Facile synthetic route for synthesis of cobalt nanorods and dendritic structures using a bomb digestion vessel

In this article, we report a simple and fast route for the synthesis of cobalt in the shape of nanorods (Co-NRs). It involves a modified polyol process in which a cobalt hydrazine complex was taken as a precursor with poly(vinylpyrrolidone) (PVP) molecules as a stabiliser in ethylene glycol (solvent) in a stainless steel bomb digestion vessel with Teflon inner lining. The solution was heated in the bomb at 200 degrees C for three different reaction times 30, 60 and 90 min in performing the reaction. After the scheduled reaction, which resulted in a blackish colour turned-up from an initially pink-coloured sample, the samples were cooled down to room temperature. Recovered powders by repeated washing in water were studied for further characterisations. Reactions were analysed with Fourier transform-infrared spectroscopy and the XRD patterns of the samples reveal that the PVP molecules promptly control the formation of surface modified Co-NRs of a primarily face-centred cubic phase. These samples exhibit a ferromagnetic hysteresis loop showing a reasonably smaller saturation magnetisation comparing to bulk cobalt. SEM images reveal that the 30-min reaction product consists of nearly spherical nanoparticles (with an average size of 38 nm), whereas that of the 90-min reaction product displays a different shape of tiny nanorods, similar to 25 nm diameter and 30-50 nm length.