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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 properties of iron-containing nanoparticles stressing their application potential
Kubíčková, Lenka ; Kohout, Jaroslav (advisor) ; Javorský, Pavel (referee) ; Mašláň, Miroslav (referee)
Magnetic nanoparticles offer a plethora of application possibilities in various fields of human endeavors. The fundamental understanding of their physical properties, related to the constituent magnetic phase, surface termination, and possible coating, synthesis method, size, shape, or even clustering, is crucial for their effective use and optimization for the intended applications. This thesis aims to contextualize original results, concerning especially the structure and magnetic properties, obtained during fundamental research on nanoparticles of selected iron-containing systems and employ these findings in testing the nanoparticles in chosen applications. Iron presents an ideal constituting element due to its low cost, high abundance in the Earth's crust, exploitability, and low toxicity. The selected systems involved in this thesis comprise iron-containing oxides (ferrites, and various polymorphs of iron(III) oxide, including ε-Fe2O3 and doped counterparts), and sulfides (greigite, chalcopyrite), all of which exhibit specific properties such as magnetic or structural transitions. Among the studied applications, the largest attention is devoted to the use of magnetic nanoparticles as contrast agents in magnetic resonance imaging, and the analysis of their efficacy in contrast enhancement -...
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Relaxivity of magnetic iron oxide nanoparticles containing diamagnetic cations
Kubíčková, Lenka ; Kohout, Jaroslav (advisor)
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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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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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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