Portail HAL ENSCP
Not a member yet
9647 research outputs found
Sort by
High-resolution optical spectroscopy of europium nitrate hexahydrate crystals
No full textInternational audienceWe report the optical study of europium nitrate hexahydrate crystals Eu(NO3) 6H2O and their deuterated version Eu(NO3) 6D2O conducted at 50 mK. The crystals show sub-GHz inhomogeneous linewidths for the transition and optical coherence times up to 136 μs for the non-deuterated crystal and 750 μs for the deuterated one. In addition, using the spectral hole burning technique, the hyperfine splittings in the absence of an external field have been estimated for the ground and optical levels. These results suggest that rare-earth nitrate crystals could represent a promising class of materials for quantum information applications as well as for fundamental physics experiments requiring narrow optical transitions and good coherence properties
Multimodal Purcell enhancement and optical coherence of Eu 3+ ions in a single nanoparticle coupled to a microcavity
No full textInternational audienceEuropium-doped nanocrystals constitute a promising material for a scalable future quantum computing platform. Long-lived nuclear spin states could serve as qubits addressed via coherent optical transitions. In order to realize an efficient spin-photon interface, we couple the emission from a single nanoparticle to a fiber-based microcavity under cryogenic conditions. The spatial and spectral tunability of the cavity permits us to place individual nanoparticles in the cavity, to measure the inhomogeneous linewidth of the ions, and to show a multi-modal Purcell-enhancement of two transition in Eu 3+ . A halving of the free-space lifetime to 1.0 ms is observed, corresponding to a 140-fold enhancement of the respective transition. Furthermore, we observe a narrow optical linewidth of 3.3 MHz for a few-ion ensemble in the center of the inhomogeneous line. The results represent an important step towards the efficient readout of single Eu 3+ ions, a key requirement for the realization of single-ion-level quantum processing nodes in the solid state
Parchment preservation state of the Prayer book of Mary of Guelders
No full textInternational audienceIlluminated medieval manuscripts are of outstanding value and their preservation is of great importance, not only because of their beauty but also because of the information they contain about medieval society. This work focuses on the evaluation of the parchment state of preservation of the Prayer book of Mary of Guelders, which comprises about 600 folios. The knowledge gained should support the decision-making process regarding suitable conservation measures. An assessment of the preservation state of the parchment was performed from the macro- down to the microscale. Optical observations of cracks in the parchment and colour measurements preceded chemical analyses. The hydrothermal stability of the fibres was evaluated by means of observations using a micro hot table (MHT). The chemical state of preservation of parchment was evaluated using Laboratory-based Fourier transform (FT) Infrared (IR) analysis in reflection mode as well as synchrotron FTIR imaging in transmission mode at the IRIS beamline at BESSY II/ HZB in Berlin. The study allowed the conclusion that the parchment of the Prayer book of Mary of Guelders was in good state of preservation and indicated that the parchment changes were mainly caused by mechanical stress on the folios due to tight binding of the book and not by chemical processes
Polymer conformation changes observed with the naked eye in a liquid crystal elastomer and their use to produce adjustable and multidirectional deformations
No full textThe monodomain nematic liquid crystal elastomer (LCE) is a nonporous material with one-dimension (1D) negative thermal expansion (NTE) along the direction of orientation. This stimuli-responsive size change is comparable with the contractile response of a muscle fibre. Recently, LCEs have become more and more popular and increasingly investigated as a full-fledged class of stimuli-responsive materials.However, the nematic LCE is limited to a single, unidirectional deformation unless complex hybrid architectures are made. We develop here a special LCE based on a liquid crystal polymer with an extraordinary phase transition sequence, "re-entrant nematic (NRe) -smectic A (SmA) -nematic (N) -isotropic (I) phase", along with "prolate -oblate -weakly oblate -spherical" chain conformation evolution. In the aligned LCE film, these conformational changes of polymer chain are observed with the naked eye through their macroscopic translations into a unique sequence of "contraction -expansion -second expansion" deformations. Notably, a switch from NTE to positive thermal expansion (PTE) occurs upon heating. Moreover, a bilayer actuator composed of aligned and non-aligned LCE layers can perform 2D to 3D shape transformation with "curling -uncurling -second uncurling" actuation sequence. This LCE capable of multiple deformations in response to a single stimulus paves the way to multimodal single-material actuators. It provides a new strategy for the development of advanced materials with adjustable and multidirectional deformations.</div
Incorporating MXene with Redox Carriers on Capacitive Carbon Cloth-Based Freestanding Electrodes for Power Applications
No full textInternational audienceBattery-like organic materials including quinone-based electrodes with electrochemical activity have been extensively investigated for their use as electrode materials in energy storage devices due to their economic competitiveness and sustainable benefits. However, the intrinsic electrical insulating nature of organic quinones and their electrochemical reactivity limit power capability and stability upon charge/discharge cycling, respectively. Here, we report the preparation of a concentric layered architecture, MXene/Anthraquinone/Carbon Cloth (M/AQ/CC), by physisorption of anthraquinone onto the surface of carbon cloth via non-covalent π – π interactions, followed by dipping in exfoliated MXene suspension. The M/AQ/CC electrode, with a high mass loading (18.2 mg cm −2 ), delivered a capacity of 46 mAh g −1 (about 1 mAh cm −2 areal capacity or 6 mAh ml −1 volume) at 0.5 A g −1 , with good rate performance and an enhanced cyclability over 5 k cycles. This simple preparation method can also be applied to incorporate MXene with a series of alternative organic redox carriers on freestanding carbon cloth, including thionin acetate and anthraquinone-2-sulfonate. The improvement in electrochemical performance highlights an efficient approach to store more charges via redox reactions from organic quinones pi-stacked at carbon surfaces, thanks to a protective MXene shield that stabilizes the Faradaic behavior of quinones over repetitive charge-discharge processes. The simplicity and versatility of this method should enable design of many advanced electrode materials based on MXene/quinones/carbon cloth for power devices
Synthesis, chemical, physical and electrochemical characterizations of Manganese based oxides Na10Mn4O9 and K3MnO4
No full textInternational audienc
Ag-alloying of CIGS absorber layers: impact of the composition, rubidium fluoride post-treatment and bandgap variations
No full textInternational audienceChalcopyrite-based solar cells have achieved remarkable efficiency, yet further advancements remain challenging. The partial substitution of copper (Cu) with silver (Ag) in Cu(In,Ga)Se 2 (CIGS) thin-film solar cells presents a promising approach to enhance absorber properties and improving device performance. This study explores the moderately high-concentration Ag incorporation (Ag/(Ag + Cu) = 0.19) via thermal evaporation prior to co-evaporation of CIGS absorbers, combined with rubidium fluoride (RbF) post-deposition treatment. Additionally, the impact of Ag alloying is examined across absorbers with bandgaps ranging from 1.12 to 1.55 eV. Results indicate that Ag incorporation significantly influences gallium distribution, promotes larger grain growth, and enhances open-circuit voltage (Voc). Notably, (Ag,Cu)(In,Ga)Se 2 (ACIGS) absorber with a 1.23 eV bandgap achieves a power conversion efficiency of 18.1%, while a 1.55 eV bandgap absorber reaches 7.1%
Understanding the hard carbon's closed pore formation and Na-ion storage beyond the first charge/discharge cycle
No full textInternational audienceThe lack of accurate determination of hard carbon's (HC) open and closed pores, but also the systematic analysis of only the first charge/discharge cycle, in half-cells, impedes understanding of Na-ions storage. Therefore, a combined approach based on the adsorption of multiple gases (N 2 , O 2 , H 2 and CO 2 ) and He density is proposed to understand the HC's open porosity evolution and closed pores formation during pyrolysis. At 900 • C the pores are completely open, they partially close in the range of ~1100-1300 • C, and completely close starting from 1500 • C. The narrower pores (<0.7 nm) close firstly, with the formation of few larger open pores and plenty of closed pores, which increase with temperature. Examination of property-performance relationships from both 1st and 2nd cycles, revealed that the 1st cycle sloping capacity increases with open porosity, O-functional groups and defects, and is associated not only with reversible Na-storage but also with irreversible reactions (SEI formation).On the contrary, the 2nd cycle is only linked with reversible Na-storage, and an optimal property threshold was established. The plateau capacity was found to increase with the increase in graphitic domains and closed pores, no matter the cycle. These findings suggest an adsorption-insertion-filling mechanism
A Cathepsin B‐Triggered CO‐Releasing Molecule with a Non‐Toxic Metal Core for Targeted Tumor Delivery
No full textInternational audienceAbstract Carbon monoxide (CO) has shown therapeutic potential across various diseases, including cancer. To enable controlled delivery, many CO‐releasing molecules (CORMs) have been developed. However, their clinical translation has been limited due to concerns about stability, potential toxicity, and insufficient targeting ability. In this study, we report the synthesis and characterization of an enzyme‐triggered CO‐releasing molecule ( ET‐CORM ) that can be site‐specifically conjugated to antibodies. This novel ET‐CORM is built on a biocompatible iron core, and releases CO upon cleavage by the cancer‐associated protease cathepsin B (CatB). The incorporation of a bioorthogonal handle into ET‐CORM enabled its efficient and site‐specific conjugation to the clinically used antibody trastuzumab us of the interchain disulfide bonds. The resulting ET‐CORM–antibody conjugate ( ET‐CORM‐Ab ) exhibited an average drug‐to‐antibody ratio (DAR) of 6.8, corresponding to approximately 20 CO molecules per conjugate. This construct allowed for selective intracellular CO delivery to HER2‐overexpressing and CatB‐expressing cells in vitro. This study represents a metal‐based CORM–antibody conjugate activated by a tumor‐associated enzymatic trigger, opening new avenues for investigating CO‐mediated effects and advancing CO‐based cancer therapies to the clinics
SPARC is a new driver of early breast tumor progression via TGF-β -dependent mechanism
No full textInternational audienceAbstract Ductal carcinoma in situ (DCIS) is a pre-invasive lesion that is thought to be a precursor of invasive ductal carcinoma (IDC). The challenge lies in discriminating between DCIS progressors and DCIS non-progressors, often resulting in over- or under-treatment in many cases. Membrane type 1 (MT1)-matrix metalloproteinase (MMP) has been previously identified as an essential gene involved in DCIS progression. Here, RNA-sequencing analysis of MT1-MMP high subpopulation derived from invasive breast tumors in the intraductal xenograft model was compared against a dataset of human high-grade DCIS, and Secreted Protein Acidic and Cysteine Rich (SPARC) has emerged as a master candidate involved in early breast tumor progression. We report that SPARC is up-regulated in DCIS as compared to normal breast epithelial tissues, and further increased in IDC relative to synchronous DCIS foci. We found a positive correlation between SPARC and MT1-MMP expression in DCIS lesions. At the mechanistic level, depletion of SPARC reduced MT1-MMP expression, the degradative capacity of the cells and the activation of the TGF-β signalling canonical pathway. Pharmacological inhibition of the TGF-β signalling pathway decreased SPARC and MT1-MMP at the mRNA and protein level, and concomitantly the cell degradative capacity and 3D cell migration. Strikingly, inhibition of the TGF-β signalling pathway limits the invasive transition of breast tumors in a new triple-negative mouse intraductal syngeneic xenograft model. Moreover, high SPARC expression was positively correlated with both, TGF-β and its receptor, TGFBRI, in a basal type of breast cancer collection supporting our findings. This study identifies SPARC as a new driver of early breast tumor progression via a TGF-β-dependent mechanism, suggesting TGF-β signaling pathway as a potential target for patients with high SPARC expression