Films mesoporeux photocatalytiques de tio2 non dope et dope par differents metaux (elaboration, caracterisation et etude des proprietes photocatalytiques)

L objet de cette thèse est le développement et l étude de la photoréactivité de TiO2, absorbant dans le visible et ayant des propriétés autonettoyantes et de dépollution de l eau et de l air. Dans ce contexte, des films d épaisseur controlée et mésostructurés de TiO2 non dopés et dopés par différents métaux (platine, vanadium et tungstène) , ont été synthétisés par voie sol-gel combinée au procédé d'auto-assemblage induit par évaporation. Les propriétés structurales et optiques ainsi que la composition chimique de la surface des films ont été caractérisées par de nombreuses techniques de caractérisation telles que DRX, GISAXS, TEM, MEB ellipsoporosimétrie, DRUV et XPS. Une étude complète des propriétés photocatalytiques des films à base de TiO2 aux interfaces solide-solide, solide-liquide et solide-gaz a été réalisée en utilisant respectivement les tests avec de l acide stéarique, du bleu de méthylène et de l acétone. Durant cette étude, nous avons montré qu un contrôle adapté de l épaisseur des films, de la nature et de la quantité du dopant peut améliorer l activité photocatalytique jusqu à un facteur de 16 par rapport à des films non dopés. Des tests préliminaires de piégeage chimiques des radicaux OH par l acide téréphtalique sous irradiation UV ont montré qu il existait une bonne corrélation entre la photoréactivité et la génération des radicaux OH .The aim of this thesis is the development and study of photocatalytic properties of visible light photoactive mesoporous TiO2-based films to act as self-cleaning, and purification systems applied to air and water. Pure and doped mesoporous titania films with different metals as Pt, V and W were prepared by sol-gel method combined with evaporation induced self-assembly process at different thicknesses. Structural, optical properties and chemical composition of these films were characterized by XRD, GISAXS, TEM, SEM, ellipsoporosimetry , DRUV and XPS. In order to better characterize and compare the efficiency of these films at solid-solid, liquid-solid and air-solid interfaces, several tests were used: mineralization of stearic acid, photobleaching of methylene blue and photooxidation of acetone. In this study, it is shown how a suitable control of the film thickness, the nature and amount of the dopant can improve the photocatalytic activity up to a factor of 16 relative to un-doped films. Preliminary results on the OH radicals production using terephtalic acid as a chemical probe showed good correlation between photoreactivity and generation of these radicals.PAU-BU Sciences (644452103) / SudocSudocFranceF

Tuning the catalytic properties of rare earth borohydrides for the polymerisation of isoprene

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Non-doped and metal-doped photocatalytic tio2 mesoporous thin films : elaboration, characterisation and photocatalytic properties

L’objet de cette thèse est le développement et l’étude de la photoréactivité de TiO2, absorbant dans le visible et ayant des propriétés autonettoyantes et de dépollution de l’eau et de l‘air. Dans ce contexte, des films d’épaisseur controlée et mésostructurés de TiO2 non dopés et dopés par différents métaux (platine, vanadium et tungstène) , ont été synthétisés par voie sol-gel combinée au procédé d'auto-assemblage induit par évaporation. Les propriétés structurales et optiques ainsi que la composition chimique de la surface des films ont été caractérisées par de nombreuses techniques de caractérisation telles que DRX, GISAXS, TEM, MEB ellipsoporosimétrie, DRUV et XPS. Une étude complète des propriétés photocatalytiques des films à base de TiO2 aux interfaces solide-solide, solide-liquide et solide-gaz a été réalisée en utilisant respectivement les tests avec de l’acide stéarique, du bleu de méthylène et de l’acétone. Durant cette étude, nous avons montré qu’un contrôle adapté de l’épaisseur des films, de la nature et de la quantité du dopant peut améliorer l’activité photocatalytique jusqu’à un facteur de 16 par rapport à des films non dopés. Des tests préliminaires de piégeage chimiques des radicaux OH• par l’acide téréphtalique sous irradiation UV ont montré qu’il existait une bonne corrélation entre la photoréactivité et la génération des radicaux OH•.The aim of this thesis is the development and study of photocatalytic properties of visible light photoactive mesoporous TiO2-based films to act as self-cleaning, and purification systems applied to air and water. Pure and doped mesoporous titania films with different metals as Pt, V and W were prepared by sol-gel method combined with evaporation induced self-assembly process at different thicknesses. Structural, optical properties and chemical composition of these films were characterized by XRD, GISAXS, TEM, SEM, ellipsoporosimetry , DRUV and XPS. In order to better characterize and compare the efficiency of these films at solid-solid, liquid-solid and air-solid interfaces, several tests were used: mineralization of stearic acid, photobleaching of methylene blue and photooxidation of acetone. In this study, it is shown how a suitable control of the film thickness, the nature and amount of the dopant can improve the photocatalytic activity up to a factor of 16 relative to un-doped films. Preliminary results on the OH• radicals production using terephtalic acid as a chemical probe showed good correlation between photoreactivity and generation of these radicals

Antischistosomal and anti-inflammatory activity of garlic and allicin compared with that of praziquantel in vivo

Abstract Background Schistosomiasis is an acute and chronic zoonotic parasitic disease caused by trematode worms. The host inflammatory response to schistosome eggs leads to perioval granulomata formation, mainly in the liver and intestine. This study investigated the potential antischistosomal and anti-inflammatory activity of both garlic extract and allicin on liver fibrotic markers in BALB/c mice with schistosomiasis (S. mansoni infection) compared with that of the commonly used drug, praziquantel (PZQ). Methods In this study, 140 female BALB/c mice (7-weeks old) were divided into seven groups with 20 mice each. Six groups were infected with S. mansoni cercariae and treated with garlic, allicin, or PZQ. The seventh group was the negative control. Twenty-four hours after the final treatment, the mice were euthanised and perfused for worm recovery. The liver and intestines were harvested for parasitological and histological assessment and to analyse the proinflammatory cytokine mRNA expression. Results Prophylactic administration of garlic and allicin to the infected mice significantly reduced the worm burden. Serum concentrations of liver fibrosis markers and proinflammatory cytokines were also reduced. PZQ was the most efficacious for reduction in the number of worms. These results are similar to those normally obtained using PZQ. Conclusions Crushed garlic homogenate and allicin are potential complementary treatments that may be used with PZQ

Creating Regular Matrices of Aligned Silica Nanohelices: Theory and Realization

Here, we exercise nanoscale control over the assembly of highly anisotropic silica helices using convective flow by using the physical properties occurring during evaporation-induced self-assembly. Organizing and patterning such chiral elongated objects over large surfaces in a controllable and reproducible fashion are challenging but desirable to optimize the performance of biomimetic structures, nanosensors (mechanical properties of helices), or optical materials (chiral objects have asymmetric interactions with light as absorption is different for left- and right-handed polarization). The coupling of evaporation forces and physicochemical solution properties induce specific helix alignment, and the stick–slip phenomenon produces a periodical deposition of bands with controllable and regular spacing. Helix orientation, packing density, and spacing can then be tuned. We observe the effect of polymer additives, silica helix concentration, and substrate withdrawal speed on the quality and orientation of the helix deposition. Theoretical modeling based on capillary hydrodynamics is developed to describe the relationship between evaporative conditions and pitch distance, the band width of the stick region, and the helix orientation

Effect of solvent on silicon nanoparticle formation and size: a mechanistic study

Silicon has emerged as the most desirable material for optical dielectric metamaterials, however chemists struggle to obtain the required silicon nanoparticle dimensions. Here the average diameter of silicon nanoparticles is varied between 3 and 15 nm by changing the reaction solvent. Electrochemistry and NMR elucidate the role of solvent on the synthetic mechanism. Surprisingly the solvent does not stabilize the nanoparticles and there is no trend associated with chain length or open-chain versus cyclical solvent molecules. The solvent's main role is to stabilize the by-products, which prolongs the reaction lifetime.Initiative d'excellence de l'Université de Bordeau