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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 %.
Plný tet: SKMBT_C22015041615090 -  PDF
Plný text: content.csg - PDF
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The first experiencies with new exposure system for the whole body inhalation experiments with small animals
Večeřa, Zbyněk ; Mikuška, Pavel ; Moravec, Pavel ; Smolík, Jiří
The first experiences with an inhalation chamber constructed for long-term exposure studies of small animals to nanoparticles under strictly controlled experimental conditions. The inhalation chamber was build from a glass and stainless steel and allows possible long-term inhalation procedures with up to four discrete groups of mice or of rats population under controlled illumination, temperature, relative humidity and pressure. Doses up to 1 x 10(6) particles/cm(3) and size (10-60 nm) of nano-sized particles were synthesized via aerosol route in a hot wall tube flow reactor using thermal decomposition of metal organic precursors. The function of exposure system for whole body inhalation experiments was studied under real conditions in period from May to September 2012. No animals were used within this trial experiment.
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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.
Plný tet: SKMBT_C22014102013554 - PDF
Plný text: content.csg - PDF
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Impact of Size Effects on Formation of Nanoparticles from Supersaturated Vapor
Levdansky, V.V. ; Smolík, Jiří ; Ždímal, Vladimír ; Moravec, Pavel
The mechanism of nanoparticle formation in condensation of a supersaturated vapor is of interest for different kinds of atmospheric phenomena and processes of nanotechnology (e.g. manufacture of nanoparticles). Homogeneous nucleation is the initial stage of nanoparticle formation. The critical cluster size is one from the main parameters in the classical nucleation theory. The value of the critical cluster size is usually found from the Kelvin equation which does not depend on the condensation coefficient. In the general case the size dependence of the condensation coefficient can influence the critical cluster size (Levdansky, 2002). The size dependence of the cohesive energy in the nanoparticle can also affect the size of the critical cluster. Below we consider the joint influence of above-mentioned size effects on the critical cluster size, the rate of nucleation and the growth rate of arising nanoparticles.
Plný tet: SKMBT_C22014102013552 - PDF
Plný text: content.csg - PDF
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Synthesis of Lead and Lead Oxide Nanoparticles for Inhalation Experiments
Moravec, Pavel ; Smolík, Jiří ; Ondráček, Jakub ; Vodička, Petr ; Fajgar, Radek
From the three tested methods of NP's generation the evaporation/condensation of metallic Pb seems to be the most suitable for long lasting inhalation experiments due to its simplicity, unambiguous mechanism of NP′s formation and well defined composition. Nevertheless, NP′s can change their composition, at least on the surface layer, during the time-lag between their formation and inhalation. Thermal decomposition of PbTHD2 can produce sufficiently high concentration of NP′s but there is some uncertainty about their composition due to presence of OC in NP′s. Oxidation of PbTHD2 produces carbon free NP′s, but the number concentration of NP′s is somewhat low.
Plný tet: SKMBT_C22013101814595 - PDF
Plný text: content.csg - PDF
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Mass Size Distribution of Atmospheric Aerosols and Water Soluble Ions atMlada Boleslav in Winter
Schwarz, Jaroslav ; Zíková, Naděžda ; Vodička, Petr ; Hovorka, J. ; Moravec, Pavel ; Ždímal, Vladimír
The importance of the knowledge of aerosol mass size distribution for understanding aerosol behavior is well known for at least few decades. The water soluble ions represent a driving factor controlling hygroscopicity of aerosol particles that determines how the ambient relative humidity influences aerosol particle size. Therefore, hygroscopicity is a substantial parameter in phenomena like particle deposition in the human respiratory tract, particle – cloud interactions, aerosol optical effects etc. For these reasons, the mass size distribution of atmospheric aerosols and water soluble ions was studied at a Czech medium-size-town Mladá Boleslav in winter.
Plný tet: SKMBT_C22013101815000 - PDF
Plný text: content.csg - PDF
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Size Dependence of Incorporation of Gas Molecules into Aerosol Nanoparticles
Levdansky, V.V. ; Smolík, Jiří ; Ždímal, Vladimír ; Moravec, Pavel
The influence of size effects on the physicochemical transformations and transfer phenomena in the heterogeneous systems with nanoobjects attracts increasing attention of researchers. These problems are of interest for nanotechnology and atmospheric physics. Size effects can influence the cohesive energy as well as the activation energies of vacancy formation and diffusion of atoms in the nanoscale particles (Vanithakumari and Nanda, 2008). Phase transitions in aerosol systems with nanoscale particles (clusters) also depend on the nanoparticle size (Levdansky et al., 2010). Hear we discuss the size dependence of the mass accommodation coefficient in the aerosol system with nanoparticles.
Plný tet: SKMBT_C22013091912290 - PDF
Plný text: content.csg - PDF
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Generation of Pb/PbOx Nanoparticles for Inhalation Experiments
Moravec, Pavel ; Smolík, Jiří ; Ondráček, Jakub ; Vodička, Petr ; Fajgar, Radek
Health aspects of nanoparticles (NP′s) on living beings are considered to be important. However, the real data of the impact of NP′s inhalation are rather rare. A study of allocation of MnOx nanoparticles in organs of laboratory animals in inhalation chamber was presented by Večeřa and Mikuška (2012). For these experiments a source of continual generation of nanoparticles in duration of days or even weeks and in appropriate concentration is necessary. In this work a study of continual generation of Pb/PbOx nanoparticles in hot wall tube reactor are presented.
Plný tet: SKMBT_C22013091912130 - PDF
Plný text: content.csg - PDF
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