Abstract

Iron oxide nanoparticles are synthesised by the coprecipitation of Fe(NO<inf>3</inf>)<inf>3</inf>.9H<inf>2</inf>O, FeCl<inf>2</inf>.4H<inf>2</inf>O and NaOH under ultrasonic irradiation with comparisons on the temperature and surfactant used. Synchrotron X-ray absorption near edge structure (XANES) indicates that the predominant phase is Fe<inf>2</inf>O<inf>3</inf>, whereas extended X-ray absorption fine structure (EXAFS) confirms the presence of Fe- O and Fe-Fe bonding. Effects of synthesis temperature and surfactant are also revealed by the fitting of EXAFS spectra. The largest structural distortions compared to the Fe<inf>2</inf>O<inf>3</inf> standard is obtained in superparamagnetic particles synthesised at 60uC. The magnetisation is enhanced with the temperature increasing from 60 to 80°C. The addition of oleic acid as a surfactant leads to the ferromagnetic particles with increased magnetisation and a local structure closer to that of the Fe<inf>2</inf>O<inf>3</inf> standard.