The plant-mediated synthesis of therapeutic metal nanoparticles is an intensively exploited field in the last decade. In particular, Salvia officinalis, considered one of these plants, was used in this work to synthesize silver particles. Here, we have used harmless substances to obtain silver particles and common characterization methods for quickly estimating sizes and shapes. Thus, UV–Visible spectroscopy helped us online-monitor and optimize the synthesis of silver particles and estimate the size of metallic particles in the stock solutions. The resulting eco-friendly synthesized silver particles were then separated and re-dispersed in water, to be analyzed by laser light scattering, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to prove their nanometric size and shape polydispersity. Furthermore, the role of citric acid in stabilizing colloidal solutions of silver nanoparticles was studied. [ABSTRACT FROM AUTHOR]