Ústav fyzikální chemie J. Heyrovského

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2018-06-19
19:26
Electrochemical Study of Selected Pyrene Derivatives as Precursors to Organic Semiconductors
Koláčná, Lucie ; Tobrman, T. ; Ludvík, Jiří
A series of 9 precursors for pyrene based biodegradable organic (semi)conductors having tetrasubstituted double bond as a central organic core and photo- or redox active centers attached at this core were electrochemically investigated in order to determine the influence of individual parts of the molecule on the redox properties, to describe the location of the reduction center and to understand the structure - redox activity relationship of the mentioned compounds.

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2018-06-19
19:26
Redox Properties of Fluorinated Derivatives of 1,3-Diphenylisobenzofuran Chromophores for Singlet Fission
Šimková, Ludmila ; Ludvík, Jiří
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be advantageous for use as solar cell sensitizers. This study is focused on fluorinated derivatives of 1,3-diphenylisobenzofuran and the effect of the position of fluorine atoms on their redox properties. For characterization of the redox properties standard electrochemical methods, and in situ UV-vis and EPR spectroscopy techniques were used.

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2018-06-19
19:26
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.

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2018-06-19
19:26
Study of Metabolism of Synthetic Cannabinoids. Electrochemical Properties of JWH-018
Obluková, Michaela ; Sokolová, Romana ; Čabala, R.
In the recent years, many new substances have appeared in the drug market, which are abused for their psychoactive effect. They serve as alternative to classical drugs (heroin, cocaine, ecstasy) due to their legal status. The great concern is the ineffectiveness of the current methods of toxicological screening of biological samples to identify these new compounds. It is essential to know the metabolism pathway of these psychoactive substances for a development of a new efficient method for their detection. This report is devoted to understanding of oxidation and reduction mechanism of JWH-018 and JWH-250 by means of cyclic voltammetry and to identification of their redox products.

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2018-06-19
19:26
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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2018-06-19
19:26
Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen\nEvolution 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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2018-06-19
19:26
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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2018-06-19
19:26
Silver Solid Amalgam Electrodes as Perspective Tools for Sensitive Voltammetric Determinations of Food Azo Dyes Amaranth and Allura Red AC
Tvorynska, S. ; Barek, J. ; Josypčuk, Bohdan
In this paper, for the first time, the electrochemical behaviours of the food azo dyes Amaranth (E 123) and Allura Red AC (E 129) were investigated on two modifications of silver solid amalgam electrode, namely mercury meniscus modified, polished and compared with hanging mercury drop electrode using differential pulse voltammetry and direct current voltammetry. The effect of adsorption and the reduction mechanism on tested electrodes were described in detail. Measurements with amalgam electrodes showed good reproducibility, stability and high sensitivity. As a result, they were successfully applied for the determination of investigated azo dyes in different commercial drink samples.

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2018-06-19
19:26
Chování metalothieneinů a fytochelatinů na rtuťových a amalgámových elektrodách
Šestáková, Ivana ; Navrátil, Tomáš ; Josypčuk, Bohdan
Při použití elektrod AgSAE či CuSAE pro elektrochemická měření s metalothioneiny či fytochelatiny vznikají příslušné Ag-MT, Cu-MT, Ag-PC či Cu-PC komplexy. V čistých elektrolytech a pro nízké koncentrace analytů jsou odezvy lineárně závislé na jejich koncentraci, odezvu je možné zvýšit akumulací při vhodném potenciálu. Pro reálné vzorky je podstatný negativní vliv matrice, který může vést až k nutnosti přípravy nového povrchu a jeho aktivace pro každý jednotlivý záznam.

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2018-06-19
19:26
HPLC-ED/UV with Solid Phase Extraction for the Determination of 5-Hydroxyindole-3-acetic Acid
Makrlíková, Anna ; Dejmková, H. ; Navrátil, Tomáš ; Barek, J. ; Vyskočil, V.
Determination of 5-HIAA in human urine was succssfully performed using HPLC-ED/UV with SPE. HPLC-ED is a very sensitive technique; presented method does not need any sample pre-treatment apart from SPE procedure, which replaced filtration of samples of human urine to avoid problems with clogging a HPLC column. The found native\nconcentrations of 5-HIAA in human urine using HPLC-ED with SPE fully corresponds with published normal concentrations in urine (17.8 - 58.3 micromol l-1). The found native concentrations of 5-HIAA were 18.4 micromol L-1 (calculated from peak height). The presented method is fast and could be used for simple\nscreening of human urine, because HPLC-ED/UV allows simultaneous determination of 5-HIAA, HVA, and VMA as important tumour biomarkers.

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