The dissolution of metal sulfides, such as ZnS, is an important biogeochemical process affecting fate and transport of trace metals in the environment. However, currently studies of in-situ dissolution of metal sulfides and the effects of structural defects on dissolution are lacking. Here we have examined the dissolution behaviour 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 H2S-rich gas or Na2S solution. The size distribution, crystal structure, aggregation behaviour, and internal defects of the synthesized ZnS nanoparticles were examined using high-resolution transmission electron microscopy (TEM) coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. 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). In situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell TEM (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behaviour 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 (ω = 0.799 J/m2) have a significantly higher surface energy than the abiogenic ZnS nanoparticles (ω = 0.277 J/m2), suggesting that larger defect-bearing ZnS nanoparticles were more reactive than the smaller quantum-dot-sized ZnS nanoparticles. These findings provide new insight into the factors that affect the dissolution of metal sulfide nanoparticles in relevant natural and engineered scenarios, and have important implications for tracking the fate and transport of sulfide nanoparticles and associated metal ions in the environment. Moreover, our study exemplified the use of an in-situ method (i.e., LCTEM) to investigate nanoparticle behaviour (e.g., dissolution) in aqueous solutions.

Influence of structural defects on biomineralized ZnS nanoparticle dissolution: An in-situ electron microscopy study

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.