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Dissertations / Theses on the topic 'Magnetite Synthesis'

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Published: 10 December 2022
Last updated: 28 January 2023

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1

Ragheb, Ragy. "Synthesis and Characterization of Polylactide-siloxane Block Copolymers as Magnetite Nanoparticle Dispersion Stabilizers." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31687.

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Polylactide-siloxane triblock copolymers with pendent carboxylic acid functional groups have been designed and synthesized for study as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest in a variety of biomedical applications, including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties.

The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes.
Master of Science

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2

Pradhan, Anindya. "Synthesis and Characterization of Novel Nanoparticles for Use as Photocatalytic Probes and Radiotracers." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/689.

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Two novel synthetic routes to formation of gold-magnetite nanoparticles have been designed. Treatment of preformed magnetite nanoparticles with ultrasound in aqueous media with dissolved tetrachloroauric acid resulted in the formation of gold-magnetite nanocomposite materials. The other route involved irradiation of preformed magnetite nanoparticles by UV light in aqueous media with dissolved tetrachloroauric acid. This method resulted in the formation of gold-magnetite nanocomposite materials. These materials maintained the morphology of the original magnetite particles. The morphology of the gold particles could be controlled by adjusting experimental parameters, like addition of small amounts of solvent modifiers such as methanol, diethylene glycol, and oleic acid as well as variation of the concentration of the tetrachloroauric acid solution and time of the reaction. The nanocomposite materials were magnetic and exhibited optical properties similar to gold nanoparticles. Since we were not able to directly synthesize core shell gold magnetite nanoparticles, TiO2 was used as a bridging material. TiO2 nanoparticles with embedded magnetite were suspended in aqueous HAuCl4 and irradiated with ultraviolet light to photodeposit gold. The degree of gold coating and the wavelength of absorbance could be controlled by adjusting concentration of HAuCl4. Absorbance maxima were between 540-590 nm. Particles exhibited superparamagnetic properties (blocking temperature ~170 K) whether or not coated with gold. These particles have potential applications as drug delivery agents, magnetic imaging contrast agents, and magnetically separatable photocatalysts with unique surface properties. Another goal was to synthesize and characterize indium doped magnetite nanoparticles for application as radiotracers for in vivo fate studies. The labeled particles will be useful for determination of pharmacological behavior in biological systems. Indium doped magnetite particles with varying size and surface chemistry were synthesized with wet chemical techniques. The synthesized nanoparticles were characterized in terms of the size and shape with the help of TEM, the elemental composition by ICP and EDS, the crystal structure by XRD and magnetic properties by SQUID measurements. It was found that the indium loading could be controlled even though the magnetic properties were similar to undoped magnetite.
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3

Zhang, Qian. "Synthesis and Characterization of Novel Magnetite Nanoparticle Block Copolymer Complexes." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27327.

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Superparamagnetic Magnetite (Fe3O4) nanoparticles were synthesized and complexed with carboxylate-functionalized block copolymers, and aqueous dispersions of the complexes were investigated as functions of their chemical and morphological structures. The block copolymer dispersants possessed either poly(ethylene oxide), poly(ethylene oxide-co-propylene oxide), or poly(ethylene oxide-b-propylene oxide) outer blocks, and all contained a polyurethane center block with pendant carboxylate functional groups. The complexes were formed through interactions of the carboxylates with the surfaces of the magnetite nanoparticles. Initial efforts utilized an aqueous coprecipitation method for the synthesis of magnetite nanoparticles, which yielded polydisperse magnetite nanoparticles. The nanoparticle complexes were characterized with a range of solution- and solid-state techniques including TGA, XPS, TEM, VSM, DLS and zeta potential measurements. DLVO calculation methods, which sum the contributions from van der Waals, steric, electrostatic and magnetic forces were utilized to examine the interparticle potentials in the presence and absence of external magnetic fields. Compositions were identified wherein a shallow, attractive interparticle potential minimum appears once the magnetic term is applied. This suggested the possibility of tuning the structures of superparamagnetic nanoparticle shells to allow discrete dispersions without a field, yet permit weak flocculation upon exposure to a field. This property has important implications for biomedical applications where movement of particles with an external magnetic field is desirable. In a second study, well-defined, narrow size dispersity magnetite nanoparticles were synthesized via the thermolysis of an iron (III) acetylacetonate (Fe(acac)3) precursor in the presence of benzyl alcohol. The magnetite nanoparticles were coated with triblock and pentablock copolymers possessing poly(ethylene oxide) and poly(propylene oxide-b-ethylene oxide) tailblocks and the carboxylate-functional anchor block. DLVO calculations were applied to the new magnetite particles and diagrams of potential energy versus interparticle distance indicated the predominant effect of steric and magnetic interactions on the particle stability. Exposure of the pentablock copolymer-magnetite complexes in phosphate buffered saline to a 1500 Oe magnetic field with concomitant DLS measurements indicated flocculation of the magnetic nanoparticles. DLS measurements showed increased hydrodynamic radii and scattering intensities with time.
Ph. D.
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4

Goff, Jonathan. "Synthesis and Characterization of Novel Polyethers and Polydimethylsiloxanes for Use in Biomaterials." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26290.

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This dissertation focuses on the use of novel polyethers and polydimethylsiloxanes in the stabilization of magnetite nanoparticles as well as biomedical applications. The colloidal stabilities of magnetite nanoparticles coated with polyethers containing various functional endgroups were studied. Different variables (e.g. polymer loading, polyether molecular weight and type of functional anchor group) were investigated to determine their effect on the long-term physiological stability of the polyether magnetite complexes. One-part PDMS-magnetite nanoparticle fluids were synthesized using a high shear process and magnetic separation techniques. These one-part fluids are unique in the fact that they do not require the addition of a non-functional PDMS oligomer solvent to generate a magnetic hydrophobic fluid. A series of PDMS-magnetite nanoparticle fluids containing different molecular weight stabilizers were synthesized. A magnetic separation study was performed to determine if PDMS molecular weight influences the magnetic separation profiles of the fluids. Well-defined PDMS-b-PtBA and PDMS-b-poly(acrylic acid) copolymers were synthesized using living free radical techniques from novel PDMS precursors as well as PDMS-based ionenes with different hard segment groups.
Ph. D.
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5

Muro, Cruces Javier. "Improved synthesis routes and coating approaches of anisotropic magnetite nanoparticles for theranostics." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669374.

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Esta tesis aborda la síntesis, caracterización y funcionalización de nanoestructuras magnéticas biocompatibles y anisótropas de óxido de hierro (Fe3O4) para su aplicación en diagnóstico biomédico mediante imagen de resonancia magnética (MRI) y uso terapéutico en dos modalidades de hipertermia: magnética y fototérmica. Para ello, se escogieron dos tipos de estructuras: nanocubos y nanorods. Para sintetizar los nanocubos, se probaron varios métodos ya publicados. Sin embargo, ninguno de ellos proporcionó resultados completamente satisfactorios en cuanto a monodispersión de tamaños, reproducibilidad, pureza de fase, alta cristalinidad y definición de forma. Por ello, desarrollamos una estrategia nueva basada en la introducción de oleato de sodio y una mezcla de disolventes que permitían el control de la temperatura de reflujo y la polaridad del medio, lo que además mejoró la estabilidad química del entorno en el que tenía lugar el crecimiento, dando lugar a una síntesis más reproducible. Estos resultados mostraron el éxito a la hora de producir partículas cúbicas en un rango de tamaños muy amplio, con unas excelentes propiedades y reproducibilidad. En cuanto a los nanorods, la síntesis fue especialmente complicada, ya que la estructura cúbica del Fe3O4 dificulta la formación de morfologías tan alargadas. De entre todos los procedimientos probados, solo la síntesis solvotermal dio buenos resultados. Para tener un mejor control sobre el tamaño y la relación de aspecto, se desarrollaron nuevas estrategias basadas en el ajuste de la presión y del ratio entre surfactantes. La superficie de las partículas sintetizadas es hidrófoba y por tanto fue necesario modificarla para que éstas pudieran dispersarse en medios biológicos. Además, el recubrimiento de las partículas debería proporcionar grupos funcionales para conjugar biomoléculas y así dirigirlas contra células malignas. Se probaron varias estrategias y los resultados mostraron que, a pesar de que la repulsión electrostática puede ser suficiente para estabilizar nanopartículas pequeñas o no magnéticas, en nuestro caso era necesario combinarla con impedimento estérico para evitar la agregación irreversible. Con este fin, se desarrolló un nuevo procedimiento de encapsulación basado en la formación de bicapas lipídicas que, a pesar de dar resultados prometedores, fue descartado finalmente al tener en cuenta el tiempo que se necesitaría para optimizar completamente todo el protocolo. En su lugar, se usó un procedimiento basado en la encapsulación con copolímeros anfipáticos, que también dio unos resultados excelentes, garantizando la estabilidad coloidal en entornos biológicos. El potencial biomédico de las partículas se evaluó primero como herramienta diagnóstica midiendo el contraste T2 para resonancia magnética de partículas de diferentes tamaños y formas, resaltando el mayor contraste de las nanopartículas anisótropas respecto a las isótropas (esferas). En cuanto al uso terapéutico, se evaluó también el potencial de las partículas en hipertermia magnética. Los resultados mostraron una buena capacidad de calentamiento a pesar de las suaves condiciones que usamos en nuestro estudio. Además, gracias a un amplio estudio espectroscópico teórico y experimental, se vio que las nanopartículas de Fe3O4 son adecuadas para fototermia, sobre todo en la segunda ventana biológica del infrarrojo cercano (1000-1350 nm). Esta región espectral es especialmente interesante porque permite la aplicación de mayores potencias de irradiación y tiene una mayor penetración en los tejidos humanos. A 1064 nm se consiguieron eficiencias de calentamiento óptico similares a los mejores agentes fototérmicos. Además, se aprovecharon las anisotropías magnética y óptica para medir la temperatura local en tiempo real mediante un método relativamente nuevo. Los experimentos in vitro usando células tumorales HeLa demostraron que las nanopartículas son internalizadas fácilmente y que no son tóxicas para concentraciones inferiores a 4 mM de hierro y que la fototermia usando nanocubos de Fe3O4 es una terapia excelente para destruir células tumorales.
This thesis tackles the synthesis, characterisation and functionalisation of biocompatible anisotropic iron oxide (Fe3O4) magnetic nanostructures for their application in biomedical diagnosis by means of magnetic resonance imaging (MRI) and therapy by two different modalities of hyperthermal therapy: magnetic fluid hyperthermia and photothermia. Two different types of structures were chosen for these purposes: nanocubes and nanorods. Several approaches published in literature were tested to synthesize the nanocubes. However, none of them rendered fully satisfactory results in size monodispersity, reproducibility, phase purity, high crystallinity and well-defined shape. Thus, we developed a new strategy based on the introduction of sodium oleate and a solvent mixture enabling the control of the reflux temperature and the polarity of the medium, which also resulted in an improvement of the chemical stability of the growth environment, leading to a more reproducible synthesis. The results demonstrate the successful synthesis of highly cubic particles in a very broad size range, with excellent properties and reproducibility. Concerning the nanorods, their synthesis was particularly challenging since the cubic crystal structure of Fe3O4 complicates the formation of such elongated morphologies. Among all the tested procedures, only the solvothermal synthesis provided good results. To have a better control on the size and aspect ratio new approaches based on adjusting the pressure and surfactants have been developed. The surface of the freshly synthesized particles is hydrophobic and therefore it was necessary to modify the surface to make them dispersible in biological media. In addition, the coating should provide functional groups to attach biomolecules for targeting malignant cells. Several approaches were tested and the results showed that, despite electrostatic repulsion can be enough to stabilize smaller or non-magnetic nanoparticles, in our case it was necessary to combine it also with steric hindrance to avoid irreversible aggregation. For this purpose, a novel procedure based on the formation of a lipid bilayer coating was developed which, despite providing promising results, was eventually discarded considering the time that would be required to fully optimise the protocol. Instead, a procedure based on the coating with amphiphilic copolymers was used, which also provided excellent results, ensuring colloidal stability in biological environments. The biomedical potential of the particles was evaluated first as a diagnostic tool by measuring the MRI T2 contrast of particles of different sizes and shapes, evidencing the enhanced contrast of anisotropic nanoparticles with respect to isotropic ones (spheres). In terms of therapy, the potential of the particles in terms of magnetic hyperthermia was also evaluated. The results showed the good heating capacity of the particles despite the mild conditions used in our study. In addition, thanks to a comprehensive theoretical and experimental spectroscopic study, it was established that Fe3O4 nanoparticles are suitable for photothermia, particularly in the near infrared second biological window (1000-1350 nm). This spectral range is especially appealing because it allows the application of higher powers and has a deeper penetration in human tissues. At 1064 nm were measured some heating efficiencies similar to the best photothermal agents. In addition, the magnetic and optic anisotropies were exploited for a relatively new approach for in situ local temperature sensing. The in vitro experiments using HeLa cancerous cells demonstrated that the nanoparticles are easily internalized and are not toxic for concentrations below 4 mM Fe and that photothermia using Fe3O4 nanocubes at 1064 nm is an excellent therapy for destroying cancerous cells.
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6

Pérez, Galera Juana María. "Impregnated Cobalt, Nickel, Copper and Palladium Oxides on Magnetite: Nanocatalysts for Organic Synthesis." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/57586.

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In this manuscript, the application of different nanocatalysts derived from metal oxides impregnated on the surface of the magnetite in different reaction of general interest in Organic Chemistry is described. In the First Chapter, a cobalt derived catalyst was used to study the hydroacylation reaction of azodicarboxylates with aldehydes. In the Second Chapter, a catalyst derived from copper was used to perform different reactions, including homocoupling of terminal alkynes and the subsequent hydration reaction to obtain the corresponding 2,5-disubstituted benzofurans, the reaction of alcohols and amines (or nitroarenes) to obtain the corresponding aromatic imines, the cross-dehydrogenative coupling reaction of N-substituted tetrahydroisoquinolines using deep eutectic solvents and air as final oxidant. Finally, the formation of benzofurans from aldehydes and alkynes through a tandem coupling-allenylation-cyclization process has been performed. In the Third Chapter, a bimetallic catalyst derived from nickel and copper was used to study the multicomponent reaction between benzyl bromides, sodium azide and alkynes to obtain the corresponding triazoles. In the Fourth Chapter, a catalyst derived from palladium was used in the direct arylation of heterocycles using iodonium salts. Also the synthesis of 4-aryl coumarins through the Heck arylation reaction and subsequent cyclization using the same catalyst is described. In the last Chapter, the use of different eutectic mixtures were studied as alternative media to perform in a single vessel the cyclation reaction of N-hydroxy imidoyl chlorides and alkynes, without any type of catalyst under oxidizing conditions.
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7

Mejia-Ariza, Raquel. "Design, Synthesis, and Characterization of Magnetite Clusters using a Multi Inlet Vortex Mixer." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/45432.

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Superparamagnetic nanoparticles have potential applications in targeted drug delivery and as magnetic resonance imaging contrast agents. Magnetite clusters are of particular interest for these applications because they provide higher magnetic flux (under a magnetic field) than individual magnetite nanoparticles, are biocompatible, and their size and compositions can be controlled. This thesis involves the controlled synthesis and characterization of clusters composed of magnetite nanoparticles stabilized with an amphiphilic block copolymer. It outlines a method to design and form well-defined and colloidally stable magnetite clusters. A Multi Inlet Vortex mixer (MIVM) was used because it is a continuous process that yields particles with relatively narrow and controlled size distributions. In the MIVM, four liquid streams collide under turbulent conditions in the mixing chamber where clusters form within milliseconds. The formation of magnetite clusters was studied in the presence of amphiphilic block copolymers containing poly (ethylene oxide) to provide steric stabilization and control of size distributions using flash nanoprecipitation. First, the mixer was tested using β-carotene as a model compound to form nanoparticles stabilized with an amphiphilic triblock copolymer poly(propylene oxide)-b-poly(ethylene oxide) (F127) at different Reynolds numbers and supersaturation values. Size analysis was done using dynamic light scattering and nanoparticle tracking analysis techniques. The cluster structure was studied using electron microscopy and magnetite compositions were measured using thermogravimetric analysis. Finally, the stability of magnetite clusters was studied over time and the effect of an applied magnetite field on the colloidal stability was investigated.
Master of Science
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8

Miller, Barry William. "Synthesis and characterization of functionalized magnetite nanocomposite particles for targeting and retrieval applications." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004820.

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9

Ragheb, Ragy Tadros. "Synthesis and Characterization of Surface-Functionalized Magnetic Polylactide Nanospheres." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26719.

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Polylactide homopolymers with pendent carboxylic acid functional groups have been designed and synthesized to be studied as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest for a variety of biomedical applications including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications, it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The acid-functionalized silane endgroup was utilized as the dispersant anchor to adsorb onto magnetite nanoparticle surfaces and allowed the polylactide to extend into various solvents to impart dispersion stability. The homopolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces, and these complexes were dispersible in dichloromethane. The polylactide tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes. The resultant magnetite-polymer complexes were further incorporated into controlled-size nanospheres. The complexes were blended with poly(ethylene oxide-b-D,L-lactide) diblock copolymers to introduce hydrophilicity on the surface of the nanospheres with tailored functionality. Self-assembly of the PEO block to the surface of the nanosphere was established by utilizing an amine terminus on the PEO to react with FITC and noting fluorescence.
Ph. D.
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10

O'Brien, Kristen Wilson. "Synthesis of Functionalized Poly(dimethylsiloxane)s and the Preparation of Magnetite Nanoparticle Complexes and Dispersions." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28869.

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Poly(dimethylsiloxane) (PDMS) fluids containing magnetite nanoparticles stabilized with carboxylic acid-functionalized PDMS were prepared. PDMS-magnetite complexes were characterized using transmission electron microscopy, elemental analysis, and vibrating sample magnetometry. PDMS-magnetite complexes containing up to 67 wt% magnetite with magnetizations of ~52 emu gram-1 were prepared. The magnetite particles were 7.4 ± 1.7 nm in diameter. Calculations suggested that the complexes prepared using mercaptosuccinic acid-functionalized PDMS (PDMS-6COOH) complexes contained unbound acid groups whereas the mercaptoacetic acid-functionalized PDMS (PDMS-3COOH) complexes did not. Calculations showed that the PDMS-3COOH and PDMS-6COOH covered the same surface area on magnetite. Calculations were supported by molecular models and FTIR analyses. The complexes were dispersed into PDMS carrier fluids by ultrasonication, resulting in magnetic PDMS fluids with potential biomedical applications. Magnetite particles (100 nm to 1 mm in diameter) were prepared by crystallization from goethite/glycol/water solutions under pressure. Two methods for particle growth were investigated in which the crystallization medium was varied by adjusting the amount of water or by adding itaconic acid. Particle surfaces were analyzed by x-ray photoelectron spectroscopy (XPS). Particles with clean surfaces were coated with carboxylic acid-functionalized poly(e-caprolactone) stabilizers. Adding itaconic acid to the reactions afforded particles ~100 nm in diameter. The magnetite particles displayed magnetic hysteresis. The particles were dispersed into vinyl ester resins by ultrasonication and it was demonstrated that the ~100 nm particles remained dispersed for three days without agitation. These dispersions have applications in magnetic induction heating for composite repair. Living polymerizations of hexamethylcyclotrisiloxane were terminated with dimethylchlorosilane, phenylmethylchlorosilane, or diisopropylchlorosilane (DIPCS). Platinum-catalyzed hydrosilation of the hydrosilane-terminated PDMS with allyloxyethanol afforded a systematic series of hydroxyalkyl-terminated PDMS. The reactions were successful except for the hydrosilation of the sterically-hindered DIPCS-functionalized PDMS where no reaction was observed. Hydroxyalkyl-terminated PDMS oligomers were successful in initiating the stannous octoate-catalyzed copolymerization of e-caprolactone, which afforded PDMS-b-PCL diblock copolymers of controlled composition.
Ph. D.
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11

Carmichael-Baranauskas, Anita Yvonne. "Synthesis of Amphiphilic Block Copolymers for Use in Biomedical Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31737.

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The research presented in this thesis focuses on the synthesis of three amphiphilic block copolymer systems containing poly(ethylene oxide) (PEO) blocks. The polymer systems were developed for use in biomedical applications. The first of these is a series of poly(ethylene oxide-b¬-oxazoline) (PEO-b-POX) diblock copolymers for use in the progress towards novel non-viral gene transfer vectors. Poly(ethylene oxide-b¬-2-ethyl-2-oxazoline) (PEO-b-PEOX) and poly(ethylene oxide-b¬-2-methyl-2-oxazoline) (PEO-b-PMOX) were investigated. The PEOX block was hydrolyzed with acid to form linear polyethylenimine (L-PEI). The polycation L-PEI is well known for its DNA binding efficiency but the water solubility of the resulting DNA/polymer complex is limited. Addition of a PEO block is directed towards the formation of a water dispersible DNA/copolymer complex. Dynamic light scattering of the PEO-b-PEOX and PEO-b-PEI block copolymers indicated that both systems existed as single chains in aqueous solution at pH 7. PEO copolymers also play a significant role in the formation of magnetic magnetite nanoparticles, which are dispersible in water at biological pH (pH =7). There is significant interest in the design of magnetic nanoparticle fluids for biomedical applications including magnetic field-directed drug delivery, magnetic cell separations, and blood purification. For use in vivo, the magnetite nanoparticles must be coated with biocompatible materials. Such polymers render the nanoparticles dispersible in water. Harris1 et al. synthesized PEO based, polyurethane triblocks with pendant carboxylic acid groups for use in formation of stable aqueous magnetic fluids. Building from this work, two polyurethane and polyurethaneurea systems were synthesized with 1300 g/mol PEOX and 2500 g/mol and PEOX2070 g/mol poly(ethylene oxide-co-propylene oxide) tailblocks, respectively. The PEO/PPO random copolymer contained about 25 weight percent PPO, and this disrupted the capacity of the PEO to crystallize. The PEOX based urethane triblocks were synthesized through reacting the tailblocks with the monomers for the center block whereas the PEO/PPO based polyurethaneurea was synthesized through forming the central urethane block with pendant acid groups first and then terminating the copolymer with the monofunctional copolymer. Terminal amine groups on the PEO/PPO tailblock afforded a triblock linked with two urea groups. The new polyurethanes with the PEOX tailblocks and the new polyurethaneurea with the PEO/PPO tailblocks could be utilized to efficiently stabilize magnetite nanoparticles in water.
Master of Science
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12

Hoff, Richard. "Iron Oxide Nanoparticle Surface Modification: Synthesis and Characterization." Master's thesis, Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/592997.

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Bioengineering
M.S.
Multifunctional nanomaterials can be engineered to aid in the diagnosis of diseases, enable efficient drug delivery, monitor treatment progress over time, and evaluate treatment outcomes. This strategy, known as theranostics, focuses on the combination of diagnostic and therapeutic techniques to provide new clinically safe and efficient personalized treatments. The evaluation of different nanomaterials’ properties and their customization for specific medical applications has therefore been a significant area of interest within the scientific community. Iron oxide nanoparticles, specifically those based on iron (II, III) oxide (magnetite, Fe3O4), have been prominently investigated for biomedical, theranostic applications due to their documented superparamagnetism, high biocompatibility, and other unique physicochemical properties. The aim of this thesis is to establish a viable set of methods for preparing magnetite (iron oxide) nanoparticles through hydrothermal synthesis and modifying their surfaces with organic functional groups in order to both modulate surface chemistry and facilitate the attachment of molecules such as peptides via covalent bond formations. Modifying their surfaces with biomolecules such as peptides can further increase their uptake into cells, which is a necessary step in the mechanisms of their desired biomedical applications. The methods of nanoparticle synthesis, surface functionalization, and characterization involving electron microscopy (e.g., SEM, TEM), zeta potential measurements, size analysis (i.e., DLS), and FT-IR spectroscopy will be presented.
Temple University--Theses
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13

Changyong, Lu. "Synthesis and characterization of magnetic nanocomposites and their applications study." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/457572.

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Los nanomateriales, especialmente las nanopartículas, se convierten en una de las áreas más atractivas no sólo en la investigación científica, sino también en las aplicaciones industriales. En esta tesis se ha estudiado la preparación de nanopartículas de magnetita, sus nanocompuestos relacionados y la aplicación de los nanomateriales obtenidos. Las nanopartículas core-shell de Fe3O4@SiO2 se sintetizaron mediante métodos de microemulsión inversa estándar y de microondas. Las nanopartículas obtenidas se caracterizaron con diferentes técnicas de laboratorio y se estudiaron los diferentes efectos al cambiar algunos parámetros (temperatura, concentración, tiempo) de la reacción. Las nanopartículas se utilizaron como soporte de catalizadores de Ag y los nanocompuestos sintetizados mostraron una buena propiedad catalítica y una alta capacidad de reciclaje. También se prepararon nuevas nanocápsulas de Fe3O4@GNF@SiO2 mediante la formación in situ de nanopartículas de magnetita y el proceso de cobertura de sílica. Los nanocapsulados obtenidos tienen una buena estabilidad incluso en ambientes ácidos. También se estudió la posible aplicación de estas nanocápsulas por resonancia magnética. Por otra parte, se estudió la citotoxidad e interacción del core-shell Fe3O4 @ SiO2 de las nanopartículas unidas a células, para asegurarse una posible aplicación en investigación biomédica obteniendo un resultado favorable y de baja toxicidad. A continuación, las nanopartículas Fe3O4 @ SiO2 se decoraron añadiendo biomoléculas tales como MC540 y L-tiroxina las cuales muestran una posible aplicación en el estudio de biosensores.
Nanomaterials especially nanoparticles become one of the most attractive area not only in scientific research but also in industrial applications. In this thesis, the preparation of magnetite nanoparticles, their related nanocomposites and the application of those obtained nanomaterials have been studied. The Fe3O4@SiO2 core-shell nanoparticles were synthesized via normal and microwave assistance reverse microemulsion methods. The obtained nanoparticles were fully characterized with different laboratory techniques and the effect of reaction parameters on final products was also studied. These nanoparticles were used as a support of Ag catalysts nanoparticles and the as synthesized nanocomposites shown nice catalytic property and high recyclability. A novel Fe3O4@GNF@SiO2 nanocapsulates were also prepared via in situ formation of magnetite nanoparticles and silica coverage process. The obtained nanocapsulates have nice stabilities even in the acid environments. The potential application of these nanocapsulates in magnetic resonance imaging research was also studied. On the other hand, the cytotoxity and interaction with cell of Fe3O4@SiO2 core-shell nanoparticles were studied which indicate the possibility of using them in biomedical research. Then, the Fe3O4@SiO2 core-shell nanoparticles were further decorated with biomolecules such as MC540 and L-thyroxine. The Fe3O4@SiO2 core-shell nanoparticles with the surface functionalized with molecule imprinted polymers also suggested the potential application in biosensor research.
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14

Marinin, Aleksandr. "Synthesis and characterization of superparamagnetic iron oxide nanoparticles coated with silica." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121520.

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Multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica are a promising research field for lots of biomedical applications. The scope of this work is a preparation of SPIONs and coating them with silica to form core-shell structured nanoparticles for nanomedicine applications. SPIONs were synthesized by two chemical methods – co-precipitation and thermal decomposition of organic iron precursor. Prepared nanoparticles were carefully characterized –average size, size distribution, morphology, crystallinity, colloidal stability and magnetic properties were studied. After comparing SPIONs synthetized by two routes the most suitable method for biomedical applicable nanoparticles preparation is determined. The nanomedicine requires nanoparticles of the highest quality. The next step was coating SPIONs with silica shell. For this purpose inverse microemulsion method was chosen. TEOS was used as a silica precursor. Mean size, size distribution, magnetic properties, structure of silica shell were studied.
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15

Qu, Haiou. "Surface Functionalized Water-Dispersible Magnetite Nanoparticles: Preparation, Characterization and the Studies of Their Bioapplications." ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1536.

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Iron oxide magnetic nanoparticle synthesis and their surface functionalization hold a crucial position in the design and fabrication of functional materials for a variety of biomedical applications. Non-uniform nanoparticles with poor crystallinity, prepared by conventional methods, have only limited value in biological areas. Large scale synthesis methods that are able to produce high quality, mono-dispersed iron oxide nanoparticles using low cost and environment friendly chemicals are highly desirable. Following synthesis, appropriate surface functionalization is necessary to direct the dispersibility of nanoparticles in aqueous solution in order to provide them with acceptable colloidal stability against the ion strength and many biomolecules that nanoparticles may encounter under physiological conditions. Poorly stabilized nanoparticles that easily aggregate and form large size agglomerates would be quickly cleared by the liver and other organs and are not suitable for clinical purposes. Additionally, many interesting functionalities such as fluorescence, targeting and anti-cancer properties can be immobilized onto the surface of iron oxide magnetic nanoparticles during the surface functionalization process so as to build multifunctional platforms for disease diagnosis and treatment. Polyol method can be an effective way to prepare magnetite nanoparticles that are suitable for biological applications. In a polyol system, selected surface functionalities were introduced to the nanoparticle surface via a hot injection technique. The morphology, uniformity, crystallinity and magnetic properties were examined to understand the effect of different ligand molecules on the final product. Their surface chemistry, colloidal properties and surface reactivity were also studied to evaluate their practicability in different applications. A high efficiency in-situ method for the preparation of magnetite nanoparticles attached to silica nanospheres was also developed in a polyol system. This approach eliminates several time-consuming processing steps that are in the conventional fabrication route and directly produces water-stable magnetite-silica hybrid materials with surface availability for subsequent modifications. In addition to polyalcohol, the potential of polyamine in the preparation of water-soluble magnetite nanoparticles with amine surface functionalities was also evaluated. And it is suggested that polyamine acts as solvent, stabilizing agent and reducing agent simultaneously during the synthesis. The characterization of polyamine coated nanoparticles, their surface functionalization, and subsequent application for bioseparation and drug delivery were reported.
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16

Bessa, Raquel de Andrade. "Synthesis and characterization of composite magnetic zeolites using kaolin for softening water." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17007.

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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
The present work deals about the synthesis and characterization of magnetic zeolites obtained by hydrothermal route using kaolin from Brazilian Northeast as silicon and aluminum source. By means of the X-ray diffraction technique it was possible to identify zeolite LTA and zeolite P1 as major crystalline phases for each synthesis, with low intensity peaks referent to unreacted quartz present in the kaolin used, which is in accordance to the. FTIR spectra; the nanoparticles were identified as magnetite, with low intensity peaks referent to goethite. In scanning electron microscopy, however, it was not possible to morphologically identify these minor components, while the zeolites showed well defined morphologies, presenting unchanged morphology when in the composites form, but with nanoparticles dispersed over their surface, as expected. From transmission electron microscopy it was observed that the nanoparticles were of ca. 50 nm. Magnetic measurements indicated magnetite presence with superior diameter to critical diameter to superparamagnetic particles and remanent magnetization. Thermogravimetric analyses showed for the composites, lower mass loss than compared to the pure zeolites what may be associated to the improvement of its thermal stability. Granulometric distribution indicated nanoparticles agglomeration in variable sizes, while zeolites formed agglomerates of ca. 10 Âm. Water softening was accomplished by using both zeolites, with high efficiency on Ca2+ removal and similar behavior between the zeolite and its respective composite, being the best result observed for zeolite A, with efficiency of 97,95%, reaching equilibrium in the first contact minutes. The dependence on mass studies also showed that zeolite A and its composite presented the best efficiency, whereas zeolite P achieved the same removal levels using corresponding zeolite masses (45 mg). This way, the proposed method for zeolites synthesis proved to be efficient, so that the use of a magnet is capable to attract them, leading their excellent separation from the aqueous medium with its ionic exchange capacity unaffected.
O presente trabalho trata da sÃntese e caracterizaÃÃo de zeÃlitas magnÃticas obtidas por impregnaÃÃo de nanopartÃculas de magnetita a zeÃlitas A e P, sintetizadas por mÃtodo hidrotÃrmico utilizando caulim branco do Nordeste brasileiro como fonte de silÃcio e alumÃnio. Por meio da tÃcnica de difraÃÃo de raios-X foi possÃvel identificar como fases cristalinas majoritÃrias a zeÃlita LTA e P1 para cada sÃntese, com picos de baixa intensidade referentes a quartzo, resistente ao processo tÃrmico de tratamento prÃvio do caulim, bem como nos espectros de infravermelho; as nanopartÃculas foram identificadas como magnetita, havendo ainda indÃcios da presenÃa de goethita em pequena quantidade. Nas anÃlises de microscopia eletrÃnica de varredura, entretanto, nÃo foi possÃvel identificar esses componentes minoritÃrios morfologicamente; enquanto que a morfologia das zeÃlitas mostrou-se bem definida, sem alteraÃÃes apÃs a formaÃÃo dos compÃsitos, apenas com nanopartÃculas espalhadas em sua superfÃcie, como desejado. A partir da microscopia eletrÃnica de transmissÃo, pÃde-se observar melhor a variaÃÃo de tamanho das nanopartÃculas, em mÃdia de 50 nm. Medidas magnÃticas das amostras com essa propriedade indicaram a presenÃa de magnetita com diÃmetro superior ao diÃmetro crÃtico para partÃculas superparamagnÃticas e magnetizaÃÃo remanente. As anÃlises termogravimÃtricas mostraram que a adiÃÃo das nanopartÃculas Ãs zeÃlitas diminuiu sua perda de massa diante do aumento de temperatura e as anÃlises de distribuiÃÃo granulomÃtrica indicaram a aglomeraÃÃo das nanopartÃculas em tamanhos variÃveis, enquanto que as zeÃlitas formaram aglomerados de aproximadamente 10 Âm. Os ensaios de abrandamento de Ãguas mostraram alta eficiÃncia das zeÃlitas em remover Ca2+, com comportamento similar entre a zeÃlita e o seu respectivo compÃsito, encontrando para a zeÃlita A o maior percentual de remoÃÃo, de 97,95 %, atingindo equilÃbrio nos primeiros minutos de aplicaÃÃo. Os estudos de massa tambÃm mostraram a eficiÃncia da zeÃlita A e de seu compÃsito, tendo a zeÃlita P se aproximado dos mesmos nÃveis de remoÃÃo em massas referentes a 45 mg de zeÃlita. Assim, o mÃtodo proposto para sÃntese das zeÃlitas magnÃticas mostrou-se eficiente, de modo que a utilizaÃÃo de um Ãmà à capaz de atraÃ-las facilitando a separaÃÃo do meio apÃs a aplicaÃÃo em meio aquoso e sua capacidade de troca iÃnica nÃo foi afetada.
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17

Huffstetler, Philip Plaxico. "Synthesis and Characterization of Well-Defined Heterobifunctional Polyethers for Coating Magnetite and Their Applications in Biomedicine Resonance Imaging." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29160.

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Well-defined heterobifunctional homopolyethers and amphiphilic block copolyethers containing a variety of functionalities were designed, synthesized, and characterized via GPC and 1H NMR. These have included controlled molecular weight cholesterol-PEO-OH, mono- and trivinylsilyl-PEO-OH, monovinylsilyl-PEO-PPO-OH, monovinylsilyl-PEO-PPO-PEO-OH, maleimide-PEO-OH, stearyl alcohol-PEO-OH, propargyl alcohol-PEO-OH, trivinylsilyl-PPO-OH, trivinylsilyl-PPO-PEO-OH, and benzyl alcohol-initiated poly(allyl glycidyl ether)-OH. The focus of polymers utilized in this study involved the mono- and trivinylsilyl polyethers. The vinylsilyl endgroups on these materials were functionalized with various bifunctional thiols through free radical addition of SH groups across the vinylsilyl double bonds. The resultant end-functional polyethers were adsorbed onto magnetite nanoparticles and the stabilities of the polymer-magnetite complexes were compared as a function of the type of anchoring moiety and the number of anchoring moieties per chain. Anchoring chemistries investigated in this work included carboxylates, alkylammonium ions, and zwitterionic phosphonates. The anchor group-magnetite bond stability was investigated in water and phosphate buffered saline (PBS). Through these studies, the zwitterionic phosphonate group was shown to be a better anchoring group for magnetite than either carboxylate or ammonium ions. Tri-zwitterionic phosphonate anchor groups provided stability of the complexes in PBS for a broad range of polymer loadings. Thus, investigations into the stability of polyether-magnetite complexes in PBS focused on hydrophilic zwitterionic phosphonate-PEO-OH and amphiphilic zwitterionic phosphonate-PPO-b-PEO-OH oligomer coatings on the surface of magnetite. Superparamagnetic magnetite nanoparticles are of interest as potential contrast-enhancement agents for MRI imaging. Thus, transverse NMR relaxivities of these complexes were studied as a function of chemical composition and nanostructure size and compared to commercial contrast agents. The amphiphilic polyether-magnetite nanoparticles were shown to be stable in both aqueous media as well as physiological media and have much higher transverse relaxation values, r2, than those of commercial contrast agents and other materials in the literature.
Ph. D.
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18

Zierold, Robert [Verfasser], and Kornelius [Akademischer Betreuer] Nielsch. "Magnetite Nanotubes and Nickel Nanorods of Low Aspect Ratios : From Synthesis to Application in Ferrofluidic Suspensions / Robert Zierold. Betreuer: Kornelius Nielsch." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/104744030X/34.

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19

Ференс, М. В., Р. С. Тарас, А. І. Товарніцький, and С. М. Варваренко. "Синтез нанорозмірного магнетиту, модифікованого структурованими псевдополіамінокислотами поліестерного типу для доставки лікарських препаратів." Thesis, Сумський державний університет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/52775.

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Останніми роками особливої уваги набуло питання створення лікарських форм, які забезпечують цільову доставку лікарських засобів на полімерних носіях. Звичайно висока концентрація лікарських засобів у зоні організму, яка потребує лікування значно пришвидшує процес одужання. Проте з процесом виведення метаболітів носія не все так однозначно, оскільки введені полімерні носії можуть порушувати метаболічні процеси і їх важко відстежувати в організмі. Виходом з цієї проблеми може бути створення носіїв лікарських засобів які легко піддаються екскреції або ж створення носіїв ковалентно закріплених на поверхні частинок які можна легко відстежувати в організмі.
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20

Meduri, Kavita. "Carbon-Supported Transition Metal Nanoparticles for Catalytic and Electromagnetic Applications." Thesis, Portland State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10933285.

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Recently, there has been growing interest in using transition metals (TM) for catalytic and electromagnetic applications, due to the ability of TMs to form stable compounds in multiple oxidation states. In this research, the focus has been on the synthesis and characterization of carbon-supported TM nanoparticles (NPs), specifically palladium (Pd) and gold (Au) NPs, for catalytic applications, and transition metal oxides (TMO) NPs, specifically Fe3O4 NPs for electromagnetic applications. Carbon supports have several advantages, such as enabling even distribution of particles, offering large specific surface area with excellent electron conductivity, and relative chemical inertness.

In this dissertation, for catalytic applications, emphasis was on removal of trichloroethylene (TCE) from groundwater. For this application, carbon-supported Pd/Au NP catalysts were developed. Pd was chosen because it is more active, stable and selective for desired end-products, and Au has shown to be a good promotor of Pd’s catalytic activity. Often, commercially available Pd-based catalysts are made using harsh chemicals, which can be harmful to the environment. Here, an environmentally friendly process with aspects of green chemistry was developed to produce carbon-supported Pd/Au NP catalysts. This process uses a combination of sonochemistry and solvothermal syntheses. The carefully designed carbon-supported Pd/Au NP catalyst material was systematically characterized, tested against TCE, and optimized for increased rate of removal of TCE. Electron microscopy and spectroscopy techniques were used to study the material including structure, configuration and oxidative state. The Pd/Au NPs were found mainly to form clusters with an aggregate-PdShellAuCore structure. Using state-of-the-art direct detection with electron energy loss spectroscopy, the Pd NPs were found to have an oxidative state of zero (0). The formation of the catalyst material was studied in detail by varying several synthesis parameters including type of solvent, sonication time, synthesis temperature etc. The most optimized catalyst was found remove TCE at double the rate of corresponding commercial Pd-based catalysts in a hydrogen headspace. This material was found to catalyze the removal of TCE via traditional hydrodehalogenation and shows promise for the removal of other contaminants such as trichloropropane (TCP), carbon tetrachloride (CT).

This green approach to make and optimize TM materials for specific applications was extended to TMOs, specifically magnetite (Fe3O4) and further developed for the application of electromagnetism. As catalysts, Fe3O4 is used for removal of p-nitrophenol from water. However, since the carbon-supported Pd/Au material system was developed and optimized for catalysis, here, carbon-supported Fe3O 4 NPs were developed for electromagnetic applications. There has been growing interest in tuning the magnetic properties of materials at room temperature with the use of external electric fields, for long-term applications in data storage and spintronic devices. While a complete reversible change of material properties has not yet been achieved, some success in partial switching has been achieved using multiferroic spinel structures such as Fe3O 4. These materials experience a change in magnetic moment at room temperature when exposed to the electric fields generated by electrochemical cells such as lithium ion batteries (LIBs) and supercapacitors (SC). In the past, a 1% reversible change was observed in Fe3O4 using LIBs. Here, building on the developments from previous material system, Fe 3O4 NPs were directly hybridized onto the graphene support in order to increase the observable change in magnetic moment. The material was systematically designed and tested for this application, including a study of the material formation. A simple, environmentally friendly synthesis using the solvothermal process was implemented to make the graphene-supported Fe 3O4 NPs. This new material was found to produce a reversible change of up to 18% in a LIB. In order to overcome some of the difficulties of testing with a LIB, a corresponding hybrid SC was designed, built and calibrated. The graphene-supported Fe3O4 NPs were found to produce a net 2% reversibility in the SC, which has not been reported before. The results from both the LIB and SC were analyzed to better understand the mechanism of switching in a spinel ferrite such as Fe3O4, which can help optimize the material for future applications.

The focus of this dissertation was on the development of a methodology for carbon-supported TM and TMO NPs for specific applications. It is envisioned that this approach and strategy will contribute towards the future optimization of similar material systems for a multitude of applications.

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21

Zedan, Abdallah. "GRAPHENE-BASED SEMICONDUCTOR AND METALLIC NANOSTRUCTURED MATERIALS." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/457.

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Exciting periods of scientific research are often associated with discoveries of novel materials. Such period was brought about by the successful preparation of graphene which is a 2D allotrope of carbon with remarkable electronic, optical and mechanical properties. Functional graphene-based nanocomposites have great promise for applications in various fields such as energy conversion, opteoelectronics, solar cells, sensing, catalysis and biomedicine. Herein, microwave and laser-assisted synthetic approaches were developed for decorating graphene with various semiconductor, metallic or magnetic nanostructures of controlled size and shape. We developed a scalable microwave irradiation method for the synthesis of graphene decorated with CdSe nanocrystals of controlled size, shape and crystalline structure. The efficient quenching of photoluminescence from the CdSe nanocrystals by graphene has been explored. The results provide a new approach for exploring the size-tunable optical properties of CdSe nanocrystals supported on graphene which could have important implications for energy conversion applications. We also extended this approach to the synthesis of Au-ceria-graphene nanocomposites. The synthesis is facilely conducted at mild conditions using ethylenediamine as a solvent. Results reveal significant CO conversion percentages between 60-70% at ambient temperatures. Au nanostructures have received significant attention because of the feasibility to tune their optical properties by changing size or shape. The coupling of the photothermal effects of these Au nanostructures of controlled size and shape with GO nanosheets dispersed in water is demonstrated. Our results indicate that the enhanced photothermal energy conversion of the Au-GO suspensions could to lead to a remarkable increase in the heating efficiency of the laser-induced melting and size reduction of Au nanostructures. The Au-graphene nanocomposites are potential materials for photothermolysis, thermochemical and thermomechanical applications. We developed a facile method for decorating graphene with magnetite nanocrystals of various shapes (namely, spheres, cubes and prisms) by the microwave-assisted-reduction of iron acetylacetonate in benzyl ether. The shape control was achieved by tuning the mole ratio between the oleic acid and the oleyamine. The structural, morphological and physical properties of graphene-based nanocomposites described herein were studied using standard characterization tools such as TEM, SEM, UV-Vis and PL spectroscopy, powder X-ray diffraction, XPS and Raman spectroscopy.
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22

Verfasser], Anteneh Belete Shibeshi, Karsten [Akademischer Betreuer] [Mäder, Reinhard H. H. [Akademischer Betreuer] Neubert, and Dagmar [Akademischer Betreuer] Fischer. "Development of MRI contrast agents using hydrophobic magnetite nanocrystals : from chemical synthesis to In Vivo applications / Anteneh Belete Shibeshi. Betreuer: Karsten Mäder ; Reinhard Neubert ; Dagmar Fischer." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2009. http://d-nb.info/1024895513/34.

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23

Hetti, Mimi. "Synthesis and Characterization of Polymeric Magnetic Nanocomposites for Damage-Free Structural Health Monitoring of High Performance Composites." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-211082.

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The poly(glycidyl methacrylate)-modified magnetite nanoparticles, Fe3O4-PGMA NPs, were investigated and applied in nondestructive flaw detection of polymeric materials in this research. The Fe3O4 endowed magnetic property to the materials for flaw detection while the PGMA promoted colloidal stability and prevented particle aggregation. The magnetite nanoparticles (Fe3O4 NPs) were successfully synthesized by coprecipitation and then surface-modified with PGMA to form PGMA-modified Fe3O4 NPs by both grafting-from and grafting-to approaches. For the grafting-from approach, the Fe3O4 NPs were surface-functionalized with α-bromo isobutyryl bromide (BIBB) to form BIB-modified Fe3O4 NPs (Fe3O4-BIB NPs) with covalent linkage. The resultant Fe3O4-BIB NPs were used as surface-initiators to grow PGMA by surface-initiated atom transfer radical polymerization (SI-ATRP). For the grafting-to approach, the Fe3O4 NP were surface-functionalized with (3-mercaptopropyl)triethoxysilane (MCTES) to form MCTES-modified Fe3O4 NPs (Fe3O4-MCTES NPs). The PGMA with Br-end group was pre-synthesized by ATRP and then was grafted to the surface of the Fe3O4-MCTES NPs by coupling reaction. Both bare and modified Fe3O4 NPs exhibited superparamagnetism and the existence of iron oxide in the form of Fe3O4 was confirmed. The particle size of individual Fe3O4 NPs was about 8 – 24 nm but they aggregated to form clusters. The PGMA-modified NPs formed stable dispersion in chloroform and had larger cluster sizes than the unmodified ones because of the PGMA polymer layer. However, the uniformity of the NP clusters could be improved with PGMA surface grafting. The PGMA surface layer of the grafting-from (Fe3O4-gf-PGMA) NPs was thin and dense while that of the grafting-to (Fe3O4-gt-PGMA) NPs was thick and loose. The hydrodynamic diameters (Zave) of Fe3O4-gf-PGMA NP clusters could be controlled between 176 to 643 nm, dependent on the PGMA contents and reaction conditions. During SI-ATRP, side reactions happened and caused NP aggregation as well as increase of size of NP clusters. However, the aggregation has been minimized through optimization of reaction conditions. Oppositely, Zave values of Fe3O4-gt-PGMA NPs had little variation of about 120 – 190 nm. And the PGMA content of the Fe3O4-gt-PGMA NPs was limited to 12.5% because of the spatial hindrance during grafting process. The saturation magnetization (Ms) of the unmodified Fe3O4 NPs was about 77 emu/g, while those of the grafting-from and grafting-to Fe3O4-PGMA NPs were 50 – 66 emu/g and 63 – 70 emu/g, respectively. For Fe3O4-PGMA NPs with similar Fe3O4 contents, the grafting-to NPs had slightly higher Ms than the grafting-from counterparts. In addition, the Ms of both kinds of the Fe3O4-PGMA NPs with higher Fe3O4 content (> 87%) were also higher than that of the fluidMAG-Amine, the commercially available amine-modified MNPs. Besides, both kinds of Fe3O4-PGMA NPs also had much higher Fe3O4 contents and Ms values than most of the reported PGMA-modified MNPs. The magnetic epoxy nanocomposites (MENCs) were prepared by blending the modified Fe3O4 NPs into bisphenol A diglycidyl ether (BADGE)-based epoxy system and the distributions of both kinds of the PGMA-modified NPs were much better than that of the oleic acid-modified Fe3O4 NPs. Similar to the NPs, the MENCs also exhibited superparamagnetism. By cross-section TEM observation, the grafting-to Fe3O4-PGMA NPs formed more homogeneous distributions with smaller cluster size than the grafting-from counterparts and gave higher Ms of the MENCs. Nondestructive flaw detection of surface and sub-surface defects could be successfully achieved by brightness contrast of images given through eddy current testing (ET) method, which is firstly reported. The mechanical properties of the materials were influenced very slightly when 2.5% or lower Fe3O4-gt-PGMA NPs were present while the presence of the Fe3O4-gf-PGMA NPs (1 – 2.5 %) gave mild improvement of the storage modulus and increase of the glass-rubber transition temperature(Tg) of the MENCs. Furthermore, the Fe3O4-PGMA NPs could be evenly coated onto the functionalized ultra-high molecular weight poly(ethylene) (UHMWPE) textiles. The Fe3O4-gt-PGMA NPs were coated on the textile in order to prepare NP-coated textile-reinforced composite. Preliminary result of ET measurement showed that the Fe3O4-gt-PGMA NPs coated on the textiles could visualize the structure of the textile hidden inside and their relative depth. Accordingly, the incorporation of MNPs to polymers opens a new pathway of damage-free structural health monitoring of polymeric materials.
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24

Hou, Liwei. "Metal oxide synthesis and its application in the heterogeneous catalytic oxidation processes, using H2O2 or peroxydisulfate as oxidant." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2271/document.

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Parmi les procédés avancés d'oxydation (AOPs), les procédés de type Fenton (réactif de Fenton: Fe2+/H2O2) et les procédés d'oxydation par le persulfate, sont décrits comme des procédés très performants. Le procédé Fenton est une voie prometteuse et attractive pour le traitement d'une large variété de composés organiques polluants, difficiles à traiter par les voies classiques de dépollution. Au cours du procédé Fenton, des radicaux hydroxyles, molécules à fort pouvoir oxydant capable de réagir avec pratiquement tous types de composés organiques et inorganiques, sont générés. De même, du fait de la structure similaire entre H2O2 et les ions peroxydisulfate, ces derniers peuvent se décomposer en radicaux sulfates (SO4-•), un autre type d'oxydant hautement réactif pouvant réagir avec les composés organiques. Cependant, les procédés Fenton et d'activation du peroxydisulfate classiques présentent plusieurs inconvénients. En effet, la solution doit être acidifiée avant la réaction, et des procédés complexes de purification / séparation sont nécessaires après réaction. Afin de contourner ces inconvénients, le développement de procédés de traitement hétérogènes est proposé pour le traitement de l'eau. Dans cette optique de développement de procédés économes, les oxydes de fer comme la magnétite sont proposés comme remplaçants des sels solubles de fer. Une utilisation de tels matériaux, à l'état solide, présente des avantages indéniables, dont la séparation aisée de l'espèce active après réaction par sédimentation ou filtration. Dans le cadre de ce travail de doctorat, différents types d'oxydes de fer, hématite ou magnétite, ont été synthétisés en milieu liquide ionique. La morphologie, les propriétés structurales, les rapports de surface FeII/FeIII, les surfaces spécifiques, les tailles de domaine cristallin, etc. ont été évaluées. Deux molécules différentes, la tétracycline (TC) et le phenol, couramment utilisées dans l'industrie chimique, ont été sélectionnées comme polluants modèles afin d'évaluer les performances des matériaux préparés pour leur élimination. Une partie importante du travail de doctorat a donc été l'étude des propriétés des matériaux pour l'élimination de polluants organiques par le procédé Fenton hétérogène. Les résultats montrent clairement que les principaux facteurs affectant les performances du procédé sont reliés aux propriétés de la phase active, du fait du caractère surfacique des réactions. La stabilité des systèmes catalytiques préparés est néanmoins une propriété cruciale également étudiée. Le manuscrit de doctorat met donc l'accent sur la conception de matériaux originaux destinés à une utilisation dans les procédés avancés d'oxydation dans l'eau
Fenton reaction (Fenton reagent: (Fe2+/H2O2)) and persulfate oxidation process, as advanced oxidation processes, are powerful oxidations used world around. Fenton reaction has been evidenced to be a promising and attractive treatment method for the degradation of a wide variety of hazardous organic pollutants, which are difficult to be treated using traditional soft treatment technologies. During Fenton process, free hydroxyl radicals (HO•), strong oxidant molecules capable of reacting with practically all types of organic and inorganic compounds, are generated. In the meanwhile, due to the similar structure between H2O2 and peroxydisulfate ions, peroxydisulfate ions can be decomposed to sulfate radicals (SO4-•), another kind of highly active oxidant that can react with organic compounds. However, the classical Fenton or peroxydisulfate activation processes present some disadvantages. Indeed, the solution needed acidification before carrying out the reaction and complex separation processes have to be applied after reaction. To overcome these drawbacks, heterogeneous catalytic oxidation processes were introduced for wastewater treatment. In this line, magnetite was evidenced as potential substituent to soluble iron ions, and it offers significant advantages such as an easy separation after reaction since the active material can be easily recovered by sedimentation or filtration for further used. In this PhD work, iron oxides, hematite and magnetite, were synthesized using an ionic liquid mediated process. The morphology, structural properties, FeII/FeIII surface ratios, specific surface areas (SSA), mean particle diameters, site densities, etc. were evaluated. Two different model pollutants (tetracycline (TC) and phenol), which are widely used chemicals all over the world, were selected to evaluate the performance of the prepared active materials. A significant part of the PhD study was then on the study of heterogeneous Fenton-like reaction for phenol and TC degradation. Experiments showed that the main factors affecting the heterogeneous Fenton-like system are related to the heterogeneous active phase properties, due to the surface reaction nature occurring over iron oxide surface. However, stability of this active phase, with progressive dissolution under reaction, is also a real challenge. This PhD manuscript, focusing on the design of highly active materials for advanced oxidation processes (AOPs), is constituted of five experiment result parts
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25

Morber, Jenny Ruth. "1D nanowires understanding growth and properties as steps toward biomedical and electrical application /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24825.

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Thesis (Ph.D.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Snyder, Robert; Committee Co-Chair: Wang, Zhong Lin; Committee Member: El-Sayed, Mostafa; Committee Member: Milam, Valeria; Committee Member: Summers, Christopher; Committee Member: Wong, C. P.
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26

Radovanovic, Pavle V. "Synthesis, spectroscopy, and magnetism of diluted magnetic semiconductor nanocrystals /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8494.

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Dudchenko, N. O., A. B. Brik, Y. V. Kardanets, and O. E. Grechanivskyy. "Influence of Ultrasound Treatment on the Properties of Synthetic Magnetite Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35186.

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The paper describes creation of magnetite nanoparticles under ultrasound treatment and investigation of their phase composition and magnetic properties. Magnetite nanoparticles were synthesized via coprecipitation of Fe+2 and Fe+3 with KOH in aqueous solution at 80°C. It was shown, that ultrasound treatment of solution during the synthesis of magnetite nanoparticles leads to the increasing of size and saturation magnetization obtained nanoparticles. The results of X-ray diffraction measurements show that the synthesized particles consist of magnetite. The size of synthesized magnetite nanoparticles according to Xray diffraction measurements was approximately 10 nm. Saturation magnetization of synthesized magnetite nanoparticles is rather high (37 A*m2/kg). Synthesized magnetite nanoparticles are promising for different medical-biological applications. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35186
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28

Ding, Lei. "Synthèse et étude structurale et magnétoélectrique de composés multiferroïques de la famille des pyroxènes." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY034/document.

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Comprendre les relations entre structures et propriétés des oxydes de métaux de transition complexes a été un objectif de longue date. Les multiferroïques de type II, pour lesquels un ordre magnétique à longue distance et la polarisation électrique apparaissent simultanément, ont attiré un intérêt considérable à la fois du point de vue fondamental et technologique. Cette thèse traite de la synthèse, et de l'étude des structures cristallines et magnétiques et des propriétés de magnéto-électriques d'un système magnétique non trivial: la famille des composés pyroxène M2M1T2O6 (M2 = métal mono- ou bivalent, M1 = métal de transition di- ou trivalent, T = Si ou Ge). L'objectif de cette thèse réside dans l'étude de leurs propriétés magnétiques et multiferroïques sur la base de la compréhension de leurs structures. Cinq systèmes ont été étudiés et sont présentés, visant à comprendre comment la variation des structures affecte les propriétés magnétiques et magnéto-électriques qui en découlent.Nous avons synthétisé le pyroxène Cu0.8Mg1.2Si2O6 qui cristallise avec la structure de type bas-clinopyroxene, avec Cu2 + localisé sur le site de M2 en raison de sa nature Jahn-Teller. Cela rend Cu0.8Mg1.2Si2O6 paramagnétique à toutes températures en raison de l'arrangement isolé des cations magnétiques.Les propriétés de CaMnGe2O6, ont été réétudiées par mesures de susceptibilité magnétique, chaleur spécifique et diffraction de neutrons. Des corrélations de spins unidimensionnelles à courte portée ont été attestées par l'ajustement par un modèle phénoménologique de mesures de diffusion diffuse magnétique de neutrons. L'effet magnéto-électrique linéaire et la ferrotoroïdicité concomitante autorisés par la symétrie magnétique, ont été mis en évidence expérimentalement et théoriquement. Le composé CaMnSi2O6 a été synthétisé à haute pression et à haute température et étudié pour évaluer l'effet de la modification de taille sur le site T sur les propriétés magnétiques du système. Il apparaît que CaMnSi2O6 présente des propriétés magnétiques très similaires à celles de son homologue Ge: la symétrie magnétique et les propriétés magnéto-électriques sont conservées.Pour étudier l'effet de la substitution sur le site M1 occupé par des cations 3d magnétiques, nous avons étudié le diagramme de phase magnétique de la solution solide CaCo1-xMnxGe2O6, pour laquelle les deux membres extrêmes présentent des états fondamentaux magnétiques différent. Sauf pour le cas x = 0, tous les composés présentent deux transitions de phase magnétiques, celle a T la plus élevée correspondant à un ordre magnétique à courte portée et celle à T la plus basse à un ordre AFM. Jusqu'à x = 0,75 (riche en Co), l'ordre AFM à basses T correspond à celui du composé x = 0, la transition à T plus élevées état désordonné de spins gelés. Pour les valeurs de x plus élevées, de l'état fondamental correspond à l'ordre AFM du composé x = 1 (pur Mn). L'ordre magnétique à courte portée observé à des températures élevées est attribué à des corrélations de spin unidimensionnelles induites par la frustration.En outre, une nouvelle famille de pyroxènes à base de Sr, SrMGe2O6 (M = Mn, Co) a été synthétisée et étudiée, rendant accessible l'étude des relations magnéto-structurales liées à la substitution de cations sur le site M2. Nos mesures magnétoélectriques et les données de NPD indiquent que SrMnGe2O6 est un multiferroïque de type II avec un ordre magnétique caractérisé par une configuration de spins cycloïdale, tandis que SrCoGe2O6 devrait présenter un effet magnétoélectrique bilinéaire, comme autorisé par sa symétrie magnétique C2'/c'. La comparaison entre les pyroxènes à base de Sr et de Ca a été effectuée d'un point de vue structural, et les paramètres structuraux pertinents pour les états fondamentaux magnétiques ont été également étudiés
Understanding the relationships between the structures and properties of complex transition metal oxides has been a long-standing goal. Multiferroics of spin origin, for which magnetic long range order and electric polarization appear simultaneously, have been attracting considerable interest both from fundamental and technological point of view. This thesis deals with the synthesis, crystal and magnetic structures and magneto-electric properties on a non-trivial magnetic system: the family of pyroxene compounds M2M1T2O6 (M2 =mono- or divalent metal, M1=di- or trivalent transition metal, T=Si or Ge). The focus of this thesis lies on multiferroic and exotic magnetic properties based on the understanding of their structures. Five systems have been investigated and presented aiming to understand how the structural variation affects the magnetic properties, and the ensuing magneto-electric properties.We have synthesized a copper-bearing pyroxene Cu0.8Mg1.2Si2O6 which crystallizes with the low-clinopyroxene structure, with Cu2+ located in the M2 site due to the Jahn-Teller nature of the Cu2+ cation. This makes Cu0.8Mg1.2Si2O6 paramagnetic at all temperatures because of the isolated arrangement of the magnetic cations.The properties of CaMnGe2O6, were re-investigated by means of magnetic susceptibility, heat capacity and neutron diffraction measurements. One dimensional short-range spin correlations were evidenced by fitting a phenomenological model to diffuse magnetic neutron scattering. The linear magnetoelectric effect and concomitant ferrotoroidicity allowed by the magnetic symmetry, were evidenced experimentally and theoretically. High pressure and high temperature synthesized CaMnSi2O6 was investigated to evaluate the effect of size modification on the T site on the magnetic properties of the system. It turns out that CaMnSi2O6 displays quite similar magnetic properties to its Ge counterpart: both the magnetic symmetry and magneto-electric properties are conserved.To study the effect of substitution on the M1 site occupied by magnetic 3d cations, we investigated the magnetic phase diagram of the CaCo1-xMnxGe2O6 solid solution, for which the two end members display different magnetic ground states. Except for the x=0 case, all compounds undergo two magnetic phase transitions, the higher T one corresponding to short range magnetic ordering and the low T one to AFM ordering. Up to x=0.25 (Co rich part), the low T AFM order corresponds to that of the x=0 end member and the transition observed at higher temperatures corresponds to frozen spin disorder. For higher x values, the ground state corresponds to the AFM order of the x= 1 pure Mn end member. The magnetic transition with short-range character at high temperatures is attributed to one-dimensional short range spin correlations induced by frustration.Moreover, a new family of Sr-based pyroxenes SrMGe2O6 (M=Mn, Co) was synthesized and investigated, making the study of magneto-structural relationships accessible for the substitution of cations on the M2 site. Magnetoelectric measurements and NPD data indicate that SrMnGe2O6 is a multiferroic of spin origin with a magnetic order characterized by a cycloidal spin configuration, while SrCoGe2O6 should display bilinear magnetoelectric effect as allowed by its commensurate magnetic symmetry determined as C2'/c'. The comparison between Sr- and Ca-based pyroxenes from a structural viewpoint has been performed, and the relevant structural parameters for the magnetic ground states are also appreciated
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Han, Man Huon. "Development of synthesis method for spinel ferrite magnetic nanoparticle and its superparamagnetic properties." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26465.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Z. John Zhang; Committee Member: Angus Wilkinson; Committee Member: C P Wong; Committee Member: E. Kent Barefield; Committee Member: Mostafa El-Sayed. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Venturini, Pierre. "Synthèse et caractérisation de nanomatériaux hybrides innovants pour le biomédical." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0351/document.

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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
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Cabuil, Valérie. "Ferrofluides a base de maghemite : synthese, proprietes physicochimiques et magneto-optiques." Paris 6, 1987. http://www.theses.fr/1987PA066001.

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Les ferrofluides etudies sont constitues de particules de maghemite solubilisees en milieu aqueux (ferrofluides ioniques) ou non aqueux (ferrofluides surfactes). Le mode de synthese permet de controler les caracteristiques des grains (taille et densite superficielle de charge)
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Vaughan, Lisa Ann. "Enviromentally benign synthesis and application of some spinel ferrite nanopartilces." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44876.

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In this thesis, the commercial viability of the aminolytic synthesis method is explored through robustness, versatility, and waste reduction studies. We report the preparation of metal precursors and the development of a synthetic approach using an aminolytic reaction of metal carboxylates in oleylamine and non-coordinating solvent. Manganese doping in the cobalt ferrites allows for the investigation of the couplings. All the compositions in the series Co1-xMnxFe2O4, 0.0  x  1.0 were synthesized via the aminolytic reaction. The coercivity decreases with increasing Mn2+ concentration due to reducing of high magnetic anisotropy ion (Co2+) content. To our knowledge, this work is the first completed series of Co1-xMnxFe2O4. The method is used to synthesize manganese ferrites dope with chromium. This allows for the investigation of the effects of orbital momentum quantum coupling. All the compositions of MnFe2-xCrxO4, x= 0.0, 0.05, 0.13, 0.25, 0.43, 0.62, and 0.85, were synthesized via the In-situ aminolytic method. Chromium concentration weakens the couplings resulting in the decrease in overall magnetic moment. All by-products can be recycled for re-utilization. The "mother" solution can be used for multiple batches without treatment. Our trials have shown that the reaction could undergo ten reactions using the same solution without scarifying the quality or yield of the product. Finally, an environmental application is explored through the use of iron oxides. Samples of goethite, maghemite, magnetite, and hematite were synthesized and characterized. These nanoparticles were exposed to arsenic and chromium solutions to measure the percent uptake of contaminant by each phase. Adsorption isotherms were plotted to obtain Freundlich parameters. The adsorption constant (K) averages over a 400% increase on literature values. We synthesized hematite and maghemite core-shell particles and exposed them to arsenite and maghemite core-shell particles have the higher removal affinity due to their smaller size.
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Mashavhela, Manuel. "Synthesis and charaterization of coated and uncoated magnetic nanoparticles." Thesis, University of Limpopo (Medunsa Campus), 2009. http://hdl.handle.net/10386/243.

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Thesis (MSc (Chemistry and Biochemistry))--University of Limpopo, 2009.
Magnetic nanoparticles have been proposed for use as biomedical purposes to a large extent for several years. In recent years, nanotechnology has developed to a stage that makes it possible to produce, characterize and specifically tailor the functional properties of nanoparticles for clinical applications. This has led to various opportunities such as improving the quality of magnetic resonance imaging, hyperthemic treatment for malignant cells, site-specific drug delivery and the manipulation of cell membranes. To this end a variety of iron oxide particles have been synthesized. A common failure in targeted systems is due to the opsonization of the particles on entry into the bloodstreams, rendering the particles recognizable by the body’s major defense system, the reticulo-endothelial system. The co-precipitation method: nanoparticles comprised of gold shell and magnetite/maghemite inclusion were synthesized by overgrowing the gold shell onto the magnetic seeds using sodium citrates as a reducing agent. Oxidized magnetites (Fe3O4) fabricated by co-precipitation of Fe2+ and Fe3+ in strong alkaline solution were used as magnetic cores. These magnetic nanoparticles were characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), ultraviolet-visible (UV-vis) spectroscopy and Vibrating Sample Magnetometer (VSM). Results from x-ray diffraction show that the gold-iron oxide nanoparticles have a face-centered cubic shape, a=8.39 Å and a special group Fd3-m=227 with the dominant crystal planes of {311}. The gold-coated magnetic nanoparticles exhibited a surface plasmon resonance peak at 520 nm. The nanoparticles are well dispersed in distilled water. The particle size of the magnetite nanoparticles was about 0.5 μm (500 nm) confirmed by transmission electron microscope image. The saturation magnetization of the as-synthesized iron oxide nanopowders was 38 emu/g and the blocking temperatures for magnetization 1, magnetization 2, magnetization 3, and magnetization 4 are 150, 143, 138, and 135 K, respectively. The reverse micelle (Micro emulsion) method: a unique reverse micelle method has been developed to prepare gold-coated iron (Fe@Au) nanoparticles. X-ray diffraction, iv ultraviolet/visible, transmission electron microscope, and magnetic measurements are utilized to characterize the nanocomposites. X-ray diffraction only gives Face-Centered Cubic (FCC) patterns of gold for the obtained nanoparticles and indicated that gold exists as a metal. The absorption band of the iron@gold colloid shifts to a longer wavelength and broadens relative to that of the pure gold colloid. Transmission electron microscope results show that the average size of the iron@gold nanoparticles is about 2 μm (2000 nm) and indicated that the nanocomposite was single-nanosized and has a sharp size distribution. These nanoparticles are self-assembled into chains on micron scale under a 0.5T magnetic field. Magnetic measurements show that the particles are super paramagnetic with a blocking temperature (TB) of 42 K. At 300 K (above blocking temperature), no coercivity (Hc) and remanence (Mr) is observed in the magnetization curve, while at 2 K (below TB), coercivity and remanence are observed to be 728 Oe and 4.12 emu/g, respectively.
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Holm, Linda Josefine. "Continuous hydrothermal synthesis and crystallization of magnetic oxide nanoparticles." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/10971.

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Sabo, Daniel E. "Novel synthesis of metal oxide nanoparticles via the aminolytic method and the investigation of their magnetic properties." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50122.

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Metal oxide nanoparticles, both magnetic and nonmagnetic, have a multitude of applications in gas sensors, catalysts and catalyst supports, airborne trapping agents, biomedicines and drug delivery systems, fuel cells, laser diodes, and magnetic microwaves. Over the past decade, an inexpensive, simple, recyclable, and environmentally friendly large, scale synthesis method for the synthesis of these metal oxide nanoparticles has been sought. Many of the current techniques in use today, while good on the small, laboratory bench scale, suffer from drawbacks that make them unsuitable for the industrial scale. The aminolytic method, developed by Dr. Man Han while working for Dr. Zhang, fits industrial scale-up requirements. The aminolytic method involves a reaction between metal carboxylate(s) and oleylamine in a non-coordinating solvent. This system was shown to produce a range of spinel ferrites. Dr. Lisa Vaughan showed that this method can be recycled multiple times without degrading the quality of the produced nanoparticles. The purpose of this thesis is to test the versatility of the aminolytic method in the production of a wide range of metal oxides as well as various core/shell systems. Chapter 2 explores the effect of precursor carboxylates chain length on the aminolytic synthesis of cobalt ferrite, and manganese ferrite nanoparticles. In Chapter 3, a series of CuxMn1-xFe₂O₄, (x ranges from 0.0 to 0.2), nanoparticles were synthesized via the aminolytic method. This series allows for the investigation of the effects of orbital Jahn-Teller distortion as well as orbital angular momentum on the magnetic properties of this ferrite. The quantum couplings of magnetic ions in spinel ferrites govern their magnetic properties and responses. An understanding of the couplings between these metal ions allows for tailoring magnetic properties to obtain the desired response needed for various applications. Chapter 4 investigates the synthesis of MnO and Mn₃O₄ nanoparticles in pure single phase with high monodispersity. To the best of our knowledge, the range of sizes produced for MnO and Mn₃O₄ is the most extensive, and therefore a magnetic study of these systems shows some intriguing size dependent properties. The final part of this chapter investigates the applicability of the aminolytic method for building a MnO shell on a CoFe₂O₄ core. Chapter 5 explores the synthesis of another metal oxide, ZrO₂ in both the cubic and monoclinic phases with no impurities. The use of the aminolytic method here removes the need for dangerous/expensive precursors or equipment and eliminates the need for extensive high temperature heat treatments that destroy monodispersity which is required for most techniques. The creation of a core/shell system between CoFe₂O₄ and ZrO₂ using the aminolytic method was also tested. This core/shell system adds magnetic manipulation which is especially useful for the recovery of zirconia based photocatalyst. Chapter 6 studies the application of the aminolytic method in the synthesis of yttrium iron garnet (YIG) and yttrium iron perovskite (YIP) nanoparticles. Current synthesis techniques used to produce YIG and YIP nanoparticles often requires high temperatures, sensitive to contamination, which could be eliminated through the use of our method
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Suh, Su Kyung Ph D. Massachusetts Institute of Technology. "Controlled synthesis of magnetic particles." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/70458.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Magnetic particles have been used for many applications demanding a broad range of particles morphologies and chemistries. Superparamagnetism is advantageous over ferromagnetism because it enables us to control and recover magnetic nanoparticles during and after chemical processing. Superparamagnetic particles have an oriented magnetic moment under a magnetic field but lose this behavior in the absence of a field. Ferromagnetic materials can be superparamagnetic when they consist of a single size domain, which is on the order of 10s of nanometers. However, since the magnetic force is proportional to the volume of the particle, one needs to apply higher gradient of magnetic field to recover smaller particles. Therefore, large particles are preferred for easy manipulation using external forces. For this reason, the synthesis of large, superparamagnetic particles is very important and is desirable for future applications. The purpose of this work is (1) to examine the three synthesis methods of superparamagnetic units, (2) to understand the behavior of particles created using these methods as well as the synthesis mechanisms, and (3) to investigate the potential applications of these particles. Large paramagnetic particles can be made by assembling superparamagnetic nanoparticles. We developed a method for the process-dependent clustering of monodisperse magnetic nanoparticles using a solvent evaporation method from solid-in-oilin- water (S/O/W) type emulsions. When polymers that are incompatible with the nanoparticle coatings were included in the emulsion formulation, monolayer- and multilayer-coated polymer beads and partially coated Janus beads were prepared. The precise number of nanoparticle layers depended on the polymer/magnetic nanoparticle ratio in the oil droplet phase parent emulsion. The magnetic nanoparticle superstructures responded to the application of a modest magnetic field by forming regular chains with alignment of nonuniform structures (e.g., toroids and Janus beads) in accordance with theoretical predictions and with observations in other systems. In addition, we synthesized non-spherical magnetic microparticles with multiple functionalities, shapes and chemistries. Particle synthesis is performed in two steps; polymeric microparticles homogenously functionalized with carboxyl groups were generated AA % using stop-flow lithography, and then in situ co-precipitation was used to grow magnetic nanoparticle at these carboxyl sites. With successive growth of magnetic nanoparticles, we obtained polymeric particles with saturations magnetization up to 42 emu per gram of microparticle, which is significantly greater than what can be obtained commercially. We also investigated the physical properties of magnetic nanoparticles grown in polymeric microparticles, and provide an explanation of the properties. Lastly, we used experimentation and modeling to investigate the synthesis of opaque microparticles made via stop-flow lithography. Opaque magnetic beads incorporated into hydrogel microparticles during synthesis changed the height and the degree of cross-linking of the polymer matrices formed. The effect of the concentration of the opaque material on the particle height was determined experimentally, and agreed well with model predictions based on the photopolymerization process over a wide range of UV absorbance. We also created particles with two independent anisotropies, magnetic and geometric, by applying magnetic fields during particle synthesis. Our work provides a platform for rational design of lithographic patterned opaque particles and also a new class of structured magnetic microparticles. Overall, this work demonstrates three strategies for creating magnetic substrates containing superparamagnetic nanoparticles and characterization of their resulting properties.
by Su Kyung Suh.
Ph.D.
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37

Thomas, L. "Nanoparticle synthesis for magnetic hyperthermia." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/646236/.

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This work reports on an investigation into the synthesis, control, and stabilisation of iron oxide nanoparticles for biomedical applications using magnetic hyperthermia. A new understanding of the factors effecting nanoparticle growth in a coprecipitation methodology has been determined. This thesis challenges the highly cited Ostwald Ripening as the primary mechanism for nanoparticulate growth, and instead argues that in certain conditions, such as increasing reaction temperature, a coalescence mechanism could be favoured by the system. Whereas in a system with a slower rate of addition of the reducing agent, Ostwald ripening is the favoured mechanism. The iron oxide nanoparticles made in the study were stabilised and functionalised for the purpose of stability in physiological environments using either carboxylic acid or phosphonate functionalised ligands. It was shown that phosphonate ligands form a stronger attachment to the nanoparticle surface and promote increased stability in aqueous solutions, however, this affected the magnetic properties of the particles and made them less efficient heaters when exposed to an alternating magnetic fields. Tiopronin coated iron oxide nanoparticles were a far superior heater, being over four times more effective than the best commercially available product. Due to its strong response, experiments into the antimicrobial properties of tiopronin coated iron oxide nanoparticles were undertaken, specifically on Staphylococcus aureus, to our knowledge this is the first time magnetic hyperthermia has been used for such an application. At concentrations of 50 mg/ml the sample was capable of complete bacterial kills following exposure to the in-house magnetic hyperthermia MACH system. Aging and oxidation over a period of a month did decrease the performance of the particles to kill bacteria using MACH heating, however they were still shown to be effective in killing Staphylococcus aureus.
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Zagorskiy, D. L., V. V. Korotkov, V. N. Kudryavtsev, S. A. Bedin, S. N. Sulyanov, K. V. Frolov, V. V. Berezkin, and B. V. Mchedlishvili. "Matrix Synthesis of Magnetic Nanowires." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35260.

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In this work nanowires of magnetic metals (Co,Ni and Fe) were obtained via matrix synthesis, using etched track polymer template. The new data on electrodeposition of Ni was obtained. Two effects- the growth rate decrease (while the growing metal nanowires are filling the pores) and current density in-crease were investigated and discussed. The results of X-rays analysis obtained using synchrotrone source demonstrated the dependence of structure and composition of nanowires on the deposition voltage. Mossbauer spectroscopy was used for in-vestigation of Fe samples. The obtained data are in good agreement with X-rays results. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35260
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David, Anand. "Bioinspired synthesis of magnetic nanoparticles." [Ames, Iowa : Iowa State University], 2009.

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40

Nemati, Porshokouh Zohreh. "Novel Magnetic Nanostructures for Enhanced Magnetic Hyperthermia Cancer Therapy." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6548.

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In this dissertation, I present the results of a systematic study on novel multifunctional nanostructure systems for magnetic hyperthermia applications. All the samples have been synthesized, structurally/magnetically characterized, and tested for magnetic hyperthermia treatment at the Functional Materials Laboratory of the University South Florida. This work includes studies on four different systems: (i) Core/shell Fe/γ-Fe2O3 nanoparticles; (ii) Spherical and cubic exchange coupled FeO/Fe3O4 nanoparticles; (iii) Fe3O4 nano-octopods with different sizes; (iv) High aspect ratio FeCo nanowires and Fe3O4 nanorods. In particular, we demonstrated the enhancement of the heating efficiency of these nanostructures by creating monodisperse and highly crystalline nanoparticles, and tuning their magnetic properties, mainly their saturation magnetization (MS) and effective anisotropy, in controlled ways. In addition, we studied the influence of other parameters, such as the size and concentration of the nanoparticles, the magnitude of the applied AC magnetic field, or different media (agar vs. water), on the final heating efficiency of these nanoparticles. For the core/shell Fe/γ-Fe2O3 nanoparticles, a modest heating efficiency has been obtained, resulting mainly from the strong reduction in MS caused by the shrinkage of the core with time. However, for sizes above 14 nm, the shrinkage process is much slower and the obtained heating efficiency is better than the one exhibited by conventional solid nanoparticles of the same size. In the case of the exchange-coupled FeO/Fe3O4 nanoparticles, we successfully created two sets of comparable particles: spheres with 1.5 times larger MS than the cubes, and cubes with 1.5 times larger effective anisotropy than the spheres, while keeping the other parameters the same. Our results show that increasing the effective anisotropy of the nanoparticles gives rise to a greater heating efficiency than increasing their MS. The Fe3O4 nano-octopods, with enhanced surface anisotropy, present better heating efficiency than their spherical and cubic nanoparticles, especially in the high field region, and we have shown that by tuning their size and the effective anisotropy, we can optimize their heating response to the applied AC magnetic field. For magnetic fields, smaller than 300−400 Oe we found that the smallest nano-octopods give the best heating efficiency. Yet if we increase the AC field value, the bigger octopods show an increased heating efficiency and become more effective. Finally, the FeCo nanowires and Fe3O4 nanorods exhibit enhanced heating efficiency with increasing aspect ratio when aligned in the direction of the applied AC magnetic field, due to the combined effect of shape anisotropy and dipolar interactions. Of all the studied systems, these 1D high aspect ratio nanostructures have displayed the highest heating rates. All of these findings point toward an important fact that tuning the structural and magnetic parameters in general, and the effective anisotropy in particular, of the nanoparticles is a very promising approach for improving the heating efficiency of magnetic nanostructures for enhanced hyperthermia.
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Mishra, Shantanu, Doreen Beyer, Reinhard Berger, Junzhi Liu, Oliver Gröning, José I. Urgel, Klaus Müllen, Pascal Ruffieux, Xinliang Feng, and Roman Fasel. "Topological defect-induced magnetism in a nanographene." American Chemical Society, 2019. https://tud.qucosa.de/id/qucosa%3A73172.

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The on-surface reactions of 10-bromo-10'-(2,6-dimethylphenyl)-9,9'-bianthracene on Au(111) surface have been investigated by a combination of bond-resolved scanning tunneling microscopy, scanning tunneling spectroscopy, and tightbinding and mean-field Hubbard calculations. The reactions afford the synthesis of two open-shell nanographenes (1a and 1b) exhibiting different scenarios of all-carbon magnetism. 1a, an allbenzenoid nanographene with previously unreported triangulenelike termini, contains a high proportion of zigzag edges, which endows it with an exceedingly low frontier gap of 110 meV and edge-localized states. The dominant reaction product (1b) is a non-benzenoid nanographene consisting of a single pentagonal ring in a benzenoid framework. The presence of this nonbenzenoid topological defect, which alters the bond connectivity in the hexagonal lattice, results in a non-Kekulé nanographene with a spin S = ½, which is detected as a Kondo resonance. Our work provides evidence of all-carbon magnetism, and motivates the use of topological defects as structural elements toward engineering agnetism in carbon-based nanomaterials for spintronics.
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42

Díaz, Torres Raúl. "Synthesis, Characterization and Deposition on Surfaces of Curcuminoids-based Systems." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663059.

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Nanoscience and Nanotechnology have become research areas that promote the design and fabrication of novel devices with a number of different applications with the aim of satisfying the growing demand of the society regarding technological advances. The breakthrough in some of these subjects directly associates with the development of specific molecular systems with new and advanced features, applicable toward the development, at the nanoscale, of efficient materials that could act as molecular switches or active components in memory devices, transistors or sensors, among others. In this regard, promising molecular-based systems, to be applicable in these fields, are the so-called Curcuminoids (CCMoids). These molecules can present versatile structures, displaying always (i) a conjugated chain of seven carbon atoms, which confers the molecules with reasonable conductive properties; (ii) a β-diketone group located in the middle of the chain, that opens the possibility of coordinating with metallic centers, and (iii) two aromatic groups, located on both sides of the molecules that add fluorescent, redox active and optical properties, among others. The main goal of this thesis rest on the design and synthesis of new CCMoids that can be applied in different areas of nanoscience. Thus, different modifications on their structure were carried out in order to achieve interesting properties. The results obtained in this work have been grouped in five different sections; corresponding each one to a different area. This way: (1) Molecular Magnetism: the first section is focused on the search of systems which display interesting magnetic properties, especially systems with single molecule magnet behavior. Thus, magneto-structural studies were performed by the synthesis of several coordination compounds using magnetic metallic centers (CoII and NiII) coordinate with a CCMoid ligand called 9Accm. In addition, a study of the influence of the paramagnetic centers on the fluorescent properties derived from the CCMoid ligand was also performed together with deposition studies on HOPG (highly oriented pyrolytic graphite). (2) Molecular Electronic: the second section focuses on the study of the electronic transport of a new CCMoid system within a three terminal nanodevice containing few layer graphene (FLG) electrodes. This study centers in the improvement of the conductive properties of a previously measured CCMoid system, in which 9Accm was used as a nanowire in a molecular transistor by π-π stacking interactions with the graphene electrodes. The new CCMoid contains an elongated conjugated skeleton that improves the anchoring properties of the final system with the FLG electrodes. (3) Molecular Sensors: the third section is based on the immobilization of fluorescent CCMoids on surfaces and their used as chemical sensors for boron ions. The immobilization was carried out on functionalized SiO2 surfaces by the use of the Microcontact printing technique (μ-CP) that allowed the creation of fluorescent micropatterns on the surfaces. In addition, studies regarding the coordination of boron to the CCMoids attached on the surfaces and the effect in their fluorescent properties was performed to explore they as chemical sensors. (4) Molecular Host-Guest Chemistry: the fourth section is focused on the fabrication of supramolecular host-guest systems based on CCMoids. In the first part, a study of the CCMoid acting as a guest was performed. In this case, a novel CCMoid molecule that contain a ferrocene group is inserted in different host cavities (cyclodextrin and cucurbituril). This study was performed in solution and on Au surfaces. On the other hand, the synthesis of another CCMoid was carried out to be used as a host, being the main ligand in the formation of molecular cages. (5) Molecular Donor/Acceptor Chemistry: the fifth section is based on the study of the donor/acceptor properties of additional CCMoids with the idea of using them as components of organic photovoltaics cells (OPVs). For this study, the synthesis of two families of CCMoids with acceptor and donor moieties on the sides of the molecules was performed, and additional variations on their structure were achieved to assess their influence on the optical and electronic properties of the systems.
La nanociencia y la nanotecnología se han erigido como las áreas encargadas en diseñar y fabricar nuevos dispositivos cada vez más potentes y rápidos con el fin de satisfacer la creciente demanda tecnológica de nuestra sociedad. Una familia de moléculas muy prometedoras para ser aplicable en estos campos es la conocida como Curcuminoides (CCMoides) debido a su gran versatilidad. Esta tesis se centra en el diseño y síntesis de nuevos CCMoides para su posterior aplicación en diferentes campos de la nanociencia. Para ello, se han llevado a cabo distintas modificaciones en sus estructuras con el fin de conseguir propiedades interesantes. Los resultados obtenidos han sido agrupados en 5 secciones, cada uno de los cuales corresponde a un área de investigación diferente: (1) Magnetismo Molecular: La primera sección se centra en la búsqueda de sistemas que presenten propiedades de imán molecular. Para ello, se llevó a cabo un estudio magneto- estructural mediante la síntesis de varios compuestos de coordinación utilizando centros metálicos magnéticos (CoII y NiII) coordinados con el ligando CCMoide llamado 9Accm. (2) Electrónica Molecular: La segunda sección se centra en el estudio del transporte electrónico de un nuevo sistema CCMoide como parte activa de un sistema de tres terminales que actúa como transistor molecular de efecto campo. (3) Sensor Molecular: La tercera sección se centra en la inmovilización de CCMoides fluorescentes en superficies funcionalizadas que puedan actuar como sensores químicos de boro. Esta inmovilización se llevara a cabo en superficies de SiO2 mediante el uso de la técnica Microcontact printing. (4) Huésped-Anfitrión Molecular: La cuarta sección se centra en la fabricación de sistemas supramoleculares huésped-anfitrión. El primer estudio se centra en la utilización de ligandos CCMoide (huésped), que interaccionan con dos sistemas (ciclodextrina y cucurbiturilo) (anfitriones). Por otro lado, se realizó la síntesis de un nuevo CCMoide con el objetivo de que pudiese actuar como anfitrión mediante la formación de cajas moleculares. (5) Dador-Aceptor Molecular: La quinta sección se centra en el estudio de las propiedades aceptoras/dadoras de CCMoides para que puedan ser utilizados en la fabricación de celdas fotovoltaicas orgánicas (OPVs), llevándose a cabo la síntesis de dos familias de CCMoides con grupos aceptores y dadores.
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43

Kuznetsov, V. N., A. S. Stanislavov, S. N. Danilchenko, O. V. Kalinkevich, A. N. Kalinkevich, Leonid Fedorovych Sukhodub, Леонід Федорович Суходуб, and Леонид Федорович Суходуб. "Structural Properties of the Nanocrystallized Magnetite of Different Syntheses." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35450.

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Transmission electron microscopy (TEM) with electronic diffraction and X-ray diffraction (XRD) was used to study structural features of nanosized magnetite Fe3O4, which was synthesized using polymeric matrices (polysaccharide chitosan, at alias). From the received data it was revealed that growth inhibition and size stabilization of Fe3O4 nanoparticles were strongly affected by polysaccharide matrix. It was also observed that directional size decrease of Fe3O4 nanoparticles was accompanied by the increasing defectiveness of crystal lattice and decreasing unit cell size. The effectiveness of complementary use of both TEM with electronic diffraction and XRD techniques for structural and substructural parameters determination while studying magnetite nanosized particles synthesized in polysaccharide matrices is shown in this paper. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35450
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44

Norberg, Nicholas S. "Magnetic nanocrystals : synthesis and properties of diluted magnetic semiconductor quantum dots /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8625.

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45

Pascu, Oana. "Synthesis of Magnetic Nanoparticles and nanoparticles and Strategies towards Magneto-Photonic Materials." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/96878.

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El proyecto propuso obtener un sistema óptico que responda a estímulos externos, en concreto, a campos magnéticos. Cristales fotónicos de dos y tres dimensiones fueron seleccionados como sistemas ópticos para ser funcionalizados con nanopartículas magnéticas para obtener cristales magneto-fotónicos (MPCs). La funcionalización de cristales fotónicos tuvo como objeto no solamente permitir los cambios en la posición espectral del bandgap utilizando un campo magnético externo, sino también permitir respuestas magneto-ópticas aumentadas a determinadas longitudes de onda debido a la interacción luz-materia. Previamente se ha demostrado que la respuesta magneto-óptica en un cristal fotònico 1D aumenta significativamente para frecuencias en el borde del bandgap. Sin embargo, lograr cristales 3D de alta calidad es mucho más complejo y, por lo tanto, conseguir una respuesta magneto-óptica óptima, comparable a la de los cristales magneto-fotónicos 1D, sigue siendo un tema difícil. Los cristales magneto-fotónicos tridimensionales con una respuesta magneto-óptica aumentada pueden ser una plataforma adecuada para el desarrollo, por ejemplo, de una nueva generación de aislantes ópticos rápidos y compactos para transmisión en comunicaciones ópticas, disminuyendo drásticamente su espesor y en consecuencia las pérdidas ópticas (la cual es ventajoso para la óptica integrada). Los objetivos de esta tesis doctoral han sido : 1) sintetizar nanopartículas magnéticas de alta cristalinidad (níquel, óxido de hierro y ferrita de manganeso) a través de métodos químicos, con el fin de controlar el tamaño de las nanopartículas a través de diversos parámetros experimentales y para estudiar la estabilidad de las soluciones coloidales magnéticas, 2) la fabricación de materiales magneto-fotònicos mediante: i) técnicas ¨bottom-up´´-para la incorporación de nanopartículas magnéticas en un cristal fotónico prefabricado (2D o 3D) y ii) métodos ¨top-down¨ -p.e., mediante técnicas litográficas (haz de electrones y litografía nanoimprint), 3) la caracterización estructural y morfológica de los materiales fotónicos preparados, 4) optimizar la fabricación de los cristales magneto-fotónicos para garantizar una respuesta magneto-óptica aumentada a longitudes de onda cerca del bandgap óptico. La presente tesis está dividida en seis capítulos El capítulo 1 incluye una introducción general a las nanopartículas magnéticas, los materiales cristales fotónicos convencionales y funcionalizados (magneto-fotónicos). Las nanopartículas magnéticas de tipo metálico (níquel) y de óxido metálico (óxido de hierro y manganeso de ferrita) se describen a través de sus propiedades, la síntesis, estabilidad de las soluciones coloidales y sus aplicaciones. Se presentan los materiales fotònicos y magneto-fotònicos con sus características estructurales y óptica y magneto-óptica. El capítulo 2 describe la síntesis química de nanopartículas magnéticas por tres vías diferentes: la descomposición térmica, calentamiento por microondas y la síntesis continua en etanol supercrítico. El control del tamaño de las nanopartícula y la estabilidad de las soluciones coloidales magnéticas son analizadas. También se aborda la caracterización estructural, morfológica y funcional de las nanopartículas preparadas. El capítulo 3 está enfocado a la fabricación de los cristales magneto-fotònicos bidimensionales por técnicas de ´´top-down´´ (haz de electrones y la litografía por nanoimprint) y bottom-up (depósito de partículas magnéticas asistida por microondas). Para ambas estrategias se describe el protocolo de fabricación desarrollado, junto con la caracterización estructural, morfológica y funcional de los materiales fabricados. El capítulo 4 describe la fabricación de los materiales magneto-fotónicos tridimensionales mediante técnicas bottom-up basadas en dos estrategias, utilizando: i) nanopartículas sintetizadas ex-situ (método de dip-coating asistido por motor paso a paso) y ii) nanopartículas sintetizadas in-situ (depósito asistido por microondas). En el capítulo 5 se enumeran las principales conclusiones de la tesis y se hacen sugerencias para trabajos futuros. El capítulo 6 incluye los anexos. El anexo i. presenta la lista de las publicaciones relacionadas con esta tesis. El anexo ii. incluye una breve descripción de las técnicas experimentales utilizadas y protocolos aplicados para la preparación de las muestras. Los anexos III. y IV contienen las tablas detalladas con las condiciones experimentales y los datos de fabricación de nanopartículas magnéticas y ópalos magnéticos, respectivamente.
The project aimed to obtain an optical system responding to an external stimulus (magnetic field). Photonic crystal materials (two and three dimensions) were selected as the optical systems to be further functionalized with magnetic nanoparticles, to obtain magneto-photonic crystals (MPCs). This functionalization not only would enable the tunability of photonic band gap spectral position using an external magnetic field, but also would enable an enhanced magneto-optical response near photonic band-edge frequencies due to light-matter interaction. It has previously been demonstrated that the magneto-optical response of one-dimensional (1D) MPCs is significantly enhanced at band-edge frequencies. The achievement of high-quality 3D-MPCs is much more complex and the attainment of an optimal magneto-optical response, comparable to that of 1D-MPCs, remains a challenging issue and the work of this thesis goes in this direction. Three dimensional magnetophotonic crystals with enhanced magneto-optical response can be a suitable platform for the development, for instance, of a new generation of fast and compact optical isolators for optical transmission, drastically reducing their thickness and optical losses (advantageous for integrated optics). The objectives of this PhD thesis have been: 1 ) to synthesize highly crystalline magnetic nanoparticles (nickel, iron oxide and manganese ferrite) via a chemical method, to tune the nanoparticles size by playing with various experimental parameters and to study the stability of the obtained liquid magnetic colloids; 2 ) to fabricate magnetophotonic materials by: i) bottom-up techniques – incorporating magnetic nanoparticles into a prefabricated photonic crystal (2D or 3D) and ii) top-down method – nanopatterning of magnetic composite material by lithographic techniques (electron beam and nanoimprint lithography); 3 ) to characterize the prepared photonic materials structurally and morphologically ; 4 ) and to optimize magneto-photonic materials fabrication to ensure appropriate magneto-optical response , namely enhanced magento-optical response near photonic band-edge frequencies. The PhD thesis report is divided into six chapters: Chapter 1 provides a general introduction to magnetic nanoparticles, conventional photonic crystal materials and functionalized magnetophotonic crystals. Magnetic nanoparticles such as metallic (nickel) and metal oxide (iron oxide and manganese ferrite) nanoparticles are discussed through their properties, synthesis, stabilization and applications. Photonic and magnetophotonic materials with their structural and optical/magneto-optical characteristics are presented. Chapter 2 describes the chemical synthesis of magnetic nanoparticles by three different pathways: thermal decomposition, microwave heating and continuous supercritical ethanol synthesis. The tunability of the nanoparticles size and stability of the magnetic colloids are studied. Structural, morphological and functional characterizations of the prepared nanoparticles are discussed. Chapter 3 deals with the fabrication of two-dimensional magneto-photonic materials by top-down (electron beam and nanoimprint lithography) and bottom-up (microwave-assisted deposition) approaches. For both strategies, an individual fabrication protocol was developed. Structural, morphological and functional characterizations of the fabricated materials are discussed. Chapter 4 describes the fabrication of three-dimensional magneto-photonic materials by bottom-up approaches using both ex-situ synthesized nanoparticles (vertical dip-casting deposition) and in-situ synthesized nanoparticles (microwave-assisted coating). Characterization and optimization of these materials are furthermore presented. Chapter 5 lists the main conclusions of the thesis and makes suggestions for future works. Chapter 6 includes the annexes. Annex i. lists the publication I have co-authored related to this thesis. Annex ii. includes a brief description of the experimental techniques used and protocols applied for samples preparation. Annex iii. and iv contains tables with detailed experimental conditions and measurements for magnetic nanoparticles and magnetic opals, respectively.
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46

Fang, Mei. "3D Magnetic Photonic Crystals : Synthesis and Characterization." Licentiate thesis, KTH, Materials Science and Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11983.

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47

Gao, Jinhao. "Multifunctional magnetic nanoparticles : design, synthesis, and applications /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202008%20GAO.

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48

Green, L. A. W. "Synthesis and characterisation of FePt magnetic nanoparticles." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1427377/.

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Magnetic nanoparticles (MNPs) are intensively researched due to their high potential in biomedicine, catalysis and high density information storage. FePt NPs are a potential alternative magnetic material to commonly used magnetite NPs for biomedical applications and the synthesis of FePt NPs is an active area of research. The purpose of this thesis has been to develop wet chemical synthetic methods to tune and improve the properties of FePt magnetic nanoparticles. The morphology of magnetic nanoparticles affects the way they interact with each other, and with their surroundings. Changes in shape and composition with varying synthetic conditions can also give clues to the mechanism of formation. Changes in volume, solvent and the nature of the stabiliser have been shown to yield varying morphology in the FePt system. Multicore FePt nanoparticles up to 44 nm in diameter and composed of Pt rich FePt nanocrystals within an iron rich FePt matrix not previously seen in the literature are presented here. Magnetic properties of multicore nanoparticles are size dependent; in dioctyl ether and dibenzyl ether and with decreasing amount of oleic acid, saturation magnetisation and blocking temperature increase with size. The results indicate that coordination of Fe and Pt intermediates with oleic acid and oleylamine respectively hinders deposition of each respective metal in the growth of discrete and multicore nanoparticles. L-glutathione and albumin immediately transferred 20 nm multicore nanoparticles into water and show that large FePt nanoparticles may be stable under physiological conditions following stability tests. The use of an autoclave is shown to increase the Fe content, crystallinity and subsequent magnetic properties of FePt pseudo cube nanoparticles compared to those synthesised under atmospheric pressure. Decreasing amount of oleic acid is also shown to increase the iron content and can lead to elongated FePt nanoparticles under normal pressure. Infra-red studies indicate mono and bi dentate coordination with oleic acid, however shifts of spectra show that the strength of the bi-dentate interactions weaken with increasing oleic acid amount.
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49

Hudgins, Daniel. "The Design and Synthesis of Magnetic Nanocomposites." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/573.

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Magnetism lies at the core of modern technology and can be found in industries such as oil refining, automotive, telecommunications, personal electronics, and power generation that are integral to our day to day lives. This permeation into everyday life has been enhanced in the past several decades with improvements in material design based upon the principles of nanotechnology leading to smaller, faster, and more efficient devices. The presented research will discuss the synthesis and processing of multiple magnetic nanoparticle structures designed for the enhancement of various, application specific, properties. In the first experiments a tunable core/shell structure was developed with either enhanced optical properties or enhanced catalytic reactivity based solely upon small manipulations in the synthesis resulting in alternate morphologies. Essentially reaction times were controlled to direct core nucleation followed by shell growth and based upon addition times and concentration the final product could be manipulated as either a Fe/Ag or Ag/Fe core/shell. The modifications also resulted in Fe particles decorated with Ag islands that showed significant Plasmon shifts while still maintaining their high magnetization. These particles present applications in catalysts, sensors, and separations. Secondly FexCo100-x alloys were generated in order to determine the atomic compositions with the best magnetic properties. Several post-processing cleaning and annealing regimes were used to determine the most effective method of preparing the particles for utilization in devices. Annealing temperatures of 450°C were found most effective at enhancing magnetic properties while minimizing grain growth. Finally the synthesis of exchange-coupled hard magnetic core/shell nanoparticles was conducted. In this synthesis SmCo5 was synthesized via solvent assisted ball milling in oleic acid. Once completed these particles were processed in a multistep cleaning process which removed excess solvent and much of the surface oxidation. The particles were then suspended in a non-aqueous solvent and a magnetically coupled Co shell was carefully grown under sub-zero conditions. The resulting composite material demonstrated greatly enhanced magnetic properties and a unique laminated structure that had been elusive in nanoparticle research. Several magnetic nanoparticles and compositions were studied resulting in increased functionality based upon the bottom-up nanostructuring of materials. This work allows for the understanding of the effect of synthetic conditions on the control of nucleation and growth dynamics within nanoparticle synthesis and the generation of high quality functional magnetic materials.
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50

Li, Keran. "Surfactant-free synthesis of magnetic latex particles." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10211/document.

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Ce travail de thèse décrit l'élaboration de latex hybrides oxyde de fer (OF)/polymère par polymérisation en émulsion sans tensioactif. Des nanoparticules d'OF cationiques ont été tout d'abord synthétisées par co-précipitation de sels de fer dans l'eau. Des latex hybrides magnétiques ont été ensuite obtenus par deux voies de polymérisation. La première consiste en la synthèse de particules de latex de morphologie 'carapace' par polymérisation en émulsion Pickering du styrène et du méthacrylate de méthyle (MMA). Un comonomère auxiliaire (acide (méth)acrylique ou acide 2-acrylamido-2-méthyl-1-propane sulfonique) a été utilisé pour favoriser l'adsorption des OF à la surface des particules de polymère produites. Les analyses par MET indiquent la présence d'OF à la surface des particules de polymère (structure carapace). L'analyse thermogravimétrique a permis de quantifier l'efficacité d'incorporation des OF, i.e. la fraction d'OF initialement introduits effectivement adsorbés à la surface des particules. L'efficacité d'incorporation augmente avec la quantité de comonomère auxiliaire, le pH et la concentration en OF et dépend de la nature du monomère hydrophobe. Dans la deuxième voie, les OF ont été encapsulés par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) en émulsion aqueuse. La stratégie utilisée repose sur l'utilisation de macroagents RAFT amphiphiles comportant des groupements acide carboxylique connus pour interagir avec la surface des OF. L'interaction entre les macroRAFTs et les OF a été étudiée à travers le tracé de l'isotherme d'adsorption. Des analyses SAXS et DLS indiquent la formation de clusters d'oxyde de fer. Ces derniers ont été ensuite engagés dans la polymérisation en émulsion du styrène ou d'un mélange de MMA et d'ABu (ratio massique : 90/10) pour former une écorce de polymère à leur surface. Les particules carapace et les OF encapsulés affichent un comportement superparamagnétique
This work describes the elaboration of polymer/iron oxide (IO) hybrid latexes through surfactant-free emulsion polymerization. Cationic iron oxide nanoparticles stabilized by nitrate counterions were first synthesized by the co-precipitation of iron salts in water. Magnetic hybrid latexes were next obtained by two polymerization routes carried out in the presence of IO. The first route consists in the synthesis of polymer latexes armored with IO via Pickering emulsion polymerization of methyl methacrylate (MMA) or styrene (St). An auxiliary comonomer (namely methacrylic acid, acrylic acid or 2-acrylamido-2-methy-1- propane sulfonic acid) was used to promote IO particle adhesion to the surface of the generated polymer particles. TEM showed the presence of IO at the surface of the polymer particles and the successful formation of IO-armored polymer particles. TGA was used to quantify the IO incorporation efficiency, which corresponds to the fraction of IO effectively located at the particle surface. The incorporation efficiency increased with increasing the amount of auxiliary comonomer, suspension pH and IO content or with increasing monomer hydrophobicity. In the second route, IO encapsulation was investigated via reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. The developed strategy relies on the use of water-soluble amphipathic macromolecular RAFT agents containing carboxylic acid groups, designed to interact with IO surface. The interaction between the macroRAFT agents and IO was investigated by the study of the adsorption isotherms. Both DLS and SAXS measurements indicated the formation of dense IO clusters. These clusters were then engaged in the emulsion polymerization of St or of MMA and nbutyl acrylate (90/10 wt/wt) to form a polymer shell at their surface. Both IO-armored latex particles and polymer-encapsulated clusters display a superparamagnetic behavior
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