Národní úložiště šedé literatury Nalezeno 30 záznamů.  1 - 10dalšíkonec  přejít na záznam: Hledání trvalo 0.00 vteřin. 
3D Printed Microfluidic Cell for Spectroelectrochemical Analysis
Šikula, M. ; Vaněčková, Eva ; Hromadová, Magdaléna ; Kolivoška, Viliam
Recent advances in fused deposition modeling 3D printing (FDM 3DP) enabled \nthe manufacture of customized spectroelectrochemical (SEC) devices. Despite significant progress, \nreported designs still rely on conventional optical components (windows and cuvettes). In this \nwork, we apply bi-material FDM 3DP combining electrically conductive and optically \ntranslucent filaments to manufacture a fully integrated microfluidic SEC device. Employing cyclic \nvoltammetric measurements with redox probes, we demonstrate that the platform allows SEC sensing of \nreactants, intermediates, and products of charge transfer reactions in an oxygen- free \nenvironment. Developed approaches pave the way for SEC d vices with dramatically\nreduced costs compared to currently available commercial platforms.\n
Manufacture of 3D Printed Microfluidic Channels and Their Characterization by Impedance Spectroscopy and Optical Microscopy Measurements
Štěrba, O. ; Vaněčková, Eva ; Choińska-Mlynarczyk, Marta ; Navrátil, Tomáš ; Kolivoška, Viliam
Fused deposition modeling 3D printing employing high-resolution extrusion nozzles and specialized manufacturing protocols have recently attracted attention as an inexpensive tool to create microfluidic devices. In this work, we have applied such an approach to create measurement cells with integrated microchannels of systematically varied dimensions. The real width of channels was inspected by two techniques, namely (A) impedance spectroscopy employing an aqueous sensing electrolyte and (B) optical microscopic imaging of silicone imprints hardened in the interior of printed structures. Both techniques have demonstrated that fused deposition modeling 3D printing enables precise manufacturing of channels with truly microfluidic dimensions.
Electrochemical Characterization of Self-Assembled Monolayers Containing Redox Switching Element
Nováková Lachmanová, Štěpánka ; Kocábová, Jana ; Vavrek, František ; Sebechlebská, Táňa ; Šebera, Jakub ; Kolivoška, Viliam ; Lukášek, J. ; Balzer, N. ; Valášek, M. ; Hromadová, Magdaléna
Adsorption properties of molecules containing [Ru(terpy)2]2+ and [Os(terpy)2]2+ redox switching element connected to the electrode surface by tripodal thiolate anchoring groups have been studied together with their charge transfer properties in the adsorbed form. STM-based current-voltage measurements confirmed that the conductance of self-assembled monolayer containing [Os(terpy)2]2+ redox switching element is lower than that containing [Ru(terpy)2]2+ element. This observation agrees with previously observed differences in the electron transfer rate constants of these molecules in their adsorbed state.
Electrochemical Techniques in Monitoring of Nervous System Drugs
Choińska-Mlynarczyk, Marta ; Hrdlička, Vojtěch ; Skopalová, J. ; Šelešovská, R. ; Kolivoška, Viliam ; Navrátil, Tomáš
Drugs of the nervous system (ATC group N) belong generally to the most commonly (mis)used substances worldwide. Their determination and monitoring of these drugs and their metabolites in various body fluids or environmental matrices represent a challenge for analytical chemists. Our research is focused on the application of electrochemical methods in the monitoring of the most frequently prescribed and the newly introduced nervous system drugs of precisely specified structures and/or of defined properties. For toxicological and pharmacokinetic reasons, emphasis has been placed on investigating the reaction mechanisms of their metabolite formation. New or alternative to commonly used electroanalytical methods applicable for monitoring and characterization of target compounds in their pure state, in body fluids, wastewaters, and other environmental matrices, has been developed. To improve the chemometric parameters and sensing characteristics, attention was paid to the construction of new electrochemical sensors, detectors (e.g. screen-printed, 3D printed), or cells, based on (modified/unmodified) traditional or nontraditional materials, preferably usable at the point-of-care.
Electroplating of 3D Printed Electrodes for Selective Electrochemical Reduction of C02
Vaněčková, Eva ; Bouša, Milan ; Shestivska, Violetta ; Kubišta, Jiří ; Rathouský, Jiří ; Sebechlebská, Táňa ; Kolivoška, Viliam
In this work, computer assisted design and fused deposition modelling 3D printing are\nemployed to devise and manufacture electrodes from polylactic acid-carbon nanotube\nconductive composite. Electrodes are further modified by copper electroplating to prepare\ncatalysts for the electrochemical reduction of carbon dioxide. Scanning electron microscopy\nand energy dispersive X-ray analysis are used to inspect the surface morphology and chemical\ncomposition of obtained catalysts. Cyclovoltammetric investigations reveal that the copper\nelectroplating leads to the increase of electrode activity by three orders of magnitude.
Electrochemical Characterization of Molecular Conductors Containing Redox Switching Element
Nováková Lachmanová, Štěpánka ; Vavrek, František ; Sebechlebská, Táňa ; Šebera, Jakub ; Kolivoška, Viliam ; Lukášek, J. ; Balzer, N. ; Valášek, M. ; Mayor, M. ; Hromadová, Magdaléna
Electrochemical properties of new molecules containing tripodal anchor and redox switching\nelement have been studied by cyclic voltammetry and DFT quantum mechanical calculations.\nComparison of their redox properties with individual organometallic [Ru(terpy)2]2+t3+ and\n[Os(terpy)2]2+t3+ redox centers shows that covalently bonded tripodal anchor does not\ncompromise the reversibility of a redox process and has no effect on the stability of new\nmolecules. New molecular conductors have smaller HOMO-LUMO gap and both are oxidized\nat only slightly more positive potentials after tripodal substitution making them suitable for the\ndevelopment of molecular conductors with switching abilities.
2-D simulations of electromigration processes
Kolivoška, Viliam ; Gaš, Bohuslav (vedoucí práce) ; Koval, Dušan (oponent)
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...
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...
Charge Transport through Molecular Towers Based on Tetraphenyhmethane 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 robusi coupling between molecular electronic components and metallic electrodes. In this work, charge transport in tower-shaped single molecule conductors based on tetraphenylmethane tripod possessing three thiol anchors is investigated by scanning tunneling microscopy break junction technique. The effect of tripod substitution pattern and number of repeating units in molecule is addressed. The substitution was found to influence conductance value in early stages of molecular junction evolution, where tower lays parallel to surface. In late stages, the charge is transported through principal molecular axis and junction breaks thermally in tilted configuration.

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