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Reference : UMR3685-SOPLEC-003
Workplace : GIF SUR YVETTE
Date of publication : Tuesday, June 15, 2021
Type of Contract : FTC Scientist
Contract Period : 18 months
Expected date of employment : 1 December 2021
Proportion of work : Full time
Remuneration : between 2675 and 3000 € gross monthly depending on experience
Desired level of education : PhD
Experience required : 1 to 4 years
Nanosized materials are nowadays present in various domains ranging from consumer products (food industry, cosmetics…) to technical devices (energy storage …). Together with the enhancement or apparition of new properties due to their nanometric size and in relation with the high surface to volume ratio, comes the high sensitivity of surfaces very prone to modification and poisoning. Thus, when used in a particular environment, aging phenomena take place and may have dramatic consequences on their possible use. In this context, a method to generate and analyze aging processes repeatedly and swiftly is essential to optimize/control the properties of nanomaterials during aging. During this process, the nature of the species interacting with the nanoparticles (NPs) governs the evolution (positive or negative) of properties. In order to predict and possibly mitigate some effects, it is an important objective to invest a great deal of effort into understanding the mechanism accounting for the formation of these species. Such mechanisms can be quite complex. Beyond the formation of these species, potentially interacting with the NPs, it is reasonable to think that this interaction will not occur indiscriminately on the different surfaces. For example, some parameters will be the atomic arrangements (symmetry…) and/or to the chemical potential (oxidation power…),.
During this 18-months post-doctoral position, we will focus on the interaction of TiO2 NPs with molecules of biological interest, a domain of large concern. Indeed, TiO2 considered as a biocompatible material is present in many daily products (food, paints, hygiene products, cosmetics, medicines, etc.). Therefore, consumers are widely exposed to TiO2 that can interact with living cells. In vitro-studies show that ultrafine TiO2 particles (10-20 nm) induce oxidative DNA damage, lipid peroxidation… in human bronchial epithelial cells, leading to an inflammatory response and formation of reactive oxygen species (ROS). Such ROS are free radicals, which create damages if the antioxidant response is not sufficient to inactivate them. Radiolysis (i.e., the chemical reactivity induced by interaction between ionizing radiation and matter) is a very convenient and powerful tool to generate ROS, study their fate, and thus investigate aging processes due to oxidative stress. Cell membranes, essentially composed of phospholipids, constitute the first barrier to NPs penetration in the cell. As the phosphate group of phospholipids plays an essential role in adsorption, we will focus on the TiO2 NPs/phosphate molecules interaction. Radiolysis will be used here to determine how different conditions perturb/modify the NPs/phosphate molecules interactions, which can also depend on the surface chemistry of TiO2. We intend here to understand how aging (oxidative stress) phenomena in TiO2/phosphate molecule samples are affected by the nature of the phosphate molecule, the crystalline phase of TiO2, the nature of the exposed facet… in order to mitigate these effects.
• Using sol gel chemistry, you will synthesize perfectly controlled TiO2 NPs with well-controlled exposed facets and characterize them (DRX, TEM…) at Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP, Sorbonne Université, Paris). You will also characterize surface groups on the NPs by near-infrared spectroscopy and zeta potential measurements.
• You will characterize solutions of TiO2 NPs/phosphate molecules (ethylphosphate, diethylphosphate; or even phospholipids…) and describe adsorption at the atomic level by taking into account the role played by the NPs crystalline facet. You will measure adsorption isotherms of small phosphate molecules at different pH, ionic forces (by adding NaCl) and concentrations on TiO2 NPs differing by their exposed facet (for example). You will use zeta potential measurements, vibrational and UV-visible spectroscopies. This work will be performed at NIMBE (CEA/Saclay) and at Institut des Matériaux Jean Rouxel, Nantes (IMN).
• You will irradiate these NPs/phosphate molecule solutions by .a gamma irradiator available at NIMBE under various experimental conditions and identify degradation products under aging using high performance liquid chromatography and mass spectrometry techniques. You will also determine how irradiation (aging) affects the TiO2 NPs/phosphate interactions. Moreover, at IMN, similar experiments will be conducted in the liquid cell of an electron microscope, which will be used as an irradiation source enabling visualizing aging processes at stake.
• You will perform pulse-radiolysis experiments at Institut de Chimie Physique (ICP, Université Paris Saclay) in order to obtain time-resolved information on aging processes. You will propose mechanisms to account for aging processes in these systems.
You hold a PhD in physical chemistry.
You have excellent experience in the synthesis of (nano)materials, their characterizations and in various spectroscopies.
You have excellent experience in various analytical techniques (HPLC, mass spectrometry….).
You are enthusiastic and greatly interested on performing accurate experimental work using advanced equipment, as well as understanding and interpreting data.
You would like an interdisciplinary project with great synergy with various groups.
You are quality-oriented, conscientious, creative, and cooperative, with a taste for scientific rigor.
You are able to communicate to different audiences and have high level of English.
Experience in radiation chemistry and/or PDF analysis would be an asset.
This postdoc is funded as part of a National Agency for Research (ANR) PRC ACETONE project.
The host laboratory is Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Energie (NIMBE, UMR 3685, CEA/Saclay, Université Paris Saclay, http://iramis.cea.fr/nimbe/). NIMBE is a joined research centre between CNRS and CEA/Saclay, composed by over 200 staff members including over 120 permanent staff members and around 70 PhD students and postdocs. The postdoctoral researcher will benefit from interaction with numerous colleagues. He/she will also work at LCMCP (Sorbonne Université, Paris) for the synthesis and characterization of TiO2 NPs, at ICP (Université Paris Saclay) for pulse-radiolysis experiments and also at IMN (Université de Nantes) to characterize equilibria between nanoparticles and solution.
Constraints and risks
Chemical risks and use of ionizing radiation.
It should be noted that strict safety rules are applied.
All applications must be sent through the “portail emploi CNRS” and must include a CV and a cover letter outlining your motivation.
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