Oxidative Dissolution of Silver Nanoparticles by Chlorine: Implications to Silver Nanoparticle Fate and Toxicity

The kinetics of oxidative dissolution of silver nanoparticles (AgNPs) by chlorine is investigated in this work, with results showing that AgNPs are oxidized in the presence of chlorine at a much faster rate than observed in the presence of dioxygen and/or hydrogen peroxide. The oxidation of AgNPs by chlorine occurs in air-saturated solution in stoichiometric amounts with 2 mol of AgNPs oxidized for each mole of chlorine added. Dioxygen plays an important role in OCl(-)-mediated AgNP oxidation, especially at lower OCl(-) concentrations, with the mechanism shifting from stoichiometric oxidation of AgNPs by OCl(-) in the presence of dioxygen to catalytic removal of OCl(-) by AgNPs in the absence of dioxygen. These results suggest that the presence of chlorine will mitigate AgNP toxicity by forming less-reactive AgCl(s) following AgNP oxidation, although the disinfection efficiency of OCl(-) may not be significantly impacted by the presence of AgNPs because a chlorine-containing species is formed on OCl(-) decay that has significant oxidizing capacity. Our results further suggest that the antibacterial efficacy of nanosilver particles embedded on fabrics may be negated when treated with detergents containing strong oxidants, such as chlorine.