H2O2-mediated oxidation of zero-valent silver and resultant interactions among silver nanoparticles, silver ions, and reactive oxygen species

Langmuir. 2012 Jul 10;28(27):10266-75. doi: 10.1021/la300929g. Epub 2012 Jun 26.

Abstract

The H(2)O(2)-mediated oxidation of silver nanoparticles (AgNPs) over a range of pH (3.0-14.0) is investigated here, and an electron charging-discharging model capable of describing the experimental results obtained is developed. AgNPs initially react with H(2)O(2) to form Ag(+) and superoxide, with these products subsequently reacting to reform AgNPs (in-situ-formed AgNPs) via an electron charging-discharging mechanism. Our experimental results show that the AgNP reactivity toward H(2)O(2) varies significantly with pH, with the variation at high pH (>10) due particularly to the differences in the reactivity of H(2)O(2) and its conjugate base HO(2)(-) with AgNPs whereas at lower pH (3-10) the pH dependence of H(2)O(2) decay is accounted for, at least in part, by the pH dependence of the rate of superoxide disproportionation. Our results further demonstrate that the in-situ-formed AgNPs resulting from the superoxide-mediated reduction of Ag(+) have a different size and reactivity compared to those of the citrate-stabilized particles initially present. The turnover frequency for AgNPs varies significantly with pH and is as high as 1776.0 min(-1) at pH 11.0, reducing to 144.2 min(-1) at pH 10.0 and 3.2 min(-1) at pH 3.0.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cations, Monovalent
  • Citrates / chemistry
  • Hydrogen Peroxide / chemistry*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Metal Nanoparticles / chemistry*
  • Metal Nanoparticles / ultrastructure
  • Microscopy, Electron, Transmission
  • Models, Chemical
  • Oxidation-Reduction
  • Particle Size
  • Reactive Oxygen Species / chemistry*
  • Silver / chemistry*
  • Superoxide Dismutase / chemistry

Substances

  • Cations, Monovalent
  • Citrates
  • Reactive Oxygen Species
  • trisodium citrate
  • Silver
  • Hydrogen Peroxide
  • Superoxide Dismutase