High-performance asymmetric supercapacitor based on a CdCO3/CdO/Co3O4 composite supported on Ni foam - part II: a three-electrode electrochemical study.

A binder-free CdCO3/CdO/Co3O4 compound with a micro-cube-like morphology on a nickel foam (NF) made via a facile two-step hydrothermal + annealing procedure has been developed. The morphological, structural and electrochemical behavior of both the single compounds constituting this final product and the final product itself has been studied. The synergistic contribution effect of the single compounds in the final compounded resulting specific capacitance values are presented and discussed. The CdCO3/CdO/Co3O4@NF electrode exhibits excellent supercapacitive performance with a high specific capacitance (C S) of 1.759 × 103 F g-1 at a current density of 1 mA cm-2 and a C S value of 792.3 F g-1 at a current density of 50 mA cm-2 with a very good rate capability. The CdCO3/CdO/Co3O4@NF electrode also demonstrates a high coulombic efficiency of 96% at a current density as high as 50 mA cm-2 and also exhibits a good cycle stability with capacitance retention of ca. 100% after 1000 cycles at a current density of 10 mA cm-2 along with a potential window of 0.4 V. The obtained results suggest that the facilely synthesized CdCO3/CdO/Co3O4 compound has great potential in high-performance electrochemical supercapacitor devices.

ZnO Materials as Effective Anodes for the Photoelectrochemical Regeneration of Enzymatically Active NAD.

This work reports the study of ZnO-based anodes for the photoelectrochemical regeneration of the oxidized form of nicotinamide adenine dinucleotide (NAD+). The latter is the most important coenzyme for dehydrogenases. However, the high costs of NAD+ limit the use of such enzymes at the industrial level. The influence of the ZnO morphologies (flower-like, porous film, and nanowires), showing different surface area and crystallinity, was studied. The detection of diluted solutions (0.1 mM) of the reduced form of the coenzyme (NADH) was accomplished by the flower-like and the porous films, whereas concentrations greater than 20 mM were needed for the detection of NADH with nanowire-shaped ZnO-based electrodes. The photocatalytic activity of ZnO was reduced at increasing concentrations of NAD+ because part of the ultraviolet irradiation was absorbed by the coenzyme, reducing the photons available for the ZnO material. The higher electrochemical surface area of the flower-like film makes it suitable for the regeneration reaction. The illumination of the electrodes led to a significant increase on the NAD+ regeneration with respect to both the electrochemical oxidation in dark and the only photochemical reaction. The tests with formate dehydrogenase demonstrated that 94% of the regenerated NAD+ was enzymatically active.

High-performance asymmetric supercapacitor based on CdCO3/CdO/Co3O4 composite supported on Ni foam.

A CdCO3/CdO/Co3O4 composite has been prepared on nickel foam through a combined hydrothermal-annealing method. An asymmetric hybrid supercapacitor (SC) device was assembled with this composite as the positive electrode and activated carbon was the negative electrode. The SC exhibited a high specific capacitance of 84 F g-1 @ 1 mA cm-2, a maximum energy density of 26.3 W h kg-1, and a power density of 2290 W kg-1, along with a wide potential window of 1.5 V and long cycle life (92% after 6000 cycles). SCs assembled in series powered various light-emitting diodes and moved an electrical mini-motor.

Inclusion body myositis: a view from the Caenorhabditis elegans muscle.

Inclusion body myositis (IBM) is the most common myopathy in people over 50 years of age. It involves an inflammatory process that, paradoxically, does not respond to anti-inflammatory drugs. A key feature of IBM is the presence of amyloid-beta-peptide aggregates called amyloid deposits, which are also characteristic of Alzheimer's disease. The use of animals that mimic at least some characteristics of a disease has become very important in the quest to elucidate the molecular mechanisms underlying this and other pathogeneses. Although there are some transgenic mouse strains that recreate some aspects of IBM, in this review, we hypothesize that the great degree of similarity between nematode and human genes known to be involved in IBM as well as the considerable conservation of biological mechanisms across species is an important feature that must be taken into consideration when deciding on the use of this nematode as a model. Straightforward laboratory techniques (culture, transformation, gene knockdown, genetic screenings, etc.) as well as anatomical, physiological, and behavioral characteristics add to the value of this model. In the present work, we review evidence that supports the use of Caenorhabditis elegans as a biological model for IBM.

Electrosynthesis of Cu-Se films on copper electrodes in alkaline media: a voltammetric, electrochemical quartz crystal microbalance and I/t transient study.

The electroformation of Cu-Se phases, obtained by selenizing a thin film of copper deposited on the quartz/gold electrode system, was studied with an electrochemical quartz crystal microbalance (EQCM) and by cyclic voltammetry (CV) in an alkaline solution (0.05 M Na(2)B(4)O(7)) containing selenide ion. Potentiodynamic parameters showed that the formation of the initial Cu-Se phases (Cu(2-x)Se/Cu(3)Se(2)) is ruled by an irreversible diffusion controlled mechanism, where a first electron transfer is the rate-determining step. A CV study was also performed with a bulk copper electrode in 1 M NaOH solution containing selenide ion. The deconvolution of the anodic and cathodic I/E profiles corresponding to the electroformation and electroreduction of the Cu-Se film formed allowed us to establish that, depending on the anodic potential limit of the potentiodynamic scan, the Cu-Se phases formed were either a mixture of Cu(2)(-x)Se/Cu(3)Se(2) or Cu(2-x)Se/Cu(3)Se(2)/CuSe. An EQCM study showed that, during the initial stage of Cu-Se phase electroformation, water molecules were released from the electrode. In advanced stages of the process, when the electrode was completely covered by Cu-Se compounds, selenide anions were adsorbed on the formed phase. When the anodic potential limit was extended to -0.2 V, copper oxide compounds were formed. The analysis of the cathodic charge related to Cu-Se phase electroreduction and Energy Dispersive X-ray Spectroscopy (EDXS) analysis confirmed that when the anodic limit was -0.8 V, a mixture of different Cu-Se phases was formed. A I/t transient study performed with a bulk copper electrode in alkaline solution containing selenide established that the nucleation and growth mechanism (NGM) of the Cu-Se phases takes place through an initial bidimensional-instantaneous nucleation (IN2D), followed by four bidimensional-progressive nucleations (PN2D). These results and atomic force microscopy (AFM) experiences supported that the growth of the Cu-Se films occurs through a layer-by-layer mechanism.

New aspects of the electroadsorption of ethyl xanthate on copper electrodes.

The interaction of the ethyl xanthate (EX) anion with a copper electrode in a borate buffer solution, pH 9.2, has been investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), and measurements of contact angle (CA) under controlled potential. The results obtained allow establishing that, in the potential range from -0.80 and -0.60 V, two parallel reactions were characterized. These reactions were the ethyl xanthate electroadsorption and the hydrogen evolution reaction (HER). This last reaction has not been described by previous authors. Besides, the EIS measurements show that the mechanism of the HER on copper electrodes is not affected by the presence of a ethyl xanthate species. The EQCM study shows that in the electrodesorption process the departure of each ethyl xanthate species from the copper electrode is accompanied with the simultaneous entry of four to five water molecules. This fact is in accordance with the number of copper atoms involved in the adsorption of one ethyl xanthate species.

A chemical, morphological, and electrochemical (XPS, SEM/EDX, CV, and EIS) analysis of electrochemically modified electrode surfaces of natural chalcopyrite (CuFeS2) and pyrite (FeS2) in alkaline solutions.

Electrodic surfaces of natural chalcopyrite and natural pyrite minerals (El Teniente mine, Chile) have been studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy including microanalysis (SEM/EDX). For comparison, fractured and polished mineral surfaces were also studied by XPS. In both electrodes, the formation of Fe(III) species containing oxygen were detected and Cu(II) species containing oxygen were additionally detected for chalcopyrite at advanced oxidation states. The presence of Cu(II) species containing oxygen was not detected by XPS for the initial oxidation states of the chalcopyrite. For pyrite, the present results do not allow confirmation of the presence of polysulfurs such as have been previously proposed. In both minerals, the measurements of SEM and EDX show relevant alterations in the respective surfaces when different potential values were applied. The chalcopyrite surface shows the formation of protrusions with a high concentration of oxygen. The pyrite surface shows a layer of modified material with high oxygen content. The modifications detected by XPS, SEM, and EDX allowed the explanation of the complexity of the equivalent circuit used to simulate the experimental EIS data. At high oxidation states, both minerals showed a pseudoinductive loop in the equivalent circuit, which was due to the active electrodissolution of the minerals which takes place through a surface film previously formed.

Intracellular amyloid formation in muscle cells of Abeta-transgenic Caenorhabditis elegans: determinants and physiological role in copper detoxification.

BACKGROUND: The amyloid beta-peptide is a ubiquitous peptide, which is prone to aggregate forming soluble toxic oligomers and insoluble less-toxic aggregates. The intrinsic and external/environmental factors that determine Abeta aggregation in vivo are poorly understood, as well as the cellular meaning of this process itself. Genetic data as well as cell biological and biochemical evidence strongly support the hypothesis that Abeta is a major player in the onset and development of Alzheimer's disease. In addition, it is also known that Abeta is involved in Inclusion Body Myositis, a common myopathy of the elderly in which the peptide accumulates intracellularly. RESULTS: In the present work, we found that intracellular Abeta aggregation in muscle cells of Caenorhabditis elegans overexpressing Abeta peptide is affected by two single amino acid substitutions, E22G (Arctic) and V18A (NIC). Both variations show decrease intracellular amyloidogenesis compared to wild type Abeta. We show that intracellular amyloid aggregation of wild type Abeta is accelerated by Cu2+ and diminished by copper chelators. Moreover, we demonstrate through toxicity and behavioral assays that Abeta-transgenic worms display a higher tolerance to Cu2+ toxic effects and that this resistance may be linked to the formation of amyloid aggregates. CONCLUSION: Our data show that intracellular Abeta amyloid aggregates may trap excess of free Cu2+ buffering its cytotoxic effects and that accelerated intracellular Abeta aggregation may be part of a cell protective mechanism.