| Summary: | 碩士 === 國立中正大學 === 化學暨生物化學研究所 === 99 === Monodispersed magnetic nanoparticles ( NPs ) recently have been actively studied due to their potential applications in data storage and magnetic resonance imaging (MRI).
Cobalt nanostructures were prepared by thermal decomposition of dicobalt octacarbonyl, Co2(CO)8, in o-xylene and n-decane in this study. Significantly monodiapersed Co nanoparticles were obtained by tuning the reaction conditions such as precursor : surfactant ( oleylamine : oleic acid ) mole ratio, the reaction temperature and reaction time. Interestingly, the crucial role of the precursor: surfactant ( oleylamine : oleic acid ) mole ratio on the shape of the nanoparticles was demonstrated by altering the ratio from 1:10:1 ( spherical particles ) to 1:10:2 at 175°C leading to rectangular particles.
Besides the observations of spherical particles in the former case with precursor: surfactant mole ratio of 1:10:1, the lowering the reaction temperature to 165°C led to formation of rectangular particles. This observation was explained by the controlled growth of the nanocrystals at lower temperature lead to special structures. Further examination by tuning the mole ratio to 1:12:1.2 at 165°C led to elongated rectangular particles.
Characterization of the cobalt nanoparticles was conducted by transmission electron microscope ( TEM ) and EDS. The crystal structures of the nanoparticles were analyzed by powder x-ray diffraction and electron diffraction from the HR-TEM images. Hysteresis curve was found in magnetism analysis of Co nanoparticles.
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