Layered double hydroxides (LDHs) are fascinating clay-like materials that display versatile properties, making them an extremely fertile playground for diverse applications, ranging from bio-compatible materials to the pharmaceutical industry to catalysis and photocatalysis. When intercalating organic and bio-organic species between the inorganic layers, such materials are named hybrid LDHs. The structure–property relation in these systems is particularly relevant, since most of the properties of the materials may be fine-tuned if a comprehensive understanding of the microscopic structure in the interlamellar space is achieved, especially with respect to the reorganization under water uptake (swelling). In this work, we combined experiments and simulations to rationalize the behavior of LDHs intercalating three carboxylates, the general structure of which can be given as [Mg4Al2(OH)12]A2−·XH2O (with A2− = succinate, aspartate, or glutamate and X representing increasing water content). Following this strategy, we were able to provide an interpretation of the different shapes observed for the experimental water adsorption isotherms and for the evolution of the infrared carboxylate band of the anions. Apart from small differences, due to the different reorganization of the conformational space under confinement, the behavior of the two amino acids is very similar. However, such behavior is quite different in the case of succinate. We were able to describe the different response of the anions, which has a significant impact on the isotherm and on the size of the interlamellar region, in terms of a different interaction mechanism with the inorganic layer.

A vertical-flow unit containing four filters filled with shale was used to study the removal of phosphorous, nitrogen and organic matter of an urban residual wastewater during a period of 90 days. The influence of both the shale granulometry and the plant density of Panicum Maximum were studied. The decrease of the shale granulometry led to a significant improvement of all the measured parameters, while the presence of plants did only influence the phosphate retention with a lower extent. By comparing the results to previous studies, we hypothesised that the effect of the root system of Panicum maximum would be different depending on the size and the depth of the reactors. For practical application, adjusting the material granulometry was proposed to be the most important parameter for improving the filtration efficiency. Concomitantly, adjusting the plant density helps to control the clogging percentage of the filters.

Synchrotron radiation near ambient pressure X-ray photoemissionspectroscopy (SR NAP-XPS) has been an invaluable tool for examininggas/liquid and liquid/solid interfaces. Despite its benefits, concernshave emerged regarding beam damage in NAP-XPS experiments, particularlyinvolving condensed liquid water, because of the high dose rates,greater than 10(5) Gy & BULL;s(-1). This studyinvestigates the radiolytic effects on the chemistry of concentratedNaX sodium halide solutions (X = Cl, Br, I) and Mg-Cl solutionformed over the layered double hydroxide [Mg2Al(OH)(6)](+)[Cl-]. The formation of oxidizedspecies XO- as the radiolytic end product undersoft X-ray irradiation is discussed in detail. We examine the impactof known parameters (such as the dose rate) on the abundance of XO-. The observed scatter in the data likely arises fromstill unrecognized or insufficiently controlled parameters (such assolute concentration or solution hydrodynamics). Deciphering theseradiolytic effects in halide solutions allows us to propose guidelinesfor their better identification, understanding and control, ultimatelyimproving the reliability of synchrotron NAP-XPS analysis for interfacesrelevant to environmental chemistry and electrochemistry.

Layered double hydroxides, shortly LDH, are commonly used in medical applications, particularly in human therapies for their abilities to sorb and/or entrap, and then release active drugs. In this work, we synthesized several original LDH nanocarriers that strictly host antibiotics into their interlayer space and can be used for antimicrobial purpose. Combining Infrared and XRD analyses, we evidenced the total antibiotic intercalation within the nanocarriers. Our results also highlighted the high stability of synthesized LDH in solution and particularly in rich nutritive medium used as surrogate for biological media. According to our microbial toxicity assays, we demonstrated that the antibacterial activity of LDH was purely bacteriostatic in absence of hosted biocides molecules. Besides, we observed an additive effect in LDH antibacterial activity when antibiotics were hosted and released from these nanocarriers. The use of LDH as nanocarriers for the delivery of antimicrobial agents should be of major interest in antimicrobial purpose as they offer the possibility to be recycled and reloaded with antimicrobial agents after total release.

For several decades now, modulating and controlling the mechanical properties of hydrogels, and in particular exponentially growing polyelectrolyte multilayer films (PEMs), have been a major challenge, given their importance in a wide range of applications, including tissue engineering, implantable biomaterials, and drug delivery systems. In this work, we compared the cross-linking reaction of hydrogels based on the association of poly(allylamine) (PAH) and hyaluronic acid (HA) with either 1,4-butanediol diglycidyl ether (BDDE) or divinyl sulfone (DVS) at different concentrations. On the basis of infrared data analysis by means of a chemometric method, we demonstrated that the cross-linking reaction led to significant changes in their chemical features. We deciphered how the affinity of each cross-linker to alcohol and amino chemical functions drives the chemical features of the PEMs. These features can be described by a linear combination of pure HA-BDDE, PAH-BDDE or HA-DVS, and PAH-DVS-based hydrogels with ratios of 80 and 16% for the BDDE and 55 and 45% for the DVS reactions, respectively. Furthermore, the mechanical properties resulting from the BDDE cross-linking reaction were consistent with a high mechanical contribution of HA-BDDE, as estimated by the chemometric analysis. However, this linear combination cannot be applied for DVS. Indeed, the cross-linked PEM was softer than expected, regarding the chemical contributions of HA-DVS and PAH-DVS. Our results show that it is possible to control the mechanical and chemical features by the choice of the cross-linkers alone or in a mixture.

The hydration of [Mg2Al(OH)6]+[Cl-, yH2O] LDH was investigated by volumetric water adsorption, X-ray diffraction, Fourier Transformed Infrared (FTIR) sepctroscopy, and Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS). It was demonstrated that water uptake into interlayer region can be quantified by NAP-XPS. The LDH's electronic structure is assessed for increasing relative humidity (RH) up to 0.044. The Cl 2p level appears essentially unaffected by water uptake, but as supported by DFT calculation, H-bonds between chloride and water induce Cl 3p orbitals splitting. At RH = 0.7, LDH is covered by a water film that contains Mg and Cl species but no Al. Soft X-ray radiolysis of hydrated Cl species induces the formation of oxidized Cl species.

The aim of this work is to investigate the consequences of lattice distortion on the vibrational features of rare-earth perovskites. To this end, a series of REMO3 compounds has been synthesized with different rare earths (RE = La, Pr, Nd, Sm) and different transition metals (M = Fe, Co) to evaluate their respective role on lattice distortion. Thin films of these materials have been deposited by magnetron cosputtering in the reactive mode and followed by annealing in air with the same experimental conditions. Characterizations including energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy have been completed by density functional theory periodic calculations to investigate the octahedra tilt angles and to assign the vibrational spectra. The decrease of RE radius enhances the distortion of the chains of octahedra that can be followed both through the calculated mean tilt angle and experimentally by the profile of the M-O-M bending region. The magnitude of the distortion depends on the dimension of the cuboctahedric site hosting the RE that is controlled by the M radius.

This paper reports on the first study of the chemical, optical, and structural properties of lanthanum ferrite oxynitride thin films deposited by reactive magnetron sputtering. The thin films were deposited in an Ar/O-2/N-2 mixture as reactive plasma, from two elemental La and Fe targets, at a room and high temperature (25 and 800 degrees C). The films deposited at room temperature are amorphous and have been flash annealed to crystallize the perovskite. The oxynitride properties were investigated and compared to the oxide films deposited in Ar/O-2 gas mixture. All the oxide and oxynitride films present an orthorhombic structure. However, the nitrogen doping is limited to 1-1.5% and leads to the lattice expansion (4%), the bandgap narrowing, a lower electrical resistivity in range [25-350 degrees C], and a modification of Infrared and Raman spectra. Electron Energy Loss Spectroscopy measurements clearly show the presence of two nitrogen sites with an "active" intra-granular nitrogen associated to a variation of the physical properties. (C) 2017 Elsevier B.V. All rights reserved.

Carbonated layered double hydroxides were fully characterized by vibrational spectroscopies, powder X-ray diffraction and solid-state NMR tuning the cations, the layer charge density, and the preparation method to get original structural and dynamical features within the materials. It clearly appears that carbonate and hydrogenocarbonate coexist in the same interlayer after contact with air and also that the hydrogenocarbonate quantity is correlated to the MII/MIII molar ratio constituting a strong pH probe of the interlayer space. Likewise, these two species are involved in an exchange process with atmospheric carbon dioxide, and hydrogenocarbonate proves to be the key parameter of exchange kinetics. These crucial results, extended to various cationic couples, could lead to new alternatives for carbon dioxide storage.

Co-, Cu-substituted ZnAl ternary layered double hydroxides (LDHs) were synthesized and explored as efficient photocatalysts for dye degradation. LDH materials were fully characterized with various methods including elemental analysis, X-ray diffraction, infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, which revealed that LDH materials were well crystallized without any amorphous phase as impurity. In addition, the plates of LDH were well dispersed, one plate being easily distinguished from another plate, and their size could also be controlled by varying the Co, Cu substitution ratio. As an application, the adsorption characteristics and photocatalytic degradation of orange II, a model pollutant, were investigated. In particular, Co-substituted LDHs exhibit an excellent photocatalytic activity with the optimal Co/Zn substitution ratio of 1:3. Interestingly, LDH materials having a higher ratio didn't show any improvement of the photocatalytic activity, suggesting that the amount of Zn is the crucial factor. Furthermore, the photocatalytic performance of Zn1.5Co0.5Al1 (Co/Zn = 1:3) was compared with other materials such as metal oxides prepared by heat or microwave treatment, and the result could prove the efficiency of LDH materials of this work. Therefore, Co, Cu substitution in ZnAl ternary LDHs could be a straightforward approach for designing efficient photocatalysts with various potential applications such as the remediation of wastewater.

Cu, Co doped mixed metal oxides (MMOs) were synthesized from their ternary layered double hydroxides (LDHs) precursors, ZnCu(or Co)Al-CO3 via simple calcination at different temperatures. Interestingly, MMO prepared at 400 degrees C (MMOs-400) showed only weakly crystallized ZnO phase, suggesting that other metals such as Al, Cu(or Co) remain as amorphous phase around ZnO nanoparticles. Moreover, by increasing Cu(or Co) substitution content into ZnAl-LDHs framework, the amorphous phase on the surface of MMOs was clearly observed as 'hole'-like structure by transmission electron microscopy (TEM). This amorphous phase composed of Co(or Cu) Al would play a crucial role, as doping agent of ZnO, in the improvement of photocatalytic ability towards orange II degradation, as only MMOs-400 showed significantly fast degradation rate. However, no meaningful improvement was observed for MMOs-600 or 800 that contain lower amounts of amorphous phase. Furthermore, the optimal substitution ratio of Zn/Cu(or Co) was also found to be of 19 (Zn1.9Cu0.1Al1-400), giving the best performance for dye degradation. Therefore, this report would provide a facile approach for the synthesis of efficient photocatalysts based on LDHs and their MMOs.

Due to their good chemical and thermal inertness, SiCxNy:H films are suitable for a variety of applications in electronic, tribology, optic, photovoltaic and more recently gas separation membranes. For these applications, film evolution can be attractively probed by FTIR spectroscopy. In this work, a systematic quantum mechanical study of the vibrational modes position in the pattern of a-SiCxNy(O):H is presented. Vibrational frequencies of SiC, SiN, CN, SiH, CH and NH moieties have been calculated at DFT/B3LYP level of theory using the 6-311++G(3df,3pd) basis set. Characteristic absorption domains have been compared with FTIR data from the literature. In particular, DFT calculations provide guidelines to discriminate SiH from CN stretching bands, which are calculated to lie below and above ~2230cm−1, respectively. As an example, the oxidation of a microwave PECVD SiCxNy:H films during ageing was evidenced in this work through the progressive increase of SiO stretching band (~1040cm−1). The simultaneous decay of the band centered at 2170cm−1 was attributed to the vanishing of SiH bond upon oxidation. This example illustrates that unambiguous band assignment is required to provide a molecular description of the ageing process, which is in turn required to optimize the material composition and stability. Results of these calculations will be helpful to identify both the chemical moieties and their environment in future investigations on a-SiCxNy:H materials but also on materials containing additional elements such as B- or O-doped SiCN-based systems.

In order to shed light,on molecular dynamics and structure in layered materials, (27)AI NMR spectra of layered double hydroxides (LDHs) were investigated by varying the layer charge density, the cations of the sheets, the interlayer anions, the hydration state, and the temperature. This study reveals that most of the broadening of (27)AI satellite transitions in LDHs is due to dynamics within the interlayer space rather than the chemical environment of (27)AI in the sheets, i.e., cation disorder. This finding provides a new solid-state NMR tool to probe dynamics in aluminum-bearing layered materials which does not require tensor calculations, which is based on direct acquisition spectra and which provides long-range information as the (27)AI spectra are sensitive to dynamics that occur 3-5 angstrom away from the observed nuclei.

Remarkable mechanical and structural properties of out-of equilibrium poly(diallyldimethylammonium chloride) (PDADMAC)-poly(acrylic acid) (PAA) multilayer films are elucidated from in situ atomic force microscopy and spatially resolved Raman spectroscopy analyses complemented by density functional theory (DFT) computations. Surprisingly, fresh exponentially grown (PDADMAC-PAA)(n) polyelectrolyte films behave as glassy materials with Young moduli as large as 2 MPa. Their organization is governed by a competition between PDADMAC-PAA electrostatic interactions and water stabilization of PAA charges that limits association between polycationic and polyanionic chains. At pH 3 where PAA is weakly deprotonated, this competition leads to the formation of water-free PDADMAC-PAA polyelectrolyte complexes within well-defined donut-like structures (2-12 mu m in diameter, 100-200 nm in height) that confer upon the film a mechanical rigidity comparable to that classically achieved for linearly growing films. The relaxation of (PDADMAC-PAA)(n) films to equilibrium occurs over 5 days and is marked by a gradual disappearance of all donut-like structures, resulting in a 3-fold decrease of the Young modulus. This mechanical softening of the film is significantly accelerated by increasing the diffusion rate of PDADMAC and PAA chains upon heating: the morphological and mechanical features of the 5-day old, naturally aged films are recovered after 2 h heating treatment at 60 degrees C. In combination, this invokes a transition from intrinsic to extrinsic film charge compensation; i.e., the tightly compacted polyelectrolyte complexes progressively change to coacervates that are loosely associated by electrostatics. It is shown that such atypical structure transition of exponentially grown films can be used for reversible laser-assisted printing applications at microscales.

Co(2+) and Cu(2+) substituted MgAl layered double hydroxides with an M(2+)/M(3+) atomic ratio of 2.0 were synthesized by a co-precipitation method and fully characterized using various techniques including powder X-ray diffraction, ICP-AES analysis, FT-IR, DR UV-Vis spectroscopy, N2 adsorption-desorption and transmission electron microscopy. The materials revealed a good crystallinity with no phase impurity and successful substitution of cobalt and copper ions in the framework of binary LDH with the target ratio of metals in the sheet. The adsorption characteristics (kinetic and isotherm) and the catalytic oxidation of organic pollutants, methylene blue (cationic dye) and orange II (anionic) were carried out to investigate a potential use of LDH materials as catalysts. In particular, Co3Cu1Al2 LDH exhibited an excellent catalytic activity towards catalytic dye degradation, especially for orange II with good stability and reusability over several times. Furthermore, this LDH material showed good catalytic performance for several chlorophenol compounds, suggesting its practical application in wastewater treatment. Therefore, layered double hydroxides substituted with Co(2+) and Cu(2+) could be promising candidates in various applications, such as the abatement of organic pollutants.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMolecular Sieving with Vertically Aligned Mesoporous Silica Films and Electronic Wiring through Isolating NanochannelsNeus Vilà†, Erwan André†, Roberto Ciganda‡, Jaime Ruiz‡, Didier Astruc*‡, and Alain Walcarius*†View Author Information† Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS-Université de Lorraine, 405 rue de Vandoeuvre, 54600 Villers-les-Nancy, France‡ Institut des Sciences Moléculaires (ISM), UMR 5255, CNRS − Université de Bordeaux, 33405 Talence, Cedex, France*(D.A.) E-mail: [email protected]*(A.W.) E-mail: [email protected]Cite this: Chem. Mater. 2016, 28, 8, 2511–2514Publication Date (Web):April 4, 2016Publication History Received23 February 2016Revised4 April 2016Published online7 April 2016Published inissue 26 April 2016https://pubs.acs.org/doi/10.1021/acs.chemmater.6b00716https://doi.org/10.1021/acs.chemmater.6b00716rapid-communicationACS PublicationsCopyright © 2016 American Chemical SocietyRequest reuse permissionsArticle Views1596Altmetric-Citations59LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Dendrons,Electrodes,Sandwich compounds,Silica,Thin films Get e-Alerts

The ease of preparation as well as the fine tuning of their chemical composition makes layered double hydroxides (LDH) very attractive for a large variety of applications. The aim of this feature article is to provide the keys that permit to finely tune the structure of the materials in controlling simple parameters involved in the synthesis procedures. In a first part, the influence of the synthesis parameters on the crystallinity and morphology of MII-FeIII LDH (MII = NiII, MgII and CoII) is studied. In a second part, further insight into the variability of composition of the layer is proposed to explain the interdependence between the cationic nature of the layer and its layer charge flexibility. The third part is devoted to the anion exchange property of LDH. We showed that a previously proposed method for anionic exchange can be successfully applied to all couple of cations in their range of composition. Finally, a molecular description of the interlayer organisation is given. Keywords: Anionic exchange, layered double hydroxide, structure, synthesis, vibrational spectroscopies.

This chapter contains sections titled: Introduction Experimental Details Computational Details Construction and Validation of the Model Vibrational Spectra Conclusion