Facile and rapid synthesis of nickel nanowires and their magnetic properties

The present work reports a facile and rapid microwave-assisted route to synthesize nickel nanowires with a necklace-like morphology and lengths up to several hundreds of microns. The wires consist of many crystallites with an average size of 25 ± 2 nm. The synthesis does not use templates or magnetic fields and needs only 6 min, which is more than 480 times faster than that needed for Ni wires prepared at 180 °C using conventional heating. Nickel nanostructures with various morphologies including spheres, chains and irregular particles with porous surfaces can also be obtained by adjusting reaction parameters. Polyvinylpyrrolidone (PVP) is found to be vital for the formation of the one-dimensional chains and a high concentration of PVP smoothes their surfaces to result in the appearance of wires. This rapid one-pot procedure combines the formation of nanoparticles, their oriented assembly into chains, and the subsequent shaping of wires. The Ni nanostructures show variable magnetic properties. The prepared nickel wires have a high mechanical stability and exhibit much higher coercivity than bulk nickel, Ni nanoparticles and their aggregations, which promise potential applications in micromechanical sensors, memory devices and other fields.