Determination of the Size of Complex Iron Oxide Nanoparticles Using Various Physical Experimental Methods

A series of organically coated iron oxide nanoparticles obtained via the thermal decomposition of iron–oleate complexes via a “heating-up” process were investigated using the methods of transmission electron microscopy, X-ray diffraction and fine magnetometry, accompanied by elaborate mathematical analysis. The analysis of dependencies of field dependencies on the magnetization of the shape and broadening of maxima of X-ray diffraction patterns and fine refinement of transmission electron microscopy data allowed us to demonstrate that all of the samples under consideration had a tripartite structure: (i) the magnetic crystalline core of iron oxide, (ii) the paramagnetic stratum of amorphous iron oxide and (iii) the organic coater. The new approach toward synthesis for organic coated iron oxide shows that it could be applied to the preparation of magnetic nanoparticles with different and controlled magnetic properties and sizes depending on necessary applications, especially biomedical.