L’objectif de ce travail a été de procéder au design de nouvelles structures hyperramifiées en procédant à la synthèse de polymères à base de glycidol utilisables dans l’élaboration de copolymères biodégradables, de macromonomères fonctionnels et de nanocomposites magnétiques biocompatibles. Une première partie de ces travaux s’est intéressée, à la synthèse de macromonomères hyperramifiés amorcés par l’hydroxyéthyle méthacrylate (HEMA), l’hydroxyéthyle acrylate (HEA) et le polyéthylène glycol méthacrylate (PEGMA), par polymérisation anionique, anionique coordinée ou cationique du glycidol. La synthèse de macromonomères poly(ε-caprolactone) en présence de différents systèmes catalytiques et amorceurs a également été investiguée. Cette partie se termine par la synthèse de dendrigrafts issus de la polymérisation de ces macromonomères, par voie radicalaire classique ou contrôlée (RAFT/ATRP). La seconde partie de ce travail a été consacrée à la synthèse de copolymères hyperramifiés biocompatibles obtenus par copolymérisation statistique du glycidol en présence d’ε-caprolactone, en vu de l’obtention de copolymères hydrolysables. L’impact de la structure sur les propriétés physico-chimiques des copolymères obtenus a été étudié. Enfin, le caractère biodégradable de ces polymères a été investigué à travers différents tests de dégradation enzymatique. Enfin, ce travail s’est focalisé sur l’élaboration de nanocomposites magnétiques biocompatibles par la synthèse de nanoparticules magnétiques, puis l’immobilisation de polymères linéaires ou hyperramifiés à leur surface selon différentes méthodes de greffage chimique. / The aim of this work was to proceed to the design of new hyperbranched structures through the synthesis of glycidol-based polymers which can be used in the development of biodegradable copolymers, functional macromonomers and biocompatible magnetic nanocomposites. The first part of this work was the synthesis of hyperbranched macromonomer initiated by hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA) and polyethylene glycol methacrylate (PEGMA), through the study of the synthesis of polyglycerol (PG) by anionic, anionic coordinated and cationic polymerization of glycidol. Synthesis of poly (ε-caprolactone) macromonomers in the presence of various catalyst systems and initiators was also investigated. This part ends by the synthesis of dendrigrafts derived from the copolymerization of the macromonomers, by free radical polymerization or by controlled radical polymerization. The 2nd part of this work has been devoted to the synthesis of hyperbranched biocompatible copolymers obtained by random copolymerization of glycidol with ε-caprolactone in order to obtain hydrolyzable copolymers. The impact of the structure of the copolymers on their physico-chemical properties was then investigated. The biodegradable behavior of these polymers was then investigated through different enzymatic degradation tests. Finally, this work was focused on the development of biocompatible magnetic nanocomposites by the synthesis of magnetic nanoparticles and the immobilization of linear or hyperbranched polymers on their surface by different chemical grafting methods.

Thesis is aimed at studying of magnetic iron oxide particles of submicron and nanoscale dimensions by means of nuclear magnetic resonance (NMR). 57 Fe NMR inves- tigations were carried out in composite bentonite/maghemite with respect to tempera- ture of calcination (Tcalc) during the sample preparation and in magnetite submicron powders with respect to various range of the particles size. One of the main findings is that increasing Tcalc improves resolution in the NMR spectra, which is most likely connected with higher degree of atomic ordering in the spinel structure. Evaluating the integral intensities of NMR spectra allowed us to determine the relative content of maghemite phase in particular samples of the series: the content rapidly grows for Tcalc up to ∼420 deg. An approach to distinguish signal from tetrahedral and octahedral irons was developed and tested on pure maghemite sample. Analysis based on vacancy- distribution models was performed in the spinel structure and the results were compared to the experiment. 57 Fe NMR spectra in submicron magnetite samples were found to differ markedly from spectrum of a single crystal. It was concluded that the investigated powders possess high amount of defects in the crystal structure or contain additional phase (probably closely related to the maghemite phase).

Interaction between minerals and bacteria represents an abundant natural phenomenon depictingnature's complexity and how abiotic and biotic components are intertwined. This interaction is evidentin modern-day ecosystems, and it significantly shaped the early stage of life on Earth by influencinggeochemical processes. Evidence of this interaction includes microbialites. In the first part, this master's thesis explores the impact of iron-redox bacteria on the magneticproperties of synthetic and natural magnetic materials, with significant implications for understandingearly Earth conditions and paleoenvironments. In the second part, the magnetic signal recorded in thesediment core from the Baltic Sea is examined to identify the ferrimagnetic minerals responsible for itand their origin (biotic versus abiotic). A better understanding of the origin of ferrimagnetic mineralsallows for a more conclusive interpretation of palaeomagnetism and palaeoenvironmental history of theBaltic Sea. In both parts, the change in magnetic susceptibility was used as the main method to depictmechanisms of mineral-bacteria interaction. Experiment with iron-oxidising bacteria (Leptothrix mobilis) showed a decrease in magneticsusceptibility over time, consistent with the oxidation of solid iron/magnetic materials. However, asmall difference between bacteria culture and control samples points out that the decrease is caused byabiotic oxidation rather than bacterial. Supporting evidence is the absence of viable cells in all bacterialsamples, suggesting that L. mobilis did not grow in these experiments. In experiments with iron-reducing bacteria (Geobacter sulfurreducens), magnetic susceptibility increased by 7%. Controlsamples with the same reducing media did not show a change in magnetic susceptibility, indicating thatthe susceptibility change is caused by bacterial reduction of iron oxides. Magnetic susceptibility signal obtained in the sediment core from the Baltic Sea indicates rapidlyoxidising, ferrimagnetic nanoparticles in two organic-rich sapropels. The pattern of the signal isconsistent with the presence of bacterial greigite (magnetofossils). Contrary to previous research, nomagnetic enhancement is observed in these layers.  Magnetic susceptibility, as a non-destructive and relatively simple method, may serve as a significantindicator of mineral-bacterial interactions. Combining it with other techniques and methods can providedeeper insights into the mechanisms behind these interactions. This approach can reveal the importanceof these interactions on early Earth, enhance our understanding of palaeomagnetism, and unveil possibleconditions of ancient environments.

It is the study of banded iron formations (BIFs) that provides understanding into the conditions of the Earth's oceans and atmosphere during the Archean and Early Proterozoic. The aim of this thesis is to provide a detailed mineralogical and geochemical understand of BIFs from two separate localities separated by the Archean Proterozoic boundary. Close attention is paid to their carbonate and iron oxide mineralogy.The BIFs of the 2.7 Ga Manjeri Formation, Zimbabwe and 2.4 Ga Itabira Group, Brazil were both precipitated from oxygenated mixed marine-hydrothermal fluids. This is demonstrated by the presence of nano-hematite inclusions in the chert (Itabira and Manjeri) and dolomite (Itabira only) laminae, which is interpreted as the oldest mineral phase within the samples. Additionally, focused ion beam transmission electron microscopy (FIB-TEM) reveals the presence of nano ferrihydrite platelets within the dolomitic BIFs (carbonate itabirite). The dolomite is interpreted to be a primary phase precipitated at higher temperatures (~100°C) from CO2-rich hydrothermal fluids. Positive Eu anomalies in both formations indicate a hydrothermal component, likely to be the source of the reduced iron. Facies changes in both units are the result of transgression/regression and post depositional hydrothermal events mask primary conditions. Iron-rich carbonates in both facies have different origins; diagenetic (Itabira) and post depositional hydrothermal (Manjeri). However, the iron-rich carbonates of both formations have negative ∂13C values, indicating that at least part of the carbon in the carbonates is of organic origin. Curie Balance analyses into the carbonate itabirite reveals that maghemite is the transformation product of the ferrihydrite when dolomite decomposes at ~790°C. The maghemite has a Curie temperature between 320 and 350°C and is stable up to temperatures of 925°C.FIB-TEM investigations into the martitisation process revealed two possible mechanisms from two martite samples, from Brazil and India. Depending of the cause of the martitisation, here found to be deformation and hydrothermalism, the martitisation occurs respectively via either: 1. Ordering of point defects caused by vacancies in the spinel structure of maghemite, due to the removal of excess Fe3+ ions during the oxidation of magnetite, to form twins. It is in this twinning that the martitisation mechanism occurs.2. Grain boundary migration by hematite at the expense of magnetite is due to the presence of fluid along the crystal interfaces, where maghemite forms due to excess Fe3+ produced during martitisation of the magnetite, moving towards the surface of the magnetite crystals.

Depuis quelques décennies, les nanomatériaux et tout particulièrement les nanoparticules d’oxyde de fer (magnétite/maghémite) superparamagnétiques ont connus un intérêt croissant en nano-médecine. Leur biocompatibilité et leurs propriétés magnétiques permettent notamment leur utilisation à des fins de diagnostic (IRM, Imagerie optique et nucléaire…) et de thérapie (Hyperthermie, nano vectorisation…). Au cours de cette thèse, la première étape a consisté à étudier en détails l’influence de plusieurs paramètres de synthèse sur les propriétés finales des nanoparticules d’oxyde de fer magnétique. Cette étude avait pour but de développer et d’optimiser une méthode de synthèse dérivée de la méthode de synthèse classique dite de co-précipitation mais modifiée par ajout de ligand citrates au cours de la synthèse. Des nanoparticules d’oxyde de fer d’une taille pouvant être contrôlée entre 4 et 13 nm recouvertes par une couronne de ligands citrates ont ainsi été synthétisées, celles-ci présentent une aimantation à saturation atteignant jusqu’à 75 emu/g d’oxyde de fer qui est une valeur particulièrement haute pour des nanoparticules de cette taille. Tout au long de ce travail, la caractérisation de ces nanoparticules par un panel étendu de techniques (MET, DRX, Mössbauer, IRTF, XPS, mesures magnétiques, DLS …) à permis notamment d’étudier de façon précise les relations existantes entre la taille, le taux de ligand, la composition et les propriétés magnétiques des nanoparticules synthétisées. Ces nanoparticules fonctionnalisées par des citrates ont ensuite été testées en milieu biologique afin d’évaluer leur internalisation dans les cellules et leur cytotoxicité. Dans un deuxième temps, d’autres travaux ont été menés sur les nanoparticules d’oxyde de fer. Notamment le remplacement des ligands citrates par un polymère bio-inspiré pouvant, selon les fonctions chimiques qui lui sont adjointes, avoir de multiples applications dans le domaine biomédical / From decades now, nanomaterials and especially superparamagnetic iron oxide nanoparticles are studied for their numerous applications in nanomedecine area. The biocompatibility and the magnetic properties of such nano-objects allow their utilization for diagnostic (MRI, optical imagery, PET…) and for therapy application (nanovectorization, hyperthermia…) During this thesis work, the first step was to study the influence of several synthesis parameters on the final properties of the magnetic iron oxide nanoparticles. The aim of this study was the development and the optimization of the widely used way of synthesis by co-precipitation modified by a ligand addition during the growth step of the synthesis. Citrate capped iron oxide nanoparticles with a controlled size between 4 and 13 nm have been synthesized, the saturation magnetization of these nanoparticles reach 75 emu/g of iron oxide, this value is particularly high for nanoparticles of such sizes. During this work, the large panel of characterizations performed on these nanoparticles (TEM, XRD, Mössbauer, FTIR, XPS, DLS, Magnetic measurement) allowed to study precisely the relations between size, ligand ratio, composition and magnetic properties of the synthesized nanoparticles. The interaction between the synthesized citrate capped nanoparticles and biological materials such as human cells have been investigated in-vitro notably to evaluate cells internalization and citotoxicity. In a second step, some additional works have been performed on the citrate capped iron oxide nanoparticles in order to replace the citrate ligand by a bio-inspired polymer (poly-oxazoline). This polymer can have multiple biomedical applications depending of the pendent chemical groups that have been fixed on it

Ce travail de thèse traite de la dynamique ultrarapide de spins et de charges dans des oxydes de fer. Dans un premier temps, on montre à l'aide d'un montage pompe-sonde résolu en temps et exploitant l'effet Faraday magnéto-optique, que le temps de désaimantation dans une assemblée de nanoparticules de maghémite est plus rapide que le temps de désaimantation dans une assemblée de nanoparticules de magnétite. Une superposition des temps de thermalisation des électrons et de désaimantation est observée dans la maghémite. Cette accélération du temps de désaimantation est interprétée comme étant la conséquence d'un renforcement des interactions antiferromagnétiques dans la maghémite. La seconde partie prouve qu'il est possible de caractériser la transition de Verwey dans un film de magnétite grâce à des signaux de dynamique de charges et de spins. La dynamique ultrarapide d'aimantation se caractérise par un mouvement de précession dépendant de la température. D'importantes modifications des oscillations sont visibles de part et d'autre de la température de Verwey, reflétant un changement d'anisotropie caractéristique de cette transition. / This work deals with spins and charges ultrafast dynamics in iron oxide. Thanks to a time-resolved magneto-optical Faraday effect measurements, we show the demagnetization time in an assembly of maghemite nanoparticles is faster than the demagnetization time in an assembly of magnetite nanoparticles. A superposition of thermalization times of electron and demagnetization times is observed in maghemite. This acceleration of the demagnetization time is interpreted as the effect of an enhancement of antiferromagnetic interactions in maghemite. The second part demonstrates the possibility to characterize the Verwey transition in a thin film of magnetite thanks to charges and spins dynamics signals. The ultrafast magnetization dynamic shows a temperature-dependent precession motion. Huge modifications of oscillations are visible on both side of Verwey temperature, reflecting an anisotropy change typical of this transition.

Made available in DSpace on 2014-07-29T15:12:47Z (GMT). No. of bitstreams: 1 dissetacao michelly.pdf: 1756345 bytes, checksum: 8d8e696af201df577651d9a67b7d21e1 (MD5) Previous issue date: 2008-11-25 / Magnetic nanoparticles coated with several kinds of materials have been the focus of intense research due to their potential applications in biomedicine. This type of material contains a magnetic core that is involved by a shell of different composition. The coating of magnetic nanoparticles with amino-functionalized silica is particularly important because of its reactivity which allows the coupling with biological molecules such as fragments of DNA, antibodies, proteins, among others. In this work, maghemite nanoparticles were coated with silica and with amino-functionalized silica, the incorporation of them being achieved by using tetraethoxysilane (TEOS) and aminopropyltrimethoxysilane (APTS) as the precursors of the sol-gel system. Firstly, the magnetic fluids of maghemita were prepared and afterwards they were employed in the silica-coating procedures which were based on the Stöber method. Some experimental parameters were varied, such as the number of maghemita nanoparticles, pH of the reaction medium, time of reaction and amount of TEOS, with the aim of modulating the characteristics of the solids and obtaining stable aqueous suspensions of the materials. All products were analyzed by the following techniques: X- ray diffraction, diffuse reflectance infrared spectroscopy, dynamic light scattering, electrophoretic mobility (zeta potential) and transmission electron microscopy. / Nanopartículas magnéticas recobertas com diversos tipos de materiais tem recebido sido o foco de intensa pesquisa devido a suas aplicações potenciais na área biomédica. Este tipo de material contém um núcleo magnético ( core ) que é envolvido por uma coroa ( shell ) de composição diferente da nanopartícula. O recobrimento de nanopartículas magnéticas com sílica funcionalizada por grupos amino é particularmente importante dada à reatividade deste, possibilitando inclusive o acoplamento de moléculas biológicas, como fragmentos de DNA, anticorpos, peptídeos, dentre outros. Neste trabalho nanopartículas de maguemita foram recobertas com sílica e com sílica funcionalizada com grupos amina, sendo que a incorporação desses materiais ocorreu por meio dos precursores tetraetoxissilano (TEOS) e aminopropiltrimetoxissilano (APTS) utilizando-se de princípios do processo solgel. Primeiramente, foram preparados os fluidos magnéticos de maguemita e, em seguida, estes foram utilizados nos procedimentos de recobrimento da maguemita com sílica, os quais se basearam no método de Stöber. Alguns parâmetros experimentais foram variados, como o número de partículas de maguemita, pH do meio reacional, tempo de síntese e quantidade de TEOS, visando modular as características dos sólidos e obter suspensões aquosas estáveis dos materiais preparados. Os produtos obtidos foram analisados pelas seguintes técnicas: difratometria de raios-X, espectroscopia no infravermelho médio por refletância difusa, espalhamento dinâmico de luz, mobilidade eletroforética (potencial zeta) e microscopia eletrônica de transmissão.

The presence of deposits leading to corrosion of the steam generator (SG) systems is a major contributor to operation and maintenance cost of pressurized water reactor (PWR) plants. Formation and transport of corrosion products formed due to the presence of impurities, metallic oxides and cations in the secondary side of the SG units result in formation of deposits. This research deals with the characterization of deposit samples collected from the two SG units (unit 1 and unit 2) at Comanche Peak Steam Electric Station (CPSES). X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques have been used for studying the compositional and structural properties of iron oxides formed in the secondary side of unit 1 and unit 2. Magnetite (Fe3O4) was found to be predominant in samples from unit 1 and maghemite (g-Fe2O3) was found to be the dominant phase in case of unit 2. An attempt has been made to customize FTIR technique for analyzing different iron oxide phases present in the deposits of PWR-SG systems.

Flow accelerated corrosion (FAC) is a major concern in the power industry as it causes thinning of the pipes by the dissolution of the passive oxide layer formed on the pipe surface. Present research deals with comparing the protection offered by the magnetite (Fe3O4) versus maghemite (γ-Fe2O3) phases thickness loss measurements. Fourier transform infrared spectroscopy (FTIR) is used in distinguishing these two elusive phases of iron oxides. Representative pipes are collected from high pressure steam extraction line of the secondary cycle of unit 2 of Comanche Peak Steam Electric Station (CPSES). Environmental scanning electron microscopy (ESEM) is used for morphological analysis. FTIR and X-ray diffraction (XRD) are used for phase analysis. Morphological analysis showed the presence of porous oxide surfaces with octahedral crystals, scallops and "chimney" like vents. FTIR revealed the predominance of maghemite at the most of the pipe sections. Results of thickness measurements indicate severe thickness loss at the bend areas (extrados) of the pipes.

One of the most challenging goals in nanoparticle research is to develop successful protocols for the large-scale, simple and possibly low-cost preparation of morphologically pure nanoparticles with enhanced properties. The work presented in this thesis was focused on the synthesis, characterisation and testing of magnetic nanoparticles and their potential applications. There are a number of magnetic nano-materials prepared for specific applications such as metal oxide nanoparticles encapsulated with various porous materials including Fe₃O₄/Fe₂O₃ coated with soft bio-organic materials such as glycol chitosan and bovine serum albumin and hard materials such as silica (SiO₂) and zinc sulphide (ZnS). The preparation of these materials was achieved principally by bottom-up methods with different approaches including micro-emulsion, precipitation, electrostatic and thermolysis processes. The thesis also presents the uses of various analytical techniques for characterising different types of nano-materials including Attenuated Total Reflection Fourier Transformer Infrared Vibrational Spectroscopy (ATR-FTIR), Ultraviolet Visible- Near Infrared (UV-Vis-NIR) Spectroscopy, Zeta Potentiometric Surface Charge Analysis, Superconducting Quantum Interference Device (SQUID) and Vibration Sample Magnetometry (VSM) for magnetic analysis and powder X-Ray Diffraction (XRD) for crystallographic pattern analysis. There are many applications of magnetic nanoparticles, including nano-carriers for biological and catalytic reagents. The magnetic nanoparticles can facilitate separation in order to isolate the carriers from solution mixtures as compared to many inefficient and expensive classic methods, which include dialysis membrane, electrophoresis, ultracentrifugation, precipitation and column separation methods. There are six key chapters in this thesis: the first chapter introduces the up-to-date literature regarding magnetic nano-materials. The uses of magnetic nano-materials in drug binding and for protein separation are discussed in the second and third chapters. The fourth chapter presents the use of magnetic nanoparticle in conjunction with a photo-catalytic porous overlayer for the photo-catalytic reduction of organic molecules. The fifth chapter describes different analytical techniques used for the characterisation of nanoparticles and the underlying principles and the experimental details are also given. The sixth chapter summarises the results and provides an overview of the work in a wider context of future applications of magnetic nanoparticles.