Silver nanoparticles synthesis in aqueous solutions using sulfite as reducing agent and sodium dodecyl sulfate as stabilizer

The synthesis of silver nanoparticles has been carried out in aqueous solutions in a stirred semibatch reactor through the reduction of silver ions (Ag⁺) by sulfite ions (SO₃ ²⁻), which were added at a tightly controlled rate up to a final sulfite/silver molar ratio of 0.45. Sodium dodecyl sulfate (SDS) was used as the stabilizer at concentrations below its critical micelle concentration. The effects of temperature, sulfite addition rate, and SDS concentration have been assessed. Ag⁺ turned to Ag⁰ in 5 min or less only when the synthesis was performed at 97 °C and not below. The sulfite addition rates studied were 0.5, 7.5, 15, and 90 μmol/min. The size, shape, polydispersity, and stability of the nanoparticles were determined by the sulfite addition rate and SDS concentration. At low SDS concentration (4 mM), stable, spherical shape, small size nanoparticles were formed only at the two intermediate sulfite addition rates. At the highest sulfite addition rate, 9 nm mean size spherical nanoparticles having a low ±5 nm polydispersity were produced at a high SDS concentration of 10 mM. With the low SDS concentration, larger truncated and spherical shape nanoparticles were obtained. UV–Vis spectrophotometry and transmission electron microscopy were used to characterize the nanoparticles.