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Unique Properties of Amalgam Electrodes
Josypčuk, Bohdan ; Josypčuk, Oksana
Depending on metal-mercury ratio and on the method of preparation amalgam can be: 1) solid compact; 2) paste; 3) liquid; 4) monocrystalline; 5) porous; 6) powdered. High potential of hydrogen overvoltage is observed on amalgam electrodes and it is comparable with one on Hg-electrodes. Another important benefit is the possibility to prepare amalgam electrode, detector or reactor of required size and shape. From amalgams have been prepared and tested many types of electrodes for batch and flow-through systems. The diversity of amalgam materials provides some unique electrochemical properties of electrodes, the most important of which are described in this paper.
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Magnetic Beads-Based Electrochemical Techniques for DNA-Protein Interaction Monitoring
Fojta, Miroslav ; Pivoňková, Hana ; Němcová, Kateřina ; Horáková Brázdilová, Petra ; Havran, Luděk ; Orság, Petr ; Vidláková, Pavlína ; Macíčková-Cahová, Hana ; Balintová, Jana ; Hocek, Michal
Electrochemical techniques, in connection with separation of nucleoprotein complexes at magnetic beads, are suitable for the monitoring of DNA-protein interactions. For the detection of complexes captured at the beads it is possible to utilize intrinsic electrochemical activity of the protein, intrinsic structure-selective signals of the DNA, or indicator DNA substrates tail-labeled with electroactive moieties.
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Electrochemistry of Polynitrocalix-[4]-arenes
Liška, Alan ; Ludvík, Jiří
Calix[4]arene is a suitable inert and stable frame for building "smart" molecules and supramolecular assemblies. Polynitrocalix[4]arenes where reducible nitro groups are located at the upper rim are promising precursors for aimed development of sensors. In this work a series of mono-, di-, tri- and tetra nitroderivatives was reduced, the sequence of individual steps was described and the mechanism discussed. It was found that in this molecule with several redox centers all nitro groups are electronically isolated and thus are reduced independently yielding poly-radical ions. Two different couples of equivalent nitro groups were proved in tetranitro derivatives. The experimental results were confirmed by quantum chemical calculations.
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Electrochemical Reduction of 1,3-Alt-tetranitrothiacalix[4]arenes
Liška, Alan ; Ludvík, Jiří
Calixarenes are organic molecules which contain several aromatic units (in this work four) connected by methylene („calixarenes“) or sulfur („thiacalixarenes“) bridges. Calix[4]arenes can exist in four defined conformations: cone-, partial cone-, 1,2- and 1,3-alternating (Fig. 1). The conformational stability of a (thia)calix[4]arene is controlled by the size of the substituents on the upper or the lower rim, or by other interactions (e.g. hydrogen bonds). These compounds are very attractive for supramolecular chemists, since they have the shape of a cavity, being able to exhibit host-guest interaction according to the substitution 1,2. The calixarene skeleton itself is not reducible. Therefore it´s necessary to introduce a suitable redox probe in the calixarene frame in order to use electrochemical methods for investigations of calixarene properties. For the purpose of this study the nitro group was chosen because its electrochemical reduction proceeds easily in a well-defined way.
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Diagnostické biosenzory pro encefalopatie způsobené priony
Šobrová, Pavlína
Prionové onemocnění jsou lidské a živočišné fatální přenosné neurodegenerativní onemocnění (TSE) charakterizované strukturální změnou buněčného prionového proteinu (PrPC) na jeho pozměněnou isoformu PrPSc. Hlavním cílem této práce bylo sumarizovat současné poznatky o jednotlivých TSE a možnostech jejich detekce se zaměřením na elektrochemické metody. Pro tyto účely byla použita cyklická voltametrie (CV), diferenční pulzní voltametrie (DPV), diferenční pulzní voltametrie ve spojení s Brdičkovou reakcí (DPV -- Brdičkova reakce) a chronopotenciometrická rozpouštěcí analýza (CPSA). Limity detekce jednotlivých technik byly stanoveny na 32 ug/ml u CV, 16 ug/ml u DPV, 16 ug/ml u DPV -- Brdičkova reakce a 8 ug/ml u CPSA. Dále byl sledován vliv působení teploty denaturace. Jak jasně vyplývá z výsledků, získané signály prionových proteinů lineárně klesaly v závislosti na délce trvání denaturační teploty (99 °C) po dobu 0, 15, 30, 45 a 60 min. Dále jsme se zaměřili na studium prionových proteinů a jejich interakce s CdTe kvantovými tečkami (QD) za použití elektrochemie. Primárně jsme elektrochemicky charakterizovali QD a stanovili jejich detekční limit na 100 fg/ml. Následně jsme se zaměřili na elektrochemické studium interakcí QD s prionovým proteinem. Detekční limit byl stanoven na 1 fg v 5 ul při 3S/N. Toto by mohlo hrát důležitou úlohu při značení prionových proteinů QD kvůli velmi snadné aplikovatelnosti a možnosti miniuaturizace zařízení, které může být použitelné in situ. a otevřít taknové možnosti stanovení přítomnosti prionových proteinů na chirurgických nástrojích a jiných materiálech, které jimi mohou být kontaminovány vlivem špatné degrability při daných sterilujících technikách.
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Electrochemical Characterization of TiO2 Blocking Layers for Dye-Sensitized Solar Cells
Kavan, Ladislav
Thin compact layers of TiO2 are grown by thermal oxidation of Ti, by spray pyrolysis, by electrochemical deposition, and by atomic layer deposition. These layers are used in dye-sensitized solar cells to prevent recombination of electrons from the substrate (FTO or Ti) with the hole-conducting medium at this interface. The quality of blocking is evaluated electrochemically by methylviologen, ferro/ferricyanide, and spiro-OMeTAD as the model redox probes. Two types of pinholes in the blocking layers are classified, and their effective area is quantified. Frequency-independent Mott–Schottky plots are fitted from electrochemical impedance spectroscopy. Certain films of the thicknesses of several nanometers allow distinguishing the depletion layer formation both in the TiO2 film and in the FTO substrate underneath the titania film. The excellent blocking function of thermally oxidized Ti, electrodeposited film (60 nm), and atomic-layer-deposited films (>6 nm) is documented by the relative pinhole area of less than 1%. However, the blocking behavior of electrodeposited and atomic-layer-deposited films is strongly reduced upon calcination at 500 °C. The blocking function of spray-pyrolyzed films is less good but also less sensitive to calcination. The thermally oxidized Ti is well blocking and insensitive to calcination.
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Electrochemistry as a Tool for an Enzyme Characterization
Gál, M. ; Krahulec, J. ; Jiríčková, K. ; Sokolová, Romana ; Híveš, J.
Basic biochemical properties such as Michaelis constant (KM) and turnover number (kcat) of enzyme enteropeptidase was measured by electrochemical impedance spectroscopy. Both values determined by impedance measurements are in good agreement with those obtained by traditional spectroscopic techniques. Therefore one can suppose that electrochemical methods might be successful for such measurements also in the case where usual ones (UV-Vis, fluorescence spectroscopy) are not able to determine these enzyme characteristics.
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150 LET OLOVĚNÉHO AKUMULÁTORU
Micka, Karel
Jsou objasněny okolnosti, za jakých vznikal nejrozšířenější chemický zdroj elektrické energie, olověný akumulátor. Jsou zmíněny technologické pokroky, které přinesly široké možnosti praktického využití tohoto zdroje.
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