Highly-defective nanocrystals of ZnS formed via dissimilatory bacterial sulfate reduction: A comparative study with their abiogenic analogues

Journal Article · Thu Feb 11 00:00:00 EST 2016 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2016.02.007· OSTI ID:1735699

Xu, Jie ^[1]; Murayama, Mitsuhiro ^[1]; Roco, Charles M. ^[1]; Veeramani, Harish  ^[2]; Michel, F. Marc ^[1]; Rimstidt, J. Donald ^[1]; Winkler, Christopher ^[1]; Hochella, Michael F.  ^[3]

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1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
2. Univ. of Glasgow, Scotland (United Kingdom)
3. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

The physicochemical properties of a (nano)mineral are strongly affected by its formation processes, and thus, may indicate the (nano)mineral’s formation environment and mechanism. This correlation, although relevant to a myriad of geological, environmental, and material-science processes, has not yet been fully appreciated and systematically explored. In this study, using the Zn–S system, we demonstrate that biological and abiotic processes at similar experimental conditions can produce distinctive particle size, morphology, and crystal structure in the formed ZnS. Specifically, bacterial sulfate reduction led to the formation of highly-defective nanocrystals of mixed sphalerite and wurtzite in a range of ~4–12 nm. By comparison, the abiotic procedures of titration- or diffusion-controlled precipitation resulted in the formation of polycrystalline aggregates that contained randomly-oriented, ultrafine crystals below ~2–3 nm. The poor crystallinity in the abiogenic samples, regardless of the sulfide addition rates, reveals an overall nucleation-dominated, crystal growth-restricted pathway for the formation of ZnS from low-temperature aqueous solutions. The difficulty in the ZnS crystallization likely stems from the intrinsic surface instability of the ZnS growth units (i.e., in the form of nanoclusters) resulting from the dipole–dipole interactions of the unit with surrounding water molecules. In the biogenic samples, the ZnS crystallinity was significantly improved, indicating that the presence of bacterial metabolites somehow promoted the crystallization process. With evidence for the enlarged {1 1 1} planes in the biogenic nanocrystals, we attribute this enhancement mainly to the selective interaction of the bacterial metabolites with polar faces of the ZnS growth units, which might have effectively screened the dipole moments in the growth units and enabled their crystallographic assembly. By revealing the intrinsic difficulty and specific pathways for the ZnS crystallization, we also present viable explanations for the exclusive occurrence of structural defects in {1 1 1} planes of the biogenic nanocrystals. The findings of our study provide insight into the origin and fate of metal sulfide nanoparticles in the environment, and have implications for biomineralization, bioremediation of metal-contaminated sites, and bacterial production of functional nanomaterials.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-76RL01830; SC-FOA-0000768
• OSTI ID: 1735699
• Alternate ID(s): OSTI ID: 1359152
• Report Number(s): PNNL-SA-120162
• Journal Information: Geochimica et Cosmochimica Acta, Vol. 180; ISSN 0016-7037
• Publisher: Elsevier; The Geochemical Society; The Meteoritical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY