Dual Oxygen Research Articles

A novel growth control of nanoplates WO3 photoanodes with dual oxygen and tungsten vacancies for efficient photoelectrochemical water splitting performance

Recently, there has been attractive attention over the defect-engineering where the optimum extent of oxygen deficiency has been considered as an effective route towards enhancing the solar-driven water oxidation photocurrent. In this study, a nanoplate-like tungsten oxide with dual oxygen and tungsten vacancies (WO3-x) was successfully fabricated on tungsten foil by acid-mediated hydrothermal treatment to highly improve the photoelectrochemical (PEC) performance of WO3-x photoanode. Thermal annealing at 550 °C in air led to an oxygen deficient surface with a sub-stoichiometric by phase transformation from orthorhombic WO3·.nH2O to γ-monoclinic. However, the optimum number of oxygen vacancies in WO3-x fabricated at 2 h (W-2 h) with compact, porous and uniform nanoplate film that provide a large surface area for efficient charge collecting capability, caused an enhanced photocurrent density of 4.12 mA/cm2 (41.2 mA/W) at 1.6 V vs. Ag/AgCl, as compared to W-3 h (2.59 mA/cm2, or 25.9 mA/W) and W-30 min (1.79 mA/cm2 or 17.9 mA/W). Finally, local variations in dual oxygen and tungsten vacancies and in the electronic band structure of a WO3-x thin film was analyzed with ultraviolet photoelectron spectroscopy (UPS) and UV–visible diffuse reflectance spectroscopy (UV-DRS).

Improved production of docosahexaenoic acid in batch fermentation by newly-isolated strains of Schizochytrium sp. and Thraustochytriidae sp. through bioprocess optimization

Thraustochytrids, rich in docosahexaenoic acid (DHA, C22:6ω3), represent a potential source of dietary fatty acids. Yet, the effect of culture conditions on growth and fatty acid composition vary widely among different thraustochytrid strains. Two different thraustochytrid strains, Schizochytrium sp. PKU#Mn4 and Thraustochytriidae sp. PKU#Mn16 were studied for their growth and DHA production characteristics under various culture conditions. Although they exhibited similar fatty acid profiles, PKU#Mn4 seemed a good candidate for industrial DHA fermentation while PKU#Mn16 displayed growth tolerance to a wide range of process conditions. Relative DHA content of 48.5% and 49.2% (relative to total fatty acids), respectively, were achieved on glycerol under their optimal flask culture conditions. Maximum DHA yield (Yp/x) of 21.0% and 18.9% and productivity of 27.6 mg/L-h and 31.9 mg/L-h were obtained, respectively, in 5-L bioreactor fermentation operated with optimal conditions and dual oxygen control strategy. A 3.4- and 2.8-fold improvement of DHA production (g/L), respectively, was achieved in this study. Overall, our study provides the potential of two thraustochytrid strains and their culture conditions for efficient production of DHA-rich oil.

Estimation of cloud liquid water over oceans from dual oxygen absorption band to support the assimilation of second generation of microwave observation on board the Chinese FY-3 satellite

ABSTRACTTo make up for the absence of observation-based information of cloud liquid water (CLW) in assimilation of second generation of microwave observation on board the Chinese FengYun-3 satellite, two algorithms using double oxygen-absorption band microwave sounding observation at 52.80 and 118.75 ± 2.5 GHz, one using brightness temperatures directly and the other utilizing a cloud emission and scattering index derived from the brightness temperature, are proposed to estimate CLW over oceans. Their performance was evaluated by verifying the estimations from FY-3C double oxygen absorption band microwave observations and that from the traditional Grody scheme applied to microwave measurements at 23.8 and 31.4 GHz from the MetOp-B satellite. An additional experiment was conducted to investigate the impact of regression analysis on the actual brightness temperature and reanalysis data, or the simulated measurements. It is demonstrated that CLW can be retrieved from double oxygen absorption band microwave sounding measurements. The estimations are comparable to the results obtained using the traditional scheme applied to Advanced Microwave Sounding Unit measurements. While total precipitable water was not well obtained as the traditional scheme did, it is feasible to perform regression analysis on actual brightness temperature and reanalysis data; however, for all estimations that the regression was conducted on, the results obtained using actual brightness temperature and reanalysis data were weaker than those obtained using regression coefficients from the simulated data set. The results could be improved by better matching the satellite observations and CLW data used in the regression analysis.

Origin of EL3 chondrites: Evidence for variable C/O ratios during their course of formation—A state of the art scrutiny

AbstractMineral inventories of enstatite chondrites; (EH and EL) are strictly dictated by combined parameters mainly very low dual oxygen (fO2) and sulfur (fS2) fugacities. They are best preserved in the Almahata Sitta MS‐17, MS‐177 fragments, and the ALHA 77295 and MAC 88136 Antarctic meteorites. These conditions induce a stark change of the geochemical behavior of nominally lithophile elements to chalcophile or even siderophile and changes in the elemental partitioning thus leading to formation of unusual mineral assemblages with high abundance of exotic sulfide species and enrichment in the metallic alloys, for example, silicides and phosphides. Origin and mode of formation of these exotic chondrites, and their parental source regions could be best scrutinized by multitask research experiments of the most primitive members covering mineralogical, petrological, cosmochemical, and indispensably short‐lived isotopic chronology. The magnitude of temperature and pressure prevailed during their formation in their source regions could eventually be reasonably estimated: pre‐ and postaccretionary could eventually be deduced. The dual low fugacities are regulated by the carbon to oxygen ratios estimated to be >0.83 and <1.03. These parameters not only induce unusual geochemical behavior of the elements inverting many nominally lithophile elements to chalcophile or even siderophile or anthracophile. Structure and mineral inventories in EL3 and EH3 chondrites are fundamentally different. Yet EH3 and EL3 members store crucial information relevant to eventual source regions and importantly possible variation in C/O ratio in the course of their evolution. EL3 and EH3 chondrites contain trichotomous lithologies (1) chondrules and their fragments, (2) polygonal enstatite‐dominated objects, and (3) multiphase metal‐rich nodules. Mineralogical and cosmochemical inventories of lithologies in the same EL3 indicate not only similarities (REE inventory and anomalies in oldhamite) but also distinct differences (sinoite‐enstatite‐graphite relationship). Oldhamite in chondrules and polygonal fragments in EL3 depict negative Eu anomaly attesting a common cosmochemical source. Metal‐dominated nodules in both EL3 and EH3 are conglomerates of metal clasts and sulfide fragments in EH3 and concentrically zoned C‐bearing metal micropebbles (≥25 μm ≤50 μm) in EL3 thus manifesting a frozen in unique primordial accretionary metal texture and composition. Sinoite‐enstatite‐diopside‐graphite textures reveal a nucleation and growth strongly suggestive of fluctuating C/O ratio during their nucleation and growth in the source regions. Mineral inventories, sulfide phase relations, sinoite‐enstatite‐graphite intergrowth, carbon and nitrogen isotopic compositions of graphite, spatial nitrogen abundance in graphite in metal nodules, and last but not least 129I/129Xe and 53Mn/53Cr systematics negate any previously suggested melting episode, pre‐accretionary or dynamic, in parental asteroids.

Catalytic conversion of methane and carbon dioxide (greenhouse gases) into syngas over samarium-cobalt-trioxides perovskite catalyst

The catalytic behaviour of samarium-cobalt-trioxides perovskite catalyst was investigated for the mitigation of greenhouse gases (carbon dioxide and methane) to provide cleaner energy (hydrogen and carbon monoxide) and environment. X-ray photoelectron spectroscopy analysis of the as-synthesized catalyst showed peaks corresponding to complexes of cobalt (II), dual oxygen species, and samarium (III) ions. X-ray diffraction pattern showed a monophasic samarium-cobalt-trioxides perovskite structure, while post-reaction analysis showed modification of the perovskite. The temperature-programmed reduction analysis showed peaks corresponding to reduction of cobalt (II) to Coo. The temperature-programmed desorption displayed peaks ascribed to medium strength basic and acidic sites. Performance test carried out on the catalyst via methane dry reforming, showed excellent reactants conversions of above 90% which was maintained for the duration (30 h) of the experiment. The catalyst remained active over the time of experiment, even though the temperature-programmed oxidation, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses of the used catalyst showed evidence of carbon deposit.

Dual Oxygen and Tungsten Vacancies on a WO3 Photoanode for Enhanced Water Oxidation

AbstractAlleviating charge recombination at the electrode/electrolyte interface by introducing an overlayer is considered an efficient approach to improve photoelectrochemical (PEC) water oxidation. A WO3 overlayer with dual oxygen and tungsten vacancies was prepared by using a solution‐based reducing agent, LEDA (lithium dissolved in ethylenediamine), which improved the PEC performance of the mesoporous WO3 photoanode dramatically. In comparison to the pristine samples, the interconnected WO3 nanoparticles surrounded by a 2–2.5 nm thick overlayer exhibited a photocurrent density approximately 2.4 times higher and a marked cathodic shift of the onset potential, which is mainly attributed to the facilitative effect on interface charge transfer and the improved conductivity by enhanced charge carrier density. This simple and effective strategy may provide a new path to improve the PEC performance of other photoanodes.

Dual Oxygen and Tungsten Vacancies on a WO3 Photoanode for Enhanced Water Oxidation.

Alleviating charge recombination at the electrode/electrolyte interface by introducing an overlayer is considered an efficient approach to improve photoelectrochemical (PEC) water oxidation. A WO3 overlayer with dual oxygen and tungsten vacancies was prepared by using a solution-based reducing agent, LEDA (lithium dissolved in ethylenediamine), which improved the PEC performance of the mesoporous WO3 photoanode dramatically. In comparison to the pristine samples, the interconnected WO3 nanoparticles surrounded by a 2-2.5 nm thick overlayer exhibited a photocurrent density approximately 2.4 times higher and a marked cathodic shift of the onset potential, which is mainly attributed to the facilitative effect on interface charge transfer and the improved conductivity by enhanced charge carrier density. This simple and effective strategy may provide a new path to improve the PEC performance of other photoanodes.

Nitro-Triarylmethyl Radical as Dual Oxygen and Superoxide Probe.

Superoxide radical is involved in numerous physiological and pathophysiological processes. Tetrathiatriarylmethyl (TAM) radicals are known to react with superoxide allowing measurement of superoxide production in biological media. We report the synthesis of a Nitro conjugated TAM radical showing a rate constant of 7×105M-1s-1 which is two order of magnitude higher than other TAMs, allowing high sensitivity measurement of superoxide.

Quadruple labelled dual oxygen and pH-sensitive ratiometric nanosensors

Nanosensors capable of simultaneously measuring dissolved oxygen concentrations from 0 to 100% saturation and pH over the full physiological range, from pH3.5 to 7.5, that advance the methods towards understanding of key biological gradients, were synthesised. A library of water soluble oxygen-sensitive porphyrins, with three substituted charged functional groups and a chemically flexible carboxylate functional group were spectroscopically analysed to assess their sensitivity to changes in dissolved oxygen concentrations as free species in solution and in suspension as nanoparticle conjugates. A platinum cationic porphyrin was taken forward to fabricate ratiometric oxygen-sensitive nanosensors, using 5-(and-6)-carboxytetramethylrhodamine (TAMRA) as internal standard. In addition, quadruple labelled dual oxygen and pH-sensitive nanosensors were synthesised using the cationic Pt porphyrin, pH-sensitive fluorescein dyes, carboxyfluorescein (FAM) and Oregon Green (OG), in a 1:1 ratio, and TAMRA. We envisage the dual oxygen and pH nanosensors will find broad utility in the characterisation of diverse microenvironments, where there are complex interactions between molecular oxygen and pH.

Cloud and precipitation features of Super Typhoon Neoguri revealed from dual oxygen absorption band sounding instruments on board FengYun‐3C satellite

AbstractA new methodology is developed to detect the cloud structures at different vertical levels using the dual oxygen absorption bands located near 60 GHz and 118 GHz, respectively. Observations from Microwave Temperature Sounder (MWTS) and Microwave Humidity Sounder (MWHS) on board the recently launched Chinese FengYun‐3C satellite are used to prove the concept. It is shown that a paired oxygen MWTS and MWHS sounding channel with the same peak weighting function altitude allows for detecting the vertically integrated cloud water path above that level. A cloud emission and scattering index (CESI) is defined using dual oxygen band measurements to indicate the amounts of cloud liquid and ice water paths. The CESI distributions from three paired channels reveal unique three‐dimensional structures of clouds and precipitation within Super Typhoon Neoguri that occurred in July 2014.

Aluminum Electrode Modulated Bipolar Resistive Switching of Al/Fuel-Assisted NiOx/ITO Memory Devices Modeled with a Dual-Oxygen-Reservoir Structure

Bipolar resistive switching in Al/fuel-assisted NiO(x) (40 nm)/ITO devices is demonstrated in this work. XPS analysis reveals the simultaneous presence of metallic Ni, Ni(2)O(3), and NiO components in the fuel-assisted NiO(x). The concentration, as well as spreading of the metallic Ni and accompanying oxygen vacancies, are related to the Al/NiO(x) interfacial reaction, which is enhanced by the increasing thickness of the Al top electrode. Correspondingly, the preswitching-on voltage decreases while the preswitching-off voltage increases with increasing thickness (from 15 to 60 nm) of Al. However, in regular switching operation, set and reset voltages are considerably lowered for devices with an increased thickness of the Al top electrode. The bipolar resistive switching behaviors of Al/fuel-assisted NiO(x)/ITO devices are therefore discussed based on the formation of conductive paths and their correlation with the Al-electrode modulated composition in the fuel-assisted NiO(x). The Al/NiO(x) interfacial reaction region pairs with ITO to form a dual-oxygen-reservoir structure. Mechanisms of construction/destruction of conducting paths originating from the electrochemical redox reactions at the interface between NiO(x), and the dual oxygen reservoirs will also be explicated.

Oxygen scavenging polyolefin nanocomposite films containing an iron modified kaolinite of interest in active food packaging applications

Abstract A synthetic iron containing kaolinite was evaluated as an oxygen scavenger additive for food packaging plastics having an active performance of ca. 43 ml O 2 /g at 100%RH and of ca. 37 ml O 2 /g of additive at 50%RH. The corresponding polyolefin films containing 10 wt.% of the active filler also exhibited significant oxygen scavenger activity (up to 4.3 ml of oxygen/g composite, at 24 °C and 100%RH). The effect of oxygen scavenging capacity of HDPE films with temperature and %RH was also assessed. The oxygen permeability tests carried out after inactivation of the additive suggested that the iron containing clay plays in fact a dual oxygen fighting role: active performance (trapping and reacting with molecular oxygen) as well as a passive barrier performance (imposing a more tortuous diffusion path to the permeant). Migration tests into two food simulants indicated that iron (from active ingredient) and aluminum (from clay migration) are hardly detectable in commonly used simulants. This study suggests that there is significant potential for the use of this novel oxygen scavenger additive to constitute active packaging of value in the shelf-life extension of oxygen sensitive food products. Industrial relevance Oxygen penetration in food and beverages leads to, for instance, oxidative rancidity of unsaturated fats, loss of vitamin C, browning of fresh meat, oxidation of aromatic flavor oils and pigments and fostering the growth of aerobic spoilage microorganisms. These undesirable effects on the product quality indicate that the elimination or exclusion of oxygen is one of the main targets for preserving foods and beverages in the food packaging industry. The industrial relevance of this study is very significant because it proves that the technology generated and characterized in the paper can uniquely fight oxygen by two means, i.e active and passive performance. This should enable the food packaging industry to package foods in relatively inexpensive, low barrier commodity plastic materials such as polyolefins, that will allow the shelf-life extension of the packaged products with a safe use, since migration of the components is negligible.

Platinum (II) porphyrin-containing thermoresponsive poly( N-isopropylacrylamide) copolymer as fluorescence dual oxygen and temperature sensor

A random copolymer, poly(NIPAAm- co-PtPorphyrin), consisting of N-isopropylacrylamide (NIPAAm) and platinum (II) porphyrin units, behaves as an optical dual sensor for oxygen and temperature. The dual sensor is designed by incorporating an oxygen-sensitive platinum (II) porphyrin ( M1) into a temperature-sensitive polymer (PNIPAAm). The polymer exhibited low critical solution temperature (LCST) property at 31.5 °C. This LCST affected the polymer's aggregation status, which in turn affected the nanostructures, fluorescence intensities, and responses to dissolved oxygen. This enables the polymer to functionalize as a dual temperature and dissolved oxygen sensor. Oxygen response of the platinum (II) porphyrin probes in the polymer followed a two-site Stern–Volmer model, indicating the nonuniform distribution of the probes. The copolymer was used to preliminarily monitor the oxygen consumption of Escherichia coli ( E. coli) bacteria. The results indicate a potential application of the polymer in biological fields.

Dual oxygen and Ir oxide regeneration of glucose oxidase in nanostructured thin film glucose sensors

A nanoparticulate iridium oxide (IrOx) thin film has been developed as a redox-active matrix material for an advanced generation glucose biosensor, in which IrOx serves as the non-physiological mediator, replacing oxygen in the enzymatic re-oxidation of glucose oxidase (GOx). Ethanolic solutions of Nafion and an Ir sol were mixed with an aqueous GOx solution and then deposited on a Au support. The Ir nanoparticles were then oxidized electrochemically to IrOx and the resulting films (IrOx–GOx–Nafion) were tested for their glucose response in both oxygen- and argon-saturated solutions, with the oxygen content in both solutions monitored by a Pt electrode. The sensors that are regenerated largely by O 2 are characterized by a Michaelis–Menten K ′ m value of ∼30 mM or more and i max values of at least 20 μA cm −2. Under fully deareated conditions, the sensors lose only ∼50% of their response to glucose, clearly indicating that a dual oxygen-regeneration and IrOx mediation mechanism is operative for the biosensor under these conditions. Under optimized conditions, involving a controlled GOx:Ir ratio, only the Ir oxide sites in the film serve to mediate GOx regeneration, giving K ′ m (10–15 mM) and i max values that are independent of the O 2 content of the solution.

Improvement of the Performance of TiHfO MIM Capacitors by Using a Dual Plasma Treatment of the Lower Electrode

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Dual Fluorescence Sensor for Trace Oxygen and Temperature with Unmatched Range and Sensitivity

An optical dual sensor for oxygen and temperature is presented that is highly oxygen sensitive and covers a broad temperature range. Dual sensing is based on luminescence lifetime measurements. The novel sensor contains two luminescent compounds incorporated into polymer films. The temperature-sensitive dye (ruthenium tris-1,10-phenanthroline) has a highly temperature-dependent luminescence and is incorporated in poly(acrylonitrile) to avoid cross-sensitivity to oxygen. Fullerene C70 was used as the oxygen-sensitive probe owing to its strong thermally activated delayed fluorescence at elevated temperatures that is extremely oxygen sensitive. The cross-sensitivity of C70 to temperature is accounted for by means of the temperature sensor. C70 is incorporated into a highly oxygen-permeable polymer, either ethyl cellulose or organosilica. The two luminescent probes have different emission spectra and decay times, and their emissions can be discriminated using both parameters. Spatially resolved sensing is achieved by means of fluorescence lifetime imaging. The response times of the sensor to oxygen are short. The dual sensor exhibits a temperature operation range between at least 0 and 120 degrees C, and detection limits for oxygen in the ppbv range, operating for oxygen concentrations up to at least 50 ppmv. These ranges outperform all dual oxygen and temperature sensors reported so far. The dual sensor presented in this study is especially appropriate for measurements under extreme conditions such as high temperatures and ultralow oxygen levels. This dual sensor is a key step forward in a number of scientifically or commercially important applications including food packaging, for monitoring of hyperthermophilic microorganisms, in space technology, and safety and security applications in terms of detection of oxygen leaks.

Highly stable dendritic trityl radicals as oxygen and pH probe

Novel dendritic trityl radicals (DTR1 and DTR2) with a TAM radical core, PAMAM branching and carboxylate exterior surface exhibit high stability towards oxidoreductants as evidenced by their electrochemical and EPR properties, offering potential application as dual oxygen and pH probe.

Scanning spreading resistance microscopy of defect engineered low dose SIMOX samples

Modification of SiO 2 precipitate formation by defect engineering of SIMOX (separation by implanted oxygen) process was studied using cross section scanning spreading resistance microscopy (SSRM). Firstly, open volume defects, nanocavities, have been introduced by He + ion implantation in the region, where SiO 2 precipitates were subsequently formed. Secondly, dual (simultaneous) oxygen (O +) and silicon (Si +) implantation was used to modify SiO 2 reaction kinetics too. The results show that the He-induced nanocavities enhance the SiO 2 formation presumably releasing excess strain associated with Si oxidation, while the use of a dual O +/Si + beam do not influence significantly the oxidation kinetics in the initial state of the SIMOX process in our samples. Overall, SSRM was shown to be a suitable method for observation of the early stage of buried oxide formation in Si, since it measures the local resistivity, the main functional parameter of a SIMOX structure.

Laboratory and field measurements of aquatic productivity made by a minicomputer employing a dual oxygen electrode system

Laboratory and field measurements of aquatic productivity made by a minicomputer employing a dual oxygen electrode system

Laboratory and field measurements of aquatic productivity made by a minicomputer employing a dual oxygen electrode system

Rates of change in oxygen concentration can be measured in the laboratory and in natural waters by using a measuring system consisting of two independent oxygen electrodes sending readings to a minicomputer ten times per second. Laboratory and experimental measurements were made under the control of the minicomputer, and differ from those made using standard approaches in two regards. First, the computer removes some of the statistical fluctuation in the data by selectively saving readings only when both electrode readings have changed in the same direction. Second, the computer alters the frequency at which data points are collected during the experiment. A predetermined number of data point pairs consisting of oxygen concentration values and time are collected by the computer. A linear regression analysis is conducted and the values of slope, intercept, sums of squares, and linear correlation coefficient are calculated and printed out. Next, the average of the absolute displacement of the data points about the regression line is calculated. Using the previously acquired value of slope, the computer calculates the length of time required for the change in oxygen concentration to be twice the average dispersion of data points about the regression line. This length of time over which n data points are to be collected is divided by (n-l) to give the waiting period between the samplings in the next round of data acquisition and linear regression. By employing a minicomputer to dynamically alter the experimental sampling frequency and to select the data points to be retained for the subsequent linear regression, it is possible to routinely obtain respiration rate estimates smaller than 20 μM (O2) h-1 with associated linear correlation coefficients exceeding 0.97. This system has enabled us to measure the rates of oxygen production and consumption in nearshore water samples using light/dark incubations. On 24 March 1981, it was found that following the influex of the kelp Ecklonia radiata (C. Ag.) J. Agardh to nearshore waters off Perth, Western Australia, the rates of oxygen evolution and consumption by the particulate fraction (nominal diam<124 μm) increase exponentially for the first 10 h. Subsequently, the rate of change of oxygen in the light decreases to the same negative value as that measured in the dark incubation. This time-varying dark respiration rate, if analyzed as an exponential function, has a doubling time of 8.2 h, a value consistent with bacterial growth rates at the ambient water temperatures (19° to 20°C).