Synthesis of Fe3O4 nanoparticles with various sizes and magnetic properties by controlled hydrolysis.

Nanoparticles of Fe(3)O(4) were synthesized by hydrolysis in an aqueous solution containing ferrous and ferric salts at various ratios with 1,6-hexanediamine as a base. It was found that the ferrous to ferric ratio influences the reaction mechanism for the formation of Fe(3)O(4). When the ratio of ferrous to ferric ions was increased, the formation of large hydroxide particles as a precursor of Fe(3)O(4) was promoted, which resulted in an increase in the size of Fe(3)O(4) nanoparticles. As a result, the mean diameter of Fe(3)O(4) nanoparticles increased from approximately 9 to approximately 37 nm as the molar percentage of ferrous ions with respect to the total iron ions was increased from 33 to 100%. Furthermore, it was demonstrated that magnetic properties of Fe(3)O(4) nanoparticles can be controlled by adjusting the molar ratio of ferrous to ferric ions as well as the particle diameter.