Morphological aspects of sulfate-induced reconstruction of Cu(1 1 1) in sulfuric acid solution: in situ STM study

Using in situ STM the atomic structure and the morphology of a Cu(1 1 1) surface exposed to a dilute sulfuric acid solution have been studied depending on the applied electrode potential. At anodic potentials near the onset of copper dissolution the electrode surface is reconstructed (expanded) caused by the specific adsorption of sulfate anions. The extent of the surface reconstruction strongly depends on the sulfate adsorption rate. Fast sulfate adsorption results in a mainly disordered sulfate adlayer on an unreconstructed copper surface. Conversely, slow sulfate adsorption produces a mainly reconstructed copper surface with a highly ordered sulfate/water coadsorption layer. This adsorbate structure shows an additional long-range Moiré modulation, due to a misfit between the first reconstructed and the second unreconstructed copper layer. This is verified by spectroscopy-like STM experiments, which allow the imaging not only of the adsorbate overlayer, but also of the underlying reconstructed substrate. This type of adsorbate-induced reconstruction is characterized by an expansion of the topmost copper layer. The kinetically slow process of reconstruction can be easily followed by dynamic STM measurements revealing a mass transport out of the topmost copper layer during the slow sulfate adlayer formation. Characteristically, new copper islands nucleate and grow, while the sulfate Moiré adlayer expands over the electrode surface. At cathodic electrode potentials the desorption of the sulfate adlayer is accompanied by the lifting of the surface reconstruction and the massive formation of surface defects, such as small pits and vacancy islands. A continuous cycling of the electrode potential leads to an enormous roughening of the surface morphology.     

聚邻氨基苯甲酸-铜复合薄膜修饰电极的制备及其电化学性能

利用聚合物官能团对金属离子的配位作用,在电极表面原位制备了金属粒子。 首先在玻碳电极（GCE）表面电沉积聚邻氨基苯甲酸(PoABA),再化学吸附铜离子(Cu2+),用水合肼还原得到单质铜(Cu0)。 采用扫描电子显微镜和能谱分析表征了聚邻氨基苯甲酸 铜(PoABA-Cu0)复合薄膜的表面形貌和元素构成,研究了PoABA-Cu0修饰电极的电化学性能,并以其检测了过氧化氢（H2O2）。 结果表明,电极表面被修饰上了一层PoABA-Cu0复合薄膜;制备的修饰电极对H2O2具有良好的电催化性能,在邻氨基苯甲酸的聚合圈数为10、Cu2+的吸附时间为10 min、工作电压为-0.3 V时,该修饰电极对H2O2表现出了最佳的检测性能,其线性浓度范围为5.0×10-5～1.0×10-2 mol/L,灵敏度为96.3 μA·L/(mmol·cm),检测限为5.0×10-5 mol/L,且具有较好的稳定性。     

Fabrication of Nanoporous Copper Film for Electrochemical Detection of Glucose

A nanoporous copper film was fabricated on a copper wire by electrodeposition of copper/zinc alloy and chemically etching of zinc. The surface morphology was investigated by SEM. When applied to detect glucose in an amperometric flow injection system the porous copper electrode provided 12 times higher sensitivity than solid copper. It could be continuously used up to 50 times (%RSD=5.7). Different preparations of the porous film provided reproducible responses (P<0.05). Detection of glucose in E. coli cultivation medium compared well with spectrophotometric technique (P<0.05). This simple technique can produce a nanoporous electrode with good performances and can easily be applied to other metals and analytes.     

Assembly process of CuHCF/MPA multilayers on gold nanoparticles modified electrode and characterization by electrochemical SPR

Gold nanoparticles were deposited onto 2-mercaptoethylamine (MEA)-assembled planar gold thin film to construct gold nanoparticles modified electrode by virtue of a solution-based self-assembly strategy. Subsequently, 3-mercaptopropionic acid (MPA)-bridged copper hexacyanoferrate (CuHCF) multilayers were constructed on the as-prepared gold nanoparticles modified electrode. The resulted multilayer nanostructures were investigated by electrochemical surface plasmon resonance (EC-SPR) and atomic force microscopy (AFM) with primary emphasis upon the effect of the gold nanoparticles on the MPA/CuHCF multilayers growth and their surface morphology. Compared with the multilayer system on a planar gold electrode, the different electrochemical and optical properties might result from higher curvature effect and extraordinary surface-to-volume ratio characteristic of gold nanoparticles and the nanoparticle-selective growth of CuHCF. A dendrimer-like assembly process was proposed to explain the experiment results. This new motif of multilayer on the gold nanoparticles modified electrode was different from that of on a planar gold electrode, indicating a potential application of EC-SPR technique in the study of nanocomposite materials.     

Total-reflection X-ray fluorescence study of electrochemical deposition of metals on a glass-ceramic carbon electrode surface

The features of electrochemical deposition and co-deposition of copper, cadmium and lead from aqueous solutions on disc glass-ceramic carbon (GCC) electrode surfaces were studied by total-reflection X-ray fluorescence analysis (TXRF). This method was found to be highly sensitive to the varieties of electrodeposit morphology and depth distribution of elements on the electrode surface. It allows identification of the mechanisms of metal nucleation and growth of thin film electrodeposits. The results of the TXRF study are in good agreement with the recent data of a number of spectroscopic and microscopic methods of solid surface analysis. The polished GCC was shown to be an excellent material for preparation of the sample carriers for TXRF analysis.     

Influence of High Voltage Needle Electrode Material on Hydrogen Peroxide Formation and Electrode Erosion in a Hybrid Gas–Liquid Series Electrical Discharge Reactor

Formation rates of hydrogen peroxide and electrode erosion rates for a range of different electrode materials were determined in a gas–liquid pulsed electrical discharge reactor with a high voltage electrode needle in the liquid and a ground electrode suspended in the gas over the liquid. It was found that the H₂O₂ formation rates and efficiencies did not depend on the electrode material. Electrode erosion from lowest to highest followed the series: nickel chromium, thoriated tungsten, diamond-coated tungsten, stainless steel, tungsten carbide and tungsten copper alloy. Smooth crater-like morphology was found for nickel chromium, titanium and tungsten carbide and a much finer surface structure with small protrusions for the tungsten, tungsten copper and the copper. Doubling the electrode diameter lead to an increase in the H₂O₂ formation per eroded length by a factor of three but it also decreased the energy efficiency yield of H₂O₂ by more than 20%.     

Highly enhanced electrocatalytic oxidation of glucose on Cu(OH)2/CuO nanotube arrays modified copper electrode

A highly sensitive and fast-response biosensor based on cupric hydroxide/oxide (Cu(OH)₂/CuO) nanotube arrays (CNA) was successfully fabricated in this work. CNAs were prepared on copper electrode surface by simply immersing copper electrode in an aqueous solution of NaOH and (NH₄)₂S₂O₈. The morphology and the composition of the CNAs were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD), respectively. The electrocatalytic activity of the CNA modified copper electrodes (CNA/Cu) towards glucose oxidation was investigated by cyclic voltammetry and amperometry. The CNA/Cu showed good non-enzymatic electrocatalytic responses to glucose in alkaline media and can be used for the development of enzyme-free glucose sensors.     

AFM study of the behavior of polystyrene and glass particles during the electrodeposition of copper

In this paper, the behavior of polystyrene and glass particles on a copper electrode during the electrodeposition of copper was studied using an atomic force microscope (AFM). Polystyrene or glass particles glued to the tip of the AFM cantilever were kept in contact with the surface of the electrode. The surface forces between the polystyrene or glass particle and the copper electrode were measured before, during, and after electrodeposition. These experiments revealed that glass particles do not make contact with the electrode, probably due to the repulsive hydration force. Polystyrene particles, on the other hand, make contact with the electrode, due to the attractive hydrophobic force. The AFM experiments were correlated with sedimentation co-deposition experiments of polystyrene and glass particles with copper. It was found that 80% of the polystyrene particles added to the plating solution incorporated with copper, while only 0.25% of the glass particles co-deposited under the same conditions.     

Use of sodium dodecyl sulphate to clarify the end-point of anodic-stripping complexometric titrations

It has been found that addition of sodium dodecyl sulphate will completely suppress the dissociation of the copper-EDTA complex at the electrode surface in the anodic-stripping complexometric titration of copper and make the end-point of the titration very clear. The addition of SDS also makes it possible to titrate traces of nitrilotriacetic acid, which forms a copper complex that is less stable than the EDTA complex. The effect of SDS is presumed to be due to electrostatic repulsion between the negative charges of adsorbed SDS and the metal complex at the electrode surface.     

Current oscillations during copper electrodissolution under solution sparging in acidic NaCl solutions

Potentiostatic current oscillations were observed during electrodissolution of a helical coiled copper wire electrode in acidic sodium chloride when nitrogen was sparged through the solution. The oscillations were studied as a function of solution pH, chloride ion concentration and sparging rate over the potential range of 0.2 to 0.7 V versus Ag/AgCl (3 M NaCl). The surface morphology of the copper was observed during the oscillatory process using in situ, real-time optical microscopy, and the formation of a surface film was correlated with the oscillations.     

The effect of magnetic fields on the electrodeposition of iron

The effect of a uniform magnetic field with flux density up to 1 T on the electrodeposition of Fe from sulphate electrolyte has been investigated under different field configurations relative to the electrode surface. Voltammetric and chronoamperometric experiments have been carried out coupled with an electrochemical quartz crystal microbalance for in situ mass change measurements. The structure and morphology of the deposited films were determined by scanning electron microscopy, atomic force microscopy and X-ray diffraction measurements. Results show that, when the magnetic field is applied parallel to the electrode surface, the limiting current density and the deposition rate are increased due to the magnetohydrodynamic effect. The nucleation process is also affected in parallel configuration; the current density of the maximum on the chronoamperograms is decreased, and an additional nucleation step might be observed. This effect is attributed to the hydrodynamic response of the electrochemical system. No significant influence on the electrochemical reaction was observed when a magnetic field was applied perpendicular to the electrode. But in this configuration, the morphology of deposited layers is changed by the magnetic field. The morphology changes are discussed. No effect of the magnetic field on the crystallographic structure was observed.     

Bimetallic nano-structured glucose sensing electrode composed of copper atoms deposited on gold nanoparticles

We describe the preparation and sensing capabilities of a bimetallic electrode consisting of copper atoms deposited on gold nanoparticles (GNPs). The electrode was obtained by first constructing a GNP template on the surface of a glassy carbon electrode by exploiting the hydrogen-bonding interactions between pyridine groups on the surface of the GNPs and the carboxy groups of poly(acrylic acid). GNPs (60?nm in diameter) were homogeneously and densely deposited in the template (as revealed by scanning electron microscopy). The electro-deposition of copper ad-atoms on GNPs occurred at an underpotential and was proven by electrochemical techniques. The presence of GNPs in the template accelerated the deposition at low potential due to its beneficial effect on the rate of electron transfer. The new electrode was studied for its response to glucose. Highly stable and reproducible catalytic activity towards glucose oxidation is observed and attributed to the synergistic catalytic effect of the copper atoms on the surface of the GNPs. The detection limit is as low as 50?nM (at a signal-to-noise ratio of 3), and the response is between 200?nM and 10?mM of glucose.

Biosensor for atrazin based on aligned carbon nanotubes modified with glucose oxidase

A sensitive method was developed for the determination of the hebicide atrazine. It based on the use of glucose oxidase that is self-assembled on aligned carbon nanotubes on the surface of a copper electrode. The surface morphology and electrochemical properties of the electrode were characterized by field emission scanning electron microscopy and cyclic voltammetry. The effects of buffer solution and incubation time on the response of the electrode were investigated. Response to atrazine is linear in the range from 0.58 µM to 42 µM, and the detection limit is 39 nM. The performance of the biosensor was verified by determination of atrazine in environmental water samples.     

Comparison of copper(II) ion-selective electrodes for measurements at micromolar concentrations

Four types of copper ion-selective electrodes have been tested for determining copper at concentrations below lO^-6 mol 1^l-1. None of the electrodes has a Nemstian response in dilute copper solutions in this concentration range, though their responses are linear in pCu buffer solutions. The causes of the deviations are a direct redox effect in the case of an electrode with a Cu_1.8,Se single crystal membrane, production of copper ions by oxidation of the membrane itself in Ag₂S—CuS membrane electrodes, and a combination of the two in the case of the R??i?ka Selectrode. The electrode potentials are affected by the oxygen content and pH of the sample solution and the condition of the membrane surface. Precision tests on two types of electrode are described.     

Corrosion of Copper in Presence of Acetic Acid Derivatives

The anodic corrosion of copper in presence of acetic acid derivatives were determined by measuring the limiting current. It is found that the rate of corrosion increased by decreasing H₃PO₄ concentration and electrode height. The experimental results showed that the inhibition efficiency increased with increasing concentration of the investigated compounds at a fixed temperature, but decreases with increasing temperature. Values of activation energy indicate that the reaction is diffusion controlled. The isotherm Langmuir, Temkin, and Flory Huggins are applied. The values of free energy of adsorption (ΔG_ads) obtained indicate the spontaneous adsorption of the inhibitor. The overall mass transfer correlations under the present conditions have been obtained using dimensional analysis method. The results agreed with the previous studies of mass transfer to rotating cylinder in turbulent flow.At the end of the corrosion process the morphology of the specimens after experiment is monitored using scanning electron microscope (SEM). SEM examination of the copper surface revealed that these compounds inhibited copper from corrosion by adsorption on its surface to form protective film. The presence of these organic compounds adsorbed on the electrode surface was confirmed by SEM investigations.     

Surface enhanced Raman spectra of benzotriazole adsorbed on a copper electrode

The surface enhanced Raman spectrum of benzotriazole (BTAH) adsorbed on a copper electrode has been studied as a function of the potential applied to the electrode. The effect of pH and of the type of halide in the electrolyte solution has also been investigated. The presence of some complexes involving Cu(I), benzotriazole or benzotriazolate (BTA^-) and the halide has been characterized. The protective film formed on copper surface, in the presence of benzotriazole, has been identified as cuprous benzotriazolate [Cu(I)BTA].     

Effect of chloride ions on the behaviour of the orion copper(II) ion-selective electrode

The normal shiny surface of a copper(II) ion-selective electrode tarnishes when exposed to chloride ions. Polishing with fine emery cloth easily removes this dull surface layer and fully restores the proper potential response characteristics of the electrode. No such loss of character is evident with a non-chloride based reference electrode except in the presence of added chloride ions. The electrode also seems less affected in premixed solutions of copper(II) and chloride. the chloride ions then being largely bound as copper(II) chloro-complexes.     

Voltammetry determination of dopamine by the electrocatalytic response of an electrode modified by a polyaniline film with an inclusion of copper(II) tetrasulfophthalocyanine

A polyaniline composite film with an inclusion of copper(II) tetrasulfophthalocyanine, applied on a glassy-carbon electrode (GC) has demonstrated a mediatory activity in the oxidation of dopamine in acidic and neutral media. The conditions for the formation of a polymer film on the surface of a glassy-carbon electrode for registering the maximum electrocatalytic effect in the oxidation of dopamine are found. A method of voltammetric and amperometric detection of dopamine on the composite film electrode under static and flow conditions is proposed. The use of a polyaniline composite with an inclusion of copper(II) tetrasulfophthalocyanine, coated with a Nafion film, made possible the reduction of the detection limit for dopamine to 1 × 10^?8 M under static conditions and to 5.0 nmol under the conditions of flow-injection analysis.     

Nanotribology under electrochemical conditions: influence of a copper (sub)monolayer deposited on single crystal electrodes on friction forces studied with atomic force microscopy

Friction force measurements performed by means of an atomic force microscope (AFM) under electrochemical conditions on a pure Au(111) electrode surface and one modified with a foreign metal are presented; after deposition of a (sub)monolayer copper on a Au(111) single crystal electrode a large increase of the friction force is observed compared to the pure Au(111) electrode surface; the extent of the increase not only depends on the copper coverage, but also on the normal load and may be explained by a higher energy dissipation due to motion of the sulfate anions adsorbed on the copper atoms induced by the AFM tip.     

Investigation of Copper(II) Interference on the Anodic Stripping Voltammetry of Lead(II) and Cadmium(II) at Bismuth Film Electrode

The bismuth‐coated electrode is known to be prone to errors caused by copper(II). This study investigates copper(II) interference at bismuth film electrode for the detection of lead(II) and cadmium(II). It was conducted using glassy carbon electrode, while the bismuth film was plated in situ simultaneously with the target metal ions at ? 1200 mV. Copper(II) presented in solution significantly reduced the sensitivity of the electrode, for example there was an approximately 70 % and 90 % decrease in peak signals for lead(II) and cadmium(II), respectively, at a 10‐fold molar excess of copper(II). The decrease in sensitivity was ascribed to the competition between copper and bismuth or the metal ions for surface active sites. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) analysis suggested a large decrease in the amount of bismuth nanoparticles formed on the electrode surface in the presence of copper(II) occurred, validating the competition between copper and bismuth ions for surface active sites. Recovery of the stripping signal of lead(II) and cadmium(II) was obtained by adding ferrocyanide ion to the solution. Finally, the proposed method was successfully applied to determine lead(II) and cadmium(II) in water samples and the method was validated by ICP‐MS technique.