquid metals (LMs) have emerged as promising functional materials that combine the properties of both liquid and metal. These characteristics enabled them to find applications in many fields. However, the LMs usually can only display a silver-white physical appearance, which limits their further applications in the fields with the imposition of stringent requirements for color and aesthetics. Herein, we report that the surface of LMs was transformed directly from metal to fluorescent semiconductor layer by an example of eutectic GaInSn (eGaInSn) induced by thermal oxidation. Specifically, a core-shell structure is formed from the fluorescent layer and the LMs. The shell endows the LMs with fluorescence without affecting their interior fluidity and conductivity. In particular, the formation process as well as the degree of crystallization, phase transformation, and light emission of the fluorescent oxide shell on the surface of LMs is regulated by the component content. A thorough analysis of surface morphology, composition, structure, and properties of the fluorescent shell suggests that the Ga2O3 layer is formed on the surface of gallium-based LMs after their immersion in deionized water. Subsequently, thermal oxidation results in the formation of the β-Ga2O3 shell on the surface of liquid metals. Importantly, abundant oxygen vacancies (VO) in β-Ga2O3 as the donors and the gallium vacancies (VGa), gallium-oxygen vacancy pairs (VO-VGa), defect energy levels, and intrinsic defects as the acceptors enabled the light emission. The fluorescent LMs have promising potential for flexible lighting and displays, anticounterfeiting measures, sensing, and chameleon robots.
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Affiliation(s)
- Liangfei Duan
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Yumin Zhang
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Jianhong Zhao
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Jin Zhang
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Qian Li
- CAS Key Laboratory of Cryogenics and Beijing Key Laboratory of Cryo- Biomedical Engineering, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Qingjie Lu
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Li Fu
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
| | - Jing Liu
- CAS Key Laboratory of Cryogenics and Beijing Key Laboratory of Cryo- Biomedical Engineering, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- Department of Biomedical Engineering School of Medicine Tsinghua University, Beijing 100084, China
| | - Qingju Liu
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, China
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16
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Du C, Wang Z, Chen J, Martin A, Raturi D, Thuo M. Role of Nanoscale Roughness and Polarity in Odd–Even Effect of Self‐Assembled Monolayers. Angew Chem Int Ed Engl 2022; 61:e202205251. [PMID: 35580255 PMCID: PMC9400998 DOI: 10.1002/anie.202205251] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Indexed: 11/13/2022]
Abstract
The dependency of substrate roughness on wetting properties of self‐assembled monolayers (SAMs) has been studied extensively, but most previous studies used limited selection of probing liquid and range of surface roughness. These studies disregarded the limit to observation of sub‐nanometer odd–even parity effect, hence are inconclusive. In this work we report the role of solvent polarity on the roughness‐dependency of wetting behavior of SAMs by studying static con‐tact angle of a variety of probing liquids, with different polarities, on SAMs formed on Ag‐based substrate with different surface morphology. By overlapping the roughness ranges with previous studies on Au, the limitation of surface roughness (RMS=1 nm) to observation of the odd–even effect using water as probing liquid was confirmed, but other probing liquid yielded different roughness‐dependent behaviors, with more polar solvent showing more roughness‐dependent behavior. Based on these observations, we concluded that there exists a phase‐transition like behavior in SAMs due to substrate roughness and molecule chain length, but whose determination is dependent on the probing liquid.
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Affiliation(s)
- Chuanshen Du
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Zhengjia Wang
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Jiahao Chen
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
| | - Andrew Martin
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Dhruv Raturi
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Martin Thuo
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
- Biopolymer and Biocomposites Research Team Center for Bioplastics and Biocomposites Iowa State University 1041 Food Sciences Building Ames IA 50011 USA
- Department of Electrical Engineering Iowa State University 2215 Coover Hall Ames IA 50011 USA
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17
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Du C, Wang Z, Chen J, Martin A, Raturi D, Thuo M. Role of Nanoscale Roughness and Polarity in Odd–Even Effect of Self‐Assembled Monolayers. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Chuanshen Du
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Zhengjia Wang
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Jiahao Chen
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
| | - Andrew Martin
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Dhruv Raturi
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Martin Thuo
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
- Biopolymer and Biocomposites Research Team Center for Bioplastics and Biocomposites Iowa State University 1041 Food Sciences Building Ames IA 50011 USA
- Department of Electrical Engineering Iowa State University 2215 Coover Hall Ames IA 50011 USA
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18
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Liu R, Gong L, Zhu X, Zhu S, Wu X, Xue T, Yan L, Du J, Gu Z. Transformable Gallium-Based Liquid Metal Nanoparticles for Tumor Radiotherapy Sensitization. Adv Healthc Mater 2022; 11:e2102584. [PMID: 35114075 DOI: 10.1002/adhm.202102584] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 01/10/2022] [Indexed: 12/23/2022]
Abstract
The past decades have witnessed an increasing interest in the exploration of room temperature gallium-based liquid metal (LM) in the field of microfluidics, soft robotics, electrobiology, and biomedicine. Herein, this study for the first time reports the utilization of nanosized gallium-indium eutectic alloys (EGaIn) as a radiosensitizer for enhancing tumor radiotherapy. The sodium alginate (Alg) functionalized EGaIn nanoparticles (denoted as EGaIn@Alg NPs) are prepared via a simple one-step synthesis method. The coating of Alg not only prevents the aggregation and oxidation of EGaIn NPs in an aqueous solution but also enables them low cytotoxicity, good biocompatibility, and in-situ formation of gels in the Ca2+ enriched tumor physiological microenvironment. Due to the metallic nature and high density, EGaIn can increase the generation of reactive oxygen species under the irradiation of X-ray, which can not only directly promote DNA damage and cell apoptosis, but also show an efficient tumor inhibition rate in vivo. Moreover, EGaIn@Alg NPs hold good performance as computed tomography (CT) and photoacoustic tomography (PAT) imaging contrast agents. This work provides an alternative nanotechnology strategy for tumor radiosensitization and also enlarges the biomedical application of gallium-based LM.
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Affiliation(s)
- Ruixue Liu
- School of Forensic Medicine Shanxi Medical University Jinzhong Shanxi Province 030619 China
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
| | - Linji Gong
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
- College of Materials Science and Optoelectronic Technology University of Chinese Academy of Sciences Beijing 100049 China
| | - Xianyu Zhu
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
| | - Shuang Zhu
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
- College of Materials Science and Optoelectronic Technology University of Chinese Academy of Sciences Beijing 100049 China
| | - Xiaochen Wu
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
| | - Tingyu Xue
- Collaborative Innovation Center for Molecular Imaging of Precision Medicine Shanxi Medical University Taiyuan Shanxi Province 030001 China
| | - Liang Yan
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
| | - Jiangfeng Du
- School of Forensic Medicine Shanxi Medical University Jinzhong Shanxi Province 030619 China
- Collaborative Innovation Center for Molecular Imaging of Precision Medicine Shanxi Medical University Taiyuan Shanxi Province 030001 China
- Department of Radiology First Hospital of Shanxi Medical University Taiyuan Shanxi Province 030001 China
| | - Zhanjun Gu
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety and CAS Center for Excellence in Nanoscience Institute of High Energy Physics and National Center for Nanoscience and Technology Chinese Academy of Sciences Beijing 100049 China
- College of Materials Science and Optoelectronic Technology University of Chinese Academy of Sciences Beijing 100049 China
- GBA Research Innovation Institute for Nanotechnology Guangzhou 510700 China
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19
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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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20
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Park S, Kang S, Yoon HJ. Thermopower of Molecular Junction in Harsh Thermal Environments. NANO LETTERS 2022; 22:3953-3960. [PMID: 35575639 DOI: 10.1021/acs.nanolett.2c00422] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Molecular junctions can be miniaturized devices for heat-to-electricity conversion application, yet these operate only in mild thermal environments (less than 323 K) because thiol, the most widely used anchor moiety for chemisorption of active molecules onto surface of electrode, easily undergoes thermal degradation. N-Heterocyclic carbene (NHC) can be an alternative to traditional thiol anchor for producing ultrastable thermoelectric molecular junctions. Our experiments showed that the NHC-based molecular junctions withstood remarkably high temperatures up to 573 K, exhibiting consistent Seebeck effect and thermovoltage up to approximately |1900 μV|. Our work advances our understanding of molecule-electrode contact in the Seebeck effect, providing a roadmap for constructing robust and efficient organic thermoelectric devices.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Seohyun Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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21
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Duan L, Zhang Y, Zhao J, Zhang J, Li Q, Chen Y, Liu J, Liu Q. Unique and Excellent Paintable Liquid Metal for Fluorescent Displays. ACS APPLIED MATERIALS & INTERFACES 2022; 14:23951-23963. [PMID: 35537086 DOI: 10.1021/acsami.2c02714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A liquid metal (LM) generally has excellent electrical conductivity, thermal conductivity, flexibility, fluidity, and reflectivity. Innovative electronics using a LM to paint colorful fluorescent patterns may be applied to many important fields. Herein we propose, for the first time, the use of a LM to paint fluorescent patterns in the field of natural science. An LM containing a main-group metal (Ga50.25Bi8.28In28.2Sn13.27) is used to paint a uniform alloy film on a ceramic substrate. The painting is not restricted by any curved surface, shape, or size, which therefore gives the LM diverse adaptability. We have adopted the strategy of "painting-annealing-dealloying" through which LM can easily be diffused and doped into the substrate to produce various defects. Defects, my themselves or through their interactions, can produce different colors of emitted light. The primary fluorescence colors, such as purple, yellow, blue, and white, have been painted with the LM. Importantly, the brightness and color coordinates can be adjusted by changing the LM composition or annealing temperature, and intricate, delicate, colorful fluorescence patterns can be produced. Due to the unique painting form, colorful fluorescence, high stability, corrosion resistance, and low cost of the technique used for the LM, it can be used for displays, lighting panels, flexible electronic circuits, anticounterfeiting devices, and sensors.
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Affiliation(s)
- Liangfei Duan
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
| | - Yumin Zhang
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
| | - Jianhong Zhao
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
| | - Jin Zhang
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
| | - Qian Li
- CAS Key Laboratory of Cryogenics and Beijing Key Laboratory of Cryo- Biomedical Engineering, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Yu Chen
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
| | - Jing Liu
- CAS Key Laboratory of Cryogenics and Beijing Key Laboratory of Cryo- Biomedical Engineering, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Qingju Liu
- Yunnan Key Laboratory for Micro/Nano Materials & Technology, International Joint Research Center for Optoelectronic and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, People's Republic of China
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22
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Electrocapillary Actuation of Liquid Metal in Microchannels. MICROMACHINES 2022; 13:mi13040572. [PMID: 35457877 PMCID: PMC9032191 DOI: 10.3390/mi13040572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/01/2022] [Accepted: 04/01/2022] [Indexed: 11/16/2022]
Abstract
Controllable deformation of liquid metal by electrocapillary actuation (ECA) is empirically characterized in fluidic channels at the sub-millimeter-length scale. In 100-µm-deep channels of varying widths, the Galinstan liquid metal could move at velocities of more than 40 mm/s. The liquid metal could extend more than 2.5 mm into the channels at an electrocapillary actuation voltage of 3 V DC. The dynamic behavior of the liquid metal as it moves in the microchannels is described. These results are useful for designing microsystems that use liquid metal as a functional material.
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23
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Ashkarran AA, Hosseini A, Loloee R, Perry G, Lee KB, Lund M, Ejtehadi MR, Mahmoudi M. Conformation- and phosphorylation-dependent electron tunnelling across self-assembled monolayers of tau peptides. J Colloid Interface Sci 2022; 606:2038-2050. [PMID: 34749450 DOI: 10.1016/j.jcis.2021.09.185] [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: 05/31/2021] [Revised: 09/17/2021] [Accepted: 09/28/2021] [Indexed: 10/20/2022]
Abstract
We report on charge transport across self-assembled monolayers (SAMs) of short tau peptides by probing the electron tunneling rates and quantum mechanical simulation. We measured the electron tunneling rates across SAMs of carboxyl-terminated linker molecules (C6H12O2S) and short cis-tau (CT) and trans-tau (TT) peptides, supported on template-stripped gold (AuTS) bottom electrode, with Eutectic Gallium-Indium (EGaIn)(EGaIn) top electrode. Measurements of the current density across thousands of AuTS/linker/tau//Ga2O3/EGaIn single-molecule junctions show that the tunneling current across CT peptide is one order of magnitude lower than that of TT peptide. Quantum mechanical simulation demonstrated a wider energy bandgap of the CT peptide, as compared to the TT peptide, which causes a reduction in its electron tunneling current. Our findings also revealed the critical role of phosphorylation in altering the charge transport characteristics of short peptides; more specifically, we found that the presence of phosphate groups can reduce the energy band gap in tau peptides and alter their electrical properties. Our results suggest that conformational and phosphorylation of short peptides (e.g., tau) can significantly change their charge transport characteristics and energy levels.
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Affiliation(s)
- Ali Akbar Ashkarran
- Precision Health Program and Department of Radiology, Michigan State University, East Lansing, MI 48824, USA.
| | - Atiyeh Hosseini
- Division of Theoretical Chemistry, Lund University, Lund, Sweden; Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, Iran
| | - Reza Loloee
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
| | - George Perry
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Ki-Bum Lee
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Mikael Lund
- Division of Theoretical Chemistry, Lund University, Lund, Sweden.
| | | | - Morteza Mahmoudi
- Precision Health Program and Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
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24
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Park S, Yoon HJ. Thermal and Thermoelectric Properties of SAM-Based Molecular Junctions. ACS APPLIED MATERIALS & INTERFACES 2021; 14:22818-22825. [PMID: 34961308 DOI: 10.1021/acsami.1c20840] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In molecular thermoelectrics, the thermopower of molecular junctions is closely interlinked with their thermal properties; however, the detailed relationship between them remains uncertain. This study systematically investigates the thermal properties of self-assembled monolayer (SAM)-based molecular junctions and relates them to the thermoelectric performance of the junctions. The electrode temperatures for the bare AuTS, AuTS/EGaIn, and AuTS/TPT SAM//Ga2O3/EGaIn samples placed on a hot chuck were measured under different conditions, such as air vs vacuum and the presence and absence of thermal grease, which generates a heat conduction channel from a hot chuck to gold. It was revealed that the SAM was the most efficient thermal resistor, which was responsible for the creation of a temperature differential (ΔT) across the junction; ΔT in an air atmosphere is overestimated to some extent, and air mainly contributes to large dispersions of thermovoltage (ΔV) data. While junction measurements in air were possible at low ΔT (up to 13 K), the new optimal condition, under a vacuum and with thermal grease, allowed us to examine a wide temperature range up to ΔT = 40 K and obtain a more reliable Seebeck coefficient (S, μV/K). The value of S under the new condition was ∼1.4 times higher than that measured in air without thermal grease. Our study shows the potential of liquid-metal-based junctions to reliably investigate heat conduction across nanometer-thick organic films and elaborates on how the thermal properties of molecular junctions affect their thermoelectric performance.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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25
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Tian L, Martine E, Yu X, Hu W. Amine-Anchored Aromatic Self-Assembled Monolayer Junction: Structure and Electric Transport Properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12223-12233. [PMID: 34606290 DOI: 10.1021/acs.langmuir.1c02194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We studied the structure and transport properties of aromatic amine self-assembled monolayers (NH2-SAMs) on an Au surface. The oligophenylene and oligoacene amines with variable lengths can form a densely packed and uniform monolayer under proper assembly conditions. Molecular junctions incorporating an eutectic Ga-In (EGaIn) top electrode were used to characterize the charge transport properties of the amine monolayer. The current density J of the junction decreases exponentially with the molecular length (d), as J = J0 exp(-βd), which is a sign of tunneling transport, with indistinguishable values of J0 and β for NH2-SAMs of oligophenylene and oligoacene, indicating a similar molecule-electrode contact and tunneling barrier for two groups of molecules. Compared with the oligophenylene and oligoacene molecules with thiol (SH) as the anchor group, a similar β value (∼0.35 Å-1) of the aromatic NH2-SAM suggests a similar tunneling barrier, while a lower (by 2 orders of magnitude) injection current J0 is attributed to lower electronic coupling Γ of the amine group with the electrode. These observations are further supported by single-level tunneling model fitting. Our study here demonstrates the NH2-SAMs can work as an effective active layer for molecular junctions, and provide key physical parameters for the charge transport, paving the road for their applications in functional devices.
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Affiliation(s)
- Lixian Tian
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Esther Martine
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Xi Yu
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
| | - Wenping Hu
- Tianjin Key Laboratory of Molecular Optoelectronic Science, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
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26
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Park S, Kim HR, Kim J, Hong BH, Yoon HJ. Enhanced Thermopower of Saturated Molecules by Noncovalent Anchor-Induced Electron Doping of Single-Layer Graphene Electrode. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2103177. [PMID: 34453364 DOI: 10.1002/adma.202103177] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 06/22/2021] [Indexed: 06/13/2023]
Abstract
Enhancing thermopower is a key goal in organic and molecular thermoelectrics. Herein, it is shown that introducing noncovalent contact with a single-layer graphene (SLG) electrode improves the thermopower of saturated molecules as compared to the traditional gold-thiolate covalent contact. Thermoelectric junction measurements with a liquid-metal technique reveal that the value of Seebeck coefficient in large-area junctions based on n-alkylamine self-assembled monolayers (SAMs) on SLG is increased up to fivefold compared to the analogous junction based on n-alkanethiolate SAMs on gold. Experiments with Raman spectroscopy and field-effect transistor analysis indicate that such enhancements benefit from the creation of new in-gap states and electron doping through noncovalent interaction between the amine anchor and the SLG electrode, which leads to a reduced energy offset between the Fermi level and the transport channel. This work demonstrates that control of interfacial bonding nature in molecular junctions improves the Seebeck effect in saturated molecules.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
| | - Hwa Rang Kim
- Department of Chemistry, Seoul National University, Seoul, 08826, South Korea
| | - Juhee Kim
- Department of Chemistry, Seoul National University, Seoul, 08826, South Korea
| | - Byung-Hee Hong
- Department of Chemistry, Seoul National University, Seoul, 08826, South Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
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27
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Gehring P, Sowa JK, Hsu C, de Bruijckere J, van der Star M, Le Roy JJ, Bogani L, Gauger EM, van der Zant HSJ. Complete mapping of the thermoelectric properties of a single molecule. NATURE NANOTECHNOLOGY 2021; 16:426-430. [PMID: 33649585 DOI: 10.1038/s41565-021-00859-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 12/16/2020] [Indexed: 06/12/2023]
Abstract
Theoretical studies suggest that mastering the thermocurrent through single molecules can lead to thermoelectric energy harvesters with unprecedentedly high efficiencies.1-6 This can be achieved by engineering molecule length,7 optimizing the tunnel coupling strength of molecules via chemical anchor groups8 or by creating localized states in the backbone with resulting quantum interference features.4 Empirical verification of these predictions, however, faces considerable experimental challenges and is still awaited. Here we use a novel measurement protocol that simultaneously probes the conductance and thermocurrent flow as a function of bias voltage and gate voltage. We find that the resulting thermocurrent is strongly asymmetric with respect to the gate voltage, with evidence of molecular excited states in the thermocurrent Coulomb diamond maps. These features can be reproduced by a rate-equation model only if it accounts for both the vibrational coupling and the electronic degeneracies, thus giving direct insight into the interplay of electronic and vibrational degrees of freedom, and the role of spin entropy in single molecules. Overall these results show that thermocurrent measurements can be used as a spectroscopic tool to access molecule-specific quantum transport phenomena.
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Affiliation(s)
- Pascal Gehring
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
- IMCN/NAPS, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
| | - Jakub K Sowa
- Department of Materials, University of Oxford, Oxford, United Kingdom
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Chunwei Hsu
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Joeri de Bruijckere
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Martijn van der Star
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jennifer J Le Roy
- Department of Materials, University of Oxford, Oxford, United Kingdom
| | - Lapo Bogani
- Department of Materials, University of Oxford, Oxford, United Kingdom
| | - Erik M Gauger
- SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, UK
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28
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Kang S, Byeon SE, Yoon HJ. N
‐Heterocyclic
Carbene Anchors in Electronics Applications. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12261] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Seohyun Kang
- Department of Chemistry Korea University Seoul 02841 Republic of Korea
| | - Seo Eun Byeon
- Department of Chemistry Korea University Seoul 02841 Republic of Korea
| | - Hyo Jae Yoon
- Department of Chemistry Korea University Seoul 02841 Republic of Korea
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29
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Lee HJ, Cho SJ, Kang H, He X, Yoon HJ. Achieving Ultralow, Zero, and Inverted Tunneling Attenuation Coefficients in Molecular Wires with Extended Conjugation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2005711. [PMID: 33543557 DOI: 10.1002/smll.202005711] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/22/2020] [Indexed: 06/12/2023]
Abstract
Molecular tunnel junctions are organic devices miniaturized to the molecular scale. They serve as a versatile toolbox that can systematically examine charge transport behaviors at the atomic level. The electrical conductance of the molecular wire that bridges the two electrodes in a junction is significantly influenced by its chemical structure, and an intrinsically poor conductance is a major barrier for practical applications toward integrating individual molecules into electronic circuitry. Therefore, highly conjugated molecular wires are attractive as active components for the next-generation electronic devices, owing to the narrow highest occupied molecular orbital-lowest occupied molecular orbital gaps provided by their extended π-building blocks. This article aims to highlight the significance of highly conductive molecular wires in molecular electronics, the structures of which are inspired from conductive organic polymers, and presents a body of discussion on molecular wires exhibiting ultralow, zero, or inverted attenuation of tunneling probability at different lengths, along with future directions.
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Affiliation(s)
- Hyun Ju Lee
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
| | - Soo Jin Cho
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
| | - Hungu Kang
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
| | - Xin He
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul, 02841, South Korea
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30
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Bhadra P, Siu SWI. Effect of Concentration, Chain Length, Hydrophobicity, and an External Electric Field on the Growth of Mixed Alkanethiol Self-Assembled Monolayers: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:1913-1924. [PMID: 33503375 DOI: 10.1021/acs.langmuir.0c03414] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Growing functionalized self-assembled monolayers (SAMs) with fewer defects and lower cost is the focus of ongoing investigations. In the present study, molecular dynamics simulations were performed to investigate the process of SAM formation on a gold substrate from mixed alkanethiolates in ethanol solution. Using the mixed-SAM system of 11-mercaptoundecanoic acid (MUA) with either 1-decanethiol (C9CH3) or 6-mercaptohexanol (C6OH) in a 3:7 ratio as the standard SAM model, we systematically investigated the effects of the concentration, chain length, functional group, and an external electric field on SAM growth. The results showed that the initial growth rate and surface coverage of the SAM are dependent on the ligand concentration. At a certain high concentration (about 1.2-1.5 times the minimum concentration), the final surface coverage is optimal. Reducing the chain length and increasing the proportion of hydrophobic diluting molecules are effective ways to improve the surface coverage, but the compositional ligands have to be changed, which may not be desirable for the functional requirements of SAMs. Furthermore, by investigating the behavior of the alkanethiolates and ethanol solvent under an applied external field, we find that a strong electric field with a proper field direction can facilitate the generation of defect-free monolayers. These findings will contribute to the understanding of mixed-SAM formation and provide insight into experimental design for efficient and effective SAM formation.
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Affiliation(s)
- Pratiti Bhadra
- Department of Computer and Information Science, University of Macau, Taipa, Macau
| | - Shirley W I Siu
- Department of Computer and Information Science, University of Macau, Taipa, Macau
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31
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Cho N, Kang S, Lee H, Kang H, Kong GD, Yoon HJ. Superexchange Coupling-Induced Enhancements of Thermoelectric Performance in Saturated Molecules. NANO LETTERS 2021; 21:360-366. [PMID: 33275442 DOI: 10.1021/acs.nanolett.0c03736] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
To develop thermoelectric devices, it is of the utmost importance to design organic building blocks to have efficient thermopower. Whereas conjugated and aromatic molecules with intrinsic narrow band gaps are attractive candidates to achieve efficient thermoelectric properties, saturated molecules are usually avoided owing to intrinsically poor thermopower. Here we demonstrate that thermopower of saturated molecules can be enhanced by superexchange coupling. Specifically, thermoelectric properties of large-area junctions that contain self-assembled monolayers of oligo(ethylene glycol) thiolates and alkanethiolates are compared. Through large-area thermopower measurements using a liquid metal top electrode, we show that the superexchange coupling enhances the Seebeck coefficient and counterintuitively leads to an increase in the Seebeck coefficient with increasing the length in a certain conformation. The improved thermoelectric performance is attributed to the superexchange-induced enhanced ability to mediate metal wave function in junctions. Our work offers new insights for improving the thermoelectric performance of nonconjugated, saturated molecules.
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Affiliation(s)
- Nayoung Cho
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Seohyun Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyunju Lee
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hungu Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Gyu Don Kong
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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32
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Thermal Transport in Graphene Oxide Films: Theoretical Analysis and Molecular Dynamics Simulation. NANOMATERIALS 2020; 10:nano10020285. [PMID: 32046079 PMCID: PMC7075120 DOI: 10.3390/nano10020285] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/19/2020] [Accepted: 01/20/2020] [Indexed: 11/16/2022]
Abstract
As a derivative material of graphene, graphene oxide films hold great promise in thermal management devices. Based on the theory of Fourier formula, we deduce the analytical formula of the thermal conductivity of graphene oxide films. The interlaminar thermal property of graphene oxide films is studied using molecular dynamics simulation. The effect of vacancy defect on the thermal conductance of the interface is considered. The interfacial heat transfer efficiency of graphene oxide films strengthens with the increasing ratio of the vacancy defect. Based on the theoretical model and simulation results, we put forward an optimization model of the graphene oxide film. The optimal structure has the minimum overlap length and the maximum thermal conductivity. An estimated optimal overlap length for the GO (graphene-oxide) films with degree of oxidation 10% and density of vacancy defect 2% is 0.33 μm. Our results can provide effective guidance to the rationally designed defective microstructures on engineering thermal transport processes.
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