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Plasmonic Antennas
Kvapil, Michal ; Brzobohatý, Oto (referee) ; Novák, Stanislav (referee) ; Šikola, Tomáš (advisor)
Tato disertační práce pojednává o plazmonických anténách. Rezonanční vlastnosti plazmonických antén jsou studovány teoreticky i experimentálně. Teoretické výpočty jsou prováděny v programu Lumerical FDTD Solutions užitím numerické metody konečných diferencí v časové doméně. Pro experimentální studium byly antény vyrobeny pomocí elektronové litografie. Rezonanční vlastnosti vyrobených antén jsou studovány fourierovskou infračervenou spektroskopií. Práce se zaměřuje na studium rezonančních vlastností antén vyrobených na vrstvě nanokrystalického diamantu. Dále zkoumá možnost využití antén jako plazmonického senzoru funkcionalizovaného k detekci streptavidinu. Nakonec je představena anténa tvaru písmene V, u které dochází v důsledku porušení symetrie antény ke směrovému rozptylu dopadajícího světla. Tato směrovost se ovšem projevuje jen na vlnových délkách blízkých kvadrupólovému módu antény.
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Preparation and Plasmachemical Reduction of Model Corrosion Layers on Iron.
Sázavská, Věra ; Novák, Stanislav (referee) ; Zahoranová, Anna (referee) ; Krčma, František (advisor)
The plasmachemical removal process of corrosion layers is based on a reduction effect of RF hydrogen low-pressure plasma, and it is used for archaeological objects. Incrustation layers on artifact surface become brittle and porous due to plasma processing. The structure and composition of corrosion layers is changed. Therefore, it is much easier to recover the original surface of the plasma treated artifacts in contrary to those treated by conventional ways. Moreover, we can save time on invasive and thus dangerous mechanical removal of corrosion layers as for example sanding is. After plasma treatment, we can observe fine details of the original surface and memory of tools used during its manufacturing. These details are important information on the origin and manufacturing methods of the artifacts. The plasma reduction process leads to the removal of impurities from cavities as well, and a function of mechanical components of archaeological object can be restored. Moreover, chlorides can be easily removed from the corrosion layers and thus any significant post-corrosion is protected. Each archaeological object is original and it has its own “corrosion history”. First, the object had been exposed to the atmosphere for a long time. Then, it had been often placed in a tomb or grave or it otherwise got into the soil or sea. Thus, each archaeological object was exposed to different corrosion stress (humidity, composition of corrosive environment, etc.). Due to these facts, any universal way of a corroded object treatment is very difficult or even impossible to propose. In this work, the problem was solved using model samples of common metals which were treated at various plasma treatment conditions. Archaeological objects made of iron are the most common artifacts, and the typical corrosion products on iron are akaganeite, rokuhnite, and szomolnokite. These three corrosion products were created on the model samples in laboratory and then, the plasmachemical reduction was applied for their removal. The experiment was done in a Quartz cylindrical reactor with capacitive coupled RF plasma created using outer electrodes. We used discharge power from 100 W to 400 W in a continuous or pulsed regime (duty cycle of 75 %, 50 % and 25 %). Flowing plasma was created in pure hydrogen at pressure of 150200 Pa. Sample temperature was monitored by a thermocouple, and it did not exceed 200C during all these experiments. This temperature is regarded as a limit temperature for metallographic changes of archaeological iron. Higher temperature can cause destruction of archaeological iron objects. The optical emission spectroscopy of OH radical was used for the process monitoring. We focused on the monitoring of OH-radicals generated in the plasma, which are characteristic species formed by this process. Each corrosion product has a different time evaluation of generated OH-radicals, which is closely related to the degradation of a given corrosion product. Corrosion layers were analyzed before and after the plasmachemical reduction by SEM-EDX. We have found that the plasmachemical reduction is not very suitable for the szomolnokite corrosion product, which is degraded with difficulty and at high applied powers, only. However, very good removal efficiency was obtained for the rokuhnite and akaganeite corrosion.
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Application of methods of computational physics for the study of plasma-solid interaction
Hromádka, Jakub ; Hrach, Rudolf (advisor) ; Novák, Stanislav (referee)
Low-temperature plasma and its interaction with immersed solids is studied in this work. The research of the physical processes on this interface is performed by two-dimensional particle computer model. The model uses molecular dynamic method. Mutual forces between particles are computed by Particle- in-Cell method. The main application of the model is in the area of the probe diagnostic of plasma. Simple problems are compared with theory and two dimensional effects are discused. Contribution of particle modeling to plasma research is showed on the problem of interaction of sheaths around cylidrical probes. We deal with question whether we are able to get some information about unevennesses at the surface of solid immersed in plasma by measuring probe characteristics in its surroundings. We also studied the influence of plasma electronegativity on the parameters of sheaths around cylidrical probes. Powered by TCPDF (www.tcpdf.org)
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Modification of polymeric substrates by means of non-equilibrium plasma
Kuzminova, Anna ; Kylián, Ondřej (advisor) ; Čech, Vladimír (referee) ; Novák, Stanislav (referee)
Title: Modification of polymeric substrates by means of non-equilibrium plasma Author: Anna Kuzminova Department: Department of Macromolecular Physics Supervisor of the doctoral thesis: doc. RNDr. Ondřej Kylián, Ph.D. Abstract: Processing of polymeric materials by means of non-equilibrium plasma is a topic that reaches increasing attention, which is due to the wide range of possible applications. As an example can be mentioned processing of polymeric foils used for food packaging, where plasma treatment enables to improve their functional properties (e.g. increase their printability or enhance their barrier properties). In the frame of this PhD. thesis two different strategies suitable for the modification of polymeric materials were followed. The first one was based on treatment of polymers by atmospheric plasma. The main attention was devoted to the investigation of influence of atmospheric pressure plasma on surface properties of 8 commonly used polymers, namely on their chemical composition, morphology and wettability. In addition, it was observed that plasma treatment causes also alteration of their mechanical properties, may lead to their substantial etching and in some cases improves their biocompatibility. The second studied strategy was based on coating of polymers with thin functional...
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Study of Positive Column in Glow Discharge under Medium Pressures Using Computational Experiment
Laca, Marek ; Hrachová, Věra (advisor) ; Novák, Stanislav (referee) ; Roučka, Štěpán (referee)
The positive column of the oxygen and argon-oxygen direct current glow discharge was investigated using a fluid plasma model at pressures around hundreds of pascals and discharge currents from ten to forty miliampers. The model describes the infinitely long positive column in cylindrical discharge tube. It is based on the continuity equation for particle concentration with the collisional right hand side. The model utilises the drift-diffusion approximation of particle flux and the mean-electron-energy approximation for the description of the electron interaction. The radial profile of particle concentration and interaction with the glass wall of the discharge tube is taken into account. The model predicts the electric field and the particle concentration in the positive column. The simulation results were compared with the measured intensity of electric field strength in the oxygen and argon-oxygen mixture. The impact of discharge conditions, like the pressure and gas composition, on the properties of the positive column was investigated. The model confirmed that the strength of longitudinal electric field at medium pressures is about 40 V/cm in oxygen, molecular gas, and it is about 3 V/cm in argon, noble gas.
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Laboratory astrochemistry and applications of computer simulations
Roučka, Štěpán ; Hrach, Rudolf (advisor) ; Bonaventura, Zdeněk (referee) ; Novák, Stanislav (referee)
This work is focused on laboratory studies of ion chemistry at conditions relevant for astrophysics. The three main outcomes of the thesis are: (1) The experimental study of the reaction rate coefficient of the associative detachment reaction H- + H -> H2 + e-; measurement of the thermal rate coefficient at the temperatures in the range 10-135 K is described. (2) The design of a novel apparatus for detecting the electrons produced in the RF trap and measuring their energy; numerical simulations and preliminary experimental results are presented. (3) The development of a model of the electron cooling in the afterglow plasma and the application of the model in the analysis of the H3+ recombination measurements.
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XPS analysis of plasma polymers and nanocomposite films without breaking vacuum
Artemenko, Anna ; Biederman, Hynek (advisor) ; Čech, Vladimír (referee) ; Novák, Stanislav (referee)
Title: XPS analysis of plasma polymers and nanocomposite films without breaking vacuum Author: Anna Artemenko Institute: Charles University in Prague, Department of Macromolecular Physics Supervisor of the doctoral thesis: Prof. RNDr. Hynek Biederman, DrSc., Charles University in Prague, Department of Macromolecular Physics. Abstract: Plasma polymers and metal/ plasma polymer nanocomposites have been widely used for various biomedical proposes. Naturally, surface properties of the coatings such as high wettability, stability on the open air and in aqueous media, resistance towards different sterilization processes and cells adhesion are required for bioapplications. This thesis is mainly dedicated to the investigation of chemical composition of deposited coatings using XPS analysis. Nylon-like plasma polymer, PEO-like coatings, fluorocarbon plasma polymer (PTFE) films and Au/PEO-like, Ag/C:H, Al/C:H nanocomposites were chosen as the subject material. In addition, results of XPS measurements were used for the computer simulation for calculation of filling factor of metal/ plasma polymer nanocomposites. These results were in a good agreement with experimental data. Keywords: plasma polymer, nanocomposite, XPS analysis, bioapplication, simulation.
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Structuring of plasma polymers: new methods for fabrication of nano-architectured thin films
Nikitin, Daniil ; Shukurov, Andrey (advisor) ; Novák, Stanislav (referee) ; Straňák, Vítězslav (referee)
Title: Structuring of plasma polymers: new methods for fabrication of nano-architectured thin films Author: Daniil Nikitin Department / Institute: Department of Macromolecular Physics/Charles University Supervisor of the doctoral thesis: Doc. Ing. Andrey Shukurov, PhD, Department of Macromolecular Physics/Charles University Abstract: The PhD thesis aims at the investigation of nanostructures based on plasma polymers. The main attention is paid to the combination of a gas aggregation cluster source with plasma-assisted vapor phase deposition for the fabrication of metal-polymer nanocomposites with bactericidal potential. Copper nanoparticles were incorporated into a biocompatible matrix of plasma polymerized poly(ethylene oxide) (ppPEO). The efficiency of such nanocomposite against multi-drug resistant bacteria was demonstrated. It was found that the segmental dynamics of the plasma polymer significantly changed in the presence of nanoparticles as revealed by the measurements of the dynamic glass transition temperature. The nanoscale confinement crucially influences the non-fouling properties of poly(ethylene oxide). A separate chapter is dedicated to the examination of the nanoparticle formation, growth and transport inside the source. Copper and silver nanoparticles were detected in situ in the gas phase...
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