Nickel nanocrystals: Fast synthesis of cubes, pyramids and tetrapods

We report the use of organometallic precursors in microwave and microfluidic reactors to synthesize Ni nanoparticles of various shapes: spheres, cubes, trigonal pyramids and tetrapods. Each route has the ability to yield a preferential shape based on kinetic control of crystal growth. Tetrapods are obtained only in a microfluidic reactor. Trigonal pyramids crystallize in the metastable hexagonally close-packed (HCP) phase while spheres, cubes and tetrapods crystallize in the thermodynamically stable face-centred cubic (FCC) phase. The magnetic properties of nanocubes (in particular the magnetic coercive field) are found to be greatly enhanced compared to bulk and previous examples of nanostructured Ni materials.