LDHs Layers Research Articles

Mg-Al layered double hydroxides modified by 2,4,6-trimercapto-s-triazine for effective removal heavy metals from soil

Since 2,4,6-trimercapto-s-triazine (TMT) possesses advantages of multiple adsorption sites and strong binding ability with heavy metals, in this study, layered double hydroxides modified by TMT are prepared (LDHs-TMT) for removing Cu(II)/Pb(II) from contaminated soil. The characterization of structure indicated TMT is intercalated between LDHs layers, and affects growth of crystal structure. The data of kinetics fits pseudo-second-order and intraparticle diffusion models. The isotherms is conformed to Langmuir model, and the adsorption capacity reaches 102.8 mg/g for Cu(II) and 105.8 mg/g for Pb(II). For adsorption mechanism, when concentration of Cu(II)/Pb(II) is low, Cu(II)/Pb(II) is preferentially immobilized by interlayered TMT molecule. As concentration increases, since adsorption sites on TMT are fully occupied, Cu(II)/Pb(II) grab the hydroxy of LDHs and form hydroxide precipitation. The effects of pH, coexistence ions, column leaching and leaching experiments are conducted. The results indicate LDHs-TMT have high adsorption stability and possesses appreciable interception for heavy metal migration.

Zeolite/ZnAl-layer double hydroxides with different Zn/Al ratios and intercalated anions as the substrate of constructed wetlands: synthesis, characterization and purification effect of Hexavalent chromium.

The study aimed to synthesize novel zeolite substrates modified with four types of ZnAl-LDHs including Cl-LDHs(1:1), Cl-LDHs(3:1), CO3-LDHs(1:1), and CO3-LDHs(3:1); investigate Cr(VI) removal efficiencies in lab-scale constructed wetlands (CWs); and explore the effect of different Zn/Al ratios and intercalated anions on the removal efficiencies of Cr(VI) by modified zeolite. Different ZnAl-LDHs were prepared by co-precipitation method and coated onto the surface of original zeolite. Field emission scanning electron microscope and energy dispersive spectrometer were used to analyze physicochemical properties of zeolite/ZnAl-LDHs. Obtained results confirmed the successful LDHs-coating modification. The results of both X-ray diffraction and Fourier transform infrared suggested that the typical diffraction peak and functional groups of ZnAl-LDHs were detected in modified zeolites, and the peak of CO32- in CO3-LDHs at 1362cm-1 was stronger and sharper than Cl-LDHs. It could be demonstrated by above results that the synthesis crystallinity and coating effect of CO3-LDHs was better than Cl-LDHs. Furthermore, it could be found that under the condition of same intercalated anion, LDHs with metal molar ratio of 1:1 had better crystallinity than LDHs with metal molar ratio of 3: 1. Subsequent determination of the removal performance of Cr(VI) by purification experiments revealed that zeolite/Cl-LDHs(3:1) showed the best Cr(VI) removal performance, and the removal rate of Cr(VI) was improved by 32.81% compared with the original zeolite, which suggested that could be an efficient substrate of CWs for Cr(VI) removal. The high crystallinity indicated that the structure of LDHs was stable and it was difficult to remove Cr(VI) by ion exchange. The above explained why the Cr(VI) removal efficiency by zeolite/Cl-LDHs is superior to that by zeolite/CO3-LDHs under the condition of same metal molar ratio. With the increase of metal molar ratio, the charge density of LDHs layers and intercalated anion increased, thus enhancing the electrostatic attraction of LDHs layers to Cr(VI) and the interlayer anion exchange capacity. However, the effect of charge density on Cr(VI) removal efficiency may be greater than crystallinity on removal efficiency, which could be responsible for the fact that zeolite/ZnAl-LDHs(3:1) had better Cr(VI) removal efficiency than zeolite/ZnAl-LDHs(1:1) under the condition of same intercalated anion.

Constructing supported Ag antibacterial nano-agent with high activity and stability for broad-spectrum antibiosis

The developing a green and facile synthetic approach of Ag-based antibacterial nanomaterials with controlled composition, size, and shape, to acquire high antibacterial activity and long-term durability, is of vital importance and remains a challenging goal. Herein, a novel LDHs-supported Ag antibacterial nanomaterial (Ag/CoAl-LDHs) are fabricated via an in situ deposition of the Ag nanoparticles onto the CoAl-LDHs surface. X-ray diffraction pattern (XRD) and High-resolution TEM (HRTEM) measurements confirm that the uniform Ag nanoparticles (the average particle size of 16.5 nm) are highly dispersed and firmly anchored onto CoAl-LDHs surface. As revealed by x-ray photoelectron spectroscopy (XPS), the CoAl-LDHs nanoplates play the roles of both a support and a reductant without any external, and there was a redox reaction between Co2+ in LDHs layers and Ag+ in AgNO3 solution, giving rise to in situ loading of Ag nanoparticles onto LDHs. Moreover, antibacterial experiments verify that Ag/CoAl-LDHs not only have efficient antibacterial activity against both Escherichia coli and Staphylococcus aureus, but also exhibit very stable antibacterial properties for both bacteria. Therefore, this research demonstrates a successful paradigm for the rational design and preparation of new antibacterial nanomaterials with high antibacterial activity and long-term durability.

Facile synthesis of novel hierarchical core@shell structural magnetic nanovehicle Fe3O4@ZnAlCe-MoO4-LDHs for carbon steel protection

A novel dual-stimuli-responsive inhibitor nanovehicle Fe3O4@ZnAlCe-MoO4-LDHs was synthesized via a facile double-drop co-precipitation method. The obtained Fe3O4@ZnAlCe-MoO4-LDHs presents well-defined hierarchical core–shell structure with MoO42− corrosion inhibitor intercalated lamellar ZnAlCe-LDHs nanocrystals of ~30 nm assembling closely to Fe3O4 microspheres surface, possessing moderate inhibitor loading of 9.72% and strong superparamagnetism. The release results reveal that in the same NaCl solution, the releq (equilibrium release amount, 49.1%) and t0.5 (the time for release fraction of 50%, 4.5 h) were delayed much by magnetic field relative to non-magnetic field case (51.6%, 2.5 h). And the releq decreased with magnetic field strength, accompanied by the prolongation of t0.5, up to 6 h under a 1350 Gs magnet. Similarly, with keeping the magnetic field unvaried, the decline of NaCl solution concentration led to lower releq and longer t0.5. The kinetic fittings displayed that for all cases, the release process is inclusive of interlayer diffusion between LDHs layers (path I), interparticle diffusion among stacked LDHs crystals (path II) and diffusion between magnetic nanoparticles (path III). Compared to non-magnetic field, diffusion difficulties of path III was greatly enhanced under magnetic field. While for low-Cl− concentration system, the path I were limited effectively. Thus these two stimulus response factors can be used to regulate release behavior. Meanwhile, the protection efficiency of the nanovehicle for Q235 steel is higher than 88% because of the formation of inhibition film (ferrous or iron molybdate and hydroxide of zinc and cerium) on Q235 surface and the reduction of Cl− concentration in the solution via ion exchange. Moreover, the nanovehicle, presenting outstanding structural and magnetic stabilities, can be regenerated by a series of experiments, owning appreciable recycling performance and good anticorrosion activity in six recycles.

Maire Tecnimont invests in Siluria

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Elevance advances metathesis route

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Advances in Catalysis – Volume 59

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

INEOS Oligomers has announced updated plans to build a new PAO plant

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

BASF introduces Portable Fluid Catalytic Cracking (FCC) Catalyst Addition System for Refinery Catalysts in Europe

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Iron-sulfur gel provides possible green route to ammonia

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Modified graphene catalyzes CO2 reduction

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Catalyst combo could oxidize biomass alcohols

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Dry reforming puts CO2 to work

Aiming at integration of CO2 capture and utilization, we put forward a nanocatalyst for coupling photocatalytic CO2 reduction with 5-hydroxymethylfurfural (5-HMF) oxidation. Specifically, we synthesize a carbonate-type CuCoAl-layered double hydroxide (LDH) to pre-enrich the raw material of the half reduction reaction. In the inert atmosphere, CO32− located in the interlayers realized in situ reduction catalyzed by the metal cations on the layers, and this was coupled with 5-HMF oxidation catalyzed by the hydroxyl sites, thus generating CO as a reduction product and 2.5-furandiformaldehyde (DFF), 5-formyl-2-furanacarboxylic acid (FFCA), and 2.5-furan dicarboxylic acid (FDCA) as oxidation products. A series of in situ Fourier transform infrared (FTIR) spectroscopy with assistance of 13C labeling characterizations clarified the above in situ transformation process and further revealed the important role of tuning the electronic structure by selectively etching the LDHs layers in promoting catalytic performance. More importantly, the consumed CO32− could be easily supplied by CO2 in air, which would endowed the nanocatalyst with good recycle performance.

Novel morphology-controlled hierarchical core@shell structural organo-layered double hydroxides magnetic nanovehicles for drug release.

Novel hierarchical core@shell structured salicylate (SA) intercalated ZnAl-LDH (layered double hydroxides) magnetic nanovehicles were obtained via a special double-drop coprecipitation strategy assembling organo-ZnAl-LDH nanocrystals onto the surface of Fe3O4 submicrospheres (∼480 nm) from cheap aspirin and Zn- and Al-nitrates in alkaline solutions. The obtained Fe3O4@SA-LDH-r nanovehicles exhibit varied morphologies with hexagonal LDH ab-face horizontal, vertical, and vertical/slant/horizontal to the surfaces of Fe3O4 upon proper mass ratio (r) of Zn-salt to Fe3O4 from 1.93 to 7.71 in a low supersaturation system and possess moderate drug loadings and strong superparamagnetism. An in vitro release study reveals that under "no MF" mode (without external magnetic field) the SA release exhibits the higher accumulated release amount and smaller half-life (t0.5) for Fe3O4@SA-LDH-3.85 (41.2%, 1.63 min) and Fe3O4@SA-LDH-7.71 (51.1%, 1.66 min) probably owing to their mainly vertical LDH orientations, while the dramatically reduced SA release (10.0%) and greatly elongated t0.5 (25.6 min) for Fe3O4@SA-LDH-1.93 may be due to its relatively stronger host-guest interaction and compact horizontally oriented LDH shell stack. Under "MF on" mode, all the magnetic samples show a detectable reduced SA release owing to the particle-particle interactions among the magnetic nanovehicles. The kinetic fittings show that the release processes of all the samples involve the bulk and surface diffusion. The SA release from Fe3O4@SA-LDH-1.93 is mainly determined by the interparticle diffusion among the horizontally oriented LDH shell nanocrystals while those of Fe3O4@SA-LDH-3.85 and Fe3O4@SA-LDH-7.71 mainly involve the interlayer intraparticle diffusion between LDHs layers due to their largely vertical LDH shell nanocrystals.

Coassembly of exfoliated Ni–In LDHs nanosheets with DNA and infrared emissivity study

The biomolecule–inorganic hybrid materials are potential candidates for low infrared emissivity materials due to the combined functionalities of the biomolecules and the inorganic components. In this study, we describe a facile approach to fabricate DNA/layered double hydroxides (LDHs) nanohybrid by coassembly of exfoliated Ni–In LDHs nanosheets with DNA. In the assembly progress, exfoliated LDHs nanosheets and DNA with different initial DNA/LDHs mass ratio were mixed together, and the DNA intercalated LDHs nanohybrid was obtained only when the input DNA/LDHs mass ratio is ≤0.3 mg/mg. The structure and morphology of as-fabricated hybrid materials were characterized by X-ray diffraction (XRD), UV–Vis absorption spectra, Fourier transform infrared (FT-IR) spectra, thermogravimetry (TG), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicate that the reassembled product has layered structures incorporated with DNA biomolecule. The nanohybrid with expanding LDHs structure of d 003 = 2.6 nm confirms the intercalation of DNA molecules into the LDHs interlayer. The helix chain oriented parallel to the basal plane of host layer forming ordered sandwich structure. The infrared emissivity value of the DNA/LDHs nanohybrid was then investigated. It was found that the infrared emissivity values were significantly reduced by coassembly of exfoliated LDHs nanosheets with DNA, which may be attributed to the synergistic effect and interfacial interaction between the DNA biomolecule and inorganic LDHs layers reinforced by the construction of ordered sandwich structure.

Methotrexate intercalated layered double hydroxides with different particle sizes: Structural study and Controlled release properties

To study the influence of particle size on release properties, drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) nanohybrids with different particle sizes were synthesized through traditional coprecipitation method, by using the mixture of water and polyethylene glycol (volume ratio is 3:1) as solvent. The relationship between particle size and hydrothermal treatment conditions (i.e., time and temperature) had been systematically investigated, and the results indicate that the particle size can be precisely controlled between 70 and 300nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different hydrothermal treatment almost has no effect on compositions of the nanohybrids. X-ray diffraction (XRD) patterns and fourier transform infrared spectroscopy (FTIR) investigations manifested the successful intercalation of MTX anions. MTX/LDHs particles exhibited hexagonal platelet morphology with round corner, due to the adsorption of MTX anions on positively charged LDHs surface. In addition, the crystallinity of MTX/LDHs increased with the particle diameters and the thermal stability of MTX anions was enhanced by holding together with LDHs layers. The in vitro release showed that bigger particles have much longer release duration, and the bioassay tests indicated that bigger particles are more efficient in the suppression of the tumor cells.

An advanced preparation and characterization of the PET/MgAl-LDH nanocomposites

A new nanocomposite poly(ethylene terephthalate)/sulfanilic acid salt-modified layered double hydroxide (PET/MgAl LDH-SAS) was synthesized by an in situ polymerization method using MgAl LDH-SAS as a catalyst. This study employed a magnesium–aluminum layered double hydroxide (MgAl LDHs) with various particle sizes, which was modified by sulfanilic acid salt (SAS) through the hydrothermal process to form the MgAl LDH-SAS, and then intercalated by bis-hydroxy ethylene terephthalate (BHET) to form PET/MgAl LDH-SAS. Because of MgAl LDH-SAS, catalytic activity increased the polymerization rate, and nanocomposites also exhibited good thermal stability without the decomposition during the PET polymerization. The results indicated that the modified MgAl LDH-SAS improves the interlayer compatibility between the PET and MgAl LDH-SAS layers, thus making it easier for the oligomer to enter the gallery of MgAl LDH-SAS layers. Thus, the polymer chains can be included between the LDHs layers during the polymerization of the polymer matrix. The gas barrier, thermomechanical properties, and crystallization behavior of these new types of PET nanocomposites are investigated.

Improving thermal stability and light fastness of Acid Red 114 by incorporating its anions in a ZnAl-layered double hydroxides matrix

Incorporation of anions of Acid Red 114 dye (1,3-naphthalenedisulfonic acid, 8-[2-[3,3′-dimethyl-4′-[2-[4-[[(4-methylphenyl)sulfonyl]oxy] phenyl]diazenyl] [1,1′-biphenyl]-4-yl]diazenyl]-7-hydroxy-, disodium salt) (denoted as NPDA) into ZnAl-layered double hydroxides (LDHs) has been carried out by an anion-exchange method in an effort to improve their thermal stability and light fastness. After intercalation of NPDA anions, the interlayer distance of the LDHs increases from 0.87 to 2.18nm, confirming their incorporation into the interlayer galleries of the LDHs host. Infrared spectroscopy and thermogravimetric analysis revealed the presence of host–guest interactions between LDHs layers and NPDA anions. The thermal stability of NPDA and ZnAl–NPDA–LDHs was compared by thermogravimetric-differential thermal analysis, UV–visible spectroscopy and infrared spectroscopy. It was found that the thermal stability of NPDA anions was markedly improved by incorporation into the ZnAl–LDHs matrix, while the light fastness was also enhanced.

Single-step synthesis of layered double hydroxides ultrathin nanosheets

A novel single-step approach was developed to prepare large-scale MgAl–LDHs ultrathin nanosheets. The key point of the successful realization was that we employed a high concentration of H2O2. Oxygen molecules, derived from in situ decomposition of H2O2, were speculated to be the decisive factor leading to complete separation of LDHs layers. The ultrathin nanosheets were characterized by XRD, TEM, AFM, FT-IR, and TG–DSC. The results indicated that the thickness of these nanosheets was about 1.44nm, which was almost in perfect agreement with the theoretical thickness of two LDHs layers. From the TG–DSC curves, the weight loss of these exfoliated MgAl–LDHs ultrathin nanosheets at 500°C was 18.5%, which was much smaller compared to the 32.3% weight loss of unexfoliated MgAl–LDHs.

Intercalation of Mg–Al layered double hydroxides by l-proline: synthesis and characterization

The intercalations of l-proline into Mg–Al layered double hydroxides (LDH-CO3) have been prepared by three different methods: calcine-recovering, coprecipitation and anion exchange. The products thus obtained have been characterized by several experimental techniques: XRD, FT-IR and DSC-TG. The results show that the original interlayer carbonate ions can be replaced by the organic anions under the controlled conditions. The interlayer spaces of the materials are expanded to 0.86, 1.12 and 1.07 nm. l-proline entered into the layers as vertical and horizontal, the molecules of l-proline may stay in the layers in a bilayer with the carboxylate groups pointing towards the LDHs layers, and the structure models are shown. The crystal has a good regularity of the layered structure, which increases thermal stability of l-proline, and thermal analysis confirms that the intercalation can make l-proline stable up to 429 °C, which is 200 °C higher than that for pure l-proline.