ED Sciences Chimiques
Rational synthesis of metal-TiO2 nanoheterodimers: application to hydrogen generation by heterogeneous liquid-phase photocatalysis
by Eugénie PARIENTE (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 14h00 - Amphithéatre de l'ICMCB 87 Avenue du Dr Albert Schweitzer, 33600 Pessac
in front of the jury composed of
- Marie-Hélène DELVILLE - Directrice de recherche - Institut de Chimie de la matière consensée de Bordeaux (ICMCB) - Directeur de these
- Jean-Pierre DELVILLE - Directeur de recherche - Laboratoire Onde et matière d'Aquitaine (LOMA) - CoDirecteur de these
- Sophie CASSAIGNON - Professeure - Sorbonne université - Institut de Science des Matériaux (iMAT) - Rapporteur
- Peter HESEMANN - Directeur de recherche - Université de Montpellier - Institut Charles Gerhardt Montpellier (ICGM) - Rapporteur
- Stéphane PAROLA - Professeur - Ecole Normale Suppérieure de Lyon (ENS) - Examinateur
- Laurence CROGUENNEC - Directrice de recherche - Institut de Chimie de la matière consensée de Bordeaux (ICMCB) - Examinateur
Colloidal metal-semiconductor (M-SC) nanocrystals represent a significant breakthrough in the field of photocatalysis, offering promising performance for converting solar energy into fuel. Their efficiency relies on two key aspects: optimal separation of photoexcited electrons and holes, and enhanced light harvesting. Among SCs, metal oxides such as TiO2 are chemically stable but face a limitation due to their wide band gap, which restricts their photocatalytic efficiency to only 4-5% of the solar spectrum, within the UV range. To overcome this issue, this work proposes combining a metal with TiO2 using laser photodeposition to produce M-TiO2 heterodimers. Unlike conventional techniques that involve a UV lamp, this approach uses a focused laser beam to photoactivate redox reactions at the surface of TiO2 nanoparticles (NPs), allowing precise control over the size and localization of the metals. The reaction medium consists of TiO2 NPs (either bipyramidal anatase with controlled {101} and {001} facets, or non-faceted ellipsoids) dispersed in a hydro-alcoholic mixture containing metal salts. The goal is then to use these dimers for hydrogen (H2) production and to compare their photochemical efficiency. Two types of TiO2 NPs were therefore synthesized and characterized: bipyramids, which enable regioselectivity of redox reactions through their {101} and {001} facets, and ellipsoids, used as a reference for comparative study. The photodeposited metals (gold (Au), platinum (Pt), and palladium (Pd)) form metallic nanodots (NDs) on both types of NPs. Their characterization relies on electron microscopy (TEM/HRTEM) to analyze ND size, morphology, and distribution, as well as UV-vis spectroscopy for optical properties. In the case of gold, the size and growth of a single nanodot per TiO2 nanoparticle are controlled by adjusting the illumination time and the ratios of precursors. Their localization occurs preferentially on the {101} facet of bipyramids, and precise prediction of their final size is achieved via a mass conservation criterion. For palladium, the number of nanodots can be controlled while maintaining their localization on the {101} facet, by adjusting the amount of sacrificial agent (methanol). For platinum, the distribution of nanodots varies depending on the presence or absence of MeOH, shifting from a uniform distribution (without MeOH) to preferential localization on a specific facet (with MeOH), though with no precise control over the number of nanodots. The performance of Au-TiO2, Pd-TiO2, and Pt-TiO2 systems in H2 production tests in the presence of methanol yielded the following results. For gold, where only a single nanodot is observed, deposition on bipyramids results in higher activity than on ellipsoids, attributed to the presence of TiO2 facets. For palladium, multiple nanodots allow investigation of the influence of nanodot number on H2 production for the same deposited metal mass. Platinum appears to be the most efficient co-catalyst. Finally, a new model was developed to better understand the mechanisms involved in H2 production reactions under conditions where either a single metallic nanodot or multiple nanodots are present. This model was also successfully compared with data from the literature, thereby reinforcing the obtained conclusions.
ED Sciences et environnements
Grapevine susceptibility to esca: exploring the underlying mechanisms in a range of cultivars through a physiopathology-based approach.
by Pierre GASTOU (SAVE - Santé et Agroécologie du VignoblE)
The defense will take place at 9h30 - Amphithéâtre de l'ISVV Institut des Sciences de la Vigne et Vin 210 Chemin de Leysotte CS50008 - 33882 Villenave d'Ornon
in front of the jury composed of
- Chloé DELMAS - Directrice de recherche - INRAE - UMR SAVE - Directeur de these
- Hervé COCHARD - Directeur de recherche - INRAE - UMR PIAF - Rapporteur
- Katia GINDRO - Directrice de recherche - Agroscope - Groupe Mycologie - Rapporteur
- Eric GOMES - Professeur des universités - Université de Bordeaux - UMR EGFV - Examinateur
- Mireia GOMEZ-GALLEGO - Ingénieure de recherche - INRAE - UMR IAM - Examinateur
- Christophe MOUGEL - Directeur de recherche - INRAE - UMR IGEPP - Examinateur
Harnessing the high intraspecific diversity of woody plants in planting and breeding programs is a promising lever for sustainably managing their health. The biotic component of woody plant decline (in both wild and cultivated species) has been less studied than its abiotic counterpart. However, clear differences in susceptibility to such stresses exist among genotypes, probably linked to their physiological diversity and their interactions with microorganisms. In this work, we used esca, a complex vascular disease of major economic concern due to its role in grapevine decline and the scarcity and difficulty of implementing effective management strategies, as a model system. The objectives of this thesis, in which we used an integrated physiopathological approach, were: (i) to describe the susceptibility of 46 grapevine cultivars (Vitis vinifera L. ssp. vinifera) to esca and dieback; (ii) to identify varietal traits associated with esca susceptibility, and (iii) to compare the response to esca of cultivars with contrasting susceptibilities. First, between 2017 and 2023, we monitored the incidence and severity of esca and declining phenotypes (apoplexy, mortality) in these 46 cultivars grown in a common garden vineyard. We identified a broad varietal gradient in the incidence of esca foliar symptoms, consistent over time and correlated with the gradient observed at the national scale in France. Cultivars with low vigour and high water-use efficiency appeared to be weakly susceptible. We then compared hydraulic and anatomical properties, as well as physiological responses to esca, in a subset of cultivars. The least susceptible genotypes displayed the lowest stomatal and minimum leaf conductances. We identified a syndrome of responses to esca (vascular occlusions, reduced carbon assimilation and storage), common to all cultivars regardless of their susceptibility. We demonstrated that the accumulation of certain secondary metabolites (terpenes and phenylpropanoids, including glycosylated compounds) in esca-symptomatic stems was more pronounced in the most susceptible cultivars. At the trunk level, we investigated the influence of wood–microorganism interactions on esca expression. Among the types of necroses identified, only the abundance of white-rot necrotic wood was correlated with esca expression. Its abundance in esca-symptomatic plants was higher for the most susceptible cultivars. Microbial communities of healthy wood did not vary significantly along the gradient of susceptibility. However, the wood of susceptible cultivars was depleted in extractives and marginally enriched in hemicellulose. It also accumulated certain phenylpropanoids in response to esca, although to a lesser extent than stems. Overall, these results show that cultivars whose physiology favors wood degradability (through its composition), deregulated production of specific secondary metabolites, and their transport from trunk to leaves - via the sap flow - appear to be constitutively more susceptible to white-rot and foliar symptoms. The biological origin of these metabolites and their spatio-temporal dynamics within the plant remain to be explored to better understand the link between wood degradation and esca foliar symptom expression. More broadly, this thesis demonstrates the major role of physiological functioning in shaping intraspecific diversity of woody plant susceptibility to complex diseases. It paves the way for further integrative studies aiming to identify genotypes resilient to stresses and adapted to global change.
ED Sociétés, Politique, Santé Publique
Epidemiology of chronic respiratory diseases and environmental factors
by Nolwenn JESTIN-GUYON (Bordeaux Population Health Research Center)
The defense will take place at 14h00 - Amphithéâtre Louis PA Institut de Santé Publique d'Epidémiologie et de Développement (ISPED) Université de Bordeaux, Campus Carreire 146 Rue Léo Saignat 33000 Bordeaux France
in front of the jury composed of
- Chantal RAHERISON-SEMJEN - Professeure des universités - praticienne hospitalière - Université de Bordeaux - Directeur de these
- Nicolas ROCHE - Professeur des universités - praticien hospitalier - Université Paris Cité - Rapporteur
- Gaëtan DESLéE - Professeur des universités - praticien hospitalier - Université de Reims - Rapporteur
- Claire ANDREJAK - Professeure des universités - praticienne hospitalière - Université de Picardie Jules Verne - Examinateur
- Mathieu MOLIMARD - Professeur des universités - praticien hospitalier - Université de Bordeaux - Examinateur
- Isabelle BALDI - Professeure des universités - praticienne hospitalière - Université de Bordeaux - Examinateur
Symptoms of chronic obstructive pulmonary disease (COPD) and asthma appear at an early age. They result from multiple environmental exposures throughout life (air pollution, occupational exposures, etc.) in interaction with genetics factors. Considering the current and future worldwide burden of these diseases (especially among women), whose effects may be worsened due to climate change, the aim of this thesis work was to identify the importance of environmental factors in COPD and asthma, by proposing a global approach of their understanding. The 1st chapter aimed to investigate the relation between chronic exposure to biomass fuel and respiratory symptoms among 661 children (<15 years old) included in the madabiomasse cross-sectional study (2016>