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Synthesis and Self‐Assembly of Perylene Imide‐Containing Hydrophilic Polymers in Water
No full textInternational audienceNew advances in synthetic strategies have greatly expanded the structural diversity of perylene imides (PIs), increasing the tunability of their molecular properties and assemblies in organic solvents. More recent studies also show molecular assemblies in aqueous media when the hydrophobic perylene core is functionalized with hydrophilic groups, allowing their use not only in optoelectronics or catalysis, but also in biological applications. However, PIs are usually too hydrophobic to be used in water, and their molecular assemblies usually result in ill‐defined nanostructures with a significant loss of their emissive properties. Therefore, a powerful and promising strategy to enhance PI solubility in water is to incorporate them into hydrophilic polymer chains. Compared to small hydrophilic groups, the length and architecture of the polymer can be controlled and adapted to modulate the nanostructure morphology while preserving the perylene's properties in water. This review summarizes the current literature on the self‐assembly in water of PI‐based hydrophilic polymers, with a focus on their synthesis and the different parameters that influence the self‐assembly and properties of the materials
Synchrotron-Assisted HPHT Annealing Of Quantum Nanodiamonds: In Situ Control Of Phase Stability
No full textInternational audienceGroup-IV color centers in nanodiamond, such as silicon-vacancy (SiV) defects, are promising quantum emitters for sensing and photonics due to their bright and narrow zero-phonon line (ZPL) emission, representing up to 80% of their total luminescence [1–3]. However, in as-grown CVD nanodiamonds, residual lattice strain induces significant spectral broadening, preventing access to the fine electronic structure of SiV centers even at cryogenic temperatures. To mitigate this effect, we carried out a controlled high-pressure and high-temperature (HPHT) annealing process using the Paris–Edinburgh press, performed in situ at the PSICHE beamline of Synchrotron SOLEIL [4]. The synchrotron X-ray diffraction and tomography measurements were crucial for the precise calibration of pressure and temperature conditions within the assembly, enabling us to finely tune the HPHT parameters to promote strain relaxation while avoiding the onset of graphitization. These in situ synchrotron investigations provided real-time insight into nanodiamond phase stability and strain-release mechanisms, which were confirmed ex situ by optical measurements, leading to the first observation of resolved fine-structure transitions in SiV centers after HPHT treatment. Importantly, the calibrated HPHT setup can now be reliably operated off-beam, enabling systematic post-annealing studies on different types of nanodiamonds and color centers. This methodology establishes a robust experimental reference for future off-beam HPHT annealing treatments and serves as a benchmark for the broader quantum diamond research community.REFERENCES 1. T. Muller et al., Nat. Commun. 5, 3328 (2014).2. M. De Feudis et al., Adv. Mater. Interfaces 7, 1901408 (2019).3. B. Vindolet et al., Phys. Rev. B 106, 214109 (2022).4. L. Henry et al., J. Synchrotron Rad. 29, 853-861 (2022)
NKCC1 as a signaling hub regulating KCC2 stability, chloride homeostasis, and seizure susceptibility
No full textAbstract Chloride homeostasis relies on the dynamic balance between the neuronal co-transporters NKCC1 and KCC2. We reveal an unexpected mechanism by which NKCC1 governs KCC2 membrane stability. NKCC1 clusters recruits SPAK and PP1 to dynamically trap KCC2, compensating for its lack of a direct SPAK-binding site. Single-particle tracking shows that these NKCC1-rich assemblies operate as signaling hubs, enabling either SPAK-driven KCC2 phosphorylation and its membrane destabilization or PP1-mediated dephosphorylation of SPAK and KCC2 membrane stabilization. Peptides that activate SPAK by engaging NKCC1’s PP1-binding motif lower KCC2 surface levels and reduce chloride extrusion, whereas a SPAK-inhibiting peptide prevents SPAK recruitment to NKCC1, stabilizes KCC2 in membrane clusters, and enhances chloride extrusion. An optimized peptide analog preserves KCC2 clustering under hyperexcitable conditions, reduces seizure frequency and severity in PTZ-induced epilepsy, and suppresses ictal activity in human epileptic tissue. These findings identify NKCC1-KCC2 coupling as a central regulatory axis for inhibitory signaling, and position our peptides as promising therapeutic candidates to restore chloride homeostasis in epilepsy and other disorders marked by impaired KCC2 membrane stability
Na10Mn4O9: Synthesis, Structure, and Electrochemical Properties
No full textInternational audienceIn the search for sustainable cathode materials for Na–ion batteries, Mn-based oxides have emerged as attractive candidates owing to their earth abundance and structural versatility. In this context, a comprehensive investigation of the electrochemical behavior of the sodium-rich Mn2+ oxide Na10Mn4O9 toward sodium extraction/insertion is presented. The structural framework of this phase, prepared through a simple solid-state synthesis at 450 °C, is built on MnO4 and MnO3 polyhedra. Seven sodium ions per unit formula can be extracted during the first charge, and XAS analysis reveals the main transformation into a layered NaxMnO2·Na2O composite. Upon further cycling, once this phase is formed, the material delivers a reversible capacity of 110 mAh g–1 at an average potential of 2.24 V vs Na+/Na
High Potential Isoindoline‐Based Nitroxides Posolytes for Aqueous Organic Redox Flow Batteries
No full textInternational audienceThe growing transition from fossil fuels to renewable energy sources such as wind and solar requires efficient stationary energy storage systems to ensure grid stability. Among emerging technologies, redox flow batteries (RFBs) offer a promising solution due to their unique decoupling of energy and power capacities, allowing flexible system design. Recent advances in organic RFBs (ORFBs) have highlighted redox‐active organic molecules as sustainable alternatives to conventional vanadium‐based systems, addressing issues of cost and corrosivity. In particular, nitroxide radicals such as tetramethylpiperidinyloxyl (TEMPO) derivatives have demonstrated high reversibility and fast kinetics in aqueous systems, though the stability of their oxidized N‐oxoammonium form remains a challenge for long‐term storage. Isoindoline‐based nitroxides offer potential for enhanced stability but have been limited by complex and low‐yield synthetic routes. Herein, we present a convenient metal‐catalyzed [2 + 2 + 2] intermolecular cycloaddition strategy for the synthesis of isoindoline‐based nitroxides and their aza analogs, including two new candidates, TC‐TMIO and PPO. Electrochemical characterization reveals that PPO, a cationic 2,3‐dihydropyrrolo[3,4‐c]pyridinium nitroxide, exhibits an oxidation potential 220 mV higher than the benchmark 4‐TMA‐TEMPO and achieves solubility exceeding 3 M in 1 M NaCl aqueous solution. Preliminary stability assessments of the PPO and RFB testing using a methyl viologen/PPO system demonstrate its potential as a high‐performance, sustainable posolyte for aqueous ORFBs
Supramolecular rotaxanes and polyrotaxanes as potential MRI contrast agents: a comprehensive 17O NMR and relaxometric study
No full textInternational audienceRotaxanes and polyrotaxanes made of substituted cyclodextrins (CDs) were designed as potential MRI contrast agents or bimodal optical and MRI probes. After characterization of the threading kinetics and the exact composition of the polyrotaxanes, their MRI properties have been investigated by 1 H relaxometry and 17 O NMR. We demonstrated that the relaxivity of these systems is increasing with increasing size (modified CDs, rotaxanes, and polyrotaxanes). 17 O NMR studies show that the various systems have similar water exchange rates, in the same range as that of Gd-DOTA-monoamide complexes. Interestingly, NMRD data of the smaller systems can be only analyzed by considering both local and global motions via Lipari-Szabo approach, underlining the importance of internal flexibility. On the other hand, the disubsituted rotaxane and the polyrotaxanes are highly rigid and can be characterized with a single rotational correlation time. Their relaxivity is considerably enhanced by a second sphere contribution which is strongly dependent on the structure. It increases from the rotaxane to the mono-and the disubstituted polyrotaxanes, and as expected, it diminishes with decreasing coverage of the axle. The fundamental understanding provided by this comprehensive study will help the design of versatile and more efficient supramolecular interlocked systems such as rotaxanes and polyrotaxanes for MRI applications.</div
Transition-metal pincer complexes in polymer chemistry: From monomer activation to chemical recycling
No full textInternational audienceTransition-metal-catalyzed, acceptorless dehydrogenation and hydrogenative depolymerization have emerged as powerful strategies in sustainable polymer chemistry. These transformations enable reversible polymerization and chemical recycling under mild conditions. This review critically analyzes recent advances in pincer-type ruthenium and manganese catalysts that exploit metal-ligand cooperation to efficiently construct and deconstruct polyesters, polyamides, polyureas, polyurethanes and polyethyleneimine-like materials. We discuss breakthroughs in acceptorless dehydrogenative polymerization, which delivers high-molecular-weight polymers, as well as hydrogenative depolymerization protocols, which enable the recovery of up to 99% of the monomer at temperatures between 80 and 140 °C and moderate hydrogen pressures. In addition, integrated dehydrogenation-hydrogenation sequences are also featured as a blueprint for closed-loop polymer systems that offer chemically recyclable architectures preserving monomer purity and material properties across multiple cycles. We identify key challenges, including developing earth-abundant catalysts, incorporating bio-based monomers, and achieving selective recycling from mixed waste streams, as critical for scaling these methodologies. Together, these advances open new avenues for programmable, circular polymer technologies that align with global sustainability goals and transform strategies for plastic waste valorization
A 120 ka human femur from the Palaeolithic site of Caours (Somme Valley, France) showing a non-fully Neandertal condition
No full textInternational audienceThe Caours Eemian tufa sequence and associated palaeolithic site is located on the lowest terrace of the Scardon, a minor tributary of the Somme River in northern France. In 2016, a human femur (CN1-1) was discovered in the archaeological layer (N-1) contemporary with the Eemian climatic optimum based on the results of an interdisciplinary research program spanning more than two decades [2]. The thick tufa formation (3.5 to 4 m) is preserved over an area of about 30,000 m². Since 2005, a total of fifteen archaeological excavation campaigns have been conducted on the site. In the southern part of the excavation (Sector 2/S-2), corresponding to the reference area, four well-preserved archaeological levels have been identified (N-1 to N-4). Dating results, obtained by U-series on carbonates, OSL on fluvial sediments, TL on heated flints, and ESR/U-series on tooth enamel provide a robust chronological frame for the Caours sequence and the N1 level bearing the human remain, with a weighted mean age of 123.1 ±2.8 ka. Most mammalian faunal remains come from archaeological level N-1 (NISP=8,861). The species are: Palaeoloxodon antiquus, Stephanorhinus hemitoechus, Equus taubachensis, Bos primigenius, Cervus elaphus, Dama dama, Capreolus capreolus, Sus scrofa, Castor fiber, Aonyx antiqua, Canis lupus, Ursus arctos. This mammal assemblage is typical of forest environments that developed during the last interglacial. The taphonomical study of the fauna confirmed that humans were the only accumulators of the bones. The archaeological level N-1 corresponds to the last phase of occupation of the site. The area under investigation spanned 499 m². The use of fire by humans is attested in this area. Caours level N-1 yielded 1,348 lithic artifacts. The lithic production system is characterised by a discoidal debitage. A few Levallois flakes appear to have been brought to the site.The CN1-1 human remain is a diaphysis of a right femur preserved over approximately two-thirds of its length. Due to its small dimensions (175 mm), it is attributed to a young individual as confirmed by the weak thickness of the cortical part of the bone in comparison with values measured on adults (fossil hominins and Homo sapiens). For comparisons, we considered immature fossil hominins whose estimated age-at-death ranges from 5 to 12 years (Arago 38, Marillac 25, Cova Negra 1 and Teshik-Tash) as well as a series of Homo sapiens (n=12) from the New Mexico Decedent Image Database (NMDID). In addition, the study incorporated two adult specimens from the same temporal range period of CN1-1 (i.e. around 120 ky, from Hohlenstein-Stadel and La Chaise - abri Bourgeois Delaunay). Other European Middle and Upper Pleistocene fossils were added using published data including measurements of adolescent and adult femora from Sima de los Huesos and the femur from Venosa-Notarchirico. Linear measurements were obtained at standardized heights of the diaphysis with the 80% measured at the estimated subtrochanteric level on CN1-1 and the 50% taken just above the breakage of the midshaft. Furthermore, the cortical area (CA) and total cross-section area (TA) were also measured and used to calculate the CA/TA ratio. The cortical thickness of the femur was obtained by semi-automatic segmentation and a cortical thickness map was produced using Dragonfly software, version 2022.2 for Windows.Results show that the CN1-1 femur differs from Neandertals, particularly in the flattening of the bone at mid-diaphysis and in the pattern of bone distribution. The bone is thickest on the lateral edge, which is reinforced by the presence of a developed gluteal complex. Because of these traits, the CN1-1 is close to early Middle Pleistocene fossils such as those from the Arago cave (France) and Venosa-Notarchirico (Italy). It demonstrates that morphological diversity persisted at the beginning of the Upper Pleistocene, even as Neandertal-specific traits become dominant
Molecular Modification of Cu-Based Electrodes via Electrografting: Effects of Modifier Structure on CO2 Electroreduction Selectivity
No full textInternational audienceCO2 electroreduction to multicarbon products using Cu-based catalysts is one of the strategies currently developed in order to valorize CO2 and store electricity. Molecular modification of material surfaces has been recently explored in order to tune the reactivity of Cu catalysts and improve their selectivity toward C2+ products, in particular ethylene and ethanol. Here, we compare four classes of precursors of aryl radicals, namely, aryl-iodoniums, -diazoniums, -sulfoniums, and -silicates, which are used for grafting an aromatic layer onto the surface of Cu nanoparticles via electroreduction or electrooxidation. In all cases, the surface modification promotes CO–CO coupling and C2+ product formation, leading to a much higher FEC2+/FECO (FE = Faradaic efficiency) ratio. However, we show that the composition of the layer is more complex and diverse than anticipated and likely explains the unexpectedly large variations in selectivity, even though the Cu catalysts were functionalized with presumably the same aromatic layer derived from the same aryl radical generated by the four different precursors. These classes of precursor salts are thus not interchangeable and provide a much larger scope of Cu surface modifications and Cu catalysts than anticipated to be studied independently
Substitution Pattern of the Secondary Rim of ICyD Ligand Influences Stereoselectivity
No full textInternational audienceThe synthesis and evaluation of N‐heterocyclic carbene (NHC)‐capped cyclodextrins with various protecting groups were carried out. The corresponding gold complexes catalyze the stereoselective cycloisomerization of enynes. Permethylation of the cyclodextrin's hydroxyl groups improves yield and selectivity compared to its benzylated counterpart. Notably, alternating methyl and benzyl groups on the secondary rim of the cyclodextrin further enhances asymmetry, achieving even higher enantioselectivities. To synthesize this compound, we optimized the selective deprotection of all benzyl groups at the 2‐position of the sugar residues in the cyclodextrin