Effects of Aggregate Structure on the Dissolution Kinetics of Citrate-Stabilized Silver Nanoparticles

Abstract

Aggregation and dissolution kinetics are important environmental properties of silver nanoparticles (AgNPs), and characterization of the interplay between these two processes is critical to understanding the environmental fate, transport, and biological impacts of AgNPs. Time-resolved dynamic light scattering was employed to measure the aggregation kinetics of AgNPs over a range of monovalent electrolyte (NaCl) concentrations. The fractal dimensions (Df) obtained from aggregation kinetics and static light scattering were found to be dependent on the aggregation mechanism and, in accord with expectation, varied from 1.7 for diffusion-limited cluster aggregation to 2.3 for reaction-limited cluster aggregation. An aggregation-dissolution model, in which the proportion of accessible reactive sites on primary particles as well as the aggregate size and Df are assumed to be key determinants of reactivity, is found to provide an excellent description of the decline of normalized rate of dissolution of AgNPs during aggregation for different NaCl concentrations. This model also provides fundamental insights into the factors accounting for the observed change in rate of dissolution of AgNPs on injection into seawater thereby facilitating improved prediction of the likely toxicity of AgNPs in the marine environment.

Both released silver ions and particulate Ag contribute to the toxicity of AgNPs to earthwormEisenia fetida

“…This was most likely due to the higher ionic strength of the simulated soil solution as in the case of DI, which resulted in the aggregation of nanoparticles and subsequently reduced the effective surface area, and finally limited the release of soluble Ag (He et al, 2013).…”

Antibacterial activity of silver nanoparticles: A surface science insight

“…One direct consequence is that an increase in the ionic strength of the solution will screen the electrostatic repulsive potential, and lead to the aggregation of the nanoparticles. In a recent study, He et al [105] considered the ionic strength increase as a parameter that would influence the shape (and fractal dimension) of Ag NPs aggregates. At low ionic strength, a Reaction Limited Cluster Aggregation (RLCA) led to compact aggregates that dissolve slowly, while at higher ionic strength, Diffusion Limited Cluster Aggregation (DLCA) led to more open aggregates and thus to a higher dissolution rate.…”

Mechanistic Insights into Free Chlorine and Reactive Oxygen Species Production on Irradiation of Semiconducting Silver Chloride Particles

“…Reaction with AgNPs which are generated on irradiation of AgCl(s) at low Cl − concentrations (where generated OCl − concentrations are low as well; Figure 6) can explain the fast decay kinetics of OCl − in the dark for low OCl − concentrations. We are currently undertaking a detailed study to determine the mechanism and products for the reaction between OCl − and AgNP, but as shown by the data presented here ( Figure SI-9 21 and where the OCl − concentration is high ( Figure 6). …”