Number of found documents: 402
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Oxidation Mechanism of Rhamnetin, a Bioflavonoid Compound
Ramešová, Šárka; Sokolová, Romana; Degano, I.
2016 - English
The natural flavonoid rhamnetin (2-(3,4-dihydroxyfenyl)-3,5-dihydroxy-7-methoxychromen-4-one) is important bioactive compound. Rhamnetin was studied in aqueous solution by electrochemical methods. The oxidation mechanism proceeds in sequential steps, which correspond to the hydroxyl oxidation of groups in the three aromatic rings. The study is based on in situ spectroelectrochemistry and identification of products by HPLC-DAD and HPLC–ESI MS/MS. Keywords: flavonoids; electrochemistry; oxidation mechanism Available at various institutes of the ASCR
Oxidation Mechanism of Rhamnetin, a Bioflavonoid Compound

The natural flavonoid rhamnetin (2-(3,4-dihydroxyfenyl)-3,5-dihydroxy-7-methoxychromen-4-one) is important bioactive compound. Rhamnetin was studied in aqueous solution by electrochemical methods. The ...

Ramešová, Šárka; Sokolová, Romana; Degano, I.
Ústav fyzikální chemie J. Heyrovského, 2016

Poly(Methylene Blue) Modified Carbon-based Electrodes for Electrochemical Detection of Hydrogen Sulfide
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2016 - English
A comparative electrochemical study has been carried out of the electropolymerization of phenothiazine derivative, methylene blue (MB). Electrochemical properties of resulting electrocatalytically active methylene blue polymer (pMB) have been studied on three various carbon-based substrates: basal plane of highly oriented pyrolytic graphite (HOPG), pencil-graphite electrode (PGE) and carbon fibre micro electrode (CFE). Electrodes modified with the polymer (HOPG/pMB, PGE/pMB and CFE/pMB) have been prepared by potential cycling in aqueous electrolyte solution containing dissolved monomeric methylene blue. Electrocatalytic activity of three developed electrode systems towards hydrogen sulphide has been compared. Developed electrodes have been further investigated as potential sensors for sulfhydryl-containing compounds. Keywords: CFE; HOPG; electropolymerization Available at various institutes of the ASCR
Poly(Methylene Blue) Modified Carbon-based Electrodes for Electrochemical Detection of Hydrogen Sulfide

A comparative electrochemical study has been carried out of the electropolymerization of phenothiazine derivative, methylene blue (MB). Electrochemical properties of resulting electrocatalytically ...

Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
Ústav fyzikální chemie J. Heyrovského, 2016

Electrochemical Methods for Determination of Three Tumor Biomarkers for Neuroblastoma: Homovanillic Acid, Vanillylmandelic Acid, and 5-Hydroxyindoleacetic Acid
Makrlíková, A.; Ktena, A.; Fischer, J.; Navrátil, Tomáš; Vyskočil, V.
2016 - English
Tumor biomarkers – homovanillic acid, vanillylmandelic acid, and 5-hydroxyindoleacetic acid – have been determined at a screen-printed carbon electrode in small volume samples. For all measurements, Britton-Robinson buffer (0.04 moll−1, pH 3.0) was used as an optimum medium for all three analytes. Dependences of the peak current on the concentration were linear for all compounds, with the limits of quantification 0.8 μmol∙l–1 for homovanillic acid, 0.2 μmol∙l–1 for vanillylmandelic acid, and 0.2 μmol∙l–1 for 5-hydroxyindoleacetic acid. Depending on the results of the measurements, the future experiments should be performed in human urine. Keywords: Screen-printed carbon electrodes; Differential pulse voltammetry; Homovanillic acid Available at various institutes of the ASCR
Electrochemical Methods for Determination of Three Tumor Biomarkers for Neuroblastoma: Homovanillic Acid, Vanillylmandelic Acid, and 5-Hydroxyindoleacetic Acid

Tumor biomarkers – homovanillic acid, vanillylmandelic acid, and 5-hydroxyindoleacetic acid – have been determined at a screen-printed carbon electrode in small volume samples. For all measurements, ...

Makrlíková, A.; Ktena, A.; Fischer, J.; Navrátil, Tomáš; Vyskočil, V.
Ústav fyzikální chemie J. Heyrovského, 2016

Poly(methylene blue) modified carbon based electrodes for the determination of sulfhydryl-containing compounds
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2016 - English
This research presents the study of electrochemical polymerization of phenothiazine derivative, methylene blue (MB). Electrochemical pro perties and analytical application of resulting electrocatalytically active poly(methylene blue) (pMB) have been investigated. Three various carbon-based substrates: basal plane of highly oriented pyro lytic graphite (HOPG), pencil graphite electrode (PGE) and carbon fibre micro electrode (CFE) have been used. Aforementioned electrodes modified with the polymer (HOPG/pMB, PGE/pMB and CFE/pMB) have been prepared by potential cycling in aqueous electrolyte solution containing dissolved monomeric methylene blue. Electrocatalytic activity of three developed electrode systems towards hydrogen sulphide has been compared. Developed electrodes have been further investigated as potential sensors for sulfhydryl-containing compounds. Keywords: carbon-based electrodes; electropolymerization; hydrogen sulphide Available at various institutes of the ASCR
Poly(methylene blue) modified carbon based electrodes for the determination of sulfhydryl-containing compounds

This research presents the study of electrochemical polymerization of phenothiazine derivative, methylene blue (MB). Electrochemical pro perties and analytical application of resulting ...

Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
Ústav fyzikální chemie J. Heyrovského, 2016

Electrochemical Impedance Spectroscopy and Steady-State Voltammetry at the Micro-between Two Immiscible Electrolyte Solutions
Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
2016 - English
The kinetic data of simple tetraethylammonium ion transfer across the water/1,2-DCE interface obtained by electrochemical impedance spectroscopy and steady-state voltammetry are compared. It is shown that the geometry of the microcapillary tip region is of critical importance to obtain reliable kinetic data. Quasi-reversible behavior of the ion transfer reaction, corresponding to an apparent standard rate constant of about 0.2 cm s-1, is observed with both experimental methods.\n Keywords: liquid-liquid interface; ion transport; AC impedance Available at various institutes of the ASCR
Electrochemical Impedance Spectroscopy and Steady-State Voltammetry at the Micro-between Two Immiscible Electrolyte Solutions

The kinetic data of simple tetraethylammonium ion transfer across the water/1,2-DCE interface obtained by electrochemical impedance spectroscopy and steady-state voltammetry are compared. It is shown ...

Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2016

Photocatalytic active coatings-environmental way to improve quality and durability of buildings
Sázavská, T.; Jakubičková, M.; Jirkovský, Jaromír; Šubrt, Jan; Peterka, F.
2016 - English
Transparent coatings of TiO2-SiO2 nanocomposite were developed to be applied on building facades in order to prevent growth of microorganisms and thus to improve urban building sustainability. Structure and texture characteristics of the prepared nanocomposites were determined by electron microscopy (SEM, TEM + EDS), their photocatalytic activity was quantified by testing self-cleaning ability and antimicrobial activity. The self-cleaning properties were evaluated according to the standard ISO method based on photocatalytic degradation of methylene blue. The TiO2-SiO2 nanocomposite coatings were applied on various types of substrates commonly used in building industry. The antimicrobial activity was mainly investigated for algae because these microorganisms are often responsible for facades ageing. According to the laboratory tests the prepared TiO2-SiO2 nanocomposites are highly efficient. This fact was already proved by first applications in real conditions. The transparent SiO2-TiO2 nanocomposites represent an ecological and noninvasive way how to keep nice appearance of buildings for a long time. It is due to their permanent photocatalytic activity causing self-cleaning and algicidal effects. Such coatings may significantly reduce ageing processes on facades of buildings that are caused by microbiological pollution and smog exhalations. Keywords: Photocatalysis; Photocatalytic algae degradation; Photocatalytic paint Available at various institutes of the ASCR
Photocatalytic active coatings-environmental way to improve quality and durability of buildings

Transparent coatings of TiO2-SiO2 nanocomposite were developed to be applied on building facades in order to prevent growth of microorganisms and thus to improve urban building sustainability. ...

Sázavská, T.; Jakubičková, M.; Jirkovský, Jaromír; Šubrt, Jan; Peterka, F.
Ústav fyzikální chemie J. Heyrovského, 2016

Role of Intramolecular Electron Interactions in Cathodic Reduction of Three Isomeric Benzenedialdehydes in Non-aqueous Media – a (Spectro)Electrochemical Study
Kantnerová, Kristýna; Klíma, Jiří; Ludvík, Jiří
2016 - English
This contribution is focused on cathodic reduction of three isomeric benzenedialdehydes – orthophthalaldehyde (OPA), isophthalaldehyde (IPA) and terephthalaldehyde (TPA) – in non-aqueous acetonitrile and dimethylformamide. Although their electrochemical behavior in aqueous solutions has been published several times, their investigation in organic aprotic solvents is lacking. Using DC-polarography, cyclic voltammetry, preparative electrolyses, coulometry and UV/Vis spectroelectro-chemistry their reduction was described and in the case of OPA and TPA, stable radical anions were characterized by EPR spectroscopy. The role of intramolecular electron interactions in their cathodic reduction is discussed. Keywords: Orthophthalaldehyde; OPA; IPA Available at various institutes of the ASCR
Role of Intramolecular Electron Interactions in Cathodic Reduction of Three Isomeric Benzenedialdehydes in Non-aqueous Media – a (Spectro)Electrochemical Study

This contribution is focused on cathodic reduction of three isomeric benzenedialdehydes – orthophthalaldehyde (OPA), isophthalaldehyde (IPA) and terephthalaldehyde (TPA) – in non-aqueous acetonitrile ...

Kantnerová, Kristýna; Klíma, Jiří; Ludvík, Jiří
Ústav fyzikální chemie J. Heyrovského, 2016

Study of 2-Nitrofluorene Interaction with DNA at a Glassy Carbon Electrode
Skalová, Štěpánka; Stávková, K.; Vyskočil, V.; Barek, J.
2016 - English
2-Nitrofluorene (2-NF) is a nitrated polycyclic aromatic hydrocarbon (NPAH) which occurs as the environmental pollutant. It is a potential carcinogen and mutagen. Interaction of deoxyribonucleic acid (DNA) with 2-NF was monitored using an electrochemical DNA biosensor prepared from a glassy carbon electrode (GCE) and low-molecular-weight DNA by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave voltammetry (SWV).\nThere were no damaging interactions observed between DNA and 2-NF using EIS. However, CV shows intercalation of this substance into the DNA structure to form the complex 2-NF–DNA. Intercalation was also observed by SWV, confirming intercalation to reduce the number of electroactive sites and thus reducing the peak heights of adenosine and guanosine. Keywords: DNA biosensor; glassy carbon electrode; voltammetry Available at various institutes of the ASCR
Study of 2-Nitrofluorene Interaction with DNA at a Glassy Carbon Electrode

2-Nitrofluorene (2-NF) is a nitrated polycyclic aromatic hydrocarbon (NPAH) which occurs as the environmental pollutant. It is a potential carcinogen and mutagen. Interaction of deoxyribonucleic acid ...

Skalová, Štěpánka; Stávková, K.; Vyskočil, V.; Barek, J.
Ústav fyzikální chemie J. Heyrovského, 2016

Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution
Šimková, Ludmila; Ludvík, Jiří
2016 - English
The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic study of molecules based on aliphatic backbones, rather than aromatic structures. This work represents the first systematic electrochemical and spectrometric characterization of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous and aprotic solvent. Based on the results obtained from combination of electrochemistry with spectrometric methods, the actual structure of FOX-7 in various media was revealed, its reducibility described and radical intermediates as well as products were intercepted, isolated and characterized. Keywords: FOX-7; 2,2-dinitroethene-1,1-diamine; structure Available at various institutes of the ASCR
Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution

The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic ...

Šimková, Ludmila; Ludvík, Jiří
Ústav fyzikální chemie J. Heyrovského, 2016

Voltammetric determination of cancer biomarker 5-hydroxyindole-3-acetic acid at screen-printed carbon electrodes
Makrlíková, Anna; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2016 - English
Tumor biomarker 5-hydroxyindole-3-acetic acid (5-HIAA) is a breakdown product of serotonin; level of this neurotransmitter can predict carcinoid tumors. 5-HIAA has been determined at screen-printed carbpon electrodes in the iptimum medium found: Britton-Robinson buffer (0.04 mol l-1, pH=3.0). Dependence of the peak current on the concentration of 5-HIAA was linear in the concentration region from 0.1 to 100 micromol l-1, with the limit of qiantification of 0.2 micromol l-1. Keywords: differential pulse voltammetry; tumor biomarker; screen-printed carbon electrodes Available at various institutes of the ASCR
Voltammetric determination of cancer biomarker 5-hydroxyindole-3-acetic acid at screen-printed carbon electrodes

Tumor biomarker 5-hydroxyindole-3-acetic acid (5-HIAA) is a breakdown product of serotonin; level of this neurotransmitter can predict carcinoid tumors. 5-HIAA has been determined at screen-printed ...

Makrlíková, Anna; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
Ústav fyzikální chemie J. Heyrovského, 2016

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