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Highly efficient Hydrogenative depolymerisation of Polycaprolactone to 1,6-hexanediol
No full textInternational audienceWe report here our study on the development of an efficient process to make 1,6-hexanediol from the hydrogenation of polycaprolactone assisted by ethanolysis. Using a ruthenium SNS pincer catalyst, a record high turnover number of 19,600 with 98% yield of 1,6-hexanediol is obtained at 80 o C and 60 bar H2 pressure. The reported method has environmental advantages over the conventional process for the production of 1,6-hexanediol, which emits a significant amount of nitrous oxide greenhouse gas
Co‐Doping Approach for Enhanced Electron Extraction to TiO 2 for Stable Inorganic Perovskite Solar Cells
No full textInternational audienceInorganic perovskite CsPbI 3 solar cells hold great potential for improving the operational stability of perovskite photovoltaics. However, electron extraction is limited by the low conductivity of TiO 2 , representing a bottleneck for achieving stable performance. In this study, a co‐doping strategy for TiO 2 using Nb(V) and Sn(IV), which reduces the material's work function by 80 meV compared to Nb(V) mono‐doped TiO 2 , is introduced. To gain fundamental understanding of the processes at the interfaces between the perovskite and charge‐selective layer, transient surface photovoltage measurements are applied, revealing the beneficial effect of the energetic and structural modification on electron extraction across the CsPbI 3 /TiO 2 interface. Using 2D drift‐diffusion simulations, it is found that co‐doping reduces the interface hole recombination velocity by two orders of magnitude, increasing the concentration of extracted electrons by 20%. When integrated into n–i–p solar cells, co‐doped TiO 2 enhances the projected T S80 lifetimes under continuous AM1.5G illumination by a factor of 25 compared to mono‐doped TiO 2 . This study provides fundamental insights into interfacial charge extraction and its correlation with operational stability of perovskite solar cells, offering potential applications for other charge‐selective contacts
Neural Network Simulation of Original Colors in Friedrich's Abbey Among Oak Trees featuring Discoloured
No full textInternational audienceArtwork appearances change over time due to aging. Smalt, a blue cobalt-tinted glass pigment, deteriorates over time in oil paintings causing significant and irreversible color changes in many artworks. Virtual simulations can hypothesis 1 original appearances while it remains a challenge for smalt-containing paintings. A novel procedure integrates non-invasive imaging methods, X-ray absorption near-edge structure (XANES), and machine learning to simulate the original colors of a smalt-containing discolored paintings. Macro-X-ray fluorescence provided elemental distribution, reflectance imaging spectroscopy captured color spectra of pigments and XANES informed cobalt speciation in cross sections. Friedrich's Abbey Among Oak Trees (1808-1810) containing smalt and artificially aged model systems were studied. Machine learning predicted the original hues based on XANES. The procedure allowed us to simulate the original, cooler and more vibrant colors of the painting. The innovative approach visualizes a possible original state of the smalt-containing artwork that can be adapted to other alteration phenomena
A Homeostatic Photonic Device Integrating Vapor‐Regulated Thermo‐Optical Feedback Mechanisms
No full textInternational audienceSelf‐adaptation and homeostasis are features that distinguish living systems from artificial materials. Living systems, such as plants or the human eye, integrate positive and negative feedback mechanisms to autonomously manage their thermal, optical, and chemical responses to changing sunlight conditions. However, replicating such sophisticated behavior in artificial devices presents a significant challenge. Herein, an inorganic homeostatic device is proposed that integrates both positive and negative feedback mechanisms for adaptive regulation of optical properties, water chemical potential, and local temperature driven by a dynamic change of photonic colors. This device consists of a mesoporous graded one dimensional (1D) photonic crystal, acting as a temperature‐responsive shield, coupled with a photothermal layer. The architecture of the device is designed to harness the temperature‐driven vapor sorption into mesoporous to create the feedback. The lateral gradient of the photonic stop band enables achieving dual feedback across multiple wavelengths by simply shifting the light beam's position. In the presence of light, the thermo‐optical device is able to either amplify or attenuate the optical absorption, reflectivity, and local temperature and dynamically change its structural colors. The structure and performance of the device are characterized using multiple techniques such as Grazing‐Incidence Small‐Angle X‐ray Scattering and time‐resolved hyperspectral microscopy. Importantly, the device is fabricated using solution processing, making it compatible with low‐cost manufacturing and paving the way for the development of adaptive and time‐programmed systems for applications like thermo‐regulating windows, smart filters, programmable meta‐surfaces, vapor sensors, or even optical computing
Development of photocathodes with improved charge extraction for efficient solar energy conversion
No full textInternational audiencePolyoxometalates (POMs) are molecular oxides that present unique properties as reversible multi-electron reservoirs for improving charge separation in solar fuel devices. Inspired by nature’s process of decoupling the light-induced charge separation from catalysis, we intend to use POMs to overcome the problem of charge separation, to collect, store then deliver electrons to the catalyst (1). More recently, it was shown on nano-ITO that the concentration of grafted POMs can increase the photocurrent response up to 25 percent (2). Here we present different systems of mesoporous NiO dye-sensitized cathodes using organic-inorganic POM-based derivatives displaying remote carboxylic moieties that can be synthesized on different POMs leading to hybrids with tunable redox potential. These systems were investigated with different loads of POMs co-grafted with push-pull dye
Réflexions sur la puissance motrice du Soleil
No full textInternational audienceA quintessential source of heat, the Sun radiates toward the Earth a power ten thousand times greater than humanity's energy needs. Harnessing this energy bounty, however, requires capturing and converting sunlight. Today, this conversion can be achieved through several families of technologies at varying stages of maturity: photovoltaic solar, thermal, concentrated solar power, and more. While their applications differ, all these technologies must meet common fundamental constraints, and as Carnot proposed, one can 'consider in all its generality the principle of producing motion through heat' from the Sun. However, unlike traditional 'heat engines,' the coupling with the hot source here is radiative, introducing specific constraints that must be accounted for. In this presentation dedicated to radiative machines, you will encounter familiar terms as well as particular expressions that will provide the keys to understanding solar technologiesSource de chaleur par excellence, le Soleil rayonne vers la Terre une puissance dix mille fois supérieure aux besoins d'énergie de l'humanité. Tirer parti de cette manne énergétique nécessite cependant de parvenir à capter et à convertir la lumière. Cette conversion peut aujourd'hui être réalisée par plusieurs familles de technologies, à différents degrés de maturité : solaire photovoltaïque, thermique, à concentration… Si leurs applications sont différentes, toutes ces technologies doivent répondre à des contraintes fondamentales communes, et on peut comme Carnot « envisager dans toute sa généralité le principe de la production du mouvement par la chaleur » du Soleil. Mais contrairement aux « machines à feu », le couplage avec la source chaude est ici radiatif, ce qui ajoute des contraintes particulières dont il faut tenir compte. Dans cet exposé consacré aux machines radiatives, on retrouvera donc des termes familiers, mais aussi des expressions particulières qui donneront les clés de compréhension des technologies solaires
Dehydrogenative Coupling Reaction for the Synthesis of 5‐ and 6‐Heterocyclic Derivatives including Arylquinolin‐2(1H)‐ones
No full textInternational audienceHeterocycle synthesis is an intense research area due to their significant importance in pharmaceutical, material chemistry and fine synthesis. Key innovations include transition metal‐based‐catalyzed heterocyclic derivatives synthesis, which facilitates diverse structural modifications, enhances selectivities and efficiency. The necessity to develop more greener technologies for the construction of new C‐C and C‐N bonds has strived chemists to re‐design their synthetic strategy plan and to introduce abundant starting materials. Among these new transformations, acceptorless dehydrogenative coupling (ADC) reactions have received increased attention thanks to their atom‐economy, the use of alcohols as pro‐electrophiles and the formation of water and hydrogen gas as only by‐products. These methods exemplify the interplay between traditional and cutting‐edge techniques, providing a robust synthetic toolkit to address the growing demand for biologically relevant compounds with tailored functionalities. This review will focus on the acceptorless dehydrogenative coupling methodologies for the synthesis of nitrogen‐containing 5‐ and 6‐membered heterocyclic derivatives (such as pyrroles, pyrimidines, quinazolines, and quinoxalines) in the presence of 3d‐metal complexes. The state of the art of the ADC process underscores the continuous evolution of synthetic strategies and emphases its importance in creating valuable and structurally diverse compounds, ensuring their centrality in both academic and pharmaceutical research
Characterization of the oxygen properties of a hybrid glass chip designed for precise on chip oxygen control
No full textInternational audienceDespite its relevance in several research fields, the regulation of dissolved gas concentration in microfluidic chips remains overlooked. Precise control of dissolved oxygen levels is of importance for life science applications, especially for faithfully replicating in vivo tissue conditions in organ-on-chips. The current methods to control oxygen on-chip rely on the use of chemical scavengers, on the integration of an additional gas channel or on the perfusion of a liquid pre-equilibrated at a set oxygen level. However, for precise oxygen control, these microfluidic devices must be made from gas-impermeable materials. In this regard, glass is a material of choice due to its complete impermeability, but its microfabrication often requires specific clean room processes. Here, we report a low-tech fabrication method for a hybrid glass chip, which involves assembling glass components using an adhesion process. To evaluate this chip's suitability for use under highly controlled oxygen conditions, we developed a two-step assessment protocol. This involved determining the time needed to reach a target oxygen level during perfusion and measuring the reoxygenation time following the cessation of flow. Based on a dual approach of simulations and experiments, we emphasized crucial adhesive properties such as oxygen diffusion and solubility and proposed a range of well-suited adhesive materials. Finally, we demonstrated the interest of this hybrid glass chip for on-chip cell culture and cell respiration measurements. This work paves the way for broader accessibility in producing low tech gas-tight microfluidic chips for diverse applications
Towards high-performance aqueous Mg batteries: Insights into corrosion mitigation through material and electrolyte design
No full textInternational audienceAqueous Mg-air batteries have garnered significant attention from researchers due to their high theoretical discharge performance, ease of operation, and environmental friendliness. However, the slow anodic reaction kinetics caused by accumulation of discharge products significantly impedes the output discharge voltage. For cathodes, the sluggish oxygen reduction reaction (ORR) limits power density, further restricting the practical application of Mg-air batteries. Additionally, the Mg anode suffers from severe corrosion in aqueous electrolytes containing chloride ions, significantly reducing its utilization efficiency. Recent studies have demonstrated that optimizing electrolyte composition, as well as modifying both anodic and cathodic materials, can effectively enhance the discharge performance of Mg-air batteries. This comprehensive review provides an in-depth analysis of recent advancements and sheds light on the working mechanism of different aqueous Mg-air batteries. Furthermore, the advantages and disadvantages of different modification strategies on enhancing discharge performance is systematically discussed. The review also presents future perspectives by drawing insights from recently from recent findings and outlining a roadmap for further research in this field
Persistent Luminescence in Highly Nonstoichiometric GAGG Garnets Gd 3+x [Al 2 Ga 3 ] 1‐x/5 O 12 (0 ≤ x ≤ 0.6) Doped with Ce 3+ /Cr 3+
No full textInternational audienceThe gadolinium garnet Gd 3 Al 2 Ga 3 O 12 co‐doped with Ce 3+ and Cr 3+ (GAGG‐Ce,Cr) has been widely studied due to its unusual bright yellow long‐lasting persistent luminescence properties. Here, rapid containerless melt‐quenching is used as part of a two‐step glass‐crystallisation synthesis process to obtain a new highly nonstoichiometric form of this garnet, of composition Gd 3+x [Al 2 Ga 3 ] 1‐x/5 O 12 with 0 ≤ x ≤ 0.6 (ns‐GAGG). For compositions x > 0, powder X‐ray diffraction analysis confirms that excess Gd 3+ is accommodated at the Al 3+ /Ga 3+ sublattice in octahedral coordination, by substituting up to 30% of these sites. This mode of substitution complexifies the local structure of the garnet host, which is shown to influence certain luminescence properties in the analogous highly nonstoichiometric Y 3+x Al 5‐x O 12 (0 < x < 0.4) and Gd 3+x Al 5‐x O 12 (0 < x < 0.6) systems. Co‐doping ns‐GAGG with Ce 3+ and Cr 3+ produces green‐yellow persistent luminescence when x = 0, which undergoes a redshift to yellow‐orange as the Gd 3+ content increases to x = 0.4. However, this radical modification of the host composition does not strongly affect the afterglow kinetics. These results demonstrate an effective and high‐precision way of decoupling color and kinetics in persistent luminescent garnets, which is usually hard to achieve using the standard stoichiometric material engineering approach