Precise air oxidation for continuous production of superparamagnetic FeO nanoparticles at room temperature through a microfilm reactor.

Superparamagnetic iron oxide nanoparticles (SPIONs) find vast applications in biomedicine such as drug delivery, magnetic resonance imaging (MRI) contrast agents, cell separation, tissue repair, The synthesis of pure and uniform SPIONs involves tedious processes, complex precursors, the assistance of organic solvents, capping agents and/or high temperature. Herein, we report a continuous mass production of pure and uniform SPIONs in aqueous microfilm at room temperature without using any surfactant. The air oxidation rate and nanocrystal formation kinetics were precisely controlled by process intensification in the continuously flowing microfilm.