1
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Ukraintsev E, Rezek B. Non-contact non-resonant atomic force microscopy method for measurements of highly mobile molecules and nanoparticles. Ultramicroscopy 2023; 253:113816. [PMID: 37531754 DOI: 10.1016/j.ultramic.2023.113816] [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: 11/07/2022] [Revised: 04/13/2023] [Accepted: 07/25/2023] [Indexed: 08/04/2023]
Abstract
Atomic force microscopy (AFM) is nowadays indispensable versatile scanning probe method widely employed for fundamental and applied research in physics, chemistry, biology as well as industrial metrology. Conventional AFM systems can operate in various environments such as ultra-high vacuum, electrolyte solutions, or controlled gas atmosphere. Measurements in ambient air are prevalent due to their technical simplicity; however, there are drawbacks such as formation of water meniscus that greatly increases attractive interaction (adhesion) between the tip and the sample, reduced spatial resolution, and too strong interactions leading to tip and/or sample modifications. Here we show how the attractive forces in AFM under ambient conditions can be used with advantage to probe surface properties in a very sensitive way even on highly mobile molecules and nanoparticles. We introduce a stable non-contact non-resonant (NCNR) AFM method which enables to reliably perform measurements in the attractive force regime even in air by controlling the tip position in the intimate surface vicinity without touching it. We demonstrate proof-of-concept results on helicene-based macrocycles, DNA on mica, and nanodiamonds on SiO2. We compare the results with other conventional AFM regimes, showing NCNR advantages such as higher spatial resolution, reduced tip contamination, and negligible sample modification. We analyze principle physical and chemical mechanisms influencing the measurements, discuss issues of stability and various possible method implementations. We explain how the NCNR method can be applied in any AFM system by a mere software modification. The method thus opens a new research field for measurements of highly sensitive and mobile nanoscale objects under air and other environments.
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Affiliation(s)
- Egor Ukraintsev
- Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, Prague 6, 166 27, Czech Republic.
| | - Bohuslav Rezek
- Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, Prague 6, 166 27, Czech Republic
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2
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Banerjee A, Khan SUH, Broadbent S, Bulbul A, Kim KH, Noh S, Looper R, Mastrangelo CH, Kim H. Molecular bridge-mediated ultralow-power gas sensing. MICROSYSTEMS & NANOENGINEERING 2021; 7:27. [PMID: 34567741 PMCID: PMC8433217 DOI: 10.1038/s41378-021-00252-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 02/08/2021] [Accepted: 02/11/2021] [Indexed: 05/27/2023]
Abstract
We report the electrical detection of captured gases through measurement of the quantum tunneling characteristics of gas-mediated molecular junctions formed across nanogaps. The gas-sensing nanogap device consists of a pair of vertically stacked gold electrodes separated by an insulating 6 nm spacer (~1.5 nm of sputtered α-Si and ~4.5 nm ALD SiO2), which is notched ~10 nm into the stack between the gold electrodes. The exposed gold surface is functionalized with a self-assembled monolayer (SAM) of conjugated thiol linker molecules. When the device is exposed to a target gas (1,5-diaminopentane), the SAM layer electrostatically captures the target gas molecules, forming a molecular bridge across the nanogap. The gas capture lowers the barrier potential for electron tunneling across the notched edge region, from ~5 eV to ~0.9 eV and establishes additional conducting paths for charge transport between the gold electrodes, leading to a substantial decrease in junction resistance. We demonstrated an output resistance change of >108 times upon exposure to 80 ppm diamine target gas as well as ultralow standby power consumption of <15 pW, confirming electron tunneling through molecular bridges for ultralow-power gas sensing.
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Affiliation(s)
- Aishwaryadev Banerjee
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Shakir-Ul Haque Khan
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Samuel Broadbent
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112 USA
| | - Ashrafuzzaman Bulbul
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | | | - Seungbeom Noh
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - R. Looper
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112 USA
| | - C. H. Mastrangelo
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - H. Kim
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
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3
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Fu Z, Ladnorg T, Gliemann H, Welle A, Bashir A, Rohwerder M, Zhang Q, Schüpbach B, Terfort A, Wöll C. Mobility of charge carriers in self-assembled monolayers. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2019; 10:2449-2458. [PMID: 31921523 PMCID: PMC6941449 DOI: 10.3762/bjnano.10.235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 11/12/2019] [Indexed: 06/10/2023]
Abstract
We present a new approach to study charge transport within 2D layers of organic semi-conductors (OSCs) using atomic force microscopy (AFM)-based lithography applied to self-assembled monolayers (SAMs), fabricated from appropriate organothiols. The extent of lateral charge transport was investigated by insulating pre-defined patches within OSC-based SAMs with regions of insulating SAM made from large band gap alkanethiolates. The new method is demonstrated using a phenyl-linked anthracenethiolate (PAT), 4-(anthracene-2-ylethynyl)benzyl thiolate. I-V characteristics of differently shaped PAT-islands were measured using the AFM tip as a top electrode. We were able to determine a relationship between island size and electrical conductivity, and from this dependence, we could obtain information on the lateral charge transport and charge carrier mobility within the thin OSC layers. Our study demonstrates that AFM nanografting of appropriately functionalized OSC molecules provides a suitable method to determine intrinsic mobilities of charge carriers in OSC thin films. In particular, this method is rather insensitive with regard to influence of grain boundaries and other defects, which hamper the application of conventional methods for the determination of mobilities in macroscopic samples.
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Affiliation(s)
- Zhihua Fu
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
| | - Tatjana Ladnorg
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
| | - Hartmut Gliemann
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
| | - Alexander Welle
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
| | - Asif Bashir
- Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
- Thyssenkrupp Bilstein GmbH, Herner Str. 299, 44809 Bochum, Germany
| | - Michael Rohwerder
- Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
| | - Qiang Zhang
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
| | - Björn Schüpbach
- Department of Chemistry, Institute of Inorganic and Analytical Chemistry, Goethe-University, 60438 Frankfurt, Germany
| | - Andreas Terfort
- Department of Chemistry, Institute of Inorganic and Analytical Chemistry, Goethe-University, 60438 Frankfurt, Germany
| | - Christof Wöll
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Campus Nord, 76344 Eggenstein-Leopoldshafen, Germany
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4
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Cheong LZ, Zhao W, Song S, Shen C. Lab on a tip: Applications of functional atomic force microscopy for the study of electrical properties in biology. Acta Biomater 2019; 99:33-52. [PMID: 31425893 DOI: 10.1016/j.actbio.2019.08.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/17/2019] [Accepted: 08/13/2019] [Indexed: 12/11/2022]
Abstract
Electrical properties, such as charge propagation, dielectrics, surface potentials, conductivity, and piezoelectricity, play crucial roles in biomolecules, biomembranes, cells, tissues, and other biological samples. However, characterizing these electrical properties in delicate biosamples is challenging. Atomic Force Microscopy (AFM), the so called "Lab on a Tip" is a powerful and multifunctional approach to quantitatively study the electrical properties of biological samples at the nanometer level. Herein, the principles, theories, and achievements of various modes of AFM in this area have been reviewed and summarized. STATEMENT OF SIGNIFICANCE: Electrical properties such as dielectric and piezoelectric forces, charge propagation behaviors play important structural and functional roles in biosystems from the single molecule level, to cells and tissues. Atomic force microscopy (AFM) has emerged as an ideal toolkit to study electrical property of biology. Herein, the basic principles of AFM are described. We then discuss the multiple modes of AFM to study the electrical properties of biological samples, including Electrostatic Force Microscopy (EFM), Kelvin Probe Force Microscopy (KPFM), Conductive Atomic Force Microscopy (CAFM), Piezoresponse Force Microscopy (PFM) and Scanning ElectroChemical Microscopy (SECM). Finally, the outlook, prospects, and challenges of the various AFM modes when studying the electrical behaviour of the samples are discussed.
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5
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Shi C, He Y, Ding M, Wang Y, Zhong J. Nanoimaging of food proteins by atomic force microscopy. Part I: Components, imaging modes, observation ways, and research types. Trends Food Sci Technol 2019. [DOI: 10.1016/j.tifs.2018.11.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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6
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Locke GM, Bernhard SSR, Senge MO. Nonconjugated Hydrocarbons as Rigid-Linear Motifs: Isosteres for Material Sciences and Bioorganic and Medicinal Chemistry. Chemistry 2019; 25:4590-4647. [PMID: 30387906 DOI: 10.1002/chem.201804225] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 10/20/2018] [Indexed: 01/02/2023]
Abstract
Nonconjugated hydrocarbons, like bicyclo[1.1.1]pentane, bicyclo[2.2.2]octane, triptycene, and cubane are a unique class of rigid linkers. Due to their similarity in size and shape they are useful mimics of classic benzene moieties in drugs, so-called bioisosteres. Moreover, they also fulfill an important role in material sciences as linear linkers, in order to arrange various functionalities in a defined spatial manner. In this Review article, recent developments and usages of these special, rectilinear systems are discussed. Furthermore, we focus on covalently linked, nonconjugated linear arrangements and discuss the physical and chemical properties and differences of individual linkers, as well as their application in material and medicinal sciences.
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Affiliation(s)
- Gemma M Locke
- School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, 2, Ireland
| | - Stefan S R Bernhard
- School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, 2, Ireland
| | - Mathias O Senge
- School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, 2, Ireland
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7
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Ramachandran R, Li HB, Lo WY, Neshchadin A, Yu L, Hihath J. An Electromechanical Approach to Understanding Binding Configurations in Single-Molecule Devices. NANO LETTERS 2018; 18:6638-6644. [PMID: 30247037 DOI: 10.1021/acs.nanolett.8b03415] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The configuration of the molecule-electrode contact region plays an important role in determining the conductance of a single-molecule junction, and the variety of possible contact configurations have yielded multiple conductance values for a number of molecular families. In this report, we perform simultaneous conductance and electromechanical coupling parameter measurements on a series of oligophenylene-dithiol single-molecule junctions. These molecules show two distinct conductance values, and by examining the conductance changes, the electromechanical coupling, and the changes in the I- V characteristics coupled with a combination of analytical mechanical models and density functional theory (DFT) structure calculations, we are able to determine the most-probable binding configuration in each of the conductance states. We find that the lower-conductance state is likely due to the thiols binding to each electrode at a gold top site, and in the higher-conductance state, the phenylene π orbitals interact with electrodes, drastically modifying the transport behavior. This approach provides an expanded methodology for exploring the relationship between the molecule-electrode contact configuration and molecular conductance.
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Affiliation(s)
- Roohi Ramachandran
- Department of Electrical and Computer Engineering , University of California, Davis , 1 Shields Avenue , Davis , California 95616 , United States
| | - Haipeng B Li
- Department of Electrical and Computer Engineering , University of California, Davis , 1 Shields Avenue , Davis , California 95616 , United States
| | - Wai-Yip Lo
- Department of Chemistry and the James Franck Institute , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
| | - Andriy Neshchadin
- Department of Chemistry and the James Franck Institute , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
| | - Luping Yu
- Department of Chemistry and the James Franck Institute , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
| | - Joshua Hihath
- Department of Electrical and Computer Engineering , University of California, Davis , 1 Shields Avenue , Davis , California 95616 , United States
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8
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Paradinas M, Munuera C, Buck M, Ocal C. In-Situ Scrutiny of the Relationship between Polymorphic Phases and Properties of Self-Assembled Monolayers of a Biphenyl Based Thiol. J Phys Chem B 2017; 122:657-665. [DOI: 10.1021/acs.jpcb.7b05958] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Markos Paradinas
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193-Barcelona, Spain
| | - Carmen Munuera
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193-Barcelona, Spain
| | - Manfred Buck
- EaStCHEM
School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY169ST, U.K
| | - Carmen Ocal
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193-Barcelona, Spain
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9
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Zhong J, Yan J. Seeing is believing: atomic force microscopy imaging for nanomaterial research. RSC Adv 2016. [DOI: 10.1039/c5ra22186b] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Atomic force microscopy can image nanomaterial properties such as the topography, elasticity, adhesion, friction, electrical properties, and magnetism.
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Affiliation(s)
- Jian Zhong
- College of Food Science & Technology
- Shanghai Ocean University
- Shanghai 201306
- People's Republic of China
| | - Juan Yan
- College of Food Science & Technology
- Shanghai Ocean University
- Shanghai 201306
- People's Republic of China
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10
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Oyama M, Ozawa H, Nagashima T, Haga MA, Ishida T. Effects of Fe cations in ruthenium-complex multilayers fabricated by a layer-by-layer method. Phys Chem Chem Phys 2016; 18:9005-12. [DOI: 10.1039/c5cp07970e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Molecular multilayers were fabricated using a Ru complex containing Fe cations on an indium tin oxide surface to control the properties of the Ru-complex multilayers such as the multilayer orientation and the electron transport.
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Affiliation(s)
- Makiko Oyama
- Nanomaterials Research Institute (NMRI)
- Department of Materials and Chemistry
- National Institute of Advanced Industrial Science and Technology (AIST)
- Tsukuba
- Japan
| | - Hiroaki Ozawa
- Department of Applied Chemistry
- Faculty of Science and Engineering
- Chuo University
- Bunkyo-ku
- Japan
| | - Takumi Nagashima
- Department of Applied Chemistry
- Faculty of Science and Engineering
- Chuo University
- Bunkyo-ku
- Japan
| | - Masa-aki Haga
- Department of Applied Chemistry
- Faculty of Science and Engineering
- Chuo University
- Bunkyo-ku
- Japan
| | - Takao Ishida
- Nanomaterials Research Institute (NMRI)
- Department of Materials and Chemistry
- National Institute of Advanced Industrial Science and Technology (AIST)
- Tsukuba
- Japan
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11
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Tsuji Y, Movassagh R, Datta S, Hoffmann R. Exponential Attenuation of Through-Bond Transmission in a Polyene: Theory and Potential Realizations. ACS NANO 2015; 9:11109-11120. [PMID: 26390251 DOI: 10.1021/acsnano.5b04615] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
An exponential falloff with separation of electron transfer and transport through molecular wires is observed and has attracted theoretical attention. In this study, the attenuation of transmission in linear and cyclic polyenes is related to bond alternation. The explicit form of the zeroth Green's function in a Hückel model for bond-alternated polyenes leads to an analytical expression of the conductance decay factor β. The β values calculated from our model (β(CN) values, per repeat unit of double and single bond) range from 0.28 to 0.37, based on carotenoid crystal structures. These theoretical β values are slightly smaller than experimental values. The difference can be assigned to the effect of anchoring groups, which are not included in our model. A local transmission analysis for cyclic polyenes, and for [14]annulene in particular, shows that bond alternation affects dramatically not only the falloff behavior but also the choice of a transmission pathway by electrons. Transmission follows a well-demarcated system of π bonds, even when there is a shorter-distance path with roughly the same kind of "electronic matter" intervening.
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Affiliation(s)
- Yuta Tsuji
- Department of Chemistry and Chemical Biology, Cornell University , Baker Laboratory, Ithaca, New York 14853, United States
| | - Ramis Movassagh
- Department of Mathematics, Massachusetts Institute of Technology , Building E18, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Supriyo Datta
- School of Electrical and Computer Engineering, Purdue University , Electrical Engineering Building, 465 Northwestern Avenue, West Lafayette, Indiana 47907-2035, United States
| | - Roald Hoffmann
- Department of Chemistry and Chemical Biology, Cornell University , Baker Laboratory, Ithaca, New York 14853, United States
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12
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Song CK, Luck KA, Zhou N, Zeng L, Heitzer HM, Manley EF, Goldman S, Chen LX, Ratner MA, Bedzyk MJ, Chang RPH, Hersam MC, Marks TJ. “Supersaturated” Self-Assembled Charge-Selective Interfacial Layers for Organic Solar Cells. J Am Chem Soc 2014; 136:17762-73. [DOI: 10.1021/ja508453n] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Charles Kiseok Song
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Kyle A. Luck
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Nanjia Zhou
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Li Zeng
- Graduate
Program in Applied Physics, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Henry M. Heitzer
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Eric F. Manley
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Samuel Goldman
- Weinberg
College of Arts and Science, Northwestern University, 1918 Sheridan
Road, Evanston, Illinois 60208, United States
| | - Lin X. Chen
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Mark A. Ratner
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Michael J. Bedzyk
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
- Graduate
Program in Applied Physics, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Robert P. H. Chang
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Mark C. Hersam
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
| | - Tobin J. Marks
- Department
of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Department
of Materials Science and Engineering and the Argonne-Northwestern
Solar Energy Research Center, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208, United States
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13
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Amdursky N, Marchak D, Sepunaru L, Pecht I, Sheves M, Cahen D. Electronic transport via proteins. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:7142-61. [PMID: 25256438 DOI: 10.1002/adma.201402304] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/07/2014] [Indexed: 05/25/2023]
Abstract
A central vision in molecular electronics is the creation of devices with functional molecular components that may provide unique properties. Proteins are attractive candidates for this purpose, as they have specific physical (optical, electrical) and chemical (selective binding, self-assembly) functions and offer a myriad of possibilities for (bio-)chemical modification. This Progress Report focuses on proteins as potential building components for future bioelectronic devices as they are quite efficient electronic conductors, compared with saturated organic molecules. The report addresses several questions: how general is this behavior; how does protein conduction compare with that of saturated and conjugated molecules; and what mechanisms enable efficient conduction across these large molecules? To answer these questions results of nanometer-scale and macroscopic electronic transport measurements across a range of organic molecules and proteins are compiled and analyzed, from single/few molecules to large molecular ensembles, and the influence of measurement methods on the results is considered. Generalizing, it is found that proteins conduct better than saturated molecules, and somewhat poorer than conjugated molecules. Significantly, the presence of cofactors (redox-active or conjugated) in the protein enhances their conduction, but without an obvious advantage for natural electron transfer proteins. Most likely, the conduction mechanisms are hopping (at higher temperatures) and tunneling (below ca. 150-200 K).
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Affiliation(s)
- Nadav Amdursky
- Dept. of Materials & Interfaces, Weizmann Institute of Science, Rehovot, 76305, Israel
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14
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Ishida T, Oyama M, Terada KI, Haga MA. Dynamic pattern formation of liquid crystals using binary self-assembled monolayers on an ITO surface under DC voltage. Phys Chem Chem Phys 2014; 16:25008-13. [DOI: 10.1039/c4cp03622k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Kaliginedi V, V. Rudnev A, Moreno-García P, Baghernejad M, Huang C, Hong W, Wandlowski T. Promising anchoring groups for single-molecule conductance measurements. Phys Chem Chem Phys 2014; 16:23529-39. [DOI: 10.1039/c4cp03605k] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Qualitative and quantitative comparison of the results obtained with different anchoring groups reveals structural and mechanistic details of the different types of single molecular junctions.
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Affiliation(s)
| | | | | | - Masoud Baghernejad
- Department of Chemistry and Biochemistry
- University of Bern
- Bern, Switzerland
| | - Cancan Huang
- Department of Chemistry and Biochemistry
- University of Bern
- Bern, Switzerland
| | - Wenjing Hong
- Department of Chemistry and Biochemistry
- University of Bern
- Bern, Switzerland
| | - Thomas Wandlowski
- Department of Chemistry and Biochemistry
- University of Bern
- Bern, Switzerland
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16
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Shinomiya M, Higashiguchi K, Matsuda K. Evaluation of the β Value of the Phenylene Ethynylene Unit by Probing the Exchange Interaction between Two Nitronyl Nitroxides. J Org Chem 2013; 78:9282-90. [DOI: 10.1021/jo4015062] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masataka Shinomiya
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kenji Higashiguchi
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Kenji Matsuda
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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17
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Moreno-García P, Gulcur M, Manrique DZ, Pope T, Hong W, Kaliginedi V, Huang C, Batsanov AS, Bryce MR, Lambert C, Wandlowski T. Single-Molecule Conductance of Functionalized Oligoynes: Length Dependence and Junction Evolution. J Am Chem Soc 2013; 135:12228-40. [DOI: 10.1021/ja4015293] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Pavel Moreno-García
- Department of Chemistry and
Biochemistry, University of Bern, Freiestrasse
3, CH-3012, Bern, Switzerland
- Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apartado Postal J-48, Puebla
72570, México
| | - Murat Gulcur
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | | | - Thomas Pope
- Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
| | - Wenjing Hong
- Department of Chemistry and
Biochemistry, University of Bern, Freiestrasse
3, CH-3012, Bern, Switzerland
| | - Veerabhadrarao Kaliginedi
- Department of Chemistry and
Biochemistry, University of Bern, Freiestrasse
3, CH-3012, Bern, Switzerland
| | - Cancan Huang
- Department of Chemistry and
Biochemistry, University of Bern, Freiestrasse
3, CH-3012, Bern, Switzerland
| | - Andrei S. Batsanov
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Martin R. Bryce
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Colin Lambert
- Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
| | - Thomas Wandlowski
- Department of Chemistry and
Biochemistry, University of Bern, Freiestrasse
3, CH-3012, Bern, Switzerland
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18
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Martin F, Hendriksen BLM, Katan AJ, Qi Y, Mauldin C, Fréchet JMJ, Salmeron M. Sensitivity to molecular order of the electrical conductivity in oligothiophene monolayer films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1206-1210. [PMID: 23244532 DOI: 10.1021/la303609g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using conducting probe atomic force microscopy (CAFM), we show that electrical conductivity in oligothiophene molecular films deposited on SiO(2)/Si wafers is extremely sensitive to degree of crystalline order in the film. By locally distorting the molecular order in the films through the controlled application of pressure with the AFM tip, the lateral charge transport was reduced by factors varying from 2 to 10, even when no changes in the height of the film could be observed.
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Affiliation(s)
- Florent Martin
- Materials Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
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19
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Nishizawa S, Hasegawa JY, Matsuda K. Theoretical investigation of the β value of the phenylene and phenylene ethynylene units by evaluating exchange interaction between organic radicals. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2012.10.092] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Muhammad H, Koczkur KM, Kycia AH, Houmam A. Nitro-substituted arene sulfenyl chlorides as precursors to the formation of aromatic SAMs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15853-15863. [PMID: 23078107 DOI: 10.1021/la303395e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The formation of aromatic SAMs on Au(111) using three nitro-substituted arene sulfenyl chlorides (4-nitrophenyl sulfenyl chloride (1), 2-nitrophenyl sulfenyl chloride (2), and 2,4-dinitrophenyl sulfenyl chloride (3)) is studied. The formation of SAMs and their quality are investigated as a function of the position of the nitro substituent(s) on the aromatic ring. The modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), polarization modulation infrared reflection absorption spectroscopy (PMIRRAS), and cyclic voltammetry (CV). The results show that all three compounds are deposited on Au within very short times. The corresponding coverages are determined using CV. However, only compound 1 forms stable, long-range, well-ordered SAMs. The 4-nitrophenyl thiolate is adsorbed nearly vertically on the Au surface. Compounds 2 and 3 both form lower-quality SAMs where the adsorbed nitro-phenyl thiolates are more tilted. These SAMs are less stable than the ones obtained with the 4-nitrosubsituted precursor and decompose with time, leaving only sulfur on the gold surface.
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Affiliation(s)
- Hamida Muhammad
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada
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21
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Shin MJ, Yang M, Shin JS. Sensing Capability of Molecularly Imprinted Self-Assembled Monolayer Using Terphenylpropanethiol. PARTICULATE SCIENCE AND TECHNOLOGY 2012. [DOI: 10.1080/02726351.2011.613895] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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22
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Masillamani AM, Crivillers N, Orgiu E, Rotzler J, Bossert D, Thippeswamy R, Zharnikov M, Mayor M, Samorì P. Multiscale Charge Injection and Transport Properties in Self-Assembled Monolayers of Biphenyl Thiols with Varying Torsion Angles. Chemistry 2012; 18:10335-47. [DOI: 10.1002/chem.201201858] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Indexed: 11/06/2022]
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23
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Terada KI, Nakamura H, Kanaizuka K, Haga MA, Asai Y, Ishida T. Long-range electron transport of ruthenium-centered multilayer films via a stepping-stone mechanism. ACS NANO 2012; 6:1988-1999. [PMID: 22324341 DOI: 10.1021/nn300126m] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We studied electron transport of Ru complex multilayer films, whose structure resembles redox-active complex films known in the literature to have long-range electron transport abilities. Hydrogen bond formation in terms of pH control was used to induce spontaneous growth of a Ru complex multilayer. We made a cross-check between electrochemical measurements and I-V measurements using PEDOT:PSS to eliminate the risk of pinhole contributions to the mechanism and have found small β values of 0.012-0.021 Å(-1). Our Ru complex layers exhibit long-range electron transport but with low conductance. On the basis of the results of our theoretical-experimental collaboration, we propose a modified tunneling mechanism named the "stepping-stone mechanism", where the alignment of site potentials forms a narrow band around E(F), making resonant tunneling possible. Our observations may support Tuccito et al.'s proposed mechanism.
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Affiliation(s)
- Kei-ichi Terada
- Nanosystem Research Institute (NRI), National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan
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24
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Kaliginedi V, Moreno-García P, Valkenier H, Hong W, García-Suárez VM, Buiter P, Otten JLH, Hummelen JC, Lambert CJ, Wandlowski T. Correlations between Molecular Structure and Single-Junction Conductance: A Case Study with Oligo(phenylene-ethynylene)-Type Wires. J Am Chem Soc 2012; 134:5262-75. [DOI: 10.1021/ja211555x] [Citation(s) in RCA: 242] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Veerabhadrarao Kaliginedi
- Department of Chemistry and
Biochemistry, University of Berne, Freiestrasse
3, CH-3012 Berne, Switzerland
| | - Pavel Moreno-García
- Department of Chemistry and
Biochemistry, University of Berne, Freiestrasse
3, CH-3012 Berne, Switzerland
- Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apartado Postal J-48, Puebla
72570, Mexico
| | | | - Wenjing Hong
- Department of Chemistry and
Biochemistry, University of Berne, Freiestrasse
3, CH-3012 Berne, Switzerland
| | - Víctor M. García-Suárez
- Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
- Departamento de Física, Universidad de Oviedo and CINN (CSIC), ES-33007 Oviedo,
Spain
| | | | | | | | - Colin J. Lambert
- Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
| | - Thomas Wandlowski
- Department of Chemistry and
Biochemistry, University of Berne, Freiestrasse
3, CH-3012 Berne, Switzerland
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25
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SEIDEMAN TAMAR, GUO HONG. QUANTUM TRANSPORT AND CURRENT-TRIGGERED DYNAMICS IN MOLECULAR TUNNEL JUNCTIONS. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633603000616] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The modelling of nanoelectronic systems has been the topic of ever increasing activity for nearly two decades. Yet, new questions, challenges and opportunities continue to emerge. In this article we review theoretical and numerical work on two new developments in the theory of molecular-scale electronics. First we review a density functional theory analysis within the Keldysh non-equilibrium Green function formalism to predict nonlinear charge transport properties of nanoelectronic devices. Next we review a recently developed quantum mechanical formalism of current-triggered nuclear dynamics. Finally we combine these theories to describe from first principles the inelastic current and the consequent molecular dynamics in molecular heterojunctions.
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Affiliation(s)
- TAMAR SEIDEMAN
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL. 60208-3113, USA
| | - HONG GUO
- Center for the Physics of Materials & Department of Physics, McGill University, Montreal, PQ, Canada H3A 2T8, Canada
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26
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Houmam A, Muhammad H, Koczkur KM. Physical structure of standing-up aromatic SAMs revealed by scanning tunneling microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13544-13553. [PMID: 21970561 DOI: 10.1021/la202928z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs.
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Affiliation(s)
- Abdelaziz Houmam
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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27
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Maeda Y, Matsumoto T, Kawai T. Imaging of transverse electron transfer through a DNA molecule by simultaneous scanning tunneling and frequency-modulation atomic force microscopy. ACS NANO 2011; 5:3141-3145. [PMID: 21428452 DOI: 10.1021/nn200291f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Simultaneous scanning tunneling and frequency-modulation atomic force microscopy (STM/FM-AFM) was applied to a DNA molecule on a Cu(111) surface to analyze transverse electron transfer which is related to the electron transfer and the electrical contact in DNA-based devices. In particular, we demonstrated correlation mapping of the electron transfer parameters by visualizing specific combinations of the decay constant β and the contact conductance G. The results clearly revealed that electron transfer across the DNA strand varies spatially in the DNA molecule. This spatial variation is probably correlated with deformation of DNA on the surface. From quantitative analysis, the decay constant β was estimated to be 3.3 nm(-1), which is consistent with previously reported values for π-conjugated molecules.
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Affiliation(s)
- Yasushi Maeda
- Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, 1-8-31, Midorigaoka, Ikeda, Osaka 563-8577, Japan
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28
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Tsuji Y, Staykov A, Yoshizawa K. Orbital Views of Molecular Conductance Perturbed by Anchor Units. J Am Chem Soc 2011; 133:5955-65. [DOI: 10.1021/ja111021e] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuta Tsuji
- Institute for Materials Chemistry and Engineering and International Research Center for Molecular Systems, Kyushu University, Fukuoka 819-0395, Japan
| | - Aleksandar Staykov
- Institute for Materials Chemistry and Engineering and International Research Center for Molecular Systems, Kyushu University, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering and International Research Center for Molecular Systems, Kyushu University, Fukuoka 819-0395, Japan
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29
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Wang G, Kim TW, Lee T. Electrical transport characteristics through molecular layers. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm12702k] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Higashiguchi K, Yumoto K, Matsuda K. Evaluation of the β Value of the Phenylene Unit by Probing Exchange Interaction between Two Nitroxides. Org Lett 2010; 12:5284-6. [DOI: 10.1021/ol102339m] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kenji Higashiguchi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Koji Yumoto
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kenji Matsuda
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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31
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Liu H, Yu C, Gao N, Zhao J. The diversity of electron-transport behaviors of molecular junctions: correlation with the electron-transport pathway. Chemphyschem 2010; 11:1895-902. [PMID: 20379983 DOI: 10.1002/cphc.201000092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We report the electron-transport behaviors of a number of molecular junctions composed of pi-conjugated molecular wires. From calculations performed by using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method, we found that the length-conductivity relations are diverse, depending on the particular molecular structures. The results reveal that the conductance-length dependence follows an exponential law for many conjugated molecules with a single channel, such as oligothiophene, oligopyrrole and oligophenylene. Therefore, a quantitative relation between the energy gap (E(g))(infinity) of the molecular wire and the attenuation factor beta can be defined. However, when the molecular wires have multichannels, the decay of conductance does not follow the exponential relation. For example, the conductance of porphyrin-based oligomers and fused thiophene decays almost linearly. The diversity of electron-transport behaviors of molecular junctions is directly dominated by the electron-transport pathway.
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Affiliation(s)
- Hongmei Liu
- Key laboratory of Analytical Chemistry for Life Science (Ministry of Education), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008, PR China
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32
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Wang W, Wang S, Li X, Collin JP, Liu J, Liu PN, Lin N. Probing Electronic Superexchange Coupling at Isolated Poly-p-phenylene Molecules. J Am Chem Soc 2010; 132:8774-8. [DOI: 10.1021/ja102415f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Weihua Wang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Shiyong Wang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Xiuyuan Li
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Jean-Paul Collin
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Jun Liu
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Pei Nian Liu
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
| | - Nian Lin
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, Institut de Chimie, Université Louis Pasteur-CNRS/UMR 7177, 4, rue Blaise Pascal, 67070 Strasbourg, France, and Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Meilong Road 130, Shanghai, China
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33
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Liu H, Wang N, Zhao J, Guo Y, Yin X, Boey FYC, Zhang H. Length-dependent conductance of molecular wires and contact resistance in metal-molecule-metal junctions. Chemphyschem 2008; 9:1416-24. [PMID: 18512822 DOI: 10.1002/cphc.200800032] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.
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Affiliation(s)
- Hongmei Liu
- Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008, PR China
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34
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Xu Q, Ma H, Yip H, Jen AKY. Controlled assembly of large pi-conjugated aromatic thiols on Au(111). NANOTECHNOLOGY 2008; 19:135605. [PMID: 19636154 DOI: 10.1088/0957-4484/19/13/135605] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Self-assembled monolayers (SAMs) of large pi-conjugated aromatic thiols, 1-mercaptopyrene (MP), 6-mercaptobenzo[a]pyrene (MBP), and 1-(11-mercaptoundecyl)pyrene (MUP), prepared on Au(111) substrate at different temperatures were investigated by scanning tunneling microscopy. At room temperature, only MP and MBP molecules formed well-ordered SAMs with [Formula: see text] and ([Formula: see text]) Rect symmetry, respectively. In contrast, MUP molecules were adsorbed randomly on the surface. At elevated temperatures, all three molecules produce well-ordered SAMs. At 343 K, the structure of MBP remains unchanged, while MP and MUP molecules undergo thermally induced rearrangement to form a ([Formula: see text]) Rect symmetry due to improved ordering and denser packing. The results from the systematic study of controlled self-assembly of a series of pyrene-based thiols provide insights on the molecular structure-dependent and temperature-dependent organization of large pi-conjugated aromatic thiols to obtain ordered SAMs.
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Affiliation(s)
- Qingmin Xu
- Department of Materials Science and Engineering, University of Washington, Box 352120, Seattle, WA 98195-2120, USA
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35
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Tivanski AV, Li JK, Walker GC. Pressure-induced restructuring of a monolayer film nanojunction produces threshold and power law conduction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:2288-2293. [PMID: 18278960 DOI: 10.1021/la7032498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The electrical conduction of metal-molecule-metal junctions formed between Au-supported self-assembled monolayers of structurally different 1-hexanethiol, 1-decanethiol, and ferrocenyl-1-undecanethiol and a Pt-coated atomic force microscope (AFM) tip has been measured under different compression forces using conducting-probe AFM. The observed junction resistance had two distinct power law scaling changes with the compression force. Different scaling regions were assigned to the change in the contact area, tunneling distance, number of conduction pathways, and structure of the film under compression.
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Affiliation(s)
- Alexei V Tivanski
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
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36
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Abstract
Accurate measurements of electronic properties of molecular junctions are important for both fundamental and practical applications. Often the molecule-electrode contacts are poorly characterized, leading to wide variation in the measured resistance values. A new paper in this issue demonstrates the use of a reference molecule as an internal standard to compensate for the varying conditions of the molecular contact in conductive-tip atomic force microscopy measurements and yields consistent resistances relative to the reference despite variations in absolute resistance.
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Affiliation(s)
- Lloyd A Bumm
- Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 West Brooks Street, Norman, Oklahoma 73019-2061, USA.
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37
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Exploring Electronic Transport in Molecular Junctions by Conducting Atomic Force Microscopy. Top Curr Chem (Cham) 2008; 285:157-202. [DOI: 10.1007/128_2007_25] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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38
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Fang L, Park JY, Ma H, Jen AKY, Salmeron M. Atomic force microcopy study of the mechanical and electrical properties of monolayer films of molecules with aromatic end groups. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:11522-11525. [PMID: 17924672 DOI: 10.1021/la701489p] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The effect of intermolecular pi-pi stacking on the electrical and mechanical properties of monolayer film molecules containing aromatic groups was studied using atomic force microscopy. Two types of aromatic molecules, (4-mercaptophenyl) anthrylacetylene (MPAA) and (4-mercaptophenyl)-phenylacetylene (MPPA), were used as model systems with different pi-pi stacking strength. Monolayer films of these molecules on Au(111) surfaces exhibited conductivities differing by more than 1 order of magnitude, with MPAA being the most conductive and MPPA being the least conductive. The response to compressive loads by the AFM tip was also found to be very different for both molecules. In MPAA films, distinct molecular conductivity changes are observed upon mechanical perturbation. This effect, however, was not observed on the MPPA film, where intermolecular pi-pi interactions are likely weaker.
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Affiliation(s)
- Liang Fang
- Molecular Foundry, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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39
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Zhang Y, Ma Q, Zhang H, Zhu G. Measuring the Electronic Decay Constant of Alkanedithiols by Electrochemical Impedance Spectroscopy. CHEM LETT 2007. [DOI: 10.1246/cl.2007.1398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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40
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Rospigliosi A, Ehlich R, Hoerber H, Middelberg A, Moggridge G. Electron transfer of plurimodified DNA SAMs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:8264-71. [PMID: 17590024 DOI: 10.1021/la063704g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
An STM-based current-voltage (I/V) investigation of deoxyribonucleic acid (DNA) 18 base pair (bp) oligonucleotide monolayers on gold is presented. Three bases of each of the immobilized and complementary strands were modified with either iodine or phenylethylene moieties. The oligonucleotides were immobilized on template stripped gold (tsg) surfaces and characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). AFM imaging showed that monolayers of the expected height were formed. A comparative study of normal, halogenated, and phenyl-modified DNA was made with the STM in tunneling spectroscopy (TS) mode. I/V spectroscopic measurements in the range +/-250 mV on both single- and double-stranded (ds) DNA monolayers (modified and unmodified) showed that for negative substrate bias (U(sub)) electron transfer is more efficient through a phenyl-modified monolayer than through normal or halogenated DNA. This effect was particularly clear below a threshold bias of -100 mV. For positive U(sub), unmodified ds DNA was found to conduct slightly better than the modified strands. This is presumably caused by greater order in the unmodified versus modified DNA monolayers. Modifications on the immobilized (thiolated) strand seem to improve electron transport through the DNA monolayer more than modifications on the complementary (not surface-bound) strand.
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Affiliation(s)
- Alessandro Rospigliosi
- Department of Chemical Engineering, University of Cambridge, Pembroke Street, New Museum Site, Cambridge, United Kingdom.
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Szunerits S, Pust SE, Wittstock G. Multidimensional electrochemical imaging in materials science. Anal Bioanal Chem 2007; 389:1103-20. [PMID: 17602213 DOI: 10.1007/s00216-007-1374-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 05/08/2007] [Accepted: 05/10/2007] [Indexed: 11/28/2022]
Abstract
In the past 20 years the characterization of electroactive surfaces and electrode reactions by scanning probe techniques has advanced significantly, benefiting from instrumental and methodological developments in the field. Electrochemical and electrical analysis instruments are attractive tools for identifying regions of different electrochemical properties and chemical reactivity and contribute to the advancement of molecular electronics. Besides their function as a surface analytical device, they have proved to be unique tools for local synthesis of polymers, metal depots, clusters, etc. This review will focus primarily on progress made by use of scanning electrochemical microscopy (SECM), conductive AFM (C-AFM), electrochemical scanning tunneling microscopy (EC-STM), and surface potential measurements, for example Kelvin probe force microscopy (KFM), for multidimensional imaging of potential-dependent processes on metals and electrified surfaces modified with polymers and self assembled monolayers.
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Affiliation(s)
- Sabine Szunerits
- Laboratoire d'Electrochimie et de Physicochimie des Matériaux et des Interfaces (LEPMI), CNRS-INPG-UJF, St Martin d'Hères Cedex, France.
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Cyganik P, Buck M, Wilton-Ely JDET, Wöll C. Stress in self-assembled monolayers: omega-biphenyl alkane thiols on Au(111). J Phys Chem B 2007; 109:10902-8. [PMID: 16852327 DOI: 10.1021/jp051378s] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Self-assembled monolayers of omega-(4'-methylbiphenyl-4-yl) alkane thiols CH3(C6H4)2(CH2)(n)SH (BPn, n = 2, 3, and 5) on Au(111) substrates, prepared at room and elevated temperatures, were studied using scanning tunneling microscopy. In contrast to the biphenyl thiol analogues with n = 0 or 1, ordered domains of large size are formed which exhibit small, periodic height variations on a length scale of several nanometers. These are attributed to solitons (or domain walls), resulting from structural mismatch between the molecular adlayer and the gold substrate. The implications of these results for the design of aromatic thiols to cope with stress and yield low-defect density self-assembled monolayers are discussed.
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Affiliation(s)
- Piotr Cyganik
- School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK.
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Affiliation(s)
- Feng Tao
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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Bonanni B, Andolfi L, Bizzarri AR, Cannistraro S. Functional Metalloproteins Integrated with Conductive Substrates: Detecting Single Molecules and Sensing Individual Recognition Events. J Phys Chem B 2007; 111:5062-75. [PMID: 17425359 DOI: 10.1021/jp070035m] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the past decade, there has been significant interest in the integration of biomaterials with electronic elements: combining biological functions of biomolecules with nanotechnology offers new perspectives for implementation of ultrasensitive hybrid nanodevices. In particular, great attention has been devoted to redox metalloproteins, since they possess unique characteristics, such as electron-transfer capability, possibility of gating redox activity, and nanometric size, which make them appealing for bioelectronics applications at the nanoscale. The reliable connection of redox proteins to electrodes, aimed at ensuring good electrical contact with the conducting substrate besides preserving protein functionality, is a fundamental step for designing a hybrid nanodevice and calls for a full characterization of the immobilized proteins, possibly at the single-molecule level. Here, we describe how a multitechnique approach, based on several scanning probe microscopy techniques, may provide a comprehensive characterization of different metalloproteins on metal electrodes, disclosing unique information not only about morphological properties of the adsorbed molecules but also about the effectiveness of electrical coupling with the conductive substrate, or even concerning the preserved biorecognition capability upon adsorption. We also show how the success of an immobilization strategy, which is of primary importance for optimal integration of metalloproteins with a metal electrode, can be promptly assessed by means of the proposed approach. Besides the characterization aspect, the complementary employment of the proposed techniques deserves major potentialities for ultrasensitive detection of adsorbed biomolecules. In particular, it is shown how sensing of single metalloproteins may be optimized by monitoring the most appropriate observable. Additionally, we suggest how the combination of several experimental techniques might offer increased versatility, real-time response, and wide applicability as a detection method, once a reproducible correlation among signals coming from different single-molecule techniques is established.
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Affiliation(s)
- B Bonanni
- Biophysics and Nanoscience Centre, CNISM, and CNR-INFM Facoltà di Scienze, Università della Tuscia, Largo dell'Università, I-01100 Viterbo, Italy
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Liang J, Sun Q, Selloni A, Scoles G. Side-by-Side Characterization of Electron Tunneling through Monolayers of Isomeric Molecules: A Combined Experimental and Theoretical Study. J Phys Chem B 2006; 110:24797-801. [PMID: 17149895 DOI: 10.1021/jp066059v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a new experimental method for measuring relatively small differences in electron tunneling through two distinct monolayers. We place them side by side using scanning probe nanolithography and compare the tunneling currents by conductive probe atomic force microscopy under identical force, voltage, and tip contamination conditions. We demonstrate the validity of our approach by applying it to two isomeric molecules with similar length and functional groups, with only the position of two functional groups, one aromatic and the other aliphatic, being inverted with respect to each other. The relative values of the two tunneling currents, calculated using density functional theory and the Tersoff-Hamann approach, compare very well with the experimental data, providing us with an example of theory vs experiment agreement that is rather uncommon in this field.
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Cyganik P, Buck M, Strunskus T, Shaporenko A, Wilton-Ely JDET, Zharnikov M, Wöll C. Competition as a Design Concept: Polymorphism in Self-Assembled Monolayers of Biphenyl-Based Thiols. J Am Chem Soc 2006; 128:13868-78. [PMID: 17044715 DOI: 10.1021/ja0640647] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Self-assembled monolayers (SAMs) of two omega-(4'-methylbiphenyl-4-yl)alkanethiols (CH(3)(C(6)H(4))(2)(CH(2))(n)SH, BPn, n = 4, 6) on Au(111) substrates, prepared from solution at room temperature and subsequently annealed at temperatures up to 493 K under a nitrogen atmosphere, were studied using scanning tunneling microscopy (STM), high-resolution X-ray photoelectron spectroscopy (HRXPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In striking contrast to BPn SAMs with n = odd, for which only one phase is observed, the even-numbered BPn SAMs exhibit polymorphism. Irreversible phase transitions occur which involve three phases differing substantially in density and stability. Upon annealing, BP4 and BP6 transform into a beta-phase, which is characterized by an exceptionally high structural quality with virtually defect-free domains exceeding 500 nm in diameter. Exchange experiments, monitored by contact angle measurement, reveal that the beta-phase exhibits a dramatically improved stability. The fundamental differences in the phase behavior of even- and odd-numbered BPn SAMs are discussed in terms of two design strategies based on cooperative and competitive effects.
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Affiliation(s)
- Piotr Cyganik
- School of Chemistry, St Andrews University, North Haugh, St Andrews KY16 9ST, United Kingdom.
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Kitagawa T, Idomoto Y, Matsubara H, Hobara D, Kakiuchi T, Okazaki T, Komatsu K. Rigid Molecular Tripod with an Adamantane Framework and Thiol Legs. Synthesis and Observation of an Ordered Monolayer on Au(111). J Org Chem 2006; 71:1362-9. [PMID: 16468783 DOI: 10.1021/jo051863j] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tripod-shaped trithiols 1-3, containing CH2SH groups at the three bridgehead positions of the adamantane framework and a halogen-containing group [Br (1), p-BrC6H4 (2), or p-IC6H4 (3)] at the fourth bridgehead, were synthesized, and self-assembled monolayers (SAMs) were prepared on atomically flat Au111 surfaces. The three-point chemisorption of these tripods was confirmed by polarization modulation infrared reflection absorption spectroscopy, which showed the absence of a S-H stretching band. Scanning tunneling microscopy of the SAM of 1 exhibited a hexagonal arrangement of the adsorbed molecule with a lattice constant of 8.7 angstroms. A unidirectionally oriented, head-to-tail array of 1, which allows the close approach of neighboring molecules, is proposed as a reasonable model of the two-dimensional crystal, where the adsorbed sulfur atoms form a quasi-(radical3 x radical3)R30 degrees lattice. The charge of the electrochemical reductive desorption of the SAM of 1 was in good agreement with the expected surface coverage, while the SAMs of 2 and 3 showed somewhat less (ca. 70%) charge. The large negative reduction peak potentials, observed for the SAM of 1, are taken to indicate a tight anchoring of this tripod by three sulfur atoms.
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Affiliation(s)
- Toshikazu Kitagawa
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
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Quantum chemical study of coherent electron transport in oligophenylene molecular junctions of different lengths. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.07.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Muramatsu M, Akatsuka K, Ebina Y, Wang K, Sasaki T, Ishida T, Miyake K, Haga MA. Fabrication of densely packed titania nanosheet films on solid surface by use of Langmuir-Blodgett deposition method without amphiphilic additives. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:6590-5. [PMID: 15982072 DOI: 10.1021/la050293f] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Densely packed exfoliated nanosheet films such as Ti0.91O2, Ti0.8M0.2O2 (M = Co, Ni), Ti0.6Fe0.4O2, and Ca2Nb3O10 on solid substrates were prepared by the LB transfer method without any amphiphilic additives at the air-water interface. Nanosheet crystallites covered nearly 95% on the solid surface with minimum overlapping of nanosheets. The LB transfer method of the Ti0.91O2 nanosheet monolayer film is applicable for not only hydrophilic substrates such as quartz, silicon, indium-tin oxide (ITO), and glass but also the hydrophobic Au surface. On the basis of these points, the LB transfer method has advantages compared to the alternating layer-by-layer method, which makes use of oppositely charged polyelectrolytes such as poly(ethylenimine) (PEI). Adsorption of hydrophobic Ti0.91O2 nanosheets at the air-water interface is responsible for this LB transfer deposition method. The addition of tetrabutylammonium bromide into the subphase assisted the adsorption, causing an increase in the adsorbed amount of Ti0.91O2 nanosheets at the air-water interface.
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Affiliation(s)
- Masaru Muramatsu
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
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Kim YH, Jang SS, Goddard WA. Conformations and charge transport characteristics of biphenyldithiol self-assembled-monolayer molecular electronic devices: A multiscale computational study. J Chem Phys 2005; 122:244703. [PMID: 16035789 DOI: 10.1063/1.1937391] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report a computational study of conformations and charge transport characteristics of biphenyldithiol (BPDT) monolayers in the (sqrt.3 x sqrt.3)R30 degrees packing ratio sandwiched between Au(111) electrodes. From force-field molecular-dynamics and annealing simulations of BPDT self-assembled monolayers (SAMs) with up to 100 molecules on a Au(111) substrate, we identify an energetically favorable herringbone-type SAM packing configuration and a less-stable parallel packing configuration. Both SAMs are described by the (2sqrt.3 x sqrt.3)R30 degrees unit cell including two molecules. With subsequent density-functional theory calculations of one unit cell of the (i) herringbone SAM with the molecular tilt angle theta approximately 15 degrees , (ii) herringbone SAM with theta approximately 30 degrees , and (iii) parallel SAM with theta approximately 30 degrees, we confirm that the herringbone packing configuration is more stable than the parallel one but find that the energy variation with respect to the molecule tilting within the herringbone packing is very small. Next, by capping these SAMs with the top Au(111) electrode, we prepare three molecular electronic device models and calculate their coherent charge transport properties within the matrix Green's function approach. Current-voltage (I-V) curves are then obtained via the Landauer-Buttiker formula. We find that at low-bias voltages (|V| < or = 0.2 V) the I-V characteristics of models (ii) and (iii) are similar and the current in model (i) is smaller than that in (ii) and (iii). On the other hand, at higher-bias voltages (|V| > or 0.5 V), the I-V characteristics of the three models show noticeable differences due to different phenyl band structures. We thus conclude that the BPDT SAM I-V characteristics in the low-bias voltage region are mainly determined by the -Au [corrected] interaction within the individual molecule-electrode contact, while both intramolecular conformation and intermolecular interaction can affect the BPDT SAM I-V characteristics in the high-bias voltage region.
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Affiliation(s)
- Yong-Hoon Kim
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, 91125-7400, USA.
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