Characterization of CoFe2O4, NiFe2O4, and ZnFe2O4 Nanoparticles Synthesized by a Proteic Sol-gel Method

Nanoparticles of cobalt, nickel, and zinc spinel ferrites were successfully synthesized by a low-cost method named as proteic sol-gel method, and a comparative study was performed. Commercial metal nitrates and gelatin from bovine skin were used as precursors. Thermogravimetric analysis and differential scanning calorimetry were performed to investigate the thermal behavior of the precursor powders as well as to select the appropriate calcination temperature for oxide formation. Structural, morphological, optical, and magnetic properties were studied by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy, and UV/VIS diffuse reflectance spectroscopy. Spherical nanoparticles with a single cubic spinel structure were obtained. The results indicate that the average particle sizes are less than 10 nm. CoFe 2 O 4 and NiFe 2 O 4 exhibited ferrimagnetic and superparamagnetic behavior simultaneously, whereas ZnFe 2 O 4 was found to be paramagnetic. The optical band gaps obtained were 1.40, 1.75, and 2.12 eV for CoFe 2 O 4 , NiFe 2 O 4 , and ZnFe 2 O 4 samples, respectively. Graphical abstract