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Generation of TiO2 Nanoparticles for Follow-Up Inhalation Experiments with Laboratory Animals
Moravec, Pavel ; Schwarz, Jaroslav ; Vodička, Petr ; Koštejn, Martin
A method of TiO2 nanoparticle generation appropriate for follow-up long lasting inhalation experiments with laboratory animals was tested. Nanoparticles were synthesized in an externally heated tube reactor using titanium tetraisopropoxide as a precursor. Total 264 hours of particle generation in four experimental campaigns was performed with one batch of precursor without observable decrease of precursor volatility. Particle production was studied in wide range of experimental conditions such as reactor temperature, reactor flow rate and precursor vapor pressure by pyrolysis, using nitrogen as a carrier gas, and also in oxidizing atmosphere (10 vol. % of oxygen in the reaction mixture). Particle characteristics were investigated by scanning/transmission electron microscopy, energy dispersive spectroscopy, inductively coupled plasma optical emission spectrometry, elemental and organic carbon analyzer, X-ray diffraction and X-ray photoelectron spectrometry. As a result, particle production with number concentration high above 1.0 x 10(7) #/cm(3) and with primary particle size well below 50 nm can be easily achieved in most of investigated experimental conditions. Particles are free of elemental carbon, content of organic carbon is less than 10 weight %, detected crystalline phase is typically anatase, Ti is present in bonds Ti-O (TiO2) and total Ti concentration recalculated on TiO2 is approximately 80 mass %.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22015041615090 - PDF
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Preparation of Thin Layers of Ferromagnetic Semiconductors
Koštejn, Martin
The paper reports on the experiments of preparation Mn diluted in Silicon. These materials are potential ferromagnetic semiconductors. Thin layer have been prepared by reactive pulsed laser deposition of Mn target under small pressure of volatile precursor (silane or germane). We estimate initial temperature 1 mn above surface as 1.9 eV. The prepared layers can contain 1-40% of Mn atoms in form of amorphous mixture of Mn and Si or nano-crystallized mixture of Mn and Ge. High temperature annealing or rapid laser annealing is needed for recrystallization of Mn:Si layers.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22015011914541 - PDF
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Preparation of Thin Layers of Ferromagnetic Semiconductors
Koštejn, Martin
The paper reports on the experiments of preparation Mn diluted in Silicon. Si:Mn can be a material with the potential of room temperature ferromagnetism. Si:Mn have been prepared by pulsed laser deposition of Mn target under 20 Pa of silane by ArF laser. We estimate initial temperature 1 mm above surface as 1.9 eV. The prepared supersaturated layers contain 11% of manganese atoms, and they are formed by small particles. Diffraction images show no crystallization of Mn or Si, but there are signs of formation of silicides. The prepared material is amorphous or it contains only nanosized crystals below our limit of detection. Electron paramagnetic spectra show unbounded electrons which are needed for ferromagnetic properties. By annealing to 1100 ̊C changes in the crystallization and start of silicon and manganese separation were observed.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22015011914540 - PDF
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Enzymatic Sensor of Biogenic Amines with Optical Oxygen Transducer
Maixnerová, Lucie ; Horvitz, Alexandar ; Kuncová, Gabriela ; Přibyl, M. ; Šebela, M. ; Koštejn, Martin
The biogenic amines (BA) are formed by the decarboxylation of amino acids. Because of their impact on human health, they have been used as markers for assessing the freshness and quality of a wide variety of protein-containing products. We studied biosensor for BA with an optical oxygen transducer that contained a diamine oxidase from pea and ruthenium complex. Both active components were incorporated in chemically stable polymer to form sensitive films thickness of 100 - 200 μm. With aim to optimize a composition and manufacturing of the biosensor we developer a mathematical model of processes inside the sensing film. The developed mathematical model revealed qualitative dependencies of the biosensor behavior (sensitivity, response time and dynamic range) on the (i) thickness of the sensitive layer, (ii) concentrations of substrates in the solution, (iii) enzyme activity in the layer and (iv) layer permeability for the substrates.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22015011213553 - PDF
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A Comparison of Titania Nanoparticles Production in Two Different Reactors by MOCVD Method
Moravec, Pavel ; Smolík, Jiří ; Schwarz, Jaroslav ; Vodička, Petr ; Levdansky, V.V. ; Koštejn, Martin
Nanoparticles (NP's) have attracted considerable attention, because they show a quantum size effect, for which the physical and chemical properties are strongly dependent on particle size. This change of properties can also affect the toxicity and therefore NP's cannot be treated the same way as bulk material. In spite of that, inhalation studies of NP's are still rather rare. Recently, an exposure system for inhalation experiments was constructed in the Institute of Analytical Chemistry AS CR and the first experience with this system were reported by Večeřa et al., 2012. For these studies, a method of continual long-term generation of NP's in the gas phase is necessary. Methods for long-term generation of MnOx and Pb/PbOx NP's have recently been reported. The next task was to test the method for long-term generation of TiO2 NP's suitable for subsequent inhalation experiments.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22014102013554 - PDF
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