The MNPs size, and morphology were evaluated by TEM using a Tecnai T20 (FEI, Netherlands) electron microscope working at an acceleration voltage of 200 kV. TEM samples were prepared by depositing 5 µL of dilute solution on a copper grid (200 mesh) and a posterior drying at ambient temperature prior to analysis. MNPs size distributions were obtained by measuring more than 200 MNPs with the Image J software. High resolution transmission electron microscopy (HRTEM), Scanning transmission electron microscopy (STEM), and energy-dispersive X-ray (EDX) images were obtained by a Tecnai F30 microscope with an accelerating voltage of 300 kV. Elemental mapping was performed using an Oxford EDS system in the drift corrector acquisition mode.