Preparation of Elemental Cu and Ni Nanoparticles by the Polyol Method: An Experimental and Theoretical Approach

This paper discusses the relationship between synthesis conditions, crystal morphology, and theoretical modeling of copper and nickel nanoparticles prepared by a modified polyol process. The polyol serves as a solvent, a reducing agent, and a capping agent, and we investigate the role several polyol types play in the nucleation and growth of metallic nanoparticles. The nanoparticles are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Our results demonstrate that changing the solvent system from a short chain polyol (ethylene glycol) to a long chain polyol (tetraethylene glycol) greatly affects the resulting morphology of copper nanoparticles. These results suggest that the polyol is playing a major role as an in situ capping agent and that the various polyol chain lengths in-turn result in various particle morphologies by directly altering the nucleation and growth steps. We were also able to use theoretical modeling to investigate the mechanism for growth to better understand the intermediate structure stability. This work presents an alternative approach in investigating the polyol mechanism by using both theoretical and experimental results and opens new insight for the synthesis of metals and alloys by the polyol process.