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Propustnost podél hranic zrn v dobře definovaných polykrystalických vrstvách silikalitu-1 a v samostatných krystalech
Brabec, Libor ; Zikánová, Arlette ; Kočiřík, Milan
Self-supporting silicalite-1 layers were grown on mercury surface from clear solutions at temperatures 140-180 oC. Large silicalite-1 crystals were synthesized using TPABr as template. Layer morphology and thickness were characterized by SEM. Phase purity of silicalite-1 and orientation of crystals were determined by XRD. Layers with the thickness > 40 .mu.m were found to be highly compact. Wet HF etching of as-synthesized polycrystalline silicalite-1 layers caused formation of deep sharp slits at grain boundaries and thus it visualized them. Contrary to this result etching of calcined layers led to a kind of a negative image represented by preserved thin shells at crystal boundaries which were found to be impregnated by carbon residues formed during template removal. Results of etching experiments give a strong indication of the existence of a thin amorphous silica interface between neighbouring crystals. The etching patterns were somewhat different for large silicalite-1 crystals.
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Ink Films from Carbon Powders on Conventional Solid Electrodes as Alternative Disposable Sensors
Josypčuk, Bohdan ; Barek, J. ; Novotný, Ladislav
Rozšíření rozsahu pracovních potenciálů pevných elektrod bylo docíleno jejich pokrytím filmem z polymeru obsahujícího vodivé částice (grafitu, skelného uhlíku, nanotub aj.). Takový film může obsahovat 70 - 90% skelného uhlíku a 30 - 10% polystyrenu (procenta hmotnostní). Film se 70 % skelného uhlíku se chová více jako soubor mikroelektrod; s 90 % - spíše jako klasická elektroda ze skelného uhlíku. S takovým filmem lze pracovat i celý den; pro odstranění filmu stačí otřít ho o filtrační papír. Pro oxidaci ferocenu, adeninu, guaninu a jiných látek byly použity filmy s různým obsahem skelného uhlíku na podložkách ze stříbrného pevného amalgamu, zlata a platiny.
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Polished Silver Solid Amalgam Electrode
Fadrná, Renata
The polished silver solid amalgam electrode (p-AgSAE) seems to be a suitable alternative to hanging mercury drop electrode (HMDE). The structure of electrode material and working electrode surface were analyzed by RTG diffraction, atomic forces microscopy (AFM) and scanning electron microscopy (SEM). It was found that silver amalgam has crystalline structure (without the presence of different phases), any liquid mercury is not presented on the electrode surface and also mercury is not evaporated from the amalgam. p-AgSAE was applied for the determination of inorganic cations (Cu2+, Pb2+, Cd2+, Zn2+) and anions (NO3-, SCN-), amino acids (cysteine, cystin), nitro compounds (2,4´-dinitritoluene, 1,3´-dinitrobenzene, 2-nitronaftalene), aldehydes (benzaldehyde), vitamin C and purine bases of DNA (adenine, guanine) up to now.
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Voltammetric Behavior of the Heterogeneous Graphite Composite
Šebková, Světlana
Graphite composite electrodes offer high chemical inertness, which is accompanied by a wide range of working potentials (the widest range of potentials was obtained using CE30 in borax buffer - almost 4 000 mV). Graphite composite electrodes find the field of application mostly in the work in the area of considerably positive potentials (e.g. oxidation of adenine, guanine, aminonaphtalene, etc.), and they offer unique possibilities analytical measurements.
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Anodic Stripping Voltammetry on Silver Composite Electrodes
Kopanica, M. ; Šebková, Světlana ; Navrátil, Tomáš
The influences of presence of various cations (Cd, Cu, Bi, Tl) and anions (chlorides) on the anodic stripping voltammetric determination of lead on silver composite electrodes were studied. It was found that the effect of underpotential deposition at these electrodes differs from that one produced by metallic silver electrode. Their use enables the direct determination in water samples without elimination of the presence of surface-active substances or of dissolved oxygen (LOD about 3 ug L-1).
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Phytochelatins as Cadmium and Zinc Ligands in Study Using Voltammetric Methods
Šestáková, Ivana ; Navrátil, Tomáš
Complexation of synthetically prepared phytochelatin PC3 was studied using differential pulse voltammetry on HMDE. This method allows to measure reduction peak of mercury compound of original peptide simultaneously with the reduction peaks of formed cadmium or zinc complexes. Elimination voltammetry with linear scan was used at selected stoichiometric ratio to characterise diffusion current of complexes formed. Substantial differences were found between Cd and Zn complexes, both in formation and behaviour.
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