A new strategy for the synthesis of iron-oxide nanocrystals by using a single-spinneret electrospinning technique

Iron-oxide nanocrystals (IONCs) have been widely researched, owing to their unique physical and chemical properties. Herein, a new strategy that involves an electrospinning technique with the addition of a surfactant is reported as an effective method for the fabrication of shaped IONCs. With the same precursor compositions, only iron-oxide nanoparticles were obtained by using a sol-gel method without electrospinning. However, when the electrospinning technique was introduced, IONCs with special geometrical shapes (e.g., octahedral) were obtained. Characterization data indicated that the IONCs were composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3), the ratio of which could be tuned by changing the concentration of the surfactants in the precursor solutions. A mechanism for the formation of IONCs is also proposed. The effect of surfactant on the decomposition of the iron complex is the main motivation for the formation of IONCs. In the sol-gel method without electrospinning, this effect is completely inhibited by the disturbance of long molecular chains. However, in the electrospinning strategy, such disturbance can be completely or partially diminished by the electrical force field during the electrospinning process and by the spatial effect of the nanofibers, thus leading to the formation of IONCs. Finally, the magnetic properties of the obtained IONCs were investigated. This strategy is versatile and environmentally friendly and it will be applicable to the synthesis of many other functional inorganic materials.