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Electro-polymerization rates of diazonium salts are dependent on the crystal orientation of the surface. J Colloid Interface Sci 2022; 626:985-994. [PMID: 35839679 DOI: 10.1016/j.jcis.2022.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/30/2022] [Accepted: 07/03/2022] [Indexed: 02/05/2023]
Abstract
Electro-polymerization of diazonium salts is widely used for modifying surfaces with thin organic films. Initially this method was primarily applied to carbon, then to metals, and more recently to semiconducting Si. Unlike on other surfaces, electrochemical reduction of diazonium salts on Si, which is one of the most industrially dominant material, is not well understood. Here, we report the electrochemical reduction of diazonium salts on a range of silicon electrodes of different crystal orientations (111, 211, 311, 411, and 100). We show that the kinetics of surface reaction and the reduction potential is Si crystal-facet dependent and is more favorable in the hierarchical order (111) > (211) > (311) > (411) > (100), a finding that offers control over the surface chemistry of diazonium salts on Si. The dependence of the surface reaction kinetics on the crystal orientation was found to be directly related to differences in the potential of zero charge (PZC) of each crystal orientation, which in turn controls the adsorption of the diazonium cations prior to reduction. Another consequence of the effect of PZC on the adsorption of diazonium cations, is that molecules terminated by distal diazonium moieties form a compact film in less time and requires less reduction potentials compared to that formed from diazonium molecules terminated by only one diazo moiety. In addition, at higher concentrations of diazonium cations, the mechanism of electrochemical polymerization on the surface becomes PZC-controlled adsorption-dominated inner-sphere electron transfer while at lower concentrations, diffusion-based outer-sphere electron transfer dominates. These findings help understanding the electro-polymerization reaction of diazonium salts on Si en route towards an integrated molecular and Si electronics technology.
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2
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Kharintsev SS, Kazarian SG. Nanoscale Melting of 3D Confined Azopolymers through Tunable Thermoplasmonics. J Phys Chem Lett 2022; 13:5351-5357. [PMID: 35678375 PMCID: PMC9208006 DOI: 10.1021/acs.jpclett.2c01103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/20/2022] [Indexed: 05/11/2023]
Abstract
Phase transitions that are thermally induced by using light at the nanoscale play a vital role in material science. Enhanced optical heating sustained by resonant nanostructures can turn out to be insignificant when a higher thermal conductivity of a heatsink, regardless of the pumping intensity. In this Letter, we demonstrate an approach to control an operating temperature range due to excess heating of a structured heatsink. A design rationale has been performed by using a 2D array of TiN:Si voxels, consisting of stacked TiN and Si pillars. All the TiN nanoheaters responsible for enhanced light absorption at plasmon resonance are of equal size, and the height of the Si pillars varies to control heat localization. A height-dependent temperature rise of the Si pillars is found from Raman thermometry. Herein, for the first time, we have determined the melting temperature of azobenzene-functionalized polymers at the nanoscale using the tunable plasmonic metasurface.
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Affiliation(s)
- Sergey S. Kharintsev
- Department
of Optics and Nanophotonics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan 420008, Russia
| | - Sergei G. Kazarian
- Department
of Chemical Engineering, Imperial College
London, South Kensington Campus, SW7 2AZ London, United Kingdom
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3
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Rani C, Tanwar M, Ghosh T, Kandpal S, Pathak DK, Chaudhary A, Yogi P, Saxena SK, Kumar R. Raman Spectroscopy as a Simple yet Effective Analytical Tool for Determining Fermi Energy and Temperature Dependent Fermi Shift in Silicon. Anal Chem 2022; 94:1510-1514. [DOI: 10.1021/acs.analchem.1c03624] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chanchal Rani
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Manushree Tanwar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Tanushree Ghosh
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Suchita Kandpal
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Devesh K. Pathak
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Anjali Chaudhary
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Priyanka Yogi
- Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
| | | | - Rajesh Kumar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
- Centre for Indian Scientific Knowledge Systems, Indian Institute of Technology Indore, Simrol 453552, India
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4
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Bi H, Jing C, Hasch P, Gong Y, Gerster D, Barth JV, Reichert J. Single Molecules in Strong Optical Fields: A Variable-Temperature Molecular Junction Spectroscopy Setup. Anal Chem 2021; 93:9853-9859. [PMID: 34229433 DOI: 10.1021/acs.analchem.1c01633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to advance the development of molecular electronic devices, it is mandatory to improve the understanding of electron transport and functionalities in single molecules, integrated in a well-defined environment. However, limited information can be obtained by solely analyzing I-V characteristics, whence multiparameter studies are required to obtain more information on such systems including chemical bonds, geometry, and intramolecular strain. Therefore, we developed an analytical method incorporating an optical near-field technique, which allows us to investigate single-molecule junctions at variable temperatures in strong optical fields. An apertureless near-field emitter acts as a counter electrode and a plasmonic waveguide to focus surface plasmon polaritons into the molecular junctions, where a strongly enhanced evanescent field is confined to only a few nanometers around the apex of the tip. The proof of concept, even at low temperatures, is demonstrated by simultaneously investigating electronic and optical features of the molecule p-terphenyl-4,4″-dithiol in dependence of its charge state. This multichannel method can be employed to analyze a variety of nearly unexplored properties in single-molecule junctions such as photoconductance and photocurrent generation and allows a characterization of the molecular junctions by spectroscopic means as well.
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Affiliation(s)
- Hai Bi
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
| | - Chao Jing
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany.,Department of Hydrogen Technique, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jialuo Road 2019, 201800 Shanghai, China.,School of Chemistry & Molecular Engineering, East China University of Science and Technology, Meilong Road 130, 200237 Shanghai, China
| | - Peter Hasch
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
| | - Yuxiang Gong
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
| | - Daniel Gerster
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
| | - Johannes V Barth
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
| | - Joachim Reichert
- Physics-Department E20, Technical University of Munich, James Franck Str. 1, 85748 Garching, Germany
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5
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Van Dyck C, Bergren AJ, Mukundan V, Fereiro JA, DiLabio GA. Extent of conjugation in diazonium-derived layers in molecular junction devices determined by experiment and modelling. Phys Chem Chem Phys 2019; 21:16762-16770. [PMID: 31328202 DOI: 10.1039/c9cp03509e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
This paper shows that molecular layers grown using diazonium chemistry on carbon surfaces have properties indicative of the presence of a variety of structural motifs. Molecular layers grown with aromatic monomers with thickness between 1 and ∼15 nm display optical absorption spectra with significant broadening but no change in band gap or onsets of absorption as a function of layer thickness. This suggests that there is no extended conjugation in these layers, contrary to the conclusions of previous work. Density-functional theory modelling of the non-conjugated versions of the constituent aromatic monomers reveals that the experimental trends in optical spectra can be recovered, thereby establishing limits to the degree of conjugation and the nature of the order of as-grown molecular layers. We conclude that the absence of both shifts in band gap and changes in absorption onset is a consequence of resonant conjugation within the layers being less than 1.5 monomer units, and that film disorder is the main origin of the optical spectra. These findings have important implications for understanding charge transport mechanisms in molecular junction devices, as the layers cannot be expected to behave as ideal, resonantly conjugated films, but should be viewed as a collection of mixed nonresonantly- and resonantly-conjugated monomers.
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Affiliation(s)
- Colin Van Dyck
- Nanotechnology Research Centre, National Research Council of Canada, 11427 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
| | - Adam Johan Bergren
- Nanotechnology Research Centre, National Research Council of Canada, 11427 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
| | - Vineetha Mukundan
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jerry A Fereiro
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Gino A DiLabio
- Department of Chemistry, The University of British Columbia, 3247 University Way, Kelowna, British Columbia V1V 1V7, Canada. and Faculty of Management, The University of British Columbia, 1137 Alumni Ave, Kelowna, British Columbia V1V 1V7, Canada
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6
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Hu E, Zhao X, Pan S, Ye Z, He F. Sorption of Non-ionic Aromatic Organics to Mineral Micropores: Interactive Effect of Cation Hydration and Mineral Charge Density. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3067-3077. [PMID: 30794386 DOI: 10.1021/acs.est.9b00145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The influence of K+ and Ca2+ on the sorption of non-ionic aromatic contaminants (1,4-dinitrobenzene and p-xylene) on a series of microporous zeolite minerals (HZSM-5) with various surface charge densities was investigated. For zeolites with high or low charge density (>1.78 or <0.16 sites/nm2), K+ and Ca2+ had negligible influence on the sorption of organics, which mainly occurred at the hydrophobic nanosites. For zeolites with charge density in the moderate range (0.16-1.78 sites/nm2), the sorption of organics was strongly dependent upon the cation hydration effect. K+ with a lower hydration free energy greatly favored sorption of organics to the micropores compared to Ca2+. Differential scanning calorimetry and X-ray photoelectron spectroscopy results indicated that K+ can reduce the water affinity and promote specific sorption of organics in the zeolites with moderate charge density. The above mechanisms were successfully applied to explain the retention of 1,4-dinitrobenzene and p-xylene on four natural minerals (smectite, illite, kaolinite, and mordenite). This study shed new insights on how cation hydration influences sorption interactions of non-ionic aromatic contaminants at mineral-water interfaces as a function of the mineral charge density.
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Affiliation(s)
- Erdan Hu
- College of Environment , Zhejiang University of Technology , Hangzhou , Zhejiang 310014 , People's Republic of China
| | - Xinglei Zhao
- College of Environment , Zhejiang University of Technology , Hangzhou , Zhejiang 310014 , People's Republic of China
| | - Shangyue Pan
- College of Environment , Zhejiang University of Technology , Hangzhou , Zhejiang 310014 , People's Republic of China
| | - Ziwei Ye
- College of Environment , Zhejiang University of Technology , Hangzhou , Zhejiang 310014 , People's Republic of China
| | - Feng He
- College of Environment , Zhejiang University of Technology , Hangzhou , Zhejiang 310014 , People's Republic of China
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James DD, Bayat A, Smith SR, Lacroix JC, McCreery RL. Nanometric building blocks for robust multifunctional molecular junctions. NANOSCALE HORIZONS 2018; 3:45-52. [PMID: 32254109 DOI: 10.1039/c7nh00109f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Much of the motivation for developing molecular electronic devices is the prospect of achieving novel electronic functions by varying molecular structure. We describe a "building block" approach for molecular junctions resulting in one, two or three nanometer-thick molecular layers in a commercially proven junction design. A single layer of anthraquinone between carbon electrodes provides a tunnel device with applications in electronic music, and a second layer of a thiophene derivative yields a molecular rectifier with quite different audio characteristics. A third layer of lithium benzoate produces a redox-active device with possible applications in non-volatile memory devices or on-chip energy storage. The building block approach forms a basis for "rational design" of electronic functions, in which layers of varying structure produce distinct and desirable electronic behaviours.
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Affiliation(s)
- David D James
- National Institute for Nanotechnology, University of Alberta, 11421 Saskatchewan Dr Edmonton, AB T6G 2M9, Canada.
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8
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Kharintsev SS, Fishman AI, Saikin SK, Kazarian SG. Near-field Raman dichroism of azo-polymers exposed to nanoscale dc electrical and optical poling. NANOSCALE 2016; 8:19867-19875. [PMID: 27878200 DOI: 10.1039/c6nr07508h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Azobenzene-functionalized polymer films are functional materials, where the (planar vs. homeotropic) orientation of azo-dyes can be used for storing data. In order to characterize the nanoscale 3D orientation of the pigments in sub-10 nm thick polymer films we use two complementary techniques: polarization-controlled tip-enhanced Raman scattering (TERS) microscopy and contact scanning capacity microscopy. We demonstrate that the homeotropic and planar orientations of the azo-dyes are produced by applying a local dc electrical field and a resonant longitudinal optical near-field, respectively. For a non-destructive probe of the azo-dye orientation we apply a non-resonant optical near-field and compare the intensities of the Raman-active vibrational modes. We show that near-field Raman dichroism, a characteristic similar to the absorption dichroism used in far-field optics, can be a quantitative indicator of the 3D molecular orientation of the azo-dye at the nanoscale. This study directly benefits the further development of photochromic near-field optical memory that can lead to ultrahigh density information storage.
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Affiliation(s)
- Sergey S Kharintsev
- Department of Optics and Nanophotonics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia. and Institute of Perspective Technologies, Tatarstan Academy of Sciences, Baumana, 20, Kazan, 420111, Russia
| | - Alexandr I Fishman
- Department of Optics and Nanophotonics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia.
| | - Semion K Saikin
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA and Department of Theoretical Physics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia
| | - Sergei G Kazarian
- Department of Chemical Engineering, Imperial College, London, SW7 2AZ, UK
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9
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Berisha A, Chehimi M, Pinson J, Podvorica F. Electrode Surface Modification Using Diazonium Salts. ELECTROANALYTICAL CHEMISTRY: A SERIES OF ADVANCES 2015. [DOI: 10.1201/b19196-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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10
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Hasegawa G, Sato T, Kanamori K, Sun CJ, Ren Y, Kobayashi Y, Kageyama H, Abe T, Nakanishi K. Effect of Calcination Conditions on Porous Reduced Titanium Oxides and Oxynitrides via a Preceramic Polymer Route. Inorg Chem 2015; 54:2802-8. [DOI: 10.1021/ic502972v] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- George Hasegawa
- Department of Energy & Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Tatsuya Sato
- Department of Chemistry, Graduate School
of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kazuyoshi Kanamori
- Department of Chemistry, Graduate School
of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
| | - Cheng-Jun Sun
- X-ray Science Division, Advanced Photon Source (APS), Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Yang Ren
- X-ray Science Division, Advanced Photon Source (APS), Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Yoji Kobayashi
- Department of Energy & Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Hiroshi Kageyama
- Department of Energy & Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
- CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Takeshi Abe
- Department of Energy & Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kazuki Nakanishi
- Department of Chemistry, Graduate School
of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
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11
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Ekşi H, Gupta VK, Üstündağ Z, Atar N, Çağlayan MO, Solak AO. Surface characterization of dinitrophenyl-diaminophenyl nanoplatform on glassy carbon. J Mol Liq 2013. [DOI: 10.1016/j.molliq.2013.05.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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Schmucker AL, Barin G, Brown KA, Rycenga M, Coskun A, Buyukcakir O, Osberg KD, Stoddart JF, Mirkin CA. Electronic and optical vibrational spectroscopy of molecular transport junctions created by on-wire lithography. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:1900-1903. [PMID: 23129396 DOI: 10.1002/smll.201201993] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Indexed: 06/01/2023]
Affiliation(s)
- Abrin L Schmucker
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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13
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Hines T, Díez-Pérez I, Nakamura H, Shimazaki T, Asai Y, Tao N. Controlling formation of single-molecule junctions by electrochemical reduction of diazonium terminal groups. J Am Chem Soc 2013; 135:3319-22. [PMID: 23405987 DOI: 10.1021/ja3106434] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report controlling the formation of single-molecule junctions by means of electrochemically reducing two axialdiazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in situ between the molecule and gold electrodes. We report a yield enhancement in molecular junction formation as the electrochemical potential of both junction electrodes approach the reduction potential of the diazonium terminal groups. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond.
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Affiliation(s)
- Thomas Hines
- Center for Biosensors and Bioelectronics, The Biodesign Institute, and School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
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Chernyy S, Bousquet A, Torbensen K, Iruthayaraj J, Ceccato M, Pedersen SU, Daasbjerg K. Elucidation of the mechanism of redox grafting of diazotated anthraquinone. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:9573-9582. [PMID: 22686253 DOI: 10.1021/la301391s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Redox grafting of aryldiazonium salts containing redox units may be used to form exceptionally thick covalently attached conducting films, even in the micrometers range, in a controlled manner on glassy carbon and gold substrates. With the objective to investigate the mechanism of this process in detail, 1-anthraquinone (AQ) redox units were immobilized on these substrates by electroreduction of 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate. Electrochemical quartz crystal microbalance was employed to follow the grafting process during a cyclic voltammetric sweep by recording the frequency change. The redox grafting is shown to have two mass gain regions/phases: an irreversible one due to the addition of AQ units to the substrate/film and a reversible one due to the association of cations from the supporting electrolyte with the AQ radical anions formed during the sweeping process. Scanning electrochemical microscopy was used to study the relationship between the conductivity of the film and the charging level of the AQ redox units in the grafted film. For that purpose, approach curves were recorded at a platinum ultramicroelectrode for AQ-containing films on gold and glassy carbon surfaces using the ferro/ferricyanide redox system as redox probe. It is concluded that the film growth has its origin in electron transfer processes occurring through the layer mediated by the redox moieties embedded in the organic film.
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Affiliation(s)
- Sergey Chernyy
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark
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15
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González-Fuentes MA, Díaz-Sánchez BR, Vela A, González FJ. Radical grafting of carbon surfaces by oxidation of 5-nitroindole derived anions. J Electroanal Chem (Lausanne) 2012. [DOI: 10.1016/j.jelechem.2012.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Bonifas AP, McCreery RL. Solid State Spectroelectrochemistry of Redox Reactions in Polypyrrole/Oxide Molecular Heterojunctions. Anal Chem 2012; 84:2459-65. [DOI: 10.1021/ac2032047] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrew P. Bonifas
- Department of Materials Science
and Engineering, The Ohio State University, 2041 College Road, Columbus, Ohio 43210, United States
- National Institute for Nanotechnology, National Research Council Canada, Canada, T6G 2G2
| | - Richard L. McCreery
- National Institute for Nanotechnology, National Research Council Canada, Canada, T6G 2G2
- Department of Chemistry, University of Alberta, Canada, T6G 2R3
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17
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Bousquet A, Ceccato M, Hinge M, Pedersen SU, Daasbjerg K. Redox grafting of diazotated anthraquinone as a means of forming thick conducting organic films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:1267-1275. [PMID: 22175534 DOI: 10.1021/la203657n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thick conductive layers containing anthraquinone moieties are covalently immobilized on gold using redox grafting of the diazonium salt of anthraquinone (i.e., 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate). This grafting procedure is based on using consecutive voltammetric sweeping and through this exploiting fast electron transfer reactions that are mediated by the anthraquinone redox moieties in the film. The fast film growth, which is followed by infrared reflection absorption spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and coverage calculation, results in a mushroom-like structure. In addition to varying the number of sweeps, layer thickness control can easily be exerted through appropriate choice of the switching potential and sweep rate. It is shown that the grafting of the diazonium salt is essentially a diffusion-controlled process but also that desorption of physisorbed material during the sweeping process is essentially for avoiding blocking of the film due to clogging of the electrolyte channels in the film. In general, sweep rates higher than 0.5 V s(-1) are required if thick, porous, and conducting films should be formed.
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Affiliation(s)
- Antoine Bousquet
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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18
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Elliott ABS, Horvath R, Gordon KC. Vibrational spectroscopy as a probe of molecule-based devices. Chem Soc Rev 2012; 41:1929-46. [DOI: 10.1039/c1cs15208d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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19
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Coskun A, Spruell JM, Barin G, Dichtel WR, Flood AH, Botros YY, Stoddart JF. High hopes: can molecular electronics realise its potential? Chem Soc Rev 2012; 41:4827-59. [PMID: 22648395 DOI: 10.1039/c2cs35053j] [Citation(s) in RCA: 261] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Ali Coskun
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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20
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Mccreery RL. The merger of electrochemistry and molecular electronics. CHEM REC 2011; 12:149-63. [DOI: 10.1002/tcr.201100006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Indexed: 01/30/2023]
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21
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Yan H, Bergren AJ, McCreery RL. All-Carbon Molecular Tunnel Junctions. J Am Chem Soc 2011; 133:19168-77. [DOI: 10.1021/ja206619a] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Haijun Yan
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada
| | - Adam Johan Bergren
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada
| | - Richard L. McCreery
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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Phillips H, Prociuk A, Dunietz BD. Bias effects on the electronic spectrum of a molecular bridge. J Chem Phys 2011; 134:054708. [DOI: 10.1063/1.3531695] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Bergren AJ, McCreery RL. Analytical chemistry in molecular electronics. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2011; 4:173-195. [PMID: 21370986 DOI: 10.1146/annurev-anchem-061010-113847] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This review discusses the analytical characterization of molecular electronic devices and structures relevant thereto. In particular, we outline the methods for probing molecular junctions, which contain an ensemble of molecules between two contacts. We discuss the analytical methods that aid in the fabrication and characterization of molecular junctions, beginning with the confirmation of the placement of a molecular layer on a conductive or semiconductive substrate. We emphasize methods that provide information about the molecular layer in the junction and outline techniques to ensure molecular layer integrity after the complete fabrication of a device. In addition, we discuss the analytical information derived during the actual device operation.
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Affiliation(s)
- Adam Johan Bergren
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta T6G 2M9, Canada.
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Ru J, Szeto B, Bonifas A, McCreery RL. Microfabrication and integration of diazonium-based aromatic molecular junctions. ACS APPLIED MATERIALS & INTERFACES 2010; 2:3693-3701. [PMID: 21121640 DOI: 10.1021/am100833e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Microfabrication techniques common in commercial semiconductor manufacturing were used to produce carbon/nitroazobenzene/Cu/Au molecular junctions with a range of areas from 3×3 to 400×400 μm, starting with 100-mm-diameter silicon wafers. The approach exhibited high yield (90-100%) and excellent reproducibility of the current density (relative standard deviation of typically 15%) and 32 devices on a chip. Electron-beam-deposited carbon films are introduced as substrates and may be applied at the full wafer level before dicing and electrochemical deposition of the molecular layer. The current scaled with the device area over a factor of >600, and the current density was quantitatively consistent with structurally similar molecular junctions made by other techniques. The current densities were weakly dependent on temperature over the range of 100-390 K, and maximum current densities above 400 A/cm2 were observed without breakdown. To simulate processing and operation conditions, the junction stability was tested at elevated temperatures. The JV curves of microfabricated junctions were unchanged after 22 h at 100 °C. A ∼50% increase in the current density was observed after 20 h at 150 °C but then remained constant for an additional 24 h. Parallel fabrication, thermal stability, and high yield are required for practical applications of molecular electronics, and the reported results provide important steps toward integration of molecular electronic devices with commercial processes and devices.
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Affiliation(s)
- Jie Ru
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta T6G 2M9, Canada
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25
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Modification of carbon surfaces with methyl groups by using ferrocene derivatives as redox catalysts of the oxidation of acetate ions. J Electroanal Chem (Lausanne) 2010. [DOI: 10.1016/j.jelechem.2010.09.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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26
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Yeşildağ A, Ekinci D. Covalent attachment of pyridine-type molecules to glassy carbon surfaces by electrochemical reduction of in situ generated diazonium salts. Formation of ruthenium complexes on ligand-modified surfaces. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2010.06.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Bonifas AP, McCreery RL. 'Soft' Au, Pt and Cu contacts for molecular junctions through surface-diffusion-mediated deposition. NATURE NANOTECHNOLOGY 2010; 5:612-617. [PMID: 20581834 DOI: 10.1038/nnano.2010.115] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 05/13/2010] [Indexed: 05/29/2023]
Abstract
Virtually all types of molecular electronic devices depend on electronically addressing a molecule or molecular layer through the formation of a metallic contact. The introduction of molecular devices into integrated circuits will probably depend on the formation of contacts using a vapour deposition technique, but this approach frequently results in the metal atoms penetrating or damaging the molecular layer. Here, we report a method of forming 'soft' metallic contacts on molecular layers through surface-diffusion-mediated deposition, in which the metal atoms are deposited remotely and then diffuse onto the molecular layer, thus eliminating the problems of penetration and damage. Molecular junctions fabricated by this method exhibit excellent yield (typically >90%) and reproducibility, and allow examination of the effects of molecular-layer structure, thickness and contact work function.
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Affiliation(s)
- Andrew P Bonifas
- Department of Materials, Science and Engineering, The Ohio State University, 2041 College Road, Columbus, Ohio, 43210, USA
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Yao KX, Yin XM, Wang TH, Zeng HC. Synthesis, Self-Assembly, Disassembly, and Reassembly of Two Types of Cu2O Nanocrystals Unifaceted with {001} or {110} Planes. J Am Chem Soc 2010; 132:6131-44. [DOI: 10.1021/ja100151f] [Citation(s) in RCA: 236] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ke Xin Yao
- Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, and Minerals, Metals, and Materials Technology Center, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, and Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education and State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, P. R. China
| | - Xiao Ming Yin
- Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, and Minerals, Metals, and Materials Technology Center, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, and Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education and State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, P. R. China
| | - Tai Hong Wang
- Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, and Minerals, Metals, and Materials Technology Center, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, and Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education and State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, P. R. China
| | - Hua Chun Zeng
- Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, and Minerals, Metals, and Materials Technology Center, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, and Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education and State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, P. R. China
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Nigmatulin R, Alekhin A, Baleanu D, Dinç E, Üstündağ Z, Ekşi H, Solak A. Analysis of the Effect of Potential Cycles on the Reflective Infrared Signals of Nitro Groups in Nanofilms: Application of the Fractional Moments Statistics. ELECTROANAL 2010. [DOI: 10.1002/elan.200900369] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Burckel DB, Washburn CM, Raub AK, Brueck SRJ, Wheeler DR, Brozik SM, Polsky R. Lithographically defined porous carbon electrodes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2792-2796. [PMID: 19823996 DOI: 10.1002/smll.200901084] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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31
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McCreery RL, Bergren AJ. Progress with molecular electronic junctions: meeting experimental challenges in design and fabrication. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2009; 21:4303-4322. [PMID: 26042937 DOI: 10.1002/adma.200802850] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 01/26/2009] [Indexed: 05/28/2023]
Abstract
Molecular electronics seeks to incorporate molecular components as functional elements in electronic devices. There are numerous strategies reported to date for the fabrication, design, and characterization of such devices, but a broadly accepted example showing structure-dependent conductance behavior has not yet emerged. This progress report focuses on experimental methods for making both single-molecule and ensemble molecular junctions, and highlights key results from these efforts. Based on some general objectives of the field, particular experiments are presented to show progress in several important areas, and also to define those areas that still need attention. Some of the variable behavior of ostensibly similar junctions reported in the literature is attributable to differences in the way the junctions are fabricated. These differences are due, in part, to the multitude of methods for supporting the molecular layer on the substrate, including methods that utilize physical adsorption and covalent bonds, and to the numerous strategies for making top contacts. After discussing recent experimental progress in molecular electronics, an assessment of the current state of the field is presented, along with a proposed road map that can be used to assess progress in the future.
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Affiliation(s)
- Richard L McCreery
- Department of Chemistry, University of Alberta Edmonton, AB T6G 2G2 (Canada).
- National Institute for Nanotechnology, National Research Council Canada Edmonton, AB T6G 2M9 (Canada).
| | - Adam Johan Bergren
- National Institute for Nanotechnology, National Research Council Canada Edmonton, AB T6G 2M9 (Canada)
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32
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Üstündağ Z, Solak AO. EDTA modified glassy carbon electrode: Preparation and characterization. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2009.06.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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33
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Hauquier F, Matrab T, Kanoufi F, Combellas C. Local direct and indirect reduction of electrografted aryldiazonium/gold surfaces for polymer brushes patterning. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2009.01.059] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Mahmoud AM, Bergren AJ, McCreery RL. Derivatization of Optically Transparent Materials with Diazonium Reagents for Spectroscopy of Buried Interfaces. Anal Chem 2009; 81:6972-80. [DOI: 10.1021/ac901052v] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Amr M. Mahmoud
- University of Alberta, Edmonton, Alberta, Canada T6G 2G2, and National Institute for Nanotechnology, Edmonton, Alberta, Canada T6G 2M9
| | - Adam Johan Bergren
- University of Alberta, Edmonton, Alberta, Canada T6G 2G2, and National Institute for Nanotechnology, Edmonton, Alberta, Canada T6G 2M9
| | - Richard L. McCreery
- University of Alberta, Edmonton, Alberta, Canada T6G 2G2, and National Institute for Nanotechnology, Edmonton, Alberta, Canada T6G 2M9
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Hansen CR, Sørensen TJ, Glyvradal M, Larsen J, Eisenhardt SH, Bjørnholm T, Nielsen MM, Feidenhans'l R, Laursen BW. Structure of the buried metal-molecule interface in organic thin film devices. NANO LETTERS 2009; 9:1052-1057. [PMID: 19199753 DOI: 10.1021/nl803393m] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
By use of specular X-ray reflectivity (XR) the structure of a metal-covered organic thin film device is measured with angstrom resolution. The model system is a Langmuir-Blodgett (LB) film, sandwiched between a silicon substrate and a top electrode consisting of 25 A titanium and 100 A aluminum. By comparison of XR data for the five-layer Pb2+ arachidate LB film before and after vapor deposition of the Ti/Al top electrode, a detailed account of the structural damage to the organic film at the buried metal-molecule interface is obtained. We find that the organized structure of the two topmost LB layers (approximately 5 nm) is completely destroyed due to the metal deposition.
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Affiliation(s)
- Christian R Hansen
- Danish National Research Foundations Centre for Molecular Movies, Nano-Science Center, Niels Bohr Institute, and Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Denmark
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Shoute LCT, Bergren AJ, Mahmoud AM, Harris KD, McCreery RL. Optical interference effects in the design of substrates for surface-enhanced Raman spectroscopy. APPLIED SPECTROSCOPY 2009; 63:133-140. [PMID: 19215642 DOI: 10.1366/000370209787392102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This paper presents results showing that the design of substrates used for surface-enhanced Raman spectroscopy (SERS) can impact the apparent enhancement factors (EFs) obtained due to optical interference effects that are distinct from SERS, providing additional enhancement of the Raman intensity. Thus, a combination of SERS and a substrate designed to maximize interference-based enhancement is demonstrated to give additional Raman intensity above that observed for SERS alone. The system explored is 4-nitroazobenzene (NAB) and biphenyl (BP) chemisorbed on a nanostructured silver film obtained by vacuum deposition of Ag on thermally oxidized silicon wafers. The enhancing silver layer is partially transparent, enabling a standing wave to form as a result of the combination of the incident light and light reflected from the underlying Si substrate (i.e., light that passes through the Ag and the intervening dielectric layer of SiO(x)). The Raman intensity is measured as a function of the thickness of the thermal oxide layer in the range from approximately 150 to approximately 400 nm, and despite a lack of morphological variation in the silver films, there is a strong dependence of the Raman intensity on the oxide thickness. The Raman signal for the optimal SiO(x) interlayer thickness is 38 times higher than the intensity obtained when the Ag particles are deposited directly onto Si (with native oxide). To account for the trends observed in the Raman intensity versus thickness data, calculations of the relative mean square electric field (MSEF) at the surface of the SiO(x) are carried out. These calculations are also used to further optimize the experimental setup.
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Affiliation(s)
- Lian C T Shoute
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
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37
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Bergren AJ, Harris KD, Deng F, McCreery RL. Molecular electronics using diazonium-derived adlayers on carbon with Cu top contacts: critical analysis of metal oxides and filaments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:374117. [PMID: 21694424 DOI: 10.1088/0953-8984/20/37/374117] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Evaporation of Cu metal onto thin (less than 5 nm) molecular layers bonded to conductive carbon substrates results in electronic junctions with an ensemble of molecules sandwiched between two conductors. The resulting devices have previously been characterized through analysis of current density-voltage (j-V) curves for several different molecular layers and as a function of layer thickness. The approach represents an 'ensemble' rather than 'single molecule' technique, in which the electronic response represents that of a large number of molecules (10(6)-10(12)) in parallel as well as the conducting contacts contained in the molecular junction. In this paper, we extend a more detailed investigation of two critical issues: the possibility of conduction by metal filaments, and the potential role of top contact oxidation contributing to the electronic properties of the junctions. The results show that the conductance of the junctions can be modulated by changes in the deposition environment, but that the changes are not related to Cu oxide in the top contact. Based on these results, we propose that the conditions during top contact deposition change the way in which the molecules contact the metal, leading to differences in the effective junction area. Finally, through systematic studies using variation of the temperature, we show that metal filament conduction is distinct from that observed for the molecular junctions and that if the current observed experimentally passed through nanoscopic metal filaments the Joule heating would lead to rapid melting. For a series of junctions with structurally related aromatic molecules (including biphenyl, nitrobiphenyl, fluorene, and nitroazobenzene), the electron transfer mechanism is briefly investigated using area-independent analysis methods. It is shown that field emission and/or transport through bands formed by the molecular layer is likely, based on the weak temperature dependence of junction conductance.
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Affiliation(s)
- Adam Johan Bergren
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada
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Breton T, Bélanger D. Modification of carbon electrode with aryl groups having an aliphatic amine by electrochemical reduction of in situ generated diazonium cations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:8711-8718. [PMID: 18652500 DOI: 10.1021/la800578h] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The electrochemically induced functionalization of glassy carbon electrode by aryl groups having an aliphatic amine group was achieved by reduction of in situ generated diazonium cations in aqueous media. The corresponding diazonium cations of 4-aminobenzylamine, 2-aminobenzylamine, 4-(2-aminoethyl)aniline, N-methyl-1,2-phenylenediamine, and N, N-dimethyl- p-phenylenediamine were generated in situ with sodium nitrite in aqueous HCl. The kinetics of electrochemical grafting were investigated with electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance measurements (with carbon-coated quartz crystal), and the barrier properties of the grafted layers were evaluated by cyclic voltammetry in the presence of electroactive redox probes such as Fe(CN)6 3-/4- and Ru(NH 3)6 (3+). The grafting efficiency of aryl groups was found to depend on the nature of the amine (primary, secondary, and tertiary), the chain length of the alkyl substituent, and the substitution position on the aromatic ring. The nitrosation of the "aliphatic" amine, in the case of secondary and tertiary amines, was also evidenced by X-ray photoelectron spectroscopy.
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Affiliation(s)
- Tony Breton
- Département de Chimie, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec, Canada
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Turan A, Üstündağ Z, Solak A, Kılıç E, Avseven A. Characterization of a 2-Benzo[c]cinnoline Modified Glassy Carbon Electrode by Raman Spectroscopy, Electrochemical Impedance Spectroscopy, and Ellipsometry. ELECTROANAL 2008. [DOI: 10.1002/elan.200804230] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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40
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McCreery RL. Advanced carbon electrode materials for molecular electrochemistry. Chem Rev 2008; 108:2646-87. [PMID: 18557655 DOI: 10.1021/cr068076m] [Citation(s) in RCA: 1432] [Impact Index Per Article: 89.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard L McCreery
- National Institute for Nanotechnology, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2M9, Canada.
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41
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Radical grafting of carbon surfaces with alkylic groups by mediated oxidation of carboxylates. J Electroanal Chem (Lausanne) 2007. [DOI: 10.1016/j.jelechem.2007.07.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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42
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Tian H, Bergren AJ, McCreery RL. Ultraviolet-visible spectroelectrochemistry of chemisorbed molecular layers on optically transparent carbon electrodes. APPLIED SPECTROSCOPY 2007; 61:1246-53. [PMID: 18028705 DOI: 10.1366/000370207782597094] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Pyrolysis of diluted commercial photoresist spun onto quartz slides yields optically transparent graphitic films. Transparent carbon electrodes approximately 6 nm thick can be reproducibly prepared, with a maximum absorbance in the ultraviolet-visible (UV-vis) range of 0.25 at 270 nm. These electrodes are sufficiently conductive for electrochemistry, enabling modification of the surface via diazonium ion reduction and spectroelectrochemistry. Good quality ultraviolet-visible absorption spectra of covalently bonded molecular layers of nitroazobenzene, nitrobiphenyl, and azobenzene, with thicknesses of 1.4-4 nm, were obtained after subtracting the spectrum of the unmodified substrate. The spectra of all three molecules immobilized on the carbon surface showed red shifts of the absorption maxima relative to a solution of free molecules, indicating substantial electronic interactions between chemisorbed molecules and the Pi system of the substrate and/or intermolecular coupling. Spectroelectrochemical measurements show that reduction of free and chemisorbed molecules produce new absorption features in the 500-800 nm range; these spectral changes are partially reversible upon repeated potential cycling. Finally, density functional calculations correlate the new bands to the formation of anion radical or "methide" species that have more extensive electron delocalization than the parent molecules. The results from this work are useful for linking structural transformations in molecular layers "buried" under conductive top contacts in a type of molecular junction to changes in the electronic properties of the junction.
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Affiliation(s)
- Hong Tian
- Department of Chemistry, The Ohio State University, 100 W 18th Avenue, Columbus, OH 43210, USA
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Ricci A, Rolli C, Rothacher S, Baraldo L, Bonazzola C, Calvo EJ, Tognalli N, Fainstein A. Electron transfer at Au surfaces modified by Tethered Osmium bipyridine–pyridine complexes. J Solid State Electrochem 2007. [DOI: 10.1007/s10008-007-0339-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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44
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Liang H, Tian H, McCreery RL. Normal and surface-enhanced Raman spectroscopy of nitroazobenzene submonolayers and multilayers on carbon and silver surfaces. APPLIED SPECTROSCOPY 2007; 61:613-20. [PMID: 17650372 DOI: 10.1366/000370207781269765] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Raman and ultraviolet-visible (UV-Vis) absorption spectra were obtained for nitroazobenzene (NAB) chemisorbed on smooth and rough silver, and they were compared to published spectra for NAB on sp(2) hybridized pyrolyzed photoresist film (PPF) surfaces. High signal-to-noise ratio Raman spectra were obtained for 4.5 nm thick NAB films on PPF and smooth Ag due to significant enhancement of the NAB scattering relative to that observed in solution. The UV-Vis spectra of chemisorbed NAB exhibited a significant shift toward longer wavelength, thus bringing the NAB absorption closer to the 514.5 nm laser wavelength. The red shift was larger for PPF than for smooth Ag, consistent with the approximately 5x stronger Raman signal obtained on PPF. Deposition of Ag onto quartz without a chromium adhesion layer produced a rough Ag surface that enhanced the Raman spectrum of chemisorbed NAB by a factor of approximately 1000, as expected for roughened Ag due to electromagnetic field enhancement. The strong Raman signal permitted observation of NAB at low coverage and revealed changes in the NAB spectrum as the film progressed from submonolayer to multilayer thicknesses. Finally, deposition of Ag onto PPF/NAB samples through a metal grid produced Ag squares on top of the NAB, which enhanced the Raman scattering of the NAB layer by a factor of approximately 100. Deposition of a final conducting film on the Ag squares should permit in situ observation of a wide range of molecules in operating molecular electronic junctions.
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Affiliation(s)
- Haihe Liang
- Department of Chemistry, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, USA
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45
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Ssenyange S, Yan H, McCreery RL. Redox-driven conductance switching via filament formation and dissolution in carbon/molecule/TiO2/Ag molecular electronic junctions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:10689-96. [PMID: 17129047 DOI: 10.1021/la061153o] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Carbon/molecule/TiO2/Au molecular electronic junctions show robust conductance switching, in which a metastable high conductance state may be induced by a voltage pulse which results in redox reactions in the molecular and TiO2 layers. When Ag is substituted for Au as the "top contact", dramatically different current/voltage curves and switching behavior result. When the carbon substrate is biased negative, an apparent breakdown occurs, leading to a high conductance state which is stable for at least several hours. Upon scanning to positive bias, the conductance returns to a low state, and the cycle may be repeated hundreds of times. Similar effects are observed when Cu is substituted for Au and for three different molecular layers as well as "control" junctions of the type carbon/TiO2/Ag/Au. The polarity of the "switching" is reversed when the Ag layer is between the carbon and molecular layers, and the conductance change is suppressed at low temperature. Pulse experiments show very erratic transitions between high and low conductivity states, particularly near the switching threshold. The results are consistent with a switching mechanism based on Ag or Cu oxidation, transport of their ions through the TiO2, and reduction at the carbon to form a metal filament.
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Affiliation(s)
- Solomon Ssenyange
- Department of Chemistry, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, USA
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Ricci A, Bonazzola C, Calvo EJ. An FT-IRRAS study of nitrophenyl mono- and multilayers electro-deposited on gold by reduction of the diazonium salt. Phys Chem Chem Phys 2006; 8:4297-9. [PMID: 16986072 DOI: 10.1039/b609497j] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Formation of an organometallic junction by direct bonding of 4-nitrobenzene monolayer on gold surface by diazonium chemistry has been demonstrated by Fourier transform reflection-absorption spectroscopy with s- and p-polarized radiation.
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Affiliation(s)
- Alejandra Ricci
- Inquimae, DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, Buenos Aires, CP1428, Argentina
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Isbir AA, Solak AO, Ustündağ Z, Bilge S, Kiliç Z. Preparation and characterization of diethylene glycol bis(2-aminophenyl) ether-modified glassy carbon electrode. Anal Chim Acta 2006; 573-574:26-33. [PMID: 17723501 DOI: 10.1016/j.aca.2006.03.056] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 03/07/2006] [Accepted: 03/15/2006] [Indexed: 11/30/2022]
Abstract
Diethylene glycol bis(2-aminophenyl) ether (DGAE) diazonium salt was covalently electrografted on a glassy carbon (GC) surface and behavior of this novel surface was investigated. Synthesis of DGAE diazonium salt (DGAE-DAS) and in situ modification of GC electrode were performed in aqueous media containing NaNO2, keeping the temperature below +4 degrees C. For the characterization of the modified electrode surface by cyclic voltammetry, dopamine (DA) was used to prove the attachment of the DGAE-DAS on the GC surface. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used to observe the molecular bound properties of the adsorbates at the DGAE-modified GC surface (GC-DGAE). The EIS results were analyzed using the Randles equivalent circuit. The charge transfer resistance on bare GC and the modified surface were calculated using the model equivalent circuit for the ferrocene redox system. Surface coverage was found as 0.4 showing the presence of high pinhole and defects in the modified electrode. The rate constant of electron transfer through the monolayer was calculated for ferrocene. Working potential range and the stability of the DGAE-modified GC electrode was also determined.
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Affiliation(s)
- Aybüke A Isbir
- Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandoğan, Ankara, Turkey
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DeIonno E, Tseng HR, Harvey DD, Stoddart JF, Heath JR. Infrared Spectroscopic Characterization of [2]Rotaxane Molecular Switch Tunnel Junction Devices. J Phys Chem B 2006; 110:7609-12. [PMID: 16610848 DOI: 10.1021/jp0607723] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Langmuir-Blodgett monolayers of a bistable [2]rotaxane were prepared at packing densities of 118, 73, and 54 A(2)/molecule. The monolayers were both characterized via infrared spectroscopy before and after evaporation of a 2 nm film of titanium and incorporated into molecular switch tunnel junction devices. The study suggests that the evaporation process primarily affects portions of the molecule exposed to the metal atom source. Thus, in tightly packed monolayers (73 and 54 A(2)/molecule), only the portions of the [2]rotaxane that are present at the molecule/air interface are clearly affected, leaving key functionality necessary for switching intact. Monolayers transferred at a lower pressure (118 A(2)/molecule) exhibit nonspecific damage and poor switching behavior following Ti deposition. These results indicate that tightly packed monolayers and sacrificial functionality displayed at the molecule/air interface are important design principles for molecular electronic devices.
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Affiliation(s)
- Erica DeIonno
- Department of Chemistry, California Institute of Technology, 1200 East California Blvd, MC 127-72 Pasadena, CA 91125, USA
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49
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Anariba F, Viswanathan U, Bocian DF, McCreery RL. Determination of the Structure and Orientation of Organic Molecules Tethered to Flat Graphitic Carbon by ATR-FT-IR and Raman Spectroscopy. Anal Chem 2006; 78:3104-12. [PMID: 16643000 DOI: 10.1021/ac052042h] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mono- and multilayers of nitroazobenzene (NAB), azobenzene (AB), nitrobiphenyl (NBP), biphenyl (BP), and fluorene (FL) were covalently bonded to flat pyrolyzed photoresist films (PPF) by electrochemical reduction of their diazonium derivatives. The structure and orientation of the molecular layers were probed with ATR-FT-IR and Raman spectroscopy. A hemispherical germanium ATR element used with p-polarized light at 65 degrees incidence angle yielded high signal/noise IR spectra for monolayer coverage of molecules on PPF. The IR spectra are dominated by in-plane vibrational modes in the 1000-2000-cm(-1) spectral range but also exhibit weaker out-of-plane deformations in the 650-1000-cm(-1) region. The average tilt angle with respect to the surface normal for the various molecules varied from 31.0 +/- 4.5 degrees for NAB to 44.2 +/- 5.4 degrees for FL with AB, NBP, and BP exhibiting intermediate adsorption geometries. Raman intensity ratios of NAB and AB for p- and s-polarized incident light support the conclusion that the chemisorbed molecules are in a predominantly upright orientation. The results unequivocally indicate that molecules electroreduced from their diazonium precursors are not chemisorbed flat on the PPF surface, but rather at an angle, similar to the behavior of Au/thiol self-assembled monolayers, Langmuir-Blodgett films, and porphyrin molecules chemisorbed thermally on silicon and PPF from alkyne and alkene precursors.
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Affiliation(s)
- Franklin Anariba
- Department of Chemistry, University of California, Riverside, California 92521, USA
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Maldonado S, Smith TJ, Williams RD, Morin S, Barton E, Stevenson KJ. Surface modification of indium tin oxide via electrochemical reduction of aryldiazonium cations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:2884-91. [PMID: 16519499 DOI: 10.1021/la052696l] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The facile deposition of para-substituted aryl films onto indium-tin oxide (ITO) electrodes by the electrochemical reduction of aryl diazonium salts in acetonitrile is reported. For the deposition conditions used in this report, the aryl film thicknesses are on the order of 1-6 nm, suggesting a multilayer structure. Regardless of the functional group on the aryl diazonium cation, (NO(2), CO(2)H, or fluorene) the electrodeposition behavior onto ITO electrodes is similar to that seen on other electrode materials. XPS and UV-vis data support the introduction of organic functional surface groups to ITO. The blocking behavior of the aryl films on ITO toward the Ru(NH(3))(6)(3+/2+) redox couple is in agreement with electron transfer through conjugated organic layers. The facile preparation of patterned aryl films with regular-spaced 700 nm voids on ITO is also described. Atomic force microscopy and scanning surface potential microscopy on patterned NO(2) aryl films are used to assess the molecular structure and orientation. A 100 mV decrease in the contact potential over NO(2) aryl films relative to bare ITO suggests that the aryl films are loosely structured as deposited with the NO(2) groups oriented at a small angle away from the ITO surface.
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Affiliation(s)
- Stephen Maldonado
- Department of Chemistry and Biochemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA
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