


Vol 52, No 2 (2016)
- Year: 2016
- Articles: 12
- URL: https://journal-vniispk.ru/1023-1935/issue/view/11757
Article
Multilayer film of thiourea and gold nanoparticles as an effective platform for immobilization of activated non-labeled-DNA and construction of an ultrasensitive electrochemical DNA biosensor
Abstract
In this work, self assembly of thiourea and gold nano-particle multilayer built up on a thiourea modified gold nanoparticles Au electrode, has been used as a platform for immobilization of activated ss-DNA. Two NH2 group of thiourea on a multilayer surface can interact with an activated phosphate group of non-labeled ss-DNA. Activated non-labeled ss-DNA was prepared using N-(3 dimethylaminopropyl)-N-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxy-succinimide (NHS). The whole DNA biosensor fabrication process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods with the use of ferricyanide as an electrochemical redox indicator. Methylene Blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction after hybridized with the target ssDNA and the reduction current of MB intercalation decreased with increasing the concentration of target DNA, ranging from 7.9 × 10–13 to 1.2 × 10–8 M with a very low detection limit of 3.8 × 10–13 M (S/N = 3).



Preparation and electrocatalytic property of lead dioxide prepared by pulse electrodeposition with different pulse current density
Abstract
Lead dioxide electrodes were prepared by pulse electrodeposition in the lead nitrate solution with different pulse current density. The effects of pulse current density on the morphology and structure of lead dioxide electrodes were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SEM and XRD results show that the increase of pulse current density can make the morphology more fine, and the crystal size of lead dioxide decreases with the increase of pulse current density. The anodic polarization curves demonstrate that the oxygen evolution overpotentials of lead dioxide electrodes also enhance with the increase of pulse current density. The stability of lead dioxide electrodes enhances with the increase of pulse current density until 15 mA cm–2, then the stability decreases. The electrocatalytic property of lead dioxide electrodes was examined for the electrochemical oxidation of rhodamine B (RhB). The results show that the RhB removal efficiency on the lead dioxide electrodes increases with the increase of pulse current density, which can be attributed to the increase of oxygen evolution overpotential.



Effect of Ce content on structure and electrochemical properties of La0.8–xCexPr0.1Nd0.1B5 (B = Ni, Co, Mn; 0 ⩽ x ⩽ 0.3) hydrogen storage alloys
Abstract
The structure and electrochemical properties of La0.8–xCexPr0.1Nd0.1B5 (B5 ≡ Ni3.8Co1.1Mn0.1; x = 0, 0.1, 0.2, 0.3) hydrogen storage alloys have been investigated. The results show that all alloys consist of CaCu5-type single phase. The maximum discharge capacity of the alloy electrodes decreases from 368.7 mA h g–1 (x = 0) to 294.9 mA h g–1 (x = 0.30), the cyclic stability (S100) increases from 37.6% (x = 0) to 69.8% (x = 0.20) after 100 charge/discharge cycles, and the HRD1200 first increases from 69.5% (x = 0) to 85.2% (x = 0.20), then decreases to 80.8% (x = 0.30). Meanwhile, the electrochemical kinetic characteristics of the La0.8‒xCexPr0.1Nd0.1B5 alloy electrodes are also improved by increasing Ce content.



Tyrosine sensing on phthalic anhydride functionalized chitosan and carbon nanotube film coated glassy carbon electrode
Abstract
Phthaloylchitosan (PHCS) has been synthesized by a simple and low-cost method using chitosan and phthalic anhydride as organic precursors by microwave irradiation. Techniques of nuclear magnetic resonance (NMR), FT-IR spectroscopy and transmission electron microscope (TEM) were used to characterize the structure and properties of the Phthaloylchitosan. Moreover, glassy carbon electrode modified with Phthaloylchitosan and carbon nanotube (PHCS–CNT/GCE) was prepared by casting of the PHCS–CNT solution on GCE. The electrochemical behavior of PHCS–CNT/GCE was investigated and compared with the electrochemical behavior of Phthaloylchitosan modified GC (PHCS/GC), carbon nanotube modified GC (CNT/GC) and unmodified GC using cyclic voltammetry (CV). The Phthaloylchitosan film is electrochemically inactive; similar background charging currents are observed at bare GC. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)63-/4- redox probe at PHCS–CNT/GCE is comparable to values reported for GCE, CNT/GCE and PHCS/GCE. The PHCS–CNT/GCE sensor responded linearly to tyrosine (Tyr) in the concentration of 1.0 × 10–6 to 8.0 × 10–4 M with detection limit of 3.0 × 10–7 M at 3σ using amperometry. In addition, the PHCS–CNT/GCE displayed good reproducibility, high sensitivity and good selectivity towards the determination of Tyr, making it suitable for the determination of Tyr in clinical and medicine.



Electrochemical deposition of indium: nucleation mode and diffusional limitation
Abstract
the electrochemical deposition of indium metal from InCl3 solutions was investigated. Cyclovoltammetric experiments showed that the initial hydrogen evolution reaction, observed together with the metal deposition on Pt surface, is blocked when the surface is covered by In. At large cathodic potentials, the current is diffusion-limited. The scan rate dependence of cyclovoltammograms allowed the determination of the diffusion coefficient of In3+ ions, 8.18 × 10–6 cm2/s, using the Delahay equation. The activation energy of diffusion, determined from the temperature dependence of cyclovoltammograms, is about 0.3 eV (23 kJ/mol). Chrono-amperometric experiments are consistent with the cyclovoltammetry; the In3+ diffusion coefficient determined using the Cottrell law is in good agreement with the value determined by the Randles-Ševčik equation. Moreover the use of the nucleation models developed by Scharifker and Hills showed a progressive nucleation mode. Electron microscopy observations and X-ray diffraction patterns confirmed the formation of crystalline indium deposits.



Electroless deposition and properties of Co–Re–B alloys
Abstract
The data on the mechanism of electroless (catalytic) deposition of Co–Re–B coatings are obtained by determining the donor capacitance of dimethylamine borane (DMAB) (CH3)2HN · BH3 reductant and the oxidation level of its hydride hydrogen. From the results of the study of isotopic composition of evolved hydrogen, it is concluded that the oxidation level of DMAB hydride hydrogen depends on the catalytic activity of the alloy. The alloys containing up to 46 at % rhenium were produced by the electroless deposition.



A hydrogen peroxide biosensor based on multiwalled carbon nanotubes-polyvinyl butyral film modified electrode
Abstract
A novel approach to construct a amperometric biosensor for determination of H2O2 is described. Horseradish peroxidase (HRP) as a base enzyme was immobilized into the mixture of multiwalled carbon nanotubes (MWNTs) and polyvinyl butyral (PVB). Taking the classical hydroquinone as mediator, cyclic voltammetry and amperometric measurements were used to study and optimize the performance of the resulting H2O2 biosensor. The effect of the concentration of MWNTs, HRP, hydroquinone, solution pH, and the working potential of amperometry on the electrochemical biosensor was systematically studied. The results showed that the fabricated biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with wide linear range from 0.000832 to 0.6 mM, and low detection limit 0.000167 mM (S/N = 3) with fast response time less than 8 s. The apparent Michaelis–Menten constant was determined to be 0.049 mM. Additionally, the biosensor exhibited high sensitivity, rapid response and good long-term stability.



Computer-aided simulation of the cathodic active layer in fuel cells with solid polymer electrolyte: the nature of overall current transient
Abstract
Total computer-aided simulation of the structure and current-generation processes in the cathodic active layer of a fuel cell with solid polymer electrolyte is carried out. Not only the transport structure of the active layer but also the structure of support grains (agglomerates of carbon particles with platinum-covered surface) are modeled. The process of active layer functioning under potentiostatic conditions is studied. It is demonstrated for the first time how the moisture exchange in the pores of support grains affects the cathode overall characteristics. The time variations of the overall current, the average temperature of the active layer, and the total degree of water-flooding of support-grain pores within the active layer are calculated by numerical methods. It is shown that for the fuel cell voltage of 0.6 V and its working temperature of 80°C, the flooding process dominates over the process of drying of pores in support grains. In 10–15 s, all support-grain pores turn out to be entirely filled with water. Then they begin functioning not in the kinetic mode (in the moment of switching-on the current, the Knudsen diffusion of oxygen in the support grains is observed) but in the inner-diffusion mode. As a result, the overall cathodic current decreases from its initial value of 4.323 A/cm2 to its final value of 0.526 A/cm2 and the active layer temperature decreases from the initial value of 102°C to the final value of 82.5°C. The overall current transient is studied also experimentally, the qualitative coincidence of theoretical and experimental data is demonstrated.



Synthesis and catalytic activity to Li/SOCl2 battery of asymmetric and symmetric binuclear metal phthalocyanines
Abstract
In our present work, the asymmetric and symmetric binuclear metal phthalocyanines (M2(PcTN)2 and M2(PcTN)2S), battery catalysts, were synthesized through microwave reaction and characterized by EA, IR and UV-vis spectroscopy. Their catalytic activity in the Li/SOCl2 battery was evaluated by adding right amount catalysts into the electrolyte. The results indicated that the capacity of the catalyzed battery increased by 6.74–67.26% and 13.41–84.36%, and the energy increased by 9.29–65.72% and 14.77–88.15% respectively, compared with the battery without phthalocyanines.



Theoretical analysis of the enzyme reaction processes within the multiscale porous biocatalytic electrodes
Abstract
Mathematical model describing the oxidation of glucose in a multiscale porous biocatalytic electrode is discussed. The model considers herein is composed of two nonlinear differential equations accounting for reaction and diffusion within the hydrogel film. In this letter, approximate analytical expressions for the concentration of mediator, substrate and current have been obtained using the Adomian decomposition method (ADM). Furthermore, a comparison confirmed that our analytical result fitted very well with the numerical solution (Matlab). Sensitivity analysis of the parameters is also reported.



Short Communications
Preparation and lithium storage performance of silicon and carbon microrods by chemical vapor co-deposition
Abstract
Silicon/carbon microrods are co-deposited on copper substrate and graphite spheres surface using dimethyl dichlorosilance as carbon and silicon precursor. The obtained composites are characterized by X-ray diffraction and scanning electron microscopy. The experimental results show that silicon/carbon microrods deposited on the copper substrate, whose diameter is about 500 nm, are accumulated into sisallike morphology, those deposited on the graphite spheres surface form hedgehog-like feature, whose diameter is about 200 nm and whose top is like cauliflower. When current density of 50 mA/g is applied, charge capacity of silicon/carbon microrods is 1492 mA h/g (deposited on copper substrate) and 693 mA h/g (deposited on the graphite spheres surface). Moreover, silicon/carbon microrods deposited on the graphite spehres and copper substrate respectively deliver the capacity of 592, 985 mA h/g, and display no capacity decay at all after the 20 cycles, when cycled under current density of 500 mA/g.



The effect of carbon black mixture composition on the structural and electrochemical characteristics of gas diffusion electrodes for electrosynthesis of hydrogen peroxide
Abstract
Gas-diffusion electrodes containing polytetrafluoroethylene, acetylene black A437E and its mixtures with two types of furnace black (P702 and P268E) with different size of particles are studied. The electrode capacitance, the average diameter and volume of pores and their surface area are investigated as a function of the electrode composition. The kinetic characteristics of electrodes in the oxygen electroreduction are assessed. The slope of polarization curves in Tafel coordinates and the transfer coefficient value are shown to be virtually independent of the electrode composition. The preparative synthesis of Н2О2 is carried out.


