RESUMEN

Air, and thus also molecular oxygen (O2), is incorporated in wheat flour dough during mixing. O2 participates in several (enzymatic) reactions, including those resulting in the oxidation of free sulfhydryl groups, thereby increasing dough strength and bread volume. We here incorporated different O2 levels in dough by mixing dough samples for a fixed time under different modified atmospheres which led to significant changes in dough free sulfhydryl contents and bread volumes. Although altering the mixing time not only impacted how much O2 was incorporated in dough but also the mechanical input, the changes in dough and bread properties when using different mixing times, largely depended on differences in O2 uptake. When used in bread recipes, redox agents such as azodicarbonamide (ADA) and ascorbic acid (AH2) impact the dough sulfhydryl contents and bread volumes. The effect of different levels of O2 incorporation on dough samples which contained ADA or AH2 was studied by altering the mixing time or the O2 content in the mixing atmosphere. Lower ADA levels were needed when dough was mixed under an atmosphere enriched in O2. As AH2 requires O2 to be converted to dehydroascorbic acid (DHA) to exert its improver effect, it came as a surprise that when it was included in a dough which was prepared under O2 enriched conditions, no additional impact was obtained and that, even under reduced O2 conditions, its use still resulted in an increased bread volume. These findings suggest that AH2 oxidase very effectively uses O2 to form DHA.

Asunto(s)

Pan , Triticum , Ácido Ascórbico , Compuestos Azo , Ácido Deshidroascórbico , Harina , Oxidorreductasas , Oxígeno

RESUMEN

The phenomenon of oxygen incorporation-induced superconductivity in iron telluride (Fe1+yTe, with antiferromagnetic (AFM) orders) is intriguing and quite different from the case of FeSe. Until now, the microscopic origin of the induced superconductivity and the role of oxygen are far from clear. Here, by combining in situ scanning tunneling microscopy/spectroscopy (STM/STS) and X-ray photoemission spectroscopy (XPS) on oxygenated FeTe, we found physically adsorbed O2 molecules crystallized into c (2/3 × 2) structure as an oxygen overlayer at low temperature, which was vital for superconductivity. The O2 overlayer were not epitaxial on the FeTe lattice, which implied weak O2 -FeTe interaction but strong molecular interactions. The energy shift observed in the STS and XPS measurements indicated a hole doping effect from the O2 overlayer to the FeTe layer, leading to a superconducting gap of 4.5 meV opened across the Fermi level. Our direct microscopic probe clarified the role of oxygen on FeTe and emphasized the importance of charge transfer effect to induce superconductivity in iron-chalcogenide thin films.

RESUMEN

Molybdenum disulfide (MoS2) was incorporated controllably by oxygen in order to modify the hydrophobic surfaces and thus to improve the adsorption of Hg2+ on MoS2 in aqueous solutions in this work. The experimental results indicated that the incorporation of oxygen could dramatically improve the adsorption of Hg2+ on MoS2. With 11% oxygen atom incorporation, the adsorption rate and capacity increased over 17 times and 21 folds, respectively, compared with that without oxygen incorporation. This vast improvement was found to be contributed to that the incorporation of oxygen would greatly enhance the complexation between S atoms and Hg2+ on MoS2 surfaces, resulting in the great increase of the Hg2+ adsorption. The increase of the adsorption capacity with increasing incorporated oxygen reached a plateau, which might be due to the saturation of covalent bond. In addition, the incorporation of oxygen atom greatly enhanced the hydrophilicity of MoS2 surfaces, facilitating the hydrated Hg2+ ions to approach to MoS2 surfaces. This finding might provide a highly potential adsorbent for efficiently removing Hg2+ from water.

RESUMEN

Aqueous Zn-ion batteries present low-cost, safe, and high-energy battery technology but suffer from the lack of suitable cathode materials because of the sluggish intercalation kinetics associated with the large size of hydrated zinc ions. Herein we report an effective and general strategy to transform inactive intercalation hosts into efficient Zn2+ storage materials through intercalation energy tuning. Using MoS2 as a model system, we show both experimentally and theoretically that even hosts with an originally poor Zn2+ diffusivity can allow fast Zn2+ diffusion. Through simple interlayer spacing and hydrophilicity engineering that can be experimentally achieved by oxygen incorporation, the Zn2+ diffusivity is boosted by 3 orders of magnitude, effectively enabling the otherwise barely active MoS2 to achieve a high capacity of 232 mAh g-1, which is 10 times that of its pristine form. The strategy developed in our work can be generally applied for enhancing the ion storage capacity of metal chalcogenides and other layered materials, making them promising cathodes for challenging multivalent ion batteries.

RESUMEN

As a popular strategy, interlayer expansion significantly improves the Li-ion diffusion kinetics in the MoS2 host, while the large interlayer spacing weakens the van der Waals force between MoS2 monolayers, thus harming its structural stability. Here, an oxygen-incorporated MoS2 (O-MoS2 )/graphene composite as a self-supported intercalation host of Li-ion is prepared. The composite delivers a specific capacity of 80 mAh g-1 in only 36 s at a mass loading of 1 mg cm-2 , and it can be cycled 3000 times (over 91% capacity retention) with a 5 mg cm-2 loading at 2 A g-1 . The O-MoS2 exhibits a dominant 1T phase with an expanded layer spacing of 10.15 Å, leading to better Li-ion intercalation kinetics compared with pristine MoS2 . Furthermore, ex situ X-ray diffraction tests indicate that O-MoS2 sustains a stable structure in cycling compared with the gradual collapse of pristine MoS2 , which suffers from excessive lattice breathing. Density functional theory calculations suggest that the MoOx (OH)y pillars in O-MoS2 interlayers not only expand the layer spacing, but also tense the MoS2 layers to avoid exfoliation in cycling. Therefore, the O-MoS2 shows a pseudolayered structure, leading to remarkable durability besides the outstanding rate capability as a Li-ion intercalation host.

RESUMEN

Developing a high-performance anode with high reversible capacity, rate performance, and great cycling stability is highly important for sodium-ion batteries (SIBs). MoS2 has attracted extensive interest as the anode for SIBs. Herein, the vertically oxygen-incorporated MoS2 nanosheets/carbon fibers are constructed via a facile hydrothermal method and then by simple calcination in air. Oxygen incorporation into MoS2 can increase the defect degree and expand the interlayer spacing. Vertical MoS2 nanosheet array coated on carbon fibers not only can expose rich active sites and reduce the diffusion distance of Na+, but also improve the electronic conductivity and enhance structural stability. Meanwhile, interlayer-expanded MoS2 can decrease Na+ diffusion resistance and increase accessible active sites for Na+. In this work, the electrode combining the oxygen-incorporated strategy with vertical MoS2 nanosheet-integrated carbon fibers displays high specific capacities of 330 mAh g-1 over 100 cycles at a current density of 0.1 A g-1 together with excellent rate behavior as the anode for SIBs. This strategy offers a helpful way for improving the electrochemical performance.

RESUMEN

Electrochemical water splitting to produce hydrogen renders a promising pathway for renewable energy storage. Considering limited electrocatalysts have good oxygen-evolution reaction (OER) catalytic activity in acid solution while numerous economical materials show excellent OER catalytic performance in alkaline solution, developing new strategies that enhance the alkaline hydrogen-evolution reaction (HER) catalytic activity of cost-effective catalysts is highly desirable for achieving highly efficient overall water splitting. Herein, it is demonstrated that synergistic regulation of water dissociation and optimization of hydrogen adsorption free energy on electrocatalysts can significantly promote alkaline HER catalysis. Using oxygen-incorporated Co2 P as an example, the synergistic effect brings about 15-fold enhancement of alkaline HER activity. Theory calculations confirm that the water dissociation free energy of Co2 P decreases significantly after oxygen incorporation, and the hydrogen adsorption free energy can also be optimized simultaneously. The finding suggests the powerful effectiveness of synergetic regulation of water dissociation and optimization of hydrogen adsorption free energy on electrocatalysts for alkaline HER catalysis.

RESUMEN

A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6 O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6 O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.

RESUMEN

Growth conditions have a tremendous impact on the unintentional background impurity concentration in gallium nitride (GaN) synthesized by molecular beam epitaxy and its resulting chemical and physical properties. In particular for oxygen identified as the dominant background impurity we demonstrate that under optimized growth stoichiometry the growth temperature is the key parameter to control its incorporation and that an increase by 55 °C leads to an oxygen reduction by one order of magnitude. Quantitatively this reduction and the resulting optical and electrical properties are analyzed by secondary ion mass spectroscopy, photoluminescence, capacitance versus voltage measurements, low temperature magneto-transport and parasitic current paths in lateral transistor test structures based on two-dimensional electron gases. At a growth temperature of 665 °C the residual charge carrier concentration is decreased to below 1015 cm-3, resulting in insulating behavior and thus making the material suitable for beyond state-of-the-art device applications.

RESUMEN

Three-dimensional oxygen-incorporated MoS2 ultrathin nanosheets decorated on reduced graphene oxide (O-MoS2/rGO) had been successfully fabricated through a facile solvent-assisted hydrothermal method. The origin of the incorporated oxygen and its incorporation mechanism into MoS2 were carefully investigated. We found that the solvent N,N-dimethylformamide (DMF) was the key as the reducing agent and the oxygen donor, expanding interlayer spaces and improving intrinsic conductivity of MoS2 sheets (modulating its electronic structure and vertical edge sites). These O dopants, vertically aligned edges and decoration with rGO gave effectively improved double-layer capacitance and catalytic performance for hydrogen evolution reaction (HER) of MoS2. The prepared O-MoS2/rGO catalysts showed an exceptional small Tafel slope of 40 mV/decade, a high current density of 20 mA/cm(2) at the overpotential of 200 mV and remarkable stability even after 2000th continuous HER test in the acid media.