Micro- and nano-structures of iron oxide with tunable morphologies fabricated via solvothermal process

Abstract

Micro- and nano-structures of iron oxide with tunable morphologies were fabricated through a solvothermal process by adjusting experimental parameters. In this route, the ethylene glycol (EG) solution of ferric chloride hexahydrate (FeCl₃·6H₂O), sodium bicarbonate (NaHCO₃), and ethylenediamine (EDA) was heat-treated to create the micro- and nano-structures of Fe₃O₄, where EG acted as both solvent and reducing agent. NaHCO₃ and EDA were crucial for the morphology and size of these micro- and nano-structures. Fe₃O₄ micro- and nano-structures revealed solid, porous and hollow morphologies by changing the reaction time, the type of solvent, and the amount of EDA and NaHCO₃. Fe₃O₄ nanoparticles were created by controlling experimental parameters. As the reaction progressed, nanoparticles aggregated together to form solid Fe₃O₄ spheres, and then inner nanoparticles dissolved and recrystallized onto the outer shell of Fe₃O₄ spheres having been obtained through agglomerating together and then gradually developing into hollow micro- and nano-spheres due to an Ostwald ripening mechanism. Hematite (α-Fe₂O₃) was synthesized using ethyl alcohol instead of EG. These magnetic micro- and nano-structures revealed excellent magnetic properties.