Morphogenesis of Branched Coaxial Nanorods Formed in Supercritical Carbon Dioxide

Fe3O4/a-C branched and multibranched coaxial nanowires with a diameter around 40 nm were synthesized by pyrolysis of ferrocene in supercritical CO2 at 450 °C. The single-crystal Fe3O4 cores of the coaxial nanowires are continuous. Every trunk, branch, and subbranch has a similar diameter, different from fractals, dendritics, or other hierarchical structures. The branches of the coaxial nanowires are vertical to the trunks, connected together with double-wedge junctions. The branched Fe3O4 core is a single crystal, with each branch having a growth orientation of 〈100〉, forming a three-dimensional framework-like three-divisional branched nanorod structure. A possible growth mechanism was proposed.