Synthesis and characterization of superparamagnetic maghemite nanoparticles prepared by coprecipitation technique

We have synthesized the maghemite (gamma-Fe2O3) nanoparticles by a chemical coprecipitation technique of ferric and ferrous ions in alkali solution through the pipette drop method (pipette diameter: 2000 mum) and the piezoelectric nozzle method (nozzle size: 50 mum). The microstructures of nanoparticles were characterized by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The size distribution of the maghemite nanoparticles prepared by typical pipette drop method is from 5 to 8 nm. However, the nanoparticles made by piezoelectric nozzle method shows a small size and a very narrow size distribution from 3 to 5 nm. Zero-field-cooling (ZFC) and field-cooling (FC) magnetization measurements were performed using a superconducting quantum interference device magnetometer from 2 to 300 K to investigate the magnetic properties of nanoparticles. The FC/ZFC magnetization measurements showed a typical superparamagnetic behavior with very narrow size distribution. (C) 2004 Elsevier B.V. All rights reserved.