Long time effect on the stability of silver nanoparticles in aqueous medium: Effect of the synthesis and storage conditions

Silver nanoparticles (Ag NPs, ∼5 nm) were prepared, in presence of citrate, by borohydride reduction and characterized by UV–vis and TEM images. Different experimental conditions were used in order to induce changes in the size distribution of the Ag NPs and to study the effect of those experimental conditions on the long range stability of the Ag NPs. The stability of the Ag NP solutions was studied for a period of 1 year. fect of the storage conditions was studied. After preparation, each of the Ag NP solutions was divided and part of it was stored, in dark, at 4.0 ± 2.0 °C and the other part at 23.0 ± 2.0 °C. Both UV–vis and TEM techniques were used to follow the changes observed in the Ag NP solutions. NP solutions stored at room temperature show more dramatic changes in UV–vis spectraʹs evolution comparing with those stored at 4.0 ± 2.0 °C. The use of lower BH4−/Ag+ ratio promotes the formation of Ag NPs with various shapes and sizes during the storage time.