| 초록 |
Spherical iron oxide and carbon-encapsulated iron nanoparticles have been prepared by ultrasonic irradiation followed by annealing at various temperatures. As the annealing temperature of the as-prepared α-Fe2O3 nanoparticles was increased, the sample transformed into γ-Fe2O3, Fe3O4, and Fe nanoparticles via the reduction process without requiring any additional reducing agents such as H2 gas, thus creating a carbon shell surrounding the nanoparticles. By controlling the experimental conditions, Fe nanoparticles of various sizes can be formed with diameters in the range 100 - 800 nm; these nanoparticles are tightly encapsulated by 20 nm thick carbon shells. Because of their high saturation magnetization 212 emu·g-1, the carbon-encapsulated Fe nanoparticles can be used for magnetic resonance imaging (MRI) with a dramatically enhanced efficiency compared to commercially available T2 contrast agents. Moreover, the carbon-encapsulated Fe nanoparticles showed its superior catalytic avtivity and reusability for hydrogenation of biomass-derived levulinic acid to GVL(99.6%) in ligand phase. |
