| Nanotechnology is one of the current major research fields. Due to numerous applications, magnetic nanoparticles have become one of the most interesting areas of research. In a previous study Mn-Fe mixed oxide nanoparticles were synthesized by irradiating the solution of Mn and Fe carbonyls with high intensity ultrasound. They exhibited crystal structure and magnetism which changed with the Mn:Fe ratio. However, since these materials were amorphous, they had to be annealed and this led to aggregation decreasing the surface:volume ratio. In order to prevent this sintering, we have now adopted a wet chemical method in which organometals were decomposed by heating to form metals or metal oxides. Micelles of the polymer PluronicRTM, were used for dimensional confinement, leading to the control of the particle size. Pluronic RTM stabilizes the surface of the particles and the heating crystallizes the particles, so that the resulting products are non-aggregated crystals. By using this synthetic method, we have accomplished the following objectives. (1) Iron/iron oxide particles are obtained from thermo decomposition of Fe(CO)5 solution. The size of the particles is controlled by adjusting the concentration of surfactant. The particles size changed from 5.6 to 22.3 nm from high to low concentration of PluronicRTM. (2) Mn-Fe or Co-Fe mixed oxide particles are obtained by the thermal decomposition of Mn2(CO)10 and Fe(CO)5 or Co2(CO)8 and Fe(CO)5 solutions. We observed crystal structure and magnetism transformations when the Mn:Fe or Co:Fe ratio was increased. (3) Heterostructure core/shell nanoparticles were obtained by using Fe nanoparticles to catalyze the decomposition of chromium hexacarbonyl. The resulting particles have a Cr core and a gamma-Fe2O 3 shell.; The materials were characterized by synchrotron power XRD for their crystal structure, SQUID and Mossbauer spectra for their magnetic properties, and TEM and HRTEM for their morphology. |
