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 °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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)