Hydroxy Double Salt Research Articles

Formation of porous Cu hydroxy double salt nanoflowers derived from metal-organic frameworks with efficient peroxidase-like activity for label-free detection of glucose.

Currently, nanomaterials with peroxidase activity have become an important colorimetric tool for biomolecular detection. However, compared with natural enzymes, the efficiency of most nanozymes is still lower. Here, with a leaf-like metal-organic-framework-5 as both a precursor and a template and copper acetate as a second precursor, hierarchical Cu hydroxy double salt (HDS) nanoflowers have been prepared and used as a label-free glucose colorimetric detection platform. We have demonstrated a scalable and facile synthesis of hierarchical Cu HDS nanoflowers, and density functional theory (DFT) calculations confirmed that there exists a hydrogen bond between the terephthalate anions and the layer OH group. The composition of Cu hydroxyl double salt is [Cu4(OH)6][BDC]·2H2O. Importantly, for the first time, the as-prepared Cu HDSs were demonstrated as peroxidase mimics to catalyze the oxidation of the enzyme substrate, 3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, which accompanies a color change from colorless to blue and followed classic Michaelis-Menten models. Based on these findings, a colorimetric method based on Cu HDSs that is highly sensitive and selective for the detection of glucose was developed, with a low detection limit of 0.5 μM. The clinical applicability of the sensor is also proven to be suitable for sensing glucose in blood, suggesting that Cu HDSs could be used in the construction of portable sensors for point-of-care diagnosis and on-site tests.

Electrochemical Growth of Copper Hydroxy Double Salt Films and Their Conversion to Nanostructured p-Type CuO Photocathodes.

New electrochemical synthesis methods were developed to produce copper hydroxy double salt(Cu-HDS) films with four different intercalated anions (NO3-, SO42-, Cl-, and dodecyl sulfate (DS)) as pure crystalline films as deposited (Cu2NO3(OH)3, Cu4SO4(OH)6, Cu2Cl(OH)3, and Cu2DS(OH)3). These methods are based on p-benzoquinone reduction, which increases the local pH at the working electrode and triggers the precipitation of Cu2+ and appropriate anions as Cu-HDS films on the working electrode. The resulting Cu-HDS films could be converted to crystalline Cu(OH)2 and CuO films by immersing them in basic solutions. Because Cu-HDS films were composed of 2D crystals as a result of the atomic-level layered structure of HDS, the CuO films prepared from Cu-HDS films have unique low-dimensional nanostructures, creating high surface areas that cannot be obtained by direct deposition of CuO, which has a 3D atomic-level crystal structure. The resulting nanostructures allowed the CuO films to facilitate electron-hole separation and demonstrate great promise for photocurrent generation when investigated as a photocathode for a water-splitting photoelectrochemical cell. Electrochemical synthesis of Cu-HDS films and their facile conversion to CuO films will provide new routes to tune the morphologies and properties of the CuO electrodes that may not be possible by other synthesis means.

Synthesis of Water-Sensitive Metal–Organic Frameworks within Fiber Sorbent Modules

We report a synthetic route for the production of water-sensitive metal–organic frameworks (MOFs) in polymer fiber sorbents by use of metal oxides as seeding intermediates. Cellulose acetate/ZnO (48 wt %) fibers were spun via a dry-jet wet-quench method and converted through hydroxy double salt (HDS) intermediates into HKUST-1 and ZIF-8. MOF loadings within the fiber sorbent reached 85 and 66 wt %, respectively. We demonstrate this process on module-packaged fibers, in which ready-to-use fiber sorbents are synthesized in a moisture-free environment. Modules are then employed in proof-of-concept CO2/N2 breakthrough experiments.

Hydroxy double salts intercalated with Mn(II) complexes as potential contrast agents

A series of Mn(II) aminophosphonate complexes were successfully synthesized and intercalated into the hydroxy double salt [Zn5(OH)8]Cl2·yH2O. Complex incorporation led to an increase in the interlayer spacing from 7.8 to 10–12 Å. Infrared spectroscopy showed the presence of the characteristic vibration peaks of the Mn(II) complexes in the intercalates' spectra, indicating successful incorporation. The complex-loaded composites had somewhat lower proton relaxivities than the pure complexes. Nevertheless, these intercalates may have use as MRI contrast agents for patients with poor kidney function, where traditional Gd(III)-based contrast agents cause severe renal failure.

Green emission and Ag(+) sensing of hydroxy double salt supported gold nanoclusters.

In this paper, a complex of Zn-containing hydroxy double salt (Zn-HDS) supported gold nanoclusters (AuNCs) has been synthesized. The formation of the complex (denoted as the AuNCs/Zn-HDS complex) has been analyzed by Transmission Electron Microscopy (TEM), IR spectroscopy and X-ray Photoelectron Spectroscopy (XPS). It is noteworthy that the AuNCs/Zn-HDS complex emits green fluorescence and the quantum yield is 7.6%. Based on the fluorescence quenching effect, the AuNCs/Zn-HDS complex has been employed for the sensitive detection of Ag(+) and the limit of detection is 2.32 nM. The mechanisms of fluorescence generation and quenching are discussed in detail.

Facile Conversion of Hydroxy Double Salts to Metal-Organic Frameworks Using Metal Oxide Particles and Atomic Layer Deposition Thin-Film Templates.

Rapid room-temperature synthesis of metal-organic frameworks (MOFs) is highly desired for industrial implementation and commercialization. Here we find that a (Zn,Cu) hydroxy double salt (HDS) intermediate formed in situ from ZnO particles or thin films enables rapid growth (<1 min) of HKUST-1 (Cu3(BTC)2) at room temperature. The space-time-yield reaches >3 × 10(4) kg·m(-3)·d(-1), at least 1 order of magnitude greater than any prior report. The high anion exchange rate of (Zn,Cu) hydroxy nitrate HDS drives the ultrafast MOF formation. Similarly, we obtained Cu-BDC, ZIF-8, and IRMOF-3 structures from HDSs, demonstrating synthetic generality. Using ZnO thin films deposited via atomic layer deposition, MOF patterns are obtained on pre-patterned surfaces, and dense HKUST-1 coatings are grown onto various form factors, including polymer spheres, silicon wafers, and fibers. Breakthrough tests show that the MOF-functionalized fibers have high adsorption capacity for toxic gases. This rapid synthesis route is also promising for new MOF-based composite materials and applications.

Efficient 1,4-Addition of Enones and Boronic Acids Catalyzed by a Ni–Zn Hydroxyl Double Salt-Intercalated Anionic Rhodium(III) Complex

Intercalation of an in situ prepared [Rh(OH)6]3– complex into an anion exchangeable Ni–Zn layered hydroxy double salt (Rh/NiZn) was demonstrated. The resulting Rh/NiZn effectively catalyzed the 1,4-addition of diverse enones and phenylboronic acids to their corresponding β-substituted carbonyl compounds. In the case of 2-cyclohexen-1-one and phenylboronic acid, a turnover frequency (TOF) of 920 h–1 based on Rh was achieved. The [Rh(OH)6]3– complex maintained its original monomeric trivalent state within the NiZn interlayer following catalysis, attributable to a strong electrostatic interaction between the NiZn host and anionic Rh(III) complex.

Interstratified composite of the anionic clays, Zn5(OH)8(NO3)2∙2H2O and Ni3Zn2(OH)8(NO3)2∙2H2O, by delamination-costacking

The anionic clays zinc hydroxysalt and nickel zinc hydroxy double salt were delaminated in 1-butanol to get monolayer dispersions after interlayer modification with surfactant anion, dodecyl sulfate. When these dispersions were mixed and the mixture treated with excess of acetone, layers from the two clays co-stacked to give a composite in which the layers from the two clays were interstratified. The surfactant anion of the composite could be exchanged with nitrate ions. The nitrate intercalated composite showed increased thermal stability compared to zinc hydroxynitrate. In addition the composite showed improved alkali resistance. When treated with alkaline solution the zinc hydroxysalt layers partially dissolved leading to the formation of a zincate intercalated anionic clay composite.

The first hydroxy double salt tablet formulation

For the first time, a hydroxy double salt containing an active pharmaceutical agent has been formulated into tablets. The tablets have excellent pharmaceutical properties and release the drug slowly over around 4 h when in conditions representative of the gastrointestinal tract.

Intercalation and Controlled Release of Bioactive Ions Using a Hydroxy Double Salt

Two bioactive drug molecules (mefenamic acid and 4-biphenylacetic acid) were successfully intercalated into the hydroxy double salt (HDS) [Zn5(OH)8](NO3)2·yH2O. The resulting nanocomposites were fu...

An anionic d-valine–palladium(ii) complex supported on a hydroxy double salt with a Brønsted basic phosphate anion: application for a heterogeneous catalyst toward aerobic alcohol oxidation

An anionic D-valine–Pd(II) complex intercalated into an anion exchangeable Ni–Zn mixed basic salt (NiZn), which is classified as a layered hydroxy double salt, was synthesised in situ via a simple anion exchange procedure. A Bronsted basic PO43− anion was also intercalated into the NiZn interlayer along with the anionic D-valine–Pd(II) complex. The Bronsted basic clay–Pd(II) nanocomposite catalysed the aerobic oxidation of a wide variety of alcohols to the corresponding aldehydes and ketones. In the aerobic oxidation of 1-phenylethanol, for example, a turnover number (TON) of 2000 based on Pd was achieved. During the aerobic alcohol oxidation, the D-valine–Pd(II) complex in the NiZn interlayer maintained its original monomeric Pd(II) structure due to the strong electrostatic interaction between the NiZn host and the anionic Pd(II) complex. This catalyst could be reused without loss of either catalytic activity or selectivity for the aerobic oxidation of alcohols.

Thermal stability and fire retardancy of PMMA (nano)composites with layered metal hydroxides containing dodecyl sulfate anions

AbstractLayered double hydroxides (LDHs) with Mg/Al, Zn/Al, Ca/Al metal hydroxide layers, and a Zn/Ni hydroxy double salt (HDS) were prepared with a common anion, dodecyl sulfate [CH3(CH2)10COO−, DS]. The LDH and HDS additives were melt blended with poly(methyl methacrylate) (PMMA). The dispersion and morphology were characterized via X‐ray diffraction (XRD) and transmission electron microscopy. Mg/Al‐DS and Zn/Al‐DS LDHs were found to form nanocomposites with PMMA, exhibiting good dispersion and some degree of exfoliated morphology for the Zn/Al‐DS/PMMA combination and mixed intercalation and exfoliation behavior for Mg/Al‐DS in PMMA. The Ca/Al‐DS LDH and Zn/Ni‐DS HDS formed microcomposites with PMMA. Thermal stability was investigated via thermogravimetric analysis; each of the additives increased the thermal stability of PMMA. Cone calorimetry was used to measure the fire properties; the microcomposite of Zn/Ni‐DS HDS at 10% loading provided the best improvement in peak heat release rate, with a 40% reduction over the pure polymer. The residue composition after burning the composites was investigated. Copyright © 2010 John Wiley &amp; Sons, Ltd.

ChemInform Abstract: Creation of Highly Stable Monomeric Pd(II) Species in an Anion‐Exchangeable Hydroxy Double Salt Interlayer: Application to Aerobic Alcohol Oxidation under an Air Atmosphere.

AbstractChemInform 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.

Creation of highly stable monomeric Pd(II) species in an anion-exchangeable hydroxy double salt interlayer: Application to aerobic alcohol oxidation under an air atmosphere

An active Pd(II) catalyst supported on the Ni–Zn mixed basic salt (NiZn), which is classified by the anion-exchangeable layered hydroxy double salts, was synthesized by simple intercalation of the anionic Pd(II) hydroxyl complex. The divalent Pd species in the interlayer of NiZn maintained their original monomeric structure during the aerobic alcohol oxidation, due to the strong electrostatic interaction between the NiZn host and anionic Pd(II) species. This catalyst could be reused without any loss of the catalytic activity and selectivity in the aerobic alcohol oxidation.

Surfactant-Assisted Alignment of ZnO Nanocrystals to Superstructures

Self-organization of ZnO nanoparticles into various superstructures (sheet, platelet, ring) has been achieved with the assistance of micelles formed by surfactant cetyltrimethylammonium bromide (CTAB) under one-pot condition. The CTAB-modified zinc hydroxy double salt (Zn-HDS) mesocrystals act as intermediates to form ZnO hexagonal superstructures at temperatures as low as 50 degrees C. The decomposition temperature of Zn-HDS mesocrystals is much lower than that of the corresponding bulk crystals because the organic additive CTAB effectively decreases the degree of crystallinity. Taking advantage of temperature-induced phase transformation of micelles, two-stage self-organization can form ZnO platelets and ring mesocrystals, that is, ZnO ellipsoidal superstructures formed through vertical attachment on (0001) facets of basic units can further assemble to form ZnO platelets and rings through vertical attachment on (0001) facets of ZnO ellipsoidal superstructures. The structural transformation of micelles as shape templates can offer a new route for self-assembly of nonspherical colloids into three-dimensional photonic crystals. ZnO sheet, ring, and platelet mesocrystals with a high population of polar Zn-(0001) plane are expected to have high photocatalytic activity.

Anionic clays as hosts for anchored synthesis: Interlayer bromination of maleate and fumarate ions in nickel–zinc layered hydroxy double salt

Anionic clay-like nickel zinc hydroxyacetate, Ni 3Zn 2(OH) 8(OAc) 2·2H 2O was ion exchanged with maleate and fumarate ions. While the maleate enters as monoanion, fumarate enters as dianion. Also these anions take up different orientations in the interlayer region. The intercalated organic species could be reacted with bromine water in such a way that the brominated product remains intercalated making the reaction a true intracrystalline reaction. The stereochemistry of the reaction of the intercalated fumarate was identical to that of the free fumarate ion – both yielding only the anti addition product. While free maleate ion yielded only the anti addition product, the intercalated maleate ion yielded a small percentage of the syn addition product along with the anti addition product. The organic products could be quantitatively recovered by anion exchange with oxalate ions.

Catalytic combustion of toluene over mixed Cu–Mn oxides

The influence of the synthesis pH and of the Zn and/or Al additives on the Cu–Mn precursors, obtained by co-precipitation at a constant pH from aqueous solutions of appropriate nitrates at (Cu + Zn)/(Mn + Al) ratio equal 2, was investigated. The relative content of Mn increased with the pH of precipitation. Depending on the sample composition the identified crystalline phases included layered hydroxy double salt, hydrotalcite-like structure, CuO and ZnO. Some precursors had strongly amorphous character. Calcination of the precursors at 673 K resulted in mixed oxides, in which CuO of various degrees of crystallinity could be identified. The Mn-containing phases remained amorphous. All calcined materials proved extremely active in catalytic combustion of toluene. Some catalysts reached 100% conversion already at 403 K. High conversions observed in the low temperature regime were partially due to the strong sorption of toluene. In the catalysts containing Al additive this effect was suppressed.

Synthesis and anion exchange reactions of a layered copper-zinc hydroxy double salt, Cu1.6Zn0.4(OH)3(OAc)·H2O

A mixed-metal hydroxysalt of formula Cu1.6Zn0.4(OH)3(OAc)·H2O has been synthesized by an acetate hydrolysis route. Acetate ions can be exchanged with simple inorganic anions such as chloride and nitrate, and organic anions such as benzoate and large surfactant anions such as dodecyl sulphate. Structures of these hydroxysalts are derived from that of Cu2(OH)3NO3·H2O with some of the Cu2+ ions being replaced by Zn2+.

Macroporous materials from crystalline single-source precursors through decomposition followed by selective leaching

There are a number of pairs of elements A and B in the periodic table that do not form binary oxides AxByO. We have used this fact to seek out crystalline precursors containing such metals that can be decomposed at elevated temperatures to form intimate mixtures of the individual oxides, AxO and ByO. Selective leaching of one of these oxide components from the monolithic mixture results in a macroporous material. We demonstrate this scheme by decomposing a hydroxy double salt containing Ni and Zn. The ZnO from the decomposition product can be leached out, leaving behind a macroporous NiO monolith that can be further reduced to yield porous metallic Ni.