Synthesis and colloidal polymerization of ferromagnetic Au-Co nanoparticles into Au-Co₃O₄ nanowires

(Figure Presented) The preparation of cobalt oxide nanowires with gold nanoparticle (AuNP) inclusions (Au-Co₃O₄ nanowires) via colloidal polymerization of dipolar core-shell NPs is reported. Polystyrene-coated ferromagnetic NPs composed of a dipolar metallic cobalt shell and a gold NP core (PS-AuCoNPs) were synthesized by thermolysis of octacarbonyldicobalt [Co₂(CO)₈] in the presence of AuNP seeds and polymeric ligands. The colloidal polymerization process of these dipolar PS-AuCoNPs comprises dipolar nanoparticle assembly and solution oxidation of preorganized NPs to form interconnected cobalt oxide nanowires via the nanoscale Kirkendall effect, with AuNP inclusions in every repeating unit of the one-dimensional mesostructure. Calcination of the polymer-coated nanowires afforded polycrystalline Au-Co₃O₄ nanowires that were determined to be electroactive. Nanocomposite materials were characterized by transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and cyclic voltammetry. We demonstrate that the optical and electrochemical properties of Au-Co ₃O₄ nanowires are significantly enhanced in comparison with hollow Co₃O₄ nanowires prepared via colloidal polymerization.