Phase transformation and shape evolution of iron oxide nanocrystals synthesized in the ethylene glycol-water system

Iron oxide particles with various shapes, sizes and phase concentrations (including alpha-Fe2O3 and Fe3O4) have been synthesized through a simple hydrothermal method in the ethylene glycol (EG)-water system. In the preparation conditions, ferric chloride (FeCl3 center dot 6H(2)O) was used as the iron source in the presence of sodium hydroxide (NaOH) without any surfactants. By adjusting the experimental parameters (EG/H2O ratio, base content, iron ions concentration, etc.), the shape, the size, the phase and the magnetic property of the products could be easily controlled. The products were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and a vibrating sample magnetometer (VSM). A further investigation revealed that high EG content and high alkaline condition favored the formation of Fe3O4 phase. A possible growth mechanism was proposed based on the experimental results. The magnetic properties were deeply affected by the morphology and phase of the as-synthesized products. The controlled shape, size and phase structure of the iron oxides through simple synthetic procedures provides potential opportunities to realize the promising size and shape-dependent applications.