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Aggregation and Charge Behavior of Metallic and Nonmetallic Nanoparticles in the Presence of Competing Similarly-Charged Inorganic Ions
Citation:
Mukherjee, B. AND J. W. WEAVER. Aggregation and Charge Behavior of Metallic and Nonmetallic Nanoparticles in the Presence of Competing Similarly-Charged Inorganic Ions. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 44(9):3332-3338, (2010).
Impact/Purpose:
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Description:
The influence of competing, similarly charged, inorganic ions on the size and charge behavior of suspended titanium-dioxide (nTiO2), silver (nAg) and fullerene (nC60) nanoparticles (NPs) was investigated. Under pH and ionic conditions similar to natural water bodies, Ca2+ induced aggregation of nTiO2 and nAg NPs more strongly than K+ and Na+. Although K+ and Na+ had a similar effect on aggregation, K+ provided better screening of the particle surface charge presumably because of its small hydrated radius. These effects were decidedly more prominent for TiO2 than Ag. Anions (co-ions), SO42− and Cl−, affected the surface charge behavior of nTiO2 but not of nAg NPs. The zeta potential (ZP) of nTiO2 NPs was more negative at higher SO42−/Cl− ratios than lower. When Mg2+ was the counterion, charge inversion and rapid aggregation of nC60 NPs occurred under alkaline conditions, with a more pronounced effect for Cl− than SO42−. Response dissimilarities suggest fundamental differences in the interfacial-interaction characteristics of these NPs in the aquatic environment with corresponding differences in transport of these particles. Our study also shows the important role played by the iso-electric point pH (pHiep) of the NPs in determining their aggregation kinetics in the environment.
