|
|
Generation of metallic nanoparticles by non-thermal plasma in liquids
Čechová, Ludmila ; Blahová, Lucie (referee) ; Kozáková, Zdenka (advisor)
This thesis focuses on the process of nanoparticle generation using new source of nonthermal plasma combining corona and pin-hole discharge in liquids. The theoretical part is focused on generation of metallic nanoparticles using various types of plasma discharge, the properties of metallic nanoparticles, their preparation by other methods and methods of characterization of nanoparticles. The experimental part deals with the preparation of copper, silver and gold nanoparticles from solutions of their precursors. The influence of experimental conditions, such as the influence of voltage polarity, effect of precursor concentration, effect of added electrolyte or reducing agent were investigated. All samples were analyzed by UV-VIS spectroscopy. Dynamic light scattering was used to determine the sice of nanoparticles. To confirm the presence of nanoparticles, samples were analyzed using scanning microscope with and energy dispersion spectrometer for elemental analysis.
|
|
| |
|
|
Ranking of Silver Mining Companies for Hedge Fund Management
Lišková, Petra ; Ptáček, Roman (referee) ; Rejnuš, Oldřich (advisor)
This bachelor thesis deals with an analysis of actual status of silver mining companies in order to rank these companies on the basis of one selected criterion. The subject of this thesis is also a sectoral analysis of silver mining industry and an analysis of individual pre-selected companies which deal with silver mining and meet the requirements set by the hedge fund management. This analysis will include an evaluation of their business indicators. An investment proposal for management of hedge fund will be made based on the evaluation of analyses and a comparison of selected companies.
|
|
|
Toxicity study of antimicrobial wound dressings and perspective novel nanomaterials
Kozlíčková, Hana ; Vojtová, Lucy (referee) ; Zajíčková, Lenka (advisor)
This bachelor thesis deals with the study of toxicity of selected commercial antimicrobial wound dressings (StopBac STERILE, containing silver ions and Traumacel Biodress Disinfect, containing chlorhexidine) and antimicrobial nanomaterial, provided by CEITEC BUT laboratories. The experimental part of the work describes the preparation of this polycaprolactone nanomaterial, on which a layer of copper was subsequently deposited by the magnetron sputtering system BESTEC (MAGNETRON). Furthermore, a method was designed to study the cytotoxicity of individual shelters with antimicrobial additives. These tests were performed in vitro on cell cultures by leaching the materials in the laboratories of the Faculty of Science, Masaryk University in Brno. We found that, with the exception of chlorhexidine, low concentrations of active substances extracted from the materials promoted the proliferation of the studied cells, while at high concentrations there were also cytotoxic effects. The analysis of individual materials was also performed using scanning electron microscopy and energy dispersive X-ray spectroscopy.
|
|
|
Nanospray processing of silver nanoparticles for formation of dried deposits
Týčová, Anna ; Jonas, Vladimír ; Přikryl, Jan ; Kotzianová, A. ; Velebný, V. ; Foret, František
Nanospray transfers liquid into an aerosol via electrostatic forces created between an emitter and a counter electrode. Herein, we present compact laboratory-made instrumentation for nanospray-processing of silver colloid. The instrumentation is based on the pressurized polysulfone chamber fixing a disposable vial with an immersed platinum electrode and a long fused silica capillary supplying the sprayed liquid to the emitter. The combination of low flow rates (70 nL/min) with a sharp emitter, fabricated on a 3D printed grinding station, resulted in a fine aerosol. The low volume of released droplets allowed full evaporation of water during their flight towards the counter electrode without any need for drying gas or the addition of volatile solvents. The constructed device was successfully used for the deposition of water-free silver colloid without any requirement of its pretreatment. The deposition of completely dried nanoparticles on planar substrates eliminated undesirable coffee ring effect and deposits of increased homogeneity could be obtained. Electron microscopy confirmed no significant changes in the character of nanospray-processed nanoparticles. Finally, we also investigated several approaches for the improvement of the surface density of nanoparticles on the substrate at preserved time scale.
|
|
|
Ranking of Silver Mining Companies for Hedge Fund Management
Lišková, Petra ; Ptáček, Roman (referee) ; Rejnuš, Oldřich (advisor)
This bachelor thesis deals with an analysis of actual status of silver mining companies in order to rank these companies on the basis of one selected criterion. The subject of this thesis is also a sectoral analysis of silver mining industry and an analysis of individual pre-selected companies which deal with silver mining and meet the requirements set by the hedge fund management. This analysis will include an evaluation of their business indicators. An investment proposal for management of hedge fund will be made based on the evaluation of analyses and a comparison of selected companies.
|
|
|
Toxicity study of antimicrobial wound dressings and perspective novel nanomaterials
Kozlíčková, Hana ; Vojtová, Lucy (referee) ; Zajíčková, Lenka (advisor)
This bachelor thesis deals with the study of toxicity of selected commercial antimicrobial wound dressings (StopBac STERILE, containing silver ions and Traumacel Biodress Disinfect, containing chlorhexidine) and antimicrobial nanomaterial, provided by CEITEC BUT laboratories. The experimental part of the work describes the preparation of this polycaprolactone nanomaterial, on which a layer of copper was subsequently deposited by the magnetron sputtering system BESTEC (MAGNETRON). Furthermore, a method was designed to study the cytotoxicity of individual shelters with antimicrobial additives. These tests were performed in vitro on cell cultures by leaching the materials in the laboratories of the Faculty of Science, Masaryk University in Brno. We found that, with the exception of chlorhexidine, low concentrations of active substances extracted from the materials promoted the proliferation of the studied cells, while at high concentrations there were also cytotoxic effects. The analysis of individual materials was also performed using scanning electron microscopy and energy dispersive X-ray spectroscopy.
|
|
|
The content and binding of silver in galena
Němec, Matěj ; Goliáš, Viktor (advisor) ; Zachariáš, Jiří (referee)
Galena as the most important silverbearing ore is found in almost every Ag deposit. If the content of Ag is higher than 0,5 wt. % then is called galena solid solution - PbSss. The galena Ag has two forms of occurrence - inclusions and isomorphic silver. Aboat ninety percent of galena Ag is product of retrograde proces of PbSss cooling. These are matildite (AgBiS2), miargyrite (AgSbS2), diaforite (PbAg3Sb3S8), freislebenite (AgPbSbS3), pyrargyrite (Ag3SbS3) aramayoite (Ag(Sb,Bi)S2), freibergite (Ag12Sb4S13), gustavite (AgPbBi3S6) etc. The smaller amounth of isomorphic Ag is substituted as 2Ag+ = PbII+ . Under the usual conditions of deposition (200 - 300řC) , the solubility of Ag2S is to low. The content of Ag in galena under these conditions is not higher then 0,4 mol. % at 615řC. Most of the isomorphic Ag is bound in coupled substitution Ag+ + Bi III+ /Sb III+ = 2 PbII+ . In this case the content of Ag in PbS can be as high as 9 wt. % at 350 - 400řC. At the deposites where wasn't activated this Bi/Sb - Pb coupled substitution the content of Ag in galena is very low. The content of trace elements of Ag, Bi and Sb can also influence the galena crystal habit. Galena rich on Bi ususaly creates octahedral crystals. Galena with a higher content of Ag and Sb usualy creates cubic crystals.
|
|
|
Late Roman Silver Coinage (from Arcadius and Honorius to the end of the 5th century AD)
Gambacorta, Federico ; Marek, Václav (advisor) ; Kolniková, Eva (referee) ; Militký, Jiří (referee)
This PhD research has furnished the occasion to update the outdated works about Late Roman coinage focusing especially on a topic not so commonly examined like the Late Roman silver coinage. More precisely, it is analysed and discussed some of its more intriguing aspects. First of all how silver, as metal, was considered and perceived in Late Roman society and, therefore, why during fifth century AD silver bullion was used to produce fine silver objects rather than coins. Two different Late Roman customs concerning silver coinage are then reviewed: hoarding, with a list of most recent findings, and clipping. Finally a chapter is dedicated to the metrology and fineness of Late Roman silver coins together with an accurate analysis of the 7 different denominations. This extensive and deep discussion about Late Roman silver coinage's main problematics is completed by the most recent and updated catalogue of all the Late Roman silver denominations known so far. Such a review has given not only the possibility of updating or modifying some of the previous theories but also the opportunity to suggest some new ideas. --------------------------------------- Podrobně jsou zkoumány některé konkrétní zásadsní otázky, především jakým způsobem bylo v pozdně římské společnosti vnímáno stříbro jako kov a proč tedy...
|
|
|
Effect of silver in homogeneous gold catalysis
Motloch, Petr ; Roithová, Jana (advisor) ; Hocek, Michal (referee)
Gold catalysis has recently experienced a sustained upswing in interest from scientific community. The amount of new reactions catalysed by gold is so significant that little is known about mechanisms of most of these reactions. Research into mechanisms of (not only) gold catalysed reactions is therefore very significant area of interest and important to the continued improvement of gold catalysed reactions. Formation of cationic π-complexes is considered a first mechanistic step in reactions catalysed by gold(I). The bond dissociation energies of gas phase cationic π-complexes were investigated by mass spectrometry and theory calculations in this thesis. These complexes consisted of differently substituted unsaturated hydrocarbons (alkenes, alkynes, alkadienes and allenes) and complex cations of silver and gold containing second ligand (triphenylphosphine, acetonitrile). On the basis of the results obtained from this study, a possible origin of the "silver effect" in gold(I) catalysis is discussed. Key words catalysis, gold, silver, mass spectrometry, DFT calculations, reaction intermediates
|
guest ::
