Anodic oxidation of cyanide on a reticulated three-dimensional electrode

The preparation of a three-dimensional electrode suitable for the oxidation of dilute solutions of cyanide, by the electrodeposition of Pb0₂ on a reticulated vitreous carbon substrate is described. The electrode obtained (RVC-Pb0₂) is corrosion resistant and allows the oxidation of less than 5 p.p.m. of CN⁻ with a faradaic yield estimated at 50%. The mass transfer coefficient for the oxidation of the potassium ferrocyanide and the specific surface area of the RVC-Pb0₂ electrode has been determined.     

Electrochemical reduction of 2-ethyl-9,10-anthraquinoneon reticulated vitreous carbon and mediated formationof hydrogen peroxide

Hydrogen peroxide formation by the intermediate electroreduction of 2-ethylanthraquinone (EAQ) has been examined. The medium used for this preparative electrolysis was dimethoxyethane (DME) with tetraethylammonium tetrafluoroborate (TEATFB) salt as supporting electrolyte in the presence of a small percentage of water. In this process EAQ is reduced on a reticulated vitreous carbon (RVC) cathode in the presence of oxygen. It has been demonstrated that in this medium, the presence of EAQ enhances the hydrogen peroxide formation when compared to the direct reduction of oxygen in the same medium. The influence of EAQ on the oxygen reduction has also been examined by cyclic voltammetry on a vitreous carbon cathode.     

New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

A new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1-1000 mbars and as a continuous flow cell for pressure lower than 10(-3) mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd(8)Ni(92)(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules.     

High aspect ratio gold nanorods displayed augmented cellular internalization and surface chemistry mediated cytotoxicity

Due to their unique properties, gold nanorods (GNRs) have shown tremendous potential for advancing bio-imaging and sensing applications. As these nanoparticles display size-dependent optical properties, high aspect ratio GNRs are of particular interest for these applications because of their increased scattering contrast. While studies are emerging that demonstrate successful synthesis of high aspect ratio GNRs, their behavior and fate in a physiological environment has yet to be investigated. The goal of this study was to evaluate the rate of cellular internalization and cytotoxicity of long GNRs (aspect ratio 32) in a human keratinocyte cell line. Additionally, the critical role of surface chemistry in extent of cellular interactions and cytotoxicity was evaluated. Through comparison with aspect ratio 3 GNRs, it was identified that high aspect ratio GNRs displayed enhanced cellular internalization. Furthermore, surface functionalization dictated the quantity of GNRs internalized, with tannic acid having a significant increase over polyethylene glycol. However, the augmented intracellular concentration identified with long, tannic acid GNRs resulted in a considerable degree of cytotoxicity, which was not associated with other GNR conditions. Therefore, while the inclusion of high aspect ratio GNRs may increase the capabilities for nano-based applications, there exist some unintentional toxicological consequences that must also be considered.     

Ruthenium oxide–niobium hydroxide composites for pseudocapacitor electrodes

A simple solution-based method has been developed to vary the composition of redox active ruthenium oxide with highly proton-conducting niobium hydroxide to create stable, high capacitance electrodes at elevated temperatures. This method presents a dramatic departure from most other ruthenium oxide systems, which are prepared through annealing of hydrous ruthenium oxide. Typically RuO₂ processed at high temperature only exhibits high electrical conductivity and suffers from poor proton conduction, giving low overall capacitances. Here, the optimized Ru/Nb oxide composition can be used to achieve high power densities, high capacitances, and stabilized electrodes while significantly reducing ruthenium content. Extensive materials characterization including high-resolution cross-sectional TEM, elemental mapping, XRD, electrochemical impedance spectroscopy, and proton NMR were used to evaluate the structure of the material system. The electrochemically inert niobium oxide serves as a network former enhancing accessibility to redox active ruthenium oxide. The dispersion of RuO₂ in the NbO(OH)_x matrix results in reduced RuO₂ particle size, as observed via TEM and XRD, while also increasing the proton concentration in the material. Interconnected RuO₂ particles provide electrically conducting pathways, even at low Ru contents, where percolation networks remain intact. Ruthenium is more efficiently utilized in the Ru/Nb composites and ruthenium content can be significantly reduced without decreasing capacitive performance. In addition, the composite electrodes, with the fine mixing of Ru and Nb, give higher power performance than for RuO₂ alone.     

Sensory acceptability of white bread with added Australian sweet lupin (Lupinus angustifolius) kernel fibre and its glycaemic and insulinaemic responses when eaten as a breakfast

The aim of this study was to determine whether lupin kernel fibre (LKF) could lower the glycaemic and insulinaemic responses of bread without reducing palatability. Healthy adults (n = 21) consumed control (white) bread (2.7% total dietary fibre (TDF)) once and LKF bread (8.5% TDF) once, as 50 g available carbohydrate breakfasts, in random order on different occasions. Venous blood samples were taken fasting, then post‐prandially over 2 h and analysed for plasma glucose and insulin. Incremental areas under curves (IAUC) for glucose and insulin, glycaemic index (GI) and insulinaemic index (II) were calculated. Sensory acceptability of a control (white) bread (3.5% TDF) and two LKF breads (6.6 and 8.3% TDF) was determined (n = 54). A reduction of 18.8% (P < 0.05) was seen in IAUC for insulin of LKF bread compared with the control (white) bread breakfast. No significant differences were seen in the other glucose or insulin measures. Mean sensory ratings for all breads were ‘acceptable’, with no significant differences between the ratings of the breads. In conclusion, LKF can be formulated into palatable bread and beneficially influenced the IAUC for insulin. Further studies are required to determine unequivocally whether LKF has beneficial effects on blood glucose and insulin measures. Copyright © 2003 Society of Chemical Industry     

Development of tailored high-performance and durable electrocatalysts for advanced PEM fuel cells

A family of novel carbon materials with intermediate surface area and varying morphology and surface chemistry were used to prepare Pt/C catalysts by two different preparation procedures; a chemical impregnation method and a microwave-assisted polyol method. The catalysts were thoroughly characterized, and their electrochemical performance and stability were investigated with rotating disc electrode (RDE) cyclic voltammetric (CV) measurements. The intermediate-surface-area carbon supports gave catalysts with much greater support stability than a widely used standard catalyst. The novel catalysts had lower electrochemical surface area than the reference, but their specific electrocatalytic activity towards the oxygen-reduction reaction (ORR) was much higher, and some of them also featured higher mass-specific ORR activity than the reference. The series of catalysts prepared by the microwave-assisted polyol method featured smaller Pt nanoparticles and higher activities than those prepared by impregnation. On the other hand, the impregnated catalysts showed better durability of the Pt particles. The most promising catalysts were selected and elaborated in further optimized preparation procedures to obtain quantities sufficient for their use in proton-exchange membrane fuel cells (PEMFCs).     

Frequency- and time-domain FEM models of EMG: capacitive effects and aspects of dispersion

Electromyography (EMG) simulations have traditionally been based on purely resistive models, in which capacitive effects are assumed to be negligible. Recent experimental studies suggest these assumptions may not be valid for muscle tissue. Furthermore, both muscle conductivity and permittivity are frequency-dependent (dispersive). In this paper, frequency-domain and time-domain finite-element models are used to examine the impact of capacitive effects and dispersion on the surface potential of a volume conductor. The results indicate that the effect of muscle capacitance and dispersion varies dramatically. Choosing low conductivity and high permittivity values in the range of experimentally reported data for muscle can cause displacement currents that are larger than conduction currents with corresponding reduction in surface potential of up to 50% at 100 Hz. Conductivity and permittivity values lying toward the middle of the reported range yield results which do not differ notably from purely resistive models. Also, excluding dispersion can also cause large error-up to 75% in the high frequency range of the EMG. It is clear that there is a need to establish accurate values of both conductivity and permittivity for human muscle tissue in vivo in order to quantify the influence of capacitance and dispersion on the EMG signal.     

Independence of myoelectric control signals examined using a surface EMG model

The detection volume of the surface electromyographic (EMG) signal was explored using a finite-element model, to examine the feasibility of obtaining independent myoelectric control signals from regions of reinnervated muscle. The selectivity of the surface EMG signal was observed to decrease with increasing subcutaneous fat thickness. The results confirm that reducing the interelectrode distance or using double-differential electrodes can increase surface EMG selectivity in an inhomogeneous volume conductor. More focal control signals can be obtained, at the expense of increased variability, by using the mean square value, rather than the root mean square or average rectified value.     

Electrochemical studies in a molten CF3COOK-CF3COONa eutectic at platinum,gold and pyrolytic graphite electrodes

Electrolysis at platinum, gold and pyrolytic graphite anodes of a molten mixture of CF₃COOK-CF₃ COONa leads to mainly C₂F₆ and CO₂. Smaller quantities of CF₄, C₃F₈ and C₂F₄ are also observed particularly at gold and pyrolytic graphite. Voltammetric studies of some oxidation and reduction reactions in this medium are presented.