National Repository of Grey Literature 16 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Electrochemical Properties of Mixed Self-Assembled Monolayers Based on Terpyridine Transition Metal Complexes
Kocábová, Jana ; Nováková Lachmanová, Štěpánka ; Vavrek, František ; Valášek, M. ; Hromadová, Magdaléna
This work presents the electrochemical characterization of mixed self-assembled monolayers\n(SAMs) of [Os(terpy)2]2+ and terpyridine connected by tripodal anchoring groups to the\npolycrystalline gold bead electrode and provides a comparison with SAM based on\n[Os(terpy)2]2+ tripodal molecules without diluting terpyridine tripodal molecules. It is shown\nthat both arrangements enable reproducible preparation of well-defined compact films. The\nelectron transfer rate constant for mixed SAM was determined from cyclic voltammograms\naccording to Laviron’s analysis and compared with the rate constant obtained previously for\nSAM containing only [Os(terpy)2]2+ tripod.
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.
Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study
Sokolová, Romana ; Fiedler, Jan ; Ramešová, Šárka ; Kocábová, Jana ; Degano, I. ; Quinto, A. ; Křen, Vladimír
The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The oxidation mechanism and formation of oxidation products depends on the chemical structure. Only small differences in the chemical structure of compounds with flavone, flavanone and flavonol motif result in extremely variable oxidation pathways and products. Products of oxidation and further decomposition were determined by HPLC-ESIMS/MS and HPLC-DAD.
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.
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.
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.
Oxidation of Bioflavonoids in Respect to their Chemical Structure
Sokolová, Romana ; Ramešová, Šárka ; Kocábová, Jana ; Degano, I.
The electrochemical oxidation of flavone luteolin, flavanone taxifolin and flavonols derived from quercetin was studied by cyclic voltammetry. Only small differences in the chemical structure of bioflavonoids resulted in extremely variable oxidation pathways and products. Products of oxidation and further decomposition were determined by HPLC-ESI-MS/MS and HPLC-DAD.
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.
Electrochemistry of Flavonolignans in Acetonitrile and Dimethylsulfoxide
Sokolová, Romana ; Kocábová, Jana ; Fiedler, Jan ; Vacek, J. ; Marhol, Petr ; Vavříková, Eva ; Křen, Vladimír
This study is focused on investigation of oxidation pathways of silybin and 2,3-dehydrosilybin in nonaqueous solutions. The oxidation mechanism of both flavonolignans differs and depends strongly on their chemical structure. The cyclic voltammetry, UV/Vis and IR spectroelectrochemistry were used for identification of electrooxidation (semiquinone) intermediates. HPLC with diode array detection was applied for identification of oxidation and degradation products. Molecular orbital calculations supported the experimental findings.
Adsorption of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine on Au(111) and HOPG
Kocábová, Jana ; Sokolová, Romana
Atomic force microscopy (AFM) was used to study the formation of layers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on Au(111) and highly oriented pyrolytic graphite (HOPG) in microscopic level. Both substrates were found to support the DPPC layers. The nanoshaving technique was applied to determine the layer thickness. In addition, the influence of deionized water on the DPPC ordering at the substrates was studied by ex-situ and in-situ AFM intermittent contact mode measurements.

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