How microbial biofilms impact the interactions of Quantum Dots with mineral surfaces?

Abstract

The increasing use of Quantum Dots (QDs) -nanoparticles exhibiting unique optical propertiesand their incorporation in multiple engineering products is likely to result in the release of this new class of contaminants into natural systems. In soils, bacterial biofilms and mineral surfaces form highly reactive interfaces, which may control QDs' environmental fate. However, little is known regarding QDs' stability in, and modes of interactions with, biofilm/mineral interfaces. This study examines the interactions, distributions and stability of thioglycolic acid-capped CdSe/ZnS QDs at the corundum (-Al 2 O 3 )/Shewanella oneidensis MR-1 interface, for exposure times ranging between 1h to 24h. Long Period -X-ray Standing Wave -Fluorescence Yield spectroscopy and Grazing Incidence -X-ray Absorption Spectroscopy were used. Results indicate increases in Zn and Se concentrations within the biofilm/crystal system with time, demonstrating its high accumulation capacity over 24h. In addition, dissolution of a part of the ZnS shell occurs within 1h, highlighting the potential degradation of QDs when exposed to the biofilm/crystal compartment. Once released, Zn(II) migrates toward the biofilm-crystal interface and interacts preferentially with the crystal surface. In contrast, the remaining CdSe core is mostly preserved, and stays within the biofilm thickness. However, at 24h, Se and Zn present similar distribution profiles indicating a general reduction in ZnS shell dissolution at this longer exposure time.

Lignin-Based CdS Dots as Multifunctional Platforms for Sensing and Wearable Photodynamic Coatings

“…The promising SOQY value led us to explore the antibacterial photodynamic activity of the newly developed L@CdS QDs. Throughout the last few years, QDs have emerged as promising candidates for antibacterial therapy owing to their high surface area and small size. , Figure a illustrates the mechanism of ROS production; concisely, the electrons present in the ground state are excited to the singlet excited state in the presence of adequate light energy. The electrons are supposed to undergo two different phenomena either by releasing their energy in the form of fluorescence and returning to the ground state or by converting into the long-lived triplet excited state by intersystem crossing. ,,− In the latter step, the electron can transfer energy to another triplet (ground-state oxygen) or carry out electron transfer to the oxygen, producing a range of ROS via superoxide and hydroxyl radicals, further facilitating the antibacterial activity by cell lysis .…”

“…Throughout the last few years, QDs have emerged as promising candidates for antibacterial therapy owing to their high surface area and small size. 71,72 Figure 7a illustrates the mechanism of ROS production; concisely, the electrons present in the ground state are excited to the singlet excited state in the presence of adequate light energy. The electrons are supposed to undergo two different phenomena either by releasing their energy in the form of fluorescence and returning to the ground state or by converting into the longlived triplet excited state by intersystem crossing.…”

Contrasted fate of zinc sulfide nanoparticles in soil revealed by a combination of X-ray absorption spectroscopy, diffusive gradient in thin films and isotope tracing

“…66 Neutrophilic sulfur-oxidizing Thiobacillus bacteria have been detected in agricultural soils, including T. thioparus, T. denitrificans and/or T. plumbophilus. 64,65 In addition, ZnS dissolution could occur in bacterial biofilms that form in soils, as shown by Desmau et al (2020) 67 for CdSe/ZnS quantum dots in Shewanella oneindensis biofilms. Our results did not show a significant difference between total bacterial activity in the Nitisol and Arenosol (supporting data, Part IV).…”

Organic waste-borne ZnS nanoparticles: The forgotten ones

“…Only one study assessed the fate of organic waste-borne ZnS-NPs in soil, reporting complete transformation of ZnS in a clayey soil within 6 months, followed by rapid immobilization of released Zn due to sorption by the soil matrix (Formentini et al, 2017). Similarly, studies of the fate of manufactured CdSe/ZnS core-shell quantum dots (3-14 nm, i.e., almost the same size as organic waste-borne ZnS-NPs) also suggest partial or total dissolution of the nano-ZnS shell in soil solution (Faucheur et al 2018) or at the mineral/biofilm interface within hours (Desmau et al, 2020). Although synthetic ZnS-NP (3-5 nm) were shown to dissolve much more slowly in a sandy soil than in a clayey soil, the released Zn was more freely available in the sandy soil, and consequently potentially more toxic for soil organisms (Le Bars et al 2022).…”