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A multistep procedure, employing akaganeite FeO(OH,Cl) as a precursor, was developed for the preparation of rod-like maghemite particles for medical applications. At first, akaganeite rods with length of several hundred nm and width of approximate to 85 nm were prepared under hydrothermal conditions and were subsequently coated with mesoporous silica. Such coating enabled to maintain the shape of rods during the following steps that involved structural transformation of akaganeite to maghemite, i.e. gamma-Fe2O3. Then the original protective coating was removed by alkaline leaching, bare maghemite rods were isolated, and their structure and ferrimagnetic order were characterized by X-ray diffraction, TEM inspection, Mossbauer spectroscopy and SQUID magnetometry. The magnetization of the bare maghemite rods, that were formed by elongated clusters of approximate to 10-20 nm crystallites, made 47.0 and 41.7 Am-2/kg in magnetic field of 3 T at 5 K and 300 K, respectively. The hysteresis loops of both the bare and coated products at 300 K and ZFC/FC studies showed that the maghemite particles were largely blocked at room temperature in spite of the small size of crystallites. Finally, the particles were equipped with standard silica coating for biological studies. An evaluation of cytotoxicity of this silica-coated product was performed on two cell lines, namely A549 and MCF-7. The viability of cells incubated with particles at the concentration of 0.10, 0.21 and 0.42 mmol(Fe)/L was determined after 24 h and 48 h of incubation, and the values normalized to the viability of negative control were generally higher than 95%. Moreover, the real-time monitoring of cell adhesion, proliferation, and cytotoxicity by an xCELLigence system during 72 h of the incubation with particles revealed only some decrease of the cell index for the MCF-7 cells at the high concentration. Pro přípravu tyčovitých maghemitových částic pro lékařské aplikace byl vyvinut vícestupňový postup využívající akaganeit FeO (OH, Cl) jako prekurzor. Nejprve byly za hydrotermálních podmínek připraveny akaganeitové tyče s délkou několika stovek nm a šířkou přibližně 85 nm a následně byly potaženy mesoporézním oxidem křemičitým. Takový povlak umožnil udržet tvar tyčinek v následujících krocích, které zahrnovaly strukturální přeměnu akaganeitu na maghemit, tj. gama-Fe203. Poté byl původní ochranný povlak odstraněn alkalickým vyluhováním, byly izolovány holé maghemitové tyčinky a jejich struktura a ferrimagnetické uspořádání byly charakterizovány rentgenovou difrakcí, TEM kontrolou, Mossbauerovou spektroskopií a SQUID magnetometrií. Magnetizace holých maghemitových tyčí, které byly vytvořeny protáhlými shluky přibližně 10 až 20 nm krystalů, vytvořila 47,0 a 41,7 Am-2 / kg v magnetickém poli 3 T při 5 K a 300 K. Hysterezní smyčky holých i potažených produktů při 300 K a ZFC / FC studie ukázaly, že částice maghemitu byly z velké části blokovány při pokojové teplotě navzdory malé velikosti krystalů. Nakonec byly částice potaženy silikou pro účely biologických testů. Vyhodnocení cytotoxicity bylo provedeno na dvou buněčných liniích, konkrétně A549 a MCF-7. Viabilita buněk inkubovaných s částicemi v koncentraci 0,10, 0,21 a 0,42 mmol (Fe) / l byla stanovena po 24 hodinách a 48 hodinách a hodnoty byly vztaženy k viabilitě negativní kontroly. Viabilita byla vyšší než 95%. Kromě toho, monitorování buněčné adheze, proliferace a cytotoxicity v reálném čase pomocí systému xCELLigence po dobu 72 hodin, ukázalo pouze nepatrné snížení buněčného indexu u buněčné linie MCF-7 při vysoké koncentraci částic.

Multiferroic materials, in which spontaneous orderings (especially magnetic and electrical, in some cases elastic) jointly exist and may mutually interact, are currently in the center of attention in many fields of research due to their high application potential. They are already used in many applications, as in various sensors, microwave filters or electro / magneto- mechanical manipulators and actuators. Nevertheless, many features of microstructure and moment arrangements are not yet fully explained and understood. The presented work is mostly experimental and focuses on the investigation of several promising multiferroic materials: Pb1 − xBax(Fe0.5Nb0.5)O3 (x = 0 - 1) and Pb(Fe0.5Sb0.5)O3 with a perovskite structure and labeled as multiferroics of the I. type according to the Khomsky classification, BaYFeO4, which belongs to the multiferroics of the II. Khomsky class, and LiFePO4, which is a potentially multiferroic substance containing Fe2+ and are used in electric accumulators at present. Mössbauer spectroscopy of the 57 Fe isotope was used as a key experimental method, which can provide new information about the local arrangement in the vicinity of resonantly absorbing nuclei in the investigated substances. Data evaluation and interpretation would not be possible without the using results...

The synthesis and characterization of a new line of magnetic hybrid nanostructured materials composed of spinel-type iron oxide to iron carbide nanoparticles grown on nanodiamond nanotemplates is reported in this study. The realization of these nanohybrid structures is achieved through thermal processing under vacuum at different annealing temperatures of a chemical precursor, in which very fine maghemite (&gamma, Fe2O3) nanoparticles seeds were developed on the surface of the nanodiamond nanotemplates. It is seen that low annealing temperatures induce the growth of the maghemite nanoparticle seeds to fine dispersed spinel-type non-stoichiometric ~5 nm magnetite (Fe3&minus, xO4) nanoparticles, while intermediate annealing temperatures lead to the formation of single phase ~10 nm cementite (Fe3C) iron carbide nanoparticles. Higher annealing temperatures produce a mixture of larger Fe3C and Fe5C2 iron carbides, triggering simultaneously the growth of large-sized carbon nanotubes partially filled with these carbides. The magnetic features of the synthesized hybrid nanomaterials reveal the properties of their bearing magnetic phases, which span from superparamagnetic to soft and hard ferromagnetic and reflect the intrinsic magnetic properties of the containing phases, as well as their size and interconnection, dictated by the morphology and nature of the nanodiamond nanotemplates. These nanohybrids are proposed as potential candidates for important technological applications in nano-biomedicine and catalysis, while their synthetic route could be further tuned for development of new magnetic nanohybrid materials.

Title: Preparation and characterization of bi-phasic magnetic nanoparticles Author: Bc. Adam Alemayehu Department: Department of Innorganic Chemistry Supervisors: doc. RNDr. Daniel Nižňanský, Ph.D. RNDr. Václav Tyrpekl, Ph.D. Consultant: M.Sc. Dominika Zákutná Abstract The work is focusing on the magnetic properties of ferrimagnetic spinel ferrites before and after the introduction of a shell on a core particle with different magnetic properties. The core nanoparticles were prepared by hydrothermal decomposition of oleate precursors. The introduction of shell was carried out by hydrothermal treatment of the already prepared core particles. The phase composition, spinel structure and the sizes of the prepared samples were investigated by powder X-ray diffraction and by transmission electron microscopy. Formation of the shell on top of the core particle was determined indirectly, using Mössbauer spectroscopy at room temperature. The interparticle interactions and the particle shape was studied by small angle X-ray scattering. The magnetic properties of the prepared samples were measured on a SQUID magnetometer. Key words: magnetic nanoparticles, core, shell, spinel structure, powder X-ray diffraction, Mössbauer spectroscopy, magnetic measurements, TEM

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

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....

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

Bohemian garnets have been known as a jewellery stone for many centuries. There is still a lot of interest in them, however, the reserves in traditional locations are getting smaller. That is why search for alternative source of similar garnets in gem quality started. Shavaryn Tsaram deposit in Mongolia is considered as one of the potential sources. Pyrope samples from eight Bohemian localities of two areas (České středohoří [The Central Bohemian Uplands] and Podkrkonoší [The Giant Mountains]) and from Shavaryn Tsaram deposit in Mongolia were analysed using electron microprobe, LA-ICP-MS, ICP-OES, Mössbauer spectroscopy and x-ray powder diffraction. The data were compared with the conclusion that the Mongolian garnets from Shavaryn Tsaram deposit are so different from the Bohemian ones that it will not be possible to use them as a gem material of similar qualities. Bohemian garnet can be characterised as a red garnet with refraction index 1.747 (+/- 0.001) with dominant pyrope component of the average composition Py78Alm17Gr5 and Cr2O3 content above 1 wt.%. The data were also evaluated from two classification schemes point of view. The schemes by Schulze (2003) and Grütter (2004) are used in determining source materials and in diamond prospection. According to them source rocks of Bohemian garnets...