Effect Of Oxygen Deficiency Research Articles

On the Structure of Oxygen Deficient Amorphous Oxide Films.

Understanding defects in amorphous oxide films and heterostructures is vital to improving performance of microelectronic devices, thin-film transistors, and electrocatalysis. However, to what extent the structure and properties of point defects in amorphous solids are similar to those in the crystalline phase are still debated. The validity of this analogy and the experimental and theoretical evidence of the effects of oxygen deficiency in amorphous oxide films are critically discussed. The authors start with the meaning and significance of defect models, such as "oxygen vacancy" in crystalline oxides, and then introduce experimental and computational methods used to study intrinsic defects in amorphous oxides and discuss their limitations and challenges. To test the validity of existing defect models, ab initio molecular dynamics is used with a non-local density functional to model the structure and electronic properties of oxygen-deficient amorphous alumina. Unlike some previous studies, the formation of deep defect states in the bandgap caused by the oxygen deficiency is found. Apart from atomistic structures analogous to crystal vacancies, the formation of more stable defect states characterized by the bond formation between under-coordinated Al ions is shown. The limitations of such defect models and how they may be overcome in simulations are discussed.

Morphological Changes of Erythrocytes in Neonates with Perinatal Hypoxia

Despite active research on the functional properties of erythrocytes under pathological conditions, this problem is of great importance. One of the causes of fetal and neonatal distress is hypoxia. The consequences of the negative effects of oxygen deficiency on the embryo and fetus can manifest both in utero and after birth, leading to various diseases. The aim of this work is to investigate the effects of acidosis as a marker of perinatal hypoxia on the erythrocyte membrane of newborns in the early neonatal period. The use of an atomic force microscope made it possible to obtain images and cell profiles to assess the morphological and structural characteristics of erythrocytes during hypoxia in children in the early neonatal period. Perinatal hypoxia has been shown to alter erythrocyte morphology and damage membrane structure. The early neonatal period is characterized by changes in the morphological forms and instability of erythrocyte membranes.

The impact of oxygen deficiency on giant exchange bias in perovskite oxide: SrFe0.5Co0.5O3−δ (δ = 0.37)

Perovskite and double perovskite oxides exhibit various interesting phenomena depending on the presence of magnetic and non-magnetic ions, degree of disorder, oxygen vacancies, etc. In this study, the effect of oxygen deficiency on the giant exchange bias of a cubic perovskite SrFe0.5Co0.5O3−δ (δ = 0.37) is investigated. X-ray diffraction and scanning electron microscopy were used to confirm the crystal structure and grain size, while magnetic relaxation and memory effects suggest a spin-glass nature. This work sheds light on the importance of oxygen vacancies and defects in perovskites, which continue to be an active area of research in materials science.

Effect of oxygen deficiency on organic matter decomposition during the early stage of composting.

This study aimed to elucidate the recovery of organic matter decomposition after oxygen deficiency in the early stage was replaced by aerobic conditions during composting. Oxygen deficiency at the early stage was created by supplying nitrogen gas into the composting for 3days (LN3dA) and 5days (LN5dA). Subsequently, air was introduced until the end of composting instead of nitrogen gas. Runs LN3dA and LN5dA had lower organic matter decomposition by 10% and 19%, respectively, compared with fully aerobic composting (LA) after oxygen deficiency was changed to aerobic conditions. Compared with fully aerobic composting, composting with oxygen deficiency at the early thermophilic stage had a different bacterial community, as analyzed by high-throughput sequencing. During vigorous organic matter decomposition, Bacillus was dominant in Run LA, whereas Caldibacillus proliferated in Runs LN3dA and LN5dA. Bacillus thermoamylovorans, Bacillus arbutinivorans, and Bacillus kokeshiiformis were hypothesized to be inhibited by Caldibacillus. Moreover, dissimilarity analysis indicated that different bacterial communities remained until the end of composting, which could be a reason for the incomplete recovery of organic matter decomposition. As analyzed by the API-ZYM kit, the enzymatic activities were also different between all composting runs. One of the characterized enzymes, α-galactosidase, displayed low activity during oxygen deficiency and could not achieve high activity with sufficient oxygen until composting was completed. Overall, our study showed that oxygen deficiency at the early thermophilic stage caused incomplete recovery of organic matter decomposition.

Enhancing reversibility of LiNi0.5Mn1.5O4 by regulating surface oxygen deficiency

AbstractOxygen deficiency has crucial effects on the crystal structure and electrochemical performance of spinel oxide lithium electrode materials such as LiNi0.5Mn1.5O4 (LNMO) cathode. In particular, the oxygen stoichiometry on the crystal surface differs from that on the crystal interior in LNMO. The detection of local oxygen loss in LNMO and its correlation with the crystal structure and the cycling stability of LNMO remain challenging. In this study, the effect of oxygen deficiency in LNMO controlled by sintering temperature on the surface crystal structure and electrochemical performance of LNMO is comprehensively investigated. The high concentration of oxygen vacancies segregates at the surface regions of LNMO forming a thin rock‐salt and/or deficient spinel surface layer. The atomic‐level surface structure reconstruction was demonstrated by annular dark‐field and annular bright‐field techniques. For the synthesis of LNMO, the higher sintering temperature results in higher crystallinity but the higher oxygen deficiency in LNMO. The high crystallinity of LNMO would increase the thermal stability of LNMO cathodes while the high content of oxygen deficiency would decrease the surface structural stability of LNMO. Therefore, the LNMO sintered at a medium temperature of 850°C achieved the best capacity retention. The results suggest a competitive function mechanism between oxygen stoichiometry and the crystallinity of LNMO on the cycling performance of LNMO.

Adsorption and decomposition of CO2 on γ-Al2O3(1 0 0): First-principles investigation

The adsorption and dissociation of CO2 on perfect and oxygen-deficient γ-Al2O3(100) is comparatively studied using first-principles calculations. CO2 molecules are found to physically absorb at perfect γ-Al2O3(100) with a linear configuration without the tendency to decompose. By contrast, the presence of oxygen vacancies at the γ-Al2O3(100) surface results in direct CO2 decomposition at the oxygen vacancy sites or the CO2 adsorption at the Al site adjacent to the oxygen vacancy, followed by the CO2 molecular rotation to the oxygen vacancy site and subsequent decomposition. The charge transfer between adsorbed CO2 and the γ-Al2O3(100) surface is further analyzed to understand the oxygen deficiency effect on CO2 adsorption and decomposition. These results demonstrate the promoting effect of oxygen vacancies of the oxide catalysts on CO2 activation, which have practical importance in catalytic CO2 conversion to value-added chemicals and controlling the oxidation of alumina-forming alloys in CO2 containing atmospheres.

Evolution of lattice defects in nickel ferrite spinel: Oxygen vacancy and cation substitution

Oxygen deficiency is a common phenomenon in the sintering process of nickel ferrite spinel, and has a significant impact on the properties of the NiFe 2 O 4 sintered body. This work investigated the effects of oxygen deficiency on the evolution of the lattice defects in spinel crystal. The oxygen deficiency led to the generation of a non-stoichiometric nickel ferrite containing oxygen vacancies (NiFe 2 O 4- δ ). As the sintering temperature increased from 1150 °C to 1400 °C, the concentration of oxygen vacancies in NiFe 2 O 4-δ increased, with a δ value increasing from 0.0014 to 0.0355 and a lattice parameter increasing from 8.3485 to 8.3567 Å. X-ray photoelectron (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy all showed that the crystal structure of NiFe 2 O 4- δ belonged to the Fd3m space group with Fe 2+ ions partially replacing Fe 3+ in the octahedral sites. Furthermore, a tendency for NiFe 2 O 4- δ to decompose to Ni alloy and Fe 3 O 4 during sintering could be observed. • Validation of the oxygen deficiency phenomenon during sintering. • Investigation of the effects of oxygen deficiency on microstructure. • Verification of the evolution mechanism of lattice defects.

2D Z-scheme heterojunction and oxygen deficiency synergistically boosting the photocatalytic activity of a layered BaTiO3/BiOIO3 composite

Simultaneously enhancing the quantity, separation efficiency and redox capability of photo-excited carriers to boost the catalytic activity has always been the toughest challenge for a photocatalyst. Herein, we presented a novel BaTiO3/BiOIO3 layered composite by proposing a synergistic strategy of 2D Z-scheme heterojunction and rich oxygen deficiency. Due to the high-quality interfaces with strong coupling interaction and stable IO3−/I− redox pairs between BaTiO3 and BiOIO3 layers, the composite was endowed concurrently with the strengthened photo response, separation efficiency and high redox capability of photo-excited carriers through a Z-scheme migration pathway. DFT computation emphasized that the formation of IO3−/I− redox pair and band gap of the composite were highly related to oxygen deficiency. Moreover, the ·O2− radicals can be expansively stimulated by the well-known local surface plasmon resonance effect of oxygen deficiency via inducing extra hot electrons. As a result, the composite performed a 4.4-fold enhanced photocatalytic activity than pure BaTiO3 toward the photo-degradation of tetracycline, which can be completed in just a few minutes. Therefore, we hope that the proposed heterojunction and oxygen deficiency synergistic boosting the photocatalytic activity of BaTiO3 could open a lot of insights for developing more efficient composite photocatalysts to solve the water pollutions.

Density Functional Theory Study of Oxygen Deficiencies in SrCoO25

We report the effects of oxygen deficiency to the electronic and magnetic properties of SrCoO3 calculated using spin-polarized Density Functional Theory. The correlation effects of the Co 3d orbitals are considered explicitly using the effective Hubbard U eff parameter. The U eff consists of the subtraction between the U value of 3 eV to denote the Coulomb interaction and the Hund’s coupling parameter J of 0.95 eV. Our results show that the localized character of the Co 3d orbitals strongly depends on the oxygen content. The magnetic exchange interaction between two neighboring Co ions is therefore altered. As a consequence, a change of magnetic ground state using the same U eff value from ferromagnetic ordering in full oxygen content to antiferromagnetic ordering in SrCoO2.5 is obtained.

Tuning the Metal-Insulator Transition Properties of VO2 Thin Films with the Synergetic Combination of Oxygen Vacancies, Strain Engineering, and Tungsten Doping.

Vanadium oxide (VO2) is considered a Peierls–Mott insulator with a metal–insulator transition (MIT) at Tc = 68° C. The tuning of MIT parameters is a crucial point to use VO2 within thermoelectric, electrochromic, or thermochromic applications. In this study, the effect of oxygen deficiencies, strain engineering, and metal tungsten doping are combined to tune the MIT with a low phase transition of 20 °C in the air without capsulation. Narrow hysteresis phase transition devices based on multilayer VO2, WO3, Mo0.2W0.8O3, and/or MoO3 oxide thin films deposited through a high vacuum sputtering are investigated. The deposited films are structurally, chemically, electrically, and optically characterized. Different conductivity behaviour was observed, with the highest value towards VO1.75/WO2.94 and the lowest VO1.75 on FTO glass. VO1.75/WO2.94 showed a narrow hysteresis curve with a single-phase transition. Thanks to the role of oxygen vacancies, the MIT temperature decreased to 35 °C, while the lowest value (Tc = 20 °C) was reached with Mo0.2W0.8O3/VO2/MoO3 structure. In this former sample, Mo0.2W0.8O3 was used for the first time as an anti-reflective and anti-oxidative layer. The results showed that the MoO3 bottom layer is more suitable than WO3 to enhance the electrical properties of VO2 thin films. This work is applied to fast phase transition devices.

Effect of Oxygen Deficiency on Mechanical and Thermomechanical Properties of Ferroic La0.6Sr0.4Co0.2Fe0.8O3−δ

The mechanical and thermomechanical behaviors of ferroic La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) with different oxygen nonstoichiometries are investigated around room temperature. The effects of oxygen deficiency on these behaviors are discussed by comparing LSCFs annealed in air and Ar. X‐ray diffraction analysis and the scanning electron microscopy observation demonstrate that the formation of oxygen vacancy reduces the rhombohedral distortion in the lattice, resulting in the disappearance of ferroic domains of LSCF. The measurements of electrical conductivity at high temperatures confirm that LSCF annealed in Ar has a higher oxygen nonstoichiometry than the one annealed in air. The thermomechanical analysis and the uniaxial compression test reveal that the introduction of oxygen vacancies can significantly influence the ferroic characteristics of LSCF such as ferromagnetism and ferroelasticity, whereas the intrinsic lattice stability would remain unchanged.

Interval normobaric hypoxic therapy as a method of correction in neurological patients

This article is devoted to the analysis of modern literature on the use of interval normobaric hypoxic therapy among neurological patients. Its relevance is determined by the need to find measures to prevent the negative effects of oxygen deficiency, as hypoxia is a key factor in the development of many pathological conditions in the human body and in the central nervous system in particular. Hypoxic effects of excessive strength or duration, leads to decompensation of adaptation mechanisms, triggers a chain of irreversible metabolic disorders that lead to cell death, destruction of intercellular and neural network interactions in the brain and, consequently,to the development of neurological deficit and disability ofthe patient.However,when the body adapts to hypoxia,which can be achieved by using interval normobaric hypoxic therapy, it is possible to achieve a positive effect in the correction of patients with various diseases of the central nervous system. We have considered both general mechanisms of the body’s defense formation during adaptation to hypoxia, and individualmechanisms related directly to the central nervous system. The role of biologicalmarkers and markers of oxidative stress determining the body’s individual response to oxygen deficiency has been evaluated. An analysis of studies evaluating the effect of interval normobaric hypoxic therapy on the course of such diseases as Alzheimer’s disease, Parkinson’s disease, discirculatory encephalopathy and the consequences of craniocerebral injuries was performed. It was found that properly performed interval normobaric hypoxic therapy contributes to the correction and compensation of impaired functions, improves the quality of life of patients and increases the adaptive reserve of the body to stressful influences.

Effect of oxygen defects in tuning the half-metallic and optical nature of Sr2CoXO6 (X=Mo & W): A first-principles study

Over the last few decades, double perovskites have been studied extensively because they exhibit exotic properties, such as magnetoresistance, ferroelectricity, superconductivity, half-metallicity, multiferroic, and many more. In this article, we used density functional theory based first-principles calculations to understand the effect of oxygen deficiency on the structural, electronic, optical and spin-oriented properties of cubic Sr2CoXO6 (X = Mo & W). The pure structures exhibit half-metallicity along with ductile nature. The band structures (using GGA-PBE) suggest that the conduction band and the valence band of both structures are overlapped in both spin-state after introducing oxygen defects, meaning that point defects in the oxygen-site make the structure lose its half-metallic nature. But, using HSE06 exchange correlation functional, we obtain half-metallic characteristics of Sr2CoWO5.75 structure. Further, the broad peak of absorption and optical conductivity of both structures occur in the UV region, and they dissipate with increasing energy. We obtain plasmon peaks from the loss function at 13.26 eV for Sr2CoMoO6 and 13.561 eV for Sr2CoWO6. Due to oxygen defects in the UV region, the peaks of absorption coefficient, reflectivity, optical conductivity, and plasmon peaks are red-shifted. We claim that these structures have a huge probability in spintronics and optoelectronic applications, although oxygen vacancies may reduce some applicability.

Enhanced gas sensing performance of Bi2MoO6 with introduction of oxygen vacancy: Coupling of experiments and first-principles calculations

Bismuth molybdate (Bi2MoO6) is a multi-elemental metal oxide of the molybdate series, which could show great potentials for the application of gas sensors with outstanding sensitivity. Oxygen vacancy is a ubiquitous defect in this class of materials, and their introduction may be an effective strategy to regulate gas sensing performance. In this work, coupling investigations of experiment and first-principles calculations were performed to gain insight into the effect of oxygen deficiency on the gas-sensitive properties of Bi2MoO6. The oxygen vacancies existed in surface lattice changes the adsorption reaction pathway of the gas by modifying the coordination state and geometry of lattice oxygens, which is more favorable for the adsorption or dissociation of target gas and oxygen molecule. Further, the oxygen-deficient Bi2MoO6 was synthesized experimentally by a one-step solvothermal method. The gas sensor based on the oxygen-deficient Bi2MoO6 could respond to NH3 gas sensitively and selectively, with a high response value of 53.97 (5 ppm) at the optimal temperature of 75 °C. Combining the clarifications by first-principles calculations, the satisfactory sensing performance exhibited experimentally could be understood based on the promotion of adsorption activity and adsorption capability.

Effect of Non-stoichiometry and oxygen deficiency in In2O3 thin films on gas sensing performance

The non-stoichiometric and oxygen deficiencies in Indium oxide (In2O3) are the key properties which help to improve the gas sensitivity of the In2O3. In2O3 thin films were deposited using simple spin coating method with varying precursor solution concentration. The variation of solution concentration has revealed the systematic growth of leaflet like structure. The In2O3 thin films coated at solution concentration of 0.15 M showed maximum sensor response of ∼ 25.27 at optimum temperature of 200 °C against NO2 gas for 100 ppm concentration. The highest performance of In2O3 gas sensor can be attributed to the defects present in In2O3 as confirmed by PL spectra.

Running with Face Masks or Respirators Can Be Detrimental to the Respiratory and Cardiovascular Systems

Since the first cases of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were reported at the end of 2019, this infection has spread around the globe, becoming a pandemic. The use of face masks and respirators is an important public health measure to reduce or prevent transmission of SARS-CoV-2. Here we discuss the hypothetical mechanisms by which exercise with face masks or respirators can induce detrimental effects on the cardiovascular system, potentially explaining adverse events such as cardiac arrhythmias and spontaneous pneumothorax. Although sudden death associated with the wearing of a face mask during running is a rare event, the risk is higher especially in those with existing cardiac comorbidities. In such cases, a mask designed specifically for runners with no or few side effects of oxygen deficiency should be considered instead.

Physiological justification of the choice of the artificial gas environments composition potentially applicable for improving the fire safety of inhabited sealed objects

One of the trends for ensuring the safe operation of sealed inhabited objects is the creation of hypoxic gas environments, suitable for breathing and reducing the risk of fires. The aim was to test the effect of normobaric hypoxic environments of various compositions on a person, to select envitonments that are potentially applicable to improve fire safety of inhabited sealed objects. Methods. The randomized controlled study involved 60 men aged 20-55 years, divided into 3 groups (20 people each) depending on the composition of the gas environment in which they were kept for 4 hours. The composition of the tested gas environments: No. 1 - oxygen = 1617 %, nitrogen - the rest; No. 2 - oxygen = 14-15 %, nitrogen - the rest; No. 3 - oxygen = 14 %, argon = 35 %, nitrogen - the rest. The functional state of the subjects was assessed using complaint forms, physiological criteria and functional tests. Results. The most pronounced negative changes in subject's functionality were found when the subjects were in the gas environment No. 2, and the most of the indicators showed significant (p < 0.05-0.001) differences compared to other groups. The revealed facts indicate the inadmissibility of using such environments. The stay in gas environments No. 1 and No. 3 was accompanied by comparable and acceptable changes in the functional state of the subjects, despite the significantly lower oxygen content in the argon-containing medium (No. 3). Conclusions. 1. To increase the fire safety of inhabited pressurized objects, it is permissible to use gas environments No. 1 and No. 3. 2. Addition of argon to hypoxic environments reduces the negative effects of oxygen deficiency, which makes it possible to use gas environments with a higher degree of hypoxia and, therefore, more effective for ensuring fire protection of inhabited sealed objects.

Experimental study and DFT calculation of the oxygen deficiency effects on structural, magnetic and optical properties of La0.8□0.2MnO3-δ (δ = 0, 0.1 and 0.2) compounds

In this work, our main focus is to study the effect of oxygen vacancy on structural, magnetic, and optical properties of La0.8□0.2MnO3-δ (δ = 0, 0.1 and 0.2) manganites. The refinement of X-ray diffraction patterns shows that the samples with δ = 0 and 0.1 crystallize in the rhombohedral phase with R3¯c space group. Also, for δ = 0.2 the refinement has revealed the coexistence of R3¯c rhombohedral and Pnmaorthorhombic phases. The magnetic measurements M (T) shows that our samples have a transition from the ferromagnetic (FM) state to the paramagnetic (PM) state by increasing the temperature. The increase of oxygen deficiency rate causes a spin-glass-like state at low temperature with the presence of Griffiths phase above Curie temperature. Moreover, the hysteresis loop analysis shows an increase in the remanent magnetization and the coercive field when the creation of oxygen deficiency. Also, we find an agreement between experimental results and a theoretical study using ab initio density functional theory (DFT) based on correct Spin polarized Generalized Gradient Approximation SGGA + U. The results of the optical properties calculation revealed that our compounds could produce high absorption in the ultraviolet range.

Oxygen deficiency effect on the magnetocaloric and critical phenomena for La0.8□0.2MnO3-Δ (Δ = 0, 0.1 and 0.2) compounds: significant enhancement of relative cooling power

In this article, we focused on the study of magnetocaloric properties and the critical phenomena of $${La}_{0.8}{\square }_{0.2}Mn{O}_{3-\Delta }$$ ( $$\Delta$$ = 0, 0.1 and 0.2) manganites. The analysis of X-ray diffraction patterns shows that for $$\Delta$$ = 0 and 0.1 the samples crystallize in the rhombohedral phase with the $$R\stackrel{-}{3}C$$ space group. For $$\Delta$$ = 0.2, the refinement has reveals the coexistence of the $$R\stackrel{-}{3}C$$ rhombohedral and $$Pnma$$ orthorhombic phases. The grain size distribution for our samples was evaluated by scanning electron microscopy (SEM). The elemental and chemical properties were investigated using energy-dispersive X-ray 'EDX) measurement. The magnetic measurements prove that our samples exhibit a second-order ferromagnetic state (FM)/paramagnetic state (PM) phase transition. The study of the inverse of the magnetic susceptibility and the calculated value of Seff show the presence of a griffiths phase in $$\Delta$$ = 0.2 sample. In addition, the change in the magnetic entropy ( $$-\Delta S\left(M\right)$$ ) of representative samples was calculated using Landau theory and Maxwell relation. Remarkably, these compounds have very interesting magnetocaloric properties. In fact, the relative cooling power (RCP) reaches 126 (J. Kg−1. K−1) for an applied field at 2 T for ( $$\Delta$$ = 0.2) Which makes it considered a potentially candidate that can be used in the cooling system based on magnetic refrigeration. The calculated critical exponents values β, γ and δ using through various techniques are comparable to those predicted by the Tricritical mean field model for $$\Delta$$ = 0, $$\Delta$$ = 0.1 and by the mean field model for $$\Delta$$ = 0.2. Additionally, the magnetic interaction nature in our samples is described by the calculation of exchange distance J(r).

Synthesis and investigation of oxygen deficiency effect on electric properties of La0.75Ba0.10Sr0.15FeO2.875-δ (δ = 0.00, 0.125 and 0.25) ferrites

In the present investigation, La0.75Ba0.10Sr0.15FeO2.875-δ oxygen-deficient ferrites with δ = 0.00, 0.125 and 0.25 were synthesized by sol–gel method. The physical characterization has been carried out by X-ray diffraction, scanning electron microscope SEM, Raman spectroscopy, and complex impedance. All samples are formed in orthorhombic crystal symmetry with Pnma space group. Synthesized compounds have nanocrystallite size of 32–46 nm. Raman spectrum shows the oxygen vacancy effect on the tilt and stretching phonon modes. Electric properties were investigated in the framework of impedance and electric conductivity. The complex impedance was measured over a wide range of temperatures (300–380 K) and frequencies (40 Hz–1 MHz). The electrical measurements indicate semiconductor behavior for the three compositions and emphasize the evidence of contribution of grain boundaries in the transport properties. The ac conductivity curves obey the Jonsher universal power law and are assigned to hopping conduction mechanism. It is found that the values of activation energy, estimated from the conductivity analysis, are in the same order with those deduced from relaxation process. Such result proves that both processes, conduction and relaxation, are related to the same defect.