Fabrication and characterization of α‑Fe2O3/Fe3O4 magnetic heterogeneous nanorods with PEG2k as restricted growth agent

For realizing the control of the preparation process for α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods (MHNRs), the influence rules of key factors on the preparations of β-FeOOH nanorods (NRs) and α-Fe₂O₃/Fe₃O₄ MHNRs were revealed. Firstly, β-FeOOH nanorods (NRs) were fabricated with polyethylene glycol 2000 (PEG_2k) as the growth inhibitor in specific directions via the hydrolysis process, for smaller size, the fabrication conditions for β-FeOOH NRs including Fe³⁺ concentration, PEG_2k volume, hydrolytic temperature, and hydrolytic duration were optimized, and the optimal conditions were selected as 0.02 M of Fe³⁺, 0.20 g/L of PEG_2k, 80 °C of hydrolytic temperature, and 2 h of hydrolytic duration, the β-FeOOH NRs with average length and diameter of 199 nm and 55 nm were obtained. Secondly, α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods (MHNRs) were prepared with PEG_2k as the reductant via the calcination-reduction process. For larger saturation magnetization (Ms) of α-Fe₂O₃/Fe₃O₄ MHNRs, the mass ratio of PEG_2k and β-FeOOH NRs, calcination temperature, and calcination time were investigated as were 3:1, 450 °C, and 2 h, respectively. And α-Fe₂O₃/Fe₃O₄ MHNRs with the average length of 229 nm, average diameter of 55 nm, and Ms of 81.3 emu/g were obtained. The novel and facile preparation process for α-Fe₂O₃/Fe₃O₄ MHNRs shortened the preparation period, omitted the reduction process using hydrogen enhancing the preparation security, and relized the controlled particle size and properties, there were not heavy metal elements in the nanosystem, laying the groundwork for the biomedical applications of α-Fe₂O₃/Fe₃O₄ MHNRs.