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Model study of biomolecules bonding to cerium oxide nanoparticles
Pittnerová, Daniela ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
In the last few years cerium oxide due to its convenient properties for biomedical applications has been studied as a promising material for fabrication of third-generation of mediator-less enzymatic biosensors. The bonding of biomolecules with cerium oxide is a crucial parameter, which is difficult to study due to the complexity of the problem. Therefore the model studies on epitaxial and polycrystalline cerium oxide were carried out. In this thesis we continued in this line of the research with the complex study of bonding of amino acids histidine, glycine and sarcosine to cerium oxide nanoparticles. The nanoparticles' properties as the size and chemical composition were measured by electron microscopies and related techniques (TEM, SEM, EDX), and a series of photoemission spectroscopies (XPS, SRPES, RPES and NEXAFS). The dependence of zeta potential on the pH was measure by DLS technique.
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Study of the effect of gaseous poisons on magnetron-sputtered catalyst for hydrogen fuel cell
Kalabis, David ; Vorokhta, Mykhailo (advisor) ; Kúš, Peter (referee)
Title: Study of the effect of gaseous poisons on magnetron-sputtered catalyst for hydrogen fuel cell Author: David Kalabis Department: Department of Electronics and Vacuum Physics Supervisor: Mgr. Mykhailo Vorokhta, Ph.D., Department of Surface and Plasma Science Abstract: This bachelor thesis aims at studying effects and processes occurring on the surface of different PtRu catalysts for hydrogen fuel cells in connection with gaseous poisoning by CO. For these purposes the catalytic layers containing different proportions of Pt and Ru were made on porous membranes and glassy carbon. The technology of magnetron sputtering and plasma etching were used for their preparation. The layers were studied by several techniques and the properties of the alloys with respect to CO poisoning were determined. It was shown that increasing the concentration of Ru in the PtRu catalyst leads to higher catalyst resistivity against CO poisoning. However, starting from some point the catalyst total activity in fuel cell started to decrease, indicating that there is a defined upper limit for the Ru concentration in the bimetallic catalyst equal to about 50% in the alloy. The results of this work clearly indicate the high potential of magnetron sputtered PtRu catalysts in fuel cell applications. Keywords: fuel cell, hydrogen,...
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Model study of biomolecules bonding to cerium oxide nanoparticles
Pittnerová, Daniela ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
In the last few years cerium oxide due to its convenient properties for biomedical applications has been studied as a promising material for fabrication of third-generation of mediator-less enzymatic biosensors. The bonding of biomolecules with cerium oxide is a crucial parameter, which is difficult to study due to the complexity of the problem. Therefore the model studies on epitaxial and polycrystalline cerium oxide were carried out. In this thesis we continued in this line of the research with the complex study of bonding of amino acids histidine, glycine and sarcosine to cerium oxide nanoparticles. The nanoparticles' properties as the size and chemical composition were measured by electron microscopies and related techniques (TEM, SEM, EDX), and a series of photoemission spectroscopies (XPS, SRPES, RPES and NEXAFS). The dependence of zeta potential on the pH was measure by DLS technique.
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Tip modification for high-resolution AFM imaging of nanostructures
Faitová, Hana ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
Atomic force microscopy (AFM) is a young and widely used method of ima- ging surface, nanostructures, biological and other sensitive objects using sharp tip on a flexible cantilever scanning the sample surface. When operating in air it reaches resolution of about several nanometers. The resolution is mainly depen- dent on the used tip. The thesis deals with modification of old tips by carbon nanotubes (CNT) in scanning electron microscope (SEM) using techniques inclu- ding focused ion beam (FIB) and gas injection system (GIS). Several procedures of CNT sample preparation and attaching the CNT on tip are presented. The functionality of modified tips was checked in AFM using the calibration sample consisting of well-defined nanostructures. 1
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Investigation of membrane electrode assembly (MEA) for fuel cells
Fuka, Šimon ; Matolínová, Iva (advisor) ; Vorokhta, Mykhailo (referee)
Title: Investigation of membrane electrode assembly (MEA) for fuel cells Author: Šimon Fuka Department: Department of surface and plasma science Supervisor: doc. Mgr. Iva Matolínová, Dr., Department of surface and plasma science Abstract: This bachelor thesis is focused on the study of degradation of the fuel cell, specifically on the study of the catalyst diffusion into the membrane and of the chemical and morphological changes at the interface. The catalyst is prepared by magnetron sputtering directly on the membrane. Morphological changes at the interface will be monitored either by scanning electron microscope (SEM) or by using the focused ion beam (FIB). Diffusion of the catalyst will be observed using energy-dispersive X-ray spectroscopy (EDX). The bachelor thesis will contribute to the lifetime of the fuel cell type PEMFC (proton exchange membrane fuel cell). Keywords: Catalyst, Diffusion, Membrane, Fuel cell, SEM
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Investigation of magnetron sputtered Pt-CeO2 thin film catalyst for fuel cell applications
Vorokhta, Mykhailo ; Matolín, Vladimír (advisor) ; Lykhach, Yaroslava (referee) ; Jiříček, Petr (referee)
Title: Investigation of magnetron sputtered Pt-CeO2 thin film catalyst for fuel cell applications. Author: Mgr. Mykhailo Vorokhta Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Vladimír Matolín, DrSc. matolin@mbox.troja.mff.cuni.cz Abstract: This doctoral thesis focuses on magnetron sputtered Pt-doped CeO2 thin films that were found to be very active catalysts in proton exchange membrane fuel cells (PEMFC). The films were prepared on different substrates (silicon wafers, carbon nanotubes and flat carbon substrates) and investigated mainly by means of Hard x-ray photoelectron spectroscopy (HAXPES). The HAXPES method showed that deposition of the Pt doped cerium oxide catalyst layers on carbon nanotubes and flat carbon substrates by magnetron sputtering leads to growth of a highly porous "Pt-Ce-O" solid solution film, where platinum is mostly in ionic states, Pt2+ , Pt4+ . The results obtained showed that the mechanism of film growth is strongly influenced by interaction of the Ce atoms with the substrate and their oxidation by oxygen containing RF plasma. The formation of Ptn+ states together with the porous character of the catalyst films are used to explain the high activity of Pt-CeO2 catalyst in PEMFCs. Keywords: magnetron sputtering, cerium oxide, Pt, XPS, SRPES.
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