201
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202
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Guo X, Zhang F, Evans DG, Duan X. Layered double hydroxide films: synthesis, properties and applications. Chem Commun (Camb) 2010; 46:5197-210. [DOI: 10.1039/c0cc00313a] [Citation(s) in RCA: 364] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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203
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Gomes Silva C, Bouizi Y, Fornés V, García H. Layered double hydroxides as highly efficient photocatalysts for visible light oxygen generation from water. J Am Chem Soc 2009; 131:13833-9. [PMID: 19725513 DOI: 10.1021/ja905467v] [Citation(s) in RCA: 241] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxygen generation through photocatalytic water splitting under visible light irradiation is a challenging process. In this work we have synthesized a series of Zn/Ti, Zn/Ce, and Zn/Cr layered double hydroxides (LDH) at different Zn/metal atomic ratio (from 4:2 to 4:0.25) and tested them for the visible light photocatalytic oxygen generation. The most active material was found to be (Zn/Cr)LDH with an atomic ratio of 4:2 that exhibits two absorption bands in the visible region at lambda(max) of 410 and 570 nm. It was found that the efficiency of these chromium layered double oxides for oxygen generation increases asymptotically with the Cr content. Using iron oxalate as chemical actinometer we have determined that the apparent quantum yields for oxygen generation (Phi apparent = 4 x mol oxygen/mol incident photons) are of 60.9% and 12.2% at 410 and 570 nm, respectively. These quantum yields are among the highest values ever determined with visible light for solid materials in the absence of light harvesting dye. The overall efficiency of (Zn/Cr)LDH for visible light oxygen generation was found to be 1.6 times higher than that of WO(3) under the same conditions.
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Affiliation(s)
- Cláudia Gomes Silva
- Instituto de Tecnologia Quimica, UPV-CSIC, Universidad Politecnica de Valencia, Avda. de Los Naranjos s/n, 46022 Valencia, Spain
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204
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Iyi N, Tamura K, Yamada H. One-pot synthesis of organophilic layered double hydroxides (LDHs) containing aliphatic carboxylates: Extended “homogeneous precipitation” method. J Colloid Interface Sci 2009; 340:67-73. [DOI: 10.1016/j.jcis.2009.08.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 08/17/2009] [Accepted: 08/18/2009] [Indexed: 10/20/2022]
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205
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Manzi-Nshuti C, Songtipya P, Manias E, Jimenez-Gasco MDM, Hossenlopp JM, Wilkie CA. Polymer nanocomposites using zinc aluminum and magnesium aluminum oleate layered double hydroxides: Effects of the polymeric compatibilizer and of composition on the thermal and fire properties of PP/LDH nanocomposites. Polym Degrad Stab 2009. [DOI: 10.1016/j.polymdegradstab.2009.07.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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206
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Guo X, Zhang F, Xu S, Cui Z, Evans DG, Duan X. Effects of Varying the Preparation Conditions on the Dielectric Constant of Mixed Metal Oxide Films Derived from Layered Double Hydroxide Precursor Films. Ind Eng Chem Res 2009. [DOI: 10.1021/ie900671b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xiaoxiao Guo
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Fazhi Zhang
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Sailong Xu
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Zhaohui Cui
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - David G. Evans
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xue Duan
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
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207
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Bellezza F, Cipiciani A, Latterini L, Posati T, Sassi P. Structure and catalytic behavior of myoglobin adsorbed onto nanosized hydrotalcites. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:10918-10924. [PMID: 19735144 DOI: 10.1021/la901448a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The adsorption of myoglobin (Mb) onto nanosized nickel aluminum hydrotalcite (NiAl-HTlc) surface was studied, and the structural properties of the resulting protein layer were analyzed by using FT-IR, Raman, and fluorescence spectroscopies. Upon adsorption onto the nanoparticle surface, the protein molecules maintained their secondary structure, while the tertiary structure was altered. The fluorescence spectra and anisotropy values of adsorbed Mb revealed that the emitting amino acid residues are affected by different microenvironments when compared to the native protein behavior. Moreover, the decrease of fluorescence decay times of tryptophan indicated the occurrence of interactions among the fluorophores and the constituents of the nanoparticles, such as the metal cations, which can take place when conformational changes of Mb occur. Raman spectra indicated that the interaction of Mb molecules with NiAl-HTlc nanoparticles modified the porphyrin core, changing the spin state of the heme iron from high spin (HS) to low spin (LS). The enzymatic activity of the nanostructured biocomposite was evaluated in the oxidation of 2-methoxyphenol by hydrogen peroxide and discussed on the basis of structural properties of adsorbed myoglobin.
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Affiliation(s)
- Francesca Bellezza
- Dipartimento di Chimica, Università di Perugia, via Elce di Sotto, 8, 06123 Perugia, Italy
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208
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Othman MR, Helwani Z, Martunus, Fernando WJN. Synthetic hydrotalcites from different routes and their application as catalysts and gas adsorbents: a review. Appl Organomet Chem 2009. [DOI: 10.1002/aoc.1517] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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209
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Vyalikh A, Massiot D, Scheler U. Structural characterisation of aluminium layered double hydroxides by (27)Al solid-state NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2009; 36:19-23. [PMID: 19477101 DOI: 10.1016/j.ssnmr.2009.04.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 02/27/2009] [Accepted: 04/22/2009] [Indexed: 05/27/2023]
Abstract
(27)Al solid-state NMR has been applied to study the local structure of pristine and chemically modified aluminium layered double hydroxides (LDH). The pristine LDH only shows six-fold coordinated, octahedral, aluminium, while the calcined and subsequently surfactant treated LDH sample shows a significant fraction of four-fold coordinated tetrahedral aluminium. The co-existence of two types of octahedral sites with different quadrupolar parameters is clearly observed in both samples. Quadrupolar coupling constants and isotropic chemical shifts have been measured from the (27)Al triple-quantum MAS NMR allowing to fit the (27)Al MAS spectra and quantify the different species in the samples. The quantitative analysis reveals that 30% of the aluminium is in four-fold coordination in the surfactant-modified LDH. We show that this chemical modification retains the two types of AlO(6) sites with a decreased intensity of the site showing the lowest quadrupolar coupling constant.
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Affiliation(s)
- Anastasia Vyalikh
- Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, D-01069 Dresden, Germany
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210
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Palmer SJ, Frost RL. The effect of synthesis temperature on the formation of hydrotalcites in Bayer liquor: a vibrational spectroscopic analysis. APPLIED SPECTROSCOPY 2009; 63:748-752. [PMID: 19589211 DOI: 10.1366/000370209788701152] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The seawater neutralization process is currently used in the alumina industry to reduce the pH and dissolved metal concentrations in bauxite refinery residues through the precipitation of Mg, Al, and Ca hydroxide and carbonate minerals. This neutralization method is very similar to the co-precipitation method used to synthesize hydrotalcite (Mg6Al2(OH)16CO3.4H2O). This study looks at the effect of temperature on the type of precipitates that form from the seawater neutralization process of Bayer liquor. The Bayer precipitates have been characterized by a variety of techniques, including X-ray diffraction (XRD), Raman spectroscopy, and infrared spectroscopy. The mineralogical composition of Bayer precipitates largely includes hydrotalcite, hydromagnesite, and calcium carbonate species. Analysis with XRD determined that Bayer hydrotalcites that are synthesized at 55 degrees C have a larger interlayer distance, indicating that more anions are removed from Bayer liquor. Vibrational spectroscopic techniques have identified an increase in hydrogen bond strength for precipitates formed at 55 degrees C, suggesting the formation of a more stable Bayer hydrotalcite. Raman spectroscopy identified the intercalation of sulfate and carbonate anions into Bayer hydrotalcites using these synthesis conditions.
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Affiliation(s)
- Sara J Palmer
- Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, Queensland, Australia
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211
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Bellezza F, Cipiciani A, Costantino U, Nocchetti M, Posati T. Hydrotalcite-Like Nanocrystals from Water-in-Oil Microemulsions. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200801114] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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212
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Debecker D, Gaigneaux E, Busca G. Exploring, Tuning, and Exploiting the Basicity of Hydrotalcites for Applications in Heterogeneous Catalysis. Chemistry 2009; 15:3920-35. [DOI: 10.1002/chem.200900060] [Citation(s) in RCA: 386] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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213
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Costantino U, Bugatti V, Gorrasi G, Montanari F, Nocchetti M, Tammaro L, Vittoria V. New polymeric composites based on poly(-caprolactone) and layered double hydroxides containing antimicrobial species. ACS APPLIED MATERIALS & INTERFACES 2009; 1:668-677. [PMID: 20355989 DOI: 10.1021/am8001988] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Benzoate (Bz), 2,4-dichlorobenzoate (BzDC), and p- and o-hydroxybenzoate (p- and o-BzOH) anions with antimicrobial activity have been intercalated into [Zn(0.65)Al(0.35)(OH)(2)](NO(3))(0.35).0.6H(2)O, layered double hydroxide (LDH), via anion-exchange reactions. The composition of the obtained intercalation compounds, determined by chemical, thermogravimetric, and ion chromatographic analyses, indicates that benzoate and benzoate derivative anions replace the nitrate counteranions, almost completely. Information on the interactions of the intercalated anions with the inorganic layer have been obtained from Fourier transform IR absorption spectroscopy and powder X-ray diffraction of the samples. It has been found that both the nature and the position of the aromatic ring substituents affect the value of the basal distance and the host-guest hydrogen bond network. Knowledge of the chemical composition, basal distance, and van der Waals dimensions of the guests has finally allowed the proposal of structural models of the intercalation compounds that have been used as fillers of poly(caprolactone), a biodegradable polymer. Films of polymeric composites were obtained by hot-pressing the powders of polymer and filler previously milled by a high-energy ball milling procedure. X-ray diffraction analysis and optical and scanning electron microscopy of the composites indicate that the LDH samples containing BzDC anions are delaminated into the polymeric matrix, whereas those containing p-BzOH anions maintain for the most part the crystal packing and give rise to microcomposites. Intermediate behavior was found for LDH modified with Bz and o-BzOH anions because exfoliated and partly intercalated composites were obtained. Preliminary antimicrobial tests indicate that the composites are able to inhibit the Saccharomyces cerevisiae growth of 40% in comparison with the growth in a pure culture medium. The composites can be studied as the model for "active packaging" systems because of the antimicrobial properties of the anions anchored to the LDH layer.
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Affiliation(s)
- Umberto Costantino
- CEMIN, Department of Chemistry, and INSTM, University of Perugia, Via Elce di Sotto 8, Perugia (PG), Italy.
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214
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Padmanabhan SC, Ledwith D, Pillai SC, McCormack DE, Kelly JM. Microwave-assisted synthesis of ZnO micro-javelins. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b912537j] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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215
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Kaluza S, Muhler M. On the precipitation mechanism and the role of the post-precipitation steps during the synthesis of binary ZnO–Al2O3 composites with high specific surface area. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b902004g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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216
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Effect of hydrothermal treatment on properties of Ni–Al layered double hydroxides and related mixed oxides. J SOLID STATE CHEM 2009. [DOI: 10.1016/j.jssc.2008.09.014] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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217
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Guo X, Zhang F, Xu S, Evans DG, Duan X. Preparation of layered double hydroxide films with different orientations on the opposite sides of a glass substrate by in situ hydrothermal crystallization. Chem Commun (Camb) 2009:6836-8. [DOI: 10.1039/b911216b] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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218
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Almansa JJ, Coronado E, Martí-Gastaldo C, Ribera A. Magnetic Properties of NiIICrIIILayered Double Hydroxide Materials. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800658] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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219
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Das A, Costa FR, Wagenknecht U, Heinrich G. Nanocomposites based on chloroprene rubber: Effect of chemical nature and organic modification of nanoclay on the vulcanizate properties. Eur Polym J 2008. [DOI: 10.1016/j.eurpolymj.2008.08.025] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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220
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Structure analysis of hydrotalcite intercalated with pyrenetetrasulfonate; experiments and molecular modelling. J Mol Model 2008; 14:1119-29. [DOI: 10.1007/s00894-008-0355-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Accepted: 07/15/2008] [Indexed: 10/21/2022]
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221
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Lü Z, Zhang F, Lei X, Yang L, Xu S, Duan X. In situ growth of layered double hydroxide films on anodic aluminum oxide/aluminum and its catalytic feature in aldol condensation of acetone. Chem Eng Sci 2008. [DOI: 10.1016/j.ces.2008.05.007] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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222
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Decarbonation of MgAl-LDHs (layered double hydroxides) using acetate–buffer/NaCl mixed solution. J Colloid Interface Sci 2008; 322:237-45. [DOI: 10.1016/j.jcis.2008.02.047] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 02/22/2008] [Accepted: 02/24/2008] [Indexed: 11/18/2022]
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223
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Pavel O, Bîrjega R, Che M, Costentin G, Angelescu E, Şerban S. The activity of Mg/Al reconstructed hydrotalcites by “memory effect” in the cyanoethylation reaction. CATAL COMMUN 2008. [DOI: 10.1016/j.catcom.2008.03.027] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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224
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Benito P, Herrero M, Barriga C, Labajos FM, Rives V. Microwave-Assisted Homogeneous Precipitation of Hydrotalcites by Urea Hydrolysis. Inorg Chem 2008; 47:5453-63. [DOI: 10.1021/ic7023023] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- P. Benito
- GIR-QUESCAT, Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain, and Departamento de Ingeniería Química y Química Inorgánica, Universidad de Córdoba, 14071 Córdoba, Spain
| | - M. Herrero
- GIR-QUESCAT, Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain, and Departamento de Ingeniería Química y Química Inorgánica, Universidad de Córdoba, 14071 Córdoba, Spain
| | - C. Barriga
- GIR-QUESCAT, Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain, and Departamento de Ingeniería Química y Química Inorgánica, Universidad de Córdoba, 14071 Córdoba, Spain
| | - F. M. Labajos
- GIR-QUESCAT, Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain, and Departamento de Ingeniería Química y Química Inorgánica, Universidad de Córdoba, 14071 Córdoba, Spain
| | - V. Rives
- GIR-QUESCAT, Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain, and Departamento de Ingeniería Química y Química Inorgánica, Universidad de Córdoba, 14071 Córdoba, Spain
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225
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Ni(II)-Al(III) layered double hydroxide as catalyst precursor for ethanol steam reforming: Activation treatments and kinetic studies. Catal Today 2008. [DOI: 10.1016/j.cattod.2007.11.032] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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226
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Goh KH, Lim TT, Dong Z. Application of layered double hydroxides for removal of oxyanions: a review. WATER RESEARCH 2008; 42:1343-68. [PMID: 18061644 DOI: 10.1016/j.watres.2007.10.043] [Citation(s) in RCA: 718] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 10/25/2007] [Accepted: 10/29/2007] [Indexed: 05/17/2023]
Abstract
Layered double hydroxides (LDHs) are lamellar mixed hydroxides containing positively charged main layers and undergoing anion exchange chemistry. In recent years, many studies have been devoted to investigating the ability of LDHs to remove harmful oxyanions such as arsenate, chromate, phosphate, etc. from contaminated waters by both surface adsorption and anion exchange of the oxyanions for interlayer anions in the LDH structure. This review article provides an overview of the LDH synthesis methods, the LDH characterization techniques, and the recent advancement that has been achieved in oxyanion removal using LDHs, highlighting areas of consensus and currently unresolved issues. Experimental studies relating to the sorption behaviors of LDHs with various oxyanions, and the kinetic models adopted to explain the adsorption rate of oxyanions from aqueous solution onto LDHs, have been comprehensively reviewed. This review discusses several key factors such as pH, competitive anions, temperature, etc., that influence the oxyanion adsorption on LDHs. The reusability of LDHs is discussed and some mechanistic studies of oxyanion adsorption on LDHs are highlighted. The sorption capacities of LDHs for various oxyanions are also compared with those of other adsorbents. In addition, this review critically identifies the shortcomings in current research on LDHs, such as the common weaknesses in the adopted methodology, discrepancies among reported results and ambiguous conclusions. Possible improvement of LDHs and potential areas for future application of LDHs are also proposed.
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227
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Kovář P, Melánová K, Zima V, Beneš L, Čapková P. Layered double hydroxide intercalated with p-methylbenzoate and p-bromobenzoate: Molecular simulations and XRD analysis. J Colloid Interface Sci 2008; 319:19-24. [DOI: 10.1016/j.jcis.2007.10.060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2007] [Revised: 10/19/2007] [Accepted: 10/25/2007] [Indexed: 11/16/2022]
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228
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Ma R, Takada K, Fukuda K, Iyi N, Bando Y, Sasaki T. Topochemical Synthesis of Monometallic (Co2+–Co3+) Layered Double Hydroxide and Its Exfoliation into Positively Charged Co(OH)2 Nanosheets. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200703941] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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229
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Manzi-Nshuti C, Wang D, Hossenlopp JM, Wilkie CA. Aluminum-containing layered double hydroxides: the thermal, mechanical, and fire properties of (nano)composites of poly(methyl methacrylate). ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b802553c] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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230
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Naghash A, Etsell TH, Lu B. Mechanisms involved in the formation and growth of Al–Cu–Ni hydrotalcite-like precipitates using the urea hydrolysis scheme. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b715712f] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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231
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Ma R, Takada K, Fukuda K, Iyi N, Bando Y, Sasaki T. Topochemical Synthesis of Monometallic (Co2+–Co3+) Layered Double Hydroxide and Its Exfoliation into Positively Charged Co(OH)2 Nanosheets. Angew Chem Int Ed Engl 2008; 47:86-9. [DOI: 10.1002/anie.200703941] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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232
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Latterini L, Nocchetti M, Aloisi GG, Costantino U, De Schryver FC, Elisei F. Structural, photophysical, and photochemical characterization of 9-anthracenecarboxylate-hydrotalcite nanocomposites: evidence of a reversible light-driven reaction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:12337-12343. [PMID: 17960941 DOI: 10.1021/la7014989] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
ZnAl hydrotalcites containing increasing amounts of 9-anthracenecarboxylate anion (9AC) have been obtained via an anion-exchange procedure. In particular, intercalated and/or surface-exchanged samples were prepared to study the effect of the chromophore packing on their photophysical and photochemical behavior. Surface-exchanged samples were obtained by equilibrating the carbonate form of the ZnAl hydrotalcite with dilute solutions of 9AC. The nitrate form of the ZnAl hydrotalcite was instead chosen for the preparation of intercalation compounds. The maximum loading of 9AC was found to be 44% of the anion-exchange capacity. The obtained nanostructured materials were characterized by chemical and thermal analysis and X-ray powder diffractometry and studied for their photophysical and photochemical properties. The absorption and emission spectra of the materials revealed the formation of 9AC aggregates. The time-resolved fluorescence properties of the hybrid materials were investigated in bulk and under space-resolved conditions. The fluorescence decays appeared to be quite complex and were affected by the microenvironment and the experimental conditions. Generally, a shortening of the main fluorescence decay component was observed with increasing matrix loading, thus suggesting the occurrence of nonradiative processes in competition with fluorescence at high chromophore concentrations. Indeed, the occurrence of an electron-transfer process to water molecules, which led to the formation of 9AC radical, was observed spectrophotometrically in the sample with high 9AC loading. The electron-transfer process was completely reversible under air-equilibrated conditions.
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Affiliation(s)
- Loredana Latterini
- CEMIN-Centro Eccellenza Materiali Innovativi Nanostrutturati, Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto 8, Perugia, Italy.
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233
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Atake I, Nishida K, Li D, Shishido T, Oumi Y, Sano T, Takehira K. Catalytic behavior of ternary Cu/ZnO/Al2O3 systems prepared by homogeneous precipitation in water-gas shift reaction. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.molcata.2007.05.040] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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234
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Unal U. Short-time hydrothermal synthesis and delamination of ion exchangeable Mg/Ga layered double hydroxides. J SOLID STATE CHEM 2007. [DOI: 10.1016/j.jssc.2007.07.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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235
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Chitrakar R, Tezuka S, Sonoda A, Sakane K, Ooi K, Hirotsu T. Synthesis and phosphate uptake behavior of Zr4+ incorporated MgAl-layered double hydroxides. J Colloid Interface Sci 2007; 313:53-63. [PMID: 17509605 DOI: 10.1016/j.jcis.2007.04.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 03/28/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
We synthesized Zr(4+) incorporated MgAl-layered double hydroxides, Mg(AlZr)-LDH(A) (where A denotes a counteranion in the interlayer space and is expressed as CO(3) for carbonate and Cl for chloride ions), with different molar ratios of Mg/(Al+Zr). Then we characterized their uptake behavior toward phosphate ions. CO(3)-type tertiary LDH materials synthesized at room temperature show low crystallinity, whereas the highly crystalline Cl-type tertiary LDH, [Mg(0.68)Al(0.17)Zr(0.14)(OH)(2)][Cl(0.26)(CO(3))(0.04)1.24H(2)O], was synthesized for the first time using a hydrothermal treatment at 120 degrees C. The distribution coefficients (K(d)) of oxo-anions were measured with a mixed solution containing trace amounts of the anions. The selectivity sequences were Cl(-), NO(-)(3)<SO(2-)(4)<<HPO(2-)(4) for CO(3)-type materials and SO(2-)(4)<HPO(2-)(4)<NO(-)(3) for the crystalline Cl-type material. The uptake of phosphate ions from model wastewater (2.0 mg-P/dm(3)) and phosphate-enriched natural seawater (0.33 mg-P/dm(3)) was investigated in detail. The CO(3)-type materials have higher phosphate uptakes than the Cl-type materials. The maximum phosphate uptake of the CO(3)-type material with a molar ratio of Mg/(Al+Zr) of 3 is 30 mg-P/g at pH 8.7 with the wastewater, and 16 mg-P/g at pH 8.1 with the seawater, in contrast to the case of the usual binary MgAl-LDH(CO(3)): 10 mg-P/g with the wastewater and less than 1 mg-P/g with the seawater. The large uptake and high selectivity of the CO(3)-type tertiary LDH materials is well explained by complex formation of phosphate ions directly with Zr(IV) centers in the layers.
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Affiliation(s)
- Ramesh Chitrakar
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology, Takamatsu, Japan.
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236
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Shimura N, Ogawa M. Preparation of hexagonal platy particles of nanoporous silica using hydrotalcite as morphology template. J Colloid Interface Sci 2007; 312:311-6. [PMID: 17482202 DOI: 10.1016/j.jcis.2007.02.091] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2006] [Revised: 02/21/2007] [Accepted: 02/28/2007] [Indexed: 10/23/2022]
Abstract
Hexagonal platy composite particles with a hydrotalcite core and a nanoporous silica shell with a thickness of ca. 100 nm were synthesized by the reaction of a Mg-Al hydrotalcite with a homogeneous aqueous solution containing tetraethoxysilane, hexadecyltrimethylammonium chloride, ammonia and methanol at 3 degrees C. The calcination of the products at 500 degrees C in air led to the composite particle with a Mg/Al mixed oxide core and a nanoporous silica shell. Hexagonal platy particles of nanoporous silica with a pore diameter of 2.3 nm and BET surface area of 700 m(2) (g of silica)(-1) were obtained by removing the Mg/Al mixed oxide core.
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Affiliation(s)
- Naoki Shimura
- Graduate School of Science and Engineering, Waseda University, Nishiwaseda 1-6-1, Tokyo 169-8050, Japan
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237
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Radha AV, Kamath PV, Ravishankar N, Shivakumara C. Suppression of the reversible thermal behavior of the layered double hydroxide (LDH) of Mg with Al: stabilization of nanoparticulate oxides. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:7700-6. [PMID: 17559238 DOI: 10.1021/la063276e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The layered double hydroxide of Mg with Al decomposes below 600 degrees C with the loss of nearly 48% mass, resulting in the formation of an oxide residue having the rock salt structure and nanoparticulate morphology. However, this product reconstructs back into the parent LDH, owing to its compositional and morphological metastability. The oxide can be kinetically stabilized within an amorphous phosphate network built up through an ex situ reaction with a suitable phosphate source such as (NH4)H2PO4. This oxide transforms into a thermodynamically more stable phase with a spinel structure on soaking in an aqueous medium. The oxide residue has a nanoparticulate morphology as revealed by the Scherrer broadening of the Bragg reflections as well as by electron microscopy. This work shows that the hydroxide reconstruction reaction and spinel formation are competing reactions. Suppression of the former catalyzes spinel formation as the excess free energy of the metastable oxide residue is unlocked to promote the diffusion of Mg2+ ions from octahedral to tetrahedral sites, which is the essential precondition to the formation of a normal spinel. This reaction taking place as it does at ambient temperature and in solution helps in the retention of a nanostructured morphology for the spinel. Another way of stabilizing the oxide is by incorporating the thermally stable borate anion into the LDH. This paves the way for an in situ reaction between the cations of the host LDH and the borate guest. The in situ reaction directly leads to the formation of an oxide with a spinel structure.
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Affiliation(s)
- A V Radha
- Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India
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238
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Kovár P, Pospísil M, Nocchetti M, Capková P, Melánová K. Molecular modeling of layered double hydroxide intercalated with benzoate, modeling and experiment. J Mol Model 2007; 13:937-42. [PMID: 17558525 DOI: 10.1007/s00894-007-0217-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 05/14/2007] [Indexed: 11/26/2022]
Abstract
The structure of Zn4Al2 Layered Double Hydroxide intercalated with benzencarboxylate (C6H5COO-) was solved using molecular modeling combined with experiment (X-ray powder diffraction, IR spectroscopy, TG measurements). Molecular modeling revealed the arrangement of guest molecules, layer stacking, water content and water location in the interlayer space of the host structure. Molecular modeling using empirical force field was carried out in Cerius(2) modeling environment. Results of modeling were confronted with experiment that means comparing the calculated and measured diffraction pattern and comparing the calculated water content with the thermogravimetric value. Good agreement has been achieved between calculated and measured basal spacing: d(calc) = 15.3 A and d(exp) = 15.5 A. The number of water molecules per formula unit (6H2O per Zn4Al2(OH)12) obtained by modeling (i.e., corresponding to the energy minimum) agrees with the water content estimated by thermogravimetry. The long axis of guest molecules are almost perpendicular to the LDH layers, anchored to the host layers via COO- groups. Mutual orientation of benzoate ring planes in the interlayer space keeps the parquet arrangement. Water molecules are roughly arranged in planes adjacent to host layers together with COO- groups.
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Affiliation(s)
- Petr Kovár
- Faculty of Mathematics and Physics, Charles University Prague, Ke Karlovu 3, Prague 2, Czech Republic.
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239
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Tsujimura A, Uchida M, Okuwaki A. Synthesis and sulfate ion-exchange properties of a hydrotalcite-like compound intercalated by chloride ions. JOURNAL OF HAZARDOUS MATERIALS 2007; 143:582-6. [PMID: 17079079 DOI: 10.1016/j.jhazmat.2006.09.073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 09/12/2006] [Accepted: 09/25/2006] [Indexed: 05/12/2023]
Abstract
To reduce the generation of hydrogen sulfide gas from sulfate ions, we synthesized a layered double hydroxide hydrotalcite-like compound intercalated with chloride ions in the interlayer (HT-Cl) using a coprecipitation reaction. The resultant HT-Cl material had a Mg/Al molar ratio of approximately 2, and the molar fraction of the chloride ions on the intercalated anion layer of the HT was 0.90. A higher molar fraction of chloride ions can be inserted into the interlayers of the HT by increasing the initial concentration ratio of chloride ions to aluminum ions [Cl(-)](0)/[Al(3+)](0) in the solution. Approximately 98% of the sulfate ions in the solution were removed within 10 min after adding 1.12 times the stoichiometric quantity of synthesized HT-Cl, which contained a Mg/Al molar ratio of 2 equal to a solution containing a 12 mM calcium sulfate solution.
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Affiliation(s)
- Akino Tsujimura
- Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki, Aoba-ku, Sendai 980-8579, Japan
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240
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Shishido T, Yamamoto Y, Morioka H, Takehira K. Production of hydrogen from methanol over Cu/ZnO and Cu/ZnO/Al2O3 catalysts prepared by homogeneous precipitation: Steam reforming and oxidative steam reforming. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.molcata.2006.12.018] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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241
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Tammaro L, Costantino U, Bolognese A, Sammartino G, Marenzi G, Calignano A, Tetè S, Mastrangelo F, Califano L, Vittoria V. Nanohybrids for controlled antibiotic release in topical applications. Int J Antimicrob Agents 2007; 29:417-23. [PMID: 17303393 DOI: 10.1016/j.ijantimicag.2006.11.019] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 11/28/2006] [Accepted: 11/28/2006] [Indexed: 11/30/2022]
Abstract
New polymeric composite materials containing a nanohybrid to be used for the controlled release of an antibiotic molecule, chloramphenicol succinate, have been formulated, prepared and characterised. The nanohybrid consists of a layered double hydroxide of Mg-Al hydrotalcite-type, in which the nitrate anions present in the host galleries were replaced with chloramphenicol succinate anions (CFS(-)) by a simple ion-exchange reaction. Different amounts of the hybrid material were incorporated in polycaprolactone and processed as films of 0.15mm thickness. The composite materials were analysed by X-ray diffractometry and thermogravimetry and their mechanical properties were determined. They showed properties even better than those of the pristine polymer. The release process of the antibiotic molecules was found to be very interesting and promising for tuneable drug delivery. It consists of two stages: an initial stage of a very rapid burst, in which a small fraction of drug is released; and a second stage that is much slower, extending for a longer and longer time. This behaviour is profoundly different and much slower than that of a sample in which the antibiotic molecule is directly incorporated into the polymeric matrix. The parameters influencing drug release have been individuated and discussed.
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Affiliation(s)
- L Tammaro
- Department of Chemical and Food Engineering, University of Salerno, via Don Melillo, 84084 Fisciano (Sa), Italy
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242
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LIU J, LI H, LI H. Liquid-Phase Selective Hydrogenation of Phenol to Cyclohexanone over Pd-Ce-B/Hydrotalcite Catalyst. CHINESE JOURNAL OF CATALYSIS 2007. [DOI: 10.1016/s1872-2067(07)60029-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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243
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Ma R, Liu Z, Takada K, Iyi N, Bando Y, Sasaki T. Synthesis and Exfoliation of Co2+−Fe3+ Layered Double Hydroxides: An Innovative Topochemical Approach. J Am Chem Soc 2007; 129:5257-63. [PMID: 17394321 DOI: 10.1021/ja0693035] [Citation(s) in RCA: 320] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper describes a topochemical synthetic approach to Co2+-Fe3+ layered double hydroxides (LDHs). Micrometer-sized hexagonal platelets of brucite-like Co2/3Fe1/3(OH)2 were first prepared by a homogeneous precipitation of an aqueous solution of divalent cobalt and ferrous ions through hexamethylenetetramine (HMT) hydrolysis under a nitrogen gas atmosphere. A subsequent oxidative intercalation process, by the action of iodine (I2) in chloroform (CHCl3), transformed the precursory brucite-like Co2+-Fe2+ hydroxides into hydrotalcite-like Co2+-Fe3+ LDHs, in which the oxidization of Fe2+ into Fe3+ induced positive charges to the octahedral hydroxyl layers while anions (I-) were intercalated into the interlayer space. Co2+-Fe3+ LDHs inherited the high crystallinity and hexagonal platelet morphology from their brucite-like precursor due to the topotactic nature of the transformation, which was verified by abundant microscopic and spectroscopic characterizations. After a normal ion-exchange process, Co2+-Fe3+ LDHs accommodating perchlorate anions were exfoliated into unilamellar nanosheets in formamide by an ultrasonic treatment.
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Affiliation(s)
- Renzhi Ma
- Nanoscale Materials Center, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
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244
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Radha AV, Kamath PV, Shivakumara C. Conservation of Order, Disorder, and “Crystallinity” during Anion-Exchange Reactions among Layered Double Hydroxides (LDHs) of Zn with Al. J Phys Chem B 2007; 111:3411-8. [PMID: 17388484 DOI: 10.1021/jp0684170] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carbonate and chloride ions mediate an ordered stacking of metal hydroxide slabs to yield ordered layered double hydroxides (LDHs) of Zn with Al, by virtue of their ability to occupy crystallographically well-defined interlayer sites. Other anions such as ClO(4)- (T(d)), BrO(3)- (C(3v)), and NO(3)- (coordination symmetry C(2v)) whose symmetry does not match the symmetry of the interlayer sites (D(3h) or O(h)) introduce a significant number of stacking faults, leading to turbostratic disorder. SO(4)(2-) ions (coordination symmetry C(3v)) alter the long-range stacking of the metal hydroxide slabs to nucleate a different polytype. The degree of disorder is also affected by the method of synthesis. Anion-exchange reactions yield a solid with a greater degree of order if the incoming ion is a CO3(2-) or Cl-. Incoming NO(3)- ions yield an interstratified phase, whereas incoming SO(4)(2-) ions generate turbostratic disorder. Conservation or its converse, elimination, of stacking disorders during anion exchange is the net result of several competing factors such as (i) the orientation of the hydroxyl groups in the interlayer region, (ii) the symmetry of the interlayer sites, (iii) the symmetry of the incoming ion, and (iv) the configuration of the anion. These short-range interactions ultimately affect the long-range stacking order or "crystallinity" of the LDH.
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Affiliation(s)
- A V Radha
- Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India
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245
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Chitrakar R, Tezuka S, Sonoda A, Sakane K, Ooi K, Hirotsu T. A Solvent-free Synthesis of Zn–Al Layered Double Hydroxides. CHEM LETT 2007. [DOI: 10.1246/cl.2007.446] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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246
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247
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Mangiacapra P, Raimondo M, Tammaro L, Vittoria V, Malinconico M, Laurienzo P. Nanometric Dispersion of a Mg/Al Layered Double Hydroxide into a Chemically Modified Polycaprolactone. Biomacromolecules 2007; 8:773-9. [PMID: 17319719 DOI: 10.1021/bm0605964] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polycaprolactone (PCL) was chemically modified by grafting maleic anhydride on it, through a radical reaction induced by benzoyl peroxide as initiator. To improve the grafting degree, a second unsaturated comonomer such as glycidyl methacrylate (GMA) has been added, demonstrating a good reactivity in melt grafting without leading to long grafted chains. The quantitative determination of grafted maleic anhydride, performed by FTIR analysis, revealed a grafting weight percentage of 9.5 +/- 0.9, and the NMR characterization made it possible to propose a structure for the grafted polymer (PCLgMA). The modified polymer was analyzed by DSC and X-ray diffraction, showing a structural organization even better than that of the pristine polymer. An exchange reaction with a layered double hydroxide (LDH), hydrotalcite-like solid in the nitrate form, led to the disappearance of the crystalline basal peak of LDH in the X-ray diffractograms, suggesting a possible exfoliation of the inorganic sample. An oxidative etching on the composite surface followed by atomic force microscopy analysis made it possible to enlighten the lamellar structure in the pristine sample. In the composite sample, the well identifiable narrow fissures homogeneously distributed on the surface demonstrate that nanometer stacks of LDH sheets, embedded in a highly textured PCLgMA matrix, are present in the composite sample. The comparison of X-ray diffractograms and AFM analysis suggests either a partial exfoliation or an intercalation of the polymer in a lamellar texture with a basal spacing higher than 5 nm. In any case, the process of ionic exchange between nitrate LDH and PCLgMA led to the formation of nanocomposites, in which no large hydrotalcite aggregates are present. This is an interesting method to obtain a direct intercalation of the modified polymer into the inorganic solid with a simple ionic exchange reaction.
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Affiliation(s)
- Pasqualina Mangiacapra
- Dipartimento di Ingegneria Chimica e Alimentare, Università di Salerno, Via Don Melillo 1, 84084 Fisciano (Sa), Italy
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248
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Lenarda M, Casagrande M, Moretti E, Storaro L, Frattini R, Polizzi S. Selective catalytic low pressure hydrogenation of acetophenone on Pd/ZnO/ZnAl2O4. Catal Letters 2007. [DOI: 10.1007/s10562-007-9046-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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249
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Jobbágy M, Blesa MA, Regazzoni AE. Homogeneous precipitation of layered Ni(II)-Cr(III) double hydroxides. J Colloid Interface Sci 2007; 309:72-7. [PMID: 17316671 DOI: 10.1016/j.jcis.2007.01.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2006] [Revised: 12/22/2006] [Accepted: 01/05/2007] [Indexed: 11/16/2022]
Abstract
An adequate account of the hydrolytic properties of Cr3+ and Ni2+ allows setting the conditions for homogeneous nucleation of layered Ni(II)-Cr(III) double hydroxides; water exchange and hydrolysis rate constants indicate that, at very high rates of base dosing, formation of heteronuclear Cr(III)-Ni(II) hydroxo species should prevail over precipitation of active Cr(OH)3. This is realized by the urea method under microwave-assisted hydrothermal conditions. This approach yields crystalline Ni1-xCrx(OH)2(CO3)x/2nH2O (x approximately 0.32-0.36) in less than 5 min at 453 K; higher degrees of crystallinity are obtained at higher temperatures and/or longer aging times. Formation of Ni(II)-Cr(III) LDHs upon microwave-assisted hydrothermal aging of freshly coprecipitated Ni(OH)2+Cr(OH)3 mixtures takes longer, due to a different operating mechanism. The implications of the advanced rationale for the design of synthesis procedures are stressed. It is proposed that homogeneous nucleation of Ni(II)-Cr(III) LDHs involves the edge-on condensation of planar heteronuclear Cr(III)-Ni(II) hydroxo trimers. Ordered aggregation of primary particles leads to the final platelet crystals, a process that involves the exchange of CO2-(3) ions dangling at the crystallites' edges by bridging OH-.
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Affiliation(s)
- Matías Jobbágy
- INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
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