Magnetic Analysis of MgFe Hydrotalcites as Powder and Dispersed in Thin Films within a Keratin Matrix

Hydrotalcites (HTlcs) are a class of nanostructured layered materials that may be employed in a variety of applications, from green to bio technologies. In this paper, we report an investigation on HTlcs made of Mg and Fe, recently employed to improve the growth in vitro of osteoblasts within a keratin sponge. We carried out an analysis of powder materials and of HTlcs dispersed in keratin and spin-coated on a Si/SiO₂ substrate at different temperatures. A magnetic study of the powders was carried out with a Quantum Design Physical Property Measurement System equipped with a Vibrating Sample Magnetometer. The data gathered prove that these HTlcs are fully paramagnetic, and keratin showed a very small magnetic response. Optical and Atomic Force Microscopy analyses of the thin films provide a detailed picture of clusters randomly dispersed in the films with various dimensions. The magnetic properties of these films were characterized using the Nano Magneto Optical Kerr Effect (NanoMOKE) down to 7.5 K. The data collected show that the local magnetic properties can be mapped with a micrometric resolution distinguishing HTlc regions from keratin ones. This approach opens new perspectives in the characterization of these composite materials.

Multifunctional Cross-Linked Shrimp Waste-Derived Chitosan/MgAl-LDH Composite for Removal of As(V) from Wastewater and Antibacterial Activity

This work synthesized a novel chitosan-loaded MgAl-LDH (LDH = layered double hyroxide) nanocomposite, which was physicochemically characterized, and its performance in As(V) removal and antimicrobial activity was evaluated. Chitosan-loaded MgAl-LDH nanocomposite (CsC@MgAl-LDH) was prepared using cross-linked natural chitosan from shrimp waste and modified by Mg-Al. The main mechanisms predominating the separation of As(V) were elucidated. The characteristic changes confirming MgAl-LDH modification with chitosan were analyzed through Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis-differential thermal analysis, and Brunauer-Emmett-Teller measurements. Porosity and the increased surface area play an important role in arsenic adsorption and microbial activity. Adsorption kinetics follows the general order statistically confirmed by Bayesian Information Criterion differences. To understand the adsorption process, Langmuir, Freundlich, and Liu isotherms were studied at three different temperatures. It was found that Liu's isotherm model was the best-fitted model. CsC@MgAl-LDH showed the maximum adsorption capacity of 69.29 mg g^-1 toward arsenic at 60 °C. It was observed that the adsorption capacity of the material rose with the increase in temperature. The spontaneous behavior and endothermic nature of adsorption was confirmed by the thermodynamic parameters study. Minimal change in percentage removal was observed with coexisting ions. The regeneration of material and adsorption-desorption cycles revealed that the adsorbent is economically efficient. The nanocomposite was very effective against Staphylococcus aureus and Bacillus subtilus.

Nanoarchitectured two-dimensional layered double hydroxides-based nanocomposites for biomedical applications

Despite the exceptional physicochemical and morphological characteristics, the pristine layered double hydroxides (LDHs), or two-dimensional (2D) hydrotalcite clays, often suffer from various shortcomings in biomedicine, such as deprived thermal and chemical stabilities, acid-prone degradation, as well as lack of targeting ability, hampering their scale-up and subsequent clinical translation. Accordingly, diverse nanocomposites of LDHs have been fabricated by surface coating of organic species, impregnation of inorganic species, and generation of core-shell architectures, resulting in the complex state-of-the-art architectures. In this article, we initially emphasize various bothering limitations and the chemistry of these pristine LDHs, followed by discussions on the engineering strategies of different LDHs-based nanocomposites. Further, we give a detailed note on diverse LDH nanocomposites and their performance efficacy in various biomedical applications, such as drug delivery, bioimaging, biosensing, tissue engineering and cell patterning, deoxyribonucleic acid (DNA) extraction, as well as photoluminescence, highlighting the influence of various properties of installed supramolecular assemblies on their performance efficacy. In summary, we conclude with interesting perspectives concerning the lessons learned to date and the strategies to be followed to further advance their scale-up processing and applicability in medicine.

Layered Double Hydroxide Catalysts Preparation, Characterization and Applications for Process Development: An Environmentally Green Approach

The adage of new generation of fine chemicals process is the best process applied in the absence of conventional methods. However, many methods use different reaction parameters, such as basic and acidic catalysts, for example oxidation, reduction, bromination, water splitting, cyanohydrin, ethoxylation, syngas, aldol condensation, Michael addition, asymmetric ring opening of epoxides, epoxidation, Wittig and Heck reaction, asymmetric ester epoxidation of fatty acids, combustion of methane, NOx reduction, biodiesel synthesis, propylene oxide polymerization. Layered Double Hydroxides (LDHs) have received considerable attention due their potential applications in flame retardant and has excellent medicinal property for reducing acidity. These catalysts are characterized using analytical techniques, such as: X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), Raman spectroscopy, Thermogravimetric-Differential Thermal Analyzer (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscopes (TEM), Brunauer-Emmett-Teller (BET) surface area, N2 Adsorption-desorption, Temperature programmed reduction (TPR), X-ray photoelectrons spectroscopy (XPS), which gives its overall picture of its structure, porosity, morphology, thermal stability, reusability, and activity of catalysts. LDHs catalysts have proven to be economic and environmentally friendly. The above discussed applications make these catalysts unique from Green Chemistry point of view since they are reusable, and eco-friendly catalysts. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Effect of Drying on the Fabrication of MgAl Layered Double Hydroxides

This study aimed to evaluate the synthesis of MgAl/LDH from the drying process perspective, evaluating the influence of temperature (75-90 °C) and time (16-20 h) in the drying process. The synthesis was performed, maintaining a ratio of 2:1 of Mg/Al, and the drying was conducted according to a 2² experimental design: four axial points and three repetitions at the central point. The surface area and pore diameter ranged from 4.09 to 18.55 m²/g and 12.50 to 24.46 nm. Fourier transform infrared (FTIR) analysis indicated the drying-caused variation of the LDH typical bands intensities. Scanning electron microscopy (SEM) images showed the tendency of the increase of agglomeration with the temperature elevation. The drying parameters' influence was evident for X-ray diffraction (XRD) analysis observing the crystallite size increment, from 13.10 to 38.94 nm, and basal spacing variation, from 7.52 to 7.64 Å. The statistical models for growing crystal and reduction of the basal spacing were physically consistent but with low values of R ². The drying time and temperature had a considerable influence on the chemical, physical, structural, and morphological properties of LDH.

Systematic utilization of layered double hydroxide nanosheets for effective removal of methyl orange from an aqueous system by π-π stacking-induced nanoconfinement

Systematic utilization of carbonated Mg-Al layered double hydroxide (LDH) nanosheets for methyl orange removal was investigated with respect to particle dimensions. LDHs with the smallest dimensions were carefully synthesized to have a small lateral size as well as high dispersibility. The other particles, with medium and large sizes, were prepared by hydrothermal treatment and urea hydrolysis to have larger sizes and higher crystallinity. According to kinetics and isotherm analyses, the smallest LDH showed efficient adsorption of methyl orange (1250 mg/g-LDH), which was remarkably higher than the adsorption by the other LDHs with larger lateral sizes. Unlike the larger lateral-sized LDHs, the small ones were shown to utilize all accessible adsorption sites on the nanosheets, generating nanoconfinement of methyl orange molecules. Transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD) patterns indicated that the LDHs with lateral dimensions of ~40 nm fully utilized interlayer nanospace. Monte Carlo simulation suggested that the intercalated methyl orange was stabilized not only through electrostatic interactions with the LDH layer but also by π-π stacking between the methyl orange molecules, which is thought to be the driving force for replacement of carbonate anions.

Selective Covalent Modification of Layered Double Hydroxide Nanoparticles with Tripodal Ligands on Outer and Interlayer Surfaces

Layered double hydroxides (LDHs) have occupied an important place in the fields of catalysts, electrocatalysts, and fillers, and their applicability can be greatly enhanced by interlayer organic modifications. In contrast to general organic modification based on noncovalent modification using ionic organic species, this study has clarified in situ interlayer covalent modification of LDH nanoparticles (LDHNPs) with the tripodal ligand tris(hydroxymethyl)aminomethane (Tris-NH₂). Interlayer-modified CoAl LDHNPs were obtained by a one-pot hydrothermal treatment of an aqueous solution containing metal salts and Tris-NH₂ at 180 °C for 24 h. Tris-NH₂ was covalently bonded on the interlayer surface of LDHNPs. Interlayer-modified NiAl LDHNPs were also similarly synthesized. Some comparative experiments under different conditions indicate that the important parameters for interlayer modification are the number of bonding sites per a modifier, the electronegativity of a constituent divalent metal element, and the concentration of a modifier; this is because these parameters affect the hydrolytic stability of alkoxy-metal bonds between a modifier and a layer of LDHNPs. The synthesis of interlayer-modified MgAl LDHNPs was achieved by adjusting these parameters. This achievement will enable new potential applications because modification of only the outer surface has been achieved until now. Interlayer-modified LDHNPs possessing CO₃^2- in the interlayer space were delaminated into monolayers under ultrasonication in water. The proposed method provides a rational approach for interlayer modification and facile delamination of LDHNPs.

Facile Synthetic Route To Prepare Ultrathin Silver Nanosheets by Reducing Silver Thiolates in Interlayer Surface of Layered Double Hydroxides

Silver metal nanostructures have gained much interest, due to their utility in various fields, based on their unique properties at nanosize. Tremendous research efforts have been made to establish synthetic methods to manipulate their shape and size. The most challenging synthesis in silver nanostructures has been known as a plate-like shape having a few nanometers size thickness and high aspect ratio. Here, we demonstrate a novel and facile synthetic route for ultrathin (≤1 nm) silver nanosheets using silver carboxylthiolate as precursor. Such silver thiolate formed single-layered colloid in aqueous basic solution, due to the electrostatic repulsion between carboxylate groups. These single layers of silver thiolates were stabilized within the interlayer space of layered double hydroxide (LDH). When silver thiolates confined in LDHs were calcined under reductive atmosphere, the LDHs effectively suppressed the vertical growth of silver crystals.

Zein-layered hydroxide biohybrids: strategies of synthesis and characterization

This work constitutes a basic study about the first exploration on the preparation of biohybrids based on the corn protein zein and layered metal hydroxides, such as layered double hydroxides (LDH) and layered single hydroxides (LSHs). For this purpose, MgAl layered double hydroxide and the Co₂(OH)₃ layered single hydroxide were selected as hosts, and various synthetic approaches were explored to achieve the formation of the zein-layered hydroxide biohybrids, profiting from the presence of negatively charged groups in zein in basic medium. Zein-based layered hydroxide biohybrids were characterized by diverse physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential thermal analysis (TG/DTA), solid state ¹³C cross-polarization magical angle spinning nuclear magnetic resonance (CP-MAS NMR), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), etc., which suggest that the different synthesis procedures employed and the anion located in the interlayer region of the inorganic host material seem to have a strong influence on the final features of the biohybrids, resulting in mixed, single intercalated, or highly exfoliated intercalated phases. Thus, the resulting biohybrids based on zein and layered hydroxides could have interest in applications in biomedicine, biosensing, materials for electronic devices, catalysis, and photocatalysis.

Anion exchange behavior of MIIAl layered double hydroxides: a molecular dynamics and DFT study

The ion exchange reaction has been extensively used in the field of synthesis of functionalized supramolecular materials such as layered double hydroxides (LDHs), ion-embedded batteries, sewage disposal and so on. In this work, the factors influencing the anion exchange behavior in the LDH gallery, such as the exchange domain, the exchange order, the driving force, and the diffusion of the anions, are investigated systematically using molecular dynamics (MD) simulations and density functional theory (DFT) methods in view of both thermodynamics and dynamics. 159 models of MIIRAl-A-LDHs (MII = Mg, Ni, Zn; R = 1.4-8, A = OH-, Cl-, Br-, NO3-, HCOO-, C6H5SO3-, CO32-, SO42-, and PO43-, respectively) are calculated. The results reveal that the anion exchange domain (interlayer distance) in LDHs is determined not only by the size and their arrangement modes of the guest anions, but also by the charges the anions carry. The relative binding energies of different anions and the Gibbs free energy changes of the anion exchange reactions in LDHs decrease in the order of PO43- > CO32- > SO42- > OH- > Cl- > Br- > HCOO- > NO3- > C6H5SO3-, which is in accordance with the experimental anion exchange order. The stronger the hydrogen bonding between the anion and the host, the larger the charge transfer, and the smaller the electronegativity of the anion, the more difficult it is for the anion to be exchanged out from LDH interlayer. In addition, for the anions with the same charges, the relative binding energy is linearly well correlated with the interlayer spacing. By analyzing the contribution of each energetic item comprising the total potential energy, it is found that the major driving force of anion exchange is the electrostatic force. The diffusion coefficient (D) along the c direction is nearly equal to zero, suggesting that the diffusion of anions occurs mainly in the ab plane of the LDH cell. It also can be inferred that when the cell parameter c < 24.0 Å, the anion exchange order is mainly determined by the thermodynamic factors, whereas when c > 24.0 Å, both the thermodynamic and the dynamic factors cast the same effect on the anion exchange behavior. This work provides an in-depth understanding of the anion exchange behavior, and is helpful guidance for the design and synthesis of functionalized guest anion intercalated LDHs and related materials using the anion-exchange method.

Layered Double Hydroxides: A Toolbox for Chemistry and Biology

Layered double hydroxides (LDHs) are an emergent class of biocompatible inorganic lamellar nanomaterials that have attracted significant research interest owing to their high surface-to-volume ratio, the capability to accumulate specific molecules, and the timely release to targets. Their unique properties have been employed for applications in organic catalysis, photocatalysis, sensors, drug delivery, and cell biology. Given the widespread contemporary interest in these topics, time-to-time it urges to review the recent progresses. This review aims to summarize the most recent cutting-edge reports appearing in the last years. It firstly focuses on the application of LDHs as catalysts in relevant chemical reactions and as photocatalysts for organic molecule degradation, water splitting reaction, CO2 conversion, and reduction. Subsequently, the emerging role of these materials in biological applications is discussed, specifically focusing on their use as biosensors, DNA, RNA, and drug delivery, finally elucidating their suitability as contrast agents and for cellular differentiation. Concluding remarks and future prospects deal with future applications of LDHs, encouraging researches in better understanding the fundamental mechanisms involved in catalytic and photocatalytic processes, and the molecular pathways that are activated by the interaction of LDHs with cells in terms of both uptake mechanisms and nanotoxicology effects.

Investigation of Thermal Behavior of Layered Double Hydroxides Intercalated with Carboxymethylcellulose Aiming Bio-Carbon Based Nanocomposites

Carboxymethylcellulose (CMC), a polymer derived from biomass, was intercalated into layered double hydroxides (LDH) composed by M2+/Al3+ (M2Al-CMC, M = Mg or Zn) and evaluated as precursors for the preparation of biocarbon-based nanocomposites by pyrolysis. M2Al-CMC hybrids were obtained by coprecipitation and characterized by X ray diffraction (XRD), vibrational spectroscopies, chemical analysis, and thermal analysis coupled to mass spectrometry. Following, pyrolyzed materials obtained between 500–1000 °C were characterized by XRD, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Above 600 °C, Raman spectra of all samples showed the presence of graphitic carbon, which plays a role in the degree of crystallinity of produced inorganic phases (for comparison purposes, M2Al-CO3 materials were investigated after calcination in the same experimental conditions). XRD patterns of Mg2Al-CMC pyrolyzed between 600–1000 °C showed poorly crystallized MgO and absence of spinel reflections, whereas for Zn2Al-CMC, it was observed well crystallized nanometric ZnO at 800 °C, and ZnAl2O4 and γ-Al2O3 phases at 1000 °C. Above 800 °C, the carbothermic reaction was noticed, transforming ZnO to zinc vapour. This study opens perspectives for nanocomposites preparation based on carbon and inorganic (mixed) oxides through precursors having organic-inorganic interactions at the nanoscale domain.

Effect of Synthesis Conditions on the Controlled Growth of MgAl–LDH Corrosion Resistance Film: Structure and Corrosion Resistance Properties

In this study, a series of MgAl–layered double hydroxide (LDH) thin films were synthesized by a single step hydrothermal process at different synthetic conditions on AA6082, and the combined effect of reaction temperatures and crystallization times on in situ growth MgAl–LDH structural geometry, growth rate, and more importantly on the corresponding corrosive resistance properties are briefly discussed. The synthesis of LDH was performed at reaction temperatures of 40, 60, 80, and 100 °C, while the treatment time was varied at 12, 18, and 24 h. The as-prepared synthetic coatings were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), while the corresponding corrosion protection efficiency of the developed coating was studied through potentiodynamic polarization studies and electrochemical impedance spectra. The findings demonstrated that extended crystallization time and reaction temperature impart a significant effect on the oriented growth of layered double hydroxide, the surface morphology, and on the film thickness, which had a remarkable influence on the LDH corrosion resistance ability. The LDH coated specimen developed at 100 °C for 18 h reaction time showed a more compact and dense structure compared to the traditional platelet structure obtained at 80 °C for 24 h crystallization time, and interestingly that compact structure exhibited the lowest corrosion current density, up to five orders of magnitude lower than that of bare AA6082.

Coprecipitation Preparation of Cu/Zn/Al-Hydrotalcite-Like Compound for Copper Removal from Electroplating Wastewater

Cu/Zn/Al-hydrotalcite-like compound (Cu/Zn/Al-HTlc) was prepared by the coprecipitation method with ZnII, AlIII cations solution, and electroplating wastewater containing CuII cation. The preparation conditions of Cu/Zn/Al-HTlc were optimized. The metal ion pollutants removal effect and iodide maximum adsorption capacity of Cu/Zn/Al-HTlc were also studied. The physicochemical properties of the Cu/Zn/Al-HTlc were analyzed by X-ray diffraction, FTIR, SEM, N2 adsorption-desorption isotherms, and TG-DTG. The results showed that Cu/Zn/Al-HTlc should be prepared with the ZnII-AlIII molar ratio of 1.5 : 1, pH = 11, and aged at room temperature for 0.5 d. Structural analysis showed that the Cu/Zn/Al-HTlc was a layered compound. CuII and other metal ion pollutants can also be successfully removed from electroplating wastewater in the preparation process of Cu/Zn/Al-HTlc and reached Chinese National Emission Standard (GB 21900-2008). The optimal adsorption condition of calcinated Cu/Zn/Al-HTlc for iodide was as follows: the solid-liquid ratio was 1 : 250, the pH value was 8, and the adsorption process was carried out at 25°C for 30 min. The saturated adsorption capacity reached 1000 mg·g−1 at the optimal adsorption condition. The main reason for this high-saturated adsorption capacity of Cu/Zn/Al-HTlc was that iodide penetrated into the layered structure of Cu/Zn/Al-HTlc by physical adsorption and CuII undergoes a specific redox reaction, producing CuI. Hence, coprecipitation synthetic technology and prepared Cu/Zn/Al-HTlc could be potentially used for electroplating wastewater treatment.

A highly proton-/vanadium-selective perfluorosulfonic acid membrane for vanadium redox flow batteries

The polar clusters of Nafion are blocked by the incorporation of the nanohybrid, which contributes to suppress vanadium ions crossover.

Highly dispersed layered double oxide hollow spheres with sufficient active sites for adsorption of methyl blue

The adsorption of dyes in contaminated water is an effective approach to solving the environmental crisis. Layered double hydroxide (LDH) and its calcinated product layered double oxide (LDO) show great potential as adsorbents. However, the conventional preparation of LDH or LDO typically suffers from aggregation and blocked active sites, hampering the adsorption efficiency of the adsorbent. Herein, three-dimensional, hollow MgFe-LDO spheres were constructed through the sacrifice of a carbon template. The hollow structure and the monodisperse state provided MgFe-LDO with sufficient microchannels and abundant active sites for adsorption. Through the memory effect of LDO, the anion methyl blue (MB) can be effectively adsorbed with a high uptake capacity of 398 mg g^-1. Isotherm simulations demonstrated the monolayer adsorption of MB and the heterogeneous surfaces of the reconstructed LDHs. Moreover, the adsorbents can be recycled and reutilized at least five times through magnetic separation followed by calcination. Our proposed strategy is expected to provide new possibilities for the construction of adsorbents with well-controlled architecture and abundant active sites to deal with anionic pollutants.

A magnetic study of a layered lanthanide hydroxide family: Ln8(OH)20Cl4·nH2O (Ln = Tb, Ho, Er)

Three layered lanthanide hydroxides (LLHs), with the general formula Ln8(OH)20Cl4·nH2O (Ln = Tb (1), Ho (2), Er (3)), were prepared and magnetically characterized both as pure compounds and diluted within a yttrium diamagnetic matrix, LYH : xLn, LYH : 0.044Tb (1'), LYH : 0.045Ho (2'), and LYH : 0.065Er (3'). This study was complemented with theoretical calculations in order to understand the electronic configuration and the contributions to the slow relaxation behavior. In the pure compounds dominant 3D ferromagnetic interactions are observed, with a small magnetization hysteresis at 1.8 K for 1, while the magnetically diluted solid solutions display slow relaxation of magnetization at low temperatures.

Adsorption of Oligo-DNA on Magnesium Aluminum-Layered Double-Hydroxide Nanoparticle Surfaces: Mechanistic Implication in Gene Delivery

Magnesium aluminum-layered double-hydroxide nanoparticles (LDH NPs) are promising drug-delivery vehicles for gene therapy, particularly for siRNA interference; however, the interactions between oligo-DNA and LDH surfaces have not been adequately elucidated. Through a mechanistic study, oligo-DNA initially appears to rapidly bind strongly to the LDH outer surfaces through interactions with their phosphate backbones via ligand exchange with OH^- on Mg²⁺ centers and electrostatic forces with Al³⁺. These initial interactions might precede diffusion into interlayer spaces, and this knowledge can be used to design better gene therapy delivery systems.

Porous Layered Double Hydroxides Synthesized using Oxygen Generated by Decomposition of Hydrogen Peroxide

Porous magnesium-aluminium layered double hydroxides (LDH) were prepared through intercalation and decomposition of hydrogen peroxide (H₂O₂). This process generates oxygen gas nano-bubbles that pierce holes in the layered structure of the material by local pressure build-up. The decomposition of the peroxide can be triggered by microwave radiation or chemically by reaction with iodide (I⁻) ions. The carbonate LDH version [Mg_0.80Al_0.20(OH)₂](CO₃)_0.1∙mH₂O was synthesized by microwave-assisted urea coprecipitation and further modified by iodide or H₂O₂ intercalation. High resolution Scanning Electron Microscopy (HR-SEM) and Brunauer-Emmet-Teller (BET) analysis were used to assess the morphology and surface area of the new porous materials. The presence of H₂O₂ in the interlayer region and later decomposition triggered by microwave radiation generated more pores on the surface of the LDH platelets, increasing their specific surface area from initially 9 m²/g to a maximum of 67 m²/g. X-Ray Diffraction showed that the formation of the pores did not affect the remaining crystal structure, allowing possible further functionalization of the material.

Thermal and aqueous stability improvement of graphene oxide enhanced diphenylalanine nanocomposites

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications.

Design of latex-layered double hydroxide composites by tuning the aggregation in suspensions

Colloidal stability of polymeric latex particles was studied in the presence of oppositely charged layered double hydroxide (LDH) platelets of different interlayer anions. Adsorption of the LDH particles led to charge neutralization and to overcharging of the latex at appropriate concentrations. Mixing stable colloidal suspensions of individual particles results in rapid aggregation once the LDH adsorption neutralizes the negative charges of the polymer spheres, while stable suspensions were observed at high and low LDH doses. The governing interparticle interactions included repulsive electrical double layer forces as well as van der Waals and patch-charge attractions, whose strength depended on the amount of LDH particles adsorbed on the latex surface. The type of the LDH interlayer anions did not affect the colloidal stability of the samples. Structural investigation of the obtained latex-LDH composites revealed that the polymer spheres were completely coated with the inorganic platelets once their concentration was sufficiently high. These results are especially important for designing synthetic routes for hybrid systems in suspensions, where stable colloids are required for uniform film-formation and for the homogeneous distribution of the inorganic filler within the composite materials.

Layered host-guest long-afterglow ultrathin nanosheets: high-efficiency phosphorescence energy transfer at 2D confined interface

Tuning and optimizing the efficiency of light energy transfer play an important role in meeting modern challenges of minimizing energy loss and developing high-performance optoelectronic materials. However, attempts to fabricate systems giving highly efficient energy transfer between luminescent donor and acceptor have achieved limited success to date. Herein, we present a strategy towards phosphorescence energy transfer at a 2D orderly crystalline interface. We first show that new ultrathin nanosheet materials giving long-afterglow luminescence can be obtained by assembling aromatic guests into a layered double hydroxide host. Furthermore, we demonstrate that co-assembly of these long-lived energy donors with an energy acceptor in the same host generates an ordered arrangement of phosphorescent donor-acceptor pairs spatially confined within the 2D nanogallery, which affords energy transfer efficiency as high as 99.7%. Therefore, this work offers an alternative route to develop new types of long-afterglow nanohybrids and efficient light transfer systems with potential energy, illumination and sensor applications.

Intercalation and structural aspects of macroRAFT agents into MgAl layered double hydroxides

Increasing attention has been devoted to the design of layered double hydroxide (LDH)-based hybrid materials. In this work, we demonstrate the intercalation by anion exchange process of poly(acrylic acid) (PAA) and three different hydrophilic random copolymers of acrylic acid (AA) and n-butyl acrylate (BA) with molar masses ranging from 2000 to 4200 g mol^-1 synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, into LDH containing magnesium(II) and aluminium(III) intralayer cations and nitrates as counterions (MgAl-NO₃ LDH). At basic pH, the copolymer chains (macroRAFT agents) carry negative charges which allowed the establishment of electrostatic interactions with the LDH interlayer and their intercalation. The resulting hybrid macroRAFT/LDH materials displayed an expanded interlamellar domain compared to pristine MgAl-NO₃ LDH from 1.36 nm to 2.33 nm. Depending on the nature of the units involved into the macroRAFT copolymer (only AA or AA and BA), the intercalation led to monolayer or bilayer arrangements within the interlayer space. The macroRAFT intercalation and the molecular structure of the hybrid phases were further characterized by Fourier transform infrared (FTIR) and solid-state ¹³C, ¹H and ²⁷Al nuclear magnetic resonance (NMR) spectroscopies to get a better description of the local structure.

A Nanoscale Interface Promoting Molecular and Functional Differentiation of Neural Cells

Potassium channels and aquaporins expressed by astrocytes are key players in the maintenance of cerebral homeostasis and in brain pathophysiologies. One major challenge in the study of astrocyte membrane channels in vitro, is that their expression pattern does not resemble the one observed in vivo. Nanostructured interfaces represent a significant resource to control the cellular behaviour and functionalities at micro and nanoscale as well as to generate novel and more reliable models to study astrocytes in vitro. However, the potential of nanotechnologies in the manipulation of astrocytes ion channels and aquaporins has never been previously reported. Hydrotalcite-like compounds (HTlc) are layered materials with increasing potential as biocompatible nanoscale interface. Here, we evaluate the effect of the interaction of HTlc nanoparticles films with primary rat neocortical astrocytes. We show that HTlc films are biocompatible and do not promote gliotic reaction, while favouring astrocytes differentiation by induction of F-actin fibre alignment and vinculin polarization. Western Blot, Immunofluorescence and patch-clamp revealed that differentiation was accompanied by molecular and functional up-regulation of both inward rectifying potassium channel Kir 4.1 and aquaporin 4, AQP4. The reported results pave the way to engineering novel in vitro models to study astrocytes in a in vivo like condition.

A luminescent ultrathin film with reversible sensing toward pressure

A flexible ultrathin film based on alternate assembly of a sodium polyacrylate (PAA) modified styrylbiphenyl derivative (BTBS) and layered double hydroxide nanosheets is fabricated, which exhibits pressure-responsive photoluminescence with a high sensitivity and good reversibility.

Chemisorption Mechanism of DNA on Mg/Fe Layered Double Hydroxide Nanoparticles: Insights into Engineering Effective SiRNA Delivery Systems

Layered double hydroxide nanoparticles (LDH NPs) have attracted interest as an effective gene delivery vehicle in biomedicine. Recent advances in clinic trials have demonstrated the efficacy of Mg/Fe LDHs for hyperphosphatemia treatment, but their feasibility for gene delivery has not been systematically evaluated. As a starting point, we aimed to study the interaction between oligo-DNA and Mg/Fe LDH NPs. Our investigation revealed the chemisorption mechanism of DNA on Mg/Fe LDH surfaces, wherein the phosphate backbone of the DNA polymer coordinates with the metal cations of the LDH lattice via the ligand-exchange process. This mechanistic insight may facilitate future gene delivery applications using Mg/Fe LDH NPs.

Ni-based catalyst derived from Ni/Al hydrotalcite-like compounds by the urea hydrolysis method for CO methanation

The catalytic methanation of CO was investigated at atmospheric pressure over Ni-based catalysts derived from Ni/Al hydrotalcite-like compounds.