Interlayer Space Of Layered Double Hydroxides Research Articles

Synthesis and characterisation of nanohybrids of olsalazine-intercalated Al–Mg layered double hydroxide

In this study, olsalazine (3,3′-azobis 6-hydroxy benzoic acid) was intercalated into Mg–Al layered double hydroxides (LDHs) by ion exchange or coprecipitation methods to obtain olsalazine–LDH nanohybrids. Powder X-ray diffraction (XRD), Fourier transform infrared spectra and elemental analyses indicate a successful intercalation of olsalazine with a vertical orientation. Intercalation of organic anion of olsalazine into Mg–Al LDH caused the interlayer spacing of LDH to increase from 0.884 to 1.665–1.666 nm as determined by XRD studies. Thermogravimetric analyses propose that the thermal stability of the intercalated organic anion of olsalazine is largely improved compared to the pure form before intercalation due to the host–guest interaction involving the hydrogen bond. Furthermore, in vitro drug release experiments in pH 7.4 phosphate buffer solution have been investigated. The drug molecules during dissolution were exchanged with anions in the medium, thus leading to a slow release, much slower than when the same matrix was used simply mixed with the drug.

INTERCALATION OF HYDROGEN PHOSPHATE INTO Mg/Al-LAYERED DOUBLE HYDROXIDES WITH DBS

Intercalation of hydrogen phosphate ( HPO 4) into Mg / Al -Layered Double Hydroxides (LDH) with DodecylBenzeneSulfonate (DBS) was investigated with regard to anion exchange, rehydration and a combination of delamination and anion exchange. HPO 4 could not be intercalated into the interlayer space of LDH with DBS when using either anion exchange or rehydration methods. However, HPO 4 was successfully intercalated into the Mg / Al -LDH using a combination of delamination and anion exchange methods.

INTERCALATION OF POLYHYDRIC ALCOHOLS INTO Mg-Al LAYERED DOUBLE HYDROXIDE BY CALCINATION-REHYDRATION REACTION

Layered double hydroxide (LDH) has an anion exchange property, and the intercalation of various organic molecules into LDH has been investigated in recent years. We have reported the intercalation of non-ionized guests such as pentose, hexose and cyclodextrin, into Mg-Al LDH by the calcination-rehydration reaction. In this paper, the intercalation behavior of non-ionized guests, various straight chain polyhydric alcohols (carbon number 3-5), into Mg-Al LDH by the same reaction has been examined. According to the XRD patterns and FT-IR spectra, the solid product was found to contain polyhydric alcohol and to show the restorable LDH structures. The amount of polyhydric alcohols intercalated was as follows: glycerin (C3) < erythritol (C4) < ribitol (C5) < arabitol (C5) < xylitol (C5) and greatly influenced by the conformation of C5 polyhydric alcohol isomers. It was confirmed that these polyhydric alcohols were intercalated into the LDH interlayer space by the formation of hydrogen bond between hydroxyl groups of guest polyhydric alcohols and the host LDH basal layer.

Inorganic-polymer nanohybrid carrier for delivery of a poorly-soluble drug, ursodeoxycholic acid

Delivery of poorly soluble drugs has been problematic due to its low absorption profile and bioavailability. In this work, ursodeoxycholic acid (UDCA), a poorly-soluble drug, was intercalated into inorganic nanovehicle, layered double hydroxides (LDHs), with a molecular level to enhance its solubility in biological fluid. The UDCA-loaded nanovehicle (i.e., UDCA-LDHs) was also coated with an anionic polymer, Eudragit ® S100, to increase the dissolution rate of UDCA. According to the powder X-ray diffraction (PXRD) patterns of UDCA-LDHs, the gallery height of LDHs was expanded from 3.6 Å to 28.3 Å, indicating that the UDCA molecules were successfully intercalated into the interlayer space of LDHs. Fourier transform infrared (FT-IR) spectra also revealed that the UDCA molecules were well stabilized in the LDHs through electrostatic interaction. The in vitro dissolution test in a simulated biological fluid (pH = 6.8) showed that the total dissolved fraction of UDCA for the first 2 h was about 60.2% for the Eudragit ® S100 coated UDCA-LDHs, which was a dramatic increase as compared with 19.0% dissolution from intact UDCA. It is, therefore, concluded that LDHs nanovehicle coated with an anionic polymer is a promising delivery system for improving aqueous solubility of poorly soluble drugs.

Porphyrin-layered double hydroxide/polymer composites as novel ecological photoactive surfaces

Nanocontainer and nanofiller aspects of layered double hydroxides (LDH) were combined to prepare porphyrin-LDH/polymer composites for photoactive coatings. The suggested properties are derived from cytotoxicity of singlet oxygen, O2(1Δg), produced by interaction of molecular oxygen with excited porphyrin molecules located within the interlayer space of ZnRAl and MgRAl LDH. Porphyrins, Pd(II)-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin (PdTPPC) and 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) photoproducing O2(1Δg), were successfully intercalated into LDH hosts using the co-precipitation procedure and then used as fillers in two eco-friendly polymers, namely polyurethane (PU) and poly(butylene succinate) (PBS). Porphyrin-LDH/polymer composites were prepared either by the solvent cast/cross-linking technique or melt-compounding with different porphyrin-LDH filler loadings (up to 1.3 wt%). Both X-ray diffraction and transmission electron microscopy measurements indicate a good dispersion of porphyrin-LDH fillers into the polymer matrices and that the porphyrin molecules remain intercalated within LDH layers. The polymers do not block the diffusion of oxygen and the triplet states of the intercalated porphyrins in the composite films have enough long lifetimes to produce O2(1Δg) upon irradiation by visible light. The present composites allow the elaboration of photoactive surfaces with a precise control of the O2(1Δg) concentration depending on porphyrin-LDH filler loadings.

Dodecylsulfate Anion Embedded Layered Double Hydroxide Supported Nanopalladium Catalyst for the Suzuki Reaction

Abstract The dodecylsulfate anion (DS − ) embedded layered double hydroxide (LDH) supported nanopalladium catalyst (LDH-DS-Pd 0 ) is a novel phosphine free recyclable heterogeneous catalytic system for palladium catalyzed Suzuki coupling reactions and has been prepared for the first time. The intercalation of DS − changed the interlayer spacing of LDH from a microsize to a mesosize (2.9 nm) range, which favors the diffusion of average sized organic molecules. The Pd 0 clusters obtained from the reduction of PdCl 4 2– -interlayered LDH were intercalated between the LDH layers and hence the growth of Pd 0 clusters was effectively hindered by the limited space created by the intercalation of DS − . This lipophilic catalyst was highly efficient in promoting the Suzuki reaction of aryl halides with phenylboronic acid. As a heterogeneous nanocatalyst, LDH-DS-Pd 0 could be reused five times without significant loss of catalytic activity.

Nano-hybrid materials and nano-composite materials based on PVA

Layered double hydroxides (LDHs) are a class of synthetic two-dimensional nano-structured anionic clays whose structure can be described as nano-layered ordered material. This study aims to use nano-layered materials as a host for Azo-compounds to form nano-hybrid materials and as filler for poly vinyl alcohol (PVA) to form nano-composite materials. A large anionic pigment (phenyl azobenzoic sodium salt; orange colour) has been intercalated into Zn-Al LDH and X-ray diffraction patterns showed that the interlayer spacing of Zn-Al LDH increased from 0.77 nm to 1.9-2.8 nm. Thermal analyses (TG and DTA) revealed the presence of a complex system of supra-molecular host-guest interactions. Nano-composite based on nano-hybrid Zn-Al-Azo LDH and PVA was prepared through intercalation reactions. It was characterised by X-ray diffraction, UV-Visible absorption spectra and thermal analyses. The results suggest that the nano-composites are formed via the re-aggregation of the delaminated LDH lamellar with the interlayer spacing 3 nm, and the thermal stability of the nano-composite improved compared with the original PVA.

INTERCALATION BEHAVIOR OF 5-FLUOROURACIL INTO Mg-Al LAYERED DOUBLE HYDROXIDE

As described in this paper, the intercalation behavior of 5-fluorouracil (5-FU) into Mg-Al layered double hydroxide (LDH) was investigated using coprecipitation and ion-exchange methods. Actually, 5-FU/LDH has been characterized using element chemical analysis, powder X-ray diffraction, FT-IR spectroscopy, thermal analysis and SEM. Intercalation of 5-FU was achieved using both methods; the amount and orientation of 5-FU intercalated differed considerably by the intercalation method and co-existed anion. The d-value of 5-FU/LDH expanded to d 003 = 0.80-1.10 nm, suggesting that 5-FU was intercalated into the LDH interlayer space. Results of the thermal analysis showed that the thermal stability of 5-FU was improved by intercalation in the LDH interlayer space. We propose LDH as a good host material for storage and carriage of drugs.

Intercalation of Collagen and Soybean Peptides into Zn–Al Layered Double Hydroxide

In order to develop a new type biocompatible organic/inorganic nanohybrid material, an intercalation of collagen peptides (CP) and soybean peptide (SP) into Zn-Al layered double hydroxide (LDH) by the coprecipitation reaction has been investigated. The peptide/LDH has been characterized by chemical analysis, powder X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TG) and transmission electron microscopy (TEM). According to the XRD patterns and Raman spectra, the solid products were found to contain peptide and to show broad diffraction peaks with LDH structures. The CP/LDH and SP/LDH possess the expanding LDH structure, d(00l) = 2-3 nm, confirming that both peptides were intercalated into the LDH interlayer space with low organized stacking arrangement.

Preparation and characterization of dye-intercalated Zn–Al-layered double hydroxide and its surface modification by silica coating

The new organic–inorganic hybrid pigments have been prepared via the direct co-precipitation method involving the simultaneous formation of the inorganic layers of Zn–Al (3:1) the layered double hydroxide (LDH) and intercalation of the anionic dye species. Intercalation of bulky colored organic anions into Zn/Al LDH caused the interlayer spacing of LDH to increase from 4.8 to 18.7–24.3 Å. Intercalation compounds have high optical selectivity and purity due to the spatial confinement. In this study, the shape of hybrid material was controlled by the synthetic method and the shape of anion dye. Then they were subsequently surrounded by homogeneous silica shell by the coating procedure containing hydrolysis of tetraethyl orthosilicate (TEOS). The acid treatment for the above silica-coated particles led to the selective removal of Zn–Al hydroxide inorganic lattices, resulting in the low-density hybrid pigment of molecular dyes encapsulated in silica hollow sphere.

Synthesis of biopolymer intercalated inorganic-layered materials: Intercalation of collagen peptide and soybean peptide into Zn–Al layered double hydroxide and layered zinc hydroxide

In order to develop a new type biocompatible organic/inorganic nanohybrid material, we have been investigated an intercalation of collagen peptides (CP) and soybean peptide (SP) into Zn–Al layered double hydroxide (LDH) and layered zinc hydroxide (LZH) by coprecipitation reaction. The solid products have been characterized by element chemical analysis, powder X-ray diffraction (XRD), Raman spectroscopy, thermal analysis and transmission electron microscopy. According to the XRD patterns and Raman spectra, the solid products were found to show broad diffraction peaks with layered structures and to incorporate peptide. The CP/LDH and SP/LDH has the expanding LDH structure, d 003=2–3 nm, confirming that both peptides were intercalated into the LDH interlayer space with a disordered arrangement. The CP/LZH has an ordered layered structure in comparison with the peptide/LDH. The d-values are 3.0 nm for the CP1000/LZH and 4.4 nm for the CP2000/LZH, supporting that CP was orderly intercalated into the LZH interlayer space. These results confirmed that the orientation of the intercalated peptide depends on amino acid composition of peptide.

An Exfoliated Polyamide-6/Layered Double Hydroxide Nanocomposite via &lt;I&gt;In Situ&lt;/I&gt; Intercalative Polymerization Between Positively Charged Inorganic Platelets

An exfoliated polyamide 6 (PA6)/layered double hydroxide (LDH) nanocomposite has been successfully prepared via an in situ intercalative polymerization procedure. The original LDH surface is hydrophilic. After an ion exchange reaction of LDH with sodium stearate (SS), the organic anions intercalated into the interlayer space of LDH, adopting a double-layer inclined structure, and the surface of the organic-modified LDH became hydrophobic. An exfoliated PA6/LDH nanocomposite has been obtained via in situ intercalative polymerization. Its microstructure was characterized by a combination of wide-angle X-ray diffraction (WAXD) and transmission electron microscopic (TEM) techniques. The positively charged inorganic platelets of LDH were dramatically exfoliated and homogeneously dispersed in the PA6 matrix.

Intracrystalline structure of DNA molecules stabilized in the layered double hydroxide

Abstracts DNA was successfully intercalated into layered double hydroxide (LDH), Mg2Al(OH)6NO3·0.1H2O, through ion exchange reaction to form DNA–LDH nanohybrid. Powder X-ray diffraction (PXRD) and fourier-transform infrared (FT-IR) spectroscopic results demonstrate that the DNA molecules are stabilized between the hydroxide layers. According to the circular dichroism (CD) spectroscopic studies, the B-form DNA molecules are electrostatically bound in the interlayer space of LDHs upon satisfying the charge neutralization condition. However, the intercalated DNA molecules are supposed to be more or less twisted due to the charge mismatch between anionic DNA and cationic LDH. To verify the size of DNA strands in the LDH lattice, the DNA molecules with different length of 0.2–5 kbps were intercalated into the LDHs with various particle size. Three kinds of LDHs with discrete particle size were synthesized through both coprecipitation and hydrothermal methods. From the scanning electron microscopy (SEM), the particle sizes were determined as ∼80, 150, and 300 nm, respectively. Thus prepared DNA–LDH nanohybrids with various particle size were treated with DNA destroying enzyme such as DNase I. Since the LDHs (80, 150, 300 nm) are smaller in size than the DNA molecules, some parts of the intercalated DNA chains are eventually dangling outside of the host LDH layer. Therefore, the dangling part of DNA chains and the surface adsorbed DNA were decomposed quickly by DNase I treatment. The DNA strands protected by LDH layers could intentionally be recovered by treating with an acidic solution. The length of DNA strands thus recovered were confirmed by electrophoresis, and determined to be ∼200 bps irrespective of the particle size of LDHs.

Synthesis and adsorption properties of p-sulfonated calix[4 and 6]arene-intercalated layered double hydroxides

The intercalation of water-soluble p-sulfonated calix[4 and 6]arene (CS4 and CS6) in the interlayer of the Mg–Al and Zn–Al layered double hydroxide (LDH) by the coprecipitation method has been investigated, as well as the adsorption properties of the resulting CS/LDHs for benzyl alcohol (BA) and p-nitrophenol (NP) to prepare new microporous organic–inorganic hybrid adsorbents. The amount and arrangement of CS intercalated was different by the kind of the host metal ions. CS4 cavity axis was perpendicular for the Mg–Al LDH basal layer and parallel for the Zn–Al LDH basal layer, while CS6 cavity axis was perpendicular for both the LDH basal layers. In the BET surface area measurement, the surface area of the Zn–Al/CS4/LDH was four times than that of the Mg–Al/CS4/LDH, expecting that the former has higher adsorption capacity than the latter. In fact, the adsorption ability of the CS/LDHs for BA and NP in aqueous solution was found to be larger in the Zn–Al/CS4/LDH than in the Mg–Al/CS4/LDH. In addition, the adsorption ability of both the LDHs was larger in the CS6/LDHs than in the CS4/LDHs. These results were explained by the difference in the amount and arrangement of CS intercalated in the LDH interlayer space.

Polymerization reaction in restricted space of layered double hydroxides (LDHs)

This paper reported the preparation of styrene sulfonate intercalated layered double hydroxides (LDHs) material, SS-LDHs by coprecipitation method, followed byin-situ polymerization of the monomers in the interlayer space of LDHs. The polymerization reaction was monitored by UV and NMR. It is confirmed that when the reaction occurred at 100°C for 24 h, part of monomers did not react. When the reaction was carried out at 150°C., the polymerization of the intercalated monomers is complete to afford the polymer intercalated product PSS-LDHs. During the polymerization process, the layered structure remains well. At the same time the gallery height increases with the lengthening of reaction time. This is preliminarily because that the PSS becomes more swelling with the amount of water it absorbs due to its hygroscopicity property.

Intercalation of nucleotides into layered double hydroxides by ion-exchange reaction

We have investigated the intercalation behavior of nucleotides (AMP, ADP, ATP, CMP, GMP and UMP) for the NO 3/Zn–Al and Mg–Al LDHs by ion-exchange reaction as well as the thermal stability of the AMP and CMP/LDHs. According to XRD and FT-IR, the solid products were found to have the layered double hydroxide (LDH) structure. The basal spacing (003) of the nucleotides/LDH was expanded to 1.38–1.67 nm, and the absorption peak of NO 3 − at 1385 cm −1 was decreased with increasing the amount of nucleotides intercalated, indicating that nucleotides were intercalated for the LDH. The expanding interlayer space of the nucleotide/LDH supported that nucleotides were vertically oriented to the LDH layer. The basal spacing of the AMP, ADP and ATP/LDHs was reduced with increasing number of phosphate groups, because the electrostatic force of attraction was increased between the negative nucleotides and the positive LDH layer. In the experiments for thermal stability of the AMP and CMP/LDHs, 80–90% of the intercalated nucleotide were stable at 100 °C, whereas 80–90% of the pure nucleotides were decomposed. The thermal stability of nucleotide, therefore, was improved by the intercalation for the LDH interlayer space. Furthermore, the disintegration of the LDH structure and the formation of the metal oxide and phosphate were also observed at 500 and 800 °C.

Synthesis of iron oxide nanocomposites using layered double hydroxides

In the present work, an original method for the preparation of oxide nanostructured materials is discussed. The method is based on chemical modification of anion-substituted layered double hydroxides (LDH). It combines the simplicity of chemical methods and the possibility to prepare nanostructures directly in the matrix. During chemical reactions of anions in the interlayer space of LDHs, the reaction zone is spatially constrained by the hydroxide layers, giving rise to the conditions similar to those in 2D nanoreactors, such as Langmuir–Blodgett films and self-assembling monolayers. It was found that chemical modification of intercalated LDHs results in the formation of iron oxide nanoparticles with different morphology and composition (α-Fe2O3, γ-Fe2O3), depending on the composition of initial precursors and conditions of chemical modifications. Obtained nanostructures were investigated by X-ray diffraction, TEM and Mossbauer spectroscopy.

Layered Double Hydroxides as a Matrix for Luminescent Rare Earth Complexes

ABSTRACTIn the present work new luminescent materials with high quantum efficiencies based on layered double hydroxides (LDH) were obtained. Intercalation of complexes into the interlayer space of LDH doesn't affect their luminescent properties, forming non-volatile solid state material with good optical properties. The Coulomb interactions between LDH layers and complex can result in a change of complex structure in comparison with free complexes and in decreasing the number of the organic ligands per Ln atom. The energy transfer in the system was also studied.

Sugar–anionic clay composite materials: intercalation of pentoses in layered double hydroxide

The intercalation of non-ionized guest pentoses (ribose and 2-deoxyribose) into the Mg–Al and Zn–Al layered double hydroxides (LDHs) was carried out at 298 K by the calcination–rehydration reaction using the Mg–Al and Zn–Al oxide precursors calcined at 773 K. The resulting solid products reconstructed the LDH structure with incorporating pentoses, and the maximum amount of ribose intercalated by the Mg–Al oxide precursor was approximately 20 times that by the Zn–Al oxide precursor. The ribose/Mg–Al LDH was observed to have the expanded LDH structure with a broad (003) spacing of 0.85 nm. As the thickness of the LDH hydroxide basal layer is 0.48 nm, the interlayer distance of the ribose/Mg–Al LDH is 0.37 nm. This value corresponds to molecular size of ribose in thickness (0.36 nm), supporting that ribose is horizontally oriented in the interlayer space of LDH. The maximum amount of ribose intercalated by the Mg–Al oxide precursor was approximately 5 times that of 2-deoxyribose. Ribose is substituted only by the hydroxyl group at C-2 position for 2-deoxyribose. Therefore, the number of hydroxyl group of sugar is essentially important for the intercalation of sugar molecule into the LDH, suggesting that the intercalation behavior of sugar for the LDH was greatly influenced by hydrogen bond between hydroxyl group of the intercalated pentose and the LDH hydroxide basal layers.

Intercalative route to heterostructured nanohybrids

Abstract We have successfully synthesized inorganic–inorganic, organic–inorganic and bio-inorganic nanohybrids by applying an intercalation technique systematically to layered titanate, molybdenum disulfide (MoS 2 ), Bi-based cuprate superconductors (Bi 2 Sr 2 Ca m −1 Cu m O y ( m =1, 2, and 3; BSCCO)), and to layered double hydroxides (LDHs), those which are of high importance in terms of basic understanding of intercalation reactions and of their practical applications. The inorganic–inorganic systems such as TiO 2 -pillared titanate, TiO 2 -pillared MoS 2 , and CdS–MoS 2 hybrids were synthesized by exfoliation–restacking method. A novel pillaring process using an osmotic swelling was developed to prepare TiO 2 -pillared layered titanate with a large surface area, high thermal stability, and enhanced photocatalytic activity. And the intercalation of TiO 2 and/or CdS nanocluster into the two dimensional MoS 2 lattice could be also realized by exfoliating and reassembling the lithiated molybdenum disulfide (LiMoS 2 ) in the presence of cationic TiO 2 and/or CdS nanocluster in an aqueous solution, respectively, to obtain the semiconductor–semiconductor hybrids. On the other hands, the organic–inorganic hybrids were achieved via intercalative complexation of iodine intercalated BSCOO with organic salt of Py–C n H 2 n +1 I (Py=pyridine). The high- T c superconducting intercalate with its remarkable lattice expansion can be applied as a precursor for superconducting colloids when dispersed in an appropriate solvent. This superconducting hybrid material had an unique structural feature of a superconducting-insulating-superconducting multilayer with atomically clean interfaces. Especially, this organic–inorganic nanohybrid is expected to be a promising precursor for preparing the superconducting colloidal suspension, which could be applied to the fabrication of superconducting films or wires. Recently, we were very successful in demonstrating in which the formation of bio-inorganic hybrids stabilized in the interlayer space of LDH retain their chemical and biological integrity. If necessary, LDH, as a reservoir, can be intentionally removed by dissolving it in an acidic media in such a way the interlayer biomolecules can be recovered or the intercalated biomolecules can be released from the LDH via ion-exchange reaction in electrolyte. It is, therefore, concluded that the inorganic LDH can play a role as a gene reservoir or carrier for various unstable organic or bio-molecules such as drugs and genes.