The evolution of the particle shape distribution during the formation of iron nanoparticles in the presence of tubular lecithin assemblies

Iron particles were prepared by the sodium borohydride reduction of ferrous ion in tubular lecithin assemblies and a 1200 Oe magnetic field. When the reaction was quenched after two minutes more than 90% of the particles were acicular, single crystal iron. As the reaction proceeded the percentage of acicular particles decreased, while spherical and chains-of-sphere particles were formed. After 30 minutes the predominant particle shape was chains-of-spheres. This change in particle shape distribution was attributed to the break-up of the lecithin assemblies during the course of the reduction