Impacts of surfactants on dissolution and sulfidation of silver nanowires in aquatic environments

Abstract

Due to their excellent properties, silver nanowires (AgNWs) have been applied increasingly in many optical and electronic products, and may be inevitably discharged in aquatic environments. Dissolution and sulfidation are two of the most important processes of AgNWs occurring in aquatic environments and may significantly affect their fate and toxicities. This study aimed to investigate the impacts of four types of surfactants on the dissolution and sulfidation of AgNWs. Anionic, zwitterionic, and nonionic surfactants, including sodium dodecylbenzenesulfonate, cetyl betaine, and glycerol monostearate, did not affect the dissolution and sulfidation of AgNWs. However, cationic surfactants (cetyltrimethylammonium bromide, cetyltrimethylammonium nitrate and benzyldimethyldodecylammonium nitrate) promoted the dissolution and sulfidation of AgNWs significantly. The cationic surfactants, especially cetyltrimethylammonium bromide, preferred to bind with the (111) planes of AgNWs, leading to the corrosion of the initial wire structure of AgNWs to shorter nanorods. The increased surface area of AgNWs resulted in faster dissolution. The dissolved Ag⁺ ions reacted with sulfide quickly, leading to faster sulfidation of AgNWs. In addition, the cationic surfactants interacted with AgNWs and decreased the electrostatic repulsion between the sulfide ions and the surface of AgNWs, thus promoting the direct oxysulfidation. As a consequence, the cationic surfactants facilitated the sulfidation of AgNWs to a greater extent than dissolution. The interaction of AgNWs and surfactants could significantly affect their bioavailability and ecotoxicities in aquatic environments.