Oxygen Atoms Research Articles

Removal of Residual Additive Enabling Perfect Crystallization of Photovoltaic Perovskites.

Achieving high-efficiency perovskite solar cells (PSCs) hinges on the precise control of the perovskite film crystallization process, often improved by the inclusion of additives. While dimethyl sulfoxide (DMSO) is traditionally used to manage this process, its removal from the films is problematic. In this work, methyl phenyl sulfoxide (MPSO) was employed instead of DMSO to slow the crystallization rate, as MPSO is more easily removed from the perovskite structure. The electron delocalization associated with the benzene ring in MPSO decreases the electron density around the oxygen atom in the sulfoxide group, thus reducing its interaction with PbI2. This strategy not only sustains the formation of a crystallization-slowing intermediate phase but also simplifies the elimination of the additive. Consequently, the optimized PSCs achieved a leading power conversion efficiency (PCE) of 25.95% along with exceptional stability. This strategy provides a novel method for fine-tuning perovskite crystallization to enhance the overall performance of photovoltaic devices.

Heteroaryl Group Containing Trisubstituted Alkenes: Synthesis and Anti-Tumor Activity.

Pancreatobililary cancers are fatal solid tumors that pose a significant threat to human life. It is imperative to investigate novel small molecule active compounds for controlling these cancers. Heterocyclic compounds (e. g. gemcitabine) and multi-substituted alkenes (e. g. resveratrol) are commonly applied in tumor treatment. Researchers have proposed that the synthesis of new trisubstituted alkenes containing heteroaromatic rings by combining these two scaffolds may be a fresh strategy to develop new active molecules. In this study, we utilized alkenyl bromide and heteroaryl boronic acid as substrates, employing Suzuki coupling to generate a series of triarylethylenes featuring nitrogen, oxygen, and sulfur atoms. Through in vitro experiments, the results indicated that some compounds exhibited remarkable anti-tumor efficacy (e. g. IC50[3be, GBC-SD]=0.13 μM and IC50[3be, PANC-1]=0.27 μM). The results further demonstrated that the antitumor efficacy of these compounds was dependent on the heteroatom, π-system, skeleton-bonding site, and substituent type.

In‐Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water‐Gas Shift Reaction

AbstractIn situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water‐gas shift (RWGS) reaction. Surface oxygen atoms in various Mo‐based catalysts are removed in H2‐containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt‐dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal−1 ⋅ h−1 at 600 °C has been achieved over in situ carbonized H‐intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Neuroevolution machine learning potential to study high temperature deformation of entropy-stabilized oxide MgNiCoCuZnO5

Entropy stabilized oxide of MgNiCoCuZnO5, also known as J14, is a material of active research interest due to a high degree of lattice distortion and tunability. Lattice distortion in J14 plays a crucial role in understanding the elastic constants and lattice thermal conductivity within the single-phase crystal. In this work, a neuroevolution machine learning potential (NEP) is developed for J14, and its accuracy has been compared to density functional theory calculations. The training errors for energy, force, and virial are 5.60 meV/atom, 97.90 meV/Å, and 45.67 meV/atom, respectively. Employing NEP potential, lattice distortion, and elastic constants is studied up to 900 K. In agreement with experimental findings, this study shows that the average lattice distortion of oxygen atoms is relatively higher than that of all transition metals in entropy-stabilized oxide. The observed distortion saturation in the J14 arises from the competing effects of minimum site distortion, which increases with increasing temperature due to enhanced thermal vibrations, and maximum site distortion, which decreases with increasing temperature. Furthermore, a series of molecular dynamics simulations up to 900 K are performed to study the stress–strain behavior. The elastic constants, bulk modulus, and ultimate tensile strength obtained from these simulations indicate a linear decrease in these properties with temperature, as J14 becomes softer owing to thermal effects. Finally, to gain some insight into thermal transport in these materials, with the so-developed NEP potential, and using non-equilibrium molecular dynamics simulations, we study the lattice thermal conductivity (κ) of the ternary compound MgNiO2 as a function of temperature. It is found that κ decreases from 4.25 W m−1 K−1 at room temperature to 3.5 W m−1 K−1 at 900 K. This suppression is attributed to the stronger scattering of low-frequency modes at higher temperatures.

Mechanochemical Synthesis of High-Entropy MOF-74 with Multiple Active Sites for CO2 Adsorption and Synergistic Conversion.

Compared with monometallic metal-organic frameworks (MOFs), the synergistic effect of multiple metals significantly enhances the catalytic performance of the CO2 cycloesterification reaction, leading to improved CO2 adsorption and catalytic conversion capabilities. To investigate this concept, a high-entropy MOF-74 (HE-MOF-74) with a uniform distribution of five distinct metal ions (Zn2+, Mg2+, Ni2+, Co2+, and Cu2+) was successfully synthesized using a straightforward mechanical ball milling technique and comprehensively characterized (including structural, morphological, and physicochemical properties). The results reveal that HE-MOF-74 exhibits significantly increased specific surface area and CO2 adsorption capacity compared with those of monometallic MOF-74. The presence of multiple unsaturated metal centers as Lewis acid sites, oxygen atoms linking the metals, and ligand-based hydroxyl groups serving as base sites enable efficient immobilization of CO2 into cyclic carbonate. This study introduces a novel synthetic approach for the green and efficient production of HE-MOF-74 and proposes a new application for CO2 utilization.

Direct oxygen insertion into C-C bond of styrenes with air.

Skeletal editing of single-atom insertion to basic chemicals has been demonstrated as an efficient strategy for the discovery of structurally diversified compounds. Previous endeavors in skeletal editing have successfully facilitated the insertion of boron, nitrogen, and carbon atoms. Given the prevalence of oxygen atoms in biologically active molecules, the direct oxygenation of C-C bonds through single-oxygen-atom insertion like Baeyer-Villiger reaction is of particular significance. Herein, we present an approach for the skeletal modification of styrenes using O2 via oxygen insertion, resulting in the formation of aryl ether frameworks under mild reaction conditions. The broad functional-group tolerance and the excellent chemo- and regioselectivity are demonstrated in this protocol. A preliminary mechanistic study indicates the potential involvement of 1,2-aryl radical migration in this reaction.

In-Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water-Gas Shift Reaction.

In situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water-gas shift (RWGS) reaction. Surface oxygen atoms in various Mo-based catalysts are removed in H2-containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt-dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal -1 ⋅ h-1 at 600 °C has been achieved over in situ carbonized H-intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Reactivity of Atomic Oxygen Radical Anions in Metal Oxide Clusters.

Atomic oxygen radical anion (O⋅-) represents an important type of reactive centre that exists in both chemical and biological systems. Gas-phase atomic clusters can be studied under isolated and well controlled conditions. Studies of O⋅--containing clusters in the gas-phase provide a unique strategy to interpret the chemistry of O⋅- radicals at a strictly molecular level. This review summarizes the research progresses made since 2013 for the reactivity of O⋅- radicals in the atomically precise metal oxide clusters including negatively charged, nanosized, and neutral heteronuclear metal clusters benefitting from the development of advanced experimental techniques. New electronic and geometric factors to control the reactivity and product selectivity of O⋅- radicals under dark and photo-irradiation conditions have been revealed. The detailed mechanisms of O⋅- generation have been discussed for the reaction systems of nanosized and heteroatom-doped metal oxide clusters. The catalytic reactions mediated by the O⋅- radicals in metal clusters have also been successfully established and the microscopic mechanisms about the dynamic generation and depletion of O⋅- radicals have been clearly understood. The studies of O⋅- containing metal oxide clusters in the gas-phase provided new insights into the chemistry of reactive oxygen species in related condensed-phase systems.

Influence of bias voltage and oxygen addition on the discharge aspects of a diffuse argon plume in an atmospheric pressure plasma jet

A remote plasma, also referred to as a plasma plume (diffuse or filamentary), is normally formed downstream of an atmospheric pressure plasma jet. In this study, a diffuse plume is formed by increasing the bias voltage (U b) applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage. The results indicate that the plume is filamentary when U b is low, which transits to the diffuse plume with increasing U b. The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume, while that at the falling edge contributes to the filament in the plume. For the diffuse plume, the discharge intensity decreases with the increasing oxygen content (C o). Fast photography reveals that the diffuse plume results from a negative streamer, which has a dark region near the nozzle with C o = 0%. However, the dark region is absent with C o = 0.5%. From the optical emission spectrum, the electron density, electron excitation temperature, gas temperature, and oxygen atom concentration are investigated.

Mechanistic insights into multimetal synergistic and electronic effects in a hexanuclear iron catalyst with a [Fe3(μ3-O)(μ2-OH)]2 core for enhanced water oxidation.

Multinuclear molecular catalysts mimicking natural photosynthesis have been shown to facilitate water oxidation; however, such catalysts typically operate in organic solutions, require high overpotentials and have unclear catalytic mechanisms. Herein, a bio-inspired hexanuclear iron(III) complex I, Fe6(μ3-O)2(μ2-OH)2(bipyalk)2(OAc)8 (H2bipyalk = 2,2'-([2,2'-bipyridine]-6,6'-diyl)bis(propan-2-ol); OAc = acetate) with desirable water solubility and stability was designed and used for water oxidation. Our results showed that I has high efficiency for water oxidation via the water nucleophilic attack (WNA) pathway with an overpotential of only ca. 290 mV in a phosphate buffer of pH 2. Importantly, key high-oxidation-state metal-oxo intermediates formed during water oxidation were identified by in situ spectroelectrochemistry and oxygen atom transfer reactions. Theoretical calculations further supported the above identification. Reversible proton transfer and charge redistribution during water oxidation enhanced the electron and proton transfer ability and improved the reactivity of I. Here, we have shown the multimetal synergistic and electronic effects of catalysts in water oxidation reactions, which may contribute to the understanding and design of more advanced molecular catalysts.

A Study on Oxygen Vacancy Resistance Mechanism of V2O5

Introduction: Due to its magnetic and semiconductor properties, V2O5 has shown tremendous potential in resistive switching memory. Method: Therefore, this paper investigates the resistive mechanism of oxygen vacancies in V2O5. The formation energies of different oxygen vacancies are calculated. Results: The results indicate that oxygen vacancies tend to form single-component conductive filaments. In mixed oxygen vacancies clusters, the charge transfer characteristics and density of states of the V2O5-VO 13 vacancies are the most significant, which is consistent with the analysis of formation energy data. Conclusions: Additionally, the charge transfer of cluster oxygen vacancies was calculated, showing that V atoms directly connected to oxygen vacancies tend to lose electrons, while adjacent oxygen atoms are more likely to gain electrons. In V2O5-VO 12 and V2O5-VO 13, the number of electrons obtained by O2 and O16 exceeds the average by 36.4% and 33.2%. Thus, the formation of oxygen vacancies effectively improves the resistance characteristics of the V2O5.

A Computational Study of Heteroatom Analogues of Selenoxide and Selenone syn Eliminations.

Selenoxide syn elimination is a widely used method for the synthesis of alkenes because it proceeds under exceptionally mild conditions, typically with excellent regio- and stereoselectivity. Surprisingly, hetero-selenoxide eliminations, where one or both olefinic carbon atoms are replaced with heteroatoms, have been little investigated, and their selenonyl counterparts even less so. A variety of such reactions, where the heteroatoms included combinations of O, N and S, as well as C, were investigated computationally. Selenoxides typically have lower activation energies and are slightly endothermic, while the corresponding selenones display higher activation energies and are exothermic in the gas state. The results are consistent with concerted, five-centre processes, leading to the formation of dioxygen, aldehydes, diazenes and imines from seleninyl or selenonyl peroxides, esters, hydrazines and amines, respectively. The more acidic selenenyl hydrodisulfide analogue undergoes proton transfer to the basic selenoxide oxygen atom instead of concerted elimination, resulting in the formation of a zwitterion. However, the formation of the corresponding selenonyl zwitterion is disfavoured compared to concerted syn elimination. The effects of solvents were also computed along with changes in enthalpy, entropy and free energy. Solvent effects were variable, while free energy calculations indicated overall ΔG values ranging between 3.60 and -32.12 kcal mol-1 for the syn eliminations of methyl methanethioseleninate and methaneperoxyselenonic acid, respectively. These computations suggest that the olefin-forming selenoxide syn elimination may be more general than currently understood and that replacement of the two carbon atoms with heteroatoms can lead to viable processes.

X-RAY SPECTROSCOPY OF SILICON DOPED WITH GERMANIUM ATOMS

This paper presents X-ray diffraction results of p-Si doped with germanium and tin atoms. It was found that after heat treatment of the initial silicon sample at a temperature of 1100°C, a new energetically favorable direction of crystallites appears. It was determined that germanium and silicon atoms form bonds in high-potential regions of the silicon crystal lattice and this leads to a deterioration in its monocrystallinity, that is, to an increase in the number of polycrystalline regions. It has been discovered that tin atoms in silicon combine with oxygen atoms and form SnO2 crystallites in the crystal lattice and this leads to an improvement in the monocrystallinity of silicon.

Multidisciplinary space shield origami composite: Incorporating cosmic radiation shielding, space debris impact protection, solar radiative heat shielding, and atomic oxygen erosion resistance

Origami composites have been extensively utilized in space structures with constrained payload volumes due to their capability to efficiently transform compact structures into larger surface area or volume configurations. The proposed origami composite incorporates hydrogen-rich benzoxazine polymers known for their high radiation shielding capability and ultra-high-molecular-weight polyethylene fibers known for their high ballistic performance, radiation shielding capability, and flexibility. The proposed origami composite and manufacturing method can enhance bonding strength by achieving precise origami shapes and utilizing the same matrix for both flexible and rigid components. Membrane sheets are manufactured at a low curing temperature to provide flexibility, while rigid facets are separately manufactured at a high curing temperature to increase rigidity. The integration of a polyimide protection layer significantly enhances space environment resistance and reduces mass loss due to atomic oxygen erosion. Despite a slight decrease in ballistic performance after exposure to space conditions, the proposed origami composite maintains superior ballistic performance compared to conventional space materials and conventional origami composites. Compared to existing origami composites or conventional space materials, the proposed origami composite exhibited superior radiation shielding performance. The laminated structure of the proposed origami composite can offer some solar radiation shielding capability. The proposed origami composite offers a multifunctional origami solution as a membrane-space shield material, fulfilling requirements for high ballistic performance, cosmic radiation shielding, solar radiative heat shielding, and space environmental resistance.

Novel Zn(II), Co(II) and Cu(II) diflunisalato complexes with neocuproine and their exceptional antiproliferative activity against cancer cell lines.

Three novel complexes of deprotonated diflunisal (dif) with neocuproine (neo) were synthesized and characterized via elemental, spectral (UV-vis, FTIR, fluorescence, and mass spectrometry), and single-crystal X-ray diffraction analyses. Although the compounds shared a similar composition of [MCl(dif)(neo)], where M represents Zn(II) (1), Co(II) (2) and Cu(II) (3), only 1 and 2 were isostructural, while 3 differed in both the molecular and supramolecular structures. In all three complex molecules, the central atom is coordinated by two nitrogen atoms of neo in a bidentate chelate mode, and one chlorido ligand and dif is bonded in either a monodentate mode via one oxygen atom of the carboxylate in 1 and 2 or in a bidentate chelate mode via both carboxylate oxygen atoms in 3. All three compounds demonstrated remarkable antiproliferative activity against human prostate (PC-3), colon (HCT116) and breast (MDA-MB-468) cancer cell lines with IC50 values in the nanomolar range, with the lowest values observed in the case of PC-3 and MDA-MB-468 with 2 (20.0 nM) and 3 (31.1 nM), respectively. Moreover, complex 2, as the most active, was further investigated for its potential to induce perturbations in the cell cycle of PC-3 cells. The results indicated an induction of caspase-independent apoptosis. The interaction of the complexes with genomic DNA isolated from the respective cancer cell lines was evaluated for the intercalative mode, with binding strength correlated with the antiproliferative activity against PC-3 and MDA-MB-468 cancer cell lines.

Synthesis and DFT investigations of novel 13-(pyrimidin-2-yl)-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocine derivatives

Heterocyclic compounds containing nitrogen and oxygen atoms are of great importance and wide applications in the fields of biomedicine and functional materials. In this paper, novel 13-aryl-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocines generated from cascade reactions between arylamines and 2-hydroxybenzaldehyde have been explored through both experiments and theoretical calculations. Experimental investigations showed that pyrimidin-2-amine could react with 2-hydroxybenzaldehyde in acetonitrile at 80 °C to afford the desired 13-(pyrimidin-2-yl)-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocines with 50 mol % of p-toluenesulfonic acid as catalyst, but aniline reacted with 2-hydroxybenzaldehyde to generate aldimine instead of the target bridged heterocylic compound. Density functional theory (DFT) computations were conducted to investigate the reaction mechanisms of 2-hydroxybenzaldehyde reacting with pyrimidin-2-amine and aniline, respectively. The experimental findings can be reasonably explained by theoretical calculations. Both the experimental explorations and suggested mechanisms indicate that the reactivity of the model reaction is sensitive to the electron density on the amino group of arylamine and the aldehyde group of 2-hydroxybenzaldehyde, which can be finely tuned with the aromatic ring structure and the substituents on it.

Phase Heterojunction by Constructing Built‐In Electric Field toward Sodium‐Rich Cathode Material

AbstractAn artificial built‐in electric field from phase heterojunction is constructed within sodium‐rich manganese‐based layer‐structured oxide O3‐Na[Ni0.3Mn0.55Cu0.1Ti0.05]O2@Na2MoO4 through shared oxygen atoms. The spinel Na2MoO4 phase behaves as a p‐type semiconductor, while the O3‐Na[Ni0.3Mn0.55Cu0.1Ti0.05]O2 phase functions as an n‐type semiconductor. It can efficiently reduce the diffusion barrier and enhance electron transport, which can adequately promote the interfacial desolvation ability and reduce bulk lattice strains. The formed spinel heterostructure with crystal structure stability can also enhance the interface Na+ diffusion and protect the electrode against moisture and carbon dioxide corrosion. Besides, the molybdenum introduction within the lattice bulk can enhance the bond covalency, fortifying lattice oxygen stability and restraining structural distortion effectively. The obtained cathode demonstrates a high up to 224.61 mAh g−1 discharge specific capacity at 0.1 C and a long cycle stability with a 60.44% capacity retention after 265 cycles at 0.5 C. This study illuminates the potential of Na‐rich Mn‐based oxide cathodes for high‐energy‐density sodium battery utilizations.

The structure of tetranuclear zirconium pivalate ZR<sub>4</sub>O<sub>2</sub> [(CH<sub>3</sub>)<sub>3</sub>CCO<sub>2</sub>]<sub>12</sub> according to X-ray diffraction analysis and quantum chemical calculations

The crystal and molecular structure of a polynuclear pivalate complex obtained by the interaction of ZrCl4 with pivalic acid was determined by X-ray diffraction analysis. The compound C71H124O28Zr4 (compound 1) crystallizes in the monoclinic crystal system. The crystal structure was refined in the nonstandard space group I2. The asymmetric part of the structure includes three Zr atoms, six pivalate ligands, a bridging µ3-O oxygen atom, as well as disordered crystallization molecules of pivalic acid with an occupancy of 50% and benzene with an occupancy of 50%. The zirconium complex molecule is a tetranuclear cluster that contains three types of Zr atoms that differ in ligand environment. Comparison of the results of quantum chemical calculations of the model reaction ZrCl4 with acetic acid with the literature data on reactions of ZrCl4 with aliphatic acids have shown the possibility of the formation of both mononuclear Zr(RCO2)4 and polynuclear clusters in this reaction, which is a new route for obtaining polynuclear zirconium clusters. The structure of the clusters formed depends on the steric properties of carboxylate ligands.

Enhanced 3 μm emission in Ho3+/Yb3+ co-doped bismuth-fluoride glasses by Gd2O3

In this work, (100-b)(45Bi2O3-40GeO2-15BaF2)-bGd2O3-2Yb2O3-0.5Ho2O3 glass was prepared to use a high-temperature melting method(where b= 0, 2.5, 5, 7.5, 10). The absorption and fluorescence spectra indicate that the optimal Gd2O3 content is 7.5 mol% (BGBG7.5HY), with an Ω2 value of 6.20×10−20 cm2 for the main glass, which is superior to that of BGBG0HY glass. This suggests that the incorporation of Gd2O3 enhances the mid-infrared emission capacity. Raman spectroscopy studies demonstrate that the introduction of Gd₂O₃ results in a substantial influx of oxygen atoms into the glass network, accompanied by a transition of [BiO₆] to [BiO₃] within the glass mesh. This is evidenced by a notable redshift of the characteristic peaks at 509 cm−1 and 677 cm−1 in comparison to BGB glass. The introduction of Gd2O3 also expands the distance between Ho3+/Yb3+ ions, inhibits rare earth ion clusters, improves the Ho3+ luminescence center environment, and thus enhances the 3 μm emission performance of bismuth fluoride glass. The maximum emission cross section is 1.82 × 10−20 cm2 and the maximum gain coefficient is 3.71 cm−1. The results show that the bismuth fluoride glass prepared in this paper is an excellent gain material for mid-infrared fiber lasers.

Investigating the Role of Anions in the Adsorption of Pyrrolidinium Based Ionic Liquids on Pt(111) Surface Using Density Functional Theory

ABSTRACTThe adsorption properties of ionic liquids containing pyrrolidinium cations and various inorganic anions as electrolytes on a platinum surface were analyzed using first principle density functional theory. Three different orientations of the alkyl cation chain were observed during the adsorption process. The strength and structural stability varied between non‐fluorinated and fluorinated anions upon adsorption, with oxygen atoms influencing the mechanism of adsorption and driving the structural stability of the anion, while fluorine atoms played a role in determining the orientation of the cation during adsorption. Net atomic charges analysis, electron density difference methods, and electron density accumulation for this complex system were utilized to further investigate these phenomena. The results of this study provide valuable insights into the role of anions in the adsorption behavior of pyrrolidinium‐based ionic liquids on platinum surfaces, shedding light on the factors that influence their adsorption properties and structural stability on a molecular level. The findings of this study contribute to a better understanding of the interplay between anions and platinum surfaces in the adsorption of pyrrolidinium based ionic liquids, which can have implications for various applications such as electrochemistry, catalysis, and energy storage.