Description:

How Biofilm/Mineral System Impact Quantum Dots Fate?

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. Thus, this environmental key compartment could impact the QDs fate. However, little is known of QDs stability and modes of interactions with the biofilm/mineral system.
This study examines the interactions, distributions and stability of thioglycolic acid-capped CdSe/ZnS QDs at a Shewanella oneidensis MR-1 – corundum (Al2O3) interface at 1h and 3h. Then, to investigate the role of functional groups on QDs fate, QDs distributions were also investigated in different film/mineral system. First, the role of carboxyl functional groups was investigated using an alginate film 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 and Grazing Incidence – X-ray Absorption Spectroscopy were used.
Results indicate an important increase in Zn and Se concentrations at the biofilm/mineral system with time, demonstrating the high accumulation potential of the system. In addition, an extremely fast dissolution of a part of ZnS shell was observed, highlighted by the loss of Se and Zn co-localization after only one hour of exposure. The released Zn(II) interacts preferentially with the mineral surface and the first nanometer of the biofilm. In the alginate/mineral system, carboxyl groups seems to be able to favor ZnS dissolution but do not impact QDs and Zn(II) transport. Conversely, the thiol functions in cysteine could allow the formation of a corona around the QDs that stabilize QDs against aggregation, favoring their transport through the interface, but also lead to the ZnS shell dissolution.
My research is directed towards understanding geochemistry related to radioactive waste disposal, environmental restoration, and climate change. My research has focused on coupling laboratory or field studies with state-of-the-art analytical techniques and/or geochemical modeling to determine important rock-water interactions that control water composition and the eventual transport of contaminants. My current focus is on the role that geochemical reactions play in geological sequestration of carbon dioxide.

Biography:
Morgane Desmau was graduated from the University Paris-Saclay (France) in 2013 on geology. She did a master degree at the Institut de Physique du Globe de Paris and University Paris Diderot in Geochemistry where she works on nanoparticle behavior in simplified soil column system. She started her PhD in 2015, and she worked on the impact of bacterial biofilm on quantum dots fate.