Solvothermal synthesis of cobalt ferrite hollow spheres with chitosan

Cobalt ferrite hollow spheres with chitosan (CoFe₂O₄/CS) were synthesized by two different approaches using the solvothermal method. The first approach involves in-situ incorporation of FeCl₃:6H₂O and CoNO₃:6H₂O in the solvothermal reaction (M1) and in second approach already prepared CoFe₂O₄ nanoparticles (NPs) using the thermal decomposition method was placed in the solvothermal reaction to form the hollow spheres (M2). Structural identification of the samples were characterized by Fourier transform infrared spectra (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analyses (DSC-TGA) and energy dispersive X-ray spectroscopy (EDX). The magnetic properties were evaluated using a vibrating sample magnetometer (VSM). The presence of chitosan on the hollow sphere was confirmed by FTIR. The XRD analyses proved that the synthesized samples were cobalt ferrite with spinel structure. The structure of the surface and the average particle size of the spheres were observed by SEM and TEM showing the nano scale of the CoFe₂O₄ component. Structural characterization demonstrating that chitosan does not affect the crystallinity, chemical composition, and magnetic properties of the CoFe₂O₄/CS. This work demonstrates that the CoFe₂O₄/CS prepared using the as synthesized CoFe₂O₄ NPs have better structural and magnetic properties. - Highlights: • Cobalt spheres with chitosan were synthesized by two different approaches. • Structure and magnetic properties depend of the synthesis method. • Cobalt spheres synthesized ex situ exhibit superior magnetic properties. • This approach can be an efficient route to fabricate cobalt ferrite spheres in large scale.