Le cancer est une cause majeure de décès dans le monde, 7,6 millions de décès en 2008. Bien que de nombreux progrès ont été réalisés dans le traitement du cancer, de nouvelles approches sont nécessaires afin de minimiser les effets secondaires délétères et d'augmenter le taux de survie. Par conséquent, l'avenir de la nanomédecine réside dans le développement de nano-plateformes multifonctionnelles. Il ne fait aucun doute que les hybrides organique / inorganique à base de dendrons représentent des outils très avancés, capables de cibler spécifiquement et d'être suivis par imagerie en même temps. Dans ce contexte, les objectifs de cette thèse sont non seulement la conception de nano-objets magnétiques dendronisés biocompatibles permettant à la fois le diagnostic par imagerie à résonance magnétique (IRM) ainsi que par imagerie optique (IO) mais également la validation in vitro et in vivo des propriétés de ces nano-objets et la démonstration de leur efficacité pour le ciblage spécifique de tumeurs. / Cancer is a worldwide leading cause of death, 7.6 million deaths in 2008 with 13% mortality. Although much progress has been made in early cancer diagnosis and treatment, new approaches are needed to minimize the deleterious side effects while increasing survival rate. Therefore, the future of Nanomedicine relies in the development of multifunctional nano-platforms that combine therapeutic components, multimodal imaging and active targeting. Organic/inorganic dendrimer-based hybrids are very advanced tools, especially for targeting a specific cell type or a particular organ and for being followed by imaging techniques at the same time.In this context, the objective of this thesis is not only the design of multifunctional magnetic dendronized nano-objects, but also their in vitro and in vivo validation and assessment of their active targeting effectiveness.

Comme les propriétés physiques d'un matériau à l’échelle nanométrique sont largement dépendantes de la taille et de la forme des nanostructures, il est inutile de synthétiser de nouvelles compositions et morphologies. L’étude avancée de leur structure par les techniques de caractérisation usuelles (MET, MEB, DRX, Raman…) permettra de collecter toutes les informations nécessaires à la compréhension de leurs propriétés physiques (magnétiques, optiques, électriques). Dans ce manuscrit, nous décrirons plusieurs approches d’élaboration de nanostructures 0D, 1D et 2D multifonctionnelles afin de mieux connaître les paramètres qui contrôlent leur composition chimique et leur structure. De plus, ce travail de recherche a abouti à la synthèse de nouveaux matériaux à base d’oxyde et de carbure de fer. Des nanofibres magnétiques ayant des morphologies originales « Ruban » et « tube » ont été élaborées par la technique d’électrospinning en modifiant plusieurs paramètres expérimentaux : concentration de la solution, atmosphères de traitement thermique, température de recuit… De plus, des couches minces guidantes dopées par des nanostructures magnétiques ont été préparées par la technique dip-coating. Nous avons mené une étude complexe et détaillée sur les propriétés structurales de ces matériaux afin de définir les paramètres expérimentaux qui permettront d’obtenir des nano objets de bonne qualité. Dans un but ultime, nous souhaiterons explorer les possibilités d’application de ces matériaux qui présentent à la fois des caractéristiques électriques et magnétiques. / The physical properties of a nanomaterial strongly depend on the size and the shape of the nanostructure. As a consequence, it is interesting to elaborate new materials with different compositions and morphologies. The advanced study on the structure using common characterization techniques (TEM, MEB, XRD, Raman…) allows us to collect all the important information on their physical properties (magnetic, optical and electrical properties). In this thesis, we describe multiple ways to elaborate multifunctional nanostructures with 0D, 1D and 2D in order to study the parameters that control their chemical composition and structure. Besides, this research lead to the elaboration of new nanomaterials based on the oxide and the carbide forms of iron. Magnetic nanofibers with different morphologies (belts, tubes) were prepared using the electrospinning technique while controlling several experimental parameters : solution concentration, pyrolysis atmosphere, thermal treatment temperature… Moreover, thin layers doped with magnetic nanostructures were deposited on a pyrex substrate using the dip-coating technique. A full and detailed study on their structural properties was performed in order to reach the experimental parameters that allow us to obtain high quality products. Finally, we wish to explore the possible applications of these materials that present interesting electrical and magnetic characteristics.

Le soudage à l’arc avec fil fusible est un procédé très utilisé, mais la compréhension des mécanismes régissant son fonctionnement comporte toujours quelques interrogations compte tenu de sa complexité. La composition du gaz de protection a une très forte influence sur le procédé : l’ajout de gaz actif modifie, par exemple, le courant nécessaire à la transition entre les différents régimes et est responsable de l’apparition d’oxyde de fer (gangue) à l’extrémité du fil fusible. Pour mener à bien l’étude du soudage MIG-MAG sous mélanges Ar-CO₂-O₂, plusieurs études sont réalisées pour caractériser et mieux comprendre les phénomènes physico-chimiques qui gouvernent le soudage MIG-MAG afin d’optimiser à terme le procédé. Un diagnostic spectroscopique, avec la mise en place d’un système d’acquisition composé de deux spectromètres qui permet d’enregistrer simultanément les raies spectrales de fer et d’argon, permet d’évaluer les distributions radiales de température et densité électronique dans la colonne de plasma. Une étude par cinématographie rapide est également menée pour tenter d’évaluer la formation et l’écoulement de la couche d’oxyde apparaissant en régime globulaire à la surface de l’anode fusible. Et enfin, des analyses micrographiques des électrodes sont réalisées pour étudier l’influence des modifications chimiques et structurales sur le comportement général du procédé pour différents types de paramètres utilisés. Les conséquences d’un changement de gaz de protection sont également appréhendées : Ar-CO₂, Ar-O₂ et Ar-CO₂-O₂. Il s’avère que la température électronique de l’arc évolue en présence d’oxygène dans le gaz de protection et que la modification du gaz actif modifie le type d’oxyde de fer formé. / The arc welding with consumable wire is a process widely used, but understanding the mechanisms governing its operation still has some questions given its complexity. The composition of the shielding gas has a very strong influence on the process: the addition of active gas changes, for example, the current necessary for the transition between the different metal transfers and is responsible for the appearance of an iron oxide (gangue) at the end of the consumable wire. To carry out the study of MIG-MAG welding under mixtures Ar-CO₂-O₂, several studies are performed to characterize and understand the physical and chemical phenomena that govern the MIG-MAG welding to optimize the process. A spectroscopic diagnosis, with the establishment of an acquisition system consisting of two spectrometers to record simultaneously the iron and argon spectral lines, allows to estimate the radial distributions of temperature and electron density in the plasma column. A study by rapid cinematography is also conducted to try to estimate the formation and flow of the iron oxide layer appearing in globular regime on the surface of the anode consumable. And finally, micrographic analyzes of the electrodes are made to study the influence of chemical and structural changes on the general behavior of the process for different types of parameters used. The consequences of a shielding gas change are also apprehended: Ar-CO₂, Ar-O₂ and Ar-CO₂-O₂. It turns out that the electron temperature of the arc changes in the presence of oxygen in the shielding gas and the change of the active gas modifies the type of iron oxide formed.

L’objectif de ce travail a été la préparation de nanoparticules pour l’administration intratumorale. Ladouble functionalisation de ces nanoparticules est rapidement approuve comme extrement intéressant, car ellespeuvent être utilisé pour le diagnostic in vivo et la thérapie (théranostics). Pour réaliser ce type desnanoparticules, l’oxyde de fer a été choisi comme agent de contraste pour une utilisation en imagerie parrésonance magnétique (IRM) pour le diagnostic de cellules cancéreuse. Les nanoparticules d’oxyde de fer ont étépréparées dans des milieux aqueux et organique. La méthode d’émulsification multiple suivie de l’évaporationde solvant a été utilisée pour l’encapsulation concomitante d’un principe actif et des nanoparticules de l’oxydede fer. Tous les paramètres affectant la taille des nanoparticules pendant le procédé ont été étudiés en utilisantune molécule active hydrophile modèle (une dérivative de la Stilbene) et le protocole standard a ensuite étéévalué. Dans une seconde étape, les particules d’oxyde de fer ont été encapsulées par la même méthoded’émulsion évaporation et entièrement caractérisées en termes de morphologie, taille, magnétisation, etcomposition chimique. La visualisation in vitro des particules modèles a été réalisée par IRM et comparée a unproduit commercial à base de Gadolinium (Gd). D’autre part, la quantité nécessaire d’oxyde de fer permettantune bonne visualisation par IRM a été déterminée par une étude in vivo menée sur des souris. Enfin la doubleencapsulation d’oxyde de fer avec une molécule anticancéreuse a été effectuée par la méthode développée, laformulation obtenue a été entièrement caractérisée. / The objective of this work was the preparation of nanoparticles for intratumoral administration.Important characteristic was dual functionality of these nanoparticles that they can be used for diagnosis andtherapy so the resulting nanoparticles will serve as theranostic agents. For this purpose iron oxide was chosen asa contrast agent to be used in Magnetic resonance imaging (MRI) for diagnosis of cancerous cells. Iron oxidenanoparticles (IONPs) were prepared in aqueous and organic medium. A multiple emulsion evaporation methodwas designed for the encapsulation of active ingredient (hydrophilic drug i-e Stilbene) and the IONPs. All theparameters affecting the colloidal properties final hybrid particles were studied and characterization was done forfinal particles. Then prepared particles were evaluated for in vitro MRI and also compared with commerciallyavailable products such as gadolinium (Gd). At same time, the minimum detectable quantity of iron oxide in vivowas determined using a commercialized iron oxide emulsion on rat models. Finally an anticancer agent wasencapsulated with IONPs using same multiple emulsion method and characterization was done.

Metal oxide reactions at metal oxide surfaces or at metal-metal oxide interfaces are of exceptional significance in areas such as catalysis, micro- and nanoelectronics, chemical sensors, and catalysis. Such reactions are frequently complicated by the presence of high electric fields and/or H2O-containing environments. The focus of this research was to understand (1) the iron oxide growth mechanism on Fe(111) at 300 K and 500 K together with the effect of high electric fields on these iron oxide films, and (2) the growth of alumina films on two faces of Ni3Al single crystal and the interaction of the resulting films with water vapor under non-UHV conditions. These studies were conducted with AES, LEED, and STM. XPS was also employed in the second study. Oxidation of Fe(111) at 300 K resulted in the formation of Fe2O3 and Fe3O4. The substrate is uniformly covered with an oxide film with relatively small oxide islands, i.e. 5-15 nm in width. At 500 K, Fe3O4 is the predominant oxide phase formed, and the growth of oxide is not uniform, but occurs as large islands (100 - 300 nm in width) interspersed with patches of uncovered substrate. Under the stress of STM induced high electric fields, dielectric breakdown of the iron oxide films formed at 300 K occurs at a critical bias voltage of 3.8 ± 0.5 V at varying field strengths. No reproducible result was obtained from the high field stress studies of the iron oxide formed at 500 K. Ni3Al(110) and Ni3Al(111) were oxidized at 900 K and 300 K, respectively. Annealing at 1100 K was required to order the alumina films in both cases. The results demonstrate that the structure of the 7 Å alumina films on Ni3Al(110) is k-like, which is in good agreement with the DFT calculations. Al2O3/Ni3Al(111) (γ'-phase) and Al2O3/Ni3Al(110) (κ-phase) films undergo drastic reorganization and reconstruction, and the eventual loss of all long-range order upon exposure to H2O pressure > 10-5 Torr. Al2O3/Ni3Al(110) film is significantly more sensitive to H2O vapor than the Al2O3/Ni3Al(111) film, and this may be due to the incommensurate nature of the oxide/Ni3Al(110) interface. STM measurements indicate that this effect is pressure- rather than exposure- dependent, and that the oxide instability is initiated at the oxide surface, rather than at the oxide/metal interface. The effect is not associated with formation of a surface hydroxide, yet is specific to H2O (similar O2 exposures have no effect).

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.

Egg (the whole, the yolk or the white) is a natural product used since ancient times as tempera painting medium mainly in Europe and the Mediterranean Basin countries. In addition, egg is a complex multicomponent microstructured system susceptible of being influenced by the pigments that compose the paints, as well as a source of nutrient susceptible of biodeterioration. Modifying effect of artists' pigments on the binding medium as well as, the microbial biodeterioration are responsible for changes in the structure and composition of the binding medium and, consequently, on the physico-chemical properties of the paint. For this purpose, analytical techniques such as Fourier transform infrared spectroscopy - attenuated total reflection (FTIR-ATR) was used for the chemical characterization, Field emission scanning microscopy (FESEM) and Atomic force microscopy - nanoindentation (AFM-nanoindentation) were run for morphological and mechanical characterization of the deterioration processes resulted from the pigment-binder interactions involved in tempera painting. On the other hand, the current research report the application of the voltammetry of microparticles (VMP), complemented with FTIR-ATR, FESEM and AFM-nanoindentation techniques to monitor the deterioration of a series of tempera reconstructed model paint specimens under the action of different biological agents. This methodology would be of application for identifying the type of biological agent causing deterioration of painting, which is an important problem affecting cultural heritage. The analysis of biodeterioration processes is complicated by the fact that the action of microorganisms can affect both pigment and binding media. The deterioration of pictorial specimens by Acremonium chrysogenum, Aspergillus niger, Mucor rouxii, Penicillium chrysogenum and Trichoderma pseudokoningii fungi and Arthrobacter oxydans, Bacillus amyloliquefaciens and Streptomyces cellulofans bacteria was tested using sample-modified graphite electrodes immersed into aqueous electrolytes. Finally, the study carried out by means of FTIR-ATR, FESEM and AFM-nanoindentation confirms that egg proteins attached to the pigment grains changes their secondary structures. The results obtained also confirm that proteins and phospholipids are prevalently established linkages with the solid particles of pigment whereas triglycerides should be integrated in the complex binding network responsible for the cohesion of the paint film. Interactions between egg components with solid pigment particles are described and correlated with micromorphology and mechanical properties determined at micro- and nano-scale on the reconstructed model paint specimens. As a result of the crossing of VMP data with the results obtained by means of FTIR, FESEM and AFM-nanoindentation, the voltammetric signals obtained were associated to the electrochemical reduction of pigments and different complexes associated to the binding media. These results were particularly relevant in the study of biodeterioration, to allowing the electrochemical monitoring of biological attack. / El huevo (entero, yema o clara) es un producto natural utilizado desde la antigüedad como medio aglutinante en la pintura al temple, principalmente en Europa y los países de la cuenca mediterránea. Además, el huevo es un complejo sistema multicomponente microestructurado susceptible de ser alterado por los pigmentos que componen las pinturas, así como fuente de nutrientes susceptible de biodeterioro. El efecto de los pigmentos sobre el medio aglutinante, así como el biodeterioro microbiano son responsables de cambios en la estructura y composición del medio aglutinante y, por consiguiente, en las propiedades fisicoquímicas de la pintura. Es por esto que, se utilizaron técnicas analíticas como la Espectroscopía Infrarroja por Transformada de Fourier en modo Reflexión Total Atenuada (FTIR-ATR), para la caracterización química de los procesos de deterioro resultantes de las interacciones pigmento-aglutinante en la pintura al temple. Así mismo, se utilizó Microscopía Electrónica de Emisión de Barrido (FESEM) para el estudio morfológico de las muestras, y para el estudio de las propiedades mecánicas Microscopía de Fuerza Atómica en modo Nanoindentación (AFM-nanoindentación). Por otro lado, la presente investigación propone el uso de la Voltamperometría de Micropartículas (VMP), en conjunto con otras técnicas de análisis como FTIR-ATR, FESEM y AFM-nanoindentación para el estudio del biodeterioro producido por hongos y bacterias sobre una serie muestras pictóricas sometidas. El estudio de las alteraciones causadas por el biodeterioro es complicado por el hecho de que la acción de los microorganismos puede afectar tanto al pigmento como al medio aglutinante. Para esto, se prepararon una serie de muestras de pinturas al temple y emulsión que fueron inoculadas con los hongos Acremonium chrysogenum, Aspergillus niger, Mucor rouxii, Penicillium chrysogenum, y Trichoderma pseudokoningii, y las bacterias Arthrobacter oxydans, Bacillus amyloliquefaciens y Streptomyces cellulofans. El estudio voltamperometrico se realizó utilizando electrodos de grafito modificados con las muestras inmersos en un electrolito acuoso. Las conclusiones obtenidas de manera general, apuntan a que las proteínas presentes en el huevo cambian su estructura secundaria al adherirse a los granos de pigmento. La información química, morfológica y mecánica obtenida por las diferentes técnicas de análisis instrumental es consistente. Finalmente, como resultado del cruce de los datos VMP con los resultados obtenidos mediante FTIR, FESEM y AFM-nanoindentación, las señales voltamperometricas obtenidas se asociaron a la reducción electroquímica de los pigmentos y a los complejos formados con el medio aglutinante. Estos resultados fueron particularmente relevantes en el estudio del biodeterioro de las películas pictóricas inoculadas, para permitir la monitorización electroquímica del ataque microbiológico. / L'ou (sencer, rovell o clara) és un producte natural utilitzat des de l'antiguitat com a mitjà aglutinant en la pintura al tremp, principalment a Europa i els països de la conca mediterrània. A més, l'ou és un complex sistema multicomponent MICROESTRUCTURAT susceptible de ser alterat pels pigments que componen les pintures, així com a font de nutrients susceptible de biodeterioració. L'efecte dels pigments sobre el medi aglutinant, així com el BIODETERIORI microbià són responsables de canvis en l'estructura i composició del medi aglutinant i, per tant, en les propietats fisicoquímiques de la pintura. És per això que, es van utilitzar tècniques analítiques com l'Espectroscòpia Infraroja per Transformada de Fourier en mode Reflexió Total Atenuada (FTIR-ATR), per a la caracterització química dels processos de deteriorament resultants de les interaccions pigment-aglutinant en la pintura al tremp. Així mateix, es va utilitzar Microscòpia Electrònica d'emissió de Rastreig (FESEM) per a l'estudi morfològic de les mostres, i per a l'estudi de les propietats mecàniques Microscòpia de Força Atòmica en mode Nanoindentació (AFM-nanoindentació). D'altra banda, la present investigació proposa l'ús de la Voltamperometría de Micropartícules (VMP), en conjunt amb altres tècniques d'anàlisi, com FTIR-ATR, FESEM i AFM-nanoindentació per a l'estudi de l'biodeterioració produït per fongs i bacteris sobre una sèrie de mostres pictòriques sotmeses. L'estudi de les alteracions causades pel biodeteriori és complicat pel fet que l'acció dels microorganismes pot afectar tant el pigment com al medi aglutinant. Per això, es van preparar una sèrie de mostres de pintures al tremp i emulsió que van ser inoculades amb els fongs Acremonium chrysogenum, Aspergillus niger, Mucor rouxii, Penicillium chrysogenum, i Trichoderma pseudokoningii i els bacteris Arthrobacter oxydans, Bacillus amyloliquefaciens i Streptomyces cellulofans. L'estudi voltamperomètric es va realitzar utilitzant electrodes de grafit modificats amb les mostres immersos en un electròlit aquós. Les conclusions obtingudes de manera general, apunten que les proteïnes presents en l'ou canvien la seva estructura secundària al adherir-se als grans de pigment. La informació química, morfològica i mecànica obtinguda per les diferents tècniques d'anàlisi instrumental és consistent. Finalment, com a resultat de l'encreuament de les dades VMP amb els resultats obtinguts mitjançant FTIR, FESEM i AFM-nanoindentació, els senyals voltamperomètrics obtinguts es van associar a la reducció electroquímica dels pigments i als complexos formats amb el medi aglutinant. Aquests resultats van ser particularment rellevants en l'estudi del biodeteriori de les pel·lícules pictòriques inoculades, per tal de permetre la monitorització electroquímica de l'atac microbiològic. / Ortiz Miranda, A. (2017). Development of analytical methods for the characterization of tempera paintings at micro- and nano-scale and their deterioration and biodeterioration processes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90571 / TESIS

Development of microsized batteries plays an important role in the design of in-situ electrochemical investigation systems and portable/wearable electronics. This emerging field intimately correlates with the topics of rechargeable batteries, nanomaterials, on-chip microfabrication, flexibility with reliable mechanical properties etc. Among the various energy materials, conversion-type materials have been proposed as high-energy-density alternatives to traditional intercalation-based materials. However, these materials usually show complex reaction processes accompanied by multi-reaction intermediates, which poses a great challenge to understand the chemical mechanisms. Benefiting from the merits of microsized battery devices, we develop a novel strategy to investigate and then optimize the electrochemical performance of a specific conversion-type material: nickel-iron oxide (NFO). Subsequently, this kind of materials are employed for flexible minimized energy storage systems. Unlike traditional characterization methods based on slurry-coated electrodes, micro-platforms directly probe the intrinsic electrochemical properties of a single active material in real-time due to the elimination of other additives. In this thesis, we firstly design a micro-lithium batteries (MLBs), based on a single “Swiss-roll” microtubular nanomembrane electrode. This platform enables us to investigate the electrochemical mechanisms of electrode materials in lithium batteries by in-situ Raman spectroscopy, electrical conductivity measurements, and electrochemistry characterization. With this designed MLBs, we systematically studied NFO nanomembranes. Using in-situ Raman spectroscopy during the delithiation/lithiation process, we monitored the transition of the chemical component directly. Guided by our investigations of micro-batteries, composite NFO nanomembrane electrodes were fabricated and tested in coin cells, which showed an excellent rate performance: 440 mAh g-1 at a high rate of 20 A g-1 and a long-term stable cycling performance over 1600 cycles. One step further, a flexible energy storage micro-device is achieved using such optimized materials. We demonstrate a thin, lightweight, and flexible micro-full lithium-ion battery based on nickel-iron oxide with a high-rate performance and energy density that can be repeatedly bent to 180° without structural failure and performance loss. It delivers a stable output capacity of 140 mAh g-1 over 1000 charge/discharge cycles. Meanwhile, the excellent rate performance guarantees high energy output up to 255 W h kg-1 at a high power density of 12000 W kg-1 at the microscale.

The synthesis, characterization and biological evaluation of different graphene-based nanoparticles with potential biomedical applications are explored. The results presented within this work show that eukaryotic cells can respond differently not only to different types of nanoparticles, but also identify slight differences in the morphology of nanoparticles, such as size. This highlights the great importance of the synthesis and thorough characterization of nanoparticles in the design of effective nanoparticle platforms for biological applications. In order to test the influence of morphology of graphene-based nanoparticles on the cell response, nanoparticles with different sizes were synthesized and tested on different cells. The synthesis of spherical iron-oxide nanoparticles coated with graphene was accomplished using a colloidal chemistry route. This synthesis route was able to render nanoparticle samples with narrow size distributions, which can be taken as monodispersed. Four different samples varying in diameter from 10 to 20 nm were produced and the material was systematically characterized prior to the biological tests. The characterization of the material suggests that the iron oxide nanoparticles consist of a mix of both magnetite and maghemite phases and are coated with a thin graphitic layer. All samples presented functional groups and were similar in all aspects except in diameter. The results suggest that cells can respond differently even to small differences in the size of the nanoparticles. An in situ study of the coating of the iron-oxide nanoparticles using a transmission electron microscope revealed that it is possible to further graphitize the remaining oleic acid on the nanoparticles. The thickness of the graphitic coating was controlled by varying the amount of oleic acid on the nanoparticles. The in situ observations using an electron beam were reproduced by annealing the nanoparticles in a dynamic vacuum. This procedure showed that it is not only possible to coat large amounts of iron oxide nanoparticles with graphene using oleic acid, but also to improved their magnetic properties for other applications such as hyperthermia. This study therefore revealed a facile route to grow 2D graphene takes on substrates using oleic acid as a precursor. The synthesis of nanographene oxide nanoparticles of different sizes was in a second approach accomplished by using the Hummers method to oxidize and expand commercially available graphite. The size of the oxidized graphite was adjusted by sonicating the samples for different periods of time. The material was also thoroughly characterized and demonstrated to have two distinctive average size distributions and possess functional groups. The results suggest that different size flakes can trigger different cell response. The synthesis, characterization and biological evaluation of graphene nanoshells were performed. The graphene nanoshells were produced by using magnesia nanoparticles as a template to the graphene nanoshells. The coating of magnesia with graphene layers was accomplished using chemical vapor deposition. The nanoshells were obtained by removing the magnesia core. The size of the nanoshells was determined by the size of the magnesia nanoparticles and presented a broad size distribution since the diameter of the magnesia nanoparticles could not be controlled. The nanoshells were also characterized and the biological evaluation was performed in the Swiss Federal Laboratories for Materials Science and Technology (EMPA), in Switzerland. The results suggest that despite inducing the production of reactive oxygen species on cells, the nanoshells did not impede cell proliferation. / Die Herstellung, Charakterisierung und biologische Auswertung von verschiedenen Graphen-basierten Nanopartikeln mit einer potenziellen biomedizinischen Anwendung wurden erforscht. Die vorgestellten Ergebnisse im Rahmen dieser Arbeit zeigen, dass eukaryotische Zellen unterschiedlich reagieren können, wenn sie mit Nanopartikeln unterschiedlicher Morphologie interagieren. Die Zellen können geringe Unterschiede in der Morphologie, insbesondere der Größe der Nanopartikeln, identifizieren. Dies unterstreicht den Einfluss der Herstellungsmethoden und die Notwendigkeit einer gründlichen Charakterisierung, um ein effektives Design von Nanopartikeln für biologische Anwendungen zu erreichen. Um den Einfluss der Größe von Graphen-basierten Nanopartikel auf das Zellverhalten zu erforschen, wurden verschiedene Graphen-beschichte Eisenoxid-Nanopartikelproben durch eine kolloidchemische Methode hergestellt. Dieses Herstellungsverfahren ermöglicht die Synthese von Nanopartikeln mit engen Größenverteilungen, die als monodispers gelten können. Vier Proben mit unterschiedlichen Durchmessern (von 10 bis 20 nm) wurden hergestellt und vor den biologischen Untersuchungen systematisch charakterisiert. Die Probencharakterisierung deutet auf eine Mischung aus Magnetit- und Maghemit-Kristallphasen hin, außerdem besitzen die Nanopartikel eine dünne Graphitschicht. Die spektroskopischen Ergebnisse auch zeigen außerdem, dass alle Proben funktionelle Gruppen auf ihrer Oberfläche besitzen, sodass sie in allen Aspekten, außer Morphologie (Durchmesser), ähnlich sind. Die biologischen Untersuchungen deuten darauf hin, dass Zellen unterschiedliche Größen von Eisenoxid-Nanopartikeln reagieren können. Ein in situ Untersuchung der Beschichtung der Eisenoxid-Nanopartikel wurde mit einem Transmissionelektronenmikroskop durchgeführt. Die Ergebnisse zeigen, dass eine dünne Schicht von Ölsäure aus dem Syntheseprozess auf den Nanopartikeln verbleibt. Diese Schicht kann mit einem Elektronstrahl in Graphen umgewandelt werden. Die Dicke der Graphitschicht auf den Nanopartikeln kann durch die Menge der eingesetzten Ölsäure kontrolliert werden. Die in situ Beobachtungen der Graphenumwandlung konnte durch erhitzen der Nanopartikeln in einem dynamischen Vakuum reproduziert werden. Das Brennen der Eisenoxid-Nanopartikel ermöglicht nicht nur die Graphitisierung der Ölsäure, sondern auch eine Verbesserung der magnetischen Eigenschaften der Nanopartikel für weitere Anwendungen, z. B. der Hyperthermie. Die Umwandlung der Ölsäure in Graphen konnte so als relativ einfaches Verfahren der Beschichtung von zweidimensionalen (2D) Substraten etabliert werden. Die Herstellung von Nanographenoxid mit unterschiedlichen Größen wurde mit der Hummers-Method durchgeführt. Die unterschiedlichen Größen der Nanographenoxidpartikel wurde durch eine Behandlung in Ultraschallbad erreicht. Zwei Proben mit deutlicher Verteilung wurden mit mehreren Verfahren charakterisiert. Beide Proben haben Nanographenoxid Nanoteilchen mit verschiedenen funktionellen Gruppen. Die biologische Charakterisierung deutet darauf hin, dass unterschiedliche Größen des Nanographens ein unterschiedliches Zellverhalten auslösen. Abschließend, wurde die Herstellung, Charakterisierung und biologische Auswertung von Graphen-Nanoschalen durchgeführt. Die Graphen-Nanoschalen wurden mit Magnesiumoxid-Nanopartikeln als Template hergestellt. Die Beschichtung des Magnesia mit Graphen erforgte durch die chemische Gasphasenabscheidung. Die Nanoschalen wurden durch Entfernen des Magnesia-Kerns erhalten. Die Größe der Nanohüllen ist durch die Größe der Magnesia-Kerns bestimmt und zeigt eine breite Verteilung, da der Durchmesser der Magnesiumoxid-Nanopartikel gegeben war. Die Nanoschalen wurden ebenfalls mit Infrarot- und Röntgen Photoemissionspektroskopie charakterisiert und die biologische Bewertung wurde im Eidgenössische Materialprüfungs- und Forschungsanstalt (EMPA) durchgeführt, in der Schweiz. Die Ergebnisse zeigen, dass zwar die Produktion von reaktiven Sauerstoffspezies in den Zellen ausgelöst wird, diese sich aber weiterhin vermehren können.

There is a demand for new straightforward approaches for stabilization and solubilization of various nanoparticulate materials in their colloidal form, that pave way for fabrication of materials possessing compatibility with wide range of dispersing media. Therefore in this thesis a new general method to form stable nanocrystals in water and organics using amphiphilic polymers generated through simple and low cost techniques is presented and discussed. Amphiphilic coating agents are formed using thiolated or carboxylated polyethylene glycol methyl ether (mPEG-SH) as a starting material. These materials are available with a wide variety of chain lengths. The method of obtaining of amphiphilic NPs is quite general and applicable for semiconductor CdTe nanocrystals as well as nanoscale noble metal (Au) and magnetic (Fe3O4) particles. This approach is based on anchoring PEG segment to the surface of a nanoparticle to form an amphiphilic palisade. Anchoring is realized via interaction of –SH (for CdTe and Au) or –COOH (in the case of magnetite) functional groups with particle’s surface. The resulting amphiphilicity of the nanocrystals is an inherent property of their surface and it is preserved also after careful washing out of solution of any excess of the ligand. The nanocrystals reversibly transfer between different phases spontaneously, i.e. without any adjustment of ionic strength, pH or composition of the phases. Such reversible and spontaneous phase transfer of nanocrystals between solvents of different chemical nature has a great potential for many applications as it constitutes a large degree of control of nanocrystals compatibility with technological processes or with bio-environments such as water, various buffers and cell media as well as their assembly and self-assembly capabilities.