Structural, morphological and magnetic investigations on cobalt ferrite nanoparticles obtained through green synthesis routes

This paper describes for the first time two processing routes—the precursor method and the two-step wet chemical process—for the synthesis of magnetic cobalt ferrite using the Tamarindus indica fruit extract. These green approaches are eco-friendly, safe and efficient alternatives to classical chemical methods. The aqueous extract from tamarind fruit contains numerous metabolites (organic acids, aminoacids). All these bioactive components are able to chelate metal ions leading to the formation of the multimetallic complex (precursor of cobalt ferrite). The obtained precursor was characterized by Fourier transform infrared spectroscopy (FTIR), thermal analysis, X-ray diffraction analysis (XRD) and magnetic measurements. The structure, morphology and magnetic behavior of the cobalt ferrite samples prepared through both synthesis routes were investigated by various characterization techniques: FTIR, XRD, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), Mössbauer spectroscopy and magnetic measurements. XRD data confirmed that a cubic spinel structure was obtained for both ferrite powders with average crystallite size of 13 and 5 nm, respectively. The microstructure study by SEM revealed the formation of nanocrystallites assemblies using the precursor method and carbon-rich particles forming granulated micron-sized agglomerates, embedding ferrite nanocrystallites obtained through the two-step wet chemical process. Mössbauer spectroscopy results evidenced relaxation processes in the CoFe 2 O 4 samples at room temperature, and the main characteristics of the involved sublattices were derived. The magnetic investigation revealed a typical magnetic behavior for a spinel, with CoFe 2 O 4 nanoparticles ferrimagnetic at low temperature and superparamagnetic at room temperature.