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Preparation of CoCr2O4 nanoparticles by the molecular precursors method
Soroka, Miroslav ; Nižňanský, Daniel (advisor) ; Havlíček, David (referee)
This work is focused on preparation and characterization of cobalt chromite nanoparticles embedded in silica matrix. The preparation of nanocomposites is based on preparation of molecular precursor, which is transformed to inorganic-organic xerogel using sol-gel process and subsequently pyrolysed and annealed at temperatures up to 1300 řC. The molecular precursor was prepared by reaction of dianhydride of ethylenediaminetetraacetic acid with (3-aminopropyl)trimethoxysilane and by subsequent complexation of Co2+ and Cr3+ and therefore, it contains both the precursor for nanoparticles and silica matrix. The system with Fe3+ was used to study an influence of the cations on the rate of condensation of the gel. A specially modified molecular precursor was prepared for the investigations of the complexation using UV-Vis spectroscopy. This precursor does not contain -Si(OR)3 groups to avoid the problems with formation of the gel, which would cause the inhomogeneities in the absorbing medium. Cobalt and chromium distribution in the xerogel was studied by EDS and ICP-AES. The results of powder X-ray diffraction showed that the oxides of cobalt and chromium reacted only partialy during the pyrolysis, which caused that nanocomposite contained except for the CoCr2O4 nanoparticles with a length of coherently diffracting...
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Preparation and characterization of the photocatalytic active TiO2 nanoparticles
Volfová, Lenka ; Nižňanský, Daniel (advisor) ; Lančok, Adriana (referee)
Bachelor thesis Preparation and characterization of the photocatalytic active TiO2 nanoparticles Lenka Volfová 2015, ABSTRACT The present work concerns the preparation of photocatalytically active TiO2 nanoparticles, their characterization and study of their photocatalytic properties. The colloidal solution was obtained by hydrolysis of aqueous solutions of TiOSO4. The samples were lyophilized and the product was annealed at 500 řC, 650 řC, 800 řC and 950 řC. The microstructure, morphology and other characteristics of the products were analysed by several physical and chemical methods: X-ray, EPR, SEM, HRTEM and BET. The measurements of IR, UV/VIS and DTA spectra have also been carried out. Photocatalytic activities were investigated by measurement of kinetics of degradation of 4-chlorophenol or methylene blue aqueous solutions under UV light. Measurement of photocatalytic activity of the samples was compared with the standard Degussa P25. It was found that the efficiency of the samples was higher than the standard. Keywords: hydrolysis, titania nanoparticles, microstructure, photocatalytic activity, photocatalytic degradation
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Preparation of magnetic nanoparticles by hydrothermal method
Repko, Anton ; Nižňanský, Daniel (advisor) ; Buršík, Josef (referee) ; del Puerto Morales, Maria (referee)
Hydrothermal method of nanoparticle preparation, involving oleic acid, has received certain attention in the last years. However, the published works lack systematic approach to the subject, and the mechanism was not thoroughly investigated, so as to achieve a predictable outcome of the synthesis. The present work investigated the influence of composition of organic and water phase on the synthesis of cobalt ferrite (cobalt(II)-iron(III) oxide) and magnetite nanoparticles, and the mechanism of nanoparticle formation was proposed. Organic phase was based on pentanol, octanol or toluene, containing the precursor - metal oleate. Besides hydrophobic particles, it was even possible to directly prepare hydrophilic oleate-coated particles by using water phase with sodium oleate. Synthetic procedure was then simplified by a separate preparation of cobalt-iron oleate, which led also to a product of narrower size distribution and better phase purity. Size control in the range of 6-11 nm and a batch yield of ca. 500 mg was achieved. Attention was given also to the surface modification of the particles, thus imparting them hydrophilicity. Small di- or tricarboxylic acids were utilized, as well as carboxylmethyl dextran and titanium dioxide. Titanium dioxide required additional protection with...
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Demonstrations as an illustrative tool in chemistry education
Hájková, Zdeňka ; Šmejkal, Petr (advisor) ; Klečková, Marta (referee) ; Nižňanský, Daniel (referee)
Demonstrations are considered an important illustrative tool in chemistry education. Quite often teachers use demonstrations of experiments and multimedia demonstrations. Besides, "non-experimental" demonstrations might also be useful, such as material models and demonstrations based on macroscopic analogy that can be usually carried out only with household items and materials. This dissertation is especially aimed at selecting appropriate demonstrations, at their design, development and use of "non-experimental" demonstrations. Moreover, special attention was paid to the interdisciplinary demonstrations concerning the nanoworld, so called "nanodemonstrations". All "nanodemonstrations" presented are safe, cheap and rather timesaving. Furthermore, they can be carried out in a form of lecture and / or students' demonstration. Newly created as well as adopted (and modified) "nanodemonstrations" were collected into the Czech database of "nanodemonstrations". The database was additionally accompanied with following educational materials concerning "nano": two PowerPoint presentations, worksheets that supplement students' "nanodemonstrations" and worksheets with interdisciplinary tasks. This thesis also deals with the evaluation of "nanodemonstrations" and worksheets in secondary school classes. The...
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Preparation and Characterization of Iron (III) Oxide Nanocomposites Substituted with Scandium
Kaščáková, Dorota ; Nižňanský, Daniel (advisor) ; Tyrpekl, Václav (referee)
In this work a preparation and characterization of nanoparticles of iron(III) oxide substituted with scandium in SiO2 matrix is described. The nanoparticles were prepared by the sol-gel method yielding mostly β-Fe2O3 substituted with various amount of scandium(III) ions. Mossbauer spectroscopy was carried out to determine purity of the samples and the content of other iron oxides phases. System was characterized by magnetic measurements. Powder X - ray diffraction was used to verify the composition and to determine the lattice parameter and particle size. β-Fe2O3 is formed at the temperatures of 1000 and 1100 ◦ C at composition Fe2−xScxO3 for x ≥ 0.2 and at temperature 1100 ◦ C for x = 0.1. Lattice parameter is linearly dependent on the scandium content and depends also on the annealing temperature. At temperatures higher than 1250 ◦ C, β-Fe2O3 is transformed into hematite. Key words: iron(III) oxide, scandium, sol-gel, Mossbauer spectroscopy, X-ray diffraction, magnetic measurements 1
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High-temperature X-ray Diffractometry of Thin Layers
Valeš, Václav ; Holý, Václav (advisor) ; Jergel, Matej (referee) ; Nižňanský, Daniel (referee)
In this work, the crystallographic structure and its changes under thermal treatment of different systems consisting of metal oxide nanoparticles is studied. The principal method used throughout the thesis is x-ray powder diffraction enriched with grazing incidence small angle x-ray scattering when the nanoparticles form an ordered structure or with x-ray absorption spectroscopy when additional information on local crystallographic structure is required. For all the systems the preparation conditions were optimized according to the crystallographic data for further applications.
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Preparation of magnetic nanostructures of chromites and their characterization
Zákutná, Dominika ; Nižňanský, Daniel (advisor) ; Honecker, Dirk Olaf (referee)
The present Diploma thesis provides an original synthesis for the preparation magnetic cobalt chromite nanoparticles (CoCr2O4 NPs) well dispersed in non-polar solvents and extensive structural, morphological, phonon and magnetic characterization. Particular emphasis is on determination of the spiral magnetic structure in CoCr2O4 NPs prepared by various procedures such as hydrothermal synthesis and sol-gel method. CoCr2O4 NPs with diameters in the range of 3.0 - 4.1 nm are prepared by high temperature hydrothermal method. For the first time, the CoCr2O4 NPs are stable in non-polar solvents and they are prepared by one-step synthesis without post treatment. The structure of prepared NPs is refined by Rietveld analysis. Size of prepared NPs is determined and compared using various techniques as powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Magnetic measurements reveal the transition from superparamagnetic (SPM) state to super spin glass - like (SSG) state. From a.c. susceptibility measurements, the spin dynamics studies and strength of inter-particles interaction are investigated. CoCr2O4 NPs with mean diameter of 26.9(1) nm are prepared by sol-gel method. The magnetization measurements reveal the transition from superparamagnetic to...
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Titania-based nanomaterials
Zabloudil, Adam ; Kubíček, Vojtěch (advisor) ; Nižňanský, Daniel (referee)
Titanium dioxide colloid with a size of particles between 20 - 40 nm was prepared. Subsequently, three substances were syntetized - methylen bis(phosphonic) acid H4L1 , 4-phosphono-butyric acid H3L2 and 4-hydroxy-4,4-diphosphono-butyric acid H5L3 . Surface of the colloidal nanoparticles was modified using these substances (H4L1 , H3L2 and H5L3 ). Then stability of these systems was studied using acid-base titration and addition of calcium ions. Keywords: TiO2, nanoparticles, surface modification
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Magnetic nanoparticles and nanocomposites with spinel structure, their preparation and characterization
Holec, Petr ; Nižňanský, Daniel (advisor) ; Šubrt, Jan (referee) ; Sedmidubský, David (referee)
This work presents the preparation and physical properties of spinel nanoparticles and nanocomposites. All nanocomposites in diamagnetic matrix like chromites CoCr2O4, CuCr2O4, NiCr2O4, ZnCr2O4 and ferrite MgFe2O4 were prepared using sol-gel method. On the other hand, isolated nanoparticles such as MgCr2O4, MnCr2O4, CuCr2O4, NiCr2O4, and FeCr2O4, were prepared using autocombustion a co-precipitation methods. CoFe2O4 and MgFe2O4 were prepared by microemulsion alkoxide method. This microemulsion method was used for the spinel nanoparticles preparation for the first time. This work describes the influence of heat treatment temperature on the final particle size and influence of particle size on physical properties of material. The study of the influence of twovalent cationt in the spinel structure on the magnetic properties of chromites was also carried out. The final samples were characterized by XRD powder diffraction, Mössbauer spectroscopy, infrared and Raman spectroscopy, and HRTEM. The dependence of magnetization on applied magnetic field at constant temperature and ZFC (zero-field cooling) - FC (field cooling) measurement was carried out on the prepared sample.
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Synthesis and sorption properties of bis(phosphonates)
Zabloudil, Adam ; Kubíček, Vojtěch (advisor) ; Nižňanský, Daniel (referee)
Three compounds were synthesized in this bachelor thesis- hydroxy(phenyl)methandiyl- bis(phosphonic) acid - disodium salt (Na2H2L1 ), 1-hydroxy-2-phenylethan-1,1-diyl- bis(phosphonic) acid - disodium salt (Na2H2L2 ) and tetraethyl hepta-1,6-diyne-4,4-diyl- bis(phosphonate) (L4 ). The next part of the thesis is focused on sorption towards to powdered titanium dioxide surface. Following compounds were used for these sorption experiments: Na2H2L1 , Na2H2L2 and 1-hydroxy-2-(4-nitrophenyl)ethan-1,1-diyl-bis(phosphonic) acid (H4L3 ). The experimental results show that compounds Na2H2L1 and Na2H2L2 have the ability to solubilize titanium dioxide into solution - for this reason there is no possibility to use UV-Vis spectroscopy to evaluate their sorption. In the case of H4L3 there are no solubilizing properties. The compound interacts intensively with titanium dioxide surface and forms monomolecular layer. Keywords: Bis(phosphonates), sorption, titanium dioxide.
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