Changes of electrochemical responses of the bulk solution species by thermotropic permeability of liquid crystalline membranes coated on electrodes

Liquid crystalline/polymer composite membrane-coated electrodes were prepared by casting a 1,2-dichloroethane solution of N-(4-ethoxybenzylidene)-4′-n-butylaniline (EBBA) and polycarbonate (PC) on an electrode surface. The temperature-dependence of the permeability of the EBBA/PC composite membrane on electrodes to Fe(CN)^3?₆ ion as a solution-phase redox ion was investigated by means of hydrodynamic voltammetry at a rotating disk electrode. The permeability changed with temperature over the range of the crystalline-nematic-phase transition temperature of EBBA. It is demonstrated that the observed temperature-dependence of the permeability reflects the thermotropic properties of EBBA in the EBBA/PC composite membrane. Furthermore, the dependence of the limiting current of the steady-state current-potential curves for the reduction of Fe(CN)^—₆ at the EBBA/PC composite membrane-coated electrode upon the membrane thickness, the blend ratio of EBBA and PC and the concentration of Fe(CN)^3?₆ in a bulk solution was examined in order to understand the transport process of Fe(CN)^?3₆ through the EBBA/PC composite membrane from the membrane/solution interface to the electrode/membrane interface. The transport process of Fe(CN)^3?₆ within the membrane was found to obey Fick's Law.     

Analysis of the temperature dependence of the high-frequency EMR spectra of Mn ions in the lithium-ion battery material LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>

This paper deals with the analysis of the temperature dependence of high-frequency EMR (HF-EMR) spectra due to Mn³⁺ and Mn⁴⁺ ions in the lithium manganese spinel LiMn₂O₄. A range of powder samples obtained by the sol-gel method with calcinations in several temperature ranges were prepared for this study. Based on the initial characterization carried out by a number of techniques, the physicochemical and structural properties of the samples were earlier determined. Independently, temperature magnetization and HF-EMR measurements were carried out. The EMR spectra vary strongly between samples, indicating possible structural or chemical changes. Quantitative analysis of the temperature dependence of the HF-EMR spectra due to Mn³⁺ and Mn⁴⁺ ions in LiMn₂O₄ is presented in this paper. The spectral analysis concerns the line shape, linewidth, intensity and g-factors. Fittings using the Lorentzian spectral shape and, to a certain extent, the Gaussian spectral shape have been carried out in order to parameterize the temperature dependence of the HF-EMR spectra. This parameterization of the HF-EMR experimental data enables a deeper characterization of the samples. Subsequently, a better insight into the role of the Mn³⁺ and Mn⁴⁺ ions in accounting for the characteristics most suitable for application of LiMn₂O₄ as a cathode material may be gained.     

聚酚藏花红功能碳纳米管生物阳极制备及其在乙醇传感器应用

应用电化学法聚合酚藏花红（PPS）功能化的单壁碳纳米管,以其作为烟酰胺辅酶（NADH）氧化的电化学催化剂（电极）,构建基于乙醇脱氢酶的安培型乙醇生物电化学传感器.该电极于0.0 V时,对NADH具有很好的催化性能.而单体酚藏花红则由于其电位过低（-0.48 V）,不能显示催化性能.循环伏安和计时安培法测试表明：该传感器...     

Removal of phosphate by aluminum oxide hydroxide

The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The adsorption of phosphate onto aluminum oxide hydroxide was influenced by pH in solution: the amount adsorbed was greatest at pH 4, ranging with pH from 2 to 9. The optimum pH for phosphate removal by aluminum oxide hydroxide is 4. The selectivity of phosphate adsorption onto aluminum oxide hydroxide was evaluated based on the amount of phosphate ion adsorbed onto aluminum oxide hydroxide from several anion complex solutions. It is phosphate that aluminum oxide hydroxide can selectively adsorb. The selectivity of phosphate onto aluminum oxide hydroxide was about 7000 times that of chloride. This result indicated that the hydroxyl groups on aluminum oxide hydroxide have selective adsorptivity for phosphate and could be used for the removal of phosphate from seawater.     

电化学氧化增强金属钴卟啉的自组装研究

应用电化学方法将钴(Ⅱ)卟啉氧化成钴(Ⅲ)卟啉以增强它与4-巯基吡啶(MP)自组装膜的轴向配位作用,从而快速制备了有序钴卟啉自组装修饰电极CoTMPP/MP/Au(E).电化学石英晶体微天平(EQCM)测试证实电化学氧化对钴卟啉膜生长过程的增强作用.Ram an光谱及修饰电极电催化还原氧研究显示,该修饰电极与经过长时间浸渍法得到的CoTMPP/MP/Au(I)修饰电极具有完全相似的有序结构和性质.与直接将钴卟啉吸附在电极表面的CoTMPP/Au修饰电极相比,以巯基吡啶为桥键得到的钴卟啉修饰电极具有更好的电催化活性和稳定性.     

Role of Al or Eu on thermoluminescence of Al- and/or Eu-doped SiO2 crystals

Although SiO₂ crystals have been used in electroluminescence devices and thermoluminescence (TL) dosimeters, the emission mechanism of TL has not yet been clearly explained. Recently, as we could get amorphous and highly pure SiO₂ prepared by the sol-gel method, we have investigated the TL emission mechanism using Al³⁺- and/or Eu³⁺-doped SiO₂ crystalline samples prepared by the heat-treatment under much lower temperature that the melting point of SiO₂. The TL spectrum of the Eu³⁺-doped sample displayed several peaks, including two main peaks due to the electron transitions from ⁵D₂ to ⁷F₅ (ca. 570 nm) and from ⁵D₀ to ⁷F₂ (ca. 610 nm). As doping concentration increased, all the peak intensities reduced from maximum values except that due to the electron transition from ⁵D₀ to ⁷F₂. These observations are thought to result from a cross-relaxation process due to the lack of inversion symmetry at the Eu³⁺ site.     

Preconcentration of trace silver with yeast for river water analysis

A new preconcentration method with yeast is presented. The method was evaluated for the determination of trace silver in river waters by graphite furnace atomic absorption spectrometry (GFAAS). A suitable cultivation bed for preconcentration of silver was 1.75 mg ml-1 2-ammonium hydrogen phosphate. The optimal cultivation time and temperature were 2 h and 25 degrees C. Under optimal conditions, silver in aqueous sample was concentrated to 6.9-fold by yeast. The detection limit was 4.6 pg ml-1 (3S/N) for silver in river water. The yeast preconcentration method was applied to the determination of silver in river waters. The recovery of spiked silver was in the range of 89 to 110%. By the preconcentration, it was found that ultra trace silver in river waters could be determined without interferences of matrix elements, after only the cultivation and with no chemical treatment.     

Radical cascade reaction with 1,4-dienes and 1,4-enynes using 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor: one-step synthesis of bicyclo[3.3.0]octane derivatives

[reaction: see text] Radical cascade reaction with various 1,4-dienes and 1,4-enynes using dimethyl 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor smoothly proceeds through an iodine atom transfer mechanism to give functionalized bicyclo[3.3.0]octane derivatives in good yields.