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Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
Hromadová, Magdaléna ; Kolivoška, Viliam ; Šebera, Jakub ; Sebechlebská, Táňa ; Gasior, Jindřich ; Nováková Lachmanová, Štěpánka ; Mészáros, G. ; Lindner, M. ; Mayor, M. ; Valášek, M.
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule conductance G was obtained by a scanning tunneling microscopy break junction technique complemented by theoretical calculations based on the density functional theory and non-equilibrium Green’s function formalism. Two molecules were compared where the same oligophenylene wire is connected to one of the electrodes via a tripod substituted on each leg by a thiol group either in the meta or para position. By combined experimental and theoretical analysis it was possible to confirm that single molecule conductance in the metal-molecule-metal junction of both molecules corresponds to a fully extended molecular wire, which is attached to one of the electrodes by all three thiolate bonds of the tripod. Experimental results confirmed that G value of meta-connected molecules is lower than that of para, whereas junction formation probability was higher for meta functionalization.
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Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
Hromadová, Magdaléna ; Kolivoška, Viliam ; Šebera, Jakub ; Sebechlebská, Táňa ; Gasior, Jindřich ; Nováková Lachmanová, Štěpánka ; Mészáros, G. ; Lindner, M. ; Mayor, M. ; Valášek, M.
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule conductance G was obtained by a scanning tunneling microscopy break junction technique complemented by theoretical calculations based on the density functional theory and non-equilibrium Green’s function formalism. Two molecules were compared where the same oligophenylene wire is connected to one of the electrodes via a tripod substituted on each leg by a thiol group either in the meta or para position. By combined experimental and theoretical analysis it was possible to confirm that single molecule conductance in the metal-molecule-metal junction of both molecules corresponds to a fully extended molecular wire, which is attached to one of the electrodes by all three thiolate bonds of the tripod. Experimental results confirmed that G value of meta-connected molecules is lower than that of para, whereas junction formation probability was higher for meta functionalization.
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Electrochemical Investigation of Polylactic Acid/Carbon Black Composite Filament for the Manufacture of 3D Printed Electrodes
Sebechlebská, Táňa ; Vaněčková, Eva ; Shestivska, Violetta ; Kolivoška, Viliam
Fused deposition modeling 3D printing has recently attracted increasing attention as an inexpensive, fast, reliable, adaptable and environmentally friendly tool to fabricate electrodes and electrochemical cells from composites of thermoplastics and carbon nanostructures. In this work, we use electric conductance measurements and cyclic voltammetry employing Ru(acac)30/1- as an electroactive probe to demonstrate that commercial polylactic acid(PLA)/carbon black composite filaments may be readily used as functional working electrodes in aqueous electrolytes. We further devise a procedure that leads to an improvement of their electrochemical performance. Characteristics of composite filaments treated by the optimized procedure approach those of classical metallic electrodes.
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Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
Hromadová, Magdaléna ; Kolivoška, Viliam ; Šebera, Jakub ; Sebechlebská, Táňa ; Gasior, Jindřich ; Nováková Lachmanová, Štěpánka ; Mészáros, G. ; Lindner, M. ; Mayor, M. ; Valášek, M.
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule conductance G was obtained by a scanning tunneling microscopy break junction technique complemented by theoretical calculations based on the density functional theory and non-equilibrium Green’s function formalism. Two molecules were compared where the same oligophenylene wire is connected to one of the electrodes via a tripod substituted on each leg by a thiol group either in the meta or para position. By combined experimental and theoretical analysis it was possible to confirm that single molecule conductance in the metal-molecule-metal junction of both molecules corresponds to a fully extended molecular wire, which is attached to one of the electrodes by all three thiolate bonds of the tripod. Experimental results confirmed that G value of meta-connected molecules is lower than that of para, whereas junction formation probability was higher for meta functionalization.
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Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen Evolution Reaction on the Surface Structure
Novák, M. ; Kocábová, Jana ; Kolivoška, Viliam ; Pospíšil, Lubomír ; Macák, J. ; Cichoň, Stanislav ; Cháb, Vladimír ; Hromadová, Magdaléna
Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials negative of the open circuit potential value. Two main characteristic parameters were obtained from the ex situ AFM height images, namely, the roughness factor and fractal dimension of the studied surface. The effect of hydrogen evolution reaction on the electrode surface morphology was discussed. Fractal dimension values were used successfully to explain the non ideality of the interfacial capacitance.
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Investigation of Single Molecule Charge Transport Properties and Geometrical Arrangement in Terpyridine Architectures Supported by the Tetraphenylmethane Tripod
Kolivoška, Viliam ; Sebechlebská, Táňa ; Šebera, Jakub ; Gasior, Jindřich ; Lindner, M. ; Lukášek, J. ; Valášek, M. ; Mayor, M. ; Mészáros, G. ; Hromadová, Magdaléna
Tripodal platforms were engineered recently to realize a well-defined directional contact between metallic electrodes and molecular architectures dedicated to serve as working elements for electronic applications. In this work we employ cyclic voltammetry, scanning tunneling microscopy break junction technique and theoretical approaches based on the combination of density functional theory and non-equilibrium Green´s function to investigate the geometrical arrangement and single molecule charge transport in terpyridine-based architectures supported by tetraphenylmethane tripod. We demonstrate that this architecture adopts a favorable geometrical arrangement capable of forming highly conductive molecular junctions and is thus suitable to serve as a basis for working molecular switches.
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Preparation, characterization and study of electron transfer in self-organized structures on solid electrodes
Kolivoška, Viliam
The presented thesis focuses on electrochemical, spectroelectrochemical, adsorption, complexation and conductivity properties of extended viologens of variable length (the compounds 1 to 6). In the future, their molecules could serve as conducting molecular wires in the devices of molecular electronics. At the mercury/electrolyte interface, all studied compounds were found to form a compact monolayer with flat-lying molecules with the diffusion as the rate-determining step. The presence of adsorbed molecules on Au(111) surface was confirmed by STM and PM IRRAS techniques. The extended viologen molecule consisting of one repeating unit (the compound 1) was found to reversibly transfer four electrons, behaving as a fully delocalized system. On the other hand, the molecule of the compound 2 transfers two electrons independently, having thus two non-communicating centers. The molecules containing higher number of repeating units (n) transfer 2(n-1) electrons in the first two closely-positioned reduction steps (with n-1 electrons being independently consumed in each of them). Chemical stability of reduced forms of the compounds 1 to 6 was confirmed by UV/VIS/NIR in-situ spectroelectrochemical techniques. Electric conductance of junctions containing extended viologen molecules (scrutinized by Tao's...
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Effect of pH on the Oxide Film Formation on a Pristine Zr Electrode
Hromadová, Magdaléna ; Kocábová, Jana ; Kolivoška, Viliam ; Pospíšil, Lubomír
Effect of pH on the oxidation of zirconium metal was studied by cyclic voltammetry in\naqueous borate buffer solutions as a function of the potential scan rate and pH from 4.80 to\n9.17. The results show that the oxide growth kinetics depends on pH of the electrolyte\nsolution and the total amount of irreversibly formed oxide under the potentiodynamic\nconditions decreases with decreasing buffer pH in accord with thermodynamic considerations.\nCathodic current corresponding to hydrogen evolution reaction diminishes in the presence of\nanodically modified electrode compared to bare zirconium.
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Charge Transport through Molecular Towers Based on Tetraphenylmethane Tripods
Kolivoška, Viliam ; Šebera, Jakub ; Lindner, M. ; Valášek, M. ; Mayor, M. ; Mészáros, G. ; Gasior, Jindřich ; Hromadová, Magdaléna
Molecular platforms with multiple anchors were introduced recently to provide robust\ncoupling between molecular electronic components and metallic electrodes. In this work,\ncharge transport in tower-shaped single molecule conductors based on tetraphenylmethane\ntripod possessing three thiol anchors is investigated by scanning tunneling microscopy break\njunction technique. The effect of tripod substitution pattern and number of repeating units in\nmolecule is addressed. The substitution was found to influence conductance value in early\nstages of molecular junction evolution, where tower lays parallel to surface. In late stages, the\ncharge is transported through principal molecular axis and junction breaks thermally in tilted\nconfiguration.
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