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1

Layered Double Hydroxides (LDH): A Multifunctional Versatile System for Nanocomposites  

Microsoft Academic Search

Layered Double Hydroxides gained tremendous research efforts in the last years as a filler for polymer nanocomposites similar to montmorillonite in order to increase barrier properties, improve mechanical properties and reduce flammability. Due to its broad variety in composition and possibility to organically modify the layers LDH might be used in very different applications. This summary intends to show possibilities

A. Leuteritz; B. Kutlu; J. Meinl; D. Wang; A. Das; U. Wagenknecht; G. Heinrich

2012-01-01

2

Thermal and Morphological Properties of Poly(vinyl alcohol) and Layered Double Hydroxide (LDH) Nanocomposites  

Microsoft Academic Search

Poly(vinyl alcohol) (PVA)\\/layered double hydroxide (LDH) nanocomposites were synthesized with different compositions: 0, 2, 4, 6, and 8 wt% of LDH by the solution intercalation method. The effects of the layered double hydroxide platelet concentration on the properties of the PVA\\/LDH films were investigated by thermogravimetric analysis (TGA), optical microscopy, and Fourier transform infrared spectroscopy (FTIR). A reduction in the onset

B. Ramaraj; S. N. Jaisankar

2008-01-01

3

Ageing behaviour of unary hydroxides in trivalent metal salt solutions: Formation of layered double hydroxide (LDH)-like phases  

Microsoft Academic Search

The hydroxides of Mg, Ni, Cu and Zn transform into layered double hydroxide (LDH)-like phases on ageing in solutions of Al\\u000a or Cr salts. This reaction is similar to acid leaching and proceeds by a dissolution-reprecipitation mechanism offering a\\u000a simple method of LDH synthesis, with implications for the accepted theories of formation of LDH minerals in the earth’s crust.

Michael Rajamathi; P. Vishnu Kamath

2000-01-01

4

The layered double hydroxide (LDH) of Zn with Ga: Synthesis and reversible thermal behaviour  

NASA Astrophysics Data System (ADS)

The carbonate containing layered double hydroxide (LDH) of Zn with Ga, crystallizes in an ordered 3R 1 polytype having the rhombohedral structure with a fixed composition corresponding to [Zn 2+]/[Ga 3+] = 2.0. The sulphate containing LDH on the other hand crystallizes in the turbostratically disordered '11 Å' phase. The layered structure collapses at 400 °C. The oxide residue obtained from the carbonate containing LDH has the wurtzite structure with Ga 3+ occupying the Zn 2+ sites. The defect wurtzite is metastable and reconstructs the LDH either on standing in a water saturated humidity chamber or on soaking in a Na 2CO 3 solution. The oxide residue obtained from the sulphate containing LDH has an unspecified structure and also reconstructs back into the original LDH on soaking in a Na 2SO 4 solution. However on heating to 800 °C, spinel (ZnGa 2O 4) formation is observed subsequent to which the reversible thermal behaviour is lost.

Thomas, Grace S.; Kamath, P. Vishnu

2006-10-01

5

Morphology and fracture behaviour of polyethylene\\/Mg–Al layered double hydroxide (LDH) nanocomposites  

Microsoft Academic Search

Fracture behaviour of polyethylene (PE)\\/Mg–Al layered double hydroxide (LDH) based nanocomposites has been studied by essential work of fracture (EWF) approach. Transmission electron microscopy (TEM and X-ray diffraction (XRD) analysis have been used to investigate the morphological features of these nanocomposites. A maximum in the non-essential work of fracture was observed at 5wt.% LDH demonstrating enhanced resistance to crack propagation

F. R. Costa; B. K. Satapathy; U. Wagenknecht; R. Weidisch; G. Heinrich

2006-01-01

6

The layered double hydroxide (LDH) of Zn with Ga: Synthesis and reversible thermal behaviour  

Microsoft Academic Search

The carbonate containing layered double hydroxide (LDH) of Zn with Ga, crystallizes in an ordered 3R1 polytype having the rhombohedral structure with a fixed composition corresponding to [Zn2+]\\/[Ga3+] = 2.0. The sulphate containing LDH on the other hand crystallizes in the turbostratically disordered ‘11 Å’ phase. The layered structure collapses at 400?°C. The oxide residue obtained from the carbonate containing

Grace S. Thomas; P. Vishnu Kamath

2006-01-01

7

Solution decomposition of the layered double hydroxide (LDH) of Zn with Al  

Microsoft Academic Search

The layered double hydroxides (LDH) of Zn with Al containing intercalated CO32? and NO3? ions undergo solution decomposition to yield a highly crystalline oxide mixture comprising ZnO and ZnAl2O4 at temperatures as low as 150–180°C under hydrothermal conditions. In contrast solid-state decomposition takes place at a much higher temperature (240–315°C) in air. Solution decomposition is not only guided by the

Sylvia Britto; A. V. Radha; N. Ravishankar; P. Vishnu Kamath

2007-01-01

8

[Role of layered double hydroxide (LDH) in the protection of herring testis DNA from heavy metals].  

PubMed

The role of layered double hydroxide (LDH) in the protection of herring testis DNA from heavy metals Cd2+ and Pb2+ was studied by X-ray diffraction ( XRD) spectra, Fourier transform infrared (FTIR) spectra, Scanning Electron Microscopy (SEM), Cyclic Voltammetry and Ultraviolet Spectrometry. Size expansion of the basal spacing (003) from 0. 76 nm in LDH to 2. 30 nm was observed in the resulting DNA-LDH nanohybrids and it gave peaks corresponding to C=O (1 534 cm(-1) and 1488 cm(-1)) in skeleton and bases, C-O stretching vibration (1228 cm(-1)), and P-O symmetrical stretching vibration (1096 cm(-1)) in functional groups of DNA, indicating that DNA were intercalated into the LDH by the ion exchange. However, the displacement of NO3(-) was not fully complete (partial intercalation of DNA). The DNA outside LDH interlayers was absorbed on the surface of LDH. The cyclic voltammetric curves showed that DNA in the composites exhibited a very similar peaks, which corresponded to the two reduction current peaks (E(P) = - 1.2 mV and E(P) = -2.4 mV) of free DNA. Also there was no cathode sag emerging in cyclic voltammetric curves, suggesting that both Cd2+ and Pb2+ cannot insert into the groove of DNA to associate with base pairs or other groups when DNA was bound on LDH. The results showed that, on the one hand, both Cd2+ and Pb2+ were absorbed on the external surface of LDH for immobilization, on the other hand, the layer of LDH provided ideal space for DNA by the action of protecting DNA molecules from Cd2+ and Pb2+. PMID:23233994

Tang, Yi-Ni; Wu, Ping-Xiao; Zhu, Neng-Wu

2012-10-01

9

Layered double hydroxide (LDH) derived catalysts for simultaneous catalytic removal of soot and NOx.  

PubMed

Nitrogen oxides (NOx) and soot which come from vehicle engine exhausts cause serious environmental pollution and human health problems. Recently, the catalytic purification technology, particularly the simultaneous catalytic removal of soot and NOx, has received more and more attention. For this technology, the key is to develop highly efficient and robust catalysts. Due to the unique chemical and structural properties of layered double hydroxides (LDHs), LDH-derived catalysts have shown great potential, and much effort has been devoted to this type of catalyst. In this manuscript, we reviewed the latest progress in the LDH derived catalysts by classifying the LDH precursors according to the number of metals into binary, ternary, and quaternary, and discussed their advantages and disadvantages in detail. We hope that this review paper could provide a clearer picture of this topic and theoretical support for its better development. PMID:24492318

Yang, Ruoyan; Gao, Yanshan; Wang, Junya; Wang, Qiang

2014-07-21

10

Layered double hydroxide/polyethylene terephthalate nanocomposites. Influence of the intercalated LDH anion and the type of polymerization heating method  

SciTech Connect

Conventional and microwave heating routes have been used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate had been previously intercalated in the LDH. PXRD and TEM were used to detect the degree of dispersion of the filler and the type of the polymeric composites obtained, and FTIR spectroscopy confirmed that the polymerization process had taken place. The thermal stability of these composites, as studied by thermogravimetric analysis, was enhanced when the microwave heating method was applied. Dodecyl sulphate was more effective than terephthalate to exfoliate the samples, which only occurred for the terephthalate ones under microwave irradiation. - Graphical abstract: Conventional and microwave heating routes were used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate was previously intercalated into the LDH. The microwave process improves the dispersion and the thermal stability of nanocomposites due to the interaction of the microwave radiation and the dipolar properties of EG and the homogeneous heating. Highlights: > LDH-PET compatibility is enhanced by preintercalation of organic anions. > Dodecylsulphate performance is much better than that of terephthalate. > Microwave heating improves the thermal stability of the composites. > Microwave heating improves as well the dispersion of the inorganic phase.

Herrero, M.; Martinez-Gallegos, S.; Labajos, F.M. [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain); Rives, V., E-mail: vrives@usal.es [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain)

2011-11-15

11

Synthesis, structure and morphology of organic layered double hydroxide (LDH) hybrids: Comparison between aliphatic anions and their oxygenated analogs  

Microsoft Academic Search

Intercalation of organic anions is an important aspect of layered double hydroxide (LDH) chemistry in the development of polymer–LDH composites. In the research, we intercalated short and lengthy straight-chain organic anions with the carbon number up to 50 into the interlayer of MgAl and ZnAl-LDHs. We also noted that the packing mode of the straight-chain organic species and the basal

Zhi Ping Xu; Paul S. Braterman

2010-01-01

12

Preparation of ultrathin membranes by layer-by-layer deposition of layered double hydroxide (LDH) and polystyrene sulfonate (PSS)  

Microsoft Academic Search

Nanofilms were prepared by consecutively alternating adsorption of Mg–Al (2:1) layered double hydroxide (LDH) and polysodium 4-styrenesulfonate (PSS). The charge density of oppositely charged materials strongly affect film properties like thickness and ordering. The specific charge of the colloid particles (LDH) and macromolecules was determined with the particle charge detector. The sequential build-up of the thin films was followed by

V. Hornok; A. Erd?helyi; I. Dékány

2005-01-01

13

Self-assembling organomodified Co\\/Al based layered double hydroxides (LDH) via one-step route  

Microsoft Academic Search

The preparation of self-assembling organomodified Co\\/Al-layered double hydroxide (LDH) via one-step route was studied. A common surfactant, sodium dodecylbenzenesulfonate (DBS), was employed as an organic modifier. The behavior and structure of self-assembled intercalated organic Co\\/Al-LDH were investigated by FTIR, SEM, WAXS, element analysis and TGA. Based upon the WAXS results and calculation by Bragg equation, the interlayer distance (d value)

De-yi WANG; A. LEUTERITZ; U. WAGENKNECHT; G. HEINRICH

2009-01-01

14

Synergistic effects of layered double hydroxide with phosphorus-nitrogen intumescent flame retardant in PP\\/EPDM\\/IFR\\/LDH nanocomposites  

Microsoft Academic Search

Synergistic effects of layered double hydroxide (LDH) with intumescent flame retardanct (IFR) of phosphorus-nitrogen (NP)\\u000a compound in the polypropylene\\/ethylene-propylene-diene\\/IFR\\/LDH (PP\\/EPDM\\/IFR\\/LDH) nanocomposites and related properties were\\u000a studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), limiting oxygen\\u000a index (LOI), UL-94 test, cone calorimeter test (CCT) and thermo-gravimetric analysis (TGA). The XRD and TEM results show that\\u000a the

Zhe Cui; Bao-jun Qu

2010-01-01

15

Synthesis of layered double hydroxides (LDHs) with varying pH: A valuable contribution to the study of Mg\\/Al LDH formation mechanism  

Microsoft Academic Search

Very few papers deal with comprehension of mechanisms leading to the formation of layered double hydroxide (LDH) compounds which are usually obtained by coprecipitation at constant pH value. In this paper, we study the influence of pH values of coprecipitation on the formation of LDH phases, their crystallinity and chemical composition, and then discuss about LDH formation mechanisms, using a

A. Seron; F. Delorme

2008-01-01

16

Adsorption study of anionic reactive dye from aqueous solution to Mg-Fe-CO3 layered double hydroxide (LDH)  

NASA Astrophysics Data System (ADS)

Mg-Fe-Cl Layered double hydroxides (LDHs) have been prepared using a method involving separate nucleation and aging steps with Mg/Fe = 3. The interlayer anions readily replaced by carbonate are characterized by X-ray diffraction (XRD) and FTIR. The effects of different parameters, such as pH, contact time, concentration of dye and temperature on the capacity and adsorption mechanism of Mg-Fe-CO3-LDH in removing an anionic dye (congo red, CR) from aqueous solution were separately investigated. The results show that Mg-Fe-CO3-LDH is particularly efficient in removing CR and the dye removal increases with decreasing pH. The adsorption of CR on Mg-Fe-CO3-LDH reached equilibrium after 15 min where 100 mg/L CR was removed. The equilibrium isotherm indicates that the adsorption of CR onto Mg-Fe-CO3-LDH fits to Langmuir and Freundlich equation as well. The adsorption data obtained from the Langmuir model gave good values of the determination coefficient and the saturated adsorption capacity of Mg-Fe-CO3-LDH for CR was found to be 104.6 mg/g. The regeneration study indicates that the prepared LDH could be used for several cycles. The thermodynamic parameters have been calculated, and the adsorption process was found to be spontaneous, endothermic in nature and follows a pseudo-second-order kinetic model.

Ahmed, I. M.; Gasser, M. S.

2012-10-01

17

Hybridization of the natural antibiotic, cinnamic acid, with layered double hydroxides (LDH) as green pesticide  

Microsoft Academic Search

Background, aim, and scope  Heavy application of highly toxic synthetic pesticides has been committed to protect crops against insects and diseases, which\\u000a have brought about serious environmental problems. Thus, an inevitable and fundamental issue has been how to protect crops\\u000a without harmful effects on nature. As a fascinating nature-compatible approach, we have attempted to hybridize soil-compatible\\u000a layered double hydroxides (LDHs) with

Man Park; Chang-Il Lee; Young Jin Seo; Sang Ryung Woo; Dongill Shin; Jyung Choi

2010-01-01

18

Water-swellable MgAl-LDH (layered double hydroxide) hybrids: synthesis, characterization, and film preparation.  

PubMed

LDH hybrids were synthesized from Cl (-)MgAl-LDHs by anion exchange with short-chain alkyl carboxylate intercalants: C n H 2 n+1 COO (-) ( n = 0-3). Among them, LDH3 (LDH with Mg/Al = 3) hybrids containing acetate ( n = 1) and propionate ( n = 2) exhibited swelling behavior in water. The action of water on acetate-LDH3 (AcO-LDH3) and propionate-LDH3 (PrO-LDH3) led to semitransparent suspensions via a viscous gel state. From the X-ray diffraction profiles of the gels, only a broad feature was observed by the loss of the sharp reflections. The reflections reappeared for the films obtained by drying the gel, indicating the restacking of the LDH nanosheets into the original stacked structure. Observation using atomic force microscopy revealed delaminated nanosheets with a thickness of 1.1-1.5 nm with the same morphological features as the starting LDHs. XRD measurement and AFM observation supported the formation of unilamellar LDH sheets. Semitransparent self-standing LDH films were obtained by peeling off the films formed on a PE (polyethylene) substrate by drying the colloidal suspension thereon. The thickness of the obtained flexible films ranged from 10 to 25 microm, and they could be anion exchanged with inorganic and organic anions in the film state. PMID:18442277

Iyi, Nobuo; Ebina, Yasuo; Sasaki, Takayoshi

2008-05-20

19

Use of a layered double hydroxide (LDH) to buffer nitrate in soil: long-term nitrate exchange properties under cropping and fallow conditions  

Microsoft Academic Search

The potential use of a layered double hydroxide (LDH) to act as a nitrate buffer system in soil in order to reduce the movement\\u000a of nitrate was investigated. Long-term plant and soil experiments were carried out under greenhouse conditions with the following\\u000a objectives: (i) evaluate the nitrate adsorption capacity of the LDH during crop growth, and its influence on N

Luis Omar Torres-Dorante; Joachim Lammel; Hermann Kuhlmann

2009-01-01

20

Preparation and mechanical properties of exfoliated CoAl layered double hydroxide (LDH)\\/polyamide 6 nanocomposites by in situ polymerization  

Microsoft Academic Search

Novel exfoliated nanocomposites based on polyamide 6 (PA6)\\/CoAl layered double hydroxide (CoAl-LDH) have been successfully prepared via in situ polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that the inorganic nanoplatelets of CoAl-LDH were homogeneously dispersed in the PA6 matrix. Mechanical testing (by tensile tests and nanoindentation measurements) shows that, compared with neat PA6, the tensile modulus,

Hongdan Peng; Wuiwui Chauhari Tjiu; Lu Shen; Shu Huang; Chaobin He; Tianxi Liu

2009-01-01

21

Hexacyanoferrate (III) as an electroactive probe for the investigation of the interlayer basicity of the layered double hydroxide (LDH) of Mg with Al  

Microsoft Academic Search

Hexacyanoferrate on intercalation within the interlayer region of the layered double hydroxide (LDH) of Mg with Al retains its electroactivity. Within the confined region of the interlayer, the redox potential of the intercalated ion, as estimated from cyclic voltammetric studies, is shifted by almost 126mV higher than that of the free ion in solution. We attribute this to the activity

Belavalli E. Prasad; M. Dinamani; P. Vishnu Kamath; S. H. Mehta

2010-01-01

22

Composition and structure of an iron-bearing, layered double hydroxide (LDH) – Green rust sodium sulphate  

Microsoft Academic Search

Mixed-valent Fe(II),Fe(III)-layered hydroxide, known as green rust, was synthesized from slightly basic, sodium sulphate solutions in an oxygen-free glove box. Solution conditions were monitored with pH and Eh electrodes and optimized to ensure a pure sulphate green-rust phase. The solid was characterised using Mössbauer spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The composition of the solution from

B. C. Christiansen; T. Balic-Zunic; P.-O. Petit; C. Frandsen; S. Mørup; H. Geckeis; A. Katerinopoulou; S. L. Svane Stipp

2009-01-01

23

Facile synthesis via a solvothermal route and characterization of Mg–Al layered double hydroxide (LDH) 3D micro–nano structures  

Microsoft Academic Search

Different Mg–Al layered double hydroxide (LDH) 3D micro–nano structures had been synthesized via a facile solvothermal method. By carefully controlling the fundamental experimental parameters, the morphologies of hexagonal nanoplates, rose-like micro–nano structures, chrysanthemum-like micro–nano structures, and spherical micro–nano structures have been efficiently obtained, respectively. And these micro–nano structures are formed from self-assembly of nanoplates in a spontaneous process in solvothermal

Lingna Sun; Changwen Hu

2011-01-01

24

Synthesis of well-dispersed layered double hydroxide core@ordered mesoporous silica shell nanostructure (LDH@mSiO?) and its application in drug delivery.  

PubMed

We demonstrate an efficient synthesis of novel layered double hydroxide mesoporous silica core-shell nanostructures (LDH@mSiO(2)) that have a hexagonal MgAl-LDH nanoplate core and an ordered mesoporous silica shell with perpendicularly oriented channels via a surfactant-templating method. Transmission electron microscopy, X-ray diffraction and N(2) sorption analyses confirmed that the obtained nanostructures have uniform accessible mesopores (?2.2 nm), high surface area (?430 m(2) g(-1)), and large pore volume (?0.22 cm(3) g(-1)). Investigations of drug release and bio-imaging showed that this material has a slow release effect of ibuprofen and good biocompatibility. This work provides an economical approach to fabricate LDH@mSiO(2) core-shell nanostructures, which may have great potential in broad drug delivery and hyperthermia therapy applications. PMID:21858347

Bao, Haifeng; Yang, Jianping; Huang, Yan; Xu, Zhi Ping; Hao, Na; Wu, Zhangxiong; Lu, Gao Qing Max; Zhao, Dongyuan

2011-10-01

25

Synthesis of well-dispersed layered double hydroxide core@ordered mesoporous silica shell nanostructure (LDH@mSiO2) and its application in drug delivery  

NASA Astrophysics Data System (ADS)

We demonstrate an efficient synthesis of novel layered double hydroxide mesoporous silica core-shell nanostructures (LDH@mSiO2) that have a hexagonal MgAl-LDH nanoplate core and an ordered mesoporous silica shell with perpendicularly oriented channels via a surfactant-templating method. Transmission electron microscopy, X-ray diffraction and N2 sorption analyses confirmed that the obtained nanostructures have uniform accessible mesopores (~2.2 nm), high surface area (~430 m2 g-1), and large pore volume (~0.22 cm3 g-1). Investigations of drug release and bio-imaging showed that this material has a slow release effect of ibuprofen and good biocompatibility. This work provides an economical approach to fabricate LDH@mSiO2 core-shell nanostructures, which may have great potential in broad drug delivery and hyperthermia therapy applications.We demonstrate an efficient synthesis of novel layered double hydroxide mesoporous silica core-shell nanostructures (LDH@mSiO2) that have a hexagonal MgAl-LDH nanoplate core and an ordered mesoporous silica shell with perpendicularly oriented channels via a surfactant-templating method. Transmission electron microscopy, X-ray diffraction and N2 sorption analyses confirmed that the obtained nanostructures have uniform accessible mesopores (~2.2 nm), high surface area (~430 m2 g-1), and large pore volume (~0.22 cm3 g-1). Investigations of drug release and bio-imaging showed that this material has a slow release effect of ibuprofen and good biocompatibility. This work provides an economical approach to fabricate LDH@mSiO2 core-shell nanostructures, which may have great potential in broad drug delivery and hyperthermia therapy applications. Electronic supplementary information (ESI) available: Additional XRD, SEM, TEM, DLS and LSCM data. See DOI: 10.1039/c1nr10718f

Bao, Haifeng; Yang, Jianping; Huang, Yan; Xu, Zhi Ping; Hao, Na; Wu, Zhangxiong; Lu, Gao Qing (Max); Zhao, Dongyuan

2011-10-01

26

Synthesis and characterization of layered double hydroxides (LDH) intercalated with non-steroidal anti-inflammatory drugs (NSAID)  

Microsoft Academic Search

Layered double hydroxides (LDHs) with the hydrotalcite type structure and a Mg:Al ratio of two have been prepared, with salicylate or naproxen in the interlayer. Two synthetic routes have been used: reconstruction from a mildly calcined hydrotalcite-CO3 precursor, and a coprecipitation method with chlorides of the metals. The solids have been characterized using several physicochemical techniques, i.e., powder X-ray diffraction,

Margarita del Arco; Sonia Gutiérrez; Cristina Martín; Vicente. Rives; Joao Rocha

2004-01-01

27

Durability of nickel-metal hydride (Ni-MH) battery cathode using nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite  

NASA Astrophysics Data System (ADS)

We report the durability of the optimized nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite prepared by liquid phase deposition (LPD) as cathode active materials in nickel metal hydride (Ni-MH) secondary battery. The positive electrode was used for charge-discharge measurements under two different current: 5 mA for 300 cycles in half-cell conditions, and 5.8 mA for 569 cycles in battery regime, respectively. The optimized Ni-Al LDH/C composite exhibits a good lifespan and stability with the capacity retention above 380 mA h gcomp-1 over 869 cycles. Cyclic voltammetry shows that the ?-Ni(OH)2/?-NiOOH redox reaction is maintained even after 869 cycles, and the higher current regime is beneficial in terms of materials utilization. X-ray diffraction (XRD) patterns of the cathode after charge and discharge confirms that the ?-Ni(OH)2/?-NiOOH redox reaction occurs without any intermediate phase.

Béléké, Alexis Bienvenu; Higuchi, Eiji; Inoue, Hiroshi; Mizuhata, Minoru

28

Synthesis and characterization of layered double hydroxides (LDH) intercalated with non-steroidal anti-inflammatory drugs (NSAID)  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDHs) with the hydrotalcite type structure and a Mg:Al ratio of two have been prepared, with salicylate or naproxen in the interlayer. Two synthetic routes have been used: reconstruction from a mildly calcined hydrotalcite-CO 3 precursor, and a coprecipitation method with chlorides of the metals. The solids have been characterized using several physicochemical techniques, i.e., powder X-ray diffraction, FTIR and 13C CP/MAS NMR spectroscopies and thermal analysis (thermogravimetric and differential thermal analyses). The gallery height determined is in all cases larger than the size of the drug, 11.5 Å for salicylate and 15.8 and 16.6 Å for naproxen, depending on the specific synthesis route followed. Experimental data suggest the anion molecules form a tilted bilayer, with the carboxylate groups pointing towards the brucite-like layers. The solids are stable up to 230 °C and their evolution from 350 °C upwards is very similar to that observed for a carbonate-containing hydrotalcite, forming mostly amorphous solids with a large specific surface area.

del Arco, Margarita; Gutiérrez, Sonia; Martín, Cristina; Rives, Vicente; Rocha, Joao

2004-11-01

29

Mid- and near-infrared spectroscopic investigation of homogeneous cation distribution in Mg(x)Zn(y)Al(x+y)/2-layered double hydroxide (LDH).  

PubMed

In this report, a detailed FTIR fitting analysis was used to recognize Mg, Zn and Al homogeneous distribution in Mg(x)Zn(y)Al(x+y)/2-Layered double hydroxide (LDH) hydroxyl layer. In detail, OH-Mg2Al:OH-Mg3 ratios decreased from 95.2:4.8 (MIR) and 94.2:5.8 (NIR) to 58.9:41.1 (MIR) and 61.8:38.2 (NIR), when Mg:Al increased from 2.2:1.0 to 4.1:1.0 in MgAl-LDHs. These fitting results were similar with theoretical calculations of 94.3:5.7 and 59.0:41.0. In a further analysis of Mg(x)Zn(y)Al(x+y)/2-LDHs, OH bonded Zn2Mg, Zn2Al, MgZnAl, Mg2Al and Mg2Zn peaks were identified at 3420, 3430, 3445-3450, 3454 and 3545 cm(-1), respectively. With the decrease of Mg:Zn from 3:1 to 1:3, metal-hydroxyl bands changed from OH-Mg2Al and MgZnAl (with a ratio of 49.4:50.6) to OH-MgZnAl and Zn2Al (with a ratio of 55.0:45.0). They were also similar with theoretical calculations of 47.6:52.4 and 54.6:45.4. As a result, these results show that there is an ordered cation distribution in Mg(x)Zn(y)Al(x+y)/2-LDH, and FTIR is feasible in recognizing this structure. PMID:24050636

Zhang, Jia; Su, Huimin; Zhou, Jizhi; Qian, Guangren; Xu, Zhiping; Xi, Yunfei; Xu, Yunfeng; Theiss, Frederick L; Frost, Ray

2013-12-01

30

Computational NMR, IR/RAMAN calculations in sodium pravastatin: Investigation of the Self-Assembled Nanostructure of Pravastatin-LDH (Layered Double Hydroxides) Systems  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDH) can be used as nanocontainers for immobilization of Pravastatin, in order to obtain suitable drug carriers. The material's structure and spectroscopic properties were analyzed by NMR, IR/RAMAN and supported by theoretical calculations. Density Functional Theory (DFT) calculations were performed using the Gaussian03 package [1]. The geometry optimizations were performed considering the single crystal X-ray diffraction data of tert-octylamonium salt of Pravastatin [2]. Tetramethylsilane (TMS), obtained with the same basis set, was used as reference for calculating the chemical shift of 13C. A scaling factor was used to compare theoretical and experimental harmonic vibrational frequencies. Through the NMR and IR/RAMAN spectra, we were able to make precise assignments of the NMR and IR/RAMAN of Sodium Pravastatin. [4pt] [1] Frisch, M.J. et al. Gaussian 03, Revision A.1, Gaussian Inc., Pittsburgh, PA,(2003). [0pt] [2] Sato, S.; Furukawa, Y. J. Antibiot. 41, 1265-1267 (1988).

Petersen, Philippe; Cunha, Vanessa; Gonçalves, Marcos; Petrilli, Helena; Constantino, Vera

2013-03-01

31

Comparison of different synthesis routes for Mg–Al layered double hydroxides (LDH): Characterization of the structural phases and anion exchange properties  

Microsoft Academic Search

Nitrate forms of layered double hydroxides (LDHs) were synthesized based on the co-precipitation method under different synthesis conditions (aqueous ammonia solution or potassium hydroxide to control the pH of the solution; magnesium to aluminium ratios of 2:1 and 5:1). In a second step the lab procedure was up-scaled to pilot plant scale. The effects of the synthesis conditions on the

H.-W. Olfs; L. O. Torres-Dorante; R. Eckelt; H. Kosslick

2009-01-01

32

Solubility and release of fenbufen intercalated in Mg, Al and Mg, Al, Fe layered double hydroxides (LDH): The effect of Eudragit ® S 100 covering  

Microsoft Academic Search

Following different preparation routes, fenbufen has been intercalated in the interlayer space of layered double hydroxides with Mg2+ and Al3+ or Mg2+, Al3+ and Fe3+ in the layers. Well crystallized samples were obtained in most of the cases (intercalation was not observed by reconstruction of the MgAlFe matrix), with layer heights ranging between 16.1 and 18.8Å. The presence of the

M. del Arco; A. Fernández; C. Martín; V. Rives

2010-01-01

33

Catalytic oxidations by in situ generated peroxotungsten complexes immobilized on layered double hydroxides ( LDH): Relation between catalytic properties and peroxotungstate micro-environment  

Microsoft Academic Search

Tungstate is exchanged on a Cl-LDH and converted into peroxo complexes by the action of H2O2. This hydrophilic material is an efficient catalyst for the truly heterogeneous epoxidation of allylic alcohols. The alkaline nature of the LDH suppresses hydrolysis of the epoxides. For simple olefins such as cyclohexene, the use of a lipophilic LDH, exchanged with WO42? and an organic

B. F. Sels; D. E. De Vos; P. A. Jacobs

1997-01-01

34

Effective inhibition of colon cancer cell growth with MgAl-layered double hydroxide (LDH) loaded 5-FU and PI3K/mTOR dual inhibitor BEZ-235 through apoptotic pathways  

PubMed Central

Colon cancer is the third most common cancer and the third largest cause of cancer-related death. Fluorouracil (5-FU) is the front-line chemotherapeutic agent for colon cancer. However, its response rate is less than 60%, even in combination with other chemotherapeutic agents. The side effects of 5-FU also limit its application. Nanoparticles have been used to deliver 5-FU, to increase its effectiveness and reduce side effects. Another common approach for colon cancer treatment is targeted therapy against the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. A recently-invented inhibitor of this pathway, BEZ-235, has been tested in several clinical trials and has shown effectiveness and low side effects. Thus, it is a very promising drug for colon cancer treatment. The combination of these two drugs, especially nanoparticle-packed 5-FU and BEZ-235, has not been studied. In the present study, we demonstrated that nanoparticles of layered double hydroxide (LDH) loaded with 5-FU were more effective than a free drug at inhibiting colon cancer cell growth, and that a combination treatment with BEZ-235 further increased the sensitivity of colon cancer cells to the treatment of LDH-packed 5-FU (LDH-5-FU). BEZ-235 alone can decrease colon cancer HCT-116 cell viability to 46% of the control, and the addition of LDH-5-FU produced a greater effect, reducing cell survival to 8% of the control. Our data indicate that the combination therapy of nanodelivered 5-FU with a PI3K/Akt inhibitor, BEZ-235, may promise a more effective approach for colon cancer treatment.

Chen, Jiezhong; Shao, Renfu; Li, Li; Xu, Zhi Ping; Gu, Wenyi

2014-01-01

35

Adsorption of Cr(VI) in layered double hydroxides  

Microsoft Academic Search

Adsorption of Cr(VI) by various uncalcined and calcined layered double hydroxides (LDH) of Mg–Al, Ni–Al and Zn–Cr types was investigated. Adsorption of Cr2O72? through ion exchange in uncalcined LDH is slower in rate and smaller in amount than in calcined one where the adsorption occurs via rehydration. The nature and content of bi- and trivalent metal ions in LDH influence

Rajib Lochan Goswamee; Pinaki Sengupta; Krishna Gopal Bhattacharyya; Dipak Kumar Dutta

1998-01-01

36

An intercalated hybrid of polyacrylamide\\/layered double hydroxide prepared via in situ intercalative polymerization  

Microsoft Academic Search

A new intercalated hybrid of polyacrylamide (PAM)\\/layered double hydroxide (LDH) prepared via in situ intercalative polymerization procedure is reported. LDH with counterion ion of nitrate or dodecyl sulfate anion was employed for comparison. The obtained PAM\\/LDH hybrid was characterized by X-ray diffraction, infrared spectra, differential scanning microcalorimetry and X-ray photoelectron spectrum. The results reveal that the LDH modified with dodecyl

Pingjun Fu; Guangming Chen; Jun Liu; Jiping Yang

2009-01-01

37

Intracellular release of fluorescein anion from layered double hydroxide nanoparticles indicating endosomal escape  

NASA Astrophysics Data System (ADS)

In recent years, layered double hydroxide (LDH) has been attempted to be applied to a molecular container due to their anion exchange ability, low cytotoxicity and good biocompatibility. In this paper, we investigated the intracellular behaviour of LDH particles in mammalian cells after internalization. Nanoparticles of fluorescein (Fluo) intercalated LDH, Fluo/LDH, were prepared by the coprecipitation followed by subsequent hydrothermal treatment. As-prepared Fluo/LDH particles have the LDH structure and morphology of hexagonal sheet of 100 nm on the average. In addition, Fluo/LDH also exhibited high green fluorescence and low cytotoxicity. By a confocal laser scanning microscopy, the dim green fluorescence was observed throughout cells, including the nucleus. This result indicated that Fluo/LDH released guest anion (Fluo) from LDH structure inside cells. Furthermore, because the fluorescence was observed throughout the cell, Fluo was not retained within endosome structure, i.e., Fluo/LDH was dissolved to release Fluo from endosome.

Tanaka, M.; Aisawa, S.; Hidetoshi, H.; Narita, E.; Dong, Q.; Yin, S.; Sato, T.

2013-12-01

38

Part I. Layered Double Hydroxides  

NASA Astrophysics Data System (ADS)

A new general method for the preparation of well -ordered layered double hydroxides (LDHs), (Mg_ {rm 1-x}Al_{ rm x} (OH)_2) (X^{rm n-}) _{rm n/x}{cdot}yH _2O, interlayered by organic anions has been developed. It is based on the reaction of meixnerite, (Mg_3Al(OH)_8) (OH) cdot2H_2O, with the free acid form of the desired anion--using glycerol as a swelling agent--to yield single crystalline products that are not readily available by conventional synthetic methods. The (Mg_3Al(OH) _8) -adipate and -p-toluenesulfonate derivatives undergo facile ion exchange reactions with Keggin-type (XM_{12}O_ {40}) ^{rm n -} or lacunary (XM_{11 }O_{39}) ^{rm m-} polyoxometalates (POMs) to form well-ordered, microporous pillared derivatives with the highest N_2 BET surface areas reported to date, namely 107 and 155 m^2 /g, respectively. Meixnerite, (Mg_3Al(OH) _8) (OH) cdot2H _2O, has unexpectedly been found to undergo similar ion exchange reactions, in a topotactic way, with retention of the structure of the intercalated POMs. The meixnerite was conveniently prepared for the first time from calcination of (Mg_3Al(OH) _8) (CO_3) _{0.5}{cdot}2H _2O and aqueous hydrolysis of the resulting NaCl-type solid solution. Metal carbonyl clusters have also been examined for ion-exchange (i.e., { (Pt _3(CO)_6) _{rm n}}^ {2-}) in these LDH-precursors. This chemistry is compared with the surface chemistry of (Mg_3 Al(OH)_8) (X^ {rm n-}) _{ rm 1/n}{cdot}2H _2O (X = CO_3^{2 -} or OH^{-}). It has been shown that the surface hydrolysis reaction: CO _3^{2-} + H _2O longrightarrow HCO_3^{-} + OH ^-, causes reductive condensation reactions of neutral carbonyl clusters with the LDH. The reactions were as efficient as with Na metal in solution. In part II of this work, Li-fluorohectorite, has been pillared with titanium polyoxocations derived from the acidic hydrolysis of TiCl_4 or Ti(i-OC_3H_7) _4. Raman spectroscopy of the product indicates that the pillars have a structure analogous to TiO_2(B) phase. It is proposed that the pillars consist of aggregates of condensed (Ti _8O_{12} (H_2O)_{24 }) ^{8+} cations.

Dimotakis, Emmanuel Dimitrios

39

Synthesis of layered double hydroxide nanosheets by coprecipitation using a T-type microchannel reactor  

NASA Astrophysics Data System (ADS)

The synthesis of Mg2Al-NO3 layered double hydroxide (LDH) nanosheets by coprecipitation using a T-type microchannel reactor is reported. Aqueous LDH nanosheet dispersions were obtained. The LDH nanosheets were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy and particle size analysis, and the transmittance and viscosity of LDH nanosheet dispersions were examined. The two-dimensional LDH nanosheets consisted of 1-2 brucite-like layers and were stable for ca. 16 h at room temperature. In addition, the co-assembly between LDH nanosheets and dodecyl sulfate (DS) anions was carried out, and a DS intercalated LDH nanohybrid was obtained. To the best of our knowledge, this is the first report of LDH nanosheets being directly prepared in bulk aqueous solution. This simple, cheap method can provide naked LDH nanosheets in high quantities, which can be used as building blocks for functional materials.

Pang, Xiujiang; Sun, Meiyu; Ma, Xiuming; Hou, Wanguo

2014-02-01

40

Compositional and structural control on anion sorption capability of layered double hydroxides (LDHs)  

Microsoft Academic Search

Layered double hydroxides (LDHs) have shown great promise as anion getters. In this paper, we demonstrate that the sorption capability of a LDH for a specific oxyanion can be greatly increased by appropriately manipulating material composition and structure. We have synthesized a large set of LDH materials with various combinations of metal cations, interlayer anions, and molar ratios of divalent

Yifeng Wang; Huizhen Gao

2006-01-01

41

Layered double hydroxide-like materials: nanocomposites for use in concrete  

Microsoft Academic Search

Nitrobenzoic acid (NBA), naphthalene-2, 6-disulfonic acid (26NS), and naphthalene-2 sulfonic acid (2NS) salts were intercalated into a layered double hydroxide-like host material (LDH). The intercalation process was achieved by anion exchange of nitrates in the host material, Ca2Al(OH)6NO3, nH2O (CaAl LDH), which was prepared by a coprecipitation technique. The resulting organo derivatives CaAlNBA LDH, CaAl26NS LDH, and CaAl2NS LDH produced

L. Raki; J. J. Beaudoin; L. Mitchell

2004-01-01

42

Fluorescein dye intercalated layered double hydroxides for chemically stabilized photoluminescent indicators on inorganic surfaces.  

PubMed

A new photoactive thin film of layered double hydroxide (LDH) nanocrystals containing fluorescein dyes (LDH-F) has been developed by self-assembly of the LDH nanocrystals and well-controlled intercalation of the dyes in organic media. XRD results and absorption spectra confirmed the highly oriented interlayer arrangement of the dianionic form of the fluorescein dyes in the LDH interlayers, in which the dye molecules were electrostatically immobilized between the positively charged LDH layers with a monolayer packing structure. An intensity weighted average PL lifetime was estimated to be 1.45 ns and fluorescence lifetime imaging microscopy revealed that the individual LDH nanocrystals on the LDH-F film had largely similar lifetimes, which were ascribed to the uniform loading of fluorescein dyes onto the LDH matrix without photoluminescence quenching. PMID:24759944

Lee, Jong Hyeon; Jung, Duk-Young; Kim, Eunchul; Ahn, Tae Kyu

2014-06-14

43

Adsorption of sodium dodecyl sulfate on layered double hydroxides  

Microsoft Academic Search

Layered double hydroxides (LDH), or the so-called anionic clays, are hydrotalcite-like compounds which can be represented by the general formula [M1 ? x2+Mx3+ (OH)2]x+Xx\\/mm? ·nH2O. They can be used as adsorbents, catalysts and catalyst supports and they present many other industrial applications such as polymer stabilisers and anion exchangers. On the other hand, the surfactants have been widely applied in

Paulo C. Pavan; Gilmar de A. Gomes; João B. Valim

1998-01-01

44

Thermal stability and flammability characteristics of ethylene vinyl acetate (EVA) composites blended with a phenyl phosphonate-intercalated layered double hydroxide (LDH), melamine polyphosphate and\\/or boric acid  

Microsoft Academic Search

A phenyl phosphonate-intercalated MgAl–LDH (MgAl–PPh), melamine polyphosphate (MP), and boric acid (BA) were independently and concomitantly added to neat ethylene vinyl acetate (EVA) copolymer at loading fractions of 10% (w\\/w). The structural morphology of MgAl–PPh was established via powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) while the presence of phenyl phosphonate in the galleries was confirmed by Fourier

Calistor Nyambo; Everson Kandare; Charles A. Wilkie

2009-01-01

45

Layered double hydroxide as an efficient drug reservoir for folate derivatives  

Microsoft Academic Search

Folic acid derivatives such as folinic acid and methotrexate (MTX) have been successfully hybridized with layered double hydroxide (LDH) by ion-exchange reaction. The X-ray diffraction patterns and spectroscopic analyses indicate that these molecules intercalated into the hydroxide interlayer space are stabilized in the tilted longitudinal monolayer mode by electrostatic interaction. No significant changes in their structural and functional properties are

Jin-Ho Choy; Ji-Sun Jung; Jae-Min Oh; Man Park; Jinyoung Jeong; Young-Koo Kang; Ok-Jin Han

2004-01-01

46

Magnetic alginate-layered double hydroxide composites for phosphate removal.  

PubMed

The objective of this study was to investigate phosphate removal using magnetic alginate-layered double hydroxide (LDH) composites. The magnetic composites were prepared by entrapping synthetic magnetic iron oxide and calcined Mg-Al LDH in polymer matrix (alginate). Results showed that the magnetic composites (2% magnetic iron oxide and 6% calcined Mg-Al LDH) were effective in the removal of phosphate with the sorption capacity of 5.0 +/- 0.1 mgP/g under given experimental conditions (adsorbent dose = 0.05 g in 30 ml solution; initial phosphate concentration = 10 mgP/l; reaction time = 24 h). Both magnetic iron oxide and calcined Mg-Al LDH have the ability to adsorb phosphate, with the latter having much higher sorption capacity. In the magnetic composites, calcined Mg-Al LDH functions as a phosphate adsorbent while magnetic iron oxide provides both magnetic and sorption properties. Results also demonstrated that phosphate sorption to the magnetic composites reached equilibrium at 24 h. The maximum phosphate sorption capacity was determined to be 39.1 mgP/g. In addition, phosphate removal was not sensitive to initial solution pH between 4.1 and 10.2. Only 9% of the phosphate sorption capacity was reduced as the solution pH increased from 4.1 to 10.2. This study demonstrated that magnetic alginate-LDH composites could be used for phosphate removal in combination with magnetic separation. PMID:24527638

Lee, Chang-Gu; Kim, Song-Bae

2013-01-01

47

Facile synthesis of deoxycholate intercalated layered double hydroxide nanohybrids via a coassembly process  

NASA Astrophysics Data System (ADS)

In this paper, we describe a synthesis strategy of deoxycholate (DC) intercalated layered double hydroxide (LDH) nanohybrids via a coassembly method at room temperature. For this strategy, LDH particles were delaminated to well-dispersed 2D nanosheets in formamide, and the resulting LDH nanosheets were then coassembled with DC anions into the DC intercalated LDH (DC-LDH) nanohybrids. The so-synthesized nanohybrids were characterized by XRD, TEM, FT-IR, elemental analyses and TG-DSC. It was found that the loading amount of DC in the nanohybrids could be easily controlled by changing the ratio of DC to LDH. In addition, the nanohybrids have similar characteristics with the DC-LDH nanohybrids synthesized by the hydrothermal method, including their DC loading, crystal structure, morphology and thermal gravimetric behavior. However, this strategy exhibited the advantages of short reaction time and mild experimental conditions compared with the hydrothermal method.

Wu, Xiaowen; Wang, Shuang; Du, Na; Zhang, Renjie; Hou, Wanguo

2013-07-01

48

A hybrid Mg-Al layered double hydroxide/graphene nanostructure obtained via hydrothermal synthesis  

NASA Astrophysics Data System (ADS)

A hybrid Mg-Al layered double hydroxide/graphene (LDH-GR) material nanostructure has been fabricated by employing the hydrothermal treatment at 140 °C for 10 h. Graphene oxide is simultaneously reduced to graphene during the hydrothermal treatment. The LDH and LDH-GR have high degree of crystallinity and assembled layer structure, which is attributed to electrostatic interaction mechanism. The obtained hybrid nanostructure materials can be used as flame retardant or conductor of electricity and heat due to the combination of different properties arising from graphene and LDH.

Zhao, Xiaodong; Cao, Jian-Ping; Zhao, Jun; Hu, Guo-Hua; Dang, Zhi-Min

2014-06-01

49

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

NASA Astrophysics Data System (ADS)

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.

Aisawa, Sumio; Hirahara, Hidetoshi; Ishiyama, Kayoko; Ogasawara, Wataru; Umetsu, Yoshio; Narita, Eiichi

2003-09-01

50

An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation.  

PubMed

Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts. PMID:23701670

Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie

2013-06-12

51

[Sorption of nitrobenzene to anionic surfactant modified layered double hydroxides].  

PubMed

Sodium dodecyl sulfate (SDS) modified MgAl layered double hydroxides (LDHs) were synthesized at different surfactant concentrations (0.5-2.0 TAEC) by the co-precipitation method. The LDH-DS samples obtained were characterized by powder X-ray diffraction and FT-IR spectroscopy. The results showed that SDS was successfully intercalated into the interlayer of the LDH, and the basal spacing was expanded from 0.80 nm to 3.98 nm. The intercalated SDS was considered consistent with a paraffin bilayers arrangement. The sorption of nitrobenzene on LDH-DS was examined, and the results showed that linear model could fit the sorption isotherms well (R2 > 0.99), which implied a partitioning sorption process. The sorption coefficient of nitrobenzene (K(d)) on LDH-DS was positively related to the DS - loading amount, but the organic carbon content normalized sorption coefficient of nitrobenzene (K(oc)) was shown to remain relatively constant. The sorption thermodynamics results showed that the sorption of nitrobenzene on LDH-DS was an endothermic process, and the increase of entropy was the driving force for the sorption process. PMID:23487943

Xia, Yan; Zhu, Run-Liang; Tao, Qi; Liu, Han-Yang

2013-01-01

52

Active protection coatings with layered double hydroxide nanocontainers of corrosion inhibitor  

Microsoft Academic Search

Novel LDH-based nanocontainers of corrosion inhibitor are developed in the present work. The reservoirs are composed by nanostructured layered double Mg\\/Al and Zn\\/Al hydroxides with divanadate anions located in the interlayer regions. The nanocrystalline LDHs (layered double hydroxides) are able to release vanadate ions in a controllable way.XRD, EDS and SEM methods were used in this work to study morphological

M. L. Zheludkevich; S. K. Poznyak; L. M. Rodrigues; D. Raps; T. Hack; L. F. Dick; T. Nunes; M. G. S. Ferreira

2010-01-01

53

A solution blending route to ethylene propylene diene terpolymer/layered double hydroxide nanocomposites  

PubMed Central

Ethylene propylene diene terpolymer (EPDM)/MgAl layered double hydroxide (LDH) nanocomposites have been synthesized by solution intercalation using organically modified LDH (DS-LDH). The molecular level dispersion of LDH nanolayers has been verified by the disappearance of basal XRD peak of DS-LDH in the composites. The internal structures, of the nanocomposite with the dispersion nature of LDH particles in EPDM matrix have been studied by TEM and AFM. Thermogravimetric analysis (TGA) shows thermal stability of nanocomposites improved by ?40 °C when 10% weight loss was selected as point of comparison. The degradation for pure EPDM is faster above 380 °C while in case of its nanocomposites, it is much slower.

Acharya, H; Bhowmick, Anil K

2007-01-01

54

MgFe-layered double hydroxide modified electrodes for direct electron transfer of heme proteins.  

PubMed

In this study, the Fe-based layered double hydroxides (Mg(3)Fe LDH) were used to immobilize heme proteins including hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP) for fabrication of heme/Mg(3)Fe LDH film on glassy carbon electrode (Mg(3)Fe-heme/GCE). The possible role of iron in framework of LDH to promote direct electron transfer (DET) of heme proteins was investigated using an LDH containing non-iron as a reference. Hb was selected as a model protein for studying the electrocatalytic activity of immobilized heme in LDH film. The Mg(3)Fe-Hb/GCE displayed an enhanced electrocatalytic reduction towards H(2)O(2). The biosensor showed a very low detection limit (0.036 ?M) and apparent Michaelis-Menten constant (7.98 ?M). This work outlines that Fe-based LDH modified electrode provides a promising platform for immobilization of heme proteins and development of sensitive biosensors. PMID:22721646

Li, Maoguo; Ji, Huiqin; Wang, Yinling; Liu, Lin; Gao, Feng

2012-01-01

55

Dispersion and size control of layered double hydroxide nanoparticles in aqueous solutions.  

PubMed

We report a simple but efficient method to prepare stable homogeneous suspensions containing monodispersed MgAl layered double hydroxide (LDH) nanoparticles that have wide promising applications in cellular drug (gene) delivery, polymer/LDH nanocomposites, and LDH thin films for catalysis, gas separation, sensing, and electrochemical materials. This new method involves a fast coprecipitation followed by controlled hydrothermal treatment under different conditions and produces stable homogeneous LDH suspensions under variable hydrothermal treatment conditions. Moreover, the relationship between the LDH particle size and the hydrothermal treatment conditions (time, temperature, and concentration) has been systematically investigated, which indicates that the LDH particle size can be precisely controlled between 40 and 300 nm by adjusting these conditions. The reproducibility of making the identical suspensions under identical conditions has been confirmed with a number of experiments. The dispersion of agglomerated LDH aggregates into individual LDH crystallites during the hydrothermal treatment has been further discussed. This method has also been successfully applied to preparing stable homogeneous LDH suspensions containing various other metal ions such as Ni(2+), Fe(2+), Fe(3+), Co(2+), Cd(2+), and Gd(3+) in the hydroxide layers and many inorganic anions such as Cl(-), CO(3)(2-), NO(3)(-), and SO(4)(2-). PMID:16927982

Xu, Zhi Ping; Stevenson, Gregory; Lu, Chao-Qing; Lu, Gao Qing Max

2006-08-31

56

Elution Behavior of Phosphate Contained in Mg/Fe and Zn/Fe Layered Double Hydroxides  

NASA Astrophysics Data System (ADS)

Layered double hydroxide (LDH) is a layered hydroxide and exchangeable anion is intercalated in its interlayer. Application of the LDH as a controlled-release material of interlayer anions has become of interest, thus it is important to clarify the elution behavior of interlayer anions. We synthesized hydrogenphosphate-intercalated Mg/Fe and Zn/Fe LDH and elution of phosphate from these LDH were tested in deionized water, sodium chloride solution, sodium sulfate solution, and sodium carbonate solution. For Mg/Fe LDH, the amount of eluted phosphate increased with time and reached to maximum that increased as higher concentrate solution was used. The elution of phosphate from Mg/Fe LDH could be described by the pseudo second-order equation. This elution behavior was explained as ion-exchange reaction of phosphate with sulfate or carbonate in tested solution by means of kinetic simulation using Runge-Kutta method. In the eluted solution, metal ions contained in the LDH were detected and its amount depended on pH of the tested solution, that is, amounts of eluted Mg and Zn ions were small at higher pH (ca. 10) for Mg/Fe and Zn/Fe LDH respectively, but large amount of Zn ion was detected when 2.03 mol·l-1 carbonate solution (pH = 13) was used. Thus elution of phosphate was caused by two main reactions: ion exchange and decomposition of the LDH.

Kurashina, Masashi; Amatsu, Tomohiro; Ochi, Takaaki; Ohigashi, Nozomi; Kanezaki, Eiji

57

Zn–Cr layered double hydroxide: Visible light responsive photocatalyst for photocatalytic degradation of organic pollutants  

Microsoft Academic Search

Heterogeneous photocatalysis, one of the important steps in advanced oxidative process (AOPs) that was found to be promising for the elimination of toxic organic and inorganic compounds from wastewater. Herein, we reported Zn–Cr-CO3, a novel layered double hydroxide (LDH) for visible-light-driven photocatalytic degradation of organic chemicals. The physicochemical properties of the synthesized Zn\\/Cr-CO3 LDH, prepared by co-precipitation method at constant

Lagnamayee Mohapatra; K. M. Parida

58

Nanocomposites based on polyethylene and Mg–Al layered double hydroxide. I. Synthesis and characterization  

Microsoft Academic Search

Low density polyethylene (LDPE)\\/Mg–Al layered double hydroxide (LDH) nanocomposites have been synthesized with different compositions by melt-mixing technique using maleic anhydride grafted polyethylene as compatibilizer. LDH has been modified by sodium dodecylbenzene sulfonate using reconstruction method and characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The nanocomposites are characterized by different techniques such as, transmission electron microscopy

Francis Reny Costa; Mahmoud Abdel-Goad; Udo Wagenknecht; Gert Heinrich

2005-01-01

59

Molecular dynamics simulation of layered double hydroxides  

SciTech Connect

The interlayer structure and the dynamics of Cl{sup {minus}} ions and H{sub 2}O molecules in the interlayer space of two typical LDH [Layered Double Hydroxide] phases were investigated by molecular dynamics computer simulations. The simulations of hydrocalumite, [Ca{sub 2}Al(OH){sub 6}]Cl{center_dot}2H{sub 2}O reveal significant dynamic disorder in the orientations of interlayer water molecules. The hydration energy of hydrotalcite, [Mg{sub 2}Al(0H){sub 6}]Cl{center_dot}nH{sub 2}O, is found to have a minimum at approximately n = 2, in good agreement with experiment. The calculated diffusion coefficient of Cl{sup {minus}} as an outer-sphere surface complex is almost three times that of inner-sphere Cl{sup {minus}}, but is still about an order of magnitude less than that of Cl{sup {minus}} in bulk solution. The simulations demonstrate unique capabilities of combined NMR and molecular dynamics studies to understand the structure and dynamics of surface and interlayer species in mineral/water systems.

KALINICHEV,ANDREY G.; WANG,JIANWEI; KIRKPATRICK,R. JAMES; CYGAN,RANDALL T.

2000-05-19

60

Facile synthesis of NiAl-layered double hydroxide\\/graphene hybrid with enhanced electrochemical properties for detection of dopamine  

Microsoft Academic Search

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH\\/graphene

Meixia Li; Jun E. Zhu; Lili Zhang; Xu Chen; Huimin Zhang; Fazhi Zhang; Sailong Xu; David G. Evans

2011-01-01

61

The use of layered double hydroxides as DNA vaccine delivery vector for enhancement of anti-melanoma immune response  

Microsoft Academic Search

Our previous studies have shown that Mg:Al 1:1 layered double hydroxides (LDH(R1)) nanoparticles could be taken up by the MDDCs effectively and had an adjuvant activity for DC maturation. Furthermore, these LDH(R1) nanoparticles could up-regulate the expression of CCR7 and augment the migration of DCs in response to CCL21. In current study, we have evaluated whether LDH(R1) as DNA vaccine

Ang Li; Lili Qin; Wenrui Wang; Rongrong Zhu; Yongchun Yu; Hui Liu; Shilong Wang

2011-01-01

62

Dry reforming of methane over catalysts derived from nickel-containing Mg–Al layered double hydroxides  

Microsoft Academic Search

We present the synthesis and structural characterization of new nickel-containing Mg–Al layered double hydroxides (LDH), which adopt a structure in which nickel, chelated with ethylenediaminetetraacetate to a divalent anion [Ni(EDTA)]2?, is nested between brucite-like layers of LDH. The corresponding LDH-derived Ni–Mg–Al mixed oxides demonstrated high and stable catalytic function toward the reaction of methane reforming with carbon dioxide into synthesis gas

Andrey I. Tsyganok; Tatsuo Tsunoda; Satoshi Hamakawa; Kunio Suzuki; Katsuomi Takehira; Takashi Hayakawa

2003-01-01

63

Factors influencing the hydration of layered double hydroxides (LDHs) and the appearance of an intermediate second staging phase  

Microsoft Academic Search

The hydration of layered double hydroxides (LDHs) was investigated by changing the interlayer anion species, the Mg\\/Al ratio of the LDH hosts and the relative humidity (RH). The anions were CO32?, Cl?, Br?, NO3?, I?, SO42?, and ClO4? (listed in the order of ion size, small to large) and LDHs with Mg\\/Al=1.90 (LDH2) and 2.91 (LDH3) were used. Their XRD

Nobuo Iyi; Kazuko Fujii; Kentaro Okamoto; Takayoshi Sasaki

2007-01-01

64

Layered double hydroxides as templates for nanocasting porous N-doped graphitic carbons via chemical vapour deposition  

Microsoft Academic Search

Porous carbon materials have been prepared using Mg–Al (Mg\\/Al=2) layered double hydroxides (LDH) as template via chemical vapour deposition (CVD) at 600–800°C, with acetonitrile as carbon precursor. Depending on the CVD temperature, the carbons exhibit microporosity, mesoporosity and significant levels of graphitisation. The layer structural ordering of the LDH is somewhat retained in the LDH\\/carbon composite obtained after CVD, but

Aleksandra Pacu?a; Robert Mokaya

2007-01-01

65

Particle-particle interactions between layered double hydroxide nanoparticles.  

PubMed

Changes in chemical properties of nanoscale particles include quantum size effect, changes in the cell parameters and lattice symmetry, and surface and interface effects. In the case of layered double hydroxides (LDHs), surface and interface effects dominate for nanoparticles of MgAl LDHs. Using TEM micrographs of nanoparticle-sized LDHs, we have found that the increased number of surface atoms relative to the internal atoms increases the surface-to-surface interparticle attractions. As a result, nanosize LDH particles are able to form continuous oriented films that adhere well to a polar substrate. PMID:16802784

Gursky, Jennifer A; Blough, Sandra D; Luna, Cesar; Gomez, Clarissa; Luevano, Amber N; Gardner, Elizabeth A

2006-07-01

66

Intercalation of Anionic Oxalato Complexes into Layered Double Hydroxides  

NASA Astrophysics Data System (ADS)

Intercalation compounds of layered double hydroxide (LDH), MII1- xMIIIx(OH) 2Ax/ y· nH 2O (with MII=Zn, Cu and MIII=Al, Cr, Ga), with oxalato complexes of aluminium, gallium, chromium, copper, and beryllium, were obtained via anion-exchange processes. Powder X-ray diffraction indicated that the intercalation reactions were successful. The basal spacings measured after intercalation are near 0.98±0.02 nm, whatever the host matrix composition. Studies by FTIR spectroscopy confirmed the intercalation of the oxalato complex, too. In order to study the thermal decomposition of the exchanged products, TGA-coupled mass spectrometry was performed.

Prevot, V.; Forano, C.; Besse, J. P.

2000-09-01

67

Layered Double Hydroxide-Based Nanocarriers for Drug Delivery  

PubMed Central

Biocompatible clay materials have attracted particular attention as the efficient drug delivery systems (DDS). In this article, we review developments in the use of layered double hydroxides (LDHs) for controlled drug release and delivery. We show how advances in the ability to synthesize intercalated structures have a significant influence on the development of new applications of these materials. We also show how modification and/or functionalization can lead to new biotechnological and biomedical applications. This review highlights the most recent progresses in research on LDH-based controlled drug delivery systems, focusing mainly on: (i) DDS with cardiovascular drugs as guests; (ii) DDS with anti-inflammatory drugs as guests; and (iii) DDS with anti-cancer drugs as guests. Finally, future prospects for LDH-based drug carriers are also discussed.

Bi, Xue; Zhang, Hui; Dou, Liguang

2014-01-01

68

Structural characterisation of a layered double hydroxide nanosheet.  

PubMed

We report the atomic-scale structure of a Zn2Al-borate layered double hydroxide (LDH) nanosheet, as determined by reverse Monte Carlo (RMC) modelling of X-ray total scattering data. This study involves the extension of the RMC method to enable structural refinement of two-dimensional nanomaterials. The refined LDH models show the intra-layer geometry in this highly-exfoliated phase to be consistent with that observed in crystalline analogues, with the reciprocal-space scattering data suggesting a disordered arrangement of the Zn(2+) and Al(3+) cations within the nanosheet. The approach we develop is generalisable and so offers a method of characterising the structures of arbitrary nanosheet phases, including systems that support complex forms of disorder within the nanosheets themselves. PMID:24906206

Funnell, Nicholas P; Wang, Qiang; Connor, Leigh; Tucker, Matthew G; O'Hare, Dermot; Goodwin, Andrew L

2014-06-26

69

Study of organo-hybrid layered double hydroxides by medium and near infrared spectroscopy  

Microsoft Academic Search

An Mg\\/Al layered double hydroxide (LDH) containing carbonate ion in its interlayer region was examined by medium infrared (MIR) and near infrared reflectance spectroscopy (NIRS). The MIR and NIR spectroscopy techniques was also used to study two organo-hybrid LDHs containing interlayer dodecylbenzenesulphonate (DBS) and dodecylsulphate (DS) ions, respectively. The NIR spectra for the latter solids were found to exhibit the

Manuel Mora; M. Isabel López; César Jiménez-Sanchidrián; J. Rafael Ruiz

2011-01-01

70

Specific DNA extraction through fluid channels with immobilization of layered double hydroxides on polycarbonate surface  

Microsoft Academic Search

The purpose of this study was to immobilize inorganic layered double hydroxides (LDHs) on the polycarbonate (PC) substrate as the media to extract the specific DNA molecules through fluidic system and to enhance the extraction efficiency of specific DNA molecules from extreme low concentration in sample solution. LDH immobilized through solvent swelling and plasma treatment on the polymer surface captured

Chia-Hao Chan; Jem-Kun Chen; Feng-Chih Chang

2008-01-01

71

Layered double hydroxide as nanofiller in the development of polyurethane nanocomposites.  

PubMed

Polyurethane (PU)/Dodecyl sulphate intercalated layered double hydroxide (DS-LDH) nanocomposites were successfully synthesized from PU prepolymer and polyol TG (mixtures of glycerol and trimethylolpropane) for the first time. Formation of partially exfoliated structures of PU/DS-LDH nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Analysis of tensile properties showed significant improvements in tensile strength (TS) and elongation at break (EB) of about 407% and 83% for PU/DS-LDH (3 wt%) nanocomposite. The observed excellent concurrent improvement in TS and EB is attributed to the relatively better reinforcing effect of partially exfoliated DS-LDH layers in PU making the present investigation most noteworthy. In addition, gradual improvement in thermal stability and limiting oxygen index (LOI) with increasing DS-LDH loading makes these nanocomposites versatile and hence suitable for many critical applications. PMID:21133098

Kotal, M; Srivastava, S K; Manu, S K

2010-09-01

72

APPLICATIONS OF LAYERED DOUBLE HYDROXIDES IN REMOVING OXYANIONS FROM OIL REFINING AND COAL MINING WASTEWATER  

SciTech Connect

Western Research Institute (WRI), in conjunction with the U.S. Department of Energy (DOE), conducted a study of using the layered double hydroxides (LDH) as filter material to remove microorganisms, large biological molecules, certain anions and toxic oxyanions from various waste streams, including wastewater from refineries. Results demonstrate that LDH has a high adsorbing capability to those compounds with negative surface charge. Constituents studied include model bacteria, viruses, arsenic, selenium, vanadium, diesel range hydrocarbons, methyl tert-butyl ether (MTBE), mixed petroleum constituents, humic materials and anions. This project also attempted to modify the physical structure of LDH for the application as a filtration material. Flow characterizations of the modified LDH materials were also investigated. Results to date indicate that LDH is a cost-effective new material to be used for wastewater treatment, especially for the treatment of anions and oxyanions.

Song Jin; Paul Fallgren

2006-03-01

73

A novel nanocomposite material prepared by intercalating photoresponsive dendrimers into a layered double hydroxide  

SciTech Connect

A novel combination for an inorganic-organic nanocomposite material was demonstrated. Anthryl dendron, i.e., poly(amidoamine) dendron with an anthracene chromophore group at the focal point, was incorporated in the interlayer space of ZnAl-NO{sub 3} type layered double hydroxide (LDH) through an anion-exchange reaction. The photoabsorption and fluorescence properties of the resulting material were different from those of the bare anthryl dendron molecule. It was suggested that the change in photochemical properties was due to the organization and pi-pi interaction of anthracene chromophores within the interlayer of the LDH. - Graphical abstract: A novel inorganic-organic nanocomposite material, a layered double hydroxide (LDH) containing photoresponsive dendrimers in the interlayer space, was successfully prepared through an ion-exchange reaction. The resulting material exhibited unique photochemical properties, compared to those of the bare photoresponsive dendrimer molecule.

Tanaka, Toshiyuki; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Matsukawa, Junpei; Fujita, Yasuhiko; Takaguchi, Yutaka; Matsuda, Motohide [Department of Material and Energy Science, Graduate School of Environmental Science, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530 (Japan); Miyake, Michihiro, E-mail: mmiyake@cc.okayama-u.ac.j [Department of Material and Energy Science, Graduate School of Environmental Science, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530 (Japan)

2010-02-15

74

Layered double hydroxide nanoparticles as cellular delivery vectors of supercoiled plasmid DNA  

PubMed Central

We prepared stable homogeneous suspensions with layered double hydroxide (LDH) nanoparticles for in vitro gene delivery tests. The viability of HEK 293T cells in the presence of LDH nanoparticles at different concentrations was investigated. This revealed 50% cell viability at 500 ?g/mL of LDH nanoparticles that is much higher than 50–100 ?g/mL used for the delivery tests. The supercoiled pEF-eGFP plasmid (ca. 6100 base pairs) was mixed with LDH nanoparticle suspensions for anion exchange at a weight ratio of DNA/LDH between 1:25 and 1:100. In vitro experiments show that GFP expression in HEK 293T cells starts in the first day, reaches the maximum levels by the second day and continues in the third day. The GFP expression generally increases with the increase in DNA loading in DNA-LDH nanohybrids. However, the delivery efficiency with LDH nanoparticles as the agent is low. For example, the relative efficiency is 7%–15% of that of the commercial agent FuGENE®6. Three to 6% of total cells expressed GFP in an amount detectable by the FACS cytometry 2 days after transfection at 1 ?g/mL of plasmid DNA with 25 ?g/mL of LDH nanomaterial. The lower delivery efficiency could be attributed to the aggregation of LDH nanoparticles caused by the long-chain plasmid DNA.

Xu, Zhi Ping; Walker, Tara L; Liu, Kerh-lin; Cooper, Helen M; Lu, GQ Max; Bartlett, Perry F

2007-01-01

75

Nanocage structure derived from sulfonated ?-cyclodextrin intercalated layered double hydroxides and selective adsorption for phenol compounds.  

PubMed

Nanocage structures derived from decasulfonated ?-cyclodextrin (SCD) intercalated ZnAl- and MgAl- layered double hydroxides (LDHs) were prepared through calcination-rehydration reactions. The ZnAl- and MgAl-LDH layers revealed different basal spacings (1.51 nm for SCD-ZnAl-LDH and 1.61 nm for SCD-MgAl-LDH) when contacting SCD, while producing similar monolayer and vertical SCD orientations with cavity axis perpendicular to the LDH layer. The structures of the SCD-LDH and carboxymethyl-?-cyclodextrin (CMCD)-LDH intercalates were fully analyzed and compared, and a structural model for the SCD-LDH was proposed. The thermal stability of SCD after intercalation was remarkably enhanced, with decomposition temperature increased by 230 °C. The adsorption property of the SCD-LDH composites for phenol compounds (the effects of adsorption time and phenol concentration on adsorption) was investigated completely. The monolayer arrangement of the interlayer SCD did not affect the adsorption efficiency toward organic compounds, which verified the highly swelling ability of the layered compounds in solvents. Both composites illustrated preferential adsorptive efficiency for 2,3-dimethylphenol (DMP) in comparison with other two phenols of hydroquinone (HQ) and tert-butyl-phenol (TBP), resulting from appropriate hydrophobicity and steric hindrance of DMP. For the two phenols of HQ and TBP, SCD-MgAl-LDH gave better adsorption capacity compared with SCD-ZnAl-LDH. The double-confinement effect due to the combination of the parent LDH host and intercalated secondary host may impose high selectivity for guests. This kind of nanocage structure may have potential applications as adsorbents, synergistic agents, and storage vessels for particular guests. PMID:24422491

Xue, Xiangyu; Gu, Qingyang; Pan, Guohua; Liang, Jie; Huang, Gailing; Sun, Genban; Ma, Shulan; Yang, Xiaojing

2014-02-01

76

Bionanocomposites based on layered double hydroxides as drug delivery systems  

NASA Astrophysics Data System (ADS)

The present work introduces new biohybrid materials involving layered double hydroxides (LDH) and biopolymers to produce bionanocomposites, able to act as effective drug delivery systems (DDS). Ibuprofen (IBU) and 5-aminosalicylic acid (5-ASA) have been chosen as model drugs, being intercalated in a Mg-Al LDH matrix. On the one side, the LDHIBU intercalation compound prepared by ion-exchange reaction was blended with the biopolymers zein, a highly hydrophobic protein, and alginate, a polysaccharide widely applied for encapsulating drugs. On the other side, the LDH- 5-ASA intercalation compound prepared by co-precipitation was assembled to the polysaccharides chitosan and pectin, which show mucoadhesive properties and resistance to acid pH values, respectively. Characterization of the intercalation compounds and the resulting bionanocomposites was carried out by means of different experimental techniques: X-ray diffraction, infrared spectroscopy, chemical and thermal analysis, as well as optical and scanning electron microscopies. Data on the swelling behavior and drug release under different pH conditions are also reported.

Aranda, Pilar; Alcântara, Ana C. S.; Ribeiro, Ligia N. M.; Darder, Margarita; Ruiz-Hitzky, Eduardo

2012-10-01

77

Thermal Behavior of Phosphate Intercalated Mg/Al-LAYERED Double Hydroxides  

NASA Astrophysics Data System (ADS)

The thermal behavior of Mg and Al layered double hydroxide with interlayer hydrogen phosphate (abb. as Mg/Al-HPO4-LDH) is investigated below 1273 K by means of XRD, TG-DTA, SEM and FT-IR. The basal spacing of Mg/Al-HPO4-LDH decreases with increasing heating temperature stepwise in two stages; from 1.07 nm at 293 K to 0.85 nm at 333 K in the first stage and to 0.73 nm between 373 K and 443 K in the second one. The LDH becomes amorphous above 443 K until Mg3 (PO4)2, MgO and MgAl2O4 (spinel) appear at 1273 K. SEM images of the LDH show plate-like crystallites both before and after heating at 473 K.

Shimamura, Akihiro; Kurashina, Masashi; Kanezaki, Eiji

78

Scalable preparation of alginate templated-layered double hydroxide mesoporous composites with enhanced surface areas and surface acidities.  

PubMed

Layered double hydroxides (LDHs), also known as hydrotalcite-like layered clays, have previously been investigated as a potential solid alkaline catalyst. A necessary calcinations/rehydration procedure, however, is utilized to enhance surface area and catalytic activity of LDHs involved. Here we report on a scalable preparation of sodium alginate-templated MgAI-LDH (LDH/SA) mesoporous composites with high surface area and surface acidity. The powdery LDH/SA mesoporous composites are prepared using alginate as template by a scalable method of separate nucleation and aging steps (SNAS). Comparison with the pristine MgAl-LDH shows that the obtained LDH/SA composites exhibit the greatly enhanced surface area and surface activity of surface acid sites at the elevated high temperatures which have scarcely been reported previously. Our results may allow designing a variety of mesoporous LDH-containing composites with potential applications in specific catalysis and purification processes. PMID:21776699

Zhao, Lina; Xu, Ting; Lei, Xiaodong; Xu, Sailong; Zhang, Fazhi

2011-04-01

79

Exfoliation and immobilization of anionic iron porphyrin in layered double hydroxides.  

PubMed

Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with an aqueous iron porphyrin (FeTDFSPP) solution. The new composite was characterized by powder X-ray diffraction, UV-vis, FTIR, and electron paramagnetic spectroscopies and thermal analyses (simultaneous TG/DSC). The analyses demonstrated that glycinate anions continue to be intercalated and the anionic iron porphyrin is adsorbed at the surface of the layered double hydroxide crystals. PMID:12885536

Wypych, F; Bubniak, G A; Halma, M; Nakagaki, S

2003-08-01

80

Mechanism of the anion exchange reactions of the layered double hydroxides (LDHs) of Ca and Mg with Al  

Microsoft Academic Search

The nitrate containing layered double hydroxide (LDH) of Ca with Al on reaction with aqueous solutions of Na2CO3 and Na3PO4 yields CaCO3 and Ca5(PO4)3OH respectively rather than the carbonate\\/phosphate containing LDHs. The LDH of Mg with Al on reacting with dissolved phosphate ions also leads to the formation of unitary phosphates. This shows that the anion exchange reactions of layered

A. V. Radha; P. Vishnu Kamath; C. Shivakumara

2005-01-01

81

Nickel–aluminum layered double hydroxide as a nanosorbent for selective solid-phase extraction and spectrofluorometric determination of salicylic acid in pharmaceutical and biological samples  

Microsoft Academic Search

The nickel–aluminum layered double hydroxide (Ni–Al LDH) was synthesized by a simple co-precipitation method and used as a solid-phase extraction (SPE) sorbent for separation and pre-concentration of trace levels of salicylic acid (SA) from aqueous solutions. Extraction of analyte is based on the adsorption of salicylate ions on the Ni–Al (NO3?) LDH and\\/or their exchanging with LDH interlayer NO3? ions.

H. Abdolmohammad-Zadeh; S. Kohansal; G. H. Sadeghi

2011-01-01

82

Treatment of gaseous hydrogen chloride using Mg-Al layered double hydroxide intercalated with carbonate ion.  

PubMed

It is important to treat gaseous HCl from incineration streams efficiently to avoid adverse environmental consequences. In this paper, a new treatment method for gaseous HCl is presented-the application of Mg-Al layered double hydroxide (LDH) intercalated with CO(3)(2-) (CO(3)·Mg-Al LDH) to treat gaseous HCl continuously. The degree of HCl removal without water vapor is higher than that with water vapor; further, this reaction does not require H(2)O. In addition, the degree of HCl removal increases with increasing temperature, CO(3)·Mg-Al LDH quantity, HCl concentration, and improved contact between CO(3)·Mg-Al LDH and HCl gas. The treatment of HCl gas by CO(3)·Mg-Al LDH leads to the production of Mg-Al LDH intercalated with Cl(-). Further, HCl is also absorbed on the surface of CO(3)·Mg-Al LDH. Our proposed treatment method works effectively for the treatment of gaseous HCl from incinerator streams. PMID:20800264

Kameda, Tomohito; Uchiyama, Naoya; Yoshioka, Toshiaki

2010-10-01

83

An effect of alginate on the stability of LDH nanosheets in aqueous solution and preparation of alginate/LDH nanocomposites.  

PubMed

Nanosheets under 10nm in thickness are obtained by exfoliating layered double hydroxide (LDH) in formamide. The LDH nanosheets are dispersed and stabilized in an alginate aqueous solution after removing formamide by water washing and ultracentrifugation. During the water washing stage LDH nanosheets can be prevented from restacking by electrostatic stabilization of the surface of LDH sheets through the adsorption of alginate. Alginate/LDH nanocomposites can be prepared by drying the dispersion, and sandwich-like structures in the nanocomposites are formed with two alginate layers contained between two LDH sheets. LDH nanosheets in the dried alginate/LDH nanocomposites can be re-dispersed in water. The thermal stability of alginate in the nanocomposite is increased by LDH. Alginate membranes containing this layered nanocomposite can be prepared. The addition of LDH into the alginate matrix leads to an increase in the mechanical properties of the nanocomposite. PMID:24188850

Kang, Hongliang; Shu, Yang; Li, Zhuang; Guan, Bo; Peng, Shunjin; Huang, Yong; Liu, Ruigang

2014-01-16

84

Large-scale synthesis of highly dispersed layered double hydroxide powders containing delaminated single layer nanosheets.  

PubMed

A facile method for the synthesis of Zn2Al-borate and Mg3Al-borate layered double hydroxides (LDHs) with extremely high specific surface areas of 458.6 and 263 m(2) g(-1) and containing delaminated nanosheets is reported. To the best of our knowledge, this is the first report of LDH powders that still remain exfoliated on drying. PMID:23739826

Wang, Qiang; O'Hare, Dermot

2013-07-18

85

Highly basic catalysts obtained by intercalation of La-containing anionic complexes in layered double hydroxides  

Microsoft Academic Search

Nanocomposites have been obtained by intercalation of preformed negatively charged guest La hydroxy citrate colloids into host Mg\\/Al layered double hydroxides (LDH). These compounds have been used as precursors for La\\/Mg(Al)O mixed oxides catalysts. The La loading has been controlled by the colloids exchange rate in order to achieve a better dispersion of the lanthanum cations and thus improve the

Iuliana Cota; Eliana Ramírez; Francisco Medina; Jesús E. Sueiras; Géraldine Layrac; Didier Tichit

2010-01-01

86

Chemical composition and interlayer arrangement of polytype 3R 2 Mg–Al layered double hydroxides  

Microsoft Academic Search

The polytype 3R2 of Mg–Al layered double hydroxide (LDH) can be synthesized either directly by hydrothermal treatment of magnesium oxide (MgO) and aluminium trihydroxide (ATH) at 170°C or by a two-step synthesis. By the latter method, first polytype 3R1 is hydrothermally formed with a Mg\\/Al ratio of 2.2 at 90°C, which is subsequently converted at 170°C into polytype 3R2 with

W. N. Budhysutanto; D. van Agterveld; E. Schomaker; B. D. Rossenaar; G. M. van Rosmalen; H. J. M. Kramer

2011-01-01

87

A sustained folic acid release system based on ternary magnesium\\/zinc\\/aluminum layered double hydroxides  

Microsoft Academic Search

This study first synthesized and characterized the ternary magnesium\\/zinc\\/aluminum layered double hydroxides (Mg\\/Zn\\/Al-LDHs)\\u000a intercalated with folic acid. We prepared the ternary (Mg, Zn, Al) LDH carrier by the introduction of zinc, because magnesium\\u000a and zinc are both vital minerals of human body. The nanohybrids were prepared by the method of coprecipitation and were characterized\\u000a by powdered sample X-ray diffraction (XRD),

Rong Xiao; Wenrui Wang; Longlong Pan; Rongrong Zhu; Yongchun Yu; Huiping Li; Hui Liu; Shi-Long Wang

2011-01-01

88

Synthesis and characterization of arsenate-intercalated layered double hydroxides (LDHs): Prospects for arsenic mineralization  

Microsoft Academic Search

The arsenate-intercalated layered double hydroxide (LDH) of Mg and Al is synthesized by coprecipitation. The higher thermodynamic stability and the consequent lower solubility of the unitary arsenates preclude the formation of arsenate-intercalated LDHs of other metals directly from solution. However other M\\/Al-AsO4 (M=Co, Ni, Zn) LDHs could be prepared by anion exchange, showing that arsenate intercalation proceeds topotactically. The intercalation

S. V. Prasanna; P. Vishnu Kamath

2009-01-01

89

Reversible thermal behavior of the layered double hydroxides (LDHs) of Mg with Ga and In  

Microsoft Academic Search

The layered double hydroxides (LDHs) of Mg with Ga and In decompose completely on heating to 500°C to yield poorly ordered oxide residues. In the Mg–Ga system, the oxide residue has a rock-salt structure with Ga incorporated in the MgO matrix. In the Mg–In system, the oxide residue is X-ray amorphous. These oxide residues revert back to the original LDH

Grace S. Thomas; P. Vishnu. Kamath

2005-01-01

90

Polymer-dispersed liquid crystal\\/layered double hydroxide nanocomposite: A new emerging optical application  

Microsoft Academic Search

This paper describes the preparation and characterization of polymer-dispersed liquid crystal (PDLC)\\/layered double hydroxides (LDHs) nanocomposites. In this study, Mg–Al LDH was applied as two-dimensional host material, with the unique properties of higher anionic exchange capacity (AEC) and higher aspect ratio. Preparation of nanomaterials with a uniform, higher crystalline and surface charge density could be performed by a hydrothermal method.

Tsung-Yen Tsai; Shau-Wen Lu; Yuan-Pin Huang; Fu-Shou Li

2006-01-01

91

Sorption/desorption of arsenate on/from Mg-Al layered double hydroxides: influence of phosphate.  

PubMed

We have studied: (i) the sorption of arsenate on Mg-Al layered double hydroxides (LDHs) containing chloride (LDH-Cl) or carbonate (LDH-CO(3)) in the absence or presence of phosphate; (ii) the competitive sorption of arsenate and phosphate as affected by reaction time and pH and; (iii) the desorption of arsenate previously sorbed on the LDH by phosphate. The LDH samples were uncalcined (LDH-Cl-20 and LDH-CO(3)-20) or calcined at 450 degrees C (LDH-Cl-450 and LDH-CO(3)-450). More phosphate than arsenate was sorbed onto all the minerals but LDH-Cl-450 sorbed much lower amounts of both the ligands than LDH-Cl-20; vice versa LDH-CO(3)-450 showed a capacity to sorb arsenate and phosphate much greater than LDH-CO(3)-20. XRD analysis showed that arsenate was included into the layer spaces of LDH-Cl-20, but not in those of LDH-CO(3)-20. Competition in sorption between arsenate and phosphate was affected by pH, reaction time, surface coverage and sequence of addition of the ligands. Phosphate showed a greater affinity for LDHs than arsenate. The final arsenate sorbed/phosphate sorbed molar ratio increased with reaction time or by adding arsenate before phosphate, but decreased by increasing pH and by adding phosphate before arsenate. The effect of reaction time on the desorption of arsenate by phosphate was also studied. PMID:19211108

Violante, Antonio; Pucci, Marianna; Cozzolino, Vincenza; Zhu, Jun; Pigna, Massimo

2009-05-01

92

Three-dimensional NiFe layered double hydroxide film for high-efficiency oxygen evolution reaction.  

PubMed

Fabricating active materials into specific macrostructures is critical in the pursuit of high electro-catalytic activity. Herein we demonstrate that a three-dimensional (3D) architecture of NiFe layered double hydroxide (NiFe-LDH) significantly reduced the onset potential, yielded high current density at small overpotentials, and showed outstanding stability in electrochemical oxygen evolution reaction. PMID:24817324

Lu, Zhiyi; Xu, Wenwen; Zhu, Wei; Yang, Qiu; Lei, Xiaodong; Liu, Junfeng; Li, Yaping; Sun, Xiaoming; Duan, Xue

2014-06-21

93

Facile synthesis of NiAl-layered double hydroxide/graphene hybrid with enhanced electrochemical properties for detection of dopamine  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH/graphene (NiAl-LDH/G) nanocomposites using a conventional coprecipitation process under low-temperature conditions and subsequent reduction of the supporting graphene oxide. Electrochemical tests showed that the NiAl-LDH/G modified electrode exhibited highly enhanced electrochemical performance of dopamine electrooxidation in comparison with the pristine NiAl-LDH modified electrode. Results of high-resolution transmission electron microscopy and Raman spectra provide convincing information on the nanostructure and composition underlying the enhancement. Our results of the NiAl-LDH/G modified electrodes with the enhanced electrochemical performance may allow designing a variety of promising hybrid sensors via a simple and feasible approach.Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH/graphene (NiAl-LDH/G) nanocomposites using a conventional coprecipitation process under low-temperature conditions and subsequent reduction of the supporting graphene oxide. Electrochemical tests showed that the NiAl-LDH/G modified electrode exhibited highly enhanced electrochemical performance of dopamine electrooxidation in comparison with the pristine NiAl-LDH modified electrode. Results of high-resolution transmission electron microscopy and Raman spectra provide convincing information on the nanostructure and composition underlying the enhancement. Our results of the NiAl-LDH/G modified electrodes with the enhanced electrochemical performance may allow designing a variety of promising hybrid sensors via a simple and feasible approach. Electronic supplementary information (ESI) available: Fig. S1 showing 2D fast Fourier transform (FFT) image of NiAl-LDH phase in NiAl-LDH/G composites, and Fig. S2 showing CV curve of the pristine G modified electrode. See DOI: 10.1039/c1nr10592b.

Li, Meixia; Zhu, Jun E.; Zhang, Lili; Chen, Xu; Zhang, Huimin; Zhang, Fazhi; Xu, Sailong; Evans, David G.

2011-10-01

94

Enhancement of relaxivity rates of Gd-DTPA complexes by intercalation into layered double hydroxide nanoparticles.  

PubMed

In this paper we report the preparation and characterization of [Gd(dtpa)](2-) intercalated layered double hydroxide (LDH) nanomaterials. [Gd(dtpa)](2-) (gadolinium(III) diethylene triamine pentaacetate) was transferred into LDH by anionic exchange. The intercalation of [Gd(dtpa)](2-) into LDH was confirmed by X-ray diffraction for the new phase with the interlayer spacing of 3.5-4.0 nm and by FTIR for the characteristic vibration peaks of [Gd(dtpa)](2-). The morphology of the nanoparticles was influenced by the extent of [Gd(dtpa)](2-) loading, in which the poly-dispersity quality decreased as the [Gd(dtpa)](2-) loading was increased. Compared with the morphology of the original Mg(2)Al-Cl-LDH nanoparticles (hexagonal plate-like sheets of 50-200 nm), the modified LDH-Gd(dtpa) nanoparticles are bar-like with a width of 30-60 nm and a length of 50-150 nm. LDH-Gd(dtpa) was expected to have an increased water proton magnetic resonance relaxivity due to the intercalation of [Gd(dtpa)](2-) into the LDH interlayer that led to slower molecular anisotropic tumbling compared with free [Gd(dtpa)](2-) in solution. Indeed, LDH-nanoparticle suspension containing approximately 1.6 mM [Gd(dtpa)](2-) exhibits a longitudinal proton relaxivity r(1) of approximately 16 mM(-1) s(-1) and a transverse proton relaxivity r(2) of approximately 50 mM(-1) s(-1) at room temperature and a magnetic field of 190 MHz, which represents an enhancement four times (r(1)) and 12 times (r(2)) that of free [Gd(dtpa)](2-) in solution under the same reaction conditions. We have thus tailored LDH-nanoparticles into a novel contrast agent with strong relaxivity, promising for great potential applications in magnetic resonance imaging. PMID:17186555

Xu, Zhi Ping; Kurniawan, Nyoman D; Bartlett, Perry F; Lu, Gao Qing

2007-01-01

95

Structural Aspects of Layered Double Hydroxides  

Microsoft Academic Search

Layered double hydroxides (LDHs) have been known for a considerable time and have been\\u000a widely studied. The basic features of their structure, involving positively charged brucite-like\\u000a layers together with charge-balancing anions and water in interlayer galleries are well understood,\\u000a but some detailed aspects of their structure have been the subject of controversy in the literature.\\u000a In this article we review the

David G. Evans; Robert C. T. Slade

96

Mg-Al layered double hydroxide-methotrexate nanohybrid drug delivery system: evaluation of efficacy.  

PubMed

Mg-Al layered double hydroxide nanoparticles were synthesized by one-pot co-precipitation method and anticancerous drug methotrexate was incorporated into it by in-situ ion exchange. The LDH-MTX nanohybrid produced moderately stable suspension in water, as predicted by zeta potential measurement. X-ray diffraction revealed that the basal spacing increased to nearly twice the same for pristine LDH on MTX intercalation. Thermogravimetric analyses confirmed an increase in thermal stability of the intercalated drug in the LDH framework. A striking enhancement in efficacy/sensitivity of MTX on the HCT-116 cells was obtained when intercalated within the LDH layers, as revealed by the attainment of half maximal inhibitory concentration of LDH-MTX nanohybrid by 48 h, whereas, bare MTX required 72 h for the same. The MTX release from MgAl-LDH-MTX hybrids in phosphate buffer saline at pH7.4 followed a relatively slow, first order kinetics and was complete within 8 days following diffusion and crystal dissolution mechanism. PMID:23498245

Chakraborty, Jui; Roychowdhury, Susanta; Sengupta, Somoshree; Ghosh, Swapankumar

2013-05-01

97

The in vitro sustained release profile and antitumor effect of etoposide-layered double hydroxide nanohybrids  

PubMed Central

Magnesium-aluminum layered double hydroxides intercalated with antitumor drug etoposide (VP16) were prepared for the first time using a two-step procedure. The X-ray powder diffraction data suggested the intercalation of VP16 into layers with the increased basal spacing from 0.84–1.18 nm was successful. Then, it was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, and transmission electron microscopy. The prepared nanoparticles, VP16-LDH, showed an average diameter of 62.5 nm with a zeta potential of 20.5 mV. Evaluation of the buffering effect of VP16-LDH indicated that the nanohybrids were ideal for administration of the drugs that treat human stomach irritation. The loading amount of intercalated VP16 was 21.94% and possessed a profile of sustained release. The mechanism of VP16-LDH release in the phosphate buffered saline solution at pH 7.4 is likely controlled by the diffusion of VP16 anions from inside to the surface of LDH particles. The in vitro cytotoxicity and antitumor assays indicated that VP16-LDH hybrids were less toxic to GES-1 cells while exhibiting better antitumor efficacy on MKN45 and SGC-7901 cells. These results imply that VP16-LDH is a potential antitumor drug for a broad range of gastric cancer therapeutic applications.

Qin, Lili; Wang, Mei; Zhu, Rongrong; You, Songhui; Zhou, Ping; Wang, Shilong

2013-01-01

98

Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide  

NASA Astrophysics Data System (ADS)

Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg-Al and Mg-Fe layered double hydroxides (LDHs) have been synthesized by the calcination-rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV-vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO32- solutions imply that Mg3Al-VC LDH is a better controlled release system than Mg3Fe-VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO32- solution.

Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

2013-07-01

99

High pseudocapacitive cobalt carbonate hydroxide films derived from CoAl layered double hydroxides  

NASA Astrophysics Data System (ADS)

A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g-1 at 5 mA cm-2) and higher rate capability and cycling stability (92% maintained after 2000 cycles).A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g-1 at 5 mA cm-2) and higher rate capability and cycling stability (92% maintained after 2000 cycles). Electronic supplementary information (ESI) available: Detailed experimental procedure, specific capacitance calculation, EDS and FTIR results, electrochemical results of CoAl-LDH and SEM image. See DOI: 10.1039/c2nr30617d

Lu, Zhiyi; Zhu, Wei; Lei, Xiaodong; Williams, Gareth R.; O'Hare, Dermot; Chang, Zheng; Sun, Xiaoming; Duan, Xue

2012-05-01

100

Mechanical and flame-retardant properties of epoxy\\/Mg–Al LDH composites  

Microsoft Academic Search

Layered double hydroxides (LDH) are a class of chemical compounds that can be used to modify or incorporate characteristics into a variety of thermoplastics or thermosets polymer matrices. The focus of the present work is to synthesize organo modified-LDH MgAl intercalated with glycinate, to use them to formulate epoxy composites with distinct LDH content, and to evaluate their mechanical, thermal

Cristiane M. Becker; Aline D. Gabbardo; Fernando Wypych; Sandro C. Amico

2011-01-01

101

Isomorphous substitution of divalent metal ions in layered double hydroxides through a soft chemical hydrothermal reaction.  

PubMed

We have successfully incorporated Co(2+) ions into layered double hydroxides (LDHs) comprising Mg and Al hydroxides via isomorphous substitution utilizing a soft chemical hydrothermal reaction. The inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis showed that the incorporation of Co(2+) into an LDH was highly dependent on the dissolution of Mg(2+). The X-ray diffraction (XRD) patterns showed that the crystalline phase, as well as the crystallinity of pristine LDH, was well preserved without the evolution of impurities during the substitution reaction. It was notable that the size (?250 nm) and hexagonal plate-like morphology of LDHs did not change significantly upon Co(2+) substitution. Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) exhibited homogeneous distribution of Co(2+) in the LDH particles obtained by this substitution reaction. Solid-state UV-vis and X-ray absorption spectroscopy (XAS) verified that the incorporated Co(2+) ions were well stabilized in the octahedral sites of an LDH, which were formerly occupied by Mg(2+) ions. PMID:24671432

Kim, Tae-Hyun; Lee, Won-Jae; Lee, Ji-Yeong; Paek, Seung-Min; Oh, Jae-Min

2014-07-21

102

Sorption of U(VI) from aqueous solutions on layered double hydroxides of Mg, Al, and Nd  

Microsoft Academic Search

Sorption of U(VI) from aqueous solutions of various compositions on layered double hydroxides (LDHs) of Mg, Al, and Nd, and\\u000a also on layered double oxides (LDOs) of Mg and Al was studied. Experiments on sorption of UO22+ carbonate complexes from aqueous solution on LDO-Mg-Al showed that [UO2(CO3)3]4? ions are weakly captured by LDH-Mg-Al formed by contact of LDO-Mg-Al with water.

S. A. Kulyukhin; E. P. Krasavina; I. V. Gredina; L. V. Mizina

2010-01-01

103

Anticancer Drug-Incorporated Layered Double Hydroxide Nanohybrids and Their Enhanced Anticancer Therapeutic Efficacy in Combination Cancer Treatment  

PubMed Central

Objective. Layered double hydroxide (LDH) nanoparticles have been studied as cellular delivery carriers for anionic anticancer agents. As MTX and 5-FU are clinically utilized anticancer drugs in combination therapy, we aimed to enhance the therapeutic performance with the help of LDH nanoparticles. Method. Anticancer drugs, MTX and 5-FU, and their combination, were incorporated into LDH by reconstruction method. Simply, LDHs were thermally pretreated at 400°C, and then reacted with drug solution to simultaneously form drug-incorporated LDH. Thus prepared MTX/LDH (ML), 5-FU/LDH (FL), and (MTX + 5-FU)/LDH (MFL) nanohybrids were characterized by X-ray diffractometer, scanning electron microscopy, infrared spectroscopy, thermal analysis, zeta potential measurement, dynamic light scattering, and so forth. The nanohybrids were administrated to the human cervical adenocarcinoma, HeLa cells, in concentration-dependent manner, comparing with drug itself to verify the enhanced therapeutic efficacy. Conclusion. All the nanohybrids successfully accommodated intended drug molecules in their house-of-card-like structures during reconstruction reaction. It was found that the anticancer efficacy of MFL nanohybrid was higher than other nanohybrids, free drugs, or their mixtures, which means the multidrug-incorporated LDH nanohybrids could be potential drug delivery carriers for efficient cancer treatment via combination therapy.

Lee, Gyeong Jin; Kang, Joo-Hee

2014-01-01

104

Intercalation of IR absorber into layered double hydroxides: Preparation, thermal stability and selective IR absorption  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer PMIDA anions were intercalated into Mg{sub 2}Al-NO{sub 3} LDH by anion-exchange method. Black-Right-Pointing-Pointer The prepared material has highly selective IR absorption property in 9-11 {mu}m. Black-Right-Pointing-Pointer The obtained material has practical applications as heat-retaining additive. -- Abstract: N-phosphonomethyl aminodiacetic acid (PMIDA) was intercalated into the interlayer spacing of layered double hydroxides (LDH) by an anion-exchange method. The intercalated LDHs were characterized by various techniques such as powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and simultaneous thermogravimetric and mass spectrometry (TG-MS) in details. The results show the formation of Mg{sub 2}Al-PMIDA LDH based on the expansion of d-spacing from 0.89 nm to 1.22 nm and the disappearance of the characteristic IR absorption band at 1384 cm{sup -1} for NO{sub 3}{sup -} anions. The incorporation of Mg{sub 2}Al-PMIDA LDH into the low density polyethylene (LDPE) as an additive enhances the selectivity of IR absorption in the main wavelength region 9-11 {mu}m for radiant heat loss at night. Mg{sub 2}Al-PMIDA LDH as a heat-retaining additive has practical application in agricultural plastic films.

Zhu, Haifeng; Tang, Pinggui [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)] [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Feng, Yongjun, E-mail: yjfeng@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)] [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Wang, Lijing; Li, Dianqing [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)] [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

2012-03-15

105

Thermokinetic study of the rehydration process of a calcined MgAl-layered double hydroxide.  

PubMed

The rehydration process of a calcined MgAl-layered double hydroxide (LDH) with a Mg/Al molar ratio of 3 was systematically analyzed at different temperatures and relative humidity. Qualitative and quantitative experiments were done. In the first set of samples, the temperature or the relative humidity was varied, fixing the second variable. Both adsorption and absorption phenomena were present; absorption process was associated to the LDH regeneration. Of course, in all cases the LDH regeneration was confirmed by other techniques such as TGA, solid state NMR, and SAXS. In the second set of experiments, a kinetic analysis was performed, the results allowed to obtain different activation enthalpies for the LDH regeneration as a function of the relative humidity. The activation enthalpies varied from 137.6 to 83.3 kJ/mol as a function of the relative humidity (50 and 80%, respectively). All these experiments showed that LDH regeneration is highly dependent on the temperature and relative humidity. PMID:19947638

Pfeiffer, Heriberto; Lima, Enrique; Lara, Víctor; Valente, Jaime S

2010-03-16

106

Direct Intercalation of Amino Acids into Layered Double Hydroxides by Coprecipitation  

NASA Astrophysics Data System (ADS)

First, the direct intercalation of amino acids into various layered double hydroxides (Mg-Al, Mn-Al, Ni-Al, Zn-Al, and Zn-Cr LDHs) by coprecipitation has been investigated using phenylalanine (Phe) as a guest amino acid. The degree of Phe coprecipitation was strongly influenced by the solution pH and kind of LDH system and reached a maximum in the pH 8-10 region. The solid products were found to have an expanded LDH structure, which supported the belief that Phe was intercalated into LDHs as an amphoteric ion or anion. Two kinds of configuration for Phe in the gallery, either vertical (Mn-Al, Zn-Al, and Zn-Cr LDHs) or horizontal (Mg-Al LDH) in orientation were observed. Only in the Ni-Al system was the solid product a mixture of Phe/Ni-Al LDH and Phe/Ni(OH) 2 composite. Next, the thermal decomposition of the intercalated Phe was revealed to be accelerated by the catalytic action of metal ions in the host basal layer. The formation of Phe/Mg-Al, Mn-Al, and Zn-Al LDHs was also elucidated as being appreciably different by the kind of LDH system. Moreover, for various amino acids, the degree of coprecipitation was found to be strongly influenced by amino acid sidechains, i.e., length, structure, and physicochemical properties.

Aisawa, Sumio; Takahashi, Satoshi; Ogasawara, Wataru; Umetsu, Yoshio; Narita, Eiichi

2001-11-01

107

Synthesis and characterization of 10-hydroxycamptothecin - sebacate - layered double hydroxide nanocomposites  

NASA Astrophysics Data System (ADS)

10-Hydroxycamptothecin (HCPT) as a hydrophobic anticancer drug brings many challenges in the clinical applications due to its poor water solubility and the presence of a chemically unstable lactone ring. In this work, the nanocomposites of HCPT intercalated layered double hydroxide (LDH) were prepared by a secondary intercalation method, and the encapsulated HCPT could keep the biologically active lactone form. A Zn-Al-NO3 LDH was pillared with sebacate anions by a co-precipitation method in an aqueous medium, and then HCPT was intercalated into the LDH's gallery via hydrophobic interaction in an ethanol medium. The parallel alkyl chains of perpendicularly arranged sebacate anions in the LDH gallery provide a hydrophobic space for the drug intercalation. The in vitro release kinetics of HCPT from the nanocomposites could be fitted with the pseudo-second-order kinetic model, and the diffusion of HCPT through the LDH particles played an important role in controlling the drug release. The nanocomposites can be considered as a potential drug delivery system.

Pang, Xiujiang; Ma, Xiuming; Li, Dongxiang; Hou, Wanguo

2013-02-01

108

Prolate spheroidal hematite particles equatorially belt with drug-carrying layered double hydroxide disks: Ring Nebula-like nanocomposites  

PubMed Central

A new nanocomposite architecture is reported which combines prolate spheroidal hematite nanoparticles with drug-carrying layered double hydroxide [LDH] disks in a single structure. Spindle-shaped hematite nanoparticles with average length of 225 nm and width of 75 nm were obtained by thermal decomposition of hydrothermally synthesized hematite. The particles were first coated with Mg-Al-NO3-LDH shell and then subjected to anion exchange with salicylate ions. The resulting bio-nanohybrid displayed a close structural resemblance to that of the Ring Nebula. Scanning electron microscope and transmission electron microscopy images showed that the LDH disks are stacked around the equatorial part of the ellipsoid extending along the main axis. This geometry possesses great structural tunability as the composition of the LDH and the nature of the interlayer region can be tailored and lead to novel applications in areas ranging from functional materials to medicine by encapsulating various guest molecules.

2011-01-01

109

Superhydrophobic and UV-blocking cotton fabrics prepared by layer-by-layer assembly of organic UV absorber intercalated layered double hydroxides  

NASA Astrophysics Data System (ADS)

A dual-functional coating with both superhydrophobic and UV-blocking properties was prepared on cotton fabric using a hybrid layered double hydroxide (LDH) nanoplatelet intercalated with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMBS) molecules and an electrostatic layer-by-layer (LbL) assembly technique. The thermal stability of HMBS was greatly enhanced by the host-guest interaction with LDH layers. The as-prepared HMBS@LDH hybrid had a nearly neutral surface charge. To make it carry enough charge for the electrostatic LbL assembly, the HMBS@LDH nanoplatelet was further modified with 3-aminopropyltriethoxy silane. The nanoscale roughness generated by LDH nanoplatelets, together with low-surface-energy fluoroalkylsilane, endowed cotton fabrics with superhydrophobicity. The HMBS@LDH coating showed up to four-fold increase in the UV protection ability of cotton fabrics.

Zhao, Yan; Xu, Zhiguang; Wang, Xungai; Lin, Tong

2013-12-01

110

Accommodating unwelcome guests in inorganic layered hosts: inclusion of chloranil in a layered double hydroxide.  

PubMed

The host-guest chemistry of most inorganic layered solids is limited to ion-exchange reactions. The guest species are either cations or anions to compensate for the charge deficit, either positive or negative, of the inorganic layers. Here, we outline a strategy to include neutral molecules like ortho- and para-chloranil, that are known to be good acceptors in donor-acceptor or charge-transfer complexes, within the galleries of a layered solid. We have succeeded in including neutral ortho- and para-chloranil molecules within the galleries of an Mg-Al layered double hydroxide (LDH) by using charge-transfer interactions with preintercalated p-aminobenzoate ions as the driving force. The p-aminobenzoate ions are introduced in the Mg-Al LDH via ion exchange. The intercalated LDH can adsorb ortho- and para-chloranil from chloroform solutions by forming charge-transfer complexes with the p-aminobenzoate anions present in the galleries. We use X-ray diffraction, spectroscopy, and molecular dynamics simulations to establish the nature of interactions and arrangement of the charge-transfer complex within the galleries of the layered double hydroxide. PMID:22813077

Dutta, Dipak; Vasudevan, Sukumaran

2012-08-01

111

Double layered hydroxides as potential anti-cancer drug delivery agents.  

PubMed

The emergence of nanotechnology has changed the scenario of the medical world by revolutionizing the diagnosis, monitoring and treatment of cancer. This nanotechnology has been proved miraculous in detecting cancer cells, delivering chemotherapeutic agents and monitoring treatment from non-specific to highly targeted killing of tumor cells. In the past few decades, a number of inorganic materials have been investigated such as calcium phosphate, gold, carbon materials, silicon oxide, iron oxide, and layered double hydroxide (LDH) for examining their efficacy in targeting drug delivery. The reason behind the selection of these inorganic materials was their versatile and unique features efficient in drug delivery, such as wide availability, rich surface functionality, good biocompatibility, potential for target delivery, and controlled release of the drug from these inorganic nanomaterials. Although, the drug-LDH hybrids are found to be quite instrumental because of their application as advanced anti-cancer drug delivery systems, there has not been much research on them. This mini review is set to highlight the advancement made in the use of layered double hydroxides (LDHs) as anti-cancer drug delivery agents. Along with the advantages of LDHs as anti-cancer drug delivery agents, the process of interaction of some of the common anti-cancer drugs with LDH has also been discussed. PMID:23170959

Riaz, Ufana; Ashraf, S M

2013-04-01

112

A thermally induced metastable solid phase of Mg\\/Al-layered double hydroxides by means of in situ high temperature powder X-ray diffraction  

Microsoft Academic Search

It has been reported recently that some aromatic compounds with anionic substituents are intercalated between layers of Mg=Al-layered double hydroxide (Mg=Al-LDH) (1-7) in an ion-exchanging manner with small interlayer inorganic anions, thereby enhancing the interlayer distance. The layers in Mg=Al-LDH have a brucite-like structure although a fraction of octahedral Mg 2á sites are occupied by Al 3á and resulting excess

E. Kanezaki

1998-01-01

113

Pulsed laser deposition of Mg-Al layered double hydroxide with Ag nanoparticles  

NASA Astrophysics Data System (ADS)

Powdered layered double hydroxides (LDHs)—also known as hydrotalcite-like (HT)—compounds have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic or organic molecules. Assembling thin films of nano-sized LDHs onto flat solid substrates is an expanding area of research, with promising applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices. The exploitation of LDHs as vehicles to carry dispersed metal nanoparticles onto a substrate is a new approach to obtain composite thin films with prospects for biomedical and optical applications. We report the deposition of thin films of Ag nanoparticles embedded in a Mg-Al layered double hydroxide matrix by pulsed laser deposition (PLD). The Ag-LDH powder was prepared by co-precipitation at supersaturation and pH = 10 using aqueous solutions of Mg and Al nitrates, Na hydroxide and carbonate, and AgNO3, having atomic ratios of Mg/Al = 3 and Ag/Al = 0.55. The target to be used in laser ablation experiments was a dry pressed pellet obtained from the prepared Ag-LDH powder. Three different wavelengths of a Nd:YAG laser (266, 532 and 1064 nm) working at a repetition rate of 10 Hz were used. X-Ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and secondary ions mass spectrometry (SIMS) were used to investigate the structure, surface morphology and composition of the deposited films.

Matei, A.; Birjega, R.; Vlad, A.; Luculescu, C.; Epurescu, G.; Stokker-Cheregi, F.; Dinescu, M.; Zavoianu, R.; Pavel, O. D.

2013-03-01

114

Mixed metal oxides for dye-sensitized solar cell using zinc titanium layered double hydroxide as precursor  

NASA Astrophysics Data System (ADS)

Mixed metal oxides (MMO) are always obtained from layered double hydroxide (LDH) by thermal decomposition. In the present work, a zinc titanium LDH with the zinc titanium molar ratio of 4.25 was prepared by urea method and ZnO-based mixed oxides were obtained by calcining at or over 500°C. The MMO was used as electrodes for dye sensitized solar cell (DSSC). The cells constructed by films of prepared composite materials using a N719 as dye were prepared. The efficiency values of these cells are 0.691%, 0.572% and 0.302% with MMO prepared at 500, 600 and 700°C, respectively.

Liu, Jianqiang; Qin, Yaowei; Zhang, Liangji; Xiao, Hongdi; Song, Jianye; Liu, Dehe; Leng, Mingzhe; Hou, Wanguo; Du, Na

2013-12-01

115

Arsenic removal from water using calcined Mg–Al layered double hydroxide  

Microsoft Academic Search

Arsenic (As) in drinking water and its related toxicology are serious concerns nowadays. Development of better techniques\\u000a related to removal of As from drinking water is an urgent need. Layered double hydroxide (LDH) or hydrotalcite-like compound\\u000a with the general formula [M1?x\\u000a 2+ M\\u000a x\\u000a 3+ (OH)2]\\u000a x+ A\\u000a x?·nH2O can be considered as a good adsorbent for the removal of

Mridul ChetiaRajib; Rajib L. Goswamee; Saumen Banerjee; Soumya Chatterjee; Lokendra Singh; Ravi B. Srivastava; Hari P. Sarma

116

Cobalt-based layered double hydroxides as oxygen evolving electrocatalysts in neutral electrolyte  

NASA Astrophysics Data System (ADS)

Co-M (M= Co, Ni, Fe, Mn) layered double hydroxides (LDHs) were successfully fabricated by a hexamethylenetetramine (HMT) pyrolysis method. Composite electrodes were made using a self-assembly fashion at inorganic/organic surface binder-free and were used to catalyze oxygen evolution reaction. Water oxidation can take place in neutral electrolyte operating with modest overpotential. The doping of other transitional metal cations affords mix valences and thus more intimate electronic interactions for reversible chemisorption of dioxygen molecules. The application of employing LDH materials in water oxidation process bodes well to facilitate future hydrogen utilization.

Lin, Hong; Zhang, Ye; Wang, Gang; Li, Jian-Bao

2012-06-01

117

Surface and interfacial properties of polymer-intercalated layered double hydroxide nanocomposites  

Microsoft Academic Search

The surface and interfacial properties of the layered double hydroxide (LDH) phase Mg6Al2(OH)16CO3·4H2O (LDHCO3) and its nanocomposites with poly(styrenesulfonate) (LDHPSS) and poly(vinylsulfonate) (LDHPVS) were characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, He pycnometry, and electrophoretic light scattering. Polymer incorporation within the inter-gallery space resulted in a shift of the d003 reflection from 7.7 Å

O. C Wilson; T Olorunyolemi; A Jaworski; L Borum; D Young; A Siriwat; E Dickens; C Oriakhi; M Lerner

1999-01-01

118

Characterization of hemoglobin immobilized in MgAl-layered double hydroxides by the coprecipitation method.  

PubMed

Hemoglobin was immobilized in Mg(2)Al-Layered Double Hydroxides (LDH) by coprecipation method at pH 9.0. Interactions between Hb and LDH particles were investigated by X-ray diffraction patterns, FTIR, UV-vis, circular dichroism, and fluorescence spectroscopies. Morphology and porosity of Mg(2)Al-Hb(cop) biohybrid are analyzed from SEM and TEM images and permeability measurement. The direct electron transfer of immobilized Hb was studied by cyclic voltammetry, and the electrocatalytic activity was evaluated at glassy carbon modified with this Mg(2)Al-Hb(cop) biohybrid. Even though the percentage of electroactive Hb was less than 2%, this bioelectrode showed a low detection limit (1.5 x 10(-8) M) and a very high sensitivity (37 A/M cm(2)) for the amperometric detection of H(2)O(2). PMID:20394402

Charradi, Khaled; Forano, Claude; Prevot, Vanessa; Madern, Dominique; Ben Haj Amara, Abdesslem; Mousty, Christine

2010-06-15

119

Sepiocite, sepiolite-like nanoclay derived from hydrotalcite-like layered double hydroxide.  

PubMed

Sepiocite, a synthetic sepiolite-like nanoclay, was derived from hydrotalcite-like Mg2Al(CO3)0.5-layered double hydroxide (LDH) under phase transformation at 270 +/- 3 degrees C. The crystal structure of sepiocite is conceptually very similar to that of sepiolite derived from montmorillonite clay because sepiocite is formed through the alternation of the blocks and tunnels along the crystallographic c-axis, with a partial dehydroxylation of the octahedral Mg-(OH)-Al configuration into tetrahedral ones. Three important findings regarding sepiocite were arrived at: (i) its high specific surface area of 128.25 m2/g with an average particle size of 200 nm, which is approimately equal to 3.5 times larger than the specific surface area of the pristine LDH (34.21 m2/g); (ii) its non-swelling property; and (iii) its strongly reduced anion-exchange capacity. PMID:21446460

Park, Dae-Hwan; Jang, Myung Wook; Shul, Yong-Gun; Choy, Jin-Ho

2011-01-01

120

Synthesis and characterization of 5-fluorocytosine intercalated Zn-Al layered double hydroxide  

SciTech Connect

In this paper, the intercalation of 5-fluorocytosine (5-FC) into a layered inorganic host, Zn-Al layered double hydroxide (LDH), has been carried out using coprecipitation method to obtain 5-FC/LDH nanohybrids. The intercalated amount (A{sub In}) of 5-FC into the LDH is remarkably dependent on the molar ratio (R{sub F/M}) of 5-FC to metal ions and the pH of coprecipitation system. The morphology of 5-FC molecules in 5-FC/LDH nanohybrids is dependent on the A{sub In}. It is interestingly found that the morphology of the nanohybrid particles may be changed with the increase of R{sub F/M} from hexagonal plate particles to threadlike particles. The in vitro drug release from the nanohybrids is remarkably lower than that from the corresponding physical mixture and pristine 5-FC at either pH 4.8 or pH 7.5. In addition, the release rate of 5-FC from the nanohybrid at pH 7.5 is remarkably lower than that at pH 4.8, this is due to a possible difference in the release mechanism. The obtained results show these drug-inorganic nanohybrids can be used as a potential drug delivery system. - Graphical abstract: The 5-fluorocytosine (5-FC) has been intercalated into layered double hydroxide using coprecipitation method. The morphology of 5-FC molecules in obtained nanohybrids was dependent on the intercalated amount of 5-FC. The in vitro drug release from the nanohybrids was remarkably lower than that from the corresponding physical mixture, which shows these drug-inorganic nanohybrids can be used as a potential drug delivery system.

Liu Chunxia [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China); Hou Wanguo [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China); College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China)], E-mail: wghou@sdu.edu.cn; Li Lifang [College of Chemistry and Material Science, Shandong Agriculture University, Taian 271018 (China); Li Yan; Liu Shaojie [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China)

2008-08-15

121

Cyanide Self-Addition, Controlled Adsorption, and Other Processes at Layered Double Hydroxides  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDH) are anion-exchanging materials of the type M(III)-M(II)_x(OH)_(2x+2)Y that occur abundantly in nature, and can concentrate, protect, and activate simple organic anionic species of possible relevance to the earliest organisms. We now wish to report progress in the following areas: 1) Internal vs. external uptake of anions. Ferrocyanide does not displace carbonate from synthetic hydrotalcite (Mg:Al LDH carbonate) but is nevertheless taken up on the outside of the particles. In other cases, anion uptake is controlled by specific hydrogen bonding requirements rather than by charge density alone, a feature that can be used to control whether uptake will be both internal and external, or external only. These two findings taken together have important implications for specific catalysis by LDH, since specific hydrogen bonding will affect the individual and relative conformations of substrate anions, and anions occupying space in the interlayer will be under tighter constraints than those adsorbed externally. 2) Specific reactions catalyzed by LDH. We have found that the LDH Mg_2Al(OH)_6Cl catalyzes the self-addition of cyanide, to give in a one-pot reaction at low concentrations an increased yield of diaminomaleonitrile and in addition, at higher (>= 0.05M) concentrations, a purple-pink material that adheres to the LDH. We are investigating whether this reaction also occurs with hydrotalcite itself, what is the minimum effective concentration of cyanide, and what can be learned about the products and how they compare with those reported at high HCN concentrations in the absence of catalyst.

Boclair, Joseph W.; Braterman, Paul S.; Brister, Brian D.; Jiang, Jianping; Lou, Shaowei; Wang, Zhiming; Yarberry, Faith

2001-02-01

122

Two steps in situ structure fabrication of Ni-Al layered double hydroxide on Ni foam and its electrochemical performance for supercapacitors  

NASA Astrophysics Data System (ADS)

In this paper, two steps in situ growth method has been used to solve the accumulation of layered double hydroxide (LDH) in oriented growth. Moreover, the petal-like Ni-Al LDH displays excellent pseudocapacitance performance: a specific capacitance of 795 F g-1, a long cycle life with 80% performance remains after 1000 cycles and good charge/discharge stability, owing to the improvement of pseudocapacitive reaction by the large sheet structure of Ni-Al LDH on Ni foam. And the comparison results of different electrode preparation process and different growth process reflect the great advantages of our synthesis method.

Wang, Bin; Liu, Qi; Qian, Zhongyu; Zhang, Xiaofei; Wang, Jun; Li, Zhanshuang; Yan, Huijun; Gao, Zan; Zhao, Fangbo; Liu, Lianhe

123

Facile assembly for fast construction of intercalation hybrids of layered double hydroxides with anionic metalloporphyrin.  

PubMed

Anionic manganese tetrasulfonatophenyl porphyrin (MnTSPP) has been intercalated into the interlamellar space of Mg-Al and Ni-Al layered double hydroxides (LDHs) through the exfoliation/restacking approach by using exfoliated LDH nanosheets and guest molecules as building blocks. The obtained hybrids were characterized by a variety of analytical techniques such as CHN analysis, XRD, FTIR, SEM, HRTEM, UV-vis spectroscopy and thermal analysis. Interlayer spacings determined from XRD patterns reveal a perpendicular orientation of the MnTSPP anions between the hyroxylated layers of both LDHs. The results of zeta potential measurements give information about the surface charge change of LDH nanoparticles associated with the spontaneous coassembly process. The catalytic performance of the heterogeneous catalysts MnTSPP/Mg-Al LDH2.0 and MnTSPP/Ni-Al LDH1.0 for the epoxidation of cyclohexene was investigated using molecular oxygen as an oxidant and isobutylaldehyde as a co-reductant. The intercalated hybrids appear to be promising catalysts owing to their good catalytic activity and selectivity. PMID:24849716

Ma, Juanjuan; Liu, Lin; Li, Shanzhong; Chen, Yonghao; Zhuo, Meng; Shao, Feng; Gong, Junyan; Tong, Zhiwei

2014-07-14

124

Novel route for layered double hydroxides preparation by enzymatic decomposition of urea  

NASA Astrophysics Data System (ADS)

This study presents a new route for the preparation of a series of layered double hydroxide materials with controlled textural properties. It concerns the biogenesis of hydrotalcite like phases by Jack bean urease through the enzymatic decomposition process of urea. Different conditions of LDH biogenesis are investigated (urease activity, urea concentration). A comparative study with the precipitation method based on the thermal decomposition of urea (90 °C) is conducted in order to asses the effect of the various urea hydrolysis conditions (kinetic, temperature) and the presence of enzyme in the reaction medium on the structural and textural properties of the as prepared LDH materials. Mechanisms of formation of the LDH phases for both synthesis processes are discussed on basis of their pH control. The PXRD and SEM analysis of samples prepared by the thermal process evidence higher crystallinity and greater particle sizes than LDH obtained in mild biogenic conditions. In the latter case, presence of urease or effect of some M(II) metals may inhibit the crystallization.

Vial, S.; Prevot, V.; Forano, C.

2006-05-01

125

Synthesis and characterization of 5-fluorocytosine intercalated Zn Al layered double hydroxide  

NASA Astrophysics Data System (ADS)

In this paper, the intercalation of 5-fluorocytosine (5-FC) into a layered inorganic host, Zn-Al layered double hydroxide (LDH), has been carried out using coprecipitation method to obtain 5-FC/LDH nanohybrids. The intercalated amount ( AIn) of 5-FC into the LDH is remarkably dependent on the molar ratio ( RF/M) of 5-FC to metal ions and the pH of coprecipitation system. The morphology of 5-FC molecules in 5-FC/LDH nanohybrids is dependent on the AIn. It is interestingly found that the morphology of the nanohybrid particles may be changed with the increase of RF/M from hexagonal plate particles to threadlike particles. The in vitro drug release from the nanohybrids is remarkably lower than that from the corresponding physical mixture and pristine 5-FC at either pH 4.8 or pH 7.5. In addition, the release rate of 5-FC from the nanohybrid at pH 7.5 is remarkably lower than that at pH 4.8, this is due to a possible difference in the release mechanism. The obtained results show these drug-inorganic nanohybrids can be used as a potential drug delivery system.

Liu, Chunxia; Hou, Wanguo; Li, Lifang; Li, Yan; Liu, Shaojie

2008-08-01

126

Thermal, solution and reductive decomposition of Cu-Al layered double hydroxides into oxide products  

SciTech Connect

Cu-Al layered double hydroxides (LDHs) with [Cu]/[Al] ratio 2 adopt a structure with monoclinic symmetry while that with the ratio 0.25 adopt a structure with orthorhombic symmetry. The poor thermodynamic stability of the Cu-Al LDHs is due in part to the low enthalpies of formation of Cu(OH){sub 2} and CuCO{sub 3} and in part to the higher solubility of the LDH. Consequently, the Cu-Al LDH can be decomposed thermally (150 deg. C), hydrothermally (150 deg. C) and reductively (ascorbic acid, ambient temperature) to yield a variety of oxide products. Thermal decomposition at low (400 deg. C) temperature yields an X-ray amorphous residue, which reconstructs back to the LDH on soaking in water or standing in the ambient. Solution decomposition under hydrothermal conditions yields tenorite at 150 deg. C itself. Reductive decomposition yields a composite of Cu{sub 2}O and Al(OH){sub 3}, which on alkali-leaching of the latter, leads to the formation of fine particles of Cu{sub 2}O (<1 {mu}m). - Graphical abstract: SEM image of (a) the Cu{sub 2}O-Al(OH){sub 3} composite obtained on reductive decomposition of CuAl{sub 4}-LDH and (b) Cu{sub 2}O obtained on leaching of Al(OH){sub 3} from (a).

Britto, Sylvia [Department of Chemistry, Central College, Bangalore University, Bangalore 560 001 (India); Vishnu Kamath, P., E-mail: vishnukamath8@hotmail.co [Department of Chemistry, Central College, Bangalore University, Bangalore 560 001 (India)

2009-05-15

127

Fire and thermal properties of layered double hydroxides and polyurea nanocomposites  

NASA Astrophysics Data System (ADS)

Layered double hydroxide (LDH) intercalated with linear alkyl carboxylates (CH3(CH2)n COO-, n = 8, 10, 12, 14, 16, 20), borate and benzyl anions were prepared. The effect on fire and thermal properties of the mode of preparation for LDHs (i.e. ion exchange, coprecipitation and rehydration of the calcined LDH methods) has been studied. After characterization, the LDHs were used to prepare nanocomposites with a range of polar and non-polar polymers. Characterization of the LDHs and the nanocomposites was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TGA), transmission electron microscopy (TEM) and cone calorimetry. FTIR and XRD analyses confirmed the presence of the charge balancing anions in the galleries of the LDHs. Improvements in fire and thermal properties of the nanocomposites were observed. The cone calorimeter revealed that the addition of LDHs reduces the peak heat release rate significantly. LDHs were combined with commercial fire retardants. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both LDH and ammonium polyphosphate (APP). Physical and chemical interactions between LDH and APP are responsible for the observed synergy in thermal stability and fire performance.

Nyambo, Calistor

128

Facile preparation of pure CaAl-layered double hydroxides and their application as a hardening accelerator in concrete  

Microsoft Academic Search

CaAl-layered double hydroxide (CaAl-LDH), one of anionic functional layered materials, has recently been proposed as potential concrete hardening accelerators. Previous laboratory synthesis shows the necessity of employing a protective nitrogen atmosphere to avoid the formation of large amounts of CaCO3 byproduct. Here, we present a preparation of pure CaAl-LDHs which are readily free of contamination by CaCO3. The CaAl-LDHs were

Sailong Xu; Zhanrui Chen; Bowen Zhang; Jianhui Yu; Fazhi Zhang; David G. Evans

2009-01-01

129

One-pot synthesis of organophilic layered double hydroxides (LDHs) containing aliphatic carboxylates: Extended “homogeneous precipitation” method  

Microsoft Academic Search

One-pot synthesis of aliphatic carboxylate\\/LDH hybrids (org-LDHs) was accomplished via the so-called “homogeneous precipitation” method developed for preparing carbonate-type layered double hydroxides (CO32- LDHs) with ammonia-releasing reagents such as hexamethylenetetramine (HMT) and urea. An aqueous solution of an aliphatic carboxylate (C2–C18) was added to a mixed aqueous solution of metal salts and HMT and then heated at 140–160°C in a

Nobuo Iyi; Kenji Tamura; Hirohisa Yamada

2009-01-01

130

Effect of hydrothermal treatment on properties of Ni–Al layered double hydroxides and related mixed oxides  

Microsoft Academic Search

The Ni–Al layered double hydroxides (LDHs) with Ni\\/Al molar ratio of 2, 3, and 4 were prepared by coprecipitation and treated under hydrothermal conditions at 180°C for times up to 20h. Thermal decomposition of the prepared samples was studied using thermal analysis and high-temperature X-ray diffraction. Hydrothermal treatment increased significantly the crystallite size of coprecipitated samples. The characteristic LDH diffraction

Frantisek Kovanda; Tomás Rojka; Petr Bezdicka; Kveta Jirátová; Lucie Obalová; Katerina Pacultová; Zdenek Bastl; Tomás Grygar

2009-01-01

131

Preparation of layered double hydroxide films with different orientations on the opposite sides of a glass substrate by in situ hydrothermal crystallization.  

PubMed

MgAl-Layered double hydroxide (LDH) films with different orientations on the two sides of a glass substrate, one of which was modified with poly(vinyl alcohol), have been obtained by a one-step in situ hydrothermal crystallization method, and the growth mechanisms of the two films are discussed. PMID:19885496

Guo, Xiaoxiao; Zhang, Fazhi; Xu, Sailong; Evans, David G; Duan, Xue

2009-11-28

132

Self-assembled dye-layered double hydroxide-Pt nanoparticles: a novel H2 evolution system with remarkably enhanced stability  

NASA Astrophysics Data System (ADS)

A novel photocatalytic hydrogen evolution system was constructed by using well-dispersed layered double hydroxide (LDH) to immobilize the photosensitizer (rose bengal, RB) and photocatalyst (Pt). The produced amount of H2 from such a self-assembled RB-LDH-Pt system is a few times more than that from the Free system (without LDH). Moreover, RB-LDH-Pt can be reused for at least 6 times (still having 64% of the activity in the 6th run) by a simple method of centrifugation which makes this system more economical by recycling the expensive Pt. The total turnover number (TON) obtained after six runs for RB-LDH-Pt was calculated to be 304 based on Pt, which gave at least 13-fold enhancement compared with that from the Free system.

Hong, Jindui; Wang, Yabo; Pan, Jisheng; Zhong, Ziyi; Xu, Rong

2011-11-01

133

Intercalation of biomolecules into NiAl-NO 3 layered double hydroxide films synthesized in situ on anodic alumina/aluminium support  

NASA Astrophysics Data System (ADS)

Layered double hydroxide (LDH) films were synthesized in situ on anodic alumina/aluminium (AAO/Al). Glucose oxidase (GOD) and L-ascorbic acid (vitamin C, VC) were intercalated respectively into the in-situ grown LDH films by anion-exchange in aqueous solutions. Dodecylsulfate (SDS) was used to expand the lamellar structure before GOD intercalation into the LDH film. The resulting products were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA). The results showed that VC and GOD were successfully intercalated into the in-situ synthesized LDH film. These biomolecules loaded LDH films could have potential applications in electrode modification, safe storage and effective delivery of bioactive compounds.

Zhao, Hua-Zhang; Chang, Ying-Yue; Yang, Jing; Yang, Qin-Zheng

2013-03-01

134

Interlayer structure of iodide intercalated layered double hydroxides (LDHs)  

Microsoft Academic Search

The iodide-containing layered double hydroxides (LDHs) of Mg and Zn with Al crystallize by the inclusion of extensive positional disorder of I? ions in the interlayer region. I? ion given its poor charge to size ratio can neither screen effectively the positive charge nor participate in H-bonding with the metal hydroxide layers. Thereby the I? ions are not stabilized in

S. V. Prasanna; P. Vishnu Kamath; C. Shivakumara

2010-01-01

135

One-pot synthesis of organophilic layered double hydroxides (LDHs) containing aliphatic carboxylates: extended "homogeneous precipitation" method.  

PubMed

One-pot synthesis of aliphatic carboxylate/LDH hybrids (org-LDHs) was accomplished via the so-called "homogeneous precipitation" method developed for preparing carbonate-type layered double hydroxides (CO(3)(2-) LDHs) with ammonia-releasing reagents such as hexamethylenetetramine (HMT) and urea. An aqueous solution of an aliphatic carboxylate (C2-C18) was added to a mixed aqueous solution of metal salts and HMT and then heated at 140-160 degrees C in a pressure vessel for 1day. Two kinds of LDHs were investigated: MgAl-LDH and NiAl-LDH. We found that only aliphatic carboxylates longer than decanoate (C10) and dodecanoate (C12) were incorporated successfully in the MgAl-LDH and NiAl-LDH interlayers without any CO(3)(2-) contamination, respectively. Shorter carboxylates were not incorporated, only yielding CO(3)(2-)LDHs. Isolation of the hydrophobic org-LDH phase from the aqueous medium containing carbonate ions was assumed to be the main reason for the lack of CO(3)(2-) contamination in the org-LDHs having longer-alkyl carboxylates. This method was also used successfully for preparing MgAl-LDHs containing dodecylbenzene sulfonate(DBS), a sulfonate-type anionic surfactant. PMID:19762037

Iyi, Nobuo; Tamura, Kenji; Yamada, Hirohisa

2009-12-01

136

Preparation and wetting properties of layered double hydroxide colloidal nano/microspheres with tunable flower-like morphologies.  

PubMed

Layered double hydroxides (LDHs), known as a type of multifunctional anionic layered clay, typically exhibit stability and intrinsic hydrophilicity at neutral and alkaline pH. We herein report a polymer bead-templated preparation of flower-like LDH shell microspheres with the LDH platelets tuned under different aging durations and temperatures. Thickness of LDH shell walls was tuned readily by varying preparation conditions such as aging durations and temperatures. After a simple chemical surface modification using fluorine-silane molecule, the flower-like LDH nano/microspheres show the distinctly different transitions from the intrinsic hydropholicity to the superhydrophobicity at pH 2 and neutral pH. In contrast, at alkaline condition of pH 12 small flower-like spheres were formed atop of the parent microspheres, which may be argued in terms of a process of desorption of silane molecule at the alkaline condition combined with dissolution and reassembly of LDH platelets. Our finding of the superhydrophobic LDH spheres may find useful applications in chemical and biosensors against harsh acidic conditions. PMID:22754995

Xu, Ting; Yang, Yingsheng; Kuang, Ye; Zhang, Fazhi; Xu, Sailong

2012-03-01

137

Tailoring surface properties and structure of layered double hydroxides using silanes with different number of functional groups  

NASA Astrophysics Data System (ADS)

Four silanes, trimethylchlorosilane (TMCS), dimethyldiethoxylsilane (DMDES), 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS), were adopted to graft layered double hydroxides (LDH) via an induced hydrolysis silylation method (IHS). Fourier transform infrared spectra (FTIR) and 29Si MAS nuclear magnetic resonance spectra (29Si MAS NMR) indicated that APTES and TEOS can be grafted onto LDH surfaces via condensation with hydroxyl groups of LDH, while TMCS and DMDES could only be adsorbed on the LDH surface with a small quantity. A combination of X-ray diffraction patterns (XRD) and 29Si MAS NMR spectra showed that silanes were exclusively present in the external surface and had little influence on the long range order of LDH. The surfactant intercalation experiment indicated that the adsorbed and/or grafted silane could not fix the interlamellar spacing of the LDH. However, they will form crosslink between the particles and affect the further surfactant intercalation in the silylated samples. The replacement of water by ethanol in the tactoids and/or aggregations and the polysiloxane oligomers formed during silylation procedure can dramatically increase the value of BET surface area (SBET) and total pore volumes (Vp) of the products.

Tao, Qi; He, Hongping; Li, Tian; Frost, Ray L.; Zhang, Dan; He, Zisen

2014-05-01

138

Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis.  

PubMed

The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chemical compositions and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures. Specifically, liquid phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alkaline conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a commercial iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic conductivity. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction. PMID:25030209

Song, Fang; Hu, Xile

2014-01-01

139

Synthesis, characterization, and controlled release anticorrosion behavior of benzoate intercalated Zn-Al layered double hydroxides  

SciTech Connect

Graphical abstract: The benzoate anion released from Zn-Al LDHs provides a more effective long-term protection against corrosion of Q235 carbon steel in 3.5% NaCl solution. Highlights: {yields} A benzoate anion corrosion inhibitor intercalated Zn-Al layered double hydroxides (LDHs) has been assembled by coprecipitation method. {yields} The kinetic simulation indicates that the ion-exchange one is responsible for the release process and the diffusion through particle is the rate limiting step. {yields} A significant reduction of the corrosion rate is observed when the LDH nanohybrid is present in the corrosive media. -- Abstract: Corrosion inhibitor-inorganic clay composite including benzoate anion intercalated Zn-Al layered double hydroxides (LDHs) are assembled by coprecipitation. Powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectrum analyses indicate that the benzoate anion is successfully intercalated into the LDH interlayer and the benzene planes are vertically bilayer-positioned as a quasi-guest ion-pair form in the gallery space. Kinetic simulation for the release data, XRD and FT-IR analyses of samples recovered from the release medium indicate that ion-exchange is responsible for the release process and diffusion through the particle is also indicated to be the rate-limiting step. The anticorrosion capabilities of LDHs loaded with corrosion inhibitor toward Q235 carbon steel are analyzed by polarization curve and electrochemical impedance spectroscopy methods. Significant reduction of corrosion rate is observed when the LDH nanohybrid is present in the corrosive medium. This hybrid material may potentially be applied as a nanocontainer in self-healing coatings.

Wang, Yi [Shandong Provincial Key Lab of Corrosion Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China)] [Shandong Provincial Key Lab of Corrosion Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China); Zhang, Dun, E-mail: zhangdun@qdio.ac.cn [Shandong Provincial Key Lab of Corrosion Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China)] [Shandong Provincial Key Lab of Corrosion Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China)

2011-11-15

140

Optimized immobilization of transketolase from E. coli in MgAl-layered double hydroxides.  

PubMed

Immobilization of TK from Escherichia coli (TKec) on MgAl-NO3 layered double hydroxides (LDH) was carried out by two processes: adsorption and coprecipitation. As a comparison, the adsorption method was realized either at pH 7.5 in buffered solutions (MOPS and Gly-Gly) or in pure water. For the coprecipitation method, the formation of the inorganic LDH support was realized directly in the presence of TKec solubilized in Gly-Gly. The prepared biohybrids, called respectively TKec@LDHads and TKec@LDHcop, were characterized by powder X-ray diffraction, FTIR spectroscopy in comparison with TKec free reference products, i.e. MgAl-NO3, MgAl-Gly-Gly. The enzymatic activities of the various TKec@LDH biohybrids as well as their stabilities over time were investigated by UV-vis assay. A maximum of activity (12 U/mg of solid) was reached for TKec@MgAl-Gly-Gly biohybrid prepared by coprecipitation. Finally, thin films were prepared through a one-step deposition on a polished support. The enzymatic activity of the resulting TKec@MgAl-Gly-Glycop film was tested over four recycling processes with a reproducible activity of 2.7 U/mg cm(2). PMID:24055860

Touisni, Nadia; Charmantray, Franck; Helaine, Virgil; Forano, Claude; Hecquet, Laurence; Mousty, Christine

2013-12-01

141

Layered double hydroxides as supports for intercalation and sustained release of antihypertensive drugs  

NASA Astrophysics Data System (ADS)

Zn/Al layered double hydroxides (LDHs) were intercalated with the anionic antihypertensive drugs Enalpril, Lisinopril, Captopril and Ramipril by using coprecipitation or ion-exchange technique. TG-MS analyses suggested that the thermal stability of Ena -, Lis - (arranged with monolayer, resulted from X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR) analysis was enhanced much more than Cap - and Ram - (arranged with bilayer). The release studies show that the release rate of all samples markedly decreased in both pH 4.25 and 7.45. However, the release time of Ena -, Lis - were much longer compared with Cap -, Ram - in both pH 4.25 and 7.45, it is possible that the intercalated guests, arranged with monolayer in the interlayer, show lesser repulsive force and strong affinity with the LDH layers. And the release data followed both the Higuchi-square-root law and the first-order equation well. Based on the analysis of batch release, intercalated structural models as well as the TG-DTA results, we conclude that for drug-LDH, stronger the affinity between intercalated anions and the layers is, better the thermal property and the stability to the acid attack of drug-LDH, and the intercalated anions are easier apt to monolayer arrangement within the interlayer, were presented.

Xia, Sheng-Jie; Ni, Zhe-Ming; Xu, Qian; Hu, Bao-Xiang; Hu, Jun

2008-10-01

142

Bone cement/layered double hydroxide nanocomposites as potential biomaterials for joint implant.  

PubMed

Poly(methyl methacrylate)-based bone cement and layered double hydroxide (LDH) nanocomposites have been used as a grouting material for total joint arthroplasty. Few weight percentage of nanoLDH was uniformly dispersed in the bone cement matrix to have adequate interaction with matrix polymer. Mechanical strength, stiffness, toughness, and fatigue resistance of the nanocomposites are found to be higher than that of pure bone cement. Nanocomposites are thermally stable as compared to pristine bone cement. Direct mixing of the nanoLDH without any organic solvent makes these nanocomposites biocompatible. Biocompatibility was evaluated and compared with that of commercial bone cement by measuring hydrophilic nature, hemolysis assay, thrombosis assay, and deposition of apatite in simulated body fluid immersion. Finally, the viability of human osteoblast cells on the above developed nanocomposites was testified for actual biocompatibility. The experiment showed better cell growth in nanocomposites as compared to pure bone cement. Thus, these nanocomposites are found to be better grouting material than bone cement. PMID:22733710

Kapusetti, Govinda; Misra, Nira; Singh, Vakil; Kushwaha, R K; Maiti, Pralay

2012-12-01

143

Phosphate recovery from wastewater using engineered superparamagnetic particles modified with layered double hydroxide ion exchangers.  

PubMed

An innovative nanocomposite material is proposed for phosphate recovery from wastewater using magnetic assistance. Superparamagnetic microparticles modified with layered double hydroxide (LDH) ion exchangers of various compositions act as phosphate adsorbers. Magnetic separation and chemical regeneration of the particles allows their reuse, leading to the successful recovery of phosphate. Based upon the preliminary screening of different LDH ion exchanger modifications for phosphate selectivity and uptake capacity, MgFe-Zr LDH coated magnetic particles were chosen for further characterization and application. The adsorption kinetics of phosphate from municipal wastewater was studied in dependence with particle concentration, contact time and pH. Adsorption isotherms were then determined for the selected particle system. Recovery of phosphate and regeneration of the particles was examined via testing a variety of desorption solutions. Reusability of the particles was demonstrated for 15 adsorption/desorption cycles. Adsorption in the range of 75-97% was achieved in each cycle after 1 h contact time. Phosphate recovery and enrichment was possible through repetitive application of the desorption solution. Finally, a pilot scale experiment was carried out by treating 125 L of wastewater with the particles in five subsequent 25 L batches. Solid-liquid separation on this scale was carried out with a high-gradient magnetic filter (HGMF). PMID:23863389

Drenkova-Tuhtan, Asya; Mandel, Karl; Paulus, Anja; Meyer, Carsten; Hutter, Frank; Gellermann, Carsten; Sextl, Gerhard; Franzreb, Matthias; Steinmetz, Heidrun

2013-10-01

144

Evidences for decarbonation and exfoliation of layered double hydroxide in N,N-dimethylformamide-ethanol solvent mixture  

SciTech Connect

The behavior of a Hydrotalcite-like material (carbonate-containing Mg,Al-layered double hydroxide) in N,N-dimethylformamide (DMF)-ethanol mixture, at ambient temperature, has been investigated. The releasing of CO{sub 2} and production of a formate-containing material occurred mainly for 1:1 (v/v) solvent mixture. Decarbonation of Hydrotalcite is promoted by DMF hydrolysis followed by neutralization of brucite-like layers through HCOO{sup -} intercalation. Translucent colloidal dispersion of LDH nanoparticles from the formate-containing phase was characterized by transmission electron (TEM) and atomic force (AFM) microscopies. The absence of (00l) reflection at X-ray diffraction (XRD) pattern for dried colloidal dispersion indicated delamination of Hydrotalcite. The restacked sample exhibited broad reflections and typical hydroxide ordered layers non-basal (110) diffraction peaks. A LDH-HCOO{sup -} material was also prepared and characterized by FTIR and FT-Raman spectroscopies. Decarbonation and exfoliation of Hydrotalcite in N,N-dimethylformamide-ethanol mixed solvent provide an interesting method for preparation of new intercalated LDH materials. - Graphical abstract: Hydrotalcite suspended in 1:1 (v/v) N,N-dimethylformamide-ethanol solvent mixture, at ambient temperature, undergoes decarbonation and exfoliation. The process is promoted by DMF hydrolysis. Restacking of LDH layers is achieved by evaporating the solvent.

Gordijo, Claudia R. [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, CP 26077, CEP 05513-900, Sao Paulo, SP (Brazil); Leopoldo Constantino, Vera R. [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, CP 26077, CEP 05513-900, Sao Paulo, SP (Brazil); Oliveira Silva, Denise de [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, CP 26077, CEP 05513-900, Sao Paulo, SP (Brazil)], E-mail: deosilva@iq.usp.br

2007-07-15

145

Highly dispersed TiO6 units in a layered double hydroxide for water?splitting.  

PubMed

A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO(6) units in an MTi-layered double hydroxide matrix (M = Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H(2)-production rate of 31.4??mol? h(-1) as well as excellent recyclable performance. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mapping and XPS measurement reveal that a high dispersion of TiO(6) octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M(2+)-O-Ti network, rather different from the aggregation state of TiO(6) in the inorganic layered material K(2)Ti(4)O(9). Both transient absorption and photoluminescence spectra demonstrate that the electron-hole recombination process was significantly depressed in the Ti-containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X-ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO(6) units was modified by the adjacent MO(6) octahedron by means of covalent interactions, with a much decreased bandgap of 2.1?eV, which accounts for its superior water-splitting behavior. Therefore, the dispersion strategy for TiO(6) units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion. PMID:22927368

Zhao, Yufei; Chen, Pengyun; Zhang, Bingsen; Su, Dang Sheng; Zhang, Shitong; Tian, Lei; Lu, Jun; Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Min; Evans, David G; Duan, Xue

2012-09-17

146

Preparation of Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate by coprecipitation and its uptake of rare earth ions from aqueous solution  

NASA Astrophysics Data System (ADS)

A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta•Cu-Al LDH) was prepared by the dropwise addition of a Cu-Al nitrate solution to an edta solution at constant pH values of 8.0, 9.0, and 10.0. The edta•Cu-Al LDH had Hedta3- in the interlayer. Furthermore, the preparation at pH 8.0 resulted in the intercalation of Cu(edta)2-. The edta•Cu-Al LDH was found to take up rare earth ions from aqueous solution. The uptake of Sc3+ and Y3+ by edta•Cu-Al LDH was attributed to both the chelating functions of the edta ion in the interlayer and the chemical properties of Cu-Al LDH itself. The uptake of La3+ by edta•Cu-Al LDH was primarily caused by the chelating function of edta ions in the interlayer. The edta ions in the edta•Cu-Al LDH interlayer formed chelate complexes in the order Sc3+ > Y3+ > La3+ due to their relative stabilities, Sc(edta)- > Y(edta)- > La(edta)-. Thus, edta ions retain their chelating function even when intercalated in a Cu-Al LDH interlayer.

Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

2013-03-01

147

Characterization and film properties of electrophoretically deposited nanosheets of anionic titanate and cationic MgAl-layered double hydroxide.  

PubMed

Anionic hydrated titanate (H(n)TiO(m): HTO) nanosheets and cationic magnesium-aluminum layered double hydroxide (Mg-Al LDH) nanosheets were electrophoretically deposited on positively and negatively charged indium tin oxide (ITO)-coated glass substrates, respectively. The HTO nanosheets and Mg-Al LDH nanosheets obtained were identified in neutral water as H(2)Ti(4)O(9)·nH(2)O with a ?-potential of -23 mV and Mg(6)Al(2)(OH)(18)·4.5H(2)O with a ?-potential of +41 mV, respectively. Dense and smooth HTO and Mg-Al LDH films with layered structures with thicknesses of about 10-15 ?m were prepared in 300 s at 7.5 V by electrophoretic deposition (EPD) from the nanosheet suspensions. Both EPD HTO and LDH films showed elasticity because of their layered laminate structures. The HTO thick films demonstrated large adsorption properties and high photocatalytic activity, while the Mg-Al LDH thick films showed relatively high ionic conductivity of 10(-5) S cm(-1) at 80 °C and 80% relative humidity. PMID:23205857

Matsuda, Atsunori; Sakamoto, Hisatoshi; Mohd Nor, Mohd Arif Bin; Kawamura, Go; Muto, Hiroyuki

2013-02-14

148

Mg-Al and Zn-Fe layered double hydroxides used for organic species storage and controlled release.  

PubMed

Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400°C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic-mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn3Fe sample obtained by ionic exchange for 6h with Phe solution. A delivery test in PBS of pH=7.4 showed the release of the Phe in several steps up to 25 h indicating different host-guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer. PMID:24094226

Seftel, E M; Cool, P; Lutic, D

2013-12-01

149

The structure and stability of CaFe layered double hydroxides with various Ca:Fe ratios studied by Mössbauer spectroscopy, X-ray diffractometry and microscopic analysis  

NASA Astrophysics Data System (ADS)

The effects of the Ca(II)/Fe(III) ratios on the structure and Fe microenvironments have been studied in layered double hydroxides comprising of Ca(II) and Fe(III) (CaFe-LDH) prepared by the co-precipitation method. The Ca(II)/Fe(III) ratios were varied systematically from 2 to 6 and for characterisation 57Fe Mössbauer spectroscopy, powder X-ray diffractometry and scanning electron microscopy were applied. XRD patterns of the samples at all Ca(II)/Fe(III) ratios exhibited reflections corresponding to CaFe-LDH and 57Fe Mössbauer measurements revealed that Fe(III) was in a high-spin, somewhat disordered octahedral environment. Above the Ca(II)/Fe(III) ratio of 2 the reflections of Ca(OH)2 also appeared. This phase was found to stabilise the LDH phase, while the phase-pure LDH decomposed on ageing.

Sipiczki, M.; Kuzmann, E.; Homonnay, Z.; Megyeri, J.; Pálinkó, I.; Sipos, P.

2013-07-01

150

Nanometric dispersion of a Mg/Al layered double hydroxide into a chemically modified polycaprolactone.  

PubMed

Polycaprolactone (PCL) was chemically modified by grafting maleic anhydride on it, through a radical reaction induced by benzoyl peroxide as initiator. To improve the grafting degree, a second unsaturated comonomer such as glycidyl methacrylate (GMA) has been added, demonstrating a good reactivity in melt grafting without leading to long grafted chains. The quantitative determination of grafted maleic anhydride, performed by FTIR analysis, revealed a grafting weight percentage of 9.5 +/- 0.9, and the NMR characterization made it possible to propose a structure for the grafted polymer (PCLgMA). The modified polymer was analyzed by DSC and X-ray diffraction, showing a structural organization even better than that of the pristine polymer. An exchange reaction with a layered double hydroxide (LDH), hydrotalcite-like solid in the nitrate form, led to the disappearance of the crystalline basal peak of LDH in the X-ray diffractograms, suggesting a possible exfoliation of the inorganic sample. An oxidative etching on the composite surface followed by atomic force microscopy analysis made it possible to enlighten the lamellar structure in the pristine sample. In the composite sample, the well identifiable narrow fissures homogeneously distributed on the surface demonstrate that nanometer stacks of LDH sheets, embedded in a highly textured PCLgMA matrix, are present in the composite sample. The comparison of X-ray diffractograms and AFM analysis suggests either a partial exfoliation or an intercalation of the polymer in a lamellar texture with a basal spacing higher than 5 nm. In any case, the process of ionic exchange between nitrate LDH and PCLgMA led to the formation of nanocomposites, in which no large hydrotalcite aggregates are present. This is an interesting method to obtain a direct intercalation of the modified polymer into the inorganic solid with a simple ionic exchange reaction. PMID:17319719

Mangiacapra, Pasqualina; Raimondo, Marialuigia; Tammaro, Loredana; Vittoria, Vittoria; Malinconico, Mario; Laurienzo, Paola

2007-03-01

151

An optical sensor based on H-acid/layered double hydroxide composite film for the selective detection of mercury ion.  

PubMed

A novel optical chemosensor was fabricated based on 1-amino-8-naphthol-3,6-disulfonic acid sodium (H-acid) intercalated layered double hydroxide (LDH) film via the electrophoretic deposition (EPD) method. The film of H-acid/LDH with the thickness of 1 ?m possesses a well c-orientation of the LDH microcrystals confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fluorescence detection for Hg(II) in aqueous solution was performed by using the H-acid/LDH film sensor at pH 7.0, with a linear response range in 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) and a detection limit of 6.3 × 10(-8) mol L(-1). Furthermore, it exhibits excellent selectivity for Hg(II) over a large number of competitive cations including alkali, alkaline earth, heavy metal and transitional metals. The specific fluorescence response of the optical sensor is attributed to the coordination between Hg(II) and sulfonic group in the H-acid immobilized in the LDH matrix, which was verified by NMR spectroscopy and UV-vis spectra. In addition, density functional theory (DFT) calculation further confirms that the coordination occurs between one Hg(2+) and two O atoms in the sulfonic group, which is responsible for the significant fluorescence quenching of the H-acid/LDH film. The results indicate that the H-acid/LDH composite film can be potentially used as a chemosensor for the detection of Hg(2+) in the environmental and biomedical field. PMID:21819865

Sun, Zhiyong; Jin, Lan; Zhang, Shitong; Shi, Wenying; Pu, Min; Wei, Min; Evans, David G; Duan, Xue

2011-09-19

152

Reduced graphene oxide/Ni1-xCoxAl-layered double hydroxide composites: preparation and high supercapacitor performance.  

PubMed

Reduced graphene oxide (rGO) sheet and ternary-component Ni1-xCoxAl-layered double hydroxide (Ni1-xCoxAl-LDH) hybrid composites with an interesting sandwich structure have been fabricated by an in situ growth route. The as-obtained composite displays a sandwich architecture constructed by the self-assembly of sheet-like LDH crystals on both sides of the rGO sheets. It was found that the Co content doped in Ni1-xCoxAl-LDH plays an important role in the shape and structure of the final products. When the Co doped content is 17%, the rGO/Ni0.83Co0.17Al-LDH has a high surface area (171.5 m(2) g(-1)) and exhibits a perfect sandwich structure. In addition, this structure and morphology is favorable for a supercapacitor electrode material with a high performance. The influence of cobalt content on the electrochemical behavior of rGO/Ni1-xCoxAl-LDH has been systematically studied. The results indicate that the rGO/Ni0.83Co0.17Al-LDH composite exhibits the highest electrochemical performance, with a specific capacitance of 1902 F g(-1) at 1 A g(-1), and an excellent cycling stability. The markedly improved electrochemical performance is superior to undoped rGO/NiAl-LDH and can be attributed to the enhanced conductivity achieved through cobalt doping. Such composites could be used as a type of potential energy storage/conversion material for supercapacitors. PMID:24950435

Xu, Jie; Gai, Shili; He, Fei; Niu, Na; Gao, Peng; Chen, Yujin; Yang, Piaoping

2014-08-14

153

Surface-charging behavior of Zn-Cr layered double hydroxide.  

PubMed

A Zn-Cr layered double hydroxide (LDH) having the formula Zn(2)Cr(OH)(6)Cl(0.7)(CO(3))(0.15)2.1H(2)O was synthesized and characterized by powder X-ray diffraction, infrared spectroscopy, acid-base potentiometric titration, mass titration, electrophoretic mobility, and modeling of the electrical double layer. Adsorption of alizarin was also performed in order to show some particular features of the HDL. Net hydroxyl adsorption, which increases with increasing pH and decreasing supporting electrolyte concentration, takes place above pH 5. The electrophoretic mobility of the particles was always positive and it decreased when the pH was higher than 9. An isoelectric point of 12 could be estimated by extrapolating the data. The modified MUSIC model was used to estimate deprotonation constants of surface groups and different adsorption models were compared. Good fit of hydroxyl adsorption and electrophoresis could be achieved by considering both OH(-)/Cl(-) exchange at structural sites and proton desorption from surface hydroxyl groups. The modeling, in agreement with alizarin adsorption, indicates that most of the structural positive charge of the LDH is screened at the surface by exchanged anions and negatively charged surface groups. It also suggests that only structural charge sites initially neutralized by chloride ions are active for anion exchange. The remaining sites are blocked by carbonate and do not participate in the exchange. PMID:15533416

Rojas Delgado, R; Arandigoyen Vidaurre, M; De Pauli, C P; Ulibarri, M A; Avena, M J

2004-12-15

154

Sorption of Cs, Sr, and Y radionuclides on mixed layered double hydroxides of Mg, Al, and Nd from the aqueous phase  

Microsoft Academic Search

Sorption of 137Cs, 90Sr, and 90Y radionuclides from aqueous solutions on the solid phase of layered double hydroxides (LDHs) of Mg, Al, and Nd was studied.\\u000a Sorption of 137Cs from 10?5 M aqueous CsNO3 solutions on the LDH-Mg-Al-Nd solid phase is extremely weak. At the same time, 90Sr and 90Y are efficiently sorbed on the LDH-Mg-Al-Nd solid phase from 10?5

S. A. Kulyukhin; E. P. Krasavina; I. V. Gredina; I. A. Rumer

2009-01-01

155

Novel inorganic host layered double hydroxides intercalated with guest organic inhibitors for anticorrosion applications.  

PubMed

Zn-Al and Mg-Al layered double hydroxides (LDHs) loaded with quinaldate and 2-mercaptobenzothiazolate anions were synthesized via anion-exchange reaction. The resulting compounds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Spectrophotometric measurements demonstrated that the release of organic anions from these LDHs into the bulk solution is triggered by the presence of chloride anions, evidencing the anion-exchange nature of this process. The anticorrosion capabilities of LDHs loaded with organic inhibitors toward the AA2024 aluminum alloy were analyzed by electrochemical impedance spectroscopy. A significant reduction of the corrosion rate is observed when the LDH nanopigments are present in the corrosive media. The mechanism by which the inhibiting anions can be released from the LDHs underlines the versatility of these environmentally friendly structures and their potential application as nanocontainers in self-healing coatings. PMID:20355873

Poznyak, S K; Tedim, J; Rodrigues, L M; Salak, A N; Zheludkevich, M L; Dick, L F P; Ferreira, M G S

2009-10-01

156

Uptake of Sc 3+ and La 3+ from aqueous solution using ethylenediaminetetraacetate-intercalated Cu-Al layered double hydroxide reconstructed from Cu-Al oxide  

NASA Astrophysics Data System (ADS)

A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta·Cu-Al LDH) was prepared by suspending Cu-Al oxide, obtained by the calcination of CO32--intercalated Cu-Al LDH, in edta solution. It was found that the reconstruction of Cu-Al oxide to Cu-Al LDH was promoted with an increase in the temperature and time. The reaction in the pH range of around 8 suggests that Hedta 3- was intercalated in the interlayer of Cu-Al LDH. Edta·Cu-Al LDH was found to take up rare metal ions such as Sc 3+ and La 3+ in an aqueous solution at a pH of around 6-6.5. The uptake of Sc 3+ was caused not only by the chelating function of Hedta 3- in the interlayer but also by the chemical behavior of Cu-Al LDH itself. On the other hand, the uptake of La 3+ was caused only by the chelating function of Hedta 3- in the interlayer. The Hedta 3- in the interlayer of edta·Cu-Al LDH had the potential to form a chelate complex more preferentially with Sc 3+ than with La 3+.

Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

2011-02-01

157

Effect of inorganic and organic ligands on the sorption/desorption of arsenate on/from Al-Mg and Fe-Mg layered double hydroxides.  

PubMed

This paper describes the sorption of arsenate on Al-Mg and Fe-Mg layered double hydroxides as affected by pH and varying concentrations of inorganic and organic ligands, and the effect of residence time on the desorption of arsenate by ligands. The capacity of ligands to inhibit the fixation of arsenate followed the sequence: nitrateLDH and nitrateLDH. The inhibition of arsenate sorption increased by increasing the initial ligand concentration and was greater on Al-Mg-LDH than on Fe-Mg-LDH. The longer the arsenate residence time on the LDH surfaces the less effective the competing ligands were in desorbing arsenate from sorbents. A greater percentage of arsenate was removed by phosphate from Al-Mg-LDH than from Fe-Mg-LDH, due to the higher affinity of arsenate for iron than aluminum. PMID:22071258

Caporale, A G; Pigna, M; Dynes, J J; Cozzolino, V; Zhu, J; Violante, A

2011-12-30

158

Use of high-pressure CO2 for concentrating CrVI from electroplating wastewater by Mg-Al layered double hydroxide.  

PubMed

The desorption of Cr(VI) from Cr(VI)-adsorbed layered double hydroxide (Cr(VI)-LDH) and the recycling of LDH adsorbent are the bottlenecks that limit the practical application of LDH in treating Cr(VI)-containing industrial wastewater. Given the strong affinity of LDH for CO2, we studied desorption and enrichment of Cr(VI) from Cr(VI)-LDH as well as recycling of LDH in the presence of high-pressure CO2. Results showed that Cr(VI) solution with concentration of 500 mg/L could be enriched more than 20 times in each adsorption-desorption cycle. The regenerated LDH maintained the layer structure and the sheets as revealed by XRD and TEM patterns. FT-IR data showed CO2 formed HCO3(-) at high pressure. The transformation from CO2 to HCO3(-) followed by the anion-exchange with CrO4(2-) was the critical factor for Cr(VI) desorption and LDH regeneration. A pilot-scale experiment was carried out with 20 L Cr(VI)-containing electroplating wastewater. The concentration of the desorbed Cr(VI) solution could reach up to 10000 mg/L, which could be used in electroplating after appropriate adjustment. The main advantages of this method are high concentration of Cr(VI), direct reuse of enriched Cr(VI), and efficient regeneration of LDH adsorbent. This method showed promises in recycling Cr(VI) and regenerating LDH in treating industrial wastewater. PMID:24083820

Lv, Xiangying; Chen, Zhi; Wang, Yongjing; Huang, Feng; Lin, Zhang

2013-11-13

159

Modified layered double hydroxides in polycaprolactone as a tunable delivery system: in vitro release of antimicrobial benzoate derivatives  

Microsoft Academic Search

2,4-Dichlorobenzoate (BzDC) and para-hydroxybenzoate (p-BzOH), having antimicrobial activity, have been intercalated into [Zn0.65 Al0.35(OH)2](NO3)0.35 · 0.6H2O layered double hydroxide (ZnAl-LDH), via anion-exchange reactions. The obtained nanohybrids (ZnAl-BzDC and ZnAl-p-BzOH) have been dispersed into polycaprolactone (PCL), giving rise to different composite morphologies: an exfoliated nanocomposite with ZnAl-BzDC and a microcomposite with ZnAl-p-BzOH. The different dispersion of the fillers was related to

Valeria Bugatti; Giuliana Gorrasi; Francesca Montanari; Morena Nocchetti; Loredana Tammaro; Vittoria Vittoria

2011-01-01

160

Carbon Quantum Dot/NiFe Layered Double-Hydroxide Composite as a Highly Efficient Electrocatalyst for Water Oxidation.  

PubMed

The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction is crucial to a variety of important energy conversion and storage processes. Here, we use carbon quantum dots (CQDs, ?5 nm) to form hybrids with the ultrathin nickel-iron layered double-hydroxide (NiFe-LDH) nanoplates. The resulting CQD/NiFe-LDH complex exhibits high electrocatalytic activity (with an overpotential of ?235 mV in 1 M KOH at a current density of 10 mA cm(-2)) and stability for oxygen evolution, which almost exceed the values of all previously reported Ni-Fe compounds and were comparable to those of the most active perovskite-based catalyst. PMID:24735390

Tang, Di; Liu, Juan; Wu, Xuanyu; Liu, Ruihua; Han, Xiao; Han, Yuzhi; Huang, Hui; Liu, Yang; Kang, Zhenhui

2014-05-28

161

Inorganic thin films self-assembled from lamellar TiO\\/sub 2\\/ and layered double hydroxide and their electrochemical behaviour  

Microsoft Academic Search

Inorganic thin films composed of nanoplatelets of Ni and Co containing layered double hydroxides (LDH) and exfoliated TiO2 have been fabricated onto various substrates via the electrostatic self-assembly technique. Dense coverage of the substrate surface by the nanoplatelets was visualized confirmed by scanning electron microscopy. UV-vis absorption spectroscopy provided evidence for the subsequent growth of multilayer, exhibiting progressive enhancement of

Lianzhou Wang; Z. P. Xu; S. Z. Qiao; G. Q. Max Lu

2006-01-01

162

Comparison and characterization of chemical surfactants and bio-surfactants intercalated with layered double hydroxides (LDHs) for removing naphthalene from contaminated aqueous solutions  

Microsoft Academic Search

Chemical surfactants or bio-surfactants intercalated into layered double hydroxides (LDHs) are considered as potential organic pollutant sorbents. This study evaluates the effects of (1) using either calcined or uncalcined LDH, and various solid\\/solution ratios, (2) the concentrations of the chemical surfactant sodium dodecyl sulfate (SDS) or the bio-surfactant rhamnolipid (RL), and (3) reaction temperatures and times on the synthesis of

Ya-Hui Chuang; Cheng-Hua Liu; Yu-Min Tzou; Jo-Shu Chang; Po-Neng Chiang; Ming-Kuang Wang

2010-01-01

163

Thermal behaviour of Ni Mn layered double hydroxide and characterization of formed oxides  

NASA Astrophysics Data System (ADS)

Thermal behaviour of the Ni-Mn layered double hydroxide (LDH) with Ni/Mn molar ratio equal to 2 prepared by coprecipitation was studied in temperature range 200-1100 °C by thermal analysis (TG/DTA/EGA), powder X-ray diffraction (XRD), infrared spectroscopy and voltammetry of microparticles. A loss of interlayer water (dehydration) and sample decomposition accompanied by H 2O and CO 2 evolution were observed at 175 and 265 °C, respectively. Thermal decomposition of Ni-Mn LDH resulted in formation of a predominantly amorphous mixture of oxides. A relatively high content of amorphous part was observed in samples heated at 200-500 °C. The onset of Ni 6MnO 8 crystallization was detected by XRD in samples heated at 300 °C. Together with Ni 6MnO 8, NiMnO 3 was detected by XRD in samples heated at 500 °C. According to the voltammetry, the further reconstruction of oxides took place above 600 °C. NiMnO 3 and Ni 6MnO 8 were converted to spinel (Ni,Mn) 3O 4 occurring together with NiO. These oxides were observed in diffraction patterns of samples heated at high temperatures (800-1100 °C).

Kovanda, František; Grygar, Tomáš; Dorni?ák, V?´t.

2003-07-01

164

Uptake of chloride ion from aqueous solution by calcined layered double hydroxides: equilibrium and kinetic studies.  

PubMed

Layered double hydroxides (LDH) calcined within a certain temperature range (denoted as CLDH) have been shown to recover their original layered structure in the presence of appropriate anions. In the light of this so-called "memory effect", uptake of chloride ion from aqueous solution by calcined MgAl-CO3 LDH was investigated in batch mode. The equilibrium isotherm showed that the uptake of chloride ion by CLDH was consistent with the Langmuir and Freundlich equations and that the Langmuir model gave a better fit to the experimental data than the Freundlich model. The maximum uptake capacity of CLDH for chloride ion was 149.5 mg/g, close to the stoichiometric uptake (168 mg/g). The influence of varying pH of solution, initial chloride concentration, adsorbent quantity, and temperature on the kinetics of chloride removal has also been explored. Four kinetic models were used to fit the experimental data, and it was found that the pseudo-second-order kinetics model could be used to describe the uptake process satisfactorily. The calculated value of Ea was found to be 56.8 kJ/mol, which suggests that the process of uptake of chloride ion is controlled by the rate of reaction of chloride ion with the CLDH rather than diffusion. A mechanism for removal of chloride ion has been confirmed by X-ray diffraction, FT-IR spectroscopy and TG-MS measurements. PMID:16426658

Lv, Liang; He, Jing; Wei, Min; Evans, D G; Duan, Xue

2006-02-01

165

Potential for layered double hydroxides-based, innovative drug delivery systems.  

PubMed

Layered Double Hydroxides (LDHs)-based drug delivery systems have, for many years, shown great promises for the delivery of chemical therapeutics and bioactive molecules to mammalian cells in vitro and in vivo. This system offers high efficiency and drug loading density, as well as excellent protection of loaded molecules from undesired degradation. Toxicological studies have also found LDHs to be biocompatible compared with other widely used nanoparticles, such as iron oxide, silica, and single-walled carbon nanotubes. A plethora of bio-molecules have been reported to either attach to the surface of or intercalate into LDH materials through co-precipitation or anion-exchange reaction, including amino acid and peptides, ATPs, vitamins, and even polysaccharides. Recently, LDHs have been used for gene delivery of small molecular nucleic acids, such as antisense, oligonucleotides, PCR fragments, siRNA molecules or sheared genomic DNA. These nano-medicines have been applied to target cells or organs in gene therapeutic approaches. This review summarizes current progress of the development of LDHs nanoparticle drug carriers for nucleotides, anti-inflammatory, anti-cancer drugs and recent LDH application in medical research. Ground breaking studies will be highlighted and an outlook of the possible future progress proposed. It is hoped that the layered inorganic material will open up new frontier of research, leading to new nano-drugs in clinical applications. PMID:24786098

Zhang, Kai; Xu, Zhi Ping; Lu, Ji; Tang, Zhi Yong; Zhao, Hui Jun; Good, David A; Wei, Ming Qian

2014-01-01

166

Carboxylate-intercalated layered double hydroxides aged under microwave-hydrothermal treatment  

NASA Astrophysics Data System (ADS)

Carboxylate-intercalated (terephthalate, TA and oxalate, ox) layered double hydroxides (LDHs) are aged under a microwave-hydrothermal treatment. The influence of the nature of the interlayer anion during the ageing process is studied. Characterization results show that the microwave-hydrothermal method can be extended to synthesize LDHs with anions different than carbonate, like TA. LDH-TA compounds are stable under microwave irradiation for increasing periods of time and the solids show an improved order both in the layers and in the interlayer region as evidenced by powder X-ray diffraction (PXRD), 27Al MAS NMR and FT-IR spectroscopy. Furthermore, cleaning of the surface through removal of some organic species adsorbed on the surface of the particles also occurs during the microwave-hydrothermal treatment. Conversely, although the expected increase in crystallinity is observed in LDH-ox samples, the side-reaction between Al 3+ and ox is also enhanced under microwave irradiation, and a partial destruction of the structure takes place with an increase in the M 2+/M 3+ ratio and consequent modification of the cell parameters.

Benito, P.; Labajos, F. M.; Mafra, L.; Rocha, J.; Rives, V.

2009-01-01

167

Potential for Layered Double Hydroxides-Based, Innovative Drug Delivery Systems  

PubMed Central

Layered Double Hydroxides (LDHs)-based drug delivery systems have, for many years, shown great promises for the delivery of chemical therapeutics and bioactive molecules to mammalian cells in vitro and in vivo. This system offers high efficiency and drug loading density, as well as excellent protection of loaded molecules from undesired degradation. Toxicological studies have also found LDHs to be biocompatible compared with other widely used nanoparticles, such as iron oxide, silica, and single-walled carbon nanotubes. A plethora of bio-molecules have been reported to either attach to the surface of or intercalate into LDH materials through co-precipitation or anion-exchange reaction, including amino acid and peptides, ATPs, vitamins, and even polysaccharides. Recently, LDHs have been used for gene delivery of small molecular nucleic acids, such as antisense, oligonucleotides, PCR fragments, siRNA molecules or sheared genomic DNA. These nano-medicines have been applied to target cells or organs in gene therapeutic approaches. This review summarizes current progress of the development of LDHs nanoparticle drug carriers for nucleotides, anti-inflammatory, anti-cancer drugs and recent LDH application in medical research. Ground breaking studies will be highlighted and an outlook of the possible future progress proposed. It is hoped that the layered inorganic material will open up new frontier of research, leading to new nano-drugs in clinical applications.

Zhang, Kai; Xu, Zhi Ping; Lu, Ji; Tang, Zhi Yong; Zhao, Hui Jun; Good, David A.; Wei, Ming Qian

2014-01-01

168

Synthesis and phosphate uptake behavior of Zr4+ incorporated MgAl-layered double hydroxides.  

PubMed

We synthesized Zr(4+) incorporated MgAl-layered double hydroxides, Mg(AlZr)-LDH(A) (where A denotes a counteranion in the interlayer space and is expressed as CO(3) for carbonate and Cl for chloride ions), with different molar ratios of Mg/(Al+Zr). Then we characterized their uptake behavior toward phosphate ions. CO(3)-type tertiary LDH materials synthesized at room temperature show low crystallinity, whereas the highly crystalline Cl-type tertiary LDH, [Mg(0.68)Al(0.17)Zr(0.14)(OH)(2)][Cl(0.26)(CO(3))(0.04)1.24H(2)O], was synthesized for the first time using a hydrothermal treatment at 120 degrees C. The distribution coefficients (K(d)) of oxo-anions were measured with a mixed solution containing trace amounts of the anions. The selectivity sequences were Cl(-), NO(-)(3)LDH(CO(3)): 10 mg-P/g with the wastewater and less than 1 mg-P/g with the seawater. The large uptake and high selectivity of the CO(3)-type tertiary LDH materials is well explained by complex formation of phosphate ions directly with Zr(IV) centers in the layers. PMID:17509605

Chitrakar, Ramesh; Tezuka, Satoko; Sonoda, Akinari; Sakane, Kohji; Ooi, Kenta; Hirotsu, Takahiro

2007-09-01

169

Preparation of polymer/LDH nanocomposite by UV-initiated photopolymerization of acrylate through photoinitiator-modified LDH precursor  

SciTech Connect

Graphical abstract: This is the HR-TEM micrograph of UV cured nanocomposite at 5 wt% LDH-2959 loading for a-5 sample. The dark lines are the intersections of LDH platelets. It can be seen that samples a-5 dispersed in the polymer matrix and lost the ordered stacking-structure and show the completely exfoliation after UV curing. This can be explained by the fact that the sample a-5 only containing LDH-2959 exhibited a relative lower photopolymerization rate, which was propitious to further expand the LDH intergallery to form the exfoliated structure. Research highlights: {yields} The UV cured polymer/LDH nanocomposites were prepared through the photopolymerization initiated by the photoinitiator-modified LDH precursor, LDH-2959. {yields} The exfoliated UV cured nanocomposites were achieved in the presence of LDH-2959 only. However, the UV cured nanocomposites prepared using both LDH-2959 and Irgacure 2959 showed the intercalated structure. {yields} Compared with the pure polymer, the exfoliated polymer/LDH nanocomposite showed remarkable enhanced thermal stability and mechanical properties because of their well dispersion in the polymer matrix. -- Abstract: The exfoliated polymer/layered double hydroxide (LDH) nanocomposite by UV-initiated photopolymerization of acrylate systems through an Irgacure 2959-modified LDH precursor (LDH-2959) as a photoinitiator complex was prepared. The LDH-2959 was obtained by the esterification of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) with thioglycolic acid, following by the addition reaction with 3-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), finally intercalation into the sodium dodecyl sulfate-modified LDH. For comparison, the intercalated polymer/LDH nanocomposite was obtained with additive Irgacure 2959 addition. From the X-ray diffraction (XRD) measurements and HR-TEM observations, the LDH lost the ordered stacking-structure and well dispersed in the polymer matrix at 5 wt% LDH-2959 loading. The glass transition temperature of UV-cured exfoliated nanocomposites increased to 64 {sup o}C from 55 {sup o}C of pure polymer without LDH addition. The tensile strength was improved from 10.1 MPa to 25.2 MPa, as well the Persoz hardness enhanced greatly, while the elongation at break remained an acceptable level.

Hu, Lihua; Yuan, Yan [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shi, Wenfang, E-mail: wfshi@ustc.edu [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2011-02-15

170

Comparative X-ray diffraction and infrared spectroscopy study of Zn-Al layered double hydroxides: Vanadate vs nitrate  

NASA Astrophysics Data System (ADS)

Zn-Al layered double hydroxides (LDH) are promising as nanocontainers of corrosion inhibitors in self-healing corrosion protection coatings. Zn(2)Al-vanadate (Zn/Al = 2:1) is prepared by anion exchange from the parent composition Zn(2)Al-nitrate at pH ˜ 8. Crystal structure and vibrational spectra of both LDHs have been studied in comparison. Their interlayer distances are rather larger than those corresponding to the most compact arrangement of the intercalated anions. Nevertheless, no sign of a turbostratic disorder has been detected in these LDH. Based on the analysis of the spectroscopic data in combination with the XRD results, it has been shown that vanadate anion, which substitutes nitrate at the anion exchange, is pyrovanadate, VO74-. The observed disorder in the hydroxide layers in Zn(2)Al-V2O7 is likely to result from strong interactions between V5+ and Zn2+/Al3. Although Zn(2)Al-NO3 is less disordered than Zn(2)Al-V2O7, it exhibits no long-range order in arrangement of cations in the hydroxide layers.

Salak, Andrei N.; Tedim, João; Kuznetsova, Alena I.; Ribeiro, José L.; Vieira, Luís G.; Zheludkevich, Mikhail L.; Ferreira, Mário G. S.

2012-03-01

171

The removal and recovery of Cr(VI) by Li\\/Al layered double hydroxide (LDH)  

Microsoft Academic Search

Hexavalent Cr has been identified as one of the toxic metals commonly present in industrial effluents. Among the treatment techniques developed for removing Cr(VI) from waste waters, sorption is most commonly applied, due to its simplicity and efficiency. However, few adsorbents can be recycled and reused cost-effectively. In this study, the removal and recovery of Cr(VI) from water using Li\\/Al

L. C. Hsu; S. L. Wang; Y. M. Tzou; C. F. Lin; J. H. Chen

2007-01-01

172

Reactivity and applications of layered silicates and layered double hydroxides.  

PubMed

Layered materials, such as layered sodium silicates and layered double hydroxides (LDHs), are well-known for their remarkable adsorption, intercalation and swelling properties. Their tunable interlayers offer an interesting avenue for the fabrication of pillared nanoporous materials, organic-inorganic hybrid materials and catalysts or catalyst supports. This perspective article provides a summary of the reactivity and applications of layered materials including aluminium-free layered sodium silicates (kanemite, ilerite (RUB-18 or octosilicate) and magadiite) and layered double hydroxides (LDHs). Recent developments in the use of layered sodium silicates as precursors for the preparation of various porous, functional and catalytic materials including zeolites, mesoporous materials, pillared layered silicates, organic-inorganic nanocomposites and synthesis of highly dispersed nanoparticles supported on silica are reviewed in detail. Along this perspective, we have attempted to illustrate the reactivity and transformational potential of LDHs in order to deduce the main differences and similarities between these two types of layered materials. PMID:24841986

Selvam, Thangaraj; Inayat, Alexandra; Schwieger, Wilhelm

2014-07-21

173

Production of succinate by a pfl B ldh A double mutant of Escherichia coli overexpressing malate dehydrogenase  

Microsoft Academic Search

The gene encoding malate dehydrogenase (MDH) was overexpressed in a pflB ldhA double mutant of Escherichia coli, NZN111, for succinic acid production. With MDH overexpression, NZN111\\/pTrc99A-mdh restored the ability to metabolize glucose anaerobically and 0.55 g\\/L of succinic acid was produced from 3 g\\/L of glucose\\u000a in shake flask culture. When supplied with 10 g\\/L of sodium bicarbonate (NaHCO3), the succinic acid yield

Wei Wang; Zhimin Li; Jingli Xie; Qin Ye

2009-01-01

174

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

Microsoft Academic Search

This paper reported the preparation of styrene sulfonate intercalated layered double hydroxides (LDHs) material, SS-LDHs by\\u000a coprecipitation method, followed byin-situ polymerization of the monomers in the interlayer space of LDHs. The polymerization reaction was monitored by UV and NMR.\\u000a It is confirmed that when the reaction occurred at 100°C for 24 h, part of monomers did not react. When the

Lichun Si; Ge Wang; Fuli Cai; Zhiqiang Wang; Xue Duan

2004-01-01

175

Organic chemical conversions catalyzed by intercalated layered double hydroxides (LDHs)  

Microsoft Academic Search

In this review we examine recent advances in the use of crystalline layered double hydroxides (LDHs) intercalation compounds as catalysts for selected organic chemical conversions. Simple anion exchanged forms of LDHs exhibit catalytic properties toward organic halide exchange reactions, whereas others exhibit acid\\/base character as revealed by the catalytic conversions of 2-methyl-3-butyn-2-ol (MBOH) as a probe molecule. The catalytic properties

Thomas J. Pinnavaia; Malama Chibwe; Vera R. L. Constantino; Sang Kyeong Yun

1995-01-01

176

Solution-processed Li-Al layered-double-hydroxide platelet structures for high efficiency InGaN light emitting diodes.  

PubMed

High-oriented Li-Al layered double hydroxide (LDH) films were grown on an InGaN light-emitting diode (LED) structures by immersing in an aqueous alkaline Al(3+)- and Li+-containing solution. The stand upward and adjacent Li-Al LDH platelet structure was formed on the LED structure as a textured film to increase the light extraction efficiency. The light output power of the LED structure with the Li-Al LDH platelet structure had a 31% enhancement compared with a conventional LED structure at 20 mA. The reverse leakage currents, at -5V, were measured at -2.3 × 10(-8) A and -1.0 × 10(-10)A for the LED structures without and with the LDH film that indicated the Li-Al LDH film had the insulated property acted a passivation layer that had potential to replace the conventional SiO2 and Si3N4 passivation layers. The Li-Al LDH layer had the textured platelet structure and the insulated property covering whole the LED surface that has potential for high efficiency InGaN LED applications. PMID:23037533

Lin, Chia-Feng; Tsai, Peng-Han; Lin, Zhi-Yu; Uan, Jun-Yen; Lin, Chun-Min; Yang, Chung-Chieh; Shieh, Bing-Cheng

2012-09-10

177

A kinetic and mechanistic study into the formation of the Cu-Cr layered double hydroxide.  

PubMed

The formation of the layered double hydroxide [Cu2Cr(OH)6]Cl·yH2O from the reaction between CuO and aqueous CrCl3·6H2O was explored using synchrotron X-ray diffraction and ex situ analyses. The use of hard X-rays permitted time-resolved in situ studies to be performed as the reaction proceeded under a range of conditions. Additional information was obtained from ex situ experiments in which aliquots of the reaction mixture were removed, quenched, and subsequently analysed by laboratory X-ray diffraction, IR, UV-visible, and atomic emission spectroscopies. On the basis of these data, it is proposed that the reaction involves three steps. First, the solid CuO starting material is hydrolysed to give Cu(OH)2 chains, releasing Cu(2+) ions into solution. The Cu hydroxide chains subsequently condense with aqueous Cr(3+) species, Cl(-) ions and water molecules to give a hydrated form of the LDH. This material then extrudes some water to form a phase with a reduced interlayer spacing. PMID:23407586

Williams, Gareth R; Clout, Alexander; Burley, Jonathan C

2013-06-14

178

Bioinorganic magnetic core-shell nanocomposites carrying antiarthritic agents: intercalation of ibuprofen and glucuronic acid into Mg-Al-layered double hydroxides supported on magnesium ferrite.  

PubMed

This paper describes the synthesis and characterization of a composite constituted by an antiarthritic agent (AA) intercalated into a layered double hydroxide (LDH) supported on magnesium ferrite. Core-shell nanocomposites were prepared by depositing Mg-Al-NO(3)-LDH on a MgFe(2)O(4) core prepared by calcination of a nonstoichiometric Mg-Fe-CO(3)-LDH. Intercalation of ibuprofen and glucuronate anions was performed by ion-exchange with nitrate ions. The structural characteristics of the obtained products were investigated by powder X-ray diffraction, element chemical analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Morphologies of the nanocomposite particles were examined by scanning electron microscopy and transmission electron microscopy. The products were shown to intercalate substantial amounts of AA with enhanced thermal stabilities. Room-temperature magnetic measurements by vibrating sample magnetometry revealed that the products show soft ferromagnetic properties suitable for potential utilization in magnetic arthritis therapy. PMID:19691269

Ay, Ahmet Nedim; Zümreoglu-Karan, Birgül; Temel, Abidin; Rives, Vicente

2009-09-21

179

Synthesis of mesoporous Cu/Mg/Fe layered double hydroxide and its adsorption performance for arsenate in aqueous solutions.  

PubMed

The mesoporous Cu/Mg/Fe layered double hydroxide (Cu/Mg/Fe-LDH) with carbonate intercalation was synthesized and used for the removal of arsenate from aqueous solutions. The Cu/Mg/Fe-LDH was characterized by Fourier transform infrared spectrometry, X-ray diffraction crystallography, scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller. Effects of various physico-chemical parameters such as pH, adsorbent dosage, contact time and initial arsenate concentration on the adsorption of arsenate onto Cu/Mg/Fe-LDH were investigated. Results showed that it was efficient for the removal of arsenate, and the removal efficiency of arsenate increased with the increment of the adsorbent dosage, while the arsenate adsorption capacity decreased with increase of initial pH from 3 to 11. The adsorption isotherms can be well described by the Langmuir model with R2 > 0.99. Its adsorption kinetics followed the pseudo second-order kinetic model. Coexisting ions such as HPO4(2-), CO3(2-), SO4(2-) and NO3(-) could compete with arsenate for adsorption sites on the Cu/Mg/Fe-LDH. The adsorption of arsenate on the adsorbent can be mainly attributed to the ion exchange process. It was found that the synthesized Cu/Mg/Fe-LDH can reduce the arsenate concentration down to a final level of < 10 microg/L under the experimental conditions, and makes it a potential material for the decontamination of arsenate polluted water. PMID:24218824

Guo, Yanwei; Zhu, Zhiliang; Qiu, Yanling; Zhao, Jianfu

2013-05-01

180

Factors influencing the removal of fluoride from aqueous solution by calcined Mg-Al-CO3 layered double hydroxides.  

PubMed

Layered double hydroxides (LDH) calcined at different temperatures (denoted as CLDH) have been demonstrated to recover their original layered structure in the presence of appropriate anions. In the light of this so-called "memory effect", a study of removal of fluoride from aqueous solution by calcined Mg-Al-CO(3)-LDH has been carried out. The LDH calcined at 500 degrees C had the highest capacity of removal of fluoride ion, because of retention of its intrinsic structure. The CLDH with an Mg/Al ratio of 2 has a remarkable ability to adsorb anions. The adsorption loading is higher for the calcined Mg-Al-LDH than for calcined Zn-Al and Ni-Al-LDH. The influence of varying the conditions for removal of fluoride, such as the pH of aqueous solution, the initial fluoride concentration, the dosage of adsorbent, and temperature on removal of fluoride have been investigated. The influence of co-existing anions in fluoride aqueous solution indicates that the percentage of removal of fluoride increased in order PO(4)(3-) < Cl(-) approximately SO(4)(2-) < Br(-) < NO(3)(-). It was found that maximum removal of fluoride from aqueous solutions was obtained in 6h at pH 6.0 with an initial concentration of 50 mg/L, and that the retention of fluoride ions by the CLDH material was 98% or higher. The residual fluoride concentration was found to be 0.4 mg/L with an initial concentration of 20 mg/L, which meets the national standard for drinking water quality. The Freundlich isotherm and Langmuir isotherm were used to fit the data of equilibrium experiments. The results of X-ray diffraction, FT-IR and TG-MS demonstrate that the adsorption phenomenon is accompanied by rehydration with concomitant uptake of fluoride ions to rebuild the initial layered structure. PMID:16343753

Lv, Liang; He, Jing; Wei, Min; Evans, D G; Duan, Xue

2006-05-20

181

New polymeric composites based on poly(-caprolactone) and layered double hydroxides containing antimicrobial species.  

PubMed

Benzoate (Bz), 2,4-dichlorobenzoate (BzDC), and p- and o-hydroxybenzoate (p- and o-BzOH) anions with antimicrobial activity have been intercalated into [Zn(0.65)Al(0.35)(OH)(2)](NO(3))(0.35).0.6H(2)O, layered double hydroxide (LDH), via anion-exchange reactions. The composition of the obtained intercalation compounds, determined by chemical, thermogravimetric, and ion chromatographic analyses, indicates that benzoate and benzoate derivative anions replace the nitrate counteranions, almost completely. Information on the interactions of the intercalated anions with the inorganic layer have been obtained from Fourier transform IR absorption spectroscopy and powder X-ray diffraction of the samples. It has been found that both the nature and the position of the aromatic ring substituents affect the value of the basal distance and the host-guest hydrogen bond network. Knowledge of the chemical composition, basal distance, and van der Waals dimensions of the guests has finally allowed the proposal of structural models of the intercalation compounds that have been used as fillers of poly(caprolactone), a biodegradable polymer. Films of polymeric composites were obtained by hot-pressing the powders of polymer and filler previously milled by a high-energy ball milling procedure. X-ray diffraction analysis and optical and scanning electron microscopy of the composites indicate that the LDH samples containing BzDC anions are delaminated into the polymeric matrix, whereas those containing p-BzOH anions maintain for the most part the crystal packing and give rise to microcomposites. Intermediate behavior was found for LDH modified with Bz and o-BzOH anions because exfoliated and partly intercalated composites were obtained. Preliminary antimicrobial tests indicate that the composites are able to inhibit the Saccharomyces cerevisiae growth of 40% in comparison with the growth in a pure culture medium. The composites can be studied as the model for "active packaging" systems because of the antimicrobial properties of the anions anchored to the LDH layer. PMID:20355989

Costantino, Umberto; Bugatti, Valeria; Gorrasi, Giuliana; Montanari, Francesca; Nocchetti, Morena; Tammaro, Loredana; Vittoria, Vittoria

2009-03-01

182

Anticancer drug-layered hydroxide nanohybrids as potent cancer chemotherapy agents  

Microsoft Academic Search

Methotrexate-layered double hydroxide (MTX-LDH) nanohybrid showed considerably enhanced cellular uptake and drug efficacy compared to free MTX. To evaluate the potential of drug-LDH nanohybrids as cancer chemotherapy agents, the present study was extended to encapsulate another anticancer drug, 5-fluorouracil (5-Fu) into LDH through coprecipitation method. The powder X-ray pattern of 5-Fu-LDH nanohybrid showed interlayer distance of 5.8Å, which well corresponds

Soo-Jin Choi; Jae-Min Oh; Jin-Ho Choy

2008-01-01

183

Synthesis, characterization and release of a-naphthaleneacetate from thin films containing Mg/Al-layered double hydroxide  

NASA Astrophysics Data System (ADS)

An active agent a-naphthaleneacetate (NAA), a plant growth regulator was intercalated into the layered double hydroxides Mg/Al–LDH by ion-exchange method. And we prepared the films by the method of layer-by-layer self-assembly with Cationic Polyacrylamide, Polyacrylic acid sodium and LDH. The obtained compounds were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) and Scanning Electron Microscopy (SEM) techniques. The XRD datas demonstrated the guest size and the orientation of anions between the layers was determined. After intercalation, it was proposed that the NAA anions were accommodated in the interlayer region as a bilayer of species with the carboxyl attaching to the upper and lower layers. The FT-IR of the powder from film shows that Mg/Al–NAA–LDH was absorbed on the quartz glass. The film was putted into various solutions, and the release of NAA from the film showed obvious release effect. The release mechanism may be based on the dissolution and ion-exchange process according to first-order kinetics.

Liu, Yanfang; Song, Jian; Jiao, Feipeng; Huang, Jian

2014-05-01

184

Evolution of biogenic amine concentrations in foods through their induced chemiluminescence inactivation of layered double hydroxide nanosheet colloids.  

PubMed

Turn-on/off fluorescence and visual sensors through hydrogen bonding recognition have been clearly established in the literature. There is apparently no good reason to disregard hydrogen bonding-induced inactivation of chemiluminescence (CL). In this work, serving as novel CL catalyst and CL resonance energy transfer acceptor (CRET), layered double hydroxide (LDH) nanosheet colloids can induce a significant increase in the CL intensity of bis(2,4,6-trichlorophenyl) oxalate (TCPO)-H2O2 system. On the other hand, biogenic amines can selectively inhibit the CL intensity of the LDH nanosheet-TCPO-H2O2 system as a result of inactivation of photoluminescence LDH nanosheets through the displacement of O-H?O bonding by O-H?N bonding. In addition, histamine is used as a common indicator of food spoilage, and it is found that the CL intensity is linear with histamine concentration in the range of 0.1-100µM, and the detection limit for histamine (S/N=3) is 3.2nM. The proposed method has been successfully applied to trace histamine evolution of spoiled fish and pork meat samples, displaying a time-dependent increase in the biogenic amines levels in such samples. PMID:24813913

Wang, Zhihua; Liu, Fang; Lu, Chao

2014-10-15

185

Synthesis, Characterization, and 1H and 71Ga MAS NMR Spectroscopy of a Novel Mg/Ga Double Layered Hydroxide  

NASA Astrophysics Data System (ADS)

A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg 0.174Ga 0.256(OH) 2](CO 3) 0.134· mH 2O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073 K were characterized by X-ray diffraction, diffuse reflectance infrared spectroscopy, high-resolution solid-state nuclear magnetic resonance (MAS NMR), and thermogravimetric analysis. The surface properties of the solid (specific surface) and its basicity were also determined. The Mg/Ga LDH was found to be stable up to 523K and to decompose into a mixture of periclase MgO and amorphous Ga 2O 3at 823 K. Its changes with temperature were monitored by using 1H and 71Ga MAS NMR; 1H MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823K.

Aramendía, María. Angeles; Borau, Victor; Jiménez, César; Marinas, José Maria; Romero, Francisco José; Ruiz, José Rafael

1997-06-01

186

Hydrophobic layered double hydroxides (LDHs): Selective adsorbents for liquid mixtures  

Microsoft Academic Search

The external and internal surface area of the calcium aluminum double hydroxide [Ca2Al(OH)6] NO3 · 2H2O were hydrophobized by the anionic surfactants sodium dodecylsulfate and sodium dodecylbenzene sulfonate. The adsorption\\u000a behavior towards liquid mixtures (benzene\\/n-heptane and n-propanol\\/toluene) was studied by determining the surface excess adsorption isotherms, the heats of immersion in these liquids,\\u000a and the basal spacing, i.e. the expansion

I. Dékány; F. Berger; K. Imrik; G. Lagaly

1997-01-01

187

Removal of boron from oilfield wastewater via adsorption with synthetic layered double hydroxides.  

PubMed

Hydrotalcite is a layered double hydroxide (LDH) consisting of brucite-like sheets of metal ions (Mg-Al). In this work, hydrotalcites were synthesized, and boron removal from oilfield wastewater was evaluated. LDHs were synthesized using the co-precipitation method. The calcined products (CLDHs) were obtained by heating at 500°C and characterized using X-ray diffraction, X-ray fluorescence, thermogravimetric analysis and the specific surface area (BET). The affinity of LDHs for borate ions was evaluated for calcined and uncalcined LDHs as a function of contact time, initial pH of the oilfield wastewater (pH ? 9) and the LDH surface area. The tests were conducted at room temperature (approximately 25ºC). The results indicated that 10 min were needed to reach a state of equilibrium during boron removal for calcined LDHs due to the high surface area (202.3 m(2) g(-1)) regardless of the initial pH of the oilfield wastewater, which resulted from the high buffering capacity of the LDHs. The adsorption capacity increased as the adsorbents levels increased for the range studied. After treatment of the oilfield wastewater containing 30 mg L(-1) of boron with Mg-Al-CO3-LDHs, the final concentration of boron was within the discharge limit set by current Brazilian environmental legislation, which is 5 mg L(-1). Pseudo-first-order and pseudo-second-order kinetic models were tested, and the latter was found to fit the experimental data better. Isotherms for boron adsorption by CLDHs were well described using the Langmuir and Freundlich equations. PMID:24766593

Delazare, Thais; Ferreira, Letícia P; Ribeiro, Nielson F P; Souza, Mariana M V M; Campos, Juacyara C; Yokoyama, Lídia

2014-07-01

188

Temperature-controlled electrochemical switch based on layered double hydroxide/poly(N-isopropylacrylamide) ultrathin films fabricated via layer-by-layer assembly.  

PubMed

In this paper we report the fabrication of layered double hydroxide (LDH) nanoparticles/poly(N-isopropylacrylamide) (pNIPAM) ultrathin films (UTFs) via the layer-by-layer assembly technique, and their switchable electrocatalytic performance in response to temperature stimuli was demonstrated. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of the (LDH/pNIPAM)(n) UTFs; an interaction based on hydrogen bonding between LDH nanoparticles and pNIPAM was confirmed by X-ray-photoelectron spectroscopy and Fourier transform infrared spectroscopy. Temperature-triggered cyclic voltammetry and electrochemical impedance spectroscopy switch for the UTFs was obtained between 20 and 40 °C, accompanied by reversible changes in surface topography and film thickness revealed by atomic force microscopy and ellipsometry, respectively. The electrochemical on-off property of the temperature-controlled (LDH/pNIPAM)(n) UTFs originates from the contraction-expansion configuration of pNIPAM with low-high electrochemical impedance. In addition, a switchable electrocatalytic behavior of the (LDH/pNIPAM)(n) UTFs toward the oxidation of glucose was observed, resulting from the temperature-controlled charge transfer rate. Therefore, this work provides a facile approach for the design and fabrication of a well-ordered command interface with a temperature-sensitive property, which can be potentially applied in electrochemical sensors and switching. PMID:22650232

Dou, Yibo; Han, Jingbin; Wang, Tengli; Wei, Min; Evans, David G; Duan, Xue

2012-06-26

189

Influence of Hydrothermal Treatment on Physicochemical Properties and Drug Release of Anti-Inflammatory Drugs of Intercalated Layered Double Hydroxide Nanoparticles  

PubMed Central

The synthesis method of layered double hydroxides (LDHs) determines nanoparticles’ performance in biomedical applications. In this study, hydrothermal treatment as an important synthesis technique has been examined for its influence on the physicochemical properties and the drug release rate from drug-containing LDHs. We synthesised MgAl–LDHs intercalated with non-steroidal anti-inflammatory drugs (i.e., naproxen, diclofenac and ibuprofen) using a co-precipitation method with or without hydrothermal treatment (150 °C, 4 h). After being hydrothermally treated, LDH–drug crystallites increased in particle size and crystallinity, but did not change in the interlayer anion orientation, gallery height and chemical composition. The drug release patterns of all studied LDH–drug hybrids were biphasic and sustained. LDHs loaded with diclofenac had a quicker drug release rate compared with those with naproxen and ibuprofen, and the drug release from the hydrothermally-treated LDH–drug was slower than the freshly precipitated LDH–drug. These results suggest that the drug release of LDH–drugs is influenced by the crystallite size of LDHs, which can be controlled by hydrothermal treatment, as well as by the drug molecular physicochemical properties.

Gu, Zi; Wu, Aihua; Li, Li; Xu, Zhi Ping

2014-01-01

190

Influence of hydrothermal treatment on physicochemical properties and drug release of anti-inflammatory drugs of intercalated layered double hydroxide nanoparticles.  

PubMed

The synthesis method of layered double hydroxides (LDHs) determines nanoparticles' performance in biomedical applications. In this study, hydrothermal treatment as an important synthesis technique has been examined for its influence on the physicochemical properties and the drug release rate from drug-containing LDHs. We synthesised MgAl-LDHs intercalated with non-steroidal anti-inflammatory drugs (i.e., naproxen, diclofenac and ibuprofen) using a co-precipitation method with or without hydrothermal treatment (150 °C, 4 h). After being hydrothermally treated, LDH-drug crystallites increased in particle size and crystallinity, but did not change in the interlayer anion orientation, gallery height and chemical composition. The drug release patterns of all studied LDH-drug hybrids were biphasic and sustained. LDHs loaded with diclofenac had a quicker drug release rate compared with those with naproxen and ibuprofen, and the drug release from the hydrothermally-treated LDH-drug was slower than the freshly precipitated LDH-drug. These results suggest that the drug release of LDH-drugs is influenced by the crystallite size of LDHs, which can be controlled by hydrothermal treatment, as well as by the drug molecular physicochemical properties. PMID:24858732

Gu, Zi; Wu, Aihua; Li, Li; Xu, Zhi Ping

2014-01-01

191

Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity  

NASA Astrophysics Data System (ADS)

In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

2013-06-01

192

Nickel-aluminum layered double hydroxide as a nanosorbent for selective solid-phase extraction and spectrofluorometric determination of salicylic acid in pharmaceutical and biological samples.  

PubMed

The nickel-aluminum layered double hydroxide (Ni-Al LDH) was synthesized by a simple co-precipitation method and used as a solid-phase extraction (SPE) sorbent for separation and pre-concentration of trace levels of salicylic acid (SA) from aqueous solutions. Extraction of analyte is based on the adsorption of salicylate ions on the Ni-Al (NO(3)(-)) LDH and/or their exchanging with LDH interlayer NO(3)(-) ions. The retained analyte on the LDH was stripped by 3 mol L(-1) NaOH solution and its concentration was subsequently determined spectrofluorometrically at ?(em)=400 nm with excitation at ?(ex)=270 nm. Various parameters affecting the extraction efficiency of SA on the Ni-Al (NO(3)(-)) LDH, such as pH, amount of nano-sorbent, sample loading flow rate, elution conditions, sample volume and matrix effects were investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12 ?g L(-1) and 40, respectively. The relative standard deviation (RSD) for six replicate determinations of 10 ?g L(-1) SA was 2.3%. The calibration graph using the pre-concentration system was linear in the range of 0.3-45 ?g L(-1) with a correlation coefficient of 0.9985. The optimized method was successfully applied to the determination of SA in blood serum, willow leaf and aspirin tablet. PMID:21376959

Abdolmohammad-Zadeh, H; Kohansal, S; Sadeghi, G H

2011-04-15

193

Biodiesel synthesis using calcined layered double hydroxide catalysts  

SciTech Connect

The catalytic properties of calcined Li-Al, Mg-Al and Mg-Fe layered double hydroxides (LDHs) were examined in two transesterification reactions, namely, the reaction of glyceryl tributyrate with methanol, and the reaction of soybean oil with methanol. While the Li-Al catalysts showed high activity in these reactions at the reflux temperature of methanol, the Mg-Fe and Mg-Al catalysts exhibited much lower methyl ester yields. CO2 TPD measurements revealed the presence of sites of weak, medium and strong basicity on both Mg-Al and Li-Al catalysts, the latter showing higher concentrations of medium and strong base sites; by implication, these are the main sites active in transesterification catalyzed by calcined Li-Al LDHs. Maximum activity was observed for the Li-Al catalysts when a calcination temperature of 450-500 aC was applied, corresponding to decomposition of the layered double hydroxide to the mixed oxide without formation of crystalline lithium aluminate phases.

Schumaker, J. Link [University of Kentucky; Crofcheck, Czarena [University of Kentucky; TAckett, S. Adam [University of Kentucky; Santillan-Jimenez, Eduardo [University of Kentucky; Morgan, Tonya [University of Kentucky; Ji, Yaying [University of Kentucky; Crocker, Mark [University of Kentucky; Toops, Todd J [ORNL

2008-01-01

194

Three dimensionally honeycomb layered double hydroxides framework as a novel fiber coating for headspace solid-phase microextraction of phenolic compounds.  

PubMed

A new solid phase microextraction (SPME) fiber based on high-temperature three dimensionally honeycomb layered double hydroxide (TDH-LDH) material is presented. The fiber coating can be prepared easily, it is mechanically stable and exhibits relatively high thermal stability. This study shows that three dimensionally honeycomb layered double hydroxide generated porous morphology. The TDH-LDH material was tested for the extraction of some phenolic and polycyclic aromatic hydrocarbon compounds from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). The TDH-LDH fiber contains polar groups and its efficiency for non-polar polycyclic aromatic hydrocarbon compounds was lower than phenolic compounds. On the other hand, a high tendency towards the adsorption of polar phenolic compounds was observed for the proposed fiber. The effects of the extraction and desorption parameters including extraction temperature, extraction time, ionic strength, stirring rate, pH and desorption temperature and time have been studied. In optimum conditions, the repeatability for one fiber (n=5), expressed as relative standard deviation (R.S.D. %), was between 2.8% and 7.1% for the phenolic compounds. The detection limits for the studied phenolic compounds were between 0.02 and 5.8ngmL(-1). The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis. PMID:24780259

Abolghasemi, Mir Mahdi; Yousefi, Vahid

2014-06-01

195

Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.  

PubMed

Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ?1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (?0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical stability. PMID:21861530

Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

2011-09-28

196

Ion exchange and intercalation properties of layered double hydroxides towards halide anions.  

PubMed

A layered double hydroxide (LDH) obtained by the urea method, having an empirical formula [Zn0.61Al0.39(OH)2](CO3)0.195·0.50H2O, has been converted into the corresponding chloride form [Zn0.61Al0.39(OH)2]Cl0.39·0.47H2O by making the solid come into contact with a suitable HCl solution. The intercalation of the other halide anions (X(-) = F(-), Br(-), I(-)) via the Cl(-)/X(-) anion exchange has been attained and the respective anion exchange isotherms have been obtained with the batch method. The analysis of the isotherms indicates that the selectivity of LDH towards the halides decreases with the increase of the X(-) ionic radius, the selectivity order being F(-) > Cl(-)? Br(-) > I(-). The CO3(2-)/Cl(-) isotherm has also been reported to highlight the extraordinary selectivity of LDH towards carbonate anions. Samples taken from the isotherms at different exchange degrees were analyzed by X-ray diffraction, thermogravimetry and thermodiffractometry to obtain information about the ion exchange mechanism. The Cl(-)/Br(-) and the reverse Br(-)/Cl(-) exchanges occur with the formation of solid solutions, very likely because of the similar ionic radius of the exchanging anions. In contrast, in the Cl(-)/F(-) and Cl(-)/I(-) exchange, the co-existence of the Cl(-) and F(-) (or I(-)) phases in the same sample was detected, indicating the occurrence of a first order phase transition, in which the starting phase is transformed into the final phase, as the process goes on. The variation of the interlayer distances of ZnAl-X intercalation compounds with the hydration degree has been interpreted with a structural model based on the nesting of the guest species into the trigonal pockets of the brucite-like layer surface. Rietveld refinements of the phases with the maximum F(-), Br(-) and I(-) content were also performed and compared with the above model, giving indications of the arrangement and order/disorder of the halide anions in the interlayer region. PMID:24940938

Costantino, Umberto; Vivani, Riccardo; Bastianini, Maria; Costantino, Ferdinando; Nocchetti, Morena

2014-08-14

197

Immobilization of layered double hydroxides in the fluidic system for nanoextraction of specific DNA molecules  

NASA Astrophysics Data System (ADS)

The purpose of this study was to immobilize inorganic layered double hydroxides (LDHs) on the poly(methylmethacrylate) substrate as the media to extract the specific DNA molecules through fluidic system to enhance the efficiency of extract specific DNA molecules from extremely low concentration in sample solution. LDH immobilized through solvent swelling and plasma treatment on the polymer surface captured the specific DNA molecules lysed from Escherichia coli (E. coli) cells as the target DNA molecules with 2×10-4 g/l of concentration in sample solution mixed biomacromolecules lysed from human blood. The encapsulated DNA molecules released through dissolving of LDHs by slight acid (pH=4-5) solution then amplified by polymerase chain reaction (PCR) process through the primers for E. coli cells. The DNA molecules amplified by PCR process were characterized by gel electrophoresis to recognize the existence of E. coli cells. The results show that immobilized LDHs could be regarded as the specific DNA detector for rapid disease diagnosis through fluidic system.

Chen, Jem-Kun; Chan, Chia-Hao; Chang, Feng-Chih

2008-02-01

198

Large scale synthesis of porous microspheres of Mg-Al-layerd double hydroxide with improved fire suppression effectiveness  

NASA Astrophysics Data System (ADS)

Porous microspheres of Mg-Al layered double hydroxide (LDH) were fabricated in large scale through a simple sonication-assisted method in the mixed solvent of ethylene glycol and water. Contrast experiments showed that sonication and ethylene glycol both played important roles for the formation of the porous nanostructures of Mg-Al-LDHs. A series of techniques of XRD (X-ray Diffraction), FTIR (Fourier Transmission Infrared Spectroscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), BET (Brunauer-Emmett-Teller surface analysis) and TG-DTA (Thermalgravimetric-Differential Thermal Analysis) were used to characterize the product. Laboratory-scale fire extinguishment tests showed that thus-prepared porous LDHs showed much superior performance to that of the solid particulate counterpart for relatively shorter extinguishing time and smaller amount of agents required. Such an improvement could be reasonably ascribed to the special porous structure and nanosize of as-prepared Mg-Al-LDHs microspheres.

Ni, Xiaomin; Kuang, Kaiqian; Jin, Xiang; Xiao, Xiukun; Liao, Guangxuan

2010-04-01

199

Cu-Ce-O mixed oxides from Ce-containing layered double hydroxide precursors: Controllable preparation and catalytic performance  

NASA Astrophysics Data System (ADS)

Cu/Zn/Al layered double hydroxide (LDH) precursors have been synthesized using an anion exchange method with anionic Ce complexes containing the dipicolinate (pyridine-2,6-dicarboxylate) ligand. Cu-Ce-O mixed oxides were obtained by calcination of the Ce-containing LDHs. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry-differential thermal analysis, elemental analysis, and low temperature N 2 adsorption/desorption measurements. The results reveal that the inclusion of Ce has a significant effect on the specific surface area, pore structure, and chemical state of Cu in the resulting Cu-Ce-O mixed metal oxides. The resulting changes in composition and structure, particularly the interactions between Cu and Ce centers, significantly enhance the activity of the Ce-containing materials as catalysts for the oxidation of phenol by hydrogen peroxide.

Chang, Zheng; Zhao, Na; Liu, Junfeng; Li, Feng; Evans, David G.; Duan, Xue; Forano, Claude; de Roy, Marie

2011-12-01

200

Exchange of interlayer terephthalate anions from a Mg Al layered double hydroxide: formation of intermediate interstratified phases  

NASA Astrophysics Data System (ADS)

The exchange of interlayer terephthalate (TA) anions from a Mg-Al layered double hydroxide (LDH) by carbonate, sulfate, chloride and nitrate anions is reported. It is shown that TA is readily exchanged by CO 32- and SO 42- but only partly by Cl - and NO 3-. We demonstrate that during the exchange process interstratified phases are observed. Such interstratification has previously been reported only for directly synthesised materials. The origin of the interstratification is believed to be associated with two preferred orientations of TA anions within the layers, i.e. vertical or horizontal to the clay sheets. Two models for the possible exchange mechanism which is operating in these systems are proposed.

Kaneyoshi, Masami; Jones, William

1998-10-01

201

ISOLATION OF CAFFEIC ACID FROM EUPATORIUM ADENOPHORUM SPRENG BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY AND SYNTHESIS OF CAFFEIC ACID-INTERCALATED LAYERED DOUBLE HYDROXIDE.  

PubMed

Preparative high-speed countercurrent chromatography (HSCCC) was successfully used for isolation and purification of caffeic acid from Eupatorium adenophorum Spreng with a solvent system composed of ethyl acetate-methanol-water at a volume ratio of 10:1:10, v/v. Using a preparative unit of the HSCCC centrifuge, about a 938 mg amount of the crude extract was separated, yielding 63.2 mg of caffeic acid at purity of 96.0%. Then, the anti-microbial and anti-virus drug caffeic acid (C(9)H(8)O(4)) was intercalated into layered double hydroxides for the first time by anion exchange under a nitrogen atmosphere. The product caffeic acid-LDH has been characterized by powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), Scanning electron micrographs (SEM), indicating that the drug has been successfully intercalated into LDH. PMID:20454592

Wei, Yun; Gao, Yali; Zhang, Kai; Ito, Yoichiro

2010-01-01

202

Hybrid inorganic/organic composites of Mg-Al layered double hydroxides intercalated with citrate, malate, and tartrate prepared by co-precipitation  

SciTech Connect

Inorganic/organic composite materials composed of Mg-Al layered double hydroxides (Mg-Al LDHs) intercalated with citrate (C{sub 6}H{sub 5}O{sub 7}{sup 3-}), malate (C{sub 4}H{sub 4}O{sub 5}{sup 2-}), or tartrate (C{sub 4}H{sub 4}O{sub 6}{sup 2-}) anions were prepared by a co-precipitation technique and characterized by X-ray diffraction and compositional analyses. The molecular orientation of the organic component in the interlayer space was determined. At low intercalation levels, citrate ion was inclined at an angle of 26 deg. relative to the brucite-like layers of Mg-Al LDH. At higher solution concentrations, both the Mg(C{sub 6}H{sub 5}O{sub 7}){sup -} complex and free C{sub 6}H{sub 5}O{sub 7}{sup 3-} were isotropically oriented in the interlayer space. For both malate.Mg-Al LDH and tartrate.Mg-Al LDH, the organic anions were inclined at 26 deg. relative to the Mg-Al LDH layers regardless of anion concentration.

Kameda, Tomohito [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)], E-mail: kameda@env.che.tohoku.ac.jp; Takeuchi, Hidenori; Yoshioka, Toshiaki [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2009-04-02

203

Synthesis and characterization of sulfate and dodecylbenzenesulfonate intercalated zinc iron layered double hydroxides by one-step coprecipitation route  

NASA Astrophysics Data System (ADS)

Inorganic sulfate- and organic dodecylbenzenesulfonate (DBS)-intercalated zinc-iron layered double hydroxides (LDHs) materials were prepared by one-step coprecipitation method from a mixed salt solutions containing Zn(II), Fe(II) and Fe(III) salts. The as-prepared samples have been characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption, scanning electron microscopy (SEM), inductively coupled plasma emission spectroscopy (ICP), and Mössbauer spectroscopy (MS). The XRD analyses demonstrate the typical LDH-like layered structural characteristics of both products. The room temperature MS results reveal the characteristics of both the Fe(II) and Fe(III) species for SO 42--containing product, while only the Fe(III) characteristic for DBS-containing one. The combination characterization results and Rietveld analysis illustrate that the SO 42--containing product possesses the Green Rust two (GR2)-like crystal structure with an approximate chemical composition of [Zn 0.435·Fe II0.094·Fe III0.470·(OH) 2]·(SO 42-) 0.235·1.0H 2O, while the DBS-containing one exhibits the common LDH compound-like structure. The contact angle measurement indicates the evident hydrophobic properties of DBS-containing nanocomposite, compared with SO 42--containing product, due to the modification of the internal and external surface of LDHs by the organic hydrophobic chain of DBS.

Zhang, Hui; Wen, Xing; Wang, Yingxia

2007-05-01

204

Coexistence of adsorption and coagulation processes of both arsenate and NOM from contaminated groundwater by nanocrystallined Mg/Al layered double hydroxides.  

PubMed

In this study, nanocrystallined Mg/Al layered double hydroxides (LDH-CO3) and chloridion intercalated nanocrystallined Mg/Al LDHs (LDH-Cl) were synthesized and used for simultaneous removal of arsenic and natural organic matter (NOM) from contaminated groundwater. Humic acid (HA) was selected as a model compound of NOM. The maximum adsorption capacities of arsenate (As(V)) on LDH-CO3 and LDH-Cl are 44.66 and 88.30 mg/g, respectively, and those of HA on LDH-CO3 and LDH-Cl are 53.16 and 269.24 mg/g, respectively. It was found that more than 98% of arsenic and 94% of NOM were eliminated by LDH-Cl from both arsenic and NOM-rich groundwater, which is used as drinking water in Togtoh County, Inner Mongolia, China. The arsenic concentration declined from 231 to 4 ?g/L, which meets the drinking water standard. The adsorption mechanisms were determined by using X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and extended X-ray absorption fine structure spectroscopy techniques (EXAFS). The results showed that the removal of HA was mainly via surface complexation as well as coagulation at the surface of LDHs, while the adsorption of As(V) was mainly via ion-exchange process. The presence of HA exhibited little inhibiting effect on As(V) adsorption by occupying partial binding sites on LDH surfaces. Nevertheless, it could not affect the ion-exchange process of As(V) with the interlayer anions of LDHs. The removal of As(V) and HA can be carried out independently due to the different adsorption mechanisms. By integrating the experimental results, it is clear that LDH-Cl can be potentially used as a cost-effective material for the purification of both arsenic and NOM contaminated groundwater. PMID:23582669

Wu, Xilin; Tan, Xiaoli; Yang, Shitong; Wen, Tao; Guo, Hongli; Wang, Xiangke; Xu, Anwu

2013-08-01

205

Formation of Zn-rich phyllosilicate, Zn-layered double hydroxide and hydrozincite in contaminated calcareous soils  

SciTech Connect

Recent studies demonstrated that Zn-phyllosilicate- and Zn-layered double hydroxide-type (Zn-LDH) precipitates may form in contaminated soils. However, the influence of soil properties and Zn content on the quantity and type of precipitate forming has not been studied in detail so far. In this work, we determined the speciation of Zn in six carbonate-rich surface soils (pH 6.2 to 7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322 to 30090 mg/kg Zn). Based on 12 bulk and 23 microfocused extended X-ray absorption fine structure (EXAFS) spectra, the number, type and proportion of Zn species were derived using principal component analysis, target testing, and linear combination fitting. Nearly pure Zn-rich phyllosilicate and Zn-LDH were identified at different locations within a single soil horizon, suggesting that the local availabilities of Al and Si controlled the type of precipitate forming. Hydrozincite was identified on the surfaces of limestone particles that were not in direct contact with the soil clay matrix. With increasing Zn loading of the soils, the percentage of precipitated Zn increased from {approx}20% to {approx}80%, while the precipitate type shifted from Zn-phyllosilicate and/or Zn-LDH at the lowest studied soil Zn contents over predominantly Zn-LDH at intermediate loadings to hydrozincite in extremely contaminated soils. These trends were in agreement with the solubility of Zn in equilibrium with these phases. Sequential extractions showed that large fractions of soil Zn ({approx}30% to {approx}80%) as well as of synthetic Zn-kerolite, Zn-LDH, and hydrozincite spiked into uncontaminated soil were readily extracted by 1 M NH{sub 4}NO{sub 3} followed by 1 M NH{sub 4}-acetate at pH 6.0. Even though the formation of Zn precipitates allows for the retention of Zn in excess to the adsorption capacity of calcareous soils, the long-term immobilization potential of these precipitates is limited.

Jacquat, Olivier; Voegelin, Andreas; Villard, Andre; Marcus, Matthew A.; Kretzschmar, Ruben

2007-10-15

206

CO? sorbents with scaffold-like Ca-Al layered double hydroxides as precursors for CO? capture at high temperatures.  

PubMed

A highly stable high-temperature CO? sorbent consisting of scaffold-like Ca-rich oxides (Ca-Al-O) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing Ca-Al-NO? layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i)P)? and Ca(NO?)? with Ca(2+)/Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+)/Al(3+) ratios of 2:1. However, both LDH and Ca(OH)? phases were produced at higher ratios. Both TEM and SEM observations indicated that the Ca-Al-NO? LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based Ca-Al-O mixed oxide (CAMO), composed of CaO and Ca??Al??O??, was still present. The CAMO exhibited high specific surface areas (up to 191 m(2)g(-1)) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO? into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO? absorption at 700 °C. Thermogravimetric analysis results indicated that a CO? capture capacity of approximately 49 wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98% of the initial CO? capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments. PMID:23650194

Chang, Po-Hsueh; Lee, Tai-Jung; Chang, Yen-Po; Chen, San-Yuan

2013-06-01

207

New Varieties of Zinc Chromium Sulfate Lamellar Double Hydroxides  

NASA Astrophysics Data System (ADS)

The synthesis of zinc-chromium lamellar double hydroxides (LDHs) intercalated by sulfate anions is carried out with a one-step method that combines coprecipitation and anionic exchange. The materials obtained in a reactor containing a sodium sulfate solution are compared with those prepared from lithium, potassium, and ammonium sulfate solutions. The compounds are characterized by chemical analysis, powder X-ray diffraction, and infra-red spectroscopy. Depending on pH conditions, the washing process, and the nature of the monovalent cation, the sulfate intercalated compounds exhibit two 2H hexagonal varieties with different layer spacings d?8.9 Å and d?11 Å at room temperature; this last phase is related to the insertion of alkaline interlamellar cations. Under dry air, the loss of intercalated water leads to a 3R rhombohedral variety with d?8.2 Å. A second rhombohedral variety with d?10.9 Å is reversibly obtained from the "8.9 Å" phase under high relative humidity. These four [Zn-Cr-SO 4] LDHs differ by their stacking sequences and interlamellar distances and can be selectively obtained.

Khaldi, M.; De Roy, A.; Chaouch, M.; Besse, J. P.

1997-04-01

208

LDPE\\/Mg–Al layered double hydroxide nanocomposite: Thermal and flammability properties  

Microsoft Academic Search

Layered double hydroxides (LDHs) are new nanofillers which exhibit improved thermal and flammability properties in various kinds of polymer matrices. These materials have certain advantages over conventional metal hydroxides and also layered silicates so far as the flame retardancy is concerned. In this article, flammability and thermal properties of the nanocomposite based on low density polyethylene (LDPE) and Mg–Al based

Francis Reny Costa; Udo Wagenknecht; Gert Heinrich

2007-01-01

209

Study of 2,4-dichlorophenoxyacetic acid (2,4-D) removal by Cu-Fe-layered double hydroxide from aqueous solution  

NASA Astrophysics Data System (ADS)

The hydrotalcite-like compound of Cu-Fe-layered double hydroxide was studied as a potential adsorbent of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The nanoparticles of Cu-Fe layered double hydroxide were prepared by Cu/Fe molar ratio of 2:1 using a coprecipitation method at pH 8.5 and characterized by the X-ray powder diffraction (XRD), the Fourier transform infrared spectroscopy (FT-IR), the thermal gravimetric analysis (TGA) and the elemental analysis. The size and morphology of nanoparticles were examined by the transmission electron microscopy (TEM). The adsorption experiments on LDH, on the other hand, were conducted in three different procedures, namely, time-dependent, pH-dependent and temperature-dependent. Characterization of the adsorption products by the XRD method indicates that the intercalation of 2,4-D between the LDH layers has not occurred and the surface adsorption had taken place. The adsorption kinetic was tested for pseudo-first-order, pseudo-second-order, Elovich and Intra-particle diffusion kinetic models and the rate constants were calculated. The equilibrium adsorption data were described by Langmuir and Freundlich equations. It was observed that, the Langmuir isotherm slightly better fitted to the experimental data rather than that of Freundlich. In the adsorption experiments, the Gibbs free energy values, ?G°, the enthalpy, ?H°, and the entropy, ?S° were also determined.

Nejati, Kamellia; Davary, Soheila; Saati, Marziye

2013-09-01

210

Ordering double perovskite hydroxides by kinetically controlled aqueous hydrolysis.  

PubMed

The precipitation of crystals with stoichiometric and ordered arrangements of distinct metal cations often requires carefully designed molecular precursors and/or sufficient activation energy in addition to the necessary mass transport. Here, we study the formation of ordered double perovskite hydroxides, MnSn(OH)(6) and CoSn(OH)(6), of the generic chemical formula, BB'(OH)(6) (no A site), using kinetic control of aqueous hydrolysis from simple metal salt solutions. We find that the precipitation yields ordered compounds only when the B ion is Mn(II) or Co(II), and not when it is any other divalent transition metal ion, or Zn(II). The key step in forming the compounds is the prevention of rapid and uncontrolled hydrolysis of Sn(IV), and this is achieved by a fluoride counteranion. The two compounds, MnSn(OH)(6) and CoSn(OH)(6), are studied by high-resolution synchrotron X-ray diffraction and from the temperature dependence of magnetic behavior. From maximum entropy image restoration of the electron density and from Rietveld analysis, the degree of octahedral distortion and tilting and the small extent of anti-site disorder are determined. From the nonoverlapping electron density, we infer strongly ionic character of bonding. As the first magnetic study of such materials, we report simple paramagnetic behavior with no long-range magnetic order down to 2 K for the Mn(II) compound, while the cobalt compound presents uncompensated antiferromagnetic interactions, attributed to the single-ion anisotropy of octahedral Co(II). PMID:21381669

Neilson, James R; Kurzman, Joshua A; Seshadri, Ram; Morse, Daniel E

2011-04-01

211

Reversible thermally-responsive electrochemical energy storage based on smart LDH@P(NIPAM-co-SPMA) films.  

PubMed

A smart supercapacitor was fabricated by loading a thermosensitive polymer P(NIPAM-co-SPMA) onto the surface of NiAl-layered double hydroxide (LDH) nanowalls grown on a flexible Ni foil substrate, which displays temperature-triggered on-off ion channels for controlling the electrochemical behavior. PMID:23939250

Dou, Yibo; Pan, Ting; Zhou, Awu; Xu, Simin; Liu, Xiaoxi; Han, Jingbin; Wei, Min; Evans, David G; Duan, Xue

2013-10-01

212

A facile synthesis of strong near infrared fluorescent layered double hydroxide nanovehicles with an anticancer drug for tumor optical imaging and therapy.  

PubMed

In this work, a new multifunctional nanovehicle for tumor optical imaging and therapy was developed using Y2O3:Er(3+),Yb(3+) nanoparticles as near infrared fluorescent nanophosphors, and MgAl-layered double hydroxide (LDH) nanosheets as anticancer drug nanovehicles. Monodispersed Y2O3:Er(3+),Yb(3+) nanophosphors were readily synthesized by the urea assisted homogenous precipitation method. Hierarchically structured LDH nanosheets intercalated with an anticancer drug, fluorouracil (5FU), were deposited on the surface of Y2O3:Er(3+),Yb(3+)@SiO2 by a simple precipitation method followed by hydrothermal treatment. The resultant Y2O3:Er(3+),Yb(3+)@SiO2@LDH-5FU nanovehicles exhibit strong red upconversion fluorescence under the excitation of a 980 nm laser, which allows tracking of the nanovehicles after localization in cancer cells. A better anticancer efficiency was obtained over the nanovehicles than the free drug which can be attributed to their positively charged surfaces for favorable interaction with the negatively charged cell membranes. The multifunctional nanovehicles designed in this work are expected to be promising material candidates for simultaneous tumor optical imaging and therapy. PMID:23558400

Chen, Chunping; Yee, Lee Kim; Gong, Hua; Zhang, Yong; Xu, Rong

2013-05-21

213

Swelling and gel/sol formation of perchlorate-type layered double hydroxides in concentrated aqueous solutions of amino acid-related zwitterionic compounds.  

PubMed

ClO(4)(-)MgAl-LDH3, a MgAl (Mg/Al = 3) layered double hydroxide (LDH) containing perchlorate, swells and forms colloidal suspensions (sols) via the gel state in concentrated aqueous solutions of zwitterionic compounds related to amino acids. In total, 36 zwitterionic compounds with different molecular structures and additional functional groups were examined at various concentrations, and the sol-formation ability was judged by the transmittance (at ? = 589 nm) of the resulting suspensions. At low concentration, the obtained suspensions were turbid, with transmittances of ~0%. However, above the threshold concentration (0.3-1.0 M), osmotic swelling occurred and the transmittances of the suspensions increased sharply with increases in concentration to reach maximum values of 70-95%. The threshold concentration and maximum transmittance value depended on the structure and the location of the functional groups. The enhancement of the permittivity of water by the zwitterions and the formation of H-bond networks were assumed to be the reasons for the swelling phenomenon. Similar gel/sol formation was observed for ClO(4)(-)LDHs with Mg/Al = 2, Ni/Al = 2, 3, and Co/Al = 2 and some NO(3)(-)LDHs. Large ClO(4)(-)LDH films could be prepared by filtration of the colloidal suspensions followed by washing and drying processes. PMID:23409803

Iyi, Nobuo; Ishihara, Shinsuke; Kaneko, Yoshiro; Yamada, Hirohisa

2013-02-26

214

8-Hydroxypyrene-1,3,6-trisulphonate and octanesulphonate co-assembled layered double hydroxide and its controllable solid-state luminescence by hydrothermal synthesis  

NASA Astrophysics Data System (ADS)

8-Hydroxy-pyrene-1,3,6-trisulphonate (HPTS) and octanesulphonate (OS) have been co-intercalated into the ZnAl layered double hydroxide (LDH) host by a hydrothermal co-precipitation method, with samples denoted as HPTS ( x%)-OS/Zn 2Al-LDH ( x stands for the molar percentage content of HPTS with respect to total amount of HPTS and OS). The structure and chemical compositions of the as-prepared compounds were characterized by X-ray diffraction (XRD) and elemental analysis. The steady-state and time-decay fluorescent studies show that HPTS (2%)-OS/Zn 2Al-LDH has the optimal luminous emission and the longest fluorescent lifetime. Moreover, these samples exhibit controllable dual fluorescence between the blue and green regions upon changing the interlayer HPTS content, external pH values, and host-guest interaction, illustrating that these organic-inorganic samples have potential application in the field of tunable solid luminescent materials.

Dang, Sile; Yan, Dongpeng; Lu, Jun

2012-01-01

215

Layer-by-layer assembled multilayer films of exfoliated layered double hydroxide and carboxymethyl-?-cyclodextrin for selective capacitive sensing of acephatemet.  

PubMed

Novel organic-inorganic hybrid ultrathin films were fabricated by alternate assembly of cationic exfoliated Mg-Al-layered double hydroxide (LDH) nanosheets and carboxymethyl-?-cyclodextrin (CMCD) as a polyanion onto a glassy carbon electrode (GCE) via a layer-by-layer (LBL) approach. The multilayer films were then characterized by means of X-ray powder diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). These films were found to possess a long range stacking order in the normal direction of the substrate with a continuous and uniform morphology. Its electrochemical performance was systematically investigated. Our results demonstrate that such a newly designed (LDH/CMCD)n multilayer film, combining the individual properties of CMCD (a high supramolecule recognition and enrichment capability) together with LDH nanosheets (a rigid inorganic matrix), can be applied to a sensitive, simple, and label-free capacitive detection of acephatemet (AM). Molecular docking calculations further disclose that the selective sensing behavior toward AM may be attributed to the specific binding ability of CMCD to AM. Under the optimized conditions, the capacitive change of AM was proportional to its concentration ranging from 0.001 to 0.10?gmL(-1) and 0.1 to 0.8?gmL(-1) with a detection limit 0.6ngmL(-1) (S/N=3). Toward the goal for practical applications, this simple probe was further evaluated by monitoring AM in real samples. PMID:24912039

Gong, Jingming; Han, Xinmei; Zhu, Xiaolei; Guan, Zhangqiong

2014-11-15

216

Uptake properties of phosphate on a novel Zr-modified MgFe-LDH(CO(3)).  

PubMed

We prepared a novel Zr-modified MgFe-LDH(CO(3)) composite by adding a mixed solution of MgCl(2), FeCl(3), and ZrOCl(2) and another mixed solution of 1mol/dm(3) NaOH and 1mol/dm(3) Na(2)CO(3) to distilled water at a constant pH of 10. The composite exhibited only a poorly crystalline structure, resembling that of layered double hydroxides (LDH) from X-ray diffraction. The phosphate uptake is dependent on pH, decreasing with an increase in pH. This composite shows a much greater uptake of phosphate ions in P-enriched seawater (0.33mg-P/dm(3)) than amorphous zirconium oxide and MgFe-LDH(CO(3)). The uptake isotherm was fitted with a Freundlich relation. These phosphate-uptake behaviors closely resemble those of the relevant Zr-MgAl-LDH, which is estimated to be a composite of MgAl-LDH with amorphous zirconium hydroxide on the surface from X-ray absorption spectroscopy. Therefore, a similar structure of Zr-modified MgFe-LDH(CO(3)) composite probably causes the marked increase in phosphate uptake from P-enriched seawater. PMID:20621813

Chitrakar, Ramesh; Tezuka, Satoko; Hosokawa, Junji; Makita, Yoji; Sonoda, Akinari; Ooi, Kenta; Hirotsu, Takahiro

2010-09-01

217

Preferential growth of short aligned, metallic-rich single-walled carbon nanotubes from perpendicular layered double hydroxide film  

NASA Astrophysics Data System (ADS)

Direct bulk growth of single-walled carbon nanotubes (SWCNTs) with required properties, such as diameter, length, and chirality, is the first step to realize their advanced applications in electrical and optical devices, transparent conductive films, and high-performance field-effect transistors. Preferential growth of short aligned, metallic-rich SWCNTs is a great challenge to the carbon nanotube community. We report the bulk preferential growth of short aligned SWCNTs from perpendicular Mo-containing FeMgAl layered double hydroxide (LDH) film by a facile thermal chemical vapor deposition with CH4 as carbon source. The growth of the short aligned SWCNTs showed a decreased growth velocity with an initial value of 1.9 nm s-1. Such a low growth velocity made it possible to get aligned SWCNTs shorter than 1 ?m with a growth duration less than 15 min. Raman spectra with different excitation wavelengths indicated that the as-grown short aligned SWCNTs showed high selectivity of metallic SWCNTs. Various kinds of materials, such as mica, quartz, Cu foil, and carbon fiber, can serve as the substrates for the growth of perpendicular FeMoMgAl LDH films and also the growth of the short aligned SWCNTs subsequently. These findings highlight the easy route for bulk preferential growth of aligned metallic-rich SWCNTs with well defined length for further bulk characterization and applications.Direct bulk growth of single-walled carbon nanotubes (SWCNTs) with required properties, such as diameter, length, and chirality, is the first step to realize their advanced applications in electrical and optical devices, transparent conductive films, and high-performance field-effect transistors. Preferential growth of short aligned, metallic-rich SWCNTs is a great challenge to the carbon nanotube community. We report the bulk preferential growth of short aligned SWCNTs from perpendicular Mo-containing FeMgAl layered double hydroxide (LDH) film by a facile thermal chemical vapor deposition with CH4 as carbon source. The growth of the short aligned SWCNTs showed a decreased growth velocity with an initial value of 1.9 nm s-1. Such a low growth velocity made it possible to get aligned SWCNTs shorter than 1 ?m with a growth duration less than 15 min. Raman spectra with different excitation wavelengths indicated that the as-grown short aligned SWCNTs showed high selectivity of metallic SWCNTs. Various kinds of materials, such as mica, quartz, Cu foil, and carbon fiber, can serve as the substrates for the growth of perpendicular FeMoMgAl LDH films and also the growth of the short aligned SWCNTs subsequently. These findings highlight the easy route for bulk preferential growth of aligned metallic-rich SWCNTs with well defined length for further bulk characterization and applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr00043a

Zhao, Meng-Qiang; Tian, Gui-Li; Zhang, Qiang; Huang, Jia-Qi; Nie, Jing-Qi; Wei, Fei

2012-03-01

218

Preparation and controlled-release studies of a protocatechuic acid-magnesium/aluminum-layered double hydroxide nanocomposite  

PubMed Central

In the study reported here, magnesium/aluminum (Mg/Al)-layered double hydroxide (LDH) was intercalated with an anticancer drug, protocatechuic acid, using ion-exchange and direct coprecipitation methods, with the resultant products labeled according to the method used to produce them: “PANE” (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the ion-exchange method) and “PAND” (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the direct method), respectively. Powder X-ray diffraction and Fourier transform infrared spectroscopy confirmed the intercalation of protocatechuic acid into the inter-galleries of Mg/Al-LDH. The protocatechuic acid between the interlayers of PANE and PAND was found to be a monolayer, with an angle from the z-axis of 8° for PANE and 15° for PAND. Thermogravimetric and differential thermogravimetric analysis results revealed that the thermal stability of protocatechuic acid was markedly enhanced upon intercalation. The loading of protocatechuic acid in PANE and PAND was estimated to be about 24.5% and 27.5% (w/w), respectively. The in vitro release study of protocatechuic acid from PANE and PAND in phosphate-buffered saline at pH 7.4, 5.3, and 4.8 revealed that the nanocomposites had a sustained release property. After 72 hours incubation of PANE and PAND with MCF-7 human breast cancer and HeLa human cervical cancer cell lines, it was found that the nanocomposites had suppressed the growth of these cancer cells, with a half maximal inhibitory concentration of 35.6 ?g/mL for PANE and 36.0 ?g/mL for PAND for MCF-7 cells, and 19.8 ?g/mL for PANE and 30.3 ?g/mL for PAND for HeLa cells. No half maximal inhibitory concentration for either nanocomposite was found for 3T3 cells.

Barahuie, Farahnaz; Hussein, Mohd Zobir; Hussein-Al-Ali, Samer Hasan; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

2013-01-01

219

Effect of hydrothermal treatment on properties of Ni-Al layered double hydroxides and related mixed oxides  

NASA Astrophysics Data System (ADS)

The Ni-Al layered double hydroxides (LDHs) with Ni/Al molar ratio of 2, 3, and 4 were prepared by coprecipitation and treated under hydrothermal conditions at 180 °C for times up to 20 h. Thermal decomposition of the prepared samples was studied using thermal analysis and high-temperature X-ray diffraction. Hydrothermal treatment increased significantly the crystallite size of coprecipitated samples. The characteristic LDH diffraction lines disappeared completely at ca. 350 °C and a gradual crystallization of NiO-like mixed oxide was observed at higher temperatures. Hydrothermal treatment improved thermal stability of the Ni2Al and Ni3Al LDHs but only a slight effect of hydrothermal treatment was observed with the Ni4Al sample. The Rietveld refinement of powder XRD patterns of calcination products obtained at 450 °C showed a formation of Al-containing NiO-like oxide and a presence of a considerable amount of Al-rich amorphous component. Hydrothermal aging of the LDHs resulted in decreasing content of the amorphous component and enhanced substitution of Al cations into NiO-like structure. The hydrothermally treated samples also exhibited a worse reducibility of Ni 2+ components. The NiAl 2O 4 spinel and NiO still containing a marked part of Al in the cationic sublattice were detected in the samples calcined at 900 °C. The Ni2Al LDHs hydrothermally treated for various times and related mixed oxides obtained at 450 °C showed an increase in pore size with increasing time of hydrothermal aging. The hydrothermal treatment of LDH precursor considerably improved the catalytic activity of Ni2Al mixed oxides in N 2O decomposition, which can be explained by suppressing internal diffusion effect in catalysts grains.

Kovanda, František; Rojka, Tomáš; Bezdi?ka, Petr; Jirátová, Kv?ta; Obalová, Lucie; Pacultová, Kate?ina; Bastl, Zden?k; Grygar, Tomáš

2009-01-01

220

Preparation and controlled-release studies of a protocatechuic acid-magnesium/aluminum-layered double hydroxide nanocomposite.  

PubMed

In the study reported here, magnesium/aluminum (Mg/Al)-layered double hydroxide (LDH) was intercalated with an anticancer drug, protocatechuic acid, using ion-exchange and direct coprecipitation methods, with the resultant products labeled according to the method used to produce them: "PANE" (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the ion-exchange method) and "PAND" (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the direct method), respectively. Powder X-ray diffraction and Fourier transform infrared spectroscopy confirmed the intercalation of protocatechuic acid into the inter-galleries of Mg/Al-LDH. The protocatechuic acid between the interlayers of PANE and PAND was found to be a monolayer, with an angle from the z-axis of 8° for PANE and 15° for PAND. Thermogravimetric and differential thermogravimetric analysis results revealed that the thermal stability of protocatechuic acid was markedly enhanced upon intercalation. The loading of protocatechuic acid in PANE and PAND was estimated to be about 24.5% and 27.5% (w/w), respectively. The in vitro release study of protocatechuic acid from PANE and PAND in phosphate-buffered saline at pH 7.4, 5.3, and 4.8 revealed that the nanocomposites had a sustained release property. After 72 hours incubation of PANE and PAND with MCF-7 human breast cancer and HeLa human cervical cancer cell lines, it was found that the nanocomposites had suppressed the growth of these cancer cells, with a half maximal inhibitory concentration of 35.6 ?g/mL for PANE and 36.0 ?g/mL for PAND for MCF-7 cells, and 19.8 ?g/mL for PANE and 30.3 ?g/mL for PAND for HeLa cells. No half maximal inhibitory concentration for either nanocomposite was found for 3T3 cells. PMID:23737666

Barahuie, Farahnaz; Hussein, Mohd Zobir; Hussein-Al-Ali, Samer Hasan; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

2013-01-01

221

A comparative study of supercapacitive performances of nickel cobalt layered double hydroxides coated on ZnO nanostructured arrays on textile fibre as electrodes for wearable energy storage devices  

NASA Astrophysics Data System (ADS)

We demonstrated an efficient method for the fabrication of novel, flexible electrodes based on ZnO nanoflakes and nickel-cobalt layered double hydroxides (denoted as ZnONF/NiCoLDH) as a core-shell nanostructure on textile substrates for wearable energy storage devices. NiCoLDH coated ZnO nanowire (denoted as ZnONW/NiCoLDH) flexible electrodes are also prepared for comparison. As an electrode for supercapacitors, ZnONF/NiCoLDH exhibits a high specific capacitance of 1624 F g-1, which is nearly 1.6 times greater than ZnONW/NiCoLDH counterparts. It also shows a maximum energy density of 48.32 W h kg-1 at a power density of 27.53 kW kg-1, and an excellent cycling stability with capacitance retention of 94% and a Coulombic efficiency of 93% over 2000 cycles. We believe that the superior performance of the ZnONF/NiCoLDH hybrids is due primarily to the large surface area of the nanoflake structure and the open spaces between nanoflakes, both of which provide a large space for the deposition of NiCoLDH, resulting in reduced internal resistance and improved capacitance performance. Our results are significant for the development of electrode materials for high-performance wearable energy storage devices.We demonstrated an efficient method for the fabrication of novel, flexible electrodes based on ZnO nanoflakes and nickel-cobalt layered double hydroxides (denoted as ZnONF/NiCoLDH) as a core-shell nanostructure on textile substrates for wearable energy storage devices. NiCoLDH coated ZnO nanowire (denoted as ZnONW/NiCoLDH) flexible electrodes are also prepared for comparison. As an electrode for supercapacitors, ZnONF/NiCoLDH exhibits a high specific capacitance of 1624 F g-1, which is nearly 1.6 times greater than ZnONW/NiCoLDH counterparts. It also shows a maximum energy density of 48.32 W h kg-1 at a power density of 27.53 kW kg-1, and an excellent cycling stability with capacitance retention of 94% and a Coulombic efficiency of 93% over 2000 cycles. We believe that the superior performance of the ZnONF/NiCoLDH hybrids is due primarily to the large surface area of the nanoflake structure and the open spaces between nanoflakes, both of which provide a large space for the deposition of NiCoLDH, resulting in reduced internal resistance and improved capacitance performance. Our results are significant for the development of electrode materials for high-performance wearable energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04764d

Trang, Nguyen Thi Hong; Ngoc, Huynh Van; Lingappan, Niranjanmurthi; Kang, Dae Joon

2014-01-01

222

Nickel–iron layered double hydroxide (LDH): Textural properties upon hydrothermal treatments and application on dye sorption  

Microsoft Academic Search

NiFeCO3 hydrotalcites with Ni\\/Fe molar ratio of 3 were synthesized by co-precipitation method at constant pH, followed by hydrothermal treatment at various temperatures 85–180°C for 3–360h. The obtained materials were characterized by XRD analysis, FT-IR spectroscopy, SEM and TEM microscopy, TGA and BET techniques. The resulting materials were found to be similar to the hydrotalcite with a well-defined hexagonal morphology

Fatiha Boukraa Djellal Saiah; Bao-Lian Su; Nourredine Bettahar

2009-01-01

223

A new method for fast intercalation of bulk crown ether guest into LDH.  

PubMed

Fast intercalation of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) into the interlayer of Mg/Al-layered double hydroxide (Mg/Al-LDH) via a "one-step" reaction in formamide was carried out. Compared with swelling/restoration and ion-exchange reactions, this method can markedly decrease the reaction time (even shorter than 10 min), thus give high yield of the products and well-retain the hexagonal morphology of the starting LDH. The investigation of the reaction process demonstrated that the preceding combination of TECA and formamide accelerated the swelling of LDH, and the quasi-homogeneous colloidal system promoted the facile incorporation of TECA with the LDH sheets to cause their quick restoration. The obtained staging structure may originate from the flexibility of crown ether guest and LDH host layer, and the structural transformation from homogeneous to second-staging suggests the Daumas-Hérold model rarely observed in LDH system. The simple and fast one-step method can conveniently fabricate new multifunctional hybrid materials with combined advantages of the organic/inorganic intercalates plus those of LDH host. PMID:23141706

Ma, Shulan; Wang, Juan; Du, Li; Sun, Yahong; Gu, Qingyang; Sun, Genban; Yang, Xiaojing

2013-03-01

224

Intercalation and grafting of benzene derivatives into zinc-aluminum and copper-chromium layered double hydroxide hosts: an XPS monitoring study.  

PubMed

We report an original strategy to describe, via X-ray photoelectron spectroscopy (XPS) measurements, the interactions between the organic and the mineral sub-systems within a multifunctional hybrid material. A tunable layered double hydroxide (LDH) host system, either a Zn(2)Al- or Cu(2)Cr-hydrotalcite like compound, is modified with the insertion of the organic guest entities, 4-phenol-sulfonate (HBS) or -carboxylate (HBC). The resulting interactions are studied at two levels: after the organic molecules' insertion in the host LDH (ionic exchange between the LDH counter-ions and the organic anions) and after the condensation (grafting) of the organic species onto the mineral layers when thermally treated. For the inserted material, the main XPS results show a stabilization of the organic molecules within the mineral sheets via H bonding as found elsewhere with FTIR study, the mineral matrix being unchanged. The XPS signal of the organic molecules slightly changes with a widening of core peaks, attesting to some local surrounding modifications. When heating up the Zn(2)Al hybrid material, stronger interactions between organic and inorganic systems appeared from around 80 °C with some obvious electronic changes as monitored with the XPS S2p signal of the HBS guest molecules. At the same time, the PXRD pattern clearly shows a decrease of the basal spacing according to a two step contraction process which could be interpreted as a progressive organic molecule condensation onto the inorganic layers via iono-covalent bonds. A copper-chromium LDH is also studied to probe the same kind of interactions with the HBS molecules. The ability of distortion of such mineral material involves a peculiar process of contraction from 40 °C with the immediate and effective anchorage of organic molecules. PMID:21892473

Fleutot, Solenne; Dupin, Jean-Charles; Renaudin, G; Martinez, Hervé

2011-10-21

225

Layered Double Hydroxides Intercalated by Polyoxometalate Anions with Keggin (alpha-H(2)W(12)O(40)(6)(-)), Dawson (alpha-P(2)W(18)O(62)(6)(-)), and Finke (Co(4)(H(2)O)(2)(PW(9)O(34))(2)(10)(-)) Structures.  

PubMed

The pillaring of Mg(3)Al layered double hydroxides (LDHs) by the title polyoxometalates (POMs) was accomplished by ion exchange reaction of the LDH-hydroxide and -adipate precursors with the POM anion at ambient or refluxing temperatures. The structural, thermal and textural properties of the LDH-POM intercalates were elucidated based on XRD, FTIR, TEM, EDS, and N(2) adsorption-desorption studies. A gallery height of approximately 10 Å was observed for the LDH intercalated by the symmetrical Keggin POM, whereas two different gallery heights were found for the cylindrical Dawson (14.5 and 12.8 Å) and Finke (13.3 and 12.6 Å) anions, depending on the preparation temperature. The differences in POM orientations were rationalized in terms of different electrostatic and hydrogen-bonding interactions between the POM pillars and the LDH layers. Upon thermal treatment at >/=100 degrees C, the intercalated Dawson and Finke POM ions exhibited only one gallery orientation, regardless of synthesis conditions. The crystalline microporous structures were retained upon heating each LDH-POM intercalate in N(2) to 200 degrees C. Pillaring in all cases was accompanied by the formation of a poorly ordered Mg(2+)/Al(3+) salt impurity that formed on the external surfaces of the LDH crystals. PMID:11666853

Yun, Sang Kyeong; Pinnavaia, Thomas J.

1996-11-01

226

Intercalation of a molybdenum ?3-allyl dicarbonyl complex in a layered double hydroxide and catalytic performance in olefin epoxidation.  

PubMed

A Zn-Al layered double hydroxide (LDH) intercalated by [Mo(?(3)-C3H5)Cl(CO)2(bpdc)](2-) anions (bpdc = 2,2'-bipyridine-5,5'-dicarboxylate) has been prepared by coprecipitation from aqueous solution and characterised by various techniques. The one-pot method gives rise to a highly organised intercalate with an interlayer spacing of 18.3 Å and up to six (00l) basal reflections in the powder X-ray diffraction pattern. Spectroscopic studies (FT-IR, FT-Raman, (13)C CP MAS NMR and UV-Vis) confirm the presence of structurally intact [Mo(?(3)-C3H5)Cl(CO)2(bpdc)](2-) anions. The interlayer spacing of 18.3 Å indicates that the material contains a monolayer of guest anions positioned in such a way that the bpdc ligands are arranged with their longest dimension roughly perpendicular to the hydroxide layers of the host. Thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. The intracrystalline reactivity of intercalated dicarbonyl complexes was probed by using the hybrid nanocomposite as a precatalyst in the liquid phase epoxidation of cis-cyclooctene with tert-butylhydroperoxide as oxidant. Under the reaction conditions used, oxidative decarbonylation of the guest molecules takes place (with release of CO and CO2 as confirmed by on-line gas chromatography experiments) to give intercalated molybdenum oxide/bipyridine species that selectively catalyse the epoxidation reaction. The intracrystalline oxidative decarbonylation reaction is topotactic in nature. PMID:23588706

Gomes, Ana C; Bruno, Sofia M; Gamelas, Carla A; Valente, Anabela A; Abrantes, Marta; Gonçalves, Isabel S; Romão, Carlos C; Pillinger, Martyn

2013-06-21

227

Synthesis of Mg-Al-Fe-NO3 layered double hydroxides via a mechano-hydrothermal route  

NASA Astrophysics Data System (ADS)

Mg-Al-Fe-NO3 layered double hydroxides (LDHs) with a constant Mg2+/(Al3+ + Fe3+) molar ratio but varying Al3+/Fe3+ molar ratios were successfully synthesized by a mechano-hydrothermal (MHT) method from Mg(OH)2, Al(OH)3 and Fe(NO3)3·9H2O or Mg(NO3)2·6H2O as starting materials. The resulting LDHs (MHT-LDHs) were characterized by XRD, TEM, SEM, FT-IR, and zeta potential, size distribution and specific surface area analyses. It was found that pre-milling played a key role in the LDH formation during subsequent hydrothermal treatment. The MHT route is advantageous in terms of low reaction temperature compared with the conventional hydrothermal method, and the target products are of high crystallinity and good dispersion compared with the conventional mechanochemical (MC) method. The MHT-LDHs had higher specific surface area and zeta potential, and lower hydrodynamic diameter than LDHs obtained by MC method (MC-LDHs). Furthermore, the removal of Cr(VI) from aqueous solutions using the LDHs was examined, showing that the MHT-LDHs are of higher removal efficiency than MC-LDHs for the heavy metal pollutant.

Zhang, Fengrong; Du, Na; Li, Haiping; Liu, Jianqiang; Hou, Wanguo

2014-06-01

228

Cellular toxicity of inorganic hydroxide nanoparticles.  

PubMed

Layered double hydroxides (LDHs), anionic clays, have attracted increasing interest as nanovehicles for delivering genes, drugs, and bio-active molecules into cells. However, no attempts have been made to evaluate the potential undesirable effects of LDH nanoparticles. The cytotoxicity of LDHs with different chemical compositions (ZnAl- and MgAl-LDH) was systematically evaluated in various cell types, such as human normal cells, carcinoma cells, and red blood cells, by measuring cell viability, cell proliferation, membrane damage, and hemolytic effect. No significant cytotoxic effects could be seen in both cases, but ZnAl-LDH was determined to be slightly more toxic than MgAl-LDH in terms of membrane damage and hemolysis induction. It is, therefore, expected that LDHs could be promising candidates for novel inorganic drug delivery carriers. PMID:18047108

Choi, Soo-Jin; Oh, Jae-Min; Park, Taeun; Choy, Jin-Ho

2007-11-01

229

A facile synthesis of strong near infrared fluorescent layered double hydroxide nanovehicles with an anticancer drug for tumor optical imaging and therapy  

NASA Astrophysics Data System (ADS)

In this work, a new multifunctional nanovehicle for tumor optical imaging and therapy was developed using Y2O3:Er3+,Yb3+ nanoparticles as near infrared fluorescent nanophosphors, and MgAl-layered double hydroxide (LDH) nanosheets as anticancer drug nanovehicles. Monodispersed Y2O3:Er3+,Yb3+ nanophosphors were readily synthesized by the urea assisted homogenous precipitation method. Hierarchically structured LDH nanosheets intercalated with an anticancer drug, fluorouracil (5FU), were deposited on the surface of Y2O3:Er3+,Yb3+@SiO2 by a simple precipitation method followed by hydrothermal treatment. The resultant Y2O3:Er3+,Yb3+@SiO2@LDH-5FU nanovehicles exhibit strong red upconversion fluorescence under the excitation of a 980 nm laser, which allows tracking of the nanovehicles after localization in cancer cells. A better anticancer efficiency was obtained over the nanovehicles than the free drug which can be attributed to their positively charged surfaces for favorable interaction with the negatively charged cell membranes. The multifunctional nanovehicles designed in this work are expected to be promising material candidates for simultaneous tumor optical imaging and therapy.In this work, a new multifunctional nanovehicle for tumor optical imaging and therapy was developed using Y2O3:Er3+,Yb3+ nanoparticles as near infrared fluorescent nanophosphors, and MgAl-layered double hydroxide (LDH) nanosheets as anticancer drug nanovehicles. Monodispersed Y2O3:Er3+,Yb3+ nanophosphors were readily synthesized by the urea assisted homogenous precipitation method. Hierarchically structured LDH nanosheets intercalated with an anticancer drug, fluorouracil (5FU), were deposited on the surface of Y2O3:Er3+,Yb3+@SiO2 by a simple precipitation method followed by hydrothermal treatment. The resultant Y2O3:Er3+,Yb3+@SiO2@LDH-5FU nanovehicles exhibit strong red upconversion fluorescence under the excitation of a 980 nm laser, which allows tracking of the nanovehicles after localization in cancer cells. A better anticancer efficiency was obtained over the nanovehicles than the free drug which can be attributed to their positively charged surfaces for favorable interaction with the negatively charged cell membranes. The multifunctional nanovehicles designed in this work are expected to be promising material candidates for simultaneous tumor optical imaging and therapy. Electronic supplementary information (ESI) available: TEM images of Y2O3:Er3+,Yb3+@SiO2 synthesized by using different amounts of TEOS, and confocal scanning laser microscopy images (Z stack) of MCF-7 cells incubated with Y2O3:Er3+,Yb3+@SiO2@LDH-5FU for 30 min and 24 h. See DOI: 10.1039/c3nr00781b

Chen, Chunping; Yee, Lee Kim; Gong, Hua; Zhang, Yong; Xu, Rong

2013-05-01

230

Synthesis and characterisation of a new stable organo-mineral hybrid nanomaterial: 4-Chlorobenzenesulfonate in the zinc-aluminium layered double hydroxide  

SciTech Connect

4-Chlorobenzenesulfonate (4-CBS) was intercalated between layers of Zn-Al layered double hydroxides (LDHs). Two methods of incorporation were applied: (1) direct synthesis by coprecipitation of metal nitrates and sodium 4-CBS and (2) ion exchange of the LDH nitrate with the organic ion. The solids were characterized by X-ray diffraction and infrared spectroscopy. The direct method, effected at different pH values, led to a hybrid material with good degree of intercalation. In order to optimise the exchange conditions, particular attention was given to the effect of solution pH, 4-CBS/NO{sub 3} ratio and exchange temperature. The total exchange was successful and a new stable hybrid nanostructured material was obtained at pH 8 and with a 4-CBS concentration of 0.0028 M. This solid was further characterised by chemical and thermal analyses.

Lakraimi, Mohamed [Ecole Normale Superieure, B.P. S41, Marrakech 40001 (Morocco); Legrouri, Ahmed [School of Science and Engineering, Al Akhawayn University, P.O. Box 1871, Ifrane 53000 (Morocco)]. E-mail: legrouri@aui.ma; Barroug, Allal [Laboratoire de Chimie-Physique, Faculte des Sciences Semlalia, Universite Cadi Ayyad, B.P. 2390, Marrakech 40001 (Morocco); De Roy, Andre [Laboratoire des Materiaux Inorganiques, UPRES-A 6002, Universite Blaise Pascal, 63177 Aubiere-Cedex (France); Besse, Jean Pierre [Laboratoire des Materiaux Inorganiques, UPRES-A 6002, Universite Blaise Pascal, 63177 Aubiere-Cedex (France)

2006-09-14

231

Direct coating for layered double hydroxide/4,4'-diaminostilbene-2,2'-disulfonic acid nanocomposite with silica by seeded polymerization technique  

NASA Astrophysics Data System (ADS)

Organic ultraviolet (UV) ray absorbents have been used as sunscreen materials, but may pose a safety problem when used at high concentration. In order to prevent direct contact of organic UV rays absorbent by the human skin, an organic UV absorbent such as 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDSA) was intercalated into Zn 2Al-layered double hydroxide (Zn 2Al-LDHs) by coprecipiation reaction. The problem of deintercalation of organic molecules from LDHs by the anion exchange reaction with carbonate ion could be greatly depressed by forming a protection film of silica on the surface. Zn 2Al-LDH/DASDSA was directly coated with silica by means of a polymerization technique based on the Stöber method. The deintercalation behavior as well as UV-shielding properties were investigated for coated particles.

El-Toni, Ahmed Mohamed; Yin, Shu; Sato, Tsugio

2004-09-01

232

Mg–Al layered double hydroxides (LDHs) and their derived mixed oxides grown by laser techniques  

Microsoft Academic Search

Layered double hydroxides (LDHs) have been widely studied due to their applications as multifunctional materials, catalysts, host materials, anionic exchangers, adsorbents for environmental contaminants and for the immobilization of biological materials. As thin films, LDHs are good candidates for novel applications as sensors, corrosion resistant coatings or components in electro optical devices. For these applications, lamellar orientation-controlled film has to

A. Matei; R. Birjega; A. Nedelcea; A. Vlad; D. Colceag; M. D. Ionita; C. Luculescu; M. Dinescu; R. Zavoianu; O. D. Pavel

2011-01-01

233

The enhanced immune response of hepatitis B virus DNA vaccine using SiO2@LDH nanoparticles as an adjuvant.  

PubMed

Various approaches have been used to improve systemic immune response to infectious disease or virus, and DNA vaccination has been demonstrated to be one of these effective ways to elicit protective immunity against pathogens. Our previous studies showed that layered double hydroxides (LDH) nanoparticles could be efficiently taken up by the MDDCs and had an adjuvant activity for DC maturation. To further enhance the immune adjuvant activity of LDH, core-shell structure SiO2@LDH nanoparticles were synthesized with an average diameter of about 210 nm. And its high transfection efficiency in vitro was demonstrated by using GFP expression plasmid as model DNA. Exposing SiO2@LDH nanoparticles to macrophages caused a higher dose-dependent expression of IFN-?, IL-6, CD86 and MHC II, compared with SiO2 and LDH respectively. Furthermore, in vivo immunization of BALB/c mice indicated that, DNA vaccine loaded-SiO2@LDH nanoparticles not only induced much higher serum antibody response than naked DNA vaccine and plain nanoparticles, but also obviously promoted T-cell proliferation and skewed T helper to Th1 polarization. Additionally, it was proved that the caveolae-mediated uptake of SiO2@LDH nanoparticles by macrophage lead to macrophages activation via NF-?B signaling pathway. Our results indicate that SiO2@LDH nanoparticles could serve as a potential non-viral gene delivery system. PMID:24099705

Wang, Jin; Zhu, Rongrong; Gao, Bo; Wu, Bin; Li, Kun; Sun, Xiaoyu; Liu, Hui; Wang, Shilong

2014-01-01

234

Sorption of cesium, strontium, and yttrium radionuclides from the aqueous phase on layered double hydroxides  

Microsoft Academic Search

Sorption of 137Cs, 85,90Sr, and 90Y from aqueous solutions on the solid phase of layered double hydroxides (LDHs) and layered double oxides (LDOs) of various\\u000a compositions was studied. On the solid phase of Mg-Al and Cu-Al LDHs and Mg-Al LDO, the Sr and Cs radionuclides are very weakly\\u000a sorbed from aqueous solutions containing 10?5 M of the corresponding element (Cs+

S. A. Kulyukhin; E. P. Krasavina; I. V. Gredina; I. A. Rumer; L. V. Mizina

2008-01-01

235

Structural characterization and thermal properties of polyamide 6.6/Mg, Al/adipate-LDH nanocomposites obtained by solid state polymerization  

SciTech Connect

A new nanocomposite was obtained by dispersing an adipate-modified layered double hydroxide (Ad-LDH) with adipic acid and hexamethylene diamine. These samples were polymerized in the solid phase under a nitrogen flow for 200 min at 190 {sup o}C. The structural and compositional details of the nanocomposite were determined by powder X-ray diffraction (PXRD), fourier transform infrared (FTIR) spectroscopy, focused ion beam (FIB), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The PXRD patterns and FIB images show a partially intercalated and partially exfoliated dispersion of layered crystalline materials in the polyamide 6.6 matrix. The best dispersion level is achieved in polyamide 6.6/LDH nanocomposites with low LDH loading. Some residual tactoids and particle agglomerates are also evident at high concentration. The best thermal stability of the nanocomposites is shown by the sample with 0.1% LDH content, for which it is higher than that of pure polyamide. - Graphical abstract: A new nanocomposite was obtained by compounding an adipate-modified layered double hydroxides (LDH) with adipic acid and hexamethylene diamine. These samples were polymerized in the solid phase under a nitrogen flow for 200 min at 190 {sup o}C. The nanodispersion of LDH in polyamide 6.6 may be qualitatively estimated from the analysis and PXRD patterns and FIB images. The decomposition temperature in the nanocomposite with 0.1 % LDH increases significantly compared to that for pristine PA6.6. .

Herrero, M.; Benito, P.; Labajos, F.M. [GIR-QUESCAT-Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain); Rives, V., E-mail: vrives@usal.e [GIR-QUESCAT-Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain); Zhu, Y.D.; Allen, G.C. [Interface Analysis Centre, University of Bristol, Bristol BS2 8BS (United Kingdom); Adams, J.M. [School of Engineering and Computer Science, University of Exeter, Exeter EX4 4QF (United Kingdom)

2010-07-15

236

Degradability Enhancement of Poly(Lactic Acid) by Stearate-Zn3Al LDH Nanolayers  

PubMed Central

Recent environmental problems and societal concerns associated with the disposal of petroleum based plastics throughout the world have triggered renewed efforts to develop new biodegradable products compatible with our environment. This article describes the preparation, characterization and biodegradation study of poly(lactic acid)/layered double hydroxide (PLA/LDH) nanocomposites from PLA and stearate-Zn3Al LDH. A solution casting method was used to prepare PLA/stearate-Zn3Al LDH nanocomposites. The anionic clay Zn3Al LDH was firstly prepared by co-precipitation method from a nitrate salt solution at pH 7.0 and then modified by stearate anions through an ion exchange reaction. This modification increased the basal spacing of the synthetic clay from 8.83 Å to 40.10 Å. The morphology and properties of the prepared PLA/stearate-Zn3Al LDH nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TGA), tensile tests as well as biodegradation studies. From the XRD analysis and TEM observation, the stearate-Zn3Al LDH lost its ordered stacking-structure and was greatly exfoliated in the PLA matrix. Tensile test results of PLA/stearate-Zn3Al LDH nanocomposites showed that the presence of around 1.0–3.0 wt % of the stearate-Zn3Al LDH in the PLA drastically improved its elongation at break. The biodegradation studies demonstrated a significant biodegradation rate improvement of PLA in the presence of stearate-Zn3Al LDH nanolayers. This effect can be caused by the catalytic role of the stearate groups in the biodegradation mechanism leading to much faster disintegration of nanocomposites than pure PLA.

Eili, Mahboobeh; Shameli, Kamyar; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan

2012-01-01

237

Layer-by-layer assembly of Na9[EuW10O36]·32H2O and layered double hydroxides leading to ordered ultra-thin films: cooperative effect and orientation effect.  

PubMed

Well-ordered, ultra-thin films (UTFs) based on the hybrid assembly of Na(9)[EuW(10)O(36)]·32H(2)O (denoted as EuW(10)) and exfoliated MgAl layered double hydroxide (LDH) monolayers have been fabricated by utilising a layer-by-layer (LBL) technique. The assembly process was monitored by UV/Vis absorption and fluorescence spectroscopy measurements to get a stepwise and regular growth of the UTFs upon increasing the deposited cycles. In the resulting (EuW(10)/LDH)(n) UTFs, the intercalation of EuW(10) anions into LDH monolayers allows the UTFs to retain their optical properties. Meanwhile, LDH monolayers provide EuW(10) with a confined and protective microenvironment to isolate them from each other between adjacent layers. The UTFs exhibit a periodic, long-range, ordered structure. Anisotropic luminescence spectroscopy measurements show that the (EuW(10)/LDHs)(n) UTFs display well-defined red luminescence with an anisotropy value, r, of about 0.15. Therefore, the cooperative and orientation effects between the host layers and guest anions play significant roles for the improved properties of the (EuW(10)/LDHs)(n) UTFs. This work could benefit the design and fabrication of novel electro-optical devices based on the UTFs of hybrid materials. PMID:21837721

Xu, Junhua; Zhao, Shen; Han, Zhenzhen; Wang, Xiaoting; Song, Yu-Fei

2011-09-01

238

Preparation of melt-spun antimicrobially modified LDH/polyolefin nanocomposite fibers.  

PubMed

Layered double hydroxide (LDH) was synthesized and organically modified with camphorsulfonic acid (CSA) and ciprofloxacin. The thermal stability of CSA was improved remarkably under LDH shielding. A minimal inhibitory concentration of free CSA against tested bacteria was determined in order to define the essential quantity in LDH modification. The modified LDHs were melt-compounded with high density polyethylene and the prepared nanocomposites were further melt-spun using a piston-type spinning device. The melt-spun fibers were tested for their antimicrobial activity against Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Enterobacter cloacae, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. CSA integrated fibers show susceptibility against Gram-positive bacteria and ciprofloxacin integrated fibers showed activity against both Gram-positive and Gram-negative bacteria. PMID:24907731

Kutlu, Burak; Schröttner, Percy; Leuteritz, Andreas; Boldt, Regine; Jacobs, Enno; Heinrich, Gert

2014-08-01

239

Plane-wave density functional theory study on the structural and energetic properties of cation-disordered Mg-Al layered double hydroxides.  

PubMed

Periodic solid models have been employed to investigate the structural and energetic properties of cation-disordered Mg-Al layered double hydroxides (LDHs), including composition, ordering, and stacking pattern of layers. The geometry, lattice energy and density of states (DOS) of the periodic models were computed using the plane-wave pseudopotential implementation of density functional theory (DFT) with the virtual crystal approximation (VCA). The calculation results for the MgAl-Cl-LDH model show that a pure LDH phase is difficult to sustain when the Mg/Al ratio (R) is R > or = 4. The stability of the cation-disordered MgAl-Cl-LDH unit cell increases upon increasing R, owing to the decrease in the number of Al(III)-O-Al(III) linkages in the LDH sheets. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of MgAl-Cl-LDH receive contributions from the 3s and 3p orbitals of Mg and Al and the 2p orbitals of O and Cl, respectively, implying significant host-guest interactions. The increase of R leads to the decrease in electron density of 3s and 3p of metal cation and that of 2p in Cl. Consequently, the HOMO-LUMO energy gap as well as the systematical stability increase upon increasing R. From this point of view, it has been demonstrated that the cations distribute in an ordered arrangement with the absence of Al(III)-O-Al(III) linkages if R is in the low range (R = 2-3). It was also found that the 3R polytype is the most stable stacking pattern with the same Mg/Al ratio, owing to the fact that the conductive band energy levels decline with the increase of electron density of 3s and 3p of the metal cation in the 3R-stacking system. These findings agree well with the experimental results and provide a profound understanding of critical factors influencing the structure of LDHs, including metal composition and ordering, the stacking sequence, as well as the host-guest interactions. PMID:20550158

Yan, Hong; Wei, Min; Ma, Jing; Evans, David G; Duan, Xue

2010-07-15

240

[Removal of PO4(3-) from solution, wastewater and seawater by modification and granulation magnesium and aluminium layered double hydroxide].  

PubMed

Powder layered double hydroxide of Mg-Al LDH were prepared by hydrothermal technology with 500 kg x batch(-1), modified and granulated (MG Mg-Al CLDH) by deposition method. After the modification and granulation, the fixed bed can not be accumulated and clogged by the adsorbents. The PO4(3-) is removed from aqueous solution, wastewater and seawater by MG Mg-Al CLDH with column experiments. It shows that MG Mg-Al CLDH is an effective adsorbent. After removal, the water quality can satisfy with the first degree of integrated wastewater discharge or seawater standards. The mechanism of removal PO4(3-) is ion exchange and 'memory effect'. The breakthrough adsorption capacity of PO4(3-) from solution is 13.49 mg x g(-1), more than 6 times higher than that by Mg-Al LDH without modification. The exhausted MG Mg-Al CLDH can be desorbed with 0.1 mol x L(-1) NaOH and 3 mol x L(-1) NaCl and regenerated with 25% MgCl2. The regeneration rate is 126.24%. The breakthrough curves are influenced by bed depth, flow rate, initial concentration and initial pH. The adsorption processes are controlled by film diffusion. When the initial concentration is as low as 0.38 micromol x L(-1), PO4(3-) can be removed from seawater to satisfy with the first degree of seawater quality. So this work is very useful for the practical application of Mg-Al LDH and the removal of phosphorus. PMID:23798150

Xing, Kun; Wang, Hai-Zeng

2013-04-01

241

Bifunctional sensor of pentachlorophenol and copper ions based on nanostructured hybrid films of humic acid and exfoliated layered double hydroxide via a facile layer-by-layer assembly.  

PubMed

A new, highly sensitive bifunctional electrochemical sensor for the simultaneous determination of pentachlorophenol (PCP) and copper ions (Cu(2+)) has been developed, where organic-inorganic hybrid ultrathin films were fabricated by alternate assembly of humic acid (HA) and exfoliated Mg-Al-layered double hydroxide (LDH) nanosheets onto ITO substrates via a layer-by-layer (LBL) approach. The multilayer films were then characterized by means of UV-vis spectrometry, scanning electron microscopy (SEM), and atomic force microscope (AFM). These films were found to have a relatively smooth surface with almost equal amounts of HA incorporated in each cycle. Its electrochemical performance was systematically investigated. Our results demonstrate that such a newly designed (LDH/HA)n multilayer films, combining the individual properties of HA (dual recognition ability for organic herbicides and metal ions) together with LDH nanosheets (a rigid inorganic matrix), can be applied to the simultaneous analysis of PCP and Cu(II) without interference from each other. The LBL assembled nanoarchitectures were further investigated by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR), which provides insight for bifunctional sensing behavior. Under the optimized conditions, the detection limit was found to be as low as 0.4 nM PCP, well below the guideline value of PCP in drinking water (3.7 nM) set by the United States Environmental Protection Agency (U.S. EPA), and 2.0 nM Cu(2+), much below the guideline value (2.0 mg L(-1), ~31.2 nM) from the World Health Organization (WHO), respectively. Toward the goal for practical applications, this simple and cost-effective probe was further evaluated by monitoring PCP and Cu(II) in water samples. PMID:23764441

Yuan, Shuang; Peng, Dinghua; Hu, Xianluo; Gong, Jingming

2013-06-27

242

Removal of perchlorate in water by calcined MgAl-CO3 layered double hydroxides.  

PubMed

Perchlorate is widely known as an inorganic endocrine disruptor. In this study, MgAl-CO3 layered double hydroxides with different Mg/Al molar ratios were prepared using a coprecipitation method and followed by a calcination process at a temperature range of 300 to 700 degrees C. Results showed that the best synthesis conditions were a calcination temperature of 550 degrees C and Mg/Al molar ratio of 3. Further, the adsorbent and its adsorption product were characterized by x-ray diffraction, Fourier transform-infrared spectroscopy, and thermogravimetric-differential thermal analysis. The layered double hydroxides structures in the adsorbent were lost during calcination at 550 degrees C but were reconstructed subsequent to adsorption of perchlorate, indicating that the "memory effect" appeared to play an important role in perchlorate adsorption. The perchlorate adsorption pattern was best described by the pseudo-second-order kinetics model, while the Freundlich isotherms appropriately explained perchlorate adsorption data. PMID:23697237

Yang, Yiqiong; Gao, Naiyun; Deng, Yang; Yu, Guoping

2013-04-01

243

Synthesis and properties of Mg{sub 2}Al layered double hydroxides containing 5-fluorouracil  

SciTech Connect

A pharmaceutically active compound, 5-fluorouracil (5-FU) has been firstly intercalated into layered double hydroxide with the restructure method. Powder X-ray diffraction and spectroscopic analysis indicate that 5-FU molecule is stabilized in the host interlayer by electrostatic interaction and intermolecular interaction, and that the orientation of 5-FU is different when changing the pattern of aging treatment or the swelling agent. The release studies show that a rapid release of the drug during the first 40min is followed by a more sustained one, and that the total amount of drug released from hybrid material into the aqueous solution is almost 87% and 74% at pH 4 and 7, respectively. The studies mentioned above suggest that layered double hydroxide might be used as the basis of a tunable drug delivery carrier.

Wang Zhongliang [Faculty of Chemistry, Institute of Polyoxometalate Chemistry, Northeast Normal University, Number 138, Renmin Street, Changchun City, Jilin Province 130024 (China); Wang Enbo [Faculty of Chemistry, Institute of Polyoxometalate Chemistry, Northeast Normal University, Number 138, Renmin Street, Changchun City, Jilin Province 130024 (China)]. E-mail: wangenbo@public.cc.jl.cn; Gao Lei [Faculty of Chemistry, Institute of Polyoxometalate Chemistry, Northeast Normal University, Number 138, Renmin Street, Changchun City, Jilin Province 130024 (China); Xu Lin [Faculty of Chemistry, Institute of Polyoxometalate Chemistry, Northeast Normal University, Number 138, Renmin Street, Changchun City, Jilin Province 130024 (China)

2005-03-15

244

Magnetic, luminescent Eu-doped Mg-Al layered double hydroxide and its intercalation for ibuprofen.  

PubMed

A magnetic, luminescent Eu-doped Mg-Al layered double hydroxide with ibuprofen (IBU) intercalated in the gallery has been successfully prepared by a simple coprecipitation method. The physicochemical properties of the samples were well characterized by powder XRD, TEM, FTIR, TGA, inductively coupled plasma MS (ICP-MS), vibrating sample magnetometry (VSM), and fluorospectrophotometry. The results revealed that Fe(3)O(4) nanoparticles are coated on the surface of layered double hydroxides and the obtained (Mg(2)Al(0.95)Eu(0.05))(Fe)-(IBU) sample exhibits both superparamagnetic and luminescent properties, with a saturation magnetization value of 1.86?emu? g(-1) and a strong emission band at 610?nm, respectively. Additionally, it was found that the ibuprofen loading amount is about 31?% (w/w), and the intercalated ibuprofen possesses sustained release behavior when the magnetic, luminescent composite is immersed in simulated body fluid (SBF). PMID:21038324

Wang, Jun; Zhou, Jideng; Li, Zhanshuang; Song, Yanchao; Liu, Qi; Jiang, Zhaohua; Zhang, Milin

2010-12-27

245

Synthesis and properties of Mg 2Al layered double hydroxides containing 5-fluorouracil  

NASA Astrophysics Data System (ADS)

A pharmaceutically active compound, 5-fluorouracil (5-FU) has been firstly intercalated into layered double hydroxide with the restructure method. Powder X-ray diffraction and spectroscopic analysis indicate that 5-FU molecule is stabilized in the host interlayer by electrostatic interaction and intermolecular interaction, and that the orientation of 5-FU is different when changing the pattern of aging treatment or the swelling agent. The release studies show that a rapid release of the drug during the first 40 min is followed by a more sustained one, and that the total amount of drug released from hybrid material into the aqueous solution is almost 87% and 74% at pH 4 and 7, respectively. The studies mentioned above suggest that layered double hydroxide might be used as the basis of a tunable drug delivery carrier.

Wang, Zhongliang; Wang, Enbo; Gao, Lei; Xu, Lin

2005-03-01

246

Inclusion of poly-aromatic hydrocarbon (PAH) molecules in a functionalized layered double hydroxide  

Microsoft Academic Search

The internal surface of an Mg-Al layered double hydroxide has been functionalized by anchoring carboxy-methyl derivatized\\u000a ?-cyclodextrin cavities to the gallery walls. Neutral polyaromatic hydrocarbon (PAH) molecules have been included within the\\u000a functionalized solid by driving the hydrophobic aromatic molecules from a polar solvent into the less polar interior of the\\u000a anchored cyclodextrin cavities by a partitioning process. The optical

L. Mohanambe; S. Vasudevan

2006-01-01

247

Preparation and characterization of new Ca–Al–polycarboxylate layered double hydroxides  

Microsoft Academic Search

The synthesis and characterization of composite materials based on calcium–aluminum layered double hydroxides (Ca–Al-LDHs), intercalated with organic polycarboxylate (PC) polymers, is described. The PC polymers, which exhibit a “comb-like” architecture, contain ethylene oxide side chains of different lengths. They are intercalated between the cationic Ca–Al–OH-layers when tricalcium aluminate is rehydrated in the presence of PC polymers. The intercalation compounds are

J. Plank; Z. Dai; P. R. Andres

2006-01-01

248

Sorption of an anionic dye by uncalcined and calcined layered double hydroxides: a case study  

Microsoft Academic Search

Layered double hydroxides (LDHs) with a Mg\\/Al molar ratio of 2:1 were synthesized by using a co-precipitation method and their calcined products (CLDHs) were obtained by heating Mg\\/Al-LDHs at 500°C. Sorption of a weak acid dye, Brilliant Blue R (BBR), by LDHs and CLDHs indicated equilibrium time required for BBR sorption by CLDHs was less than 12h, regardless of initial

Mao-Xu Zhu; Yan-Ping Li; Mei Xie; Hui-Zhen Xin

2005-01-01

249

Stabilization of Co 2+ in layered double hydroxides (LDHs) by microwave-assisted ageing  

Microsoft Academic Search

Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis–UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at ?196°C. The best conditions found to preserve

M. Herrero; P. Benito; F. M. Labajos; V. Rives

2007-01-01

250

Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing  

Microsoft Academic Search

Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis-UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at -196 deg. C. The best conditions found

M. Herrero; P. Benito; F. M. Labajos; V. Rives

2007-01-01

251

Stabilization of Co2+ in layered double hydroxides (LDHs) by microwave-assisted ageing  

Microsoft Academic Search

Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at -196 °C. The best conditions found

M. Herrero; P. Benito; F. M. Labajos; V. Rives

2007-01-01

252

Bioinorganic clays: synthesis and characterization of amino- and polyamino acid intercalated layered double hydroxides  

Microsoft Academic Search

Negatively charged amino acids (aspartic acid, glutamic acid) and a related polymer, poly(a,b-aspartate), have been intercalated within the gallery spaces of layered double hydroxides. Synthesis of these bioinorganic nanocomposites was achieved via co- precipitation involving simultaneous formation of the inorganic layers and intercalation of the anionic species. In situ thermal polymerization of pre-intercalated aspartate monomers aords a second route to

Nicola T. Whilton; Paula J. Vickers; Stephen Mann

1997-01-01

253

Immobilization of enzymatic extract from Penicillium camemberti with lipoxygenase activity onto a hybrid layered double hydroxide  

Microsoft Academic Search

A Zn\\/Al layered double hydroxide was synthesized by alkaline co-precipitation with azelate ions (?OOC(CH2)7COO?). The interlayer space of the layered material is occupied by organic ions as confirmed by X-ray diffraction and FTIR spectroscopy. The resulting hybrid material was tested as support for Penicillium camemberti enzymatic extract, containing lipoxygenase (LOX) activity. The optimal condition for LOX immobilization is done with

Rogelio Morales Borges; Gregorio Guadalupe Carbajal Arizaga; Fernando Wypych

2009-01-01

254

Study on adsorption of glyphosate ( N-phosphonomethyl glycine) pesticide on MgAl-layered double hydroxides in aqueous solution  

Microsoft Academic Search

MgAl-layered double hydroxides with different interlayer anions (nitrate, carbonate and chloride) were evaluated for their abilities to adsorb the organic pesticide glyphosate (N-phosphonomethyl glycine, Gly). The adsorption isotherms of Gly on layered double hydroxides (LDHs) nitrate were described by the Langmuir equation at lower equilibrium concentration of Gly (Ce<1.0mmol\\/L), and the Gly adsorption capacity on LDHs increased with the layer

Feng Li; Yunfeng Wang; Qiaozhen Yang; David G. Evans; Claude Forano; Xue Duan

2005-01-01

255

Preparation of Tween 80-Zn/Al-Levodopa-Layered Double Hydroxides Nanocomposite for Drug Delivery System  

PubMed Central

We incorporated anti-Parkinsonian drug, levodopa (dopa), in Zn/Al-LDH by coprecipitation method to form dopa-LDH nanocomposite. Further coating of Tween-80 on the external surfaces of dopa-LDH nanocomposite was achieved through the oxygen of C=O group of Tween-80 with the layer of dopa-LDH nanocomposite. The final product is called Tween-dopa-LDH nanocomposite. The X-ray diffraction indicates that the Tween-dopa-LDH nanocomposite was formed by aggregation structure. From the TGA data, the Tween-80 loading on the surface of LDH and dopa-LDH was 8.6 and 7.4%, respectively. The effect of coating process on the dopa release from Tween-dopa-LDH nanocomposite was also studied. The release from Tween-dopa-LDH nanocomposite shows slower release compared to the release of the drug from dopa-LDH nanocomposite as done previously in our study, presumably due to the retarding shielding effect. The cell viability study using PC12 showed improved viability with Tween-80 coating on dopa-LDH nanocomposite as studied by mitochondrial dehydrogenase activity (MTT assay).

Kura, Aminu Umar; Hussein-Al-Ali, Samer Hasan; Hussein, Mohd Zobir; Fakurazi, Sharida

2014-01-01

256

Preparation of tween 80-zn/al-levodopa-layered double hydroxides nanocomposite for drug delivery system.  

PubMed

We incorporated anti-Parkinsonian drug, levodopa (dopa), in Zn/Al-LDH by coprecipitation method to form dopa-LDH nanocomposite. Further coating of Tween-80 on the external surfaces of dopa-LDH nanocomposite was achieved through the oxygen of C=O group of Tween-80 with the layer of dopa-LDH nanocomposite. The final product is called Tween-dopa-LDH nanocomposite. The X-ray diffraction indicates that the Tween-dopa-LDH nanocomposite was formed by aggregation structure. From the TGA data, the Tween-80 loading on the surface of LDH and dopa-LDH was 8.6 and 7.4%, respectively. The effect of coating process on the dopa release from Tween-dopa-LDH nanocomposite was also studied. The release from Tween-dopa-LDH nanocomposite shows slower release compared to the release of the drug from dopa-LDH nanocomposite as done previously in our study, presumably due to the retarding shielding effect. The cell viability study using PC12 showed improved viability with Tween-80 coating on dopa-LDH nanocomposite as studied by mitochondrial dehydrogenase activity (MTT assay). PMID:24782658

Kura, Aminu Umar; Hussein-Al-Ali, Samer Hasan; Hussein, Mohd Zobir; Fakurazi, Sharida

2014-01-01

257

ESR spectra and thermal diffusivity of Zn-Al layered double hydroxide  

NASA Astrophysics Data System (ADS)

Zn-Al-NO3-LDH was synthesized using the co-precipitation method at pH 7±0.1 and ratio Zn/Al=4. The heat treatment of LDH was studied by X-ray diffraction (XRD) and thermogravimetric analysis (TGA/DTG) to investigate the stability of the LDH structure. The in situ electron spin resonance (ESR) spectra of fresh LDH from room temperature up to 190 °C were obtained, which are due to the presence of nitrate radicals in LDH interlayer. ESR spectra of sintered LDH below 200 °C (ex situ ESR spectra) were investigated, which are also due to the nitrate radicals. However, at 200 °C and above, spectra were due to the oxygen vacancies of ZnO, which was formed during the thermal treatment of LDH. Thermal diffusivity of LDH as a function of in situ temperatures results in a nonlinear relation, which is due to the changing water content of LDH when temperature increases. However, thermal diffusivity of LDH as a function of sintered temperatures showed a linear relation and the slope of these data demonstrated the dependency between thermal diffusivity and water content of LDH below 200 °C. For temperature above 180 °C, the thermal diffusivity behavior was mainly due to the ZnO phase in LDH.

Ali Ahmed, Abdullah Ahmed; Abidin Talib, Zainal; Hussein, Mohd Zobir bin

2012-01-01

258

Efficient delivery of anticancer drug MTX through MTX-LDH nanohybrid system  

NASA Astrophysics Data System (ADS)

We have been successful to intercalate anticancer drug, methotrexate (MTX), into layered double hydroxides (LDHs), Mg2Al(OH)6(NO3)·0.1H2O, through conventional co-precipitation method. Layered double hydroxides (LDHs) are endowed with great potential for delivery vector, since their cationic layers lead to safe reservation of biofunctional molecules such as drug molecules or genes. And their ion exchangeability and solubility in acidic media (pH<4) give rise to the controlled release of drug molecules. Moreover, it has been partly confirmed that LDH itself is non-toxic and facilitate the cellular permeation. To check the toxicity of LDHs, the osteosarcoma cell culture lines (Saos-2 and MG-63) and the normal one (human fibroblast) were used for in vitro test. The anticancer efficacy of MTX intercalated LDHs (MTX-LDH nanohybrids) was also estimated in vitro by the bioassay such as MTT and BrdU (5-bromo-2-deoxyuridine) with the bone cancer cell culture lines (Saos-2 and MG-63). According to the toxicity test results, LDHs do not harm to both the normal and cancer cells upto the concentration of 500 ug/mL. The anticancer efficacy test for the MTX-LDH nanohybrids turn out to be much more effective in cell suppression compared to the MTX itself. According to the cell-line tests, the MTX-LDH shows same drug efficacy to the MTX itself in spite of the low concentration by ˜5000 times. Such a high cancer suppression effect of MTX-LDH hybrid is surely due to the excellent delivery efficiency of inorganic delivery vector, LDHs.

Oh, Jae-Min; Park, Man; Kim, Sang-Tae; Jung, Jin-Young; Kang, Yong-Gu; Choy, Jin-Ho

2006-05-01

259

Synthesis and characterization of layered double hydroxides (LDHs) with intercalated chromate ions  

Microsoft Academic Search

Chromate intercalated layered double hydroxides (LDHs) having the formula MII6M?III2(OH)16CrO4·4H2O (MII=Ca, Mg, Co, Ni, Zn with M?III=Al and MII=Mg, Co, Ni with M?III=Fe) have been prepared by coprecipitation. The products obtained are replete with stacking disorders. DIFFaX simulations show that the stacking disorders are of three kinds: (i) turbostratic disorder of an originally single layered hexagonal (1H) crystal, (ii) random

Srinivasa V. Prasanna; P. Vishnu. Kamath; C. Shivakumara

2007-01-01

260

Preparation and characterization of polystyrene (PS)\\/layered double hydroxides (LDHs) composite by a heterocoagulation method  

Microsoft Academic Search

Polystyrene (PS)\\/layered double hydroxides (LDHs) composites were prepared for the first time from LDHs aqueous suspension\\u000a and PS emulsion by electrostatic assembly. The morphology characterization based on XRD and TEM showed that the LDHs were\\u000a partially exfoliated in PS matrix. By using a reactive emulsifier, i.e., sodium 2-hydroxyl-3-(methacryloxy)propane-1-sulfonate\\u000a (HMPS), which was able to copolymerize with styrene, a strong polymer-LDHs platelets

Jintao Yang; Feng Chen; Yongchang Ye; Zhengdong Fei; Mingqiang Zhong

2010-01-01

261

The use of Mg/Al layered double hydroxide for color removal of textile wastewater.  

PubMed

Layered double hydroxide of Mg-Al-carbonate system (MACH) was prepared and its heat-treated product (MACHT) was obtained by calcination at 500 degrees C. The resulting materials were used as an adsorbent for removal of color from synthetic textile wastewater (STW) and textile wastewater (TWW). Batch kinetic study showed that these materials are an efficient adsorbent for textile dye. The maximum adsorption capacities between 16 to 32 mg of dyes per g of adsorbent was obtained by fitting the adsorption data to the Langmuir adsorption Isotherm. It was found that the adsorption capacity of MACHT is higher than MACH. PMID:11413839

Hussein, M Z; Zainal, Z; Yaziz, I; Beng, T C

2001-01-01

262

Mössbauer and XRD study of intercalated CaFe-layered double hydroxides  

NASA Astrophysics Data System (ADS)

N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

Sipiczki, Mónika; Kuzmann, Ern?; Pálinkó, István; Homonnay, Zoltán; Sipos, Pál; Kukovecz, Ákos; Kónya, Zoltán

2014-04-01

263

Synthesis and reversible hydration behavior of the thiosulfate intercalated layered double hydroxide of Zn and Al  

NASA Astrophysics Data System (ADS)

The thiosulfate-intercalated layered double hydroxide of Zn and Al undergoes reversible hydration with a variation in the relative humidity of the ambient. The hydrated and dehydrated phases, which represent the end members of the hydration cycle, both adopt the structure of the 3R1 polytype. In the intermediate range of relative humidity values (40-60%), the hydrated and dehydrated phases coexist. The end members of the hydration cycle adopt the structure of the same polytype, and vary only in their basal spacings. This points to the possibility that all the intermediate phases have a kinetic origin.

Radha, S.; Milius, Wolfgang; Breu, Josef; Kamath, P. Vishnu

2013-08-01

264

Double layer hydroxide minerals as host structures for bioorganic molecules. [Abstract only  

NASA Technical Reports Server (NTRS)

A central problem in molecular evolution concerns the selective concentration from dilute, multicomponent solution of source molecules into a reactive environment, where formation of larger molecular assemblages can take place. Minerals consisting of positively charged, separable metal hydroxide sheets have proven capable of these functions. This common structural type is represented by minerals such as pyroaurite (Mg-Fe(3+) hydroxide), hydrotalcite (Mg-Al), green rust Fe(2+)-Fe(3+) and others. Effective interlayer sorption is demonstrated for orthophosphate and condensed phosphates, anionic alkyl compounds, polypeptides, nucleic acids, cyanide complexes and glycolaldehyde phosphate, the latter shown to readily oligomerize to form and selectively retain racemic hexose -2, 4, 6-phosphates, preferentially of altrose (Pitsch, et al, 1993). The selective aldomerization and retention effects correlate with the charge distribution in the host mineral structure and the stereochemistry of the substrate molecules. Interaction between nucleic acid bases, and between the cyanide groups of glycolaldehyde phosphate nitrile at the low water activity in the mineral interlayer is indicated by doubling of the monomeric separation of the hydroxide mineral sheets.

Lee, Ton; Arrhenius, Meichia L.; Hui, Stella S.-Y.; Ring, Ken M.; Gedulin, Benjamin I.; Orgel, Leslie E.; Arrhenius, Gustaf

1994-01-01

265

Improved Succinic Acid Production in the Anaerobic Culture of an Escherichia coli pflB ldhA Double Mutant as a Result of Enhanced Anaplerotic Activities in the Preceding Aerobic Culture  

Microsoft Academic Search

Escherichia coli NZN111 is a pflB ldhA double mutant which loses its ability to ferment glucose anaerobically due to redox imbalance. In this study, two-stage culture of NZN111 was carried out for succinic acid production. It was found that when NZN111 was aerobically cultured on acetate, it regained the ability to ferment glucose with succinic acid as the major product

Hui Wu; Zhi-min Li; Li Zhou; Qin Ye

2007-01-01

266

Nickel-aluminum layered double hydroxides prepared via inverse micelles formation  

SciTech Connect

Nickel-aluminum layered double hydroxides have been prepared by conventional coprecipitation and by coprecipitation in the presence of a surfactant. The solids have been characterised by several physicochemical techniques. Calcination leads to formation of homogeneously dispersed mixed oxides, which have been characterised as well. The colour properties (lightness and chromaticity coordinates) of both series of solids (layered precursors and calcined ones) have been measured. It has been found that both the preparation method and the calcination treatment have an important effect on the luminosity (whiteness/darkness) of the solids, although the effect on the precise chromaticity coordinates (green/red and blue/yellow) is less marked. - Graphical abstract: Nickel-aluminum layered double hydroxides have been prepared by conventional coprecipitation and by coprecipitation in the presence of a surfactant. It has been found that both the preparation method and the calcination treatment have an important effect on the luminosity (whiteness/darkness) of the solids, although the effect on the precise chromaticity coordinates (green/red and blue/yellow) is less marked.

Perez-Bernal, Maria E.; Ruano-Casero, Ricardo J.; Benito, Fatima [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain); Rives, Vicente, E-mail: vrives@usal.e [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, 37008 Salamanca (Spain)

2009-06-15

267

Shape and size control of nano dispersed Mg/Al layered double hydroxide.  

PubMed

Controlling the shape and size of the layered inorganic-organic hybrid particles is a challenge with conventional methods of synthesis. The co-precipitation method has been modified to synthesize Mg/Al Layered double hydroxide by controlling the particle growth using ultrasonic wave at the time of nucleation. In this project, magnesium and aluminum ions were considered as model systems with carbonate anion as intercalating agent. The resulting particles are compared with those of LDHs produced by conventional co-precipitation method at constant pH. Powder X-ray diffraction confirmed formation of the layered double hydroxide phases having crystallite size 19-20 nm in both 'a' and 'c' crystallographic directions. Transmission electron microscope and dynamic light scattering revealed nano disperse hexagonal platelets with narrow size distribution and average size was around 48 nm. The modified method reduces the particle size, increases the surface charge, narrows down the size distribution and also reduces the aspect ratio of the particles. Therefore, it is suggested that low amplitude ultrasonic wave prevents the aggregation of the nuclei, thus restricting the particle growth and results in uniform size particles. PMID:19049206

Panda, H S; Srivastava, R; Bahadur, D

2008-08-01

268

Organo/layered double hydroxide nanohybrids used to remove non ionic pesticides.  

PubMed

The preparation and characterization of organo/layered double hydroxide nanohybrids with dodecylsulfate and sebacate as interlayer anion were studied in detail. The aim of the modification of the layered double hydroxides (LDHs) was to change the hydrophilic character of the interlayer to hydrophobic to improve the ability of the nanohybrids to adsorb non-ionic pesticides such as alachlor and metolachlor from water. Adsorption tests were conducted on organo/LDHs using variable pH values, contact times and initial pesticide concentrations (adsorption isotherms) in order to identify the optimum conditions for the intended purpose. Adsorbents and adsorption products were characterized several physicochemical techniques. The adsorption test showed that a noticeable increase of the adsorption of the non-ionic herbicides was produced. Based on the results, the organo/LDHs could be good adsorbents to remove alachlor and metolachlor from water. Different organo/LDHs complexes were prepared by a mechanical mixture and by adsorption. The results show that HTSEB-based complex displays controlled release properties that reduce metolachlor leaching in soil columns compared to a technical product and the other formulations. The release was dependent on the nature of the adsorbent used to prepare the complexes. Thus, it can be concluded that organo/LDHs might act as suitable supports for the design of pesticide slow release formulations with the aim of reducing the adverse effects derived from rapid transport losses of the chemical once applied to soils. PMID:21978582

Chaara, D; Bruna, F; Ulibarri, M A; Draoui, K; Barriga, C; Pavlovic, I

2011-11-30

269

Retention of heavy metals on layered double hydroxides thin films deposited by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Heavy metals are toxic and hazardous pollutants in the environment due to their nonbiodegradability and persistence, which can pose serious threats to living organisms. The ability of Mg-Al based layered double hydroxides (LDHs) thin films to retain heavy metals from aqueous solutions at different concentrations is a novel topic with prospects of attractive applications, such as detection of heavy metals. We report on the ability of a series of Mg-Al based layered double hydroxides thin films to detect Ni and Co cations in aqueous solutions. Uptake of heavy metals ions such as Ni2+, Co2+ from aqueous solutions was studied as function of contact time at a standard metal ion concentration. The LDHs thin films were deposited using pulsed laser deposition (PLD). The different adsorption mechanisms were studied in connection with different heavy metals used as probe cations. X-ray diffraction, atomic force microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Fourier transform infra-red spectroscopy were the techniques used for the investigation of as deposited and after heavy metals retention thin films.

Vlad, A.; Birjega, R.; Matei, A.; Luculescu, C.; Mitu, B.; Dinescu, M.; Zavoianu, R.; Pavel, O. D.

2014-05-01

270

Speciation of As(III)/As(V) in water samples by a magnetic solid phase extraction based on Fe3O4/Mg-Al layered double hydroxide nano-hybrid followed by chemiluminescence detection.  

PubMed

A novel magnetic solid phase extraction method was developed for the speciation of As(III)/As(V) in aqueous solutions utilizing Fe3O4-doped Mg-Al layered double hydroxide (LDH) as a nano-sorbent. The method is based on the separation and pre-concentration of As(V) by Fe3O4/Mg-Al LDH nano-hybrid prior to determination by a chemiluminescence (CL) technique. The CL route involves the oxidation of luminol by vanadomolybdoarsenate heteropoly acid in a basic media. Since the existing cations cannot be adsorbed by positively charged layers of the LDH and other potentially interferent anions had no considerable effect on the CL reaction, it provides a very selective and sensitive determination approach for As(V). The determination of total arsenic and hence indirectly As(III) involve the pre-oxidation of As(III) to As(V) by a mixture of hydrogen peroxide and potassium hydroxide. Several factors affecting the extraction and determination of the analyte were investigated and optimized. Under optimum conditions, the calibration graph was linear in the range of 5.0-5000ngL(-1). The limit of detection and enrichment factor was 2.0ngL(-1) and 80, respectively. The method was validated by the analysis of a standard reference material (NIST SRM 1643e), and successfully applied to the speciation of arsenic in several water samples with recoveries in the range of 93.3-106.7% for the spiked samples. PMID:25059142

Abdolmohammad-Zadeh, Hossein; Talleb, Zeynab

2014-10-01

271

Synthesis of Zn\\/Co\\/Fe-layered double hydroxide nanowires with controllable morphology in a water-in-oil microemulsion  

Microsoft Academic Search

The Zn\\/Co\\/Fe-layered double hydroxide nanowires were synthesized via a reverse microemulsion method by using cetyltrimethyl ammonium bromide (CTAB) \\/n-hexane\\/n-hexanol\\/water as Soft-Template. ZnSO4, CoSO4, Fe2(SO4)3 and urea were used as raw materials. The influence of reaction temperature, time, urea concentration and Cn (molar ratio of cetyltrimethyl ammonium bromide to water) on the structure and morphology of Zn\\/Co\\/Fe-layered double hydroxides was investigated.

Hongyu Wu; Qingze Jiao; Yun Zhao; Silu Huang; Xuefei Li; Hongbo Liu; Mingji Zhou

2010-01-01

272

Microwave-assisted melt reaction method for the intercalation of carboxylic acid anions into layered double hydroxides.  

PubMed

Carboxylic acid anions intercalated layered double hydroxides are currently gaining increasing interest due to their potential applications in pharmaceutical field for controlled drug release in novel tunable drug delivery systems. In this work different aliphatic carboxylic acid anions were intercalated into the interlayers of commercial as well as synthetically prepared layered double hydroxides, through a novel microwave mediated melt reaction approach. The volumetric nature of microwave dielectric heating was exploited in order to rapidly heat the intimate mixture of the lamellar inorganic precursor and the appropriate organic acid, at the melting temperature of the particular mono- or dicarboxylic acid used, reaching the intercalation in approximately two hours treatment. PMID:24779132

Rosa, Roberto; Leonelli, Cristina; Villa, Carla; Priarone, Giulia

2013-01-01

273

The effect of trivalent cations on the performance of Mg-M-CO(3) layered double hydroxides for high-temperature CO(2) capture.  

PubMed

The effect of trivalent cations on the performance of Mg-M-CO(3) (M=Al, Fe, Ga, Mn) layered double hydroxides (LDHs) for high-temperature CO(2) capture is systematically investigated for the first time. We demonstrate that the M(3+) determines the structure evolution of LDH derivatives under thermal treatment, and finally influences the CO(2) capture capacity. Very different calcination temperatures are required for the different LDHs to obtain their maximum CO(2) capture capacities. To have a clear understanding of the reason behind these big differences the physicochemical properties, thermal stability, and memory effect of the LDHs were investigated. Both the thermal stability and the memory effect of LDHs are greatly influenced by the type of trivalent cation. The CO(2) capture capacities were also evaluated under various conditions. Another important finding of this work is that the quasi-amorphous phase obtained by thermal treatment at the lowest possible temperature gives the highest CO(2) capture capacity. PMID:20607714

Wang, Qiang; Tay, Hui Huang; Ng, Desmond Jia Wei; Chen, Luwei; Liu, Yan; Chang, Jie; Zhong, Ziyi; Luo, Jizhong; Borgna, Armando

2010-08-23

274

Effect of Ni cations and microwave hydrothermal treatment on the related properties of layered double hydroxide-ethylene vinyl acetate copolymer composites.  

PubMed

The effect of Ni cations and synthetic methods on the crystallinity, morphology, thermal stability and hydrophobic properties of carbonate-containing layered double hydroxides (LDHs) was investigated. The conventional hydrothermal treatment (CHT) and microwave hydrothermal treatment (MHT) methods were used to synthesize LDHs. The microwave treatment LDHs (MgAl-MHT and NiMgAl-MHT) have higher crystallinity and smaller crystal sizes than the conventional hydrothermal treatment LDHs (MgAl-CHT and NiMgAl-CHT). IR results indicate that the interactions of both OH(-)-CO(3)(2-) and CO(3)(2-)-CO(3)(2-) in NiMgAl-MHT are weaker. Furthermore, the thermal decomposition of OH(-) and CO(3)(2-) in the NiMgAl-MHT sample occurred earlier and faster than that of other LDHs. The contact angle values indicate that NiMgAl-MHT has the highest hydrophobicity. The influences of the LDHs on the thermal degradation and flame retardance of ethylene vinyl acetate copolymer (EVA)-LDH composites have also been studied in detail. NiMgAl-MHT has the more homogeneous nano-dispersed layers in EVA matrix. All composites enhance the thermal stability compared with the pure EVA because of the release of H(2)O and CO(2). Flame retardance of NiMgAl-MHT-EVA was obviously higher than that of the pure EVA and other composites. PMID:21316061

Wang, Lili; Li, Bin; Yang, Mingfei; Chen, Chunxia; Liu, Yongsheng

2011-04-15

275

Effect of intercalated aromatic sulfonates on uptake of aromatic compounds from aqueous solutions by modified Mg-Al layered double hydroxide  

SciTech Connect

In this study, we utilized Mg-Al layered double hydroxide (Mg-Al LDH) modified by intercalation with three aromatic sulfonates-2,7-naphthalene disulfonate (2,7-NDS{sup 2-}), benzenesulfonate (BS{sup -}), and benzenedisulfonate (BDS{sup 2-})-for the uptake of two aromatics-1,3-dinitrobenzene (DNB) and anisole (AS)-from aqueous solution and determined the effect of the aromatic sulfonates on the uptake of these aromatics. We found that the electron-rich aromatic ring of the intercalated aromatic sulfonates such as 2,7-NDS{sup 2-} undergoes strong {pi}-{pi} stacking interactions with the electron-poorer benzene ring of DNB in aqueous solution, and these interactions result in a higher uptake of DNB by the modified Mg-Al LDHs. In contrast, the electron-poor aromatic ring of the aromatic sulfonates such as BDS{sup 2-} undergoes weak {pi}-{pi} stacking interactions with the electron-poorer benzene ring of DNB, and these interactions result in a lower uptake of DNB by the modified Mg-Al LDHs.

Kameda, Tomohito, E-mail: kameda@env.che.tohoku.ac.jp [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)] [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yamazaki, Takashi; Yoshioka, Toshiaki [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)] [Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2010-06-15

276

Radiation induced topotactic [2 + 2] dimerisation of acrylate derivatives among the layers of a CaFe layered double hydroxide followed by IR spectroscopy  

NASA Astrophysics Data System (ADS)

Various acrylates [E-phenylpropenoate, E-3(4?-nitrophenyl)propenoate, E-3(2?,5?-difluorphenyl)propenoate, E-3(2?-thienyl)propenoate, E-3(4?-imidazolyl)propenoate or E-2,3-dimethylpropenoate] were successfully intercalated into Ca(II)Fe(III) layered double hydroxide (CaFe-LDH) verified by a range of instrumental methods. The possible arrangements for the organic anions were suggested on the basis of basal spacing data, layer thickness and the dimensions of the quantum chemically optimised structures of the acrylate ions. Using the acrylate-CaFe-LDHs as reactant-filled nanoreactors, photoinitiated topotactic [2 + 2] cyclisation reactions followed by IR spectroscopy could be performed with many representatives [E-phenylpropenoate-, E-3(4?-nitrophenyl)propenoate-, E-3(2?,5?-difluorphenyl)propenoate- or E-3(2?-thienyl)propenoate-CaFe-LDHs] resulting in cyclobutane derivatives within the layers of the host material indicating that there were domains where the intercalated anions were in close proximity to each other and in proper arrangement for the reaction to occur.

Srankó, D. F.; Canton, S.; Enghdahl, A.; Muráth, Sz.; Kukovecz, Á.; Kónya, Z.; Sipiczki, M.; Sipos, P.; Pálinkó, I.

2013-07-01

277

Structural characterization and thermal and chemical stability of bioactive molecule-hydrotalcite (LDH) nanocomposites.  

PubMed

Layered double hydroxides (LDH) are versatile materials used for intercalating bioactive molecules, both in pharmaceutical and cosmetic fields, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability, and/or obtaining modified release properties. The properties of the intercalation compounds of Mg/Al_LDH and Zn/Al_LDH with different drugs and sunscreens, namely diclofenac, ketoprofen, gliclazide, retinoic acid, furosemide, para-aminobenzoic acid and 2-phenylbenzimidazolsulfonic (Eusolex) acid, have been studied by crystallographic, spectroscopic and thermogravimetric techniques and by solid state NMR, to shed light on their structure, their molecular interactions and their stability from the thermal and chemical viewpoint. The structural features were described with particular attention to the interaction between the organic and inorganic components and to the stability of the intercalation products. For the first time two synchrotron radiation powder diffraction patterns of organic-containing LDH were solved and refined by Rietveld methods to obtain an experimental crystal structure. PMID:23873340

Conterosito, Eleonora; Croce, Gianluca; Palin, Luca; Pagano, Cinzia; Perioli, Luana; Viterbo, Davide; Boccaleri, Enrico; Paul, Geo; Milanesio, Marco

2013-08-28

278

Mesoporous mixed metal oxides derived from P123-templated Mg-Al layered double hydroxides  

NASA Astrophysics Data System (ADS)

We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg-Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 °C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg-Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m 2/g, and wide distribution of pore size (2-18 nm). An investigation of the "memory effect" of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers.

Wang, Jun; Zhou, Jideng; Li, Zhanshuang; He, Yang; Lin, Shuangshuang; Liu, Qi; Zhang, Milin; Jiang, Zhaohua

2010-11-01

279

Boron removal by hydrotalcite-like, carbonate-free Mg–Al–NO 3-LDH and a rationale on the mechanism  

Microsoft Academic Search

Removal of boron from boric acid and tetraborate solutions by hydrotalcite (HT)-like, carbonate-free, Mg–Al–NO3-layered double hydroxide (LDH) was studied. Data from batch experiments were computed as a function of the adsorbent dose and contact time. Synthesis in CO2-free conditions provided a material with high anion exchange capacity and more than 95% adsorption could be achieved. The physical and structural properties

Ahmet Nedim Ay; Birgül Zümreoglu-Karan; Abidin Temel

2007-01-01

280

The intercalation of carboxylic acids into layered double hydroxides: a critical evaluation and review of the different methods  

Microsoft Academic Search

This review paper details the literature which is currently available concerning the intercalation of aliphatic and aromatic mono- and dicarboxylic acids into layered double hydroxides (LDHs) and their calcined oxides (LDOs). We present a critical overview of the major synthetic routes and detail, where possible, the main mechanisms of intercalation. The structure of the intercalates formed in the various methods

Simon Carlino

1997-01-01

281

Synthesis of Zn/Co/Fe-layered double hydroxide nanowires with controllable morphology in a water-in-oil microemulsion  

SciTech Connect

The Zn/Co/Fe-layered double hydroxide nanowires were synthesized via a reverse microemulsion method by using cetyltrimethyl ammonium bromide (CTAB) /n-hexane/n-hexanol/water as Soft-Template. ZnSO{sub 4}, CoSO{sub 4}, Fe{sub 2}(SO{sub 4}){sub 3} and urea were used as raw materials. The influence of reaction temperature, time, urea concentration and Cn (molar ratio of cetyltrimethyl ammonium bromide to water) on the structure and morphology of Zn/Co/Fe-layered double hydroxides was investigated. The samples were characterized using Transmission Electron Microscopy (TEM), Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD) and Infrared Absorption Spectrum (IR). The results indicate that higher temperature is beneficial to the formation of layered double hydroxides, but particles apart from nanowires could be produced if temperature is up to 120 deg. C. By varying the temperature, reaction time, urea concentration and Cn, we got the optimum conditions of synthesizing uniform Zn/Co/Fe-layered double hydroxide nanowires: 100 deg. C, more than 12 h, Cn: 30-33, urea concentration: 0.3 M.

Wu Hongyu; Jiao Qingze [School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081 (China); Zhao Yun, E-mail: zhaoyun@bit.edu.cn [School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081 (China); Huang Silu; Li Xuefei; Liu Hongbo; Zhou Mingji [School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081 (China)

2010-02-15

282

Friction behavior of Mg-Al-CO3 layered double hydroxide prepared by magnesite  

NASA Astrophysics Data System (ADS)

In this paper, Mg-Al-CO3 LDH was prepared by magnesite under chemical precipitation and hydrothermal methods. In order to improve the dispersion of LDH in base oil, the as-prepared sample was modified with sodium laurate. The obtained material (GMAC-LDH) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry and thermo gravimetric analyzer (DSC-TGA) and scanning electron microscope (SEM). The results show that the modified LDH has platelet morphology with a near hexagon shape. In addition, the tribological properties of GMAC-LDH were evaluated by four-ball friction tester and gear tester. As a lubricant, GMAC-LDH possesses an excellent property on reducing friction and wear of friction pair. The results of friction tests indicated that the friction coefficient, diameter of wear scar and power consumption of the oil with GMAC-LDH was reduced by 11.0%, 8.5% and 2.1% as compared with that of base oil.

Wang, Xiaobo; Bai, Zhimin; Zhao, Dong; Zhao, Fuyan

2013-07-01

283

DOUBLE SHELL TANK (DST) HYDROXIDE DEPLETION MODEL FOR CARBON DIOXIDE ABSORPTION  

SciTech Connect

This document generates a supernatant hydroxide ion depletion model based on mechanistic principles. The carbon dioxide absorption mechanistic model is developed in this report. The report also benchmarks the model against historical tank supernatant hydroxide data and vapor space carbon dioxide data. A comparison of the newly generated mechanistic model with previously applied empirical hydroxide depletion equations is also performed.

OGDEN DM; KIRCH NW

2007-10-31

284

Synthesis and characterization of layered double hydroxides with a high aspect ratio  

SciTech Connect

A new route for synthesis of Mg/Al layered double hydroxide (Mg{sub 6}Al{sub 2}(OH){sub 16}(CO{sub 3}).4H{sub 2}O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1-6 {mu}m and the thickness at ca. 35-60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO{sub 3} {sup -} and CO{sub 3} {sup 2-} keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio.

Tao, Qi [Department of Chemistry, Institute of Nano-Chemistry, Jinan University, Guangzhou 510632 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Zhang Yuanming [Department of Chemistry, Institute of Nano-Chemistry, Jinan University, Guangzhou 510632 (China)]. E-mail: tzhangym@vip.163.com; Zhang Xiang [Department of Chemistry, Institute of Nano-Chemistry, Jinan University, Guangzhou 510632 (China); Yuan Peng [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); He Hongping [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China)]. E-mail: hehp@gig.ac.cn

2006-03-15

285

Methotrexate intercalated layered double hydroxides with different particle sizes: structural study and controlled release properties.  

PubMed

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 300 nm. 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. PMID:24632036

Zhang, Xiao-Qing; Zeng, Mei-Gui; Li, Shu-Ping; Li, Xiao-Dong

2014-05-01

286

Mechanochemical approach to get layered double hydroxides: Mechanism explore on crystallite growth  

NASA Astrophysics Data System (ADS)

In this paper, the mechanochemical approach, which includes solid state reactions and hydrothermal treatment, has been proposed to synthesize magnesium-aluminum-layered double hydroxides (Mg-Al-LDHs). Specially, the reaction process of solid state reactions has been explored, and it presents that crystallite growth is the rate-controlling process. The hydrothermal treatment is performed after solid state reactions, on one hand, the crystallinity and monodispersity of final LDHs particles can be improved, on the other hand, such treatment can tailor the particle size efficiently. Furthermore, the relationship between particle size and hydrothermal conditions (time and temperature) has been systematically investigated, which indicates that the particle size and monodispersity can be effectively controlled. The crystallite growth along a-b plane and c-axis has been emphatically discussed, and the results show that under relatively low temperatures such as 100 °C, the gradual growth along c-axis has been found in the range of 48 h, and high temperatures will hider its growth on the contrary. Crystal growth along a-b plane could be accelerated by higher hydrothermal temperature and longer treatment time. Our studies also show that during the hydrothermal treatment, such events as aggregation, disaggregation and particle growth, occur in series or in parallel with time. At last, the Mg-Al-CO3-LDHs samples (synthesized at 100 °C for 24, 36 and 48 h) which were acid activated by HCOOH were used to adsorb fluoride ions present in aqueous solution.

Zeng, Mei-Gui; Huo, Xiao-Lei; Liu, Su-Qing; Li, Shu-Ping; Li, Xiao-Dong

2014-02-01

287

Morphologies developed by the drying of droplets containing dispersed and aggregated layered double hydroxide platelets.  

PubMed

Despite much interest in the structures formed from droplets of suspension as they dry, there are few studies involving plate-like particles. Layered double hydroxide suspensions were prepared with pH adjusted to give well-dispersed and flocculated variants that were characterised by sedimentation and rheology measurements. In the well-dispersed suspension, the three-phase boundary was pinned and radial flow created a peripheral wall. The platelet structure involved local flat packing but was replete with scrolls that result from the recirculation flows in the droplets as they dry. In contrast, the flocculating suspension produced flatter droplet relics and the microstructure consisted of ordered domains which were disoriented with respect to each other. Although of scientific interest, the control of these structures will make it possible to use direct ink-jet printing to build 3D shapes for the preparation of aligned, ordered nanocomposites based on plate-like particles in which platelet preferred orientation mimics the structures found in nacre. PMID:23375870

Zhang, Yan; Evans, Julian R G

2013-04-01

288

Preparation of layered double hydroxide/chlorophyll a hybrid nano-antennae: a key step.  

PubMed

In the first step to obtain an efficient nano-antenna in a bottom-up approach, new hybrid materials were synthesized using a set of layered double hydroxides (LDHs) with basic properties and pure chlorophyll a (Chl a). The stability of the adsorbed monolayer of Chl a was shown to be dependent on the nature and the ratio of the different metal ions present in the LDHs tested. The hybrid materials turned out to be adequate for stabilizing Chl a on Mg/Al LDHs for more than a month under ambient conditions while a limited catalytic decomposition was observed for the Ni/Al LDHs leading to the formation of pheophytin. These changes were followed by namely XRD, DR-UV-vis and fluorescence spectroscopies of the hybrid antennae and of the solutions obtained from their lixiviation with acetone or diethylether. On Mg/Al hydrotalcites the stability of the adsorbed Chl a was equivalent for values of the metal atom ratio ranging from 2 to 4. The latter hybrids should constitute a good basis to form efficient nanoscale light harvesting units following intercalation of selected dyes. This work describes an efficient preparation of Chl a that allows scale-up as well as the obtention of a stable Chl a monolayer on the surface of various LDHs. PMID:24676400

Sommer Márquez, Alicia E; Lerner, Dan A; Fetter, Geolar; Bosch, Pedro; Tichit, Didier; Palomares, Eduardo

2014-07-21

289

An acetylcholinesterase biosensor based on graphene-gold nanocomposite and calcined layered double hydroxide.  

PubMed

In this study, a novel acetylcholinesterase-based biosensor was fabricated. Acetylcholinesterase (AChE) was immobilized onto a glassy carbon electrode (GCE) with the aid of Cu-Mg-Al calcined layered double hydroxide (CLDH). CLDH can provide a bigger effective surface area for AChE loading, which could improve the precision and stability of AChE biosensor. However, the poor electroconductibility of CLDHs could lead to the low sensitivity of AChE biosensor. In order to effectively compensate the disadvantages of CLDHs, graphene-gold nanocomposites were used for improving the electron transfer rate. Thus, the graphene-gold nanocomposite (GN-AuNPs) was firstly modified onto the GCE, and then the prepared CLDH-AChE composite was immobilized onto the modified GCE to construct a sensitive AChE biosensor for pesticides detection. Relevant parameters were studied in detail and optimized, including the pH of the acetylthiocholine chloride (ATCl) solution, the amount of AChE immobilized on the biosensor and the inhibition time governing the analytical performance of the biosensor. The biosensor detected chlorpyrifos at concentrations ranging from 0.05 to 150?g/L. The detection limit for chlorpyrifos was 0.05?g/L. PMID:24731819

Zhai, Chen; Guo, Yemin; Sun, Xia; Zheng, Yuhe; Wang, Xiangyou

2014-05-10

290

Deconstruction of Lignin Model Compounds and Biomass-Derived Lignin using Layered Double Hydroxide Catalysts  

SciTech Connect

Lignin is an underutilized value stream in current biomass conversion technologies because there exist no economic and technically feasible routes for lignin depolymerization and upgrading. Base-catalyzed deconstruction (BCD) has been applied for lignin depolymerization (e.g., the Kraft process) in the pulp and paper industry for more than a century using aqueous-phase media. However, these efforts require treatment to neutralize the resulting streams, which adds significantly to the cost of lignin deconstruction. To circumvent the need for downstream treatment, here we report recent advances in the synthesis of layered double hydroxide and metal oxide catalysts to be applied to the BCD of lignin. These catalysts may prove more cost-effective than liquid-phase, non-recyclable base, and their use obviates downstream processing steps such as neutralization. Synthetic procedures for various transition-metal containing catalysts, detailed kinetics measurements using lignin model compounds, and results of the application of these catalysts to biomass-derived lignin will be presented.

Chmely, S. C.; McKinney, K. A.; Lawrence, K. R.; Sturgeon, M.; Katahira, R.; Beckham, G. T.

2013-01-01

291

From layered double hydroxide to spinel nanostructures: facile synthesis and characterization of nanoplatelets and nanorods.  

PubMed

Mg-Al spinel (MgAl2O4) nanorods and nanoplatelets transformed from Mg-Al layered double hydroxide (Mg-Al-LDHs) were synthesized via a combined hydrothermal method and calcination route using Al(NO3).9H2O and Mg(NO3)2.6H2O as raw materials. The nanorods and nanoplatelets were characterized by means of physical techniques, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microcopy (HRTEM), selected-area electron diffraction (SAED), Fourier transform infrared spectra (FT-IR), thermogravimetric (TG), and nitrogen adsorption-desorption isotherms. XRD patterns reveal that the Mg-Al-LDHs nanostructures were obtained under a hydrothermal reaction temperature of 200 degrees C and Mg-Al spinel nanostructures were fabricated via calcination of the Mg-Al-LDHs nanostructures at 750 degrees C. It can be seen from TEM that the sizes of the Mg-Al-LDHs nanoplatelets were about 20-40 nm and the diameters of the MgAl2O4 nanorods were ca. 6 nm. The HRTEM images indicate that the crystal lattice spaces of the MgAl2O4 nanorods and nanoplatelets are 0.282 and 0.287 nm, respectively. PMID:16821857

Sun, Genban; Sun, Lingna; Wen, He; Jia, Zhiqian; Huang, Kunlin; Hu, Changwen

2006-07-13

292

Catalytic performance of Ni-Al layered double hydroxides in CO purification processes  

NASA Astrophysics Data System (ADS)

Ni-Al layered double hydroxides with Ni2+/Al3+ molar ratios of 1.5 and 3.0 have been synthesized by co-precipitation and studied as catalyst precursors for purification of CO-containing gas-mixtures by means of CO oxidation to CO2 and conversion of CO by water vapor (water-gas shift reaction). The influence of the alkali additives (K+ ions) on the water-gas shift activity has been also examined. It was established that the catalytic activity of both reactions increases with the temperature and the nickel content. Hypothetic schemes are proposed about activation of the catalysts in the WGSR and CO oxidation including redox Ni2+ ? Ni3+ transition on the catalyst surface. The activity in WGSR is positively affected by the presence of potassium promoter, depending on its amount. The sample with higher nickel loading is the most effective catalyst as for CO oxidation as well as for WGSR at intermediate temperatures after potassium promotion.

Gabrovska, M.; Idakiev, V.; Tenchev, K.; Nikolova, D.; Edreva-Kardjieva, R.; Crisan, D.

2013-12-01

293

Characterization and friction performance of Zn/Mg/Al-CO3 layered double hydroxides  

NASA Astrophysics Data System (ADS)

Zn/Mg/Al-CO3 layered double hydroxides (LDHs) were synthesized by coprecipitation method and the products were surface modified by oleic acid. The materials were characterized by X-ray diffraction, scanning electron microscopy, wavelength dispersive X-ray fluorescence, Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The tribological property of LDHs in base oil was studied by using a four-ball friction test machine. The results showed that Zn/Mg/Al-CO32--LDHs had high crystallinity and hexagonal lamellar structure with average disk diameter of about 150 nm and the chemical formula was Zn0.40Mg0.28Al0.32(OH)2(CO3)0.16·0.28H2O. The interaction between LDHs and oleic acid molecules was based on chemisorption with a monomolecular layer on the surface of laminate. The friction test results indicated that base oil with 0.5 wt% LDHs performed optimal antifriction property and the friction coefficient and wear scar diameter reduced by 68.6% and 24.6% respectively.

Li, Shuo; Bai, Zhimin; Zhao, Dong

2013-11-01

294

Synthesis and characterization of layered double hydroxides with a high aspect ratio  

NASA Astrophysics Data System (ADS)

A new route for synthesis of Mg/Al layered double hydroxide (Mg 6Al 2(OH) 16(CO 3)·4H 2O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1-6 ?m and the thickness at ca. 35-60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO 3- and CO 32- keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio.

Tao, Qi; Zhang, Yuanming; Zhang, Xiang; Yuan, Peng; He, Hongping

2006-03-01

295

Mesoporous mixed metal oxides derived from P123-templated Mg-Al layered double hydroxides  

SciTech Connect

We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg-Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 {sup o}C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg-Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m{sup 2}/g, and wide distribution of pore size (2-18 nm). An investigation of the 'memory effect' of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers. - Graphical abstract: Ordered mesoporous Mg-Al MMOs can be obtained through the calcination of P123-templated Mg-Al-CO{sub 3} LDHs. The pore diameter is 2.2 nm. At the presence of ibuprofen, the Mg-Al MMOs can recover to Mg-Al-IBU LDHs, based on its 'remember effect'. Display Omitted

Wang Jun, E-mail: zhqw1888@sohu.co [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); College of Chemical Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, 150001 (China); Zhou Jideng; Li Zhanshuang; He Yang; Lin Shuangshuang; Liu Qi [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); Zhang Milin [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, 150001 (China); Jiang Zhaohua [College of Chemical Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2010-11-15

296

Structure transition and tuning pattern in the double (tetramethylammonium hydroxide + gaseous guests) clathrate hydrates.  

PubMed

In this study, we present an extraordinary structural transition accompanying the occurrence of more than two coexisting clathrate hydrate phases in the double (CH4 + tetramethylammonium hydroxide (Me(4)NOH)) and (H2 + Me(4)NOH) ionic clathrate hydrates using solid-state NMR spectroscopy (high-powered decoupling and CP/MAS) and powder X-ray diffraction. It was confirmed that structure-I (sI) and structure-II (sII) hydrates coexist as the water concentration increases. In the Me(4)NOH-depleted region, the unique tuning phenomenon was first observed at a chemical shift of -8.4 ppm where relatively small gaseous CH4 molecules partly occupy the sII large cages (sII-L), pulling out large cationic Me(4)N+ that is considered to be strongly bound with the surrounding host lattices. Moreover, we note that, while pure Me(4)NOH.16H(2)O clathrate hydrates melted at 249 K under atmospheric pressure conditions, the double (CH4 + Me(4)NOH) clathrate hydrate maintained a solid state up to approximately 283 K under 120 bar of CH4 with a conductivity of 0.065 S cm(-1), suggesting its potential use as a solid electrolyte. The present results indicate that ionic contributions must be taken into account for ionic clathrate hydrate systems because of their distinctive guest dynamic behavior and structural patterns. In particular, microscopic analyses of ionic clathrate hydrates for identifying physicochemical characteristics are expected to provide new insights into inclusion chemistry. PMID:17676892

Choi, Sukjeong; Shin, Kyuchul; Lee, Huen

2007-08-30

297

A Strongly Coupled Graphene and FeNi Double Hydroxide Hybrid as an Excellent Electrocatalyst for the Oxygen Evolution Reaction.  

PubMed

Cost-effective electrocatalysts for the oxygen evolution reaction (OER) are critical to energy conversion and storage processes. A novel strategy is used to synthesize a non-noble-metal-based electrocatalyst of the OER by finely combining layered FeNi double hydroxide that is catalytically active and electric conducting graphene sheets, taking advantage of the electrostatic attraction between the two positively charged nanosheets. The synergy between the catalytic activity of the double hydroxide and the enhanced electron transport arising from the graphene resulted in superior electrocatalytic properties of the FeNi-GO hybrids for the OER with overpotentials as low as 0.21?V, which was further reduced to 0.195?V after the reduction treatment. Moreover, the turnover frequency at the overpotential of 0.3?V has reached 1?s(-1) , which is much higher than those previously reported for non-noble-metal-based electrocatalysts. PMID:24910179

Long, Xia; Li, Jinkai; Xiao, Shuang; Yan, Keyou; Wang, Zilong; Chen, Haining; Yang, Shihe

2014-07-14

298

Study on adsorption of glyphosate (N-phosphonomethyl glycine) pesticide on MgAl-layered double hydroxides in aqueous solution.  

PubMed

MgAl-layered double hydroxides with different interlayer anions (nitrate, carbonate and chloride) were evaluated for their abilities to adsorb the organic pesticide glyphosate (N-phosphonomethyl glycine, Gly). The adsorption isotherms of Gly on layered double hydroxides (LDHs) nitrate were described by the Langmuir equation at lower equilibrium concentration of Gly (C(e)<1.0 mmol/L), and the Gly adsorption capacity on LDHs increased with the layer charge density, i.e. the structural Al3+/Mg2+ ratio. Gly adsorption on LDHs nitrate generally occurred through two processes, external surface adsorption and interlayer anion exchange. The adsorption amount on LDHs at C(e)=1.0 mmol/L decreased in the order of interlayer anions: Cl(-)>NO3(-)>CO3(2-). PMID:16005566

Li, Feng; Wang, Yunfeng; Yang, Qiaozhen; Evans, David G; Forano, Claude; Duan, Xue

2005-10-17

299

Synthesis and Characterization of Intercalated Layered Double Metal Hydroxides With Interlayer Aromatic Molecular Anions: Intercalation of 9,10-Anthraquinonedisulfonates Between Layers of Mg and Al Layered Double Hydroxides(MgAl-LDH)  

Microsoft Academic Search

9,10-Anthraquinonedisulfonates (AQij; ij=15, 18, 26 and 27) are intercalated between layers of synthetic hydrotalcite. Two or three values of enhanced interlayer distance are observed in powder X-ray diffraction (XRD) patterns of separate solid samples when AQ26 or AQ27 is intercalated, respectively. Dimensions are compared between the distance and the guest molecular size which is estimated in a semiempirical MO calculation.

Eiji Kanezaki

1996-01-01

300

An anionic photo-sensitizer intercalated in a layered double hydroxide: Preparation, characterization and photo-oxidation efficiency  

Microsoft Academic Search

The synthesis and complete characterization of layered double hydroxides (LDHs) where 4-benzoyl benzoate is either intercalated or adsorbed has been achieved and their photo-sensitizing efficiency for the oxidation of di-n-butylsulfide has been compared. XRD data are noticeably different for the two materials and the presence of an intercalated new phase is obvious for the first material. Elemental analysis and thermogravimetric

T. Pigot; J. C. Dupin; H. Martinez; C. Cantau; M. Simon; S. Lacombe

2005-01-01

301

Novel hollow microspheres of hierarchical zinc–aluminum layered double hydroxides and their enhanced adsorption capacity for phosphate in water  

Microsoft Academic Search

Hollow microspheres of hierarchical Zn–Al layered double hydroxides (LDHs) were synthesized by a simple hydrothermal method using urea as precipitating agent. The morphology and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption–desorption isotherms and fourier transform infrared (FTIR) spectroscopy. It was found that the morphology of hierarchical Zn–Al LDHs can

Jiabin Zhou; Siliang Yang; Jiaguo Yu; Zhan Shu

2011-01-01

302

Modulating effect of Mg–Al–CO 3 layered double hydroxides on the thermal stability of PVC resin  

Microsoft Academic Search

Mg–Al–CO3 layered double hydroxides (hydrotalcite-like materials) with different Mg\\/Al molar ratios and having small particle size and narrow size distribution have been prepared by a method involving separate nucleation and aging steps and characterized by XRD, FT-IR and TG-DTA, which clearly demonstrated that the charge density of the layers decreased with increasing Mg\\/Al molar ratio. Therefore, the electrostatic force of

Yan-Jun Lin; Dian-Qing Li; David G. Evans; Xue Duan

2005-01-01

303

Structure, flame retarding and smoke suppressing properties of Zn-Mg-Al-CO3 layered double hydroxides  

Microsoft Academic Search

Zn-Mg-Al-CO3 layered double hydroxides (LDHs) have been synthesized by a new method involving separate nucleation and aging steps. The\\u000a Zn-Mg-Al-CO3 LDHs were characterized by XRD, FT-IR, ICP and TG-DTA. The limiting oxygen index and smoke density of composites of the LDHs\\u000a with EVA-28 were determined. Incorporation of Zn in the layers of the LDHs was found promoting material charring and

Ling Shi; Dianqing Li; Sufeng Li; Jianrong Wang; D. G. Evans; Xue Duan

2005-01-01

304

Studies on Me\\/Al-layered double hydroxides (Me = Ni and Co) as electrode materials for electrochemical capacitors  

Microsoft Academic Search

Me\\/Al-layered double hydroxides (Me=Ni and Co) prepared by the chemical co-precipitation method have been shown to be outstanding novel materials for electrochemical capacitors. The crystalline structure and the electrochemical properties of the electrodes have been studied by considering the effect of the mole ratio of nickel\\/cobalt. X-ray diffraction analysis shows that the materials belong to hexagonal system with layered structure.

Xian-Ming Liu; Yi-He Zhang; Xiao-Gang Zhang; Shao-Yun Fu

2004-01-01

305

Deintercalation of carbonate ions from carbonate-type layered double hydroxides (LDHs) using acid–alcohol mixed solutions  

Microsoft Academic Search

Because of the high affinity of carbonate ions (CO32?) for LDHs (layered double hydroxides), their decarbonation—deintercalation of carbonate ions and conversion into LDHs containing other anions—has been considered difficult. So far, dilute acids have been used for decarbonation with additional salt to enhance the reaction. We found that the acid resistance of the LDHs is much higher in alcohols such

Nobuo Iyi; Hirohisa Yamada; Takayoshi Sasaki

2011-01-01

306

Novel application of CoFe layered double hydroxide nanoplates for colorimetric detection of H(2)O(2) and glucose.  

PubMed

The present communication demonstrates the proof of concept of using CoFe layered double hydroxide (CoFe-LDHs) nanoplates as an effective peroxidase mimetic to catalyze the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H(2)O(2) to produce a blue solution. We further demonstrate successfully CoFe-LDHs nanoplate-based colorimetric assay to detect H(2)O(2) and glucose. PMID:22290215

Zhang, Yingwei; Tian, Jingqi; Liu, Sen; Wang, Lei; Qin, Xiaoyun; Lu, Wenbo; Chang, Guohui; Luo, Yonglan; Asiri, Abdullah M; Al-Youbi, Abdulrahman O; Sun, Xuping

2012-03-21

307

Sono-assisted preparation of magnetic magnesium–aluminum layered double hydroxides and their application for removing fluoride  

Microsoft Academic Search

A simple ultrasound-assisted co-precipitation method in combination with a calcination treatment was developed to prepare magnetic Mg–Al layered double hydroxides composite as an adsorbent material to remove fluoride ions from aqueous solutions. The application of ultrasound in the preparation process promoted the formation of the hydrotalcite-like phase and drastically shortened the time being required for preparation of the crystalline composite.

Qing Chang; Lihua Zhu; Zhihong Luo; Min Lei; Suicheng Zhang; Heqing Tang

308

Influence of reduction temperature on composition, particle size, and magnetic properties of CoFe alloy nanomaterials derived from layered double hydroxide precursors.  

PubMed

Individual CoFe alloy nanoparticles and CoFe-MgO nanocomposites were prepared through thermal reduction of single-source layered double hydroxide (LDH) precursors at various temperatures. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analyses to investigate the influence of reduction temperature on the composition, particle size and size distribution, as well as the magnetic properties of the resulting materials. XRD and SEM results show that the as-prepared CoFe alloy nanoparticles and CoFe-MgO nanocomposites display high crystallinity and high purity. The average particle size of individual CoFe nanoparticles increases with the increase of reduction temperature. In the presence of the MgO matrix, uniform CoFe alloy nanoparticles with a narrow diameter distribution (8-11 nm) were obtained. Magnetic measurements indicate that the saturation magnetization strength (Ms) of the resulting materials increases with reduction temperature. The individual CoFe alloy nanoparticles exhibit excellent soft magnetic behavior with an extremely high Ms value (213 emu g(-1) at 800 °C), comparable to that of bulk CoFe alloy (230 emu g(-1)). For CoFe-MgO nanocomposites, small Ms values were obtained due to the small CoFe alloy particle size and low percentage of magnetic component. However, the coercivities are greatly enhanced (663 Oe at 450 °C) for the composites, implying their potential applications in data storage and other magnetic devices. PMID:24695765

Yang, Shuangxia; Wang, Lianying; Yue, Shuang; Lu, Yanluo; He, Jing; Zhao, Dongye

2014-06-14

309

A temperature sensor based on CdTe quantum dots-layered double hydroxide ultrathin films via layer-by-layer assembly.  

PubMed

Ordered ultrathin films based on alternate assembly of CdTe QDs and layered double hydroxide monolayers have been fabricated, which can be used as a photoluminescence temperature sensor with dual-parameter signals and high response sensitivity. PMID:23232650

Liang, Ruizheng; Tian, Rui; Shi, Wenying; Liu, Zhihui; Yan, Dongpeng; Wei, Min; Evans, David G; Duan, Xue

2013-02-01

310

Photophysical properties of donor-?-acceptor azoic chromophores adsorbed and intercalated into Mg?Al?LDH  

NASA Astrophysics Data System (ADS)

Ethyl Orange (EO) and 4-aminoazobenzene-4-sulfonic (AS) anions with Donor-?-Acceptor structure have been intercalated into the layered double hydroxide (LDH), [Mg0.66 Al0.34 (OH)2] (CO3)0.17·0.67H2O or adsorbed on the external surface of the host by the method of ion-exchange procedures. The photoabsorption and fluorescence properties of the obtained compounds were different from the pure solid phase of EO and AS. It was suggested that the photophysical properties of guests were closely related to the geometry and electrical structure of the guest molecule, which can affect the distribution and orientation of the guests in the layers or on the surface of the host. The host-guest interactions modulate photophysical properties of guest. In addition, the guest having higher molecular dipole moments surface exchanged on Mg?Al?CO3?LDH are beneficial to the enhancement of the blue emission than that of intercalation into LDH.

Li, Lei; Liu, Pengfei; Zhang, Li; Chen, Dazhou

2013-02-01

311

Glyphosate and glufosinate detection at electrogenerated NiAl-LDH thin films.  

PubMed

An amperometric sensor based on Ni(1-x)Al(x)(OH)(2)NO(3x).nH(2)O layered double hydroxide (LDH) has been developed for the electrochemical analysis in one step of two herbicides: glyphosate (N-(phosphonomethyl)glycine, Glyp) and glufosinate ((DL-homoalanine-4-yl)-methylphosphinic acid, Gluf). NiAl-LDH was prepared by coprecipitation or by electrodeposition at the Pt electrode surface. Inorganic films were fully characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. Adsorption isotherms of Glyp onto this inorganic lamellar material have been established. Electrocatalytic oxidation of Glyp and Gluf is possible at the Ni(3+) centres of the structure. The electrochemical responses of the NiAl-LDH modified electrode were obtained by cyclic voltammetry and chronoamperometry at 0.49V/SCE as a function of herbicide concentration in 0.1M NaOH solution. The electrocatalytic response showed a linear dependence on the Glyp concentration ranging between 0.01 and 0.9mM with a detection limit of 1muM and sensitivity 287mA/Mcm(2). The sensitivity found for Gluf was lower (178mA/Mcm(2)). PMID:19854339

Khenifi, Aicha; Derriche, Zoubir; Forano, Claude; Prevot, Vanessa; Mousty, Christine; Scavetta, Erika; Ballarin, Barbara; Guadagnini, Lorella; Tonelli, Domenica

2009-11-10

312

Synthesis, structure refinement and chromate sorption characteristics of an Al-rich bayerite-based layered double hydroxide  

NASA Astrophysics Data System (ADS)

“Imbibition” of Zn2+ ions into the cation vacancies of bayerite-Al(OH)3 and NO3- ions into the interlayer gallery yields an Al-rich layered double hydroxide with Al/Zn ratio ~3. NO3- ions are intercalated with their molecular planes inclined at an angle to the plane of the metal hydroxide slab and bonded to it by hydrogen bonds. Rietveld refinement of the structure shows that the monoclinic symmetry of the precursor bayerite is preserved in the product, showing that the imbibition is topochemical in nature. The nitrate ion is labile and is quantitatively replaced by CrO42- ions from solution. The uptake of CrO42- ions follows a Langmuir adsorption isotherm, thus showing that the hydroxide is a candidate material for green chemistry applications for the removal of CrO42- ions from waste water. Rietveld refinement of the structure of the hydroxide after CrO42- inclusion reveals that the CrO42- ion is intercalated with one of its 2-fold axes parallel to the b-crystallographic axis of the crystal, also the principal 2 axis of the monoclinic cell.

Britto, Sylvia; Kamath, P. Vishnu

2014-07-01

313

Structural change from homogenous structure to staging in benzoic acid intercalated LDH: experimental and molecular dynamics simulation insights.  

PubMed

The intercalation the of 4,4'-oxybis(benzoic acid) anion (OBA(2-)) into MgAl-layered double hydroxide (LDH) was carried out in formamide, and the structural change of the nanocomposites from homogenous to staging was investigated through in situ XRD, FT-IR, TG-DSC, SEM and molecular dynamics (MD) simulations. In both formamide and water, the nanocomposites had a homogenous structure with a basal spacing of ?1.7 nm, showing the configuration of OBA(2-) was vertical to the LDH layers; however, with a decrease in water content after drying, the structure changed to a staging with a basal spacing of 2.62 nm. This resulted from the 1.72 nm phase and another one of 0.85 nm, which was produced by the configuration of OBA(2-) horizontal to the LDH layers. MD simulations revealed that the LDH layers distorted surrounding OBA(2-), and the deformation became more severe with decreasing water content in the interlayer, leading to the staging formation. The simulated XRD pattern confirmed that the staging observed in the experimental pattern was of the Daumas-Hérold type. PMID:22635008

Zhang, Yanru; Tan, Hongwei; Zhao, Jing-xiang; Li, Xinxin; Ma, Hui; Chen, Xiaoduan; Yang, Xiaojing

2012-07-01

314

Aging of trivalent metal hydroxide\\/oxide gels in divalent metal salt solutions: Mechanism of formation of layered double hydroxides (LDHs)  

Microsoft Academic Search

While the aging of freshly precipitated Al(OH)3 gels in solutions of Mg and Ni salts leads to LDH formation at high (> 12) pH, aging of ‘Fe(OH)3“ leads to LDH formation in Mg salt solutions but not in Ni salt3’ gels do not form LDHs on aging in any of the divalent metal salts. In general, conditions that promote the

A V Radha; P Vishnu Kamath

2003-01-01

315

Gel polymer electrolyte nanocomposites PEGDA with Mg–Al layered double hydroxides  

Microsoft Academic Search

Polymer electrolyte nanocomposite films composed of PEGDA\\/LiCF3SO3 with various wt.% Mg–Al LDH-2 fillers were prepared. Gel structure was obtained by thermal crosslinking reaction of residual terminal acrylate groups of PEGDA. The molecular weight of PEGDA was ca. 258, 575, and 700, respectively. The ionic conductivity and mechanical properties of resulting nanocomposites were characterized by impedance measurements, X-ray diffraction, and tensile

M. S. Cho; B. Shin; S. D. Choi; Y. Lee; K. G. Song

2004-01-01

316

New SnO2/MgAl-layered double hydroxide composites as photocatalysts for cationic dyes bleaching.  

PubMed

A new type of nanocomposite containing SnO(2) has been obtained by wet impregnation of dehydrated Mg/Al-hydrotalcite-type compounds with ethanolic solutions of SnCl(4).2H(2)O. Tin chloride hydrolysis was achieved using NaOH or NH(4)OH aqueous solutions, at pH around 9, followed by the conversion into corresponding hydroxides through calcinations. The powder X-ray diffraction (PXRD) and UV-Vis diffuse reflectance (UV-DR) methods confirmed the structure of as-synthesized solids. The chemical composition and morphology of the synthesized materials were investigated by energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-synthesized materials were used for photocatalytic studies showing a good activity for methylene blue decolourization, which varies with SnO(2) content and used as a hydrolysing agent. The proposed mechanism is based on the shifting of flat band potential of SnO(2) due to the interaction with Mg/Al-LDH, this being energetically favourable to the formation of hydroxyl radicals responsible for methylene blue degradation. PMID:20045244

Dvininov, E; Ignat, M; Barvinschi, P; Smithers, M A; Popovici, E

2010-05-15

317

Dramatic activities of vanadate intercalated bismuth doped LDH for solar light photocatalysis.  

PubMed

To harvest solar energy efficiently, a series of Zn/Bi layered double hydroxide (LDH) photocatalysts with different molar ratios of Zn/Bi (2?:?1, 3?:?1, 4?:?1) has been synthesized by a coprecipitation method at constant pH. All the Bi doped LDH samples displayed hydrotalcite-like structure with interlayer carbonate, in which crystallinity decreases as the bismuth content increases. The Zn/Bi (4?:?1) LDH with a small amount of bismuth in the brucite layer and possessing high crystallinity was further modified hydrothermally by intercalating decavanadate and it showed high photochemical stability and photocatalytic activity for the degradation of different organic pollutants for practical applications under solar light irradiation. The structural integrity of the materials has been successfully characterized by studying their structural, morphological, electronic and optical properties by various physico-chemical techniques. The present study provided an insight into oxo-bridged MMCT of the LDH and established that the Zn(ii)-O-Bi(iii) units resulted in the generation of superoxide radicals which is clearly observed by the EPR technique. The ?OH radicals formed during photocatalysis were revealed by means of the terephthalic acid fluorescence probe method. The photoelectrochemical measurement confirmed that the intercalated vanadate anion was crucial to obtain an optimal synergistic effect for the degradation of organic pollutants. The prolonged lifetime of photogenerated charges and improved charge transfer capability were confirmed by time-resolved fluorescence emission spectra. Furthermore, a detailed mechanism for the enhanced photocatalytic activity was discussed. PMID:25005613

Mohapatra, Lagnamayee; Parida, K M

2014-07-23

318

Adsorption and intercalation of Acid Blue 9 on Mg–Al layered double hydroxides of variable metal composition  

Microsoft Academic Search

Layered double hydroxides (LDHs) of the type [Mg1-XAlX(OH)2]X+[(CO32-)X\\/2·mH2O] with variable Mg\\/Al molar ratios have been prepared by co-precipitation of Mg2+ and Al3+ ions at constant pH. The ability of these compounds to adsorb Acid Blue 9 has been evaluated by UV–Vis spectrophotometry, FT-IR spectroscopy, powder X-ray diffraction analysis, N2 adsorption\\/desorption analysis, scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy

Anthony R. Auxilio; Philip C. Andrews; Peter C. Junk; Leone Spiccia; Daniel Neumann; Warwick Raverty; Nafty Vanderhoek

2007-01-01

319

Change in the electric double-layer capacitance of magnetite in sodium hydroxide solutions  

Microsoft Academic Search

Conclusions  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Measurements of the differential capacitance of monocrystalline natural magnetite in sodium hydroxide solutions by the impedance\\u000a method have shown that the measured capacitance on magnetite markedly depends on the sodium hydroxide concentration. This\\u000a indicates significant electrochemical conversions of magnetite in these solutions.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a Hysteresis of the current density and impedance components is observed during polarization; this is probably

S. F. Naumova; G. S. Nesterov

1978-01-01

320

Topochemical synthesis of alkali-metal hydroxide layers within double- and triple-layered perovskites.  

PubMed

The formation of alkali-metal hydroxide layers within lamellar perovskites has been accomplished by a two-step topochemical reaction strategy. Reductive intercalation of ALaNb2O7 with alkali metal (A = K, Rb) and RbCa2Nb3O10 with Rb leads to A2LaNb2O7 and Rb2Ca2Nb3O10, respectively. Oxidative intercalation with stoichiometric amounts of water vapor, produced by the decomposition of calcium oxalate monohydrate in a sealed ampule, allows the insertion hydroxide species. Compounds of the form (A2OH)LaNb2O7 (A = K, Rb) and (Rb2OH)Ca2Nb3O10 are accessible. X-ray diffraction data indicates a clear layer expansion of almost 3 Å on the insertion of hydroxide relative to that of the parent. Rietveld refinement of neutron diffraction data collected on deuterated samples of (Rb2OD)LaNb2O7 (P4/mmm space group, a = 3.9348(1) Å, c = 14.7950(7) Å) finds that both rubidium and oxygen species reside in cubic sites forming a CsCl-like interlayer structure between niobate perovskite blocks. Hydrogens, attached to the interlayer oxygens, are disordered over a 4-fold site in the x-y plane and have O-H bond distances (0.98 Å) consistent with known hydroxide species. This synthetic approach expands the library of available topochemical reactions, providing a facile method for the construction of alkali-metal hydroxide layers within receptive perovskite hosts. PMID:24410708

Montasserasadi, Dariush; Mohanty, Debasish; Huq, Ashfia; Heroux, Luke; Payzant, Edward Andrew; Wiley, John B

2014-02-01

321

Layered double hydroxides as efficient photocatalysts for visible-light degradation of Rhodamine B.  

PubMed

A series of Zn/M-NO3-LDHs (M=Al, Fe, Ti, and Fe/Ti) have been synthesized by two different methods, and their activities for visible-light photocatalytic degradation on Rhodamine B (RB) were tested. Solids were analyzed by XRD, FT-IR, and ICP characterization, confirming the formation of pure LDH phase with good crystal structure. It was observed that the band gap of these nitrate LDH materials was following this order: Zn/Fe-NO3-LDHs (2.55 eV)>Zn/Fe/Ti-NO3-LDHs (2.88 eV)>Zn/Ti-NO3-LDHs (3.0 3eV)>Zn/Al-NO3-LDHs (3.23 eV); however, the degradation performance of RB by four materials followed the order: Zn/Ti-NO3-LDHs (98%)>Zn/Al-NO3-LDHs (96%)>Zn/Fe/Ti-NO3-LDHs (88%)>Zn/Fe-NO3-LDHs (72%). In addition, a possible mechanism for photocatalytic degradation on RB has also been presumed. Moreover, after three regeneration cycles, the percentage of RB degradation rate was still close to 90%. PMID:23786832

Xia, Sheng-Jie; Liu, Feng-Xian; Ni, Zhe-Ming; Xue, Ji-Long; Qian, Ping-Ping

2013-09-01

322

Decarbonation of MgAl-LDHs (layered double hydroxides) using acetate-buffer/NaCl mixed solution.  

PubMed

By using acetate-buffer (sodium acetate and acetic acid)/NaCl mixed solutions, the deintercalation of carbonate ions (CO(2-)3) was conducted on MgAl--LDHs at different Mg/Al ratios-LDH2 (LDH with Mg/Al approximately 2) and LDH3 (LDH with Mg/Al approximately 3). When only an acetate-buffer solution was used, decarbonation did not take place even if the buffer solution was made acidic enough to dissolve LDH itself; however, the addition of NaCl to the buffer solution caused deintercalation of the carbonate ions from the MgAl-LDHs and the reaction was conducted without any morphological and weight change at 25 degrees C. Under the optimum conditions, full decarbonation was attained for the two MgAl-LDHs in minutes, and the obtained LDHs contained Cl(-) in the interlayer space without incorporation of any acetate anions due to their extremely low anion selectivity of acetate ion. The allowable range for the concentration of the decarbonation solution is wide, and the change in pH due to the decarbonation reaction is slight because of the buffering effect. The decarbonation was affected by the Mg/Al ratio of the LDH; i.e., the present LDH2 was slightly more difficult to decarbonate than LDH3, probably due to the higher layer-charge density of LDH2. PMID:18377921

Iyi, Nobuo; Sasaki, Takayoshi

2008-06-01

323

Toxicity and Metabolism of Layered Double Hydroxide Intercalated with Levodopa in a Parkinson's Disease Model  

PubMed Central

Layered hydroxide nanoparticles are generally biocompatible, and less toxic than most inorganic nanoparticles, making them an acceptable alternative drug delivery system. Due to growing concern over animal welfare and the expense of in vivo experiments both the public and the government are interested to find alternatives to animal testing. The toxicity potential of zinc aluminum layered hydroxide (ZAL) nanocomposite containing anti-Parkinsonian agent may be determined using a PC 12 cell model. ZAL nanocomposite demonstrated a decreased cytotoxic effect when compared to levodopa on PC12 cells with more than 80% cell viability at 100 ?g/mL compared to less than 20% cell viability in a direct levodopa exposure. Neither levodopa-loaded nanocomposite nor the un-intercalated nanocomposite disturbed the cytoskeletal structure of the neurogenic cells at their IC50 concentration. Levodopa metabolite (HVA) released from the nanocomposite demonstrated the slow sustained and controlled release character of layered hydroxide nanoparticles unlike the burst uptake and release system shown with pure levodopa treatment.

Kura, Aminu Umar; Ain, Nooraini Mohd; Hussein, Mohd Zobir; Fakurazi, Sharida; Hussein-Al-Ali, Samer Hasan

2014-01-01

324

Molecular-scale heteroassembly of redoxable hydroxide nanosheets and conductive graphene into superlattice composites for high-performance supercapacitors.  

PubMed

Artificial superlattice nanocomposites are successfully prepared by electrostatic heteroassembly of redoxable Co-Al or Co-Ni layered double hydroxide (LDH) nanosheets with graphene. The superlattice electrodes exhibit a high capacity up to ca. 650 F/g, which is approximately 6 times that of pure graphene. The composites are found to be capable of superfast charging and discharging, up to ca. 100 Hz, comparable with the high-power performance of graphene electrodes. PMID:24753376

Ma, Renzhi; Liu, Xiaohe; Liang, Jianbo; Bando, Yoshio; Sasaki, Takayoshi

2014-06-01

325

Synergetic effect of SLN-curcumin and LDH-5-Fu on SMMC-7721 liver cancer cell line.  

PubMed

Curcumin and 5-Fluorouracil (5-Fu) have been reported to have anticancer potentials and show certain synergetic effect on some cancer cell lines. However, the poor bioavailability and rapid metabolism limited their medical application. In this study, we encapsulated curcumin with solid lipid nanoparticles (SLN), 5-Fu with Layered double hydroxides (LDHs) separately and tested its properties and anticancer potentials. SLN-curcumin and LDH-5-Fu were determined to be 100 and 60?nm by Transmission Electron Microscopy detection, and the loading efficiency were 28%±2.5% and 16.7%±1.8%, individually. Furthermore, SLN-curcumin and LDH-5-Fu showed a significantly synergetic effect on SMMC-7721 cell stronger than plain drugs together, of which the Idrug loaded nano-carriers was only 0.315. FACS analysis revealed that the combination of SLN-curcumin and LDH-5-Fu induced 80.1% apoptosis in SMMC-7721 cells, which were 1.7-folds of the sum of the two plain drug loaded carriers. The results demonstrated the significant synergetic anticancer potentials of nano-encapsulated curcumin and 5-Fu, which could be further explored for the treatment of other carcinoma. PMID:23808828

Zhu, Rongrong; Wu, Xianzheng; Xiao, Yu; Gao, Bo; Xie, Qian; Liu, Hui; Wang, Shilong

2013-10-01

326

Pectins filled with LDH-antimicrobial molecules: Preparation, characterization and physical properties.  

PubMed

Nanohybrids of layered double hydroxide (LDH) with intercalated active molecules: benzoate, 2,4-dichlorobenzoate, para-hydroxybenzoate and ortho-hydroxybenzoate, were incorporated into pectins from apples through high energy ball milling in the presence of water. Cast films were obtained and analysed. X-ray diffraction analysis showed a complete destructuration of all nanohybrids in the pectin matrix. Thermogravimetric analysis showed a better thermal resistance of pectin in the presence of fillers, especially para-hydroxybenzoate and ortho-hydroxybenzoate. Mechanical properties showed an improvement of elastic modulus in particular for LDH-para-hydroxybenzoate nanohybrid, due probably to a better interaction between pectin matrix and nanohybrid layers. Barrier properties (sorption and diffusion) to water vapour showed improvement in the dependence on the intercalated active molecule, the best improvement was achieved for composites containing para-hydroxybenzoate molecules, suggesting that the interaction between the filler phase and the polymer plays an important role in sorption and diffusion phenomena. Incorporation of these active molecules gave antimicrobial properties to the composite films giving opportunities in the field of active packaging. PMID:24750614

Gorrasi, Giuliana; Bugatti, Valeria; Vittoria, Vittoria

2012-06-01

327

Structural adjustment during intercalation of macrocyclic crown ether into LDH via swelling/restoration reaction: staging formation and mechanism insights.  

PubMed

The structural control involving staging formation was studied in the nanocomposites of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) and layered double hydroxide (LDH) obtained by an osmotic swelling/restoration process. After NO(3)-type MgAl-LDH was osmotically swollen in formamide, TECA was added, leading to a restoration of the LDH sheets and formation of TECA-LDH nanocomposites. In the wet state, the structure of the composites was homogenous, and the basal spacings of ?2.0 or 1.8 nm were not changed by the water-washing process that removed formamide and caused the replacement of NO(3)(-) by CO(3)(2-). However, in the drying process, both the orientation of TECA in the interlayer and the formed staging structure varied with the TECA content. The TECA orientation changed from horizontal to tilted/twisted and finally to vertical with interlayer TECA density. The staging structure occurred for samples with both TECA and small inorganic guests coexisting in the interlayer. Third-staging, second-staging, and homogenous structures were observed at TECA/LDH weight ratios of low (0.125 and 0.25), medium (0.5) and large (1 and 2) values, respectively. The decrease of negative charge of TECA ions from -4 to -1 led to the co-existence of small ions (NO(3)(-)) with TECA in the gallery and the formation of a NO(3)(-)-containing staging structure, even at a high TECA/LDH ratio of 2. The study of the influence of CO(3)(2-) on the composite structure indicates that a TECA/CO(3)(2-) ion exchange progressed reversibly and the staging structure formed is thermodynamically stable, depending mainly on the chemical composition of the interlayer guests. The staging formation could be explained by the Daumas-Hérold model, which differs markedly from the Rüdorff model previously proposed for the LDH system. The treatment in formamide of the composite such as T2L+Na(2)CO(3) with staging structure shows that the transformation process is reversible, and these kinds of composites may be used as an adsorbent for some harmful organic solvents. PMID:21860873

Ma, Shulan; Du, Li; Wang, Juan; Chu, Nankai; Sun, Yahong; Sun, Genban; Yang, Xiaojing; Ooi, Kenta

2011-10-14

328

Preparation of layered double hydroxides and their applications as additives in polymers, as precursors to magnetic materials and in biology and medicine  

Microsoft Academic Search

In recent years layered double hydroxides (LDHs), also known as hydrotalcite-like materials, have attracted considerable interest from both industry and academia. In this article, we discuss methods of preparing LDHs with an emphasis on the way in which particle size and morphology can be controlled with regard to specific target applications; scale-up of one such preparation procedure is also described.

David G. Evans; Xue Duan

2006-01-01

329

Clarification of possible ordered distributions of trivalent cations in layered double hydroxides and an explanation for the observed variation in the lower solid-solution limit  

PubMed Central

The sequence of hexagonal ordered distributions of trivalent cations that are possible in the octahedral layer of layered double hydroxides is clarified, including the link between the composition and the supercell a parameter. A plausible explanation is provided for the observed variation in the lower solid-solution limit.

Richardson, Ian G.

2013-01-01

330

Aluminum Hydroxide and Magnesium Hydroxide  

MedlinePLUS

Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They may be used to ... with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription.This medication ...

331

Nanohybrids from NiCoAl-LDH coupled with carbon for pseudocapacitors: understanding the role of nano-structured carbon  

NASA Astrophysics Data System (ADS)

Transition metal layered double hydroxides (LDHs) are one of the great potential electrode materials for pseudocapacitors. However, the aggregation and low conductivity of these metal compounds will constrain electrolyte ion and electron transfer and further affect their electrochemical performances. The nano-structured carbon coupled with the LDH matrix can act as an active component or conducting scaffold to enhance or improve the rate capacity and cycle life. Here, various nano-structured carbon species, including zero-dimensional carbon black (CB), one-dimensional carbon nanotubes (CNTs), two-dimensional reduced graphene oxide (RGO), and CNT/RGO composites were used to couple with the NiCoAl-LDHs to construct LDH-carbon nanohybrid electrodes for pseudocapacitors, and the role of the nanostructured carbon was investigated and discussed in terms of the pore structure of nanohybrids and electrical conductivity. The results show that all of the carbons can be well incorporated into the LDH nanosheets to form homogeneous nanohybrid materials. The pore structure properties and electrical conductivity of nanohybrids have statistically significant effects on the electrochemical performances of the LDH-carbon nanohybrids. Of the electrodes adopted, the nanohybrid electrode consisting of NiCoAl-LDHs, CNTs, and RGO exhibits excellent electrochemical performance with a specific capacitance as high as 1188 F g-1 at a current density of 1 A g-1 due to the synergistic effect of NiCoAl-LDHs, RGO, and CNTs, in which the RGO nanosheets are favorable for high specific surface area while the CNT has a fast electron transport path for enhancing the electrical conductivity of nanohybrids. This will shed a new light on the effect of nano-structured carbon within the electrode matrix on the electrochemical activity and open a new way for the carbon-related electrode configuration/design for supercapacitors, and other energy storage and conversion devices.Transition metal layered double hydroxides (LDHs) are one of the great potential electrode materials for pseudocapacitors. However, the aggregation and low conductivity of these metal compounds will constrain electrolyte ion and electron transfer and further affect their electrochemical performances. The nano-structured carbon coupled with the LDH matrix can act as an active component or conducting scaffold to enhance or improve the rate capacity and cycle life. Here, various nano-structured carbon species, including zero-dimensional carbon black (CB), one-dimensional carbon nanotubes (CNTs), two-dimensional reduced graphene oxide (RGO), and CNT/RGO composites were used to couple with the NiCoAl-LDHs to construct LDH-carbon nanohybrid electrodes for pseudocapacitors, and the role of the nanostructured carbon was investigated and discussed in terms of the pore structure of nanohybrids and electrical conductivity. The results show that all of the carbons can be well incorporated into the LDH nanosheets to form homogeneous nanohybrid materials. The pore structure properties and electrical conductivity of nanohybrids have statistically significant effects on the electrochemical performances of the LDH-carbon nanohybrids. Of the electrodes adopted, the nanohybrid electrode consisting of NiCoAl-LDHs, CNTs, and RGO exhibits excellent electrochemical performance with a specific capacitance as high as 1188 F g-1 at a current density of 1 A g-1 due to the synergistic effect of NiCoAl-LDHs, RGO, and CNTs, in which the RGO nanosheets are favorable for high specific surface area while the CNT has a fast electron transport path for enhancing the electrical conductivity of nanohybrids. This will shed a new light on the effect of nano-structured carbon within the electrode matrix on the electrochemical activity and open a new way for the carbon-related electrode configuration/design for supercapacitors, and other energy storage and conversion devices. Electronic supplementary information available: FE-SEM images, TEM images, TGA curves, nitrogen adsorption/desorption isotherms, and the corresponding pore s

Yu, Chang; Yang, Juan; Zhao, Changtai; Fan, Xiaoming; Wang, Gang; Qiu, Jieshan

2014-02-01

332

Relevance and performance of LDH platelets in coatings.  

PubMed

The present article presents a review devoted to Layered Double Hydroxide (LDH) as filler in coatings from the patent domain and the applicative literature. Other than bulk properties generally encountered in polymer nanocomposite aspect, LDHs filler relevance for coatings concerns surface properties as well as requiring diffusion barrier into limited width by isolating or healing substrate from aggressive medium. Enhancement of the substrate is performed with rather low pigment/filler concentration underlining the importance of nanometric dispersion to create large interfacial exposure between filler and polymer as well as being crucial for substrate adhesion. Largely exemplified with corrosion coating protection, LDHs is reported here as a corrosion inhibitor nano-container (C.I.NC.), and the self-healing protective effect is occurring from the delivery of inhibitor on demand, the guest interleaved species possess corrosion inhibition ability triggered when it is spontaneously released from the host matrix into aqueous environments in contact with corroding metal substrates. From the academic and patent literature, the review enlists the strategy to employ LDHs as efficient filler for bare metal substrate, mostly aluminum, magnesium and steel, as well as for polymer coatings and conversion films to prevent corrosion, as well as other properties: anti-UV, anti-abrasion and impact resistance, bactericide and antifouling. LDHs platelets dispersion either exfoliated or intercalated is found to be a key to provide great properties such as barrier properties and energy dissipation through nano-spring effect, respectively. The accent is also underlined on the concerns relative to ecological and economic considerations for coatings in an industrial setting and the chemicals regulation. Finally perspectives point out the topical relevance of LDHs nanofiller to supply adaptive and multifunctional properties to coatings. PMID:22747726

Leroux, Fabrice; Stimpfling, Thomas; Hintze-Bruening, Horst

2012-11-01

333

Reversible intercalation of ammonia molecules into a layered double hydroxide structure without exchanging nitrate counter-ions  

SciTech Connect

A zinc/aluminum LDH was precipitated with recycled ammonia from a chemical vapor deposition reaction. The LDH presented a crystalline phase with basal distance of 8.9 A, typical for nitrate-containing LDHs, and another phase with a basal distance of 13.9 A. Thermal treatment at 150 {sup o}C eliminated the phase with the bigger basal distance leaving only the anhydrous nitrate-intercalated LDH structure with 8.9 A. Intense N-H stretching modes in the FTIR spectra suggested that the expansion was due to intercalation of ammonia in the form of [NH{sub 4}(NH{sub 3}){sub n}]{sup +} species. When additional samples were precipitated with pure ammonia, the conventional LDH nitrate structure was obtained (8.9 A basal distance) at pH=7, as well as a pure crystalline phase with 13.9 A basal distance at pH=10 due to ammonia intercalation that can be removed by heating at 150 {sup o}C or by stirring in acetone, confirming a unusual sensu stricto intercalation process into a LDH without exchanging nitrate ions. - Graphical abstract: LDH-nitrate precipitated with ammonia expands the interlayer space if ammonia is bubbled up to pH 10. The basal distance decreased when the compound was heated at 150 {sup o}C or stirred in acetone. Nitrate ions are not exchanged.

Carbajal Arizaga, Gregorio Guadalupe, E-mail: gregoriocarbajal@yahoo.com.m [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km. 107 Carretera Tijuana-Ensenada, Apdo. Postal 14, C.P. 22800. Ensenada, Baja California (Mexico); Wypych, Fernando [CEPESQ-Research Centre of Applied Chemistry, Department of Chemistry, Federal University of Parana, P.O. Box 19081, 81531-980 Curitiba, PR (Brazil); Castillon Barraza, Felipe; Contreras Lopez, Oscar Edel [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km. 107 Carretera Tijuana-Ensenada, Apdo. Postal 14, C.P. 22800. Ensenada, Baja California (Mexico)

2010-10-15

334

Variable charge and electrical double layer of mineral-water interfaces: silver halides versus metal (hydr)oxides.  

PubMed

Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface complexation modeling (SCM) as applied to metal (hydr)oxide interfaces. Ag halides and metal (hydr)oxides behave quite differently in some respect. The location of charge in the interface of Ag halides is not a priori obvious. For AgI(s), SCM indicates the separation of interfacial charge in which the smaller silver ions are apparently farther away from the surface than iodide. This charge separation can be understood from the surface structure of the relevant crystal faces. Charge separation with positive charge above the surface is due to monodentate surface complex formation of Ag(+) ions binding to I sites located at the surface. Negative surface charge is due to the desorption of Ag(+) ions out of the lattice. These processes can be described with the charge distribution (CD) model. The MO/DFT optimized geometry of the complex is used to estimate the value of the CD. SCM reveals the EDL structure of AgI(s), having two Stern layers in series. The inner Stern layer has a very low capacitance (C(1) = 0.15 ± 0.01 F/m(2)) in comparison to that of metal (hydr)oxides, and this can be attributed to the strong orientation of the (primary) water molecules on the local electrostatic field of the Ag(+) and I(-) ions of the surface (relative dielectric constant ?(r) ? 6). Depending on the extent of water ordering, mineral surfaces may in principle develop a second Stern layer. The corresponding capacitance (C(2)) will depend on the degree of water ordering that may decrease in the series AgI (C(2) = 0.57 F/m(2)), goethite (C(2) = 0.74 F/m(2)), and rutile (C(2) = ?), as discussed. The charging principles of AgI minerals iodargyrite and miersite may also be applied to minerals with the same surface structure (e.g., sphalerite and würtzite (ZnS)). PMID:23057539

Hiemstra, Tjisse

2012-11-01

335

Fluorescence of Zn-Al-Eu ternary layered hydroxide response to phenylalanine.  

PubMed

We reported the fluorescence of a Zn-Al-Eu ternary layered double hydroxide (LDH) response to an amino acid (phenylalanine) for the first time. As shown in fluorescence, the red emissions attributed to (5)D(0)-(7)F(J) transitions (J=1, 2, 3, 4) of Eu(3+) ions were quenched by the phenylalanine (Phe), and a strong blue emission at around 445 nm appeared. The fluorescent changes may be due to ligand-to-metal charges transfer, which was caused by the interaction between the Zn-Al-Eu LDH and Phe. This interaction was manifested by markedly different chemical shift positions of the Zn 3p(3/2), Al 2p, Eu 4d(3/2), O 1s, and C 1s peaks in the XPS spectra from those of the Zn-Al-Eu LDH and Zn-Al-Eu/Phe composite. Furthermore, the interaction between the LDH and Phe was supported by the results of X-ray diffraction (XRD) measurements, Fourier transform infrared (FT-IR) spectra, and thermogravimetric and differential thermogravimetric (TG-DTG) analysis. The fluorescence of Zn-Al-Eu LDH response to Phe may be potential application in biological techniques. PMID:22153739

Chen, Yufeng; Li, Fei; Yu, Gensheng; Yang, Xiaojing

2012-02-01

336

A ratiometric fluorescence sensor for Be2+ based on Beryllon II/layered double hydroxide ultrathin films.  

PubMed

A ratiometric fluorescence sensor for Be(2+) has been fabricated via alternate assembly of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate (Beryllon II) and MgAl-LDH nanosheets on quartz substrates using the layer-by-layer (LBL) deposition technique. UV-vis absorption and the fluorescence emission spectroscopy indicate a stepwise and regular growth of the Beryllon II/LDH UTFs upon increasing deposition cycle. The film of Beryllon II/LDH possesses a periodic layered structure perpendicular to the substrate revealed by X-ray diffraction and scanning electron microscopy. Atomic force microscopy images show that the film surface is continuous and uniform. The Beryllon II/LDH UTFs display ratiometric fluorescence response for Be(2+) with a linear response range in 1.0×10(-7)-1.9×10(-6) mol L(-1) and a detection limit of 4.2×10(-9) mol L(-1). Furthermore, the ratiometric sensor exhibits good repeatability, high stability (thermal, storage and mechanical) as well as excellent selectivity toward Be(2+). XPS and Raman measurements demonstrate that the specific response of the sensor is attributed to the coordination between Be(2+) and Beryllon II in the UTF. The Beryllon II/LDH UTFs in this work can be potentially used as a chemosensor for the detection of Be(2+) in the environmental and biomedical field. PMID:22560284

Ji, Xiaolan; Shi, Wenying; Zhang, Shitong; Wei, Min; Evans, David G; Duan, Xue

2012-05-30

337

Removal efficiency of fluoride by novel Mg-Cr-Cl layered double hydroxide by batch process from water.  

PubMed

The fluoride ion removal from aqueous solution using synthesized Mg-Cr-Cl layered double hydroxide has been reported. Mg-Cr-Cl was characterized by X-ray powder diffraction, Fourier-transform infrared, thermo-gravimetric analysis, differential thermal analysis, and scanning electron microscope. Adsorption experiments were carried out in batch mode as a function of adsorption dosages, contact time, pH, and initial fluoride concentration to get optimum adsorption capacity. The adsorption kinetic study showed that the adsorption process followed first order kinetics. The fluoride removal was 88.5% and 77.4% at pH 7 with an adsorbent dose of 0.6 g/100 mL solution and initial fluoride concentration of 10 mg/L and 100 mg/L, respectively. The equilibrium was established at 40 min. Adsorption experiment data were fitted well with Langmuir isotherm with R2 = 0.9924. Thermodynamic constants were also measured and concluded that the adsorption process was spontaneous and endothermic in nature. The removal percentage decreased slowly with increasing pH. This process is suitable for industrial effluents. The regeneration of the material is not possible. PMID:24218830

Mandal, Sandip; Tripathy, Swagatika; Padhi, Tapswani; Sahu, Manoj Kumar; Patel, Raj Kishore

2013-05-01

338

Bromide ion removal from contaminated water by calcined and uncalcined MgAl-CO3 layered double hydroxides.  

PubMed

A fundamental investigation on the uptake of bromide ion from contaminated water by calcined and uncalcined MgAl-CO3 layered double hydroxides (LDHs) were conducted in batch mode. The uptake capacity of calcined LDHs (CLDH) is higher than that of uncalcined LDHs, due to their different mechanisms which are confirmed by powder X-ray diffraction, FT-IR spectroscopy and TG-MS measurements. The former mechanism is based on the reconstruction of CLDH to Br-LDHs, whilst the latter is related to the surface adsorption. It has been found that the LDHs calcined at 500 degrees C with Mg/Al molar ratio of 4 represents the highest capacity to remove bromide ion from aqueous solution. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation, and thermodynamic parameters such as Delta G0, Delta H0 and Delta S0 were calculated from Langmuir constants. The negative value of Delta H0 confirms the exothermic nature of adsorption. Three kinetics models were used to fit the kinetics experimental data, and it was found that the pseudo-second order kinetics model could be used to describe the uptake process appropriately. The value of Ea was calculated to be 79.9 kJ/mol, which suggests that the process of uptake bromide is controlled by the reaction rate of bromide with the CLDH rather than diffusion. PMID:17850959

Lv, Liang; Wang, Yulin; Wei, Min; Cheng, Jianjun

2008-04-15

339

Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides  

PubMed Central

Background The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported. Methodology/Principal Findings The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail. Conclusions/Significance S-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites.

Wang, Lili; Li, Bin; Zhao, Xiaohong; Chen, Chunxia; Cao, Jingjing

2012-01-01

340

Sono-assisted preparation of magnetic magnesium-aluminum layered double hydroxides and their application for removing fluoride.  

PubMed

A simple ultrasound-assisted co-precipitation method in combination with a calcination treatment was developed to prepare magnetic Mg-Al layered double hydroxides composite as an adsorbent material to remove fluoride ions from aqueous solutions. The application of ultrasound in the preparation process promoted the formation of the hydrotalcite-like phase and drastically shortened the time being required for preparation of the crystalline composite. It was found that the ultrasound irradiation assistance decreased the size of the composite particles and increased the specific surface area, being favorable to the improvement of the adsorption capacity. The composite prepared under the ultrasound irradiation exhibited fairly high maximum adsorption capacity of fluoride (47.7 mg g(-1)), which was 60% higher than that of the composite prepared without the ultrasound irradiation assistance with the same aging time. The thermodynamic and kinetic studies demonstrated that the adsorption of fluoride ions involved the reconstruction of the layered structure in the composite. In addition, the magnetic composite can be effectively and simply separated by using an external magnetic field, and then regenerated by desorption and calcination. PMID:21036653

Chang, Qing; Zhu, Lihua; Luo, Zhihong; Lei, Min; Zhang, Suicheng; Tang, Heqing

2011-03-01

341

Preparation and antibacterial property of waterborne polyurethane/Zn-Al layered double hydroxides/ZnO nanocomposites.  

PubMed

In this work, a novel environmental-friendly waterborne polyurethane/ZnAl-layered double hydroxides/ZnO nanoparticles composite (WPU/ZnAl-LDHs/ZnO) was synthesized via in-situ polymerization. ZnAl-LDHs and ZnAl-LDHs/ZnO were synthesized by refluxing in an oil bath. In order to disperse ZnAl-LDHs/ZnO homogeneously into WPU matrix, ZnAl-LDHs/ZnO was firstly functionalized by isophorone diisocyanate. The incorporated content of ZnAl-LDHs/ZnO in the composite has profound effect on such physical properties as mechanical strength, thermal stability and water swelling. It is demonstrated that appropriate amount of ZnAl-LDHs/ZnO with good dispersion in the WPU matrix significantly improves the physical performance of the composites. Finally, the antibacterial activity of the composite was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus. The results indicate that WPU incorporated with ZnAl-LDHs/ZnO shows strong antibacterial activity upon contact. PMID:23646747

Zhang, Wei-De; Zheng, Yun-Min; Xu, Yang-Sen; Yu, Yu-Xiang; Shi, Qing-Shan; Liu, Lihong; Peng, Hong; Ouyang, Yousheng

2013-01-01

342

Functionalization of layered double hydroxides by intumescent flame retardant: Preparation, characterization, and application in ethylene vinyl acetate copolymer  

NASA Astrophysics Data System (ADS)

A phosphorussbnd nitrogen containing compound, N-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)-hexylacetamide-2-propyl acid (PAHPA), is synthesized and characterized. A novel flame retardant, namely layered double hydroxides (LDHs) modified with PAHPA (PAHPA-LDHs), is prepared by ion-exchange of LDHs with PAHPA. The results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray analysis with a high-angle annular dark-field scanning transmission electron microscope show that PAHPA intercalated LDHs. The X-ray diffraction and transmission electron microscopy (TEM) results show that PAHPA-LDHs achieve well dispersion in ethylene vinyl acetate copolymer (EVA) matrix and the EVA/PAHPA-LDHs nanocomposites (i.e. EVA filled with 5 wt% PAHPA-LDHs) are formed by polymer melt intercalation. Thermal stability and flammability properties are investigated by thermogravimetric analysis and cone calorimeter tests. The results show that the addition of PAHPA-LDHs improves thermal stability and reduces obviously the flammability of EVA resin. Compared with pure EVA resin, the peak heat release rate of the EVA/PAHPA-LDHs nanocomposites is reduced by about 43%. The results of scanning electron microscopy and TEM indicate that a compact and dense intumescent char is formed for the EVA/PAHPA-LDHs nanocomposites after combustion.

Huang, Guobo; Fei, Zhengdong; Chen, Xiaoying; Qiu, Fangli; Wang, Xu; Gao, Jianrong

2012-10-01

343

Synthesis, characterization and magnetic behavior of Mg-Fe-Al mixed oxides based on layered double hydroxide  

NASA Astrophysics Data System (ADS)

In the present work, Mg-Al-Fe layered double hydroxides were prepared by coprecipitation reaction with hydrothermal treatment. The characterization of precursors and their corresponding calcinated products (mixed oxides) were carried out by X ray diffraction, X-ray photoelectron spectroscopy (XPS), termogravimetric analysis and differential scanning calorimetry, diffuse reflectance UV-vis spectroscopy, specific surface area, Mössbauaer and magnetic properties. The Fe3+ species were observed in tetrahedrally and octahedrally coordination in brucite layered. The XPS analysis shows that the Fe3+ ions can be found in two coordination environments (tetrahedral and octahedral) as mixed oxides, and as spinel-structure. Oxides show a decrease in the specific surface areas when the iron loading is increased. The magnetic and Mössbauaer response show that MgAlFe mixed oxides are different behaviours such as different population ratios of ferromagnetic, weak-ferromagnetic, paramagnetic and superparamagnetic phases. The better crystallization of spinel structure with increased temperature, is correlated with the improved magnetic properties.

Heredia, Angélica C.; Oliva, Marcos I.; Agú, Ulises; Zandalazini, Carlos I.; Marchetti, Sergio G.; Herrero, Eduardo R.; Crivello, Mónica E.

2013-09-01

344

Treatment of high fluoride concentration water by MgAl-CO3 layered double hydroxides: kinetic and equilibrium studies.  

PubMed

MgAl-CO(3) layered double hydroxides (LDHs) have been employed to treat high fluoride concentration solution. The influences of solution pH, initial fluoride concentration and other anions in the solution were investigated by a series of batch experiments. A marked decrease in the amount of adsorbed fluoride by LDHs is observed with increasing pH. The extent of fluoride removal in the presence of other anions decreases in the order HCO(3)(-)>Cl(-)>H(2)PO(4)(-)>SO(4)(2-). The equilibrium isotherm for fluoride uptake corresponds closely to the Langmuir-Freundlich (L-F) model. The maximum capacity of LDHs for fluoride ions and the Gibbs free energy (DeltaG(0)) for the defluoridation process were calculated to be 319.8+/-5.7mg/g and -9.0+/-0.66kJ/mol, respectively. The negative value of DeltaG(0) indicates the spontaneous nature of the treatment process. Four kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second order, the modified multiplex and the double exponential models. It was found that the modified multiplex model, involving a rapid first order step and a slow second order step most closely described the kinetics. The activation energies for the two steps are 37.2+/-5.26 and 72.6+/-4.52kJ/mol, respectively, suggesting that the rapid step is controlled by diffusion processes, whilst the second step is controlled by the reaction of fluoride with the LDHs. PMID:17316743

Lv, Liang; He, Jing; Wei, Min; Evans, D G; Zhou, Zhaoliang

2007-04-01

345

Synthesis, sustained release properties of magnetically functionalized organic-inorganic materials: Amoxicillin anions intercalated magnetic layered double hydroxides via calcined precursors at room temperature  

NASA Astrophysics Data System (ADS)

Zinc-aluminum-carbonate-layered double hydroxides (ZnAl-CO 3-LDHs), loaded with magnetic substrates (Fe 3O 4), were prepared for sustained drug-targeting delivery. From the X-ray diffraction results, it was found that the magnetic substrates were successfully incorporated with LDHs and highly dispersed in the hydrotalcite structure. After intercalation with an antibiotic drug (amoxicillin) by using a calcinations-reconstruction method, the basal spacing of layered double hydroxides increased from 7.51 Å to 12.35 Å, indicating that amoxicillin was successfully intercalated into the interlay space of LDHs as a monolayer. Furthermore, in vitro drug release experiments in pH 7.4 phosphate buffer solution (PBS) showed sustained release profiles with amoxicillin as a model drug. Magnetic measurements revealed that the composite possessed paramagnetic properties at room temperature.

Wang, Jun; Liu, Qi; Zhang, Guangchun; Li, Zhanshuang; Yang, Piaoping; Jing, Xiaoyan; Zhang, Milin; Liu, Tianfu; Jiang, Zhaohua

2009-09-01

346

Studies on the intercalation of naproxen into layered double hydroxide and its thermal decomposition by in situ FT-IR and in situ HT-XRD  

NASA Astrophysics Data System (ADS)

Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system.

Wei, Min; Shi, Shuxian; Wang, Ji; Li, Yong; Duan, Xue

2004-07-01

347

Fire retardancy of bis[2-(methacryloyloxy)ethyl] phosphate modified poly(methyl methacrylate) nanocomposites containing layered double hydroxide and montmorillonite  

Microsoft Academic Search

Copolymer nanocomposites were prepared by suspension copolymerization of bis[2-(methacryloyloxy)ethyl] phosphate and methyl methacrylate, together with bis(2-ethylhexyl) phosphate layered double hydroxide and a montmorillonite, Cloisite 93A. X-ray diffraction and transmission electron microscopy were used to characterize the morphology of nanocomposites and the dispersion of additives in the polymer. The thermal stability of the nanocomposites has been assessed by thermogravimetric analysis and

Linjiang Wang; Shengpei Su; Dan Chen; Charles A. Wilkie

2009-01-01

348

The pH effects on the formation of Ni\\/Al nitrate form layered double hydroxides (LDHs) by chemical precipitation and hydrothermal method  

Microsoft Academic Search

The Ni\\/Al nitrate form layered double hydroxides (LDHs) were successfully synthesized at atmosphere condition by chemical precipitation and hydrothermal methods through pH control. Samples obtained at various pH conditions were characterized by XRD, FT-IR, TG–MS, ICP\\/AES and CHN element analyses. It was found that at low pH value, nitrate hydrotalcite was obtained, while at high pH value, carbonate hydrotalcite was

KunWei Li; Nobuhiro Kumada; Yoshinori Yonesaki; Takahiro Takei; Nobukazu Kinomura; Hao Wang; Chao Wang

2010-01-01

349

The influence of carbon nanotubes, organically modified montmorillonites and layered double hydroxides on the thermal degradation and fire retardancy of polyethylene, ethylene–vinyl acetate copolymer and polystyrene  

Microsoft Academic Search

Nanocomposites of polyethylene, ethylene–vinyl acetate copolymer and polystyrene with single- and multi-wall carbon nanotubes, organically modified montmorillonites and layered double hydroxides were prepared by melt blending. Their morphologies were assessed by X-ray diffraction and transmission electron microscopy, while the flammability properties were evaluated by thermogravimetric analysis and cone calorimetry. The relative amounts and the identity of the degradation products are

Marius C. Costache; Matthew J. Heidecker; E. Manias; Giovanni Camino; Alberto Frache; Gunter Beyer; Rakesh K. Gupta; Charles A. Wilkie

2007-01-01

350

Comparative study of Mg/Al- and Zn/Al-layered double hydroxide-perindopril erbumine nanocomposites for inhibition of angiotensin-converting enzyme  

PubMed Central

The intercalation of a drug active, perindopril, into Mg/Al-layered double hydroxide for the formation of a new nanocomposite, PMAE, was accomplished using a simple ion exchange technique. A relatively high loading percentage of perindopril of about 36.5% (w/w) indicates that intercalation of the active took place in the Mg/Al inorganic interlayer. Intercalation was further supported by Fourier transform infrared spectroscopy, and thermal analysis shows markedly enhanced thermal stability of the active. The release of perindopril from the nanocomposite occurred in a controlled manner governed by pseudo-second order kinetics. MTT assay showed no cytotoxicity effects from either Mg/Al-layered double hydroxide or its nanocomposite, PMAE. Mg/Al-layered double hydroxide showed angiotensin-converting enzyme inhibitory activity, with 5.6% inhibition after 90 minutes of incubation. On incubation of angiotensin-converting enzyme with 0.5 ?g/mL of the PMAE nanocomposite, inhibition of the enzyme increased from 56.6% to 70.6% at 30 and 90 minutes, respectively. These results are comparable with data reported in the literature for Zn/Al-perindopril.

Hussein Al Ali, Samer Hasan; Al-Qubaisi, Mothanna; Hussein, Mohd Zobir; Ismail, Maznah; Zainal, Zulkarnain; Hakim, Muhammad Nazrul

2012-01-01

351

Photocatalytic degradation of 2,4-dichlorophenol with MgAlTi mixed oxides catalysts obtained from layered double hydroxides.  

PubMed

MgAl and MgAlTi mixed oxides were obtained from the thermal treatment of LDH materials synthesized by the sol-gel method; these materials were characterized by N2 physisorption, XRD, UV-vis, XPS, EDS-SEM and TEM techniques. According to the results, Ti was incorporated in the LDH layer when content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60 min. According to the results, Ti was incorporated in the LDH layer when the content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP with the MgAl and MgAlTi mixed oxides, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60 min. PMID:24184126

Mendoza-Damián, G; Tzompantzi, F; Mantilla, A; Barrera, A; Lartundo-Rojas, L

2013-12-15

352

Synthesis, characterization and photocatalytic activity of mixed oxides derived from ZnAlTi ternary layered double hydroxides  

NASA Astrophysics Data System (ADS)

A new series of Ti4+ containing ZnAl-LDHs with varying Zn:Al:Ti (~3:1:0-3:0.5:0.5) ratio were prepared by coprecipitation of homogeneous solution metal salts and characterized by various physicochemical methods. Powder XRD revealed the formation of well crystallized LDH even at the highest Ti4+ content. On thermal treatment at 450 °C, the well crystallized LDH precursors yielded mixed oxides with BET surface area in the range 92-118 m2/g. UV-vis diffuse reflection spectroscopy (DRS) showed a marginal decrease of band gap energy for calcined ZnAlTi-LDHs in comparison to either ZnO or TiO2-P25. The TEM analyses of a representative sample (as-synthesized and calcined) indicated more or less uniform distribution of titanium species. The derived mixed oxides from titanium containing LDH precursors demonstrated better activity toward photodegradation of methylene blue and rhodamine B than those of a physical mixture of ZnO and TiO2. Moreover, the present work not only provided a first hand understanding about semiconductor properties of ZnAlTi-LDHs but also demonstrated their potential as photocatalysts for degradation of organic pollutants.

Sahu, R. K.; Mohanta, B. S.; Das, N. N.

2013-09-01

353

Hybrid inorganic\\/organic composites of Mg–Al layered double hydroxides intercalated with citrate, malate, and tartrate prepared by co-precipitation  

Microsoft Academic Search

Inorganic\\/organic composite materials composed of Mg–Al layered double hydroxides (Mg–Al LDHs) intercalated with citrate (C6H5O73?), malate (C4H4O52?), or tartrate (C4H4O62?) anions were prepared by a co-precipitation technique and characterized by X-ray diffraction and compositional analyses. The molecular orientation of the organic component in the interlayer space was determined. At low intercalation levels, citrate ion was inclined at an angle of

Tomohito Kameda; Hidenori Takeuchi; Toshiaki Yoshioka

2009-01-01

354

Photoresponsive materials: photo-switching in a hybrid material made of magnetic layered double hydroxides intercalated with azobenzene molecules (adv. Mater. 24/2014).  

PubMed

On page 4156, H. Garcia, C. Marti-Gastaldo, E. Coronado and co-workers describe the intercalation of a switchable trans-azobenzene-4,4'-dicarboxylate guest in a ferromagnetic Co(2+) Al(3+) -layered double hydroxide, yielding a magnetic photoresponsive hybrid. Exposure to UV light triggers the guest's isomerization, which modifies the structure of the layered hybrid to reduce the magnetization at 2 K by 27% and increase the TM by ca. 1 K. This change can be reverted with water, thus enabling reversible switching of the magnetism of the solid. PMID:24946998

Abellán, Gonzalo; Coronado, Eugenio; Martí-Gastaldo, Carlos; Ribera, Antonio; Jordá, Jose Luis; García, Hermenegildo

2014-06-01

355

Comparative Study of Mg/ M(III) ( M=Al, Ga, In) Layered Double Hydroxides Obtained by Coprecipitation and the Sol-Gel Method  

NASA Astrophysics Data System (ADS)

Various layered double hydroxides (LDHs) consisting of magnesium and a trivalent metal (Al, Ga or In) in an Mg/ M(III) ratio of 3 were prepared by precipitation from the corresponding nitrates and also from magnesium ethoxide and the acetylacetonates of the trivalent metals using the sol-gel method. The six LDHs thus obtained were calcined at 500°C. All solids were characterized by XRD and IR spectroscopy prior to and after calcination. Their textural properties were determined from nitrogen adsorption measurements and their surface chemical properties by CO 2 chemisorption.

Aramendía, María. A.; Borau, Victoriano; Jiménez, César; Marinas, José M.; Ruiz, José R.; Urbano, Francisco J.

2002-10-01

356

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

357

Magnesium Hydroxide  

MedlinePLUS

Magnesium hydroxide is used on a short-term basis to treat constipation.This medication is sometimes prescribed ... Magnesium hydroxide come as a tablet and liquid to take by mouth. It usually is taken as ...

358

In Vitro Inhibition of Histamine Release Behavior of Cetirizine Intercalated into Zn/Al- and Mg/Al-Layered Double Hydroxides  

PubMed Central

The intercalation of cetirizine into two types of layered double hydroxides, Zn/Al and Mg/Al, has been investigated by the ion exchange method to form CTZAN and CTMAN nanocomposites, respectively. The basal spacing of the nanocomposites were expanded to 31.9 Å for CTZAN and 31.2 Å for CTMAN, suggesting that cetirizine anion was intercalated into Layered double hydroxides (LDHs) and arranged in a tilted bilayer fashion. A Fourier transform infrared spectroscopy (FTIR) study supported the formation of both the nanocomposites, and the intercalated cetirizine is thermally more stable than its counterpart in free state. The loading of cetirizine in the nanocomposite was estimated to be about 57.2% for CTZAN and 60.7% CTMAN. The cetirizine release from the nanocomposites show sustained release manner and the release rate of cetirizine from CTZAN and CTMAN nanocomposites at pH 7.4 is remarkably lower than that at pH 4.8, presumably due to the different release mechanism. The inhibition of histamine release from RBL2H3 cells by the free cetirizine is higher than the intercalated cetirizine both in CTZAN and CTMAN nanocomposites. The viability in human Chang liver cells at 1000 ?g/mL for CTZAN and CTMAN nanocomposites are 74.5 and 91.9%, respectively.

Hussein-Al-Ali, Samer Hasan; Al-Qubaisi, Mothanna; Hussein, Mohd Zobir; Ismail, Maznah; Zainal, Zulkarnain; Hakim, Muhammad Nazrul

2012-01-01

359

Controlled release and angiotensin-converting enzyme inhibition properties of an antihypertensive drug based on a perindopril erbumine-layered double hydroxide nanocomposite  

PubMed Central

Background The intercalation of perindopril erbumine into Zn/Al-NO3-layered double hydroxide resulted in the formation of a host-guest type of material. By virtue of the ion-exchange properties of layered double hydroxide, perindopril erbumine was released in a sustained manner. Therefore, this intercalated material can be used as a controlled-release formulation. Results Perindopril was intercalated into the interlayers and formed a well ordered, layered organic-inorganic nanocomposite. The basal spacing of the products was expanded to 21.7 Å and 19.9 Å by the ion-exchange and coprecipitation methods, respectively, in a bilayer and a monolayer arrangement, respectively. The release of perindopril from the nanocomposite synthesized by the coprecipitation method was slower than that of its counterpart synthesized by the ion-exchange method. The rate of release was governed by pseudo-second order kinetics. An in vitro antihypertensive assay showed that the intercalation process results in effectiveness similar to that of the antihypertensive properties of perindopril. Conclusion Intercalated perindopril showed better thermal stability than its free counterpart. The resulting material showed sustained-release properties and can therefore be used as a controlled-release formulation.

Al Ali, Samer Hasan Hussein; Al-Qubaisi, Mothanna; Hussein, Mohd Zobir; Ismail, Maznah; Zainal, Zulkarnain; Hakim, Muhammad Nazrul

2012-01-01

360

LDH isoenzymes in cerebrospinal fluid in various brain tumours.  

PubMed Central

This study examined the isoenzymatic pattern of LDH in the cerebrospinal fluid (CSF) as well as the ratio between the five fractions of LDH among patients with various brain tumours, carcinomatous meningitis and control groups. LDH 1/LDH 2 less than 1 was found significant for carcinomatous meningitis (p less than 0.001) and brain metastases (p less than 0.001). LDH 1/LDH 2 ratio was found to be significantly lower in carcinomatous meningitis than in brain metastases (p less than 0.05). No LDH 1/LDH 2 ratios smaller than 1 were found in the other groups. The LDH 1/LDH 2 ratio smaller than 1 was found in the early stage of carcinomatous meningitis without other evidences of the involvement of the leptomeninges. Examination of LDH 1/LDH 2 can be found as an adjunctive method to identify brain metastases and carcinomatous meningitis at the initial stage.

Lampl, Y; Paniri, Y; Eshel, Y; Sarova-Pinhas, I

1990-01-01

361

Structure and luminescence behaviour of as-synthesized, calcined, and restored MgAlEu-LDH with high crystallinity.  

PubMed

Highly crystalline Eu(3+)-incorporated MgAl layered double hydroxides (LDHs) were synthesized by the homogeneous precipitation method. For the crystals as-prepared, after their calcination from 200-1000 °C, and, further, after restoration in a Na(2)CO(3) solution, the structural and luminescent changes were investigated for the first time. Eu(3+) ions with a coordination number of, probably, 8, were incorporated into the hydrotalcite layer, which led to a basal spacing (d(basal)) increase, microstrain formation, and crystalline morphology imperfections, while retaining the original lattice symmetry, R3[combining macron]m. In the deconstruction process due to calcination, the Eu(3+) ions restrained the formation of the spinel phase from the layered double oxide (LDO), but did not significantly change the memory effect, by which LDOs can convert to LDHs during the hydration process. For the reversible phase transformation between LDH and LDO, the morphology observation revealed that, in addition to the formation of pores on the surface, nano-slabs were formed, especially for the restored crystals. A layered phase with a d(basal) of 5.8 Å, due to bridging bidentate carbonates with the hydrotalcite layer, was formed in the calcination process at low temperature (300 °C) before the formation of LDO, but could not be restored to a large spacing. Typical (5)D(0) ? (7)F(J) (J = 0-4) transitions of Eu(3+) at 579, 593, 615, 653, and 698 nm were observed in the photoluminescence spectra and the intensity of the dominating 615 nm band decreased with the LDH deconstruction and the formation of free water, and then increased with the formation of LDOs in the calcination process, and vice versa in the reconstruction process. The Eu(3+) ions had a probable 9- or 10-coordination mode in addition to the probable 8-coordination mode as the spinel phase appeared. PMID:22930336

Zhao, Yushuang; Li, Ji-Guang; Fang, Fang; Chu, Nankai; Ma, Hui; Yang, Xiaojing

2012-10-21

362

Comparative values of CSF-LDH isoenzymes in neurological disorders.  

PubMed

The present study was carried out to evaluate the usefulness of Cerebrospinal fluid (CSF) Lactate dehydrogenase (LDH) isoenzymes in the diagnosis in tuberculous meningitis (TBM), pyogenic meningitis (PM), viral encephalitis (VE) and hydrocephalus (HC). A characteristic dominance of isoenzymes in cerebrospinal fluid was observed: LDH4 in TBM while LDH3 in PM. However, in VE and HC, LDH2 and LDH1 were dominant respectively. The control subjects revealed the presence of isoenzymes LDH1 and LDH2 in very low concentrations. Pattern of LDH isoenzymes in CSF may serve as a diagnostic tool to differentiate these neurological disorders. PMID:10798016

Kamat, D V; Chakravorty, B P

1999-01-01

363

Synthesis and characterization of a new Sn-incorporated CoAl-layered double hydroxide (LDH) and catalytic performance of Co-spinel microcrystallites in the partial oxidation of methanol  

Microsoft Academic Search

M(II)AlSn-LDHs with M(II) being Mg, Ni or Co were synthesized by a coprecipitation method. The influence of Sn on the thermal transformations and redox properties were investigated in detail using XRD, TG\\/DTA, SEM, TPR, 119Sn-MAS NMR and UV-visible diffuse-reflectance (DR) spectroscopy methods. Some of these samples calcined at 450°C were tested as catalysts in the partial oxidation of methanol (POM)

S. Velu; K. Suzuki

2000-01-01

364

[Supra-molecular assembly and magnetic targeted slow-release effect of "dextran-magnetic layered double hydroxide-fluorouracil" drug delivery system].  

PubMed

The drug-loading system of DMF (dextran - magnetic layered double hydroxide - fluorouracil) was synthesized by "co-precipitation intercalated assembly - dextran composite in situ - solvent conversion" technology. The crystal-phase characteristic and slow-release performance of DMF were investigated through X-ray diffraction (XRD), infrared spectrum (IR), transmission electron microscopy (TEM), thermogravimetry (TG) and in vitro release experiment. The targeted transshipment and slow-release effect of DMF system were evaluated by in vivo animal experiment. It was showed that the XRD of DMF matched with R-sixtetragonum type layered double hydroxide and Fd-3m cubic type ferrite. IR test demonstrated that the DMF system was a supra-molecular complex consisted of Dextran (DET), magnetic layered double hydroxide (MLDH) and fluorouracil (FU) components. The two-level supra-molecular MLDH-FU presented six-edge lozenge TEM morphology, with layered characteristics. DET on the surface of DMF was capable of protecting the layered structure of MLDH-FU, improving particle dispersion properties, and strengthening the slow-release performance of the drug delivery system. The drug release model of DMF at pH 7.35 of PBS in vitro fit to the zero-order kinetics equation C = 1.1716 x 10(-5) + 4.4626 x 10(-7) t. The drug delivery system DMF could transport drugs principally to in vivo target organs with a local effect, targeted specificity, and excellent circulation transshipment performance. The pharmacokinetic process of DMF presented multi-peak phenomenon with peak attenuation and cyclic growth. The peaks appeared at 0.25, 1, 3, 5 and 9 d separately after dosing intervention. The first peak process of DMF accorded with a pharmacokinetic equation of C(FU) = 14.34 e(-0.530t) + 36.04 e(-0.321t) + 24.18 e(-0.96t), and presented the characteristic of slow absorption and fast elimination. As for subsequent peak processes, half-life increased, bioavailability increased, and plasma clearance decreased. The highest peak value of DMF was 1/37 of original value of FU, and the relative bioavailability was 419% to original FU. PMID:22260036

Gou, Guo-jing; Liu, Yan-hong; Sun, Yue; Huang, Je; Xue, Bing; Dong, Li-e

2011-11-01

365

Layer-by-layer engineered Co-Al hydroxide nanosheets/graphene multilayer films as flexible electrode for supercapacitor.  

PubMed

Multilayer films of Co-Al layered double hydroxide nanosheets (Co-Al LDH-NS) and graphene oxide (GO) were fabricated through layer-by-layer (LBL) assembly. By using a three-electrode system, the electrochemical performances of the films were investigated to evaluate their potential as electrode materials to be used in flexible supercapacitor devices. The Co-Al LDH-NS/GO multilayer films exhibited a high specific capacitance of 880 F/g and area capacitance of 70 F/m(2) under the scan rate of 5 mV/s. And the film exhibited good cycle stability over 2000 cycles. After treating the films at 200 °C in H(2) atmosphere, the specific capacitance and area capacitance were largely increased up to 1204 F/g and 90 F/m(2) due to partial reduction of GO. A flexible electrode by depositing Co-Al LDH-NS/GO multilayer film onto PET substrate was prepared to show the potential of Co-Al LDH-NS/GO films for flexible energy storage. PMID:22124210

Dong, Xinyi; Wang, Lei; Wang, Dong; Li, Cheng; Jin, Jian

2012-01-10

366

Purification and Properties of the Threespine Stickleback ( Gasterosteus aculeatus) Lactate Dehydrogenase LDH-B 4 and LDH-C 4 Isoenzymes  

Microsoft Academic Search

In the threespine stickleback (Gasterosteus aculeatus) lactate dehydrogenase (LDH, EC 1.1.1.27) is encoded by three loci, Ldh-A, Ldh-B, and Ldh-C. LDH-B4 isoenzyme restricted its function to eye and brain, while LDH-C4 isoenzyme functions in the eye. In the Dead Vistula stickleback population, none of LDH loci is polymorphic. The LDH-B4 and LDH-C4 isoenzymes from the eye were purified to homogeneity

Marek S. Zitara; Jadwiga Gronczewska; Edward F. Skorkowski

1997-01-01

367

DNA-enhanced peroxidase-like activity of layered double hydroxide nanosheets and applications in H2O2 and glucose sensing.  

PubMed

LDH nanosheets were obtained via continuous impaction and exfoliation by herring sperm DNA molecules using a constant vibration method. DNA-LDH nanohybrids were composed by electrostatic forces and they exhibited DNA-enhanced peroxidase-like activity. The morphology and structure of DNA-LDH nanohybrids were analyzed by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and atomic force microscopy (AFM) characterization. On the basis of the high catalytic activity of DNA/CuAl-LDH nanosheets, a rapid, sensitive, and convenient approach was developed for colorimetric detection of H2O2 and blood glucose. This method can be potentially applied in medical diagnostics and biotechnology fields. PMID:24065121

Chen, Lijian; Sun, Kaifang; Li, Peipei; Fan, Xianzhong; Sun, Jianchao; Ai, Shiyun

2013-11-21

368

NICKEL HYDROXIDES  

SciTech Connect

Nickel hydroxides have been used as the active material in the positive electrodes of several alkaline batteries for over a century. These materials continue to attract a lot of attention because of the commercial importance of nickel-cadmium and nickel-metal hydride batteries. This review gives a brief overview of the structure of nickel hydroxide battery electrodes and a more detailed review of the solid state chemistry and electrochemistry of the electrode materials. Emphasis is on work done since 1989.

MCBREEN,J.

1997-11-01

369

Synthesis and anion exchange properties of a Zn/Ni double hydroxide salt with a guarinoite structure  

NASA Astrophysics Data System (ADS)

In this study, the first route to synthesize a compound with the guarinoite structure (Zn,Co,Ni) 6(SO 4)(OH,Cl) 10·5H 2O is reported. Zn/Ni guarinoite is obtained from the reaction of NiSO 4·7H 2O with solid ZnO in aqueous solution. The resulting green Zn/Ni guarinoite ((Zn 3.52Ni 1.63)(SO 4) 1.33(OH 7.64)·4.67H 2O) was characterized by X-ray diffraction, infrared spectrometry, UV-Visible spectrometry and thermal analysis. It is shown that its structure is similar to the one described for the layered Zn sulfate hydroxide hydrate, i.e. brucite layers with {1}/{4} empty octahedra presenting tetrahedrally coordinated divalent atoms above and below the empty octahedra. Ni atoms are located in the octahedra and zinc atoms in tetrahedra and octahedra. In this structure the exchangeable anions are located at the apex of tetrahedra. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the Zn/Ni guarinoite is composed of aggregates of hexagonal plates of several hundreds of nanometers. Due to its interest for industrial or environmental applications, the exchange of sulfate groups by carbonates has been investigated. Results show a limited exchange and a higher affinity of the Zn/Ni guarinoite for sulfates compared to carbonates.

Delorme, F.; Seron, A.; Licheron, M.; Veron, E.; Giovannelli, F.; Beny, C.; Jean-Prost, V.; Martineau, D.

2009-09-01

370

Synthesis and anion exchange properties of a Zn/Ni double hydroxide salt with a guarinoite structure  

SciTech Connect

In this study, the first route to synthesize a compound with the guarinoite structure (Zn,Co,Ni){sub 6}(SO{sub 4})(OH,Cl){sub 10}.5H{sub 2}O is reported. Zn/Ni guarinoite is obtained from the reaction of NiSO{sub 4}.7H{sub 2}O with solid ZnO in aqueous solution. The resulting green Zn/Ni guarinoite ((Zn{sub 3.52}Ni{sub 1.63})(SO{sub 4}){sub 1.33}(OH{sub 7.64}).4.67H{sub 2}O) was characterized by X-ray diffraction, infrared spectrometry, UV-Visible spectrometry and thermal analysis. It is shown that its structure is similar to the one described for the layered Zn sulfate hydroxide hydrate, i.e. brucite layers with 1/4 empty octahedra presenting tetrahedrally coordinated divalent atoms above and below the empty octahedra. Ni atoms are located in the octahedra and zinc atoms in tetrahedra and octahedra. In this structure the exchangeable anions are located at the apex of tetrahedra. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the Zn/Ni guarinoite is composed of aggregates of hexagonal plates of several hundreds of nanometers. Due to its interest for industrial or environmental applications, the exchange of sulfate groups by carbonates has been investigated. Results show a limited exchange and a higher affinity of the Zn/Ni guarinoite for sulfates compared to carbonates. - Graphical abstract: SEM micrograph (secondary electrons) of the synthesized Zn/Ni guarinoite showing that aggregates are composed of small plate-like particles.

Delorme, F., E-mail: delormef@corning.co [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 ORLEANS Cedex 2 (France); CORNING SAS, CETC, 7 bis Avenue Valvins, 77210 AVON (France); Seron, A. [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 ORLEANS Cedex 2 (France); Licheron, M.; Veron, E. [CEMHTI, 1D avenue de la Recherche Scientifique 45071 ORLEANS Cedex 2 (France); Giovannelli, F. [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures 41029, BLOIS (France); Beny, C.; Jean-Prost, V.; Martineau, D. [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 ORLEANS Cedex 2 (France)

2009-09-15

371

Chromium (VI) and zinc (II) waste water co-treatment by forming layered double hydroxides: mechanism discussion via two different processes and application in real plating water.  

PubMed

Two processes, adsorption after synthesis (AAS) and adsorption during synthesis (ADS) were compared in CrO4(2-) and Zn2+/CrO4(2-) removal. Kinetic results showed that ADS was a better method than AAS, since Cr content was 0.65/0.81 mmol/g in Cr-ADS/ZnCr-ADS, but it was only 0.37/0.56 mmol/g in Cr-AAS/ZnCr-AAS. Then, a low-cost mixture was proposed to function as ADS raw materials in treating real plating waters. This mixture first got an isothermal saturation of 1.1 mmol/g in simulated CrO4(2-) water. When Zn2+ was co-treated, it was increased to 1.3 mmol/g. At the same time, a Zn2+ removal of 1.5 mmol/g was attained. Furthermore, real plating water co-treatment reached equilibrium in 6h and obtained 1.4/0.9 mmol/g for Zn2+/CrO4(2-), respectively. According to XRD analysis, this co-treatment enhancement resulted from the formation of Zn and Cr contained layered double hydroxide. PMID:22230757

Zhang, Jia; Li, Yang; Zhou, Jizhi; Chen, Dan; Qian, Guangren

2012-02-29

372

Synthesis of self-assembled layered double hydroxides/carbon composites by in situ solvothermal method and their application in capacitors  

SciTech Connect

Nickel-aluminum layered double hydroxides/carbon (Ni-Al LDHs/C) composites have been successfully fabricated via a facile in situ water-ethanol system. LDHs nanosheets could highly disperse on the surface of colloidal carbonaceous spheres through the interfacial electrostatic force. Ni-Al LDHs/C composite electrode prepared at 50% ethanol system exhibits the highest capacitance of 1064 F g{sup -1} at a current of 2.5 A g{sup -1}, leading to a significant improvement in relation to each individual counterpart (3.5 and 463 F g{sup -1} for carbon and Ni-Al LDHs at 2.5 A g{sup -1}, respectively). And a possible mechanism was proposed for the formation of the composites. Highlights: Black-Right-Pointing-Pointer Ni-Al LDHs/C composites have been self-assembled by an in situ solvothermal method. Black-Right-Pointing-Pointer A possible growth mechanism to explain the composite is proposed. Black-Right-Pointing-Pointer Ni-Al LDHs/C composites display better electrochemical performance.

Wei, Jinbo [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Wang, Jun, E-mail: junwangzhqw1888@sohu.com [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Song, Yanchao; Li, Zhanshuang; Gao, Zan; Mann, Tom; Zhang, Milin [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

2012-12-15

373

Synthesis of a novel layered double hydroxides [MgAl(4)(OH)(12)](Cl)(2)·2.4H(2)O and its anion-exchange properties.  

PubMed

A novel layered double hydroxide of Mg and Al with composition [Mg(0.96)Al(4.00)(OH)(12)]Cl(1.86)(CO(3))(0.03)·2.4H(2)O, designated as MgAl(4)-Cl, was synthesized by mixing crystalline gibbsite (?-Al(OH)(3)) and solid MgCl(2)·6H(2)O with subsequent hydrothermal treatment at 160 °C for 72h. The MgAl(4)-Cl exhibited a crystalline material of a layered structure, as evidenced from X-ray diffraction. Anion uptake experiments with the MgAl(4)-Cl showed that Cl(-) in the interlayer space can be exchanged with anions such as Br(-), H(2)PO(4)(-), CO(3)(2-) or dodecyl sulfate (DS(-)) from aqueous solutions with preservation of the layered structure. Uptake of NO(3)(-), BrO(3)(-) or SO(4)(2-) on the MgAl(4)-Cl showed different behavior; these anions can be exchanged within 1h maintaining the layered structure, but a release of Mg(2+) cations from the sample was observed with increased reaction time, resulting in collapse of the layered structure and formation of the gibbsite phase, as determined from chemical analyses and X-ray diffraction. PMID:21074937

Chitrakar, Ramesh; Makita, Yoji; Sonoda, Akinari; Hirotsu, Takahiro

2011-01-30

374

Preservation of Fe complexes into layered double hydroxides improves the efficiency and the chemical stability of Fe complexes used as heterogeneous photo-Fenton catalysts  

NASA Astrophysics Data System (ADS)

Fe complexes ([Fe(Ox)3]3- and [Fe(Cit)2]3-) have been heterogenized through preservation into MgAl-layered double hydroxides (LDHs). The SEM images and N2 adsorption-desorption isotherm showed that the obtained products were mesoporous materials and the specific surface area of LDHs/Fe-complex composites were obviously greater than pristine LDHs, which is beneficial for the adsorption of organic pollutants. Measurement of adsorptive and heterogeneous photo-Fenton degradation of methylene blue (MB) suggested that the LDHs/Fe-complex composites had an excellent adsorption capacity at different pHs and the adsorption isotherm modeled well with the Langmuir equation. The enhancement of adsorption capacity may be attributed to the external hydroxyl groups of LDHs. MB was enriched on the surface of LDHs/Fe-complex composites, which favors MB degradation in situ. The obtained composites displayed an high photocatalytic activity in a pH range from 4.0 to 6.0 with dissolved Fe cation at a low concentration. Therefore, Fe complexes intercalated into LDHs can be an effective heterogeneous Fenton catalyst for oxidation of organic pollutants in a relatively wide pH range.

Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Lu, Yonghong; Zhu, Nengwu; Hu, Zhixian

2013-12-01

375

Determination of Iodate in Food, Environmental, and Biological Samples after Solid-Phase Extraction with Ni-Al-Zr Ternary Layered Double Hydroxide as a Nanosorbent  

PubMed Central

Nanostructured nickel-aluminum-zirconium ternary layered double hydroxide was successfully applied as a solid-phase extraction sorbent for the separation and pre-concentration of trace levels of iodate in food, environmental and biological samples. An indirect method was used for monitoring of the extracted iodate ions. The method is based on the reaction of the iodate with iodide in acidic solution to produce iodine, which can be spectrophotometrically monitored at 352?nm. The absorbance is directly proportional to the concentration of iodate in the sample. The effect of several parameters such as pH, sample flow rate, amount of nanosorbent, elution conditions, sample volume, and coexisting ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12??g?mL?1 and 20, respectively. The calibration graph using the preconcentration system was linear in the range of 0.2–2.8??g?mL?1 with a correlation coefficient of 0.998. In order to validate the presented method, a certified reference material, NIST SRM 1549, was also analyzed.

Abdolmohammad-Zadeh, Hossein; Tavarid, Keyvan; Talleb, Zeynab

2012-01-01

376

Enhancing electrochemical reaction sites in nickel-cobalt layered double hydroxides on zinc tin oxide nanowires: a hybrid material for an asymmetric supercapacitor device.  

PubMed

Conducting nanowires are of particular interest in energy-related research on devices such as supercapacitors, batteries, water splitting electrodes and solar cells. Their direct electrode/current collector contact and highly conductive 1D structure enable conducting nanowires to provide ultrafast charge transportation. In this paper, we report the facile synthesis of nickel cobalt layered double hydroxides (LDHs) on conducting Zn(2)SnO(4) (ZTO) and the application of this material to a supercapacitor. This study also presents the first report of an enhancement of the active faradic reaction sites (electroactive sites) resulting from the heterostructure. This novel material demonstrates outstanding electrochemical performance with a high specific capacitance of 1805 F g(-1) at 0.5 A g(-1), and an excellent rate performance of 1275 F g(-1) can be achieved at 100 A g(-1). Furthermore, an asymmetric supercapacitor was successfully fabricated using active carbon as a negative electrode. This asymmetric device exhibits a high energy density of 23.7 W h kg(-1) at a power density of 284.2 W kg(-1). Meanwhile, a high power density of 5817.2 W kg(-1) can be achieved at an energy density of 9.7 W h kg(-1). More importantly, this device exhibits long-term cycling stability, with 92.7% capacity retention after 5000 cycles. PMID:23076678

Wang, Xu; Sumboja, Afriyanti; Lin, Mengfang; Yan, Jian; Lee, Pooi See

2012-11-21

377

Efficient removal of dyes by a novel magnetic Fe3O4/ZnCr-layered double hydroxide adsorbent from heavy metal wastewater.  

PubMed

A novel magnetic Fe(3)O(4)/ZnCr-layered double hydroxide adsorbent was produced from electroplating wastewater and pickling waste liquor via a two-step microwave hydrothermal method. Adsorption of methyl orange (MO) from water was studied using this material. The effects of three variables have been investigated by a single-factor method. The response surface methodology (RSM) based on Box-Behnken design was successfully applied to the optimization of the preparation conditions. The maximum adsorption capacity of MO was found to be 240.16 mg/g, indicating that this material may be an effective adsorbent. It was shown that 99% of heavy metal ions (Fe(2+), Fe(3+), Cr(3+), and Zn(2+)) can be effectively removed into precipitates and released far less in the adsorption process. In addition, this material with adsorbed dye can be easily separated by a magnetic field and recycled after catalytic regeneration with advanced oxidation technology. Meanwhile, kinetic models, FTIR spectra and X-ray diffraction pattern were applied to the experimental data to examine uptake mechanism. The boundary layer and intra-particle diffusion played important roles in the adsorption mechanisms. PMID:23122732

Chen, Dan; Li, Yang; Zhang, Jia; Li, Wenhui; Zhou, Jizhi; Shao, Li; Qian, Guangren

2012-12-01

378

Application of dissolvable layered double hydroxides as sorbent in dispersive solid-phase extraction and extraction by co-precipitation for the determination of aromatic acid anions.  

PubMed

Three types of magnesium-aluminum layered double hydroxides were synthesized and employed as solid-phase extraction (SPE) sorbents to extract several aromatic acids (protocatechuic acid, mandelic acid, phthalic acid, benzoic acid, and salicylic acid) from aqueous samples. An interesting feature of these sorbents is that they dissolve when the pH of the solution is lower than 4. Thus, the analyte elution step, as needed in conventional sorbent-based extraction, was obviated by dissolving the sorbent in acid after extraction and separation from the sample solution. The extract was then directly injected into a high-performance liquid chromatography-ultraviolet detection system for analysis. In the key adsorption process, both dispersive SPE and co-precipitation extraction with the sorbents were conducted and experimental parameters such as pH, temperature, and extraction time were optimized. The results showed that both extraction methods provided low limits of detection (0.03-1.47 ?g/L) and good linearity (r(2) > 0.9903). The optimized extraction conditions were applied to human urine and sports drink samples. This new and interesting extraction approach was demonstrated to be a fast and efficient procedure for the extraction of organic anions from aqueous samples. PMID:23855757

Tang, Sheng; Lee, Hian Kee

2013-08-01

379

Ultratrace determination of arsenic in water samples by electrothermal atomic absorption spectrometry after pre-concentration with Mg-Al-Fe ternary layered double hydroxide nano-sorbent.  

PubMed

A selective solid phase extraction method, based on nano-structured Mg-Al-Fe(NO3(-)) ternary layered double hydroxide as a sorbent, is developed for the pre-concentration of ultra-trace levels of arsenic (As) prior to determination by electrothermal atomic absorption spectrometry. It is found that both As(III) and As(V) could be quantitatively retained on the sorbent within a wide pH range of 4-12. Accordingly, the presented method is applied to determination of total inorganic As in aqueous solutions. Maximum analytical signal of As is achieved when the pyrolysis and atomization temperatures are close to 900 °C and 2300 °C, respectively. Several variables affecting the extraction efficiency including pH, sample flow rate, amount of nano-sorbent, elution conditions and sample volume are optimized. Under the optimized conditions, the limit of detection (3Sb/m) and the relative standard deviation are 4.6 pg mL(-1) and 3.9%, respectively. The calibration graph is linear in the range of 15.0-650 pg mL(-1) with a correlation coefficient of 0.9979, sorption capacity and pre-concentration factor are 8.68 mg g(-1) and 300, respectively. The developed method is validated by the analysis of a standard reference material (SRM 1643e) and is successfully applied to the determination of ultra-trace amounts of As in different water samples. PMID:24148451

Abdolmohammad-Zadeh, Hossein; Jouyban, Abolghasem; Amini, Roghayeh

2013-11-15

380

Facile synthesis of three dimensional hierarchical Co-Al layered double hydroxides on graphene as high-performance materials for supercapacitor electrode.  

PubMed

A facile simple hydrothermal method combined with a post-solution reaction is developed to grow interconnected three dimensional (3D) hierarchical Co-Al layered double hydroxides (LDHs) on reduced graphene oxide (rGO). The obtained 3D hierarchical rGO-LDHs are characterized by field emission scanning electron microscopy, X-ray diffraction, and X-ray photo-electron spectroscopy. As LDHs nanosheets directly grow on the surface of rGO via chemical covalent bonding, the rGO could provide facile electron transport paths in the electrode for the fast Faradaic reaction. Moreover, benefiting from the rational 3D hierarchical structural, the rGO-LDHs demonstrate excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the 3D hierarchical rGO-LDHs exhibit specific capacitance values of 599Fg(-1) at a constant current density of 4Ag(-1). The rGO-LDHs also show high charge-discharge reversibility with an efficiency of 92.4% after 5000 cycles. PMID:24863775

Hao, Jinhui; Yang, Wenshu; Zhang, Zhe; Lu, Baoping; Ke, Xi; Zhang, Bailin; Tang, Jilin

2014-07-15

381

One-pot synthesis of water-swellable Mg-Al layered double hydroxides and graphene oxide nanocomposites for efficient removal of As(V) from aqueous solutions.  

PubMed

In this Article, we report a remarkably simple and efficient method for the preparation of layered double hydroxides and graphene oxide (LDHs/GO) nanocomposites with varying GO amounts via a hydrothermal process. The graphene nature in the resulting LDHs/GO nanocomposites was confirmed by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). The LDHs/GO nanocomposites exhibited swelling behavior in water and forming a gel. The adsorption performance of the LDHs/GO nanocomposites was evaluated for the removal of arsenate (As(V)) from aqueous solutions, and the results showed that the ratio of GO to LDHs in the nanocomposites significantly affected the adsorption capacity. Higher and lower amounts of GO in LDHs/GO nanocomposites showed lower adsorption capacity of As(V). A maximum adsorption capacity of 183.11 mg/g (2.44 mmol/g) was achieved on the LDHs/GO containing 6.0% GO due to the higher Brunauer-Emmett-Teller (BET) surface area than other samples. Owing to their high uptake capability of As(V), water-swellable LDHs/GO nanocomposites are expected to have potential applications as adsorbents for As(V) polluted water cleanup. PMID:23528072

Wen, Tao; Wu, Xilin; Tan, Xiaoli; Wang, Xiangke; Xu, Anwu

2013-04-24

382

Antituberculosis nanodelivery system with controlled-release properties based on para-amino salicylate-zinc aluminum-layered double-hydroxide nanocomposites  

PubMed Central

We report the intercalation and characterization of para-amino salicylic acid (PASA) into zinc/aluminum-layered double hydroxides (ZLDHs) by two methods, direct and indirect, to form nanocomposites: PASA nanocomposite prepared by a direct method (PASA-D) and PASA nanocomposite prepared by an indirect method (PASA-I). Powder X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis revealed that the PASA drugs were accommodated within the ZLDH interlayers. The anions of the drug were accommodated as an alternate monolayer (along the long-axis orientation) between ZLDH interlayers. Drug loading was estimated to be 22.8% and 16.6% for PASA-D and PASA-I, respectively. The in vitro release properties of the drug were investigated in physiological simulated phosphate-buffered saline solution of pH 7.4 and 4.8. The release followed the pseudo-second-order model for both nanocomposites. Cell viability (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide [MTT] assays) was assessed against normal human lung fibroblast MRC-5 and 3T3 mouse fibroblast cells at 24, 48, and 72 hours. The results showed that the nanocomposite formulations did not possess any cytotoxicity, at least up to 72 hours.

Saifullah, Bullo; Hussein, Mohd Zobir; Hussein-Al-Ali, Samer Hasan; Arulselvan, Palanisamy; Fakurazi, Sharida

2013-01-01

383

Validation of an LDH Assay for Assessing Nanoparticle Toxicity  

PubMed Central

Studies showed that certain cytotoxicity assays were not suitable for assessing nanoparticle (NP) toxicity. We evaluated a lactate dehydrogenase (LDH) assay for assessing copper (Cu-40, 40 nm), silver (Ag-35, 35 nm; Ag-40, 40 nm), and titanium dioxide (TiO2-25, 25 nm) NPs by examining their potential to inactivate LDH and interference with ?-nicotinamide adenine dinucleotide (NADH), a substrate for the assay. We also performed a dissolution assay for some of the NPs. We found that the copper NPs, because of their high dissolution rate, could interfere with the LDH assay by inactivating LDH. Ag-35 could also inactivate LDH probably because of the carbon matrix used to cage the particles during synthesis. TiO2-25 NPs were found to adsorb LDH molecules. In conclusion, NP interference with the LDH assay depends on the type of NPs and the suitability of the assay for assessing NP toxicity should be examined case by case.

Han, Xianglu; Gelein, Robert; Corson, Nancy; Wade-Mercer, Pamela; Jiang, Jingkun; Biswas, Pratim; Finkelstein, Jacob N.; Elder, Alison; Oberdorster, Gunter

2014-01-01

384

Homogeneous precipitation of nickel hydroxide powders  

NASA Astrophysics Data System (ADS)

Structure of nickel precipitate from decomposition of urea was found to be alpha-Ni(OH)2. FTIR analysis revealed the intercalation of cyanate (OCN), which is an intermediate product of urea decomposition. This observation implied that the assumption of single step decomposition of urea to carbon dioxide and ammonia was over simplified. Role of critical experimental parameters like initial pH and metal ion concentration on the powder characteristics was carried out. Numerical solutions to reaction pathways predicted significant accumulation of the intermediate cyanate in the time-temperature range investigated. Numerical simulations included the effects of hydrolysis products of Ni2+ and Ni-amine, Ni-cyanate, and Ni-carbonate complexes. Chemical analysis of the precipitate showed a decrease in nitrogen content with increasing reaction times. This was consistent with the predicted decrease in concentration of Ni-cyanate complexes with time. Layer double hydroxides (LDHs) are intercalation compounds represented by the formula [M2+1-xM3+ x(OH)2]x+[An-x/n ]x-·mH2O. alpha-Ni(OH) 2 and Ni-Al layer double hydroxides precipitated by urea were investigated with FTIR and XPS. The role of cyanate in nucleation and growth of precipitates is demonstrated. In the early stages, cyanate ion is found mainly to be grafted into alpha-Ni(OH)2 via nitrogen, whereas later in the growth stages, it is bonded through oxygen. In LDHs cyanate remains N-bonded. Precipitation with substituted ureas, revealed the link between spectral features and structures observed in XRD patterns. With slower decomposition rates and low levels of supersaturation an extensively hydrated structure was observed. From the two phases of Ni(OH)2, alpha-phase, with its larger interlayer spacing, offers enhanced electrochemical properties but it transforms into thermodynamically stable beta-phase. Stabilizing effects of Ni2+ substitution with Co2+ and Al3+ was investigated. A number of three-component LDHs (TCLDHs) with Ni2+1-(x+y) /Co2+x and Al3+y (x and y were varied between 0.00 and, 0.25) were produced by urea precipitation. From the compositions studied, the ones containing [Al3+] o ? 0.015 M resulted with the LDH structure and proved to be stable in the electrolyte for prolonged times. Chronopotentiometry results indicated that TC-LDHs could deliver capacities up to about 30% higher than the beta-phase.

Mavis, Bora

385

Hydroxide-promoted core conversions of molybdenum-iron-sulfur edge-bridged double cubanes: oxygen-ligated topological PN clusters.  

PubMed

The occurrence of a heteroatom X (C, N, or O) in the MoFe7S9X core of the iron-molybdenum cofactor of nitrogenase has encouraged synthetic attempts to prepare high-nuclearity M-Fe-S-X clusters containing such atoms. We have previously shown that reaction of the edge-bridged double cubane [(Tp)2Mo2Fe6S8(PEt3)4] (1) with nucleophiles HQ- affords the clusters [(Tp)2Mo2Fe6S8Q(QH)2](3-) (Q = S, Se) in which HQ- is a terminal ligand and Q(2-) is a mu2-bridging atom in the core. Reactions with OH- used as such or oxygen nucleophiles generated in acetonitrile from (Bu3Sn)2O or Me3SnOH and fluoride were examined. Reaction of 1 with Et4NOH in acetonitrile/water generates [(Tp)2Mo2Fe6S9(OH)2]3- (3), isolated as [(Tp)2Mo2Fe6S9(OH)(OC(=NH)Me)(H2O)](3-) and shown to have the [Mo2Fe6(mu2-S)2(mu3-S)6(mu6-S)] core topology very similar to the P(N) cluster of nitrogenase. The reaction system 1/Et4NOH in acetonitrile/methanol yields the P(N)-type cluster [(Tp)2Mo2Fe6S9(OMe)2(H2O)](3-) (5). The system 1/Me3SnOH/F- affords the oxo-bridged double P(N)-type cluster {[(Tp)2Mo2Fe6S9(mu2-O)]2}5- (7), convertible to the oxidized cluster {[(Tp)2Mo2Fe6S9(mu2-O)]2}4- (6), which is prepared independently from [(Tp)2Mo2Fe6S9F2(H2O)](3-)/(Bu3Sn)2O. In the preparations of 3-5 and 7, hydroxide liberates sulfide from 1 leading to the formation of P(N)-type clusters. Unlike reactions with HQ-, no oxygen atoms are integrated into the core structures of the products. However, the half-dimer composition [Mo2Fe6S9O] relates to the MoFe7S9 constitution of the putative native cluster with X = O. (Tp = hydrotris(pyrazolyl) borate(1-)). PMID:17892284

Hlavinka, Mark L; Miyaji, Taichi; Staples, Richard J; Holm, R H

2007-10-29

386

A composite of layered double hydroxides obtained through random costacking of layers from Mg Al and Co Al LDHs by delamination restacking: Thermal decomposition and reconstruction behavior  

NASA Astrophysics Data System (ADS)

A composite of dodecylsulfate intercalated Mg-Al and Co-Al LDHs in which the layers of the two LDHs are randomly costacked was prepared starting from the monolayer colloidal dispersions of the individual surfactant intercalated LDHs obtained through delamination in 1-butanol. The surfactant ion of the composite could be exchanged for acetate ions. The thermal decomposition and reconstruction behavior of the acetate-intercalated composite was found to be different from those of an LDH in which each layer contains Mg, Co and Al and a physical mixture of Mg-Al and Co-Al LDHs. While the composite shows partial reconstruction to LDH phase even after heating up to 1000 °C the other samples do not show reconstruction beyond 800 °C.

Venugopal, B. R.; Shivakumara, C.; Rajamathi, Michael

2007-03-01

387

Intercalation chemistry in a LDH system: anion exchange process and staging phenomenon investigated by means of time-resolved, in situ X-ray diffraction.  

PubMed

Using time-resolved, in situ energy-dispersive X-ray diffraction (EDXRD), the formation of interstratified LDH structures, with alternate interlayer spaces occupied by different anions, have been demonstrated during anion exchange reactions. Novel hybrid LDH nanostructures can thus be prepared, combining the physicochemical properties of two intercalated anions plus those of the LDH host. A general trend is that inorganic-inorganic anion exchange reactions occur in a one-step process while inorganic-organic exchanges may proceed via a second-stage intermediate, suggesting that staging occurs partly as a result of organic-inorganic separation. Yet, other influencing parameters must be considered such as LDH host composition, LDH affinity for different anions and LDH particle size as well as extrinsic parameters like the reaction temperature. Hence, a correlation between the occurrence of staging phenomenon and the difficulty of the exchange of the initial anion is observed, suggesting that staging is needed to overcome the energy barrier in the case of the exchange by organic anions. Notwithstanding the LiAl(2) system, staging has mainly been observed with Zn(2)Cr LDH host so far, a peculiar LDH composition with a unique Zn/Cr ratio of two and a local order of the cations within the hydroxide layers. The formation of a higher order-staged intermediate than stage two, observed during the exchange reaction of CO(3)(2-) or SO(4)(2-) anions with Zn(2)Cr-tartrate, is in favour of a Daumas-Herold model although this model implies a bending of LDH layers. The analysis of the X-ray powder diffraction pattern of Zn(2)Cr-Cl/tartrate second-stage intermediate, isolated almost as a pure phase during the exchange of Cl(-) with tartrate anions in Zn(2)Cr LDH, indicates a disorder in the stacking sequence and a relative proportion of the two kinds of interlayers slightly different from 50/50. Besides, the microstructural analysis of the XRD pattern reveals a great reduction of the stacking thickness during the anion exchange process but with no change of the in-plane coherent length, therefore no in-plane deformation of LDH host layers. Finally, the anion exchange properties of Zn(2)Cr-Cl/tartrate, investigated by means of EDXRD, show highly selective anion-exchange reactions, leading to the formation of new second-stage intermediates that cannot be prepared starting from the mono-intercalated Zn(2)Cr-Cl. This "Zn(2)Cr-Cl/tartrate approach" might constitute a new route for the synthesis of various mixed organic-inorganic anions-exchanged forms of LDH. PMID:20485821

Taviot-Guého, Christine; Feng, Yongjun; Faour, Azzam; Leroux, Fabrice

2010-07-14

388

The Effect of Single, Binary and Ternary Anions of Chloride, Carbonate and Phosphate on the Release of 2,4-Dichlorophenoxyacetate Intercalated into the Zn-Al-layered Double Hydroxide Nanohybrid  

NASA Astrophysics Data System (ADS)

Intercalation of beneficial anion into inorganic host has lead to an opportunity to synthesize various combinations of new organic-inorganic nanohybrids with various potential applications; especially, for the controlled release formulation and storage purposes. Investigation on the release behavior of 2,4-dichlorophenoxyacetate (2,4-D) intercalated into the interlayer of Zn-Al-layered double hydroxide (ZAN) have been carried out using single, binary and ternary aqueous systems of chloride, carbonate and phosphate. The release behavior of the active agent 2,4-D from its double-layered hydroxide nanohybrid ZANDI was found to be of controlled manner governed by pseudo-second order kinetics. It was found that carbonate medium yielded the highest accumulated release of 2,4-D, while phosphate in combination with carbonate and/or nitrate speeds up the release rate of 2,4-D. These results indicate that it is possible to design and develop new delivery system of latex stimulant compound with controlled release property based on 2,4-D that is known as a substance to increase latex production of rubber tree, Hevea brasiliensis.

Hussein, Mohd Zobir; Jaafar, Adila Mohamad; Yahaya, Asmah Hj.; Zainal, Zulkarnain

2009-11-01

389

Small-molecule inhibitors of human LDH5.  

PubMed

The latest findings on the role played by human LDH5 (hLDH5) in the promotion of glycolysis in invasive tumor cells indicates that this enzyme subtype is a promising therapeutic target for invasive cancer. Compounds able to selectively inhibit hLDH5 hold promise for the cure of neoplastic diseases. hLDH5 has so far been a rather unexplored target, since its importance in the promotion of cancer progression has been neglected for decades. This enzyme should also be considered as a challenging target due the high polar character (mostly cationic) of its ligand cavity. Recently, significant progresses have been reached with small-molecule inhibitors of hLDH5 displaying remarkable potencies and selectivities. This review provides an overview of the newly developed hLDH5 inhibitors. The roles of hLDH isoforms will be briefly discussed, and then the inhibitors will be grouped into chemical classes. Furthermore, general pharmacophore features will be emphasized throughout the structural subgroups analyzed. PMID:24175747

Granchi, Carlotta; Paterni, Ilaria; Rani, Reshma; Minutolo, Filippo

2013-10-01

390

Acetate-intercalated Ni-In layered double hydroxides with low infrared emissivity: Synthesis, delamination and restacked to form the multilayer films  

NASA Astrophysics Data System (ADS)

The low-emissive membrane materials have potential applications in infrared detecting technologies. Herein, we report a novel LDHs film with low infrared emissivity, which was based on the deposition of the exfoliated LDH nanosheets. The monodispersed hexagonal plate-like particles of Ni-In-CO32- LDHs were prepared by coprecipitation method with hydrothermal treatment under optimized conditions. In order to exfoliate the LDHs into nanosheets, acetate-intercalated Ni-In LDHs were prepared by anion-exchange of Ni-In-CO32- LDHs. The as-prepared acetate-intercalated LDHs exhibited excellent delaminating behavior in water and unilamellar nanosheets were easily obtained. The resulting positive-charged nanosheets were assembled onto quartz substrates to produce the multilayer films. The infrared emissivity values of all the samples were characterized. It was found that the incorporation of Ni2+ and In3+ in the host layer significantly reduced the infrared emissivity value. Moreover, the value was further reduced by the fabrication of multilayer ultrathin films, which can be ascribed to the dense orderly structure and smooth surface morphology.

Wang, Yongjuan; Zhou, Yuming; Zhang, Tao; He, Man; Bu, Xiaohai; Yang, Xiaoming

2014-01-01

391

Aluminum hydroxide production  

SciTech Connect

A method is described for the production of aluminum hydroxide, comprising reacting water in the liquid phase and aluminum of surface area of at least 20 mm/sup 2/ per gram at a pH above about 12.4 for producing a reaction mixture containing aluminum hydroxide, and collecting solid aluminum hydroxide from the reaction mixture, the reaction being carried out in the presence of choline at a concentration of about 0.05 to 2 mols per liter.

Martin, E.S.; Weaver, M.L.

1988-07-05

392

Oxamic acid analogues as LDH-C4-specific competitive inhibitors.  

PubMed

We performed kinetic studies to determine whether oxamate analogues are selective inhibitors of LDH-C4, owing to their potential usefulness in fertility control and treatment of some cancers. These substances were shown to be competitive inhibitors of LDH isozymes and are able to discriminate among subtle differences that differentiate the active sites of LDH-A4, LDH-B4 and LDH-C4. N-Ethyl oxamate was the most potent inhibitor showing the highest affinity for LDH-C4. However, N-propyl oxamate was the most selective inhibitor showing a high degree of selectivity towards LDH-C4. Non-polar four carbon atoms chains, linear or branched, dramatically diminished the affinity and selectivity towards LDH-C4. N-Propyl oxamate significantly reduced ATP levels, capacitation and mouse sperm motility, in line with results shown by others, suggesting that LDH-C4 plays an essential role in mouse fertility. PMID:21438710

Rodríguez-Páez, Lorena; Chena-Taboada, Miguel Angel; Cabrera-Hernández, Arturo; Cordero-Martínez, Joaquín; Wong, Carlos

2011-08-01

393

Evolutionary Relationships of Lactate Dehydrogenases (LDHs) from Mammals, Birds, an Amphibian, Fish, Barley, and Bacteria: LDH cDNA Sequences from Xenopus, Pig, and Rat  

Microsoft Academic Search

The nucleotide sequences of the cDNAs encoding LDH (EC 1.1.1.27) subunits LDH-A (muscle), LDH-B (liver), and LDH-C (oocyte) from Xenopus laevis, LDH-A (muscle) and LDH-B (heart) from pig, and LDH-B (heart) and LDH-C (testis) from rat were determined. These seven newly deduced amino acid sequences and 22 other published LDH sequences, and three unpublished fish LDH-A sequences kindly provided by

Soichi Tsuji; Masood A. Qureshi; Esther W. Hou; Walter M. Fitch; Steven S.-L. Li

1994-01-01

394

Vibrational spectroscopic study of the sulphate mineral glaucocerinite (Zn,Cu)10Al6(SO4)3(OH)32?18H2O - A natural layered double hydroxide  

NASA Astrophysics Data System (ADS)

We have studied the molecular structure of the mineral glaucocerinite (Zn,Cu)5Al3(SO4)1.5(OH)16?9(H2O) using a combination of Raman and infrared spectroscopy. The mineral is one of the hydrotalcite supergroup of natural layered double hydroxides. The Raman spectrum is characterised by an intense Raman band at 982 cm-1 with a low intensity band at 1083 cm-1. These bands are attributed to the sulphate symmetric and antisymmetric stretching mode. The infrared spectrum is quite broad with a peak at 1020 cm-1. A series of Raman bands at 546, 584, 602, 625 and 651 cm-1 are assigned to the ?4 (SO4)2- bending modes. The observation of multiple bands provides evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 762 cm-1 is attributed to a hydroxyl deformation mode associated with AlOH units. Vibrational spectroscopy enables aspects of the molecular structure of glaucocerinite to be determined.

Frost, Ray L.; Theiss, Frederick L.; López, Andrés; Scholz, Ricardo

2014-06-01

395

Phylogenetic Analysis of Vertebrate Lactate Dehydrogenase (LDH) Multigene Families  

Microsoft Academic Search

.   In this paper we analyzed 49 lactate dehydrogenase (LDH) sequences, mostly from vertebrates. The amino acid sequence differences\\u000a were found to be larger for a human–killifish pair than a human–lamprey pair. This indicates that some protein sequence convergence\\u000a may occur and reduce the sequence differences in distantly related species. We also examined transitions and transversions\\u000a separately for several species

Yi-Ju Li; Stephen C.-M. Tsoi

2002-01-01

396

Unusual hydrocarbon chain packing mode and modification of crystallite growth habit in the self-assembled nanocomposites zinc-aluminum-hydroxide oleate and elaidate (cis-and trans-[Zn2Al(OH)6(CH3(CH2)7CH=CH(CH2)7COO-)] and magnesium analogues.  

SciTech Connect

We report a novel packing mode specific to the cis unsaturated hydrocarbon chain in the title compound, a self-assembled layered double hydroxide-surfactant hybrid nanomaterial, and its influence on crystallite morphology and structure. The kink imposed by the cis double bond in oleate leads to partial overlap between chains on adjacent layers, with incomplete space filling, in contrast to the more usual (and more efficient) mono- and bilayer packings exhibited by the trans analogues. Incorporation of surfactant into the growing crystallite leads to a reversal of the usual LDH growth habit and results in crystallite shapes featuring ribbonlike sheets. The thermal decomposition behavior of the as-prepared organic/inorganic nanocomposites in air and N{sub 2} is described.

Wang, Yifeng (Sandia National Laboratories, Carlsbad, NM); Braterman, Paul S. (University of North Texas, Denton, TX); Xu, Zhi-Ping (University of North Texas, Denton, TX); Brinker, C. Jeffrey; Xu, Huifang (University of New Mexico, Albuquerque, NM); Yu, Kui

2004-05-01

397

The heterogeneity of LDH isoenzyme patterns of human uterine sarcomas and cultured sarcoma cell lines.  

PubMed Central

Both the tissue lactate dehydrogenase (LDH) isoenzyme pattern and total LDH activity were investigated in a series of human uterine sarcomas and cell lines derived from these tumors. Abnormal LDH isoenzyme patterns characterized by shifts toward the muscle isoenzyme forms (LDH4 and 5) were found in some, but not all, of the sarcomas. The tumors containing rhabdomyosarcomatous elements usually had normal or only slightly altered LDH isoenzyme patterns. The LDH isoenzyme patterns expressed by cultured cell lines established from the uterine sarcomas, in general, resembled those found in the primary tumors. These results suggest that the normal or near normal LDH isoenzyme distributions found in uterine sarcomas with rhabdomyosarcomatous differentiation may be a potential characteristic which may be used for distinguishing these tumors from other uterine sarcomas. Images Figure 1 Figure 3

Nelson, K. G.; Siegfried, J. M.; Siegal, G. P.; Becker, R.; Walton, L. A.; Kaufman, D. G.

1984-01-01

398

Relative Catalytic Efficiency of ldhL- and ldhD-Encoded Products Is Crucial for Optical Purity of Lactic Acid Produced by Lactobacillus Strains  

PubMed Central

NAD-dependent l- and d-lactate dehydrogenases coexist in Lactobacillus genomes and may convert pyruvic acid into l-lactic acid and d-lactic acid, respectively. Our findings suggest that the relative catalytic efficiencies of ldhL- and ldhD-encoded products are crucial for the optical purity of lactic acid produced by Lactobacillus strains.

Zheng, Zhaojuan; Sheng, Binbin; Zhang, Haiwei; Gao, Chao; Su, Fei

2012-01-01

399

pLDH level of clinically isolated Plasmodium vivax and detection limit of pLDH based malaria rapid diagnostic test  

PubMed Central

Background The malaria rapid diagnostic tests (RDTs) are now widely used in the world. Compared to Plasmodium falciparum, a poor sensitivity of RDTs was reported against Plasmodium vivax based on the adopted antibody against pan-Plasmodium antigen lactate dehydrogenase (pLDH) or aldolase. Levels of pLDH were measured from patient with P. vivax, and the correlations between the levels of pLDH and the sensitivities of RDTs were analysed among Republic of Korea (ROK) isolates. Methods Three RDTs, OptiMAL test, SD BIOLINE Malaria Ag P.f/Pan test, Humasis Malaria Pf/Pan antigen test, and the Genedia pLDH antigen ELISA were performed with blood samples from 152 febrile patients and 100 healthy controls. Results Three malaria RDTs revealed sensitivities between 85.5 (131/152) and 86.8% (132/152) with highest sensitivity for the detection of P.vivax by pLDH antigen ELISA test (145/152, 95.4%) in comparison to traditional microscopy using Giemsa–stained slides. None of the healthy control tested positive by three RDTs or ELISA, indicating 100% specificity in their respective test. Levels of pLDH among Korean P. vivax isolates ranged between 0 ng/mL and 22,387.2 ng/mL (mean?±?standard deviation 3,917.5?±?6,120.9 ng/mL). The lower detection limits of three RDTs were between 25 and 50 ng/mL with artificially diluted samples. The moderate degree of correlation was observed between parasitaemia and concentrations of pLDH (r?=?0.4, p?LDH levels of P. vivax are the main explanation for the variations in the performance of pLDH-based RDTs. Therefore, comparing sensitivities of RDT may need to include targeted biomarker value of patients.

2013-01-01

400

Skeletal muscle PGC-1? controls whole-body lactate homeostasis through estrogen-related receptor ?-dependent activation of LDH B and repression of LDH A  

PubMed Central

The peroxisome proliferator-activated receptor-? coactivator 1? (PGC-1?) controls metabolic adaptations. We now show that PGC-1? in skeletal muscle drives the expression of lactate dehydrogenase (LDH) B in an estrogen-related receptor-?–dependent manner. Concomitantly, PGC-1? reduces the expression of LDH A and one of its regulators, the transcription factor myelocytomatosis oncogene. PGC-1? thereby coordinately alters the composition of the LDH complex and prevents the increase in blood lactate during exercise. Our results show how PGC-1? actively coordinates lactate homeostasis and provide a unique molecular explanation for PGC-1?–mediated muscle adaptations to training that ultimately enhance exercise performance and improve metabolic health.

Summermatter, Serge; Santos, Gesa; Perez-Schindler, Joaquin; Handschin, Christoph

2013-01-01

401

Ferrimagnetic copper chloride hydroxide  

Microsoft Academic Search

Magnetic properties of copper chloride hydroxide were studied by using a superconducting quantum interference device. The coercivity of this material was more than 10 000 Oe at 2 K, which is the highest observed in the copper compounds. The magnetic susceptibility as a function of temperature revealed ferrimagnetism in the sample.

S G Yang; T Li; B L Xu; Y W Du

2003-01-01

402

RED Facts: Triphenyltin Hydroxide.  

National Technical Information Service (NTIS)

This fact sheet summarizes the information in the RED document for reregistration case 0099, triphenyltin hydroxide (TPTH). TPTH is a non-systemic foliar fungicide used to control early and late blight on potatoes; leaf spot on sugar beets; and scab, brow...

1999-01-01

403

Physiological Basis for Swimming Endurance Differences between LDH-B Genotypes of Fundulus heteroclitus  

Microsoft Academic Search

Adenosine triphosphate levels in erythrocytes are correlated with LDH-B genotype in Fundulus heteroclitus. Adenosine triphosphate is the fish's allosteric modifier of hemoglobin oxygen affinity. Since oxygen delivery to muscle affects swimming performance, fish of each homozygous LDH-B phenotype were swum to exhaustion at 10circ or 25circC to determine whether in vitro differences attributed to the LDH-B allelic isozymes were manifest

Leonard Dimichele; Dennis A. Powers

1982-01-01

404

No CoExpression of LDH-C In Amazon Cichlids  

Microsoft Academic Search

As commonly found among other advanced teleosts, lactate dehydrogenase (LDH, EC. 1.1.1.27) from cichlid fish exhibits the eye-specific LDH-C4 isozyme. In the last few years, some authors have described the co-expression of a distinct liver-specific form in addition to the eye-specific LDH isozymes in cichlid fish. Because liver-specific isozymes have been described before in Gadiformes as the product of the

I. P Farias; M. N Paula-Silva; V. M. F Almeida-Val

1997-01-01

405

Electrochemical performance of cobalt hydroxide nanosheets formed by the delamination of layered cobalt hydroxide in water.  

PubMed

We report the preparation of monometallic Co(2+)/Co(3+) layered double hydroxide, intercalated with lactate anions (LCoH-Lactate), and its spontaneous delamination in water to form cobalt hydroxide nanosheets. These hydroxide nanosheets formed stable aqueous dispersions. The thickness of a nanosheet was estimated to be approximately 1 nm by atomic force microscopy and small angle X-ray scattering experiments, and corresponds to a single hydroxide layer. Some of the Co(2+) cations were oxidised by oxygen, resulting in a mixed Co(2+)0.76Co(3+)0.24 layer composition. Upon water evaporation, the nanosheets restacked to form transparent self-standing films with a layered structure like that of the original material. The coverage of the surface with side-by-side stacks of nanosheets indicated two-dimensional agglomeration and suggested that these dispersions could be applied to prepare large monolayers of nanosheets. The layers prepared by spin-coating were stable and featured reversible and reproducible redox properties in an alkaline electrolyte. In an evaluation of their electrochemical performance, the cobalt hydroxide nanosheets exhibited durability and fast charge transfer kinetics during repetitive potential cycling up to 200 mV s(-1). The nanosheets prepared by the present method show promise for use in nanocomposite materials for energy storage applications. PMID:24647991

Schneiderová, B; Demel, J; Pleštil, J; Tarábková, H; Bohuslav, J; Lang, K

2014-07-21

406

Hydroxide-catalyzed bonding  

NASA Technical Reports Server (NTRS)

A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

Gwo, Dz-Hung (Inventor)

2003-01-01

407

Duplication of the LDH gene loci by polyploidization in the fish order Clupeiformes  

Microsoft Academic Search

Within the order Clupeiformes, chromosome analysis and DNA measurements have indicated a diploid-tetraploid relationship among closely related species. To confirm the presence of polyploidization at single gene loci we studied the LDH isoenzyme system. The results obtained are in agreement with the hypothesis of polyploidization. While the diploid species show two gene loci for LDH, the tetraploid species exhibit four

J. Klose; U. Wolf; H. Hitzeroth; H. Ritter; N. B. Atkin; S. Ohno

1968-01-01

408

21 CFR 582.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 2013-04-01 false Potassium hydroxide. 582.1631 Section 582.1631...General Purpose Food Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use....