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This content will become publicly available on December 19, 2018

Title: Influence of Structural Defects on Biomineralized ZnS Nanoparticle Dissolution: An In-Situ Electron Microscopy Study

The dissolution of metal sulfides, such as ZnS, plays an important role in the fate of metal contaminants in the environment. Here we have examined the dissolution behavior of ZnS nanoparticles synthesized via several abiotic and biological pathways. Specifically, the biogenic ZnS nanoparticles were produced by an anaerobic, metal-reducing bacterium Thermoanaerobacter sp. X513 in a Zn-amended, thiosulfate-containing growth medium, whereas the abiogenic ZnS nanoparticles were produced by mixing an aqueous Zn solution with either H 2S-rich gas or Na 2S solution. For biogenic synthesis, we prepared two types of samples, in the presence or absence of trace silver (Ag). The size distribution, crystal structure, aggregation behavior, and internal defects of the synthesized ZnS nanoparticles were primarily examined using high-resolution transmission electron microscopy coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. In the absence of Ag, the biogenic ZnS nanoparticles were significantly larger (i.e., ~10 nm) than the abiogenic ones (i.e., ~3–5 nm) and contained structural defects (e.g., twins and stacking faults). The presence of trace Ag showed a restraining effect on the particle size of the biogenic ZnS, resulting in quantum-dot-sized nanoparticles (i.e., ~3 nm). Inmore » situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell coupled to a transmission electron microscope (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behavior using the biogenic and abiogenic ZnS nanoparticle samples with the largest average particle size. Analysis of the dissolution results (i.e., change in particle radius with time) using the Kelvin equation shows that the defect-bearing biogenic ZnS nanoparticles (γ = 0.799 J/m 2) have a significantly higher surface energy than the abiogenic ZnS nanoparticles (γ = 0.277 J/m 2), suggesting that larger defect-bearing ZnS nanoparticles may be more reactive than the smaller quantum-dot-sized ZnS nanoparticles. These findings provide new insight into the factors that govern the dissolution of metal sulfide nanoparticles in relevant natural and engineered scenarios, and have implication for tracking the fate of zinc at contaminated sites. Moreover, our study exemplified the use of an in situ method (i.e., LCTEM) to investigate nanoparticle behavior (e.g., dissolution) in aqueous solutions.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [3] ;  [1] ; ORCiD logo [3] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  2. Univ. of Texas, El Paso, TX (United States). Geological Sciences
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Name: Environmental Science and Technology; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; liquid cell electron microscopy; metal sulfides; nanoparticles; dissolution; structural defect; sphalerite; zinc blende; wurtzite
OSTI Identifier:
1414703