Synthesis of High-Coercive Epsilon-Iron Oxide Nanoparticles for Biomedical Applications

Epsilon-iron oxide (ε-Fe2O3) is one of Fe2O3 polymorphs existing in the narrow grainsize range (8–30 nm). Epsilon-iron oxide has higher coercive force compared to the traditional hard magnetic materials (e.g. Sm-Co or Nd-Fe-B alloys). At the same time, it does not contain rare-earth elements. Nanoparticles of ε-Fe2O3 can be used in biomedicine as magnetic hyperthermia agents with high specific absorption rate due to hysteresis losses, and low toxicity. In this work, ε-Fe2O3 nanoparticles have been prepared using silica gel matrices with specific surface area of about 70–500 m
²
/g. The matrices were impregnated with iron (II) sulfate, dried in air at 110 °С for 24 h and finally calcined in air at 900 °С for 4 h. According to X-ray diffraction, the obtained samples contain 39–73 weight % of ε-Fe2O3, and show coercivity of up to 12 kOe at room temperature.