Monitoring formation of poly(neutral red) film by EQCM

An electrochemical quartz crystal microbalance (EQCM) is employed for monitoring the growth of poly(neutral red) films on platinum in the electrolytic solution containing 5.0 mmol dm⁻³ neutral red, 0.3 mol dm⁻³ H₂SO₄, and 0.5 mol dm⁻³ Na₂SO₄. The in situ measurement of the frequency changes of the EQCM reveals that both the adsorption/desorption of neutral red and the formation of poly(neutral red) film can be observed together with anion sorption/desorption during the redox transformation of the polymer, and that the polymerization rate of neutral red increases slowly before the 11th cycle and then increases quickly with increasing number of potential cycles. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 3, pp. 284–289. The text was submitted by the authors in English.     

微波合成铝掺杂钻酸锂材料及性能研究

以LiOH·H2O，Al2O3和Co3O4为原料，微波加热合成Li离子电池正极材料LiAlxCo（1-x）O2．通过XRD测试表征了不同Al加入量时合成产物的晶体结构，确定当x≤0．4时，产物为单一相层状结构．计算了不同x时LiAlxCo（1-x）O2的晶胞参数，随着x的增大，a值减小，c值增大．对合成LiAlxCo（1-x）O2样品进行DSC—TGA测试，结果表明，当x不同时，合成样品的热稳定性不同．SEM测试表明，合成晶体粒度较均匀，粒径在5μm左右．电化学测试表明，LiAl0.2Co0.8O2的电化学性能最好，首次循环放电容量为127mAh／g，多次循环容量损失率小于LiCoO2．     

Shot noise sets the limit of quantification in electrochemical measurements

Detection of single molecules, particles, and rapid redox events is a challenge of electrochemical investigations and requires either an amplification strategy or significant averaging for the electrochemical current to exceed the noise level. We consider the minimum number of electrons required to reach the limit of quantification in these electrochemical measurements. A survey of the literature indicates that the state-of-the-art limit in current detection for different types of measurements (e.g. voltammetry, single-molecule redox cycling, ion channel recordings of single molecules, metal nanoparticle collision, and phase nucleation) is independent of the nature of the measurement and increases linearly with reciprocal response time, Δt^?1, over ～5 orders of magnitude (from ～10 to ～10⁶ s^?1). We demonstrate that the practical limit of quantification requires cumulative measurement of ～2100 electrons during Δt and is determined by statistics of counting electrons, that is, the shot noise in the current.     

电化学方法获得具有表面增强拉曼活性镍电极的研究

利用纯电化学手段获得了具有较强表面增强拉曼活性的镍电极, 改进了原有的镍电极表面预处理方法. 结果表明, 在0.5 mol/L的NaClO4溶液中, 结合电化学阶跃技术和循环伏安技术, 可以得到合适的粗糙镍电极; 同时, 还得到了探针分子吡啶在该粗糙镍电极表面随电极电位变化的表面增强拉曼光谱(SERS), 此时谱峰强度获得了极大的增强; 还研究了粗糙镍电极的扫描电子显微镜(SEM)图像, 并估算出其SERS增强因子约为104, 此结果比以前的镍电极表面粗糙方法所能达到的增强因子高一个数量级.     

Vanadium Doped Sol-Gel TiO2 Coatings

A study of the experimental conditions required to obtain vanadium doped sol-gel TiO2 coatings is presented. Tetraethyl orthotitanate was employed as the TiO2 source and VCl3, VOSO4 · H2O and VOSO4 dissolved H2SO4 where employed as vanadium sources.Dip coating has been used to produce coatings on silicon wafers, spectral carbon electrodes and titanium electrodes. Both supported and unsupported films have been studied by UV-Vis spectra, IR spectroscopy and X-ray diffraction (XRD). The measurements have been made on samples as prepared and treated thermally at temperatures between 100°C and 300°C. The thermal treatment temperatures have been established from DTA/TGA measurements.The vanadium doped sol-gel TiO2 coatings have been tested as sensors for redox potential measurements in electrochemical processes. The influence of both the thickness of films and the nature of substrate has been investigated.     

ZnO纳米线的电化学制备研究

High-quality ZnO nanowires have been synthesized at relatively low temperature via one-step electrochemical anodization technique. In this method, Zn sheet acted as the anode and Pb sheet served as the counter electrode, and the complex solution of HF-C₂H₅OH-H₂O was used as electrolyte. ZnO nanowires were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED) and X-ray Diffraction (XRD). The results show that the nanowires were wurtzite crystalline ZnO, and the ZnO nanowires with the diameters of 70 nm and 30～40 nm were obtained by adjusting preparation conditions, respectively.     

Synthesis, structure, and electrochemical properties of 12,42-dioxo-21,31-diphenyl-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane

The oxidative dehydrocyclization of the 3-(indolizin-2′-yl)-2-oxoquinoxaline monopodand performed either electrochemically or under the action of molecular iodine affords new redox-active heterocyclophane consisting of the redox-switchable biindolizine fragment combined with the polyether-bridged π-deficient quinoxaline systems. The single-crystal X-ray diffraction study showed that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane in MeCN and DMF showed the three-step oxidation of the indolizine fragments accompanied by the single-electron transfer in each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a _2N = 0.26 mT). Dedicated to Professor E. A. Berdnikov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–2003, October, 2007.     

Polarization Dependence of a Hydrophobized Electrode for Electrosynthesis of a Soluble Product

An equation for a polarization curve of a hydrophobized electrode is proposed for electrosynthesis of a soluble electroactive product in an inner-kinetic mode. The equation contains the concentration of the target product (TP) in an explicit form. The shape of the curve depends on the biquadratic root of the TP concentration and the square root of the ratio between exchange currents of the side and target reactions.     

Electrochemical characterization of solid materials in volume range I. Chemical effects on the matrix-phase separation

The electrochemical phase isolation (EPI) is described as a preparation method for determining specific precipitations in solid materials in microamounts and microdimensions. Fundamental criteria are examined as a function of the main parameter (polarization current) on the system Fe₃C in a Fe-matrix. The influence of the electrolyte composition on the electrochemical behaviour of the matrix, on the one hand, and of the phase, on the other hand, are investigated and utilized.     

超声波处理对球形β-Ni(OH)2结构及电化学性能的影响

A method of ultrasonic treatment （UST） was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of nickel series alkaline batteries. The experimental results showed that UST was an effective method to improve the electrochemical performance of β-Ni（OH）2 such as specific discharge capacity, discharge potential, electrochemical reversibility and oxygen evolution over-potential. The results of electrochemical impedance spectroscopy, powder X-ray diffraction and particle size distribution indicated that the improvement of the performance of β-Ni（OH）2 through UST was attributed to the reduction of the charge-transfer resistance （Rt） and the diffusion impedance （Zw）, which resulted from the decrease of the crystallite and particle size and the increase of interlayer spacing. Diffusion coefficient of proton DH of ultrasonic treated β-Ni（OH）2 gained by CV tests was 1.13 × 10^-11 cm^2/s, and the average discharge specific capacity of ultrasonic treated β-Ni（OH）2 electrode was 301 mAh/g.