Praparation, structure and properties of hybrid nanoparticles with perovskite and spinel type cores

Charles University in Prague Faculty of Science Department of Inorganic Chemistry and Academy of Sciences of the Czech Republic Institute of Physics Department of Magnetics and Superconductors ondřej Kuman Preparation, structure and properties of hybrid nanoparticles with perovskite and spinel type cores Summary oÍ Thesis Praha 2009 Introduction The presented work Preparation, stntcture- and properties of lrybrid nanoparticles withperovskite and spinel ýpe cores was primarily dedicate- to the synit,esis *á .,uav of hybridmagnetic nanoparticles based on La1."Sr*Mnól perovskite phase as core material and silicashell. The motivatio^n for this topic is the chancó that the mentioned nanomaterials could beused as mediators for magnetically induced hyperthermia or at least they could show thedirection for future development of new agent inlended for magnetic hyperthermia. Moreover,it turned out that these nanoparticles are interesting as contrast agents for MRI and thereforethe sense of the intended work obtained anothei dimension. In order to achieve certaingenerality of the developed procedures. and- to _enable por.1t1" comparison oiu.q.ri." d. data,we have involved some aspects concerning the CoFezo+ andCot.*ZdF";ó;.pt"el phases. Aims of Thesis I' To study of po_ssible preparation of Lar-*sr*Mnol nanoparticles...Univerzita Karlova v Praze Přírodovědeclcífa kulta Katedra anorganické chemie a Akademie věd českéRepublilry Fyzikální ústav oddělení magnetik a supravodičů ondřej Kaman Příprava, struktura a vlastnosti hybridních nanočástic s jádry perovskitového a spinelového typu So uhrn disertačníprdce Praha 2009 Uvod PředloŽená disertačnípráce Příprava, struHura a vlastnosti lrybridních nanočástic s jádry perovskitového a spinelového typu byla od samého počátku pŤeváůnévedena motivací připravovat a studovat hybridní magnetické nanočástice zaloŽené na perovskitové fázi Lar *Sr*Mno3 jako magnetickém jádru a vrstvě oxidu lďemičitého jako obalu. Takové zaměření vychazelo z předpokladu, Že by dané nanomateiály mohly bý využityjako mediátory pro magneticky indukovanou h1pertermii nebo by alespoň mohly ukáuat směr budoucího vývoje nových prosťedkůpro tuto terapeutickou metodu. Nadto se však ukáza|o, ževyvíjenéčástice jsou zajímavéi co kontrastní látky pro MR[, a tím se ke smyslu pojaté práce přidal další zétmér.Pro dosaženíjistéobecnosti vyvíjených postupů a pro zajištěnímožnéhosrovnávání získávaných poznatků jsme k hlavní náplni, jiŽby| tedy manganit, připojili i aspekty ýkajici se spinelov éfáue CoFezol, resp. Co r -*Zn*Fezo+. Cíledisertačníprdce I. Prostudovat možnosti přípravy nanočástic Lat.*Sr*Mnor ruzného složenía...Department of Inorganic ChemistryKatedra anorganické chemieFaculty of SciencePřírodovědecká fakult

Evoluce skupiny Parnassiinae

Tato přehledová práce je věnována evoluční historii Parnassiinae a to zejména nominátnímu rodu Parnassius, který představuje hlavní skupinu Parnassiinae. Nejdříve bude pojednáno taxonomické pojetí Parnassiinae, monofyletický charakter skupiny a její fylogenetické postavení. Bude ukázáno, že osm rodů Parnassiinae vytváří tři vývojové větve klasifikované jako triby. Dále bude představen možný časový scénář vzniku Parnassiinae spolu s popisem fosilních druhů. Následující část bude zaměřena na rod Parnassius, jehož vnitřní fylogenese z větší části potvrzuje tradiční klasifikaci na osm podrodů. Tyto jednotlivé evoluční větve budou systematicky diskutovány s důrazem na fylogeneticky zajímavé případy druhových komplexů a blízce příbuzných taxonů, přičemž výklad doprovodí taxonomický komentář. Poslední tři kapitoly se budou věnovat fylogeografii P. mnemosyne, P. apollo a komplexu P. phoebus, jejichž evoluční historie bude vyložena s ohledem na klimatické změny v pleistocénu a holocénu. Práce se snaží podat ucelený přehled založený na morfologických, molekulárních a biogeografických aspektech, který by umožnil základní fylogenetickou a taxonomickou diskusi.This review is devoted to the evolutionary history of the Parnassiinae subfamily of the family Papilionidae and particularly to the nominate genus Parnassius which is the main group among the eight extant Parnassiinae genera. At first, the taxonomic concept, monophyly, and phylogenetic position of Parnassiinae are thoroughly discussed. It is shown that all its genera form three clades that are currently classified as tribes. Further, the estimated time of the divergence of Parnassiinae is given together with the description of all fossil taxa. The subsequent part is entirely focused on Parnassius whose internal phylogeny largely corroborates the traditional classification on eight subgenera, although the phylogenetic relationships among these clades remain mostly unresolved. All the clades are systematically discussed and interesting phylogenetic cases of species complexes and closely related taxa are analysed and supplemented by taxonomic remarks. The last three chapters are dedicated to the phylogeography of P. mnemosyne, P. apollo, and P. phoebus complex. Their evolutionary history is discussed in relation to glacial events in Pleistocene and warming of the climate in Holocene. The whole treatment attempts to integrate morphological, molecular, and biogeographical views together in order to provide a...Department of ZoologyKatedra zoologiePřírodovědecká fakultaFaculty of Scienc

Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient

In arthropod community ecology, species richness studies tend to be prioritised over those investigating patterns of abundance. Consequently, the biotic and abiotic drivers of arboreal arthropod abundance are still relatively poorly known. In this cross-continental study, we employ a theoretical framework in order to examine patterns of covariance among herbivorous and predatory arthropod guilds. Leaf-chewing and leaf-mining herbivores, and predatory ants and spiders, were censused on > 1000 trees in nine 0.1 ha forest plots. After controlling for tree size and season, we found no negative pairwise correlations between guild abundances per plot, suggestive of weak signals of both inter-guild competition and top-down regulation of herbivores by predators. Inter-guild interaction strengths did not vary with mean annual temperature, thus opposing the hypothesis that biotic interactions intensify towards the equator. We find evidence for the bottom-up limitation of arthropod abundances via resources and abiotic factors, rather than for competition and predation.publishedVersio

Evolutionary history of Parnassiinae

This review is devoted to the evolutionary history of the Parnassiinae subfamily of the family Papilionidae and particularly to the nominate genus Parnassius which is the main group among the eight extant Parnassiinae genera. At first, the taxonomic concept, monophyly, and phylogenetic position of Parnassiinae are thoroughly discussed. It is shown that all its genera form three clades that are currently classified as tribes. Further, the estimated time of the divergence of Parnassiinae is given together with the description of all fossil taxa. The subsequent part is entirely focused on Parnassius whose internal phylogeny largely corroborates the traditional classification on eight subgenera, although the phylogenetic relationships among these clades remain mostly unresolved. All the clades are systematically discussed and interesting phylogenetic cases of species complexes and closely related taxa are analysed and supplemented by taxonomic remarks. The last three chapters are dedicated to the phylogeography of P. mnemosyne, P. apollo, and P. phoebus complex. Their evolutionary history is discussed in relation to glacial events in Pleistocene and warming of the climate in Holocene. The whole treatment attempts to integrate morphological, molecular, and biogeographical views together in order to provide a..

Praparation, structure and properties of hybrid nanoparticles with perovskite and spinel type cores

Charles University in Prague Faculty of Science Department of Inorganic Chemistry and Academy of Sciences of the Czech Republic Institute of Physics Department of Magnetics and Superconductors ondřej Kuman Preparation, structure and properties of hybrid nanoparticles with perovskite and spinel type cores Summary oÍ Thesis Praha 2009 Introduction The presented work Preparation, stntcture- and properties of lrybrid nanoparticles withperovskite and spinel ýpe cores was primarily dedicated to the synit,esis *á .,uav of hybridmagnetic nanoparticles based on La1."Sr*Mnól perovskite phase as core material and silicashell. The motivatio^n for this topic is the chancó that the mentioned nanomaterials could beused as mediators for magnetically induced hyperthermia or at least they could show thedirection for future development of new agent inlended for magnetic hyperthermia. Moreover,it turned out that these nanoparticles are interesting as contrast agents for MRI and thereforethe sense of the intended work obtained anothei dimension. In order to achieve certaingenerality of the developed procedures. and- to _enable por.1t1" comparison oiu.q.ri." d. data,we have involved some aspects concerning the CoFezo+ andCot.*ZdF";ó;.pt"el phases. Aims of Thesis I' To study of po_ssible preparation of Lar-*sr*Mnol nanoparticles..

Preparation and study of acid salts as potential proton conductors

Department of Inorganic ChemistryKatedra anorganické chemiePřírodovědecká fakultaFaculty of Scienc

Tunneling magnetoresistance of hydrothermally sintered La1-Sr MnO3-silica nanocomposites

The study deals with tunneling magnetoresistance in a series of composite systems of so-called 0–3 connectivity, in which highly conducting manganite nanoparticles of ferromagnetic groundstate (0-dim objects) are embedded in the (3-dim) insulating matrix of silica. The sample fabrication included the sol-gel preparation of La1–xSrxMnO3 particles of the x = 0.35 composition and 25 nm mean crystallite size, their coating by silica of controlled thicknesses in the 1–5 nm range, and subsequent consolidation by hydrothermal sintering at 300 °C. Temperature dependent electric resistivities of the materials were measured in magnetic fields of 0 and 40 kOe down to 5 K, and field-dependent isothermal curves were taken by sweeping magnetic field up to 140 kOe. The field-dependent effects were interpreted in terms of the low- and high-field magnetoconductance. It is important that extents of these phenomena are markedly independent of the silica amount, despite the five orders change in absolute resistivity values. Microscopic mechanisms of the intergrain transport, applicable to polycrystalline manganites, nanogranular compacts and nanocomposites in general, are proposed

Development of novel nanoparticles for MPI

Abstract: A modified procedure for preparation of iron oxide nanoparticles was used to produce nanoparticles suitable for magnetic particle imaging (MPI). Cationic and anionic maghemite particles were prepared and coated by poly(N-(2-hydroxypropyl)methacrylamide)-co-N-[2-(hydroxyamino)-2-oxo-ethyl]-2-methyl-prop-2-enamide. Bare and coated particles were characterized by magnetometry, dynamic light scattering, MR relaxometry, transmission electron microscopy and tested in vitro in a field-free-point MPI scanner. The nanoparticles were compared to Resovist and to differently oxidized particles dedicated for magnetic resonance imaging (control NP). The cores of particles had an average diameter 8.0 nm (cationic ones) and 8.7 nm (anionic ones), hydrodynamic diameter of coated particles in water colloids was 88 nm, and zeta potential +52 mV or –60 mV for cationic or anionic particles respectively).Cationic particles provided at MPI lower signal-to-noise ratio than Resovist, while anionic higher by 25%. Also signal dispersion to surrounding voxel was smaller. The worst results were reached in the case of control NP.   Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009019, DOI: 10.18416/IJMPI.2020.200901

Magnetoconductivity of the La 1–xSrxMnO3@TiO2 Nanocomposite

This paper deals with tunneling magnetoresistance in a composite system of the so-called 0–3 connectivity, in which ferromagnetic (FM) metallic nanoparticles La1–xSrxMnO3 (0-D objects) are embedded in the (3-D) insulating matrix of TiO2. The sample fabrication included the sol–gel preparation of manganite particles of the x = 0.35 composition and 25 nm mean crystallite size, their coating by TiO2, and compacting the products by spark plasma sintering (SPS). A comparative nanogranular sample was prepared by SPS of bare manganite particles. The resistivities of the composite and comparative samples are 100 000 and 100 times higher compared to those of bulk metallic La1–xSrxMnO3. Otherwise, the temperature dependence observed in the nanogranular La1–xSrxMnO3 sample is similar to single crystal data, and marked localization is absent also in the La1–xSrxMnO3@TiO2 nanocomposite. The data taken in applied fields up to 4 T reveal effects typical for grain-boundary tunneling in manganites, namely, the coexistence of the low-field magnetoconductance (LFMC), reflecting the field-induced alignment of FM cores, and high-field linear magnetoconductance (HFMC) that is generally ascribed to the effect of spin canting at localized Mn4+ sites in the interface. This is considered as a signature for resonant tunneling of spin-polarized carriers, theoretically treated by Lee et al [1]. The present results show that the total extent of LFMC makes 45% in the La1–xSrxMnO3@TiO2 nanocomposite and 21% in the La1–xSrxMnO3 nanogranular sample. The slope of HFMC has been determined to 5.4% and 4.9% per Tesla, respectively. The large LFMC effect observed in the nanocomposite exceeds the theoretical prediction of 33% for the second-order tunneling, which might suggest for higher order tunneling via resonant states

Klastry magnetických nanočástic jako kontrastní látky pro MRI: Vliv agregace na příčnou relaxivitu

The effect of aggregation of magnetic nanoparticles on the transverse relaxivity (r2) is analyzed with respect to the size of clusters. The nanoparticles employed are based on La0.75Sr0.25MnO3 ferromagnetic phase with the mean size of crystallites dXRD = 26 nm synthetized via sol-gel method followed by thermal treatment and mechanical processing. The subsequent silica coating provides colloidally stable particles whose magnetic cores are mostly composed of compact clusters of manganite crystallites. The product has been subjected to repeated differential centrifugation and several size fractions, possessing the same dXRD but differing in the effective size of magnetic cores, are isolated. The highest r2 values are clearly observed for midsized clusters and the temperature dependence of r2 resembles the evolution of magnetization with temperature. Supplemental samples with different thicknesses of the silica shell are also synthetized and thoroughly analyzed.Vliv agregace magnetických nanočástic na příčnou relaxivitu (r2) je analyzován s ohledem na velikost klastrů. Použité nanočástice jsou založeny na La0,75Sr0,25MnO3 feromagnetické fázi se střední velikostí krystalitů dXRD = 26 nm syntetizované sol-gel metodou následovanou tepelným a mechanickým zpracováním. Následné pokrytí silikou poskytuje koloidně stabilní částice, jejichž magnetická jádra jsou převážně tvořená kompaktními klastry manganitových krystalitů. Produkt byl podroben opakované rozdělovací centrifugaci a několik velikostních frakcí, vlastnící stejné dXRD, ale lišící se v efektivní velikosti magnetických jader, je izolováno. Nejvyšší hodnoty r2 jsou jasně pozorovány pro středně velké klastry a teplotní závislost r2 se podobá vývoji magnetizace s teplotou. Dodatečné vzorky s různou tloušťkou silikové slupky jsou rovněž syntetizovány a podrobně analyzovány