The Synthesis And Characterization Of Monodisperse Iron Series Nanoparticles By A Microwave-assisted Two-phase Method

Monodisperse nanoparticles have been widely applied in many fileds, such as fluorescent labeling, bio-contained medicine, magnetic resonance imaging, high-density information storage, catalysis and building functional nanomaterials due to their special physical and chemical properties. However, the present methods for preparing the monodisperse nanoparticles have some disadvantages. For example, the reaction temperature of the thermal decomposition method is too high and the prices of reagents are very expensive. The quality of the products prepared by LSS strategy is poor. Therefore, synthesis of monodisperse nanoparticles with simple method and cheap raw materials has been a hotspot.Co₃O₄ nanocubes, Ni(OH)₂ nanosheets, nanocakes and sub-microspheres and iron oxide nanoparticles were synthesized by a microwave assisted two-phase method. These samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).1) Monodisperse iron oxide nanoparticles were synthesized with different iron source. All the particles were nanospheres when the trivalent iron salt was used; however, Fe₃O₄ nanorods and nanocubes were prepared with bivalent iron salt. With the same precursor and hydrazine hydrate as the reducing agent, monodisperse Fe₃O₄ nanoparticles were synthesized. Also, both cobalt oleate complex and iron oleate were used as the mixed precursors, monodisperse CoFe2O4 nanospheres were obtained with this method.2) Spinel Co₃O₄ nanocubes were synthesized with this two-phase method, and then the gas sensing properties of these nanoparticles were tested. These Co₃O₄ nanocubes had higher responses to ethanol and xylene at a low temperature of 200 oC. And the responses to the benzene increased with the number of the replace methyl. 3) Ni(OH)₂ nanosheets, nanocakes and sub-microspheres were synthesized with the method by tuning the amount of the precursor. And NiO nanoparticles were also prepared through heated treatment of the corresponding Ni(OH)₂ nanostructures. It is found that the Ni(OH)₂ nanosheets and sub-microspheres were destroyed annealed at 600 oC for 3 h. However, the nanocakes kept their initial morphologies even under the harsh conditions, which indicated that these nanoparticles could be used in some high temperature conditions.This microwave assisted method has advantages, such as the agents are not so expensive, and the reaction speed is very fast so we can get amouts of nanomaterials in a short time. In addition, the process is simple and convenient. Therefore, this method might be used as a general preparation method for the nanoparticles and need further exploration.