Preparation of Spherical and Triangular Silver Nanoparticles by a Convenient Method

Silver nanoparticles with spherical and triangular shapes were prepared in a convenient way (simple and rapid) at room temperature by chemical reduction method. The obtained Ag NPs were characterized by transmission electron microscopy and UV-visible spectrophotometer. The results indicated that, as silver nitrate, polyvinyl pyrrolidone and sodium borohydride were used as reagent, protective agent and reducing agent respectively, spherical and monodisperse Ag NPs with their sizes about 9.0 nm were prepared. In addition, using hydrazine hydrate as reducing agent in stead of sodium borohydride, Ag NPs with triangular shape and edge lengths in the range of 50–200 nm were obtained. It was speculated that, these triangular Ag NPs were transformed from small quasi-spherical Ag NPs formed at the beginning of the reaction. Ostward ripening is most likely the driving force for the shape evolution.