High-Density Magnetite Nanoparticles Located in Carbon Hollow Microspheres with Good Dispersibility and Durability: Their One-Pot Preparation and Magnetic Properties

We report, for the first time, a one-step, rapid, template-free and continuous strategy for synthesising high-density magnetite (Fe3O4) nanoparticles located in carbon hollow microspheres (MCHMs) in which Fe3O4 nanoparticles (8-20 nm) are randomly dispersed in the shells of carbon hollow microspheres. The synthesis is achieved through ultrasonic spray pyrolysis of aqueous solutions containing ferrous chloride and citric acid. Interestingly, it was found that there are some pores (2-6 nm) in the carbon shell. Magnetic hysteresis loop measurements show that the saturation magnetisation of MCHMs is as high as 48.2 emu g(-1) which probably makes them more pliable to manipulation by the external magnetic field. Most importantly, because of the presence of carbon on their surfaces, MCHMs not only exhibit good resistance to acid but can also be easily dispersed in both polar and non-polar solvents. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)