A hydrothermal reduction route to single-crystalline hexagonal cobalt nanowires

Hexagonal close-packed (hcp) cobalt nanowires with diameters of 150-300 nm and lengths of up to several hundreds of micrometers have been synthesized by a hydrothermal reduction method. These cobalt nanowires were generated by the reduction of cobalt(II) citrate complexes by hypophosphite (H2PO2-) in basic solution at 160 degrees C. High-resolution TEM and SAED reveal that the as-prepared Co nanowires have a single-crystalline structure with a [001] growth direction. The room-temperature hysteresis loop of these nanowires shows a ferromagnetic behavior with enhanced coercivity. A formation mechanism for these Co nanowires is proposed.