A microemulsion-mediated chemical reaction was used to synthesize acic
ular particles of gamma-Fe2O3 with an equivalent spherical diameter (E
SD) of 7-8 nm. From a comparison of the measured values of the hydrody
namic diameter of the water-in-oil microemulsion droplets and the ESD
of the resulting gamma-Fe2O3 particles, we show that each microemulsio
n droplet gives birth to a single particle of gamma-Fe2O3.