Rational design of hollow oxygen deficiency-enriched NiFe_(2)O_(4)@N/rGO as bifunctional electrocatalysts for overall water splitting

Bimetallic metal organic framework(MOF)as a precursor to prepare catalysts with bifunctional catalytic activity of oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)attracts more and more attention.Herein,hollow oxygen deficiency-enriched NiFe_(2)O_(4) is synthesized by pyrolytic FeNi bimetallic MOF.The defects of rGO during carbonization can act as nucleation sites for FeNi particles.After nucleation and N doping,the FeNi particles were served as catalysts for the deposition of dissolved carbon in the defects of the N/rGO.These deposited carbon,like a bridge,connect N/rGO and hollow oxygen deficiency-enriched NiFe_(2)O_(4) together,which giving full play to the advantages of N/rGO in fast electron transfer,thereby improving its catalytic activity.The resultant NiFe_(2)O_(4)@N/rGO-800 exhibits a low overpotential of 252 mV at 20 mA cm^(-2) for OER and 157 mV at 10 mA cm^(-2) for HER in 1 M KOH,respectively.When used as bifunctional electrodes for overall water splitting,it also shows low cell voltage of 1.60 V and 1.67 V at 10 and 20 mA cm^(-2),respectively.

Impacts of oxygen deficiency on embryo life-history traits of migratory locust Locusta migratoria from low and high altitudes

Hypoxia challenges aerobic organisms in numerous environments,and hypoxic conditions may become more severe under future climate-change scenarios.The impact of hypoxia on the development of terrestrial insect embryos is not well understood.Here,to address this gap,embryonic life-history traits of migratory locust Locusta migratoria from low-altitude and high-altitude regions were compared under 2 oxygen levels:normoxia(i.e.,21 kPa oxygen partial pressure and mild hypoxia(i.e.,10 kPa oxygen partial pressure).Our results demonstrated that,whether reared under normoxia or mild hypoxia,L.migratoria from high-altitude populations had longer developmental times,reduced weight,and lower mean relative growth rate as compared with those from low-altitude populations.When transferred from normoxia to mild hypoxia,nearly all the tested lifehistory traits presented significant negative changes in the low-altitude populations,but not in the high-altitude populations.The factor'strain'alone explained 18.26%-54.59%of the total variation for traits,suggesting that the phenotypic differences between L.migratoria populations from the 2 altitudes could be driven by genetic variation.Significant genetic correlations were found between life-history traits,and most of these showed differentiation between the 2 altitudinal gradients.G-matrix comparisons showed significant structural differences between L.migratoria from the 2 regions,as well as several negative covariances(i.e.,trade-offs)between traits in the low-altitude populations.Overall,our study provides clear evidence that evolutionary divergence of embryonic traits between L.migratoria populations from different altitudes has occurred.

Enhanced visible-light photocatalytic activity of Z-scheme graphitic carbon nitride/oxygen vacancy-rich zinc oxide hybrid photocatalysts

With the objectives of enhancing the stability,optical properties and visible-light photocatalytic activity of photocatalysts,we modified oxygen vacancy-rich zinc oxide（Vo-ZnO） with graphitic carbon nitride（g-C3N4）. The resulting g-C3N4/Vo-ZnO hybrid photocatalysts showed higher visible-light photocatalytic activity than pure Vo-ZnO and g-C3N4. The hybrid photocatalyst with a g-C3N4 content of 1 wt% exhibited the highest photocatalytic degradation activity under visible-light irradiation（λ≥ 400 nm）. In addition,the g-C3N4/Vo-ZnO photocatalyst was not deactivated after five cycles of methyl orange degradation,indicating that it is stable under light irradiation. Finally,a Z-scheme mechanism for the enhanced photocatalytic activity and stability of the g-C3N4/Vo-ZnO hybrid photocatalyst was proposed. The fast charge separation and transport within the g-C3N4/Vo-ZnO hybrid photocatalyst were attributed as the origins of its enhanced photocatalytic performance.

Membrane-less MoO_(3-x)@TiO_(2)-bromine battery with excellent rate capability and cyclic stability

Bromine has attracted significant attention as a cathode material for aqueous batteries due to its high reduction potential of 1.05 V(Br_(3)^(-)+2e~-■3Br~-),impressive theoretical specific capacity of 223 mA h g^(-1),and rapid reaction kinetics in the electrolyte.However,searching for compatible anode materials to match with bromine has posed a challenge due to its highly corrosive nature.In this study,we developed oxygen-deficient MoO_(3) with TiO_(2) coating(referred to as MoO_(3-x)@TiO_(2))as an anode material to pair with a bromine cathode in static full batteries.The oxygen deficiency contributes to enhanced electronic and protonic diffusion within the MoO_(3-x)lattice,while the TiO_(2) coating mitigates structural dissolution and proton trapping during cycling.The MoO_(3-x)@TiO_(2) demonstrates fast charge storage kinetics and excellent resistance to bromine corrosion.The impressive compatibility between MoO_(3-x)@TiO_(2) and bromine enables the construction of membrane-less full batteries with exceptional rate capability and cyclic stability.The MoO_(3-x)@TiO_(2)-bromine battery achieves an energy density of70.8 W h kg^(-1)at a power density of 328.1 W kg^(-1),showcasing an impressive long-term cyclic life of 20,000 cycles.Our study provides valuable insights for the development of high-performance aqueous secondary batteries.

Reduction of foaming and enhancement of ascomycin production in rational Streptomyces hygroscopicus fermentation

Foaming reduces the working volume and limits the biosynthesis of macrolide immunosuppressant ascomycin(FK520) in the batch fermentation process of Streptomyces hygroscopicus FS-35 in a 7.5 L bioreactor. To find the relation between FK520 production and foaming, effects of 10 fermentation parameters including organic acids and membrane permeability were investigated. The results suggest that acetate accumulation caused by short period oxygen de ficiency and fast consumption of glucose is the reason for increased foaming and declined FK520 production. Therefore, a fed-batch fermentation strategy was developed to reduce the accumulation of acetate. After optimization, the maximum acetate concentration dropped from 320 mg·L-1to 157 mg·L-1, decreased by 50.8%, and the maximum foam height reduced from 5.32 cm to 3.74 cm, decreased by 29.7%, while the maximum FK520 production increased from 375 mg·L-1to 421 mg·L-1, improved by 12%.

Constructing oxygen-deficient V_(2)O_(3)@C nanospheres for high performance potassium ion batteries

Potassium ion batteries(PIBs) have been regarded as promising alternatives to lithium ion batteries(LIBs)on account of their abundant resource and low cost in large scale energy storage applications. However,it still remains great challenges to explore suitable electrode materials that can reversibly accommodate large size of potassium ions. Here, we construct oxygen-deficient V_(2)O_(3)nanoparticles encapsulated in amorphous carbon shell(Od-V_(2)O_(3)@C) as anode materials for PIBs by subtly combining the strategies of morphology and deficiency engineering. The MOF derived nanostructure along with uniform carbon coating layer can not only enables fast K+migration and charge transfer kinetics, but also accommodate volume change and maintain structural stability. Besides, the introduction of oxygen deficiency intrinsically tunes the electronic structure of materials according to DFT calculation, and thus lead to improved electrochemical performance. When utilized as anode for PIBs, Od-V_(2)O_(3)@C electrode exhibits superior rate capability(reversible capacities of 262.8, 227.8, 201.5, 179.8, 156.9 mAh/g at 100, 200, 500, 1000 and2000 mA/g, respectively), and ultralong cycle life(127.4 mAh/g after 1000 cycles at 2 A/g). This study demonstrates a feasible way to realize high performance PIBs through morphology and deficiency engineering.

Structural and transport properties of Sr_2VO_(3-δ)FeAs superconductors with different oxygen deficiencies

Sr2VO3-δFeAs superconductors with different oxygen deficiencies have been successfully fabricated.It is found that the superconducting transition temperature drops down monotonically with the increase of nominal oxygen deficiency.The diminishing of superconductivity is accompanied by the enhancement of residual resistivity,indicating an anomalous scattering effect induced by the oxygen deficiency.The highest superconducting transition temperature at about 36 K is achieved near the stoichiometrical sample Sr2VO2.9FeAs.The Hall effect measurements reveal that the density of charge carriers(electron-like here) varies qualitatively with the increase of nominal oxygen deficiency.Magnetotransport measurements show that the superconducting transition changes from one-step-like shape at low fields to two-step-like one at high fields,indicating an enhanced vortex motion due to the high anisotropy.

Rare earth elements(lanthanum,cerium and erbium)doped black oxygen deficient Bi_(2)O_(3)-Bi_(2)O_(3-x) as novel photocatalysts enhanced photocatalytic performance

Novel black oxygen deficient bismuth oxide(Bi_(2)O_(3)-Bi_(2)O_(3-x))photocatalytic material was successfully prepared by a two zone temperature controlled muffle furnace method.The lanthanum,cerium and erbium ions are successfully doped into Bi_(2)O_(3)-Bi_(2)O_(3-x) with the average contents of 10.77 wt%,7.62 wt%and 8,14 wt%,respectively.The re sults show that a large number of oxygen vacancies exist in Bi_(2)O_(3)-Bi_(2)O_(3-x).La^(3+)Ce^(3+)and Er^(3+)act as electron acceptors to temporarily trap the photo-generated electrons.The XPS spectrum show Bi-O band in Bi_(2)O_(3)-Bi_(2)O_(3-x) and the O 1s peak of Ce/Bi_(2)O_(3)-Bi_(2)O_(3-x) move toward the direction of low binding energy.These phenomena fully prove that the separation of photogenerated electron-hole pairs will be more effectual,so as to reduce the possibility of charge carrier recombination.The radical scavenging experiments and electron spin resonance detections confirm that the conduction band of the original Bi_(2)O_(3)can easily receive photogenerated electrons,while the valence band of the modified Bi_(2)O_(3)-Bi_(2)O_(3-x) tends to accept photogenerated holes and then forms the circulation system.Therefore,Ce/Bi_(2)O_(3)-Bi_(2)O_(3-x) can degrade tetracycline hydrochloride up to 90.15%.This research provides some new insights into developing green and recyclable photocatalysts for the remediation of antibiotic contamination.

Terminal sulfur atoms formation via defect engineering strategy to promote the conversion of lithium polysulfides

The defect engineering shows great potential in boosting the conversion of lithium polysulfides intermediates for high energy density lithium-sulfur batteries(LSBs),yet the catalytic mechanisms remain unclear.Herein,the oxygen-defective Li_(4)Ti_(5)O_(12)-xhollow microspheres uniformly encapsulated by N-doped carbon layer(OD-LTO@NC)is delicately designed as an intrinsically polar inorganic sulfur host for the research on the catalytic mechanism.Theoretical simulations have demonstrated that the existence of oxygen deficiencies enhances the adsorption capability of spinel Li_(4)Ti_(5)O_(12)towards soluble lithium polysulfides.Some-S-S-bonds of the Li2S6on the defective Li_(4)Ti_(5)O_(12)surface are fractured by the strong adsorption force,which allows the inert bridging sulfur atoms to be converted into the susceptible terminal sulfur atoms,and reduces the activation energy of the polysulfide conversion in some degree.In addition,with the N-doped carbon layer,secondary hollow microspheres architecture built with primary ultrathin nanosheets provide a large amount of void space and active sites for sulfur storage,adsorption and conversion.The as-designed sulfur host exhibits a remarkable rate capability of 547 m Ah g^(-1)at 4C(1 C=1675 m A g^(-1))and an outstanding long-term cyclability(519 m Ah g^(-1)after 1000 cycles at 3 C).Besides,a high specific capacity of 832 m Ah g^(-1)is delivered even after 100 cycles under a high sulfur mass loading of 3.2 mg cm^(-2),indicating its superior electrochemical performances.This work not only provides a strong proof for the application of oxygen defect in the adsorption and catalytic conversion of lithium polysulfides,but offers a promising avenue to achieve high performance LSBs with the material design concept of incorporating oxygen-deficient spinel structure with hierarchical hollow frameworks.

Confined structure regulations of molybdenum oxides for efficient tumor photothermal therapy

Molybdenum oxide nanoparticles(NPs) with tunable plasmonic resonance in the near-infrared region display superior semiconducting features and photothermal properties, which are highly related to the crystalline and defective structures such as oxygen deficiencies. However,fundamental understanding on the structure-function relationship between crystalline/defective structures and photothermal properties is still unclear. To address this, herein,we have developed an "in-situ confined oxidation-reduction"strategy to regulate the defect features of molybdenum oxide NPs in the dual-mesoporous silica nanoreactor. Especially, the effects of crystalline structure/oxygen defects of molybdenum oxides on the photothermal performances were investigated by facilely tuning the amount of molybdenum resource and the reduction temperature. As a photothermal nanoagent, the optimal defective molybdenum oxide NPs encapsulated in PEGylated porous silica nanoreactor(designated as MoO_(3)@PPSNs) exhibit excellent biological stability and strong localized surface plasmon resonance effect in nearinfrared absorption range with the highest photothermal conversion efficiency up to 78.7% under 808 nm laser irradiation. More importantly, the remarkable photothermal effects of MoO_(3)@PPSNs were comprehensively demonstrated both in vitro and in vivo. Consequently, we envision that the plasmonic MoO_(3)NPs in a biocompatible porous silica nanoreactor could be used as an efficient photothermal therapy agent for photothermal ablation of tumors.

Apoplastic barriers of Populus×canescens roots in reaction to different cultivation conditions and abiotic stress treatments

Populus is an important tree genus frequently cultivated for economical purposes.However,the high sensitivity of poplars towards water deficit,drought,and salt accumulation significantly affects plant productivity and limits biomass yield.Various cultivation and abiotic stress conditions have been described to significantly induce the formation of apoplastic barriers(Casparian bands and suberin lamellae)in roots of different monocotyledonous crop species.Thus,this study aimed to investigate to which degree the roots of the dicotyledonous gray poplar(Populus×canescens)react to a set of selected cultivation conditions(hydroponics,aeroponics,or soil)and abiotic stress treatments(abscisic acid,oxygen deficiency)because a differing stress response could potentially help in explaining the observed higher stress susceptibility.The apoplastic barriers of poplar roots cultivated in different environments were analyzed by means of histochemistry and gas chromatography and compared to the available literature on monocotyledonous crop species.Overall,dicotyledonous poplar roots showed only a remarkably low induction or enhancement of apoplastic barriers in response to the different cultivation conditions and abiotic stress treatments.The genetic optimization(e.g.,overexpression of biosynthesis key genes)of the apoplastic barrier development in poplar roots might result in more stress-tolerant cultivars in the future.

CeO_(2)and CeO_(2)-based nanomaterials for photocatalytic,antioxidant and antimicrobial activities

Cerium oxide(CeO_(2)),one of the most significant rare-earth oxides,has attracted considerable interest over the past decades.This is primarily due to the ease in Ce^(3+)/Ce^(4+)redox ability as well as other factors that affect the efficacy of CeO_(2)and CeO_(2)-based materials.CeO_(2)and CeO_(2)-based materials have shown enhanced responses in catalytic and photocatalytic activities for environmental and biological applications.In addition,the formation of Ce^(3+)and oxygen vacancies in CeO_(2)has aided in enhancing CeO_(2)activities.In order to produce oxygen-deficient CeO_(2)and CeO_(2)-based materials,a variety of synthesis methods were used and are highlighted in this review.Therefore,this review compiles and discusses the mechanisms that involve oxygen vacancies,defects,and Ce^(3+)formation for environmental applications,such as photocatalytic dye degradation,photocatalytic CO_(2)reduction,and non-colored pollutants removal.The biological applications of CeO_(2),such as antioxidant enzyme mimetic,antioxidant reactive oxygen species/reactive nitrogen species,and antimicrobial activities,are also discussed.Additionally,future prospects are also suggested for future development and detailed investigations.