Synthesis of magnetic nanoparticles: effects of polyelectrolyte concentration and pH

This study refers to the effect of sodium polyacrylate concentration (1 to 5 mass %) and pH (10 to 12) on the synthesis of magnetic nanoparticles (magnetite–maghemite) and their characterization by Mössbauer spectroscopy. The magnetic particles were obtained by coprecipitation method using iron chloride (II) and iron chloride (III) as precursor reagents and sodium polyacrylate as stabilizing agent. All samples showed Mössbauer broad resonance lines in typical doublet and sextets patterns of magnetite or maghemite with corresponding wide particle size distributions. The stability of magnetic particles was carried out by measuring particle sizes with dynamic light scattering (DLS). The z-average values for magnetic particles were in the range 24 to 590 nm and no significant change in size was observed on aging by leaving this material in air for 20 days. X-ray diffraction patterns showed characteristic peaks of the spinel structure and have an increase in their broadening as the pH decreases, effect that is dominated by the decrease in crystallite sizes. The nanoparticles showed to be magnetic at pH 12 and at room temperature.