Controlled synthesis of spherical and cubic magnetite nanocrystal clusters

•Magnetite nanocrystal clusters were prepared via a simple solvothermal method.•The concentration of sodium acetate leads to the morphology variation from sphere to cube.•Possible mechanisms are proposed to explain the morphology evolution.

Spherical Fe3O4 nanocrystal clusters were prepared via a simple solvothermal method using FeCl2·4H2O and NaOH as starting materials. When sodium acetate (NaAc) was added into the reaction system, the final products turned from sphere to cube. The as-prepared clusters are uniform in size. The possible mechanism was proposed to elucidate the changes of the clusters shape. The chemical compositions were characterized by X-ray diffraction (XRD). The morphology was determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic properties were investigated on a superconducting quantum interference device (SQUID) magnetometer.