Starch functionalized magnetite nanoparticles: New insight into the structural and magnetic properties

Highlights: • Starch-functionalized magnetic nanoparticles (MNPs) are prepared by one pot method. • Morphology and structural properties of MNPs can be tuned by varying starch amount. • Gradual evolution from bulk-like to the superparamagnetic behaviour was evidenced by Mössbauer spectroscopy. -- Abstract: In this study we report the preparation of starch-functionalized magnetic nanoparticles (Starch@MNPs) by the oxidation-precipitation method of iron (II). Special attention was devoted to the characterization of the modification of structural and magnetic properties depending on the starch to iron mass ratio R. Transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), Raman, Mössbauer, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopies (XPS) and thermogravimetric analysis (TGA) were used to carefully characterize and compare the as-synthesized products. TEM and PXRD revealed the reduction of the crystallite size as R increases. The size varies from 67 ± 5 to 12 ± 4 nm by changing R from 0 to 10. The formation of a cubic inverse spinel iron oxide phase was demonstrated by PXRD and the discrimination between magnetite Fe₃O₄ and maghemite Fe₂O₃ was realized by Raman and Mössbauer spectroscopy. Mössbauer spectroscopy allowed to monitor the evolution of the magnetic properties with respect to R. The superparamagnetic behaviour was evidenced by the appearance of a doublet in the Mössbauer spectra that strongly increased in intensity with R ratio. The relative abundance (RA) of the doublet at room temperature was observed to increase from 10 to 36% for R equal 1 to 10. Lastly, the iron environment was highly perturbed by the presence of starch.