Description du sujet de thèse

Populations are exposed to environmental risks related to pollution phenomena by harmful gases, toxic gases, or suspended particles called aerosols. They are also exposed through the consumption of food and beverages by contamination linked to pathogens or fraud. TeraHertz Time Domain Spectroscopy (THz-TDS) is a technique covering a wide spectral range and nowadays sufficiently compact and reliable for applications in industrial and environmental fields. A main advantage of this technique is its ability to detect and quantify multiple species simultaneously as well as its ability to differentiate isotopic species or conformational isomers. This makes it a technique of great interest both in the field of environmental studies and for agri-food safety. Our recent work has demonstrated the possibility of working with this technique at detection thresholds in the order of ppm for molecules in the gas phase or for the detection of suspended particles (aerosols). Air quality monitoring, understanding atmospheric physicochemical processes for the development of better predictive meteorological models (intensities and locations) and the distribution of pollutant contamination in the air, thus helping in political decision-making, whether for the preservation of population health. The scientific issue of gas-particle synergy (multiphase chemical reactions, catalytic effects of aerosols) is still poorly understood to date. It is therefore necessary to be able to study them simultaneously. This may concern the monitoring of different chemical species in different physical states but can also lead to the study of aerosol formation from reactions between molecules in the gas phase. Traditionally, different types of equipment are used, requiring specific logistics, multiple expertise and restitution of results inherent to the temporal, spatial, spectral resolutions and detection thresholds specific to each device. This project proposes the development of a TeraHertz spectrometer enabling the simultaneous detection and temporal monitoring of aerosols and gaseous pollutants, with better detection thresholds than currently available. Since its cost is no higher than that of other targeted gas or particle measuring devices, it could be deployed in the future at various strategic locations across our region. As a proof of concept, the reaction between gaseous hydrochloric acid and ammonia leading to the formation of ammonium chloride particles could be studied. By adapting a sampling module to this bench, specifically designed for studying the gas phase from liquids, it would also be possible to extend the spectrometer's capabilities to include the analysis of volatile compounds from liquid samples such as beverages. This versatile spectrometer will thus be able to address atmospheric issues requiring the simultaneous study of both the gas and particle phases, as well as address issues related to prevention in the food industry, with the ability to analyze liquids.

Contexte de travail

The candidate will be located at the IEMN, Avenue Poincaré, Villeneuve d'Ascq, one of the laboratories in the network of major Renatech and RF-NET power plants in France. They will have full access to the various technical solutions required for the project's implementation. The IEMN brings together, within a single structure, the bulk of regional research in a vast scientific field ranging from materials physics, nanostructures, nanoelectronics, microelectronics, microwaves, microsystems, telecommunications systems, and instrumentation. The thesis will be conducted within the laboratory's Terahertz Photonics Team and the Optical and Photonics and Microwave Characterization Center. This center brings together the experimental resources required for the thesis. The position is located in a sector covered by the Protection of Scientific and Technical Potential (PPST) and therefore requires, in accordance with regulations, that your arrival be authorized by the competent MESR authority.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

- Use of lasers.
- Use of pressurized gas.