Synthesis of Capped Ultrafine γ-Fe₂O₃Particles from Iron(III) Hydroxide Caprylate: A Novel Starting Material for Readily Attainable Organosols

The synthesis of capped γ-Fe 2 O 3 ultrafine particles from thermal treatment of iron(III) hydroxide caprylate in boiling tetraline with retention of the integrity of the caprylate units during the reaction process is reported. This novel material due to the organophilic mantle around the particle surfaces can be easily dissolved in organic solvents and thus the availability of stable magnetic organosols is straightforward. The formation of capped magnetic particles is accomplished only under anaerobic conditions, while the state of hydration of the starting iron(III) hydroxide caprylate precursor was found to play a critical role for the magnetic-phase formation. The various steps in the synthesis as well as the nature of the magnetic particles were studied by means of X-ray powder diffraction and IR and Mössbauer spectroscopies, while the morphology and particle size of the final magnetic nanocrystallites were evaluated by the TEM technique. Finally, ESR spectroscopy provided strong evidence for the isolated state of the magnetic particles in their solvated state.