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The electrochemical impedance spectroscopy (EIS) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) techniques were employed to study the ionophore properties of valinomycin in a model floating bilayer lipid membrane (fBLM) in perchlorate supporting electrolytes with potassium and sodium cations. Valinomycin decreases the membrane resistance of the fBLM in KClO4 solution by about 180 times, while it has a negligible effect on the membrane resistivity in NaClO4 solution. The IR spectra indicate that valinomycin forms a complex with K+, but not with Na+. The valinomycin-K+ complex adopts a small tilt angle with respect to the electrode surface normal and is well interdigitated between the acyl chains of the bilayer. The EIS and PM-IRRAS results indicate that valinomycin forms complexes with K+ and transports K+ across the lipid bilayer. This transport is potential independent and hence has a passive character.

Natural Sciences and Engineering Research Council of Canada (NSERC)

Complementary electrochemical and spectroscopic techniques were used to characterize the behavior and composition of the passive layer formed at the gold surface in a thiosulfate electrolyte in the presence of cupric ions. Raman studies of three different cationic (calcium, ammonium, and sodium) thiosulfate leaching solutions revealed that the concentrations of thiosulfate, trithionate, sulfate, and tetrathionate remained constant in the bulk solution over a 3-h time period. The initial leaching current densities of these three systems were identical; however, significant differences in the open circuit potentials of these systems were observed. To provide additional information about the nature of the passive layer, gold nanorod array electrodes were fabricated and employed as substrates for studying the species present at the gold–thiosulfate interface using surface-enhanced Raman spectroscopy (SERS). The composition and behavior of the passive layer at the gold–thiosulfate interface greatly differed from those of the bulk solutions. The passive layer consisted primarily of elemental sulfur and sulfide-like species, with thiosulfate and its oxidation products, such as tri- and tetrathionates, as minority components. The nature of the cation (calcium, sodium, or ammonium) of the thiosulfate salt showed no significant effect on the composition of the passive layer at leaching times longer than 100 min. In addition, the presence of cupric ions also had no significant effect on the formation of the passive layer. However, copper is a much better oxidant than oxygen in gold–thiosulfate leaching reactions.

The first version of this article was published in January issue of the Canadian Chemical News in 2000. This issue featured Electrochemistry and coincided with the 200th anniversary of the famous. Volta pile experiment. It also coincided with the 50th anniversary of the International Society of Electrochemistry. In that article I reflected on the past and I pondered on the future of electrochemistry. It was written for general community of Canadian chemists. The present version has been updated. However most of my original thoughts have been retained. I have also retained the original language of an article written to a non-specialized readership.

Ni electrodeposition experiments at a constant current density 220 A/m2 were performed to determine the optimum concentrations of chloride and an organic additive used for an industrial Ni electrowinning. White light interference microscopy was used to acquire digital images of the morphology of the electrodeposited nickel. The scaling analysis was employed to parameterize the morphological information encoded in the images. The standard deviation of the surface height, δ, the critical scaling length, L c, and the optical roughness, 4δ/L c, were determined as a function of the chloride concentration and the amount of organic additives. These parameters were plotted as a function of the two compositional variables. These three-dimensional plots allowed us to find conditions corresponding to the minimum of 4δ/L c, at which the deposited nickel is well leveled.

We have synthesized colloidal Pt nanoparticles with a mean particle size of 2.6±0.4 nm by reducing PtCl2 dissolved in N,N-dimethylacetamide with t-BuMe2SiH. The latter compound acted both as a reducing agent and a stabilizer of the Pt nanoparticles. Pt nanoparticles were deposited onto the Au substrate and IR reflectance absorption spectroscopy (IRRAS) was applied to investigate CO adsorption and oxidation at the surface of the catalyst. The reactivity of the catalyst covered with Nafion was compared with the reactivity of the catalyst without Nafion. In addition, the reactivity of the colloidal Pt was compared with the reactivity of bulk polycrystalline Pt. We found that CO oxidation proceeds at lower over-potentials at nanoparticles than at polycrystalline Pt. The IRRAS data indicate that the difference in the reactivity may be explained by a different mechanism of the oxidation reaction; Langmuir–Hinshelwood at Pt nanoparticles and island formation and growth at polycrystalline Pt. We have also observed that a film of Nafion slows down the CO oxidation reaction. The IRRAS spectra for CO adsorbed at Pt nanoparticles covered by Nafion were significantly different from the spectra recorded for the nanoparticles in the absence of Nafion. The spectroscopic features suggest that in the presence of Nafion the nanoparticles experience regions of lower and higher proton concentration.

Electrochemical measurements including cyclic voltammetry, differential capacity, and chronocoulometry have been used to characterize the adsorption behaviors of the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) on the Au(111) electrode surface. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DDAPS has a multistate character. The first two states are observed at potentials close to zero charge. At low bulk DDAPS concentrations, it corresponds to the formation of a film of nearly flat adsorbed molecules. At higher concentrations it is converted into a hemimicellar state. The second state is formed at negative potentials and charge densities close to 0 μC cm−2. It corresponds to a film of tilted molecules oriented with the hydrocarbon tail towards the metal and the polar head toward the solution.