在NaCl和SCN~-存在下浮选铜(Ⅱ)间接测定十六烷基三甲基溴化铵

研究了NaCl和NH4SCN浮选Cu(Ⅱ)间接测定十六烷基三甲基溴化铵的新方法。在水溶液中,Cu(Ⅱ)与SCN-和CTMAB缔合生成沉淀,在NaCl存在下,此沉淀被浮选。实验表明,Cu(Ⅱ)的浮选率与CTMAB的量在3.6~54.7 mg/L范围内呈良好的线性关系。CTMAB的检出限为1.8μg/mL。方法已用于合成水样和自来水中CTMAB的测定。     

多巴胺和抗坏血酸在十六烷基三甲基溴化铵/碳纳米管电极上的检测

研究了十六烷基三甲基溴化铵(CTMAB)/多壁碳纳米管修饰玻碳电极的制备以及多巴胺和抗坏血酸在该修饰电极上的电化学行为。在CTMAB和多壁碳纳米管的协同作用下,该修饰电极对多巴胺和抗坏血酸均具有显著的催化氧化作用,多巴胺和抗坏血酸的氧化峰电位分别为223mV和15mV,实现了在抗坏血酸共存时测定多巴胺。在pH7.0的磷酸盐缓冲溶液中,多巴胺和抗坏血酸的线性范围分别为2.0×10-6～2.0×10-3mol/L和4.0×10-5～1.0×10-2mol/L,检出限分别为6.0×10-7mol/L和1.0×10-5mol/L。     

Study on the Interaction between a Novel Ionic Liquid Probe and Anionic Surfactants Using Resonance Light Scattering Spectra and Its Analytical Application

The interaction between anionic surfactants (AS) and 1‐hexadecyl‐3‐methylimidazolium bromide [C₁₆mim]Br was studied by using resonance light scattering (RLS) technique, UV‐Vis spectrophotometry and fluorometric methods. In Britton Robinson (BR) buffer (pH 6.0), [C₁₆mim]Br reacted with AS to form supermolecular complex which resulted in enhancement in RLS intensity. Their maximum RLS wavelengths were all at 390 nm. Some important interacting experimental variables, such as the solution acidity, [C₁₆mim]Br concentration, salt effect and addition order of the reagents, were investigated and optimized. Under the optimum conditions, quantitative determination ranges were 0.001–7 μg·mL^?1 for dodecyl sodium sulfate (SDS), 0.001–6 μg·mL^?1 for sodium dodecylbenzene sulfonate (SDBS) and 0.005–7 μg·mL^?1 for sodium lauryl sulfonate (SLS), respectively, while the detection limits were 1.3 ng·mL^?1 for SDS, 1.0 ng·mL^?1 for SDBS and 5.1 ng·mL^?1 for SLS, respectively. Based on the ion‐association reaction, a highly sensitive, simple and rapid method has been established for the determination of AS.     

Cationic polymerization of hydrocarbon monomers induced by complexes of acycl halides with lewis acids

The block polymerization of isobutylene with α-methylstyrene induced by acyl initiators was investigated. Thek _el/k _p values (the criterion for “closeness to the living state,”), wherek _el is the rate constant of proton elimination from a growing carbocation andk _p is the rate constant of chain growth, were analyzed. The minimumk _el/k _p values are characteristic of processes occurring in the presence of PhCOCl·2AlBr₃ and an equimolar mixture of MeCOBr·AlBr₃ with PhCOCl·AlBr₃. It was concluded that these complexes are efficient initators for the synthesis of block copolymers with a relatively narrow molecular-weight distribution and a low content of homopolymers. For Part 10, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1944–1948, October, 1999.     

A Volumetric Study of Water–Decyltrimethylanimonium Bromide–Pentanol Ternary System from 25 to 130°C at 2 and 19 MPa

Density measurements on decyltrimethylammonium bromide (DeTAB)–water and pentanol (PentOH)–DeTAB–water systems as functions of both alcohol and surfactant m _S concentrations were carried out at 2 and 19 MPa from 25 to 130°C. From experimental data for the water–DeTAB binary system, the standard (infinite dilution) partial molar volumes, expansibilities, and compressibilities of DeTAB, and the corresponding properties in the micellar phase are calculated. The trends of the standard partial molar volumes of PentOH V _R ^o in DeTAB micellar solutions as functions of m _S reflect the transfer of PentOH from the aqueous to the micellar phase, except at 130°C and 19 MPa. On the basis of an equation previously used, the distribution constant of PentOH between the aqueous and the micellar phases and the standard partial molar volume of alcohol in the aqueous and the micellar phases are obtained from V _R ^o data. Comparisons with data for PentOH in dodecyltrimethylammonium bromide are made.     

Study on Separation/Enrichment and Determination of Mercury(II) using Microcrystalline Thymolphthalein Loaded with Ternary Association Complex

The paper presents a novel method for the separation/enrichment of Hg²⁺ using microcrystalline thymolphthalein loaded with ternary association complex prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTAB) and thymolphthalein, various salts and acidity etc. on the enrichment yield of Hg²⁺ have been investigated to select the experimental conditions. The results showed that in the presence of 1.0 g NaCl, when the dosage of 0.1 M KI solution was 1.50 mL and 5.0 × 10⁻³ M dodecyl trimethyl ammonium bromide (DTAB) solution was 1.50 mL respectively, the water‐insoluble ternary association complex of (DTAB)₂(HgI₄) which produced by Hg²⁺ and I⁻, DTAB cation (DTAB⁺) was quantificationally absorbed on the surface of microcrystalline thymolphthalein Therefore, Hg²⁺ was separated completely from Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe³⁺, Al³⁺, Pb²⁺, Bi³⁺ and Cr³⁺ etc. by contolling acidity. The possible enrichment mechanism of Hg²⁺ was deduced. The proposed method has been successfully applied to the determination of Hg²⁺ in the sample of industrial waster water, and the results agreed well with the dithizone method. The recoveries were 94.5%∼106.5%, and the RSD was 2.0%∼2.8%.     

A short formal synthesis of three epimers of penmacric acid

An extremely short formal synthesis of three epimers of penmacric acid is accomplished starting from pyroglutamate in one or two steps. Stereochemical outcome in the reaction of Li and Ti enolates of pyroglutamate with imines is found to be dependent on both chelation and steric factors.     

Synthesis and electrochemical performance of hole-rich Li4Ti5O12 anode material for lithium-ion secondary batteries

Hole-rich Li₄Ti₅O₁₂ composites are synthesized by spray drying using carbon nanotubes as additives in precursor solution, subsequently followed calcinated at high temperature in air. The structure, morphology, and texture of the as-prepared composites are characterized with XRD, Raman, BET and SEM techniques. The electrochemical properties of the as-prepared composites are investigated systematically by charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the pristine Li₄Ti₅O₁₂, the hole-rich Li₄Ti₅O₁₂ induced by carbon nanotubes exhibits superior electrochemical performance, especially at high rates. The obtained excellent electrochemical performances of should be attributed to the hole-rich structure of the materials, which offers more connection-area with the electrolyte, shorter diffusion-path length as well faster migration rate for both Li ions and electrons during the charge/discharge process.     

Adsorption, association and precipitation in hexadecyltrimethylammonium bromide/sodium dodecyl sulfate mixtures

The phase equilibria of surfactant aqueous mixtures, hexadecyltrimethylammonium bromide and sodium dodecyl sulfate, have been studied by polarizing microscopy, quasielastic light scattering, conductivity, potentiometric, electrophoretic, and surface tension measurements. Adsorption at the air/solution interface, association and precipitation in bulk solution strongly depended on the molar ratio and the concentration of surfactants. Catanionic vesicles coexisted with crystalline catanionic salts in a broad concentration range. The relative proportions of crystallites and vesicles varied according to the concentration and the molar ratio of the surfactants. The solid crystalline phase was progressively converted to catanionic vesicles with increasing surfactant molar ratio. At the highest excess of one of the surfactants transition from catanionic vesicles to mixed micelles occurred. The formation and stability of different phases are discussed in terms of surfactant molecular packing constraints and electrostatic interactions in the headgroup region. Surfactant tail-length asymmetry and the change of electrostatic interactions in the headgroup region from attractive to repulsive are governing factors for the transition from planar to curved bilayers. Received: 9 June 1998 Accepted: 18 August 1998     

Preparation of LiNiO2 and LiM y Ni1- y O2 (M=Co,Al) films by electrostatic spray deposition

Syntheses of LiNiO₂, LiCo_0.5Ni_0.5O₂, and LiAl_0.25Ni_0.75O₂ as thin films were carried out by electrostatic spray deposition (ESD) onto a gold substrate. Single-phase LiNiO₂ film was obtained using a precursor solution of Li(OCOCH₃)+Ni(OCOCH₃)₂/ethanol, and by heating the deposit at 700 °C under an oxygen stream. In the case of cobalt or aluminum doping, Co(NO₃)₂/ethanol or Al(NO₃)₃/ethanol were added to the precursor solution in a given ratio. X-ray diffractometry revealed that all films had a crystal structure of space group R3ˉm; a=2.879, c=14.197 ? for LiNiO₂; a=2.844, c=14.152 ? for LiCo_0.5Ni_0.5O₂; a=2.855, c=14.148 ? for LiAl_0.25Ni_0.75O₂ (in hexagonal setting). Although these products were highly porous, it was observed that the average film thickness of LiNiO₂ increased almost proportionally with the deposition time. Electrochemical measurements (cyclic voltammetry, charge/discharge measurement at a constant current) were carried out in organic solutions of LiClO₄ (1 mol dm⁻³ LiClO₄/propylene carbonate+ethylene carbonate). The results indicated that thin films fabricated by ESD were electrochemically active for lithium ion extraction/insertion. The effect of cobalt or aluminum doping on the voltammograms is also described. Received: 1 April 1998 / Accepted: 23 July 1998