MgAl-layered Double Hydroxide Nanosheets Research Articles

In-situ Mg-Al LDH infused lignin-derived laser scribed graphene for facilitated ion transport in flexible supercapacitor application

BackgroundInnovations in the synthesis of hybrid materials have led to technology advancement of the microsupercapacitor. Delaminated layered double hydroxide (LDH) reduces self-agglomeration and increases energy density in graphene-based supercapacitors. The incorporation of delaminated LDH with oil palm lignin derived laser scribed graphene in neutral PAAS/K2SO4 gel electrolyte for flexible microsupercapacitor applications was investigated. MethodVarious concentrations of positively charged sucrose-delaminated Mg-Al LDH nanosheets produced through the coprecipitation method were hybridised with negatively charged oil palm lignin-derived laser scribed graphene (L-LSG) through electrostatic interaction. Significant FindingsHybrid laser scribed graphene developed from delaminated Mg-Al LDH at a concentration of 10 gL−1 (L-LSG/D-MgAl-10) had the largest surface area of 49.335 m2g−1. The incorporation of Mg-Al LDH nanosheets on l-LSG were further validated by FESEM, TEM, XRD, Zeta potential and other characterizations. It also had the highest areal capacitance and energy density, measuring 40 mFcm−2 and 0.00296 mWhcm−2, respectively, at a current density of 0.08 mAcm−2. The fabricated microsupercapacitor has exceptional bending capabilities and capacitance retention of 89.2% after 5000 cycles. In summary, by inducing additional pseudocapacitance, delaminated Mg-Al LDH improved the overall effectiveness of the oil palm lignin derived graphene electrode compared to pristine graphene.

Influence of Mg[sbnd]Al layered double hydroxide nanosheets on the structure and properties of Ni[sbnd]Fe[sbnd]P composite coatings

NiFeP/MgAl layered double hydroxide (LDH) composite coatings with high corrosion and wear resistance were prepared by electroless deposition. A series of test methods was used to comprehensively evaluate the crystal structure, surface morphology, element composition, roughness of the composite coating. The anti-wear and anti-corrosion performances of NiFeP/MgAl LDH (the following are all expressed as NiFeP/LDH) composite coatings were investigated. The deposition mechanism of the NiFeP/LDH alloy was rationalised. The results show that the MgAl LDH nanosheets were uniformly distributed in the NiFeP coating due to ion adsorption. The corrosion potential of NiFeP coatings in 3.5 wt% NaCl solution at 25 °C was −0.458 V vs. SCE, while the corrosion potential of NiFeP/LDH (0.4 g L−1) was −0.334 V vs. SCE. The coating shows adhesive wear during the friction test. The wear resistance of the NiFeP/LDH composite coating was much higher than that of the NiFeP coating. The two-dimensional lamellar nanomaterial LDH was good reinforcement phases for the NiFeP matrix.

Enhanced removal performance and mechanistic study of Cu2+, Cd2+, and Pb2+ by magnetic layered double hydroxide nanosheets assembled on graphene oxide

Devising effective measures for removing heavy metals from water has become a serious concern. In this study, MgAl-layered double hydroxide nanosheets were assembled on graphene oxide (GL) and its magnetic product (Fe3O4@GL) as excellent adsorbents for Cu2+, Cd2+, and Pb2+ and were synthesized by a simple hydrothermal method. The morphology and surface chemical properties were observed to establish the construct-activity relationships. The characterization results showed that the adsorbents combined rich functional groups with large specific surface areas. The effective removal of heavy metals by GL and Fe3O4@GL was achieved under neutral and weakly alkaline conditions. The pseudo-second-order kinetic equation described the experimental results well, and the equilibrium data were in good agreement with the Freundlich model for Cu2+ and Cd2+ and the Langmuir model for Pb2+. The maximum adsorption capacity of GL (Cu2+: 89.26 mg/g, Cd2+: 76.67 mg/g, Pb2+: 226.98 mg/g) was slightly larger than that of Fe3O4@GL (Cu2+: 80.72 mg/g, Cd2+: 70.26 mg/g, Pb2+: 213.96 mg/g). The main mechanisms include the surface complexation of hydroxyl groups, precipitation reactions of metal hydroxides and metal carbonates, and isomorphic substitution of divalent metal cations. Thus, the enhanced adsorption capacity and mechanistic study provide new insights into the environmental remediation of heavy metals.

Dual Inhibitions on Glucose/Glutamine Metabolisms for Nontoxic Pancreatic Cancer Therapy.

Glucose and glutamine are two principal nutrients in mammalian cells that provide energy and biomass for cell growth and proliferation. Especially in cancer cells, glutamine could be a main alternative for energy and biomass supply once glucose metabolism is suppressed. Therefore, single inhibition of enzymes in either glucose metabolism or glutaminolysis, though maybe efficient in vitro, is far from being satisfactory for efficient in vivo cancer therapy. Here, we proposed a new strategy for dual inhibitions on both glucose and glutamine metabolisms concurrently by silencing mutated gene Kras and glutaminase 1 (GLS1) via nanomaterial-based siKras and siGLS1 delivery, rather than conventional highly toxic chemodrugs. Such a combination therapy could overcome the challenge that glucose and glutamine are alternatives to each other in the biosynthesis and energy production for cancer cells, resulting in much elevated treatment efficacy. In addition, layered double hydroxide (LDH), the siRNA carrier, enables an enhanced gene delivery efficiency compared to the commercial transfection agent Lipofectamine 2000. Briefly, Mg-Al LDH nanosheets, loaded with siKras and siGLS1 onto their surfaces by electrostatic adsorption, could release siRNA from lysosomes into the cytoplasm via the proton sponge effect of LDH, favoring the siRNA stability and gene silencing efficiency enhancements. The thus released siRNA could downregulate the expressions of Kras, GLS1, and other enzymes involved in glucose metabolism, resulting in the downregulations of ATP and other metabolites. Such a biosafe LDH/siRNA nanomedicine is able to efficiently suppress the growth of xenografts through cancer cell proliferation suppression, displaying its great potential as a simultaneous glucose/glutamine metabolism coinhibitor for treating pancreatic cancer.

Partial Exchange between Inorganic and Organic Anions in MgAl Layered Double Hydroxide Nanosheets for Humidity Sensing

Partial Exchange between Inorganic and Organic Anions in MgAl Layered Double Hydroxide Nanosheets for Humidity Sensing

Moisture- and mould-proof characteristics of surface modified wood for musical instrument soundboards.

Wood is the main material used for musical instrument soundboard fabrication, for practical and cultural reasons. As a natural material, however, wood is easily degraded due to moisture or fungal corrosion. Most traditional wood protection methods were devised for structural materials, and may thus not be suitable for application in musical instrument soundboard materials. In the current study, a novel nanomaterial-based modification method was applied to wood. The surface of wood was coated with polyurethane and MgAl-layered double hydroxide nanosheets after a convenient impregnation process. The modified wood exhibited improved hydrophobicity and mould-resistance, while maintaining its acoustic properties. This modified wood may facilitate the construction of soundboards with longer lifespans.

Adsorption of SeO42− by delaminated Mg-Al layered double hydroxide nanosheets

Layered double hydroxides (LDHs) are excellent anion-exchange materials, and are useful in adsorbing hazardous anions. The LDHs form nanosheets upon delamination, which improves their efficiency. In this study, we investigated the SeO42− adsorption properties of the nanosheets obtained by the delamination of NO3⋅Mg-Al LDH in an aqueous solution and compared them with those of the NO3⋅Mg-Al LDH. The SeO42− adsorption by both substances was a “pseudo-second-order rate reaction”. The reaction-rate constant during the early stage was greater for the nanosheets as their surface area was larger than the NO3⋅Mg-Al LDH. The amorphous nanosheets reverted to an ordered LDH structure after the anion exchange. Atomic force microscopy (AFM) imaging and the corresponding height profile analysis of the samples confirmed the nanosheets stacking post SeO42− adsorption. We propose a mechanism of the SeO42− adsorption by the NO3⋅Mg-Al LDH nanosheets. These findings may improve the understanding of the anion exchange by the LDHs, which may lead to the development of high-efficiency materials that extract metals such as Se from wastewater.

Pd Nanoparticles Supported on Amine-Functionalized MgAl Layered Double Hydroxides for Solvent-Free Aerobic Oxidation of Benzyl Alcohol

Pd nanoparticles (NPs) supported on amine-functionalized layered double hydroxides (LDHs) (Pd/NH2-LDH-NS) were successfully obtained by implanting aminopropyltriethoxysilane (APTS) on MgAl LDH nanosheets (LDH-NS), followed by impregnating [Pd(NH3)4]Cl2 and reduction with NaBH4. The physicochemical characteristics of the obtained Pd/NH2-LDH-NS were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR),, N2 adsorption–desorption, inductive coupled plasma (ICP), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS), and their catalytic performance was tested in the selective oxidation of benzyl alcohol with molecular oxygen under solvent-free and base-free conditions. The results showed that the implanted –NH2 groups can promote the dispersion of the supported Pd NPs via complexation of the implanted –NH2 groups to Pd NPs, and they can increase the surface basicity of the catalysts, thus enhancing the catalytic activity and selectivity to benzylaldehyde. Pd/NH2-LDH-NS exhibited enhanced catalytic activity (31.6%) and selectivity (>98%) compared to the corresponding Pd/LDH-NS, Pd/LDH, Pd/SiO2, and Pd/Al2O3. Moreover, Pd/NH2-LDH-NS was remarkably stable and could be reused at least four times without a significant loss in activity and selectivity.

In Situ Nanoassembly of Mg-Al Layered Double Hydroxide on Polyester Fabric Surface: Mechanism, Tunable Wettability, and Boosted Thermal Features

In this study, nanosheets of Mg-Al layered double hydroxide (LDH) were introduced on the polyester fabric surface through the conventional coprecipitation method with further hydrothermal treatment at various temperatures (80, 100, and 120 °C). The in situ growth mechanism of Mg-Al LDHs in the vertical direction in an alkaline synthesis bath along with polyester fabric hydrolysis was discussed. Different analyses including X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric (TG) analysis, UV–visible, and Fourier transform infrared (FTIR) spectroscopy were utilized to characterize the synthesized nanosheets. Furthermore, vertical wicking, static contact angle, tensile strength, air permeability, bending, and burning length of fabric samples were investigated. The results showed successful synthesis of Mg-Al LDH nanosheets on the fabric surface with tunable wettability and boosted thermal features. Interestingly, there is no adverse effect on the ph...

Mechanism of MgAl-LDH-induced enhancement in the plasmonic photocatalytic performance over bismuth nanospheres

The rapid development of industry, automobiles and manufacturing has emitted an ever-growth amount of the atmospheric gas pollutants to the atmosphere, such as nitric oxide (NO x ), sulfur oxide (SO x ), volatile organic compounds (VOC) and particle matters (PM). NO is deemed as one critical air pollutant as it is the leading origins of several environmental issues, such as the acidic rain, haze, and photochemical smog. To eliminate its environmental risk, it is highly desired to develop one effective, cost-effective and environmental-friendly technology to detect, regulate and remove them. Till now, various technologies have been developed, including the selective physical/chemical adsorption, heterogeneous catalytic reduction/oxidation and photocatalysis, to show high efficiency in separation, conversion and detoxification of NO. Among them, photocatalysis is receiving an ever-increased attention by its high efficiency, low cost and green feature (this technology enables the direct utilization of solar light to trigger the generation of highly active oxidative free radicals for pollutant degradation and mineralization). In the development of photocatalytic technology, the core part is the design and synthesis of highly effective and durable photocatalyst. Plasmonic metal with a unique localized surface plasmon resonance (LSPR) feature have now emerged as one appealing class of photocatalysts with wide applications in environmental remediation and energy conversion. In the plasmonic metal-directed photocatalysis, the surface electrons of plasmonic metal oscillate resonated with the incident photon, giving rise to the generation of hot carriers for catalytic redox reactions. However, most of the current LSPR-directed photocatalysis is limited to the noble metal (Au and Ag). Very recently, the earth-abundant bismuth metal (Bi) was confirmed to show a unique LSPR feature in visible light region, and more importantly, can serve as a direct plasmonic photocatalyst in ppb-level NO removal from a gas flow under UV illumination. However, bare Bi particles do not show enough redox capability as the hot carriers produced via LSPR in Bi metal cannot travel over distances longer than tens of nanometers. In this study, we attempt to introduce the MgAl-layered double hydroxide (MgAl-LDH) to intensify photocatalytic efficiency of the Bi metal. A facile liquid-phase ultrasound-assisted assembly approach was firstly used to synthesize the Bi@MgAl-LDH nanocomposite, in which Bi-NPs are uniformly supported on MgAl-LDH nanosheets. This composite can efficiently and steadily photocatalyze the removal of ppb-level NO from a continuous air flow under ultraviolet light irradiation via the plasmonic effect Bi metal. The removal efficiency reaches 43% for Bi@MgAl-LDH, much higher than the bare Bi-NPs (43%). The combined study of the composite phase/morphology/structure, its optical property, band structure and ESR oxidation radical capture experiments reveal that MgAl-LDH cannot form a heterojunction with Bi-NPs, and the enhanced photocatalysis on Bi@MgAl-LDH originates from the abundant hydroxide ions (OH−) on the surface of MgAl-LDH. These OH− can quickly capture the photoexcited holes to generate ·OH radicals, and simultaneously promote the electron-hole separation by consuming the holes, both of which can raise the utilization efficiency of the photoexcited hot carriers and provide sufficient oxidative radicals for NO oxidation. Additionally, MgAl-LDH has a unique water molecule memory effect, and the OH− that is consumed in photocatalysis can be replenished by adsorbing water from the air, leading to a stable photocatalytic performance. The reaction pathway study of the photocatalytic NO oxidation over Bi@MgAl-LDH by in-situ DRIFTS reveals that NO is completely mineralized into nitrate. The present work should contribute to a deeper understanding of the photocatalytic mechanism and then the design of robust catalysts for air purification.

Small-Sized Mg-Al LDH Nanosheets Supported on Silica Aerogel with Large Pore Channels: Textural Properties and Basic Catalytic Performance after Activation.

Layered double hydroxides (LDHs) have been widely used as an important subset of solid base catalysts. However, developing low-cost, small-sized LDH nanoparticles with enhanced surface catalytic sites remains a challenge. In this work, silica aerogel (SA)-supported, small-sized Mg–Al LDH nanosheets were successfully prepared by one-pot coprecipitation of Mg and Al ions in an alkaline suspension of crushed silica aerogel. The supported LDH nanosheets were uniformly dispersed in the SA substrate with the smallest average radial diameter of 19.2 nm and the thinnest average thickness of 3.2 nm, both dimensions being significantly less than those of the vast majority of LDH nanoparticles reported. The SA/LDH composites also showed large pore volume (up to 1.3 cm3·g) and pore diameter (>9 nm), and therefore allow efficient access of reactants to the edge catalytic sites of LDH nanosheets. In a base-catalyzed Henry reaction of benzaldehyde with nitromethane, the SA/LDH catalysts showed high reactant conversions and favorable stability in 6 successive cycles of reactions. The low cost of the SA carrier and LDH precursors, easy preparation method, and excellent catalytic properties make these SA/LDH composites a competitive example of solid-base catalysts.

Layered double hydroxide materials coated carbon electrode: New challenge to future electrochemical power devices

Layered double hydroxides (LDHs) have been widely used in the past years due to their unique physicochemical properties and promising applications in electroanalytical chemistry. The present paper is going to focus exclusively on magnesium-aluminum and zinc-aluminum layered double hydroxides (MgAl & ZnAl LDHs) in order to investigate the property and structure of active cation sites located within the layer structure. The MgAl and ZnAl LDH nanosheets were prepared by the constant pH co-precipitation method and uniformly supported on carbon-based electrode materials to fabricate an LDH electrode. Characterization by powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy revealed the LDH form and well-crystallized materials. Wetting surface properties (hydrophilicity and hydrophobicity) of both prepared LDHs were recorded by contact angle measurement show hydrophilic character and basic property. The electrochemical performance of these hybrid materials was investigated by mainly cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry techniques to identify the oxidation/reduction processes at the electrode/electrolyte interface and the effect of the divalent metal cations in total reactivity. The hierarchy of the modified electrode proves that the electronic conductivity of the bulk material is considerably dependent on the divalent cation and affects the limiting parameter of the overall redox process. However, MgAl LDH shows better performance than ZnAl LDH, due to the presence of magnesium cations in the layers. Following the structural, morphological and electrochemical behavior studies of both synthesized LDHs, the prepared LDH modified electrodes were tested through microbial fuel cell configuration, revealing a remarkable, potential new pathway for high-performance and cost-effective electrode use in electrochemical power devices.

A novel method for the preparation of Co Schiff-base functionalized MgAl layered double hydroxides

In order to immobilize neutral or positive metal complexes on layered double hydroxides (LDHs) and increase the amount of immobilized metal complexes, a novel strategy for the preparation of metal complex functionalized LDHs is proposed. This strategy involves exfoliating glycine-intercalated MgAl LDH in formamide under an ultrasound treatment, and then grafting silylated metal complexes on MgAl LDH nanosheets, as exemplified by immobilization of Co Schiff-base on MgAl LDHs. The prepared hybrids were characterized by XRD, AFM, FT-IR, TG, N2 adsorption–desorption and ICP techniques and their catalytic performances were investigated in H2O2 decomposition and styrene epoxidation with O2. The results showed that the hybrid prepared by this strategy had higher Co Schiff-base loading than the sample prepared by directly grafting silylated Co Schiff-base on glycine-intercalated MgAl LDHs due to the more accessible grafting sites on the exfoliated MgAl LDH nanosheets. Additionally, it was found that the grafted complexes could effectively impede the restack of LDH nanosheets after removal of the solvent. Thus, the prepared hybrid exhibited higher surface area and more accessible active centers, which made the prepared hybrid exhibit high catalytic activity in H2O2 decomposition and styrene epoxidation with O2. This work gives us a new way to prepare LDH hybrids functionalized with various metal complexes.

A chiroptical switch based on DNA/layered double hydroxide ultrathin films.

A highly oriented film was fabricated by layer-by-layer self-assembly of DNA and MgAl-layered double hydroxide nanosheets, and its application in chiroptical switch was demonstrated via intercalation and deintercalation of an achiral molecule into the DNA cavity. DNA molecules are prone to forming an ordered and dispersive state in the interlayer region of rigid layered double hydroxide (LDH) nanosheets as confirmed by scanning electron microscopy and atomic force microscopy. The induced chiroptical ultrathin film (UTF) is achieved via the intercalation of an achiral chromophore [5,10,15,20-tetrakis(4-N-methylpyridyl)porphine tetra(p-toluenesulfonate) (TMPyP)] into the spiral cavity of DNA stabilized in the LDH matrix [denoted as TMPyP-(DNA/LDH)20]. Fluorescence and circular dichroism spectroscopy are utilized to testify the intercalation of TMPyP into (DNA/LDH)20 UTF that involves two steps: the electrostatic binding of TMPyP onto the surface of (DNA/LDH)20 followed by intercalation into base pairs of DNA. In addition, the TMPyP-(DNA/LDH)20 UTF exhibits good reversibility and repeatability in induced optical chirality, based on the intercalation and deintercalation of TMPyP by alternate exposure to HCl and NH3/H2O vapor, which can be potentially used as a chiroptical switch in data storage.