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Rational synthesis of zeolitic materials and their characterization by advanced electron microscopy methods
Li, Ang ; Mazur, Michal (advisor) ; Chmielarz, Lucjan (referee) ; Zima, Vítězslav (referee)
Supported metal nanoparticles are a prominent class of catalysts due to their high activity in redox reactions and wide applications in numerous industrial processes. They often suffer from deactivation by sintering. One of the recognized and effective strategies to prevent sintering is to confine them into a zeolite matrix thus improving the stability of metal nanoparticles. The aim of my Ph. D. thesis was the rational design and synthesis of zeolite-supported metal nanoparticles (metal@zeolite materials). I have put my main focus on the interactions of nanoparticles with the zeolite supports. The essential experimental tool utilized in this work was advanced electron microscopy. I used this method for the investigation of the structure, location, and stability of supported metal species. Synthesized novel metal@zeolite materials were used as model systems for detailed investigation of metal-zeolite interactions. Prepared materials were investigated as heterogeneous catalysts in the hydrogenation of benzonitrile and dry reforming of methane. My thesis covered the following aspects: i) Rh nanoparticles were incorporated into hierarchical zeolitic materials (Rh@IPCs) via swelling of layered zeolite precursor IPC-1P. The final morphology and porosity of prepared materials were tuned by differing the...
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Design of a measurement circuit for electrochemical cells cycling in SEM chamber
Tran, Quoc Bao ; Trochta, David (referee) ; Klvač, Ondřej (advisor)
This diploma thesis deals with the design of a measurement circuit consisting of two separate modules for measuring electric current in the order of nanoamperes (nA) for the in-situ analysis of lithium-ion cells in microscopic dimensions. The aim of this thesis is to build a prototype measurement circuit to solve the electromagnetic interference (EMI) problems associated with in-situ analysis and to perform subsequent testing of this circuit or modules. The diploma thesis is divided into two parts, namely a theoretical and an experimental part. In the theoretical part, research on electrochemical cells is described, where the focus is directed towards lithium-ion cells. The principle of the function of these cells is described and research on their degradation mechanisms has also been carried out. Furthermore, the testing methods of lithium-ion cells such as GCPL, OCV and CV have been described. In the theoretical part, the in-situ experiments already performed at Thermo Fisher Scientific Brno are described. One experiment consisted of assembling an electrochemical cell on a MEMS chip and the other experiment was performed using a micromanipulator as a current collector. Measured data were affected by electromagnetic interference. The practical part discusses the design of a measurement circuit that would theoretically solve the problems of measuring very small currents from an EMI perspective. It also describes how the measurement circuit was tested.
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Utilization of advanced techniques of electron microscopy in altrastructural analysis of microbial cells and microbial biotechnology products
Havlíčková, Anna ; Sedláček, Petr (referee) ; Krzyžánek,, Vladislav (advisor)
In the theoretical part, this thesis deals with direct and indirect mechanisms of plant growth-promoting rhizobacteria, which is followed by a section on the selected model organism Azotobacter vinelandii. The second part of the theoretical section deals with electron microscopy starting with the possible interactions of the electron beam with the sample, through types of electron microscopes to various methods of preparing biological samples. The experimental part discusses the cultivation of selected bacterial cultures, the gelation of the cell cultures using chosen cross-linking agents (calcium chloride, malic acid, glucono--lactone with calcium carbonate) and, above all, various methods of preparation and analysis of pure and encapsulated cultures by the means of electron microscopy. In particular, cryogenic scanning electron microscopy and scanning transmission electron microscopy imaging were selected. Using both techniques, poly-3-hydroxybutyrate granules, which were confirmed to be elastic even at cryogenic temperatures, were observed inside the bacteria. Furthermore, it was found that cross-linking of extracellular alginate occurs even in samples without the addition of cross-linking agents. However, the hydrogel network present in these samples was significantly thinner than in samples with the addition of all cross-linking agents used. In this work, the density of the hydrogel network cross-linked with glucono--lactone was also compared. When using this agent with the addition of calcium carbonate, a significantly denser hydrogel network was observed in comparison with using the agent alone. Last but not least, when comparing the obtained results with the literature, it was found that the A. vinelandii bacteria form capsules, during the formation of the capsules the shape of the cells changes from an oval to a spherical bacterium and also the size of the given cell is reduced. From the resulting images, it was found that these capsules are made up of two layers, to which literature refers as electron-transparent intine and electron-dense exine.
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Design of a nitrogen Dewar vessel for electron microscopes
Brauner, Tomáš ; Voňka,, Jakub (referee) ; Urban, Pavel (advisor)
Observation of biological samples in electron microscopes in a state closest to the native state requires reaching cryogenic temperatures, most often with the use of liquid nitrogen (LN2). For this purpose a Dewar vessel with cooled copper thumb for cooling the sample holder and anticontamination shield inside the vacuum chamber of the scanning electron microscope (SEM) and focused ion beam (FIB) source was designed. Characteristics of the designed LN2 Dewar vessel were validated by measuring executed on the real functional sample. The reached temperature at the tip of the thumb under estimated heat load 2 W was 90,8 K. Corresponding refilling interval of LN2 is about 11 h. Experimentally measured data correlate with theoretically calculated characteristics. The designed Dewar vessel with a cooled thumb fulfills the required properties specified in the thesis assignment with a margin.
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SMV-2023-57: EM analysis of microorganisms II
Hrubanová, Kamila
The aim of the contract research was the expert analysis of microbiological samples with biotechnological significance with the intention of describing the ultrastructure of the cells, which depends on the cultivation conditions of the industrial process. The collaboration included cryogenic preparation of samples, followed by microbial microscopy using low-temperature electron microscopy (cryo-SEM), and selected samples were processed for transmission electron microscopy (TEM). Furthermore, spectroscopic measurements were performed using Raman spectroscopy.
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SMV-2023-56: EM analysis of microorganisms
Hrubanová, Kamila
The aim of the contract research was the expert analysis of microbiological samples with the intention of describing morphological changes dependent on culture conditions. The collaboration included cryogenic preparation of samples, followed by microbial microscopy using low-temperature electron microscopy (cryo-SEM), and selected samples were processed for transmission electron microscopy (TEM). Furthermore, spectroscopic measurements were performed using Raman spectroscopy.
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SMV-2023-54: EM Nematodes II 2023
Hrubanová, Kamila
The aim of the contract research was the expert analysis of biological samples with the intention of describing morphological features for species classification. As part of the collaboration, chemical preparation of the samples was carried out, followed by observation of the bodies of the nematodes themselves in different positions so that individual morphological characters could be distinguished using an electron microscope.
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SMV-2023-55: EM Nematodes I 2023
Hrubanová, Kamila
The aim of the contract research was the expert analysis of biological samples with the intention of describing morphological features for species classification. As part of the collaboration, chemical preparation of the samples was carried out, followed by observation of the bodies of the nematodes themselves in different positions so that individual morphological characters could be distinguished using an electron microscope.
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