Xuan Li

The Ohio State University, Columbus, OH, United States

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Publications (3)14.03 Total impact

  • Xuan Li, John J Lenhart
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    ABSTRACT: This study investigated aggregation and silver release of silver nanoparticles suspended in natural water in the absence and presence of artificial sun light. The influence of the capping layer was investigated using uncoated particles and particles coated with citrate or Tween 80. The experiments were conducted over 15 days in batch mode using a river water matrix. Silver release was monitored over this time while the aggregation state and morphological changes of the silver nanoparticles were tracked using dynamic light scattering and transmission electron microscopy. Results indicate sterically dispersed particles coated with Tween released silver quicker than did bare- and citrate-coated particles, which rapidly aggregated. A dissolved silver concentration of 40 μg/L was reached after just 6 h in the Tween-coated particle systems, accounting for ca. 3% of the total silver. Similar levels of dissolved silver were reached in the uncoated and citrate-coated systems at the end of the 15 days. Silver release was not significantly impacted by the artificial sun light; however, the light (and citrate) imparted significant morphological changes to the particles. Their impact was masked by aggregation, which seemed to be the controlling process in this study.
    Environmental Science & Technology 04/2012; 46(10):5378-86. · 5.26 Impact Factor
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    ABSTRACT: Determining the fate of manufactured nanomaterials in the environment is contingent upon understanding how stabilizing agents influence the stability of nanoparticles in aqueous systems. In this study, the aggregation and dissolution tendencies of uncoated silver nanoparticles and the same particles coated with three common coating agents, trisodium citrate, sodium dodecyl sulfate (SDS), and Tween 80 (Tween), were evaluated. Early stage aggregation kinetics of the uncoated and coated silver nanoparticles were assessed by dynamic light scattering over a range of electrolyte types (NaCl, NaNO(3), and CaCl(2)) and concentrations that span those observed in natural waters. Although particle dissolution was observed, aggregation of all particle types was still consistent with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The aggregation of citrate-coated particles and SDS-coated particles were very similar to that for the uncoated particles, as the critical coagulation concentrations (CCC) of the particles in different electrolytes were all approximately the same (40 mM NaCl, 30 mM NaNO(3), and 2 mM CaCl(2)). The Tween-stabilized particles were significantly more stable than the other particles, however, and in NaNO(3) aggregation was not observed up to an electrolyte concentration of 1 M. Differences in the rate of aggregation under diffusion-limited aggregation conditions at high electrolyte concentrations for the SDS and Tween-coated particles, in combination with the moderation of their electrophoretic mobilities, suggest SDS and Tween imparted steric interactions to the particles. The dissolution of the silver nanoparticles was inhibited by the SDS and Tween coatings, but not by the citrate coating, and in chloride-containing electrolytes a secondary precipitate of AgCl was observed bridging the individual particles. These results indicate that coating agents could significant influence the fate of silver nanoparticles in aquatic systems, and in some cases these stabilizers may completely prevent particle aggregation.
    Langmuir 12/2011; 28(2):1095-104. · 4.38 Impact Factor
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    ABSTRACT: Bare silver nanoparticles with diameters of 82 ± 1.3 nm were synthesized by the reduction of the Ag(NH(3))(2)(+) complex with D-maltose, and their morphology, crystalline structure, UV-vis spectrum, and electrophoretic mobilities were determined. Dynamic light scattering was employed to assess early stage aggregation kinetics by measuring the change in the average hydrodynamic diameter of the nanoparticles with time over a range of electrolyte types (NaCl, NaNO(3), and CaCl(2)) and concentrations. From this the critical coagulation concentration values were identified as 30, 40, and 2 mM for NaNO(3), NaCl, and CaCl(2), respectively. Although the silver nanoparticles were observed to dissolve in all three electrolyte solutions, the aggregation results were still consistent with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The dissolution of the silver nanoparticles, which were coated with a layer of Ag(2)O, was highly dependent on the electrolyte type and concentration. In systems with Cl(-) a secondary precipitate, likely AgCl, also formed and produced a coating layer that incorporated the silver nanoparticles. Aggregation of the silver nanoparticles was also examined in the presence of Nordic aquatic fulvic acid and was little changed compared to that evaluated under identical fulvic acid-free conditions. These results provide a fundamental basis for further studies evaluating the environmental fate of silver nanoparticles in natural aquatic systems.
    Langmuir 09/2010; 26(22):16690-8. · 4.38 Impact Factor

Publication Stats

74 Citations
14.03 Total Impact Points

Institutions

  • 2010–2012
    • The Ohio State University
      • Department of Civil, Environmental and Geodetic Engineering
      Columbus, OH, United States