  Today, spinel ferrite nanoparticles are widely used in the medical field for
cancer treatment, drug delivery, and magnetic resonance imaging contrast agent
due to their superior magnetic properties and biocompatibility. Due to the
strong dependence of magnetic properties on morphology and other structural
aspects, the magnetic properties of these nanoparticles depend on their
manufacturing process. One of the goals of the researchers is to improve the
magnetic properties of these nanoparticles by substituting elements such as
manganese, cobalt, zinc, nickel, magnesium and iron. In this research, first,
magnetic Zn0.3Fe0.6O4 nanoparticles were synthesized by hydrothermal method in
the presence of citric acid as a reducing agent. In order to reduce the amount
of impurity and obtain the pure spinel phase and reduce the size of magnetic
nanoparticles, the hydrothermal process was carried out in the presence of
different concentrations of the reducing agent and pH level of the medium. The
structural investigations of the resulting nanoparticles were carried out by
X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results
showed that in order to obtain pure and single-phase spinel nanoparticles with
appropriate particle size and size distribution, it is necessary to control the
concentration of reducing agent and pH.
