Effect of Reaction Temperature on the Shape of FePt Nanoparticles

Nanorod-like, cubic, and spherical FePt nanoparticles (NPs) are synthesized by adjusting the reaction temperature at 220 °C, 250 °C, and 298 °C, respectively. It has been found that the shapes of FePt NPs can be controlled by changing the preparing temperature while fixing the molar ratio of metal precursors, surfactants, and other parameters. Investigation shows that both the seed crystal structure and reaction temperature have an effect on the growth process and final shape of the particles. For nanorod particles prepared at a reaction temperature of 220 °C, it grows along with the axis direction of the twin-crystal seeds resulting in the nanorod shape. However, for cubic and spherical NPs prepared at higher temperatures, their shapes are dominantly determined by the competition of surface energy between {111} and {100} whaich is influenced by reaction temperature. The as-synthesized NPs were found to be superparamagnetic at room temperature and their blocking temperatures are size and shape dependent.