Application of the electrochemical quartz crystal microbalance technique to copper sonoelectrochemistry: Part 1. Sulfate-based electrolytes

The applicability of the electrochemical quartz crystal microbalance technique in an ultrasonic field created by an ultrasound probe is demonstrated for the electrodeposition of copper. Cyclic voltammetry and potentiostatic depositions in acidic sulfate-based copper electrolytes were performed at different ultrasonic intensities. The electrochemical quartz crystal microbalance was operated in ultrasonic fields with intensities up to 30 W cm⁻². For cyclic voltammetry, potential resolved and averaged (apparent) current efficiencies were calculated from mass and charge data in function of the amplitude of the ultrasonic horn. Ultrasound slightly affected the current efficiencies during copper deposition in cyclic voltammetry, but did not change the efficiencies during dissolution. During potentiostatic depositions the current efficiency increased from 84% to almost 100% upon application of ultrasound. Morphology of deposits prepared by potentiostatic depositions was analyzed by scanning electron microscopy, and found to be different at high ultrasonic intensities.     

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.     

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.     

Investigation of interfacial processes at tetraruthenated zinc porphyrin films using electrochemical surface plasmon resonance and electrochemical quartz crystal microbalance

In the present work we describe the investigation of interfacial and superficial processes on tetraruthenated zinc porphyrin (ZnTRP) films immobilized on gold electrode surface. In situ and real time measurements employing electrochemical surface plasmon resonance (ESPR) and electrochemical quartz crystal microbalance (EQCM) have given new insights into the electrochemical oxidation of ferrocyanide and phenolic compounds (acetaminophen, dopamine, and catechol) on ZnTRP modified electrodes. The decrease of diode like behavior in the presence of such phenolic species in contrast with ferrocyanide was clearly assigned to the inclusion of those species in the porphyrin film, creating new conduction pathways connecting the gold electrode surface with the film/solution interface. In fact, there are evidences that they can intercalate in the film (catechol > dopamine > acetaminophen), whereas ferrocyanide is completely excluded. Accordingly, the molecular size may play a fundamental role in such a process.     

Ion exchange properties of polypyrrole studied by electrochemical quartz crystal microbalance (EQCM)

The electrochemical polymerization of pyrrole in aqueous solution was studied as a function of a variety of parameters, such as magnitude of current density and monomer concentration. The possibility of quantitative replacement of counterions by solution anions was studied in detail using the electrochemical quartz crystal microbalance (EQCM) technique. It was found that the polymer structure can be manipulated, even after synthesis. The manipulation was revealed to be dependent on various factors, including the nature of the counterion and of the electrolyte concentration. On the basis of these observations, a two-layer structure is suggested for polypyrrole-based polymers. © 1999 Society of Chemical Industry     

Electrodeposition of antimony telluride thin films from acidic nitrate-tartrate baths

Electrochemical quartz crystal microbalance (EQCM) and rotating disk electrode (RDE) techniques were utilized to systematically investigate the electrodeposition of Sb_xTe_1−x (0.1 < x < 0.8). In addition, the effect of applied potential and agitation were correlated to the film composition, crystal structure, and morphology. Although the film composition was independent of the agitation rate, the deposition rate, current efficiency, crystallinity and phase of Sb_xTe_1−x were all strongly influenced by it. The deposition rate monotonically increased with increases in the rotation rate because of the faster diffusion rate of HTeO₂⁺ ions to the cathode. Amorphous thin films were electrodeposited in the absence of agitation, whereas polycrystalline Sb₂Te₃ with elemental Sb and Te were co-deposited at a higher agitation independent of the applied deposition potential.     

Electrochemical behavior of thin polycrystalline rhodium layers studied by cyclic voltammetry and quartz crystal microbalance

Electrochemical behavior of thin polycrystalline Rh layers has been studied in 0.5 M H₂SO₄ solution by cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). The properties of surface oxide formed on freshly electrodeposited Rh are different than on electrochemically aged Rh. The analysis of frequency changes in both hydrogen and oxygen regions is presented. It is suggested that hydrogen desorption occurs simultaneously with the adsorption of HSO₄⁻ ions, whose maximum surface coverage reaches ca. 8%. The EQCM results indicate that RhO is the main species formed during Rh surface oxidation. Metal dissolution proceeds during electrode cycling to sufficiently high potentials. The amount of dissolved metal increases with an increase in potential and a decrease in scan rate.     

The influence of lead upd on the oxidation of glucose at platinum electrodes an electrochemical quartz crystal microbalance study

The oxidation of glucose at Pt electrodes with upd deposits of Pb in acid media has been investigated using the electrochemical quartz crystal microbalance (EQCM). Glucose alone has a small effect on the mass response but changes in upd Pb coverage have a large effect. This allows changes in upd Pb coverage to be followed easily despite the fact that the associated current is largely obscured in the cyclic voltammogram. Cyclic voltammetry at low glucose concentrations shows a multiple peak structure in the double layer region of potential at low upd coverages that is charged to the more familiar single peak as upd coverage increases. Mass responses also reveal some blockage of Pb upd by glucose or species derived from it during cyclic voltammetry. Data from mass transients show that the deliberate formation of poisons prior to addition of Pb²⁺ ions to the electrolyte results in a substantial suppression of upd coverage especially between −0.1 and 0.1 V (sce). Finally, mass transients accompanying injections of Pb²⁺ in the presence of glucose in the electrolyte reveal the suppression of adsorption of Pb²⁺ cations on an oxidised Pt surface by species derived from glucose.     

Preparation of the molecularly imprinted polymers-based capacitive sensor specific for tegafur and its characterization by electrochemical impedance and piezoelectric quartz crystal microbalance

Molecularly imprinted polymers (MIPs)-based capacitive sensor specific for tegafur was constructed by electropolymerization of m-aminophenol onto the surface of gold electrode and the Au-coated quartz crystal electrodes. Electrochemical impedance (EI) and quartz crystal microbalance (QCM) were employed to characterize the modified gold electrodes and the modified Au-coated quartz crystals, respectively. Unlike the capacitive sensors reported in the previous literatures, the present sensors were not treated with alkanethiol after electropolymerization and show even more satisfactory performance. QCM measurements also confirmed the imprinting effect of the polymer layers.     

Electropolymerization of ethylene dioxythiophene (EDOT) in micellar aqueous solutions studied by electrochemical quartz crystal microbalance and surface plasmon resonance

Electropolymerization of 3,4-ethylene dioxythiophene (EDOT) on gold electrodes was studied in situ by means of an electrochemical quartz crystal microbalance (EQCM) and by surface plasmon resonance spectroscopy (SPR) using aqueous micellar monomer solutions. Electrodeposition from micellar solutions performed by cyclic voltammetry (CV) displayed an enhanced rate as compared to surfactant concentrations lower than the critical micelle concentration (cmc) or in surfactant-free monomer solutions. EQCM data indicate the occurrence of additional film growth during the reductive scan to large negative potentials which does not occur in electropolymerization experiments using potentiostatic pulses or cyclovoltammetric cycles with less negative potential scans. Our results further suggest that in the case of the anionic surfactant the oxidation potential of the monomer is lowered even at surfactant concentrations below the cmc. AFM investigations show a slightly enhanced roughness of the films obtained from micellar monomer solutions.     

Trichloroacetic acid‐imprinted polypyrrole film and its property in piezoelectric quartz crystal microbalance and electrochemical sensors to application for determination of haloacetic acids disinfection by‐product in drinking water

A molecularly trichloroacetic acid (TCAA) imprinted non‐crosslinked polypyrole (TCAA‐MIPpy) has been successfully prepared and evaluated in its properties for both piezoelectric quartz crystal microbalance (QCM) and electrochemical means of detection, and application of such sensors for determination of haloacetic acid concentrations in water. Haloacetic acid selectivity was demonstrated in gravimetric or in electrochemical sensors via either cyclic voltammetric or inter‐digitated conductometric (IDC) analyses studies upon comparison with nonimprinted polypyrrole and TCAA‐imprinted polypyrrole. The measurement results with all these systems revealed that the prepared molecularly imprinted polymer can recognize TCAA well from structurally similar compounds. The TCAA‐MIPpy incorporated with only the IDC transduction system produced the specific signal for TCAA detection in aqueous environment, which is useful for the quantifying TCAA disinfection by‐product in water. The analytical application for determination of TCAA in real‐life samples was readily achieved with the incorporation of TCAA‐MIPpy in the IDC analysis system, the results revealing the high sensitivity and selectivity of the method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrochemical quartz crystal microbalance study on carbon oxides adsorption in the presence of electrosorbed hydrogen on Pd alloys with Pt and Rh

CO₂ and CO adsorption on Pd-Pt and Pd-Rh alloys has been studied by cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). Adsorbed CO₂ inhibits partially hydrogen adsorption on Pt and Rh surface atoms but does not block significantly hydrogen absorption into alloy bulk. In the presence of adsorbed CO both hydrogen adsorption and absorption are strongly suppressed. On electrodes covered with adsorbed CO the oxidation of previously absorbed hydrogen is significantly shifted into higher potentials. The EQCM response in CO₂/CO adsorption experiments is affected by both the effects connected with the changes in mass attached to the resonator and the non-mass effects including changes in metal-solution interactions and variation of solution density and viscosity in the vicinity of the electrode. Differences in the EQCM behavior suggest that the products of CO₂ and CO adsorption on the alloys studied are not totally identical.     

Electropolymerization of o‐phenylenediamine on Pt‐electrode from aqueous acidic solution: Kinetic,mechanism, electrochemical studies and characterization of the polymer obtained

Electropolymerization of O‐phenylenediamine (o‐PD) on Pt‐electrode from a deoxygenated aqueous acid medium was carried out using cyclic voltammetry technique. The kinetic parameters were calculated by means of electrochemical data. The experimentally obtained kinetic equation was R_P,_E = k_E [monomer]^1.19 [acid]^1.23 [electrolyte]^0.87 from the value of the anodic current density using cyclic voltammetry technique. The apparent activation energy (E_a) is found to be 28.34 kJ mol^?1. The polymer films obtained have been characterized by X‐ray diffraction, elemental analysis, scanning electron microscopy, ¹H‐NMR, ¹³C‐NMR, UV‐visible, and IR spectroscopy. The mechanism of the electrochemical polymerization reaction has been discussed. TGA is used to confirm the proposed structure and determination of the number of water molecules in the polymeric chain unit. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electropolymerization of p‐phenylenediamine on Pt‐electrode from aqueous acidic solution: Kinetics,mechanism, electrochemical studies,and characterization of the polymer obtained

Ar plasma‐induced graft polymerization of poly(ethylene glycol) (PEG) on Ar plasma pretreated poly(methyl methacrylate) (PMMA) surfaces was carried out to improve the antistatic properties. The surface composition and microstructure of the PEG‐grafted PMMA surfaces from plasma induction were characterized by attenuated total reflectance Fourier transfer infrared (ATR‐FTIR) spectroscopy, water contact angles (CA), and atomic force microscopy (AFM) measurements. The measurements revealed that the antistatic properties can be remarkably improved with the surface resistivity of PEG‐grafted PMMA surface decreasing significantly by 3–6 orders of magnitude, with the optimum condition for polymerization grafted onto the Ar plasma pretreated PMMA surface being 40 W for RF power and 3 min for glow discharge time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010