Superoxide-mediated formation and charging of silver nanoparticles.
Contemporary studies indicate that reactive oxygen species (ROS) such as superoxide play a key role in the toxicity and behavior of silver nanoparticles (AgNPs). While there have been suggestions that superoxide is able to reduce silver(I) ions with resultant production of AgNPs, no experimental evidence that this process actually occurs has been produced. Here we present definitive experimental evidence for the reduction of silver(I) by superoxide. A second-order rate constant of 64.5 ± 16.3 M(-1)·s(-1) is determined for this reaction in the absence of AgNPs. The overall rate constant, however, increases by at least 4 orders of magnitude in the presence of AgNPs. A model based on electron charging and discharging of AgNPs satisfactorily describes the kinetics of this process. The ability for AgNPs to undergo catalytic cycling provides a pathway for the continual generation of ROS and the regeneration of AgNPs following oxidation.
School of Civil and Environmental Engineering, The University of New South Wales , Sydney, New South Wales, Australia 2052.
Adele M
AM
Jones
Shikha
S
Garg
Di
D
He
A Ninh
AN
Pham
T David
TD
Waite
D007477:Ions; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D053758:Nanoparticles; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000737:chemistry*; D013481:Superoxides
D007477:Ions; D017382:Reactive Oxygen Species; D013481:Superoxides; D012834:Silver