One-step synthesis of colloidal Mn3O4 and γ-Fe2O3 nanoparticles at room temperature

A facile room-temperature synthesis has been developed to prepare colloidal Mn3O4 and γ-Fe2O3 nanoparticles (5 to 25 nm) by an ultrasonic-assisted method in the absence of any additional nucleation and surfactant. The morphology of the as-prepared samples was observed by transmission electron microscopy. High-resolution transmission electron microscopy observations revealed that the as-synthesized nanoparticles were single crystals. The magnetic properties of the samples were investigated with a superconducting quantum interference device magnetometer. The possible formation process has been proposed.