Room temperature synthesis of rod-like FeC₂O₄·2H₂O and its transition to maghemite, magnetite and hematite nanorods through controlled thermal decomposition

FeC₂O₄·2H₂O nanorods with diameter of about 50 nm and length of up to several micrometers were synthesized at room temperature in a surfactant-assisted system, which was obtained by dissolving bis(2-ethylhexyl)sodium sulfosuccinate (AOT) in a mixed solution composed of water and ethylene glycol (EG). The influence of reaction conditions on the morphology of FeC₂O₄·2H₂O is discussed in detail. Through direct thermal decomposition of FeC₂O₄·2H₂O under different calcination conditions, maghemite (γ-Fe₂O₃), magnetite (Fe₃O₄) and hematite (α-Fe₂O₃) can be selectively obtained, preserving the rod-like morphology. Transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) characterizations showed that the as-obtained iron oxide nanorods were composed of fine particles with different crystal orientations. The magnetic properties of the as-obtained iron oxide nanorods were systematically investigated.