Electrically conductive coatings of nickel and polypyrrole/poly(2-methoxyaniline-5-sulfonic acid) on nylon Lycra textiles

Woven nylon Lycra^® has been coated with finely-divided electroless nickel-phosphorus, polypyrrole and electroless nickel/polypyrrole to produce flexible and electrically conductive textiles. The coated textiles were tested for their electrochemical activity, electrical resistivity and resistivity in response to mechanical strain. Pre-dyeing the textile with poly(2-methoxyaniline-5-sulfonic acid) (PMAS) prior to electroless metallization by electroless nickel and via chemical polymerization of polypyrrole was found to be beneficial in enhancing the resultant coating as well as stabilizing surface resistance responses when exposed to a wide range of strain. The mass gain due to the nickel coating was found to increase linearly with deposition time. The surface resistivity of the coated textile was found to decrease at longer nickel deposition times.     

An electrochemical quartz crystal microbalance study into the deposition of manganese dioxide

An electrochemical quartz crystal microbalance (EQCM) has been used to study the effects of electrolyte composition (MnSO₄ and H₂SO₄ concentrations) and anodic current density on the electrodeposition of manganese dioxide. The EQCM, in tandem with the electrode voltage during deposition, has been used to characterize features of the deposition mechanism such as the relative lifetime of the Mn(III) intermediate, the rate of soluble Mn(III) hydrolysis to form MnOOH, and the porosity of the resultant manganese dioxide deposit as a function of crystal nucleation. The connection between the results obtained here and commercial electrodeposition of manganese dioxide were also discussed.     

The activation effect of Pd nanoparticles on electroless nickel-phosphorous deposition

Active colloids regarding responsible for charge transfer and electron transfer are in electroless metal bath. Herein, the electrochemical analysis for the catalytic effect of Pd nanoparticles on deposition kinetic and microstructure in the electroless nickel-phosphorous bath was studied. As supported analysis by leaner sweep voltammetry (LSV), the currents for oxidation peaks corresponding to Pd nanoparticles of increasing amount are measured to be enhanced. It shows that Pd nanoparticles have excellent catalytic power for EN_pD bath. In addition, the deposition rate analyzed by mixed potential theory (MPT) was found and increased from 0.063 to 0.091 μg/cm² s. However, based on the same nanocatalyst quantity, the deposition rates which actually occurred and are in situely monitored by EQCM are measured to be faster than theoretical value given by MPT. It shows that that the cathodic currents for depositing hydrogen and phosphorous in mixed potential theory could not be neglected when the equilibrium potential reached. As an additional information supported by FE-SEM, the continuous growth of nickel crystal is found after the induction time measured by EQCM. The narrowest distribution of nanosize grain is obtained at 120 s. In addition, the deposited layer of P of higher content is found to exist in the deposited microstructure catalyzed by the Pd nanoparticles of high concentration.     

Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction

Hollow Ag/Pd nanoparticles have been successfully prepared by a galvanic displacement reaction, in which a small amount of Pd(NO₃)₂ is allowed to react with previously synthesized Ag nanoparticles that act as templates. The resulting hollow Ag/Pd (Ag/Pd_hollow) nanoparticles are found to be icosahedral and decahedral in structure. The kinetics of electroless copper deposition (ECD) catalyzed by these bimetallic (Ag/Pd_hollow) nanoparticles are analyzed using an electrochemical quartz crystal microbalance (EQCM). The results reveal that these Ag/Pd_hollow nanoparticles have better catalytic activities than monometallic Ag and Pd nanoparticles. Furthermore, the catalytic activities of these hollow nanoparticles in the ECD bath can be controlled by tuning their alloy ratios in a suitable manner.     

Effect of Cu(II) ligands on electroless copper deposition rate in formaldehyde solutions: An EQCM study

The electroless copper deposition rate for 6 Cu^II complexes decreases in the ligand sequence: nitrilotriacetic acid (NTA) > N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylenediamine (Quadrol) > glycerol > L(+)-tartrate ~ sucrose > -tartrate. Both Cu^II complex stability and specific ligand effects were found to influence the Cu deposition process. The specific ligand effects are most obvious in the case of Quadrol (high kinetic activity at a high Cu^II complex stability), glycerol and sucrose (additional reaction of Cu₂O formation by interaction of Cu^II with ligand). According to the EQCM data for 11 Cu^II complexes (including data from the former study) the higher kinetic activity is demonstrated by complexes with ligands containing amino groups; this factor is more important for Cu deposition rate than copper complex stability. A potential dependence of the Cu reduction partial current on the electrode potential has been extracted from the EQCM data in the complete electroless plating bath. An increase in Cu^II reduction rate was found to occur in electroless plating solution for Cu^II complexes with NTA and Quadrol compared with that in formaldehyde-free solutions. Possible reasons for the acceleration of the partial Cu^II reduction reaction and the overall process kinetics are discussed using a hypothetical reaction sequence involving intermediate copper oxy-species and active Cu* formation as well as development of the preferred Cu surface structure.     

Mechanism of the electrochemical deposition of samarium-based coatings

Samarium-based films have been shown to form from aqueous solutions on the surfaces of metallic substrates such as steel or aluminum, and their presence has been reported to decrease substantially the corresponding corrosion rate of the underlying metallic substrate. Based on previous reports on the deposition of oxides or hydroxides of the closely related element cerium, this work demonstrates that samarium films are formed following a similar mechanism, which involves as the fundamental step an increase in interfacial pH resulting from cathodic oxygen-reduction or hydrogen-evolution reactions. With cyclic voltammetry (CV), electrochemical quartz-crystal microbalance (EQCM) measurements, rotating-disk electrode (RDE) tests, and surface characterization techniques, namely, scanning electron microscopy (SEM) and X-ray surface microanalysis (EDX), the postulated mechanism was verified, and the surface morphology of the resulting films was correlated with the nature of the reduction reaction that triggers film formation.     

硫脲稳定化学镀镍的机理

测定了硫脲对镍的沉积速度和氢的析出量的影响。结果表明，一定量的硫脲（大于３ｍｇ／Ｌ）可同时抑制镍的沉积和氢的析出，用电化学方法研究了化学镀镍液的电化学行为。并借助ＸＰＳ对化学镀镍层进行了分析。提出了硫脲稳定化学镀镍的机理。     

Characterization of polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) film and its application for the immobilization of vitamin B12

Vitamin B12 (B12) - possessing a redox active cobalt centre - is a candidate to be used as a mediator in bioelectrochemical processes. In order to exploit the possible redox activity of B12, Pt has been modified by a bio-conform conducting layer polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) PPy/PIPES. The electrochemical and spectral behaviour of this film proved to be similar to PPy/dodecyl-sulfate (DS), widely considered and accepted as one of the best combinations of conducting polymer films. The capability of the PPy/PIPES film for acting as adsorbant in the accumulation of B12 has been evidenced by the electrochemical quartz crystal microbalance (EQCM) technique. B12 could also be incorporated into the polymer layer during its electrochemical deposition. The results proving the preserved redox activity of B12 within the film open new perspectives towards redox mediated bioelectrochemical applications based on the immobilization of this biomolecule.     

Electroless deposition of Ni–B, Co–B and Ni–Co–B alloys using dimethylamineborane as a reducing agent

Fundamental aspects of electroless Ni–B, Co–B and Ni–Co–B alloys have been systematically examined. The composition, crystal structure and deposition rate of the alloys were determined as a function of the concentration of reducing agent (dimethylamineborane) and complexing agents (tartrate, citrate, malonate and succinic acid), bath pH and Ni2+/Co2+ ratio. Changes in the deposition rate and metallurgical features of the alloys induced by the change in plating parameters are discussed, based on electrochemical polarization data and the formation enthalpy of the nickel and cobalt borides.     

Electrochemical and spontaneous deposition of ruthenium at platinum electrodes for methanol oxidation: an electrochemical quartz crystal microbalance study

PtRu electrodes with Ru surface concentration ranging from 20 to 50% were prepared by electrolysis of Ru(NO)(NO₃)₃ at a constant potential and/or by spontaneous Ru deposition performed at open circuit potential from a RuCl₃ solution. The amount of either spontaneously or electrochemically deposited ruthenium on the platinum electrode was determined by means of an electrochemical quartz crystal microbalance (EQCM). The effect of the Ru surface concentration on the rate of methanol electrooxidation was also investigated and correlated to the EQCM measurements.     

Correlation between conductance and mass changes during p-doping of 2-methoxynaphthalene films

The redox response of 2-methoxynaphthalene films electrosynthesized in two different organic solvents, acetonitrile (ACN) and nitrobenzene (NB) has been studied by different in situ electrochemical techniques: the in situ conductance technique, electrochemical quartz crystal microbalance (EQCM) and electrochemical voltage spectroscopy (EVS). In situ measurements of conductance as a function of the potential during p-doping of 2-methoxynaphthalene films, electrosynthesized in TBAPF₆-ACN and TBAPF₆-NB, show that the conductance properties are strongly dependent on the solvent used during electrosynthesis, resulting in higher conductance values for films electrosynthesized in NB solutions. The EQCM technique has been used to correlate the frequency changes (mass changes) at the electrode surface with conductance changes during p-doping of the different films. The molar mass of the species involved in the charging-discharging reactions has been estimated from the EQCM results. For the determination of the electrochemical bandgap of the two different films, cyclic voltammetry (CV) and EVS were applied. Films electrosynthesized in NB solutions have a lower value of the bandgap (1.34 eV) than films electrosynthesized in ACN solutions (2.00 eV).     

Sensitivity variation of the electrochemical quartz crystal microbalance in response to energy trapping

The spatial sensitivity of the electrochemical quartz crystal microbalance (EQCM) to deposited mass is known to vary, from a maximum at the electrode centre to a low value at its edge. For small mass loadings, the effects of such spatially non-uniform deposition can be described by simple convolution of the added mass and the spatial sensitivity function; the response is linear with added mass. However, when the added mass is large, the phenomenon of “energy trapping” is significant; the EQCM sensitivity is predicted to be non-linear with locally added mass. These deviations have been found experimentally (via local Cu deposition) to be significant. A model based on the Rayleigh principle of energy balance and energy trapping phenomena is able to describe the observed deviations. Heavy deposits change the shape of the resonator oscillations: their amplitude decreases exponentially from the edge of the deposit with a decay length that depends on the deposit mass. This effect allows one to vary the differential sensitivity of the EQCM in a desirable way while retaining conductivity of the complete electrode surface.     

The influence of 2,2′-dipyridyl on non-formaldehyde electroless copper plating

High electroless copper deposition rates can be achieved using hypophosphite as the reducing agent. However, the high deposition rate also results in dark deposits. In the hypophosphite baths, nickel ions (0.0057 M with Ni²⁺/Cu²⁺ mole ratio 0.14) were used to catalyze hypophosphite oxidation. In this study, additives (e.g. 2,2′-dipyridyl) were investigated to improve the microstructure and properties of the copper deposits in the hypophosphite (non-formaldehyde) baths. The influence of 2,2′-dipyridyl on the deposit composition, structure, properties, and the electrochemical reactions of hypophosphite (oxidation) and cupric ion (reduction) have been investigated. The electroless deposition rate decreased with the addition of 2,2′-dipyridyl to the plating solution and the color of the deposits changed from dark brown to a semi-bright with improved uniformity. The deposits also had smaller crystallite size and higher (1 1 1) plane orientation with the use of 2,2′-dipyridyl. The resistivity and nickel content of the deposit were not affected by 2,2′-dipyridyl additions to the bath. The electrochemical current-voltage results show that 2,2′-dipyridyl inhibits the catalytic oxidation of hypophosphite at the active nickel site. This results in a more negative electroless deposition potential and lower deposition rate.     

化学镀铜体系的电化学性能

对乙二胺四乙酸二钠(EDTA×2Na)与酒石酸钾钠(TART)双络合化学镀铜液进行了电化学研究,考察了络合剂与2,2￠-联吡啶对阴、阳极极化反应的影响. 结果表明,化学镀铜阳极极化受电化学与扩散混合控制,阴极极化受扩散控制;EDTA×2Na与TART通过竞争络合与竞争放电影响极化反应,而2,2￠-联吡啶以弥散吸附方式改变极化阻抗影响铜的沉积;在优化镀液(EDTA×2Na 13.35 g/L, TART 13.35 g/L, 2,2￠-联吡啶15 mg/L)中化学镀铜,镀速达14.83 mg/min,所得镀层均匀致密.     

Copper nanowires within the central channel of tobacco mosaic virus particles

Simple electrochemical deposition techniques can produce highly defined metal nanostructures in templates. Electroless deposition (ELD) can be effectively used for depositing metals on insulators such as biological or plastic surfaces. With biomolecular templates, metallization methods are often restricted to mild reductions, and the deposition of copper at pH values above 12 is usually not applicable. We produced copper nanowires of 3 nm in diameter and up to 150 nm in length by electroless deposition within the 4 nm wide channel of tobacco mosaic virus (TMV) particles. We employed a low pH (7.5) copper electroless deposition solution that is compatible with biomolecules. The fabrication process of the nanowires is based on sensitization of tobacco mosaic virus with Pd(II) prior to the electroless deposition. We analyzed the chemical composition of the nanowires by energy-filtering transmission electron microscopy, and used the method also for nickel and cobalt nanowires deposited within the viral channel.     

Electrochemical activation of the electroless deposition of Ni–P alloy and phase structure characterization of the deposit. Part I: Dual bath system

A typical low temperature alkaline bath was chosen for the investigation of the effect of electrochemical activation on the efficiency of the electroless deposition of Ni and on the phase structure of the Ni–P alloys obtained. Electrochemical deposition was separated from chemical deposition by employing a two bath sequence, the first (i.e., the bath for electrochemical activation) being free of reducing agent. It was found that an activation current density, as well as an amount of precursors at the surface larger than a critical value (0.5mA cm^–2 and 8 mC cm^–2, respectively) are required for the electroless process to take place. The phenomenon was explained in terms of nucleation theory. Anodic linear sweep voltammetry (ALSV) of the Ni–P alloys obtained after electrochemical activation, as well as of those obtained after chemical (Sn–Pd) activation, indicated the presence of two dominant phases, that is, a solid solution of P in Ni, and a nickel phosphide compound, most probably Ni2P. It was also shown that changes in the phase structure of the electroless Ni–P deposit upon thermal treatment may be followed by employing (ALSV).     

Interaction of BSA protein with copper evaluated by electrochemical impedance spectroscopy and quartz crystal microbalance

The interaction of bovine serum albumin (BSA) protein with copper in phosphate buffer solution has been studied by a combination of electrochemical impedance spectroscopy (EIS) close to the open circuit potential, with simultaneous monitoring by the electrochemical quartz crystal microbalance (EQCM), in order to throw light on BSA adsorption. Copper films were electroplated onto gold quartz crystals and mounted in the EQCM. Experiments were conducted in the presence and absence of dissolved oxygen and of BSA and the results show the influence of O₂ on the protein/metal interaction and also show specific interactions between BSA and copper. The good reproducibility obtained in these experiments suggests future application to other systems and which should lead to a better understanding of the use of such types of protein as corrosion inhibitors.     

Anodic oxidation of Co(II) complexes with amines on a rotating Au electrode: Ligand effects in relation to the application for autocatalytic metal deposition

For the comparison of the electrochemical activity of Co(II)-amine complexes, the electrochemical response of an Au rotating disk electrode in alkaline Co(II)-glycine solutions to six amines: ethylenediamine (en), propane-1,2-diamine (pn-1,2), propane-1,3-diamine (pn-1,3), cyclohexane-1,2-diamine (chn), butane-1,4-diamine (bn), diethylenetriamine (dien), was studied. Addition of amines tested (except for bn) in mM levels shifts the open-circuit potential to more negative values by up to 0.5 V and enhances dramatically the anodic Co(II) oxidation current, as a result of Co(II) complex transformation into more stable and electrochemically active Co(II)-amine species. The effect of amines on the open-circuit potential changes in the line: dien ∼ en > pn-1,2 ∼ chn > pn-1,3 ? bn, and on the anodic current in the sequence: dien ∼ en > pn-1,2 > chn > pn-1,3 ? bn. The procedure described helps to select ligands for Co(II) complexes used as reducing agents in electroless plating solutions. The amines of high electrochemical response: dien, en, pn-1,2, and possibly, chn, are suitable for electroless copper deposition, pn-1,3 (a lower response), for electroless silver deposition, and bn (no response), not suitable for electroless plating solutions.     

Synthesis and characterization of chemically and electrochemically prepared conducting polymer/iron oxalate composites

Poly(3-octyl-thiophene) (POT) and polypyrrole (PPy) iron oxalate composites were synthesized through a post-polymerization oxidative treatment. The composite of the latter has been prepared also by electrochemical polymerization. The samples have been characterized by X-ray diffraction (XRD), impedance spectroscopy, scanning electron microscope (SEM) combined with energy dispersive X-ray (EDX) spectroscopy, Mössbauer spectroscopy, cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). In case of PPy, two peaks in the XRD spectra show the presence of iron containing composite, while with POT only the layered structure originating from the octyl side-chain interactions was modified by the composite formation. The assumption of the weakening of short- and long-range interactions was proven by the decrease in conductivity of the composite. The successful electrochemical synthesis resulted a composite of ∼5% iron content, determined by EDX. Mössbauer spectroscopy measurements evidenced a composite containing mixed valence iron oxalate doping ions, which supports the indirect EQCM data.     

化学镀镍-磷合金机理的研究

通过对化学镀Ni—P合金过程中线性极化电阻及沉积速度的测量,得出极化电阻的倒数1/Rp与电流密度i呈线性关系。用阳极极化曲线的方法,较详细地研究了次磷酸钠在镍电极上的氧化过程。提出了化学镀Ni—P合金是按电化学机理进行的。