Moderating effect of ammonia on particle growth and stability of quasi-monodisperse silver nanoparticles synthesized by the Turkevich method

The formation of diamine silver complex prevents the reduction of silver ion. [Display omitted] . ► Stable silver nanoparticles of 2nm were obtained using ammonia to control the particle growth mechanism. ► Stable silver nanoparticles with sizes as small as 1.6nm were obtained after 17min of reaction. ► Soluble diamine silver (I) complexes played an important role in the nanoparticles stabilization. ► Morphology and particle size at ambient temperature do not change in the course of several months. A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90°C. After approximately 12min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6nm after 17min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy.