Neuartige funktionelle tripodale monomolekulare Filme
Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Zusammenfassung der Projektergebnisse
When employing self-assembled monolayers (SAMs) for tuning surface and interface properties, organic molecules that enable strong binding to the substrate, large-area structural uniformity, precise alignment of functional groups, and control of their density are highly desirable. To achieve these goals, tripod systems bearing multiple bonding sites have been developed as an alternative to conventional monodentate systems. Bonding of all three sites has, however, hardly been achieved, with the consequence that structural uniformity and orientational order in tripodal SAMs are usually quite poor. Facing this challenge, we have established a new type of tripodal monomolecular films based on the triptycene unit within the given project. A large variety of the respective SAM-forming molecules, decorated with different anchoring and functional tail groups in the tripodal and bridgehead configurations, was custom-designed, synthesized (by our partners), and used for the SAM assembly. Homogeneous, tripodal-anchored SAMs could be successfully prepared on application-relevant, coinage metal (Au and Ag) and oxide (indium tin oxide) substrates. On Ag(111), these SAM exhibited distinct polymorphism, with a particular interesting chiral arrangement of the molecules in the honeycomb network in one of the structural phases. The decoration of the triptycene framework with nitrile tail groups allowed the monitoring of the charge transfer (CT) dynamics in these systems, with the particular emphasis on the relative weights of alternative CT pathways. This issue was further extended by design and characterization of a series of monopodal SAMs, allowing to address matrix effects in CT across monomolecular assemblies. In addition, nitrile-decorated triptycene SAMs provided a showcase for the work function tuning by tripodal SAMs – an issue important in context of organic electronics and photovoltaics. Introduction of ethynyl tail groups allowed to create tripodal monomolecular template suitable for click reaction with functional azide-decorated substituents. The on-surface fabrication of tailor-designed, functional tripodal SAMs become thus possible, without timeintensive synthesis of individual precursors in each particular case. Introduction of ferrocene tail group resulted in rectification behavior of the respective molecular assembly at the exceptionally low bias, with two distinctly different conductance states observed at specific bias sweeping modes in two-terminal molecular junctions. Introduction of fullerene tail groups provided important insights in the mechanisms of molecular assembly. Generally, applicability and broad versatility of triptycene-based, tripodal SAMs was demonstrated, opening new ways for further research and applications.
Projektbezogene Publikationen (Auswahl)
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Cyano-Substituted Triptycene-Based Monolayers on Au(111): Tripodal Adsorption, Dipole Engineering, and Charge Transfer. The Journal of Physical Chemistry C, 125(34), 18968-18978.
Das, Saunak; Asyuda, Andika; Shoji, Yoshiaki; Kosaka, Atsuko; Fukushima, Takanori & Zharnikov, Michael
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Porous Honeycomb Self-Assembled Monolayers: Tripodal Adsorption and Hidden Chirality of Carboxylate Anchored Triptycenes on Ag. ACS Nano, 15(7), 11168-11179.
Das, Saunak; Nascimbeni, Giulia; de la Morena Rodrigo, Ortiz; Ishiwari, Fumitaka; Shoji, Yoshiaki; Fukushima, Takanori; Buck, Manfred; Zojer, Egbert & Zharnikov, Michael
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Probing Matrix Effects in the Course of Electron Transfer across a Self-Assembled Monolayer. The Journal of Physical Chemistry C, 126(40), 17415-17423.
Das, Saunak; Zhao, Zhiyong; Terfort, Andreas & Zharnikov, Michael
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Appearance of Different Conductance States in Monomolecular Films of Ferrocene-Decorated Triptycene-Based Tripods. The Journal of Physical Chemistry C, 127(50), 24458-24466.
Liu, Yangbiao; Sanjayan, Sajisha; Shoji, Yoshiaki; Fukushima, Takanori & Zharnikov, Michael
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Dynamics of electron transfer across a monomolecular film: Matrix effects and competitive pathways, The 11th International Conference on Materials for Advanced Technologies, Singapore, June 2023 (talk)
M. Zharnikov, T. Fukushima & A. Terfort
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Electron-Induced Modification of Triptycene Self-Assembled Monolayers in Context of Lithography and Nanofabrication. The Journal of Physical Chemistry C, 127(31), 15582-15590.
Zhao, Zhiyong; Fukushima, Takanori & Zharnikov, Michael
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Probing alternative pathways for electron transfer across a monomolecular film, 2023 Spring Meeting of the German Physical Society, Dresden, March 2023 (poster)
S. Das, Z. Zhao, T. Fukushima, A. Terfort & M. Zharnikov
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Triptycene as a versatile building block for monomolecular self-assembly on solid supports, 18th International Conference on Organized Molecular Films (ICOMF), Frankfurt-am-Main, August 2023 (poster)
T. Fukushima, M. Buck, E. Zojer & M. Zharnikov
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Triptycene-Based Self-Assembled Monolayer as a Template for Successive Click Reactions. The Journal of Physical Chemistry C, 127(10), 5178-5185.
Das, Saunak; Ishiwari, Fumitaka; Shoji, Yoshiaki; Fukushima, Takanori & Zharnikov, Michael
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Triptycene-Based Tripodal Self-Assembled Monolayer on Indium Tin Oxide. The Journal of Physical Chemistry C, 127(4), 2088-2097.
Das, Saunak; Ishiwari, Fumitaka; Shoji, Yoshiaki; Fukushima, Takanori & Zharnikov, Michael
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Phosphonic acid anchored tripodal molecular films on indium tin oxide. Physical Chemistry Chemical Physics, 26(15), 11360-11369.
Zhang, Chaoran; Das, Saunak; Sakurai, Naoya; Imaizumi, Takaki; Sanjayan, Sajisha; Shoji, Yoshiaki; Fukushima, Takanori & Zharnikov, Michael
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Triptycene as a versatile building block for self-assembled monolayers, 2024 Spring Meeting of the German Physical Society, Berlin, March 2024 (poster)
T. Fukushima, M. Buck, E. Zojer & M. Zharnikov
