Self-assembly, structural order and mechanism of γ-Fe₂O₃@SiO₂ ellipsoids induced by magnetic fields

Monodispersed γ-Fe₂O₃@SiO₂ ellipsoids are prepared by the three-step approach of hydrothermal synthesis, reduction-oxidation and SiO₂ coating. The magnetic field induced self-assembly processes are designed and carried out in different conditions. Influences of magnetic field strength, solvent, temperature, concentration and substrate are carefully investigated and evaluated by SEM and reflective spectra. The optimal self-assembly conditions of γ-Fe₂O₃@SiO₂ ellipsoid ordered structures are confirmed to be dispersed in ethanol at 0.06 mol L^-1 followed by evaporation on a glass substrate in a magnetic field of strength 5000 Oe at 35 °C. Finally, an air-liquid interfacial mechanism is suggested to understand the self-assembly processes.