Microstructure and electrical properties of BaTiO<Subscript>3</Subscript> and (Ba,Sr)TiO<Subscript>3</Subscript> ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO₂ substrates with TiO₂ as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO₃ and (Ba,Sr)TiO₃ dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.     

电化学合成聚苯胺粉末电极的电化学行为研究

我们曾用慢速动电位扫描法研究化学合成聚苯胺粉末的电化学行为.本文对恒电位电解合成聚苯胺粉末进行了研究.用这种方法制备的粉末由于合成溶液中不含氧化剂因而纯度高.本文还报导了这种聚苯胺粉末电极的交流阻抗测量结果.交流阻抗法曾用于聚苯胺膜的电导和化学合成聚吡咯的电阻测定. 所用盐酸、氟硼酸、硅氟酸、苯胺均为分析纯;苯胺经常压蒸馏提纯;硫酸为超纯;磷酸为分析纯;高氯酸为优级纯.溶液皆用两次蒸馏水配制.     

铁氰化锰修饰玻碳电极的制备及其电化学性能

A thin film of manganese hexacyanoferrate （MnHCF） was electrochemically formed on a glassy carbon （GC） electrode to prepare a chemically modified electrode （CME）. The mechanism of film formation of MnHCF and its growth process were investigated in detail by cyclic voltammetry. The results show that the stoichiometric composition of MnHCF is Mn^ⅢFe^Ⅲ（CN）6, an analogue of prussian yellow. There exist three clear-cut stages in the whole modification process and the last stage is indispensable to the fabrication of homogenized, stable MnHCF film and must last for an appropriate time. The surface morphology of MnHCF/GC electrode was characterized by scanning electron microscopy （SEM）, which further verified the effective deposition of MnHCF film on GC. The kinetic constants of MnHCF/GC electrode process were also evaluated. The resulting MnHCF film modified electrode presented good stability and high electrocatalytic activity toward the oxidation of H2O2, indicating that MnHCF film possesses function of catalase and can be expected for analytical purposes.     

Mass transport in gas channels of electrochemical cells with a solid-oxide electrolyte: Allowing for the electrode reaction rates in numerical calculations

The concentration fields, Nusselt number distributions along the electrode, and ratios of concentrations of electrochemically active components at the entrance into and exit out of an electrochemical cell are determined by numerical integration of the convective-diffusion equation for a broad range of rate constants of electrode reactions, Peclet numbers, and geometrical parameters of channels. Three regions of parameter values are revealed. At low reaction rates (K _l < 0.5), mass transfer is completely determined by electrode kinetics; at high rates (K _l > 20), it is completely determined by the diffusion in the gas phase; and in the intermediate region of values of K _l it is necessary to allow for both the diffusion processes and the electrode reactions.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 317–324.Original Russian Text Copyright © 2005 by Ezin, Somov.     

Electrochemical Detection of MS2 Phage Using a Bead‐based Immunoassay and a NanoIDA

A microbead based sandwich immunoassay for MS2 bacteriophage was developed using an interdigitated array (IDA) electrode with nanoscale dimensions (220 nm electrode width, 620 nm gap). The IDA was fabricated using an electron beam lithographic lift‐off technique. After an antibody‐assisted capture of MS2 using paramagnetic microbeads, a β‐galactosidase labeled secondary antibody was used to convert p‐aminophenyl‐β‐D ‐galactopyranoside (PAPG) into the redox active p‐aminophenol (PAP). Amperometric detection of PAP with IDA electrodes at +300 and ?200 mV vs. a Ag/AgCl reference electrode was used to measure the result, detecting MS2 concentrations as low as 10 ng/mL.     

一种新的磷酸根离子敏感电极研究

一种新的磷酸根离子敏感电极研究肖丹，俞汝勤，李军，袁孔铨（湖南大学化学化工系，长沙，４１００８２）关键词磷酸根，离子选择电极，磷酸二氢根磷酸根离子浓度的测定在化学化工、环境保护、生命科学和临床医学等领域有着重要的意义。对磷酸根离子敏感电极的研究和探索...     

Voltammetric Characterization of Micro‐ and Submicrometer‐Electrode Arrays of Conical Shape for Electroanalytical Use

Densely packed micro‐ and submicrometer electrode arrays of platinum and gold (the nominal number, N, of electrodes in each array varies between 225 and 3600) are fabricated by photolithographic technique and vapor deposition processes of metal films. The electrodes are conical‐shaped and only their apexes are exposed to the electrolytic solution. The electrode arrays are characterized electrochemically in Ru(NH₃)₆Cl₃ aqueous solutions by using cyclic voltammetry at low scan rates, to establish the number of electrochemically active electrodes (N_ac) in each array; the geometric characterization is performed by scanning electron microscopy. All the investigated arrays provide steady‐state voltammograms, indicating diffusionally independent behavior of each microelectrode. The number of microelectrodes that are active in the fabricated arrays depends on microelectrode density. In particular, for the arrays with N=3600 and N=225, the fraction of active sites is about 45% and 90%, respectively. The analytical performance of some of the Pt version of the arrays is tested in hydrogen peroxide solutions, allowing verifying that linear calibration plots over the concentration range (0.1–20 mM) are obtained. This dynamic range is larger than that typically recorded at smooth polycrystalline platinum electrodes (0.5–5 mM), and the better performance is attributed to both the higher aspect ratio of the cone geometry and the higher mass transport associated to each microelectrode of the array. Reproducibility (within 3.5%, r.s.d.) and long‐term stability (within 5%, r.s.d., after 8 h continuous use) of the electrode systems are satisfactory. A low detection limit, based on the signal to noise ratio equal to 3, of 0.05 mM is found, which is adequate for a rapid monitoring of H₂O₂ in real samples and industrial processes.     

TiO2与ZnO复合纳米结构电极的光电化学研究

利用尿素加压共沉淀法以Ti(SO4)2与Zn(NO3)2为原料制备了TiO2-ZnO复合纳米粒子, 其纳米结构电极的光电化学研究结果表明, 反应物摩尔比为3∶1, 于530 ℃煅烧制备的复合纳米结构电极的光电转换效率最高. 对吸附染料RuL2(SCN)2∶2TBA的纳米结构TiO2和各种复合纳米粒子的纳米结构电极进行光电研究的结果表明, 染料对各纳米结构电极都起到了敏化作用, 其中也是由反应物摩尔比为3∶1, 于530 ℃煅烧制备的纳米结构电极的光电转换效率最高. 对聚3-甲基噻吩修饰的纳米结构TiO2和摩尔比为3∶1, 于530 ℃煅烧的复合纳米粒子构成的纳米结构电极进行光电性能研究, 结果表明, 聚3-甲基噻吩与半导体纳米粒子之间存在p-n结, 在一定条件下p-n结的存在有利于光生电子/空穴的分离, 从而提高了光电转化效率.     

Cobalt(II) and nickel(II) complexes of a cyclam derivative as carriers in iodide-selective electrodes

The ligand 1,4,8-tri(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L¹) containing pendant octyl groups has been synthesised. L¹ is a tetraazamacrocycle derived from the well-known cyclam unit, and the Ni²⁺ and Co²⁺ complexes, [Ni(L¹)]²⁺ and [Co(L¹)]²⁺, have been isolated and characterised. The ability of the nickel(II) and cobalt(II) complexes to act as anion receptors has been studied by using them as ionophores in membrane-based ion-selective electrodes (ISEs). The PVC membrane containing the complex [Ni(L¹)]²⁺ and 2-nitrophenyloctylether as plasticizer shows a Nernstian response against iodide in a concentration range from 1×10⁻¹ to 4×10⁻⁵ M I⁻ with a detection limit of 1.6×10⁻⁵ M I⁻ and a slope of 58.6 mV/pI⁻ at pH 7 (25 °C). In comparison, the electrode containing [Co(L¹)]²⁺ as ionophore gave a sub-Nernstian slope and a low lifetime. A comparison between the iodide-selective electrode containing [Ni(L¹)]²⁺ and other reported iodide-selective electrodes is also reported.     

Potentiodynamic and cyclic voltammetric behaviour of a lead electrode in NaOH solution

Summary The electrochemical behaviour of lead in NaOH solution was studied by potentiodynamic and cyclic voltammetric techniques in combination with X-ray diffraction analysis. The active dissolution of lead involves a small shoulderA1 followed by a peakA1 prior to a passive region. The shoulderA1 is assigned to the electroformation of a Pb(OH)₂ film, whereas peakA1 is due to the formation of PbO. Beyond the passive region, the current density increases again, forming a small shoulderA2 and a peakA2 prior to the oxygen evolution potential. The shoulderA2 and the peakA2 are correlated to the electrooxidation of PbO to Pb₃O₄ and PbO₂, respectively. The intensity of the anodic peaks increases with increasing alkali concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan shows two cathodic peaksC1 andC2 which are correlated to the electroreduction of PbO and PbO₂ respectively, to Pb.

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Potentiodynamisches und cyclovoltammetrisches Verhalten einer Bleielektrode in NaOH-Lösung

Zusammenfassung Das elektrochemische Verhalten von Blei in NaOH wurde mittels potentiodynamischer und cyclovoltammetrischer Techniken unter Zuhilfenahme der Röntgenbeugungsanalyse untersucht. Die aktive Auflösung von Blei verläuft über eine SchulterA1, die von einem einer passiven Region vorgelagerten PeakA1 gefolgt wird. Die SchulterA1 wird der elektrochemischen Bildung eines Pb(OH)₂-Films, der PeakA1 der Bildung von PbO zugeschrieben. Jenseits der passiven Region steigt die Stromdichte wieder an, und vor Erreichen des Sauerstoffpotentials treten eine kleine SchulterA2 und ein PeakA2 auf, die mit der Elektrooxidation von PbO zu Pb₃O₄ und PbO₂ korrelieren. Analog dazu beobachtet man in der cyclischen Voltammetrie zwei kathodische PeaksC1 undC2, die der Elektroreduktion von PbO und PbO₂ zu Pb entsprechen. Die Intensität der anodischen Peaks steigt mit steigender Alkalikonzentration, Temperatur und Scangeschwindigkeit.