Interleaved Electroactive Molecules into LDH Working on Both Electrodes of an Aqueous Battery-Type Device.

By selecting two electroactive species immobilized in a layered double hydroxide backbone (LDH) host, one able to act as a positive electrode material and the other as a negative one, it was possible to match their capacity to design an innovative energy storage device. Each electrode material is based on electroactive species, riboflavin phosphate (RF) on one side and ferrocene carboxylate (FCm) on the other, both interleaved into a layered double hydroxide (LDH) host structure to avoid any possible molecule migration and instability. The intercalation of the electroactive guest molecules is demonstrated by X-ray diffraction with the observation of an interlayer LDH spacing of about 2 nm in each case. When successfully hosted into LDH interlayer space, the electrochemical behavior of each hybrid assembly was scrutinized separately in aqueous electrolyte to characterize the redox reaction occurring upon cycling and found to be a rapid faradic type. Both electrode materials were placed face to face to achieve a new aqueous battery (16C rate) that provides a first cycle-capacity of about 7 mAh per gram of working electrode material LDH/FCm at 10 mV/s over a voltage window of 2.2 V in 1M sodium acetate, thus validating the hybrid LDH host approach on both electrode materials even if the cyclability of the assembly has not yet been met.

Olive Mill Wastewater Valorization in Multifunctional Biopolymer Composites for Antibacterial Packaging Application.

Olive mill wastewater (OMW) is the aqueous waste derived from the production of virgin olive oil. OMW typically contains a wide range of phenol-type molecules, which are natural antioxidants and/or antibacterials. In order to exploit the bioactive molecules and simultaneously decrease the environmental impact of such a food waste stream, OMW has been intercalated into the host structure of ZnAl layered double hydroxide (LDH) and employed as an integrative filler for the preparation of poly(butylene succinate) (PBS) composites by in situ polymerization. From the view point of the polymer continuous phase as well as from the side of the hybrid filler, an investigation was performed in terms of molecular and morphological characteristics by gel permeation chromatography (GPC) and X-ray diffraction (XRD); also, the thermal and mechanical properties were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic thermomechanical analysis (DMTA). Antibacterial properties have been assessed against a Gram-positive and a Gram-negative bacterium, Staphylococcus aureus and Escherichia coli, respectively, as representatives of potential agents of foodborne illnesses.

Efficient Microwave-Assisted Functionalization of the Aurivillius-Phase Bi2SrTa2O9.

A new method of acidification and subsequent functionalization of the Aurivillius-phase Bi2SrTa2O9 (BST), using microwave irradiation, was developed. This method enables to obtain hybridized phases from layered BST. Functionalization of BST by various kinds of amines and diamines can be achieved in a few hours only, compared to much longer time (over a week) using conventional heating. Good crystallinity of the compounds is kept. In addition, a microwave-assisted preintercalation strategy was developed, allowing inserting new amines (bearing cyclic or aromatic groups) between the oxide layers previously unseen in this type of compound. This work opens new perspectives for the fast and easy functionalization of layered oxides with more elaborated molecules.

Post-Synthesis Modification of the Aurivillius Phase Bi2SrTa2O9 via In Situ Microwave-Assisted "Click Reaction".

A new strategy for the functionalization of layered perovskites is presented, based on the in situ post-synthesis modification of a prefunctionalized phase by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC). The microwave-assisted protonation and grafting of an alkyne alcohol provides the alkyne-functionalized precursor within a few hours, starting from Bi2SrTa2O9. The subsequent microwave-assisted in situ "click reaction" allows the post-synthesis modification of the precursor within ∼2 h, providing a layered perovskite functionalized by an alcohol-grafted 1,4-disubstituted-1H-1,2,3-triazole. Two compounds are described here, bearing an aliphatic and an aromatic substituent, which illustrates the general application of the method. This work opens new perspectives for the functionalization of layered perovskites, going beyond mere insertion/grafting reactions, and thus broadens the design possibilities and the range of applications of these hybrid systems.

Efficient fluorinating agent through topochemical fluorination of Co-Fe layered double hydroxides.

Mixed-metal inorganic fluoride, Co0.60Fe0.40F3, solid solutions are obtained through topochemical reactions of Co2FeCl(OH)6·2H2O LDH with molecular fluorine, F2, at temperatures as low as 100 °C. This solid solution possesses interesting F(•)-releasing ability, and its efficiency as a solid-state fluorinating agent is demonstrated on a commercial polyethylene film. (19)F solid state NMR and contact angle measurements underline the efficient fluorination of this polymer.

Intimately mixed copper, cobalt, and iron fluorides resulting from the insertion of fluorine into a LDH template.

The advancement of lithium-ion batteries (LIBs) with high performance is crucial across various sectors, notably in space exploration. This advancement hinges on the development of innovative cathode materials. Our research is dedicated to pioneering a new category of cathodes using fluorinated multimetallic materials, with a specific focus on diverging from the traditional Ni, Co, and Mn-based NMC chemistries by substituting nickel and manganese with copper and iron which are more sustainable elements. Our goal is also to enhance the robustness of cathodes upon cycling by substituting oxygen with fluorine as the metal-ligand. To achieve this, an intimate composite blend of CuF2 and FeF3, through the multi-metallic template fluorination (MMTF) methodology using a layered double hydroxide (LDH) as a precursor has been designed. Each of these components was carefully selected for its distinct attributes, including high redox potential, elevated energy density, substantial theoretical capacity, and improved cyclability. The composition denoted as (Cu1.5Co0.5)2+(Fe0.75Al0.25)3+ has been selected for fluorination because it maximizes Fe3+ and Cu2+ amount in the screened LDHs. Subsequently, this particular LDH was fluorinated through solid-gas fluorination at different temperatures (200, 350, and 500 °C) using gaseous molecular fluorine (F2). A comprehensive characterization of these materials using various techniques, including X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and inductively coupled plasma analyses (ICP-AES) was conducted, and the evolution of LDH upon fluorination has revealed an intermediate porous texture particularly sensitive to hydration. Two original crystallographic phases are else obtained by fluorination: one formed by the hydration of the amorphous intermediate compound: Cu3Fe1.5Al0.5F12(H2O)12 an anti-perovskite structure and another stabilized through the combination of solid gas fluorination and LDH precursor yielding an original CoFeF5-type phase. Raman operando during cyclic voltammetry measurement applied on a sample fluorinated at 500 °C and used as a cathode in front of lithium metal was finally conducted to validate redox activity and mechanism.

Enhanced dispersion of prussian blue via intercalation into layered double hydroxides for efficient solar seawater evaporation.

Prussian blue (PB) is favored for its photothermal absorption capability in solar vapor generation applications. However, the photothermal conversion efficiency of current PB-based devices is limited by the material's poor dispersion. Herein, we report a method of incorporating PB in the interlayers of layered double hydroxides (LDHs) to prevent its aggregation. The dispersion is further enhanced and stabilized by the addition of sodium dodecyl sulfate (SDS). The thermal and water stability of PB is improved due to the rigid structure of LDHs and interactions between layers and anions. Elemental analysis confirms that with the increase of molar ratio of Mg/Al and the introduction of SDS, concentrations of PB are decreased accordingly. As a result, the rate of solar vapor generation is increased by 35.9% for powders containing 50 mg of equivalent PB. Of note, converting this material into a three-dimensional structure of high rebound foam further enhances solar water evaporation rate, from 0.79 kg m-2 h-1 to 0.98 kg m-2 h-1, with only 20 mg of equivalent PB, increasing the corresponding photothermal conversion efficiency from 53.8% to 66.3%.

A triazolium-based fluorophore intercalated in layered double hydroxides: from simple syntheses to bright solid-state luminescence.

This study presents the intercalation into Layered Double Hydroxides (LDHs) of two sulfonated organic molecules featuring the mesoionic triazolium scaffold. These sulfonated fluorophores exhibited excellent solubility in aqueous basic solutions, facilitating their compatibility with the synthesis of LDHs through coprecipitation methods. We applied the size-matching interlayer space (SMIS) approach by substituting a portion of a mono- or dianionic surfactant used in LDH preparation by the sulfonated fluorophore, we aimed to match the size of the luminescent interleaved guest effectively. Our investigation focused on two anion spacers: the classic monoanionic dodecyl sulfate (DS) and the dianionic phenylene dipropionate (PPA). Our results indicated that the latter spacer allowed a more efficient insertion of the fluorescent guest. Thermal resistance analysis underscored the robustness of the final hybrid materials, suggesting a promising design strategy for luminescent materials when applied in diverse applications.

Development of Dipeptide N-acetyl-L-cysteine Loaded Nanostructured Carriers Based on Inorganic Layered Hydroxides.

N-acetyl-L-cysteine (NAC), a derivative of the L-cysteine amino acid, presents antioxidant and mucolytic properties of pharmaceutical interest. This work reports the preparation of organic-inorganic nanophases aiming for the development of drug delivery systems based on NAC intercalation into layered double hydroxides (LDH) of zinc-aluminum (Zn2Al-NAC) and magnesium-aluminum (Mg2Al-NAC) compositions. A detailed characterization of the synthesized hybrid materials was performed, including X-ray diffraction (XRD) and pair distribution function (PDF) analysis, infrared and Raman spectroscopies, solid-state 13carbon and 27aluminum nuclear magnetic resonance (NMR), simultaneous thermogravimetric and differential scanning calorimetry coupled to mass spectrometry (TG/DSC-MS), scanning electron microscopy (SEM), and elemental chemical analysis to assess both chemical composition and structure of the samples. The experimental conditions allowed to isolate Zn2Al-NAC nanomaterial with good crystallinity and a loading capacity of 27.3 (m/m)%. On the other hand, NAC intercalation was not successful into Mg2Al-LDH, being oxidized instead. In vitro drug delivery kinetic studies were performed using cylindrical tablets of Zn2Al-NAC in a simulated physiological solution (extracellular matrix) to investigate the release profile. After 96 h, the tablet was analyzed by micro-Raman spectroscopy. NAC was replaced by anions such as hydrogen phosphate by a slow diffusion-controlled ion exchange process. Zn2Al-NAC fulfil basic requirements to be employed as a drug delivery system with a defined microscopic structure, appreciable loading capacity, and allowing a controlled release of NAC.

Folic acid and sodium folate salts: Thermal behavior and spectroscopic (IR, Raman, and solid-state 13C NMR) characterization.

Folic acid (FA; vitamin B9) and its associated sodium salts, strongly relevant for many scientific and technological applications - from nutrition to pharmacology and nanomedicine, suffer from a lack of characterization combining experimental and theoretical. In this work, a spectroscopic investigation of FA and its synthesized sodium salts in the form of dianion (Na2HFol) or trianion (Na3Fol) was scrutinized in their solid state. The spectroscopic (infrared, Raman, and solid state 13C-nuclear magnetic resonance) data interpretation was supported by theoretical calculations using the Density Functional Theory (DFT). Additionally, the compounds were characterized by UV-VIS diffuse-reflectance spectroscopy, combined thermal analysis (TG/DTG-DSC) coupled to mass spectrometry, and X-ray diffractometry. The main signatures of each species were identified, as well as the influence of the protonation level on their physicochemical properties. These distinct properties for the three compounds are mainly based on signals assigned to glutamic acid (glutamate) and pterin (neutral or anionic) moieties. This work should help developing new products based on FA or its anionic forms, such as theragnostic/drug delivery systems, supramolecular structures, nanocarbons, or metal complexes.

Fast and efficient shear-force assisted production of covalently functionalized oxide nanosheets.

HYPOTHESIS: While controlled and efficient exfoliation of layered oxides often remains a time consuming challenge, the surface modification of inorganic nanosheets is of outmost importance for future applications. The functionalization of the bulk material prior to exfoliation should allow the application of tools developped for Van der Waals materials to directly produce functionalized oxide nanosheets. EXPERIMENTS: The Aurivillius phase Bi2SrTa2O9 is functionalized by a linear aliphatic phosphonic acid via microwave-assisted reactions. The structure of the hybrid material and the coordination of the phosphonate group is scrutinized, notably by Pair Distribution Function. This functionalized layered oxide is then exfoliated in one hour in organic solvent, using high shear force dispersion. The obtained nanosheets are characterized in suspension and as deposits to check their chemical integrity. FINDINGS: The covalent functionalization decreases the electrostatic cohesion between the inorganic layers leading to an efficient exfoliation in short time under shearing. The functionalization of the bulk material is preserved on the nanosheets upon exfoliation and plays a major role to enable liquid-phase exfoliation and in the stability of the resulting suspensions. This strategy is very promising for the straighforward preparation of functionalized nanosheets, paving the way for versatile design of new (multi)functional hybrid nanosheets for various potential applications.

A First Wide-Open LDH Structure Hosting InP/ZnS QDs: A New Route Toward Efficient and Photostable Red-Emitting Phosphor.

The architecture of Zn-Al layered double hydroxides (LDHs), organo-modified with bola-amphiphiles molecules, is matching its interlayer space to the size of narrow-band red-emitting InP/ZnS core-shell quantum dots (QDs) to form original high-performance functional organic-inorganic QD-bola-LDH hybrids. The success of size-matching interlayer space (SMIS) approach is confirmed by X-ray diffraction, small angle X-ray scattering (SAXS), TEM, STEM-HAADF, and photoluminescence investigations. The QD-Bola-LDH hybrid exhibits a photoluminescence quantum yield three times higher than that of pristine InP/ZnS QDs and provides an easy dispersion into silicone-based resins, what makes the SMIS approach a change of paradigm compared to intercalation chemistry using common host structures. Moreover, this novel hybrid presents low QD-QD energy transfer comparable to that obtained for QDs in suspension. Composite silicone films incorporating InP/ZnS (0.27 wt%) QD-bola-LDH hybrids further show remarkable improved photostability relative to pristine QDs. An LED overlay consisting of a blue LED chip and silicone films loaded with QD-bola-LDH hybrids and YAG:Ce phosphors exhibits a color rendering index close to 94.

Recent Progress on Adsorption Materials for Phosphate Removal.

BACKGROUND: High concentration of phosphate has been threatening human health and the ecosystem. Adsorption is one of high-efficiency and low-cost techniques to reduce the concentration of phosphate. This mini review aims to summarize the recent development of adsorption materials for phosphate removal. METHOD: We conducted a detailed search of "adsorption of phosphate" in the published papers and the public patents on the adsorbents for phosphate based on Web of Science database in the period from January 1 2012 to December 31 2017. The corresponding literature was carefully evaluated and analyzed. RESULTS: One hundred and forty one papers and twenty two recent patents were included in this review. An increased trend in scientific contributions was observed in the development of adsorption materials for phosphate removal. Three kinds of promising adsorbents: layered double hydroxides, natural materials, and metal oxides were paid special attention including removal mechanism, performance as well as the relationship between adsorption performance and structure. Both the chemical composition and the morphology play a key role in the removal capacity and rate. CONCLUSION: The findings of this review confirm the importance of phosphate removal, show the development trend of high-performance and low-cost adsorption materials for phosphate removal, and provide a helpful guide to design and fabricate high-efficiency adsorbents.

Outstanding chain-extension effect and high UV resistance of polybutylene succinate containing amino-acid-modified layered double hydroxides.

Polybutylene succinate (PBS) nanocomposite materials were prepared using a melt compounding process. The Mg2Al-based PBS nanocomposites, dispersed with inorganic-organic hybrid materials (layered double hydroxides, LDHs), were functionalized with the amino acids L-histidine (HIS) and L-phenylalanine (PHE). The rheological and anti-ultraviolet (anti-UV) properties were investigated and compared to filler-free PBS as well as LDH Mg2Al/nitrate as references. Both organo-modified LDHs exhibited a remarkable chain-extension effect for PBS with an outstanding increase in the zero-shear viscosity η0 for PBS-Mg2Al/PHE (two order of magnitude increase as compared to filler-free PBS). These results were compared to data found in the literature. Moreover, HIS and PHE anions embedded into the LDH structure can successfully prevent the chain scission reactions that usually occur during photo-ageing of PBS under UV radiation exposure. This highlights the outstanding performance of the LDH hybrid materials, and in particular, their application as a polymer chain extender and UV stabilizer for PBS, which can likely be extended to other biodegradable polymers.

Towards rare-earth-free white light-emitting diode devices based on the combination of dicyanomethylene and pyranine as organic dyes supported on zinc single-layered hydroxide.

A new luminescent composite film resulting from the dispersion of luminescent organic dyes in a single-layered hydroxide (SLH)-type inorganic matrix has been developed. Two fluorescent organic dyes emitting visible light upon blue LED excitation were investigated in this study: dicyanomethylene (DCM) and pyranine (HPTS). These dyes exhibit broad emission bands that cover a large part of the visible spectrum. The concept developed in our work consisted in keeping SLH in its wet form to ensure a good dispersion of the fluorescent dyes prior to immobilizing the hybrid materials in a silicone polymer to achieve luminescent composite films. We demonstrate that these coatings stacked upon each other and placed above a blue LED lead to white-light emission with suitable photometric parameters for applications in lighting or display devices: colour temperature of 5409 K and colour rendering index (CRI) of 81.

In situ generation of layered single- or double-hydroxide inorganic platelets (LSH and LDH) assisted by bola amphiphiles.

A novel preparation route for layered hydroxide based hybrid phases has been investigated combining the polyol route with the in situ generation of inorganic platelets, in the presence of an amphiphilic polymer as well as bola-amphiphiles. The polyol route consists of hydrolysis in an alcoholic medium containing acetate metal cations as precursor(s), to yield an LDH Zn2Al cation composition or LSH-Zn (layered single hydroxide). A bola amphiphile is described as hydrophobic polymer segment-telechelic-chains terminated by two anionic hydrophilic end groups, using volatile ammonium cations as counter ions. The impact of both process conditions as well as the chosen system with regard to the metal hydroxide framework on the morphology of the obtained hybrid phases is scrutinized by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and compared to that of the corresponding physical mixture. For the ex situ approach, the diffusion of large cumbersome polymers or amphiphilic bolas between the inorganic platelets was found to be efficient, mostly driven by an anion exchange reaction between interleaved acetate anions and carboxylate functions of the molecular backbones, and keeping intact the inner sheet integrity through a topotactic process. In particular with LSH-Zn, a multi-stratified assembly has been observed combining an acetate pristine structure and a partly bola diffused structure, leading to a biphasic structure, aggregated and intercalated. To the best of our knowledge, observation of LSH-Zn single platelets has never been reported, making the combined process polyol/in situ an interesting new route to reach exfoliation. Indeed, it leads to the generation of either LSH or LDH platelets of lateral size ranging from 10 up to 200 nm. However, the platelets were found to be porous; it is considered as a drawback for barrier properties. It is our belief that such porosity may open new insights in "tectonic" architecture by intertwining 2D and 1D-type fillers. Rather counterintuitively, the ex situ approach based on a topotactic exchange reaction matches the in situ templating reaction in many cases as a function of the dispersion state regardless of the polymer or bolas as well as the platelet cation composition.

Co-intercalated layered double hydroxides as thermal and photo-oxidation stabilizers for polypropylene.

An elegant and efficient approach consisting in the co-intercalation of stabilizing molecular anions is described here. The thermal stabilizer calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (Irganox 1425, MP-Ca) and a photo-oxidation stabilizer (hindered amine light stabilizer, HALS) are co-intercalated into the interlayer regions of layered double hydroxides (LDH) in a one-step coprecipitation. These hybrid organic-inorganic materials are successively dispersed in polypropylene to form H n M n '-Ca2Al/PP composite films (with H = HALS and M = MP) through a solvent casting method. The corresponding crystalline structure, chemical composition, morphology as well as the resistance against thermal aging and photo-oxidation are carefully investigated by various techniques. The results show that the powdered H n M n '-Ca2Al-LDHs hybrid materials have a much higher thermal stability than MP-Ca and HALS before intercalation. In addition, the H n M n '-Ca2Al/PP composites exhibit a higher overall resistance against thermal degradation and photo-oxidation compared to LDHs intercalated with only HALS or MP. This underlines the benefit of the co-intercalation. The co-intercalated LDH materials pave a new way in designing and fabricating high-performance multifunctional additives for polymers.

Micrometer-sized dihydrogenphosphate-intercalated layered double hydroxides: synthesis, selective infrared absorption properties, and applications as agricultural films.

High-performance heat-retention agents for multifunctional green agricultural films are today largely suitable to increase the production yield as well as to save energy. Here, an adapted ammonia releasing hydrothermal method was used to produce a series of micrometer-sized carbonate-layered double hydroxide (CO3-LDH) precursors of sizes ranging from 1.32 µm to 8.64 µm by simply adjusting the feeding Mg2+ concentration from 0.80 mol L-1 to 0.20 mol L-1. From these pristine LDH materials, µm-sized dihydrogenphosphate-intercalated LDHs (H2PO4-LDHs) were prepared by an anion-exchange method. The structure, the platelet size, and the associated selective IR absorption properties of the H2PO4-LDH and the derivative H2PO4-LDH/EVA composite as well as the related visible transmittance and the photostability of the H2PO4-LDH/EVA film were investigated. The results show that the selective IR absorption in the wavelength range of 7-14 µm enabling the heat retention of the H2PO4-LDHs and H2PO4-LDH/EVA composites depends on the corresponding number-averaged particle size of H2PO4-LDH in the range of 2.01 µm to 8.80 µm. Compared with EVA, the H2PO4-LDH/EVA composites demonstrate a significant improvement of selective IR absorption, while maintaining acceptable visible transmittance, and similar photostability. An optimized particle size of H2PO4-LDH of ca. 5.85 µm leads to 60% selective IR absorption and 64% selective IR absorption when dispersed in EVA, while the polymer free of filler exhibits less than 50% absorption in the 7-14 µm IR domain.

Microwave-assisted functionalization of the Aurivillius phase Bi2SrTa2O9: diol grafting and amine insertion vs. alcohol grafting.

Microwave-assisted functionalization of the layered Aurivillius phase Bi2SrTa2O9 by alcohols is thoroughly investigated. The grafting of linear aliphatic and bulky alcohols is studied as a function of the starting material, underlining the importance of the prefunctionalization of the layered perovskite, for instance by butylamine. In addition, the functionalization by α,ω-alkanediols is explored. α,ω-alkanediols bearing long alkyl chains (n C > 3) adopt an unprecedented pillaring arrangement, whereas 1,3-propanediol and ethyleneglycol adopt a bilayer arrangement, only one out of the two hydroxyl groups being coordinated. Finally, the reactivities of alcohols and amines towards insertion are compared: the preferential reactivity of the two functional groups appears to be strongly dependent of the reaction conditions, and especially of the water content. This study is further extended to the case of amino-alcohol insertion. In this case, the amine group is preferentially bound, but it is possible to control the grafting of the alcohol moiety, thus going from a bilayer arrangement to a pillaring one. This work is of particular importance to be able to functionalize easily and rapidly layered oxides with elaborated molecules, bearing several different potentially reactive groups.

Dual chain extension effect and antibacterial properties of biomolecules interleaved within LDH dispersed into PBS by in situ polymerization.

Nanocomposites based on poly(butylene succinate) (PBS) and hydrotalcite-type anionic clays (HTs) organo-modified with biomolecules characterized by antibacterial and/or antioxidant activities, such as l-ascorbic acid (ASA), phloretic acid (HPP), l-tyrosine (TYR) and l-tryptophan (TRP), have been prepared by in situ polymerization. From XRD analysis and rheology experiments in a molten polymer state, intercalated HT hybrid platelets acting here as a hybrid filler are found to be well dispersed into polymers while providing a chain extension effect on PBS. Moreover, the molecules, when hosted within a HT interlayer gap, do preserve their pristine antibacterial activity, both in HT and in the resulting PBS composites. In particular, under the experimental conditions tested, HT/ASA and HT/TYR present the best combination of both properties (chain extension effect and antibacterial), especially versus E. coli as high as 90 and 97% of inhibition, respectively, using 2.5 wt% hybrid filler only. These findings open future applications for PBS associated with the hybrid HT filler as multifunctional materials in active packaging applications.