Joseph Murphy


Boris Lau

Publication Date

Winter 1-2017


The transformation of silver nanoparticles (AgNPs) due to environmental factors can play a role in their fate and transport in aquatic systems. Sulfidation has the potential to alter these particles’ physio-chemical properties and their subsequent mobilization in aquatic environments. The water chemistry (e.g. pH, dissolved organic carbon) of these systems can also change the behavior of AgNPs. To better understand the effects of sulfidation on the characteristics and deposition of AgNPs, techniques such as quartz crystal microgravimetry (QCM) and dynamic light scattering (DLS) were used. In this study, AgNPs with two different ligand types, Polyvinylpyrrolidone (PVP)-capped AgNPs (PVP-AgNPs) and Polyethylene glycol (PEG)-capped AgNPs (PEG-AgNPs), were modified through sulfidation in the presence of natural organic matter (NOM). Sulfidation of PVP-AgNPs resulted in a 5 to 23 times greater extent of deposition to a silica substrate than unmodified PVP-AgNPs in tested conditions. This probably caused by the loss of steric repulsion due to the loss of PVP ligand during sulfidation. The dependence of ligand type on the effects of sulfidation were observed in the same conditions with sulfidized PEG-AgNPs having a 28%-98% decrease in deposition extent compared to pristine PEG-AgNPs. This decrease in particle-substrate interaction is attributed to the increase in electrostatic repulsion. Rates of deposition of each particle type were also reported to better understand the potential of these AgNPs to persist in engineered and natural aquatic environments. Hydrophobicity of AgNP types were not found to play a dominant role in the deposition dynamics. AgNP deposition extent to silica substrate provides insight on the potential for persistence in aquatic environments as well as a predisposition towards removal through media filtration. Based on deposition results, after sulfidation, PEG-AgNPs are more likely to persist than that of PVP-AgNPs.