Kinetics and Mechanisms of Nanosilver Oxysulfidation

Liu, Jingyu; Pennell, Kelly G.; Hurt, Robert H.

doi:10.1021/es201539s

Cited by 235 publications

(261 citation statements)

References 30 publications

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“…NP size has also been found to affect the rate and extent of dissolution, since surface area increases with decreasing size, exposing more atoms per volume to the surrounding medium. For both CuO and coated Ag NPs, decreasing the size of the NPs increases the dissolution (both the rate and the equilibrium concentration), whereas the size of ZnO nanoparticles does not appear to significantly increase dissolution (Baek and An 2011;Franklin et al 2007;Levard et al 2012;Liu et al 2011;Ma et al 2012;Misra et al 2012;Mortimer et al 2010;Navarro et al 2008;Xia et al 2008).…”

Section: Dissolution In Watermentioning

confidence: 98%

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

2014

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A comprehensive assessment of the environmental risks posed by engineered nanomaterials (ENMs) entering the environment is necessary, due in part to the recent predictions of ENM release quantities and because ENMs have been identified in waste leachate. The technical complexity of measuring ENM fate and transport processes in all environments necessitates identifying trends in ENM processes. Emerging information on the environmental fate and toxicity of many ENMs was collected to provide a better understanding of their environmental implications. Little research has been conducted on the fate of ENMs in the atmosphere; however, most studies indicate that ENMs will in general have limited transport in the atmosphere due to rapid settling. Studies of ENM fate in realistic aquatic media indicates that in general, ENMs are more stable in freshwater and stormwater than in seawater or groundwater, suggesting that transport may be higher in freshwater than in seawater. ENMs in saline waters generally sediment out over the course of hours to days, leading to likely accumulation in sediments. Dissolution is significant for specific ENMs (e.g., Ag, ZnO, copper ENMs, nano zero-valent iron), which can result in their transformation from nanoparticles to ions, but the metal ions pose their own toxicity concerns. In soil, the fate of ENMs is strongly dependent on the size of the ENM aggregates, groundwater chemistry, as well as the pore size and soil particle size. Most groundwater studies have focused on unfavorable deposition conditions, but that is unlikely to be the case in many natural groundwaters with significant ionic strength due to hardness or salinity. While much still needs to be better understood, emerging patterns with regards to ENM fate, transport, and exposure combined with emerging information on toxicity indicate that risk is low for most ENMs, though current exposure estimates compared with current data on toxicity indicates that at current production and release levels, exposure to Ag, nZVI, and ZnO may cause toxicity to freshwater and marine species.

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Section: Dissolution In Watermentioning

confidence: 98%

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

2014

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“…Thus, sulfidation occurred much slower than had been observed in laboratory studies using Na 2 S as the source of sulfide. 31,32 The slower sulfidation of the AgNPs in the sediments compared to laboratory sulfidation may be a result of the relatively low AVS/Ag molar ratio (0.5−1 in the terrestrial soil and sediment) and the presence of other metals (e.g., Fe) that would compete for the sulfide. The slower sulfidation could also be due to a limited amount of oxidant (e.g., dissolved oxygen) that would be required to oxidize the AgNPs during the sulfidation process.…”

Section: +mentioning

confidence: 99%

“…Given the low levels of AVS in the sediment, sulfidation may be occurring as a two step process whereby the particles oxidize and dissolve to release free Ag + ion which is then transformed to Ag 2 S and the Ag-sulfhydryl phases observed. 32 Silver thiosulfate complexes may also form, but a model compound for this complex was not included in the EXAFS study. Fortin and Campbell (2001) 55 found that silver uptake in aquatic systems was greater in the presence of thiosulfate than based on the free Ag + water concentrations, and importantly, their studies suggest the presence of an inorganic anion transport system where a Ag−thiosulfate complex could give rise to increased uptake in higher organisms, including fish.…”

Section: +mentioning

confidence: 99%

Long-Term Transformation and Fate of Manufactured Ag Nanoparticles in a Simulated Large Scale Freshwater Emergent Wetland

Lowry

Espinasse

Badireddy

et al. 2012

Environ. Sci. Technol.

363

298

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Transformations and long-term fate of engineered nanomaterials must be measured in realistic complex natural systems to accurately assess the risks that they may pose. Here, we determine the long-term behavior of poly(vinylpyrrolidone)-coated silver nanoparticles (AgNPs) in freshwater mesocosms simulating an emergent wetland environment. AgNPs were either applied to the water column or to the terrestrial soils. The distribution of silver among water, solids, and biota, and Ag speciation in soils and sediment was determined 18 months after dosing. Most (70 wt %) of the added Ag resided in the soils and sediments, and largely remained in the compartment in which they were dosed. However, some movement between soil and sediment was observed. Movement of AgNPs from terrestrial soils to sediments was more facile than from sediments to soils, suggesting that erosion and runoff is a potential pathway for AgNPs to enter waterways. The AgNPs in terrestrial soils were transformed to Ag 2 S (∼52%), whereas AgNPs in the subaquatic sediment were present as Ag 2 S (55%) and Ag-sulfhydryl compounds (27%). Despite significant sulfidation of the AgNPs, a fraction of the added Ag resided in the terrestrial plant biomass (∼3 wt % for the terrestrially dosed mesocosm), and relatively high body burdens of Ag (0.5−3.3 μg Ag/g wet weight) were found in mosquito fish and chironomids in both mesocosms. Thus, Ag from the NPs remained bioavailable even after partial sulfidation and when water column total Ag concentrations are low (<0.002 mg/L).

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“…36,53,59,60,[63][64][65][66][67][68] Henglein and coworkers, who pioneered work on the interactions between ligands and AgNPs, explained this observation by postulating that a "pre-complexation" or "pre-oxidation" occurred when nucleophiles adsorbed to the nanoparticle surface. [65][66][67] According to their hypothesis, the coordination of a nucleophile to a surface silver atom results in the partial oxidation of that atom.…”

Section: Effects Of Ligands and Surface Coating On Agnp Dissolutionmentioning

confidence: 99%

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

Kent

Vikesland

2012

Environ. Sci. Technol.

127

129

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Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ≥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, and the height increased by 6-12 nm. Subsequently, particle height and inplane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of unaggregated AgNP dissolution.iii Acknowledgements I thank my advisor, Dr. Peter Vikesland, for his insight, guidance, and innovative ideas throughout my time at Virginia Tech, and for giving me the opportunity to work on this research project. He was ready and available to help whenever I needed his input. I also thank the other members of my committee,

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Kinetics and Mechanisms of Nanosilver Oxysulfidation

Cited by 235 publications

References 30 publications

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

Long-Term Transformation and Fate of Manufactured Ag Nanoparticles in a Simulated Large Scale Freshwater Emergent Wetland

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

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