1
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Insight mechanism of nano iron difluoride cathode material for high-energy lithium-ion batteries: a review. J Solid State Electrochem 2022. [DOI: 10.1007/s10008-022-05287-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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2
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Nanofabrication Techniques in Large-Area Molecular Electronic Devices. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10176064] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.
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3
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Nano-engineering the material structure of preferentially oriented nano-graphitic carbon for making high-performance electrochemical micro-sensors. Sci Rep 2020; 10:9444. [PMID: 32523076 PMCID: PMC7286892 DOI: 10.1038/s41598-020-66408-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/11/2020] [Indexed: 12/28/2022] Open
Abstract
Direct synthesis of thin-film carbon nanomaterials on oxide-coated silicon substrates provides a viable pathway for building a dense array of miniaturized (micron-scale) electrochemical sensors with high performance. However, material synthesis generally involves many parameters, making material engineering based on trial and error highly inefficient. Here, we report a two-pronged strategy for producing engineered thin-film carbon nanomaterials that have a nano-graphitic structure. First, we introduce a variant of the metal-induced graphitization technique that generates micron-scale islands of nano-graphitic carbon materials directly on oxide-coated silicon substrates. A novel feature of our material synthesis is that, through substrate engineering, the orientation of graphitic planes within the film aligns preferentially with the silicon substrate. This feature allows us to use the Raman spectroscopy for quantifying structural properties of the sensor surface, where the electrochemical processes occur. Second, we find phenomenological models for predicting the amplitudes of the redox current and the sensor capacitance from the material structure, quantified by Raman. Our results indicate that the key to achieving high-performance micro-sensors from nano-graphitic carbon is to increase both the density of point defects and the size of the graphitic crystallites. Our study offers a viable strategy for building planar electrochemical micro-sensors with high-performance.
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4
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Droghetti A, Rungger I. Enhanced thermopower in covalent graphite-molecule contacts. Phys Chem Chem Phys 2020; 22:1466-1474. [PMID: 31867588 DOI: 10.1039/c9cp05474j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Seebeck effect is very attractive for technological applications as it leads to the direct conversion of heat into electricity. One of the key quantities determining the efficiency of such conversion is the thermopower S. In this paper we explore theoretically what electronic properties are responsible for the Seebeck effect in molecular junctions with graphite or graphene electrodes. We propose that S can be enhanced because of the combined effect of the dip in the density of states at the Fermi energy of these materials and the molecular resonance. Then to understand the impact of the covalent vs. non-covalent molecule-carbon bonding we calculate from first principles the electronic and transport properties of graphite/molecule/Au junctions, where both types of bonding have been reported experimentally. We ultimately predict that S is about 120 μV K-1 at room temperature for a 3,5-dimethyl-4-aminobenzene (DMAB) molecule covalently attached to the graphite electrode. This value is one order of magnitude larger than the typical values measured to date for molecular junctions and it is a signature of the direct C-C molecule-graphite bond. Finally we also demonstrate how one can control not just the absolute magnitude of S, but also its sign by designing the graphite-molecule contact. Our results lead the way towards the use of junctions with molecules covalently attached to a C-based substrate as possible new improved platforms for molecular thermoelectric devices.
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Affiliation(s)
- Andrea Droghetti
- Nano-Bio Spectroscopy Group and European Theoretical Spectroscopy Facility (ETSF), Materials Physics Center, Universidad del Pais Vasco, Av. Tolosa 72, 20018 San Sebastian, Spain.
| | - Ivan Rungger
- National Physical Laboratory, Hampton Road, TW11 0LW, UK.
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5
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Wu T, Alharbi A, Kiani R, Shahrjerdi D. Quantitative Principles for Precise Engineering of Sensitivity in Graphene Electrochemical Sensors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1805752. [PMID: 30548684 PMCID: PMC6823930 DOI: 10.1002/adma.201805752] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/11/2018] [Indexed: 05/15/2023]
Abstract
A major difficulty in implementing carbon-based electrode arrays with high device-packing density is to ensure homogeneous and high sensitivities across the array. Overcoming this obstacle requires quantitative microscopic models that can accurately predict electrode sensitivity from its material structure. Such models are currently lacking. Here, it is shown that the sensitivity of graphene electrodes to dopamine and serotonin neurochemicals in fast-scan cyclic voltammetry measurements is strongly linked to point defects, whereas it is unaffected by line defects. Using the physics of point defects in graphene, a microscopic model is introduced that explains how point defects determine sensitivity. The predictions of this model match the empirical observation that sensitivity linearly increases with the density of point defects. This model is used to guide the nanoengineering of graphene structures for optimum sensitivity. This approach achieves reproducible fabrication of miniaturized sensors with extraordinarily higher sensitivity than conventional materials. These results lay the foundation for new integrated electrochemical sensor arrays based on nanoengineered graphene.
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Affiliation(s)
- Ting Wu
- Electrical and Computer Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Abdullah Alharbi
- Electrical and Computer Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Roozbeh Kiani
- Center for Neural Science, New York University, New York, NY, 10003, USA
- Neuroscience Institute, New York University Langone Medical Center, New York, NY, 10016, USA
| | - Davood Shahrjerdi
- Electrical and Computer Engineering, New York University, Brooklyn, NY, 11201, USA
- Center for Quantum Phenomena, Physics Department, New York University, New York, NY, 10003, USA
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6
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Najarian AM, McCreery RL. Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions. ACS NANO 2019; 13:867-877. [PMID: 30604970 DOI: 10.1021/acsnano.8b08662] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established "all-carbon" device design were illuminated with UV-vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, light intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm-1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5-10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
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Affiliation(s)
| | - Richard L McCreery
- Department of Chemistry , University of Alberta , Edmonton , Canada T6G 2R3
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7
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Zhang X, Marschewski E, Penner P, Weimann T, Hinze P, Beyer A, Gölzhäuser A. Large-Area All-Carbon Nanocapacitors from Graphene and Carbon Nanomembranes. ACS NANO 2018; 12:10301-10309. [PMID: 30156406 DOI: 10.1021/acsnano.8b05490] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on the fabrication of large-area all-carbon capacitors (ACCs) composed of multilayer stacks of carbon nanomembranes as dielectrics sandwiched between two carbon-based conducting electrodes. Carbon nanomembranes (CNMs) are prepared from aromatic self-assembled monolayers of phenylthiol homologues via electron irradiation. Two types of carbon-based electrode materials, (1) trilayer graphene made by chemical vapor deposition and mechanical stacking and (2) pyrolyzed graphitic carbon made by pyrolysis of cross-linked aromatic molecules, have been employed for this study. The capacitor area is defined by the width of electrode ribbons, and the separation between two electrodes is tuned by the number of CNM layers. Working ACCs with an area of up to 1200 μm2 were successfully fabricated by a combination of bottom-up molecular self-assembly and top-down lithographic approaches. Then ACCs were characterized by Raman spectroscopy, helium ion microscopy, and impedance spectroscopy. A dielectric constant of 3.5 and an average capacitance density of 0.3 μF/cm2 were derived from the obtained capacitances. A dielectric strength of 3.2 MV/cm was determined for CNMs embedded in graphene electrodes with the interfacial capacitance being taken into account. These results show the potential of carbon nanomembranes to be used as dielectric components in next-generation environment-friendly carbon-based energy storage devices.
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Affiliation(s)
- Xianghui Zhang
- Physics of Supramolecular Systems and Surfaces , Bielefeld University , 33615 Bielefeld , Germany
| | - Emanuel Marschewski
- Physics of Supramolecular Systems and Surfaces , Bielefeld University , 33615 Bielefeld , Germany
| | - Paul Penner
- Physics of Supramolecular Systems and Surfaces , Bielefeld University , 33615 Bielefeld , Germany
| | - Thomas Weimann
- Physikalisch-Technische Bundesanstalt , 38116 Braunschweig , Germany
| | - Peter Hinze
- Physikalisch-Technische Bundesanstalt , 38116 Braunschweig , Germany
| | - André Beyer
- Physics of Supramolecular Systems and Surfaces , Bielefeld University , 33615 Bielefeld , Germany
| | - Armin Gölzhäuser
- Physics of Supramolecular Systems and Surfaces , Bielefeld University , 33615 Bielefeld , Germany
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8
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Supur M, Smith SR, McCreery RL. Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy. Anal Chem 2017; 89:6463-6471. [DOI: 10.1021/acs.analchem.7b00362] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Mustafa Supur
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Scott R. Smith
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Richard L. McCreery
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National
Institute for Nanotechnology, National Research Council Canada, 11421
Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
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9
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Rudnev AV, Kaliginedi V, Droghetti A, Ozawa H, Kuzume A, Haga MA, Broekmann P, Rungger I. Stable anchoring chemistry for room temperature charge transport through graphite-molecule contacts. SCIENCE ADVANCES 2017; 3:e1602297. [PMID: 28630901 PMCID: PMC5466367 DOI: 10.1126/sciadv.1602297] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 04/12/2017] [Indexed: 06/07/2023]
Abstract
An open challenge for single-molecule electronics is to find stable contacts at room temperature with a well-defined conductance. Common coinage metal electrodes pose fabrication and operational problems due to the high mobility of the surface atoms. We demonstrate how molecules covalently grafted onto mechanically robust graphite/graphene substrates overcome these limitations. To this aim, we explore the effect of the anchoring group chemistry on the charge transport properties of graphite-molecule contacts by means of the scanning tunneling microscopy break-junction technique and ab initio simulations. Molecules adsorbed on graphite only via van der Waals interactions have a conductance that decreases exponentially upon stretching the junctions, whereas the molecules bonded covalently to graphite have a single well-defined conductance and yield contacts of unprecedented stability at room temperature. Our results demonstrate a strong bias dependence of the single-molecule conductance, which varies over more than one order of magnitude even at low bias voltages, and show an opposite rectification behavior for covalent and noncovalent contacts. We demonstrate that this bias-dependent conductance and opposite rectification behavior is due to a novel effect caused by the nonconstant, highly dispersive density of states of graphite around the Fermi energy and that the direction of rectification is governed by the detailed nature of the molecule/graphite contact. Combined with the prospect of new functionalities due to a strongly bias-dependent conductance, these covalent contacts are ideal candidates for next-generation molecular electronic devices.
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Affiliation(s)
- Alexander V. Rudnev
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow 119991, Russia
| | - Veerabhadrarao Kaliginedi
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Andrea Droghetti
- Nano-Bio Spectroscopy Group, Department of Materials Science, Universidad del País Vasco, Avenida Tolosa 72, 20018 San Sebastian, Spain
| | - Hiroaki Ozawa
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Akiyoshi Kuzume
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Masa-aki Haga
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Peter Broekmann
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Ivan Rungger
- National Physical Laboratory, Teddington TW11 0LW, UK
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10
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Bock S, Al‐Owaedi OA, Eaves SG, Milan DC, Lemmer M, Skelton BW, Osorio HM, Nichols RJ, Higgins SJ, Cea P, Long NJ, Albrecht T, Martín S, Lambert CJ, Low PJ. Single-Molecule Conductance Studies of Organometallic Complexes Bearing 3-Thienyl Contacting Groups. Chemistry 2017; 23:2133-2143. [PMID: 27897344 PMCID: PMC5396322 DOI: 10.1002/chem.201604565] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Indexed: 01/09/2023]
Abstract
The compounds and complexes 1,4-C6 H4 (C≡C-cyclo-3-C4 H3 S)2 (2), trans-[Pt(C≡C-cyclo-3-C4 H3 S)2 (PEt3 )2 ] (3), trans-[Ru(C≡C-cyclo-3-C4 H3 S)2 (dppe)2 ] (4; dppe=1,2-bis(diphenylphosphino)ethane) and trans-[Ru(C≡C-cyclo-3-C4 H3 S)2 {P(OEt)3 }4 ] (5) featuring the 3-thienyl moiety as a surface contacting group for gold electrodes have been prepared, crystallographically characterised in the case of 3-5 and studied in metal|molecule|metal junctions by using both scanning tunnelling microscope break-junction (STM-BJ) and STM-I(s) methods (measuring the tunnelling current (I) as a function of distance (s)). The compounds exhibit similar conductance profiles, with a low conductance feature being more readily identified by STM-I(s) methods, and a higher feature by the STM-BJ method. The lower conductance feature was further characterised by analysis using an unsupervised, automated multi-parameter vector classification (MPVC) of the conductance traces. The combination of similarly structured HOMOs and non-resonant tunnelling mechanism accounts for the remarkably similar conductance values across the chemically distinct members of the family 2-5.
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Affiliation(s)
- Sören Bock
- School of Chemistry and BiochemistryUniversity of Western Australia35 Stirling HighwayCrawley6009WAAustralia
| | - Oday A. Al‐Owaedi
- Department of PhysicsLancaster UniversityLancasterLA1 4YBUK
- Department of Laser Physics, Women Faculty of ScienceBabylon UniversityIraq
| | - Samantha G. Eaves
- School of Chemistry and BiochemistryUniversity of Western Australia35 Stirling HighwayCrawley6009WAAustralia
- Department of ChemistryDurham UniversitySouth Rd.DurhamDH1 3LEUK
| | - David C. Milan
- Department of ChemistryUniversity of LiverpoolCrown St.LiverpoolL69 7ZDUK
| | - Mario Lemmer
- Department of ChemistryImperial College LondonLondonSW7 2AZUK
| | - Brian W. Skelton
- School of Chemistry and BiochemistryUniversity of Western Australia35 Stirling HighwayCrawley6009WAAustralia
- Centre for Microscopy, Characterisation and AnalysisUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Henrry M. Osorio
- Departamento de Química Física, Facultad de CienciasUniversidad de Zaragoza50009ZaragozaSpain
- Instituto de Nanociencia de Aragón (INA) y Laboratorio de Microscopias, Avanzadas (LMA), Edificio I+D Campus Rio EbroUniversidad de ZaragozaC/Mariano Esquillor, s/n50018ZaragozaSpain
- Departamento de FísicaEscuela Politécnica NacionalAv. Ladrón de Guevara, E11-253170525QuitoEcuador
| | - Richard J. Nichols
- Department of ChemistryUniversity of LiverpoolCrown St.LiverpoolL69 7ZDUK
| | - Simon J. Higgins
- Department of ChemistryUniversity of LiverpoolCrown St.LiverpoolL69 7ZDUK
| | - Pilar Cea
- Departamento de Química Física, Facultad de CienciasUniversidad de Zaragoza50009ZaragozaSpain
- Instituto de Nanociencia de Aragón (INA) y Laboratorio de Microscopias, Avanzadas (LMA), Edificio I+D Campus Rio EbroUniversidad de ZaragozaC/Mariano Esquillor, s/n50018ZaragozaSpain
| | | | - Tim Albrecht
- Department of ChemistryImperial College LondonLondonSW7 2AZUK
| | - Santiago Martín
- Departamento de Química Física, Facultad de CienciasUniversidad de Zaragoza50009ZaragozaSpain
- Instituto de Ciencias de Materiales de Aragón (ICMA)Universidad de Zaragoza-CSIC50009ZaragozaSpain
| | | | - Paul J. Low
- School of Chemistry and BiochemistryUniversity of Western Australia35 Stirling HighwayCrawley6009WAAustralia
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11
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Novev JK, Compton RG. Thermal convection in electrochemical cells. Boundaries with heterogeneous thermal conductivity and implications for scanning electrochemical microscopy. Phys Chem Chem Phys 2017; 19:12759-12775. [DOI: 10.1039/c7cp01797a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Substrate heterogeneity influences the natural convective flows arising in electrochemical cells thermostated from below through a solid substrate.
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Affiliation(s)
- Javor K. Novev
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- Oxford University
- Oxford
- UK
| | - Richard G. Compton
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- Oxford University
- Oxford
- UK
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12
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Xie Z, Shi S, Liu F, Smith DL, Ruden PP, Frisbie CD. Large Magnetoresistance at Room Temperature in Organic Molecular Tunnel Junctions with Nonmagnetic Electrodes. ACS NANO 2016; 10:8571-7. [PMID: 27598057 DOI: 10.1021/acsnano.6b03853] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We report room-temperature resistance changes of up to 30% under weak magnetic fields (0.1 T) for molecular tunnel junctions composed of oligophenylene thiol molecules, 1-2 nm in length, sandwiched between gold contacts. The magnetoresistance (MR) is independent of field orientation and the length of the molecule; it appears to be an interface effect. Theoretical analysis suggests that the source of the MR is a two-carrier (two-hole) interaction at the interface, resulting in spin coupling between the tunneling hole and a localized hole at the Au/molecule contact. Such coupling leads to significantly different singlet and triplet transmission barriers at the interface. Even weak magnetic fields impede spin relaxation processes and thus modify the ratio of holes tunneling via the singlet state versus the triplet state, which leads to the large MR. Overall, the experiments and analysis suggest significant opportunities to explore large MR effects in molecular tunnel junctions based on widely available molecules.
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Affiliation(s)
- Zuoti Xie
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Sha Shi
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Feilong Liu
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Darryl L Smith
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - P Paul Ruden
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
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13
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McCreery RL. Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:32-46. [PMID: 26925350 PMCID: PMC4734416 DOI: 10.3762/bjnano.7.4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/15/2015] [Indexed: 06/05/2023]
Abstract
Molecular junctions consisting of 2-20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp(2)-hybridized carbon contacts and an aromatic molecular layer is distinct from the more common metal/molecule or silicon/molecule structures in many reported molecular junctions. Theoretical observations based on density functional theory are presented here, which model carbon-based molecular junctions as single molecules and oligomers between fragments of graphene. Electronic coupling between the molecules and the contacts is demonstrated by the formation of hybrid orbitals in the model structure, which have significant electron density on both the graphene and the molecule. The energies of such hybrid orbitals correlate with tunneling barriers determined experimentally, and electronic coupling between the two graphene fragments in the model correlates with experimentally observed attenuation of transport with molecular layer thickness. Electronic coupling is affected significantly by the dihedral angle between the planes of the graphene and the molecular π-systems, but is absent only when the two planes are orthogonal. Coupling also results in partial charge transfer between the graphene contacts and the molecular layer, which results in a shift in electrostatic potential which affects the observed tunneling barrier. Although the degree of partial charge transfer is difficult to calculate accurately, it does provide a basis for the "vacuum level shift" observed in many experiments, including transport and ultraviolet photoelectron spectroscopy of molecular layers on conductors.
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Affiliation(s)
- Richard L McCreery
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada and National Institute for Nanotechnology, National Research Council, Canada
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14
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Zhou M, Wang HL, Guo S. Towards high-efficiency nanoelectrocatalysts for oxygen reduction through engineering advanced carbon nanomaterials. Chem Soc Rev 2016; 45:1273-307. [DOI: 10.1039/c5cs00414d] [Citation(s) in RCA: 530] [Impact Index Per Article: 66.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We summarize and discuss recent developments of different-dimensional advanced carbon nanomaterial-based noble-metal-free high-efficiency oxygen reduction electrocatalysts, including heteroatom-doped, transition metal-based nanoparticle-based, and especially iron carbide (Fe3C)-based carbon nanomaterial composites.
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Affiliation(s)
- Ming Zhou
- Key Laboratory of Polyoxometalate Science of Ministry of Education
- Faculty of Chemistry, and National & Local United Engineering Laboratory for Power Batteries
- Northeast Normal University
- Changchun
- P. R. China
| | - Hsing-Lin Wang
- Physical Chemistry and Applied Spectroscopy
- Chemistry Division
- Los Alamos National Laboratory
- Los Alamos
- USA
| | - Shaojun Guo
- Department of Materials Science and Engineering & Department of Energy and Resources Engineering
- College of Engineering
- Peking University
- Beijing 100871
- P. R. China
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15
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Wan A, Suchand Sangeeth CS, Wang L, Yuan L, Jiang L, Nijhuis CA. Arrays of high quality SAM-based junctions and their application in molecular diode based logic. NANOSCALE 2015; 7:19547-56. [PMID: 26537895 DOI: 10.1039/c5nr05533d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
This paper describes a method to fabricate a microfluidic top-electrode that can be utilized to generate arrays of self-assembled monolayer (SAM)-based junctions. The top-electrodes consist of a liquid-metal of GaOx/EGaIn mechanically stabilized in microchannels and through-holes in polydimethylsiloxane (PDMS); these top-electrodes form molecular junctions by directly placing them onto the SAM supported by template-stripped (TS) Ag or Au bottom-electrodes. Unlike conventional techniques to form multiple junctions, our method does not require lithography to pattern the bottom-electrode and is compatible with TS bottom-electrodes, which are ultra-flat with large grains, free from potential contamination of photoresist residues, and do not have electrode-edges where the molecules are unable to pack well. We formed tunneling junctions with n-alkanethiolate SAMs in yields of ∼80%, with good reproducibility and electrical stability. Temperature dependent J(V) measurements indicated that the mechanism of charge transport across the junction is coherent tunneling. To demonstrate the usefulness of these junctions, we formed molecular diodes based on SAMs with Fc head groups. These junctions rectify currents with a rectification ratio R of 45. These molecular diodes were incorporated in simple electronic circuitry to demonstrate molecular diode-based Boolean logic.
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Affiliation(s)
- Albert Wan
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
| | - C S Suchand Sangeeth
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
| | - Lejia Wang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
| | - Li Yuan
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
| | - Li Jiang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
| | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore. and Solar Energy Research Institute of Singapore (SERIS), 7 Engineering Drive 1 and National University of Singapore, Singapore 117574, Singapore
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Güell AG, Cuharuc AS, Kim YR, Zhang G, Tan SY, Ebejer N, Unwin PR. Redox-dependent spatially resolved electrochemistry at graphene and graphite step edges. ACS NANO 2015; 9:3558-71. [PMID: 25758160 DOI: 10.1021/acsnano.5b00550] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The electrochemical (EC) behavior of mechanically exfoliated graphene and highly oriented pyrolytic graphite (HOPG) is studied at high spatial resolution in aqueous solutions using Ru(NH3)6(3+/2+) as a redox probe whose standard potential sits close to the intrinsic Fermi level of graphene and graphite. When scanning electrochemical cell microscopy (SECCM) data are coupled with that from complementary techniques (AFM, micro-Raman) applied to the same sample area, different time-dependent EC activity between the basal planes and step edges is revealed. In contrast, other redox couples (ferrocene derivatives) whose potential is further removed from the intrinsic Fermi level of graphene and graphite show uniform and high activity (close to diffusion-control). Macroscopic voltammetric measurements in different environments reveal that the time-dependent behavior after HOPG cleavage, peculiar to Ru(NH3)6(3+/2+), is not associated particularly with any surface contaminants but is reasonably attributed to the spontaneous delamination of the HOPG with time to create partially coupled graphene layers, further supported by conductive AFM measurements. This process has a major impact on the density of states of graphene and graphite edges, particularly at the intrinsic Fermi level to which Ru(NH3)6(3+/2+) is most sensitive. Through the use of an improved voltammetric mode of SECCM, we produce movies of potential-resolved and spatially resolved HOPG activity, revealing how enhanced activity at step edges is a subtle effect for Ru(NH3)6(3+/2+). These latter studies allow us to propose a microscopic model to interpret the EC response of graphene (basal plane and edges) and aged HOPG considering the nontrivial electronic band structure.
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Affiliation(s)
- Aleix G Güell
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Anatolii S Cuharuc
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Yang-Rae Kim
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Guohui Zhang
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Sze-yin Tan
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Neil Ebejer
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Patrick R Unwin
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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Zhang G, Cuharuc AS, Güell AG, Unwin PR. Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models. Phys Chem Chem Phys 2015; 17:11827-38. [DOI: 10.1039/c5cp00383k] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electron transfer kinetics for outer-sphere redox couples is fast on the basal surface of highly oriented pyrolytic graphite (HOPG).
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Affiliation(s)
- Guohui Zhang
- Department of Chemistry
- University of Warwick
- Coventry
- UK
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Abstract
This contribution provides a personal overview and summary of Faraday Discussion 172 on “Carbon in Electrochemistry”, covering some of the key points made at the meeting within the broader context of other recent developments on carbon materials for electrochemical applications. Although carbon electrodes have a long history of use in electrochemistry, methods and techniques are only just becoming available that can test long-established models and identify key features for further exploration. This Discussion has highlighted the need for a better understanding of the impact of surface structure, defects, local density of electronic states, and surface functionality and contamination, in order to advance fundamental knowledge of various electrochemical processes and phenomena at carbon electrodes. These developments cut across important materials such as graphene, carbon nanotubes, conducting diamond and high surface area carbon materials. With more detailed pictures of structural and electronic controls of electrochemistry at carbon electrodes (and electrodes generally), will come rational advances in various technological applications, from sensors to energy technology (particularly batteries, supercapacitors and fuel cells), that have been well-illustrated at this Discussion.
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Affiliation(s)
- Patrick R. Unwin
- Department of Chemistry
- University of Warwick
- Coventry CV4 7AL, UK
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