Influence of dissolved oxygen on aggregation kinetics of citrate-coated silver nanoparticles

Aggregation, an important environmental behavior of silver nanoparticles (AgNPs) influences their bioavailability and cytotoxicity. The work studied the influence of dissolved oxygen (DO) or the redox potential on the stability of AgNPs in aqueous environments. This study employed time-resolved dynamic light scattering (TR-DLS) to investigate the aggregation kinetics of citrate-coated AgNPs. Our results demonstrated that when DO was present, the aggregation rates became much faster (e.g., 3-8 times) than those without DO. The hydrodynamic sizes of AgNPs had a linear growth within the initial 4-6 h and after the linear growth, the hydrodynamic sizes became random for AgNPs in the presence of DO, whereas in the absence of DO the hydrodynamic sizes grew smoothly and steadily. Furthermore, the effects of primary particles sizes (20, 40, and 80 nm) and initial concentrations (300 and 600 μg/L) of AgNPs on aggregation kinetics were also investigated. - Graphical abstract: Physiochemical processes occurring in the suspension of silver nanoparticles (NPs) in the presence of dissolved oxygen and carbon dioxide transfer. Display Omitted Highlights: → Aggregation kinetics of AgNPs is influenced by dissolved oxygen in the aqueous media. → Aggregation rate of AgNPs increased in the presence of DO. → Aggregation rate did not increase with increasing H2O2 concentrations. → Small sized AgNPs aggregated faster than large ones. → Increasing the initial concentration of AgNPs increased aggregation rate. - This work emphasized the importance of accounting dissolved oxygen into the assessment of the stability of AgNPs in aqueous environments.