Nanostructured bioelectrodes were designed and assembled into a biofuel cell with no separating membrane. The glassy carbon electrodes were modified with mediator-functionalized carbon nanotubes. Ferrocene (Fc) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) bound chemically to the carbon nanotubes were found useful as mediators of the enzyme catalyzed electrode processes. Glucose oxidase from Aspergillus niger AM-11 and laccase from Cerrena unicolor C-139 were incorporated in a liquid-crystalline matrix-monoolein cubic phase. The carbon nanotubes-nanostructured electrode surface was covered with the cubic phase film containing the enzyme and acted as the catalytic surface for the oxidation of glucose and reduction of oxygen. Thanks to the mediating role of derivatized nanotubes the catalysis was almost ten times more efficient than on the GCE electrodes: catalytic current of glucose oxidation was 1 mA cm(-2) and oxygen reduction current exceeded 0.6 mA cm(-2). The open circuit voltage of the biofuel cell was 0.43 V. Application of carbon nanotubes increased the maximum power output of the constructed biofuel cell to 100 μW cm(-2) without stirring of the solution which was ca. 100 times more efficient than using the same bioelectrodes without nanotubes on the electrode surface.

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Glassy carbon electrodes modified with films composed of a network of single-wall carbon nanotubes (SWCNTs) and liquid-crystalline cubic phase were used for dioxygen reduction catalyzed by laccase. In the presence of pristine SWCNTs, the overpotential of dioxygen reduction was decreased by 0.5 V (E 1/2 ¼ À 0.09 V). Adding laccase to the system shifted the potential of oxygen reduction to þ 0.52 V vs. Ag/AgCl reference electrode. Carbon nanotubes increased the electrode working area and improved the conductivity of the film. The current density of oxygen reduction was further enhanced by using a common mediator, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS). Two procedures for modifying carbon nanotubes with ABTS were compared: by adsorption and by covalent binding. Covalent binding of ABTS to the nanotubes is advantageous since it completely eliminates leaching of mediator to the solution and leads to a stable biocathode system.

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Ammonium metavanadate, NH4VO3, plays an important role in the preparation of vanadium oxides and other ammonium compounds, such as NH4V3O8, (NH4)2V3O8, and NH4V4O10, which were found to possess interesting electrochemical properties. In this work, a new route for the synthesis of NH4VO3 is proposed by mixing an organic ammonium salt and V2O5 in a suitable solvent. The one-step procedure is carried out at room temperature. Additionally, the need for pH control and use of oxidants necessary in known methods is eliminated. The mechanism of the NH4VO3 formation is explained. It is presented that it is possible to tailor the morphology and size of the obtained NH4VO3 crystals, depending on the combination of reagents. Nano- and microcrystals of NH4VO3 are obtained and used as precursors in the hydrothermal synthesis of higher ammonium vanadates. It is proven that the size of the precursor particles can significantly affect the physical and chemical properties of the resulting products.

2014 Les densités des mélanges binaires de 4,4'-dipentylazoxybenzène (DPAB) et 4-éthyl-4'-pentylazoxybenzène (EPAB) avec 4-pentyl-4'-cyanobiphényle (PCB) pour les concentrations moyennes et dans l'intervalle des températures 25-80 °C sont mesurées. Les volumes isothermes de mélange des solutions Vs (égaux aux volumes d'excès VE, en cas d'existence des deux composants dans la même phase que la solution) sont aussi calculés à partir des interpolations de volumes molaires. Les coefficients isobares de dilatation thermique, pour un mélange de EPAB + PCB sont aussi calculés. La présence de complexes molaires de type A-B est confirmée. Abstract.-Densities of binary mixtures of 4,4'-dipentylazoxybenzene (DPAB) and 4-ethyl-4'-pentylazoxybenzene (EPAB) with 4-pentyl-4'-cyanobiphenyl (PCB) were measured over the temperature range of 25 to 80 °C and in the middle area of concentrations. Isothermal volumes of mixing Vs (equal to the excess volume VE when both pure components and solution are in the same phase) were also calculated from interpolated molar volumes. Isobaric thermal expansion coefficients were also calculated for one of the mixture concentrations EPAB + PCB. The presence of a molecular A-B complex has been confirmed.

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