Synthesis And Properties Of Fe₃O₄ Micro/Nanostructured Materials

The synthesis of low-dimensional Fe3O4 nanomaterials enjoys great popularity because of their promise in advanced magnetic materials, ferrofluids, colored pigments, catalysts, high-density magnetic recording media, and medical diagnostics. Fe3O4 hollow spheres have been considered an ideal candidate for drug-delivery carriers owing to their biocompatible and high magnetization properties. One-dimensional (1D) Fe3O4 nanorods or nanobelts have attracted considerable attention, due to their potential application in perpendicular data recording and spintronic devices. Meanwhile, Fe3O4-conducting polymer nanocomposites can act as promising wave-adsorption and electromagnetic shielding materials. Therefore, low-dimensional Fe3O4 nanomaterials and their composites have attracted significant interest because of their promise in scientific and technological applications.We reported a solvothermal method for the fabrication of monodisperse and single-crystal Fe3O4 hollow microspheres with a diameter of 200 nm in the presence of Na2CO3. The effects of reaction parameters like the reaction time and the reagent concentration on the structure of the resultant samples were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM and scanning electron microscopy (SEM) were used to characterize the as-prepared products. The formation mechanism for Fe3O4 hollow spheres was illustrated by an Ostwald ripening process. The obtained Fe3O4 hollow spheres revealed a ferromagnetic behavior with a saturation magnetization of 75.3 emu g-1, a remnant magnetization of 2.0 emu g-1, and a coercivity of 31.3 Oe at room temperature.1D Fe3O4 nanobelts with width around 70-80 nm and length up to several micrometers were prepared through a hydrothermal method in the presence of Na2CO3. The effects of various reaction parameters on the structure and the component of the resultant samples were examined. It was found that these Fe3O4 nanobelts exhibited almost a super-paramagnetic behavior with a slight remnant magnetization and coercivity, and a high magnetization (Ms= 44-56 emu g-1) at room temperature. Magnetite Fe3O4 nanocrystal clusters (50 nm in diameter) with good dispersibility in aqueous medium were prepared by modified co-precipitation method in the presence of surfactants including sodium dodecylsulfate (SDS), trisodium citrate dehydrate (TSCD), and polyacrylic acid sodium salt (PAASS). The influence of surfactant on the formation of Fe3O4 nanocrystal clusters was studied. It was found that Fe3O4 nanocrystal clusters exhibited almost super-paramagnetic behavior with very small eoercivity and a high magnetization (Ms= 44-56 emu g-1). Magnetite (Fe3O4) nanocrystal clusters-polyaniline (PANI) composites were further synthesized via a self-assembly process in the presence of Fe3O4 nanoclusters containing SDS as the dopant. It was also noted that the morphology, the magnetic and electrical properties of Fe3O4-PANI composites could be adjusted by altering the contents of Fe3O4 and SDS.