Influence of capping agents on fraction of Fe atoms occupying octahedral site and magnetic property of magnetite (Fe3O4) nanoparticles by one-pot co-precipitation method

Magnetite (Fe3O4) nanoparticles were synthesized by one-pot coprecipitation method using five different capping agents: Sodium citrate, Poly vinyl pyrrolidone (PVP), Chitosan, Cetyltrimethylammonium bromide (CTAB) and Citric acid. The influence of the various capping agents on the size, oxidation and fraction of Fe atoms occupying Octahedral against Tetrahedral sites in relation to the saturation magnetization (Ms) of the magnetite nanoparticles were studied. X-ray Absorption Fine Structure (XAFS) spectroscopy, X-ray Absorption Near Edge Structure (XANES), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier-Transform Infra-Red (FTIR) spectroscopy, Zeta potential, and Vibrating Sample Magnetometery (VSM) are used to study the various effects. The results reveal that the capping agents affect the size, oxidation and ratio of Fe atoms occupying octahedral vs tetrahedral site. The graph of Ms against size, oxidation and fraction of Fe atoms are plotted. Statistical analysis shows that Ms of the magnetite nanoparticles is highly dependent on the fraction of Fe atoms and the Size of the nanoparticles. The results reveal the Ms increases with size of the nanoparticles but decreases with the fraction of Fe atoms occupying octahedral vs tetrahedral site. However, there is no direct correlation between oxidation of Fe and Ms.