Solvothermal synthesis of NiCo alloy icosahedral nanocrystals.

New dimensional NiCo alloy icosahedral nanocrystals with controllable size have been first reported and synthesized through an Ostwald ripening process in a template-absent solvothermal reaction system. The proposed synthesis is corroborated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The as-obtained NiCo icosahedral nanocrystals exhibit the size- and component-dependent magnetic behaviors. The coercivity (H(c)) depends on both the magnetocrystalline and structure anisotropy, and the saturation magnetizations (M(s)) decided by the content of Co. H(c) decreases from 189.02 to 147.95 Oe with the increase of the icosahedral NCs size from 200 to 850 nm. Especially, the H(c) of the icosahedral NCs at 157.38 Oe is higher than that of nanospheres at 104.02 Oe. In addition, M(s) and H(c) increased with the increasing Co content. It can be an ideal building block for applications in magnetic media, sensors, and other devices.