Distribution Of Anions Research Articles

Correlated N/O anion orders in melilite phosphors

The N/O anion distributions in the melilite-type phosphor host material Y2Si3O3N4 and a Ce-doped sample Y1.5Ce0.5Si3O3N4 have been determined from powder neutron diffraction. Both materials have a highly ordered N/O distribution that is not changed significantly by the disorder introduced by Ce doping. This distribution evidences the presence of SiN3O and SiN2O2 tetrahedra and although these are not fully long range-ordered, local structural correlations follow simple connectivity rules that lead to an estimated residual molar entropy of R ln3. A broad range of N/O environments is found around 8-coordinate Y(Ce) sites which is expected to broaden their spectroscopic features.

Initial Structural Changes of Porous Alumina Film via High-Resolution Microscopy Observations

The initial growth of a porous alumina film with a large-scale cell structure formed by galvanostatic anodizing in etidronic acid was investigated in detail by high-resolution microscopy. High-purity aluminum plates were galvanostatically anodized in etidronic acid at 2.5–20.0 Am−2. The formation of an anodic oxide and the subsequent instability of the outer oxide simultaneously occurred at the early stage of the linear voltage increase during the anodizing process. Accordingly, a wavy interface boundary between the aluminum oxide that contained incorporated anions and the nearly pure aluminum oxide formed in the anodic oxide. The surviving pores grew as the thickness of the oxide film increased, and a clear porous alumina film with a pore at the center of each cell formed until the voltage reached its maximum value. Finally, steady-state growth of the porous alumina film occurred at the plateau voltage region after a slight voltage decrease. Eggplant-like anion distributions were measured at the head of the pores due to the viscous flow of the anodic oxide. The nanomorphology of the porous alumina film strongly depended on the current density due to the difference in the degree of oxide formation and localized oxide dissolution.

Enhancement of photovoltaic efficiency in CdSexTe1−x (where 0 ⩽ x ⩽ 1): insights from density functional theory

Recent advancements in CdTe photovoltaic efficiency have come from selenium grading, which reduces the band gap and significantly improves carrier lifetimes. In this work, density functional theory calculations were performed to understand the structural and electronic effects of Se alloying. Special quasirandom structures were used to simulate a random distribution of Se anions. Lattice parameters decrease linearly as Se concentration increases in line with Vegard’s Law. The simulated band gap bowing shows strong agreement with experimental values. Selenium, by itself, does not introduce any defect states in the band gap and no significant changes to band structure around the point are found. Band offset values suggest a reduction of recombination across the CdSeTe/MgZnO interface at , which corresponds with the Se concentration used experimentally. Band structure analysis of two cases and x = 0.4375, shows a change from dominant Cd/Te contributions in the conduction band minimum to Cd/Se contributions as Se concentration is increased, hinting at a change in optical transition characteristics. Further calculations of optical absorption spectra suggest a reduced transition probability particularly at higher energies, which confirms experimental predictions that Se passivates the non-radiative recombination centres.

Composition and Ligand Microstructure of Arsenopyrite from Gold Ore Deposits of the Yenisei Ridge (Eastern Siberia, Russia)

The Mössbauer spectroscopy method was used to study the ligand microstructure of natural arsenopyrite (31 specimens) from the ores of the major gold deposits of the Yenisei Ridge (Eastern Siberia, Russia). Arsenopyrite and native gold are paragenetic minerals in the ore; meanwhile, arsenopyrite is frequently a gold carrier. We detected iron positions with variable distribution of sulfur and arsenic anions at the vertexes of the coordination octahedron {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, {6As} in the mineral structure. Iron atoms with reduced local symmetry in tetrahedral cavities, as well as iron in the high-spin condition with a high local symmetry of the first coordination sphere, were identified. The configuration {3S3As} typical for the stoichiometric arsenopyrite is the most occupied. The occupation degree of other configurations is not subordinated to the statistic distribution and varies within a wide range. The presence of configurations {6S}, {3S3As}, {6As} and their variable occupation degree indicate that natural arsenopyrites are solid pyrite {6S}, arsenopyrite {3S3As}, and loellingite {6As} solutions, with the thermodynamic preference to the formation of configurations in the arsenopyrite–pyrite–loellingite order. It is assumed that in the variations as part of the coordination octahedron, the iron output to the tetrahedral positions and the presence of high-spin Fe cations depend on the physical and chemical conditions of the mineral formation. It was identified that the increased gold concentrations are typical for arsenopyrites with an elevated content of sulfur or arsenic and correlate with the increase of the occupation degree of configurations {5S1As}, {4S2As}, {1S5As}, reduction of the share of {3S3As}, and the amount of iron in tetrahedral cavities.

Insights into Non‐Ideal Behavior of Double Salt Ionic Liquids with Common Cation: Volumetric Behaviour, Molecular Dynamics Simulations and NMR Experiments

AbstractThe designer concept of ionic liquid (ILs) allows combination of different types of cation with anion to manipulate desire sets of physico‐chemical properties. The additional degree of freedom to improve these properties is addition of second IL, i. e. mixture of two pure ILs, known as “Double Salt Ionic Liquids (DSILs)”. Depending on variation in physico chemical properties, DSILs could be ideal or non‐ideal solution. The present study was explores non‐ideal behaviour of three novel combination of imidazolium based DSILs using physico‐chemical properties. The proposed DSILs are homogeneous mixtures of two pure ILs with common cation and two different anions: ethylsulfate and bis(trifluoromethylsulfonyl)imide / trifluoromethanesulfonate / thiocyanate. The densities, ρ and speeds of sound, u for proposed DSILs were determined at different temperatures. The excess molar volumes VmE and excess molar isentropic compressibilities KS,mE were calculated and discussed in view of chemical structures of pure ILs, nature of anions and type of interaction between ions. The VmE were found to be positive for all cases, whereas positive or negative KS,mE were observed for studied DSILs. The behaviour of DSILs was explained by molecular dynamics simulations in terms of interaction energies and hydrogen bonds between components of DSILs as well as 1H NMR results. The results indicate random distribution of anions around imidazolium cation and structural changes during formulation of DSILs.

Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing in Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites.

Mixed anion compounds in the Fm3̅m vacancy ordered perovskite structure were synthesized and characterized experimentally and computationally with a focus on compounds where A = Cs+. Pure anion Cs2SnX6 compounds were formed with X = Cl, Br, and I using a room temperature solution phase method. Mixed anion compounds were formed as solid solutions of Cs2SnCl6 and Cs2SnBr6 and a second series from Cs2SnBr6 and Cs2SnI6. Single phase structures formed across the entirety of both composition series with no evidence of long-range anion ordering observed by diffraction. A distortion of the cubic A2BX6 structure was identified in which the spacing of the BX6 octahedra changes to accommodate the A site cation without reduction of overall symmetry. Optical band gap values varied with anion composition between 4.89 eV in Cs2SnCl6 to 1.35 eV in Cs2SnI6 but proved highly nonlinear with changes in composition. In mixed halide compounds, it was found that lower energy optical transitions appeared that were not present in the pure halide compounds, and this was attributed to lowering of the local symmetry within the tin halide octahedra. The electronic structure was characterized by photoemission spectroscopy, and Raman spectroscopy revealed vibrational modes in the mixed halide compounds that could be assigned to particular mixed halide octahedra. This analysis was used to determine the distribution of octahedra types in mixed anion compounds, which was found to be consistent with a near-random distribution of halide anions throughout the structure, although some deviations from random halide distribution were noted in mixed iodide–bromide compounds, where the larger iodide anions preferentially adopted trans configurations.

Investigation of the Ionic Structure of Molten 1.5–8 KF-AlF3 Salts with Raman Spectroscopy

The form and concentration distribution of anions in a molten KF-AlF3 system with different molar ratios (1.5–8) at different temperatures were analyzed with Raman spectroscopy. The results indicate that for molar ratios in the range of 1.5–5, AlF63−, AlF52−, AlF4−, and F−, were all present in the system, while for molar ratios in the range of 6–8, only AlF63−, AlF52−, and F−, were present. For molar ratios in the range of 1.5–2.5, the AlF52− ion content was the most sensitive to temperature among all the complex ions in the system, whereas for molar ratios in the range of 4–8, minor variations in the constituent anion contents were observed as a function of temperature. The Al3+ ions in the system with the molar ratios of 1.5–5, 6, and 7 or 8 tended to form AlF4−, AlF52−, and AlF63−, respectively, as the temperature increased.

Accelerated solar steam generation for efficient ions removal

Solar-driven evaporation as a sustainable water purification technology exhibits great potential in solving the global water crisis. In this paper, a novel solar evaporator was successfully prepared with the reduced graphene oxide (rGO) and silver (Ag) nanowires as photothermal conversion media which were loaded into the sodium alginate (SA) hydrogel. It was found that the evaporation rate of the prepared evaporator reached 2.02 kg m−2 h−1 and the solar energy efficiency was 91% under one sun irradiation intensity. Furthermore, this novel solar evaporator exhibited expectant evaporation performance in the treatment of seawater and heavy metal sewage with excellent ion removal ability, with the removal efficiency of various ions higher than 99.9%. The ion-crosslinked SA hydrogel contained in the evaporator ensured the rejection of multivalentions based on the distribution of carboxylate anions, and the three-dimensional porous channel of the super-hydrophilic hydrogel provided the convenient path for the transport of water molecules and the escape of water vapor. The binary composition of rGO and silver nanowires enhanced the photothermal conversion and the thermal conductivity, which was beneficial to the stable supply of thermal energy for evaporation. The purpose of this paper is to provide reference for promoting the practical application of solar evaporation.

Preparation and thermal stability of oxynitride perovskite solid solution Sr1-xLaxTa1-xTixO2N

The thermal stability of oxynitride perovskites is very important for the fabrication of their dense ceramics. In this study, a solid solution of the oxynitride perovskite Sr1-xLaxTa1-xTixO2N was prepared via the ammonia nitridation of oxide precursors. The oxynitrides products obtained at x ≤ 0.2 and x ≥ 0.7 had tetragonal and triclinic perovskite-type structures, respectively. A neutron diffraction study on the oxynitride product obtained at x = 0.2 indicated that this tetragonal perovskite had a cis-type anion distribution similarly to SrTaO2N. The tetragonal perovskite released a part of nitrogen at approximately 1000 °C in a nitrogen atmosphere while maintaining the perovskite structure at least to 1450 °C. The oxynitride perovskites at x ≥ 0.5 gradually decomposed to a mixture of LaTiO2N, LaTiO3, La(OH)3, La2O3, TiN and TaO above 1100 °C.

Ionic Polymerization in Cold Plasmas of Acetylene with Ar and He.

The ionic polymerization of acetylene in cold plasmas of C2H2/He and C2H2/Ar has been experimentally studied and modeled in radio frequency (rf) discharges with conditions selected to avoid particle formation. Steady-state distributions of positive and negative ions were measured with mass spectrometry. All the measured distributions are dominated by ions with an even number of carbon atoms, reflecting the characteristic polyyne structures typical for the polymerization of acetylene. The distributions show a monotonic decrease in intensity from ions with two carbon atoms until the highest number of atoms detected. For cations, the distributions extend until 12 carbon atoms. The anion distributions extend further, and negative ions with 20 C atoms are observed in the C2H2/Ar plasma. From the measured mass spectra it is not possible to decide on the possible presence of aromatic species in ions with more than six carbon atoms. A simple model assuming a homogeneous discharge was used to describe the plasma kinetics and could account for the measured ion distributions with reasonable values of charge density and electron temperature. The results of this work stress the important role of the vinylidene anion and indicate that Ar and He do not have much influence on the carbon chemistry.

Iron polyphosphate glasses for waste immobilization

AbstractIron polyphosphate glasses resist attack by water, can dissolve large concentrations of species that are otherwise insoluble in borosilicate glass melts, and can be processed at relatively low temperatures (1000‐1200°C), and so are viable hosts for vitrifying hazardous and radioactive wastes. The properties of iron polyphosphate glasses depend on the distributions of phosphate anions and the nature of the bonds between those anions and various metal polyhedra, and quantitative information can be obtained about those structures using a variety of spectroscopic, diffraction, and chromatographic techniques. This structural information helps explain compositional trends in properties, including dissolution rates, electrical conductivity, thermal properties and crystallization tendency. Studies of waste forms made with low activity and high level wastes are reviewed and related back to an understanding of the structures and properties of simpler iron polyphosphate glasses.

Oxalic Acid Enabled Emission Enhancement and Continuous Extraction of Chloride from Cesium Lead Chloride/Bromide Perovskite Nanocrystals.

All-inorganic cesium lead halide perovskite nanocrystals (NCs) have demonstrated excellent optical properties and an encouraging potential for optoelectronic applications; however, mixed-halide perovskites, especially CsPb(Cl/Br)3 NCs, still show lower photoluminescence quantum yields (PL QY) than the corresponding single-halide materials. Herein, anhydrous oxalic acid is used to post-treat CsPb(Cl/Br)3 NCs in order to initially remove surface defects and halide vacancies, and thus, to improve their PL QY from 11% to 89% for the emission of 451 nm. Furthermore, due to the continuous chelating reaction with the oxalate ion, chloride anions from the mixed-halide CsPb(Cl/Br)3 perovskite NCs could be extracted, and green emitting CsPbBr3 NCs with PL QY of 85% at 511 nm emission are obtained. Besides being useful to improve the emission of CsPb(Cl/Br)3 NCs, the oxalic acid treatment strategy introduced here provides a further tool to adjust the distribution of halide anions in mixed-halide perovskites without using any halide additives.

Natural and Anthropogenic Sources of Groundwater Salinization in Parts of Karachi, Pakistan

This study is aimed to evaluate the groundwater quality of Gulshan-e-Iqbal and Liaquatabad towns inKarachi. Thirty (n=30) groundwater samples were randomly collected from different locations by electrically pumpedwells at various depths (14-91m). All the water samples were analyzed to determine their suitability for drinkingpurpose based on various physicochemical parameters. Data reveal that high concentration of TDS and hardness havedeteriorated the groundwater quality of study area. The main phenomenon responsible for groundwater pollution is theseawater intrusion due to the proximity of study area to the Arabian sea. Large scale unplanned urbanization, poorwaste management and other anthropogenic activities have also triggered the deterioration of groundwater quality.Study showed that local geology plays vital role in the distribution of major cations and anions. Data suggested thatground water of this study area is highly contaminated by seawater intrusion and considered not fit for drinkingpurpose.

Natural and Anthropogenic Sources of Groundwater Salinization in Parts of Karachi, Pakistan

This study is aimed to evaluate the groundwater quality of Gulshan-e-Iqbal and Liaquatabad towns inKarachi. Thirty (n=30) groundwater samples were randomly collected from different locations by electrically pumpedwells at various depths (14-91m). All the water samples were analyzed to determine their suitability for drinkingpurpose based on various physicochemical parameters. Data reveal that high concentration of TDS and hardness havedeteriorated the groundwater quality of study area. The main phenomenon responsible for groundwater pollution is theseawater intrusion due to the proximity of study area to the Arabian sea. Large scale unplanned urbanization, poorwaste management and other anthropogenic activities have also triggered the deterioration of groundwater quality.Study showed that local geology plays vital role in the distribution of major cations and anions. Data suggested thatground water of this study area is highly contaminated by seawater intrusion and considered not fit for drinkingpurpose.

Organic Anion-Transporting Polypeptide 1a4 (Oatp1a4/Slco1a4) at the Blood-Arachnoid Barrier is the Major Pathway of Sulforhodamine-101 Clearance from Cerebrospinal Fluid of Rats.

The blood-arachnoid barrier (BAB), which is formed by arachnoid epithelial cells linked by tight junctions, has generally been considered impermeable to water-soluble substances. However, we recently demonstrated that organic anion transporters 1 and 3 (Oat1 and Oat3) play roles in drug clearance at the BAB. Here, we examined whether an organic anion-transporting polypeptide (Oatp) also plays a role, using the fluorescent organic anion sulforhodamine-101 (SR-101) as a model substrate. SR-101 was injected into the cisterna magna of rats in order to minimize the contribution of choroid plexus transport. The in vivo cerebrospinal fluid (CSF) elimination clearance of SR-101 after intracisternal administration was ninefold greater than that of fluorescein-labeled inulin, a bulk flow marker. In the case of pre-administration of taurocholate, a broad-spectrum inhibitor of Oatps, or digoxin, a strong substrate/inhibitor for Oatp1a4 but not for Oatp1a1, Oat1, and Oat3, the CSF elimination of SR-101 was significantly reduced, becoming similar to that of inulin, and thus indicating complete inhibition of SR-101 clearance from the CSF. The distribution of SR-101 fluorescence was restricted to the arachnoid mater in the absence of inhibitor, whereas the fluorescence was increased in the parenchyma of the spinal cord after co-injection of taurocholate or digoxin. Immunostaining confirmed the localization of Oatp1a4 in the arachnoid mater. These results indicate that Oatp1a4 at the BAB acts as an avid clearance pathway of SR-101 in the CSF to the blood. Thus, Oatp1a4 appears to play a major role in CSF detoxification by limiting the distribution of organic anions to the brain and spinal cord.

Hysteretic order-disorder transitions of ionic liquid double layer structure on graphite

Understanding the electrical double layer (EDL) structure at the solid/liquid interface is critical towards realizing the full potential of electrochemical applications using ionic liquids. In this work, the out-of-plane and in-plane EDL structures of PYR14-TFSI on graphite (HOPG) have been studied by in-situ electrochemical atomic force microscopy (AFM) and molecular dynamics (MD) simulation. AFM results revealed that the first adsorbed ion layer on HOPG consists of both disordered and ordered lateral domains. It has been found that the neighboring molecules in the x-y plane form intricate ordered lateral structures on length scale of hundreds of nanometers, and the out-of-plane EDL structure is independent of the in-plane structure. MD simulations under zero polarization showed that in the first adsorbed layer, cations have one preferred orientation while anions have two preferred orientations in relation to the HOPG surface, which might be the origin of the complex lateral ordering. When polarizing the surface, a hysteretic order-disorder transition of the lateral ordering in the first adsorbed layer can be observed by in-situ AFM, and the ordered domains disappear for high positive or negative voltages. Comparison with bias-dependent MD reveals that the existence of a bimodal anion distribution in the first absorbed layer can be linked to the observed transitions giving new insights into the origin of the structural domains, which can help understand unusual charge and discharge kinetics observed in similar systems.

The structure and properties of xZnO–(67–x)SnO–33P2O5 glasses: (IV) Mechanical properties

The Vickers hardness, Young's modulus, and shear modulus of xZnO–(67–x)SnO–33P2O5 glasses increase with increasing values of x, in agreement with predictions that consider the quantitative structural information regarding coordination numbers of Zn2+ and Sn2+ ions by diffraction methods, and phosphate anion distributions by NMR methods, reported in an earlier study. The compositional dependence of the shear modulus falls into two ranges which correlate with trends in photoelasticity, and the elastic and photoelastic properties are explained considering changes in ion packing ratio and average bond strengths when ZnO replaces SnO.

Structure and Electronic Properties of [Ca24Al28O64]4+·4e– Surfaces: Opportunities for Termination-Controlled Electron Transfer

We investigate the structure, thermodynamic stability, and electronic properties of (001), (110), and (111) surfaces of mayenite (12CaO·7Al2O3 or C12A7) in its oxygen-deficient phase known as mayenite-derived electride Ca12Al14O32 using simulations based on the density functional theory. Seven types of surface terminations were identified, depending on the orientation of the lattice nanosize cages with respect to the surface plane. We find that the surface termination has a strong effect on the distribution of electron anions in the near-surface region, as demonstrated by the range of the ionic charges and binding energies of adsorbed Au atoms and dimers. Notably, in all cases, Au species acquire a negative charge and preferentially adsorb as isolated ions rather than aggregate into clusters. These results show that C12A7 electride can provide a simple, yet versatile substrate to achieve high adsorption capacity and steric selectivity for single atom catalysts.

The structure and properties of cesium loaded Mo-Fe-phosphate glasses

Chemically durable iron phosphate glasses are promising candidates for hosting nuclear wastes containing constituents like Cs2O and MoO3 that have lower solubility in more conventional borosilicate glasses. In this work, two series of Cs-Mo-Fe-phosphate glasses were prepared and characterized. For glasses in Series A (xCs2O∙(100-x)∙(15MoO3∙22.5Fe2O3∙62.5P2O5), x = 0, 7.5, 15.0, 22.5), increasing Cs2O contents increase the molar volume and decrease the glass transition temperature. Raman spectroscopy reveals that adding Cs2O breaks down linkages between MoO6 octahedra, replacing MoOMo and MoO bonds with Mo-O−Cs+ bonds. Phosphate anion chromatography reveals that adding Cs2O has little effect on the phosphate anion distributions. For glasses in Series B (15Cs2O∙ yMoO3∙(28.75-y)Fe2O3∙56.25P2O5, y = 0, 5.75, 11.50, 17.25, 23.00, 28.75), the glass transition temperature decreases and the aqueous dissolution rates increase when MoO3 replaces Fe2O3. The formation of isolated MoO6 octahedra with Mo-O−Cs+ bonds results in an increase in the average phosphate anion-length in the MoO3-rich glasses. Mössbauer spectroscopy indicates that ferric ions dominate in both series, and that the average Fe-coordination number increases with increasing Cs2O content (series A) and with increasing MoO3 content (series B).

Advantages of adding just enough alkalis

Solar Cells For organic-inorganic hybrid solar cells, addition of cesium or rubidium cations can improve power conversion efficiency. Correa-Baena et al. used nanoscale x-ray fluorescence imaging to show that the addition of metal cations at low concentrations homogenized the distribution of bromide and iodide anions and also increased charge-carrier lifetimes. However, at high concentrations, aggregation and cluster formation led to increased charge recombination. Science , this issue p. [627][1] [1]: /lookup/doi/10.1126/science.aah5065