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1

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

2

Alkaline phosphatase biosensors based on layered double hydroxides matrices: Role of LDH composition  

Microsoft Academic Search

Alkaline phosphatase (AlP) biosensors were developed based on the immobilization of this enzyme by adsorption or coprecipitation methods in different layered double hydroxides (LDH) matrices: Zn2Al–Cl and Mg2Al–CO3. Several characteristics of the AlP\\/LDH membranes, such as the enzyme immobilization procedure, permeability, buffering effect were investigated. It appeared that the basic nature of the MgAl–LDH nanomaterial improved the stability of the

Christine Mousty; Oznur Kaftan; Vanessa Prevot; Claude Forano

2008-01-01

3

Synergistic effects of layered double hydroxide with hyperfine magnesium hydroxide in halogen-free flame retardant EVA\\/HFMH\\/LDH nanocomposites  

Microsoft Academic Search

The synergistic effects of layered double hydroxide (LDH) with hyperfine magnesium hydroxide (HFMH) in halogen-free flame retardant ethylene-vinyl acetate (EVA)\\/HFMH\\/LDH nanocomposites have been studied by X-ray diffraction (XRD), transmission electron spectroscopy (TEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI), mechanical properties' tests, and dynamic mechanical thermal analysis (DMTA). The XRD results show that the exfoliated EVA\\/HFMH\\/LDH can be obtained by

Guobing Zhang; Peng Ding; Ming Zhang; Baojun Qu

2007-01-01

4

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

NASA Astrophysics Data System (ADS)

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.

Herrero, M.; Martínez-Gallegos, S.; Labajos, F. M.; Rives, V.

2011-11-01

5

Removal of Trace Levels of Arsenic and Selenium from Aqueous Solutions by Calcined and Uncalcined Layered Double Hydroxides (LDH)  

Microsoft Academic Search

The adsorption of As and Se from dilute aqueous solutions, representing model power-plant effluent streams, by calcined and uncalcined layered double hydroxide (LDH) adsorbents has been investigated. The results indicate that As(V) has a greater adsorption capacity than Se(IV) for both calcined and uncalcined LDHs. An mth-order kinetic rate equation describes the adsorption kinetics of As and Se on these

Li Yang; Zoya Shahrivari; Paul K. T. Liu; Muhammad Sahimi; Theodore T. Tsotsis

2005-01-01

6

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

7

Layered double hydroxides (LDH) intercalated with metal coordination compounds and oxometalates  

Microsoft Academic Search

This paper reviews the synthesis, properties and applications of layered double hydroxides (LDHs), also known as anionic clays or hydrotalcite-like materials, containing intercalated anions constituted by metal complexes or oxometalates. After an introduction describing the main features of these compounds, emphasis is put on the synthesis methods, characterization and applications.

Vicente Rives; Mar??a Angeles Ulibarri

1999-01-01

8

Kinetic and spectroscopic study of 1O2 generation from H2O2 catalyzed by LDH-MoO4(2-) (LDH=layered double hydroxide).  

PubMed

Layered double hydroxides (LDHs), exchanged with molybdate, decompose H2O2 to form one molecule of singlet-state dioxygen (1O2) from two molecules of H2O2. The dependence of the kinetics of H2O2 decomposition on Mo and H2O2 concentrations and on temperature has been related to structural characteristics of the material (X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectroscopy, N2 adsorption, thermogravimetry) and to molybdate speciation as revealed by in-situ studies in the presence of peroxide (FT Raman, diffuse reflectance UV/visible spectroscopy). The H2O2 decomposition rate is linearly correlated with the amount of LDH-exchanged molybdate, except when a considerable fraction of the molybdate occupies less accessible interlayer positions. A maximum in the H2O2 decomposition rate as the H2O2 concentration is increased is due to the successive formation of mono-, di-, tri-, and tetraperoxomolybdates. This behavior was modeled successfully by using the equilibrium constants for formation of the Mo-peroxo complexes, and the rate constants for decay of the peroxomolybdates with 1O2 liberation. Time-resolved diffuse reflectance and Raman observations of the various MoO4(2-)-peroxide adducts are in line with the proposed kinetic scheme. Of all the Mo-peroxo species on the LDH, the triperoxomolybdate has the highest rate for decay to 1O2. Comparison with the kinetics of dissolved molybdate shows that the monomolecular decay of all peroxomolybdate species proceeds much faster at the LDH surface than in solution. Consequently, maximal rates per Mo atom are at least twice as high for the heterogeneous LDH catalyst as for the homogeneous systems. PMID:11465446

Sels, B F; De Vos, D E; Grobet, P J; Jacobs, P A

2001-06-18

9

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

NASA Astrophysics Data System (ADS)

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 which the green rust precipitated was established by mass and absorption spectroscopy. The sulphate form of green rust is composed of brucite-like layers with Fe(II) and Fe(III) in an ordered distribution. The interlayers contain sulphate, water and sodium in an arrangement characteristic for the nikischerite group. The crystal structure is highly disordered by stacking faults. The composition, formula and crystallographic parameters are: NaFe(II) 6Fe(III) 3(SO 4) 2(OH) 18·12H 2O, space group P-3, a = 9.528(6) Å, c = 10.968(8) Å and Z = 1. Green rust sodium sulphate, GR, crystallizes in thin, hexagonal plates. Particles range from less than 50 nm to 2 ?m in diameter and are 40 nm thick or less. The material is redox active and reaction rates are fast. Extremely small particle size and high surface area contribute to rapid oxidation, transforming green rust to an Fe(III)-phase within minutes.

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

2009-06-01

10

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

11

A New Approach to Reducing the Flammability of Layered Double Hydroxide (LDH)-Based Polymer Composites: Preparation and Characterization of Dye Structure-Intercalated LDH and Its Effect on the Flammability of Polypropylene-Grafted Maleic Anhydride/d-LDH Composites.  

PubMed

Dye structure-intercalated layered double hydroxide (d-LDH) was synthesized using a one-step method, and its intercalated behaviors have been characterized by Fourier transform infrared spectroscopy (FTIR), wide angle X-ray scattering (WAXS), scanning electron microscopy, thermogravimetric analysis (TGA), etc. As a novel functional potential fire-retarding nanofiller, it was used to prepare a polypropylene-grafted maleic anhydride (PP-g-MA)/d-LDH composite by refluxing the mixture of d-LDH and PP-g-MA in xylene, aiming to investigate its effect on the flammability of the PP-g-MA composite. The morphological properties, thermal stability, and flame retardant properties of the PP-g-MA/d-LDH composite were determined by FTIR, WAXS, transmission electron microscopy, TGA, and microscale combustion calorimetry. Compared with NO3-LDH (unmodified LDH) and LDH intercalated by sodium dodecylbenzenesulfonate (conventional organo-modified LDH), d-LDH can significantly decrease the heat release rate and the total heat release of the PP-g-MA composite, offering a new approach to imparting low flammability to LDH-based polymer composites. PMID:23927608

Kang, Nian-Jun; Wang, De-Yi; Kutlu, Burak; Zhao, Peng-Cheng; Leuteritz, Andreas; Wagenknecht, Udo; Heinrich, Gert

2013-09-03

12

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

SciTech Connect

Following different preparation routes, fenbufen has been intercalated in the interlayer space of layered double hydroxides with Mg{sup 2+} and Al{sup 3+} or Mg{sup 2+}, Al{sup 3+} and Fe{sup 3+} 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 18.8 A. The presence of the LDH increases the solubility of fenbufen, especially when used as a matrix. The dissolution rate of the drug decreases when the drug is intercalated, and is even lower in those systems containing iron; release takes place through ionic exchange with phosphate anions from the solution. Preparation of microspheres with Eudragit S 100 leads to solids with an homogeneous, smooth surface with efficient covering of the LDH surface, as drug release was not observed at pH lower than 7. - Graphical abstract: LDHs containing Mg, Al, Fe increase fenbufen solubility, release takes place through ionic exchange with phosphate anions from the medium. Spherical solids with homogeneous, smooth surface are formed when using Eudragit S 100, efficiently covering the LDH surface. Display Omitted

Arco, M. del; Fernandez, A.; Martin, C. [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)

2010-12-15

13

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-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, 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

14

Mid- and near-infrared spectroscopic investigation of homogeneous cation distribution in MgxZnyAl(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 MgxZnyAl(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 MgxZnyAl(x+y)/2-LDHs, OH bonded Zn2Mg, Zn2Al, MgZnAl, Mg2Al and Mg2Zn peaks were identified at 3420, 3430, 3445-3450, 3454 and 3545cm(-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 MgxZnyAl(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

2013-08-30

15

Polymer nanocomposites using zinc aluminum and magnesium aluminum oleate layered double hydroxides: Effects of LDH divalent metals on dispersion, thermal, mechanical and fire performance in various polymers  

Microsoft Academic Search

Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and\\/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates

Charles Manzi-Nshuti; Ponusa Songtipya; E. Manias; Maria M. Jimenez-Gasco; Jeanne M. Hossenlopp; Charles A. Wilkie

2009-01-01

16

Fluorescent layered double hydroxide nanoparticles for biological studies  

Microsoft Academic Search

Layered double hydroxide (LDH) nanoparticles have the potential to benefit a myriad of medical, consumer and industrial products if intricate control of the nanoscale architecture and understanding of the biological interactions and potential toxicity of the LDH nanomaterials are achieved. Here, we report the synthesis and fractionation of LDH nanomaterials of well defined spatial characteristics through the careful control of

Anthony W. Musumeci; Gysell M. Mortimer; Margaret K. Butler; Zhi Ping Xu; Rodney F. Minchin; Darren J. Martin

2010-01-01

17

Cellular Uptake Behavior of Fluorescein: Intercalated Layered Double Hydroxide  

NASA Astrophysics Data System (ADS)

In order to define the ability of layered double hydroxide (LDH) as materials for drug delivery, fluorescein (Fluo) anion intercalated LDH (Fluo/LDH) was synthesized by hydrothermal treatment and observed the cellular uptake of the Fluo/LDH for mammalian cell (L929). The synthesized Fluo/LDH showed a LDH structure, high fluorescence and low cytotoxicity. According to the fluorescence, confocal and TEM images of cells, the Fluo/LDH seemed to be internalized into the L929 cell by cellular endocytosis and dissolved inside the cell to exhibit the fluorescence of cellular cytoplasm.

Tanaka, Miyuki; Aisawa, Sumio; Hirahara, Hidetoshi; Narita, Eiichi; Yin, Shu; Sato, Tsugio

2012-06-01

18

Synthesis of a novel cone-shaped CaAl-layered double hydroxide (LDH): its potential use as a reversible oil sorbent.  

PubMed

A novel cone-shaped superhydrophobic and oleophilic CaAl-LDH intercalated with dodecyl sulphate (DS(-)) anions was synthesized from calcium dodecyl sulphate as a precursor via a one-step hydrothermal method. The synthesized LDH has been successfully utilized in mopping and regeneration of oil from oil-water mixtures. PMID:23752334

Dutta, Kingshuk; Pramanik, Amitava

2013-07-21

19

Dendrimer intercalation in layered double hydroxides  

Microsoft Academic Search

New organic\\/inorganic (O\\/I) hybrid assemblies based on Layered Double Hydroxide (LDH) with polyamide amine dendrimer (PAMAM,\\u000a generation ?0.5 and generation +0.5) were prepared by two different routes using either the direct coprecipitation at constant\\u000a pH or the anion exchange procedure in double surfactant S+S? phases. The obtained materials were characterized by means of powder X-ray diffraction, thermal gravimetric analysis associated

Márcio José dos Reis; Vanessa Prévot; Fabrice Leroux; Fabiano Silvério; João Barros Valim

2010-01-01

20

Methotrexate intercalated ZnAl-layered double hydroxide  

SciTech Connect

The anticancerous drug methotrexate (MTX) has been intercalated into an ZnAl-layered double hydroxide (LDH) using an anion exchange technique to produce LDH-MTX hybrids having particle sizes in the range of 100-300 nm. X-ray diffraction studies revealed increases in the basal spacings of ZnAl-LDH-MTX hybrid on MTX intercalation. This was corroborated by the transmission electron micrographs, which showed an increase in average interlayer spacing from 8.9 A in pristine LDH to 21.3 A in LDH-MTX hybrid. Thermogravimetric analyses showed an increase in the decomposition temperature for the MTX molecule in the LDH-MTX hybrid indicating enhanced thermal stability of the drug molecule in the LDH nanovehicle. The cumulative release profile of MTX from ZnAl-LDH-MTX hybrids in phosphate buffer saline (PBS) at pH 7.4 was successfully sustained for 48 h following Rigter-Peppas model release kinetics via diffusion. - Graphical abstract: ZnAl-layered double hydroxide intercalated with methotrexate ({approx}34% loading) promises the possibility of use of ZnAl-LDH material as drug carrier and in controlled delivery. Highlights: > ZnAl-layered double hydroxide methotrexate nanohybrid has been synthesized. > XRD and TEM studies on nanohybrid revealed successful intercalation of methotrexate. > TG and CHN analyses showed {approx}34 wt% of methotrexate loading into the nanohybrid. > Possibility of use of ZnAl-LDH material as drug carrier and in delivery.

Chakraborty, Manjusha; Dasgupta, Sudip; Soundrapandian, Chidambaram [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata 700032 (India); Chakraborty, Jui, E-mail: jui@cgcri.res.in [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata 700032 (India); Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Mitra, Manoj K. [Department of Metallurgical and Materials Engineering, Jadavpur University, Kolkata 700032 (India); Basu, Debabrata [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata 700032 (India)

2011-09-15

21

Layered double hydroxide as novel antibacterial drug delivery system  

Microsoft Academic Search

The cephalosporin class antibacterial agent, cefazolin, was intercalated into layered double hydroxides (LDHs) in order to improve the drug efficiency as well as to achieve the controlled release property. Cefazolin molecules were incorporated into LDH through conventional ion exchange reaction. X-ray diffraction pattern analyses confirmed that cefazolin molecules were intercalated between the interlayer spaces of LDH. Fourier-transform infrared spectra and

Seung-Jin Ryu; Hyun Jung; Jae-Min Oh; Jin-Kyu Lee; Jin-Ho Choy

2010-01-01

22

Chromate uptake characteristics of the pristine layered double hydroxides of Mg with Al  

Microsoft Academic Search

The layered double hydroxides (LDHs) of Mg with Al readily scavenge dissolved chromate ions under a wide range of conditions. While the chromate uptake is quantitative in the LDH containing 33mol% Al, the uptake is only 58% of the stoichiometric value in the LDH containing 25mol% Al. This indicates that the lower symmetry of the NO3? ions in the LDH

Srinivasa V. Prasanna; P. Vishnu Kamath

2008-01-01

23

Preparation and nonisothermal crystallization behavior of polypropylene\\/layered double hydroxide nanocomposites  

Microsoft Academic Search

Polypropylene (PP)\\/layered double hydroxide (LDH) nanocomposites were prepared via melt intercalation using dodecyl sulfate anion modified LDH and maleated PP as compatibilizing agent. Evidently the interlayer anions in LDH galleries react with maleic anhydride groups of PP-g-MA and lead to a finer dispersion of individual LDH layers in the PP matrix. The nanostructure was characterized by XRD and TEM; the

Sunil P. Lonkar; S. Morlat-Therias; N. Caperaa; F. Leroux; J. L. Gardette; R. P. Singh

2009-01-01

24

Layered double hydroxides as anion- and cation-exchanging materials  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDH) have been principally known as anion-exchanging, clay-like materials for several decades, and continues to be the main driving force for current and future research. The chemical interactions of LDH, with transition metallocyanides, have been a popular topic of investigation for many years, partly due to the use of powder x-ray diffraction and infrared spectroscopy as the main characterization tools. Each transition metallocyanide has a characteristic infrared stretching frequency that can be easily observed, and their respective sizes can be observed while intercalated within the interlayer of the LDH. The ability of LDH to incorporate metal cations or any ions/molecules/complexes, that have a postive charge, have not been previously investigated, mainly due to the chemical and physical nature of LDH. The possibility of cationic incorporation with LDH would most likely occur by surface adsorption, lattice metal replacement, or by intercalation into the LDH interlayers. Although infrared spectroscopy finds it main use through the identification of the anions incorporated with LDH, it can also be used to study and identify the various active and inactive bending and stretching modes that the metal hydroxide layers have.

Richardson, Mickey Charles

25

Removal of endocrine active compounds using layered double hydroxide material  

Microsoft Academic Search

A granular form of a layered double hydroxide (LDH) material was used as an anionic adsorbent in packed column and slurry experiments to remove endocrine active compounds (EACs) from river water downstream from wastewater treatment plants and from laboratory water spiked with 17?-estradiol (E2). The estrogenic activity of the samples was estimated using the biological yeast estrogen screen (YES) assay

J. M. Morris; S. Jin; K. Cui

2008-01-01

26

Sorption of Anionic Surfactants on Layered Double Hydroxides  

Microsoft Academic Search

In the present study we investigated the adsorption of sodium dodecyl- and octylsulfate, and sodium dodecyl- and octylbenzenesulfonate, on a layered double hydroxide (LDH) under controlled conditions. The results were compared to those obtained for the adsorption of surfactants on mineral oxides and on LDHs, showing that the behavior of surfactant adsorption on LDHs can be approximately explained by the

Paulo César Pavan; Eduardo Luis Crepaldi; João Barros Valim

2000-01-01

27

Methotrexate intercalated ZnAl-layered double hydroxide  

NASA Astrophysics Data System (ADS)

The anticancerous drug methotrexate (MTX) has been intercalated into an ZnAl-layered double hydroxide (LDH) using an anion exchange technique to produce LDH-MTX hybrids having particle sizes in the range of 100-300 nm. X-ray diffraction studies revealed increases in the basal spacings of ZnAl-LDH-MTX hybrid on MTX intercalation. This was corroborated by the transmission electron micrographs, which showed an increase in average interlayer spacing from 8.9 Å in pristine LDH to 21.3 Å in LDH-MTX hybrid. Thermogravimetric analyses showed an increase in the decomposition temperature for the MTX molecule in the LDH-MTX hybrid indicating enhanced thermal stability of the drug molecule in the LDH nanovehicle. The cumulative release profile of MTX from ZnAl-LDH-MTX hybrids in phosphate buffer saline (PBS) at pH 7.4 was successfully sustained for 48 h following Rigter-Peppas model release kinetics via diffusion.

Chakraborty, Manjusha; Dasgupta, Sudip; Soundrapandian, Chidambaram; Chakraborty, Jui; Ghosh, Swapankumar; Mitra, Manoj K.; Basu, Debabrata

2011-09-01

28

Intercalation of Hydrogen Phosphate Into Mg/Al-LAYERED Double Hydroxides with Dbs  

NASA Astrophysics Data System (ADS)

Intercalation of hydrogen phosphate (HPO4) into Mg/Al-Layered Double Hydroxides (LDH) with DodecylBenzeneSulfonate (DBS) was investigated with regard to anion exchange, rehydration and a combination of delamination and anion exchange. HPO4 could not be intercalated into the interlayer space of LDH with DBS when using either anion exchange or rehydration methods. However, HPO4 was successfully intercalated into the Mg/Al-LDH using a combination of delamination and anion exchange methods.

Shimamura, Akihiro; Jones, Mark I.; Metson, James B.

29

Pyrene sorption in organic-layered double-metal hydroxides  

SciTech Connect

Myristic, hexanoic, and succinic acids were incorporated into a lithium- and aluminum-containing layered double-metal hydroxide (LDH), resulting in materials with interlayer spacings of 21.6, 17.8, and 7.5 [angstrom], respectively. Comparison of these spacings with the dimensions of the all-trans form of the acid molecules indicates an interlayer monolayer arrangement for myristic and succinic acids, and a bilayer arrangement for hexanoic acid. Sorption isotherms of pyrene by these organic-exchange LDH's were carried out in methanol/water mixtures, because of the limited solubility of pyrene in water. Using cosolvent theory, partition coefficients (log K[sub oc]) for pyrene into myristic acid-LiAl-LDH and hexanoic acid-LiAl-LDH were determined to be 4.38 and 3.44, respectively. No sorption of pyrene was observed in succinic acid-LiAl-LDH, suggesting that partitioning into the interlayer space was controlled by the width of the interlayer spacings. Infrared studies showed distortion of the acid chain packing upon incorporation of pyrene into hexanoic acid-LiAl-LDH. The conclusions of this study are that organic-exchanged LDH's exhibit novel sieving effects toward hydrophobic compounds based on interlayer spacings, and that the interlayer packing of the alkyl chains influences the extent of sorption. 33 refs., 7 figs., 1 tab.

Dutta, P.K.; Robins, D.S. (Ohio State Univ., Columbus, OH (United States))

1994-06-01

30

Sorption\\/desorption of arsenate on\\/from Mg–Al layered double hydroxides: Influence of phosphate  

Microsoft Academic Search

We have studied: (i) the sorption of arsenate on Mg–Al layered double hydroxides (LDHs) containing chloride (LDH-Cl) or carbonate (LDH-CO3) 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

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

2009-01-01

31

Molecular dynamics in aluminum layered double hydroxides as studied by 1H T1? NMR measurements  

NASA Astrophysics Data System (ADS)

Proton dynamics in pristine and organically-modified layered double hydroxide has been studied by 1H T1?. Inverse Laplace transform with spectral resolution results in a correlation of T1? and chemical shift. In LDH two contributions are resolved. They are assigned to the metal hydroxides, forming the LDH sheets (4-8 ms), and mobile interlayer water (2 ms). Apparent T1? values of OH-protons in surfactant-modified LDH are different in dodecylbenzenesulfonate- (SDBS) and sodium octasulfonate- (C8) modified LDH. This difference is explained by the presence of water in LDH-SDBS. The effects of spin diffusion have been studied by performing 2D 1H RFDR in the LDH-SDBS.

Vyalikh, Anastasia; Wang, De-Yi; Wagenknecht, Udo; Heinrich, Gert; Scheler, Ulrich

2011-06-01

32

New antimony substituted Mg-Al layered double hydroxides.  

PubMed

No antimony hydroxide has been previously reported not only in solid state but also in aqueous solution, surely due to the fact that the formation of antimony oxide, Sb2O3, is thermodynamically more favorable than that of the hydroxide phase, Sb(OH)3. According to the pH dependent solubility diagram of Sb2O3, antimony (III) hydroxide may not exist as a definite compound but be proposed as a hydrated monomeric molecular species, Sb(OH)3(aq), which is in equilibrium with Sb2O3, under a condition of very small ionic strength. This is probably the reason why no Sb(3+)-containing layered double hydroxide, LDH, has been reported as yet. In the present study, an attempt has been made to prepare new Sb(3+)-LDH by substituting the Al3+ in octahedral site partially with Sb3+ up to approximately 10%. From the X-ray diffraction analysis, we found that the lattice constants (a = 3.075 angstroms, c = 23.788 angstroms) of the pristine, Mg-Al LDH, increased gradually upto those (a = 3.087 angstroms, c = 24.167 angstroms) of Sb-LDH (8%-substituted). Beyond 10%, the Sb substitution does not lead to any further increases of lattice constants but the impurity Sb2O3 phase is formed. It is, therefore, concluded that the solubility limit of Sb3+ in LDH would be around 10%. In addition, we were able to determine the chemical formula of Sb-substituted LDHs as follows, Mg4Al(1-x)Sb(x)OH10(CO3)(1/2) x H2O (x = 0 approximately 0.08) on the basis of energy dispersive X-ray spectroscopy. PMID:19198414

Kim, Jin A; Hwang, Seong-Ju; Choy, Jin-Ho

2008-10-01

33

Applications of Layered Double Hydroxides in Removing Oxyanions from Oil Refining and Coal Mining Wastewater. Final Report.  

National Technical Information Service (NTIS)

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 oxy...

S. Jin P. Fallgren

2006-01-01

34

Inorganic layered double hydroxides as a drug delivery system—intercalation and in vitro release of fenbufen  

Microsoft Academic Search

Layered double hydroxides (LDHs), or so-called anionic clays, consist of cationic brucite-like layers and exchangeable interlayer anions. Because of their biocompatibility, some LDHs, such as Mg\\/Al, Zn\\/Al, Fe\\/Al and Li\\/Al-LDH, can be used as host materials for drug-LDH host–guest supramolecular structures. The anti-inflammatory drug fenbufen has been intercalated into layered double hydroxides for the first time by co-precipitation under a

Bingxin Li; Jing He; David G. Evans; Xue Duan

2004-01-01

35

Adsorption of dicamba (3,6-dichloro-2-methoxy benzoic acid) in aqueous solution by calcined–layered double hydroxide  

Microsoft Academic Search

Layered double hydroxides (LDHs) are anionic clays with high anion exchange capacities. Calcination of LDHs increases their anion-exchange capacities significantly, resulting in calcined-LDHs that are better adsorbents for removal of anion pollutants than uncalcined-LDHs. In this study, layered double hydroxides, LDH–CO32? and calcined-LDH, were prepared and characterized by FT-IR and X-ray diffraction analysis, with the products evaluated for their ability

Youwen You; Hongting Zhao; George F Vance

2002-01-01

36

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

37

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

38

Cellulose supported layered double hydroxides for the adsorption of fluoride from aqueous solution.  

PubMed

Cellulose supported layered double hydroxides (CSLDHs) were synthesized and tested for adsorption of fluoride in aqueous medium. Three samples of cellulose supported LDHs were synthesized by varying the LDH loading on cellulose. The raw cellulose, unsupported LDH and cellulose supported LDHs were characterized by XRD, SEM and BET surface area. Batch adsorption as well as fixed-bed column experiments were performed for determining the fluoride adsorption characteristics of CSLDHs. The fluoride adsorption properties of CSLDHs were found to be superior to that of reported adsorbents, including activated alumina and carbon nanotubes. Defluoridation capacity of the CSLDHs was 2-4 times higher than that of unsupported LDH. The cellulose supported LDH, CSLDH-50, having an LDH loading of 27% showed maximum fluoride uptake capacity (5.29 mg g(-1) of CSLDH, 25.18 mg g(-1) of LDH) in fixed-bed column study. PMID:18474392

Mandal, S; Mayadevi, S

2008-05-12

39

Hybrid layered double hydroxides-polypyrrole composites for construction of glucose\\/O 2 biofuel cell  

Microsoft Academic Search

In this work, two layered double hydroxides, Zn2Cr–ABTS and Zn2Al–Fe(CN)6 LDH, have been synthesized and characterized by X ray diffraction and FTIR spectroscopy to confirm the intercalation of redox anions between inorganic layers. These redox active hybrid materials have been used to electrically connect laccase (Lac) and glucose oxidase (GOx) in biofuel cell devices. Co-immobilization of hybrid LDH and enzymes

Abdelkader Zebda; Sophie Tingry; Christophe Innocent; Serge Cosnier; Claude Forano; Christine Mousty

40

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

Microsoft Academic Search

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 CO32- (CO3·Mg?Al LDH) to treat gaseous HCl continuously. The degree of HCl removal without water vapor is higher than that with water vapor;

Tomohito Kameda; Naoya Uchiyama; Toshiaki Yoshioka

2010-01-01

41

New polyol route to keggin ion-pillared layered double hydroxides  

Microsoft Academic Search

A new route to polyoxometalate pillared layered double hydroxides (LDHs) of the type [Mg1?x2+Alx3+?(OH)2][POMn?]x\\/n' where POMn? is the Keggin ion H2W12O406?, is reported based on the atopotactic reactions of the corresponding LDH carbonate with glycerol or triethyleneglycol at 120–130°C and subsequent ion-exchange reaction of the polyol-solvated LDH intermediates with the pillaring Keggin anion. This new synthesis strategy offers important advantages

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

1995-01-01

42

Aldol condensation of acetone over layered double hydroxides of the meixnerite type  

Microsoft Academic Search

Aldol condensation of acetone is performed at 273 K in liquid phase using as catalysts Mg–Al layered double hydroxides (LDH) with Cl? and\\/or CO32? as compensating anions. The products of the reaction are mainly diacetone alcohol and mesityl oxide. The catalytic activities increase with the Al content of the LDH and a conversion around 20% is reached when the carbonated

D Tichit; M Naciri Bennani; F Figueras; R Tessier; J Kervennal

1998-01-01

43

Preparation of the poly(vinyl alcohol)/layered double hydroxide nanocomposite  

SciTech Connect

Intercalated nanocomposite based on Mg, Al layered double hydroxide (LDH) and poly(vinyl alcohol) (PVA) was prepared using exfoliation-adsorption technique, and characterized by X-ray diffraction and thermal gravimetric analysis. The results suggest that the intercalated species are formed via the re-aggregation of the delaminated LDH lamellar with the interlayer spacing 14.5 A, and the thermal stability of the nanocomposite improved compared with the original PVA.

Li Baoguang; Hu Yuan; Zhang Rui; Chen Zuyao; Fan Weicheng

2003-10-01

44

Fabrication and electrochemical characterization of cobalt-based layered double hydroxide nanosheet thin-film electrodes  

Microsoft Academic Search

A continuous cobalt-based layered double hydroxide (LDH) nanosheet thin-film electrode has been fabricated by drying a nearly transparent colloidal solution of cobalt-based LDH nanosheets on an indium tin oxide (ITO)-coated glass plate substrate. The effects of varying the Al content, the film thickness, and the heating temperature on the electrochemical properties of the as-deposited thin-film electrode have been investigated. A

Yi Wang; Wensheng Yang; Chen Chen; David G. Evans

2008-01-01

45

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

Microsoft Academic Search

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

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

2006-01-01

46

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

47

Dye-interleaved nanocomposite: Indigo carmine and methyl orange in the lamella of zinc-aluminium-layered double hydroxide  

Microsoft Academic Search

Layered organic–inorganic hybrid nanocomposite, containing an organic dye in an inorganic interlayer was prepared using indigo carmine (IC) and methyl orange (OM) as a guest in Zn2-Al layered double hydroxide (LDH) inorganic host by a ion exchange , with [Zn2-Al-Cl] LDH in aqueous solution. The affinity of the LDH with the dyes was studied as a function of contact time,

Layla El Gaini; Mohamed Lakraimi; Mina Bakasse

2011-01-01

48

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

49

Factors influencing the removal of fluoride from aqueous solution by calcined Mg–Al–CO 3 layered double hydroxides  

Microsoft Academic Search

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–CO3-LDH has been carried out. The LDH calcined at 500°C had the highest capacity of

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

2006-01-01

50

Synthesis mechanism study of layered double hydroxides based on nanoseparation.  

PubMed

Colloidal layered double hydroxides (LDH) nanosheets were sorted by their lateral sizes using a density gradient ultracentrifuge separation technique. Composition investigations on these size-sorted nanosheets indicated that larger sheets had higher Mg:Al ratio than the smaller ones. Experiments using different Mg:Al feed ratios confirmed that high Mg:Al ratio induced fast sheet growth speed. Tracking the source of the Mg:Al spatial distribution difference in one batch of synthesis at the nucleation process revealed the coprecipitation-redissolution of Mg(2+). Thus the discriminative separation of these nanosheets led to a new insight into the structure-composition relationship of LDH nanomaterials and more understanding on their formation mechanism. PMID:23879682

Chang, Zheng; Wu, Caiying; Song, Sha; Kuang, Yun; Lei, Xiaodong; Wang, Liren; Sun, Xiaoming

2013-07-23

51

Immobilization of the Aminopeptidase from Aeromonas Proteolytica on Mg2+/Al3+ Layered Double Hydroxide Particles  

PubMed Central

A novel biomaterial formed by the immobilization of the Aminopeptidase from Aeromonas Proteolytica (AAP) on synthetic Mg2+ and Al3+ ion-containing layered double hydroxide (LDH) particles was prepared. Immobilization of AAP on the LDH particles in a buffered, aqueous mixture is rapid such that the maximum loading capacity, 1 × 10-9 moles of AAP/mg LDH, is achieved in a few minutes. X-ray powder diffraction of LDH samples before and after treatment with AAP indicates that the enzyme does not intercalate between the layers of LDH, but instead binds to the surface. Treatment of AAP/LDH with various amounts of salt in a buffered mixture demonstrates that between 15 and 20% of AAP can be removed from the LDH by washing the composite material in 0.2 M NaCl. However, the residual AAP remains bound to the LDH even at 1 M salt concentrations. A suspension of the AAP/LDH biomaterial in 10 mM Tricine buffered, aqueous solution (pH 8.0 and 25 ° C) catalyzes the hydrolysis of l-leucine-p-nitroanilide demonstrating that immobilized AAP remains available to substrate and retains its catalytic activity. Recycling experiments reveal that the AAP/LDH particles can be recovered and reused multiple times without appreciable loss of activity. This work provides the foundation for the development of materials that will function in the degradation or detection of peptide hormones or neurotoxins.

Frey, Steven T.; Guilmet, Stephanie L.; Egan, Richard G.; Bennett, Alyssa; Soltau, Sarah R.; Holz, Richard C.

2010-01-01

52

Epoxidation of allylic alcohols on self-assembled polyoxometalates hosted in layered double hydroxides with aqueous H 2O 2 as oxidant  

Microsoft Academic Search

A series of self-assembled polyoxometalate (POM) catalysts were directly immobilized into layered double hydroxides (LDH) by a selective ion-exchange method. Sandwich-type POM species are found to be more favorable than Keggin-type POM for the direct immobilization in LDH, because strict pH controlling is not needed and the LDH hosts can be kept intact. The resulting LDH–POM catalysts were evaluated in

Peng Liu; Changhao Wang

2009-01-01

53

Control of Nanoparticle Size, Crystal Structure and Growth of Layered Double Hydroxide by Hydrothermal Treatment  

NASA Astrophysics Data System (ADS)

Here, we showed the effect of hydrothermal treatment and aging process of urea hydrolysis on crystal structure, particle size and particle size distribution of Mg-Al layered double hydroxide (LDH) materials. The obtained materials were characterized by X-ray crystallography and scanning electron microscopy. The studied synthetic parameters showed a great influence on the physicochemical properties of the selected LDH materials. At insufficient conditions of hydrothermal treatments, the formed LDH particles were amorphous and the non-LDH phases dominated the X-ray diffraction chart. The crystal growth increased with increasing hydrothermal temperature. Aging process improved the crystal morphology up to18 hours, while further aging destroyed the LDH particles. The increase of hydrothermal aging led to a wide particle size distribution.

Berber, Mohamed R.; Hafez, Inas H.; Minagawa, Keiji; Katoh, Masahiro; Tanaka, Masami; Mori, Takeshi

54

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

55

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

56

Dispersion control and nematic ordering of Ni/Al layered double hydroxide suspensions  

SciTech Connect

In this paper, we report the preparation of aqueous suspensions of Ni/Al layered double hydroxide (LDH) nanoparticles by a non-steady co-precipitation followed by peptization. By choosing suitable peptization temperature and time, well-dispersed suspensions were obtained. Meanwhile, the particle size, shape and size polydispersity can be efficiently controlled. Nematic ordering is observed in colloidal Ni/Al LDH suspensions and confirmed by birefringence observations and SAXS measurements. Furthermore, we showed that the sol-gel transition takes place after a liquid crystalline phase transition in concentrated Ni/Al LDH suspensions. The absence of isotropic-nematic phase separation can be attributed to the fact that the nematic phase droplets are too small to settle to the bottom of the cuvette. - Graphical abstract: Well-defined Ni/Al LDH nanoparticles were prepared and nematic ordering confirmed by birefringence observations and SAXS measurements is observed in concentrated Ni/Al LDH suspensions.

Luan Lingyu; Liu Shangying [Key Laboratory for Colloid and Interface Chemistry of the Ministry of Education, Shandong University, Jinan, Shandong 250100 (China); Sun Dejun, E-mail: djsun@sdu.edu.c [Key Laboratory for Colloid and Interface Chemistry of the Ministry of Education, Shandong University, Jinan, Shandong 250100 (China)

2009-06-15

57

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

58

Formulation of Polyacrylic Acid-Layered Double Hydroxide Composite System as a Soil Conditioner for Water Management  

NASA Astrophysics Data System (ADS)

An efficient strategy of soil-conditioner application was offered by incorporating a high molecular weight organic polymer (polyacrylic acid; PAA) into a soil-friendly inorganic material (layered double hydroxide; LDH). The prepared materials were characterized by different spectroscopic techniques to confirm the formed nanocomposite structure. The SEM images captured the morphological ability of PAA-LDH nanocomposites to absorb and keep water molecules during soil-water application. The IR analysis indicated an electrostatic grafting process between PAA units and LDH moieties. The platform of PAA-LDH nanocomposite formulation stabilized the soil aggregates and improved the water-stability.

Hafez, Inas H.; Berber, Mohamed R.; Minagawa, Keiji; Mori, Takeshi; Tanaka, Masami

59

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

60

Pillaring of layered double hydroxides (LDH's) by polyoxometalate anions  

Microsoft Academic Search

Layered silicate clays (LSC's) intercalated by pillaring polyoxocations are precursors to an important class of microporous catalysts for a large number of reactions, including shape selective petroleum cracking. To date, smectite clays are the only host structures known to be pillarable by purely inorganic oxo ions. In the present work they report the oxo ion pillaring of a new family

Taehyun. Kwon; George A. Tsigdinos; Thomas J. Pinnavaia

1988-01-01

61

Alkoxylation reaction catalysed by layered double hydroxides  

Microsoft Academic Search

Layered double hydroxides (LDHs) are extensively studied as precursors for catalysts, following a calcination at high temperatures to yield mixed oxides. However, these materials are less used as layered materials, i.e., without undergoing thermal activation. We have focused in this work on the use of a series of as-synthesised LDHs for the catalytic preparation of glycol ethers, which is a

François Malherbe; C Depège; C Forano; J. P Besse; M. P Atkins; B Sharma; S. R Wade

1998-01-01

62

Mg/Al layered double hydroxide-Pt nanoparticle composite by delamination-restacking route  

NASA Astrophysics Data System (ADS)

Platinum nanoparticle intercalated magnesium-aluminum layered double hydroxide (LDH) composite was prepared by restacking the colloidal dispersion of organically modified LDH in the presence of preformed oleylamine capped platinum nanoparticles in n-butanol. The resultant nanocomposite was characterized using powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction and energy dispersive X-ray spectroscopy (EDX). The PXRD pattern of the composite indicates an expanded interlayer due to the intercalation of the Pt-nanoparticles into the LDH interlayer region. PXRD patterns along with the IR spectra confirm the formation of the precursors and the composite. TEM image of Pt-nanoparticles shows spherical particles with an average particle size of ~3 nm and that of the composite shows dispersed Pt-nanoparticles on the LDH matrix. The presence of Pt, Mg and Al in the composite is indicated in the EDX data.

Nityashree, N; Menezes, Premitha

2013-08-01

63

Synthesis and Thermal Decomposition of Mn-Al Layered Double Hydroxides  

NASA Astrophysics Data System (ADS)

In this paper, the synthesis and thermal decomposition behavior of hydrotalcite-like Mn-Al layered double hydroxide (LDH) have been investigated. First, the Mn-Al LDH was synthesized by the coprecipitation method using various anions such as Cl-, CO2-3, NO-3, SO2-4 or dicarboxylic acids (DCA). The single phase of the Mn-Al LDH was obtained when Cl-, NO-3 or DCA was used as a guest anion. In the case of CO2-3 or SO2-4, the solid products included MnCO3 or shigaite as a by-product. The crystallinity of the Cl/Mn-Al LDH was greatly influenced by a drying temperature and that the crystallinity of the Cl/Mn-Al LDH dried at room temperature was found to rise about 6 times in comparison with that dried at 333 K. The DCA/Mn-Al LDH was found to have an expanding LDH structure, supporting that the LDH basal layers were bridged by the intercalated DCA anion. Then, the thermal decomposition of the DCA/Mn-Al LDH has been examined, and the intercalated DCA was found to be decomposed at lower temperature than DCA itself. The oxidation number of Mn ion rose with increasing the heat treatment temperature and was +2.70 with crystallizing Mn3O4 after being heated at 973 K. The thermal decomposition of guest DCA was thought to be accelerated by the strong catalytic action of Mn ion in the host hydroxide basal layers.

Aisawa, Sumio; Hirahara, Hidetoshi; Uchiyama, Hiroaki; Takahashi, Satoshi; Narita, Eiichi

2002-08-01

64

Thermal Evolution of the Structure of a Mg?Al?CO 3 Layered Double Hydroxide:  Sorption Reversibility Aspects  

Microsoft Academic Search

In our prior study, we employed several in-situ techniques to investigate the thermal evolution of the structure of a Mg-Al-CO3 layered double hydroxide (LDH) under an inert atmosphere and proposed a model to describe the structural evolution of the Mg-Al-CO3 LDH structure. In this paper we present results of our ongoing investigations with these materials pertaining to their sorption characteristics

Yongman Kim; Weishen Yang; Paul K. T. Liu; Muhammad Sahimi; Theodore T. Tsotsis

2004-01-01

65

Sorption characteristics and mechanisms of oxyanions and oxyhalides having different molecular properties on Mg\\/Al layered double hydroxide nanoparticles  

Microsoft Academic Search

The sorption ability of fast-coprecipitated and hydrothermally-treated Mg\\/Al layered double hydroxide nanoparticles (FCHT-LDH) for various oxyhalides and oxyanions was evaluated. Interactions of oxyhalide such as monovalent bromate or oxyanions such as divalent chromate and divalent vanadate with FCHT-LDH were investigated using a combination of macroscopic (batch sorption\\/desorption studies and electrophoretic mobility (EM) measurements) and microscopic techniques (CHNS\\/O, XRD, FTIR, XPS,

Kok-Hui Goh; Teik-Thye Lim; Agnieszka Banas; Zhiling Dong

2010-01-01

66

Preparation and flame resistance properties of revolutionary self-extinguishing epoxy nanocomposites based on layered double hydroxides  

Microsoft Academic Search

Layered double hydroxides\\/epoxy (LDHs\\/EP) nanocomposites were prepared from organo-modified LDHs, a diglycidyl ether of bisphenol A monomer (DGEBA) and amine curing agents. The organo-modified LDHs were obtained by ionic exchange of a magnesium–aluminum carbonate LDH in an acid medium. X-ray diffraction and transmission electron microscopy showed a dispersion of the layers at a nanometer scale, indicating the formation of LDH\\/EP

Mauro Zammarano; Massimiliano Franceschi; Séverine Bellayer; Jeffrey W. Gilman; Sergio Meriani

2005-01-01

67

Preparation of Glycy- l-Tyrosine intercalated layered double hydroxide film and its in vitro release behavior  

Microsoft Academic Search

This paper describes the preparation of films of peptide (Glycy-l-Tyrosine, denoted as GlyTyr) intercalated layered double hydroxide (LDH) and its release performances. GlyTyr has been intercalated into a magnesium–aluminum LDH, and the resulting film was fabricated by solvent evaporation method in order to exploit new formulation in drug carrier especially used in skin medicament. Based on the results of XRD,

Xianggui Kong; Shuxian Shi; Jingbin Han; Fengjie Zhu; Min Wei; Xue Duan

2010-01-01

68

Intercalation behavior of amino acids into Zn–Al-layered double hydroxide by calcination–rehydration reaction  

Microsoft Academic Search

The intercalation of amino acids for the Zn–Al-layered double hydroxide (LDH) has been investigated by the calcination–rehydration reaction at 298K using mainly phenylalanine (Phe) as a guest amino acid. The Zn–Al oxide precursor prepared by the calcination of Zn–Al-carbonated LDH at 773K for 2h was used as the host material. The amount of Phe intercalated by the rehydration was remarkably

Sumio Aisawa; Hiroko Kudo; Tomomi Hoshi; Satoshi Takahashi; Hidetoshi Hirahara; Yoshio Umetsu; Eiichi Narita

2004-01-01

69

Synthesis and characterization of a novel nano-scale magnetic solid base catalyst involving a layered double hydroxide supported on a ferrite core  

Microsoft Academic Search

A nano-scale magnetic solid base catalyst MgAl-OH-LDH\\/MgFe2O4 (where LDH denotes layered double hydroxide) composed of MgAl-OH-LDH Brønsted base catalytic layers coated on MgFe2O4 spinel cores has been prepared. A magnetic precursor MgAl-CO3-LDH\\/MgFe2O4 was prepared by a method involving separate nucleation and aging steps, and subsequently calcined to give a mixed metal oxide composite MgAl(O)\\/MgFe2O4 which was rehydrated to give MgAl-OH-LDH\\/MgFe2O4.

Hui Zhang; Rong Qi; David G Evans; Xue Duan

2004-01-01

70

Enhanced thermal- and photo-stability of acid yellow 17 by incorporation into layered double hydroxides  

SciTech Connect

2,5-dichloro-4-(5-hydroxy-3-methyl-4-(sulphophenylazo) pyrazol-1-yl) benzenesulphonate (DHSB) anions, namely acid yellow 17 anions, have been successfully intercalated into Zn-Al layered double hydroxides (LDH) to produce a novel organic-inorganic pigment by a simple method involving separate nucleation and aging steps (SNAS), and the dye-intercalated LDH was analyzed by various techniques, e.g., XRD, SEM, FT-IR, TG-DTA and ICP. The d-spacing of the prepared LDH is 2.09 nm. Furthermore, the incorporation of the DHSB aims to enhance the thermal- and photo-stability of the guest dye molecule, for example, the less color change after accelerated thermal- and photo-aging test. - Graphical abstract: Acid yellow anions were successfully assembled into ZnAl layered double hydroxides (LDH) to produce a novel organic-inorganic composite pigment by a simple method involving separate nucleation and aging steps (SNAS). Highlights: > Acid yellow 17 was directly intercalated into ZnAl-LDH to form a novel pigment. > The pigment was prepared by a method involving separate nucleation and aging steps. > The intercalation of dye anions enhances its thermal- and photo-stability.

Wang Qian; Feng Yongjun; Feng Junting [College of Science, State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Li Dianqing, E-mail: lidq@mail.buct.edu.cn [College of Science, State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

2011-06-15

71

In vitro and in vivo behavior of ketoprofen intercalated into layered double hydroxides  

Microsoft Academic Search

Ketoprofen (Ket) was intercalated into layered double hydroxides (ZnAlLDH and MgAlLDH) using the ionic exchange method. The\\u000a drug intercalation was confirmed by X-ray diffraction (XRD) and FTIR spectroscopy. Ket release from the inorganic matrix was\\u000a studied at pH 7.4 in continuous regime with a flow rate of 0.5 and respectively 1.0 ml\\/min. The kinetical data were interpreted\\u000a using the Ritger and

Mihaela Silion; Doina Hritcu; Irina M. Jaba; Bogdan Tamba; Dunarea Ionescu; Ostin C. Mungiu; Ionel Marcel Popa

2010-01-01

72

Synthesis of organic-inorganic hybrid nanocomposite material: alizarin-3-sulfonate in the lamella of zinc-aluminium-layered double hydroxide  

Microsoft Academic Search

A series of new organic dye-interleaved nanocomposites (NCs) were prepared by intercalation of alizarin-3-sulfonate anion (Az3S) into Zn-Al-layered double hydroxide (LDH) inorganic lamella host at different concentrations via self-assembly method. The physicochemical properties of the as-synthesized LDH and NCs were studied using PXRD, FTIR, ICP-AES, CHNS, true density and SEM techniques. Basal spacing expansions from 9.0 Å in LDH to

Mohd Zobir b. Hussein; Chan W. Long; Zulkarnain Zainal; Asmah H. Yahaya

2005-01-01

73

Study on UV-shielding mechanism of layered double hydroxide materials.  

PubMed

The development of UV-shielding materials has attracted considerable attention in the field of coatings and sunscreen. This paper reports the UV-shielding mechanism of layered double hydroxide (LDH) materials in terms of chemical composition, structure and morphology, by using (LDH/PAA)n films (n stands for bilayer number) through alternate LBL assembly of LDH nanoparticles and poly(acrylic acid) (PAA) on quartz substrates as a model system. A combination investigation based on experimental and theoretical study demonstrates that the maximum UV scattering can be achieved when ?/d ? 1.98; the introduction of Zn element is an effective way to tune the electron structure, band gap, transition mode and resulting UV-shielding property of LDH materials. A UV-shielding efficiency as high as 95% can be obtained by modulating the particle size, composition and thickness of the LDHs. Furthermore, the UV anti-aging capacity of LDH-modified bitumen was studied, which demonstrates a large improvement in UV-resistance performance of bitumen by the incorporation of LDH materials. Therefore, this work systematically discloses the relationship between UV-shielding property and chemical/structural parameters of LDH materials, which can be potentially used as anti-aging agents in various organic matrices and polymer areas. PMID:24064552

Shi, Wenying; Lin, Yanjun; Zhang, Shitong; Tian, Rui; Liang, Ruizheng; Wei, Min; Evans, David G; Duan, Xue

2013-10-01

74

Adsorption and photodegradation properties of anionic dyes by layered double hydroxides  

NASA Astrophysics Data System (ADS)

The adsorption and photodegradation behavior of methyl orange (MO) and fast green (FG) over ZnAl- and MgAl-based layered double hydroxide (LDH) adsorbents have been examined. ZnAl-LDHs were prepared with Zn/Al ratios of 2 to 4 by co-precipitation at pH 8. The ZnAl-LDHs and a commercial MgAl-LDH with a Mg/Al ratio of 3 were evaluated for their ability to adsorb MO and FG and for the photodegradation behavior of these dyes under UV irradiation. Structure analysis of the LDH-dyes-adsorbed complexes revealed that the adsorption produced two types of structures, an intercalation complex for MO and a surface-adsorbed complex for FG. The maximum adsorption of MO on the LDHs was significantly higher (more than tenfold) than FG. Results indicated the adsorption isotherms for the retention of both dyes by ZnAl- and MgAl-LDHs could be fitted to a Freundlich equation, showing a higher affinity for dyes on MgAl-LDH compared to those on ZnAl-LDH. The catalytic degradation ability of dye-LDH complex solid films on a quartz plate was superior to pure dye films under UV irradiation. The FG non-intercalated LDH complexes showed much faster photodegradation under UV irradiation than the MO-intercalated LDH complexes, which pointed to the important role of the LDH materials containing sensitized dyes in enhancing the generation of labile hydroxyl ions from the hydrophilic LDH surface.

Morimoto, Kazuya; Tamura, Kenji; Iyi, Nobuo; Ye, Jinhua; Yamada, Hirohisa

2011-09-01

75

Magnetic behavior of Mg-Al-Zn-Fe mixed oxides from precursors layered double hydroxide  

NASA Astrophysics Data System (ADS)

Mixed oxides of Mg-Al-Zn-Fe were obtained by calcination of layered double hydroxides (LDH) prepared by coprecipitation reaction with hydrothermal treatment. The structural characterization of precursors and oxides was carried out by X rays diffraction, showing increases of ZnO phase with the increase of the zinc content. Magnetic behavior was studied by vibrating sample magnetometer (VSM) and by a superconducting quantum interference device (SQUID) showing both paramagnetic and super paramagnetic behavior depending on both particles size and composition.

Oliva, M. I.; Heredia, A.; Zandalazini, C. I.; Crivello, M.; Corchero, E.

2012-08-01

76

Structure and conductive properties of poly(ethylene oxide)\\/layered double hydroxide nanocomposite polymer electrolytes  

Microsoft Academic Search

The oligo(ethylene oxide) modified layered double hydroxide (LDH) prepared by template method was added as a nanoscale nucleating agent into poly(ethylene oxide) (PEO) to form PEO\\/OLDH nanocomposite electrolytes. The effects of OLDH addition on morphology and conductivities of nanocomposite electrolytes were studied using wide-angle X-ray diffractometer, polarized optical microscopy, differential scanning calorimetry and ionic conductivity measurement. The results show that

Chien-Shiun Liao; Wei-Bin Ye

2004-01-01

77

Antireflection\\/antifogging coatings based on nanoporous films derived from layered double hydroxide  

Microsoft Academic Search

Multifunctional mixed metal oxide (MMO) thin films on quartz substrates have been fabricated by layer-by-layer assembly of layered double hydroxide (LDH) nanoparticles and poly(sodium styrene 4-sulfonate) (PSS) followed by calcination, which exhibited properties of both antireflection (AR) and antifogging (AF). The AR and AF performances are related to the low refractive index and superhydrophilicity originating from the nanoporous structure. The

Jingbin Han; Yibo Dou; Min Wei; David G. Evans; Xue Duan

2011-01-01

78

Organic inorganic dye filler for polymer: Blue-coloured layered double hydroxides into polystyrene  

Microsoft Academic Search

A series of blue dye molecules, Evans blue (EB), Chicago sky blue (CB), Niagara blue (NB) were incorporated by direct co-precipitation within the galleries of negatively charge layered double hydroxide (LDH). The materials of cation composition Zn\\/Al = 2 lead to well-defined organic inorganic assemblies. The molecular arrangement of the interleaved dye molecule is proposed by 1D electronic density projection

Rafael Marangoni; Christine Taviot-Guého; Abdallah Illaik; Fernando Wypych; Fabrice Leroux

2008-01-01

79

Direct Intercalation of Amino Acids into Layered Double Hydroxides by Coprecipitation  

Microsoft Academic Search

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

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

2001-01-01

80

Layered Double Hydroxide Based Polymer Nanocomposites  

Microsoft Academic Search

Nanocomposites based on polymers and inorganic filler materials not only create enormous interest\\u000a among researchers because of their unique way of preparation and properties, but also promise development\\u000a of new hybrid materials for specific applications in the field of polymer composites. The present article\\u000a deals with the application of a relatively new class of inorganic materials, namely layered double\\u000a hydroxides (LDHs),

Francis Reny Costa; Marina Saphiannikova; Udo Wagenknecht; Gert Heinrich

81

Preparation and wettability of Zn–Al layered double hydroxide film directly grown on highly porous anodic alumina oxide template  

Microsoft Academic Search

Zinc–aluminum layered double hydroxide (Zn–Al LDH) thin films were prepared by direct precipitation on the surface of porous anodic alumina oxide (AAO) template. The Zn–Al LDH was assigned to Zn6All2(OH)16CO3·nH2O according to the XRD and EDX data. The nano-pores provided channels and the nano-sized wall-edges for supplying Al3+and highly active reaction sites, thereby the Zn–Al LDH films can be grown

Feng Yang; Bo Yu Xie; Jing Zhi Sun; Jia Ke Jin; Mang Wang

2008-01-01

82

Bio-LDH nanohybrid for gene therapy  

Microsoft Academic Search

Nano-sized inorganic clay, such as layered double hydroxide (LDH), has been demonstrated as delivery carrier for genes and drugs by hybridizing with DNA and c-antisense oligonucleotide (As-myc). Upon intercalating biomolecules into hydroxide layers, the basal spacing of LDH increases from 8.7 Å (for NO3?) to 23.9 Å (DNA) and 17.1 Å (As-myc), respectively. A strong suppression of cell growth (65%)

Seo-Young Kwak; Yong-Joo Jeong; Jong-Sang Park; Jin-Ho Choy

2002-01-01

83

The preparation of layered double hydroxide wrapped carbon nanotubes and their application as a flame retardant for polypropylene.  

PubMed

Carbon nanotubes (CNTs) wrapped with layered double hydroxide (LDH-w-CNTs) were facilely obtained through in situ introduction of CNTs into the hydrothermal reaction system of LDH, with the goal of combining their unique physical and chemical characteristics to meet new advanced applications. Morphological observations indicated that LDH lamellae enwrapped the surface of CNTs and the wrapping degree was dependent on the functionalization of CNTs. Zeta-potential measurements showed that the interaction between the positive charge of LDH and the negative charge of CNTs was the main driving force of the wrapping process. Both hybrids led to a reduction in the peak heat release rate (PHRR) of polypropylene, indicating that they could confer better flame retardancy on polypropylene with respect to LDH and CNTs. PMID:20634567

Du, Baoxian; Fang, Zhengping

2010-07-15

84

The preparation of layered double hydroxide wrapped carbon nanotubes and their application as a flame retardant for polypropylene  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) wrapped with layered double hydroxide (LDH-w-CNTs) were facilely obtained through in situ introduction of CNTs into the hydrothermal reaction system of LDH, with the goal of combining their unique physical and chemical characteristics to meet new advanced applications. Morphological observations indicated that LDH lamellae enwrapped the surface of CNTs and the wrapping degree was dependent on the functionalization of CNTs. ?-potential measurements showed that the interaction between the positive charge of LDH and the negative charge of CNTs was the main driving force of the wrapping process. Both hybrids led to a reduction in the peak heat release rate (PHRR) of polypropylene, indicating that they could confer better flame retardancy on polypropylene with respect to LDH and CNTs.

Du, Baoxian; Fang, Zhengping

2010-08-01

85

Eu-doped Mg-Al layered double hydroxide as a responsive fluorescent material and its interaction with glutamic acid  

NASA Astrophysics Data System (ADS)

The paper describes a study on the fluorescence of a Eu-doped Mg-Al layered double hydroxide (Eu-doped LDH) response to glutamic acid (Glu). Various characterizations (UV-Vis transmittance, TG-DTA and IR-spectrum) indicated that there is an interaction between the Eu-doped LDH and Glu. Fluorescent study was found that the red emissions resulted from 5D0-7FJ transition (J = 1, 2) of Eu3+ markedly decreased, while the blue emission at 440 nm contributed to Glu shifted to low energy after the addition of Glu to the Eu-doped LDH. The fluorescent changes may be relevant to the hydrogen-bond interaction between the Eu-doped LDH and Glu, and the mechanism of the interaction between Eu-doped LDH and Glu was discussed.

Chen, Yufeng; Li, Fei; Yu, Gensheng; Wei, Junchao

2012-10-01

86

Synthesis and characterization of Cd-Cr and Zn-Cd-Cr layered double hydroxides intercalated with dodecyl sulfate  

SciTech Connect

Cd-Cr and Zn-Cd-Cr layered double hydroxides (CdCr-LDH and ZnCdCr-LDH) containing alkyl sulfate as the interlamellar anion have been prepared through a coprecipitation technique. The resulting compounds were characterized using X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Magnetic property measurements indicate that antiferromagnetic interactions occur between the chromium ions in the two compounds at low temperatures. The introduction of zinc influences the ligand field of Cr{sup III} and the Cr{sup III}-Cr{sup III} interactions in the LDH compound. It is found that both CdCr-LDH and ZnCdCr-LDH can be delaminated by dispersion in formamide, leading to translucent and stable colloidal solutions.

Guo Ying [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Zhang He [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Zhao Lan [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Li Guodong [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Chen Jiesheng [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)]. E-mail: chemcj@mail.jlu.edu.cn; Xu Lin [Institute of Polyoxometalate Chemistry, College of Chemistry, Northeast Normal University, Changchun 130024 (China)

2005-06-15

87

Synthesis and selective IR absorption properties of iminodiacetic-acid intercalated MgAl-layered double hydroxide  

NASA Astrophysics Data System (ADS)

An MgAl-NO3-layered double hydroxide (LDH) precursor has been prepared by a method involving separate nucleation and aging steps (SNAS). Reaction with iminodiacetic acid (IDA) under weakly acidic conditions led to the replacement of the interlayer nitrate anions by iminodiacetic acid anions. The product was characterized by XRD, FT-IR, TG-DTA, ICP, elemental analysis and SEM. The results show that the original interlayer nitrate anions of LDHs precursor were replaced by iminodiacetic acid anions and that the resulting intercalation product MgAl-IDA-LDH has an ordered crystalline structure. MgAl-IDA-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-IDA-LDH showed a higher mid to far infrared absorption than films filled with MgAl-CO3-LDH in the 7-25 ?m range, particularly in the key 9-11 ?m range required for application in agricultural plastic films.

Wang, Lijing; Xu, Xiangyu; Evans, David G.; Duan, Xue; Li, Dianqing

2010-05-01

88

Tungstocobaltate-pillared layered double hydroxides: Preparation, characterization, magnetic and catalytic properties  

SciTech Connect

A new polyoxometalate anion-pillared layered double hydroxide (LDH) was prepared by aqueous ion exchange of a Mg-Al LDH precursor in nitrate form with the tungstocobaltate anions [CoW{sub 12}O{sub 40}]{sup 5-}. The physicochemical properties of the product were characterized by the methods of powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. It was confirmed that [CoW{sub 12}O{sub 40}]{sup 5-} was intercalated between the brucite-type layers of the LDHs without a change in the structure. Magnetic measurement shows the occurrence of antiferromagnetic interactions between the magnetic centers. The investigation of catalytic performance for this sample exhibits high activity for the oxidation of benzaldehyde by hydrogen peroxide. - Graphical abstract: A tungstocobaltate anion [CoW{sub 12}O{sub 40}]{sup 5-} pillared layered double hydroxide (LDH) was prepared by aqueous ion exchange with a Mg-Al LDH precursor in nitrate form, demonstrating that [CoW{sub 12}O{sub 40}]{sup 5-} was intercalated between the brucite-type layers of the LDHs without change in structure. Magnetic measurement shows the occurrence of antiferromagnetic interactions between the magnetic centers. The investigation of catalytic performance for this sample exhibits high activity for the oxidation of benzaldehyde by hydrogen peroxide.

Wei Xiaocui [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); Baicheng College of Higher Medicine, Baicheng 137000 (China); Fu Youzhi [Department of Chemistry, Baicheng Teacher's College, Baicheng 137000 (China); Xu Lin [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China)], E-mail: linxu@nenu.edu.cn; Li Fengyan; Bi Bo; Liu Xizheng [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China)

2008-06-15

89

Synthesis of ultrafine layered double hydroxide (LDHs) nanoplates using a continuous-flow hydrothermal reactor  

NASA Astrophysics Data System (ADS)

We report a novel continuous-flow hydrothermal method for the synthesis of layered double hydroxide (LDH) nanoplates. The precursor solutions may be fed to the reactor so that the production of LDHs occurs in a continuous mode. By control of the synthesis temperature, pressure and contact time, the synthesis of LDH nanoplates can be tuned with constant and consistent product quality. This very general and simple approach shows high potential for commercial scale-up.We report a novel continuous-flow hydrothermal method for the synthesis of layered double hydroxide (LDH) nanoplates. The precursor solutions may be fed to the reactor so that the production of LDHs occurs in a continuous mode. By control of the synthesis temperature, pressure and contact time, the synthesis of LDH nanoplates can be tuned with constant and consistent product quality. This very general and simple approach shows high potential for commercial scale-up. Electronic supplementary information (ESI) available: Experimental details and more characterisations. See DOI: 10.1039/c2nr32568c

Wang, Qiang; Tang, Selina Yu, Vi; Lester, Edward; O'Hare, Dermot

2012-12-01

90

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

91

Enhanced thermal- and photo-stability of acid yellow 17 by incorporation into layered double hydroxides  

NASA Astrophysics Data System (ADS)

2,5-dichloro-4-(5-hydroxy-3-methyl-4-(sulphophenylazo) pyrazol-1-yl) benzenesulphonate (DHSB) anions, namely acid yellow 17 anions, have been successfully intercalated into Zn-Al layered double hydroxides (LDH) to produce a novel organic-inorganic pigment by a simple method involving separate nucleation and aging steps (SNAS), and the dye-intercalated LDH was analyzed by various techniques, e.g., XRD, SEM, FT-IR, TG-DTA and ICP. The d-spacing of the prepared LDH is 2.09 nm. Furthermore, the incorporation of the DHSB aims to enhance the thermal- and photo-stability of the guest dye molecule, for example, the less color change after accelerated thermal- and photo-aging test.

Wang, Qian; Feng, Yongjun; Feng, Junting; Li, Dianqing

2011-06-01

92

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

Microsoft Academic Search

Nanocontainer and nanofiller aspects of layered double hydroxides (LDH)\\u000a were combined to prepare porphyrin-LDH\\/polymer composites for\\u000a photoactive coatings. The suggested properties are derived from\\u000a cytotoxicity of singlet oxygen, O(2)((1)Delta(g)), produced by\\u000a interaction of molecular oxygen with excited porphyrin molecules located\\u000a within the interlayer space of Zn(R)Al and Mg(R)Al LDH. Porphyrins,\\u000a Pd(II)-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin (PdTPPC) and\\u000a 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) photoproducing\\u000a O(2)((1)Delta(g)), were

Eva Kafunkova; Kamil Lang; Pavel Kubat; Mariana Klementova; Jiri Mosinger; Miroslav Slouf; Anne-Lise Troutier-Thuilliez; Fabrice Leroux; Vincent Verney; Christine Taviot-Gueho

2010-01-01

93

In vivo anticancer activity of methotrexate-loaded layered double hydroxide nanoparticles.  

PubMed

A methotrexate (MTX)-loaded layered double hydroxide (LDH) nanoparticle system was synthesized by intercalating MTX into the interlayer spaces of LDH. In vivo pharmacokinetic study demonstrated that the MTX-LDH hybrid had similar kinetic behaviors as free MTX, showing a rapid decline in the plasma MTX level, with characteristics of a biexponential function. However, the hybrid system remarkably suppressed tumor growth in human osteosarcoma-bearing mice compared to an equivalent amount of free MTX. Using MTX-LDH nanoparticles, a significantly high amount of MTX was delivered to target tumor tissue, whereas a low level was found in normal tissues. Moreover, LDH nanocarriers did not accumulate in any specific tissue nor cause acute toxicity up to the applied dose for the hybrid system. These results suggest that the MTX-LDH nanohybrid system has great potential as an anti-cancer drug with enhanced in vivo anti-tumor activity and bioavailability in target tumor tissue along with reduced side effects. PMID:23489199

Choi, Soo-Jin; Oh, Jae-Min; Chung, Hae-Eun; Hong, Seung-Hee; Kim, In-Hoo; Choy, Jin-Ho

2013-03-12

94

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

95

Low temperature steam reforming of methanol over layered double hydroxide-derived catalysts.  

SciTech Connect

The catalytic production of hydrogen by steam reforming of methanol (SRM) has been carried out over Mg/Al, Cu/Al, Co/Al, and Ni/Al layered double hydroxides (LDHs). The catalytic reactions were performed at temperatures of 150-400 C and atmospheric pressure. The most efficient catalyst was the Cu/Al LDH, which became active at {approx}230 C, with concomitant H{sub 2} production. The Ni/Al and Co/Al LDHs were also active in SRM, however, the activation temperature was significantly higher (315-320 C). No catalytic activity was observed for the Mg/Al LDH. Significant LDH decomposition occurred during the catalytic reactions. The reducibility of the divalent cations present in the LDH was a crucial parameter in determining the steam reforming activity of the catalysts. Pre-activation of the Cu/Al LDH by calcination in air (400 C), followed by reduction in dilute H2, did not significantly change the catalytic activity. The onset of H2 production was slightly lower for the pre-activated versus as-prepared Cu/Al LDH ({approx}218 C), also the CH{sub 3}OH conversion was 5-10% lower.

Segal, S. R.; Anderson, K. B.; Carrado, K. A.; Marshall, C. L.

2002-05-10

96

Preparation and antibacterial activity of lysozyme and layered double hydroxide nanocomposites.  

PubMed

It is necessary to develop "green" disinfection technology which does not produce disinfection by-products. Lysozyme-layered double hydroxide nanocomposites (LYZ-LDHs) were prepared by intercalating LYZ in LDH for the first time. Their antibacterial activity was evaluated using staphylococcus aureus as a target. The bacteria removal mechanism was also studied. Characterization of LYZ-LDHs by X-ray diffraction and Fourier transform infrared spectroscopy indicated that LYZ was successfully intercalated in LDH, compressed and deformed without secondary structural change. LYZ-LDHs showed excellent bactericidal effectiveness against staphylococcus aureus. The antibacterial performance of LYZ-LDHs was found to be affected by the LYZ/LDH ratio and the pH of the bacteria-containing water. The bacteria removal efficiency of LYZ-LDHs with LYZ/LDH mass ratio of 0.8 was consistently above 94% over the pH range of 3-9. LYZ-LDHs adsorbed bacteria to their surface by LDH and then killed them by the immobilized LYZ. This new material integrated the bactericidal ability of LYZ and adsorption ability of LDH. Moreover, the antibacterial ability of LYZ-LDHs was persistent and not limited by the adsorption capacity. PMID:24053938

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

2013-09-11

97

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

2013-01-28

98

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

SciTech Connect

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

Sasaki, Satoru [Department of Material Science, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Aisawa, Sumio [Department of Material Science, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Hirahara, Hidetoshi [Department of Material Science, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Sasaki, Akira [Department of Sanitary Science, Research Institute for Environmental Sciences and Public Health of Iwate Prefecture, 1-36-1 Iiokashinden, Morioka 020-0852 (Japan); Nakayama, Hirokazu [Department of Functional Molecular Chemistry, Kobe Pharmaceutical University, 4-19-1 Motoyamakitamachi, Higashinada-ku, Kobe 658-8558 (Japan); Narita, Eiichi [Department of Material Science, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan)]. E-mail: enarita@iwate-u.ac.jp

2006-04-15

99

Grafting Interlayer MoO42- in Mg/Al Layered Double Hydroxide by Thermal Treatment Below Collapsing the Layered Structure  

NASA Astrophysics Data System (ADS)

Some kinds of Mg/Al layered double hydroxide (LDH) with oxometalate have been prepared by mean of anion exchange. Products were characterized by powder X-ray diffraction (XRD), chemical analysis and Thermogravimetry - Differential Thermal Analysis (TG-DTA). Results showed that the basal spacing of heated LDH decreased with heating to 300 °C. This revealed the decrease of interlayer spacing and the interlayer anion being grafted to the layer of LDH because the decreased interlayer spacing of the heated LDH was smaller than the size of the interlayer anion.

Muranishi, Kennichi; Shimamura, Akihiro; Kurashina, Masashi; Kanezaki, Eiji

100

Surface-charging behavior of Zn–Cr layered double hydroxide  

Microsoft Academic Search

A Zn–Cr layered double hydroxide (LDH) having the formula Zn2Cr(OH)6Cl0.7(CO3)0.15?2.1H2O 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

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

2004-01-01

101

Direct observation of grafting interlayer phosphate in Mg/Al layered double hydroxides  

SciTech Connect

The grafting of interlayer phosphate in synthetic Mg/Al layered double hydroxides with interlayer hydrogen phosphate (LDH-HPO{sub 4}) has been studied by XRD, TG/DTA, FT-IR, XPS and XANES. The basal spacing of crystalline LDH-HPO{sub 4} decreases in two stages with increasing temperature, from 1.06 nm to 0.82 nm at 333 K in the first transition, and to 0.722 nm at 453 K in the second. The first stage occurs due to the loss of interlayer water and rearrangement of the interlayer HPO{sub 4}{sup 2-}. In the second transition, the interlayer phosphate is grafted to the layer by the formation of direct bonding to metal cations in the layer, accompanied by a change in polytype of the crystalline structure. The grafted phosphate becomes immobilized and cannot be removed by anion-exchange with 1-octanesulfonate. The LDH is amorphous at 743 K but decomposes to Mg{sub 3}(PO{sub 4}){sub 2}, AlPO{sub 4}, MgO and MgAl{sub 2}O{sub 4} after heated to 1273 K. - Graphical abstract: The cross section of the synthetic Mg, Al layered double hydroxides in Phase 1, with interlayer hydrogen phosphate Phase 2, and with grafted phosphate, Phase 3. Highlights: Black-Right-Pointing-Pointer The grafting of hydrogen phosphate intercalated Mg/Al-LDH has been studied. Black-Right-Pointing-Pointer The basal spacing of crystalline LDH-HPO{sub 4} decreases in two stages with increasing temperature. Black-Right-Pointing-Pointer The first decrease is due to loss of interlayer water, the second is attributed to phosphate grafting. Black-Right-Pointing-Pointer The grafted interlayer phosphate becomes immobilized and cannot be removed by anion-exchange.

Shimamura, Akihiro [School of Chemical Sciences, University of Auckland 23 Symonds St, 1142 Auckland (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand); Kanezaki, Eiji, E-mail: kanezaki@chem.tokushima-u.ac.jp [Department of Chemical Science and Technology, Graduate School of Advanced Technology and Science, University of Tokushima, 2-1 Minamijosanjima, Tokushima 770-8506 (Japan); Jones, Mark I. [Department of Chemical and Material Engineering, University of Auckland, 20 Symonds St, 1142 Auckland (New Zealand); Metson, James B. [School of Chemical Sciences, University of Auckland 23 Symonds St, 1142 Auckland (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand)

2012-02-15

102

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

NASA Astrophysics Data System (ADS)

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.

Nedim Ay, Ahmet; Konuk, Deniz; Zümreoglu-Karan, Birgul

2011-12-01

103

Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate  

NASA Astrophysics Data System (ADS)

The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO3- compound and its H2PO4--intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO42- caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO42- and H2PO4-. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

2011-01-01

104

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

105

Competition between three organic anions during regeneration process of calcined LDH  

Microsoft Academic Search

The calcination of Layered Double Hydroxides (LDH) produces mixed oxides which can undergo rehydration when in contact with aqueous solution containing anions, regenerating the layered structure of LDH, with these anions in the interlayer space. This process is known as ‘memory effect’. In this work we studied the regeneration of LDH, by sorption of organic anions as terephthalate (TA), benzoate

Lucelena Patricio Cardoso; João Barros Valim

2004-01-01

106

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

107

Synthesis and selective IR absorption properties of iminodiacetic-acid intercalated MgAl-layered double hydroxide  

SciTech Connect

An MgAl-NO{sub 3}-layered double hydroxide (LDH) precursor has been prepared by a method involving separate nucleation and aging steps (SNAS). Reaction with iminodiacetic acid (IDA) under weakly acidic conditions led to the replacement of the interlayer nitrate anions by iminodiacetic acid anions. The product was characterized by XRD, FT-IR, TG-DTA, ICP, elemental analysis and SEM. The results show that the original interlayer nitrate anions of LDHs precursor were replaced by iminodiacetic acid anions and that the resulting intercalation product MgAl-IDA-LDH has an ordered crystalline structure. MgAl-IDA-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-IDA-LDH showed a higher mid to far infrared absorption than films filled with MgAl-CO{sub 3}-LDH in the 7-25 {mu}m range, particularly in the key 9-11 {mu}m range required for application in agricultural plastic films. - Graphical abstract: Intercalation of iminodiacetic acid (IDA) anions in a MgAl-NO{sub 3}-layered double hydroxide host leads to an enhancement of its infrared absorbing ability for application in agricultural plastic films.

Wang Lijing; Xu Xiangyu; Evans, David G.; Duan Xue [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, College of Science, Number 15 , Beisanhuandonglu, Box 98, Beijing 100029 (China); Li Dianqing, E-mail: lidq@mail.buct.edu.c [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, College of Science, Number 15 , Beisanhuandonglu, Box 98, Beijing 100029 (China)

2010-05-15

108

Intercalation of Vitamer into LDH and Their Controlled Release Properties  

Microsoft Academic Search

Biofunctional nanohybrids are synthesized from layered double hydroxide (LDH) and the vitamins such as ascorbic acid and topopherol acid succinate. Either ion exchange or copricipitaion leads to successful intercalation of the vitamins into gallery space of LDH that offers a new route to safe preservation of bioactivity as well as controlled release. Intercal ations of vitamins are cl early reflected

Jin-Ho Choy; You-Hwan Son

109

Platelets to rings: Influence of sodium dodecyl sulfate on Zn-Al layered double hydroxide morphology  

NASA Astrophysics Data System (ADS)

In the current study, influence of sodium dodecyl sulfate (SDS) on the crystallization of Zn-Al layered double hydroxide (LDH) was investigated. Depending on the SDS concentration coral-like and for the first time ring-like morphologies were obtained in a urea-hydrolysis method. It was revealed that the surfactant level in the starting solution plays an important role in the morphology. Concentration of surfactant equal to or above the anion exchange capacity of the LDH is influential in creating different morphologies. Another important parameter was the critical micelle concentration (CMC) of the surfactant. Surfactant concentrations well above CMC value resulted in ring-like structures. The crystallization mechanism was discussed.

Yilmaz, Ceren; Unal, Ugur; Yagci Acar, Havva

2012-03-01

110

Mechano-hydrothermal synthesis of Mg2Al-NO3 layered double hydroxides  

NASA Astrophysics Data System (ADS)

A mechano-hydrothermal method was developed to synthesize Mg2Al-NO3 layered double hydroxide (LDH) from MgO, Al2O3 and NaNO3 as starting materials. A two-step synthesis was conducted, that is, a mixture of MgO and Al2O3 was milled for 1 h, followed by hydrothermal treatment with NaNO3 solution. The resulting LDHs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared and elemental analyses. Pre-milling played a key role in the LDH formation during subsequent hydrothermal treatment. The process is advantageous in terms of low reaction temperature and short reaction time compared with the conventional hydrothermal method, and the target products are of high crystallinity, good dispersion and regular shape compared with the conventional mechanochemical method.

Zhang, Fengrong; Du, Na; Song, Shue; Liu, Jianqiang; Hou, Wanguo

2013-10-01

111

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

112

Controlled release of a plant growth regulator, ?-naphthaleneacetate from the lamella of Zn–Al-layered double hydroxide nanocomposite  

Microsoft Academic Search

Formation of the so-called organic–inorganic nanohybrid material was exploited for the preparation of a controlled release formulation. The inorganic Zn–Al-layered double hydroxide (LDH) was used as a matrix, hosting an active agent or a guest, ?-naphthaleneacetate (NAA), a plant growth regulator by self-assembly technique. The reverse process, i.e., the deintercalation or release of the guest, NAA was found to be

Mohd Zobir bin Hussein; Zulkarnain Zainal; Asmah Hj Yahaya; Dickens Wong Vui Foo

2002-01-01

113

Electrocatalytic oxidation of methanol at Ni–Al layered double hydroxide film modified electrode in alkaline medium  

Microsoft Academic Search

Ni–Al–NO3 layered double hydroxides (LDH) are electrodeposited on the glassy carbon (GC) electrodes and the electrocatalytic activities of the modified electrodes toward methanol oxidation are studied in detail by cyclic voltammetry and chronoamperometry. Various factors affecting the electro-oxidation of methanol are investigated for optimizing the electrocatalytic properties and making the mechanism clearly such as methanol concentration, scan rate, KOH concentration,

Yinling Wang; Dandan Zhang; Wei Peng; Lin Liu; Maoguo Li

2011-01-01

114

Layered double hydroxide\\/eggshell membrane: An inorganic biocomposite membrane as an efficient adsorbent for Cr(VI) removal  

Microsoft Academic Search

Hexavalent chromium, Cr(VI), is carcinogenic and mutagenic to the living organisms, and hence more hazardous than other heavy metals. The choice of Cr(VI) removal adsorbents has always been a hot issue in environmental protection. Here we report a novel inorganic biocomposite membrane, layered double hydroxide\\/eggshell membrane (LDH\\/ESM) as adsorbent for Cr(VI) removal, in which ESM serves as the substrate and

Xiaoxiao Guo; Fazhi Zhang; Qing Peng; Sailong Xu; Xiaodong Lei; David G. Evans; Xue Duan

2011-01-01

115

In vitro and in vivo behavior of ketoprofen intercalated into layered double hydroxides.  

PubMed

Ketoprofen (Ket) was intercalated into layered double hydroxides (ZnAlLDH and MgAlLDH) using the ionic exchange method. The drug intercalation was confirmed by X-ray diffraction (XRD) and FTIR spectroscopy. Ket release from the inorganic matrix was studied at pH 7.4 in continuous regime with a flow rate of 0.5 and respectively 1.0 ml/min. The kinetical data were interpreted using the Ritger and Peppas model. The data prove that the release kinetics and mechanism depend on the eluent flow rate. Quantification of gastric tolerance shows that the ulcerogenic effect of the intercalated drug is lower than the one of the raw Ket. The antinociceptive effect of both formulations was studied by the hot-plate method performed on mice. The MgAlLDH_Ket formulation shows a tendency towards a stronger antinociceptive effect than its ZnAlLDH_Ket counterpart during the 210 min recorded period. PMID:20820886

Silion, Mihaela; Hritcu, Doina; Jaba, Irina M; Tamba, Bogdan; Ionescu, Dunarea; Mungiu, Ostin C; Popa, Ionel Marcel

2010-09-05

116

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

117

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

118

Controlling of the morphology of Co–Ti LDH  

Microsoft Academic Search

It is known that Mg–Al layer double hydroxide (Mg–Al LDH) possesses plate-like morphology if carefully crystallized. This work focuses on the preparation of Co–Ti LDH having fibrous morphology or mixture of plate-like and fibrous morphologies. The Co–Ti LDH obtained by precipitation for relatively short aging time showed plate-like morphology. By increasing aging time, the plate-like morphology was transformed into fibrous

O. Saber; B. Hatano; H. Tagaya

2005-01-01

119

Synergistic effect of organically modified layered double hydroxide on thermal and flame-retardant properties of poly(butyl acrylate–vinyl acetate)  

Microsoft Academic Search

Organically modified layered double hydroxide (O-LDH) was successfully synthesized by coprecipitation and characterized through\\u000a Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). O-LDH\\/poly(butyl acrylate–vinyl acetate) (P(BA-VAc)\\u000a emulsion was prepared via in situ polymerization, then ammonium polyphosphate (APP) was introduced to obtain the O-LDH\\/APP\\/P(BA-VAc)\\u000a flame-retardant latex. The flame retardancy and thermal behavior of the latexes after evaporation of water were

Chunxia Zhao; Gang Peng; Bailing Liu; Zhengwu Jiang

120

Controlled release compound based on metanilate-layered double hydroxide nanohybrid.  

PubMed

Metanilate-layered double hydroxide nanohybrid compound was synthesized for controlled release purposes through co-precipitation method of the metal cations and organic anion. The effect of various divalent metal cations (M2+), namely Zn2+, Mg2+ and Ca2+ on the formation of metanilate-LDH nanohybrids, in which metanilate anion was intercalated into three different layered double hydroxide (LDH) systems; Zn-Al, Mg-Al and Ca-Al were investigated. The syntheses were carried out with M2+ to Al3+ initial molar ratio, R of 4. The pH of the mother liquor was maintained at pH 7.5 and 10 during the synthesis, and the resulting mixture was aged at around 70 degrees C for about 18 h. The intercalation of metanilate anion into the host was found to be strongly influenced by the M2+ that formed the inorganic metal hydroxide layers. Under our experimental condition, the formation of the nanohybrid materials was found to be more feasible for the Zn-Al than for the other two systems, in which the former showed well-ordered layered organic-inorganic nanohybrid structure with good crystallinity. Intercalation is confirmed by the expansion of the interlayer spacing to about 15-17 A when metanilate was introduced into the interlamellae of Zn-Al LDHs. In addition, CHNS and FTIR analyses also support that metanilate anion has been successfully intercalated into the interlamellae of the inorganic LDH. Apart from M2+, this study also shows that the initial pH of the mother liquor plays an important role in determining the physicochemical properties of the resulting nanohybrids, especially the mole fraction of the Zn2+ substituted by the Al3+ ion in the LDH inorganic sheets which in turn controlled the loading percentage of the organic anion, surface properties and the true density. Preliminary study shows that LDH can be used to host beneficial guests, active agent with controlled release capability of the guests. Generally the overall process is governed by pseudo second order kinetic but for the first 180 min, the release process can be slightly better described by parabolic diffusion than the other models. PMID:19198327

Hussein, Mohd Zobir; Nasir, Norashikin Mat; Yahaya, Asmah Hj

2008-11-01

121

Synthesis and release behavior of composites of camptothecin and layered double hydroxide  

SciTech Connect

A simple method, reconstruction of calcinated layered double hydroxides (CLDH) in an organic (ethanol)-water mixed solvent medium containing drug, was developed to intercalate partially a non-ionic and poorly water-soluble drug (camptothecin) into the gallery of layered double hydroxides (LDHs) to form the drug-LDH composites. The purpose of choosing organic-water mixed solvent is to increase remarkably the solubility of camptothecin (CPT) in the reconstruction medium. A probable morphology of CPT molecules in the gallery of LDHs is that CPT molecules arrange as monolayer with the long axis parallel to the LDH layers. The in vitro drug release from the composites was remarkably lower than that from the corresponding physical mixture, which shows these drug-inorganic composites can be used as a potential drug delivery system. - Graphical abstract: A simple method, reconstruction of calcinated LDHs in an organic-water medium containing drug, was developed to intercalate non-ionic and poorly water-soluble camptothecin into the gallery of LDHs.

Dong Lun [School of Medicine, Shandong University, Jinan 250100 (China); Yan Li [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China); Hou Wanguo, E-mail: wghou@sdu.edu.c [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); Liu Shaojie [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China)

2010-08-15

122

Synthesis of partially exfoliated EPDM\\/LDH nanocomposites by solution intercalation: Structural characterization and properties  

Microsoft Academic Search

Partially exfoliated ethylene propylene diene terpolymer (EPDM)\\/Mg–Al layered double hydroxide (LDH) nanocomposites have been synthesized by solution intercalation using organically modified LDH (DS-LDH) as nanofiller obtained by reconstruction method using sodium dodecyl sulfate and LDH. The nanocomposite structure has been elucidated by the X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and

H. Acharya; S. K. Srivastava; Anil K. Bhowmick

2007-01-01

123

Hierarchical structures based on functionalized magnetic cores and layered double-hydroxide shells: concept, controlled synthesis, and applications.  

PubMed

The combination of magnetic particles and layered double hydroxide (LDHs) materials leads to the formation of hierarchical composites that can take full advantages of each component; this is an effective approach for achieving multifunctional materials with intriguing properties. This Concept article summarizes several important strategies for the fabrication of magnetic-core/LDH-shell hierarchical nanocomposites, including direct coprecipitation, layer-by-layer assembly, and in situ growth methods. The obtained nanocomposites exhibit excellent performance as multifunctional materials for promising applications in targeted drug delivery, efficient separation, and catalysis. The fabrication and application of magnetic-core/LDH-shell nanocomposite materials represent a new direction in the development of LDH-based multifunctional materials, which will contribute to the progress of chemistry and material science. PMID:23424036

Shao, Mingfei; Wei, Min; Evans, David G; Duan, Xue

2013-02-19

124

Electrochemistry and electrocatalysis of myoglobin intercalated in Mg2Al-Cl layered double hydroxide and ionic liquid composite material.  

PubMed

A novel biocompatible nanocomposite prepared by Mg(2)Al-Cl layered double hydroxide (LDH) and ionic liquid (IL) 1-carboxyl-methyl-3-methylimidazolium tetrafluoroborate was used as the matrix for the immobilization of myoglobin (Mb). The IL-LDH-Mb composite was characterized by UV-vis adsorption spectroscopy and the results indicated that Mb retained its native structure in the IL-LDH nanocomposite. The IL-LDH-Mb bionanocomposite was modified on the surface of carbon ionic liquid electrode to get an Mb modified electrode. Electrochemical experiments showed that direct electrochemistry of Mb in the composite was realized with a pair of well-defined redox peaks appeared, which could be attributed to the specific microenvironment provided by layer structured LDH and high ionic conductive IL present for Mb molecule. The modified electrode exhibited good direct electrocatalytic ability to the reduction of trichloroacetic acid and hydrogen peroxide with good stability and reproducibility. Different kinds of real samples were detected by the modified electrode with satisfactory results. So the IL-LDH nanocomposite provided a novel and efficient platform for the immobilization of enzymes, which had potential applications in the fabrication of third-generation biosensors. PMID:22608434

Zhan, Tianrong; Guo, Yaqing; Xu, Li; Zhang, Weili; Sun, Wei; Hou, Wanguo

2012-03-12

125

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

SciTech Connect

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{sup -}, Lis{sup -} (arranged with monolayer, resulted from X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR) analysis was enhanced much more than Cap{sup -} and Ram{sup -} (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{sup -}, Lis{sup -} were much longer compared with Cap{sup -}, Ram{sup -} 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. - Graphical abstract: A series of antihypertensive drugs including Enalpril, Lisinopril, Captopril and Ramipril were intercalated into Zn/Al-NO{sub 3}-LDHs successfully by coprecipitation or ion-exchange technique. We focus on the structure, thermal property and low/controlled release property of as-synthesized drug-LDH composite intended for the possibility of applying these LDH-antihypertensive nanohybrids in drug delivery and controlled release systems.

Xia Shengjie [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China); Ni Zheming [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)], E-mail: jchx@zjut.edu.cn; Xu Qian; Hu Baoxiang; Hu Jun [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)

2008-10-15

126

Compositional and Structural Control on Anion Sorption Capability of Layered Double Hydroxides (LDHS)  

SciTech Connect

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. A large set of LDH materials have been synthesized with various combinations of metal cations, interlayer anions, and the molar ratios of divalent cation M(II) to trivalent cation M(III). The synthesized materials have then been tested systematically for their sorption capabilities for pertechnetate (TcO{sub 4}{sup -}). It is discovered that for a given interlayer anion (either CO{sub 3}{sup 2-} or NO{sub 3}{sup -}) the Ni-Al LDH with a Ni/Al ratio of 3:1 exhibits the highest sorption capability among all the materials tested. The distribution coefficient (K{sub d}) is determined to be as high as 307 mL/g for Ni{sub 6}Al{sub 2}(0H){sub 16}CO{sub 3}nH{sub 2}O and 1390 mL/g for Ni{sub 6}Al{sub 2}(OH){sub 16}NO{sub 3}nH{sub 2}O at a pH of 8. The sorption of TcO{sub 4}{sup -} on M(II)-M(III)-CO{sub 3} LDHs is dominated by the edge sites of LDH layers and strongly correlated with the basal spacing d{sub 003} of the materials, which increases with the decreasing radii of both divalent and trivalent cations. The sorption reaches its maximum when the layer spacing is just large enough for a pertechnetate anion to fit into a cage space between two neighboring octahedra of metal hydroxides at the edge. Furthermore, the sorption is found to increase with the crystallinity of the materials. For a given combination of metal cations and an interlayer anion, a best crystalline LDH material is obtained generally with a M(II)/M(III) ratio of 3:1. Replacement of interlayer carbonate with readily exchangeable nitrate greatly increases the sorption capability of a LDH material for pertechnetate, due to the enhanced adsorption on edge sites and the possible contribution from interlayer anion exchanges. The work reported here will help to establish a general structure-property relationship for the related layered materials.

Y. Wang; H. Gao

2006-03-16

127

Aluminium substitution in iron(II III)-layered double hydroxides: Formation and cationic order  

NASA Astrophysics Data System (ADS)

The formation and the modifications of the structural properties of an aluminium-substituted iron(II III)-layered double hydroxide (LDH) of formula Fe4IIFe(2-6y)IIIAl6yIII (OH)12 SO4, 8H2O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO42-), i.e. y=0, in which a bilayer of sulphate anions points to the Fe3+ species. A cationic order is proposed to occur in both GR(SO42-) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO42-) is preceded by the successive precipitation of FeIII and AlIII (oxy)hydroxides. Adsorption of more soluble AlIII species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y˜0.01) could be an interesting way for increasing the surface reactivity of iron(II III) LDH that maintains constant the quantity of the reactive FeII species of the material.

Ruby, Christian; Abdelmoula, Mustapha; Aissa, Rabha; Medjahdi, Ghouti; Brunelli, Michela; François, Michel

2008-09-01

128

Direct observation of grafting interlayer phosphate in Mg/Al layered double hydroxides  

NASA Astrophysics Data System (ADS)

The grafting of interlayer phosphate in synthetic Mg/Al layered double hydroxides with interlayer hydrogen phosphate (LDH-HPO4) has been studied by XRD, TG/DTA, FT-IR, XPS and XANES. The basal spacing of crystalline LDH-HPO4 decreases in two stages with increasing temperature, from 1.06 nm to 0.82 nm at 333 K in the first transition, and to 0.722 nm at 453 K in the second. The first stage occurs due to the loss of interlayer water and rearrangement of the interlayer HPO42-. In the second transition, the interlayer phosphate is grafted to the layer by the formation of direct bonding to metal cations in the layer, accompanied by a change in polytype of the crystalline structure. The grafted phosphate becomes immobilized and cannot be removed by anion-exchange with 1-octanesulfonate. The LDH is amorphous at 743 K but decomposes to Mg3(PO4)2, AlPO4, MgO and MgAl2O4 after heated to 1273 K.

Shimamura, Akihiro; Kanezaki, Eiji; Jones, Mark I.; Metson, James B.

2012-02-01

129

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

2013-07-01

130

Anionic surfactant enhanced phosphate desorption from Mg/Al-layered double hydroxides by micelle formation.  

PubMed

Desorption of interlayer hydrogen phosphate (HPO4) from hydrogen phosphate intercalated Mg/Al-layered double hydroxide (LDH-HPO4) by anion exchange with surfactant anions has been investigated under controlled conditions. Three types of surfactant, Dodecylbenzenesulphonate (DBS), Dodecylsulphate (DS) and 1-Octanesulphonate (OS), anions were used for intercalation experiments over a range of concentrations, and for all solutions, it was shown that the desorption of hydrogen phosphate is enhanced at concentrations close to the critical micelle concentration (CMC). Intercalation of the surfactant anions into LDH-HPO4 was confirmed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning electron microscopy (SEM). More than 90% removal of the hydrogen phosphate was achieved at CMC. Repeat adsorption tests to investigate recyclability showed that desorption with 0.005M DBS improved subsequent phosphate re-adsorption, allowing around 90% of the original adsorption over three cycles. This is much higher than when desorption was conducted using either Na2CO3 or NaCl-NaOH solutions, even at much higher concentrations. This study suggests potential economic and environmental advantages in using these surfactants in improving the cycling performance of LDH materials as absorbents for clean-up of water systems. PMID:24112833

Shimamura, Akihiro; Jones, Mark I; Metson, James B

2013-09-07

131

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

132

Synthesis and characterization of metal (Core) - layered double hydroxide (Shell) nanostructures  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDH) which belong to a class of inorganic ceramic layered materials have been studied since the mid-19th century for a variety of applications including catalysis, anion exchange, adsorbents and antacid, but more recently as a potential drug and gene delivery platform. Drug delivery platforms based on nano-sized geometries are nanovectors which promise a revolutionary impact on the therapy and imaging of various types of cancers and diseases. To date, various polymeric platforms have been the focus of intense research, but the development of inorganic, bio-hybrid nanoparticles for therapeutics and molecular imaging are at a stage of infancy. The hybridization of LDH with bioactive agents or the fabrication of metal (Core)---LDH (Shell) nanostructures could have many beneficial effects including multimodality, active targetability, and efficacy. For example, Core---Shell nanostructures may be designed to have a high scattering optical cross-section for imaging, but may also be tailored to strongly absorb near infrared (NIR) light for hyperthermic ablation. The central theme of this thesis was to demonstrate proof-of-concept of spherical silver and gold metal (Core)---LDH (Shell) nanostructures that have uniform size distribution and are agglomeration free. The effects of processing parameters on the characteristics of LDH as well as LDH-coated spherical metal (Ag, Au) nanoparticles have been evaluated using X-ray Diffraction, Dynamic Light Scattering, Scanning Electron Microscopy, Transmission Electron Microscopy, Rutherford Backscattering Spectrometry, and Inductively Coupled Plasma Emission Spectrometry to arrive at appropriate process windows. The core---shell nanostructures were also characterized for their optical properties in the ultra---violet---visible region, and the data were compared with simulated data, computed by using a quasi static model from Mie scattering theory. Moreover, in order to achieve a strong plasmon resonance band in the NIR region, silver nanorods were synthesized to demonstrate the precise control of the plasmon resonance behavior through aspect ratio adjustments. Consequently, it is proposed that LDH-coated metal nanorods must be the primary platform for a potential multimodel nanovector.

Noh, Woo C.

133

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 25h 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

2013-09-06

134

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

2012-12-28

135

Composition Driven Monolayer to Bilayer Transformation in a Surfactant Intercalated Mg-Al Layered Double Hydroxide.  

PubMed

The structure and organization of dodecyl sulfate (DDS) surfactant chains intercalated in an Mg-Al layered double hydroxide (LDH), Mg((1-x))Al(x)(OH)(2), with differing Al/Mg ratios has been investigated. The Mg-Al LDHs can be prepared over a range of compositions with x varying from 0.167 to 0.37 and therefore provides a simple system to study how the organization of the alkyl chains of the intercalated DDS anions change with packing density; the Al/Mg ratio or x providing a convenient handle to do so. Powder X-ray diffraction measurements showed that at high packing densities (x ? 0.3) the alkyl chains of the intercalated dodecyl sulfate ions are anchored on opposing LDH sheets and arranged as bilayers with an interlayer spacing of ?27 Å. At lower packing densities (x < 0.2) the surfactant chains form a monolayer with the alkyl chains oriented flat in the galleries with an interlayer spacing of ?8 Å. For the in between compositions, 0.2 ? x < 0.3, the material is biphasic. MD simulations were performed to understand how the anchoring density of the intercalated surfactant chains in the Mg-Al LDH-DDS affects the organization of the chains and the interlayer spacing. The simulations are able to reproduce the composition driven monolayer to bilayer transformation in the arrangement of the intercalated surfactant chains and in addition provide insights into the factors that decide the arrangement of the surfactant chains in the two situations. In the bilayer arrangement, it is the dispersive van der Waals interactions between chains in opposing layers of the anchored bilayer that is responsible for the cohesive energy of the solid whereas at lower packing densities, where a monolayer arrangement is favored, Coulomb interactions between the positively charged Mg-Al LDH sheets and the negatively charged headgroup of the DDS anion dominate. PMID:21319770

Naik, Vikrant V; Chalasani, Rajesh; Vasudevan, S

2011-02-14

136

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

137

Anion capture with calcium, aluminium and iron containing layered double hydroxides  

NASA Astrophysics Data System (ADS)

The competitive adsorption of nitrate, chloride and carbonate in layered double hydroxides (LHD) with the general formula Ca(1-x)2+Al(1-y)3+,Fe(y)3+x(OH)2xNO3-·nHO was investigated. Both normal ion exchange by exposure to a solution containing different anions, as well as addition of calcined material to solution thereby exploiting the memory effect of LDHs was studied. Changes in the interlayer anion changed the interlayer spacing of the LDH. The order of preference of intercalation was Cl?CO32->NO3-. When multiple anions were present in the exchange solution, LDHs with several distinct interlayer spacing were produced indicating that LDHs with different anions in the interlayer existed at the same time. However for extended exchange times (14 days) where high concentrations of carbonate anion were present, the layered structure was destroyed resulting in the formation of calcite, CaCO3.

Phillips, J. D.; Vandeperre, L. J.

2011-09-01

138

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

139

Thermal behavior of the hydrotalcite-like layered structure of Mg and Al-layered double hydroxides with interlayer carbonate by means of in situ powder HTXRD and DTA\\/TG  

Microsoft Academic Search

High temperature powder X-ray diffraction (HTXRD) patterns of Mg\\/Al-layered double hydroxides (LDH) with interlayer carbonate (Mg\\/Al\\/CO3-LDH) indicate that a solid phase having a hydrotalcite-like layered structure (Phase I) is not stable when the temperature of solid samples is elevated. Another phase (Phase II) grows eminently and simultaneously with the degradation of Phase I. Phase II has smaller basal spacing than

Eiji Kanezaki

1998-01-01

140

Structure and photoluminescence of Mg-Al-Eu ternary hydrotalcite-like layered double hydroxides  

SciTech Connect

A series of Mg-Al-Eu ternary hydrotalcite-like layered double hydroxides (LDHs), with Eu/Al atomic ratios of {approx}0.06 and Mg/(Al+Eu) atomic ratios ranging from 1.3 to 4.0, were synthesized by a coprecipitation method. The Mg-Al-Eu ternary LDHs were investigated by various techniques. X-ray diffraction (XRD) results indicated that the crystallinity of the ternary LDHs was gradually improved with the increase of Mg{sup 2+}/(Al{sup 3+}+Eu{sup 3+}) molar ratio from 1.3/1 to 4/1, and all the samples were a single phase corresponding to LDH. The photoluminescent (PL) spectra of the ternary Mg-Al-Eu LDHs were described by the well-known {sup 5}D{sub 0}-{sup 7}F{sub J} transition (J=1, 2, 3, 4) of Eu{sup 3+} ions with the strongest emission for J=2, suggesting that the host LDH was favorable to the emissions of Eu{sup 3+} ions. The asymmetry parameter (R) relevant to {sup 5}D{sub 0}-{sup 7}F{sub J} transition (J=1, 2) dependant of the atomic ratios of Mg{sup 2+}/(Al{sup 3+}+Eu{sup 3+}) was discussed, and was consistent with the result of XRD. - Graphical abstract: A series of Mg-Al-Eu ternary hydrotalcite-like layered double hydroxides (LDHs), with Mg/(Al+Eu) atomic ratios ranging from 1.3/1, 2/1 3/1 to 4/1, were synthesized by a coprecipitation method. The photoluminescent spectra of the Mg-Al-Eu ternary LDHs are described by the well-known {sup 5}D{sub 0}-{sup 7}F{sub J} transition (J=1, 2, 3, 4) of Eu{sup 3+} ions with the strongest emission for J=2.

Chen Yufeng, E-mail: yfchen@ncu.edu.c [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Li Fei; Zhou Songhua; Wei Junchao; Dai Yanfeng [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Chen Yiwang, E-mail: ywchen@ncu.edu.c [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Institute of Polymers, Nanchang University, Nanchang 330031 (China)

2010-09-15

141

Photochemistry in constrained spaces: Zeolites and layered double metal hydroxides. Progress report, August 1, 1992--September 15, 1993  

SciTech Connect

The authors have continued their research in the field of preparation and reactions of photochemical systems in zeolites and layered lithium aluminates. The study on zeolite focused on faujasitic zeolites. The experimental strategy is to build Ru(bpy){sub 3}{sup 2+} inside the supercage and examine the photoelectron transfer from this entrapped complex to acceptor molecules (viologens) through the ring openings. The effort on layered lithium aluminum double hydroxides (LDH) of composition LiAl{sub 2}(OH){sub 6}{sup +}X{sup {minus}} has been on incorporation of photoactive molecules in these interlayers, with particular emphasis on pyrene and Zn porphyrins.

Dutta, P.K.

1993-12-31

142

Influence of high-pressure processing on the structure and memory effect of synthetic layered double hydroxides  

Microsoft Academic Search

We investigate the structural evolution of synthetic layered double hydroxides (LDH) samples, processed at room temperature\\u000a and high-pressure (up to 7.7 GPa) in a toroidal chamber with two pressure-transmitting media, lead and graphite, using X-ray\\u000a diffraction, thermogravimetry and N2-adsorption isotherms techniques. The X-ray patterns of compacted samples show a decrease in the peak intensities. For both\\u000a pressure-transmitting media, our samples revealed

Jaqueline C. Rodrigues; Tania Maria Haas Costa; Márcia R. Gallas; Celso C. Moro

2009-01-01

143

Improvement of the capacitive performances for Co-Al layered double hydroxide by adding hexacyanoferrate into the electrolyte.  

PubMed

This paper reports on the improvement on the capacitive properties of Co-Al layered double hydroxide (Co-Al LDH) by adding hexacyanoferrate(II) and (III) solely or jointly into 1 M KOH aqueous solution. Owing to the high reversibility, the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) ion pair acts as an electron relay at the electrode/electrolyte interface during charge and discharge by coupling in the redox transition of Co(II)/Co(III) in the Co-Al LDH electrode. Electrochemical impedance spectra and Tafel curves provide direct evidences with decreased charge-transfer resistance and increased exchange current density in the alkaline solution containing hexacyanoferrate ions, respectively. PMID:19305892

Su, Ling-Hao; Zhang, Xiao-Gang; Mi, Chang-Huan; Gao, Bo; Liu, Yan

2009-02-10

144

Preparation and intercalation chemistry of magnesium-iron(III) layered double hydroxides containing exchangeable interlayer chloride and nitrate ions  

SciTech Connect

Layered double hydroxides (LDHs) with Mg{sup 2+} and Fe{sup 3+} cations in the brucite-like layers and having chloride or nitrate ions in the interlayer region have been prepared and characterized by powder X-ray diffraction (PXRD), elemental analysis and thermal analysis. Thermal decomposition of the LDH-nitrate occurs in two steps, with loss of water followed by simultaneous dehydroxylation of the layers and loss of NO{sub x}/O{sub 2} arising from the nitrate anions. Thermal decomposition of the LDH-chloride involves an additional step, with chloride ions becoming grafted to the layers, prior to loss of HCl. The interlayer anions may be readily replaced by sulfate, thiosulfate, tartrate and vinylbenzenesulfonate ions suggesting that these materials may be useful precursors to Mg-Fe(III) LDHs intercalated with a variety of inorganic and organic anions.

Meng Weiqing; Li Feng; Evans, David G.; Duan Xue

2004-07-02

145

Metabolic engineering of a Lactobacillus plantarum double ldh knockout strain for enhanced ethanol production  

Microsoft Academic Search

Lactobacillus plantarum ferments glucose through the Embden–Meyerhof–Parnas pathway: the central metabolite pyruvate is converted into lactate via\\u000a lactate dehydrogenase (LDH). By substituting LDH with pyruvate decarboxylase (PDC) activity, pyruvate may be redirected toward\\u000a ethanol production instead of lactic acid fermentation. A PDC gene from the Gram-positive bacterium Sarcina ventriculi (Spdc) was introduced into an LDH-deficient strain, L. plantarum TF103, in

Siqing Liu; Nancy N. Nichols; Bruce S. Dien; Michael A. Cotta

2006-01-01

146

Synthesis of layered organic–inorganic nanohybrid material: an organic dye, naphthol blue black in magnesium–aluminum layered double hydroxide inorganic lamella  

Microsoft Academic Search

Open lamella systems such as layered double hydroxides (LDHs) can be used to generate new nanostructured materials of layered organic–inorganic nanohybrid type. The synthesis of a new nanocomposite material consisting of inorganic layers, Mg–Al-LDH (MAL) as a host and naphthol blue black (NBB), an organic dye as a guest was successfully done. Various concentrations of NBB, ranging from 0.001 to

Mohd Zobir bin Hussein; Zulkarnain Zainal; Asmah Hj Yahaya; Azira binti Abd Aziz

2002-01-01

147

Laccase electrodes based on the combination of single-walled carbon nanotubes and redox layered double hydroxides: Towards the development of biocathode for biofuel cells  

Microsoft Academic Search

Single-walled carbon nanotubes (SWCNT) were combined with layered double hydroxides (LDH) intercalated with 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt [ZnCr-ABTS] to entrap and electrically connect laccase enzyme. The resulting laccase electrodes exhibited an electro-enzymatic activity for O2 reduction. To improve this electrocatalytic activity, varying SWCNT quantities and loading methods were tested to optimize the configuration of the laccase electrodes. Furthermore, the resulting bioelectrode

Shou-Nian Ding; Michael Holzinger; Christine Mousty; Serge Cosnier

2010-01-01

148

Morphology and thermal stabilization mechanism of LLDPE\\/MMT and LLDPE\\/LDH nanocomposites  

Microsoft Academic Search

The morphology and thermal stabilization mechanism of polymeric nanocomposites prepared by solution intercalation of linear low density polyethylene (LLDPE) with montmorillonite (MMT), MgAl layered double hydroxide (LDH), and ZnAl LDH have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Both LLDPE\\/MMT and LLDPE\\/MgAl LDH nanocomposites exhibit mixed intercalated–exfoliated

Longzhen Qiu; Wei Chen; Baojun Qu

2006-01-01

149

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

150

Reduction in the size of layered double hydroxide nanoparticles enhances the efficiency of siRNA delivery.  

PubMed

Small interfering RNAs (siRNAs) are a potentially powerful new class of pharmaceutical drugs for many disease. However, the delivery of unprotected siRNAs is ineffective due to their susceptibility to degradation by ubiquitous nucleases under physiological conditions. Layered double hydroxide nanoparticles (LDHs) have been found to be efficient carriers of anionic drugs and nucleic acids. Our previous research has shown that LDHs (with the Z-average particle size of approximately 110 nm) can mediate siRNA delivery in mammalian cells, resulting in gene silencing. However, short double-stranded nucleic acids are mostly adsorbed onto the external surface and not well protected by LDHs. In order to enhance the intercalation of siRNA into the LDH interlayer and the efficiency of subsequent siRNA delivery, we prepared smaller LDHs (with the Z-average particle size of approximately 45 nm) with an engineered non-aqueous method. We demonstrate here that dsDNA/siRNA is more effectively intercalated into these small LDH nanoparticles, more dsDNA/siRNA is transfected into HEK 293T cells, and more efficient silencing of the target gene is achieved using smaller LDHs. Thus, smaller LDH particles have greater potential as a delivery system for the application of RNA interference. PMID:23084868

Chen, Min; Cooper, Helen M; Zhou, Ji Zhi; Bartlett, Perry F; Xu, Zhi Ping

2012-09-26

151

Formation of crystalline Zn-Al layered double hydroxide precipitates on ?-alumina: the role of mineral dissolution.  

PubMed

To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) as layered double hydroxide (LDH) phases in soils, we systematically examined the presence of Al and the role of mineral dissolution during Zn sorption/precipitation on ?-Al(2)O(3) (?-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder X-ray diffraction (SR-XRD), and (27)Al solid-state NMR. The EXAFS analysis indicates the formation of Zn-Al LDH precipitates at Zn concentration ?0.4 mM, and both HR-TEM and SR-XRD reveal that these precipitates are crystalline. These precipitates yield a small shoulder at ?(Al-27) = +12.5 ppm in the (27)Al solid-state NMR spectra, consistent with the mixed octahedral Al/Zn chemical environment in typical Zn-Al LDHs. The NMR analysis provides direct evidence for the existence of Al in the precipitates and the migration from the dissolution of ?-alumina substrate. To further address this issue, we compared the Zn sorption mechanism on a series of Al (hydr)oxides with similar chemical composition but differing dissolubility using EXAFS and TEM. These results suggest that, under the same experimental conditions, Zn-Al LDH precipitates formed on ?-alumina and corundum but not on less soluble minerals such as bayerite, boehmite, and gibbsite, which point outs that substrate mineral surface dissolution plays an important role in the formation of Zn-Al LDH precipitates. PMID:23043294

Li, Wei; Livi, Kenneth J T; Xu, Wenqian; Siebecker, Matthew G; Wang, Yujun; Phillips, Brian L; Sparks, Donald L

2012-10-25

152

Synthesis and characterization of a novel nano-scale magnetic solid base catalyst involving a layered double hydroxide supported on a ferrite core  

NASA Astrophysics Data System (ADS)

A nano-scale magnetic solid base catalyst MgAl-OH-LDH/MgFe2O4 (where LDH denotes layered double hydroxide) composed of MgAl-OH-LDH Brønsted base catalytic layers coated on MgFe2O4 spinel cores has been prepared. A magnetic precursor MgAl-CO3-LDH/MgFe2O4 was prepared by a method involving separate nucleation and aging steps, and subsequently calcined to give a mixed metal oxide composite MgAl(O)/MgFe2O4 which was rehydrated to give MgAl-OH-LDH/MgFe2O4. The structure and magnetic properties of the nano-scale magnetic solid base MgAl-OH-LDH/MgFe2O4, together with those of the magnetic precursor MgAl-CO3-LDH/MgFe2O4 and MgFe2O4 were characterized by XRD, XPS, low temperature N2 adsorption and vibrating sample magnetometry (VSM). The MgAl-OH-LDH/MgFe2O4 composite possesses a mesoporous structure with pore size ranging from 2 to 20nm with particle size mainly in the range 35-130nm. The catalytic properties of MgAl-OH-LDH/MgFe2O4 were evaluated using the self-condensation of acetone at 273K as a probe reaction. The results showed that the conversion of acetone to diacetone alcohol reached the thermodynamic equilibrium value of 23% at 273K. The catalyst was easily recovered through application of an external magnetic field, and when the reclaimed catalyst was used in a second run for the same reaction, the reactivity remained unchanged.

Zhang, Hui; Qi, Rong; Evans, David G.; Duan, Xue

2004-03-01

153

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

SciTech Connect

Chromate intercalated layered double hydroxides (LDHs) having the formula M{sup II} {sub 6}M'{sup III} {sub 2}(OH){sub 16}CrO{sub 4}.4H{sub 2}O (M{sup II} = Ca, Mg, Co, Ni, Zn with M'{sup III} = Al and M{sup II} = Mg, Co, Ni with M'{sup 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 intergrowth of polytypes with hexagonal (2H) and rhombohedral (3R) symmetries and (iii) translation of randomly chosen layers by (2/3, 1/3, z) and (1/3, 2/3, z) leading to stacking faults having a local structure of rhombohedral symmetry. IR spectra show that the CrO{sub 4} {sup 2-} ion is incorporated either in the T {sub d} or in the C {sub 3v} symmetry. The interlayer spacing in the latter case is 7.3 A characteristic of a single atom thick interlayer showing that the CrO{sub 4} {sup 2-} ion is grafted to the metal hydroxide slab. On thermal treatment, the CrO{sub 4} {sup 2-} ion transforms into Cr(III) and is incorporated into the spinel oxide or phase separates as Cr{sub 2}O{sub 3}. In the LDH of Mg with Al, Cr(III) remains in the MgO lattice as a defect and promotes the reconstruction of the LDH on soaking in water. In different LDHs, 18-50% of the CrO{sub 4} {sup 2-} ion is replaceable with carbonate anions showing only partial mineralization of the water-soluble chromate. The extent of replaceable chromates depends upon the solubility of the corresponding LDH, which in turn is determined by the solubility of the MCrO{sub 4}. These studies have profound implications for the possible use of LDHs for chromate amelioration in green chemistry.

Prasanna, Srinivasa V. [Department of Chemistry, Central College, Bangalore University, Bangalore, Karnataka 560001 (India); Kamath, P. Vishnu [Department of Chemistry, Central College, Bangalore University, Bangalore, Karnataka 560001 (India)]. E-mail: vishnukamath8@hotmail.com; Shivakumara, C. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India)

2007-06-05

154

Synthesis of organo cobalt-aluminum layered double hydroxide via a novel single-step self-assembling method and its use as flame retardant nanofiller in PP.  

PubMed

Synthesis of polypropylene/organo-layered double hydroxide (PP/OLDH) has been carried out based on self-assembled organocobalt-aluminum LDH (O-CoAl-LDH). The novel method of synthesizing self-assembled CoAl-LDH and its characterization have also been reported in details. This method is proven to be very efficient way of producing OLDH in a single step with homogeneous composition and structure. As flame-retardant nanofiller, O-CoAl-LDH shows significant decrease in heat release rate (HRR), the total heat release (THR) and the heat release capacity (HRC) of the PP composites, though the thermal stability of the compounds decreases slightly compared to the base polymer. Morphological analyses show that the LDH particles are dispersed in PP matrix in a partially exfoliated form. The activation energy calculation based on the Kissinger method reveals that O-CoAl-LDH has a positive effect on the activation energy of thermal decomposition of PP. However, in the presence of this filler, decomposition of the composites starts at an earlier stage than that of pure PP. PMID:20712354

Wang, De-Yi; Das, Amit; Costa, Francis Reny; Leuteritz, Andreas; Wang, Yu-Zhong; Wagenknecht, Udo; Heinrich, Gert

2010-09-01

155

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

156

Efficient removal of heavy metal ions from aqueous systems with the assembly of anisotropic layered double hydroxide nanocrystals@carbon nanosphere.  

PubMed

We report on the efficient removal of heavy metal ions from simulated wastewater with a nanostructured assembly. The nanoassembly was obtained via direct assembling the performed anisotropic layered double hydroxide nanocrystals (LDH-NCs) onto the surface of carbon nanospheres (labeled as LDH-NCs@CNs). It was found that the maximum adsorption capacity of the nanoassembly toward Cu(2+) was ? 19.93 mg g(-1) when the initial Cu(2+) concentration was 10.0 mg L(-1), displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Cu(2+) removal was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared building unit of the assembly, including LDH-NCs, CNs, and the assembly, as well as Cu(2+)-adsorbed assembly, were carefully examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Cu(2+) removal with the assembly of LDH-NCs@CNs was proposed. Comparison experiments show that the adsorption capacity of the resulting LDH-NCs@CNs assembly was much higher than its any building unit alone (CNs or LDH-NCs), exhibiting the deliberation of the assembly on water decontamination. This work provides a very efficient, fast and convenient approach for exploring promising nanoassembly materials for water treatment. PMID:21692502

Gong, Jingming; Liu, Ting; Wang, Xiaoqing; Hu, Xianluo; Zhang, Lizhi

2011-06-21

157

Visible-Light-Responsive Photocatalysts toward Water Oxidation Based on NiTi-Layered Double Hydroxide/Reduced Graphene Oxide Composite Materials.  

PubMed

A visible-light responsive photocatalyst was fabricated by anchoring NiTi-layered double hydroxide (NiTi-LDH) nanosheets to the surface of reduced graphene oxide sheets (RGO) via an in situ growth method; the resulting NiTi-LDH/RGO composite displays excellent photocatalytic activity toward water splitting into oxygen with a rate of 1.968 mmol g(-1) h(-1) and a quantum efficiency as high as 61.2% at 500 nm, which is among the most effective visible-light photocatalysts. XRD patterns and SEM images indicate that the NiTi-LDH nanosheets (diameter: 100-200 nm) are highly dispersed on the surface of RGO. UV-vis absorption spectroscopy exhibits that the introduction of RGO enhances the visible-light absorption range of photocatalysts, which is further verified by the largely decreased band gap (?1.78 eV) studied by cyclic voltammetry measurements. Moreover, photoluminescence (PL) measurements indicate a more efficient separation of electron-hole pairs; electron spin resonance (ESR) and Raman scattering spectroscopy confirm the electrons transfer from NiTi-LDH nanosheets to RGO, accounting for the largely enhanced carrier mobility and the resulting photocatalytic activity in comparison with pristine NiTi-LDH material. Therefore, this work demonstrates a facile approach for the fabrication of visible-light responsive NiTi-LDH/RGO composite photocatalysts, which can be used as a promising candidate in solar energy conversion and environmental science. PMID:24066609

Li, Bei; Zhao, Yufei; Zhang, Shitong; Gao, Wa; Wei, Min

2013-10-09

158

Metabolic engineering of a Lactobacillus plantarum double ldh knockout strain for enhanced ethanol production.  

PubMed

Lactobacillus plantarum ferments glucose through the Embden-Meyerhof-Parnas pathway: the central metabolite pyruvate is converted into lactate via lactate dehydrogenase (LDH). By substituting LDH with pyruvate decarboxylase (PDC) activity, pyruvate may be redirected toward ethanol production instead of lactic acid fermentation. A PDC gene from the Gram-positive bacterium Sarcina ventriculi (Spdc) was introduced into an LDH-deficient strain, L. plantarum TF103, in which both the ldhL and ldhD genes were inactivated. Four different fusion genes between Spdc and either the S. ventriculi promoter or three Lactococcus lactis promoters in pTRKH2 were introduced into TF103. PDC activity was detected in all four recombinant strains. The engineered strains were examined for production of ethanol and other metabolites in flask fermentations. The recombinant strains grew slightly faster than the parent TF103 and produced 90-130 mM ethanol. Although slightly more ethanol was observed, carbon flow was not significantly improved toward ethanol, suggesting that a further understanding of this organism's metabolism is necessary. PMID:16193282

Liu, Siqing; Nichols, Nancy N; Dien, Bruce S; Cotta, Michael A

2005-09-29

159

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

160

Nanoincorporation of layered double hydroxides into a miscible blend system of cellulose acetate with poly(acryloyl morpholine).  

PubMed

Blend miscibility of cellulose acetate (CA) with poly(acryloyl morpholine) (PACMO) was examined by thermal transition measurements and solid-state (13)C NMR spectroscopy, in which CA materials of acetyl DS=1.80-2.95 were used. All the blends prepared gave a single Tg and formed an amorphous monophase homogeneous within a distance of ?2.0nm. An Al/Mg-based, layered double hydroxide (LDH) was modified with different ionic oligomers, and an attempt was made to incorporate the respective organophilic LDHs (3-3.5wt%) into blend films of the miscible PACMO/CA pair, via bulk polymerization of an ACMO monomer/organo-LDH mixture and then blending CA with the polymer/inorganic hybrid precursor. Particularly, 12-hydroxystearic acid-modified LDH was well exfoliated and ultimately dispersed in the PACMO/CA matrix on a scale of less than a few tens of nanometers in thickness. This gave rise to a successful reinforcement effect leading to the improvement in thermo-mechanical property of the polymer blends. PMID:23465938

Yoshitake, Sachi; Suzuki, Tetsuya; Miyashita, Yoshiharu; Aoki, Dan; Teramoto, Yoshikuni; Nishio, Yoshiyuki

2012-03-23

161

Drug intercalation in layered double hydroxide clay: application in the development of a nanocomposite film for guided tissue regeneration.  

PubMed

It has been proposed that localized and controlled delivery of alendronate and tetracycline to periodontal pocket fluids via guided tissue regeneration (GTR) membranes may be a valuable adjunctive treatment for advanced periodontitis. The objectives of this work were to develop a co-loaded, controlled release tetracycline and alendronate nanocomposite plasticized poly(lactic-co-glycolic acid) (PLGA) film that would form a suitable matrix supporting osteoblast proliferation and differentiation. Alendronate release was successfully controlled, with complete suppression of the burst phase of release by intercalation of alendronate anions in magnesium/aluminum layered double hydroxide (LDH) clay nanoparticles and dispersed in the PLGA film matrix. Tetracycline, loaded as free drug into the film together with alendronate-LDH clay complex released more rapidly than alendronate, but showed evidence of intercalation in the LDH clay particles. The dual drug loaded nanocomposite films were biocompatible with osteoblasts and after 5 week incubations, significant increase in alkaline phosphatase activity and bone nodule formation were observed. PMID:21708236

Chakraborti, Michelle; Jackson, John K; Plackett, David; Brunette, Donald M; Burt, Helen M

2011-06-17

162

Characterization of self-assembled films of NiGa layered double hydroxide nanosheets and their electrochemical properties  

SciTech Connect

In this study, we have demonstrated the synthesis and delamination of a rarely studied NiGa layered double hydroxide (LDH) system. Hydrothermal treatment under agitation conditions at 200 deg. C for 4 h resulted in the formation of highly crystalline NiGa LDHs in a shorter time than those synthesized without agitation. The LDH was delaminated into the individual nanosheets in formamide. The most significant finding in this study is the electrochemical behavior of interlayer ferricyanide anions intercalated with the layer-by-layer (LBL) assembly method. The morphology of LBL film with one layer is also monitored with atomic force microscopy. The cyclic voltammogram is similar to potassium metal hexacyanoferrate systems with its unique two-peak wave. Raman spectrum of the film revealed that the metal center of the interlayer cyano complex is in interaction with the Ni{sup 2+} of the host layer. It was concluded that the two-peak cyclic voltammogram of the film is a result of two different forms of the hexacyanoferrate in the interlayer. - Graphical abstract: The thin film deposited from the nanosheets of ion-exchangeable NiGa LDH and ferricyanide molecule with LBL method gives the typical redox reaction of metal hexacyanoferrates in the interlayer. Current density depends on the number of layers.

Altuntasoglu, Ozge [Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555 (Japan)], E-mail: 082d9101@gsst.stud.kumamoto-u.ac.jp; Unal, Ugur [Department of Chemistry, Faculty of Arts and Sciences, Koc University, Rumelifeneri yolu, Sariyer, Istanbul (Turkey); Ida, Shintaro; Goto, Motonobu; Matsumoto, Yasumichi [Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555 (Japan)

2008-12-15

163

Intercalation of an oxalatooxoniobate complex into layered double hydroxide and layered zinc hydroxide nitrate.  

PubMed

A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH(4)[NbO(C(2)O(4))(2)(H(2)O)(2)]2H(2)O. In a similar way, the layered zinc hydroxide nitrate, Zn(5)(OH)(8)(NO(3))(2)2H(2)O, was synthesized, preexpanded with azelate ions ((-)OOC(CH(2))(7)COO(-)), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV-vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix. PMID:19022456

Arizaga, Gregorio Guadalupe Carbajal; Gardolinski, José Eduardo Ferreira da Costa; Schreiner, Wido Herwig; Wypych, Fernando

2008-11-20

164

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

SciTech Connect

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), {sup 27}Al 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{sup 3+} and ox is also enhanced under microwave irradiation, and a partial destruction of the structure takes place with an increase in the M{sup 2+}/M{sup 3+} ratio and consequent modification of the cell parameters. - Graphical Abstract: The influence of the nature of the interlayer anion during the ageing process of carboxylate-intercalated (TA and ox) hydrotalcite-like compounds (HTlcs) is studied. Well crystallized for TA-containing compounds were obtained. However, the non-desired side-reaction of ox with the aluminum of the layers is enhanced by the microwaves and a partial destruction of the structure takes place.

Benito, P.; Labajos, F.M. [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, Salamanca 37008 (Spain); Mafra, L.; Rocha, J. [Departamento de Quimica, Universidade de Aveiro, Aveiro, CICECO (Portugal); Rives, V. [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, Salamanca 37008 (Spain)], E-mail: vrives@usal.es

2009-01-15

165

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

166

Incorporation of transition metals into Mg Al layered double hydroxides: Coprecipitation of cations vs. their pre-complexation with an anionic chelator  

NASA Astrophysics Data System (ADS)

A comparative study on two different methods for preparing Mg Al layered double hydroxides (LDH) containing various divalent transition metals M (M=Co, Ni, Cu) has been carried out. The first (conventional) method involved coprecipitation of divalent metals M(II) with Mg(II) and Al(III) cations using carbonate under basic conditions. The second approach was based on the ability of transition metals to form stable anionic chelates with edta4- (edta4-=ethylenediaminetetraacetate) that were synthesized and further introduced into LDH by coprecipitation with Mg and Al. The synthesized LDHs were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods, thermogravimetry with mass-selective detection of decomposition products (TG-MSD), Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The results obtained were discussed in terms of efficiency of transition metal incorporation into the LDH structure, thermal stability of materials and the ability of metal chelates to intercalate the interlayer space of Mg Al LDH. Vibrational spectroscopy studies confirmed that the integrity of the metal chelates was preserved upon incorporation into the LDH.

Tsyganok, Andrey; Sayari, Abdelhamid

2006-06-01

167

Mechanochemical approach for synthesis of layered double hydroxides  

NASA Astrophysics Data System (ADS)

In this paper, a mechanochemical approach is used to prepare layered double hydroxides (LDHs). This approach involves manually grinding the precursor, nitrates and then the hydrothermal treatment. The study indicates that grinding leads to the incomplete formation of LDHs phase, LDHs-M. The reaction degree of precursor salts to LDHs after grinding depends on the melting points of the precursors. As expected, hydrothermal treatment is beneficial for the good crystallization and regularity of LDHs. Especially, the effect of hydrothermal treatment has been emphatically explored. The hydration of LDHs-M, increment of zeta potentials and the complete exchange of NO3- by CO32- anions occur successively or in parallel during the hydrothermal treatment. It can be found that combination of grinding and hydrothermal treatment gives rise to the formation of uniform and monodispersed particles of LDHs.

Zhang, Xiaoqing; Li, Shuping

2013-06-01

168

LDH isoenzymes  

MedlinePLUS

... is called a "flipped" LDH pattern. The LDH level rises within 24 - 72 hours after a heart attack, peaks in 3 - 4 days, and returns to normal in about 14 days. Greater-than-normal LDH levels may suggest: Heart attack Hemolytic anemia Hypotension Infectious ...

169

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

NASA Astrophysics Data System (ADS)

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 be fabricated. In this work, the successful deposition of LDH and their derived mixed oxides thin films by laser techniques is reported. Pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) were the methods used for thin films deposition. The ability of Mg-Al LDHs as a carrier for metallic particles (Ag) has been considered. Frozen targets containing 10% powder in water were used for MAPLE, while for PLD the targets consisted in dry-pressed pellets. The structure and the surface morphology of the deposited films were examined by X-ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy and Secondary Ion Mass Spectrometry.

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

2011-04-01

170

Structural and spectroscopic study of tripeptide/layered double hydroxide hybrids.  

PubMed

A tripeptide (Glutathione, GSH) is chosen as a model drug to intercalate into layered double hydroxides (LDHs) by ion exchange, and a systematic study combining experimental and theoretical investigation is carried on X-ray diffraction (XRD) demonstrates that GSH had been intercalated into LDHs. IR and Raman spectroscopies, and the (13)C NMR chemical shifts, are applied to clarify the characteristic changes in functional groups after intercalation. These results are interpreted with the density functional theory (DFT) calculations in order to verify the experimental data. For the first time, by using XPS for N 1s detecting, the related content of the native guest NO(3)(-) and the GSH in the LDHs' interlayer are investigated, and the research results show that the reaction temperature affects the intercalation of GSH based on the XRD patterns. Furthermore, the reaction mechanism of intercalating GSH into LDHs was explained by the intrinsic reaction coordinate (IRC). The present study reveals that GSH as zwitterions (NH(3+)COO(-) formation) in water solvent first suffers hydrogen transfer and proton migration and then could be intercalated into LDH through ion exchange to occupy an interlayer site of NO(3)(-). PMID:23266024

Wang, Yongliao; Wu, Pingxiao; Li, Yuewu; Zhu, Nengwu; Dang, Zhi

2012-12-05

171

Mechanism of interaction of hydrocalumites (Ca/Al-LDH) with methyl orange and acidic scarlet GR.  

PubMed

The development of new materials for water purification is of universal importance. Among these types of materials are layered double hydroxides (LDHs). Non-ionic materials pose a significant problem as pollutants. The interaction of methyl orange (MO) and acidic scarlet GR (GR) adsorption on hydrocalumite (Ca/Al-LDH-Cl) was studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), scanning electron microscope (SEM), and near-infrared spectroscopy (NIR). The XRD results revealed that the basal spacing of Ca/Al-LDH-MO was expanded to 2.45 nm, and the MO molecules were intercalated with a interpenetrating bilayer model in the gallery of LDH, with 49° tilting angle. Yet, Ca/Al-LDH-GR was kept the same d-value as Ca/Al-LDH-Cl. The NIR spectrum for Ca/Al-LDH-MO showed a prominent band around 5994 cm(-1), assigned to the combination result of the NH stretching vibrations, which was considered as a mark to assess MO(-) ion intercalation into Ca/Al-LDH-Cl interlayers. From SEM images, the particle morphology of Ca/Al-LDH-MO mainly changed to irregular platelets, with a "honey-comb" like structure. Yet, the Ca/Al-LDH-GR maintained regular hexagon platelets, which was similar to that of Ca/Al-LDH-Cl. All results indicated that MO(-) ion was intercalated into Ca/Al-LDH-Cl interlayers, and acidic scarlet GR was only adsorbed upon Ca/Al-LDH-Cl surfaces. PMID:21963204

Zhang, Ping; Qian, Guangren; Shi, Huisheng; Ruan, Xiuxiu; Yang, Jing; Frost, Ray L

2011-09-10

172

Anionic poly(p-phenylenevinylene)/layered double hydroxide ordered ultrathin films with multiple quantum well structure: a combined experimental and theoretical study.  

PubMed

The sulfonated phenylenevinylene polyanion derivate (APPV) and exfoliated Mg-Al-layered double hydroxide (LDH) monolayers were alternatively assembled into ordered ultrathin films (UTFs) employing a layer-by-layer method, which shows uniform yellow luminescence. UV-vis absorption and fluorescence spectroscopy present a stepwise and regular growth of the UTFs upon increasing deposited cycles. X-ray diffraction, atomic force microscopy, and scanning electron microscopy demonstrate that the UTFs are orderly periodical layered structure with a thickness of 3.3-3.5 nm per bilayer. The APPV/LDH UTFs exhibit well-defined polarized photoemission characteristic with the maximum luminescence anisotropy of approximately 0.3. Moreover, the UTF exhibit longer fluorescence lifetime (3-3.85-fold) and higher photostability than the drop-casting APPV film under UV irradiation, suggesting that the existence of a LDH monolayer enhances the optical performance of the APPV polyanion. A combination study of electrochemistry and periodic density functional theory was used to investigate the electronic structure of the APPV/LDH system, illustrating that the APPV/LDH UTF is a kind of organic-inorganic hybrid multiple quantum well (MQW) structure with a low band energy of 1.7-1.8 eV, where the valence electrons of APPV can be confined into the energy wells formed by the LDH monolayers effectively. Therefore, this work not only gives a feasible method for fabricating a luminescence ultrathin film but also provides a detailed understanding of the geometric and electronic structures of photoactive polyanions confined between the LDH monolayers. PMID:20092347

Yan, Dongpeng; Lu, Jun; Ma, Jing; Wei, Min; Wang, Xinrui; Evans, David G; Duan, Xue

2010-05-18

173

Intercalation of papain enzyme into hydrotalcite type layered double hydroxide  

NASA Astrophysics Data System (ADS)

Intercalation of proteolytic enzyme papain into hydrotalcite type LDH structure was achieved by controlled co-precipitation at pH=9.0 in the presence of papain. Characterization of the MgAl-papain-LDH phase was carried out using X-ray powder diffraction (XRD), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). According to XRD, papain was successfully intercalated. The d-value for the basal spacing of MgAl-papain-LDH was found at ˜5.3 nm. Consequently, original papain (hydrodynamic diameter ˜7.2 nm) attains a compressed conformation during intercalation.Formation of MgAl-papain-LDH was confirmed by elemental analysis and transmission electron microscopy (TEM). Under SEM, MgAl-papain-LDH phases appear as nanothin platelets which are intergrown to flower-like aggregates. Steric size and activity of the enzyme was retained after deintercalation from MgAl-LDH framework, as was evidenced by light scattering and UV/vis measurements. Thus, papain is not denatured during intercalation, and LDH is a suitable host structure which can provide a time-controlled release of the biomolecule.

Zou, N.; Plank, J.

2012-09-01

174

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 N2 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

175

Preparation and thermal decomposition studies of l-tyrosine intercalated MgAl, NiAl and ZnAl layered double hydroxides  

Microsoft Academic Search

l-Tyrosine (represented as l-Tyr) intercalated MgAl, NiAl and ZnAl layered double hydroxides (LDHs) have been obtained by the method of coprecipitation. In situ FT-IR, in situ HT-XRD and TG-DTA measurements allow a detailed understanding of the thermal decomposition process for the three intercalated composites. In situ HT-XRD reveals that the layered structure of l-Tyr\\/MgAl-LDH collapses completely at 450°C with the

Min Wei; Xiangyu Xu; Jing He; Qi Yuan; Guoying Rao; David G. Evans; Min Pu; Lan Yang

2006-01-01

176

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

SciTech Connect

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{sub 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. - Graphical Abstract: Cu-Ce-O mixed oxides calcined from [Ce(dipic){sub 3}]{sup 3-}- intercalated Cu/Zn/Al layered double hydroxides were synthesized and displayed good catalytic performances in phenol oxidation due to the Cu-Ce interactions. Highlights: Black-Right-Pointing-Pointer [Ce(dipic){sub 3}]{sup 3-}-intercalated Cu/Zn/Al layered double hydroxides were synthesized. Black-Right-Pointing-Pointer Cu-Ce-O mixed oxides derivated from the LDHs were characterized as catalysts. Black-Right-Pointing-Pointer Presence of Ce influenced physicochemical property and catalytic performance. Black-Right-Pointing-Pointer Cu-Ce interaction was largely responsible for enhanced catalytic ability.

Chang Zheng, E-mail: changzheng@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Zhao Na; Liu Junfeng [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Li Feng, E-mail: lifeng_70@163.com [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Evans, David G.; Duan Xue [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Forano, Claude; Roy, Marie de [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002, Universite Blaise Pascal, 24 avenue des Landais, 63177 Aubiere (France)

2011-12-15

177

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

PubMed Central

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 (C9H8O4) 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.

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

2010-01-01

178

Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase  

NASA Astrophysics Data System (ADS)

Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2-5 nm-thick tactoids with a radial dimension of 0.2-0.5 ?m.

Manohara, G. V.; Vishnu Kamath, P.; Milius, Wolfgang

2012-12-01

179

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

180

Catalytic air oxidation of thiols mediated at a Mo(VI)O{sub 2} complex center intercalated in a Zn(II)-Al(III) layered double hydroxide host  

SciTech Connect

While bis(2-mercapto-2,2-diphenyl-ethanoate) dioxomolybdate (VI), (MoO{sub 2}(OOCC(S)(C{sub 6}H{sub 5}){sub 2}){sub 2}){sup 2-} (I), ethanolic solutions stoichiometrically react with aromatic and aliphatic thiols to give the corresponding disulfides, the intercalation of I within a Zn(II)-Al(III) layered double hydroxide (LDH) allows their catalytic oxidation by dioxygen. A reaction scheme is proposed in which a Mo{sup IV}O species activates O{sub 2}, regenerating the parent Mo{sup VI}O{sub 2} complex (I), which then acts as a true catalyst. Kinetic data for the thiol oxidation reaction have been determined. The results obtained here demonstrate that the intercalation of I into a Zn(II)-Al(III) LDH host inhibits the formation of catalytically inactive Mo{sup V}O species that are always formed under homogeneous conditions.

Corma, A.; Fornes, V.; Rey, F.; Cervilla, A.; Llopis, E.; Ribera, A.

1995-04-01

181

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

SciTech Connect

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{sub 2}Al-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{sub 2}Al-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. - Graphical Abstract: 8-Hydroxy-pyrene-1,3,6-trisulphonate and octanesulfonate co-intercalated ZnAl layered double hydroxide can exhibit tunable solid-state blue and green fluorescence by treating the sample at acid and neutral media under hydrothermal condition. Highlights: Black-Right-Pointing-Pointer 8-hydroxy-pyrene-1,3,6-trisulphonate (HPTS) was intercalated into ZnAl LDHs. Black-Right-Pointing-Pointer They show the controllable dual fluorescence response to the HPTS content and pH values. Black-Right-Pointing-Pointer Fluorescence of the HPTS/LDH film was insensitive to the quencher (Cu{sup 2+}) concentration.

Dang Sile; Yan Dongpeng [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Lu Jun, E-mail: lujun@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

2012-01-15

182

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 SO42--containing product, while only the Fe(III) characteristic for DBS-containing one. The combination characterization results and Rietveld analysis illustrate that the SO42--containing product possesses the Green Rust two (GR2)-like crystal structure with an approximate chemical composition of [Zn0.435·FeII0.094·FeIII0.470·(OH)2]·(SO42-)0.235·1.0H2O, 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 SO42--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

183

Thermodynamical and structural insights of orange II adsorption by MgRAlNO3 layered double hydroxides  

NASA Astrophysics Data System (ADS)

[Mg1-x Alx(OH)2][(NO3)x, nH2O] Layered Double Hydroxide (LDH) sorbents with variable Mg/Al molar (R=(1-x)/x) ratios were investigated for adsorption of azo dye, orange II (OII) at various pH and temperature conditions. Mg2AlNO3 displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg2AlNO3 at 40 °C. Adsorption isotherms have been fitted using the Langmuir model and free energy of adsorption (?G°), enthalpy (?H°) and entropy (?S°) were calculated. The experimental values for ?G° in temperature range between 10 and 40 °C were found to be negative indicating that a spontaneous process occurred. Positive calculated enthalpy values, characteristic of an endothermic process were found. Characterization of solids (PXRD, FTIR, UV-vis, TGA/DTA, adsorption isotherm BET analysis, SEM and Zetametry) before and after adsorption showed that adsorption proceeds in two steps. First, adsorption occurs at the LDH surface, followed by intercalation via anion exchange.

Mustapha Bouhent, Mohamed; Derriche, Zoubir; Denoyel, Renaud; Prevot, Vanessa; Forano, Claude

2011-05-01

184

Layered double hydroxides as efficient drug delivery system of ciprofloxacin in the middle ear: an animal study in rabbits.  

PubMed

Chronic otitis media is a common disease often accompanied by recurrent bacterial infections. These may lead to the destruction of the middle ear bones such that prostheses have to be implanted to restore sound transmission. Surface coatings with layered double hydroxides (LDHs) are evaluated here as a possibility for drug delivery systems with convenient advantages such as low cytotoxicity and easy synthesis. Male New Zealand White rabbits were implanted with Bioverit(®) II middle ear prostheses coated with the LDH Mg(4)Al(2)(OH)(12)(SO(4))(2)·6H(2)O impregnated with ciprofloxacin. 12 (group 1) were directly infected with Pseudomonas aeruginosa and another 12 (group 2) 1 week after the implantation. Clinical outcome, blood counts, histological analyses and microbiological examination showed an excellent antimicrobial activity for group 1, whereas this effect was attenuated in animals where infection was performed 1 week after implantation. This is the first study to demonstrate an efficient drug delivery system with an LDH coating on prostheses in the middle ear. PMID:23053799

Hesse, Daniela; Badar, Muhammad; Bleich, André; Smoczek, Anna; Glage, Silke; Kieke, Marc; Behrens, Peter; Müller, Peter Paul; Esser, Karl-Heinz; Stieve, Martin; Prenzler, Nils Kristian

2012-10-10

185

Application of layered double hydroxides for removal of oxyanions: A review  

Microsoft Academic Search

Layered double hydroxides (LDHs) are lamellar mixed hydroxides containing positively charged main layers and undergoing anion exchange chemistry. In recent years, many studies have been devoted to investigating the ability of LDHs to remove harmful oxyanions such as arsenate, chromate, phosphate, etc. from contaminated waters by both surface adsorption and anion exchange of the oxyanions for interlayer anions in the

Kok-Hui Goh; Teik-Thye Lim; Zhili Dong

2008-01-01

186

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

187

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

188

High-temperature chemical and microstructural transformations of an organic-inorganic nanohybrid captopril intercalated Mg-Al layered double hydroxide  

SciTech Connect

The thermal evolution of a crystalline organic-inorganic nanohybrid captopril intercalated Mg-Al layered double hydroxide (LDH) [Mg{sub 0.68}Al{sub 0.32}(OH){sub 2}] (C{sub 9}H{sub 13}NO{sub 3}S){sub 0.130}(CO{sub 3}){sub 0.030}.0.53H{sub 2}O obtained by coprecipitation method is studied based upon in situ high-temperature X-ray diffraction, in situ infrared and thermogravimetric analysis coupled with mass spectroscopy analysis. The results reveal that a metastable quasi-interstratified layered nanohybrid involving carbonate-LDH and reoriented less ordered captopril-LDH was firstly observed as captopril-LDH heat-treated between 140 and 230 deg. C. The major decomposition/combustion of interlayer organics occur between 270 and 550 deg. C. A schematic model on chemical and microstructural evolution of this particular drug-inorganic nanohybrid upon heating in air atmosphere is proposed.

Zhang Hui [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Box 98, Beijing 100029 (China)], E-mail: huizhang67@gst21.com; Guo Shaohuan; Zou Kang; Duan Xue [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Box 98, Beijing 100029 (China)

2009-05-06

189

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

190

Dye-interleaved nanocomposite: Evan's Blue in the lamella of Mg–Al-layered double hydroxide  

Microsoft Academic Search

Layered organic–inorganic hybrid nanocomposite, containing an organic dye in an inorganic interlayer was prepared using Evan's Blue (EB) as a guest in Mg–Al layered double hydroxide inorganic host by a self-assembly technique, with the Mg–Al ratio of 4 in the mother liquor at pH=7.5. Powder X-ray diffractogram shows that the basal spacing of the Mg–Al layered double hydroxide with nitrate

Mohd Zobir bin Hussein; Asmah Hj Yahaya; Lai Mee Ping

2004-01-01

191

Structure and morphology of Mg-Al-Fe-mixed oxides derived from layered double hydroxides.  

PubMed

The influences of the nature and the extent of M(III) ion substitution on the structure, morphology and surface properties of layered double hydroxides, LDHs [Mg(1-x) M(III)(x)(OH)(2)](CO(3))(x/n).mH(2)O, M(III) being Al or/and Fe and x= M(III)/[(Mg+M(III)], and derived mixed oxides were investigated. Three series: Mg-Al, Mg-Al-Fe and Mg-Fe were synthesized using low supersaturation co-precipitation method at constant pH, with different Mg : Al : Fe ratio and x in the wide range from 0.15 to 0.7 in order to obtain complex, multi-phase systems with disordered structure, developed surface area, acid-base and redox properties favourable for catalytic application. The morphology of LDHs and their derived mixed oxides did not change considerably although pronounced changes in structural and surface properties occur by thermal decomposition. The increase in Al amount, as well as the deviation of M(III) content from the optimal range for the single LDH phase synthesis, causes the formation of smaller particles and decrease of mixed oxide crystallite size. The nature and amount of M(III) influence the development of surface area, after thermal treatment, depending mainly on the presence of smaller mesopores, not visible by scanning electron microscope. Although the particle size has no considerable influence on the value of the surface area, it was observed that the samples with smaller particles (Mg-Al and Mg-Al-Fe series) have also higher surface area compared with the samples with larger particles (Mg-Fe series). PMID:19094052

Vuli?, T; Hadnadjev, M; Marinkovi?-Neducin, R

2008-12-01

192

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

193

Effective removal of pyrophosphate by Ca–Fe–LDH and its mechanism  

Microsoft Academic Search

Pyrophosphate (PP), as a dispersant in industrial activities, has attracted much attention due to its contribution to the eutrophication in aquatic ecosystem. This study investigated the efficient PP removal over Ca-based layered double hydroxide (LDH). The PP removal amount was 4.54mmolP\\/g LDH at initial total phosphate concentration [P] ranging from 1.61 to 6.45mmol\\/L in which LDH dissolved and Ca2P2O7·2H2O precipitated.

Yueying Wu; Ying Yu; Ji Zhi Zhou; Jianyong Liu; Ying Chi; Zhi Ping Xu; Guangren Qian

194

Synthesis, characterization, and {sup 1}H and {sup 71}Ga MAS NMR spectroscopy of a novel Mg/Ga double layered hydroxide  

SciTech Connect

A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg{sub 0.174}Ga{sub 0.256}(OH){sub 2}](CO{sub 3}){sub 0}.134 {center_dot}mH{sub 2}O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073K 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 523 K and to decompose into a mixture of periclase MgO and amorphous Ga{sub 2}O{sub 3} at 823 K. Its changes with temperature were monitored by using {sup 1}H and {sup 71}Ga MAS NMR; {sup 1}H MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823 K.

Aramendia, M.A.; Borau, V.; Jimenez, C. [Cordoba Univ. (Spain)] [and others

1997-06-01

195

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/Zn2Al-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/Zn2Al-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

196

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

197

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 Ni2+ components. The NiAl2O4 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 N2O 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

198

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

199

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

2013-05-20

200

Controlled release of ketorolac through nanocomposite films of hydrogel and LDH nanoparticles  

Microsoft Academic Search

A novel nanocomposite film for sustained release of anionic ophthalmic drugs through a double-control process has been examined\\u000a in this study. The film, made as a drug-loaded contact lens, consists principally of a polymer hydrogel of 2-hydroxyethyl\\u000a methacrylate (HEMA), in whose matrix MgAl-layered double hydroxide (MgAl-LDH) nanoparticles intercalated with the anionic\\u000a drug are well dispersed. Such nanocomposite films (hydrogel-LDH-drug) contained

Zhi Ping Xu; Zi Gu; Xiaoxi Cheng; Firas Rasoul; Andrew K. Whittaker; Gao Qing Max Lu

2011-01-01

201

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

SciTech Connect

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 deg. 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 deg. 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 deg. 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{sup 2+} components. The NiAl{sub 2}O{sub 4} spinel and NiO still containing a marked part of Al in the cationic sublattice were detected in the samples calcined at 900 deg. C. The Ni2Al LDHs hydrothermally treated for various times and related mixed oxides obtained at 450 deg. 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{sub 2}O decomposition, which can be explained by suppressing internal diffusion effect in catalysts grains. - Graphical Abstract: Hydrothermal treatment of Ni-Al LDH precursors influenced the porous structure of related mixed oxides and considerably improved their catalytic activity in N{sub 2}O decomposition; the higher catalytic activity of hydrothermally treated samples can be explained by suppressing internal diffusion effect in catalysts grains.

Kovanda, Frantisek [Department of Solid State Chemistry, Institute of Chemical Technology, Prague, Technicka 5, 166 28 Prague (Czech Republic)], E-mail: Frantisek.Kovanda@vscht.cz; Rojka, Tomas [Department of Solid State Chemistry, Institute of Chemical Technology, Prague, Technicka 5, 166 28 Prague (Czech Republic); Bezdicka, Petr [Institute of Inorganic Chemistry of the ASCR, v. v. i., 250 68 Rez (Czech Republic); Jiratova, Kveta [Institute of Chemical Process Fundamentals of the ASCR, v. v. i., Rozvojova 135, 165 02 Prague (Czech Republic); Obalova, Lucie; Pacultova, Katerina [Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava (Czech Republic); Bastl, Zdenek [J. Heyrovsky Institute of Physical Chemistry of the ASCR, v. v. i., Dolejskova 3, 182 23 Prague (Czech Republic); Grygar, Tomas [Institute of Inorganic Chemistry of the ASCR, v. v. i., 250 68 Rez (Czech Republic)

2009-01-15

202

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

2013-04-16

203

Acid and redox properties of mixed oxides prepared by calcination of chromate-containing layered double hydroxides  

SciTech Connect

Layered double hydroxides (LDHs) with Mg and Al in the layers and carbonate, nitrate or chloride in the interlayer, or with Zn and Al in the layers and chloride in the interlayer, have been prepared by coprecipitation, and have been used as precursors to prepare chromate-containing LDHs. All these systems, as well as those obtained upon their calcination up to 800 deg. C, have been characterised by powder X-ray diffraction, FT-IR and vis-UV spectroscopies, temperature-programmed reduction (TPR), nitrogen adsorption at -196 deg. C for surface texture and porosity assessment, and FT-IR monitoring of pyridine adsorption for surface acidity determination. The results obtained show that the crystallinity of the chromate-containing LDH depends on the precursor used. The layered structure of the Mg, Al systems is stabilised up to 400 deg. C upon incorporation of chromate; however, the Zn,Al-chromate samples collapse between 200 and 300 deg. C, with simultaneous formation of ZnO. Calcination of the samples above 400 deg. C gives rise to a reduction of Cr(VI) to Cr(III), as concluded from vis-UV spectroscopic studies. The TPR profiles show that chromate in ZnAl hydrotalcite is more easily reduced than that incorporated in the magnesium ones. Moderately strong surface Lewis acid sites exist in all samples calcined below 500 deg. C.

Arco, M. del [Dpto. Quimica Inorganica, Universidad de Salamanca, 37008-Salamanca (Spain); Carriazo, D. [Dpto. Quimica Inorganica, Universidad de Salamanca, 37008-Salamanca (Spain); Martin, C. [Dpto. Quimica Inorganica, Universidad de Salamanca, 37008-Salamanca (Spain); Perez-Grueso, A.M. [Dpto. Quimica Inorganica, Universidad de Salamanca, 37008-Salamanca (Spain); Rives, V. [Dpto. Quimica Inorganica, Universidad de Salamanca, 37008-Salamanca (Spain)]. E-mail: vrives@usal.es

2005-11-15

204

Absorption of the selenite anion from aqueous solutions by thermally activated layered double hydroxide  

Microsoft Academic Search

The presence of selenite or selenate in potable water is a health hazard especially when consumed over a long period of time. Its removal from potable water is of importance. This paper reports technology for the removal of selenite from water through the use of thermally activated layered double hydroxides.Mg\\/Al hydrotalcites with selenite in the interlayer were prepared at different

Rui Liu; Ray L. Frost; Wayde N. Martens

2009-01-01

205

Use of layered double hydroxides and their derivatives as adsorbents for inorganic and organic pollutants  

Microsoft Academic Search

Contamination of surface and groundwaters by hazardous inorganic and organic pollutants has become an increasing threat to the safety of drinking waters. Cleanup of contaminated surface and groundwaters has, therefore, become a major focus of environmental research. Primary objectives of this dissertation study were to examine the adsorption properties of layered double hydroxides (LDHs) and their derivatives for inorganic and

Youwen You

2002-01-01

206

Zn-Al layered double hydroxide prepared at different molar ratios: Preparation, characterization, optical and dielectric properties  

SciTech Connect

The co-precipitation method was used to prepare Zn-Al-NO{sub 3}-LDH at different Zn{sup 2+}/Al{sup 3+} molar ratios (2, 3, 4, 5 and 6) and pH value of 7.5. The structure, textural, composition and morphological properties were investigated using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) and scanning electron microscope (SEM), respectively. The crystallinity of LDH samples were found to improve as molar ratio decreased which is attributed to the distortion of the hydroxide layers networks of the LDH crystal by the larger difference in ionic radii of Zn{sup 2+} and Al{sup 3+}. The optical band gap energy of LDH samples were evaluated using absorbance data from UV-Vis-NIR Diffuse reflectance spectroscopy. Band gaps were affected by the variation of the Zn{sup 2+}/Al{sup 3+} molar ratio is due to the formation of the low crystalline phases (ZnO and ZnAl{sub 2}O{sub 4}). The water molecules and anionic NO{sub 3}{sup -} in the LDH interlayer were responsible for the generation of the dielectric response. This response can be described by an anomalous low frequency dispersion using the second type of Universal Power Law. The dominance of ZnO dipoles and charge carriers (NO{sub 3}{sup -} ions) in the dielectric relaxation increases with the increasing molar ratio. - Graphical abstract: (a) Schematic diagram of Zn-Al- NO{sub 3}-LDH shows the LDH structure, (b) Kubelka-Munk transformed reflectance spectra and c. The dielectric constant versus frequency of Zn-Al- NO{sub 3}-LDH samples. Highlights: Black-Right-Pointing-Pointer Zn-Al-NO{sub 3}-LDH was prepared at different Zn{sup 2+}/Al{sup 3+} molar ratios (2, 3, 4, 5 and 6). Black-Right-Pointing-Pointer The crystallinity of LDH phase decreased with increase of Zn{sup 2+}/Al{sup 3+} molar ratio. Black-Right-Pointing-Pointer The optical band gaps of LDH samples have been measured. Black-Right-Pointing-Pointer Dielectric response of LDH can be described by anomalous low frequency dispersion.

Ahmed, Abdullah Ahmed Ali [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Talib, Zainal Abidin, E-mail: zainalat@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Zobir bin Hussein, Mohd [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Zakaria, Azmi [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

2012-07-15

207

Successful transfer of plasmid DNA into in vitro cells transfected with an inorganic plasmid-Mg\\/Al-LDH nanobiocomposite material as a vector for gene expression  

Microsoft Academic Search

The delivery of a full plasmid, encoding the green fluorescent protein gene into African monkey kidney (Vero3) cells, was successfully achieved using nanobiocomposites based on layered double hydroxides. This demonstrated the potential of using the system as an alternative DNA delivery vector. Intercalation of the circular plasmid DNA, pEGFP-N2, into Mg\\/Al-NO3- layered double hydroxides (LDH) was accomplished through anion exchange

Mas Jaffri Masarudin; Khatijah Yusoff; Raha Abdul Rahim; Mohd Zobir Hussein

2009-01-01

208

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

209

Intercalation studies of zinc hydroxide chloride: Ammonia and amino acids  

SciTech Connect

Zinc hydroxide chloride (ZHC) is a layered hydroxide salt with formula Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}2H{sub 2}O. It was tested as intercalation matrix for the first time and results were compared with intercalation products of the well-known zinc hydroxide nitrate and a Zn/Al layered double hydroxide. Ammonia was intercalated into ZHC, while no significant intercalation occurred in ZHN. Aspartic acid intercalation was only achieved by co-precipitation at pH=10 with ZHC and pH=8 with zinc hydroxide nitrate. Higher pH resistance in ZHC favored total deprotonation of both carboxylic groups of the Asp molecule. ZHC conferred more thermal protection against Asp combustion presenting exothermic peaks even at 452 Degree-Sign C while the exothermic event in ZHN was 366 Degree-Sign C and in the LDH at 276 Degree-Sign C. - Graphical abstract: The zinc hydroxide chloride (ZHC) with formula Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}2H{sub 2}O was tested as intercalation matrix. In comparison with the well-known zinc hydroxide nitrate (ZHN) and layered double hydroxides (LDH), ZHC was the best matrix for thermal protection of Asp combustion, presenting exothermic peaks even at 452 Degree-Sign C, while the highest exothermic event in ZHN was at 366 Degree-Sign C, and in the LDH it was at 276 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Zinc hydroxide chloride (ZHC) was tested as intercalation matrix for the first time. Black-Right-Pointing-Pointer ZHC has higher chemical and thermal stability than zinc hydroxide nitrate and LDH. Black-Right-Pointing-Pointer NH{sub 3} molecules can be intercalated into ZHC. Black-Right-Pointing-Pointer The amino group of amino acids limits the intercalation by ion-exchange.

Arizaga, Gregorio Guadalupe Carbajal, E-mail: gregoriocarbajal@yahoo.com.mx [Departamento de Quimica, Universidad de Guadalajara, Marcelino Garcia Barragan 1421, CP 44430, Guadalajara, Jalisco, Mexico (Mexico)

2012-01-15

210

Synthesis and adsorption properties of nanosized Mg-Al layered double hydroxides with Cl-, NO{3/-} or SO{4/2-} as interlayer anion  

NASA Astrophysics Data System (ADS)

Nanosized Mg-Al layered double hydroxides (LDHs) with Cl-, NO{3/-} or SO{4/2-} as the interlayer anion have been synthesized by a modified coprecipitation method. The obtained LDHs were confirmed to be composed of a single phase and to be highly substituted by Al (Mg/Al ratio ˜1.9). The abilities of the LDHs to adsorb several harmful anions (F-, CrO{4/2-}, HAsO{4/2-} and HSeO3-) in aqueous solution were studied. The LDHs exhibit high adsorption abilities. The amount of adsorption onto the LDHs differed between the starting interlayer anions, and decreased in the following order of the interlayer anions: NO{3/-} > Cl- > SO{4/2-}. The NO3-formed Mg-Al LDH reached a CrO{4/2-} adsorption equilibrium state within only 30 min, much faster than those in previous reports. Thus, the nanocrystallized, highly Al substituted phase of the NO3-formed Mg-Al LDH is found to markedly enhance the anion adsorption ability.

Hongo, T.; Wakasa, H.; Yamazaki, A.

2011-06-01

211

Enhanced photocatalytic performances of hierarchical ZnO/ZnAl2O4 microsphere derived from layered double hydroxide precursor spray-dried microsphere.  

PubMed

Layered double hydroxides (LDHs), also called hydrotalcites, have been widely investigated for degradation of dye molecules, in the forms of direct photocatalysts, supports or precursors to ZnO-containing photocatalysts. LDH precursor-derived ZnO/ZnAl2O4 photocatalytic nanostructures have hitherto been created, involving ZnO/ZnAl2O4 powder and templated hierarchical frameworks with laboratory-scale preparations. We herein report a scalable preparation of ZnO/ZnAl2O4 microsphere derived from ZnAl-LDH precursor spray-dried microsphere. Survey of textural properties shows that ZnO/ZnAl2O4 microspheres maintain the hierarchically spherical feature and the relatively large surface area. Photocatalytic evaluation under UV irradiation shows that the ZnO/ZnAl2O4 microspheres exhibit highly enhanced photodegradation performance to methylene blue (MB) in comparison with the commercial ZnO powder. A preferential photodegradation to methyl orange (MO) of the MO/MB mixture was also observed, which was illustrated experimentally in terms of the favorable interaction and distribution between basic MO molecules and the acidic-site ZnO/ZnAl2O4 photocatalyst. Our results may initiate large-scale production of microspheres with promising photocatalytic performances. PMID:23899457

Huo, Ruijie; Kuang, Ye; Zhao, Zhiping; Zhang, Fazhi; Xu, Sailong

2013-07-12

212

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

213

Sorption of MS2 Bacteriophage to Layered Double Hydroxides: Effects of Reaction Time, pH, and Competing Anions  

Microsoft Academic Search

suggested that some materials such as coal-based media, clay minerals, metal oxides-hydroxides, and activated Batch sorption and column breakthrough studies were conducted carbon could be used for virus removal. For example, to investigate the potential of layered double hydroxides (LDHs) to

Youwen You; George F. Vance; Donald L. Sparks; Jie Zhuang; Yan Jin

214

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

215

Adsorption properties of Mg–Al layered double hydroxides thin films grown by laser based techniques  

Microsoft Academic Search

Powdered layered double hydroxides (LDHs) have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic and\\/or organic molecules. Assembling nano-sized LDHs onto flat solid substrates forming thin films is an expanding area of research due to the prospects of novel applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices.Continuous and adherent

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

216

Calcined layered double hydroxides as a “biomolecular vessel” for bromelain: Immobilization, storage and release  

Microsoft Academic Search

Calcined layered double hydroxide (LDO) has been used as the novel biomolecular vessel for the immobilization, storage as well as release of bromelain. The immobilization is attributed to physical adsorption without affecting the structure of LDO, and the optimum initial amount of bromelain was 20ml of 4mg\\/ml for 1g LDO and the immobilized enzyme activity express was 33.4% at pH

Wenying Shi; Min Wei; Lan Jin; Congju Li

2007-01-01

217

Water dispersible avermectin-layered double hydroxide nanocomposites modified with sodium dodecyl sulfate  

Microsoft Academic Search

Sodium dodecyl sulfate was utilized to modify the avermectin-layered double hydroxide nanohybrids for the preparation of water dispersible nanocomposites, resulting in the successful conversion of hydrophobic surfactant monolayer structure on the solid surface to hydrophilic bilayer. Concentrations of SDS and NaCl had important effects on the bilayer formation, and the highest suspensibility of the obtained nanocomposites reached 97.6%. All the

Jikuan Zhao; Xiaomei Fu; Shouzhi Zhang; Wanguo Hou

2011-01-01

218

Room temperature magnetism in layered double hydroxides due to magnetic nanoparticles.  

PubMed

Some recent reports claiming room temperature spontaneous magnetization in layered double hydroxides (LDHs) have been published; however, the reported materials cause serious concern as to whether this cooperative magnetic behavior comes from extrinsic sources, such as spinel iron oxide nanoparticles. The syntheses of crystalline Fe(3+)-based LDHs with and without impurities have been developed, highlighting the care that must be taken during the synthetic process in order to avoid misidentification of magnetic LDHs. PMID:23795549

Abellán, Gonzalo; Carrasco, Jose A; Coronado, Eugenio

2013-06-24

219

Selenium adsorption on Mg–Al and Zn–Al layered double hydroxides  

Microsoft Academic Search

Layered double hydroxides (LDHs) have high anion exchange capacities that enhances their potential to remove anionic contaminants from aqueous systems. In this study, different Mg–Al and Zn–Al LDHs were synthesized by a coprecipitation method, with the products evaluated for their ability to adsorb selenite (SeO32?) and selenate (SeO42?). Results indicated the adsorption isotherm for SeO32? retention by Mg–Al and Zn–Al

Youwen You; George F Vance; Hongting Zhao

2001-01-01

220

Effect of surfactant concentration on the stacking modes of organo-silylated layered double hydroxides  

Microsoft Academic Search

The effects of the surfactant concentration on the structure, morphology and thermal property of silylated hydrotalcites have been investigated. By in-situ coprecipitation, the surfaces of layered double hydroxides (LDHs) have been modified by using 3-aminopropyltriethoxysilane (APTS) and anionic surfactant, Na-dodecylsulfate (SDS). Two different stacking modes in the resultant materials were detected by X-ray diffraction (XRD). One has an identical structure

Qi Tao; Jie Yuan; Ray L. Frost; Hongping He; Peng Yuan; Jianxi Zhu

2009-01-01

221

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides  

Microsoft Academic Search

A series of layered double hydroxides (LDHs) with different metal cations were synthesized to remove phosphate in waste sludge filtrate from a municipal wastewater treatment plant for phosphorus recovery and to help control eutrophication. The highest phosphate adsorption capacity was obtained by using Zn–Al-2-300, that is LDHs with Zn\\/Al molar ratio of 2 and calcined at 300°C for 4h. Circumneutral

Xiang Cheng; Xinrui Huang; Xingzu Wang; Bingqing Zhao; Aiyan Chen; Dezhi Sun

2009-01-01

222

Thermodynamical and structural insights of orange II adsorption by Mg{sub R}AlNO{sub 3} layered double hydroxides  

SciTech Connect

[Mg{sub 1-x} Al{sub x}(OH){sub 2}][(NO{sub 3}){sub x}, nH{sub 2}O] Layered Double Hydroxide (LDH) sorbents with variable Mg/Al molar (R=(1-x)/x) ratios were investigated for adsorption of azo dye, orange II (OII) at various pH and temperature conditions. Mg{sub 2}AlNO{sub 3} displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg{sub 2}AlNO{sub 3} at 40 {sup o}C. Adsorption isotherms have been fitted using the Langmuir model and free energy of adsorption ({Delta}G{sup o}), enthalpy ({Delta}H{sup o}) and entropy ({Delta}S{sup o}) were calculated. The experimental values for {Delta}G{sup o} in temperature range between 10 and 40 {sup o}C were found to be negative indicating that a spontaneous process occurred. Positive calculated enthalpy values, characteristic of an endothermic process were found. Characterization of solids (PXRD, FTIR, UV-vis, TGA/DTA, adsorption isotherm BET analysis, SEM and Zetametry) before and after adsorption showed that adsorption proceeds in two steps. First, adsorption occurs at the LDH surface, followed by intercalation via anion exchange. -- Graphical Abstract: Structural and thermodynamical insight of adsorption/Intercalation of OII in Mg{sub R}Al LDH Display Omitted Highlights: {yields} The nitrate containing hydrotalcite-like compounds (Mg{sub R}AlNO{sub 3} LDH) were prepared by the coprecipitation method. {yields} Adsorption of anionic orange dye(OII) is studied on LDHs at different temperatures. {yields} The adsorption process is well described by the Langmuir isotherm model. {yields} Mg{sub 2}AlNO{sub 3} displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg{sub 2}AlNO{sub 3} at 40 {sup o}C. {yields} Adsorption process does not occur on the surface of the LDH only but an intercalation process is also occurring concomitantly according to the thermodynamical values.

Mustapha Bouhent, Mohamed [Laboratoire de Physico-Chimie des Materiaux, Catalyse et Environnement, UST d'Oran, Bp 1505 Oran El M'naouer (Algeria); Laboratoire des Materiaux Inorganiques, UMR CNRS 6002, Universite Blaise Pascal, F-63177 Aubiere Cedex (France); Derriche, Zoubir, E-mail: derriche_zoubir@yahoo.co [Laboratoire de Physico-Chimie des Materiaux, Catalyse et Environnement, UST d'Oran, Bp 1505 Oran El M'naouer (Algeria); Denoyel, Renaud [MADIREL, Laboratoire Chimie Provence, Universite d'Aix-Marseille I, II et III, UMR CNRS 6264, Campus de Saint Jerome, Avenue Escadrille-Normandie-Niemen, F-13397 Marseille Cedex 20 (France); Prevot, Vanessa; Forano, Claude [Laboratoire des Materiaux Inorganiques, UMR CNRS 6002, Universite Blaise Pascal, F-63177 Aubiere Cedex (France)

2011-05-15

223

[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

224

Acid fuchsin-interleaved Mg–Al-layered double hydroxide for the formation of an organic–inorganic hybrid nanocomposite  

Microsoft Academic Search

Layered organic–inorganic hybrid nanocomposite, containing an organic dye in an inorganic interlayer was prepared using acid fuchsin (AF) as a guest in Mg–Al layered double hydroxide inorganic host by a self-assembly technique, with the Mg–Al ratio in the mother liquor of 4 and pH=7.5. Powder X-ray diffractogram shows that the basal spacing of the Mg–Al layered double hydroxide with nitrate

Mohd Zobir bin Hussein; Asmah Hj Yahaya; Mohd Shamsul; Hairi Mohd Salleh; Taufiq Yap; Jacqueline Kiu

2004-01-01

225

Interplay between chemical composition and cation ordering in the magnetism of Ni/Fe layered double hydroxides.  

PubMed

We report the synthesis of a family of ferrimagnetic NiFe layered double hydroxides (LDHs) with a variable Ni(2+)/Fe(3+) in-plane composition of [Ni(1-x)Fe(x)(OH)2](CO3)(x/2)·yH2O (x = 0.20, 0.25, and 0.33) by following a modified homogeneous precipitation. These layered magnets display high crystallinity, homogeneous hexagonal morphologies, and micrometric size that enable their quantitative exfoliation into single layers by sonomechanical treatment of the solids in polar solvents. This was confirmed by dynamic light scattering, UV-vis spectroscopy, high-resolution transmission electron miscroscopy, and atomic force microscopy methodologies to study the resulting steady suspensions. Our magnetic study reflects that the iron content in the LDH layers controls the overall magnetism of these lamellae. Hence, the gradual replacement of Ni(2+) with Fe(3+) centers introduces a larger amount of antiferromagnetically coupled Fe-OH-Fe pairs across the layers, provoking that the compound with the highest Fe/Ni ratio displays spontaneous magnetization at higher temperatures (T(irr) = 15.1 K) and the hardest coercive field (3.6 kG). Mössbauer spectroscopy confirms that the cation distribution in the layers is not random and reflects the occurrence of Fe clustering due to the higher affinity of Fe(3+) ions to accommodate other homometallic centers in their surroundings. In our opinion, this clarifies the origin of the glassy behavior, also reported for other magnetic LDHs, and points out spin frustration as the most likely cause. PMID:23961761

Abellán, Gonzalo; Coronado, Eugenio; Martí-Gastaldo, Carlos; Waerenborgh, Joao; Ribera, Antonio

2013-08-20

226

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

227

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

228

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

229

Structure and surface characteristics of Cu-based composite metal oxides derived from layered double hydroxides  

Microsoft Academic Search

Layered double hydroxides (LDHs) with Cu2+\\/Zn2+\\/Al3+ atomic ratios from 1:1:1 to 3:1:1 have been synthesized by coprecipitation method. The physicochemical properties of both the as-synthesized LDHs and their calcined products obtained at 773K for 3h have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), chemical analysis, transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), N2

Lihong Zhang; Feng Li; David G. Evans; Xue Duan

2004-01-01

230

Characterization of adsorbed arsenate on amorphous and nano crystalline MgFe-layered double hydroxides  

Microsoft Academic Search

This article investigated sorption of toxic and carcinogenic arsenate (AsO4\\u000a 3?) ions on positively charged surface of amorphous and nano crystalline MgFe-layered double hydroxides (LDHs). Based on Brunauer–Emmett–Teller\\u000a (BET) and Transmission Electron Microscopy (TEM), average size, and specific surface area of nano crystalline MgFe-LDHs, which\\u000a was about range of about 50–200 nm and 90.2 m2\\/g, was lower and higher when compared to

Joo-Yang Park; Jung-Hwan Kim

2011-01-01

231

A study on the structure and electrochemical characteristics of a Ni\\/Al double hydroxide  

Microsoft Academic Search

Aluminium-substituted nickel based layered double hydroxides (LDHs), Ni0.78Zn0.04Co0.04Co0.02Al0.16(OH)2(CO3)0.08· 1.0H2O, were synthesized by a chemical co-precipitating process. It was shown that the structure of the LDHs is similar with that\\u000a of ?-Ni(OH)2 investigated by X-ray diffraction and transmission electron microscopy. The electrode comprising the LDHs was charged\\/discharged\\u000a according to a galvanostatic model, and displayed better discharge capacity than the common ?-Ni(OH)2

Fu Zhong Zhen; Jiang Wen Quan; Yu Li Min; Zhang Peng; Jiang Li Jun

2004-01-01

232

Anion exchange in Zn-Al layered double hydroxides: In situ X-ray diffraction study  

NASA Astrophysics Data System (ADS)

Anion exchange capacity is a key factor for the application of Zn-Al layered double hydroxides (LDHs) as nano-containers in active corrosion protection. In this work, the nitrate-pyrovanadate anion exchange/re-exchange processes in these LDHs were investigated in situ. We demonstrate that the exchange reactions lead to a decrease of the average crystallite size of LDHs as a result of mechanical fragmentation of the crystallites rather than dissolution/recrystallization. The fragmentation occurs due to fast anion exchange in the initial stage, and can be controlled by changing the ratio of the available substituent anions to the replacement anions and application of a mechanical activation.

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

2010-07-01

233

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

234

Co-Ni layered double hydroxides for water oxidation in neutral electrolyte.  

PubMed

The electrochemical properties of Co-Ni layered double hydroxides (LDHs) as efficient electrocatalysts for water oxidation were investigated in potassium phosphate electrolyte under neutral pH condition. The Co-Ni LDHs with a core-shell structure were fabricated using a facile route from a Co-Ni hydroxide precursor with iodine as a topotactic oxidizer. The unique core-shell morphology is likely due to the enrichment of Co(III) hydroxide in the inner core indicated by selected area electron diffraction and energy-dispersive spectroscopy. Through a self-assembling process at the organic/inorganic interface and dip-coating, the Co-Ni LDHs were deposited onto FTO glass substrates to prepare composite electrodes. Low over-potential and high current density was achieved in the oxygen evolution reaction. The excellent electrocatalytic activity of Co-Ni LDHs may be attributed to more accessible Co active sites and rapid movement of interlayer ions within their layered structure. PMID:23579333

Zhang, Ye; Cui, Bai; Zhao, Chunsong; Lin, Hong; Li, Jianbao

2013-05-21

235

Degradability Enhancement of Poly(Lactic Acid) by Stearate-Zn(3)Al LDH Nanolayers.  

PubMed

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-Zn(3)Al LDH. A solution casting method was used to prepare PLA/stearate-Zn(3)Al LDH nanocomposites. The anionic clay Zn(3)Al 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-Zn(3)Al 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-Zn(3)Al LDH lost its ordered stacking-structure and was greatly exfoliated in the PLA matrix. Tensile test results of PLA/stearate-Zn(3)Al LDH nanocomposites showed that the presence of around 1.0-3.0 wt % of the stearate-Zn(3)Al 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-Zn(3)Al 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. PMID:22942682

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

2012-06-26

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

Mg/Al Ordering in Layered Double Hydroxides Revealed by Multinuclear NMR Spectroscopy  

SciTech Connect

The anion-exchange ability of layered double hydroxides (LDHs) has been exploited to create materials for use in catalysis, drug delivery, and environmental remediation. The specific cation arrangements in the hydroxide layers of hydrotalcite-like LDHs, of general formula Mg2+1–xAl3+xOH2(Anionn– x/n)·yH2O, have, however, remained elusive, and their elucidation could enhance the functional optimization of these materials. We applied rapid (60 kilohertz) magic angle spinning (MAS) to obtain high-resolution hydrogen-1 nuclear magnetic resonance (1H NMR) spectra and characterize the magnesium and aluminum distribution. These data, in combination with 1H-27Al double-resonance and 25Mg triple-quantum MAS NMR data, show that the cations are fully ordered for magnesium:aluminum ratios of 2:1 and that at lower aluminum content, a nonrandom distribution of cations persists, with no Al3+-Al3+ close contacts. The application of rapid MAS NMR methods to investigate proton distributions in a wide range of materials is readily envisaged.

Sideris, Paul J.; Nielsen, Ulla G.; Gan, Zhehong; Grey, Clare P.

2008-07-04

238

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

239

Adsorption of Reactive Orange 16 from aqueous solutions by MgAlNO3-LDH: Kinetic and equilibrium studies  

Microsoft Academic Search

An anionic MgAlNO3 layered double hydroxides (MgAlNO3-LDH) with Mg\\/Al molar ratio 4?1, was investigated for its ability to adsorb an anionic dye, Reactive Orange 16 (RO16), with the objective of evaluating its suitability as an adsorbent. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. Equilibrium data fitted well with Langmuir model for the concentration range of

Siti Mariam Sumari; Zaini Hamzah; Yamin Yasin

2010-01-01

240

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

241

Zinc/Aluminum layered double hydroxide-titanium dioxide composite nanosheet film as novel solid phase microextraction fiber for the gas chromatographic determination of valproic acid.  

PubMed

A nanosheet thin film based on Zn/Al layered double hydroxide (LDH) and TiO(2) composite was prepared via sol-gel process on capillary glass rod. Characterization of the fiber coating using X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) images showed that it consists of a large number of intercrossed and curved nanosheets with hexagonal architecture. The thickness of these plates is about few nanometers, and the lateral dimension is varying from 400 to 1000 nm. Application of the proposed coating as a solid phase microextraction fiber was investigated. As a model analyte, valproic acid (VPA, antiepileptic drug) was selected and its extraction from biological (human serum) and pharmaceutical (tablet and syrup) samples were performed without any considerable matrix effect. Analytical merits of the method, under optimum conditions (extraction temperature: 50 ± 1°C, extraction time: 15 min, desorption temperature: 250°C, desorption time: 2 min, solution pH: 1.5, salt concentration: 5 mol L(-1)), are 70 ?g L(-1) and 0.20-100 mg L(-1) for LOD and LDR, respectively. PMID:23200379

Matin, Amir Abbas; Biparva, Pourya; Amanzadeh, Hatam; Farhadi, Khalil

2012-10-16

242

Folic acid conjugated self-assembled layered double hydroxide nanoparticles for high-efficacy-targeted drug delivery.  

PubMed

Enhanced selectivity and efficacy is important for advanced drug delivery. Herein, a novel type of folic acid conjugated self-assembled layered double hydroxide nanoparticles is reported. These nanoparticles have a drug loading capacity of 27 wt% and are able to enter cell nuclei and dramatically improve the efficacy of MTX. PMID:24129414

Yan, Li; Chen, Wei; Zhu, Xiaoyue; Huang, Longbiao; Wang, Zhigang; Zhu, Guangyu; Roy, V A L; Yu, K N; Chen, Xianfeng

2013-10-29

243

Influence of M II\\/M III ratio in surface-charging behavior of Zn–Al layered double hydroxides  

Microsoft Academic Search

Zn–Al layered double hydroxides with different MII\\/MIII ratios were synthesized by the coprecipitation method and the obtained solids were characterized by powder X-ray diffraction, infrared spectroscopy, acid–base potentiometric titrations, electrophoretic mobility and modeling of the electrical double layer. As general behavior, increasing hydroxyl adsorption with increasing pH and decreasing supporting electrolyte concentration takes place between pH 7 and 12. The

R. Rojas Delgado; C. P. De Pauli; C. Barriga Carrasco; M. J. Avena

2008-01-01

244

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

245

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

Microsoft Academic Search

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

2007-01-01

246

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

247

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

248

Hydrolysis of mixed Ni(2+)-Fe(3+) and Mg(2+)-Fe(3+) solutions and mechanism of formation of layered double hydroxides.  

PubMed

The hydrolytic behavior of mixed metallic solutions containing Ni(2+)-Fe(3+) and Mg(2+)-Fe(3+) has been studied with respect to the relative proportion of the divalent and trivalent cations in solution as well as the quantity of NaOH added. The combination of X-ray diffraction and vibrational spectroscopy provides a deep insight into both the nature of the phases and the structure of the formed LDH. The relative abundance of each phase is determined by using a mass balance diagram and is in good agreement with the solid characterization. We showed that the slow hydrolysis of mixed metallic solutions involved first the precipitation of Fe(3+) to form an akaganeite phase, and then the formation of a precursor on the iron oxyhydroxide surface, which transforms into LDH by diffusion of Fe(III) species from the akaganeite phase to the precursor. Interestingly, whatever the iron content in solution, the same fraction of Fe(III) is incorporated into the LDH phase which is correlated to the nature of the formed precursor. For Ni(2+)-Fe(3+) solution, the precursor is an ?-Ni hydroxide, which formed a LDH phase with a very low iron content (xlayer = 0.1), but a high charge density provided by structural hydroxyl default. This result unambiguously demonstrated that the LDH phase is formed from the precursor structure. For Mg(2+)-Fe(3+) solution, the precursor is structurally equivalent to a ?-Mg(OH)2 phase, leading to a LDH with a higher xlayer value of ?0.2. In both cases, at the end of the titration experiments, a mixture of different phases was systematically observed. Hydrothermal treatment allows the recovery of a pure LDH phase exclusively for the Ni(2+)-Fe(3+) solution. PMID:24048362

Grégoire, Brian; Ruby, Christian; Carteret, Cédric

2013-10-22

249

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

2013-01-08

250

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

251

Glucose oxidase immobilized in alginate/layered double hydroxides hybrid membrane and its biosensing application.  

PubMed

A new type of amperometric glucose biosensor based on alginate (Alg)/layered double hydroxides (LDHs) organic-inorganic composite film is described. This hybrid material combines the advantages of an organic biopolymer, Alg and inorganic LDHs. Glucose oxidase (GOD) immobilized in the material maintained its activity. The composite films were characterized by UV-Vis. The results indicated that GOD retained the essential feature of its native structure in the composite film. The Alg/LDHs/GOD-modified platinum electrode exhibited a fast response to glucose (achieve 95% of the maximum in 10 s), which provided a linear response to glucose over a concentration range of 1.6 x 10(-5)-2 x 10(-3) M with a detection limit of 4 x 10(-5) M based on S/N = 3. Furthermore, the biosensor exhibited excellent long-term stability, and satisfactory reproducibility. It retained 87% of its original activity after being used for 28 days. PMID:20009328

Ding, Shou-Nian; Shan, Dan; Xue, Huai-Guo; Zhu, Dao-Bin; Cosnier, Serge

2009-12-01

252

Synthesis and UV absorption properties of 5-sulfosalicylate-intercalated Zn Al layered double hydroxides  

NASA Astrophysics Data System (ADS)

5-sulfosalicylic acid (SSA) anions have been intercalated into layered double hydroxides (LDHs) by an anion-exchange reaction using ZnAl NO3 LDHs as a precursor. The samples were characterized by XRD, FT-IR, TG-DTA/MS and UV visible spectroscopy. The results show that the NO3- anions in the precursor have been completely replaced by SSA anions to give ZnAl SSA LDHs having a high degree of crystallinity. Detailed studies reveal the existence of a supramolecular structure in ZnAl SSA LDHs involving electrostatic attraction between opposite charges, hydrogen bonding and other weak chemical bonding interactions between host layers and SSA anions. The thermal stability of ZnAl SSA LDHs is considerably enhanced compared with that of a mixture of ZnAl NO3 LDHs and SSA. After addition of 2.0 wt% ZnAl SSA LDHs to polypropylene (PP), the resistance of the polymer to UV degradation is significantly improved.

Zhang, Linyan; Lin, Yanjun; Tuo, Zhenjun; Evans, David G.; Li, Dianqing

2007-04-01

253

Preparation and characterization of "dextran-magnetic layered double hydroxide-fluorouracil" targeted liposomes.  

PubMed

This work was aimed at assessing the preparation and characteristics of "dextran-magnetic layered double hydroxide-fluorouracil" liposomes (DMFL). DMFL was prepared by the optimized reverse evaporation method, which concerned the entrapment efficiency and slow-released effect. The factors affecting the entrapment efficiency of DMFL were studied using orthogonal design, and the optimum conditions are: weight ratio of lecithin to cholesterol (2:1), weight ratio of lecithin to DMF (7:1), emulsification time (30 min) and temperature (50 °C). The characteristics of optimized DMFL on encapsulation efficiency, mean diameter and pH value were 85.47±0.83, 160.4±0.55 nm and 6.58±0.05, respectively. In vitro drug release profile of DMFL followed the Higuchi release model equation Q=9.2338t(1/2)+22.821. The magnetic targeting results showed that DMFL had sensitive magnetic targeted responsibility. The results of XRD, FT-IR and TEM indicated that the structure and property of DMF were not destroyed during the process of forming DMFL, and the phospholipid bilayer and the hexagonal skeleton DMF were obvious and complete after being lyophilized powder. This lyophilized method could be used to store the DMFL easily. These results suggested that DMFL had the potential for developing as a practical preparation for administration. PMID:23591010

Huang, Jie; Gou, Guojing; Xue, Bing; Yan, Qianshun; Sun, Yue; Dong, Li-E

2013-04-13

254

Incorporation of rare-earth ions in Mg-Al layered double hydroxides: intercalation with an [Eu(EDTA)]- chelate  

NASA Astrophysics Data System (ADS)

Reaction of an aqueous slurry of an Mg2Al-NO3 layered double hydroxide with a four-fold excess of Na[Eu(EDTA)] gives a material which analyses for Mg0.68Al0.32(OH)2[Eu(EDTA)]0.10(CO3)0.11·0.66H2O. The interlayer spacing of the material is 13.8 Å, corresponding to a gallery height of 9.0 Å, which accords with the maximal dimensions (9-10 Å) of the anion in metal-EDTA complex salts as determined by single crystal X-ray diffraction. Geometrical considerations show that the charge density on the layered double hydroxide layers is too high to be balanced by intercalation of [Eu(EDTA)]- alone, necessitating the co-intercalation of carbonate ions which have a much higher charge density.

Li, Cang; Wang, Ge; Evans, David G.; Duan, Xue

2004-12-01

255

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

Microsoft Academic Search

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

Hui Zhang; Xing Wen; Yingxia Wang

2007-01-01

256

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

257

Mg and Ni-containing layered double hydroxides as soda substitutes in the aldol condensation of acetone  

Microsoft Academic Search

A series of layered double hydroxides (LDHs) containing Mg2+ or Ni2+ as divalent and Al3+ or Ga3+ as trivalent cations were used as catalysts in order to substitute NaOH in the selective condensation of acetone into diacetonealcohol. With this aim the LDHs were totally exchanged with OH? anions and acquired the meixnerite-like structure, showing a high concentration of active basic

Federica Prinetto; Didier Tichit; Remi Teissier; Bernard Coq

2000-01-01

258

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

259

Deposition of LDH on plasma treated polylactic acid to reduce water permeability.  

PubMed

A simple and scalable deposition process was developed to prepare polylactic acid (PLA) coatings with enhanced water barrier properties for food packaging applications. This method based on electrostatic interactions between the positively charged layers of layered double hydroxides (LDHs) modified with ionic liquids (ILs) and the negatively charged plasma treated polylactic acid leads to homogeneous, stable, and highly durable coatings. Deposition of the LDH coatings increases the surface hydrophobicity of the neat PLA, which results to a decrease in water permeability by about 35%. PMID:23403108

Bugatti, Valeria; Livi, Sebastien; Hayrapetyan, Suren; Wang, Yue; Estevez, Luis; Vittoria, Vittoria; Giannelis, Emmanuel P

2013-01-24

260

Near-infrared and mid-infrared investigations of Na-dodecylbenzenesulfate intercalated into hydrocalumite chloride (CaAl-LDH-Cl)  

NASA Astrophysics Data System (ADS)

Hydrocalumite (CaAl-LDH-Cl) belongs to layered double hydroxides (LDHs). The intercalation of Na-dodecylbenzenesulfate (SDBS) into CaAl-LDH-Cl has been investigated by X-ray diffraction (XRD), mid-infrared (MIR) spectroscopy and near-infrared (NIR) spectroscopy. The mid-infrared spectra indicated that SDBS could be intercalated into CaAl-LDH-Cl, with the same lattice structure to that of CaAl-LDH-Cl, and the interlayer distance of resultant product was expanded to 2.78 nm as confirmed by XRD. The near-infrared spectra (9200-4000 cm -1) showed that a special spectral range from 6200 to 5600 cm -1 and prominent bands of CaAl-LDH-Cl intercalated with SDBS around 8300 cm -1. This band was assigned to the second overtone of the first fundamental of C-H stretching vibrations of SDBS, and can be used to determinate the result of CaAl-LDH-Cl modified by anionic surfactants. The bands of water stretching vibrations and -OH groups shifted to higher wavenumbers when CaAl-LDH-Cl was intercalated by SDBS, and their intensity of MIR and NIR spectra became lower in intensity.

Zhang, Ping; Qian, Guangren; Cheng, Hongfei; Yang, Jing; Shi, Huisheng; Frost, Ray L.

2011-08-01

261

Pathways of phosphate uptake from aqueous solution by ZnAl layered double hydroxides.  

PubMed

ZnAl layered double hydroxides (LDHs) were prepared by urea hydrolysis-based coprecipitation for removing phosphate from aqueous solutions. The chemical formula of the product was determined as Zn5.54Al3.02(OH)8.73(CO3)0.57Cl5.66·7.84H2O. Chloride ion was the major interlayer anion of the ZnAl LDHs. Adsorption of phosphate onto the ZnAl sorbent over the entire study period was not in close agreement with pseudo-first-order or pseudo-second-order models. The adsorption can be divided into two steps. A fast adsorption was observed during the first 10 h with a marked increase in the concentration of Cl(-) in the bulk solution. This indicated that the adsorption of phosphate was largely attributed to the ion exchange between phosphate and the interlayer Cl(-). A second fast adsorption of phosphate occurred after 10 h. During this period, the pH increased slowly, whereas the Cl(-) concentration was stable. The uptake of phosphate was likely attributed to OH(-)-H2PO4(-)/HPO4(2-) ion exchange as well as surface adsorption/complexation. Acidic conditions favored adsorption of phosphate by ZnAl LDHs, which is consistent with the pH increases during the adsorption. Coexisting anions, e.g., SO4(2-) and CO3(2-), are competitive ions for the adsorption of phosphate. The results verify the contribution of ion exchange and surface adsorption/complexation in the removal of phosphate by ZnAl LDHs. PMID:23579830

Cheng, X; Wang, Y; Sun, Z; Sun, D; Wang, A

2013-01-01

262

Spongy gel-like layered double hydroxide-alkaline phosphatase nanohybrid as a biosensing material.  

PubMed

Formation of new bio-nanohybrid material was obtained by immobilization of alkaline phosphatase within a Mg(2)Al LDH by "soft chemistry" coprecipitation synthesis, resulting in an original spongy gel-like morphology allowing the preservation of the enzyme structure and activity even at low pH values thanks to the buffering property of the basic host structure. PMID:18354797

Geraud, Erwan; Prevot, Vanessa; Forano, Claude; Mousty, Christine

2008-01-28

263

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

264

Flexible CoAl LDH@PEDOT core/shell nanoplatelet array for high-performance energy storage.  

PubMed

A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction. PMID:22961997

Han, Jingbin; Dou, Yibo; Zhao, Jingwen; Wei, Min; Evans, David G; Duan, Xue

2012-09-10

265

Mössbauer and XRD investigations of layered double hydroxides (LDHs) with varying Mg/Fe ratios  

NASA Astrophysics Data System (ADS)

The effects of the Mg(II)/Fe(III) ratio on the structure and Fe microenvironments in MgFe LDH substances were investigated. The LDHs were prepared by the co-precipitation method with Mg(II)/Fe(III) ratios from 2:1 to 6:1. The materials were characterized by 57Fe Mössbauer spectroscopy and powder X-ray diffractometry. The 57Fe Mössbauer spectra exhibited asymmetric doublet corresponding to high-spin Fe(III) microenvironments in all LDH structure. It was found that the quadrupole splitting decreased with increasing Mg(II)/Fe(III)ratio reflecting change in the electric field gradient due to the incorporation of different amounts of iron into the Mg-containing layers.

Sipiczki, Mónika; Kuzmann, Ern?; Homonnay, Zoltán; Megyeri, József; Kovács, Krisztina; Pálinkó, István; Sipos, Pál

2013-04-01

266

Preparation and photocatalytic behavior of Zn\\/Al\\/W(Mn) mixed oxides via polyoxometalates intercalated layered double hydroxides  

Microsoft Academic Search

Zn\\/Al\\/W(Mn) mixed oxides were prepared via calcination of the precursors of monovacant and monosubstituted Keggin type polyoxometalate (POM) intercalated layered double hydroxides (LDHs) such as Zn2Al(OH)6[SiW11O39]0.12·0.2H2O and Zn2Al(OH)6[SiW11O39Mn(H2O)]0.16·0.3H2O at 600–700 °C. The physicochemical properties of the products were characterized by the methods of powder X-ray diffraction, elemental analysis, scanning electron microscopy, UV diffusion reflectance spectroscopy, infrared spectroscopy, thermogravimetric analysis, electron

Yihang Guo; Danfeng Li; Changwen Hu; Enbo Wang; Yongchun Zou; Hong Ding; Shouhua Feng

2002-01-01

267

Thermal behaviour of Cu–Mg–Mn and Ni–Mg–Mn layered double hydroxides and characterization of formed oxides  

Microsoft Academic Search

Thermal behaviour of synthetic Cu–Mg–Mn and Ni–Mg–Mn layered double hydroxides (LDHs) with MII\\/Mg\\/Mn molar ratio of 1:1:1 was studied in the temperature range 200–1100 °C by thermal analysis (TG\\/DTA\\/EGA), powder X-ray diffraction (XRD), Raman spectroscopy, and voltammetry of microparticles. Powder XRD patterns of prepared LDHs showed characteristic hydrotalcite-like phases, but further phases were indirectly found as admixtures. The Cu–Mg–Mn precipitate

František Kovanda; Tomáš Grygar; Vít Dorni?ák; Tomáš Rojka; Petr Bezdi?ka; Kv?ta Jirátová

2005-01-01

268

LDH variants in India  

Microsoft Academic Search

17 examples of genetically controlled variation of LDH have been encountered in a survey of 1331 Indian blood samples collected in Calcutta and Madras. 15 of the variants (10 in Calcutta and 5 in Madras) were identical and have been given the trivial name ‘Calcutta-1’. The other 2 examples were found in Madras and have been called ‘Madras-1’. ‘Calcutta-1’ is

S. R. Das; B. N. Mukherjee; S. K. Das; R. ANANTHAKRISItNAN; N. M. Blake; R. L. Kirk

1970-01-01

269

Synthesis of layered zinc hydroxide chlorides in the presence of Al(III)  

SciTech Connect

Zinc hydroxide chloride particles were synthesized by hydrolysis of ZnCl{sub 2} solutions dissolving AlCl{sub 3} at different atomic Al/Zn ratios from 0 to 1.0 and characterized by various techniques. Increasing Al/Zn ratio changed the crystal phases of the products as ZnO{sup {yields}}ZnO+ZHC (Zn{sub 5}(OH){sub 8}Cl{sub 2}.H{sub 2}O){sup {yields}}ZHC{sup {yields}}LDH (layered double hydroxides, Zn-Al-Cl) and the particle morphology as agglomerates (ZnO){sup {yields}}fine particles (ZnO){sup {yields}}plates (ZHC)+rods (ZnO){sup {yields}}plates (ZHC){sup {yields}}plates (LDH). The atomic Cl/Zn ratios of LDH particles formed at Al/Zn{>=}0.3 were ca. 0.3 despite the increase of Al/Zn ratio, being due to the intercalation of CO{sub 3} {sup 2-} into the LDH crystal. The OH{sup -} content of LDH estimated by TG was reduced by the deprotonation of OH{sup -} to counteract the excess positive charge produced by replacing Zn(II) with Al(III). ZHC exhibited a high adsorption selectivity of H{sub 2}O.

Ishikawa, Tatsuo [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan)]. E-mail: ishikawa@cc.osaka-kyoiku.ac.jp; Matsumoto, Kumi [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Kandori, Kazuhiko [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Nakayama, Takenori [Materials Research Laboratory, Kobe Steel, Ltd., 5-5 Takatsukadai 1-Chome, Nishi-ku, Kobe, Hyogo 615-2271 (Japan)

2006-04-15

270

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

271

Synthesis and physical properties of new layered double hydroxides based on ionic liquids: application to a polylactide matrix.  

PubMed

Ionic liquids based on tetraalkylphosphonium salts combined with different anions (decanoate and dodecylsulfonate) have been used as intercalating agents of layered double hydroxides (LDHs) by ion exchange. The synthesized phosphonium-treated LDHs display a dramatically improved thermal degradation and a significant increase in the interlayer distance as confirmed by thermogravimetric analysis (TGA) and X-ray Diffraction (XRD), respectively. To highlight the effect of thermostable ionic liquids, a very low amount of LDHs has been introduced within a polylactide (PLA) matrix and PLA/LDHs nanocomposites have been processed in melt by twin-screw extrusion. Then, transmission electron microscopy (TEM) analysis has been used to investigate the influence of ILs on the different morphologies of these nanocomposites. Even though the thermal stability of PLA matrix decreased, an excellent stiffness-toughness compromise has been obtained. PMID:22999461

Livi, Sébastien; Bugatti, Valeria; Estevez, Luis; Duchet-Rumeau, Jannick; Giannelis, Emmanuel P

2012-08-28

272

The Synthesis and Characterization of Gold-Core/LDH-Shell Nanoparticles  

NASA Astrophysics Data System (ADS)

In recent years, the field of nanomedicine has progressed at an astonishing rate, particularly with respect to applications in cancer treatment and molecular imaging. Although organic systems have been the frontrunners, inorganic systems have also begun to show promise, especially those based upon silica and magnetic nanoparticles (NPs). Many of these systems are being designed for simultaneous therapeutic and diagnostic capabilities, thus coining the term, theranostics. A unique class of inorganic systems that shows great promise as theranostics is that of layered double hydroxides (LDH). By synthesis of a core/shell structures, e.g. a gold nanoparticle (NP) core and LDH shell, the multifunctional theranostic may be developed without a drastic increase in the structural complexity. To demonstrate initial proof-of-concept of a potential (inorganic) theranostic platform, a Au-core/LDH-shell nanovector has been synthesized and characterized. The LDH shell was heterogeneously nucleated and grown on the surface of silica coated gold NPs via a coprecipitation method. Polyethylene glycol (PEG) was introduced in the initial synthesis steps to improve crystallinity and colloidal stability. Additionally, during synthesis, fluorescein isothiocyanate (FITC) was intercalated into the interlayer spacing of the LDH. In contrast to the PEG stabilization, a post synthesis citric acid treatment was used as a method to control the size and short-term stability. The heterogeneous core-shell system was characterized with scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), dynamic light scattering (DLS), and powder x-ray diffraction (PXRD). A preliminary in vitro study carried out with the assistance of Dr. Kaushal Rege's group at Arizona State University was to demonstrate the endocytosis capability of homogeneously-grown LDH NPs. The DLS measurements of the core-shell NPs indicated an average particle size of 212nm. The PXRD analysis showed that PEG greatly improved the crystallinity of the system while simultaneously preventing aggregation of the NPs. The preliminary in vitro fluorescence microscopy revealed a moderate uptake of homogeneous LDH NPs into the cells.

Rearick, Colton

273

The influence of carbon nanotubes, organically modified montmorillonites and layered double hydroxides on the thermal degradation and fire retardancy of polyethylene, ethyleneevinyl acetate copolymer and polystyrene  

Microsoft Academic Search

Nanocomposites of polyethylene, ethyleneevinyl acetate copolymer and polystyrene with single- and multi-wall carbon nanotubes, organi- cally 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

Marius C. Costache; Matthew J. Heidecker; E. Manias; Giovanni Camino; Alberto Frache; Gunter Beyer; Rakesh K. Gupta; Charles A. Wilkie

274

Graphene as a carbon source effects the nanometallurgy of nickel in Ni,Mn layered double hydroxide-graphene oxide composites.  

PubMed

Thermal treatment of the hybrid material formed by the spontaneous precipitation of graphene oxide and Ni,Mn layered double hydroxide leads to the segregation of nickel metal nanoparticles (Ni NPs) and the decomposition of graphene to CO(2). Increasing the temperature increases the Ni NP size and results in the complete disappearance of graphene. PMID:23086405

Abellán, Gonzalo; Latorre-Sánchez, Marcos; Fornés, Vicente; Ribera, Antonio; García, Hermenegildo

2012-10-19

275

Successful transfer of plasmid DNA into in vitro cells transfected with an inorganic plasmid-Mg/Al-LDH nanobiocomposite material as a vector for gene expression  

NASA Astrophysics Data System (ADS)

The delivery of a full plasmid, encoding the green fluorescent protein gene into African monkey kidney (Vero3) cells, was successfully achieved using nanobiocomposites based on layered double hydroxides. This demonstrated the potential of using the system as an alternative DNA delivery vector. Intercalation of the circular plasmid DNA, pEGFP-N2, into Mg/Al-NO3- layered double hydroxides (LDH) was accomplished through anion exchange routes to form the nanobiocomposite material. The host was previously synthesized at the Mg2+ to Al3+ molar ratio Ri = 2 and subsequently intercalated with plasmid DNA. Size expansion of the interlamellae host from 8.8 Å in LDH to 42 Å was observed in the resulting nanobiocomposite, indicating stable hybridization of the plasmid DNA. The powder x-ray diffraction (PXRD) results, supplemented with Fourier-transform infrared (FTIR) spectroscopy, compositional and electrophoresis studies confirmed the encapsulation episode of the biomaterial. In order to elucidate the use of this resulting nanobiocomposite as a delivery vector, an MTT assay was performed to determine any cytotoxic effects of the host towards cells. The intercalated pEGFP-N2 anion was later successfully recovered through acidification with HNO3 after treatment with DNA-degrading enzymes, thus also showing the ability of the LDH host to protect the intercalated biomaterial from degradation. Cell transfection studies on Vero3 cells were then performed, where cells transfected with the nanobiocomposite exhibited fluorescence as early as 12 h post-treatment compared to naked delivery of the plasmid itself.

Jaffri Masarudin, Mas; Yusoff, Khatijah; Rahim, Raha Abdul; Zobir Hussein, Mohd

2009-01-01

276

Layered double hydroxides reconstructed in NiSO 4 aqueous solution as highly efficient photocatalysts for degrading two industrial dyes  

Microsoft Academic Search

Nanostructured photocatalysts, that can effectively photodegrade the industrial dyes drimaren red and drimaren navy (Clariant Produkte), were obtained by the structural reconstruction of MgAlLDH and MgFeAlLDH anionic clays in NiSO4 aqueous solution. X-ray diffraction (XRD), energy dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), N2 adsorption at 77K and UV–vis

Gabriela Carja; Elena Husanu; Carmen Gherasim; Horia Iovu

2011-01-01

277

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

278

Inorganic layered double hydroxides as ascorbic acid (vitamin C) delivery system--intercalation and their controlled release properties.  

PubMed

ZnFe- and MgFe-LDHs were prepared by the anion exchange method, with the aim of adsorption of the ascorbic acid from the aqueous solutions by ion exchange process between anionic derivatives in LDH (Cl) and the anionic vitamin. This leads to successful intercalation of the vitamin into gallery space of LDH that offers a new route to safe preservation of bioactivity as well as controlled release. The prepared LDHs were characterized by XRD, TG-DTA and FT-IR spectroscopy. Adsorption of the ascorbic acid by the LDH under investigation was studied in terms of pH value, amount of LDH, contact time, VC (ascorbate) concentration and chemical composition of the host materials. The results indicate the relatively fast adsorption of the anionic vitamin by ZnFe-LDH-Cl and MgFe-Cl-LDH; reaches the equilibrium in 60 min. The shapes of the adsorption isotherms suggest specific interaction and high affinity. The batch kinetics of ascorbic acid adsorption onto ZnFe-Cl and MgFe-Cl-LDHs were studied. Furthermore, their release behaviors are also examined by spontaneous deintercalation with carbonate anion. PMID:19502014

Gasser, M S

2009-05-14

279

Effect of added zinc on the properties of cobalt-containing ceramic pigments prepared from layered double hydroxides  

SciTech Connect

Layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al, or Zn, Co and Al in the brucite-like layers and carbonate in the interlayer have been prepared by coprecipitation. The Zn/Co molar ratio was kept to 1 in all samples, while the divalent/trivalent molar ratio was varied from 2/1 to 1/2. The samples have been characterised by element chemical analysis, powder X-ray diffraction, differential thermal and thermogravimetric analysis, temperature-programmed reduction and FT-IR spectroscopy. A single hydrotalcite-like phase is formed for samples with molar ratio 2/1, which crystallinity decreases as the Al content is increased, developing small amounts of diaspore and dawsonite and probably an additional amorphous phase. Calcination at 1200 deg. C in air led to formation of spinels; a small amount of NaAlO{sub 2} was observed in the Al-rich samples, which was removed by washing. The nature of the spinels formed (containing Co{sup II}, Co{sup III}, Al{sup III} and Zn{sup II}) strongly depends on the cations molar ratio in the starting materials and the calcination treatment, leading to a partial oxidation of Co{sup II} species to Co{sup III} ones. Colour properties (L*a*b*) of the original and calcined solids have been measured. While the original samples show a pink colour (lighter for the series containing Zn), the calcined Co,Al samples show a dark blue colour and the Zn,Co,Al ones a green colour. Changes due to the different molar ratios within a given calcined series are less evident than between samples with the same composition in different series. These calcined materials could be usable as ceramic pigments. - Abstract: Mixed oxides from layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al or Zn, Co and Al in the brucite-like layers are potential candidates for ceramic pigments with tunable colour properties. Display Omitted

Perez-Bernal, M.E.; Ruano-Casero, R.J. [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)

2009-09-15

280

A magnetic organic-inorganic composite: Synthesis and characterization of magnetic 5-aminosalicylic acid intercalated layered double hydroxides  

SciTech Connect

A core-shell structured magnetic layered organic-inorganic material involving 5-aminosalicylic acid (5-ASA) intercalated Zn-Al layered double hydroxides (LDHs) and magnesium ferrite (MgFe{sub 2}O{sub 4}) is assembled by a coprecipitation method. The powder X-ray diffraction results show the coexistence of the clear but weak diffractions of MgFe{sub 2}O{sub 4} and ordered relatively stronger reflections of 5-ASA intercalated LDHs. The TEM image of magnetic 5-ASA intercalated LDHs reveals that the LDHs layer covers the MgFe{sub 2}O{sub 4} particles or their aggregates with particle size of 50-80 nm. The vibration sample magnetization (VSM) measurements exhibit the increase in saturation magnetization of magnetic 5-ASA intercalated LDHs samples with increasing amount of magnetic core. The XPS analyses account for a majority of Zn, Al and O atoms on the surface of magnetic particles. It is suggested that the magnetic core MgFe{sub 2}O{sub 4} was coated with LDHs layer probably through Zn-O-Mg and Al-O-Mg linkages, and a core-shell structured model is tentatively proposed.

Zhang Hui [Ministry of Education Key Laboratory of Science and Technology of Controllable Chemical Reactions, Box 98, Beijing University of Chemical Technology, Beijing 100029 (China)]. E-mail: huizhang67@gst21.com; Zou Kang [Ministry of Education Key Laboratory of Science and Technology of Controllable Chemical Reactions, Box 98, Beijing University of Chemical Technology, Beijing 100029 (China); Sun Hui [Ministry of Education Key Laboratory of Science and Technology of Controllable Chemical Reactions, Box 98, Beijing University of Chemical Technology, Beijing 100029 (China); Duan Xue [Ministry of Education Key Laboratory of Science and Technology of Controllable Chemical Reactions, Box 98, Beijing University of Chemical Technology, Beijing 100029 (China)]. E-mail: duanx@mail.buct.edu.cn

2005-11-15

281

Stripping voltammetric analysis of organophosphate pesticides using Ni/Al layered double hydroxides as solid-phase extraction.  

PubMed

A sensitive electrochemical stripping voltammetric biosensor is designed for organophosphate pesticides (OPs) based on solid-phase extraction (SPE) using Ni/Al layered double hydroxides (LDHs) modified glassy carbon electrode (labeled as Ni/Al-LDHs/GCE). The Ni/Al-LDHs as the host are highly efficient to capture OPs, which dramatically facilitates the enrichment of nitroaromatic OPs onto their surface and realizes the stripping voltammetric detection of OPs. The stripping voltammetric performances of methyl parathion (MP) intercalated into LDHs were evaluated by cyclic voltammetric and square-wave voltammetric (SWV) analysis. The combination of the host-guest supramolecular structure, SPE, and stripping voltammetry provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs by using MP as a model. The stripping analysis is linear over the MP concentration ranges of 0.001-0.1 and 0.2-1.0 microg mL(-1) with a detection limit of 0.6 ng mL(-1) (S/N=3). The developed biosensor exhibits good reproducibility and acceptable stability. This study offers a new promising protocol for OPs analysis. PMID:19647988

Gong, Jingming; Wang, Lianyi; Song, Dandan; Zhu, Xiaolei; Zhang, Lizhi

2009-07-16

282

Novel hollow microspheres of hierarchical zinc-aluminum layered double hydroxides and their enhanced adsorption capacity for phosphate in water.  

PubMed

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 be tuned from irregular platelets to hollow microspheres by simply varying concentrations of urea. The effects of initial phosphate concentration and contact time on phosphate adsorption using various Zn-Al LDHs and their calcined products (LDOs) were investigated from batch tests. Our results indicate that the equilibrium adsorption data were best fitted by Langmuir isothermal model, with the maximum adsorption capacity of 54.1-232 mg/g; adsorption kinetics follows the pseudo-second-order kinetic equation and intra-particle diffusion model. In addition, Zn-Al LDOs are shown to be effective adsorbents for removing phosphate from aqueous solutions due to their hierarchical porous structures and high specific surface areas. PMID:21719194

Zhou, Jiabin; Yang, Siliang; Yu, Jiaguo; Shu, Zhan

2011-06-12

283

Biosensor based on acetylcholinesterase immobilized onto layered double hydroxides for flow injection/amperometric detection of organophosphate pesticides.  

PubMed

We developed a highly sensitive flow injection/amperometric biosensor for the detection of organophosphate pesticides (OPs) using layered double hydroxides (LDHs) as the immobilization matrix of acetylcholinesterase (AChE). LDHs provided a biocompatible microenvironment to keep the bioactivity of AChE, due to the intrinsic properties of LDHs (such as a regular structure, good mechanical, chemical and thermal stabilities, and swelling properties). By integrating the flow injection analysis (FIA) with amperometric detection, the resulting AChE-LDHs modified electrode greatly catalyzed the oxidation of the enzymatically generated thiocholine product, and facilitated the detection automation, thus increasing the detection sensitivity. The analytical conditions for the FIA/amperometric detection of OPs were optimized by using methyl parathion (MP) as a model. The inhibition of MP was proportional to its concentration ranging from 0.005 to 0.3?g mL(-1) and 0.3 to 4.0?g mL(-1) with a detection limit 0.6ng mL(-1) (S/N=3). The developed biosensor exhibited good reproducibility and acceptable stability. PMID:22868055

Gong, Jingming; Guan, Zhangqiong; Song, Dandan

2012-07-21

284

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

285

Layered double hydroxides as carriers for quantum dots@silica nanospheres.  

PubMed

Quantum dot-hydrotalcite layered nanoplatforms were successfully prepared following a one-pot synthesis. The process is very fast and a priori delamination of hydrotalcite is not a prerequisite for the intercalation of quantum dots. The novel materials were extensively characterized by X-ray diffraction, thermogravimetry, infrared spectroscopy, transmission electron microscopy, true color fluorescence microscopy, photoluminescence, and nitrogen adsorption. The quantum dot-hydrotalcite nanomaterials display extremely high stability in mimicking physiological media such as saline serum (pH 5.5) and PBS (pH 7.2). Yet, quantum dot release from the solid structure is noted. In order to prevent the leaking of quantum dots we have developed a novel strategy which consists of using tailor made double layered hydrotalcites as protecting shells for quantum dots embedded into silica nanospheres without changing either the materials or the optical properties. PMID:22825338

Stoica, Georgiana; Castelló Serrano, Iván; Figuerola, Albert; Ugarte, Irati; Pacios, Roberto; Palomares, Emilio

2012-07-24

286

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

287

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

2012-04-07

288

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

289

Efficient stripping voltammetric detection of organophosphate pesticides using NanoPt intercalated Ni\\/Al layered double hydroxides as solid-phase extraction  

Microsoft Academic Search

We developed a simple strategy for designing a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs) based on solid-phase extraction (SPE) using nanosized Pt intercalated Ni\\/Al layered double hydroxides (labeled as NanoPt-LDHs). By assembling NanoPt with LDHs together, the resulting NanoPt-LDHs are highly efficient to capture OPs. It dramatically facilitates the enrichment of OPs onto their surface and realizes

Jingming Gong; Lianyi Wang; Xingju Miao; Lizhi Zhang

2010-01-01

290

Fluorescence of Zn-Al-Eu ternary layered hydroxide response to phenylalanine  

NASA Astrophysics Data System (ADS)

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 5D 0- 7F 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.

Chen, Yufeng; Li, Fei; Yu, Gensheng; Yang, Xiaojing

2012-02-01

291

Synergetic Effect of SLN-Curcumin and LDH-5-Fu on SMMC-7721 Liver Cancer Cell Line.  

PubMed

Abstract 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

2013-06-29

292

Intercalation of naphthalene-2,6-disulfonate between layers of Mg and Al double hydroxide: preparation, powder X-Ray diffraction, fourier transform infrared spectra and X-Ray photoelectron spectra  

Microsoft Academic Search

By means of the coprecipitation method, a Mg\\/Al-layered double hydroxide with interlayer naphthalene-2,6-disulfonates having a basal spacing of 1.68 nm was prepared for the first time. Results are compared here with those of other layered double hydroxides having interlayer naphthalene disulfonates. Fourier transform infrared spectra of the intercalated compounds reveal that the organic anions located at the interlayer gallery are

Eiji Kanezaki

1999-01-01

293

Synthesis and characterization of Ni{sub 1-x}Zn {sub x}Fe{sub 2}O{sub 4} spinel ferrites from tailored layered double hydroxide precursors  

SciTech Connect

In this paper, a series of pure Ni{sub 1-x}Zn {sub x}Fe{sub 2}O{sub 4} (0 {<=} x {<=} 1) spinel ferrites have been synthesized successfully using a novel route through calcination of tailored hydrotalcite-like layered double hydroxide molecular precursors of the type [(Ni + Zn){sub 1-x-y}Fe {sub y} {sup 2+}Fe {sub x} {sup 3+}(OH){sub 2}] {sup x+}(SO{sub 4} {sup 2-}) {sub x/2}.mH{sub 2}O at 900 deg. C for 2 h, in which the molar ratio of (Ni{sup 2+} + Zn{sup 2+})/(Fe{sup 2+} + Fe{sup 3+}) was adjusted to the same value as that in single spinel ferrite itself. The physico-chemical characteristics of the LDHs and their resulting calcined products were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Moessbauer spectroscopy. The results indicate that calcination of the as-synthesized LDH precursor affords a pure single Ni{sub 1-x}Zn {sub x}Fe{sub 2}O{sub 4} (0 {<=} x {<=} 1) spinel ferrite phase. Moreover, formation of pure ferrites starting from LDHs precursors requires a much lower temperature and shorter time, leading to a lower chance of side-reactions occurring, because all metal cations on the brucite-like layers of LDHs can be uniformly distributed at an atomic level.

Li Feng [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China); Liu Xiaofeng [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China); Yang Qiaozhen [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China); Liu Junjie [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China); Evans, David G. [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China); Duan Xue [Education Ministry Key Laboratory of Science and Technology of Controllable Chemical Reactions, University of Chemical Technology, P.O. Box 98, Beijing 100029 (China)]. E-mail: duanx@mail.buct.edu.cn

2005-08-11

294

Effect of added zinc on the properties of cobalt-containing ceramic pigments prepared from layered double hydroxides  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al, or Zn, Co and Al in the brucite-like layers and carbonate in the interlayer have been prepared by coprecipitation. The Zn/Co molar ratio was kept to 1 in all samples, while the divalent/trivalent molar ratio was varied from 2/1 to 1/2. The samples have been characterised by element chemical analysis, powder X-ray diffraction, differential thermal and thermogravimetric analysis, temperature-programmed reduction and FT-IR spectroscopy. A single hydrotalcite-like phase is formed for samples with molar ratio 2/1, which crystallinity decreases as the Al content is increased, developing small amounts of diaspore and dawsonite and probably an additional amorphous phase. Calcination at 1200 °C in air led to formation of spinels; a small amount of NaAlO2 was observed in the Al-rich samples, which was removed by washing. The nature of the spinels formed (containing CoII, CoIII, AlIII and ZnII) strongly depends on the cations molar ratio in the starting materials and the calcination treatment, leading to a partial oxidation of CoII species to CoIII ones. Colour properties (L*a*b*) of the original and calcined solids have been measured. While the original samples show a pink colour (lighter for the series containing Zn), the calcined Co,Al samples show a dark blue colour and the Zn,Co,Al ones a green colour. Changes due to the different molar ratios within a given calcined series are less evident than between samples with the same composition in different series. These calcined materials could be usable as ceramic pigments.

Pérez-Bernal, M. E.; Ruano-Casero, R. J.; Rives, V.

2009-09-01

295

LDH nanocontainers as bio-reservoirs and drug delivery carriers.  

PubMed

This review outlines research and patents relating to the use of inorganic nanomaterial, layered double hydroxide, as nanocontainers for drug delivery and gene reservoirs. Various intercalative synthetic routes including coprecipitation, ion exchange, reconstruction and exfoliation-reassembly have been explored to incorporate drug or gene molecules. Its unique two-dimensional structure allows layered double hydroxide to act as a nanospace for the stabilization, targeted delivery or controlled release of gene or drug molecules. Intercalative hybrid nanomaterials have uses such as pharmaceutically active ingredients, in oral- or cellular delivery systems, cosmetic ingredients, molecular coding units and etc. Toxicological studies have found layered double hydroxides to be biocompatible compared with widely used nanoparticles such as iron oxide, silica, and single-walled carbon nanotubes. Due to their versatile functionality and biocompatibility, layered double hydroxides have been widely studied and their applicability can be expanded to other nanoparticle based bio-medical applications. PMID:22747720

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

2012-11-01

296

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

297

Stoichiometric synthesis of perovskite-like Ca 2Fe x Co 2? x O 5 compounds from layered double hydroxide precursor  

Microsoft Academic Search

Pure perovskite-like Ca2FexCo2?xO5 (x=0.8, 1.0, 1.2) compounds have been successfully prepared by calcination of tailored layered double hydroxides (LDHs) precursors containing Ca2+, Co2+ and Fe3+ cations. In the novel method, due to uniform distribution of metal cations at an atomic level and appropriate composition of precursors, perovskite-like complex metal oxides can form at a low calcination temperature of 900°C. Furthermore,

Z. J. Gu; X. Xiang; F. Li; S. B. Liu; D. G. Evans

2008-01-01

298

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 ...

299

Microscopic examination of nanosized mixed Ni-Al hydroxide surface precipitates on pyrophyllite.  

PubMed

The nature of Ni-hydroxide precipitates on pyrophyllite were reexamined by analytical electron microscopy (AEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), powder X-ray diffraction (PXRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy. Chemical analysis of precipitates showed that the precipitate contains about 20% Al. HRTEM imaging showed that the precipitate was amorphous and PXRD failed to find any crystalline peaks associated with cnrystalline Ni-Al layered double-hydroxide (LDH) or alpha-Ni(OH)2. These results confirmed the conclusion from EXAFS spectroscopic data that Al coprecipitated with Ni on Al-rich substrates to form Ni-Al LDH surface precipitates. However, the HRTEM data clarifies that although the bonding environment of the precipitate is like that of Ni-AI LDH, no long-range ordering of the structure exists. The study illustrates the need for TEM observations to complement EXAFS data and the potential importance of amorphous materials in environmental settings. PMID:19350894

Livi, Kenneth J T; Senesi, Giorgio S; Scheinost, Andreas C; Sparks, Donald L

2009-03-01

300

Incorporation of rare-earth ions in Mg-Al layered double hydroxides: intercalation with an [Eu(EDTA)]{sup -} chelate  

SciTech Connect

Reaction of an aqueous slurry of an Mg{sub 2}Al-NO{sub 3} layered double hydroxide with a four-fold excess of Na[Eu(EDTA)] gives a material which analyses for Mg{sub 0.68}Al{sub 0.32}(OH){sub 2}[Eu(EDTA)]{sub 0.10}(CO{sub 3}){sub 0.11}.0.66H{sub 2}O. The interlayer spacing of the material is 13.8A, corresponding to a gallery height of 9.0A, which accords with the maximal dimensions (9-10A) of the anion in metal-EDTA complex salts as determined by single crystal X-ray diffraction. Geometrical considerations show that the charge density on the layered double hydroxide layers is too high to be balanced by intercalation of [Eu(EDTA)]{sup -} alone, necessitating the co-intercalation of carbonate ions which have a much higher charge density.

Li Cang [Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology (China); Wang Ge [Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology (China); Evans, David G. [Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology (China); Duan Xue [Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology (China)]. E-mail: duanx@mail.buct.edu.cn

2004-12-01

301

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

302

LDH Isoenzyme Distribution in Human Eosinophils  

Microsoft Academic Search

The lactate dehydrogenase (LDH) isoenzyme pattern has been determined in human eosinophils isolated from the peripheral blood of healthy donors and patients with parasitic diseases. Almost equal LDH1 and LDH5 values appear to be a characteristic of the eosinophils obtained from healthy subjects. Eosinophilic granulocytes which have been isolated from the peripheral blood of patients with eosinophilia due to parasitic

C. De Simone; M. Ferrari; F. Sorice

1983-01-01

303

Synthesis of self-assembled layered double hydroxides/carbon composites by in situ solvothermal method and their application in capacitors  

NASA Astrophysics Data System (ADS)

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-1 at a current of 2.5 A g-1, leading to a significant improvement in relation to each individual counterpart (3.5 and 463 F g-1 for carbon and Ni-Al LDHs at 2.5 A g-1, respectively). And a possible mechanism was proposed for the formation of the composites.

Wei, Jinbo; Wang, Jun; Song, Yanchao; Li, Zhanshuang; Gao, Zan; Mann, Tom; Zhang, Milin

2012-12-01

304

New layered double hydroxides intercalated with substituted pyrroles. 1. In situ polymerization of 4-(1H-pyrrol-1-yl)benzoate  

NASA Astrophysics Data System (ADS)

The two-dimensional hybrid organic inorganic materials Zn2 Cr and Zn2 Al-LDHs (Layered Double Hydroxides) containing 4-(1H-pyrrol-1yl)benzoate anions as the interlayer anions were synthesized by the co-precipitation method at constant pH followed by subsequent hydrothermal treatment for 72 h. The materials were characterized by PXRD, 13C CP-MAS NMR, ESR, TGA, and TEM. The basal spacing found by the X-ray diffraction technique is coincident with the formation of bilayers of the intercalated anions. Solid-state 13C NMR and ESR data strongly suggest the partial in situ polymerization of the 4-(1H-pyrrol-1yl)benzoate anions during coprecipitation.

Tronto, Jairo; Leroux, Fabrice; Crepaldi, Eduardo Luis; Naal, Zeki; Klein, Stanlei Ivair; Valim, João Barros

2006-05-01

305

The kinetic properties and sensitivities to inhibitors of lactate dehydrogenases (LDH1 and LDH2) from Toxoplasma gondii: comparisons with pLDH from Plasmodium falciparum  

Microsoft Academic Search

Toxoplasma gondii differentially expresses two forms of lactate dehydrogenase in tachyzoites and bradyzoites, respectively, designated LDH1 and LDH2. Previously it was demonstrated that LDH1 and LDH2 share a unique structural feature with LDH from the malarial parasite Plasmodium falciparum (pLDH), namely, the addition of a five-amino acid insert into the substrate specificity loops. pLDH exhibits a number of kinetic properties

Caroline Dando; Eric R Schroeder; Lucy A Hunsaker; Lorraine M Deck; Robert E Royer; Xiulan Zhou; Stephen F Parmley; David L Vander Jagt

2001-01-01

306

The role of trivalent cations and interlayer anions on the formation of layered double hydroxides in an oxic-CO2 medium  

NASA Astrophysics Data System (ADS)

Most common occurrences of magnesium (Mg2+), aluminum (Al3+), iron (Fe3+), carbonate (CO32?), and sulfate (SO42?) in environmental settings can lead to formation of layered double hydroxides. This study investigated the role of different trivalent cations and divalent interlayer anions on the physicochemical properties of hydrotalcite-like layered double hydroxides. Hydrotalcite-like compounds (HTLCs) were synthesized at ambient temperature by co-precipitation while maintaining Mg2+ as the primary divalent cation and varying Al3+ and Fe3+ as the trivalent cations and SO42? and CO32? as the interlayer anions. X-ray diffractograms, Raman and infrared spectra, and scanning electron microscopy images confirmed the precipitation of rounded fibrous HTLCs. BET analyses showed that the MgAlCO3-type HTLC had the greatest surface area (101.7 m2/g), followed by MgAlSO4 (93.9 m2/g), MgFeCO3 (81.3 m2/g), and MgFeSO4 (17.8 m2/g). Substitution of Fe3+ increased lattice parameters compared to Al3+ substitution. Incorporation of SO42? as an interlayer anion was favored during Fe3+ substitution but reduced the crystallinity of the HTLC. Carbonate was the preferred interlayer anion, but available SO42? occupied the interlayer spaces together with CO32? if a high charge deficiency was maintained during HTLC precipitation. Two major stages of mass loss occurred (?250 and 250-450 °C) for all the samples with better thermal stability for SO42? vs. CO32? as interlayer anion and Al3+ vs. Fe3+ as trivalent cation.

Paikaray, Susanta; Hendry, M. Jim

2012-12-01

307

Immune responses of goats against foot-and-mouth disease quadrivalent vaccine: comparison of double oil emulsion and aluminium hydroxide gel vaccines in eliciting immunity.  

PubMed

The epidemiological role of small ruminants in foot-and-mouth disease (FMD) outbreaks has been generally neglected. Although, the disease in these species is sub-clinical in nature, their role as virus carriers represents a reservoir for further infection and spread of disease. Data on the usefulness of polyvalent FMD vaccine (FMDV) in goats is scant. Thus, the present study was undertaken to evaluate the benefits of a highly potent polyvalent FMDV in goats. In the present investigations, FMDV quadrivalent double oil emulsion (Montanide ISA 206) vaccines were tested in goats at reduced doses of 2 ml per animal (antigen payload 3.5 microg per serotype per dose). The oil adjuvant elicited superior immune response at any given period than aluminium hydroxide gel (AGS) vaccine and the rapidity of development of response was quicker. The duration of immunity also appeared to be maintained for long period. The differences in immune response between two adjuvant groups were statistically significant (P<0.05). The differences were apparent even in kinetics of immune response. Unlike cattle, goats were found to be late responders for oil-adjuvanted vaccine. Our results indicate possible universal usage of double oil emulsion vaccines for disease control programs irrespective of species of animals. PMID:12034105

Patil, P K; Bayry, J; Ramakrishna, C; Hugar, B; Misra, L D; Natarajan, C

2002-06-21

308

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

309

[Prognostic value of SGOT, LDH and LDH1 activity in myocardial infarct].  

PubMed

The authors follow up SGOt, LDH and LDH1 enzyme activity in 102 patients with first transmural myocardial infarction. The results confirm the considerable diagnostic value of that enzyme spectrum and its significance for the prognostic assessment of the state of such patients. The high values of SGOT and primarily of LDH and LDH1, their persistence during the acute period of myocardial infarction correlate with the percentage of the patients with severe progress of the disease and high lethality. Prognostically unfavourable are especially the values over 800 mU/ml for LDH and 80% for LDH1. In 56.2% of the decreased LDH was over 800 mU/ml and in 70% of the decreased--80% LDH1 enzyme activity was found. PMID:1224623

Tsekov, M; Zheleva, L; Kotsev, G

1975-01-01

310

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

2013-09-24

311

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

312

LDH elevation after autologous stem cell transplantation  

Microsoft Academic Search

We have anecdotally noted that serum LDH values rise after the infusion of autologous peripheral blood progenitor cells (PBPCs), presumably the result of cellular lysis. To further study this issue, we retrospectively reviewed 203 consecutive patients undergoing autologous PBPC transplant from August 1996 to December 1997. 194 patients were evaluable, having documented LDH values on day ?1 to day +5

B Bolwell; B Pohlman; M Kalaycio; K Wise; M Goormastic; S Andresen

1999-01-01

313

Three-dimensional hierarchical flower-like Mg-Al-layered double hydroxides: highly efficient adsorbents for As(v) and Cr(vi) removal  

NASA Astrophysics Data System (ADS)

3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(v) and Cr(vi) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(v) and Cr(vi) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(v) and Cr(vi) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features.3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(v) and Cr(vi) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(v) and Cr(vi) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(v) and Cr(vi) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr30457k

Yu, Xin-Yao; Luo, Tao; Jia, Yong; Xu, Ren-Xia; Gao, Chao; Zhang, Yong-Xing; Liu, Jin-Huai; Huang, Xing-Jiu

2012-05-01

314

Use of WO(4)(2-) on layered double hydroxides for mild oxidative bromination and bromide-assisted epoxidation with H(2)O(2).  

PubMed

Tungstate, exchanged on a (Ni,Al) layered double hydroxide, is applied as a heterogeneous catalyst in the oxidation of bromide with H(2)O(2) and the ensuing electrophilic bromination of olefins. The high halogenation activity of the catalyst in essentially neutral conditions mimicks the activity of V-bromoperoxidase enzymes. In water, aromatic and aliphatic olefins are selectively converted to bromohydrins; in methanol, methoxybromides are produced. In appropriate solvent conditions, the bromohydroxylation of geminally di-, tri-, and tetrasubstituted olefins proceeds via dehydrobromination to the epoxide. Evidence for this mechanism is provided by kinetic and labeling experiments. This one-pot alternative for the two-step halohydrin epoxidation process is enabled by the mild pH conditions; bromide is effective in substoichiometric, catalytic amounts. All new catalytic procedures are characterized by a high oxidative stability of the catalyst, high productivity of the catalyst on weight basis, high W turnover frequencies in ambient conditions (up to 50 mol of product per W per h), and high chemo-, regio-, and stereoselectivities. PMID:11516284

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

2001-08-29

315

Three-dimensional hierarchical flower-like Mg-Al-layered double hydroxides: highly efficient adsorbents for As(V) and Cr(VI) removal.  

PubMed

3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(V) and Cr(VI) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(V) and Cr(VI) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(V) and Cr(VI) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features. PMID:22538297

Yu, Xin-Yao; Luo, Tao; Jia, Yong; Xu, Ren-Xia; Gao, Chao; Zhang, Yong-Xing; Liu, Jin-Huai; Huang, Xing-Jiu

2012-04-26

316

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 4.6pgmL(-1) and 3.9%, respectively. The calibration graph is linear in the range of 15.0-650pgmL(-1) with a correlation coefficient of 0.9979, sorption capacity and pre-concentration factor are 8.68mgg(-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

2013-07-26

317

Nanostructural drug-inorganic clay composites: Structure, thermal property and in vitro release of captopril-intercalated Mg Al-layered double hydroxides  

NASA Astrophysics Data System (ADS)

A nanostructural drug-inorganic clay composite involving a pharmaceutically active compound captopril (Cpl) intercalated Mg Al-layered double hydroxides (Cpl-LDHs) with Mg/Al molar ratio of 2.06 has been assembled by coprecipitation method. Powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR) and Raman spectra analysis indicate a successful intercalation of Cpl between the layers with a vertical orientation of Cpl disulphide-containing S S linkage. SEM photo indicates that as-synthesized Cpl-LDHs possess compact and non-porous structure with approximately and linked elliptical shape particles of ca. 50 nm. TG-DTA analyses suggest that the thermal stability of intercalated organic species is largely enhanced due to host guest interaction involving the hydrogen bond compared to pure form before intercalation. The in vitro release studies show that both the release rate and release percentages markedly decrease with increasing pH from 4.60 to 7.45 due to possible change of release mechanism during the release process. The kinetic simulation for the release data, and XRD and FT-IR analyses for samples recovered from release media indicate that the dissolution mechanism is mainly responsible for the release behaviour of Cpl-LDHs at pH 4.60, while the ion-exchange one is responsible for that at pH 7.45.

Zhang, Hui; Zou, Kang; Guo, Shaohuan; Duan, Xue

2006-06-01

318

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

2013-07-29

319

Preparation and characterization of lactate-intercalated Co-Fe layered double hydroxides and exfoliated nanosheet film with low infrared emissivity  

NASA Astrophysics Data System (ADS)

Lactate-intercalated Co-Fe layered double hydroxides (LDHs) were successfully prepared by coprecipitation and hydrothermal method. In this process, divalent metal ions as precursors can be obtained from the reduction reaction of lactic acid and metal powder (cobalt and ferrous). In order to obtain Fe3+, H2O2 (30%) was used to oxidize Fe2+. Meanwhile, the produced lactate was intercalated into the LDHs interlayers to compensate the positively charged layers. The as-synthesized LDHs were studied by element chemical analysis, powder X-ray diffraction (XRD), FT-IR spectroscopy, thermogravitry (TG) and differential scanning calorimetry (DSC), TEM. The results indicated that the basal spacing value of the LDHs was larger than that of lactate-intercalated Mg-Al or Zn-Al LDHs. It proved that the lactate anions were inserted into the gallery in the form of dimers which made it easy to be delaminated in water. The obtained nanosheets were deposited on the substrates to form the film which was characterized by TEM and AFM, and infrared emissivity value (8-14 ?m) was also investigated. The infrared emissivity values of Co-Fe LDHs were lower than that of Zn-Al which took advantage of the special electronic structure in Co and Fe. Besides, the orderly structure and the reduction of the interfacial deficiency of the film made the values further reduced.

Zhu, Yunxia; Zhou, Yuming; Zhang, Tao; He, Man; Wang, Yongjuan; Yang, Xiaoming; Yang, Yong

2012-12-01

320

Fe(II)-Al(III) layered double hydroxides prepared by ultrasound-assisted co-precipitation method for the reduction of bromate.  

PubMed

Bromate is recognized as an oxyhalide disinfection byproduct in drinking water. In this paper, Fe(II)-Al(III) layered double hydroxides (Fe-Al LDHs) prepared by the ultrasound-assisted co-precipitation method were used for the reduction of bromate in solution. The Fe-Al LDHs particles were characterized by X-ray diffractometer, scanning electron microscopy and thermogravimetry-differential scanning calorimetry. It was found that ultrasound irradiation assistance promoted the formation of the hydrotalcite-like phase and then improved the removal efficiency of bromate. In addition, the effects of solid-to-solution ratio, contact time, initial bromate concentration, initial pH, coexisting anions on the bromate removal were investigated. The results showed the bromate with an initial concentration of 1.56 ?mol/L could be completely removed from solution by Fe-Al LDHs within 120 min. When the initial bromate concentration was 7.81 ?mol/L, the Fe-Al LDHs with irradiation time of 30 min exhibited the optimum removal efficiency and the bromate removal capacity (qe) was 6.80 ?mol/g. In addition, the appearance of sulfate and production of bromide were observed simultaneously in this process, which suggested that ion-exchange between sulfate and bromate, and the reduction of bromate to bromide by Fe(2+) were the main mechanisms responsible for the bromate removal by Fe-Al LDHs. PMID:23474408

Zhong, Yu; Yang, Qi; Luo, Kun; Wu, Xiuqiong; Li, Xiaoming; Liu, Yang; Tang, Wangwang; Zeng, Guangming; Peng, Bo

2013-02-14

321

Multifunctional Fe?O? core/Ni-Al layered double hydroxides shell nanospheres as labels for ultrasensitive electrochemical immunoassay of subgroup J of avian leukosis virus.  

PubMed

A novel electrochemical immunosensor for ultrasensitive detection of subgroup J of avian leukosis virus (ALVs-J) was designed by using graphene sheets (GS)-layered double hydroxides (LDHs) composites modified electrode with multifunctional Fe(3)O(4) core/Ni-Al LDHs shell (LDHs@Fe(3)O(4)) nanospheres as labels. At first, the GS-LDHs were used for the immunosensor platform for improving the electronic transmission rate as well as increasing the surface area to capture a large amount of primary antibodies (Ab(1)). After that, ferrocene (Fc), secondary antibodies (Ab(2)) and horseradish peroxidase (HRP) multifunctional LDHs@Fe(3)O(4) nanospheres were used as labels with high load amount and good biological activity. Subsequently, in presence of H(2)O(2), amplified signals were obtained by an electrochemical sandwich immunoassay protocol. To embody the signal amplification property of the protocol, the analytical properties of various immunosensor platform and labels were compared in detail. Under optimal conditions, the reduction peak currents of the electrochemical immunosensor were proportional to the ALVs-J concentration over the range from 10(2.32) to 10(5.50) TCID(50)/mL with a low detection limit (180 TCID(50)/mL, S/N=3). The resulting immunosensor also displayed a good selectivity, reproducibility and stability. PMID:22621982

Shang, Kun; Zhu, Jianying; Meng, Xiaomeng; Cheng, Ziqiang; Ai, Shiyun

2012-04-30

322

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

323

NiTi-layered double hydroxide intercalated with ?-CD and CM-?-CD: Interaction between the interlayer guests and the laminates  

NASA Astrophysics Data System (ADS)

?-CD and CM-?-CD intercalated into the gallery of LDH with their cavity axes perpendicular to replaced NO3- in the interlayer, and they were connected with the laminates by the dehydration-condensation reaction between COH in them and TiOH in the laminates.

Hu, Li-Fang; Gao, Wei; He, Jie; Liu, Hong; Li, Bing; Zhang, Xiao-Mei

2013-06-01

324

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

325

In situ space- and time-resolved sorption kinetics of anionic dyes on individual LDH crystals.  

PubMed

Fluorescence spectroscopy is employed to follow the ion exchange of an emissive dye--a carboxylated perylene imide--on a layered double hydroxide. The exchange of the carboxylate ions starts at the edges of the layered double hydroxide crystals and is followed by diffusion to the basal plane. Such space-resolved observations provide a solid basis for modelling and studying the mechanisms of exchange. PMID:16224759

Roeffaers, Maarten B J; Sels, Bert F; Loos, Davey; Kohl, Christopher; Müllen, Klaus; Jacobs, Pierre A; Hofkens, Johan; De Vos, Dirk E

2005-11-11

326

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

327

Synthesis and characterization of the LDH hydrotalcite-pyroaurite solid-solution series  

SciTech Connect

A layered double hydroxide (LDH) hydrotalcite-pyroaurite solid-solution series Mg{sub 3}(Al{sub x}Fe{sub 1-x})(CO{sub 3}){sub 0.5}(OH){sub 8} with 1 - x = 0.0, 0.1...1.0 was prepared by co-precipitation at 23 {+-} 2 {sup o}C and pH = 11.40 {+-} 0.03. The compositions of the solids and the reaction solutions were determined using ICP-OES (Mg, Al, Fe, and Na) and TGA techniques (CO{sub 3}{sup 2-}, OH{sup -}, and H{sub 2}O). Powder X-ray diffraction was employed for phase identification and determination of the unit cell parameters a{sub o} and c{sub o} from peak profile analysis. The parameter a{sub o} = b{sub o} was found to be a linear function of the composition. This dependency confirms Vegard's law and indicates the presence of a continuous solid-solution series in the hydrotalcite-pyroaurite system. TGA data show that the temperatures at which interlayer H{sub 2}O molecules and CO{sub 3}{sup 2-} anions are lost, and at which dehydroxylation of the layers occurs, all decrease with increasing mole fraction of iron within the hydroxide layers. Features of the Raman spectra also depend on the iron content. The absence of Raman bands for Fe-rich members (x{sub Fe} > 0.5) is attributed to possible fluorescence phenomena. Based on chemical analysis of both the solids and the reaction solutions after synthesis, preliminary Gibbs free energies of formation have been estimated. Values of {Delta}G{sup o}{sub f}(hydrotalcite) = - 3773.3 {+-} 51.4 kJ/mol and {Delta}G{sup o}{sub f}(pyroaurite) = - 3294.5 {+-} 95.8 kJ/mol were found at 296.15 K. The formal uncertainties of these formations constants are very high. Derivation of more precise values would require carefully designed solubility experiments and improved analytical techniques.

Rozov, K., E-mail: urs.berner@psi.c [Waste Management Laboratory, Paul Scherrer Institute, 5210 Villigen (Switzerland); Rock-Water Interaction Group, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, CH-3012 (Switzerland); Berner, U. [Waste Management Laboratory, Paul Scherrer Institute, 5210 Villigen (Switzerland); Taviot-Gueho, C.; Leroux, F.; Renaudin, G. [Laboratoire de Materiaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal, F-63177 Aubiere Cedex (France); Kulik, D. [Waste Management Laboratory, Paul Scherrer Institute, 5210 Villigen (Switzerland); Diamond, L.W. [Rock-Water Interaction Group, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, CH-3012 (Switzerland)

2010-08-15

328

Water Types and Their Relaxation Behavior in Partially Rehydrated CaFe-Mixed Binary Oxide Obtained from CaFe-Layered Double Hydroxide in the 155-298 K Temperature Range.  

PubMed

Heat-treated CaFe-layered double hydroxide samples were equilibrated under conditions of various relative humidities (11%, 43% and 75%). Measurements by FT-IR and dielectric relaxation spectroscopies revealed that partial to full reconstruction of the layered structure took place. Water types taking part in the reconstruction process were identified via dielectric relaxation measurements either at 298 K or on the flash-cooled (to 155 K) samples. The dynamics of water molecules at the various positions was also studied by this method, allowing the flash-cooled samples to warm up to 298 K. PMID:24083485

Bugris, Valéria; Haspel, Henrik; Kukovecz, Akos; Kónya, Zoltán; Sipiczki, Mónika; Sipos, Pál; Pálinkó, István

2013-10-15

329

Serum Total LDH Activity and LDH-2 Isozyme in Nephrotic Syndrome  

Microsoft Academic Search

Background\\/Aims: Proteinuria, hypoproteinaemia, hypoalbuminaemia and oedema are major characteristics of nephrotic syndrome. Aims of this study were to detect serum total LDH activity and its isozymes in nephrotic syndrome. Methods: In a cross-sectional study, clinical parameters were compared in three cohorts, namely kidney patients with or without nephrotic syndrome and hypoalbuminaemic controls (NEPHR, NON-NEPHR, CONTR, respectively). Results: Serum total LDH

Márton Mohás; Nóra Szigeti; Lajos Markó; Judit Cseh; Boglárka Laczy; Mónika Tamaskó; József Balla; János Kappelmayer; László Wagner; Zoltán Wagner; Botond Csiky; Judit Nagy; István Wittmann

2008-01-01

330

SEPARATION OF PLUTONIUM HYDROXIDE FROM BISMUTH HYDROXIDE  

DOEpatents

An tmproved method is described for separating plutonium hydroxide from bismuth hydroxide. The end product of the bismuth phosphate processes for the separation amd concentration of plutonium is a inixture of bismuth hydroxide amd plutonium hydroxide. It has been found that these compounds can be advantageously separated by treatment with a reducing agent having a potential sufficient to reduce bismuth hydroxide to metalltc bisinuth but not sufficient to reduce the plutonium present. The resulting mixture of metallic bismuth and plutonium hydroxide can then be separated by treatment with a material which will dissolve plutonium hydroxide but not metallic bismuth. Sodiunn stannite is mentioned as a preferred reducing agent, and dilute nitric acid may be used as the separatory solvent.

Watt, G.W.

1958-08-19

331

Preparation and photoluminescence property of a loose powder, Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+} by calcination of a layered double hydroxide precursor  

SciTech Connect

A novel red light-emitting material, Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+}, which is the first example found in the Ca{sub 3}Al{sub 2}O{sub 6} host, was prepared by calcination of a layered double hydroxide precursor at 1350 deg. C. The precursor, [Ca{sub 2.9-x}Al{sub 2}Eu{sub x}(OH){sub 9.8}](NO{sub 3}){sub 2+x}.2.5H{sub 2}O, was prepared by coprecipitation of metal nitrates with sodium hydroxide. The material is a loose powder composed of irregular particles formed from aggregation of particles of a few nanometers, as shown in scanning electron microscope (SEM) images. It was found that the photoluminescence intensity reached the maximum when the calcination temperature was 1350 deg. C and the concentration of Eu{sup 3+} was 1.0%. The material emits bright red emission at 614 nm under a radiation of {lambda}=250 nm. - Graphical abstract: Calcination of a layered double hydroxide precursor produces Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+}, which is very easy to be pulverized. It is proposed that Eu{sup 3+} takes the place of one Ca{sup 2+} (green spheres in the picture, pink pyramids are [AlO{sub 4}] tetrahedrons) in the cell of Ca{sub 3}Al{sub 2}O{sub 6}. The Ca{sup 2+} could be any one of the bigger green spheres without inversion symmetry, and emits red light under a UV radiation of {lambda}=250 nm. Display Omitted.

Gao Xiaorui [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Lei Lixu [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China)], E-mail: lixu.lei@seu.edu.cn; Lv Changgui [Advanced Photonics Center, Southeast University, Nanjing 210096 (China); Sun Yueming [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Zheng Hegen [State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093 (China); Cui Yiping [Advanced Photonics Center, Southeast University, Nanjing 210096 (China)

2008-08-15

332

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.  

PubMed

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. PMID:20628454

Hussein, Mohd Zobir; Jaafar, Adila Mohamad; Yahaya, Asmah Hj; Zainal, Zulkarnain

2009-08-01

333

Temperature effect on the sorption of cholate anions on calcined LDH  

Microsoft Academic Search

Layered Double Hydroxides are a class of materials that can be described as positively charged layers of divalent and trivalent cations in the centre of edge-sharing octahedra. Cholesterol derivatives such as cholic acid are substances that play an important role in the digestion of fat components by the organism. This work presents a study on the intercalation of cholate anions

José Francisco Naime Filho; João Barros Valim

2010-01-01

334

Utilization of LDH isoenzymes in the diagnosis of myocardial infarction.  

PubMed

With the arrival of managed care, increased pressure is being placed on the health-care system to reduce the use of laboratory services. When evaluating less expensive methods to measure CK-MB to help reduce costs of triaging patients suspected of having myocardial infarction (MI), we also had an opportunity to evaluate the ordering pattern of LDH isoenzymes for these same patients. We found that LDH isoenzymes were continuously ordered as a routine test at least 14% of the time. We worked with the Division of Cardiology to reduce the use of LDH isoenzymes in two ways: 1) by changing the protocol of triaging suspected MI patients and 2) by reporting the test result only after director approval. This article summarizes our approach to reducing the use of LDH isoenzymes, an expensive test in terms of reagent cost and technician time. PMID:10172984

Petersen, J R; Smith, E; Okorodudu, A O; Valbuena, G; Bissell, M G

335

Pediococcus acidilactici ldhD gene: cloning, nucleotide sequence, and transcriptional analysis.  

PubMed Central

The gene encoding D-lactate dehydrogenase was isolated on a 2.9-kb insert from a library of Pediococcus acidilactici DNA by complementation for growth under anaerobiosis of an Escherichia coli lactate dehydrogenase and pyruvate-formate lyase double mutant. The nucleotide sequence of ldhD encodes a protein of 331 amino acids (predicted molecular mass of 37,210 Da) which shows similarity to the family of D-2-hydroxyacid dehydrogenases. The enzyme encoded by the cloned fragment is equally active on pyruvate and hydroxypyruvate, indicating that the enzyme has both D-lactate and D-glycerate dehydrogenase activities. Three other open reading frames were found in the 2.9-kb insert, one of which (rpsB) is highly similar to bacterial genes coding for ribosomal protein S2. Northern (RNA) blotting analyses indicated the presence of a 2-kb dicistronic transcript of ldhD (a metabolic gene) and rpsB (a putative ribosomal protein gene) together with a 1-kb monocistronic rpsB mRNA. These transcripts are abundant in the early phase of exponential growth but steadily fade away to disappear in the stationary phase. Primer extension analysis identified two distinct promoters driving either cotranscription of ldhD and rpsB or transcription of rpsB alone.

Garmyn, D; Ferain, T; Bernard, N; Hols, P; Delplace, B; Delcour, J

1995-01-01

336

REPORT ON QUALITATIVE VALIDATION EXPERIMENTS USING LITHIUM-ALUMINUM LAYERED DOUBLE-HYDROXIDES FOR THE REDUCTION OF ALUMINUM FROM THE WASTE TREATMENT PLANT FEEDSTOCK  

SciTech Connect

A process for removing aluminum from tank waste simulants by adding lithium and precipitating Li-Al-dihydroxide (Lithiumhydrotalcite, [LiAl{sub 2}(OH){sub 6}]{sup +}X{sup -}) has been verified. The tests involved a double-shell tank (DST) simulant and a single-shell tank (SST) simulant. In the case of the DST simulant, the product was the anticipated Li-hydrotalcite. For the SST simulant, the product formed was primarily Li-phosphate. However, adding excess Li to the solution did result in the formation of traces of Li-hydrotalcite. The Li-hydrotalcite from the DST supernate was an easily filterable solid. After four water washes the filter cake was a fluffy white material made of < 100 {micro}m particles made of smaller spheres. These spheres are agglomerates of {approx} 5 {micro}m diameter platelets with < 1 {micro}m thickness. Chemical and mineralogical analyses of the filtrate, filter cake, and wash waters indicate a removal of 90+ wt% of the dissolved Al for the DST simulant. For the SST simulant, the main competing reaction to the formation of lithium hydrotalcite appears to be the formation of lithium phosphate. In case of the DST simulant, phosphorus co-precipitated with the hydrotalcite. This would imply the added benefit of the removal of phosphorus along with aluminum in the pre-treatment part of the waste treatment and immobilization plant (WTP). For this endeavor to be successful, a serious effort toward process parameter optimization is necessary. Among the major issues to be addressed are the dependency of the reaction yield on the solution chemistry, as well as residence times, temperatures, and an understanding of particle growth.

HUBER HJ; DUNCAN JB; COOKE GA

2010-05-11

337

[Thiol groups of chicken liver LDH (author's transl)].  

PubMed

Crystallized chicken liver H4 lactatedehydrogenase with PCBM and DTNB, proved to have sic thiol groups per enzyme molecule. Sulphydryl groups seemed necessary for activity since the enzyme became inactive when the groups were blocked by PCMB, DTNB or by Zn (II), Cu (II) or Hg (II). LDH inhibited by Hg (II) recovered its activity after treatment with beta-mercaptoentanol. LDH reversible inactivation, caused by PCMB, was partially impeded by NAD, NADH hand L-lactate but inactivation caused by DTNB was impeded in any way by coenzymes or substrates. PCMB is a competitive inhibitor with the coenzymes but is non-competitive with the substrates whereas DTNB is a competitive inhibitor with NADH or L-lactate. Kinetic studies of the DTNB inactivation suggest the possible formation of a DTNB-LDH-NADH complex. The formation of LDH-NADH and LDH-NAD pyruvate inactive complexes have been detected by U.V. absorbancy measurements. Such inactive complexes have equally been observed experimenting with the PCMB of Hg (II) previously treated enzyme. The results showed that these essential sulphydryl groups are not involved in th attaching of coenzymes or substrates to the chicken liver LDH molecule, but they seem to suggest the participation of --SH groups during the reversible hydrogen transfer between NADH and pyruvate. PMID:1257566

Lluís, C; Bozal, J

1976-03-01

338

Nickel Hydroxide Electrode Research.  

National Technical Information Service (NTIS)

The report discusses results of work performed to develop an improved nickel hydroxide electrode for use in rechargable alkaline electrodes for aerospace applications. Voltametric cycling studies have shown that all deliberate additions of cations (cobalt...

H. A. Christopher J. L. Weininger J. G. Ruzzo R. F. Thornton P. J. Moran

1970-01-01

339

Calcium hydroxide poisoning  

MedlinePLUS

... powder produced by mixing calcium oxide ("lime") with water. Calcium hydroxide poisoning occurs when someone swallows this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have ...

340

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

341

Genetic control of LDH isozymes in the Rana esculenta complex  

Microsoft Academic Search

Summary Studies of LDH isozymes in the European green frogs showed that the synthesis of the B subunits is controlled by 3 alleles at a single genetic locus. The genetic evidence supports the hypothesis thatRana esculenta is the hybrid ofR. lessonae x R. ridibunda.

P. Vogel; P. S. Chen

1976-01-01

342

Space confinement and rotation stress induced self-organization of double-helix nanostructure: a nanotube twist with a moving catalyst head.  

PubMed

Inorganic materials with double-helix structure have attracted intensive attention due to not only their elegant morphology but also their amazing morphology-related potential applications. The investigation on the formation mechanism of the inorganic double-helix nanostructure is the first step for the fundamental studies of their materials or physical properties. Herein, we demonstrated the space confinement and rotation stress induced self-organization mechanism of the carbon nanotube (CNT)-array double helices under scanning electron microscopy by directly observing their formation process from individual layered double hydroxide flakes, which is a kind of hydrotalcite-like material composed of positively charged layers and charge-balancing interlayer anions. Space confinement is considered to be the most important extrinsic factor for the formation of CNT-array double helices. Synchronous growth of the CNT arrays oppositely from LDH flakes with space confinement on both sides at the same time is essential for the growth of CNT-array double helices. Coiling of the as-grown CNT arrays into double helices will proceed by self-organization, tending to the most stable morphology in order to release their internal rotation stress. Based on the demonstrated mechanism, effective routes were carried out to improve the selectivity for CNT-array double helices. The work provides a promising method for the fabrication of double-helix nanostructures with their two helices connected at the end by self-assembly. PMID:22519687

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

2012-04-27

343

Spontaneous in vitro Hybridization of LDH Homopolymers in the Undenatured State.  

National Technical Information Service (NTIS)

A hybridization between M and H LDH is described. The reaction conditions mimic the physiological milieu. Slight variations in environment regulate the products. In this manner, we are able to duplicate clinical observations of alterations of the LDH patt...

D. B. Millar M. R. Summers J. A. Niziolek

1970-01-01

344

Regulation of the ldhA gene, encoding the fermentative lactate dehydrogenase of Escherichia coli  

Microsoft Academic Search

The fermentative lactate dehydrogenase (LDH) of Escherichia coli is induced by low pH under anaerobic conditions. Both translational and transcriptional gene fusions to ldhA, which encodes the fermentative LDH, have now been made. Both types of ldhA-lacZ fusion were induced by low pH, but only in the absence of air. However, the translational fusions were consistently expressed at a five-

Gene Ruijun Jiang; Sonia Nikolova; David P. Clark

2001-01-01

345

IMMUNOCAPTURE DIAGNOSTIC ASSAYS FOR MALARIA USING PLASMODIUM LACTATE DEHYDROGENASE (pLDH)  

Microsoft Academic Search

We have developed two diagnostic assays based on the specific detection of Plasmodium lactate de- hydrogenase (pLDH) activity. These assays exploit a panel of monoclonal antibodies that capture the parasite enzyme and allow for the quantitation and speciation of human malaria infections. An immunocapture pLDH activity assay (ICpLDH) allows for the rapid purification and measurement of pLDH from infected blood

ROBERT PIPER; JACQUES LEBRAS; LAURA WENTWORTH; ANGELA HUNT-COOKE; SANDRA HOUZE; PETER CHIODINI; MICHAEL MAKLER

346

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

347

Four Types of Genetic Variants of LDH Found in India  

Microsoft Academic Search

The four types of genetic variants of lactate dehydrogenase (LDH) found so far in the Indian populations surveyed by starch-gel electrophoresis of haemolysates are described, pointing out their characteristic features. Two of these variant types, namely, ‘Calcutta-1’ and ‘Madras-1, were reported earlier. The other two discovered subsequently and named trivially as ‘Calcutta-2’ and ‘Delhi-1 are now reported for the first

S. R. Das; B. N. Mukherjee; S. K. Das; K. C. Malhotra

1972-01-01

348

Profiles and prognostic values of LDH isoenzymes in patients with non-Hodgkin’s lymphoma  

Microsoft Academic Search

Serum lactic dehydrogenase (LDH) is an important prognostic factor in patients with non-Hodgkin’s lymphoma (NHL). We have examined the LDH isoenzyme content in serum and CSF of patients with NHL, at diagnosis and at relapse. In patients with increased serum LDH at diagnosis, the percentage of isoenzyme 2 was increased in 52% of patients and the absolute value of isoenzyme

C Dumontet; J Drai; J Bienvenu; E Neidhardt Berard; C Thieblemont; F Bouafia; F Bayle; I Moullet; G Salles; B Coiffier

1999-01-01

349

The comparison of spontaneous LDH release activity from cultured PBMC with sera LDH activity in non-Hodgkin’s lymphoma patients  

Microsoft Academic Search

Based on the fact that lactate dehydrogenase (LDH) enzyme is a very sensitive indicator of the cellular metabolic state, aerobic\\u000a or anaerobic direction of glycolysis, activation status, and malignant transformation, in this study we compared values of\\u000a the spontaneous LDH release from circulating PBMC with sera LDH activity in 53 different subtypes of non-Hodgkin’s lymphoma\\u000a (NHL) patients. Results shows that

V. Juriši?; G. Konjevi?; R. Jan?i?-Nedeljkov; M. Sretenovi?; B. Bani?evi?; M. Colovi?; I. Spuži?

2004-01-01

350

Molecular Structure of Hydroxide ion  

NSDL National Science Digital Library

In 1923, Johannes Bronsted and Thomas Lowry proposed that a Bronsted-Lowry base is any substance that can accept a proton. They found that hydroxide anion acts as a proton acceptor. When high concentrations of hydroxide are present in solution, the solution is said to be basic, having a pH above 7. It falls into the Bronstead-Lowry definition of a base because it acts as a proton acceptor. Hydroxide, when combined with other elements, serves many purposes. Aluminum hydroxide is a safe antacid used to treat indigestion, gastric and duodenal ulcers, and efflux oesophagitis.

2002-09-11

351

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....

2013-04-01

352

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2010 CFR

...Potassium hydroxide. (a) Potassium hydroxide (KOH, CAS Reg...sticks, lumps, and powders. Potassium hydroxide is obtained commercially from the electrolysis of potassium chloride solution in the presence of...

2010-01-01

353

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

354

Relative catalytic efficiency of ldhL- and ldhD-encoded products is crucial for optical purity of lactic acid produced by lactobacillus strains.  

PubMed

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. PMID:22344644

Zheng, Zhaojuan; Sheng, Binbin; Ma, Cuiqing; Zhang, Haiwei; Gao, Chao; Su, Fei; Xu, Ping

2012-02-17

355

Homogeneous Precipitation of Nickel Hydroxide Powders  

SciTech Connect

Precipitation and characterization of nickel hydroxide powders were investigated. A comprehensive precipitation model incorporating the metal ion hydrolysis, complexation and precipitation reactions was developed for the production of the powders with urea precipitation method. Model predictions on Ni{sup 2+} precipitation rate were confirmed with precipitation experiments carried out at 90 C. Experimental data and model predictions were in remarkable agreement. Uncertainty in the solubility product data of nickel hydroxides was found to be the large contributor to the error. There were demonstrable compositional variations across the particle cross-sections and the growth mechanism was determined to be the aggregation of primary crystallites. This implied that there is a change in the intercalate chemistry of the primary crystallites with digestion time. Predicted changes in the concentrations of simple and complex ions in the solution support the proposed mechanism. The comprehensive set of hydrolysis reactions used in the model described above allows the investigation of other systems provided that accurate reaction constants are available. the fact that transition metal ions like Ni{sup 2+} form strong complexes with ammonia presents a challenge in the full recovery of the Ni{sup 2+}. On the other hand, presence of Al{sup 3+} facilitates the complete precipitation of Ni{sup 2+} in about 3 hours of digestion. A challenge in their predictive modeling studies had been the fact that simultaneous incorporation of more than one metal ion necessitates a different approach than just using the equilibrium constants of hydrolysis, complexation and precipitation reactions. Another limitation of using equilibrium constants is that the nucleation stage of digestion, which is controlled mainly by kinetics, is not fully justified. A new program released by IBM Almaden Research Center (Chemical Kinetics Simulator{trademark}, Version 1.01) lets the user change the order of kinetic components of a reaction which was set to stoichiometric constant with which the species appear in the reaction in KINSIM by default. For instance, in the case of LDH precipitation, the new program allows to change the order of species in the reactions associated with Al{sup 3+} and let the Ni{sup 2+} reactions take over. This could be carried on iteratively until a good fit between the experimental data and the predictions were observed. However for such studies availability of accurate equilibrium constants (especially for the solubility products for the solid phase) is a prerequisite.

Bora Mavis

2003-12-12

356

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

357

Inhibition of testicular LDH-X from laboratory animals and man by gossypol and its isomers  

Microsoft Academic Search

Summary. The inhibitory effect of (+)-, (\\\\m=-\\\\)-, (\\\\m=+-\\\\)-gossypoland (\\\\m=+-\\\\)-gossypolacetic acid upon testicular cytosolic LDH-X was measured in vitro. Gossypol acetic acid (0-100 \\\\g=m\\\\mol\\/l)inhibited LDH-X prepared from the testes of the mouse > rabbit > human > rat > hamster. There was no relationship between inhibition and in-vivo antifertility activity. LDH activity measured in vitro in serum of men and hamsters

I. D. Morris; C. Higgins; S. A. Matlin

1986-01-01

358

Serum and Tissue LDH Levels in Patients with Breast\\/Gynaecological Cancer and Benign Diseases  

Microsoft Academic Search

Background: Lactate dehydrogenase A (LDHA) is involved in anaerobic glycolysis. In cancer patients, serum total lactate dehydrogenase (LDH) levels are often increased, and the gene for one of its isoenzymes, LDHA, is up-regulated. These features have been linked to poor prognosis in several studies. Methods: We investigated comparatively the total serum LDH activity and tissue isoenzyme LDH5 and hypoxia-inducible factor

Michael I. Koukourakis; Emmanuel Kontomanolis; Alexandra Giatromanolaki; Efthimios Sivridis; Vassilios Liberis

2009-01-01

359

Isolation and partial characterization of rat LDH A-genomic sequences  

Microsoft Academic Search

As a part of the study to elucidate the mechanism by which the transcription of LDH A-gene is regulated by cAMP, we aimed\\u000a to isolate rat LDH A gene and characterize cAMP-responsive element (CRE). We have screened 1.2×106 recombinant phages of rat Charon 4A genomic library and isolated 33 positive clones among which we identified 12 different\\u000a LDH A gene-related

Mi Young Lee; Sun Young Yim; Seung Ki Lee

1990-01-01

360

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

361

Nickel Hydroxide Battery Electrode Development.  

National Technical Information Service (NTIS)

The report terminates the work on a three-year program aimed at the development of an improved nickel hydroxide electrode for the use in rechargeable alkaline batteries for aerospace applications. The improvements sought were primarily concerned with achi...

H. H. Kroger

1972-01-01

362

Attenuation of LDH-A expression uncovers a link between glycolysis, mitochondrial physiology, and tumor maintenance  

Microsoft Academic Search

Summary Alterations in cellular metabolism are among the most consistent hallmarks of cancer. Herein we have investigated the re- lationship between increased aerobic lactate production and mitochondrial physiology in tumor cells. To diminish the ability of malignant cells to metabolize pyruvate to lactate, lactate dehydrogenase A (LDH-A) levels were knocked down by means of LDH-A short hairpin RNAs. Reduction in

Valeria R. Fantin; Julie St-Pierre; Philip Leder

2006-01-01

363

Histamine and lactate dehydrogenase (LDH) release in ischemic myocardium of the guinea-pig  

Microsoft Academic Search

Histamine has been proved to be released during myocardial infarction and ischemic arrhythmias in dogs. The aim of the present experiments was to evaluate if ischemia and reperfusion modify histamine and lactate dehydrogenase (LDH) release in isolated guinea-pig heart. The results obtained show a steady increase of LDH release both in the ischemic and reperfusion phases. The release of histamine

E. Masini; E. Giannella; S. Bianchi; P. F. Mannaioni

1987-01-01

364

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

365

Cloning of a Neisseria meningitidis gene for L-lactate dehydrogenase (L-LDH): evidence for a second meningococcal L-LDH with different regulation.  

PubMed Central

We report the cloning of lldA, a Neisseria meningitidis gene for L-lactate dehydrogenase (L-LDH). Escherichia coli contains a single L-LDH gene (lldD) in the lld operon (previously lct). E. coli grown in complex media does not have L-LDH activity, but the activity is induced by growth in defined medium with L-lactate as the carbon source. In contrast, meningococci contain at least one L-LDH in addition to the lldA gene product. These enzymes are active in meningococci grown in complex media and are not dependent on growth in L-lactate. The predicted amino acid sequence of lldA is homologous to that of E. coli lldD and of other prokaryotic and eukaryotic flavin mononucleotide-containing enzymes that catalyze the oxidation of L-lactate and other small alpha-hydroxy acids. A mutant with a deletion in lldA was found to have reduced L-LDH activity. However, this mutant was able to grow on L-lactate, indicating that a second L-LDH must exist. Activity of the lldA enzyme was affected by growth conditions, being increased by growth on a defined medium with either L-lactate or pyruvate as the carbon source. For meningococci grown on a complex medium, activity of the lldA enzyme was increased by growth on plates or in well-aerated broth. A second L-lactate-oxidizing activity was seen in bacteria grown in poorly aerated broth. Neisseria gonorrhoeae contains a homolog of lldA. As for meningococci, mutation of the gonococcal lldA reduced L-LDH activity but did not affect growth on L-lactate.

Erwin, A L; Gotschlich, E C

1996-01-01

366

Aluminum hydroxide issue closure package  

SciTech Connect

Aluminum hydroxide coatings on fuel elements stored in aluminum canisters in K West Basin were measured in July and August 1998. Good quality data was produced that enabled statistical analysis to determine a bounding value for aluminum hydroxide at a 99% confidence level. The updated bounding value is 10.6 kg per Multi-Canister Overpack (MCO), compared to the previously estimated bounding value of 8 kg/MCO. Thermal analysis using the updated bounding value, shows that the MCO generates oxygen concentrate that are below the lower flammability limits during the 40-year interim storage period and are, therefore, acceptable.

Bergman, T.B.

1998-08-26

367

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2010 CFR

... Potassium hydroxide. (a) Potassium hydroxide (KOH, CAS Reg. No. 1310-58-3) is also known as caustic potash, potash lye, and potassa. The empirical formula is KOH. It is a white, highly deliquescent caustic solid, which...

2009-04-01

368

Reaction of Calcium Hydroxide with Carbon Dioxide.  

National Technical Information Service (NTIS)

Details for carrying out an experiment on the reaction of calcium hydroxide with carbon dioxide are given. The addition of water is necessary for a reaction between dry calcium hydroxide and carbon dioxide. (ERA citation 02:005491)

F. W. Dorst

1975-01-01

369

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2013 CFR

...Sodium hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d...

2013-04-01

370

Two ldh genes from tomato and their expression in different organs, during fruit ripening and in response to stress  

Microsoft Academic Search

Two different ldh genes have been isolated from a tomato genomic library and sequenced. Both contain a single intron and correspond to cDNA clones LeLdh1 and LeLdh2 isolated from a library constructed from hypoxically induced tomato roots. Southern blots indicate that the two genes comprise the entire ldh gene family in tomato. Both genes are expressed at low levels in

Véronique Germain; Bérénice Ricard

1997-01-01

371

Anoxia- and hypoxia-induced expression of LDH-A* in the Amazon Oscar, Astronotus crassipinis  

PubMed Central

Adaptation or acclimation to hypoxia occurs via the modulation of physiologically relevant genes, such as erythropoietin, transferrin, vascular endothelial growth factor, phosphofructokinase and lactate dehydrogenase A. In the present study, we have cloned, sequenced and examined the modulation of the LDH-A gene after an Amazonian fish species, Astronotus crassipinis (the Oscar), was exposed to hypoxia and anoxia. In earlier studies, we have discovered that adults of this species are extremely tolerant to hypoxia and anoxia, while the juveniles are less tolerant. Exposure of juveniles to acute hypoxia and anoxia resulted in increased LDH-A gene expression in skeletal and cardiac muscles. When exposed to graded hypoxia juveniles show decreased LDH-A expression. In adults, the levels of LDH-A mRNA did not increase in hypoxic or anoxic conditions. Our results demonstrate that, when given time for acclimation, fish at different life-stages are able to respond differently to survive hypoxic episodes.

Almeida-Val, Vera Maria Fonseca; Oliveira, Alice Reis; de Nazare Paula da Silva, Maria; Ferreira-Nozawa, Monica Stropa; Araujo, Roziete Mendes; Val, Adalberto Luis; Nozawa, Sergio Ricardo

2011-01-01

372

LDH (laser\\/detector\\/hologram) unit for thin optical pick-up head of CD player  

Microsoft Academic Search

The LDH unit with the size of 4.8×8.2×4.3 mm for a thin optical pickup head of a CD player has been successfully developed. The technology to make the LDH unit thin and small is based upon (1) the most efficient optical combination of the low operation current laser diode with the 45° built-in micro-mirror which is formed on the Si

A. Yoshikawa; H. Nakanishi; K. Itoh; T. Yamazaki; T. Komino; T. Musha

1994-01-01

373

Comparison of the LDH and MTT assays for quantifying cell death: validity for neuronal apoptosis?  

Microsoft Academic Search

Neuronal apoptosis induced in cortical cultures by exposure to serum deprivation, staurosporine, nifedipine, or C2-ceramide was assayed by lactate dehydrogenase (LDH) release or inhibition of 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) reduction. The protective effects of neurotrophin-4, Z-Val-Ala-Asp-fluoromethylketone (ZVAD), and cycloheximide against each insult were also assayed. The level of injury for each insult was similar whether determined by LDH release or inhibition

Doug Lobner

2000-01-01

374

Serum Lactic Dehydrogenase (LDH) Levels in Acute Leukemia: Marked Elevations in Lymphoblastic Leukemia  

Microsoft Academic Search

Serum total lactic dehydrogenase (LDH) levels were examined in 42 patients with acute leukemia. 9 patients with chronic myeloid leukemia. 6 of them in blastic crisis, and 53 patients with lymphoma and other lymphoproliferative disorders. The mean range of serum LDH levels in Hodgkin's and non-Hodgkin's lymphoma was 402 ± 210 lU\\/liter and 313 ± 1 13 lU\\/liter, while that

Abraham Kornberg; Aaron Polliack

1980-01-01

375

Regulation of ldh expression during biotin-limited growth of Corynebacterium glutamicum.  

PubMed

Corynebacterium glutamicum is a biotin-auxotrophic bacterium and some strains efficiently produce glutamic acid under biotin-limiting conditions. In an effort to understand C. glutamicum metabolism under biotin limitation, growth of the type strain ATCC 13032 was investigated in batch cultures and a time-course analysis was performed. A transient excretion of organic acids was observed and we focused our attention on lactate synthesis. Lactate synthesis was due to the ldh-encoded l-lactate dehydrogenase (Ldh). Features of Ldh activity and ldh transcription were analysed. The ldh gene was shown to be regulated at the transcriptional level by SugR, a pleiotropic transcriptional repressor also acting on most phosphotransferase system (PTS) genes. Electrophoretic mobility shift assays (EMSAs) and site-directed mutagenesis allowed the identification of the SugR-binding site. Effector studies using EMSAs and analysis of ldh expression in a ptsF mutant revealed fructose 1-phosphate as a highly efficient negative effector of SugR. Fructose 1,6-bisphosphate also affected SugR binding. PMID:19332837

Dietrich, Christiane; Nato, Aimé; Bost, Bruno; Le Maréchal, Pierre; Guyonvarch, Armel

2009-04-01

376

Comparative Study of Some Layered Hydroxide Salts Containing Exchangeable Interlayer Anions  

NASA Astrophysics Data System (ADS)

Anion-exchange reactions of layered Zn, Cu, Ni, or La hydroxide nitrates with the organic anions acetate, terephthalate, and benzoate are compared. Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry combined with mass spectrometry (TG-MS) are used to characterize the materials. Exchange of the interlayer nitrate anions for these organic anions is generally possible, although no exchange is observed for the parent nickel hydroxide material. The organo derivatives obtained may be considered inorganic-organic hybrids, consisting of alternating hydroxide and A- layers, where A is the incorporated organic anion. The materials are structurally similar to the layered double hydroxide family of materials, which also exhibit an anion-exchange capacity.

Newman, Steven P.; Jones, William

1999-11-01

377

Aluminum chlorohydrate III: Conversion to aluminum hydroxide.  

PubMed

Bayerite, an aluminum hydroxide polymorph, readily forms when the hydroxyl to aluminum ratio of aluminum chlorohydrate is raised to 3 by titration with sodium hydroxide. Dilution of aluminum chlorhydrate solutions with water leads to the formation of gibbsite, another aluminum hydroxide polymorph. The mechanism of conversion in each instance is related to the structure of the Al13O4(OH)24(H2O)7+(12) complex. PMID:7264935

Teagarden, D L; White, J L; Hem, S L

1981-07-01

378

Increased pretreatment levels of serum LDH and ALP as poor prognostic factors for nasopharyngeal carcinoma.  

PubMed

Serum enzymes that play potential roles in tumor growth have recently been reported to have prognostic relevance in a diverse array of tumors. However, prognosis-related serum enzymes are rarely reported for nasopharyngeal carcinoma(NPC). To clarify whether the level of serum enzymes is linked to the prognosis of NPC, we reviewed the pretreatment data of lactate dehydrogenase(LDH), alkaline phosphatase (ALP), and glutamyl transferase (GGT) in 533 newly diagnosed NPC patients who underwent radical radiotherapy between May 2002 and October 2003 at Sun Yat-sen University Cancer Center. Patients were grouped according to the upper limit of normal values of LDH, ALP, and GGT. The Kaplan-Meier method and log-rank test were used for selecting prognostic factors from clinical characteristics and serum enzymes, and the chi-square test was applied to analyze the relationships of clinical characteristics and serum enzymes. Finally, a Cox proportional hazards model was used to identify the independent prognostic factors. We found that increased levels of LDH had poor effects on both overall survival and distant metastasis-free survival (P = 0.009 and 0.035, respectively), and increased pretreatment level of serum ALP had poor effects on both overall survival and local recurrence-free survival (P = 0.037 and 0.039, respectively). In multivariate analysis, increased LDH level was identified as an independent prognostic factor for overall survival. Therefore, we conclude that increased pretreatment serum LDH and ALP levels are poor prognostic factors for NPC. PMID:22237040

Li, Guo; Gao, Jin; Tao, Ya-Lan; Xu, Bing-Qing; Tu, Zi-Wei; Liu, Zhi-Gang; Zeng, Mu-Sheng; Xia, Yun-Fei

2012-01-09

379

Physical and functional association of lactate dehydrogenase (LDH) with skeletal muscle mitochondria.  

PubMed

The intracellular lactate shuttle hypothesis posits that lactate generated in the cytosol is oxidized by mitochondrial lactate dehydrogenase (LDH) of the same cell. To examine whether skeletal muscle mitochondria oxidize lactate, mitochondrial respiratory oxygen flux (JO2) was measured during the sequential addition of various substrates and cofactors onto permeabilized rat gastrocnemius muscle fibers, as well as isolated mitochondrial subpopulations. Addition of lactate did not alter JO2. However, subsequent addition of NAD(+) significantly increased JO2, and was abolished by the inhibitor of mitochondrial pyruvate transport, ?-cyano-4-hydroxycinnamate. In experiments with isolated subsarcolemmal and intermyofibrillar mitochondrial subpopulations, only subsarcolemmal exhibited NAD(+)-dependent lactate oxidation. To further investigate the details of the physical association of LDH with mitochondria in muscle, immunofluorescence/confocal microscopy and immunoblotting approaches were used. LDH clearly colocalized with mitochondria in intact, as well as permeabilized fibers. LDH is likely localized inside the outer mitochondrial membrane, but not in the mitochondrial matrix. Collectively, these results suggest that extra-matrix LDH is strategically positioned within skeletal muscle fibers to functionally interact with mitochondria. PMID:23873936

Elustondo, Pia A; White, Adrienne E; Hughes, Meghan E; Brebner, Karen; Pavlov, Evgeny; Kane, Daniel A

2013-07-20

380

M-LDH serves as a sarcolemmal KATP channel subunit essential for cell protection against ischemia  

PubMed Central

ATP-sensitive K+ (KATP) channels in the heart are normally closed by high intracellular ATP, but are activated during ischemia to promote cellular survival. These channels are heteromultimers composed of Kir6.2 subunit, an inwardly rectifying K+ channel core, and SUR2A, a regulatory subunit implicated in ligand-dependent regulation of channel gating. Here, we have shown that the muscle form (M-LDH), but not heart form (H-LDH), of lactate dehydrogenase is directly physically associated with the sarcolemmal KATP channel by interacting with the Kir6.2 subunit via its N-terminus and with the SUR2A subunit via its C-terminus. The species of LDH bound to the channel regulated the channel activity despite millimolar concentration of intracellular ATP. The presence of M-LDH in the channel protein complex was required for opening of KATP channels during ischemia and ischemia-resistant cellular phenotype. We conclude that M-LDH is an integral part of the sarcolemmal KATP channel protein complex in vivo, where, by virtue of its catalytic activity, it couples the metabolic status of the cell with the KATP channels activity that is essential for cell protection against ischemia.

Crawford, Russell M.; Budas, Grant R.; Jovanovic, Sofija; Ranki, Harri J.; Wilson, Timothy J.; Davies, Anthony M.; Jovanovic, Aleksandar

2002-01-01

381

Preparationand thermal decomposition study of pyridinedicarboxylate intercalated layereddouble hydroxides  

Microsoft Academic Search

Supramolecular 2,3- and 2,5-pyridinedicarboxylate (PDC) intercalated\\u000a ZnAl-layered double hydroxides (2,3- and 2,5-PDC–ZnAl–LDHs) have\\u000a been prepared by ion exchange method. The structure and composition of the\\u000a intercalated materials have been studied by X-ray diffraction (XRD) and inductively\\u000a coupled plasma emission spectroscopy (ICP). The study indicates that the 2,3-PDC\\u000a and 2,5-PDC anions are accommodated as interdigitated bilayer and monolayer\\u000a arrangement respectively between

M. Wei; X. Y. Xu; J. He; G. Y. Rao; H. L. Yang

2006-01-01

382

Functional Replacement of the Escherichia colid-(-)-Lactate Dehydrogenase Gene (ldhA) with the l-(+)-Lactate Dehydrogenase Gene (ldhL) from Pediococcus acidilactici†  

PubMed Central

The microbial production of l-(+)-lactic acid is rapidly expanding to allow increased production of polylactic acid (PLA), a renewable, biodegradable plastic. The physical properties of PLA can be tailored for specific applications by controlling the ratio of l-(+) and d-(?) isomers. For most uses of PLA, the l-(+) isomer is more abundant. As an approach to reduce costs associated with biocatalysis (complex nutrients, antibiotics, aeration, product purification, and waste disposal), a recombinant derivative of Escherichia coli W3110 was developed that contains five chromosomal deletions (focA-pflB frdBC adhE ackA ldhA). This strain was constructed from a d-(?)-lactic acid-producing strain, SZ63 (focA-pflB frdBC adhE ackA), by replacing part of the chromosomal ldhA coding region with Pediococcus acidilactici ldhL encoding an l-lactate dehydrogenase. Although the initial strain (SZ79) grew and fermented poorly, a mutant (SZ85) was readily isolated by selecting for improved growth. SZ85 exhibited a 30-fold increase in l-lactate dehydrogenase activity in comparison to SZ79, functionally replacing the native d-lactate dehydrogenase activity. Sequencing revealed mutations in the upstream, coding, and terminator regions of ldhL in SZ85, which are presumed to be responsible for increased l-lactate dehydrogenase activity. SZ85 produced l-lactic acid in M9 mineral salts medium containing glucose or xylose with a yield of 93 to 95%, a purity of 98% (based on total fermentation products), and an optical purity greater than 99%. Unlike other recombinant biocatalysts for l-lactic acid, SZ85 remained prototrophic and is devoid of plasmids and antibiotic resistance genes.

Zhou, Shengde; Shanmugam, K. T.; Ingram, L. O.

2003-01-01

383

The ldhA Gene, Encoding Fermentative L-Lactate Dehydrogenase of Corynebacterium glutamicum, Is under the Control of Positive Feedback Regulation Mediated by LldR  

Microsoft Academic Search

Corynebacterium glutamicum ldhA encodes L-lactate dehydrogenase, a key enzyme that couples L-lactate production to reoxidation of NADH formed during glycolysis. We previously showed that in the absence of sugar, SugR binds to the ldhA promoter region, thereby repressing ldhA expression. In this study we show that LldR is another protein that binds to the ldhA promoter region, thus regulating ldhA

Koichi Toyoda; Haruhiko Teramoto; Masayuki Inui; Hideaki Yukawa

2009-01-01

384

[Comparative study between CPK, LDH and their isoenzymes in the detection of carriers of Duchenne's type muscular dystrophy].  

PubMed

Results of a comparative study of serum activity levels of creatine kinase, lactodehydrogenase and their isoenzyme in mothers of 13 children with Duchenne progressive muscular distrophy are presented. CPK sensibility was 100%, while that of LDH1/LDH2 and LDH5 were 23% and 38,4% respectively. It is concluded that CPK has a great liability index, and that it is superior to LDT and their isoenzyme for detection of carriers of Duchenne progressive muscular distrophy. PMID:4073685

Castro-Gago, M; Rodríguez-Segade, S; Paz, M; Novo, I; Pombo, M; Tojo, R

1985-09-01

385

LDH-A silencing suppresses breast cancer tumorigenicity through induction of oxidative stress mediated mitochondrial pathway apoptosis  

Microsoft Academic Search

LDH-A, as the critical enzyme accounting for the transformation from pyruvate into lactate, has been demonstrated to be highly\\u000a expressed in various cancer cells and its silencing has also been approved relating to increased apoptosis in lymphoma cells.\\u000a In this study, we intend to investigate the correlation between LDH-A and other clinicopathological factors of breast cancer\\u000a and whether LDH-A silencing

Zhi-Yu Wang; Tjing Yung Loo; Jian-Gang Shen; Neng Wang; Dong-Mei Wang; De-Po Yang; Sui-Lin Mo; Xin-Yuan Guan; Jian-Ping Chen

386

21 CFR 872.3250 - Calcium hydroxide cavity liner.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Calcium hydroxide cavity liner. 872.3250 Section 872.3250 Food... § 872.3250 Calcium hydroxide cavity liner. (a) Identification. A calcium hydroxide cavity liner is a device material intended to...

2009-04-01

387

21 CFR 872.3250 - Calcium hydroxide cavity liner.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Calcium hydroxide cavity liner. 872.3250 Section 872.3250 Food... § 872.3250 Calcium hydroxide cavity liner. (a) Identification. A calcium hydroxide cavity liner is a device material intended to...

2010-04-01

388

Metal Value Recovery from Metal Hydroxide Sludges.  

National Technical Information Service (NTIS)

A two-year study investigating the potential for metal value recovery from metal hydroxide sludges has been completed. The objectives of the study were to: Develop a flowsheet to separate and recover metal values from metal finishing hydroxide sludge mate...

L. G. Twidwell

1985-01-01

389

Molten Hydroxide Trapping Process for Radioiodine  

SciTech Connect

A molten hydroxide trapping process has been considered for removing radioiodine species from off-gas streams whereby iodine is reacted directly with molten hydroxides such as NaOH or KOH. The resulting product is the corresponding iodide, which can be separated by simple cooling of the molten mixture to grow the iodide primary phase once the mixture reaches 70-80 mol% in the iodide component. Thermodynamic analysis indicates that such a chemical process is highly favorable. Experimental testing of the trapping process using molecular iodine showed trapping of up to 96% of the volatile iodine. The trapping efficiency was dependent on operational parameters such as temperature and gas-melt contact efficiency, and higher efficiencies are expected as the process is further developed. While an iodide phase could be effectively isolated by slow cooling of a molten iodide-hydroxide mixture, the persistent appearance of hydroxide indicated that an appreciable solubility of hydroxide occurred in the iodide phase.

Trowbridge, L.D.

2003-01-28

390

Contribution to the Knowledge of Nickel Hydroxide Electrodes. 5. Analysis and Electrochemical Behavior of Cadmium Nickel Hydroxides.  

National Technical Information Service (NTIS)

Electrochemical experiments performed at sintered and bulk electrodes show that beta nickel hydroxide contains an electrochemically inactive proportion of cadmium hydroxide of up to 10%. The electrochemically ineffective cadmium hydroxide is homogeneously...

H. Bode W. Dennstedt

1981-01-01

391

Particle-induced artifacts in the MTT and LDH viability assays  

PubMed Central

In vitro testing is a common first step in assessing combustion generated and engineered nanoparticle related health hazards. Commercially available viability assays are frequently used to compare the toxicity of different particle types and to generate dose response data. Nanoparticles, well known for having large surface areas and chemically active surfaces, may interfere with viability assays, producing a false assessment of toxicity and making it difficult to compare toxicity data. The objective of this study is to measure the extent of particle interference in two common viability assays, the MTT reduction and the lactate dehydrogenase (LDH) release assays. Diesel particles, activated carbon, flame soot, oxidized flame soot, and titanium dioxide particles are assessed for interactions with the MTT and LDH assay under cell-free conditions. Diesel particles, at concentrations as low as 0.05 ?g/ml, reduce MTT. Other particle types reduce MTT only at a concentration of 50 ?g/ml and higher. The activated carbon, soot, and oxidized soot particles bind LDH to varying extents, reducing the concentration measured in the LDH assay. The interfering effects of the particles explain in part the different toxicities measured in human bronchial epithelial cells (16HBE14o). We conclude that valid particle toxicity assessments can only be assured after first performing controls to verify that the particles under investigation do not interfere with a specific assay at the expected concentrations.

Holder, Amara L.; Goth-Goldstein, Regine; Lucas, Donald; Koshland, Catherine P.

2012-01-01

392

Simple isoelectric focusing method to quantitate LDH isoenzymes in cultured cells for cell characterization  

Microsoft Academic Search

Isoelectric focusing is a high-resolving electrophoretic technique which separates proteins {includ- ing isoenzymes) on the basis of isoelectric point. Staining techniques are available for visual detec- tion of specific isoenzymes and, when coupled with isoelectric focusing, produce an enzyme profile which is characteristic for a particular cell line. The procedure described below is specific for LDH (lactate dehydrogenase) isoenzymes although

R. D. Ellender; B. L. Middlebrooks; P. M. Toom

1977-01-01

393

Hypoxia and cobalt stimulate lactate dehydrogenase (LDH) activity in vascular smooth muscle cells  

Microsoft Academic Search

O2 plays a dominant role in the metabolism and viability of cells; changes in O2 supply lead to many physiological responses in the cell. Recent reports have shown that hypoxia induces the transcription of a number of genes, among them those for the glycolytic enzymes. We have investigated signalling events that may lead to enhanced activity of lactate dehydrogenase (LDH)

Hugo H. Marti; Hans H. Jung; Josef Pfeilschifter; Christian Bauer

1994-01-01

394

Investigation of histidine stabilizing effects on LDH during freeze-drying.  

PubMed

The objective of this study was to investigate the effect of histidine on the stability of the model protein lactate dehydrogenase (LDH) during freeze-drying. Several parameters were varied including pH of the bulk solution, histidine concentration, and performance of an annealing step during freezing. First, histidine was used as a buffer in the protein formulations and compared with "conventional" potassium phosphate and citrate buffer systems. For this purpose, sucrose or mannitol was used as stabilizers. Second, the possibility of using histidine as both buffer and stabilizer (cryoprotectant and lyoprotectant) in the protein formulations was evaluated with focus on protein stability and the physical state of histidine in the final product, in addition to cake elegance. Protein stability was evaluated both functionally by measuring the activity recovery of the model protein LDH after freeze-drying and structurally by analyzing the protein secondary structure. LDH showed improved stability in histidine buffer in comparison with other buffers. Protein stability and the tendency of histidine to crystallize during freeze-drying were pH dependent. Annealing destabilized LDH and resulted in a decrease of the activity recovery. However, the extent of protein destabilization caused by annealing appears to be also pH dependent. PMID:23280685

Al-Hussein, Anas; Gieseler, Henning

2012-12-20

395

Very high levels of SGOT and LDH in patients with extrahepatic biliary tract obstruction  

Microsoft Academic Search

Very high levels of SGOT (1710, 2450 and >1250) and LDH (1275, 1740 and 1300) are reported in 3 cases of extrahepatic obstruction due to gallstones. The diagnoses were established at operation, and viral hepatitis was ruled out by liver biopsy. Marked SGOT elevations in extrahepatic biliary obstruction are rare, but isolated case reports and experimental biliary obstruction in animals

Allen L. Ginsberg

1970-01-01

396

Controllable synthesis of zinc-substituted alpha- and beta-nickel hydroxide nanostructures and their collective intrinsic properties.  

PubMed

A new controllable homogeneous precipitation approach has been developed to synthesize zinc-substituted nickel hydroxide nanostructures with different Zn contents from a zinc nanostructured reactant. As typical layered double hydroxides (LDHs), zinc-substituted nickel hydroxide nanostructures can be formulated as NiZnx(Cl)y(OH)2(1+x)-y.z H2O (x=0.34-0.89, y=0-0.24, z=0-1.36). The structure and morphology of zinc-substituted nickel hydroxide nanostructures can be systematically controlled by adjustment of the zinc content. The effects of temperature and the amounts of ammonia and zinc nanostructured precursor on the reaction were systematically investigated. In our new method, although zinc-substituted alpha-and beta-nickel hydroxides have the typical 3D flowerlike architecture and stacks-of-pancakes nanostructures, respectively, their growth processes are different from those previously reported. A coordinative homogeneous precipitation mechanism is proposed to explain the formation process of zinc-substituted nickel hydroxide nanostructures. The zinc-substituted nickel hydroxide nanostructures exhibit some interesting intrinsic properties, and changing the zinc content can effectively tune their optical, magnetic, and electrical properties. PMID:18720335

Hu, Bo; Chen, Shao-Feng; Liu, Shu-Juan; Wu, Qing-Song; Yao, Wei-Tang; Yu, Shu-Hong

2008-01-01

397

Copper, silver, gold and zinc, cadmium, mercury oxides and hydroxides  

SciTech Connect

This book provides a compilation of solubility data published up to 1984, including evaluations of the data. Data are presented on the following: copper (I) oxide; copper (II) oxide and hydroxide; silver (I) oxide; silver (II) oxide; gold (III) hydroxide; zinc oxide and hydroxide; cadmium oxide and hydroxide; and mercury (II) oxide.

Dirkse, T.P.

1986-01-01

398

Homogeneous Precipitation of Nickel Hydroxide Powders.  

National Technical Information Service (NTIS)

Precipitation and characterization of nickel hydroxide powders were investigated. A comprehensive precipitation model incorporating the metal ion hydrolysis, complexation and precipitation reactions was developed for the production of the powders with ure...

B. Mavis

2003-01-01

399

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2013 CFR

...several forms, including pellets, flakes, sticks, lumps, and powders. Potassium hydroxide is obtained commercially from the electrolysis of potassium chloride solution in the presence of a porous diaphragm. (b) The ingredient meets the...

2013-04-01

400

Associative detachment of rubidium hydroxide  

NASA Astrophysics Data System (ADS)

We performed calculations of the optimized structure, harmonic vibrational frequencies, and dissociation energies of RbOH and its anion, and investigate the interactions between Rb and OH- leading to possible associative detachment pathways. The electron affinity of RbOH was computed to be 0.2890 eV, with a bond energy of Rb+OH- half that of Rb+OH. To determine other possible charge loss pathways, the Rb+OH and Rb+OH- dissociation curves were computed using coupled-cluster methods along all possible collisional angles. An adiabatic curve crossing between the neutral and charged molecule was found at the inner wall of the molecular potential curve for linear geometries. Associative detachment rates were estimated using the Langevin ion capture cross section for hydroxide. We find for v?2 an associative detachment rate of >2×10-9 cm3s-1, while for v=0 and 1 no appreciable rate exists. This strong dependence on vibrational level suggests the ability to control the associative detachment rate directly.

Byrd, Jason N.; Michels, H. Harvey; Montgomery, John A., Jr.; Côté, Robin

2013-09-01

401

Potassium hydroxide for shale stability  

SciTech Connect

Use of potassium hydroxide (KOH) in lime mud treated with modified starch deflocculant provides excellent shale stability in either weighted or unweighted muds. The added benefits are achieved with little difference in mud cost per barrel when compared to conventional lime muds. Also, the muds have reduced hole enlargement, cuttings dispersion and mud costs in comparison to lignosulfonate and KCl/ polymer muds. No problems with gelation have occurred in any of the wells drilled to date, and muds have remained stable at bottomhole temperatures to 300/sup 0/F. Lignosulfonate dispersants are not recommended and have not been required in any of the wells drilled with this system. Commonly available treating agents, except for the modified starch deflocculant, are used for routine system maintenance. The unique interaction of lime and potassium in these systems is partially responsible for their ability to control wellbore instability caused by shale hydration. Elimination of strong dispersants also has aided in combating hole erosion. Keys to successful use of the KLM system have been proper planning of the mud program, preparation of the rig, careful rig-site monitoring and maintenance of mud composition and properties. Rig-site pilot testing was done to prepare for changing drilling conditions. Overall, it has been found that lime muds treated with KOH and modified starch deflocculant combine many features considered desirable in today's complex drilling environments, and the combination of old and new technology has proven to be a cost-effective alternative to other popular mud systems.

Walker, T.O.; Dearing, H.L.; Simpson, J.P.

1983-11-01

402

Nickel hydroxide precipitation from aqueous sulfate media  

NASA Astrophysics Data System (ADS)

Hydrometallurgical processing of laterite ores constitutes a major industrial and R&D activity in extractive metallurgy. In some of the process flowsheets, nickel hydroxide precipitation is incorporated. For these operations, the optimization of nickel hydroxide precipitation is important to assure efficiency and product quality. The main objective of this investigation was to study and improve the precipitation characteristics of Ni(OH)2 in a sulfate system using supersaturation controlled precipitation.

Sist, Cinziana; Demopoulos, George P.

2003-08-01

403

Caustic cracking from potassium hydroxide in syngas  

SciTech Connect

Potassium hydroxide (KOH) stress corrosion cracking (SCC) caused failure of a type 304L (UNS S30403) stainless steel bypass in a steam methane reforming unit. KOH was from a potassium-promoted catalyst. A test program determined that hydrogen and/or carbon monoxide (CO) were necessary to promote this cracking at relatively low temperatures. Sodium hydroxide (NaOH) was found to cause SCC at lower temperatures than KOH.

Dean, S.W.

1999-01-01

404

Molecular and functional characterization of the murine ldh2 promoter region: Sp-binding GC-box domains are the key cis-elements regulating ldh2 gene expression during spermatogenesis.  

PubMed

The goal of the present study was to elucidate the specific transcriptional mechanisms that regulate ldh2 gene expression during the early stages of spermatogenesis. DNA sequence analysis of the 1.0-kb ldh2 promoter region directly upstream of the transcriptional start site indicated the presence of three SP-protein binding GC-box elements and the absence of TATA and CAAT boxes. Functional characterization studies of the mouse ldh2 promoter were performed in the SV40 transformed mouse spermatogonial cell line, GC-1 spg. Transfection/transient expression studies using full-length and truncated ldh2 promoter/luciferase reporter constructs revealed that all three of the SP-binding cis-regulatory GC-box elements are required for optimal ldh2 promoter activity. Additional site-directed mutagenesis studies indicated that the two most proximal GC-box sites play essential regulatory roles in mediating basal ldh2 promoter activity. These studies suggest that the expression of the ldh2 gene in spermatogonia and early spermatocytes are regulated by SP-mediated transcriptional mechanisms. PMID:18790003

Chen, Xing; Yang, Jun; Sung, Dae-Yong; Thompson, Winston; Walker, William; Thomas, Kelwyn

2008-08-23

405

Lactate dehydrogenase-5 (LDH-5) overexpression in non-small-cell lung cancer tissues is linked to tumour hypoxia, angiogenic factor production and poor prognosis  

Microsoft Academic Search

Lactate dehydrogenase-5 (LDH-5) catalyses the reversible transformation of pyruvate to lactate, having a principal position in the anaerobic cellular metabolism. Induction of LDH-5 occurs during hypoxia and LDH-5 transcription is directly regulated by the hypoxia-inducible factor 1 (HIF1). Serum LDH levels have been correlated with poor prognosis and resistance to chemotherapy and radiotherapy in various neoplastic diseases. The expression, however,

M I Koukourakis; A Giatromanolaki; E Sivridis; G Bougioukas; V Didilis; K C Gatter; A L Harris

2003-01-01

406

Molecular mechanism of SugR-mediated sugar-dependent expression of the ldhA gene encoding l -lactate dehydrogenase in Corynebacterium glutamicum  

Microsoft Academic Search

This paper reports on the transcriptional regulation mechanism of the Corynebacterium glutamicum ldhA gene encoding l-lactate dehydrogenase responsible for production of l-lactate. DNA affinity purification allowed us to identify SugR, a global repressor of genes involved in sugar uptake and\\u000a glycolysis, as a protein binding to the ldhA promoter region. Whereas ldhA gene expression and ldhA promoter activity were completely

Koichi Toyoda; Haruhiko Teramoto; Masayuki Inui; Hideaki Yukawa

2009-01-01

407

Enhanced hydrogen production from glucose using ldh - and frd -inactivated Escherichia coli strains  

Microsoft Academic Search

We improved the hydrogen yield from glucose using a genetically modified Escherichia coli. E. coli strain SR15 (?ldhA, ?frdBC), in which glucose metabolism was directed to pyruvate formate lyase (PFL), was constructed. The hydrogen yield of wild-type strain of 1.08 mol\\/mol glucose, was enhanced to 1.82 mol\\/mol glucose in strain SR15. This figure is greater than 90 % of the theoretical hydrogen

Akihito Yoshida; Taku Nishimura; Hideo Kawaguchi; Masayuki Inui; Hideaki Yukawa

2006-01-01

408

d -lactic acid production from cellooligosaccharides and ?-glucan using l -LDH gene-deficient and endoglucanase-secreting Lactobacillus plantarum  

Microsoft Academic Search

In order to achieve direct fermentation of an optically pure d-lactic acid from cellulosic materials, an endoglucanase from a Clostridium thermocellum (CelA)-secreting plasmid was introduced into an l-lactate dehydrogenase gene (ldhL1)-deficient Lactobacillus plantarum (?ldhL1) bacterial strain. CelA expression and its degradation of ?-glucan was confirmed by western blot analysis and enzyme assay,\\u000a respectively. Although the CelA-secreting ?ldhL1 assimilated cellooligosaccharides up

Kenji Okano; Qiao Zhang; Shogo Yoshida; Tsutomu Tanaka; Chiaki Ogino; Hideki Fukuda; Akihiko Kondo

2010-01-01

409

Hydroxide and Proton Migration in Aquaporins  

PubMed Central

Hypothetical hydroxide and proton migration along the linear water chain in Aquaporin GlpF from Escherichia coli are studied by ab initio Car-Parrinello molecular dynamics simulations. It is found that the protein stabilizes a bipolar single file of water. The single file features a contiguous set of water-water hydrogen bonds in which polarization of the water molecules vary with position along the channel axis. Deprotonation of the water chain promotes the reorientation of water molecules while the hydroxide ion rapidly migrates by sequentially accepting protons from the neighboring water molecules. The hydroxide ion is not attracted by a conserved, channel-lining arginine residue, but is immobilized at two centrally located, conserved Asparagine-Proline-Alanine motifs where fourfold coordination stabilizes the ion. Hydroxide transition from the channel vestibules into the channel lumen is strongly influenced by electrostatic coupling to two conserved oppositely aligned macrodipoles. This suggests that the macrodipole's negative poles play a role in preventing hydroxide ions from entering into the channel's inner vestibules. Water protonation within the lumen facilitates water reorientation and subsequent proton expelling occurs. In the periplasmic half-channel, expelling occurs via the Grotthuss mechanism. Protonation within the cytoplasmic half-channel implies wire-breakage at the Asn-Pro-Ala motifs. The proton is here diffusively rejected as (H5O2)+.

Jensen, Morten ?.; Rothlisberger, Ursula; Rovira, Carme

2005-01-01

410

Effect of neem limonoids on lactate dehydrogenase (LDH) of the rice leaffolder, Cnaphalocrocis medinalis (Guenée) (Insecta: Lepidoptera: Pyralidae).  

PubMed

Neem is derived from the neem tree Azadirachta indica A. Juss. (Meliaceae), and its primary insecticidal component is the tetranortriterpenoid azadirachtin and other limonoids. The effect of neem limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin on enzyme lactate dehydrogenase (LDH) activity of the rice leaffolder (RLF) Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) larvae was investigated. There was a decrease in enzyme activity relative to the control at all concentrations tested. When fed a diet of rice leaves treated with neem limonoids in bioassays, gut tissue enzyme, LDH levels in rice leaffolder larvae are affected. These results indicate neem limonoids affect LDH activity. These effects are most pronounced in early instar larvae. Azadirachtin was the most potent in of all the limonoids in all experiments indicating strong enzyme inhibition. Clear dose-response relationships were established with respect to LDH activity. PMID:16154614

Senthil Nathan, Sengottayan; Kalaivani, Kandaswamy; Chung, Paul Gene; Murugan, Kadarkarai

2005-09-12

411

Iodine Sequestration Using Delafossites and Layered Hydroxides  

SciTech Connect

The objective of this document is to report on early success for sequestering {sup 129}I. Sorption coefficients (K{sub d}) for I{sup -} and IO{sub 3}{sup -} onto delafossites, spinels and layered metal hydroxides were measured in order to compare their applicability for sequestering {sup 129}I. The studies were performed using a dilute fluid composition representative of groundwater indigenous to the Yucca mountain area. Delafossites generally exhibited relatively poor sorption coefficients (< 10{sup 1.7} mL/g). In contrast, the composition of the layered hydroxides significantly affects their ability to sorb I. Cu/Al and Cu/Cr layered hydroxide samples exhibit K{sub d}'s greater than 10{sup 3} mL/g for both I{sup -} and IO{sub 3}{sup -}.

J.D. Pless; J.B. Chwirka; J.L. Krumhansl

2006-03-28

412

Alteration of hydrogen metabolism of ldh- deleted Enterobacter aerogenes by overexpression of NAD(+)-dependent formate dehydrogenase  

Microsoft Academic Search

The NAD+-dependent formate dehydrogenase FDH1 gene (fdh1), cloned from Candida boidinii, was expressed in the ldh-deleted mutant of Enterobacter aerogenes IAM1183 strain. The plasmid of pCom10 driven by the PalkB promoter was used to construct the fdh1 expression system and thus introduce a new dihydronicotinamide adenine dinucleotide (NADH) regeneration pathway from formate\\u000a in the ldh-deleted mutant. The knockout of NADH-consuming

Yuan Lu; Hongxin Zhao; Chong Zhang; Qiheng Lai; Xi Wu; Xin-Hui Xing

2010-01-01

413

Protein and LDH-isoenzyme pattern of the urine from patients with diabetes mellitus determined by disc-electrophoresis  

Microsoft Academic Search

Summary  We have examined U-LDH excretion, protein excretion (a.m. Kjeldahl) and, by means of disc electrophoresis, the pattern of protein and LDH isoenzymes in urine from 73 diabetics. The diabetics are classified into JDM: 0–24 years, ADM: 25–64 years, EDM: > 65 years, Recent JDM: duration 1 year, nephropathy: protein excretion 500 mg\\/24h. — Conclusions: There is increased urinary protein excretion

L. Hemmingsen; N. Høiby; P. Kragh-Søbensen

1970-01-01

414

Measurement of intracellular LDH activity in 96-well cultures: A rapid and automated assay for cytotoxicity studies  

Microsoft Academic Search

Summary  The present paper describes a rapid, easy, sensitive, and automated spectrophotometric assay for intracellular lactate dehydrogenase\\u000a (LDH) measurement in 96-well plates of adherent cells for cytotoxicity studies. The procedure involves “in situ” homogenization\\u000a of cells, followed by measurement of LDH activity with a colorimetric method based on the reduction of a tetrazolium salt\\u000a to a violet formazan by the NADH

Xavier Ponsoda; Ramiro Jover; José Vicente Castell; María José Gómez-Lechón

1991-01-01

415

Method of manufacturing positive nickel hydroxide electrodes  

DOEpatents

A method of manufacturing a positive nickel hydroxide electrode is discussed. A highly porous core structure of organic material having a fibrous or reticular texture is uniformly coated with nickel powder and then subjected to a thermal treatment which provides sintering of the powder coating and removal of the organic core material. A consolidated, porous nickel support structure is thus produced which has substantially the same texture and porosity as the initial core structure. To provide the positive electrode including the active mass, nickel hydroxide is deposited in the pores of the nickel support structure.

Gutjahr, M.A.; Schmid, R.; Beccu, K.D.

1975-12-16

416

Inhibition of LDH-A by oxamate induces G2/M arrest, apoptosis and increases radiosensitivity in nasopharyngeal carcinoma cells.  

PubMed

An elevated rate of glucose consumption and the dependency on aerobic glycolysis for ATP generation have long been observed in cancer cells, a phenomenon known as the Warburg effect. the altered energy metabolism in cancer cells provides an attractive opportunity for developing novel cancer therapeutic strategies. Lactate dehydrogenase (LDH), which catalyzes the transformation of pyruvate to lactate, plays a vital role in the process of glycolysis. It has been reported that the level of LDH-A expression is increased both in head and neck cancer cells and in the blood serum of nasopharyngeal carcinoma (NPC) patients, and is associated with poor prognosis. However, the effect of LDH-A inhibition on NPC cells remains unknown. Here, in the present study, we found that oxamate, a classical inhibitor of LDH-A, suppressed cell proliferation in a dose- and time-dependent manner both in CNE-1 and CNE-2 cells, two NPC cancer cell lines. LDH inhibition by oxamate induced G2/M cell cycle arrest via downregulation of the CDK1/cyclin B1 pathway and promoted apoptosis through enhancement of mitochondrial ROS generation. N-acetylcysteine, a specific scavenger of ROS, significantly blocked the growth inhibition effect induced by oxamate. We also identified that oxamate increased sensitivity to ionizing radiation in the two NPC cancer cell lines. Furthermore, we verified similar results in tumor xenograft models. collectively, these results suggest that LDH-A may serve as a promising therapeutic target for NPC treatment. PMID:24064966

Zhai, Xiaoming; Yang, Yang; Wan, Jianmei; Zhu, Ran; Wu, Yiwei

2013-09-19

417

Regulation of lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH) synthesis in liver nuclei, following their transfer into oocytes.  

PubMed

The regulatory effect of oocyte cytoplasm on the synthetic activity of transferred somatic cell nuclei was studied using an interspecific hybrid combination of Ambystoma texanum and Ambystoma mexicanum (axolotl). The enzymes lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH) were used as markers of gene activity. In both species of salamanders, LDH is synthesized in the liver and oocytes, while ADH is tissue-specific being synthesized in the liver but not oocytes. Both LDH and ADH show species-specific patterns on starch gels which permit detection of enzymes synthesized by texanum liver nuclei following their transfer into axolotl oocytes. Analysis of recipient oocytes after 1-3 weeks in culture reveals the presence of newly synthesized texanum LDH but not ADH. These results indicate that the transferred texanum liver cell nuclei continue to synthesize a product (LDH) found in both liver cells and oocytes, but fail to synthesize the liver-specific product (ADH) which is normally absent in oocytes. Thus, in the case of ADH and LDH the oocyte cytoplasm appears to be able to regulate the synthetic activity of the transferred somatic cell nuclei so as to conform to the oocytes' normal synthetic output. PMID:12194433

Etkin, L D

1976-09-01

418

Cetuximab Reverses the Warburg Effect by Inhibiting HIF-1-Regulated LDH-A.  

PubMed

Hypoxia-inducible factor-1 (HIF-1) plays a critical role in reprogramming cancer metabolism toward aerobic glycolysis (i.e., the Warburg effect), which is critical to supplying cancer cells with the biomass needed for proliferation. Previous studies have shown that cetuximab, an EGF receptor-blocking monoclonal antibody, downregulates the alpha subunit of HIF-1 (HIF-1?) through the inhibition of EGF receptor downstream cell signaling and that downregulation of HIF-1? is required for cetuximab-induced antiproliferative effects. However, the mechanism underlying these actions has yet to be identified. In this study, we used the Seahorse XF96 extracellular flux analyzer to assess the effect of cetuximab treatment on changes in glycolysis and mitochondrial respiration, the two major energy-producing pathways, in live cells. We found that cetuximab downregulated lactate dehydrogenase A (LDH-A) and inhibited glycolysis in cetuximab-sensitive head and neck squamous cell carcinoma (HNSCC) cells in an HIF-1? downregulation-dependent manner. HNSCC cells with acquired cetuximab resistance expressed a high level of HIF-1? and were highly glycolytic. Overexpression of a HIF-1? mutant (HIF-1?/?ODD) conferred resistance to cetuximab-induced G1 phase cell-cycle arrest, which could be overcome by knockdown of LDH-A expression. Inhibition of LDH-A activity with oxamate enhanced the response of cetuximab-resistant cells to cetuximab. Cetuximab had no noticeable inhibitory effect on glycolysis in nontransformed cells. These findings provide novel mechanistic insights into cetuximab-induced cell-cycle arrest from the perspective of cancer metabolism and suggest novel strategies for enhancing cetuximab response. Mol Cancer Ther; 12(10); 2187-99. ©2013 AACR. PMID:23920275

Lu, Haiquan; Li, Xinqun; Luo, Zhongguang; Liu, Jie; Fan, Zhen

2013-08-06

419

BAM R73: 1 N Sodium Hydroxide Solution  

Center for Food Safety and Applied Nutrition (CFSAN)

... BAM R73: 1 N Sodium Hydroxide Solution. January 2001. Bacteriological Analytical Manual. R73 1 N Sodium Hydroxide Solution. ... More results from www.fda.gov/food/foodscienceresearch/laboratorymethods

420

Structural transformation of nickel hydroxide films during anodic oxidation.  

National Technical Information Service (NTIS)

The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode ev...

R. H. Muller R. W. Crocker

1992-01-01

421

21 CFR 872.3250 - Calcium hydroxide cavity liner.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3250 Calcium hydroxide cavity liner. (a) Identification. A calcium hydroxide cavity...

2013-04-01

422

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...Specifications. Alumina (dried aluminum hydroxide) shall conform to the...more than 1 part per million. Aluminum oxide (Al2 O3 ), not less than...restrictions. Alumina (dried aluminum hydroxide) may be safely...

2010-04-01

423

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...Specifications. Alumina (dried aluminum hydroxide) shall conform to the...more than 1 part per million. Aluminum oxide (Al2 O3 ), not less than...restrictions. Alumina (dried aluminum hydroxide) may be safely...

2009-04-01

424

Structural transformation of nickel hydroxide films during anodic oxidation  

SciTech Connect

The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably