Structural and optical properties of Cu2O crystalline electrodeposited films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Study of copper electrodeposition mechanism from a strike alkaline bath prepared with 1-hydroxyethane-1,1-diphosphonic acid through cyclic voltammetry technique

Copper strike baths are extensively used in metal plating industry as they present the ability to plate adherent copper layers on less-noble metal substrates such as steel and zinc die castings. However, in the last few years, due to environmental controls and safety policies for operators, the plating industry has been interested in replacing the toxic cyanide copper strike baths with environmentally friendly baths. A broad bibliographic review showed that the published papers, referring to the new nontoxic copper strike baths, are patents, having little or no emphasis focused on electrodeposition mechanisms. Therefore, it was decided to study the copper electrodeposition mechanism from a strike alkaline bath prepared with one of the most nontoxic chelating agents cited in many patents which is the 1-hydroxyethane-1,1-diphosphonic acid, known as HEDP. This acid forms very stable water soluble complexes with Cu(2+) ions, thus cupric sulfate was used for preparing the plating bath. The results obtained through a cyclic voltammetry technique showed that Cu(2+) ion reduction to Cu from an HEDP electrodeposition bath occurs via a direct reduction reaction without a formation of Cu(+) intermediates. (C) 2010 Elsevier Ltd. All rights reserved.

Electrocatalytic oxidation of urea by nanostructured nickel/cobalt hydroxide electrodes

The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nickel/cobalt hydroxide modified electrodes by using both electrodeposited films and nanoparticles. The incorporation of Co foreign atoms leads to a slight increase in sensitivity besides the shift in redox process, avoiding the oxygen reaction. Nanostructured Ni80Co20(OH)(2) was synthesized by sonochemical route producing 5 nm diameter particles characterized by high-resolution transmission electron microscopy (HRTEM) being immobilized onto electrode by using the electrostatic Layer-by-layer technique, yielding attractive modified electrodes for sensor development. (C) 2007 Elsevier Ltd. All rights reserved.

Fabrication of disposable voltammetric electronic tongues by using Prussian Blue films electrodeposited onto CD-R gold surfaces and recognition of milk adulteration

A new approach to fabricate a disposable electronic tongue is reported. The fabrication of the disposable sensor aimed the integration of all electrodes necessary for measurement in the same device. The disposable device was constructed with gold CD-R and copper sheets substrates and the sensing elements were gold, copper and a gold surface modified with a layer of Prussian Blue. The relative standard deviation for signals obtained from 20 different disposable gold and 10 different disposable copper electrodes was below 3.5%. The performance, electrode materials and the capability of the device to differentiate samples were evaluated for taste substances model, milk with different pasteurization processes (homogenized/pasteurized, ultra high temperature (UHT) pasteurized and UHT pasteurized with low fat content) and adulterated with hydrogen peroxide. In all analysed cases, a good separation between different samples was noticed in the score plots obtained from the principal component analysis (PCA). Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Electrodeposited thin mercury films on Pt-Ir alloy electrodes

Mercury thin films prepared by electrochemical deposition on Pt-Ir alloy and after partial removing of mercury at different temperatures were studied by means of an interferometric surface mapping microscope and by X-ray photoelectronic spectroscopy. Mercury film samples having mercury partially removed by anodic stripping at a potential more positive than the corresponding peak in the voltammogram were also studied using the same techniques. For blank samples the surface topographic studies showed well defined grain boundaries. Mercury film samples when heated up to different temperatures showed as material is removed and that the surface roughness decreases as the temperature increases. For samples heated up to 800 degrees C the surface roughness is approximately the same that for the blank. A model for the interphase of volumetric mercury electrodeposited on a Pt-Ir alloy has been proposed using samples both electrochemically and thermally removed of their Hg coatings. The model includes a layered three-region structure, containing at least two Pt-Hg intermetallics: PtHg4 and PtHg2. A substrate modified region, iridium rich, has also been detected. (C) 1999 Elsevier B.V. S.A. All rights reserved.

Combined Secondary Ion Mass Spectrometry Depth Profiling and Focused Ion Beam Analysis of Cu Films Electrodeposited under Oscillatory Conditions

The recrystallization behavior of Cu films electrodeposited under oscillatory conditions in the presence of plating additives was studied by means of secondary ion mass spectrometry (SIMS) and focused ion beam analysis. When combined with bis-(sodium-sulfopropyl)-disulfide (SPS), Imep levelers (polymerizates of imidazole and epichlorohydrin) show characteristic oscillations in the galvanostatic potential/time transient measurements. These are related to the periodic degradation and restoration of the active leveler ensemble at the interface. The leveler action relies on adduct formation between the Imep and MPS (mercaptopropane sulfonic acid)-stabilized CuI complexes that appear as intermediates of the copper deposition when SPS is present in the electrolyte. SIMS depth profiling proves that additives are incorporated into the growing film preferentially under transient conditions during the structural breakdown of the leveler ensemble and its subsequent restoration. In contrast, Cu films electrodeposited in the presence of a structurally intact Imep–CuI–MPS ensemble remain largely contamination free.

Patterning optically clear films: co-planar transparent and color-contrasted thin films from interdiffused electrodeposited and solution-processed metal oxides

Transparent thin films can now be site-selectively patterned and positioned on surface using mask-defined electrodeposition of one oxide and overcoating with a different solution-processed oxide, followed by thermal annealing. Annealing allows an interdiffusion process to create a new oxide that is entirely transparent. A primary electrodeposited oxide can be patterned and the secondary oxide coated over the entire substrate to form high color contrast coplanar thin film tertiary oxide. The authors also detail the phase formation and chemical state of the oxide and how the nature of the electrodeposited layer and the overlayer influence the optical clearing of the patterned oxide film.

Pt/TiO(2)/poly(vinyl sulfonic acid) Layer-by-Layer Films for Methanol Electrocatalytic Oxidation

One major challenge for the widespread application of direct methanol fuel cells (DMFCs) is to decrease the amount of platinum used in the electrodes, which has motivated a search for novel electrodes containing platinum nanoparticles. In this study, platinum nanoparticles were electrodeposited on layer-by-layer (LbL) films from TiO(2) and poly(vinyl sulfonic) (PVS), by immersing the films into a H(2)PtCl(6) solution and applying a 100 mu A current during different electrode position times. Scanning tunnel microscopy (STM) and atomic force microscopy (AFM) images showed increased platinum particle size and electrode roughness for increasing electrodeposition times. The potentiodynamic profile of the electrodes indicated that oxygen-like species in 0.5 mol L(-1) H(2)SO(4) were formed at less positive potentials for the smallest platinum particles. Electrochemical impedance spectroscopy measurements confirmed the high reactivity for the water dissociation and the large amount of oxygen-like species adsorbed on the smallest platinum nanoparticles. This high oxophilicity of the smallest nanoparticles was responsible for the electrocatalytic activity of Pt-TiO(2)/PVS systems for methanol electrooxidation, according to the Langmuir-Hinshelwood bifunctional mechanism. Significantly, the approach used here combining platinum electrodeposition and LbL matrices allows one to both control the particle size and optimize methanol electrooxidation, being therefore promising for producing membrane-electrode assemblies of DMFCs.

Characterisation and electrochemical behaviour of electrodeposited Cu-Fe foams applied as pseudocapacitor electrodes

Copper iron (Cu-Fe) 3D porous foams for supercapacitor electrodes were electrodeposited in the cathodic regime, on stainless steel current collectors, using hydrogen bubbling dynamic template. The foams were prepared at different current densities and deposition times. The foams were submitted to thermal conditioning at temperatures of 150 and 250 degrees C. The morphology, composition and structure of the formed films were studied by SEM, EDS and XRD, respectively. The electrochemical behaviour was studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry. The morphology of the 3D Cu-Fe foams is sensitive to the electrodeposition current and time. The increase of the current density produces a denser, larger and more ramified dendritic structure. Thermal conditioning at high temperature induces a coarser grain structure and the formation of copper oxides, which affect the electrochemical behaviour. The electrochemical response reveals the presence of various redox peaks assigned to the oxidation and reduction of Cu and Fe oxides and hydroxides in the foams. The specific capacitance of the 3D Cu Fe foams was significantly enhanced by thermal conditioning at 150 degrees C. The highest specific capacitance values attained 297 Fg(-1) which are much above the ones typically observed for single Cu or Fe Oxides and hydroxides. These values highlight a synergistic behaviour resulting from the combination of Cu and Fe in the form of nanostructured metallic foams. Moreover, the capacitance retention observed in an 8000 charge/discharge cycling test was above 66%, stating the good performance of these materials and its enhanced electrochemical response as supercapacitor negative electrodes. (C) 2014 Elsevier B.V. All rights reserved.

Analysis of S-rich CuIn(S,Se)2 layers for photovoltaic applications: Influence of the sulfurization temperature on the crystalline properties of electrodeposited and sulfurized CuInSe2 precursors

This paper reports the microstructural analysis of S-rich CuIn(S,Se)2 layers produced by electrodeposition of CuInSe2 precursors and annealing under sulfurizing conditions as a function of the temperature of sulfurization. The characterization of the layers by Raman scattering, scanning electron microscopy, Auger electron spectroscopy, and XRD techniques has allowed observation of the strong dependence of the crystalline quality of these layers on the sulfurization temperature: Higher sulfurization temperatures lead to films with improved crystallinity, larger average grain size, and lower density of structural defects. However, it also favors the formation of a thicker MoS2 interphase layer between the CuInS2 absorber layer and the Mo back contact. Decreasing the temperature of sulfurization leads to a significant decrease in the thickness of this intermediate layer and is also accompanied by significant changes in the composition of the interface region between the absorber and the MoS2 layer, which becomes Cu rich. The characterization of devices fabricated with these absorbers corroborates the significant impact of all these features on device parameters as the open circuit voltage and fill factor that determine the efficiency of the solar cells.

Comparison of SERS performances of Co and Ni ultrathin films over silver to electrochemically activated Co and Ni electrodes

In this work, the surface-enhanced Raman scattering (SERS) spectra of pyridine (py) on thin films of Co and Ni electrodeposited on an Ag electrode activated by oxidation-reduction cycles (ORC) are presented. The SERS spectra from the thin films were compared to those of py on activated bare transition metal electrodes. It was verified that the SERS spectra of py on 3 monolayers (ML)-thick films of Ni and Co presented only bands assignable to the py adsorbed on transition metal surfaces. It was also observed that even for 50 ML-thick transition metal films, the py SERS intensity was ca. 40% of the intensity from the 3 ML-thick films. The relative intensities of the SERS bands depended on the thickness of the films, and for films thicker than 7 ML for Co and 9 ML for Ni they were very similar to those of the bare transition metal electrodes. The transition metal thin films over Ag activated electrodes presented SERS intensities 3 orders of magnitude higher than the ones from bare transition metal electrodes. These films are more suitable to study the adsorption of low Raman cross-section molecules than are ORC-activated transition metal electrodes.

Electrodeposition and characterization of undoped and nitrogen-doped ZnSe films

Semiconducting films of (n-type) ZnSe and (p-type) nitrogen-doped ZnSe were electrodeposited by a linear-sweep voltammetric technique on to a substrate of fluorine-tin oxide (FM) glass ceramics. The films were characterized by scanning electron microscopy, energy-dispersive X-ray analysis and grazing-incidence X-ray diffraction. The results indicated that the material was deposited uniformly over the substrate, forming clusters when the Zn content of the bath was 0.1 mol L(-1) and a film when it was 0.2 or 0.3 mol L(-1). The effectiveness of doping the films with nitrogen by adding ammonium sulfate to the deposition solution was assessed by measuring the film-electrolyte interface capacitance (C) at various applied potentials (E(ap)) and plotting Mott-Schottky curves (C(-2) vs E(ap)), whose slope sign was used to identify p-type ZnSe. (C) 2009 Elsevier B.V. All rights reserved.

Structural, morphological and magnetic characterization of electrodeposited Co-Fe-W alloys

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrodeposition of catalytic and magnetic gold nanoparticles on dendrimer-carbon nanotube layer-by-layer films

Magnetic and catalytic gold nanoparticles were electrodeposited through potential pulse on dendrimer-carbon nanotube layer-by-layer (LbL) films. A plasmon absorption band at about 550 nm revealed the presence of nanoscale gold in the film. The location of the Au nanoparticles in the film was clearly observed by selecting the magnetic force microscopy mode. To our knowledge, this is the first report on the electrochemical synthesis of magnetic Au nanoparticles. In addition to the magnetic properties, the Au nanoparticles also exhibited high catalytic activity towards ethanol and glycerol oxidation in alkaline medium.

Evaluation of corrosion resistance and cytotoxicity of electrodeposited gold on various types of intermediate layers

Gold plated surfaces are widely applied in several technical and decorative fields. The two main issues regarding the discussion on the field of precious metal coatings concern the increase in the use of thinner gold layers and 'Ni free' substrates. In order to ensure the quality of the final products, the effects of the plated surfaces on their performance require thorough and accurate research. In this paper, the corrosion resistance of gold plated nickel, copper and bronze was investigated by electrochemical methods specifically potentiodynamic polarisation and electrochemical impedance spectroscopy in phosphate buffered saline. The cytotoxicity of the gold plated substrates was also evaluated and compared. The results showed that the substrate related to the best corrosion resistance and cytotoxicity among the tested ones was bronze, and the one with the lowest performance was nickel.