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Hydroxyl radical measurement in atmospheric pressure dimethyl ether-air laminar premixed flat flame using tunable diode laser absorption spectroscopy
Nevrlý, V.; Dostál, Michal; Bitala, P.; Zelinger, Zdeněk; Suchánek, Jan; Válek, V.; Klečka, V.; Kubát, Pavel; Engst, Pavel; Vašinek, M.; Wild, J.
2017 - English
Spectroscopic detection of hydroxyl (OH) radical and determination of its concentration in flames have an elusive history and considerable influence on combustion research. Electronic transitions in ultraviolet spectral region were extensively studied in this context and until recent time chemiluminescence or laser induced fluorescence of excited hydroxyl (OH*) radical is broadly used for absolute concentration and temperature measurement in flames.\nHowever, number densities of molecular species and population of relevant quantum levels in ground electronic state can be directly estimated from intensities of absorption lines observed by probing rovibrational transitions in infrared spectral region. Application of near-infrared tunable diode laser absorption spectroscopy (NIR-TDLAS) for the given purpose was demonstrated in an earlier work of Aizawa et al. [1]. Following his pioneering studies summarized in [2], we further explored feasibility of NIR-TDLAS (especially 2f-WMS technique) for monitoring minor species within combustion experiments particularly when dealing with dimethyl ether (DME) flames. Here we report our first results of NIR-TDLAS measurements focused on hydroxyl radical detection in laminar premixed flame burning DME-air mixture under fuel-lean conditions.
Keywords:
spectroscopy; tunable diode laser absorption spectroscopy; hydroxyl
Available in digital repository of the ASCR
Hydroxyl radical measurement in atmospheric pressure dimethyl ether-air laminar premixed flat flame using tunable diode laser absorption spectroscopy
Spectroscopic detection of hydroxyl (OH) radical and determination of its concentration in flames have an elusive history and considerable influence on combustion research. Electronic transitions in ...
Mystery of Ageing of „Zero-Valent Iron“ (ZVI)
Wouafo, M. T.; Donkeng Dazie, Joel; Tchatchueng, J. B.; Noubactep, Ch.; Ludvík, Jiří
2017 - English
So called „zero-valent iron“, (ZVI), is used for water treatment, or, more generally for\nenvironmental remediation. In fact, the surface of the metallic iron powder in the presence of\nwater and oxygen cannot be considered as pure Fe0 but as a mixture of its corrosion products.\nThe remediation process occurs on the surface of these iron particles, hence, the degree of\n„corrosion“ is crucial for the process itself. Therefore, investigation of „aging“ of ZVI is an\nimportant prerequisite for deeper understanding of its activity.\nIn this work, the first results of the systematic study of aging of iron metal powder are\npresented. The investigation was performed in batch conditions in aqueous buffered solutions\npH 4, 4.7, 5.5 and in the presence of air oxygen. Increasing and then decreasing concentration\nof the Fe2+ ion in the solution appeared to be the important marker of aging process.\nIn the second part of the work, removal of Zn2+ ions using ZVI was investigated.\nElectrochemical techniques, namely polarography and its differential pulse form (DPP) were\nused for permanent monitoring of the presence of Fe2+ and Zn2+ ions in the studied solution.\nChanging concentrations of both ions revealed that at pH 5.5 the optimum aging time of ZVI\nfor removal of Zn2+ from aqueous solution is 6 hours.
Keywords:
zero-valent iron; aging effect; zinc ion removal
Available on request at various institutes of the ASCR
Mystery of Ageing of „Zero-Valent Iron“ (ZVI)
So called „zero-valent iron“, (ZVI), is used for water treatment, or, more generally for\nenvironmental remediation. In fact, the surface of the metallic iron powder in the presence of\nwater and ...
Redox Properties of Quasi Dimer of 1,3-diphenylisobenzofuran for Singlet Fission
Šimková, Ludmila; Ludvík, Jiří
2017 - English
Molecules on the base of 1,3-diphenylisobenzofuran attract an interest because of their\npossible efficiency for singlet fission This study is focused on electrochemical behaviour of\nthe „quasi dimer“ of 1,3-diphenylisobenzofuran. For characterization of reduction mechanism\nin situ UV-vis and EPR spectroscopy were used. The monomer 1,3-diphenylisobenzofuran\nand its CH2 dimer were added to this study for comparison. The redox properties of both\ncompared molecules are similar. The location and the nature of the covalent bridging unit in\nCH2dimer have small effect onthe redox potentials. But the pi-conjugation in the molecule of\nquasi dimer causes approximately 0.2 V easier oxidization and reduction.
Keywords:
1,3-diphenylisobenzofuran; dimer; Singlet fission
Available on request at various institutes of the ASCR
Redox Properties of Quasi Dimer of 1,3-diphenylisobenzofuran for Singlet Fission
Molecules on the base of 1,3-diphenylisobenzofuran attract an interest because of their\npossible efficiency for singlet fission This study is focused on electrochemical behaviour of\nthe „quasi ...
Labile Lead Phytochelatin Complexes Could Enhance Transport of Lead Ions across Biological Membrane
Šestáková, Ivana; Navrátil, Tomáš
2017 - English
In connection with studies of hazardous metals transport across model phospholipid\nmembranes, behavior of complexes of lead with phytochelatin PC2 has been examined. Using\nstripping chronopotentiometry with different values of reducing current, the release of free\nlead ions confirms labile behavior. Similar conclusion resulted from voltammetry on silica gel\nmodified carbon paste electrode.
Keywords:
phytochelatin; lead; voltammetry
Available on request at various institutes of the ASCR
Labile Lead Phytochelatin Complexes Could Enhance Transport of Lead Ions across Biological Membrane
In connection with studies of hazardous metals transport across model phospholipid\nmembranes, behavior of complexes of lead with phytochelatin PC2 has been examined. Using\nstripping ...
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 ...
Fosfolipidy modifikovaná elektroda ze skelného uhlíku a její využití pro stanovení pesticidů
Švecová, H.; Sokolová, Romana; Součková, J.; Skopalová, J.; Barták, P.
2016 - Czech
Lipidové membrány jsou již mnoho let studovány jako modely biomembrán. Formování lipidových membrán na povrchu pevných elektrod poprvé popsali Tien a Salamon 1. Od té doby byly použity jako substráty pro lipidové vrstvy různé materiály jako např. stříbro 2, zlato 3, rtuť 4 nebo skelný uhlík 5. Lipidový film na povrchu elektrody je schopen akumulovat organické molekuly v závislosti na jejich náboji a na jejich hydrofilním respektive hydrofobním charakteru. Je známé, že mnoho organických látek, jako jsou pesticidy, léčiva a jiné farmakologicky významné látky, interagují s fosfolipidovou vrstvou a mastnými kyselinami v membráně a mohou být silně akumulovány v lipidové tkáni. In this article we described glassy carbon electrode modified with Asolectin (mixture of phosholipids). Properties of phospholipid layer, such as its thickness or solidity, were investigated using atomic force microscopy (AFM). The modified electrode was applied for square wave voltammetry (SWV) measurements to study interactions of pesticide paraquat with phospholipid layer and to detect paraquat selectively in real samples of river water.
Keywords:
paraquat; electrochemistry; phospholipids
Available at various institutes of the ASCR
Fosfolipidy modifikovaná elektroda ze skelného uhlíku a její využití pro stanovení pesticidů
Lipidové membrány jsou již mnoho let studovány jako modely biomembrán. Formování lipidových membrán na povrchu pevných elektrod poprvé popsali Tien a Salamon 1. Od té doby byly použity jako substráty ...
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 ...
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 ...
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 ...
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 ...
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