Number of found documents: 404
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Využití voltametrické metody pro sledování obsahu antioxidantu v biopalivech
Tomášková, M.; Chýlková, J.; Navrátil, Tomáš; Šelešovská, R.
2016 - Czech
Z hlediska kvality biopaliv je hlavním problémem jejich oxidační degradace během skladování, která vede ke vzniku produktů, které mohou způsobit ucpání palivových filtrů nebo korozi kovových částí motoru. Kromě toho má oxidační stabilita běžné motorové nafty podstatný vliv na stabilitu směsí s bionaftou. Právě nestabilita bionafty v porovnání s běžně používanou naftou vede k řadě otázek a obav při skladování biopaliv. Pro zpomalení oxidace a zajištění dostatečné stability je nutné nalézt vhodná aditiva a znát jejich přesné množství. Mezi antioxidanty používané pro zvýšení oxidační stability bionafty a jejich směsí s běžnou naftou patří i propyl galát 1-4. The simple and fast method for analysis of Propyl gallate (PG) in biofuels was proposed in this paper. Voltammograms of antioxidant under study were recorded using linear sweep voltammetry method at a gold disc electrode in supporting electrolyte containing 0.18 mol L-1 H2SO4 and 10 % ethanol. For purposes to monitor effects on fuel quality caused by oxidative degradation, the proposed method was applied to samples of biodiesel and Ekodiesel® (the blend of biodiesel with fuel diesel). The analysis of PG can be performed without pretreatment of Ekodiesel samples, and after extraction using distilled water in case of biodiesel samples. Keywords: propyl gallate; antioxidant; voltammetry Available at various institutes of the ASCR
Využití voltametrické metody pro sledování obsahu antioxidantu v biopalivech

Z hlediska kvality biopaliv je hlavním problémem jejich oxidační degradace během skladování, která vede ke vzniku produktů, které mohou způsobit ucpání palivových filtrů nebo korozi kovových částí ...

Tomášková, M.; Chýlková, J.; Navrátil, Tomáš; Šelešovská, R.
Ústav fyzikální chemie J. Heyrovského, 2016

Graphene Field-Effect Transistor as a Probe of Doping by Adsorbed Oxygen Molecules
Blechta, Václav; Mergl, Martin; Drogowska, Karolina; Kučera, Lukáš; Valeš, Václav; Červenka, Jiří; Kalbáč, Martin
2016 - English
Graphene has high potential in chemical sensing, thus understanding adsorption and charge transfer between graphene and adsorbed molecules is essential. We show that graphene field-effect transistor exhibits a moderate sensoric response towards oxygen at temperature of 150 °C. Field-effect transistors serve as a tool to probe electronic properties of graphene. We demonstrate that adsorption of oxygen molecules onto graphene leads to an upshift of Dirac point and light changes in mobility of charge carriers. Keywords: graphene; sensor; transistor Available at various institutes of the ASCR
Graphene Field-Effect Transistor as a Probe of Doping by Adsorbed Oxygen Molecules

Graphene has high potential in chemical sensing, thus understanding adsorption and charge transfer between graphene and adsorbed molecules is essential. We show that graphene field-effect transistor ...

Blechta, Václav; Mergl, Martin; Drogowska, Karolina; Kučera, Lukáš; Valeš, Václav; Červenka, Jiří; Kalbáč, Martin
Ústav fyzikální chemie J. Heyrovského, 2016

Charge Transport in Single Molecule Junctions of Spirobifluorene Scaffold
Hromadová, Magdaléna; Kolivoška, Viliam; Sokolová, Romana; Šebera, Jakub; Mészáros, G.; Valášek, M.; Mayor, C.
2016 - English
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. Keywords: single molecule conductance; spirobifluorene; break junction Available at various institutes of the ASCR
Charge Transport in Single Molecule Junctions of Spirobifluorene Scaffold

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 ...

Hromadová, Magdaléna; Kolivoška, Viliam; Sokolová, Romana; Šebera, Jakub; Mészáros, G.; Valášek, M.; Mayor, C.
Ústav fyzikální chemie J. Heyrovského, 2016

Voltammetric determination of homovanillic acid at boron doped diamond electrode for hollow fibre microextraction
Hrdlička, V.; Barek, J.; Navrátil, Tomáš
2016 - English
Presented work deals with hollow-fibre assisted liquid/liquid/liquid microextraction (HF-LPME) and subsequent voltammetric detection of clinical biomarker homovanillic acid (HVA). Three main areas are discussed: hollow fibre assisted extraction of HVA, voltammetric detection of HVA under basic conditions, and sensing in very small volumes. Using HF-PLME, HVA was extracted with 1-octanol as a supported liquid membrane with enrichment factor of 55 after 60 minutes of extraction. A novel method of miniaturized voltammetric determination of HVA using cathodically pretreated boron doped diamond electrode was also developed. Using differential pulse voltammetry, limit of detection, limit of quantificati was 1.9 mu mol dm(-3) on 6.6 mu mol dm(-3). Keywords: biomarkers; boron doped diamond electrode; hollow-fibre Available at various institutes of the ASCR
Voltammetric determination of homovanillic acid at boron doped diamond electrode for hollow fibre microextraction

Presented work deals with hollow-fibre assisted liquid/liquid/liquid microextraction (HF-LPME) and subsequent voltammetric detection of clinical biomarker homovanillic acid (HVA). Three main areas are ...

Hrdlička, V.; Barek, J.; Navrátil, Tomáš
Ústav fyzikální chemie J. Heyrovského, 2016

Electrochemical determination of 2-nitrofluorene and investigation of its interaction with DNA
Skalová, Štěpánka; Stávková, K.; Barek, J.; Vyskočil, V.
2016 - English
2-Nitrofluorene (2-NF) belongs to the group of nitrated polycyclic aromatic hydrocarbons. These compounds are categorized as environmental pollutants and they can manifest mutagenic and carcinogenic effects. A differential pulse voltammetric method at a glassy carbon electrode (GCE) was developed for sensitive determination of 2-NF. Under the optimum conditions found, a linear calibration dependence was obtained in the concentration range of 2 x 10(-7) - 1 x 10(-5) mol L-1, with the limit of quantification of 2 x 10 mol L-1. The practical applicability of this method was verified on the direct determination of 2-NF in a model sample of sand. Moreover, the mutual interaction between 2-NF and DNA was investigated using an electrochemical DNA biosensor (DNA-modified GCE). Cyclic voltammetry, electrochemical impedance spectroscopy, and square-wave voltammetry were employed in this study, confirming the formation of a 2-NF-DNA complex.\n Keywords: DNA biosensors; DNA interaction; glassy carbon electrode Available at various institutes of the ASCR
Electrochemical determination of 2-nitrofluorene and investigation of its interaction with DNA

2-Nitrofluorene (2-NF) belongs to the group of nitrated polycyclic aromatic hydrocarbons. These compounds are categorized as environmental pollutants and they can manifest mutagenic and carcinogenic ...

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

Possibilities of Hollow Fiber Microextraction and Voltammetric Detection of Homovanillic acid
Hrdlička, V.; Barek, J.; Navrátil, Tomáš
2016 - English
The contribution deals with hollow fiber liquid phase microextraction (HF-LPME) of homovanillic acid (HVA) and its subsequent voltammetric detection. In HF-LPME, HVA is extracted from acidic sample through thin supported liquid membrane into basic aqueous acceptor solution. Since common electrode materials such as gold, platinum or glassy carbon are only able to detect HVA under acidic or neutral conditions, a new method was developed, utilizing silica gel modified carbon paste electrode (CPE). Reached limit of detection in a 10 μL drop of the HVA extract of pH 13 was 1·10-5 mol L-1. Keywords: Hollow-fibers; Liquid phase microextraction; voltammetry Available at various institutes of the ASCR
Possibilities of Hollow Fiber Microextraction and Voltammetric Detection of Homovanillic acid

The contribution deals with hollow fiber liquid phase microextraction (HF-LPME) of homovanillic acid (HVA) and its subsequent voltammetric detection. In HF-LPME, HVA is extracted from acidic sample ...

Hrdlička, V.; Barek, J.; Navrátil, Tomáš
Ústav fyzikální chemie J. Heyrovského, 2016

Metalothioneiny u drobných volně žijících savců jako bioindikátor znečištění životního prostředí
Křivská, D.; Šestáková, Ivana
2016 - Czech
Metalothioneiny (MT) jsou cysteinem bohaté nízkomolekulární proteiny, schopné vázat esenciální i toxické kovy. Jejich syntéza je indukována přítomností zejména kadmia a zinku, ale také dalších kovů jako Pb, Ni, Hg, Ag a i jinými faktory (např. stres, kortikoidy) 1. Pro práce věnující se studiu biologických funkcí metalothioneinů jako homeostáze, prevence oxidačního stresu, detoxifikace či studie vlivu znečištění životního prostředí na různé živočichy je důležitý celkový obsah metalothioneinů v jednotlivých tkáních 2. U vodních organismů, zejména Mytilus galloprovincialis 3 a Ruditapes decussatus 4 je obsah MT užíván jako bioindikátor znečištění mořské vody a je proto snaha mít obdobnou možnost pro zjišťování kontaminace půdy a životního prostředí. Animals living in the contaminated areas are exposed to elevated concentrations of risk elements. Příbramsko is one of most contaminated sites in Czech Republic. This area is loaded with sources of geological and metallurgical industry influence resulting in extremely high Pb, Cd, and Zn contents in soil. We analyzed eighteen subjects trapped on selected locations, belonging to the species Apodemus sylvaticus and Microtus arvalis. By differential pulse voltammetry and modified Brdička reaction, concentrations of metallothionein (MT) in their livers were measured. The influence of field sample treatment on resulting voltammetric record has been demonstrated. Differences of MT concentrations were found between species and among places of trapping. Keywords: Small terrestrial mammals; Příbram region; Brdička reaction Available at various institutes of the ASCR
Metalothioneiny u drobných volně žijících savců jako bioindikátor znečištění životního prostředí

Metalothioneiny (MT) jsou cysteinem bohaté nízkomolekulární proteiny, schopné vázat esenciální i toxické kovy. Jejich syntéza je indukována přítomností zejména kadmia a zinku, ale také dalších kovů ...

Křivská, D.; Šestáková, Ivana
Ústav fyzikální chemie J. Heyrovského, 2016

Závislost vodivosti pyridiniových molekul na jejich struktuře
Lachmanová, Štěpánka; Hromadová, Magdaléna; Kolivoška, Viliam; Pospíšil, Lubomír; Gasior, Jindřich; Mészáros, G.; Lainé, P. P.
2016 - Czech
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. The derivates of pyridinium belong to promising group of molecules applicable in molecular electronics. For this purpose, four expanded branched pyridinium compounds were synthetized and the influence of the molecular structure on their electrochemical properties and single-molecule conductances has been studied. The highest values of conductance provided compounds 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium tetrafluoroborate and 3,5-dimethyl-2´,6´-diphenyl-[4,1´:4´,4´´-terpyridin]-1´-ium tetrafluoroborate. By the electrochemical reduction both of these compounds received two electrons in two separated one-electron steps. On the other hand, the compounds 2´,6´-diphenyl-[4,1´:4´,4´´-terpyridin]-1´-ium tetrafluoroborate and 2,6-diphenyl-4-(4-(pyridin-4-yl)phenyl)-[1,4´-bipyridin]-1-ium tetrafluoroborate are reduced by different mechanism and their conductance was lower. Keywords: single molecule conductance; expanded pyridinium derivatives; scanning tunneling microscopy break junction Available at various institutes of the ASCR
Závislost vodivosti pyridiniových molekul na jejich struktuře

Vývojáři elektronických součástek stojí před palčivým problémem. Podle Moorova zákona 1, empirického pravidla odhadujícího možnosti v miniaturizaci elektronických součástek, již brzy nebude možné ...

Lachmanová, Štěpánka; Hromadová, Magdaléna; Kolivoška, Viliam; Pospíšil, Lubomír; Gasior, Jindřich; Mészáros, G.; Lainé, P. P.
Ústav fyzikální chemie J. Heyrovského, 2016

Oxidation of Bioflavonoids in Respect to their Chemical Structure
Sokolová, Romana; Ramešová, Šárka; Kocábová, Jana; Degano, I.
2016 - English
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. Keywords: oxidation; flavonoids; voltammetry Available at various institutes of the ASCR
Oxidation of Bioflavonoids in Respect to their Chemical Structure

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 ...

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

Voltammetric Behavior of Explosive Potassium Salt of 2,4-Dinitrobenzofuroxan\non Electrodes with Mercury Surface
Šelešovská, R.; Sokolová, Romana; Matyáš, R.; Janíková, L.
2016 - English
Voltammetric behavior of potassium salt of 2,4-dinitrobenzofuroxan (KDNBF) has been\nfirstly studied using hanging mercury drop electrode (HMDE) and silver solid amalgam\nelectrode (AgSAE). Cyclic voltammetry was applied for the measurements of dependences on\npH and scan rate required for the elucidation of the ongoing electrode reactions and\ndifferential pulse voltammetry served for the development of sensitive method for KDNBF\ndetermination. Keywords: Potassium salt of 2,4-dinitrobenofuroxan; Hanging mercury drop electrode; voltammetry Available at various institutes of the ASCR
Voltammetric Behavior of Explosive Potassium Salt of 2,4-Dinitrobenzofuroxan\non Electrodes with Mercury Surface

Voltammetric behavior of potassium salt of 2,4-dinitrobenzofuroxan (KDNBF) has been\nfirstly studied using hanging mercury drop electrode (HMDE) and silver solid amalgam\nelectrode (AgSAE). Cyclic ...

Šelešovská, R.; Sokolová, Romana; Matyáš, R.; Janíková, L.
Ústav fyzikální chemie J. Heyrovského, 2016

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