For example, magnetite is ferromagnetic when the particle diameter is larger than 15 nm and superparamagnetic when smaller. For a certain type of magnetic nanoparticles, their size and/or geometry define the magnetic transitions. The surface of the nanoparticle increases with decreasing particle size and also depends on its geometry.
However, certain applications require a rigorous selection of the nanoparticles by size and shape because these parameters determine the number of surface atoms, which is decisive for their properties. The interest in iron oxide nanoparticles and their use in an extremely large number of applications is motivated by stability, biocompatibility, magnetic properties and their availability. Nanometer-sized iron oxides proved to be of interest in several fields such as medicine, applied physics, chemistry and engineering. When it was found that materials formed from small particles exhibit different properties from their bulk form, numerous researchers became interested in discovering new properties and applications. The first evidence dates from about 100,000 years found in tools for production and storage of ochre (iron oxides and hydroxides) used for painting bodies. The iron oxide-based materials have been a constant presence in human life throughout mankind’s existence. Keywords: iron coordination compounds mixed oxide nanoparticles morphology control nanoparticle shape control optimization procedure The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering.
The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis.
Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The mixed valence trinuclear iron acetate, ♲H 2O (FeAc1), μ 3-oxo trinuclear iron(III) acetate, NO 3∙4H 2O (FeAc2), iron furoate, NO 3∙2CH 3OH (FeF), iron chromium furoate, FeCr 2O(C 4H 3OCOO) 6(CH 3OH) 3]NO 3∙2CH 3OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions.