Synthesis of highly stable graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles

Graphite-encapsulated metal magnetic nanoparticles have been attracted for biological applications because of their high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well-controlled graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles can be synthesized by a hydrothermal method, simply by mixing metal source with sucrose as a carbon source. The saturation magnetization (Ms) values of Fe/C, Co/C, and Ni/C were 86.6, 43.8, and 113.1?emu/g, respectively. The Fe/C and Ni/C showed higher Ms values than bulk Fe₃O₄ (75.5?emu/g). The graphite-encapsulated metal nanoparticles showed good stability against acid and base environments.