Synthesis of Fe3O4 nanoparticles from emulsions

A unique oil-in-water emulsion route has been devised to synthesize nanosiz ed magnetite (Fe3O4) particles using a small amount of cyclohexane as the o il phase, NP5 + NP9 as the surfactant phase, and a Fe(II)/Fe(III) salt solu tion as the aqueous phase. The Fe3O4 powder thus derived from the emulsion containing 88 wt% 0.3 M FeSO4 + Fe(NO3)(3) in the aqueous phase possesses a n equiaxial morphology and an average particle size of < 10 nm. Studies on the electrical conductivity of the emulsions as a function of Fe2+/Fe3+ con centration in the aqueous phase revealed the complexation effect of the NP5 + NP9 surfactant towards Fe2+/Fe3+ ions. The resulting particle size and m orphology are therefore dependent on the amounts of surfactant and aqueous phase in the emulsion. A strongly alkaline aqueous phase favors the formati on of Fe3O4, while a low alkalinity favors the formation of alpha -FeOOH. M agnetic property measurements and Mossbauer spectroscopic studies indicate that the emulsion-derived iron oxide powder is superparamagnetic, which bec omes ferrimagnetic with decreasing measurement temperature.