L-Aspartic acid/L-cysteine/gold nanoparticle modified microelectrode for simultaneous detection of copper and lead

This paper presents an electrochemical microsensor for simultaneous detection of copper (II) and lead (II) using an l-aspartic acid/l-cysteine/gold nanoparticle modified microelectrode. The microelectrode was fabricated by Micro Electro-Mechanical System technique. The complex of gold nanoparticles (AuNPs) and amino acid with carboxyl group was used as the selective ligand for metal ions. The microelectrode was firstly modified with AuNPs to increase the sensitive area of the working electrode. Subsequently, the AuNPs/gold electrode was modified with l-cysteine and then covalently linked with a monolayer of l-aspartic acid using glutaraldehyde. Electrochemical analysis of metal ions was achieved by using square wave voltammetry without stirring. The microsensor exhibited an excellent linear range from 5 μg L^− 1 to 2000 μg L^− 1 with the limit of detection of 1 μg L^− 1. This metal ion detection method based on l-aspartic acid/l-cysteine/gold nanoparticle modified microelectrode is simple, sensitive and it could be used for electrochemical analysis of copper (II) and lead (II).     

Nucleation and growth of copper particles on Pt and Pt/poly-3-methylthiophene modified electrode in presence of Cl complexing agent

The kinetics of electrochemical deposition of copper particles from Cu²⁺ solution on platinum and poly-3-methylthiophene modified platinum electrode was studied in potentiostatic conditions in presence of Cl⁻ anions. The complex behavior of current transients suggests that the deposition process involves several stages with different kinetics. Results obtained on platinum show that after an initial adsorption process, the copper deposition is accomplished through two different models: a three-dimensional nucleation and growth under diffusive control (3DPD model) and a progressive nucleation and two-dimensional growth (2DP model). The analysis of current transients recorded on platinum poly-3-methylthiophene modified electrode (Pt/PMT) shows a very different behavior. On Pt modified electrode a process of growth related to a semi-infinite diffusion to a planar surface was accompanied by two different mechanisms of nucleation and growth: a three-dimensional nucleation and growth with no diffusive control (3DP model) and an instantaneous nucleation with two-dimensional growth (2DP model).     

Effect of acetic acid on wet patterning of copper/molybdenum thin films in phosphoric acid solution

Copper metallization is a key issue for high performance thin film transistor (TFT) technology. A phosphoric acid based copper etchant is a potentially attractive alternative to the conventional hydrogen peroxide based etchant due to its longer-life expectancy time and higher stability in use. In this paper, it is shown that amount of the acetic acid in the phosphoric based copper etchant plays an important role in controlling the galvanic reaction between the copper and the molybdenum. As the concentration of acetic acid in the phosphoric mixture solution increased from 0 M to 0.4 M, the measured galvanic current density dropped from 32 mA/cm² to 26 mA/cm², indicating that the acetic acid induces the lower galvanic reaction between the copper and the molybdenum in the solution. From the XPS analysis, with the addition of the acetic acid, the thickness of the protective MoO₂ passive film covering the molybdenum surface grew and the dissolution rate of the molybdenum thin film decreased. However, the dissolution rate of the copper thin film increased as the concentration of acetic acid in the mixture solution increased.     

Enhanced crystal grain size by bromine doping in electrodeposited Cu2O

Extremely large crystal grains are obtained by bromine doping in electrodeposited Cu₂O on indium tin oxide (ITO) substrate through an acetate bath. The grains are as large as 10,000 μm² in area, or ~ 100 μm in linear dimension, while the film is only 1-5 μm thick. The enhanced grain size is explained by the effect of over-potential for the Cu²⁺/Cu⁺ redox couple on nucleation density of Cu₂O on ITO substrate. The over-potential is a function of several deposition conditions including solution pH, deposition potential, deposition temperature, bromine precursor concentration, and copper precursor concentration. In addition, undoped Cu₂O displays a high resistivity of 100 MΩcm. Bromine doping in Cu₂O significantly reduces the resistivity to as low as 42 Ωcm after vacuum annealing. Br-doped Cu₂O shows n-type behavior.     

Fabrication of Cu2S on Cu film electrode and its application in lithium ion battery

Cu₂S film electrode direct growth on Cu foil is prepared by a simple hydrothermal approach. The electrochemical properties of the as-prepared Cu₂S electrode are investigated via conventional discharge and charge tests. When applying a current density of 0.1 mA cm^− 2, the as-prepared Cu₂S electrode exhibits discharge and charge capacity of 0.27, 0.32, 0.35, 0.34 and 0.34 mAh cm^− 2 at the 100th, 200th, 300th, 400th and 500th cycle, respectively. Such good performance of the as-prepared Cu₂S electrode is attributed to the fine electric contact between Cu₂S and Cu foil and the possible hollow structure of Cu₂S film.     

Control of oxidation state of copper in flame deposited films

The deposition of thin copper based films onto carbon steel surface is described, using premixed flames with different oxygen/methane ratios doped with aqueous copper nitrate as precursor. We investigated the chemical properties of the copper as a function of oxygen/methane ratio. Using fuel rich flames (equivalence ratio 0.665), the deposited copper film was entirely metallic. When the equivalence ratio was increased to 0.850 or greater the copper film contained predominantly Cu^2 +. Furthermore, the flame can be used for post deposition modification, as demonstrated by reduction of Cu^2 + containing films to Cu metal. All the films were characterised by X-ray diffraction, Raman and scanning electron microscopy (SEM). A rotating sample holder was employed to avoid over heating of the sample and the critical variables such as sample height in the flame and deposition time were optimised. Deposition for 20 min, which translated to a total residence time in the flame of approx. 76 s, produces metallic copper films of thickness 169 ± 18 nm as determined by anodic stripping and SEM. The microstructure of the metallic films was clearly composed of fused copper spheres of 100-150 nm, which are probably formed in the flame and subsequently deposited on the surface with good adhesion.     

pH and iodide ion effect on corrosion inhibition of histidine self-assembled monolayer on copper

Self-assembled monolayer (SAM) of histidine (His) was prepared on copper surface at various pH values. The effect of KI additives on corrosion protection efficiency of His SAM was also studied. The protection abilities of these films against copper corrosion in 0.5 M HCl aqueous solution were investigated using electrochemical impedance spectroscopy and polarization techniques. The results show that the film formed on the electrode is more stable at pH = 10 than that at other pH values. When the iodide ions were added into the His self-assembly solution (pH = 10), protection efficiency was further improved. The inhibition mechanism has been discussed by quantum chemical calculations.     

A three-step copper chemical mechanical planarization model including the dissolution effects of a commercial slurry

The etching behavior of copper oxide by diluted oxidant-free slurry as a function of temperature was characterized and a three-step copper removal rate model was proposed. Pre-oxidized wafers were exposed to the diluted slurry for times up to 500 s for three temperatures and mass loss was monitored. For the highest temperature, 60 °C, all of the oxide available for reaction was etched in 90 s, however the 25 and 40 °C results did not reach saturation. Measurements up to saturation were used for modeling. A one-dimensional model was proposed where the diffusion of the complexant through a byproduct film found to exist on the wafer surface after etching controlled the process. The model fits the data well with two parameters, E_a and A, which were found to be 86.9 kJ mol^− 1 and 4.12 × 10^− 2 mol cm^− 1 s^− 1, respectively. Similar to a previous copper oxidation study, the rate of copper consumption from dissolution was found to be a function of a characteristic reaction byproduct film thickness. However, the dissolution rates demonstrated a much weaker function of film thickness than the oxidation profiles. For this slurry, the etching process controls the combined oxidation and etching system and static oxidation-dissolution experiments agreed well with the dissolution model. The methodology and modeling developed in this work can be directly applied to other commercial or experimental slurry formulations to quantify the dissolution characteristics of the formulation. Once the static dissolution characteristics of a slurry formulation are quantified, use of the proposed three-step removal rate model will provide a more accurate depiction of the relative chemical and mechanical contributions of a given consumable set.     

Synthesis of copper nanoparticles from refractory sulfides using a semi-industrial mechanochemical approach

The large-scale mechanochemical reduction of binary sulfides chalcocite (Cu₂S) and covellite (CuS) by elemental iron was investigated in this work. The reduction of Cu₂S was almost complete after 360 min of milling, whereas in the case of CuS, a significant amount of non-reacted elemental iron could still be identified after 480 min. Upon application of more effective laboratory-scale planetary ball milling, it was possible to reach almost complete reduction of CuS. Longer milling leads to the formation of ternary sulfides and oxidation product, namely cuprospinel CuFe₂O₄. The rate constant calculated from the magnetometry measurements using a diffusion model for Cu₂S and CuS reduction by iron in a large-scale mill is 0.056 min^−0.5 and 0.037 min^−0.5, respectively, whereas for the CuS reduction in a laboratory-scale mill, it is 0.1477 min⁻¹. The nanocrystalline character of the samples was confirmed by TEM and XRD, as the produced Cu exhibited sizes up to 16 nm in all cases. The process can be easily scaled up and thus copper can be obtained much easier from refractory minerals than in traditional metallurgical approaches.     

Electrochemical fabrication of complex copper oxide nanoarchitectures via copper anodization in aqueous and non-aqueous electrolytes

Described is the synthesis of various copper oxide nanostructured thin films by anodization of Cu foil in aqueous and ethylene glycol electrolytes containing hydroxide, chloride and/or fluoride ions at room temperature. The nanostructure topology was found to depend on the pH of the anodization electrolyte, KOH concentration, applied voltage and the presence of chloride and fluoride ions. Our results demonstrate the opportunity to grow complex copper oxide nanostructured films possessing sub-micron thick layers by a simple and straightforward electrochemical route. Although no film was observed on the Cu surface when the anodization was carried out at 10 V in KOH solutions with pH ≤ 10, various nanoarchitectures were formed upon increasing the electrolyte pH in the presence of chloride ions. Replacing chloride ions with fluoride ions resulted in the formation of highly porous nanoarchitectures. A simple mechanism for the formation of such porous structures is proposed. Anodizing in ethylene glycol-based electrolytes resulted in the formation of leaf-like nanoarchitectures up to 500 nm in thickness. XPS analysis was performed to study the composition of the formed nanoarchitectures. Vacuum annealing of the material at 280 °C resulted in the formation of porous Cu₂O nanoarchitectures.     

Voltammetric detection of bisphenol a by a chitosan-graphene composite modified carbon ionic liquid electrode

In this paper 1-ethyl-3-methylimidazolium tetrafluoroborate based carbon ionic liquid electrode (CILE) was fabricated and further modified with chitosan (CTS) and graphene (GR) composite film. The fabricated CTS-GR/CILE was further used for the investigation on the electrochemical behavior of bisphenol A (BPA) by cyclic voltammetry and differential pulse voltammetry. A well-defined anodic peak appeared at 0.436 V in 0.1 mol/L pH 8.0 Britton-Robinson buffer solution, which was attributed to the electrooxidation of BPA on the modified electrode. The electrochemical parameters of BPA on the modified electrode were calculated with the results of the charge transfer coefficient (α) as 0.662 and the apparent heterogeneous electron transfer rate constant (k_s) as 1.36 s^− 1. Under the optimal conditions, a linear relationship between the oxidation peak current of BPA and its concentration can be obtained in the range from 0.1 μmol/L to 800.0 μmol/L with the limit of detection as 2.64 × 10^− 8 mol/L (3σ). The CTS-GR/CILE was applied to the detection of BPA content in plastic products with satisfactory results.     

Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution

Oxygen evolution reaction (OER) is one of the important half-reactions in energy conversion equipment such as water-spitting devices, rechargeable metal-air batteries, and so on. It is beneficial to develop efficient and low-cost catalysts that understand the reaction mechanism of OER and analyze the reconstruction phenomenon of transition metal sulfide. Interestingly, copper sulfide and cuprous sulfide with the same components possess different reconstruction behaviors due to their different metal ion valence states and different atomic arrangement modes. Because of a unique atomic arrangement sequence and certain cationic defects, the reconstruction phenomenon of CuS nanomaterials are that S²⁻ is firstly oxidized to SO₄²⁻ and then Cu^x+ is converted into CuO via Cu(OH)₂. In addition, the specific “modified hourglass structure” of CuS with excellent conductivity is easier to produce intermediates. Compared with Cu₂S, CuS exhibits excellent OER activity with a lower overpotential of 192 mV at 10 mA cm⁻² and remarkable electrochemical stability in 1.0 m KOH for 120 h. Herein, this study elucidates the reconstruction modes of CuS and Cu₂S in the OER process and reveals that CuS has a stronger Cu S bond and a faster electronic transmission efficiency due to “modified hourglass structure,” resulting in faster reconstruction of CuS than Cu₂S.     

Magneto-optical Kerr-effect studies on copper oxide thin films produced by atomic layer deposition on SiO2

This work demonstrates the sensitivity of magneto-optical Kerr-effect (MOKE) spectroscopy to ultra-thin nonmagnetic films using the example of copper oxide. The films with an effective thickness between 0.6 nm and 6 nm are produced by atomic layer deposition (ALD) on silicon oxide substrates based on the Cu(I) β-diketonate precursor [(ⁿBu₃P)₂Cu(acac)] (acac = acetylacetonate) at a process temperature of 120 °C. The copper oxide films exhibit magneto-optical activity in the spectral ranges around 2.6 eV and above 4 eV. The evolution of the spectral features as a function of the number of ALD cycles is simulated numerically using the dielectric function and the Voigt constant of Cu₂O as input parameters. The comparison between experimental and simulated MOKE spectra strengthens the conclusion drawn from spectroscopic ellipsometry studies that the thin film optical constants differ markedly from the bulk ones.     

Electron diffraction studies of thin secondary product films on electrochemically reacting metal sulfides

Utilizing large mineral crystals (about 3 cm cubes) of CuFeS₂ and FeS₂, a series of novel electrochemical experiments was undertaken by wrapping these specimens with copper wire (either individually or in a contacting pair) and coating them with silicone cement except for a 1 cm² exposed surface window on one face. These specimens were then immersed in an acid lixiviant (pH 2.3) containing bacteria to catalyze the reaction rates, and reactions were monitored by measuring the copper in solution with time. Surface coatings formed on the CuFeS₂ were observable through visible color changes. Voltage and current variations for individually prepared specimens connected through a simple voltmeter-ammeter circuit were also measured and correlated with surface film formation. Fragments of coatings formed over reaction periods of 32 days were scraped from the surfaces and examined by electron diffraction in a transmission electron microscope. Copper, sulfur, Cu₅FeS₄, Cu₂S, CuS and other more complex compounds were readily identified. Some of these secondary reaction products have been postulated on the basis of reaction pathways for the anodic dissolution of CuFeS₂.     

Formation and dissolution of copper-based nanoparticles in SiO2 sol-gel film using heat treatment and/or UV light exposure

We report in this paper, results on the formation and dissolution of Cu-based nanoparticles in sol-gel SiO₂ thin films using heat treatment and UV light exposure, respectively. Using UV-vis-NIR spectroscopy, we have shown that Cu₂O nanoparticles can be generated by controlling the aging of the sol prior to film deposition while the Cu⁰ nanoparticles can be synthesized using a heat treatment in H₂ atmosphere at 550 °C for 6 h. It has been also demonstrated that irradiation with an UV pulsed (Q-switched Nd:YAG) or continuous black ray UV lamp can dissolve these Cu-based nanoparticles with controlled, spatial selectivity. The mechanism of the dissolution process was found to be mainly thermal. Finally, we report a new analytical technique for detecting/confirming the presence of low densities of Cu nanoparticles in the films, based on a relative heat flow measurement of such films using a micro-thermal analyzer (e.g., TA Instruments μTA model 2990).     

Solvothermal synthesis of copper sulfide semiconductor micro/nanostructures

Covellite copper sulfide (CuS) micro/nanometer crystals in the shape of hierarchical doughnut-shaped, superstructured spheric-shaped and flowerlike architectures congregated from those nanoplates with the thickness of 20-100 nm have been prepared by a solvothermal method. The as-obtained CuS products were characterized by means of scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopy (EDS). A systematic investigation has been carried out to understand the factors influencing the evolution of CuS particle morphology which found to be predominant by solvent, surfactant, sulfur resource and copper salt. The possible formation mechanism for the nanostructure formation was also discussed. These CuS products show potential applications in solar cell, photothermal conversion and chemical sensor.     

Nanostructured Cu2O thin film electrodes prepared by electrodeposition for rechargeable lithium batteries

Uniform films of Cu₂O with thickness below 1 μm were prepared from a Cu(II) lactate solution. The deposits were compact and of high purity with the particle size varying from 60 to 400 nm. They were tested as electrodes in lithium batteries and their electrochemical response was consistent with the Cu₂O + 2e⁻ + 2Li⁺ ↔ 2Cu + Li₂O reaction. Nevertheless, the reversibility of this reaction was dependent on thickness. Kinetic factors associated with the poor electronic conductivity of Cu₂O could account for the relevance of the influence of film thickness. The thinnest film, about 300 nm thick, exhibited the best electrochemical performance by sustaining a specific capacity as high as 350 Ah kg^− 1.     

Electrodeposition and electrochemical investigation of thin film Sn-Co-Ni alloy anode for lithium-ion batteries

The thin film Sn-Co-Ni alloy electrodes were prepared by electroplating on copper foil as current collector. The structure of the electroplated porous thin film Sn-Co-Ni alloy electrode is investigated by XRD, FE-SEM, and EDAX. The electrochemical performance is analyzed by using a battery cycler at the current rate of 0.1 C to cut-off potentials of 0.01 and 1.20 V vs. Li/Li⁺ and also cyclic voltammeter. Experimental results illustrate that the initial discharge capacity of the Sn-Co-Ni alloy anode is 717 mAh g⁻¹. The discharge capacity has been in increasing order between 2nd and 10th cycling and then maintained the stable capacity. It is found that the charge and discharge capacity of thin film Sn-Co-Ni alloy electrode obtained an average reversibility behavior and the better cycle stability.     

Structural, morphological, and electrical characteristics of the electrodeposited cobalt oxide electrode for supercapacitor applications

Cobalt oxide (Co₃O₄) thin films were prepared through electrodeposition on copper substrates using an ammonia-complexed cobalt chloride solution. The structural and morphological properties of the film were studied using an X-ray diffractometer and scanning electron microscopy, and the results showed that the electrodeposited cobalt oxide film had a nanocrystalline and porous structure. The electrochemical behavior of the electrodeposited cobalt oxide electrode was evaluated in a KOH solution using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The electrodeposited cobalt oxide electrode exhibited a specific capacitance of 235 F/g at a scan rate of 20 mV/s. The specific energy and the specific power of the electrode were 4.0 Wh/kg and 1.33 kW/kg, respectively.     

The influence of thiourea on copper electrodeposition: Adsorbate identification and effect on electrochemical nucleation

The effect of thiourea on copper deposition onto a copper seed layer from an electrolyte composed of CuSO₄, H₂SO₄, deionized water, and thiourea was investigated. Even in the presence of very low concentrations of thiourea, extremely smooth and bright copper deposits were obtained. From the results of X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electrochemical analyses, thiourea was found to react with copper or copper ions leading to the generation of CuS. CuS adsorption onto the copper seed layer seemed to inhibit the initial nucleation of the copper adions, resulting in the formation of smaller Cu grains compared to those forming in the absence of thiourea. CuS was observed to cover all active sites of the 1 cm² copper seed layer above 0.017 g/L thiourea. The surface roughness as well as the mean grain size of the deposits also approached minimum values above this thiourea concentration. Adsorbed CuS was incorporated into the deposits during electroplating, which was believed to be the major factor for the increased resistivity of the deposits.