Synchrotron X-ray absorption of iron oxide (Fe2O3) nanoparticles: Effects of reagent concentration and sonication in co-precipitation synthesis

Synchrotron X-ray absorption spectroscopy was used to complement X-ray diffraction in the characterization of iron oxide nanoparticles synthesized by ultrasonic-assisted co-precipitation. We studied the effects of ultrasonication on the nanoparticle synthesis and used X-ray diffraction to show that impurity phases were present in samples synthesized without ultrasonication. The hematite phase was shown to be absent from our X-ray diffraction results, and X-ray absorption spectroscopy revealed a preference for the maghemite phase over magnetite. Our results showed that maghemite nanoparticles formed with larger crystallite sizes and lower structural distortion when higher reagent concentrations and longer sonication/reaction times were used. Moreover, the synthesis at low reagent concentration gave rise to materials with an amorphous maghemite phase.