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Electrochemical experimental evidence of facilitated electron transfer in a sub-micrometer biosensor is presented. Layer-by-layer self-assembled deposition provides the unique advantage to specifically control the thickness of the biosensors, allowing an oxygen-insensitive device with a film thickness of 70 nanometers to be obtained. The biosensor is based on a poly(allylamine) osmium redox mediator and glucose 1-oxidase. The immobilized enzyme contributes to the signal generation through the full biosensor thickness, with no loss of 'active enzyme' in the outer layer of the biosensor through reaction with oxygen, as reported in the case of thick redox hydrogels. The application of the biosensor in complex matrices was approached with tests in wastewater. Encapsulation of the biosensor with Nafion® membrane ensured the protection of the enzyme molecules from the external environment, allowing the successful application of the sensor in a complex matrix. [ABSTRACT FROM AUTHOR]

The content of the article is about the principle of maximum entropy production rate applied to the description of uniform corrosion. The corroding metal surface is described as an ensemble of microcells randomly moving on the surface. The theory allows to calculate the ratio of the anodic to cathodic areas, as well as the corrosion current, under the hypothesis that the concentration overvoltages and the ohmic drops are both negligible. [ABSTRACT FROM AUTHOR]

Abstract: It was investigated the feasibility of decolorization of an azo dye (DG 26) using a large scale nanotubular TiO2 structured electrode in a laboratory photoelectrochemical reactor (0.8L). Catalyst was grown by anodic oxidation directly on Ti surface and its microstructure and crystalline structure were characterized with SEM and XRD. TiO2/Ti photoactivity under different anodic polarization values was evaluated via photoelectrochemical tests. The nanostructured TiO2 was used in a reactor as photo-anode under UV monochromatic irradiation (254nm) and it was subjected to bias (+1.5V vs. SCE). A comparison with photolysis and photocatalysis processes was carried out under the same operating conditions to evaluate the synergistic action of photocatalysis and TiO2/Ti electrochemical polarization. Electrophotocatalysis was proven to be more effective than photocatalysis in DG 26 decolorization. Catalyst polarization resulted in synergistic effect on process yields. The complete decolorization of a 40mg/L solution of DG 26 was achieved in 24h, without adding chemical reagents, and catalyst durability was demonstrated over 360h tests. Therefore, the work done is challenging to prove that the process (irradiation+catalyst+polarization) is feasible and effectively up-grading to pilot and demonstrative scale applications after a fluid dynamics optimization of the photoreactor. [Copyright &y& Elsevier]

Manganese-nickel mixed oxide thin films were deposited by anodic electrodeposition on stainless steel substrate from an acetate solution using a potentiodynamic technique, at scan rate of 100 mV s −1 and room temperature. The effect of electrolyte pH, varied in the range from 4 to 7, on composition, morphology and capacitance behavior of oxide thin films was investigated. The nickel content in the oxide increased with increasing deposition pH, allowing to investigate the effect of the oxide composition on the capacitive behavior of as-grown manganese-nickel mixed oxides. Oxide films deposited from the electrolyte at pH 6, having a composition close to Ni 0.10 Mn 0.90 O x showed the highest specific capacitance and the lowest charge transfer resistance. After annealing, the oxide had a complex structure of composite nature, consisting of intermixed amorphous and nanocrystalline phases. A birnessite type oxide with turbostratic disorder was identified as the major phase, in the presence of nickel hydroxide as a finely dispersed second phase. Annealing caused a drastic reduction of the charge transfer resistance and a limited increase of the specific capacitance, probably as the result of diverging effects on oxide properties, i.e. enhanced conductivity and porosity sintering. Cycle life testing of this material revealed a 25% increase of the specific capacitance over 5,000 cycles to a final value of 225 F g −1 (1 M Na 2 SO 4 , 50 mV s −1 , 0.11 mg cm −2 mass loading). [ABSTRACT FROM AUTHOR]

Abstract: In this work, the corrosion behavior of three differently treated AISI 316 stainless steel plates is investigated, viz. (1) pristine, (2) coated with a carbon nanotube (CNT) layer and (3) coated with a carbon nanofiber (CNF) layer. CNTs and CNFs were directly grown on stainless steel via a CVD method, using ethylene as the carbon source and without the addition of an external catalyst. The corrosion behavior of these materials was investigated by a combination of microstructural and electrochemical methods. Electrochemical tests included potentiodynamic and potentiostatic techniques in hot sulfuric acid solutions. A strong deterioration in corrosion resistance was revealed by the electrochemical tests and confirmed by microstructural examination of the samples. It was found that carbon diffusion into the substrate material during the CNT/CNF growth process results in chromium depletion of the near-surface region of 316 SS and chromium carbide precipitation at grain boundaries causing accelerated intergranular corrosion. Accordingly, notwithstanding the obvious inability of CNT/CNF layers to provide protection to the substrate due to their porous nature, a real corrosion damage arises from the high temperature exposure of stainless steel to the CVD atmosphere, suggesting that a similar risk may be present even for compact carbon coating deposited by CVD process, in the event of local damage of the coating. [Copyright &y& Elsevier]