Hydrogen peroxide (H2O2) electrosynthesis viathe 2e-Oxygen Reduction Reaction (ORR) represents a highly challenging, environmentally friendly and cost-effective alternative to the current anthraquinone-based technology. Various lightweight element hetero-doped carbon nanostructures are promising and cheap metal-free electrocatalysts for H2O2synthesis, particularly those containing O-functionalities. The exact role of O-containing functional groups as electroactive sites for the process remains debated if not highly controversial. Herein, we have reported on the covalent exohedral functionalization to the outer surface of extra-pure Multi-walled Carbon Nanotubes (MWCNTs) with discrete O-functional groups as a unique approach to prepare selective electrocatalysts for the process. This kind of decoration has added fundamental tiles to the puzzling structure/reactivity relationship of O-containing carbon-based catalysts for ORR, clearing doubts on the controversial role of hydroxyl/phenol groups as key functionalities for the design of more performing 2e-ORR electrocatalysts.

Acetonitrile is used as an effective, non-corrosive selectivity enhancer for the direct synthesis of hydrogen peroxide (HP). Palladium catalysts supported by activated carbon or poly-divinylbenzene are poisoned by acetonitrile, which makes them very little productive. Conversely the catalysts supported by strongly acidic ion-exchange resin are much more selective and productive in the presence of acetonitrile, and for relatively long time. TEM shows that the size of their metal nanoparticles can be decreased by a reconstruction process, possibly sustained by leached palladium(II) species. HP decomposition experiments show that acetonitrile inhibits the O-O bonds splitting.

Palladium catalysts supported by a mesoporous form of sulfonated poly-divinylbenzene, Pd/µS-pDVB10 (1%, w/w) and Pd/µS-pDVB35 (3.6% w/w), were applied to the direct synthesis of hydrogen peroxide from dihydrogen and dioxygen. The reaction was carried for 4 h out in a semibatch reactor with continuous feed of the gas mixture (H /O = 1/24, v/v; total flow rate 25 mL.min ), at 25°C and 101 kPa. The catalytic performances were compared with those of a commercial egg-shell Pd/C catalyst (1%, w/w) and of a palladium catalyst supported by a macroreticular sulfonated ion-exchange resin, Pd/mS-pSDVB10 (1%, w/w). Pd/µS-pDVB10 and Pd/C showed the highest specific activity (H consumption rate of about 75-80 h ), but the resin supported catalyst was much more selective (ca 50% with no promoters). The nanoparticles (NP) size was somewhat larger in Pd/µS-pDVB10, showing that either the reaction was structure insensitive or diffusion limited to some extent over Pd/C, in which the support is microporous. The open pore structure of Pd/µS-pDVB10, possibly ensuring the fast removal of H O from the catalyst, could also be the cause of the relatively high selectivity of this catalyst. In summary, Pd/µS-pDVB10 was the most productive catalyst, forming ca 375 molH O .kg .h , also because it retained a constant selectivity, while the other ones underwent a more or less pronounced loss of selectivity after 80-90 min. Ageing experiments showed that for a palladium catalyst supported on sulfonated mesoporous poly-divinylbenzene storage under oxidative conditions implied some deactivation, but a lower drop in the selectivity; regeneration upon a reductive treatment or storage under strictly anaerobic conditions (dry-box) lead to an increase of the activity but to both a lower initial selectivity and a higher drop of selectivity with time.

The hydrogen peroxide, a green impregnating agent suitable for lignocellulosic biomass to bioethanol process, was used to pretreat sugarcane bagasse by steam explosion. Two different concentrations of hydrogen peroxide (0.2% and 1%) were investigated. Then, the biomass was hydrolyzed after pretreatment using cellulase. The amount released of: (i) cellobiose; (ii) monosaccharides, as glucose, xylose, arabinose and mannose and (iii) lignocellulose derived by-products, as furans and small organic acids (acetic, formic, and levulinic acid), was evaluated in the hydrolysate samples, previously pretreated both in the presence and absence of impregnating agent. By adding of hydrogen peroxide in steam-pretreatment, the average yield increase was 12% for glucose and as high as 34% for xylose, and cellobiose yield was decreased of about 30%. No significant increase has been observed in arabinose and mannose yield. Furthermore, the hydrogen peroxide seems not increased the formation of lignocellulose derived by-products during pretreatment process, with the exception of the levulinic acid. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Schwann cells are key players in neuro-regeneration: They sense "alarm" signals released by degenerating nerve terminals and differentiate toward a proregenerative phenotype, with phagocytosis of nerve debris and nerve guidance. At the murine neuromuscular junction, hydrogen peroxide (H2O2) is a key signal of Schwann cells' activation in response to a variety of nerve injuries. Here we report that Schwann cells exposed to low doses of H2O2 rewire the expression of several RNAs at both transcriptional and translational levels. Among the genes positively regulated at both levels, we identified an enriched cluster involved in cytoskeleton remodeling and cell migration, with the Annexin (Anxa) proteins being the most represented family. We show that both Annexin A2 (Anxa2) transcript and protein accumulate at the tips of long pseudopods that Schwann cells extend upon H2O2 exposure. Interestingly, Schwann cells reply to this signal and to nerve injury by locally translating Anxa2 in pseudopods, and undergo an extensive cytoskeleton remodeling. Our results show that, similarly to neurons, Schwann cells take advantage of local protein synthesis to change shape and move toward damaged axonal terminals to facilitate axonal regeneration.

Niobium-containing mesoporous silica (Nb-SiO2) catalysts, which showed previously promising per: formances in the liquid-phase epoxidation of alkenes, were here applied to the epoxidation of unsaturated fatty acid methyl esters (FAMEs), selectively hydrogenated FAMEs and rapeseed oil triglyceride with aqueous hydrogen peroxide. Niobium-silica solids were prepared via grafting of niobocene dichloride onto the surface of different porous silica-based supports (non-ordered SiO2, ordered mesoporous MCM-41 and SBA-15 molecular sieves) via a dry impregnation procedure. Promising performance with very good selectivity towards desired monoepoxides were obtained, in particular over a Nb-grafted silica catalyst prepared from a commercial non-ordered silica support. (C) 2017 Elsevier Ltd. All rights reserved.

The importance of sensing hydrogen peroxide (H2O2) is due to its ubiquity, being extensively used in industry and also being a biologically relevant side-product of several enzymatic processes. Electrochemical sensing is one of the most robust and simple methods for sensing H2O2 and the discovery of new electroactive materials, particularly at the nanoscale, represents a very hot topic of research. Here, we prove that upon appropriate integration of oxidized single-walled carbon nanohorns (ox-SWCNHs) into a per se moderate H2O2 sensor such as cerium dioxide (CeO2), the sensitivity toward H2O2 is enhanced by almost two orders of magnitude (from 0.4 to 160 ?A cm-2 mM-1), on par with that of state-of-the-art metal or metal oxide-based sensors. The modified electrode is also very stable (82% response after 2 weeks of continuous use) and the results highly reproducible. The developed nanohybrid ox-SWCNHs@CeO2, characterized fully and whose average size is about 70 nm as measured by both TEM and AFM, was also tested in real case studies such as washing liquids and milk and was confirmed to be a robust and highly selective material, being not affected neither by the presence of complex matrices, nor by interferents in several organic substrates. The high recovery confirmed the excellent specificity and flexibility of this new electrocatalytic material.

The neuromuscular junction is a tripartite synapse composed of the presynaptic nerve terminal, the muscle and perisynaptic Schwann cells. Its functionality is essential for the execution of body movements and is compromised in a number of disorders, including Miller Fisher syndrome, a variant of Guillain-Barré syndrome: this autoimmune peripheral neuropathy is triggered by autoantibodies specific for the polysialogangliosides GQ1b and GT1a present in motor axon terminals, including those innervating ocular muscles, and in sensory neurons. Their binding to the presynaptic membrane activates the complement cascade, leading to a nerve degeneration that resembles that caused by some animal presynaptic neurotoxins. Here we have studied the intra- and inter-cellular signaling triggered by the binding and complement activation of a mouse monoclonal anti-GQ1b/GT1a antibody to primary cultures of spinal cord motor neurons and cerebellar granular neurons. We found that a membrane attack complex is rapidly assembled following antibody binding, leading to calcium accumulation, which affects mitochondrial functionality. Consequently, using fluorescent probes specific for mitochondrial hydrogen peroxide, we found that this reactive oxygen species is rapidly produced by mitochondria of damaged neurons, and that it triggers the activation of the MAP kinase pathway in Schwann cells. These results throw light on the molecular and cellular pathogenesis of Miller Fisher syndrome, and may well be relevant to other pathologies of the motor axon terminals, including some subtypes of the Guillain Barré syndrome.

Atmospheric pressure air dielectric barrier discharges were applied to phosphate-buffered saline and complete Dulbecco's modified Eagle medium (DMEM) supplemented with 10% fetal bovine serum to investigate their oxidative chemical modifications induced in liquids that are relevant for cell culture experiments in the field of Plasma Medicine. The study mainly identified long-living reactive species. Hydrogen peroxide, superoxide anion radicals, and nitrite and nitrate ions were detected in DMEM. The density of the reactive species was correlated with the energy dose delivered to the liquids by the discharges.

Ce-doped SrFeO perovskites with different cerium content have been prepared by solution combustion synthesis and investigated as electrocatalytic materials for H2O2 oxidation. Cyclic voltammetry in alkaline medium have been used to evaluate the electrochemical behaviors towards H2O2 of perovskite modified screen printed carbon electrodes (SPCE). The structural, surface and morphological properties of the investigated samples along with their reduction behavior and interaction with oxygen have been correlated with their electrochemical sensing characteristics. Results demonstrated that the contemporary presence of Ce and Fe in the perovskite structure enhances the electrocatalytical activity towards the oxidation of H2O2. An amperometric sensor based on the Sr0.85Ce0.15FeO3 perovskite has been also developed for hydrogen peroxide determination in aqueous solution showing a sensitivity of about 60 ?A mM -1 cm -2 and a lower detection limit of 10 ?M (S/N = 3).

Background: The introduction of an heterogeneously catalyzed gold-based alcohol oxidation process of broad applicability using a clean primary oxidant would be highly desirable. Gold is non toxic and carbonyl and carboxyl compounds are widely used to produce medicines, plastics, colorants, paints, detergents, fragrances, flavors, and other valued functional products. Results: The sol-gel entrapment of gold nanoparticles in hybrid silica improves gold-based oxidation catalysis applied to the selective oxidation of alcohols with aqueous hydrogen peroxide as eco-friendly primary oxidant. Pronounced physical and chemical stabilization of the sol-gel entrapped Au nanoparticles is reflected in catalyst recyclability. Conclusions: Potential implications of these findings are significant, especially considering that the highly stable, mesoporous glassy catalyst is ideally suited for application in microreactors for carrying out the reaction under flow.

Herein, the first multi-purpose antifouling and foul-release photocatalytic coating based on ORMOSIL thin films doped with nanoflower-like Bi2WO6 is described. Irradiation with visible light of the new films immersed in water produces significant amounts of H2O2 by photocatalytic oxidation of water, and allows the degradation of (bio)organic pollutants at the outer surface of the xerogel film.

Microwave-assisted epoxidation of unsaturated fatty acid methyl esters using zinc polyoxometalate

Two types of niobium-containing silica catalysts, (i) in-framework mixed oxide, obtained by co-precipitation type synthesis, and (ii) grafted niobium sites on silica supports, obtained via post-synthesis deposition from niobocene dichloride, were prepared. Both solids were tested in a series of five repeated batch-wise liquid-phase epoxidation tests of limonene with 50% aqueous hydrogen peroxide.

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The direct synthesis of hydrogen peroxide is catalyzed by palladium catalysts supported over different solids. With the aid of a suitable plug-flow reaction cell, we carried out a preliminary X-ray absorption fine structure spectroscopy (EXAFS) characterization of a palladium catalyst supported on the commercial resin K2621 under reaction conditions (in situ). Whereas the catalyst, which in the dry catalyst presents metal Pd and PdO when fresh, is practically unaffected by the reaction medium (methanol) or by the reaction mixture (CO2/H2/O2, 86/10/4, v/v) it undergoes an apparent reduction of part of PdO to metal Pd and some metal leaching during the reaction in the presence of bromide ions. These findings suggest the role of bromide ions as enhancers of the selectivity of palladium catalysts in the direct synthesis of hydrogen peroxide could not be limited to the selective blocking of the sites responsible for the undesired formation of water, but could also entail phase modifications of the active metal.

In this study, the flavonoid didymin was administered in vitro in neuronal cells after hydrogen peroxide (H2O2)-induced injury (neurorescue) in order to investigate the effects of this natural molecule on cell damage in a neuronal membrane system. The results showed the effects of didymin in neuronal cells by using a polycaprolactone biodegradable membrane system as an in vitro model. Two major findings are presented in this study: first is the antioxidant property of didymin and, second, for the first time we provide evidence concerning its ability to rescue neuronal cells from oxidative damage. Didymin showed radical scavenging activities and it protected the neuronal cells against H2O2-induced neurotoxicity. Didymin increased cell viability, decreased intracel-lular reactive oxygen species generation, stimulated superoxide dismutase, catalase and glutathione peroxidase activity in neuronal cells which were previously insulted with H2O2. In addition, didymin strikingly inhibited H2O2-induced mitochondrial dysfunctions in terms of reduction of mitochondria membrane potential and the activation of cleaved caspase-3, and also decreased dramatically the H2O2-induced phosphorylation of c-Jun N-terminal kinase. Therefore, this molecule is capable of inducing recovery from oxidative damage, and promoting and/or restoring normal cellular conditions. Moreover, the mechanism underlying the protective effects of didymin in H2O2-injured neuronal cells might be related to the activation of antioxidant defense enzymes as well as to the inhibition of apoptotic features, such as p-JNK and caspase-3 activation. These data suggest that didymin may be a potential therapeutic molecule for the treatment of neurodegenerative disorders associated with oxidative stress. (C) 2014 S. Karger AG, Basel

Cytochrome bd is a prokaryotic respiratory quinol:02 oxidoreductase, phylogenetically unrelated to the extensively studied heme-copper oxidases (HCOs). The enzyme contributes to energy conservation by generating a proton motive force, though working with a lower energetic efficiency as compared to HCOs. Relevant to patho-physiology, members of the bd-family were shown to promote virulence in some pathogenic bacteria, which makes these enzymes of interest also as potential drug targets. Beyond its role in cell bioenergetics, cytochrome bd accomplishes several additional physiological functions, being apparently implicated in the response of the bacterial cell to a number of stress conditions. Compelling experimental evidence suggests that the enzyme enhances bacterial tolerance to oxidative and nitrosative stress conditions, owing to its unusually high nitric oxide (NO) dissociation rate and a notable catalase activity; the latter has been recently documented inane of the two bd-type oxidases of Escherichia coli. Current knowledge on cytochrome bd and its reactivity with O-2, NO and H2O2 is summarized in this review in the light of the hypothesis that the preferential (over HCOs) expression of cytochrome bd in pathogenic bacteria may represent a strategy to evade the host immune attack based on production of NO and reactive oxygen species (ROS). This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. (C) 2014 Elsevier B.V. All rights reserved.

Two kinds of niobium(V)-silica catalysts for the selective epoxidation were synthesised by post-synthesis modification of non-ordered mesoporous silica supports, starting from niobocene dichloride via solventless organometallic precursor dry impregnation or conventional liquid-phase grafting technique. Grafted Nb/SiO2 solids were used as catalysts, in the presence of aqueous H2O2, for the epoxidation of unsaturated cyclic and terpenic compounds of interest for fine and specialty chemistry, in particular: cyclohexene, 1-methylcyclohexene, limonene, carveol, alpha-terpineol, isopulegol, carvotanacetol, carvone, as well as squalene and isopulegyl acetate. These catalysts showed high yields (up to 73%) and excellent chemoselectivities to the desired epoxides (up to 98%), also in short reaction times (down to 1 h). (C) 2014 Elsevier B.V. All rights reserved.

Catalytic properties of Ti-containing porous solids were compared in the oxidation of 2,3,6-trimethylphenol (TMP) with H2O2 to produce 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate). Mesoporous titanium-silicates with di(oligo)nuclear Ti centers, metal-organic framework MIL-125 and amorphous TiO2 demonstrated 100 % selectivity toward TMBQ. Titanium-silicates prepared by evaporation-induced self-assembly revealed superior performance in terms of product yield and catalyst reusability.