Synthesis and Functionalization of Iron Oxide Nanoparticles and their Application in Hybrid Materials

Abstract

Nanomaterials have been in the center of interest for several decades now, and the number of publications and applications still grows. However, there are many aspects of nanoparticle formation and behavior still unknown. In particular, the coordination of ligands onto a particle surface holds many questions because of the intermediate states of nanoparticles, lying between bulk and molecule-like behavior. In this work, two synthetic methods were used to make spherical and spindle-shaped particles of different iron oxides. Strongly magnetic maghemite (γ-Fe2O3) spheres were used as a model system to investigate the binding of the surfactant molecules oleic acid, 3,4- dihydroxyhydrocinamic acid and tetramethylammonium hydroxide. Here the focus was on the nature of the exchange of one ligand against another one. The magnetic properties inside solid polymer matrices were investigated with particles of different functionalization in PMMA and polydopamineacrylate (PDAm). Particles incorporated in PDAm exhibited interesting changes in the magnetic moment which resulted from a chemical reaction of the polymer bound to the particle and forming a shell with opposite magnetic moment. Such chemically controllable magnetism might be applied in data storage and switchable technologies. Weakly ferromagnetic spindle-shaped hematite (α-Fe2O3) particles were synthesized using variable reaction parameters. This research was meant to show how these parameters affect the length and the aspect ratio of the particles. The particles were used to make mesogenic phases in polyethylene glycol (400) as a solvent. The orientation of the lyotropic liquid crystal phase could be directed by an external magnetic field. The flow of light can thus be directed magnetically. Furthermore, different concentrations of hematite particles were embedded in polyvinyl alcohol via an electrospinning process and their peroxidase-like behavior and wound healing properties were probed. The particles inside the fiber meshes catalytically convert reactive H2O2 to H2O and O2 and thus promote the healing process of skin tissue. This composite offers a cheap and easy way to produce band-aids for wound treatment.