Preparation of three-dimensional flower-like Ni(OH)2 nanostructures by a facile template-free solution process

Three-dimensional (3D) flower-like Ni(OH)2 nanostructures have been successfully synthesized by a facile template-free solution process, in which F− and NH3 were used as Ni2+ coordination agents, and ammonia hydroxide solution was used as OH− supplier to accelerate the hydrolyzation of nickel complex species. The flower-like Ni(OH)2 nanostructures consisted of many intercrossed nanoflakelets with a mixed crystal structure of α- and β-Ni(OH)2. The F− and NH3 in reactive solutions played important roles in the nanostructure growth process. The Ni(II) concentration had great influence on the morphologies of Ni(OH)2 nanostructures. The possible growth mechanisms including aggregation growth, surface growth and surface dissolution were also proposed. The magnetization measurement indicated that the flower-like Ni(OH)2 nanostructures exhibited paramagnetic behavior above the critical temperature (10 K) and ferromagnetic behavior below the critical temperature.