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Influence of Adsorption on Electrochemical Reduction of Pyridinium Derivatives
Nováková Lachmanová, Štěpánka ; Dupeyre, G. ; Lainé, P. P. ; Hromadová, Magdaléna
Two expanded pyridinium-based compounds 1 and 2 were studied by cyclic voltammetry in two different environments. The nonaqueous solution suppresses the adsorption of the compounds on the electrode surface. Adsorption process in aqueous environment was confirmed by typical shape of the curve as well as by the linear dependence of peak current on the scan rate. The shift of standard redox potential in aqueous solution compared to nonaqueous environment toward more negative potential indicates the adsorption of reactant on the electrode surface. Larger shift observed for flat conjugated molecule 1 confirms its stronger adsorption than for the second molecule.
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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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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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Charakterizace elektrody modifikované pyridinoporfyrazinátovým filmem a její využití v elektrochemickém senzoru
Klusáčková, Monika ; Nesměrák, Karel (vedoucí práce) ; Hromadová, Magdaléna (oponent)
V diplomové práci jsou presentovány výsledky studia reakce přenosu náboje na tenké vrstvě mediátoru, N,N',N'',N'''-tetramethyl-tetra-3,4-pyridinoporfyrazinát kobaltu, deponovaného na povrchu elektrody tvořené základní rovinou vysoce orientovaného pyrolytického grafitu. Modifikovaná elektroda, která projevila elektrokatalytickou aktivitu k oxidaci propylenu, byla charakterizována elektrochemicky, spektroskopicky a mikroskopicky.
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Závislost vodivosti pyridiniových molekul na jejich struktuře
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Kolivoška, Viliam ; Pospíšil, Lubomír ; Gasior, Jindřich ; Mészáros, G. ; Lainé, P. P.
Vývojáři elektronických součástek stojí před palčivým problémem. Podle Moorova zákona 1, empirického pravidla odhadujícího možnosti v miniaturizaci elektronických součástek, již brzy nebude možné pokračovat ve zvyšování výkonu elektronických zařízení při zachování jejich rozměrů. Současná věda navrhuje hned několik možných směrů, jak nahradit doposud sloužící technologie na bázi křemíku. Jednou z nich je vývoj a použití specializovaných molekul 2.
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Comparison of Techniques for Single-Molecule Conductance Measurements of Expanded Pyridinium Molecules
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Sokolová, Romana ; Kocábová, Jana ; Gasior, Jindřich ; Mészáros, G. ; Lainé, P. P.
This work is focused on the comparison of two techniques of single-molecule conductance measurements: Scanning Tunneling Microscopy Break Junction technique and Mechanically Controlled Break Junction technique. The structure of studied compound 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium allows the formation of the molecular bridge between two gold electrodes, which are connected to a source of the constant voltage in both of the used methods. The differences, advantages and disadvantages of both of the techniques will be discussed. Both techniques provided two values of conductance of studied compound depending on the experimantal conditions.
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