Interlayer Space Of Layered Double Hydroxides Research Articles

(Invited) Layered Double Hydroxides with Enhanced Interlayer Space for Electrochemical Energy Storage and Deionization

Layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, we presented a series of investigations on enhanced interlayer space of LDHs for electrochemical energy and deionization.Firstly, using acetate anions (Ac-) as an intercalating element, NiCo-LDH nanosheets arraying on Ni Foam with different amounts of Ac- anions intercalation or volumes of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac- anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g-1 at 1 A g-1 (690 C g-1 without Ac- anions), outstanding rate capability of 72.5% at 30 A g-1 and cycle stability of 79.90% after 4500 cycles, which were mainly attributed to the higher interlayer spacing of Ac- anions intercalation.Moreover, CoAl-LDH nanosheets intercalated by sodium dodecyl sulfate (SDS) with an enhanced interlayer spacing from 0.76 to 1.33 nm are synthesized and used as an anode of electrosorption. The enlarged interlayer spacing provides an enhanced ion diffusion channel and improves the utilization of the interlayer electroactive sites, while heat treatment transferring LDHs to layered metal oxides offers additional active oxidation reaction sites to facilitate the electro-sorption rate, contributing to the high salt adsorption capacity (31.78 mg g-1) and average salt adsorption rate (3.75 mg g-1 min-1) at 1.2 V in 500 mg L-1 NaCl solution. In addition, the excellent long-term cycling stability (92.9%) after 40 cycles proves the strong electronic interaction between SDS and the host layer, which is validated by density functional theory calculations later on.In addition, ionic surfactants like SDS and cetyl trimethyl ammonium bromide (CTAB) can be used to modify the morphology of LDH. The original LDH shows microspheres formed by nanorods, and LDH-CTAB is similar, yet more tangled, while LDH-SDS is like micro flowers consisting of interwoven nanosheets. LDH-SDS achieved better electrochemical performance (1003.6 C g-1 at 1 A g-1 and 73.84% after 3500 cycles) than LDHs-CTAB (430.54 C g-1, 57.3%), and both higher than the original LDH (278.5 C g-1, 54.3%), while the electrocatalytic performance like Tafel slope follows an opposite trend owing to the difficulty of bubbles detachment from the nanosheets or nanorods, clearly showing the importance of morphology regulation in the synthesis of nanomaterials.

Synthesis of phenylalanine and tartaric acid intercalated layered double hydroxide (LDH): Investigation of two kinds of chiral molecules interaction in interlayer space of LDH using solid-state vibrational circular dichroism

Recently, the applicability of solid-state vibrational circular dichroism (SD-VCD) for the evaluation of organoclay nanohybrids has attracted much attention. Herein, the intercalation of two kinds of chiral molecules, phenylalanine (Phe) and tartaric acid (Tart), into Zn-Al layered double hydroxide (LDH) was carried out by a standard coprecipitation method. The Phe/Tart/LDH was characterized by XRD, FT-IR, TG-DTA, and SD-VCD. The chemical composition and interlayer distance expansion of Phe/Tart/LDH indicated that Phe and Tart were intercalated into the LDH. The VCD and theoretical calculation results showed that Phe and Tart coexisted in the same interlayer space of LDH with the formation of electrostatic interaction and hydrogen bonding between Phe-Tart, LDH-Phe, and LDH-Tart. The results demonstrated the utility of the SD-VCD method for determining the detailed conformation of chiral molecules in the LDH interlayer space.

Optimization of parameters for adsorption of acid yellow 36 dye onto nitrate‐intercalated MgAl LDH nanoparticle using Box–Behnken design

AbstractBACKGROUNDLayered double hydroxide nanoparticles have been extensively investigated and exploited for the removal of harmful anions from contaminated water. For adsorption of acid yellow dye (AY) from contaminated water, nitrate‐intercalated MgAl layered double hydroxide (LDH) nanoparticles were synthesized using the co‐precipitation method with the refluxing condition in a nitrogen atmosphere.RESULTSThe X‐ray diffraction pattern of LDH nanoparticles showed that LDH nanopowder with nitrate in the interlayer position was successfully synthesized. The shift in (003) basal plane diffraction peak to a lower angle (2θ) of 7.75° in the LDH‐AY from 10.40° in the pristine LDH confirmed the intercalation of AY in the interlayer space of LDH. Variable factors for the adsorption of the AY on the LDH nanoparticles were examined in the batch process using ultraviolet–visible spectroscopy and those included the adsorbent dose (5–30 mg), the incubation time (3–60 min), the temperature (25–50 °C), the pH of the AY aqueous suspension (5–9) and the AY concentration (0.03–0.1 mg mL−1). Box–Behnken design was used to optimize the three independent variables of temperature, incubation time and pH of AY solution for the adsorption of the dye. The optimized values of the incubation time, temperature and pH were found to be 25.89 min, 35.99 °C and 5.16, respectively. A maximum adsorption rate of 0.00515 g mg−1 min−1 of AY onto LDH nanoparticles was found at a solution pH of 5 and a temperature of 50 °C. The adsorption kinetics of the AY at different suspension pH values and temperature followed a pseudo‐second‐order kinetic model. Furthermore, an adsorption isotherm study for the adsorption of AY at a temperature of 40 °C and pH 5 followed a Langmuir isotherm model, and the maximum adsorption capacity of the AY was calculated to be 412.55 mg g−1 with excellent regeneration capacity.CONCLUSIONThe study revealed that the synthesized nitrate intercalated Mg Al LDH nanoparticles using the reflux conditions offered promising potential to adsorb acid yellow 36 dye form its aqueous solution. © 2023 Society of Chemical Industry (SCI).

Synthesis of bifunctional nanostructured adsorbents based on anionic/cationic clays: effect of arrangement on simultaneous adsorption of cadmium and arsenate.

The development of bifunctional hybrid materials based on natural clays and layered double hydroxide (LDH) and their application on the simultaneous adsorption of Cd(II) and As(V) was investigated in this work. Two different synthesis routes, in situ and assembly, were employed to obtain the hybrid materials. Three types of natural clays, namely bentonite (B), halloysite (H), and sepiolite (S), were used in the study. These clays are characterized by a laminar, tubular, and fibrous structural arrangement, respectively. The physicochemical characterization results indicate that the hybrid materials were formed through interactions between the Al-OH and Si-OH groups present in the natural clays, and the Mg-OH and Al-OH groups present in the LDH for both synthesis routes. However, the "in situ" route yields a more homogenous material because the LDH formation is performed on the natural clay surface. The hybrid materials showed an anion and cation exchange capacity up to 200.7meq/100g and an isoelectric point near 7. The arrangement of natural clay has no impact on the properties of hybrid material but influences the adsorption capacity. The adsorption of Cd(II) onto hybrid materials was enhanced in comparison with natural clays, obtaining adsorption capacities of 80, 74, 65, and 30mg/g for 15:1 (LDH:H)INSITU, 1:1 (LDH:S)INSITU, 1:1 (LDH:B)INSITU, and 1:1 (LDH:H)INSITU, respectively. The adsorption capacities of hybrid materials to adsorb As(V) were between 20 and 60μg/g. The 15:1 (LDH:H)INSITU sample showed the best adsorption capacity being ten folds greater than halloysite and LDH. In all cases, the hybrid materials showed a synergistic effect for Cd(II) and As(V) adsorption. The adsorption study of Cd(II) onto hybrid materials showed that the primary adsorption mechanism is cation exchange between the interlayer cations in natural clay and Cd(II) in the aqueous solution. The adsorption of As(V) showed that the adsorption mechanism is attributed to anion exchange between CO23- in the interlayer space of LDH and H2ASO4- in the solution. The simultaneous adsorption of As (V) and Cd (II) shows that, during the As(V) adsorption, there is no competition by the adsorption sites. Still, the adsorption capacity towards Cd(II) was enhanced 1.2-folds. This study ultimately revealed that the arrangement of clay has a significant influence on the adsorption capacity of the hybrid material. This can be attributed to the similar morphology between the hybrid material and natural clays, as well as the important diffusion effects observed in the system.

Enhanced adsorption effect of defect ordering Mg/Al on layered double hydroxides nanosheets with highly efficient removal of Congo red

The non-conventional structure layered double hydroxides (LDHs) as pollutant adsorbents with significant adsorption efficiency are promising valuable research topics. In this work, the defect ordering MgAl-LDHs nanosheets for the highly efficient removal of Congo red (CR) are designed and fabricated by a facile environmental-friendly hydrothermal method based on solid insoluble substances magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) as precursors. The decrease of Mg/Al ordering changes the interlayer spacing of LDHs and improves the defect sites with low oxygen coordination on the LDHs laminate, which enhances the removal efficiency of CR from 45.6 to 97.7%. This study reveals that a defect enhancing combined mechanism of surface adsorption and the anion-exchange in MgAl-LDHs can obtain an outstanding adsorption efficiency for removing CR. The reactivity of the Mg/Al disorder with O defect on the LDHs laminate increases with the reduction of frontier orbitals energy gap (ΔEgap), resulting in a high adsorption capacity for CR. The uncover of the defect enhancing adsorption mechanism provides a new strategy to fabricate MgAl-LDHs with high capability for wastewater remediation.

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.

Regulation of Structure and Anion-Exchange Performance of Layered Double Hydroxide: Function of the Metal Cation Composition of a Brucite-like Layer.

As anion-exchange materials, layered double hydroxides (LDHs) have attracted increasing attention in the fields of selective adsorption and separation, controlled drug release, and environmental remediation. The metal cation composition of the laminate is the essential factor that determines the anion-exchange performance of LDHs. Herein, we review the regulating effects of the metal cation composition on the anion-exchange properties and LDH structure. Specifically, the internal factors affecting the anion-exchange performance of LDHs were analyzed and summarized. These include the intercalation driving force, interlayer domain environment, and LDH morphology, which significantly affect the anion selectivity, anion-exchange capacity, and anion arrangement. By changing the species, valence state, size, and mole ratio of the metal cations, the structural characteristics, charge density, and interlayer spacing of LDHs can be adjusted, which affect the anion-exchange performance of LDHs. The present challenges and future prospects of LDHs are also discussed. To the best of our knowledge, this is the first review to summarize the essential relationship between the metal ion composition and anion-exchange performance of laminates, providing important insights for regulating the anion-exchange performance of LDHs.

First-Principles Study on Interlayer Spacing and Structure Stability of NiAl-Layered Double Hydroxides.

Interlayer spacing and structure stability of layered double hydroxides (LDHs) on their application performance in adsorption, ion exchange, catalysis, carrier, and energy storage is important. The effect of different interlayer anions on the interlayer spacing and structure stability of LDHs has been less studied, but it is of great significance. Therefore, based on density functional theory (DFT), the computational model with 10 kinds of anions intercalated Ni3Al-A-LDHs (A = Cl-, Br-, I-, OH-, NO3 -, CO3 2-, SO4 2-, HCOO-, C6H5SO3 -, C12H25SO3 -) and four Ni R Al-Cl-LDH models with different Ni2+/Al3+ ratios (R = 2, 3, 5, 8) were constructed to calculate and analyze interlayer spacing, structural stability, and their influence factors. It was found that the interlayer spacing order of Ni3Al-A-LDHs intercalated with different anions is OH- < CO3 2- < Cl- < Br- < I- < HCOO- < SO4 2- < NO3 - < C6H5SO3 - < C12H25SO3 -. The hydrogen bond network between the base layer and the interlayer anions affects the arrangement structure of the interlayer anions, which affects the interlayer spacing. For interlayer monatomic anions Cl-, Br-, and I- and the anion of comparable size in each direction SO4 2-, the interlayer spacing is positively correlated with the interlayer anion diameter. The larger difference between the long-axis and short-axis dimensions of the polyatomic anions results in the long axis of the anion being perpendicular to the basal layer, increasing interlayer spacing. The long-chain anion C12H25SO3 - intercalation system exhibits the largest layer spacing of 24.262 Å. As R value increases from 2 to 8, the interlayer spacing of Ni R Al-Cl-LDHs gradually increases from 7.964 to 8.124 Å. The binding energy order between the interlayer anion and basal layer is CO3 2- > SO4 2- > OH- > Cl- > Br- > I- > HCOO- > NO3 - > C12H25SO3 - > C6H5SO3 -. The smaller the interlayer spacing, the higher the binding energy and the stronger the structural stability of LDHs. The factors affecting structural stability mainly include the bond length and bond angle of the hydrogen bond and the charge interaction between the basal layer and interlayer anion. In the CO3 2- intercalated system, the hydrogen bond length exhibits the shortest of 1.95 Å and the largest bond angle of 163.68°. The density of states and energy band analysis show that the higher the number of charges carried by the anion, the stronger its ability to provide electrons to the basal layer.

Ultra-sensitive detection of pyridine in water using zinc porphyrin incorporated in a transparent hydrophobic film

In this study, we investigated the axial coordination reaction between pyridine and zinc meso-tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) incorporated in a transparent layered double hydroxide (LDH) film modified with 1-decanesulfonate (C10S) in an aqueous solution. The apparent equilibrium constant ({K}_{11}) of the axial coordination reaction between pyridine and ZnTPPS incorporated in the transparent ZnTPPS/C10S/LDH film was approximately 260 times that of the corresponding reaction in an aqueous solution. The hydrophobisation of the LDH interlayer space by C10S, which led to the elimination of water molecules surrounding ZnTPPS and enabled the accumulation of pyridine molecules, was responsible for such a significant increase in the apparent {K}_{11} value. The developed film can detect pyridine in aqueous solutions with ultra-high sensitivity in the order of 10−5 mol/L through changes in the colour tone, which is comparable to the molecular detection ability of insect antennae. The sensing response was also observed at pyridine concentrations as low as 10−9 mol/L.

Zeolitic imidazolate framework-L-assisted synthesis of inorganic and organic anion-intercalated hetero-trimetallic layered double hydroxide sheets as advanced electrode materials for aqueous asymmetric super-capacitor battery

Fine-tuning the interlayer space and composition of the layered double hydroxide (LDH) is a promising strategy to obtain high-performance battery-type electrode materials for super-capacitor battery. In this work, a series of two-dimensional (2D) porous hetero-trimetallic Zinc-Nickel-Cobalt LDHs sheets intercalated with nitrate anion and different Zn/Ni ratios (ZnxNi1-xCo-LDH-NO3–, x = 0, 0.25, 0.5, 0.75, and 1.0) are firstly synthesized through a Zeolitic imidazolate framework-L (ZIF-L)-assisted co-precipitation reaction and ion etching procedure. Among which, the Zn0.25Ni0.75Co-LDH-NO3– electrode, with a Zn/Ni ratio of 1:3, provides a high specific capacity (275 mAh g−1 at 1 A g−1). To further tune the interlayer space, Zn0.25Ni0.75Co-LDH-BA–/AA– (BA– = benzoate anion and AA– = acetate anion) sheets intercalated with BA– or AA– are synthesized by an anion-exchange method. A super-capacitor battery device (Zn0.25Ni0.75Co-LDH-BA–//activated carbon) using Zn0.25Ni0.75Co-LDH-BA– as the positive electrode can achieve a high energy density (51.8 Wh kg−1 at 789 W kg−1) and superb durability (94.6% over 10,000 cycles). This work can shed light on regulating the interlayer space of LDHs for advanced electrochemical energy storage applications.

Different Interlayer Anions Controlled Zinc Cobalt Layered Double Hydroxide Nanosheets for Ethanol Electrocatalytic Oxidation

Layered double hydroxides (LDHs) have been known as highly desired anode materials in the alkaline electrolyte. With regard to non-noble metal electrocatalysts, the interlayer spacing of LDHs has important influences on the electrocatalytic activity toward ethanol oxidation. Herein, ZnCo-LDHs with different interlayer spacing controlled by different interlayer anions (NO3–, Cl–, and CH3COO–) are used as effective non-noble metal electrocatalysts for the ethanol oxidation reaction (EOR). The interlayer spacing of three non-noble metal electrocatalysts follows the order: ZnCo-LDH-CH3COO– (0.763 nm) > ZnCo-LDH-Cl– (0.733 nm) > ZnCo-LDH-NO3– (0.719 nm). ZnCo-LDH-CH3COO– exhibits the highest mass activity (345.4 mA mg–1) for the EOR, which is 1.22 and 1.37 times higher than that of ZnCo-LDH-Cl– (283.8 mA mg–1) and ZnCo-LDH-NO3– (252.8 mA mg–1), respectively, attributed to the enlarged interlayer space. This work proposes a potential mechanism of the catalytic process toward the EOR, which may provide a new idea to design non-noble metal electrocatalysts with high catalytic activity in direct ethanol fuel cells (DEFCs).

Interlayer expanded nickel-iron layered double hydroxide by intercalation with sodium dodecyl sulfate for enhanced oxygen evolution reaction

Layered double hydroxides (LDH), a typical two-dimensional nanomaterial, has received vigorous attention in water splitting for its typically weak van der Waals interactions that can tunable for its interlayer spacing. Opening LDH with expanded interlayer is highly desirable to expose more active sites for electrocatalysis and more accessible surface for ion transfer in the interlayer, which can greatly boost the performance of LDH. Herein, interlayer expanded nickel-iron layered double hydroxide (NiFe-LDH) was fabricated by the intercalation with sodium dodecyl sulfate (SDS) using a one-pot hydrothermal route. For compassion, the NiFe-LDH without SDS were also prepared as hierarchical hollow spheres (NiFe-LDH HSs), while hollow spheres were transformed into hierarchical nanosheets (NiFe(SDS)-LDH NSs) with the addition of SDS. Moreover, the interlayer spacing of NiFe(SDS)-LDH NSs was effectively enlarged to 2.36 nm contrast to 0.77 nm of NiFe-LDH HSs. As expected, a highly enhanced oxygen evolution reaction (OER) performance was obtained on NiFe(SDS)-LDH NSs with a current density of 10 mA cm−2 at overpotential of 115 mV, while 225 mV for NiFe-LDH HSs. The intercalation of SDS in NiFe-LDH plays an indispensable role in boosting OER. It indicates the importance of enlarging the interlayer space of LDH for high-performance OER.

Unique Adsorption Properties of Malachite Green on Interlayer Space of Cu-Al and Cu-Al-SiW12O40 Layered Double Hydroxides

Cu-Al layered double hydroxide (LDH) was intercalated with Keggin ion of polyoxometalate K4[a-SiW12O40] to form Cu-Al-SiW12O40 LDH. The obtained materials were analyzed by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy, and Brunaur-Emmett-Teller (BET) surface area analysis. Furthermore, the materials were used as adsorbents of malachite green from aqueous solution. Some variables for adsorption, such as: effect of adsorption times, malachite green concentration, and also adsorption temperature, were explored. The results showed that diffraction at 11.72° on Cu-Al LDH has interlayer distance of 7.56 Å. The intercalation of that LDH with [a-SiW12O40]4− ion resulted increasing interlayer distance to 12.10 Å. The surface area of material was also increased after intercalation from 46.2 m2/g to 89.02 m2/g. The adsorption of malachite green on Cu-Al and Cu-Al-SiW12O40 LDHs followed pseudo second order kinetic and isotherm Langmuir model with adsorption capacity of Cu-Al and Cu-Al-SiW12O40 LDHs was 55.866 mg/g and 149.253 mg/g, respectively. That adsorption capacity is equal with increasing interlayer space and surface area properties of material after intercalation. Thus, the adsorption of malachite green on Cu-Al and Cu-Al-SiW12O40 LDHs is unique and dominantly occurred on interlayer space of LDH as active site adsorption. 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).

Naproxen/Layered Double Hydroxide Composites for Tissue-Engineering Applications: Physicochemical Characterization and Biological Evaluation

AbstractInjured bone tissues can be healed with bone grafts, but this procedure may cause intense pain to the patient. A slow and localized delivery of nonsteroidal anti-inflammatory drugs (NSAIDs) could help to reduce the pain without affecting bone regeneration. The objective of the present study was to use [Mg-Al]-layered double hydroxide (LDH) as a matrix for controlled release of sodium naproxen (NAP). This system could be applied in biomaterial formulations (such as bone grafts) to achieve a local delivery of naproxen. [Mg-Al]-LDH successfully incorporated up to 80% (w/w) of naproxen by the structural reconstruction route, with the [Mg-Al]-LDH interlayer space increasing by 0.55 nm, corresponding to the drug molecule size. The evaluation of the naproxen release kinetics showed that 40% of the drug was delivered over 48 h in aqueous medium (pH 7.4 ± 0.1), indicating the potential of [Mg-Al]-LDH/NAP for local release of naproxen at adequate concentrations. Kinetic modeling showed that the naproxen release process was closely related to the Higuchi model, which considers the drug release as a diffusional process based on Fick’s law. The chemical stability of NAP after the release tests was verified by 1H NMR. The [Mg-Al]-LDH/NAP also exhibited low cytotoxicity toward fibroblast cells (L929 cell line), without modifications in their morphology and adhesion capacity. These results describe a suitable approach for preparing efficient systems for local delivery of nonsteroidal anti-inflammatory drugs for biomedical applications.

Layered double hydroxide–indomethacin hybrid: A promising biocompatible compound for the treatment of neuroinflammatory diseases

Indomethacin (INDO) demonstrates therapeutic efficacy in the treatment of neuroinflammatory diseases. Despite its importance as a drug, INDO causes gastrointestinal problems and adverse reactions in the central nervous system (CNS). In this study, we prepared nanoparticles of layered double hydroxide (LDH) loaded with INDO. The structure of the nanohybrid (LDH-INDO) was synthesized via a coprecipitation method, and the nanohybrid was characterized using X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis–differential scanning colorimetry (TGA–DSC), field-emission scanning electron microscopy (FE-SEM), and ultraviolet (UV)–vis spectroscopy. Moreover, the drug release profiles of the nanohybrid were investigated using kinetic models. INDO was incorporated within the LDH interlayer space with 50% intercalation. The release of INDO anions from LDH-INDO after 10 h was 90% at pH 4.8 ± 0.02 and 51% at pH 7.4 ± 0.02. The results show that the release profiles follow a pseudo-second-order model. In addition, lipopolysaccharide (LPS)-induced sickness behavior in animals and treatment with INDO and LDH-INDO suggest recovery of the variables (weight and food intake) used in this study. LDH-INDO did not alter hepatic and renal biomarkers. Moreover, LPS increased the number of Iba1+ cells (microgliosis) and caused morphological alterations in these cells in the hippocampus and somatosensory cortex. However, the LPS effect was attenuated after treatment with INDO, both free and LDH-intercalated, in both regions of the brain.

The effect of Pd(II) chloride complexes anchoring on the formation and properties of Pd/MgAlOx catalysts

Pd(II) chloride complexes were anchored using magnesium-aluminum layered double hydroxides (LDHs) with interlayer anions (CO32– and OH–), which possess different exchange properties, and MgAl mixed oxide during its rehydration. It was shown that the catalysts of the same chemical composition with different size, morphology and electronic state of supported palladium particles can be synthesized by varying the localization of Pd precursor. The properties of Pd/MgAlOx catalysts were studied in aqueous-phase hydrogenation of furfural. Anchoring of the Pd precursor in the interlayer space of LDHs is accompanied by the formation of non-isometric agglomerated palladium particles which contain less oxidized metal and show a higher activity toward hydrogenation of furfural. Magnesium-aluminum oxides in Pd/MgAlOx catalysts are rehydrated in the aqueous-phase reaction to yield the activated MgAl-LDH species as a support, which promotes the furfural conversion via hydrogenation of the furan cycle.

Studies on conducting polymer intercalated layered double hydroxide nanocomposites: Antituberculosis drug delivery agents

AbstractThe synthesis of layered double hydroxide (LDH) was carried out using different ratios of Mg:Al. The intercalation of polypyrrole (Ppy) within interlayer space of LDH was carried out via ultrasonication using different loadings of the conducting polymer. Fourier transform infrared (FTIR) spectra and XRD analysis showed successful intercalation of Ppy in LDH while UV‐visible spectra confirmed polaronic state of the conducting polymer within the LDH. Scanning electron microscopy and transmission electron microscopy studies showed successful incorporation of Ppy and loading of the drug was also established. The concentration of Rifampicin, an antituberculosis drug in LDH/Ppy, was confirmed by Langmuir adsorption isotherm. The in vitro release characteristics showed sustained release behaviour at pH 7.4 for a period of 180 hours. The nanocomposites exhibited immense potential for their application as Rifampicin drug carriers.

Dual-functional Sites for Selective Adsorption of Mercury and Arsenic ions in [SnS4]4-/MgFe-LDH from Wastewater

Heavy metals existed as multiple types in wastewater, enhanced the difficulty for disposal, and aroused huge environmental issues. High selective adsorption of the most hazardous heavy metals is one important method for water purification and resource utilization. In this study, we assembled the [SnS4]4- clusters and MgFe-based layered double hydroxide (LDH) to synthesize the [SnS4]4-/LDH composites, to capture mercury and arsenic ions simultaneously. The results indicated that such composite exhibited excellent mercury and arsenic removal performance with higher than 99% removal efficiency at a wide pH range. The uptake of mercury was ascribed to the [SnS4]4- clusters sites while the arsenic removal was mainly due to the existence of Fe site in LDH composite. The inserted [SnS4]4- clusters can enlarge the surface areas and create a hierarchical pore channel due to the increased interlayer spacing of LDH, which can enhance the adsorption capacity. The different adsorption mechanisms were also indicated by dynamic analysis. Pseudo-second-order kinetic model was more suitable for both Hg(II) and As(III) adsorption in the dual-heavy metal solution, and neither Langmuir isotherm model nor Freundlich isotherm model fitted the Hg(II) and As(III) adsorption in the mixed solution. The adsorption progress was influenced due to the coexistence of another heavy metal. Besides, mercury can be collected from the spent materials using a thermal-heating method. Such composite exhibits promising potential for mercury recycling.

Synthesis and Properties of New Multilayer Chitosan@layered Double Hydroxide/Drug Loaded Phospholipid Bilayer Nanocomposite Bio-Hybrids.

A novel bio-hybrid drug delivery system was obtained involving a Mg/Al-NO3 layered double hydroxide (LDH) intercalated either with ibuprofenate anions (IBU) or a phospholipid bilayer (BL) containing a neutral drug, i.e., 17β-estradiol, and then embedded in chitosan beads. The combination of these components in a hierarchical structure led to synergistic effects investigated through characterization of the intermediates and the final bio-composites by XRD, TG, SEM, and TEM. That allowed determining the presence and yield of IBU and of BL in the interlayer space of LDH, and of the encapsulated LDH in the beads, as well as the morphology of the latter. Peculiar attention has been paid to the intercalation process of the BL for which all available data substantiate the hypothesis of a first interaction at the defect of the LDH, as well as on the interaction mode of these components. 1H, 31P and 27Al MAS-NMR studies allowed establishing that the intercalated BL is not homogeneous and likely formed patches. Release kinetics were performed for sodium ibuprofenate as well as for the association of 17β-estradiol within the negatively charged BL, each encapsulated in the LDH/chitosan hybrid materials. Such new bio-hybrids offer an interesting outlook into the pharmaceutical domain with the ability to be used as sustained release systems for a wide variety of anionic and, importantly, neutral drugs.

Synthesis and fine spectroscopy tuning of the hyperspectral simulation material based on organic anions intercalated Mg-Al layered double hydroxide

Organic anions have been intercalated into the interlayer of Mg-Al layered double hydroxides (LDHs) via a hydrothermal method to tune the visible and near-infrared reflection spectrum of hybrid pigments based on LDHs. The prepared samples were analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric-differential scanning calorimetry, visible and near-infrared spectrophotometry, and CIE 1976 L*a*b* color scales. The effects of the intercalated organic anions on the structure, morphology, color, and spectral characteristics of Mg-Al LDH materials were systematically investigated. The results show that the colored anions of acid green (AG) and acid yellow (AY) have been successfully intercalated into the interlayer space of LDHs through the anion displacement process. The visible light reflection spectrum of LDH matrix can be easily tuned by adjusting the intercalated concentration of anions and the relative ratio of AG and AY, which leads to the color of prepared samples changing from the original white into blue, yellow, green, and dark black. Combined with the color adjusting ability of organic anions and the high hydroxyl property of LDH substrate, the typical visible and near-infrared spectral characteristics of natural green plants can be accurately simulated. The correlation coefficient of spectrum shape between the prepared pigment and green plant in the whole range of 400–2500 nm is as high as 0.94. Moreover, the thermal stability of LDH materials is improved by the intercalated organic anions, whose spectral properties can withstand high temperatures of at least 250 °C. The hybrid materials could be used as a functional pigment to prepare green camouflage coatings, showing their potential application in the field of hyperspectral camouflage.