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1

Start | Author Index 741-8 Real Time Kinetics of Ni-Al Layered Double Hydroxide (LDH) Formation on Pyrophyllite.  

E-print Network

research show that nickel preferably co-precipitates with aluminum, in a Ni-Al hydroxide phase. The rateStart | Author Index 741-8 Real Time Kinetics of Ni-Al Layered Double Hydroxide (LDH) Formation, DE 19717-1303 Metal sorption on clays and oxides often results in mixed-cation hydroxide surface

Sparks, Donald L.

2

A pH-Responsive Layered Double Hydroxide (LDH)-Phthalocyanine Nanohybrid for Efficient Photodynamic Therapy.  

PubMed

A pH-responsive nanohybrid (LDH-ZnPcPS4 ), in which a highly hydrophilic zinc(II) phthalocyanine tetra-?-substituted with 4-sulfonatophenoxy groups (ZnPcPS4 ) is incorporated with a cationic layered double hydroxide (LDH) based on electrostatic interaction, has been specially designed and prepared through a facile co-precipitation approach. ZnPcPS4 is an excellent singlet-oxygen generator with strong absorption at the near-infrared region (692?nm) in cellular culture media, whereas the photoactivities of ZnPcPS4 were remarkably inhibited after incorporation with the LDH. The nanohybrid is essentially stable in aqueous media at pH?7.4; nevertheless, in slightly acidic media of pH?6.5 or 5.0, ZnPcPS4 can be efficiently released from the LDH matrix, thus leading to restoration of the photoactivities. The nanohybrid shows a high photocytotoxicity against HepG2 cells as a result of much more efficient cellular uptake and preferential accumulation in lysosomes, whereby the acidic environment leads to the release of ZnPcPS4 . The IC50 value of LDH-ZnPcPS4 is as low as 0.053??M, which is 24-fold lower than that of ZnPcPS4 . This work provides a facile approach for the fabrication of photosensitizers with high photocytotoxicity, potential tumor selectivity, and rapid clearance character. PMID:25639348

Li, Xing-Shu; Ke, Mei-Rong; Huang, Wei; Ye, Chun-Hong; Huang, Jian-Dong

2015-02-16

3

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

4

ZnCr Layered Double Hydroxide (LDH) Nanosheets Assisted Formation of Hierarchical Flower-Like CdZnS@LDH Microstructures with Improved Visible-Light-Driven H2 Production.  

PubMed

The development of new semiconductor photocatalysts toward splitting water has supplied a promising way to obtain sustainable and clean hydrogen energy. Herein, CdZnS@layered double hydroxide (LDH) composites with a hierarchical flower-like microstructure have been fabricated with the aid of ZnCr-LDH nanosheets as templates. XRD, SEM and HRTEM show that the ZnCr-LDH nanosheets are uniformly dispersed within the composites. The surface of the hierarchical structures is rough and composed of numerous nanocrystals of CdZnS. The HRTEM images indicate that the surface of CdZnS nanocrystals is mainly composed of the (111) plane. Moreover, the visible-light-driven H2 production performance of the CdZnS in the presence and absence of ZnCr-LDH nanosheets has been measured. The results show that ZnCr-LDH nanosheets play an important role in the hierarchical morphology and photocatalytic activity of the as-prepared samples. In the water-splitting process, the visible-light-driven H2 -production rate of hierarchical flower-like CdZnS@LDH is 4.03 times and nearly 10 times higher than that of pristine CdZnS microsphere and pure commercial CdS, respectively. Therefore, this work not only achieves enhanced catalytic performance of the CdZnS by the introduction of ZnCr-LDH nanosheets, but also supplies an insight into the relationship between the hierarchical morphology and the semiconductor photocatalytic activity. PMID:25641903

Yao, Lihua; Wei, Ding; Yan, Dongpeng; Hu, Changwen

2015-03-01

5

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

NASA Astrophysics Data System (ADS)

Following different preparation routes, fenbufen has been intercalated in the interlayer space of layered double hydroxides with Mg 2+ and Al 3+ or Mg 2+, Al 3+ and Fe 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 Å. 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.

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

2010-12-01

6

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

7

Highly biocompatible behaviour and slow degradation of a LDH (layered double hydroxide)-coating on implants in the middle ear of rabbits.  

PubMed

Chronic inflammation can irreversibly damage components of the ossicular chain which may lead to sound conduction deafness. The replacement of impaired ossicles with prostheses does not reduce the risk of bacterial infections which may lead to loss of function of the implant and consequently to additional damage of the connected structures such as inner ear, meninges and brain. Therefore, implants that could do both, reconstruct the sound conduction and in addition provide antibacterial protection are of high interest for ear surgery. Layered double hydroxides (LDHs) are promising novel biomaterials that have previously been used as an antibiotic-releasing implant coating to curb bacterial infections in the middle ear. However, animal studies of LDHs are scarce and there exist only few additional data on the biocompatibility and hardly any on the biodegradation of these compounds. In this study, middle ear prostheses were coated with an LDH compound, using suspensions of nanoparticles of an LDH containing Mg and Al as well as carbonate ions. These coatings were characterized and implanted into the middle ear of healthy rabbits for 10 days. Analysis of the explanted prostheses showed only little signs of degradation. A stable health constitution was observed throughout the whole experiment in every animal. The results show that LDH-based implant coatings are biocompatible and dissolve only slowly in the middle ear. They, therefore, appear as promising materials for the construction of controlled drug delivery vehicles. PMID:25577215

Duda, Franziska; Kieke, Marc; Waltz, Florian; Schweinefuß, Maria E; Badar, Muhammad; Müller, Peter Paul; Esser, Karl-Heinz; Lenarz, Thomas; Behrens, Peter; Prenzler, Nils Kristian

2015-01-01

8

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

9

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

PubMed Central

Colon cancer is the third most common cancer and the third largest cause of cancer-related death. Fluorouracil (5-FU) is the front-line chemotherapeutic agent for colon cancer. However, its response rate is less than 60%, even in combination with other chemotherapeutic agents. The side effects of 5-FU also limit its application. Nanoparticles have been used to deliver 5-FU, to increase its effectiveness and reduce side effects. Another common approach for colon cancer treatment is targeted therapy against the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. A recently-invented inhibitor of this pathway, BEZ-235, has been tested in several clinical trials and has shown effectiveness and low side effects. Thus, it is a very promising drug for colon cancer treatment. The combination of these two drugs, especially nanoparticle-packed 5-FU and BEZ-235, has not been studied. In the present study, we demonstrated that nanoparticles of layered double hydroxide (LDH) loaded with 5-FU were more effective than a free drug at inhibiting colon cancer cell growth, and that a combination treatment with BEZ-235 further increased the sensitivity of colon cancer cells to the treatment of LDH-packed 5-FU (LDH-5-FU). BEZ-235 alone can decrease colon cancer HCT-116 cell viability to 46% of the control, and the addition of LDH-5-FU produced a greater effect, reducing cell survival to 8% of the control. Our data indicate that the combination therapy of nanodelivered 5-FU with a PI3K/Akt inhibitor, BEZ-235, may promise a more effective approach for colon cancer treatment. PMID:25075187

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

2014-01-01

10

Layered double hydroxide stability. 1. Relative stabilities of layered double hydroxides and their simple counterparts  

NASA Technical Reports Server (NTRS)

Solutions containing di- and trivalent metal chlorides [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+; M(III) = Al3+, Fe3+] were titrated with NaOH to yield hydrotalcite-like layered double hydroxides (LDH), [[M(II)]1-x[M(III)]x(OH)2][Cl]x yH2O, by way of M(III) hydroxide/hydrous oxide intermediates. Analysis of the resultant titration curves yields nominal solubility constants for the LDH. The corresponding LDH stabilities are in the order Mg < Mn < Co approximately Ni < Zn for M(II) and Al < Fe for M(III). The stability of LDH relative to the separate metal hydroxides/hydrous oxides is discussed.

Boclair, J. W.; Braterman, P. S.

1999-01-01

11

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

12

Layered double hydroxide: Inorganic organic conjugate nanocarrier for methotrexate  

Microsoft Academic Search

Layered double hydroxide (LDH)–methotrexate (MTX) nanohybrids were successfully synthesized using ex situ and in situ processes. X-ray diffraction patterns of the synthesized nanopowders revealed that intercalated MTX molecules were stabilized in tilted longitudinal conformation into the hydroxide interlayer space. Two separate hydroxyl peaks were found in the FTIR spectra of LDH–MTX nanopowders suggesting successful intercalation of the MTX molecule into

Manjusha Chakraborty; Sudip Dasgupta; Poulomi Bose; Akhilesh Misra; Tapan Kumar Mandal; Manoj Mitra; Jui Chakraborty; Debabrata Basu

2011-01-01

13

Oxidative leaching of chromium from layered double hydroxides: Mechanistic studies  

Microsoft Academic Search

The layered double hydroxide (LDH) of Zn with Cr on treatment with a hypochlorite solution releases chromate ions as a result\\u000a of oxidative leaching by a dissolution-reprecipitation mechanism. The residue is found to be ?-Zn(OH)2. The LDH of Mg with Cr on the other hand is resistant to oxidative leaching. In contrast, a X-ray amorphous gel of the coprecipitated\\u000a hydroxides

A. V. Radha; P. Vishnu Kamath

2004-01-01

14

Hierarchical layered double hydroxide nanocomposites: structure, synthesis and applications.  

PubMed

Layered double hydroxide (LDH)-based nanocomposites, constructed by interacting LDH nanoparticles with other nanomaterials (e.g. silica nanoparticles and magnetic nanoparticles) or polymeric molecules (e.g. proteins), are an emerging yet active area in healthcare, environmental remediation, energy conversion and storage. Combining advantages of each component in the structure and functions, hierarchical LDH-based nanocomposites have shown great potential in biomedicine, water purification, and energy storage and conversion. This feature article summarises the recent advances in LDH-based nanocomposites, focusing on their synthesis, structure, and application in drug delivery, bio-imaging, water purification, supercapacitors, and catalysis. PMID:25562489

Gu, Zi; Atherton, John James; Xu, Zhi Ping

2015-02-01

15

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

16

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

SciTech Connect

The synthesis of Mg{sub 2}Al–NO{sub 3} layered double hydroxide (LDH) nanosheets by coprecipitation using a T-type microchannel reactor is reported. Aqueous LDH nanosheet dispersions were obtained. The LDH nanosheets were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy and particle size analysis, and the transmittance and viscosity of LDH nanosheet dispersions were examined. The two-dimensional LDH nanosheets consisted of 1–2 brucite-like layers and were stable for ca. 16 h at room temperature. In addition, the co-assembly between LDH nanosheets and dodecyl sulfate (DS) anions was carried out, and a DS intercalated LDH nanohybrid was obtained. To the best of our knowledge, this is the first report of LDH nanosheets being directly prepared in bulk aqueous solution. This simple, cheap method can provide naked LDH nanosheets in high quantities, which can be used as building blocks for functional materials. - Graphical abstract: Layered double hydroxide (LDH) nanosheets were synthesized by coprecipitation using a T-type microchannel reactor, and could be used as basic building blocks for LDH-based functional materials. Display Omitted - Highlights: • LDH nanosheets were synthesized by coprecipitation using a T-type microchannel reactor. • Naked LDH nanosheets were dispersed in aqueous media. • LDH nanosheets can be used as building blocks for functional materials.

Pang, Xiujiang; Sun, Meiyu; Ma, Xiuming [State Key Laboratory Base of Eco-chemical Engineering, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Hou, Wanguo, E-mail: wghou@sdu.edu.cn [Key Laboratory of Colloid and Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100 (China)

2014-02-15

17

Biological evaluation of layered double hydroxides as efficient drug vehicles  

NASA Astrophysics Data System (ADS)

Recently there has been a rapid expansion of the development of bioinorganic hybrid systems for safe drug delivery. Layered double hydroxides (LDH), a variety of available inorganic matrix, possess great promise for this purpose. In this study, an oxidative stress biomarker system, including measurement of reactive oxygen species, glutathione content, endogenous nitric oxide, carbonyl content in proteins, DNA strand breaks and DNA-protein crosslinks, was designed to evaluate the biocompatibility of different concentrations of nano-Zn/Al-LDH with a Hela cell line. The drug delivery activity of the LDH-folic-acid complex was also assessed. The resulting data clearly demonstrated that nano-LDH could be applied as a relatively safe drug vehicle with good delivery activity, but with the caveat that the effects of high dosages observed here should not be ignored when attempting to maximize therapeutic activity by increasing LDH concentration.

Li, Yan; Liu, Dan; Ai, Hanhua; Chang, Qing; Liu, Dandan; Xia, Ying; Liu, Shuwen; Peng, Nanfang; Xi, Zhuge; Yang, Xu

2010-03-01

18

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

19

Subcellular compartment targeting of layered double hydroxide nanoparticles.  

PubMed

Current investigations show that layered double hydroxide (LDH) nanoparticles have high potential as effective non-viral agents for cellular drug delivery due to their low cytotoxicity, good biocompatibility, high drug loading, control of particle size and shape, targeted delivery and drug release control. Two types of Mg(2)Al-LDH nanoparticles with fluorescein isothiocyanate (FITC) were controllably prepared. One is morphologically featured as typical hexagonal sheets (50-150 nm laterally wide and 10-20 nm thick), while the other as typical rods (30-60 nm wide and 100-200 nm long). These LDH(FTIC) nanoparticles are observed to immediately transfect into different mammalian cell lines. We found that internalized LDH(FITC) nanorods are quickly translocated into the nucleus while internalized LDH(FITC) nanosheets are retained in the cytoplasm. Inhibition experiments show that the cellular uptake is a clathrin-mediated time- and concentration-dependent endocytosis. Endosomal escape of LDH(FITC) nanoparticles is suggested to occur through the deacidification of LDH nanoparticles. Since quick nuclear targeting of LDH(FITC) nanorods requires an active process, and although the exact mechanism is yet to be fully understood, it probably involves an active transport via microtubule-mediated trafficking processes. Targeted addressing of two major subcellular compartments by simply controlling the particle morphology/size could find a number of applications in cellular biomedicine. PMID:18614254

Xu, Zhi Ping; Niebert, Marcus; Porazik, Katharina; Walker, Tara L; Cooper, Helen M; Middelberg, Anton P J; Gray, Peter P; Bartlett, Perry F; Lu, Gao Qing Max

2008-08-25

20

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

21

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

23

Polymer coated CaAl-layered double hydroxide nanomaterials for potential calcium supplement.  

PubMed

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 ?g/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement. PMID:25490138

Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

2014-01-01

24

Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement  

PubMed Central

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 ?g/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement. PMID:25490138

Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

2014-01-01

25

Synthesis, characterization, and sorption capacity of layered double hydroxides and their complexes with polymerin.  

PubMed

Mg-Al layered double hydroxides (LDHs) containing chloride (LDH-Cl) or carbonate (LDH-CO(3)) in the interlayer were obtained at room temperature and after calcitation at 450 degrees C (LDH-Cl-450 and LDH-CO(3)-450) and were characterized by X-ray diffraction and Fourier transform infrared analyses. Sorption isotherms of a humic acidlike fraction naturally occurring in olive oil mill waste waters, named polymerin, on these LDH minerals were carried out. Because LDH-CO(3) showed the highest capacity to sorb polymerin among the four LDH minerals synthesized, two organo-mineral complexes named LDH-CO(3)-LP (low polymerin) and LDH-CO(3)-HP (high polymerin) were prepared by coprecipitation (LDH-CO(3)-LP) and sorption onto a preformed LDH-CO(3) mineral (LDH-CO(3)-HP). These complexes were characterized chemically and physicochemically, and their stability to pH and after thermal treatment at 80 degrees C were evaluated. The diffuse reflectance infrared Fourier transform and X-ray analysis of the complexes indicated that polymerin was sorbed only on the external surfaces of LDH-CO(3) and no intercalation occurred. The LDH-polymerin complexes appeared to be more stable than LDH-CO(3) at pH 4.0 and showed that they were able to sorb both As(V) and Zn. Because the waste waters are usually contaminated with mixtures of pollutants in cationic and anionic forms, the LDH-polymerin complexes appear more suitable than the sorbents in a potential water remediation process. PMID:20405846

Iorio, Marianna; De Martino, Antonio; Violante, Antonio; Pigna, Massimo; Capasso, Renato

2010-05-12

26

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

27

Preparation and characterization of rare earth-containing layered double hydroxides  

Microsoft Academic Search

Novel Layered Double Hydroxide (LDH) phases containing Rare Earth Elements (Ce3+ and Eu3+) have been prepared by ion exchange method using Ln(dipic)33? complexes as guest anions ([C7H3NO4]2?=dipic ligand). Intercalation of Ce3+ and more generally of rare earth cations in the opened structure of LDH displays many interests for applications as catalysts or catalyst precursors and materials with luminescence properties. The

Z. Chang; D. Evans; X. Duan; P. Boutinaud; M. de Roy; C. Forano

2006-01-01

28

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

29

Layered Double Hydroxide-Based Nanocarriers for Drug Delivery  

PubMed Central

Biocompatible clay materials have attracted particular attention as the efficient drug delivery systems (DDS). In this article, we review developments in the use of layered double hydroxides (LDHs) for controlled drug release and delivery. We show how advances in the ability to synthesize intercalated structures have a significant influence on the development of new applications of these materials. We also show how modification and/or functionalization can lead to new biotechnological and biomedical applications. This review highlights the most recent progresses in research on LDH-based controlled drug delivery systems, focusing mainly on: (i) DDS with cardiovascular drugs as guests; (ii) DDS with anti-inflammatory drugs as guests; and (iii) DDS with anti-cancer drugs as guests. Finally, future prospects for LDH-based drug carriers are also discussed. PMID:24940733

Bi, Xue; Zhang, Hui; Dou, Liguang

2014-01-01

30

Treatment with coated layer double hydroxide clays decreases the toxicity of copper-contaminated water.  

PubMed

Copper is a common pollutant found in watersheds that exerts toxic effects on both invertebrates and vertebrates. Layer double hydroxide (LDH) clays are able to adsorb a wide range of contaminants through ion-exchange mechanisms. Coating LDH clays with various materials alters the aggregation of clay particles into the nano-size range, thus increasing relative surface area and offering great potential for contaminant remediation. The goal of this study was to determine if treatment with coated LDH clays decreases the toxicity of copper-containing solutions to Daphnia magna. Four LDH clays with different coatings used to alter hydrophobicity were as follows: used: Na(+) montmorillonite, Zn-Al LDH-nitrate, Zn-Al LDH-stearate, and Zn-Al LDH-carbonate. It was determined that coated LDH clays decreased copper toxicity by decreasing bioavailability and that smaller aggregate sizes decreased bioavailability the most. 96 h LC50 values increased by as much as 4.2 times with the treatment of the solutions with 100 mg/L LDH clay. Copper analysis of the clay and solutions indicated that the clays work by decreasing copper bioavailability by way of a binding mechanism. Coated LDH clays hold promise as a small-scale remediation tool or as an innovative tool for toxicity identification and evaluation characterization of metals. PMID:24442186

Blake, Deanne; Nar, Mangesh; D'Souza, Nandika Anne; Glenn, J Brad; Klaine, Stephen J; Roberts, Aaron P

2014-05-01

31

Complex formation with layered double hydroxides for the remediation of hygroscopicity.  

PubMed

Layered double hydroxides (LDHs) have been used commercially as antacids, to stabilize drugs, to allow the controlled release of incorporated drugs, and to act as drug carriers to reduce drug accumulation within the body. Several types of LDH were investigated: nitrate type (LDH-NO3); chloride type (LDH-Cl); and carbonate type (LDH-CO3). Each type was added to an aqueous or methanol (MeOH) solution containing a drug (pravastatin or nateglinide). With pravastatin sodium, the interlayer distance expanded after reaction with LDH-NO3 and LDH-Cl in aqueous solution. In contrast, the interlayer distance of LDH-CO3 increased in methanol with nateglinide. Each drug was intercalated into the interlayer space of LDH by ion exchange. The hygroscopicity of the drug substances, complexes, and physical mixtures were determined at 70% relative humidity. Increases in weight (%) of the complexes were less than those of the physical mixtures, which demonstrates that hygroscopicity was reduced upon complexation with LDH due to the layer of LDH over the drugs. PMID:25743189

Hayashi, Aki; Kubota, Mai; Okamura, Miki; Nakayama, Hirokazu

2015-01-01

32

Synthesis and bromate reduction of sulfate intercalated Fe(II)–Al(III) layered double hydroxides  

Microsoft Academic Search

The objectives of this study were to (i) synthesize layered double hydroxides (LDH) of Fe2+ and Al3+ containing sulfate ion in the interlayer space, and (ii) to evaluate the reduction of bromate in NaBrO3 solution. The LDH was synthesized by co-precipitation method. The LDH was crystalline having a chemical formula [Fe2+0.67Al3+0.33(OH)2][(SO4)0.16·1.3H2O]. The kinetic study showed that bromate was reduced from

Ramesh Chitrakar; Akinari Sonoda; Yoji Makita; Takahiro Hirotsu

2011-01-01

33

Structural characterisation of a layered double hydroxide nanosheet  

NASA Astrophysics Data System (ADS)

We report the atomic-scale structure of a Zn2Al-borate layered double hydroxide (LDH) nanosheet, as determined by reverse Monte Carlo (RMC) modelling of X-ray total scattering data. This study involves the extension of the RMC method to enable structural refinement of two-dimensional nanomaterials. The refined LDH models show the intra-layer geometry in this highly-exfoliated phase to be consistent with that observed in crystalline analogues, with the reciprocal-space scattering data suggesting a disordered arrangement of the Zn2+ and Al3+ cations within the nanosheet. The approach we develop is generalisable and so offers a method of characterising the structures of arbitrary nanosheet phases, including systems that support complex forms of disorder within the nanosheets themselves.We report the atomic-scale structure of a Zn2Al-borate layered double hydroxide (LDH) nanosheet, as determined by reverse Monte Carlo (RMC) modelling of X-ray total scattering data. This study involves the extension of the RMC method to enable structural refinement of two-dimensional nanomaterials. The refined LDH models show the intra-layer geometry in this highly-exfoliated phase to be consistent with that observed in crystalline analogues, with the reciprocal-space scattering data suggesting a disordered arrangement of the Zn2+ and Al3+ cations within the nanosheet. The approach we develop is generalisable and so offers a method of characterising the structures of arbitrary nanosheet phases, including systems that support complex forms of disorder within the nanosheets themselves. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01265h

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

2014-06-01

34

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

35

Efficient uranium capture by polysulfide/layered double hydroxide composites.  

PubMed

There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2(2+)) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of Sx-LDH composites (LDH is Mg/Al layered double hydroxide, [Sx](2-) is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (qm = 330 mg/g), large Kd(U) values (10(4)-10(6) mL/g at 1-300 ppm U concentration), and high % removals (>95% at 1-100 ppm, or ?80% for ppb level seawater) for UO2(2+) species. The Sx-LDHs are exceptionally efficient for selectively and rapidly capturing UO2(2+) both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value Kd(U) of 3.4 × 10(6) mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca(2+)/Na(+), Sx-LDH exhibits superior selectivity for UO2(2+), over previously reported sorbents. Under low U concentrations, (S4)(2-) coordinates to UO2(2+) forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)(2-) binds to UO2(2+) to generate neutral UO2S4 salts outside the gallery, with NO3(-) entering the interlayer to form NO3-LDH. In the presence of high Cl(-) concentration, Cl(-) preferentially replaces [S4](2-) and intercalates into LDH. Detailed comparison of U removal efficiency of Sx-LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of Sx-LDH materials for selective uranium capture. PMID:25714654

Ma, Shulan; Huang, Lu; Ma, Lijiao; Shim, Yurina; Islam, Saiful M; Wang, Pengli; Zhao, Li-Dong; Wang, Shichao; Sun, Genban; Yang, Xiaojing; Kanatzidis, Mercouri G

2015-03-18

36

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

37

Nitrogen-enriched, double-shelled carbon/layered double hydroxide hollow microspheres for excellent electrochemical performance  

NASA Astrophysics Data System (ADS)

A unique, double-shelled, hollow, carbon-based composite with enriched nitrogen has been prepared through a facile and versatile synthetic strategy. The hierarchical composite employs the nitrogen-enriched carbon hollow sphere as an interior shell and intercrossed Ni/Al layered double hydroxide (LDH) nanosheets as an exterior shell. The obtained N-C@LDH hollow microspheres (HMS) have high nitrogen enrichment, large specific surface area (337 m2 g-1), and uniform and open mesoporous structure. Taking advantage of these characteristics, the composite exhibits obviously superior capacitive behavior, including high specific capacitance, excellent rate capability and good cycling stability, compared with nitrogen-free carbon@LDH composite and hollow LDH without carbon shell. The composite displays high specific capacitance of 1711.51 F g-1 at a current density of 1 A g-1. In particular, the high specific capacitance can be kept to 997.3 F g-1 at a high current density of 10 A g-1, which still retains 94.97% of the initial specific capacitance after 500 cycles at this high current density. This N-enriched, hollow carbon/LDH composite can be expected to be a promising electrode material for electrochemical capacitors due to its high electrochemical performance.A unique, double-shelled, hollow, carbon-based composite with enriched nitrogen has been prepared through a facile and versatile synthetic strategy. The hierarchical composite employs the nitrogen-enriched carbon hollow sphere as an interior shell and intercrossed Ni/Al layered double hydroxide (LDH) nanosheets as an exterior shell. The obtained N-C@LDH hollow microspheres (HMS) have high nitrogen enrichment, large specific surface area (337 m2 g-1), and uniform and open mesoporous structure. Taking advantage of these characteristics, the composite exhibits obviously superior capacitive behavior, including high specific capacitance, excellent rate capability and good cycling stability, compared with nitrogen-free carbon@LDH composite and hollow LDH without carbon shell. The composite displays high specific capacitance of 1711.51 F g-1 at a current density of 1 A g-1. In particular, the high specific capacitance can be kept to 997.3 F g-1 at a high current density of 10 A g-1, which still retains 94.97% of the initial specific capacitance after 500 cycles at this high current density. This N-enriched, hollow carbon/LDH composite can be expected to be a promising electrode material for electrochemical capacitors due to its high electrochemical performance. Electronic supplementary information (ESI) available: IR spectrum of N-C@LDH hollow microspheres, Enlarged TEM images of SiO2@C and carbon hollow spheres, TEM image of N-enriched carbon spheres, SEM images of LDH HMS and C@LDH HMS, EDS analysis of N-enriched carbon spheres, SEM image of the product prepared under the same condition of C@LDH HMS without the AlOOH sol layer deposited on carbon spheres, survey and element XPS spectra of LDH HMS, C@LDH HMS and N-C@LDH HMS, the specific capacitance of as-prepared N-C@LDH HMS, C@LDH HMS and LDH HMS at different discharge current densities. See DOI: 10.1039/c4nr02756f

Xu, Jie; He, Fei; Gai, Shili; Zhang, Shenghuan; Li, Lei; Yang, Piaoping

2014-08-01

38

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

NASA Astrophysics Data System (ADS)

The nitrate containing layered double hydroxide (LDH) of Ca with Al on reaction with aqueous solutions of Na 2CO 3 and Na 3PO 4 yields CaCO 3 and Ca 5(PO 4) 3OH respectively rather than the carbonate/phosphate containing LDHs. The LDH of Mg with Al on reacting with dissolved phosphate ions also leads to the formation of unitary phosphates. This shows that the anion exchange reactions of layered double hydroxides take place by the dissolution-reprecipitation mechanism rather than by the topotactic mechanism.

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

2005-10-01

39

Preparation and burning behaviors of flame retarding biodegradable poly(lactic acid) nanocomposite based on zinc aluminum layered double hydroxide  

Microsoft Academic Search

A flame retarding biodegradable polylactic acid (PLA) nanocomposite based on flame retardant composites (containing ammonium polyphosphate (APP), pentaerythritol (PER) and melamine cyanurate (MC) by controlling the weight ratio was 2:2:1) and organomodified zinc aluminum layered double hydroxide (Zn-Al-LDH) has been prepared by melt-compounding directly. The morphology and burning behaviour of nanocomposite with 2 wt% Zn-Al-LDH loadings were investigated. The extent of

De-Yi Wang; Andreas Leuteritz; Yu-Zhong Wang; Udo Wagenknecht; Gert Heinrich

2010-01-01

40

In situ growth of layered double hydroxide films on anodic aluminum oxide\\/aluminum and its catalytic feature in aldol condensation of acetone  

Microsoft Academic Search

Mg\\/Al layered double hydroxide (LDH) films were fabricated in situ with anodic aluminum oxide (AAO)\\/aluminum as both the substrate and the sole aluminum source by means of urea hydrolysis. The structure and morphology of the LDH films were investigated by X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FT-IR) and scanning electron microscopy (SEM), which show that hexagonal plate-shaped LDH

Zhi Lü; Fazhi Zhang; Xiaodong Lei; Lan Yang; Sailong Xu; Xue Duan

2008-01-01

41

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

42

Zn-Al-NO(3)-layered double hydroxides with intercalated diclofenac for ocular delivery.  

PubMed

This study was aimed to evaluate the potential use of a drug delivery system, drug-layered double hydroxide (LDH) nanocomposites for ocular delivery. Diclofenac was successfully intercalated into Zn-Al-NO(3)-LDH by coprecipitation method. The nanocomposites were characterized by particle size, elemental chemical analysis, thermogravimetric analysis, etc. A tilt bilayer of diclofenac molecules formed in the interlayer with the gallery height of 1.868 nm. In vivo precorneal retention studies were conducted with diclofenac sodium (DS) saline, diclofenac-LDH nanocomposite dispersion, 2% polyvinylpyrrolidone (PVP) K30-diclofenac-LDH nanohybrid dispersion and 10% PVP K30-diclofenac-LDH nanohybrid dispersion, separately. Compared with DS saline, all the dispersions have extended the detectable time of DS from 3h to 6h; C(max) and AUC(0-t) of diclofenac-LDH nanocomposite dispersion showed 3.1-fold and 4.0-fold increase, respectively; C(max) and AUC(0-t) of 2% PVP K30-LDH nanohybrid dispersion were about 5.3-fold and 6.0-fold enhancement, respectively. Results of the Draize test showed that no eye irritation was demonstrated in rabbits after single and repeated administration. These results suggest that this novel ocular drug delivery system appears to offer promise as a means to improving the bioavailability of drugs after ophthalmic applications. PMID:21093561

Cao, Feng; Wang, Yanjun; Ping, Qineng; Liao, Zhenggen

2011-02-14

43

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

SciTech Connect

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. - Graphical abstract: Dependence of ZnAl LDH Morphology on SDS concentration. Highlights: Black-Right-Pointing-Pointer In-situ intercalation of SDS in ZnAl LDH was achieved via urea hydrolysis method. Black-Right-Pointing-Pointer Morphology of ZnAl LDH intercalated with SDS depended on the SDS concentration. Black-Right-Pointing-Pointer Ring like morphology for SDS intercalated ZnAl LDH was obtained for the first time. Black-Right-Pointing-Pointer Growth mechanism was discussed. Black-Right-Pointing-Pointer Template assisted growth of ZnAl LDH was proposed.

Yilmaz, Ceren [Graduate School of Science and Engineering, Koc University, Rumelifeneri Yolu, Sariyer 34450, Istanbul (Turkey); Unal, Ugur [Graduate School of Science and Engineering, Koc University, Rumelifeneri Yolu, Sariyer 34450, Istanbul (Turkey); Koc University, Chemistry Department, Rumelifeneri yolu, Sariyer 34450, Istanbul (Turkey); Koc University, Surface Science and Technology Center, KUYTAM, Rumelifeneri yolu, Sariyer 34450, Istanbul (Turkey); Yagci Acar, Havva, E-mail: fyagci@ku.edu.tr [Graduate School of Science and Engineering, Koc University, Rumelifeneri Yolu, Sariyer 34450, Istanbul (Turkey); Koc University, Chemistry Department, Rumelifeneri yolu, Sariyer 34450, Istanbul (Turkey); Koc University, Surface Science and Technology Center, KUYTAM, Rumelifeneri yolu, Sariyer 34450, Istanbul (Turkey)

2012-03-15

44

Novel HCN sorbents based on layered double hydroxides: sorption mechanism and performance.  

PubMed

Layered double hydroxides (LDHs) and layered double oxides (LDOs) have been prepared and used as sorbents for hydrogen cyanide (HCN). Based on results from sorbent optimization experiments, the optimal performance for HCN removal was found in Ni-Al LDH. As evidenced by fixed-bed sorption studies, the Ni-Al LDO with the greatest surface area showed better performance and outperformed products calcined at 200, 400, or 500 °C, whereas, the Ni-Al LDH showed a more twofold higher sorption capacity than the Ni-Al LDO. Investigation of the mechanisms between HCN and sorbents reveals that the HCN removal by the Ni-Al LDH and Ni-Al LDO leads to the formation of the complex anion, [Ni(CN)4](2-). Nevertheless, the [Ni(CN)4](2-) can enter interlayer region of the Ni-Al LDH due to its anion exchangeability, which endows this LDH with more binding sites, not only on its external surfaces, but also on its internal surfaces located in the interlayer region. In contrast, [Ni(CN)4](2-) were only adsorbed on the external surface of the Ni-Al LDO. As a result, the sorption capacity of the Ni-Al LDH for HCN is twice as high as that of the Ni-Al LDO, which is at 21.55 mg/g. PMID:25497317

Zhao, Qian; Tian, Senlin; Yan, Linxia; Zhang, Qiulin; Ning, Ping

2015-03-21

45

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

PubMed

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

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

2009-05-01

46

Highly stable layered double hydroxide colloids: a direct aqueous synthesis route from hybrid polyion complex micelles.  

PubMed

Aqueous suspensions of highly stable Mg/Al layered double hydroxide (LDH) nanoparticles were obtained via a direct and fully colloidal route using asymmetric poly(acrylic acid)-b-poly(acrylamide) (PAA-b-PAM) double hydrophilic block copolymers (DHBCs) as growth and stabilizing agents. We showed that hybrid polyion complex (HPIC) micelles constituted of almost only Al(3+) were first formed when mixing solutions of Mg(2+) and Al(3+) cations and PAA3000-b-PAM10000 due to the preferential complexation of the trivalent cations. Then mineralization performed by progressive hydroxylation with NaOH transformed the simple DHBC/Al(3+) HPIC micelles into DHBC/aluminum hydroxide colloids, in which Mg(2+) ions were progressively introduced upon further hydroxylation leading to the Mg-Al LDH phase. The whole process of LDH formation occurred then within the confined environment of the aqueous complex colloids. The hydrodynamic diameter of the DHBC/LDH colloids could be controlled: it decreased from 530 nm down to 60 nm when the metal complexing ratio R (R = AA/(Mg + Al)) increased from 0.27 to 1. This was accompanied by a decrease of the average size of individual LDH particles as R increased (for example from 35 nm at R = 0.27 down to 17 nm at R = 0.33), together with a progressive favored intercalation of polyacrylate rather than chloride ions in the interlayer space of the LDH phase. The DHBC/LDH colloids have interesting properties for biomedical applications, that is, high colloidal stability as a function of time, stability in phosphate buffered saline solution, as well as the required size distribution for sterilization by filtration. Therefore, they could be used as colloidal drug delivery systems, especially for hydrosoluble negatively charged drugs. PMID:25087853

Layrac, Géraldine; Destarac, Mathias; Gérardin, Corine; Tichit, Didier

2014-08-19

47

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

Microsoft Academic Search

Corrosion inhibitor-inorganic clay composite including benzoate anion intercalated Zn–Al layered double hydroxides (LDHs) are assembled by coprecipitation. Powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectrum analyses indicate that the benzoate anion is successfully intercalated into the LDH interlayer and the benzene planes are vertically bilayer-positioned as a quasi-guest ion-pair form in the gallery space. Kinetic simulation for the

Yi Wang; Dun Zhang

2011-01-01

48

Hierarchical construction of an ultrathin layered double hydroxide nanoarray for highly-efficient oxygen evolution reaction  

NASA Astrophysics Data System (ADS)

Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (?) of 257 mV is needed for a current density of 80 mA cm-2 with a Tafel slope of 53 mV per decade. The hierarchical LDH nanoarray also shows excellent structural stability in alkaline media. After continuous testing under a high OER current density (~300 mA cm-2) for 10 h, the sample maintains the ordered hierarchical structure with no significant deactivation of the catalytic properties.Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (?) of 257 mV is needed for a current density of 80 mA cm-2 with a Tafel slope of 53 mV per decade. The hierarchical LDH nanoarray also shows excellent structural stability in alkaline media. After continuous testing under a high OER current density (~300 mA cm-2) for 10 h, the sample maintains the ordered hierarchical structure with no significant deactivation of the catalytic properties. Electronic supplementary information (ESI) available: SEM images of the Ni foam and Co-based nanowire arrays; XPS and EDS results of the hierarchical LDH nanoarrays, and gas bubble adhesive force data. See DOI: 10.1039/c4nr03371j

Yang, Qiu; Li, Tian; Lu, Zhiyi; Sun, Xiaoming; Liu, Junfeng

2014-09-01

49

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

SciTech Connect

Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg–Al and Mg–Fe layered double hydroxides (LDHs) have been synthesized by the calcination–rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV–vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO{sub 3}{sup 2?} solutions imply that Mg{sub 3}Al–VC LDH is a better controlled release system than Mg{sub 3}Fe–VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO{sub 3}{sup 2?} solution. - Graphical abstract: Vitamin C anions have been intercalated in the interlayer space of layered double hydroxide and released in CO{sub 3}{sup 2?} solution and deionised water. - Highlights: • Vitamin C intercalated Mg–Al and Mg–Fe layered double hydroxides were prepared. • Release property of vitamin C in aqueous CO{sub 3}{sup 2?} solution is better. • Avrami-Erofe’ev and first-order models provide better fit for release results. • Diffusion-controlled and ion exchange processes occur in deionised water. • An ion exchange process occurs in CO{sub 3}{sup 2?} solution.

Gao, Xiaorui, E-mail: gxr_1320@sina.com [College of Science, Hebei University of Engineering, Handan 056038 (China); School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA (United Kingdom); Lei, Lixu [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); O'Hare, Dermot [Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA (United Kingdom); Xie, Juan [College of Science, Hebei University of Engineering, Handan 056038 (China); Gao, Pengran [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Chang, Tao [College of Science, Hebei University of Engineering, Handan 056038 (China)

2013-07-15

50

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

51

Nanosized Ni–Al layered double hydroxides—Structural characterization  

SciTech Connect

Highlights: ? The takovite anionic clays were obtained using the sol–gel method. ? The effect of samples’ composition on the structural and textural characteristics has been investigated. ? X-ray analysis. ? FTIR spectroscopy evidenced a disordered interlayer structure. ? FESEM and TEM analysis showed that the samples have high porosity. - Abstract: Takovite, a natural mineral with the formula Ni{sub 6}Al{sub 2}(OH){sub 6}CO{sub 3}·5H{sub 2}O belongs to the large class of layered double hydroxides (LDHs) and contains positively charged Ni(II) and Al(III) layers alternating with layers containing carbonate ions and water molecules. Mesoporous takovite-type layered double hydroxides (LDH) of the general formula [Ni{sub 1?x}Al{sub x}(OH){sub 2}]{sup x+}(CO{sub 3}{sup 2?}){sub x/2}·nH{sub 2}O with different Ni/Al molar ratios (1.9–2.8) have been successfully synthesized by the sol–gel method, followed by anionic exchange using nickel acetylacetonate and aluminum isopropylate as cation precursors. A single LDH phase and an anisotropic growth of very small crystallites (below 4 nm) have been evidenced by X-ray diffraction. The effect of samples’ composition on their structural and textural characteristics has been investigated. The BET surface area values are in the range of 100–122 m{sup 2}/g. BJH pore radius decreased with increase in the Al(III) content in the LDHs. FESEM micrographs show large aggregates of highly porous LDH particles, while TEM analysis reveals irregular agglomerates of crystallites, among which some of them displayed a developing hexagonal shape. The average particle size variation with the Al(III) content in the samples follows the same trend as the pore radius, the sample with the highest Ni/Al ratio displaying also the smallest particle size. This sample becomes even more interesting, since TEM analysis shows agglomerates with inside circular structures, feature not observed for the other Ni/Al ratios investigated.

Jitianu, Mihaela, E-mail: jitianum@wpunj.edu [William Paterson University, Department of Chemistry, 300 Pompton Road, Wayne, NJ 07470 (United States); Gunness, Darren C. [William Paterson University, Department of Chemistry, 300 Pompton Road, Wayne, NJ 07470 (United States); Aboagye, Doreen E. [Lehman College – City University of New York, Department of Chemistry, Davis Hall, 250 Bedford Boulevard West, Bronx, NY 10468 (United States); Zaharescu, Maria [Institute of Physical Chemistry, 202 Splaiul Independentei, 060021 Bucharest (Romania); Jitianu, Andrei, E-mail: andrei.jitianu@lehman.cuny.edu [Lehman College – City University of New York, Department of Chemistry, Davis Hall, 250 Bedford Boulevard West, Bronx, NY 10468 (United States)

2013-05-15

52

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

53

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

54

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

2013-01-01

55

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. PMID:23737669

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

2013-01-01

56

Enhanced Cellular Delivery and Biocompatibility of a Small Layered Double Hydroxide–Liposome Composite System  

PubMed Central

The various classes of gene delivery vectors possess distinct advantages and disadvantages, each of which impacts on cargo loading, delivery and, ultimately, its function. With this in mind, herein we report on a small layered double hydroxide (sLDH)–liposome composite system, drawing upon the salient features of LDH and liposome classes of vectors, while avoiding their inherent shortfalls when used independently. sLDH–liposome composites were prepared by the hydration of freeze-dried matrix method. These composite systems, with a Z-average size of ?200 nm, exhibited low cytotoxicity and demonstrated good suspension stability, both in water and cell culture medium after rehydration. Our studies demonstrate that short dsDNAs/ssDNAs were completely bound and protected in the composite system at an sLDH:DNA mass ratio of 20:1, regardless of the approach to DNA loading. This composite system delivered DNA to HCT-116 cells with ?3-fold greater efficiency, when compared to sLDH alone. Our findings point towards the sLDH-liposome composite system being an effective and biocompatible gene delivery system. PMID:25431895

Dong, Haiyan; Parekh, Harendra S.; Xu, Zhi Ping

2014-01-01

57

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

PubMed

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

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

2013-05-01

58

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

59

Ni(3+) doped monolayer layered double hydroxide nanosheets as efficient electrodes for supercapacitors.  

PubMed

Ni(3+) doped NiTi layered double hydroxide (NiTi-LDH) monolayer nanosheets with a particle size of ?20 nm and a thickness of ?0.9 nm have been successfully prepared through a facile bottom-up approach. These NiTi-LDH monolayer nanosheets exhibit excellent supercapacitor performance, including a high specific pseudocapacitance (2310 F g(-1) at 1.5 A g(-1)) and long durability compared with bulk LDH, owing to highly exposed conductive Ni(3+) species (NiOOH) which lead to the increased mobility rate of surface charge and electrolyte-transfer. Therefore, this work is expected to take a significant step towards exploring novel 2D monolayer electrode materials with unique physical and chemical properties for applications in energy storage and conversion. PMID:25815801

Zhao, Yufei; Wang, Qing; Bian, Tong; Yu, Huijun; Fan, Hua; Zhou, Chao; Wu, Li-Zhu; Tung, Chen-Ho; O'Hare, Dermot; Zhang, Tierui

2015-04-01

60

Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution  

NASA Technical Reports Server (NTRS)

Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

1999-01-01

61

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

PubMed

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

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

2014-07-21

62

Hierarchical NiAl layered double hydroxide/multiwalled carbon nanotube/nickel foam electrodes with excellent pseudocapacitive properties.  

PubMed

The performances of pseudocapacitors usually depend heavily on their hierarchical architectures and composition. Herein, we report a three-dimensional hierarchical NiAl layered double hydroxide/multiwalled carbon nanotube/nickel foam (NiAl-LDH/MWCNT/NF) electrode prepared by a facile three-step fabrication method: in situ hydrothermal growth of NiAl-LDH film on a Ni foam, followed by direct chemical vapor deposition growth of dense MWCNTs onto the NiAl-LDH film, and finally the growth of NiAl-LDH onto the surface of the MWCNTs via an in situ hydrothermal process in the presence of surfactant sodium dodecyl sulfate. The MWCNT surface was fully covered by NiAl-LDH hexagonal platelets, and this hierarchical architecture led to a much enhanced capacitance. The NiAl-LDH/MWCNT/NF electrode has an areal loading mass of 5.8 mg of LDH per cm(2) of MWCNT/NF surface. It also possesses exceptional areal capacitance (7.5 F cm(-2)), specific capacitance (1293 F g(-1)), and cycling stability (83% of its initial value was preserved after 1000 charge-discharge cycles). The NiAl-LDH/MWCNT/NF material is thus a highly promising electrode with potential applications in electrochemical energy storage. PMID:25185026

Wang, Bo; Williams, Gareth R; Chang, Zheng; Jiang, Meihong; Liu, Junfeng; Lei, Xiaodong; Sun, Xiaoming

2014-09-24

63

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

PubMed Central

Objective. Layered double hydroxide (LDH) nanoparticles have been studied as cellular delivery carriers for anionic anticancer agents. As MTX and 5-FU are clinically utilized anticancer drugs in combination therapy, we aimed to enhance the therapeutic performance with the help of LDH nanoparticles. Method. Anticancer drugs, MTX and 5-FU, and their combination, were incorporated into LDH by reconstruction method. Simply, LDHs were thermally pretreated at 400°C, and then reacted with drug solution to simultaneously form drug-incorporated LDH. Thus prepared MTX/LDH (ML), 5-FU/LDH (FL), and (MTX + 5-FU)/LDH (MFL) nanohybrids were characterized by X-ray diffractometer, scanning electron microscopy, infrared spectroscopy, thermal analysis, zeta potential measurement, dynamic light scattering, and so forth. The nanohybrids were administrated to the human cervical adenocarcinoma, HeLa cells, in concentration-dependent manner, comparing with drug itself to verify the enhanced therapeutic efficacy. Conclusion. All the nanohybrids successfully accommodated intended drug molecules in their house-of-card-like structures during reconstruction reaction. It was found that the anticancer efficacy of MFL nanohybrid was higher than other nanohybrids, free drugs, or their mixtures, which means the multidrug-incorporated LDH nanohybrids could be potential drug delivery carriers for efficient cancer treatment via combination therapy. PMID:24860812

Lee, Gyeong Jin; Kang, Joo-Hee

2014-01-01

64

Hierarchical construction of an ultrathin layered double hydroxide nanoarray for highly-efficient oxygen evolution reaction.  

PubMed

Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (?) of 257 mV is needed for a current density of 80 mA cm(-2) with a Tafel slope of 53 mV per decade. The hierarchical LDH nanoarray also shows excellent structural stability in alkaline media. After continuous testing under a high OER current density (?300 mA cm(-2)) for 10 h, the sample maintains the ordered hierarchical structure with no significant deactivation of the catalytic properties. PMID:25162938

Yang, Qiu; Li, Tian; Lu, Zhiyi; Sun, Xiaoming; Liu, Junfeng

2014-10-21

65

Layered double hydroxide-alginate/polyvinyl alcohol beads: fabrication and phosphate removal from aqueous solution.  

PubMed

In the water treatment field, powder form of layered double hydroxides (LDHs) has wide applications in adsorptions. However, its applications are limited because of low hydraulic conductivity. Here, LDH-alginate/polyvinyl alcohol (PVA) beads were fabricated by entrapment of the Mg-Al LDH powder into alginate/PVA beads. The obtained Mg-Al LDH-alginate/PVA beads were characterized by X-ray diffraction scanning electron microscopy. Their performance for phosphate removal by batch and column adsorption mode was evaluated. The Mg-Al LDH-alginate/PVA beads were found to be efficient adsorbents for phosphate removal. Batch adsorption experiment showed that the phosphate sorption process on the Mg-Al LDH-alginate/PVA beads followed pseudo-second-order reaction order kinetic model and the adsorption isotherm date could be simulated using both Langmiur and Freundlich models. In the column study, the flow rate and inlet phosphate concentration were maintained at 29.62 m³/m² h and 10 mgP/L, respectively. Using 20 cm column depth, the breakthrough and exhaust time were found to be 5 and 31 h, respectively. The percentage of phosphate removal by column was 80.09%. The values of adsorption rate coefficient (K) and the adsorption capacity coefficient (N) were 0.0125 L/mg h and 258.32 mg/L, respectively. PMID:25176487

Kim Phuong, Nguyen Thi

2014-01-01

66

Solid-state chelation of metal ions by ethylenediaminetetraacetate intercalated in a layered double hydroxide.  

PubMed

The solid-state chelation of transition metal ions (Co(2+), Ni(2+), and Cu(2+)) from aqueous solutions into the lithium aluminum layered double hydroxide ([LiAl(2)(OH)(6)]Cl x 0.5H(2)O or LDH) which has been pre-intercalated with EDTA (ethylenediaminetetraacetate) ligand has been investigated. The intercalated metal cations form [M(edta)](2)(-) complexes between the LDH layers as indicated by elemental analysis, powder X-ray diffraction, and IR and UV-vis spectroscopies. If metal chloride or nitrate salts are used in the reaction with the LDH then co-intercalation of either the Cl(-) or NO(3)(-) anions is observed. In the case of metal acetate salts the cations intercalate without the accompanying anion. This can be explained by the different intercalation selectivity of the anions in relation to the LDH. In the latter case the introduction of the positive charge into LDH structure was compensated for by the release from the solid of the equivalent quantity of lithium and hydrogen cations. Time-resolved in-situ X-ray diffraction measurements have revealed that the chelation/intercalation reactions proceed very quickly. The rate of the reaction found for nickel acetate depends on concentration as approximately k[Ni(Ac)(2)](3). PMID:12639125

Tarasov, Konstantin A; O'Hare, Dermot; Isupov, Vitaly P

2003-03-24

67

Direct Intercalation of Amino Acids into Layered Double Hydroxides by Coprecipitation  

NASA Astrophysics Data System (ADS)

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

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

2001-11-01

68

Polarized immune responses modulated by layered double hydroxides nanoparticle conjugated with CpG.  

PubMed

Modulation of the immune response is an important step in the induction of protective humoral and cellular immunity against pathogens. In this study, we investigated the possibility of using a nanomaterial conjugated with the toll-like receptor (TLR) ligand CpG to modulate the immune response towards the preferred polarity. MgAl-layered double hydroxide (LDH) nanomaterial has a very similar chemical composition to Alum, an FDA approved adjuvant for human vaccination. We used a model antigen, ovalbumin (OVA) to demonstrate that MgAl-LDH had comparable adjuvant activity to Alum, but much weaker inflammation. Conjugation of TLR9 ligand CpG to LDH nanoparticles significantly enhanced the antibody response and promoted a switch from Th2 toward Th1 response, demonstrated by a change in the IgG2a:IgG1 ratio. Moreover, immunization of mice with CpG-OVA-conjugated LDH before challenge with OVA-expressing B16/F10 tumor cells retarded tumor growth. Together, these data indicate that LDH nanomaterial can be used as an immune adjuvant to promote Th1 or Th2 dominant immune responses suitable for vaccination purposes. PMID:25145853

Yan, Shiyu; Rolfe, Barbara E; Zhang, Bing; Mohammed, Yousuf H; Gu, Wenyi; Xu, Zhi P

2014-11-01

69

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

70

In situ monitoring of crystal growth and dissolution of oriented layered double-hydroxide crystals immobilized on silicon  

NASA Astrophysics Data System (ADS)

Layered double-hydroxide (LDH) minerals have recently attracted attention through their potential industrial application as fillers in mineral-polymer nanocomposite materials and, separately, as solid base catalysts to promote a range of reactions in an environmentally sound way. Little research has been undertaken on the crystal growth mechanism of LDHs using in situ methods. Recently, advances have been made in the controlled deposition and immobilisation of nanometre-sized LDH crystals onto a silicon substrate with preferred orientation. In this work we present initial studies using atomic force microscopy to image in real time immobilised LDH crystals during stages of hydration, growth and dissolution. The various stages were recorded by adjusting the reactant concentrations of the surrounding aqueous solution, allowing crystal dynamics to be visualised. Under certain conditions preferred stability of certain-sized LDH crystals relative to others was observed, indicating the operation of an Ostwald ripening process in samples containing a heterogeneous distribution of crystallite sizes.

Greenwell, H. C.; Bindley, L. A.; Unwin, P. R.; Holliman, P. J.; Jones, W.; Coveney, P. V.; Barnes, S. L.

2006-08-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

72

Antimycobacterial, antimicrobial, and biocompatibility properties of para-aminosalicylic acid with zinc layered hydroxide and Zn/Al layered double hydroxide nanocomposites.  

PubMed

The treatment of tuberculosis by chemotherapy is complicated due to multiple drug prescriptions, long treatment duration, and adverse side effects. We report here for the first time an in vitro therapeutic effect of nanocomposites based on para-aminosalicylic acid with zinc layered hydroxide (PAS-ZLH) and zinc-aluminum layered double hydroxides (PAS-Zn/Al LDH), against mycobacteria, Gram-positive bacteria, and Gram-negative bacteria. The nanocomposites demonstrated good antimycobacterial activity and were found to be effective in killing Gram-positive and Gram-negative bacteria. A biocompatibility study revealed good biocompatibility of the PAS-ZLH nanocomposites against normal human MRC-5 lung cells. The para-aminosalicylic acid loading was quantified with high-performance liquid chromatography analysis. In summary, the present preliminary in vitro studies are highly encouraging for further in vivo studies of PAS-ZLH and PAS-Zn/Al LDH nanocomposites to treat tuberculosis. PMID:25114509

Saifullah, Bullo; El Zowalaty, Mohamed E; Arulselvan, Palanisamy; Fakurazi, Sharida; Webster, Thomas J; Geilich, Benjamin M; Hussein, Mohd Zobir

2014-01-01

73

Antimycobacterial, antimicrobial, and biocompatibility properties of para-aminosalicylic acid with zinc layered hydroxide and Zn/Al layered double hydroxide nanocomposites  

PubMed Central

The treatment of tuberculosis by chemotherapy is complicated due to multiple drug prescriptions, long treatment duration, and adverse side effects. We report here for the first time an in vitro therapeutic effect of nanocomposites based on para-aminosalicylic acid with zinc layered hydroxide (PAS-ZLH) and zinc-aluminum layered double hydroxides (PAS-Zn/Al LDH), against mycobacteria, Gram-positive bacteria, and Gram-negative bacteria. The nanocomposites demonstrated good antimycobacterial activity and were found to be effective in killing Gram-positive and Gram-negative bacteria. A biocompatibility study revealed good biocompatibility of the PAS-ZLH nanocomposites against normal human MRC-5 lung cells. The para-aminosalicylic acid loading was quantified with high-performance liquid chromatography analysis. In summary, the present preliminary in vitro studies are highly encouraging for further in vivo studies of PAS-ZLH and PAS-Zn/Al LDH nanocomposites to treat tuberculosis. PMID:25114509

Saifullah, Bullo; El Zowalaty, Mohamed E; Arulselvan, Palanisamy; Fakurazi, Sharida; Webster, Thomas J; Geilich, Benjamin M; Hussein, Mohd Zobir

2014-01-01

74

Energetics of order-disorder in layered magnesium aluminum double hydroxides with interlayer carbonate.  

PubMed

Laboratory synthesis of layered double hydroxides (LDH) often results in materials replete with stacking faults. Faults are known to affect several properties including sorption, electrochemical, and catalytic activity of this important class of materials. Understanding the occurrence of faults thus calls for a comprehensive analysis of formation and stability of ordered and faulted LDHs. High-temperature oxide melt solution calorimetric measurements made on an ordered and a faulted Mg-Al LDH with carbonate interlayer anion shows that ordered LDH is energetically more stable than the faulted one by ?6 kJ/mol. The stacking faults are an intergrowth of 3R1 and 2H1 polytypes, and faults could thus mediate transformation of 3R1 to 2H1 polytypes. Several factors including pH and temperature of precipitation also affect layer stacking. The formation of stacking faults could therefore have its origin in kinetics. Water content in the interlayer also affects layer stacking, and hence it may affect properties of LDH. Improved understanding of the distribution of water molecules in LDH is also crucial in an environmental context, as LDH occur as minerals and are important for contaminant amelioration in the environment. Water adsorption calorimetry on dehydrated LDH shows a continuous decrease in the magnitude of adsorption enthalpy with increasing coverage, indicating the presence of energetically heterogeneous sites where the water molecules reside. The results also indicate that the energy of several sites where the water molecules may reside (whether in the interlayer or on the surface) overlaps, and hence it is hard to differentiate among them. PMID:25750986

Shivaramaiah, Radha; Navrotsky, Alexandra

2015-04-01

75

A unique growth mechanism of donut-shaped Mg–Al layered double hydroxides crystals revealed by AFM and STEM–EDX  

Microsoft Academic Search

Donut-like crystals of Mg–Al layered double hydroxides (LDH) are synthesized using a hydrothermal method with microwave heating. This morphology provides enlargement of the specific surface area of the {hk0} faces, needed for adsorption application. The growth mechanism for donut-shaped crystals is proposed on the basis of AFM and STEM–EDX images. The nucleation of Mg–Al LDH starts on the amorphous surface

W. N. Budhysutanto; F. J. Van Den Bruele; B. D. Rossenaar; D. Van Agterveld; W. J. P. van van Enckevort; H. J. M. Kramer

2011-01-01

76

Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state 1H and 71Ga NMR spectroscopy  

SciTech Connect

Ordering of gallium(III) in a series of magnesium gallium layered double hydroxides (LDH’s), [Mg1-xGax(OH)2(NO3)x yH2O], was determined using solid-state 1H and 71Ga NMR spectroscopy. Depletion of Ga in these LDH’s is demonstrated to be the result of soluble [Ga(OH)4]-complexes formed during synthesis.

Petersen, Line B.; Lipton, Andrew S.; Zorin, Vadim; Nielsen, Ulla Gro

2014-11-01

77

Intercalation of p-methycinnamic acid anion into Zn-Al layered double hydroxide to improve UV aging resistance of asphalt  

NASA Astrophysics Data System (ADS)

A UV absorber, p-methycinnamic acid (PMCA), was intercalated into Zn-Al layered double hydroxide (LDH) by calcination recovery. Fourier transform infrared spectroscopy showed that the PMCA anions completely replaced the CO32- anions in the interlayer galleries of Zn-Al-LDH containing PMCA anions (Zn-Al-PMCA-LDH). X-ray diffraction and transmission electron microscopy showed that the interlayer distance increased from 0.78 nm to 1.82 nm after the substitution of PMCA anions for CO32- anions. The similar diffraction angles of the CO32- anion-containing Zn-Al-LDH (Zn-Al-CO32--LDH) and the Zn-Al-CO32--LDH/styrene-butadiene-styrene (SBS) modified asphalt implied that the asphalt molecules do not enter into the LDH interlayer galleries to form separated-phase structures. The different diffraction angles of Zn-Al-PMCA-LDH and Zn-Al-PMCA-LDH/SBS modified asphalt indicated that the asphalt molecules penetrated into the LDH interlayer galleries to form an expanded-phase structure. UV-Vis absorbance analyses showed that Zn-Al-PMCA-LDH was better able to block UV light due to the synergistic effects of PMCA and Zn-Al-LDH. Conventional physical tests and atomic force microscopy images of the SBS modified asphalt, Zn-Al-CO32--LDH/SBS modified asphalt and Zn-Al-PMCA-LDH/SBS modified asphalt before and after UV aging indicated that Zn-Al-PMCA-LDH improved the UV aging resistance of SBS modified asphalts.

Peng, Chao; Dai, Jing; Yu, Jianying; Yin, Jian

2015-02-01

78

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

79

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

PubMed

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, and EXAFS analyses). The sorption studies on various oxyanions and oxyhalides suggested that their sorption characteristics on FCHT-LDH were largely governed by their ionic potentials and molecular structures. Oxyanions which have ionic potentials higher than 7 nm(-1) were found to be more readily sorbed by FCHT-LDH than oxyhalides with ionic potentials lower than 5 nm(-1). The results obtained also demonstrated that trigonal pyramid oxyhalides showed a lower degree of specificity for FCHT-LDH than the tetrahedral coordinated oxyanions. From the macroscopic and microscopic studies, monovalent oxyhalide sorption on FCHT-LDH was postulated to occur mainly via anion exchange mechanism with subsequent formation of outer-sphere surface complexes. For polyvalent oxyanion sorption on FCHT-LDH, the mechanisms were possibly associated with both anion exchange and ligand exchange reactions, resulting in the coexistence of outer-sphere and inner-sphere surface complexes. PMID:20399010

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

2010-07-15

80

Synthesis and carbon dioxide sorption of layered double hydroxide/silica foam nanocomposites with hierarchical mesostructure.  

PubMed

Layered double hydroxides (LDHs) with a hierarchical mesostructure are successfully synthesized on mesoporous silica foams by simple impregnation and hydrothermal treatment. The as-synthesized LDH/silica foam nanocomposites show well-defined mesostructures with high surface areas, large pore volumes, and mesopores of 6-7 nm. The nanocomposites act as carbon dioxide (CO2 ) sorbents under simulated flue gas conditions. They also exhibit significantly enhanced CO2 capacities under high-pressure conditions and high CO2 /N2 and CO2 /CH4 selectivities. PMID:24596070

Fu, Liling; Qi, Genggeng; Shekhah, Osama; Belmabkhout, Youssef; Estevez, Luis; Eddaoudi, Mohamed; Giannelis, Emmanuel P

2014-04-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

82

Layered double hydroxide-based nanomaterials as highly efficient catalysts and adsorbents.  

PubMed

Layered double hydroxides (LDHs) are a class of anion clays consisting of brucite-like host layers and interlayer anions, which have attracted increasing interest in the fields of catalysis/adsorption. By virtue of the versatility in composition, morphology, and architecture of LDH materials, as well as their unique structural properties (intercalation, topological transformation, and self-assembly with other functional materials), LDHs display great potential in the design and fabrication of nanomaterials applied in photocatalysis, heterogeneous catalysis, and adsorption/separation processes. Taking advantage of the structural merits and various control synthesis strategies of LDHs, the active center structure (e.g., crystal facets, defects, geometric and electronic states, etc.) and macro-nano morphology can be facilely manipulated for specific catalytic/adsorbent processes with largely enhanced performances. In this review, the latest advancements in the design and preparation of LDH-based functional nanomaterials for sustainable development in catalysis and adsorption are summarized. PMID:25137218

Li, Changming; Wei, Min; Evans, David G; Duan, Xue

2014-11-01

83

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

NASA Astrophysics Data System (ADS)

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 12O 40] 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 12O 40] 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.

Wei, Xiaocui; Fu, Youzhi; Xu, Lin; Li, Fengyan; Bi, Bo; Liu, Xizheng

2008-06-01

84

New synthetic route to Mg–Al–CO{sub 3} layered double hydroxide using magnesite  

SciTech Connect

Highlights: ? The use of magnesite to prepare Mg–Al–CO{sub 3} LDH is novel. ? The result sample is systematically studied. ? Furthermore, the cost of preparing Mg–Al–CO{sub 3} LDH may be reduced through this synthetic route. ? In the synthesis process, there is no CO{sub 2} released. That is significant to environmental protection. - Abstract: A novel synthesis of Mg–Al–CO{sub 3} layered double hydroxide (LDH) through chemical precipitation and hydrothermal methods has been investigated in this paper. The advantages of this method are using magnesite as magnesium source and no CO{sub 2} released in the process of preparation. Mg–Al–CO{sub 3} LDH (ZY) prepared under the optimized condition (the molar ratio of magnesite and Al(NO{sub 3}){sub 3}·9H{sub 2}O was 2.5:1; the aging time and temperature were 16 h and 100 °C, respectively) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analyser (TG–DTA) and scanning electron microscope (SEM). The crystal morphology of the prepared LDH displays platelet-like structure with a hexagonal shape, which is agreed with the LDH produced by industrial chemicals. Through elemental analysis and inductively coupled plasma-atomic emission spectrometry (ICP-AES), the chemical formula of ZY is determined as Mg{sub 0.70}Al{sub 0.30}(OH){sub 2}(CO{sub 3}){sub 0.15}·0.6H{sub 2}O.

Wang, Xiaobo [School of Materials Science and Technology, China University of Geosciences (Beijing), 100083 Beijing (China); Bai, Zhimin, E-mail: zhimibai@cugb.edu.cn [School of Materials Science and Technology, China University of Geosciences (Beijing), 100083 Beijing (China); Zhao, Dong; Chai, Yupu; Guo, Man; Zhang, Jingyu [School of Materials Science and Technology, China University of Geosciences (Beijing), 100083 Beijing (China)

2013-03-15

85

Fe-Al layered double hydroxides in bromate reduction: Synthesis and reactivity.  

PubMed

This study presents a rare use of layered double hydroxides of Fe(II) and Al(III) (Fe-Al LDH), as reported for the first time for bromate removal from aqueous solutions. The Fe-Al LDH samples were prepared with Fe/Al molar ratios of 1-4 using a co-precipitation method at pH 7, with subsequent hydrothermal treatment at 120°C. The Fe-Al LDH (molar ratio of Fe/Al=1, 2) with a layered structure exhibited nearly complete removal of bromate from initial concentration of 100?mol/dm(3) at a wide pH range of 4.0-10.5 over a 2h reaction period; the residual bromate concentration in the solution was lower than the detection limit of 0.07?mol/dm(3) (9?g-BrO(3)(-)/dm(3)). During the reaction period, bromide was released into the solution via a reduction process. Reactivity of Fe-Al LDH with a Fe/Al molar ratio of 2 did not decrease the bromate reduction efficiency during 30days. PMID:21126742

Chitrakar, Ramesh; Makita, Yoji; Sonoda, Akinari; Hirotsu, Takahiro

2011-02-15

86

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

87

Hydrothermal continuous flow synthesis and exfoliation of NiCo layered double hydroxide nanosheets for enhanced oxygen evolution catalysis.  

PubMed

We report the controlled synthesis of NiCo layered double hydroxide (LDH) nanoplates using a newly developed high temperature high pressure hydrothermal continuous flow reactor (HCFR), which enables direct growth onto conductive substrates in high yield and, most importantly, better control of the precursor supersaturation and, thus, nanostructure morphology and size. The solution coordination chemistry of metal-ammonia complexes was utilized to synthesize well-defined NiCo LDH nanoplates directly in a single step without topochemical oxidation. The as-grown NiCo LDH nanoplates exhibit a high catalytic activity toward the oxygen evolution reaction (OER). By chemically exfoliating LDH nanoplates to thinner nanosheets, the catalytic activity can be further enhanced to yield an electrocatalytic current density of 10 mA cm(-2) at an overpotential of 367 mV and a Tafel slope of 40 mV dec(-1). Such enhancement could be due to the increased surface area and more exposed active sites. X-ray photoelectron spectroscopy (XPS) suggests the exfoliation also caused some changes in electronic structure. This work presents general strategies to controllably grow nanostructures of LDH and ternary oxide/hydroxides in general and to enhance the electrocatalytic performance of layered nanostructures by exfoliation. PMID:25633476

Liang, Hanfeng; Meng, Fei; Cabán-Acevedo, Miguel; Li, Linsen; Forticaux, Audrey; Xiu, Lichen; Wang, Zhoucheng; Jin, Song

2015-02-11

88

Mechano-hydrothermal synthesis of Mg{sub 2}Al–NO{sub 3} layered double hydroxides  

SciTech Connect

A mechano-hydrothermal method was developed to synthesize Mg{sub 2}Al–NO{sub 3} layered double hydroxide (LDH) from MgO, Al{sub 2}O{sub 3} and NaNO{sub 3} as starting materials. A two-step synthesis was conducted, that is, a mixture of MgO and Al{sub 2}O{sub 3} was milled for 1 h, followed by hydrothermal treatment with NaNO{sub 3} 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. - Graphical abstract: The novel mechano-hydrothermal route to synthesize LDH has advantages in low reaction temperature and short reaction time, and the target product was of high crystallinity, good dispersion and regular shape. Display Omitted - Highlights: • A mechano-hydrothermal route was developed for layered double hydroxide synthesis. • Synthesis could be achieved at low temperature and in a short time. • Resulting layered double hydroxide samples were well dispersed and of regular shape. • A dissolution–recrystallization mechanism was proposed for the formation process.

Zhang, Fengrong [Environment Research Institute, Shandong University, Jinan 250100 (China); Du, Na; Song, Shue [Key Laboratory of Colloid and Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100 (China); Liu, Jianqiang [School of Physics, Shandong University, Jinan 250100 (China); Hou, Wanguo, E-mail: wghou@sdu.edu.cn [Environment Research Institute, Shandong University, Jinan 250100 (China); Key Laboratory of Colloid and Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100 (China)

2013-10-15

89

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

90

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

SciTech Connect

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-NO{sub 3}{sup -} compound and its H{sub 2}PO{sub 4}{sup -}-intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO{sub 4}{sup 2-} 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 HPO{sub 4}{sup 2-} and H{sub 2}PO{sub 4}{sup -}. 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. -- Graphical abstract: We synthesized phosphate-intercalated Ca-Fe-LDH materials that can act as bifunctional inorganic vectors for the slow release of phosphate fertilizer and also the neutralization of acid soil. 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. Display Omitted Research Highlights: {yields} The phosphate forms of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) were synthesized via co-precipitation method. The crystal structure, bonding character, and release kinetics of phosphate of the phosphate-intercalates were investigated. These Ca-Fe-LDH materials are 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 [Center for Intelligent Nano-Bio Materials (CINBM), Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Hwang, Seong-Ju, E-mail: hwangsju@ewha.ac.k [Center for Intelligent Nano-Bio Materials (CINBM), Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul 120-750 (Korea, Republic of)

2011-01-15

91

Ultrathin cobalt-manganese layered double hydroxide is an efficient oxygen evolution catalyst.  

PubMed

Cost-effective production of solar fuels requires robust and earth-abundant oxygen evolution reaction (OER) catalysts. Herein, we report that ultrathin nanoplates of cobalt-manganese layered double hydroxide (CoMn LDH) are a highly active and stable oxygen evolution catalyst. The catalyst was fabricated by a one-pot coprecipitation method at room temperature, and its turnover frequency (TOF) is more than 20 times higher than the TOFs of Co and Mn oxides and hydroxides, and 9 times higher than the TOF of a precious IrO2 catalyst. The activity of the catalyst was promoted by anodic conditioning, which was proposed to form amorphous regions and reactive Co(IV) species on the surface. The stability of the catalyst was demonstrated by continued electrolysis. PMID:25380057

Song, Fang; Hu, Xile

2014-11-26

92

Multi-level three-dimensional Mg-Al layered double hydroxide hierarchical microstructures with enhanced basic catalytic property.  

PubMed

Novel three-dimensional (3D) rosette-like carbonate-type Mg-Al layered double hydroxide (MgAl-LDH) hierarchical microstructures were fabricated successfully by a surfactant-assisted coprecipitation method in the presence of hexamethylenetetramine as precipitant, and the morphology-dependent basic catalytic property was exploited. The morphologies of MgAl-LDH aggregates were diversified depending on the synthesis parameters including the type of precipitant, concentration of sodium stearate surfactant, and hydrothermal aging time. Specifically, the morphology of MgAl-LDH particles could change progressively from platelet-like aggregates to rosette-like microspheres with the increasing concentration of sodium stearate. A possible formation mechanism for special 3D flower-like MgAl-LDH microstructures was proposed based on the synergistic effect of precipitant with surfactant. Moreover, the resulting activated rosette-like MgAl-LDH, which was prepared through calcination-rehydration process, showed a higher catalytic activity in the transesterification of tributyrin with methanol, compared with that derived from the conventional platelet-like MgAl-LDH precursor, which was attributed to its higher specific basicity originating from multi-level hierarchical superstructure offering an advantage in contact with more exposed base sites. PMID:25036381

Yu, Jiaying; Fan, Guoli; Yang, Yang; Li, Feng

2014-10-15

93

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

94

Polypropylene/layered double hydroxide nanocomposites Qiang Wang,a  

E-print Network

)/ Zn­Al­LDH,22 PMMA/Mg­Al­LDH,23 polyvinyl chloride (PVC)/Mg­Al­LDH,24 PVC/Zn­Al­LDH,25 PVC/Mg­Al­Ce­ LDH,26 PVC/Mg­Cu­Al­LDH,27 polystyrene (PS)/Mg­Al­ LDH, PS/Co­Al­LDH, PS/Ni­Al­LDH, PS/Cu­Al­LDH, PS

Guo, John Zhanhu

95

Structural and morphological transformations of Zn-Al layered double hydroxides through hydrothermal treatment  

NASA Astrophysics Data System (ADS)

The Zn-Al layered double hydroxides (LDH) with Zn/Al molar ratio of 2 were prepared by coprecipitation, followed by hydrothermal treatment at various hydrothermal conditions. The phase transformation was observed, accompanied by drastical morphological changes. As the results indicated, in aqueous system the decomposition product was phase segregated into wurtzite ZnO and spinel ZnAl 2O 4 by dissolution of the precursor hydroxide followed by recoprecipitation of the oxide phases. As a single-source precursor, LDH facilitated the formation of ZnAl 2O 4 crystallites and their coating on ZnO nanowires via the inherent linkage through interactions of coordination as well as hydrogen bonding via medium of surface -OH on particles. The addition of ethanol with high vapor tension and low polarity was against the adsorptive attachment of ZnAl 2O 4 on ZnO but in favor of the crystallization and size decrease of the resulting oxides. Improved crystallization in LDH precursors was beneficial to intensify the interactions to overcome the breaking effect of ethanol, achieving better coating of ZnAl 2O 4 on ZnO. With the silane grafting of KH570, hydrothermal treatment promoted the formation of four phases by partial decomposition of layered structure of ZnAl-CO 3 and new emergence of smectite-like materials with basal spacing of 12.35 Å. As the aging time for LDH precursors gradually elongated, the whole products finally transformed to ultrafine nanorods with mean size of 50 nm in length which were segregated without any type of attachment.

Sun, Yanqing; Zhou, Yuming; Wang, Zhiqiang; Ye, Xiaoyun

2009-04-01

96

Equilibrium and kinetics studies on As(V) and Sb(V) removal by Fe(2+)-doped Mg-Al layered double hydroxides.  

PubMed

Mg-Al layered double hydroxides (Mg-Al LDHs) doped with Fe(2+) adsorbed As(V) [Formula: see text] and Sb(V) [Formula: see text] from an aqueous solution through anion exchange with Cl(-) intercalated in the LDH interlayer. Fe(2+)-doped Mg-Al LDH exhibited superior As(V) removal compared with Mg-Al LDH. The oxidation of Fe(2+) doped in the Mg-Al LDH host layer to Fe(3+) increased the positive layer charge of the LDH, thus increasing the anion-uptake capacity owing to stronger electrostatic attractive force between the positively charged layer and the anion. However, Fe(2+)-doped Mg-Al LDH was not superior to Mg-Al LDH in terms of Sb(V) removal. This was attributed to the preferential intercalation of OH(-) over [Formula: see text] . The As(V) and Sb(V) removal by LDH followed Langmuir-type adsorption, which proceeded via a pseudo-first-order reaction. The equilibrium and kinetics studies confirm that the adsorption of As(V) and Sb(V) by Fe(2+)-doped Mg-Al LDH was the result of chemical adsorption, involving the anion exchange of [Formula: see text] and [Formula: see text] with the intercalated Cl(-). PMID:25585143

Kameda, Tomohito; Kondo, Eisuke; Yoshioka, Toshiaki

2015-03-15

97

Electrochemical synthesis of nickel-iron layered double hydroxide: application as a novel modified electrode in electrocatalytic reduction of metronidazole.  

PubMed

A new and simple approach based on the electrochemical method was used for preparation of reproducible nanostructure thin film of Ni/Fe-layered double hydroxides (Ni/Fe-LDH) on the glassy carbon electrode (GCE). The electrochemical behavior of the Ni/Fe-LDH deposited on GCE electrode is studied. Study of the scanning electron microscopy shows the formation of a nanostructure thin film on the glassy carbon electrode. Electrochemical experiments show that Ni/Fe-LDH modified glassy carbon electrode exhibits excellent electrocatalytic reduction activity with Metronidazole. The method was successfully applied for the analysis of Metronidazole in tablets. The results were favorably compared to those obtained by the reported BP method. PMID:24411366

Nejati, Kamellia; Asadpour-Zeynali, Karim

2014-02-01

98

On the intercalation of the iodine-iodide couple on layered double hydroxides with different particle sizes.  

PubMed

Molecular iodine was intercalated from nonaqueous solution into microsized ZnAl-layered double hydroxide (LDH) in the iodide form, generating the I(3)(-)/I(-) redox couple into the interlayer region. Chloroform, ethanol, acetonitrile, or diethyl ether were used as solvents to dissolve the molecular iodine. The intercalation compounds were characterized by thermogravimetric analysis, X-ray powder diffraction, UV-vis spectroscopy, and scanning and transmission electron microscopy. The stability of iodine-solvent adducts and the iodine concentration affected the LDH iodine loading, and samples with I(2)/I(-) molar ratio ranging from 0.14 to 0.82 were prepared. Nanosized, well dispersible LDH, synthesized by the urea method in water-ethylene glycol media, were also prepared and successfully functionalized with the I(3)(-)/I(-) redox couple applying the conditions optimized for the micrometric systems. PMID:22316278

Bastianini, Maria; Costenaro, Daniele; Bisio, Chiara; Marchese, Leonardo; Costantino, Umberto; Vivani, Riccardo; Nocchetti, Morena

2012-02-20

99

Improvement of pharmacokinetic and antitumor activity of layered double hydroxide nanoparticles by coating with PEGylated phospholipid membrane  

PubMed Central

Layered double hydroxide (LDH) has attracted considerable attention as a drug carrier. However, because of its poor in vivo behavior, polyethylene glycolylated (PEGylated) phospholipid must be used as a coformer to produce self-assembled core–shell nanoparticles. In the present study, we prepared a PEGylated phospholipid-coated LDH (PLDH) (PEG-PLDH) delivery system. The PEG-PLDH nanoparticles had an average size of 133.2 nm. Their core–shell structure was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. In vitro liposome-cell-association and cytotoxicity experiments demonstrated its ability to be internalized by cells. In vivo studies showed that PEGylated phospholipid membranes greatly reduced the blood clearance rate of LDH nanoparticles. PEG-PLDH nanoparticles demonstrated a good control of tumor growth and increased the survival rate of mice. These results suggest that PEG-PLDH nanoparticles can be a useful drug delivery system for cancer therapy. PMID:25364245

Yan, Mina; Zhang, Zhaoguo; Cui, Shengmiao; Lei, Ming; Zeng, Ke; Liao, Yunhui; Chu, Weijing; Deng, Yihui; Zhao, Chunshun

2014-01-01

100

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

101

Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis  

NASA Astrophysics Data System (ADS)

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

Song, Fang; Hu, Xile

2014-07-01

102

Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis.  

PubMed

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

Song, Fang; Hu, Xile

2014-01-01

103

Facile synthesis of methotrexate intercalated layered double hydroxides: particle control, structure and bioassay explore.  

PubMed

To study the influence of particle size on drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) were synthesized through the traditional coprecipitation method, using a mixture of water and polyethylene glycol (PEG-400) as the solvent. To adjust the particle size of MTX/LDHs, the dropping way, the volume ratio of water to PEG-400 and different hydrothermal treatment time changed accordingly, and the results indicate that the particle size can be controlled between 90 and 140 nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different synthesis conditions almost have no effect on the compositions of the nanohybrids. X-ray diffraction (XRD) patterns manifested the successful intercalation of MTX anions into the LDH interlayers, and it's also found out that different volume ratios of water to PEG-400 and variable dropping way can affect the crystallinity of the final samples, i.e., the volume ratio of 3:1 and pH decreasing are proved to be optimum conditions. Furthermore, both antiparallel monolayer and bilayers adopting different orientations are suggested for four samples from XRD results. Fourier transform infrared spectroscopy (FTIR) investigations proved the coexistence of CO3(2-) and MTX anions in the interlayer of the nanohybrids. MTX/LDH particles exhibited hexagonal platelet morphology with round corner and different dropping ways can affect the morphology greatly. Moreover, a DSC study indicated that longer time treatment can weaken the bond between the MTX anions and LDH layers. The kinetic release profiles told us that larger MTX/LDH particles have enhanced the ability of LDH layers to protect interlayer molecules. At last, the bioassay study indicated that the nanohybrids with larger diameters have higher tumor suppression efficiency. PMID:25491832

Tian, De-Ying; Liu, Zhen-Lei; Li, Shu-Ping; Li, Xiao-Dong

2014-12-01

104

Effective self-purification of polynary metal electroplating wastewaters through formation of layered double hydroxides.  

PubMed

Heavy metal ions (Ni(2+), Zn(2+), and Cr(3+)) can be effectively removed from real polynary metal ions-bearing electroplating wastewaters by a carbonation process, with ?99% of metal ions removed in most cases. The synchronous formation of layered double hydroxide (LDH) precipitates containing these metal ions was responsible for the self-purification of wastewaters. The constituents of formed polynary metals-LDHs mainly depended on the Ni(2+):Zn(2+):Cr(3+) molar ratio in wastewaters. LDH was formed at pH of 6.0-8.0 when the Ni(2+)/Zn(2+) molar ratio ? 1 where molar fraction of trivalent metal in the wastewaters was 0.2-0.4, otherwise ZnO, hydrozincite, or amorphous precipitate was observed. In the case of LDH formation, the residual concentration of Ni(2+), Zn(2+), and Cr(3+) in the treated wastewaters was very low, about 2-3, ?2, and ?1 mg/L, respectively, at 20-80 °C and pH of 6.0-8.0, indicating the effective incorporation of heavy metal ions into the LDH matrix. Furthermore, the obtained LDH materials were used to adsorb azoic dye GR, with the maximum adsorption amount of 129-134 mg/g. We also found that the obtained LDHs catalyzed more than 65% toluene to decompose at 350 °C under ambient pressure. Thus the current research has not only shown effective recovery of heavy metal ions from the electroplating wastewaters in an environmentally friendly process but also demonstrated the potential utilization of recovered materials. PMID:21062046

Zhou, Ji Zhi; Wu, Yue Ying; Liu, Chong; Orpe, Ajay; Liu, Qiang; Xu, Zhi Ping; Qian, Guang Ren; Qiao, Shi Zhang

2010-12-01

105

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

SciTech Connect

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

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

2011-11-15

106

Optimization of UV absorptivity of layered double hydroxide by intercalating organic UV-absorbent molecules.  

PubMed

Intercalation of Zn/Al layered double hydroxide (LDH) with benzophenone 9 (B9), a strong ultraviolet (UV) absorber, had been carried out by two different routes; co-precipitation and ion exchange method. Powder X-ray diffraction (PXRD) patterns of co-precipitated (ZB9C) and ion exchanged product (ZB91) showed basal spacing of 15.9 angstrom and 16.6 angstrom, respectively, as a result of the intercalation of B9 anions into the lamellae spaces of LDH. Intercalation was further confirmed by Fourier transform infrared spectra (FTIR), carbon, hydrogen, nitrogen and sulfur (CHNS) and thermogravimetric and differential thermogravimetric (TGA/DTG) studies. UV-vis absorption properties of the nanocomposite was investigated with diffuse reflectance UV-visible spectrometer and showed broader UV absorption range. Furthermore, stability of sunscreen molecules in LDH interlayer space was tested in deionized water, artificial sea water and skin pH condition to show slow deintercalation and high retention in host. Cytotoxicity study of the synthesized nanocomposites on human dermal fibroblast (HDF) cells shows no significant cytotoxicity after 24 h exposure for test concentrations up to 25 microg/mL. PMID:25016649

Mohsin, Sumaiyah Megat Nabil; Hussein, Mohd Zobir; Sarijo, Siti Halimah; Fakurazi, Sharida; Arulselvan, Palanisamy; Taufiq-Yap, Yun Hin

2014-08-01

107

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 SO 4, 8H 2O 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(SO 42-), i.e. y=0, in which a bilayer of sulphate anions points to the Fe 3+ species. A cationic order is proposed to occur in both GR(SO 42-) 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(SO 42-) is preceded by the successive precipitation of Fe III and Al III (oxy)hydroxides. Adsorption of more soluble Al III 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 Fe II species of the material.

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

2008-09-01

108

Influences of co-existing species on the sorption of toxic oxyanions from aqueous solution by nanocrystalline Mg/Al layered double hydroxide.  

PubMed

The influences of common oxyanions (i.e. nitrate, silica, sulfate, carbonate, and phosphate) and natural organic matter (NOM) on the sorption of arsenate, chromate, bromate and vanadate (toxic oxyanions) by nanocrystalline Mg/Al layered double hydroxide (LDH) were investigated. Besides the type and concentration of the co-existing species, sorption competition was greatly dependent on the solution pH. In general, based on their sorption competitiveness with the toxic oxyanions, the co-existing common oxyanions were ranked in the order of nitrate < silica < or = sulfate < carbonate < phosphate, while the toxic oxyanions could be ranked in the order of bromate < arsenate approximately chromate < or = vanadate, indicating the oxyanions with lower ionic potentials were less preferably sorbed by the LDH. Based on the comprehensive study on sorption of arsenate by the LDH, the decrease in sorption of toxic oxyanions could be attributed to the competition of common oxyanions for common sorption sites on the LDH which predominantly occurred via ion exchange mechanism. NOM inhibited toxic oxyanion sorption through shielding LDH surface sites, directly competing for sorption sites of LDH, and co-precipitating the LDH. The presence of common oxyanions and NOM generally did not affect the mineral stability of the nanocrystalline LDH. PMID:20452119

Goh, Kok-Hui; Lim, Teik-Thye

2010-08-15

109

Synthesis and investigation of magnetic nanocomposite of Fe3O4 with cetirizine-intercalated layered double hydroxide  

NASA Astrophysics Data System (ADS)

In this research work the nanocomposite CT-LDH/Fe3O4 was prepared by deposition of cetirizine (CT) intercalated-Mg-Al layered double hydroxide (LDH) on Fe3O4 using a co-precipitation method for sustained drug-targeting delivery. The obtained products were characterized by the variety of methods such as (XRD), (FT-IR), (TG) and the elemental analysis. The size and morphology of nanoparticles were examined by the transmission electron microscopy (TEM). The XRD results, showed the coexistence of the strong diffractions of Fe3O4 and cetirizine intercalated LDH. Also, after intercalation, the basal spacing of LDH increased from 0.88 nm to 2.52 nm, indicating that cetirizine anions were successfully intercalated into the interlayer space of LDH as a monolayer. The thermal gravimetric studies indicate the thermal stability of cetirizine molecule has increased with intercalation. In vitro drug release experiments in phosphate buffer solution (pH = 7.4) have been investigated. Magnetic measurements revealed that the nanocomposite displayed superparamagnetic properties at room temperature.

Nejati, K.; Davaran, S.; Baggalzadeh, R.

2014-11-01

110

Layer-by-layer assembly of bi-protein/layered double hydroxide ultrathin film and its electrocatalytic behavior for catechol.  

PubMed

This paper reports the fabrication of a bi-protein/layered double hydroxide (LDH) ultrathin film in which hemoglobin (HB) and horseradish peroxidase (HRP) molecules were assembled alternately with LDH nanosheets via the layer-by-layer (LBL) deposition technique, and its electrocatalytic performances for oxidation of catechol were demonstrated. The results of XRD indicate that the HB-HRP/LDH ultrathin film possesses a long range stacking order in the normal direction of the substrate, with the two proteins accommodated in the LDH gallery respectively as monolayer arrangement. SEM images show that the film surface exhibits a continuous and uniform morphology, and AFM reveals the Root-Mean-Square (RMS) roughness of ?10.2 nm for the film. A stable direct electrochemical redox behavior of the proteins was successfully obtained for the HB-HRP/LDH film modified electrode. In addition, it exhibits remarkable electrocatalytic activity towards oxidation of catechol, based on the synergistic effect of the two proteins. The catechol biosensor in this work displays a wide linear response range (6-170 ?M, r=0.999), low detection limit (5 ?M), high sensitivity and good reproducibility. PMID:20678920

Kong, Xianggui; Rao, Xiuying; Han, Jingbin; Wei, Min; Duan, Xue

2010-10-15

111

Intercalation of [Cr(C2O4)3]3 - complex in mg,al layered double hydroxides.  

PubMed

A Mg,Al layered double hydroxide (LDH) with [Cr(C(2)O(4))(3)](3)(-) anions in the interlayer has been synthesized following two different routes: reconstruction from a mildly calcined Mg,Al-carbonate LDH, and anion exchange from a Mg,Al-nitrate LDH. The solids prepared have been characterized by elemental chemical analysis, powder X-ray diffraction, FT-IR and UV-vis/DR (diffuse reflectance) spectroscopies, thermal methods, nitrogen adsorption at -196 degrees C, and FT-IR monitoring of pyridine adsorption. The results obtained indicate that the most appropriate method is anion exchange, leading to a well crystallized LDH with an interlayer spacing of 10 A. Due to the high pH value (>8) of the solution in the reconstruction method, however, a polyphasic system is obtained, where, in addition to a phase with the LDH structure, amorphous magnesium oxalate and chromium oxohydroxides are also formed due to hydrolysis of the complex. The interlayer complex is stable up to 200 degrees C, but the layered structure is stable up to 330 degrees C, probably because of the presence of interlayer oxalate anions formed during decomposition of the complex. Calcination leads to oxidation of Cr(3+) ions to the six-valent state, which reverts to Cr(3+) when the calcination temperature is further increased. PMID:12817985

del Arco, M; Gutiérrez, S; Martín, C; Rives, V

2003-06-30

112

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

PubMed

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

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

2013-12-01

113

In vitro antioxidant activity and in vivo antifatigue effect of layered double hydroxide nanoparticles as delivery vehicles for folic acid  

PubMed Central

Folic acid antioxidants were successfully intercalated into layered double hydroxides (LDH) nanoparticles according to a previous method with minor modification. The resultant folic acid-LDH constructs were then characterized by X-ray powder diffraction and transmission electron microscopy. The in vitro antioxidant activities, cytotoxicity effect, and in vivo antifatigue were examined by a series of assays. The results showed that folic acid-LDH antioxidant system can scavenge 1,1-diphenyl-2-picrylhydrazyl and hydroxyl free radicals and chelate pro-oxidative Cu2+. The in vitro cytotoxicity assays indicated that folic acid-LDH antioxidant system had no significant cytotoxic effect or obvious toxicity to normal cells. It also prolonged the forced swimming time of the mice by 32% and 51% compared to folic acid and control groups, respectively. It had an obvious effect on decreasing the blood urea nitrogen and blood lactic acid, while increasing muscle and hepatic glycogen levels. Therefore, folic acid-LDH might be used as a novel antioxidant and antifatigue nutritional supplement. PMID:25506219

Qin, Lili; Wang, Wenrui; You, Songhui; Dong, Jingmei; Zhou, Yunhe; Wang, Jibing

2014-01-01

114

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

115

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

SciTech Connect

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

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

2011-02-15

116

A novel and easy chemical-clock synthesis of nanocrystalline iron-cobalt bearing layered double hydroxides.  

PubMed

A novel synthesis of cobalt-iron layered double hydroxide (LDH) with interlayer chlorides was investigated. The method consists in mixing concentrated solutions of hexaamminecobalt(III) trichloride with ferrous chloride at room temperature and in anoxic conditions. Four initial Fe/Co atomic ratios have been tried out (0.12, 0.6, 1.2 and 1.8). Neither heating nor addition of alkali was employed for adjusting the pH and precipitating the metal hydroxides. Still, each mixture led to the spontaneous precipitation of a LDH-rich solid having a crystal-chemistry that depended on the initial solution Fe/Co. These LDHs phases were carefully characterized by mean of X-ray diffraction, (57)Fe Mössbauer spectrometry, transmission electron microscopy and chemical analysis (total dissolution and phenanthroline method). Solution Eh and pH were also monitored during the synthesis. Increasing initial Fe/Co ratio impacted the dynamic of the observed stepwise reaction and the composition of the resulting product. Once the two solutions are mixed, a spontaneous and abrupt color change occurs after an induction time which depends on the starting Fe/Co ratio. This makes the overall process acting as a chemical clock. This spontaneous generation of CoFe-LDH arises from the interplay between redox chemistries of iron and cobalt-ammonium complexes. PMID:25173991

Hadi, Jebril; Grangeon, Sylvain; Warmont, Fabienne; Seron, Alain; Greneche, Jean-Marc

2014-11-15

117

A novel thermotropic elastomer based on highly-filled LDH-SSB composites.  

PubMed

Elastomeric composites are prepared based on solution styrene butadiene elastomer and zinc-aluminium layered double hydroxides (LDH), using a conventional sulphur cure system. Up to 100 parts per hundred rubber of LDH are incorporated into the elastomer matrix. The composites exhibit an interesting phenomenon of thermoreversible transparency, i.e. the transparent sample becomes opaque at warm condition and restores the transparency at room temperature. The transparency is found to be increased as the amount of LDH was increased. The addition of LDH gradually improved the mechanical, dynamic mechanical performance and thermal stability of the base elastomer. These developped elastomers could be utilised as smart materials in different applications. PMID:22271599

Das, Amit; George, Jinu Jacob; Kutlu, Burak; Leuteritz, Andreas; Wang, De-Yi; Rooj, Sandip; Jurk, René; Rajeshbabu, Ramanujam; Stöckelhuber, Klaus Werner; Galiatsatos, Vassilios; Heinrich, Gert

2012-02-27

118

In situ oligomerization of 2-(thiophen-3-yl)acetate intercalated into Zn2Al layered double hydroxide  

NASA Astrophysics Data System (ADS)

A layered double hydroxide (LDH) with cation composition Zn2Al was intercalated with 2-(thiophen-3-yl)acetate (3-TA) monomers. To achieve in situ polymerization and/or oligomerization of the intercalated monomers, soft thermal treatments were carried out, and subsequent hybrid LDH materials were analyzed by means of several characterization techniques using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), 13C CP-MAS nuclear magnetic resonance (NMR), electron spin resonance (EPR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and elemental analysis. PXRD analysis suggested that the intercalated monomers formed a bilayer. Thermal treatment of the hybrid LDH assembly above 120 °C provokes partially the breakdown of the layered structure, generating the phase zincite. EPR results indicated that vicinal monomers (oligomerization) were bound to each other after hydrothermal or thermal treatment, leading to a polaron response characteristic of electron conductivity localized on a restricted number of thiophene-based monomer segments. Localized unpaired electrons exist in the material and interact with the 27Al nuclei of the LDH layers by superhyperfine coupling. These unpaired electrons also interact with the surface of ZnO (O2- vacancies), formed during the thermal treatments.

Tronto, Jairo; Pinto, Frederico G.; da Costa, Liovando M.; Leroux, Fabrice; Dubois, Marc; Valim, João B.

2015-01-01

119

Strong interfacial attrition developed by oleate/layered double hydroxide nanoplatelets dispersed into poly(butylene succinate).  

PubMed

Poly(butylene succinate) (PBS) nanocomposite structure was studied as a function of the filler percentage loading. The resulting state of dispersion was evaluated by XRD and TEM, and the interfacial attrition between PBS chain and lamellar platelets by the melt rheological properties. Hybrid organic inorganic (O/I) layered double hydroxide (LDH) organo-modified by oleate anions was used as filler. It was found that the confinement supplied by the LDH framework forces the interleaved organic molecule to be more distant from each other than in the case of oleate salt, this having as an effect to decrease strongly the homonuclear intermolecular (1)H(1)H dipolar interaction. An additional consequence of this relatively free molecular rotation, affecting the (13)C CPMAS response as well, is to facilitate the delamination of the 2D-stacked layers during extrusion since an quasi-exfoliated PBS:Mg(2)Al/oleate structure is observed for filler loading lower than 5% w/w. This is in association to a non-linear viscoelasticity in the low-omega region and the observed shear-thinning tendency compares better than other PBS:silicate nanocomposite derivatives and is here explained by the presence of a percolated LDH nanoparticle network. Indeed the plastic deformation in the low-omega region is found to be restricted by well-dispersed LDH tactoids in association with a rather strong attrition phenomenon between tethered oleate anions and PBS chains. PMID:20605578

Zhou, Qian; Verney, Vincent; Commereuc, Sophie; Chin, In-Joo; Leroux, Fabrice

2010-09-01

120

Co-delivery of siRNAs and anti-cancer drugs using layered double hydroxide nanoparticles.  

PubMed

In this research we employed layered double hydroxide nanoparticles (LDHs) to simultaneously deliver an anticancer drug 5-fluorouracil (5-FU) and Allstars Cell Death siRNA (CD-siRNA) for effective cancer treatment. The strategy takes advantage of the LDH anion exchange capacity to intercalate 5-FU into its interlayer spacing and load siRNA on the surface of LDH nanoparticles. LDH nanoparticles have been previously demonstrated as an effective cellular delivery system for 5-FU and siRNA separately in various investigations. More excitedly, the combination of CD-siRNA and anticancer drug 5-FU with the same LDH particles significantly enhanced cytotoxicity to three cancer cell lines, e.g. MCF-7, U2OS and HCT-116, compared to the single treatment with either CD-siRNA or 5-FU. This enhancement is probably a result of coordinate mitochondrial damage process. Thus, the strategy to co-deliver siRNA and an anticancer drug by LDHs has great potential to overcome the drug resistance and enhance cancer treatment. PMID:24456604

Li, Li; Gu, Wenyi; Chen, Jiezhong; Chen, Weiyu; Xu, Zhi P

2014-03-01

121

Synthesis and characterization of Mg-Al-layered double hydroxides intercalated with cubane-1,4-dicarboxylate anions.  

PubMed

In the present work, Mg2Al-layered double hydroxide (LDH) intercalated with cubane-1,4-dicarboxylate anions was prepared from the reaction of solutions of Mg(ii) and Al(iii) nitrate salts with an alkaline solution of cubane-1,4-dicarboxylic acid by using the coprecipitation method. The successful preparation of a nanohybrid of cubane-1,4-dicarboxylate(cubane-dc) anions with LDH was confirmed by powder X-ray diffraction, FTIR spectroscopy and thermal gravimetric analysis (TGA). The increase in the basal spacing of LDHs from 8.67 Å to 13.40 Å shows that cubane-dc anions were successfully incorporated into the interlayer space. Thermogravimetric analyses confirm that the thermal stability of the intercalated cubane-dc anions is greater than that of the pure form before intercalation because of host-guest interactions involving hydrogen bonds. The interlayer structure, hydrogen bonding, and subsequent distension of LDH compounds containing cubane-dc anions were shown by molecular simulation. The RDF (radial distribution function), mean square displacement (MSD), and self-diffusion coefficient were calculated using the trajectory files on the basis of molecular dynamics (MD) simulations, and the results indicated that the cubane-dc anions were more stable when intercalated into the LDH layers. A good agreement was obtained between calculated and measured X-ray diffraction patterns and between experimental and calculated basal spacings. PMID:25407836

Rezvani, Zolfaghar; Arjomandi Rad, Farzad; Khodam, Fatemeh

2015-01-21

122

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

PubMed Central

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

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

2014-01-01

123

Layered double hydroxide functionalized textile for effective oil/water separation and selective oil adsorption.  

PubMed

The removal of oil and organic pollutants from water is highly desired due to frequent oil spill accidents, as well as the increase of industrial oily wastewater. Here, superhydrophobic and superoleophilic textile has been successfully prepared for the application of effective oil/water separation and selective oil adsorption. This textile was fabricated by functionalizing the commercial textile with layered double hydroxide (LDH) microcrystals and low surface energy molecules. The LDH microcrystals were immobilized on the microfibers of the textile through an in situ growth method, and they formed a nestlike microstructure. The combination of the hierarchical structure and the low surface energy molecules made the textile superhydrophobic and superoleophilic. Further experiments demonstrated that the as-prepared textile not only can be applied as effective membrane materials for the separation of oil and water mixtures with high separation efficiency (>97%), but also can be used as a bag for the selective oil adsorption from water. Thus, such superhydrophobic and superoleophilic textile is a very promising material for the application of oil spill cleanup and industrial oily wastewater treatment. PMID:25490110

Liu, Xiaojuan; Ge, Lei; Li, Wei; Wang, Xiuzhong; Li, Feng

2015-01-14

124

Synthesis, characterization, and controlled release antibacterial behavior of antibiotic intercalated Mg–Al layered double hydroxides  

SciTech Connect

Graphical abstract: The antibiotic anion released from Mg–Al LDHs provides a controlled release antibacterial activity against the growth of Micrococcus lysodeikticus in 3.5% NaCl solution. Highlights: ? Antibiotic anion intercalated LDHs were synthesized and characterized. ? The ion-exchange one is responsible for the release process. ? The diffusion through particle is the release rate limiting step. ? LDHs loaded with antibiotic anion have high antibacterial capabilities. -- Abstract: Antibiotic–inorganic clay composites including four antibiotic anions, namely, benzoate (BZ), succinate (SU), benzylpenicillin (BP), and ticarcillin (TC) anions, intercalated Mg–Al layered double hydroxides (LDHs) were synthesized via ion-exchange. Powder X-ray diffraction and Fourier transform infrared spectrum analyses showed the successful intercalation of antibiotic anion into the LDH interlayer. BZ and BP anions were accommodated in the interlayer region as a bilayer, whereas SU and TC anions were intercalated in a monolayer arrangement. Kinetic simulation of the release data indicated that ion-exchange was responsible for the release process, and the diffusion through the particles was the rate-limiting step. The antibacterial capabilities of LDHs loaded with antibiotic anion toward Micrococcus lysodeikticus growth were analyzed using a turbidimetric method. Significant high inhibition rate was observed when LDH nanohybrid was introduced in 3.5% NaCl solution. Therefore, this hybrid material may be applied as nanocontainer in active antifouling coating for marine equipment.

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

2012-11-15

125

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

PubMed

The arsenate-intercalated layered double hydroxide (LDH) of Mg and Al is synthesized by coprecipitation. The higher thermodynamic stability and the consequent lower solubility of the unitary arsenates preclude the formation of arsenate-intercalated LDHs of other metals directly from solution. However other M/Al-AsO(4) (M=Co, Ni, Zn) LDHs could be prepared by anion exchange, showing that arsenate intercalation proceeds topotactically. The intercalation of various species of As(V) into the interlayer of LDHs and the subsequent arsenate carrying capacity are dependent upon the pH of the solution. Upon thermal decomposition, the intercalated arsenate ion undergoes reductive deintercalation to give a mixture of As(III) and As(V) oxides. The product oxides revert back to the LDH upon soaking in water on account of the compositional and morphological metastability of the former. This is in contrast with the phosphate-intercalated LDHs, in which the reversibility is suppressed, consequent to the formation of stable metal phosphates. PMID:19135682

Prasanna, S V; Kamath, P Vishnu

2009-03-15

126

Removal of Remazol Blue 19 from wastewater by zinc-aluminium-chloride-layered double hydroxides  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDHs), also called anionic clays, consist of cationic brucite-like layers and exchangeable interlayer anions. These hydrotalcite-like compounds, with Zn and Al in the layers and chloride in the interlayer space, were prepared following the coprecipitation method at constant pH. The affinity of this material for Remazol Blue 19, RB19 [ 2- (3- (4- Amino- 9,10- dihydro- 3- sulpho- 9,10- dioxoanthracen- 4- yl) aminobenzenesulphonyl) vinyl) disodiumsulphate], was studied as a function of contact time, pH of the solutions LDH dose and the RB19/[Zn-Al-Cl] mass ratio. It was found that 48 h is enough time for the equilibrium state to be reached with maximum RB19 retention at pH of 9 for an LDH dose equal to 100 mg and with an RB19/[Zn-Al-Cl] mass ratio higher than 3. The adsorption isotherm, described by the Langmuir model, is of L-type. The results demonstrate that RB19 retention on LDHs occurs by adsorption on external surface when RB19/[Zn-Al-Cl] mass ratio is equal or <3 and by both adsorption and interlayer ion exchange for ratios higher than 3. A mechanism for removal of RB19 anion has been confirmed by X-ray diffraction, IR spectroscopy and TG analysis (TG and DTG curves).

Elkhattabi, El Hassan; Lakraimi, Mohamed; Badreddine, Mohamed; Legrouri, Ahmed; Cherkaoui, Omar; Berraho, Moha

2013-06-01

127

Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols  

NASA Astrophysics Data System (ADS)

M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h-1) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h-1) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen. Electronic supplementary information (ESI) available: Details in experimental and further characterization. See DOI: 10.1039/c3nr05604j

Li, Lun; Dou, Liguang; Zhang, Hui

2014-03-01

128

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

129

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

2013-10-23

130

Computer simulation study of the structural stability and materials properties of DNA-intercalated layered double hydroxides.  

PubMed

The intercalation of DNA into layered double hydroxides (LDHs) has various applications, including drug delivery for gene therapy and origins of life studies. The nanoscale dimensions of the interlayer region make the exact conformation of the intercalated DNA difficult to elucidate experimentally. We use molecular dynamics techniques, performed on high performance supercomputing grids, to carry out large-scale simulations of double stranded, linear and plasmid DNA up to 480 base pairs in length intercalated within a magnesium-aluminum LDH. Currently only limited experimental data have been reported for these systems. Our models are found to be in agreement with experimental observations, according to which hydration is a crucial factor in determining the structural stability of DNA. Phosphate backbone groups are found to align with aluminum lattice positions. At elevated temperatures and pressures, relevant to origins of life studies which maintain that the earliest life forms originated around deep ocean hydrothermal vents, the structural stability of LDH-intercalated DNA is substantially enhanced as compared to DNA in bulk water. We also discuss how the materials properties of the LDH are modified due to DNA intercalation. PMID:18345669

Thyveetil, Mary-Ann; Coveney, Peter V; Greenwell, H Chris; Suter, James L

2008-04-01

131

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

2012-11-01

132

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

PubMed

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

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

2013-06-14

133

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

PubMed

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

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

2013-05-01

134

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

PubMed

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

Wang, Zhihua; Liu, Fang; Lu, Chao

2014-10-15

135

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

136

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

PubMed Central

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

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

2014-01-01

137

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 edta 4- (edta 4-=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

138

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

139

Abatement of aqueous anionic contaminants by thermo-responsive nanocomposites: (Poly(N-isopropylacrylamide))-co-silylanized Magnesium/Aluminun layered double hydroxides.  

PubMed

A series of novel thermo-responsive composite sorbents, were prepared by free-radical co-polymerization of N-isopropylacrylamide (NIPAm) and the silylanized Mg/Al layered double hydroxides (SiLDHs), named as PNIPAm-co-SiLDHs. For keeping the high affinity of Mg/Al layered double hydroxides towards anions, the layered structure of LDHs was assumed to be reserved in PNIPAm-co-SiLDHs by the silanization of the wet LDH plates as evidenced by the X-ray powder diffraction. The sorption capacity of PNIPAm-co-SiLDH (13.5mg/g) for Orange-II from water was found to be seven times higher than that of PNIPAm (2.0mg/g), and the sorption capacities of arsenate onto PNIPAm-co-SiLDH are also greater than that onto PNIPAm, for both As(III) and As(V). These sorption results suggest that reserved LDH structure played a significant role in enhancing the sorption capacities. NO3(-) intercalated LDHs composite showed the stronger sorption capacity for Orange-II than that of CO3(2-). After sorption, the PNIPAm-co-SiLDH may be removed from water because of its gel-like nature, and may be easily regenerated contributing to the accelerated desorption of anionic contaminants from PNIPAm-co-SiLDHs by the unique phase-transfer feature through slightly heating (to 40°C). These recyclable and regeneratable properties of thermo-responsive nanocomposites facilitate its potential application in the in-situ remediation of organic and inorganic anions from contaminated water. PMID:25721857

Chen, Hua; Qian, Guangren; Ruan, Xiuxiu; Frost, Ray L

2015-06-15

140

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

PubMed

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

Abolghasemi, Mir Mahdi; Yousefi, Vahid

2014-06-01

141

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

142

Synthesis of protocatechuic acid-zinc/aluminium-layered double hydroxide nanocomposite as an anticancer nanodelivery system  

NASA Astrophysics Data System (ADS)

Protocatechuic acid, an active anticancer agent, has been intercalated into Zn/Al-layered double hydroxide at Zn/Al=2) using two different preparation methods, co-precipitation and ion-exchange, which are labelled as PZAE and PZAC, respectively. The release of protocatechuate from the nanocomposites occurred in a controlled manner and was fitted satisfactorily to pseudo-second order kinetics. The basal spacing of the resulting nanocomposites PZAE and PZAC was 10.2 and 11.0 Å, respectively, indicating successful intercalation of protocatechuate anions into the interlayer galleries of Zn/Al-NO3-LDH in a monolayer arrangement with angles of 24 and 33° from the z-axis in PZAE and PZAC, respectively. The formation of nanocomposites was further confirmed by a Fourier transform infrared study. Thermogravimetric and differential thermogravimetric analyses indicated that the thermal stability of the intercalated protocatechuic acid was significantly enhanced compared to its free protocatechuic acid, and the drug content in the nanocomposites was estimated to be approximately 32.6% in PZAE and 29.2% in PZAC. Both PZAE and PZAC nanocomposites inhibit the growth of human cervical, liver and colorectal cancer cell lines and exhibit no toxic effects towards normal fibroblast 3T3 cell after 72 h of treatment.

Barahuie, Farahnaz; Hussein, Mohd Zobir; Gani, Shafinaz Abd; Fakurazi, Sharida; Zainal, Zulkarnain

2015-01-01

143

Bacteria encapsulated in layered double hydroxides: Towards an efficient bionanohybrid for pollutant degradation.  

PubMed

A soft chemical process was successfully used to immobilize Pseudomonas sp. strain ADP (ADP), a well-known atrazine (herbicide) degrading bacterium, within a Mg2Al-layered double hydroxide host matrix. This approach is based on a simple, quick and ecofriendly direct coprecipitation of metal salts in the presence of a colloidal suspension of bacteria in water. It must be stressed that by this process the mass ratio between inorganic and biological components was easily tuned ranging from 2 to 40. This ratio strongly influenced the biological activity of the bacteria towards atrazine degradation. The better results were obtained for ratios of 10 or lower, leading to an enhanced atrazine degradation rate and percentage compared to free cells. Moreover the biohybrid material maintained this biodegradative activity after four cycles of reutilization and 3 weeks storage at 4°C. The ADP@MgAl-LDH bionanohybrid materials were completely characterized by X-ray diffraction (XRD), FTIR spectroscopy, thermogravimetric analysis and scanning and transmission electronic microscopy (SEM and TEM) evidencing the successful immobilization of ADP within the inorganic matrix. This synthetic approach could be readily extended to other microbial whole-cell immobilization of interest for new developments in biotechnological systems. PMID:25497161

Halma, Matilte; Mousty, Christine; Forano, Claude; Sancelme, Martine; Besse-Hoggan, Pascale; Prevot, Vanessa

2015-02-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

145

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

PubMed

We demonstrated an efficient method for the fabrication of novel, flexible electrodes based on ZnO nanoflakes and nickel-cobalt layered double hydroxides (denoted as ZnONF/NiCoLDH) as a core-shell nanostructure on textile substrates for wearable energy storage devices. NiCoLDH coated ZnO nanowire (denoted as ZnONW/NiCoLDH) flexible electrodes are also prepared for comparison. As an electrode for supercapacitors, ZnONF/NiCoLDH exhibits a high specific capacitance of 1624 F g(-1), which is nearly 1.6 times greater than ZnONW/NiCoLDH counterparts. It also shows a maximum energy density of 48.32 W h kg(-1) at a power density of 27.53 kW kg(-1), and an excellent cycling stability with capacitance retention of 94% and a Coulombic efficiency of 93% over 2000 cycles. We believe that the superior performance of the ZnONF/NiCoLDH hybrids is due primarily to the large surface area of the nanoflake structure and the open spaces between nanoflakes, both of which provide a large space for the deposition of NiCoLDH, resulting in reduced internal resistance and improved capacitance performance. Our results are significant for the development of electrode materials for high-performance wearable energy storage devices. PMID:24441593

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

2014-02-21

146

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

147

Efficient noble metal-free (electro)catalysis of water and alcohol oxidations by zinc-cobalt layered double hydroxide.  

PubMed

Replacing rare and expensive noble metal catalysts with inexpensive and earth-abundant ones for various renewable energy-related chemical processes as well as for production of high value chemicals is one of the major goals of sustainable chemistry. Herein we show that a bimetallic Zn-Co layered double hydroxide (Zn-Co-LDH) can serve as an efficient electrocatalyst and catalyst for water and alcohol oxidation, respectively. In the electrochemical water oxidation, the material exhibits a lower overpotential, by ~100 mV, than monometallic Co-based solid-state materials (e.g., Co(OH)2 and Co3O4)-catalytic systems that were recently reported to be effective for this reaction. Moreover, the material's turnover frequency (TOF) per Co atoms is >10 times as high as those of the latter at the same applied potentials. The Zn-Co-LDH also catalyzes oxidation of alcohols to the corresponding aldehydes or ketones at relatively low temperature, with moderate to high conversion and excellent selectivity. PMID:24116900

Zou, Xiaoxin; Goswami, Anandarup; Asefa, Tewodros

2013-11-20

148

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 6.2-7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322-30,090 mg/kg Zn). Based on 12 bulk and 23 micro-focused 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}30-80%) as well as of synthetic Zn-kerolite, Zn-LDH, and hydrozincite spiked into uncontaminated soil were readily extracted by 1 M NH4NO3 followed by 1 M NH4-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, O.; Voegelin, A; Villard, A; Marcus, M; Kretaschmar, R

2008-01-01

149

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

150

Synthesis of Highly Efficient Flame Retardant High-Density Polyethylene Nanocomposites with Inorgano-Layered Double  

E-print Network

burning.10 One of the fast growing classes of halogen-free flame retardants is aluminum hydroxide (Al(OH)3 with Inorgano-Layered Double Hydroxides As Nanofiller Using Solvent Mixing Method Yanshan Gao, Qiang Wang Zn2Al-X (X= CO3 2- , NO3 - , Cl- , SO4 2- ) layered double hydroxide (LDH) nanoparticles

Guo, John Zhanhu

151

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

152

Concentration of Simple Aldehydes by Sulfite-Containing Double-Layer Hydroxide Minerals: Implications for Biopoesis  

E-print Network

Concentration of Simple Aldehydes by Sulfite-Containing Double-Layer Hydroxide Minerals of production, concentration, and interaction of aldehydes and aldehyde phosphates, potential precursors aldehydes, we investigated their adduct formation with sulfite ion bound in the interlayer of positively

Arrhenius, Gustaf

153

A Ni-Fe Layered Double Hydroxide-Carbon Nanotube Complex for Water Oxidation  

E-print Network

Highly active, durable and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions including water splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel iron layered double hydroxide nanoplates on mildly oxidized multi-walled carbon nanotubes. Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-layered double hydroxide. The nanoplates were covalently attached to a network of nanotubes, affording excellent electrical wiring to the nanoplates. The ultra-thin Ni-Fe layered double hydroxide nanoplates/carbon nanotube complex was found to exhibit unusually high electro-catalytic activity and stability for oxygen evolution and outperformed commercial precious metal Ir catalysts.

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

2013-01-01

154

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

155

Aniosotropically Organized LDH on PVDF: A Geometrically Templated Electrospun Substrate for Advanced Anion Conducting Membranes.  

PubMed

A bioinspired geometric templating of an electrospun PVDF substrate with hexagonal platelets of Mg-Al layered double hydroxide (LDH), an intrinsic anion conductor, is presented. The distinctive morphology restructures the internal pore geometry and modulates the dynamic wetting profile of PVDF, transforming it into a highly functional substrate for SAFC anion conducting membranes. The membrane fabricated with PVDF-LDH substrate exhibited exceptionally high durability (>140 °C), high anionic conductivity, ion exchange capacity (IEC), restricted swelling, and improved tensile strength, overcoming critical challenges associated with PVDF electrospun substrates and validating its immense potential as a high-temperature-stable and durable substrate for advanced fuel cell membrane applications. PMID:25782625

Sailaja, G S; Zhang, Peilin; Anilkumar, Gopinathan M; Yamaguchi, Takeo

2015-04-01

156

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. PMID:23737666

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

2013-01-01

157

Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition  

PubMed Central

The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids. PMID:25080007

Nakayama, Hirokazu; Hayashi, Aki

2014-01-01

158

Synthesis of NiGa layered double hydroxides. A combined EXAFS, SAXS, and TEM study. 2. Hydrolysis of a Ni2+/Ga3+ solution.  

PubMed

Takovites are nickel-based layered double hydroxides (LDH) with a general formula that can be written as Ni(1-x)Al(x)(OH)2, A(z-)(x/z), yH(2)O, where A is a compensating interlayer anion. As in some other LDH samples, the positive charge of the layer can be adjusted upon synthesis and various anions can be exchanged in the interlayer region. It is then important to understand the synthesis pathway of these materials. We then undertook a study on the hydrolytic behavior of pure Ni salts and mixtures of Ni and Ga salts. This paper focuses on the hydrolysis of Ni(2+) and Ga(3+) ions, together in solution, carried out by base addition. The samples will be defined by their hydrolysis ratio R = [OH(-)]/([Ni(2+)] + [Ga(3+)]). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used to obtain information on the colloidal species size and shape on a large scale. Each hydrolyzed sample was also studied by Ni K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS) to obtain information on the local structure of the species in suspension. SAXS curves reveal the presence of bidimensional objects whatever the R values. The platelets formed for R values >/=1.1 are slightly thicker and smaller in size, which may be linked to their different natures. Complementary information is provided by TEM analysis: the first colloids formed have a structure very close to that of alpha-GaOOH, as shown by electronic diffraction. Those structures are progressively replaced by Ni-Ga LDH platelets with increasing hydrolysis ratio, which are the only species in suspension for R = 2.0, as shown by XRD. EXAFS results confirm the complete hydrolysis of gallium before the formation of Ni-Ga LDH phases. PMID:15491222

Defontaine, Guillaume; Michot, Laurent J; Bihannic, Isabelle; Ghanbaja, Jaafar; Briois, Valérie

2004-10-26

159

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

160

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

161

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

162

Structure Analysis and Fluorescence of Mg-Al-Tb Ternary Layered Double Hydroxides and Their Calcined Products  

NASA Astrophysics Data System (ADS)

Layered double hydroxides (LDHs) doped with Tb3+ ions in the brucite-like layers were prepared successfully by the co-precipitation method. The structure and fluorescence properties of Mg-Al-Tb ternary LDHs and their products calcined at different temperatures were studied for the first time. X-ray diffraction patterns indicated that as-synthesized LDH samples maintained a hexagonal crystal structure, and Tb(OH)3 was detected as Tb3+ dopant content increasing to 5 at.%. In the fluorescent spectra, the green emission intensity arising from 5D4 ? 7F5 transition became stronger with the increasing ratio of Tb3+ dopant. When the annealing temperature rose above 500°C, the layer structure collapsed and phases of MgO and MgAl2O4 formed. Meanwhile, compared with MgAlTb-LDHs, the Tb-doped calcined LDHs (CLDHs) showed stronger luminescent intensity of 5D4 ? 7F5 transition. These results revealed that the calcined Mg-Al-Tb ternary LDHs may become a series of novel materials with potential applications in fluorescent devices.

Chen, Junfei; Lei, Zhigao; Wang, Anqi; Liu, Jie; Wu, Xiuling; Chang, Tianci; Zhang, Yang; Li, Muqing

2015-02-01

163

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

E-print Network

Sorption of MS2 Bacteriophage to Layered Double Hydroxides: Effects of Reaction Time, p,to investigate the potential of layered double hydroxides (LDHs) to remove bacteriophage MS2 from contaminated waters. All four of 70% of bacteriophages (T4 and MS2) were removed the LDHs evaluated in this study had

Sparks, Donald L.

164

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. PMID:22942682

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

2012-01-01

165

Transesterification of edible, non-edible and used cooking oils for biodiesel production using calcined layered double hydroxides as reusable base catalysts.  

PubMed

Fatty acid methyl esters (FAME) were produced from edible, non-edible and used cooking oils with different fatty acid contents by transesterification with methanol using calcined layered double hydroxides (LDHs) as solid base catalysts. Among the catalysts, calcined CaAl2-LDH (hydrocalumite) showed the highest activity with >90% yield of FAME using low methanol:oil molar ratio (<6:1) at 65 °C in 5 h. The activity of the catalyst was attributed to its high basicity as supported by Hammett studies and CO(2)-TPD measurements. The catalyst was successfully reused in up to four cycles. Some of the properties such as density, viscosity, neutralization number and glycerol content of the obtained biodiesel matched well with the standard DIN values. It is concluded that a scalable heterogeneously catalyzed process for production of biodiesel in high yields from a wide variety of triglyceride oils including used oils is possible using optimized conditions. PMID:22305480

Sankaranarayanan, Sivashunmugam; Antonyraj, Churchil A; Kannan, S

2012-04-01

166

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

167

Soft Chemical Conversion of Layered Double Hydroxides to Superparamagnetic Spinel Platelets  

E-print Network

Soft Chemical Conversion of Layered Double Hydroxides to Superparamagnetic Spinel Platelets Yoji report the synthesis of a wide range of single-crystal spinel platelets with exposed (111) faces, lateral thickness, mosaic structure, shape anisotropy, and surface porosity, NiCoAlO4 and NiCo2O4 platelets exhibit

168

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

PubMed

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

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

2014-08-01

169

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

170

Ni/Ti layered double hydroxide: synthesis, characterization and application as a photocatalyst for visible light degradation of aqueous methylene blue.  

PubMed

Visible light responsive 2?:?1 Ni/Ti layered double hydroxide (LDH) was synthesized by a single step hydrothermal route using commercially available Ni(NO3)2·6H2O, TiCl4 and urea. The material exhibited significant absorption in the visible range with a very narrow band gap (2.68 eV). This could be attributed to structural defects as confirmed by diffuse reflectance spectroscopy (DRS), photoluminescence (PL), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. FT-IR, TGA, DTA, DSC, HR-TEM and SEM-EDX measurements yielded information about structural aspects, thermal stability and surface morphology. Surface and pore characteristics of the material were obtained from the BET isotherm for N2 adsorption at 77 K. Zeta potential measurements were used to characterize the electrical properties of the surface while XPS revealed changes in surface states and oxygen deficiencies. The material was found to be an excellent photocatalyst for the degradation of aqueous methylene blue in visible light. The photocatalytic properties of the material were explained on the basis of the narrow band gap, the high surface area and the presence of surface defects. The photocatalytic activity improved in alkaline media [pH 11.0, catalyst load 15 mg in 200 ml dye solution, dye concentration 1 × 10(-6) M (= 0.3198 mg L(-1))] due to the electrostatic attractions between the dye cations and the negative charges on the Ni/Ti LDH surface. The catalytic activity was found to be higher than the common commercial catalysts like ZnO, ZnS, NiO, TiO2 and Degussa P25. The catalytic activity was retained even after five methylene blue degradation cycles, demonstrating that the LDH could be an important addition to the field of wastewater treatment. PMID:25763803

Roy Chowdhury, Priyadarshi; Bhattacharyya, Krishna G

2015-04-01

171

Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets  

Microsoft Academic Search

Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11?12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were tailored to different sizes and aspect ratios. Amino-modified polyisobutylene molecules were grafted onto the platelets following a convenient new

Maurice C. D. Mourad; Edwin J. Devid; Matti M. van Schooneveld; Chantal Vonk; Henk N. W. Lekkerkerker

2008-01-01

172

Water dispersiblity and ultrovoilet light shielding properties of layered double hydroxide intercalated with avermectin  

Microsoft Academic Search

Water dispersible avermectin-layered double hydroxide nanocomposites were successfully prepared using sodium dodecyl sulfate as surface modifier. Concentrations of sodium dodecyl sulfate and NaCl had important effects on the product suspensibility, the highest value of which reached 97.6%. All the samples were characterized using zeta potential and contact angle measurements. Experimental results showed that the prepared nanocomposites could protect effectively the

Jikuan Zhao; Wanguo Hou

2011-01-01

173

Thermal properties and combustion characterization of nylon 6\\/MgAl-LDH nanocomposites via organic modification and melt intercalation  

Microsoft Academic Search

The nylon 6\\/MgAl layered double hydroxide (MgAl-LDH) nanocomposites have been prepared by melt intercalation of nylon 6 into the part organic dodecyl sulfate (DS) anion-modified MgAl(H-DS) interlayers. The structures and properties of MgAl(H-DS) and corresponding nanocomposites were characterized by ion chromotography, X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and cone calorimeter test (CCT).

Longchao Du; Baojun Qu; Ming Zhang

2007-01-01

174

MgCoAl–LDH derived heterogeneous catalysts for the ethanol transesterification of canola oil to biodiesel  

Microsoft Academic Search

Mixed oxide catalysts derived from Mg–Co–Al–La layered double hydroxide (LDH) with various Mg:Co:Al:La ratios were prepared by co-precipitation and calcination. Their catalytic performance as heterogeneous base catalysts for the transesterification of canola oil with ethanol to produce biodiesel was compared over 5h in a batch reactor at 473K. Amending the catalyst by the addition of La, a possible stabilizer and

Eugena Li; Zhi Ping Xu; Victor Rudolph

2009-01-01

175

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

176

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

NASA Astrophysics Data System (ADS)

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 °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.

Herrero, M.; Benito, P.; Labajos, F. M.; Rives, V.; Zhu, Y. D.; Allen, G. C.; Adams, J. M.

2010-07-01

177

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

PubMed Central

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

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

2014-01-01

178

In situ synthesis of MOF membranes on ZnAl-CO3 LDH buffer layer-modified substrates.  

PubMed

We develop here a urea hydrolysis method to in situ prepare asymmetric ZnAl-CO3 layered double hydroxide (LDH) buffer layers with various stable equilibrium morphology on porous Al2O3 substrates. In particular it is found that well-intergrown ZIF-8 membranes can be directly synthesized on the ZnAl-CO3 LDH buffer layer-modified substrates, owing to the specific metal-imidazole interaction between ZnAl-CO3 LDHs and ZIF-8. Other Zn-based MOF membranes, like ZIF-7 and ZIF-90, can also be synthesized with this method. Our finding demonstrates that LDH buffer layer represents a new concept for substrate modification. PMID:25280264

Liu, Yi; Wang, Nanyi; Pan, Jia Hong; Steinbach, Frank; Caro, Jürgen

2014-10-15

179

Drug delivery system for an anticancer agent, chlorogenate-Zn/Al-layered double hydroxide nanohybrid synthesised using direct co-precipitation and ion exchange methods  

NASA Astrophysics Data System (ADS)

A nano-structured drug-inorganic clay hybrid involving an active anticancer compound, which is chlorogenic acid (CA) intercalated into Zn/Al-layered double hydroxide, has been assembled via ion-exchange and co-precipitation methods to form a nanohybrid CZAE (a chlorogenic acid-Zn/Al nanohybrid synthesised using an ion-exchange method) and CZAC (a chlorogenic acid-Zn/Al nanohybrid synthesised using a direct method), respectively. The X-ray diffraction (XRD) results confirmed that the CA-LDH had a hybrid structure in which the anionic chlorogenate is arranged between the interlayers as a horizontal monolayer at 90 and 20° angles from the x axis for CZAE and CZAC, respectively. Both nanohybrids have the properties of mesoporous materials. The high loading percentage of chlorogenic acid (approximately 43.2% for CZAE and 45.3% for CZAC) with basal spacings of 11.7 and 12.6 Å for CZAE and CZAC, respectively, corroborates the successful intercalation of chlorogenic acid into the interlayer gallery of layered double hydroxides. Free chlorogenic acid and the synthesised nanocomposites (CZAE, CZAC) were assessed for their cytotoxicity against various cancer cells. The Fourier transform infrared data supported the formation of both nanohybrids, and a thermal analysis showed that the nanohybrids are more thermally stable than their counterparts. The chlorogenate shows a sustained release, and the release rate of chlorogenate from CZAE and CZAC nanohybrids at pH 7.4 is remarkably lower than that at pH 4.8 due to their different release mechanisms. The release rate of chlorogenate from both nanohybrids can be described as pseudo-second order. The present investigation revealed the potential of the nanohybrids to enhance the in vitro anti-tumour effect of chlorogenic acid in liver and lung cancer cells in vitro.

Barahuie, Farahnaz; Hussein, Mohd Zobir; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

2014-09-01

180

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

181

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

182

Synthesis of NiGa layered double hydroxides. A combined EXAFS, SAXS, and TEM study. 3. Synthesis at constant pH.  

PubMed

The present paper focuses on the direct synthesis of NiGa layered double hydroxides (LDHs) by concomitant addition of Ni and Ga chloride in solution with NaOH solution, at a constant pH value of 6.5. Various Ni/Ga ratios (Ni/Ga = 2, Ni/Ga = 4, or Ni/Ga = 6) were investigated, and samples were collected after successive additions. Each sample was then analyzed by small-angle X-ray scattering (SAXS) to derive information about the shape of the objects formed upon synthesis. In parallel Ni K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS) analysis were carried out on relevant samples to obtain information on the local structure of the species in suspension. SAXS curves reveal significant changes. At the beginning of the synthesis, for low added volumes (V(s)), the suspension appears to contain both monodimensional and bidimensional objects. For higher V(s), the monodimensional objects disappear and only platelike particles are detected in the suspension. EXAFS results show that all the added gallium atoms are involved in a solid Ni-Ga LDH phase throughout the whole synthesis. In contrast, some nickel cations do not precipitate in the Ni-Ga LDH. At the beginning of the synthesis, for low added volumes they are also involved in the formation of fibrous polycations. For higher added volumes, the fibers are not observed anymore and monomeric nickel species are then present in the suspension. PMID:15568878

Defontaine, Guillaume; Michot, Laurent J; Bihannic, Isabelle; Ghanbaja, Jaafar; Briois, Valérie

2004-12-01

183

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

184

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

185

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

PubMed

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

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

2011-11-30

186

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

PubMed

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

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

2013-01-01

187

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

188

Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-} redox in the interlayer determined by the charge density of Zn{sub n}Cr-layered double hydroxides  

SciTech Connect

Redox of Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} in the ZnCr layered double hydroxide interlayer has been investigated. The conversion from Fe(CN){sub 6}{sup 3-} to Fe(CN){sub 6}{sup 4-} or from Fe(CN){sub 6}{sup 4-} to Fe(CN){sub 6}{sup 3-} in the ZnCr-LDH interlayer has been confirmed, depending on the Zn:Cr molar ratio. Both Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} are observed in all samples no matter whether the initial anion is Fe(CN){sub 6}{sup 3-} or Fe(CN){sub 6}{sup 4-} before precipitation. Deconvolution of the FTIR band around 2100 cm{sup -1} reveals that the relative amount of Fe(CN){sub 6}{sup 4-} and Fe(CN){sub 6}{sup 3-} in the LDH interlayer is considerably dependent on the Zn:Cr molar ratio. In brief, Fe(CN){sub 6}{sup 4-} is preferred at the ratio of 2:1 while there is more Fe(CN){sub 6}{sup 3-} in the ratio of 4:1. Therefore, it is our hypothesis that the charge density of the hydroxide layer is a key factor that directs the redox of Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-}. The possible redox processes have also been proposed. - Graphical abstract: Redox reactions of Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} take place in the ZnCr layered double hydroxide (LDH) interlayer, which are reflected by Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-} FTIR area ratio. Highlights: Black-Right-Pointing-Pointer An interlayer redox phenomena was observed in Fe(CN){sub 6}{sup 3/4-} intercalated ZnCr-LDHs. Black-Right-Pointing-Pointer The ratio of interlayer redox was examined by FTIR fitting analysis. Black-Right-Pointing-Pointer The tendency of redox was influenced by Zn:Cr molar ratio. Black-Right-Pointing-Pointer The mechanism relies on the charge density of metal hydroxyl layer.

Zhang, Jia; Xu, Yunfeng; Liu, Jiangyong; Zhou, Jizhi [School of Environmental and Chemical Engineering, Shanghai University, No. 333 Nanchen Rd, Shanghai 200444 (China)] [School of Environmental and Chemical Engineering, Shanghai University, No. 333 Nanchen Rd, Shanghai 200444 (China); Xu, Zhi Ping, E-mail: gordonxu@uq.edu.au [ARC Centre of Excellence for Functional Nanomaterials, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072 (Australia); Qian, Guangren, E-mail: grqian@shu.edu.cn [School of Environmental and Chemical Engineering, Shanghai University, No. 333 Nanchen Rd, Shanghai 200444 (China)] [School of Environmental and Chemical Engineering, Shanghai University, No. 333 Nanchen Rd, Shanghai 200444 (China)

2013-02-15

189

Preparation of Mg-Al layered double hydroxides intercalated with 1,3,6-naphthalenetrisulfonate and 3-amino-2,7-naphthalenedisulfonate and assessment of their selective uptake of aromatic compounds from aqueous solutions  

NASA Astrophysics Data System (ADS)

Mg-Al layered double hydroxides (Mg-Al LDHs) intercalated with 1,3,6-naphthalenetrisulfonate (NTS 3-) and 3-amino-2,7-naphthalenedisulfonate (ANDS 2-) ions were prepared by coprecipitation and were characterized by X-ray diffraction and chemical analyses. Based on X-ray diffraction patterns, the naphthalene rings of NTS 3- and ANDS 2- were most likely oriented parallel to the brucite-like host layers of the Mg-Al LDH, midway between layers. The prepared Mg-Al LDHs were able to selectively take up aromatics from aqueous solutions, and the order of percentage uptake was as follows: 1,3-dinitrobenzene > nitrobenzene > benzaldehyde > N,N-dimethylaniline > anisole > 1,2-dimethoxybenzene. The differences in the extent of ?-? stacking interactions occurring between the benzene rings of the aromatics and the naphthalene ring of the intercalated NTS 3- and ANDS 2- probably resulted in these differences among the absorbed quantities of the various aromatics.

Kameda, Tomohito; Yamazaki, Takashi; Yoshioka, Toshiaki

2010-05-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

191

Pectin-coated chitosan-LDH bionanocomposite beads as potential systems for colon-targeted drug delivery.  

PubMed

This work introduces results on a new drug delivery system (DDS) based on the use of chitosan/layered double hydroxide (LDH) biohybrid beads coated with pectin for controlled release in the treatment of colon diseases. Thus, the 5-aminosalicylic acid (5ASA), the most used non-steroid-anti-inflammatory drug (NSAID) in the treatment of ulcerative colitis and Crohn's disease, was chosen as model drug aiming to a controlled and selective delivery in the colon. The pure 5ASA drug and the hybrid material prepared by intercalation in a layered double hydroxide of Mg2Al using the co-precipitation method, were incorporated in a chitosan matrix in order to profit from its mucoadhesiveness. These compounds processed as beads were further treated with the polysaccharide pectin to create a protective coating that ensures the stability of both chitosan and layered double hydroxide at the acid pH of the gastric fluid. The resulting composite beads presenting the pectin coating are stable to water swelling and procure a controlled release of the drug along their passage through the simulated gastrointestinal tract in in vitro experiments, due to their resistance to pH changes. Based on these results, the pectin@chitosan/LDH-5ASA bionanocomposite beads could be proposed as promising candidates for the colon-targeted delivery of 5ASA, with the aim of acting only in the focus of the disease and minimizing side effects. PMID:24374607

Ribeiro, Lígia N M; Alcântara, Ana C S; Darder, Margarita; Aranda, Pilar; Araújo-Moreira, Fernando M; Ruiz-Hitzky, Eduardo

2014-03-10

192

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

193

Direct synthesis of Co2Al(OH)7-2x(CO3)x·nH2O layered double hydroxide nanolayers by successive ionic layer deposition and their capacitive performance  

NASA Astrophysics Data System (ADS)

New method of synthesis of Co2Al(OH)7-2x(CO3)x·nH2O layered double hydroxide (LDH) films by successive ionic layer deposition (SILD) is presented in this paper. The obtained nanolayers were characterized by SEM, EDX, XRD, XPS, FTIR spectroscopy and electrochemical techniques. The results showed that the as-synthesized product is formed by nanosheets with a thickness of 3-5 nm, having hydrotalcite crystal structure. Electrochemical characterization of the sample prepared by 50 cycles of SILD indicated a capacitive behavior with the specific capacitance value of 900 F/g at a current density of 1 A/g and 950 F/g at 0.5 A/g in 1 mol/L KOH aqueous solution. Repeated cycling for 1000 charge-discharge cycles demonstrate that capacitance increases by 6%, so such electrodes may be used as electrodes of hybrid supercapacitors. The presented convenient route of synthesis may be used for the preparation of LDH films with high surface area and a large capacitance.

Lobinsky, A. A.; Tolstoy, V. P.; Gulina, L. B.

2014-11-01

194

Synthesis of Magnetite-Graphene Oxide-Layered Double Hydroxide Composites and Applications for the Removal of Pb(II) and 2,4-Dichlorophenoxyacetic Acid from Aqueous Solutions.  

PubMed

Magnetic composites consisting of magnetite (Fe3O4), graphene oxide (GO), and Mg3Al-OH layered double hydroxide (LDH), denoted as MGL composites, with varying GO contents (RGO) were synthesized by a mechano-hydrothermal (MHT) route using Fe3O4, Mg(OH)2, and Al(OH)3 as the inorganic starting materials. The application of the synthesized MGLs for removing the heavy-metal Pb(II) and the hydrophobic organic pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was investigated. Chemical bonding among the GO, Fe3O4, and LDH components was observed in the MGLs. The MGL composites showed good water-dispersity, strong magnetic response, and high sorption capacities and removal efficiencies for both Pb(II) and 2,4-D pollutants. The sorption capacities of the MGL for the pollutants significantly increased with an increase in RGO. Increasing pH could increase the removal efficiency for Pb(II) but decrease that for 2,4-D. The MGLs showed more affinity for Pb(II) than for 2,4-D in the competitive sorption. In addition, the MGLs could remain almost constant removal efficiency for the pollutants after reuse over six cycles, indicating their potential use as sorbents in wastewater treatment. Furthermore, a Cs effect was observed in the sorption equilibriums, which could be described using the Langmuir-SCA and Freundlich-SCA isotherms. The removal mechanisms of the MGL for Pb(II) and 2,4-D were discussed. The MHT method provided a simple and environmentally friendly route for synthesizing GO-LDH composite materials. PMID:25791354

Zhang, Fengrong; Song, Yawen; Song, Shue; Zhang, Renjie; Hou, Wanguo

2015-04-01

195

Study on the adsorption of DNA on the layered double hydroxides (LDHs).  

PubMed

Four kinds of layered double hydroxides (LDHs) were prepared by chemical coprecipitation method and used as DNA adsorbents. Multiple characterization tools such as power X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Standard electronic modules (SEM) were employed to characterize the LDHs. By examining the effect of initial concentration, solution pH, adsorption experiments were carried out to investigate the adsorption capacities of LDHs for DNA. The results revealed that the LDHs with Mg/Al=3 had higher ability on adsorbing the DNA and were not affected by pH values. The LDHs exhibited excellent adsorption properties and completely adsorbed DNA within 2h. The adsorption equilibrium data were fitted to the Langmuir and Freundlich models, showing that the Langmuir model which represented monolayer adsorption had better correlation with the adsorption linear equation. In addition, Circular dichroism (CD) spectrum, UV-vis spectorscopy and agarose gel electrophoresis revealed the integrity of DNA structure, suggesting that there had no damage on the DNA structure during the adsorption process. PMID:24280301

Li, Bin; Wu, Pingxiao; Ruan, Bo; Liu, Paiyu; Zhu, Nengwu

2014-01-01

196

Heterogeneous photocatalytic degradation of pesticides using decatungstate intercalated macroporous layered double hydroxides.  

PubMed

Decatungstate W10O32(4-) was efficiently intercalated between the layers of three-dimensionally ordered macroporous Mg2Al-layered double hydroxide. The structural and textural properties of as-prepared intercalated compound were characterized using different solid-state characterization techniques such as X-ray powder diffraction, FTIR and Raman spectroscopies and electronic microscopy. The photocatalytic properties of immobilized W10O32 (4-) within Mg2Al structure were investigated using 2-(1-naphthyl) acetamide (NAD) as a model of pesticide. The influence of different parameters such as amount of catalyst, pH and oxygen concentration were investigated. An optimal NAD degradation was obtained for a photocatalyst concentration of 60 mg l(-1). Under our experimental conditions, this heterogeneous photocatalyst induces photodegradation of 60 % of NAD after 17 h of irradiation at 365 nm and at pH 6.6. Interestingly, pesticide photodegradation leads to the mineralization of substrates to H2O and CO2 and the photocatalyst can be recycled and reused without any loss of activity over four cycles. PMID:24838128

Da Silva, Eliana S; Prevot, Vanessa; Forano, Claude; Wong-Wah-Chung, Pascal; Burrows, Hugh D; Sarakha, Mohamed

2014-10-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

198

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

PubMed

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

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

2014-05-10

199

Concentration of simple aldehydes by sulfite-containing double-layer hydroxide minerals: implications for biopoesis  

NASA Technical Reports Server (NTRS)

Environmental conditions play an important role in conceptual studies of prebiotically relevant chemical reactions that could have led to functional biomolecules. The necessary source compounds are likely to have been present in dilute solution, raising the question of how to achieve selective concentration and to reach activation. With the assumption of an initial 'RNA World', the questions of production, concentration, and interaction of aldehydes and aldehyde phosphates, potential precursors of sugar phosphates, come into the foreground. As a possible concentration process for simple, uncharged aldehydes, we investigated their adduct formation with sulfite ion bound in the interlayer of positively charged expanding-sheet-structure double-layer hydroxide minerals. Minerals of this type, initially with chloride as interlayer counter anion, have previously been shown to induce concentration and subsequent aldolization of aldehyde phosphates to form tetrose, pentose, and hexose phosphates. The reversible uptake of the simple aldehydes formaldehyde, glycolaldehyde, and glyceraldehyde by adduct formation with the immobilized sulfite ions is characterized by equilibrium constants of K=1.5, 9, and 11, respectively. This translates into an observable uptake at concentrations exceeding 50 mM.

Pitsch, S.; Krishnamurthy, R.; Arrhenius, G.; Bada, J. L. (Principal Investigator)

2000-01-01

200

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

SciTech Connect

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

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

2013-01-01

201

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

SciTech Connect

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

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

2010-11-15

202

Ephemeral Fe(II)/Fe(III) layered double hydroxides in hydromorphic soils: A review  

NASA Astrophysics Data System (ADS)

Ephemeral green rust is formed seasonally in some hydromorphic soils. It consists of Fe(II)/Fe(III) layered double hydroxides with different types of interlayer anions and different oxidation degrees of iron ( x). In synthetized stoichiometric green rust, x = 0.25-0.33; in soil fougerite, it may reach 0.50-0.66. The mineral stability is provided by the partial substitution of Mg2+ for Fe2+. The ephemeral properties of the green rust are manifested in the high sensitivity to the varying redox regime in hydromorphic soils. Green rust disappears during oxidation stages, which complicates its diagnostics in soils. For green rust formation, excessively moist mineral soil needs organic matter as a source of energy for the vital activity of iron-reducing bacteria. In a gleyed Cambisol France, where fougerite is formed in the winter, the index of hydrogen partial pressure rH2 is 7.0-8.2, which corresponds to highly reducing conditions; upon the development of oxidation, fougerite is transformed into lepidocrocite. In the mineral siderite horizon of peatbogs in Belarus, where green rust is formed in the summer, rH2 is 11-14, which corresponds to the lower boundary of reducing conditions ( rH2 = 10-18); magnetite is formed in these soils in the winter season upon dehydration of the soil mass.

Vodyanitskii, Yu. N.; Shoba, S. A.

2015-03-01

203

Simultaneous incorporation of palladium and zirconium ions in Mg–Al layered double hydroxides by co-precipitation  

Microsoft Academic Search

Simultaneous incorporation of palladium and zirconium ions in Mg–Al layered double hydroxides (LDHs) was attempted by co-precipitation. Mixed oxides were obtained by calcination at 500°C. XRD patterns of as-synthesized samples showed the formation of well-crystallized LDHs at lower Zr contents. The CO32? content of the solids has been determined to have information on the possible incorporation of Zr4+ into the

Yanming Shen; Dongbin Liu; Lihui Fan; Shifeng Li; Liping Gao

2011-01-01

204

Synthesis, structure refinement and chromate sorption characteristics of an Al-rich bayerite-based layered double hydroxide  

NASA Astrophysics Data System (ADS)

“Imbibition” of Zn2+ ions into the cation vacancies of bayerite-Al(OH)3 and NO3- ions into the interlayer gallery yields an Al-rich layered double hydroxide with Al/Zn ratio ~3. NO3- ions are intercalated with their molecular planes inclined at an angle to the plane of the metal hydroxide slab and bonded to it by hydrogen bonds. Rietveld refinement of the structure shows that the monoclinic symmetry of the precursor bayerite is preserved in the product, showing that the imbibition is topochemical in nature. The nitrate ion is labile and is quantitatively replaced by CrO42- ions from solution. The uptake of CrO42- ions follows a Langmuir adsorption isotherm, thus showing that the hydroxide is a candidate material for green chemistry applications for the removal of CrO42- ions from waste water. Rietveld refinement of the structure of the hydroxide after CrO42- inclusion reveals that the CrO42- ion is intercalated with one of its 2-fold axes parallel to the b-crystallographic axis of the crystal, also the principal 2 axis of the monoclinic cell.

Britto, Sylvia; Kamath, P. Vishnu

2014-07-01

205

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

PubMed

Layered double hydroxides (LDHs) with a Mg/Al molar ratio of 2:1 were synthesized by using a co-precipitation method and their calcined products (CLDHs) were obtained by heating Mg/Al-LDHs at 500 degrees C. Sorption of a weak acid dye, Brilliant Blue R (BBR), by LDHs and CLDHs indicated equilibrium time required for BBR sorption by CLDHs was less than 12h, regardless of initial concentration of BBR, whereas BBR sorption by LDHs was longer than 20 h. Sorption capacity of CLDHs was much larger than that of LDHs. Therefore, CLDHs could be used to remove anionic dyes of relatively high concentrations while LDHs may only be used to remove anionic dyes of low concentrations. Isotherms for BBR sorption by CLDHs and LDHs were well described using the Freundlich and Langmuir equations, respectively. When the initial pH of BBR solutions was lower than 8.0, the final pH of the solution after sorption was enhanced and stabilized at 10.6-10.8. The effect of initial pH (<8.0) on BBR removal was negligible, which would be environmentally important for precipitation/co-precipitation of co-existing metal cations. The effects of both Cl- and SO4(2-) on BBR sorption by CLDHs were minimal; but the presence of CO(3)2- markedly reduced BBR removal. Thermal regeneration for re-use of LDHs and CLDHs after BBR sorption was feasible only within the first two cycles, after which the regenerated materials suffered from a large loss in their sorption capacities. PMID:15811678

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

2005-04-11

206

New SnO2/MgAl-layered double hydroxide composites as photocatalysts for cationic dyes bleaching.  

PubMed

A new type of nanocomposite containing SnO(2) has been obtained by wet impregnation of dehydrated Mg/Al-hydrotalcite-type compounds with ethanolic solutions of SnCl(4).2H(2)O. Tin chloride hydrolysis was achieved using NaOH or NH(4)OH aqueous solutions, at pH around 9, followed by the conversion into corresponding hydroxides through calcinations. The powder X-ray diffraction (PXRD) and UV-Vis diffuse reflectance (UV-DR) methods confirmed the structure of as-synthesized solids. The chemical composition and morphology of the synthesized materials were investigated by energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-synthesized materials were used for photocatalytic studies showing a good activity for methylene blue decolourization, which varies with SnO(2) content and used as a hydrolysing agent. The proposed mechanism is based on the shifting of flat band potential of SnO(2) due to the interaction with Mg/Al-LDH, this being energetically favourable to the formation of hydroxyl radicals responsible for methylene blue degradation. PMID:20045244

Dvininov, E; Ignat, M; Barvinschi, P; Smithers, M A; Popovici, E

2010-05-15

207

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

208

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

209

Photoluminescence property of a novel inorganic-organic red emitting phosphor based on Mg/Al/Eu layered double hydroxide  

NASA Astrophysics Data System (ADS)

A novel inorganic-organic red light emitting phosphor was synthesized by intercalating a sensitizer anion, terephthalate into Mg/Al/Eu layered double hydroxides through an ion exchange method. The basal spacing is 13.9 Å, indicating that a vertical arrangement of terephthalate anions within the gallery is adopted. This material displays much enhanced red luminescence from Eu3+ ions, suggesting that there is an efficient energy transfer from the excited state of the intercalated terephthalate anions to Eu3+ centres in the host layers. The optimal doping concentration of Eu3+ is 10 mol %.

Gao, Xiaorui; Lei, Lixu; Yin, Yaobing; Xie, Juan; Wang, Yuqiao; Gu, Wei

2014-07-01

210

Nanostructured ZnS and CdS films synthesized using layered double hydroxide films as precursor and template.  

PubMed

Anion exchange reactions in layered double hydroxide films (M(OH)(2-x)(NO(3))(x).mH(2)O) followed by solid state conversion reactions are shown to yield micrometer-sized unsupported metal sulfide (M = Zn, Cd) films with unique textured morphologies. The characteristic three-dimensional nanostructured film morphology and crystallinity of the initial films are retained in the metal sulfide films although these conversion reactions involve anion exchanges concomitant with significant rearrangements of the crystal structures. Surface areas of 42 m(2)/g for zinc sulfide and 50 m(2)/g for cadmium sulfide thin films are observed. These values correspond to an increase in surface area of 75% for the Zn(5)(OH)(8)(NO(3))(2).2H(2)O to zinc sulfide conversion, while the cadmium sulfide films exhibit more than three times the surface area of their precursor material, Cd(OH)(NO(3)).H(2)O. The three-dimensional morphology of the resulting films is thus observed to combine the physical properties of the bulk materials with the advantages of higher surface areas typically associated with nanostructured or porous materials. The layered double hydroxide materials used in this study to provide both structural and chemical templates were prepared using the mild conditions of a biologically inspired vapor-diffusion catalytic synthesis. PMID:19149465

Schwenzer, Birgit; Pop, Lia Z; Neilson, James R; Sbardellati, Timothy B; Morse, Daniel E

2009-02-16

211

Bioinspired design and assembly of layered double hydroxide/poly(vinyl alcohol) film with high mechanical performance.  

PubMed

Inspired by the hierarchical structure and excellent mechanical performance of nacre, LDH nanosheets with an appropriate aspect ratio to withstand significant loads and at the same time allow for rupture under the pull-out mode were synthesized as artificial building blocks for the fabrication of nacre-like films. Multilayered PVA/LDH films with a high tensile strength and ductility were prepared for the first time by bottom-up layer-by-layer assembly of pretreated LDH nanosheets and spin-coating of PVA. The weight fraction of inorganic LDH platelets in the hybrid PVA/LDH films (wp) was controlled by changing the concentration of PVA solution applied in the spin-coating process. The resulting films revealed that the PVA/LDH hybrid films were piled close together to form a well-defined stratified structure resembling the brick-and-mortar structure of natural nacre. In the hybrid films, the content of inorganic LDH platelets was comparable to the value in nacre, up to 96.9 wt %. It could be clearly seen that the mechanical performance of the as-prepared PVA/LDH films was greatly improved by increasing the rigid building-block LDHs. The tensile strength of the 2 wt % PVA/LDH hybrid film reached a value of 169.36 MPa, thus exceeding the strength of natural nacre and reaching 4 times that of a pure PVA film. Meanwhile, its elastic modulus was comparable to that of lamellar bone. PMID:25138146

Shu, Yingqi; Yin, Penggang; Liang, Benliang; Wang, Hao; Guo, Lin

2014-09-10

212

Synthesis and characterization of a mixture of CoFe2O4 and MgFe2O4 from layered double hydroxides: Band gap energy and magnetic responses  

NASA Astrophysics Data System (ADS)

A mixture of nanocrystals of cobalt ferrite and magnesium ferrite was obtained from Layered Double Hydroxides (LDH) through a co-precitation method with a theoretical molar ratio M2+:Fe3+=3:1, where M2+represents Mg2+ and/or Co2+. The molar ratios between Co2+:Fe3+ were 0.0 (0Co), 0.2 (5Co), and 0.4 (10Co). In order to assess the effect on the properties of the LDH and their oxides, the molar percentages were 0, 5 and 10%. Two different synthesis methods were evaluated; (i) ageing at room temperature (rt), and (ii) hydrothermal ageing at 200 °C in autoclave (ht), both methods needed 15 h of ageing. Then, these LDH were calcined in air atmosphere at 550 °C for 10 h. The calcined materials were characterized by X-ray diffraction (XRD), thermogravymetric analysis (TGA), temperature-programmed reduction (TPR), infrared spectroscopy with Fourier transform (FTIR), Diffuse Reflectance UV-visible spectroscopy (UV-vis-DRS), Mössbauer spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES). The magnetic response was analyzed using a vibrating sample magnetometer (VSM). The band gap energy of the iron oxides was determined through the UV-vis-DRS analysis. Through these studies it was possible to identify the presence of a mixture of cobalt ferrite and magnesium ferrite. Samples did not show hematite and cobalt oxides, but the presence of MgO in the periclase phase was determined. This magnesium oxide promoted a good dispersion of the ferrites. Moreover, when a single ferrite phase of Co or Mg was formed, a diminution of the crystal size with consequent enlarged values of band gap energy was observed. Thus, materials synthesized by room temperature ageing promoted the superparamagnetic behaviour of samples, attributed to the content of the cobalt ferrite structure in nanocrystals. In regard to the estimated band gap energy, all samples exhibited low levels. These results indicate that these solids would be suitable for photocatalysts use in all visible light range, and that they could be easily removed from the reaction medium by a simple magnetic separation procedure.

Agú, Ulises A.; Oliva, Marcos I.; Marchetti, Sergio G.; Heredia, Angélica C.; Casuscelli, Sandra G.; Crivello, Mónica E.

2014-11-01

213

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

PubMed Central

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

2013-01-01

214

Toxicity and metabolism of layered double hydroxide intercalated with levodopa in a Parkinson's disease model.  

PubMed

Layered hydroxide nanoparticles are generally biocompatible, and less toxic than most inorganic nanoparticles, making them an acceptable alternative drug delivery system. Due to growing concern over animal welfare and the expense of in vivo experiments both the public and the government are interested to find alternatives to animal testing. The toxicity potential of zinc aluminum layered hydroxide (ZAL) nanocomposite containing anti-Parkinsonian agent may be determined using a PC 12 cell model. ZAL nanocomposite demonstrated a decreased cytotoxic effect when compared to levodopa on PC12 cells with more than 80% cell viability at 100 µg/mL compared to less than 20% cell viability in a direct levodopa exposure. Neither levodopa-loaded nanocomposite nor the un-intercalated nanocomposite disturbed the cytoskeletal structure of the neurogenic cells at their IC50 concentration. Levodopa metabolite (HVA) released from the nanocomposite demonstrated the slow sustained and controlled release character of layered hydroxide nanoparticles unlike the burst uptake and release system shown with pure levodopa treatment. PMID:24722565

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

2014-01-01

215

Development of a biocompatible nanodelivery system for tuberculosis drugs based on isoniazid-Mg/Al layered double hydroxide.  

PubMed

The primary challenge in finding a treatment for tuberculosis (TB) is patient non-compliance to treatment due to long treatment duration, high dosing frequency, and adverse effects of anti-TB drugs. This study reports on the development of a nanodelivery system that intercalates the anti-TB drug isoniazid into Mg/Al layered double hydroxides (LDHs). Isoniazid was found to be released in a sustained manner from the novel nanodelivery system in humans in simulated phosphate buffer solutions at pH 4.8 and pH 7.4. The nanodelivery formulation was highly biocompatible compared to free isoniazid against human normal lung and 3T3 mouse fibroblast cells. The formulation was active against Mycobacterium tuberculosis and gram-positive bacteria and gram-negative bacteria. Thus results show significant promise for the further study of these nanocomposites for the treatment of TB. PMID:25336952

Saifullah, Bullo; Arulselvan, Palanisamy; El Zowalaty, Mohamed Ezzat; Fakurazi, Sharida; Webster, Thomas J; Geilich, Benjamin M; Hussein, Mohd Zobir

2014-01-01

216

Aluminum Hydroxide and Magnesium Hydroxide  

MedlinePLUS

Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They ... They combine with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription. ...

217

New approach to the synthesis of layered double hydroxides and associated ultrathin nanosheets in de-ionized water by laser ablation  

NASA Astrophysics Data System (ADS)

This paper introduces a new method to synthesize layered double hydroxides and its ultrathin nanosheets in de-ionized water. By employing pulsed laser ablation, ultrathin layered double hydroxide nanosheets of Zn-Al, Co-Fe, Co-Al, and Mg-Fe were formed with a molecular thickness, corresponding to the thickness of the exfoliated two-dimensional nanosheets. The nanosheets formed directly were well-defined with a hexagonal shape, and were stable without any chemical for preventing agglomeration or formation of three-dimensional lamellar crystals. The nanosheets are assembled layer-by-layer up to the finite thickness on solid surface by the incorporation of carbonate anions from the atmospheric CO2. Observation of the seedlike layered double hydroxide nanosheets as well as the lamellar structures shows a similar structural relationship. Consequently, the laser ablation technique is deemed to have played a critical role in the formation of nanosheets. This suggests that the contamination of the as-synthesized layered double hydroxide colloidal solutions by carbonate is considerably insignificant.

Hur, Tae-Bong; Phuoc, Tran X.; Chyu, Minking K.

2010-12-01

218

Zn- and Co-based layered double hydroxides: prediction of the a parameter from the fraction of trivalent cations and vice versa  

PubMed Central

A recently proposed method to calculate the a parameter of the unit cell of layered double hydroxides from the fraction of trivalent cations is extended to Zn- and Co-based phases. It is shown to be useful as a sanity test for extant and future structure determinations and computer-simulation studies. PMID:23873067

Richardson, Ian G.

2013-01-01

219

Electrostatic trapping of double-stranded DNA by using cadmium hydroxide nanostrands.  

PubMed

Cadmium ions (Cd(2+)) spontaneously grew into cadmium hydroxide nanostrands at the proper pH range in water, and the nanostrands efficiently captured negatively charged DNA. The DNA chain adsorbed parallel to the nanostrand due to the numerous positive charges on the extremely long and thin structure of 1.9 nm, giving weakly gelled white precipitates. By the filtration, more than 95% of DNA was separated from the dilute solution with a concentration less than 40 ng/mL. The nanostrands quickly disappeared after adding aqueous EDTA, and DNA was released quantitatively. These characteristics gave a novel separation technique for short DNA fragments without the use of organic solvents. PMID:15792420

Ichinose, Izumi; Huang, Jianguo; Luo, Yan-Hong

2005-01-01

220

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

221

Design of magnetic and fluorescent Mg-Al layered double hydroxides by introducing Fe{sub 3}O{sub 4} nanoparticles and Eu{sup 3+} ions for intercalation of glycine  

SciTech Connect

We describe a novel route for the preparation of magnetic and fluorescent magnesium-aluminum layered double hydroxides by introducing Fe{sub 3}O{sub 4} nanoparticles and Eu{sup 3+} ions. From the powder X-ray diffraction results, it was found that the Fe{sub 3}O{sub 4} nanoparticles were highly dispersed in the inner void of octahedral lattice, and the Eu{sup 3+} ions substituted for the Al{sup 3+} ions and entered into hydrotalcite lattice through isomorphous replacement. Moderate introduction of Fe{sub 3}O{sub 4} nanoparticles and Eu{sup 3+} ions did not change the lamellar structure of magnesium-aluminum layered double hydroxides. Glycine can also be intercalated into this magnetic and fluorescent layered double hydroxides by ion-exchange method. After intercalation of glycine, the basal spacing of magnetic and fluorescent layered double hydroxides increased from 7.6 to 8.8 A, indicating that glycine was successfully intercalated into the interlayer space of layered double hydroxides. Magnetic measurements reveal that these novel layered double hydroxides possess paramagnetic property at room temperature, and the emission and excitation spectra indicate the layered double hydroxides exhibit fluorescent property.

Wang, Jun; Zhou, Jideng; Li, Zhanshuang; Liu, Qi; Yang, Piaoping; Jing, Xiaoyan [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China) [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, 150001 (China); Zhang, Milin, E-mail: zhqw1888@sohu.com [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China) [College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, 150001 (China)

2010-05-15

222

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

223

Part I. Manganese oxide containing layered double hydroxides materials: Synthesis and characterization. Part II. Manganese oxide octahedral molecular sieves (OMS-2): Synthesis, particle size control, characterization, and catalytic applications  

NASA Astrophysics Data System (ADS)

The work presented here comprises the development of new routes for the preparation of manganese oxide-based materials with controlled properties. The first part of the research consists of the preparation of a new series of layered double hydroxide (LDH) materials containing intercalated manganese oxide species. Characterization of the resulting materials will be sub-divided in two major parts: (1) Composition, structural, and textural properties and (2) Determination of the oxidation state of the manganese species formed. The process of incorporating manganese oxides into the LDH materials takes place by a simple two-step method which involves the ion-exchange of nitrate anions with high valence manganese precursor anions followed by the in-situ reaction between the manganese anions and organic reducing agents. The method developed allows the preparation of a wide range of Mn-intercalated LDHs by simply changing the reducing agent used. In the second part of the research a new "soft" chemistry method to prepare manganese oxide octahedral molecular sieves (OMS-2) materials with controlled crystalline particle sizes will be presented. The synthesis is based on the use of H2O2 to reduce MnO4- under acidic conditions. The particle size is controlled by the concentration of H2O2 in the reaction media. The structural and textural properties of the synthesized OMS-2 are investigated. The catalytic activity and structural properties of these OMS-2 nanomaterials for oxidation catalysis will also be discussed. The work will continue with the investigation on the framework substitution of higher valency transition metal ions (TM = Nb, V) into the OMS-2 materials. The incorporation of TM into the structure of OMS-2 occurs by reacting the manganese and TM source with an oxidant under hydrothermal conditions. The structural properties, oxidation state of manganese, TM loading, and location of the TM in the OMS-2 structure will be investigated. The versatility of OMS-2 to accommodate higher valence TM metals is demonstrated. The last part of the research comprises the study of the electrical resistivity of OMS-2 materials. The effect of the different OMS-2 synthesis method and the framework doping is investigated. A correlation of the resistivities of all the OMS materials prepared in our laboratory and their structures is presented.

Villegas, Josanlet C.

224

Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides  

PubMed Central

Background The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported. Methodology/Principal Findings The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail. Conclusions/Significance S-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites. PMID:22693627

Wang, Lili; Li, Bin; Zhao, Xiaohong; Chen, Chunxia; Cao, Jingjing

2012-01-01

225

Preparation and antibacterial property of waterborne polyurethane/Zn-Al layered double hydroxides/ZnO nanocomposites.  

PubMed

In this work, a novel environmental-friendly waterborne polyurethane/ZnAl-layered double hydroxides/ZnO nanoparticles composite (WPU/ZnAl-LDHs/ZnO) was synthesized via in-situ polymerization. ZnAl-LDHs and ZnAl-LDHs/ZnO were synthesized by refluxing in an oil bath. In order to disperse ZnAl-LDHs/ZnO homogeneously into WPU matrix, ZnAl-LDHs/ZnO was firstly functionalized by isophorone diisocyanate. The incorporated content of ZnAl-LDHs/ZnO in the composite has profound effect on such physical properties as mechanical strength, thermal stability and water swelling. It is demonstrated that appropriate amount of ZnAl-LDHs/ZnO with good dispersion in the WPU matrix significantly improves the physical performance of the composites. Finally, the antibacterial activity of the composite was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus. The results indicate that WPU incorporated with ZnAl-LDHs/ZnO shows strong antibacterial activity upon contact. PMID:23646747

Zhang, Wei-De; Zheng, Yun-Min; Xu, Yang-Sen; Yu, Yu-Xiang; Shi, Qing-Shan; Liu, Lihong; Peng, Hong; Ouyang, Yousheng

2013-01-01

226

Functionalization of layered double hydroxides by intumescent flame retardant: Preparation, characterization, and application in ethylene vinyl acetate copolymer  

NASA Astrophysics Data System (ADS)

A phosphorussbnd nitrogen containing compound, N-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)-hexylacetamide-2-propyl acid (PAHPA), is synthesized and characterized. A novel flame retardant, namely layered double hydroxides (LDHs) modified with PAHPA (PAHPA-LDHs), is prepared by ion-exchange of LDHs with PAHPA. The results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray analysis with a high-angle annular dark-field scanning transmission electron microscope show that PAHPA intercalated LDHs. The X-ray diffraction and transmission electron microscopy (TEM) results show that PAHPA-LDHs achieve well dispersion in ethylene vinyl acetate copolymer (EVA) matrix and the EVA/PAHPA-LDHs nanocomposites (i.e. EVA filled with 5 wt% PAHPA-LDHs) are formed by polymer melt intercalation. Thermal stability and flammability properties are investigated by thermogravimetric analysis and cone calorimeter tests. The results show that the addition of PAHPA-LDHs improves thermal stability and reduces obviously the flammability of EVA resin. Compared with pure EVA resin, the peak heat release rate of the EVA/PAHPA-LDHs nanocomposites is reduced by about 43%. The results of scanning electron microscopy and TEM indicate that a compact and dense intumescent char is formed for the EVA/PAHPA-LDHs nanocomposites after combustion.

Huang, Guobo; Fei, Zhengdong; Chen, Xiaoying; Qiu, Fangli; Wang, Xu; Gao, Jianrong

2012-10-01

227

The decomposition of the layered double hydroxides of Co and Al: Phase segregation of a new single phase spinel oxide.  

PubMed

Monophasic Co-Al-CO3-like layered double hydroxides has been prepared by the coprecipitation method. It has been characterised by Rietveld refinement of the X-ray powder diffraction pattern, DTA-TGA, infrared and Raman spectroscopies. Its structure is trigonal, R3¯m with cell parameters a=0.3061(4) nm and c=2.252 (3) nm. The decomposition of this hydrotalcite-like structure on heating up to 800°C yields to a single phase spinel oxide. Besides, infrared and Raman spectroscopies showed the presence of spinel-like domains. The results of Rietveld refinement have revealed that this compound has the Fd3¯m space group (a=0.8088(4) nm), with crystallographic formula [Co(II)0.75Al0.25](8a)[Co(II)0.252Co(III)0.77Al0.98](16d)O4, which is of the general formula Co1.77Al1.23O4. This structure is also validated by the charge distribution (CD) analysis. PMID:25659816

Babay, Salem; Bulou, Alain; Mercier, Anne Marie; Toumi, Mouhamed

2015-04-15

228

Preparation of single phase Zn2TiO4 spinel from a new ZnTi layered double hydroxide precursor.  

PubMed

A single-source ZnTi-layered double hydroxide precursor was used to prepare single phase Zn2TiO4. This approach involves two steps: the calcination of a ZnTi-layered double hydroxide precursor and selective leaching zinc oxide from the resultant calcined products. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) thermogravimetric and differential thermal analysis (TG-DTA), transmission electron microscope (TEM), surface area measurement and UVvis diffuse reflection spectroscopy. The results indicated that a single phase Zn2TiO4 could be successfully obtained from a ZnTi-layered double hydroxide precursor at a relatively low temperature in short calcination time. The TEM and SEM show that the diameter of Zn2TiO4 particles prepared at 900 degrees C is in the range of 20-100 nm and smaller than that prepared by the solid-state method. UV-Vis diffuse reflection spectroscopy demonstrates that the material has an energy bandgap around 3.7 eV. PMID:24738443

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

2014-06-01

229

[Comparison of the adsorption of arsenite and arsenate anions from aqueous solution by calcined Mg-Al layered double hydroxides].  

PubMed

The comparison of calcined Mg-Al layered double hydroxides (Mg-Al CLDH) for adsorption of arsenite and arsenate anions from aqueous solution was investigated by batch method. The results show that Mg-Al CLDH is an effective adsorbent for the removal of arsenite and arsenate anions. The adsorption processes are followed 'memory effect'. When the initial concentration of arsenic is lower than 10 mg x L(-1) for arsenite and 40 mg x L(-1) for arsenate, the equilibrium concentration of arsenic is lower than 10 microg x L(-1). In the range of 4-500 mg x L(-1) for initial arsenic concentration, the maximum adsorption capacity of arsenite and arsenate on Mg-Al CLDH from 298 to 323 K is 150.46-224.03 mg x g(-1) and 149.62-224.76 mg x g(-1), respectively, which are much larger than other adsorbents. But the adsorption capacity is not reached saturation, it is continued to increase significantly. L and H model can be used to describe the adsorption isotherm of arsenite and arsenate, respectively. The adsorption data are corresponded to the Freundlich model for arsenite and Langmuir model for arsenate at lower equilibrium concentration, but corresponded to Freundlich model for arsenite and arsenate at higher equilibrium concentration. Under the same temperature and initial concentration, the adsorption rate and removal rate of arsenate are higher than those of arsenite. And they are increased with temperate but decreased with increase in initial concentration. Adsorption processes follow the pseudo-second-order kinetic model for both arsenite and arsenate. The removal rate is not influenced by the initial pH (3.0-10.0). The adsorption capacity is influenced insignificantly by ionic strength. Arsenate anions are adsorbed firstly from arsenite and arsenate solution on Mg-Al CLDH. PMID:19432322

Xing, Kun; Wang, Hai-Zeng; Li, Xiao-Yu

2009-03-15

230

Magnesium Hydroxide  

MedlinePLUS

Magnesium hydroxide is used on a short-term basis to treat constipation.This medication is sometimes prescribed ... Magnesium hydroxide come as a tablet and liquid to take by mouth. It usually is taken as ...

231

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 ...

232

Controlled release and angiotensin-converting enzyme inhibition properties of an antihypertensive drug based on a perindopril erbumine-layered double hydroxide nanocomposite  

PubMed Central

Background The intercalation of perindopril erbumine into Zn/Al-NO3-layered double hydroxide resulted in the formation of a host-guest type of material. By virtue of the ion-exchange properties of layered double hydroxide, perindopril erbumine was released in a sustained manner. Therefore, this intercalated material can be used as a controlled-release formulation. Results Perindopril was intercalated into the interlayers and formed a well ordered, layered organic-inorganic nanocomposite. The basal spacing of the products was expanded to 21.7 Å and 19.9 Å by the ion-exchange and coprecipitation methods, respectively, in a bilayer and a monolayer arrangement, respectively. The release of perindopril from the nanocomposite synthesized by the coprecipitation method was slower than that of its counterpart synthesized by the ion-exchange method. The rate of release was governed by pseudo-second order kinetics. An in vitro antihypertensive assay showed that the intercalation process results in effectiveness similar to that of the antihypertensive properties of perindopril. Conclusion Intercalated perindopril showed better thermal stability than its free counterpart. The resulting material showed sustained-release properties and can therefore be used as a controlled-release formulation. PMID:22619549

Al Ali, Samer Hasan Hussein; Al-Qubaisi, Mothanna; Hussein, Mohd Zobir; Ismail, Maznah; Zainal, Zulkarnain; Hakim, Muhammad Nazrul

2012-01-01

233

Dissolvable layered double hydroxide coated magnetic nanoparticles for extraction followed by high performance liquid chromatography for the determination of phenolic acids in fruit juices.  

PubMed

A magnesium-aluminum layered double hydroxide coated on magnetic nanoparticles was synthesized and used as a sorbent to extract some phenolic acids including p-hydroxy benzoic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid from fruit juices. After extraction, the elution step was performed through dissolving double hydroxide layers containing the analytes by changing the solution pH. The extracted phenolic acids were separated and quantified using high performance liquid chromatography-photodiode array detection. Experimental parameters such as sorbent amount, solution pH, desorption solvent volume and extraction time were studied and optimized. The linearity range of the method was between 2 and 500?gL(-1) with the determination coefficient (r(2)) higher than 0.991. Relative standard deviations for intra- and inter-day precision for the analytes at 100?gL(-1) were in the range of 4.3-9.2% and 4.9-8.6%, respectively. Batch-to-batch reproducibility at 100?gL(-1) concentration level was in the range of 7.8-11% (n=3). The limits of detection were between 0.44 and 1.3?gL(-1). Relative recoveries higher than 81% with RSDs in the range of 4.2-9.7% were obtained in the analysis of fruit juice samples. PMID:25260344

Saraji, Mohammad; Ghani, Milad

2014-10-31

234

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. PMID:22754339

Hussein-Al-Ali, Samer Hasan; Al-Qubaisi, Mothanna; Hussein, Mohd Zobir; Ismail, Maznah; Zainal, Zulkarnain; Hakim, Muhammad Nazrul

2012-01-01

235

Facile assembly of Ni-Co hydroxide nanoflakes on carbon nanotube network with highly electrochemical capacitive performance.  

PubMed

Herein, we demonstrate the high-density assembly of Ni-Co hydroxide nanoflakes on conductive carbon nanotube (CNT) network through a simple and rapid chemical precipitation method, presenting a low-cost and high-performance scaffold for pseudosupercapacitor. It is found that the Ni-Co layered double hydroxide (LDH) nanoflakes prefer to proliferate around large-diameter CNTs (diameter>50 nm), with conductive CNT network well-maintained. Such hierarchical nanostructures show greatly improved specific surface areas compared with bare CNT network and are freestanding without other organic binder, which can be directly employed as a binder-free compact electrode assembly. By optimizing the chemical composition of as-precipitated LDH nanoflakes, the resultant Co0.4Ni0.6(OH)2 LDH/CNT composite nanostructures exhibit the largest specific electrochemical capacitance and the best rate performance, with their capacitance up to 1843 F/g under a low current density of 0.5 A/g and maintained at 1231 F/g when the current density is increased 20 times to 10 A/g. Importantly, such hierarchical nanostructures tend to prevent the electrode from severe structural damage and capacity loss during hundreds of charge/discharge under a high rate (2 A/g), ensuring the electrode with high-energy density (51 W h/kg) at power density of 3.3 kW/kg. PMID:25314093

Chen, Hongyuan; Cai, Feng; Kang, Yiran; Zeng, Sha; Chen, Minghai; Li, Qingwen

2014-11-26

236

Toxicity and Metabolism of Layered Double Hydroxide Intercalated with Levodopa in a Parkinson’s Disease Model  

PubMed Central

Layered hydroxide nanoparticles are generally biocompatible, and less toxic than most inorganic nanoparticles, making them an acceptable alternative drug delivery system. Due to growing concern over animal welfare and the expense of in vivo experiments both the public and the government are interested to find alternatives to animal testing. The toxicity potential of zinc aluminum layered hydroxide (ZAL) nanocomposite containing anti-Parkinsonian agent may be determined using a PC 12 cell model. ZAL nanocomposite demonstrated a decreased cytotoxic effect when compared to levodopa on PC12 cells with more than 80% cell viability at 100 ?g/mL compared to less than 20% cell viability in a direct levodopa exposure. Neither levodopa-loaded nanocomposite nor the un-intercalated nanocomposite disturbed the cytoskeletal structure of the neurogenic cells at their IC50 concentration. Levodopa metabolite (HVA) released from the nanocomposite demonstrated the slow sustained and controlled release character of layered hydroxide nanoparticles unlike the burst uptake and release system shown with pure levodopa treatment. PMID:24722565

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

2014-01-01

237

Quick and efficient co-treatment of Zn(2+)/Ni(2+) and CN(-) via the formation of Ni(CN)4(2-) intercalated larger ZnAl-LDH crystals.  

PubMed

The wide use of metal electroplating involving CN(-) necessitates the cost-effective treatment of both CN and metals (Zn, Cu, Ni etc.). In this research, we developed a novel strategy - Ni(2+)-assisted layered double hydroxide (LDH) precipitation - to simultaneously remove aqueous CN and Zn/Ni metals. The strategy is to convert CN(-)/Zn(CN)4(2-) to Ni(CN)4(2-) first, and then to quickly precipitate Ni(CN)4(2-)/CN(-) into LDH crystals. The conversion has been clearly evidenced by the change of CN characteristic FTIR bands of Zn-CN solution before and after adding Ni(NO3)2. The intercalation and efficient removal of CN have also been confirmed through the formation of LDH crystals XRD and SEM. In particular, a set of optimized experimental factors has been obtained by investigating their effects on CN removal efficiency in the simulated tests. Remarkably, over 95% CN were removed with high removal efficiencies of metals. Our results thus suggest that the current strategy is a quick, efficient and promising way to simultaneously treat both Ni and metals/CN rich electroplating wastewaters. PMID:25058935

Zhou, Ji Zhi; Liang, Ying; Zhang, Jia; Li, Li; Xu, Yunfeng; Ruan, Xiuxiu; Qian, Guangren; Xu, Zhi Ping

2014-08-30

238

DNA-enhanced peroxidase-like activity of layered double hydroxide nanosheets and applications in H2O2 and glucose sensing  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03031h

Chen, Lijian; Sun, Kaifang; Li, Peipei; Fan, Xianzhong; Sun, Jianchao; Ai, Shiyun

2013-10-01

239

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

240

This article was downloaded by: [Marquette University] On: 05 April 2013, At: 14:08  

E-print Network

a magnesium aluminum hydroxide LDH modified with interlayer undecenoate anions mixed with poly nanocomposites containing layered double hydroxide (LDH) additives offer great potential for improving polymer

Reid, Scott A.

241

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

242

Efficient removal of dyes by a novel magnetic Fe3O4/ZnCr-layered double hydroxide adsorbent from heavy metal wastewater.  

PubMed

A novel magnetic Fe(3)O(4)/ZnCr-layered double hydroxide adsorbent was produced from electroplating wastewater and pickling waste liquor via a two-step microwave hydrothermal method. Adsorption of methyl orange (MO) from water was studied using this material. The effects of three variables have been investigated by a single-factor method. The response surface methodology (RSM) based on Box-Behnken design was successfully applied to the optimization of the preparation conditions. The maximum adsorption capacity of MO was found to be 240.16 mg/g, indicating that this material may be an effective adsorbent. It was shown that 99% of heavy metal ions (Fe(2+), Fe(3+), Cr(3+), and Zn(2+)) can be effectively removed into precipitates and released far less in the adsorption process. In addition, this material with adsorbed dye can be easily separated by a magnetic field and recycled after catalytic regeneration with advanced oxidation technology. Meanwhile, kinetic models, FTIR spectra and X-ray diffraction pattern were applied to the experimental data to examine uptake mechanism. The boundary layer and intra-particle diffusion played important roles in the adsorption mechanisms. PMID:23122732

Chen, Dan; Li, Yang; Zhang, Jia; Li, Wenhui; Zhou, Jizhi; Shao, Li; Qian, Guangren

2012-12-01

243

Solvothermal synthesis of NiAl double hydroxide microspheres on a nickel foam-graphene as an electrode material for pseudo-capacitors  

SciTech Connect

In this paper, we demonstrate excellent pseudo-capacitance behavior of nickel-aluminum double hydroxide microspheres (NiAl DHM) synthesized by a facile solvothermal technique using tertbutanol as a structure-directing agent on nickel foam-graphene (NF-G) current collector as compared to use of nickel foam current collector alone. The structure and surface morphology were studied by X-ray diffraction analysis, Raman spectroscopy and scanning and transmission electron microscopies respectively. NF-G current collector was fabricated by chemical vapor deposition followed by an ex situ coating method of NiAl DHM active material which forms a composite electrode. The pseudocapacitive performance of the composite electrode was investigated by cyclic voltammetry, constant charge–discharge and electrochemical impedance spectroscopy measurements. The composite electrode with the NF-G current collector exhibits an enhanced electrochemical performance due to the presence of the conductive graphene layer on the nickel foam and gives a specific capacitance of 1252 F g{sup ?1} at a current density of 1 A g{sup ?1} and a capacitive retention of about 97% after 1000 charge–discharge cycles. This shows that these composites are promising electrode materials for energy storage devices.

Momodu, Damilola; Bello, Abdulhakeem; Dangbegnon, Julien; Barzeger, Farshad; Taghizadeh, Fatimeh; Fabiane, Mopeli; Manyala, Ncholu, E-mail: ncholu.manyala@up.ac.za [Department of Physics, Institute of Applied Materials, SARChI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028, South Africa. (South Africa); Johnson, A. T. Charlie [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2014-09-15

244

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

SciTech Connect

Nickel-aluminum layered double hydroxides/carbon (Ni-Al LDHs/C) composites have been successfully fabricated via a facile in situ water-ethanol system. LDHs nanosheets could highly disperse on the surface of colloidal carbonaceous spheres through the interfacial electrostatic force. Ni-Al LDHs/C composite electrode prepared at 50% ethanol system exhibits the highest capacitance of 1064 F g{sup -1} at a current of 2.5 A g{sup -1}, leading to a significant improvement in relation to each individual counterpart (3.5 and 463 F g{sup -1} for carbon and Ni-Al LDHs at 2.5 A g{sup -1}, respectively). And a possible mechanism was proposed for the formation of the composites. Highlights: Black-Right-Pointing-Pointer Ni-Al LDHs/C composites have been self-assembled by an in situ solvothermal method. Black-Right-Pointing-Pointer A possible growth mechanism to explain the composite is proposed. Black-Right-Pointing-Pointer Ni-Al LDHs/C composites display better electrochemical performance.

Wei, Jinbo [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Wang, Jun, E-mail: junwangzhqw1888@sohu.com [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Song, Yanchao; Li, Zhanshuang; Gao, Zan; Mann, Tom; Zhang, Milin [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)] [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

2012-12-15

245

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

2013-04-15

246

Determination of iodate in food, environmental, and biological samples after solid-phase extraction with Ni-Al-Zr ternary layered double hydroxide as a nanosorbent.  

PubMed

Nanostructured nickel-aluminum-zirconium ternary layered double hydroxide was successfully applied as a solid-phase extraction sorbent for the separation and pre-concentration of trace levels of iodate in food, environmental and biological samples. An indirect method was used for monitoring of the extracted iodate ions. The method is based on the reaction of the iodate with iodide in acidic solution to produce iodine, which can be spectrophotometrically monitored at 352?nm. The absorbance is directly proportional to the concentration of iodate in the sample. The effect of several parameters such as pH, sample flow rate, amount of nanosorbent, elution conditions, sample volume, and coexisting ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12??g?mL(-1) and 20, respectively. The calibration graph using the preconcentration system was linear in the range of 0.2-2.8??g?mL(-1) with a correlation coefficient of 0.998. In order to validate the presented method, a certified reference material, NIST SRM 1549, was also analyzed. PMID:22619590

Abdolmohammad-Zadeh, Hossein; Tavarid, Keyvan; Talleb, Zeynab

2012-01-01

247

Antituberculosis nanodelivery system with controlled-release properties based on para-amino salicylate-zinc aluminum-layered double-hydroxide nanocomposites.  

PubMed

We report the intercalation and characterization of para-amino salicylic acid (PASA) into zinc/aluminum-layered double hydroxides (ZLDHs) by two methods, direct and indirect, to form nanocomposites: PASA nanocomposite prepared by a direct method (PASA-D) and PASA nanocomposite prepared by an indirect method (PASA-I). Powder X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis revealed that the PASA drugs were accommodated within the ZLDH interlayers. The anions of the drug were accommodated as an alternate monolayer (along the long-axis orientation) between ZLDH interlayers. Drug loading was estimated to be 22.8% and 16.6% for PASA-D and PASA-I, respectively. The in vitro release properties of the drug were investigated in physiological simulated phosphate-buffered saline solution of pH 7.4 and 4.8. The release followed the pseudo-second-order model for both nanocomposites. Cell viability (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide [MTT] assays) was assessed against normal human lung fibroblast MRC-5 and 3T3 mouse fibroblast cells at 24, 48, and 72 hours. The results showed that the nanocomposite formulations did not possess any cytotoxicity, at least up to 72 hours. PMID:24255593

Saifullah, Bullo; Hussein, Mohd Zobir; Hussein-Al-Ali, Samer Hasan; Arulselvan, Palanisamy; Fakurazi, Sharida

2013-01-01

248

Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: kinetics and equilibrium isotherms study.  

PubMed

In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir-Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration. PMID:24486617

Ma, Wei; Lv, Tengfei; Song, Xiaoyan; Cheng, Zihong; Duan, Shibo; Xin, Gang; Liu, Fujun; Pan, Decong

2014-03-15

249

Application of dissolvable layered double hydroxides as sorbent in dispersive solid-phase extraction and extraction by co-precipitation for the determination of aromatic acid anions.  

PubMed

Three types of magnesium-aluminum layered double hydroxides were synthesized and employed as solid-phase extraction (SPE) sorbents to extract several aromatic acids (protocatechuic acid, mandelic acid, phthalic acid, benzoic acid, and salicylic acid) from aqueous samples. An interesting feature of these sorbents is that they dissolve when the pH of the solution is lower than 4. Thus, the analyte elution step, as needed in conventional sorbent-based extraction, was obviated by dissolving the sorbent in acid after extraction and separation from the sample solution. The extract was then directly injected into a high-performance liquid chromatography-ultraviolet detection system for analysis. In the key adsorption process, both dispersive SPE and co-precipitation extraction with the sorbents were conducted and experimental parameters such as pH, temperature, and extraction time were optimized. The results showed that both extraction methods provided low limits of detection (0.03-1.47 ?g/L) and good linearity (r(2) > 0.9903). The optimized extraction conditions were applied to human urine and sports drink samples. This new and interesting extraction approach was demonstrated to be a fast and efficient procedure for the extraction of organic anions from aqueous samples. PMID:23855757

Tang, Sheng; Lee, Hian Kee

2013-08-01

250

Theoretical investigations on the layer-anion interaction in Mg-Al layered double hydroxides: Influence of the anion nature and layer composition.  

PubMed

The influence of the anion nature and layer composition on the anion-layer interaction in Mg-Al layered double hydroxides (LDHs) is investigated using density functional theory. Changes in the strength of the anion-layer interaction are assessed calculating the potential energy surface (PES) associated to the interlayer anion (OH(-)/Cl(-)) in Mg-Al-OH and Mg-Al-Cl LDHs. The layer composition is varied changing the divalent to trivalent cation proportion (R). Mg-Al-OH is thus investigated with R = 2, 3, 3.5 and Mg-Al-Cl with R = 3. It is found that the PES for OH(-) in Mg-Al-OH/R = 3 presents wider energy basins and lower energy barriers than any other of the investigated compositions. It is shown that the latter is connected to the number of hydrogen bonds formed by the anions. These results have interesting implications for understanding the enhancement of the physicochemical properties of LDHs upon changing composition. PMID:25747096

Cuautli, Cristina; Ireta, Joel

2015-03-01

251

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

252

Determination of Iodate in Food, Environmental, and Biological Samples after Solid-Phase Extraction with Ni-Al-Zr Ternary Layered Double Hydroxide as a Nanosorbent  

PubMed Central

Nanostructured nickel-aluminum-zirconium ternary layered double hydroxide was successfully applied as a solid-phase extraction sorbent for the separation and pre-concentration of trace levels of iodate in food, environmental and biological samples. An indirect method was used for monitoring of the extracted iodate ions. The method is based on the reaction of the iodate with iodide in acidic solution to produce iodine, which can be spectrophotometrically monitored at 352?nm. The absorbance is directly proportional to the concentration of iodate in the sample. The effect of several parameters such as pH, sample flow rate, amount of nanosorbent, elution conditions, sample volume, and coexisting ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12??g?mL?1 and 20, respectively. The calibration graph using the preconcentration system was linear in the range of 0.2–2.8??g?mL?1 with a correlation coefficient of 0.998. In order to validate the presented method, a certified reference material, NIST SRM 1549, was also analyzed. PMID:22619590

Abdolmohammad-Zadeh, Hossein; Tavarid, Keyvan; Talleb, Zeynab

2012-01-01

253

Theoretical investigations on the layer-anion interaction in Mg-Al layered double hydroxides: Influence of the anion nature and layer composition  

NASA Astrophysics Data System (ADS)

The influence of the anion nature and layer composition on the anion-layer interaction in Mg-Al layered double hydroxides (LDHs) is investigated using density functional theory. Changes in the strength of the anion-layer interaction are assessed calculating the potential energy surface (PES) associated to the interlayer anion (OH-/Cl-) in Mg-Al-OH and Mg-Al-Cl LDHs. The layer composition is varied changing the divalent to trivalent cation proportion (R). Mg-Al-OH is thus investigated with R = 2, 3, 3.5 and Mg-Al-Cl with R = 3. It is found that the PES for OH- in Mg-Al-OH/R = 3 presents wider energy basins and lower energy barriers than any other of the investigated compositions. It is shown that the latter is connected to the number of hydrogen bonds formed by the anions. These results have interesting implications for understanding the enhancement of the physicochemical properties of LDHs upon changing composition.

Cuautli, Cristina; Ireta, Joel

2015-03-01

254

Solvothermal synthesis of NiAl double hydroxide microspheres on a nickel foam-graphene as an electrode material for pseudo-capacitors  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate excellent pseudo-capacitance behavior of nickel-aluminum double hydroxide microspheres (NiAl DHM) synthesized by a facile solvothermal technique using tertbutanol as a structure-directing agent on nickel foam-graphene (NF-G) current collector as compared to use of nickel foam current collector alone. The structure and surface morphology were studied by X-ray diffraction analysis, Raman spectroscopy and scanning and transmission electron microscopies respectively. NF-G current collector was fabricated by chemical vapor deposition followed by an ex situ coating method of NiAl DHM active material which forms a composite electrode. The pseudocapacitive performance of the composite electrode was investigated by cyclic voltammetry, constant charge-discharge and electrochemical impedance spectroscopy measurements. The composite electrode with the NF-G current collector exhibits an enhanced electrochemical performance due to the presence of the conductive graphene layer on the nickel foam and gives a specific capacitance of 1252 F g-1 at a current density of 1 A g-1 and a capacitive retention of about 97% after 1000 charge-discharge cycles. This shows that these composites are promising electrode materials for energy storage devices.

Momodu, Damilola; Bello, Abdulhakeem; Dangbegnon, Julien; Barzeger, Farshad; Taghizadeh, Fatimeh; Fabiane, Mopeli; Johnson, A. T. Charlie; Manyala, Ncholu

2014-09-01

255

Karchevskyite, [Mg 18 Al 9 (OH) 54 ][Sr 2 (CO 3 ,PO 4 ) 9 (H 2 O,H 3 O) 11 ], a new mineral species of the layered double hydroxide family  

Microsoft Academic Search

Karchevskyite, a new mineral related to the family of layered double hydroxides (LDHs), has been found in the Iron open pit\\u000a at the Kovdor carbonatite massif, Kola Peninsula, Russia. The mineral occurs as spherulites of up to 1.5 mm in diameter composed\\u000a of thin, curved lamellae. Dolomite, magnetite, quintinite-3T, strontium carbonate, and fluorapatite are associated minerals. Karchevskyite is white in

S. N. Britvin; N. V. Chukanov; G. K. Bekenova; M. A. Yagovkina; A. V. Antonov; A. N. Bogdanova; N. I. Krasnova

2008-01-01

256

The layered double hydroxide route to Bi-Zn co-doped TiO2 with high photocatalytic activity under visible light.  

PubMed

In this work, a co-doped Bi-Zn-TiO2 photocatalist is synthesized by an original synthesis route of layered double hydroxide followed by heat treatment at 670°C. After characterization the photocatalyst efficiency is estimated by the photo-discoloration of an anionic dye (indigo carmine) under visible light and compare to TiO2-P25 as reference material. In this new photocatalyst, anatase and ZnO wurtzite are the only identified crystalline phase, rutile and Bi2O3 being undetected. Moreover, the binding energy of Bi determined (XPS analysis) is different from the one of Bi in Bi2O3. Compared to TiO2-P25, the absorption is red shifted (UV-vis DRS) and the Bi-Zn-TiO2 photocatalyst showed sorption capacity toward indigo carmine higher than that TiO2-P25. The kinetics of the photo-discoloration is faster with Bi-Zn-TiO2 than with TiO2-P25. Indeed, a complete discoloration is obtained after 70min and 120min in the presence of Bi-Zn-TiO2 and TiO2-P25 respectively. The identification of the responsible species on photo-discoloration was carried out in the presence of different scavengers. The study showed that the first responsible is h(+) specie with a moderate contribution of superoxide anion radical and a minor contribution of the hydroxyl radical. The material showed high stability after five uses with the same rate of photo-discoloration. PMID:25699677

Benalioua, Bahia; Mansour, Meriem; Bentouami, Abdelhadi; Boury, Bruno; Elandaloussi, El Hadj

2015-05-15

257

Automated dispersive solid-phase extraction using dissolvable Fe3O4-layered double hydroxide core-shell microspheres as sorbent.  

PubMed

Automation of dispersive solid-phase extraction (d-SPE) presents significant challenges. Separation of the sorbent from the spent sample cannot be conducted without manual operations, including centrifugation, a widely used means of isolating a solid material from solution. In this work, we report an approach to d-SPE using dissolvable magnetic Fe3O4-layered double hydroxide core-shell microspheres as sorbent to enable automation of the integrative extraction and analytical processes. Through magnetic force, the sorbent, after extraction, was isolated from the sample and then dissolved by acid to release the analytes. Thus the customary analyte elution step in conventional SPE was unnecessary. The automated d-SPE step was coupled to high-performance liquid chromatography (HPLC) with photodiode array detection for determination of several pharmaceuticals and personal care products (PPCPs) [acetylsalicylic acid (ASA), 2,5-dihydroxybenzoic acid (DBA), 2-phenylphenol (PP), and fenoprofen (FP)] in aqueous samples. For the automated d-SPE process, experimental parameters such as agitation speed, temperature, time, and pH were optimized. The results showed that this method provided low limits of detection (between 0.021 and 0.042 ?g/L), good linearity (r(2) ? 0.9956), and good repeatability of extractions (relative standard deviations ?4.1%, n = 6). The optimized procedure was then applied to determination of PPCPs in a sewage sample and ASA and FP in drug preparations. This fully automated extraction-HPLC approach was demonstrated to be an efficient procedure for extraction and analysis of ASA, DBA, PP, and FP in these samples. PMID:25320871

Tang, Sheng; Chia, Guo Hui; Chang, Yuepeng; Lee, Hian Kee

2014-11-18

258

Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH  

PubMed Central

Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs. PMID:25380526

Hussein, Mohd Zobir; Mohamad Jaafar, Adila; Hj. Yahaya, Asmah; Masarudin, Mas Jaffri; Zainal, Zulkarnain

2014-01-01

259

HYDROXIDE-PROMOTED CORE CONVERSIONS OF MOLYBDENUM-IRON-SULFUR EDGE-BRIDGED DOUBLE CUBANES: OXYGEN-LIGATED TOPOLOGICAL PN CLUSTERS  

PubMed Central

The occurence of a heteroatom X (C, N, or O) in the MoFe7S9X core of the iron-molybdenum cofactor of nitrogenase has encouraged synthetic attempts to prepare high nuclearity M-Fe-S-X clusters containing such atoms. We have previously shown that reaction of the edge-bridged double cubane [(Tp)2Mo2Fe6S8(PEt3)4] (1) with nucleophiles HQ? affords the clusters [(Tp)2Mo2Fe6S8Q(QH)2]3? (Q = S, Se) in which HQ? is a terminal ligand and Q2? is a ?2-bridging atom in the core. Reactions with OH- used as such or oxygen nucleophiles generated in acetonitrile from (Bu3Sn)2O or Me3SnOH and fluoride were examined. Reaction of 1 with Et4NOH in acetonitrile/water generates [(Tp)2Mo2Fe6S9(OH)2]3? (3), isolated as [(Tp)2Mo2Fe6S9(OH)(OC(=NH)Me)(H2O)]3? and shown to have the [Mo2Fe6(?2-S)2(?3-S)6(?6-S)] core topology very similar to the PN cluster of nitrogenase. The reaction system 1/Et4NOH in acetonitrile/methanol yields the PN-type cluster [(Tp)2Mo2Fe6S9(OMe)2(H2O)]3? (5). The system 1/Me3SnOH/F? affords the oxo-bridged double PN-type cluster {[(Tp)2Mo2Fe6S9(?2-O)]2}5? (7), convertible to the oxidized cluster {[(Tp)2Mo2Fe6S9(?2-O)]2}4? (6), which is prepared independently from [(Tp)2Mo2Fe6S9F2(H2O)]3?/(Bu3Sn)2O. In the preparations of 3–5 and 7, hydroxide liberates sulfide from 1 leading to the formation of PN-type clusters. Unlike reactions with HQ?, no oxygen atoms are integrated into the core structures of the products. However, the half-dimer composition [Mo2Fe6S9O] relates to the MoFe7S9 consitution of the putative native cluster with X = O. (Tp = hydrotris(pyrazolyl) borate(1-)). PMID:17892284

Hlavinka, Mark L.; Miyaji, Taichi; Staples, Richard J.; Holm, R. H.

2008-01-01

260

A composite of layered double hydroxides obtained through random costacking of layers from Mg Al and Co Al LDHs by delamination restacking: Thermal decomposition and reconstruction behavior  

NASA Astrophysics Data System (ADS)

A composite of dodecylsulfate intercalated Mg-Al and Co-Al LDHs in which the layers of the two LDHs are randomly costacked was prepared starting from the monolayer colloidal dispersions of the individual surfactant intercalated LDHs obtained through delamination in 1-butanol. The surfactant ion of the composite could be exchanged for acetate ions. The thermal decomposition and reconstruction behavior of the acetate-intercalated composite was found to be different from those of an LDH in which each layer contains Mg, Co and Al and a physical mixture of Mg-Al and Co-Al LDHs. While the composite shows partial reconstruction to LDH phase even after heating up to 1000 °C the other samples do not show reconstruction beyond 800 °C.

Venugopal, B. R.; Shivakumara, C.; Rajamathi, Michael

2007-03-01

261

Detection of Necrosis by Release of Lactate Dehydrogenase (LDH) Activity  

PubMed Central

Summary Apoptosis and necrosis are two major forms of cell death observed in normal and disease pathologies. Although there are many assays for detection of apoptosis, relatively few assays are available for measuring necrosis. A key signature for necrotic cells is the permeabilization of plasma membrane. This event can be quantified in tissue culture settings by measuring the release of the enzyme lactate dehydrogenase (LDH). When combined with other methods, measuring LDH release is a useful method for detection of necrosis. In this chapter, we describe the step-by-step procedure for detection of LDH release from necrotic cells using a microtiter plate based colorimetric absorbance assay. PMID:23397389

Chan, Francis Ka-Ming; Moriwaki, Kenta; De Rosa, María José

2013-01-01

262

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

263

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. PMID:7539419

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

1995-01-01

264

Calcium hydroxide poisoning  

MedlinePLUS

Calcium hydroxide is a white powder produced by mixing calcium oxide ("lime") with water. Calcium hydroxide poisoning ... Blood in the stool Burns in the esophagus (food pipe) Severe abdominal pain Vomiting Vomiting blood Heart ...

265

Synthesis of polypropylene/Mg3AlX (X CO3 ) LDH nanocomposites using a solvent mixing  

E-print Network

a solvent mixing method: thermal and melt rheological properties Yanshan Gao,a Jingwen Wu,a Zhang Zhang ) intercalated Mg3Al layered double hydroxides (LDHs) as nanofillers were prepared using a solvent mixing method. The incorporation of LDHs increased the melting temperature (Tm) and the recrystallization temperature (Tc) of PP

Guo, John Zhanhu

266

Vibrational spectroscopic study of the sulphate mineral glaucocerinite (Zn,Cu)10Al6(SO4)3(OH)32?18H2O - A natural layered double hydroxide  

NASA Astrophysics Data System (ADS)

We have studied the molecular structure of the mineral glaucocerinite (Zn,Cu)5Al3(SO4)1.5(OH)16?9(H2O) using a combination of Raman and infrared spectroscopy. The mineral is one of the hydrotalcite supergroup of natural layered double hydroxides. The Raman spectrum is characterised by an intense Raman band at 982 cm-1 with a low intensity band at 1083 cm-1. These bands are attributed to the sulphate symmetric and antisymmetric stretching mode. The infrared spectrum is quite broad with a peak at 1020 cm-1. A series of Raman bands at 546, 584, 602, 625 and 651 cm-1 are assigned to the ?4 (SO4)2- bending modes. The observation of multiple bands provides evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 762 cm-1 is attributed to a hydroxyl deformation mode associated with AlOH units. Vibrational spectroscopy enables aspects of the molecular structure of glaucocerinite to be determined.

Frost, Ray L.; Theiss, Frederick L.; López, Andrés; Scholz, Ricardo

2014-06-01

267

Vibrational spectroscopic study of the sulphate mineral glaucocerinite (Zn,Cu)(10)Al(6)(SO(4))(3)(OH)(32)?18H(2)O - a natural layered double hydroxide.  

PubMed

We have studied the molecular structure of the mineral glaucocerinite (Zn,Cu)(5)Al(3)(SO(4))1.5(OH)16?9(H2O) using a combination of Raman and infrared spectroscopy. The mineral is one of the hydrotalcite supergroup of natural layered double hydroxides. The Raman spectrum is characterised by an intense Raman band at 982cm(-1) with a low intensity band at 1083cm(-1). These bands are attributed to the sulphate symmetric and antisymmetric stretching mode. The infrared spectrum is quite broad with a peak at 1020cm(-1). A series of Raman bands at 546, 584, 602, 625 and 651cm(-1) are assigned to the ?4 (SO4)(2)(-) bending modes. The observation of multiple bands provides evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 762cm(-1) is attributed to a hydroxyl deformation mode associated with AlOH units. Vibrational spectroscopy enables aspects of the molecular structure of glaucocerinite to be determined. PMID:24637273

Frost, Ray L; Theiss, Frederick L; López, Andrés; Scholz, Ricardo

2014-06-01

268

Unusual hydrocarbon chain packing mode and modification of crystallite growth habit in the self-assembled nanocomposites zinc-aluminum-hydroxide oleate and elaidate (cis-and trans-[Zn2Al(OH)6(CH3(CH2)7CH=CH(CH2)7COO-)] and magnesium analogues.  

SciTech Connect

We report a novel packing mode specific to the cis unsaturated hydrocarbon chain in the title compound, a self-assembled layered double hydroxide-surfactant hybrid nanomaterial, and its influence on crystallite morphology and structure. The kink imposed by the cis double bond in oleate leads to partial overlap between chains on adjacent layers, with incomplete space filling, in contrast to the more usual (and more efficient) mono- and bilayer packings exhibited by the trans analogues. Incorporation of surfactant into the growing crystallite leads to a reversal of the usual LDH growth habit and results in crystallite shapes featuring ribbonlike sheets. The thermal decomposition behavior of the as-prepared organic/inorganic nanocomposites in air and N{sub 2} is described.

Wang, Yifeng (Sandia National Laboratories, Carlsbad, NM); Braterman, Paul S. (University of North Texas, Denton, TX); Xu, Zhi-Ping (University of North Texas, Denton, TX); Brinker, C. Jeffrey; Xu, Huifang (University of New Mexico, Albuquerque, NM); Yu, Kui

2004-05-01

269

Evaluation of the rapid diagnostic test CareStart pLDH Malaria (Pf-pLDH/pan-pLDH) for the diagnosis of malaria in a reference setting  

PubMed Central

Background The present study evaluated CareStart pLDH Malaria, a three-band rapid diagnostic test detecting Plasmodium falciparum-specific parasite lactate dehydrogenase (Pf-pLDH) and pan Plasmodium-specific pLDH (pan-pLDH) in a reference setting. Methods CareStart pLDH was retrospectively and prospectively assessed with a panel of stored (n?=?498) and fresh (n?=?77) blood samples obtained in international travelers suspected of malaria. Both panels comprised all four Plasmodium species; the retrospective panel comprised also Plasmodium negative samples. The reference method was microscopy corrected by PCR. The prospective panel was run side-to-side with OptiMAL (Pf-pLDH/pan-pLDH) and SDFK60 (histidine-rich protein-2 (HRP-2)/pan-pLDH). Results In the retrospective evaluation, overall sensitivity for P. falciparum samples (n?=?247) was 94.7%, reaching 98.7% for parasite densities?>?1,000/?l. Most false negative results occurred among samples with pure gametocytaemia (2/12, 16.7%) and at parasite densities???100/?l (7/12, 58.3%). None of the Plasmodium negative samples (n?=?96) showed visible test lines. Sensitivities for Plasmodium vivax (n?=?70), Plasmodium ovale (n?=?69) and Plasmodium malariae (n?=?16) were 74.3%, 31.9% and 25.0% respectively. Wrong species identification occurred in 10 (2.5%) samples and was mainly due to P. vivax samples reacting with the Pf-pLDH test line. Overall, Pf-pLDH test lines showed higher line intensities compared to the pan-pLDH lines (67.9% and 23.0% medium and strong line intensities for P. falciparum). In the prospective panel (77 Plasmodium-positive samples), CareStart pLDH showed higher sensitivities for P. falciparum compared to OptiMAL (p?=?0.008), lower sensitivities for P. falciparum as compare to SDFK60 (although not reaching statistical significance, p?=?0.08) and higher sensitivities for P. ovale compared to both OptiMAL (p?=?0.03) and SDFK60 (p?=?0.01). Inter-observer and test reproducibility were good to excellent. Conclusion CareStart pLDH performed excellent for the detection of P. falciparum, well for P. vivax, but poor for P. ovale and P. malariae. PMID:22704733

2012-01-01

270

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

271

Evolutionary relationships of lactate dehydrogenases (LDHs) from mammals, birds, an amphibian, fish, barley, and bacteria: LDH cDNA sequences from Xenopus, pig, and rat.  

PubMed Central

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 G. N. Somero and D. A. Powers, were used to construct the most parsimonious phylogenetic tree of these 32 LDH subunits from mammals, birds, an amphibian, fish, barley, and bacteria. There have been at least six LDH gene duplications among the vertebrates. The Xenopus LDH-A, LDH-B, and LDH-C subunits are most closely related to each other and then are more closely related to vertebrate LDH-B than LDH-A. Three fish LDH-As, as well as a single LDH of lamprey, also seem to be more related to vertebrate LDH-B than to land vertebrate LDH-A. The mammalian LDH-C (testis) subunit appears to have diverged very early, prior to the divergence of vertebrate LDH-A and LDH-B subunits, as reported previously. Images PMID:7937776

Tsuji, S; Qureshi, M A; Hou, E W; Fitch, W M; Li, S S

1994-01-01

272

Epilepsy treatment. Targeting LDH enzymes with a stiripentol analog to treat epilepsy.  

PubMed

Neuronal excitation is regulated by energy metabolism, and drug-resistant epilepsy can be suppressed by special diets. Here, we report that seizures and epileptiform activity are reduced by inhibition of the metabolic pathway via lactate dehydrogenase (LDH), a component of the astrocyte-neuron lactate shuttle. Inhibition of the enzyme LDH hyperpolarized neurons, which was reversed by the downstream metabolite pyruvate. LDH inhibition also suppressed seizures in vivo in a mouse model of epilepsy. We further found that stiripentol, a clinically used antiepileptic drug, is an LDH inhibitor. By modifying its chemical structure, we identified a previously unknown LDH inhibitor, which potently suppressed seizures in vivo. We conclude that LDH inhibitors are a promising new group of antiepileptic drugs. PMID:25792327

Sada, Nagisa; Lee, Suni; Katsu, Takashi; Otsuki, Takemi; Inoue, Tsuyoshi

2015-03-20

273

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

274

Surface modification of inorganic layer compound with organic compound and preparation of thin films  

Microsoft Academic Search

Water treated ZnAl layered double hydroxide (LDH) was prepared by the reaction of LDH oxide and water. By the reaction of the water treated ZnAl LDH or amorphous metal hydroxide and organic oxychloride, surface modified inorganic layer compounds were prepared. Their layer structures were similar to those of the orginal LDHs except the reaction product of amorphous metal hydroxide and

Hideyuki Tagaya; Hiroyuki Morioka; Sumikazu Ogata; Masa Karasu; Jun-ichi Kadokawa; Koji Chiba

1997-01-01

275

Hydroxide-catalyzed bonding  

NASA Technical Reports Server (NTRS)

A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

Gwo, Dz-Hung (Inventor)

2003-01-01

276

Nickel hydroxide electrode. 3: Thermogravimetric investigations of nickel (II) hydroxides  

NASA Technical Reports Server (NTRS)

Water contained in Ni hydroxide influences its electrochemical reactivity. The water content of alpha and beta Ni hydroxides is different with respect to the amount and bond strength. Thermogravimetric experiments show that the water of the beta Ni hydroxides exceeding the stoichiometric composition is completely removed at 160 deg. The water contained in the interlayers of the beta hydroxide, however, is removed only at higher temperatures, together with the water originating from the decomposition of the hydroxide. These differences are attributed to the formation of II bonds within the interlayers and between interlayers and adjacent main layers. An attempt is made to explain the relations between water content and the oxidizability of the Ni hydroxides.

Dennstedt, W.; Loeser, W.

1982-01-01

277

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

278

Karchevskyite, [Mg18Al9(OH)54][Sr2(CO3,PO4)9(H2O,H3O)11], a new mineral species of the layered double hydroxide family  

NASA Astrophysics Data System (ADS)

Karchevskyite, a new mineral related to the family of layered double hydroxides (LDHs), has been found in the Iron open pit at the Kovdor carbonatite massif, Kola Peninsula, Russia. The mineral occurs as spherulites of up to 1.5 mm in diameter composed of thin, curved lamellae. Dolomite, magnetite, quintinite-3 T, strontium carbonate, and fluorapatite are associated minerals. Karchevskyite is white in aggregates and colorless in separate platelets. Its luster is vitreous with a pearly shine on the cleavage surface. The new mineral is nonfluorescent. The Mohs hardness is 2. The cleavage is eminent (micalike), parallel to {001}. The measured density is 2.21(2) g/cm3, and the calculated value is 2.18(1) g/cm3. Karchevskyite is colorless and nonpleochroic in immersion liquids. It is uniaxial, negative, ? = 1.542(2), and ? = 1.534(2). The chemical composition (electron microprobe, average of ten point analyses, standard deviation in parentheses, wt %) is as follows: 29.7(1.1) MgO, 18.3(0.7) Al2O3, 7.4(0.4) SrO, 0.2(0.1) CaO, 1.3(0.2) P2O5, 14.5(0.4) CO2, and 28.6 H2O (estimated by difference); the total is 100. The empirical formula calculated on the basis of nine Al atoms is Mg18.00Al9.00(OH)54.00(Sr1.79Mg0.48Ca0.09)2.36 (Ca3)8.26(PO4)0.46(H2O)6.54(H3O)4.18. The idealized formula is [Mg18Al9(OH)54][Sr2(CO3, PO4)9(H2O, H3O)11]. The new mineral slowly dissolves in 10% HCl with weak effervescence. Karchevskyite is trigonal; possible space groups are P3, P3, P overline 3 1 m, P31 m, P312, P312, P3 m1, or P3 m1; unit-cell dimensions are a = 16.055(6), c = 25.66(1) Å, V = 5728(7) Å3, Z = 3. The strongest reflections in the X-ray powder diffraction pattern [ d, ( I, %)( hkl)] are: 8.52(10)(003), 6.41(4)(004), 5.13(3)(005), 4.27(6)(006), 3.665(9)(007), 3.547(9)(107), 3.081(6)(315). Wavenumbers of absorption bands in the infrared spectrum of the new mineral are (cm-1; s is shoulder): 3470, 3420s, 3035, 2960s, 1650, 1426, 1366, 1024, 937, 860, 779, 678, 615s, 553, 449, 386. Results of thermogravimetric analysis: total weight loss is 42.0 wt %, with three stages of loss: 12.2%, maximum rate at 230°C; 6.1%, maximum rate at 320°C; and 23.7%, maximum rate at 440°C. Karchevskyite is a late-stage hydrothermal mineral. The mineral is named in memory of Russian mineralogist Pavel Karchevsky (1976-2002), who made a significant contribution to the study of carbonatites. The type material of karchevskyite is deposited at the Mineralogical Museum, Division of Mineralogy, St. Petersburg State University, and the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Britvin, S. N.; Chukanov, N. V.; Bekenova, G. K.; Yagovkina, M. A.; Antonov, A. V.; Bogdanova, A. N.; Krasnova, N. I.

2008-12-01

279

21 CFR 184.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2010 CFR

...hydroxide. (a) Magnesium hydroxide (Mg(OH)2 , CAS Reg. No. 1309-42-8) occurs naturally as the colorless, crystalline mineral brucite. It is prepared as a white precipitate by the addition of sodium hydroxide to a water soluble...

2010-04-01

280

21 CFR 582.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2011 CFR

... 2011-04-01 2011-04-01 false Potassium hydroxide. 582.1631 Section 582.1631...General Purpose Food Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use....

2011-04-01

281

21 CFR 582.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 2010-04-01 false Magnesium hydroxide. 582.1428 Section 582.1428...General Purpose Food Additives § 582.1428 Magnesium hydroxide. (a) Product. Magnesium hydroxide. (b) Conditions of use....

2010-04-01

282

21 CFR 582.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2014 CFR

... 2014-04-01 2014-04-01 false Magnesium hydroxide. 582.1428 Section 582.1428...General Purpose Food Additives § 582.1428 Magnesium hydroxide. (a) Product. Magnesium hydroxide. (b) Conditions of use....

2014-04-01

283

21 CFR 582.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 2013-04-01 false Magnesium hydroxide. 582.1428 Section 582.1428...General Purpose Food Additives § 582.1428 Magnesium hydroxide. (a) Product. Magnesium hydroxide. (b) Conditions of use....

2013-04-01

284

21 CFR 582.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 2012-04-01 false Magnesium hydroxide. 582.1428 Section 582.1428...General Purpose Food Additives § 582.1428 Magnesium hydroxide. (a) Product. Magnesium hydroxide. (b) Conditions of use....

2012-04-01

285

21 CFR 582.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2011 CFR

... 2011-04-01 2011-04-01 false Magnesium hydroxide. 582.1428 Section 582.1428...General Purpose Food Additives § 582.1428 Magnesium hydroxide. (a) Product. Magnesium hydroxide. (b) Conditions of use....

2011-04-01

286

21 CFR 582.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 2010-04-01 false Potassium hydroxide. 582.1631 Section 582.1631...General Purpose Food Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use....

2010-04-01

287

Reduced diagnostic value of lactate dehydrogenase (LDH) in the presence of radiographic contrast media.  

PubMed

Isoforms of the enzyme lactate dehydrogenase (LDH) were found in almost all cells of the organism and an elevated activity of LDH in the circulation is thought to be a clear indicator of elevated cell destruction coinciding with an increased release of components from the cellular cytoplasm, e.g. LDH. Here, we report on an in-vitro examination to test whether radiographic contrast media (RCM) could induce cell destruction followed by an increase in LDH release. The RCM were tested in non-flow cultures of human umbilical venous endothelial cells (HUVEC) of the fourth passage seeded on extracellular matrix and the results were compared to those from control cultures not exposed to contrast media. The examination revealed that the addition of contrast media to the cell culture media supplemented with pooled human serum (HSP) as source of exogenous LDH was followed by a strong decrease in LDH activity both in the absence and presence of HUVEC. Within 1.5 min after the addition of contrast media to the culture medium supplemented with HSP (30% vol of the culture medium were replaced by either of two contrast media, Iodixanol or Iopromide) the LDH activity decreased about 80% compared to the initial values. In contrast, the LDH activity did not change in cell culture media not supplemented with RCM. The partial replacement of HSP supplemented cell culture medium by RCM will cause a dilution of cell culture medium constituents. The decrease of LDH activity, however, was much stronger than the decrease thought to be attributable to the effects of dilution of cell culture medium, so that the role of dilution seems to be a minor one in this case. It has to be assumed that the RCM could interact with the LDH available in the culture medium as well as with the substrates delivered with the measurement system for the assessment of LDH activity, so that both, the amount of LDH and the activities of enzymes involved might be influenced. In the presence of HUVEC a similar effect was observed. Here, a little less strong decrease of LDH activity occurred compared to the decrease in cell culture medium without HUVEC. This was unexpected because a considerable amount of HUVEC were detached after the addition of contrast media and many of these cells were damaged seriously so that a significant amount of endogenous LDH should have been released. These unexpected results make it necessary to re-evaluate those past time examinations focussed on cell damage/destruction in the presence of contrast media, where the measurement of LDH activity was used as indicator or cell vitality and where cell decease rates were correlated to questionable toxic influences. According to the results of the examination reported here it is difficult to uphold the interpretation of recently published findings that contrast media almost exclusively induce cellular apoptosis and not necrosis. PMID:20675892

Franke, R-P; Fuhrmann, R; Mrowietz, C; Rickert, D; Hiebl, B; Jung, F

2010-01-01

288

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

289

Serum LDH concentration in non-Hodgkin's lymphomas. Relationship to histologic type, tumor mass, and presentation features.  

PubMed

Serum lactate dehydrogenase (LDH) activity is increased in many tumor-bearing patients and can be used as a prognostic marker. We studied serum LDH concentration in 94 consecutive patients with non-Hodgkin's lymphoma who were histologically classified according to the Kiel Classification and were grouped according to the Non-Hodgkin's Lymphoma Pathologic Classification Project Working Formulation. 74 patients were studied at diagnosis, and 20 of them (27%) had an LDH level higher than 250 U/l. High LDH levels were more frequent in cases of true histiocytic, high-grade, and intermediate-grade malignancy lymphoma (4 of 7, 7 of 14, and 7 of 20, respectively) than in cases of low-grade lymphoma (2 of 33). A close relationship of LDH to several prognosis-related disease features was found, including general symptoms, bulky disease, big mediastinal tumor, huge hepatosplenomegaly, bone marrow involvement, and a leukemic syndrome. LDH was higher than normal in a high proportion of cases who were studied in relapse (13 of 20, 65%). These data suggest that in non-Hodgkin's lymphomas the LDH serum concentration is not independent of other disease features, so that the prognostic value of LDH is probably lower than expected from previous studies. Serum LDH activity decreased to normal in all cases of complete remission, but also in cases of partial remission, suggesting that measuring enzyme activity is of a limited usefulness for detecting and monitoring minimal residual disease. For that purpose, LDH isoenzyme studies would be more appropriate. PMID:6438991

Fasola, G; Fanin, R; Gherlinzoni, F; Galieni, P; Taruscio, D; Frezza, G; Mazza, P; Pileri, S; Baccarani, M

1984-01-01

290

Mild hypoxia in vivo regulates cardioprotective SUR2A: A role for Akt and LDH.  

PubMed

High-altitude residents have lower mortality rates for ischaemic heart disease and this is ascribed to cardiac gene remodelling by chronic hypoxia. SUR2A is a cardioprotective ABC protein serving as a subunit of sarcolemmal ATP-sensitive K(+) channels. The purpose of this study was to determine whether SUR2A is regulated by mild hypoxia in vivo and to elucidate the underlying mechanism. Mice were exposed to either 21% (control) or 18% (mild hypoxia) oxygen for 24h. Exposure to 18% oxygen did not affect partial pressure of O2 (PO2) and CO2 (PCO2) in the blood, haematocrit or level of ATP in the heart. However, hypoxia increased myocardial lactate dehydrogenase (LDH) and lactate as well as NAD(+) without affecting total NAD. SUR2A levels were significantly increased as well as myocardial resistance to ischaemia-reperfusion. Exposure to 18% oxygen did not phosphorylate extracellular signal regulated kinases (ERK1/2) or AMP activated protein kinase (AMPK), but it phosphorylated protein kinase B (Akt). An inhibitor of phosphoinositide 3-kinases (PI3K), LY294002 (0.2mg/mouse), abolished all observed effects of hypoxia. LDH inhibitors, galloflavin (50?M) and sodium oxamate (80mM) significantly decreased levels of SUR2A in heart embryonic H9c2 cells, while inactive mutant LDH form, gly193-M-LDH increased cellular sensitivity towards stress induced by 2,4-dinitrophenol (10mM). Treatment of H9c2 cells with sodium lactate (30mM) increased intracellular lactate, but did not affect LDH activity or SUR2A levels. We conclude that PI3K/Akt signalling pathway and LDH play a crucial role in increase of cardiac SUR2A induced by in vivo exposure to 18% oxygen. PMID:25576887

Mohammed Abdul, Khaja Shameem; Jovanovi?, Sofija; Du, Qingyou; Sukhodub, Andriy; Jovanovi?, Aleksandar

2015-05-01

291

[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

292

Recovery of renal lactate dehydrogenase (LDH) isoenzyme pattern after obstruction relief in experimental hydronephrosis.  

PubMed

The release of ureteral occlusion leads to a progressive recovery in LDH isoenzyme pattern with gradual increase of anodic fractions and decrease of middle and cathodic ones. Our findings demonstrate that the recovery is accomplished on the 10-14th day, in agreement with morphological and metabolic observation. PMID:467572

Emanuelli, G; Anfossi, G; Camussi, G; Calcamuggi, G; Cestonaro, G; Gatti, G

1979-06-15

293

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

294

Protection mechanism of Tween 80 during freeze-thawing of a model protein, LDH.  

PubMed

The purpose of the study was to investigate the protective mechanism of a non-ionic surfactant, Tween 80, at freeze-thawing with controlled temperature history of a model protein, lactate dehydrogenase (LDH). The system was examined by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). LDH activity assays were performed spectrophotometrically. In all samples, independent of temperature history and addition of surfactant, all water was crystallized to polycrystalline ice at temperatures below -20 degrees C. The size and perfection of the ice crystals could be varied by a range of cooling rates giving different degrees of undercooling. At Tween concentrations below the cmc at crystallization, lower concentrations were required at low cooling rates compared to higher cooling rates to protect LDH. Concentrations above cmc of Tween reduced the protection at a cooling rate of 5 degrees C min(-1) and at quenching in N(2)(l). The amount of Tween needed for complete protection correlated to the surface area of the ice crystals at a certain temperature history. Tween 80 protects LDH from denaturation at freeze-thawing by hindering its destructive interaction with the ice crystals. The protective effect might be obtained when Tween molecules compete with the protein for sites on the ice surface. The optimum concentration of Tween needed for complete protection is dependent on the temperature history. PMID:11955804

Hillgren, Anna; Lindgren, Jan; Aldén, Maggie

2002-04-26

295

High-Throughput Screening to Identify Plant Derived Human LDH-A Inhibitors  

PubMed Central

Aims Lactate dehydrogenase (LDH)-A is highly expressed in diverse human malignant tumors, parallel to aggressive metastatic disease, resistance to radiation/chemotherapy and clinically poor outcome. Although this enzyme constitutes a plausible target in treatment of advanced cancer, there are few known LDH-A inhibitors. Study Design In this work, we utilized a high-throughput enzyme micro-array format to screen and evaluate > 900 commonly used medicinal plant extracts (0.00001-.5 mg/ml) for capacity to inhibit activity of recombinant full length human LDHA; EC .1.1.1.27. Methodology The protein sequence of purified enzyme was confirmed using 1D gel electrophoresis- MALDI-TOF-MS/MS, enzyme activity was validated by oxidation of NADH (500?M) and kinetic inhibition established in the presence of a known inhibitor (Oxalic Acid). Results Of the natural extracts tested, the lowest IC50s [<0.001 mg/ml] were obtained by: Chinese Gallnut (Melaphis chinensis gallnut), Bladderwrack (Fucus vesiculosus), Kelp (Laminaria Japonica) and Babul (Acacia Arabica). Forty-six additional herbs contained significant LDH-A inhibitory properties with IC50s [<0.07 mg/ml], some of which have common names of Arjun, Pipsissewa, Cinnamon, Pink Rose Buds/Petals, Wintergreen, Cat’s Claw, Witch Hazel Root and Rhodiola Root. Conclusion These findings reflect relative potency by rank of commonly used herbs and plants that contain human LDH-A inhibitory properties. Future research will be required to isolate chemical constituents within these plants responsible for LDH-A inhibition and investigate potential therapeutic application. PMID:24478981

Deiab, S.; Mazzio, E.; Messeha, S.; Mack, N.; Soliman, K. F. A.

2014-01-01

296

Analysis of Quaternary Structure of a [LDH-like] Malate Dehydrogenase of Plasmodium falciparum with Oligomeric Mutants  

Technology Transfer Automated Retrieval System (TEKTRAN)

L-Malate dehydrogenase (PfMDH) from Plasmodium falciparum, the causative agent for the most severe form of malaria, has shown remarkable similarities to L-lactate dehydrogenase (PfLDH). PfMDH is more closely related to [LDH-like] MDHs characterized in archea and other prokaryotes. Initial sequence a...

297

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2010 CFR

...empirical formula is NaOH. 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...

2010-04-01

298

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2011 CFR

...caustic soda, white caustic, and lye. The empirical formula is NaOH. Sodium hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The...

2011-04-01

299

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2014 CFR

...caustic soda, white caustic, and lye. The empirical formula is NaOH. Sodium hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The ingredient...

2014-04-01

300

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2012 CFR

...caustic soda, white caustic, and lye. The empirical formula is NaOH. Sodium hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The...

2012-04-01

301

21 CFR 184.1763 - Sodium hydroxide.  

Code of Federal Regulations, 2013 CFR

...caustic soda, white caustic, and lye. The empirical formula is NaOH. Sodium hydroxide is prepared commercially by the electrolysis of sodium chloride solution and also by reacting calcium hydroxide with sodium carbonate. (b) The...

2013-04-01

302

Purification of mercury contaminated lithium hydroxide  

Microsoft Academic Search

The object of this investigation was to determine an economical method of preparing pure lithium hydroxide from a mercury-contaminated lithium hydroxide monohydrate salt presently produced as a waste product. Pure lithium hydroxide has application for chemical removal of carbon dioxide from air and general open market sale if the mercury contamination is reduced to approximately one part per billion. Because

B. R. Bronfin; D. M. Jenkins; E. E. Jr. Wright

1960-01-01

303

21 CFR 184.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2013 CFR

...Affirmed as GRAS § 184.1428 Magnesium hydroxide. (a) Magnesium hydroxide (Mg(OH)2 , CAS Reg. No. 1309-42-8...prepared as a white precipitate by the addition of sodium hydroxide to a water soluble magnesium salt or by...

2013-04-01

304

21 CFR 184.1428 - Magnesium hydroxide.  

Code of Federal Regulations, 2014 CFR

...Affirmed as GRAS § 184.1428 Magnesium hydroxide. (a) Magnesium hydroxide (Mg(OH)2 , CAS Reg. No. 1309-42-8...prepared as a white precipitate by the addition of sodium hydroxide to a water soluble magnesium salt or by...

2014-04-01

305

LDH isoenzymes  

MedlinePLUS

... antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to ... or tube attached to the needle. The elastic band is removed from your arm. The needle is ...

306

Eigenschaften der Laktatdehydrogenase (LDH) in der Embryogenese von Acheta domesticus L  

Microsoft Academic Search

LDH activity of cricket eggs decreases during the first two days of development and then increases again with nearly constant rate. Before and after the depression of activity the molecular weight (100000), Michaelis constant (1,33 mM) and pH optimum (6.9) are identical. However, the pattern of isoenzymes and the inhibition by excess substrate are different. It is therefore assumed, that

Elisabeth Hansen-Delkeskamp; F. Duspiva

1973-01-01

307

Reducing lactate secretion by ldhA Deletion in L-glutamate- producing strain Corynebacterium glutamicum GDK-9  

PubMed Central

L-lactate is one of main byproducts excreted in to the fermentation medium. To improve L-glutamate production and reduce L-lactate accumulation, L-lactate dehydrogenase-encoding gene ldhA was knocked out from L-glutamate producing strain Corynebacterium glutamicum GDK-9, designated GDK-9?ldhA. GDK-9?ldhA produced approximately 10.1% more L-glutamate than the GDK-9, and yielded lower levels of such by-products as ?-ketoglutarate, L-lactate and L-alanine. Since dissolved oxygen (DO) is one of main factors affecting L-lactate formation during L-glutamate fermentation, we investigated the effect of ldhA deletion from GDK-9 under different DO conditions. Under both oxygen-deficient and high oxygen conditions, L-glutamate production by GDK-9?ldhA was not higher than that of the GDK-9. However, under micro-aerobic conditions, GDK-9?ldhA exhibited 11.61% higher L-glutamate and 58.50% lower L-alanine production than GDK-9. Taken together, it is demonstrated that deletion of ldhA can enhance L-glutamate production and lower the unwanted by-products concentration, especially under micro-aerobic conditions. PMID:25763057

Zhang, Dalong; Guan, Dan; Liang, Jingbo; Guo, Chunqian; Xie, Xixian; Zhang, Chenglin; Xu, Qingyang; Chen, Ning

2014-01-01

308

Decomposition processes of nickel hydroxide  

Microsoft Academic Search

The dehydration processes of nickel hydroxide were studied by means of thermogravimetry in a temperature range from 300 to\\u000a 900 K. The kinetics of the low-temperature dehydroxylation (?300–600 K) was studied under non-isothermal conditions. A model-free\\u000a method was used to calculate the activation energy and to analyze the stepwise checking; the non-linear regression method\\u000a was applied to calculate the kinetic parameters of

V. Logvinenko; V. Bakovets; L. Trushnikova

309

Zinc-substituted {alpha}-nickel hydroxide as an electrode material for alkaline secondary cells  

SciTech Connect

Double hydroxides of the formula Ni{sub 1{minus}x}Zn{sub 2x} (OH){sub 2}(CO{sub 3}){sub x}{center_dot}nH{sub 2}O (x = 0.1 to 0.25) having the same structure as that of {alpha}-nickel hydroxide have been synthesized by partial substitution of zinc for nickel. The hydroxide having the composition x = 0.25 exhibited prolonged stability in 6 M KOH. Pasted electrodes comprising this material are rechargeable with a stabilized reversible discharge capacity of 410 {+-} 15 mAh/g of nickel even under suboptimal conditions of electrode fabrication. This compares favorably with the capacity values achieved for {beta}-nickel hydroxide (221 mAh/g, this work; 297 mAh/g, Delahaye-Vidal and Figlarz; 456 mAh/g, theoretical).

Dixit, M.; Kamath, P.V. [Bangalore Univ. (India). Dept. of Chemistry] [Bangalore Univ. (India). Dept. of Chemistry; Gopalakrishnan, J. [Indian Inst. of Science, Bangalore (India). Solid State and Structural Chemistry Unit] [Indian Inst. of Science, Bangalore (India). Solid State and Structural Chemistry Unit

1999-01-01

310

Utility of serum LDH isoforms in the assessment of mycobacterium tuberculosis induced pathology in TB patients of Sahariya tribe  

Microsoft Academic Search

The present study was carried out in the Sahariya tribe of Central India, which reportedly have high prevalence of pulmonary\\u000a tuberculosis. Total serum LDH and its tissue specific isoforms were estimated in TB patients and matched healthy controls\\u000a to test the utility of LDH as diagnostic marker for tuberculosis. About 210 sputum positive cases and 328 age and sex matched

P. R. Sharma; S. Jain; R. N. K. Bamezai; P. K. Tiwari

2010-01-01

311

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

PubMed

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, of LDH in tumours has never been investigated in the past. In the present study, we established an immunohistochemical method to evaluate the LDH-5 overexpression in tumours, using two novel antibodies raised against the rat muscle LDH-5 and the human LDH-5 (Abcam, UK). The subcellular patterns of expression in cancer cells were mixed nuclear and cytoplasmic. In direct contrast to cancer cells, stromal fibroblasts were reactive for LDH-5 only in a minority of cases. Serum LDH, although positively correlated with, does not reliably reflect the intratumoral LDH-5 status. Lactate dehydrogenase-5 overexpression was directly related to HIF1alpha and 2alpha, but not with the carbonic anhydrase 9 expression. Patients with tumours bearing high LDH-5 expression had a poor prognosis. Tumours with simultaneous LDH-5 and HIF1alpha (or HIF2alpha) overexpression, indicative of a functional HIF pathway, had a particularly aggressive behaviour. It is concluded that overexpression of LDH-5 is a common event in non-small-cell lung cancer, can be easily assessed in paraffin-embedded material and provides important prognostic information, particularly when combined with other endogenous markers of hypoxia and acidity. PMID:12942121

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

2003-09-01

312

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Surface modified magnesium hydroxide (generic). 721.10504...Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical...identified generically as surface modified magnesium hydroxide (PMN P-06-682) is...

2013-07-01

313

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Surface modified magnesium hydroxide (generic). 721.10504...Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical...identified generically as surface modified magnesium hydroxide (PMN P-06-682) is...

2014-07-01

314

21 CFR 73.2326 - Chromium hydroxide green.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Chromium hydroxide green. 73.2326 ...CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity...specifications. The color additive chromium hydroxide green shall...

2010-04-01

315

21 CFR 73.1326 - Chromium hydroxide green.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Chromium hydroxide green. 73.1326 Section...CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally...

2010-04-01

316

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Alumina (dried aluminum hydroxide). 73.1010 Section... § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity...The color additive alumina (dried aluminum hydroxide) is a white,...

2011-04-01

317

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Alumina (dried aluminum hydroxide). 73.1010 Section... § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity...The color additive alumina (dried aluminum hydroxide) is a white,...

2010-04-01

318

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Alumina (dried aluminum hydroxide). 73.1010 Section... § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity...The color additive alumina (dried aluminum hydroxide) is a white,...

2013-04-01

319

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Alumina (dried aluminum hydroxide). 73.1010 Section... § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity...The color additive alumina (dried aluminum hydroxide) is a white,...

2014-04-01

320

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Alumina (dried aluminum hydroxide). 73.1010 Section... § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity...The color additive alumina (dried aluminum hydroxide) is a white,...

2012-04-01

321

21 CFR 73.1326 - Chromium hydroxide green.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Chromium hydroxide green. 73.1326 Section...CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally...

2013-04-01

322

21 CFR 73.1326 - Chromium hydroxide green.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Chromium hydroxide green. 73.1326 Section...CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally...

2011-04-01

323

21 CFR 73.2326 - Chromium hydroxide green.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Chromium hydroxide green. 73.2326 ...CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity...specifications. The color additive chromium hydroxide green shall...

2013-04-01

324

21 CFR 73.2326 - Chromium hydroxide green.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Chromium hydroxide green. 73.2326 ...CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity...specifications. The color additive chromium hydroxide green shall...

2012-04-01

325

21 CFR 73.2326 - Chromium hydroxide green.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Chromium hydroxide green. 73.2326 ...CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity...specifications. The color additive chromium hydroxide green shall...

2011-04-01

326

21 CFR 73.1326 - Chromium hydroxide green.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Chromium hydroxide green. 73.1326 Section...CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally...

2012-04-01

327

21 CFR 73.2326 - Chromium hydroxide green.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Chromium hydroxide green. 73.2326 ...CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity...specifications. The color additive chromium hydroxide green shall...

2014-04-01

328

21 CFR 73.1326 - Chromium hydroxide green.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Chromium hydroxide green. 73.1326 Section...CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally...

2014-04-01

329

Removal of phosphate by aluminum oxide hydroxide  

Microsoft Academic Search

The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The

Seiki Tanada; Mineaki Kabayama; Naohito Kawasaki; Toru Sakiyama; Takeo Nakamura; Mamiko Araki; Takamichi Tamura

2003-01-01

330

XAFS Study of Arsenical Nickel Hydroxide  

NASA Astrophysics Data System (ADS)

To Investigate the role played by nickel co-ions in contributing to the stability of arsenic, fluorescence XAFS measurements at both arsenic K-edge and nickel K-edge, respectively, on amorphous arsenical nickel hydroxide, crystalline arsenical nickel hydroxide, and annabergite reference compounds have been carried out. The XAFS results indicate that the arsenic-bearing nickel hydroxides have a well-defined arsenic local structure with multiple coordination shells, suggesting a compound formation mechanism instead of surface adsorption. The degradation of the arsenic local structure in the crystalline arsenical nickel hydroxide is observed. The XAFS of annabergites are compared to that of the arsenical nickel hydroxide and possible structural models are discussed.

Chen, N.; Kim, E.; Arthur, Z.; Daenzer, R.; Warner, J.; Demopoulos, G. P.; Joly, Y.; Jiang, D. T.

2013-04-01

331

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

332

Renal lactate dehydrogenase (LDH) isoenzyme pattern in short-term experimental obstructive nephropathy.  

PubMed

The lactate dehydrogenase isoenzyme pattern of different zones of rat kidney has been investigated at different stages after unilateral ureteral obstruction. In the obstructed kidney, the cortical tissue showed an early (3 days) progressive shift toward a cathodic zymogram; at 7 days LDH-5 isoenzyme was the predominant fraction (44.7 +/- 2.5). In the outer medullary tissue a similar change was observed even though middle fractions were always quite evident. No significant changes were found in the inner medullary tissue. The observed enzymatic abnormalities are related to renal hypoxia and to the occurrence of a less differentiated nephronic cell population. They represent a metabolic marker of the morphologic and functional alterations which occur in obstructive nephropathy. PMID:447486

Cestonaro, G; Emanuelli, G; Calcamuggi, G; Anfossi, G; Gatti, G

1979-07-01

333

Thermodynamics of Volatile Silicon Hydroxides Studied  

NASA Technical Reports Server (NTRS)

Silicon-based ceramics are promising candidate structural materials for heat engines. The long-term stability of these materials to environmental degradation is dependent on the formation and retention of a protective SiO2 layer. It is well known that SiO2 forms stable volatile hydroxides in the presence of water vapor at elevated temperatures. Combustion conditions, which characteristically are at high velocities, contain significant water vapor pressures, and high temperatures tend to promote continuous formation of these hydroxides with resulting material degradation. For the degradation of silicon-based ceramics to be predicted, accurate thermodynamic data on the formation of silicon hydroxides are needed.

Copland, Evan H.; Opila, Elizabeth J.; Jacobson, Nathan S.

2001-01-01

334

Layered double hydroxides as nanoreactors for prebiotic chemistry  

NASA Astrophysics Data System (ADS)

The conversion of simple organic molecules to macromolecules, possessing functional activities is one of the key hurdles limiting our understanding on how life began on Earth in the Hadean period. Here, we aim to report new data showing the potential of anionic lamellar compounds to concentrate, protect, and catalyze the condensation reactions of aminoacids to form oligopeptides.

Grégoire, B.; Carteret, C.; Erastova, V.; Greenwell, H. C.; Fraser, D.

2013-09-01

335

Abstract We had previously shown that succinic acid production in a pfl ldhA double mutant strain of Escheri-  

E-print Network

or the introduction of new ones, using recombinant DNA technology (Bailey 1991; Lee and Papoutsakis 1999; Nielsen of Escheri- chia coli could be enhanced by amplifying the malic en- zyme activity. However, recombinant E employed to re-orient the metabolic fluxes in Escheri- chia coli and to create recombinant E. coli strains

336

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2014 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...

2014-04-01

337

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2010 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...

2010-04-01

338

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

339

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2012 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...

2012-04-01

340

21 CFR 184.1631 - Potassium hydroxide.  

Code of Federal Regulations, 2011 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...

2011-04-01

341

Aluminum hydroxide nanoparticles show a stronger vaccine adjuvant activity than traditional aluminum hydroxide microparticles  

PubMed Central

Aluminum hydroxide is used as a vaccine adjuvant in various human vaccines. Unfortunately, despite its favorable safety profile, aluminum hydroxide can only weakly or moderately potentiate antigen-specific antibody responses. When dispersed in an aqueous solution, aluminum hydroxide forms particulates of 1–20 µm. There is increasing evidence that nanoparticles around or less than 200 nm as vaccine or antigen carriers have a more potent adjuvant activity than large microparticles. In the present study, we synthesized aluminum hydroxide nanoparticles of 112 nm. Using ovalbumin and Bacillus anthracis protective antigen protein as model antigens, we showed that protein antigens adsorbed on the aluminum hydroxide nanoparticles induced a stronger antigen-specific antibody response than the same protein antigens adsorbed on the traditional aluminum hydroxide microparticles of around 9.3 µm. The potent adjuvant activity of the aluminum hydroxide nanoparticles was likely related to their ability to more effectively facilitate the uptake of the antigens adsorbed on them by antigen-presenting cells. Finally, the local inflammation induced by aluminum hydroxide nanoparticles in the injection sites was milder than that induced by microparticles. Simply reducing the particle size of the traditional aluminum hydroxide adjuvant into nanometers represents a novel and effective approach to improve its adjuvanticity. PMID:24188959

Li, Xinran; Aldayel, Abdulaziz M.; Cui, Zhengrong

2013-01-01

342

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

343

POSTNATAL EFFECTS OF HEXACHLOROBENZENE (HCB) ON CARDIAC LACTIC DEHYDROGENASE (LDH) AND CREATINE KINASE (CK) ISOZYMES IN CD-1 MICE  

EPA Science Inventory

Pregnant CD-1 mice were treated with hexachlorobenzene (HCB) by gavage at doses of 0, 1, 10 and 50 mg HCB/kg body weight on days 6-17 of gestation and studied on day 1 or 21 postpartum (pp). Hearts of the dams and pups were assayed for lactic dehydrogenase (LDH) and creatine kina...

344

Analyses of Nuclear ldhA Gene and mtDNA Control Region Sequences of Atlantic Northern Bluen Tuna  

E-print Network

Analyses of Nuclear ldhA Gene and mtDNA Control Region Sequences of Atlantic Northern Blue®n Tuna: There has been considerable debate about whether the Atlantic northern blue®n tuna exist as a single®n tuna from the Mediterranean Sea and the northwestern Atlantic Ocean. Pairwise comparisons of multiple

Ely, Bert

345

SEM-EBSD based Realistic Modeling and Crystallographic Homogenization FE Analyses of LDH Formability Tests  

NASA Astrophysics Data System (ADS)

Homogenization algorithm is introduced to the elastic/crystalline viscoplastic finite element (FE) procedure to develop multi-scale analysis code to predict the formability of sheet metal in macro scale, and simultaneously the crystal texture and hardening evolutions in micro scale. The isotropic and kinematical hardening lows are employed in the crystalline plasticity constitutive equation. For the multi-scale structure, two scales are considered. One is a microscopic polycrystal structure and the other a macroscopic elastic plastic continuum. We measure crystal morphologies by using the scanning electron microscope (SEM) with electron back scattered diffraction (EBSD), and define a three dimensional representative volume element (RVE) of micro ploycrystal structure, which satisfy the periodicity condition of crystal orientation distribution. Since nonlinear multi-scale FE analysis requires large computation time, development of parallel computing technique is needed. To realize the parallel analysis on PC cluster system, the dynamic explicit FE formulations are employed. Applying the domain partitioning technique to FE mesh of macro continuum, homogenized stresses based on micro crystal structures are computed in parallel without solving simultaneous linear equation. The parallel FEM code is applied to simulate the limit dome height (LDH) test problem and hemispherical cup deep drawing problem of aluminum alloy AL6022, mild steel DQSK, high strength steel HSLA, and dual phase steel DP600 sheet metals. The localized distribution of thickness strain and the texture evolution are obtained.

Kuramae, Hiroyuki; Ngoc Tam, Nguyen; Nakamura, Yasunori; Sakamoto, Hidetoshi; Morimoto, Hideo; Nakamachi, Eiji

2007-05-01

346

Dissolution mechanism of aluminum hydroxides in acid media  

NASA Astrophysics Data System (ADS)

The effects of the concentration, temperature, and potential at the hydroxide/electrolyte interface on the aluminum hydroxide dissolution in sulfuric, hydrochloric, and perchloric acids are studied. The limiting stage of the aluminum hydroxide dissolution in the acids is found to be the transition of the complexes that form on the aluminum hydroxide surface from the solid phase into the solution. The results of the calculation of the acid-base equilibrium constants at the oxide (hydroxide)/solution interface using the experimental data on the potentiometric titration of Al2O3 and AlOOH suspensions are analyzed. A mechanism is proposed for the dissolution of aluminum hydroxides in acid media.

Lainer, Yu. A.; Gorichev, I. G.; Tuzhilin, A. S.; Gololobova, E. G.

2008-08-01

347

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

348

Enhanced expression of the LDH-A gene after gravity-changing stress in human RSa cells.  

PubMed

A major issue in radiation and space biology is whether gene expression levels are altered in cells exposed to gravity-changing stress. In the present study, genes up- or down-regulated in radiation-sensitive human RSa cells cultured under gravity-changing conditions, were identified using a PCR-based mRNA differential display method. Exposure of cells to gravity-changing stress was performed by free-fall with a drop-shaft facility or by an airplane-conducted parabolic flight. Among the candidates for gravity-changing stress-responsive genes obtained by the differential display analysis, the lactate dehydrogenase A gene (LDH-A) was confirmed by Northern blotting analysis to exhibit increased expression levels. The gravity-changing stress consisted of a combination of microgravity and hypergravity. However, exposure of the cells to hypergravity produced by centrifuge only slightly affected the LDH-A mRNA expression. Thus, LDH-A was found to be a candidate for the genes which play a role in the cellular response to gravity-changing stress, and mainly to microgravity. PMID:12101348

Moriya, Tetsuhiro; Kita, Kazuko; Sugaya, Shigeru; Wano, Chieko; Suzuki, Nobuo

2002-03-01

349

Investigation of the stabilizing effects of hydroxyethyl cellulose on LDH during freeze drying and freeze thawing cycles.  

PubMed

The objective of this study was to investigate both the cryoprotective and lyoprotective effects of the polymer hydroxyethyl cellulose (HEC) on the model protein lactate dehydrogenase (LDH) during freeze thawing and freeze drying cycles. The effect of annealing on both protein stability and the physical state of HEC was evaluated. HEC was used as a sole excipient in the protein formulations, and its stabilizing was compared to that of other excipients which are commonly used in freeze dried protein formulations. Furthermore, other quality aspects of the freeze dried samples containing solely HEC were investigated, such as, reconstitution time and product elegance. Protein stability was evaluated functionally by measuring the activity recovery of the model protein LDH. The physical state of HEC after freeze drying was investigated and compared to this of other studied solutes using differential scanning calorimetry and X-ray powder diffractometry. HEC showed superior cryoprotective effects on LDH during freeze thawing, and considerable lyoprotective effects during the freeze drying process. Annealing had limited influence on the stabilizing effect of HEC. The extensive reconstitution times of the HEC lyophilisates could be greatly improved by incorporation of the surfactant Tween 80 into the formulations prior to freeze drying. PMID:24286265

Al-Hussein, Anas; Gieseler, Henning

2015-01-01

350

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

351

21 CFR 872.3250 - Calcium hydroxide cavity liner.  

Code of Federal Regulations, 2010 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...

2010-04-01

352

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 more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 {endash} 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.

Crocker, R.W.; Muller, R.H.

1992-05-01

353

Recycling Lithium Carbonate/Lithium Hydroxide Waste  

NASA Technical Reports Server (NTRS)

Hazardous waste disposal problem eliminated by regeneration. Li2CO3/ LiOH recycling process relies on low solubility of alkali carbonates in corresponding hydroxides. Li2CO3 precipitate calcined to LI2O, then rehydrated LiOH. Regeneration eliminates need to dispose caustic waste and uses less energy than simple calcination of entire waste mass.

Flowers, J.; Flowers, J.

1983-01-01

354

Flame retardant effects of magnesium hydroxide  

Microsoft Academic Search

Magnesium hydroxide has all the characteristics required for use as a flame retardant filler. It can be made synthetically with high purity and in a range of useful morphologies, responds well to surface modifiers and decomposes endothermically with release of water at temperatures close to those of polymer degradation and high enough to allow incorporation into most polymer types. Crystal

R. N. Rothon; P. R. Hornsby

1996-01-01

355

Study of nickel hydroxide electrodes. 2: Oxidation products of nickel (2) hydroxides  

NASA Technical Reports Server (NTRS)

Pure phases of some oxidized Ni oxides were prepared galvanimetrically with the Ni(2) hydroxide electrode of an alkaline battery. The crystallographic data of these phases, their chemical behavior, and conditions of transition were studied.

Bode, H.; Demelt, K.; White, J.

1986-01-01

356

Oxygen isotope indicators of selenate reaction with Fe(II) and Fe(III) hydroxides.  

PubMed

Selenate (SeO(4)(2-)) reduction to elemental selenium is an important Se immobilization process in subsurface environments that could be mediated by Fe(II)-rich minerals or selenate-respiring microorganisms. We report the kinetic isotope effects for (18)O within selenate during abiotic reactions with iron-bearing hydroxides within laboratory experiments. Selenate was reduced to Se(0) by a green rust (chloride interlayer type) and ferrous hydroxide, the two known environmentally relevant mineral reductants for selenate. Reaction kinetics are described by a rapid, low-fractionating uptake step caused by diffusive exchange between selenate and chloride followed by a slower, high-fractionating reduction step caused by electron transfer from structural Fe(II). The dual-phase kinetics cannot be described with the traditional Rayleigh fractionation model; however, well after the initial uptake step, the extent of selenate reaction is well correlated with ?(18)O values in accordance with the Rayleigh model. Selenate-(18)O enrichment (?O) was nearly identical for reaction with chloride green rust (22.7 ± 2.2‰) and ferrous hydroxide (22.1 ± 1.1‰) which suggests a common reduction mechanism by structural Fe(II). The minor enrichment due to anion exchange alone (1.4 ± 0.2‰) was confirmed using iowaite, a nonredox active Mg(II)-Fe(III) layered double hydroxide. Our ?O results may contribute to Se isotope forensics to identify selenate reduction within field sites and to possibly distinguish between abiotic and biotic reduction processes. PMID:23662584

Schellenger, Alexandra E P; Larese-Casanova, Philip

2013-06-18

357

Dangerous Doubles (Doubling Numbers)  

NSDL National Science Digital Library

This lesson teaches students to use the strategy doubling numbers and doubles plus or minus one in order to use mental math to add one digit numbers. The students are engaged in learning through the read aloud of Double the Ducks by Stephen Murphy and then get to work with a partner to draw doubles and write equations that relate to their drawings. Students individually work on solving word problems using these strategies and manipulatives as necessary to solve.

Stephanie Sharrer

2012-07-14

358

Understanding Arsenate Reaction Kinetics with Ferric Hydroxides  

PubMed Central

Understanding arsenic reactions with ferric hydroxides is important in understanding arsenic transport in the environment and in designing systems for removing arsenic from potable water. Many experimental studies have shown that the kinetics of arsenic adsorption on ferric hydroxides is biphasic, where a fraction of the arsenic adsorption occurs on a time scale of seconds while full equilibrium may require weeks to attain. This research employed density functional theory modeling in order to understand the mechanisms contributing to biphasic arsenic adsorption kinetics. The reaction energies and activation barriers for three modes of arsenate adsorption to ferric hydroxides were calculated. Gibbs free energies of reaction depended on the net charge of the complexes, which is a function of the system pH value. Physical adsorption of arsenate to ferric hydroxide proceeded with no activation barrier, with Gibbs free energies of reaction ranging from ?21 to ?58 kJ/mol. The highest Gibbs free energies of reaction for physical adsorption resulted from negative charge assisted hydrogen bonding between H atoms on the ferric hydroxide and O atoms in arsenate. The conversion of physically adsorbed arsenate into monodentate surface complexes had Gibbs free energies of activation ranging from 62 to 73 kJ/mol, and Gibbs free energies of reaction ranging from ?23 to ?38 kJ/mol. The conversion of monodentate surface complexes to bidentate, binuclear complexes had Gibbs free energies of activation ranging from 79 to 112 kJ/mol, and Gibbs free energies of reaction ranging from ?11 to ?55 kJ/mol. For release of arsenate from uncharged bidentate complexes, energies of activation as high as 167 kJ/mol were encountered. Increasingly negative charges on the complexes lowered the activation barriers for desorption of arsenate, and in complexes with ?2 charges, the highest activation barrier was 65 kJ/mol. This study shows that the slow kinetics associated with arsenic adsorption and desorption can be attributed to the high Gibbs free energies of activation for forming and breaking bonds with the ferric hydroxide. PMID:23806140

Farrell, James; Chaudhary, Binod K.

2015-01-01

359

Detoxification of endotoxin by aluminum hydroxide adjuvant  

Microsoft Academic Search

Langmuir adsorption isotherms of endotoxin and aluminum-containing adjuvants at pH 7.4 and 25°C revealed that aluminum hydroxide adjuvant has a greater adsorption capacity (283 ?g\\/mg Al) and adsorption coefficient (1.3×104 ml\\/?g) than aluminum phosphate adjuvant (3.0 ?g\\/mg Al, 0.20 ml\\/?g). The difference in endotoxin adsorption was related to two adsorption mechanisms: electrostatic attraction and covalent bonding. The isoelectric point (iep)

Yi Shi; Harm HogenEsch; Fred E. Regnier; Stanley L. Hem

2001-01-01

360

Hydrothermal crystallization of iron(III) hydroxide  

Microsoft Academic Search

The crystallization of amorphous iron(III) hydroxide during hydrothermal treatment in aqueous suspensions was studied by x-ray\\u000a diffraction and transmission electron microscopy. The results demonstrate that, by varying the hydrothermal synthesis conditions\\u000a (pH, temperature, duration, nature and amount of additives), one can control the phase composition, shape, and size of the\\u000a forming particles. Factors that increase the concentration of soluble iron(III)

V. V. Popov; A. I. Gorbunov

2006-01-01

361

Pressure-induced decomposition of indium hydroxide.  

PubMed

A static pressure-induced decomposition of indium hydroxide into metallic indium that takes place at ambient temperature is reported. The lattice parameter of c-In(OH)(3) decreased upon compression from 7.977(2) to approximately 7.45 A at 34 GPa, corresponding to a decrease in specific volume of approximately 18%. Fitting the second-order Birch-Murnaghan equation of state to the obtained compression data gave a bulk modulus of 99 +/- 3 GPa for c-In(OH)(3). The c-In(OH)(3) crystals with a size of approximately 100 nm are comminuted upon compression, as indicated by the grain-size reduction reflected in broadening of the diffraction reflections and the appearance of smaller (approximately 5 nm) incoherently oriented domains in TEM. The rapid decompression of compressed c-In(OH)(3) leads to partial decomposition of indium hydroxide into metallic indium, mainly as a result of localized stress gradients caused by relaxation of the highly disordered indium sublattice in indium hydroxide. This partial decomposition of indium hydroxide into metallic indium is irreversible, as confirmed by angle-dispersive X-ray diffraction, transmission electron microscopy imaging, Raman scattering, and FTIR spectroscopy. Recovered c-In(OH)(3) samples become completely black and nontransparent and show typical features of metals, i.e., a falling absorption in the 100-250 cm(-1) region accompanied by a featureless spectrum in the 250-2500 cm(-1) region in the Raman spectrum and Drude-like absorption of free electrons in the region of 4000-8000 cm(-1) in the FTIR spectrum. These features were not observed in the initial c-In(OH)(3), which is a typical white wide-band-gap semiconductor. PMID:20731389

Gurlo, Aleksander; Dzivenko, Dmytro; Andrade, Miria; Riedel, Ralf; Lauterbach, Stefan; Kleebe, Hans-Joachim

2010-09-15

362

Sodium hydroxide ions in the stratosphere  

Microsoft Academic Search

It is suggested that nonproton hydrate ions observed at 37 km by Arnold, Boehringer, and Henschen are protonated sodium hydroxide cluster ions of the form NaOH2(+)(H2O)n(NaOH)m. It is also suggested that n ranges from 0 to 4 while m ranges from 0 to 2. Since the NaOH believed to be formed from NaO, has a very large proton affinity, protons

Eldon E. Ferguson

1978-01-01

363

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Final technical report, September 1, 1991--August 31, 1992  

SciTech Connect

In this project, the ISGS is investigating the pelletization of fine coal with calcium hydroxide, a sulfur-capturing sorbent. The objective is to produce a readily-transportable fuel which will burn in compliance with the recently passed Clean Air Act Amendment (CAAA). To improve the economics of pelletizing, carbonation, or, the reaction of carbon dioxide with calcium hydroxide, which produces a binding matrix of calcium carbonate, is being investigated as a method of hardening pelletized coal fines. This year, pellets were produced from 28 {times} 0 coal fines collected from an Illinois preparation plant using a laboratory version of a California Pellet Mill (CPM), a commercially available pellet machine. The CPM effectively pelletized coal fines at the moisture content they were dewatered to at the plant. Carbonation nearly doubled the strength of pellets containing 10 wt % calcium hydroxide. Other results from this year`s work indicate that inclusion of calcium hydroxide into pellets resulted in chlorine capture of approximately 20 wt % for combustion tests conducted at both 850 and 1100{degrees}C. Arsenic emissions were reduced from near 38 wt% at 850 C to essentially nil with inclusion of 10 wt % calcium hydroxide into the pellets. At 110{degrees}C, arsenic emissions were reduced from about 90 wt % to about 15 wt %. Sodium emissions, however, increased with the addition of calcium hydroxide. At 850{degrees}C, sodium capture dropped from about 98 wt % to 73 wt % for pellets containing 10 wt % calcium hydroxide; at 1100{degrees}C, capture dropped from about 92 wt % to about 20 wt %.

Rapp, D.M.; Lytle, J.M.; Hackley, K.C. [Illinois State Geological Survey, Champaign, IL (United States); Strickland, R. [Tennessee Valley Authority, Muscle Shoals, AL (United States); Berger, R.; Schanche, G. [Illinois Univ., Champaign, IL (United States)

1992-12-31

364

Hydroxide catalysis bonding for astronomical instruments  

NASA Astrophysics Data System (ADS)

Hydroxide catalysis bonding (HCB) as a jointing technique has been under development for astronomical applications since ˜1998 (patented by D.-H. Gwo). It uses an aqueous hydroxide solution to form a chemical bond between oxide or oxidisable materials (e.g., SiO2, sapphire, silicon and SiC). It forms strong, extremely thin bonds, and is suitable for room temperature bonding, precision alignment, operation in ultra-low vacuum and down to temperatures of 2.5 K. It has been applied in the NASA satellite mission Gravity Probe B and in the ground-based gravitational wave (GW) detector GEO600. It will soon fly again on the ESA LISA Pathfinder mission and is currently being implemented in the Advanced LIGO and Virgo ground-based GW detectors. This technique is also of considerable interest for use in other astronomical fields and indeed more broadly, due to its desirable, and adjustable, combination of properties. This paper gives an overview of how HCB has been and can be applied in astronomical instruments, including an overview of the current literature on the properties of hydroxide catalysis bonds.

van Veggel, Anna-Maria A.; Killow, Christian J.

2014-06-01

365

Self-assembly of densely packed and aligned bilayer ZnO nanorod arrays L. Chow,1,2,a  

E-print Network

several reports of the self-assembly of ZnO nanorods on Zn­Al layered doubled hydroxide Zn1-xAlx OH 2 CO3 2- ·nH2O .15 Liu et al.16 described the synthesis of ZnO/Zn­Al layered double hydroxide LDH used aluminum-coated silicon as a substrate to synthesize hydro- talcitelike Zn­Al LDH in zinc acetate

Chow, Lee

366

Pseudo?Hydroxide Extraction in the Separation of Sodium Hydroxide from Aqueous Solutions Using Alkyl Phenols  

Microsoft Academic Search

Pseudo?hydroxide extraction of sodium hydroxide from aqueous solution using four alkyl phenols of nearly identical molecular weight in 1?octanol at 25°C was examined to understand the effect of alkyl substituents. The order of extraction strength among the four alkyl phenols tested was 4?tert?octylphenol>3,5?di?tert?butylphenol>2,4?di?tert?butylphenol>2,6?di?tert?butyl?4?methylphenol. A good correlation with phenol pKa was observed, indicating that extraction strength is determined by phenol acidity,

Bruce A. Moyer

2006-01-01

367

Initial LDH level can predict the survival benefit from bevacizumab in the first-line setting in Chinese patients with metastatic colorectal cancer  

PubMed Central

Background Markers to predict the efficacy of bevacizumab treatment have been not fully validated in most cancers, including metastatic colorectal cancer (mCRC). The aim of this study was to investigate the potential role of lactate dehydrogenase (LDH) in predicting the survival benefit from first-line bevacizumab treatment, in Chinese patients with mCRC. Methods All the patients were diagnosed with mCRC at the Sun Yat-sen University Cancer Center from 2003 to 2013. The study group and the control group were classified by receiving bevacizumab or not. The serum LDH value of all the patients had been detected before the first-line treatment. The primary end point was progression-free survival (PFS). Results The median PFS of the study and the control group (patients who received bevacizumab or not) was 11.3 and 9.1 months, respectively (P=0.004). In the control group, the median PFS of the high LDH level and the low LDH level groups was 6.9 and 10.2 months, respectively (P<0.001). However, in the study group, the corresponding median PFS was 9.9 and 11.9 months, respectively (P=0.145). In addition, for the low LDH level group, the median PFS was 11.9 and 10.2 months for patients who received bevacizumab or not, respectively (P=0.066); however, the median PFS of patients receiving bevacizumab or not was significantly different in the high LDH level group (9.9 and 6.9 months, respectively) (P=0.012). Conclusion The addition of bevacizumab in the first-line treatment setting could improve the PFS of mCRC patients notably. However, the benefit could only be potentially reflected on patients with high serum LDH level. PMID:25143746

Yin, Chenxi; Jiang, Chang; Liao, Fangxin; Rong, Yuming; Cai, Xiuyu; Guo, Guifang; Qiu, Huijuan; Chen, Xuxian; Zhang, Bei; He, Wenzhuo; Xia, Liangping

2014-01-01

368

A double mutant of highly purified Geobacillus stearothermophilus lactate dehydrogenase recognises l-mandelic acid as a substrate.  

PubMed

Lactate dehydrogenase from the thermophilic organism Geobacillus stearothermophilus (formerly Bacillus stearothermophilus) (bsLDH) has a crucial role in producing chirally pure hydroxyl compounds. ?-Hydroxy acids are used in many industrial situations, ranging from pharmaceutical to cosmetic dermatology products. One drawback of this enzyme is its limited substrate specificity. For instance, l-lactate dehydrogenase exhibits no detectable activity towards the large side chain of 2-hydroxy acid l-mandelic acid, an ?-hydroxy acid with anti-bacterial activity. Despite many attempts to engineer bsLDH to accept ?-hydroxy acid substrates, there have been no attempts to introduce the industrially important l-mandelic acid to bsLDH. Herein, we describe attempts to change the reactivity of bsLDH towards l-mandelic acid. Using the Insight II molecular modelling programme (except 'program' in computers) and protein engineering techniques, we have successfully introduced substantial mandelate dehydrogenase activity to the enzyme. Energy minimisation modelling studies suggested that two mutations, T246G and I240A, would allow the enzyme to utilise l-mandelic acid as a substrate. Genes encoding for the wild-type and mutant enzymes were constructed, and the resulting bsLDH proteins were overexpressed in Escherichia coli and purified using the TAGZyme system. Enzyme assays showed that insertion of this double mutation into highly purified bsLDH switched the substrate specificity from lactate to l-mandelic acid. PMID:23608509

Binay, Bar??; Sessions, Richard B; Karagüler, Nevin Gül

2013-05-10

369

Intramuscular Oxygen-Ozone Therapy in the Treatment of Acute Back Pain With Lumbar Disc Herniation A Multicenter, Randomized, Double-Blind, Clinical Trial of Active and Simulated Lumbar Paravertebral Injection  

Microsoft Academic Search

Study Design. Multicenter randomized, double-blind, simulated therapy-controlled trial in a cohort of patients with acute low back pain (LBP) due to lumbar disc herni- ation (LDH). Objective. To assess the benefit of intramuscular-para- vertebral injections of an oxygen-ozone (O2O3) mixture. Summary of Background Data. Recent findings have shown that O2O3 therapy can be used to treat LDH that fails to

Marco Paoloni; Angelo Cacchio; Dario Apuzzo; Salvatore Marotta; Michele Razzano; Marianno Franzini; Valter Santilli

370

Proton intercalation hysteresis in charging and discharging nickel hydroxide electrodes  

Microsoft Academic Search

A reproducible hysteresis in charge-discharge cycling of thin-film (10--40 nm thickness) electroprecipitated nickel hydroxide electrodes was quantified. Thin-film electrodes were prepared both with and without coprecipitated cobalt hydroxide, a common additive to nickel hydroxide electrodes. The ascending and descending branches of the hysteretic loop were determined. Experimental data were gathered using commonly employed techniques to capture electrode behavior on short-

Kathryn Podolske Ta; J. Newman

1999-01-01

371

Infrared band intensities in ammonium hydroxide and ammonium salts  

NASA Technical Reports Server (NTRS)

We have applied Kramers-Kronig analysis to reflection spectra to determine the optical constants of ammonium hydroxide and of aqueous solutions of ammonium chloride and bromide. From considerations of the absorption indices k(nu) we conclude that ammonium hydroxide consists of a solution of NH3 in water, in which NH3 molecules are hydrogen bonded to neighboring water molecules. The spectrum of ammonium hydroxide differs from the spectra of ammonium salts, in which bands characteristic of NH4(+) ions are prominent. The existence of ammonium hydroxide as an aerosol in planetary atmospheres is briefly discussed

Sethna, P. P.; Downing, H. D.; Pinkley, L. W.; Williams, D.

1978-01-01

372

The alpha-form of the hydroxides of bivalent metals  

NASA Technical Reports Server (NTRS)

X-ray analyses were made of the hydroxides of the bivalent metals. The freshly pptd. hydroxide is usually in the alpha-form, which on standing is converted to another form or other forms. The alpha and c grating dimensions of the alpha-form and the C6-type of Co, Zn, C, Co-Zn and Ni-Zn hydroxides are tabulated. Ni hydroxide does not exhibit an alpha-form. The alpha-Co(OH)2, the blue form, is stabilized by sugar or by the higher alcohols: these compounds do not stabilize alpha-Zn(OH)2.

Feitknecht, W.

1984-01-01

373

Microwave Spectroscopy and Molecular Structure of Isonitrosyl Hydroxide (hoon)  

NASA Astrophysics Data System (ADS)

Nitrous acid (HONO) is an important member of the atmospheric nitrogen cycle whose chemistry involves a variety of gas-phase, photochemical, and heterogeneous processes. Among its formation pathways in the atmosphere is the ternary association of hydroxyl (OH) with nitric oxide (NO), but the formation of the isonitrosyl hydroxide (HOON) isomer has largely been ignored owing to early theoretical studies that questioned its stability. Guided by new high-level ab initio calculations, we have detected the rotational spectrum of trans-HOON in an electrical discharge of a dilute mixture of NO and water vapor by a combination of Fourier transform microwave spectroscopy and double resonance methods. No evidence for the cis isomer was found in any of our spectroscopic surveys between 15.4--17.0 GHz. A semi-experimental equilibrium structure for trans-HOON has been derived to high precision from isotopic substitution (DOON, H18OON, HO18ON, HOO15N) along with zero-point vibrational corrections calculated at the CCSD(T)/aug-cc-pVTZ level of theory. Most notably, the central O--O bond in trans-HOON is found to be 1.9149 ± 0.0005 Å in length, which is the longest known O--O bond in a molecule (nearly 20% longer than the analogous bond in the HOOO radical).

Crabtree, Kyle N.; Talipov, Marat R.; O'Connor, Gerard; Martinez, Oscar, Jr.; Khursan, Sergey L.; McCarthy, Michael C.

2014-06-01

374

The role of SO42- surface distribution in arsenic removal by iron oxy-hydroxides  

NASA Astrophysics Data System (ADS)

This study investigates the contribution of chemisorbed SO42- in improving arsenic removal properties of iron oxy-hydroxides through an ion-exchange mechanism. An analytical methodology was developed for the accurate quantification of sulfate ion (SO42-) distribution onto the surface and structural compartments of iron oxy-hydroxides synthesized by FeSO4 precipitation. The procedure is based on the sequential determination of SO42- presence in the diffuse and Stern layers, and the structure of these materials as defined by the sulfate-rich environments during the reaction and the variation in acidity (pH 3-12). Physically sorbed SO42-, extracted in distilled water, and physically/chemically adsorbed ions on the oxy-hydroxide's surface leached by a 5 mM NaOH solution, were determined using ion chromatography. Total sulfate content was gravimetrically measured by precipitation as BaSO4. To validate the suggested method, results were verified by X-ray photoelectron and Fourier-transformed infrared spectroscopy. Results showed that low precipitation pH-values favor the incorporation of sulfate ions into the structure and the inner double layer, while under alkaline conditions ions shift to the diffuse layer.

Tresintsi, S.; Simeonidis, K.; Pliatsikas, N.; Vourlias, G.; Patsalas, P.; Mitrakas, M.

2014-05-01

375

40 CFR 415.310 - Applicability; description of the calcium hydroxide production subcategory.  

Code of Federal Regulations, 2012 CFR

...false Applicability; description of the calcium hydroxide production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Hydroxide Production Subcategory § 415.310 Applicability; description of the calcium hydroxide production subcategory....

2012-07-01

376

40 CFR 415.310 - Applicability; description of the calcium hydroxide production subcategory.  

Code of Federal Regulations, 2014 CFR

...true Applicability; description of the calcium hydroxide production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Hydroxide Production Subcategory § 415.310 Applicability; description of the calcium hydroxide production subcategory....

2014-07-01

377

40 CFR 415.310 - Applicability; description of the calcium hydroxide production subcategory.  

Code of Federal Regulations, 2013 CFR

...true Applicability; description of the calcium hydroxide production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Hydroxide Production Subcategory § 415.310 Applicability; description of the calcium hydroxide production subcategory....

2013-07-01

378

40 CFR 415.310 - Applicability; description of the calcium hydroxide production subcategory.  

Code of Federal Regulations, 2011 CFR

...true Applicability; description of the calcium hydroxide production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Hydroxide Production Subcategory § 415.310 Applicability; description of the calcium hydroxide production subcategory....

2011-07-01

379

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Magnesium hydroxide surface treated with substituted...Chemical Substances § 721.10573 Magnesium hydroxide surface treated with substituted...chemical substance identified generically as magnesium hydroxide surface treated with...

2013-07-01

380

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Magnesium hydroxide surface treated with substituted...Chemical Substances § 721.10573 Magnesium hydroxide surface treated with substituted...chemical substance identified generically as magnesium hydroxide surface treated with...

2014-07-01

381

40 CFR 415.310 - Applicability; description of the calcium hydroxide production subcategory.  

Code of Federal Regulations, 2010 CFR

...true Applicability; description of the calcium hydroxide production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Hydroxide Production Subcategory § 415.310 Applicability; description of the calcium hydroxide production subcategory....

2010-07-01

382

STRUCTURAL CHANGES DURING THE DECOMPOSITION OF CALCIUM HYDROXIDE  

EPA Science Inventory

The paper discusses the production of calcium hydroxides with surface areas of 6-74 sq m/g, in an attempt to develop more reactive sorbents for SO2 capture during furnace injection. It was found that adding alcohol to the water of hydration yielded hydroxides with surface areas u...

383

Astronauts Newman, Walz and Bursch change out lithium hydroxide canister  

NASA Technical Reports Server (NTRS)

Three members of the astronaut class of 1990 change out a lithium hydroxide canister beneath Discovery's middeck during STS-51 mission. Left to right are astronauts James H. Newman, Carl E. Walz and Daniel W. Bursch, all mission specialists. Note the lithium hydroxide canister floating between them.

1993-01-01

384

Standard enthalpies of formation of francium hydroxide hydrates  

Microsoft Academic Search

Available experimental data on standard enthalpies of formation of alkali metal hydroxide hydrates have been summarized. Using equations derived, the authors have calculated previously unknown enthalpies of formation of some lithium, sodium, potassium, rubidium, and cesium hydroxide hydrates. Taking into account the contribution of water to the enthalpies of formation of monohydrates, the authors have estimated the enthalpies of formation

Burylev

1995-01-01

385

ACUTE TOXICITY OF TRIPHENYLTIN HYDROXIDE TO THREE CLADOCERAN SPECIES  

EPA Science Inventory

The toxicity of an organotin pesticide, triphenyltin hydroxide, was assessed with several freshwater cladoceran species, Daphnia pulex, Daphnia magna, and Ceriodaphnia dubia were exposed for 48 h to triphenyltin hydroxide in static acute toxicity tests. Values of the 48-h trimmed...

386

Electrochemical behavior of cobalt hydroxide used as additive in the nickel hydroxide electrode  

Microsoft Academic Search

As an attempt to understand better how cobalt hydroxide additives improve the nickel electrode performance, the Co(OH)â\\/CoOOH redox system has been investigated through electrochemical cycling starting from a commercial Co(OH)â sample. A study of the influence of texture and morphology as well as cycling parameters was performed. For charge rates greater than C\\/5, relative to the amount of Co(OH)â, the

V. Pralong; A. Delahaye-Vidal; B. Beaudoin; J. B. Leriche; J. M. Tarascon

2000-01-01

387

Regulation of Metabolic Flux in Lactobacillus casei for Lactic Acid Production by Overexpressed ldhL Gene with Two-Stage Oxygen Supply Strategy.  

PubMed

This study describes a novel strategy to regulate the metabolic flux for lactic acid production in Lactobacillus casei. The ldhL gene encoding L-lactate dehydrogenase (L-LDH) was overexpressed in L. casei, and a two-stage oxygen supply strategy (TOS) that maintained a medium oxygen supply level during the early fermentation phase, and a low oxygen supply level in the later phase was carried out. As a consequence, a maximum L-LDH activity of 95.6 U/ml was obtained in the recombinant strain, which was over 4-fold higher than that of the initial strain. Under the TOS for L. casei (pMG-ldhL), the maximum lactic acid concentration of 159.6 g/l was obtained in 36 h, corresponding to a 62.8% increase. The results presented here provide a novel way to regulate the metabolic flux of L. casei for lactic acid production in different fermentation stages, which is available to enhance organic acid production in other strains. PMID:25179900

Ge, Xiang-Yang; Xu, Yan; Chen, Xiang; Zhang, Long-Yun

2015-01-28

388

New Ideas for an Old Enzyme: A Short, Question-Based Laboratory Project for the Purification and Identification of an Unknown LDH Isozyme  

ERIC Educational Resources Information Center

Enzyme purification projects are an excellent way to introduce many aspects of protein biochemistry, but can be difficult to carry out under the constraints of a typical undergraduate laboratory course. We have designed a short laboratory project for the purification and identification of an "unknown" lactate dehydrogenase (LDH) isozyme that can…

Coleman, Aaron B.

2010-01-01

389

On-chip cell lysis by local hydroxide generation.  

PubMed

We present a novel method for on-chip cell lysis based on local hydroxide electro-generation. Hydroxide ions porate the cell membrane, leading to cell lysis. After lysis occurs, hydrogen ions, also generated on chip, react with excess hydroxide, creating a neutral pH lysate and eliminating the need for a wash step. Three different cell types are shown to be effectively lysed by this method: red blood cells, HeLa (human tumor line) and Chinese Hamster Ovary (CHO) cell lines. The release of cytoplasmic molecules from HeLa and CHO cells is demonstrated by monitoring the escape of a membrane impermeant dye from the cytoplasm. In the vicinity of the cathode, the hydroxide concentration is predicted by finite element simulations and shown to fit the lysis rates at different distances from the generating cathode. For flow-through experiments, a second device integrating a mechanical filter with hydroxide generation is fabricated and tested. The purpose of the filter is to trap whole cells and only allow lysate to pass through. The flow rate dependence of hydroxide concentration at the lysis filter is modeled and lysis efficiency is experimentally determined to be proportional to the hydroxide concentration for flow rates from 15 to 30 microl min(-1). PMID:15672131

Di Carlo, Dino; Ionescu-Zanetti, Cristian; Zhang, Yolanda; Hung, Paul; Lee, Luke P

2005-02-01

390

Layered and intercalated hydrotalcite-like materials as thermal stabilizers in PVC resin  

Microsoft Academic Search

In the light of the accepted mechanism of thermal stabilization of PVC by layered double hydroxides (LDHs), the layer cations and interlayer counterions in LDHs were tailored to give MgZnAl-CO3-LDH and MgZnAl-maleate-LDH. These materials were characterized by XRD, FT-IR, and TG–DTA. The thermal stability of PVC composites containing different LDH additives was tested in sheets having a thickness of about

Yanjun Lin; Jianrong Wang; David G. Evans; Dianqing Li

2006-01-01

391

Paper microfluidic-based enzyme catalyzed double microreactor.  

PubMed

We describe a paper microfluidic-based enzyme catalyzed double microreactor assay using fluorescent detection. Here, solutions of lactate dehydrogenase (LDH) and diaphorase (DI) were directly spotted onto the microfluidic paper-based analytical device (?PAD). Samples containing lactic acid, resazurin, and nicotinamide adenine dinucleotide oxidized form (NAD(+) ), potassium chloride (KCl), and BSA, in MES buffer were separately spotted onto the ?PAD and MES buffer flowed through the device. A cascade reaction occurs upon the sample spot overlapping with LDH to form pyruvate and nicotinamide adenine dinucleotide reduced form (NADH). Subsequently, NADH is used in the conversion of resazurin to fluorescent resorufin by DI. The ?PAD avoids the need of surface functionalization or enzyme immobilization steps. These microreactor devices are low cost and easy to fabricate and effect reaction based solely on buffer capillary action. PMID:24913741

Ferrer, Ivonne M; Valadez, Hector; Estala, Lissette; Gomez, Frank A

2014-08-01

392

The highest prognostic impact of LDH among International Prognostic Indices (IPIs): an explorative study of five IPI factors among patients with DLBCL in the era of rituximab.  

PubMed

Although the International Prognostic Index (IPI) is considered as the current standard prognostication system for diffuse large B-cell lymphoma (DLBCL), prognostic heterogeneity is suggested to exist among the patients within the same IPI risk group. Hence, we investigated the pattern of distribution and prognostic impact of five IPI factors within the same IPI score. We retrospectively reviewed the medical records of 387 patients newly diagnosed as pathologically proven DLBCL between February 2002 and February 2010. We classified patients to IPI risk scores and categorized them according to the combinations of IPI. Then, we explored the frequency of five IPI factors and analyzed the correlation between these subgroups and efficacy outcomes: complete response (CR), event-free survival (EFS), and overall survival (OS). Survival estimates by IPI score in this cohort corresponded to the classic IPI. Elevated serum level of lactate dehydrogenase (LDH) was the most prevalently distributed factor throughout the scores, and patients with elevated serum level of LDH tended to have lower CR, inferior EFS, and/or OS irrespective of IPI scores. Particularly, among the subgroups of IPI score of 2, elevated serum level of LDH was significantly associated with inferior CR (73.1 vs 95.2 %), 3-year EFS (57 vs 87 %), and 3-year OS (58 vs 82 %). In addition, the higher serum level of LDH, particularly above 2,000 IU/L, was significantly correlated with the inferior survival outcomes (3-year EFS 78.0 vs 58.5 vs 45.5 vs 20.0 %, 3-year OS 86.0 vs 66.2 vs 58.2 vs 40.0 %). In conclusion, among five factors of IPI, elevated serum level of LDH seems to be the most frequently distributed and, more importantly, the most relevant IPI factor with the highest prognostic impact. These findings still warrant further validation in larger cohorts. PMID:25027115

Park, J H; Yoon, D H; Kim, D Y; Kim, S; Seo, S; Jeong, Y; Lee, S W; Park, C S; Huh, J; Suh, C

2014-10-01

393

Nickel hydroxide/cobalt-ferrite magnetic nanocatalyst for alcohol oxidation.  

PubMed

A magnetically separable, active nickel hydroxide (Brønsted base) coated nanocobalt ferrite catalyst has been developed for oxidation of alcohols. High surface area was achieved by tuning the particle size with surfactant. The surface area of 120.94 m2 g(-1) has been achieved for the coated nanocobalt ferrite. Improved catalytic activity and selectivity were obtained by synergistic effect of transition metal hydroxide (basic hydroxide) on nanocobalt ferrite. The nanocatalyst oxidizes primary and secondary alcohols efficiently (87%) to corresponding carbonyls in good yields. PMID:25075969

Bhat, Pooja B; Inam, Fawad; Bhat, Badekai Ramachandra

2014-08-11

394

Complications of sodium hydroxide chemical matrixectomy: nail dystrophy, allodynia, hyperalgesia.  

PubMed

Ingrown toenails are seen most commonly in young adults, and they can seriously affect daily life. Partial nail avulsion with chemical matrixectomy, generally by using either sodium hydroxide or phenol, is one of the most effective treatment methods. Known complications of phenol matrixectomy are unpredictable tissue damage, prolonged postoperative drainage, increased secondary infection rates, periostitis, and poor cosmetic results. To our knowledge, there have been no reports about the complications related to sodium hydroxide matrixectomy. Herein, we describe three patients who developed nail dystrophy, allodynia, and hyperalgesia after sodium hydroxide matrixectomy. PMID:25514278

Bostanc?, Seher; Koçyi?it, Pelin; Güngör, Hilayda Karakök; Parlak, Nehir

2014-11-01

395

Product development of FGD recovered magnesium hydroxide  

SciTech Connect

The ThioClear FGD processes developed by the Dravo Lime Company (DLC) produce a high brightness gypsum and magnesium hydroxide (Mg(OH){sub 2}) by-product. Both originate as white precipitates from a solution of magnesium sulfate. The use of magnesium-enhanced lime avoids the mineral impurities from direct neutralization when using pulverized limestone rock. White, pure FGD synthetic gypsum can be used to produce higher value products such as mineral fillers and industrial plasters. This paper focuses on the product development of the Mg(OH){sub 2} by-product. Commercial Mg(OH){sub 2} sells at over $200/Ton for a variety of uses, most of which is wastewater treatment and a feedstock to make magnesium chemicals and refractories. Beneficial uses in the power plant are pH control of acidic coal pile stormwater runoff and bottom ash quench water. A future use being explored is injection into coal fired boilers to neutralize sulfur trioxide (SO{sub 3}) to prevent stack gas opacity related emission problems and minimize air preheater corrosion and fouling. The objective of this project is to improve the purity and solids content of the by-product after it is separated from the gypsum. Several options were investigated to convert it into a more marketable or usable form. Test results and economic evaluations are reported during the different process steps needed to improve the product quality: (1) dissolving or washing out the gypsum impurity; (2) thickening the washed solids and using the overflow for makeup water within the FGD water balance; (3) finding the best means to dewater the washed, thickened slurry; and (4) repulp the dewatered cake into a stabilized slurry or dry it to powder. Flash drying the dewatered cake is compared to spray drying the thickened slurry. FGD Mg(OH){sub 2} is shown to have equal reactivity as an acid neutralization reagent on a Mg(OH){sub 2} molar basis to commercial Mg(OH){sub 2} products and other alkaline reagents. Its use for pH control in wastewater treatment is shown to produce a much smaller sludge volume than lime or sodium hydroxide.

Beeghly, J.H.; Babu, M.; Smith, K.J.

1999-07-01

396

Conversion coatings prepared or treated with calcium hydroxide solutions  

NASA Technical Reports Server (NTRS)

A conversion coating process that forms a stable and corrosion-resistant oxide layer on metal or metal oxide substrates or layers. Particularly, the conversion coating process involves contacting the metal or metal oxide substrate or layer with the aqueous calcium hydroxide solutions in order to convert the surface of the substrate to a stable metal oxide layer or coating. According to the present invention, the calcium hydroxide solution is prepared by removing carbon dioxide from water or an aqueous solution before introducing the calcium hydroxide. In this manner, formation of calcium carbonate particles is avoided and the porosity of the conversion coating produced by the calcium hydroxide solution is reduced to below about 1%.

Minevski, Zoran (Inventor); Clarke, Eric (Inventor); Maxey, Jason (Inventor); Nelson, Carl (Inventor); Eylem, Cahit (Inventor)

2002-01-01

397

68. INTERIOR VIEW LOOKING OF THE CAUSTIC SODA (SODIUM HYDROXIDE) ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

68. INTERIOR VIEW LOOKING OF THE CAUSTIC SODA (SODIUM HYDROXIDE) BUILDING, LOOKING AT CAUSTIC SODA MEASURING TANKS. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

398

The natural occurrence of hydroxide in olivine  

NASA Astrophysics Data System (ADS)

Polarized infrared (IR) spectra of olivine single crystals from 17 different localities show a tremendous variability in both mode and abundance of hydroxide (OH) incorporation. Kimberlitic olivines contain the most total OH at an estimated concentration level of 976 H/106Si, whereas olivines from basalts contain the least at 3 H/106Si. Olivines of metamorphic and hydrothermal origin have widely varying concentration levels intermediate between those of basalts and kimberlites. Over 30 distinct OH absorption bands have been identified. Most of these bands are not unique to individual localities but may be found in samples from several different localities. Pleochroism is consistent among localities, but relative band intensities vary. No evidence is found for molecular H2 in olivine. Hydrous minerals have been identified in olivine by their characteristic OH absorption bands. Serpentine is commonly found and is clearly distinguishable from intrinsic OH. Talc is present in one sample. Prominent OH bands at 3572 and 3525 cm-1 are attributed to humite group minerals. San Carlos, Arizona, olivines annealed in the presence of H2O develop absorption bands which are found in natural samples, however the OH absorption spectra of these annealed olivines are not identical to those of any single natural crystal. Sharp-band OH abundances in annealed samples are an order of magnitude lower than the maximum measured in natural specimens. The mechanical properties determined from these annealed olivines may not be directly applicable to mantle olivine because both the OH sites and concentrations are different.

Miller, Gregory H.; Rossman, George R.; Harlow, George E.

1987-09-01

399

Sodium Hydroxide Extraction From Caustic Leaching Solutions  

SciTech Connect

This report describes experiments conducted to demonstrate the proof-of-principle of a method to recover NaOH from Hanford tank sludge leaching solutions. Aqueous solutions generated from leaching actual Hanford tank waste solids were used. The process involves neutralization of a lipophilic weak acid (t-octylphenol was used in these experiments) by reaction with NaOH in the aqueous phase. This results in the transfer of Na into the organic phase. Contacting with water reverses this process, reprotonating the lipophilic weak acid and transferring Na back into the aqueous phase as NaOH. The work described here confirms the potential application of solvent extraction to recover and recycle NaOH from solutions generated by leaching Hanford tank sludges. Solutions obtained by leaching sludges from tanks S-110 and T-110 were used in this work. It was demonstrated that Na+ is transferred from caustic leaching solution to the organic phase when contacted with t-octylphenol solutions. This was accompanied by a concomitant decrease in the aqueous-phase hydroxide ion concentration. Seventy to 80 % of the extracted Na was recovered by 3 to 4 sequential contacts of the organic phase with water. Cesium was co-extracted by the procedure, but Al and Cr remained in the feed stream.

Lumetta, Gregg J.; Garza, Priscilla A.; Levitskaia, Tatiana G.; Brown, Gilbert M.

2002-09-18

400

Electrochemical Recovery of Sodium Hydroxide from Alkaline Salt Solution  

Microsoft Academic Search

A statistically designed set of tests determined the effects of current density, temperature, and the concentrations of nitrate\\/nitrite, hydroxide and aluminate on the recovery of sodium as sodium hydroxide (caustic) from solutions simulating those produced from the Savannah River Site (SRS) In-Tank Precipitation process. These tests included low nitrate and nitrite concentrations which would be produced by electrolytic nitrate\\/nitrite destruction.

D. T. Hobbs; T. B. Edwards

1996-01-01

401

Solvent and process for recovery of hydroxide from aqueous mixtures  

DOEpatents

Hydroxide values and associated alkali metal may be recovered from alkaline aqueous solutions using classes of fluorinated alcohols in a water immiscible solvent. The alcohols are characterized by fluorine substituents which are proximal to the acidic alcohol protons and are located to adjust the acidity of the extractant and the solubility of the extractant in the solvent. A method for stripping the extractant and solvent to regenerate the extractant and purified aqueous hydroxide solution is described.

Moyer, Bruce A. (Oak Ridge, TN); Chambliss, C. Kevin (Macon, GA); Bonnesen, Peter V. (Knoxville, TN); Keever, Tamara J. (Oak Ridge, TN)

2001-01-01

402

Intrinsic hydration of monopositive uranyl hydroxide, nitrate, and acetate cations  

Microsoft Academic Search

The intrinsic hydration of three monopositive uranyl-anion complexes (UO2A)+ (where A = acetate, nitrate, or hydroxide) was investigated using ion-trap mass spectrometry (IT-MS). The relative rates\\u000a for the formation of the monohydrates [(UO2A)(H2O)]+, with respect to the anion, followed the trend: Acetate ? nitrate ? hydroxide. This finding was rationalized in terms of\\u000a the donation of electron density by the

Winnie Chien; Victor Anbalagan; Melvin Zandler; Michael Van Stipdonk; Dorothy Hanna; Garold Gresham; Gary Groenewold

2004-01-01

403

Hot-molding of stabilized zirconia produced by hydroxide coprecipitation  

Microsoft Academic Search

Conclusions An investigation was carried out of the apparent density, open porosity, crystalline structure and electrical conductance of specimens produced by hot-molding from powders of ZrO2 + Sc2O3. The compounds were mixed by coprecipitating their hydroxides. An analysis was made of the effect of the temperature of the preliminary heat treatment of the mixture of hydroxides, of activating additives, and

A. S. Lipilin; A. D. Neuimin; S. F. Pal'guev; F. Ya. Gul'bis

1974-01-01

404

Diffusion extraction of rapeseed glucosinolates with ethanolic sodium hydroxide  

Microsoft Academic Search

Glucosinolates are readily diffused from whole rapeseed by repeated extractions with ethanolic sodium hydroxide. Four 2 hr\\u000a extractions or six 1 hr extractions were most efficient for the diffusion of glucosinolates with minimum losses of other seed\\u000a constituents. The ethanolic sodium hydroxide treatment inhibited myrosinase activity and lowered sulfur concentration in the\\u000a oil. The oil from treated seed gave a

R. S. Bhatty; F. W. Sosulski

1972-01-01

405

Physical and electrochemical characteristics of nanostructured nickel hydroxide powder  

Microsoft Academic Search

Nanostructured nickel hydroxide powder has been synthesized by a chemical precipitation method with the aid of ultrasound radiation, and the physical properties of the synthesized material were characterized by scanning electron microscopy, specific surface area, X-ray diffraction and differential scanning calorimetry. It was found that nanostructured nickel hydroxide was crystalline ß-Ni(OH)2 with a nanocrystalline and nanoporous surface structure. The crystallite

Q. S. Song; Y. Y. Li; S. L. I. Chan

2005-01-01

406

Proton intercalation hysteresis in charging and discharging nickel hydroxide electrodes  

SciTech Connect

A reproducible hysteresis in charge-discharge cycling of thin-film (10--40 nm thickness) electroprecipitated nickel hydroxide electrodes was quantified. Thin-film electrodes were prepared both with and without coprecipitated cobalt hydroxide, a common additive to nickel hydroxide electrodes. The ascending and descending branches of the hysteretic loop were determined. Experimental data were gathered using commonly employed techniques to capture electrode behavior on short- and long-time scales. Cyclic voltammetry and galvanostatic discharge experiments were performed, and a macroscopic model of the nickel hydroxide solid material was constructed and used to interpret the simultaneous mass-transfer, kinetic, and thermodynamic phenomena occurring at the nickel hydroxide intercalation electrode. The persistent hysteresis exhibited by these thin-film electrodes cannot be due only to solid-state mass-transfer limitations. Agreement between calculated and experimental results is achieved with treatment of the hysteresis effect as a permanent, thermodynamic quantity. The numerical model may be applied to most rechargeable cells and is especially suited for systems which exhibit a permanent hysteretic loop or in which side reactions are prevalent. Model results agree with current and potential waveforms gathered from experiments performed with nickel hydroxide thin-film electrodes.

Ta, K.P.; Newman, J.

1999-08-01

407

High glutamate attenuates S100B and LDH outputs from rat cortical slices enhanced by either oxygen-glucose deprivation or menadione.  

PubMed

One hour incubation of rat cortical slices in a medium without oxygen and glucose (oxygen-glucose deprivation, OGD) increased S100B release to 6.53 ± 0.3 ng/ml/mg protein from its control value of 3.61 ± 0.2 ng/ml/mg protein. When these slices were then transferred to a medium containing oxygen and glucose (reoxygenation, REO), S100B release rose to 344 % of its control value. REO also caused 192 % increase in lactate dehydrogenase (LDH) leakage. Glutamate added at millimolar concentration into the medium decreased OGD or REO-induced S100B release and REO-induced LDH leakage. Alpha-ketoglutarate, a metabolic product of glutamate, was found to be as effective as glutamate in decreasing the S100B and LDH outputs. Similarly lactate, 2-ketobutyrate and ethyl pyruvate, a lipophilic derivative of pyruvate, also exerted a glutamate-like effect on S100B and LDH outputs. Preincubation with menadione, which produces H2O2 intracellularly, significantly increased S100B and LDH levels in normoxic medium. All drugs tested in the present study, with the exception of pyruvate, showed a complete protection against menadione preincubation. Additionally, each OGD-REO, menadione or H2O2-induced mitochondrial energy impairments determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining and OGD-REO or menadione-induced increases in reactive oxygen substances (ROS) determined by 2,7-dichlorofluorescin diacetate (DCFH-DA) were also recovered by glutamate. Interestingly, H2O2-induced increase in fluorescence intensity derived from DCFH-DA in a slice-free physiological medium was attenuated significantly by glutamate and alpha-keto acids. All these drug actions support the conclusion that high glutamate, such as alpha-ketoglutarate and other keto acids, protects the slices against OGD- and REO-induced S100B and LDH outputs probably by scavenging ROS in addition to its energy substrate metabolite property. PMID:24710790

Demircan, Celaleddin; Gül, Zülfiye; Büyükuysal, R Levent

2014-07-01

408

Thermodynamic Properties of Alkali Metal Hydroxides. Part II. Potassium, Rubidium, and Cesium Hydroxides  

SciTech Connect

The data on thermodynamic and molecular properties of the potassium, rubidium and cesium hydroxides have been collected, critically reviewed, analyzed, and evaluated. Tables of the thermodynamic properties [C{sub p}{sup {circ}}, {Phi}{degree}={minus}(G{degree}{minus}H{degree}(0)/T, S{degree}, H{degree}{minus}H{degree}(0), {Delta}{sub f}H{degree}, {Delta}{sub f}G{degree})] of these hydroxides in the condensed and gaseous states have been calculated using the results of the analysis and some estimated values. The recommendations are compared with earlier evaluations given in the JANAF Thermochemical Tables and Thermodynamic Properties of Individual Substances. The properties considered are: the temperature and enthalpy of phase transitions and fusion, heat capacities, spectroscopic data, structures, bond energies, and enthalpies of formation at 298.15 K. The thermodynamic functions in solid, liquid, and gaseous states are calculated from T=0 to 2000 K for substances in condensed phase and up to 6000 K for gases. {copyright} {ital 1997 American Institute of Physics and American Chemical Society.}

Gurvich, L.V.; Bergman, G.A.; Gorokhov, L.N.; Iorish, V.S.; Leonidov, V.Y.; Yungman, V.S. [Thermocenter of the Russian Academy of Sciences, Izhorskaya st. 13/19, IVTAN, Moscow 127412 (Russia)

1997-07-01

409

Pseudo-hydroxide extraction in the separation of sodium hydroxide from aqueous solutions using alkyl phenols  

SciTech Connect

Pseudo-hydroxide extraction of sodium hydroxide from aqueous solution using four alkyl phenols of nearly identical molecular weight in 1-octanol at 25 degrees C was examined to understand the effect of alkyl substituents. The order of extraction strength among the four alkyl phenols tested was 4-tert-octylphenol. 3,5-di-tertbutylphenol. 2,4-di-tert-butylphenol. 2,6-di-tert-butyl-4-methylphenol. A good correlation with phenol pK(a) was observed, indicating that extraction strength is determined by phenol acidity, as modified by steric effects in proximity to the phenol - OH group. The effective partition ratios (P-eff) of two phenols from 1 M NaOH solution were determined, showing that the phenols remain predominantly in the 1-octanol phase even when converted to their sodium salts. However, the hydrophobicity of the tested phenols may not be sufficient for process purposes. The equilibrium constants for the governing extraction equilibria were determined by modeling the data using the program SXLSQI, supporting the cation-exchange extraction mechanism. The proposed mechanism consists of two simple sets of equilibria for a. Ion-pair extraction to give Na+OH- ion pairs and corresponding free ions in 1-octanol the phase and b. Cation exchange by monomeric phenol molecules (HAs) to form monomeric organic-phase Na(+)A(-) ion pairs and corresponding free organic-phase ions.

Kang, Hyun Ah [ORNL] [ORNL; Moyer, Bruce A [ORNL] [ORNL

2006-01-01

410

Form and stability of aluminum hydroxide complexes in dilute solution  

USGS Publications Warehouse

Laboratory studies of solutions 4.53 x 10 -4 to 4.5 x 10 -5 molal (12.2-1.2 ppm) in aluminum, in 0.01 molal sodium perchlorate, were conducted to obtain information as to the probable behavior of aluminum in natural water. When the solutions were brought to pH 7.5-9.5 and allowed to stand for 24 hours, a precipitate was obtained which was virtually amorphous as shown by X-rays, and which had a solubility equivalent to that of boehmite. This precipitate had a hydrolysis constant (*Ks4) of 1.93 x 10 -13a. When solutions were allowed to stead at this pH range for 10 days, their precipitates gave the X-ray pattern of bayerite (*Ks4 = 1.11 > (10- 4). These hydrolysis constants were obtained at 25?C. and corrected to zero ionic strength and are in close agreement with other published values. The predominant dissolved form in this pH range is Al(OH) -4. Below neutral pH (7.0) the dissolved aluminum species consist of octahedral units in which each aluminum ion is surrounded by six water molecules or hydroxide ions. Single units such as Al(OH2)6 + 3 and AlOH(OH2)5+2 are most abundant below pH 5.0, and where the molar ratio (r) of combined hydroxide to total dissolved aluminum is low. When r is greater than 1.0, polymerization of the octahedral units occurs. When r is between 2.0 and 3.0, solutions aged for 10 days or more contained colloidal particles between 0.10 and 0.45 ? in diameter. Particles whose diameters were greater than 0.10 ? were identified by X-ray diffraction as gibbsite. Particles smaller than 0.10 ? were also present and were shown by means of the electron microscope to have a hexagonal crystal pattern. Structured material consisting of sheets of coalesced six-membered rings of aluminum ions held together by double OH bridges has a distinctive kinetic behavior. This property was used to determine amounts of polymerized material in solutions having r between 1.0 and 3.0 after aging times ranging from a few hours to more than 4 months. Aging increased the size and orderliness of the polymeric aggregates and was accompanied by a decrease in the pH of the solution. The kinetic experiments and stoichiometric data for solutions aged for long periods provided a means of determining activities of polymerized aluminum. From these values the solubility product for microcrystalline gibbsite was determined to be 2.24 x 10 -3, and its free energy of formation, -? 272.3 0.4 kcal per mole. Where polymerization was observed, the process did not stop with small polynuclear complexes containing a few aluminum ions, but proceeded with aging until macromolecules or colloidal-sized particles were formed.

Hem, John David; Roberson, Charles Elmer

1967-01-01

411

Comparative characterization of a temperature responsive gene (lactate dehydrogenase-B, ldh-b) in two congeneric tropical fish, Lates calcarifer and Lates niloticus  

PubMed Central

The characterization of candidate loci is a critical step in obtaining insight into adaptation and acclimation of organisms. In this study of two non-model tropical (to sub-tropical) congeneric perciformes (Lates calcarifer and Lates niloticus) we characterized both coding and non-coding regions of lactate dehydrogenase-B (ldh-b), a locus which exhibits temperature-adaptive differences among temperate and sub-tropical populations of the North American killifish Fundulus heteroclitus. Ldh-b was 5,004 and 3,527 bp in length in L. calcarifer and L. niloticus, respectively, with coding regions comprising 1,005 bp in both species. A high level of sequence homology existed between species for both coding and non-coding regions of ldh-b (> 97% homology), corresponding to a 98.5% amino acid sequence homology. All six known functional sites within the encoded protein sequence (LDH-B) were conserved between the two Lates species. Ten simple sequence repeat (SSR) motifs (mono-, di-, tri- and tetranucleotide) and thirty putative microRNA elements (miRNAs) were identified within introns 1, 2, 5 and 6 of both Lates species. Five single nucleotide polymorphisms (SNPs) were also identified within miRNA containing intron regions. Such SNPs are implicated in several complex human conditions and/or diseases (as demonstrated by extensive genome-wide association studies). This novel characterization serves as a platform to further examine how non-model species may respond to changes in their native temperatures, which are expected to increase by up to 6°C over the next century. PMID:19787021

Edmunds, Richard C.; van Herwerden, Lynne; Smith-Keune, Carolyn; Jerry, Dean R.

2009-01-01

412

A Simple Protocol for Using a LDH-Based Cytotoxicity Assay to Assess the Effects of Death and Growth Inhibition at the Same Time  

PubMed Central

Analyzing the effects on cell growth inhibition and/or cell death has been an important component of biological research. The MTS assay and LDH-based cytotoxicity assays are two of the most commonly used methods for this purpose. However, data here showed that MTS cell proliferation assay could not distinguish the effects of cell death or cell growth inhibition. In addition, the original LDH-based cytotoxicity protocol grossly underestimated the proportion of dead cells in conditions with growth inhibition. To overcome the limitation, we present here a simple modified LDH-based cytotoxicity protocol by adding additional condition-specific controls. This modified protocol thus can provide more accurate measurement of killing effects in addition to the measurement of overall effects, especially in conditions with growth inhibition. In summary, we present here a simple, modified cytotoxicity assay, which can determine the overall effects, percentage of cell killing and growth inhibition in one 96-well based assay. This is a viable option for primary screening for many laboratories, and could be adapted for high throughput screening. PMID:22125603

Smith, Shilo M.; Wunder, Michael B.

2011-01-01

413

Toxicity of triphenyltin hydroxide to fish.  

PubMed

Triphenyltin (TPhT) is used worldwide in pesticide formulas for agriculture. Toxic effects of this compound to aquatic life have been reported; however, the biochemical response of fish exposed to different concentrations of TPhT hydroxide (TPhTH) was investigated for the first time in this study. The lethal concentration (LC50) of TPhTH to silver catfish, Rhamdia quelen, was calculated from an acute-exposure experiment (96 h). In addition, acethylcholinesterase (AChE) activity in brain and muscle-as well as glucose, glycogen, lactate, total protein, ammonia, and free amino acids in liver and muscle-were evaluated in a chronic-exposure experiment (15-day exposure). Speciation analysis of tin (Sn) was performed in fish tissues at the end of both experiments using gas chromatography coupled to a pulsed-flame photometric detector (GC-PFPD). Concentrations of TPhT, diphenyltin, and monophenyltin (reported as Sn) were lower than limits of quantification (10? criteria). Waterborne TPhTH concentration used through the experiment was also evaluated by GC-PFPD, and no degradation of this species was observed. The LC50 value for silver catfish juveniles was 9.73 ?g L(-1) (as Sn). Decreased brain and muscle AChE activities were observed in fish exposed to TPhTH in relation to unexposed fish (control). Liver glycogen and lactate levels were significantly higher in fish kept at the highest waterborne TPhTH concentration compared with the control. Liver and muscle glucose levels of fish exposed to all TPhTH concentrations were significantly lower than those of control fish. Silver catfish exposed to all TPhTH concentrations showed lower total protein values and higher total free amino acids levels in liver and muscle compared with controls. Total ammonia levels in liver and muscle were significantly higher for the highest TPhTH concentration compared with controls. In conclusion, TPhTH caused metabolic alterations in silver catfish juveniles, and the analyzed parameters can also be used as bioindicators for TPhTH contamination. PMID:23929383

Antes, Fabiane G; Becker, Alexssandro G; Parodi, Thaylise V; Clasen, Barbara; Lópes, Thais; Loro, Vania L; Baldisserotto, Bernardo; Flores, Erico M M; Dressler, Valderi L

2013-11-01

414

Quaternized graphene oxide nanocomposites as fast hydroxide conductors.  

PubMed

Nanocomposites play a key role in performance improvements of hydroxide conductors employed in a wide range of alkaline-electrochemical systems such as fuel cells and metal-air batteries. Graphene oxide (GO) nanosheets are considered to be outstanding nanofillers for polymeric nanocomposites on account of their excellent physicochemical strength and electrochemical properties. In this work, a fast hydroxide conductor was developed on the basis of a chemically modified GO nanocomposite membrane. The high surface area of GO was functionalized with highly stable hydroxide-conductive groups using a dimethyloctadecyl [3-(trimethoxysilyl)propyl]ammonium chloride (DMAOP) precursor, named QAFGO, and then composed with porous polybenzimidazole PBI (pPBI) as a well-suited polymeric backbone. The nanocomposite exhibited outstanding hydroxide conductivity of 0.085 S cm(-1), high physicochemical strength, and electrochemical stability for 21 days. An alkaline fuel cell (AFC) setup was fabricated to determine the functionality of QAFGO/pPBI nanocomposite in an alkaline-based system. The high AFC performance with peak power density of 86.68 mW cm(-2) demonstrated that QAFGO/pPBI nanocomposite membrane has promising potential to be employed as a reliable hydroxide conductor for electrochemical systems working in alkaline conditions. PMID:25644712

Zarrin, Hadis; Fu, Jing; Jiang, Gaopeng; Yoo, Skylar; Lenos, Jared; Fowler, Michael; Chen, Zhongwei

2015-02-24

415

ALUMINUM REMOVAL AND SODIUM HYDROXIDE REGENERATION FROM HANFORD TANK WASTE BY LITHIUM HYDROTALCITE PRECIPITATION SUMMARY OF PRIOR LAB-SCALE TESTING  

SciTech Connect

Scoping laboratory scale tests were performed at the Chemical Engineering Department of the Georgia Institute of Technology (Georgia Tech), and the Hanford 222-S Laboratory, involving double-shell tank (DST) and single-shell tank (SST) Hanford waste simulants. These tests established the viability of the Lithium Hydrotalcite precipitation process as a solution to remove aluminum and recycle sodium hydroxide from the Hanford tank waste, and set the basis of a validation test campaign to demonstrate a Technology Readiness Level of 3.

SAMS TL; GUILLOT S

2011-01-27

416

Standard enthalpies of formation of francium hydroxide hydrates  

SciTech Connect

Available experimental data on standard enthalpies of formation of alkali metal hydroxide hydrates have been summarized. Using equations derived, the authors have calculated previously unknown enthalpies of formation of some lithium, sodium, potassium, rubidium, and cesium hydroxide hydrates. Taking into account the contribution of water to the enthalpies of formation of monohydrates, the authors have estimated the enthalpies of formation of francium hydroxide hydrates FrOH{center_dot}H{sub 2}O, FrOH{center_dot}2H{sub 2}O, and FrOH{center_dot}3H{sub 2}O (-745.8, -1085.8, and -1515.8 kJ mol{sup -1}, respectively).

Burylev, B.P.

1995-03-01

417

Synthesis, characterization and application of two-dimensional layered metal hydroxides for environmental remediation purposes  

NASA Astrophysics Data System (ADS)

Two-dimensional layered nano composites, which include layered double hydroxides (LDHs), hydroxy double salts (HDSs) and layered hydroxide salts (LHSs) are able to intercalate different molecular species within their gallery space. These materials have a tunable structural composition which has made them applicable as fire retardants, adsorbents, catalysts, catalyst support materials, and ion exchangers. Thermal treatment of these materials resul