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Study of hyperfine interactions in nanoparticles present in biological systems
Kubániová, Denisa ; Kohout, Jaroslav (advisor) ; Závěta, Karel (referee)
In the submitted bachelor thesis we studied iron oxides by zero-field and in-field Mössbauer spectroscopy at room and liquid helium temperature. The relative composition in synthe- tically prepared nanoparticles of ferric oxide in SiO2 matrix is investigated in dependence on ferric oxide concentration and heating temperature and further the phase composi- tion and structure of biological nanoparticles produced by Geoalkalibacter ferrihydriticus bacteries in dependence on concentration of quinone in the cultivating solution. By data analysis the chemical and phase composition of the samples and hyperfine parametres of 57 Fe cations in nonequivalent crystallographic positions are determined. 1
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Relaxivity of magnetic nanoparticles
Kubíčková, Lenka ; Kohout, Jaroslav (advisor) ; Lančok, Adriana (referee)
Magnetic nanoparticles have found broad applications in medicine, in particular as contrast agents for T1- and T2-weighted magnetic resonance imaging (MRI). The ability of a contrast agent to influence the proton relaxation rate in a tissue is described by its relaxivity. In the submitted bachelor thesis we characterise physical properties of samples of ε-Fe2O3 nanoparticles coated with amorphous silica (SiO2), particularly with the aim to determine the dependences of their relaxivities on the magnetic field, temperature and thickness of silica coating. The distribution of the particle sizes was derived from the TEM pictures giving the median ~ 20 nm and the thickness of the silica coating ~4; 8; 13; 19 nm. The lattice parameters and presence of ˂ 2% admixtures of α phase were ascertained by XRD analysis; hyperfine parameters obtained by Mössbauer spectroscopy indicate no change of magnetic properties of the particles by silica coating. The relative amount of ε-Fe2O3 and SiO2 in the samples was specified from the magnetic measurements. Aqueous suspensions of different concentrations of coated nanoparticles were prepared, and their relaxivities r1, r2 were measured in different magnetic fields. Temperature dependence of relaxivities of a chosen sample was obtained in fields 0.47 T and 11.75 T....
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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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Relaxivity of magnetic iron oxide nanoparticles containing diamagnetic cations
Kubíčková, Lenka ; Kohout, Jaroslav (advisor) ; Chlan, Vojtěch (referee)
Magnetic nanoparticles have received extensive attention in the biomedical research, e.g. as prospective contrast agents for T2-weighted magnetic resonance imaging. The ability of a contrast agent to enhance the relaxation rate of 1 H in its vicinity is quantified by relaxivity. The main aim of this thesis is to evaluate the transversal re- laxivity of ε-Fe2−x Alx O3 nanoparticles coated with amorphous silica or citrate - its dependence on external magnetic field, temperature and thickness of silica coating - by means of nuclear magnetic resonance. The aluminium content x = 0.23(1) was determined from XRF, the material was further characterised by XRPD, Möss- bauer spectroscopy, DLS, TEM and magnetic measurements. The size of magnetic cores was ∼ 21 nm, the thickness of silica coating ∼ 6,10,17 and 21 nm. Magne- tization of the ε-Fe2−x Alx O3 nanoparticles increased by ∼ 30 % when compared to ε-Fe2O3. The saturating dependence of relaxivity on external magnetic field and on the linear decrease with increase of thickness of silica coating contravene the theo- retical model of motional averaging regime (MAR); nevertheless, the temperature dependence acquired in 0.47 T and 11.75 T may be explained by MAR. In compari- son to ε-Fe2O3 nanoparticles, the relaxivity of examined samples was higher for par-...
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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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Relaxivity of magnetic nanoparticles
Kubíčková, Lenka ; Kohout, Jaroslav (advisor) ; Lančok, Adriana (referee)
Magnetic nanoparticles have found broad applications in medicine, in particular as contrast agents for T1- and T2-weighted magnetic resonance imaging (MRI). The ability of a contrast agent to influence the proton relaxation rate in a tissue is described by its relaxivity. In the submitted bachelor thesis we characterise physical properties of samples of ε-Fe2O3 nanoparticles coated with amorphous silica (SiO2), particularly with the aim to determine the dependences of their relaxivities on the magnetic field, temperature and thickness of silica coating. The distribution of the particle sizes was derived from the TEM pictures giving the median ~ 20 nm and the thickness of the silica coating ~4; 8; 13; 19 nm. The lattice parameters and presence of ˂ 2% admixtures of α phase were ascertained by XRD analysis; hyperfine parameters obtained by Mössbauer spectroscopy indicate no change of magnetic properties of the particles by silica coating. The relative amount of ε-Fe2O3 and SiO2 in the samples was specified from the magnetic measurements. Aqueous suspensions of different concentrations of coated nanoparticles were prepared, and their relaxivities r1, r2 were measured in different magnetic fields. Temperature dependence of relaxivities of a chosen sample was obtained in fields 0.47 T and 11.75 T....
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Study of hyperfine interactions in nanoparticles present in biological systems
Kubániová, Denisa ; Kohout, Jaroslav (advisor) ; Závěta, Karel (referee)
In the submitted bachelor thesis we studied iron oxides by zero-field and in-field Mössbauer spectroscopy at room and liquid helium temperature. The relative composition in synthe- tically prepared nanoparticles of ferric oxide in SiO2 matrix is investigated in dependence on ferric oxide concentration and heating temperature and further the phase composi- tion and structure of biological nanoparticles produced by Geoalkalibacter ferrihydriticus bacteries in dependence on concentration of quinone in the cultivating solution. By data analysis the chemical and phase composition of the samples and hyperfine parametres of 57 Fe cations in nonequivalent crystallographic positions are determined. 1
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