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Azzam W, Subaihi A, Rohwerder M, Bashir A, Terfort A, Zharnikov M. Odd-even effects in aryl-substituted alkanethiolate SAMs: nonsymmetrical attachment of aryl unit and its impact on the SAM structure. Phys Chem Chem Phys 2024; 26:7563-7572. [PMID: 38362712 DOI: 10.1039/d4cp00311j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Aryl-substituted alkanethiolate (AT) self-assembled monolayers (SAMs) exhibit typically so-called odd-even effects, viz. systematic variations in the film structure, packing density, and molecular inclination depending on the parity of the number of the methylene units in the alkyl linker, n. As an exception to this rule, ATs carrying an anthracen-2-yl group (Ant-n) as tail group were reported to have different behavior due the non-symmetric attachment of the anthracene unit to the AT linker, providing additional degree of freedom for the molecular organization and allowing for partial compensation of the odd-even effects. In this context, the structure of SAMs formed by adsorption of anthracene-substituted ATs (Ant-n; n = 1-6) at room temperature on Au(111) substrate was investigated by high-resolution scanning tunnelling microscopy (STM). Most of these SAMs exhibit a coexistence of two different ordered phases, some of which are common for either n = odd or n = even while other vary over the series, showing a broad variety of different structures. The average packing density of the Ant-n SAMs, derived from the analysis of the STM data, varies by 7.5-10% depending on the parity of n, being, as expected, higher for n = odd. The respective extent of the odd-even effects is noticeably lower than that usually observed for other aryl-substituted monolayers (∼25%), which goes in line with the previous findings and emphasizes the impact of the non-symmetric attachment of the aromatic unit.
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Affiliation(s)
- Waleed Azzam
- Department of Chemistry, Tafila Technical University, P.O. Box 179, Tafila-66110, Jordan.
| | - Abdu Subaihi
- Department of Chemistry, University College in Al-Qunfudah, Umm Al-Qura University, 1109 Makkah Al-Mukarramah, Saudi Arabia
| | - Michael Rohwerder
- Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
| | - Asif Bashir
- Thyssenkrupp Bilstein GmbH, Thyssenkrupp Allee 1, 45143 Essen, Germany
| | - Andreas Terfort
- Institute of Inorganic and Analytical Chemistry, Goethe-University, D-60438 Frankfurt, Germany.
| | - Michael Zharnikov
- Applied Physical Chemistry, Heidelberg University, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany.
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Azzam W, Subaihi A, Rohwerder M, Zharnikov M, Bashir A. Polymorphism and Building-Block-Resolved STM Imaging of Self-Assembled Monolayers of 4-Fluorobenzenemethanethiol on Au(111). Chemphyschem 2022; 23:e202200347. [PMID: 35856831 DOI: 10.1002/cphc.202200347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 06/17/2022] [Indexed: 11/06/2022]
Abstract
Self-assembled monolayers (SAMs) of 4-fluorobenzenemethanethiol (p-FBMT) on Au(111), prepared by immersion procedure (1 mM ethanolic solution; 60 °C; 18 h), were characterized by scanning tunneling microscopy (STM). The data suggest the formation of highly ordered monolayer with a commensurate structure, described by the 2 3 × 13 R 13 ∘ unit cell. The STM appearance of this cell occurs, however, in two different forms, with either well-localized individual spots or splitting of these spots in two components. These components are assigned to the tunneling through the entire molecule or sulfur docking group only. The respective spots correspond then to the terminal fluorine atom and sulfur docking group, manifesting, thus, building-block-resolving STM imaging. The accessibility of the docking group for direct tunneling is most likely related to a specific molecular organization for one of the two possible internal structures of the unit cell. The above results represent a showcase for potential of STM for imaging of upright-arranged and densely packed molecular assemblies, such as SAMs.
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Affiliation(s)
- Waleed Azzam
- Department of Chemistry, Tafila Technical University, P.O. Box 179, Tafila, 66110, Jordan.,Department of Chemistry, University College in Al-Qunfudah, Umm Al-Qura University, 1109, Makkah, Al-Mukarramah, Saudi Arabia
| | - Abdu Subaihi
- Department of Chemistry, University College in Al-Qunfudah, Umm Al-Qura University, 1109, Makkah, Al-Mukarramah, Saudi Arabia
| | - Michael Rohwerder
- Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Str. 1, 40237, Düsseldorf, Germany
| | - Michael Zharnikov
- Applied Physical Chemistry, Heidelberg University, Im Neuenheimer Feld 253, 69120, Heidelberg, Germany
| | - Asif Bashir
- Thyssenkrupp Bilstein GmbH, Herner Str. 299, 44809, Bochum, Germany
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Azzam W, Al-Rashdi A, Subaihi A, Rohwerder M, Zharnikov M, Bashir A. Annealing effect for self-assembled monolayers formed from terphenylethanethiol on Au(111). Phys Chem Chem Phys 2020; 22:13580-13591. [DOI: 10.1039/d0cp02374d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Formation of several different structural phases and desorption took place from a standing-up phase at an annealing temperature of 473 K.
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Affiliation(s)
- Waleed Azzam
- Department of Chemistry
- Tafila Technical University
- Tafila 66110
- Jordan
- Department of Chemistry
| | - Awad Al-Rashdi
- Department of Chemistry
- University College in Al-Qunfudah
- Umm Al-Qura University
- 1109 Makkah Al-Mukarramah
- Saudi Arabia
| | - Abdu Subaihi
- Department of Chemistry
- University College in Al-Qunfudah
- Umm Al-Qura University
- 1109 Makkah Al-Mukarramah
- Saudi Arabia
| | | | - Michael Zharnikov
- Angewandte Physikalische Chemie
- Universität Heidelberg
- 69120 Heidelberg
- Germany
| | - Asif Bashir
- Thyssenkrupp Bilstein GmbH
- 44809 Bochum
- Germany
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Liu J, Kind M, Schüpbach B, Käfer D, Winkler S, Zhang W, Terfort A, Wöll C. Triptycene-terminated thiolate and selenolate monolayers on Au(111). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:892-905. [PMID: 28503400 PMCID: PMC5405688 DOI: 10.3762/bjnano.8.91] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 03/30/2017] [Indexed: 06/02/2023]
Abstract
To study the implications of highly space-demanding organic moieties on the properties of self-assembled monolayers (SAMs), triptycyl thiolates and selenolates with and without methylene spacers on Au(111) surfaces were comprehensively studied using ultra-high vacuum infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and thermal desorption spectroscopy. Due to packing effects, the molecules in all monolayers are substantially tilted. In the presence of a methylene spacer the tilt is slightly less pronounced. The selenolate monolayers exhibit smaller defect densities and therefore are more densely packed than their thiolate analogues. The Se-Au binding energy in the investigated SAMs was found to be higher than the S-Au binding energy.
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Affiliation(s)
- Jinxuan Liu
- Institute of Artificial Photosynthesis, State Key Laboratory of Fine Chemicals, Dalian University of Technology, 116024 Dalian, China
| | - Martin Kind
- Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt am Main, 60325 Frankfurt, Germany
| | - Björn Schüpbach
- Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt am Main, 60325 Frankfurt, Germany
| | - Daniel Käfer
- Physikalische Chemie I, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Stefanie Winkler
- Physikalische Chemie I, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Wenhua Zhang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China
| | - Andreas Terfort
- Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt am Main, 60325 Frankfurt, Germany
| | - Christof Wöll
- Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany
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Bashir A, Sauter E, Al-Refaie N, Rohwerder M, Zharnikov M, Azzam W. Side-Group-Induced Polymorphism in Self-Assembled Monolayers: 3,5-Bis(trifluoromethyl)benzenethiolate Films on Au(111). Chemphyschem 2017; 18:702-714. [DOI: 10.1002/cphc.201700030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Asif Bashir
- Thyssenkrupp Bilstein GmbH; Niederkell 25 54429 Mandern Germany
- Max-Planck-Institut für Eisenforschung GmbH; Max-Planck-Str. 1 40237 Düsseldorf Germany
| | - Eric Sauter
- Applied Physical Chemistry; Heidelberg University; Im Neuenheimer Feld 253 69120 Heidelberg Germany
| | - Najd Al-Refaie
- Department of Chemistry; University College in Al-Qunfudah, Umm Al-Qura University; 1109 Makkah Al-Mukarramah Saudi Arabia
| | - Michael Rohwerder
- Max-Planck-Institut für Eisenforschung GmbH; Max-Planck-Str. 1 40237 Düsseldorf Germany
| | - Michael Zharnikov
- Applied Physical Chemistry; Heidelberg University; Im Neuenheimer Feld 253 69120 Heidelberg Germany
| | - Waleed Azzam
- Department of Chemistry; University College in Al-Qunfudah, Umm Al-Qura University; 1109 Makkah Al-Mukarramah Saudi Arabia
- Department of Chemistry; Tafila Technical University; P.O. Box 179 Tafila 66110 Jordan
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Operamolla A, Punzi A, Farinola GM. Synthetic Routes to Thiol-Functionalized Organic Semiconductors for Molecular and Organic Electronics. ASIAN J ORG CHEM 2016. [DOI: 10.1002/ajoc.201600460] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Alessandra Operamolla
- Dipartimento di Chimica; Università degli Studi di Bari Aldo Moro; Via Orabona 4 70126 Bari Italy
- CNR-ICCOM Istituto di Chimica dei Composti Organometallici; Via Orabona 4 70126 Bari Italy
| | - Angela Punzi
- Dipartimento di Chimica; Università degli Studi di Bari Aldo Moro; Via Orabona 4 70126 Bari Italy
| | - Gianluca M. Farinola
- Dipartimento di Chimica; Università degli Studi di Bari Aldo Moro; Via Orabona 4 70126 Bari Italy
- CNR-ICCOM Istituto di Chimica dei Composti Organometallici; Via Orabona 4 70126 Bari Italy
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Zhang Z, Wächter T, Kind M, Schuster S, Bats JW, Nefedov A, Zharnikov M, Terfort A. Self-Assembled Monolayers of Perfluoroanthracenylaminoalkane Thiolates on Gold as Potential Electron Injection Layers. ACS APPLIED MATERIALS & INTERFACES 2016; 8:7308-7319. [PMID: 26926185 DOI: 10.1021/acsami.6b00532] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
As a material with relatively small band gap and low lying valence orbitals, perfluoroanthracene (PFA) is of interest for the modification of electrode surfaces, for example, as charge injection layers for n-type organic semiconductors. To covalently attach PFA in the form of self-assembled monolayers (SAMs), we developed a synthesis of derivatives with a sulfur termination, linked to the 2-position of the PFA moieties by an -NH- group and a short alkane chain with two and three methylene groups, respectively. Spectroscopic characterization of the SAMs reveals that the molecules adopt an almost upright orientation on the gold surface, with the packing density mostly determined by the steric demands of the PFA units. The number of the methylene groups in the -NH-alkyl linker has only a minor impact on the SAM structure because of the nonsymmetric attachment of the PFA units, which permits the compensation of the orientational constraints imposed by the bending potential. The investigated SAMs alter the work function of gold by +(0.59-0.64) eV, suggesting comparably strong depolarization effects, affecting the extent of the work function modification.
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Affiliation(s)
| | - Tobias Wächter
- Applied Physical Chemistry, University of Heidelberg , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | | | - Swen Schuster
- Applied Physical Chemistry, University of Heidelberg , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | | | - Alexei Nefedov
- Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Michael Zharnikov
- Applied Physical Chemistry, University of Heidelberg , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
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The Porter-Whitesides Discrepancy: Revisiting Odd-Even Effects in Wetting Properties of n-Alkanethiolate SAMs. COATINGS 2015. [DOI: 10.3390/coatings5041034] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Stan RC, Kros A, Akkilic N, Appel J, Sanghamitra NJM. Conductance switching and organization of two structurally related molecular wires on gold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:953-958. [PMID: 25590414 DOI: 10.1021/la5042713] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The self-assembly and electron transfer properties of adsorbed organic molecules are of interest for the construction of miniaturized molecular circuitries. We have investigated with scanning probe microscopy the self-organization of two structurally related molecular wires embedded within a supportive alkanethiol matrix. Our results evidence heterogeneous adsorption patterns of the molecular wires on gold with either incommensurate unit cells driven into assembly by lateral interactions or a dynamic, commensurate distribution on gold, along with formation of distinct 2D phases. We also observed diffusion-based conductance switching for one of the molecular wires, due to its propensity toward weaker lateral interactions and Au-S adatom formation. We have further demonstrated through the use of scanning tunneling spectroscopy differential current-voltage response for each molecular wire, despite their close structural similarity. Such molecular wires embedded in alkanethiol matrix and exhibiting conductance-switching phenomena have the potential to be used for the functionalization of electrodes in bioelectronic devices.
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Affiliation(s)
- Razvan C Stan
- Leiden Institute of Physics-Huygens Laboratories and ‡Leiden Institute of Chemistry-Gorlaeus Laboratories, Leiden University , P.O. Box 9504, 2300 RA Leiden, The Netherlands
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Shrestha BR, Bashir A, Ankah GN, Valtiner M, Renner FU. Localized dealloying corrosion mediated by self-assembled monolayers used as an inhibitor system. Faraday Discuss 2015; 180:191-204. [DOI: 10.1039/c4fd00256c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The structure and chemistry of thiol or selenol self-assembled organic monolayers have been frequently addressed due to the unique opportunities in functionalization of materials. Such organic films can also act as effective inhibition layers to mitigate oxidation or corrosion. Cu–Au alloy substrates covered by self-assembled monolayers show a different dealloying mechanism compared to bare surfaces. The organic surface layer inhibits dealloying of noble metal alloys by a suppression of surface diffusion at lower potentials but at higher applied potentials dealloying proceeds in localized regions due to passivity breakdown. We present an in situ atomic force microscopy study of a patterned thiol layer applied on Cu–Au alloy surfaces and further explore approaches to change the local composition of the surface layers by exchange of molecules. The pattern for the in situ experiment has been applied by micro-contact printing. This allows the study of corrosion protection with its dependence on different molecule densities at different sites. Low-density thiol areas surrounding the high-density patterns are completely protected and initiation of dealloying proceeds only along the areas with the lowest inhibitor concentration. Dealloying patterns are highly influenced and controlled by molecular thiol to selenol exchange and are also affected by introducing structural defects such as scratches or polishing defects.
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Affiliation(s)
- B. R. Shrestha
- Max-Planck-Institut für Eisenforschung GmbH
- D-40237 Düsseldorf
- Germany
| | - A. Bashir
- Max-Planck-Institut für Eisenforschung GmbH
- D-40237 Düsseldorf
- Germany
| | - G. N. Ankah
- Max-Planck-Institut für Eisenforschung GmbH
- D-40237 Düsseldorf
- Germany
| | - M. Valtiner
- Max-Planck-Institut für Eisenforschung GmbH
- D-40237 Düsseldorf
- Germany
| | - F. U. Renner
- Max-Planck-Institut für Eisenforschung GmbH
- D-40237 Düsseldorf
- Germany
- Institute of Materials Research (IMO)
- Hasselt University
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Kim HC, Kim E, Lee SG, Lee SJ, Kim H, Jeong SW. Thiol-responsive micelles based on nonionic gemini surfactants with a cystine disulfide spacer. ACTA ACUST UNITED AC 2013. [DOI: 10.1002/pola.27036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Hyun-Chul Kim
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
| | - Eunjoo Kim
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
| | - Se Guen Lee
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
| | - Sung Jun Lee
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
| | - Hyunmin Kim
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
| | - Sang Won Jeong
- Nano and Bio Research Division; Daegu Gyeongbuk Institute of Science and Technology (DGIST); Daegu 711-873 Korea
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12
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Ito E, Kang H, Lee D, Park JB, Hara M, Noh J. Spontaneous desorption and phase transitions of self-assembled alkanethiol and alicyclic thiol monolayers chemisorbed on Au(111) in ultrahigh vacuum at room temperature. J Colloid Interface Sci 2013; 394:522-9. [DOI: 10.1016/j.jcis.2012.12.035] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 12/16/2012] [Accepted: 12/17/2012] [Indexed: 10/27/2022]
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Muglali MI, Erbe A, Chen Y, Barth C, Koelsch P, Rohwerder M. Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold. Electrochim Acta 2013; 90. [PMID: 24235778 DOI: 10.1016/j.electacta.2012.11.116] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum-frequency-generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two-dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre-orientation of water present in the nanometer-sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.
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Affiliation(s)
- Mutlu I Muglali
- Max-Planck-Institut für Eisenforschung GmbH, Department of Interface Chemistry and Surface Engineering, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
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Canepa M, Maidecchi G, Toccafondi C, Cavalleri O, Prato M, Chaudhari V, Esaulov VA. Spectroscopic ellipsometry of self assembled monolayers: interface effects. The case of phenyl selenide SAMs on gold. Phys Chem Chem Phys 2013; 15:11559-65. [DOI: 10.1039/c3cp51304a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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15
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Nanotribology of self-assembled monolayer with a probe tip investigated using molecular dynamics simulations. Micron 2013; 44:410-8. [DOI: 10.1016/j.micron.2012.09.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 09/10/2012] [Accepted: 09/10/2012] [Indexed: 11/22/2022]
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16
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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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17
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Liu J, Shekhah O, Stammer X, Arslan HK, Liu B, Schüpbach B, Terfort A, Wöll C. Deposition of Metal-Organic Frameworks by Liquid-Phase Epitaxy: The Influence of Substrate Functional Group Density on Film Orientation. MATERIALS 2012. [PMCID: PMC5449017 DOI: 10.3390/ma5091581] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The liquid phase epitaxy (LPE) of the metal-organic framework (MOF) HKUST-1 has been studied for three different COOH-terminated templating organic surfaces prepared by the adsorption of self-assembled monolayers (SAMs) on gold substrates. Three different SAMs were used, mercaptohexadecanoic acid (MHDA), 4’-carboxyterphenyl-4-methanethiol (TPMTA) and 9-carboxy-10-(mercaptomethyl)triptycene (CMMT). The XRD data demonstrate that highly oriented HKUST-1 SURMOFs with an orientation along the (100) direction was obtained on MHDA-SAMs. In the case of the TPMTA-SAM, the quality of the deposited SURMOF films was found to be substantially inferior. Surprisingly, for the CMMT-SAMs, a different growth direction was obtained; XRD data reveal the deposition of highly oriented HKUST-1 SURMOFs grown along the (111) direction.
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Affiliation(s)
- Jinxuan Liu
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von-Helmholty-Platz 1, B 330, Eggenstein-Leopoldshafen D-76344, Germany; E-Mails: (J.L.); (X.S.); (H.K.A.)
| | - Osama Shekhah
- Advanced Membranes & Porous Materials Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia; E-Mail:
| | - Xia Stammer
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von-Helmholty-Platz 1, B 330, Eggenstein-Leopoldshafen D-76344, Germany; E-Mails: (J.L.); (X.S.); (H.K.A.)
| | - Hasan K. Arslan
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von-Helmholty-Platz 1, B 330, Eggenstein-Leopoldshafen D-76344, Germany; E-Mails: (J.L.); (X.S.); (H.K.A.)
| | - Bo Liu
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, UK; E-Mail:
| | - Björn Schüpbach
- Institute of Inorganic and Analytical Chemistry, Goethe-University Frankfurt am Main, Frankfurt 60438, Germany; E-Mails: (B.S.); (A.T.)
| | - Andreas Terfort
- Institute of Inorganic and Analytical Chemistry, Goethe-University Frankfurt am Main, Frankfurt 60438, Germany; E-Mails: (B.S.); (A.T.)
| | - Christof Wöll
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von-Helmholty-Platz 1, B 330, Eggenstein-Leopoldshafen D-76344, Germany; E-Mails: (J.L.); (X.S.); (H.K.A.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-721-6082-3934; Fax: +49-721-6082-3478
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Li C, Wang B, Liu Y, Cao J, Feng T, Chen Y, Luo X. Synthesis and evaluation of star-shaped poly(ϵ-caprolactone)-poly(2-hydroxyethyl methacrylate) as potential anticancer drug delivery carriers. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2012; 24:741-57. [PMID: 23565913 DOI: 10.1080/09205063.2012.709417] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Novel star-shaped poly(ϵ-caprolactone)-b-poly(2-hydroxyethyl methacrylate) (sPCL-b-PHEMA) with 3 arm and 6 arm was synthesized by a combination of ring-opening polymerization and atom transfer radical polymerization. The structure of copolymers was confirmed by nuclear magnetic resonance ((1)H and (13)C NMR) and Fourier transform infrared spectroscopy. The thermal behavior was measured by differential scanning calorimetry. The results showed that Tc, Tm, and Xc of the sPCL-b-PHEMA were reduced along with the increase in the length of the PHEMA block. The copolymers could self-assemble into dispersed micelles with quite low (×10(-4)mg/mL) critical micelle concentration. The size and morphology of the micelles were characterized by dynamic light scattering and HAADF scanning transmission electron microscopy. It was found that the micelles were around 20-70 nm with a regular spherical shape. Moreover, drug loading content and encapsulation efficiency of paclitaxel by 3sPCL-b-PHEMA micelles were much lower than the values of 6sPCL-b-PHEMA micelles. The drug release experiments demonstrated that paclitaxelrelease was two-phase release profile and relative to the structure of sPCL-b-PHEMA.The in vitro cytotoxicity of sPCL-b-PHEMA micelles was evaluated using methylthiazoletetrazolium assay. The results showed no apparent inhibition effect on the Hela cells. These preliminary studies suggest that sPCL-b-PHEMA has a possible application as anticancer drug delivery carriers.
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Affiliation(s)
- Chenglong Li
- College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, PR China
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Azzam W, Bashir A, Biedermann PU, Rohwerder M. Formation of highly ordered and orientated gold islands: effect of immersion time on the molecular adlayer structure of pentafluorobenzenethiols (PFBT) SAMs on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:10192-10208. [PMID: 22690878 DOI: 10.1021/la301601c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Self-assembled monolayers (SAMs) of pentafluorobenzenethiol (PFBT) on Au(111) substrates, prepared with different immersion times (ITs) at room temperature, were studied using scanning tunneling microscopy (STM) and infrared reflection-absorption spectroscopy (IRRAS). In the present study, the focus was on several important points of interest in the field of SAMs. First, the gold islands formed upon adsorption of PFBT molecules on the gold surface were monitored at different ITs in terms of their size, density, and shape. After short ITs (5 to 30 min), small gold islands with rounded shape were formed. These gold islands were arranged in a rather regular fashion and found to be quite mobile under the influence of the STM-tip during the scanning. When the IT was increased to 16 h, the results revealed the formation of highly ordered and orientated gold islands with very unusual shapes with straight edges meeting at 60° or 120° running preferentially along the [11(-)0] substrate directions. The density of the gold islands was found to decrease with increasing IT until they almost disappeared from the SAMs prepared after 190 h of IT. On top of the gold islands, the PFBT molecules were found to adopt the closely packed (10√3 × 2) structure. Second, a number of structural defects such as disordered regions at the domain boundaries and dark row(s) of molecules within the ordered domains of the PFBT SAMs were observed at different ITs. The SAMs prepared after 190 h of IT were found to be free of these defects. Third, at low and moderate ITs, a variation in the PFBT molecular contrast was observed. This contrast variation was found to depend mainly on the tunneling parameters. Finally, our results revealed that the organization process of PFBT SAMs is IT-dependent. Consequently, a series of structural phases, namely, α, β, γ, δ, and ε were found. The α-, β-, γ-, and δ-phases were typically accompanied by the ε-phase that appeared on top of gold islands. With increasing IT, the α→β→ γ→δ→ε phase transitions took place. The resulting ε-phase, which covered the entire gold surface after 190 h of IT, yielded well-ordered self-assembled monolayers with large domains having a (10√3 × 2) superlattice structure.
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Muglali MI, Bashir A, Terfort A, Rohwerder M. Electrochemical investigations on stability and protonation behavior of pyridine-terminated aromatic self-assembled monolayers. Phys Chem Chem Phys 2011; 13:15530-8. [DOI: 10.1039/c1cp21469a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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von Wrochem F, Gao D, Scholz F, Nothofer HG, Nelles G, Wessels JM. Efficient electronic coupling and improved stability with dithiocarbamate-based molecular junctions. NATURE NANOTECHNOLOGY 2010; 5:618-624. [PMID: 20562871 DOI: 10.1038/nnano.2010.119] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 05/17/2010] [Indexed: 05/29/2023]
Abstract
Molecular electronic devices require stable and highly conductive contacts between the metal electrodes and molecules. Thiols and amines are widely used to attach molecules to metals, but they form poor electrical contacts and lack the robustness required for device applications. Here, we demonstrate that dithiocarbamates provide superior electrical contact and thermal stability when compared to thiols on metals. Ultraviolet photoelectron spectroscopy and density functional theory show the presence of electronic states at 0.6 eV below the Fermi level of Au, which effectively reduce the charge injection barrier across the metal-molecule interface. Charge transport measurements across oligophenylene monolayers reveal that the conductance of terphenyl-dithiocarbamate junctions is two orders of magnitude higher than that of terphenyl-thiolate junctions. The stability and low contact resistance of dithiocarbamate-based molecular junctions represent a significant step towards the development of robust, organic-based electronic circuits.
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Affiliation(s)
- Florian von Wrochem
- Sony Deutschland GmbH, Materials Science Laboratory, Hedelfinger Strasse 61, 70327 Stuttgart, Germany.
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Bruno G, Babudri F, Operamolla A, Bianco GV, Losurdo M, Giangregorio MM, Hassan Omar O, Mavelli F, Farinola GM, Capezzuto P, Naso F. Tailoring density and optical and thermal behavior of gold surfaces and nanoparticles exploiting aromatic dithiols. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:8430-8440. [PMID: 20433150 DOI: 10.1021/la101082t] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Self-assembled monolayers (SAMs) derived of 4-methoxy-terphenyl-3'',5''-dimethanethiol (TPDMT) and 4-methoxyterphenyl-4''-methanethiol (TPMT) have been prepared by chemisorption from solution onto gold thin films and nanoparticles. The SAMs have been characterized by spectroscopic ellipsometry, Raman spectroscopy and atomic force microscopy to determine their optical properties, namely the refractive index and extinction coefficient, in an extended spectral range of 0.75-6.5 eV. From the analysis of the optical data, information on SAMs structural organization has been inferred. Comparison of SAMs generated from the above aromatic thiols to well-known SAMs generated from the alkanethiol dodecanethiol revealed that the former aromatic SAMs are densely packed and highly vertically oriented, with a slightly higher packing density and a absence of molecular inclination in TPMT/Au. The thermal behavior of SAMs has also been monitored using ellipsometry in the temperature range 25-500 degrees C. Gold nanoparticles functionalized by the same aromatic thiols have also been discussed for surface enhanced Raman spectroscopy applications. This study represents a step forward tailoring the optical and thermal behavior of surfaces as well as nanoparticles.
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Affiliation(s)
- Giovanni Bruno
- Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari, Italy.
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Interface dynamics and mechanisms of nanoindented alkanethiol self-assembled monolayers using molecular simulations. J Colloid Interface Sci 2010; 345:19-26. [DOI: 10.1016/j.jcis.2010.01.052] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/30/2009] [Accepted: 01/19/2010] [Indexed: 11/23/2022]
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Schüpbach B, Bolte M, Zharnikov M, Terfort A. Grafting Organic n-Semiconductors to Surfaces: (Perfluoro-p-terphenyl-4-yl)alkanethiols. European J Org Chem 2010. [DOI: 10.1002/ejoc.201000151] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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25
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Gutzler R, Sirtl T, Dienstmaier JF, Mahata K, Heckl WM, Schmittel M, Lackinger M. Reversible Phase Transitions in Self-Assembled Monolayers at the Liquid−Solid Interface: Temperature-Controlled Opening and Closing of Nanopores. J Am Chem Soc 2010; 132:5084-90. [DOI: 10.1021/ja908919r] [Citation(s) in RCA: 208] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rico Gutzler
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Thomas Sirtl
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Jürgen F. Dienstmaier
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Kingsuk Mahata
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Wolfgang M. Heckl
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Michael Schmittel
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
| | - Markus Lackinger
- Department of Earth and Environmental Sciences and Center for NanoScience (CeNS), Ludwig-Maximilians-University, Theresienstrasse 41, 80333 Munich, Germany, Center of Micro and Nanochemistry and Engineering, Organische Chemie I, University Siegen, Adolf-Reichwein-Strasse 2, 57068 Siegen, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, and Department of Physics, TUM School of Education, Technical University Munich, Schellingstrasse 33, 80333 Munich, Germany
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Dietrich PM, Graf N, Gross T, Lippitz A, Schüpbach B, Bashir A, Wöll C, Terfort A, Unger WES. Self-assembled monolayers of aromatic omega-aminothiols on gold: surface chemistry and reactivity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:3949-3954. [PMID: 20041682 DOI: 10.1021/la903293b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Amino-terminated self-assembled monolayers on gold substrates were studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) measurements, and atomic force microscopy (AFM). Two different omega-amino-4,4'-terphenyl substituted alkanethiols of the general structure H(2)N-(C(6)H(4))(3)-(CH(2))(n)-SH (ATPn) were used: 2-(4''-amino-1,1':4',1''-terphenyl-4-yl)ethane-1-thiol (n = 2, ATP2) and 3-(4''-amino-1,1':4',1''-terphenyl-4-yl)propane-1-thiol (n = 3, ATP3). Moreover, the addressability of amino groups within the films was investigated by chemical derivatization of ATPn SAMs with 3,5-bis(trifluoromethyl)phenyl isothiocyanate (ITC) forming fluorinated thiourea ATPn-F films. Evaluation of high-resolution C 1s and N 1s XPS data revealed successful derivatization of at least 50% of surface amino species. Furthermore, it could be demonstrated by angle-resolved NEXAFS spectroscopy that chemical derivatization with ITC has no noticeable influence on the preferential upright orientation of the molecules in the SAMs.
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Affiliation(s)
- Paul M Dietrich
- BAM Bundesanstalt für Materialforschung und -prüfung, D-12203 Berlin, Germany
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Liu J, Schüpbach B, Bashir A, Shekhah O, Nefedov A, Kind M, Terfort A, Wöll C. Structural characterization of self-assembled monolayers of pyridine-terminated thiolates on gold. Phys Chem Chem Phys 2010; 12:4459-72. [PMID: 20407720 DOI: 10.1039/b924246p] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Self-assembled monolayers (SAMs) fabricated on Au(111) substrates from a homologous series of pyridine-terminated organothiols have been investigated using ultra high vacuum infrared reflection adsorption spectroscopy (UHV-IRRAS), X-ray photoelectron spectroscopy (XPS), scanning tunnelling microscopy (STM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A total of 4 different pyridine-based organothiols have been investigated, consisting of a pyridine unit, one or two phenyl units, a spacer of between one and three methylene units and, finally, a thiol unit. For all pyridine-terminated thiols the immersion of Au-substrates in the corresponding ethanolic solutions was found to result in the formation of highly ordered and densely packed SAMs. For an even number of the methylene spacers between the SH group and the aromatic moieties, the SAM unit-cell is rather large, (5sq.rt(3) x 3)rect, whereas in case of an odd number of methylene units a smaller unit cell is adopted, (2sq.rt(3) x sq.rt(3))R30 degrees. The tilt angle of the molecules amounts to 15 degrees . In contrast to expectation, the pyridine-terminated organic surfaces exposed by the corresponding SAMs showed a surprisingly strong resistance with regard to protonation.
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Affiliation(s)
- Jinxuan Liu
- Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, 44780 Bochum, Germany
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Schüpbach B, Terfort A. A divergent synthesis of oligoarylalkanethiols with Lewis-basic N-donor termini. Org Biomol Chem 2010; 8:3552-62. [DOI: 10.1039/c003795h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Chesneau F, Schüpbach B, Szelągowska-Kunstman K, Ballav N, Cyganik P, Terfort A, Zharnikov M. Self-assembled monolayers of perfluoroterphenyl-substituted alkanethiols: specific characteristics and odd–even effects. Phys Chem Chem Phys 2010; 12:12123-37. [DOI: 10.1039/c0cp00317d] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
AbstractSelf-assembled monolayers (SAMs) of ω-(4′-methylbiphenyl-4-yl)ethanethiol (CH3(C6H4)2(CH2)2SH, BP2) prepared at different temperatures on Au(111) substrates were investigated using scanning tunneling microscopy (STM). Also, the effect of the incubation time of the gold substrate in the thiol solution was examined. The STM results showed that samples prepared at room temperature were significantly different from those prepared at elevated temperatures in their surface morphology, space group and size of unit cell. The micrographs of samples prepared at higher temperatures revealed a pronounced and progressive increase in the size of the well-known etch-pits at the expense of their density with increasing preparation temperature (but the increase did not continue for SAMs prepared at 348 K). The average domain size was found to increase significantly with increasing preparation temperature. In addition, polymorphism was observed in BP2 SAMs at all investigated temperatures. This study has demonstrated that solution temperature and incubation time are key factors controlling the two-dimensional SAM structure of BP2 molecules.
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Chang WY, Fang TH, Fang CN. Molecular dynamics on interface and nanoscratch mechanisms of alkanethiol self-assembled monolayers. J Phys Chem B 2009; 113:14994-5001. [PMID: 19831411 DOI: 10.1021/jp905389w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interface dynamics and nanoscratched mechanisms of alkanethiol self-assembled monolayers (SAM) chemisorbed on a gold surface are investigated using molecular dynamics simulation. The characteristic mechanisms mainly include the nanoscratched depths, the workpiece temperatures, the scratched speed, the SAM chain lengths, and the shapes of the indenters. The simulation results show that the disorder and the plastic mobility of SAM structures increased with increasing nanoscratched depth. The scratched forces, the potential energy, the friction force, and the friction coefficient increased with increasing scratched depth. The larger scratched depth required a larger force to overcome the resistance, which leads to the increases in the friction force. The variations of the scratched forces and the friction forces after scratching at various temperatures are very similar. An increase in the scratched force, friction force, and friction coefficient with increasing scratched speed is observed. The scratched shape after scratching is clearer for a longer SAM chain. The SAM structures are easily tilted and bent when the chain length is longer. The reaction forces after scratching using a spherical indenter are higher than those after scratching using a Vickers indenter.
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Affiliation(s)
- Wen-Yang Chang
- Microsystems Technology Center, Industrial Technology Research Institute, Tainan 709, Taiwan
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Shen C, Haryono M, Grohmann A, Buck M, Weidner T, Ballav N, Zharnikov M. Self-assembled monolayers of a bis(pyrazol-1-yl)pyridine-substituted thiol on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:12883-12891. [PMID: 18950209 DOI: 10.1021/la8019974] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Self-assembled monolayers (SAMs) of a bis(pyrazol-1-yl)pyridine-substituted thiol (bpp-SH) on Au (111)/mica were studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Using substrates precoated with perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), preparation at elevated temperatures yields highly ordered layers whose structure is described by a rectangular (5 x radical3) unit cell containing one molecule. The bis(pyrazol-1-yl)pyridine (bpp) units exhibit pi-stacking along the 112 direction, and they are tilted significantly. We conclude the three imine nitrogen atoms in the bpp headgroup adopt a trans,trans arrangement.
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Affiliation(s)
- Cai Shen
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews KY16 9ST, United Kingdom
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Hallmann L, Bashir A, Strunskus T, Adelung R, Staemmler V, Wöll C, Tuczek F. Self-assembled monolayers of benzylmercaptan and p-cyanobenzylmercaptan on Au(111) surfaces: structural and spectroscopic characterization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5726-5733. [PMID: 18459749 DOI: 10.1021/la702836r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The formation of self-assembled monolayers of benzylmercaptan (BM) and p-cyanobenzylmercaptan (pCBM) on Au(111) surfaces is investigated by a combination of X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and scanning tunneling microscopy (STM). The NEXAFS results of pCBM are supported by ab initio calculations. It is found that BM as well as pCBM form well-ordered monolayers with the molecules oriented almost perpendicular to the surface. BM forms a ( radical 3 x radical 3)R30 degrees structure whereas pCBM forms a slightly different c(7 x 7) hexagonal structure. No phase separation is detected for the adsorption of a 1:1 mixture of the two molecules. The implications of the results for the covalent attachment of transition-metal complexes to thiol-functionalized surfaces are discussed.
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Affiliation(s)
- L Hallmann
- Institut für Anorganische Chemie der Christian-Albrechts-Universität zu Kiel, Otto Hahn Platz 6/7, D-24098 Kiel, Germany
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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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From Self-Assembly to Charge Transport with Single Molecules – An Electrochemical Approach. Top Curr Chem (Cham) 2008; 287:181-255. [DOI: 10.1007/128_2008_152] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Su GJ, Aguilar-Sanchez R, Li Z, Pobelov I, Homberger M, Simon U, Wandlowski T. Scanning Tunneling Microscopy and Spectroscopy Studies of 4-Methyl- 4′-(n-mercaptoalkyl)biphenyls on Au(111)-(1×1). Chemphyschem 2007; 8:1037-48. [PMID: 17476662 DOI: 10.1002/cphc.200600781] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
4-methyl-4'-(n-mercaptoalkyl)biphenyl (CH3-C6H4-C6H4-(CH2)n-SH, n=3-6, BPn) monolayers assembled on Au(111)-(1x1) in 1,3,5,-trimethylbenzene (TMB) at various temperatures are studied by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). High resolution STM images reveal that BP3 and BP5 form a (sqrt 3x2sqrt 3) repeating motif superimposed on a temperature-dependent Moire pattern. BP4 and BP6 adlayers are characterized by a coexisting (2sqrt 3x5sqrt 3) majority phase and a temperature-dependent (3xpsqrt 3) minority phase. Assembly at 60 degrees C or 90 degrees C leads to p=5. Compression of the adlayer was found at higher temperatures. Combined with high-resolution structure experiments, the electronic characteristics of BP3 and BP4 self-assembled monolayers (SAMs) were studied by monitoring current-distance (iT-Deltaz) and current-voltage (iT-Ebias) characteristics in TMB employing a gold STM tip|BPn|Au(111)-(1x1) configuration. The semilogarithmic (iT-Deltaz) plots yielded three linear regions in the range 10 pA<or=iT<or=20 microA, which were attributed to the different positions of the STM tip with respect to the molecular adlayer (I outside, II in contact with and/or within the adlayer, and III just before the formation of Au-Au nanocontacts). The effective decay constants kappaeff and the corresponding barrier heights phi(eff) decrease with decreasing tip-substrate distance. The iT-Ebias curves at low bias voltages are represented by the Simmons tunneling model. Based on measurements in the high current limit, the electric field strength of the dielectric breakdown was estimated to range between |0.85+/-0.05|x10(9) V m-1 and |1.5+/-0.1|x10(9) V m-1.
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Affiliation(s)
- Gujin J Su
- Institute of Bio- and Nanosystems (IBN3), Research Center Jülich, Germany
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