Impact of functional groups present in biofilm thickness on Quantum Dots dissolution: a model study
Abstract
The increasingly wide use of Quantum Dots (QDs) is likely to result in their entry into environments and raises societal and environmental concerns. In soils, bacterial biofilms coat mineral surfaces, forming a highly reactive interface due to the high site densities within the biofilm thickness and at the mineral surface. In previous work, the impact of the biofilm/mineral interface on CdSe/ZnS QDs distribution and stability were demonstrated. After only one hour of exposure, an extremely fast dissolution of the ZnS shell was observed, highlighted by the presence of Se within the biofilm, while the Zn migrate to the mineral surface. Nevertheless, the mechanism that can explain this fast dissolution has not been determined.
Here we propose to investigate the role of different functional groups present at bacterial cells surfaces on this dissolution process. To do so, the distribution of thioglycolic acid-capped CdSe/ZnS QDs within model systems, used to mimic the Shewanella oneidensisMR-1 - corundum (Al2O3) interface, was studied at one hour of exposure. The first system was used to examine the role of carboxyl functional groups. Thus, an alginate film was crosslinked at the surface of Al2O3 (1-102) mineral. Then, cysteine was added to an alginate film in order to investigate the role of thiol functions. To study the behavior of QDs in those different systems, Long Period - X-ray Standing Waves - Fluorescence Yield spectroscopy was used. In the alginate/mineral system, the distribution profile obtained after one hour is quite different from the one observed within the system "Shewanella oneidensisMR-1 biofilm/mineral", with the Zn and the Se co-localized after one hour of exposure. That can indicate that the ZnS shell is stable in presence of carboxyl function, or that even if the dissolution occurred, the bound between Zn and carboxyl function are strong enough to limit Zn transport through the interface. Conversely, in presence of thiol function, the absence of co-localization between Zn and Se is observed. Thus, the thiol functions in cysteine could allow the formation of a corona around the QDs that stabilize QDs against aggregation, favor their transport through the interface, but also lead to the ZnS shell dissolution.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H41J1834B
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0432 Contaminant and organic biogeochemistry;
- BIOGEOSCIENCES;
- 1834 Human impacts;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY