Magnetic Fe₂P Nanowires and Fe₂P@C Core@Shell Nanocables

We report the synthesis of one-dimensional (1-D) magnetic Fe₂P nanowires and Fe₂P@C core@shell nanocables by the reactions of triphenylphosphine (PPh₃) with Fe powder (particles) and ferrocene (Fe(C₅H₅)₂), respectively, in vacuum-sealed ampoules at 380–400 ℃. The synthesis is based on chemical conversion of micrometer or nanometer sized Fe particles into Fe₂P via the extraction of phosphorus from liquid PPh₃ at elevated temperatures. In order to control product diameters, a convenient sudden-temperature-rise strategy is employed, by means of which diameter-uniform Fe₂P@C nanocables are prepared from the molecular precursor Fe(C₅H₅)₂. In contrast, this strategy gives no obvious control over the diameters of the Fe₂P nanowires obtained using elemental Fe as iron precursor. The formation of 1-D Fe₂P nanostructures is ascribed to the cooperative effects of the kinetically induced anisotropic growth and the intrinsically anisotropic nature of hexagonal Fe₂P crystals. The resulting Fe₂P nanowires and Fe₂P@C nanocables display interesting ferromagnetic–paramagnetic transition behaviors with blocking temperatures of 230 and 268 K, respectively, significantly higher than the ferromagnetic transition temperature of bulk Fe₂P (T_C = 217 K).