The bioelectrocatalytic properties of cytochrome C by direct electrochemistry on DNA film modified electrode

The direct electrochemistry of cytochrome C can be performed in weak acidic and basic aqueous solutions. Cytochrome C can be deposited as a stable and electrochemically active film on a deoxyribonucleic acid (DNA) modified glassy carbon electrode. These films can also be produced on gold, platinum, and transparent semiconducting tin oxide electrodes. Two-layer modified electrodes containing cytochrome C and a DNA film were prepared by the deposition of cytochrome C on a DNA film modified electrode. The cytochrome C/DNA film was electrocatalytically oxidation active for l-cysteine in a pH 8.3 tris(hydroxymethyl)aminomethane (TRIS)-buffered aqueous solution through both Fe^III and Fe^IV species. The electrocatalytic oxidation current developed from the anodic peak of the redox couple. The electrocatalytic oxidation properties of ascorbic acid, NH₂OH, N₂H₄, and SO₃²⁻ by a cytochrome C/DNA film were also determined, and shown to be electrocatalytically active. An electrochemical quartz crystal microbalance, cyclic voltammetry, and direct spectroelectrochemistry were used to study in situ DNA deposition on a gold disc electrode and cytochrome C deposition on DNA/Au and DNA/GC films. The direct electrochemistry of cytochrome C can also be performed, and it can be deposited as a stable and electrochemically active film on polyvinyl sulfonate, polystyrene sulfonate, TiO₂, and polyethylene glycol modified glassy carbon electrodes. The results show that cytochrome C interacts with, and deposits on, a DNA film modified electrode, and that the cytochrome C (Fe^III) oxidized form is more easily deposited on a DNA film than the cytochrome C (Fe^II) reduced form.     

Improved performance of dense TiO2/CdSe coupled thin films by low temperature process

Dense TiO₂ and TiO₂/CdSe coupled nanocrystalline thin films were synthesized onto ITO coated glass substrate by chemical route at relatively low temperature (≤100 °C). TiO₂ films were nanocrystalline and crystallinity disappears after CdSe deposition as evidenced by X-ray powder diffraction. Surface morphology and physical appearance of films were studied from SEM and actual photo-images, reveals dense nature of TiO₂ (10-12 nm spherical grains, faint violet) and CdSe (80-90 nm spherical grains, deep brown), respectively. Presence of two absorption edges in UV spectra implies existence of separate phases rather than composite formation. TiO₂ film was found to have higher water contact angle (71°) than TiO₂/CdSe (61°) and CdSe (56°). I-V and stability tests of photo-electrochemical cells were performed with TiO₂ and TiO₂/CdSe film electrodes (under light of illumination intensity 80 mW/cm²) in lithium iodide as an electrolyte using two-electrode system.     

Fabrication and investigation of the optoelectrical properties of MoS2/CdS heterojunction solar cells

Molybdenum disulfide (MoS₂)/cadmium sulfide (CdS) heterojunction solar cells were successfully synthesized via chemical bath deposition (CBD) and chemical vapor deposition (CVD). The as-grown CdS film on a fluorine tin oxide (FTO) substrate deposited by CBD is continuous and compact. The MoS₂ film deposited by CVD is homogeneous and continuous, with a uniform color and a thickness of approximately 10 nm. The optical absorption range of the MoS₂/CdS heterojunction covers the visible and near-infrared spectral regions of 350 to 800 nm, which is beneficial for the improvement of solar cell efficiency. Moreover, the MoS₂/CdS solar cell exhibits good current-voltage (I-V) characteristics and pronounced photovoltaic behavior, with an open-circuit voltage of 0.66 V and a short-circuit current density of 0.227 × 10^-6 A/cm², comparable to the results obtained from other MoS₂-based solar cells. This research is critical to investigate more efficient and stable solar cells based on graphene-like materials in the future.     

Microscopic and electrochemical characterization of lead film electrode applied in adsorptive stripping analysis

Lead film electrodes (PbFEs) deposited in situ on glassy carbon or carbon paste supports have recently found application in adsorptive stripping voltammetric determination of inorganic ions and organic substances. In this work, the PbFE, prepared in ammonia buffer solutions, was investigated using scanning electron microscopy, atomic force microscopy and various voltammetric techniques. The microscopic images of the lead films deposited on the glassy carbon substrate showed a considerable variability in microstructure and compactness of the deposited layer depending on the selected experimental conditions, such as the concentration of Pb(II) species, the nucleation and deposition potential, and the time applied. The catalytic adsorptive systems of cobalt and nickel in a solution containing 0.1 ammonia buffer, 2.5 × 10⁻⁵ M nioxime and 0.25 M NaNO₂ were employed to investigate the electrochemical characteristics and utility of the in situ prepared lead films.The optimal parameters, i.e. the lead concentration in the solution, the procedure of film removal, and the time and potential of lead nucleation and film deposition for the adsorptive determination of metal traces, were selected, resulting in the very good reproducibility (RSD = 4.2% for 35 scans) of recorded signals. The voltammetric utility of the lead film electrode was compared to that of glassy carbon, mercury film and bismuth film electrodes, and was subsequently evaluated as superior.     

An investigation of lithium transport through vanadium pentoxide xerogel film electrode by analyses of current transient and ac-impedance spectra

Lithium transport through vanadium pentoxide xerogel film electrode has been investigated in a 1 M solution of LiClO₄ in propylene carbonate by employing potentiostatic current transient technique and ac-impedance spectroscopy. From the comparison of the initial current experimentally measured with those initial currents theoretically calculated from the Ohm’s law and the Cottrell equation, it was confirmed that the cell-impedance-controlled constraint at the electrode surface is changed to the real potentiostatic boundary condition (diffusion-controlled constraint) when the potential step exceeds a critical value over the whole range of the lithium content. It was also found that the slope of the logarithmic current transient obtained at the lithium contents above 0.4 positively deviates in absolute value from 0.5 even under the real potentiostatic boundary condition, but the phase angle of the diffusion impedance under the semi-infinite diffusion condition negatively deviates in absolute value from 45° with increasing lithium content. With the aid of the X-ray diffractometry, the anomalous behaviours of the current transient and the diffusion impedance were discussed in terms of lithium transport through the interlayers with widely distributed spacings across the quasi-ordered xerogel film electrode. Furthermore, the current transient theoretically determined by employing the concept of interlayer spacing distribution coincided fairly well in form with that current transient experimentally measured.     

The ultrasonic electropolymerization of an 5-[o-(4-bromine amyloxy)phenyl]-10,15,20-triphenylporphrin (o-BrPETPP) film electrode and its electrocatalytic properties to dopamine oxidation in aqueous solution

5-[o-(4-Bromine amyloxy)phenyl]-10,15,20-triphenylporphrin (o-BrPETPP) was electropolymerized on a glassy carbon electrode (GCE), and the electrocatalytic properties of the prepared film electrode response to dopamine (DA) oxidation were investigated. A stable o-BrPETPP film was formed on the GCE under ultrasonic irradiation through a potentiodynamic process in 0.1 M H₂SO₄ between −1.1 V and 2.2 V versus a saturated calomel electrode (SCE) at a scan rate of 0.1 V s⁻¹. The film electrode showed high selectivity for DA in the presence of ascorbic acid (AA) and uric acid (UA), and a 6-fold greater sensitivity to DA than that of the bare GCE. In the 0.05 mol L⁻¹ phosphate buffer (pH 6.0), there was a linear relationship between the oxidation current and the concentration of DA solution in the range of 5 × 10⁻⁷ mol L⁻¹ to 3 × 10⁻⁵ mol L⁻¹. The electrode had a detection limit of 6.0 × 10⁻⁸ mol L⁻¹(S/N = 3) when the differential pulse voltammetric (DPV) method was used. In addition, the charge transfer rate constant k = 0.0703 cm s⁻¹, the transfer coefficient α = 0.709, the electron number involved in the rate determining step n_α = 0.952, and the diffusion coefficient D_o = 3.54  10⁻⁵ cm² s⁻¹ were determined. The o-BrPETPP film electrode provides high stability, sensitivity, and selectivity for DA oxidation.     

BDD薄膜电极电催化氧化处理DDNP生产废水的实验研究

采用新型膜电极——BDD薄膜电极,运用电催化氧化方法处理DDNP生产废水,考察了槽电压、极板间距、废水初始COD、电解质(NaCl)投加量等因素对废水降解效果的影响.研究发现,槽电压和废水初始COD对COD去除率的影响最大,而电解质的加入对电催化氧化影响不显著.此外对影响废水降解的主要因素进行了动力学分析.     

铋膜电极测定辣椒制品中苏丹红Ⅱ的研究

用循环伏安法(CV)、线性扫描伏安法(LSV)研究了苏丹红Ⅱ在铋膜电极上的电化学行为。结果表明,在最佳条件下,BR缓冲溶液(pH=2),无水乙醇作助溶剂(体积分数27.5%),苏丹红Ⅱ在-0.50附近有一灵敏还原吸收峰。用线性扫描伏安法测定标准品,扫描速度为100 mV/s,浓度在7.49×10-6~1.87×10-5范围内和峰高呈线性关系。回归线方程:pí=1.722 2+0.751 7c(×10-3mmol/L),r=0.994 8。检出限为3.74×10-4mmol/L。据此建立了一种快速、简便测定苏丹红Ⅱ的方法。     

Use of a thiophene-based conducting polymer in microbial biosensing

Immobilization of whole viable Pseudomonas fluorescens cells was achieved on a graphite electrode modified with a thiophene-based conducting polymer. Microbial electrodes were constructed by the entrapment of bacterial cells on conducting copolymer matrix using a dialysis membrane. The biosensor was characterized using glucose as the substrate. As well as analytical characterization, effects of electropolymerization time, pH and temperature on the sensor response were examined. Finally, operational stability was also tested.     

Dynamic behavior of nanometer-scale amorphous intergranular film in silicon nitride by in situ high-resolution transmission electron microscopy

We report about the dynamic behavior of a nanometer-scale amorphous intergranular film (IGF) in a Si₃N₄ ceramic by an in situ heating experiment in a high-resolution transmission electron microscopy (HRTEM). During the experiment the IGF gradually vanishes at 820 °C accompanied by the formation of crystal planes within the IGF. The IGF reappears after cooling back to room temperature. The results cannot be explained within the framework of a force balance model. We argue that the dynamic behavior of the IGF in our experiment originates from the open system observed.     

CoAl2O4 spinel catalyst for soot combustion with NOx/O2

Mesoporous and nanosized cobalt aluminate spinel with high specific surface area was prepared using microwave assisted glycothermal method and used as soot combustion catalyst in a NO_x + O₂ stream. For comparison, zinc aluminate spinel and alumina supported platinum catalysts were prepared and tested. All samples were characterised using XRD, (HR)TEM, N₂ adsorption–desorption measurements. The CoAl₂O₄ spinel was able to oxidise soot as fast as the reference Pt/Al₂O₃ catalyst. Its catalytic activity can be attributed to a high NO_x chemisorption on the surface of this spinel, which leads to the fast oxidation of NO to NO₂.     

Effect of pore structure on anomalous behaviour of the lithium intercalation into porous V2O5 film electrode using fractal geometry concept

The effect of pore structure on anomalous behaviour of the lithium intercalation into porous V₂O₅ film electrode has been investigated in terms of fractal geometry by employing ac-impedance spectroscopy combined with N₂ gas adsorption method and atomic force microscopy (AFM). For this purpose, porous V₂O₅ film electrodes with different pore structures were prepared by the polymer surfactant templating method. From the analysis of N₂ gas adsorption isotherms and the triangulation analysis of AFM images, it was found that porous V₂O₅ surfaces exhibited self-similar scaling properties with different fractal dimensions depending upon amount of the polymer surfactant in solution and the spatial cut-off ranges. All the ac-impedance spectra measured on porous V₂O₅ film electrodes showed the non-ideal behaviour of the charge-transfer reaction and the diffusion reaction, which resulted from the interfacial capacitance dispersion and the frequency dispersion of the diffusion impedance, respectively. From the comparison between the surface fractal dimensions by using N₂ gas adsorption method and AFM, and the analysis of ac-impedance spectra by employing a constant phase element (CPE), it is experimentally confirmed that the lithium intercalation into porous V₂O₅ film electrode is crucially influenced by the pore surface irregularity and the film surface irregularity.     

A diffusion kinetics study of Li-ion in LiV3O8 thin film electrode

The kinetic behaviors of Li-ion insertion/extraction in LiV₃O₈ thin film have been investigated using cyclic voltammetry (CV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) method. This LiV₃O₈ thin film with a mixed amorphous-nanocrystalline microstructure was fabricated by RF sputtering. For the first time, the intrinsic kinetics of LiV₃O₈ thin film electrode is obtained. The DLi+ value is about 10⁻¹³ cm²/s in mixed amorphous-nanocrystalline microstructure LiV₃O₈ thin film. Different to crystalline LiV₃O₈ thin film, the DLi+ values do not change a lot with the increase of cell potential which is due to the absence of structural phase transition behavior in mixed microstructure LiV₃O₈ thin film during Li⁺ insertion/extraction process. This is also the reason for excellent capacity retention performance of LiV₃O₈ film with a mixed microstructure.     

A composite poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]-dioxepine) and Pt film as a counter electrode catalyst in dye-sensitized solar cells

A composite poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]-dioxepine) and platinum (PProDOT-Et₂/Pt) film was prepared for using as a counter electrode (CE) catalyst in a dye-sensitized solar cell (DSSC). Four composite films were prepared by electropolymerization of ProDOT-Et₂ on indium tin oxide (ITO) conducting glass, followed by Pt sputtering for 10, 30, 120, and 720 s. The Pt content in the composite film was verified by energy dispersive X-ray spectroscopy (EDX). The composite films possessed three-dimensional (3D) porous structures, as determined by scanning electron microscopy (SEM). The DSSC with the composite film that was subject to 10 s of Pt deposition (PProDOT-Et₂/Pt-10 s) exhibited the highest solar to electricity conversion efficiency (η) of 6.68%, while the cells with the bare polymer film (PProDOT-Et₂) and Pt that was sputtered for 720 s (s-Pt-720 s) demonstrated efficiencies of 4.76% and 6.43%, respectively. The cell photovoltaic parameters were substantiated through dark current, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analyses. Incident photon-to-current conversion efficiency (IPCE) curves were used to explain the cell photocurrent behaviors.     

Determination of sulfur compounds in gasoline using mercury film electrode by square wave voltammetry

A sensitive method based on square wave voltammetry is described for the quantitative determination of elemental sulfur, disulfide and mercaptan in gasoline using a mercury film electrode. These sulfur compounds can be quantified by direct dissolution of gasoline in a supporting electrolyte followed by subsequent voltammetric measurement. The supporting electrolyte is 1.4 mol L⁻¹ sodium acetate and 2% acetic acid in methanol. Chemical and optimum operational conditions for the formation of the mercury film were analyzed in this study. The values obtained were a 4.3 μm thickness for the mercury film, a 1000 rpm rotation frequency, −0.9 V applied potential and 600 s depositing time. Voltammetric measurements were obtained using square wave voltammetry with detection limits of the 3.0 × 10⁻⁹, 1.6 × 10⁻⁷ and 4.9 × 10⁻⁷ mol L⁻¹ for elemental sulfur, disulfide and mercaptan, respectively.     

A study on structure and electrochemical properties of (La, Ce, Pr, Nd)2MgNi9 hydrogen storage electrode alloys

(La, Ce, Pr, Nd)₂MgNi₉ hydrogen storage alloys were prepared through induction melting followed by a long annealing treatment. The structure and electrochemical properties of annealed alloys have been investigated by orthogonal design experiments. Both the individual effects of each substituting element and their interaction in alloys were studied systemically. It has been shown that the structure of main phase in alloys belongs to PuNi₃-type with a space group R-3m. Substituting rare-earth elements have a significant effect on both the phase structure of alloys and microstructure. The anisotropic change in the crystal structure of alloys can cause the acceleration of pulverization of alloy particles and result in the deterioration of the cyclic stability of alloy electrodes. Misch metals can raise the plateau pressure of hydrogen absorption/desorption. The discharge capacity of alloy ranges from 342.97 to 380.68 mAh g⁻¹ depending on the sort and content of substituting elements. Both cerium and neodymium can obviously reduce the discharge capacity of alloy electrodes. When compared to the La₂MgNi₉ alloy electrode, mish metals can significantly improve the high rate dischargeability of alloy electrodes. The improvement of the kinetic characteristic of alloy electrodes mainly results from the increase of the hydrogen diffusion rate in alloy bulk.     

Colloidal silver nanoparticles modified electrode and its application to the electroanalysis of Cytochrome c

A colloidal silver nanoparticles (CSNs) chemically modified electrode was prepared and its application to the electroanalysis of Cytochrome c (Cyt. c) was studied. The CSNs were prepared by reduction of AgNO₃ with NaBH₄, and were stabilized by oleate. They could be efficiently immobilized on the surface of a silver electrode. The result showed that the CSNs could clearly enhance the electron transfer process between Cyt. c and the electrode compared with bulk silver electrode. Linear sweep voltammetric measurement of Cyt. c at the chemical modified electrode indicated that the oxidative peak current of Cyt. c was linear to its concentration ranging from 8.0 nmol L⁻¹ to 3.0 μmol L⁻¹ with the calculated detection limit was about 2.6 nmol L⁻¹. The direct electrochemistry of Cyt. c was also studied by cyclic voltammetry.     

Effects of specific surface area of electrode and different electrolyte on capacitance properties in nano porous-structure CrN thin film electrode for supercapacitor

Thickness and specific surface area of the film electrode are critical parameters for supercapacitors. The relationship between the thickness and the specific surface area of the film directly affects the capacitance and electrochemical stability performance of super supercapacitors, which virtually affects the contact chance of ion in the electrolyte on the surface of electrode and the ion transport path of electrode. In this paper, the CrN thin films with a thickness of 200–3500 nm are prepared using direct current magnetron sputtering. Atomic force microscopy (AFM) technique is introduced to investigate the relationship between thickness and the specific surface area of the CrN films. The electrochemical performances of CrN electrode with the nanoporousper structure is analyzed in different electrolytes H₂SO₄, Na₂SO₄ and NaCl aquous solutions. The specific surface area of the film increases linearly with the film thickness increases. The areal capacitance is also linearly related to the specific surface area. The spurtted CrN film with a thickness of 3370 nm has a specific surface of up to 43.59 cm² per cm² footprint area. Its areal and volume capacitances reache to 53.92 mF cm^?2 and 650 F cm^?3 at 5 mV s^?1, respectively. In addition, the areal capacitance of CrN film electrode with 655 nm possesses reaches to 40.53 mF cm^?2 for 0.5 M H₂SO₄ solution, 32.69 mF cm^?2 for 0.5 M Na₂SO₄ solution and 9.17 mF cm^?2 for NaCl solution at a scan rate of 5 mV s^?1. Furthermore, the CrN film electrode exhibits excellent capacitance retention of 95.3%, 93.8% and 89.9% in H₂SO₄, Na₂SO₄ and NaCl electrolytes, respectively, after 2000 cycles. Therefore, the sputtered CrN thin film is an potential electrode material for electrochemical supercapacitors.     

Electrochemical atomic layer deposition of a CuInSe2 thin film on flexible multi-walled carbon nanotubes/polyimide nanocomposite membrane: Structural and photoelectrical characterizations

This study describes a method for the fabrication of an electrochemical atomic layer deposition (EC-ALD) used to fabricate the ternary, semiconducting compound, CuInSe₂ (CISe), onto a flexible, carboxyl-functionalized multi-walled carbon nanotube/polyimide (COOH-MWCNT/PI) nanocomposite membrane. The elements were deposited using amperometric methods (I–t) in the following sequence: Se/Cu/Se/In/Se/Cu/Se/In and so on, in which the optimum deposition potential for each element was obtained via a cyclic voltammetry (CV) technique. Field emission scanning electron microscopy (FE-SEM) showed that the deposits consisted of many spherical nanoparticles, and energy dispersive spectroscopy (EDS) analysis indicated that the atomic ratio of the deposits (CuInSe) was 1.14 1.00 2.18, similar to the stoichiometric value of the compound. Near Fourier transform infrared spectroscopy (FT-IR) transmission measurements provided a band gap of 1.05 eV, which was confirmed by the absorption spectrum. Open-circuit potential (OCP) and current-voltage (I–V) measurements showed the resulting composite had a good p-type property. CISe spherical NPs electrodeposited on the CNTs/PI membrane may have promising applications in optoelectronic nanodevices and nanotechnologies; in addition, the CNTs/PI membrane could be used as raw material for manufacturing solar cells.     

Ultrasonic spray pyrolysis of nano crystalline spinel LiMn2O4 showing good cycling performance in the 3 V range

Spherical lithium manganese oxide spinel was synthesized by an ultrasonic spray pyrolysis method, and has been characterized using X-ray diffraction, scanning electron microscopy, transimission electron microscopy and electrochemical cycling at 3 V regions. The LiMn₂O₄ powders were composed of about 10 nm-sized primary particles. The delivered discharge capacity of the synthesized nano-material was 125 mAh g⁻¹ between 2.4 and 3.5 V and its retention was about 96% upon 50 cycling. From the high resolution transmission electron microscopic study, it was found that structural transition of the parent material did not occur even after the 50th electrochemical cycling on the 3 V region. It seems that the reversible structural change is possible for nanocrystalline LiMn₂O₄ as observed by the X-ray diffraction and transition electron microscopic observations.