Oxidative Dissolution of Silver Nanoparticles by Biologically Relevant Oxidants: A Kinetic and Mechanistic Study

The oxidative dissolution of silver nanoparticles (AgNPs) plays an important role in the synthesis of well‐defined nanostructured materials , and may be responsible for their activities in biological systems . In this study, we use stopped‐flow spectrophotometry to investigate the kinetics and mechanism of the oxidative dissolution of AgNPs by H 2 O 2 in quasi‐physiological conditions. Our results show that the reaction is first order with respect to both [Ag 0 ] and [H 2 O 2 ], and parallel pathways that involve the oxidation of H 2 O 2 and HO 2 − are proposed. The order of the reaction is independent of the size of the AgNPs (≈5–20 nm). The rate of dissolution increases with increasing pH from 6.0 to 8.5. At 298 K and I =0.1  M , the value of k b is five orders of magnitude higher than that of k a (where k a and k b are the rate constants for the oxidative dissolution of AgNPs by H 2 O 2 and HO 2 − , respectively). In addition , the effects of surface coating and the presence of halide ions on the dissolution rates are investigated. A possible mechanism for the oxidative dissolution of AgNPs by H 2 O 2 is proposed. We further demonstrate that the toxicities of AgNPs in both bacteria and mammalian cells are enhanced in the presence of H 2 O 2 , thereby highlighting the biological relevance of investigating the oxidative dissolution of AgNPs.