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801 results on '"Zharnikov, Michael"'

53. Aromatic self-assembled monolayers with pentafluoro-λ6-sulfanyl (−SF5) termination: Molecular organization and charge transport properties.

Author

Liu, Yangbiao, Zeplichal, Marc, Katzbach, Sonja, Wiesner, Adrian, Das, Saunak, Terfort, Andreas, and Zharnikov, Michael

Subjects
MOLECULAR orientation, CONTACT angle, ORGANIC electronics, ELECTRONICS engineers, SPINE, MONOMOLECULAR films, PHOTOVOLTAIC power generation
Abstract

A series of molecules with oligophenylene backbone, thiolate anchoring group, and pentafluoro-λ6-sulfanyl (−SF5) tail group was synthesized and used as precursors to form self-assembled monolayers (SAMs) on Au(111) substrates. The resulting SAMs feature dense molecular packing, upright molecular orientation, and chemically homogeneous SAM-ambient interface, comprised entirely of the −SF5 moieties. These SAMs exhibit exceptional wetting and electrostatic properties, showing advancing water contact angles up to 103° and work function values up to 5.96 eV—probably the highest values reported for any aromatic monolayers on gold. They also feature a comparably low value of the tunnelling decay coefficient (0.38 ± 0.07 Å−1), typical of oligophenylene backbone, which is not affected by the introduction of the −SF5 group. The latter also hardly affects the current densities at a specific bias compared to analogous monolayers with other electronegative tail groups. The superior electrostatic and good charge transport properties of the designed, SF5-terminated SAMs make them potentially useful for interface engineering in organic electronics and photovoltaics. [ABSTRACT FROM AUTHOR]

Published
2023
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72. Intermolecular Effects on Tunneling through Acenes in Large-Area and Single-Molecule Junctions

Author

Liu, Yuru (author), Ornago, L. (author), Carlotti, Marco (author), Ai, Yong (author), El Abbassi, M. (author), Soni, Saurabh (author), Asyuda, A. (author), Zharnikov, Michael (author), van der Zant, H.S.J. (author), Chiechi, Ryan C. (author), Liu, Yuru (author), Ornago, L. (author), Carlotti, Marco (author), Ai, Yong (author), El Abbassi, M. (author), Soni, Saurabh (author), Asyuda, A. (author), Zharnikov, Michael (author), van der Zant, H.S.J. (author), and Chiechi, Ryan C. (author)

Abstract

This paper describes the conductance of single-molecules and self-assembled monolayers comprising an oligophenyleneethynylene core, functionalized with acenes of increasing length that extend conjugation perpendicular to the path of tunneling electrons. In the Mechanically Controlled Break Junction (MCBJ) experiment, multiple conductance plateaus were identified. The high conductance plateau, which we attribute to the single molecule conformation, shows an increase of conductance as a function of acene length, in good agreement with theoretical predictions. The lower plateau is attributed to multiple molecules bridging the junctions with intermolecular interactions playing a role. In junctions comprising a self-assembled monolayer with eutectic Ga-In top-contacts (EGaIn), the pentacene derivative exhibits unusually low conductance, which we ascribe to the inability of these molecules to pack in a monolayer without introducing significant intermolecular contacts. This hypothesis is supported by the MCBJ data and theoretical calculations showing suppressed conductance through the PC films. These results highlight the role of intermolecular effects and junction geometries in the observed fluctuations of conductance values between single-molecule and ensemble junctions, and the importance of studying molecules in both platforms., QN/van der Zant Lab, Applied Sciences

Published
2020
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73. Understanding the Role of Parallel Pathways via In-Situ Switching of Quantum Interference in Molecular Tunneling Junctions

Author

Soni, Saurabh, Ye, Gang, Zheng, Jueting, Zhang, Yanxi, Asyuda, Andika, Zharnikov, Michael, Hong, Wenjing, Chiechi, Ryan C., Soni, Saurabh, Ye, Gang, Zheng, Jueting, Zhang, Yanxi, Asyuda, Andika, Zharnikov, Michael, Hong, Wenjing, and Chiechi, Ryan C.

Abstract

This study describes the modulation of tunneling probabilities in molecular junctions by switching one of two parallel intramolecular pathways. A linearly conjugated molecular wire provides a rigid framework that allows a second, cross-conjugated pathway to be effectively switched on and off by protonation, affecting the total conductance of the junction. This approach works because a traversing electron interacts with the entire quantum-mechanical circuit simultaneously; Kirchhoff's rules do not apply. We confirm this concept by comparing the conductances of a series of compounds with single or parallel pathways in large-area junctions using EGaIn contacts and single-molecule break junctions using gold contacts. We affect switching selectively in one of two parallel pathways by converting a cross-conjugated carbonyl carbon into a trivalent carbocation, which replaces destructive quantum interference with a symmetrical resonance, causing an increase in transmission in the bias window.

Published
2020

75. Self-assembled monolayers of ferrocene-substituted biphenyl ethynyl thiols on gold

Author

Shaporenko, Andrey, Rossler, Katrin, Lang, Heinrich, and Zharnikov, Michael

Subjects
Thiols -- Chemical properties, Monomolecular films -- Chemical properties, Spectrum analysis -- Usage, Chemicals, plastics and rubber industries
Abstract

Homogeneous and mixed [with biphenylthiol (BPT)] self-assembled (SAMs) of ferrocene substituted biphenyl ethynyl thiols (Fc) were prepared on Au(111) substrates and characterized by several complementary spectroscopic techniques. The results show that the Fc molecules when competing with BPT, preferably adsorb onto Au(111) substrate, suggesting a significant impact of the ferrocene groups onto the structure-binding interactions responsible for molecular self-assembly.

Published
2006

76. Competition as a design concept: Polymorphism in self-assembled monolayers of biphenyl-based thiols

Author

Cyganik, Piotr, Buck, Manfred, Strunskus, Thomas, Shaporenko, Andrei, Wilton-Ely, James D.E.T., Zharnikov, Michael, and Woll, Christof

Subjects
Biphenyl compounds -- Chemical properties, Biphenyl compounds -- Structure, Thiols -- Chemical properties, Monomolecular films -- Structure, Monomolecular films -- Chemical properties, Chemistry
Abstract

A study investigates self-assembled monolayers (SAMs) of two omega-(4'methylbiphenyl-4-yl)alkanethiois { C[H.sub.3][(C6H4).sub.2]-[(C[H.sub.2]).sub.n]SH, BPn, n = 4,6 } on Au(111) substrates, prepared from solution at room temperature and subsequently annealed at temperatures up to 493 K under a nitrogen atmosphere. Results show that, in striking contrast to BPn SAMs with n = odd, for which only one phase is observed, the even-numbered BPn SAMs exhibit polymorphism.

Published
2006

77. Molecular self-assembly at bare semiconductor surfaces: Preparation and characterization of highly organized octadecanethiolate monolayers on GaAs(001)

Author

McGuiness, Christine L., Shaporenko, Andrey, Mars, Carole K., Uppili, Sundararajan, Zharnikov, Michael, and Allara, David L.

Subjects
Thiols -- Atomic properties, Monomolecular films -- Design and construction, Gallium arsenide -- Atomic properties, Semiconductor preparation -- Methods, Chemistry
Abstract

A study was conducted to show that through rigorous control of preparation conditions, organized monolayers with a highly reproducible structure could be formed by solution self-assembly of octadecanethiol on GaAs(001) at ambient temperature. Despite differences in assembly rates and the thermal stability, exchange experiments with isotopically tagged molecules show that the octadecanethiol on GaAs(001) monolayers undergo exchange with solute thiol molecules at roughly the same rate as the corresponding exchanges of the same monolayers on Au{111}.

Published
2006

82. Effect of irradiation does in making an insulator from a self-assembled monolayer

Author

Yian Tai, Shaporenko, Andrey, Grunze, Michael, and Zharnikov, Michael

Subjects
Monomolecular films -- Research, Irradiation -- Research, Molecular electronics -- Mechanical properties, Molecular electronics -- Research, Chemicals, plastics and rubber industries
Abstract

A combination of functionalization and irradiation-induced cross-linking allows fabrication of stable metal film on top of an aromatic self-assembled monolayer, [1,1';4'1'-terphenyl]-4,4'-dimethanethiol (TPDMT) on Au. The optimal radiation exposure is a balance between a sufficient degree of cross-linking to close both static and dynamic diffusion channels at the self-assembled monolayers (SAM)-ambient interface and the limitation to keep the amount of the functional tailgroups at this interface as high as possible.

Published
2005

83. Surface chemistry of ultrathin films of histidine on gold as probed by high-resolution synchrotron photoemission

Author

Zubavichus, Yan, Zharnikov, Michael, Yongjie Yang, Fuchs, Oliver, Heske, Clemens, Umbach, Eberhard, Tzvetkov, George, Netzer, Falko P., and Grunze, Michael

Subjects
Histidine -- Chemical properties, Photoelectron spectroscopy -- Usage, Silver compounds -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

Various procedures for the vacuum deposition of thin histidine films on polycrystalline Au(111) and their characterization with high-resolution synchrotron-radiation-based photoelectron spectroscopy are reported. Water adsorption on pre-prepared film at 100 K results in protonation of histidine molecules and partial formation of hydroxyl anions.

Published
2005

96. Functionalized Tetrapodal Diazatriptycenes for Electrostatic Dipole Engineering in n‐Type Organic Thin Film Transistors

Author

Rohnacher, Valentina, primary, Benneckendorf, Frank S., additional, Münch, Maybritt, additional, Sauter, Eric, additional, Asyuda, Andika, additional, Barf, Marc‐Michael, additional, Tisserant, Jean‐Nicolas, additional, Hillebrandt, Sabina, additional, Rominger, Frank, additional, Jänsch, Daniel, additional, Freudenberg, Jan, additional, Kowalsky, Wolfgang, additional, Jaegermann, Wolfram, additional, Bunz, Uwe H. F., additional, Pucci, Annemarie, additional, Zharnikov, Michael, additional, and Müllen, Klaus, additional

Published
2020
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