Chemical Stability of Silver Nanoparticles: Environmental Fate

The environmental fate of commercial metallic nanoparticles is of significant interest to regulatory authorities. This research investigated the stability of silver nanoparticles (AgNPs) as popular representative of nanomaterials increasingly used in commercial products due to their antimicrobial properties. Pure, ion-free, citrate-stabilized AgNPs were synthesized as model system. The effects of ionic strength, pH (3-9) and the presence of surfactant molecules on the stability of AgNP was investigated using UV-Vis spectroscopy, ICP-MS, dynamic light scattering (DLS), transmission electron microscopy (TEM) and electrochemical methods. Aggregation behavior, ion release and surface charge properties were used as parameters for stability evaluation. Obtained results revealed that high ionic strength, as well as significant increase and/or decrease in pH of medium, destabilizes citrate-coated AgNPs. It was also observed that AgNP aggregation and silver ion release from the AgNP surface were significantly reduced in the presence of negatively charged surfactant molecules. The results showed that the understanding of the influence of pH, ionic strength and different biomolecules is essential for predicting the stability and fate of silver nanomaterial as an unavoidable part of afterwards exposure modeling.