Torres, Marco Antonio MoralesRodrigues, Eloise Cristina de Souza2017-06-162017-06-162017-02-03RODRIGUES, Eloise Cristina de Souza. Síntese e caracterização de nanocompósitos de partículas de α-Fe, wüstita e magnetita para aplicações biomédicas. 2017. 118f. Tese (Doutorado em Física) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2017.https://repositorio.ufrn.br/jspui/handle/123456789/23512Oxide nanoparticles have been used in several biomedical applications due to their biocompatibility and biodegradability. Among these applications, magnetic hyperthermia of tumors has been proposed as an alternative treatment of several neoplastic diseases. In this work, we have used high energy milling to produce iron oxide nanoparticles with sizes smaller than 70 nm. We have prepared two groups of samples, the first group is composed of magnetite and α-Fe, samples S1 and S3, the second group is composed of magnetite, wüstite and α-Fe nanoparticles, samples S2 and S4. To improve the sample´s dispersibility in aqueous medium, the samples were functionalized with oleic acid and Pluronic-F127 three-block copolymer. The structural and chemical properties of samples were studied through x-ray diffraction, transmission electron microscopy (TEM) and Mössbauer spectroscopy. The magnetic properties were studied through AC susceptibility and DC magnetization as a function of temperature and field. From the Mössbauer studies, for the sample S4, we observed a ratio between the areas of the spectra for the octahedral and tetrahedral compatible with stoichiometry magnetite. The magnetic measurements showed the Verwey transition at about 120 K, for the two groups of samples. From the TEM images, S4, we verified that the wüstite phase is formed on the magnetite nanoparticles. Therefore, we showed that the wüstite phase and oleic acid surfactant prevent the magnetite nanoparticles from further oxidation. The shift of hystereis loops observed in the field cooled samples is ascribed to exchange interaction between the wüstite and magnetite phases. The AC susceptibility, from S4, showed characteristic peaks of magnetite wall domains, this result indicated that a fraction of particles are multidomain. The samples were submitted to an AC magnetic field and we observed an increase in temperature of e 11º C and 53º C for samples functionalized and bare, for S1 and S4 respectively, for sample S4, the increase in temperature, was of 14° C. The combination of magnetic properties, the ability to release heat in presence of an AC, and the stability of particles in aqueous suspension suggest that these samples are good candidates for magnetic hyperthermia.Acesso AbertoNanopartículasMagnetita e hipertermia magnéticadoctoralThesisCNPQ::CIENCIAS EXATAS E DA TERRA::FISICA