Silver nanoparticles produced via a green synthesis using the rhamnolipid as a reducing agent and stabilizer

Silver nanoparticles (AgNPs) stabilized by rhamnolipid (RL), which was separated from the supernatant of the genus Pseudomonas sp. PS-17, were synthesized. Using TEM it was found that the mean size of obtained AgNPs does not depend on the initial concentration of Ag+ but is increased with the decrease of the concentration of RL. During XRD-phase analysis it was determined, that the Ag (space group Fm-3m, Cu-structure type) is the main phase that was identified. The kinetics of the formation of AgNPs was studied in detail using the UV-Vis spectroscopy. It was observed that in all cases the kinetic curves are sigmoidal shape and are characterized by a well-notable induction period that permits to assume the homogeneous nucleation of AgNPs and their autocatalytic growth. Experimental kinetic curves were fitted using different types of Finke-Watzky schemes of continuous nucleation and fast autocatalytic growth of particles and the observable rate constants of nucleation and growth were estimated. Based on the established regularities of "green " synthesis of AgNPs stabilized by RL, the method of obtaining their colloidal solutions was optimized. A laboratory model of a flow tubular reactor for the synthesis of colloidal solutions of AgNPs has been created.