Université PSL

Publications

RECHERCHER

Laboratoire :
Auteur :
Revue :
Année :
The Quantitative Assessment of the Secreted IgG Repertoire after Recall to Evaluate the Quality of Immunizations
Laboratoire Colloïdes et Matériaux Divisés - Klaus Eyer, Carlos Castrillon, Guilhem Chenon, Jérôme Bibette, Pierre Bruhns, Andrew D. Griffiths and Jean Baudry
The Journal of Immunology - 205 8 - DOI: https://doi.org/10.4049/jimmunol.2000112 - 2020
One of the major goals of vaccination is to prepare the body to rapidly secrete specific Abs during an infection. Assessment of the vaccine quality is often difficult to perform, as simple measurements like Ab titer only partly correlate with protection. Similarly, these simple measurements are not always sensitive to changes in the preceding immunization scheme. Therefore, we introduce in this paper a new, to our knowledge, method to assay the quality of immunization schemes for mice: shortly after a recall with pure Ag, we analyze the frequencies of IgG-secreting cells (IgG-SCs) in the spleen, as well as for each cells, the Ag affinity of the secreted Abs. We observed that after recall, appearance of the IgG-SCs within the spleen of immunized mice was fast (<24 h) and this early response was free of naive IgG-SCs. We further confirmed that our phenotypic analysis of IgG-SCs after recall strongly correlated with the different employed immunization schemes. Additionally, a phenotypic comparison of IgG-SCs presented in the spleen during immunization or after recall revealed similarities but also significant differences. The developed approach introduced a novel (to our knowledge), quantitative, and functional highly resolved alternative to study the quality of immunizations.
Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers
Laboratoire Colloïdes et Matériaux Divisés - Marco Molari, Klaus Eyer, Jean Baudry, Simona Cocco, Rémi Monasson
Nature Protocols - 15 2920–2955 - DOI: 10.7554/eLife.55678 - 2020
Affinity maturation is a complex dynamical process allowing the immune system to generate antibodies capable of recognizing antigens. We introduce a model for the evolution of the distribution of affinities across the antibody population in germinal centers. The model is amenable to detailed mathematical analysis and gives insight on the mechanisms through which antigen availability controls the rate of maturation and the expansion of the antibody population. It is also capable, upon maximum-likelihood inference of the parameters, to reproduce accurately the distributions of affinities of IgG-secreting cells we measure in mice immunized against Tetanus Toxoid under largely varying conditions (antigen dosage, delay between injections). Both model and experiments show that the average population affinity depends non-monotonically on the antigen dosage. We show that combining quantitative modeling and statistical inference is a concrete way to investigate biological processes underlying affinity maturation (such as selection permissiveness), hardly accessible through measurements.
Deep phenotypic characterization of immunization-induced antibacterial IgG repertoires in mice using a single-antibody bioassay
Laboratoire Colloïdes et Matériaux Divisés - Millie Heo, Guilhem Chenon, Carlos Castrillon, Jérôme Bibette, Pierre Bruhns, Andrew D. Griffiths, Jean Baudry & Klaus Eyer
Communications Biology - 614 5337-5342 - https://doi.org/10.1038/s42003-020-01296-3 - 2020
Antibodies with antibacterial activity need to bind to the bacterial surface with affinity, specificity, and sufficient density to induce efficient elimination. To characterize the anti-bacterial antibody repertoire, we developed an in-droplet bioassay with single-antibody resolution. The assay not only allowed us to identify whether the secreted antibodies recognized a bacterial surface antigen, but also to estimate the apparent dissociation constant (KD app) of the interaction and the density of the recognized epitope on the bacteria. Herein, we found substantial differences within the KD app/epitope density profiles in mice immunized with various species of heat-killed bacteria. The experiments further revealed a high cross-reactivity of the secreted IgG repertoires, binding to even unrelated bacteria with high affinity. This application confirmed the ability to quantify the anti-bacterial antibody repertoire and the utility of the developed bioassay to study the interplay between bacteria and the humoral response.

Apollonian packing in polydisperse emulsions
Laboratoire Colloïdes et Matériaux Divisés - Sylvie Kwok, Robert Botet, Lewis Sharpnack and Bernard Cabane
Nature Protocols - 16 2426-2430 - https://doi.org/10.1039/C9SM01772K - 2020
We have discovered the existence of polydisperse high internal-phase-ratio emulsions (HIPE) in which the internal-phase droplets, present at 95% volume fraction, remain spherical and organise themselves according to Apollonian packing rules. These polydisperse HIPEs are formed by emulsifying oil dropwise in a surfactant-poor aqueous continuous phase. After stirring has ceased, their droplet size distributions begin to evolve spontaneously and continuously through coalescence towards well-defined power laws with the Apollonian exponent. Small-angle X-ray Scattering performed on aged HIPEs demonstrate that the droplet packing structure agrees with that of a numerically simulated random Apollonian packing. We argue that when such concentrated emulsions are allowed to evolve, the coalescing droplets must obey volume and sphericity conservation. This leads to a mechanism that differs from typical coalescence in dilute emulsions.

Swelling, dewetting and breakup in thin polymer films for cultural heritage
Laboratoire Colloïdes et Matériaux Divisés - Amélie Castel, Philipp Gutfreund, Bernard Cabaned and Yahya Rharbi
Soft Matter - 16 1485-1497 - https://doi.org/10.1039/C9SM01976F - 2020
The removal of ultrathin amorphous polymer films in contact with nonsolvent/solvent binary mixtures is addressed by means of neutron reflectometry and atomic force microscopy. The high resolution of neutron scattering makes it possible to resolve the distribution profiles of heavy water and benzyl alcohol inside Laropal®A81, often employed as a protective varnish layer for Culture Heritage in restoration of easel paintings. The swelling kinetics and distribution profiles were recorded as a function of time and increasing benzyl alcohol concentration in water. The varnish film swells by penetration of the good solvent. At higher concentrations water-filled cavities appear inside the varnish and grow with time. Contrary to homogeneous dissolution dewetting is observed at late stages of exposure to the liquid which leads to the Breakup of the film. The high resolution measurements are compared to bulk behaviour characterized by the ternary phase diagram and the Flory–Huggins interaction parameters are calculated and used to predict the swelling and solvent partition in the films. Distinct differences of the thin film to bulk behaviour are found. The expectations made previously for the behaviour of solvent/non-solvent mixtures on the removal of thin layers in the restoration of easel paintings should be revised in view of surface interactions.


Optimised hyperbolic microchannels for the mechanical characterisation of bio-particles
Laboratoire Complex Suspensions - Yanan Liu, Konstantinos Zografos, Joana Fidalgo, Charles Duchene, Clement Quintard, Thierry Darnige, Vasco Filipe, Sylvain Huille, Olivia du Roure, Monica S. N. Oliveira and Anke Lindner
Soft Matter - 16 9844 - DOI: 10.1039/d0sm01293a - 2020
The transport of bio-particles in viscous flows exhibits a rich variety of dynamical behaviour, such as
morphological transitions, complex orientation dynamics or deformations. Characterising such complex
behaviour under well controlled flows is key to understanding the microscopic mechanical properties of
biological particles as well as the rheological properties of their suspensions. While generating regions of
simple shear flow in microfluidic devices is relatively straightforward, generating straining flows in which
the strain rate is maintained constant for a sufficiently long time to observe the objects’ morphologic
evolution is far from trivial. In this work, we propose an innovative approach based on optimised design
of microfluidic converging–diverging channels coupled with a microscope-based tracking method to
characterise the dynamic behaviour of individual bio-particles under homogeneous straining flow.
The tracking algorithm, combining a motorised stage and a microscopy imaging system controlled by
external signals, allows us to follow individual bio-particles transported over long-distances with highquality
images. We demonstrate experimentally the ability of the numerically optimised microchannels
to provide linear velocity streamwise gradients along the centreline of the device, allowing for extended
consecutive regions of homogeneous elongation and compression. We selected three test cases (DNA,
actin filaments and protein aggregates) to highlight the ability of our approach for investigating dynamics
of objects with a wide range of sizes, characteristics and behaviours of relevance in the biological world
Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions
Laboratoire INDYSOFT - Gabriel Guyard Alexandre Vilquin Nicolas Sanson Frederic Restagno Joshua D. Mcgraw
HAL - 1 - https://hal.archives-ouvertes.fr/hal-03029154 - 2020
Understanding confined flows of complex fluids requires simultaneous access to the mechanical behaviour of the liquid and the boundary condition at the interfaces. Here, we use evanescent wave microscopy to investigate near-surface flows of semi-dilute, unentangled polyacrylamide solutions. By using both neutral and anionic polymers, we show that monomer charge plays a key role in confined polymer dynamics. For solutions in contact with glass, the neutral polymers display chain-sized adsorbed layers, while a shear-rate-dependent apparent slip length is observed for anionic polymer solutions. The slip lengths measured at all concentrations collapse onto a master curve when scaled using a simple two-layer depletion model with non-Newtonian viscosity. A transition from an apparent slip boundary condition to a chain-sized adsorption layer is moreover highlighted by screening the charge with additional salt in the anionic polymer solutions. We anticipate that our study will be a starting point for more complex studies relating the polymer dynamics at interfaces to their chemical and physical composition.
Interface-Sensitive Raman Microspectroscopy of Water via Confinement with a Multimodal Miniature Surface Forces Apparatus
Laboratoire INDYSOFT - Hilton B. de Aguiar, Joshua D. McGraw, and Stephen H. Donaldson Jr.
Langmuir - 35(48) 15543–15551 - doi.org/10.1021/acs.langmuir.9b01889 - 2020
Modern interfacial science is increasingly multidisciplinary. Unique insight into interfacial interactions requires new multimodal techniques for interrogating surfaces with simultaneous complementary physical and chemical measurements. Here, we describe the design and testing of a microscope that incorporates a miniature surface forces apparatus (μSFA) in sphere vs flat geometry for force–distance measurements, while simultaneously acquiring Raman spectra of the confined zone. The simple optical setup isolates independent optical paths for (i) the illumination and imaging of Newton’s rings and (ii) Raman scattering excitation and efficient signal collection. We benchmark the methodology by examining Teflon thin films in asymmetric (Teflon–water–glass) and symmetric (Teflon–water–Teflon) configurations. Water is observed near the Teflon–glass interface with nanometer-scale sensitivity in both the distance and Raman signals. We perform chemically resolved, label-free imaging of confined contact regions between Teflon and glass surfaces immersed in water. Remarkably, we estimate that the combined approach enables vibrational spectroscopy with single water monolayer sensitivity within minutes. Altogether, the Raman-μSFA allows exploration of molecular confinement between surfaces with chemical selectivity and correlation with interaction forces.
Multimodal Miniature Surface Forces Apparatus (μSFA) for Interfacial Science Measurements
Laboratoire INDYSOFT - Kai Kristiansen, Stephen H. Donaldson Jr., Zachariah J. Berkson, Jeffrey Scott, Rongxin Su, Xavier Banquy, Dong Woog Lee, Hilton B. de Aguiar, Joshua D. McGraw, George D. Degen, and Jacob N. Israelachvili
Langmuir - 35(48) 15500–15514 - doi.org/10.1021/acs.langmuir.9b01808 - 2020
Advances in the research of intermolecular and surface interactions result from the development of new and improved measurement techniques and combinations of existing techniques. Here, we present a new miniature version of the surface forces apparatus—the μSFA—that has been designed for ease of use and multimodal capabilities with the retention of the capabilities of other SFA models including accurate measurements of the surface separation distance and physical characterization of dynamic and static physical forces (i.e., normal, shear, and friction) and interactions (e.g., van der Waals, electrostatic, hydrophobic, steric, and biospecific). The small physical size of the μSFA, compared to previous SFA models, makes it portable and suitable for integration into commercially available optical and fluorescence light microscopes, as demonstrated here. The large optical path entry and exit ports make it ideal for concurrent force measurements and spectroscopy studies. Examples of the use of the μSFA in combination with surface plasmon resonance (SPR) and Raman spectroscopy measurements are presented. Because of the short working distance constraints associated with Raman spectroscopy, an interferometric technique was developed and applied to calculate the intersurface separation distance based on Newton’s rings. The introduction of the μSFA will mark a transition in SFA usage from primarily physical characterization to concurrent physical characterization with in situ chemical and biological characterization to study interfacial phenomena, including (but not limited to) molecular adsorption, fluid flow dynamics, the determination of surface species and morphology, and (bio)molecular binding kinetics.
Time dependence of advection-diffusion coupling for nanoparticle ensembles
Laboratoire INDYSOFT - Alexandre Vilquin Vincent Bertin Pierre Soulard Gabriel Guyard Elie Raphaël Frederic Restagno Thomas Salez Joshua Mcgraw
HAL - 1 - https://hal.archives-ouvertes.fr/hal-02896493 - 2020
Particle transport in fluids at micro-and nano-scales is important in many domains. As compared to the quiescent case, the time evolution of particle dispersion is enhanced by coupling: i) advection along the flow; and ii) diffusion along the associated velocity gradients. While there is a well-known, long-time limit for this advection-diffusion enhancement, understanding the short-time limit and corresponding crossover between these two asymptotic limits is less mature. We use evanescent-wave video microscopy for its spatio-temporal resolution. Specifically, we observe a near-surface zone of where the velocity gradients, and thus dispersion, are the largest within a simple microfluidic channel. Supported by a theoretical model and simulations based on overdamped Langevin dynamics, our experiments reveal the crossover of this so-called Taylor dispersion from short to long time scales. Studying a range of particle size, viscosity and applied pressure, we show that the initial spatial distribution of particles can strongly modify observed master curves for short-time dispersion and its crossover into the long-time regime.
Influence of outer-layer finite-size effects on the dewetting dynamics of a thin polymer film embedded in an immiscible matrix
Laboratoire INDYSOFT - M. S. Chebil,a J. D. McGraw, T. Salez, C. Sollogoub and G. Miquelard-Garnier
Soft Matter - 14 6256-6263 - doi.org/10.1039/C8SM00592C - 2020
In capillary-driven fluid dynamics, simple departures from equilibrium offer the chance to quantitatively model the resulting relaxations. These dynamics in turn provide insight on both practical and fundamental aspects of thin-film hydrodynamics. In this work, we describe a model trilayer dewetting experiment elucidating the effect of solid, no-slip confining boundaries on the bursting of a liquid film in a viscous environment. This experiment was inspired by an industrial polymer processing technique, multilayer coextrusion, in which thousands of alternating layers are stacked atop one another. When pushed to the nanoscale limit, the individual layers are found to break up on time scales shorter than the processing time. To gain insight on this dynamic problem, we here directly observe the growth rate of holes in the middle layer of the trilayer films described above, wherein the distance between the inner film and solid boundary can be orders of magnitude larger than its thickness. Under otherwise identical experimental conditions, thinner films break up faster than thicker ones. This observation is found to agree with a scaling model that balances capillary driving power and viscous dissipation with a no-slip boundary condition at the solid substrate/viscous environment boundary. In particular, even for the thinnest middle-layers, no finite-size effect related to the middle film is needed to explain the data. The dynamics of hole growth is captured by a single master curve over four orders of magnitude in the dimensionless hole radius and time, and is found to agree well with predictions including analytical expressions for the dissipation.
Adsorption-induced slip inhibition for polymer melts on ideal substrates
Laboratoire INDYSOFT - Mark Ilton, Thomas Salez, Paul D. Fowler, Marco Rivetti, Mohammed Aly, Michael Benzaquen, Joshua D. McGraw, Elie Raphaël, Kari Dalnoki-Veress & Oliver Bäumchen
Nat Commun - 9 1172 - doi.org/10.1039/C8SM00592C - 2020
Hydrodynamic slip, the motion of a liquid along a solid surface, represents a fundamental phenomenon in fluid dynamics that governs liquid transport at small scales. For polymeric liquids, de Gennes predicted that the Navier boundary condition together with polymer reptation implies extraordinarily large interfacial slip for entangled polymer melts on ideal surfaces; this Navier-de Gennes model was confirmed using dewetting experiments on ultra-smooth, low-energy substrates. Here, we use capillary leveling—surface tension driven flow of films with initially non-uniform thickness—of polymeric films on these same substrates. Measurement of the slip length from a robust one parameter fit to a lubrication model is achieved. We show that at the low shear rates involved in leveling experiments as compared to dewetting ones, the employed substrates can no longer be considered ideal. The data is instead consistent with a model that includes physical adsorption of polymer chains at the solid/liquid interface.
Self-Similar Relaxation of Confined Microfluidic Droplets
Laboratoire INDYSOFT - Margaux Kerdraon1, Joshua D. McGraw1, Benjamin Dollet2, and Marie-Caroline Jullien
Phys. Rev. Lett. - 123 024501 - doi.org/10.1103/PhysRevLett.123.024501 - 2020
We report an experimental study concerning the capillary relaxation of a confined liquid droplet in a microscopic channel with a rectangular cross section. The confinement leads to a droplet that is extended along the direction normal to the cross section. These droplets, found in numerous microfluidic applications, are pinched into a peanutlike shape thanks to a localized, reversible deformation of the channel. Once the channel deformation is released, the droplet relaxes back to a pluglike shape. During this relaxation, the liquid contained in the central pocket drains towards the extremities of the droplet. Modeling such viscocapillary droplet relaxation requires considering the problem as 3D due to confinement. This 3D consideration yields a scaling model incorporating dominant dissipation within the droplet menisci. As such, the self-similar droplet dynamics is fully captured.
Natural Abundance Oxygen-17 Solid-State NMR of Metal Organic Frameworks Enhanced by Dynamic Nuclear Polarization
Laboratoire Institut des Matériaux Poreux de Paris - Carnevale D, Mouchaham G, Wang S, Baudin M, Serre C, Bodenhausen G, Abergel D
ChemRxiv - - DOI: 10.26434/chemrxiv.12477449.v1 - 2020
The 17O resonances of Zirconium-oxo clusters that can be found in porous Zr carboxylate metal-organic frameworks (MOFs) have been investigated by magic-angle spinning (MAS) NMR spectroscopy enhanced by dynamic nuclear polarization (DNP). High-resolution 17O spectra at 0.037 % natural abundance could be obtained in 48 hours, thanks to DNP enhancement of the 1H polarization by factors e(1H) = Swith/Swithout = 28, followed by 1H®17O cross-polarization, allowing a saving in experimental time by a factor of ca. 800. The distinct 17O sites from the oxo-clusters can be resolved at 18.8 T. Their assignment is supported by density functional theory (DFT) calculations of chemical shifts and quadrupolar parameters.
One‐step versatile room temperature synthesis of metal(IV) carboxylate MOFs
Laboratoire Institut des Matériaux Poreux de Paris - Shan Dai, Farid Nouar, Sanjun Zhang, Antoine Tissot, and Christian Serre
Angew. Chem. Int. Ed - - : https://doi.org/10.1002/anie.202014184 - 2020
This manuscript has been accepted after peer review and appears as an Accepted Article online prior to editing, proofing, and formal publication of the final Version of Record (VoR). This work is currently citable by using the Digital Object Identifier (DOI) given below. The VoR will be published online in Early View as soon as possible and may be different to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published to ensure accuracy of information. The authors are responsible for the content of this Accepted Article.
Principal Component Analysis (PCA) for Powder Diffraction Data: Towards Unblinded Applications
Laboratoire Institut des Matériaux Poreux de Paris - Shan Dai, Farid Nouar, Sanjun Zhang, Antoine Tissot, and Christian Serre
Angew. Chem. Int. Ed - - doi.org/10.1002/anie.202014184 - 2020
The development of room temperature green syntheses of robust MOFs is of great interest to meet the demand of the sustainable chemistry and is a pre‐requisite for the incorporation of functional but fragile compounds in water stable MOFs. However, only few ambient conditions routes to produce metal(IV) based MOFs have been reported and most of them suffer from a very low yield and/or multiple steps that preclude their use for most applications. We report here a new versatile one‐step synthesis of a series of highly porous M 6 oxoclusters based MOFs (M= Zr, Hf, Ce) at room temperature, including 8 or 12‐connected micro/mesoporous solids with different functionalized organic ligands. The resulting compounds show varying degrees of defectivity, particularly for 12‐connected phases, while maintaining the chemical stability of the parent MOFs. We propose first insights for the efficient MOF preparation based on In‐situ kinetics observations. Remarkably, the synthetic versatility not only allows an efficient room temperature synthesis with a high space‐time yield, but also gives possibility to tune the particle size, which therefore paves the way for their practical use.
Principal Component Analysis (PCA) for Powder Diffraction Data: Towards Unblinded Applications
Laboratoire Institut des Matériaux Poreux de Paris - Dmitry Chernyshov, Iurii Dovgaliuk, Vadim Dyadkin and Wouter van Beek
CRYSTALS - 10 7 - https://doi.org/10.3390/cryst10070581 - 2020
We analyze the application of Principal Component Analysis (PCA) for untangling the main contributions to changing diffracted intensities upon variation of site occupancy and lattice dimensions induced by external stimuli. The information content of the PCA output consists of certain functions of Bragg angles (loadings) and their evolution characteristics that depend on external variables like pressure or temperature (scores). The physical meaning of the PCA output is to date not well understood. Therefore, in this paper, the intensity contributions are first derived analytically, then compared with the PCA components for model data; finally PCA is applied for the real data on isothermal gas uptake by nanoporous framework γ –Mg(BH 4 ) 2 . We show that, in close agreement with previous analysis of modulation diffraction, the variation of intensity of Bragg lines and the displacements of their positions results in a series of PCA components. Every PCA extracted component may be a mixture of terms carrying information on the average structure, active sub-structure, and their cross-term. The rotational ambiguities, that are an inherently part of PCA extraction, are at the origin of the mixing. For the experimental case considered in the paper, the extraction of the physically meaningful loadings and scores can only be achieved with a rotational correction. Finally, practical recommendations for non-blind applications, i.e., what boundary conditions to apply for the the rotational correction, of PCA for diffraction data are given.
Non-Isothermal Kinetics of Kr Adsorption by Nanoporous γ-Mg(BH4)2 from in Situ Synchrotron Powder Diffraction
Laboratoire Institut des Matériaux Poreux de Paris - Iurii Dovgaliuk*, Vadim Dyadkin, Mathieu Vander Donckt, Yaroslav Filinchuk*, and Dmitry Chernyshov
ACS Publications - 12(6) 7710–7716 - https://doi.org/10.1021/acsami.9b19239 - 2020
Crystalline materials with pore dimensions comparable to the kinetic diameters of the guest molecules are attractive for their potential use in adsorption and separation applications. The nanoporous γ-Mg(BH4)2 features one-dimensional channels matching this criterion for Kr uptake, which has been probed using synchrotron powder diffraction at various pressures and temperatures. It results in two coexisting crystalline phases with the limiting composition Mg(BH4)2·0.66Kr expecting the highest Kr content (50.7 wt % in the crystalline phase) reported for porous materials. Quasi-equilibrium isobars built from Rietveld refinements of Kr site occupancies were rationalized with a noncooperative lattice gas model, yielding the values of the thermodynamic parameters. The latter were independently confirmed from Kr fluorescence. We have also parameterized the pronounced kinetic hysteresis with a modified mean-field model adopted for the Arrhenius kinetics.
Factors Determining Microporous Material Stability in Water: The Curious Case of SAPO-37
Laboratoire Institut des Matériaux Poreux de Paris - Georgios N. Kalantzopoulos, Fredrik Lundvall, Knut Thorshaug, Anna Lind, Ponniah Vajeeston, Iurii Dovgaliuk, Bjørnar Arstad, David S. Wragg, and Helmer Fjellvåg
ACS Publications - 32(4) 1495–1505 - https://doi.org/10.1021/acs.chemmater.9b04510 - 2020
Silicoaluminophosphates (SAPOs) are a special class of zeolites that, due to their acidic and shape-selective properties, play a major role in ion exchange and separation processes and in crude oil cracking. SAPO-37 has the faujasite (FAU) topology same as zeolites X and Y, which are involved in more than 40% of the total crude oil conversion worldwide. A critical parameter that promotes detrimental structural transformations in SAPOs during real-life applications is the presence of humidity. In this study, we employ a multidisciplinary approach combining in situ synchrotron radiation powder X-ray diffraction (SR-PXRD), water adsorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) calculations to describe the mechanism and reveal the reasons why SAPO-37 collapses upon contact with humidity below 345 K. SR-PXRD revealed that the sodalite (SOD) cages (subunits of the FAU structure) have the strongest affinity to water during hydration below 345 K. Furthermore, below 345 K, the faujasite framework takes up an order of magnitude more water molecules than at temperatures above 345 K. DRIFTS confirmed the presence of Si–OH and P–OH surface structural defects that act as hydration centers, accelerating the loss of a long-range order. Finally, DFT calculations showed that the enthalpy of water adsorption in the sodalite cage and the faujasite supercage is −212 and −13 kJ/mol, respectively. The results presented in this work are highly topical for understanding the effect of water on the frameworks of the SAPO microporous catalysts family. The notorious instability of SAPO-37 is the result of the accumulative contribution of topological, physical, and chemical effects, leading to an array of rapidly evolving cascading effects. Our work shows how advancements in SR-PXRD methodology and hardware give new insight into highly dynamic features previously difficult to observe. In addition, this work introduces the conceptual insight that nonhomogeneous sorption of molecular species will induce dynamic features with dramatic consequences at both molecular and atomic levels. This is a highly impactful factor opening research paths for further work within catalysis, porous material design and chemistry, and sorption reactions and processes.
Metal-organic magnets with large coercivity and ordering temperatures up to 242°C
Laboratoire Institut des Matériaux Poreux de Paris - Panagiota Perlepe, Itziar Oyarzabal, Aaron Mailman4, Morgane Yquel, Mikhail
Science - 370(6516) 587-592 - DOI: 10.1126/science.abb3861 - 2020
Permanent magnets are generally produced from solid metals or alloys. Less dense compositions involving lighter elements tend to demagnetize well below room temperature or under modest applied external fields. Perlepe et al. now report that chemical reduction of a low-density chromium-pyrazine network produces a magnet that remains stable above 200°C and resists demagnetization with 7500-oersted coercivity at room temperature. The straightforward synthetic route to the material shows promise for broad exploration of potential applications.

583 publications.