National Repository of Grey Literature 41 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Magnetic resonance imaging with multimodal T2 contrast agents based on fluorescence-labelled magnetic cores with the spinel structure
Kikerlová, Soňa ; Kaman, Ondřej (advisor) ; Nižňanský, Daniel (referee)
This diploma thesis was focused on the preparation of magnetic and fluorescently labelled spinel type nanoparticles, specifically nanoparticles of zinc-doped cobalt ferrite intended for application in magnetic resonance imaging and fluorescence microscopy in experimental practice. In previous studies, various ferrite nanoparticles exhibited relatively high transverse relaxation times and strong negative T2 contrast. These properties were also supposed for the zinc-doped cobalt ferrite nanoparticles. This assumption was confirmed by studying their magnetic and contrasting properties. Fluorescence properties of the prepared nanoparticles were also successfully studied. With respect to the intended applications of these particles, the issue of suitable surface modification of magnetic cores, their colloidal stabilization in an aqueous suspension and toxicity in biological systems were studied. Key words: nanoparticles, ferrites, MRI, relaxation
Selective Catalytic Reduction of NOx by Propane in Oxidizing Atmosphere on Catalysts Based on Metals in Zeolite Matrices
Schwarze, Michael ; Sobalík, Zdeněk (advisor) ; Nižňanský, Daniel (referee) ; Dědeček, Jiří (referee)
5. CONCLUSIONS A set of spectroscopic techniques (electron spin resonance, infrared spectroscopy and Móssbauer spectroscopy) usď under conditions near to in-siÍu experiments provided for the frrst complex identification of individual řon species present in a group of pentasil zeolites, i.e. FER, BEA, and MFI' Identifiď structural parameters of individual iron sites and their redox properties in various types of zeolites provide9ttr::S1qilthe relationship between structure and catalyic performance of such materials for selective catalýic reduction of No* by propane in the presence ofoxygen. It has been shown that, while the individual types of Fe-zeolites differ in structural conditions for the individual processes controlling the final SCR perforrnance, in the temperature range 200 - 250.C these individual effects are effectively compensatď. on the other hand, Fe-BEA displays the best combination of structural features for supporting the reaction in the temperature range between 300 and 350.C. The catalýic activity above 350oC is then dominated by a catalyst ability to suppress the nonselective oxidation of propane, connectď to lower efficiency in targeting the řon cationic positions during catalyst preparation. Nevertheless, all three zeolites used provide structural conditions for preparation of highly...
Preparation and study of molybdenum disulfide layers
Jurková, Kateřina ; Kalbáč, Martin (advisor) ; Nižňanský, Daniel (referee)
This work deals with preparation and study of sandwich heterostructures of MoS2 and graphene. MoS2 layers prepared by mechanical exfoliation were detected by optical microscopy and characterized by Raman spectroscopy and atomic force microscopy (AFM). Spectroelectrochemical cells were created for sandwich heterostructures MoS2/graphene and Raman and photoluminiscence spectra were studied in dependence on applied electrical potential. Also spectroelectrochemical measurements were performed on mono- to four-layer MoS2 in microdroplet. Changes in the parametres of E1 2g (E') a A1g (A1') peaks in the Raman spectra and both direct and indirect photoluminiscence transitions in the photoluminiscence spectra of MoS2 were observed in dependence on the applied voltage. Splitting of the indirect transition into two parts I- and I+ was observed during the measurent in the microdroplet. Keywords: MoS2, graphene, Raman, spectroscopy, spectroelectrochemistry 1
Iron Functionalized Nanoparticles of Titanium Dioxide
Volfová, Lenka ; Nižňanský, Daniel (advisor) ; Tabor, Edyta (referee)
Diploma thesis Iron Functionalized Nanoparticles of Titanium Dioxide Lenka Volfová 2017, ABSTRACT Iron-functionalized TiO2 were obtained by hydrolysis of aqueous solutions of titanyl sulfate with addition of ferric nitrate with ammonium hydroxide and the reaction filtered and washed with hydrogen peroxide. The colloid solutions thus prepared were lyophilized and the products were subsequently annealed at three different temperatures of 650 řC, 800 řC and 950 řC. The prepared doped materials were characterized by powder X-ray diffractometry, electron microscopy, infrared spectroscopy, Mössbauer spectroscopy, UV/VIS spectroscopy, thermogravimetric analysis and differential thermal analysis, and measurement of the specific surface area. Photocatalytic activity was determined by measuring of the decomposition of kinetics of 4-chlorophenol in an aqueous solution in the ultraviolet and visible area. For comparison of activity in the UV area and in the visible area were used a previously prepared highly photoactive specimen and standard TiO2 from Kronos, respectively. Keywords: Doped titanium dioxide, nanostructure, X-ray diffraction, electron microscopy, Mössbauer spectroscopy, suppression of photoactivity
Size evolution of spiral magnetic structure in cobalt chromite nanoparticles
Alemayehu, Adam ; Nižňanský, Daniel (advisor) ; Klicpera, Milan (referee)
Název práce: ývoj spirální magnetické chromitových nanočásticích Katedra anorganické chemie, PřF UK Vedoucí bakalářské práce: RNDr. Daniel Nižňanský, Ph. mail vedoucího: Magnetické nanomateriály hrají důležitou roli v posledních desetiletích díky zajímavým aplikacím . Multiferroické materiály jsou materiály, u nichž existují dva typy jevů, magnetické a feroelektrické uspořádání. To znamená, že se může indukovat magnetizac ým polem nebo elektrická magnetickým polem. chromitý patří do druhé skupiny feroických látek, nazývaných multiferroika typu II. Tyto eroické materiály jsou relativně nové. V případě, že v těchto materiálech existuje feroelektrika, musí být v těchto materiálech přítomen zvláštní typ magnetického uspořádání. chromitý ) krystalizuje ve struktuře kubického spinelu, kde jsou umístěny v tetraedrických a okta ický polohách zhlucích dochází k ferrimagnetickému uspořádání CoCr při systém dále prochází magnetickým fázovým přechodem uspořádání do řady magnetických spirál s dlouhým dosahem při přechodové teplotě 26 K Současně byla pozorovaná dielektrická anomálie pod spirálním magnetickým přechodem této práci je prezentován vývoj spirálového uspořádání se změnou velikosti částic. íčová slova: prášková röntgenová difrakce, difuzní rozptyl neutronů, hydrotermální metoda
Preparation and characterization of substituted Y ferrites in the form of ceramics and thin films
Pulmannová, Dorota ; Nižňanský, Daniel (advisor) ; Prokleška, Jan (referee)
Title: Preparation and characterization of substituted Y ferrites in the form of ceramics and thin films Author: Dorota Pulmannová Department: Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague Supervisor: RNDr. Daniel Nižňanský, Ph.D. Consultant: Ing. Josef Buršík, CSc. Abstract: In this work we describe a preparation and characterization of a hexagonal ferrite series with composition BaSrCoZnXFe11O22 where X=Fe, Al, Ga, In and Sc. We have prepared these ferrites in the powder and ceramic form using the citrate synthesis and in the thin film form using the chemical solution deposition method. Using the powder neutron diffraction we have found that the sample containing only Fe has collinear magnetic structure that belongs to the C2/m or C2'/m' group. Magnetic structure of the samples substituted with In and Sc is similar, but the magnetic moments of the 18hVI site atoms are not aligned parallely with the other moments. Magnetic structure of Ga-substituted sample is different, it is modulated with a propagation vector k ≈ (0, 0, 3/4). Propagation vector of the Al-substituted ferrite is k ≈ (0, 0, 3/2). Substituting elements show strong preferences for the cation sites. Al and Ga prefer the 3bVI site, Zn prefers the tetrahedral 6cIV and In and Sc prefer the 6cVI site. Room...

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