Thesis topic: Silver nanoparticles with bio-inspired coating: understanding surface interactions to design safer nanoparticles

Working place: Grenoble – France
Salary range: To negociate

Description of workplace

The Université Grenoble Alpes is a major player in higher education and research in France.

The Université Grenoble Alpes already features in the top 100 and top 200 universities in major international rankings (Reuters, Shanghai, Times Higher Education and QS for example) for some of its scientific fields. The UGA rivals the best universities in the world thanks to the strength of its research and the numerous educational innovations it has implemented. (http://www.univ-grenoble-alpes.fr/en/)

Grenoble is a lively city in the French Alps. Its attractive location and stimulating social and scientific environment make it an interesting place to live and study.

Subject of the thesis

Silver nanoparticles (AgNPs) are introduced in a variety of commercial products for their biocidal activity, due to the release of Ag(I) ions from their surface. Therefore, the environment and humans are highly exposed to AgNPs, which are also toxic to eukaryotic cells. This fosters the production of “safer-by-design” AgNPs. To this end, our interdisciplinary consortium is currently working at the design and synthesis of AgNPs coated by bioinspired sulfur ligands [1]. These ligands that mimic the copper binding sites of Cu(I)-proteins, proved to also efficiently bind ionic Ag(I) [2]. We observed that bioinspired and biological sulfur ligands can either foster AgNP dissolution or exert a protective effect, depending on the number of thiolate functions and on the chelating power of the molecule.
Our goal is to achieve controlled ion release from the NP surface in such a way that the biocidal effect is retained while the toxicity to eukaryotic cells is limited. Other bioinspired coatings with sulfur or nitrogen ligands are being considered, and the surface phenomena leading to ion release are under study.
The PhD project will be part of a collaborative project between theoreticians and experimentalists (biologists, chemists and physicists) that develops along the following axis:
– Synthesis of AgNPs coated with S or N ligands
– Analysis of their structure by X-ray based techniques
– Study of the surface reactivity of AgNPs by theoretical approaches
– Bioassays

The PhD work will involve two main tasks:
1)XAS and XPS analysis of the structure of NPs coated with bioinspired ligands
A panel of X-ray based techniques will be used to probe the surface of the coated NPs. Sulfur K-edge X-ray Absorption Spectroscopy (XAS) allows for the selective interrogation of S atoms; this technique will be used to retrieve the binding mode of sulfur in coated NPs. X-ray Photoelectron Spectroscopy (XPS) will bring insight into surface Ag-S and Ag-N bonds.
2)Study of the surface reactivity of AgNPs by theoretical approaches
The process of adhesion of sulfur ligands on AgNPs will be studied using theoretical models. Large AgNPs will be approximated by various crystal planes of Ag and modelled by ab initio calculations with the program VASP using plane waves basis sets. In parallel, we will investigate smaller NPs using the CP2K code based on the density functional theory (DFT) and partially localized basis sets. Finally, atomic models of NPs parameterized from the quantum calculations and XAS measurements will be used to predict the interactions between different NPs using a classical Molecular Mechanics force field.

[1] Pujol et al. Chemistry Eur. J. (2011) 17(16), 4418-4428
[2] Veronesi et al Inorg. Chem., (2015), 54, 11688−11696

Required

The candidate will be in charge of X-ray spectroscopy experiments and of the theoretical chemistry part of the project. He/she will run state of the art calculations using mainly theoretical chemistry programs on UNIX/Linux workstation clusters and super-computers. Prior practice in X-ray spectroscopy and/or computational chemistry will be an asset.

Contact

Please send a CV and motivation letter to giulia.veronesi@cea.fr The candidate will be associated to the Modelling and Theoretical Chemistry group of the Laboratoire de Chimie et Biologie des Métaux (LCBM, UMR 5249 CNRS/CEA/Université Grenoble Alpes), under the supervision of Serge Crouzy and Giulia Veronesi (http://orcid.org/0000-0001-9228-6082)

and more information:http://big.cea.fr/drf/big/english/CBM/GMCT

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