Low-temperature deposited ZnO thin films on the flexible substrate by cathodic vacuum arc technology

In this paper, un-doped zinc oxide (ZnO) films with various thicknesses (150, 250, 350, 450 and 550 nm) were successfully prepared onto PET substrates using cathodic vacuum arc technique at low-temperature (<40 °C). Their microstructure, optical and electrical properties were investigated and discussed. The films showed (0 0 2) peaks, an average transmittance over 80% in the visible region. Calculated values of the band gap are around 3.29-3.33 eV when the film thickness increased, indicating a slight blue shift of optical transmission spectra. The lowest resistivity about 5.26 × 10⁻³ Ω cm could be achieved for the un-doped ZnO film with thickness of 550 nm.     

Determination of Selenium Traces on Cyclic Renewable Mercury Film Silver Electrode in Presence of Copper Ions Using Cathodic Stripping Voltammetry

The new cyclic renewable mercury film silver based electrode (Hg(Ag)FE), applied for the determination of selenium(IV) traces in the presence of copper ions using differential pulse cathodic stripping voltammetry (DP CSV) is presented. The preparation of the Hg(Ag)FE is very simple. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimized. The calibration graph is linear from 0.5 nM (39 ng L^?1) to 100 nM (7.9 μg L^?1) for a preconcentration time of 45 s, with correlation coefficient of 0.9995. For a Hg(Ag)FE with a surface area of 8 mm² the detection limit for a preconcentration time of 90 s is as low as 17 ng L^?1. The repeatability of the method at a concentration level of the analyte as low as 2 μg L^?1, expressed as RSD is 2.7% (n=7). The proposed method was successfully applied and validated by studying the certified reference material (bovine liver BCR‐185) and simultaneously recovery of Se(IV) from spiked water samples.     

Development of a Creatinine Sensor Based on a Molecularly Imprinted Polymer‐Modified Sol‐Gel Film on Graphite Electrode

An electrochemical creatinine sensor based on a molecularly imprinted polymer (MIP)‐modified sol‐gel film on graphite electrode was developed. The surface coating of MIP over sol‐gel was advantageous to obtain a porous film with outwardly exposed MIP cavities for unhindered selective rebinding of creatinine from aqueous and biological samples. A fast differential pulse, cathodic stripping voltammetric response of creatinine can be obtained after being preanodized the sensor in neutral medium containing appropriate amount of creatinine at +1.8 V versus SCE for 120 s. A linear response over creatinine concentration in the range of 1.23 to 100 μg mL^?1 was exhibited with a detection limit of 0.37 μg mL^?1 (S/N=3).     

Nanogold-penetrated poly(amidoamine) dendrimer for enzyme-free electrochemical immunoassay of cardiac biomarker using cathodic stripping voltammetric method

Methods based on immunoassays have been developed for cardiac biomarkers, but most involve the low sensitivity and are unsuitable for early disease diagnosis. Herein we design an electrochemical immunoassay for sensitive detection of myoglobin (a cardiac biomarker for acute myocardial infarction) by using nanogold-penetrated poly(amidoamine) dendrimer (AuNP-PAMAM) for signal amplification without the need of natural enzymes. The assay was carried out on the monoclonal mouse anti-myoglobin (capture) antibody-anchored glassy carbon electrode using polyclonal rabbit anti-myoglobin (detection) antibody-labeled AuNP-PAMAM as the signal tag. In the presence of target myoglobin, the sandwiched immunocomplex could be formed between capture antibody and detection antibody. Accompanying AuNP-PAMAM, the carried gold nanoparticles could be directly determined via stripping voltammetric method under acidic conditions. Under optimal conditions, the detectable electrochemical signal increased with the increasing target myoglobin in the sample within a dynamic working range from 0.01 to 500 ng mL⁻¹ with a detection limit of 3.8 pg mL⁻¹. The electrochemical immunoassay also exhibited high specificity and good precision toward target myoglobin. Importantly, our strategy could be applied for quantitative monitoring of myoglobin in human serum specimens, giving well matched results with those obtained from commercialized enzyme-linked immunosorbent assay (ELISA) method.     

A novel high selective and sensitive metronidazole voltammetric sensor based on a molecularly imprinted polymer-carbon paste electrode

The design and construction of a highly selective voltammetric sensor for metronidazole by using a molecularly imprinted polymer (MIP) as recognition element were introduced. A metronidazole selective MIP and a nonimprinted polymer (NIP) were synthesized and then incorporated in the carbon paste electrodes (CPEs). The sensor was applied for metronidazole determination using cathodic stripping voltammetric method. The MIP-CP electrode showed very high recognition ability in comparison to NIP-CPE. Some parameters affecting the sensor response were optimized and then the calibration curve was plotted. Two dynamic linear ranges of 5.64 × 10⁻⁵ to 2.63 × 10⁻³ mg L⁻¹ and 2.63 × 10⁻³ to 7.69 × 10⁻² mg L⁻¹ were obtained. The detection limit of the sensor was calculated as 3.59 × 10⁻⁵ mg L⁻¹. This sensor was used successfully for metronidazole determination in biological fluids.     

Cathodic and Adsorptive Stripping Votammetry of Naftazone

Abstract

Naftazone (1,2-naphthoquinone-2-semicarbazone) undergoes a reversible two-electron transfer in both acidic and alkaline solutions and also gives rise at pH > 7 to an anodic wave attributed to the formation of a mercury derivative. Cathodic stripping voltammetry is proposed to determine the compound down to 5 × 10^?9 M after accumulation of its mercury salt formed at -0.05V in a 0.05M sodium hydroxide solution. These results have been compared with those obtained by performing an adsorptive collection of the drug in a pH 3 sodium perchlorate solution. Concentrations ranging from 1 × 10^?7 to 2 × 10^?7M can be easily investigated, the detection limit being 7 × 10^?11M. The influence of several operational parameters has also been considered.     

Formation characteristics of calcium phosphate deposits on a metal surface by H2O2-electrolysis reaction under various conditions

The cathodic electrolysis of H₂O₂ (H₂O₂ + e⁻ → OH⁻ + OH) on a metal surface in the presence of calcium and phosphate ions results in the formation of calcium phosphate deposits on the metal surface. In this study, the deposits formed under various treatment conditions (pHs, concentrations and ratios of calcium/phosphate ions, and so on) were characterized by scanning electron spectroscopy (SEM), and X-ray diffractometry. The exclusive formation of hydroxyapatite, HAP, was observed under comparatively narrow conditions (pH 3–4, [Ca+]/[PO₄³⁻] = 25 mM/15 mM), which is clearly different from the reported conditions for the deposition of HAP on titanium substrates. HAP was deposited in the form of a layer, comprised of morphologically amorphous HAP flakes that were less than 20 nm thick. SEM and FTIR analyses of the deposit at different stages of H₂O₂-electrolysis revealed that a few dozen nanometer-sized spheres of amorphous calcium phosphate were formed in the first step and then fused with each other to form ribbon-like flakes of HAP or broken glass-like brushite, depending on the pH. The pH for HAP formation on a stainless steel surface was markedly lower than that used for titanium, and the observed process by which amorphous calcium phosphate is converted to HAP was markedly different from that for the electrochemical deposition (electrolysis of water) of HAP on a titanium substrate.     

Square‐wave Amplitude Effect in Cathodic and Anodic Stripping Square‐wave Voltammetry

In this paper a theoretical study of stripping processes at planar electrodes under conditions of square‐wave voltammetry is presented. A mechanistic examination for cathodic stripping electrode mechanisms, a simple anodic striping mechanism, and anodic stripping mechanisms coupled with adsorption equilibrium of the analyte are discussed using varying square‐wave amplitudes. The methodologies described here use two typical features: the peak potential separation of square‐wave components and the amplitude‐based quasireversible maximum. Both methods can be applied at a constant frequency, i. e., constant scan rate. The received data are combined with the critical parameters of electrode reaction kinetics. Thus, the established methodologies allow for a simple kinetic characterization. The received diagnostic criteria are verified with experiments at a glassy carbon electrode for lead ions.     

Kathodische Reduktion von Säureaziden Elektrolytische Untersuchungen an Vinylaziden, 8. Mitt.

The cathodic reduction of the O=C-N₃-system in aprotic solvent in the presence of anhydrides proves to be a convenient way to triacylammonia derivatives. Using the complexation of Li⁺ ions with the acid azide this synthetic methods can start from non-dangerous acid halides.The complex formation constant has been estimated and the chemical stability of N,N-diacylamides produced has been investigated. Mechanistic details about the role of Li⁺-ions in these electrolyses are given. Further reduction of the triacylammonia derivatives at more negative potentials results in protected aldehydic functions, i.e. 1-acyloxy-1-diacylaminomethanes, in good yields.

     

表面活性剂存在下碘阴极溶出特性及其应用的研究

研究了十六烷基三甲基溴化铵对碘富集效果的影响。由于该表面活性剂的作用,大大提高了碘阴极溶出的灵敏度。线性范围为5×10~(-10)～10~(-7)g·ml~(-1)。用于自来水中痕量碘的测定,其平均回收率为96.6％。