Preparação e caracterização de nanocompósitos de Fe@SiO2, Fe@Fe3O4 e Fe3O4@PNIPAM

• Ano de defesa: 2015
• Autor(a) principal: Nunes, Eloiza da Silva [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Nanoestruturas; Magnetita; Silica; Nanogéis; Nanopartículas; Nanoparticles
• Link de acesso: http://hdl.handle.net/11449/124538

In this work the obtainment of metallic iron nanoparticles in several non-aqueous (glycols) and in aqueous media through chemical reduction with sodium borohydride and the obtainment of core@shell structures Fe@SiO2 and Fe@Fe3O4, was investigated. The characterization results of poly(N-isoproprylacrylamide) (PNIPAM) based magnetic nanocomposites and bare polymeric nanogels (controls) synthesized through radical precipitation polymerization were also presented. The composition of the polymeric nanocomposites was varied as the type of co-monomer (acrylic acid and poly(ethyleneglycol) methylether methacrylate (PEGMA)), crosslinker (methylene bis-acrylamide (MBA) and poly(ethyleneglycol) diacrylate (PEGDA)) and precursor magnetic nanoparticle. The metallic nanoparticles and the core@shell Fe@SiO2 and Fe@Fe3O4 nanostructures were characterized by XRD, Mössbauer spectroscopy, XPS, SEM and TEM. The results show that the iron nanoparticles were composed of α-Fe and varying amounts of Fe1-xBx alloy and the size and morphology of the particles was dependent of the reaction media used. The strategies for metallic nanoparticles coating was efficient and chemically stabilized the magnetic cores. The Fe@SiO2 nanostructures was prepared by using alkoxysilanes precursors through the sol-gel process to produce the silica coating. The silica thickness could be controlled more efficiently in the case of bigger particles produced from chemical reduction in aqueous media. In the case of small nanoparticles the formation of aggregates was observed. The Fe@Fe3O4 core@shell structures were obtained by passivation of the metallic iron nanoparticles in a glycol solvent. The method of passivation enabled good oxidation control of the metallic surface to magnetite phase, avoiding the formation of non-magnetic oxy-hydroxides. The metallic to oxide phase ratio was determined by Rietveld refinement and was dependent of the type...