Carbon Coating, Carburization, and High-Temperature Stability Improvement of Cobalt Nanorods

Abstract

The reactivity of highly crystalline hcp cobalt nanorods (NRs) with organic solvents at high temperature was studied. Cobalt NRs with a mean diameter of 15 nm were first synthesized by the polyol process and then heated at 300 °C in octadecene (ODE), oleylamine (OA) or mixtures of these two solvents. The surface and structural modifications of the Co NRs were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning and transmission electron microscopy (SEM and TEM). A disordered carbon shell was formed at the cobalt rod surface, the thickness of which can be tuned from 5 to 25 nm by increasing the amount of oleylamine in the solvent mixture. This carbon shell partially reduced the native cobalt oxide observed at the surface of the NRs and drastically improved their temperature stability as inferred from in-situ XRD study and TEM. The shape anisotropy and the crystallite anisotropy of the hcp phase are both preserved up to 400 °C for the carbon coated cobalt rods whereas the uncoated NRs lose their anisotropy at 225 °C. Treatments at 300 °C in ODE/OA mixtures for different durations allowed the progressive carburization of Co to Co 2 C. The crystallographic orientation of the Co 2 C grains within the cobalt NRs combined with the different carbon shell thickness on the {1010} and (0001) facets of the rods suggested a preferential carburization from the lateral facets of the hcp cobalt rods.

Graphene/cobalt nanocarrier for hyperthermia therapy and MRI diagnosis

“…The O/C ratio decrease from 0.9 for GO, to 0.18 for graphene/cobalt nanocomposites. The obtained results illustrate the deoxygenation of GO sheets [8,26]. This shows proper reduction of GO, which is in consistency with the XRD and UV-vis spectra results.…”

“…The deconvoluted peaks of Co 2p3/2 were obtained at 778, 781.38 and 783.74 eV. The peak at 781.38 eV is associated with binding energy of CoO and/or metal-carboxylate binding (Co-O) [13,26,27,46], whereas the signature at 783.74 eV is shake-up satellite line for…”

“…The application of hyperthermia therapy was first introduced in 1993 by Jordan [18]. Afterwards, other synthesis methods and designs for making magnetic nanocomposites were reported [13,26,27]. Recently, it was reported that due to remarkable electromagnetic performance, graphene magnetic nanocomposites can be used for microwave absorption [12,15].…”

An Efficient Support-Free Nanoporous Co Catalyst for Reverse Water–Gas Shift Reaction

“…After reduction, the Co-400R catalyst was characterized by the BE of the Co 2p 3/2 component of 780.9 eV and a low intensity of the shake-up satellite peak at ca. 786.0 eV, which was typical for Co 2+ ions in the CoO phase [20]. Additionally, the BE centered at 778.0 eV assigned to Co 0 could be also observed.…”

Fabrication of superstable gold nanorod–carbon nanocapsule as a molecule loading material

“…Monodispersed AuNR@carbon core-shell nanocapsules were prepared by a hydrothermal treatment in aqueous glucose solutions (AuNR@Carbon, Fig. 1) [14][15][16][17].…”