Synthesis of cobalt-based magnetic nanocrystals from cobalt(II) heterocyclic amine complexes.

Cobalt nanocrystals with different morphologies and magnetic properties were prepared from three cobalt(II) heterocyclic amine precursors in alcoholic solution by a chemical reduction route. Complexes of cobalt(II) with heterocyclic amines such as pyridine, piperidine, and piperazine were reacted with hydrazine at 70 °C and pH 10-12. The obtained cobalt metallic nanocrystals (Co1-Co3) were characterized by using infrared (IR) spectroscopy, X-ray powder diffraction analysis, scanning electron microscopy, and vibrating-sample magnetometry. Powder X-ray diffraction patterns revealed the presence of two phases of hcp-Co and fcc-Co nanocrystals in the resulting cobalt metal. By changing the precursors, significant variation of magnetic properties and crystallite size was observed in Co1-Co3. This work provides new insight into the synthesis of metallic nanocrystals via chemical reduction of metal complexes and their magnetic properties. Graphical Abstract: [ABSTRACT FROM AUTHOR]