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Double Hydroxides (double + hydroxide)
Kinds of Double Hydroxides Selected AbstractsTris(8-hydroxyquinoline-5-sulfonate)aluminum Intercalated Mg,Al Layered Double Hydroxide with Blue Luminescence by Hydrothermal SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Shuangde Li Abstract Blue luminescent hybrid materials (DDS,AQS(x%)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3,) and dodecyl sulfonate (DDS,) with different molar ratios into Mg,Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450,470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS,AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan,blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host,guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac -AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic,organic hybrid photofunctional material. [source] ChemInform Abstract: Electrochemical Synthesis of Zn,Al Layered Double Hydroxide (LDH) Films.CHEMINFORM, Issue 41 2008Matthew S. Yarger Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Electrochemical Study of Anionic Ferrocene Derivatives Intercalated in Layered Double Hydroxides: Application to Glucose Amperometric BiosensorsELECTROANALYSIS, Issue 3-5 2009Christine Mousty Abstract Layered double hydroxides (Zn2Cr(OH)6X,nH2O LDH) containing (3-sulfopropyl)ferrocene-carboxylate (FcPSO3) and 1,1,-bis(3-sulfopropyl)ferrocene-carboxylate (Fc(PSO3)2) as interlayer anions (X) have been prepared by the co-precipitation method and characterized by PXRD, FTIR, SEM and XPS. The electrochemical behavior of these hybrid materials has been evaluated by cyclic voltammetry. A new amperometric biosensor based on the immobilization of glucose oxidase in ZnCr-FcPSO3 hybrid material was presented, the intercalated anions playing the role of mediators that shuttle electrons between the FAD centers in the enzyme and the electrode surface. The performance of the resulting biosensor for glucose determination under anaerobic conditions was evaluated by chronoamperometry at 0.5,V. The sensitivity (65,mA M,1 cm,2) determined in the concentration range 10,25,,M is higher than sensitivities reported for other glucose biosensors based on LDH host matrices. [source] Luminescent Polyoxotungstoeuropate Anion-Pillared Layered Double HydroxidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Filipa L. Sousa Abstract Novel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn,Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9,, [Eu(BW11O39)(H2O)3]6, and [Eu(PW11O39)2]11,. The host,guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analysis, powder X-ray diffraction (XRD), infra-red (IR) and Raman spectroscopy, solid state magic-angle spinning (MAS) 11B and 31P NMR spectroscopy, and photoluminescence spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Carbon Nanotube Composites: Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Mater. On page 677, M. Q. Zhao et al. report the fabrication of a hierarchical composite combining one-dimensional single/double walled carbon nanotubes (CNTs) and two-dimensional flakes through direct carbon deposition on layered double hydroxides. The composites can be easily transformed into continuously interlinked CNT layers alternating with calcined lamellar flakes structure. They are found to have the potential for applications in a number or areas, including as an excellent filler for strong polyimide film. [source] Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double HydroxidesADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Meng-Qiang Zhao Three-dimensional hierarchical nanocomposites consisting of one-dimensional carbon nanotubes (CNTs) and two-dimensional lamellar flakes (such as clay, layered double hydroxides) show unexpected properties for unique applications. To achieve a well-designed structure with a specific function, the uniform distribution of CNTs into the used matrix is a key issue. Here, it is shown that a hierarchical composite of single/double-walled CNTs interlinked with two-dimensional flakes can be constructed via in-situ CNT growth onto layered double hydroxide (LDH) flakes. Both the wall number and diameter of the CNTs and the composition of the flakes can be easily tuned by changing the proportion of the transition metal in the LDH flakes. Furthermore, a structure with continuously interlinked CNT layers alternating with lamellar flakes is obtained after compression. The hierarchical composite is demonstrated to be an excellent filler for strong polyimide films. This study indicates that LDH is an extraordinary catalyst for the fabrication of hierarchical composites with high-quality single/double-walled CNTs. The as-obtained CNTs/calcined LDHs nanocomposite is a novel structural platform for the design of mechanically robust materials, catalysts, ion-transportation, energy-conversion, and other applications. [source] Erasable Nanoporous Antireflection Coatings Based on the Reconstruction Effect of Layered Double Hydroxides,ANGEWANDTE CHEMIE, Issue 12 2010Jingbin Han Auf Wunsch Entspiegelung: Die Entspiegelungseigenschaften eines nanoporösen Überzugs, der aus Nanopartikel aus einem schichtförmigen Doppelhydroxid und Polyanionen aufgebaut wurde, ändern sich reversibel beim Schalten zwischen porösem und nichtporösem Zustand durch Kalzinieren und Rehydratisieren. [source] Luminescent Polyoxotungstoeuropate Anion-Pillared Layered Double Hydroxides.CHEMINFORM, Issue 19 2006Filipa L. Sousa Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] ChemInform Abstract: Use of WO2- 4 on Layered Double Hydroxides for Mild Oxidative Bromination and Bromide-Assisted Epoxidation with H2O2.CHEMINFORM, Issue 1 2002Bert F. Sels Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] The Effect of Trivalent Cations on the Performance of Mg-M-CO3 Layered Double Hydroxides for High-Temperature CO2 CaptureCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2010Qiang Wang Dr. Abstract The effect of trivalent cations on the performance of Mg-M-CO3 (M=Al, Fe, Ga, Mn) layered double hydroxides (LDHs) for high-temperature CO2 capture is systematically investigated for the first time. We demonstrate that the M3+ determines the structure evolution of LDH derivatives under thermal treatment, and finally influences the CO2 capture capacity. Very different calcination temperatures are required for the different LDHs to obtain their maximum CO2 capture capacities. To have a clear understanding of the reason behind these big differences the physicochemical properties, thermal stability, and memory effect of the LDHs were investigated. Both the thermal stability and the memory effect of LDHs are greatly influenced by the type of trivalent cation. The CO2 capture capacities were also evaluated under various conditions. Another important finding of this work is that the quasi-amorphous phase obtained by thermal treatment at the lowest possible temperature gives the highest CO2 capture capacity. [source] Sorption Removal of Pb(II) from Solution by Uncalcined and Calcined MgAl-Layered Double HydroxidesCHINESE JOURNAL OF CHEMISTRY, Issue 10 2007Shu-Qin ZHANG Abstract Layered double hydroxide (LDH) with a Mg/Al molar ratio of 1:1 was synthesized by using a co-precipitation method and its calcined product (CLDH) was obtained by calcination of the MgAl-LDH at 500 °C. The sorption removal of Pb2+ from solution was investigated, finding that both LDH and CLDH show good sorption ability and they could be used as a new type of environmental sorbent for the removal of Pb2+ from water. The sorption kinetics and the sorption isotherms of Pb2+ on both LDH and CLDH can be described by the pseudo-second order kinetics and Freundlich isotherm, respectively, under the studied conditions. The sorption amounts of Pb2+ on LDH and CLDH are independent of pH in a pH range of about 3,10. The presence of NaNO3 may inhibit the sorption ofPb2+ on LDH while hardly affect that on CLDH. The sorption mechanism of Pb2+ on LDH and CLDH may be attributed to the surface precipitation and the surface complex adsorption. The surface complex adsorption may be further distinguished to the chemical binding adsorption forming the inner-sphere surface complexes and the electrostatic binding adsorption forming the outer-sphere surface complexes. The sorption mechanism of Pb2+ on LDH may be attributed to the surface precipitation and the electrostatic binding adsorption, while that on CLDH may be attributed to the surface precipitation and the chemical binding adsorption. [source] Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double HydroxidesADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Meng-Qiang Zhao Three-dimensional hierarchical nanocomposites consisting of one-dimensional carbon nanotubes (CNTs) and two-dimensional lamellar flakes (such as clay, layered double hydroxides) show unexpected properties for unique applications. To achieve a well-designed structure with a specific function, the uniform distribution of CNTs into the used matrix is a key issue. Here, it is shown that a hierarchical composite of single/double-walled CNTs interlinked with two-dimensional flakes can be constructed via in-situ CNT growth onto layered double hydroxide (LDH) flakes. Both the wall number and diameter of the CNTs and the composition of the flakes can be easily tuned by changing the proportion of the transition metal in the LDH flakes. Furthermore, a structure with continuously interlinked CNT layers alternating with lamellar flakes is obtained after compression. The hierarchical composite is demonstrated to be an excellent filler for strong polyimide films. This study indicates that LDH is an extraordinary catalyst for the fabrication of hierarchical composites with high-quality single/double-walled CNTs. The as-obtained CNTs/calcined LDHs nanocomposite is a novel structural platform for the design of mechanically robust materials, catalysts, ion-transportation, energy-conversion, and other applications. [source] Inorganic Drug-Delivery Nanovehicle Conjugated with Cancer-Cell-Specific LigandADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Jae-Min Oh Abstract The surface of layered double hydroxide nanoparticles, a potential drug-delivery nanovehicle, is modified with the cancer-cell-specific ligand, folic acid. The surface modification is successfully accomplished through step-by-step coupling reactions with aminopropyltriethoxysilane and 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide. In order to evaluate the cancer-cell targeting effect of folic-acid-grafted layered double hydroxide utilizing fluorescence-related assay, both layered double hydroxide with and without folic acid moiety are labeled with fluorescein 5,-isothiocyanate. The uptake of layered double hydroxide and folic acid conjugated into KB and A549 cells is visualized using fluorescence microscopy and measured by flow cytometry. Both chemical and biological assay results demonstrate that the folic acid molecules are indeed conjugated to the surface of layered double hydroxide and thus the selectivity of nanovehicles to cancer cells overexpressing folate receptors increases. In this study, it is suggested that layered double hydroxide nanoparticles can be used as drug-delivery carriers with a targeting function due to the chemical conjugation with specific ligand. [source] Novel Multi-functional Mixed-oxide Catalysts for Effective NOx Capture, Decomposition, and Reduction,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007J. Yu Abstract In this paper, novel multi-functional mixed-oxide catalysts have been rationally designed and developed for the effective abatement of NOx. CaxCo3,,,xAl hydrotalcite-like compounds (where x,=,0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) are first synthesized by co-precipitation and calcined at 800,°C for 4,h in air to derive the mixed oxides. The resultant mixed oxides are generally of spinel phase, where the CaO phase is segregated when x,,,2.5. It has subsequently been found that the derived oxides are catalytically multi-functional for NOx decomposition, capture, and reduction. For example, the mixed Ca2Co1Al1 -oxide can decompose 55,% NO at 300,°C in 8,% oxygen, completely trap NO for 750,s, and capture 12.88,and 18.06,mg,g,1 NO within 30,and 60,min, respectively. The catalytic activities of the Ca2Co1Al1 -oxide catalyst have been further improved by incorporating La to form a quaternary catalyst Ca2Co1La0.1Al0.9 -oxide. This catalyst significantly enhances the NO decomposition to 75,%, extends the complete trapping time to 1100,s, and captures more NO at 300,°C in 8,% O2 (19.02,mg,g,1 NO within 60,min). The in-situ IR spectra of the catalysts with adsorbed NO indicates that the major nitrogen species formed on the catalysts are various kinds of nitrites and nitrates, which can be readily reduced by H2 within 6,min at 350,°C. Therefore, the excellent catalytic activity of layered double hydroxide (LDH)-based mixed oxides for NO decomposition, storage, and reduction can be achieved by the elegant combination of normal transition metals. [source] In,Situ Microstructure Control of Oriented Layered Double Hydroxide Monolayer Films with Curved Hexagonal Crystals as Superhydrophobic Materials,ADVANCED MATERIALS, Issue 23 2006H. Chen Oriented NiAl-layered double hydroxide (LDH) films with micro-/nanometer scale binary structures are prepared by in,situ crystallization, without using any external aluminum source or shape-directing surfactant, on a porous anodic alumina/aluminum substrate. The NiAl-LDH film structures can be controlled by tuning crystallization temperature and time. Facile hydrophobic modification of the film surface leads to superhydrophobicity, as shown in the figure. [source] Layered Double Hydroxide Surface Modified with (3-aminopropyl)triethoxysilane by Covalent Bonding,ADVANCED MATERIALS, Issue 1 2005A.-Y. Park Interlayer surfaces of layered double hydroxide (LDH) have been functionalized with amine moieties by condensation between the hydroxyl groups and (3-aminopropyl)triethoxysilane (APS) molecules via the covalent oxane bonds M-O-Si (M=Zn and Cr) (see Figure). Since the galleries of the modified LDHs have a hydrophobic field, various functional molecules such as enzymes, catalysts, and organic molecules can be incorporated between the LDH layers. [source] Layered Double Hydroxide Supported Nanoplatinum and Nanopalladium Catalyzed Allylation of Aldehydes: A Mechanistic StudyADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005M. Choudary Abstract Layered double hydroxide (LDH)-supported nanoplatinum(0) and nanopalladium(0) catalysts were prepared by a simple ion exchange technique and subsequent reduction with hydrazine hydrate and used for the allylation of aldehydes to give moderate to good yields of homoallylic alcohols. Detailed mechanistic studies of LDH-Pd(0)-catalyzed allylation using XPS and TGA-MS reveal that a monoallyl-palladium complex is the key intermediate for the catalytic cycle. [source] Synthesis of a magnesium/aluminum/iron layered double hydroxide and its flammability characteristics in halogen-free, flame-retardant ethylene/vinyl acetate copolymer compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Chuan-Mei Jiao Abstract Mg,Al,Fe ternary hydrotalcites were synthesized by a coprecipitation method and characterized with powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The flame-retardant effects of Mg/Al,CO3 layered double hydroxides (LDHs) and Mg/Al/Fe,CO3 LDHs in an ethylene/vinyl acetate copolymer (EVA) were studied with the limited oxygen index (LOI), the UL-94 test, and the cone calorimeter test (CCT), and the thermal degradation behavior of the composites was examined by thermogravimetric analysis. The results showed that the LOI values of the EVA/(Mg/Al/Fe,CO3 LDH) composites were basically higher than those of the EVA/(Mg/Al,CO3 LDH) composites at the same additive level. In the UL-94 test, there was no rating for the EVA/(Mg/Al,CO3 LDH) composite at the 50% additive level, and a dripping phenomenon occurred. However, the EVA/(Mg/Al/Fe,CO3 LDH) composites at the same loading level of LDHs containing a suitable amount of Fe3+ ion reached the V-0 rating, the dripping phenomenon disappearing. The CCTs indicated that the heat release rate (HRR) of the EVA composites with Mg/Al/Fe,CO3 LDHs containing a suitable amount of Fe3+ decreased greatly in comparison with that of the composites with Mg/Al,CO3 LDHs. The introduction of a given amount of Fe3+ ion into Mg/Al,CO3 LDHs resulted in an increase in the LOI, a decrease in the HRR, and the achievement of the UL-94 V-0 rating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Electrostatic-induced interfacial assembly of enzymes with nanosheets: Controlled orientation and optimized activityAICHE JOURNAL, Issue 10 2010Zhe An Abstract In this work, an electrostatic-induced interfacial assembly of porcine pancreatic lipase (PPL) with the nanosheets of layered double hydroxide (LDHNSs) is designed to rationally control the orientation of bound PPL. The PPL orientation in the bidimensional confinement spacing alters relying on the PPL loading, with the majority of active sites facing the LDH layer at low PPL loading and facing the adjacent protein molecule at high PPL loading. The biocatalytic activity of the bound PPL significantly depends on its orientation. Remarkable enhancement of the bio-activity has been observed when the PPL/LDHNSs mass ratio is less than 9, and a maximum activity is met with at PPL/LDHNSs = 0.5. In addition, the thermal stability of PPL-LDHNSs bioactivity has been obviously improved in comparison with soluble PPL. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Ethylene vinyl acetate/Mg-Al LDH nanocomposites by solution blendingPOLYMER COMPOSITES, Issue 4 2009T. Kuila Partially exfoliated ethylene vinyl acetate (EVA-40, 40% vinyl acetate content)/layered double hydroxide (LDH) nanocomposites using organically modified layered double hydroxide (DS-LDH) have been synthesized by solution intercalation method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies of nanocomposites shows the formation of exfoliated LDH nanolayers in EVA-40 matrix at lower DS-LDH contents and partially intercalated/exfoliated EVA-40/MgAl LDH nanocomposites at higher DS-LDH contents. These EVA-40/MgAl LDH nanocomposites demonstrate a significant improvement in tensile strength and elongation at break for 3 wt% of DS-LDH filler loading compare to neat EVA-40 matrix. Thermogravimetric analysis also shows that the thermal stability of the nanocomposites increases with DS-LDH content in EVA-40. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] The influence of layered compounds on the properties of starch/layered compound compositesPOLYMER INTERNATIONAL, Issue 6 2003Helena-M Wilhelm Abstract Glycerol-plasticized starch films were modified by addition of various layered compounds as fillers, two being of natural origin (kaolinite, a neutral mineral clay, and hectorite, a cationic exchanger mineral clay) and two synthetic (layered double hydroxide, LDH, an anionic exchanger, and brucite, having a neutral structure). The effects of the filler type and the plasticizer were analyzed by X-ray diffraction, dynamic mechanical analysis and thermogravimetry. The storage modulus was higher for kaolinite > brucite > hectorite than for LDH starch composites. However, only the hectorite filler presented a shift of the interplanar basal distance to higher values, which represents the intercalation of glycerol molecules between the clay layers. The glycerol intercalation is minimized in plasticized,oxidized starch films where the oxidized starch chains are preferentially intercalated. Copyright © 2003 Society of Chemical Industry [source] Sorption Removal of Pb(II) from Solution by Uncalcined and Calcined MgAl-Layered Double HydroxidesCHINESE JOURNAL OF CHEMISTRY, Issue 10 2007Shu-Qin ZHANG Abstract Layered double hydroxide (LDH) with a Mg/Al molar ratio of 1:1 was synthesized by using a co-precipitation method and its calcined product (CLDH) was obtained by calcination of the MgAl-LDH at 500 °C. The sorption removal of Pb2+ from solution was investigated, finding that both LDH and CLDH show good sorption ability and they could be used as a new type of environmental sorbent for the removal of Pb2+ from water. The sorption kinetics and the sorption isotherms of Pb2+ on both LDH and CLDH can be described by the pseudo-second order kinetics and Freundlich isotherm, respectively, under the studied conditions. The sorption amounts of Pb2+ on LDH and CLDH are independent of pH in a pH range of about 3,10. The presence of NaNO3 may inhibit the sorption ofPb2+ on LDH while hardly affect that on CLDH. The sorption mechanism of Pb2+ on LDH and CLDH may be attributed to the surface precipitation and the surface complex adsorption. The surface complex adsorption may be further distinguished to the chemical binding adsorption forming the inner-sphere surface complexes and the electrostatic binding adsorption forming the outer-sphere surface complexes. The sorption mechanism of Pb2+ on LDH may be attributed to the surface precipitation and the electrostatic binding adsorption, while that on CLDH may be attributed to the surface precipitation and the chemical binding adsorption. [source] Preparation of LLDPE/MgAl-LDH Exfoliation Nanocomposites with Enhanced Thermal Properties by Melt IntercalationCHINESE JOURNAL OF CHEMISTRY, Issue 10 2006Long-Chao Du Abstract The interlayer surface of MgAl layered double hydroxide (MgAl-LDH) was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions (DS) to get MgAl(H-DS) LDH, and then the MgAl(H-DS) was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), ion chromatography, transmission electron microscopy (TEM), and thermogravimetry analysis (TGA). The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of (00l) XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 °C and a higher thermal stability above 370 °C than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl(H-DS) can be 42 °C higher than that of LLDPE at 40% weight loss. [source] Electrochemical Study of Anionic Ferrocene Derivatives Intercalated in Layered Double Hydroxides: Application to Glucose Amperometric BiosensorsELECTROANALYSIS, Issue 3-5 2009Christine Mousty Abstract Layered double hydroxides (Zn2Cr(OH)6X,nH2O LDH) containing (3-sulfopropyl)ferrocene-carboxylate (FcPSO3) and 1,1,-bis(3-sulfopropyl)ferrocene-carboxylate (Fc(PSO3)2) as interlayer anions (X) have been prepared by the co-precipitation method and characterized by PXRD, FTIR, SEM and XPS. The electrochemical behavior of these hybrid materials has been evaluated by cyclic voltammetry. A new amperometric biosensor based on the immobilization of glucose oxidase in ZnCr-FcPSO3 hybrid material was presented, the intercalated anions playing the role of mediators that shuttle electrons between the FAD centers in the enzyme and the electrode surface. The performance of the resulting biosensor for glucose determination under anaerobic conditions was evaluated by chronoamperometry at 0.5,V. The sensitivity (65,mA M,1 cm,2) determined in the concentration range 10,25,,M is higher than sensitivities reported for other glucose biosensors based on LDH host matrices. [source] Study on the Photochromism of Ni,Al Layered Double Hydroxides Containing Nitrate AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006Min Wei Abstract The photochromism of nitrate-containing nickel,aluminum layered double hydroxides (NiAl-NO3 -LDHs) has been studied. Powder X-ray diffraction (PXRD), FTIR, UV/Vis, XPS, ESR, EXAFS, and elemental analysis were used to investigate the structure, composition, and photochromic behavior of NiAl-NO3 -LDHs. A possible photochromic mechanism in NiAl-NO3 -LDHs has been proposed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Luminescent Polyoxotungstoeuropate Anion-Pillared Layered Double HydroxidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Filipa L. Sousa Abstract Novel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn,Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9,, [Eu(BW11O39)(H2O)3]6, and [Eu(PW11O39)2]11,. The host,guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analysis, powder X-ray diffraction (XRD), infra-red (IR) and Raman spectroscopy, solid state magic-angle spinning (MAS) 11B and 31P NMR spectroscopy, and photoluminescence spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Tris(8-hydroxyquinoline-5-sulfonate)aluminum Intercalated Mg,Al Layered Double Hydroxide with Blue Luminescence by Hydrothermal SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Shuangde Li Abstract Blue luminescent hybrid materials (DDS,AQS(x%)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3,) and dodecyl sulfonate (DDS,) with different molar ratios into Mg,Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450,470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS,AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan,blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host,guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac -AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic,organic hybrid photofunctional material. [source] Carbon Nanotube Composites: Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Mater. On page 677, M. Q. Zhao et al. report the fabrication of a hierarchical composite combining one-dimensional single/double walled carbon nanotubes (CNTs) and two-dimensional flakes through direct carbon deposition on layered double hydroxides. The composites can be easily transformed into continuously interlinked CNT layers alternating with calcined lamellar flakes structure. They are found to have the potential for applications in a number or areas, including as an excellent filler for strong polyimide film. [source] Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double HydroxidesADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Meng-Qiang Zhao Three-dimensional hierarchical nanocomposites consisting of one-dimensional carbon nanotubes (CNTs) and two-dimensional lamellar flakes (such as clay, layered double hydroxides) show unexpected properties for unique applications. To achieve a well-designed structure with a specific function, the uniform distribution of CNTs into the used matrix is a key issue. Here, it is shown that a hierarchical composite of single/double-walled CNTs interlinked with two-dimensional flakes can be constructed via in-situ CNT growth onto layered double hydroxide (LDH) flakes. Both the wall number and diameter of the CNTs and the composition of the flakes can be easily tuned by changing the proportion of the transition metal in the LDH flakes. Furthermore, a structure with continuously interlinked CNT layers alternating with lamellar flakes is obtained after compression. The hierarchical composite is demonstrated to be an excellent filler for strong polyimide films. This study indicates that LDH is an extraordinary catalyst for the fabrication of hierarchical composites with high-quality single/double-walled CNTs. The as-obtained CNTs/calcined LDHs nanocomposite is a novel structural platform for the design of mechanically robust materials, catalysts, ion-transportation, energy-conversion, and other applications. [source] A comparative in situ Rietveld refinement study: thermal decomposition and transformation of CoAl and CoZnAl layered double hydroxidesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2008Rune E. Johnsen Rietveld refinement based on in situ X-ray powder diffraction (XRPD) data was combined with thermogravimetric analysis (TGA) and mass spectrometry (MS) to study and compare the phase transformations, thermal stability, microstructural and structural changes of two cobalt-containing nitrate-based layered double hydroxides (LDHs) upon heating in a controlled inert atmosphere of nitrogen. The XRPD data were collected, using synchrotron X-ray radiation, with a time resolution of 107,s, which made it possible to carry out detailed structural studies of the initial layered double hydroxides as well as their decomposition products: spinel for a CoAl,NO3 LDH and spinel/zincite for a CoZnAl,NO3 LDH. Correlating these data with those from the TGA,MS analyses gives us information about the transformation mechanisms. Rietveld refinements of the two spinel phases reveal remarkable differences. The a axis of the spinel formed by decomposition of the CoAl,NO3 LDH increases almost linearly from approximately 598 to 1163,K, mainly due to the dominating thermal expansion, whereas the a axis of the spinel formed by decomposition of the CoZnAl,NO3 shows a more complex temperature dependency. Between approximately 698 and 1073,K, the a axis is almost constant due to pronounced chemical interaction with an additional amorphous phase and the zincite phase, whereas from 1073 up to 1163,K it increases linearly. Calculations, based on the results of the Rietveld refinements, of the size of the octahedral and tetrahedral coordination polyhedra in the spinel show that the octahedra shrink and the tetrahedra expand with increasing temperature. The unusual thermal behaviour of the octahedra is discussed and attributed to the low formation temperature of the cobalt aluminium spinel phase. Finally, the intensity of a low-angle scattering (LAS) signal observed in the XRPD patterns was correlated with the decomposition of the LDH, and determination of the specific surface areas gave the temperature-dependent BET surface areas. [source] | |||||||||||||||||||||||||