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The Development of a New Bi12ZnO20/AgI Heterosystem for the Degradation of Dye-Contaminated Water by Photocatalysis Under Solar Irradiation: Synthesis, Characterization and Kinetics
No full textInternational audienceThis study explores the efficiency of heterogeneous photocatalysis in wastewater treatment, which is recognized for inducing significant rates of degradation and mineralization of various contaminants, including dyes. The study focuses on the development of an innovative composite via a combination of the sillenite type semiconductor Bi12ZnO20 and the halide-type semiconductor AgI. Both semiconductors were synthesized via co-precipitation, and their phases were identified using X-ray diffraction and characterized by scanning electron microscopy, Raman spectroscopy, Brunauer–Emmett–Teller analysis for specific surface area, UV–Visible diffuse reflectance spectroscopy, and the point of zero charge. The evaluation of the photocatalytic activity of the Bi12ZnO20/AgI heterosystem was carried out by monitoring the degradation process of Basic Blue 41 (BB41) under solar irradiation conditions. The results of this study revealed that the Bi12ZnO20/AgI heterosystem achieved the efficient degradation of BB41, with a removal rate of 98% after 150 min of treatment. The mineralization study showed that the TOC value decreased from 19.89 mg L−1 to 6.87 mg L−1, indicating that a significant portion of BB41 was mineralized. Via kinetic research, it was established that the degradation process followed a pseudo-first-order mechanism. Furthermore, recycling tests showed that the synthesized heterostructures maintained good structural stability and acceptable reusability over several cycles. These findings highlight the potential of heterogeneous photocatalysis as a promising approach to addressing environmental challenges associated with azo dyes
Experimental and Numerical Simulation Study of a Semiconductor Opening Switch
No full textInternational audienceThis article examines the nanosecond interruption of high current in Semiconductor Opening Switch (SOS) diodes, with the goal of bridging the gap between experimental results and numerical simulations. The experimental results of SOS diodes (0.25 cm 2 , 0.9 kV) operating as a nanosecond interrupter are presented in a wide range of cutoff current density from 300 A/cm 2 to 5 kA/cm 2 to analyze the two modes of operation, i.e., Drift Step Recovery Diode (DSRD) and SOS. In addition, the numerical simulations of the SOS diode are conducted to investigate the dynamics of the SOS diode in the DSRD and the SOS modes using the Synopsys TCAD. A mixed-mode device with a circuit simulator is utilized to simulate the SOS effect and the dynamic processes occurring during the current cutoff stage. Finally, the experimental and numerical simulation results of the SOS current and load voltage are compared indicating (i) the accuracy of the TCAD model in the commercially available software and (ii) the possibility of operating the SOS diode in a DSRD mode.</div
Extraction des composés volatils des feuilles de sequoia sempervirens
No full textInternational audienceLe sequoia sempervirens (D. Don) est une essence encore peu utilisée dans le domaine forestier. Ses capacités d’adaptation au changement climatique et sa très forte croissance en font une potentielle source de biomolécules pour l’industrie chimique. Les feuilles sont une source de molécules de faible poidsmoléculaire. Cet article présente les différentes méthodes utilisées et les extractions des différentes molécules contenues dans ce compartiment de l’arbre. Les monoterpènes sont bien présents dans le séquoia toujours vert. On retrouve une bonne part des monoterpènes présents dans le pin maritime, à l’exception du δ-3-carène et du β-pinène, mais dans des proportions différentes. . Les concentrations de monoterpènes mesurées dans les macérations au cyclohexane durant 48 h sont de 1,741 mg/g de feuilles sèches
Indicateur Hydromorphologique résultant de la méthode Carhyce ou IHC : pour l'évaluation intégratrice et multiparamétrique du fonctionnement physique des cours d’eau. Programme Carhyce IV - Rapport scientifique et technique final
No full textMercury compound-specific stable isotope fractionation in high-altitude lake ecosystems of the Bolivian Altiplano
No full textInternational audienceA combination of mercury (Hg) speciation and compound-specific stable isotope analyses was employed to trace the origin and fate of monomethylmercury (MMHg) in the high-altitude food webs of Lakes Titicaca (TTKK) and Uru Uru (UU). Significant MMHg biomagnification was observed, with concentrations reaching up to 2 μg.g−1 Hg in top predators. Hg isotopes lake-specific trends were identified in relation to trophic position (δ15N) and MMHg fractions. In particular, Δ199MMHg increased from 0 ‰ in UU epiphytic biofilm to ≈2 ‰ and ≈4 ‰ in UU and TTKK piscivorous fish, respectively. Both δ202MMHg and Δ199MMHg signatures indicate that the sediment and/or the epibenthic environment is the primary MMHg source in both food webs. However, an additional MMHg pool, associated with photodegraded MMHg, was identified entering the two food webs at a different trophic level. Photodemethylation was estimated to account for 21 % of MMHg degradation before it entered TTKK Lake food web at the fish level, and 16 % before reaching UU Lake food web at the invertebrate level. Even-Hg MIF (Δ200Hg) shows that both Hg(0) atmospheric deposition and geogenic inputs contributed to Hg accumulation in sediments, while the food web adds significant atmospheric Hg(II) signatures, with up to 94 % of Hg(II) contributing to Lake TTKK fish MMHg. These findings underscore the high potential of Hg-CSIA revealing the dominant role of atmospheric Hg(II) deposition and distinct MMHg pools in driving MMHg bioaccumulation in high-altitude lake food webs
Low-cost carbazole and phenothiazine based trimer molecules as hole transporting materials for inverted perovskite solar cells
No full textInternational audiencePhenothiazine (P) and Carbazole (C) are low-cost scaffolds widely used in the synthesis of Hole Transporting Materials (HTMs) for Perovskite Solar Cells (PSCs). So far, these compounds have been assembled together forming HTMs applied exclusively in direct cell architectures with the necessity of dopants to improve power conversion efficiencies (PCEs). In this work, two trimer molecules with opposite structure, namely CPC and PCP, have been designed, synthesized and implemented without any dopant in inverted PSCs. We assessed the impact of the molecular design on the final device performances, in view of the different intrinsic features. Both HTMs optoelectronic properties have been investigated along with a computational study by DFT. For optimizing the implementation in PSCs, thermal annealings and decrease of HTM concentration have been considered. PCP outperformed CPC, with an average PCE of 14.1 % against 10.4 %, achieving comparable performances to PTAA reference device (14.5 %). No hysteresis was observed for all devices and high FF reaching almost 80 % were obtained with PCP-based devices. The performances of the HTMs were correlated with the electronic behaviour observed by synchrotron-based soft X-ray photoelectron spectroscopy (PES). Secondary electron cut-off analysis highlighted a favourable work-function modification and the presence of high intermolecular interaction along with better energetic alignment for PCP, which contributed to its enhanced performances. Complementary characterizations by transient photocurrent and transient photovoltage confirmed the positive effect of decreasing the HTM concentration as observed in devices. Steady state and time resolved photoluminescence experiments corroborated the improved charge carrier dynamics and recombination features for PCP.</div
New initialization strategy for two- and three-phase flash calculations in CO2/water/hydrocarbon mixtures
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La « personne transfrontalière » : poser les jalons d'une recherche juridique collective
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Comparative analysis of species-specific dissolved gaseous mercury oxidation in phytoplankton cultures
No full textInternational audiencePhytoplankton species influence mercury cycling through bioaccumulation and Hg(II) reduction, however their contribution to oxidation of Hg(0) in aquatic systems remains largely overlooked. The present study aims at investigating the oxidation of Hg(0) by two phytoplankton species: the diatom Cyclotella meneghiniana and the green alga Chlamydomonas reinhardtii. The algae were exposed to gaseous Hg(0) at concentrations in the range of 6–12 μg m−3, representative for contaminated environments, under various experimental conditions (open vs. closed systems, light vs dark, and alive vs dead cells). The obtained results revealed, for a first time, that Hg(0) oxidation in C. meneghiniana cultures was light-dependent and limited to live cells, whereas C. reinhardtii maintained similar oxidation rates in both live and dead cells. C. reinhardtii cultures exhibited nearly tenfold higher Hg(0) oxidation efficiency than C. meneghiniana, demonstrating a strong species-dependent effect. Both species facilitated Hg(0) uptake from air into water, demonstrating a potential route for atmospheric Hg(0) to enter aquatic food webs. This novel evidence of phytoplankton-mediated Hg(0) oxidation highlights the importance of species identity and environmental conditions in governing Hg transformations and bioavailability. The results could have significant implications for understanding mercury bioaccumulation and toxicity in aquatic ecosystems. Further research is needed to clarify their contribution to Hg(0) oxidation in aquatic systems and to elucidate the underlying mechanisms driving the process
Pour une nouvelle lecture des bastides du Sud-Ouest : réorganisation de l'habitat, gouvernance et marchés
No full textAquitaine qu’ils animent. Jean-Paul Valois est en outre chercheur associé à l’UPPA (laboratoire ITEM) ; Pierre Simon, docteur en histoire médiévale, est secrétaire de l’Académie des Sciences, Lettres et Arts d’Agen.International audienceIn the south-west of France between around 1250 and 1350, there was a reorganisation of settlements, providing localities known as bastida. They are famous for their grid layout with a central square, but this only concerns part of the corpus, and the planimetric approach does not correctly reflect the diversity highlighted by the authors according to zone or time period. Their approach emphasises the power relationships in the context of the rise of centralised authority of states or principalities, the extension of the market economy (establishment of markets, monetarisation of taxes, etc.), and finally the relationship with the agrarian economy (extension of crops and their valorization). A European dimension to these factors is noticed. The authors draw on the lists of bastides published in the 1960s-2000s, with GIS mapping; the historiography is revisited and updated, and the link to the territory discussed. Different geomorphological situations have been identified, to which different plan-types correspond.Le sud-ouest de la France entre 1250 et 1350 environ, donne lieu à une réorganisation de l’habitat, fournissant des localités nommées bastida. Leur célébrité vient d’un plan en damier à place centrale, il ne concerne toutefois qu’une partie de ce corpus, en outre l’approche planimétrique ne reflète pas bien la diversité soulignée par les auteurs selon les zones ou les tranches de temps. Leur approche met l’accent sur les rapports de pouvoir dans le cadre de la montée de l’autorité centralisée des états ou principautés, sur l’extension de l’économie marchande (mise en place des marchés, monétarisation des taxes…), enfin sur les relations à l’économie agraire avec extension des cultures et de leur valorisation. Une dimension européenne de ces facteurs est évoquée. Les auteurs s’appuient sur les listes des bastides publiées dans les années 1960-2000 avec cartographie SIG, l’historiographie est reprise et actualisée, le lien au territoire discuté. Différentes situations géomorphologiques sont identifiées, auxquelles correspondent différents plans-types