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Design and synthesis of Indol-PHOX: a new class of modular phosphine–oxazoline ligands for palladium-catalyzed enantioselective decarboxylative allylation
No full textInternational audienceA new class of modular phosphine–oxazoline ligands (Indol-PHOX) has been developed and successfully applied in Pd-catalyzed enantioselective decarboxylative allylation to access valuable α-allyl-α-fluoro ketones with yields up to 99% and 96% ee
Determination of defects properties in semiconductor through temperature dependent of Photoluminescence techniques : comparison between modulated and time-resolved regime
No full textInternational audienceOptimising the performance of photovoltaic cells depends primarily on understanding and reducing non-radiative recombination, which is mainly caused by defects involving energy levels in the band gap of semiconductor materials. It is therefore essential to characterise these defects precisely.Being contactless and non-destructive, photoluminescence (PL) is a powerful technique for studying carrier dynamics. PL can be developed in various regimes, in particular, modulated photoluminescence (MPL) [1] and time-resolved photoluminescence (TRPL) [2]. TRPL exploits the temporal decay after a short pulse of light, while MPL examines the phase shift and amplitude under frequency-modulated excitation. The two regimes are in principle sensitive to defects, but they have different sensitivities and exploitation issues, so it is interesting to compare them.In particular, in presence of a minority carrier trap, the TRPL decay curve can be fitted with two decreasing exponential functions: TRPL(t) = A1 exp(-t/τ1) + A2 exp(-t/τ2), where the characteristic times τ1 and τ2 are linked to capture and emission from the trap as well as to recombination [3,4]. In the MPL method, our recent works highlight the appearance of specific V-shaped structures in the Bode diagram (frequency response) of the phase of the MPL [1,5]. We have shown that is the sum of 3 arctangent functions: = - arctan(ω/ω1) + arctan(ω/ω2) - arctan(ω/ω3), the characteristic frequency ω2 being directly related to the emission of minority carriers from the trap, thus allowing an easy determination of the trap energy position from the temperature dependence.In this work, comparisons were made between MPL and TRPL on an AlGaAs sample. We notice that the appearance of V-shapes in the MPL phase corresponds to the appearance of a bi-exponential decay in the TRPL for the same temperature range. Using the 2 methods, we found similar values for the energy position of the minority carrier trap, confirming the link between the 2 methods from an experimental point of view. However, we emphasize that MPL provides a more direct signature of the presence of minority carrier traps through the V-shaped structure in the Bode diagram of the MPL phase, as opposed to TRPL that always presents a decreasing time signal and requires careful analysis. Finally, we also discuss the extraction of the minority carrier capture cross section of the defect, which is also much easier from the MPL analysis as compared to TRPL. [1] N. Moron et al J. Phys. D: Appl. Phys. 55 (2022) 105103 ; doi: 10.1088/1361-6463/ac39c4.[2] R. K. Ahrenkiel, Solid-State Electronics 35, (1992) 239 ; doi: 10.1016/0038-1101(92)90228-5.[3] M. Maiberg et al. J. Appl. Phys. 118 (2015) 105701 ; doi: 10.1063/1.4929877.[4] M. Maiberg et al. Appl. Phys. Lett. 107 (2015) 122104, doi: 10.1063/1.4931632.[5] B. Bérenguier et al. EPJ Photovolt. 16 (2025) 11, doi: 10.1051/epjpv/2024045
Evidence of a Kondo lattice quantum critical point and of non-Fermi liquid behavior in the intercalated layered system V5S8
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Improving a green process for Cryptophycin production from cyanobacteria biomass
No full textInternational audienceIntroductionA filamentous strain, Nostoc sp. ATCC 53789 is known to produce a bioactive cyclo-depsipeptide, Cryptophycin (Cr) (1). The objective of this study is to enhance the green Cr yield through the utilisation of ecophysiological analysis of cyanobacteria cultures and the performance of unit operations involved in biomass treatment.Materials and MethodsThe strain is cultivated in a specially formulated, artificial medium, enabling precise modulation of its composition. Continuous or semi-continuous cultures are carried out in closed photobioreactors. It allows for precise control of the environmental parameters necessary for eco-physiological studies. Extraction and purification used liquid/ solid and liquid/liquid separative and preparative techniques (CPC and LC-prep). The focus is on achieving a criticalequilibrium of Cr between two immiscible bio-renewable solvents. Cr content is monitored by LC-DAD and LC-MS.ResultsOptimal values for the composition of the culture medium and light fluxes were determined to increase the biomass productivity of the cyanobacteria. An increase in Cr content is observed when dinitrogen is the only N-source (diazotrophy). Then Cr productivity was also improved.Studying the filamentous aggregation process of this species led to the implementation of a pre-harvest process.This involves the use of a simple fine filter screen, which reduces power consumption.The study demonstrated the potential for highly efficient extraction and purification, even with biorenewable solvents like limonene.ConclusionThe results demonstrate that biological production involves fewer steps than chemical synthesis and, most notably, utilises a range of bio-renewable inputs, including N2 and limonene. The scalability of the process is addressed in the context of the quantities requested for potential pharmaceutical applications
Encapsulating NHC‐capped Copper(I) Complexes inside Cyclodextrin for Catalysis in Living Cells
No full textInternational audienceThe development of "non-natural" chemical reactions inside living organisms is an expanding field of research. In this area, metal-based catalysis has been particularly scrutinised. However, most examples of catalysts developed so far are based on expensive and rare heavy metals such as ruthenium, iridium or palladium. For this reason, the development of catalysis in cells or in vivo with more accessible first-row metals is of great interest and could significantly increase the catalogue of reactions applicable in these complex environments. Herein, we demonstrate that encapsulating copper(I) N-heterocyclic carbene (NHC) catalysts inside the cavity of modified cyclodextrins, renders these notoriously toxic complexes harmless towards CT26 cells at high concentrations. Nevertheless, the catalytic activity of cyclodextrin(CD)-encapsulated NHC-copper complexes is preserved, allowing the deprotection of pinacol boronate ester groups outside and inside living cells to release phenol-based fluorophores. In cells, the production of fluorophore in the presence of CD-NHC-copper catalysts outperforms that induced by the cellular machinery alone and endogeneous ROS
BPS2025 - The glycoprotein-rich cell wall architecture of Chlamydomonas reinhardtii
No full textInternational audienceCellulose is the most abundant biopolymer on earth as it represents the major component of the cell wall of vascular plants. As a polymer of glucose molecules, its biosynthesis by photosynthetic organisms accounts for a significant annual reduction in atmospheric carbon dioxide. In addition to plant and fungal cell walls, cellulose also serves as a bacterial biofilm component and as a tissue scaffold in some tunicates. Cellulose is synthesized and secreted across the plasma membrane by cellulose synthase, a membrane-embedded, processive glycosyltransferase. While the core biosynthetic machinery is evolutionarily conserved, cellulose biosynthesis shows species-specific variations for the production of tailored cellulosic biomaterials. These include the alignment of cellulose chains into cablelike fibers as the load-bearing components of plant cell walls and the chemical modification of cellulose with small molecules in certain biofilms. We present detailed mechanistic insights into cellulose biosynthesis in plants and bacteria. Combining structural and functional analyses, we explain how cellulose synthase elongates a nascent cellulose polymer, how the elongated chain is translocated across the plasma membrane, and how plant cellulose synthase promotes the alignment of cellulose polymers into fibrillar structures. We also provide insights into the chemical modification of cellulose with lipid-derived phosphoethanolamine by Enterobacteriaceae. Here, cellulose synthase is part of a macromolecular complex that catalyzes the synthesis, chemical modification, and secretion of cellulose across the gram-negative cell envelope. Together, our work provides insights into the molecular and mechanistic principles necessary to design novel cellulosic biomaterials.95-Symp BPS2025 -The glycoprotein-rich cell wall architecture of Chlamydomonas reinhardtii</p
Tunable Charge Transfer in Functionalised Betainoïd Pyridinium-Benzimidazole Scaffolds: Computational and Experimental Insights into Optical Properties
No full textInternational audienceDonor acceptor systems are promising systems for applications in optoelectronics. The zwitterionic nature of betainoid pyridinium compounds allows for a unique set of tunable electronic properties but their rationalisation remains challenging. Here, the optical properties of a series of five derivatives were studied experimentally and computationally to unveil and rationalize their distinctive intramolec-ular charge transfer properties. These compounds consist of 4-functionalised-pyridine with H, tert-butyl, dimethylamino, trifluoroborate and oxo linked through their nitrogen atom to benzimidazole at its C2 position (1-5 respectively). The transitions responsible for the absorption and emission proper-ties observed experimentally were investigated using DFT and TDDFT. Calculated absorption ener-gies systematically match the experimental λmax, while the prediction of emission energy seems to be less straightforward. By use of the molecular orbitals, charge distribution evolution, change in electric dipole moment and calculated vertical excitations, we are able to rationalise structure-properties relations involved in these transitions. This study allows to gain insights into the optoelec-tronic properties of a series of unique donor-acceptor systems using computationally cost-efficient methods
Modulation of amyloid β peptide self-assembly by polyoxometalates complexed with lanthanides
No full textInternational audienceAβ peptide aggregation is one of the main hallmarks of Alzheimer’s disease (AD), with different degrees of self-assembly, from the oligomeric assemblies recognized as being the most toxic species, to the fibril state leading to amyloid plaques. Controlling and limiting the presence of oligomers is thus a key paradigm in the rationale for therapeutic strategies against the development of AD. Here, we used polyoxometalates (POM) which are polyanionic oxoclusters of early transition metals that can be complexed with extremely high affinities with d-block and f-block metals. We investigated several lanthanide-complexed POM for the modulation of Aβ self-assembly by the combination of several biophysical techniques. We used the simplified Aβ1-28 peptide which can still aggregate but slower than Aβ1-40 in order to simplify NMR experiments. ThT fluorescence assays showed that low ratios of these complexes can accelerate Aβ aggregation, when lanthanides or lacunary POM alone rather tend to slow this process down. 1D 1H spectra and 2D TOCSY NMR experiments were employed to monitor the binding of these polyanions on the peptide, displaying 2 binding sites containing carboxylate residues (glutamates and aspartate) with an apparent affinity in the μM range. Altogether, this data leads us to a better comprehension to potential ways of restraining amyloid progression in AD
Growth of “quantum-grade” single crystal diamond films and their integration into hybrid structures
No full textInternational audienceDue to a set of favourable properties, diamond is foreseen as the ultimate semiconductor for power electronic devices operating under harsh environments. In the past decades, efforts on material development have contributed to improve the crystalline quality of the diamond films produced by the chemical vapour deposition (CVD) technique, which includes a strong reduction in impurities and extended defects such as dislocations. In addition, significant success has been achieved in increasing the lateral size of the diamond films, by exploiting either a “mosaic” approach1 or heteroepitaxial growth on a foreign substrate2. Thanks to this, the first diamond wafers for electronics are on the verge of being commercialized at an industrial scale. Leveraging on those developments, the use of diamond as a solid-state material for quantum technologies has also witnessed tremendous progress3. It essentially relies on the use of a specific point defect, the nitrogen-vacancy (NV) centre which spin-state can be optically read-out and manipulated with exceptionally long coherence time (up to 2 ms) even at room temperature. Based on this property, disrupting quantum devices having a far superior performance to standard classical systems are foreseen for a wide range of fields including health, communications, security and environment. Nanoscale magnetic or electric sensors, temperature sensors, single photon emitters for cryptography and information processing are among the many devices that could find industrial application in quantum technologies. The material requirements though are even more stringent than for electronics, with the need to control isotopic enrichment (i.e. 13C depleted growth), strain and purity to an unprecedented level. The spatial positioning of the colour centres as well as their crystallographic orientation is also crucial. In all these areas, important progresses in material fabrication have already been achieved. In addition to all-diamond based devices, the combination of NV centres with other quantum platforms can open interesting perspectives to extend the functionalities of the devices, by favouring for example operation in the infrared range or taking benefit from longer spin coherence times offered by other systems. In this context, the first demonstrations of hybrid diamond-based sensors combined with other quantum systems are just starting to emerge. In this presentation, I will review the efforts dedicated to improving single crystal diamond films from the point of view of synthesis and material enhancement technologies that are key resources. The constraints inherent to the creation of colour centres with good properties in an ultra-pure matrix either by in-situ doping or by implantation using a focused ion beam will be described. Eventually, the combination of diamond films containing NV centres together with oxide thin films doped with rare-earth elements, another successful platform for quantum applications, will be assessed4. 1 S. Ohmagari, H. Yamada, N. Tsubouchi, H. Umezawa, A. Chayahara, A. Seki, F. Kawaii, H. Saitoh, and Y. Mokuno, “Schottky barrier diodes fabricated on diamond mosaic wafers: Dislocation reduction to mitigate the effect of coalescence boundaries,” Appl. Phys. Lett. 114(8), 082104 (2019).2 J.-C. Arnault, S. Saada, and V. Ralchenko, “Chemical Vapor Deposition Single-Crystal Diamond: A Review,” Physica Status Solidi (RRL) – Rapid Research Letters 16(1), 2100354 (2022).3 J. Achard, V. Jacques, and A. Tallaire, “CVD diamond single crystals with NV centres: a review of material synthesis and technology for quantum sensing applications,” J. Phys. D: Appl. Phys., (2020).4 I.G. Balașa, M.A. Arranz-Martinez, P. Perrin, M. Ngandeu Ngambou, A. Hebbrecht, D. Serrano, J. Achard, A. Tallaire, and P. Goldner, “Rare Earth-Diamond Hybrid Structures for Optical Quantum Technologies,” Advanced Optical Materials 12(31), 2401487 (2024).Acknowledgements: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (RareDiamond, grant agreement No 101019234)
Advancements in dislocation reduction for large area diamond substrates: toward scalable high performance materials
No full textInternational audienceDiamond’s exceptional properties such as high thermal conductivity, high breakdown voltage and high charge carrier mobility make it a prime candidate for next-generation of power electronic devices and high-energy particle detectors [1- 2]. The properties of specific defects in diamond such as NV centers stands as a highly promising platform for quantum technologies. It offers excellent spin properties, including millisecond coherence times at room temperature, paving the way for the development of ultra-sensitive, high-performance quantum sensors, offering new avenues for exploring characteristics inaccessible to conventional devices. However, translating these benefits into real-world applications is hampered by three main challenges: controlling defect densities, producing sufficiently large substrate surfaces, and ensuring reliable material availability for viable market use cases.HiQuTe Diamond is a founded start-up emerging from the LSPM-CNRS, an internationally recognized research center with over 30 years of expertise in diamond growth. Our goal is bridging the gap between state-of-the-art diamond research and commercial product development. By focusing on advanced process engineering and scalable manufacturing approaches, we aim to overcome the hurdles of defect control, substrate size, and material supply.As an example of recent developments through joined effort between HiQuTe and LSPM, we have demonstrated a two-order-of-magnitude reduction in dislocation density from 107 to 105 dislocations/cm² on 1 cm² single-crystal diamond substrates [3] . This progress enables up to 80% of the surface to reach or stay below that threshold. This key milestone paves the way for our exploratory phase on 1-inch substrates, where iterative or combined techniques will be used to further enhance uniformity and yield.Through our dedication to both fundamental research and entrepreneurial agility, our start-up strives to unleash diamond’s full potential for high-performance electronic devices and other emerging applications, positioning diamond as a truly transformative material for the 21st century.References[1] J. Isberg, et al., Diamond and Related Materials, 13 (2004) 320-324.[2] C. Masante, et al., Journal of Physics D: Applied Physics, 54 (2021) 233002.[3] L. Mehmel, et al, Appl. Phys. Lett. 118, 061901 (2021