Investigations on poly(vinyl chloride). IV. Effects of metal chlorides on the thermal decomposition of poly(vinyl chloride)

The effects of various metal oxides upon the thermal decomposition of poly(vinyl chloride) (PVC) were previously reported. In this work, 23 metal chlorides were investigated to determine their effects on the thermal decomposition of PVC by pyrolysis–gas chromatography at 500°C. Each metal chloride exhibits influences on the course of thermal decomposition of PVC almost similar to the corresponding metal oxide except for a few elements; the metal chlorides from acidic metal oxides accelerate the thermal decomposition of PVC, but the metal chlorides from basic metal oxides do not. On comparing the effects of metal oxides and metal chlorides on the thermal decomposition of PVC, most metal chlorides were found to accelerate the thermal decomposition of PVC more than the corresponding metal oxides, owing to ease of addition of the chlorine atoms released from metal chloride to the dehydrochlorinated chains. It is concluded from these results that the thermal decomposition of PVC containing metal salts is markedly influenced by the ease with which chlorine atoms are released from the corresponding metal chloride.     

Effective octadecylamine system for nanocrystal synthesis

New chemical reactions and synthetic systems are of key importance for materials fabrication. In this work, we reported a facile and effective octadecylamine (ODA) synthetic system for various nanocrystals including metals, mixed metal oxides, metal/metal oxide heterostructured nanocrystals, intermetallics, and alloys. We found that the products were mainly determined by metal ions used in our synthetic system: noble metal ions led to the formation of metals; two kinds of non-noble metal ions led to the formation of mixed metal oxides; silver ions and non-noble metal ions led to the formation of metal/metal oxide heterostructured nanocrystals; non-noble metal ions and noble metal (excluding Ag) ions led to the formation of intermetallics and alloys. The difference was attributed to different ability to attract electrons from ODA solvent among these metal ions. This effective system provides a general strategy for various nanocrystals which would find potential applications in many significant fields.     

Direct electrical measurement of the conversion of metal acetates to metal sulfides by hydrogen sulfide

Copper acetate and related metal salt films react directly with hydrogen sulfide at room temperature to form metal sulfides, resulting in conductivity changes as large as 108. The observed changes in conductivity are related to the solubility product constant (Ksp) and the difference in conductivity between the metal salt and the resulting metal sulfide. A smaller Ksp indicates a more stable metal sulfide and, therefore, greater metal salt reactivity. Polyaniline nanofiber/metal salt composites were also examined and show metal sulfide conversion with changes in resistance up to 106. The direct electrical measurement of the conversion of metal salt to metal sulfide has the potential to be the basis of a new type of sensitive, thin-film chemical sensor.     

Review: recent advances in the chemistry of metal chelate monomers

This review summarizes recent advances in the chemistry of metal chelate monomers. Depending on the character of bonding of the metal to the chelating fragment, metal chelate monomers are divided into four main types: molecular metal chelates, intracomplex compounds, macrocyclic complexes, and polynuclear metal chelates. The synthetic methodologies for preparing metal chelate monomers are systematized. Special attention is paid to the effect of a metal on both the polymerization transformations of the metal chelate monomers and properties of the products formed. The bibliography includes papers published after 2010.     

离子色谱法分析金属离子的研究进展

综述了离子色谱法(IC)分析金属离子的研究进展,对目前应用于分析金属离子的阳离子交换IC、阴离子交换IC和螯合离子色谱进行了评述。阳离子交换IC是IC分析金属离子的主要形式,固定相为强酸(磺酸)型阳离子交换剂和弱酸(羧酸)型阳离子交换剂,结合适当的检测方法,阳离子交换IC可以测定碱金属、碱土金属、过渡金属、稀土离子、铵离子及低相对分子质量的有机胺类分子等。阴离子交换IC可以分析碱土金属、过渡金属、稀土离子等,对金属离子的分析具有更好的选择性,并可以实现金属离子和无机阴离子的同时测定。螯合离子色谱可以对复杂基体中的痕量金属离子进行测定。引用文献125篇。     

Transient Behavior of the Metal Interface in Lithium Metal–Garnet Batteries

The interface between solid electrolytes and Li metal is a primary issue for solid‐state batteries. Introducing a metal interlayer to conformally coat solid electrolytes can improve the interface wettability of Li metal and reduce the interfacial resistance, but the mechanism of the metal interlayer is unknown. In this work, we used magnesium (Mg) as a model to investigate the effect of a metal coating on the interfacial resistance of a solid electrolyte and Li metal anode. The Li–Mg alloy has low overpotential, leading to a lower interfacial resistance. Our motivation is to understand how the metal interlayer behaves at the interface to promote increased Li‐metal wettability of the solid electrolyte surface and reduce interfacial resistance. Surprisingly, we found that the metal coating dissolved in the molten piece of Li and diffused into the bulk Li metal, leading to a small and stable interfacial resistance between the garnet solid electrolyte and the Li metal. We also found that the interfacial resistance did not change with increase in the thickness of the metal coating (5, 10, and 100 nm), due to the transient behavior of the metal interface layer.     

Binding cadmium and copper ions with chemically modified cellulosic materials

Equilibrium sorption of cadmium and copper ions by modified and unmodified maize stalk was studied using a range of metal-ion concentrations and temperatures at various metal ion-substrate contact periods. The amount of metal ion removed from solution depended on the metal ion concentration, the metal ion-substrate contact period and the metal ion type. The level of metal ion uptake reached 15 mg/g of the substrate for cadmium ions at 0 degree C and was of the order Cd(II) greater than Cu(II). Modification improved the metal ion binding capacity of the substrate and increased the rate of metal ion uptake. The influence of temperature on the level and rate of metal ion uptake by the substrate was investigated.     

聚苯胺/贵金属复合纳米材料的可控合成及催化应用

导电高分子/贵金属复合纳米材料因其在催化、传感、表面增强拉曼、光热治疗等诸多领域的应用前景而受到广泛关注.本文主要介绍我们课题组近年来利用可控合成策略制备的负载型和包埋型两种结构聚苯胺/贵金属复合纳米材料,以及利用复合纳米材料的结构和功能特性,对其在多相催化领域的应用、结构与催化性能之间构效关系的探索.     

Effect of alkali metal cationization and multiple alkali metal exchange on the collision-induced dissociation of loganic acid studied by electrospray ionization tandem mass spectrometry

Under electrospray ionization conditions loganic acid undergoes alkali metal (Li, Na and K) exchange and alkali metal cationization. Multiple exchanges of up to four alkali metal ions are observed. Different populations of metal exchanged species are produced during electrospray ionization. Collision-induced dissociation of ammonium cationized species is compared with that of metal cationized species to study the effect of metal cationization. Glycosidic cleavage and ring cleavages of aglycone and sugar moieties are the major fragmentation pathways observed during collision-induced dissociation. The fragmentations of the highly metal exchanged species indicate the opening of the pyran ring. Collision-induced dissociation of the various metal exchanged and metal cationized species also reveals the nature of the different populations. Copyright 2000 John Wiley & Sons, Ltd.     

Fabrication of mesoporous metal chalcogenide nanoflake silica thin films and spongy mesoporous CdS and CdSe

Mesoporous silica metal oxide (ZnO and CdO) thin films have been used as metal ion precursors to produce the first examples of mesoporous silica metal sulfide (meso-SiO(2) @ZnS, meso-SiO(2) @CdS) or silica metal selenide (meso-SiO(2) @ZnSe, meso-SiO(2) @CdSe) thin films, in which the pore walls are made up of silica and metal sulfide or metal selenide nanoflakes, respectively. A gentle chemical etching with a dilute HF solution of the meso-SiO(2) @CdS (or meso-SiO(2) @CdSe) produces mesoporous cadmium sulfide (meso-CdS) (or cadmium selenide, meso-CdSe). Surface modified meso-CdS displays bright blue photoluminescence upon excitation with a UV light. The mesoporous silica metal oxides are formed as metal oxide nanoislands over the silica walls through a self-assembly process of a mixture of metal nitrate salt-two surfactants-silica source followed by calcination step. The reactions, between the H(2) S (or H(2) Se) gas and solid precursors, have been carried out at room temperature and monitored using spectroscopy and microscopy techniques. It has been found that these reactions are: 1)?taking place through the diffusion of sulfur or selenium species from the top metal oxide layer to the silica metal oxide interface and 2)?slow and can be stopped at any stage to obtain mesoporous silica metal oxide metal sulfide or silica metal oxide metal selenide intermediate thin films.     

STUDY ON THE INTERACTION BETWEEN POLYVINYLPYRROLIDONE AND PLATINUM METALS DURING THE FORMATION OF THE COLLOIDAL METAL NANOPARTICLES

Several PVP-stabilized colloidal platinum metals nanoparticles have been synthesized and characterized by FTIR and TEM.Comparing with the pure PVP,carbonyl groups of PVP in the mixture of PVP and the metal precursors or in the PVP-stabilized metal nanoparticles have obvious peak shifts in FTIR spectra.The peak shifts reveal the interaction between PVP and the metal species.The interaction between PVP and metal precursors has effect on the formation of the colloidal metal nanoparticles.Strength of the int...     

Growth of layered basic zinc acetate in methanolic solutions and its pyrolytic transformation into porous zinc oxide films

Photo-induced reduction of gold and platinum metal salt solutions was carried out using viologen graft copolymerized on low-density polyethylene (LDPE) films and viologen-containing poly(vinylidene fluoride) (PVDF-PVBV) microporous membranes. The effects of the UV irradiation time and concentration of the metal salt solutions on the metal ion reduction process and the resultant metal deposition on the polymeric substrates were investigated. The metal-polymer composites were characterized using X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and UV-visible absorption spectroscopy. The amount of metal uptake, the state of the metal, and the size of the metal particles were found to be strongly dependent on the UV irradiation time and the type and concentration of the metal salt solution. The microporous structure and the high viologen content of the PVDF-PVBV membrane constitute an effective matrix for metal ion reduction and preparation of metal nanoparticles.     

Tandem mass spectra of ammonium ion,metal ion and ligated metal ion adducts of acyclic sugar derivatives

The tandem mass (MS/MS) spectra of ammonium ion, metal ion and ligated metal ion adducts of chain-extended acyclic nitro-containing deoxyglucose and deoxygalactose derivatives have been studied. The ammonium adducts fragment primarily by elimination of ammonia followed by acetic acid, thus not giving much structural information. In contrast, cationization of these compounds by metal ions and ligated metal ions gave structurally informative and useful fragment ions on MS/MS. The metal ions and ligated metal ions play an important role in controlling and directing fragmentation. Retro-aldol fragmentation is facilitated by metal ions such as Li(+), Na(+), Ag(+) and Cu(+), whereas the adducts with higher alkali metal ions such as Rb(+) and Cs(+) fragment to give only the corresponding metal ions. The divalent metal ions such as Cu(2+) and Ba(2+) also induce retro-aldol fragmentation. However, the charge is carried by the aldehyde fragment in the case of Cu(2+) adducts, whereas the nitroalkane fragment carries the charge in the case of Ba(2+) adducts. Ligated metal ions such as ZnCl(+), CuCl(+), InCl(2) (+) and BaCl(+) also behave similarly and induce retro-aldol fragmentation in these acyclic sugars. Both the metal ion and ligated metal ion adducts can fragment by elimination of metal-containing neutral molecules.     

Study on some metal–metal quadruple bonds

In the present paper, the role of (n ? 1)? orbitals in metal–metal quadruple bonds was studied. It was shown by the calculations that the probabilities for finding the σ-, π-, and δ-electrons between two metal atoms, under the influence of the ? orbitals on the metal–metal quadruple bonds, increased while their mean kinetic energy components along the metal bond axis decreased. In addition, the effects of the ? orbitals upon the σ, π, and δ metal–metal bonds were different. In general, σ < π < δ.     

How to affect number, size, and location of metal particles deposited in conducting polymer layers

This paper presents a review on a series of recent investigations focused on the understanding of the role of various factors for the number, size, and location of the metal particles electrodeposited in conducting polymer (CP) layers. It is demonstrated that the initial oxidation state of the CP layer and its surface and bulk structure play an important role for the location of the metal particles. The use of metal anion complexes instead of the corresponding metal cations presents a helpful tool for affecting the location and number of metal crystals. The involvement of special metal/polymer interactions in the metal electrocrystallization process is another way for influencing the metal deposit. An alternative to the electrodriven deposition is the electroless metal precipitation based on the reducing ability of the CP layers. This approach results in metal particles deposition at the polymer surface and may be effectively controlled through parameters such as CP reduction charge, dipping time, and concentration of the metal-plating solution.     

Synthesis, characterization and formation process of transition metal oxide nanotubes using carbon nanofibers as templates

Mono and binary transition metal oxide nanotubes could be synthesized by the immersion of carbon nanofiber templates into metal nitrate solutions and removal of the templates by heat treatment in air. The transition metal oxide nanotubes were composed of nano-crystallites of metal oxides. The functional groups on the carbon nanofiber templates were essential for the coating of these templates: they acted as adsorption sites for the metal nitrates, ensuring a uniform metal oxide coating. During the removal of the carbon nanofiber templates by calcination in air, the metal oxide coatings promoted the combustion reaction between the carbon nanofibers and oxygen.     

New synthetic route for preparing rattle-type silica particles with metal cores

Rattle-type silica particles with metal cores, applicable to catalysts and metal/inorganic composite coating materials, were prepared by the pre-shell/post-core method that can control the size of metal cores inside silica capsules and exchange from metal cores into different ones with a metal displacement reaction.     

Precipitation of metal ions by organic acids as a mean for metal recovery and decontamination of wastewater

The dicarboxylic and oxycarboxylic acids known as complexing agents for metal ions under the conditions when the amount of metal ions exceeds that in metal complexes, act as precipitants for metal ions. The completeness of precipitation, depends on the kind of metal and organic acid, pH and the concentrations of substances. The abundance of metals in metal finishing industry enables to use such precipitation for regeneration and decontamination of the complexing agents containing solutions.     

Metal bioavailability: how does its significance change in the time?

The significance of terms "metal bioavailability" and "bioavailable metal fraction" is evolved in the time, passing from a very simple concept to a complex concept bound to abiotic and biotic aspects. At the beginning metal toxicity was related to metal fraction present in water phase, than only free metal ion activity was considered and the free ion activity model (FIAM) was proposed. Successively, due to the exceptions observed and to the consciousness that metal bioavailability could be considered as dynamic characteristic the concept of metal bioavailability became very complex, depending on physical, chemical and biological factors.     

Polymer assisted deposition

Polymer assisted deposition (PAD) is a chemical solution route to high quality thin films of metal oxides. This technique employs metal ions coordinated to polymers as the film precursor. The use of polymer bound metals has several advantages. The polymer controls the viscosity and binds metal ions, resulting in a homogeneous distribution of metal precursors in the solution and the formation of uniform metal oxide films. The nature of the metal oxide deposition is dominated by bottom-up growth, leading to ready formation of crack-free epitaxial metal oxides and the ability to coat nanofeatured substrates in a conformal fashion.