This investigation reports a simple, controllable, chemical reduction method for the formation of copper nanoparticles by reducing copper sulfate with sodium hypophosphite in ethylene glycol using different capping agents: sodium dodecyl sulfate (SDS), polyethylene glycol 2000 (PEG2000), and polyethylene glycol 4000 (PEG4000). The synthetic parameters influencing the purity, size, and morphology of the copper nanoparticles such as reaction time, reaction temperature, reaction solvent, initial copper sulfate concentration, and capping agent were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results revealed that pure copper nanoparticles with an average crystallite size of 28nm were successfully prepared in the presence of PEG4000 capping agent, at 70
C, and in 45 min. The formation mechanism of the as-prepared Cu nanoparticles was also proposed.