Hetero-bimetallic 2D coordination network constructed by azacrown ether carboxylic acid with lanthanide(III) and sodium ions

Two lanthanide-based coordination polymers [Na₃La(L)Cl·(H₂O)₆]·NO₃ (La-L) and [Na₃Eu(L)Cl·(H₂O)₆]·NO₃ (Eu-L) were newly synthesized by reaction of an azacrown ether carboxylic acid ligand H₄L (4,7,13,16-tetracarboxymethyl-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane) with La(III)/Eu(III). Complexes La-L and Eu-L exhibited two-dimensional (2D) coordination architectures built up by Ln–L coordinating subunits and one-dimensional (1D) Na–O bridging chains. Four versatile coordination modes of carboxyl groups and Na–O coordination bi-chains linked by novel μ-O bridges (μ2-O and μ3-O) were demonstrated in the structure. Photoluminescence spectra of Eu-L were investigated to reveal characteristic emissions of Eu(III). This is the first example of hetero-bimetallic complex of the tetraazacrown ether ligand with lanthanide and sodium ions.     

A paradoxical flame-retardant effect of nitrates in ATH-filled ethylene–vinyl acetate copolymer

In the course of a study of metal salts as flame retardants, it was surprisingly found that metal nitrates reduced the flammability of ATH-filled ethylene–vinyl acetate copolymer (EVA). The limiting oxygen index (LOI) of ATH-filled EVA was increased by the nitrates in the order of Cu(NO₃)₂·3H₂O > (NH₄)₂Ce(NO₃)₆ > Zn(NO₃)₂·6H₂O > Fe(NO₃)₃·9H₂O > Al(NO₃)₃·9H₂O > NaNO₃. The effects were not caused by the water of hydration. All metal nitrates except NaNO₃ reached a UL 94 V-2 rating at 3 phr. Based on TGA, DSC, FTIR, and gas detection, the proposed mechanism of the flame-retardant effect of nitrates is the oxidative degradation of the polymer to produce noncombustible products (CO₂ and nitrogen oxides) at a rate sufficient to interfere with the normal combustion process despite the exothermicity of the oxidative degradation. It is possible that surface carboxylic acid structures also contribute to the flame-retardant effect. © 1995 John Wiley & Sons, Inc.     

Direct functionalization with 3,5‐substituted benzoic acids of multiwalled carbon nanotube/epoxy composites

Directly functionalized multiwalled carbon nanotubes (MWCNTs) with benzene‐1,3,5‐tricarboxylic acid (BTC) and 3,5‐diaminobenzoic acid (DAB) were successfully accomplished with less structural damage as confirmed by XPS and FT‐Raman results. Their dispersibility and thermal stability were achieved after the functionalization. The functional groups on MWCNT surfaces can accelerate the curing reaction of epoxy composites remarkable inducing rather low exothermic peak temperature (T_p) and exothermic heat of reaction (ΔH). The values of activation energy (E_a) obtained from Kissinger and Ozawa methods obviously decreased with the introduction of MWCNTs, especially DAB‐MWCNTs. The dynamic mechanical properties notably enhanced with the incorporation of unmodified and functionalized MWCNTs. The crosslink density (ρ) increased and free volume fraction (f_g) decreased, resulting in dramatic increase of glass transition temperatures (T_g) and decrease of coefficient of thermal expansion. Additionally, epoxy composites exhibited low dielectric constant close to that of neat epoxy resin. From these remarkable properties, MWCNT/epoxy composites can be considered as a good candidate for high performance insulation materials. POLYM. ENG. SCI., 53:2194–2204, 2013. © 2013 Society of Plastics Engineers     

Transparent conductive film based on carbon nanotubes and PEDOT composites

Single-walled nanotubes (SWNTs), thin multiwalled carbon nanotubes (t-MWNTs) and multiwalled carbon nanotubes (MWNTs) were treated with H₂SO₄–HNO₃ acid solution, under different chemical conditions. The acid-treated CNTs were dispersed in DI water and in poly (3,4-ethylenedioxythiophene) (PEDOT) solution. Furthermore, the finely dispersed CNTs/PEDOT solutions were employed to a simple method of bar coating to obtain the transparent conductive films on the glass and polyethylene terephthalate (PET) film. A sheet resistance of 247 Ω/sq and a transmission of 84.7% were obtained at a concentration of the acid-treated CNTs of 0.01 wt.%.     

Green Synthesis of Salicylic Acid-Based Poly(amide-imide) in Ionic Liquid and Composite Formation with Multiwalled Carbon Nanotube

A new salicylic acid-containing diacid monomer was synthesized by an established synthetic procedure from readily available reagents. The obtained diacid was used in the preparation of a thermally stable poly(amide-imide) by direct polycondensation with 4,4′-diphenylmethanediamine using 1,3-diisopropylimidazolium bromide ionic liquid as a green medium. The prepared polymer was used as matrix for preparation of multiwalled carbon nanotube/poly(amide-imide) composites in three multiwalled carbon nanotube concentrations (5, 10, and 15?wt%). The products were characterized for assessing the spectroscopic, thermal, and morphological properties by several methods. A homogeneous dispersion of multiwalled carbon nanotubes in the poly(amide-imide) matrix was observed by microscopy techniques.     

Syntheses,structures, and magnetic properties of ethoxy-bridged dinuclear iron(III) complexes containing tetradentate ligands

Dinuclear iron(III) complexes, [(phenO)Fe(SO₄)]₂·2CH₃OH (1) and [(bpmapO)Fe(NO₃)]₂(NO₃)₂·3CH₃OH (2) have been prepared by the reaction of phenOH/bpmapOH and FeSO₄·7H₂O/Fe(NO₃)₃·9H₂O in methanol, respectively (phenOH = N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine, bpmapOH = N-(bis(2-pyridylmethyl)amino)-2-methylpropan-2-ol). Both complexes are ethoxy-bridged dinuclear species and the iron(III) ions in 1 and 2 have distorted octahedral geometries. Both complexes show strong antiferromagnetic interactions through the bridged ethoxy groups within the dimeric units.     

New nanohybrids from poly(propylene imine) dendrimer stabilized silver nanoparticles on multiwalled carbon nanotubes for effective catalytic and antimicrobial applications

Five types of multiwalled carbon nanotubes noncovalently functionalized with poly (propylene imine) dendrimer (PPI (G2))-silver nanoparticle hybrids were prepared by varying the [Ag⁺] load from 2 to 6 mM. These nanohybrids were characterized with FTIR, UV-Vis, FESEM, EDS, HRTEM and Raman analyses. The catalytic potential was studied through the reduction of 4-nitrophenol as a model reaction under pseudo first-order reaction conditions. The calculated k_obs value (16.94 × 10^?2 min^?1) reveals that the 4 mM [Ag⁺] loaded catalyst showed higher efficiency than with rest of the catalysts. Further, the in vitro antimicrobial activities of all nanohybrids were inspected against Pseudomonas aeruginosa and Staphylococcus aureus.     

A novel hydrogen peroxide sensor based on multiwalled carbon nanotubes/poly(pyrocatechol violet)‐modified glassy carbon electrode

In this work, a new hydrogen peroxide (H₂O₂) sensor was reported based on electropolymerizing pyrocatechol violet (PCV) on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNTs). The modified electrode was characterized by cyclic voltammetry (CV) and scanning electron micrography. The result of electrochemical experiments showed a favorable catalytic activity toward the reduction of H₂O₂ at ?0.4 V with a linear response range from 2.0 μM to 2.4 mM and a detection limit of 0.7 μM (at a S/N = 3). The well catalytic activity of proposed sensor could be attributed to the poly‐PCV/MWCNTs composite film on the electrocatalytic reduction of H₂O₂. In addition, the sensor also exhibited a high sensitivity, good stability, and reproducibility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Magnesia–Carbon Nanotubes (MgO–CNTs) Nanocomposite: Novel Support of Ru Catalyst for the Generation of COx-Free Hydrogen from Ammonia

Magnesia–carbon nanotubes (abbreviated as MgO–CNTs) nanocomposites were prepared by impregnation of CNTs with Mg(NO₃)₂·6H₂O in ethanol solution, followed by drying at 353 K and calcination at 873 K, respectively. The nanocomposites are thermally more stable than CNTs in a H₂ flow. The use of the nanocomposites as support yielded more efficient Ru catalysts for the generation of CO _x -free hydrogen from NH₃ decomposition.     

Self-Recognition of 3D Porous Frameworks: Fourfold Diamondoid or Threefold Cuboidal Interpenetrating Nets Formed by Varying Pillar Motifs

Compound [Ni(2,6-ndc)(bpe)(H₂O)] _n (1) was prepared by the hydrothermal reaction of 2,6-naphthalenedicarboxylic acid (2,6-H₂ndc) and trans-1,2-bis(4-pyridyl)ethylene (bpe) with Ni(NO₃)₂·6H₂O under alkaline (NaOH) conditions. Treatment of 2,6-H₂ndc, 4,4′-bipyridine (4,4′-bpy) with M(NO₃)₂·6H₂O (M = Ni or Co) under similar conditions afforded compounds [Ni₂(2,6-ndc)₂(4,4′-bpy)] _n (2) and [Co₂(2,6-ndc)₂(4,4′-bpy)] _n (3), respectively. A single-crystal X-ray diffraction study revealed that compound 1 adopts a 3D fourfold interpenetrating diamondoid network stabilized by inter-net OH···O hydrogen bonds. The anionic 2,6-ndc ligand presents two different bonding characteristics, bis(monodentate) and bis(chelating bidentate) modes. A solid-state structural analysis revealed that compounds 2 and 3 are isomorphous and isostructural. Both present a 3D threefold interpenetrating cuboidal framework, consisting of a 2D (4,4)-net of interconnected [M ₂(O₂C)₄] (M = Ni, Co) paddle-wheel dinuclear units, and pillared by 4,4′-bpy ligands. The degree of interpenetration of these compounds could be adjusted successfully by varying only the organic pillar motifs.     

Quality optimization of Bi2212 films prepared by aqueous solvent sol-gel method with nonionic surfactants

In this paper, Bi2212 films were prepared on LaAlO₃(100) and SrTiO₃(100) substrates by the sol-gel method using Bi(NO₃)₃·5H₂O, Sr(NO₃)₂, Ca(NO₃)₂·4H₂O and Cu(NO₃)₂·3H₂O as raw materials. TritonX-100 (TX-100), fatty alcohol poly oxyethylene ether (AEO-9), poly (vinylpyrrolidone) (PVP) and poly (vinyl alcohol) (PVA) were used as surfactants, respectively, to improve the wettability between the sol and the substrate. When glycine and glycolic acid were used as complexing agents, these surfactants were stably miscible with the sols. The effects of different surfactant sol-gel systems on the wettability of substrates as well as the crystallinity, morphology, surface roughness and electrical transport properties of Bi2212 superconducting films were investigated. The results showed that flat and continuous c-axis epitaxial Bi2212 films were obtained using all these sol-gel systems. In particular, TX-100 and AEO-9 as surfactants showed stronger wettability of the sol-gel for both substrates. In addition, the films prepared using polymer surfactants PVP and PVA sol-gel systems showed less surface roughness. The same patterns were found in all the film samples prepared using precursor sols of different complexing agents, and all the films exhibited good electrical transport properties. This work lays a certain research foundation for the preparation of thin films by aqueous solvent sol-gel method. The method also shows great potential in terms of the stability of different sol-gel systems and the improvement of the wettability of different substrates.     

Effects of carbon on the sulfidation and hydrodesulfurization of CoMo hydrating catalysts

The effects of carbon addition on CoMo catalyst performance for sulfidation and hydrodesulfurization (HDS) were investigated. The carbon-containing catalyst was prepared by impregnation of γ-Al₂O₃ support with NH₃ aqueous solution containing Co(NO₃)₂·6H₂O, (NH₄)₆Mo₇O₂₄·4H₂O and ethylenediamine. The results indicated that the incorporation of proper carbon on CoMo catalyst can improve its HDS performance. The carbon species on the catalyst were characterized by temperature-programmed oxidation and reduction, temperature-programmed desorption of ammonia and ultraviolet-visible diffuse reflectance spectra. Two forms of carbon species were differentiated: one is spread over the catalyst surface, similar to coke formed from reaction; the other interacts with active phase as an intermediate support. The carbon species acting as intermediate support may decrease the interaction of active metals with support, which enhances the sulfidation and HDS activities of CoMo catalyst. This work was presented at the 7th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Synthesis and Characterization of New Poly(ether-amide-imide)/Amino-Functionalized Fe3O4 Nanocomposites

New poly(amide-imide)/amino functionalized Fe₃O₄ nanocomposites were successfully fabricated through solution intercalation technique. A poly(amide-imide) derived from an imide-containing diacid and ether linkage diamine was synthesized and characterized. Aiming to have better compatibility, the hydrophilic nature of Fe₃O₄@SiO₂ was changed into organophilic using N-[3-(trimethoxysilyl)propyl]ethylenediamine. The amino-functionalized Fe₃O₄ showed well dispersion in the poly(amide-imide) matrix. Thermal gravimetric analysis results indicated that char yields of the nanocomposites were improved. Microscale combustion calorimetry results showed that poly(amide-imide) had good flame retardancy and amino-functionalized Fe₃O₄ has further improved this property of poly(amide-imide).     

The effect of carbon microfiber substrate pretreatment on the growth of carbon nanomaterials

The floating catalyst method was used to obtain carbon nanotubes, carbon submicrotubes and other carbon nanomaterials by changing the pretreatment conditions of carbon microfiber substrate. The morphology and microstructure of the obtained products were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results showed that on untreated carbon microfiber surface, only some carbon particles and several carbon nanotubes were deposited. However, after carbon microfibers were boiled in the solution of H₂SO₄/HNO₃ and were immersed in the solutions of Fe(NO₃)₃/xylene, Fe(NO₃)₃/acetone, ferrocene/acetone and Fe(NO₃)₃/ferrocene/acetone, the obtained products were a high-density carbon nanotubes, carbon nanotubes with many carbon particles, carbon submicrotubes and a mixture of carbon nanomaterial, respectively. Thus the pretreatment of the carbon microfiber substrate greatly influenced the morphology and microstructure of the synthesized products.     

Synthesis of carbon nanotubes grown by hot filament plasma-enhanced chemical vapor deposition method

We prepared two kinds of catalytic layers onto n-typed silicon substrate—nickel by r.f.-magnetron sputtering and iron (III) nitrate metal oxide by spin coating. For iron (III) nitrate metal oxide 0.5 mol of ferric nitrate nonahydrate [Fe₂(NO₃)₃·9H₂O] ethanol solution was coated onto silicon by spin coater at different rotation speeds (rev./min). Carbon nanotubes were synthesized on both Ni and iron (III) nitrate metal oxide layers by the HFPECVD (hot filament plasma-enhanced chemical vapor deposition) method. We used ammonia (NH₃) and acetylene (C₂H₂) for the dilution gas and a carbon precursor for the growth of the carbon nanotubes, respectively. We could observe the relationship between the catalytic cluster density and the nanotube density with scanning electron microscopy (SEM) images. The density of carbon nanotubes on iron (III) nitrate metal oxide was controlled by the rev./min of the spin coater. Transmission electron microscopy (TEM) image shows multi-walled carbon nanotube where the catalyst was found in the tip of the carbon nanotube. Electron dispersive X-ray spectrometry (EDS) peaks for CNT's tip show that it was constituted with nickel and iron, respectively. Raman spectroscopy of nanotubes shows D-band and G-band peaks approximately 1370 and 1590 cm⁻¹.     

Salen Type Sandwich Triple-Decker Tri- and Di-nuclear Lanthanide Complexes

Four N,N′-bis(salicylidene)-1,2-(phenylene-ediamine) (H₂L) trinuclear lanthanide complexes, namely, [Ln₃L₃(CH₃OH)₂(NO₃)₃]·(CH₂Cl₂)·(CH₃OH)·(H₂O)₂ [Ln = Tb (1), Ho (2), Er (3) and Lu (4)], have been isolated by the reactions of H₂L and Ln(NO₃)₃·6H₂O. And one N,N′-bis(salicylidene)-1,2-(phenylene-ediamine) dinuclear neodymium complex [Nd₂L₃(CH₃OH)] (5) has been harvested from the reaction of H₂L with Nd(OAc)₃·4H₂O. X-ray crystallographic analysis reveals that complexes 1?4 are of triple-decker trinuclear sandwich structure, while complex 5 is of a triple-decker dinuclear sandwich structure, expanding upon the recent reports of the multinuclear pure lanthanide complexes.     

Effects of thermal imidization on mechanical properties of poly(amide‐co‐imide)/multiwalled carbon nanotube composite films

In this study, experimental and numerical studies were performed to investigate the relationship among the functionalization method, weight fraction of MWCNTs, thermal imidization cycle, and mechanical properties of various PAI/MWCNT composite films. Poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were prepared by solution mixing and film casting. The effects of chemical functionalization and weight fraction of multiwalled carbon nanotubes on thermal imidization and mechanical properties were investigated through experimental and numerical studies. The time needed to achieve sufficient thermal imidization was reduced with increasing multiwalled carbon nanotube content when compared with that of a pure poly(amide‐co‐imide) film because multiwalled carbon nanotubes have a higher thermal conductivity than pure poly(amide‐co‐imide) resin. Mechanical properties of pure poly(amide‐co‐imide) and poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were increased with increasing imidization time and were improved significantly in the case of the composite film filled with hydrogen peroxide treated multiwalled carbon nanotubes. Both the tensile strength and strain to failure of the multiwalled carbon nanotube filled poly(amide‐co‐imide) film were increased substantially because multiwalled carbon nanotube dispersion was improved and covalent bonding was formed between multiwalled carbon nanotubes and poly(amide‐co‐imide) molecules. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of chemical functionalization of carbon nanotubes on their dispersibility in alkyl methacrylate polymer matrix

Nanocomposites based on poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate‐co‐octadecyl methacrylate) (M/O) matrices and four different types of multiwall carbon nanotubes: pristine, oxidized (MWCNT–COOH), methyl ester (MWCNT–COOCH₃), and dodecyl ester (MWCNT–COOC₁₂H₂₅) functionalized, were prepared in situ by radical (co)polymerization. The effectiveness of preparation of nanocomposites regarding dispersion and distribution of various MWCNT in polymer matrices was sized by Scanning electron microscopy. In case of PMMA matrix, the best dispersion and distribution were accomplished for MWCNT–COOCH₃ due to their chemical resemblance with polymer matrix. After the introduction of 10 mol % of octadecyl methacrylate in polymer matrix a fairly good dispersion and distribution of MWCNT–COOCH₃ were retained. The addition of 1 wt % of MWCNTs caused a significant reduction in the degree of polymerization of the PMMA matrix. But at the same time, the present MWCNTs increased storage modulus of PMMA nanocomposites except for dodecyl ester functionalized MWCNT. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46113.     

Copper(II) and cadmium(II) complexes with an imide tethered imidazole and a copper(II) coordination polymer through ring opening reaction

The reactions of 2-(3-(1H-imidazol-1-yl)propyl)isoindoline-1,3-dione (L) with copper (II) chloride or copper(II) nitrate resulted in mononuclear complexes [CuL₄Cl₂]·12H₂O (1) or [CuL₄(H₂O)NO₃]NO₃·2H₂O (2) respectively; whereas the copper(II) acetate reacted with L to give a three dimensional coordination polymer {[Cu(L′)₂]·4H₂O}n (3), (where L′ = 2-(3-(1H-imidazol-1-yl)propylcarbamoyl)benzoate). The reaction of cadmium(II) acetate with L led to the formation of a seven-coordinated complex [CdL₃(O₂CCH₃)₂]·2H₂O (4).     

Benign enzymatic synthesis of multiwalled carbon nanotube composites uniformly coated with polypyrrole for supercapacitors

BACKGROUND: Recently, various composites of carbon nanomaterials and conducting polymers have been actively investigated as potential electrode materials for supercapacitors which can store and deliver large amounts of electrical energy promptly. Harsh chemical or complex electrodeposition methods have been studied to prepare such composites. In this report, the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) was utilized for the first time to prepare composites of multiwalled carbon nanotubes and polypyrrole. RESULTS: Electron micrographs show that in situ enzymatic reaction by horseradish peroxidase enables the uniform coating of multiwalled carbon nanotubes with polypyrrole without containing the polymer aggregates. The specific capacitance of the composites (46.2 F g^?1) measured with a two‐electrode cell containing an electrolyte of 1 mol L^?1 NaNO₃ increased more than four‐fold compared with that obtained with bare multiwalled carbon nanotubes (10.8 F g^?1). CONCLUSIONS: Horseradish peroxidase‐catalyzed in situ synthesis of the composites of multiwalled carbon nanotubes and polypyrrole requires neither the derivatization of multiwalled carbon nanotubes and/or pyrrole monomers nor the post‐doping of the synthesized composites to enhance the capacitance of the composites. © 2012 Society of Chemical Industry