Characterization of the Oxidation of Magnetite Nanoparticles during Their Synthesis by Different Structural Analysis Techniques

Water colloidal solutions of iron oxide nanoparticles coated with tetramethylammonium hydroxide were synthesized by co-precipitation methods. Dimensional analyses were accomplished by transmission electron microscopy (TEM) and the crystalline features of nanoparticles were studied by means of X-ray diffraction (XRD). The iron oxide nanoparticle structure was characterized by the use of the attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopic techniques. For the nanoparticle samples prepared at higher temperatures during synthesis, the Raman spectra demonstrated that magnetic core of iron oxide nanoparticles is composed of a mixture of magnetite (Fe3O4) and maghemite (γ-Fe2O3) phases. We believe that the oxidation of magnetite to maghemite has been occurred during the preparation protocol of nanoparticles performed at higher temperature.