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

Abstract

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°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, ∼25 nm diameter and 30–50 nm length.