Národní úložiště šedé literatury Nalezeno 12 záznamů.  1 - 10další  přejít na záznam: Hledání trvalo 0.00 vteřin. 
Preparation, characterization and study of electron transfer in self-organized structures on solid electrodes
Kolivoška, Viliam
Předkládaná dizertační práce se zaměřuje na elektrochemické, spektroelektrochemické, adsorpční, komplexační a vodivostní vlastnosti prodloužených viologenů různé délky (sloučeniny 1 až 6). Jejich molekuly by v budoucnosti mohli sloužit jako vodivé molekulární dráty v přístrojích molekulární elektroniky. Všechny studované sloučeniny vytvářejí na rozhraní rtuť/elektrolyt kompaktní monovrstvu paralelně ležících molekul s difúzně řízeným vznikem. Přítomnost adsorbovaných molekul na povrchu Au(111) byla potvrzena pomocí technik STM a PM IRRAS. Molekula prodlouženého viologenu obsahující jednu opakující se jednotku (sloučenina 1) reverzibilně přijímá čtyři elektrony, jako plně delokalizovaný systém. Molekula sloučeniny 2 však přijímá dva elektrony nezávisle a má proto dvě nekomunikující centra. Molekuly obsahující větší počet jednotek (n) přijímají v prvních dvěch redukčních krocích 2(n-1) elektronů (n-1 v každém). Chemická stabilita redukovaných forem sloučenin 1 až 6 byla potvrzena pomocí in-situ UV/VIS/NIR spektroelektrochemických technik. Vodivost elektrických spojů obsahujících molekuly prodloužených viologenů (měřena Taovou metodou) klesá exponencielně s délkou molekuly. V případě jiných typů prodloužených viologenů (sloučeniny 1' a 4') se zjistilo, že na jejich elektrochemické chování má výrazný...
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.
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.
Supported Phospholipid Bilayer at the Conductive Interface
Sokolová, Romana ; Kocábová, Jana ; Kolivoška, Viliam ; Gál, M.
The interactions of ethanol and flavonoid compounds with supported phospholipid bilayer\nwere studied by means of electrochemical methods and scanning probe techniques. The\nstability of a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipid bilayer\nsupported on different types of conductive substrate was investigated. The relationship\nbetween the method of lipid deposition and the formation of several types of lipid structures\nincluding vesicles, hemimicelles, patches and single bilayers on the interface is discussed.
2-D simulations of electromigration processes
Kolivoška, Viliam ; Koval, Dušan (oponent) ; Gaš, Bohuslav (vedoucí práce)
6 Abstract In the presented thesis we introduce a computational model that can be used for 2-D and 3-D computer simulations of experiments in electrophoresis. The simulations are carried out by the aid of the finite element method (FEM). In particular, commercially available program Comsol Multiphysics 3.3 is employed. A general shape of continuity equation is chosen to express the mass, electric charge, momentum and energy conservation law. Diffusion, migration and convection terms are taken into account when formulating the mass conservation law. Both external (driving voltage) and internal (diffusion currents) terms are considered in the electric charge conservation law. Both constant voltage mode and constant current mode can be handled. A solvent is regarded as an incompressible Newtonian fluid. Both pressure-driven and electroosmotic flows can be taken into consideration. The heat convection as well as the heat diffusion is governed by the energy conservation law. Both strong and weak electrolytes (of any attainable valency) may be regarded as system constituents. Furthermore, the model can handle the ionic strength correction if desired. A task may be assigned either in Cartesian or cylindrical coordinates. The presented model was employed to solve four particular tasks. The first one inspects the...
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.
Charge Transport in Single Molecule Junctions of Spirobifluorene Scaffold
Hromadová, Magdaléna ; Kolivoška, Viliam ; Sokolová, Romana ; Šebera, Jakub ; Mészáros, G. ; Valášek, M. ; Mayor, C.
Single molecule conductance of two spirobifluorene molecules of different length have been studied by scanning tunneling break junction (STM–BJ) methodology. First molecule contains a tripodal spirobifluorene platform, whereas a second one contains the same platform with chemically attached p-phenyleneethynylene molecular wire. The conductance values change only slightly between these two molecules, which demonstrated that such a platform provides both highly conducting pathway and stable anchor for the future molecular electronic devices.
Reduction and Oxidation of Hydroxyquinolines in Acetonitrile and Dimethylsulfoxide
Sokolová, Romana ; Ramešová, Šárka ; Fiedler, Jan ; Kolivoška, Viliam ; Degano, I. ; Gál, M. ; Szala, M. ; Nycz, J. E.
This study is focused on investigation of oxidation and reduction pathways of selected hydroxyquinoline compounds in nonaqueous solutions. The experimentally obtained reduction potentials are reported to well correlate with calculated values of LUMO energies as well as the obtained oxidation potentials are in a good agreement with theoretical HOMO energies. The cyclic voltammetry, in situ UV/Vis spectroelectrochemistry and in situ IR spectroelectrochemistry confirmed that the oxidation mechanism is complicated. Oxidation unexpectedly proceeds together with protonation of the starting compound. This behaviour was found for all studied compounds, hydroxyquinoline carboxylic acids and also for compounds, where a methyl group is present instead of carboxylic group.
Spectroelectrochemical Study of Electron Transfer in the Extended 1,1 '-Bipyridinium Cation
Hromadová, Magdaléna ; Kolivoška, Viliam ; Pospíšil, Lubomír ; Valášek, M. ; Tarábek, Ján
Electron transfer (ET) in the extended 1, 1 ' -bipyridinium has been investigated by UV Nis/NIR and EPR in-situ spectroelectrochemical techniques. During the in-situ cyclic voltammetric scan no EPR signal was observed at the potential corresponding to the first electron transfer at room temperature, whereas the EPR signal for the subsequent ET steadily increased and was observed even at the potentials corresponding to the fourth electron transfer. The EPR signal was detected for the first electron transfer step only at elevated temperature. The evidence for the presence of comproportionation processes and for the formation of n-dimer is discussed.
Properties of some radiosensitizers studied by means of the electrochemical methods
Gál, Miroslav ; Kolivoška, Viliam ; Ambrová, M. ; Híveš, J. ; Sokolová, Romana ; Hromadová, Magdaléna
To determine the correlation between reduction potential and some physicochemical properties of selected radiosensitizers cyclic voltammetry and theoretical calculations based on the DFT method with B3LYP functional of the level of 6-311++G** basis set in vacuum were utilized. Very good correlation was found between electron affinities of radiosensitizers and their reduction potential and so called E1(7) potential.

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