title: Oxidative dissolution of silver nanoparticles by biologically relevant oxidants: a kinetic and mechanistic study.
abstract: 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 (approximately 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.
authors.affiliation: Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong, China. rickyho@hku.hk
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Ho
authors.forename: Sammi King-Woon
authors.initials: SK
authors.lastname: Yau
authors.forename: Chun-Nam
authors.initials: CN
authors.lastname: Lok
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: So
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
mesh_terms: D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D012834:Silver; D006861:Hydrogen Peroxide