Hierarchical synthesis of iron oxide nanoparticles by polyol cum calcination method and determination of its optical and magnetic behaviour

Iron oxide nanoparticles (NPs) were prepared using a polyol method from Fe(III) acetylacetonate in the presence of polyvinylpyrrolidone (PVP). These particles were subsequently calcined and annealed using a digitally controlled furnace from 200 to 1000 ̊C producing crystallization. The morphology of the untreated nanoclusters and each calcined NP sample were observed under a scanning electron microscope (SEM) coupled with energy-dispersive X-ray (EDX) and their correlation explored. The SEM confirmed that the spherical NPs produced by the polyol method maintained their morphology during calcination at different temperatures. The extent of agglomeration was analyzed using dynamic light spectroscopy (DLS), which were measured as 1.0 μm. The effect of calcination on structural changes was monitored by X-ray diffraction (XRD), this revealed the presence of both hematite (α-Fe2O3) and maghemite (γ-Fe2O3) phases at low temperatures and the complete transformation into hematite at higher temperature. UV–Visible and fluorescent spectroscopy were used to analyze the optical properties and vibratory sample magnetometer (VSM) confirmed its paramagnetic characters.