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Colin-Molina A, Nematiaram T, Cheung AMH, Troisi A, Frisbie CD. The Conductance Isotope Effect in Oligophenylene Imine Molecular Wires Depends on the Number and Spacing of 13C-Labeled Phenylene Rings. ACS NANO 2024; 18:7444-7454. [PMID: 38411123 DOI: 10.1021/acsnano.3c11327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
We report a strong and structurally sensitive 13C intramolecular conductance isotope effect (CIE) for oligophenyleneimine (OPI) molecular wires connected to Au electrodes. Wires were built from Au surfaces beginning with the formation of 4-aminothiophenol self-assembled monolayers (SAMs) followed by subsequent condensation reactions with 13C-labeled terephthalaldehyde and phenylenediamine; in these monomers the phenylene rings were either completely 13C-labeled or the naturally abundant 12C isotopologues. Alternatively, perdeuterated versions of terephthalaldehyde and phenylenediamine were employed to make 2H(D)-labeled OPI wires. For 13C-isotopologues of short OPI wires (<4 nm) in length where the charge transport mechanism is tunneling, there was no measurable effect, i.e., 13C CIE ≈ 1, where CIE is defined as the ratio of labeled and unlabeled wire resistances, i.e., CIE = Rheavy/Rlight. However, for long OPI wires >4 nm, in which the transport mechanism is polaron hopping, a strong 13C CIE = 4-5 was observed. A much weaker inverse CIE < 1 was evident for the longest D-labeled wires. Importantly, the magnitude of the 13C CIE was sensitive to the number and spacing of 13C-labeled rings, i.e., the CIE was structurally sensitive. The structural sensitivity is intriguing because it may be employed to understand polaron hopping mechanisms and charge localization/delocalization in molecular wires. A preliminary theoretical analysis explored several possible explanations for the CIE, but so far a fully satisfactory explanation has not been identified. Nevertheless, the latest results unambiguously demonstrate structural sensitivity of the heavy atom CIE, offering directions for further utilization of this interesting effect.
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Affiliation(s)
- Abraham Colin-Molina
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Tahereh Nematiaram
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G11XL, United Kingdom
| | - Andy Man Hong Cheung
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Alessandro Troisi
- Department of Chemistry, University of Liverpool, Liverpool L697ZD, United Kingdom
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Joshi J, Homburg SV, Ehrmann A. Atomic Force Microscopy (AFM) on Biopolymers and Hydrogels for Biotechnological Applications-Possibilities and Limits. Polymers (Basel) 2022; 14:1267. [PMID: 35335597 PMCID: PMC8949482 DOI: 10.3390/polym14061267] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/15/2022] [Accepted: 03/19/2022] [Indexed: 02/01/2023] Open
Abstract
Atomic force microscopy (AFM) is one of the microscopic techniques with the highest lateral resolution. It can usually be applied in air or even in liquids, enabling the investigation of a broader range of samples than scanning electron microscopy (SEM), which is mostly performed in vacuum. Since it works by following the sample surface based on the force between the scanning tip and the sample, interactions have to be taken into account, making the AFM of irregular samples complicated, but on the other hand it allows measurements of more physical parameters than pure topography. This is especially important for biopolymers and hydrogels used in tissue engineering and other biotechnological applications, where elastic properties, surface charges and other parameters influence mammalian cell adhesion and growth as well as many other effects. This review gives an overview of AFM modes relevant for the investigations of biopolymers and hydrogels and shows several examples of recent applications, focusing on the polysaccharides chitosan, alginate, carrageenan and different hydrogels, but depicting also a broader spectrum of materials on which different AFM measurements are reported in the literature.
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Affiliation(s)
- Jnanada Joshi
- Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, 33619 Bielefeld, Germany
| | - Sarah Vanessa Homburg
- Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, 33619 Bielefeld, Germany
| | - Andrea Ehrmann
- Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, 33619 Bielefeld, Germany
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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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Metal complex oligomer and polymer wires on electrodes: Tactical constructions and versatile functionalities. POLYMER 2013. [DOI: 10.1016/j.polymer.2013.04.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Jett JE, Lederman D, Wollenberg LA, Li D, Flora DR, Bostick CD, Tracy TS, Gannett PM. Measurement of electron transfer through cytochrome P450 protein on nanopillars and the effect of bound substrates. J Am Chem Soc 2013; 135:3834-40. [PMID: 23427827 PMCID: PMC3876957 DOI: 10.1021/ja309104g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron transfer in cytochrome P450 enzymes is a fundamental process for activity. It is difficult to measure electron transfer in these enzymes because under the conditions typically used they exist in a variety of states. Using nanotechnology-based techniques, gold conducting nanopillars were constructed in an indexed array. The P450 enzyme CYP2C9 was attached to each of these nanopillars, and conductivity measurements made using conducting probe atomic force microscopy under constant force conditions. The conductivity measurements were made on CYP2C9 alone and with bound substrates, a bound substrate-effector pair, and a bound inhibitor. Fitting of the data with the Poole-Frenkel model indicates a correlation between the barrier height for electron transfer and the ease of CYP2C9-mediated metabolism of the bound substrates, though the spin state of iron is not well correlated. The approach described here should have broad application to the measurement of electron transfer in P450 enzymes and other metalloenzymes.
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Affiliation(s)
- John E. Jett
- West Virginia University, Basic Pharmaceutical Sciences, Morgantown, WV 26506-9530
| | - David Lederman
- West Virginia University, Department of Physics, Morgantown, WV 26506-6315
| | - Lance A. Wollenberg
- West Virginia University, Basic Pharmaceutical Sciences, Morgantown, WV 26506-9530
| | - Debin Li
- West Virginia University, Department of Physics, Morgantown, WV 26506-6315
| | - Darcy R. Flora
- University of Minnesota, College of Pharmacy, Minneapolis, MN, 55455
| | | | - Timothy S. Tracy
- University of Kentucky, College of Pharmacy, Lexington, KY 40536
| | - Peter M. Gannett
- West Virginia University, Basic Pharmaceutical Sciences, Morgantown, WV 26506-9530
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Käfer D, Bashir A, Dou X, Witte G, Müllen K, Wöll C. Evidence for band-like transport in graphene-based organic monolayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:384-388. [PMID: 20217724 DOI: 10.1002/adma.200902123] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Affiliation(s)
- Daniel Käfer
- Physical Chemistry I, Department of Chemistry, Ruhr-University Bochum, 44780 Bochum, Germany
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McKendry JE, Allen CS, Critchley K, Górzny ML, Walton AS, Evans SD. Magnetic field enhanced nano-tip fabrication for four-probe STM studies. NANOTECHNOLOGY 2008; 19:085201. [PMID: 21730719 DOI: 10.1088/0957-4484/19/8/085201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present an improved method for fabricating tungsten STM tips for measuring nanoscale objects using a multiprobe STM. The tips were prepared by a 'drop-off' technique combined with a magnetic field. For magnetic field strengths above 150 Oe the electrolyte was seen to rotate about the tungsten anode. This rotation reduced the adhesion of bubbles and led to a reduction in the cone angle of the tips produced. This property is advantageous for multiprobe measurements as it allows one to bring multiple tips into close proximity.
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Affiliation(s)
- J E McKendry
- School of Physics and Astronomy, University of Leeds, West Yorkshire, UK
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Krapchetov DA, Ma H, Jen AKY, Fischer DA, Loo YL. High-sensitivity transmission IR spectroscopy for the chemical identification and structural analysis of conjugated molecules on gallium arsenide surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:9491-4. [PMID: 17073469 DOI: 10.1021/la0623984] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We demonstrate the use of high-sensitivity, off-normal transmission IR spectroscopy with s-polarized light to probe the chemical identity and orientation of quaterphenyldithiol (QPDT) molecular assemblies on GaAs as a function of ammonium hydroxide (NH4OH) concentration. NH4OH is added to the assembly solution to convert the thioacetyl groups on the QPDT precursor to thiolates. When assembled at high NH4OH concentrations, the acetyl groups are completely removed, and QPDT is disordered on GaAs. Assembly at low NH4OH concentrations, however, results in QPDT assemblies that are preferentially upright. The molecular orientation is further quantified with near-edge X-ray absorption fine structure spectroscopy.
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Affiliation(s)
- Dmitry A Krapchetov
- Chemical Engineering Department and Center for Nano- and Molecular Science and Technology, University of Texas at Austin, Austin, Texas 78712, USA
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Beebe JM, Engelkes VB, Liu J, Gooding JJ, Eggers PK, Jun Y, Zhu X, Paddon-Row MN, Frisbie CD. Length Dependence of Charge Transport in Nanoscopic Molecular Junctions Incorporating a Series of Rigid Thiol-Terminated Norbornylogs. J Phys Chem B 2005; 109:5207-15. [PMID: 16863186 DOI: 10.1021/jp044630p] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Four tetrathiol-terminated norbornane homologues were synthesized and self-assembled monolayers (SAMs) of these molecules were formed on Au via adsorption from CH2Cl2. SAMs were characterized structurally via spectroscopic ellipsometry (SE), reflection-absorption infrared spectroscopy (RAIRS), Rutherford backscattering spectrometry (RBS), and X-ray photoelectron spectroscopy (XPS). Results of these analyses show that the rigid norbornylogs form monolayers that have a surface coverage slightly lower than that of alkanethiols, and that they exhibit a nonmonotonic dependence of film thickness on molecular length. Nanoscale molecular junctions incorporating these SAMs were formed and characterized electrically using conducting probe atomic force microscopy (CP-AFM). The resistances of these junctions scale exponentially with the contour length of the molecules, with beta = 0.9 A(-1), consistent with a nonresonant tunneling mechanism. Further, the resistance of norbornyl SAMs correlates well with the resistance of alkanedithiol SAMs of similar length, suggesting that the norbornyl molecules form sulfur-metal bonds on both ends of the junction.
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Affiliation(s)
- Jeremy M Beebe
- Department of Chemistry, University of Minnesota, 209 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
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Davis JJ, Morgan DA, Wrathmell CL, Axford DN, Zhao J, Wang N. Molecular bioelectronics. ACTA ACUST UNITED AC 2005. [DOI: 10.1039/b417712f] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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