Kenneth G. Nebesny

The University of Arizona, Tucson, AZ, United States

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Publications (2)12.03 Total impact

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    ABSTRACT: In this report, functional one-dimensional (1-D) Pt-Co3O4 heterostruc-tures with enhanced electrochemical properties were synthesized via colloidal polymerization of polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs). Colloidal polymerization of dipolar nanoparticles into hollow metal−semiconductor nanowires was achieved via a consecutive galvanic replacement reaction between Co0 and Pt2+ precursors, followed by a nanoscale Kirkendall oxidation reaction and a calcination treatment. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-angle annular dark field scanning TEM (HAADF-STEM), and field-emission scanning electron microscopy (FESEM) revealed the structural and morphological evolution of the hollow cobalt oxide nanowires (D = 40 nm) with platinum nanoparticles (PtNPs; D 2 nm) entrapped within the growing oxide shell. Various calcination conditions were investigated via X-ray photoelectron spectroscopy (XPS) to obtain the optimal surface composition of the metallic Pt and semiconducting Co3O4 phases. Cyclic voltammetry of the 1-D Pt-Co3O4 heterostructures demonstrated a sevenfold enhancement in specific capacitance in comparison to the pristine Co3O4 nanowires. Preliminary results also showed that the calcined 1-D Pt-Co3O4 heterostructures catalytically hydrogenate methyl orange, and the rates of the hydrogenation were dependent on surface composition.Keywords: colloids; hybrid inorganic/organic materials; magnetic materials
    Chemistry of Materials. 02/2011; 23(5).
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    ABSTRACT: The preparation of polystyrene-coated cobalt oxide nanowires is reported via the colloidal polymerization of polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs). Using a combination of dipolar nanoparticle assembly and a solution oxidation of preorganized metallic colloids, interconnected nanoparticles of cobalt oxide spanning micrometers in length were prepared. The colloidal polymerization of PS-CoNPs into cobalt oxide (CoO and Co(3)O(4)) nanowires was achieved by bubbling O(2) into PS-CoNP dispersions in 1,2-dichlorobenzene at 175 degrees C. Calcination of thin films of PS-coated cobalt oxide nanowires afforded Co(3)O(4) metal oxide materials. Transmission electron microscopy (TEM) revealed the formation of interconnected nanoparticles of cobalt oxide with hollow inclusions, arising from a combination of dipolar assembly of PS-CoNPs and the nanoscale Kirkendall effect in the oxidation reaction. Using a wide range of spectroscopic and electrochemical characterization techniques, we demonstrate that cobalt oxide nanowires prepared via this novel methodology were electroactive with potential applications as nanostructured electrodes for energy storage.
    ACS Nano 10/2009; 3(10):3143-57. · 12.03 Impact Factor