Spinel iron oxide nanoparticles were obtained under supercritical water conditions in a continuous and fast (less than 10 s) way by modifying the initial stoichiometric FeII/FeIII molar ratio from (1/2) to (3/0), without base solution, and using citrates directly with iron precursors. This result opens the way to an economical and environmentally benign approach to synthesize superparamagnetic iron oxide nanoparticles (SPIONs) in high yields.
