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Sample records for octahedral anions hexacyanoferrateiii

  1. Structural studies on encapsulation of tetrahedral and octahedral anions by a protonated octaaminocryptand cage

    PubMed Central

    Ravikumar, I; Lakshminarayanan, P S

    2009-01-01

    Summary Structural aspects of the binding of inorganic anions such as perchlorate, hydrogen sulfate, and hexafluorosilicate with the proton cage of octaaminocryptand L 1, N(CH2CH2NHCH2-p-xylyl-CH2NHCH2CH2)3N), are examined thoroughly. Crystallographic results for a hexaprotonated perchlorate complex of L 1, [(H6L1)6+(ClO4 −)]5(ClO4 −)·11H2O·CH3CN (1), an octaprotonated hydrogen sulfate complex of L 1, [(H8 L 1)8+(HSO4 −)]7(HSO4 −)·3H2O·CH3OH (2) and an octaprotonated fluorosilicate complex of L 1, [(H8 L 1)8+(HSiF6 −)]3(SiF6 2−)·(HSiF6 −)·15H2O (3), show encapsulation of one perchlorate, hydrogen sulfate and hexafluorosilicate, respectively inside the cage of L 1 in their protonated states. Further, detailed structural analysis on complex 1 reveals that the hexaprotonated L 1 encapsulates a perchlorate via two N–H···O and five O–H···O hydrogen bonds from protonated secondary nitrogen atoms of L 1 and lattice water molecules, respectively. Encapsulated hydrogen sulfate in complex 2 is “glued” inside the octaprotonated cage of L 1 via four N–H···O and six C–H···O hydrogen bonds whereas encapsulated HSiF6 − in complex 3 has short contacts via six N–H···F and three C–H···F hydrogen bonds with [H8 L 1]8+. In the cases of complexes 2 and 3, the cryptand L 1 in octaprotonated state shows monotopic encapsulation of the guest and the final conformation of these receptors is spherical in nature compared to the elongated shape of hexaprotonated state of L 1 in complex 1. PMID:19936273

  2. Ionic Strength Effect on the Rate of Reduction of Hexacyanoferrate(III) by Ascorbic Acid: A Flow Injection Kinetic Experiment

    NASA Astrophysics Data System (ADS)

    Nobrega, Joanquim A.; Rocha, Fabio R. P.

    1997-05-01

    Flow injection analysis (FIA) is a well recognized tool for solutions management. In spite of the use of this technique mainly for quantitative determination of analytes in solution, FIA systems can also be used for obtaining physical chemistry data. This work describes the use of a flow diagram to perform a kinetic experiment: the effect of ionic strength on the rate of reduction of hexacyanoferrate(III) by ascorbic acid. The rate determining step of this reaction involves the collision between two anionic species. The increase of the ionic strength of the medium alters the ionic atmosphere and changes the charge densities around the anions. Consequently, there is an increment of the rate constants for higher ionic strengths. In the proposed system, the flow is stopped by commutation when the center of the sample zone attained the flow cell and a gradual decrease in signal, related to the redox reaction, is registered as function of time. This allowed the determination of the rate constants as a function of the ionic strength. The product of the charges of the ions involved in the rate determining step was estimated in 3.2 that is close to the expected value considering the proposed mechanism.

  3. Ruthenium(VI)-Catalyzed Oxidation of Alcohols by Hexacyanoferrate(III): An Example of Mixed Order

    ERIC Educational Resources Information Center

    Mucientes, Antonio E.; de la Pena, Maria A.

    2006-01-01

    The absorbance decay of hexacyanoferrate(III) as a function of time shows a progressive deviation from zero to first order. This variation follows an experimental rate law that has been analyzed. The change in reaction order is due to a change in the relative rate of substrate oxidation with respect to that of catalyst regeneration. (Contains 2…

  4. Investigation of cobalt interference on lead hydride generation with tetrahydroborate(III) in the presence of hexacyanoferrate(III)

    NASA Astrophysics Data System (ADS)

    Zheng, Lin; Lin, Li; Zhu, Lihui; Jiang, Mindi

    2009-03-01

    The interference of Co(II) on plumbane generation with tetrahydroborate in the presence of hexacyanoferrate(III) was studied with a new mechanism proposed to explain the interference. The products that were obtained, following reactions of a CoCl 2 solution with tetrahydroborate(III), which interfere with plumbane generation, were precipitated and investigated by inductively-coupled plasma-atomic emission spectrometry and -mass spectrometry (ICP-OES and ICP-MS). Batch experiments of the potentiometer analysis and pH determination were performed to investigate a mechanism of Co(II) interference on plumbane generation, the role of hexacyanoferrate(III) on plumbane generation, and the function of the masking agent on Co(II) interference. The preferentially formed nanoscale catalytic and magnetic cobalt borides in the redox system cause a potential for a strong reducing condition and induces the precipitation of Fe(III) and Pb(II) in the solution, which is counter to plumbane generation. Potassium thiocyanate/oxalic acid/1,10-phenanthroline, as the combined masking agent and working with hexacyanoferrate(III), decreases the amount of borides in the precipitates and acts as a kind of buffer of the redox potential, which maintains the conditions for plumbane generation. This hydride generation method has been applied to the direct determination of trace Pb in cobalt oxide standard reference materials with a detection limit of 0.3 µg L - 1 .

  5. Study on Octahedral Spherical Hohlraum

    NASA Astrophysics Data System (ADS)

    Lan, Ke; Liu, Jie; Huo, Wenyi; Li, Zhichao; Yang, Dong; Li, Sanwei; Ren, Guoli; Chen, Yaohua; Jiang, Shaoen; He, Xian-Tu; Zhang, Weiyan

    2015-11-01

    In this talk, we report our recent study on octahedral spherical hohlraum which has six laser entrance holes (LEHs). First, our study shows that the octahedral hohlraums have robust high symmetry during the capsule implosion at hohlraum-to- capsule radius ratio larger than 3.7 and have potential superiority on low backscatter without supplementary technology. Second, we study the laser arrangement and constraints of the octahedral hohlraums and give their laser arrangement design for ignition facility. Third, we propose a novel octahedral hohlraum with LEH shields and cylindrical LEHs, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. Fourth, we study the sensitivity of capsule symmetry inside the octahedral hohlraums to laser power balance, pointing accuracy, deviations from the optimal position and target fabrication accuracy, and compare the results with that of tradiational cylinders and rugby hohlraums. Finally, we present our recent experimental studies on the octahedral hohlraums on SGIII prototype laser facility.

  6. The role of intermolecular interactions in the assemblies of Fe{sup II} and Co{sup II} tetrakis-isothiocyanatometalates with tris(1,10-phenanthroline)-Ru{sup II}: Crystal structures of two dual-metal assemblies featuring octahedral cationic and tetrahedral anionic modules

    SciTech Connect

    Ghazzali, Mohamed Langer, Vratislav; Ohrstroem, Lars

    2008-09-15

    Two new dual-metal assemblies: 2[Ru(phen){sub 3}]{sup 2+}.[Fe(SCN){sub 4}]{sup 2-}.2SCN{sup -}.4H{sub 2}O 1 and [Ru(phen){sub 3}]{sup 2+}.[Co(SCN){sub 4}]{sup 2-}2, (phen:1,10-phenanthroline), have been prepared and their structures were characterized by X-ray diffraction. In 1, the cationic octahedral enantiomers are arranged with a {lambda}{delta}{lambda}{delta}{lambda} sequence supported by {pi}-{pi} stacking and the anionic inorganic tetrahedral units are oriented between these stacks by interacting with the nearby water molecules through strong O-H...O and O-H...S hydrogen bonds. In 2, homochiral double helices in the b-direction are revealed, with tetrakis-isothiocyanate Co{sup II} anions arranged in the crystal to furnish one-dimensional (1D)-helical chains with S...S intermolecular interactions at 3.512(2) and 3.966(2) A supporting [Ru(phen){sub 3}]{sup 2+}{lambda}- and {delta}-helices with Ru...Ru shortest distance of 8.676(7) A. In both 1 and 2, the supramolecular assembly is maintained by C-H...S hydrogen bonds extending between the phenanthroline aromatic carbons in the cationic nodes and the sulphur atoms of the isothiocyanates anions. Analysis of S...S interactions in isothiocyanate containing compounds using Cambridge structural database (CSD) showed an angle dependence categorizing these interactions into 'type-I' and 'type-II'. - Graphical abstract: Side projection in 2 showing the crankshaft caused by S...S interactions in [Co(NCS){sub 4}]{sup 2-} in-between [Ru{sup II}(phen){sub 3}]{sup 2+} helices. Only isothiocyanates arms of [Co(NCS){sub 4}]{sup 2-} that are part of S...S interactions are shown and [Ru{sup II}(phen){sub 3}]{sup 2+} are presented as polyhedra.

  7. Synthesis, structure and bonding of hexaphenyl thorium(IV): observation of a non-octahedral structure.

    PubMed

    Pedrick, Elizabeth A; Hrobárik, Peter; Seaman, Lani A; Wu, Guang; Hayton, Trevor W

    2016-01-14

    We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME)3]2[Th(C6H5)6] (1) and [Li(THF)(12-crown-4)]2[Th(C6H5)6] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry. The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-H···Th interactions, which arise from σ(C-H) → Th(5f) donation. The non-octahedral structure is also favoured in solution at low temperatures. PMID:26569166

  8. Niobate-based octahedral molecular sieves

    DOEpatents

    Nenoff, Tina M.; Nyman, May D.

    2006-10-17

    Niobate-based octahedral molecular sieves having significant activity for multivalent cations and a method for synthesizing such sieves are disclosed. The sieves have a net negatively charged octahedral framework, comprising niobium, oxygen, and octahedrally coordinated lower valence transition metals. The framework can be charge balanced by the occluded alkali cation from the synthesis method. The alkali cation can be exchanged for other contaminant metal ions. The ion-exchanged niobate-based octahedral molecular sieve can be backexchanged in acidic solutions to yield a solution concentrated in the contaminant metal. Alternatively, the ion-exchanged niobate-based octahedral molecular sieve can be thermally converted to a durable perovskite phase waste form.

  9. Niobate-based octahedral molecular sieves

    DOEpatents

    Nenoff, Tina M.; Nyman, May D.

    2003-07-22

    Niobate-based octahedral molecular sieves having significant activity for multivalent cations and a method for synthesizing such sieves are disclosed. The sieves have a net negatively charged octahedral framework, comprising niobium, oxygen, and octahedrally coordinated lower valence transition metals. The framework can be charge balanced by the occluded alkali cation from the synthesis method. The alkali cation can be exchanged for other contaminant metal ions. The ion-exchanged niobate-based octahedral molecular sieve can be backexchanged in acidic solutions to yield a solution concentrated in the contaminant metal. Alternatively, the ion-exchanged niobate-based octahedral molecular sieve can be thermally converted to a durable perovskite phase waste form.

  10. Regioselective placement of alkanethiolate domains on tetrahedral and octahedral gold nanocrystals.

    PubMed

    Wang, Yifeng; Zeiri, Offer; Meshi, Louisa; Stellacci, Francesco; Weinstock, Ira A

    2012-10-01

    Electrostatically stabilized monolayer shells of metal-oxide cluster anions (polyoxometalates, or POMs) on the surfaces of ca. 8 nm tetrahedral and octahedral gold nanocrystals regioselectively direct water-soluble alkanethiolate ligands to the corners and edges of the gold polyhedra. PMID:22918232

  11. Syntheses, crystal structures and Raman spectra of Ba(BF{sub 4})(PF{sub 6}), Ba(BF{sub 4})(AsF{sub 6}) and Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}); the first examples of metal salts containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} anions

    SciTech Connect

    Lozinsek, Matic; Bunic, Tina; Goreshnik, Evgeny; Meden, Anton; Tramsek, Melita; Tavcar, Gasper; Zemva, Boris

    2009-10-15

    In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen fluoride (aHF) a compound Ba(BF{sub 4})(PF{sub 6}) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF{sub 4})(PF{sub 6}) crystallizes in a hexagonal P6-bar2m space group with a=10.2251(4) A, c=6.1535(4) A, V=557.17(5) A{sup 3} at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF{sub 4}{sup -} and PF{sub 6}{sup -} anions. In the analogous system with AsF{sub 5} instead of PF{sub 5} the compound Ba(BF{sub 4})(AsF{sub 6}) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) A, b=6.325(3) A, c=11.8297(17) A, V=779.3(4) A{sup 3} at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF{sub 6}{sup -} and four F atoms from BF{sub 4}{sup -} anions. When the system BaF{sub 2}/BF{sub 3}/AsF{sub 5}/aHF is made basic with an extra addition of BaF{sub 2}, the compound Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}) was obtained. It crystallizes in a hexagonal P6{sub 3}/mmc space group with a=6.8709(9) A, c=17.327(8) A, V=708.4(4) A{sup 3} at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF{sub 4}{sup -}, three AsF{sub 6}{sup -} and three H{sub 3}F{sub 4}{sup -} anions. All F atoms, except the central atom in H{sub 3}F{sub 4} moiety, act as mu{sub 2}-bridges yielding a complex 3-D structural network. - Graphical abstract: The first three compounds, containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} (A=P, As) anions have been synthesized and characterized by Raman spectroscopy and X-ray single crystal diffraction. In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen fluoride (a

  12. A Simple Method for Drawing Chiral Mononuclear Octahedral Metal Complexes

    ERIC Educational Resources Information Center

    Mohamadou, Aminou; Haudrechy, Arnaud

    2008-01-01

    Octahedral transition-metal complexes are involved in a number of reactions and octahedral coordination geometry, frequently observed for metallic centers, includes important topographical stereochemistry. Depending on the number and nature of different ligands, octahedral coordination units with at least two different monodentate ligands give…

  13. Desymmetrization of an Octahedral Coordination Complex Inside a Self-Assembled Exoskeleton.

    PubMed

    Johnstone, Mark D; Schwarze, Eike K; Ahrens, Jennifer; Schwarzer, Dirk; Holstein, Julian J; Dittrich, Birger; Pfeffer, Frederick M; Clever, Guido H

    2016-07-25

    The synthesis of a centrally functionalized, ribbon-shaped [6]polynorbornane ligand L that self-assembles with Pd(II) cations into a {Pd2 L4 } coordination cage is reported. The shape-persistent {Pd2 L4 } cage contains two axial cationic centers and an array of four equatorial H-bond donors pointing directly towards the center of the cavity. This precisely defined supramolecular environment is complementary to the geometry of classic octahedral complexes [M(XY)6 ] with six diatomic ligands. Very strong binding of [Pt(CN)6 ](2-) to the cage was observed, with the structure of the host-guest complex {[Pt(CN)6 ]@Pd2 L4 } supported by NMR spectroscopy, MS, and X-ray data. The self-assembled shell imprints its geometry on the encapsulated guest, and desymmetrization of the octahedral platinum species by the influence of the D4h -symmetric second coordination sphere was evidenced by IR spectroscopy. [Fe(CN)6 ](3-) and square-planar [Pt(CN)4 ](2-) were strongly bound. Smaller octahedral anions such as [SiF6 ](2-) , neutral carbonyl complexes ([M(CO)6 ]; M=Cr, Mo, W) and the linear [Ag(CN)2 ](-) anion were only weakly bound, showing that both size and charge match are key factors for high-affinity binding. PMID:27245358

  14. Octahedral molecular sieve sorbents and catalysts

    DOEpatents

    Li, Liyu [Richland, WA; King, David L [Richland, WA

    2010-04-20

    Octahedral molecular sieve sorbents and catalysts are disclosed, including silver hollandite and cryptomelane. These materials can be used, for example, to catalyze the oxidation of CO.sub.x (e.g., CO), NO.sub.x (e.g., NO), hydrocarbons (e.g., C.sub.3H.sub.6) and/or sulfur-containing compounds. The disclosed materials also may be used to catalyze other reactions, such as the reduction of NO.sub.2. In some cases, the disclosed materials are capable of sorbing certain products from the reactions they catalyze. Silver hollandite, in particular, can be used to remove a substantial portion of certain sulfur-containing compounds from a gas or liquid by catalysis and/or sorption. The gas or liquid can be, for example, natural gas or a liquid hydrocarbon.

  15. Octahedral tilting in the tungsten bronzes.

    PubMed

    Whittle, Thomas A; Schmid, Siegbert; Howard, Christopher J

    2015-06-01

    Possibilities for 'simple' octahedral tilting in the hexagonal and tetragonal tungsten bronzes (HTB and TTB) have been examined, making use of group theory as implemented in the computer program ISOTROPY. For HTB, there is one obvious tilting pattern, leading to a structure in space group P6₃/mmc. This differs from the space group P6₃/mcm frequently quoted from X-ray studies – these studies have in effect detected only displacements of the W cations from the centres of the WO6 octahedra. The correct space group, taking account of both W ion displacement and the octahedral tilting, is P6₃22 – structures in this space group and matching this description have been reported. A second acceptable tilting pattern has been found, leading to a structure in P6/mmm but on a larger '2 × 2 × 2' unit cell – however, no observations of this structure have been reported. For TTB, a search at the special points of the Brillouin zones revealed only one comparable tilting pattern, in a structure with space-group symmetry I4/m on a '2(1/2) × 2(1/2) by 2' unit cell. Given several literature reports of larger unit cells for TTB, we conducted a limited search along the lines of symmetry and found structures with acceptable tilt patterns in Bbmm on a '2(1/2)2 × 2(1/2) × 2' unit cell. A non-centrosymmetric version has been reported in niobates, in Bbm2 on the same unit cell. PMID:26027010

  16. Large tunneling magnetoresistance in octahedral Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Mitra, Arijit; Barick, Barun; Mohapatra, Jeotikanta; Sharma, H.; Meena, S. S.; Aslam, M.

    2016-05-01

    We have observed large tunneling Magnetoresistance (TMR) in amine functionalized octahedral nanoparticle assemblies. Amine monolayer on the surface of nanoparticles acts as an insulating barrier between the semimetal Fe3O4 nanoparticles and provides multiple tunnel junctions where inter-granular tunneling is plausible. The tunneling magnetoresistance recorded at room temperature is 38% which increases to 69% at 180 K. When the temperature drops below 150 K, coulomb staircase is observed in the current versus voltage characteristics as the charging energy exceeds the thermal energy. A similar study is also carried out with spherical nanoparticles. A 24% TMR is recorded at room temperature which increases to 41% at 180 K for spherical particles. Mössbauer spectra reveal better stoichiometry for octahedral particles which is attainable due to lesser surface disorder and strong amine coupling at the <111> facets of octahedral Fe3O4 nanoparticles. Less stoichiometric defect in octahedral nanoparticles leads to a higher value of spin polarization and therefore larger TMR in octahedral nanoparticles.

  17. Octahedral spherical hohlraum and its laser arrangement for inertial fusion

    SciTech Connect

    Lan, Ke; He, Xian-Tu; Liu, Jie; Zheng, Wudi; Lai, Dongxian

    2014-05-15

    A recent publication [K. Lan et al., Phys. Plasmas 21, 010704 (2014)] proposed a spherical hohlraum with six laser entrance holes of octahedral symmetry at a specific hohlraum-to-capsule radius ratio of 5.14 for inertial fusion study, which has robust high symmetry during the capsule implosion and superiority on low backscatter without supplementary technology. This paper extends the previous one by studying the laser arrangement and constraints of octahedral hohlraum in detail. As a result, it has serious beam crossing at θ{sub L}≤45°, and θ{sub L}=50° to 60° is proposed as the optimum candidate range for the golden octahedral hohlraum, here θ{sub L} is the opening angle that the laser quad beam makes with the Laser Entrance Hole (LEH) normal direction. In addition, the design of the LEH azimuthal angle should avoid laser spot overlapping on hohlraum wall and laser beam transferring outside hohlraum from a neighbor LEH. The octahedral hohlraums are flexible and can be applicable to diverse inertial fusion drive approaches. This paper also applies the octahedral hohlraum to the recent proposed hybrid indirect-direct drive approach.

  18. Specific features of technetium mononuclear octahedral oxo complexes: A review

    SciTech Connect

    Sergienko, V. S. Churakov, A. V.

    2013-01-15

    The specific structural features of technetium mononuclear octahedral oxo complexes have been considered. The structures of d{sup 2}-Tc(V) mono- and dioxo complexes, d{sup 2}-Tc(V) pseudodioxo compounds (Tc(V) mono-oxo complexes with an additional multiply bonded RO{sup -} ligand), and d{sup 0}-Tc(VII) trioxo compounds are analyzed.

  19. Charge transfer transitions within the octahedral uranate group

    NASA Astrophysics Data System (ADS)

    Bleijenberg, K. C.

    1980-07-01

    In this paper the excitation spectra of the luminescence of the octahedral uranate group (UO6-6) are presented for various uranium-doped compounds. The excitation bands have been assigned using the results of theoretical and experimental investigations into the spectroscopic properties of uranium hexafluoride which is isoelectronic with the octahedral uranate group. Charge transfer transitions from orbitals having mainly oxygen 2p character to orbitals having mainly uranium 5f charcter have been observed in the region 2.24-˜4 eV. Charge transfer transitions to orbitals having mainly uranium 6d character have been observed at 4.4 eV and at 5.4 eV.

  20. Tungsten hexahydride (WH6) - An equilibrium geometry far from octahedral

    NASA Technical Reports Server (NTRS)

    Shen, Mingzuo; Schaefer, Henry F., III; Partridge, Harry

    1993-01-01

    Ab initio all-electron quantum mechanical studies of the tungsten hexahydride molecule WH6 are reported. The results suggest that the ground state of WH6 molecule is a closed-shell triangular prism belonging to the C(3v) point group, with a set of three hydrogens stacked on top of another set of three hydrogens. The octahedral structure lies 130 kcal/mole above the C(3v) ground state, a remarkable result in inorganic chemistry. Another C(3v) structure, with one set of three hydrogens staggered with respect to the other set, is energetically nearby.

  1. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS).

    SciTech Connect

    Rigali, Mark J.; Stewart, Thomas Austin

    2016-01-01

    Sandia National Laboratories has collaborated with Pleasanton Ridge Research Company (PRRC) to determine whether Sandia Octahedral Molecular Sieves (SOMS) and modified SOMs materials can be synthesized in large batches and produced in granular form. Sandia National Laboratories tested these SOMS and its variants based in aqueous chemical environments for an application-based evaluation of material performance as a sorbent. Testing focused primarily on determining the distribution coefficients (K d ) and chemical selectivity SOMs for alkali earth (Sr) ions in aqueous and dilute seawater solutions. In general the well-crystallized SOMS materials tested exhibited very high K d values (>10 6 ) in distilled water but K d values dropped substantially (%7E10 2 -10 3 ) in the dilute seawater (3%). However, one set of SOMS samples (1.4.2 and 1.4.6) provided by PRRC yielded relatively high K d (approaching 10 4 ) in dilute seawater. Further examination of these samples by scanning electron microscopy (SEM) revealed the presence of at least two phases at least one of which may be accounting for the improved K d values in dilute seawater. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS) January 20, 2016

  2. An electron transfer series of octahedral chromium complexes containing a redox non-innocent α-diimine ligand.

    PubMed

    Shen, Jingmei; Yap, Glenn P A; Barker, William E; Geiger, William E; Theopold, Klaus H

    2014-09-21

    An electron-transfer series of octahedral α-diimine complexes [((H)L(Cy))3Cr](n+)(BARF)n (n = 2, 1, 0) has been synthesized and crystallographically characterized. Cyclic voltammetry indicated additional formation of [((H)L(Cy))3Cr](3+). The molecular structures suggested that all redox processes were ligand-based. Magnetic moments were consistent with spin ground states of S = 0 for [(H)L(Cy)3Cr](0), S = 1/2 for [(H)L(Cy)3Cr](+1), and S = 1 for [(H)L(Cy)3Cr](+2). The experimental data is consistent with chromium maintaining the +III oxidation state throughout, while being coordinated by varying numbers of neutral diimines ((H)L(Cy)) and diimine radical anions ((H)L(Cy)˙(-)). PMID:25073609

  3. Octahedral boron nitride fullerenes formed by electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Golberg, D.; Bando, Y.; Stéphan, O.; Kurashima, K.

    1998-10-01

    Here we report on the formation of fullerenes with a reduced number of layers (typically ⩽3) in boron nitride (BN) which was subjected to in situ electron irradiation at 20 and 490 °C in a high resolution 300 kV transmission electron microscope (HRTEM). The BN fullerenes exhibited B/N stoichiometry of ˜1 as confirmed by electron energy loss spectroscopy using a 1 nm electron probe. The fullerene HRTEM images revealed rectangle-like shapes when viewed in specific projections, unlike the quasispherical carbon fullerene morphology. The octahedral BN fullerene model [O. Stéphan, Y. Bando, A. Loiseau, F. Willaime, N. Shramchenko, T. Tamiya, and T. Sato, Appl. Phys. A 67, 107 (1998)] is verified by the BN fullerene observations at different viewing angles.

  4. Carbon dioxide sorption in a nanoporous octahedral molecular sieve

    NASA Astrophysics Data System (ADS)

    Williamson, Izaak; Nelson, Eric B.; Li, Lan

    2015-08-01

    We have performed first-principles density functional theory calculations, incorporated with van der Waals interactions, to study CO2 adsorption and diffusion in nanoporous solid—OMS-2 (Octahedral Molecular Sieve). We found the charge, type, and mobility of a cation, accommodated in a porous OMS-2 material for structural stability, can affect not only the OMS-2 structural features but also CO2 sorption performance. This paper targets K+, Na+, and Ba2+ cations. First-principles energetics and electronic structure calculations indicate that Ba2+ has the strongest interaction with the OMS-2 porous surface due to valence electrons donation to the OMS-2 and molecular orbital hybridization. However, the Ba-doped OMS-2 has the worst CO2 uptake capacity. We also found evidence of sorption hysteresis in the K- and Na-doped OMS-2 materials.

  5. Effect of interfacial octahedral behavior in ultrathin manganite films.

    PubMed

    Moon, E J; Balachandran, P V; Kirby, B J; Keavney, D J; Sichel-Tissot, R J; Schlepütz, C M; Karapetrova, E; Cheng, X M; Rondinelli, J M; May, S J

    2014-05-14

    We investigate structural coupling of the MnO6 octahedra across a film/substrate interface and the resultant changes of the physical properties of ultrathin La2/3Sr1/3MnO3 (LSMO) films. In order to isolate the effect of interfacial MnO6 octahedral behavior from that of epitaxial strain, LSMO films are grown on substrates with different symmetry and similar lattice parameters. Ultrathin LSMO films show an increased magnetization and electrical conductivity on cubic (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) compared to those grown on orthorhombic NdGaO3 (NGO) substrates, an effect that subsides as the thickness of the films is increased. This study demonstrates that interfacial structural coupling can play a critical role in the functional properties of oxide heterostructures. PMID:24697503

  6. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  7. Anions in Cometary Comae

    NASA Technical Reports Server (NTRS)

    Charnley, Steven B.

    2011-01-01

    The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

  8. Structural evolution of small ruthenium cluster anions

    SciTech Connect

    Waldt, Eugen; Hehn, Anna-Sophia; Ahlrichs, Reinhart; Kappes, Manfred M.; Schooss, Detlef

    2015-01-14

    The structures of ruthenium cluster anions have been investigated using a combination of trapped ion electron diffraction and density functional theory computations in the size range from eight to twenty atoms. In this size range, three different structural motifs are found: Ru{sub 8}{sup −}–Ru{sub 12}{sup −} have simple cubic structures, Ru{sub 13}{sup −}–Ru{sub 16}{sup −} form double layered hexagonal structures, and larger clusters form close packed motifs. For Ru{sub 17}{sup −}, we find hexagonal close packed stacking, whereas octahedral structures occur for Ru{sub 18}{sup −}–Ru{sub 20}{sup −}. Our calculations also predict simple cubic structures for the smaller clusters Ru{sub 4}{sup −}–Ru{sub 7}{sup −}, which were not accessible to electron diffraction measurements.

  9. Evidences of Electron Transfer of a Fullerene Anion Radical (C60(•-)) Prepared under Visible-Light Illumination at a Nitrobenzene/Water Interface.

    PubMed

    Watariguchi, Shigeru; Fujimori, Masaaki; Atsumi, Kosuke; Hinoue, Teruo

    2016-01-01

    Fullerene (C60) changes to its anion radical (C60(•-)) in the presence of tetraphenylborate (TPB(-)) under visible-light illumination. Using voltammetry at a liquid/liquid interface, we investigated the electron transfer (ET) between C60(•-), previously prepared based on this photochemical reaction, in a nitrobenzene (NB) solution and hexacyanoferrate(III) ([Fe(CN)6](3-)) or proton in an aqueous solution. We suggest that positive currents appearing in voltammograms are due to the ion transfer of decomposition products of TPB(-) and ET from C60(•-) in the NB phase to [Fe(CN)6](3-), or proton in the W phase. (11)B NMR revealed that TPB(-) decomposed to some borate anions during the photochemical reaction of fullerene. Furthermore, when the NB solution containing C60(•-) was mixed with an aqueous solution containing [Fe(CN)6](3-) or proton, absorption bands of C60(•-) in a visible/near infrared absorption spectrum disappeared. This disappearance supports the ET across the NB/W interface. This finding is significant as both an example of ET at a liquid/liquid interface including photochemical reactions and the photochemistry of C60. PMID:27063721

  10. Controlling Octahedral Rotations in a Perovskite via Strain Doping.

    PubMed

    Herklotz, A; Wong, A T; Meyer, T; Biegalski, M D; Lee, H N; Ward, T Z

    2016-01-01

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film can be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO3 films coherently grown on SrTiO3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. These results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials. PMID:27215804

  11. N-rich fluid inclusions in octahedrally-grown diamond

    NASA Astrophysics Data System (ADS)

    Smith, Evan M.; Kopylova, Maya G.; Frezzotti, Maria Luce; Afanasiev, Valentin P.

    2014-05-01

    Nitrogen is generally considered a trace component in the Earth's mantle. Mantle volatiles sampled from mid-ocean ridge basalts or preserved as fluid inclusions in xenoliths are dominated by CO2, with only traces of nitrogen. Here we describe CO2-N2 fluid inclusions with 40 mol% N2 and silicate melt inclusions with ∼0.1 wt% dissolved N2 in mantle-derived diamonds from 3 different cratons. The diamonds are octahedrally-grown, which is the most common growth habit and rarely reported to contain fluid inclusions. The inclusions have C/N ratios <1, more than two orders of magnitude below typical mantle values. We propose that nitrogen can become concentrated to high degrees by processes related to diamond growth. A growing diamond does not readily consume the nitrogen available, suggesting incompatible behaviour. Residual N2 from this process represents a concentrated nitrogen flux escaping the convecting mantle. Hidden nitrogen fluxes like this might be significant in counteracting the large apparent net influx by subduction. Based on nitrogen and carbon speciation in the inclusions, we propose that redox processes control the liberation of nitrogen from the convecting mantle, by the oxidation of NH+4 in silicates to mobile N2, concurrent with a parallel oxidation process releasing carbonate melt from the asthenosphere. Isotopic fractionation accompanying changes in nitrogen speciation could help account for the apparent isotopic mismatch between surficial and mantle nitrogen.

  12. Controlling Octahedral Rotations in a Perovskite via Strain Doping

    PubMed Central

    Herklotz, A.; Wong, A. T.; Meyer, T.; Biegalski, M. D.; Lee, H. N.; Ward, T. Z.

    2016-01-01

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film can be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO3 films coherently grown on SrTiO3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. These results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials. PMID:27215804

  13. Controlling octahedral rotations in a perovskite via strain doping

    DOE PAGESBeta

    Herklotz, Andreas; Biegalski, Michael D.; Lee, Ho Nyung; Ward, Thomas Zac; Wong, A. T.; Meyer, T.

    2016-05-24

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film canmore » be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO3 films coherently grown on SrTiO3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. Lastly, these results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials.« less

  14. Controlling Octahedral Rotations in a Perovskite via Strain Doping

    NASA Astrophysics Data System (ADS)

    Herklotz, A.; Wong, A. T.; Meyer, T.; Biegalski, M. D.; Lee, H. N.; Ward, T. Z.

    2016-05-01

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film can be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO3 films coherently grown on SrTiO3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. These results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials.

  15. Regenerable magnetic octahedral layer catalyst for gaseous UPOPs removal.

    PubMed

    Yang, Yang; Huang, Jun; Zhang, Shuzhen; Wang, Siwen; Deng, Shubo; Wang, Bin; Yu, Gang

    2014-09-15

    Hexachlorobenzene (HCBz), pentachlorobenzene (PeCBz), and polychlorinated biphenyls (PCBs) are a group of unintentionally produced persistent organic pollutants (UPOPs) emitted from waste combustion and industrial processes. In this study, Fe3O4 fabricated manganese oxide octahedral layer (Fe/OL) and Cu-doped OL (Fe/Cu-OL) catalysts were synthesized and they exhibited high activity for catalytic destruction of UPOPs, but also suffered from deactivation. The deactivation of Fe/Cu-OL can be assigned to the formation of surface MnClx species. As for Fe/OL, Mn sites are protected from chlorination by tunnel K(+), and the deactivation is ascribed to the blocking of active sites by KCl crystal. Simple water washing can completely regenerate the spent catalysts due to the dissolution of surface MnClx or KCl. With the advantage of magnetism, catalysts can be easily separated from water. Although Fe/Cu-OL has higher catalytic activity than Fe/OL, it is less stable in water washing due to the collapse of Mn framework structure. Considering the protection role of K(+), the spent Fe/Cu-OL was regenerated by KNO3 solution to induce additional K(+) onto the structure. In this way, the activity can be recovered while the unwanted dissolution of Mn is avoided. PMID:25218261

  16. Octahedral tilting, monoclinic phase and the phase diagram of PZT

    NASA Astrophysics Data System (ADS)

    Cordero, F.; Trequattrini, F.; Craciun, F.; Galassi, C.

    2011-10-01

    Anelastic and dielectric spectroscopy measurements on PbZr1-xTixO3 (PZT) close to the morphotropic (MPB) and antiferroelectric boundaries provide new insight into some controversial aspects of its phase diagram. No evidence is found of a border separating monoclinic (M) from rhombohedral (R) phases, in agreement with recent structural studies supporting a coexistence of the two phases over a broad composition range x < 0.5, with the fraction of M increasing toward the MPB. It is also discussed why the observed maximum of elastic compliance appears to be due to a rotational instability of the polarization linearly coupled to shear strain. Therefore it cannot be explained by extrinsic softening from finely twinned R phase alone, but indicates the presence also of M phase, not necessarily homogeneous. A new diffuse transition is found within the ferroelectric phase near x ˜ 0.1, at a temperature TIT higher than the well established boundary TT to the phase with tilted octahedra. It is proposed that around TIT the octahedra start rotating in a disordered manner and finally become ordered below TT. In this interpretation, the onset temperature for octahedral tilting monotonically increases up to the antiferroelectric transition of PbZrO3, and the depression of TT(x) below x = 0.18 would be a consequence of the partial relief of the mismatch between the average cation radii with the initial stage of tilting below TIT.

  17. Anion solvation in alcohols

    SciTech Connect

    Jonah, C.D.; Xujia, Zhang; Lin, Yi

    1996-03-01

    Anion solvation is measured in alcohols using pump-probe pulse radiolysis and the activation energy of solvation is determined. Solvation of an anion appears to be different than excited state solvation. The continuum dielectric model does not appear to explain the results.

  18. Interfacial Octahedral Rotation Mismatch Control of the Symmetry and Properties of SrRuO3.

    PubMed

    Gao, Ran; Dong, Yongqi; Xu, Han; Zhou, Hua; Yuan, Yakun; Gopalan, Venkatraman; Gao, Chen; Fong, Dillon D; Chen, Zuhuang; Luo, Zhenlin; Martin, Lane W

    2016-06-15

    Epitaxial strain can be used to tune the properties of complex oxides with perovskite structure. Beyond just lattice mismatch, the use of octahedral rotation mismatch at heterointerfaces could also provide an effective route to manipulate material properties. Here, we examine the evolution of the structural motif (i.e., lattice parameters, symmetry, and octahedral rotations) of SrRuO3 films grown on substrates engineered to have the same lattice parameters, but different octahedral rotations. SrRuO3 films grown on SrTiO3 (001) (no octahedral rotations) and GdScO3-buffered SrTiO3 (001) (with octahedral rotations) substrates are found to exhibit monoclinic and tetragonal symmetry, respectively. Electrical transport and magnetic measurements reveal that the tetragonal films exhibit higher resistivity, lower magnetic Curie temperatures, and more isotropic magnetism as compared to those with monoclinic structure. Synchrotron-based quantification of the octahedral rotation network reveals that the tilting pattern in both film variants is the same (albeit with slightly different magnitudes of in-plane rotation angles). The abnormal rotation pattern observed in tetragonal SrRuO3 indicates a possible decoupling between the internal octahedral rotation and lattice symmetry, which could provide new opportunities to engineer thin-film structure and properties. PMID:27219026

  19. Anion-π Enzymes

    PubMed Central

    2016-01-01

    In this report, we introduce artificial enzymes that operate with anion-π interactions, an interaction that is essentially new to nature. The possibility to stabilize anionic intermediates and transition states on an π-acidic surface has been recently demonstrated, using the addition of malonate half thioesters to enolate acceptors as a biologically relevant example. The best chiral anion-π catalysts operate with an addition/decarboxylation ratio of 4:1, but without any stereoselectivity. To catalyze this important but intrinsically disfavored reaction stereoselectively, a series of anion-π catalysts was equipped with biotin and screened against a collection of streptavidin mutants. With the best hit, the S112Y mutant, the reaction occurred with 95% ee and complete suppression of the intrinsically favored side product from decarboxylation. This performance of anion-π enzymes rivals, if not exceeds, that of the best conventional organocatalysts. Inhibition of the S112Y mutant by nitrate but not by bulky anions supports that contributions from anion-π interactions exist and matter, also within proteins. In agreement with docking results, K121 is shown to be essential, presumably to lower the pKa of the tertiary amine catalyst to operate at the optimum pH around 3, that is below the pKa of the substrate. Most importantly, increasing enantioselectivity with different mutants always coincides with increasing rates and conversion, i.e., selective transition-state stabilization. PMID:27413782

  20. Anion-π Enzymes.

    PubMed

    Cotelle, Yoann; Lebrun, Vincent; Sakai, Naomi; Ward, Thomas R; Matile, Stefan

    2016-06-22

    In this report, we introduce artificial enzymes that operate with anion-π interactions, an interaction that is essentially new to nature. The possibility to stabilize anionic intermediates and transition states on an π-acidic surface has been recently demonstrated, using the addition of malonate half thioesters to enolate acceptors as a biologically relevant example. The best chiral anion-π catalysts operate with an addition/decarboxylation ratio of 4:1, but without any stereoselectivity. To catalyze this important but intrinsically disfavored reaction stereoselectively, a series of anion-π catalysts was equipped with biotin and screened against a collection of streptavidin mutants. With the best hit, the S112Y mutant, the reaction occurred with 95% ee and complete suppression of the intrinsically favored side product from decarboxylation. This performance of anion-π enzymes rivals, if not exceeds, that of the best conventional organocatalysts. Inhibition of the S112Y mutant by nitrate but not by bulky anions supports that contributions from anion-π interactions exist and matter, also within proteins. In agreement with docking results, K121 is shown to be essential, presumably to lower the pK a of the tertiary amine catalyst to operate at the optimum pH around 3, that is below the pK a of the substrate. Most importantly, increasing enantioselectivity with different mutants always coincides with increasing rates and conversion, i.e., selective transition-state stabilization. PMID:27413782

  1. Spin propensities of octahedral complexes from density functional theory.

    PubMed

    Mortensen, Sara R; Kepp, Kasper P

    2015-04-30

    The fundamental balance between high- and low-spin states of transition metal systems depends on both the metal ion and the ligands surrounding it, as often visualized by the spectrochemical series. Most density functionals do not reproduce this balance, and real spin state propensities depend on orbital pairing and vibrational entropies absent in the spectrochemical series. Thus, we systematically computed the tendency toward high or low spin of "text-book" octahedral metal complexes versus ligand and metal type, using eight density functionals. Dispersion effects were generally <5 kJ/mol, favoring low-spin states. Zero-point energies favored high-spin states up to 33 kJ/mol for strong ligands, but down to a few kilojoules per mole for weak ligands. Vibrational entropy also favored high-spin states up to 40 kJ/mol, most for strong ligands. Jahn-Teller distortion in Co(II) low-spin states, particularly stable d(6) low-spin states, and entropy corrections were consistent with experiment. Entropy and zero-point energy corrections were markedly lower for Co(II) and Mn(III), viz., the differential ligand field stabilization energy, and can only be ignored for weak ligands. The data enable simple assessment of spin state propensities versus ligand and metal type and reveal, e.g., that CN(-) is consistently weaker than CO for M(II) but stronger than CO for M(III) and SCN(-) and NCS(-) change order in M(II) versus M(III) complexes. Contrary to expectation based on the spectrochemical series, Cl(-) and Br(-) are very close in spin state propensity because the pairing penalty for low spin is smaller in Br(-). Thus, for the M(II) complexes, we find a consensus order of Br(-) ∼ Cl(-) < H2O < SCN(-) < NCS(-) ∼ NH3 < CN(-) < CO, whereas for the M(III) complexes, an approximate order is Br(-) ∼ Cl(-) < H2O ∼ NCS(-) ∼ SCN(-)< NH3 < CO < CN(-). PMID:25856244

  2. Intrinsic anion oxidation potentials.

    PubMed

    Johansson, Patrik

    2006-11-01

    Anions of lithium battery salts have been investigated by electronic structure calculations with the objective to find a computational measure to correlate with the observed (in)stability of nonaqueous lithium battery electrolytes vs oxidation often encountered in practice. Accurate prediction of intrinsic anion oxidation potentials is here made possible by computing the vertical free energy difference between anion and neutral radical (Delta Gv) and further strengthened by an empirical correction using only the anion volume as a parameter. The 6-311+G(2df,p) basis set, the VSXC functional, and the C-PCM SCRF algorithm were used. The Delta Gv calculations can be performed using any standard computational chemistry software. PMID:17078600

  3. Anion exchange polymer electrolytes

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  4. Truncated Hexa-Octahedral Magnetites: Biosignatures in Terrestrial Samples and Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2001-01-01

    We suggest that the observation of truncated hexa-octahedral magnetites in ALH84001 are both consistent with, and in the absence of terrestrial inorganic analogs, likely formed by biogenic processes. Additional information is contained in the original extended abstract.

  5. The diastereoselective synthesis of octahedral cationic iridium hydride complexes with a stereogenic metal centre.

    PubMed

    Humbert, Nicolas; Mazet, Clément

    2016-08-23

    We report herein the highly diastereoselective synthesis of octahedral cationic Ir(iii) hydride complexes with a stereogenic metal centre following various strategies. The configurational stability of these compounds has also been investigated. PMID:27498763

  6. Higher-rank discrete symmetries in the IBM I. Octahedral shapes: General Hamiltonian

    NASA Astrophysics Data System (ADS)

    Van Isacker, P.; Bouldjedri, A.; Zerguine, S.

    2015-06-01

    In the context of the interacting boson model with s, d and g bosons, the conditions for obtaining an intrinsic shape with octahedral symmetry are derived for a general Hamiltonian with up to two-body interactions.

  7. Au@TiO2 double-shelled octahedral nanocages with improved catalytic properties.

    PubMed

    Lv, Xiaoming; Zhu, Yihua; Jiang, Hongliang; Zhong, Hua; Yang, Xiaoling; Li, Chunzhong

    2014-10-28

    A novel and facile strategy has been successfully developed to synthesize uniform gold@titanium dioxide octahedral nanocages (Au@TiO2), which have a well-defined double-shelled structure with Au as the internal shell and TiO2 as the external shell. The unique Au@TiO2 double-shelled octahedral nanocages were elaborately fabricated by a Cu2O-templated strategy combining with spatially confined galvanic replacement. The formation process of these delicate hierarchical octahedral architectures is discussed in detail. The catalytic performance of the Au@TiO2 double-shelled octahedral nanocages was investigated using the reduction of 4-nitrophenol as a model reaction. The mesoporous structure of both the Au and TiO2 shells provides direct access for the reactant molecules to diffuse and subsequently interact with the Au shell. This novel catalyst shows excellent and stable activity for the catalytic reduction of 4-nitrophenol, which can be recycled for ten successive cycles of the reaction with a conversion efficiency of more than 90%. The superior catalytic activity attributes to mesoporous double shells, enhanced synergistic effects between the Au and TiO2 shells and the unique properties of the octahedral structure. More importantly, the as-obtained Au@TiO2 double-shelled octahedral nanocages also show potential applications in solar cells, organocatalysis and water splitting. PMID:25166883

  8. Direct mapping of Li-enabled octahedral tilt ordering and associated strain in nanostructured perovskites

    NASA Astrophysics Data System (ADS)

    Zhu, Ye; Withers, Ray L.; Bourgeois, Laure; Dwyer, Christian; Etheridge, Joanne

    2015-11-01

    Self-assembled nanostructures with periodic phase separation hold great promise for creating two- and three-dimensional superlattices with extraordinary physical properties. Understanding the mechanism(s) driving the formation of such superlattices demands an understanding of their underlying atomic structure. However, the nanoscale structural fluctuations intrinsic to these superlattices pose a new challenge for structure determination methods. Here we develop an optimized atomic-level imaging condition to measure TiO6 octahedral tilt angles, unit-cell-by-unit-cell, in perovskite-based Li0.5-3xNd0.5+xTiO3, and thereby determine the mathematical formula governing this nanoscale superstructure. We obtain a direct real-space correlation of the octahedral tilt modulation with the superstructure geometry and lattice-parameter variations. This reveals a composition-dependent, self-ordered octahedral superlattice. Amazingly, we observe a reversible annihilation/reconstruction of the octahedral superlattice correlated with the delithiation/lithiation process in this promising Li-ion conductor. This approach to quantify local octahedral tilt and correlate it with strain can be applied to characterize complex octahedral behaviours in other advanced oxide systems.

  9. Anion-π catalysis.

    PubMed

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  10. Halogen bonding anion recognition.

    PubMed

    Brown, Asha; Beer, Paul D

    2016-07-01

    A halogen bond is an attractive non-covalent interaction between an electrophilic region in a covalently bonded halogen atom and a Lewis base. While these interactions have long been exploited as a tool in crystal engineering their powerful ability to direct supramolecular self-assembly and molecular recognition processes in solution has, until recently, been overlooked. During the last decade however an ever-increasing number of studies on solution-phase halogen-bond-mediated anion recognition processes has emerged. This Feature Article summarises advancements which have been made thus far in this rapidly developing research area. We survey the use of iodoperfluoroarene, haloimidazolium and halotriazole/triazolium halogen-bond-donor motifs in anion receptor design, before providing an account of our research into the application of mechanically interlocked rotaxane and catenane frameworks as halogen bonding anion host systems. PMID:27273600

  11. Vanadogermanate cluster anions.

    PubMed

    Whitfield, T; Wang, X; Jacobson, A J

    2003-06-16

    Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the (V(18)O(42)) Keggin cluster shell by substitution of V=O(2+) "caps" by Ge(2)O(OH)(2)(4+) species. In Cs(8)[Ge(4)V(16)O(42)(OH)(4)].4.7H(2)O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, beta = 101.376(1) degrees ) and (pipH(2))(4)(pipH)(4)[Ge(8)V(14)O(50).(H(2)O)] (pip = C(4)N(2)H(10)), 2 (tetragonal, space group P4(2)/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO(2+) caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K(5)H(8)Ge(8)V(12)SO(52).10H(2)O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO(2+) caps are replaced by Ge(2)O(OH)(2)(4+) species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V(18)(-)(n)()As(2)(n)()O(42)(X)](m)(-) (X = SO(3), SO(4), Cl; n = 3, 4) previously reported. PMID:12793808

  12. Hexacyanoferrate-intercalated nickel zinc hydroxy double salts

    NASA Astrophysics Data System (ADS)

    Rajamathi, Jacqueline T.; Raviraj, N. H.; Ahmed, Mohammed F.; Rajamathi, Michael

    2009-12-01

    When anionic clay like nickel zinc hydroxyacetate was subjected to anion exchange reaction with either hexacyanoferrate(II) or hexacyanoferrate(III) ions, the complex anion intercalation was accompanied by auto redox reactions. In both the cases a mixture of hexacyanoferrate(II) and hexacyanoferrate(III) ions was found to be intercalated in the anionic clay. The mixed anion intercalated anionic clays could be oxidized by hydrogen peroxide to get pure hexacyanoferrate(III) intercalated anionic clay. Thermal decomposition of the intercalated anionic clays yields mixed oxides of Ni, Zn and Fe.

  13. ION CHROMATOGRAPHY OF ANIONS

    EPA Science Inventory

    A Dionex Model 10 Ion Chromatograph was evaluated for the measurement of anionic species in water. The theoretical effect of hydrogen ion activity (pH) on the elution time of phosphate and arsenate was tested and empirical selectivity coefficients were determined for the major pr...

  14. Oxygen octahedral distortions in LaMO3/SrTiO3 superlattices

    DOE PAGESBeta

    Sanchez-Santolino, Gabriel; Cabero, Mariona; Varela, Maria; Garcia-Barriocanal, Javier; Leon, Carlos; Pennycook, Stephen J.; Santamaria, Jacobo

    2014-04-24

    Here we study the interfaces between the Mott insulator LaMnO3 (LMO) and the band insulator SrTiO3 (STO) in epitaxially grown superlattices with different thickness ratios and different transport and magnetic behaviors. Using atomic resolution electron energy-loss spectrum imaging, we analyze simultaneously the structural and chemical properties of these interfaces. We find changes in the oxygen octahedral tilts within the LaMnO3 layers when the thickness ratio between the manganite and the titanate layers is varied. Superlattices with thick LMO and ultrathin STO layers present unexpected octahedral tilts in the STO, along with a small amount of oxygen vacancies. On the othermore » hand, thick STO layers exhibit undistorted octahedra while the LMO layers present reduced O octahedral distortions near the interfaces. In conclusion, these findings will be discussed in view of the transport and magnetic differences found in previous studies.« less

  15. Hydrothermal fabrication of octahedral-shaped Fe3O4 nanoparticles and their magnetorheological response

    NASA Astrophysics Data System (ADS)

    Jung, H. S.; Choi, H. J.

    2015-05-01

    Octahedral-shaped Fe3O4 nanoparticles were synthesized in the presence of 1,3-diaminopropane using a hydrothermal method and assessed as a potential magnetorheological (MR) material. Their morphology, crystal structure, and magnetic properties were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. The MR characteristics of the octahedral-shaped, Fe3O4 nanoparticle-based MR particles when dispersed in silicone oil with a 10 vol. % particle concentration were examined using a rotational rheometer under an external magnetic field. The resulting MR fluids exhibited a Bingham-like behavior with a distinctive yield stress from their flow curves.

  16. Simple Treatment of the Symmetry Labels for the d-d States of Octahedral Complexes

    NASA Astrophysics Data System (ADS)

    Smith, Derek W.

    1996-06-01

    The derivation of the symmetry labels for d-d states of cubic (octahedral and tetrahedral) complexes of d block elements is not readily accessible to students having an elementary knowledge of group theory. This paper shows how the d-d states of octahedral d^n complexes (in the point group O) can be worked out by descent in symmetry to D2, using the relevant character tables and multiplication tables for their irreducible representations. A letter from Derek W. Smith in our April 2000 issue addresses the above.

  17. Oxygen octahedral rotation mapping in calcium titanate/strontium titanate superlattices by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Stone, Greg; Ciston, Jim; Haislmaier, Ryan; Vanleeuwen, Brian; Alem, Nasim; Schlom, Darrell; Gopalan, Venkatraman

    2014-03-01

    We report the investigation of oxygen octahedral rotation mapping in calcium titanate/barium titanate superlattices epitaxially grown on LSAT (001) with transmission electron microscopy. Analysis of the images shows induced antiphase rotations of the oxygen octahedral the strontium titanate layers that is absent in the bulk material at room temperature. These rotations play a key role in breaking the centrosymmetry of the material leading to polar properties as seen by second harmonic generation. We also map the local position of the cations to provide a complete picture of any relative local displacements and the oxygen-cation-oxygen bond angles.

  18. Calculated optical and magnetic properties of hexafluorouranate (V) anion: UF6-

    NASA Astrophysics Data System (ADS)

    Arratia-Pérez, Ramiro; Hernandez-Acevedo, Lucia; Malli, Gulzari L.

    2004-10-01

    Our ab initio all-electron Dirac-Fock and the corresponding nonrelativistic limit calculations performed at four U-F bond distances yield for octahedral UF6- the optimized U-F bond distance of 2.091 and 2.088 Å, respectively. We have also performed Dirac scattered wave calculations at the optimized U-F bond distances using the first-order pertubational procedure to obtain the Zeeman and hyperfine magnetic tensors for the octahedral anion UF6-. The calculated isotropic Zeeman tensor of Δg=-2.87 is in fairly good agreement with the value of Δg=-2.78±0.10 obtained in electron spin resonance experiments on the H3O+UF6- adduct and the unpaired electron-spin spends ˜2.5% of its time on the fluorine 2p3/2 spinors. The calculated relativistic transition energies of the near-IR and visible absorption bands are also in good agreement with the experimental results. The octahedral uranium hexafluoride anion has a simple crystal field f1 configuration; however, relativistic four-component wave functions are necessary to interpret correctly the available magnetic data, while a relativistic treatment taking into account double group symmetrized basis functions should suffice for the interpretation of the optical data.

  19. Calculated optical and magnetic properties of hexafluorouranate (V) anion: UF- 6.

    PubMed

    Arratia-Pérez, Ramiro; Hernandez-Acevedo, Lucia; Malli, Gulzari L

    2004-10-22

    Our ab initio all-electron Dirac-Fock and the corresponding nonrelativistic limit calculations performed at four U-F bond distances yield for octahedral UF(6) (-) the optimized U-F bond distance of 2.091 and 2.088 A, respectively. We have also performed Dirac scattered wave calculations at the optimized U-F bond distances using the first-order pertubational procedure to obtain the Zeeman and hyperfine magnetic tensors for the octahedral anion UF(6) (-). The calculated isotropic Zeeman tensor of Deltag=-2.87 is in fairly good agreement with the value of Deltag=-2.78+/-0.10 obtained in electron spin resonance experiments on the H(3)O(+)UF(6) (-) adduct and the unpaired electron-spin spends approximately 2.5% of its time on the fluorine 2p(3/2) spinors. The calculated relativistic transition energies of the near-IR and visible absorption bands are also in good agreement with the experimental results. The octahedral uranium hexafluoride anion has a simple crystal field f(1) configuration; however, relativistic four-component wave functions are necessary to interpret correctly the available magnetic data, while a relativistic treatment taking into account double group symmetrized basis functions should suffice for the interpretation of the optical data. PMID:15485235

  20. Studies of oxide anions

    NASA Astrophysics Data System (ADS)

    Castleman, A. W., Jr.

    1991-06-01

    Several metal and metal oxide anion sources were used to investigate the formation and reactivity of species of relevance to the AFGL program. A new class of reactions were identified between anions of the form H(x)M(y)O(z) for several metals including M=W, Ta, Ti, Mo, and HCl. The reactions have analogy to acid-base reactions. In another series of experiments, reactions of Al(n)(-), and these clusters bound with V and or Nb, with O2 were investigated. It was found that the Jellium model, though by no means a compendious concept, provides a good guide to the electronic structure of clusters and their general patterns of reactivity.

  1. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  2. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-01-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  3. Anion permselective membrane

    NASA Astrophysics Data System (ADS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-07-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  4. Anion-directed assembly of a non-interpenetrated square-grid metal-organic framework with nanoscale porosity.

    PubMed

    Mitra, Atanu; Hubley, Christian T; Panda, Dillip K; Clark, Ronald J; Saha, Sourav

    2013-07-28

    A non-interpenetrated square grid metal-organic framework (MOF) comprised of octahedral Zn(II) ions and linear N,N'-di(4-pyridyl)-1,4,5,8-naphthalenediimide (DPNDI) ligands was formed in the presence of noncoordinating perchlorate counterions that occupied the cavities of the porous network by forming CH···anion hydrogen bonds with DPNDI ligands, whereas a linear coordination polymer was obtained when Zn(II)-coordinated nitrate ions were present as counterions. PMID:23775140

  5. Atomic level observation of octahedral distortions at the perovskite oxide heterointerface

    PubMed Central

    Aso, Ryotaro; Kan, Daisuke; Shimakawa, Yuichi; Kurata, Hiroki

    2013-01-01

    For perovskite oxides, ABO3, slight octahedral distortions have close links to functional properties. While perovskite oxide heterostructures offer a good platform for controlling functionalities, atomistic understanding of octahedral distortion at the interface has been a challenge as it requires precise measurements of the oxygen atomic positions. Here we demonstrate an approach to clarify distortions at an atomic level using annular bright-field imaging in aberration-corrected scanning transmission electron microscopy, which provides precise mappings of cation and oxygen atomic positions from distortion-minimized images. This technique revealed significant distortions of RuO6 and ScO6 octahedra at the heterointerface between a SrRuO3 film and a GdScO3 substrate. We also found that structural mismatch was relieved within only four unit cells near the interface by shifting the oxygen atomic positions to accommodate octahedral tilt angle mismatch. The present results underscore the critical role of the oxygen atom in the octahedral connectivity at the perovskite oxide heterointerface. PMID:23856752

  6. Strain Engineering of Octahedral Rotations and Physical Properties of SrRuO3 Films

    PubMed Central

    Lu, Wenlai; Song, Wendong; Yang, Ping; Ding, Jun; Chow, Gan Moog; Chen, Jingsheng

    2015-01-01

    Strain engineering is an effective way to modify functional properties of thin films. Recently, the importance of octahedral rotations in pervoskite films has been recognized in discovering and designing new functional phases. Octahedral behavior of SrRuO3 film as a popular electrode in heterostructured devices is of particular interest for its probable interfacial coupling of octahedra with the functional overlayers. Here we report the strain engineering of octahedral rotations and physical properties that has been achieved in SrRuO3 films in response to the substrate-induced misfit strains of almost the same amplitude but of opposite signs. It shows that the compressively strained film on NdGaO3 substrate displays a rotation pattern of a tetragonal phase whilst the tensilely strained film on KTaO3 substrate has the rotation pattern of the bulk orthorhombic SrRuO3 phase. In addition, the compressively strained film displays a perpendicular magnetic anisotropy while the tensilely strained film has the magnetic easy axis lying in the film plane. The results show the prospect of strain engineered octahedral architecture in producing desired property and novel functionality in the class of perovskite material. PMID:26018639

  7. Research Update: Interface-engineered oxygen octahedral tilts in perovskite oxide heterostructures

    SciTech Connect

    Kan, Daisuke Aso, Ryotaro; Kurata, Hiroki; Shimakawa, Yuichi

    2015-06-01

    Interface engineering of structural distortions is a key for exploring the functional properties of oxide heterostructures and superlattices. In this paper, we report on our comprehensive investigations of oxygen octahedral distortions at the heterointerface between perovskite oxides SrRuO{sub 3} and BaTiO{sub 3} on GdScO{sub 3} substrates and of the influences of the interfacially engineered distortions on the magneto-transport properties of the SrRuO{sub 3} layer. Our state-of-the-art annular bright-field imaging in aberration-corrected scanning transmission electron microscopy revealed that the RuO{sub 6} octahedral distortions in the SrRuO{sub 3} layer have strong dependence on the stacking order of the SrRuO{sub 3} and BaTiO{sub 3} layers on the substrate. This can be attributed to the difference in the interfacial octahedral connections. We also found that the stacking order of the oxide layers has a strong impact on the magneto-transport properties, allowing for control of the magnetic anisotropy of the SrRuO{sub 3} layer through interface engineering. Our results demonstrate the significance of the interface engineering of the octahedral distortions on the structural and physical properties of perovskite oxides.

  8. Spatial Control Of Functional Properties Via Octahedral Modulations In Complex Oxide Superlattices

    SciTech Connect

    Moon, E. J.; Colby, Robert J.; Wang, Q.; Karapetrova, E.; Schleputz, C. M.; Fitzsimmons, M. R.; May, Steven J.

    2014-12-15

    The design of distortions and rotations of the corner-connected BO6 octahedra across interfaces has emerged as an exciting platform to control electronic or ferroic behavior in ABO3 perovskite heterostructures. Here, we investigate isovalent manganite superlattices, [(La0.7Sr0.3MnO3)n/(Eu0.7Sr0.3MnO3)n]×m, as a route to spatial control over electronic bandwidth and ferromagnetism through the creation of octahedral superstructures. Electron energy loss spectroscopy confirms a uniform Mn valence state throughout the superlattices. In contrast, the presence of modulations of the MnO6 octahedral rotations along the growth direction commensurate with the superlattice period is revealed by scanning transmission electron microscopy and x-ray diffraction. We show that the Curie temperatures of the constituent materials can be systematically engineered via the octahedral superstructures leading to a modulated magnetization in samples where the superlattice period is larger than the interfacial octahedral coupling length scale, while a single magnetic transition is observed in the short period superlattices.

  9. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1980-01-01

    The efforts on the synthesis of polymer anion redox membranes were mainly concentrated in two areas, membrane development and membrane fabrication. Membrane development covered the preparation and evaluation of experimental membranes systems with improved resistance stability and/or lower permeability. Membrane fabrication covered the laboratory scale production of prime candidate membranes in quantities of up to two hundred and sizes up to 18 inches x 18 inches (46 cm x 46 cm). These small (10 in x 11 in) and medium sized membranes were mainly for assembly into multicell units. Improvements in processing procedures and techniques for preparing such membrane sets lifted yields to over 90 percent.

  10. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1982-01-01

    The synthesis and fabrication of polymeric anion permselective membranes for redox systems are discussed. Variations of the prime candidate anion membrane formulation to achieve better resistance and/or lower permeability were explored. Processing parameters were evaluated to lower cost and fabricate larger sizes. The processing techniques to produce more membranes per batch were successfully integrated with the fabrication of larger membranes. Membranes of about 107 cm x 51 cm were made in excellent yield. Several measurements were made on the larger sample membranes. Among the data developed were water transport and transference numbers for these prime candidate membranes at 20 C. Other work done on this system included characterization of a number of specimens of candidate membranes which had been returned after service lives of up to sixteen months. Work with new polymer constituents, with new N.P.'s, catalysts and backing fabrics is discussed. Some work was also done to evaluate other proportions of the ingredients of the prime candidate system. The adoption of a flow selectivity test at elevated temperature was explored.

  11. Pseudorotation in fullerene anions

    NASA Astrophysics Data System (ADS)

    Dunn, Janette L.; Hands, Ian D.; Bates, Colin A.

    2007-07-01

    Jahn-Teller (JT) problems are often characterised by an adiabatic potential energy surface (APES) containing either a set of isoenergetic wells or a trough of equivalent-energy points, which may be warped by higher-order coupling terms or anisotropic effects. In all three cases, the JT effect will be dynamic. Either tunnelling between the wells or rotation (of a distortion) around the trough will restore the original symmetry of the system. This motion is referred to as pseudorotation. It should be possible to observe a JT system in a distorted geometry if measurements are made on a sufficiently short timescale. In various cubic systems, this timescale has been calculated to be the order of picoseconds. Such timescales are accessible using modern methods of ultrafast spectroscopy. Measurements of pseudorotation rates can lead to important information on the strength and nature of the JT coupling present. We will present analytical calculations that allow the rate of pseudorotation to be determined in terms of the vibronic coupling parameters. We will show how these results can be applied to E ⊗ e systems and then to the more complicated system applicable to C60- anions. This is of particular interest because of the high icosahedral symmetry of fullerene ions and also because of the many potential uses of materials containing these ions. We conclude by outlining experiments that should be capable of measuring pseudorotation in C 60 anions.

  12. Dynamic chemistry of anion recognition

    SciTech Connect

    Custelcean, Radu

    2012-01-01

    In the past 40 years, anion recognition by synthetic receptors has grown into a rich and vibrant research topic, developing into a distinct branch of Supramolecular Chemistry. Traditional anion receptors comprise organic scaffolds functionalized with complementary binding groups that are assembled by multistep organic synthesis. Recently, a new approach to anion receptors has emerged, in which the host is dynamically self-assembled in the presence of the anionic guest, via reversible bond formation between functional building units. While coordination bonds were initially employed for the self-assembly of the anion hosts, more recent studies demonstrated that reversible covalent bonds can serve the same purpose. In both cases, due to their labile connections, the molecular constituents have the ability to assemble, dissociate, and recombine continuously, thereby creating a dynamic combinatorial library (DCL) of receptors. The anionic guests, through specific molecular recognition, may then amplify (express) the formation of a particular structure among all possible combinations (real or virtual) by shifting the equilibria involved towards the most optimal receptor. This approach is not limited to solution self-assembly, but is equally applicable to crystallization, where the fittest anion-binding crystal may be selected. Finally, the pros and cons of employing dynamic combinatorial chemistry (DCC) vs molecular design for developing anion receptors, and the implications of both approaches to selective anion separations, will be discussed.

  13. Targeting Large Kinase Active Site with Rigid, Bulky Octahedral Ruthenium Complexes

    SciTech Connect

    Maksimoska, Jasna; Feng, Li; Harms, Klaus; Yi, Chunling; Kissil, Joseph; Marmorstein, Ronen; Meggers, Eric

    2009-09-02

    A strategy for targeting protein kinases with large ATP-binding sites by using bulky and rigid octahedral ruthenium complexes as structural scaffolds is presented. A highly potent and selective GSK3 and Pim1 half-sandwich complex NP309 was successfully converted into a PAK1 inhibitor by making use of the large octahedral compounds {Lambda}-FL172 and {Lambda}-FL411 in which the cyclopentadienyl moiety of NP309 is replaced by a chloride and sterically demanding diimine ligands. A 1.65 {angstrom}cocrystal structure of PAK1 with {Lambda}-FL172 reveals how the large coordination sphere of the ruthenium complex matches the size of the active site and serves as a yardstick to discriminate between otherwise closely related binding sites.

  14. Molecular orbital calculations of octahedral molybdenum cluster complexes with the DV-X{alpha} method

    SciTech Connect

    Imoto, Hideo; Saito, Taro; Adachi, Hirohiko

    1995-04-26

    Discrete variational-{Chi}{alpha} molecular orbital methods were applied to octahedral cluster complexes, [Mo{sub 6}X{sub 8}-(PH{sub 3}){sub 6}](X = S and Se). This structure is of interest due to its role in superconductivity of Chevrel plates. Level energies are discussed and factors contributing to their separations are categorized. Agreement with empirical XPS data is excellent.

  15. Towards the first theoretical scale of the trans effect in octahedral complexes.

    PubMed

    Guégan, Frédéric; Tognetti, Vincent; Joubert, Laurent; Chermette, Henry; Luneau, Dominique; Morell, Christophe

    2016-01-14

    In this paper, we show that trans effects in octahedral complexes can primarily be related to differences in the ability, for a given ligand, to cede electron density to the metal cation under the influence of the ligand at the trans position. Using tools from conceptual DFT or from related paradigms, we highlight these effects on a set of representative examples and further provide the basis for a computational trans effect scale. This quantification notably retrieves the experimental trans orienting series. PMID:26662022

  16. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Wentworth, S. J.; Vali, H.; Gibson, E. K. Jr; McKay, M. F.; Romanek, C. S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

  17. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling

    NASA Astrophysics Data System (ADS)

    Liao, Z.; Huijben, M.; Zhong, Z.; Gauquelin, N.; Macke, S.; Green, R. J.; van Aert, S.; Verbeeck, J.; van Tendeloo, G.; Held, K.; Sawatzky, G. A.; Koster, G.; Rijnders, G.

    2016-04-01

    Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network could allow the development of correlated oxide-based magnetic tunnelling junctions with non-collinear magnetization, with possible practical applications as miniaturized high-switching-speed magnetic random access memory (MRAM) devices. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic-scale design of the oxygen octahedral rotation.

  18. Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive biosignatures

    PubMed Central

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, Hojatollah; Gibson, Everett K.; McKay, Mary Fae; Romanek, Christopher S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924–930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe3O4) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  19. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures.

    PubMed

    Thomas-Keprta, K L; Clemett, S J; Bazylinski, D A; Kirschvink, J L; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; McKay, M F; Romanek, C S

    2001-02-27

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  20. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling

    NASA Astrophysics Data System (ADS)

    Huijben, Mark

    Ultimate miniaturization of magnetic random access memory (MRAM) devices is expected by the utilization of spin-transfer torques, because they present an efficient means to switch elements with a very high magnetic anisotropy. To overcome the low switching speed in current collinearly magnetized devices, new routes are being explored to realize magnetic tunnel junction stacks with non-collinear magnetization between two magnetic electrodes. Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network would provide a promising direction for non-collinear magnetization in correlated oxide magnetic tunneling junctions. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic scale design of the oxygen octahedral rotation. Membership Pending.

  1. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling.

    PubMed

    Liao, Z; Huijben, M; Zhong, Z; Gauquelin, N; Macke, S; Green, R J; Van Aert, S; Verbeeck, J; Van Tendeloo, G; Held, K; Sawatzky, G A; Koster, G; Rijnders, G

    2016-04-01

    Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network could allow the development of correlated oxide-based magnetic tunnelling junctions with non-collinear magnetization, with possible practical applications as miniaturized high-switching-speed magnetic random access memory (MRAM) devices. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic-scale design of the oxygen octahedral rotation. PMID:26950593

  2. Novel combustion method to prepare octahedral NiO nanoparticles and its photocatalytic activity

    SciTech Connect

    Jegatha Christy, A.; Umadevi, M.

    2013-10-15

    Graphical abstract: - Highlights: • NiO nanoparticles were synthesized by solution combustion method. • Prepared NiO nanoparticles are fcc structure. • Synthesized NiO nanoparticles are octahedral shape. • Shows good photocatalytic activity. - Abstract: Nickel oxide nanoparticles (NiO NPs) were synthesized by solution combustion method using glycine and citric acid as fuels. The X-ray diffraction (XRD) result confirms the face centered cubic (fcc) structure of NiO. The octahedral shape of NiO NPs was confirmed by field emission scanning electron microscope (FESEM) and high resolution transmission electron microscopy (HRTEM). It is possible to suggest that the organic fuel (citric acid/glycine) is responsible for the formation of the octahedral shape due to the easier complex formation. Photocatalytic activity of NiO NPs also evaluated and found that the prepared NiO NPs have high photocatalytic degradation. In the present study, the crystalline nature and shape of the NiO nanoparticles plays a vital role in determining the photocatalytic activity.

  3. Correlation between the Stereochemistry and Bioactivity in Octahedral Rhodium Prolinato Complexes.

    PubMed

    Rajaratnam, Rajathees; Martin, Elisabeth K; Dörr, Markus; Harms, Klaus; Casini, Angela; Meggers, Eric

    2015-08-17

    Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model. PMID:26251218

  4. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Alexander, S.; Hodgdon, R. B.

    1977-01-01

    The objective of NAS 3-20108 was the development and evaluation of improved anion selective membranes useful as efficient separators in a redox power storage cell system being constructed. The program was divided into three parts, (a) optimization of the selected candidate membrane systems, (b) investigation of alternative membrane/polymer systems, and (c) characterization of candidate membranes. The major synthesis effort was aimed at improving and optimizing as far as possible each candidate system with respect to three critical membrane properties essential for good redox cell performance. Substantial improvements were made in 5 candidate membrane systems. The critical synthesis variables of cross-link density, monomer ratio, and solvent composition were examined over a wide range. In addition, eight alternative polymer systems were investigated, two of which attained candidate status. Three other alternatives showed potential but required further research and development. Each candidate system was optimized for selectivity.

  5. Organic Anion Transporting Polypeptides

    PubMed Central

    Stieger, Bruno; Hagenbuch, Bruno

    2013-01-01

    Organic anion transporting polypeptides or OATPs are central transporters in the disposition of drugs and other xenobiotics. In addition, they mediate transport of a wide variety of endogenous substrates. The critical role of OATPs in drug disposition has spurred research both in academia and in the pharmaceutical industry. Translational aspects with clinical questions are the focus in academia, while the pharmaceutical industry tries to define and understand the role these transporters play in pharmacotherapy. The present overview summarizes our knowledge on the interaction of food constituents with OATPs, and on the OATP transport mechanisms. Further, it gives an update on the available information on the structure-function relationship of the OATPs, and finally, covers the transcriptional and posttranscriptional regulation of OATPs. PMID:24745984

  6. Synthesis of octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals and their structure-activity relationship for the decomposition of hydrazine in aqueous solution to hydrogen

    NASA Astrophysics Data System (ADS)

    Li, Chun; Wang, Tao; Chu, Wei; Wu, Ping; Tong, Dong Ge

    2016-03-01

    We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1-aminoheptadecane solution in the presence of tetraethylgermanium and borane trimethylamine complexes is proposed. A preliminary probing of the structure-activity dependence of the surface ``clean'' Rh2Ni nanocrystals supported on carbon towards hydrazine (N2H4) in aqueous solution dehydrogenation revealed that the higher the percentage of {111} facets, the higher is the activity and H2 selectivity of the nanocrystals. This result was attributed to the {111} facets not only introducing more basic sites, but also weakening the interaction between the produced adspecies (including H2 and NHx) and surface metal atoms in comparison with those of {100} facets. Furthermore, the as-prepared Rh2Ni nanooctahedra exhibited 100% H2 selectivity and high activity at room temperature for H2 generation via N2H4 decomposition. The activation energy of the Rh2Ni nanooctahedra was 41.6 +/- 1.2 kJ mol-1. The Rh2Ni nanooctahedra were stable catalysts for the hydrolytic dehydrogenation of N2H4, providing 27 723 total turnovers in 30 h. Our work provides a new perspective concerning the possibility of constructing hydrogen-producing systems based on N2H4 and surface ``clean'' Rh2Ni nanocrystal catalysts with defined shapes supported on carbon that possess a competitive performance in comparison with NaBH4 and NH3BH3 hydrogen-producing systems for fuel cell applications.We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1

  7. Synthesis of octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals and their structure-activity relationship for the decomposition of hydrazine in aqueous solution to hydrogen.

    PubMed

    Li, Chun; Wang, Tao; Chu, Wei; Wu, Ping; Tong, Dong Ge

    2016-04-01

    We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1-aminoheptadecane solution in the presence of tetraethylgermanium and borane trimethylamine complexes is proposed. A preliminary probing of the structure-activity dependence of the surface "clean" Rh2Ni nanocrystals supported on carbon towards hydrazine (N2H4) in aqueous solution dehydrogenation revealed that the higher the percentage of {111} facets, the higher is the activity and H2 selectivity of the nanocrystals. This result was attributed to the {111} facets not only introducing more basic sites, but also weakening the interaction between the produced adspecies (including H2 and NHx) and surface metal atoms in comparison with those of {100} facets. Furthermore, the as-prepared Rh2Ni nanooctahedra exhibited 100% H2 selectivity and high activity at room temperature for H2 generation via N2H4 decomposition. The activation energy of the Rh2Ni nanooctahedra was 41.6 ± 1.2 kJ mol(-1). The Rh2Ni nanooctahedra were stable catalysts for the hydrolytic dehydrogenation of N2H4, providing 27 723 total turnovers in 30 h. Our work provides a new perspective concerning the possibility of constructing hydrogen-producing systems based on N2H4 and surface "clean" Rh2Ni nanocrystal catalysts with defined shapes supported on carbon that possess a competitive performance in comparison with NaBH4 and NH3BH3 hydrogen-producing systems for fuel cell applications. PMID:26869098

  8. Chemical Modeling of Cometary Anions

    NASA Astrophysics Data System (ADS)

    Cordiner, Martin; Charnley, S. B.

    2009-09-01

    The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not previously been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydrodynamical model of Rodgers & Charnley (2002), we investigate the role of the hydrocarbon and nitrile anions Cn-, CnH- and CnN- in the coma. We calculate the effects of these anions on the charge balance and examine their impact on cometary coma chemistry. References: Chaizy, P. et al. 1991, Nature, 349, 393 Rodgers, S.D. & Charnley, S.B. 2002, MNRAS, 330, 660

  9. Island of Rare Earth Nuclei with Tetrahedral and Octahedral Symmetries: Possible Experimental Evidence

    SciTech Connect

    Dudek, J.; Dubray, N.; Pangon, V.; Dobaczewski, J.; Olbratowski, P.; Schunck, N.

    2006-08-18

    Calculations using realistic mean-field methods suggest the existence of nuclear shapes with tetrahedral T{sub d} and/or octahedral O{sub h} symmetries sometimes at only a few hundreds of keV above the ground states in some rare earth nuclei around {sup 156}Gd and {sup 160}Yb. The underlying single-particle spectra manifest exotic fourfold rather than Kramers's twofold degeneracies. The associated shell gaps are very strong, leading to a new form of shape coexistence in many rare earth nuclei. We present possible experimental evidence of the new symmetries based on the published experimental results--although an unambiguous confirmation will require dedicated experiments.

  10. Quasi-relativistic SCF X. cap alpha. study of octahedral 5f/sup 1/ complexes

    SciTech Connect

    Thornton, G.; Roesch, N.; Edelstein, N.

    1980-05-01

    Quasi-relativistic SCF X..cap alpha.. calculations have been carried out for the octahedral 5f/sup 1/ complexes Pa/sup IV/X/sub 6//sup 2 -/, U/sup V/X/sub 6//sup -/(X = F, Cl, Br, I), and Np/sup VI/F/sub 6/. The 5f ..-->.. 5f excitation energies calculated by using the transition-state method agree well with the available absorption spectra. Ionic effects appear to dominate the trends observed in the f-orbital ligand field splitting.

  11. A Facile Solvothermal Synthesis of Octahedral Fe3O4 Nanoparticles

    SciTech Connect

    Ooi, Frances; DuChene, Joseph S.; Qiu, Jianqing; Graham, Jeremy O.; Engelhard, Mark H.; Cao, Guixin; Gai, Zheng; Wei, Wei

    2015-06-01

    Magnetic nanoparticles are of great technological interest because they promise numerous potential opportunities in biomedicine and data storage. Although intriguing, these applications require exquisite control over nanostructure morphology in order to appropriately harness their magnetic properties. Most synthesis strategies reported to date are unable to routinely produce anisotropic Fe3O4 nanostructures with appropriate sizes to enable integration into biological systems. Here, we report a simple solvothermal synthesis for obtaining octahedral Fe3O4 nanoparticles with suitable sizes for cellular internalization. Furthermore, these ferromagnetic Fe3O4 octahedrons exhibit substantial saturation magnetization with minimal remanence, suggesting their potential applicability for a host of biomedical applications.

  12. Dynamic octahedral fluctuations and the effects on orbital ordering in YTiO3

    SciTech Connect

    Li, Bing; Louca, Despina; Hu, Biao; Niedziela, Jennifer L; Zhou, Jianshi; Goodenough, J. B.

    2014-01-01

    YTiO3 is revisited to investigate the influence of local lattice dynamics on orbital ordering using inelastic neutron scattering. Orbital order survives well above the ferromagnetic transition, into the paramagnetic state, but what eventually leads to disorder is not well understood. By probing the local lattice dynamics via the dynamic pair density function analysis, it is found that local fluctuations associated with octahedral tilting and rotational modes and Y displacements persist up to 60 meV. The local fluctuations exhibit a temperature dependence that may lead to the suppression of the Ti orbital overlap leading to a temperature dependent orbital disorder.

  13. Transformational part-count in layered octahedral-tetrahedral truss configurations

    NASA Technical Reports Server (NTRS)

    Lalvani, Haresh

    1990-01-01

    The number of component part (nodes, struts and panels) termed part count, is an important factor in the design, manufacture, and assembly of modular space structures. Part count expressions are presented for a variety of profiles derived from the layered octahedral-tetrahedral truss configuration. Referred to as the tetrahedral truss in the NASA projects, this specific geometry has been used in several missions. The general expressions presented here transforms to others as one profile changes to another. Such transformational part count relations provide a measure of flexibility and generality, and may be useful when dealing with a wider range of geometric configurations.

  14. Anion Transport with Chalcogen Bonds.

    PubMed

    Benz, Sebastian; Macchione, Mariano; Verolet, Quentin; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2016-07-27

    In this report, we introduce synthetic anion transporters that operate with chalcogen bonds. Electron-deficient dithieno[3,2-b;2',3'-d]thiophenes (DTTs) are identified as ideal to bind anions in the focal point of the σ holes on the cofacial endocyclic sulfur atoms. Anion binding in solution and anion transport across lipid bilayers are found to increase with the depth of the σ holes of the DTT anionophores. These results introduce DTTs and related architectures as a privileged motif to engineer chalcogen bonds into functional systems, complementary in scope to classics such as 2,2'-bipyrroles or 2,2'-bipyridines that operate with hydrogen bonds and lone pairs, respectively. PMID:27433964

  15. Synthesis of well-defined bicapped octahedral iron clusters [((tren) L)2 Fe8 (PMe2 Ph)2 ](n) (n=0, -1).

    PubMed

    Sánchez, Raúl Hernández; Willis, Alexander M; Zheng, Shao-Liang; Betley, Theodore A

    2015-10-01

    The synthesis of polynuclear clusters with control over size and cluster geometry remains an unsolved challenge. Herein, we report the synthesis and characterization of open-shell octairon clusters supported by two heptaamine ligands [o-H2 NC6 H4 NH(CH2 )2 ]3 N ((tren) LH9 ). The crystal structure of the all-ferrous species ([(tren) L)2 Fe8 (PMe2 Ph)2 ] (1) displays a bicapped octahedral geometry with FeFe distances ranging from 2.4071(6) to 2.8236(5) Å, where the ligand amine units are formally in amine, amide, and imide oxidation states. Several redox states of the octairon cluster are accessible, as ascertained using cyclic voltammetry. The one-electron-reduced clusters [M](+) [((tren) L)2 Fe8 (PMe2 Ph)2 ](-) (M=Bu4 N (2 a); (15-crown-5)Na(thf) (2 b)) were isolated and characterized. Variable-temperature magnetic susceptibility data indicates that the exchange coupling within the [Fe8 ] core is antiferromagnetic which is attenuated upon reduction to the mixed valent anion. PMID:26298064

  16. Hollow octahedral and cuboctahedral nanocrystals of ternary Pt-Ni-Au alloys

    NASA Astrophysics Data System (ADS)

    Shviro, Meital; Polani, Shlomi; Zitoun, David

    2015-08-01

    Hollow particles of Pt-Ni-Au alloys have been prepared through a two-step reaction with the synthesis of NiPt octahedral and cuboctahedral templates followed by a galvanic replacement reaction by Au(iii). Metal etching presents an efficient method to yield hollow particles and investigate the Au diffusion in the metallic Pt-Ni framework through macroscopic (X-ray diffraction and SQUID magnetic measurement) and microscopic (HRTEM and STEM) measurements. The hollow particles retain the shape of the original nanocrystals. The nucleation of Au is found to be induced preferentially on the tip of the polyhedral nanocrystals while the etching of Ni starts from the facets leaving hollow octahedral particles consisting of 2 nm thick edges. In the presence of oleylamine, the Au tip grows and yields a heterogeneous dimer hollow-NiPt/Au. Without oleylamine, the Au nucleation is followed by Au diffusion in the Ni/Pt framework to yield a hollow single crystal Pt-Ni-Au alloy. The Pt-Ni-Au alloyed particles display a superparamagnetic behavior at room temperature.

  17. Controllable synthesis of Cu2O petalody octahedral microcrystals and multi-patterned evolution.

    PubMed

    Ding, Yanbo; Ge, Dengteng; Yang, Lili; Li, Zhenyu; Xin, Wuhong; Li, Yao; Wu, Xiaohong; Zhao, Jiupeng

    2013-02-15

    The fabrication of cuprous oxide (Cu(2)O) with various morphologies has attracted extensive interest due to its applications in solar energy conversion, electrode materials, sensors, and catalysts. Herein, we report a facile controllable route for Cu(2)O microcrystals with various architectures via a hydrothermal method without using templates or surfactants. Six types of Cu(2)O microcrystals including petalody octahedral, concave truncated octahedron, truncated octahedron, octahedron, sphere-like, and sphere are obtained accompanying with Cu precipitation or urchin-like CuO particles due to the modifying of pH values. The petalody octahedral pattern of Cu(2)O is for the first time found here under the condition of pH 7-8. Additionally, possible growth mechanism for multi-patterned Cu(2)O and compositional evolution is discussed via preferential growths induced by selective absorption of acrylic acid and decomposition of lactic acid in the present reaction system. These experimental results prove a versatile and facile strategy for Cu(2)O microcrystals with special and complex architectures, which may highlights their potential applications due to the improved surface activity, catalytic, or photoelectric performance. PMID:23127874

  18. Surface Structures of Cubo-octahedral Pt-Mo Catalyst Nanoparticles from Monte Carlo Simulations

    SciTech Connect

    Wang, Guofeng; Van Hove, M.A.; Ross, P.N.; Baskes, M.I.

    2005-03-31

    The surface structures of cubo-octahedral Pt-Mo nanoparticles have been investigated using the Monte Carlo method and modified embedded atom method potentials that we developed for Pt-Mo alloys. The cubo-octahedral Pt-Mo nanoparticles are constructed with disordered fcc configurations, with sizes from 2.5 to 5.0 nm, and with Pt concentrations from 60 to 90 at. percent. The equilibrium Pt-Mo nanoparticle configurations were generated through Monte Carlo simulations allowing both atomic displacements and element exchanges at 600 K. We predict that the Pt atoms weakly segregate to the surfaces of such nanoparticles. The Pt concentrations in the surface are calculated to be 5 to 14 at. percent higher than the Pt concentrations of the nanoparticles. Moreover, the Pt atoms preferentially segregate to the facet sites of the surface, while the Pt and Mo atoms tend to alternate along the edges and vertices of these nanoparticles. We found that decreasing the size or increasing the Pt concentration leads to higher Pt concentrations but fewer Pt-Mo pairs in the Pt-Mo nanoparticle surfaces.

  19. Hollow octahedral and cuboctahedral nanocrystals of ternary Pt-Ni-Au alloys.

    PubMed

    Shviro, Meital; Polani, Shlomi; Zitoun, David

    2015-08-28

    Hollow particles of Pt-Ni-Au alloys have been prepared through a two-step reaction with the synthesis of NiPt octahedral and cuboctahedral templates followed by a galvanic replacement reaction by Au(iii). Metal etching presents an efficient method to yield hollow particles and investigate the Au diffusion in the metallic Pt-Ni framework through macroscopic (X-ray diffraction and SQUID magnetic measurement) and microscopic (HRTEM and STEM) measurements. The hollow particles retain the shape of the original nanocrystals. The nucleation of Au is found to be induced preferentially on the tip of the polyhedral nanocrystals while the etching of Ni starts from the facets leaving hollow octahedral particles consisting of 2 nm thick edges. In the presence of oleylamine, the Au tip grows and yields a heterogeneous dimer hollow-NiPt/Au. Without oleylamine, the Au nucleation is followed by Au diffusion in the Ni/Pt framework to yield a hollow single crystal Pt-Ni-Au alloy. The Pt-Ni-Au alloyed particles display a superparamagnetic behavior at room temperature. PMID:26202729

  20. Enhancing stability of octahedral PtNi nanoparticles for oxygen reduction reaction by halide treatment

    NASA Astrophysics Data System (ADS)

    Choi, Juhyuk; Lee, Youhan; Kim, Jihan; Lee, Hyunjoo

    2016-03-01

    Because a reduction in the amount of Pt catalysts is essential for the commercialization of fuel cells, various approaches have been tested to maximize the mass activity of Pt-based catalysts. Among these, the most successful results so far were obtained using shaped PtNi alloy nanoparticles, preferably with PtNi(111) facets. However, these nanoparticles typically suffer from much lower activity after the durability tests due to the leaching out of the surface Ni during the oxygen reduction reaction (ORR), which leads to the disappearance of the activity-enhancing effect caused by electronic structure modification. Here, we showed that halide treatment of the octahedral PtNi nanoparticles could significantly enhance their durability. Halides are adsorbed on surface Ni more strongly than on surface Pt, and the surface halides are found to preserve the surface Ni that induces the ORR activity enhancement. Especially, Br can preserve the surface Ni effectively. Durability testing by repeating cyclic voltammetry 10,000 times in the 0.6-1.1 V range showed that the mass activity decreased by 52.6% for the as-prepared PtNi octahedral nanoparticles, whereas the mass activity decreased by only 15.0% for the Br-treated PtNi nanoparticles. The simple treatment significantly enhanced the long-term stability of the highly active PtNi alloy nano-octahedra.

  1. Application of Symmetry Adapted Function Method for Three-Dimensional Reconstruction of Octahedral Biological Macromolecules

    PubMed Central

    Zeng, Songjun; Liu, Hongrong; Yang, Qibin

    2010-01-01

    A method for three-dimensional (3D) reconstruction of macromolecule assembles, that is, octahedral symmetrical adapted functions (OSAFs) method, was introduced in this paper and a series of formulations for reconstruction by OSAF method were derived. To verify the feasibility and advantages of the method, two octahedral symmetrical macromolecules, that is, heat shock protein Degp24 and the Red-cell L Ferritin, were utilized as examples to implement reconstruction by the OSAF method. The schedule for simulation was designed as follows: 2000 random orientated projections of single particles with predefined Euler angles and centers of origins were generated, then different levels of noises that is signal-to-noise ratio (S/N) = 0.1, 0.5, and 0.8 were added. The structures reconstructed by the OSAF method were in good agreement with the standard models and the relative errors of the structures reconstructed by the OSAF method to standard structures were very little even for high level noise. The facts mentioned above account for that the OSAF method is feasible and efficient approach to reconstruct structures of macromolecules and have ability to suppress the influence of noise. PMID:20150955

  2. Octahedral tin dioxide nanocrystals as high capacity anode materials for Na-ion batteries.

    PubMed

    Su, Dawei; Wang, Chengyin; Ahn, Hyojun; Wang, Guoxiu

    2013-08-14

    Single crystalline SnO2 nanocrystals (~60 nm in size) with a uniform octahedral shape were synthesised using a hydrothermal method. Their phase and morphology were characterized by XRD and FESEM observation. TEM and HRTEM analyses identified that SnO2 octahedral nanocrystals grow along the [001] direction, consisting of dominantly exposed {221} high energy facets. When applied as anode materials for Na-ion batteries, SnO2 nanocrystals exhibited high reversible sodium storage capacity and excellent cyclability (432 mA h g(-1) after 100 cycles). In particular, SnO2 nanocrystals also demonstrated a good high rate performance. Ex situ TEM analysis revealed the reaction mechanism of SnO2 nanocrystals for reversible Na ion storage. It was found that Na ions first insert into SnO2 crystals at the high voltage plateau (from 3 V to ~0.8 V), and that the exposed (1 × 1) tunnel-structure could facilitate the initial insertion of Na ions. Subsequently, Na ions react with SnO2 to form NaxSn alloys and Na2O in the low voltage range (from ~0.8 V to 0.01 V). The superior cyclability of SnO2 nanocrystals could be mainly ascribed to the reversible Na-Sn alloying and de-alloying reactions. Furthermore, the reduced Na2O "matrix" may help retard the aggregation of tin nanocrystals, leading to an enhanced electrochemical performance. PMID:23793542

  3. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  4. Ambident reactivities of pyridone anions.

    PubMed

    Breugst, Martin; Mayr, Herbert

    2010-11-01

    The kinetics of the reactions of the ambident 2- and 4-pyridone anions with benzhydrylium ions (diarylcarbenium ions) and structurally related Michael acceptors have been studied in DMSO, CH(3)CN, and water. No significant changes of the rate constants were found when the counterion was varied (Li(+), K(+), NBu(4)(+)) or the solvent was changed from DMSO to CH(3)CN, whereas a large decrease of nucleophilicity was observed in aqueous solution. The second-order rate constants (log k(2)) correlated linearly with the electrophilicity parameters E of the electrophiles according to the correlation log k(2) = s(N + E) (Angew. Chem., Int. Ed. Engl. 1994, 33, 938-957), allowing us to determine the nucleophilicity parameters N and s for the pyridone anions. The reactions of the 2- and 4-pyridone anions with stabilized amino-substituted benzhydrylium ions and Michael acceptors are reversible and yield the thermodynamically more stable N-substituted pyridones exclusively. In contrast, highly reactive benzhydrylium ions (4,4'-dimethylbenzhydrylium ion), which react with diffusion control, give mixtures arising from N- and O-attack with the 2-pyridone anion and only O-substituted products with the 4-pyridone anion. For some reactions, rate and equilibrium constants were determined in DMSO, which showed that the 2-pyridone anion is a 2-4 times stronger nucleophile, but a 100 times stronger Lewis base than the 4-pyridone anion. Quantum chemical calculations at MP2/6-311+G(2d,p) level of theory showed that N-attack is thermodynamically favored over O-attack, but the attack at oxygen is intrinsically favored. Marcus theory was employed to develop a consistent scheme which rationalizes the manifold of regioselectivities previously reported for the reactions of these anions with electrophiles. In particular, Kornblum's rationalization of the silver ion effect, one of the main pillars of the hard and soft acid/base concept of ambident reactivity, has been revised. Ag(+) does not

  5. Bound anionic states of adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S; Li, Xiang; Bowen, Kit H

    2007-03-20

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases, are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the new-found anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The discovery of these valence anionic states of adenine was facilitated by the development of: (i) a new experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a new combinatorial/ quantum chemical approach for identification of the most stable tautomers of organic molecules. The computational portion of this work was supported by the: (i) Polish State Committee for Scientific Research (KBN) Grants: DS/8000-4-0140-7 (M.G.) and N204 127 31/2963 (M.H.), (ii) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.), and (iii) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic

  6. Hydrogen in anion vacancies of semiconductors

    SciTech Connect

    Du, Mao-Hua; Singh, David J

    2009-01-01

    Density functional calculations show that, depending on the anion size, hydrogen in anion vacancies of various II-VI semiconductors can be either two-fold or four-fold coordinated, and has either amphoteric or shallow donor character. In general, the multi-coordination of hydrogen in an anion vacancy is the indication of an anionic H, H { ion, in the relatively ionic environment. In more covalent semiconductors, H would form a single cation-H bond in the anion vacancy.

  7. Versatility of the ionic assembling method to design highly luminescent PMMA nanocomposites containing [M6Q(i)8L(a)6](n-) octahedral nano-building blocks.

    PubMed

    Amela-Cortes, Maria; Molard, Yann; Paofai, Serge; Desert, Anthony; Duvail, Jean-Luc; Naumov, Nikolay G; Cordier, Stéphane

    2016-01-01

    New luminescent poly(methylmethacrylate) (PMMA) nanocomposites with high content of different hexanuclear octahedral cluster building blocks, namely [Mo6I8(C2F5COO6)](2-), [Re6Se8(CN)6](4-) and [W6Cl14](2-) have been prepared by free-radical polymerisation. To do so, cluster complexes bearing a polymerisable ammonium counter-cation have been synthesised. In this way, we demonstrate that ionic assembling is a powerful tool to functionalise easily any type of anionic cluster units to be introduced in a PMMA organic matrix. All samples remain homogeneous, stable during several months, and retain the luminescence properties of the cluster precursor. PMID:26599524

  8. Octahedral iron phosphate hydroxide microcrystals: Fast microwave-hydrothermal preparation, influencing factors and the shape evolution

    SciTech Connect

    Zhou, Quanyi; Ni, Yonghong; Ni, Hui; Ma, Xiang; Zhou, Yunyou

    2012-09-15

    Graphical abstract: Octahedral Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} microcrystals have been successfully prepared by a microwave-assisted hydrothermal route at 170 °C for 20 min. The morphology of Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} could be tuned by the Na{sub 2}SO{sub 3}/HAc molar ratio. Highlights: ► Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} octahedra had been hydrothermally prepared under the microwave assistance. ► The morphology of the final product could be tuned by the original molar ratio of Na{sub 2}SO{sub 3}/HAc. ► Low or high temperatures were unfavorable for the formation of Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} octahedra. ► The time-dependent shape evolution of the final product was investigated. -- Abstract: Octahedral Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} microcrystals have been successfully prepared by a microwave-assisted hydrothermal route at 170 °C for 20 min, employing FeCl{sub 3}·6H{sub 2}O and NaH{sub 2}PO{sub 4}·2H{sub 2}O as the starting materials in the presence of proper amounts of Na{sub 2}SO{sub 3} and acetic acid (HAc). The phase and morphology of the as-prepared product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Some factors influencing the formation of octahedral Fe{sub 4}(PO{sub 4}){sub 3}(OH){sub 3} microcrystals were systematically investigated, including the reaction temperature, time, and the molar ratio of Na{sub 2}SO{sub 3}/HAc.

  9. Pu Anion Exchange Process Intensification

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  10. Oxygen octahedral distortions in LaMO3/SrTiO3 superlattices

    SciTech Connect

    Sanchez-Santolino, Gabriel; Cabero, Mariona; Varela, Maria; Garcia-Barriocanal, Javier; Leon, Carlos; Pennycook, Stephen J.; Santamaria, Jacobo

    2014-04-24

    Here we study the interfaces between the Mott insulator LaMnO3 (LMO) and the band insulator SrTiO3 (STO) in epitaxially grown superlattices with different thickness ratios and different transport and magnetic behaviors. Using atomic resolution electron energy-loss spectrum imaging, we analyze simultaneously the structural and chemical properties of these interfaces. We find changes in the oxygen octahedral tilts within the LaMnO3 layers when the thickness ratio between the manganite and the titanate layers is varied. Superlattices with thick LMO and ultrathin STO layers present unexpected octahedral tilts in the STO, along with a small amount of oxygen vacancies. On the other hand, thick STO layers exhibit undistorted octahedra while the LMO layers present reduced O octahedral distortions near the interfaces. In conclusion, these findings will be discussed in view of the transport and magnetic differences found in previous studies.

  11. Solid-state chemistry-enabled scalable production of octahedral Pt-Ni alloy electrocatalyst for oxygen reduction reaction.

    PubMed

    Zhang, Changlin; Hwang, Sang Youp; Trout, Alexis; Peng, Zhenmeng

    2014-06-01

    Although octahedral Pt-Ni alloy nanoparticles possess an excelling property in oxygen reduction reaction (ORR) and are of great potential as an electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs), mass production of the materials at low cost remains a big challenge. By combining the advantages of both solid-state chemistry and wet synthetic chemistry, we developed one scalable, surfactant-free, and cost-effective method for producing octahedral Pt-Ni alloy nanoparticles on carbon support. The octahedral Pt-Ni samples were prepared with different compositions and studied for the ORR property. They exhibit a much improved reaction activity compared to the commercial catalyst. The experiments demonstrate an innovative strategy for preparing shaped metal nanoparticles and make significant progress in the ORR catalyst research. PMID:24827592

  12. Comparative morphology of configurations with reduced part count derived from the octahedral-tetrahedral truss

    NASA Technical Reports Server (NTRS)

    Lalvani, Haresh; Collins, Timothy J.

    1991-01-01

    Morphology (the study of structure and form) of the octahedral-tetrahedral (octet) truss is described. Both the geometry and symmetry of the octet truss are considered. Morphological techniques based on symmetry operations are presented which enable the derivation of reduced-part-count truss configurations from the octet truss by removing struts and nodes. These techniques are unique because their Morphological origination and they allow for the systematic generation and analysis of a large variety of structures. Methods for easily determining the part count and redundancy of infinite truss configurations are presented. Nine examples of truss configurations obtained by applying the derivation techniques are considered. These configurations are structurally stable while at the same time exhibiting significant reductions in part count. Some practical and analytical considerations, such as structural performance, regarding the example reduced-part-count truss geometries are briefly discussed.

  13. From Mesomorphic Phosphine Oxide to Clustomesogens Containing Molybdenum and Tungsten Octahedral Cluster Cores.

    PubMed

    Cîrcu, Viorel; Molard, Yann; Amela-Cortes, Maria; Bentaleb, Ahmed; Barois, Philippe; Dorcet, Vincent; Cordier, Stéphane

    2015-09-01

    New clustomesogens (i.e., metal atom clusters containing liquid crystalline (LC) materials) have been obtained by grafting neutral cyanobiphenyl (CB)- or cholesteryl-containing tailor-made dendritic mesomorphic triphenylphosphine oxide ligands on luminescent (M6 Cl(i) 8 )(4+) octahedral cluster cores (M=Mo, W). The LC properties were studied by a combination of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray powder diffraction analyses. While the organic ligands showed various mesophase types ranging from nematic, SmA columnar (SmACol ), SmA, and SmC phases, it turned out that the corresponding clustomesogens formed layered phases (SmA) over a wide range of temperatures that depend on the nature and density of mesogenic groups employed. Intrinsic luminescence properties of the cluster precursors are preserved over the entire range of LC phase existence. PMID:26211657

  14. Differential oxidative stress of octahedral and cubic Cu2O micro/nanocrystals to Daphnia magna.

    PubMed

    Fan, Wenhong; Wang, Xiaolong; Cui, Minming; Zhang, Dongfeng; Zhang, Yuan; Yu, Tao; Guo, Lin

    2012-09-18

    This study attempts to understand the impact of different shapes of an individual micro/nanomaterial on their biotoxicities to aquatic organisms. Two differently shaped Cu(2)O micro/nanocrystals (cubes and octahedrons with side lengths of 900 nm) were exposed to Daphnia magna for 72 h, afterward several antioxidant biomarkers such as reactive oxygen species (ROS), catalase (CAT), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) in D. magna were measured. We demonstrated the differential influences of two crystallographic Cu(2)O nanocrystals on the antioxidant process. Specifically, octahedral Cu(2)O nanocrystals showed a higher level of oxidative stress, possibly because of its larger surface area and higher reaction activity of the octahedron. The biomarker results further showed that the oxidative stress and antioxidant mechanism process involved three stages-antioxidant response, oxidation inhibition, and antioxidant inactivation. Furthermore, the accumulation of MDA was mainly responsible for the ROS-induced toxicity. PMID:22894800

  15. Behavior of hafnium fluoride octahedral complex in HF at low temperature studied by TDPAC

    NASA Astrophysics Data System (ADS)

    Dey, C. C.

    2007-02-01

    The behavior of text{HfF}6^{2-} octahedral complex in HF has been studied in the temperature range from 300 to 77 K by time differential perturbed angular correlation technique. No time dependent spin relaxation has been observed up to 223 K. At 203 and 193 K, definite nuclear spin relaxations while at 77 K a pure static interaction have been observed. These indicate that at temperatures below 223 K, a different phase of the liquid appears. The rotational correlation times characterizing the tumbling motion of the complex in HF have been determined at 203 and 193 K and found to be 1.6 ns and 2.1 ns, respectively from the measured relaxation constants at these temperatures and the value of quadrupole frequency found at 77 K. The value of rotational correlation time found at 203 K disagrees by an order of magnitude with the earlier measured value which was found to be in the picosecond range.

  16. The Octahedral Sheet of Metamorphic 2M 1-Phengites: a Combined EMPA And AXANES Study

    SciTech Connect

    Cibin, G.; Cinque, G.; Marcelli, A.; Mottana, A.; Sassi, R.

    2009-05-12

    Two types of metamorphic phengites are known: one is linked to high pressure and is 3T; the other is 2M{sub 1}, and its composition is linked to rock-compositional constraints. This work investigates the octahedral sheet crystal-chemical differences between the two phengite types. Seven dioctahedral micas were studied: (1) one 3T phengite from an ultrahigh-pressure metagranitoid in the Dora Maira massif, Italy (P {approx} 4.3 GPa, T {approx} 730 C); (2) five 2M{sub 1} phengites from medium-P orthogneisses in the Eastern Alps metamorphic basement, Italy (P {le} 0.7 GPa, T {approx} 500-600 C); and (3) one 2M{sub 1} ferroan muscovite from pegmatite in Antarctica (P {le} 0.2 GPa, T {approx}500 C). All micas display significant extents of celadonite substitution. In particular, the 2M{sub 1}-phengite formulae (calculated on the basis of 11 O) have 0.68 < {sup IV}Al < 0.82 atoms per formula unit (apfu); octahedral atoms are dominated by Al (1.6-1.8 apfu), with minor and variable Fe (0.20-0.35 apfu) and Mg (0.05-0.17 apfu), and very minor Ti, Mn, and Cr. Total octahedral occupancies are slightly above 2.00 apfu, i.e., there seems to be partial occupancy of the third M site. For all micas, we recorded XAFS spectra on mosaics of carefully separated flakes oriented flat on a plastic support that could be rotated so as to account for the polarization of the synchrotron radiation beam, and we processed them on the basis of the AXANES theory. Spectra show angle-dependent absorption variations for Al and Fe, which can be deconvoluted and fitted by dichroic effects. Pre-edges consistently show most Fe to be Fe{sup 3+} and little angle-dependent intensity variations. The 2M{sub 1}-ferroan muscovite from Antarctica displays the same AXANES behavior as 2M{sub 1}-phengites. By contrast, the ultrahigh-pressure 3T-phengite from Dora Maira (having {sup IV}Al = 0.42 apfu, and Al and Mg as the dominant octahedral constituents) has XAFS spectra that differ significantly. Not only is the

  17. Partitioning of divalent transition elements between octahedral sheets of trioctahedral smectites and water

    NASA Astrophysics Data System (ADS)

    Decarreau, Alain

    1985-07-01

    Using trioctahedral smectites synthesized at low temperature (25 and 75°C). partition coefficients have been determined for M2+ transition metals (Mn, Fe, Co, Ni, Cu, Zn) between octahedral sheets of smectites and water. These coefficients D( M2+- Mg) = ( M2+)/( Mg) solid/( M2+)/( Mg) liquid have high values near 10 4 for Cu, 1000 for Ni, Co, Zn, 300 for Fe and 30 for Mn. All transition metals are strongly stabilized in the magnesian solid phase, even Mn which leads to noncrystallized products. Within the range of experimental uncertainties, it is found that tetrahedral substitution of Si by Al and differences in temperature (from 25 to 75°C) have no influence on partition coefficients. Experimental data are closely related to thermodynamic properties of the cations and on this basis other partition coefficients can be calculated, for the ( M2+ - Fe2+) pair for instance. The behaviour of transition metals is explained using crystal field theory.

  18. Interplay of octahedral distortions in electronic and structural phase transitions in ABO3 perovskites

    NASA Astrophysics Data System (ADS)

    Balachandran, Prasanna V.; Rondinelli, James M.

    2013-03-01

    In this work, we investigate group-subgroup relationships afforded to ABO3 perovskites from combinations of BO6 distortions - bond stretching and bond angle rotations - with the objective of identifying new pathways for tuning their properties through electron-lattice interactions. Using nickelate and bismuthate perovskite compounds as a template, we decompose their low-symmetry structures into orthonormal symmetry-breaking lattice modes of the parent cubic space group. Statistical analysis of mode decomposition data uncovers previously unappreciated relationships between microscopic octahedral distortion modes and macroscopic physical properties. Finally, we propose novel crystal engineering strategies to study perovskites near phase boundaries that are otherwise extremely difficult to probe experimentally. This project is supported by The Defense Advanced Research Projects Agency (grant no. N66001-12-4224). The views, opinions, and/or findings reported here are solely those of the authors and do not represent official views of DARPA or DOD.

  19. Kinematic modeling of a double octahedral Variable Geometry Truss (VGT) as an extensible gimbal

    NASA Technical Reports Server (NTRS)

    Williams, Robert L., II

    1994-01-01

    This paper presents the complete forward and inverse kinematics solutions for control of the three degree-of-freedom (DOF) double octahedral variable geometry truss (VGT) module as an extensible gimbal. A VGT is a truss structure partially comprised of linearly actuated members. A VGT can be used as joints in a large, lightweight, high load-bearing manipulator for earth- and space-based remote operations, plus industrial applications. The results have been used to control the NASA VGT hardware as an extensible gimbal, demonstrating the capability of this device to be a joint in a VGT-based manipulator. This work is an integral part of a VGT-based manipulator design, simulation, and control tool.

  20. Suppression of Octahedral Tilts and Associated Changes in Electronic Properties at Epitaxial Oxide Heterostructure Interfaces

    SciTech Connect

    Borisevich, Albina Y; Chang, Hye Jung; Huijben, Mark; Oxley, Mark P; Okamoto, Satoshi; Niranjan, M K; Burton, J D; Tsymbal, E Y; Chu, Ying-Hao; Yu, P; Ramesh, R.; Kalinin, Sergei V; Pennycook, Stephen J

    2010-01-01

    Epitaxial oxide interfaces with broken translational symmetry have emerged as a central paradigm behind the novel behaviors of oxide superlattices. Here, we use scanning transmission electron microscopy to demonstrate a direct, quantitative unit-cell-by-unit-cell mapping of lattice parameters and oxygen octahedral rotations across the BiFeO{sub 3{sup -}}La{sub 0.7}Sr{sub 0.3}MnO{sub 3} interface to elucidate how the change of crystal symmetry is accommodated. Combined with low-loss electron energy loss spectroscopy imaging, we demonstrate a mesoscopic antiferrodistortive phase transition near the interface in BiFeO{sub 3} and elucidate associated changes in electronic properties in a thin layer directly adjacent to the interface.

  1. Growth and optical characterization of distorted octahedral (T') WTe2 and MoTe2

    NASA Astrophysics Data System (ADS)

    Chen, Shao-Yu; Goldstein, Thomas; Yan, Jun; Univ of Mass-Amherst Team

    The polymorph of transition metal dichalcogenide (TMDC) has recently attracted great attention due to its novel physical properties. We grow distorted octahedral (T') WTe2 and MoTe2 by chemical vapor transport and rapid thermal quenching methods. The bulk and few layer samples exhibit distinct optical properties as compared with the the well-investigated semiconducting hexagonal (H) TMDCs. We observe sharp intralayer, as well as interlayer optical phonon modes, that display angular dependent intensities consistent with the estimation by Raman tensor calculation. We also demonstratein-situ phase transition of MoTe2 from H to T' via rapid annealing in an electrically heated microfurnace. This enables ramping of the temperature from above 900C to room temperature within seconds. This well-controlled annealing process is promising for innovative fabrication of novel 2D materials devices.

  2. Enhanced magnetization in ultrathin manganite layers via structural ``delta-doping'' of octahedral rotations

    NASA Astrophysics Data System (ADS)

    Moon, Eun Ju; Kirby, Brian J.; May, Steven J.

    The design of rotations and distortions of the corner-shared BO6 octahedra has emerged as an exciting platform to control electronic or magnetic behavior in ABO3 perovskite heterostructures. Recent work has shown that purely structural effects can be used to spatially confined magnetism in oxide heterostructures and point to the design of rotational gradients as routes to realize novel electronic or ferroic states in oxide superlattices [Nat. Comm. 5, 5710 (2014)]. Here, we demonstrate a structural ``delta doping'' approach for controlling magnetism in ultrathin layers within isovalent manganite superlattices. Polarized neutron reflectivity and temperature dependent magnetization measurements are used to correlate enhanced magnetization with local regions of suppressed octahedral rotations in the heterostructures. This work was supported by the U. S. Army Research Office under Grant No. W911NF-15-1-0133.

  3. Cryo-Trapping the Distorted Octahedral Reaction Intermediate of Manganese Superoxide Dismutase

    NASA Technical Reports Server (NTRS)

    Borgstahl, Gloria; Snell, Edward H.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Superoxide dismutase protects organisms from potentially damaging oxygen radicals by catalyzing the disproportion of superoxide to oxygen and hydrogen peroxide. We report the use of cryogenic temperatures to kinetically trap the 6th ligand bound to the active site of manganese superoxide dismutase. Using cryocrystallography and synchrotron radiation, we describe at 1.55A resolution the six-coordinate, distorted octahedral geometry assumed by the active site during catalysis and compare it to the room temperature, five-coordinate trigonal-bipyramidal active site. Gateway residues Tyr34, His30 and a tightly bound water molecule are implicated in closing off the active site and blocking the escape route of superoxide during dismutation.

  4. Structural disorder, octahedral coordination and two-dimensional ferromagnetism in anhydrous alums

    SciTech Connect

    West, D.V. Huang, Q.; Zandbergen, H.W.; McQueen, T.M.; Cava, R.J.

    2008-10-15

    The crystal structures of the triangular lattice, layered anhydrous alums KCr(SO{sub 4}){sub 2}, RbCr(SO{sub 4}){sub 2} and KAl(SO{sub 4}){sub 2} are characterized by X-ray and neutron powder diffraction (NPD) at temperatures between 1.4 and 773 K. The compounds all crystallize in the space group P3-bar, with octahedral coordination of the trivalent cations. In all cases, small amounts of disorder in the stacking of the triangular layers of corner sharing MO{sub 6} octahedra and SO{sub 4} tetrahedra is seen, with the MO{sub 6}-SO{sub 4} network rotated in opposite directions between layers. The electron diffraction study of KCr(SO{sub 4}){sub 2} supports this model, which on an average can be taken to imply trigonal prismatic coordination for the M{sup 3+} ions; as was previously reported for the prototype anhydrous alum, KAl(SO{sub 4}){sub 2}. The temperature-dependent magnetic susceptibilities for ACr(SO{sub 4}){sub 2} (A=K, Rb, Cs) indicate the presence of predominantly ferromagnetic interactions. Low-temperature powder neutron diffraction reveals that the magnetic ordering is ferromagnetic in-plane, with antiferromagnetic ordering between planes below 3 K. - Graphical abstract: The anhydrous alums KCr(SO{sub 4}){sub 2}, RbCr(SO{sub 4}){sub 2} and KAl(SO{sub 4}){sub 2} are characterized by X-ray and neutron powder diffraction and TEM diffraction. All compounds have octahedral coordination of the trivalent cations. Stacking disorder is observed, with the MO{sub 6}-SO{sub 4} network of polyhedra rotated in opposite directions between layers. Low-temperature NPD reveals ferromagnetic in-plane ordering, with antiferromagnetic ordering between planes below 3 K.

  5. Interfacially engineered oxygen octahedral rotations and their impact on strain relief in coherently grown SrRu O3 films

    NASA Astrophysics Data System (ADS)

    Kan, Daisuke; Wakabayashi, Yusuke; Tajiri, Hiroo; Shimakawa, Yuichi

    2016-07-01

    We report synchrotron x-ray diffraction investigations of interfacially engineered oxygen octahedral rotations and their impact on strain relief in perovskite SrRu O3 films. We show that octahedral rotations with distinct patterns and magnitudes can be accommodated into coherently grown films. The SrRu O3 film grown directly on the GdSc O3 substrate has the Ru O6 octahedral rotation with the a-b+c- pattern in the Glazer notation and the rotation angles of αrot=6.6 ±0 .2∘ , βrot=5.5 ±0 .2∘ , and γrot=3.6 ±0 .2∘ . On the other hand, when a 1-nm-thick BaTi O3 layer without Ti O6 rotations is inserted between the SrRu O3 and GdSc O3 , the SrRu O3 has the Ru O6 rotation with a-b0c+ , and αrot=5.6 ±0 .8∘ and γrot=3.6 ±0 .8∘ . These results indicate that there are some degrees of freedom in the octahedral rotations accommodated in SrRu O3 depending on the interface structure and that the γrot rotations play the important roles in the film's structural properties when the rotation about the [010] pc axis is blocked. We also found that the strain relief in the film is influenced by the interfacially engineered octahedral rotations. The interfacial BaTi O3 layer results in the in-plane periodic lattice modulation in the t-SRO film, allowing for the anisotropic relief of the substrate-induced strain. The results highlight the importance of the interface structure as a factor, determining not only octahedral rotations in coherently grown SRO films but also the strain reliefs in them.

  6. Mechanism of Alcohol-Water Dehydrogenative Coupling into Carboxylic Acid Using Milstein's Catalyst: A Detailed Investigation of the Outer-Sphere PES in the Reaction of Aldehydes with an Octahedral Ruthenium Hydroxide.

    PubMed

    Hasanayn, Faraj; Al-Assi, Lara M; Moussawi, Rasha N; Omar, Boushra Srour

    2016-08-15

    In aqueous basic media, the square-pyramidal complex [Ru(PNN)(CO)(H)] (1-Ru, where PNN is a dearomatized bipyridyl-CH-P(t)Bu2 pincer ligand) catalyzes the transformation of alcohols and water into carboxylates and H2. A previous theoretical investigation reported the following mechanism for the reaction: (i) metal-catalyzed dehydrogenation of the alcohol into an aldehyde, (ii) metal-ligand cooperation (MLC) addition of water to 1-Ru to give an octahedral ruthenium hydroxide (2-Ru-OH), (iii) concerted MLC hydration of the aldehyde by 2-Ru-OH to give separated 1-Ru and a gem-diol, and (iv) concerted MLC dehydrogenation of the gem-diol by 1-Ru into an octahedral ruthenium dihydride (2-Ru-H) and a carboxylic acid. We calculate the outer-sphere PES in the reaction between the aldehyde and 2-Ru-OH to start with a localized coupling step yielding an ion-pair minimum (7-ip-OH) in which the hydroxyl group of an α-hydroxyl-alkoxide (gem-diolate) is coordinated to the metal of a cationic square-pyramidal complex. From 7-ip-OH, we identify a route to carboxylic acid that circumvents ligand deprotonation involving (i) 1,1-rearrangement of the gem-diolate within the contact ion pair through an α-OH/O(-) slippage TS into the octahedral 2-Ru-OCH(OH)R and (ii) a second 1,1-rearrangement through an α-O(-)/H slippage TS that gives a new ion-pair minimum in which the α-hydrogen of the anion is coordinated to the metal, followed by a localized hydride-transfer TS that gives a carboxylic acid and the octahedral hydride complex (2-Ru-H). The net transformation from 2-Ru-OH and the aldehyde to the carboxylic acid and 2-Ru-H can be viewed as a H/OH metathesis in which a hydride and a hydroxide are exchanged between the acyl group of the aldehyde and the metal center of 2-Ru-OH. The MLC mechanism gives the same metathesis products through the intermediacy of a gem-diol. When the SMD solvent continuum model is applied during geometry optimization with water as the solvent, the Gibbs free

  7. Anion binding in biological systems

    NASA Astrophysics Data System (ADS)

    Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

    2009-11-01

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  8. Full- or half-encapsulation of sulfate anion by a tris(3-pyridylurea) receptor: effect of the secondary coordination sphere.

    PubMed

    Zhuge, Fuyu; Wu, Biao; Liang, Jianjun; Yang, Jin; Liu, Yanyan; Jia, Chuandong; Janiak, Christoph; Tang, Ning; Yang, Xiao-Juan

    2009-11-01

    Self-assembly of the [Fe(DABP)(3)]SO(4) (DABP = 5,5'-diamino-2,2'-bipyridine) or [Fe(bipy)(3)]SO(4) (bipy = 2,2'-bipyridine) complex with a tripodal tris(3-pyridylurea) ligand (L) results in a layered structure that includes a sulfate anion in the cleft of one L molecule. The two compounds, [Fe(DABP)(3)][SO(4) L] x 10 H(2)O (2) and [Fe(bipy)(3)][SO(4) L] x 9 H(2)O (3), show very similar sheets formed by the anionic units [SO(4) L](2-) and cationic building blocks ([Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+)). However, there are different water clusters that link the adjacent layers in the two products, that is, water parallelograms and quasi "water cubes" in 2 versus single water molecules, water dimers, and hexamers in 3. The half-encapsulation of sulfate by a single L molecule contrasts with the previously reported full-encapsulation of the sulfate ion by two L molecules in [M(H(2)O)(6)][SO(4) L(2)] (1). This different anion encapsulation is traced to the hydrogen-acceptor properties of the pyridyl groups of L together with the hydrogen-bonding properties of the cation secondary coordination sphere for a solid-state packing optimization. In 1 the direct hydrogen bonding from the secondary coordination sphere of octahedral [M(H(2)O)(6)](2+) to L-pyridyl helps in the formation of an octahedral cation-anion coordination in the NaCl-type structure. In 2 and 3, crystal water instead of the cations has to satisfy the hydrogen-accepting demands of L. Consequently, a non-spherical and only partly water-surrounded half-encapsulated [SO(4) L](2-) anion allows for a closer approach of the [Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+) cations than the [SO(4) L(2)](2-) anion. Then, the similar cation and anion size in 2 and 3 with the Coulomb attraction confined to a two-dimensional plane leads to the formation of a hexagonal BN (or graphite) lattice. Competition experiments with different anions for compound 2 reveal that SO(4)(2-) can be selectively crystallized against NO(3)(-), OAc

  9. Octahedral core–shell cuprous oxide/carbon with enhanced electrochemical activity and stability as anode for lithium ion batteries

    SciTech Connect

    Xiang, Jiayuan; Chen, Zhewei; Wang, Jianming

    2015-10-15

    Highlights: • Core–shell octahedral Cu{sub 2}O/C is prepared by a one-step method. • Carbon shell is amorphous and uniformly decorated at the Cu{sub 2}O octahedral core. • Core–shell Cu{sub 2}O/C exhibits markedly enhanced capability and reversibility. • Carbon shell provides fast ion/electron transfer channel. • Core–shell structure is stable during cycling. - Abstract: Core–shell Cu{sub 2}O/C octahedrons are synthesized by a simple hydrothermal method with the help of carbonization of glucose, which reduces Cu(II) to Cu(I) at low temperature and further forms carbon shell coating at high temperature. SEM and TEM images indicate that the carbon shell is amorphous with thickness of ∼20 nm wrapping the Cu{sub 2}O octahedral core perfectly. As anode of lithium ion batteries, the core–shell Cu{sub 2}O/C composite exhibits high and stable columbic efficiency (98%) as well as a reversible capacity of 400 mAh g{sup −1} after 80 cycles. The improved electrochemical performance is attributed to the novel core–shell structure, in which the carbon shell reduces the electrode polarization and promotes the charge transfer at active material/electrolyte interface, and also acts as a stabilizer to keep the octahedral structure integrity during discharge–charge processes.

  10. Electronic Transitions as a Probe of Tetrahedral versus Octahedral Coordination in Nickel(II) Complexes: An Undergraduate Inorganic Chemistry Experiment.

    ERIC Educational Resources Information Center

    Filgueiras, Carlos A. L.; Carazza, Fernando

    1980-01-01

    Discusses procedures, theoretical considerations, and results of an experiment involving the preparation of a tetrahedral nickel(II) complex and its transformation into an octahedral species. Suggests that fundamental aspects of coordination chemistry can be demonstrated by simple experiments performed in introductory level courses. (Author/JN)

  11. Unit-cell thick BaTiO{sub 3} blocks octahedral tilt propagation across oxide heterointerface

    SciTech Connect

    Kan, Daisuke Aso, Ryotaro; Kurata, Hiroki; Shimakawa, Yuichi

    2014-05-14

    We fabricated SrRuO{sub 3}/BaTiO{sub 3}/GdScO{sub 3} heterostructures in which the BaTiO{sub 3} layer is one unit cell thick by pulsed laser deposition and elucidated how the BaTiO{sub 3} layer influences structural and magneto-transport properties of the SrRuO{sub 3} layer through octahedral connections across the heterointerface. Our X-ray-diffraction-based structural characterizations show that while an epitaxial SrRuO{sub 3} layer grown directly on a GdScO{sub 3} substrate is in the monoclinic phase with RuO{sub 6} octahedral tilts, a one-unit-cell-thick BaTiO{sub 3} layer inserted between SrRuO{sub 3} and GdScO{sub 3} stabilizes the tetragonal SrRuO{sub 3} layer with largely reduced RuO{sub 6} tilts. Our high-angle annular dark-field and annular bright-field scanning transmission electron microscopy observations provide an atomic-level view of the octahedral connections across the heterostructure and reveal that the BaTiO{sub 3} layer only one unit cell thick is thick enough to stabilize the RuO{sub 6}-TiO{sub 6} octahedral connections with negligible in-plane oxygen atomic displacements. This results in no octahedral tilts propagating into the SrRuO{sub 3} layer and leads to the formation of a tetragonal SrRuO{sub 3} layer. The magneto-transport property characterizations also reveal a strong impact of the octahedral connections modified by the inserted BaTiO{sub 3} layer on the spin-orbit interaction of the SrRuO{sub 3} layer. The SrRuO{sub 3} layer on BaTiO{sub 3}/ GdScO{sub 3} has in-plane magnetic anisotropy. This is in contrast to the magnetic anisotropy of the monoclinic SrRuO{sub 3} films on the GdScO{sub 3} substrate, in which the easy axis is ∼45° to the film surface normal. Our results demonstrate that the one-unit-cell-thick layer of BaTiO{sub 3} can control and manipulate the interfacial octahedral connection closely linked to the structure-property relationship of heterostructures.

  12. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, Gordon D.; Marsh, S. Fredric; Bartsch, Richard A.

    1997-01-01

    Anion exchange resins including at least two positively charged sites and a ell-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  13. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, G.D.; Marsh, S.F.; Bartsch, R.A.

    1997-09-23

    Anion exchange resins including at least two positively charged sites and a well-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  14. Interpenetrating metal-organic frameworks formed by self-assembly of tetrahedral and octahedral building blocks

    SciTech Connect

    Lu Yongming; Lan Yaqian; Xu Yanhong; Su Zhongmin; Li Shunli; Zang Hongying; Xu Guangjuan

    2009-11-15

    To investigate the relationship between topological types and molecular building blocks (MBBs), we have designed and synthesized a series of three-dimensional (3D) interpenetrating metal-organic frameworks based on different polygons or polyhedra under hydrothermal conditions, namely [Cd(bpib){sub 0.5}(L{sup 1})] (1), [Cd(bpib){sub 0.5}(L{sup 2})].H{sub 2}O (2), [Cd(bpib){sub 0.5}(L{sup 3})] (3) and [Cd(bib){sub 0.5}(L{sup 1})] (4), where bpib=1,4-bis(2-(pyridin-2-yl)-1H-imidazol-1-yl)butane, bib=1,4-bis(1H-imidazol-1-yl)butane, H{sub 2}L{sup 1}=4-(4-carboxybenzyloxy)benzoic acid, H{sub 2}L{sup 2}=4,4'-(ethane-1,2-diylbis(oxy))dibenzoic acid and H{sub 2}L{sup 3}=4,4'-(1,4-phenylenebis(methylene))bis(oxy)dibenzoic acid, respectively. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compounds 1-3 display alpha-Po topological nets with different degrees of interpenetration based on the similar octahedral [Cd{sub 2}(-COO){sub 4}] building blocks. Compound 4 is a six-fold interpenetrating diamondoid net based on tetrahedral MBBs. By careful inspection of these structures, we find that various carboxylic ligands and N-donor ligands with different coordination modes and conformations, and metal centers with different geometries are important for the formation of the different MBBs. It is believed that different topological types lie on different MBBs with various polygons or polyhedra. Such as four- and six-connected topologies are formed by tetrahedral and octahedral building blocks. In addition, with the increase of carboxylic ligands' length, the degrees of interpenetration have been changed in the alpha-Po topological nets. And the luminescent properties of these compounds have been investigated in detail. - Graphical abstract: A series of three-dimensional interpenetrating metal-organic frameworks based on different polygons or polyhedra

  15. Anion directed structural diversity in zinc complexes with conformationally flexible quinazoline ligand: structural, spectral and theoretical studies.

    PubMed

    Dwivedi, Nidhi; Panja, Sumit Kumar; Monika; Saha, Satyen; Sunkari, Sailaja S

    2016-08-14

    In this paper, we report the synthesis, structure and photophysical studies of four new complexes of conformationally flexible 6-chloro-4-phenyl-2-(pyridin-2-yl)quinazoline ligand (L) with Zn(ii). The coordinating ability of the ligand and geometrical preferences of the resultant complexes are tuned by varying the anion of the metal salt as confirmed by structural and DFT studies. The choice of the metal salt (especially anion) directs the stabilisation of different conformations of the ligand arising out of twisting of the pyridyl ring with respect to the quinazoline ring, resulting in complexes with different nuclearity (monomer/dimer) as well as different coordination geometries (tetrahedral/trigonal bipyramidal/octahedral). Photophysical properties are also found to be tuned due to conformational changes on complexation. DFT studies on the ligand establish the conformationally stable forms as observed in the reported structures. PMID:27397771

  16. Polymerization of anionic wormlike micelles.

    PubMed

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  17. Anion Solvation in Carbonate Electrolytes

    SciTech Connect

    Zhang, Zhengcheng

    2015-11-16

    With the correlation between Li+ solvation and interphasial chemistry on anodes firmly established in Li-ion batteries, the effect of cation–solvent interaction has gone beyond bulk thermodynamic and transport properties and become an essential element that determines the reversibility of electrochemistry and kinetics of Li-ion intercalation chemistries. As of now, most studies are dedicated to the solvation of Li+, and the solvation of anions in carbonate-based electrolytes and its possible effect on the electrochemical stability of such electrolytes remains little understood. As a mirror effort to prior Li+ solvation studies, this work focuses on the interactions between carbonate-based solvents and two anions (hexafluorophosphate, PF6–, and tetrafluoroborate, BF4–) that are most frequently used in Li-ion batteries. The possible correlation between such interaction and the interphasial chemistry on cathode surface is also explored.

  18. K 2Ca 6Si 4O 15—structural and spectroscopical studies on a mixed tetrahedral-octahedral framework

    NASA Astrophysics Data System (ADS)

    Arroyabe, E.; Kaindl, R.; Többens, D. M.; Kahlenberg, V.

    2009-12-01

    In the course of an excursion into the system K 2O-CaO-SiO 2, single crystalline material of the previously unknown compound K 2Ca 6Si 4O 15 has been obtained. Single crystal X-ray diffraction experiments revealed that the new phase is monoclinic (space group P12/ c1) with the following basic crystallographic data: a=7.3782(8) Å, b=5.5677(5) Å, c=17.2466(17) Å, β=90.005(8)°, Z=2. According to Liebau's nomenclature, the compound can be classified as a mixed anion silicate containing insular [SiO 4]-groups as well as [Si 2O 7]-dimers in the ratio 2:1, i.e. the crystallochemical formula can be written as K 2Ca 6[SiO 4] 2[Si 2O 7]. The silicate anions are linked by K- and Ca-ions distributed among five different non-tetrahedral M-positions and coordinated by six to eight nearest oxygen neighbors. Alternatively, the structure can be described as a heteropolyhedral framework built up by kröhnkite-type [ M(SiO 4) 2O 2]-chains in which the MO 6 octahedra are corner-linked to bridging SiO 4 tetrahedra. The chains (running parallel to [0 1 0]) are located in 4.6 Å wide layers parallel to (1 0 0). Neighboring sheets are shifted relative to each other by an amount of + δ or - δ along [0 0 1]. In the derived two layer …ABABAB… stacking sequence, chains belonging to adjacent sheets are linked by corner sharing of common oxygen atoms. The resulting network contains tunnels in which the more irregularly coordinated K- and Ca-ions are incorporated for charge compensation. A comparison between the present compound and structurally related mixed tetrahedral-octahedral frameworks is given. The characterization has been completed by Raman and FTIR-spectroscopy. An allocation of the bands to certain vibrational species has been aided by density functional theory (DFT) calculations.

  19. Aza compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.Q.; McBreen, J.

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.

  20. Aza compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.

  1. Transient Anion States of Biomolecules

    NASA Astrophysics Data System (ADS)

    Varella, Marcio

    2012-10-01

    Much of the interest on electron interactions with biomolecules is related to radiation damage [Gohlke and Illenberger, Europhys. News 33, 207 (2002)]. The high energy photons employed in radiology and radiotherapy generate a large number of fast electrons in living cells. These electrons thermalize in a picosecond scale, eventually forming dissociative matestable anions with water and biomolecules. In this work, we employ the parallel version of Schwinger Multichannel Method with Pseudopotentials [Bettega et al., Phys. Rev. A 47, 1111 (1993); Santos et al., J. Phys. Chem. 136, 084307 (2012)] to investigate transient anion states of protein and nucleic acid precursors. We address glycine in both neutral and zwitterionic forms, as well as glycine-water clusters and disulfide bonds. The interest on the two forms of glycine (and other amino acids) relies on the fact that only the neutral form is stable in the gas phase, while the zwitterion is more stable in solution, pointing out limitations of standard gas-phase studies. Electron attachment to disulfide bonds also has potential impact on protein stability. Finally we address transient anion states of substituted uracil molecules in the gas phase. [4pt] In collaboration with M. H. F. Bettega, S. d'A. Sanchez, R. F. da Costa, M. A. P. Lima, J. S. dos Santos, and F. Kossoski.

  2. Receptor-Mediated Entry of Pristine Octahedral DNA Nanocages in Mammalian Cells.

    PubMed

    Vindigni, Giulia; Raniolo, Sofia; Ottaviani, Alessio; Falconi, Mattia; Franch, Oskar; Knudsen, Birgitta R; Desideri, Alessandro; Biocca, Silvia

    2016-06-28

    DNA offers excellent programming properties for the generation of nanometer-scaled polyhedral structures with a broad variety of potential applications. Translation to biomedical applications requires improving stability in biological fluids, efficient and selective cell binding, and/or internalization of the assembled DNA nanostructures. Here, we report an investigation on the selective mechanism of cellular uptake of pristine DNA nanocages in cells expressing the receptor "oxidized low-density lipoprotein receptor-1" (LOX-1), a scavenger receptor associated with cardiovascular diseases and, more recently, identified as a tumor marker. For this purpose a truncated octahedral DNA nanocage functionalized with a single biotin molecule, which allows DNA cage detection through the biotin-streptavidin assays, was constructed. The results indicate that DNA nanocages are stable in biological fluids, including human serum, and are selectively bound and very efficiently internalized in vesicles only in LOX-1-expressing cells. The amount of internalized cages is 30 times higher in LOX-1-expressing cells than in normal fibroblasts, indicating that the receptor-mediated uptake of pristine DNA nanocages can be pursued for a selective cellular internalization. These results open the route for a therapeutic use of pristine DNA cages targeting LOX-1-overexpressing tumor cells. PMID:27214742

  3. Symmetry-Based Tunnelings in High-Resolution Rovibrational Spectra of Octahedral Molecules

    NASA Astrophysics Data System (ADS)

    Mitchell, Justin; Harter, William

    2010-06-01

    High-resolution spectra of spherical-top molecules are known to demonstrate rotational level clustering. This clustering is well described as a rotational phase-space effect Multiple equivalent phase-space regions allow tunneling and thus splitting of the rotational clusters. So far this has been done with an ad hoc tunneling Hamiltonian. Similar splittings have been shown for low dimensional systems, also with an ad hoc parameterization. While ad hoc tunneling parameterization is simple to understand, it becomes extremely difficult to apply for higher symmetries and for locally low-symmetry clustering when many tunneling paths are possible. Symmetry-based parameterization mitigates this complication. This presentation will discuss how symmetry-based tunneling is applied for octahedral molecules and demonstrate how local-C1, C2, C3 or C4 clusters may be evaluated perturbatively. Connections to non-rotational systems, such as large amplitude motion, will be discussed as well. W.G. Harter and C.W. Patterson, Phys Rev Lett 38, 224 (1977) W.G. Harter and C.W. Patterson, J Chem Phys 66, 4872 (1977) J.T. Hougen J Mol Spect 123, 197 (1987)

  4. Nonequivalence of the octahedral site of cubic Fe3O4 magnetite

    NASA Astrophysics Data System (ADS)

    Steinle-Neumann, G.; Wenzel, M. J.

    2006-12-01

    Despite considerable advances in computational methods within density functional theory (DFT) for solids the electronic structure for transition metal containing compounds are not accurately described with standard approximations to the exchange and correlation potential, due to the localized and strongly interacting electronic states. This shortcoming is prominent in the iron oxides (FeO, Fe3O4, Fe2O3) and has traditionally been attempted to be overcome by the so-called LDA+U method, where additional orbital dependent interactions are added to LDA or GGA calculations. Adding the U has improved the description of the magnetic and electronic state of transition metal oxides. Similar to previous work we here employ the GGA+U method for Fe3O4 magnetite at ambient pressure lattice constants and consider physical properties of Fe3O4, in particular local parameters that could monitor charge ordering on the octahedral B site in Fe3O4 structure (inverse spinel), breaking their symmetry equivalence. We vary the U parameter from 0 eV to 4.5 eV, covering a wide range of previously employed values. We find that for values of U ≥ 2.5 eV the B sites become inequivalent in terms of magnetic moment, charge and electric field gradient. This is in contrast to experimental findings that suggest that the B sites are equivalent.

  5. Insensitivity of the octahedral spherical hohlraum to power imbalance, pointing accuracy, and assemblage accuracy

    SciTech Connect

    Huo, Wen Yi; Zhao, Yiqing; Zheng, Wudi; Liu, Jie; Lan, Ke

    2014-11-15

    The random radiation asymmetry in the octahedral spherical hohlraum [K. Lan et al., Phys. Plasmas 21, 0 10704 (2014)] arising from the power imbalance, pointing accuracy of laser quads, and the assemblage accuracy of capsule is investigated by using the 3-dimensional view factor model. From our study, for the spherical hohlraum, the random radiation asymmetry arising from the power imbalance of the laser quads is about half of that in the cylindrical hohlraum; the random asymmetry arising from the pointing error is about one order lower than that in the cylindrical hohlraum; and the random asymmetry arising from the assemblage error of capsule is about one third of that in the cylindrical hohlraum. Moreover, the random radiation asymmetry in the spherical hohlraum is also less than the amount in the elliptical hohlraum. The results indicate that the spherical hohlraum is more insensitive to the random variations than the cylindrical hohlraum and the elliptical hohlraum. Hence, the spherical hohlraum can relax the requirements to the power imbalance and pointing accuracy of laser facility and the assemblage accuracy of capsule.

  6. Tunable ionic-conductivity of collapsed Sandia octahedral molecular sieves (SOMS).

    SciTech Connect

    Pless, Jason; Nenoff, Tina Maria; Garino, Terry J.; Axness, Marlene

    2006-11-01

    This proposal focuses on the synthesis and characterization of ''tunable'' perovskite ceramics with resulting controlled strength and temperature of dielectric constants and/or with ionic conductivity. Traditional methods of synthesis involve high temperature oxide mixing and baking. We developed a new methodology of synthesis involving the (1) low temperature hydrothermal synthesis of metastable porous phases with ''tuned'' stoichiometry, and element types, and then (2) low temperature heat treatment to build exact stoichiometry perovskites, with the desired vacancy concentrations. This flexible pathway can lead to compositions and structures not attainable by conventional methods. During the course of this program, a series of Na-Nb perovskites were synthesized by calcining and collapsing microporous Sandia Octahedral Molecular Sieve (SOMS) phases. These materials were studied by various characterization techniques and conductivity measurements to better delineate stability and stoichiometry/bulk conductivity relationships. The conductivity can be altered by changing the concentration and type of the substituting framework cation(s) or by ion exchange of sodium. To date, the Na{sub 0.9}Mg{sub 0.1}Nb{sub 0.8}Ti{sub 0.2}O{sub 3-{delta}} shows the best conductivity.

  7. A Capped Octahedral MHC6 Compound of a Platinum Group Metal.

    PubMed

    Eguillor, Beatriz; Esteruelas, Miguel A; Lezáun, Virginia; Oliván, Montserrat; Oñate, Enrique; Tsai, Jui-Yi; Xia, Chuanjun

    2016-06-27

    A MHC6 complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ(2) -C,C-(PhBIm-C6 H4 )}3 , which reacts with HBF4 to afford the 14 e(-) species [Os{κ(2) -C,C-(PhBIm-C6 H4 )}(Ph2 BIm)2 ]BF4 stabilized by two agostic interactions, has been obtained by reaction of OsH6 (PiPr3 )2 with N,N'-diphenylbenzimidazolium chloride ([Ph2 BImH]Cl) in the presence of NEt3 . Its formation takes place through the C,C,C-pincer compound OsH2 {κ(3) -C,C,C-(C6 H4 -BIm-C6 H4 )}(PiPr3 )2 , the dihydrogen derivative OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(η(2) -H2 )(PiPr3 )2 , and the five-coordinate osmium(II) species OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(PiPr3 )2 . PMID:27123555

  8. Calculation of internal valence force constants for XY 6( Oh) octahedral molecules

    NASA Astrophysics Data System (ADS)

    Fernandez-Gomez, Manuel; Lopez-Gonzalez, Juan Jesus; Cardenete Espinosa, Antonio

    1990-04-01

    The valence force constants have been calculated in terms of simple dependent rectilinear internal co-ordinates for a series of XY 6 octahedral molecules that have been amply studied from a vibrational point of view, i.e. the hexafluorides of sulphur, selenium, molybdenum, tungsten and uranium. The calculations have been carried out using the most recent force constants in symmetry co-ordinates to appear in the literature and following Kuczera's treatment, according to which the indetermination of the internal valence force constants involved in redundancies can be solved by using the transformation F* R= WTWFRWTW, which he calls the pure vibrational force field. The results show that the eleven FR dependent constants are reduced to seven F* R independent constants, the same number as the FS independent force constants. This is because of the zero value of the ƒ'* dα constants and the relationships ƒ* dα= -ƒ″* dα ƒ* αα = -ƒ″* αα ƒ* α=-2ƒ'* αα-ƒ'″* αα that are obtained from the combination of the above mentioned F* R transformation and the sum rule in Kuczera's treatment. These latter relationships can be obtained from the interactions between the displacement coordinates with which they are associated. This has allowed individual values to be assigned to the bending, bending—bending and stretching—bending constants for the above mentioned molecules without the need for recourse to any model whatsoever.

  9. Thermodynamic N-donor trans influence in labile pseudo-octahedral zinc complexes: a delusion?

    PubMed

    Aboshyan-Sorgho, Lilit; Lathion, Timothée; Guénée, Laure; Besnard, Céline; Piguet, Claude

    2014-12-15

    While the forces responsible for the chelate effect are well-established in coordination chemistry, the origin and implementation of the related thermodynamic trans influence remains debatable. This work illustrates a simple approach for quantifying this effect in labile pseudo-octahedral [Zn(Lk)3](2+) complexes lacking stereochemical preferences (Lk = L1–L4 are unsymmetrical didentate α,α′-diimine ligands). In line with statistics, the triply degenerated meridional isomers mer-[Zn(Lk)3](2+) are stabilized by 0.8 ≤ ΔGexch(mer→fac) ≤ 4.2 kJ/mol over their nondegenerated facial analogues fac-[Zn(Lk)3](2+) and therefore display no apparent trans influence at room temperature. However, the dissection of the free energy terms into opposite enthalpic (favoring the facial isomers) and entropic (favoring the meridional isomers) contributions reveals a trans influence assigned to solvation processes occurring in polar solvents. Altogether, the thermodynamic trans influence operating in [Zn(α,α′-diimine)3](2+) complexes is 1–2 orders of magnitude smaller than the chelate effect. A weak templating effect provided by a noncovalent lanthanide tripod is thus large enough to produce the wanted facial isomer at room temperature. PMID:25407515

  10. Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

    SciTech Connect

    Oliver, S. A.; Harris, V. G.; Hamdeh, H. H.; Ho, J. C.

    2000-05-08

    The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn{sub 0.55}{sup 2+}Fe{sub 0.18}{sup 3+}){sub tet}[Zr{sub 0.45}{sup 2+}Fe{sub 1.82}{sup 3+}]{sub oct}O{sub 4} through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe{sup 3+} on both sites is consistent with the measured room temperature magnetic properties. (c) 2000 American Institute of Physics.

  11. Octahedral niobium chloride clusters as building blocks of templated prussian blue framework analogues.

    PubMed

    Yan, Bangbo; Zhou, Huajun; Lachgar, Abdessadek

    2003-12-29

    The preparation, structure, and magnetic properties of the first three-dimensional framework containing octahedral niobium cyanochloride clusters as building units are reported. Reactions of aqueous solutions of (Me(4)N)(2)K(2)[Nb(6)Cl(12)(CN)(6)] (2) with aqueous solutions of MnCl(2) result in the precipitation of the compound (Me(4)N)(2)[MnNb(6)Cl(12)(CN)(6)] (3). The structure of 3 was determined from single-crystal X-ray diffraction study (crystal data: cubic, Fm3macrom(No. 225), a = 15.513(4) A, V = 3733.2(12) A(3), Z = 4). Its 3D framework is based on edge-bridged [Nb(6)Cl(12)](2+) clusters and Mn(2+) ions bridged by cyanide ligands to form a cfc lattice [MnNb(6)Cl(12)(CN)(6)](2)(-) in which all tetrahedral sites are occupied by the cations (Me(4)N)(+) which act as charge compensating template. The structure of 3 can be considered as an expansion of the Prussian blue framework in which [Fe(CN)(6)](4)(-) is replaced by the cluster [Nb(6)Cl(12)(CN)(6)](4)(-). Magnetic susceptibility measurements indicate that Mn(2+) is present in a high spin d(5) configuration. No magnetic ordering is observed. PMID:14686862

  12. Studies of oxygen species in synthetic Todorokite-like manganese oxide octahedral molecular sieves

    SciTech Connect

    Yin, Yuan-Gen; Xu, Wen-Qing; Shen, Yan-Fei; Suib, S.L. ); O'Young, C.L. )

    1994-10-01

    Manganese oxide octahedral molecular sieves of 3 x 3 tunnel structure (OMS-1) doped with various cations possess high thermal stability and were studied by means of temperature-programmed desorption and reduction by H[sub 2] and CO. Different oxygen species can be discerned according to their peak positions in the temperature-programmed desorption and reduction and assigned to chemisorbed dioxygen, oxygen atoms bound to Mn[sup 2+], and those bound to Mn[sup 4+] ions in the framework. Differences in peak positions and availabilities of these species during TPD and TPR can be explained by creation of nascent Mn[sup 2+] ions during TPR. The effects of doping cations on the reactivity and availability of these oxygen species are demonstrated to be more pronounced in TPR in H[sub 2] or CO than in TPD. In some instances, the trends of changes in reactivity and availability of the oxygen species due to doping of Cu[sup 2+], Ni[sup 2+], Zn[sup 2+], and Mg[sup 2+] correlated with the changes in the heat of formation of oxides of these cations. Temperature-programmed reactions with methane show some reactivity of these doped OMS-1 materials. Pulse reactions with CO show higher reactivity of Cu-doped OM-1 than with butane. However, the recovery of Cu-doped OMS-1 by reoxidation with oxygen pulses seems rather incomplete at the same temperature. 27 refs., 9 figs.

  13. Structural variation of babingtonite depending on cation distribution at the octahedral sites

    NASA Astrophysics Data System (ADS)

    Nagashima, Mariko; Mitani, Keiko; Akasaka, Masahide

    2014-04-01

    Babingtonite, Ca2Fe2+Fe3+[Si5O14(OH)] ( Z = 2, space group ) from Yakuki mine (Japan), Grönsjöberget (Sweden), Kandivali Quarry (India), Baveno Quarry (Italy), Bråstad Mine (Norway), and Kouragahana (Japan), and manganbabingtonite, Ca2(Mn2+, Fe2+)Fe3+[Si5O14(OH)], from Iron Cap mine (USA) were studied using electron-microprobe analysis (EMPA), 57Fe Mössbauer analysis and single-crystal X-ray diffraction methods to determine the cation distribution at M1 and M2 and to analyze its effect on the crystal structure of babingtonite. Although all studied babingtonite crystals are relatively homogeneous, chemical zonation due to mainly Fe ↔ Mn substitution is observed in manganbabingtonite. Mössbauer spectra consist of two doublets with isomer shift ( I.S.) = 1.16-1.22 mm/s and quadrupole splitting ( Q. S.) = 2.33-2.50 mm/s and with I.S. = 0.38-0.42 mm/s and Q.S. = 0.82-0.90 mm/s, assigned to Fe2+ and Fe3+ at the M1 and M2 octahedral sites, respectively. The determined ratio of Fe2+/total Fe in manganbabingtonite (0.26) was smaller than that in the others (0.35-0.44) because of high Mn2+ content instead of Fe2+. The unit-cell parameters of babingtonite are a = 7.466-7.478, b = 11.624-11.642, c = 6.681-6.690 Å, α = 91.53-91.59, β = 93.86-93.94, γ = 104.20-104.34º, and V = 560.2-562.3 Å3, and those of manganbabingtonite are a = 7.4967(3), b = 11.6632(4), c = 6.7014(2) Å, α = 91.602(2), β = 93.989(2), γ = 104.574(3)º, and V =565.09(5) Å3. Structural refinements converged to R 1 values of 1.64-3.16 %. The distance was lengthened due to the substitution of large octahedral cations such as Mn2+ for Fe2+. The increase of the M1-O8, M1-O8' and M1-O13 lengths with mean ionic radii is slightly more pronounced than of the other M1-O i lengths. The lengthened M1-O13 distance leads the positive correlation between Si5-O15-Si1 angle and M1-O13 distance. The increase of Si2-O3-Si1 and Si5-O12-Si4 angles due to the increase of mean ionic radius of M2 is also

  14. DNA hairpins promote temperature controlled cargo encapsulation in a truncated octahedral nanocage structure family

    NASA Astrophysics Data System (ADS)

    Franch, Oskar; Iacovelli, Federico; Falconi, Mattia; Juul, Sissel; Ottaviani, Alessio; Benvenuti, Claudia; Biocca, Silvia; Ho, Yi-Ping; Knudsen, Birgitta R.; Desideri, Alessandro

    2016-07-01

    In the present study we investigate the mechanism behind temperature controlled cargo uptake using a truncated octahedral DNA cage scaffold functionalized with one, two, three or four hairpin forming DNA strands inserted in one corner of the structure. This investigation was inspired by our previous demonstration of temperature controlled reversible encapsulation of the cargo enzyme, horseradish peroxidase, in the cage with four hairpin forming strands. However, in this previous study the mechanism of cargo uptake was not directly addressed (Juul, et al., Temperature-Controlled Encapsulation and Release of an Active Enzyme in the Cavity of a Self-Assembled DNA Nanocage, ACS Nano, 2013, 7, 9724-9734). In the present study we use a combination of molecular dynamics simulations and in vitro analyses to unravel the mechanism of cargo uptake in hairpin containing DNA cages. We find that two hairpin forming strands are necessary and sufficient to facilitate efficient cargo uptake, which argues against a full opening-closing of one corner of the structure being responsible for encapsulation. Molecular dynamics simulations were carried out to evaluate the atomistic motions responsible for encapsulation and showed that the two hairpin forming strands facilitated extension of at least one of the face surfaces of the cage scaffold, allowing entrance of the cargo protein into the cavity of the structure. Hence, the presented data demonstrate that cargo uptake does not involve a full opening of the structure. Rather, the uptake mechanism represents a feature of increased flexibility integrated in this nanocage structure upon the addition of at least two hairpin-forming strands.In the present study we investigate the mechanism behind temperature controlled cargo uptake using a truncated octahedral DNA cage scaffold functionalized with one, two, three or four hairpin forming DNA strands inserted in one corner of the structure. This investigation was inspired by our previous

  15. Nuclear Magnetic Resonance Observations of Octahedral Aluminum in Forsterite, Clinoenstatite and Periclase.

    NASA Astrophysics Data System (ADS)

    McCarty, R. J.; Stebbins, J. F.

    2015-12-01

    This research seeks to constrain the crystallographic site preferences of aluminum in forsterite, clinoenstatite and periclase, mantle minerals in which this element is only found at low concentrations. Improved site preference information will help constrain thermodynamic descriptions of the substitution mechanisms, making them more useful to geobarometric and geothermometric techniques. Using high field magic angle spinning nuclear magnetic resonance (NMR) and electron probe microanalysis (EPMA), we constrain the site preferences of minor and trace amounts (2000 to 400 mol ppm) of aluminum in extremely pure synthetic forsterite, clinoenstatite and periclase. The primary challenge of this research is determining how much of each of the aluminum species observed by NMR in the bulk sample (abundances and coordinations) resides in the major synthesized mineral. In our samples, the aluminum partitions between small amounts (often <1%) of impurity phases with high aluminum concentrations, such as glass and accessory crystals, and the major, intended phase with low aluminum concentrations. We use EPMA composition maps to locate scarce impurity phases and EPMA point analyses to determine the aluminum concentrations in both the intended major phase and in the impurity phases. Long NMR acquisitions (several days) and careful subtraction of rotor background signals (present in even 'low-Al' zirconia rotor materials) are required to obtain adequate signal-to-noise ratios at such low concentrations. Ordered octahedral aluminum has been identified in forsterite, clinoenstatite, and periclase. Disordered 4, 5 and 6 coordinated aluminum species have also been observed, but it is still unclear if the disordered species are in the major mineral phases, the impurity phases or both.

  16. Structural, Spectroscopic, and Photochemical Investigation of an Octahedral NO-Releasing {RuNO}(7) Species.

    PubMed

    Levin, Natalia; Codesido, Nicolás Osa; Bill, Eckhard; Weyhermüller, Thomas; Segantin Gaspari, Ana Paula; da Silva, Roberto Santana; Olabe, José A; Slep, Leonardo D

    2016-08-15

    [Ru(Me3[9]aneN3)(bpy)(NO)](BF4)2 ([1](BF4)2) was explored by single-crystal X-ray diffractometry, leading to the first crystal structure of an octahedral {RuNO}(7) complex. The metal resides on the center of a distorted octahedron, with dN-O and ∠Ru-N-O at 1.177(3) Å and 141.6(2)°, respectively. [1](BF4)2 can be stored indefinitely under argon. Solutions of [1](2+) show no signs of decomposition when protected from air and light. The electron paramagnetic resonance X-band spectrum at 85 K in vitrified acetonitrile (MeCN) shows signals consistent with an S = (1)/2 spin state, better described as Ru(II)NO(•) (g = [2.030, 1.993, 1.880] and A = [11.0, 30.4, 3.9]/10(-4) cm(-1)). In water, the {RuNO}(7) species reacts with O2 in a 1:4 stoichiometry. The reaction is first-order in both reactants with k = (1.9 ± 0.2) M(-1) s(-1) at 25 °C (ΔH(⧧) = 11.5 ± 0.3 kJ mol(-1); ΔS(⧧) = -189 ± 1 J K(-1) mol(-1)). Solutions of [1](2+) evolve NO when irradiated a 365 nm with ϕNO = 0.024 and 0.090 mol einstein(-1) in H2O and MeCN, respectively. PMID:27454920

  17. Hydrothermal fabrication of octahedral-shaped Fe{sub 3}O{sub 4} nanoparticles and their magnetorheological response

    SciTech Connect

    Jung, H. S.; Choi, H. J.

    2015-05-07

    Octahedral-shaped Fe{sub 3}O{sub 4} nanoparticles were synthesized in the presence of 1,3-diaminopropane using a hydrothermal method and assessed as a potential magnetorheological (MR) material. Their morphology, crystal structure, and magnetic properties were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. The MR characteristics of the octahedral-shaped, Fe{sub 3}O{sub 4} nanoparticle-based MR particles when dispersed in silicone oil with a 10 vol. % particle concentration were examined using a rotational rheometer under an external magnetic field. The resulting MR fluids exhibited a Bingham-like behavior with a distinctive yield stress from their flow curves.

  18. Effects of cobalt concentration on the relative resistance to octahedral and cube slip in nickle-base superalloys

    NASA Technical Reports Server (NTRS)

    Bobeck, Gene E.; Miner, R. V.

    1988-01-01

    Compression yielding tests were performed at 760 C on crystals of the Ni base superalloys Rene 150 and a modified MAR-M247, both having two different Co concentrations. For both alloy bases, increasing Co concentration was shown to decrease the critical resolved shear stress for octahedral slip, but to have little effect on that for cube slip. The results suggest that decreasing complex stacking fault energy in the gamma-prime with increasing Co could account for the observed effects.

  19. Highly selective enrichment of phosphopeptides with high-index facets exposed octahedral tin dioxide nanoparticles for mass spectrometric analysis.

    PubMed

    Ma, Rongna; Hu, Junjie; Cai, Zongwei; Ju, Huangxian

    2014-02-01

    High-index facets exposed octahedral tin dioxide (SnO2) nanoparticles were successfully synthesized and applied to selectively enrich phosphopeptides for mass spectrometric analysis. The high selectivity and capacity of the octahedral SnO2 nanoparticles were demonstrated by effectively enriching phosphopeptides from digests of phosphoprotein (α- or β-casein), protein mixtures of β-casein and bovine serum albumin, milk, and human serum samples. The unique octahedral SnO2 with abundant unsaturated coordination Sn atoms exhibited enhanced affinity and selective coordination ability with phosphopeptides due to their high chemical activity. The strong affinity led to highly selective capture and enrichment of phosphopeptides for sensitive detection through the bidentate bonds formed between surface atoms and phosphate. The phosphopeptides could be detected in β-casein down to 4 × 10(-9)M or in the mixture of β-casein and BSA with a molar ratio of even 1:100. The performance in selective enrichment of phosphopeptides from drinking milk and human serum showed powerful evidence of high selectivity and efficiency in identifying the low-abundant phosphopeptides from complicated biological samples. This work provided a way to improve the physical and chemical properties of materials by tailoring their exposed facets for selective enrichment of phosphopeptides. PMID:24401440

  20. A unified free-form representation applied to the shape optimization of the hohlraum with octahedral 6 laser entrance holes

    NASA Astrophysics Data System (ADS)

    Jiang, Shaoen; Huang, Yunbao; Jing, Longfei; Li, Haiyan; Huang, Tianxuan; Ding, Yongkun

    2016-01-01

    The hohlraum is very crucial for indirect laser driven Inertial Confinement Fusion. Usually, its shape is designed as sphere, cylinder, or rugby with some kind of fixed functions, such as ellipse or parabola. Recently, a spherical hohlraum with octahedral 6 laser entrance holes (LEHs) has been presented with high flux symmetry [Lan et al., Phys. Plasmas 21, 010704 (2014); 21, 052704 (2014)]. However, there is only one shape parameter, i.e., the hohlraum to capsule radius ratio, being optimized. In this paper, we build the hohlraum with octahedral 6LEHs with a unified free-form representation, in which, by varying additional shape parameters: (1) available hohlraum shapes can be uniformly and accurately represented, (2) it can be used to understand why the spherical hohlraum has higher flux symmetry, (3) it allows us to obtain a feasible shape design field satisfying flux symmetry constraints, and (4) a synthetically optimized hohlraum can be obtained with a tradeoff of flux symmetry and other hohlraum performance. Finally, the hohlraum with octahedral 6LEHs is modeled, analyzed, and then optimized based on the unified free-form representation. The results show that a feasible shape design field with flux asymmetry no more than 1% can be obtained, and over the feasible design field, the spherical hohlraum is validated to have the highest flux symmetry, and a synthetically optimal hohlraum can be found with closing flux symmetry but larger volume between laser spots and centrally located capsule.

  1. High flux symmetry of the spherical hohlraum with octahedral 6LEHs at the hohlraum-to-capsule radius ratio of 5.14

    SciTech Connect

    Lan, Ke; Liu, Jie; He, Xian-Tu; Lai, Dongxian; Zheng, Wudi

    2014-01-15

    We propose a spherical hohlraum with octahedral six laser entrance holes at a specific hohlraum-to-capsule radius ratio of 5.14 for inertial fusion study, which has robust high symmetry during the capsule implosion and low backscatter without supplementary technology. To produce an ignition radiation pulse of 300 eV, it needs 1.5 MJ absorbed laser energy in such a golden octahedral hohlraum, about 30% more than a traditional cylinder. Nevertheless, it is worth for a high symmetry and low backscatter. The proposed octahedral hohlraum is also flexible and can be applicable to diverse inertial fusion drive approaches.

  2. Adsorption affinity of anions on metal oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.

    2013-03-01

    The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO{4/3-}, CO{3/2-} > C2O{4/2-}, C(OH)(CH2)2(COO){3/3-}, (CHOH)2(COO){2/2-} > CrO{4/2-} ≫ SO{4/2-}.

  3. Phase transitions in new BEDT-TTF κ-phase salts with hexacyanometalate anions [M(CN) 63- M=Co(III) and Fe(III)

    NASA Astrophysics Data System (ADS)

    Pierre Le Maguerè; Ouahab, Lahcène; Corian, Nathalie; Gómez-García, Carlos J.; Delhaès, Pierre; Even, Jacky; Bertault, Marcel

    1996-01-01

    The preparation, crystal structure determination and physical properties of the compounds formulated as κ-(BEDT-TTF) 4((C 2H 5) 4N)M(CN) 6.3H 2O (M= Co III and Fe III) are presented. Organic ET layers with packing of orthogonalized dimers containing charge carriers and inorganic octahedral hexacyanometalate anions with diamagnetic or paramagnetic transition metals coexist in the title compounds. Two phase transitions occuring respectively at 150 K and in the 230-260 K range have been evidenced by magnetic (SQUID and ESR), DSC measurements. However, preliminary X-Ray studies revealed a structural change around 240 K only.

  4. Mapping octahedral tilts and polarization across a domain wall in BiFeO3 from Z-contrast STEM image atomic column shape analysis

    SciTech Connect

    Borisevich, Albina Y; Ovchinnikov, Oleg S; Chang, Hye Jung; Oxley, Mark P; Yu, P; Seidel, J; Eliseev, E. A.; Morozovska, A. N.; Ramesh, R.; Pennycook, Stephen J; Kalinin, Sergei V

    2010-01-01

    Oxygen octahedral tilts underpin the functionality of a large number of perovskite-based materials and heterostructures with competing order parameters. We show how a precise analysis of atomic column shapes in Z-contrast scanning transmission electron microscopy images can reveal polarization and octahedral tilt behavior across uncharged and charged domain walls in BiFeO3. This method is capable of visualizing octahedral tilts to much higher thicknesses than phase contrast imaging. We find that the octahedral tilt transition across a charged domain wall is atomically abrupt, while the associated polarization profile is diffuse (1.5-2 nm). Ginzburg-Landau theory then allows the relative contributions of polarization and the structural order parameters to the wall energy to be determined.

  5. Tripodal Receptors for Cation and Anion Sensors

    PubMed Central

    Kuswandi, Bambang; Nuriman; Verboom, Willem; Reinhoudt, David N.

    2006-01-01

    This review discusses different types of artificial tripodal receptors for the selective recognition and sensing of cations and anions. Examples on the relationship between structure and selectivity towards cations and anions are described. Furthermore, their applications as potentiometric ion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  6. Gels based on anion recognition between triurea receptor and phosphate anion.

    PubMed

    Yang, Cuiling; Wu, Biao; Chen, Yongming; Zhang, Ke

    2015-04-01

    Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross-linkage to build supramolecular polymer gels for the first time. A novel multi-block copolymer (3) is designed to have functional triurea groups as cross-linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block. PMID:25694389

  7. Counterintuitive interaction of anions with benzene derivatives

    NASA Astrophysics Data System (ADS)

    Quiñonero, David; Garau, Carolina; Frontera, Antonio; Ballester, Pau; Costa, Antonio; Deyà, Pere M.

    2002-06-01

    Ab initio calculations were carried out on complexes between 1,3,5-trinitrobenzene (TNB) and anions, where the anion is positioned over the ring along the C3 axis. This study combines crystallographic and computational evidences to demonstrate an attractive interaction between the anion and the π-cloud of TNB. This interaction is rationalized based on the important role of the quadrupole moment of TNB and the anion-induced polarization. In addition, this study has been extended to 1,3,5-trifluorobenzene (TFB), which possesses a very small quadrupole moment. As a result, minimum energy complexes have been found between TFB and both anions and cations due to the stabilization obtained from the ion-induced polarization.

  8. Covalent Polymers Containing Discrete Heterocyclic Anion Receptors

    PubMed Central

    Rambo, Brett M.; Silver, Eric S.; Bielawski, Christopher W.; Sessler, Jonathan L.

    2010-01-01

    This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions. PMID:20871791

  9. Creating molecular macrocycles for anion recognition

    PubMed Central

    2016-01-01

    Summary The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures. PMID:27340452

  10. Picosecond dynamics of benzophenone anion solvation

    SciTech Connect

    Lin, Y.; Jonah, C.D. )

    1993-01-14

    The dynamics of benzophenone anion solvation in alcohols are studied by pulse-radiolysis techniques. The solvation process is characterized by the blue shift of the transient absorption spectrum of the anion and is faster for the smaller alcohols. The anion is solvated more slowly than the electron in the same solvent, but the solvation times of both are similar to [tau][sub 2], the solvent dielectric relaxation time. The familiar phenomenological two-state model of solvation was found to be inappropriate for describing the anion solvation process. A multistate process appears to be a more appropriate description. The authors modeled the kinetics of the spectral relaxation. In most cases, nearly quantitative agreement between the calculated and observed spectra is achieved. The characteristic relaxation times for the alcohol solvents around the anions were also reproduced. 50 refs., 8 figs., 3 tabs.

  11. Anion conductance selectivity mechanism of the CFTR chloride channel.

    PubMed

    Linsdell, Paul

    2016-04-01

    All ion channels are able to discriminate between substrate ions to some extent, a process that involves specific interactions between permeant anions and the so-called selectivity filter within the channel pore. In the cystic fibrosis transmembrane conductance regulator (CFTR) anion-selective channel, both anion relative permeability and anion relative conductance are dependent on anion free energy of hydration--anions that are relatively easily dehydrated tend to show both high permeability and low conductance. In the present work, patch clamp recording was used to investigate the relative conductance of different anions in CFTR, and the effect of mutations within the channel pore. In constitutively-active E1371Q-CFTR channels, the anion conductance sequence was Cl(-) > NO3(-) > Br(-) > formate > SCN(-) > I(-). A mutation that disrupts anion binding in the inner vestibule of the pore (K95Q) disrupted anion conductance selectivity, such that anions with different permeabilities showed almost indistinguishable conductances. Conversely, a mutation at the putative narrowest pore region that is known to disrupt anion permeability selectivity (F337A) had minimal effects on anion relative conductance. Ion competition experiments confirmed that relatively tight binding of permeant anions resulted in relatively low conductance. These results suggest that the relative affinity of ion binding in the inner vestibule of the pore controls the relative conductance of different permeant anions in CFTR, and that the pore has two physically distinct anion selectivity filters that act in series to control anion conductance selectivity and anion permeability selectivity respectively. PMID:26779604

  12. Photoelectron spectroscopy of nitromethane anion clusters

    NASA Astrophysics Data System (ADS)

    Pruitt, Carrie Jo M.; Albury, Rachael M.; Goebbert, Daniel J.

    2016-08-01

    Nitromethane anion and nitromethane dimer, trimer, and hydrated cluster anions were studied by photoelectron spectroscopy. Vertical detachment energies, estimated electron affinities, and solvation energies were obtained from the photoelectron spectra. Cluster structures were investigated using theoretical calculations. Predicted detachment energies agreed with experiment. Calculations show water binds to nitromethane anion through two hydrogen bonds. The dimer has a non-linear structure with a single ionic Csbnd H⋯O hydrogen bond. The trimer has two different solvent interactions, but both involve the weak Csbnd H⋯O hydrogen bond.

  13. Ketoprofen as a photoinitiator for anionic polymerization.

    PubMed

    Wang, Yu-Hsuan; Wan, Peter

    2015-06-01

    A new photoinitiating system for anionic polymerization of acrylates based on the efficient photodecarboxylation of Ketoprofen (1) and the related derivatives 3 and 4 that generate the corresponding carbanion intermediates is presented. Carbanion intermediates are confirmed by deuterium incorporation in the trapped Michael adducts and by spectroscopic detection using laser flash photolysis (LFP). This novel anionic initiating system features excitation in the near UV and visible regions, potential characteristics of photocontrolled living polymerization, and metal-free photoinitiators generated from photoexcitation, different from typical anionic polymerization where the polymerizations are initiated by heat and strong base containing alkali metals. PMID:25917384

  14. Bioaccumulation and biomarker responses of cubic and octahedral Cu2O micro/nanocrystals in Daphnia magna.

    PubMed

    Fan, Wenhong; Shi, Zhiwei; Yang, Xiuping; Cui, Minming; Wang, Xiaolong; Zhang, Dongfeng; Liu, Hong; Guo, Lin

    2012-11-15

    Great progress has been made in the controlled fabrication of nanomaterials with given sizes, shapes, and geometries. However, how such changes in structure potentially affect the bioavailability and toxicity of metal nanoparticles to aquatic organisms remains mostly unknown. The present study reports the different behaviors of two types of Cu(2)O micro/nanocrystals (micro/nano-Cu(2)O) with different shapes (cubic and octahedral) and crystallographies (with exposed surfaces as {100} or {111}). The bioaccumulation, median lethal concentration, and biomarker responses of Daphnia magna exposed to the two micro/nanocrystals are also investigated. The Cu accumulation, production of metallothionein (MT), and inhibition ratio of D. magna increased gradually with increasing micro/nano-Cu(2)O concentration. The two crystals showed slight Cu accumulation differences toward D. magna, and their biomarker responses and toxicities to D. magna differed significantly as well. The octahedral Cu(2)O micro/nanocrystals were more toxic to D. magna compared with the cubic micro/nanocrystals probably because of the higher surface activities of the {111} facets compared with those of the {100} facets for cuprites. Food ingestion was the main entry pathway of the micro/nanocrystals into organisms, and toxicity was consequently determined based on the dissolution behavior of the micro/nanocrystals in vivo. PMID:22999974

  15. Octahedral Ni-nanocluster (Ni85) for Efficient and Selective Reduction of Nitric Oxide (NO) to Nitrogen (N2).

    PubMed

    Mahata, Arup; Rawat, Kuber Singh; Choudhuri, Indrani; Pathak, Biswarup

    2016-01-01

    Nitric oxide (NO) reduction pathways are systematically studied on a (111) facet of the octahedral nickel (Ni85) nanocluster in the presence/absence of hydrogen. Thermodynamic (reaction free energies) and kinetic (free energy barriers, and temperature dependent reaction rates) parameters are investigated to find out the most favoured reduction pathway for NO reduction. The catalytic activity of the Ni-nanocluster is investigated in greater detail toward the product selectivity (N2 vs. N2O vs. NH3). The previous theoretical (catalyzed by Pt, Pd, Rh and Ir) and experimental reports (catalyzed by Pt, Ag, Pd) show that direct N-O bond dissociation is very much unlikely due to the high-energy barrier but our study shows that the reaction is thermodynamically and kinetically favourable when catalysed by the octahedral Ni-nanocluster. The catalytic activity of the Ni-nanocluster toward NO reduction reaction is very much efficient and selective toward N2 formation even in the presence of hydrogen. However, N2O (one of the major by-products) formation is very much unlikely due to the high activation barrier. Our microkinetic analysis shows that even at high hydrogen partial pressures, the catalyst is very much selective toward N2 formation over NH3. PMID:27157072

  16. Morphological control and evolution of octahedral and truncated trisoctahedral Pt-Au alloy nanocrystals under microwave irradiation

    NASA Astrophysics Data System (ADS)

    Dai, Lei; Zhao, Yanxi; Chi, Quan; Liu, Hanfan; Li, Jinlin; Huang, Tao

    2014-08-01

    Uniform and well-defined truncated trisoctahedral and octahedral Pt-Au alloy nanocrystals were fabricated by co-reducing H2PtCl6-HAuCl4 with tetraethylene glycol (TEG) under microwave irradiation for only 140 s. Iodide ions were critical to the morphological control and evolution of Pt-Au alloy nanostructures. The as-prepared Pt-Au alloy nanocrystals exhibited efficient electrocatalytic activities.Uniform and well-defined truncated trisoctahedral and octahedral Pt-Au alloy nanocrystals were fabricated by co-reducing H2PtCl6-HAuCl4 with tetraethylene glycol (TEG) under microwave irradiation for only 140 s. Iodide ions were critical to the morphological control and evolution of Pt-Au alloy nanostructures. The as-prepared Pt-Au alloy nanocrystals exhibited efficient electrocatalytic activities. Electronic supplementary information (ESI) available: Experimental details; SEM, TEM and HAADF-STEM images, UV-vis absorbance spectra, XRD. See DOI: 10.1039/c4nr01864h

  17. Octahedral Ni-nanocluster (Ni85) for Efficient and Selective Reduction of Nitric Oxide (NO) to Nitrogen (N2)

    PubMed Central

    Mahata, Arup; Rawat, Kuber Singh; Choudhuri, Indrani; Pathak, Biswarup

    2016-01-01

    Nitric oxide (NO) reduction pathways are systematically studied on a (111) facet of the octahedral nickel (Ni85) nanocluster in the presence/absence of hydrogen. Thermodynamic (reaction free energies) and kinetic (free energy barriers, and temperature dependent reaction rates) parameters are investigated to find out the most favoured reduction pathway for NO reduction. The catalytic activity of the Ni-nanocluster is investigated in greater detail toward the product selectivity (N2 vs. N2O vs. NH3). The previous theoretical (catalyzed by Pt, Pd, Rh and Ir) and experimental reports (catalyzed by Pt, Ag, Pd) show that direct N-O bond dissociation is very much unlikely due to the high-energy barrier but our study shows that the reaction is thermodynamically and kinetically favourable when catalysed by the octahedral Ni-nanocluster. The catalytic activity of the Ni-nanocluster toward NO reduction reaction is very much efficient and selective toward N2 formation even in the presence of hydrogen. However, N2O (one of the major by-products) formation is very much unlikely due to the high activation barrier. Our microkinetic analysis shows that even at high hydrogen partial pressures, the catalyst is very much selective toward N2 formation over NH3. PMID:27157072

  18. Oxygen vacancy and dilute ferromagnetism of ZnGa2O4 doped with Co at the octahedral site

    NASA Astrophysics Data System (ADS)

    Nakai, Ikuo; Hisamatsu, Ryouhei; Li, Yingjie; Kurisu, Makio

    2016-05-01

    We report magnetism and structure of a diluted magnetic semiconductor Zn[Ga0.97Co0.03]2O4 preferentially doped with Co ions in the octahedral site of zinc gallate ZnGa2O4. Zn[Ga0.97Co0.03]2O4 has a small ferromagnetic component superimposed on a large paramagnetic contribution to the magnetization at room temperature, whereas ZnGa2O4 is diamagnetic. The X-ray powder diffraction confirms that both ZnGa2O4 and Zn[Ga0.97Co0.03]2O4 have a normal spinel structure (space group Fd-3m) without any impurity phases. From X-ray absorption fine structure measurements we find the following features in Zn[Ga0.97Co0.03]2O4; all of the Co dopants occupy the octahedral site, about half of which are divalent; around the Co cations there exist the oxygen vacancies and the local distortion of shrink in pair distance, while the local structure around Zn and Ga ions coincides with that expected from the X-ray diffraction. These features suggest that the local disorder including oxygen vacancies and distortions only around Co ions plays an important role in stabilizing the ferromagnetic order between some Co ions in Zn[Ga0.97Co0.03]2O4.

  19. Octahedral tilt transitions in the relaxor ferroelectric Na1/2Bi1/2TiO3

    NASA Astrophysics Data System (ADS)

    Meyer, Kai-Christian; Gröting, Melanie; Albe, Karsten

    2015-07-01

    The kinetics of octahedral tilt transitions in the lead-free relaxor material sodium bismuth titanate Na1/2Bi1/2TiO3 (NBT) is investigated by electronic structure calculations within density functional theory. Energy barriers for transitions between tetragonal, rhombohedral and orthorhombic tilts in cation configurations with [001]- and [111]-order on the A-sites are determined by nudged elastic band calculations. By tilting entire layers of octahedra simultaneously we find that the activation energy is lower for structures with 001-order compared to such with 111-order. The energetic coupling between differently tilted layers is, however, negligibly small. By introducing a single octahedral defect we create local tilt disorder and find that the deformation energy of the neighboring octahedra is less in a rhombohedral than in a tetragonal structure. By successively increasing the size of clusters of orthorhombic defects in a rhombohedral matrix with 001-order, we determine a critical cluster size of about 40 Å . Thus groups of about ten octahedra can be considered as nuclei for polar nanoregions, which are the cause of the experimentally observed relaxor behavior of NBT.

  20. Octahedral Ni-nanocluster (Ni85) for Efficient and Selective Reduction of Nitric Oxide (NO) to Nitrogen (N2)

    NASA Astrophysics Data System (ADS)

    Mahata, Arup; Rawat, Kuber Singh; Choudhuri, Indrani; Pathak, Biswarup

    2016-05-01

    Nitric oxide (NO) reduction pathways are systematically studied on a (111) facet of the octahedral nickel (Ni85) nanocluster in the presence/absence of hydrogen. Thermodynamic (reaction free energies) and kinetic (free energy barriers, and temperature dependent reaction rates) parameters are investigated to find out the most favoured reduction pathway for NO reduction. The catalytic activity of the Ni-nanocluster is investigated in greater detail toward the product selectivity (N2 vs. N2O vs. NH3). The previous theoretical (catalyzed by Pt, Pd, Rh and Ir) and experimental reports (catalyzed by Pt, Ag, Pd) show that direct N-O bond dissociation is very much unlikely due to the high-energy barrier but our study shows that the reaction is thermodynamically and kinetically favourable when catalysed by the octahedral Ni-nanocluster. The catalytic activity of the Ni-nanocluster toward NO reduction reaction is very much efficient and selective toward N2 formation even in the presence of hydrogen. However, N2O (one of the major by-products) formation is very much unlikely due to the high activation barrier. Our microkinetic analysis shows that even at high hydrogen partial pressures, the catalyst is very much selective toward N2 formation over NH3.

  1. Octahedral distortion induced magnetic anomalies in LaMn0.5Co0.5O3 single crystals

    NASA Astrophysics Data System (ADS)

    Manna, Kaustuv; Bhadram, Venkata Srinu; Elizabeth, Suja; Narayana, Chandrabhas; Anil Kumar, P. S.

    2014-07-01

    Single crystals of LaMn0.5Co0.5O3 belonging to the ferromagnetic-insulator and distorted perovskite class were grown using a four-mirror optical float zone furnace. The as-grown crystal crystallizes into an orthorhombic Pbnm structure. The spatially resolved 2D Raman scan reveals a strain-induced distribution of transition metal (TM)-oxygen (O) octahedral deformation in the as-grown crystal. A rigorous annealing process releases the strain, thereby generating homogeneous octahedral distortion. The octahedra tilt by reducing the bond angle TM-O-TM, resulting in a decline of the exchange energy in the annealed crystal. The critical behavior is investigated from the bulk magnetization. It is found that the ground state magnetic behavior assigned to the strain-free LaMn0.5Co0.5O3 crystal is of the 3D Heisenberg kind. Strain induces mean field-like interaction in some sites, and consequently, the critical exponents deviate from the 3D Heisenberg class in the as-grown crystal. The temperature-dependent Raman scattering study reveals strong spin-phonon coupling and the existence of two magnetic ground states in the same crystal.

  2. Kinetics and mechanism of exogenous anion exchange in FeFbpA-NTA: significance of periplasmic anion lability and anion binding activity of ferric binding protein A.

    PubMed

    Heymann, Jared J; Gabricević, Mario; Mietzner, Timothy A; Crumbliss, Alvin L

    2010-02-01

    The bacterial transferrin ferric binding protein A (FbpA) requires an exogenous anion to facilitate iron sequestration, and subsequently to shuttle the metal across the periplasm to the cytoplasmic membrane. In the diverse conditions of the periplasm, numerous anions are known to be present. Prior in vitro experiments have demonstrated the ability of multiple anions to fulfill the synergistic iron-binding requirement, and the identity of the bound anion has been shown to modulate important physicochemical properties of iron-bound FbpA (FeFbpA). Here we address the kinetics and mechanism of anion exchange for the FeFbpA-nitrilotriacetate (NTA) assembly with several biologically relevant anions (citrate, oxalate, phosphate, and pyrophosphate), with nonphysiologic NTA serving as a representative synergistic anion/chelator. The kinetic data are consistent with an anion-exchange process that occurs in multiple steps, dependent on the identity of both the entering anion and the leaving anion. The exchange mechanism may proceed either as a direct substitution or through an intermediate FeFbpA-X* assembly based on anion (X) identity. Our kinetic results further develop an understanding of exogenous anion lability in the periplasm, as well as address the final step of the iron-free FbpA (apo-FbpA)/Fe(3+) sequestration mechanism. Our results highlight the kinetic significance of the FbpA anion binding site, demonstrating a correlation between apo-FbpA/anion affinity and the FeFbpA rate of anion exchange, further supporting the requirement of an exogenous anion to complete tight sequestration of iron by FbpA, and developing a mechanism for anion exchange within FeFbpA that is dependent on the identity of both the entering anion and the leaving anion. PMID:19813031

  3. Molecular physiology of EAAT anion channels.

    PubMed

    Fahlke, Christoph; Kortzak, Daniel; Machtens, Jan-Philipp

    2016-03-01

    Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. After release from presynaptic nerve terminals, glutamate is quickly removed from the synaptic cleft by a family of five glutamate transporters, the so-called excitatory amino acid transporters (EAAT1-5). EAATs are prototypic members of the growing number of dual-function transport proteins: they are not only glutamate transporters, but also anion channels. Whereas the mechanisms underlying secondary active glutamate transport are well understood at the functional and at the structural level, mechanisms and cellular roles of EAAT anion conduction have remained elusive for many years. Recently, molecular dynamics simulations combined with simulation-guided mutagenesis and experimental analysis identified a novel anion-conducting conformation, which accounts for all experimental data on EAAT anion currents reported so far. We here review recent findings on how EAATs accommodate a transporter and a channel in one single protein. PMID:26687113

  4. A new class of organocatalysts: sulfenate anions.

    PubMed

    Zhang, Mengnan; Jia, Tiezheng; Yin, Haolin; Carroll, Patrick J; Schelter, Eric J; Walsh, Patrick J

    2014-09-26

    Sulfenate anions are known to act as highly reactive species in the organic arena. Now they premiere as organocatalysts. Proof of concept is offered by the sulfoxide/sulfenate-catalyzed (1-10 mol%) coupling of benzyl halides in the presence of base to generate trans-stilbenes in good to excellent yields (up to 99%). Mechanistic studies support the intermediacy of sulfenate anions, and the deprotonated sulfoxide was determined to be the resting state of the catalyst. PMID:25111259

  5. Control of oxygen octahedral rotation in BiFeO3 films using modulation of SrRuO3 bottom electrode layer

    NASA Astrophysics Data System (ADS)

    Lee, Sungsu; Jo, Ji Young

    2015-03-01

    Oxygen octahedral rotation of multiferroic BiFeO3 (BFO) has attracted great attention due to changes of electrical and magnetic properties. Coupling of octahedral rotation in BFO-bottom electrode layer interface remains unexplored. Recently, there have been reported the control of octahedral rotation in SrRuO3 (SRO) film on SrTiO3 (001) substrate by coherently controlling the oxygen pressure during growth and interfacial coupling. Here we demonstrate that the octahedral rotation of BFO film is changed using tetragonal a0a0c- tilted-SRO bottom electrodes. In this work, BFO/SRO heterostructure is fabricated to SrTiO3 (001) single crystal substrates by pulsed laser deposition at different oxygen partial pressures. The rotation pattern of FeO6 and the structural symmetry are identified from half-integer reflections using high-resolution X-ray diffraction. The effects depending on octahedral tilting of BFO films on the magnetic and ferroelectric properties will be presented.

  6. Octahedral tilt transitions in the relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

    SciTech Connect

    Meyer, Kai-Christian Gröting, Melanie; Albe, Karsten

    2015-07-15

    The kinetics of octahedral tilt transitions in the lead-free relaxor material sodium bismuth titanate Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) is investigated by electronic structure calculations within density functional theory. Energy barriers for transitions between tetragonal, rhombohedral and orthorhombic tilts in cation configurations with [001]- and [111]-order on the A-sites are determined by nudged elastic band calculations. By tilting entire layers of octahedra simultaneously we find that the activation energy is lower for structures with 001-order compared to such with 111-order. The energetic coupling between differently tilted layers is, however, negligibly small. By introducing a single octahedral defect we create local tilt disorder and find that the deformation energy of the neighboring octahedra is less in a rhombohedral than in a tetragonal structure. By successively increasing the size of clusters of orthorhombic defects in a rhombohedral matrix with 001-order, we determine a critical cluster size of about 40 Å . Thus groups of about ten octahedra can be considered as nuclei for polar nanoregions, which are the cause of the experimentally observed relaxor behavior of NBT. - Graphical abstract: Nine orthorhombic oxygen octahedral tilt defects in a rhombohedral tilt configuration. - Highlights: • Chemical order influences energy barriers of octahedral tilt transitions. • The octahedral deformation energy is lower in rhombohedral phases. • Tilt defect clusters are more likely in rhombohedral structures. • Tilt defect clusters can act as nuclei for polar nanoregions.

  7. Novel pseudo-delocalized anions for lithium battery electrolytes.

    PubMed

    Jónsson, Erlendur; Armand, Michel; Johansson, Patrik

    2012-05-01

    A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn ⇌ Li(+) + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research. PMID:22441354

  8. Molecular pharmacology of renal organic anion transporters.

    PubMed

    Van Aubel, R A; Masereeuw, R; Russel, F G

    2000-08-01

    Renal organic anion transport systems play an important role in the elimination of drugs, toxic compounds, and their metabolites, many of which are potentially harmful to the body. The renal proximal tubule is the primary site of carrier-mediated transport from blood to urine of a wide variety of anionic substrates. Recent studies have shown that organic anion secretion in renal proximal tubule is mediated by distinct sodium-dependent and sodium-independent transport systems. Knowledge of the molecular identity of these transporters and their substrate specificity has increased considerably in the past few years by cloning of various carrier proteins. However, a number of fundamental questions still have to be answered to elucidate the participation of the cloned transporters in the overall tubular secretion of anionic xenobiotics. This review summarizes the latest knowledge on molecular and pharmacological properties of renal organic anion transporters and homologs, with special reference to their nephron and plasma membrane localization, transport characteristics, and substrate and inhibitor specificity. A number of the recently cloned transporters, such as the p-aminohippurate/dicarboxylate exchanger OAT1, the anion/sulfate exchanger SAT1, the peptide transporters PEPT1 and PEPT2, and the nucleoside transporters CNT1 and CNT2, are key proteins in organic anion handling that possess the same characteristics as has been predicted from previous physiological studies. The role of other cloned transporters, such as MRP1, MRP2, OATP1, OAT-K1, and OAT-K2, is still poorly characterized, whereas the only information that is available on the homologs OAT2, OAT3, OATP3, and MRP3-6 is that they are expressed in the kidney, but their localization, not to mention their function, remains to be elucidated. PMID:10919840

  9. Studies of anions sorption on natural zeolites.

    PubMed

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. PMID:25002191

  10. Two field-induced slow magnetic relaxation processes in a mononuclear Co(ii) complex with a distorted octahedral geometry.

    PubMed

    Li, Jing; Han, Yuan; Cao, Fan; Wei, Rong-Min; Zhang, Yi-Quan; Song, You

    2016-05-31

    A distorted octahedral Co(II) complex is reported with homoscorpionate ligands. This complex comprised a field-induced single-molecule magnet, showing two slow relaxation processes under a low dc field (<800 Oe) and only one process under a high dc field (≥800 Oe), which was an unusually discovery for 3d metal ions. On the basis of the ac magnetic data, we show for the first time that one of the slow relaxation processes in the low dc field originates from intermolecular dipolar interactions. Interestingly, the Raman process is predominant in the spin reversal relaxation process. The origin of the behaviours of the complex was elucidated by ab initio calculations. PMID:27180637

  11. In silico Investigation of the PglB Active Site Reveals Transient Catalytic States and Octahedral Metal Ion Coordination.

    PubMed

    Pedebos, Conrado; Arantes, Pablo Ricardo; Giesel, Guilherme Menegon; Verli, Hugo

    2015-11-01

    The last step of the bacterial N-glycosylation pathway involves PglB, an oligosaccharyltransferase, which is responsible for the en bloc transfer of a fully assembled oligosaccharide chain to a protein possessing the extended motif D/E-X-N-X-S/T. Recently, this molecule had its full structure elucidated, enabling the description of its domains and the proposition of a catalytic mechanism. By employing molecular dynamics simulations, we were able to evaluate structural aspects of PglB, suggesting prevalent motions that may bring insights into the mechanism of the glycosylated peptide detachment. Additionally, we identified transient states at the catalytic site, in which the previously described carboxamide twisting mechanism was observed. Aided by quantum mechanics calculations for each different conformational states of the catalytic site, we determined the presence of an octahedral metal coordination, along with the presence of one water molecule at the catalytic site. PMID:26220543

  12. DNA interaction with octahedral and square planar Ni(II) complexes of aspartic-acid Schiff-bases

    NASA Astrophysics Data System (ADS)

    Sallam, S. A.; Orabi, A. S.; Abbas, A. M.

    2011-12-01

    Ni(II) complexes of (S,E)-2-(2-OHbenzilydene)aspartic acid; (S,E)-2-(2,3-diOHbenzilydene)aspartic acid-; (S,E)-2-(2,4-diOH-benzilydene)aspartic acid; (S,E)-2-(2,5-diOHbenzilydene)aspartic acid and (S,E)-2-((2-OHnaphthalene-1-yl)methylene)aspartic acid Schiff-bases have been synthesized by template method in ethanol or ammonia media. They were characterized by elemental analyses, conductivity measurements, magnetic moment, UV, IR and 1H nmr spectra as well as thermal analysis (TG, DTG, DTA). The Schiff-bases are dibasic tridentate or tetradentate donors and the complexes have square planar and octahedral structures. The complexes decompose in two or three steps where kinetic and thermodynamic parameters of the decomposition steps were computed. The interactions of the formed complexes with FM-DNA were monitored by UV and fluorescence spectroscopy.

  13. Strain accommodation by facile WO₆ octahedral distortion and tilting during WO₃ heteroepitaxy on SrTiO₃(001).

    PubMed

    Du, Yingge; Gu, Meng; Varga, Tamas; Wang, Chongmin; Bowden, Mark E; Chambers, Scott A

    2014-08-27

    In this work, we demonstrate that WO6 octahedra in tungsten trioxide (WO3) undergo an unusually large degree of distortion and tilting to accommodate interfacial strain. This motion strongly impacts nucleation, structure, and defect formation during the epitaxial growth of WO3 on SrTiO3(001). A metastable tetragonal phase can be stabilized by heteroepitaxy and a thickness-dependent phase transition (tetragonal to monoclinic) is observed. In contrast to misfit dislocation formation, facile WO6 octahedral deformation gives rise to three types of planar defects. The thicknesses of affected regions can range from several to tens of nanometers with graded lattice parameters, allowing the strain from interfacial lattice mismatch to be relieved gradually. These atomically resolved, unique interfacial defects may significantly alter the electronic, electrochromic, and mechanical properties of WO3 epitaxial films. PMID:25058665

  14. ANNUAL REPORT. SUPRAMOLECULAR CHEMISTRY OF SELECTIVE ANION RECOGNITION FOR ANIONS OF ENVIRONMENTAL RELEVANCE

    EPA Science Inventory

    This project involves the design and synthesis of receptors for anions of environmental importance, including emphasis on high level and low activity waste. Polyammonium macrocycles as receptors and nitrate as target anion were the focus of the first phase of this project. A seco...

  15. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Bowman-James, K.; Wilson, G.; Moyer, B. A.

    2004-12-11

    This project involves the design and synthesis of receptors for oxoanions of environmental importance, including emphasis on high level and low activity waste. Target anions have included primarily oxoanions and a study of the basic concepts behind selective binding of target anions. A primary target has been sulfate because of its deleterious influence on the vitrification of tank wastes

  16. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Bowman-James, Kristen

    2004-12-01

    This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical and structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.

  17. Correction of the anion gap for albumin in order to detect occult tissue anions in shock

    PubMed Central

    Hatherill, M; Waggie, Z; Purves, L; Reynolds, L; Argent, A

    2002-01-01

    Background: It is believed that hypoalbuminaemia confounds interpretation of the anion gap (AG) unless corrected for serum albumin in critically ill children with shock. Aim: To compare the ability of the AG and the albumin corrected anion gap (CAG) to detect the presence of occult tissue anions. Methods: Prospective observational study in children with shock in a 22 bed multidisciplinary paediatric intensive care unit of a university childrenrsquo;s hospital. Blood was sampled at admission and at 24 hours, for acid-base parameters, serum albumin, and electrolytes. Occult tissue anions (lactate + truly "unmeasured" anions) were calculated from the strong ion gap. The anion gap ((Na + K) - (Cl + bicarbonate)) was corrected for serum albumin using the equation of Figge: AG + (0.25 x (44 - albumin)). Occult tissue anions (TA) predicted by the anion gap were calculated by (anion gap - 15 mEq/l). Optimal cut off values of anion gap were compared by means of receiver operating characteristic (ROC) curves. Ninety three sets of data from 55 children (median age 7 months, median weight 4.9 kg) were analysed. Data are expressed as mean (SD), and mean bias (limits of agreement). Results: The incidence of hypoalbuminaemia was 76% (n = 42/55). Mean serum albumin was 25 g/l (SD 8). Mean AG was 15.0 mEq/l (SD 6.1), compared to the CAG of 19.9 mEq/l (SD 6.6). Mean TA was 10.2 mmol/l (SD 6.3). The AG underestimated TA with mean bias 10.2 mmol/l (4.1–16.1), compared to the CAG, mean bias 5.3 mmol/l (0.4–10.2). A clinically significant increase of TA >5 mmol/l was present in 83% (n = 77/93) of samples, of which the AG detected 48% (n = 36/77), and the CAG 87% (n = 67/77). Post hoc ROC analysis revealed optimal cut off values for detection of TA >5 mmol/l to be AG >10 mEq/l, and CAG >15.5 mEq/l. Conclusion: Hypoalbuminaemia is common in critically ill children with shock, and is associated with a low observed anion gap that may fail to detect clinically significant amounts of

  18. Electron impact induced anion production in acetylene.

    PubMed

    Szymańska, Ewelina; Čadež, Iztok; Krishnakumar, E; Mason, Nigel J

    2014-02-28

    A detailed experimental investigation of electron induced anion production in acetylene, C2H2, in the energy range between 1 and 90 eV is presented. The anions are formed by two processes in this energy range: dissociative electron attachment (DEA) and dipolar dissociation (DD). DEA in C2H2 is found to lead to the formation of H(-) and C2(-)/C2H(-) through excitation of resonances in the electron energy range 1-15 eV. These anionic fragments are formed with super thermal kinetic energy and reveal no anisotropy in the angular distributions. DD in C2H2 leads to the formation of H(-), C(-)/CH(-) and C2(-)/C2H(-) with threshold energies of 15.7, 20.0 and 16.5 eV respectively. The measured anion yields have been used to calculate anion production rates for H(-), C(-)/CH(-) and C2(-)/C2H(-) in Titan's ionosphere. PMID:24343432

  19. Infrared spectroscopy of anionic hydrated fluorobenzenes

    SciTech Connect

    Schneider, Holger; Vogelhuber, Kristen M.; Weber, J. Mathias

    2007-09-21

    We investigate the structural motifs of anionic hydrated fluorobenzenes by infrared photodissociation spectroscopy and density functional theory. Our calculations show that all fluorobenzene anions under investigation are strongly distorted from the neutral planar molecular geometries. In the anions, different F atoms are no longer equivalent, providing structurally different binding sites for water molecules and giving rise to a multitude of low-lying isomers. The absorption bands for hexa- and pentafluorobenzene show that only one isomer for the respective monohydrate complexes is populated in our experiment. For C{sub 6}F{sub 6}{sup -}{center_dot}H{sub 2}O, we can assign these bands to an isomer where water forms a weak double ionic hydrogen bond with two F atoms in the ion, in accord with the results of Bowen et al. [J. Chem. Phys. 127, 014312 (2007), following paper.] The spectroscopic motif of the binary complexes changes slightly with decreasing fluorination of the aromatic anion. For dihydrated hexafluorobenzene anions, several isomers are populated in our experiments, some of which may be due to hydrogen bonding between water molecules.

  20. Electroosmotic Flow Hysteresis for Dissimilar Anionic Solutions.

    PubMed

    Lim, An Eng; Lim, Chun Yee; Lam, Yee Cheong

    2016-08-16

    Electroosmotic flow (EOF) with two or more fluids is often encountered in various microfluidic applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during displacement flow of solutions with dissimilar anion species. In this investigation, EOF of dissimilar anionic solutions was studied experimentally through the current monitoring method and numerically through finite element simulations. As opposed to other conventional displacement flows, EOF involving dissimilar anionic solutions exhibits counterintuitive behavior, whereby the current-time curve does not reach the steady-state value of the displacing electrolyte. Two distinct mechanics have been identified as the causes for this observation: (a) ion concentration adjustment when the displacing anions migrate upstream against EOF due to competition between the gradients of electromigrative and convective fluxes and (b) ion concentration readjustment induced by the static diffusive interfacial region between the dissimilar fluids which can only be propagated throughout the entire microchannel with the presence of EOF. The resultant ion distributions lead to the flow rate to be directional-dependent, indicating that the flow conditions are asymmetric between these two different flow directions. The outcomes of this investigation contribute to the in-depth understanding of flow behavior in microfluidic systems involving inhomogeneous fluids, particularly dissimilar anionic solutions. The understanding of EOF hysteresis is fundamentally important for the accurate prediction of analytes transport in microfluidic devices under EOF. PMID:27426052

  1. Infrared Spectroscopy of Hydrated Nitromethane Anions

    NASA Astrophysics Data System (ADS)

    Marcum, Jesse C.; Weber, J. Mathias

    2009-06-01

    The hydration of molecular anions is still not as thoroughly explored as for atomic anions. We present IR spectra and quantum chemical calculations of hydrated nitromethane anions. In the monohydrate, the nitro group of the ion interacts with the water molecule via two hydrogen bonds, one from each O atom. This motif is partially conserved in the dihydrate. Adding the third water molecule results in a ring-like structure of the water ligands, each of which forms one H bond to one of the O atoms of the nitro group and another to a neighboring water ligand, reminiscent of the hydration motif of the heavier halides. Interestingly, while the methyl group is not directly involved in the interaction with the water ligands, its infrared signature is strongly affected by the changes in the intramolecular charge distribution through hydration.

  2. An anionic surfactant for EOR applications

    NASA Astrophysics Data System (ADS)

    Sagir, Muhammad; Tan, Isa M.; Mushtaq, Muhammad

    2014-10-01

    This work is to investigate the new anionic surfactants for the Enhanced Oil Recovery (EOR) application. Sulfonated anionic surfactant was produced by attaching SO3 to an ethoxylated alcohol to increase the performance of the surfactant. Methallyl chloride and ethoxylated alcohol was reacted followed by the reaction with sodium bisulfite to produce anionic sulfonated surfactant in 80.3 % yield. The sulfonation reaction parameters such as reactants mole ratio, reaction temperature and catalyst amount were optimized. The generation and stability of foam from the synthesized surfactant is also tested and results are reported. The synthesized novel surfactant was further investigated for the effect on the CO2 mobility in porous media and the findings are presented here. This in house developed surfactant has a great potential for CO2- EOR applications.

  3. Identification and characterization of anion binding sites in RNA

    SciTech Connect

    Kieft, Jeffrey S.; Chase, Elaine; Costantino, David A.; Golden, Barbara L.

    2010-05-24

    Although RNA molecules are highly negatively charged, anions have been observed bound to RNA in crystal structures. It has been proposed that anion binding sites found within isolated RNAs represent regions of the molecule that could be involved in intermolecular interactions, indicating potential contact points for negatively charged amino acids from proteins or phosphate groups from an RNA. Several types of anion binding sites have been cataloged based on available structures. However, currently there is no method for unambiguously assigning anions to crystallographic electron density, and this has precluded more detailed analysis of RNA-anion interaction motifs and their significance. We therefore soaked selenate into two different types of RNA crystals and used the anomalous signal from these anions to identify binding sites in these RNA molecules unambiguously. Examination of these sites and comparison with other suspected anion binding sites reveals features of anion binding motifs, and shows that selenate may be a useful tool for studying RNA-anion interactions.

  4. Electron anions and the glass transition temperature.

    PubMed

    Johnson, Lewis E; Sushko, Peter V; Tomota, Yudai; Hosono, Hideo

    2016-09-01

    Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32](2+) ⋅ (e(-))2, we demonstrate that electron anions in this system behave as glass modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. The concentration of such electron anions is a consequential control parameter: It invokes materials evolution pathways and properties not available in conventional glasses, which opens a unique avenue in rational materials design. PMID:27559083

  5. Anionic polymerization of azo substituted methacrylates

    SciTech Connect

    Dimov, D.K.; Dalton, L.R.; Hogen-Esch, T.E.

    1993-12-31

    The anionic polymerization of 4-phenylazophenyl methacrylate (PAM) and 6-(4-phenylazophenoxy)-hexyl methacrylate (PAHM) initiated by {open_quotes}living{close_quotes} PMMA with lithium counterion was studied in THF at {minus}78{degrees}C. The polymerization of PAM was prevented by a side termination reaction. The polymerization of PAHM proceeded smoothly to furnish PMMA/azopolymer block copolymers. The process showed features typical of {open_quotes}living{close_quotes} anionic polymerization. No phase transitions could be detected by DSC to prove liquid crystalline mesophase formation by the block copolymers.

  6. Tris-ureas as transmembrane anion transporters.

    PubMed

    Olivari, Martina; Montis, Riccardo; Berry, Stuart N; Karagiannidis, Louise E; Coles, Simon J; Horton, Peter N; Mapp, Lucy K; Gale, Philip A; Caltagirone, Claudia

    2016-08-01

    Nine tris-urea receptors (L(1)-L(9)) have been synthesised and shown to coordinate to a range of anionic guests both by (1)H NMR titration techniques and single crystal X-ray structural analysis. The compounds have been shown to be capable of mediating the exchange of chloride and nitrate and also chloride and bicarbonate across POPC or POPC : cholesterol 7 : 3 vesicle bilayer membranes at low transporter loadings. An interesting dependency of anion transport on the nature of the cation is evidence to suggest that a M(+)/Cl(-) cotransport process may also contribute to the release of chloride from the vesicles. PMID:27383134

  7. Negative Ion Photoelectron Spectra of Halomethyl Anions

    NASA Astrophysics Data System (ADS)

    Vogelhuber, Kristen M.; Wren, Scott W.; McCoy, Anne B.; Ervin, Kent M.; Lineberger, W. Carl

    2009-06-01

    Halomethyl anions undergo a significant geometry change upon electron photodetachment, resulting in multiple extended vibrational progressions in the photoelectron spectra. The normal mode analysis that successfully models photoelectron spectra when geometry changes are modest is unable to reproduce the experimental data using physically reasonable parameters. A three-dimensional anharmonic coupled-mode analysis was employed to accurately reproduce the observed vibrational structure. We present the 364 nm negative ion photoelectron spectra of the halomethyl anions CHX_2^- and CDX_2^- (X = Cl, Br, I) and report electron affinities, vibrational frequencies, and geometries.

  8. Synthesis and characterization of a monomeric octahedral C2-symmetric titanium complex bearing two 3,3'-diphenyl-2,2'-biphenol ligands.

    PubMed

    Diebold, Carine; Mobian, Pierre; Huguenard, Clarisse; Allouche, Lionel; Henry, Marc

    2009-12-14

    The 3,3'-diphenyl-2,2'-biphenol (dpbpolH(2)) ligand is shown to react with Ti(OPr(i))(4) in a 2:1 ratio to yield a novel C(2)-symmetric mononuclear octahedral Ti(IV) bis-biphenolate complex, cis-Ti(dpbpol)(2)(HOPr(i))(2). PMID:19921051

  9. Facile synthesis of LiMn2O4 octahedral nanoparticles as cathode materials for high capacity lithium ion batteries with long cycle life

    NASA Astrophysics Data System (ADS)

    Cai, Yanjun; Huang, Yudai; Wang, Xingchao; Jia, Dianzeng; Pang, Weikong; Guo, Zaiping; Du, Yaping; Tang, Xincun

    2015-03-01

    Spinel lithium manganate octahedral nanoparticles have been prepared by high temperature solid-state combustion reaction using cellulose as fuel. The crystal structure, morphology, and electrochemical performance of the as-prepared materials are analyzed by X-ray diffraction (XRD), electron microscopy, and electrochemical testing. The XRD results show that the materials are single-phase and perfectly crystalline with a spinel structure. Microscopic observations reveal that the nanoparticles possess octahedral morphology, with an average particle size of about 165.4 nm and a uniform particle size distribution. The lithium manganate octahedral nanoparticles exhibit excellent initial discharge capacity of 118.5 and 78.3 mAh g-1, and about 72.49% and 94.6% of its initial discharge capacity can be retained even after 1600 cycles at 10 C and 3000 cycles at 20 C, respectively. The excellent electrochemical performance of the lithium manganate can be mainly attributed to the strong MnO6 framework mitigates the occurrence of Mn dissolution, maintains structural stability, and allows higher Li+ diffusion during electrochemical cycling. Furthermore, the nano-sized octahedral structure not only facilitates fast ion diffusion, but also mitigates the manganese dissolution due to the exposed (111) crystal planes, where the solid electrolyte interphase (SEI) forms.

  10. Photoelectron spectroscopy and theoretical studies of anion-π interactions: binding strength and anion specificity.

    PubMed

    Zhang, Jian; Zhou, Bin; Sun, Zhen-Rong; Wang, Xue-Bin

    2015-02-01

    Proposed in theory and then their existence confirmed, anion-π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, anion-π interaction strengths that are free from complications of condensed-phase environments have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic, was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl(-), Br(-), I(-), linear thiocyanate SCN(-), trigonal planar nitrate NO3(-), pyramidic iodate IO3(-), and tetrahedral sulfate SO4(2-)). The binding energies of the resultant gaseous 1 : 1 complexes (1·Cl(-), 1·Br(-), 1·I(-), 1·SCN(-), 1·NO3(-), 1·IO3(-) and 1·SO4(2-)) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion-specific effects. The binding strengths of Cl(-), NO3(-), IO3(-) with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal mol(-1), but only about 40% of that between 1 and SO4(2-). Quantum chemical calculations reveal that all the anions reside in the center of the cavity of 1 with an anion-π binding motif in the complexes' optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and charge distribution analyses further support anion-π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work illustrates that size-selective photoelectron

  11. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2011-11-22

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  12. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2010-12-07

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  13. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2009-09-01

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  14. Anion-Conducting Polymer, Composition, and Membrane

    SciTech Connect

    Pivovar, Bryan S.; Thorn, David L.

    2008-10-21

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  15. Controlled one-step synthesis of Pt decorated octahedral Fe3O4 and its excellent catalytic performance for CO oxidation

    NASA Astrophysics Data System (ADS)

    Li, Gengnan; Li, Liang; Wu, Binghan; Li, Jinxia; Yuan, Yuan; Shi, Jianlin

    2015-10-01

    A facile one-step co-precipitation method has been applied for the synthesis of a Pt decorated octahedral Fe3O4 catalyst. The simple addition of a Pt4+ and Fe2+ mixture into a KOH solution leads to the simultaneous formation of an octahedral Fe3O4 and in situ reduction of Pt4+. HAADF-STEM analysis demonstrates the good dispersion of the Pt species on the Fe3O4 (111) plane, and the resulting material exhibits excellent catalytic activity for CO oxidation under moisture conditions. The inevitably existing moisture contributes to the formation of reaction intermediate [COOH] and hence promotes the catalytic activity, which has been proved through in situ DRIFTS analysis.A facile one-step co-precipitation method has been applied for the synthesis of a Pt decorated octahedral Fe3O4 catalyst. The simple addition of a Pt4+ and Fe2+ mixture into a KOH solution leads to the simultaneous formation of an octahedral Fe3O4 and in situ reduction of Pt4+. HAADF-STEM analysis demonstrates the good dispersion of the Pt species on the Fe3O4 (111) plane, and the resulting material exhibits excellent catalytic activity for CO oxidation under moisture conditions. The inevitably existing moisture contributes to the formation of reaction intermediate [COOH] and hence promotes the catalytic activity, which has been proved through in situ DRIFTS analysis. Electronic supplementary information (ESI) available: The structural analysis of the catalysts, the effect of the concentration of reactants during the CO oxidation process, the effect of pre-treatment for CO oxidation, the comparison of the present work with the literature, and the hysteresis loops of as-prepared octahedral Fe3O4 nanoparticles. See DOI: 10.1039/c5nr05933j

  16. SUPRAMOLECULAR CHEMISTRY OF SELECTIVE ANION RECOGNITION FOR ANIONS OF ENVIRONMENTAL RELEVANCE

    EPA Science Inventory

    The supramolecular chemistry of selective anion recognition by synthetic polyammonium macrocycles will be explored in a comprehensive, long term program designed to provide new solutions to problems critical to the environmental initiative of DOE. Highly shape- and charge selecti...

  17. Bipyrrole-Strapped Calix[4]pyrroles: Strong Anion Receptors That Extract the Sulfate Anion

    SciTech Connect

    Kim, Sung Kuk; Lee, Juhoon; Williams, Neil J; Lynch, Vincent M.; Hay, Benjamin; Moyer, Bruce A; Sessler, Jonathan L.

    2014-01-01

    Cage-type calix[4]pyrroles 2 and 3 bearing two additional pyrrole groups on the strap have been synthesized. Compared with the parent calix[4]pyrrole (1), they were found to exhibit remarkably enhanced affinities for anions, including the sulfate anion (TBA+ salts), in organic media (CD2Cl2). This increase is ascribed to participation of the bipyrrole units in anion binding. Receptors 2 and 3 extract the hydrophilic sulfate anion (as the methyltrialkyl(C8-10)ammonium (A336+) salt)) from aqueous media into a chloroform phase with significantly improved efficiency (>10-fold relative to calix[4]pyrrole 1). These two receptors also solubilize into chloroform the otherwise insoluble sulfate salt, (TMA)2SO4 (tetramethylammonium sulfate).

  18. Truncated Hexa-Octahedral Magnetite Crystals in Martian Meteorite ALH84001: Evidence of Biogenic Activity on Early Mars

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.; Clemett, S. J.; Schwartz, C.; McIntosh, J. R.; Bazylinski, D. A.; Kirschvink, J.; McKay, D. S.; Gibson, E. K.; Vali, H.; Romanek, C. S.

    2004-01-01

    The landmark paper by McKay et al. [1] cited four lines of evidence associated with the Martian meteorite ALH84001 to support the hypothesis that life existed on Mars approximately 4 Ga ago. Now, more than five years later, attention has focused on the ALH84001 magnetite grains embedded within carbonate globules in the ALH84001 meteorite. We have suggested that up to approx.25% of the ALH84001 magnetite crystals are products of biological activity [e.g., 2]. The remaining magnetites lack sufficient characteristics to constrain their origin. The papers of Thomas Keprta et al. were criticized arguing that the three dimensional structure of ALH84001 magnetite crystals can only be unambiguously determined using electron tomographic techniques. Clemett et al. [3] confirmed that magnetites produced by magnetotactic bacteria strain MV-I display a truncated hexa-octahedral geometry using electron tomography and validated the use of the multi-tilt classical transmission microscopy technique used by [2]. Recently the geometry of the purported martian biogenic magnetites was shown be identical to that for MV-1 magnetites using electron tomography [6].

  19. Enhanced Catalytic Activities of NiPt Truncated Octahedral Nanoparticles toward Ethylene Glycol Oxidation and Oxygen Reduction in Alkaline Electrolyte.

    PubMed

    Xia, Tianyu; Liu, Jialong; Wang, Shouguo; Wang, Chao; Sun, Young; Gu, Lin; Wang, Rongming

    2016-05-01

    The high cost and poor durability of Pt nanoparticles (NPs) are great limits for the proton exchange membrane fuel cells (PEMFCs) from being scaled-up for commercial applications. Pt-based bimetallic NPs together with a uniform distribution can effectively reduce the usage of expensive Pt while increasing poison resistance of intermediates. In this work, a simple one-pot method was used to successfully synthesize ultrafine (about 7.5 nm) uniform NiPt truncated octahedral nanoparticles (TONPs) in dimethylformamid (DMF) without any seeds or templates. The as-prepared NiPt TONPs with Pt-rich surfaces exhibit greatly improved catalytic activities together with good tolerance and better stability for ethylene glycol oxidation reaction (EGOR) and oxygen reduction reaction (ORR) in comparison with NiPt NPs and commercial Pt/C catalysts in alkaline electrolyte. For example, the value of mass and specific activities for EGOR are 23.2 and 17.6 times higher comparing with those of commercial Pt/C, respectively. Our results demonstrate that the dramatic enhancement is mainly attributed to Pt-rich surface, larger specific surface area, together with coupling between Ni and Pt atoms. This developed method provides a promising pathway for simple preparation of highly efficient electrocatalysts for PEMFCs in the near future. PMID:27093304

  20. In Situ Assembly of Octahedral Fe(II) Complexes for the Enantiomeric Excess Determination of Chiral Amines Using CD spectroscopy

    PubMed Central

    Dragna, Justin; Pescitelli, Gennaro; Tran, Lee; Lynch, Vincent M.; Anslyn, Eric V.; Di Bari, Lorenzo

    2012-01-01

    A method for discriminating between α-chiral primary amine enantiomers is reported. The method utilizes circular dichroism spectroscopy and a sensing ensemble composed of 2-formyl-3-hydroxyl pyridine (4) and Fe(II)(TfO)2. Aldehyde 4 reacts rapidly with chiral amines to form chiral imines, which complex Fe(II) to form a series of diastereomeric octahedral complexes that are CD active in both the UV and visible spectrum. NMR studies showed that, for enantiomerically pure imine complexes, the Δ-fac isomer is preferred. A statistical analysis of the distribution of stereoisomers accurately models the calibration curves for enantiomeric excess. CD signals appearing in the UV region were bisignate, and the null of the CD signals were coincident with maxima in the UV spectrum, consistent with exciton coupling. TTDFT and semi-empirical calculations confirmed that the CD signals in the UV region arise from coupling of the π-π* transitions in the imine chromophores, and can be used to accurately describe the sign and magnitudes of the curves. The CD signals in the visible region arise from metal-to-ligand charge transfer bands, and these signals can be used to determine the ee values of chiral amines with an average absolute error of ±5%. Overall, the strategy presented herein represents a facile in situ assembly that uses commercially available simple reagents to create large optical signals indicative of ee values. PMID:22272943

  1. Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt-Ni-Co Alloy Nanocatalysts.

    PubMed

    Arán-Ais, Rosa M; Dionigi, Fabio; Merzdorf, Thomas; Gocyla, Martin; Heggen, Marc; Dunin-Borkowski, Rafal E; Gliech, Manuel; Solla-Gullón, José; Herrero, Enrique; Feliu, Juan M; Strasser, Peter

    2015-11-11

    Multimetallic shape-controlled nanoparticles offer great opportunities to tune the activity, selectivity, and stability of electrocatalytic surface reactions. However, in many cases, our synthetic control over particle size, composition, and shape is limited requiring trial and error. Deeper atomic-scale insight in the particle formation process would enable more rational syntheses. Here we exemplify this using a family of trimetallic PtNiCo nanooctahedra obtained via a low-temperature, surfactant-free solvothermal synthesis. We analyze the competition between Ni and Co precursors under coreduction "one-step" conditions when the Ni reduction rates prevailed. To tune the Co reduction rate and final content, we develop a "two-step" route and track the evolution of the composition and morphology of the particles at the atomic scale. To achieve this, scanning transmission electron microscopy and energy dispersive X-ray elemental mapping techniques are used. We provide evidence of a heterogeneous element distribution caused by element-specific anisotropic growth and create octahedral nanoparticles with tailored atomic composition like Pt1.5M, PtM, and PtM1.5 (M = Ni + Co). These trimetallic electrocatalysts have been tested toward the oxygen reduction reaction (ORR), showing a greatly enhanced mass activity related to commercial Pt/C and less activity loss than binary PtNi and PtCo after 4000 potential cycles. PMID:26441293

  2. Time-Dependent CO[subscript 2] Sorption Hysteresis in a One-Dimensional Microporous Octahedral Molecular Sieve

    SciTech Connect

    Espinal, Laura; Wong-Ng, Winnie; Kaduk, James A.; Allen, Andrew J.; Snyder, Chad R.; Chiu, Chun; Siderius, Daniel W.; Li, Lan; Cockayne, Eric; Espinal, Anais E.; Suib, Steven L.

    2014-09-24

    The development of sorbents for next-generation CO{sub 2} mitigation technologies will require better understanding of CO{sub 2}/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO{sub 2} sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO{sub 2} sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a 'gate-keeping' role of the cation in the tunnel, only allowing CO{sub 2} molecules to enter fully into the tunnel via a highly unstable transient state when CO{sub 2} loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO{sub 2} is responsible for the observed hysteretic behavior.

  3. A facile and versatile methodology for cysteine specific labeling of proteins with octahedral polypyridyl d6 metal complexes

    PubMed Central

    Dwaraknath, Sudharsan; Tran, Ngoc-Han; Dao, Thanh; Colbert, Alexander; Mullen, Sarah; Nguyen, Angelina; Cortez, Alejandro; Cheruzel, Lionel

    2014-01-01

    We have synthesized and characterized four octahedral polypyridyl d6 metal complexes bearing the 5,6-epoxy-5,6-dihydro-[1,10]phenanthroline ligand (L1) as cysteine specific labeling reagents. The proposed synthetic pathways allow the preparation of the metal complexes containing Re(I), Ru(II), Os(II) and Ir(III) while preserving the epoxide functionality. The complexes were characterized by 1H and 13C NMR, mass spectrometry, UV-visible and luminescence spectroscopies as well as cyclic voltammetry. As proof of concept, a set of non-native single cysteine P450 BM3 heme domain mutants previously developed in our laboratory was used to study the labeling reaction. We demonstrate that the proposed labels can selectively react, often in high yield, with cysteine residues of the protein via the nucleophilic thiol ring opening of the epoxide moiety. In addition, under basic conditions, subsequent loss of a water molecule led to the aromatization of the phenanthroline ring on the protein-bound label compounds, as observed by mass spectrometry and luminescence measurements. PMID:24468675

  4. Catalytic degradation of Acid Orange 7 by manganese oxide octahedral molecular sieves with peroxymonosulfate under visible light irradiation.

    PubMed

    Duan, Lian; Sun, Binzhe; Wei, Mingyu; Luo, Shilu; Pan, Fei; Xu, Aihua; Li, Xiaoxia

    2015-03-21

    In this paper, the photodegradation of Acid Orange 7 (AO7) in aqueous solutions with peroxymonosulfate (PMS) was studied with manganese oxide octahedral molecular sieves (OMS-2) as the catalyst. The activities of different systems including OMS-2 under visible light irradiation (OMS-2/Vis), OMS-2/PMS and OMS-2/PMS/Vis were evaluated. It was found that the efficiency of OMS-2/PMS was much higher than that of OMS-2/Vis and could be further enhanced by visible light irradiation. The catalyst also exhibited stable performance for multiple runs. Results from ESR and XPS analyses suggested that the highly catalytic activity of the OMS-2/PMS/Vis system possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) and Mn(III)/Mn(II), while in the OMS-2/PMS system, only the redox reaction between Mn(IV)/Mn(III) occurred. Several operational parameters, such as dye concentration, catalyst load, PMS concentration and solution pH, affected the degradation of AO7. PMID:25528234

  5. Effects of octahedral molecular sieve on treatment performance, microbial metabolism, and microbial community in expanded granular sludge bed reactor.

    PubMed

    Pan, Fei; Xu, Aihua; Xia, Dongsheng; Yu, Yang; Chen, Guo; Meyer, Melissa; Zhao, Dongye; Huang, Ching-Hua; Wu, Qihang; Fu, Jie

    2015-12-15

    This study evaluated the effects of synthesized octahedral molecular sieve (OMS-2) nanoparticles on the anaerobic microbial community in a model digester, expanded granular sludge bed (EGSB) reactor. The addition of OMS-2 (0.025 g/L) in the EGSB reactors resulted in an enhanced operational performance, i.e., COD removal and biogas production increased by 4% and 11% respectively, and effluent volatile fatty acid (VFA) decreased by 11% relative to the control group. The Biolog EcoPlate™ test was employed to investigate microbial metabolism in the EGSB reactors. Results showed that OMS-2 not only increased the microbial metabolic level but also significantly changed the community level physiological profiling of the microorganisms. The Illumina MiSeq high-throughput sequencing of 16S rRNA gene indicated OMS-2 enhanced the microbial diversity and altered the community structure. The largest bacterial genus Lactococcus, a lactic acid bacterium, reduced from 29.3% to 20.4% by abundance in the presence of 0.25 g/L OMS-2, which may be conducive to decreasing the VFA production and increasing the microbial diversity. OMS-2 also increased the quantities of acetogenic bacteria and Archaea, and promoted the acetogenesis and methanogenesis. The X-ray photoelectron spectroscopy illustrated that Mn(IV)/Mn(III) with high redox potential in OMS-2 were reduced to Mn(II) in the EGSB reactors; this in turn affected the microbial community. PMID:26397455

  6. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Jonathan L. Sessler

    2007-09-21

    The major thrust of this project, led by the University of Kansas (Prof. Kristin Bowman-James), entails an exploration of the basic determinants of anion recognition and their application to the design, synthesis, and testing of novel sulfate extractants. A key scientific inspiration for the work comes from the need, codified in simple-to-appreciate terms by the Oak Ridge National Laboratory component of the team (viz. Dr. Bruce Moyer), for chemical entities that can help in the extractive removal of species that have low solubilities in borosilicate glass. Among such species, sulfate anion, has been identified as particularly insidious. Its presence interferes with the vitrification process, thus rendering the remediation of tank waste from, e.g., the Hanford site far more difficult and expensive. The availability of effective extractants, that would allow for the separation of separating sulfate from the major competing anions in the waste, especially nitrate, could allow for pre-vitrification removal of sulfate via liquid-liquid extraction. The efforts at The University of Texas, the subject of this report, have thus concentrated on the development of new sulfate receptors. These systems are designed to increase our basic understanding of anion recognition events and set the stage for the development of viable sulfate anion extractants. In conjunction with the Oak Ridge National Laboratory (ORNL) members of the research team, several of these new receptors were studied as putative extractants, with two of the systems being shown to act as promising synergists for anion exchange.

  7. Understanding and modeling removal of anionic organic contaminants (AOCs) by anion exchange resins.

    PubMed

    Zhang, Huichun; Shields, Anthony J; Jadbabaei, Nastaran; Nelson, Maurice; Pan, Bingjun; Suri, Rominder P S

    2014-07-01

    Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH. PMID:24877792

  8. High Yield C-Derivatization of Weakly Coordinating Carborane Anions

    PubMed Central

    Nava, Matthew J.

    2010-01-01

    Unlike the “parent” carborane anion CHB11H11−, halogenated carborane anions such as CHB11H5Br6− can be readily C-functionalized in high yield and purity, enhancing their utility as weakly coordinating anions. PMID:20450167

  9. Reversible photochromism of an N-salicylidene aniline anion.

    PubMed

    Jacquemin, Pierre-Loïc; Robeyns, Koen; Devillers, Michel; Garcia, Yann

    2014-01-21

    The first N-salicylidene aniline anion showing reversible solid state thermochromic and photochromic properties is described. The photo-isomerization involves a trans-keto form which is stabilized thanks to the local anion surrounding. This photochromic anion can be used as a guest for the preparation of hybrid materials by insertion into a cationic host matrix. PMID:24022381

  10. Evaluation of cation-anion interaction strength in ionic liquids.

    PubMed

    Fernandes, Ana M; Rocha, Marisa A A; Freire, Mara G; Marrucho, Isabel M; Coutinho, João A P; Santos, Luís M N B F

    2011-04-14

    Electrospray ionization mass spectrometry with variable collision induced dissociation of the isolated [(cation)(2)anion](+) and/or [(anion)(2)cation](-) ions of imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ionic liquids (ILs) combined with a large set of anions, such as chloride, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, and bis[(trifluoromethyl)sulfonyl]imide, was used to carry out a systematic and comprehensive study on the ionic liquids relative interaction energies. The results are interpreted in terms of main influences derived from the structural characteristics of both anion and cation. On the basis of quantum chemical calculations, the effect of the anion upon the dissociation energies of the ionic liquid pair, and isolated [(cation)(2)anion](+) and/or [(anion)(2)cation](-) aggregates, were estimated and are in good agreement with the experimental data. Both experimental and computational results indicate an energetic differentiation between the cation and the anion to the ionic pair. Moreover, it was found that the quantum chemical calculations can describe the trend obtained for the electrostatic cation-anion attraction potential. The impact of the cation-anion interaction strengths in the surface tension of ionic liquids is further discussed. The surface tensions dependence on the cation alkyl chain length, and on the anion nature, follows an analogous pattern to that of the relative cation-anion interaction energies determined by mass spectrometry. PMID:21425809

  11. The chemistry of gold as an anion.

    PubMed

    Jansen, Martin

    2008-09-01

    Due to relativistic and classical shell structure effects, the 6s orbital of gold is significantly contracted and energetically stabilized. This is reflected by a strikingly high electron affinity, and a distinct tendency to adopt negatively polarized valence states. This tutorial review focuses on the chemistry of gold as an anion, displaying the integral ionic charge number of 1-. Two synthetic approaches to compounds containing monoatomic gold anions have become available: (1) reacting elemental gold with molten caesium and an oxide, e.g. Cs2O; (2) metathesis reactions involving Au- dissolved in liquid ammonia. Both procedures have proven to be rather versatile. Aurides synthesized along these routes are surveyed, in particular with respect to their structures and bonding properties. PMID:18762832

  12. Anion photoelectron spectroscopy of radicals and clusters

    SciTech Connect

    Travis, Taylor R.

    1999-12-16

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C{sub 2}H and C{sub 4}H. Other radicals studied include NCN and I{sub 3}. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I{sub 3} revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

  13. Specific anion effects in Artemia salina.

    PubMed

    Lo Nostro, Pierandrea; Ninham, Barry W; Carretti, Emiliano; Dei, Luigi; Baglioni, Piero

    2015-09-01

    The specific anion effect on the vitality of Artemia salina was investigated by measuring the Lethal Time LT50 of the crustaceans in the presence of different sodium salts solutions at room temperature and at the same ionic strength as natural seawater. Fluoride, thiocyanate and perchlorate are the most toxic agents, while chloride, bromide and sulfate are well tolerated. The rates of oxygen consumption of brine shrimps were recorded in mixed NaCl+NaF or NaCl+NaSCN solutions as a function of time. The results are discussed in terms of the Hofmeister series, and suggest that, besides the biochemical processes that involve F(-), SCN(-) and ClO4(-), the different physico-chemical properties of the strong kosmotropic and chaotropic anions may contribute in determining their strong toxicity for A. salina. PMID:25978674

  14. Anion formation by neutral resonant ionization

    NASA Astrophysics Data System (ADS)

    Vogel, John S.

    2015-10-01

    A collision-radiation model of the cesium plasma that forms within a pitted or recessed sample in a Middleton-type sputter ion source showed that excited states of Cs formed. These excited states of neutral Cs undergo resonant electron transfer with neutral sputtered atoms of AMS samples to produce the accelerated anions. Numerous reported effects from over 30 years are readily explained by this mechanism, including several that puzzled Middleton.

  15. Cooling dynamics of carbon cluster anions

    NASA Astrophysics Data System (ADS)

    Shiromaru, H.; Furukawa, T.; Ito, G.; Kono, N.; Tanuma, H.; Matsumoto, J.; Goto, M.; Majima, T.; Sundén, A. E. K.; Najafian, K.; Pettersson, M. S.; Dynefors, B.; Hansen, K.; Azuma, T.

    2015-09-01

    A series of ion storage experiments on small carbon cluster anions was conducted to understand size-dependent cooling processes. The laser-induced delayed electron detachment time profile show clear even/odd alternation due to the presence of the electronic cooling. The time evolution of the internal energy distribution was simulated for Cn- (n=4 to 7) with a common procedure taking vibrational and electronic cooling into account.

  16. Lowest autodetachment state of the water anion

    NASA Astrophysics Data System (ADS)

    Houfek, Karel; Čížek, Martin

    2016-05-01

    The potential energy surface of the ground state of the water anion H2O- is carefully mapped using multireference CI calculations for a large range of molecular geometries. Particular attention is paid to a consistent description of both the O-+H2 and OH-+H asymptotes and to a relative position of the anion energy to the ground state energy of the neutral molecule. The autodetachment region, where the anion state crosses to the electronic continuum is identified. The local minimum in the direction of the O- + H2 channel previously reported by Werner et al. [J. Chem. Phys. 87, 2913 (1987)] is found to be slighly off the linear geometry and is separated by a saddle from the autodetachment region. The autodetachment region is directly accessible from the OH-+H asymptote. For the molecular geometries in the autodetachment region and in its vicinity we also performed fixed-nuclei electron-molecule scattering calculations using the R-matrix method. Tuning of consistency of a description of the correlation energy in both the multireference CI and R-matrix calculations is discussed. Two models of the correlation energy within the R-matrix method that are consistent with the quantum chemistry calculations are found. Both models yield scattering quantities in a close agreement. The results of this work will allow a consistent formulation of the nonlocal resonance model of the water anion in a future publication. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  17. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

  18. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.O.; McBreen, J.

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.

  19. Effect of anionic amphophiles on erythrocyte properties.

    PubMed

    McMillan, D E; Utterback, N G; Wujek, J J

    1983-01-01

    This preliminary study describes effects of two pharmacologic agents on erythrocyte behavior. Increased erythrocyte aggregation has been proposed as important in the pathogenesis of a number of disorders, but the exact mechanism by which it plays a role in disease production remains unclear. Several anionic amphophiles have been reported to benefit diabetic vascular disease and atherosclerosis. If anionic amphophiles enter the erythrocyte plasma membrane they can increase its negative charge, reducing the energy of attraction between red blood cells and diminishing erythrocyte aggregation. Erythrocytes were studied after suspension in phosphate-buffered saline containing dextran as an aggregation-promoting agent. A marginal reduction of the suspension's viscosity was found at low shear rate when 2,5- dihydroxybenzene sulfonate was added. Additionally, erythrocyte sedimentation rate was marginally influenced. Both dihydroxybenzene sulfonate and acetylsalicylate protected human erythrocytes from hemolysis at concentrations from 10(-3) to 10(-5) M. The removal of erythrocyte sialic acid using neuraminidase to reduce surface negative charge led to unequivocal interference with aggregation (MAI technique of CHIEN et al., J. Gen. Physiol., 1973) by both anionic amphophiles were studied. Dihydroxybenzene sulfonate and actylsalicylate reduced the aggregation propensity of sialic-free erythrocytes, suggesting that the effect on the low shear rate viscosity of sialic acid-containing erythrocytes, though modest, is real. PMID:6587820

  20. Electronically excited states of PANH anions.

    PubMed

    Theis, Mallory L; Candian, Alessandra; Tielens, Alexander G G M; Lee, Timothy J; Fortenberry, Ryan C

    2015-06-14

    The singly deprotonated anion derivatives of nitrogenated polycyclic aromatic hydrocarbons (PANHs) are investigated for their electronically excited state properties. These include single deprotonation of the two unique arrangements of quinoline producing fourteen different isomers. This same procedure is also undertaken for single deprotonation of the three nitrogenation isomers of acridine and the three of pyrenidine. It is shown quantum chemically that the quinoline-class of PANH anion derivatives can only produce a candidate dipole-bound excited state each, a state defined as the interaction of an extra electron with the dipole moment of the corresponding neutral. However, the acridine- and pyrenidine-classes possess valence excited states as well as the possible dipole-bound excited states where the latter is only possible if the dipole moment is sufficiently large to retain the extra electron; the valence excitation is independent of the radical dipolar strength. As a result, the theoretical vertically computed electronic spectra of deprotonated PANH anion derivatives is fairly rich in the 1.5 eV to 2.5 eV range significantly opening the possibilities for these molecules to be applied to longer wavelength studies of visible and near-IR spectroscopy. Lastly, the study of these systems is also enhanced by the inclusion of informed orbital arrangements in a simply constructed basis set that is shown to be more complete and efficient than standard atom-centered functions. PMID:25975430

  1. Several hemicyanine dyes as fluorescence chemosensors for cyanide anions

    NASA Astrophysics Data System (ADS)

    Liang, Muhan; Wang, Kangnan; Guan, Ruifang; Liu, Zhiqiang; Cao, Duxia; Wu, Qianqian; Shan, Yanyan; Xu, Yongxiao

    2016-05-01

    Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ 1H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon-carbon double bond in conjugated bridge and induces N+ CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions.

  2. The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes.

    PubMed

    Hinz, Alexander; Goicoechea, Jose M

    2016-07-18

    The synthesis and isolation of the 2-arsaethynolate anion, AsCO(-) , and its subsequent reactivity towards heteroallenes is reported. Reactions with ketenes and carbodiimides afford four-membered anionic heterocycles in formal [2+2] cycloaddition reactions. By contrast, reaction with an isocyanate yielded a 1,4,2-diazaarsolidine-3,5-dionide anion and the unprecedented cluster anions As10 (2-) and As12 (4-) . These preliminary reactivity studies hint at the enormous potential synthetic utility of this novel anion, which may be employed as an arsenide (As(-) ) source. PMID:27093942

  3. Structure Determination of Feline Calicivirus Virus-Like Particles in the Context of a Pseudo-Octahedral Arrangement

    PubMed Central

    Burmeister, Wim P.; Buisson, Marlyse; Estrozi, Leandro F.; Schoehn, Guy; Billet, Olivier; Hannas, Zahia; Sigoillot, Cécile; Poulet, Hervé

    2015-01-01

    The vesivirus feline calicivirus (FCV) is a positive strand RNA virus encapsidated by an icosahedral T=3 shell formed by the viral VP1 protein. Upon its expression in the insect cell - baculovirus system in the context of vaccine development, two types of virus-like particles (VLPs) were formed, a majority built of 60 subunits (T=1) and a minority probably built of 180 subunits (T=3). The structure of the small particles was determined by x-ray crystallography at 0.8 nm resolution helped by cryo-electron microscopy in order to understand their formation. Cubic crystals belonged to space group P213. Their self-rotation function showed the presence of an octahedral pseudo-symmetry similar to the one described previously by Agerbandje and co-workers for human parvovirus VLPs. The crystal structure could be solved starting from the published VP1 structure in the context of the T=3 viral capsid. In contrast to viral capsids, where the capsomers are interlocked by the exchange of the N-terminal arm (NTA) domain, this domain is disordered in the T=1 capsid of the VLPs. Furthermore it is prone to proteolytic cleavage. The relative orientation of P (protrusion) and S (shell) domains is alerted so as to fit VP1 to the smaller T=1 particle whereas the intermolecular contacts around 2-fold, 3-fold and 5-fold axes are conserved. By consequence the surface of the VLP is very similar compared to the viral capsid and suggests a similar antigenicity. The knowledge of the structure of the VLPs will help to improve their stability, in respect to a use for vaccination. PMID:25794153

  4. Visible light induced bactericidal and photocatalytic activity of hydrothermally synthesized BiVO4 nano-octahedrals.

    PubMed

    Sharma, Rishabh; Uma; Singh, Sonal; Verma, Ajit; Khanuja, Manika

    2016-09-01

    In the present work, monoclinic bismuth vanadate (m-BiVO4) nanostructures have been synthesized via simple hydrothermal method and employed for visible light driven antimicrobial and photocatalytic activity. Morphology (octahedral) and size (200-300nm) of the m-BiVO4 are studied using transmission electron microscopy (TEM). The crystal structure of m-BiVO4 (monoclinic scheelite structure) is confirmed by high resolution-TEM (HRTEM) and X-ray diffraction (XRD) studies. The band gap of m-BiVO4 was estimated to be ca. 2.42eV through Kubelka-Munk function F(R∞) using diffuse reflectance spectroscopy (DRS). Antimicrobial action of m-BiVO4 is anticipated by (i) shake flask method, (ii) MTT [3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide] assay for cytotoxicity. SEM analysis has been carried on Escherichia coli (E.coli) before and after treatment with nanostructure materials to reveal the mechanism underlying the antimicrobial action. Antimicrobial activity is studied as a function of m-BiVO4 concentration viz. 20, 40, 60 and 80ppm. The bacterial growth is decreased 80% to 96%, with the increase in m-BiVO4 concentration from 20ppm to 80ppm, respectively, in 2h. Photocatalytic activity and rate kinetics of m-BiVO4 nanostructures have been studied as a function of time on methylene blue (MB) dye degradation which is one of the waste products of textile industries and responsible for water pollution. PMID:27394009

  5. Octahedral rotation patterns in strained EuFeO3 and other Pbnm perovskite films: Implications for hybrid improper ferroelectricity

    NASA Astrophysics Data System (ADS)

    Choquette, A. K.; Smith, C. R.; Sichel-Tissot, R. J.; Moon, E. J.; Scafetta, M. D.; Di Gennaro, E.; Miletto Granozio, F.; Karapetrova, E.; May, S. J.

    2016-07-01

    We report the relationship between epitaxial strain and the crystallographic orientation of the in-phase rotation axis and A -site displacements in Pbnm-type perovskite films. Synchrotron diffraction measurements of EuFeO3 films under strain states ranging from 2% compressive to 0.9% tensile on cubic or rhombohedral substrates exhibit a combination of a-a+c- and a+a-c- rotational patterns. We compare the EuFeO3 behavior with previously reported experimental and theoretical work on strained Pbnm-type films on nonorthorhombic substrates, as well as additional measurements from LaGaO3,LaFeO3, and Eu0.7Sr0.3MnO3 films on SrTiO3. Compiling the results from various material systems reveals a general strain dependence in which compressive strain strongly favors a-a+c- and a+a-c- rotation patterns and tensile strain weakly favors a-a-c+ structures. In contrast, EuFeO3 films grown on Pbnm-type GdScO3 under 2.3% tensile strain take on a uniform a-a+c- rotation pattern imprinted from the substrate, despite strain considerations that favor the a-a-c+ pattern. These results point to the use of substrate imprinting as a more robust route than strain for tuning the crystallographic orientations of the octahedral rotations and A -site displacements needed to realize rotation-induced hybrid improper ferroelectricity in oxide heterostructures.

  6. X-ray Inducible Luminescence and Singlet Oxygen Sensitization by an Octahedral Molybdenum Cluster Compound: A New Class of Nanoscintillators.

    PubMed

    Kirakci, Kaplan; Kubát, Pavel; Fejfarová, Karla; Martinčík, Jiří; Nikl, Martin; Lang, Kamil

    2016-01-19

    Newly synthesized octahedral molybdenum cluster compound (n-Bu4N)2[Mo6I8(OOC-1-adamantane)6] revealed uncharted features applicable for the development of X-ray inducible luminescent materials and sensitizers of singlet oxygen, O2((1)Δg). The compound exhibits a red-NIR luminescence in the solid state and in solution (e.g., quantum yield of 0.76 in tetrahydrofuran) upon excitation by UV-vis light. The luminescence originating from the excited triplet states is quenched by molecular oxygen to produce O2((1)Δg) with a high quantum yield. Irradiation of the compound by X-rays generated a radioluminescence with the same emission spectrum as that obtained by UV-vis excitation. It proves the formation of the same excited triplet states regardless of the excitation source. By virtue of the described behavior, the compound is suggested as an efficient sensitizer of O2((1)Δg) upon X-ray excitation. The luminescence and radioluminescence properties were maintained upon embedding the compound in polystyrene films. In addition, polystyrene induced an enhancement of the radioluminescence intensity via energy transfer from the scintillating polymeric matrix. Sulfonated polystyrene nanofibers were used for the preparation of nanoparticles which form stable dispersions in water, while keeping intact the luminescence properties of the embedded compound over a long time period. Due to their small size and high oxygen diffusivity, these nanoparticles are suitable carriers of sensitizers of O2((1)Δg). The presented results define a new class of nanoscintillators with promising properties for X-ray inducible photodynamic therapy. PMID:26702498

  7. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    PubMed Central

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g−1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  8. Self-assembled growth of BiFeO3 meso-octahedral particles synthesized by a facile surfactant-free hydrothermal method

    NASA Astrophysics Data System (ADS)

    Hou, L.; Lu, Z. Y.; Dai, Y. C.; Zuo, K. H.; Xia, Y. F.; Ren, Z. M.; Wu, J.; Lu, X. G.; Zeng, Y. P.; Li, X.

    2016-01-01

    Meso-scale BiFeO3 octahedral particles were synthesized by a hydrothermal method through modulating KOH concentration in the precursor solution. The morphologies of BiFeO3 particles were observed by scanning electron microscopy (SEM), displaying a morphological transformation from sphere to regular octahedron with the increase of KOH concentration. The time-dependent particle growth was also studied by SEM and the final products, octahedral BiFeO3 particles, were characterized by electron backscatter diffraction (EBSD) for understanding the crystalline growth. EBSD results show that the rhombohedral BiFeO3 octahedron is covered by eight crystal plane (001)hex, which is different from the previous report. The possible mechanism of crystal growth is discussed.

  9. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    NASA Astrophysics Data System (ADS)

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-05-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g‑1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment.

  10. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green.

    PubMed

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g(-1)) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  11. Relationship between anion binding and anion permeability revealed by mutagenesis within the cystic fibrosis transmembrane conductance regulator chloride channel pore

    PubMed Central

    Linsdell, Paul

    2001-01-01

    Anion binding within the pores of wild-type and mutant cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channels, expressed in two different mammalian cell lines, was assayed using patch clamp recording. Specifically, experiments measured both the conductance of different anions and the ability of other permeant anions to block Cl− permeation through the pore. Under symmetrical ionic conditions, wild-type CFTR channels showed the conductance sequence Cl− >NO3− >Br−≥formate >F− >SCN−≈ ClO4−. High SCN− conductance was not observed, nor was there an anomalous mole fraction effect of SCN− on conductance under the conditions used. Iodide currents could not be measured under symmetrical ionic conditions, but under bi-ionic conditions I− conductance appeared low. Chloride currents through CFTR channels were blocked by low concentrations (10 mM) of SCN−, I− and ClO4−, implying relatively tight binding of these anions within the pore. Two mutations in CFTR which alter the anion permeability sequence, F337S and T338A, also altered the anion conductance sequence. Furthermore, block by SCN−, I− and ClO4− were weakened in both mutants. Both these effects are consistent with altered anion binding within the pore. The effects of mutations on anion permeability and relative anion conductance suggested that, for most anions, increased permeability was associated with increased conductance. This indicates that the CFTR channel pore does not achieve its anion selectivity by selective anion binding within the mutated region. Instead, it is suggested that entry of anions into the region around F337 and T338 facilitates their passage through the pore. In wild-type CFTR channels, anion entry into this crucial pore region is probably dominated by anion hydration energies. PMID:11179391

  12. Relationship between anion binding and anion permeability revealed by mutagenesis within the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Linsdell, P

    2001-02-15

    1. Anion binding within the pores of wild-type and mutant cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels, expressed in two different mammalian cell lines, was assayed using patch clamp recording. Specifically, experiments measured both the conductance of different anions and the ability of other permeant anions to block Cl- permeation through the pore. 2. Under symmetrical ionic conditions, wild-type CFTR channels showed the conductance sequence Cl- > NO3- > Br- > or = formate > F- > SCN- congruent to ClO4-. 3. High SCN- conductance was not observed, nor was there an anomalous mole fraction effect of SCN- on conductance under the conditions used. Iodide currents could not be measured under symmetrical ionic conditions, but under bi-ionic conditions I- conductance appeared low. 4. Chloride currents through CFTR channels were blocked by low concentrations (10 mM) of SCN-, I- and ClO4-, implying relatively tight binding of these anions within the pore. 5. Two mutations in CFTR which alter the anion permeability sequence, F337S and T338A, also altered the anion conductance sequence. Furthermore, block by SCN-, I- and ClO4- were weakened in both mutants. Both these effects are consistent with altered anion binding within the pore. 6. The effects of mutations on anion permeability and relative anion conductance suggested that, for most anions, increased permeability was associated with increased conductance. This indicates that the CFTR channel pore does not achieve its anion selectivity by selective anion binding within the mutated region. Instead, it is suggested that entry of anions into the region around F337 and T338 facilitates their passage through the pore. In wild-type CFTR channels, anion entry into this crucial pore region is probably dominated by anion hydration energies. PMID:11179391

  13. Hydroxy double salt anion exchange kinetics: effects of precursor structure and anion size.

    PubMed

    Kandare, Everson; Hossenlopp, Jeanne M

    2005-05-01

    (1)H NMR spectroscopy and powder X-ray diffraction have been used to explore the details of anion exchange reactions of two layered hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA), nickel zinc hydroxy acetate (NZA), and a related layered material, zinc hydroxy acetate (ZHA), at room temperature (21-22 degrees C). Reactions that followed Avrami-Erofe'ev kinetics with respect to temporal profiles for acetate release, ZCA with butyrate (k = 1.7 x 10(-3) s(-1)), and octanoate (k = 0.79 x 10(-3) s(-1)) anions, as well as ZHA with octanoate (k = 2.6 x 10(-3) s(-1)), demonstrate that rate constants for acetate release are influenced by the exchange anion relative size as well as by the solid precursor structure/composition. The reaction of NZA with octanoate deviated from expected Avrami-Erofe'ev behavior, with evidence for an intermediate species in the solid phase that may influence the rate of acetate release into solution. The reaction of ZCA with formate anions exhibited a unique zeroth-order kinetics release of acetate, providing the possibility of developing tunable nanostructured anion release sources by use of variations in the size of the exchange species. PMID:16851994

  14. The benzene radical anion: A computationally demanding prototype for aromatic anions

    SciTech Connect

    Bazante, Alexandre P. Bartlett, Rodney J.; Davidson, E. R.

    2015-05-28

    The benzene radical anion is studied with ab initio coupled-cluster theory in large basis sets. Unlike the usual assumption, we find that, at the level of theory investigated, the minimum energy geometry is non-planar with tetrahedral distortion at two opposite carbon atoms. The anion is well known for its instability to auto-ionization which poses computational challenges to determine its properties. Despite the importance of the benzene radical anion, the considerable attention it has received in the literature so far has failed to address the details of its structure and shape-resonance character at a high level of theory. Here, we examine the dynamic Jahn-Teller effect and its impact on the anion potential energy surface. We find that a minimum energy geometry of C{sub 2} symmetry is located below one D{sub 2h} stationary point on a C{sub 2h} pseudo-rotation surface. The applicability of standard wave function methods to an unbound anion is assessed with the stabilization method. The isotropic hyperfine splitting constants (A{sub iso}) are computed and compared to data obtained from experimental electron spin resonance experiments. Satisfactory agreement with experiment is obtained with coupled-cluster theory and large basis sets such as cc-pCVQZ.

  15. The benzene radical anion: A computationally demanding prototype for aromatic anions.

    PubMed

    Bazante, Alexandre P; Davidson, E R; Bartlett, Rodney J

    2015-05-28

    The benzene radical anion is studied with ab initio coupled-cluster theory in large basis sets. Unlike the usual assumption, we find that, at the level of theory investigated, the minimum energy geometry is non-planar with tetrahedral distortion at two opposite carbon atoms. The anion is well known for its instability to auto-ionization which poses computational challenges to determine its properties. Despite the importance of the benzene radical anion, the considerable attention it has received in the literature so far has failed to address the details of its structure and shape-resonance character at a high level of theory. Here, we examine the dynamic Jahn-Teller effect and its impact on the anion potential energy surface. We find that a minimum energy geometry of C2 symmetry is located below one D2h stationary point on a C2h pseudo-rotation surface. The applicability of standard wave function methods to an unbound anion is assessed with the stabilization method. The isotropic hyperfine splitting constants (Aiso) are computed and compared to data obtained from experimental electron spin resonance experiments. Satisfactory agreement with experiment is obtained with coupled-cluster theory and large basis sets such as cc-pCVQZ. PMID:26026444

  16. Anion Chemistry On Titan: Probing the Destruction Mechanisms of Nitrile Anions by Interaction with Photons

    NASA Astrophysics Data System (ADS)

    Zabka, J.; Polášek, M.; Bradyová, M.; Flenerová, Z.; Obluková, M.; Ascenzi, D.; Vuitton, V.; Giuliani, A.; Nahon, L.; Milosavljevic, A.; Romanzin, C.; Alcaraz, C.

    2013-09-01

    The aim of this work is to study the interaction with VUV photons of mass-selected negative ions relevant for the understanding of Titan atmosphere. Characterization of their formation [1] and destruction rate is of fundamental importance for modeling Titan ionosphere chemistry and understanding the observations of heavy anions by the CAPS/ELS spectrometer on board of the CASSINI spacecraft. The objective here is to measure their transformation into smaller anions through photodissociation and their destruction through photodetachment. The parent anions CN- are produced from CH3CN in the APCI source of a commercial mass spectrometer LTQ XL (Thermo Scientific) [2,3] and reacted with HC3N in the trap to produce heavier anions through the CN-+ x HC3N(HC3N)yC2p+1 N-+ z HCN processes. These product anions are then mass-selected in the trap and irradiated with VUV photons (5-21 eV) from the DESIRS beamline. Their decay is followed as a function of irradiation time as illustrated in Figure 1.

  17. Intermediate-spin state of a 3d ion in the octahedral environment and generalization of the Tanabe-Sugano diagrams.

    PubMed

    Lamonova, Karina V; Zhitlukhina, Elena S; Babkin, Roman Yu; Orel, Sergei M; Ovchinnikov, Sergei G; Pashkevich, Yurii G

    2011-11-24

    Electronic spectra of 3d(n) transition ions in an octahedral ligand surrounding have been studied using the modified crystal field approach (MCFA), which includes a relativistic spin-orbital interaction. A new variable parameter, the effective nuclear charge Z(eff) of a metal ion that allows accounting implicitly the covalence degree of a metal-ligand bond, has been introduced. Energy diagrams similar to the Tanabe-Sugano ones have been calculated. To study the spin state evolution of the metal ion in an arbitrary distorted octahedral complex, a spin state diagram approach has been proposed. The intermediate-spin (IS) state problem for 3d(4), 3d(5), and 3d(6) metal ions has been considered and conditions for the IS state realization have been formulated. The regions of the mixed high-, intermediate-, and low-spin states have been found. The possibility of coexistence of the different spin states of 3d ions in the octahedral complexes has been considered using crystallography data for the YBaCo(2)O(5.5) layered cobaltite. PMID:21936547

  18. Applications of Cu{sub 2}O octahedral particles on ITO glass in photocatalytic degradation of dye pollutants under a halogen tungsten lamp

    SciTech Connect

    Zhai, Wei; Sun, Fengqiang; Chen, Wei; Zhang, Lihe; Min, Zhilin; Li, Weishan

    2013-11-15

    Graphical abstract: - Highlights: • Photocatalytic activity of Cu{sub 2}O octahedral microcrystals on ITO glass was studied. • They showed high abilities in degradation of methylene blue in the presence of H{sub 2}O{sub 2}. • H{sub 2}O{sub 2} amount could affect the degradation efficiency. • Such particles could be easily recycled and still kept high activity. • Many dye pollutants and their mixtures could be efficiently degraded. - Abstract: Cu{sub 2}O octahedral microcrystals were prepared on the ITO glass by galvanostatic electrodeposition in CuSO{sub 4} solution with poly(vinylpryrrolidone) as the surfactant. By controlling the electrodeposition time, the microcrystals could be randomly distributed on the ITO glass and separated from each other, resulting in as many as possible (1 1 1) crystalline planes were exposed. Such microcrystals immobilized on ITO glass were employed in photodegradation of dye pollutants in the presence of H{sub 2}O{sub 2} under a 150 W halogen tungsten lamp. The photodegradation of methylene blue was taken as an example to evaluate the photocatalytic activities of the octahedral Cu{sub 2}O microcrystals. Effects of electrodeposition time and H{sub 2}O{sub 2} amount on the degradation efficiency was discussed, giving the optimum conditions and the corresponding degradation mechanism. The catalyst showed high ability in degradation of methylene blue, methyl orange, rhodamine B, eosin B and their mixtures under identical conditions.

  19. Sandwich-type electrochemical immunosensor for the detection of AFP based on Pd octahedral and APTES-M-CeO₂-GS as signal labels.

    PubMed

    Wei, Yicheng; Li, Yan; Li, Na; Zhang, Yong; Yan, Tao; Ma, Hongmin; Wei, Qin

    2016-05-15

    In the present work, an ultrasensitive sandwich-type electrochemical immunosensor based on a novel signal amplification strategy was designed for quantitative detection of alpha fetoprotein (AFP). Au nanoparticles with biocompatibility were electrodeposited on the surface of glassy carbon electrode (GCE) which can effectively capture and immobilize primary anti-AFP (Ab1) to significantly amplify the electrochemical signal. Graphene Oxide and CeO2 mesoporous nanocomposite functionalized by the 3-aminopropyltriethoxysilane supported Pd octahedral nanoparticles (Pd/APTES-M-CeO2-GS) were utilized as labels of detection anti-AFP (Ab2). Pd octahedral nanoparticles presented good catalytic activity towards the reduction of H2O2. Due to the large specific surface area and good adsorption properties of APTES-CeO2-GS nanocomposite, large amount of Pd octahedral nanoparticles could be immobilized, which could amplify the electrochemical signal and improve the sensitivity of the immunosensor. Under optimal conditions, the immunosensor exhibited wide linear range from 0.1 pg/mL to 50 ng/mL with a low detection limit of 0.033 pg/mL (S/N=3) for AFP detection. In addition, high sensitivity, excellent selectivity, good reproducibility and stability were obtained for the immunosensor, which has a promising application for quantitative detection of other tumor markers in clinical diagnosis. PMID:26745795

  20. Supramolecular chemistry of selective anion recognition for anions of environmental relevance. 1998 annual progress report

    SciTech Connect

    Bowman-James, K.; Wilson, G.S.; Kuczera, K.; Moyer, B.

    1998-06-01

    'This project has as its focus the design and synthesis of polyammonium macrocyclic receptors for oxoanions of environmental importance. The basic research aspects of this project involve: (1) synthesis (and the search for improved synthetic methods); (2) solid state structure determination and thermodynamics studies (to ascertain structural criteria for and strength of anion binding); and (3) molecular dynamics simulations (to assess solution characteristics of the interactions between anions and their receptors). Applications-oriented goals include the fabrication of more selective anion-selective electrodes and the use of these compounds in liquid-liquid separations. The latter goal comprises the subcontract with Dr. Bruce Moyer at Oak Ridge National Laboratory. This report summarizes work after 1 year and 7 months of a 3-year project. To date, the authors have focussed on the design and synthesis of selective receptors for nitrate and phosphate.'

  1. Expanded Porphyrin-Anion Supramolecular Assemblies: Environmentally Responsive Sensors for Organic Solvents and Anions.

    PubMed

    Zhang, Zhan; Kim, Dong Sub; Lin, Chung-Yon; Zhang, Huacheng; Lammer, Aaron D; Lynch, Vincent M; Popov, Ilya; Miljanić, Ognjen Š; Anslyn, Eric V; Sessler, Jonathan L

    2015-06-24

    Porphyrins have been used frequently to construct supramolecular assemblies. In contrast, noncovalent ensembles derived from expanded porphyrins, larger congeners of naturally occurring tetrapyrrole macrocycles, are all but unknown. Here we report a series of expanded porphyrin-anion supramolecular assemblies. These systems display unique environmentally responsive behavior. Addition of polar organic solvents or common anions to the ensembles leads to either a visible color change, a change in the fluorescence emission features, or differences in solubility. The actual response, which could be followed easily by the naked eye, was found to depend on the specifics of the assembly, as well as the choice of analyte. Using the ensembles of this study, it proved possible to differentiate between common solvents, such as diethyl ether, THF, ethyl acetate, acetone, alcohol, acetonitrile, DMF, and DMSO, identify complex solvent systems, as well as distinguish between the fluoride, chloride, bromide, nitrate, and sulfate anions. PMID:25965790

  2. Synthesis, crystal structure and characterization of a new mixed ligand cationic-anionic nickel(II) complex containing 1,4-diazepane

    NASA Astrophysics Data System (ADS)

    Sain, Saugata; Saha, Rajat; Pilet, Guillaume; Bandyopadhyay, Debasis

    2010-12-01

    A new mixed ligand cationic-anionic nickel(II) complex, [NiL 2][Ni(NCS) 4(H 2O) 2] ( 1), where L = 1,4-diazepane has been synthesized by reacting nickel perchlorate with 1,4-diazepane and ammonium thiocyanate in the 1:1:2 M ratio. The complex has been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal the presence of two independent mononuclear complex ions in 1 viz., a square planar [NiL 2] 2+ and an octahedral [Ni(NCS) 4(H 2O) 2] 2- which are held together by H-bonding to form a 3D supramolecular structure in the solid state.

  3. Evidence for anionic cation transport of lithium, sodium and potassium across the human erythrocyte membrane induced by divalent anions.

    PubMed Central

    Becker, B F; Duhm, J

    1978-01-01

    1. The passive net transport of Li+ and Na+ across the human red cell membrane was accelerated by the divalent anions carbonate, sulphite, oxalate, phosphite and malonate. Phthalate, maleate, sulphate and succinate were found additionally to stimulate downhill transport of K+. Marked differences in anion efficacy and selectivity were observed. 2. The effects of these 'carbonate type' anions were reversible and fully blocked by SITS, dipyridamole and other inhibitors of anion transfer. 3. Cation transport acceleration induced by the monovalent anions salicylate, benzoate, thiocyanate and 2,4-dinitrophenol were inhibited by dipyridamole, but not affected by SITS. A great number of mono- and polyvalent anions were without detectable influence on Li+ transport. 4. Li+ net uptake induced by oxalate exhibited a pH dependence similar to that reported for halide self exchange. 5. Transport acceleration by carbonate type anions displayed a linear, 1:1 dependence on the concentrations of both the anion and the cation and was symmetric with respect to the two sides of the membrane. 6. It is concluded that the divalent carbonate type anions form singly charged, negative 1:1 ion pairs with the respective alkali metal cations, the ion pairs traversing the red cell membrane via the anion exchange pathway. This concept of anionic formation of some of the ion pairs considered. The relative efficacies and cation selectivities of polyvalent anions can largely be explained on the basis of electrostatic interactions governing ion pair formation. However, the chelating properties, structural flexibility, polarizability of the anions and the accessibility of the ion pairs to the anion exchange pathway need also be considered. 7. An exchange of NaCO-3 ion pairs for internal HCO-3 or Cl- is discussed as a possible mode of cellular pH regulation. PMID:31458

  4. Origin of the Zero-Field Splitting in Mononuclear Octahedral Mn(IV) Complexes: A Combined Experimental and Theoretical Investigation.

    PubMed

    Zlatar, Matija; Gruden, Maja; Vassilyeva, Olga Yu; Buvaylo, Elena A; Ponomarev, A N; Zvyagin, S A; Wosnitza, J; Krzystek, J; Garcia-Fernandez, Pablo; Duboc, Carole

    2016-02-01

    The aim of this work was to determine and understand the origin of the electronic properties of Mn(IV) complexes, especially the zero-field splitting (ZFS), through a combined experimental and theoretical investigation on five well-characterized mononuclear octahedral Mn(IV) compounds, with various coordination spheres (N6, N3O3, N2O4 in both trans (trans-N2O4) and cis configurations (cis-N2O4) and O4S2). High-frequency and -field EPR (HFEPR) spectroscopy has been applied to determine the ZFS parameters of two of these compounds, MnL(trans-N2O4) and MnL(O4S2). While at X-band EPR, the axial-component of the ZFS tensor, D, was estimated to be +0.47 cm(-1) for MnL(O4S2), and a D-value of +2.289(5) cm(-1) was determined by HFEPR, which is the largest D-magnitude ever measured for a Mn(IV) complex. A moderate D value of -0.997(6) cm(-1) has been found for MnL(trans-N2O4). Quantum chemical calculations based on two theoretical frameworks (the Density Functional Theory based on a coupled perturbed approach (CP-DFT) and the hybrid Ligand-Field DFT (LF-DFT)) have been performed to define appropriate methodologies to calculate the ZFS tensor for Mn(IV) centers, to predict the orientation of the magnetic axes with respect to the molecular ones, and to define and quantify the physical origin of the different contributions to the ZFS. Except in the case of MnL(trans-N2O4), the experimental and calculated D values are in good agreement, and the sign of D is well predicted, LF-DFT being more satisfactory than CP-DFT. The calculations performed on MnL(cis-N2O4) are consistent with the orientation of the principal anisotropic axis determined by single-crystal EPR, validating the calculated ZFS tensor orientation. The different contributions to D were analyzed demonstrating that the d-d transitions mainly govern D in Mn(IV) ion. However, a deep analysis evidences that many factors enter into the game, explaining why no obvious magnetostructural correlations can be drawn in this

  5. Carbon Monoxide-Induced Stability and Atomic Segregation Phenomena in Shape-Selected Octahedral PtNi Nanoparticles.

    PubMed

    Ahmadi, Mahdi; Cui, Chunhua; Mistry, Hemma; Strasser, Peter; Cuenya, Beatriz Roldan

    2015-11-24

    The chemical and morphological stability of size- and shape-selected octahedral PtNi nanoparticles (NP) were investigated after different annealing treatments up to a maximum temperature of 700 °C in a vacuum and under 1 bar of CO. Atomic force microscopy was used to examine the mobility of the NPs and their stability against coarsening, and X-ray photoelectron spectroscopy to study the surface composition, chemical state of Pt and Ni in the NPs, and thermally and CO-induced atomic segregation trends. Exposing the samples to 1 bar of CO at room temperature before annealing in a vacuum was found to be effective at enhancing the stability of the NPs against coarsening. In contrast, significant coarsening was observed when the sample was annealed in 1 bar of CO, most likely as a result of Ni(CO)4 formation and their enhanced mobility on the support surface. Sample exposure to CO at room temperature prior to annealing led to the segregation of Pt to the NP surface. Nevertheless, oxidic PtOx and NiOx species still remained at the NP surface, and, irrespective of the initial sample pretreatment, Ni surface segregation was observed upon annealing in a vacuum at moderate temperature (T < 300 °C). Interestingly, a distinct atomic segregation trend was detected between 300 and 500 °C for the sample pre-exposed to CO; namely, Ni surface segregation was partially hindered. This might be attributed to the higher bonding energy of CO to Pt as compared to Ni. Annealing in the presence of 1 bar CO also resulted in the initial surface segregation of Ni (T < 400 °C) as long as PtOx and NiOx species were available on the surface as a result of the higher affinity of Ni for oxygen. Above 500 °C, and regardless of the sample pretreatment, the diffusion of Pt atoms to the NP surface and the formation of a Ni-Pt alloy are observed. PMID:26418831

  6. A relativistic DFT methodology for calculating the structures and NMR chemical shifts of octahedral platinum and iridium complexes.

    PubMed

    Vícha, Jan; Patzschke, Michael; Marek, Radek

    2013-05-28

    A methodology for optimizing the geometry and calculating the NMR shielding constants is calibrated for octahedral complexes of Pt(IV) and Ir(III) with modified nucleic acid bases. The performance of seven different functionals (BLYP, B3LYP, BHLYP, BP86, TPSS, PBE, and PBE0) in optimizing the geometry of transition-metal complexes is evaluated using supramolecular clusters derived from X-ray data. The effects of the size of the basis set (ranging from SVP to QZVPP) and the dispersion correction (D3) on the interatomic distances are analyzed. When structural deviations and computational demands are employed as criteria for evaluating the optimizations of these clusters, the PBE0/def2-TZVPP/D3 approach provides excellent results. In the next step, the PBE0/def2-TZVPP approach is used with the continuum-like screening model (COSMO) to optimize the geometry of single molecules for the subsequent calculation of the NMR shielding constants in solution. The two-component zeroth-order regular approximation (SO-ZORA) is used to calculate the NMR shielding constants (PBE0/TZP/COSMO). The amount of exact exchange in the PBE0 functional is validated for the nuclear magnetic shieldings of atoms in the vicinity of heavy transition metals. For the PBE0/TZP/COSMO setup, an exact exchange of 40% is found to accurately reproduce the experimental NMR shielding constants for both types of complexes. Finally, the effect of the amount of exact exchange on the NMR shielding calculations (which is capable of compensating for the structural deficiencies) is analyzed for various molecular geometries (SCS-MP2, BHLYP, and PBE0) and the influence of a trans-substituent on the NMR chemical shift of nitrogen is discussed. The observed dependencies for an iridium complex cannot be rationalized by visualizing the Fermi-contact (FC) induced spin density and probably originate from changes in the d-d transitions that modulate the spin-orbit (SO) part of the SO/FC term. PMID:23598437

  7. Probes for anionic cell surface detection

    DOEpatents

    Smith, Bradley D.

    2013-03-05

    Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

  8. Morphology-dependent photocatalytic activity of octahedral anatase particles prepared by ultrasonication-hydrothermal reaction of titanates

    NASA Astrophysics Data System (ADS)

    Wei, Zhishun; Kowalska, Ewa; Verrett, Jonathan; Colbeau-Justin, Christophe; Remita, Hynd; Ohtani, Bunsho

    2015-07-01

    Octahedral anatase particles (OAPs) were prepared by an ultrasonication (US)-hydrothermal (HT) reaction of partially proton-exchanged potassium titanate nanowires (TNWs). The structural/physical properties of OAP-containing samples, including specific surface area, crystallinity, crystallite size, particle aspect ratio, composition and total OAP content, were analyzed. Photocatalytic activities of samples were measured under irradiation (>290 nm) for oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H2 system) under aerobic and deaerated conditions, respectively. Total density of electron traps (ETs) was measured by double-beam photoacoustic spectroscopy (DB-PAS). Mobility and lifetime of charge carriers (electrons) were investigated by the time-resolved microwave conductivity (TRMC) method. The effects of synthesis parameters, i.e., HT duration, HT temperature and US duration, on properties and photocatalytic activities of final products were examined in detail. The sample prepared with 1 h US duration and 6 h HT duration at 433 K using 267 mg of TNWs in 80 mL of Milli-Q water exhibited the highest photocatalytic activity. It was found that change in HT duration or HT temperature while keeping the other conditions the same resulted in changes in all properties and photocatalytic activity. On the other hand, duration of US treatment, before HT reaction, influenced the morphology of both the reagent (by TNWs breaking) and final products (change in total OAP content); samples prepared with various US durations exhibited almost the same structural/physical properties evaluated in this study but were different in morphology and photocatalytic activity. This enabled clarification of the correlation between morphology and photocatalytic activity, i.e., the higher the total OAP content was, the higher was the level of photocatalytic activity, especially in the CO2 system. Although the decay after maximum TRMC signal intensity (Imax) was

  9. Charge regulation enables anionic hydroxypropyl guar-borate adsorption onto anionic and cationic polystyrene latex.

    PubMed

    Zhang, Liang; Pelton, Robert; Ketelson, Howard; Meadows, David

    2011-01-15

    Reported are adsorption isotherms for guar and hydroxypropyl guar (HPG), with and without the presence of borate ions, onto surfactant free anionic polystyrene latex. Guar and HPG formed adsorbed monolayers on the hydrophobic latex. The presence of borate ions converted the nonionic guar and HPG into an anionic polyelectrolyte. However, there was no measurable influence of bound borate ions on the adsorption of guar or HPG onto anionic, hydrophobic latex. To underscore the unusual behavior of HPG-borate, a sample of HPG was oxidized to introduce carboxyl groups, and the adsorption of the carboxylated HPG onto anionic polystyrene was measured. Unlike HPG-borate, oxidized HPG did not adsorb onto negative polystyrene latex at neutral pH because of electrostatic repulsion. To explain the adsorption of negative HPG-borate onto negative latex, we proposed that as HPG-borate segments approach the latex surface, the negative electrostatic potential near the latex surface induces the detachment of the labile borate groups from HPG. PMID:21030034

  10. PROGRESS REPORT. SUPRAMOLECULAR CHEMISTRY OF SELECTIVE ANION RECOGNITION FOR ANIONS OF ENVIRONMENTAL RELEVANCE

    EPA Science Inventory

    This project involves the design and synthesis of receptors for oxoanions of environmental importance and specifically those found in high level waste tanks. Polyammonium macrocycles as receptors and nitrate as anion were the focus of the first phase of this project. A second pha...

  11. Functional anion concept: effect of fluorine anion on hydrogen storage of sodium alanate.

    PubMed

    Yin, Li-Chang; Wang, Ping; Kang, Xiang-Dong; Sun, Cheng-Hua; Cheng, Hui-Ming

    2007-03-28

    Doping NaAlH(4) with Ti-catalyst has produced a promising hydrogen storage system that can be reversibly operated at moderate temperature conditions. Of the various dopant precursors, TiCl(3) was well recognized due to its pronounced catalytic effect on the reversible dehydrogenation processes of sodium aluminium hydrides. Quite recently we experimentally found that TiF(3) was even better than TiCl(3) in terms of the critical hydrogen storage properties of the doped hydrides, in particular the dehydriding performance at Na(3)AlH(6)/NaH + Al step at moderate temperature. We present here the DFT calculation results of the TiF(3) or TiCl(3) doped Na(3)AlH(6). Our computational studies have demonstrated that F(-) and Cl(-) anions differ substantially from each other with regard to the state and function in the doped sodium aluminium hydride. In great contrast to the case of chloride doping where Cl(-) anion constitutes the "dead weight" NaCl, the fluoride doping results in a substitution of H(-) by F(-) anion in the hydride lattice and accordingly, a favorable thermodynamics adjustment. These results well explain the observed dehydriding performance associated with TiF(3)/TiCl(3)-doping. More significantly, the coupled computational and experimental efforts allow us to put forward a "functional anion" concept. This renews the current mechanism understanding in the catalytically enhanced sodium alanate. PMID:17356758

  12. Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions.

    PubMed

    Wang, Lai-Sheng

    2015-07-28

    Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES. PMID:26233095

  13. Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

    SciTech Connect

    Wang, Lai-Sheng

    2015-07-28

    Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.

  14. The chemistry of molecular anions in circumstellar sources

    NASA Astrophysics Data System (ADS)

    Agúndez, Marcelino; Cernicharo, José; Guélin, Michel

    2015-01-01

    The detection of negatively charged molecules in the interstellar and circumstellar medium in the past four years has been one of the most impacting surprises in the area of molecular astrophysics. It has motivated the interest of astronomers, physicists, and chemists on the study of the spectroscopy, chemical kinetics, and prevalence of molecular anions in the different astronomical regions. Up to six different molecular anions have been discovered in space to date, the last one being the small ion CN-, which has been observed in the envelope of the carbon star IRC +10216 and which contrary to the other larger anions is not formed by electron attachment to CN, but through reactions of large carbon anions with nitrogen atoms. Here we briefly review the current status of our knowledge of the chemistry of molecular anions in space, with particular emphasis on the circumstellar source IRC +10216, which to date is the astronomical source harboring the largest variety of anions.

  15. Process for removing sulfate anions from waste water

    DOEpatents

    Nilsen, David N.; Galvan, Gloria J.; Hundley, Gary L.; Wright, John B.

    1997-01-01

    A liquid emulsion membrane process for removing sulfate anions from waste water is disclosed. The liquid emulsion membrane process includes the steps of: (a) providing a liquid emulsion formed from an aqueous strip solution and an organic phase that contains an extractant capable of removing sulfate anions from waste water; (b) dispersing the liquid emulsion in globule form into a quantity of waste water containing sulfate anions to allow the organic phase in each globule of the emulsion to extract and absorb sulfate anions from the waste water and (c) separating the emulsion including its organic phase and absorbed sulfate anions from the waste water to provide waste water containing substantially no sulfate anions.

  16. The chemistry of molecular anions in circumstellar sources

    SciTech Connect

    Agúndez, Marcelino; Cernicharo, José; Guélin, Michel

    2015-01-22

    The detection of negatively charged molecules in the interstellar and circumstellar medium in the past four years has been one of the most impacting surprises in the area of molecular astrophysics. It has motivated the interest of astronomers, physicists, and chemists on the study of the spectroscopy, chemical kinetics, and prevalence of molecular anions in the different astronomical regions. Up to six different molecular anions have been discovered in space to date, the last one being the small ion CN{sup −}, which has been observed in the envelope of the carbon star IRC +10216 and which contrary to the other larger anions is not formed by electron attachment to CN, but through reactions of large carbon anions with nitrogen atoms. Here we briefly review the current status of our knowledge of the chemistry of molecular anions in space, with particular emphasis on the circumstellar source IRC +10216, which to date is the astronomical source harboring the largest variety of anions.

  17. Photoelectron Spectroscopy and Theoretical Studies of Anion-pi Interactions: Binding Strength and Anion Specificity

    SciTech Connect

    Zhang, Jian; Zhou, Bin; Sun, Zhenrong; Wang, Xue B.

    2015-01-01

    Proposed in theory and confirmed to exist, anion–π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, intrinsic anion–π interaction strengths that are free from complications of condensed phases’ environments, have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl⁻, Br⁻, I⁻, linear thiocyanate SCN⁻, trigonal planar nitrate NO₃⁻, pyramidic iodate IO₃⁻, and tetrahedral sulfate SO₄²⁻). The binding energies of the resultant gaseous 1:1 complexes (1•Cl⁻,1•Br⁻, 1•I⁻, 1•SCN⁻, 1•NO₃⁻, 1•IO₃⁻ and 1•SO₄²⁻) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion specific effects. The binding strengths of Cl⁻, NO₃⁻, IO₃⁻ with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal/mol, but only about 40% of that between 1 and SO₄²⁻. Quantum chemical calculations reveal that all anions reside in the center of the cavity of 1 with anion–π binding motif in the complexes’ optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and natural bond orbital charge distribution analysis further support anion–π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work

  18. Preorganized anion traps for exploiting anion-π interactions: an experimental and computational study.

    PubMed

    Bretschneider, Anne; Andrada, Diego M; Dechert, Sebastian; Meyer, Steffen; Mata, Ricardo A; Meyer, Franc

    2013-12-01

    1,3-Bis(pentafluorophenyl-imino)isoindoline (A(F)) and 3,6-di-tert-butyl-1,8-bis(pentafluorophenyl)-9H-carbazole (B(F)) have been designed as preorganized anion receptors that exploit anion-π interactions, and their ability to bind chloride and bromide in various solvents has been evaluated. Both receptors A(F) and B(F) are neutral but provide a central NH hydrogen bond that directs the halide anion into a preorganized clamp of the two electron-deficient appended arenes. Crystal structures of host-guest complexes of A(F) with DMSO, Cl(-), or Br(-) (A(F):DMSO, A(F):Cl(-), and A(2)(F):Br(-)) reveal that in all cases the guest is located in the cleft between the perfluorinated flaps, but NMR spectroscopy shows a more complex situation in solution because of E,Z/Z,Z isomerism of the host. In the case of the more rigid receptor B(F), Job plots evidence 1:1 complex formation with Cl(-) and Br(-), and association constants up to 960 M(-1) have been determined depending on the solvent. Crystal structures of B(F) and B(F):DMSO visualize the distinct preorganization of the host for anion-π interactions. The reference compounds 1,3-bis(2-pyrimidylimino)isoindoline (A(N)) and 3,6-di-tert-butyl-1,8-diphenyl-9H-carbazole (B(H)), which lack the perfluorinated flaps, do not show any indication of anion binding under the same conditions. A detailed computational analysis of the receptors A(F) and B(F) and their host-guest complexes with Cl(-) or Br(-) was carried out to quantify the interactions in play. Local correlation methods were applied, allowing for a decomposition of the ring-anion interactions. The latter were found to contribute significantly to the stabilization of these complexes (about half of the total energy). Compounds A(F) and B(F) represent rare examples of neutral receptors that are well preorganized for exploiting anion-π interactions, and rare examples of receptors for which the individual contributions to the binding energy have been quantified. PMID

  19. Nanoheterostructure Cation Exchange: Anionic Framework Conservation

    SciTech Connect

    Jain, Prashant K.; Amirav, Lilac; Aloni, Shaul; Alivisatos, A. Paul

    2010-05-11

    In ionic nanocrystals the cationic sub-lattice can be replaced with a different metal ion via a fast, simple, and reversible place-exchange, allowing post-synthetic modification of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate for the first time that during such an exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures, this phenomenon ensures that compositional interfaces within the heterostructure are conserved throughout the transformation. For instance, a morphology composed of a CdSe nanocrystal embedded in a CdS rod (CdSe/CdS) was exchanged to a PbSe/PbS nanorod via a Cu2Se/Cu2S structure. During every exchange cycle, the seed size and position within the nanorod were preserved, as evident by excitonic features, Z-contrast imaging, and elemental line-scans. Anionic framework conservation extends the domain of cation exchange to the design of more complex and unique nanostructures.

  20. An intracellular anion channel critical for pigmentation

    PubMed Central

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. DOI: http://dx.doi.org/10.7554/eLife.04543.001 PMID:25513726

  1. Anions in laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Shabanov, S. V.; Gornushkin, I. B.

    2016-07-01

    The equation of state for plasmas containing negative atomic and molecular ions (anions) is modeled. The model is based on the assumption that all ionization processes and chemical reactions are at local thermal equilibrium and the Coulomb interaction in the plasma is described by the Debye-Hückel theory. In particular, the equation of state is obtained for plasmas containing the elements Ca, Cl, C, Si, N, and Ar. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules CaCl_2, CaCl, Cl_2, N_2, C_2, Si_2, CN, SiN, SiC, and their positive and negative ions. The model is applied to laser-induced plasmas (LIPs) by including the equation of state into a fluid dynamic numerical model based on the Navier-Stokes equations describing an expansion of LIP plumes into an ambient gas as a reactive viscous flow with radiative losses. In particular, the formation of anions Cl-, C-, Si-, {{Cl}}2^{ - }, {{Si}}2^{ - }, {{C}}2^{ - }, CN-, SiC-, and SiN- in LIPs is investigated in detail.

  2. Multiple-anion nonvolatile acetal (MANA) resists

    NASA Astrophysics Data System (ADS)

    Guevremont, Jeffrey M.; Brainard, Robert L.; Reeves, Scott D.; Zhou, Xin; Nguyen, Thinh B.; Mackevich, Joseph F.; Anderson, Erik H.; Taylor, Gary N.

    2001-08-01

    New acetal or ketal blocking reagents were investigated for use in e-beam lithography and compared with the performance of ethyl vinyl either (EVE). Three blocking groups, (alpha) -Angelicalactone (AL), 6-methylene-5,6-benzo-1,4- dioxane (MBD), and MANA50 (an undisclosed blocking group used to show the potential of this chemistry) were reacted with poly(p-hydroxystyrene) (PHS) under acid catalyzed conditions to form AL-PHS, MBD-PHS, MANA50-PHS. The performance objectives pursued in the design of these new materials was to use acetal (ketal) chemistry to deliver wide process latitudes (e.g. good PED performance and minimal PEB sensitivity), use high molecular weight blocking groups to eliminate outgassing, and use the novel concept of multiple anions to deliver lithographic performance. These new materials are called Multiple Anion Nonvolatile Acetal (MANA) resists. Resists films were exposed with 50kV electrons, post exposure baked (PEB), and developed with 0.26 N TMAH. Resists prepared with the third blocking group, MANA50, gave contrast and imaging performance independent of PEB humidity and were relatively insensitive to PEB temperature and post exposure delay (PED). These resists gave the best resolution (90 nm) and profiles of all the materials tested, as well as showing no outgassing (as measured by film thickness loss).

  3. Anionic derivatives of uracil: fragmentation and reactivity.

    PubMed

    Cole, Callie A; Wang, Zhe-Chen; Snow, Theodore P; Bierbaum, Veronica M

    2014-09-01

    Uracil is an essential biomolecule for terrestrial life, yet its prebiotic formation mechanisms have proven elusive for decades. Meteorites have been shown to contain uracil and the interstellar abundance of aromatic species and nitrogen-containing molecules is well established, providing support for uracil's presence in the interstellar medium (ISM). The ion chemistry of uracil may provide clues to its prebiotic synthesis and role in the origin of life. The fragmentation of biomolecules provides valuable insights into their formation. Previous research focused primarily on the fragmentation and reactivity of cations derived from uracil. In this study, we explore deprotonated uracil-5-carboxylic acid and its anionic fragments to elucidate novel reagents of uracil formation and to characterize the reactivity of uracil's anionic derivatives. The structures of these fragments are identified through theoretical calculations, further fragmentation, experimental acidity bracketing, and reactivity with several detected and potential interstellar species (SO2, OCS, CS2, NO, N2O, CO, NH3, O2, and C2H4). Fragmentation is achieved through collision induced dissociation (CID) in a commercial ion trap mass spectrometer, and all reaction rate constants are measured using a modification of this instrument. Experimental data are supported by theoretical calculations at the B3LYP/6-311++G(d,p) level of theory. Lastly, the astrochemical implications of the observed fragmentation and reaction processes are discussed. PMID:25036757

  4. Isobar Separator for Anions: Current status

    NASA Astrophysics Data System (ADS)

    Alary, Jean-François; Javahery, Gholamreza; Kieser, William; Zhao, Xiao-Lei; Litherland, Albert; Cousins, Lisa; Charles, Christopher

    2015-10-01

    The Isobar Separator for Anions (ISA) is an emerging separation technique of isobars applied first to the selective removal of 36S from 36Cl, achieving a relative suppression ratio of 6 orders of magnitude. Using a radio-frequency quadrupole (RFQ) column incorporating low energy gas cells, this innovative technique enables the use of a wide range of low energy ion-molecule reactions and collisional-induced dissociation processes for suppressing specific atomic of molecular anions with a high degree of selectivity. Other elemental pairs (analyte/isobar) successfully separated at AMS level include Ca/K, Sr/(Y, Zr), Cs/Ba, Hf/W and Pu/U. In view of these initial successes, an effort to develop a version of the ISA that can be used as a robust technique for routine AMS analysis has been undertaken. We will discuss the detailed layout of a practical ISA and the functional requirements that a combined ISA/AMS should meet. These concepts are currently being integrated in a pre-commercial ISA system that will be installed soon at the newly established A.E. Lalonde Laboratory in Ottawa, Canada.

  5. Porating anion-responsive copolymeric gels.

    PubMed

    England, Dustin; Yan, Feng; Texter, John

    2013-09-24

    A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted. PMID:23968242

  6. An intracellular anion channel critical for pigmentation.

    PubMed

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. PMID:25513726

  7. Advancements in Anion Exchange Membrane Cations

    SciTech Connect

    Sturgeon, Matthew R.; Long, Hai; Park, Andrew M.; Pivovar, Bryan S.

    2015-10-15

    Anion-exchange membrane fuel cells (AME-FCs) are of increasingly popular interest as they enable the use of non-Pt fuel cell catalysts, the primary cost limitation of proton exchange membrane fuel cells. Benzyltrimethyl ammonium (BTMA) is the standard cation that has historically been utilized as the hydroxide conductor in AEMs. Herein we approach AEMs from two directions. First and foremost we study the stability of several different cations in a hydroxide solution at elevated temperatures. We specifically targeted BTMA and methoxy and nitro substituted BTMA. We've also studied the effects of adding an akyl spacer units between the ammonium cation and the phenyl group. In the second approach we use computational studies to predict stable ammonium cations, which are then synthesized and tested for stability. Our unique method to study cation stability in caustic conditions at elevated temperatures utilizes Teflon Parr reactors suitable for use under various temperatures and cation concentrations. NMR analysis was used to determine remaining cation concentrations at specific time points with GCMS analysis verifying product distribution. We then compare the experimental results with calculated modeling stabilities. Our studies show that the electron donating methoxy groups slightly increase stability (compared to that of BTMA), while the electron withdrawing nitro groups greatly decrease stability in base. These results give insight into possible linking strategies to be employed when tethering a BTMA like ammonium cation to a polymeric backbone; thus synthesizing an anion exchange membrane.

  8. Protein Camouflage: Supramolecular Anion Recognition by Ubiquitin.

    PubMed

    Mallon, Madeleine; Dutt, Som; Schrader, Thomas; Crowley, Peter B

    2016-04-15

    Progress in the field of bio-supramolecular chemistry, the bottom-up assembly of protein-ligand systems, relies on a detailed knowledge of molecular recognition. To address this issue, we have characterised complex formation between human ubiquitin (HUb) and four supramolecular anions. The ligands were: pyrenetetrasulfonic acid (4PSA), p-sulfonato-calix[4]arene (SCLX4), bisphosphate tweezers (CLR01) and meso-tetrakis (4-sulfonatophenyl)porphyrin (TPPS), which vary in net charge, size, shape and hydrophobicity. All four ligands induced significant changes in the HSQC spectrum of HUb. Chemical shift perturbations and line-broadening effects were used to identify binding sites and to quantify affinities. Supporting data were obtained from docking simulations. It was found that these weakly interacting ligands bind to extensive surface patches on HUb. A comparison of the data suggests some general indicators for the protein-binding specificity of supramolecular anions. Differences in binding were observed between the cavity-containing and planar ligands. The former had a preference for the arginine-rich, flexible C terminus of HUb. PMID:26818656

  9. Isatin phenylhydrazones: anion enhanced photochromic behaviour.

    PubMed

    Cigáň, M; Jakusová, K; Gáplovský, M; Filo, J; Donovalová, J; Gáplovský, A

    2015-11-01

    The photochemical properties of two basic easily synthesized isatin N(2)-phenylhydrazones were investigated. Contrary to the corresponding isatin N(2)-diphenylhydrazones, only Z-isomers were isolated from the reaction mixtures during the synthesis due to their stabilization by intramolecular hydrogen bonding. Although the presence of the C=N double bond creates conditions for the formation of a simple on-off photoswitch, the low photochemical quantum yield and particularly the low switching amplitude in absorbance hamper their photochromic applications. However, the addition of strongly basic anions to phenylhydrazone solutions leads to isatin NH group deprotonation and creates a new diazene T-type Vis-Vis photochromic system with sufficiently separated absorption maxima. Interestingly, although the thermally stable A-form is also photostable in ambient light, its irradiation with a stronger LED source leads to thermally unstable B-form formation which rapidly isomerizes back to the corresponding A-form. The process is reversible and switching cycles can be repeated in both directions. The important advantages of this two-component organic chromophore-inorganic anion photochromic system are its easy synthesis, easy handling due to its insensitivity to room light, easy further structural modification and reversibility. The corresponding photochemical quantum yield, however, remains relatively low (Φ ∼ 0.001). The theoretically calculated properties are in agreement with the obtained experimental results and support the proposed reaction mechanism. PMID:26412034

  10. Nonvalence correlation-bound anion states of spherical fullerenes.

    PubMed

    Voora, Vamsee K; Jordan, Kenneth D

    2014-08-13

    We present a one-electron model Hamiltonian for characterizing nonvalence correlation-bound anion states of fullerene molecules. These states are the finite system analogs of image potential states of metallic surfaces. The model potential accounts for both atomic and charge-flow polarization and is used to characterize the nonvalence correlation-bound anion states of the C60, (C60)2, C240, and C60@C240 fullerene systems. Although C60 is found to have a single (s-type) nonvalence correlation-bound anion state, the larger fullerenes are demonstrated to have multiple nonvalence correlation-bound anion states. PMID:24978808

  11. Identification and characterization of anion binding sites in RNA.

    PubMed

    Kieft, Jeffrey S; Chase, Elaine; Costantino, David A; Golden, Barbara L

    2010-06-01

    Although RNA molecules are highly negatively charged, anions have been observed bound to RNA in crystal structures. It has been proposed that anion binding sites found within isolated RNAs represent regions of the molecule that could be involved in intermolecular interactions, indicating potential contact points for negatively charged amino acids from proteins or phosphate groups from an RNA. Several types of anion binding sites have been cataloged based on available structures. However, currently there is no method for unambiguously assigning anions to crystallographic electron density, and this has precluded more detailed analysis of RNA-anion interaction motifs and their significance. We therefore soaked selenate into two different types of RNA crystals and used the anomalous signal from these anions to identify binding sites in these RNA molecules unambiguously. Examination of these sites and comparison with other suspected anion binding sites reveals features of anion binding motifs, and shows that selenate may be a useful tool for studying RNA-anion interactions. PMID:20410239

  12. Approach to the Patient With a Negative Anion Gap.

    PubMed

    Emmett, Michael

    2016-01-01

    When anion gap calculation generates a very small or negative number, an explanation must be sought. Sporadic (nonreproducible) measurement errors and systematic (reproducible) laboratory errors must be considered. If an error is ruled out, 2 general possibilities exist. A true anion gap reduction can be generated by either reduced concentrations of unmeasured anions such as albumin or increased concentrations of unmeasured cations such as magnesium, calcium, or lithium. This teaching case describes a patient with aspirin (salicylate) poisoning whose anion gap was markedly reduced (-47 mEq/L). The discussion systematically reviews the possibilities and provides the explanation for this unusual laboratory result. PMID:26363848

  13. Anion recognition by oligo-(thio)urea-based receptors.

    PubMed

    Jia, Chuandong; Zuo, Wei; Zhang, Dan; Yang, Xiao-Juan; Wu, Biao

    2016-07-26

    Oligo-(thio)ureas have proven to be a promising class of receptors that are widely applied in anion recognition. This article aims to present some recent progress in the construction of oligoureas and their anion coordination (recognition) chemistry. Typical examples of metal-coordination assisted and covalently connected oligo-(thio)urea receptors are summarized, with focus on geometry characteristics required for achieving complementary binding of a target anion. Special emphasis is given to ortho-phenylene-connected oligoureas in the application of anion binding and the self-assembly of important supramolecular architectures, including helicates, tetrahedral cages, and so on. PMID:27352298

  14. Aza-Bambusurils En Route to Anion Transporters.

    PubMed

    Singh, Mandeep; Solel, Ephrath; Keinan, Ehud; Reany, Ofer

    2016-06-20

    Previous calculations of anion binding with various bambusuril analogs predicted that the replacement of oxygen by nitrogen atoms to produce semiaza-bambus[6]urils would award these new cavitands with multiple anion binding properties. This study validates the hypothesis by efficient synthesis, crystallography, thermogravimetric analysis and calorimetry. These unique host molecules are easily accessible from the corresponding semithio-bambusurils in a one-pot reaction, which converts a single anion receptor into a potential anion channel. Solid-state structures exhibit simultaneous accommodation of three anions, linearly positioned within the cavity along the main symmetry axis. The ability to hold anions at a short distance of about 4 Å is reminiscent of natural chloride channels in E. coli, which exhibit similar distances between their adjacent anion binding sites. The calculated transition-state energy for double-anion movement through the channel suggests that although these host-guest complexes are thermodynamically stable they enjoy high kinetic flexibility to render them efficient anion channels. PMID:27225332

  15. Purification Or Organic Acids Using Anion Exchange Chromatography.

    DOEpatents

    Ponnampalam; Elankovan

    2001-09-04

    Disclosed is a cost-effective method for purifying and acidifying carboxylic acids, including organic acids and amino acids. The method involves removing impurities by allowing the anionic form of the carboxylic acid to bind to an anion exchange column and washing the column. The carboxylic anion is displaced as carboxylic acid by washing the resin with a strong inorganic anion. This method is effective in removing organic carboxylic acids and amino acids from a variety of industrial sources, including fermentation broths, hydrolysates, and waste streams.

  16. Aluminum Zintl anion moieties within sodium aluminum clusters

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Schnöckel, Hansgeorg; Eichhorn, Bryan W.; Lee, Mal-Soon; Jena, P.; Kandalam, Anil K. E-mail: kiran@mcneese.edu; Kiran, Boggavarapu E-mail: kiran@mcneese.edu

    2014-02-07

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium–aluminum cluster anions, Na{sub m}Al{sub n}{sup −}, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

  17. Aluminum Zintl anion moieties within sodium aluminum clusters

    NASA Astrophysics Data System (ADS)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Schnöckel, Hansgeorg; Eichhorn, Bryan W.; Lee, Mal-Soon; Jena, P.; Kandalam, Anil K.; Kiran, Boggavarapu; Bowen, Kit H.

    2014-02-01

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, NamAln-, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

  18. Aluminum Zintl anion moieties within sodium aluminum clusters.

    PubMed

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Schnöckel, Hansgeorg; Eichhorn, Bryan W; Lee, Mal-Soon; Jena, P; Kandalam, Anil K; Kiran, Boggavarapu; Bowen, Kit H

    2014-02-01

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, Na(m)Al(n)(-), were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams. PMID:24511934

  19. Inhibition of nuclear waste solutions containing multiple aggressive anions

    SciTech Connect

    Congdon, J.W.

    1988-05-01

    The inhibition of localized corrosion of carbon steel in caustic, high-level radioactive waste solutions was studied using cyclic potentiodynamic polarization scans supplemented by partially immersed coupon tests. The electrochemical tests provided a rapid and accurate means of determining the relationship between the minimum inhibitor requirements and the concentration of the aggressive anions in this system. Nitrate, sulfate, chloride, and fluoride were identified as aggressive anions; however, no synergistic effects were observed between these anions. This observation may have important theoretical implications because it tends to contradict the behavior of aggressive anions as predicted by existing theories for localized corrosion.

  20. Structural Design Criteria for Anion Hosts: Strategies for Achieving Anion Shape Recognition through the Complementary Placement of Urea Donor Groups

    SciTech Connect

    Hay, Benjamin P.; Firman, Timothy K.; Moyer, Bruce A.

    2005-02-16

    The arrangement of urea ligands about different shaped anions has been evaluated with electronic structure calculations. Geometries and binding energies are reported for urea complexes with Cl{sup -}, NO{sub 3}{sup -}, and ClO{sub 4}{sup -}. The results yield new insight into the nature of urea-anion interactions and provide structural criteria for the deliberate design of anion selective receptors containing two or more urea donor groups.

  1. Heterometallic modular metal-organic 3D frameworks assembled via new tris-β-diketonate metalloligands: nanoporous materials for anion exchange and scaffolding of selected anionic guests.

    PubMed

    Carlucci, Lucia; Ciani, Gianfranco; Maggini, Simona; Proserpio, Davide M; Visconti, Marco

    2010-11-01

    The modular engineering of heterometallic nanoporous metal-organic frameworks (MOFs) based on novel tris-chelate metalloligands, prepared using the functionalised β-diketone 1,3-bis(4'-cyanophenyl)-1,3-propanedione (HL), is described. The complexes [M(III)L(3)] (M=Fe(3+), Co(3+)) and [M(II)L(3)](NEt(4)) (M=Mn(2+), Co(2+), Zn(2+), Cd(2+)) have been synthesised and characterised, all of which exhibit a distorted octahedral chiral structure. The presence of six exo-oriented cyano donor groups on each complex makes it a suitable building block for networking through interactions with external metal ions. We have prepared two families of MOFs by reacting the metalloligands [M(III)L(3)] and [M(II)L(3)](-) with many silver salts AgX (X=NO(3)(-), BF(4)(-), PF(6)(-), AsF(6)(-), SbF(6)(-), CF(3)SO(3)(-), tosylate), specifically the [M(III)L(3)Ag(3)]X(3)·Solv and [M(II)L(3)Ag(3)]X(2)·Solv network species. Very interestingly, all of these network species exhibit the same type of 3D structure and crystallise in the same trigonal space group with similar cell parameters, in spite of the different metal ions, ionic charges and X(-) counteranions of the silver salts. We have also succeeded in synthesising trimetallic species such as [Zn(x)Fe(y)L(3)Ag(3)](ClO(4))((2x+3y))·Solv and [Zn(x)Cd(y)L(3)Ag(3)](ClO(4))(2)·Solv (with x+y=1). All of the frameworks can be described as sixfold interpenetrated pcu nets, considering the Ag(+) ions as simple digonal spacers. Each individual net is homochiral, containing only Δ or Λ nodes; the whole array contains three nets of type Δ and three nets of type Λ. Otherwise, taking into account the presence of weak Ag-C σ bonds involving the central carbon atoms of the β-diketonate ligands of adjacent nets, the six interpenetrating pcu networks are joined into a unique non-interpenetrated six-connected frame with the rare acs topology. The networks contain large parallel channels of approximate hexagonal-shaped sections that represent 37

  2. Simulations of zwitterionic and anionic phospholipid monolayers.

    PubMed

    Kaznessis, Yiannis N; Kim, Sangtae; Larson, Ronald G

    2002-04-01

    Results of atomistic molecular dynamics simulations of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol monolayers at the air/water interface are presented. Dipalmitoylphosphatidylcholine is zwitterionic and dipalmitoylphosphatidylglycerol is anionic at physiological pH. NaCl and CaCl2 water subphases are simulated. The simulations are carried out at different surface densities, and a simulation cell geometry is chosen that greatly facilitates the investigation of phospholipid monolayer properties. Ensemble average monolayer properties calculated from simulation are in agreement with experimental measurements. The dependence of the properties of the monolayers on the surface density, the type of the headgroup, and the ionic environment are explained in terms of atomistically detailed pair distribution functions and electron density profiles, demonstrating the strength of simulations in investigating complex, multicomponent systems of biological importance. PMID:11916834

  3. Advanced polymer chemistry of organometallic anions

    SciTech Connect

    Chamberlin, R.M.; Abney, K.D.; Balaich, G.J.; Fino, S.A.

    1997-11-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to prepare and characterize new polymers incorporating cobalt dicarbollide. Specific goals were to prepare polymerizable cobalt dicarbollide monomers using the nucleophilic substitution route discovered in laboratories and to establish the reaction conditions required to form polymers from these complexes. This one-year project resulted in two publications (in press), and provided the foundation for further investigations into polymer synthesis and characterization using cobalt dicarbollide and other metallocarboranes. Interest in synthesizing organometallic polymers containing the cobalt bis(dicarbollide) anion is motivated by their possible application as cation exchange materials for the remediation of cesium-137 and strontium-90 from nuclear wastes.

  4. Anion selectivity and pumping mechanism of halorhodopsin.

    PubMed

    Otomo, J

    1995-01-01

    Comparison of the amino acid sequences in the A-B and B-C interhelical loop segments in all bacteriorhodopsins and halorhodopsins has shed light on the anion selectivity and pumping mechanism of halorhodopsin. The nucleotide sequences of two haloopsins from two new halobacterial strains, shark and port, have been determined, and shark halorhodopsin was functionally overexpressed in Halobacterium halobium. Although a series of six amino acid residues (EMPAGH) in the B-C interhelical loop segment was substituted by QMPPGH, all putative charged residues were conserved. It was also shown that His-95 mutants had lower pumping activity in low chloride concentrations. These results further support the hypothesis that His-95 is important in the halorhodopsin function. PMID:7662863

  5. Living anionic polymerization using a microfluidic reactor

    SciTech Connect

    Iida, Kazunori; Chastek, Thomas Q.; Beers, Kathryn L.; Cavicchi, Kevin A.; Chun, Jaehun; Fasolka, Michael J.

    2009-02-01

    Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 °C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions.

  6. Poly(phenylene)-based anion exchange membrane

    DOEpatents

    Hibbs, Michael; Cornelius, Christopher J.; Fujimoto, Cy H.

    2011-02-15

    A poly(phenylene) compound of copolymers that can be prepared with either random or multiblock structures where a first polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 2 pendant phenyl groups and 4 pendant tolyl groups and the second polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 6 pendant phenyl groups. The second polymer has chemical groups attached to some of the pendant phenyl groups selected from CH.sub.3, CH.sub.2Br, and CH.sub.2N(CH.sub.3).sub.3Br groups. When at least one group is CH.sub.2N(CH.sub.3).sub.3Br, the material functions as an anion exchange membrane.

  7. Gating mechanisms of a natural anion channelrhodopsin

    PubMed Central

    Sineshchekov, Oleg A.; Govorunova, Elena G.; Li, Hai; Spudich, John L.

    2015-01-01

    Anion channelrhodopsins (ACRs) are a class of light-gated channels recently identified in cryptophyte algae that provide unprecedented fast and powerful hyperpolarizing tools for optogenetics. Analysis of photocurrents generated by Guillardia theta ACR 1 (GtACR1) and its mutants in response to laser flashes showed that GtACR1 gating comprises two separate mechanisms with opposite dependencies on the membrane voltage and pH and involving different amino acid residues. The first mechanism, characterized by slow opening and fast closing of the channel, is regulated by Glu-68. Neutralization of this residue (the E68Q mutation) specifically suppressed this first mechanism, but did not eliminate it completely at high pH. Our data indicate the involvement of another, yet-unidentified pH-sensitive group X. Introducing a positive charge at the Glu-68 site (the E68R mutation) inverted the channel gating so that it was open in the dark and closed in the light, without altering its ion selectivity. The second mechanism, characterized by fast opening and slow closing of the channel, was not substantially affected by the E68Q mutation, but was controlled by Cys-102. The C102A mutation reduced the rate of channel closing by the second mechanism by ∼100-fold, whereas it had only a twofold effect on the rate of the first. The results show that anion conductance by ACRs has a fundamentally different structural basis than the relatively well studied conductance by cation channelrhodopsins (CCRs), not attributable to simply a modification of the CCR selectivity filter. PMID:26578767

  8. 8. VIEW OF GLOVE BOXES USED IN THE ANION EXCHANGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VIEW OF GLOVE BOXES USED IN THE ANION EXCHANGE PROCESS. THE ANION EXCHANGE PROCESS PURIFIED AND CONCENTRATED PLUTONIUM-BEARING NITRIC ACID SOLUTIONS TO MAKE THEM ACCEPTABLE AS FEED FOR CONVERSION TO METAL. (6/20/60) - Rocky Flats Plant, Plutonium Recovery & Fabrication Facility, North-central section of plant, Golden, Jefferson County, CO

  9. Interaction between biphenols and anions: selective receptor for dihydrogenphosphate.

    PubMed

    Ito, Kazuaki; Nishiki, Makoto; Ohba, Yoshihiro

    2005-10-01

    Biphenol was shown to bind dihydrogenphosphate (H2PO4-) selectively over various other anions (MeCO2-, Cl-, Br-, I-, NO3-, HSO4-). The highly selectivity of biphenol toward dihydrogenphosphate is explained in terms of the basicity and shape of the guest anion. PMID:16205002

  10. An anion sensor based on an organic field effect transistor.

    PubMed

    Minami, Tsuyoshi; Minamiki, Tsukuru; Tokito, Shizuo

    2015-06-11

    We propose an organic field effect transistor (OFET)-based sensor design as a new and innovative platform for anion detection. OFETs could be fabricated on low-cost plastic film substrates using printing technologies, suggesting that OFETs can potentially be applied to practical supramolecular anion sensor devices in the near future. PMID:25966040

  11. Triflyloxy-substituted carboranes as useful weakly coordinating anions.

    PubMed

    Press, Loren P; McCulloch, Billy J; Gu, Weixing; Chen, Chun-Hsing; Foxman, Bruce M; Ozerov, Oleg V

    2015-09-25

    New carborane anions carrying one or three triflyloxy substituents are described. The mono-triflyloxy substituted carborane can be halogenated to give pentabromo and decachloro derivatives with preservation of the B-OTf linkage. The use of [HCB11Cl10OTf](-) as a weakly coordinating anion is demonstrated. PMID:26251850

  12. The Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Sessler, Jonathan L.

    2004-12-01

    In this first year of funding, progress has been made towards the stated project goal of generating useful sulfate extractants. A new series of bispyrrole-pyridine sulfate anion receptors was discovered and found to show very high sulfate-to-nitrate selectivity, a key prerequisite to generating a useful extractant. Progress was made towards developing the synthetic methodology needed to solubilize this system and other known receptors prepared by project collaborator, Prof. Kristin Bowman-James.

  13. Extraction of monoclonal antibodies (IgG1) using anionic and anionic/nonionic reverse micelles.

    PubMed

    George, Daliya A; Stuckey, David C

    2010-01-01

    Purification schemes for antibody production based on affinity chromatography are trying to keep pace with increases in cell culture expression levels and many current research initiatives are focused on finding alternatives to chromatography for the purification of Monoclonal antibodies (MAbs). In this article, we have investigated an alternative separation technique based on liquid-liquid extraction called the reverse micellar extraction. We extracted MAb (IgG1) using reverse micelles of an anionic surfactant, sodium bis 2-ethyl-hexyl sulfosuccinate (AOT) and a combination of anionic (AOT) and nonionic surfactants (Brij-30, Tween-85, Span-85) using isooctane as the solvent system. The extraction efficiency of IgG1 was studied by varying parameters, such as pH of the aqueous phase, cation concentration, and type and surfactant concentration. Using the AOT/Isooctane reverse micellar system, we could achieve good overall extraction of IgG1 (between 80 and 90%), but only 30% of the bioactivity of IgG1 could be recovered at the end of the extraction by using its binding to affinity chromatography columns as a surrogate measure of activity. As anionic surfactants were suspected as being one of the reasons for the reduced activity, we decided to combine a nonionic surfactant with an anionic surfactant and then study its effect on the extraction efficiency and bioactivity. The best results were obtained using an AOT/Brij-30/Isooctane reverse micellar system, which gave an overall extraction above 90 and 59% overall activity recovery. An AOT/Tween-85/Isooctane reverse micellar system gave an overall extraction of between 75 and 80% and overall activity recovery of around 40-45%. The results showed that the activity recovery of IgG1 can be significantly enhanced using different surfactant combination systems, and if the recovery of IgG1 can be further enhanced, the technique shows considerable promise for the downstream purification of MAbs. PMID:20665658

  14. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Moyer, Bruce a.; Bostick, Debra A.; Fowler, Christopher J.; Kang, Hyun-Ah; Ruas, Alexandre; Delmau, Laetitia H.; Haverlock, Tamara J.; Llinares, Jose M.; Hossain, Alamgir; Kang, S. O.; Bowman-James, Kristin; Shriver, James A.; Marquez, Manuel; Sessler, Jonathan L.

    2005-09-22

    The major thrust of this project led by the University of Kansas (Prof. Kristin Bowman-Jones) entails the exploration of the principles of recognition and separation of sulfate by the design, synthesis, and testing of novel sulfate extractants. A key science need for the cleanup of tank wastes at Hanford has been identified in developing methods to separate those bulk waste components that have low solubilities in borosilicate glass. Sulfate has been identified as a particularly difficult and expensive problem in that its concentration in the waste is relatively high, its solubility in glass is especially low, and it interferes with the performance of both vitrification equipment and the glass waste form. The new extractants will be synthesized by the University of Kansas and the University of Texas, Austin. Oak Ridge National Laboratory (ORNL) is subjecting the new extractants to experiments that will determine their properties and effectiveness in separating sulfate from the major competing anions in the waste, especially nitrate. Such experiments will entail primarily liquid-liquid extraction. Current efforts focus on exciting new systems in which the anion receptors act as synergists for anion exchange.

  15. Several hemicyanine dyes as fluorescence chemosensors for cyanide anions.

    PubMed

    Liang, Muhan; Wang, Kangnan; Guan, Ruifang; Liu, Zhiqiang; Cao, Duxia; Wu, Qianqian; Shan, Yanyan; Xu, Yongxiao

    2016-05-01

    Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ (1)H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon-carbon double bond in conjugated bridge and induces N(+)CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions. PMID:26921604

  16. Selectivity Control in Synergistic Liquid-Liquid Anion Exchange of Univalent Anions via Structure-Specific Cooperativity between Quaternary Ammonium Cations and Anion Receptors

    SciTech Connect

    Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

    2012-01-01

    Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence upon the structure of the alkylammonium cation. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). C4P has the unique ability in its cone anion-binding conformation to accept an appropriately sized electropositive species in the resulting cup formed by its four electron-rich pyrrole groups, while BTU is not expected to be predisposed for a specific host-guest interaction with the quaternary ammonium cations. It was therefore hypothesized that synergism between C4P and methyltri(C8,10)alkylammonium chloride (Aliquat 336) would be uniquely pronounced owing to insertion of the methyl group of the Aliquat cation into the C4P cup, and we present herein data supporting this expectation. While synergism is comparatively weak for both exchangers with the BTU receptor, synergism between C4P and Aliquat 336 is indeed so strong that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, unraveling the observed selectivity behavior and resulting in the estimation of binding constants for C4P with the ion pairs of A336+ with Cl , Br , OAcF3 , NO3 , and I . The uniquely strong positive cooperativity between A336 and C4P underscores the advantage of a supramolecular approach in the design of synergistic anion exchange systems.

  17. Selectivity control in synergistic liquid-liquid anion exchange of univalent anions via structure-specific cooperativity between quaternary ammonium cations and anion receptors.

    PubMed

    Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

    2012-10-01

    Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence on the structure of the alkylammonium cation that suggests a supramolecular cooperative effect. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). Whereas synergism is comparatively weak when either methyltri(C(8,10))alkylammonium chloride (Aliquat 336) or tetraheptylammonium chloride is used with the BTU receptor, synergism between C4P and Aliquat 336 is so pronounced that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, resulting in the estimation of binding constants for C4P with the ion pairs of A336(+) with Cl(-), Br(-), OAc(F3)(-), NO(3)(-), and I(-). PMID:22931168

  18. Highly monodisperse cubic and octahedral rhodium nanocrystals: Their evolutions from sharp polyhedrons into branched nanostructures and surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Long, Nguyen Viet; Chien, Nguyen Duc; Hirata, Hirohito; Matsubara, Takashi; Ohtaki, Michitaka; Nogami, Masayuki

    2011-04-01

    We report the preparation of poly(vinylpyrrolidone) (PVP)-protected Rh nanoparticles by modified polyol method with the reduction of RhCl 3 in ethylene glycol at 160 °C using AgNO 3. This method is used to synthesize highly cubic and octahedral Rh nanoparticles with their well-controlled size ˜7-14 nm characterized by transmission electron microscopy (TEM). At a low AgNO 3 concentration, the appearance of the sharply good morphology of Rh nanoparticles due to their controlled growth of {1 0 0} and {1 1 1} selective surfaces for ˜10-15 min is observed. Their morphology between cubic and octahedral shape exhibits their competitive growth along the [1 1 1] and [1 0 0] directions. Interestingly, sharply and highly branched Rh nanoparticles with their shapes of very sharp corners or sharp-tip arms growing in the [1 1 1] directions are synthesized for ˜30 min at the same concentration of RhCl 3 and AgNO 3 precursors. However, at a higher concentration of AgNO 3, the assemblies of Rh multipods leading to large porous Rh nanoparticles are observed. The problems of reaction time and temperature are discussed to clarify the nucleation and growth of Rh nanoparticles. In addition, monolayers of Rh nanoparticles on SERS substrates using a probe as malachite green (MG) molecule exhibit the high sensitivity for their potential applications in chemical and biochemical sensing.

  19. Octahedral distortion induced magnetic anomalies in LaMn{sub 0.5}Co{sub 0.5}O{sub 3} single crystals

    SciTech Connect

    Manna, Kaustuv Elizabeth, Suja; Anil Kumar, P. S.; Bhadram, Venkata Srinu; Narayana, Chandrabhas

    2014-07-28

    Single crystals of LaMn{sub 0.5}Co{sub 0.5}O{sub 3} belonging to the ferromagnetic-insulator and distorted perovskite class were grown using a four-mirror optical float zone furnace. The as-grown crystal crystallizes into an orthorhombic Pbnm structure. The spatially resolved 2D Raman scan reveals a strain-induced distribution of transition metal (TM)–oxygen (O) octahedral deformation in the as-grown crystal. A rigorous annealing process releases the strain, thereby generating homogeneous octahedral distortion. The octahedra tilt by reducing the bond angle TM-O-TM, resulting in a decline of the exchange energy in the annealed crystal. The critical behavior is investigated from the bulk magnetization. It is found that the ground state magnetic behavior assigned to the strain-free LaMn{sub 0.5}Co{sub 0.5}O{sub 3} crystal is of the 3D Heisenberg kind. Strain induces mean field-like interaction in some sites, and consequently, the critical exponents deviate from the 3D Heisenberg class in the as-grown crystal. The temperature-dependent Raman scattering study reveals strong spin-phonon coupling and the existence of two magnetic ground states in the same crystal.

  20. Direct Synthetic Control over the Size, Composition, and Photocatalytic Activity of Octahedral Copper Oxide Materials: Correlation Between Surface Structure and Catalytic Functionality.

    PubMed

    Nguyen, Michelle A; Bedford, Nicholas M; Ren, Yang; Zahran, Elsayed M; Goodin, Robert C; Chagani, Fatima F; Bachas, Leonidas G; Knecht, Marc R

    2015-06-24

    We report a synthetic approach to form octahedral Cu2O microcrystals with a tunable edge length and demonstrate their use as catalysts for the photodegradation of aromatic organic compounds. In this particular study, the effects of the Cu(2+) and reductant concentrations and stoichiometric ratios were carefully examined to identify their roles in controlling the final material composition and size under sustainable reaction conditions. Varying the ratio and concentrations of Cu(2+) and reductant added during the synthesis determined the final morphology and composition of the structures. Octahedral particles were prepared at selected Cu(2+):glucose ratios that demonstrated a range of photocatalytic reactivity. The results indicate that material composition, surface area, and substrate charge effects play important roles in controlling the overall reaction rate. In addition, analysis of the post-reacted materials revealed photocorrosion was inhibited and that surface etching had preferentially occurred at the particle edges during the reaction, suggesting that the reaction predominately occurred at these interfaces. Such results advance the understanding of how size and composition affect the surface interface and catalytic functionality of materials. PMID:26010080

  1. Low-Lying Isomers of Free-Space Halogen Clusters with Tetrahedral and Octahedral Symmetry in Relation to Stable Molecules Such as SF6.

    PubMed

    Piris, M; March, N H

    2015-10-01

    Motivated by previous work involving one of us (N.H.M.) on some 20 stable tetrahedral (t) and octahedral (o) molecules, including XF(4) (X = C, Si, Ge), the natural orbital functional PNOF6 is here used to study the free-space halogen cluster t-F(4). We consider an extended functional PNOF6(Nc) by coupling Nc orbitals (Nc > 1) to each orbital below the Fermi level, which improves the description of the electron pairs. Similar studies are presented for t-Cl(4). The successful calculation on the stable molecule BrF(5) (Theor. Chem. Acc. 2013, 132, 1298) has prompted a study of the clusters o-F(6) and o-Cl(6) too. The size relation with calculated known stable molecules and the experimental data are finally considered. In the case of the o-SF(6), the geometry optimization with fixed octahedral symmetry has also been performed at the PNOF6(3) level of theory, leading to an equilibrium distance of 2.95 au in perfect agreement with the experiment. Our results confirm the multireferential character of Z(4) and Z(6) compounds (Z = H, F, Cl), in contrast with the single-reference character of the XZ(4) (X = C, Si, Ge) and YZ(6) (Y = S, Se, U) compounds; therefore, despite the clear patterns within a group, it is not possible to extrapolate the results to the case when the atomic number, X or Y, becomes zero. PMID:26393379

  2. Gallium based low-interaction anions

    DOEpatents

    King, Wayne A.; Kubas, Gregory J.

    2000-01-01

    The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

  3. Superoxide anion radical scavenging property of catecholamines.

    PubMed

    Kładna, Aleksandra; Berczyński, Paweł; Kruk, Irena; Michalska, Teresa; Aboul-Enein, Hassan Y

    2013-01-01

    The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals (O2•) was investigated. The reaction between 18-crown-6-ether and potassium superoxide in dimethylsulfoxide was used as a source of O2•. The reactivity of catecholamines with O2• was examined using chemiluminescence, reduction of nitroblue tetrazolium and electron paramagnetic resonance spin-trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide was included as the spin trap. The results showed that the four catecholamines were effective and efficient in inhibiting chemiluminescence accompanying the potassium superoxide/18-crown-6-ether system in a dose-dependent manner over the range 0.05-2 mM in the following order: adrenaline > noradrenaline > dopamine > isoproterenol, with, IC50 = 0.15 ± 0.02 mM 0.21 ± 0.03 mM, 0.27 ± 0.03 mM and 0.50 ± 0.04 mM, respectively. The catecholamines examined also exhibited a strong scavenging effect towards O2• when evaluated this property by the inhibition of nitroblue tetrazolium reduction (56-73% at 1 M concentration). A very similar capacity of O2• scavenging was monitored in the 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping assay. The results suggest that catecholamines tested may involve a direct effect on scavenging O2- radicals. PMID:23319391

  4. Neptunium Valence Chemistry in Anion Exchange Processing

    SciTech Connect

    KYSER, EDWARD

    2003-02-01

    The current anion resin in use in HB-Line Phase II, Reillex{trademark} HPQ, was tested in the laboratory under expected plant conditions for Np processing and was found to load between 50 and 70 g Np per liter of resin. Losses varied from 0.2 to 15 percent depending on a number of parameters. Hydrazine in the feed at 0.02 to 0.05 M appeared to keep the Np from oxidizing and increasing the losses within four to seven days after the FS addition. Losses of up to three percent were observed five days after FS addition when hydrazine was not used in the feed, compared with 0.3 percent when the feed was loaded immediately after FS addition. Based on these test results the following processing conditions are recommended: (1) Feed conditions: 8 M HNO{sub 3}, 0.02 M hydrazine, 0.05 M excess FS, less than 5 days storage of solution after FS addition. (2) Wash conditions: 100 liters of 8 M HNO{sub 3}, no FS, no hydrazine. (3) Elution conditions: 0.17 M HNO{sub 3}, 0.05 M hydrazine, no FS. (4) Precipitation feed conditions: 0.03 M excess ascorbic acid, no additional hydrazine, no FS, precipitation within three days.

  5. Ionic Block Copolymers for Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Herbst, Dan; Giffin, Guinevere A.; di Noto, Vito; Witten, Tom; Coughlin, E. Bryan

    2013-03-01

    Anion exchange membrane (AEM) fuel cells have regained interest because it allows the use of non-noble metal catalysts. Until now, most of the studies on AEM were based on random polyelectrolytes. In this work, Poly(vinylbenzyltrimethylammonium bromide)-b- (methylbutylene) ([PVBTMA][Br]-b-PMB) was studied by SAXS, TEM and dielectric spectroscopy to understand the fundamental structure-conductivity relationship of ion transport mechanisms within well-ordered block copolymers. The ionic conductivity and the formation of order structure were dependent on the casting solvent. Higher ion exchange capacity (IEC) of the membranes showed higher conductivity at as IEC values below 1.8mmol/g, as above this, the ionic conductivity decreases due to more water uptake leading to dilution of charge density. The humidity dependence of morphology exhibited the shifting of d-spacing to higher value and the alteration in higher characteristic peak of SAXS plot as the humidity increase from the dry to wet state. This phenomenon can be further explained by a newly developed polymer brush theory. Three ionic conduction pathways with different conduction mechanism within the membranes can be confirmed by broadband electric spectroscopy. US Army MURI (W911NF1010520)

  6. In situ anion diffusion experiments using radiotracers

    NASA Astrophysics Data System (ADS)

    Jansson, Mats; Eriksen, Trygve E.

    2004-02-01

    Diffusion experiments in compacted bentonite have been carried out in situ using the borehole laboratory CHEMLAB. The "ordinary" anion iodide and the redox-sensitive pertechnetate ion have been investigated. In spite of strongly reducing groundwater conditions, technetium was found to diffuse mostly unreduced as TcO 4-, although in some spots in the compacted clay, the activity was significantly higher, which may be explained by reduction of some TcO 4- by iron-containing minerals in the bentonite. The measured concentration profiles in the clay cannot be accommodated by assuming one single diffusion process. The experimental data are modeled assuming two diffusion paths, intralamellar diffusion and diffusion in external water. The apparent diffusivity for the intralamellar diffusion was found to be 8.6×10 -11 m 2 s -1 for iodide with a capacity factor of 0.1, while the apparent diffusivity for the diffusion in external water was found to be 5×10 -14 m 2 s -1 with α=2.26. The corresponding values for Tc were found to be Da=6×10 -11 m 2 s -1, α=0.1 and Da=1×10 -13 m 2 s -1, α=0.46, respectively. The diffusion constants and capacity factors obtained in this study are in accordance with data from laboratory experiments.

  7. Conformation of oligodeoxynucleotides associated with anionic liposomes

    PubMed Central

    Patil, Siddhesh D.; Rhodes, David G.

    2000-01-01

    There has been significant progress in the development of antisense therapeutics for a wide range of medicinal applications. Further improvement will require better understanding of cellular internalization, intracellular distribution mechanisms and interactions of oligodeoxynucleotides with cellular organelles. In many of these processes interactions of oligodeoxynucleotides with lipid assemblies may have a significant influence on their function. Divalent cations have been shown to assist cellular internalization of certain oligodeoxynucleotides and to affect their conformation. In this work we have investigated conformational changes of phosphorothioate oligodeoxynucleotides upon divalent cation-mediated interaction with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol (DPPG) liposomes. For the sequences investigated here the native conformation underwent significant change in the presence of anionic DPPG liposomes only when divalent cations were present. This change is sequence-specific, ion-selective and distinct from previously reported changes in oligodeoxynucleotide structure due to divalent cations alone. The conformation of one oligodeoxynucleotide in the presence of calcium and DPPG yields circular dichroism spectra which suggest C-DNA but which also have characteristics unlike any previously reported spectra of liposome-associated DNA structure. The data suggest the possibility of a unique conformation of liposome-associated ODNs and reflect a surprisingly strong tendency of single-stranded DNA to retain a characteristic conformation even when adsorbed to a surface. This conformation may be related to cellular uptake, transport of oligodeoxynucleotides in cells and/or function. PMID:11058108

  8. Interactions of anionic surfactants with methemoglobin.

    PubMed

    Gebicka, Lidia; Banasiak, Ewa

    2011-03-01

    Interactions of two anionic surfactants, sodium dodecyl sulphate (SDS) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) at concentrations below and above critical micelle concentration with methemoglobin (metHb) have been investigated by conventional as well as by stopped-flow absorption and fluorescence spectroscopy. The absorption spectra of metHb in AOT reverse micelles have been also analyzed. Both surfactants in their monomeric form convert metHb to reversible hemichrome. This is connected with a diminution of peroxidase-like activity of metHb and with an increase of the susceptibility of heme for a damage by H(2)O(2). In micellar solutions of AOT and SDS as well as in AOT reverse micelles pentacoordinated ferric species seems to be the predominant form of this protein. It has been concluded, basing on a kinetic analysis, that conformational changes in the heme environment of metHb as induced by both surfactants occur independently of the alterations in the tertiary structure of this protein. PMID:21131182

  9. Anion binding to the ubiquitin molecule.

    PubMed Central

    Makhatadze, G. I.; Lopez, M. M.; Richardson, J. M.; Thomas, S. T.

    1998-01-01

    Effects of different salts (NaCl, MgCl2, CaCl2, GdmCl, NaBr, NaClO4, NaH2PO4, Na2SO4) on the stability of the ubiquitin molecule at pH 2.0 have been studied by differential scanning calorimetry, circular dichroism, and Tyr fluorescence spectroscopies. It is shown that all of the salts studied significantly increase the thermostability of the ubiquitin molecule, and that this stabilization can be interpreted in terms of anion binding. Estimated thermodynamic parameters of binding for Cl- show that this binding is relatively weak (Kd = 0.15 M) and is characterized by a negative enthalpy of -15 kJ/mol per site. Particularly surprising was the observed stabilizing effect of GdmCl through the entire concentration range studied (0.01-2 M), however, to a lesser extent than stabilization by NaCl. This stabilizing effect of GdmCl appears to arise from the binding of Cl- ions. Analysis of the observed changes in the stability of the ubiquitin molecule in the presence of GdmCl can be adequately described by combining the thermodynamic model of denaturant binding with Cl- binding effects. PMID:9541401

  10. Theoretical study of the superoxide anion assisted firefly oxyluciferin formation

    NASA Astrophysics Data System (ADS)

    Pinto da Silva, Luís; Esteves da Silva, Joaquim C. G.

    2013-12-01

    This a theoretical Letter based on density functional theory, on the role of superoxide anion in firefly chemiluminescence in DMSO. We have found that this anion can attack luciferin radical molecules, thus forming a luciferin-like trianion. This latter molecule transfers an oxygen atom, which results in the formation of oxyluciferyl radical dianion and carbon dioxide molecules. Oxyluciferin is finally formed after an electron transfer from oxyluciferyl radical dianion to tert-BuOrad radical molecules. Thus, we have found evidence that firefly oxyluciferin can be formed in a energetically favorable superoxide anion-assisted reaction, without the need for the formation of firefly dioxetanone.

  11. Anion, cation, and zwitterion selectivity of phospholemman channel molecules.

    PubMed Central

    Kowdley, G C; Ackerman, S J; Chen, Z; Szabo, G; Jones, L R; Moorman, J R

    1997-01-01

    Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes. PMID:8994599

  12. Survey of organic acid eluents for anion chromatography

    SciTech Connect

    Book, D.E.

    1981-10-01

    Of all the potential eluents surveyed (including aromatic, sulfonic, phosphonic, among other acids), only the carboxylic acids and the nitrophenols are recommended as eluents for anion chromatography. The concentration of the eluent should be in the range 5 x 10/sup -5/ to 1 x 10/sup -3/ M. The eluent should have the same charge as inorganic anions, a higher charge than organic acid samples. Choice of eluents for separation of halides, chloride and sulfate, multivalent inorganic anions, small alkyl acids, and aromatic acids is discussed. (DLC)

  13. Photoelectron spectroscopic study of the ethyl cyanoacrylate anion

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Tang, Xin; Bowen, Kit

    2013-09-01

    Anion photoelectron spectroscopy and density functional theory have been utilized to study the parent, ethyl cyanoacrylate molecular anion, ECA-. The measured electron affinity (0.9 ± 0.2 eV), vertical detachment energy (1.3 ± 0.1 eV), and anion-to-triplet neutral, photodetachment transition energies (4.0 ± 0.1 eV and 4.5 ± 0.1 eV) all compare well with their calculated values. The relatively high electron affinity of the ECA monomer is responsible for the fact that its “anionic” polymerization mechanism proceeds even with weak nucleophiles, such as water.

  14. Anion Photoelectron Angular Distributions: Electron Scattering Resonances in Photodetachment

    NASA Astrophysics Data System (ADS)

    Mabbs, Richard

    2012-06-01

    To a large degree the photoelectron angular distributions (PAD) of anionic species represent signatures of the bound parent orbital. However, these angular distributions are also influenced by interaction of the outgoing electron with the neutral (atomic, molecular or cluster) residue. The electron kinetic energy evolution (eKE) of the PAD is presented for a number of different species (from molecular to cluster anion), showing the often striking effect of excitation of temporary excited anionic states. These cases highlight the influence of different types of electron-molecule scattering resonances in photodetachment dynamics. Additionally, the possibility of using the eKE evolution of the PAD for structural elucidation is discussed.

  15. On the ambient pressure polymorph of K2Ca3Si3O10-An unusual mixed-anion silicate and its structural and spectroscopic characterization

    NASA Astrophysics Data System (ADS)

    Schmidmair, Daniela; Kahlenberg, Volker; Perfler, Lukas; Tribus, Martina; Hildebrandt, Johannes; Többens, Daniel M.

    2015-08-01

    An ambient pressure polymorph of K2Ca3Si3O10 has been synthesized via solid state reactions. Single-crystal X-ray diffraction experiments show, that this new modification crystallizes in the triclinic space group P 1 bar with the following lattice parameters: a=5.6699(6) Å, b=7.3754(12) Å, c=11.8310(13) Å, α=86.199(11)°, β=80.625(9)°, γ=88.700(11)°. The structure was solved by direct methods and subsequently refined to a residual of R1=0.0261 for 1761 independent observed reflections (I>2σ(I)) and 163 parameters. A special feature of the crystal structure is the coexistence of two different types of silicate anions. Isolated [SiO4]- tetrahedra as well as [Si4O12]- vierer single rings occur in the ratio 2:1, resulting in the crystallochemical formula K4Ca6[SiO4]2[Si4O12]. To the best of our knowledge, this is the first example of an oxo-silicate where insular and cyclic silicate anions appear concomitantly. Charge compensation is provided by Ca and K cations. All calcium atoms are coordinated by 6 oxygen atoms, forming distorted octahedra. By sharing common corners, edges and faces, these [CaO6]-polyhedra build up octahedral layer-like motifs parallel to (010). Potassium ions are located in voids between the silicate anions and [CaO6]-octahedra and are coordinated by 8-9 oxygen atoms. Further characterization of this new compound was carried out by electron microprobe analysis and Raman spectroscopy. DFT calculations were employed (i) to assign Raman bands to certain vibrational modes and (ii) to determine the relative stabilities of the monoclinic high-pressure and the triclinic ambient pressure polymorph of K2Ca3Si3O10.

  16. ELECTROACTIVE MATERIALS FOR ANION SEPARATION-TECHNETIUM FROM NITRATE

    EPA Science Inventory

    The proposed research will provide the basis for using electroactive ion exchange materials to remove anionic contaminants from HLW wastes and process streams. An ion exchange process using electroactive materials sorbs contaminants selectively and then expels (elutes) them elec...

  17. An anion channel in Arabidopsis hypocotyls activated by blue light.

    PubMed Central

    Cho, M H; Spalding, E P

    1996-01-01

    A rapid, transient depolarization of the plasma membrane in seedling stems is one of the earliest effects of blue light detected in plants. It appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibility that activation of a Cl- conductance is part of the depolarization mechanism was raised previously and addressed here. By patch clamping hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis seedlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB 15-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel. NPPB also blocked the blue-light-induced depolarization in vivo and decreased the inhibitory effect of blue light on hypocotyl elongation. These results indicate that activation of this anion channel plays a role in transducing blue light into growth inhibition. PMID:8755616

  18. New anion-exchange polymers for improved separations

    SciTech Connect

    Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

    1997-08-01

    Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials.

  19. An anion channel in Arabidopsis hypocotyls activated by blue light

    NASA Technical Reports Server (NTRS)

    Cho, M. H.; Spalding, E. P.; Evans, M. L. (Principal Investigator)

    1996-01-01

    A rapid, transient depolarization of the plasma membrane in seedling stems is one of the earliest effects of blue light detected in plants. It appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibility that activation of a Cl- conductance is part of the depolarization mechanism was raised previously and addressed here. By patch clamping hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis seedlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB 15-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel. NPPB also blocked the blue-light-induced depolarization in vivo and decreased the inhibitory effect of blue light on hypocotyl elongation. These results indicate that activation of this anion channel plays a role in transducing blue light into growth inhibition.

  20. Nitrate anion exchange in 238Pu aqueous scrap recovery operations

    NASA Astrophysics Data System (ADS)

    Pansoy-Hjelvik, M. E.; Silver, G. L.; Reimus, M. A. H.; Ramsey, K. B.

    1999-01-01

    Strong base, nitrate anion exchange (IX) is crucial to the purification of 238Pu solution feedstocks with gross levels of impurities. This paper discusses the work involved in bench scale experiments to optimize the nitrate anion exchange process. In particular, results are presented of experiments conducted to a) demonstrate that high levels of impurities can be separated from 238Pu solutions via nitrate anion exchange and, b) work out chemical pretreatment methodology to adjust and maintain 238Pu in the IV oxidation state to optimize the Pu(IV)-hexanitrato anionic complex sorption to Reillex-HPQ resin. Additional experiments performed to determine the best chemical treatment methodology to enhance recovery of sorbed Pu from the resin and VIS-NIR absorption studies to determine the steady state equilibrium of Pu(IV), Pu(III), and Pu(VI) in nitric acid are discussed.

  1. Unmeasured anions and mortality in critically ill patients in 2016.

    PubMed

    Kotake, Yoshifumi

    2016-01-01

    The presence of acid-base disturbances, especially metabolic acidosis may negatively affect the outcome of critically ill patients. Lactic acidosis is the most frequent etiology and has largest impact on the prognosis. Since lactate measurement might not have always been available at bedside, it had been regarded as one of the unmeasured anions. Therefore, anion gap and strong ion gap has been used to as a surrogate of lactate concentration. From this perspective, the relationship between either anion gap or strong ion gap and mortality has been explored. Then, lactate became routinely measurable at bedside and the direct comparison between directly measured lactate and these surrogate parameters can be possible. Currently available evidence suggests that directly measured lactate has larger prognostic ability for mortality than albumin-corrected anion gap and strong ion gap without lactate. In this commentary, the rationale and possible clinical implications of these findings are discussed. PMID:27429758

  2. Is Nitrate Anion Photodissociation Mediated by Singlet-Triplet Absorption?

    PubMed

    Svoboda, Ondřej; Slavíček, Petr

    2014-06-01

    Photolysis of the nitrate anion is involved in the oxidation processes in the hydrosphere, cryosphere, and stratosphere. While it is known that the nitrate photolysis in the long-wavelength region proceeds with a very low quantum yield, the mechanism of the photodissociation remains elusive. Here, we present the quantitative modeling of singlet-singlet and singlet-triplet absorption spectra in the atmospherically relevant region around 300 nm, and we argue that a spin-forbidden transition between the singlet ground state and the first triplet state contributes non-negligibly to the nitrate anion photolysis. We further propose that the nitrate anion excited into the first singlet excited state relaxes nonradiatively into its ground state. The full understanding of the nitrate anion photolysis can improve modeling of the asymmetric solvation in the atmospheric processes, e.g., photolysis on the surfaces of ice or snow. PMID:26273880

  3. A carbohydrate-anion recognition system in aprotic solvents.

    PubMed

    Ren, Bo; Dong, Hai; Ramström, Olof

    2014-05-01

    A carbohydrate-anion recognition system in nonpolar solvents is reported, in which complexes form at the B-faces of β-D-pyranosides with H1-, H3-, and H5-cis patterns similar to carbohydrate-π interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate-anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CH⋅⋅⋅A(-) hydrogen bonds between the binding partners and is related to electron-withdrawing groups of the carbohydrates as well as increased hydrogen-bond-accepting capability of the anions. PMID:24616327

  4. Robust Photocatalytic H2O2 Production by Octahedral Cd3(C3N3S3)2 Coordination Polymer under Visible Light

    PubMed Central

    Zhuang, Huaqiang; Yang, Lifang; Xu, Jie; Li, Fuying; Zhang, Zizhong; Lin, Huaxiang; Long, Jinlin; Wang, Xuxu

    2015-01-01

    Herein, we reported a octahedral Cd3(C3N3S3)2 coordination polymer as a new noble metal-free photocatalyst for robust photocatalytic H2O2 production from methanol/water solution. The coordination polymer can give an unprecedented H2O2 yield of ca. 110.0 mmol • L−1 • g−1 at pH = 2.8 under visible light illumination. The characterization results clearly revealed that the photocatalytic H2O2 production proceeds by a pathway of two-electron reduction of O2 on the catalyst surface. This work showed the potential perspective of Mx(C3N3S3)y (M = transitional metals) coordination polymers as a series of new materials for solar energy storage and conversion. PMID:26582652

  5. Robust Photocatalytic H2O2 Production by Octahedral Cd3(C3N3S3)2 Coordination Polymer under Visible Light

    NASA Astrophysics Data System (ADS)

    Zhuang, Huaqiang; Yang, Lifang; Xu, Jie; Li, Fuying; Zhang, Zizhong; Lin, Huaxiang; Long, Jinlin; Wang, Xuxu

    2015-11-01

    Herein, we reported a octahedral Cd3(C3N3S3)2 coordination polymer as a new noble metal-free photocatalyst for robust photocatalytic H2O2 production from methanol/water solution. The coordination polymer can give an unprecedented H2O2 yield of ca. 110.0 mmol • L-1 • g-1 at pH = 2.8 under visible light illumination. The characterization results clearly revealed that the photocatalytic H2O2 production proceeds by a pathway of two-electron reduction of O2 on the catalyst surface. This work showed the potential perspective of Mx(C3N3S3)y (M = transitional metals) coordination polymers as a series of new materials for solar energy storage and conversion.

  6. A New Class of Octahedral Molecular Sieve Materials for the Selective Removal and Sequestration of {sup 90}Sr{sup 2+}

    SciTech Connect

    NYMAN,MAY D.; NENOFF,TINA M.; TRIPATHI,AKHILESH; PARISE,JOHN B.; MAXWELL,ROBERT S.; HARRISON,WILLIAM T.A.

    2000-07-14

    The structure of Na{sub 16}Nb{sub 12.8}Ti{sub 3.2}O{sub 44.8}(OH){sub 3.2} {center_dot} 8H{sub 2}O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M{sup IV} (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M{sup IV}:Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr{sup 2+}. The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes.

  7. Lattice distortions and octahedral rotations in epitaxially strained LaNiO{sub 3}/LaAlO{sub 3} superlattices

    SciTech Connect

    Kinyanjui, M. K. E-mail: benckise@fkf.mpg.de; Kaiser, U.; Lu, Y.; Wu, M.; Wochner, P.; Christiani, G.; Logvenov, G.; Habermeier, H.-U.; Keimer, B.; Benckiser, E. E-mail: benckise@fkf.mpg.de; Gauquelin, N.; Botton, G. A.; Frano, A.; Reehuis, M.

    2014-06-02

    Using a complementary combination of x-ray diffraction and atomically resolved imaging we investigated the lattice structure of epitaxial LaNiO{sub 3}/LaAlO{sub 3} superlattices grown on a compressive-strain inducing LaSrAlO{sub 4} (001) substrate. A refinement of the structure obtained from the x-ray data revealed the monoclinic I 2/c 1 1 space group. The (Ni/Al)O{sub 6} octahedral rotation angle perpendicular to the superlattice plane is enhanced, and the one parallel to the plane is reduced with respect to the corresponding bulk values. High-angle annular dark field imaging was used to determine the lattice parameters within the superlattice unit cell. High-resolution electron microscopy images of the oxygen atoms are consistent with the x-ray results.

  8. Strain Accommodation By Facile WO6 Octahedral Distortion and Tilting During WO3 Heteroepitaxy on SrTiO3(001)

    SciTech Connect

    Du, Yingge; Gu, Meng; Varga, Tamas; Wang, Chong M.; Bowden, Mark E.; Chambers, Scott A.

    2014-08-27

    In this paper, we show that compared to other BO6 octahedra in ABO3 structured perovskite oxides, the WO6 octahedra in tungsten trioxide (WO3) can withstand a much larger degree of distortion and tilting to accommodate interfacial strain, which in turn strongly impact the nucleation, structure, and defect formation during the epitaxial growth of WO3 on SrTiO3(001). A meta-stable tetragonal phase can be stabilized by epitaxy and a thickness dependent phase transition (tetragonal to monoclinic) is observed. In contrast to misfit dislocations to accommodate the interfacial stain, the facial WO6 octahedral distortion and tilting give rise to three types of planar defects that affect more than 15 monolayers from the interface. These atomically resolved, unusual interfacial defects may significantly alter the electronic, electrochromic, and mechanical properties of the epitaxial films.

  9. Characterization of a Saturated and Flexible Aliphatic Polyol Anion Receptor

    SciTech Connect

    Shokri, Alireza; Schmidt, Jacob C.; Wang, Xue B.; Kass, Steven R.

    2012-10-17

    Nature employs flexible molecules to bind anions in a variety of physiologically important processes whereas supramolecular chemists have been designing rigid substrates that minimize or eliminate intramolecular hydrogen bond interactions to carry out anion recogni-tion. Herein, the association of a flexible polyhydroxy alkane with chloride ion is described and the bound re-ceptor is characterized by infrared and photoelectron spectroscopy in the gas phase, computations, and its bind-ing constant as a function of temperature in acetonitrile.

  10. Gas-Grain Models for Interstellar Anion Chemistry

    NASA Technical Reports Server (NTRS)

    Cordiner, M. A.; Charnely, S. B.

    2012-01-01

    Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

  11. Boron compounds as anion binding agents for nonaqueous battery electrolytes

    DOEpatents

    Lee, Hung Sui; Yang, Xia-Oing; McBreen, James; Xiang, Caili

    2000-02-08

    Novel fluorinated boron-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boron-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boron-based anion receptors include borane and borate compounds bearing different fluorinated alkyl and aryl groups.

  12. Self-assembled 3D heterometallic Cu(II)/Fe(II) coordination polymers with octahedral net skeletons: structural features, molecular magnetism, thermal and oxidation catalytic properties.

    PubMed

    Karabach, Yauhen Y; Guedes da Silva, M Fátima C; Kopylovich, Maximilian N; Gil-Hernández, Beatriz; Sanchiz, Joaquin; Kirillov, Alexander M; Pombeiro, Armando J L

    2010-12-01

    The new three-dimensional (3D) heterometallic Cu(II)/Fe(II) coordination polymers [Cu(6)(H(2)tea)(6)Fe(CN)(6)](n)(NO(3))(2n)·6nH(2)O (1) and [Cu(6)(Hmdea)(6)Fe(CN)(6)](n)(NO(3))(2n)·7nH(2)O (2) have been easily generated by aqueous-medium self-assembly reactions of copper(II) nitrate with triethanolamine or N-methyldiethanolamine (H(3)tea or H(2)mdea, respectively), in the presence of potassium ferricyanide and sodium hydroxide. They have been isolated as air-stable crystalline solids and fully characterized including by single-crystal X-ray diffraction analyses. The latter reveal the formation of 3D metal-organic frameworks that are constructed from the [Cu(2)(μ-H(2)tea)(2)](2+) or [Cu(2)(μ-Hmdea)(2)](2+) nodes and the octahedral [Fe(CN)(6)](4-) linkers, featuring regular (1) or distorted (2) octahedral net skeletons. Upon dehydration, both compounds show reversible escape and binding processes toward water or methanol molecules. Magnetic susceptibility measurements of 1 and 2 reveal strong antiferromagnetic [J = -199(1) cm(-1)] or strong ferromagnetic [J = +153(1) cm(-1)] couplings between the copper(II) ions through the μ-O-alkoxo atoms in 1 or 2, respectively. The differences in magnetic behavior are explained in terms of the dependence of the magnetic coupling constant on the Cu-O-Cu bridging angle. Compounds 1 and 2 also act as efficient catalyst precursors for the mild oxidation of cyclohexane by aqueous hydrogen peroxide to cyclohexanol and cyclohexanone (homogeneous catalytic system), leading to maximum total yields (based on cyclohexane) and turnover numbers (TONs) up to about 22% and 470, respectively. PMID:21028781

  13. Effects of various anions on the Raman spectrum of halorhodopsin.

    PubMed Central

    Pande, C; Lanyi, J K; Callender, R H

    1989-01-01

    Resonance Raman experiments were conducted to probe and understand the effect of various anions on halorhodopsin. These included monoatomic anions Cl- and Br-, which bind to the so-called halorhodopsin binding sites I and II, and polyatomic anions NO3- and ClO4-, which bind to site I only. The two types of ions clearly show different effects on the vibrational spectrum of the chromophore. The differences are not localized to the Schiff base region of the molecule, but extend to the chromophore structure-sensitive fingerprint region as well. We find that the protonated Schiff base frequency is at 1,633 cm-1 for Cl- and Br- ions, as reported previously for Cl-. However, we find that two Schiff base frequencies characterize halorhodopsin upon binding of the polyatomic anions. One frequency lies at the same location as that found for the monoatomic anions and the other is at 1,645 cm-1. Halorhodopsin with bound NO3- and ClO4- thus may consist of two heterogeneous structures in equilibrium. This heterogeneity does not seem to correlate with a retinal isomeric heterogeneity, which we can also demonstrate in these samples. The results suggest that anions binding to site I do not bind to the Schiff base directly, but can influence chromophore and/or protein conformational states. PMID:2930828

  14. Theoretical studies of nonvalence correlation-bound anions

    NASA Astrophysics Data System (ADS)

    Voora, Vamsee; Jordan, Kenneth

    2015-03-01

    Nonvalence correlation-bound anion states have been investigated using state-of-the-art ab initio methodologies as well as by model potential approaches. In nonvalence correlation-bound anion states the excess electron occupies a very extended orbital with the binding to the molecule or cluster being dominated by long-range correlation effects. Failure of conventional Hartree-Fock reference based approaches for treating these anionic states is discussed. Ab initio approaches that go beyond Hartree-Fock orbitals, such as Green's function, and equation-of-motion methods are used to characterize nonvalence correlation-bound anion states of a variety of systems including C60 and C6F6. Edge-bound nonvalence correlation-bound anionic states are established for polycyclic aromatics. Accurate one-electron model potential approaches, parametrized using the results of ab initio calculations, are described. The model potentials are used to study nonvalence correlation-bound anion states of large water clusters as well as ``superatomic'' states of fullerene systems. Travel support through New Investigator Travel Award from Division of Chemical Physics (APS) and NSF Grant CHE-1111235 are greatfully acknowledged.

  15. Prestin's anion transport and voltage-sensing capabilities are independent.

    PubMed

    Bai, Jun-Ping; Surguchev, Alexei; Montoya, Simone; Aronson, Peter S; Santos-Sacchi, Joseph; Navaratnam, Dhasakumar

    2009-04-22

    The integral membrane protein prestin, a member of the SLC26 anion transporter family, is responsible for the voltage-driven electromotility of mammalian outer hair cells. It was argued that the evolution of prestin's motor function required a loss of the protein's transport capabilities. Instead, it was proposed that prestin manages only an abortive hemicycle that results in the trapped anion acting as a voltage sensor, to generate the motor's signature gating charge movement or nonlinear capacitance. We demonstrate, using classical radioactive anion ([(14)C]formate and [(14)C]oxalate) uptake studies, that in contrast to previous observations, prestin is able to transport anions. The prestin-dependent uptake of both these anions was twofold that of cells transfected with vector alone, and comparable to SLC26a6, prestin's closest phylogenetic relative. Furthermore, we identify a potential chloride-binding site in which the mutations of two residues (P328A and L326A) preserve nonlinear capacitance, yet negate anion transport. Finally, we distinguish 12 charged residues out of 22, residing within prestin's transmembrane regions, that contribute to unitary charge movement, i.e., voltage sensing. These data redefine our mechanistic concept of prestin. PMID:19383462

  16. Grain boundary mobility in anion doped MgO

    NASA Technical Reports Server (NTRS)

    Kapadia, C. M.; Leipold, M. H.

    1973-01-01

    Certain anions OH(-), F(-) and Gl(-) are shown to enhance grain growth in MgO. The magnitude of their effect decreases in the order in which the anions are listed and depends on their location (solid-solution, second phase) in the MgO lattice. As most anions exhibit relatively high vapor pressures at sintering temperatures, they retard densification and invariably promote residual porosity. The role of anions on grain growth rates was studied in relation to their effect on pore mobility and pore removal; the atomic process controlling the actual rates was determined from observed kinetics in conjunction with the microstructural features. With respect to controlling mechanisms, the effects of all anions are not the same. OH(-) and F(-) control behavior through creation of a defect structure and a grain boundary liquid phase while Cl(-) promotes matter transport within pores by evaporation-condensation. Studies on an additional anion, S to the minus 2nd power gave results which were no different from undoped MgO, possibly because of evaporative losses during hot pressing. Hence, the effect of sulphur is negligible or undetermined.

  17. Membrane-Active Peptides and the Clustering of Anionic Lipids

    PubMed Central

    Wadhwani, P.; Epand, R.F.; Heidenreich, N.; Bürck, J.; Ulrich, A.S.; Epand, R.M.

    2012-01-01

    There is some overlap in the biological activities of cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs). We compared nine AMPs, seven CPPs, and a fusion peptide with regard to their ability to cluster anionic lipids in a mixture mimicking the cytoplasmic membrane of Gram-negative bacteria, as measured by differential scanning calorimetry. We also studied their bacteriostatic effect on several bacterial strains, and examined their conformational changes upon membrane binding using circular dichroism. A remarkable correlation was found between the net positive charge of the peptides and their capacity to induce anionic lipid clustering, which was independent of their secondary structure. Among the peptides studied, six AMPs and four CPPs were found to have strong anionic lipid clustering activity. These peptides also had bacteriostatic activity against several strains (particularly Gram-negative Escherichia coli) that are sensitive to lipid clustering agents. AMPs and CPPs that did not cluster anionic lipids were not toxic to E. coli. As shown previously for several types of AMPs, anionic lipid clustering likely contributes to the mechanism of antibacterial action of highly cationic CPPs. The same mechanism could explain the escape of CPPs from intracellular endosomes that are enriched with anionic lipids. PMID:22853904

  18. Counterion-mediated pattern formation in membranes containing anionic lipids

    PubMed Central

    Slochower, David R.; Wang, Yu-Hsiu; Tourdot, Richard W.; Radhakrishnan, Ravi; Janmey, Paul A.

    2014-01-01

    Most lipid components of cell membranes are either neutral, like cholesterol, or zwitterionic, like phosphatidylcholine and sphingomyelin. Very few lipids, such as sphingosine, are cationic at physiological pH. These generally interact only transiently with the lipid bilayer, and their synthetic analogs are often designed to destabilize the membrane for drug or DNA delivery. However, anionic lipids are common in both eukaryotic and prokaryotic cell membranes. The net charge per anionic phospholipid ranges from −1 for the most abundant anionic lipids such has phosphatidylserine, to near −7 for phosphatidylinositol 3,4,5 trisphosphate, although the effective charge depends on many environmental factors. Anionic phospholipids and other negatively charged lipids such as lipopolysaccharides are not randomly distributed in the lipid bilayer, but are highly restricted to specific leaflets of the bilayer and to regions near transmembrane proteins or other organized structures within the plane of the membrane. This review highlights some recent evidence that counterions, in the form of monovalent or divalent metal ions, polyamines, or cationic protein domains, have a large influence of the lateral distribution of anionic lipids within the membrane, and that lateral demixing of anionic lipids has effects on membrane curvature and protein function that are important for biological control. PMID:24556233

  19. Antibacterial Co(II) and Ni(II) Complexes of N-(2-Furanylmethylene)-2-Aminothiadiazole and Role of SO42−, NO3−, C2O42− and CH3CO2− anions on Biological Properties

    PubMed Central

    Rauf, Abdul; Supuran, Claudiu T.

    2002-01-01

    Co(II) and Ni(II) complexes with a Schiff base, N-(2-furanylmethylene)-2-aminothiadiazole have been prepared and characterized by their physical, spectral and analytical data. The synthesized Schiff-bases act as tridentate ligands during the complexation reaction with Co(II) and Ni(II. metal ions. They possess the composition [M(L)2]Xn (where M=Co(II) or Ni(II), L=, X=NO3−, SO42−, C2O42− or CH3CO2− and n=1 or 2) and show an octahedral geometry. In order to evaluate the effect of anions upon chelation, the Schiff-base and its complexes have been screened for antibacterial activity against bacterial strains e.g., Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. PMID:18476008

  20. Discovery of Interstellar Anions in Cepheus and Auriga

    NASA Technical Reports Server (NTRS)

    Cordiner, M. A.; Charnely, S. B.; Buckle, J. V.; Walsh, C.

    2011-01-01

    We report the detection of microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H in the star-forming region LI251 A (in Cepheus), and the pre-stellar core LI512 (in Auriga). The carbon chain-bearing species C4H, HC3N, HC5N, HC7N, and C3S are also detected in large abundances. The observations of L1251A constitute the first detections of anions and long-chain polyynes and cyanopolyynes (with more than five carbon atoms) in the Cepheus Flare star-forming region, and the first detection of anions in the vicinity of a protostar outside of the Taurus molecular cloud complex, indicating a possible wider importance for anions in the chemistry of star formation. Rotational excitation temperatures have been derived from the HC3N hyperfine structure lines and are found to be 6.2 K for L1251A and 8.7 K for LI5l2. The anion-to-neutral ratios are 3.6% and 4.1%, respectively, which are within the range of values previously observed in the interstellar medium, and suggest a relative uniformity in the processes governing anion abundances in different dense interstellar clouds. This research contributes toward the growing body of evidence that carbon chain anions are relatively abundant in interstellar clouds throughout the Galaxy, but especially in the regions of relatively high density and high depletion surrounding pre-stellar cores and young, embedded protostars.

  1. Benzonitrile: Electron affinity, excited states, and anion solvation

    NASA Astrophysics Data System (ADS)

    Dixon, Andrew R.; Khuseynov, Dmitry; Sanov, Andrei

    2015-10-01

    We report a negative-ion photoelectron imaging study of benzonitrile and several of its hydrated, oxygenated, and homo-molecularly solvated cluster anions. The photodetachment from the unsolvated benzonitrile anion to the X ˜ 1 A 1 state of the neutral peaks at 58 ± 5 meV. This value is assigned as the vertical detachment energy (VDE) of the valence anion and the upper bound of adiabatic electron affinity (EA) of benzonitrile. The EA of the lowest excited electronic state of benzonitrile, a ˜ 3 A 1 , is determined as 3.41 ± 0.01 eV, corresponding to a 3.35 eV lower bound for the singlet-triplet splitting. The next excited state, the open-shell singlet A ˜ 1 A 1 , is found about an electron-volt above the triplet, with a VDE of 4.45 ± 0.01 eV. These results are in good agreement with ab initio calculations for neutral benzonitrile and its valence anion but do not preclude the existence of a dipole-bound state of similar energy and geometry. The step-wise and cumulative solvation energies of benzonitrile anions by several types of species were determined, including homo-molecular solvation by benzonitrile, hydration by 1-3 waters, oxygenation by 1-3 oxygen molecules, and mixed solvation by various combinations of O2, H2O, and benzonitrile. The plausible structures of the dimer anion of benzonitrile were examined using density functional theory and compared to the experimental observations. It is predicted that the dimer anion favors a stacked geometry capitalizing on the π-π interactions between the two partially charged benzonitrile moieties.

  2. DISCOVERY OF INTERSTELLAR ANIONS IN CEPHEUS AND AURIGA

    SciTech Connect

    Cordiner, M. A.; Charnley, S. B.; Buckle, J. V.; Walsh, C.; Millar, T. J.

    2011-04-01

    We report the detection of microwave emission lines from the hydrocarbon anion C{sub 6}H{sup -} and its parent neutral C{sub 6}H in the star-forming region L1251A (in Cepheus), and the pre-stellar core L1512 (in Auriga). The carbon-chain-bearing species C{sub 4}H, HC{sub 3}N, HC{sub 5}N, HC{sub 7}N, and C{sub 3}S are also detected in large abundances. The observations of L1251A constitute the first detections of anions and long-chain polyynes and cyanopolyynes (with more than five carbon atoms) in the Cepheus Flare star-forming region, and the first detection of anions in the vicinity of a protostar outside of the Taurus molecular cloud complex, indicating a possible wider importance for anions in the chemistry of star formation. Rotational excitation temperatures have been derived from the HC{sub 3}N hyperfine structure lines and are found to be 6.2 K for L1251A and 8.7 K for L1512. The anion-to-neutral ratios are 3.6% and 4.1%, respectively, which are within the range of values previously observed in the interstellar medium, and suggest a relative uniformity in the processes governing anion abundances in different dense interstellar clouds. This research contributes toward the growing body of evidence that carbon chain anions are relatively abundant in interstellar clouds throughout the Galaxy, but especially in the regions of relatively high density and high depletion surrounding pre-stellar cores and young, embedded protostars.

  3. The role of catalyst precursor anions in coal gasification

    SciTech Connect

    Abotsi, G.M.K.

    1992-08-28

    The aims of the proposed project are to enrich our understanding of the roles of various aqueous soluble catalyst precursor anions on the surface electrical properties of coal and to ascertain the influence of the surface charge on the adsorption, dispersion, and activities of calcium and potassium. These goals will be achieved by impregnating a North Dakota lignite (PSOC 1482) and its demineralized derivative with calcium or potassium catalyst precursors containing acetate (CH{sub 3}COO{sup {minus}}), chloride (Cl{sup {minus}}), nitrate (NO{sub 3}{sup {minus}}), sulfate (SO{sub 4}{sup 2{minus}}), and carbonate (CO{sub 3}{sup 2{minus}}) anions. Catalyst loading will be conducted under well-controlled conditions of solution pH and ionic strength. In the last quarter, the surface charge properties of the coal was determined as a function of acetate (CH{sub 3}COO{sup {minus}}), chloride (Cl{sup {minus}}), nitrate (NO{sup 3}{sup {minus}}), carbonate (CO{sub 3}{sup 2{minus}}) or sulfate (SO{sub 4}{sup 2{minus}})concentration using the respective potassium salts of these anions. In general, low anion concentrations (10{sup {minus}3} or 10{sup {minus}2} mol/L) had little effect on the zeta potentials of the coals. However, the surface charge densities of the coal become less negative at 10-1 mol/L of the nitrate, carbonate or sulfate anions. These trends suggest that the surface charge density of the coal is controlled by the adsorption of potassium ions (K{sup +}) onto the coal particles. The net negative charge on the coal panicles creates a repulsive force between the anions and the coal surface and prevents the anions from exerting any significant effect on the coal's electrokinetic properties.

  4. Probing and evaluating anion-π interaction in meso-dinitrophenyl functionalized calix[4]pyrrole isomers.

    PubMed

    Kim, Ajeong; Ali, Rashid; Park, Seok Ho; Kim, Yong-Hoon; Park, Jung Su

    2016-09-25

    We investigate anion-π binding modes in a cis-isomer of 3,5-dinitrophenyl-substituted calix[4]pyrrole with various anions via X-ray crystallographic analyses and compare its binding affinities with those of the corresponding trans-isomer. Sandwich-type anion-π interactions prove to not only enhancing anion binding abilities but also altering the anion-binding selectivity of the calix[4]pyrrole framework. PMID:27549578

  5. A Simplified Approach to the Basis Functions of Symmetry Operations and Terms of Metal Complexes in an Octahedral Field with d[superscript 1] to d[superscript 9] Configurations

    ERIC Educational Resources Information Center

    Lee, Liangshiu

    2010-01-01

    The basis sets for symmetry operations of d[superscript 1] to d[superscript 9] complexes in an octahedral field and the resulting terms are derived for the ground states and spin-allowed excited states. The basis sets are of fundamental importance in group theory. This work addresses such a fundamental issue, and the results are pedagogically…

  6. Vertical detachment energies of anionic thymidine: Microhydration effects

    NASA Astrophysics Data System (ADS)

    Kim, Sunghwan; Schaefer, Henry F.

    2010-10-01

    Density functional theory has been employed to investigate microhydration effects on the vertical detachment energy (VDE) of the thymidine anion by considering the various structures of its monohydrates. Structures were located using a random searching procedure. Among 14 distinct structures of the anionic thymidine monohydrate, the low-energy structures, in general, have the water molecule bound to the thymine base unit. The negative charge developed on the thymine moiety increases the strength of the intermolecular hydrogen bonding between the water and base units. The computed VDE values of the thymidine monohydrate anions are predicted to range from 0.67 to 1.60 eV and the lowest-energy structure has a VDE of 1.32 eV. The VDEs of the monohydrates of the thymidine anion, where the N1H hydrogen of thymine has been replaced by a 2'-deoxyribose ring, are greater by ˜0.30 eV, compared to those of the monohydrates of the thymine anion. The results of the present study are in excellent agreement with the accompanying experimental results of Bowen and co-workers [J. Chem. Phys. 133, 144304 (2010)].

  7. Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

    NASA Technical Reports Server (NTRS)

    West, William C.; Whitacre, Jay F.; Leifer, Nicole; Greenbaum, Steve; Smart, Marshall; Bugga, Ratnakumar; Blanco, Mario; Narayanan, S. R.

    2007-01-01

    We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

  8. Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange

    NASA Astrophysics Data System (ADS)

    Anderson, Bryan D.; Tracy, Joseph B.

    2014-10-01

    Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.

  9. Reactivity of Anions in Interstellar Media: Detectability and Applications

    NASA Astrophysics Data System (ADS)

    Senent, M. L.; Hochlaf, M.

    2013-05-01

    We propose a general rule to distinguish between detectable and undetectable astronomical anions. We believe that only few anions live long enough in the interstellar medium and thus can be detected. Our method is based on quantum mechanical calculations capable of describing accurately the evolution of electronic states during chemical processes. The still not fully understood reactivity at low temperatures is discussed considering non-adiabatic effects. The role of excited states has usually been neglected in previous works which basically focused on the ground electronic state for interpretations of experimental observations. Here, we deal with unsaturated carbon chains (e.g., C n H-), which show a high density of electronic states close to their corresponding ground electronic states, complex molecular dynamics, and non-adiabatic phenomena. Our general rule shows that it is not sufficient that anions exist in the gas phase (in the laboratory) to be present in media such as astrophysical media, since formation and decomposition reactions of these anions may allow the population of anionic electronic states to autodetach, forming neutrals. For C n H, reactivity depends strongly on n, where long and short chains behave differently. Formation of linear chains is relevant.

  10. REACTIVITY OF ANIONS IN INTERSTELLAR MEDIA: DETECTABILITY AND APPLICATIONS

    SciTech Connect

    Senent, M. L.; Hochlaf, M. E-mail: hochlaf@univ-mlv.fr

    2013-05-01

    We propose a general rule to distinguish between detectable and undetectable astronomical anions. We believe that only few anions live long enough in the interstellar medium and thus can be detected. Our method is based on quantum mechanical calculations capable of describing accurately the evolution of electronic states during chemical processes. The still not fully understood reactivity at low temperatures is discussed considering non-adiabatic effects. The role of excited states has usually been neglected in previous works which basically focused on the ground electronic state for interpretations of experimental observations. Here, we deal with unsaturated carbon chains (e.g., C{sub n} H{sup -}), which show a high density of electronic states close to their corresponding ground electronic states, complex molecular dynamics, and non-adiabatic phenomena. Our general rule shows that it is not sufficient that anions exist in the gas phase (in the laboratory) to be present in media such as astrophysical media, since formation and decomposition reactions of these anions may allow the population of anionic electronic states to autodetach, forming neutrals. For C{sub n} H, reactivity depends strongly on n, where long and short chains behave differently. Formation of linear chains is relevant.

  11. Water clusters in mixed ionic complexes with metal dipicolinate anions

    NASA Astrophysics Data System (ADS)

    Das, Babulal; Baruah, Jubaraj B.

    2013-02-01

    Formations of three different types of hydrogen-bonded water clusters in the interstices of mixed ionic complexes with metal dipicolinate anions are reported. In the complex [Co(phen)2(H2O)2][Zn(dpa)2]ṡ7H2O (1) (where phen = 1,10-phenanthroline, dpa = dipicolinate), both the cation and anion is hydrophilic in nature, exhibits an unusual 2D infinite cyclic water decamers (H2O)10 stabilized by four identical zinc dipicolinato complex anions. Modulating the cationic unit to a hydrophobic environment by replacing the aqua ligand with 2,2'-bipyridine ligand the water cluster can be modified. The complex [Ni(phen)2ṡbpy][Co(dpa)2]ṡ8H2O (2) (where bpy = 2,2'-bipyridine) has unprecedented discrete hydrogen bonded hexadecameric (H2O)16 water clusters encapsulated between eight anionic units. A rare wavelike infinite water chain (H2O)n is observed in complex [Co(phen)3][Mn(dpa)2]ṡ12H2O (3), in this case the water chain fills the interstitial space created by packing of large hydrophilic anionic units and hydrophobic cationic units. The reported clusters are indefinitely stable in their respective complex at ambient temperature, but the water loss is irreversible when thermally decomposed.

  12. Plasmon-enhanced photocatalytic properties of nano Ag@AgBr on single-crystalline octahedral Cu2O (1 1 1) microcrystals composite photocatalyst

    NASA Astrophysics Data System (ADS)

    Liu, Li; Lin, Shuanglong; Hu, Jinshan; Liang, Yinghua; Cui, Wenquan

    2015-03-01

    A new composite photocatalyst Ag@AgBr/Cu2O was prepared by loading Ag@AgBr on (1 1 1) facts of octahedral Cu2O substrate via a facile precipitation in situ photoreduction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis), nitrogen sorption and the photoelectrochemical measurements. The results show that Ag@AgBr nanoparticles are well-dispersed on Cu2O nanoparticles with narrow size distributions and controllable sizes from 10 to 30 nm. TEM results of the as-synthesized Ag@AgBr/Cu2O nanocomposite revealed that Ag@AgBr nanoparticles were attached to the surface of octahedral Cu2O. Photocatalytic degradation of methylene blue (MB) was carried out to evaluate the photocatalytic activity of Ag@AgBr/Cu2O under visible-light irradiation. The Ag@AgBr/Cu2O composite showed stronger visible light absorption capacity and higher photocatalytic activity than pure Cu2O. The Ag@AgBr (15 wt.%)/Cu2O sample presented the best photocatalytic activity, degrading 93.28% MB after irradiation for 90 min, due to their high surface area (18.499 m2 g-1), the Crystal effect of Cu2O and surface plasmon resonance of Ag NPs. Meanwhile, phenol was degraded to further prove the degradation ability of Ag@AgBr/Cu2O. In addition, the quenching effect was examined in the photocatalytic reaction process of MB. Active h+, Br0 and the resulting rad O2- played the major roles for the dye degradation, while rad OH was verified to be insignificant. Based on the experimental results, a photocatalytic mechanism for organics degradation over Ag@AgBr/Cu2O photocatalysts was proposed. The electronic interactions were systematically studied and confirmed by the photoelectrochemical measurements.

  13. Stabilizing electrodeposition in elastic solid electrolytes containing immobilized anions

    PubMed Central

    Tikekar, Mukul D.; Archer, Lynden A.; Koch, Donald L.

    2016-01-01

    Ion transport–driven instabilities in electrodeposition of metals that lead to morphological instabilities and dendrites are receiving renewed attention because mitigation strategies are needed for improving rechargeability and safety of lithium batteries. The growth rate of these morphological instabilities can be slowed by immobilizing a fraction of anions within the electrolyte to reduce the electric field at the metal electrode. We analyze the role of elastic deformation of the solid electrolyte with immobilized anions and present theory combining the roles of separator elasticity and modified transport to evaluate the factors affecting the stability of planar deposition over a wide range of current densities. We find that stable electrodeposition can be easily achieved even at relatively high current densities in electrolytes/separators with moderate polymer-like mechanical moduli, provided a small fraction of anions are immobilized in the separator. PMID:27453943

  14. Adsorption behavior of anionic polyelectrolyte for chemical mechanical polishing (CMP).

    PubMed

    Kim, Sarah; So, Jae-Hyun; Lee, Dong-Jun; Yang, Seung-Man

    2008-03-01

    In this work, we investigated the adsorption characteristics of anionic polyelectrolytes, which are used in shallow trench isolation chemical mechanical polishing with ceria abrasives. Specifically, the adsorption isotherms and chain conformation of anionic polyelectrolytes were studied in order to elucidate the difference in removal rates of silicon dioxide (SiO2) and silicon nitride (Si3N4) layers and the high selectivity characteristics of ceria slurry. Adsorption isotherms, FT-IR spectroscopy and contact angle measurements revealed that the anionic polyelectrolyte additives had much better adsorption affinities for the Si3N4 surface than for the SiO2 surface. Moreover, blanket wafer polishing results were successfully correlated with the adsorption isotherms of polyelectrolytes on the oxide particle suspensions. PMID:18078949

  15. Dependence of the benzophenone anion solvation on solvent structure

    SciTech Connect

    Lin, Y.; Jonah, C.D. )

    1992-12-10

    The solvation of the benzophenone anion has been studied at room temperature using the pulse radiolytic pump-probe technique. The time-dependent benzophenone anion absorption spectra have been monitored in several different solvents ranging from linear alcohols to branched alcohols to acetonitrile. The maximum of the steady-state spectrum shifts to the red as the solvent is changed from linear alcohols to branched alcohols to acetonitrile. Computer Monte Carlo simulations indicate that the observed spectral shift can be assigned to the position and the orientation of the dipole functional group. The experimental dynamics of the anion solvation were also studied. By fitting the time-dependent absorption data to a multistate evolution kinetic model, the solvation time for these systems is obtained. 26 refs., 8 figs., 1 tab.

  16. Cell wall bound anionic peroxidases from asparagus byproducts.

    PubMed

    Jaramillo-Carmona, Sara; López, Sergio; Vazquez-Castilla, Sara; Jimenez-Araujo, Ana; Rodriguez-Arcos, Rocio; Guillen-Bejarano, Rafael

    2014-10-01

    Asparagus byproducts are a good source of cationic soluble peroxidases (CAP) useful for the bioremediation of phenol-contaminated wastewaters. In this study, cell wall bound peroxidases (POD) from the same byproducts have been purified and characterized. The covalent forms of POD represent >90% of the total cell wall bound POD. Isoelectric focusing showed that whereas the covalent fraction is constituted primarily by anionic isoenzymes, the ionic fraction is a mixture of anionic, neutral, and cationic isoenzymes. Covalently bound peroxidases were purified by means of ion exchange chromatography and affinity chromatography. In vitro detoxification studies showed that although CAP are more effective for the removal of 4-CP and 2,4-DCP, anionic asparagus peroxidase (AAP) is a better option for the removal of hydroxytyrosol (HT), the main phenol present in olive mill wastewaters. PMID:25195693

  17. Stabilizing electrodeposition in elastic solid electrolytes containing immobilized anions.

    PubMed

    Tikekar, Mukul D; Archer, Lynden A; Koch, Donald L

    2016-07-01

    Ion transport-driven instabilities in electrodeposition of metals that lead to morphological instabilities and dendrites are receiving renewed attention because mitigation strategies are needed for improving rechargeability and safety of lithium batteries. The growth rate of these morphological instabilities can be slowed by immobilizing a fraction of anions within the electrolyte to reduce the electric field at the metal electrode. We analyze the role of elastic deformation of the solid electrolyte with immobilized anions and present theory combining the roles of separator elasticity and modified transport to evaluate the factors affecting the stability of planar deposition over a wide range of current densities. We find that stable electrodeposition can be easily achieved even at relatively high current densities in electrolytes/separators with moderate polymer-like mechanical moduli, provided a small fraction of anions are immobilized in the separator. PMID:27453943

  18. The Hofmeister anion effect and the growth of polyelectrolyte multilayers.

    PubMed

    Salomäki, Mikko; Tervasmäki, Piia; Areva, Sami; Kankare, Jouko

    2004-04-27

    The influence of a variety of counteranions on the properties of polyelectrolyte multilayers deposited by layer-by-layer technique is studied by using ellipsometry and AFM. We found out that in thin dry multilayers (20-90 nm) ofpoly(4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA), the thickness follows reasonably well the position of the counteranion in the Hofmeister series. The polyelectrolyte-counteranion interaction is studied by means of viscosity measurements of semidilute solutions of PDADMA in the presence of different anions. The dynamic viscosities follow the Hofmeister series of anions and correlate with the thickness of multilayers. Two parameters describing the interaction of ions with water, the Jones-Dole viscosity B coefficient and the hydration entropy, are used to explain the anion effect on the developing multilayer thickness. Reasonably smooth and monotonic functional dependence is observed between the layer thickness and these two parameters. PMID:15875399

  19. Solubility and transport of cationic and anionic patterned nanoparticles

    NASA Astrophysics Data System (ADS)

    Su, Jiaye; Guo, Hongxia; Olvera de La Cruz, Monica

    2012-02-01

    Diffusion and transport of nanoparticles (NPs) though nanochannels is important for desalination, drug delivery, and biomedicine. Their surface composition dictate their efficiency separating them by reverse osmosis, delivering into into cells, as well as their toxicity. We analyze bulk diffusion and transport through nanochannels of NPs with different hydrophobic-hydrophilic patterns achieved by coating a fraction of the NP sites with positive or negative charges via explicit solvent molecular dynamics simulations. The cationic NPs are more affected by the patterns, less water soluble, and have higher diffusion constants and fluxes than their anionic NPs counterparts. The NP-water interaction dependence on surface pattern and field strength explains these observations. For equivalent patterns, anionic NPs solubilize more than cationic NPs since the Coulomb interaction of free anionic NPs, which are much stronger than hydrophobic NP-water interactions, are about twice that of cationic NPs.

  20. Electron localization of anions probed by nitrile vibrations

    SciTech Connect

    Mani, Tomoyasu; Grills, David C.; Newton, Marshall D.; Miller, John R.

    2015-08-02

    Localization and delocalization of electrons is a key concept in chemistry, and is one of the important factors determining the efficiency of electron transport through organic conjugated molecules, which have potential to act as “molecular wires”. This, in turn, substantially influences the efficiencies of organic solar cells and other molecular electronic devices. It is also necessary to understand the electronic energy landscape and the dynamics of electrons through molecular chain that govern their transport capabilities in one-dimensional conjugated chains so that we can better define the design principles of conjugated molecules for their applications. We show that nitrile ν(C≡N) vibrations respond to the degree of electron localization in nitrile-substituted organic anions by utilizing time-resolved infrared (TRIR) detection combined with pulse radiolysis. Measurements of a series of aryl nitrile anions allow us to construct a semi-empirical calibration curve between the changes in the ν(C≡N) IR shifts and the changes in the electronic charges from the neutral to the anion states in the nitriles; more electron localization in the nitrile anion results in larger IR shifts. Furthermore, the IR linewidth in anions can report a structural change accompanying changes in the electronic density distribution. Probing the shift of the nitrile ν(C≡N) IR vibrational bands enables us to determine how the electron is localized in anions of nitrile-functionalized oligofluorenes, considered as organic mixed-valence compounds. We estimate the diabatic electron transfer distance, electronic coupling strengths, and energy barriers in these organic mixed-valence compounds. The analysis reveals a dynamic picture, showing that the electron is moving back and forth within the oligomers with a small activation energy of ≤ kBT, likely controlled by the movement of dihedral angles between monomer units. Thus, implications for the electron transport

  1. Electron localization of anions probed by nitrile vibrations

    DOE PAGESBeta

    Mani, Tomoyasu; Grills, David C.; Newton, Marshall D.; Miller, John R.

    2015-08-02

    Localization and delocalization of electrons is a key concept in chemistry, and is one of the important factors determining the efficiency of electron transport through organic conjugated molecules, which have potential to act as “molecular wires”. This, in turn, substantially influences the efficiencies of organic solar cells and other molecular electronic devices. It is also necessary to understand the electronic energy landscape and the dynamics of electrons through molecular chain that govern their transport capabilities in one-dimensional conjugated chains so that we can better define the design principles of conjugated molecules for their applications. We show that nitrile ν(C≡N) vibrationsmore » respond to the degree of electron localization in nitrile-substituted organic anions by utilizing time-resolved infrared (TRIR) detection combined with pulse radiolysis. Measurements of a series of aryl nitrile anions allow us to construct a semi-empirical calibration curve between the changes in the ν(C≡N) IR shifts and the changes in the electronic charges from the neutral to the anion states in the nitriles; more electron localization in the nitrile anion results in larger IR shifts. Furthermore, the IR linewidth in anions can report a structural change accompanying changes in the electronic density distribution. Probing the shift of the nitrile ν(C≡N) IR vibrational bands enables us to determine how the electron is localized in anions of nitrile-functionalized oligofluorenes, considered as organic mixed-valence compounds. We estimate the diabatic electron transfer distance, electronic coupling strengths, and energy barriers in these organic mixed-valence compounds. The analysis reveals a dynamic picture, showing that the electron is moving back and forth within the oligomers with a small activation energy of ≤ kBT, likely controlled by the movement of dihedral angles between monomer units. Thus, implications for the electron transport capability

  2. Orientational Jumps in (Acetamide + Electrolyte) Deep Eutectics: Anion Dependence.

    PubMed

    Das, Suman; Biswas, Ranjit; Mukherjee, Biswaroop

    2015-08-27

    All-atom molecular dynamics simulations have been carried out to investigate orientation jumps of acetamide molecules in three different ionic deep eutectics made of acetamide (CH3CONH2) and lithium salts of bromide (Br(–)), nitrate (NO3(–)) and perchlorate (ClO4(–)) at approximately 80:20 mole ratio and 303 K. Orientational jumps have been dissected into acetamide–acetamide and acetamide–ion catagories. Simulated jump characteristics register a considerable dependence on the anion identity. For example, large angle jumps are relatively less frequent in the presence of NO3(–) than in the presence of the other two anions. Distribution of jump angles for rotation of acetamide molecules hydrogen bonded (H-bonded) to anions has been found to be bimodal in the presence of Br(–) and is qualitatively different from the other two cases. Estimated energy barrier for orientation jumps of these acetamide molecules (H-bonded to anions) differ by a factor of ∼2 between NO3(–) and ClO4(–), the barrier height for the latter being lower and ∼0.5kBT. Relative radial and angular displacements during jumps describe the sequence ClO(4)– > NO3(–) > Br(–) and follow a reverse viscosity trend. Jump barrier for acetamide–acetamide pairs reflects weak dependence on anion identity and remains closer to the magnitude (∼0.7kBT) found for orientation jumps in molten acetamide. Jump time distributions exhibit a power law dependence of the type, P(tjump) ∝ A(tjump/τ)(−β), with both β and τ showing substantial anion dependence. The latter suggests the presence of dynamic heterogeneity in these systems and supports earlier conclusions from time-resolved fluorescence measurements. PMID:26131593

  3. Electrostatic charge confinement using bulky tetraoctylammonium cation and four anions

    NASA Astrophysics Data System (ADS)

    Andreeva, Nadezhda A.; Chaban, Vitaly V.

    2016-04-01

    Thanks to large opposite electrostatic charges, cations and anions establish strong ionic bonds. However, applications of ionic systems - electrolytes, gas capture, solubilization, etc. - benefit from weaker non-covalent bonds. The common approaches are addition of cosolvents and delocalization of electron charge density via functionalization of ions. We report fine tuning of closest-approach distances, effective radii, and cation geometry by different anions using the semi-empirical molecular dynamics simulations. We found that long fatty acid chains employed in the tetraalkylammonium cation are largely inefficient and new substituents must be developed. The reported results foster progress of task-specific ionic liquids.

  4. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Li, Xiang; Kiran, Boggavarapu E-mail: kiran@mcneese.edu; Kandalam, Anil K.

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  5. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    NASA Astrophysics Data System (ADS)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H.; Li, Xiang; Kiran, Boggavarapu; Kandalam, Anil K.

    2014-04-01

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, BxAlyHz-, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  6. Photoelectron spectroscopy of boron aluminum hydride cluster anions.

    PubMed

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H; Li, Xiang; Kiran, Boggavarapu; Kandalam, Anil K

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, BxAlyHz(-), were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms. PMID:24784280

  7. Specific Anion Effects on the Kinetics of Iodination of Acetone.

    PubMed

    Lo Nostro, Pierandrea; Mazzini, Virginia; Ninham, Barry W; Ambrosi, Moira; Dei, Luigi; Baglioni, Piero

    2016-08-18

    Specific ion effects on the kinetics of iodination of acetone in an acidic medium are investigated by UV/Vis spectrophotometry as a function of nature of the acid and temperature. The results indicate that the order of the reaction with respect to acetone is practically unaffected by the composition of the acid while the value of the mixed constant k1 K increases according to the sequence HBranion and of the interaction between the cationic intermediate and the anion. PMID:27171120

  8. A lanthanide complex for metal encapsulations and anion exchanges.

    PubMed

    Sun, Yan-Qiong; Wan, Fang; Li, Xin-Xiong; Lin, Jian; Wu, Tao; Zheng, Shou-Tian; Bu, Xianhui

    2016-08-01

    A cationic lanthanide metalloligand with 3 dangling carboxylate groups on its periphery co-assembles with nitrate into a porous thermochromic solid responsive to both external cations and anions, owing to the presence of exchangeable NO3(-) as well as cation cavities arising from cooperative orientation of free carboxylate groups. An especially interesting feature is the structural memory effect during crystallization exhibited by the metalloligand, even after dissolution and binding to secondary cations (Cu(2+), Cd(2+)…). Moreover, the porous solid can undergo ion-exchange with various anions, leading to tunable thermochromic temperature and color range. PMID:27463609

  9. Mixed anion materials and compounds for novel proton conducting membranes

    DOEpatents

    Poling, Steven Andrew; Nelson, Carly R.; Martin, Steve W.

    2006-09-05

    The present invention provides new amorphous or partially crystalline mixed anion chalcogenide compounds for use in proton exchange membranes which are able to operate over a wide variety of temperature ranges, including in the intermediate temperature range of about 100 .degree. C. to 300.degree. C., and new uses for crystalline mixed anion chalcogenide compounds in such proton exchange membranes. In one embodiment, the proton conductivity of the compounds is between about 10.sup.-8 S/cm and 10.sup.-1 S/cm within a temperature range of between about -60 and 300.degree. C. and a relative humidity of less than about 12%..

  10. Atomistic simulations of fcc Pt{sub 75}Ni{sub 25} and Pt{sub 75}Re{sub 25} cubo-octahedral nanoparticles

    SciTech Connect

    Wang, Guofeng; Van Hove, M.A.; Ross, P.N.; Baskes, M.I.

    2004-03-30

    We have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method (MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt75Ni25 and Pt75Re25 nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc cubo-octahedral shapes (terminated by {l_brace}111{r_brace} and {l_brace}100{r_brace} facets) and contain from 586 to 4033 atoms (corresponding to a diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt75Ni25 nanoparticles form a surface-sandwich structure: the Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched in the second atomic shell; (2) the equilibrium Pt75Re25 nanoparticles adopt a core-shell structure: a Pt-enriched shell surrounding a Pt-deficient core.

  11. In situ assembly of octahedral Fe(II) complexes for the enantiomeric excess determination of chiral amines using circular dichroism spectroscopy.

    PubMed

    Dragna, Justin M; Pescitelli, Gennaro; Tran, Lee; Lynch, Vincent M; Anslyn, Eric V; Di Bari, Lorenzo

    2012-03-01

    A method for discriminating between α-chiral primary amine enantiomers is reported. The method utilizes circular dichroism (CD) spectroscopy and a sensing ensemble composed of 2-formyl-3-hydroxypyridine (4) and Fe(II)(TfO)(2). Aldehyde 4 reacts rapidly with chiral amines to form chiral imines, which complex Fe(II) to form a series of diastereomeric octahedral complexes that are CD-active in both the UV and visible regions of the spectrum. NMR studies showed that for enantiomerically pure imine complexes, the Δ-fac isomer is preferred. A statistical analysis of the distribution of stereoisomers accurately modeled the calibration curves for enantiomeric excess (ee). CD signals appearing in the UV region were bisignate, and the nulls of the CD signals were coincident with maxima in the UV spectrum, consistent with exciton coupling. Time-dependent density functional theory and semiempirical calculations confirmed that the CD signals in the UV region arise from coupling of the π-π* transitions in the imine chromophores and that they can be used to describe the signs and magnitudes of the curves accurately. The CD signals in the visible region arise from metal-to-ligand charge-transfer bands, and these signals can be used to determine the ee values of chiral amines with an average absolute error of ±5%. Overall, the strategy presented herein represents a facile in situ assembly process that uses commercially available simple reagents to create large optical signals indicative of ee values. PMID:22272943

  12. [(Pb6I8){Mn(CO)5}6](2-): an octahedral (M6X8)-like cluster with inverted bonding.

    PubMed

    Wolf, Silke; Reiter, Kevin; Weigend, Florian; Klopper, Wim; Feldmann, Claus

    2015-04-20

    [BMIm]2[{PbMn(CO)5)}6I8] (BMIm: 1-butyl-3-methylimidazolium) is obtained by ionic liquid mediated reaction of PbI2 and Mn2(CO)10. Central is a cubelike (Pb6I8) unit containing a nonfilled Pb6 octahedron. Each Pb of this (Pb6I8) unit is terminated on its outside by Mn(CO)5, exhibiting Pb-Mn metal-to-metal bonding (280 pm). Structurally, the (Pb6I8) unit is similar to the well-known octahedral (M6Xn) cluster-type family (M = Zr, Nb, Ta, Mo, W; X = Cl, Br, I). In contrast to most similar cluster compounds, such as W6Br12 ([W6Br8]Br2/1Br4/2, according to Niggli notation) or the carbonyl cluster [Sn6{Cr(CO5)6}](2-), however, the nonfilled central Pb6 octahedron in [{PbMn(CO)5)}6I8](2-) does not exhibit any metal-to-metal bonding. Structure and bonding of the title compound are validated by single-crystal structure analysis, energy-dispersive X-ray analysis (EDX), infrared spectroscopy (FT-IR), and density functional theory (DFT) calculations. Based on the isolobal principle, electronegativity considerations, bond lengths, and DFT calculations including Mulliken population analysis and natural population analysis (NPA), in sum, the charge distribution of Pb is best reflected by an oxidation state of +1. PMID:25830920

  13. Anion-Anion Bonding and Topology in Ternary Iridium Seleno-Stannides.

    PubMed

    Trump, Benjamin A; Tutmaher, Jake A; McQueen, Tyrel M

    2015-12-21

    The synthesis and physical properties of two new and one known Ir-Sn-Se compound are reported. Their crystal structures are elucidated with transmission electron microscopy and powder X-ray diffraction. IrSn0.45Se1.55 is a pyrite phase which consists of tilted corner-sharing IrX6 octahedra with randomly distributed (Sn-Se)(4-) and (Se-Se)(2-) dimers. Ir2Sn3Se3 is a known trigonally distorted skutterudite that consists of cooperatively tilted corner-sharing IrSn3Se3 octahedra with ordered (Sn-Se)2(4-) tetramers. Ir2SnSe5 is a layered, distorted β-MnO2 (pyrolusite) structure consisting of a double IrSe6 octrahedral row, corner sharing in the a direction and edge sharing in the b direction. This distorted pyrolusite contains (Se-Se)(2-) dimers and Se(2-) anions, and each double row is "capped" with a (Sn-Se)n polymeric chain. Resistivity, specific heat, and magnetization measurements show that all three have insulating and diamagnetic behavior, indicative of low-spin 5d(6) Ir(3+). Electronic structure calculations on Ir2Sn3Se3 show a single, spherical, nonspin-orbit split valence band and suggest that Ir2Sn3Se3 is topologically nontrivial under tensile strain due to inversion of Ir-d and Se-p states. PMID:26636188

  14. A new anionic exchange stir bar sorptive extraction coating based on monolithic material for the extraction of inorganic anion.

    PubMed

    Huang, Xiaojia; Lin, Jianbing; Yuan, Dongxing

    2010-07-23

    A novel anionic exchange stir bar sorptive extraction (SBSE) coating based on poly(2-(methacryloyloxy)ethyltrimethylammonium chloride-co-divinylbenzene) monolithic material for the extraction of inorganic anion was prepared. The effect of preparation conditions such as ratio of functional monomer to cross-linker, content of porogenic solvent on the extraction efficiencies were investigated in detailed. The monolithic material was characterized by elemental analysis, scanning electron microscopy and infrared spectroscopy. In order to investigate the extraction capacity of the new coating for inorganic anion, the new SBSE was combined with ionic chromatography with conductivity detection, Br-, NO3-, PO4(3-) and SO4(2-) were selected as detected solutes. Several extractive parameters, including pH value and ionic strength in sample matrix, desorption solvent, extraction and desorption time were optimized. The results showed that strongly ionic strength did not favor the extraction of anlaytes. Under the optimum experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target anions were achieved within the range of 0.92-2.62 and 3.03-9.25 microg/L, respectively. The method also showed good linearity, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was successfully used to detect the two different trademarks of commercial purified water with satisfactory recovery in the range of 70.0-92.6%. To the best of our knowledge, this is the first to use SBSE to enrich inorganic anions. PMID:20576270

  15. Contact Ion Pairs on a Protonated Azamacrocycle: the Role of the Anion Basicity

    NASA Astrophysics Data System (ADS)

    Fraschetti, Caterina; Filippi, Antonello; Crestoni, Maria Elisa; Marcantoni, Enrico; Glucini, Marco; Guarcini, Laura; Montagna, Maria; Guidoni, Leonardo; Speranza, Maurizio

    2016-04-01

    A potassium-containing hexaazamacrocyclic dication, [ M•H•K]2+, is able to add in the gas phase mono- and dicarboxylate anions as well as inorganic anions by forming the corresponding monocharged adducts, the structure of which markedly depends on the basicity of the anion. With anions, such as acetate or fluoride, the neutral hexaazamacrocycle M acts as an acceptor of monosolvated K+ ion. With less basic anions, such as trifluoroacetate or chloride, the protonated hexaazamacrocycle [ M•H]+ performs the unusual functions of an acceptor of contact K+/anion pairs.

  16. Tetrathiafulvalene diindolylquinoxaline: a dual signaling anion receptor with phosphate selectivity†

    PubMed Central

    Bejger, Christopher; Park, Jung Su; Silver, Eric S.; Sessler, Jonathan L.

    2011-01-01

    Incorporation of tetrathiafulvalene into the backbone of a known neutral phosphate receptor, diindolylquinoxaline, yields a dual optical-electrochemical chemosensor for dihydrogen phosphate that functions in dichloromethane. This system shows selectivity for dihydrogen phosphate over other small anions and can be used to detect the presence of this analyte via fluorescence quenching or cyclic voltammetry. PMID:20856940

  17. PHASE BEHAVIOR OF WATER/PERCHLOROETHYLENE/ANIONIC SURFACTANT SYSTEMS

    EPA Science Inventory

    Winsor Type I (o/w), Type II (w/o), and Type III (middle phase) microemulsions have been generated for water and perchloroethylene (PCE) in combination with anionic surfactants and the appropriate electrolyte concentration. The surfactant formulation was a combination of sodium d...

  18. Efficiency of superoxide anions in the inactivation of selected dehydrogenases

    NASA Astrophysics Data System (ADS)

    Rodacka, Aleksandra; Serafin, Eligiusz; Puchala, Mieczyslaw

    2010-09-01

    The most ubiquitous of the primary reactive oxygen species, formed in all aerobes, is the superoxide free radical. It is believed that the superoxide anion radical shows low reactivity and in oxidative stress it is regarded mainly as an initiator of more reactive species such as rad OH and ONOO -. In this paper, the effectiveness of inactivation of selected enzymes by radiation-generated superoxide radicals in comparison with the effectiveness of the other products of water radiolysis is examined. We investigate three enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH). We show that the direct contribution of the superoxide anion radical to GAPDH and ADH inactivation is significant. The effectiveness of the superoxide anion in the inactivation of GAPDH and ADG was only 2.4 and 2.8 times smaller, respectively, in comparison with hydroxyl radical. LDH was practically not inactivated by the superoxide anion. Despite the fact that the studied dehydrogenases belong to the same class of enzymes (oxidoreductases), all have a similar molecular weight and are tetramers, their susceptibility to free-radical damage varies. The differences in the radiosensitivity of the enzymes are not determined by the basic structural parameters analyzed. A significant role in inactivation susceptibility is played by the type of amino acid residues and their localization within enzyme molecules.

  19. Photocatalytic Anion Oxidation and Applications in Organic Synthesis.

    PubMed

    Hering, Thea; Meyer, Andreas Uwe; König, Burkhard

    2016-08-19

    Ions and radicals of the same kind differ by one electron only. The oxidation of many stable inorganic anions yields their corresponding highly reactive radicals, and visible light excitable photocatalysts can provide the required oxidation potential for this transformation. Air oxygen serves as the terminal oxidant, or cheap sacrificial oxidants are used, providing a very practical approach for generating reactive inorganic radicals for organic synthesis. We discuss in this perspective several recently reported examples: Nitrate radicals are obtained by one-electron photooxidation of nitrate anions and are very reactive toward organic molecules. The photooxidation of sulfinate salts yields the much more stable sulfone radicals, which smoothly add to double bonds. A two-electron oxidation of chloride anions to electrophilic chlorine species reacting with arenes in aromatic substitutions extends the method beyond radical reactions. The chloride anion oxidation proceeds via photocatalytically generated peracidic acid as the oxidation reagent. Although the number of reported examples of photocatalytically generated inorganic radical intermediates for organic synthesis is still small, future extension of the concept to other inorganic ions as radical precursors is a clear perspective. PMID:27355754

  20. Aromatic oligureas as hosts for anions and cations.

    PubMed

    Connor, Alan L; Hu, Ting; Detchou, Cadnel S F; Liu, Rui; Pulavarti, Surya V S R K; Szyperski, Thomas; Lu, Zhonglin; Gong, Bing

    2016-08-01

    Aromatic oligoureas 3 and 4 have urea moieties engaging in weak intramolecular H-bonding that constrains their backbones. The shorter 3a and 3b are able to bind chloride and acetate but not their corresponding counterion. The longer 4 binds both an anion and its counterion with the same affinity. PMID:27427283

  1. BEDT-TFF salts with fluorinated sulfonate anions.

    SciTech Connect

    Geiser, U.; Schlueter, J. A.; Kini, A. M.; Wang, H. H.; Ward, B. H.; Mohtasham, J.; Gard, G. L.; Portland State Univ.

    2003-01-01

    A number of layered conducting BEDT-TTF, bis(ethylenedithio)tetrathiafulvalene, salts with heavily fluorinated organosulfonate anions have been prepared and characterized. Of particular interest are the salts containing SF{sub 5}RSO{sub 3}{sup -} anions, where R is a partially fluorinated aliphatic backbone. While structurally similar --the {beta}' packing type predominates--the ground state of these salts varies from superconducting in the case of {beta}'-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} [1] to insulating. Many of the salts with insulating ground states are metallic at room temperature, but charge localization and disproportionation over crystallographically non-equivalent sites occurs at low temperature. The organosulfonate group exhibits a propensity to bind to lithium ions, thus ternary salts incorporating Li+ into the complex anion layer are often found. The fluorophilic effect in organofluorine compounds may be exploited to form salts where the conducting BEDT-TTF layers are separated by extremely bulky anion bilayers. The crystal structure of one such system, (BEDT-TTF){sub 3}[(CF{sub 3}){sub 2}CFC{sub 2}H{sub 4}SO{sub 3}]{sub 4}(H{sub 5}O{sub 2}){sub 2}, is described here.

  2. Capturing and concentrating adenovirus using magnetic anionic nanobeads.

    PubMed

    Sakudo, Akikazu; Baba, Koichi; Ikuta, Kazuyoshi

    2016-01-01

    We recently demonstrated how various enveloped viruses can be efficiently concentrated using magnetic beads coated with an anionic polymer, poly(methyl vinyl ether-maleic anhydrate). However, the exact mechanism of interaction between the virus particles and anionic beads remains unclear. To further investigate whether these magnetic anionic beads specifically bind to the viral envelope, we examined their potential interaction with a nonenveloped virus (adenovirus). The beads were incubated with either adenovirus-infected cell culture medium or nasal aspirates from adenovirus-infected individuals and then separated from the supernatant by applying a magnetic field. After thoroughly washing the beads, adsorption of adenovirus was confirmed by a variety of techniques, including immunochromatography, polymerase chain reaction, Western blotting, and cell culture infection assays. These detection methods positively identified the hexon and penton capsid proteins of adenovirus along with the viral genome on the magnetic beads. Furthermore, various types of adenovirus including Types 5, 6, 11, 19, and 41 were captured using the magnetic bead procedure. Our bead capture method was also found to increase the sensitivity of viral detection. Adenovirus below the detectable limit for immunochromatography was efficiently concentrated using the magnetic bead procedure, allowing the virus to be successfully detected using this methodology. Moreover, these findings clearly demonstrate that a viral envelope is not required for binding to the anionic magnetic beads. Taken together, our results show that this capture procedure increases the sensitivity of detection of adenovirus and would, therefore, be a valuable tool for analyzing both clinical and experimental samples. PMID:27274228

  3. Prescription Fire and Anion Retention in Tahoe Forest Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Prescribed burning is a possible option to reduce fire potential in the Lake Tahoe Basin (California and Nevada). However, subsequent nutrient loading to the lake is a major concern. The effect of residual ash on anion leaching, primarily O-PO4 and SO42-, was studied in both the field and laboratory...

  4. Molecular Anions in Protostars, Prestellar Cores and Dark Clouds

    NASA Technical Reports Server (NTRS)

    Cordiner, Martin; Charnley, Steven; Buckle, Jane; Wash, Catherine; Millar, Tom

    2011-01-01

    From our recent survey work using the Green Bank Telescope, microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H have been detected in six new sources. Using HC3N = 10(exp -9) emission maps, we targeted the most carbon-chain-rich sources for our anion survey, which included the low-mass Class 0 protostar L1251A-IRS3, the prestellar cores L1389-SMM1 and L1512, and the interstellar clouds Ll172A, TMC-1C and L1495B. Derived [C6H(-)]/[C6H] anion-to-neutral ratios are approximately 1-10. The greatest C6H(-) column densities are found in the quiescent clouds TMC-1C and L1495B, but the anion-to-neutral ratios are greatest in the prestellar cores and protostars. These results are interpreted in terms of the physical and chemical properties of the sources, and the implications for molecular cloud chemistry are discussed.

  5. Capturing and concentrating adenovirus using magnetic anionic nanobeads

    PubMed Central

    Sakudo, Akikazu; Baba, Koichi; Ikuta, Kazuyoshi

    2016-01-01

    We recently demonstrated how various enveloped viruses can be efficiently concentrated using magnetic beads coated with an anionic polymer, poly(methyl vinyl ether-maleic anhydrate). However, the exact mechanism of interaction between the virus particles and anionic beads remains unclear. To further investigate whether these magnetic anionic beads specifically bind to the viral envelope, we examined their potential interaction with a nonenveloped virus (adenovirus). The beads were incubated with either adenovirus-infected cell culture medium or nasal aspirates from adenovirus-infected individuals and then separated from the supernatant by applying a magnetic field. After thoroughly washing the beads, adsorption of adenovirus was confirmed by a variety of techniques, including immunochromatography, polymerase chain reaction, Western blotting, and cell culture infection assays. These detection methods positively identified the hexon and penton capsid proteins of adenovirus along with the viral genome on the magnetic beads. Furthermore, various types of adenovirus including Types 5, 6, 11, 19, and 41 were captured using the magnetic bead procedure. Our bead capture method was also found to increase the sensitivity of viral detection. Adenovirus below the detectable limit for immunochromatography was efficiently concentrated using the magnetic bead procedure, allowing the virus to be successfully detected using this methodology. Moreover, these findings clearly demonstrate that a viral envelope is not required for binding to the anionic magnetic beads. Taken together, our results show that this capture procedure increases the sensitivity of detection of adenovirus and would, therefore, be a valuable tool for analyzing both clinical and experimental samples. PMID:27274228

  6. Capacity gradient anion chromatography with a borate complex as eluent.

    PubMed

    Yamamoto, A; Inoue, Y; Kodama, S; Matsunaga, A

    1999-07-30

    Complex formation between borate compounds and vicinal diols is well recognized. Generally, in a chemically bonded anion-exchange resin, many hydroxyl groups are introduced on the surface of the resin in order to make the resin hydrophilic. The borate as an eluting reagent also reacts to these hydroxyl groups, and this complex formation decreases the apparent ion-exchange capacity of the column by being dissociated to the anion depending on the eluent pH. In the present work a method is described for the simultaneous determination of anions based on the capacity gradient for suppressed ion chromatography. A Tosoh IC-Anion-PW column and dihydroxyphenylborane-mannitol eluent system were used. To maintain baseline stability, it was helpful to keep the borate concentration constant during a gradient of 16 to 0 mM mannitol as a modifier to prevent the complex formation with the hydroxyl on the resin. The chemical composition of the eluents and gradient profiles are discussed and the application to the analysis of the condensed phosphates with widely varying retention times as food additives in a cheese sample is presented. PMID:10457467

  7. The anionic biosurfactant rhamnolipid does not denature industrial enzymes

    PubMed Central

    Madsen, Jens K.; Pihl, Rasmus; Møller, Anders H.; Madsen, Anne T.; Otzen, Daniel E.; Andersen, Kell K.

    2015-01-01

    Biosurfactants (BS) are surface-active molecules produced by microorganisms. Their combination of useful properties and sustainable production make them promising industrial alternatives to petrochemical and oleochemical surfactants. Here we compare the impact of the anionic BS rhamnolipid (RL) and the conventional/synthetic anionic surfactant sodium dodecyl sulfate (SDS) on the structure and stability of three different commercially used enzymes, namely the cellulase Carezyme® (CZ), the phospholipase Lecitase Ultra® (LT) and the α-amylase Stainzyme® (SZ). Our data reveal a fundamental difference in their mode of interaction. SDS shows great diversity of interaction toward the different enzymes. It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the enzyme well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT. SDS binds with even lower stoichiometry to SZ and leads to an increase in thermal stability. In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries) to SZ. Furthermore, all enzymes maintain activity at both monomeric and micellar concentrations of RL. We conclude that RL, despite its anionic charge, is a surfactant that does not compromise the structural integrity of industrially relevant enzymes. This makes RL a promising alternative to current synthetic anionic surfactants in a wide range of commercial applications. PMID:25941516

  8. Physicochemical treatments of anionic surfactants wastewater: Effect on aerobic biodegradability.

    PubMed

    Aloui, Fathi; Kchaou, Sonia; Sayadi, Sami

    2009-05-15

    The effect of different physicochemical treatments on the aerobic biodegradability of an industrial wastewater resulting from a cosmetic industry has been investigated. This industrial wastewater contains 11423 and 3148mgL(-1) of chemical oxygen demand (COD) and anionic surfactants, respectively. The concentration of COD and anionic surfactants were followed throughout the diverse physicochemical treatments and biodegradation experiments. Different pretreatments of this industrial wastewater using chemical flocculation process with lime and aluminium sulphate (alum), and also advanced oxidation process (electro-coagulation (Fe and Al) and electro-Fenton) led to important COD and anionic surfactants removals. The best results were obtained using electro-Fenton process, exceeding 98 and 80% of anionic surfactants and COD removals, respectively. The biological treatment by an isolated strain Citrobacter braakii of the surfactant wastewater, as well as the pretreated wastewater by the various physicochemical processes used in this study showed that the best results were obtained with electro-Fenton pretreated wastewater. The characterization of the treated surfactant wastewater by the integrated process (electro-coagulation or electro-Fenton)-biological showed that it respects Tunisian discharge standards. PMID:18799262

  9. Nonadiabatic dynamics of charge transfer in diatomic anion clusters

    SciTech Connect

    Cho, Eunseog; Shin, Seokmin

    2007-12-28

    We have studied the photodissociation and recombination dynamics of the diatomic anions X{sub 2}{sup -} and XY{sup -} designed to mimic I{sub 2}{sup -} and ICl{sup -}, respectively, by using a one-electron model in size-selected N{sub 2}O clusters. The one-electron model is composed of two nuclei and an extra electron moving in a two-dimensional plane including the two nuclei. The main purpose of this study is to explain the salient features of various dynamical processes of molecular ions in clusters using a simple theoretical model. For heteronuclear diatomic anions, a mass disparity and asymmetric electron affinity between the X and Y atoms lead to different phenomena from the homonuclear case. The XY{sup -} anion shows efficient recombination for a smaller cluster size due to the effect of collision-mediated energy transfer and an inherent potential wall on excited state at asymptotic region, while the recombination for the X{sub 2}{sup -} anion is due to rearrangement of solvent configuration and faster nonadiabatic transitions. The results of the present study illustrate the microscopic details of the electronically nonadiabatic processes which control the photodissociation dynamics of molecular ions in clusters.

  10. On Helium Anions in Helium Droplets: Interpreting Recent Experiments

    NASA Astrophysics Data System (ADS)

    Mauracher, Andreas; Huber, Stefan E.

    2014-10-01

    Helium droplets provide an ideal environment to study elementary processes in atomic systems at very low temperatures. Here, we discuss properties of charged and neutral, atomic and molecular helium species formed in helium droplets upon electron impact. By studying their interaction with atomic ground state helium we find that He, He2 and excited (metastable) He*- are well bound within the helium droplet. In comparison, He* , He2* and He2* are found to be squeezed out due to energetic reasons. We also present the formation pathways of atomic and molecular helium anions in helium droplets. Transition barriers in the energetic lowest He*- - He interaction potentials prevent molecule formation at the extremely low temperatures in helium droplets. In contrast, some excited states allow a barrier-free formation of molecular helium (anions). With these theoretical results at hand we can interpret recent experiments in which the resonant formation of atomic and molecular helium anions was observed. Furthermore, we give an outlook on the implications of the presence of these anionic species in doped helium droplets with regard to charge transfer reactions. Austrian Fund Agency (FWF, I 978-N20, DK+ project Computational Interdisciplinary Modelling W1227-N16)/Austrian Ministry of Science (BMWF, Konjunkturpaket II, UniInfrastrukturprogramm of the Focal Point Scientific Computing).

  11. The Determination of Anionic Surfactants in Natural and Waste Waters.

    ERIC Educational Resources Information Center

    Crisp, P. T.; And Others

    1983-01-01

    Background information, procedures, and results of an experiment suitable for measuring subpart per million concentrations of anionic surfactants in natural waters and waste effluents are provided. The experiment required only a spectrophotometer or filter photometer and has been successfully performed by students in an undergraduate environmental…

  12. Removal of Uranium from Plutonium Solutions by Anion Exchange

    SciTech Connect

    Rudisill, T.S.

    2002-03-22

    The anion exchange capacity in the HB-Line Phase II Facility will be used to purify plutonium solutions potentially containing significant quantities of depleted uranium. Following purification, the plutonium will be precipitated as an oxalate and calcined to plutonium oxide (PuO2) for storage until final disposition.

  13. Sheathless capillary electrophoresis-mass spectrometry for anionic metabolic profiling.

    PubMed

    Gulersonmez, Mehmet Can; Lock, Stephen; Hankemeier, Thomas; Ramautar, Rawi

    2016-04-01

    The performance of CE coupled on-line to MS via a sheathless porous tip sprayer was evaluated for anionic metabolic profiling. A representative metabolite mixture and biological samples were used for the evaluation of various analytical parameters, such as peak efficiency (plate numbers), migration time and peak area repeatability, and LODs. The BGE, i.e. 10% acetic acid (pH 2.2), previously used for cationic metabolic profiling was now assessed for anionic metabolic profiling by using MS detection in negative ion mode. For test compounds, RSDs for migration times and peak areas were below 2 and 11%, respectively, and plate numbers ranged from 60 000 to 40 0000 demonstrating a high separation efficiency. Critical metabolites with low or no retention on reversed-phase LC could be efficiently separated and selectively analyzed by the sheathless CE-MS method. An injection volume of only circa 20 nL resulted in LODs between 10 and 200 nM (corresponding to an amount of 0.4-4 fmol), which was an at least tenfold improvement as compared to LODs obtained by conventional CE-MS approaches for these analytes. The methodology was applied to anionic metabolic profiling of glioblastoma cell line extracts. Overall, a sheathless CE-MS method has been developed for highly efficient and sensitive anionic metabolic profiling studies, which can also be used for cationic metabolic profiling studies by only switching the MS detection and separation voltage polarity. PMID:26593113

  14. Relationship Between Equilibrium Forms of Lysozyme Crystals and Precipitant Anions

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan

    1996-01-01

    Molecular forces, such as electrostatic, hydrophobic, van der Waals and steric forces, are known to be important in determining protein interactions. These forces are affected by the solution conditions and changing the pH, temperature or the ionic strength of the solution can sharply affect protein interactions. Several investigations of protein crystallization have shown that this process is also strongly dependent on solution conditions. As the ionic strength of the solution is increased, the initially soluble protein may either crystallize or form an amorphous precipitate at high ionic strengths. Studies done on the model protein hen egg white lysozyme have shown that different crystal forms can be easily and reproducibly obtained, depending primarily on the anion used to desolubilize the protein. In this study we employ pyranine to probe the effect of various anions on the water structure. Additionally, lysozyme crystallization was carried out at these conditions and the crystal form was determined by X-ray crystallography. The goal of the study was to understand the physico-chemical basis for the effect of changing the anion concentration on the equilibrium form of lysozyme crystals. It will also verify the hypothesis that the anions, by altering the bulk water structure in the crystallizing solutions, alter the surface energy of the between the crystal faces and the solution and, consequently, the equilibrium form of the crystals.

  15. Anion Permeation in Ca2+-Activated Cl− Channels

    PubMed Central

    Qu, Zhiqiang; Hartzell, H. Criss

    2000-01-01

    Ca2+-activated Cl channels (ClCaCs) are an important class of anion channels that are opened by increases in cytosolic [Ca2+]. Here, we examine the mechanisms of anion permeation through ClCaCs from Xenopus oocytes in excised inside-out and outside-out patches. ClCaCs exhibited moderate selectivity for Cl over Na: PNa/PCl = 0.1. The apparent affinity of ClCaCs for Cl was low: Kd = 73 mM. The channel had an estimated pore diameter >0.6 nm. The relative permeabilities measured under bi-ionic conditions by changes in Erev were as follows: C(CN)3 > SCN > N(CN)2 > ClO4 > I > N3 > Br > Cl > formate > HCO3 > acetate = F > gluconate. The conductance sequence was as follows: N3 > Br > Cl > N(CN)2 > I > SCN > COOH > ClO4 > acetate > HCO3 = C(CN)3 > gluconate. Permeant anions block in a voltage-dependent manner with the following affinities: C(CN)3 > SCN = ClO4 > N(CN)2 > I > N3 > Br > HCO3 > Cl > gluconate > formate > acetate. Although these data suggest that anionic selectivity is determined by ionic hydration energy, other factors contribute, because the energy barrier for permeation is exponentially related to anion hydration energy. ClCaCs exhibit weak anomalous mole fraction behavior, implying that the channel may be a multi-ion pore, but that ions interact weakly in the pore. The affinity of the channel for Ca2+ depended on the permeant anion at low [Ca2+] (100–500 nM). Apparently, occupancy of the pore by a permeant anion increased the affinity of the channel for Ca2+. The current was strongly dependent on pH. Increasing pH on the cytoplasmic side decreased the inward current, whereas increasing pH on the external side decreased the outward current. In both cases, the apparent pKa was voltage-dependent with apparent pKa at 0 mV = ∼9.2. The channel may be blocked by OH− ions, or protons may titrate a site in the pore necessary for ion permeation. These data demonstrate that the permeation properties of ClCaCs are different from those of CFTR or ClC-1, and provide

  16. Saturated anionic phospholipids enhance transdermal transport by electroporation.

    PubMed Central

    Sen, Arindam; Zhao, Ya-Li; Hui, Sek Wen

    2002-01-01

    Anionic phospholipids, but not cationic or neutral phospholipids, were found to enhance the transdermal transport of molecules by electroporation. When added as liposomes to the milieus of water-soluble molecules to be delivered through the epidermis of porcine skin by electroporation, these phospholipids enhance, by one to two orders of magnitude, the transdermal flux. Encapsulation of molecules in liposomes is not necessary. Dimyristoylphosphatidylserine (DMPS), phosphatidylserine from bovine brain (brain-PS), dioleoylphosphatidylserine (DOPS), and dioleoylphosphatidylglycerol (DOPG) were used to test factors affecting the potency of anionic lipid transport enhancers. DMPS with saturated acyl chains was found to be a much more potent transport enhancer than those with unsaturated acyl chains (DOPS and DOPG). There was no headgroup preference. Saturated DMPS was also more effective in delaying resistance recovery after pulsing, and with a greater affinity in the epidermis after pulsing. Using fluorescent carboxyl fluorescein and fluorescein isothiocyanate (FITC)-labeled Dextrans as test water-soluble molecules for transport, and rhodamine-labeled phospholipids to track anionic phospholipids, we found, by conventional and confocal fluorescence microscopy, that transport of water-soluble molecules was localized in local transport spots or regions (LTRs) created by the electroporation pulses. Anionic phospholipids, especially DMPS, were located at the center of the LTRs and spanned the entire thickness of the stratum corneum (SC). The degree of saturation of anionic phospholipids made no difference in the densities of LTRs created. We deduce that, after being driven into the epidermis by negative electric pulses, saturated anionic phospholipids mix and are retained better by the SC lipids. Anionic lipids prefer loose layers or vesicular rather than multilamellar forms, thereby prolonging the structural recovery of SC lipids to the native multilamellar form. In the

  17. Localization of Anionic Phospholipids in Escherichia coli Cells

    PubMed Central

    Oliver, Piercen M.; Crooks, John A.; Leidl, Mathias; Yoon, Earl J.; Saghatelian, Alan

    2014-01-01

    Cardiolipin (CL) is an anionic phospholipid with a characteristically large curvature and is of growing interest for two primary reasons: (i) it binds to and regulates many peripheral membrane proteins in bacteria and mitochondria, and (ii) it is distributed asymmetrically in rod-shaped cells and is concentrated at the poles and division septum. Despite the growing number of studies of CL, its function in bacteria remains unknown. 10-N-Nonyl acridine orange (NAO) is widely used to image CL in bacteria and mitochondria, as its interaction with CL is reported to produce a characteristic red-shifted fluorescence emission. Using a suite of biophysical techniques, we quantitatively studied the interaction of NAO with anionic phospholipids under physiologically relevant conditions. We found that NAO is promiscuous in its binding and has photophysical properties that are largely insensitive to the structure of diverse anionic phospholipids to which it binds. Being unable to rely solely on NAO to characterize the localization of CL in Escherichia coli cells, we instead used quantitative fluorescence microscopy, mass spectrometry, and mutants deficient in specific classes of anionic phospholipids. We found CL and phosphatidylglycerol (PG) concentrated in the polar regions of E. coli cell membranes; depletion of CL by genetic approaches increased the concentration of PG at the poles. Previous studies suggested that some CL-binding proteins also have a high affinity for PG and display a pattern of cellular localization that is not influenced by depletion of CL. Framed within the context of these previous experiments, our results suggest that PG may play an essential role in bacterial physiology by maintaining the anionic character of polar membranes. PMID:25002539

  18. Plasmalemmal VDAC controversies and maxi-anion channel puzzle.

    PubMed

    Sabirov, Ravshan Z; Merzlyak, Petr G

    2012-06-01

    The maxi-anion channel has been observed in many cell types from the very beginning of the patch-clamp era. The channel is highly conductive for chloride and thus can modulate the resting membrane potential and play a role in fluid secretion/absorption and cell volume regulation. A wide nanoscopic pore of the maxi-anion channel permits passage of excitatory amino acids and nucleotides. The channel-mediated release of these signaling molecules is associated with kidney tubuloglomerular feedback, cardiac ischemia/hypoxia, as well as brain ischemia/hypoxia and excitotoxic neurodegeneration. Despite the ubiquitous expression and physiological/pathophysiological significance, the molecular identity of the maxi-anion channel is still obscure. VDAC is primarily a mitochondrial protein; however several groups detected it on the cellular surface. VDAC in lipid bilayers reproduced the most important biophysical properties of the maxi-anion channel, such as a wide nano-sized pore, closure in response to moderately high voltages, ATP-block and ATP-permeability. However, these similarities turned out to be superficial, and the hypothesis of plasmalemmal VDAC as the maxi-anion channel did not withstand the test by genetic manipulations of VDAC protein expression. VDAC on the cellular surface could also function as a ferricyanide reductase or a receptor for plasminogen kringle 5 and for neuroactive steroids. These ideas, as well as the very presence of VDAC on plasmalemma, remain to be scrutinized by genetic manipulations of the VDAC protein expression. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. PMID:21986486

  19. Polymorphism of the borophosphate anion in K(Fe,Al)[BP{sub 2}O{sub 8}(OH)] and Rb(Al, Fe)[BP{sub 2}O{sub 8}(OH)] crystal structures

    SciTech Connect

    Yakubovich, O. V.; Steele, I. M.; Dimitrova, O. V.

    2010-09-15

    The crystal structure of two borophosphates, Rb(Al,Fe)[BP{sub 2}O{sub 8}(OH)] (a = 9.381(6), b = 8.398(5), c = 9.579(6) A, {beta} = 102.605(10){sup o}, sp. gr. P2{sub 1}/c) and K(Fe,Al)[BP{sub 2}O{sub 8}(OH)] (a = 5.139(2), b = 8.065(4), c = 8.290(4)A, {alpha} = 86.841(8){sup o}, {beta} = 80.346(8){sup o}, {gamma} = 86.622(8){sup o}, sp. gr. P1-bar), obtained by hydrothermal synthesis in the AlCl{sub 3}: FeCl{sub 3}: K{sub 3}PO{sub 4}(Rb{sub 3}PO{sub 4}): B{sub 2}O{sub 3}: H{sub 2}O system has been established using X-ray diffraction (Bruker Smart diffractometer, T = 100 K). Hydrogen atoms are located and their coordinates and thermal parameters are refined. It is shown that the polymorphism of the [BP{sub 2}O{sub 8}(OH)]{sup 4-} borophosphate anion has a morphotropic nature and is related to the substitutions both in the cationic part of the structure and in the octahedral position of the anionic mixed framework. The synthesis of new isotypic triclinic compounds under hydrothermal conditions is predicted.

  20. A structural and spectroscopic investigation of octahedral platinum bis(dithiolene)phosphine complexes: platinum dithiolene internal redox chemistry induced by phosphine association.

    PubMed

    Chandrasekaran, P; Greene, Angelique F; Lillich, Karen; Capone, Stephen; Mague, Joel T; DeBeer, Serena; Donahue, James P

    2014-09-01

    The complexes [Pt(mdt)2] (4; mdt = methyldithiolene, [Me2C2S2](n-)), [Pt(adt)2] (5; adt = p-anisyldithiolene, [(MeO-p-C6H4)2C2S2](n-)), and [Pd(adt)2] (10) have been prepared in yields of ≥90% via transmetalation reactions with the corresponding [R2Sn(S2C2R'2)] complexes (R = (n)Bu, R' = Me; R = Me, R' = -C6H4-p-OMe, 3). Intraligand C-S and C-Cchelate bond lengths (~1.71 and ~1.40 Å, respectively) obtained by X-ray crystallography show these compounds to be comprised of radical monoanions mdt(•-) and adt(•-). The six-coordinate octahedral adducts [Pt(adt)2(dppe)] [6; dppe = 1,2-bis(diphenylphosphino)ethane], trans-[Pt(adt)2(PMe3)2] (8), and trans-[Pt(mdt)2(PMe3)2] (9) have also been prepared, and crystal structures reveal dithiolene ligands that are fully reduced ene-1,2-dithiolates (C-S and C-C(chelate) = ~1.77 and 1.35 Å, respectively). Reduction of the dithiolene ligand thus occurs to accommodate the +IV oxidation state typical of octahedral six-coordinate platinum. The cyclic voltammogram of 5 shows two fully reversible reductions at -0.11 and -0.84 V in CH2Cl2 (vs Ag/AgCl), attributed to successive (adt(•-) + e(-) → adt(2-)) processes, and a reversible oxidation at +1.01 V. The cyclic voltammogram of 9 shows two reversible oxidations at +0.38 and +0.86 V, which are assigned as successive (adt(2-) → adt(•-) + e(-)) oxidations. Consistent with their formulation as having fully reduced dithiolene ligands, the UV-vis spectra for 6, 8, and 9 show no low-energy absorptions below 700 nm, and the S K-edge XAS spectra of 6 and 8 show dithiolene sulfur that is reduced relative to that in 5. The introduction of PMe3 to 10 did not produce the palladium analogue of 8 but rather [Pd(adt)(PMe3)2] (11). The reaction of [PdCl2(PPh3)2] with Li2(mdt) produced a mixture of [Pd(mdt)(PPh3)2] (12, 20%) and [(Ph3P)Pd(μ-1,2-mdt-S,S':S)2Pd(PPh3)] (13, 28%), with the latter having C2 symmetry with a Pd2S2 core structure folded along the S···S axis. PMID:25113575

  1. Octahedral tilt-suppression of ferroelectric domain wall dynamics and the associated piezoelectric activity in Pb(Zr,Ti)O3

    NASA Astrophysics Data System (ADS)

    Eitel, R.; Randall, C. A.

    2007-03-01

    The R3m-R3c transition is in a limited phase field in the Pb(Zr1-x,Tix)O3 (PZT) phase diagram and is a ferroelectric-ferroelectric phase transition that involves the coupling of a secondary displacive ferroelastic phase transition, associated with a structural rotation of the octahedra about the polar threefold axis. Through systematic temperature-dependent piezoelectric characterization under resonance conditions and high-field unipolar ac drive the influence of the aforementioned transition on piezoelectric and electromechanical properties is noted for two compositions x=0.30 and x=0.40mol fraction lead titanate. Applying Rayleigh law analysis to access the relative extrinsic domain wall contributions to the nonlinear permittivity and converse piezoelectric properties, we observe significant differences in the nonlinear response between the R3m and R3c phases and note a discontinuity at the transition for both PZT compositions. A complementary study was conducted through diffraction contrast transmission electron microscopy to access structure property relations. Diffraction contrast imaging reveals that antiphase boundaries (APB’s) associated with octahedral tilt may coincide with non-180° ferroelectric domain walls. This microstructural evidence suggests that APB’s suppress the motion of non-180° ferroelectric domain walls, leading to reduced extrinsic contributions to the piezoelectric and dielectric response in the low-temperature phase (R3c) . The implications of these observations are discussed in relation to both the PZT system and other perovskite-based systems such as BiMO3-PbTiO3 systems.

  2. Influence of post-treatment operations on structural properties and photocatalytic activity of octahedral anatase titania particles prepared by an ultrasonication-hydrothermal reaction.

    PubMed

    Wei, Zhishun; Kowalska, Ewa; Ohtani, Bunsho

    2014-01-01

    The influence of changes in structural and physical properties on the photocatalytic activity of octahedral anatase particles (OAPs), exposing eight equivalent {101} facets, caused by calcination (2 h) in air or grinding (1 h) in an agate mortar was studied with samples prepared by ultrasonication (US; 1 h)-hydrothermal reaction (HT; 24 h, 433 K). Calcination in air at temperatures up to 1173 K induced particle shape changes, evaluated by aspect ratio (AR; d001/d101 = depth vertical to anatase {001} and {101} facets estimated by the Scherrer equation with data obtained from X-ray diffraction (XRD) patterns) and content of OAP and semi-OAP particles, without transformation into rutile. AR and OAP content, as well as specific surface area (SSA), were almost unchanged by calcination at temperatures up to 673 K and were then decreased by elevating the calcination temperature, suggesting that calcination at a higher temperature caused dull-edging and particle sintering, the latter also being supported by the analysis of particle size using XRD patterns and scanning electron microscopic (SEM) images. Time-resolved microwave conductivity (TRMC) showed that the maximum signal intensity (Imax), corresponding to a product of charge-carrier density and mobility, and signal-decay rate, presumably corresponding to reactivity of charge carriers, were increased with increase in AR, suggesting higher photocatalytic activity of OAPs than that of dull-edged particles. Grinding also decreased the AR, indicating the formation of dull-edged particles. The original non-treated samples showed activities in the oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H2 system) comparable to and lower than those of a commercial anatase titania (Showa Denko Ceramics FP-6), respectively. The activities of calcined and ground samples for the CO2 system and H2 system showed almost linear relations with AR and Imax, respectively, suggesting that those activities may

  3. The binding of platinum hexahalides (Cl, Br and I) to hen egg-white lysozyme and the chemical transformation of the PtI{sub 6} octahedral complex to a PtI{sub 3} moiety bound to His15

    SciTech Connect

    Tanley, Simon W. M.; Starkey, Laurina-Victoria; Lamplough, Lucinda; Kaenket, Surasek; Helliwell, John R.

    2014-08-29

    The platinum hexahalides have an octahedral arrangement of six halogen atoms bound to a Pt centre, thus having an octahedral shape that could prove to be useful in interpreting poor electron-density maps. In a detailed characterization, PtI{sub 6} chemically transformed to a square-planar PtI{sub 3} complex bound to the N{sup δ} atom of His15 of HEWL was also observed, which was not observed for PtBr{sub 6} or PtCl{sub 6}. This study examines the binding and chemical stability of the platinum hexahalides K{sub 2}PtCl{sub 6}, K{sub 2}PtBr{sub 6} and K{sub 2}PtI{sub 6} when soaked into pre-grown hen egg-white lysozyme (HEWL) crystals as the protein host. Direct comparison of the iodo complex with the chloro and bromo complexes shows that the iodo complex is partly chemically transformed to a square-planar PtI{sub 3} complex bound to the N{sup δ} atom of His15, a chemical behaviour that is not exhibited by the chloro or bromo complexes. Each complex does, however, bind to HEWL in its octahedral form either at one site (PtI{sub 6}) or at two sites (PtBr{sub 6} and PtCl{sub 6}). As heavy-atom derivatives of a protein, the octahedral shape of the hexahalides could be helpful in cases of difficult-to-interpret electron-density maps as they would be recognisable ‘objects’.

  4. Contact transfer of anions from hands as a function of the use of hand lotions

    NASA Technical Reports Server (NTRS)

    Welker, R. W.; Schulman, M.

    2001-01-01

    Contact transfer of anions from human hands can result in contamination of materials, increasing their rate of corrosion. Two types of hand lotion were applied to the hands: one was specially formulated for cleanroom use and the other was a popular commercial lotion. The effect on contact transfer of anions was measured versus anion transfer from washed hands without lotions.

  5. Aryl-triazole foldamers incorporating a pyridinium motif for halide anion binding in aqueous media.

    PubMed

    Shang, Jie; Zhao, Wei; Li, Xichen; Wang, Ying; Jiang, Hua

    2016-03-15

    Aryl-triazole oligomers incorporating a pyridinium motif have been synthesized from their pyridine precursors. Anion binding studies show that methylation of the pyridine units can significantly enhance the halide anion affinities of the folded oligomers so that the foldamers are capable of binding halide anions in aqueous solutions. PMID:26933696

  6. Synthesis of unsymmetrical N-carboranyl NHCs: directing effect of the carborane anion.

    PubMed

    Asay, Matthew J; Fisher, Steven P; Lee, Sarah E; Tham, Fook S; Borchardt, Dan; Lavallo, Vincent

    2015-03-28

    The syntheses of unsymmetrical N-heterocyclic carbenes (NHCs) that contain a single N-bound icosahedral carborane anion substituent are reported. Both anionic C-2 and doubly deprotonated dianionic C-2/C-5 NHC lithium complexes are isolated. The latter species is formed selectively, which reveals a surprising directing effect conveyed by icosahedral carborane anion substituents. PMID:25387660

  7. Synthetic ion transporters that work with anion-π interactions, halogen bonds, and anion-macrodipole interactions.

    PubMed

    Vargas Jentzsch, Andreas; Hennig, Andreas; Mareda, Jiri; Matile, Stefan

    2013-12-17

    The transport of ions and molecules across lipid bilayer membranes connects cells and cellular compartments with their environment. This biological process is central to a host of functions including signal transduction in neurons and the olfactory and gustatory sensing systems, the translocation of biosynthetic intermediates and products, and the uptake of nutrients, drugs, and probes. Biological transport systems are highly regulated and selectively respond to a broad range of physical and chemical stimulation. A large percentage of today's drugs and many antimicrobial or antifungal agents take advantage of these systems. Other biological transport systems are highly toxic, such as the anthrax toxin or melittin from bee venom. For more than three decades, organic and supramolecular chemists have been interested in developing new transport systems. Over time, curiosity about the basic design has evolved toward developing of responsive systems with applications in materials sciences and medicine. Our early contributions to this field focused on the introduction of new structural motifs with emphasis on rigid-rod scaffolds, artificial β-barrels, or π-stacks. Using these scaffolds, we have constructed selective systems that respond to voltage, pH, ligands, inhibitors, or light (multifunctional photosystems). We have described sensing applications that cover the three primary principles of sensor development: immunosensors that use aptamers, biosensors (an "artificial" tongue), and differential sensors (an "artificial" nose). In this Account, we focus on our recent interest in applying synthetic transport systems as analytical tools to identify the functional relevance of less common noncovalent interactions, anion-π interactions, halogen bonds, and anion-macrodipole interactions. Anion-π interactions, the poorly explored counterpart of cation-π interactions, occur in aromatic systems with a positive quadrupole moment, such as TNT or hexafluorobenzene. To observe

  8. Photoelectron Angular Distribution and Molecular Structure in Multiply Charged Anions

    SciTech Connect

    Xing, Xiaopeng; Wang, Xue B.; Wang, Lai S.

    2009-02-12

    Photoelectrons emitted from multiply charged anions (MCAs) carry information of the intramolecular Coulomb repulsion (ICR), which is dependent on molecular structures. Using photoelectron imaging, we observed the effects of ICR on photoelectron angular distributions (PAD) of the three isomers of benzene dicarboxylate dianions C6H4(CO2)22– (o-, m- and p-BDC2–). Photoelectrons were observed to peak along the laser polarization due to the ICR, but the anisotropy was the largest for p-BDC2–, followed by the m- and o-isomer. The observed anisotropy is related to the direction of the ICR or the detailed molecular structures, suggesting that photoelectron imaging may allow structural information to be obtained for complex multiply charged anions.

  9. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    NASA Astrophysics Data System (ADS)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.

    2010-12-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  10. Electroactive Materials for Anion Separation-Technetium from Nitrate

    SciTech Connect

    Hubler, Timothy L.; McBreen, James; Smyrl, William H.; Lilga, Mike A.; Rassat, Scot D.

    2004-06-29

    The aim of the proposed research is to use electroactive ion exchange materials to remove anionic contaminants from HLW wastes and process streams. An ion exchange process using electroactive materials sorbs contaminants selectively and then expels (elutes) them electrochemically by changing the charge balance through redox reactions in the sorbent as opposed to requiring the addition of a chemical eluent. Such processes can theoretically remove anions (e.g., pertechnetate, chromate, and perchorate) and concentrate them in a separate product stream while adding no process chemicals. A practical implementation in HLW process facilities would be a breakthrough in the ability of DOE to economically minimize waste and prevent pollution throughout the complex. To enable this, our work focuses on manipulating specific properties of redox polymers to control the hydrophobicity and ion-pair properties pertinent to the reversibility, selectivity, stability, intercalation/de-intercalation rates, and capacity of the polymers.

  11. Microsolvation effects on the electron binding energies of halide anions

    NASA Astrophysics Data System (ADS)

    Dolgounitcheva, O.; Zakrzewski, V. G.; Streit, L.; Ortiz, J. V.

    2014-02-01

    Ab initio electron propagator calculations in the partial third order (P3) and P3+ approximations were performed to obtain vertical electron detachment energies (VEDEs) of fluoride and chloride clusters with one through three molecules of water. Larger clusters of F- and Cl- with six water molecules were also treated with and without the polarisable continuum model (PCM). For the smaller clusters, good agreement between calculated VEDEs and peak positions in photoelectron spectra is achieved. Large shifts in VEDEs are observed for both hexameric fluoride-water and chloride-water complexes when the PCM is applied. Significant changes in coordination geometries about the chloride anion also occur in this model. In all fluoride complexes, Dyson orbitals for the lowest VEDEs are delocalised over oxygen atoms. On the contrary, for the case of chloride-water clusters, the Dyson orbitals corresponding to the lowest VEDEs are localised on the anion.

  12. Macrocyclic bis(ureas) as ligands for anion complexation

    PubMed Central

    Kretschmer, Claudia; Dittmann, Gertrud

    2014-01-01

    Summary Two macrocyclic bis(ureas) 1 and 2, both based on diphenylurea, have been synthesized. Compound 1 represents the smaller ring with two ethynylene groups as linkers and 2 the larger ring with two butadiynylene groups. On thermal treatment to 130 °C molecule 1 splits up into two dihydroindoloquinolinone (3) molecules. Both compounds 1 and 2 form adducts with polar molecules such as dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and act as complexing agents towards a series of anions (Cl−, Br−, I−, NO3 −, HSO4 −). The crystal structures of 3, 2·2DMSO, 2·2DMF, and of the complex NEt4[Br·2] have been determined. Quantitative investigations of the complexation equilibria were performed via 1H NMR titrations. While 1 is a rather weak complexing agent, the large ring of 2 binds anions with association constants up to log K = 7.93 for chloride ions. PMID:25161744

  13. Highly Water Resistant Anion Exchange Membrane for Fuel Cells.

    PubMed

    Yang, Zhengjin; Hou, Jianqiu; Wang, Xinyu; Wu, Liang; Xu, Tongwen

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. PMID:25962480

  14. Epithelial Anion Transport as Modulator of Chemokine Signaling

    PubMed Central

    Schnúr, Andrea; Hegyi, Péter; Rousseau, Simon; Lukacs, Gergely L.; Veit, Guido

    2016-01-01

    The pivotal role of epithelial cells is to secrete and absorb ions and water in order to allow the formation of a luminal fluid compartment that is fundamental for the epithelial function as a barrier against environmental factors. Importantly, epithelial cells also take part in the innate immune system. As a first line of defense they detect pathogens and react by secreting and responding to chemokines and cytokines, thus aggravating immune responses or resolving inflammatory states. Loss of epithelial anion transport is well documented in a variety of diseases including cystic fibrosis, chronic obstructive pulmonary disease, asthma, pancreatitis, and cholestatic liver disease. Here we review the effect of aberrant anion secretion with focus on the release of inflammatory mediators by epithelial cells and discuss putative mechanisms linking these transport defects to the augmented epithelial release of chemokines and cytokines. These mechanisms may contribute to the excessive and persistent inflammation in many respiratory and gastrointestinal diseases. PMID:27382190

  15. Slow magnetic relaxation in octahedral cobalt(II) field-induced single-ion magnet with positive axial and large rhombic anisotropy.

    PubMed

    Herchel, Radovan; Váhovská, Lucia; Potočňák, Ivan; Trávníček, Zdeněk

    2014-06-16

    Pseudooctahedral mononuclear cobat(II) complex [Co(abpt)2(tcm)2] (1), where abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole and tcm = tricyanomethanide anion, shows field-induced slow relaxation of magnetization with U = 86.2 K and large axial and rhombic single-ion zero-field-splitting parameters, D = +48(2) cm(-1) and E/D = 0.27(2) (D = +53.7 cm(-1) and E/D = 0.29 from ab initio CASSCF/NEVPT2 calculations), thus presenting a new example of a field-induced single-ion magnet with transversal magnetic anisotropy. PMID:24853769

  16. Salts of alkali metal anions and process of preparing same

    DOEpatents

    Dye, James L.; Ceraso, Joseph M.; Tehan, Frederick J.; Lok, Mei Tak

    1978-01-01

    Compounds of alkali metal anion salts of alkali metal cations in bicyclic polyoxadiamines are disclosed. The salts are prepared by contacting an excess of alkali metal with an alkali metal dissolving solution consisting of a bicyclic polyoxadiamine in a suitable solvent, and recovered by precipitation. The salts have a gold-color crystalline appearance and are stable in a vacuum at -10.degree. C. and below.

  17. Development of anion-selective membranes. [for energy storage

    NASA Technical Reports Server (NTRS)

    Lacey, R. E.; Cowsar, D. R.

    1975-01-01

    Methods were studied of preparing anion-exchange membranes that would have low resistance, high selectivity, and physical and chemical stability when used in acidic media in a redox energy storage system. Of the twelve systems selected for study, only the system that was based on crosslinked poly-4-vinylpyridinium chloride produced physically strong membranes when equilibrated in l M HCl. The resistivity of the best membrane was 12 ohm-cm, and the transference number for chloride ions was 0.81.

  18. The sorption of quercetin by high-basicity anion exchangers

    NASA Astrophysics Data System (ADS)

    Udalova, N. A.; Karpov, S. I.; Selemenev, V. F.; Sharmar, I. A.

    2009-06-01

    The sorption of quercetin on anionites with various porosities in the OH- and Cl- forms was studied under static conditions. The equilibrium (distribution coefficients K p) and kinetic (effective diffusion coefficients D eff) parameters of quercetin sorption on AV-17-2P and AV-17-6M anionites in the Cl- and OH- forms were calculated. The mechanism of quercetin interactions with the anion exchangers was studied by electron microscopy and IR spectroscopy.

  19. Cobalt(II) Complex of a Diazoalkane Radical Anion.

    PubMed

    Bonyhady, Simon J; Goldberg, Jonathan M; Wedgwood, Nicole; Dugan, Thomas R; Eklund, Andrew G; Brennessel, William W; Holland, Patrick L

    2015-06-01

    β-Diketiminate cobalt(I) precursors react with diphenyldiazomethane to give a compound that is shown by computational studies to be a diazoalkane radical anion antiferromagnetically coupled to a high-spin cobalt(II) ion. Thermolysis of this complex results in formal N-N cleavage to give a cobalt(II) ketimide complex. Experimental evaluation of the potential steps in the mechanism suggests that free azine is a likely intermediate in this reaction. PMID:25986783

  20. Probing neutral atmospheric collision complexes with anion photoelectron imaging

    NASA Astrophysics Data System (ADS)

    Jarrold, Caroline

    Photodetachment of anionic precursors of neutral collision complexes offers a way to probe the effects of symmetry-breaking collision events on the electronic structure of normally transparent molecules. We have measured the anion photoelectron imaging (PEI) spectra of a series of O2- X complexes, where X is a volatile organic molecule with atmospheric relevance, to determine how the electronic properties of various X molecules affect the low-lying electronic structure of neutral O2 undergoing O2 - X collisons. The study was motivated by the catalog of vibrational and electronic absorption lines induced by O2 - O2, O2 - N2, and other collisions. The energies of electronic features observed in the anion PEI spectra of O2- X (X = hexane, hexene, isoprene and benzene) relative to O2- PEI spectroscopic features indicate that photodetachment of the anion does indeed access a repulsive part of the O2 - X potential. In addition, the spectra of the various complexes show an interesting variation in the intensities of transitions to the excited O2(1Δg) . X and O2(1Σg+) . X states relative to the ground O2(3Σg-) . X state. With X = non-polar species such as hexane, the relative intensities of transitions to the triplet and singlet states of O2 . X are very similar to those of isolated O2, while the relative intensity of the singlet band decreases and becomes lower in energy relative to the triplet band for X = polar molecules. A significant enhancement in the intensities of the singlet bands is observed for complexes with X = isoprene and benzene, both of which have low-lying triplet states. The role of the triplet states in isoprene and benzene, and the implications for induced electronic absorption in O2 undergoing collisions with these molecules, are explored. National Science Foundation NSF CHE 1265991.

  1. Interactions between anionic and neutral bromine and rare gas atoms

    SciTech Connect

    Buchachenko, Alexei A.; Grinev, Timur A.; Wright, Timothy G.; Viehland, Larry A.

    2008-02-14

    High-quality, ab initio potential energy functions are obtained for the interaction of bromine atoms and anions with atoms of the six rare gases (Rg) from He to Rn. The potentials of the nonrelativistic {sup 2}{sigma}{sup +} and {sup 2}{pi} electronic states arising from the ground-state Br({sup 2}P)-Rg interactions are computed over a wide range of internuclear separations using a spin-restricted version of the coupled cluster method with single and double excitations and noniterative correction to triple excitations [RCCSD(T)] with an extrapolation to the complete basis set limit, from basis sets of d-aug-cc-pVQZ and d-aug-cc-pV5Z quality. These are compared with potentials derived previously from experimental measurements and ab initio calculations. The same approach is used also to refine the potentials of the Br{sup -}-Rg anions obtained previously [Buchachenko et al., J. Chem. Phys. 125, 064305 (2006)]. Spin-orbit coupling in the neutral species is included both ab initio and via an atomic approximation; deviations between two approaches that are large enough to affect the results significantly are observed only in the Br-Xe and Br-Rn systems. The resulting relativistic potentials are used to compute anion zero electron kinetic energy photoelectron spectra, differential scattering cross sections, and the transport coefficients of trace amounts of both anionic and neutral bromine in the rare gases. Comparison with available experimental data for all systems considered proves a very high precision of the present potentials.

  2. Anion Exchange Membranes: Current Status and Moving Forward

    SciTech Connect

    Hickner, MA; Herring, AM; Coughlin, EB

    2013-10-29

    This short review is meant to provide the reader with highlights in anion exchange membrane research, describe current needs in the field, and point out promising directions for future work. Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol. AEMs and related stable cationic polymers also have applications in energy storage and other electrochemical technologies such as water electrolyzers and redox flow batteries. While anion exchange membranes have been known for a long time in water treatment applications, materials for electrochemical technology with robust mechanical properties in thin film format have only recently become more widely available. High hydroxide and bicarbonate anion conductivity have been demonstrated in a range of AEM formats, but intrinsic stability of the polymers and demonstration of long device lifetime remain major roadblocks. Novel approaches to stable materials have focused on new types of cations that employ delocalization and steric shielding of the positive center to mitigate nucleophilic attack by hydroxide. A number of promising polymer backbones and membrane architectures have been identified, but limited device testing and a lack of understanding of the degradation mechanisms in operating devices is slowing progress on engineered systems with alkaline fuel cell technology. Our objective is to spur more research in this area to develop fuel cell systems that approach the costs of inexpensive batteries for large-scale applications. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1727-1735, 2013

  3. Comment on "Local impermeant anions establish the neuronal chloride concentration".

    PubMed

    Luhmann, Heiko J; Kirischuk, Sergei; Kilb, Werner

    2014-09-01

    Glykys et al. (Reports, 7 February 2014, p. 670) proposed that cytoplasmic impermeant anions and polyanionic extracellular matrix glycoproteins establish the local neuronal intracellular chloride concentration, [Cl(-)]i, and thereby the polarity of γ-aminobutyric acid type A (GABAA) receptor signaling. The experimental procedures and results in this study are insufficient to support these conclusions. Contradictory results previously published by these authors and other laboratories are not referred to. PMID:25190788

  4. Spectroscopic and Computational Characterization of Hydrated Pyrimidine Anions

    NASA Astrophysics Data System (ADS)

    Kelly, John T.; Hammer, Nathan I.

    2014-06-01

    Pyrimidine is known to possess a negative electron affinity. Anions created from such molecules, whose energies are higher than those of their neutral counterparts, are unstable with respect to autodetachment. The solvation of pyrimidine with just one water molecule results in a positive electron binding energy. The addition of water molecules stabilizes the excess charge and increase the binding energy. The most interesting feature is the orientation of the hydrated pyrimidine complex to help accommodate an excess electron.

  5. Anion receptor compounds for non-aqueous electrolytes

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James

    2000-09-19

    A new family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

  6. Alkaline Anion-Exchange Membranes Containing Mobile Ion Shuttles.

    PubMed

    Ge, Xiaolin; He, Yubin; Guiver, Michael D; Wu, Liang; Ran, Jin; Yang, Zhengjin; Xu, Tongwen

    2016-05-01

    A new class of alkaline anion-exchange membranes containing mobile ion shuttles is developed. It is achieved by threading ionic linear guests into poly(crown ether) hosts via host-guest molecular interaction. The thermal- and pH-triggered shuttling of ionic linear guests remarkably increases the solvation-shell fluctuations in inactive hydrated hydroxide ion complexes (OH(-) (H2 O)4 ) and accelerates the OH(-) transport. PMID:26972938

  7. SLC5 Sodium-Anion Cotransporters and Renal Urate Transport

    NASA Astrophysics Data System (ADS)

    Mount, David B.; Kwon, Charles Y.; Plata, Consuelo; Romero, Michael F.; Zandi-Nejad, Kambiz

    2007-04-01

    Renal urate transport plays a key role in determining the concentration of circulating uric acid. The reabsorption of filtered urate by the renal proximal tubule appears to require apical sodium-dependent anion transport and the apical URAT1 urate-anion exchanger, in that sodium-dependent transport of lactate, ketoacids, nicotinate, and pyrazinoate (PZA) increases the intracellular concentration of substrates for the subsequent exchange with luminal urate. We have identified SLC5A8 and SLC5A12 as candidates for the sodium-anion cotransporter that collaborates with URAT1. Both transporters function as sodium-dependent nicotinate/monocarboxylate/PZA transporters. Localization studies reveal serial co-expression of these transporters with URAT1, with Slc5a12 in the early proximal tubule and Slc5a8 in S2 and S3 segments. Renal urate excretion is conceivably affected by changes in the activity of SLC5A8, SLC5A12, and/or URAT1, with implications for the pathogenesis of hyperuricemia, nephrolithiasis, and related disorders.

  8. Twisted and tubular silica structures by anionic surfactant fibers encapsulation.

    PubMed

    Chekini, Mahshid; Guénée, Laure; Marchionni, Valentina; Sharma, Manish; Bürgi, Thomas

    2016-09-01

    Organic molecules imprinting can be used for introducing specific properties and functionalities such as chirality to mesoporous materials. Particularly organic self-assemblies can work as a scaffold for templating inorganic materials such as silica. During recent years chiral imprinting of anionic surfactant for fabrication of twisted rod-like silica structures assisted by co-structuring directing agent were thoroughly investigated. The organic self-assemblies of anionic surfactants can also be used for introducing other shapes in rod-like silica structures. Here we report the formation of amphiphilic N-miristoyl-l-alanine self-assemblies in aqueous solution upon stirring and at presence of l-arginine. These anionic surfactant self-assemblies form fibers that grow by increasing the stirring duration. The fibers were studied using transmission electron microscopy, infra-red spectroscopy and vibrational circular dichroism. Addition of silica precursor 1,2-bis(triethoxysilyl)ethylene and co-structuring directing agent N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride at different stages of fibers' growth leads to formation of different silica structures. By controlling stirring duration, we obtained twisted tubular silica structures as a result of fibers encapsulation. We decorated these structures with gold nanoparticles by different methods and measured their optical activity. PMID:27267039

  9. Determination of selected anions in water by ion chromatography

    USGS Publications Warehouse

    Fishman, Marvin J.; Pyen, Grace

    1979-01-01

    Ion chromatography is a rapid, sensitive, precise, and accurate method for the determination of major anions in rainwater and surface waters. Simultaneous analyses of a single sample for bromide, chloride, fluoride, nitrate, nitrite, orthophosphate, and sulfate require approximately 20 minutes to obtain a chromatogram. Minimum detection limits range from 0.01 mg/L for fluoride to 0.20 mg/L for chloride and sulfate. Relative standard deviations were less than 9% for all anions except nitrite in Standard Reference Water Samples. Only one reference sample contained nitrite and its concentration was near the minimum level of detection. Similar precision was found for chloride, nitrate, and sulfate at concentrations less than 5 mg/L in rainfall samples. Precision for fluoride ranged from 12 to 22%, but is attributed to the low concentrations in these samples. The other anions were not detected. To determine accuracy of results, several samples were spiked with known concentrations of fluoride, chloride, nitrate, and sulfate; recoveries ranged from 96 to 103%. Known amounts of bromide and phosphate were added, separately, to several other waters, which contained bromide or phosphate. Recovery of added bromide and phosphate ranged from approximately 95 to 104%. No recovery data were obtained for nitrite. Chloride, nitrate, nitrite, orthophosphate, and sulfate, in several samples, were also determined independently by automated colorimetric procedures. An automated ion-selective electrode method was used to determine fluoride. Results are in agreement with results obtained by ion chromatography. (USGS).

  10. [Chromatographic separation of plasmid DNA by anion-exchange cryogel].

    PubMed

    Guo, Yantao; Shen, Shaochuan; Yun, Junxian; Yao, Kejian

    2012-08-01

    Plasmid DNA (pDNA) is used as an important vector for gene therapy, and its wide application is restricted by the purity and yield. To obtain high-purity pDNA, a chromatographic method based on anion-exchange supermacroporous cryogel was explored. The anion-exchange cryogel was prepared by grafting diethylaminoethyl-dextran to the epoxide groups of polyacrylamide-based matrix and pUC19 plasmid was used as a target to test the method. The plasmid was transferred into Escherichia coli DH5alpha, cultivated, harvested and lysed. The obtained culture was centrifuged and the supernatant was used as the plasmid feedstock, which was loaded into the anion-exchange cryogel bed for chromatographic separation. By optimizing the pH of running buffer and the elution conditions, high-purity pDNA was obtained by elution with 0.5 mol/L sodium chloride solution at pH 6.6. Compared to the traditional methods for purification of pDNA, animal source enzymes and toxic reagents were not involved in the present separation process, ensuring the safety of both the purification operations and the obtained pDNA. PMID:23185899

  11. Two supramolecular microporous frameworks stabilized by hydroxyl anionic water cluster

    NASA Astrophysics Data System (ADS)

    Jian, Fang Fang; Wang, Jing; Huang, Li Hua; Wang, Xian; Xiao, Hai Lian

    2010-06-01

    Two stable supramolecular microporous framework complexes, from the same [MCl(phen) 2] + (M = Cu, Ni), containing chiral hydroxyl anionic water cluster polymer, were synthesized, and their crystal structures were described. These supramolecular frameworks showed very high stability even if they were heated to 300 °C. Thermal analysis and powder X-ray diffraction results indicated that the water molecules were removed when heated from 150 °C to 300 °C without losing the main crystal framework. Water molecules can be reassembled by exposing the dehydrated form to an atmosphere saturated with water vapor. It indicated that the dehydrated form may be utilized as a potential absorbing agent for water and water vapor. The stable dehydrated form, [MCl(phen) 2][(OH)(H 2O)], suggested the stronger anionic H-bonding and intracluster proton transfer process OH -·H 2O → H 2O·OH -. The "anion- π interaction" was found in the crystal lattice of [MCl(phen) 2][(OH)(H 2O)]. This paper reported an example of supramolecular polymer with open channels that could be formed/collapse reversibly upon hydration/dehydration.

  12. Peroxidase activation of cytoglobin by anionic phospholipids: Mechanisms and consequences.

    PubMed

    Tejero, Jesús; Kapralov, Alexandr A; Baumgartner, Matthew P; Sparacino-Watkins, Courtney E; Anthonymutu, Tamil S; Vlasova, Irina I; Camacho, Carlos J; Gladwin, Mark T; Bayir, Hülya; Kagan, Valerian E

    2016-05-01

    Cytoglobin (Cygb) is a hexa-coordinated hemoprotein with yet to be defined physiological functions. The iron coordination and spin state of the Cygb heme group are sensitive to oxidation of two cysteine residues (Cys38/Cys83) and/or the binding of free fatty acids. However, the roles of redox vs lipid regulators of Cygb's structural rearrangements in the context of the protein peroxidase competence are not known. Searching for physiologically relevant lipid regulators of Cygb, here we report that anionic phospholipids, particularly phosphatidylinositolphosphates, affect structural organization of the protein and modulate its iron state and peroxidase activity both conjointly and/or independently of cysteine oxidation. Thus, different anionic lipids can operate in cysteine-dependent and cysteine-independent ways as inducers of the peroxidase activity. We establish that Cygb's peroxidase activity can be utilized for the catalysis of peroxidation of anionic phospholipids (including phosphatidylinositolphosphates) yielding mono-oxygenated molecular species. Combined with the computational simulations we propose a bipartite lipid binding model that rationalizes the modes of interactions with phospholipids, the effects on structural re-arrangements and the peroxidase activity of the hemoprotein. PMID:26928591

  13. Quaternized agricultural by-products as anion exchange resins.

    PubMed

    Wartelle, Lynda H; Marshall, Wayne E

    2006-01-01

    The objectives of this study were the chemical modification of readily available, low-cost agricultural by-products to anion exchange resins and the selection of the best modified by-product for further use in anion removal. Resins were prepared through the quaternization of a series of 12 agricultural by-products with N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHMAC). Phosphate ion adsorption assays were conducted at pH 7 in order to compare adsorption properties among the by-products. Quaternized corn stover showed the highest phosphorus adsorption at 0.66 mmole/g. Since corn stover exhibited the best uptake of phosphate ion, it was compared to a commercially available, cellulose-based anion exchange resin. Additionally, adsorption capacities of quaternized corn stover for arsenate, chromate, and selenate were evaluated and adsorption efficiencies were determined in simulated wastewater samples. Our results indicate that modified corn stover demonstrates good adsorption uptake for arsenate and selenate and especially for chromate. PMID:16144735

  14. Faropenem enhances superoxide anion production by human neutrophils in vitro.

    PubMed

    Sato, K; Sato, N; Shimizu, H; Tsutiya, T; Takahashi, H; Kakizaki, S; Takayama, H; Takagi, H; Mori, M

    1999-09-01

    Neutrophils are important cellular components in the defence against infections and many studies in vitro have shown that some antibiotics affect neutrophil function. We examined the effect of faropenem, a new oral penem antibiotic on neutrophil killing function by determining the generation of superoxide anion in vitro. The production of superoxide anion was measured by chemiluminescence amplified by a Cypridina luciferin analogue in the presence of N-formyl-Met-Leu-Phe (fMLP). Faropenem significantly enhanced chemiluminescence in a dose-dependent manner. The effect of faropenem was maximal at 5 min of incubation time and continued for at least 30 min. The effect of faropenem was also observed when neutrophils were stimulated by a calcium ionophore (ionomycin), while the effect of faropenem did not change in the presence of 12-O-tetra-decanoylphorbolmyristate acetate. Cytosol Ca2+ concentration ([Ca2+]i) monitored with Fura-2 increased in response to fMLP, however, faropenem did not influence the response of [Ca2+]i to fMLP. Our results suggest that faropenem enhanced the generation of superoxide anion by neutrophils, probably at the site where cytosol Ca2+ regulates NADPH oxidase. Faropenem might be potentially advantageous in the treatment of infections because a synergic interaction of antibodies and cytocidal neutrophils is necessary for the early eradication of the pathogenic bacteria. PMID:10511400

  15. Depth profile of halide anions under highly charged biological membrane

    NASA Astrophysics Data System (ADS)

    Sung, Woongmo; Wang, Wenjie; Lee, Jonggwan; Vaknin, David; Kim, Doseok

    2015-03-01

    Halide ion (Cl- and I-) distribution under a cationic Langmuir monolayer consisting of 1,2-dipalmitoyl-3 trimethylammonium-propane (DPTAP) molecules was investigated by vibrational sum-frequency generation (VSFG) and X-ray spectroscopy. From VSFG spectra, it was observed that large halide anions (I-) screen surface charge more efficiently so that interfacial water alignment becomes more randomized. On the other hand, number density of ions directly measured by X-ray fluorescence spectroscopy at grazing incidence angle reveals that the ion densities within 6 ~ 8 nm are the same for both I- and Cl-. Since the observed ion densities in both cases are almost equal to the charge density of the DPTAP monolayer, we propose that larger halide anions are attracted closer to the surface making direct binding with the charged headgroups of the molecules in the monolayer, accomplishing charge neutrality in short distance. This direct adsorption of anions also disturbs the monolayer structure both in terms of the conformation of alkyl chains and the vertical configuration of the monolayer, with iodine having the stronger effect. Our study shows that the length scale that ions neutralize a charged interface varies significantly and specifically even between monovalent ions.

  16. Anion composition of açaı́ extracts.

    PubMed

    Liao, Hongzhu; Shelor, C Phillip; Chen, Yongjing; Sabaa-Srur, Armando U O; Smith, Robert E; Dasgupta, Purnendu K

    2013-06-26

    Many products labeled açaı́ are presently marketed as natural supplements with various claimed health benefits. Authentic açaı́ is expensive; as a result, numerous products labeled as containing açaı́ are being sold that actually contain little or no açaı́. Authentic açaı́ samples from Brazil and Florida as well as several reputed açaı́ products were analyzed by suppressed conductometric anion chromatography. Columns with different selectivities were used to obtain a complete separation of all anions. Tandem mass spectrometry was used for confirmation of the less common ions. Quinate, lactate, acetate, formate, galacturonate, chloride, sulfate, malate, oxalate, phosphate, citrate, isocitrate, and myo-inositol hexakisphosphate (phytate) were found. Only the Florida açaı́ had detectable levels of hexanoate. No açaı́ sample had any detectable levels of tartrate, which is present in abundance in grape juice, the most common adulterant. The highly characteristic anion profile and in particular the absence of tartrate can readily be used to identify authentic açaı́ products. Açaı́ from Florida had a 6 times greater level of phytate. The present analytical approach for phytate may be superior to extant methods. PMID:23772604

  17. ANION EXCHANGE METHOD FOR SEPARATION OF METAL VALUES

    DOEpatents

    Hyde, E.K.; Raby, B.A.

    1959-02-10

    A method is described for selectively separating radium, bismuth, poloniums and lead values from a metallic mixture of thc same. The mixture is dissolved in aqueous hydrochloric acid and the acidity is adjusted to between 1 to 2M in hydrochloric acid to form the anionic polychloro complexes of polonium and bismuth. The solution is contacted with a first anion exchange resin such as strong base quaternary ammonia type to selectively absorb the polonium and bismuth leaving the radium and lead in the effluent. The effluent, after treatment in hydrochloric acid to increase the hydrochloric acid concentration to 6M is contacted with a second anion exchange iesin of the same type as the above to selectively adsorb the lead leaving the radium in the effluent. Radium is separately recovered from the effluent from the second exchange column. Lead is stripped from the loaded resin of the second column by treatment with 3M hydrochloric acid solution. The loaded resin of the first column is washed with 8M hydrochloric acid solution to recover bismuth and then treated with strong nitric acid solution to recover polonium.

  18. Reactivity of azole anions with CO₂ from the DFT perspective.

    PubMed

    Tang, Huarong; Wu, Chao

    2013-06-01

    Azole anions are key components in CO₂ capture materials that include ionic liquids and porous solids. Herein, we use density functional theory (DFT) and a Langmuir-type adsorption model to study azole anion-CO₂ interactions. Linear CO₂ has to be bent by approximately 45° to form an N-C bond within the azole ring. The energy cost of bending renders CO₂ absorption much more difficult compared to SO₂ absorption. For different azole anions, the number of nitrogen atoms in the ring and the natural bond orbital energy of the reacting nitrogen lone pair, both linearly correlate with the calculated reaction enthalpy and are useful handles for new sorbent designs. Unlike for SO₂, the azole parent architecture (unsubstituted) does not allow successive CO₂ absorption under mild conditions (<0.12 MPa and at room temperature). Experimental CO₂ and SO₂ absorption isotherms are reproduced by using the Langmuir model parameterized with the calibrated DFT reaction enthalpies. This study provides insight for designing azole-based CO₂-capture materials. PMID:23640877

  19. Coumarin benzothiazole derivatives as chemosensors for cyanide anions

    NASA Astrophysics Data System (ADS)

    Wang, Kangnan; Liu, Zhiqiang; Guan, Ruifang; Cao, Duxia; Chen, Hongyu; Shan, Yanyan; Wu, Qianqian; Xu, Yongxiao

    2015-06-01

    Four coumarin benzothiazole derivatives, N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (1), (Z)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide (2), 7-(diethylamino)-N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (3) and (Z)-7-(diethylamino)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide) (4), have been synthesized. Their crystal structures, photophysical properties in acetonitrile and recognition properties for cyanide anions have been investigated. All the compounds are generally planar, especially compound 1 exhibits perfect planarity with dihedral angle between benzothiazolyl group and coumarin group being only 3.63°. Coumarin benzothiazole compounds 1 and 3 can recognize cyanide anions by Michael addition reaction and compound 3 exhibits color change from yellow to colorless and green fluorescence was quenched completely, which can be observed by naked eye. Coumarin benzothiazolyliden compound 4 can recognize cyanide anions with fluorescence turn-on response based on the copper complex ensemble displacement mechanism.

  20. Cassini observations of carbon-based anions in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Desai, Ravindra; Lewis, Gethyn; Waite, J. Hunter; Kataria, Dhiren; Wellbrock, Anne; Jones, Geraint; Coates, Andrew

    2016-07-01

    Cassini observations of Titan's ionosphere revealed an atmosphere rich in positively and negatively charged ions and organic molecules. The detection of large quantities of negatively charged ions was particularly surprising and adds Titan to the growing list of locations where anion chemistry has been observed to play an important role. In this study we present updated analysis on these negatively charged ions through an enhanced understanding of the Cassini CAPS Electron Spectrometer (CAPS-ELS) instrument response. The ionisation of Titan's dominant atmospheric constituent, N2, by the HeII Solar line, results in an observable photoelectron population at 24.1eV which we use to correct for differential spacecraft charging. Correcting for further energy-angle signatures within this dataset, we use an updated fitting procedure to show how the ELS mass spectrum, previously grouped into broad mass ranges, can be resolved into specific peaks at multiples of carbon-based anion species up to over 100amu/q. These peaks are shown to be ubiquitous within Titan's upper atmosphere and reminiscent of carbon-based anions identified in dense molecular clouds beyond our Solar System. It is thus shown how the moon Titan in the Outer Solar System can be used as an analogue to study these even more remote and exotic astrophysical environments.

  1. Phosphate Removal by Anion Binding on Functionalized Nanoporous Sorbents

    SciTech Connect

    Chouyyok, Wilaiwan; Wiacek, Robert J.; Pattamakomsan, Kanda; Sangvanich, Thanapon; Grudzien, Rafal M.; Fryxell, Glen E.; Yantasee, Wasanna

    2010-03-26

    Phosphate was captured from aqueous solutions by cationic metal-EDA complexes anchored inside mesoporous silica MCM-41 supports (Cu(II)-EDA-SAMMS and Fe(III)-EDA-SAMMS). Fe-EDA-SAMMS was more effective at capturing phosphate than the Cu-EDA-SAMMS and was further studied for matrix effects (e.g., pH, ionic strength, and competing anions) and sorption performance (e.g., capacity and rate). The adsorption of phosphate was highly pH dependent; it increased with increasing pH from 1.0 to 6.5, and decreased above pH 6.5. The adsorption was affected by high ionic strength (0.1 M of NaCl). In the presence of 1000-fold molar excess of chloride and nitrate anions, phosphate removal by Fe-EDA-SAMMS was not affected. Slight, moderate and large impacts were seen with bicarbonate, sulfate and citrate anions, respectively. The phosphate adsorption data on Fe-EDA-SAMMS agreed well with the Langmuir model with the estimated maximum capacity of 43.3 mg/g. The material displayed rapid sorption rate (99% of phosphate removal within 1 min) and lowering the phosphate content to ~ 10 µg/L of phosphorus, which is lower than the EPA’s established freshwater contaminant level for phosphorous (20 µg/L).

  2. Photodetachment photoelectron spectroscopy of multiply charged anions using electrospray ionization

    SciTech Connect

    Wang, L.; Ding, C.; Wang, X. |; Barlow, S.E.

    1999-04-01

    A magnetic-bottle time-of-flight (TOF) photoelectron spectrometer, coupled with an electrospray ionization source, has been developed for the investigation of multiply charged anions in the gas phase. Anions formed in the electrospray source are guided by a radio-frequency quadrupole ion guide into a quadrupole ion trap, where the ions are accumulated. A unique feature of this apparatus involves the coupling of a TOF mass spectrometer to the ion trap with perpendicular ion extraction. The ion trap significantly improves the duty cycle of the experiments and allows photodetachment experiments to be performed with low repetition-rate lasers (10{endash}20 Hz). This novel combination makes the photodetachment photoelectron spectroscopy studies of multiply charged anions possible for the first time. Furthermore, the perpendicular extraction of ions, pulsed out of the ion trap, to the TOF mass spectrometer allows the ion energies to be conveniently referenced to ground, simplifying the configuration of the TOF mass spectrometer and the subsequent magnetic-bottle TOF photoelectron spectrometer. The mass resolution (M/{Delta}M) achieved is about 800 for smaller ions. The magnetic-bottle photoelectron spectrometer resolution is about 11 meV full width at half maximum for 0.5 eV photoelectrons with an overall resolution of {Delta}E/E{approximately}2{percent}. The detailed design, construction, and operation of the new apparatus are presented. {copyright} {ital 1999 American Institute of Physics.}

  3. pH-Regulated Nonelectrogenic Anion Transport by Phenylthiosemicarbazones.

    PubMed

    Howe, Ethan N W; Busschaert, Nathalie; Wu, Xin; Berry, Stuart N; Ho, Junming; Light, Mark E; Czech, Dawid D; Klein, Harry A; Kitchen, Jonathan A; Gale, Philip A

    2016-07-01

    Gated ion transport across biological membranes is an intrinsic process regulated by protein channels. Synthetic anion carriers (anionophores) have potential applications in biological research; however, previously reported examples are mostly nonspecific, capable of mediating both electrogenic and electroneutral (nonelectrogenic) transport processes. Here we show the transmembrane Cl(-) transport studies of synthetic phenylthiosemicarbazones mimicking the function of acid-sensing (proton-gated) ion channels. These anionophores have remarkable pH-switchable transport properties with up to 640-fold increase in transport efficacy on going from pH 7.2 to 4.0. This "gated" process is triggered by protonation of the imino nitrogen and concomitant conformational change of the anion-binding thiourea moiety from anti to syn. By using a combination of two cationophore-coupled transport assays, with either monensin or valinomycin, we have elucidated the fundamental transport mechanism of phenylthiosemicarbazones which is shown to be nonelectrogenic, inseparable H(+)/Cl(-) cotransport. This study demonstrates the first examples of pH-switchable nonelectrogenic anion transporters. PMID:27299473

  4. CO2 electrochemical reduction via adsorbed halide anions

    NASA Astrophysics Data System (ADS)

    Ogura, Kotaro; Salazar-Villalpando, Maria D.

    2011-01-01

    The electrochemical reduction of CO2 was studied utilizing halide ions as electrolytes, specifically, aqueous solutions of KCl, KBr, KI. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were a Pt wire and an Ag/AgCl electrode, respectively. The results of our work suggest a reaction mechanism for the electrochemical reduction of CO2 where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO2. Electron-transfer to CO2 may occur via the X- ad(Br-, Cl-, I-)-C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO2. The stronger the adsorption of the halide anion to the electrode, the more strongly CO2 is restrained, resulting in higher CO2 reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons; leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the over potential necessary for CO2 reduction, and thus increase the rate of electrochemical CO2 reduction.

  5. Phosphate removal by anion binding on functionalized nanoporous sorbents.

    PubMed

    Chouyyok, Wilaiwan; Wiacek, Robert J; Pattamakomsan, Kanda; Sangvanich, Thanapon; Grudzien, Rafal M; Fryxell, Glen E; Yantasee, Wassana

    2010-04-15

    Phosphate was captured from aqueous solutions by cationic metal-EDA complexes anchored inside mesoporous silica MCM-41 supports (Cu(II)-EDA-SAMMS and Fe(III)-EDA-SAMMS). Fe-EDA-SAMMS was more effective at capturing phosphate than the Cu-EDA-SAMMS and was further studied for matrix effects (e.g., pH, ionic strength, and competing anions) and sorption performance (e.g., capacity and rate). The adsorption of phosphate was highly pH dependent; it increased with increasing pH from 1.0 to 6.5, and decreased above pH 6.5. The adsorption was affected by high ionic strength (0.1 M of NaCl). In the presence of 1000-fold molar excess of chloride and nitrate anions, phosphate removal by Fe-EDA-SAMMS was not affected. Slight, moderate and large impacts were seen with bicarbonate, sulfate, and citrate anions, respectively. The phosphate adsorption data on Fe-EDA-SAMMS agreed well with the Langmuir model with the estimated maximum capacity of 43.3 mg/g. The material displayed rapid sorption rate (99% of phosphate removal within 1 min) and lowering the phosphate content to approximately 10 microg/L of phosphorus, which is lower than the EPA's established freshwater contaminant level for phosphorus (20 microg/L). PMID:20345133

  6. Solubility and transport of cationic and anionic patterned nanoparticles

    NASA Astrophysics Data System (ADS)

    Su, Jiaye; Olvera de La Cruz, Monica; Guo, Hongxia

    2012-01-01

    We analyze bulk diffusion and transport through hydrophobic nanochannels of nanoparticles (NPs) with different hydrophobic-hydrophilic patterns achieved by coating a fraction of the NP sites with positive or negative charges via explicit solvent molecular dynamics simulations. Ten different charge pattern types including Janus charged-hydrophobic NPs are studied. The cationic NPs are more affected by the patterns and have higher diffusion constants and fluxes than their anionic NPs counterparts. The NP-water interaction dependence on surface pattern and field strength explains these observations. The NP-water Coulomb interaction of anionic NPs in the bulk, which are much stronger than the hydrophobic NP-water interactions, are stronger for NPs with higher localized charge, and stronger than in the cationic NPs counterparts. The diffusion and transport of anionic NPs such as proteins and protein charge ladders with the same total charge but different surface charge patterns are slowest for the highest localized charge pattern, which also adsorb strongest onto surfaces. Our model demonstrates the separation (by reverse osmosis, capillary electrophoresis, or chromatography) of cationic NPs, including proteins with equal net charge but different surface charge distributions.

  7. Conformational equilibrium of talin is regulated by anionic lipids.

    PubMed

    Ye, Xin; McLean, Mark A; Sligar, Stephen G

    2016-08-01

    A critical step in the activation of integrin receptors is the binding of talin to the cytoplasmic domain of the β subunits. This interaction leads to separation of the integrin α and β transmembrane domains and significant conformational changes in the extracellular domains, resulting in a dramatic increase in integrin's affinity for ligands. It has long been shown that the membrane bilayer also plays a critical role in the talin-integrin interaction. Anionic lipids are required for proper interaction, yet the specificity for specific anionic headgroups is not clear. In this report, we document talin-membrane interactions with bilayers of controlled composition using Nanodiscs and a FRET based binding and structural assay. We confirm that recruitment of the talin head domain to the membrane surface is governed by charge in the absence of other adapter proteins. In addition, measurement of the donor-acceptor distance is consistent with the hypothesis that anionic lipids promote a conformational change in the talin head domain allowing interaction of the F3 domain with the phospholipid bilayer. The magnitude of the F3 domain movement is altered by the identity of the phospholipid headgroup with phosphatidylinositides promoting the largest change. Our results suggest that phoshpatidylinositol-4,5-bisphosphate plays key a role in converting talin head domain to a conformation optimized for interactions with the bilayer and subsequently integrin cytoplasmic tails. PMID:27163494

  8. Anion exchange in Zn-Al layered double hydroxides: In situ X-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Salak, Andrei N.; Tedim, João; Kuznetsova, Alena I.; Zheludkevich, Mikhail L.; Ferreira, Mário G. S.

    2010-07-01

    Anion exchange capacity is a key factor for the application of Zn-Al layered double hydroxides (LDHs) as nano-containers in active corrosion protection. In this work, the nitrate-pyrovanadate anion exchange/re-exchange processes in these LDHs were investigated in situ. We demonstrate that the exchange reactions lead to a decrease of the average crystallite size of LDHs as a result of mechanical fragmentation of the crystallites rather than dissolution/recrystallization. The fragmentation occurs due to fast anion exchange in the initial stage, and can be controlled by changing the ratio of the available substituent anions to the replacement anions and application of a mechanical activation.

  9. Experimental investigation of anion-π interactions--applications and biochemical relevance.

    PubMed

    Giese, M; Albrecht, M; Rissanen, K

    2016-01-31

    Anion-π interactions, intuitively repulsive forces, turned from controversial to a well-established non-covalent interaction over the past quarter of a century. Within this time frame the question "Anion-π interactions. Do they exist?" could be answered and even more importantly its functional relevance was proven. The present feature article summarizes the experimental findings of anion-π studies in the gas phase, solution and in the solid state and highlights the application of anion-π interactions in anion recognition, sensing and transport as well as in catalysis. Moreover, the biochemical relevance of this weak intermolecular force is comprehensively reviewed. PMID:26697947

  10. Location of a permeant anion binding site in the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Rubaiy, Hussein N; Linsdell, Paul

    2015-05-01

    In the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, lyotropic anions with high permeability also bind relatively tightly within the pore. However, the location of permeant anion binding sites, as well as their relationship to anion permeability, is not known. We have identified lysine residue K95 as a key determinant of permeant anion binding in the CFTR pore. Lyotropic anion binding affinity is related to the number of positively charged amino acids located in the inner vestibule of the pore. However, mutations that change the number of positive charges in this pore region have minimal effects on anion permeability. In contrast, a mutation at the narrow pore region alters permeability with minimal effects on anion binding. Our results suggest that a localized permeant anion binding site exists in the pore; however, anion binding to this site has little influence over anion permeability. Implications of this work for the mechanisms of anion recognition and permeability in CFTR are discussed. PMID:25673337

  11. Relationship of net chloride flow across the human erythrocyte membrane to the anion exchange mechanism

    SciTech Connect

    Knauf, P.A.; Law, F.Y.; Marchant, P.J.

    1983-01-01

    The parallel effects of the anion transport inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'disulfonate) on net chloride flow and on chloride exchange suggest that a major portion of net chloride flow takes place through the anion exchange system. The ''slippage'' model postulates that the rate of net anion flow is determined by the movement of the unloaded anion transport site across the membrane. Both the halide selectivity of net anion flow and the dependence of net chloride flux on chloride concentration over the range of 75 to 300 mM are inconsistent with the slippage model. Models in which the divalent form of the anion exchange carrier or water pores mediate net anion flow are also inconsistent with the data. The observations that net chloride flux increases with chloride concentration and that the DIDS-sensitive component tends to saturate suggest a model in which net anion flow involves ''transit'' of anions through the diffusion barriers in series with the transport site, without any change in transport site conformation such as normally occurs during the anion exchange process. This model is successful in predicting that the anion exchange inhibitor NAP-taurine, which binds to the modifier site and inhibits the conformational change, has less effect on net chloride flow than on chloride exchange.

  12. Computational simulation study on the anion recognition properties of functionalized tetraphenyl porphyrins.

    PubMed

    Xie, Ju; Chen, Xuesong; Huang, Zhiling; Zuo, Tongfei

    2015-06-01

    The anion recognitions of tetra-(2-formamido) phenyl porphyrin (APP), tetra-(2-ureido) phenyl porphyrin (UPP), and their zinc derivatives (ZnAPP and ZnUPP) to three anions (Cl(-), H2PO4 (-), CH3COO(-)) were studied using quantum mechanical calculations (QM) and molecular dynamics (MD) simulations. The density functional theory (DFT) calculations at M06-2X/6-31G (d, p) level indicated that the anion recognition ability of ZnAPP was better than that of APP, and the anion selectivity was in the order Cl(-) < H2PO4 (-) < CH3COO(-). The selectivity trends for ZnUPP and UPP were found to be H2PO4 (-) < Cl(-) < CH3COO(-). The structures, thermodynamic properties, and recognition mechanisms were discussed in detail. The 2 ns MD simulations were then carried out for anion@ZnAPP and anion@ZnUPP complexes in mixed solvent DMSO/water. The MD simulation results showed that anion@ZnUPP complexes exhibited higher stability than anion@ZnAPP, which was in good agreement with QM results. H-bonds formed between the anions and the side-chains of receptors, and zinc coordination bonds with anions contributed significantly to the stability of complexes. The anion selectivity of ZnAPP and ZnUPP in the solvent phase were also discussed and compared with those in the gas phase. PMID:25957659

  13. Efficient, non-toxic anion transport by synthetic carriers in cells and epithelia.

    PubMed

    Li, Hongyu; Valkenier, Hennie; Judd, Luke W; Brotherhood, Peter R; Hussain, Sabir; Cooper, James A; Jurček, Ondřej; Sparkes, Hazel A; Sheppard, David N; Davis, Anthony P

    2016-01-01

    Transmembrane anion transporters (anionophores) have potential for new modes of biological activity, including therapeutic applications. In particular they might replace the activity of defective anion channels in conditions such as cystic fibrosis. However, data on the biological effects of anionophores are scarce, and it remains uncertain whether such molecules are fundamentally toxic. Here, we report a biological study of an extensive series of powerful anion carriers. Fifteen anionophores were assayed in single cells by monitoring anion transport in real time through fluorescence emission from halide-sensitive yellow fluorescent protein. A bis-(p-nitrophenyl)ureidodecalin shows especially promising activity, including deliverability, potency and persistence. Electrophysiological tests show strong effects in epithelia, close to those of natural anion channels. Toxicity assays yield negative results in three cell lines, suggesting that promotion of anion transport may not be deleterious to cells. We therefore conclude that synthetic anion carriers are realistic candidates for further investigation as treatments for cystic fibrosis. PMID:26673261

  14. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

    1998-01-01

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution.

  15. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, R.; Horwitz, E.P.; Bond, A.H.

    1998-01-13

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution. 7 figs.

  16. Naked-eye detection of biologically important anions by a new chromogenic azo-azomethine sensor

    NASA Astrophysics Data System (ADS)

    Rezaeian, Khatereh; Khanmohammadi, Hamid

    2014-12-01

    A new chromogenic azo-azomethine sensor, containing active phenolic sites, has been designed and synthesized via condensation reaction of N,N,N‧,N‧-tetrakis(2-aminoethyl)-2,2-dimethyl propane-1,3-diamine with 1-(3-formyl-4-hydroxyphenylazo)-4-nitrobenzene. The anion recognition ability of the synthesized receptor was evaluated using UV-Vis spectroscopy and 1H NMR technique. The anion recognition studies exhibited that the receptor acts as a sensor for biologically important anions such as F-, AcO- and H2PO4- over other anions. The binding stoichiometry between sensor and anions was found to be 1:2. 1H NMR experiment revealed that sensor recognizes anions via H-bonds and subsequent deprotonation to elicit a vivid color change. Interestingly, the sensory system not only let for the naked eye detection without any spectroscopic instrumentation but also helped to discriminate between anions.

  17. Determination of the dissolved anion composition of ancient lakes from fossil ostracodes.

    USGS Publications Warehouse

    Forester, R.M.

    1986-01-01

    The mineralogy of evaporite and other precipitated minerals has provided traditional sources of information about the major dissolved ion composition of ancient lakes. The paleocompositional resolving power of these methods is generally greatest in high-salinity lakes. Ostracodes live in dilute saline lakes where a species occurrence is determined by the relative proportions of the lake's major dissolved anions, so that each species describes specific areas on an anion trilinear diagram. The upper salinity tolerance of each species depends upon the types of major anions in solution and is therefore anion-specific. Knowledge about both anion and anion-salinity tolerances of an ostracode may ultimately provide a means of estimating absolute anion concentrations in paleolakes. Because ostracodes are common fossils in lake sediments, they provide an important new source of original paleocompositional information suitable for many geologic, climatic, geochemical, and paleontologic studies. -from Author

  18. Efficient, non-toxic anion transport by synthetic carriers in cells and epithelia

    NASA Astrophysics Data System (ADS)

    Li, Hongyu; Valkenier, Hennie; Judd, Luke W.; Brotherhood, Peter R.; Hussain, Sabir; Cooper, James A.; Jurček, Ondřej; Sparkes, Hazel A.; Sheppard, David N.; Davis, Anthony P.

    2016-01-01

    Transmembrane anion transporters (anionophores) have potential for new modes of biological activity, including therapeutic applications. In particular they might replace the activity of defective anion channels in conditions such as cystic fibrosis. However, data on the biological effects of anionophores are scarce, and it remains uncertain whether such molecules are fundamentally toxic. Here, we report a biological study of an extensive series of powerful anion carriers. Fifteen anionophores were assayed in single cells by monitoring anion transport in real time through fluorescence emission from halide-sensitive yellow fluorescent protein. A bis-(p-nitrophenyl)ureidodecalin shows especially promising activity, including deliverability, potency and persistence. Electrophysiological tests show strong effects in epithelia, close to those of natural anion channels. Toxicity assays yield negative results in three cell lines, suggesting that promotion of anion transport may not be deleterious to cells. We therefore conclude that synthetic anion carriers are realistic candidates for further investigation as treatments for cystic fibrosis.

  19. Vibrationally resolved anion photoelectron spectroscopy of metal clusters

    NASA Astrophysics Data System (ADS)

    Miller, Stephen R.

    Vibrationally resolved anion photoelectron spectroscopy of metal clusters Vibrationally resolved anion photoelectron spectroscopy (APES) and density functional theory (DFT) are applied to the study of structure and reactivity in small metal containing molecules. The studies described fall into two general categories: the study of bare metal clusters and the study of metal/organic ligand reactions. The current lack of spectroscopic data for small, bare gas-phase metal compounds makes the experimental study of such compounds important for understanding structure and bonding in open-shell metallic species. The heteronuclear diatomic anions MCu- (M = Cr, Mo) were prepared in a flowing afterglow ion-molecule reactor, and studied experimentally with APES. Anion and neutral vibrational frequencies and MCu electron affinities were obtained for both systems. The experiments were supplemented by DFT calculations. The combined use of experiment and theory allows for the assignment of both photoelectron spectra, including a reassignment of the CrCu ground state reported in the literature. Similarly, DFT was used to assign the anionic/neutral electronic states observed in the photoelectron spectra of Al3- and Al3O-. The study of partially ligated organometallic complexes offers a means of examining the interactions between metal atoms and individual ligand molecules. DFT was used to assign electronic states observed in the photoelectron spectra of NbC2H2-, NbC4H4 -NbC6H6- and VC6H 6-. Comparison of the NbnHn - (n = 2, 4, 6) spectra (obtained through the reaction of C2 H4 and Nb) with DFT results provides the first direct spectroscopic evidence of the conversion of ethylene to benzene by a gas phase metal atom. Experiments were used to probe the reactivity of Y with C2H 4 in an effort to examine the generality of the metal induced C 2H4 dehydrogenation/cyclization reactions. Some of the key products in the Y reactions were YC2H-, YC 2H2-, and YC6H5 -. However, the results

  20. A fluorescent coumarin-thiophene hybrid as a ratiometric chemosensor for anions: Synthesis, photophysics, anion sensing and orbital interactions

    NASA Astrophysics Data System (ADS)

    Yanar, Ufuk; Babür, Banu; Pekyılmaz, Damla; Yahaya, Issah; Aydıner, Burcu; Dede, Yavuz; Seferoğlu, Zeynel

    2016-03-01

    A colorimetric and fluorimetric fluorescent chemosensor (CT-2), having a coumarin ring as a signaling unit and an acetamido thiophene ring as an H-donor receptor, has been synthesized from amino derivative (CT-1) of CT-2 for the purpose of recognition of anions in DMSO. The absorption and emission maxima were both determined for the fluorescent dye in different solvents. Both hypsochromic shift at the absorption maximum, and quenching of fluorescence after interactions between the anions and the receptoric part, were observed. This phenomenon was explained using orbital interactions based on quantum chemical calculations. The selectivity and sensitivity of CT-2 for F-, Cl-, Br-, I-, AcO-, CN-, H2PO4-, HSO4- and ClO4- anions were determined with spectrophotometric, fluorimetric and 1H NMR titration techniques and it was found that CT-2 be utilized for the detection of CN-, F- and AcO- in the presence of other ions as competitors. Color and fluorescence changes visible to the naked eye and under UV (365 nm) were observed upon addition of CN-, F- and AcO- to the solution of chemosensor (CT-2) in DMSO. The sensor showed no colorimetric and fluorimetric response for the anions such as Cl-, Br-, I-, H2PO4-, HSO4-, and ClO4-. However, 1H NMR titration shows that the chemosensor was more sensitive to CN-, than F- and AcO- at the stochiometric ratio of 1:2.5 respectively. Additionally, the compounds CT-1 and CT-2 showed good thermal stability for practical applications.

  1. Frog striated muscle is permeable to hydroxide and buffer anions.

    PubMed

    Venosa, R A; Kotsias, B A; Horowicz, P

    1994-04-01

    Hydroxide, bicarbonate and buffer anion permeabilities in semitendinosus muscle fibers of Rana pipiens were measured. In all experiments, the fibers were initially equilibrated in isotonic, high K2SO4 solutions at pHo = 7.2 buffered with phosphate. Two different methods were used to estimate permeabilities: (i) membrane potential changes were recorded in response to changes in external ion concentrations, and (ii) intracellular pH changes were recorded in response to changes in external concentrations of ions that alter intracellular pH. Constant field equations were used to calculate relative or absolute permeabilities. In the first method, to increase the size of the membrane potential change produced by a sudden change in anion entry, external K+ was replaced by Cs+ prior to changes of the anion under study. At constant external Cs+ activity, a hyperpolarization results from increasing external pH from 7.2 to 10.0 or higher, using either CAPS (3-[cyclohexylamino]-1-propanesulfonic acid) or CHES (2-[N-cyclohexylamino]-ethanesulfonic acid) as buffer. For each buffer, the protonated form is a zwitterion of zero net charge and the nonprotonated form is an anion. Using reported values of H+ permeability, calculations show that the reduction in [H+]o cannot account for the hyperpolarizations produced by alkaline solutions. Membrane hyperpolarization increases with increasing total external buffer concentration at constant external pH, and with increasing external pH at constant external buffer anion concentration. Taken together, these observations indicate that both OH- and buffer anions permeate the surface membrane. The following relative permeabilities were obtained at pHo = 10.0 +/- 0.3: (POH/PK) = 890 +/- 150, (PCAPS/PK) = 12 +/- 2, (PCHES/PK) = 5.3 +/- 0.9, and (PNO3/PK) = 4.7 +/- 0.5. PNO3/PK was independent of pHo up to 10.75. At pHo = 9.6, (PHCO3/PK) = 0.49 +/- 0.03; at pHo = 8.9, (PCl/PK) = 18 +/- 2 and at pHo = 7.1, (PHEPES/PK) = 20 +/- 2. In the second

  2. Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

    SciTech Connect

    Moyer, Bruce A; Sloop Jr, Frederick {Fred} V; Fowler, Christopher J; Haverlock, Tamara; Kang, Hyun Ah; Delmau, Laetitia Helene; Bau, Diadra; Hossain, Alamgir; Bowman-James, Kristin; Shriver, James A.; Gross, Mr. Dustin E.; Bill, Nathan; Marquez, Manuel; Lynch, Vincent M.; Sessler, Jonathan L.

    2010-01-01

    When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1 receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.

  3. Fluorene-based Cu(II)-MOF: a visual colorimetric anion sensor and separator based on an anion-exchange approach.

    PubMed

    Ma, Jian-Ping; Yu, Yang; Dong, Yu-Bin

    2012-03-21

    A new 2D Cu(II)-MOF generated from a fluorene-based ligand and Cu(NO(3))(2) was reported. It is an interesting visual colorimetric anion sensor. In addition, it can completely separate Cl(-)/Br(-), Br(-)/I(-) and SCN(-)/N(3)(-) anions under ambient conditions. PMID:22189967

  4. M8L12 cubic cages with all facial Δ or facial Λ configuration: effects of surface anions on the occupancy of the cage and anion exchange.

    PubMed

    Yang, Jing; Chang, Xiao-Yong; Sham, Kiu-Chor; Yiu, Shek-Man; Kwong, Hoi-Lun; Che, Chi-Ming

    2016-05-21

    M8L12 cubic cages (M = Mn(II), Zn(II) or Cd(II)), with all eight metal ions having all facial Δ or facial Λ configurations and having an encapsulated anion, were prepared by the self-assembly of m-xylene-bridged imidazolyl-imine ligands and MX2 (X = PF6(-), SbF6(-), TfO(-)) salts; the encapsulated anion exchange with different anions (SbF6(-), Tf2N(-), NO3(-), TsO(-)) was studied and the results with NO3(-) and TsO(-) indicate that anions on the cage surfaces affect the encapsulated anion exchange and the occupancy of the cage. PMID:27064122

  5. Solvation of benzophenone anion radical in ethanol and ethanol/2-methyltetrahydrofuran mixture

    SciTech Connect

    Ichikawa, T.; Ishikawa, Y.; Yoshida, H.

    1988-01-28

    The electron spin-echo modulations and the absoprtion spectra of benzophenone anion radicals generated by ..gamma..-irradiation in the glassy matrices of ethanol and ethanol2-methyltetrahydrofuran mixtures have been measured for elucidating the mechanism of spectral shift observed during the solvation of the anion radicals in alcohols. The anion radical generated at 4.2 K in the ethanol matrix maintains the same solvation structure as that of neutral benzophenone. At 77 K ethanol molecules solvate the anion radical by orienting the O-H dipoles toward the anion radical. The anion radical is hydrogen-bonded by two ethanol molecules through the p/sub z/ orbital on the benzophenone oxygen which composes the ..pi.. orbitals of anion radical. Three kinds of anion radicals are observed in the mixed matrix at 77 K. Two of them are essentially the same as those observed in the ethanol matrix at 4.2 and 77 K. The third has the absorption maximum at 700 nm and is attributed to the anion radical hydrogen-bonded by one ethanol molecule through the p/sub z/ orbital. It is concluded that the spectral shift observed in alcohols is caused by the stabilization of a SOMO ..pi..* orbital induced by the hydrogen bonding with the (RO)H--O--H(OR) angle perpendicular to the molecular plane of the anion radical

  6. Interactions of Polyethylenimines with Zwitterionic and Anionic Lipid Membranes.

    PubMed

    Kwolek, Urszula; Jamróz, Dorota; Janiczek, Małgorzata; Nowakowska, Maria; Wydro, Paweł; Kepczynski, Mariusz

    2016-05-17

    Interactions between polyethylenimines (PEIs) and phospholipid membranes are of fundamental importance for various biophysical applications of these polymers such as gene delivery. Despite investigations into the nature of these interactions, their molecular basis remains poorly understood. In this article, we combined experimental methods and atomistic molecular dynamics (MD) simulations to obtain comprehensive insight into the effect of linear and branched PEIs on zwitterionic and anionic bilayers used as simple models of mammalian cellular membranes. Our results show that PEIs adsorb only partially on the surface of zwitterionic membranes by forming hydrogen bonds to the lipid headgroups, whereas a large part of the polymer chains dangles freely in the aqueous phase. In contrast, PEIs readily adhere to and insert into the anionic membrane. The attraction of the polymer chains to the membrane is due to electrostatic interactions as well as hydrogen bonding between the amine groups of PEI and the phosphate groups of lipids. These interactions were found to induce a substantial reorganization of the bilayer in the polymer vicinity due to the reorientation of lipid molecules. The lipid headgroups were pulled toward the center of the membrane, which can facilitate transmembrane translocations of anionic lipids. Furthermore, the PEI-lipid interactions affect the stability of liposomal dispersions, but we did not see any evidence of disruption of the vesicular structures into small fragments at polymer concentrations typically used in gene therapy. Our results provide a detailed molecular-level description of the lipid organization in the membrane in the presence of polycations that can be useful in understanding their mechanisms of in vitro and in vivo cytotoxicity. PMID:27115556

  7. Nucleotide sequence of the tobacco (Nicotiana tabacum) anionic peroxidase gene

    SciTech Connect

    Diaz-De-Leon, F.; Klotz, K.L.; Lagrimini, L.M. )

    1993-03-01

    Peroxidases have been implicated in numerous physiological processes including lignification (Grisebach, 1981), wound-healing (Espelie et al., 1986), phenol oxidation (Lagrimini, 1991), pathogen defense (Ye et al., 1990), and the regulation of cell elongation through the formation of interchain covalent bonds between various cell wall polymers (Fry, 1986; Goldberg et al., 1986; Bradley et al., 1992). However, a complete description of peroxidase action in vivo is not available because of the vast number of potential substrates and the existence of multiple isoenzymes. The tobacco anionic peroxidase is one of the better-characterized isoenzymes. This enzyme has been shown to oxidize a number of significant plant secondary compounds in vitro including cinnamyl alcohols, phenolic acids, and indole-3-acetic acid (Maeder, 1980; Lagrimini, 1991). A cDNA encoding the enzyme has been obtained, and this enzyme was shown to be expressed at the highest levels in lignifying tissues (xylem and tracheary elements) and also in epidermal tissue (Lagrimini et al., 1987). It was shown at this time that there were four distinct copies of the anionic peroxidase gene in tobacco (Nicotiana tabacum). A tobacco genomic DNA library was constructed in the [lambda]-phase EMBL3, from which two unique peroxidase genes were sequenced. One of these clones, [lambda]POD1, was designated as a pseudogene when the exonic sequences were found to differ from the cDNA sequences by 1%, and several frame shifts in the coding sequences indicated a dysfunctional gene (the authors' unpublished results). The other clone, [lambda]POD3, described in this manuscript, was designated as the functional tobacco anionic peroxidase gene because of 100% homology with the cDNA. Significant structural elements include an AS-2 box indicated in shoot-specific expression (Lam and Chua, 1989), a TATA box, and two intervening sequences. 10 refs., 1 tab.

  8. Anion Photoelectron Spectroscopy of NbW- and W2-

    NASA Astrophysics Data System (ADS)

    Schnepper, D. Alex; Baudhuin, Melissa A.; Leopold, Doreen; Casey, Sean M.

    2015-06-01

    The 488 nm vibrationally-resolved photoelectron spectra of NbW- and W2- are reported. The electron affinity of W2 ( 1σg+ ← 2σu+ ) is found to be 1.118 ± 0.007 eV, which differs from the value reported in a previous anion photoelectron spectroscopic study of W2- (1.46 eV), but was accurately predicted by density functional calculations (1.12 eV). The fundamental vibrational frequency of W2 is measured to be 345 ± 15 wn, in agreement with the value previously reported in matrix resonance Raman studies (337 wn). The W2- anion is measured to have a fundamental frequency of 320 ± 15 wn. Several weak transitions to excited electronic states are seen and tentatively assigned based on calculated energies. NbW has an electron affinity of 0.856 ± 0.007 eV. Vibrational frequencies are found, by Franck-Condon fitting of overlapping transitions, to be 365 ± 20 cm-1 for NbW- and 410 ± 20 cm-1 for NbW. This increase in vibrational frequency upon photodetachment suggests that the extra electron is in an antibonding orbital, leading to ground state assignments of 3Δ and 2Δ for the anion and neutral, respectively. These results are compared to those obtained for other Group V and Group VI transition metal dimers and trends are discussed. H. Weidele et al., Chem. Phys. Lett. 237 (1995) 425-431 Z. J. Wu, X. F. Ma, Chem. Phys. Lett. 371 (2003) 35-39 Z. Hu, J.-G. Dong, J. R. Lombardi, D. M. Lindsay, J. Chem. Phys. 97 (1992) 8811-8812

  9. Interaction of Organic Cations with Organic Anion Transporters*

    PubMed Central

    Ahn, Sun-Young; Eraly, Satish A.; Tsigelny, Igor; Nigam, Sanjay K.

    2009-01-01

    Studies of the organic anion transporters (Oats) have focused mainly on their interactions with organic anionic substrates. However, as suggested when Oat1 was originally identified as NKT (Lopez-Nieto, C. E., You, G., Bush, K. T., Barros, E. J., Beier, D. R., and Nigam, S. K. (1997) J. Biol. Chem. 272, 6471–6478), since the Oats share close homology with organic cation transporters (Octs), it is possible that Oats interact with cations as well. We now show that mouse Oat1 (mOat1) and mOat3 and, to a lesser degree, mOat6 bind a number of “prototypical” Oct substrates, including 1-methyl-4-phenylpyridinium. In addition to oocyte expression assays, we have tested binding of organic cations to Oat1 and Oat3 in ex vivo assays by analyzing interactions in kidney organ cultures deficient in Oat1 and Oat3. We also demonstrate that mOat3 transports organic cations such as 1-methyl-4-phenylpyridinium and cimetidine. A pharmacophore based on the binding affinities of the tested organic cations for Oat3 was generated. Using this pharmacophore, we screened a chemical library and were able to identify novel cationic compounds that bound to Oat1 and Oat3. These compounds bound Oat3 with an affinity higher than the highest affinity compounds in the original set of prototypical Oct substrates. Thus, whereas Oat1, Oat3, and Oat6 appear to function largely in organic anion transport, they also bind and transport some organic cations. These findings could be of clinical significance, since drugs and metabolites that under normal physiological conditions do not bind to the Oats may undergo changes in charge and become Oat substrates during pathologic conditions wherein significant variations in body fluid pH occur. PMID:19737926

  10. Theoretical characterization of dihydrogen adducts with halide anions

    NASA Astrophysics Data System (ADS)

    Vitillo, Jenny G.; Damin, Alessandro; Zecchina, Adriano; Ricchiardi, Gabriele

    2006-06-01

    The interaction between a hydrogen molecule and the halide anions F-, Cl-, Br-, and I- has been studied at different levels of theory and with different basis sets. The most stable configurations of the complexes have a linear geometry, while the t-shaped complexes are saddle points on the potential energy surface, opposite to what is observed for alkali cations. An electrostatic analysis conducted on the resulting adducts has highlighted the predominance of the electrostatic term in the complexation energy and, in particular, of the quadrupole- and dipole-polarizability dependent contributions. Another striking difference with respect to the positive ions, is the fact that although the binding energies have similar values (ranging between 25 and 3kJ/mol for F- and I-, respectively), the vibrational shift of the ν˜H-H and in general the perturbation of the hydrogen molecule in complexes are much greater in the complexes with anions (Δν˜H-H ranges between -720 and -65cm-1). Another difference with respect to the interaction with cations is a larger charge transfer from the anion to the hydrogen molecule. The Δν˜ is the result of the cooperative role of the electrostatics and of the charge transfer in the interaction. The correlation between binding energies and vibrational shift is far from linear, contrary to what is observed for cation complexes, in accordance with the higher polarizability and dynamic polarizability of the molecule along the molecular axis. The observed correlation may be valuable in the interpretation of spectra and thermodynamic properties of adsorbed H2 in storage materials.

  11. Chemistry of nitrile anions in the interstellar medium

    SciTech Connect

    Carles, S.; Le Garrec, J.-L.; Biennier, L.; Guillemin, J.-C.

    2015-12-31

    Despite the extreme conditions of temperature (down to 10K) and density (down to 100 molecules/cm{sup 3}), the giant molecular clouds and the circumstellar envelopes present a rich and complex chemistry. To date, more than 180 molecules have been detected in the InterStellar Medium (ISM) with a large abundance of nitriles (RC≡N). In addition, several anions have been recently observed in this medium: C{sub 4}H{sup ¯}, C{sub 6}H{sup ¯}, C{sub 8}H{sup ¯}, CN{sup ¯}, C{sub 3}N{sup ¯} and C{sub 5}N{sup ¯}. These last species should play a key role in the molecular growth towards complexity. To explore this hypothesis, their reactivity must be studied in the laboratory. The FALP-MS and the CRESU experimental apparatuses of the Rennes University are able to measure absolute rate coefficient of various chemical reactions, including the ion – molecule reactions, in gas phase at low temperature (from 300K for the FALP-MS down to 15K for the CRESU). Therefore, these experimental tools are particularly adapted to the kinetic studies of reactions potentially involved in the Interstellar Medium. One of the difficulties encountered in experiments with anions is their generation. We describe here the formation of the CN{sup ¯} and C{sub 3}N{sup ¯} anions by dissociative electron attachment on the molecular precursors BrCN and BrC{sub 3}N.

  12. A New Class of Ionic Liquids: Anion Amphiprotic Ionic Liquids.

    PubMed

    Treskow, Marcel; Pitawala, Jagath; Arenz, Sven; Matic, Aleksandar; Johansson, Patrik

    2012-08-16

    We here present a new class of protic ionic liquids, anion amphiprotic ionic liquids (AAILs). These materials are protonation equilibrium free protic ionic liquids and interesting in their own right by not following the classical Brønsted acid-base neutralization concept. Due to the very simple synthesis route applied and their stable basic chemistry, we believe in a potential use for manifold applications. This is supported by the combination of practical material properties, foremost, a general intrinsic stability versus reversal of the formation reaction toward neutral species, broad liquidus ranges, long-term thermal stabilities, high conductivities, protic characteristics, and a general stability versus water. PMID:26295756

  13. Solvation Effects on Structure and Charge Distribution in Anionic Clusters

    NASA Astrophysics Data System (ADS)

    Weber, J. Mathias

    2015-03-01

    The interaction of ions with solvent molecules modifies the properties of both solvent and solute. Solvation generally stabilizes compact charge distributions compared to more diffuse ones. In the most extreme cases, solvation will alter the very composition of the ion itself. We use infrared photodissociation spectroscopy of mass-selected ions to probe how solvation affects the structures and charge distributions of metal-CO2 cluster anions. We gratefully acknowledge the National Science Foundation for funding through Grant CHE-0845618 (for graduate student support) and for instrumentation funding through Grant PHY-1125844.

  14. Electron paramagnetic resonance examination of aqueous anthrasemiquinone radical anion

    NASA Astrophysics Data System (ADS)

    Hocking, M. B.; Mattar, S. M.

    Anthrasemiquinone radical anion (AQ -·) was prepared in strictly aqueous alkaline solutions using reducing sugars. It was found to be stable in this medium at room temperature in the absence of air for periods exceeding 1 year. Reduction using an equivalent of sodium dithionite required brief exposure of the solution of dianion to air to obtain AQ -. EPR observations are reported for these solutions over the temperature range -50 to +90°C in basic ethanol, aqueous ethanol, and water and are related to redox potential measurements and electron exchange processes operating under these conditions.

  15. Electroactive Materials For Anion Separation-Technetium From Nitrate

    SciTech Connect

    William H. Smyrl, PI; Dr. Ann Gronda

    2003-10-10

    In order to increase the capacity of electroactive polymers for radioactive waste separations, we have focused on two ways of processing these polymers: phase inversion, and coating onto a porous conductive substrate. Both techniques are intended to increase the surface area for access of the guest anions to the intercalation host. Phase inversion of polyvinylferrocene (PVF) was unsuccessful, but we were able to use electroprecipitation to coat PVF onto porous carbon substrates such as Toray paper. Due to the wide molecular weight distribution and batch variations of commercial PVF, we have chosen to examine the more manageable polyaniline.

  16. An unusual case of severe high anion gap metabolic acidosis

    PubMed Central

    Bavakunji, Riaz V.; Turner, Jake D.; Jujjavarapu, Sagar; Taal, Maarten W.; Fluck, Richard J.; Leung, Janson C.; Kolhe, Nitin V.

    2011-01-01

    We present a case of high anion gap metabolic acidosis with an unusual aetiology in a 75-year-old lady with hypoglycaemia, encephalopathy and relatively preserved renal function. Full toxicology and biochemical analysis suggested that she had an inborn error of metabolism, riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency that can predispose to severe acidosis in situations where calorific intake is reduced. We believe this to be one of the few published cases and is remarkable for the presentation in late adulthood in addition to the requirement for emergency haemodialysis due to the severity of the metabolic disturbance. PMID:25984120

  17. Anion-responsive diguanidinium-based chiral organogelators.

    PubMed

    Valero, Julián; Escuder, Beatriu; Miravet, Juan F; de Mendoza, Javier

    2012-10-01

    The chiral bicyclic diguanidinium chloride 1 forms gels in aromatic apolar solvents. The gels were characterized at different levels of organization, from the macroscopic to the molecular level by using microscopy, spectroscopy, and powder X-ray diffraction. The dependency on chirality has been highlighted by circular dichroism and electron microscopy. Furthermore, the gel has been shown to be effectively responsive to anionic stimuli, thus allowing the reversible control of the organic-phase gelation in contact with different salted aqueous solutions. PMID:22936304

  18. Spectroscopic observation of nitrogen anions N(-) in solid matrices.

    PubMed

    Boltnev, R E; Bykhalo, I B; Krushinskaya, I N; Pelmenev, A A; Mao, S; Meraki, A; McColgan, P T; Lee, D M; Khmelenko, V V

    2016-06-21

    Analysis of old and recent experiments on thermoluminescence of cryocrystals and nanoclusters of N2, Ne, Ar, and Kr containing stabilized nitrogen atoms, suggests that the so-called γ-line may correspond to the bound-bound transition (1)D-(3)P of nitrogen anions N(-) formed in solids by the association of delocalized electrons and metastable nitrogen atoms N((2)D). The recent observations of the γ-line were accompanied by simultaneous luminescence of metastable nitrogen N((2)D) atoms and exoelectron emission. The fine structure of the γ-line at 793 nm has been experimentally observed and investigated for the first time. PMID:27241627

  19. Can Chlorine Anion Catalyze the Reaction fo HOCl with HCl?

    NASA Technical Reports Server (NTRS)

    Richardson, S. L.; Francisco, J. S.; Mebel, A. M.; Morokuma, K.

    1997-01-01

    The reaction of HOCl + HCl -> Cl2 + H20 in the presence of Cl has been studied using ab initio methods. This reaction has been shown to have a high activation barrier of 46.5 kcal/mol. The chlorine anion, Cl- is found to catalyze the reaction, viz. two mechanisms. The first involves Cl- interacting through the concerted four-center transition state of the neutral reaction. The other mechanism involves the formation of a HCl-HOCl-Cl- intermediate which dissociates into Cl2 + Cl- + H20. The steps are found to have no barriers. The overall exothermicity is 15.5 kcal/mol.

  20. Total Synthesis of Brevisamide Using an Oxiranyl Anion Strategy.

    PubMed

    Sakai, Takeo; Fukuta, Ayumi; Nakamura, Kumiko; Nakano, Masato; Mori, Yuji

    2016-05-01

    A total synthesis of brevisamide, a marine monocyclic ether amide isolated from the dinoflagellate Karenia brevis, has been achieved in 18 steps starting from 4-(benzyloxy)butanol. The synthesis involves oxiranyl anion coupling between an epoxy sulfone and a triflate, intramolecular etherification of a hydroxy-bromoketone, diastereoselective introduction of the axial methyl group by hydroxyl-directed hydrogenation of an exocyclic olefin, and installation of an acetamide side chain by nucleophilic substitution of an N-acetyl carbamate. The dienal side chain is assembled using a Horner-Wadsworth-Emmons reaction to complete the synthesis. PMID:27057586