Influence of growth conditions on magnetite nanoparticles electro-crystallized in the presence of organic molecules.

Abstract

Magnetite nanoparticles were synthesi zed by electrocryst allization in the presence of thiourea or sodium butanoate as an organic stabiliz er. The synthesis was performed in a thermostatic electrochemical cell containing two iron electrodes with an aqueous solution of sodium sulfate as electr olyte. The effects of organic concentration, applied potential and growth temperature on particle size, morphology, structure and magnetic properties were investigated. The ma gnetite nanoparticles were characterized by X-ray diffraction, electron microscopy, magneto metry and Mossbauer spectrometry. When the synthesis is performed in the presence of sodium butanoate at 60 ?C, a paramagnetic ferric salt is obtained as a s econd phase; it is possible to a void formation of this phase, increase the specific magnetization and improve the structure of the oxide particles by tuning the growth conditions. Room-temperature magnetization values range from 45 to 90 Am 2 kg ? 1 , depending on the particle size, type of surfactant and synthesis conditions. Mossbauer spectra, which were recorded at 290 K for all the samples, are typical of nonstoichiometric Fe 3 ?? O 4 , with a small excess of Fe 3+ , 0.05 ? ? ? 0.15.