Sequential injection technique as a tool for the automatic synthesis of silver nanoparticles in a greener way.

This paper presents a new way to the synthesis of uniform and size-controlled silver nanoparticles by means of microreaction technology. It complies with the philosophy of green chemistry by developing a process that prevents pollution at source-by automation of the manipulations using microtubes manifolds and with the use of benign reagents and photochemistry to enhance the reaction of synthesis of Ag nanoparticles. Effect of hydrodynamic parameters (reagent volumes and volume flow rate) and concentrations (reducer and stabilizer), temperature, pH and UV irradiation time on morphology and size of nanoparticles was studied. The silver nanoparticles has been characterized by transmission electronic microscopy (TEM), electron diffraction X-ray spectroscopy (EDS), UV-vis spectra analysis, dynamic light scattering (DLS) and zeta potential measurements. Particles are mostly spherical in shape and have average sizes between 7 and 20 nm. The particle size can be controlled by changing not only the flow rate and UV light time exposition but also the reducer/AgNO3 concentration ratio. This is a sustainable and cost-saving methodology that guarantees not only reproducible synthesis, but also the changing of NPs characteristics at time by simple control of the fluid transport.