Oxidation of ferrous hydroxides with nitrate: a versatile method for the preparation of magnetic colloidal particles.

Slightly over 30 years ago, Sugimoto and Matijević published an article in this journal on the synthesis of uniform magnetite particles by the partial oxidation of ferrous hydroxide gels. The article has become a widely-used reference for the preparation of magnetite particles in aqueous media. A reason for this was the thoroughness of their study and the versatility of the process: the authors described conditions under which cubic nanometric (30-100 nm) crystals, or larger (0.4-1.1 μm) spherical particles, the latter having either a smooth or a rough surface, could be obtained. Further work by Matijević and other authors has shown that small modifications of the process, such as the addition of divalent cations other than Fe(2+) to the system or the superposition of a magnetic field, can be used for the preparation of ferrite particles or rod-like particles, respectively. In this article we present a short description of the synthesis process and a brief overview of subsequent work carried out by other researchers that illustrates the versatility and the potential of this method.