Comparison of topotactic fluorination methods for complex oxide films

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E. J. Moon

2015-06-01

Full Text Available We have investigated the synthesis of SrFeO3−αFγ (α and γ ≤ 1 perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO2.5 films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

Topotactic decomposition and crystal structure of white molybdenum trioxide--monohydrate: prediction of structure by topotaxy

International Nuclear Information System (INIS)

Oswald, H.R.; Guenter, J.R.; Dubler, E.

1975-01-01

Single crystals of the white MoO 3 . H 2 O modification (''α-molybdic acid'') were transformed by heating to 160 0 C into perfect pseudomorphs built up from oriented MoO 3 crystallites of known structure. From the mutual orientation relationship of the unit cells of both phases involved in this topotactic reaction, as determined by X-ray photographs, a model for the so far unknown crystal structure of white MoO 3 . H 2 O could be deduced. Independently, this structure was determined by X-ray diffractometer data then: space group P anti 1, a = 7.388, b = 3.700, c = 6.673 A, α = 107.8, β = 113.6, γ = 91.2 0 , Z = 2. The structure was solved from the Patterson function and refined until R = 0.088. It is built up from isolated double chains of strongly distorted [MoO 5 (H 2 O)]-octahedra sharing two common edges with each other. This result agrees well with the model derived from topotaxy, and it becomes evident how the MoO 3 lattice is formed through corner linking of the isolated double chains after the water molecules are removed. The study of topotactic phenomena seems rather generally applicable to deduce the main features of structures involved and for better understanding of structural relationships. (U.S.)

Topotactic synthesis of Co3O4 nanoboxes from Co(OH)2 nanoflakes

International Nuclear Information System (INIS)

Tian Li; Huang Kelong; Liu Younian; Liu Suqin

2011-01-01

Hollow nanocubes of spinel Co 3 O 4 with the dimension of 20 nm were successfully prepared via a facile and reproducible solvothermal route. The structure and morphology of Co 3 O 4 nanoboxes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) techniques. And a possible growth mechanism of Co 3 O 4 nanoboxes were suggested that solid Co 3 O 4 nanocubes nucleate in-situ and grow epitaxially from hexagonal β-Co(OH) 2 precursors with the structural matching relationship of [0 0 1] β-Co(OH) 2 //[1 1 1] Co 3 O 4 , and then solid Co 3 O 4 nanocubes gradually hollow and convert to single-crystal nanoboxes owing to Ostwald ripening. - Graphical abstract: The formation mechanism of Co 3 O 4 nanoboxes can be expressed as epitaxial growth of Co 3 O 4 nanocubes from β-Co(OH) 2 nanoflakes due to a topotactic transformation and hollowing process owing to Ostwald ripening. Highlights: → Co 3 O 4 nanoboxes were prepared by a convenient, economical and controllable hydrothermal route. → Morphology and structure of Co 3 O 4 nanoboxes were characterized by XRD, SEM, and TEM techniques. → Co 3 O 4 nanoboxes grow epitaxially from Co(OH) 2 by topotactic transformation was suggested.

Topotactic synthesis of vanadium nitride solid foams

International Nuclear Information System (INIS)

Oyama, S.T.; Kapoor, R.; Oyama, H.T.; Hofmann, D.J.; Matijevic, E.

1993-01-01

Vanadium nitride has been synthesized with a surface area of 120 m 2 g -1 by temperature programmed nitridation of a foam-like vanadium oxide (35 m 2 g -1 ), precipitated from vanadate solutions. The nitridation reaction was established to be topotactic and pseudomorphous by x-ray powder diffraction and scanning electron microscopy. The crystallographic relationship between the nitride and oxide was {200}//{001}. The effect of precursor geometry on the product size and shape was investigated by employing vanadium oxide solids of different morphologies

2D corrugated magnesium carboxyphosphonate materials: topotactic transformations and interlayer "decoration" with ammonia.

Science.gov (United States)

Demadis, Konstantinos D; Famelis, Nikos; Cabeza, Aurelio; Aranda, Miguel A G; Colodrero, Rosario M P; Infantes-Molina, Antonia

2012-07-16

In this paper we report the synthesis and structural characterization of the 2D layered coordination polymer Mg(BPMGLY)(H(2)O)(2) (BPMGLY = bis-phosphonomethylglycine, (HO(3)PCH(2))(2)N(H)COO(2-)). The Mg ion is found in a slightly distorted octahedral environment formed by four phosphonate oxygens and two water molecules. The carboxylate group is deprotonated but noncoordinated. This compound is a useful starting material for a number of topotactic transformations. Upon heating at 140 °C one (of the two) Mg-coordinated water molecule is lost, with the archetype 2D structure maintaining itself. However, the octahedral Mg in Mg(BPMGLY)(H(2)O)(2) is now converted to trigonal bipyramidal in Mg(BPMGLY)(H(2)O). Upon exposure of the monohydrate Mg(BPMGLY)(H(2)O) compound to ammonia, one molecule of ammonia is inserted into the interlayer space and stabilized by hydrogen bonding. The 2D layered structure of the product Mg(BPMGLY)(H(2)O)(NH(3)) is still maintained, with Mg now acquiring a pseudo-octahedral environment. All of these topotactic transformations are also accompanied by changes in hydrogen bonding between the layers.

Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+\\delta

OpenAIRE

Muguerra, Hervé; Colin, Claire; Anne, Michel; Julien, M. -H.; Strobel, Pierre

2008-01-01

International audience; A new form of delafossite-type AgCoO2+δ was prepared using ion exchange from Na0.75CoO2 in molten AgNO3-NH4NO3 at 175°C. Its structure was determined by Rietveld refinement from XRD data; it is hexagonal, space group P63/mmc, a = 2.871 and c = 12.222 Å. Its structure differs from previously reported AgCoO2 (R-3m, 3R polytype) by the stacking of Co-O layers; in the new phase the 2H stacking of the precursor Na0.75CoO2, consistent with a topotactic ion exchange of Na by ...

Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.

Science.gov (United States)

Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

2007-09-12

Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab.

Topotactic oxidation pathway of ScTiO3 and high-temperature structure evolution of ScTiO3.5 and Sc4Ti3O12-type phases.

Science.gov (United States)

Shafi, Shahid P; Hernden, Bradley C; Cranswick, Lachlan M D; Hansen, Thomas C; Bieringer, Mario

2012-02-06

The novel oxide defect fluorite phase ScTiO(3.5) is formed during the topotactic oxidation of ScTiO(3) bixbyite. We report the oxidation pathway of ScTiO(3) and structure evolution of ScTiO(3.5), Sc(4)Ti(3)O(12), and related scandium-deficient phases as well as high-temperature phase transitions between room temperature and 1300 °Cusing in-situ X-ray diffraction. We provide the first detailed powder neutron diffraction study for ScTiO(3). ScTiO(3) crystallizes in the cubic bixbyite structure in space group Ia3 (206) with a = 9.7099(4) Å. The topotactic oxidation product ScTiO(3.5) crystallizes in an oxide defect fluorite structure in space group Fm3m (225) with a = 4.89199(5) Å. Thermogravimetric and differential thermal analysis experiments combined with in-situ X-ray powder diffraction studies illustrate a complex sequence of a topotactic oxidation pathway, phase segregation, and ion ordering at high temperatures. The optimized bulk synthesis for phase pure ScTiO(3.5) is presented. In contrast to the vanadium-based defect fluorite phases AVO(3.5+x) (A = Sc, In) the novel titanium analogue ScTiO(3.5) is stable over a wide temperature range. Above 950 °C ScTiO(3.5) undergoes decomposition with the final products being Sc(4)Ti(3)O(12) and TiO(2). Simultaneous Rietveld refinements against powder X-ray and neutron diffraction data showed that Sc(4)Ti(3)O(12) also exists in the defect fluorite structure in space group Fm3m (225) with a = 4.90077(4) Å. Sc(4)Ti(3)O(12) undergoes partial reduction in CO/Ar atmosphere to form Sc(4)Ti(3)O(11.69(2)).

Topotactic preparation of textured alumina ceramics from dehydroxylation of gibbsite films

Energy Technology Data Exchange (ETDEWEB)

Louaer, Seif-Eddine; Wang, Yao, E-mail: yao@buaa.edu.cn; Guo, Lin, E-mail: guolin@buaa.edu.cn

2014-11-14

In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites. - Highlights: • Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films. • Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds. • Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size. • Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work.

Topotactic preparation of textured alumina ceramics from dehydroxylation of gibbsite films

International Nuclear Information System (INIS)

Louaer, Seif-Eddine; Wang, Yao; Guo, Lin

2014-01-01

In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites. - Highlights: • Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films. • Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds. • Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size. • Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

OpenAIRE

Goto, Sho; Kura, Hiroaki; Watanabe, Eiji; Hayashi, Yasushi; Yanagihara, Hideto; Shimada, Yusuke; Mizuguchi, Masaki; Takanashi, Koki; Kita, Eiji

2017-01-01

Tetrataenite (L10-FeNi) is a promising candidate for use as a permanent magnet free of rare-earth elements because of its favorable properties. In this study, single-phase L10-FeNi powder with a high degree of order was synthesized through a new method, nitrogen insertion and topotactic extraction (NITE). In the method, FeNiN, which has the same ordered arrangement as L10-FeNi, is formed by nitriding A1-FeNi powder with ammonia gas. Subsequently, FeNiN is denitrided by topotactic reaction to ...

Topotactic Metal-Insulator Transition in Epitaxial SrFeOx Thin Films.

Science.gov (United States)

Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; Kim, Minu; Kang, Tae Dong; Lee, Jaekwang; Roh, Seulki; Jung, In-Ho; Hwang, Jungseek; Kim, Sung Wng; Noh, Tae Won; Ohta, Hiromichi; Choi, Woo Seok

2017-10-01

Topotactic phase transformation enables structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for elucidating the redox reaction and oxygen diffusion within transition metal oxides. In addition, it enables tuning of the emergent physical properties of complex oxides, through strong interaction between the lattice and electronic degrees of freedom. In this communication, the electronic structure evolution of SrFeO x epitaxial thin films is identified in real-time, during the progress of reversible topotactic phase transformation. Using real-time optical spectroscopy, the phase transition between the two structurally distinct phases (i.e., brownmillerite and perovskite) is quantitatively monitored, and a pressure-temperature phase diagram of the topotactic transformation is constructed for the first time. The transformation at relatively low temperatures is attributed to a markedly small difference in Gibbs free energy compared to the known similar class of materials to date. This study highlights the phase stability and reversibility of SrFeO x thin films, which is highly relevant for energy and environmental applications exploiting the redox reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO 2+δ

Science.gov (United States)

Muguerra, Hervé; Colin, Claire; Anne, Michel; Julien, Marc-Henri; Strobel, Pierre

2008-11-01

A new form of delafossite-type AgCoO 2+δ was prepared using ion exchange from Na 0.75CoO 2 in molten AgNO 3-NH 4NO 3 at 175 °C. Its structure was determined by the Rietveld refinement from X-ray powder diffraction measurements (XRD) data; it is hexagonal, space group P6 3/ mmc, a=2.871 and c=12.222 Å. Its structure differs from previously reported AgCoO 2 ( R3¯m, 3R polytype) by the stacking of Co-O layers; in the new phase, the 2H stacking of the precursor Na 0.75CoO 2 is consistent with a topotactic ion exchange of Na by Ag. The new phase is found to contain a slight oxygen excess ( δ=0.06). Magnetic susceptibility measurements show the absence of magnetic transition and a weak Curie term, consistent with the non-magnetic character of Co 3+ ions.

Novel Au- and Ge-based two-dimensional materials formed through topotactic transitions of AlB2-like structures

Science.gov (United States)

Tsetseris, Leonidas

2016-07-01

The topotactic reaction of a layered compound, for example CaGe2, with HCl solution is a common and facile method to produce two-dimensional (2D) materials. In this work we demonstrate with first-principles calculations that this technique can potentially lead to a whole new family of 2D materials starting from three-dimensional crystals with AlB2-like structures. As representative cases, we show here that the de-intercalation of Sc and Ca atoms from ScAuGe and Ca2AuGe3 crystals is strongly exothermic and produces the stable 2D monolayers AuGeH and AuGe3H3, respectively. Remarkably, both metals (AuGeH) and semiconductors (AuGe3H3) can be prepared by this method. Based on the broad availability of AlB2-like structures with varying stoichiometries, there are several possibilities to prepare novel functional 2D materials with suitable topotactic transitions.

Topotactic reduction and reoxidation of hexagonal RCu0.5Ti0.5O3 (R = Y, Eu-Lu) Phases

International Nuclear Information System (INIS)

Jiang, Peng; Berthelot, Romain; Li, Jun; Sleight, A.W.; Subramanian, M.A.

2013-01-01

Highlights: ► Topotactic reduction of hexagonal RCu 0.5 Ti 0.5 O 3 phases is performed. ► TGA and magnetism indicate a formula of RCu 0.5 Ti 0.5 O 2.78 for the reduced phase. ► Topotactic reoxidation occurs on heating these phases to 400 °C in air. - Abstract: Hexagonal AMO 2 and AMO 3 phases have the same basic structure, and intermediate compositions for this structure have been prepared by topotactic oxidation of AMO 2 phases such as RCuO 2 , where R is a trivalent rare earth cation. We now find that such intermediate phases can also be prepared by topotactic reduction of hexagonal RCu 0.5 Ti 0.5 O 3 (R = Y, Tb-Lu) phases. Our TGA and magnetic susceptibility studies indicate a formula of RCu 0.5 Ti 0.5 O 2.78 for these reduced phases. Topotactic reoxidation occurs on heating these phases to 400 °C in air

A novel layered titanoniobate LiTiNbO5: topotactic synthesis and electrochemistry versus lithium.

Science.gov (United States)

Colin, J-F; Pralong, V; Caignaert, V; Hervieu, M; Raveau, B

2006-09-04

A new layered titanoniobate, LiTiNbO5, an n = 2 member of the A(x)M(2n)O(4n+2) family, has been synthesized using a molten salt reaction between HTiNbO5 and an eutectic "LiOH/LiNO3". This compound crystallizes in the P2(1)/m space group with a = 6.41 A, b = 3.77 A, c = 8.08 A, and beta = 92 degrees . It exhibits |TiNbO5|(infinity) layers similar to HTiNbO5, but differs from the latter by a "parallel configuration" of its |TiNbO6|(infinity) ribbons between the two successive layers. The topotactic character of the reaction suggests that exfoliation plays a prominent role in the synthesis of this new form. This new phase intercalates reversibly 0.8 lithium through a first-order transformation leading to a capacity of 94 mAh/g at a potential of 1.67 V vs Li/Li+.

Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO3

Science.gov (United States)

Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

2013-02-01

Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33767g

Non-Topotactic Transformation of Silicate Nanolayers into Mesostructured MFI Zeolite Frameworks During Crystallization.

Science.gov (United States)

Berkson, Zachariah J; Messinger, Robert J; Na, Kyungsu; Seo, Yongbeom; Ryoo, Ryong; Chmelka, Bradley F

2017-05-02

Mesostructured MFI zeolite nanosheets are established to crystallize non-topotactically through a nanolayered silicate intermediate during hydrothermal synthesis. Solid-state 2D NMR analyses, with sensitivity enhanced by dynamic nuclear polarization (DNP), provide direct evidence of shared covalent 29 Si-O- 29 Si bonds between intermediate nanolayered silicate moieties and the crystallizing MFI zeolite nanosheet framework. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topotactic Synthesis of Porous Cobalt Ferrite Platelets from a Layered Double Hydroxide Precursor and Their Application in Oxidation Catalysis.

Science.gov (United States)

Ortega, Klaus Friedel; Anke, Sven; Salamon, Soma; Özcan, Fatih; Heese, Justus; Andronescu, Corina; Landers, Joachim; Wende, Heiko; Schuhmann, Wolfgang; Muhler, Martin; Lunkenbein, Thomas; Behrens, Malte

2017-09-12

Monocrystalline, yet porous mosaic platelets of cobalt ferrite, CoFe 2 O 4 , can be synthesized from a layered double hydroxide (LDH) precursor by thermal decomposition. Using an equimolar mixture of Fe 2+ , Co 2+ , and Fe 3+ during co-precipitation, a mixture of LDH, (Fe II Co II ) 2/3 Fe III 1/3 (OH) 2 (CO 3 ) 1/6 ⋅m H 2 O, and the target spinel CoFe 2 O 4 can be obtained in the precursor. During calcination, the remaining Fe II fraction of the LDH is oxidized to Fe III leading to an overall Co 2+ :Fe 3+ ratio of 1:2 as required for spinel crystallization. This pre-adjustment of the spinel composition in the LDH precursor suggests a topotactic crystallization of cobalt ferrite and yields phase pure spinel in unusual anisotropic platelet morphology. The preferred topotactic relationship in most particles is [111] Spinel ∥[001] LDH . Due to the anion decomposition, holes are formed throughout the quasi monocrystalline platelets. This synthesis approach can be used for different ferrites and the unique microstructure leads to unusual chemical properties as shown by the application of the ex-LDH cobalt ferrite as catalyst in the selective oxidation of 2-propanol. Compared to commercial cobalt ferrite, which mainly catalyzes the oxidative dehydrogenation to acetone, the main reaction over the novel ex-LDH cobalt is dehydration to propene. Moreover, the oxygen evolution reaction (OER) activity of the ex-LDH catalyst was markedly higher compared to the commercial material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO₃.

Science.gov (United States)

Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

2013-03-21

Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.

Topotactic reduction and reoxidation of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} (R = Y, Eu-Lu) Phases

Energy Technology Data Exchange (ETDEWEB)

Jiang, Peng, E-mail: jiangp@onid.orst.edu [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Berthelot, Romain, E-mail: berthelot.rom@gmail.com [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Li, Jun, E-mail: jli100@yahoo.com [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Sleight, A.W., E-mail: arthur.sleight@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Subramanian, M.A., E-mail: mas.subramanian@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States)

2013-06-01

Highlights: ► Topotactic reduction of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} phases is performed. ► TGA and magnetism indicate a formula of RCu{sub 0.5}Ti{sub 0.5}O{sub 2.78} for the reduced phase. ► Topotactic reoxidation occurs on heating these phases to 400 °C in air. - Abstract: Hexagonal AMO{sub 2} and AMO{sub 3} phases have the same basic structure, and intermediate compositions for this structure have been prepared by topotactic oxidation of AMO{sub 2} phases such as RCuO{sub 2}, where R is a trivalent rare earth cation. We now find that such intermediate phases can also be prepared by topotactic reduction of hexagonal RCu{sub 0.5}Ti{sub 0.5}O{sub 3} (R = Y, Tb-Lu) phases. Our TGA and magnetic susceptibility studies indicate a formula of RCu{sub 0.5}Ti{sub 0.5}O{sub 2.78} for these reduced phases. Topotactic reoxidation occurs on heating these phases to 400 °C in air.

Topotactic Consolidation of Monocrystalline CoZn Hydroxides for Advanced Oxygen Evolution Electrodes.

Science.gov (United States)

Wang, Jing; Tan, Chuan Fu; Zhu, Ting; Ho, Ghim Wei

2016-08-22

We present a room temperature topotactic consolidation of cobalt and zinc constituents into monocrystalline CoZn hydroxide nanosheets, by a localized corrosion of zinc foils with cobalt precursors. By virtue of similar lattice orientation and structure coordination, the hybrid hydroxides amalgamate atomically without phase separation. Importantly, this in situ growth strategy, in combination with configurable percolated nanosheets, renders a high areal density of catalytic sites, immobilized structures, and conductive pathways between the nanosheets and underlying foils-all of which allow monocrystalline CoZn hydroxide nanosheet materials to function as effective electrodes for electrochemical oxygen evolution reactions. This convenient and eco-friendly topotactical transformation approach facilitates high-quality single crystal growth with improved multiphase purity and homogeneity, which can be extended to other transition metals for the fabrication of advanced functional nanocomposites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iridium containing honeycomb Delafossites by topotactic cation exchange.

Science.gov (United States)

Roudebush, John H; Ross, K A; Cava, R J

2016-06-07

We report the structure and magnetic properties of two new iridium-based honeycomb Delafossite compounds, Cu3NaIr2O6 and Cu3LiIr2O6, formed by a topotactic cation exchange reaction. The starting materials Na2IrO3 and Li2IrO3, which are based on layers of IrO6 octahedra in a honeycomb lattice separated by layers of alkali ions, are transformed to the title compounds by a topotactic exchange reaction through heating with CuCl below 450 °C; higher temperature reactions cause decomposition. The new compounds display dramatically different magnetic behavior from their parent compounds - Cu3NaIr2O6 has a ferromagnetic like magnetic transition at 10 K, while Cu3LiIr2O6 retains the antiferromagnetic transition temperature of its parent compound but displays significantly stronger dominance of antiferromagnetic coupling between spins. These results reveal that a surprising difference in the magnetic interactions between the magnetic Ir ions has been induced by a change in the non-magnetic interlayer species. A combination of neutron and X-ray powder diffraction is used for the structure refinement of Cu3NaIr2O6 and both compounds are compared to their parent materials.

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4.

Science.gov (United States)

Jia, Bao-Rui; Qin, Ming-Li; Li, Shu-Mei; Zhang, Zi-Li; Lu, Hui-Feng; Chen, Peng-Qi; Wu, Hao-Yang; Lu, Xin; Zhang, Lin; Qu, Xuan-Hui

2016-06-22

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Synthesis of electronically modified carbon nitride from a processable semiconductor, 3-aminotriazole-1,2,4 oligomer, via a topotactic-like phase transition

OpenAIRE

Savateev, A.; Pronkin, S.; Epping, J.; Willinger, M.; Antonietti, M.; Dontsova, D.

2017-01-01

The thermally induced topotactic transformation of organic polymeric semiconductors is achieved using similarity of the chemical structures of the two C,N,H-containing materials. Namely, the oligomer of 3-aminotriazole-1,2,4 (OATA) is transformed into an electronically modified graphitic carbon nitride (OATA-CN) upon heating at 550 °C. During the transition, the flat band potential of the organic semiconductor is only slightly shifted from -0.11 eV to -0.06 eV, while the optical band gap is s...

Novel topotactically transformed carbon-CoO-NiO-NiCo₂O₄ nanosheet hybrid hetero-structured arrays as ultrahigh performance supercapacitors.

Science.gov (United States)

Wang, Hai; Guo, Junling; Qing, Chen; Sun, Daming; Wang, Bixiao; Tang, Yiwen

2014-08-14

A novel carbon-CoO-NiO-NiCo2O4 integrated electrode has been designed by reducing the hetero-structured NiCo2O4 nanosheet array with C2H2 on the nickel foam at a low temperature of 350 °C. The topotactical transformation from NiCo2O4 to the integrated electrode has been first conceived and investigated. Such unique nanoarchitectures exhibit excellent electrochemical performance with ultrahigh capacitance and desirable cycle life at high rates.

Evolution of nickel sulfide hollow spheres through topotactic transformation

Science.gov (United States)

Wei, Chengzhen; Lu, Qingyi; Sun, Jing; Gao, Feng

2013-11-01

In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment.In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment. Electronic supplementary information (ESI) available: XRD patterns; SEM images and TEM images. See DOI: 10.1039/c3nr03371f

Single-Crystalline Ultrathin Nickel Nanosheets Array from In Situ Topotactic Reduction for Active and Stable Electrocatalysis.

Science.gov (United States)

Kuang, Yun; Feng, Guang; Li, Pengsong; Bi, Yongmin; Li, Yaping; Sun, Xiaoming

2016-01-11

Simultaneously synthesizing and structuring atomically thick or ultrathin 2D non-precious metal nanocrystal may offer a new class of materials to replace the state-of-art noble-metal electrocatalysts; however, the synthetic strategy is the bottleneck which should be urgently solved. Here we report the synthesis of an ultrathin nickel nanosheet array (Ni-NSA) through in situ topotactic reduction from Ni(OH)2 array precursors. The Ni nanosheets showed a single-crystalline lamellar structure with only ten atomic layers in thickness and an exposed (111) facet. Combined with a superaerophobic (low bubble adhesive) arrayed structure the Ni-NSAs exhibited a dramatic enhancement on both activity and stability towards the hydrazine-oxidation reaction (HzOR) relative to platinum. Furthermore, the partial oxidization of Ni-NSAs in ambient atmosphere resulted in effective water-splitting electrocatalysts for the hydrogen-evolution reaction (HER). © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Topotactic Transformation Route to Monodisperse β-NaYF4:Ln(3+) Microcrystals with Luminescence Properties.

Science.gov (United States)

Shao, Baiqi; Feng, Yang; Song, Yan; Jiao, Mengmeng; Lü, Wei; You, Hongpeng

2016-02-15

A novel nonorganic wet route for direct synthesis of uniform hexagonal β-NaYF4:Ln(3+) (Ln = Eu, Tb, Ce/Tb, Yb/Er, and Yb/Tm) microcrystals with various morphologies has been developed wherein the intermediate routine cubic-hexagonal (α → β) phase transfer process was avoided. The morphology can be effectively tuned into hexagonal disc, prism, and novel hierarchical architectures by systematically fine manipulating the Na2CO3/F(-) feeding ratio. It has been found that the routine α → β phase transfer for NaYF4 was not detected during the growth, while NaY(CO3)F2 emerged in the initial reaction stage and fast transformed into β-NaYF4 via a novel topotactic transformation behavior. Detailed structural analysis showed that β-NaYF4 preferred the [001] epitaxial growth direction of NaY(CO3)F2 due to the structural matching of [001]NaY(CO3)F2//[0001]β-NaYF4. Besides, the potential application of the as-prepared products as phosphors is emphasized by demonstrating multicolor emissions including downconversion, upconversion, and energy transfer (Ce-Tb) process by lanthanides doping.

Topotactic reduction of YBa2Cu4O8 under the electron beam

International Nuclear Information System (INIS)

Domenges, B.; Hervieu, M.; Raveau, B.; Karpinski, J.; Kaldis, E.; Rusiecki, S.

1991-01-01

The stability of the high oxygen-pressure 80K-superconductor YBa 2 Cu 4 O 8 under the electron beam was studied by high resolution electron microscopy. Several topotactic reductions were observed for which models are proposed. The most important feature deals with the topotactic transformation of YBa 2 Cu 4 O 8 into the 125-type phase Y 1+x Ba 2+2x Cu 5-3x O 9 (x = 0.14) involving order-disorder phenomena

High-quality EuO thin films the easy way via topotactic transformation

Science.gov (United States)

Mairoser, Thomas; Mundy, Julia A.; Melville, Alexander; Hodash, Daniel; Cueva, Paul; Held, Rainer; Glavic, Artur; Schubert, Jürgen; Muller, David A.; Schlom, Darrell G.; Schmehl, Andreas

2015-07-01

Epitaxy is widely employed to create highly oriented crystalline films. A less appreciated, but nonetheless powerful means of creating such films is via topotactic transformation, in which a chemical reaction transforms a single crystal of one phase into a single crystal of a different phase, which inherits its orientation from the original crystal. Topotactic reactions may be applied to epitactic films to substitute, add or remove ions to yield epitactic films of different phases. Here we exploit a topotactic reduction reaction to provide a non-ultra-high vacuum (UHV) means of growing highly oriented single crystalline thin films of the easily over-oxidized half-metallic semiconductor europium monoxide (EuO) with a perfection rivalling that of the best films of the same material grown by molecular-beam epitaxy or UHV pulsed-laser deposition. As the technique only requires high-vacuum deposition equipment, it has the potential to drastically improve the accessibility of high-quality single crystalline films of EuO as well as other difficult-to-synthesize compounds.

Investigation of Synthesis and Magnetic Properties of Rod-Shaped CoFe2O4 via Precipitation-Topotactic Reaction Employing α-FeOOH and γ-FeOOH As Templates

Science.gov (United States)

Cao, Xiaohui; Dong, Hongfei; Tan, Yuzhuo; Meng, Jinhong

2018-03-01

Rod-shaped CoFe2O4 was prepared by chemical precipitation-topotactic reaction method, and in this preparation needle-like γ-FeOOH and α-FeOOH were synthesized to use as template materials. The evolution of phase and morphology in the process of calcination exhibits that α-FeOOH and γ-FeOOH experienced different routes to form the α-Fe2O3 middle phase with different crystallinity and morphology. The synthesis process of CoFe2O4 revealed that the crystallinity, purity and morphology of CoFe2O4 depend on the α-Fe2O3 middle phase. The magnetic measurement showed that the CoFe2O4 prepared from α-FeOOH has higher saturation magnetization and coercivity, and the crystallinity and morphology may play important roles in achieving a better magnetic performance.

DFT-Based Simulation and Experimental Validation of the Topotactic Transformation of MgAl Layered Double Hydroxides.

Science.gov (United States)

Zhang, Shi-Tong; Dou, Yibo; Zhou, Junyao; Pu, Min; Yan, Hong; Wei, Min; Evans, David G; Duan, Xue

2016-09-05

The thermal topotactic transformation mechanism of MgAl layered double hydroxides (LDHs) is investigated by a combined theoretical and experimental study. Thermogravimetric differential thermal analysis (TG-DTA) results reveal that the LDH phase undergoes four key endothermic events at 230, 330, 450, and 800 °C. DFT calculations show that the LDH decomposes into CO2 and residual O atoms via a monodentate intermediate at 330 °C. At 450 °C, the metal cations almost maintain their original distribution within the LDH(001) facet during the thermal dehydration process, but migrate substantially along the c-axis direction perpendicular to the (001) facet; this indicates that the metal arrangement/dispersion in the LDH matrix is maintained two-dimensionally. A complete collapse of the layered structure occurs at 800 °C, which results in a totally disordered cation distribution and many holes in the final product. The structures of the simulated intermediates are highly consistent with the observed in situ powder XRD data for the MgAl LDH sample calcined at the corresponding temperatures. Understanding the structural topotactic transformation process of LDHs would provide helpful information for the design and preparation of metal/metal oxides functional materials derived from LDH precursors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced photocatalytic activity of SrTiO3 photocatalyst by topotactic preparation

Science.gov (United States)

Cao, Jiafeng; Huang, Xianshan; Liu, Yi; Wu, Jianguang; Ji, Yuexia

2016-11-01

Novel SrTiO3 (ST) photocatalysts with different shapes such as plates, rods and cubes were successfully synthesized based on a topotactic approach. The rod-like ST particles formed in situ at the plates show superior photocatalytic activities towards the decomposition of Rhodamine B than the plate-like and the cubic particles under visible-light irradiation, which could be attributed to the crystal orientation exposing highly active sites accompanied by the crystallite growth in molten salt. The results reveal an effective approach for fabrication of novel photocatalysts of perovskite structure with enhanced photocatalytic activities.

Superaerophobic Ultrathin Ni-Mo Alloy Nanosheet Array from In Situ Topotactic Reduction for Hydrogen Evolution Reaction.

Science.gov (United States)

Zhang, Qian; Li, Pengsong; Zhou, Daojin; Chang, Zheng; Kuang, Yun; Sun, Xiaoming

2017-11-01

Hydrogen evolution reaction (HER) has prospect to becoming clean and renewable technology for hydrogen production and Ni-Mo alloy is among the best HER catalysts in alkaline electrolytes. Here, an in situ topotactic reduction method to synthesize ultrathin 2D Ni-Mo alloy nanosheets for electrocatalytic hydrogen evolution is reported. Due to its ultrathin structure and tailored composition, the as-synthesized Ni-Mo alloy shows an overpotential of 35 mV to reach a current density of 10 mA cm -2 , along with a Tafel slope of 45 mV decade -1 , demonstrating a comparable intrinsic activity to state-of-art commercial Pt/C catalyst. Besides, the vertically aligned assemble structure of the 2D NiMo nanosheets on conductive substrate makes the electrode "superaerophobic," thus leading to much faster bubble releasing during HER process and therefore shows faster mass transfer behavior at high current density as compared with drop drying Pt/C catalyst on the same substrate. Such in situ topotactic conversion finds a way to design and fabricate low-cost, earth-abundant non-noble metal based ultrathin 2D nanostructures for electrocatalytic issues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topotactic transformations of superstructures: from thin films to two-dimensional networks to nested two-dimensional networks.

Science.gov (United States)

Guo, Chuan Fei; Cao, Sihai; Zhang, Jianming; Tang, Haoying; Guo, Shengming; Tian, Ye; Liu, Qian

2011-06-01

Design and synthesis of super-nanostructures is one of the key and prominent topics in nanotechnology. Here we propose a novel methodology for synthesizing complex hierarchical superstructures using sacrificial templates composed of ordered two-dimensional (2D) nanostructures through lattice-directed topotactic transformations. The fabricated superstructures are nested 2D orthogonal Bi(2)S(3) networks composed of nanorods. Further investigation indicates that the lattice matching between the product and sacrificial template is the dominant mechanism for the formation of the superstructures, which agrees well with the simulation results based on an anisotropic nucleation and growth analysis. Our approach may provide a promising way toward a lattice-directed nonlithographic nanofabrication technique for making functional porous nanoarchitectures and electronic devices. © 2011 American Chemical Society

Enhanced low-temperature thermoelectrical properties of BiTeCl grown by topotactic method

International Nuclear Information System (INIS)

Jacimovic, J.; Mettan, X.; Pisoni, A.; Gaal, R.; Katrych, S.; Demko, L.; Akrap, A.; Forro, L.; Berger, H.; Bugnon, P.; Magrez, A.

2014-01-01

We developed a topotactic strategy to grow BiTeCl single crystals. Structural characterization by means of X-ray diffraction was performed, and the high crystallinity of the material was proven. Measurements of the thermoelectrical coefficients electrical resistivity, thermoelectric power and thermal conductivity show an enhanced room temperature power factor of 20 μW cm −1 K −2 . The high value of the figure of merit (ZT = 0.17) confirms that BiTeCl is a promising material for engineering in thermoelectric applications at low temperature

Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol.

Science.gov (United States)

Zhang, Jinying; Wang, Rui; Zhu, Xi; Pan, Aifei; Han, Chenxiao; Li, Xin; Dan Zhao; Ma, Chuansheng; Wang, Wenjun; Su, Haibin; Niu, Chunming

2017-09-25

Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet-visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires.T-carbon is a previously predicted but so far unobserved allotrope of carbon, with a crystal structure similar to diamond, but with each atomic lattice position replaced by a carbon tetrahedron. Here, the authors produce T-carbon nanowires via laser-irradiating a suspension of carbon nanotubes in methanol.

Synthesis and Properties of Layered-Structured Mn5O8 Nanorods

DEFF Research Database (Denmark)

Gao, Tao; Norby, Poul; Krumeich, Frank

2010-01-01

Mn5O8 nanorods were prepared by a topotactic conversion of γ-MnOOH nanorod precursors in nitrogen at 400 °C. The as-prepared Mn5O8 nanorods crystallized in a monoclinic structure (space group C2/m) with unit cell dimensions a = 10.3784(2) Å, b = 5.7337(7) Å, c = 4.8668(6) Å, and β = 109.491(6)°, ...

Topotactic changes on η-Mo4O11 caused by biased atomic force microscope tip and cw-laser

International Nuclear Information System (INIS)

Borovšak, Miloš; Šutar, Petra; Goreshnik, Evgeny; Mihailovic, Dragan

2015-01-01

Highlights: • We report influencing electronic properties of η-Mo 4 O 11 . • With the biased AFM tip we induce the surface potential changes on η-Mo 4 O 11 . • We used cw-laser to induced similar effect on surface potential on η-Mo 4 O 11 . • We do not influence the surface and topography of the samples. • No change in topography of samples indicates the topotactic transformation. - Abstract: We present topotactic changes on Mo 4 O 11 crystals induced by a biased atomic force microscope tip and continuous laser. The transformation does not change the topography of the samples, while the surface potential shows remarkable changes on areas where the biased AFM tip was applied. No structural changes were observed by Raman spectroscopy, but AFM scans revealed changes to surface potential due to laser illumination. The observed phenomenon could be potentially useful for memristive memory devices considering the fact that properties of other molybdenum oxides vary from metallic to insulators.

Topotactic conversion route to mesoporous quasi-single-crystalline Co{sub 3}O{sub 4} nanobelts with optimizable electrochemical performance

Energy Technology Data Exchange (ETDEWEB)

Tian, Li [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry State Key Laboratory of Optoelectronic Materials and Technology School of Chemistry and Chemical Engineering School of Physics and Engineering Sun Yat-Sen University Guangzhou, 510275 (China); School of Chemistry and Chemical Engineering, Hunan University of Science and Technology Xiangtan, 411201 (China); Zou, Hongli; Fu, Junxiang; Yang, Xianfeng; Wang, Yi; Fu, Xionghui; Liang, Chaolun; Wu, Mingmei; Shen, Pei Kang [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry State Key Laboratory of Optoelectronic Materials and Technology School of Chemistry and Chemical Engineering School of Physics and Engineering Sun Yat-Sen University Guangzhou, 510275 (China); Guo, Hongliang; Gao, Qiuming [State Key Laboratory of High Performance Ceramics and Superfine Microstructures Shanghai Institute of Ceramics, Graduate School, Chinese Academy of Sciences 1295 Dingxi Rd., Shanghai 200050 (China)

2010-02-22

The growth of mesoporous quasi-single-crystalline Co{sub 3}O{sub 4} nanobelts by topotactic chemical transformation from {alpha}-Co(OH){sub 2} nanobelts is realized. During the topotactic transformation process, the primary {alpha}-Co(OH){sub 2} nanobelt frameworks can be preserved. The phases, crystal structures, morphologies, and growth behavior of both the precursory and resultant products are characterized by powder X-ray diffraction (XRD), electron microscopy - scanning electron (SEM) and transmission electron (TEM) microscopy, and selected area electron diffraction (SAED). Detailed investigation of the formation mechanism of the porous Co{sub 3}O{sub 4} nanobelts indicates topotactic nucleation and oriented growth of textured spinel Co{sub 3}O{sub 4} nanowalls (nanoparticles) inside the nanobelts. Co{sub 3}O{sub 4} nanocrystals prefer [0001] epitaxial growth direction of hexagonal {alpha}-Co(OH){sub 2} nanobelts due to the structural matching of [0001] {alpha}-Co(OH){sub 2}//[111] Co{sub 3}O{sub 4}. The surface-areas and pore sizes of the spinel Co{sub 3}O{sub 4} products can be tuned through heat treatment of {alpha}-Co(OH){sub 2} precursors at different temperatures. The galvanostatic cycling measurement of the Co{sub 3}O{sub 4} products indicates that their charge-discharge performance can be optimized. In the voltage range of 0.0-3.0 V versus Li{sup +}/Li at 40 mA g{sup -1}, reversible capacities of a sample consisting of mesoporous quasi-single-crystalline Co{sub 3}O{sub 4} nanobelts can reach up to 1400 mA h g{sup -1}, much larger than the theoretical capacity of bulk Co{sub 3}O{sub 4} (892 mA h g{sup -1}). (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Textures of iron oxide ores by neutron diffraction and topotactical relation

International Nuclear Information System (INIS)

Wagner, F.; Esling, C.; Baro, R.; Englander, M.

1977-01-01

Two samples are cut from a polycrystalline haematite block. The first one is directly submitted to texture analysis by neutron diffraction, whereas the second one is first reduced into magnetite. The comparison of both textures is in agreement with a topotactical relationship previously reported for monocrystals. (orig.) [de

Low-temperature solvothermal approach to the synthesis of La4Ni3O8 by topotactic oxygen deintercalation.

Science.gov (United States)

Blakely, Colin K; Bruno, Shaun R; Poltavets, Viktor V

2011-07-18

A chimie douce solvothermal reduction method is proposed for topotactic oxygen deintercalation of complex metal oxides. Four different reduction techniques were employed to qualitatively identify the relative reduction activity of each including reduction with H(2) and NaH, solution-based reduction using metal hydrides at ambient pressure, and reduction under solvothermal conditions. The reduction of the Ruddlesden-Popper nickelate La(4)Ni(3)O(10) was used as a test case to prove the validity of the method. The completely reduced phase La(4)Ni(3)O(8) was produced via the solvothermal technique at 150 °C--a lower temperature than by other more conventional solid state oxygen deintercalation methods.

Topotactic reduction and phase transitions in (T,T′ La1.8Pr0.2CuO4

Directory of Open Access Journals (Sweden)

M.I. Houchati

2017-05-01

The X-ray powder diffraction data have revealed that this cuprate is crystallized with the so-called “pseudo-S” type structure, showing a monoclinic symmetry and space group A2/m. Concerning the EPR measurements, they have shown the presence of Cu2+ cation and a hyperfine structure suggesting a pronounced hybridization of the copper–oxygen bond. Finally, X-ray diffraction has demonstrated that the obtained La1.8Pr0.2CuO3.5, heated in oxygen at 420 °C, turns topotactically into La1.8Pr0.2CuO4 with a T′-type structure (I4/mmm.

The topotactic reduction of Sr3Fe2O5Cl2-square planar Fe(II) in an extended oxyhalide.

Science.gov (United States)

Dixon, Edward; Hayward, Michael A

2010-10-18

The topotactic reduction of the oxychloride Sr(3)Fe(2)O(5)Cl(2) with LiH results in the formation of Sr(3)Fe(2)O(4)Cl(2). Neutron powder diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts a body-centered tetragonal crystal structure (I4/mmm, a = 4.008(1) Å, c = 22.653(1) Å at 388 K) with anion vacancies located within the SrO layer of the phase. This leads to a structure consisting of infinite sheets of corner-sharing Fe(II)O(4) square planes. Variable-temperature neutron diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts G-type antiferromagnetic order below T(N) ∼ 378(10) K with an ordered moment of 2.81(9) μ(B) per iron center at 5 K consistent with the presence of high-spin Fe(II). The observed structural and chemical selectivity of the reduction reaction is discussed. The contrast between the structure of Sr(3)Fe(2)O(4)Cl(2) and the isoelectronic all-oxide analogue (Sr(3)Fe(2)O(5)) suggests that by careful selection of substrate phases, the topotactic reduction of complex transition metal oxychlorides can lead to the preparation of novel anion-deficient phases with unique transition metal-oxygen sublattices which cannot be prepared via the reduction of all-oxide substrates.

Electrochemical Li Topotactic Reaction in Layered SnP3 for Superior Li-Ion Batteries

Science.gov (United States)

Park, Jae-Wan; Park, Cheol-Min

2016-10-01

The development of new anode materials having high electrochemical performances and interesting reaction mechanisms is highly required to satisfy the need for long-lasting mobile electronic devices and electric vehicles. Here, we report a layer crystalline structured SnP3 and its unique electrochemical behaviors with Li. The SnP3 was simply synthesized through modification of Sn crystallography by combination with P and its potential as an anode material for LIBs was investigated. During Li insertion reaction, the SnP3 anode showed an interesting two-step electrochemical reaction mechanism comprised of a topotactic transition (0.7-2.0 V) and a conversion (0.0-2.0 V) reaction. When the SnP3-based composite electrode was tested within the topotactic reaction region (0.7-2.0 V) between SnP3 and LixSnP3 (x ≤ 4), it showed excellent electrochemical properties, such as a high volumetric capacity (1st discharge/charge capacity was 840/663 mA h cm-3) with a high initial coulombic efficiency, stable cycle behavior (636 mA h cm-3 over 100 cycles), and fast rate capability (550 mA h cm-3 at 3C). This layered SnP3 anode will be applicable to a new anode material for rechargeable LIBs.

Mechanism of the Topotactic Formation of gamma-Zirconium Phosphate Covalently Pillared with Diphosphonate Groups.

Science.gov (United States)

Alberti, G.; Giontella, E.; Murcia-Mascarós, S.; Vivani, R.

1998-09-07

The topotactic reaction of gamma-ZrPO(4)[O(2)P(OH)(2)].2H(2)O (gamma-ZrP) with benzenediphosphonic acid was examined in water and in acetone-water mixtures. This reaction was found to take place in water only on the external surface of the microcrystals, and pillared compounds were never obtained, even after very long reaction times. On the contrary, covalently pillared compounds were quickly obtained in acetone-water mixtures. The mechanism of the latter topotactic reaction was investigated by determining the rate of the phosphate groups released and the rate of the benzenediphosphonates taken up by gamma-ZrP over a long time (50 days). These data showed that pillared derivatives of gamma-ZrP can be obtained because colloidal dispersions of exfoliated lamellae are formed in acetone-water mixtures. The diphosphonate group acts initially as a monovalent species, replacing only one dihydrogen phosphate group on the surface of the exfoliated gamma-lamellae. The colloidal and partially derivatized lamellae thus formed can interact with each other by forming polylamellar pillared systems. When the number of pillared lamellae exceeds a given value (usually 5-6), flocculation of the colloidal gamma-ZrP takes place. Topotactic reactions between packets of pillared lamellae may also continue in the flocculated system. Therefore, the average number of the pillared lamellae slowly increases over time.

Synthesis and X-ray Powder Structure of a New Pillared Layered Cadmium Phosphonate, Giving Evidence that the Intercalation of Alkylamines into Cd(O(3)PR).H(2)O Is Topotactic.

Science.gov (United States)

Fredoueil, Florence; Massiot, Dominique; Janvier, Pascal; Gingl, Franz; Bujoli-Doeuff, Martine; Evain, Michel; Clearfield, Abraham; Bujoli, Bruno

1999-04-19

A new pillared layered phosphonate, cadmium 2-aminoethylphosphonate, Cd(O(3)PC(2)H(4)NH(2)) (1), has been synthesized, and its structure was solved ab initio from X-ray powder diffraction data and refined by Rietveld methods. Compound 1 is orthorhombic: space group Pna2(1), a = 15.4643(2) Å, b = 5.16512(7) Å, c = 6.27650(8) Å, and Z = 4. Its layer arrangement is similar to that in Cd(O(3)PR).H(2)O, except that the water molecule coordinated to cadmium in Cd(O(3)PR).H(2)O is replaced by the nitrogen atom from the amino ends of the ethyl chains borne by phosphorus of the upper and lower layers. The strong similarity of the IR, (31)P, and (113)Cd NMR data for Cd(O(3)PC(2)H(4)NH(2)) and Cd(O(3)PCH(3)).n-NH(2)C(4)H(9) clearly shows the topotactic character of the intercalation of n-alkylamines in the dehydrated form of Cd(O(3)PR).H(2)O to yield Cd(O(3)PR).n-NH(2)R'.

Coexistence of an anatase/TiO2(B) heterojunction and an exposed (001) facet in TiO2 nanoribbon photocatalysts synthesized via a fluorine-free route and topotactic transformation.

Science.gov (United States)

Wang, Changhua; Zhang, Xintong; Liu, Yichun

2014-05-21

In this work, we report a novel approach to fabricate hierarchical TiO2 microspheres (HTMS) assembled by ultrathin nanoribbons where an anatase/TiO2(B) heterojunction and high energy facet coexist. The as-adopted approach involves (1) nonaqueous solvothermal treatment of a mixture of tetrabutyl titanate and acetic acid and (2) topotactical transformation into HTMS via thermal annealing. By this approach, the TiO2(B) phase usually synthesized from an alkaline treatment route could be initially formed. Subsequently, phase transition from TiO2(B) to anatase TiO2 occurs upon thermal treatment. It is demonstrated that such phase transition is accompanied by crystallographic orientation along the c-axis of anatase and TiO2(B) crystals, resulting in not only a coherent interface between two phases but also oriented attachment of anatase mesocrystals along the [001] direction, and finally high-energy (001) facet exposure. Interestingly, this work provides an alternative fluorine-free route for the synthesis of TiO2 crystals with high-energy (001) facet exposure. The structural analysis reveals that lattice-match induced topotactic transformation from TiO2(B) to anatase is the sole reason for the (001) facet exposure of anatase TiO2. The photocatalytic test for acetaldehyde decomposition shows that HTMS with anatase/TiO2(B) heterojunction and high-energy (001) facet exhibits superior photocatalytic efficiency compared with the relevant commercial product P25, which can be ascribed to the synergistic effect of large surface area, anatase/TiO2(B) heterojunction as well as high-energy facet exposure.

Coexistence of an anatase/TiO2(B) heterojunction and an exposed (001) facet in TiO2 nanoribbon photocatalysts synthesized via a fluorine-free route and topotactic transformation

Science.gov (United States)

Wang, Changhua; Zhang, Xintong; Liu, Yichun

2014-04-01

In this work, we report a novel approach to fabricate hierarchical TiO2 microspheres (HTMS) assembled by ultrathin nanoribbons where an anatase/TiO2(B) heterojunction and high energy facet coexist. The as-adopted approach involves (1) nonaqueous solvothermal treatment of a mixture of tetrabutyl titanate and acetic acid and (2) topotactical transformation into HTMS via thermal annealing. By this approach, the TiO2(B) phase usually synthesized from an alkaline treatment route could be initially formed. Subsequently, phase transition from TiO2(B) to anatase TiO2 occurs upon thermal treatment. It is demonstrated that such phase transition is accompanied by crystallographic orientation along the c-axis of anatase and TiO2(B) crystals, resulting in not only a coherent interface between two phases but also oriented attachment of anatase mesocrystals along the [001] direction, and finally high-energy (001) facet exposure. Interestingly, this work provides an alternative fluorine-free route for the synthesis of TiO2 crystals with high-energy (001) facet exposure. The structural analysis reveals that lattice-match induced topotactic transformation from TiO2(B) to anatase is the sole reason for the (001) facet exposure of anatase TiO2. The photocatalytic test for acetaldehyde decomposition shows that HTMS with anatase/TiO2(B) heterojunction and high-energy (001) facet exhibits superior photocatalytic efficiency compared with the relevant commercial product P25, which can be ascribed to the synergistic effect of large surface area, anatase/TiO2(B) heterojunction as well as high-energy facet exposure.

Topotactic changes on η-Mo{sub 4}O{sub 11} caused by biased atomic force microscope tip and cw-laser

Energy Technology Data Exchange (ETDEWEB)

Borovšak, Miloš, E-mail: milos.borovsak@ijs.si [Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Faculty for Mathematics and Physics, Jadranska ulica 19, 1000 Ljubljana (Slovenia); Šutar, Petra; Goreshnik, Evgeny [Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Mihailovic, Dragan [Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); International Postgraduate School Jožef Stefan, Jamova cesta 39, 1000 Ljubljana (Slovenia)

2015-11-01

Highlights: • We report influencing electronic properties of η-Mo{sub 4}O{sub 11}. • With the biased AFM tip we induce the surface potential changes on η-Mo{sub 4}O{sub 11}. • We used cw-laser to induced similar effect on surface potential on η-Mo{sub 4}O{sub 11}. • We do not influence the surface and topography of the samples. • No change in topography of samples indicates the topotactic transformation. - Abstract: We present topotactic changes on Mo{sub 4}O{sub 11} crystals induced by a biased atomic force microscope tip and continuous laser. The transformation does not change the topography of the samples, while the surface potential shows remarkable changes on areas where the biased AFM tip was applied. No structural changes were observed by Raman spectroscopy, but AFM scans revealed changes to surface potential due to laser illumination. The observed phenomenon could be potentially useful for memristive memory devices considering the fact that properties of other molybdenum oxides vary from metallic to insulators.

Topotactic Solid-State Metal Hydride Reductions of Sr2MnO4.

Science.gov (United States)

Hernden, Bradley C; Lussier, Joey A; Bieringer, Mario

2015-05-04

We report novel details regarding the reactivity and mechanism of the solid-state topotactic reduction of Sr2MnO4 using a series of solid-state metal hydrides. Comprehensive details describing the active reducing species are reported and comments on the reductive mechanism are provided, where it is shown that more than one electron is being donated by H(-). Commonly used solid-state hydrides LiH, NaH, and CaH2, were characterized in terms of reducing power. In addition the unexplored solid-state hydrides MgH2, SrH2, and BaH2 are evaluated as potential solid-state reductants and characterized in terms of their reductive reactivities. These 6 group I and II metal hydrides show the following trend in terms of reactivity: MgH2 < SrH2 < LiH ≈ CaH2 ≈ BaH2 < NaH. The order of the reductants are discussed in terms of metal electronegativity and bond strengths. NaH and the novel use of SrH2 allowed for targeted synthesis of reduced Sr2MnO(4-x) (0 ≤ x ≤ 0.37) phases. The enhanced control during synthesis demonstrated by this soft chemistry approach has allowed for a more comprehensive and systematic evaluation of Sr2MnO(4-x) phases than previously reported phases prepared by high temperature methods. Sr2MnO3.63(1) has for the first time been shown to be monoclinic by powder X-ray diffraction and the oxidative monoclinic to tetragonal transition occurs at 450 °C.

Fabrication of ruthenium metal nanosheets via topotactic metallization of exfoliated ruthenate nanosheets.

Science.gov (United States)

Fukuda, Katsutoshi; Sato, Jun; Saida, Takahiro; Sugimoto, Wataru; Ebina, Yasuo; Shibata, Tatsuo; Osada, Minoru; Sasaki, Takayoshi

2013-03-04

The metallization behavior of molecularly thin RuO2 nanosheets obtained from complete delamination of layered ruthenates was studied. Interestingly, the RuO2 nanosheets in a monolayer state topotactically transformed into a single layer of Ru atoms, i.e., ruthenium metal nanosheets, which can be regarded as a new family of nanosized metals.

Topotactic dehydration of the lamellar oxide HK2Ti5NbO14 x H2O: the oxide K4Ti10Nb2O27

International Nuclear Information System (INIS)

Grandin, A.; Borel, M.M.; Hervieu, M.; Raveau, B.

1987-01-01

The lamellar oxide HK 2 Ti 5 NbO 14 x H 2 O can be topotactically dehydrated to K 4 Ti 10 Nb 2 O 27 . Electron diffraction and X-ray diffraction studies of this phase lead to a monoclinic cell with the parameters a = 17.005, b = 3.78, c = 9.01 A and β 92.14 0 . Diffusion streaks on the electron diffraction patterns indicate disorder whereas the existence of two sets of lattices on the same crystal give evidence of the topotactic character of the reaction. A structural model is proposed for K 4 Ti 10 Nb 2 O 27 , which corresponds to the intergrowth of K 3 TiNbO 14 layers with the K 2 Ti 6 O 13 tunnel structure. The possibility of formation of various intergrowths such as (KTi 5 NbO 13 )/sub n/ (HK 2 Ti 5 NbO 14 )/sub n/' is suggested

Nitrides and carbides of molybdenum and tungsten with high specific-surface area: their synthesis, structure, and catalytic properties

International Nuclear Information System (INIS)

Volpe, L.

1985-01-01

Temperature-programmed reactions between trioxides of molybdenum or tungsten and ammonia provide a new method to synthesize dimolybdenum and ditungsten nitrides with specific surface areas to two-hundred-and-twenty and ninety-one square meters per gram, respectively. These are the highest values on record for any unsupported metallic powders. They correspond to three-four nonometer particles. The reaction of molybdenum trioxide with ammonia is topotactic in the sense that one-zero-zero planes of dimolybdenum nitride are parallel to zero-one-zero planes of molybdenum trioxide. As the trioxide transforms, it passes through an oxynitride intermediate with changing bulk structure and increasing surface area and extent of reduction. The nitride product consists of platelets, pseudomorphous with the original trioxide, which can be regarded as highly porous defect single crystals. By treating small particles of dimolybdenum or ditungsten nitride with methane-dihydrogen mixtures it is possible to replace interstitial nitrogen atoms by carbon atoms, without sintering, and thus to prepare carbides of molybdenum and tungsten with very high specific surface areas. Molybdenum nitride powders catalyze ammonia synthesis. A pronounced increase in the catalytic activity with increasing particle size confirms the structure-sensitive character of this reaction

The synthesis and complex anion-vacancy ordered structure of La0.33Sr0.67MnO2.42

International Nuclear Information System (INIS)

Dixon, Edward; Hadermann, Joke; Hayward, Michael A.

2011-01-01

The low-temperature topotactic reduction of La 0.33 Sr 0.67 MnO 3 with NaH results in the formation of La 0.33 Sr 0.67 MnO 2.42 . A combination of neutron powder and electron diffraction data show that La 0.33 Sr 0.67 MnO 2.42 adopts a novel anion-vacancy ordered structure with a 6-layer OOTOOT' stacking sequence of the 'octahedral' and tetrahedral layers (Pcmb, a=5.5804(1) A, b=23.4104(7) A, c=11.2441(3) A). A significant concentration of anion vacancies at the anion site, which links neighbouring 'octahedral' layers means that only 25% of the 'octahedral' manganese coordination sites actually have 6-fold MnO 6 coordination, the remainder being MnO 5 square-based pyramidal sites. The chains of cooperatively twisted apex-linked MnO 4 tetrahedra adopt an ordered -L-R-L-R- arrangement within each tetrahedral layer. This is the first published example of a fully refined structure of this type which exhibits such intralayer ordering of the twisted tetrahedral chains. The rationale behind the contrasting structures of La 0.33 Sr 0.67 MnO 2.42 and other previously reported reduced La 1-x Sr x MnO 3-y phases is discussed. - Graphical Abstract: The topotactic reduction of the perovskite phase La 0.33 Sr 0.67 MnO 3 with NaH yields La 0.33 Sr 0.67 MnO 2.42(3) , which adopts a novel anion vacancy ordered structure with a 6-layer OOTOOT' stacking sequence of the 'octahedral' and tetrahedral layers. The anion site that links the neighbouring octahedral layers is partially occupied so only 25% of the 'octahedral' manganese sites actually have 6-fold MnO 6 coordination. Highlights: → Topotactic reduction with NaH to form a mixed valent Mn 2+ /Mn 3+ phase. → Novel layered anion-vacancy ordered structure. → Comparison to related brownmillerite structure types.

Topotactic changes on η-Mo4O11 caused by biased atomic force microscope tip and cw-laser

Science.gov (United States)

Borovšak, Miloš; Šutar, Petra; Goreshnik, Evgeny; Mihailovic, Dragan

2015-11-01

We present topotactic changes on Mo4O11 crystals induced by a biased atomic force microscope tip and continuous laser. The transformation does not change the topography of the samples, while the surface potential shows remarkable changes on areas where the biased AFM tip was applied. No structural changes were observed by Raman spectroscopy, but AFM scans revealed changes to surface potential due to laser illumination. The observed phenomenon could be potentially useful for memristive memory devices considering the fact that properties of other molybdenum oxides vary from metallic to insulators.

Recurrent intergrowths in the topotactic reduction process of LaBaCuCoO5.2.

Science.gov (United States)

Ruiz-González, Luisa; Boulahya, Khalid; Parras, Marina; Alonso, José; González-Calbet, José M

2002-12-16

A new perovskite-related oxide with the LaBaCuCoO5.2 composition has been stabilised. Its structure can be described as formed by the recurrent intergrowth of two alternating blocks of YBaCuFeO5 (2ac, i.e., two-fold perovskite superlattice) and YBa2Fe3O8 (3ac) structural types. From the starting material LaBaCuCoO5.2-delta (delta = 0), the rigorous control of the oxygen content has allowed the stabilisation of three new five fold perovskite-related superstructures with the compositions delta = 0.4, 0.8 and 1.1, which can also be described as recurrent intergrowths of two blocks showing 2ac and 3ac periodicity. The reduction process takes place through the 3ac periodic blocks, when 0 topotactic reaction, since their basic structure is kept through the reduction process.

Topotactic conversion of β-helix-layered silicate into AST-type zeolite through successive interlayer modifications.

Science.gov (United States)

Asakura, Yusuke; Takayama, Ryosuke; Shibue, Toshimichi; Kuroda, Kazuyuki

2014-02-10

AST-type zeolite with a plate morphology can be synthesized by topotactic conversion of a layered silicate (β-helix-layered silicate; HLS) by using N,N-dimethylpropionamide (DPA) to control the layer stacking of silicate layers and the subsequent interlayer condensation. Treatment of HLS twice with 1) hydrochloric acid/ethanol and 2) dimethylsulfoxide (DMSO) are needed to remove interlayer hydrated Na ions and tetramethylammonium (TMA) ions in intralayer cup-like cavities (intracavity TMA ions), both of which are introduced during the preparation of HLS. The utilization of an amide molecule is effective for the control of the stacking sequence of silicate layers. This method could be applicable to various layered silicates that cannot be topotactically converted into three-dimensional networks by simple interlayer condensation by judicious choice of amide molecules. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topotactic Metal-Insulator Transition in Epitaxial SrFeO x Thin Films

International Nuclear Information System (INIS)

Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; Kim, Minu; Kang, Tae Dong

2017-01-01

Multivalent transition metal oxides provide fascinating and rich physics related to oxygen stoichiometry. In particular, the adoptability of various valence states of transition metals enables perovskite oxides to display mixed (oxygen) ionic and electronic conduction and catalytic activity useful in many practical applications, including solid-oxide fuel cells (SOFCs), rechargeable batteries, gas sensors, and memristive devices. For proper realization of the ionic conduction and catalytic activity, it is essential to understand the reversible oxidation and reduction process, which is governed by oxygen storage/release steps in oxides. Topotactic phase transformation facilitates the redox process in perovskites with specific oxygen vacancy ordering by largely varying the oxygen concentration of a material without losing the lattice framework. The concentration and diffusion of oxide ions (O 2– ), the valence state of the transition metal cations, and the thermodynamic structural integrity together provide fundamental understanding and ways to explicitly control the redox reaction.[6] In addition, it offers an attractive route for tuning the emergent physical properties of transition metal oxides, via strong coupling between the crystal lattice and electronic structure.

Synthesis and crystal structure of the γ-modifications of US2 and USe2

International Nuclear Information System (INIS)

Kohlmann, H.; Beck, H.P.

1997-01-01

We report on γ-US 2 and γ-USe 2 which may be synthesized by a presumably topotactic reaction from the corresponding U 3 X 5 compounds and elementary chalcogen. γ-USe 2 can also be prepared by a high pressure transformation of α-USe 2 at 4 GPa and 773 K. The structure of the γ phases could be determined and refined by a Rietveld procedure from powder date. They crystallize in an anti-Fe 2 P-type arrangement. Unusual features of these structures and a possible reaction mechanism for the formation of the compounds are discussed. (orig.)

Layered rare-earth hydroxide nanocones with facile host composition modification and anion-exchange feature: topotactic transformation into oxide nanocones for upconversion.

Science.gov (United States)

Zhong, Yishun; Chen, Gen; Liu, Xiaohe; Zhang, Dan; Zhang, Ning; Li, Junhui; Liang, Shuquan; Ma, Renzhi; Qiu, Guanzhou

2017-06-22

Conical structures with hollow interiors, namely, nanocones (NCs), may exhibit better carrier transport properties than nanorods or nanotubes, which make them promising candidates for potential applications in optical/display devices, electronics and optoelectronics. Generally, conical structures belong to a metastable state between lamellar and tubular forms due to the extreme curvature causing the increase of internal strain energy. Therefore, it is very difficult to prepare NCs in high yield and purity under mild conditions. Here we firstly demonstrate a general strategy for the synthesis of layered rare-earth hydroxide (LRH) NCs intercalating dodecyl sulfate anions (C 12 H 25 SO 4 - , DS - ) using hexamethylenetetramine (C 6 H 12 N 4 , HMT) hydrolysis. The rare-earth cations (RE 3+ ) in the host layer can be conveniently modified and/or doped, resulting in a large family of monometallic (Y, Tb, Er), bi- (Y-Tb, Y-Er) and even tri-metallic (Y-Yb-Er) LRH NCs with adjustable ratios. Moreover, the DS - -intercalated LRH NCs can be readily modified with various inorganic or organic anions (e.g., NO 3 - , Cl - , and CH 3 COO - , etc.) through a conventional anion-exchange procedure, and the original conical morphology can be perfectly maintained. The anion-exchanged product, for example, NO 3 - -intercalated NCs, can be more easily and topotactically transformed into oxide NCs than the original DS - -intercalated form, exempt from the formation of rare-earth oxysulfates induced by the combustion of interlayer DS anions. Taking advantage of this protocol, tri-metallic (Y-Yb-Er) LRH NCs were anion-exchanged into the NO 3 - -intercalated form and subsequently calcined into Y 2 O 3 :Yb,Er oxide NCs, which showed efficient upconversion photoluminescence properties. The current strategy may become a general method for the designed synthesis of other related hydroxide and oxide NCs for a wide range of potential applications.

Topotactic synthesis of the overlooked multilayer silicene intercalation compound SrSi2.

Science.gov (United States)

Tokmachev, A M; Averyanov, D V; Karateev, I A; Parfenov, O E; Vasiliev, A L; Yakunin, S N; Storchak, V G

2016-09-28

Silicene, a 2D honeycomb lattice of Si atoms similar to graphene, is expected to be a platform for nanoelectronics and home to novel quantum phenomena. Unlike graphene, free-standing silicene is notoriously difficult to stabilize, while strong hybridization of silicene with substrates destroys its desirable properties. On the other hand, Dirac cones of silicene are effectively realized in a bulk - stoichiometric ionic multilayer silicene intercalation compound CaSi2. Besides, a number of new 2D silicene-based materials are synthesized employing CaSi2 as a precursor. However, the rather complex atomic structure of CaSi2 and fresh opportunities of physical and chemical breakthroughs drive the search for alternative compounds with silicene networks. Here, a new polymorph of SrSi2 is synthesized, enjoying both the structure of intercalated multilayer silicene and the simplest possible stacking of silicene sheets. The MBE-quality synthesis accomplished on Si(001) and Si(111) surfaces leads to epitaxial films of SrSi2 with orientation controlled by the substrate, as revealed by XRD, RHEED and electron microscopy studies. The structural SrSi2/Si relation is mirrored in the transport properties of the films.

Topotactic reduction of YBaCo2O5 and LaBaCo2O5: square-planar Co(I) in an extended oxide.

Science.gov (United States)

Seddon, James; Suard, Emmanuelle; Hayward, Michael A

2010-03-03

The low-temperature reduction of YBaCo(2)O(5) and LaBaCo(2)O(5) with NaH to form YBaCo(2)O(4.5) and YBaCo(2)O(4.25), respectively, demonstrates that the structures of anion-deficient materials formed by such topotactic reductions can be directed by the ordering and identity of the A-site cations. YBaCo(2)O(4.5) adopts a structure consisting of a corner-shared network of square-based pyramidal CoO(5) and distorted tetrahedral CoO(4) units. The structure of LaBaCoO(4.25) is more complex, consisting of an array of square-based pyramidal CoO(5), distorted tetrahedral CoO(4), and square planar CoO(4) units. Magnetic susceptibility and variable-temperature neutron diffraction data reveal that YBaCo(2)O(4.5) adopts a G-type antiferromagnetically ordered structure below T(N) approximately 280 K. LaBaCo(2)O(4.25) also adopts antiferromagnetic order (T(N) approximately 325 K) with ordered moments consistent with the presence of square-planar, low-spin, s = 0, Co(I) centers. A detailed analysis reveals that the different anion vacancy ordered structures adopted by the two REBaCo(2)O(5-x) phases are directed by the relative sizes and ordering of the La(3+) and Y(3+) cations. This suggests that ordered arrangements of A-cations can be used to direct the anion vacancy order in topotactically reduced phases, allowing the preparation of novel metal-oxygen networks containing unusual transition metal coordination environments.

Ln28Ti2O7 (Ln = La, Nd, Sm, Gd): a novel series of defective Ruddlesden–Popper phases formed by topotactic dehydration of HLnTiO4

OpenAIRE

Thangadurai, V; Subbanna, GN; Gopalakrishnan, J

1998-01-01

Topotactic dehydration of HLnTiO4 (Ln = La, Nd, Sm or Gd) around 480–500 °C yields a new series of metastable layered perovskite oxides, Ln28Ti2O7, that possess a defective Sr3Ti2O7 structure, where the cubooctahedral sites within the double-perovskite layers are most likely vacant.

The radiation-induced topotactic conversion of di-para anthracene to anthracene: an electron microscopic study

International Nuclear Information System (INIS)

Parkinson, G.M.; Goringe, M.J.; Thomas, J.M.

1977-01-01

A study was made of single crystals of di-para anthracene, the product of photodimerisation of anthracene. This undergoes an electron-induced topotactic conversion to anthracene, and the study of this reaction using low temperature TEM enabled the identification of separate stages in the conversion and the elucidation of probable mechanistic routes. (author)

Synthesis of ultra-long cadmium telluride nanotubes via combinational chemical transformation

Energy Technology Data Exchange (ETDEWEB)

Park, Kee-Ryung; Cho, Hong-Baek; Choa, Yong-Ho, E-mail: choa15@hanyang.ac.kr

2017-03-01

Synthesis of high-throughput cadmium telluride (CdTe) nanotubes with an ultra-long aspect ratio is presented via a combination process concept combined with electrospinning, electrodeposition, and cationic exchange reaction. Ultra-long sacrificial silver (Ag) nanofibers were synthesized by electrospinning involving two-step calcination, and were then electrodeposited to create silver telluride nanotubes. These nanotubes underwent cationic exchange reaction in cadmium nitrate tetrahydrate solution with the aid of a ligand, tributylphosphine (TBP). Analysis showed that ultra-long pure zinc blende CdTe nanotubes were obtained with controlled dimension and uniform morphology. The thermodynamic driving force induced by the coordination of methanol solvent and TBP attributed to overcome the kinetic barrier between Ag{sub 2}Te and CdTe nanotubes, facilitating the synthesis of CdTe nanotubes. This synthetic process involving a topotactic reaction route paves a way for high-throughput extended synthesis of new chalcogenide hollow nanotubes for application in photodetectors and solar cells. - Highlights: • High throughput synthetic route of hollow CdTe nanotubes with ultra-long aspect ratio. • Chemical combination of electrospinning, electrodeposition & cation exchange reaction. • Pure zinc blende CdTe by controlled dimension & structural variation of Ag nanofibers. • Potential for the high throughput synthesis of new exotic chalcogenide nanotubes.

A Chemical, High-Temperature Way to Ag1.9Te via Quasi-Topotactic Reaction of Stuetzite-type Ag1.54Te: Structural and Thermoelectric Properties.

Science.gov (United States)

Baumer, Franziska; Nilges, Tom

2017-11-20

Semiconducting silver tellurides gained reasonable interest in the past years due to its thermoelectric, magneto-caloric, and nonlinear optic properties. Nanostructuring has been frequently used to address quantum-confinement effects of minerals and synthetic compounds in the Ag-Te system. Here, we report on the structural, thermal, and thermoelectric properties of stuetzite-like Ag 1.54 Te (or Ag 4.63 Te 3 ) and Ag 1.9 Te. By a quasi-topotactic reaction upon tellurium evaporation Ag 1.54 Te can be transferred to Ag 1.9 Te after heat treatment. Crystal structures, thermal and thermoelectric properties of stuetzite-like Ag 1.54 Te (or Ag 4.63 Te 3 ) and Ag 1.9 Te were determined by ex situ and in situ experiments. This method represents an elegant chemical way to Ag 1.9 Te, which was so far only accessible electrochemically via electrochemical removal of silver from the mineral hessite (Ag 2 Te). The mixed conductors show reasonable high total electric conductivities, very low thermal conductivities, and large Seebeck coefficients, which result in a significant high thermoelectric figure of 0.57 at 680 K.

Synthesis and structural characterization of a new chiral porous hybrid organic–inorganic material based on γ-zirconium phosphates and L-(+)-phosphoserine

Energy Technology Data Exchange (ETDEWEB)

Alhendawi, Hussein M.H., E-mail: hussein.alhendawi@yahoo.com [Department of Chemistry, Faculty of Science, Al-Azhar University of Gaza, 1277 Gaza, Palestine (Country Unknown)

2013-05-01

In the present work, a chiral layered derivative of γ-zirconium phosphate (γ-ZrP) containing L-(+)-phosphoserine (γ-ZrP-PS*) covalently attached to inorganic layers has been prepared by means of topotactic exchange reaction. This organic–inorganic derivative is characterized by X-ray diffractometry, Solid {sup 13}C–NMR and FT-IR spectrophotometries and thermal analyses. A maximum level of topotactic replacement of 20% is achieved. Under both the acidic environment of the interlayer region of γ-ZrP and the acidic synthesis conditions, the hydrolysis of the ester bond of PS* is expected to take place to some extent. For this reason, it was impossible to exceed the recent percentage, which in turn reflects the relative moderate stability of the above mentioned bond under these conditions. In order to be more certain with regard to an expected further hydrolysis for this bond after separation, a sample of γ-ZrP-PS* was stored in a desiccator over a saturated solution of BaCl{sub 2} (90% relative humidity) for three months, and then the sample re-analyzed once again. Surprisingly, the results show that the sample still keeps almost the same level of exchange (i.e., 20%). Second, it is revealed that the sample almost gives the same spectroscopic and thermal behavior. This could be attributed to the less acidic character of the partially exchanged inorganic layers of the sample in comparison with that of the precursor γ-ZrP. Therefore, the PS* molecules persist and stay there into the interlayer gallery without further hydrolysis. - Graphical abstract: • Red: oxygen • White: zirconium • Cyan: carbon • Yellow: phosphorus • Blue: nitrogen. Highlights: • L-(+)-Phosphoserine (PS*) is exchanged with γ-ZrP by means of topotactic exchange. • The maximum exchange level is 20%. • γ-ZrP is functionalized with chiral amino acid group. • γ-ZrP-PS* has large chiral space for huge guest molecules to be intercalated.

Synthesis and structural characterization of a new chiral porous hybrid organic–inorganic material based on γ-zirconium phosphates and L-(+)-phosphoserine

International Nuclear Information System (INIS)

Alhendawi, Hussein M.H.

2013-01-01

In the present work, a chiral layered derivative of γ-zirconium phosphate (γ-ZrP) containing L-(+)-phosphoserine (γ-ZrP-PS*) covalently attached to inorganic layers has been prepared by means of topotactic exchange reaction. This organic–inorganic derivative is characterized by X-ray diffractometry, Solid 13 C–NMR and FT-IR spectrophotometries and thermal analyses. A maximum level of topotactic replacement of 20% is achieved. Under both the acidic environment of the interlayer region of γ-ZrP and the acidic synthesis conditions, the hydrolysis of the ester bond of PS* is expected to take place to some extent. For this reason, it was impossible to exceed the recent percentage, which in turn reflects the relative moderate stability of the above mentioned bond under these conditions. In order to be more certain with regard to an expected further hydrolysis for this bond after separation, a sample of γ-ZrP-PS* was stored in a desiccator over a saturated solution of BaCl 2 (90% relative humidity) for three months, and then the sample re-analyzed once again. Surprisingly, the results show that the sample still keeps almost the same level of exchange (i.e., 20%). Second, it is revealed that the sample almost gives the same spectroscopic and thermal behavior. This could be attributed to the less acidic character of the partially exchanged inorganic layers of the sample in comparison with that of the precursor γ-ZrP. Therefore, the PS* molecules persist and stay there into the interlayer gallery without further hydrolysis. - Graphical abstract: • Red: oxygen • White: zirconium • Cyan: carbon • Yellow: phosphorus • Blue: nitrogen. Highlights: ► L-(+)-Phosphoserine (PS*) is exchanged with γ-ZrP by means of topotactic exchange. ► The maximum exchange level is 20%. ► γ-ZrP is functionalized with chiral amino acid group. ► γ-ZrP-PS* has large chiral space for huge guest molecules to be intercalated

Structural observations of heterometallic uranyl copper(II) carboxylates and their solid-state topotactic transformation upon dehydration.

Science.gov (United States)

Olchowka, Jakub; Falaise, Clément; Volkringer, Christophe; Henry, Natacha; Loiseau, Thierry

2013-02-04

The hydrothermal reactions of uranyl nitrate and metallic copper with aromatic polycarboxylic acids gave rise to the formation of five heterometallic UO(2)(2+)-Cu(2+) coordination polymers: (UO(2))Cu(H(2)O)(2)(1,2-bdc)(2) (1; 1,2-bdc = phthalate), (UO(2))Cu(H(2)O)(2)(btec)⋅4 H(2)O (2) and (UO(2))Cu(btec) (2'; btec = pyromellitate), (UO(2))(2)Cu(H(2)O)(4)(mel) (3; mel = mellitate), and (UO(2))(2)O(OH)(2)Cu(H(2)O)(2)(1,3-bdc)⋅H(2)O (4; 1,3-bdc = isophthlalate). Single-crystal X-ray diffraction (XRD) analysis of compound 1 revealed 2D layers of chains of UO(8) and CuO(4)(H(2)O)(2) units that were connected through the phthalate ligands. In compound 2, these sheets were connected to each other through the two additional carboxylate arms of the pyromellitate, thus resulting in a 3D open-framework with 1D channels that trapped water molecules. Upon heating, free and bonded water species (from Cu-OH(2)) were evacuated from the structure. This thermal transition was followed by in situ XRD and IR spectroscopy. Heating induced a solid-state topotactic transformation with the formation of a new set of Cu-O interactions in the crystalline anhydrous structure (2'), in order to keep the square-planar environment around the copper centers. The structure of compound 3 was built up from trinuclear motifs, in which one copper center, CuO(4)(OH(2))(2), was linked to two uranium units, UO(5)(H(2)O)(2). The assembly of this trimer, "U(2)Cu", with the mellitate generated a 3D network. Complex 4 contained a tetranuclear uranyl core of UO(5)(OH)(2) and UO(6)(OH) units that were linked to two copper centers, CuO(OH)(2)(H(2)O)(2), which were then connected to each other through isophthalate ligands and U=O-Cu interactions to create a 3D structure. The common structural feature of these different compounds is a bridging oxo group of U=O-Cu type, which is reflected by apical Cu-O distances in the range 2.350(3)-2.745(5) Å. In the case of a shorter Cu-O distance, a slight lengthening

Structural observations of heterometallic uranyl copper(II) carboxylates and their solid-state topotactic transformation upon dehydration

International Nuclear Information System (INIS)

Olchowka, Jakub; Falaise, Clement; Volkringer, Christophe; Henry, Natacha; Loiseau, Thierry

2013-01-01

The hydrothermal reactions of uranyl nitrate and metallic copper with aromatic polycarboxylic acids gave rise to the formation of five heterometallic UO 2 2+ -Cu 2+ coordination polymers: (UO 2 )Cu(H 2 O) 2 (1,2-bdc) 2 (1; 1,2-bdc=phthalate), (UO 2 )Cu(H 2 O) 2 (btec).4 H 2 O (2) and (UO 2 )Cu(btec) (2'; btec=pyromellitate), (UO 2 ) 2 Cu(H 2 O) 4 (mel) (3; mel=mellitate), and (UO 2 ) 2 O(OH) 2 Cu(H 2 O) 2 (1,3-bdc).H 2 O (4; 1,3-bdc=isophthlalate). Single-crystal X-ray diffraction (XRD) analysis of compound 1 revealed 2D layers of chains of UO 8 and CuO 4 (H 2 O) 2 units that were connected through the phthalate ligands. In compound 2, these sheets were connected to each other through the two additional carboxylate arms of the pyromellitate, thus resulting in a 3D open-framework with 1D channels that trapped water molecules. Upon heating, free and bonded water species (from Cu-OH 2 ) were evacuated from the structure. This thermal transition was followed by in situ XRD and IR spectroscopy. Heating induced a solid-state topotactic transformation with the formation of a new set of Cu-O interactions in the crystalline anhydrous structure (2'), in order to keep the square-planar environment around the copper centers. The structure of compound 3 was built up from trinuclear motifs, in which one copper center, CuO 4 (OH 2 ) 2 , was linked to two uranium units, UO 5 (H 2 O) 2 . The assembly of this trimer, ''U 2 Cu'', with the mellitate generated a 3D network. Complex 4 contained a tetranuclear uranyl core of UO 5 (OH) 2 and UO 6 (OH) units that were linked to two copper centers, CuO(OH) 2 (H 2 O) 2 , which were then connected to each other through isophthalate ligands and U=O-Cu interactions to create a 3D structure. The common structural feature of these different compounds is a bridging oxo group of U=O-Cu type, which is reflected by apical Cu-O distances in the range 2.350(3)-2.745(5) Aa. In the case of a shorter Cu-O distance, a slight

Topotactic reduction as a route to new close-packed anion deficient perovskites: structure and magnetism of 4H-BaMnO(2+x).

Science.gov (United States)

Hadermann, Joke; Abakumov, Artem M; Adkin, Josephine J; Hayward, Michael A

2009-08-05

The anion-deficient perovskite 4H-BaMnO(2+x) has been obtained by a topotactic reduction, with LiH, of the hexagonal perovskite 4H-BaMnO(3-x). The crystal structure of 4H-BaMnO(2+x) was solved using electron diffraction and X-ray powder diffraction and further refined using neutron powder diffraction (S.G. Pnma, a = 10.375(2) A, b = 9.466(2) A, c = 11.276(3) A, at 373 K). The orthorhombic superstructure arises from the ordering of oxygen vacancies within a 4H (chch) stacking of close packed c-type BaO(2.5) and h-type BaO(1.5) layers. The ordering of the oxygen vacancies transforms the Mn(2)O(9) units of face-sharing MnO(6) octahedra into Mn(2)O(7) (two corner-sharing tetrahedra) and Mn(2)O(6) (two edge-sharing tetrahedra) groups. The Mn(2)O(7) and Mn(2)O(6) groups are linked by corner-sharing into a three-dimensional framework. The structures of the BaO(2.5) and BaO(1.5) layers are different from those observed previously in anion-deficient perovskites providing a new type of order pattern of oxygen atoms and vacancies in close packed structures. Magnetization measurements and neutron diffraction data reveal 4H-BaMnO(2+x) adopts an antiferromagnetically ordered state below T(N) approximately 350 K.

Silica sodalite without occluded organic matters by topotactic conversion of lamellar precursor.

Science.gov (United States)

Moteki, Takahiko; Chaikittisilp, Watcharop; Shimojima, Atsushi; Okubo, Tatsuya

2008-11-26

Novel pure silica sodalite with hollow sodalite-cages has been synthesized for the first time by topotactic conversion of layered silicate (RUB-15) precursor. This success has been achieved by stepwise syntheses from silicate monomers, through clusters and layers, to microporous crystals. The pretreatment of layered silicate with small carboxylic acids before conversion is a crucial step. The obtained sodalite possesses accessible micropores, as confirmed by physical adsorption of hydrogen molecules. This plate-like silica sodalite would be very promising as fillers in mixed-matrix membranes for hydrogen separation.

Bi[NC5H3(CO2)2](OH2)xF (x=1 and 2): New one-dimensional Bi-coordination materials—Reversible hydration and topotactic decomposition to α-Bi2O3

International Nuclear Information System (INIS)

Jeon, Hye Rim; Lee, Dong Woo; Ok, Kang Min

2012-01-01

Two one-dimensional bismuth-coordination materials, Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 ) x F (x=1 and 2), have been synthesized by hydrothermal reactions using Bi 2 O 3 , 2,6-NC 5 H 3 (CO 2 H) 2 , HF, and water at 180 °C. Structures of the two materials were determined by single-crystal X-ray diffraction. Although they have different crystal structures, both Bi-organic materials shared a common structural motif, a one-dimensional chain structure consisting of Bi 3+ cations and pyridine dicarboxylate linkers. Detailed structural analyses include infrared spectroscopy, thermogravimetric analysis, and reversible hydration reactions for the coordinated water molecules were reported. Also, thermal decomposition of the rod-shaped Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F single crystals at 800 °C led to α-Bi 2 O 3 that maintained the same morphology of the original crystals. - Graphical abstract: Calcination of the Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F single crystals at 800 °C results in the α-Bi 2 O 3 rods that maintain the original morphology of the crystals. Highlights: ► Synthesis of one-dimensional chain Bi-organic frameworks. ► Reversible hydration reactions of Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F. ► Topotactic decomposition maintaining the same morphology of the original crystals.

Topotactic condensation of layer silicates with ferrierite-type layers forming porous tectosilicates.

Science.gov (United States)

Marler, B; Wang, Y; Song, J; Gies, H

2014-07-21

medium strong hydrogen bonds (d[O···O] ≈ 2.65 Å) are transformed into poorly ordered framework silicates. Some rules of thumb can be established concerning the successful zeolite synthesis via a topotactic condensation of layered precursors. Favourably, the precursor (i) possesses already a well ordered structure without defects, (ii) contains strong inter-layer hydrogen bonds and does not contain strong intra-layer hydrogen bonds and (iii) contains a suitable cation. The nature of the organic cation (size, geometry, flexibility, thermal stability) plays a key role in the formation of a microporous tectosilicate with well ordered structure. RUB-36 which meets these criteria yields a well ordered condensation product (RUB-37).

Looking for new hybrid polymer fillers: synthesis of nanosized α-type Zr(IV) organophosphonates through an unconventional topotactic anion exchange reaction.

Science.gov (United States)

Pica, Monica; Donnadio, Anna; Troni, Elisabetta; Capitani, Donatella; Casciola, Mario

2013-07-01

Gels of α-type zirconium(IV) phosphate alkylphosphonates, ZP(Cn)x, were prepared by reacting, at room temperature, propanol intercalated nanosized α-zirconium phosphate (α-ZrP) with propanol solutions of alkylphosphonic acids (H2Cn, n = number of carbon atoms in the alkyl chain = 4, 5, 6), with (H2Cn/Zr) molar ratios in the range 0.4-4.0. (31)P MAS NMR showed the presence of resonances due to the phosphate and phosphonate groups bonded to the Zr atoms mainly by three oxygen atoms, as in the α-type layer. The composition of the ZP(Cn)x materials, obtained by thermogravimetric analysis, ranges from x ≈ 0.2 to x ≈ 1.1. On the basis of the NMR data and of the analysis of the X-ray patterns of gels and powders, it is inferred that the ZP(Cn)x compounds have an α-type layered structure and that the reaction between α-ZrP and H2Cn is a topotactic anion exchange process. The evolution of the X-ray patterns during propanol deintercalation is consistent with a random distribution of the alkylphosphonate groups on the α-type layers which gives rise to porous pathways in the interlayer region. To test the possibility of using ZP(Cn)x as mechanical reinforcement of a polymer matrix, a starch membrane filled with 5 wt % ZP(C6)0.54 was prepared and characterized by stress-strain mechanical tests. Besides an excellent flexibility, this membrane exhibited a proportional increase of the Young's modulus by 230% in comparison with neat starch.

Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

Energy Technology Data Exchange (ETDEWEB)

Dolmatov, Valerii Yu [Federal State Unitary Enterprise Special Design-Technology Bureau (FSUE SDTB) ' ' Tekhnolog' ' at the St Petersburg State Institute of Technology (Technical University) (Russian Federation)

2007-04-30

The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

International Nuclear Information System (INIS)

Dolmatov, Valerii Yu

2007-01-01

The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

Topotactic elimination of water across a C-C ligand bond in a dense 3-D metal-organic framework.

Science.gov (United States)

Yeung, Hamish H-M; Kosa, Monica; Griffin, John M; Grey, Clare P; Major, Dan T; Cheetham, Anthony K

2014-11-11

Upon heating, lithium L-malate undergoes topotactic dehydration to form a phase containing the unsaturated fumarate ligand, in which the original 3-D framework remains intact. Insight into this unusual transformation has been obtained by single crystal X-ray diffraction, MAS-NMR, in situ powder X-ray diffraction and DFT calculations.

Mechanism of the Formation of Organic Derivatives of gamma-Zirconium Phosphate by Topotactic Reactions with Phosphonic Acids in Water and Water-Acetone Media.

Science.gov (United States)

Alberti, G.; Giontella, E.; Murcia-Mascarós, S.

1997-06-18

The rates of the topotactic reactions between gamma-zirconium phosphate and phenylphosphonic acid in water and water-acetone mixtures at various temperatures were investigated. The slow rates of the process in aqueous medium or in water-acetone mixtures at temperatures lower than 50 degrees C were attributed to a slow interdiffusion of O(2)P(OH)(2)(-) and O(2)P(OH)(C(6)H(5))(-) groups in the interlayer region of gamma-ZrP. Similar to ion-exchange processes, the replacement begins in the external part of the interlayer region and progresses toward the central region with the formation of an advancing phase boundary. In water-acetone mixtures at temperatures higher than 60 degrees C an exfoliation of gamma-ZrP was found. Thus, the initial process is very fast since the substitution can take place directly on the surface of the exfoliated gamma-lamellae. However, after a certain degree of substitution, a flocculation of the colloidal dispersion, which slows down the rate of the further topotactic substitution, was observed. Some considerations on the topotactic substitution occurring on the surface of the exfoliated lamellae and on the mechanism of the diffusion of the exchanging species in the interlayer region are also reported.

Topotactic reductive synthesis of A-site cation-ordered perovskite YBaCo2O x (x = 4.5-5.5) epitaxial thin films

Science.gov (United States)

Katayama, Tsukasa; Chikamatsu, Akira; Fukumura, Tomoteru; Hasegawa, Tetsuya

2016-04-01

A-site cation-ordered perovskite YBaCo2O x epitaxial films were synthesized by combining pulsed-laser deposition and topotactic reduction using CaH2. The oxygen contents (x) of the films could be controlled in a range of 4.5-5.5 by adjusting the reaction temperature. The c-axis length of the YBaCo2O x films decreased with decreasing x when x ≥ 5.3 but drastically increased when x ˜ 4.5. In contrast, the in-plane lattice constants remained locked-in by the substrate after the reaction. The metal insulator transition observed in bulk YBaCo2O5.5 was substantially suppressed in the present film, likely because of the epitaxial strain effect. The resistivity of the films was significantly enhanced by changing the x value from ˜5.5 to ˜4.5, reflecting the distortion of the CoO x layers.

Superconductor thin films: topotactic corrosion mechanism of YBa2Cu3O7 with water vapor

International Nuclear Information System (INIS)

Boerner, R.; Schoellhorn, R.; Kabius, B.; Schubert, J.

1995-01-01

Corrosion in high-T c superconductors (HTSC) caused by water vapor is examined. HTSC thin films prepared using the laser ablation technique are shown to lose their superconducting properties due to the topotactic formation of a new hydroxylated phase which is a result of the corrosion. The mechanism of the corrosion process, which could be important in future applications of HTSC, is discussed. (orig.)

Structural observations of heterometallic uranyl copper(II) carboxylates and their solid-state topotactic transformation upon dehydration

Energy Technology Data Exchange (ETDEWEB)

Olchowka, Jakub; Falaise, Clement; Volkringer, Christophe; Henry, Natacha; Loiseau, Thierry [Unite de Catalyse et Chimie du Solide (UCCS), UMR CNRS 8181, Universite de Lille Nord de France, USTL-ENSCL, Villeneuve d' Ascq (France)

2013-02-04

The hydrothermal reactions of uranyl nitrate and metallic copper with aromatic polycarboxylic acids gave rise to the formation of five heterometallic UO{sub 2}{sup 2+}-Cu{sup 2+} coordination polymers: (UO{sub 2})Cu(H{sub 2}O){sub 2}(1,2-bdc){sub 2} (1; 1,2-bdc=phthalate), (UO{sub 2})Cu(H{sub 2}O){sub 2}(btec).4 H{sub 2}O (2) and (UO{sub 2})Cu(btec) (2'; btec=pyromellitate), (UO{sub 2}){sub 2}Cu(H{sub 2}O){sub 4}(mel) (3; mel=mellitate), and (UO{sub 2}){sub 2}O(OH){sub 2}Cu(H{sub 2}O){sub 2}(1,3-bdc).H{sub 2}O (4; 1,3-bdc=isophthlalate). Single-crystal X-ray diffraction (XRD) analysis of compound 1 revealed 2D layers of chains of UO{sub 8} and CuO{sub 4}(H{sub 2}O){sub 2} units that were connected through the phthalate ligands. In compound 2, these sheets were connected to each other through the two additional carboxylate arms of the pyromellitate, thus resulting in a 3D open-framework with 1D channels that trapped water molecules. Upon heating, free and bonded water species (from Cu-OH{sub 2}) were evacuated from the structure. This thermal transition was followed by in situ XRD and IR spectroscopy. Heating induced a solid-state topotactic transformation with the formation of a new set of Cu-O interactions in the crystalline anhydrous structure (2'), in order to keep the square-planar environment around the copper centers. The structure of compound 3 was built up from trinuclear motifs, in which one copper center, CuO{sub 4}(OH{sub 2}){sub 2}, was linked to two uranium units, UO{sub 5}(H{sub 2}O){sub 2}. The assembly of this trimer, ''U{sub 2}Cu'', with the mellitate generated a 3D network. Complex 4 contained a tetranuclear uranyl core of UO{sub 5}(OH){sub 2} and UO{sub 6}(OH) units that were linked to two copper centers, CuO(OH){sub 2}(H{sub 2}O){sub 2}, which were then connected to each other through isophthalate ligands and U=O-Cu interactions to create a 3D structure. The common structural feature of these different compounds is

Microstructures, surface properties, and topotactic transitions of manganite nanorods.

Science.gov (United States)

Gao, Tao; Krumeich, Frank; Nesper, Reinhard; Fjellvåg, Helmer; Norby, Poul

2009-07-06

Manganite (gamma-MnOOH) nanorods with typical diameters of 20-500 nm and lengths of several micrometers were prepared by reacting KMnO(4) and ethanol under hydrothermal conditions. Synchrotron X-ray diffraction (XRD) reveal that the gamma-MnOOH nanorods crystallize in the monoclinic space group P2(1)/c with unit cell dimensions a = 5.2983(3) A, b = 5.2782(2) A, c = 5.3067(3) A, and beta = 114.401(2) degrees . Transmission electron microscopy shows that the gamma-MnOOH nanorods are single crystalline and that lateral attachment occurs for primary rods elongated along 101. X-ray photoelectron spectroscopy studies indicate that the surfaces of the gamma-MnOOH nanorods are hydrogen deficient and compensated by surface complexation. The Raman scattering spectrum features five main contributions at 360, 389, 530, 558, and 623 cm(-1) along with four weak ones at 266, 453, 492, and 734 cm(-1), attributed to Mn-O vibrations within MnO(6) octahedral frameworks. The structural stability of the gamma-MnOOH nanorods was discussed by means of in situ time-resolved synchrotron XRD. The monoclinic gamma-MnOOH nanorods transform into tetragonal beta-MnO(2) upon heating in air at about 200 degrees C. The reaction is topotactic and shows distinctive differences from those seen for bulk counterparts. A metastable, intermediate phase is observed, possibly connected with hydrogen release via the interstitial (1 x 1) tunnels of the gamma-MnOOH nanorods.

Facile synthesis of ZrO2 powders: Control of morphology

International Nuclear Information System (INIS)

Grover, V.; Shukla, R.; Tyagi, A.K.

2007-01-01

Tetragonal (t-)ZrO 2 rods and spheres were prepared by simple and time-saving low-temperature synthesis and characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The morphology of the product can be changed from rods to spheres by changing the reaction conditions slightly. The t-ZrO 2 rods (0.5-0.1 mm approximately) were obtained by topotactic reaction. The work illustrates the utility of Raman spectroscopy as a powerful characterization tool when XRD is not able to conclusively identify the phases

Intercalation of alcohols in Ag sulfonates: topotactic behavior despite flexible layers.

Science.gov (United States)

Côté, Adrien P; Ferguson, Michael J; Khan, Kashif A; Enright, Gary D; Kulynych, Angela D; Dalrymple, Sean A; Shimizu, George K H

2002-01-28

This article presents the inaugural intercalation study of a layered metal sulfonate network. Silver triflate forms intercalation complexes with straight chain primary alcohols from ethanol (C(2)H(5)OH) to eicosanol (C(20)H(41)OH). Single-crystal data for the EtOH adduct, 1, are presented which show that the intercalation is coordinative to Ag. In contrast to many other layered hosts, no preheating of Ag triflate is required to liberate a coordination site for intercalation to take place, owing to the ability of the triflate ion to reorient. Crystal structure parameters for 1: C(4)H(6)F(6)S(2)O(7)Ag(2), a = 5.345(7) A, b = 11.310(2) A, c = 12.004(2) A, alpha = 116.87(1) degrees, beta = 90.46(1) degrees, gamma = 99.59(1) degrees, triclinic, space group P, Z = 2. Intercalate 1 presents the triflate ion in an unprecedented mu(5)-coordination mode. PXRD data on the family of complexes show that the intercalation is topotactic, as verified by the linear increase in d-spacing and calculated c-axis lengths for the intercalates, with increasing chain length. The data also show that the alcohol intercalates adopt an interdigitated rather than bilayer arrangement.

Synthesis and structural characterization of a new chiral porous hybrid organic-inorganic material based on γ-zirconium phosphates and L-(+)-phosphoserine

Science.gov (United States)

Alhendawi, Hussein M. H.

2013-05-01

In the present work, a chiral layered derivative of γ-zirconium phosphate (γ-ZrP) containing L-(+)-phosphoserine (γ-ZrP-PS*) covalently attached to inorganic layers has been prepared by means of topotactic exchange reaction. This organic-inorganic derivative is characterized by X-ray diffractometry, Solid 13C-NMR and FT-IR spectrophotometries and thermal analyses. A maximum level of topotactic replacement of 20% is achieved. Under both the acidic environment of the interlayer region of γ-ZrP and the acidic synthesis conditions, the hydrolysis of the ester bond of PS* is expected to take place to some extent. For this reason, it was impossible to exceed the recent percentage, which in turn reflects the relative moderate stability of the above mentioned bond under these conditions. In order to be more certain with regard to an expected further hydrolysis for this bond after separation, a sample of γ-ZrP-PS* was stored in a desiccator over a saturated solution of BaCl2 (90% relative humidity) for three months, and then the sample re-analyzed once again. Surprisingly, the results show that the sample still keeps almost the same level of exchange (i.e., 20%). Second, it is revealed that the sample almost gives the same spectroscopic and thermal behavior. This could be attributed to the less acidic character of the partially exchanged inorganic layers of the sample in comparison with that of the precursor γ-ZrP. Therefore, the PS* molecules persist and stay there into the interlayer gallery without further hydrolysis.

Topotactic Fluorine Insertion into the Channels of FeSb2O4-Related Materials.

Science.gov (United States)

de Laune, Benjamin P; Rees, Gregory J; Marco, José F; Hah, Hien-Yoong; Johnson, Charles E; Johnson, Jacqueline A; Berry, Frank J; Hanna, John V; Greaves, Colin

2017-08-21

This paper discusses the fluorination characteristics of phases related to FeSb 2 O 4 , by reporting the results of a detailed study of Mg 0.50 Fe 0.50 Sb 2 O 4 and Co 0.50 Fe 0.50 Sb 2 O 4 . Reaction with fluorine gas at low temperatures (typically 230 °C) results in topotactic insertion of fluorine into the channels, which are an inherent feature of the structure. Neutron powder diffraction and solid state NMR studies show that the interstitial fluoride ions are bonded to antimony within the channel walls to form Sb-F-Sb bridges. To date, these reactions have been observed only when Fe 2+ ions are present within the chains of edge-linked octahedra (FeO 6 in FeSb 2 O 4 ) that form the structural channels. Oxidation of Fe 2+ to Fe 3+ is primarily responsible for balancing the increased negative charge associated with the presence of the fluoride ions within the channels. For the two phases studied, the creation of Fe 3+ ions within the chains of octahedra modify the magnetic exchange interactions to change the ground-state magnetic symmetry to C-type magnetic order in contrast to the A-type order observed for the unfluorinated oxide parents.

Formation of zeolite-like zinc 1,3,5-benzenetriphosphonate open-frameworks by topotactic pillaring of anionic layers.

Science.gov (United States)

Maeda, Kazuyuki; Takamatsu, Ryohei; Mochizuki, Miki; Kawawa, Kanako; Kondo, Atsushi

2013-08-07

An ab initio powder X-ray crystal structure analysis revealed that layered zinc 1,3,5-benzenetriphosphonates containing interlayer tetramethylammonium (ZBP-TMA) or 4,4'-bipyridinium cations (ZBP-bpy) are transformed to novel isomorphous 3D open-framework compounds ZBP-M (M: K, Rb, and Cs) by treatment in aqueous alkali metal chloride solutions. ZBP-Ms have a pillared layer-type of anionic framework containing 2D zigzag channels connected with cage-like spaces. The potassium atoms in ZBP-K are located near 8MR windows in the 2D zigzag channels, and the potassium cations are successfully exchanged with ammonium cations retaining the open-framework structure. The ammonium form (ZBP-NH4) showed remarkable cation exchange selectivity for Rb(+) and Cs(+) in a mixture of alkali metal cations. It is assumed that zinc ions partially dissolved from the starting layered ZBP precursors are intercalated in ZBP layers to form pillared layered 3D open-frameworks. These results clearly show that topotactic pillared layer approaches are applicable not only to zeolite-related materials but also to novel open-framework metal organophosphonates.

Topotactic redox chemistry of NaFeAs in water and air and superconducting behavior with stoichiometry change.

Energy Technology Data Exchange (ETDEWEB)

Todorov, I.; Chung, D. Y.; Claus, H.; Malliakas, C. D.; Douvalis, A. P.; Bakas, T.; He, J.; Dravid, V. P.; Kanatzidis, M. G.; Materials Science Division; Northwestern Univ.; Univ. of Ioannina

2010-07-13

We report experimental evidence that shows superconductivity in NaFeAs occurs when it is Na deficient. The oxidation of NaFeAs progresses differently in water and in air. In water the material oxidizes slowly and slightly retaining the original anti-PbFCl structure. In air NaFeAs oxidizes topotactically quickly and extensively transforming to the ThCr{sub 2}Si{sub 2} structure type. Water acts as a mild oxidizing agent on the FeAs layer by extracting electrons and Na{sup +} cations from the structure, while oxidation in air is more extensive and leads to change in structure type from NaFeAs to NaFe{sub 2}As{sub 2}. The superconducting transition temperature moves dramatically during the oxidation process. Exposed to water for an extended time period NaFeAs shows a substantial increase in T{sub c} up to 25 K with contraction of unit cell volume. NaFe{sub 2}As{sub 2}, the air oxidized product, shows T{sub c} of 12 K. We report detailed characterization of the redox chemistry and transformation of NaFeAs in water and air using single crystal and powder X-ray diffraction, magnetization studies, transmission electron microscopy, Moessbauer spectroscopy, pOH and elemental analysis.

Reversible and Topotactic Solvent Removal in a Magnetic Ni(NCS)2 Coordination Polymer.

Science.gov (United States)

Suckert, Stefan; Rams, Michał; Rams, Marek M; Näther, Christian

2017-07-17

Reaction of Ni(NCS) 2 with 4-(Boc-amino)pyridine in acetonitrile leads to the formation of a new coordination polymer with the composition Ni(NCS) 2 (4-(Boc-amino)pyridine) 2 ·MeCN (1-MeCN). In the crystal structure the Ni(II) cations are linked by the anionic ligands into chains that are further connected into layers by intermolecular N-H···O hydrogen bonding. These layers are stacked and channels are formed, in which acetonitrile molecules are located. Solvent removal leads to the ansolvate 1, which shows microporosity as proven by sorption measurements. Single crystal X-ray investigations reveal that the solvent removal leads to a change in symmetry from primitive to C-centered, which is reversible and which proceeds via a topotactic reaction leaving the network intact. The magnetic properties of 1-MeCN and 1 are governed by the ferromagnetic exchange between spins of Ni(II) forming chains. The susceptibility and specific heat for such a quantum Heisenberg chain of S = 1 spins with zero-field splitting are calculated using the DMRG method and compared with the experimental results.

X-ray and electron microscopy investigation of the topotactic transformation of MoO3 into MoO2

International Nuclear Information System (INIS)

Bertrand, O.; Dufour, L.C.

1980-01-01

The reduction of MoO 3 is investigated by X-ray analysis and electron microscopy from MoO 3 (010) platelets between 1000 A and 5 mm long. In all cases, the following orientation relationship between both lattices is found: [100] 2 parallel [010] 3 , [122] 2 parallel [100] 3 . [-12-2] 2 parallel [001] 3 . MoO 3 crystallites twinning and misorientation are discussed in relation with the particular importance of [101] 3 directions in MoO 3 preserved in the transformation and becoming [010] 2 of MoO 2 . A model for this topotactic reduction is proposed where the reaction develops layer (010) 3 by layer (010) 3 to form [20-1] 2 type planes in MoO 2 structure. Data on the kinetics of the boundary moving in [010] 3 direction are also presented. (author)

Topotactic Epitaxy of SrTiO3 Mesocrystal Superstructures with Anisotropic Construction for Efficient Overall Water Splitting.

Science.gov (United States)

Zhang, Peng; Ochi, Tomoya; Fujitsuka, Mamoru; Kobori, Yasuhiro; Majima, Tetsuro; Tachikawa, Takashi

2017-05-02

The higher-order structures of semiconductor-based photocatalysts play crucial roles in their physicochemical properties for efficient light-to-energy conversion. A novel perovskite SrTiO 3 mesocrystal superstructure with well-defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO 2 mesocrystals through a facile hydrothermal treatment. The SrTiO 3 mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long-lived charges for enhanced photocatalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topotactic epitaxy of SrTiO3 mesocrystal superstructures with anisotropic construction for efficient overall water splitting

International Nuclear Information System (INIS)

Zhang, Peng; Fujitsuka, Mamoru; Majima, Tetsuro; Ochi, Tomoya; Kobori, Yasuhiro; Tachikawa, Takashi

2017-01-01

The higher-order structures of semiconductor-based photocatalysts play crucial roles in their physicochemical properties for efficient light-to-energy conversion. A novel perovskite SrTiO 3 mesocrystal superstructure with well-defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO 2 mesocrystals through a facile hydrothermal treatment. The SrTiO 3 mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long-lived charges for enhanced photocatalysis. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation.

Science.gov (United States)

Trávníček, Zdeněk; Zbořil, Radek; Matiková-Maľarová, Miroslava; Drahoš, Bohuslav; Cernák, Juraj

2013-01-01

The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, (57)Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙∙ 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [Fe(II)(en)2(μ-NC)Co(III)(CN)4], Fe(III)(NH2CH2CH3)2(μ-NC)2Co(II)(CN)3] and Fe(III)[Co(II)(CN)5], which were suggested mainly from (57)Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4. It has been found that the thermal

Neutron diffraction study on the mechanism of the topotactic reduction of 2HTaS 2 electrodes

Science.gov (United States)

Riekel, C.; Reznik, H. G.; Schöllhorn, R.

1980-09-01

The dynamic investigation by neutron diffraction of the topotactic reduction of 2HTaS 2 electrodes in {K+}/{D2O} electrolyte to the ionic layered hydrate K +0.5(D 2O) 0.5[TaS 2] 0.5- is shown to proceed via third-stage K +x(D 2O) y[TaS 2] 3x- , second-stage K +x(D 2O) y [TaS 2] 2x- , and first-stage K +x(D 2O) y[TaS 2] x- intermediates. A comparative study by X-ray diffraction on the cathodic intercalation of 2HTaS 2 and 2HNbS 2 electrodes with hydrated main group and transition metal ions reveals analogous behavior; the formation of higher-stage intermediates is supposedly correlated with stable electronic layer states. Influence of kinetic factors is observed for larger guest cations such as transition metal complexes and organic ions. CdI 2-type host lattices with an octahedral environment of intralayer cations shown different reaction pathways, although the occurrence of intermediate states (at least in the nucleation phase) can be demonstrated. It is concluded that the presence of ordered intermediate states is a general phenomenon in topotactic electrode processes of layered dichalcogenides.

Structural synthesis of parallel robots

CERN Document Server

Gogu, Grigore

This book represents the fifth part of a larger work dedicated to the structural synthesis of parallel robots. The originality of this work resides in the fact that it combines new formulae for mobility, connectivity, redundancy and overconstraints with evolutionary morphology in a unified structural synthesis approach that yields interesting and innovative solutions for parallel robotic manipulators.  This is the first book on robotics that presents solutions for coupled, decoupled, uncoupled, fully-isotropic and maximally regular robotic manipulators with Schönflies motions systematically generated by using the structural synthesis approach proposed in Part 1.  Overconstrained non-redundant/overactuated/redundantly actuated solutions with simple/complex limbs are proposed. Many solutions are presented here for the first time in the literature. The author had to make a difficult and challenging choice between protecting these solutions through patents and releasing them directly into the public domain. T...

Topotactic epitaxy of SrTiO{sub 3} mesocrystal superstructures with anisotropic construction for efficient overall water splitting

Energy Technology Data Exchange (ETDEWEB)

Zhang, Peng; Fujitsuka, Mamoru; Majima, Tetsuro [The Institute of Scientific and Industrial Research (SANKEN), Osaka University (Japan); Ochi, Tomoya [Department of Chemistry, Graduate School of Science, Kobe University (Japan); Kobori, Yasuhiro [Department of Chemistry, Graduate School of Science, Kobe University (Japan); Molecular Photoscience Research Center, Kobe University (Japan); Tachikawa, Takashi [Department of Chemistry, Graduate School of Science, Kobe University (Japan); Molecular Photoscience Research Center, Kobe University (Japan); PRESTO, Science and Technology Agency (JST), Saitama (Japan)

2017-05-02

The higher-order structures of semiconductor-based photocatalysts play crucial roles in their physicochemical properties for efficient light-to-energy conversion. A novel perovskite SrTiO{sub 3} mesocrystal superstructure with well-defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO{sub 2} mesocrystals through a facile hydrothermal treatment. The SrTiO{sub 3} mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long-lived charges for enhanced photocatalysis. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Synthesis and Properties of Group IV Graphane Analogues

Science.gov (United States)

Goldberger, Joshua

Similar to how carbon networks can be sculpted into low-dimensional allotropes such as fullerenes, nanotubes, and graphene with fundamentally different properties, it is possible to create similar ligand terminated sp3-hybridized honeycomb graphane derivatives containing Ge or Sn that feature unique and tunable properties. Here, we will describe our recent success in the creation of hydrogen and organic-terminated group IV graphane analogues, from the topochemical deintercalation of precursor Zintl phases, such as CaGe2. We will discuss how the optical, electronic, and thermal properties of these materials can be systematically controlled by substituting either the surface ligand or via alloying with other Group IV elements. Additionally, we have also developed an epitopotaxial approach for integrating precise thicknesses of germanane layers onto Ge wafers that combines the epitaxial deposition of CaGe2 precursor phases with the topotactic interconversion into the 2D material. Finally, we will describe our recent efforts on the synthesis and crystal structures of Sn-containing graphane alloys in order to access novel topological phenomena predicted to occur in these graphanes.

Structural basis for the transformation pathways of the sodium naproxen anhydrate–hydrate system

Science.gov (United States)

Bond, Andrew D.; Cornett, Claus; Larsen, Flemming H.; Qu, Haiyan; Raijada, Dhara; Rantanen, Jukka

2014-01-01

Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II) of the non-steroidal anti-inflammatory drug sodium (S)-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its structure is derived using powder X-ray diffraction, solid-state 13C and 23Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D) calculations. The structures of DH-I and DH-II, and in particular their relationships to the monohydrate (MH) and anhydrate (AH) structures, provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate–hydrate system. All structures contain Na+/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH-I is essentially identical to MH in the naproxen region, containing face-to-face arrangements of the naphthalene rings, whereas the structure of DH-II is comparable to AH in the naproxen region, containing edge-to-face arrangements of the naphthalene rings. This structural similarity permits topotactic transformation between AH and DH-II, and between MH and DH-I, but requires re-organization of the naproxen molecules for transformation between any other pair of structures. The topotactic pathways dominate at room temperature or below, while the non-topotactic pathways become active at higher temperatures. Thermochemical data for the dehydration processes are rationalized in the light of this new structural information. PMID:25295174

Structural basis for the transformation pathways of the sodium naproxen anhydrate–hydrate system

Directory of Open Access Journals (Sweden)

Andrew D. Bond

2014-09-01

Full Text Available Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II of the non-steroidal anti-inflammatory drug sodium (S-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its structure is derived using powder X-ray diffraction, solid-state 13C and 23Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D calculations. The structures of DH-I and DH-II, and in particular their relationships to the monohydrate (MH and anhydrate (AH structures, provide a basis to rationalize the observed transformation pathways in the sodium (S-naproxen anhydrate–hydrate system. All structures contain Na+/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH-I is essentially identical to MH in the naproxen region, containing face-to-face arrangements of the naphthalene rings, whereas the structure of DH-II is comparable to AH in the naproxen region, containing edge-to-face arrangements of the naphthalene rings. This structural similarity permits topotactic transformation between AH and DH-II, and between MH and DH-I, but requires re-organization of the naproxen molecules for transformation between any other pair of structures. The topotactic pathways dominate at room temperature or below, while the non-topotactic pathways become active at higher temperatures. Thermochemical data for the dehydration processes are rationalized in the light of this new structural information.

Structural basis for the transformation pathways of the sodium naproxen anhydrate-hydrate system.

Science.gov (United States)

Bond, Andrew D; Cornett, Claus; Larsen, Flemming H; Qu, Haiyan; Raijada, Dhara; Rantanen, Jukka

2014-09-01

Crystal structures are presented for two dihydrate polymorphs (DH-I and DH-II) of the non-steroidal anti-inflammatory drug sodium (S)-naproxen. The structure of DH-I is determined from twinned single crystals obtained by solution crystallization. DH-II is obtained by solid-state routes, and its structure is derived using powder X-ray diffraction, solid-state (13)C and (23)Na MAS NMR, and molecular modelling. The validity of both structures is supported by dispersion-corrected density functional theory (DFT-D) calculations. The structures of DH-I and DH-II, and in particular their relationships to the monohydrate (MH) and anhydrate (AH) structures, provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate-hydrate system. All structures contain Na(+)/carboxylate/H2O sections, alternating with sections containing the naproxen molecules. The structure of DH-I is essentially identical to MH in the naproxen region, containing face-to-face arrangements of the naphthalene rings, whereas the structure of DH-II is comparable to AH in the naproxen region, containing edge-to-face arrangements of the naphthalene rings. This structural similarity permits topotactic transformation between AH and DH-II, and between MH and DH-I, but requires re-organization of the naproxen molecules for transformation between any other pair of structures. The topotactic pathways dominate at room temperature or below, while the non-topotactic pathways become active at higher temperatures. Thermochemical data for the dehydration processes are rationalized in the light of this new structural information.

Synthesis and structural characterization of lithium

Indian Academy of Sciences (India)

synthesis and characterization of two new iminophos- phonamine ligands ... structures. 2.3 General synthetic method for ligands (1 and 2) ... 2.3b General method for the Synthesis of ligands ...... studies are currently underway in our laboratory.

Real-time in-situ monitoring of the topotactic transformation of TlCu3Se2 into TlCu2Se2

International Nuclear Information System (INIS)

Ångström, J.; Sahlberg, M.; Berger, R.

2015-01-01

Highlights: • Topotactic transition from TlCu 3 Se 2 to TlCu 2 Se 2 followed in situ. • Synchrotron radiation X-ray powder diffraction enabled short scans. • Relative abundance of phases refined from powder data. • Opens up for studying similar systems in the same manner. - Abstract: The solid state transformation of monoclinic TlCu 3 Se 2 into tetragonal TlCu 2 Se 2 by oxidative copper leaching in concentrated ammonia solution has been studied in situ by the use of synchrotron radiation. The diffraction patterns of parent and daughter phase are both sharp, indicating a strong topotactic relationship between them that effectuates a rapid change by “chimie douce” performed at +19 °C. The transformation rate is strongly connected to the access of oxygen from the surrounding air. The transformation was followed in a real-time mode, being almost complete after 2.5 h with 1 h incubation due to low oxygen content, as shown from refining the diffraction patterns by Rietveld profile technique

Component mode synthesis in structural dynamics

International Nuclear Information System (INIS)

Reddy, G.R.; Vaze, K.K.; Kushwaha, H.S.

1993-01-01

In seismic analysis of Nuclear Reactor Structures and equipments eigen solution requires large computer time. Component mode synthesis is an efficient technique with which one can evaluate dynamic characteristics of a large structure with minimum computer time. Due to this reason it is possible to do a coupled analysis of structure and equipment which takes into account the interaction effects. Basically in this the method large size structure is divided into small substructures and dynamic characteristics of individual substructure are determined. The dynamic characteristics of entire structure are evaluated by synthesising the individual substructure characteristics. Component mode synthesis has been applied in this paper to the analysis of a tall heavy water upgrading tower. Use of fixed interface normal modes, constrained modes, attachment modes in the component mode synthesis using energy principle and using Ritz vectors have been discussed. The validity of this method is established by solving fixed-fixed beam and comparing the results obtained by conventional and classical method. The eigen value problem has been solved using simultaneous iteration method. (author)

Olivine CPO in non-deformed peridotite due to topotactic replacement of antigorite

Science.gov (United States)

Nagaya, Takayoshi; Wallis, Simon; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi

2014-05-01

Olivine crystallographic preferred orientation (CPO) is thought to be the main cause of seismic anisotropy in the mantle, and its formation is generally considered to be the result of plastic deformation of mantle by dislocation creep. Olivine CPO has been reproduced in laboratory deformation experiments and considerable success has been achieved in understanding the deformation conditions (e.g. stress, temperature and water content) under which different olivine CPO patterns develop. This opens the possibility of mapping conditions in the mantle using seismic anisotropy and has been the subject of considerable study. Here we report an alternative mechanism for olivine CPO without the need for deformation. This process may be important in understanding the seismic properties of mantle in convergent margins. Metamorphic studies show peridotite in the Happo area, central Japan, formed by the dehydration of antigorite-schist related to contact metamorphism around a granite intrusion. Both field and microstructural observations suggest the olivine has not undergone strong plastic deformation. This was confirmed by TEM work that shows the olivine has very low dislocation densities and lacks low angle tilt boundaries. Such tilt boundaries are general stable even after annealing. These features show that peridotite in the Happo area formed in the absence of solid-state deformation. The olivine of the Happo peridotite formed dominantly by the dehydration breakdown of antigorite schist. We propose that the olivine CPO formed as a result of topotactic replacement of antigorite by the newly formed olivine. EBSD measurements in samples where both antigorite and new olivine are present and in contact show a very close crystallographic relationship between the two minerals: the a-axes are parallel, and the b- and c-axes are perpendicular. We conclude the strong olivine CPO in the Happo area was inherited from the original CPO of the antigorite. Such a process is likely to also

Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

Science.gov (United States)

Meng, Siqin; Yue, Zhenxing; Zhang, Xiaozhi; Li, Longtu

2014-01-01

Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

Energy Technology Data Exchange (ETDEWEB)

Meng, Siqin; Yue, Zhenxing, E-mail: yuezhx@tsinghua.edu.cn; Zhang, Xiaozhi; Li, Longtu

2014-01-30

Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

Non linear structures seismic analysis by modal synthesis

International Nuclear Information System (INIS)

Aita, S.; Brochard, D.; Guilbaud, D.; Gibert, R.J.

1987-01-01

The structures submitted to a seismic excitation, may present a great amplitude response which induces a non linear behaviour. These non linearities have an important influence on the response of the structure. Even in this case (local shocks) the modal synthesis method remains attractive. In this paper we will present the way of taking into account, a local non linearity (shock between structures) in the seismic response of structures, by using the modal synthesis method [fr

Epitaxial growth and electronic structure of oxyhydride SrVO2H thin films

Science.gov (United States)

Katayama, Tsukasa; Chikamatsu, Akira; Yamada, Keisuke; Shigematsu, Kei; Onozuka, Tomoya; Minohara, Makoto; Kumigashira, Hiroshi; Ikenaga, Eiji; Hasegawa, Tetsuya

2016-08-01

Oxyhydride SrVO2H epitaxial thin films were fabricated on SrTiO3 substrates via topotactic hydridation of oxide SrVO3 films using CaH2. Structural and composition analyses suggested that the SrVO2H film possessed one-dimensionally ordered V-H--V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO2H film was reversible to SrVO3 by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V3+ valence state in the SrVO2H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3- δ.

Science.gov (United States)

Jeen, H; Choi, W S; Freeland, J W; Ohta, H; Jung, C U; Lee, H N

2013-07-19

Pulsed laser epitaxy of brownmillerite SrCoO2.5 thin films and their phase transformation to the perovskite SrCoO3-δ are investigated. While the direct growth of the fully oxidized perovskite films is found to be an arduous task, filling some of oxygen vacancies into SrCoO2.5 by topotactic oxidation accompanies systematic evolution of electronic, magnetic, and thermoelectric properties, useful for many information and energy technologies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Completely oriented anatase TiO2 nanoarrays: topotactic growth and orientation-related efficient photocatalysis

Science.gov (United States)

Yang, Jingling; Wu, Qili; He, Shiman; Yan, Jing; Shi, Jianying; Chen, Jian; Wu, Mingmei; Yang, Xianfeng

2015-08-01

A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001} facets on the anatase nanoarrays with super-hydrophilicity.A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001

In Situ Tracking Kinetic Pathways of Li+/Na+ Substitution during Ion-Exchange Synthesis of LixNa1.5-xVOPO4F0.5.

Science.gov (United States)

Park, Young-Uk; Bai, Jianming; Wang, Liping; Yoon, Gabin; Zhang, Wei; Kim, Hyungsub; Lee, Seongsu; Kim, Sung-Wook; Looney, J Patrick; Kang, Kisuk; Wang, Feng

2017-09-13

Ion exchange is a ubiquitous phenomenon central to wide industrial applications, ranging from traditional (bio)chemical separation to the emerging chimie douce synthesis of materials with metastable structure for batteries and other energy applications. The exchange process is complex, involving substitution and transport of different ions under non-equilibrium conditions, and thus difficult to probe, leaving a gap in mechanistic understanding of kinetic exchange pathways toward final products. Herein, we report in situ tracking kinetic pathways of Li + /Na + substitution during solvothermal ion-exchange synthesis of Li x Na 1.5-x VOPO 4 F 0.5 (0 ≤ x ≤ 1.5), a promising multi-Li polyanionic cathode for batteries. The real-time observation, corroborated by first-principles calculations, reveals a selective replacement of Na + by Li + , leading to peculiar Na + /Li + /vacancy orderings in the intermediates. Contradicting the traditional belief of facile topotactic substitution via solid solution reaction, an abrupt two-phase transformation occurs and predominantly governs the kinetics of ion exchange and transport in the 1D polyanionic framework, consequently leading to significant difference of Li stoichiometry and electrochemical properties in the exchanged products. The findings may help to pave the way for rational design of ion exchange synthesis for making new materials.

Real-time in-situ monitoring of the topotactic transformation of TlCu{sub 3}Se{sub 2} into TlCu{sub 2}Se{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Ångström, J.; Sahlberg, M.; Berger, R.

2015-07-15

Highlights: • Topotactic transition from TlCu{sub 3}Se{sub 2} to TlCu{sub 2}Se{sub 2} followed in situ. • Synchrotron radiation X-ray powder diffraction enabled short scans. • Relative abundance of phases refined from powder data. • Opens up for studying similar systems in the same manner. - Abstract: The solid state transformation of monoclinic TlCu{sub 3}Se{sub 2} into tetragonal TlCu{sub 2}Se{sub 2} by oxidative copper leaching in concentrated ammonia solution has been studied in situ by the use of synchrotron radiation. The diffraction patterns of parent and daughter phase are both sharp, indicating a strong topotactic relationship between them that effectuates a rapid change by “chimie douce” performed at +19 °C. The transformation rate is strongly connected to the access of oxygen from the surrounding air. The transformation was followed in a real-time mode, being almost complete after 2.5 h with 1 h incubation due to low oxygen content, as shown from refining the diffraction patterns by Rietveld profile technique.

Comparison of reduction agents in the synthesis of infinite-layer LaNiO2 films

International Nuclear Information System (INIS)

Ikeda, Ai; Manabe, Takaaki; Naito, Michio

2014-01-01

Highlights: • Reduction agents were compared from a viewpoint of the facility for topotactic reduction of LaNiO 3 to LaNiO 2 films. • TiH 2 and CaH 2 yielded infinite-layer LaNiO 2 with low and metallic resistivity. • H 2 released from metal hydrides plays a dominant role in the topotactic reduction. - Abstract: Reduction agents, such as activated carbon, TiH 2 , and CaH 2 , were compared from a viewpoint of the facility for the topotactic reduction of LaNiO 3 to LaNiO 2 films. Activated carbon did not yield infinite-layer LaNiO 2 whereas both of TiH 2 and CaH 2 yielded infinite-layer LaNiO 2 with low resistivity (∼1 mΩ cm at 300 K) as well as metallic behavior down to 70 K. Thermal desorption spectroscopy indicated that H 2 released from metal hydrides plays a dominant role in the topotactic reduction

Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2}){sub x}F (x=1 and 2): New one-dimensional Bi-coordination materials-Reversible hydration and topotactic decomposition to {alpha}-Bi{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Jeon, Hye Rim [Department of Chemistry Education, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Lee, Dong Woo [Department of Chemistry, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul 156-756 (Korea, Republic of)

2012-03-15

Two one-dimensional bismuth-coordination materials, Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2}){sub x}F (x=1 and 2), have been synthesized by hydrothermal reactions using Bi{sub 2}O{sub 3}, 2,6-NC{sub 5}H{sub 3}(CO{sub 2}H){sub 2}, HF, and water at 180 Degree-Sign C. Structures of the two materials were determined by single-crystal X-ray diffraction. Although they have different crystal structures, both Bi-organic materials shared a common structural motif, a one-dimensional chain structure consisting of Bi{sup 3+} cations and pyridine dicarboxylate linkers. Detailed structural analyses include infrared spectroscopy, thermogravimetric analysis, and reversible hydration reactions for the coordinated water molecules were reported. Also, thermal decomposition of the rod-shaped Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F single crystals at 800 Degree-Sign C led to {alpha}-Bi{sub 2}O{sub 3} that maintained the same morphology of the original crystals. - Graphical abstract: Calcination of the Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F single crystals at 800 Degree-Sign C results in the {alpha}-Bi{sub 2}O{sub 3} rods that maintain the original morphology of the crystals. Highlights: Black-Right-Pointing-Pointer Synthesis of one-dimensional chain Bi-organic frameworks. Black-Right-Pointing-Pointer Reversible hydration reactions of Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F. Black-Right-Pointing-Pointer Topotactic decomposition maintaining the same morphology of the original crystals.

Epitaxial growth and electronic structure of oxyhydride SrVO{sub 2}H thin films

Energy Technology Data Exchange (ETDEWEB)

Katayama, Tsukasa; Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Yamada, Keisuke; Onozuka, Tomoya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shigematsu, Kei [Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan); Minohara, Makoto; Kumigashira, Hiroshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Mikazuki-cho, Hyogo 679-5198 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan)

2016-08-28

Oxyhydride SrVO{sub 2}H epitaxial thin films were fabricated on SrTiO{sub 3} substrates via topotactic hydridation of oxide SrVO{sub 3} films using CaH{sub 2}. Structural and composition analyses suggested that the SrVO{sub 2}H film possessed one-dimensionally ordered V-H{sup −}-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO{sub 2}H film was reversible to SrVO{sub 3} by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V{sup 3+} valence state in the SrVO{sub 2}H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

Preparation of Sr7Mn4O13F2 by the topotactic reduction and subsequent fluorination of Sr7Mn4O15.

Science.gov (United States)

Saratovsky, Ian; Lockett, Michelle A; Rees, Nicholas H; Hayward, Michael A

2008-06-16

The topotactic reduction and subsequent fluorination of Sr7Mn4O15 yields a phase of composition Sr7Mn4O13F2. Characterization of this phase utilizing powder neutron diffraction and 19F NMR shows that the fluoride ions are located on a single anion site, the same crystallographic site that is vacant in the reduced intermediate Sr7Mn4O13.

Formation, structure and magnetism of the metastable defect fluorite phases AVO3.5+x (A=In, Sc)

International Nuclear Information System (INIS)

Shafi, Shahid P.; Lundgren, Rylan J.; Cranswick, Lachlan M.D.; Bieringer, Mario

2007-01-01

We report the preparation and stability of ScVO 3.5+x and the novel phase InVO 3.5+x . AVO 3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO 3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 deg. C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO 3.5+x structures following this pathway are 0.00≤x≤0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO 3.54 and ScVO 3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)A, respectively with A 3+ /V 4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V 4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state. - Graphical abstract: Topotactic oxidation of AVO 3 bixbyite to AVO 3.5 defect fluorite structure followed by in-situ powder X-ray diffraction. The upper structural diagram shows a six coordinated (A/V)-O 6 fragment in bixbyite, the lower structure illustrates the same seven-fold coordinated (A/V)-O 7 cubic environment in the defect fluorite structure

Synthesis for Structure Rewriting Systems

Science.gov (United States)

Kaiser, Łukasz

The description of a single state of a modelled system is often complex in practice, but few procedures for synthesis address this problem in depth. We study systems in which a state is described by an arbitrary finite structure, and changes of the state are represented by structure rewriting rules, a generalisation of term and graph rewriting. Both the environment and the controller are allowed to change the structure in this way, and the question we ask is how a strategy for the controller that ensures a given property can be synthesised.

The topotactic transformation of Ti3SiC2 into a partially ordered cubic Ti(C0.67Si0.06) phase by the diffusion of Si into molten cryolite

International Nuclear Information System (INIS)

Barsoum, M.W.; El-Raghy, T.; Farber, L.; Amer, M.; Christini, R.; Adams

1999-01-01

Immersion of Ti 3 SiC 2 samples in molten cryolite at 960 C resulted in the preferential diffusion of Si atoms out of the basal planes to form a partially ordered, cubic phase with approximate chemistry Ti(C 0.67 , Si 0.06 ). The latter forms in domains, wherein the (111) planes are related by mirror planes; i.e., the loss of Si results in the de-twinning of the Ti 3 C 2 layers. Raman spectroscopy, X-ray diffraction, optical, scanning and transmission electron microscopy all indicate that the Si exists the structure topotactically, in such a way that the C atoms remain partially in their ordered position in the cubic phase

Substitutional Carbon-Modified Anatase TiO2 Decahedral Plates Directly Derived from Titanium Oxalate Crystals via Topotactic Transition.

Science.gov (United States)

Niu, Ping; Wu, Tingting; Wen, Lei; Tan, Jun; Yang, Yongqiang; Zheng, Shijian; Liang, Yan; Li, Feng; Irvine, John Ts; Liu, Gang; Ma, Xiuliang; Cheng, Hui-Ming

2018-03-30

Changing the composition and/or structure of some metal oxides at the atomic level can significantly improve their performance in different applications. Although many strategies have been developed, the introduction of heteroatoms, particularly anions to the internal part of metal oxide particles, is still not adequate. Here, an effective strategy is demonstrated for directly preparing polycrystalline decahedral plates of substitutional carbon-doped anatase TiO 2 from titanium (IV) oxalate by a thermally induced topotactic transition in an inert atmosphere. Because of the carbon concentration gradient introduced in side of the plates, the carbon-doped TiO 2 (TiO 2- x C x ) shows an increased visible light absorption and a two orders of magnitude higher electrical conductivity than pure TiO 2 . Consequently, it can be used as a photocatalyst and an active material for lithium storage and shows much superior activity in generating hydroxyl radicals under visible light and greatly increased electrical-specific capacity at high charge-discharge rates. The strategy developed could also be applicable to the atomic-scale modification of other metal oxides. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and Electrochemistry of Li3MnO4: Mn in the +5 OxidationState

Energy Technology Data Exchange (ETDEWEB)

Saint, Juliette.A.; Doeff, Marca M.; Reed, John

2007-06-19

Computational and experimental work directed at exploringthe electrochemical properties of tetrahedrally coordinated Mn in the +5oxidation state is presented. Specific capacities of nearly 700 mAh/g arepredicted for the redox processes of LixMnO4 complexes based on twotwo-phase reactions. One is topotactic extractionof Li from Li3MnO4 toform LiMnO4 and the second is topotactic insertion of Li into Li3MnO4 toform Li5MnO4. In experiments, it is found that the redox behavior ofLi3MnO4 is complicated by disproportionation of Mn5+ in solution to formMn4+ and Mn7+ and byother irreversible processes; although an initialcapacity of about 275 mAh/g in lithiumcells was achieved. Strategiesbased on structural considerations to improve the electrochemicalproperties of MnO4n- complexes are given.

Comparison of reduction agents in the synthesis of infinite-layer LaNiO{sub 2} films

Energy Technology Data Exchange (ETDEWEB)

Ikeda, Ai [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 (Japan); Research Fellow of the Japan Society for the Promotion of Science, Ichiban-cho 8, Chiyoda, Tokyo 102-8472 (Japan); Manabe, Takaaki [National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8565 (Japan); Naito, Michio, E-mail: minaito@cc.tuat.ac.jp [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 (Japan)

2014-11-15

Highlights: • Reduction agents were compared from a viewpoint of the facility for topotactic reduction of LaNiO{sub 3} to LaNiO{sub 2} films. • TiH{sub 2} and CaH{sub 2} yielded infinite-layer LaNiO{sub 2} with low and metallic resistivity. • H{sub 2} released from metal hydrides plays a dominant role in the topotactic reduction. - Abstract: Reduction agents, such as activated carbon, TiH{sub 2}, and CaH{sub 2}, were compared from a viewpoint of the facility for the topotactic reduction of LaNiO{sub 3} to LaNiO{sub 2} films. Activated carbon did not yield infinite-layer LaNiO{sub 2} whereas both of TiH{sub 2} and CaH{sub 2} yielded infinite-layer LaNiO{sub 2} with low resistivity (∼1 mΩ cm at 300 K) as well as metallic behavior down to 70 K. Thermal desorption spectroscopy indicated that H{sub 2} released from metal hydrides plays a dominant role in the topotactic reduction.

Influence the of Na-LTA synthesis route on low-carnegieite crystallization and stability

Directory of Open Access Journals (Sweden)

Radulović Aleksandra M.

2007-01-01

Full Text Available The thermal transformation of zeolite precursor is a relatively novel route for the synthesis of aluminosilicate-based ceramic materials which had found numerous uses in the production of dielectric ceramics, microelectronic packaging electromagnetic windows, high-temperature electrical insulators, glass ceramic materials, etc. The mechanism of a thermally induced transformation strongly depends on the extra framework cations and the type of used zeolites. The sodium form of LTA zeolite transforms to low-carnegieite (lt-Carn in the temperature range between 800 and 900°C. The formed low-carnegieite transforms to nepheline at >900°C. However, the mechanisms of the thermal transformation of Na-LTA zeolite into the low-carnegieite (lt-Carn phase are still not completely understood. Different structure transformation mechanisms of Na-LTA zeolite into lt-Carn heve been reported. The carnegieite can be formed by a direct solid-solid topotactic transformation: Na-LTA -> lt-Carn. A two step mechanism: Na-LTA -> Am -> lt-Carn can also take place. Such behavior is probably the consequence of the applied synthesis route in the precursor preparation. Therefore, it is of interest to consider the influence of the zeolite preparation route on the processes of thermal transformation of Na-LTA zeolite into lt-Carn. The present paper deals with a systematic study on the thermally induced phase transformation of sodium LTA zeolites synthesized by the gel route under different reaction conditionss. Different gel compositions Na2O(2.4-3.9:Al2O3(l:SiO2(1.5-2.0:H2O(90-170 were used and several zeolite samples were prepared. The prepared zeolite samples were thermally treated at different temperatures from 600 to 950°C at an interval of 20 °C and the products were analyzed by X-ray diffraction. The zeolites and formed products were characterized by various methods including XRPD, IR, DTA, SEM. It was shown that the rate of lt-Carn formation is dependent on the

Formation of tavorite-type LiFeSO4F followed by in situ X-ray diffraction

Science.gov (United States)

Eriksson, Rickard; Sobkowiak, Adam; Ångström, Jonas; Sahlberg, Martin; Gustafsson, Torbjörn; Edström, Kristina; Björefors, Fredrik

2015-12-01

The tavorite-type polymorph of LiFeSO4F has recently attracted substantial attention as a positive electrode material for lithium ion batteries. The synthesis of this material is generally considered to rely on a topotactic exchange of water (H2O) for lithium (Li) and fluorine (F) within the structurally similar hydrated iron sulfate precursor (FeSO4·H2O) when reacted with lithium fluoride (LiF). However, there have also been discussions in the literature regarding the possibility of a non-topotactic reaction mechanism between lithium sulfate (Li2SO4) and iron fluoride (FeF2) in tetraethylene glycol (TEG) as reaction medium. In this work, we use in situ X-ray diffraction to continuously follow the formation of LiFeSO4F from the two suggested precursor mixtures in a setup aimed to mimic the conditions of a solvothermal autoclave synthesis. It is demonstrated that LiFeSO4F is formed directly from FeSO4·H2O and LiF, in agreement with the proposed topotactic mechanism. The Li2SO4 and FeF2 precursors, on the other hand, are shown to rapidly transform into FeSO4·H2O and LiF with the water originating from the highly hygroscopic TEG before a subsequent formation of LiFeSO4F is initiated. The results highlight the importance of the FeSO4·H2O precursor in obtaining the tavorite-type LiFeSO4F, as it is observed in both reaction routes.

Total synthesis of the proposed structure of trichodermatide A.

Science.gov (United States)

Myers, Eddie; Herrero-Gómez, Elena; Albrecht, Irina; Lachs, Jennifer; Mayer, Peter; Hanni, Matti; Ochsenfeld, Christian; Trauner, Dirk

2014-10-17

A short total synthesis of the published structure of racemic trichodermatide A is reported. Our synthesis involves a Knoevenagel condensation/Michael addition sequence, followed by the formation of tricyclic hexahydroxanthene-dione and a diastereoselective bis-hydroxylation. The final product, the structure of which was confirmed by X-ray crystallography, has NMR spectra that are very similar, but not identical, to those of the isolated natural product. Quantum chemically computed (13)C shifts agree well with the present NMR measurements.

HRTEM and neutron diffraction study of LixMo5O17: From the ribbon (x=5) structure to the rock salt (x=12) structure

International Nuclear Information System (INIS)

Lebedev, O.I.; Caignaert, V.; Raveau, B.; Pop, N.; Gozzo, F.; Van Tendeloo, G.; Pralong, V.

2011-01-01

Structure determination of the fully intercalated phase Li 12 Mo 5 O 17 and of the deintercalated oxide Li 5 Mo 5 O 17 has been carried out by electron microscopy and neutron powder diffraction. The reversible topotactic transformation between the ordered rock salt structure of the former and the ribbon structure of the latter (closely related to that of Li 4 Mo 5 O 17 ) is explained on the following basis: both structures can be described as strips built up as an assembly of infinite ribbons of MoO 6 octahedra that are five octahedra thick, and that differ by slight displacements of the octahedral ribbons. We show that the electrochemical behavior of the Li x Mo 5 O 17 system is based on two sorts of Li + sites; those that are located within the strips between the ribbons, and those that are located at the border of the strips. The high rate of Li intercalation in this oxide and its reversibility are discussed in terms of its peculiar structure. -- Graphical abstract: Structure determination of the fully intercalated phase Li 12 Mo 5 O 17 and of the deintercalated oxide Li 5 Mo 5 O 17 has been carried out by electron microscopy and neutron powder diffraction. The reversible topotactic transformation between the ordered rock salt structure of the former and the ribbon structure of the latter is explained on the following basis: both structures can be described as strips built up as an assembly of infinite ribbons of MoO 6 octahedra that are five octahedra thick, and that differ by slight displacements of the octahedral ribbons. We show that the electrochemical behavior of the Li x Mo 5 O 17 system is based on two sorts of Li + sites; those that are located within the strips between the ribbons, and those that are located at the border of the strips. The high rate of Li intercalation in this oxide and its reversibility are discussed in terms of its peculiar structure. Research highlights: → Electron microscopy and neutron powder diffraction structure determination

PROSPECTIVE TEACHERS’ COGNITIVE STRUCTURES CONCERNING PROTEIN SYNTHESIS AND THEIR DEGREE OF UNDERSTANDING

Directory of Open Access Journals (Sweden)

Cem Gerçek

2018-02-01

Full Text Available The purpose of education is to actualise meaningful learning. Therefore, researching the issues on how students process information and how they configure it is important for meaningful learning. The issue of protein synthesis contains a number of abstract topics and concepts. Hence, it is important in biology teaching to be informed of students’ cognitive structures concerning protein synthesis. This research aims to analyse prospective teachers’ cognitive structures about protein synthesis and their degree of understanding the subject. The research group was composed of 17 volunteering prospective teachers who had been chosen through purposeful sampling. The data were collected via semi-structured interviews. Flow maps and content analysis were used in analysing the data. The results demonstrated that prospective teachers had too many misconceptions about protein synthesis and that their knowledge extent and rich connection are inadequate. The prospective teachers’ degree of understanding protein synthesis was divided into three categories. The results obtained in this research suggested that teachers should be careful in teaching the subject of protein synthesis. Students’ prior knowledge and their misconceptions should be determined and content or contexts to facilitate them to learn an abstract subject such as protein synthesis should be presented.

Ultrafast Hydro-Micromechanical Synthesis of Calcium Zincate: Structural and Morphological Characterizations

Directory of Open Access Journals (Sweden)

Vincent Caldeira

2017-01-01

Full Text Available Calcium zincate is a compound with a large panel of application: mainly known as an advantageous replacement of zinc oxide in negative electrodes for air-zinc or nickel-zinc batteries, it is also used as precursor catalyst in biodiesel synthesis and as antifungal compound for the protection of limestone monuments. However, its synthesis is not optimized yet. In this study, it was elaborated using an ultrafast synthesis protocol: Hydro-Micromechanical Synthesis. Two other synthesis methods, Hydrochemical Synthesis and Hydrothermal Synthesis, were used for comparison. In all cases, the as-synthesized samples were analyzed by X-ray diffraction, scanning electron microscopy, and LASER diffraction particle size analysis. Rietveld method was used to refine various structural parameters and obtain an average crystallite size, on a Hydro-Micromechanical submicronic sample. X-ray single crystal structure determination was performed on a crystal obtained by Hydrochemical Synthesis. It has been shown that regardless of the synthesis protocol, the prepared samples always crystallize in the same crystal lattice, with P21/c space group and only differ from their macroscopic textural parameters. Nevertheless, only the Hydro-Micromechanical method is industrially scalable and enables a precise control of the textural parameters of the obtained calcium zincate.

Iodine as an oxidant in the topotactic deintercalation of interstitial iron in Fe(1+x)Te.

Science.gov (United States)

Rodriguez, Efrain E; Zavalij, Peter; Hsieh, Ping-Yen; Green, Mark A

2010-07-28

The layered telluride, Fe(1+x)Te, is a parent compound of the isostructural and superconducting phases, Fe(1+x)(Te, Se, S). Here we show that, through a simple reaction of I(2) vapor with both powder and single crystal samples, the interstitial iron can be removed from the FeTe framework topotactically. Neutron powder diffraction and X-ray single crystal diffraction confirm that the iron being extracted is the partially occupied site that lies between the 2-D blocks of edge-sharing FeTe(4) tetrahedra. The deintercalation process has consequences for both magnetic and crystallographic phase transitions in the compound at low temperatures. This technique could be of use for the tuning of stoichiometry of the superconducting phases and therefore enable more careful studies on how chemical composition affects magnetic and superconducting properties.

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca1-xLaxFeO3-δ

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-08-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca0.5La0.5FeOz (2.5 topotactic oxygen extraction and reinsertion during discharge and charge processes.

Radiation induced topotactic [2 + 2] dimerisation of acrylate derivatives among the layers of a CaFe layered double hydroxide followed by IR spectroscopy

Science.gov (United States)

Srankó, D. F.; Canton, S.; Enghdahl, A.; Muráth, Sz.; Kukovecz, Á.; Kónya, Z.; Sipiczki, M.; Sipos, P.; Pálinkó, I.

2013-07-01

Various acrylates [E-phenylpropenoate, E-3(4‧-nitrophenyl)propenoate, E-3(2‧,5‧-difluorphenyl)propenoate, E-3(2‧-thienyl)propenoate, E-3(4‧-imidazolyl)propenoate or E-2,3-dimethylpropenoate] were successfully intercalated into Ca(II)Fe(III) layered double hydroxide (CaFe-LDH) verified by a range of instrumental methods. The possible arrangements for the organic anions were suggested on the basis of basal spacing data, layer thickness and the dimensions of the quantum chemically optimised structures of the acrylate ions. Using the acrylate-CaFe-LDHs as reactant-filled nanoreactors, photoinitiated topotactic [2 + 2] cyclisation reactions followed by IR spectroscopy could be performed with many representatives [E-phenylpropenoate-, E-3(4‧-nitrophenyl)propenoate-, E-3(2‧,5‧-difluorphenyl)propenoate- or E-3(2‧-thienyl)propenoate-CaFe-LDHs] resulting in cyclobutane derivatives within the layers of the host material indicating that there were domains where the intercalated anions were in close proximity to each other and in proper arrangement for the reaction to occur.

300% Enhancement of Carrier Mobility in Uniaxial-Oriented Perovskite Films Formed by Topotactic-Oriented Attachment.

Science.gov (United States)

Kim, Dong Hoe; Park, Jaehong; Li, Zhen; Yang, Mengjin; Park, Ji-Sang; Park, Ik Jae; Kim, Jin Young; Berry, Joseph J; Rumbles, Garry; Zhu, Kai

2017-06-01

Organic-inorganic perovskites with intriguing optical and electrical properties have attracted significant research interests due to their excellent performance in optoelectronic devices. Recent efforts on preparing uniform and large-grain polycrystalline perovskite films have led to enhanced carrier lifetime up to several microseconds. However, the mobility and trap densities of polycrystalline perovskite films are still significantly behind their single-crystal counterparts. Here, a facile topotactic-oriented attachment (TOA) process to grow highly oriented perovskite films, featuring strong uniaxial-crystallographic texture, micrometer-grain morphology, high crystallinity, low trap density (≈4 × 10 14 cm -3 ), and unprecedented 9 GHz charge-carrier mobility (71 cm 2 V -1 s -1 ), is demonstrated. TOA-perovskite-based n-i-p planar solar cells show minimal discrepancies between stabilized efficiency (19.0%) and reverse-scan efficiency (19.7%). The TOA process is also applicable for growing other state-of-the-art perovskite alloys, including triple-cation and mixed-halide perovskites. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel method of room temperature ionic liquid assisted Fe3O4 nanocubes and nanoflakes synthesis

International Nuclear Information System (INIS)

Ramalakshmi, M.; Shakkthivel, P.; Sundrarajan, M.; Chen, S.M.

2013-01-01

Graphical abstract: - Highlights: • First time [Bmim][TfO] IL is used for the Fe 3 O 4 nanoparticle synthesis. • Novel method tunes Fe 3 O 4 nanocubes and nanoflakes forms influenced by the base and IL. • Fe 3 O 4 oxidized topotactically into γ-Fe 2 O 3 nanoparticles by annealing and base. • Uniform morphology with average size of 33 nm negligible superstructure are formed. • Ms values are characterized by thin layer of γ-Fe 2 O 3 on the nanoparticle surface. - Abstract: For the first time, the nanomagnetite superparamagnetic particles are successfully synthesized by precipitation method using 1-n-butyl-3-methylimidazolium trifluoromethane sulfonate [Bmim][TfO] ionic liquid medium/surfactant. The obtained Fe 3 O 4 particles are nanocubes and nanoflakes and this formation is influenced by the base concentration and anisotropic circumstances produced by the ionic liquid and their size varies from 20 nm to 150 × 300 nm (width × length). The synthesized magnetite nanoparticles are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM) and Vibrating sample magnetometer (VSM) studies. The results show that the core of the Fe 3 O 4 nanoparticles is surrounded by a thin layer of γ-Fe 2 O 3 by topotactical partial oxidation, which is remarkably proceed with the subsequent calcination. The magnetite nanocubes have high saturation magnetization value and exhibit superparamagnetic hysteresis loop

Sonochemical assisted synthesis of SrFe12O19 nanoparticles.

Science.gov (United States)

Palomino, R L; Bolarín Miró, A M; Tenorio, F N; Sánchez De Jesús, F; Cortés Escobedo, C A; Ammar, S

2016-03-01

We present the synthesis of M-type strontium hexaferrite by sonochemistry and annealing. The effects of the sonication time and thermal energy on the crystal structure and magnetic properties of the obtained powders are presented. Strontium hexagonal ferrite (SrFe12O19) was successfully prepared by the ultrasonic cavitation (sonochemistry) of a complexed polyol solution of metallic acetates and diethylene glycol. The obtained materials were subsequently annealed at temperatures from 300 to 900 °C. X-ray diffraction analysis shows that the sonochemical process yields an amorphous phase containing Fe(3+), Fe(2+) and Sr(2+) ions. This amorphous phase transforms into an intermediate phase of maghemite (γ-Fe2O3) at 300 °C. At 500 °C, the intermediate species is converted to hematite (α-Fe2O3) by a topotactic transition. The final product of strontium hexaferrite (SrFe12O19) is generated at 800 °C. The obtained strontium hexaferrite shows a magnetization of 62.3 emu/g, which is consistent with pure hexaferrite obtained by other methods, and a coercivity of 6.25 kOe, which is higher than expected for this hexaferrite. The powder morphology is composed of aggregates of rounded particles with an average particle size of 60 nm. Copyright © 2015 Elsevier B.V. All rights reserved.

Structured synthesis of MEMS using evolutionary approaches

DEFF Research Database (Denmark)

Fan, Zhun; Wang, Jiachuan; Achiche, Sofiane

2008-01-01

In this paper, we discuss the hierarchy that is involved in a typical MEMS design and how evolutionary approaches can be used to automate the hierarchical synthesis process for MEMS. The paper first introduces the flow of a structured MEMS design process and emphasizes that system-level lumped...

Ultrathin bismuth nanosheets from in situ topotactic transformation for selective electrocatalytic CO2 reduction to formate.

Science.gov (United States)

Han, Na; Wang, Yu; Yang, Hui; Deng, Jun; Wu, Jinghua; Li, Yafei; Li, Yanguang

2018-04-03

Electrocatalytic carbon dioxide reduction to formate is desirable but challenging. Current attention is mostly focused on tin-based materials, which, unfortunately, often suffer from limited Faradaic efficiency. The potential of bismuth in carbon dioxide reduction has been suggested but remained understudied. Here, we report that ultrathin bismuth nanosheets are prepared from the in situ topotactic transformation of bismuth oxyiodide nanosheets. They process single crystallinity and enlarged surface areas. Such an advantageous nanostructure affords the material with excellent electrocatalytic performance for carbon dioxide reduction to formate. High selectivity (~100%) and large current density are measured over a broad potential, as well as excellent durability for >10 h. Its selectivity for formate is also understood by density functional theory calculations. In addition, bismuth nanosheets were coupled with an iridium-based oxygen evolution electrocatalyst to achieve efficient full-cell electrolysis. When powered by two AA-size alkaline batteries, the full cell exhibits impressive Faradaic efficiency and electricity-to-formate conversion efficiency.

Topotactic conversion of layered silicate RUB-15 to silica sodalite through interlayer condensation in N-methylformamide.

Science.gov (United States)

Koike, Masakazu; Asakura, Yusuke; Sugihara, Megumi; Kuroda, Yoshiyuki; Tsuzura, Hidehiro; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki

2017-08-08

Silica sodalite was obtained using topotactic conversion of layered silicate RUB-15 through stepwise processes that consisted of the control of stacking sequence of the layers, interlayer condensation by refluxing, and elimination of intercalated guest species. The interlayer condensation of RUB-15, in which acetic acid was pre-intercalated between the layers to control the stacking sequence, afforded a sodalite framework containing organic guest species by refluxing in N-methylformamide (NMF). The pre-intercalated acetic acid molecules were largely replaced with NMF. This formation process of silica sodalite containing large amounts of intercalated organic guest species is in clear contrast to the previously reported process that used direct calcination of an intercalation compound of layered RUB-15 accommodating acetic acid between the layers. Calcination of the condensed product provided sodalite with fewer defects than the directly calcined product, thus indicating the advantage of the stepwise process. The method reported here is useful for the preparation of pure silica sodalite with relatively low defects and plate-like morphology.

Synthesis and structure of two-dimensional transition-metal dichalcogenides

KAUST Repository

Shi, Yumeng; Zhang, Hua; Chang, Wen-Hao; Shin, Hyeon Suk; Li, Lain-Jong

2015-01-01

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) exhibit unique electrical, optical, thermal, and mechanical properties, which enable them to be used as building blocks in compact and lightweight integrated electronic systems. The controllable and reliable synthesis of atomically thin TMDCs is essential for their practical application. Recent progress in large-area synthesis of monolayer TMDCs paves the way for practical production of various 2D TMDC layers. The intrinsic optical and electrical properties of monolayer TMDCs can be defined by stoichiometry during synthesis. By manipulating the lattice structure or layer stacking manner, it is possible to create atomically thin van der Waals materials with unique and unexplored physical properties. In this article, we review recent developments in the synthesis of TMDC monolayers, alloys, and heterostructures, which shine light on the design of novel TMDCs with desired functional properties.

Synthesis and structure of two-dimensional transition-metal dichalcogenides

KAUST Repository

Shi, Yumeng

2015-07-13

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) exhibit unique electrical, optical, thermal, and mechanical properties, which enable them to be used as building blocks in compact and lightweight integrated electronic systems. The controllable and reliable synthesis of atomically thin TMDCs is essential for their practical application. Recent progress in large-area synthesis of monolayer TMDCs paves the way for practical production of various 2D TMDC layers. The intrinsic optical and electrical properties of monolayer TMDCs can be defined by stoichiometry during synthesis. By manipulating the lattice structure or layer stacking manner, it is possible to create atomically thin van der Waals materials with unique and unexplored physical properties. In this article, we review recent developments in the synthesis of TMDC monolayers, alloys, and heterostructures, which shine light on the design of novel TMDCs with desired functional properties.

Novel metal oxides prepared by ingenious synthetic routes

International Nuclear Information System (INIS)

Rao, C.N.R.; Gopalakrishnan, J.; Vidyasagar, K.; Ganguli, A.K.; Ramanan, A.; Ganapathi, L.

1986-01-01

Several novel oxides have been prepared by the decomposition of carbonate precursors of calcite structure of the general formulas Mn/sub 1-x/M/sub x/CO 3 (M = Mg,Co,Cd), Ca/sub 1-x/M/sup prime//sub x/CO 3 , and Ca/sub 1-x/-yM/sup //sub x/M/sup double-prime//sub y/CO 3 (M',M'' = Mn,Fe,Co). Typical of the oxides synthesized are a variety of monoxides, Mn/sub 1-x/M/sub x/O, of rocksalt structure and perovskite-related oxides such as Ca 2 FeCoO 5 , Ca 2 Co 2 O 5 , and Ca 3 Fe 2 MnO 8 , many of them exhibiting novel anion-vacancy-ordered superstructures. An interesting series of oxides prepared by the topotactic reduction of Ca 2 Fe/sub 2-x/Mn/sub x/O/sub 6-y/ (synthesized by the decomposition of the corresponding carbonate precursors) is Ca 2 Fe/sub 2-x/Mn/sub x/O 5 where three different coordination polyhedra (octahedra, tetrahedra, and square pyramids) of the transition metals coexist. Topotactic reduction of LaCoO 3 and LaNiO 3 yields new oxides, La 2 Co 2 O 5 and La 2 Ni 2 O 5 , possessing anion-vacancy-ordered superstructures. While La 2 Co 2 O 5 adopts the brownmillerite structure, La 2 Ni 2 O 5 exhibits a new type of vacancy ordering with octahedral and square-planar coordination of Ni 2+ . Slightly reduced LaNiO 3 seem to exhibit crystallographic shear (CS) planes similar to WO/sub 3-x/. Topotactic dehydration of isostructural Mo/sub 1-x/W/sub x/O 3 x H 2 O provides a convenient route for the synthesis of Mo/sub 1-x/W/sub x/O 3 (0 3 -related structure

Enhanced photoactivity from single-crystalline SrTaO2N nanoplates synthesized by topotactic nitridation

International Nuclear Information System (INIS)

Fu, Jie; Skrabalak, Sara E.

2017-01-01

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Enhanced Photoactivity from Single-Crystalline SrTaO2 N Nanoplates Synthesized by Topotactic Nitridation.

Science.gov (United States)

Fu, Jie; Skrabalak, Sara E

2017-11-06

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and structural characterization of a calcium coordination ...

Indian Academy of Sciences (India)

Synthesis and structural characterization of a calcium coordination polymer based on a μ3-bridging. tetradentate binding mode of glycine. SUBRAMANIAN NATARAJAN*a, BIKSHANDARKOIL R. SRINIVASANb , J. KALYANA SUNDARa, K. RAVIKUMARc , R.V. KRISHNAKUMARd , J. SURESHe,. aSchool of Physics, ...

One-Dimensional SnO2 Nano structures: Synthesis and Applications

International Nuclear Information System (INIS)

Pan, J.; Shen, H.; Mathur, S.; Pan, J.

2012-01-01

Nano scale semiconducting materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, like nano wires, nano belts, and nano tubes, have gained tremendous attention within the past decade. Among the variety of 1D nano structures, tin oxide (SnO 2 ) semiconducting nano structures are particularly interesting because of their promising applications in optoelectronic and electronic devices due to both good conductivity and transparence in the visible region. This article provides a comprehensive review of the recent research activities that focus on the rational synthesis and unique applications of 1D SnO 2 nano structures and their optical and electrical properties. We begin with the rational design and synthesis of 1D SnO 2 nano structures, such as nano tubes, nano wires, nano belts, and some heterogeneous nano structures, and then highlight a range of applications (e.g., gas sensor, lithium-ion batteries, and nano photonics) associated with them. Finally, the review is concluded with some perspectives with respect to future research on 1D SnO 2 nano structures

Superheavy Element Synthesis and Nuclear Structure

International Nuclear Information System (INIS)

Ackermann, D.

2009-01-01

The search for the next closed proton and neutron shells beyond 2 08P b has yielded a number of exciting results in terms of the synthesis of new elements [1,2,3]. The superheavy elements (SHE), however, are a nuclear structure phenomenon. They owe their existence to the quantum mechanical origin of shell correction energies without which they would not be bound. In recent years the development of efficient experimental set-ups including separators and advanced particle and photon detection arrangements allowed for more and more detailed nuclear structure studies for nuclei at and beyond Z=100. A review of those recent achievements is given in ref. [4]. Among the most interesting features is the observation of K-isomeric states. Experimentally about 14 cases have been identified in the region of Z>96 as shown in Fig. 1. K-isomers or indications of their existence have been found for almost all even-Z elements in the region Z=100 to 110. We could recently establish and/or confirm such states in the even-even isotopes 2 52,254N o [5]. The heaviest nucleus where such a state was found is 2 70D s with Z=110 as we reported in 2001 [6]. Those nuclear structure studies lay out the grounds for a detailed understanding of these heavy and high-Z nuclear systems, and contribute at the same time valuable information to preparation of strategies to successfully continue the hunt for the localisation of the next spherical proton and neutron shells after 2 08P b. The recent activities for both SHE synthesis and nuclear structure investigations at GSI will be reported.(author)

Reversal of lattice, electronic structure, and magnetism in epitaxial SrCoOx thin films

Science.gov (United States)

Jeen, H.; Choi, W. S.; Lee, J. H.; Cooper, V. R.; Lee, H. N.; Seo, S. S. A.; Rabe, K. M.

2014-03-01

SrCoOx (x = 2.5 - 3.0, SCO) is an ideal material to study the role of oxygen content for electronic structure and magnetism, since SCO has two distinct topotactic phases: the antiferromagnetic insulating brownmillerite SrCoO2.5 and the ferromagnetic metallic perovskite SrCoO3. In this presentation, we report direct observation of a reversible lattice and electronic structure evolution in SrCoOx epitaxial thin films as well as different magnetic and electronic ground states between the topotactic phases.[2] By magnetization measurements, optical absorption, and transport measurements drastically different electronic and magnetic ground states are found in the epitaxially grown SrCoO2.5 and SrCoO3 thin films by pulsed laser epitaxy. First-principles calculations confirm substantial, which originate from the modification in the Co valence states and crystallographic structures. By real-time spectroscopic ellipsometry, the two electronically and magnetically different phases can be reversibly changed by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides. The work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

MWW-type titanosilicate synthesis, structural modification and catalytic applications to green oxidations

CERN Document Server

Wu, Peng; Xu, Le; Liu, Yueming; He, Mingyuan

2013-01-01

This book provides a comprehensive review of a new generation of selective oxidation titanosilicate catalysts with the MWW topology (Ti-MWW) based on the research achievements of the past 12 years. It gives an overview of the synthesis, structure modification and catalytic properties of Ti-MWW. Ti-MWW can readily be prepared by means of direct hydrothermal synthesis with crystallization-supporting agents, using dual-structure-directing agents and a dry-gel conversion technique. It also can be post-synthesized through unique reversible structure transformation and liquid-phase isomorphous subst

Voltage-Controlled Topotactic Phase Transition in Thin-Film SrCoOx Monitored by In Situ X-ray Diffraction.

Science.gov (United States)

Lu, Qiyang; Yildiz, Bilge

2016-02-10

Topotactic phase transition of functional oxides induced by changes in oxygen nonstoichiometry can largely alter multiple physical and chemical properties, including electrical conductivity, magnetic state, oxygen diffusivity, and electrocatalytic reactivity. For tuning these properties reversibly, feasible means to control oxygen nonstoichiometry-dependent phase transitions in functional oxides are needed. This paper describes the use of electrochemical potential to induce phase transition in strontium cobaltites, SrCoOx (SCO) between the brownmillerite (BM) phase, SrCoO₂.₅, and the perovskite (P) phase, SrCoO₃₋δ. To monitor the structural evolution of SCO, in situ X-ray diffraction (XRD) was performed on an electrochemical cell having (001) oriented thin-film SrCoOx as the working electrode on a single crystal (001) yttria-stabilized zirconia electrolyte in air. In order to change the effective pO₂ in SCO and trigger the phase transition from BM to P, external electrical biases of up to 200 mV were applied across the SCO film. The phase transition from BM to P phase could be triggered at a bias as low as 30 mV, corresponding to an effective pO₂ of 1 atm at 500 °C. The phase transition was fully reversible and the epitaxial film quality was maintained after reversible phase transitions. These results demonstrate the use of electrical bias to obtain fast and easily accessible switching between different phases as well as distinct physical and chemical properties of functional oxides as exemplified here for SCO.

X-ray excited photoluminescence near the giant resonance in solid-solution Gd1-xTbxOCl nanocrystals and their retention upon solvothermal topotactic transformation to Gd1-xTbxF3

Science.gov (United States)

Waetzig, Gregory R.; Horrocks, Gregory A.; Jude, Joshua W.; Zuin, Lucia; Banerjee, Sarbajit

2015-12-01

Design rules for X-ray phosphors are much less established as compared to their optically stimulated counterparts owing to the absence of a detailed understanding of sensitization mechanisms, activation pathways and recombination channels upon high-energy excitation. Here, we demonstrate a pronounced modulation of the X-ray excited photoluminescence of Tb3+ centers upon excitation in proximity to the giant resonance of the host Gd3+ ions in solid-solution Gd1-xTbxOCl nanocrystals prepared by a non-hydrolytic cross-coupling method. The strong suppression of X-ray excited optical luminescence at the giant resonance suggests a change in mechanism from multiple exciton generation to single thermal exciton formation and Auger decay processes. The solid-solution Gd1-xTbxOCl nanocrystals are further topotactically transformed with retention of a nine-coordinated cation environment to solid-solution Gd1-xTbxF3 nanocrystals upon solvothermal treatment with XeF2. The metastable hexagonal phase of GdF3 can be stabilized at room temperature through this topotactic approach and is transformed subsequently to the orthorhombic phase. The fluoride nanocrystals indicate an analogous but blue-shifted modulation of the X-ray excited optical luminescence of the Tb3+ centers upon X-ray excitation near the giant resonance of the host Gd3+ ions.Design rules for X-ray phosphors are much less established as compared to their optically stimulated counterparts owing to the absence of a detailed understanding of sensitization mechanisms, activation pathways and recombination channels upon high-energy excitation. Here, we demonstrate a pronounced modulation of the X-ray excited photoluminescence of Tb3+ centers upon excitation in proximity to the giant resonance of the host Gd3+ ions in solid-solution Gd1-xTbxOCl nanocrystals prepared by a non-hydrolytic cross-coupling method. The strong suppression of X-ray excited optical luminescence at the giant resonance suggests a change in mechanism

Synthesis and ammonolysis of nickel and cobalt tungstates and their characterisation

Directory of Open Access Journals (Sweden)

J.L. Rico

2016-07-01

Full Text Available The synthesis and characterization of NiW and CoW compounds are herein reported. The NiWO4 and CoWO4 samples, successfully synthesised by the hydrothermal method, were treated under NH3 to obtain the metal nitride. The SEM micrographs show that this transformation is a topotactic process. Tungsten trioxide was also treated under NH3 at similar operating conditions, and used as a reference. High nitrogen contents after ammonolysis were calculated, however, the percentages were below the theoretical values assuming the formation of pure NiWN, CoWN and WN. The XRD pattern indicates that WON is likely formed after ammonolysis of tungsten oxide whereas phase segregation was observed on the nickel and cobalt samples. Furthermore, the reactivity of the nitride samples as function of temperature was measured under argon and the results show that most of the nitrogen is removed from the cobalt and nickel samples whereas it was partially released from the tungsten specimen.

Marine Nucleosides: Structure, Bioactivity, Synthesis and Biosynthesis

Directory of Open Access Journals (Sweden)

Ri-Ming Huang

2014-12-01

Full Text Available Nucleosides are glycosylamines that structurally form part of nucleotide molecules, the building block of DNA and RNA. Both nucleosides and nucleotides are vital components of all living cells and involved in several key biological processes. Some of these nucleosides have been obtained from a variety of marine resources. Because of the biological importance of these compounds, this review covers 68 marine originated nucleosides and their synthetic analogs published up to June 2014. The review will focus on the structures, bioactivities, synthesis and biosynthetic processes of these compounds.

Comparison of reduction agents in the synthesis of infinite-layer LaNiO2 films

Science.gov (United States)

Ikeda, Ai; Manabe, Takaaki; Naito, Michio

2014-11-01

Reduction agents, such as activated carbon, TiH2, and CaH2, were compared from a viewpoint of the facility for the topotactic reduction of LaNiO3 to LaNiO2 films. Activated carbon did not yield infinite-layer LaNiO2 whereas both of TiH2 and CaH2 yielded infinite-layer LaNiO2 with low resistivity (∼1 mΩ cm at 300 K) as well as metallic behavior down to 70 K. Thermal desorption spectroscopy indicated that H2 released from metal hydrides plays a dominant role in the topotactic reduction.

Synthesis of lever-blade dampers with enhanced mechanical structure

Directory of Open Access Journals (Sweden)

Igor I. Sydorenko

2015-03-01

Full Text Available Since the torsion bar represents just an elastic element, the energy dissipation in suspensions problem is highly relevant for its application. Currently in quality of a dissipation device in torsion suspension are used the hydraulic dampers with movable members reciprocating translational motion respectively to the housing or lever-type hydraulic shock absorbers of piston and vane types, with the movable member’s rotational movement respectively to the housing. These dampers are implementing only throttle-valve performance type, associated with these devices’ functional capacities and depending on design constraints. The paper presents a synthesis of innovative lever-blade dampers, whose performance is not related to the value of working chambers inner pressure. Their essential peculiarity relates to the mechanical control loop presence in the structure that determines a close relationship between the performance and the value of the shock absorber movable element displacement relatively to the body. In the process of synthesis carried out tested are the appropriate methods, built on the basis of technical systems’ modeling with modified kinematic graphs. The synthesis results are shown in the form of two structurally implemented samples. Performed is a comparative analysis of the samples with their basic performance determining.

Structural archetypes in nickel(II) hybrid vanadates. Towards a directed hydrothermal synthesis

International Nuclear Information System (INIS)

Luis, R. Fernandez de; Urtiaga, M.K.; Mesa, J.L.; Rojo, T.; Arriortua, M.I.

2009-01-01

In the present work, we relate the modifications of the initial synthesis parameters (pH value, stoichiometry and concentration) with the different structural archetypes obtained in the {Ni/Bpy/VO} and {Ni/Bpe/VO} systems (4,4'-bipyridine (Bpy), 1,2-di(4-pyridyl) ethylene (Bpe)). The vanadium coordination is partially controlled by the hydrothermal synthesis conditions, and the final crystal structures depend on the synergetic interaction between the metal-organic subnets and the vanadium oxide subunits.

Synthesis, structural and electrical characterizations of thermally ...

African Journals Online (AJOL)

Synthesis, structural and electrical characterizations of thermally evaporated Cu 2 SnS 3 thin films. ... The surface profilometer shows that the deposited films are rough. The XRD spectra identified the ... The electrical resistivity of the deposited Cu2SnS3 film is 2.55 x 10-3 Ωcm. The conductivity is in the order of 103 Ω-1cm-1.

Stability of Ruddlesden-Popper-structured oxides in humid conditions

Science.gov (United States)

Lehtimäki, M.; Yamauchi, H.; Karppinen, M.

2013-08-01

Some of layered transition-metal oxides are known to react with atmospheric humidity to form through topotactic intercalation reactions new water-containing layered structures. Here we investigate the influence of oxygen content (7-δ) of the Ruddlesden-Popper-structured Sr3FeMO7-δ (M=Ni, Mn, Ti) oxides on the water-intercalation reaction. It is found that their oxygen contents influence greatly the reactivity of the phases with water. Other factors possibly affecting the reactivity are discussed on the basis of the present data in combination with a comprehensive review of previous works on Ruddlesden-Popper and related layered oxide phases.

Combustion synthesis and structural characterization of Li–Ti mixed

Indian Academy of Sciences (India)

Combustion synthesis and structural characterization of Li–Ti mixed nanoferrites ... were prepared by combustion method at lower temperatures compared to the ... first time at low temperatures, using PEG which acts as a new fuel and oxidant.

Synthesis and X-ray structure of the dysprosium(III) complex derived ...

African Journals Online (AJOL)

Synthesis and X-ray structure of the dysprosium(III) complex derived from the ligand 5-chloro-1 ... Bulletin of the Chemical Society of Ethiopia ... synthesized and its crystal structure determined by single X-ray diffraction at room temperature.

Quasi-Topotactic Transformation of FeOOH Nanorods to Robust Fe2O3 Porous Nanopillars Triggered with a Facile Rapid Dehydration Strategy for Efficient Photoelectrochemical Water Splitting.

Science.gov (United States)

Liao, Aizhen; He, Huichao; Tang, Lanqin; Li, Yichang; Zhang, Jiyuan; Chen, Jiani; Chen, Lan; Zhang, Chunfeng; Zhou, Yong; Zou, Zhigang

2018-03-28

A facile rapid dehydration (RD) strategy is explored for quasi-topotactic transformation of FeOOH nanorods to robust Fe 2 O 3 porous nanopillars, avoiding collapse, shrink, and coalescence, and compared with a conventional treatment route. Additionally, the so-called RD process is capable of generating a beneficial porous structure for photoelectrochemical water oxidation. The obtained RD-Fe 2 O 3 photoanode exhibits a photocurrent density as high as 2.0 mA cm -2 at 1.23 V versus reversible hydrogen electrode (RHE) and a saturated photocurrent density of 3.5 mA cm -2 at 1.71 V versus RHE without any cocatalysts, which is about 270% improved photocurrent density over Fe 2 O 3 with the conventional temperature-rising route (0.75 mA cm -2 at 1.23 V vs RHE and 1.48 mA cm -2 at 1.71 V vs RHE, respectively). The enhanced photocurrent on RD-Fe 2 O 3 is attributed to a synergistic effect of the following factors: (i) preservation of single crystalline nanopillars decreases the charge-carrier recombination; (ii) formation of long nanopillars enhances light harvesting; and (iii) the porous structure shortens the hole transport distance from the bulk material to the electrode-electrolyte interface.

Crystal structure of Nd4Cu2O7

International Nuclear Information System (INIS)

Pederzolli, D.R.; Attfield, J.P.

1998-01-01

The structure of Nd 4 Cu 2 O 7 (A2/m, a = 8.449 A, b = 3.759 A, c = 12.601 A, β = 109.57 ), prepared by topotactic reduction of the high-T c superconductor parent phase Nd 2 CuO 4 , has been determined from time-of-flight neutron powder diffraction data revealing a new oxygen vacancy-ordered arrangement containing cooperatively distorted Cu 2 O 3 planes in which 2- and 4- coordinate Cu - sites are present. (orig.)

Topotactic transition of α-Co(OH)2 to β-Co(OH)2 anchored on CoO nanoparticles during electrochemical water oxidation: synergistic electrocatalytic effects.

Science.gov (United States)

Kundu, Sumana; Malik, Bibhudatta; Prabhakaran, Amrutha; Pattanayak, Deepak K; Pillai, Vijayamohanan K

2017-08-29

Herein, we report a single step, anionic surfactant-assisted, low temperature-hydrothermal synthetic strategy of CoO nanoparticles anchored on β-Co(OH) 2 nanosheets which show a low overpotential (295 mV @ 10 mA cm -2 ) for the oxygen evolution reaction (OER). They also demonstrate much better kinetic parameters compared to the state-of-the-art RuO 2 . Interestingly, under the OER operational conditions (in alkaline medium), the topotactic transformation of α-Co(OH) 2 to a stable Brucite-like β-Co(OH) 2 phase leads to a synergistic interaction between the β-Co(OH) 2 sheets on the CoO nanoparticles for enhancing the OER electrocatalytic activity.

Structural archetypes in nickel(II) hybrid vanadates. Towards a directed hydrothermal synthesis

Energy Technology Data Exchange (ETDEWEB)

Luis, R. Fernandez de; Urtiaga, M.K. [Dpto. Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); Mesa, J.L.; Rojo, T. [Dpto. Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); Arriortua, M.I. [Dpto. Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/UPV/EHU, Apdo. 644, 48080 Bilbao (Spain)], E-mail: maribel.arriortua@ehu.es

2009-07-01

In the present work, we relate the modifications of the initial synthesis parameters (pH value, stoichiometry and concentration) with the different structural archetypes obtained in the {l_brace}Ni/Bpy/VO{r_brace} and {l_brace}Ni/Bpe/VO{r_brace} systems (4,4'-bipyridine (Bpy), 1,2-di(4-pyridyl) ethylene (Bpe)). The vanadium coordination is partially controlled by the hydrothermal synthesis conditions, and the final crystal structures depend on the synergetic interaction between the metal-organic subnets and the vanadium oxide subunits.

A simulation study on the topotactic transformations from aluminophosphate AlPO(4)-21 to AlPO(4)-25.

Science.gov (United States)

Li, J; Yu, J; Wang, K; Zhu, G; Xu, R

2001-11-05

Aluminophosphate AlPO(4)-21 (AWO), formulated /(CH(3))(2)NH(2)/[Al(3)P(3)O(12)(OH)], has been synthesized solvothermally by using dimethylamine as the template. Single-crystal X-ray diffraction analysis shows that AlPO(4)-21 crystallizes in the monoclinic space group P2(1)/n with a = 8.687(2) A, b = 17.428(5) A, c = 9.159(2) A, beta = 109.60(2) degrees, V = 1306.3(5) A(3), and Z = 4. XRD analysis shows that AlPO(4)-21 transforms to AlPO(4)-25 (ATV) upon calcination at 500 degrees C. The molecular dynamics simulation approach was used to investigate the topotactic transformations from AlPO(4)-21. The simulation study suggests that AlPO(4)-21 is energetically favored to transform to AlPO(4)-25, as well as other hypothetical forms, by the changing of the UUDD chains to the UDUD chains.

Synthesis, X-ray crystal structure, DNA binding and Nuclease activity ...

Indian Academy of Sciences (India)

s12039-016-1125-x. Synthesis, X-ray crystal structure, DNA binding and Nuclease activity of lanthanide(III) complexes of 2-benzoylpyridine acetylhydrazone. KARREDDULA RAJA, AKKILI SUSEELAMMA and KATREDDI HUSSAIN REDDY. ∗.

Scandium fluorides

International Nuclear Information System (INIS)

Melnikov, P.; Nalin, M.; Messaddeq, Y.

1997-01-01

A new modification of scandium fluoride has been synthesised. The compound is deficient in fluorine, with the composition ScF 2.76 . It belongs to the tetragonal system, lattice parameters being a=3.792 and c=6.740 A and may be obtained at low temperatures by the decomposition of the precursor NH 4 ScF 4 . The reaction is topotactic, tetragonal parameters of the precursor are a=4.021 and c=6.744 A. Structural relationships with various fluorides and ammonium aminofluorides are discussed. This synthesis route with IR-assisted decomposition should be considered as a soft-chemistry approach. (orig.)

Metal Oxide Nano structures: Synthesis, Properties, and Applications

International Nuclear Information System (INIS)

Xu, L. H.; Patil, D. S.; Yang, J.; Xiao, J.

2015-01-01

In recent years, nano structured materials have attracted wide attention due to their fascinating optical and electrical properties, which make these materials potentially suitable for applications in electronics, optics, photonics, and sensors. Some metal oxides show a wide variety of morphologies such as nano wires, nano rods, nano tubes, nano rings, and nano belts. Synthesis and investigation of these metal-oxide nano structures are beneficial not only for understanding the fundamental phenomena in low dimensional systems, but also for developing new-generation nano devices with high performance.

Syntheses, structural variants and characterization of AInM′S4 (A=alkali metals, Tl; M′ = Ge, Sn) compounds; facile ion-exchange reactions of layered NaInSnS4 and KInSnS4 compounds

International Nuclear Information System (INIS)

Yohannan, Jinu P.; Vidyasagar, Kanamaluru

2016-01-01

Ten AInM′S 4 (A=alkali metals, Tl; M′= Ge, Sn) compounds with diverse structure types have been synthesized and characterized by single crystal and powder X-ray diffraction and a variety of spectroscopic methods. They are wide band gap semiconductors. KInGeS 4 (1-β), RbInGeS 4 (2), CsInGeS 4 (3-β), TlInGeS 4 (4-β), RbInSnS 4 (8-β) and CsInSnS 4 (9) compounds with three-dimensional BaGa 2 S 4 structure and CsInGeS 4 (3-α) and TlInGeS 4 (4-α) compounds with a layered TlInSiS 4 structure have tetrahedral [InM′S 4 ] − frameworks. On the other hand, LiInSnS 4 (5) with spinel structure and NaInSnS 4 (6), KInSnS 4 (7), RbInSnS 4 (8-α) and TlInSnS 4 (10) compounds with layered structure have octahedral [InM′S 4 ] − frameworks. NaInSnS 4 (6) and KInSnS 4 (7) compounds undergo facile topotactic ion-exchange, at room temperature, with various mono-, di- and tri-valent cations in aqueous medium to give rise to metastable layered phases. - Graphical abstract: NaInSnS 4 and KInSnS 4 compounds undergo, in aqueous medium at room temperature, facile topotactic ion-exchange with mono, di and trivalent cations. Display Omitted - Highlights: • Ten AInM′S 4 compounds with diverse structure types were synthesized. • They are wide band gap semiconductors. • NaInSnS 4 and KInSnS 4 compounds undergo facile topotactic ion-exchange at room temperature.

Total synthesis, structure, and oral absorption of a thiazole cyclic peptide, sanguinamide A

DEFF Research Database (Denmark)

Nielsen, Daniel S; Hoang, Huy N; Lohman, Rink-Jan

2012-01-01

The first total synthesis and three-dimensional solution structure are reported for sanguinamide A, a thiazole-containing cyclic peptide from the sea slug H. sanguineus. Solution phase fragment synthesis, solid phase fragment assembly, and solution macrocyclization were combined to give (1) in 10......% yield. Spectral properties were identical for the natural product, requiring revision of its structure from (2) to (1). Intramolecular transannular hydrogen bonds help to bury polar atoms, which enables oral absorption from the gut....

Synthesis and structure of bis(β-dibenzoyl methanato -O,O') (aquo-O ...

Indian Academy of Sciences (India)

Synthesis and structure of bis(β-dibenzoyl methanato -O,O') (aquo-O) dioxouranium (VI) compound ... Keywords. β-diketonates; uranyl ion; adduct compound; crystal structure; hydrogen bonding. 1. Introduction. Structural studies on uranyl ... crystalline product obtained was filtered, washed with ether and dried. The crystal ...

Oxygen excess in the '114' cobaltite hexagonal structure: The ferrimagnet CaBaCo4O7.50

International Nuclear Information System (INIS)

Pralong, V.; Caignaert, V.; Sarkar, T.; Lebedev, O.I.; Duffort, V.; Raveau, B.

2011-01-01

The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its excess oxygen. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic with the same T C (60 K), but differently exhibits an unusual magnetic hysteresis. This exceptional behavior of CaBaCo 4 O 7 with respect to oxidation as well as the magnetic properties of CaBaCo 4 O 7.50 is interpreted in terms of the presence of defects due to oxidation. - Graphical Abstract: The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its oxygen excess. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic. Highlights: → Topotactic oxidation by means of electrochemistry and soft chemistry of the '114' orthorhombic cobaltite CaBaCo 4 O 7 . → This new phase, CaBaCo 4 O 7.5 shows an hexagonal structure, is closely related to that of orthorhombic mother phase CaBaCo 4 O 7 . → CaBaCo 4 O 7.5 is ferrimagnetic and exhibits an unusual magnetic hysteresis, due to defect pinning centers.

X-ray excited photoluminescence near the giant resonance in solid-solution Gd(1-x)Tb(x)OCl nanocrystals and their retention upon solvothermal topotactic transformation to Gd(1-x)Tb(x)F3.

Science.gov (United States)

Waetzig, Gregory R; Horrocks, Gregory A; Jude, Joshua W; Zuin, Lucia; Banerjee, Sarbajit

2016-01-14

Design rules for X-ray phosphors are much less established as compared to their optically stimulated counterparts owing to the absence of a detailed understanding of sensitization mechanisms, activation pathways and recombination channels upon high-energy excitation. Here, we demonstrate a pronounced modulation of the X-ray excited photoluminescence of Tb(3+) centers upon excitation in proximity to the giant resonance of the host Gd(3+) ions in solid-solution Gd1-xTbxOCl nanocrystals prepared by a non-hydrolytic cross-coupling method. The strong suppression of X-ray excited optical luminescence at the giant resonance suggests a change in mechanism from multiple exciton generation to single thermal exciton formation and Auger decay processes. The solid-solution Gd1-xTbxOCl nanocrystals are further topotactically transformed with retention of a nine-coordinated cation environment to solid-solution Gd1-xTbxF3 nanocrystals upon solvothermal treatment with XeF2. The metastable hexagonal phase of GdF3 can be stabilized at room temperature through this topotactic approach and is transformed subsequently to the orthorhombic phase. The fluoride nanocrystals indicate an analogous but blue-shifted modulation of the X-ray excited optical luminescence of the Tb(3+) centers upon X-ray excitation near the giant resonance of the host Gd(3+) ions.

Synthesis and applications of one-dimensional nano-structured polyaniline: An overview

International Nuclear Information System (INIS)

Zhang Donghua; Wang Yangyong

2006-01-01

This paper summarizes and reviews the various synthesizing approaches of one-dimensional nano-structured polyaniline (PANI) and several potential applications of the nanomaterial. The synthesizing approaches can be generally categorized into template synthesis and non-template synthesis according to whether template(s), hard (physical template) or soft (chemical template), is (are) used or not. However, though the various approaches established, preparation of one-dimensional nano-structured PANI with controllable morphologies and sizes, especially well oriented arrays on a large scale is still a major challenge. Furthermore, the formation mechanisms of the nanostructures are still unclear. On the other hand, one-dimensional nano-structured PANI exhibits high surface area, high conductivity, as well as controllable chemical/physical properties and good environmental stability, rendering the nanomaterial promising candidate for application ranging from sensors, energy storage and flash welding to digital nonvolatile memory

Synthesis of Carbon nano structures by plasma discharge

International Nuclear Information System (INIS)

Jimenez L, M.L.

2007-01-01

Due to the great quantity of applications of the carbon nano structures (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, it has seen the necessity to generate new processes of synthesis of this materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither sludges. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arch discharge, in a gas mixture of He-CH 4 with 34% at. Ni/10.32% at.Y like catalyst; at a frequency of 42 kHz and low power (300 W). This method benefits the amass of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the NEC type obtained and by X-ray diffraction analysis and Raman spectroscopy for determining the purity of the samples. The NFC is relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of plasma using the Swan band for determining the temperature. (Author)

β-Telluroacroleins and β-tellurovinyl ketones: synthesis, reactions and structure

International Nuclear Information System (INIS)

Sadekov, I.D.

2002-01-01

Data on synthesis, reactivity, spectral characteristics and structure of new telluroorganic synthons, i.e. β-tellurovinylcarbonyl compounds, were generalized and systematized. Synthesis and reactions of β-telluroacroleins and similar cations were considered individually for each type of β-tellurovinylcarbonyl compounds. Special attention was paid to the use of the compounds for preparing tellurium-containing heterocycles. Reactions characteristics of carbonyl groups and tellurium-containing substituents, as well as transformation, as a result of which β-tellurovinylcarbonyl compounds and products of their reactions form tellurium-containing heterocycles, were discussed [ru

Synthesis and electrochemical sodium and lithium insertion properties of sodium titanium oxide with the tunnel type structure

Science.gov (United States)

Kataoka, Kunimitsu; Akimoto, Junji

2016-02-01

Polycrystalline sample of sodium titanium oxide Na2Ti4O9 with the tunnel-type structure was prepared by topotactic sodium extraction in air atmosphere from the as prepared Na3Ti4O9 sample. The starting Na3Ti4O9 compound was synthesized by solid state reaction at 1273 K in Ar atmosphere. The completeness of oxidation reaction from Na3Ti4O9 to Na2Ti4O9 was monitored by the change in color from dark blue to white, and was also confirmed by the Rietveld refinement using the powder X-ray diffraction data. The sodium deficient Na2Ti4O9 maintained the original Na2.08Ti4O9-type tunnel structure and had the monoclinic crystal system, space group C2/m, and the lattice parameters of a = 23.1698(3) Å, b = 2.9406(1) Å, c = 10.6038(2) Å, β = 102.422(3)°, and V = 705.57(2) Å3. The electrochemical measurements of thus obtained Na2Ti4O9 sample showed the reversible sodium insertion and extraction reactions at 1.1 V, 1.5 V, and 1.8 V vs. Na/Na+, and reversible lithium insertion and extraction reactions at around 1.4 V, 1.8 V, and 2.0 V vs. Li/Li+. The reversible capacity for the lithium cell was achieved to be 104 mAh g-1 at the 100th cycle.

Enhanced photoactivity from single-crystalline SrTaO{sub 2}N nanoplates synthesized by topotactic nitridation

Energy Technology Data Exchange (ETDEWEB)

Fu, Jie; Skrabalak, Sara E. [Department of Chemistry, Indiana University, Bloomington, IN (United States)

2017-11-06

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO{sub 2}N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO{sub 2}N nanoplates form by topotactic nitridation of aerosol-prepared Sr{sub 2}Ta{sub 2}O{sub 7} nanoplates and SrTaO{sub 2}N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO{sub 2}N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO{sub 2}N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structure-based synthesis from natural products to drug prototypes

International Nuclear Information System (INIS)

Hanessian, S.

2009-01-01

X-Ray crystallographic data available from complexes of natural and synthetic molecules with the enzyme thrombin has aided to the design and synthesis of truncated and hybrid molecules exhibiting excellent inhibition in vitro. The vital importance of natural products for the well-being of man has been known lor millennia. Their therapeutic benefits to alleviate pain or cure diseases continue to rank natural products among the primary sources of potential drugs. Great advances have been made in the methods of isolation, identification, and structure elucidation of some of the most complex natural products in recent years. The advent of molecular biology and genetic mapping has also aided in our understanding of the intriguing biosynthetic pathways leading to various classes of therapeutically relevant antibiotic, anticancer, and related natural products. Elegant and practical methodology has been developed leading to the total synthesis of virtually every class of medicinally important natural product. In some cases, natural products or their chemically modified congeners have been manufactured by total synthesis on an industrial level which is a testament to the ingenuity of process chemists. In spite of their potent activities HI enzymatic ox receptor-mediated assays, not all natural products are amenable to being developed as marketable drags. In many instances unfavorable pharmacological effects cannot be overcome without drastic structural and functional modifications, which may also result in altered efficacy. Structure modification through truncation, functional group variations, isosteric replacements, and skeletal rigidifications aided by molecular modeling, X ray crystallography of protein targets, or NMR data are valid objectives in the context of small molecule drug discovery starting with bioactive natural products. A large proportion of these pertain to chemotherapeutic agents against cancer

One-step synthesis and structural features of CdS/montmorillonite nanocomposites.

Science.gov (United States)

Han, Zhaohui; Zhu, Huaiyong; Bulcock, Shaun R; Ringer, Simon P

2005-02-24

A novel synthesis method was introduced for the nanocomposites of cadmium sulfide and montmorillonite. This method features the combination of an ion exchange process and an in situ hydrothermal decomposition process of a complex precursor, which is simple in contrast to the conventional synthesis methods that comprise two separate steps for similar nanocomposite materials. Cadmium sulfide species in the composites exist in the forms of pillars and nanoparticles, the crystallized sulfide particles are in the hexagonal phase, and the sizes change when the amount of the complex for the synthesis is varied. Structural features of the nanocomposites are similar to those of the clay host but changed because of the introduction of the sulfide into the clay.

Synthesis, structural and optical properties of nanoparticles (Al, V ...

Indian Academy of Sciences (India)

The synthesis by the sol–gel method, structural and optical properties of ZnO, Zn0.99Al0.01O (AlZ),. Zn0.9V0.1O (VZ) ... drops of the resulting suspension containing the synthesized .... ZnO films on silicon substrate, they thought that this emis-.

Topotactic Conversion of Copper(I) Phosphide Nanowires for Sensitive Electrochemical Detection of H2O2 Release from Living Cells.

Science.gov (United States)

Li, Zhenzhen; Xin, Yanmei; Wu, Wenlong; Fu, Baihe; Zhang, Zhonghai

2016-08-02

In this work, we clearly demonstrate for the first time the use of transition-metal phosphides to set up a new cathodic analysis platform for sensitive and selective electrochemical nonenzymatic detection of H2O2. With the help of a facile topotactic conversion method, the noble metal-free electrocatalyst of copper(I) phosphide nanowires on three-dimensional porous copper foam (Cu3P NWs/CF) is fabricated with electrochemical anodized Cu(OH)2 NWs as precursor. The Cu3P NWs/CF-based sensor presents excellent electrocatalytic activity for H2O2 reduction with a detection limit of 2 nM, the lowest detection limit achieved by noble-metal free electrocatalyst, which guarantees the possibility of sensitive and reliable detection of H2O2 release from living tumorigenic cells, thus showing the potential application as a sensitive cancer cell detection probe.

Design and synthesis of diverse functional kinked nanowire structures for nanoelectronic bioprobes.

Science.gov (United States)

Xu, Lin; Jiang, Zhe; Qing, Quan; Mai, Liqiang; Zhang, Qingjie; Lieber, Charles M

2013-02-13

Functional kinked nanowires (KNWs) represent a new class of nanowire building blocks, in which functional devices, for example, nanoscale field-effect transistors (nanoFETs), are encoded in geometrically controlled nanowire superstructures during synthesis. The bottom-up control of both structure and function of KNWs enables construction of spatially isolated point-like nanoelectronic probes that are especially useful for monitoring biological systems where finely tuned feature size and structure are highly desired. Here we present three new types of functional KNWs including (1) the zero-degree KNW structures with two parallel heavily doped arms of U-shaped structures with a nanoFET at the tip of the "U", (2) series multiplexed functional KNW integrating multi-nanoFETs along the arm and at the tips of V-shaped structures, and (3) parallel multiplexed KNWs integrating nanoFETs at the two tips of W-shaped structures. First, U-shaped KNWs were synthesized with separations as small as 650 nm between the parallel arms and used to fabricate three-dimensional nanoFET probes at least 3 times smaller than previous V-shaped designs. In addition, multiple nanoFETs were encoded during synthesis in one of the arms/tip of V-shaped and distinct arms/tips of W-shaped KNWs. These new multiplexed KNW structures were structurally verified by optical and electron microscopy of dopant-selective etched samples and electrically characterized using scanning gate microscopy and transport measurements. The facile design and bottom-up synthesis of these diverse functional KNWs provides a growing toolbox of building blocks for fabricating highly compact and multiplexed three-dimensional nanoprobes for applications in life sciences, including intracellular and deep tissue/cell recordings.

Synthesis, structural and ferromagnetic properties of La1–x Kx ...

Indian Academy of Sciences (India)

2016-08-26

Aug 26, 2016 ... Synthesis, structural and ferromagnetic properties of La1–KMnO3 (0.0≤ 0.25) phases by solution combustion method ... Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent ... The ratio of the Mn3+/Mn4+ was determined by the iodometric titration.

Reversal of the lattice structure in SrCoOx epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations

OpenAIRE

Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

2013-01-01

Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x = 2.5 - 3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases, i.e. the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator tran...

Wall grid structure for interior scene synthesis

KAUST Repository

Xu, Wenzhuo

2015-02-01

We present a system for automatically synthesizing a diverse set of semantically valid, and well-arranged 3D interior scenes for a given empty room shape. Unlike existing work on layout synthesis, that typically knows potentially needed 3D models and optimizes their location through cost functions, our technique performs the retrieval and placement of 3D models by discovering the relationships between the room space and the models\\' categories. This is enabled by a new analytical structure, called Wall Grid Structure, which jointly considers the categories and locations of 3D models. Our technique greatly reduces the amount of user intervention and provides users with suggestions and inspirations. We demonstrate the applicability of our approach on three types of scenarios: conference rooms, living rooms and bedrooms.

Structural study of the controlled hydrothermal synthesis of LiMn2O4 and LixMnyO2

DEFF Research Database (Denmark)

Christiansen, Troels Lindahl; Jensen, Kirsten Marie Ørnsbjerg; Shen, Yanbin

, a layered structure, which can also be described as a defective spinel structure. Here, we show that both LiMn2O4 and LixMnyO2 nanoparticles can be synthesized from a simple, low-temperature hydrothermal synthesis. By tuning a single synthesis parameter (Li-concentration) each of the 2 structures...

Some structural aspects that are relevant for synthesis of planetary gear trains

Energy Technology Data Exchange (ETDEWEB)

Rajasri, I. [Pathfinder Engineering College, Hanamkonda (India); Gupta, A.V.S.S.K.S. [JNTU, Hyderabad (India); Rao, Y.V.D. [BITS-Pilani. Dept. of Mechanical Engineering, Hyderabad (India)

2012-07-01

Gear Trains are typically used in various mechanisms including wind turbines and robots to transmit specified motion and/or torque between two or more shafts and wind turbines need drives and overdrives that amplify the speed of turbine shaft and provide high speed at generator shaft. Planetary gear trains (PGT) are compact, easy to build and operate. Therefore PGTs are most suitable for such drives including over drives. Graph theory used in synthesis of the PGTs is also useful to identify various possible structural aspects of the PGTs. Generation of PGTs is followed by the test for isomorphism in PGTs generated. In this context various structural aspects relevant for the synthesis of PGTs is described. (Author)

HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

International Nuclear Information System (INIS)

Rice, C.E.; Jackel, J.L.

1982-01-01

The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

Nitridomanganates of alkaline-earth metals. Synthesis, structure, and physical properties

Energy Technology Data Exchange (ETDEWEB)

Ovchinnikov, Alexander

2016-12-02

The main goal of the present work was the synthesis of alkaline-earth nitridomanganates (AE{sub x}Mn{sub y}N{sub z}) with extended anionic structures and the characterization of their electronic and magnetic properties. Up to now, only compounds with isolated nitridomanganate anions have been reported in the discussed ternary systems. A systematic exploratory synthesis, employing high-temperature treatment of AE nitrides and Mn under controlled N2 pressure, yielded more than ten new nitridomanganates. Their crystal structures contain anionic building blocks of different dimensionalities, ranging from isolated species to three-dimensional frameworks. In general, the formation of Mn-rich compositions was found to be driven by the emergence of Mn-Mn interactions, which creates a link between nitridometalates and transition-metal-rich binary nitrides. The obtained nitridomanganates display a plethora of interesting phenomena, such as large spin-orbit coupling, magnetic frustration, quenching of magnetism due to Mn-Mn interactions, and metal-insulator transition.

Synthesis of Structures Related to Antifreeze Glycoproteins

OpenAIRE

Fyrner, Timmy

2005-01-01

In this thesis, synthesis of structures related to antifreeze glycoproteins (AFGPs) are presented. Synthetic routes to a protected carbohydrate derivative, 2,3,4,6-tetra-O-benzyl-β-galactopyranosyl-(1→3)-2-deoxy-2-azido-4,6-di-O-benzyl-β-D-thio-1-galactopyranoside, and a tBu-Ala-Thr-Ala-Fmoc tripeptide, are described. These compounds are meant to be used in the assembly of AFGPs and analogues thereof. A Gal-GlcN disaccharide was synthesized via glycosylation between the donor, bromo-2-O-benzo...

Assembly of Layered Monetite-Chitosan Nanocomposite and Its Transition to Organized Hydroxyapatite.

Science.gov (United States)

Ruan, Qichao; Liberman, David; Zhang, Yuzheng; Ren, Dongni; Zhang, Yunpeng; Nutt, Steven; Moradian-Oldak, Janet

2016-06-13

Bioinspired synthesis of hierarchically structured calcium phosphate (CaP) material is a highly promising strategy for developing improved bone substitute materials. However, synthesis of CaP materials with outstanding mechanical properties still remains an ongoing challenge. Inspired by the formation of lamellar structure in nacre, we designed an organic matrix composed of chitosan and cis-butenediolic acid (maleic acid, MAc) that could assemble into a layered complex and further guide the mineralization of monetite crystals, resulting in the formation of organized and parallel arrays of monetite platelets with a brick-and-mortar structure. Using the layered monetite-chitosan composite as a precursor, we were able to synthesize hydroxyapatite (HAp) with multiscale hierarchically ordered structure via a topotactic phase transformation process. On the nanoscale, needlelike HAp crystallites assembled into organized bundles that aligned to form highly oriented plates on the microscale. On the large-scale level, these plates with different crystal orientations were stacked together to form a layered structure. The organized structures and composite feature yielded CaP materials with improved mechanical properties close to those of bone. Our study introduces a biomimetic approach that may be practical for the design of advanced, mechanically robust materials for biomedical applications.

Synthesis, structure analysis, anti-bacterial and in vitro anti-cancer ...

Indian Academy of Sciences (India)

DOI 10.1007/s12039-015-0824-z. Synthesis, structure analysis, anti-bacterial and in vitro anti-cancer activity of new Schiff base and its copper complex derived from sulfamethoxazole. I RAMA∗ and R SELVAMEENA. PG and Research Department of Chemistry, Seethalakshmi Ramaswami College,. Tiruchirappalli 620 002 ...

Four new dysprosium and neodymium octamolybdate hydrates: assembly of RE2(Mo8O27) sheets and topotactic transformations.

Science.gov (United States)

Kuang, Xiaojun; Evans, Ivana R

2010-07-05

Four new Dy and Nd hydrated octamolybdate materials have been prepared: [Dy(2)(H(2)O)(12)](Mo(8)O(27)) x 8 H(2)O, [Dy(2)(H(2)O)(6)](Mo(8)O(27)), [Nd(2)(H(2)O)(12)](Mo(8)O(27)) x 6 H(2)O, and [Nd(2)(H(2)O)(6)]Mo(8)O(27) x 3 H(2)O. They adopt one known and three new structure types, which we have determined ab initio from powder X-ray diffraction data. The four compounds contain the same basic structural building block, in the form of RE(2)Mo(8)O(27) (RE = Dy, Nd) chains, which are arranged differently for the two rare earths in the fully hydrated precursor materials. [Dy(2)(H(2)O)(12)](Mo(8)O(27)) x 8 H(2)O comprises isolated Dy(2)Mo(8)O(27) chains assembled in a zigzag manner along the a axis with interspersed crystallized water molecules, which differs from the parallel arrangements of isolated Nd(2)Mo(8)O(27) chains in [Nd(2)(H(2)O)(12)](Mo(8)O(27)) x 6 H(2)O. Partial dehydration of the two precursors leads to new phases [Dy(2)(H(2)O)(6)](Mo(8)O(27)) and [Nd(2)(H(2)O)(6)]Mo(8)O(27) x 3 H(2)O, respectively, prior to complete dehydration, which leads to initially amorphous and eventually crystalline rare-earth molybdenum mixed metal oxides. Both initial transformations occur topotactically. Partial dehydration of the Dy phase condenses the assembly of the Dy(2)Mo(8)O(27) chains principally along the a axis, leading to a 3-dimensional (3D) framework, with each Dy bridging two (Mo(8)O(27))(6-) sheets in the product. The partial dehydration of the Nd precursor condenses the assembly of Nd(2)Mo(8)O(27) chains along the [110] axis, leading to a 3D framework where each Nd bridges three (Mo(8)O(27))(6-) units. Both new dysprosium octamolybdates adopt noncentrosymmetric polar structures in space group P2(1) and are second harmonic generation (SHG) active.

Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

KAUST Repository

Zeng, Shangjing; Wang, Runwei; Li, Ang; Huang, Weiwei; Zhang, Zongtao; Qiu, Shilun

2016-01-01

A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity

The extended evolutionary synthesis: its structure, assumptions and predictions

Science.gov (United States)

Laland, Kevin N.; Uller, Tobias; Feldman, Marcus W.; Sterelny, Kim; Müller, Gerd B.; Moczek, Armin; Jablonka, Eva; Odling-Smee, John

2015-01-01

Scientific activities take place within the structured sets of ideas and assumptions that define a field and its practices. The conceptual framework of evolutionary biology emerged with the Modern Synthesis in the early twentieth century and has since expanded into a highly successful research program to explore the processes of diversification and adaptation. Nonetheless, the ability of that framework satisfactorily to accommodate the rapid advances in developmental biology, genomics and ecology has been questioned. We review some of these arguments, focusing on literatures (evo-devo, developmental plasticity, inclusive inheritance and niche construction) whose implications for evolution can be interpreted in two ways—one that preserves the internal structure of contemporary evolutionary theory and one that points towards an alternative conceptual framework. The latter, which we label the ‘extended evolutionary synthesis' (EES), retains the fundaments of evolutionary theory, but differs in its emphasis on the role of constructive processes in development and evolution, and reciprocal portrayals of causation. In the EES, developmental processes, operating through developmental bias, inclusive inheritance and niche construction, share responsibility for the direction and rate of evolution, the origin of character variation and organism–environment complementarity. We spell out the structure, core assumptions and novel predictions of the EES, and show how it can be deployed to stimulate and advance research in those fields that study or use evolutionary biology. PMID:26246559

Structural Ceramic Nanocomposites: A Review of Properties and Powders’ Synthesis Methods

Science.gov (United States)

Palmero, Paola

2015-01-01

Ceramic nanocomposites are attracting growing interest, thanks to new processing methods enabling these materials to go from the research laboratory scale to the commercial level. Today, many different types of nanocomposite structures are proposed in the literature; however, to fully exploit their exceptional properties, a deep understanding of the materials’ behavior across length scales is necessary. In fact, knowing how the nanoscale structure influences the bulk properties enables the design of increasingly performing composite materials. A further key point is the ability of tailoring the desired nanostructured features in the sintered composites, a challenging issue requiring a careful control of all stages of manufacturing, from powder synthesis to sintering. This review is divided into four parts. In the first, classification and general issues of nanostructured ceramics are reported. The second provides basic structure–property relations, highlighting the grain-size dependence of the materials properties. The third describes the role of nanocrystalline second-phases on the mechanical properties of ordinary grain sized ceramics. Finally, the fourth part revises the mainly used synthesis routes to produce nanocomposite ceramic powders, underlining when possible the critical role of the synthesis method on the control of microstructure and properties of the sintered ceramics. PMID:28347029

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca(1-x)La(x)FeO(3-δ).

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-01-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca(0.5)La(0.5)FeO(z) (2.5 ≤ z ≤ 2.75 and 2.75 ≤ z ≤ 3.0). Compound Ca(0.5)La(0.5)FeO(z) can undergo two kinds of reduction and reoxidation of Fe(4+)/Fe(3+) and Fe(3+)/Fe(2+), that are accompanied by reversible and repeatable topotactic oxygen extraction and reinsertion during discharge and charge processes.

Synthesis facilitates an understanding of the structural basis for translation inhibition by the lissoclimides

Science.gov (United States)

Könst, Zef A.; Szklarski, Anne R.; Pellegrino, Simone; Michalak, Sharon E.; Meyer, Mélanie; Zanette, Camila; Cencic, Regina; Nam, Sangkil; Voora, Vamsee K.; Horne, David A.; Pelletier, Jerry; Mobley, David L.; Yusupova, Gulnara; Yusupov, Marat; Vanderwal, Christopher D.

2017-11-01

The lissoclimides are unusual succinimide-containing labdane diterpenoids that were reported to be potent cytotoxins. Our short semisynthesis and analogue-oriented synthesis approaches provide a series of lissoclimide natural products and analogues that expand the structure-activity relationships (SARs) in this family. The semisynthesis approach yielded significant quantities of chlorolissoclimide (CL) to permit an evaluation against the National Cancer Institute's 60-cell line panel and allowed us to obtain an X-ray co-crystal structure of the synthetic secondary metabolite with the eukaryotic 80S ribosome. Although it shares a binding site with other imide-based natural product translation inhibitors, CL engages in a particularly interesting and novel face-on halogen-π interaction between the ligand's alkyl chloride and a guanine residue. Our analogue-oriented synthesis provides many more lissoclimide compounds, which were tested against aggressive human cancer cell lines and for protein synthesis inhibitory activity. Finally, computational modelling was used to explain the SARs of certain key compounds and set the stage for the structure-guided design of better translation inhibitors.

Photonic crystals based on opals and inverse opals: synthesis and structural features

International Nuclear Information System (INIS)

Klimonsky, S O; Abramova, Vera V; Sinitskii, Alexander S; Tretyakov, Yuri D

2011-01-01

Methods of synthesis of photonic crystals based on opals and inverse opals are considered. Their structural features are discussed. Data on different types of structural defects and their influence on the optical properties of opaline materials are systematized. The possibilities of investigation of structural defects by optical spectroscopy, electron microscopy, microradian X-ray diffraction, laser diffraction and using an analysis of Kossel ring patterns are described. The bibliography includes 253 references.

Ionothermal synthesis and crystal structures of metal phosphate chains

International Nuclear Information System (INIS)

Wragg, David S.; Le Ouay, Benjamin; Beale, Andrew M.; O'Brien, Matthew G.; Slawin, Alexandra M.Z.; Warren, John E.; Prior, Timothy J.; Morris, Russell E.

2010-01-01

We have prepared isostructural aluminium and gallium phosphate chains by ionothermal reactions in 1-ethyl-3-methylimidazolium bromide and 1-ethylpyridinium bromide under a variety of conditions. The chains can be prepared as pure phases or along with three dimensional framework phases. The chains are favoured at shorter heating times and the crystallinity can be improved by addition of transition metal acetates and amines which are not included in the final structure. The chain can be prepared with or without the presence of hydrofluoric acid. - Graphical abstract: Chain structures prepared from ionic liquid solvents under a wide variety of synthesis conditions.

Syntheses, structural variants and characterization of AInM′S{sub 4} (A=alkali metals, Tl; M′ = Ge, Sn) compounds; facile ion-exchange reactions of layered NaInSnS{sub 4} and KInSnS{sub 4} compounds

Energy Technology Data Exchange (ETDEWEB)

Yohannan, Jinu P.; Vidyasagar, Kanamaluru, E-mail: kvsagar@iitm.ac.in

2016-06-15

Ten AInM′S{sub 4} (A=alkali metals, Tl; M′= Ge, Sn) compounds with diverse structure types have been synthesized and characterized by single crystal and powder X-ray diffraction and a variety of spectroscopic methods. They are wide band gap semiconductors. KInGeS{sub 4}(1-β), RbInGeS{sub 4}(2), CsInGeS{sub 4}(3-β), TlInGeS{sub 4}(4-β), RbInSnS{sub 4}(8-β) and CsInSnS{sub 4}(9) compounds with three-dimensional BaGa{sub 2}S{sub 4} structure and CsInGeS{sub 4}(3-α) and TlInGeS{sub 4}(4-α) compounds with a layered TlInSiS{sub 4} structure have tetrahedral [InM′S{sub 4}]{sup −} frameworks. On the other hand, LiInSnS{sub 4}(5) with spinel structure and NaInSnS{sub 4}(6), KInSnS{sub 4}(7), RbInSnS{sub 4}(8-α) and TlInSnS{sub 4}(10) compounds with layered structure have octahedral [InM′S{sub 4}]{sup −} frameworks. NaInSnS{sub 4}(6) and KInSnS{sub 4}(7) compounds undergo facile topotactic ion-exchange, at room temperature, with various mono-, di- and tri-valent cations in aqueous medium to give rise to metastable layered phases. - Graphical abstract: NaInSnS{sub 4} and KInSnS{sub 4} compounds undergo, in aqueous medium at room temperature, facile topotactic ion-exchange with mono, di and trivalent cations. Display Omitted - Highlights: • Ten AInM′S{sub 4} compounds with diverse structure types were synthesized. • They are wide band gap semiconductors. • NaInSnS{sub 4} and KInSnS{sub 4} compounds undergo facile topotactic ion-exchange at room temperature.

Synthesis and characterization of Al-TON zeolite using a dialkylimizadolium as structure-directing agent

Energy Technology Data Exchange (ETDEWEB)

Lopes, Christian Wittee; Pergher, Sibele Berenice Castella, E-mail: chriswittee@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Villarroel-Rocha, Jhonny [Laboratorio de Solidos Porosos, Instituto de Fisica Aplicada, Universidad Nacional de San Luis, Chacabuco, San Luis (Argentina); Silva, Bernardo Araldi Da; Mignoni, Marcelo Luis [Universidade Regional Integrada, Erechim, RS (Brazil)

2016-11-15

In this work, the synthesis of zeolites using 1-butyl-3-methylimidazolium chloride [C{sub 4}MI]Cl as a structure-directing agent was investigated. The organic cation shows effectiveness and selectivity for the syntheses of TON zeolites under different reaction conditions compared to the traditional structure directing agent, 1,8-diaminooctane. The 1-butyl-3-methylimidazolium cation lead to highly crystalline materials and its role as OSDA in our synthesis conditions has been confirmed by characterization techniques. ICP-OES confirms the presence of Al in the samples and {sup 27}Al MAS NMR analysis indicated that aluminum atoms were incorporated in tetrahedral coordination. Scanning electron microscopy indicated that changing the crystallization condition (static or stirring), zeolites with different crystal size were obtained, which consequently affects the textural properties of the zeolites. Moreover, varying some synthesis parameters MFI zeolite can also be obtained. (author)

A new rechargeable sodium battery utilizing reversible topotactic oxygen extraction/insertion of CaFeO(z) (2.5 ≤ z ≤ 3) in an organic electrolyte.

Science.gov (United States)

Hibino, Mitsuhiro; Harimoto, Ryuji; Ogasawara, Yoshiyuki; Kido, Ryota; Sugahara, Akira; Kudo, Tetsuichi; Tochigi, Eita; Shibata, Naoya; Ikuhara, Yuichi; Mizuno, Noritaka

2014-01-08

At present, significant research efforts are being devoted both to identifying means of upgrading existing batteries, including lithium ion types, and also to developing alternate technologies, such as sodium ion, metal-air, and lithium-sulfur batteries. In addition, new battery systems incorporating novel electrode reactions are being identified. One such system utilizes the reaction of electrolyte ions with oxygen atoms reversibly extracted and reinserted topotactically from cathode materials. Batteries based on this system allow the use of various anode materials, such as lithium and sodium, without the requirement to develop new cathode intercalation materials. In the present study, this concept is employed and a new battery based on a CaFeO3 cathode with a sodium anode is demonstrated.

Versatile hydrothermal synthesis of one-dimensional composite structures

Science.gov (United States)

Luo, Yonglan

2008-12-01

In this paper we report on a versatile hydrothermal approach developed to fabricate one-dimensional (1D) composite structures. Sulfur and selenium formed liquid and adsorbed onto microrods as droplets and subsequently reacted with metallic ion in solution to produce nanoparticles-decorated composite microrods. 1D composites including ZnO/CdS, ZnO/MnS, ZnO/CuS, ZnO/CdSe, and FeOOH/CdS were successfully made using this hydrothermal strategy and the growth mechanism was also discussed. This hydrothermal strategy is simple and green, and can be extended to the synthesis of various 1D composite structures. Moreover, the interaction between the shell nanoparticles and the one-dimensional nanomaterials were confirmed by photoluminescence investigation of ZnO/CdS.

Elucidation of the electrochromic mechanism of nanostructured iron oxides films

Energy Technology Data Exchange (ETDEWEB)

Garcia-Lobato, M.A.; Martinez, Arturo I.; Castro-Roman, M. [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav Campus Saltillo, Carr. Saltillo-Monterrey Km. 13, Ramos Arizpe, Coah. 25900 (Mexico); Perry, Dale L. [Mail Stop 70A1150, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Zarate, R.A. [Departamento de Fisica, Facultad de Ciencias, Universidad Catolica del Norte, Casilla 1280, Antofagasta (Chile); Escobar-Alarcon, L. (Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico)

2011-02-15

Nanostructured hematite thin films were electrochemically cycled in an aqueous solution of LiOH. Through optical, structural, morphological, and magnetic measurements, the coloration mechanism of electrochromic iron oxide thin films was elucidated. The conditions for double or single electrochromic behavior are given in this work. During the electrochemical cycling, it was found that topotactic transformations of hexagonal crystal structures are favored; i.e. {alpha}-Fe{sub 2}O{sub 3} to Fe(OH){sub 2} and subsequently to {delta}-FeOOH. These topotactic redox reactions are responsible for color changes of iron oxide films. (author)

Investigations in the field of solid state polymerization Pt. 38

International Nuclear Information System (INIS)

Hardy, Gy.; Cser, F.; Nyitrai, K.; Fedorova, N.

1980-01-01

The stuctural and radiation chemical data of vinyl monomers with long chain paraffinic or cholesteric side groups are critically reviewed. Based on their structural and polymerization kinetical characteristics the monomers may be classified into three groups. Oblique layers are favourable for homogeneous topotactic polymerization. This is characterized by a low activation energy and a radiochemical efficiency very similar to that measured in liquid state polymerization. The tilted layers are not favourable for homogeneous topotactic polymerization. Allyl monomers yield polymers with higher molecular weights in the layer structure than in liquid states. (author)

Topotactic Transformation of Metal-Organic Frameworks to Graphene-Encapsulated Transition-Metal Nitrides as Efficient Fenton-like Catalysts.

Science.gov (United States)

Li, Xuning; Ao, Zhimin; Liu, Jiayi; Sun, Hongqi; Rykov, Alexandre I; Wang, Junhu

2016-12-27

Innovation in transition-metal nitride (TMN) preparation is highly desired for realization of various functionalities. Herein, series of graphene-encapsulated TMNs (Fe x Mn 6-x Co 4 -N@C) with well-controlled morphology have been synthesized through topotactic transformation of metal-organic frameworks in an N 2 atmosphere. The as-synthesized Fe x Mn 6-x Co 4 -N@C nanodices were systematically characterized and functionalized as Fenton-like catalysts for catalytic bisphenol A (BPA) oxidation by activation of peroxymonosulfate (PMS). The catalytic performance of Fe x Mn 6-x Co 4 -N@C was found to be largely enhanced with increasing Mn content. Theoretical calculations illustrated that the dramatically reduced adsorption energy and facilitated electron transfer for PMS activation catalyzed by Mn 4 N are the main factors for the excellent activity. Both sulfate and hydroxyl radicals were identified during the PMS activation, and the BPA degradation pathway mainly through hydroxylation, oxidation, and decarboxylation was investigated. Based on the systematic characterization of the catalyst before and after the reaction, the overall PMS activation mechanism over Fe x Mn 6-x Co 4 -N@C was proposed. This study details the insights into versatile TMNs for sustainable remediation by activation of PMS.

Micro structured reactors for synthesis/decomposition of hazardous chemicals. Challenging prospects for micro structured reaction architectures (4)

NARCIS (Netherlands)

Rebrov, E.V.; Croon, de M.H.J.M.; Schouten, J.C.

2004-01-01

A review. This paper completes a series of four publications dealing with the different aspects of the applications of micro reactor technol. This article focuses on the application of micro structured reactors in the processes for synthesis/decompn. of hazardous chems., such as unsym.

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca1–xLaxFeO3−δ

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-01-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca0.5La0.5FeOz (2.5 ≤ z ≤ 2.75 and 2.75 ≤ z ≤ 3.0). Compound Ca0.5La0.5FeOz can undergo two kinds of reduction and reoxidation of Fe4+/Fe3+ and Fe3+/Fe2+, that are accompanied by reversible and repeatable topotactic oxygen extraction and reinsertion during discharge and charge processes. PMID:22924108

Synthesis, Structure, and Properties of Refractory Hard-Metal Borides

Science.gov (United States)

Lech, Andrew Thomas

As the limits of what can be achieved with conventional hard compounds, such as tungsten carbide, are nearing reach, super-hard materials are an area of increasing industrial interest. The refractory hard metal borides, such as ReB2 and WB4, offer an increasingly attractive alternative to diamond and cubic boron nitride as a next-generation tool material. In this Thesis, a thorough discussion is made of the progress achieved by our laboratory towards understanding the synthesis, structure, and properties of these extremely hard compounds. Particular emphasis is placed on structural manipulation, solid solution formation, and the unique crystallographic manifestations of what might also be called "super-hard metals".

Effect of preparation conditions on fractal structure and phase transformations in the synthesis of nanoscale M-type barium hexaferrite

Energy Technology Data Exchange (ETDEWEB)

Pashkova, E.V. [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine); Solovyova, E.D., E-mail: solovyovak@mail.ru [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine); Kotenko, I.E., E-mail: Hab2420@yahoo.com [National Technical University of Ukraine ' KPI' , Pr. Pobedy, 37, Kyiv-57 (Ukraine); Kolodiazhnyi, T.V., E-mail: kolodiazhnyi.taras@nims.go.jp [National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Belous, A.G., E-mail: belous@ionc.kar.net [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine)

2011-10-15

The conditions of the synthesis of carbonate-hydroxide precursors (pH of FeOOH precipitation and heat treatment regimes) were studied in terms of their effect on the fractal structure and physical-chemical properties of precursors. Phase transformations which occur during the synthesis of nanosize M-type barium hexaferrite (BHF) were studied as well. The first structural level of precursors' aggregation for mass fractals, the correlation between fractal dimension and precursors' activity during the synthesis of BHF were determined. Synthesis parameters for the precursors with the optimal fractal structure were determined. These data permit an enhancement of the filtration coefficient of the precipitates by a factor of 4-5, obtaining substantial decrease in the temperature required for synthesis of a single-phase BHF, and monodispersed plate-like nanoparticles (60 nm diameter) with the shape anisotropy and good magnetic characteristics (saturation magnetization (M{sub s})=68,7 emu/g and coercitivity (H{sub c})=5440 Oe). - Highlights: > The nanosize M-type BHF obtained by precipitation of hydroxicarbonates technique. > Optimal fractal structure of a precursor for nanosize M-type BHF has been determined. > The precursor precipitated at pH 4.3 allows getting monodisperse particles of BHF.

Synthesis and optical properties of novel organic-inorganic hybrid nanolayer structure semiconductors

International Nuclear Information System (INIS)

Zhang Sanjun; Lanty, Gaetan; Lauret, Jean-Sebastien; Deleporte, Emmanuelle; Audebert, Pierre; Galmiche, Laurent

2009-01-01

We report on the synthesis of some novel organic-inorganic hybrid 2D perovskite semiconductors (R-(CH 2 ) n NH 3 ) 2 PbX 4 . These semiconductors are self-assembled intercalation nanolayers and have a multi-quantum-well energy level structure. We systematically vary the characteristic of organic groups (R-(CH 2 ) n NH 3 + ) to study the relationship between their structures and the optical properties of (R-(CH 2 ) n NH 3 ) 2 PbX 4 . From optical absorption and photoluminescence spectroscopy experiments performed on series of samples, we find some trends of choosing the organic groups to improve the optical performance of (R-(CH 2 ) n NH 3 ) 2 PbX 4 . A new organic group, which allows synthesis of nanolayer perovskite semiconductors with quite high photoluminescence efficiency and better long-term stability, has been found.

Structure, bioactivity, and synthesis of methylated flavonoids.

Science.gov (United States)

Wen, Lingrong; Jiang, Yueming; Yang, Jiali; Zhao, Yupeng; Tian, Miaomiao; Yang, Bao

2017-06-01

Methylated flavonoids are an important type of natural flavonoid derivative with potentially multiple health benefits; among other things, they have improved bioavailability compared with flavonoid precursors. Flavonoids have been documented to have broad bioactivities, such as anticancer, immunomodulation, and antioxidant activities, that can be elevated, to a certain extent, by methylation. Understanding the structure, bioactivity, and bioavailability of methylated flavonoids, therefore, is an interesting topic with broad potential applications. Though methylated flavonoids are widely present in plants, their levels are usually low. Because developing efficient techniques to produce these chemicals would likely be beneficial, we provide an overview of their chemical and biological synthesis. © 2017 New York Academy of Sciences.

Zinc Oxide Nanostructures: From Chestnut Husk-Like Structures to Hollow Nanocages, Synthesis and Structure

Directory of Open Access Journals (Sweden)

Domenica Scarano

2018-03-01

Full Text Available Tailor-made nanostructured ZnO cages have been catalytically grown on Au and Pt films covering silicon substrates, by a controlled evaporation process, which means an accurate choice of temperatures, times, gas flows (He in the heating, He/air during the synthesis, and Au/Pt film thickness. The effect of the process parameters affecting the morphology and the structure of the obtained materials has been investigated by XRD analysis, scanning electron microscopy (SEM and atomic force microscopy (AFM microscopies, and FTIR spectroscopies. In particular, the role of the synthesis temperature in affecting the size and shape of the obtained ZnO cages has been highlighted. It will be shown that by adopting higher temperatures, the protruding nanowhiskers several microns in length, covering the cages and exhibiting both basal and prismatic faces, change into very thin and narrow structures, with extended prismatic faces, prevailing with respect to the basal ones. At an even higher process temperature, the building up of Au particles aggregates inside and/or anchored to the walls of the hollow cages, without any evidence of elongated ZnO nanostructures will be highlighted. From FTIR spectra information on lattice modes of the investigated ZnO, materials have been obtained.

The crystal structure of escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis

International Nuclear Information System (INIS)

Sanishvili, R.; Beasley, S.; Skarina, T; Glesne, D; Joachimiak, A; Edwards, A; Savchenko, A.; Univ. Health Network; Univ. of Toronto

2004-01-01

The crystal structure of Escherichia coli MoaB was determined by multiwavelength anomalous diffraction phasing and refined at 1.6 Angstrom resolution. The molecule displayed a modified Rossman fold. MoaB is assembled into a hexamer composed of two trimers. The monomers have high structural similarity with two proteins, MogA and MoeA, from the molybdenum cofactor synthesis pathway in E. Coli, as well as with domains of mammalian gephyrin and plant Cnx1, which are also involved in molybdopterin synthesis. Structural comparison between these proteins and the amino acid conservation patterns revealed a putative active site in MoaB. The structural analysis of this site allowed to advance several hypothesis which can be tested in further studies

An Investigation of Porous Structure of TiNi-Based SHS-Materials Produced at Different Initial Synthesis Temperatures

Science.gov (United States)

Khodorenko, V. N.; Anikeev, S. G.; Kokorev, O. V.; Yasenchuk, Yu. F.; Gunther, V. É.

2018-02-01

An investigation of structural characteristics and behavior of TiNi-based pore-permeable materials manufactured by the methods of selfpropagating high-temperature synthesis (SHS) at the initial synthesis temperatures T = 400 and 600°C is performed. It is shown that depending on the temperature regime, the resulting structure and properties of the material can differ. It is found out that the SHS-material produced at the initial synthesis temperature T = 400°C possesses the largest number of micropores in the pore wall surface structure due to a high phase inhomogeneity of the alloy. The regime of structure optimization of the resulting materials is described and the main stages of formation of the pore wall microporous surfaces are revealed. It is demonstrated that after optimization of the surface structure of a TiNi-based fine-pore alloy by its chemical etching, the fraction of micropores measuring in size less than 50 nm increased from 59 to 68%, while the number of pores larger than 1 μm increased twofold from 11 to 22%. In addition, peculiar features of interaction between certain cell cultures with the surface of the SHS-material manufactured at different initial synthesis temperatures are revealed. It is found out that the dynamics of the cell material integration depends on the pore wall surface morphology and dimensions of macropores.

synthesis and structures

Indian Academy of Sciences (India)

Priya Saxena

2017-08-29

Aug 29, 2017 ... to a single crystal X-ray diffraction study for 1, 2 and 4-7. Keywords. Sterically .... 2.2b Mono-Schiff base 2: A suspension of I (1.00 g,. 2.27 mmol) and ...... bridge Crystallographic Data Centre, CCDC, 12 Union. Road, Cambridge .... H-C 2014 Rational design and synthesis of porous poly- mer networks: ...

Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

KAUST Repository

Zeng, Shangjing

2016-08-03

A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity is investigated by adding an organosilane surfactant as a mesopore-generating agent.

Synthesis and study of nano-structured cellulose acetate based materials for energy applications

International Nuclear Information System (INIS)

Fischer, F.

2006-12-01

Nano-structured materials have unique properties (high exchange areas, containment effect) because of their very low characteristic dimensions. The elaboration way set up in this PhD work consists in applying the classical processes for the preparation of aerogel-like materials (combining sol-gel synthesis and CO 2 supercritical extraction) to cellulosic polymers. This work is divided in four parts: a literature review, the presentation and the study of the chemical synthesis that leads to cellulose acetate-based aerogel, the characterizations (chemical, structural and thermal) of the elaborated nano-materials, and finally the study of the first carbons that were obtained after pyrolysis of the organic matrix. The formulations and the sol-gel protocol lead to chemical gels by crosslinking cellulose acetate using a poly-functional iso-cyanate. The dry materials obtained after solvent extraction with supercritical CO 2 are nano-structured and mainly meso-porous. Correlations between chemical synthesis parameters (reagent concentrations, crosslinking rate and degree of polymerisation) and porous properties (density, porosity, pore size distribution) were highlighted thanks to structural characterizations. An ultra-porous reference aerogel, with a density equals to 0,245 g.cm -3 together with a meso-porous volume of 3,40 cm 3 .g -1 was elaborated. Once in granular shape, this material has a thermal conductivity of 0,029 W.m -1 .K -1 . In addition, carbon materials produced after pyrolysis of the organic matrix and after grinding are nano-structured and nano-porous, even if important structural modifications have occurred during the carbonization process. The elaborated materials are evaluated for applications in relation with energy such as thermal insulation (organic aerogels) but also for energy conversion and storage through electrochemical way (carbon aerogels). (author)

Cell-free protein synthesis for structure determination by X-ray crystallography.

Science.gov (United States)

Watanabe, Miki; Miyazono, Ken-ichi; Tanokura, Masaru; Sawasaki, Tatsuya; Endo, Yaeta; Kobayashi, Ichizo

2010-01-01

Structure determination has been difficult for those proteins that are toxic to the cells and cannot be prepared in a large amount in vivo. These proteins, even when biologically very interesting, tend to be left uncharacterized in the structural genomics projects. Their cell-free synthesis can bypass the toxicity problem. Among the various cell-free systems, the wheat-germ-based system is of special interest due to the following points: (1) Because the gene is placed under a plant translational signal, its toxic expression in a bacterial host is reduced. (2) It has only little codon preference and, especially, little discrimination between methionine and selenomethionine (SeMet), which allows easy preparation of selenomethionylated proteins for crystal structure determination by SAD and MAD methods. (3) Translation is uncoupled from transcription, so that the toxicity of the translation product on DNA and its transcription, if any, can be bypassed. We have shown that the wheat-germ-based cell-free protein synthesis is useful for X-ray crystallography of one of the 4-bp cutter restriction enzymes, which are expected to be very toxic to all forms of cells retaining the genome. Our report on its structure represents the first report of structure determination by X-ray crystallography using protein overexpressed with the wheat-germ-based cell-free protein expression system. This will be a method of choice for cytotoxic proteins when its cost is not a problem. Its use will become popular when the crystal structure determination technology has evolved to require only a tiny amount of protein.

New routes to nitrogen-rich transition metal nitrides: Synthesis of novel polymorphs of Hf3N4

Science.gov (United States)

Salamat, Ashkan; Hector, A.; Gray, B.; Kimber, S.; Bouvier, P.; McMillan, P.

2013-06-01

One of the most obvious features of transition metal nitride chemistry is that the maximum formal oxidation state of the metal is rarely as high as in the corresponding oxides or fluorides. Much of the interest in the high oxidation phases stems from the desire to identify the next generation of photocatalytic materials with tuneable bandgaps. Experiments in the laser heated diamond anvil cell (LHDAC) between the direct reaction of metals and nitrogen have previously produced a number of important new main group nitride phases. This technique has also demonstrated its potential for formation of new nitrogen-rich transition metal nitride phases. Alternative methods with the development of ``soft'' routes to new phases with high nitrogen content also offer the possibility of obtaining metastable phases through topotactic conversions. Using LHDAC in situ with synchrotron angle dispersive diffraction techniques we have crystallised at high pressures and temperatures two novel polymorphs of Hf3N4. Starting with an amide-derived nanocrystalline Hf3N4 sample we have identified a novel tetragonal (I4/ m) polymorph at 15 GPa and 1500K and a second high pressure orthorhombic (Pnma) polymorph at 30 GPa and 2000 K. This study demonstrates that the combination of precursor-based synthesis and high-pressure crystallization could be very productive in synthesis of such nitrogen-rich phases.

Synthesis of silicon nanowires and novel nano-dendrite structures

International Nuclear Information System (INIS)

Sinha, Saion; Gao Bo; Zhou, Otto

2004-01-01

We report a study on the effects of various parameters on the synthesis of silicon nanowires (5--50 nm in diameter) by pulsed laser ablation. A novel silicon nanodendrite structure is observed by changing some of the growth parameters abruptly. This growth mechanism is explained by a qualitative model. These nanodendrites show a promise of being used as a template in fabricating nanocircuits. Thermal quantum confinement effects were also observed on the silicon nanowires and have been reported

Synthesis of carbon nano structures by plasma discharge

International Nuclear Information System (INIS)

Jimenez L, M.L.

2007-01-01

Due to the great quantity of applications of carbon neocarcinostatin (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, one has seen the necessity to generate new synthesis processes of these materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither impurities. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arc discharge, in a gas mixture He-CH 4 with 34% at.Ni/10.32%at.Y like catalyst; to a frequency of 42 k Hz and low power (300 W). This method benefits the agglomeration of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the type of obtained NEC and by X-ray diffraction analysis and Raman spectroscopy to determine the purity of the samples. The NFC are relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of the plasma using the Swan band to determine the temperature. (Author)

Materials-by-design: computation, synthesis, and characterization from atoms to structures

Science.gov (United States)

Yeo, Jingjie; Jung, Gang Seob; Martín-Martínez, Francisco J.; Ling, Shengjie; Gu, Grace X.; Qin, Zhao; Buehler, Markus J.

2018-05-01

In the 50 years that succeeded Richard Feynman’s exposition of the idea that there is ‘plenty of room at the bottom’ for manipulating individual atoms for the synthesis and manufacturing processing of materials, the materials-by-design paradigm is being developed gradually through synergistic integration of experimental material synthesis and characterization with predictive computational modeling and optimization. This paper reviews how this paradigm creates the possibility to develop materials according to specific, rational designs from the molecular to the macroscopic scale. We discuss promising techniques in experimental small-scale material synthesis and large-scale fabrication methods to manipulate atomistic or macroscale structures, which can be designed by computational modeling. These include recombinant protein technology to produce peptides and proteins with tailored sequences encoded by recombinant DNA, self-assembly processes induced by conformational transition of proteins, additive manufacturing for designing complex structures, and qualitative and quantitative characterization of materials at different length scales. We describe important material characterization techniques using numerous methods of spectroscopy and microscopy. We detail numerous multi-scale computational modeling techniques that complements these experimental techniques: DFT at the atomistic scale; fully atomistic and coarse-grain molecular dynamics at the molecular to mesoscale; continuum modeling at the macroscale. Additionally, we present case studies that utilize experimental and computational approaches in an integrated manner to broaden our understanding of the properties of two-dimensional materials and materials based on silk and silk-elastin-like proteins.

Linker-free 3D assembly of nanocrystals with tunable unit size for reversible lithium ion storage

Energy Technology Data Exchange (ETDEWEB)

Deng, Da; Lee, Jim Yang, E-mail: cheleejy@nus.edu.sg [Department of Chemical and Biomolecular Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, 119260 (Singapore)

2011-09-02

A simple and scalable procedure combining hydrothermal synthesis with post-synthesis calcination was developed to produce a linker-free, thermally stable, mesoscale 3D ordered assembly of spinel-type ZnCo{sub 2}O{sub 4} nanocrystals. The mesoscale assembly with distinctively sharp edges was formed by close-packing the ZnCo{sub 2}O{sub 4} nanocrystal building blocks with a unit size changeable by the synthesis temperature. A self-templating mechanism based on the topotactic transformation of an oxalato-bridged precursor coordination compound was proposed for the assembly. The packaging of crystalline ZnCo{sub 2}O{sub 4} nanoparticles, an active lithium ion storage compound, into a dense organized structure is an effective way to increase the volumetric capacity of ZnCo{sub 2}O{sub 4} nanoparticles for reversible lithium ion storage. The highly ordered 3D assembly of ZnCo{sub 2}O{sub 4} demonstrated excellent reversible lithium ion storage properties and a specific capacity ({approx}800 mAh g{sup -1}) much higher than that of carbon (typically {approx} 350 mAh g{sup -1}).

Linker-free 3D assembly of nanocrystals with tunable unit size for reversible lithium ion storage

International Nuclear Information System (INIS)

Deng, Da; Lee, Jim Yang

2011-01-01

A simple and scalable procedure combining hydrothermal synthesis with post-synthesis calcination was developed to produce a linker-free, thermally stable, mesoscale 3D ordered assembly of spinel-type ZnCo 2 O 4 nanocrystals. The mesoscale assembly with distinctively sharp edges was formed by close-packing the ZnCo 2 O 4 nanocrystal building blocks with a unit size changeable by the synthesis temperature. A self-templating mechanism based on the topotactic transformation of an oxalato-bridged precursor coordination compound was proposed for the assembly. The packaging of crystalline ZnCo 2 O 4 nanoparticles, an active lithium ion storage compound, into a dense organized structure is an effective way to increase the volumetric capacity of ZnCo 2 O 4 nanoparticles for reversible lithium ion storage. The highly ordered 3D assembly of ZnCo 2 O 4 demonstrated excellent reversible lithium ion storage properties and a specific capacity (∼800 mAh g -1 ) much higher than that of carbon (typically ∼ 350 mAh g -1 ).

Improved conductivity of infinite-layer LaNiO{sub 2} thin films by metal organic decomposition

Energy Technology Data Exchange (ETDEWEB)

Ikeda, Ai [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 (Japan); Research Fellow of the Japan Society for the Promotion of Science (Japan); Manabe, Takaaki [National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8565 (Japan); Naito, Michio, E-mail: minaito@cc.tuat.ac.jp [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 (Japan)

2013-12-15

Highlights: •LaNiO{sub 2} films were synthesized by metal organic decomposition and topotactic reduction. •Room-temperature resistivity as low as 0.6 mΩ cm was achieved for infinite-layer LaNiO{sub 2}. •Lattice matched substrates are important in obtaining high conductivity. -- Abstract: Infinite-layer LaNiO{sub 2} thin films were synthesized by metal organic decomposition and subsequent topotactic reduction in hydrogen, and their transport properties were investigated. LaNiO{sub 2} is isostructural to SrCuO{sub 2}, the parent compound of high-T{sub c} Sr{sub 0.9}La{sub 0.1}CuO{sub 2} with T{sub c} = 44 K, and has 3d{sup 9} configuration, which is very rare in oxides but common to high-T{sub c} copper oxides. The bulk synthesis of LaNiO{sub 2} is not easy, but we demonstrate in this article that the thin-film synthesis of LaNiO{sub 2} is rather easy, thanks to a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Our refined synthesis conditions produced highly conducting films of LaNiO{sub 2}. The resistivity of the best film is as low as 640 μΩ cm at 295 K and decreases with temperature down to 230 K but it shows a gradual upturn at lower temperatures.

Improved conductivity of infinite-layer LaNiO2 thin films by metal organic decomposition

International Nuclear Information System (INIS)

Ikeda, Ai; Manabe, Takaaki; Naito, Michio

2013-01-01

Highlights: •LaNiO 2 films were synthesized by metal organic decomposition and topotactic reduction. •Room-temperature resistivity as low as 0.6 mΩ cm was achieved for infinite-layer LaNiO 2 . •Lattice matched substrates are important in obtaining high conductivity. -- Abstract: Infinite-layer LaNiO 2 thin films were synthesized by metal organic decomposition and subsequent topotactic reduction in hydrogen, and their transport properties were investigated. LaNiO 2 is isostructural to SrCuO 2 , the parent compound of high-T c Sr 0.9 La 0.1 CuO 2 with T c = 44 K, and has 3d 9 configuration, which is very rare in oxides but common to high-T c copper oxides. The bulk synthesis of LaNiO 2 is not easy, but we demonstrate in this article that the thin-film synthesis of LaNiO 2 is rather easy, thanks to a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Our refined synthesis conditions produced highly conducting films of LaNiO 2 . The resistivity of the best film is as low as 640 μΩ cm at 295 K and decreases with temperature down to 230 K but it shows a gradual upturn at lower temperatures

Investigating the Synthesis, Structure, and Catalytic Properties of Versatile Gold-Based Nanocatalvsts

Science.gov (United States)

Pretzer, Lori A.

Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst's surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the

Characterization structural and morphology ZSM-5 zeolite by hydrothermal synthesis

International Nuclear Information System (INIS)

Silva, V.J.; Crispim, A.C.; Queiroz, M.B.; Laborde, H.M.; Rodrigues, M.G.F.; Menezes, R.R.

2009-01-01

Solid acids are catalytic materials commonly used in the chemical industry. Among these zeolites are the most important business processes including water treatment, gas separation, and cracking long hydrocarbon chains to produce high octane gasoline. Its synthesis, characterization and applications have been widely studied. The objective this study was to synthesize the ZSM-5 zeolite for future use in separation processes and catalysis. The zeolite ZSM-5 was prepared by hydrothermal synthesis at 170°C, using silica, deionized water and the director of structures (TPABr - tetrapropylammonium bromide). The materials were characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and semiquantitative chemical analysis by X ray fluorescence (XRF). According to the XRD was possible to observe the formation of ZSM-5 zeolite, with peaks intense and well defined. The SEM showed the formation of individual particles, clean, rounded shapes. (author)

Synthesis and optical properties of novel organic-inorganic hybrid nanolayer structure semiconductors

Energy Technology Data Exchange (ETDEWEB)

Zhang Sanjun; Lanty, Gaetan; Lauret, Jean-Sebastien [Laboratoire de Photonique Quantique et Moleculaire de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France); Deleporte, Emmanuelle, E-mail: Emmanuelle.Deleporte@lpqm.ens-cachan.fr [Laboratoire de Photonique Quantique et Moleculaire de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France); Audebert, Pierre; Galmiche, Laurent [Laboratoire de Photophysique et Photochimie Supramoleculaires et Macromoleculaires de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France)

2009-06-15

We report on the synthesis of some novel organic-inorganic hybrid 2D perovskite semiconductors (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. These semiconductors are self-assembled intercalation nanolayers and have a multi-quantum-well energy level structure. We systematically vary the characteristic of organic groups (R-(CH{sub 2}){sub n}NH{sub 3}{sup +}) to study the relationship between their structures and the optical properties of (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. From optical absorption and photoluminescence spectroscopy experiments performed on series of samples, we find some trends of choosing the organic groups to improve the optical performance of (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. A new organic group, which allows synthesis of nanolayer perovskite semiconductors with quite high photoluminescence efficiency and better long-term stability, has been found.

Highly dispersed spherical Bi3.25La0.75Ti3O12 nanocrystals via topotactic crystallization of aggregation-free gel particles from an effective inverse miniemulsion sol–gel approach

International Nuclear Information System (INIS)

Wang, Aijun; Zeng, Yanwei; Han, Longxiang; Ding, Chuan; Cao, Liangliang; Li, Rongjie

2015-01-01

Aggregation-free spherical lanthanum-doped bismuth titanate (Bi 3.25 La 0.75 Ti 3 O 12 , BLT) gel particles with an average size of about 150 nm were successfully obtained from an inverse miniemulsion sol–gel process, with Span-80 acting as surfactant, n-butanol as co-surfactant, cyclohexane as continuous phase, and submicro-droplets of aqueous solution containing Bi 3+ , La 3+ and Ti 4+ ions as dispersed phase, and then topotactically transformed into highly dispersed spherical BLT nanocrystals after an in situ crystallization at 600 °C for 8 h. It has been found that the BLT gel particles can be obtained via a moderate sol–gel reaction inside the miniemulsion droplets at 65 °C, but their morphology and aggregation degree are strongly affected by the relative amounts of Span-80 and n-butanol. The perfect spherical BLT gel particles with no aggregation can be achieved only under the condition of 3 wt% n-butanol relative to the mass of cyclohexane, with excessive amount of n-butanol leading to the formation of ill-gelled particles with irregular shapes, while insufficient addition of n-butanol resulting in terrible aggregation of gel particles. To understand the formation of aggregation-free spherical BLT gel particles, a tentative mechanism is proposed and discussed, which reveals that a well-coordinated oil–water interfacial film made up of Span-80 and n-butanol molecules and the appropriately enhanced evaporation of water from such interfaces should be responsible for the formation of aggregation-free spherical BLT gel particles. Graphical Abstract: Aggregation-free spherical BLT (Bi 3.25 La 0.75 Ti 3 O 12 ) gel particles can be prepared from an effective inverse miniemulsion sol–gel process, and subsequently topotactically transformed into spherical BLT nanocrystals through an in situ crystallization

The thermal stability range and magnetic properties of U-type hexaferrites

International Nuclear Information System (INIS)

Lisjak, Darja; Drofenik, Miha

2004-01-01

Single-phase polycrystalline U-hexaferrites with the composition Ba 4 A 2 Fe 36 O 60 (A=Co, Ni, Zn) were prepared by solid-state reaction synthesis employing high-energy milling or topotactic reaction and calcination at 1200-1300 deg. C. The Curie temperature and saturation magnetization of the samples were influenced by the composition, while the coercivity was more strongly influenced by the preparation conditions

Mesoporous Co{sub 3}O{sub 4} and CoO rate at C topotactically transformed from chrysanthemum-like Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O and their lithium-storage properties

Energy Technology Data Exchange (ETDEWEB)

Xiong, Shenglin; Zeng, Hua Chun [Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore (Singapore); Chen, Jun Song; Lou, Xiong Wen [School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, Singapore (Singapore)

2012-02-22

In this work, a novel hydrothermal route is developed to synthesize cobalt carbonate hydroxide, Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O. In this method, sodium chloride salt is utilized to organize single-crystalline nanowires into a chrysanthemum-like hierarchical assembly. The morphological evolution process of this organized product is investigated by examining different reaction intermediates during the synthesis. The growth and thus the final assembly of the Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O can be finely tuned by selecting preparative parameters, such as the molar ratio of the starting chemicals, the additives, the reaction time and the temperature. Using the flower-like Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O as a solid precursor, quasi-single-crystalline mesoporous Co{sub 3}O{sub 4} nanowire arrays are prepared via thermal decomposition in air. Furthermore, carbon can be added onto the spinel oxide by a chemical-vapor-deposition method using acetylene, which leads to the generation of carbon-sheathed CoO nanowire arrays (CoO rate at C). Through comparing and analyzing the crystal structures, the resultant products and their high crystallinity can be explained by a sequential topotactic transformation of the respective precursors. The electrochemical performances of the typical cobalt oxide products are also evaluated. It is demonstrated that tuning of the surface texture and the pore size of the Co{sub 3}O{sub 4} products is very important in lithium-ion-battery applications. The carbon-decorated CoO nanowire arrays exhibit an excellent cyclic performance with nearly 100% capacity retention in a testing range of 70 cycles. Therefore, this CoO rate at C nanocomposite can be considered to be an attractive candidate as an anode material for further investigation. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structure of human DNA polymerase iota and the mechanism of DNA synthesis.

Science.gov (United States)

Makarova, A V; Kulbachinskiy, A V

2012-06-01

Cellular DNA polymerases belong to several families and carry out different functions. Highly accurate replicative DNA polymerases play the major role in cell genome replication. A number of new specialized DNA polymerases were discovered at the turn of XX-XXI centuries and have been intensively studied during the last decade. Due to the special structure of the active site, these enzymes efficiently perform synthesis on damaged DNA but are characterized by low fidelity. Human DNA polymerase iota (Pol ι) belongs to the Y-family of specialized DNA polymerases and is one of the most error-prone enzymes involved in DNA synthesis. In contrast to other DNA polymerases, Pol ι is able to use noncanonical Hoogsteen interactions for nucleotide base pairing. This allows it to incorporate nucleotides opposite various lesions in the DNA template that impair Watson-Crick interactions. Based on the data of X-ray structural analysis of Pol ι in complexes with various DNA templates and dNTP substrates, we consider the structural peculiarities of the Pol ι active site and discuss possible mechanisms that ensure the unique behavior of the enzyme on damaged and undamaged DNA.

Charge and structural ordering in the brownmillerite phases: La1-xSrxMnO2.5 (0.2

International Nuclear Information System (INIS)

Casey, Peter S.; Barker, Daniel; Hayward, Michael A.

2006-01-01

The topotactic reduction of La 1-x Sr x MnO 3 (0.2 1-x Sr x MnO 2.5 brownmillerite phases with NaH is described. Neutron and electron diffraction data show the x=0.25 and 0.2 phases adopt structures with an unusual ordered L-R-L-R alternation of twisted chains of Mn(II) tetrahedra within each anion-deficient layer. This is accompanied by Mn(II)/(III) charge ordering within the remaining MnO 6 octahedral layers. In contrast, the x=0.4 phase adopts a structure in which the twisted chains of tetrahedra are disordered

Nonequilibrium phase formation in oxides prepared at low temperature: Fergusonite-related phases

International Nuclear Information System (INIS)

Mather, S.A.; Davies, P.K.

1995-01-01

Sol-gel methods have been developed to prepare YNbO 4 , YTaO 4 , and other rare-earth niobates and tantalates with fergusonite-related crystal structures. At low temperatures, all of the fergusonites, with the exception of SmTaO 4 , crystallize in a metastable tetragonal (T') structure similar to that of tetragonal zirconia. Although all of the equilibrium forms of these oxides adopt a crystal structure containing an ordered distribution of the trivalent and pentavalent cations, a random cation distribution is obtained in the metastable T' phase. Metastable phase formation is often ascribed solely to kinetically limited topotactic crystallization. However, the changes in the grain size and unit-cell volumes that accompany the metastable-to-equilibrium fergusonite conversions imply that other physical phenomena induced by small-particle synthesis, namely the Gibbs-Thompson pressure effect and the increased contribution of surface energy, cannot be ignored

Topotactic transformations of sodalite cages: synthesis and NMR study of mixed salt-free and salt-bearing sodalites.

Science.gov (United States)

Trill, Henning; Eckert, Hellmut; Srdanov, Vojislav I

2002-07-17

A series of mixed sodalite samples, Na(8)[Al(6)Si(6)O(24)]Br(x).(H(3)O(2))(2-x), with the unit cell stoichiometries varying in the 0 < x <2 region, was made by hydrothermal synthesis and subsequently transformed into Na(6+x)[Al(6)Si(6)O(24)]Br(x).(4H(2)O)(2-x) and Na(6+x)[Al(6)Si(6)O(24)]Br(x).circle(2-x) sodalites. Here, circle refers to an empty sodalite cage. The three series, referred hereafter to as the Br/basic, Br/hydro, and Br/dry series, were characterized by powder diffraction X-ray and by (23)Na, (27)Al, and (81)Br magic angle spinning (MAS) NMR and high-resolution triple quantum (TQ) MAS NMR spectroscopy. We determined that incorporation of Br(-) anions is 130 times more preferred than incorporation of H(3)O(2)(-) anions during the formation of sodalite cages, which permitted precise control of the halide content in the solid. Monotonic trends in chemical shifts were observed as a function of cage occupancy, reflecting continuous changes in structural parameters. A linear correlation between (81)Br chemical shift and lattice constant with a slope of -86 ppm/A was observed for all three series. Likewise, (23)Na chemical shifts for Na(+) cations in salt-bearing sodalite cages correlate linearly with the lattice constant. Both results indicate a universal dependence of the (23)Na and (81)Br chemical shifts on the Na-Br distance. The (27)Al chemical shifts of Br/basic and Br/hydro sodalites obey an established relation between delta(cs) and the average T-O-T bond angle of 0.72 ppm/degrees. Br/dry sodalites show two aluminum resonances, characterized by significantly different chemical shifts and quadrupolar interaction parameters. In that series, local symmetry distortions are evident from strong quadrupolar perturbations in the NMR spectra. P(Q) values for (27)Al vary between 0.8 MHz in Br/basic sodalites and 4.4 MHz in the Br/dry series caused by deviations from the tetrahedral symmetry of the salt-free sodalite cages. For (23)Na, P(Q) values of 0.8, 0

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

Directory of Open Access Journals (Sweden)

Nina Gonsior

2012-03-01

Full Text Available The synthesis of a heterocyclic mesomeric betaine by quaternization reaction of 1-butylimidazole and tetrabromo-1,4-benzoquinone is presented. The structure was verified by means of X-ray single-crystal analysis, NMR and IR spectroscopy. Inclusion complexes of the heterocyclic mesomeric betaine with randomly methylated (1.8 β-cyclodextrin were investigated by UV–vis spectroscopy. Furthermore, the reaction conditions were applied to poly(vinylimidazole and 1,4-bis(1H-imidazol-1-ylbutane to obtain functionalized polymer networks and condensate polymers, respectively.

A General Chemistry Experiment Incorporating Synthesis and Structural Determination

Science.gov (United States)

van Ryswyk, Hal

1997-07-01

An experiment for the general chemistry laboratory is described wherein gas chromatography-mass spectroscopy (GC-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are used to characterize the products of a series of microscale reactions on vanillin. A single sophisticated instrument can be incorporated into the laboratory given sufficient attention to the use of sampling accessories and software macros. Synthetic experiments coupled with modern instrumental techniques can be used in the general chemistry laboratory to illustrate the concepts of synthesis, structure, bonding, and spectroscopy.

Controlled Synthesis of Manganese Dioxide Nano structures via a Facile Hydrothermal

International Nuclear Information System (INIS)

Pang, R.S.C.; Chin, S.F.; Ye, Ch. Ling

2012-01-01

Manganese dioxide nano structures with controllable morphological structures and crystalline phases were synthesized via a facile hydrothermal route at low temperatures without using any templates or surfactants. Both the aging duration and aging temperatures were the main synthesis parameters used to influence and control the rate of morphological and structural evolution of MnO 2 nano structures. MnO 2 nano structures comprise of spherical nano particulate agglomerates and highly amorphous in nature were formed at lower temperature and/or short aging duration. In contrast, MnO 2 nano structures of sea-urchin-like and nano rods-like morphologies and nanocrystalline in nature were prepared at the combined higher aging temperatures and longer aging durations. These nano structures underwent notable phase transformation from d-MnO 2 to a-MnO 2 upon prolonged hydrothermal aging duration and exhibited accelerated rate of phase transformation at higher aging temperature.

Structure-directing effects of ionic liquids in the ionothermal synthesis of metal-organic frameworks.

Science.gov (United States)

Vaid, Thomas P; Kelley, Steven P; Rogers, Robin D

2017-07-01

Traditional synthesis of metal-organic frameworks (MOFs) involves the reaction of a metal-containing precursor with an organic linker in an organic solvent at an elevated temperature, in what is termed a 'solvothermal' reaction. More recently, many examples have been reported of MOF synthesis in ionic liquids (ILs), rather than an organic solvent, in 'ionothermal' reactions. The high concentration of both cations and anions in an ionic liquid allows for the formation of new MOF structures in which the IL cation or anion or both are incorporated into the MOF. Most commonly, the IL cation is included in the open cavities of the MOF, countering the anionic charge of the MOF framework itself and acting as a template around which the MOF structure forms. Ionic liquids can also serve other structure-directing roles, for example, when an IL containing a single enantiomer of a chiral anion leads to a homochiral MOF, even though the IL anion is not itself incorporated into the MOF. A comprehensive review of ionothermal syntheses of MOFs, and the structure-directing effects of the ILs, is given.

Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

International Nuclear Information System (INIS)

Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

2012-01-01

Graphical abstract: NiWO 4 nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: ► NiWO 4 spherical nanoparticles were synthesized via direct precipitation method. ► Taguchi robust design was used for optimization of synthesis reaction parameters. ► Composition and structural properties of NiWO 4 nanoparticles were characterized. ► EDAX, XRD, SEM, FT-IR, UV–vis and photoluminescence techniques were employed. ► Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO 4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO 4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO 4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV–vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pourmortazavi, Seied Mahdi, E-mail: pourmortazavi@yahoo.com [Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Rahimi-Nasrabadi, Mehdi, E-mail: rahiminasrabadi@gmail.com [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Khalilian-Shalamzari, Morteza [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh [Islamic Azad University, Varamin Pishva Branch, Varamin (Iran, Islamic Republic of); Omrani, Ismail [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of)

2012-12-15

Graphical abstract: NiWO{sub 4} nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: Black-Right-Pointing-Pointer NiWO{sub 4} spherical nanoparticles were synthesized via direct precipitation method. Black-Right-Pointing-Pointer Taguchi robust design was used for optimization of synthesis reaction parameters. Black-Right-Pointing-Pointer Composition and structural properties of NiWO{sub 4} nanoparticles were characterized. Black-Right-Pointing-Pointer EDAX, XRD, SEM, FT-IR, UV-vis and photoluminescence techniques were employed. Black-Right-Pointing-Pointer Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO{sub 4} nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO{sub 4} particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO{sub 4} were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV

SYNTHESIS OF THE TECHNICAL CONTROL SYSTEMS WITH VARIABLE STRUCTURE

Directory of Open Access Journals (Sweden)

2016-01-01

Full Text Available Change. Also the object as a result of an adverse effect is considered. The formal problem definition of synthesis of hardy management system is considered. Model choice criteria ensemble is set. The rule of choice algorithm implementation on the basis of different reference functions is provided. The conclusion is drawn that in case of preliminary processing of the available prior data it is possible to select reference functions correctly which reflect physical processes more precisely. The mathematical description of a dynamic object on the basis of a differential equation, or its decision is provided. Defini- tion of function of a trend is given. Criteria for selection of model of damage are given. The recommendation of modifica- tion of Demark trends algorithm by means of the sliding Yazvinsky's window and a method of self-organization for in- crease of accuracy of creation of a predictive model of damage is made. It is offered to realize a model choice by means of more complex logical analysis of an observed vector in the appropriate situation. Logic-functional control task definition is given and approach to its decision is formulated. The conclusion about what the task of synthesis management system con- sists of is given. This article describes the method of synthesis of control system with variable structure provides increasing survivability control system in a significant change of the external environment, as well as the object itself from the adverse impacts.

Synthesis and Structure of D3h-Symmetric Triptycene Trimaleimide

Directory of Open Access Journals (Sweden)

Anthony Linden

2010-01-01

Full Text Available A new D3h symmetric triptycene derivative has been synthesized with the aim of obtaining molecules that are able to assemble into porous structures, and can be used in the development of new ligands. The synthesis involves a Diels-Alder reaction as the key step, followed by an oxidation and the formation of a maleimide ring. Triptycene trimaleimide furnished single crystals which have been analyzed by means of X-ray diffraction.

Relation between structural evolution and effective Ir moments upon applied pressure during synthesis in Ba{sub 3}YIr{sub 2}O{sub 9}

Energy Technology Data Exchange (ETDEWEB)

Stummer, Hannes; Dey, Tusharkanti; Wurmehl, Sabine; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research, Dresden (Germany)

2015-07-01

The intensively investigated material class of Iridium oxide based materials provides a variety of new and unknown combinations of magnetic properties with interesting novel or exotic ground states. These Iridate compounds often appear in a perovskite type structure or a related derivative which are very favorable for crystal structure modifications under high pressure. High pressure synthesis therefore can be used to tune or change the magnetic properties appearing under normal pressure. The Iridate Ba{sub 3}YIr{sub 2}O{sub 9} crystallizes under ambient pressure synthesis in a hexagonal structure and exhibits magnetic ordering below 4 K. A synthesis pressure of 8 GPa advances the material to form a cubic double perovskite structure which is (meta-)stable at ambient pressure. For this high pressure configuration the magnetic ordering is suppressed. We will present our recent results about the systematic high pressure synthesis and characterization of Ba{sub 3}YIr{sub 2}O{sub 9} samples grown under different growth pressure. The main focus will be on the correlation between structural and magnetic properties depending on the applied pressure during the synthesis process.

Green synthesis of ZnO nanoparticles by Aspalathus linearis: Structural & optical properties

International Nuclear Information System (INIS)

Diallo, A.; Ngom, B.D.; Park, E.; Maaza, M.

2015-01-01

This contribution reports for the 1st time on the synthesis and the main physical properties of ZnO nanoparticles synthesized by an entirely green physical-chemistral process using Aspalathus linearis's natural extract as an efficient reduction/oxidizing agent. Their structural and optical properties by electron microscopy, X-rays diffraction, Raman and X-rays photoemission spectroscopies as well as room temperature photoluminescence are reported. - Highlights: • 1st time report on synthesis of ZnO nanoparticles by a green process via Aspalathus linearis extract. • A. linearis's natural extract was used as an effective reduction/oxidizing agent. • Wurtzite nature of ZnO nanoparticles was confirmed via XRD, Raman, XPS and PL

Green synthesis of ZnO nanoparticles by Aspalathus linearis: Structural & optical properties

Energy Technology Data Exchange (ETDEWEB)

Diallo, A.; Ngom, B.D. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Park, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Nelson Mandela African Institute for Science & Technology, Arusha (Tanzania, United Republic of); Maaza, M., E-mail: Maaza@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa)

2015-10-15

This contribution reports for the 1st time on the synthesis and the main physical properties of ZnO nanoparticles synthesized by an entirely green physical-chemistral process using Aspalathus linearis's natural extract as an efficient reduction/oxidizing agent. Their structural and optical properties by electron microscopy, X-rays diffraction, Raman and X-rays photoemission spectroscopies as well as room temperature photoluminescence are reported. - Highlights: • 1st time report on synthesis of ZnO nanoparticles by a green process via Aspalathus linearis extract. • A. linearis's natural extract was used as an effective reduction/oxidizing agent. • Wurtzite nature of ZnO nanoparticles was confirmed via XRD, Raman, XPS and PL.

Chemical synthesis and structure elucidation of bovine κ-casein (1-44)

International Nuclear Information System (INIS)

Bansal, Paramjit S.; Grieve, Paul A.; Marschke, Ronald J.; Daly, Norelle L.; McGhie, Emily; Craik, David J.; Alewood, Paul F.

2006-01-01

The caseins (α s1 , α s2 , β, and κ) are phosphoproteins present in bovine milk that have been studied for over a century and whose structures remain obscure. Here we describe the chemical synthesis and structure elucidation of the N-terminal segment (1-44) of bovine κ-casein, the protein which maintains the micellar structure of the caseins. κ-Casein (1-44) was synthesised by highly optimised Boc solid-phase peptide chemistry and characterised by mass spectrometry. Structure elucidation was carried out by circular dichroism and nuclear magnetic resonance spectroscopy. CD analysis demonstrated that the segment was ill defined in aqueous medium but in 30% trifluoroethanol it exhibited considerable helical structure. Further, NMR analysis showed the presence of a helical segment containing 26 residues which extends from Pro 8 to Arg 34 . This is First report which demonstrates extensive secondary structure within the casein class of proteins

Facile synthesis of gold nanomaterials with unusual crystal structures.

Science.gov (United States)

Fan, Zhanxi; Huang, Xiao; Chen, Ye; Huang, Wei; Zhang, Hua

2017-11-01

Gold (Au) nanomaterials have attracted wide research attention, owing to their high chemical stability, promising catalytic properties, excellent biocompatibility, unique electronic structure and outstanding localized surface plasmon resonance (LSPR) absorption properties; all of which are closely related to their size and shape. Recently, crystal-phase-controlled synthesis of noble metal nanomaterials has emerged as a promising strategy to tune their physicochemical properties. This protocol describes the detailed experimental procedures for the crystal-phase-controlled syntheses of Au nanomaterials with unusual crystal structures under mild conditions. Briefly, pure hexagonal close-packed (hcp) Au square sheets (AuSSs) with a thickness of ∼2.4 nm are synthesized using a graphene-oxide-assisted method in which HAuCl 4 is reduced by oleylamine in a mixture of hexane and ethanol. By using pure hexane as the solvent, well-dispersed ultrathin hcp/face-centered cubic (fcc) Au nanowires with a diameter of ∼1.6 nm on graphene oxide can be obtained. Meanwhile, hcp/fcc Au square-like plates with a side length of 200-400 nm are prepared via the secondary growth of Au on the hcp AuSSs. Remarkably, hexagonal (4H) Au nanoribbons with a thickness of 2.0-6.0 nm can be synthesized with a one-pot colloidal method in which HAuCl 4 is reduced by oleylamine in a mixed solvent of hexane and 1,2-dichloropropane. It takes 17-37 h for the synthesis of these Au nanomaterials with unusual crystal structures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) are used to characterize the resultant Au nanomaterials, which could have many promising applications, such as biosensing, near-IR photothermal therapy, catalysis and surface-enhanced Raman scattering (SERS).

Synthesis and structures of two new Cu(I) frameworks bearing1,3 ...

Indian Academy of Sciences (India)

DOI 10.1007/s12039-016-1100-6. Synthesis and structures of two new Cu(I) frameworks bearing1,3-bis(4-pyridyl)propane and inorganic linkers. ZHAOBO HUa, BO LIb,∗, WENQIANG JUa, YUNING LIANGa and ZILU CHENa,∗. aState Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources,.

Redox topotactic reactions in Fe{sup II - III} (oxy)hydroxycarbonate new minerals related to fougerite in gleysols: 'trebeurdenite and moessbauerite'

Energy Technology Data Exchange (ETDEWEB)

Genin, Jean-Marie R., E-mail: jean-marie.genin@esstin.uhp-nancy.fr [Institut Jean Barriol FR2843 CNRS-Universite de Lorraine, ESSTIN (France); Guerin, O. [Ecole Pratique des Hautes Etudes, Laboratoire de Geomorphologie (France); Herbillon, A. J. [Universite Catholique de Louvain, Unite des Sciences du Sol (Belgium); Kuzmann, E. [Eoetvoes Lorand Univ., Chemistry Department (Hungary); Mills, S. J. [Geosciences Museum Victoria (Australia); Morin, G.; Ona-Nguema, G. [Univ. P. and M. Curie, Institut Mineralogie and Phys. Milieux Condenses (France); Ruby, C. [Institut Jean Barriol FR2843 CNRS-Universite de Lorraine, ESSTIN (France); Upadhyay, C. [IT-Banaras Hindu Univ., School of Materials Science and Technology (India)

2012-03-15

Fougerite mineral responsible for the bluish-green shade of gleysols in aquifers was identified as Fe{sup II - III} oxyhydroxycarbonate, [Fe{sub 6}({sub 1-x)}{sup II} Fe{sub 6x}{sup III} O{sub 12}H{sub 2(7 - 3x)}]{sup 2 + } {center_dot} [CO{sub 3}{sup 2-} {center_dot} 3H{sub 2}O]{sup 2 - } where the average ferric molar fraction x = [Fe{sup III}/Fe{sub total}] was restricted to the [1/3-2/3] range, up till now. In this paper, Moessbauer spectra of gleys extracted from the schorre of maritime marshes have values of x in the [2/3-1] range. Magnetic properties of homologous chemical compounds studied by Moessbauer spectroscopy are explained with long range order of Fe{sup III} ions within Fe cation layers for x = 1/3, 2/3 and 1. Observed values are mixtures of topotactic domains that are in fact minerals with names proposed to IMA: fougerite for x = 1/3, trebeurdenite for x = 2/3 and moessbauerite for x = 1.

Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4

Science.gov (United States)

Lee, Dong Woo; Jo, Vinna; Ok, Kang Min

2012-10-01

A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4 (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO3)3·xH2O, 1,3,5-C6H3(CO2H)3, N(C3H7)4Cl, HNO3, and HCON(CH3)2 at 180 °C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO4 tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of α-SiO2 and the material is phase-matchable (type-1).

Metal-organic frameworks: structure, properties, methods of synthesis and characterization

International Nuclear Information System (INIS)

Butova, V V; Soldatov, M A; Guda, A A; Lomachenko, K A; Lamberti, C

2016-01-01

This review deals with key methods of synthesis and characterization of metal-organic frameworks (MOFs). The modular structure affords a wide variety of MOFs with different active metal sites and organic linkers. These compounds represent a new stage of development of porous materials in which the pore size and the active site structure can be modified within wide limits. The set of experimental methods considered in this review is sufficient for studying the short-range and long-range order of the MOF crystal structure, determining the morphology of samples and elucidating the processes that occur at the active metal site in the course of chemical reactions. The interest in metal-organic frameworks results, first of all, from their numerous possible applications, ranging from gas separation and storage to chemical reactions within the pores. The bibliography includes 362 references

Microwave-assisted hydrothermal synthesis of CePO4 nanostructures: Correlation between the structural and optical properties

International Nuclear Information System (INIS)

Palma-Ramírez, D.; Domínguez-Crespo, M.A.; Torres-Huerta, A.M.; Dorantes-Rosales, H.; Ramírez-Meneses, E.; Rodríguez, E.

2015-01-01

Highlights: • An enhancement in the hydrothermal synthesis for obtaining of CePO 4 is presented. • Microwave energy can replace the energy by convection for obtaining CePO 4 . • CePO 4 demonstrates to be an option to increase the optical properties of polymers. • Adjusting the pH, the sintering process is not necessary to obtain the desire phase. • CePO 4 morphologies undergo evolution from nanorods to semispherical nanoparticles. - Abstract: In this work, the microwave-assisted hydrothermal method is proposed as an alternative to the synthesis of cerium phosphate (CePO 4 ) nanostructures to evaluate the influence of different synthesis parameters on both the structural and optical properties. In order to reach this goal, two different sets of experiments were designed, varying the reaction temperature (130 and 180 °C), synthesis time (15 and 30 min) and sintering temperature (400 and 600 °C), maintaining a constant pH = 3. Thereafter, two experimental conditions were selected to assess changes in the properties of CePO 4 nanopowders with pH (1, 5, 9 and 11). The crystal structure and morphology of the nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Diffuse reflectance properties of CePO 4 with different microstructures were studied. The results demonstrated that by using the microwave-assisted hydrothermal method, the shape, size and structural phase of CePO 4 can be modulated by using relatively low synthesis temperatures and short reaction times, and depending on pH, a sintering process is not needed to obtain either a desired phase or size. Under the selected experimental conditions, the materials underwent an evolution from nanorods to semispherical nanoparticles, accompanied by a phase transition from hexagonal to monoclinic

Synthesis and structural studies of copper sulfide nanocrystals

Directory of Open Access Journals (Sweden)

Peter A. Ajibade

Full Text Available We report the synthesis and structural studies of copper sulfide nanocrystals from copper(II dithiocarbamate single molecule precursors. The optical studies of the as-prepared copper sulfide nanoparticles were carried out using UV–Visible and photoluminescence spectroscopy. The absorption spectra show absorption band edges at 287 nm and exhibit considerable blue shift that could be ascribed to the quantum confinement effects as a result of the small crystallite sizes of the nanoparticles and the photoluminescence spectra show emission curves that are red shifted with respect to the absorption band edges. The structural studies were carried out using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The XRD patterns revealed the formation of hexagonal structure of covellite CuS with estimated crystallite sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microsphere on the surfaces and EDS spectra confirmed the presence of CuS nanoparticles. Keywords: CuS, Dithiocarbamate, Nanoparticles, Electron microscopy, AFM

Structure-directing effects of ionic liquids in the ionothermal synthesis of metal–organic frameworks

Directory of Open Access Journals (Sweden)

Thomas P. Vaid

2017-07-01

Full Text Available Traditional synthesis of metal–organic frameworks (MOFs involves the reaction of a metal-containing precursor with an organic linker in an organic solvent at an elevated temperature, in what is termed a `solvothermal' reaction. More recently, many examples have been reported of MOF synthesis in ionic liquids (ILs, rather than an organic solvent, in `ionothermal' reactions. The high concentration of both cations and anions in an ionic liquid allows for the formation of new MOF structures in which the IL cation or anion or both are incorporated into the MOF. Most commonly, the IL cation is included in the open cavities of the MOF, countering the anionic charge of the MOF framework itself and acting as a template around which the MOF structure forms. Ionic liquids can also serve other structure-directing roles, for example, when an IL containing a single enantiomer of a chiral anion leads to a homochiral MOF, even though the IL anion is not itself incorporated into the MOF. A comprehensive review of ionothermal syntheses of MOFs, and the structure-directing effects of the ILs, is given.

Novel Fluorinated Indanone, Tetralone and Naphthone Derivatives: Synthesis and Unique Structural Features

Directory of Open Access Journals (Sweden)

Joseph C. Sloop

2012-02-01

Full Text Available Several fluorinated and trifluoromethylated indanone, tetralone and naphthone derivatives have been prepared via Claisen condensations and selective fluorinations in yields ranging from 22–60%. In addition, we report the synthesis of new, selectively fluorinated bindones in yields ranging from 72–92%. Of particular interest is the fluorination and trifluoroacetylation regiochemistry observed in these fluorinated products. We also note unusual transformations including a novel one pot, dual trifluoroacetylation, trifluoroacetylnaphthone synthesis via a deacetylation as well as an acetyl-trifluoroacetyl group exchange. Solid-state structural features exhibited by these compounds were investigated using crystallographic methods. Crystallographic results, supported by spectroscopic data, show that trifluoroacetylated ketones prefer a chelated cis-enol form whereas fluorinated bindone products exist primarily as the cross-conjugated triketo form.

Total synthesis of the putative structure of the novel triquinane natural product isocapnellenone

OpenAIRE

Mehta, Goverdhan; Murthy, Sai Krishna A; Umarye, Jayant D

2002-01-01

A total synthesis of the ‘putative structure’ 7, attributed to the novel triquinane sesquiterpene isolated recently from two Buddelia species has been accomplished. The spectral data for 7 is a complete mismatch with those reported for the natural product and warrants a revision of the assigned structure.

Uptake of hazardous radionuclides within layered chalcogenide for environmental protection

Energy Technology Data Exchange (ETDEWEB)

Sengupta, Pranesh, E-mail: praneshsengupta@gmail.com [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Dudwadkar, N.L. [Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Vishwanadh, B. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Pulhani, V. [Health Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Rao, Rekha [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Tripathi, S.C. [Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2014-02-15

Highlights: • Layered chalcogenide with CdI{sub 2} crystal structure prepared by hydrothermal route. • Exploration of the possibilities for radionuclides’ uptake using layered chalcogenide. • Proposing ‘topotactic ionic substitution’ as major uptake mechanism. -- Abstract: Ensuring environmental protection in and around nuclear facilities is a matter of deep concern. Toward this, layered chalcogenide with CdI{sub 2} crystal structure has been prepared. Structural characterizations of layered chalcogenide suggest ‘topotactic ionic substitution’ as the dominant mechanism behind uptake of different cations within its lattice structure. An equilibration time of 45 min and volume to mass ratio of 30:1 are found to absorb {sup 233}U, {sup 239}Pu, {sup 106}Ru, {sup 85+89}Sr, {sup 137}Cs and {sup 241}Am radionuclides to the maximum extents.

Synthesis and Single Crystal Structures of Substituted-1,3-Selenazol-2-amines

Directory of Open Access Journals (Sweden)

Guoxiong Hua

2016-12-01

Full Text Available The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3-selenazol-2-amines is reported. The efficient preparation of these compounds was carried out by two-component cyclization of the selenoureas with equimolar amounts of α-haloketones. The selenoureas were obtained from the reaction of Woollins’ reagent with cyanamides, followed by hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR (1H, 13C, 77Se spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.

Synthesis and crystal structure of chromium-bearing anhydrous wadsleyite

Science.gov (United States)

Sirotkina, E. A.; Bindi, L.; Bobrov, A. V.; Aksenov, S. M.; Irifune, T.

2018-04-01

A chromium-bearing wadsleyite (Cr- Wad) was synthesized in the model system Mg2SiO4-MgCr2O4 at 14 GPa and 1600 °C and studied from the chemical and structural point of views. Microprobe data gave the formula Mg1.930Cr0.120Si0.945O4, on the basis of 4 oxygen atoms. The crystal structure has been studied by single-crystal X-ray diffraction. The orthorhombic unit-cell parameters are: a = 5.6909(5) Å, b = 11.4640(10) Å, c = 8.2406(9) Å, V = 537.62(9) Å3, Z = 8. The structure, space group Imma, was refined to R 1 = 5.99% in anisotropic approximation using 1135 reflections with F o > 4σ( F o) and 43 parameters. Chromium was found to substitute for both Mg at the octahedral sites and Si at the tetrahedral site, according to the reaction VIMg2+ + IVSi4+ = VICr3+ + IVCr3+. On the whole, the structural topology is nearly identical to that of pure wadsleyite. The successful synthesis of Cr- Wad may be important for the thermobarometry of mantle phase associations.

Redox topotactic reactions in Fe II - III (oxy)hydroxycarbonate new minerals related to fougèrite in gleysols: "trébeurdenite and mössbauerite"

Science.gov (United States)

Génin, Jean-Marie R.; Guérin, O.; Herbillon, A. J.; Kuzmann, E.; Mills, S. J.; Morin, G.; Ona-Nguema, G.; Ruby, C.; Upadhyay, C.

2012-03-01

Fougèrite mineral responsible for the bluish-green shade of gleysols in aquifers was identified as FeII - III oxyhydroxycarbonate, [Fe^II_{6(1-x) }Fe^III_{6x}O12H2(7 - 3 x)]2 + · [CO3^{2-} · 3H2O]2 - where the average ferric molar fraction x = [FeIII/Fetotal] was restricted to the [1/3-2/3] range, up till now. In this paper, Mössbauer spectra of gleys extracted from the schorre of maritime marshes have values of x in the [2/3-1] range. Magnetic properties of homologous chemical compounds studied by Mössbauer spectroscopy are explained with long range order of FeIII ions within Fe cation layers for x = 1/3, 2/3 and 1. Observed values are mixtures of topotactic domains that are in fact minerals with names proposed to IMA: fougèrite for x = 1/3, trébeurdenite for x = 2/3 and mössbauerite for x = 1.

Isolation, structure, and synthesis of viridic acid, a new tetrapeptide mycotoxin of Penicillium viridicatum Westling

International Nuclear Information System (INIS)

Holzapfel, C.W.; Koekemoer, J.M.; Van Dyk, M.S.

1986-01-01

The isolation of a new toxic metabolite, viridic acid, from Penicillium viridicatum Westling is described. The chemical and spectroscopic properties of the compound are interpreted in terms of the tetrapeptide structure (N,N-dimethyl-o-aminobenzoyl)-glycyl-(N'-methyl-L-valyl)-o-aminobenzoic acid. The structure and chirality of viridic acid were confirmed by total synthesis

Synthesis and applications of nano-structured iron oxides/hydroxides

African Journals Online (AJOL)

... in numerous synthesis processes. This review outlines the work being carried out on synthesis of iron oxides in nano form and their various applications. Keywords: nano iron oxides, synthesis, catalysts, magnetic properties, biomedical application. International Journal of Engineering, Science and Technology, Vol. 2, No.

Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]- layers

Science.gov (United States)

Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

2013-01-01

A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]- layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

Comparison among structural characteristics of Ce1-xCuxO2 nanocatalysts obtained by two methods of distinct synthesis

International Nuclear Information System (INIS)

Neiva, L.S.; Bispo, A.; Santos, P.T.A.; Costa, A.C.F.M.; Gama, L.; Mascarenhas, A.J.S.

2009-01-01

The objective this work is to synthesize nano catalysts Ce 1-x Cu x O 2 type by the synthesis methods of the combustion reaction and Pechini. The value of the concentration (x) of the element dope (Cu) varies between 0,1 and 0,5 mols. It intends evaluate that form the synthesis method influences in the physical structural characteristics of this material. nano catalysts were characterized by ray- X diffraction. The results showed nano catalysts formation with a formed structure for the most part by the phase CeO 2 , as it was expected, since this is the hostess matrix of the element dope (Cu). Nano catalysts obtained by the method Pechini presents crystallinity larger deg, according with patterns of ray-X. Thus, it was concluded that synthesis employee method the kind in the methodology, as well as the value of the concentration of the element dope has influence on the final structural characteristics of the developed material. (author)

Microwave-assisted hydrothermal synthesis of CePO{sub 4} nanostructures: Correlation between the structural and optical properties

Energy Technology Data Exchange (ETDEWEB)

Palma-Ramírez, D. [Instituto Politécnico Nacional, CICATA-Unidad Altamira, Km 14.5, Carretera Tampico-Puerto Industrial Altamira, C.P. 89600 Altamira, Tamps (Mexico); Domínguez-Crespo, M.A., E-mail: mdominguezc@ipn.mx [Instituto Politécnico Nacional, CICATA-Unidad Altamira, Km 14.5, Carretera Tampico-Puerto Industrial Altamira, C.P. 89600 Altamira, Tamps (Mexico); Torres-Huerta, A.M. [Instituto Politécnico Nacional, CICATA-Unidad Altamira, Km 14.5, Carretera Tampico-Puerto Industrial Altamira, C.P. 89600 Altamira, Tamps (Mexico); Dorantes-Rosales, H. [Instituto Politécnico Nacional, ESIQIE, Departamento de Metalurgia, C.P. 07300 México D.F. (Mexico); Ramírez-Meneses, E. [Universidad Iberoamericana, Departamento de Ingeniería y Ciencias Químicas, Prolongación Paseo de la Reforma 880, Lomas de Santa Fe, C.P. 01219 México D.F. (Mexico); Rodríguez, E. [Instituto Politécnico Nacional, CICATA-Unidad Altamira, Km 14.5, Carretera Tampico-Puerto Industrial Altamira, C.P. 89600 Altamira, Tamps (Mexico)

2015-09-15

Highlights: • An enhancement in the hydrothermal synthesis for obtaining of CePO{sub 4} is presented. • Microwave energy can replace the energy by convection for obtaining CePO{sub 4}. • CePO{sub 4} demonstrates to be an option to increase the optical properties of polymers. • Adjusting the pH, the sintering process is not necessary to obtain the desire phase. • CePO{sub 4} morphologies undergo evolution from nanorods to semispherical nanoparticles. - Abstract: In this work, the microwave-assisted hydrothermal method is proposed as an alternative to the synthesis of cerium phosphate (CePO{sub 4}) nanostructures to evaluate the influence of different synthesis parameters on both the structural and optical properties. In order to reach this goal, two different sets of experiments were designed, varying the reaction temperature (130 and 180 °C), synthesis time (15 and 30 min) and sintering temperature (400 and 600 °C), maintaining a constant pH = 3. Thereafter, two experimental conditions were selected to assess changes in the properties of CePO{sub 4} nanopowders with pH (1, 5, 9 and 11). The crystal structure and morphology of the nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Diffuse reflectance properties of CePO{sub 4} with different microstructures were studied. The results demonstrated that by using the microwave-assisted hydrothermal method, the shape, size and structural phase of CePO{sub 4} can be modulated by using relatively low synthesis temperatures and short reaction times, and depending on pH, a sintering process is not needed to obtain either a desired phase or size. Under the selected experimental conditions, the materials underwent an evolution from nanorods to semispherical nanoparticles, accompanied by a phase transition from hexagonal to monoclinic.

Resistance switching in epitaxial SrCoOx thin films

Science.gov (United States)

Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

2014-08-01

We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO2.5) and conducting perovskite (SrCoO3-δ) depending on the oxygen content. The current-voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoOx thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO2.5.

Resistance switching in epitaxial SrCoOx thin films

International Nuclear Information System (INIS)

Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

2014-01-01

We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO 3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO 2.5 ) and conducting perovskite (SrCoO 3−δ ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO 2.5

Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

International Nuclear Information System (INIS)

Santos, Edson dos Anjos dos; Beatriz, Adilson; Lima, Denis Pires de; Marques, Maria Rita; Leite, Carla Braga

2009-01-01

Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H)-one (1) and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H)-one (2). The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in millimolar range. (author)

Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

Energy Technology Data Exchange (ETDEWEB)

Santos, Edson dos Anjos dos; Beatriz, Adilson; Lima, Denis Pires de [Universidade Federal Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Centro de Ciencias Exatas e Tecnologia. Dept. de Quimica], e-mail: dlima@nin.ufms.br; Marques, Maria Rita; Leite, Carla Braga [Universidade Federal Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Centro de Ciencias Biologicas. Dept. de Morfofisiologia

2009-07-01

Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H)-one (1) and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H)-one (2). The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in millimolar range. (author)

Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

Directory of Open Access Journals (Sweden)

Edson dos Anjos dos Santos

2009-01-01

Full Text Available Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H-one (1 and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H-one (2. The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in milimolar range.

Synthesis, structure and electronic structure of a new polymorph of CaGe2

International Nuclear Information System (INIS)

Tobash, Paul H.; Bobev, Svilen

2007-01-01

Reported are the flux synthesis, the crystal structure determination, the properties and the band structure calculations of a new polymorph of CaGe 2 , which crystallizes with the hexagonal space group P6 3 mc (no. 186) with cell parameters of a=3.9966(9) and c=10.211(4)A (Z=2; Pearson's code hP6). The structure can be viewed as puckered layers of three-bonded germanium atoms, ∼ 2 [Ge 2 ] 2- , which are stacked along the direction of the c-axis in an ABAB-fashion. The germanium polyanionic layers are separated by the Ca cations. As such, this structure is closely related to the structure of the other CaGe 2 polymorph, which crystallizes with the rhombohedral CaSi 2 type in the R3-bar m space group (No. 166), where the ∼ 2 [Ge 2 ] 2- layers are arranged in an AA'BB'CC'-fashion, and are also interspaced by Ca 2+ cations. LMTO calculations suggest that in spite of the formal closed-shell configuration for all atoms and the apparent adherence to the Zintl rules for electron counting, i.e., Ca 2+ [3b-Ge 1- ] 2 ), the phase will be a poor metal due to a small Ca-3d-Ge-4p band overlap. Magnetic susceptibility measurements as a function of the temperature indicate that the new CaGe 2 polymorph exhibits weak, temperature independent, Pauli-paramagnetism

Structural Synthesis of 3-DoF Spatial Fully Parallel Manipulators

Directory of Open Access Journals (Sweden)

Alfonso Hernandez

2014-07-01

Full Text Available In this paper, the architectures of three degrees of freedom (3-DoF spatial, fully parallel manipulators (PMs, whose limbs are structurally identical, are obtained systematically. To do this, the methodology followed makes use of the concepts of the displacement group theory of rigid body motion. This theory works with so-called ‘motion generators’. That is, every limb is a kinematic chain that produces a certain type of displacement in the mobile platform or end-effector. The laws of group algebra will determine the actual motion pattern of the end-effector. The structural synthesis is a combinatorial process of different kinematic chains’ topologies employed in order to get all of the 3-DoF motion pattern possibilities in the end-effector of the fully parallel manipulator.

Ferroelectric mesocrystals of bismuth sodium titanate: formation mechanism, nanostructure, and application to piezoelectric materials.

Science.gov (United States)

Hu, Dengwei; Kong, Xingang; Mori, Kotaro; Tanaka, Yasuhiro; Shinagawa, Kazunari; Feng, Qi

2013-09-16

Ferroelectric mesocrystals of Bi0.5Na0.5TiO3 (BNT) with [100]-crystal-axis orientation were successfully prepared using a topotactic structural transformation process from a layered titanate H1.07Ti1.73O4·nH2O (HTO). The formation reactions of BNT mesocrystals in HTO-Bi2O3-Na2CO3 and HTO-TiO2-Bi2O3-Na2CO3 reaction systems and their nanostructures were studied by XRD, FE-SEM, TEM, SAED, and EDS, and the reaction mechanisms were given. The BNT mesocrystals are formed by a topotactic structural transformation mechanism in the HTO-Bi2O3-Na2CO3 reaction system and by a combination mechanism of the topotactic structural transformation and epitaxial crystal growth in the HTO-TiO2-Bi2O3-Na2CO3 reaction system, respectively. The BNT mesocrystals prepared by these methods are constructed from [100]-oriented BNT nanocrystals. Furthermore, these reaction systems were successfully applied to the fabrication of [100]-oriented BNT ferroelectric ceramic materials. A BNT ceramic material with a high degree of orientation, high relative density, and small grain size was achieved.

Nd4Cu2O7: A copper(I) oxide with a novel cooperatively distorted T' type structure

International Nuclear Information System (INIS)

Pederzolli, D.R.; Attfield, J.P.

1998-01-01

The crystal structure of Nd 4 Cu 2 O 7 (monoclinic, space group A2/m, a = 8.4493(2) angstrom, b = 3.7591(1) angstrom, C = 12.6006(5) angstrom, β = 109.576(4)degree, Z = 2) prepared by topotactic reduction of the high-T c superconductor parent phase Nd 2 CuO 4 , has been determined by Rietveld fitting of time-of-flight neutron powder diffraction data (R wp = 1.90%). A novel oxygen-vacancy-ordered arrangement of cooperatively distorted Cu 2 O 3 planes containing 2- and 4-coordinate Cu + sites is found

Monitoring structural transformations in crystals. 5. A topotactic [2 + 2]-photodimerization reaction.

Science.gov (United States)

Turowska-Tyrk, Ilona

2003-10-01

The structural changes in a crystal of 5-benzylidene-2-(4-chlorobenzyl)cyclopentanone during [2 + 2]-photodimerization were monitored by means of X-ray diffraction. It was observed that the monomers moved gradually from the position occupied in the crystal at the initial stage of the photoreaction and the dimers moved towards the position assumed at the final step. The movements of the molecules possess a rotational component. Moreover, with the progress of the phototransformation the monomers in the reacting pair gradually move closer and change their relative orientation to resemble more the product molecule. The behaviour of the molecules and also the variation of the cell constants for the studied compound were compared with data for 5-benzylidene-2-benzylcyclopentanone.

Cation Effects on the Layer Structure of Biogenic Mn-Oxides

Energy Technology Data Exchange (ETDEWEB)

Zhu, M.; Ginder-Vogel, M; Parikh, S; Feng, X; Sparks, D

2010-01-01

Biologically catalyzed Mn(II) oxidation produces biogenic Mn-oxides (BioMnO{sub x}) and may serve as one of the major formation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn-oxides controls its metal sequestration properties, photochemistry, oxidizing ability, and topotactic transformation to tunneled structures. This study investigates the impacts of cations (H{sup +}, Ni(II), Na{sup +}, and Ca{sup 2+}) during biotic Mn(II) oxidation on the structure of Mn octahedral layers of BioMnO{sub x} using solution chemistry and synchrotron X-ray techniques. Results demonstrate that Mn octahedral layer symmetry and composition are sensitive to previous cations during BioMnO{sub x} formation. Specifically, H{sup +} and Ni(II) enhance vacant site formation, whereas Na{sup +} and Ca{sup 2+} favor formation of Mn(III) and its ordered distribution in Mn octahedral layers. This study emphasizes the importance of the abiotic reaction between Mn(II) and BioMnO{sub x} and dependence of the crystal structure of BioMnO{sub x} on solution chemistry.

Total chemical synthesis and X-ray structure of kaliotoxin by racemic protein crystallography.

Science.gov (United States)

Pentelute, Brad L; Mandal, Kalyaneswar; Gates, Zachary P; Sawaya, Michael R; Yeates, Todd O; Kent, Stephen B H

2010-11-21

Here we report the total synthesis of kaliotoxin by 'one pot' native chemical ligation of three synthetic peptides. A racemic mixture of D- and L-kaliotoxin synthetic protein molecules gave crystals in the centrosymmetric space group P1 that diffracted to atomic-resolution (0.95 Å), enabling the X-ray structure of kaliotoxin to be determined by direct methods.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials.

Science.gov (United States)

Hesemann, Peter; Nguyen, Thy Phung; Hankari, Samir El

2014-04-11

The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS) recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA), mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the "anionic templating" strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

Synthesis and crystal structure of the new vanadate AgCaVO{sub 4}. Comparison with the arcanite structure

Energy Technology Data Exchange (ETDEWEB)

Nenert, Gwilherm [PANalytical B.V., Almelo (Netherlands)

2017-07-01

We report the synthesis and the crystal structure of the new vanadate AgCaVO{sub 4} from laboratory powder X-ray data. Contrary to the previously reported AgBVO{sub 4} (B=Mg, Cd), AgCaVO{sub 4} exhibits the arcanite structure (β-K{sub 2}SO{sub 4}). Although it exhibits the same structure than arcanite, significant differences are observed. These differences are explained by deriving the atomic displacement field. The change of connectivity within the structure between β-K{sub 2}SO{sub 4} and AgCaVO{sub 4} results from a rotation of the VO{sub 4} tetrahedra giving rise to a change from a face sharing to an edge sharing octahedral chains. Additionally, the thermal expansion of AgCaVO{sub 4} has been investigated up to 800 C.

Template-free synthesis of sub-micrometric cobalt fibers with controlled shape and structure. Characterization and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Lakhdar, Allagui [Laboratoire de Physique des Matériaux Lamellaires et Nano-Matériaux Hybrides, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Bizerte (Tunisia); Borges, Joao P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Ben Haj Amara, Abdesslam [Laboratoire de Physique des Matériaux Lamellaires et Nano-Matériaux Hybrides, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Bizerte (Tunisia); Dakhlaoui-Omrani, Amel, E-mail: dakhlaoui_amel@yahoo.fr [Department of Chemistry, Faculty of Sciences and Arts-Khulais, University of Jeddah, Khulais, P. O. Box 355, Postal Code 21921 (Saudi Arabia); Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National des Recherches en Sciences des Matériaux, Technopôle de Bordj Cedria, BP 73, 8027 Soliman (Tunisia)

2017-03-01

Sub-micrometric Co fibers were prepared via a modified polyol process at 90 °C under an external magnetic field of about 550 Oe, using ethelyne glycol as solvent and hydrazine as reducing agent. The structure, the size and the morphology of the as-elaborated products were highly controlled through properly monitoring the synthesis parameters (amount of NaOH added, the amount of the reducing agent, precursor’ concentration and precursors mixing protocol). The XRD characterization confirmed the formation of pure cobalt powders with either hexagonal compact (hcp) or face-centered-cubic (fcc) structure depending on the concentration of the metal precursor and sodium hydroxide. The scanning electron microscopy observations of the powders shows sub-micrometric fibers with about 0.4–0.6 µm in diameter and a length that could reach 15 µm. Fibers prepared at high reducing ratio were constituted of flower-like spheres that coalesce in the direction of the applied magnetic field. For their high contact surface, these fibers offer new opportunities for catalysis applications. The hysteresis loop measurements show an enhancement of the Hc of the as-obtained fibers compared to their bulk counterparts and permit to confirm the relationship between the structure and the magnetic properties of the materials. - Highlights: • Template free synthesis of cobalt sub-micrometric fibers. • High control of the structure the structure, the size and the morphology of the products through properly monitoring the synthesis parameters. • cobalt sub-micrometric fibers with enhanced magnetic properties compared to bulk cobalt.

Synthesis of a hierarchically structured zeolite-templated carbon starting from fly ash-derived zeolite X

CSIR Research Space (South Africa)

Musyoka, Nicholas M

2014-05-01

Full Text Available A hierarchically structured zeolite derived from coal fly ash was used as a hard templating agent for the synthesis of a templated carbonaceous material. The samples were characterized using XRD, SEM, TEM, TGA, EDS and BET. The resulting carbon had...

SYNTHESIS, CRYSTAL STRUCTURE AND MAGNETIC ...

African Journals Online (AJOL)

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Much of the current effort on such extended hybrid metal organic complexes is ... In this paper, we report the synthesis, single crystal X-ray diffraction analysis and ..... with g = 2.0 (0.37 cm3 mol−1 K), and smoothly increases to a value of 0.45 ...

Aircraft interior noise prediction using a structural-acoustic analogy in NASTRAN modal synthesis

Science.gov (United States)

Grosveld, Ferdinand W.; Sullivan, Brenda M.; Marulo, Francesco

1988-01-01

The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theoretically and experimentally. The NASTRAN modal-synthesis program is used in the theoretical analysis, and the predictions are compared with experimental measurements in extensive graphs. Good general agreement is obtained, but the need for further refinements to account for acoustic-cavity damping and structural-acoustic interaction is indicated.

Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

Science.gov (United States)

Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

2012-12-01

Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV-vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

Nanomorphology Effects in Semiconductors with Native Ferromagnetism: Hierarchical Europium (II) Oxide Tubes Prepared via a Topotactic Nanostructure Transition.

Science.gov (United States)

Trepka, Bastian; Erler, Philipp; Selzer, Severin; Kollek, Tom; Boldt, Klaus; Fonin, Mikhail; Nowak, Ulrich; Wolf, Daniel; Lubk, Axel; Polarz, Sebastian

2018-01-01

Semiconductors with native ferromagnetism barely exist and defined nanostructures are almost unknown. This lack impedes the exploration of a new class of materials characterized by a direct combination of effects on the electronic system caused by quantum confinement effects with magnetism. A good example is EuO for which currently no reliable routes for nanoparticle synthesis can be established. Bottom-up approaches applicable to other oxides fail because of the labile oxidation state +II. Instead of targeting a direct synthesis, the two steps-"structure control" and "chemical transformation"-are separated. The generation of a transitional, hybrid nanophase is followed by its conversion into EuO under full conservation of all morphological features. Hierarchical EuO materials are now accessible in the shape of oriented nanodisks stacked to tubular particles. Magnetically, the coupling of either vortex or onion states has been found. An unexpected temperature dependence is governed by thermally activated transitions between these states. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular structure design and soft template synthesis of aza-, oxaaza- and thiaazamacrocyclic metal chelates in the gelatin matrix

Directory of Open Access Journals (Sweden)

Oleg V. Mikhailov

2017-01-01

Full Text Available The data about of soft template synthesis proceeding in gelatin matrices in [3d-element M(II ion – (N,S- or (N,O,S-ambidentate ligson – mono- or dicarbonyl ligson] systems, have been considered and discussed. The chemical nature of the final products of template synthesis formed under these specific conditions, has been compared with the chemical nature of the final products formed by template synthesis in solutions. It has been noted that in many cases, the nature and chemical composition of these products differ substantially. Specific features of the DFT calculated molecular structures of the macrocyclic compounds that can be formed due to the template synthesis in the systems indicated above, have been discussed, too. The review covers the period 1990–2015.

Mesoporous silicas with covalently immobilized β-cyclodextrin moieties: synthesis, structure, and sorption properties

Science.gov (United States)

Roik, Nadiia V.; Belyakova, Lyudmila A.; Trofymchuk, Iryna M.; Dziazko, Marina O.; Oranska, Olena I.

2017-09-01

Mesoporous silicas with chemically attached macrocyclic moieties were successfully prepared by sol-gel condensation of tetraethyl orthosilicate and β-cyclodextrin-silane in the presence of a structure-directing agent. Introduction of β-cyclodextrin groups into the silica framework was confirmed by the results of IR spectral, thermogravimetric, and quantitative chemical analysis of surface compounds. The porous structure of the obtained materials was characterized by nitrogen adsorption-desorption measurements, powder X-ray diffraction, transmission electron microscopy, and dynamic light scattering. It was found that the composition of the reaction mixture used in β-cyclodextrin-silane synthesis significantly affects the structural parameters of the resulting silicas. The increase in (3-aminopropyl)triethoxysilane as well as the coupling agent content in relation to β-cyclodextrin leads ultimately to the lowering or complete loss of hexagonal arrangement of pore channels in the synthesized materials. Formation of hexagonally ordered mesoporous structure was observed at molar composition of the mixture 0.049 TEOS:0.001 β-CD-silane:0.007 CTMAB:0.27 NH4OH:7.2 H2O and equimolar ratio of components in β-CD-silane synthesis. The sorption of alizarin yellow on starting silica and synthesized materials with chemically attached β-cyclodextrin moieties was studied in phosphate buffer solutions with pH 7.0. Experimental results of the dye equilibrium sorption were analyzed using Langmuir, Freundlich, and Redlich-Peterson isotherm models. It was proved that the Redlich-Peterson isotherm model is the most appropriate for fitting the equilibrium sorption of alizarin yellow on parent silica with hexagonally arranged mesoporous structure as well as on modified one with chemically immobilized β-cyclodextrin groups. [Figure not available: see fulltext.

Mechanically activated self-propagated high-temperature synthesis of nanometer-structured MgB2

International Nuclear Information System (INIS)

Radev, D.D.; Marinov, M.; Tumbalev, V.; Radev, I.; Konstantinov, L.

2005-01-01

Nanometer-sized MgB 2 was prepared via a two-step modification of the mechanically activated self-propagated high-temperature synthesis. The experimental conditions and some structural and phase characteristics of the synthesized product are reported. It is shown that a single-phase material can be prepared after 2 h of intense mechanical treatment of the starting magnesium and boron powders and a synthesis induced at a current-pulse density of 30 A cm -2 . The average size of MgB 2 particles synthesized in this way is 70-80 nm. It is also shown that using the same reagents and the 'classic' high-temperature interaction at 850 deg C with a protective atmosphere of pure Ar, mean particle size of the MgB 2 obtained is 50 μm

Insertion compounds of transition-metal and uranium oxides

International Nuclear Information System (INIS)

Chippindale, A.M.; Dickens, P.G.; Powell, A.V.

1991-01-01

Several transition-metal and actinide oxides, in which the metal occurs in a high oxidation state, have open covalent structures and are capable of incorporating alkali and other electropositive metals under mild conditions to form insertion compounds A x MO n . These are solids which have several features in common: Over a range of compositions, A x MO n exists as one or more stable or metastable phases in which the structure of the parent oxide MO n is largely retained and the insertion element A is accommodated interstitially. Insertion is accompanied by a redox process A=A i . + e - M in which M is reduced and the electronic properties of the parent oxide change to those typical of a mixed-valence compound. The insertion process xA + MO n = A x MO n can be reversed, at least to some extent, by chemical or electrochemical reaction, with retention of structure (topotactic reaction). This review concentrates on methods of synthesis, characterisation, crystal structure and thermochemistry of these insertion compounds. It updates and extends previous work. (author)

Resistance switching in epitaxial SrCoO{sub x} thin films

Energy Technology Data Exchange (ETDEWEB)

Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk, E-mail: cu-jung@hufs.ac.kr [Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Kim, Yeon Soo; Park, Bae Ho [Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-791 (Korea, Republic of); Jeong, Huiseong; Park, Ji-Yong [Department of Physics and Division of Energy System Research, Ajou University, Suwon 443-749 (Korea, Republic of); Cho, Myung Rae; Park, Yun Daniel [Department of Physics and Astronomy and Center for Subwavelength Optics, Seoul National University, Seoul 151-747 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Dong-Wook [Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Jin, Hyunwoo; Lee, Suyoun [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong [Department of Material Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of)

2014-08-11

We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO{sub 3} (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO{sub 2.5}) and conducting perovskite (SrCoO{sub 3−δ}) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO{sub x} thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO{sub 2.5}.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

Directory of Open Access Journals (Sweden)

Peter Hesemann

2014-04-01

Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

Coupling Neumann development and component mode synthesis methods for stochastic analysis of random structures

Directory of Open Access Journals (Sweden)

Driss Sarsri

2014-05-01

Full Text Available In this paper, we propose a method to calculate the first two moments (mean and variance of the structural dynamics response of a structure with uncertain variables and subjected to random excitation. For this, Newmark method is used to transform the equation of motion of the structure into a quasistatic equilibrium equation in the time domain. The Neumann development method was coupled with Monte Carlo simulations to calculate the statistical values of the random response. The use of modal synthesis methods can reduce the dimensions of the model before integration of the equation of motion. Numerical applications have been developed to highlight effectiveness of the method developed to analyze the stochastic response of large structures.

The cation-deficient Ruddlesden-Popper oxysulfide Y2Ti2O5S2 as a layered sulfide: topotactic potassium intercalation to form KY2Ti2O5S2.

Science.gov (United States)

Rutt, Oliver J; Hill, Timothy L; Gál, Zoltán A; Hayward, Michael A; Clarke, Simon J

2003-12-01

Potassium intercalation into the cation-deficient n = 2 Ruddlesden-Popper oxysulfide Y(2)Ti(2)O(5)S(2) to form KY(2)Ti(2)O(5)S(2) has been carried out by reaction of the oxysulfide with potassium vapor in sealed metal tubes at 400 degrees C, potassium naphthalide in THF at 50 degrees C, or potassium in liquid ammonia at temperatures as low as -78 degrees C. Insertion of potassium is topotactic, and although a site 12-coordinate by oxide ions is vacant in the perovskite-type oxide slabs of the structure, potassium is too large to enter this site via the 4-coordinate window, and instead enters the rock-salt-type sulfide layers of the structure which necessitates a 30% increase in the lattice parameter c normal to the layers. In contrast with one of the sodium intercalates of Y(2)Ti(2)O(5)S(2) (beta-NaY(2)Ti(2)O(5)S(2)) in which sodium occupies a tetrahedral site in the sulfide layers, potassium favors an 8-coordinate site which necessitates a relative translation of adjacent oxide slabs. KY(2)Ti(2)O(5)S(2) is tetragonal: P4/mmm, a = 3.71563(4) A, c = 14.8682(2) A (at 298 K), Z = 1. Although the resistivity (3.4(1) x 10(3) Omega cm) is larger than would be expected for a metal, temperature independent paramagnetism dominates the magnetic susceptibility, and the material is electronically very similar to the analogous sodium intercalate beta-NaY(2)Ti(2)O(5)S(2) which features reduced-titanium-containing oxide layers of very similar geometry and electron count.

Organosilane with gemini-type structure as the mesoporogen for synthesis of hierarchical porous ZSM-5 zeolite

KAUST Repository

Zhu, Haibo

2016-02-08

A new kind of organosilane (1,6-bis (diethyl(3-trimethoxysilylpropyl)ammonium) hexane bromide) with a gemini-type structure was prepared and used as a mesoporogen for the synthesis of hierarchical porous ZSM-5 zeolite. There are two quaternary ammonium centers along with double hydrolysable -RSi(OMe)3 fragments in the organosilane, which results in a strong interaction between this mesoporogen and silica-alumina gel. The organosilane can be easily incorporated into ZSM-5 zeolite structure during the crystallization process, and it was finally removed by calcination leading to secondary pores in ZSM-5. The synthesized ZSM-5 has been systematically studied by XRD, nitrogen adsorption, SEM, TEM, TG and solid-state one-dimensional (1D) and two-dimensional (2D) NMR, which reveals information on its detailed structure. It has a hierarchical porosity system, which combines the intrinsic micropores coming from the crystalline structure and irregular mesopores created by the organosilane template. Moreover, the mesoposity including pore size and volume within ZSM-5 can be systematically tuned by changing the organosilane/TEOS ratios, which confirms this organosilane has high flexibility of using as template for the synthesis of hierarchical porous zeolite.

Organosilane with gemini-type structure as the mesoporogen for synthesis of hierarchical porous ZSM-5 zeolite

KAUST Repository

Zhu, Haibo; Abou-Hamad, Edy; Chen, Yin; Saih, Youssef; Liu, Weibing; Basset, Jean-Marie; Samal, Akshaya Kumar

2016-01-01

A new kind of organosilane (1,6-bis (diethyl(3-trimethoxysilylpropyl)ammonium) hexane bromide) with a gemini-type structure was prepared and used as a mesoporogen for the synthesis of hierarchical porous ZSM-5 zeolite. There are two quaternary ammonium centers along with double hydrolysable -RSi(OMe)3 fragments in the organosilane, which results in a strong interaction between this mesoporogen and silica-alumina gel. The organosilane can be easily incorporated into ZSM-5 zeolite structure during the crystallization process, and it was finally removed by calcination leading to secondary pores in ZSM-5. The synthesized ZSM-5 has been systematically studied by XRD, nitrogen adsorption, SEM, TEM, TG and solid-state one-dimensional (1D) and two-dimensional (2D) NMR, which reveals information on its detailed structure. It has a hierarchical porosity system, which combines the intrinsic micropores coming from the crystalline structure and irregular mesopores created by the organosilane template. Moreover, the mesoposity including pore size and volume within ZSM-5 can be systematically tuned by changing the organosilane/TEOS ratios, which confirms this organosilane has high flexibility of using as template for the synthesis of hierarchical porous zeolite.

Bourbaki's structure theory in the problem of complex systems simulation models synthesis and model-oriented programming

Science.gov (United States)

Brodsky, Yu. I.

2015-01-01

The work is devoted to the application of Bourbaki's structure theory to substantiate the synthesis of simulation models of complex multicomponent systems, where every component may be a complex system itself. An application of the Bourbaki's structure theory offers a new approach to the design and computer implementation of simulation models of complex multicomponent systems—model synthesis and model-oriented programming. It differs from the traditional object-oriented approach. The central concept of this new approach and at the same time, the basic building block for the construction of more complex structures is the concept of models-components. A model-component endowed with a more complicated structure than, for example, the object in the object-oriented analysis. This structure provides to the model-component an independent behavior-the ability of standard responds to standard requests of its internal and external environment. At the same time, the computer implementation of model-component's behavior is invariant under the integration of models-components into complexes. This fact allows one firstly to construct fractal models of any complexity, and secondly to implement a computational process of such constructions uniformly-by a single universal program. In addition, the proposed paradigm allows one to exclude imperative programming and to generate computer code with a high degree of parallelism.

Analysis of random response of structure with uncertain parameters. Combination of substructure synthesis method and hierarchy method

International Nuclear Information System (INIS)

Iwatsubo, Takuzo; Kawamura, Shozo; Mori, Hiroyuki.

1995-01-01

In this paper, the method to obtain the random response of a structure with uncertain parameters is proposed. The proposed method is a combination of the substructure synthesis method and the hierarchy method. The concept of the proposed method is that the hierarchy equation of each substructure is obtained using the hierarchy method, and the hierarchy equation of the overall structure is obtained using the substructure synthesis method. Using the proposed method, the reduced order hierarchy equation can be obtained without analyzing the original whole structure. After the calculation of the mean square value of response, the reliability analysis can be carried out based on the first passage problem and Poisson's excursion rate. As a numerical example of structure, a simple piping system is considered. The damping constant of the support is considered as the uncertainty parameter. Then the random response is calculated using the proposed method. As a result, the proposed method is useful to analyze the random response in terms of the accuracy, computer storage and calculation time. (author)

Structural Studies of Silver Nanoparticles Obtained Through Single-Step Green Synthesis

Science.gov (United States)

Prasad Peddi, Siva; Abdallah Sadeh, Bilal

2015-10-01

Green synthesis of silver Nanoparticles (AGNP's) has been the most prominent among the metallic nanoparticles for research for over a decade and half now due to both the simplicity of preparation and the applicability of biological species with extensive applications in medicine and biotechnology to reduce and trap the particles. The current article uses Eclipta Prostrata leaf extract as the biological species to cap the AGNP's through a single step process. The characterization data obtained was used for the analysis of the sample structure. The article emphasizes the disquisition of their shape and size of the lattice parameters and proposes a general scheme and a mathematical model for the analysis of their dependence. The data of the synthesized AGNP's has been used to advantage through the introduction of a structural shape factor for the crystalline nanoparticles. The properties of the structure of the AGNP's proposed and evaluated through a theoretical model was undeviating with the experimental consequences. This modus operandi gives scope for the structural studies of ultrafine particles prepared using biological methods.

Synthesis and characterization of Zn-doped LiCo{sub 0.3}Ni{sub 0.4-x}Mn{sub 0.3}Zn{sub x}O{sub 2} cathode materials for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Chen Yuhong [Department of Chemical and Environmental Engineering, Hebei Chemical and Pharmaceutical Vocational Technology College, Shijiazhuang 050026 (China)], E-mail: chyh76@163.com; Chen Ruizhen [Department of Chemical and Environmental Engineering, Hebei Chemical and Pharmaceutical Vocational Technology College, Shijiazhuang 050026 (China); Tang Zhiyuan [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang Liang [Library of Hebei University of Science and Technology, Shijiazhuang 050018 (China)

2009-05-12

Zn-doped LiCo{sub 0.3}Ni{sub 0.4-x}Mn{sub 0.3}Zn{sub x}O{sub 2} cathode materials were synthesized via co-precipitation method. The structure, electrochemical performance and thermal stability were characterized by X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammograms (CV), electrochemical impedance spectroscopies (EIS) and differential scanning calorimetry (DSC). LiCo{sub 0.3}Ni{sub 0.4-x}Mn{sub 0.3}Zn{sub x}O{sub 2} had stable layered structure with a-NaFeO{sub 2} type with x up to 0.05. The compounds of x = 0.02 showed the best discharge capacity and cycle performance which was related to the most stable structure and Zn-doping prevented structural transformations during the topotactic reactions. Meanwhile, Zn-doping improved the high rate discharge capability and thermal stability.

Carbon Nanotubes Advanced Topics in the Synthesis, Structure, Properties and Applications

CERN Document Server

Jorio, Ado; Dresselhaus, Mildred S

2008-01-01

The carbon nanotubes field has evolved substantially since the publication of the bestseller "Carbon Nanotubes: Synthesis, Structure, Properties and Applications". The present volume builds on the generic aspects of the aforementioned book, which emphasizes the fundamentals, with the new volume emphasizing areas that have grown rapidly since the first volume, guiding future directions where research is needed and highlighting applications. The volume also includes an emphasis on areas like graphene, other carbon-like and other tube-like materials because these fields are likely to affect and influence developments in nanotubes in the next 5 years.

Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

International Nuclear Information System (INIS)

Caskey, Christopher M.; Holder, Aaron; Christensen, Steven T.; Biagioni, David; Ginley, David S.; Tumas, William; Perkins, John D.; Lany, Stephan; Zakutayev, Andriy; Shulda, Sarah; Diercks, David; Pylypenko, Svitlana; Richards, Ryan M.; Schwartz, Craig P.; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Sun, Wenhao; Orvananos, Bernardo

2016-01-01

Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn 3 N 4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.

Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

Energy Technology Data Exchange (ETDEWEB)

Caskey, Christopher M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Colorado School of Mines, Golden, Colorado 80401 (United States); Larix Chemical Science, Golden, Colorado 80401 (United States); Holder, Aaron; Christensen, Steven T.; Biagioni, David; Ginley, David S.; Tumas, William; Perkins, John D.; Lany, Stephan; Zakutayev, Andriy, E-mail: andriy.zakutayev@nrel.gov [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Shulda, Sarah; Diercks, David; Pylypenko, Svitlana; Richards, Ryan M. [Colorado School of Mines, Golden, Colorado 80401 (United States); Schwartz, Craig P.; Nordlund, Dennis [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kukliansky, Alon; Natan, Amir [Tel Aviv University, Tel Aviv-Yafo (Israel); Prendergast, David; Sun, Wenhao [Lawrence Berkeley National Laboratory, Berkley, California 94720 (United States); Orvananos, Bernardo [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); and others

2016-04-14

Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn{sub 3}N{sub 4} spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.

Synthesis, crystal structure and magnetic properties of U2RuGa8

International Nuclear Information System (INIS)

Grin', Yu.N.; Rogl', P.; Aksel'rud, L.G.; Pecharskij, V.K.; Yarmolyuk, Ya.P.

1988-01-01

Synthesis of a new uranium intermetallic compound of U 2 RuGa 8 composition was conducted. The compound crystallizes in Ho 2 CoGa 8 structural type, met earlier only in compounds of rare earths. Magnetic susceptibility of the compound is rather high and is practically independent of temperature in 80-300 K range. This feature is typical for paramagnetism of electron gas and testifies to the absence of localized magnetic moments on ruthenium and uranium atoms

Synthesis of C-di-saccharidic compounds by radical cyclisation. Study of biological, structural and dynamic properties

International Nuclear Information System (INIS)

Rubinstenn, Gilles

1996-01-01

The synthesis of carbohydrate mimics and particularly of C-disaccharides, molecules in which the inter-glycosidic oxygen atom has been replaced by a methylene group, has become, this past two decades, an important challenge in organic chemistry. In the first chapter we present the synthesis of C-disaccharides from the neutral series by a silaketal tethering. The key step of this C-glycosylation is a radical macro-cyclisation. This strategy is applied to the synthesis of two analogues of natural, biologically active, products, the lactose and the Lewis x tri-saccharide. The biological activity of this mimetics is then evaluated. A new tethering strategy, based on the use of phosphorus III compounds, is applied, in the second chapter, to the building of C-disaccharides of the 2'-amino 2'- deoxy series. The third chapter deals with the structural and dynamics study of the C-glycosides prepared in chapter 1 by Nuclear Magnetic Resonance. A new methodology, studying the dipolar relaxation along an effective field, generated through an off-resonance RF field, allowed the precise measurement of longitudinal and transverse cross-relaxation rates. Structural and dynamics parameter thus derived are used as restraints for molecular modeling. The results of this study are then compared to those of the biological tests. (author) [fr

Synthesis of polyaryl rigid-core carbosilane dendrimers for supported organic synthesis

NARCIS (Netherlands)

Wander, M.; Hausoul, P.J.C.; Sliedregt, L.A.J.M.; van Steen, B.J.; van Koten, G.; Klein Gebbink, R.J.M.

2009-01-01

Carbosilane dendrimers can be used as soluble supports for organic synthesis, since their structure allows separation of excess reagents from the supported products, eventually yielding products of high purity and in high yield, as in solid-phase organic synthesis (SPOS). In previous studies often

Effect of synthesis parameters on polymethacrylic acid xerogel structures and equilibrium swelling

Science.gov (United States)

Panić, V.; Jovanović, J.; Adnadjević, B.; Velicković, S.

2009-09-01

Hydrogels based on crosslinked polymethacrylic acid were synthesized via free-radical polymerization in aqueous solution, using N,N'-methylene bisacrylamide as a crosslinking agent and 2,2'-azobis-[2-(2-imidazolin-2-yl)propane] dihydrochloride as an initiator. The influence of the reaction parameters (the neutralization degree of methacrylic acid and the initial monomer concentration) on the equilibrium swelling degree, the swelling kinetic parameters and the basic structural properties of xerogels was investigated. The change of synthesis parameters leads to the change of the basic structural parameters of xerogel, as well as the equilibrium swelling degree and the initial swelling rate of the hydrogels. It is found that there are power form relationships between the equilibrium swelling degree, the initial swelling rate and the structural xerogel’s properties and the change of the neutralization degree of monomer, i.e. the monomer concentration. The examined correlations proved that the crosslinking density is the crucial parameter which determines all the other investigated structural and swelling parameters.

One-Step Synthesis of Hierarchical ZSM-5 Using Cetyltrimethylammonium as Mesoporogen and Structure-Directing Agent

OpenAIRE

Meng, Lingqian; Mezari, Brahim; Goesten, Maarten G.; Hensen, Emiel J. M.

2017-01-01

Hierarchical ZSM-5 zeolite is hydrothermally synthesized in a single step with cetyltrimethylammonium (CTA) hydroxide acting as mesoporogen and structure-directing agent. Essential to this synthesis is the replacement of NaOH with KOH. An in-depth solid-state NMR study reveals that, after early electrostatic interaction between condensed silica and the head group of CTA, ZSM-5 crystallizes around the structure-directing agent. The crucial aspect of using KOH instead of NaOH lies in the faster...

The topotactic dehydration of monoclinic {[Co(pht)(bpy)(H2O)2]·2H2O}n into orthorhombic [Co(pht)(bpy)(H2O)2]n (pht is phthalate and bpy is 4,4'-bipyridine).

Science.gov (United States)

Harvey, Miguel Angel; Suarez, Sebastián; Cukiernik, Fabio D; Baggio, Ricardo

2014-10-01

Controlled heating of single crystals of the previously reported [Köferstein & Robl (2007). Z. Anorg. Allg. Chem. 633, 1127-1130] dihydrate {[Co(pht)(bpy)(H2O)2]·2H2O}n, (II) [where pht is phthalate (C8H4O4) and bpy is 4,4'-bipyridine (C10H8N2)], produced a topotactic transformation into an unreported diaqua anhydrate, namely poly[diaqua(μ2-benzene-1,2-dicarboxylato-κ(2)O(1):O(2))(μ2-4,4'-bipyridine-κ(2)N:N')cobalt(II)], [Co(C8H4O4)(C10H8N2)(H2O)2]n, (IIa). The structural change consists of the loss of the two solvent water molecules linking the original two-dimensional covalent substructures which are the `main frame' of the monoclinic P2/n hydrate (strictly preserved during the transformation), with further reaccommodation of the latter. The anhydrate organizes itself in the orthorhombic system (space group Pmn2(1)) in a disordered fashion, where the space-group-symmetry restrictions are achieved only in a statistical sense, with mirror-related two-dimensional planar substructures, mirrored in a plane perpendicular to [100]. Thus, the asymmetric unit in the refined model is composed of two superimposed mirror-related `ghosts' of half-occupancy each. Similarities and differences with the parent dihydrate and some other related structures in the literature are discussed.

Reversal of the Lattice Structure in SrCoOx Epitaxial Thin Films Studied by Real-Time Optical Spectroscopy and First-Principles Calculations

Science.gov (United States)

Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

2013-08-01

Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

Nitrocyclopropanes: synthesis and properties

Energy Technology Data Exchange (ETDEWEB)

Averina, Elena B; Yashin, N V; Kuznetsova, Tamara S; Zefirov, Nikolai S [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2009-10-31

State-of-the-art data on the methods of synthesis, properties and transformations of nitro- and- dinitrocyclopropanes of different structure is generalized and described systematically. The attention is focused on stereoselective cyclopropanation methods, new approaches to the synthesis of natural products and their synthetic analogues with diversified biological activities, in particular, of aminocyclopropane acids based on nitrocyclopropanes, and the formation of structures of energetic compounds.

Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

Energy Technology Data Exchange (ETDEWEB)

Zhelev, Doncho V., E-mail: dontcho.jelev@nih.gov; Zheleva, Tsvetanka S. [Army Research Laboratory, 2800 Adelphi, Maryland 20783 (United States)

2014-01-28

Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we report template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.

Synthesis and Structure Characterization of Phenol-Urea-Formaldehyde Resins in the Presence of Magnesium Oxide as Catalyst

Directory of Open Access Journals (Sweden)

Dong-Bin Fan

2014-08-01

Full Text Available The objective of this research was to provide a useful approach of polymer synthesis for accelerating the fast cure of phenol-urea-formaldehyde (PUF resin as wood adhesive by optimizing its structure and composition. The PUF resins containing high contents of very reactive groups such as para-methylol groups were synthesized by reacting methylolurea, phenol, and formaldehyde in the presence of magnesium oxide (MgO as catalyst. The effects of synthesis parameters including F/(P + U, OH/P, and MgO/P mole ratios on the structure, composition, curing characteristics, and their relationships of PUF resins were investigated. The results indicated that MgO seemed to be an efficacious catalyst for PUF resin synthesis and promote its faster cure. The increase in the F/(P + U mole ratio or/and OH/P mole ratio appeared to be beneficial for the formation of para-methylol groups and cocondensed methylene linkages between phenolic methylol groups and urea units, and for the removal of unreacted urea. In case of Catalyst/P mole ratio, an appropriate dosage of added metal-ion was very important for synthesizing the high-content reactive groups of PUF resins, otherwise leading to the reverse effects.

Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

Science.gov (United States)

Tiruvalam, Ram Chandra

Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer

Synthesis and structural characterization of piperazino-modified DNA that favours hybridization towards DNA over RNA

DEFF Research Database (Denmark)

Skov, Joan; Bryld, Torsten; Lindegaard, Dorthe

2011-01-01

We report the synthesis of two C4'-modified DNA analogues and characterize their structural impact on dsDNA duplexes. The 4'-C-piperazinomethyl modification stabilizes dsDNA by up to 5°C per incorporation. Extension of the modification with a butanoyl-linked pyrene increases the dsDNA stabilizati...

Proof of the Structure of the Stemodia chilensis Tetracyclic Diterpenoid (+)-19-Acetoxystemodan-12-ol by Synthesis from (+)-Podocarpic Acid: X-ray Structure Determination of a Key Intermediate.

Science.gov (United States)

Leonelli, Francesca; Mostarda, Azzurra; De Angelis, Luca; Lamba, Doriano; Demitri, Nicola; La Bella, Angela; Ceccacci, Francesca; Migneco, Luisa M; Marini Bettolo, Rinaldo

2016-04-22

The first synthesis of (+)-19-acetoxystemodan-12-ol (1), a stemodane diterpenoid isolated from Stemodia chilensis, is described. The structure was supported by an X-ray crystallographic analysis of intermediate (+)-9a, which confirmed the proposed structure and excluded the structure of (-)-19-hydroxystemod-12-ene as a possible candidate for the Chilean Calceolaria diterpenoid to which the (-)-19-hydroxystemar-13-ene structure (9b) had been erroneously assigned.

Development of nano-structured silicon carbide ceramics: from synthesis of the powder to sintered ceramics

International Nuclear Information System (INIS)

Reau, A.

2008-12-01

The materials used inside future nuclear reactors will be subjected to very high temperature and neutrons flux. Silicon carbide, in the form of SiC f /SiC nano-structured composite is potentially interesting for this type of application. It is again necessary to verify the contribution of nano-structure on the behaviour of this material under irradiation. To verify the feasibility and determine the properties of the matrix, it was envisaged to produce it by powder metallurgy from SiC nanoparticles. The objective is to obtain a fully dense nano-structured SiC ceramic without additives. For that, a parametric study of the phases of synthesis and agglomeration was carried out, the objective of which is to determine the active mechanisms and the influence of the key parameters. Thus, studying the nano-powder synthesis by laser pyrolysis allowed to produce, with high production rates, homogeneous batches of SiC nanoparticles whose size can be adjusted between 15 and 90 nm. These powders have been densified by an innovating method: Spark Plasma Sintering (SPS). The study and the optimization of the key parameters allowed the densification of silicon carbide ceramic without sintering aids while preserving the nano-structure of material. The thermal and mechanical properties of final materials were studied in order to determine the influence of the microstructure on their properties. (author)

Plasma-polymerized alkaline anion-exchange membrane: Synthesis and structure characterization

International Nuclear Information System (INIS)

Hu Jue; Meng Yuedong; Zhang Chengxu; Fang Shidong

2011-01-01

After-glow discharge plasma polymerization was developed for alkaline anion-exchange membranes synthesis using vinylbenzyl chloride as monomer. X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were used to characterize the chemical structure properties of plasma-polymerized membranes. Ion-exchange capacities of quaternized poly(vinylbenzyl chloride) (QPVBC) membranes were measured to evaluate their capability of hydroxyl ion transport. A mechanism of plasma polymerization using VBC as monomer that accounts for the competitive effects of free radicals polymerization and plasma ablation in the plasma polymerization process was proposed. Our results indicate that plasma discharge power influences the contents of functional groups and the structure of the plasma polymer membranes, which attribute to the coactions of polymerization and ablation. The properties of uniform morphology, good adhesion to the substrate, high thermal stability and satisfying anion conduction level suggest the potential application of QPVBC membrane deposited at discharge power of 20 W in alkaline direct methanol fuel cells.

Synthesis and conductivity of heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure

Energy Technology Data Exchange (ETDEWEB)

Tong Xia; Zhu Weiming [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Wu Qingyin, E-mail: qywu@zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Qian Xueyu; Liu Zhen [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Yan Wenfu [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012 (China); Gong Jian [Key Lab of Polyoxometalate Science, the Ministry of Education, Northeast Normal University, Changchun 130024 (China)

2011-07-21

A new solid high-proton conductor, heptadecatungstovanadodiphosphoric heteropoly acid H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O with Dawson structure was synthesized by the stepwise acidification and the stepwise addition of element solutions. The optimal proportion of component compounds in the synthesis reaction was given. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD, {sup 31}P NMR, TG-DTA and electrochemical impedance spectroscopy (EIS). The results indicate that H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O possesses the Dawson structure. EIS measurements show a high conductivity (3.10 x 10{sup -2} S cm{sup -1} at 26 deg. C and 75% relative humidity), with an activation energy of 32.23 kJ mol{sup -1} for proton conduction. The mechanism of proton conduction for this heteropoly acid is Vehicle mechanism.

Synthesis and structural determination of twisted MoS2 nanotubes

International Nuclear Information System (INIS)

Santiago, P.; Schabes-Retchkiman, P.; Ascencio, J.A.; Mendoza, D.; Perez-Alvarez, M.; Espinosa, A.; Reza-SanGerman, C.; Camacho-Bragado, G.A.; Jose-Yacaman, M.

2004-01-01

In the present work we report the synthesis of MoS 2 nanotubes with diameters greater than 10 nm using a template method. The length and properties of these nanotubes are a direct result of the preparation method. High-resolution transmission electron microscopy is used to study the structure of these highly curved entities. Molecular dynamics simulations of MoS 2 nanotubes reveal that one of the stable forms of the nanotubes is a twisted one. The twisting of the nanotubes produces a characteristic contrast in the images, which is also studied using simulation methods. The analysis of the local contrast close to the perpendicular orientation shows geometrical arrays of dots in domain-like structures, which are demonstrated to be a product of the atomic overlapping of irregular curvatures in the nanotubes. The configuration of some of the experimentally obtained nanotubes is demonstrated to be twisted with a behavior suggesting partial plasticity. (orig.)

Solid‐Phase Synthesis of Structurally Diverse Heterocycles by an Amide–Ketone Condensation/N‐Acyliminium Pictet–Spengler Sequence

DEFF Research Database (Denmark)

Komnatnyy, Vitaly V.; Givskov, Michael Christian; Nielsen, Thomas Eiland

2012-01-01

An efficient approach for the solid‐phase synthesis of structurally diverse heterocyclic compounds is presented. Under acidic reaction conditions, peptidic levulinamides undergo intramolecular ketone–amide condensation reactions to form cyclic N‐acyliminium intermediates. In the presence...

3-cyanoindole-based inhibitors of inosine monophosphate dehydrogenase: synthesis and initial structure-activity relationships.

Science.gov (United States)

Dhar, T G Murali; Shen, Zhongqi; Gu, Henry H; Chen, Ping; Norris, Derek; Watterson, Scott H; Ballentine, Shelley K; Fleener, Catherine A; Rouleau, Katherine A; Barrish, Joel C; Townsend, Robert; Hollenbaugh, Diane L; Iwanowicz, Edwin J

2003-10-20

A series of novel small molecule inhibitors of inosine monophosphate dehydrogenase (IMPDH), based upon a 3-cyanoindole core, were explored. IMPDH catalyzes the rate determining step in guanine nucleotide biosynthesis and is a target for anticancer, immunosuppressive and antiviral therapy. The synthesis and the structure-activity relationships (SAR), derived from in vitro studies, for this new series of inhibitors is given.

Reversal of the lattice structure in SrCoO(x) epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.

Science.gov (United States)

Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S S Ambrose; Cooper, Valentino R; Rabe, Karin M; Lee, Ho Nyung

2013-08-30

Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoO(x) (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

Innovative synthesis of meso-structured YSZ using V2O5 complex fluids as a template

International Nuclear Information System (INIS)

Guiot, Camille; Grandjean, Stephane; Batail, Patrick

2008-01-01

Full text of publication follows: Within the framework of generation IV nuclear reactors, the prospect of a closed fuel cycle generate a need for new advanced materials integrating the actinides jointly. Researches are conducted on fuel material precursors synthesized by soft chemistry processes, which allow a fine control of the homogeneity and ordering at a nano-scale[1]. In a view to meso-structure an inorganic matrix, recent studies[2,3] have highlighted the potential of mineral liquid crystals as templates in new soft chemistry synthesis routes. The studies presently exposed relate to an original synthesis of an inorganic-inorganic hybrid material consisting in a main zirconia matrix tem plated by ribbon-like vanadium pentoxide. After eliminating the V 2 O 5 template, the obtained solid is to be a meso-porous material with ordered pores, and becomes a prime choice material, for example to immobilize actinides. The zirconia matrix has been chosen for its ability to host actinides, which are surrogated by neodymium. It is also a preliminary material for the study of the synthesis of uranium oxide based materials, thus preventing from the drawbacks of working with radioactive materials. The vanadium pentoxide is used as a template since it structure itself as ribbon-like mineral liquid crystals that can be aligned in weak magnetic field; consequently, the final material may be structured at a nano-scale over a macroscopic range. Since the shape of vanadium oxide in solution is very sensitive to the ionic strength of the medium and the pH, the real challenge is to establish a synthesis protocol which is compatible with the presence of vanadium pentoxide, remaining in its ribbon-like liquid crystal form. References: [1] Masson, M.; Grandjean, S.; Lacquement, J.; Bourg, S.; Delauzun, J. M.; Lacombe, J.; Nuclear Engineering and Design, 236 (5-6),516 (2006). [2] Camerel, F.; Gabriel, J.-C.P.; Batail, P.; Adv. Funct. Mater., 13 (5), 377 (2003). [3] Gabriel, J

Structure, morphology and melting hysteresis of ion-implanted nanocrystals

International Nuclear Information System (INIS)

Andersen, H.H.; Johnson, E.

1995-01-01

Investigations of nanosized metal and semimetal inclusions produced by ion implantation in aluminium are reviewed. The inclusions are from 1 nm to 15 nm in size and contain from 80 to 100,000 atoms. Embedded crystallites, which are topotactically aligned with the surrounding matrix, may not be produced in this size range by any other method. The inclusions offer unique possibilities for study of the influence of interfaces on the crystal structure of the inclusions as well as on their melting and solidification behaviour. Studies are made with transmission electron microscopy (TEM), electron- and x-ray diffraction and in situ RBS- channeling measurements. Bi, Cd, In, Pb and Tl inclusions all show a substantial melting/solidification temperature hysteresis, which, in all cases except for Bi, is placed around the bulk melting temperature, while bismuth melts below that temperature. (au) 46 refs

Total synthesis of ciguatoxin.

Science.gov (United States)

Hamajima, Akinari; Isobe, Minoru

2009-01-01

Something fishy: Ciguatoxin (see structure) is one of the principal toxins involved in ciguatera poisoning and the target of a total synthesis involving the coupling of three segments. The key transformations in this synthesis feature acetylene-dicobalthexacarbonyl complexation.

Microstructural transformation with heat-treatment of aluminum hydroxide with gibbsite structure

International Nuclear Information System (INIS)

Mitsui, Tomohiro; Matsui, Toshiaki; Eguchi, Koichi; Kikuchi, Ryuji

2009-01-01

Aluminum hydroxide with gibbsite structure was prepared, and the microstructural transformation of the sample heat-treated at various temperatures was investigated. The sample was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG-DTA), and BET surface area. The shape of the grains in the prepared sample was hexagonal prism-like morphology. The prepared sample kept a metastable state of alumina phase at higher temperatures than the commercially available gibbsite powders. The prepared gibbsite grains underwent characteristic structural change depending on the calcination temperature. The transformation of the surface morphology was initiated at 400degC, leading to the formation of cracks with the direction parallel to the basal plane. After calcination at 1200degC, a large number of grooves were formed on the surface of the lateral planes. The specific structural change of gibbsite induced by the heat treatment was strongly related to the topotactic dehydration from gibbsite and subsequent phase transition to aluminum oxides. (author)

An Introduction to Zeolite Synthesis Using Imidazolium-Based Cations as Organic Structure-Directing Agents.

Science.gov (United States)

Vinaches, Paloma; Bernardo-Gusmão, Katia; Pergher, Sibele B C

2017-08-06

Zeolite synthesis is a wide area of study with increasing popularity. Several general reviews have already been published, but they did not summarize the study of imidazolium species in zeolite synthesis. Imidazolium derivatives are promising compounds in the search for new zeolites and can be used to help understand the structure-directing role. Nearly 50 different imidazolium cations have already been used, resulting in a variety of zeolitic types, but there are still many derivatives to be studied. In this context, the purpose of this short review is to help researchers starting in this area by summarizing the most important concepts related to imidazolium-based zeolite studies and by presenting a table of recent imidazolium derivatives that have been recently studied to facilitate filling in the knowledge gaps.

A microbial-mineralization-inspired approach for synthesis of manganese oxide nanostructures with controlled oxidation states and morphologies

Energy Technology Data Exchange (ETDEWEB)

Oba, Manabu; Oaki, Yuya; Imai, Hiroaki [Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

2010-12-21

Manganese oxide nanostructures are synthesized by a route inspired by microbial mineralization in nature. The combination of organic molecules, which include antioxidizing and chelating agents, facilitates the parallel control of oxidation states and morphologies in an aqueous solution at room temperature. Divalent manganese hydroxide (Mn(OH){sub 2}) is selectively obtained as a stable dried powder by using a combination of ascorbic acid as an antioxidizing agent and other organic molecules with the ability to chelate to manganese ions. The topotactic oxidation of the resultant Mn(OH){sub 2} leads to the selective formation of trivalent manganese oxyhydroxide ({beta}-MnOOH) and trivalent/tetravalent sodium manganese oxide (birnessite, Na{sub 0.55}Mn{sub 2}O{sub 4}.1.5H{sub 2}O). For microbial mineralization in nature, similar synthetic routes via intermediates have been proposed in earlier works. Therefore, these synthetic routes, which include in the present study the parallel control over oxidation states and morphologies of manganese oxides, can be regarded as new biomimetic routes for synthesis of transition metal oxide nanostructures. As a potential application, it is demonstrated that the resultant {beta}-MnOOH nanostructures perform as a cathode material for lithium ion batteries. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Tetraammine(carbonato-κ2O,O′cobalt(III nitrate: a powder X-ray diffraction study

Directory of Open Access Journals (Sweden)

Armel Le Bail

2013-07-01

Full Text Available Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3(NH34]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the CoIII ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N—H...O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding interactions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3(NH34]+ and NO3− groups during the dehydration process, which produces an unusual volume increase of 4.3%.

Tetra­ammine­(carbonato-κ2 O,O′)cobalt(III) nitrate: a powder X-ray diffraction study

Science.gov (United States)

Le Bail, Armel

2013-01-01

Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3)(NH3)4]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the CoIII ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N—H⋯O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding inter­actions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3)(NH3)4]+ and NO3 − groups during the dehydration process, which produces an unusual volume increase of 4.3%. PMID:24046543

Tetra-ammine-(carbonato-κ(2) O,O')cobalt(III) nitrate: a powder X-ray diffraction study.

Science.gov (United States)

Le Bail, Armel

2013-01-01

Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3)(NH3)4]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the Co(III) ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N-H⋯O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding inter-actions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3)(NH3)4](+) and NO3 (-) groups during the dehydration process, which produces an unusual volume increase of 4.3%.

InSe monolayer: synthesis, structure and ultra-high second-harmonic generation

Science.gov (United States)

Zhou, Jiadong; Shi, Jia; Zeng, Qingsheng; Chen, Yu; Niu, Lin; Liu, Fucai; Yu, Ting; Suenaga, Kazu; Liu, Xinfeng; Lin, Junhao; Liu, Zheng

2018-04-01

III–IV layered materials such as indium selenide have excellent photoelectronic properties. However, synthesis of materials in such group, especially with a controlled thickness down to monolayer, still remains challenging. Herein, we demonstrate the successful synthesis of monolayer InSe by physical vapor deposition (PVD) method. The high quality of the sample was confirmed by complementary characterization techniques such as Raman spectroscopy, atomic force microscopy (AFM) and high resolution annular dark field scanning transmission electron microscopy (ADF-STEM). We found the co-existence of different stacking sequence (β- and γ-InSe) in the same flake with a sharp grain boundary in few-layered InSe. Edge reconstruction is also observed in monolayer InSe, which has a distinct atomic structure from the bulk lattice. Moreover, we discovered that the second-harmonic generation (SHG) signal from monolayer InSe shows large optical second-order susceptibility that is 1–2 orders of magnitude higher than MoS2, and even 3 times of the largest value reported in monolayer GaSe. These results make atom-thin InSe a promising candidate for optoelectronic and photosensitive device applications.

Highly dispersed spherical Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} nanocrystals via topotactic crystallization of aggregation-free gel particles from an effective inverse miniemulsion sol–gel approach

Energy Technology Data Exchange (ETDEWEB)

Wang, Aijun; Zeng, Yanwei, E-mail: zengyw-njut@126.com, E-mail: stephen-zeng@njtech.edu.cn, E-mail: stephen-zeng@163.com; Han, Longxiang; Ding, Chuan; Cao, Liangliang; Li, Rongjie [Nanjing Tech University, State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering (China)

2015-09-15

Aggregation-free spherical lanthanum-doped bismuth titanate (Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12}, BLT) gel particles with an average size of about 150 nm were successfully obtained from an inverse miniemulsion sol–gel process, with Span-80 acting as surfactant, n-butanol as co-surfactant, cyclohexane as continuous phase, and submicro-droplets of aqueous solution containing Bi{sup 3+}, La{sup 3+} and Ti{sup 4+} ions as dispersed phase, and then topotactically transformed into highly dispersed spherical BLT nanocrystals after an in situ crystallization at 600 °C for 8 h. It has been found that the BLT gel particles can be obtained via a moderate sol–gel reaction inside the miniemulsion droplets at 65 °C, but their morphology and aggregation degree are strongly affected by the relative amounts of Span-80 and n-butanol. The perfect spherical BLT gel particles with no aggregation can be achieved only under the condition of 3 wt% n-butanol relative to the mass of cyclohexane, with excessive amount of n-butanol leading to the formation of ill-gelled particles with irregular shapes, while insufficient addition of n-butanol resulting in terrible aggregation of gel particles. To understand the formation of aggregation-free spherical BLT gel particles, a tentative mechanism is proposed and discussed, which reveals that a well-coordinated oil–water interfacial film made up of Span-80 and n-butanol molecules and the appropriately enhanced evaporation of water from such interfaces should be responsible for the formation of aggregation-free spherical BLT gel particles. Graphical Abstract: Aggregation-free spherical BLT (Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12}) gel particles can be prepared from an effective inverse miniemulsion sol–gel process, and subsequently topotactically transformed into spherical BLT nanocrystals through an in situ crystallization.

Solid-phase synthesis of yttrium ferrites with structures of perovskite and garnet

Energy Technology Data Exchange (ETDEWEB)

Tkachenko, E V; Shapovalov, A G; Aksel' rod, N L; Pazdnikov, I P [Ural' skij Gosudarstvennyj Univ., Sverdlovsk (USSR)

1980-09-01

The solid phase synthesis of yttrium ferrites having a perovskite- and garnet-like structure has been investigated in the temperature range from 800 to 1500 deg C and temper times of up to 80 hours by reaction zone simulation and magnetic phase analysis. It is shown that for conversion degrees d<0.15 the reactions are diffusion-controlled. The rate constants and effective diffusion in the formation of YFeO/sub 3/ and Y/sub 3/Fe/sub 5/O/sub 12/ have been determined.

Fixation of CO2 in air: Synthesis and crystal structure of a µ3-CO3 ...

Indian Academy of Sciences (India)

Unknown

Fixation of CO2 in air: Synthesis and crystal structure of a ... from the reaction between copper(I) complexes and dioxygen.2,6,7 ... and co-workers from the reaction of [(L2) ..... followed by water dissociation.13h,24 While fixation of CO2 by ...

Synthesis and structural characterization of some trisulfide analoges of thiouracil-based antithyroid drugs

Science.gov (United States)

Bhabak, Krishna P.; Bhowmick, Debasish

2012-08-01

Thiourea-based antithyroid drugs are effectively used for the treatment of hyperthyroidism. In this paper, we describe the synthesis of new trisulfides (11-12) from the commonly used thiourea-based antithyroid drugs such as 6-n-propyl-2-thiouracil (PTU) and 6-methyl-2-thiouracil (MTU) in the reaction with I2/KI system. Structural analysis by single crystal X-ray diffraction studies revealed the stabilization of trisulfides by a lactam-lactim tautomerism facilitating effective intramolecular as well as intermolecular non-covalent interactions. Although the structures of both trisulfides were found to be quite similar, a notable difference in the intermolecular interactions was observed between compounds 11 and 12 leading to different structural patterns. Structural stabilization of these trisulfides by tautomerism followed by intramolecular as well as intermolecular H-bonds makes these molecules as perfect examples in molecular recognition with self-complementary donor and acceptor units within a single molecule.

Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis

Directory of Open Access Journals (Sweden)

Boyce Mark

2012-08-01

Full Text Available Abstract Background Bluetongue virus (BTV is a double-stranded RNA (dsRNA virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Results Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1 as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3′ poly(A sequence identifying the 3′ end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. Conclusions NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed

Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis.

Science.gov (United States)

Boyce, Mark; Celma, Cristina C P; Roy, Polly

2012-08-29

Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3' poly(A) sequence identifying the 3' end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein

Mechanical synthesis of copper-carbon nanocomposites: Structural changes, strengthening and thermal stabilization

International Nuclear Information System (INIS)

Nunes, D.; Livramento, V.; Mateus, R.; Correia, J.B.; Alves, L.C.; Vilarigues, M.; Carvalho, P.A.

2011-01-01

Highlights: → The study characterized Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites. → Preservation of nD crystalline structure during high-energy milling was demonstrated. → Higher refinement of matrix in Cu-nD comparing to Cu-G is due to a milling mechanism. → Remarkable thermal stability and microhardness have been achieved in Cu-nD and Cu-G. → Strengthening resulted mainly from grain refinement and second-phase reinforcement. - Abstract: Processing of copper-carbon nanocomposites by mechanical synthesis poses specific challenges as carbon phases are prone to amorphization and exhibit an intrinsically difficult bonding with copper. The present work investigates Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites produced by mechanical synthesis and subsequent heat treatments. Transmission electron microscopy observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained essentially unaffected by the mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. Particle-induced X-ray emission spectroscopy showed that the total contamination originating from the milling media remained below 0.7 wt.%. The Cu-nanodiamond composite exhibited remarkable microhardness and microstructural thermal stability when compared with pure nanostructured copper.

Mechanical synthesis of copper-carbon nanocomposites: Structural changes, strengthening and thermal stabilization

Energy Technology Data Exchange (ETDEWEB)

Nunes, D., E-mail: daniela.nunes@ist.utl.pt [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Livramento, V. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Mateus, R. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Alves, L.C. [ITN, Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Vilarigues, M. [Departamento de Conservacao e Restauro e R and D Unit Vidro e da Ceramica Para as Artes, FCT-UNL, Quinta da Torre, 2829-516 Caparica (Portugal); Carvalho, P.A. [ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Departamento de Bioengenharia, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

2011-11-15

Highlights: {yields} The study characterized Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites. {yields} Preservation of nD crystalline structure during high-energy milling was demonstrated. {yields} Higher refinement of matrix in Cu-nD comparing to Cu-G is due to a milling mechanism. {yields} Remarkable thermal stability and microhardness have been achieved in Cu-nD and Cu-G. {yields} Strengthening resulted mainly from grain refinement and second-phase reinforcement. - Abstract: Processing of copper-carbon nanocomposites by mechanical synthesis poses specific challenges as carbon phases are prone to amorphization and exhibit an intrinsically difficult bonding with copper. The present work investigates Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites produced by mechanical synthesis and subsequent heat treatments. Transmission electron microscopy observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained essentially unaffected by the mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. Particle-induced X-ray emission spectroscopy showed that the total contamination originating from the milling media remained below 0.7 wt.%. The Cu-nanodiamond composite exhibited remarkable microhardness and microstructural thermal stability when compared with pure nanostructured copper.

Ionothermal synthesis, crystal structure, and magnetic study of Co2PO4OH isostructural with caminite.

Science.gov (United States)

Wang, Guangmei; Valldor, Martin; Spielberg, Eike T; Mudring, Anja-Verena

2014-03-17

A new framework cobalt(II) hydroxyl phosphate, Co2PO4OH, was prepared by ionothermal synthesis using 1-butyl-4-methyl-pyridinium hexafluorophosphate as the ionic liquid. As the formation of Co2PO4F competes in the synthesis, the synthesis conditions have to be judiciously chosen to obtain well-crystallized, single phase Co2PO4OH. Single-crystal X-ray diffraction analyses reveal Co2PO4OH crystallizes with space group I41/amd (a = b = 5.2713(7) Å, c = 12.907(3) Å, V = 358.63(10) Å(3), and Z = 4). Astonishingly, it does not crystallize isotypically with Co2PO4F but rather isotypically with the hydroxyl minerals caminite Mg1.33[SO4(OH)0.66(H2O)0.33] and lipscombite Fe(2–y)PO4(OH) (0 ≤ y ≤ 2/3). Phosphate tetrahedra groups interconnect four rod-packed face-sharing ∞(1){CoO(6/2)} octahedra chains to form a three-dimensional framework structure. The compound Co2PO4OH was further characterized by powder X-ray diffraction, Fourier transform–infrared, and ultraviolet–visible spectroscopy, confirming the discussed structure. The magnetic measurement reveals that Co2PO4OH undergoes a magnetic transition and presents at low temperatures a canted antiferromagnetic spin order in the ground state.

Chemical synthesis of porous web-structured CdS thin films for photosensor applications

Energy Technology Data Exchange (ETDEWEB)

Gosavi, S.R., E-mail: srgosavi.taloda@gmail.com [C. H. C. Arts, S. G. P. Commerce, and B. B. J. P. Science College, Taloda, Dist., Nandurbar 425413, M. S. (India); Nikam, C.P. [B.S.S.P.M.S. Arts, Commerce and Science College, Songir, Dist., Dhule 424309, M. S. (India); Shelke, A.R.; Patil, A.M. [Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India); Ryu, S.-W. [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Bhat, J.S. [Department of Physics, Karnatak University, Dharwad 580003 (India); Deshpande, N.G., E-mail: nicedeshpande@yahoo.co.in [Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India)

2015-06-15

The photo-activity of chemically deposited cadmium sulphide (CdS) thin film has been studied. The simple chemical route nucleates the CdS films with size up to the mean free path of the electron. Growth Kinematics of crystalline hexagonal CdS phase in the thin film form was monitored using X-ray diffraction. The time limitation set for the formation of the amorphous/nano-crystalline material is 40 and 60 min. Thereafter enhancement of the crystalline orientation along the desired plane was identified. Web-like porous structured surface morphology of CdS thin film over the entire area is observed. With decrease in synthesis time, increase of band gap energy i.e., a blue spectral shift was seen. The activation energy of CdS thin film at low and high temperature region was examined. It is considered that this activation energy corresponds to the donor levels associated with shallow traps or surface states of CdS thin film. The photo-electrochemical performance of CdS thin films in polysulphide electrolyte showed diode-like characteristics. Exposure of light on the CdS electrode increases the photocurrent. This suggests the possibility of production of free carriers via excited ions and also the light harvesting mechanism due to porous web-structured morphology. These studies hint that the obtained CdS films can work as a photosensor. - Highlights: • Photoactivity of chemically synthesized cadmium sulphide (CdS) thin films was studied. • Web-like porous structured surface morphology of CdS thin film over the entire area was observed. • Blue spectral shift with lowering of the synthesis time suggests films can act as a window layer over the absorber layer. • Porous web-structured CdS thin films can be useful in light harvesting.

Chemical synthesis of porous web-structured CdS thin films for photosensor applications

International Nuclear Information System (INIS)

Gosavi, S.R.; Nikam, C.P.; Shelke, A.R.; Patil, A.M.; Ryu, S.-W.; Bhat, J.S.; Deshpande, N.G.

2015-01-01

The photo-activity of chemically deposited cadmium sulphide (CdS) thin film has been studied. The simple chemical route nucleates the CdS films with size up to the mean free path of the electron. Growth Kinematics of crystalline hexagonal CdS phase in the thin film form was monitored using X-ray diffraction. The time limitation set for the formation of the amorphous/nano-crystalline material is 40 and 60 min. Thereafter enhancement of the crystalline orientation along the desired plane was identified. Web-like porous structured surface morphology of CdS thin film over the entire area is observed. With decrease in synthesis time, increase of band gap energy i.e., a blue spectral shift was seen. The activation energy of CdS thin film at low and high temperature region was examined. It is considered that this activation energy corresponds to the donor levels associated with shallow traps or surface states of CdS thin film. The photo-electrochemical performance of CdS thin films in polysulphide electrolyte showed diode-like characteristics. Exposure of light on the CdS electrode increases the photocurrent. This suggests the possibility of production of free carriers via excited ions and also the light harvesting mechanism due to porous web-structured morphology. These studies hint that the obtained CdS films can work as a photosensor. - Highlights: • Photoactivity of chemically synthesized cadmium sulphide (CdS) thin films was studied. • Web-like porous structured surface morphology of CdS thin film over the entire area was observed. • Blue spectral shift with lowering of the synthesis time suggests films can act as a window layer over the absorber layer. • Porous web-structured CdS thin films can be useful in light harvesting

Facile and tunable synthesis of hierarchical mesoporous silica materials ranging from flower structure with wrinkled edges to hollow structure with coarse surface

Energy Technology Data Exchange (ETDEWEB)

Hao, Nanjing, E-mail: nanjing.hao@dartmouth.edu [Dartmouth College, Thayer School of Engineering (United States); Li, Laifeng; Tang, Fangqiong, E-mail: tangfq@mail.ipc.ac.cn [Chinese Academy of Sciences, Technical Institute of Physics and Chemistry (China)

2016-11-15

Mesoporous silica materials have attracted great attention in many fields. However, facile and tunable synthesis of hierarchical mesoporous silica structures is still a big challenge, and thus the development of them still lags behind. Herein, well-defined mesoporous silica flower structure with wrinkled edges and mesoporous silica hollow structure with coarse surface were synthesized simply by using poly(vinylpyrrolidone) and hexadecylamine as cotemplates in different water/ethanol solvent systems. The shape evolution from flower to hollow can be easily realized by tuning the volume ratio of water to ethanol, and the yields of both materials can reach gram scale. The formation mechanisms of mesoporous silica flower and hollow structures were also experimentally investigated and discussed. These novel hierarchical structures having unique physicochemical properties may bring many interesting insights into scientific research and technological application.

Tuning structural motifs and alloying of bulk immiscible Mo-Cu bimetallic nanoparticles by gas-phase synthesis

Science.gov (United States)

Krishnan, Gopi; Verheijen, Marcel A.; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.

2013-05-01

Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape.Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still

A Better Understanding of Protein Structure and Function by the Synthesis and Incorporation of Selenium- and Tellurium Containing Tryptophan Analogs

Energy Technology Data Exchange (ETDEWEB)

Helmey, Sherif Samir [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Bioscience Division; Belmont Univ., Nashville, TN (United States). Dept. of Chemistry and Physics; Rice, Ambrose Eugene [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Bioscience Division; Belmont Univ., Nashville, TN (United States). Dept. of Chemistry and Physics; Hatch, Duane Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Bioscience Division; Belmont Univ., Nashville, TN (United States). Dept. of Chemistry and Physics; Silks, Louis A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Bioscience Division; Marti-Arbona, Ricardo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Bioscience Division

2016-08-17

Unnatural heavy metal-containing amino acid analogs have shown to be very important in the analysis of protein structure, using methods such as X-ray crystallography, mass spectroscopy, and NMR spectroscopy. Synthesis and incorporation of selenium-containing methionine analogs has already been shown in the literature however with some drawbacks due to toxicity to host organisms. Thus synthesis of heavy metal tryptophan analogs should prove to be more effective since the amino acid tryptophan is naturally less abundant in many proteins. For example, bioincorporation of β-seleno[3,2-b]pyrrolyl-L-alanine ([4,5]SeTrp) and β-selenolo[2,3-b]pyrrolyl-L-alanine ([6,7]SeTrp) has been shown in the following proteins without structural or catalytic perturbations: human annexin V, barstar, and dihydrofolate reductase. The reported synthesis of these Se-containing analogs is currently not efficient for commercial purposes. Thus a more efficient, concise, high-yield synthesis of selenotryptophan, as well as the corresponding, tellurotryptophan, will be necessary for wide spread use of these unnatural amino acid analogs. This research will highlight our progress towards a synthetic route of both [6,7]SeTrp and [6,7]TeTrp, which ultimately will be used to study the effect on the catalytic activity of Lignin Peroxidase (LiP).

The Synthesis and Crystal Structure of Two New Hydrazone Compounds

Directory of Open Access Journals (Sweden)

Li-Hua Wang

2016-05-01

Full Text Available Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1 and 2-nitrobenzaldehyde-2-furan formylhydrazone (2, were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = 7.0321(14 Å, b = 7.3723(15 Å, c = 13.008(3 Å, α = 98.66(3°, β = 101.69(3°, γ = 92.25(3°, V = 651.2(2 Å3, Z = 2, Dc = 1.358 g·cm−3, μ = 0.106 mm−1, F(000 = 280, and final R1 = 0.0564, ｗR2 = 0.1420. Compound 2 crystallizes in monoclinic, space group P21/c with a = 17.3618(9 Å, b = 9.1506(4 Å, c = 15.5801(7 Å, β = 104.532(5°, V = 2396.05(19 Å3, Z = 8, Dc = 1.437 g·cm−3, μ = 0.111 mm−1, F(000 = 1072, and final R1 = 0.0633, wR2 = 0.1649. Compound 1 forms a 2D-layered structure via the interactions of 1D chains and Compound 2 forms a 3D network structure via the interactions of 1D chains.

Total Synthesis of Bryostatins. Development of Methodology for Atom-Economic and Stereoselective Synthesis of the C-ring Subunit

Science.gov (United States)

Trost, Barry M.; Frontier, Alison J.; Thiel, Oliver R.; Yang, Hanbiao; Dong, Guangbin

2012-01-01

Bryostatins, a family of structurally complicated macrolides, exhibit an exceptional range of biological activities. The limited availability and structural complexity of these molecules makes development of an efficient total synthesis particularly important. This article describes our initial efforts towards the total synthesis of bryostatins, in which chemoselective and atom-economical methods for stereoselective assembly of the C-ring subunit were developed. A Pd-catalyzed tandem alkyne-alkyne coupling/6-endo-dig cyclization sequence was explored and successfully pursued in the synthesis of a dihydropyran ring system. Elaboration of this methodology ultimately led to a concise synthesis of the C-ring subunit of bryostatins. PMID:21793057

Reverse Topotactic Transformation of a Cu–Zn–Al Catalyst during Wet Pd Impregnation : Relevance for the Performance in Methanol Synthesis from CO2/H2 Mixtures

NARCIS (Netherlands)

Fierro, J.L.G.; López Granados, M.; Melián-Cabrera, I.

2002-01-01

The effect of palladium metal on the performance of a CuO–ZnO–Al2O3 catalyst is studied for methanol synthesis by hydrogenation of carbon dioxide. The dramatic decrease in the methanol yield (in mol CH3OH/h · gcat) seen for the Pd-containing catalysts is discussed in terms of formation,

Redox topotactic reactions in FeII − III (oxy)hydroxycarbonate new minerals related to fougèrite in gleysols: “trébeurdenite and mössbauerite”

International Nuclear Information System (INIS)

Génin, Jean-Marie R.; Guérin, O.; Herbillon, A. J.; Kuzmann, E.; Mills, S. J.; Morin, G.; Ona-Nguema, G.; Ruby, C.; Upadhyay, C.

2012-01-01

Fougèrite mineral responsible for the bluish-green shade of gleysols in aquifers was identified as Fe II − III oxyhydroxycarbonate, [Fe 6 ( 1-x) II Fe 6x III O 12 H 2(7 − 3x) ] 2 +  · [CO 3 2- · 3H 2 O] 2 −  where the average ferric molar fraction x = [Fe III /Fe total ] was restricted to the [1/3–2/3] range, up till now. In this paper, Mössbauer spectra of gleys extracted from the schorre of maritime marshes have values of x in the [2/3–1] range. Magnetic properties of homologous chemical compounds studied by Mössbauer spectroscopy are explained with long range order of Fe III ions within Fe cation layers for x = 1/3, 2/3 and 1. Observed values are mixtures of topotactic domains that are in fact minerals with names proposed to IMA: fougèrite for x = 1/3, trébeurdenite for x = 2/3 and mössbauerite for x = 1.

Synthesis and structural characterization of nano-hydroxyapatite biomaterials prepared by microwave processing

Science.gov (United States)

Ramli, Rosmamuhamadani; Arawi, Ainaa Zafirah Omar; Talari, Mahesh Kumar; Mahat, Mohd Muzamir; Jais, Umi Sarah

2012-07-01

Synthetic hydroxyapatite, (HA, Ca10(PO4)6(OH)2), is an attractive and widely utilized bio-ceramic material for orthopedic and dental implants because of its close resemblance of native tooth and bone crystal structure. Synthetic HA exhibits excellent osteoconductive properties. Osteoconductivity means the ability to provide the appropriate scaffold or template for bone formation. Calcium phosphate biomaterials [(HA), tri-calcium phosphate (TCP) and biphasic calcium phosphate (HA/TCP)] with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive and can be effective carriers of bone cell seeds. This HA can be used in bio-implants as well as drug delivery application due to the unique properties of HA. Biomaterials synthesized from the natural species like mussel shells have additional benefits such as high purity, less expensive and high bio compatibility. In this project, HA-nanoparticles of different crystallite size were prepared by microwave synthesis of precursors. High purity CaO was extracted from the natural mussel shells for the synthesis of nano HA. Dried nano HA powders were analyzed using X-Ray Diffraction (XRD) technique for the determination of crystal structure and impurity content. Scanning Electron Microscopic (SEM) investigation was employed for the morphological investigation of nano HA powders. From the results obtained, it was concluded that by altering the irradiation time, nano HA powders of different crystallite sizes and morphologies could be produced. Crystallite sizes calculated from the XRD patterns are found to be in the range of 10-55 nm depending on the irradiation time.

Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

International Nuclear Information System (INIS)

Rubina, M.S.; Kamitov, E.E.; Zubavichus, Ya. V.; Peters, G.S.; Naumkin, A.V.; Suzer, S.; Vasil’kov, A.Yu.

2016-01-01

Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

Energy Technology Data Exchange (ETDEWEB)

Rubina, M.S.; Kamitov, E.E. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Zubavichus, Ya. V.; Peters, G.S. [National Research center «Kurchatov Institute», Moscow, 123182 Russian Federation (Russian Federation); Naumkin, A.V. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Suzer, S. [Department of Chemistry, Bilkent University, Ankara, 06800 Turkey (Turkey); Vasil’kov, A.Yu., E-mail: alexandervasilkov@yandex.ru [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation)

2016-03-15

Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

Synthesis of a mesoporous single crystal Ga2O3 nanoplate with improved photoluminescence and high sensitivity in detecting CO.

Science.gov (United States)

Yan, Shicheng; Wan, Lijuan; Li, Zhaosheng; Zhou, Yong; Zou, Zhigang

2010-09-14

A new approach is proposed to synthesize a mesoporous single crystal Ga(2)O(3) nanoplate by heating a single crystal nanoplate of GaOOH, which involves an ion exchange between KGaO(2) and CH(3)COOH at room temperature for the formation of GaOOH and pseudomorphic and topotactic phase transformation from GaOOH to Ga(2)O(3).

C8-structured carbon quantum dots: Synthesis, blue and green double luminescence, and origins of surface defects

Science.gov (United States)

Xifang, Chen; Wenxia, Zhang; Qianjin, Wang; Jiyang, Fan

Carbon quantum dots (CQDs) have attracted great attention in the past few years due to their low cytotoxicity, exploited various synthesis methods, unexampled abundance of raw materials on earth, and robust near-infrared to near-UV luminescence. Carbon nanoparticles have applications in biological labeling, delivery of drugs and biological molecules into cells, and light emitting diodes and lasing. CQDs generally exist as nanodiamonds or graphite quantum dots according to previous research reports. In this study, we report the first synthesis of the third-allotrope CQDs through carbonization of sucrose and study their luminescence properties. These CQDs have a body-centered cubic structure and each lattice point is composed of eight atoms which form a sub-cube (so called C8 crystal structure). High-resolution transmission electron microscopy and X-ray diffraction confirm the C8 structure of the synthesized carbon nanocrystallites with an average size of 2 nm. The C8 CQDs exhibit double-band luminescence with two peaks centered at around 432 and 520 nm. The study based on the photoluminescence, UV-Vis absorption, Fourier-transform infrared, and X-ray photoelectron spectroscopies reveals that the green emission originates from the C=O related surface defect.

Facile and template-free method toward chemical synthesis of polyaniline film/nanotube structures

Energy Technology Data Exchange (ETDEWEB)

Liu, Pei [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261; Zhu, Yisi [Materials Science Division, Argonne National Lab, Lemont Illinois 60439; Torres, Jorge [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261; Lee, Seung Hee [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-786 Korea; Yun, Minhee [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261

2017-09-05

A facile and template-free method is reported to synthesize a new thin film structure: polyaniline (PANI) film/nanotubes (F/N) structure. The PANI F/N is a 100-nm thick PANI film embedded with PANI nanotubes. This well-controlled method requires no surfactant or organic acid as well as relatively low concentration of reagents. Synthesis condition studies reveal that aniline oligomers with certain structures are responsible for guiding the growth of the nanotubes. Electrical characterization also indicates that the PANI F/N possesses similar field-effect transistor characteristics to bare PANI film. With its 20% increased surface-area-to-volume (S/V) ratio contributed by surface embedded nanotubes and the excellent p-type semiconducting characteristic, PANI F/N shows clear superiority compared with bare PANI film. Such advantages guarantee the PANI F/N a promising future toward the development of ultra-high sensitivity and low-cost biosensors.

Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

Directory of Open Access Journals (Sweden)

Carlos Macias

2016-01-01

Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

Synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Chi, Yang; Zhuang, Yan; Guo, Sheng-Ping [Yangzhou Univ., Jiangsu (China). College of Chemistry and Chemical Engineering

2017-03-01

The synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5} are reported. It is synthesized by high-temperature solid-state reaction and crystallizes in the monoclinic space group P2{sub 1}/c (no. 14) with the unit cell parameters a=4.8860(5), b=7.5229(8), c=9.9587(10) Aa, and β=91.709(3) . Its crystal structure features a polyanion-type layer (GeBO{sub 5}){sup 3-} constructed by BO{sub 4} and GeO{sub 4} tetrahedra connected alternatingly. Eu{sup 3+} ions are located in cavities and are coordinated by eight O atoms. Various structures of the related compounds REMM'O{sub 5} (RE=rare earth metal; M=Si, Ge, and Sn; M'=B, Al, and Ga) are also discussed.

Insertion of water into rare earth oxocuprates (Ln)Ba 2Cu 3O 7-δ

Science.gov (United States)

Günther, Wulf; Schöllhorn, Robert

1996-02-01

The solid state reaction of LnBa 2Cu 3O 7-δ bulk material with water vapour corresponds to a quantitative topotactic reaction of the solid with H 2O to a maximum stoichiometry of LnBa 2Cu 3O 7-δ(H 2O) 1. The reaction proceeds in a temperature window which depends upon the oxygen content (δ) of the starting phase and is correlated with a structural transition via intermediate states. Although the integral copper oxidation state is not affected by the water intercalation, electronic and transport properties are strongly influenced. The insertion of water into these defect perovskites has to be described as a topotactic acid/base process.

The in vitro synthesis of β-galactosidase induced in a subcellular structure of Escherichia coli (1961)

International Nuclear Information System (INIS)

Nisman, B.; Kayser, A.; Demailly, J.; Genin, C.

1961-01-01

Isopropyl-thio-galactoside (IPTG), an inducer of 3-galactosidase, makes it possible to synthesise this enzyme in vitro with the subcellular structure (P 1 ). The enzyme is isolated from the bacteria Escherichia coli K 12 which are inductive but not induced. The incorporation of radioactive amino-acids, which is stimulated by the presence of an inducer, was studied during the course of the enzyme synthesis. Saccharose suppresses the induction of β-galactosidase. The presence of a specific inhibitor in the structure studied is considered. (authors) [fr

A hierarchically assembled mesoporous ZnO hemisphere array and hollow microspheres for photocatalytic membrane water filtration.

Science.gov (United States)

Pan, Jia Hong; Zhang, Xiwang; Du, Alan J; Bai, Hongwei; Ng, Jiawei; Sun, Darren

2012-05-28

A mesoporous ZnO hemisphere array has been prepared via a topotactic transition of Zn(4)(OH)(6)CO(3)·H(2)O (ZCHH) by chemical bath deposition. Each hemisphere is comprised of a radially oriented nanoflake shell grown on the hemispherical interior. Reaction time-dependent SEM analysis shows that the morphological formation of ZCHH involves a deposition-growth-secondary growth-redeposition procedure. Upon calcination, ZCHH readily decomposes to nanocrystalline wurtzite-phase ZnO without significant change in morphology, and the release of CO(2) and H(2)O from ZCHH creates an additional mesoporous structure in both hemispherical interior and nanoflake shell. A similar process but without using a substrate has been developed for synthesis of mesoporous ZnO hollow microspheres in powder form. Both the elaborated superstructured photocatalysts consisting of mesoporous nanoflakes have been demonstrated to exhibit excellent performances in the photocatalytic membrane filtration.

On several new ternary molybdenum sulfide phases M/sub 3.4/Mo/sub 15/S/sub 19/ (M = vacancy, Li, Na, K, Zn, Cd, Sn and Tl)

International Nuclear Information System (INIS)

Tarascon, J.M.; Hull, G.W.

1986-01-01

In/sub 3.3/Mo/sub 15/Se/sub 19/ was reported a few years ago, but many attempts to date to prepare the homologue sulfide were unsuccessful. The authors report herein the first synthesis of In/sub 3.4/Mo/sub 15/S/sub 19/, isostructural to the above selenide and show that indium atoms can be removed from this phase by oxidation with HCl without disturbing the Mo chalcogenide network resulting in a new binary phase Mo/sub 15/S/sub 19/. Furthermore, this phase, with an open framework structure turns out to be an interesting system for intercalation studies. The authors have shown that Mo/sub 15/S/sub 19/ can undergo topotactic redox reactions with lithium or sodium resulting in new phases of formula Li/sub 8/Mo/sub 15/S/sub 19/ respectively. These two phases are stable at room temperature in the absence of air

Ligand-protected gold clusters: the structure, synthesis and applications

Science.gov (United States)

Pichugina, D. A.; Kuz'menko, N. E.; Shestakov, A. F.

2015-11-01

Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Aun with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au15 and Au25) and on anchorage to a support surface (Au25/SiO2, Au20/C, Au10/FeOx) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR)n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters MxAunLm (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR)x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active sites. The bibliography includes 345 references.

Structural and Biochemical Characterization of Chlamydia trachomatis Hypothetical Protein CT263 Supports That Menaquinone Synthesis Occurs through the Futalosine Pathway*

Science.gov (United States)

Barta, Michael L.; Thomas, Keisha; Yuan, Hongling; Lovell, Scott; Battaile, Kevin P.; Schramm, Vern L.; Hefty, P. Scott

2014-01-01

The obligate intracellular human pathogen Chlamydia trachomatis is the etiological agent of blinding trachoma and sexually transmitted disease. Genomic sequencing of Chlamydia indicated this medically important bacterium was not exclusively dependent on the host cell for energy. In order for the electron transport chain to function, electron shuttling between membrane-embedded complexes requires lipid-soluble quinones (e.g. menaquionone or ubiquinone). The sources or biosynthetic pathways required to obtain these electron carriers within C. trachomatis are poorly understood. The 1.58Å crystal structure of C. trachomatis hypothetical protein CT263 presented here supports a role in quinone biosynthesis. Although CT263 lacks sequence-based functional annotation, the crystal structure of CT263 displays striking structural similarity to 5′-methylthioadenosine nucleosidase (MTAN) enzymes. Although CT263 lacks the active site-associated dimer interface found in prototypical MTANs, co-crystal structures with product (adenine) or substrate (5′-methylthioadenosine) indicate that the canonical active site residues are conserved. Enzymatic characterization of CT263 indicates that the futalosine pathway intermediate 6-amino-6-deoxyfutalosine (kcat/Km = 1.8 × 103 m−1 s−1), but not the prototypical MTAN substrates (e.g. S-adenosylhomocysteine and 5′-methylthioadenosine), is hydrolyzed. Bioinformatic analyses of the chlamydial proteome also support the futalosine pathway toward the synthesis of menaquinone in Chlamydiaceae. This report provides the first experimental support for quinone synthesis in Chlamydia. Menaquinone synthesis provides another target for agents to combat C. trachomatis infection. PMID:25253688

Structure and fertilizer properties of byproducts formed in the synthesis of EDDHA.

Science.gov (United States)

Hernández-Apaolaza, Lourdes; García-Marco, Sonia; Nadal, Paloma; Lucena, Juan J; Sierra, Miguel A; Gómez-Gallego, Mar; Ramírez-López, Pedro; Escudero, Rosa

2006-06-14

The synthesis of commercial EDDHA produces o,o-EDDHA as the main reaction product, together with a mixture of regioisomers (o,p-EDDHA and p,p-EDDHA) and other unknown byproducts also able to complex Fe3+. These compounds have been obtained by direct synthesis, and their structures have been determined by ESI-MS analysis as oligomeric EDDHA-like products, formed by polysubstitution in the phenolic rings. Short-term experiments show that the iron complexes of samples enriched in these oligomeric byproducts have adequate stability in solution, but a significant amount of them is lost after interaction with soils and soil materials. Mildly chlorotic cucumber plants are able to reduce iron better from o,p-EDDHA/Fe3+ than from the iron complexes of the oligomeric byproducts. In hydroponics, the chlorotic soybean susceptible plants have a lower potential for Fe absorption from these byproducts than from o,o-EDDHA/Fe3+ and from o,p-EDDHA/Fe3+. In the studied conditions, the iron chelates of EDDHA byproducts do not have the long-lasting effect shown by o,o-EDDHA/Fe3+ and present a less efficient fast-action effect than the o,p-EDDHA/Fe3+.

Synthesis and structural characterization of bulk Sb2Te3 single crystal

Science.gov (United States)

Sultana, Rabia; Gahtori, Bhasker; Meena, R. S.; Awana, V. P. S.

2018-05-01

We report the growth and characterization of bulk Sb2Te3 single crystal synthesized by the self flux method via solid state reaction route from high temperature melt (850˚C) and slow cooling (2˚C/hour) of constituent elements. The single crystal X-ray diffraction pattern showed the 00l alignment and the high crystalline nature of the resultant sample. The rietveld fitted room temperature powder XRD revealed the phase purity and rhombohedral structure of the synthesized crystal. The formation and analysis of unit cell structure further verified the rhombohedral structure composed of three quintuple layers stacked one over the other. The SEM image showed the layered directional growth of the synthesized crystal carried out using the ZEISS-EVOMA-10 scanning electron microscope The electrical resistivity measurement was carried out using the conventional four-probe method on a quantum design Physical Property Measurement System (PPMS). The temperature dependent electrical resistivity plot for studied Sb2Te3 single crystal depicts metallic behaviour in the absence of any applied magnetic field. The synthesis as well as the structural characterization of as grown Sb2Te3 single crystal is reported and discussed in the present letter.

Synthesis and structural characterization of coaxial nano tubes intercalated of molybdenum disulfide with carbon

International Nuclear Information System (INIS)

Reza San German, C.M.

2005-01-01

In this work the study of some fundamental aspects in the growth of unidimensional systems of coaxial nano tubes from the mold method is approached. This method is an inclusion technique of a precursor reagent into oxide nano porous alumina film (mold), and later applying some processes of synthesis it is gotten to obtain the wished material. The synthesized structures are identified later because they take place by means of the initial formation of nano tubes of MoS 2 , enclosing to carbon nano tubes by the same method, with propylene flow which generates a graphitization process that 'copy' the mold through as it flows. Binary phase MoS 2 + C nano tubes were synthesized by propylene pyrolysis inside MoS 2 nano tubes prepared by template assisted technique. The large coaxial nano tubes constituted of graphite sheets inserted between the MoS 2 layers forming the outer part, and coaxial multi wall carbon nano tubes (MWCNT) intercalated with MoS 2 inside. High resolution electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), high angle annular dark field (HAADF), gatan image filter (GIF), nano beam electron diffraction patterns (NBEDP), along with molecular dynamics simulation and quantum mechanical calculations were used to characterize the samples. The one-dimensional structures exhibit diverse morphologies such as long straight and twisted nano tubes with several structural irregularities. The inter-planar spacing between MoS 2 layers was found to increase from 6.3 to 7.4 A due to intercalation with carbon. Simulated HREM images revealed the presence of these twisted nano structures, with mechanical stretch into intercalate carbon between MoS 2 layers. Our results open up the possibility of using MoS 2 nano tubes as templates for the synthesis of new one- dimensional binary phase systems. (Author)

Synthesis of nano-structured materials by laser-ablation and their application to sensors

International Nuclear Information System (INIS)

Okada, T.; Suehiro, J.

2007-01-01

We describe the synthesis of nano-structured materials of ZnO and Pd by laser ablation and their applications to sensors. The synthesis of ZnO nano-wires was performed by nano-particle assisted deposition (NPAD) where nano-crystals were grown with nano-particles generated by laser-ablating a ZnO sintered target in an Ar background gas. The synthesized ZnO nano-wires were characterized with a scanning electron microscopy and the photoluminescent characteristics were examined under an excitation with the third harmonics of a Nd:YAG laser. The nano-wires with a diameter in the range from 50 to 150 nm and a length of up to 5 μm were taken out of the substrate by laser blow-off technique and/or sonication. It was confirmed that the nano-wires showed the stimulated emission under optical pumping, indicating a high quality of the crystalinity. Pd nano-particles were generated by laser-ablating a Pd plate in pure water. The transmission electron microscope observation revealed that Pd nano-particles with a diameter in the range from 3 nm to several tens of nanometers were produced. Using these nano-structured materials, we successfully fabricated sensors by the dielectrophoresis techniques. In the case of the ultraviolet photosensor, a detection sensitivity of 10 nW/cm 2 was achieved and in the case of hydrogen sensing, the response time of less than 10 s has been demonstrated with Pd nano-particles

Structure-based mechanism of lipoteichoic acid synthesis by Staphylococcus aureus LtaS

Science.gov (United States)

Lu, Duo; Wörmann, Mirka E.; Zhang, Xiaodong; Schneewind, Olaf; Gründling, Angelika; Freemont, Paul S.

2009-01-01

Staphylococcus aureus synthesizes polyglycerol-phosphate lipoteichoic acid (LTA) from phosphatidylglycerol. LtaS, a predicted membrane protein with 5 N-terminal transmembrane helices followed by a large extracellular part (eLtaS), is required for staphylococcal growth and LTA synthesis. Here, we report the first crystal structure of the eLtaS domain at 1.2-Å resolution and show that it assumes a sulfatase-like fold with an α/β core and a C-terminal part composed of 4 anti-parallel β-strands and a long α-helix. Overlaying eLtaS with sulfatase structures identified active site residues, which were confirmed by alanine substitution mutagenesis and in vivo enzyme function assays. The cocrystal structure with glycerol-phosphate and the coordination of a Mn2+ cation allowed us to propose a reaction mechanism, whereby the active site threonine of LtaS functions as nucleophile for phosphatidylglycerol hydrolysis and formation of a covalent threonine–glycerolphosphate intermediate. These results will aid in the development of LtaS-specific inhibitors for S. aureus and many other Gram-positive pathogens. PMID:19168632

Wall grid structure for interior scene synthesis

KAUST Repository

Xu, Wenzhuo; Wang, Bin; Yan, Dongming

2015-01-01

We present a system for automatically synthesizing a diverse set of semantically valid, and well-arranged 3D interior scenes for a given empty room shape. Unlike existing work on layout synthesis, that typically knows potentially needed 3D models

Organoactinide chemistry: synthesis, structure, and solution dynamics

International Nuclear Information System (INIS)

Brennan, J.G.

1985-12-01

This thesis considers three aspects of organoactinide chemistry. In chapter one, a bidentate phosphine ligand was used to kinetically stabilize complexes of the type Cp 2 MX 2 . Ligand redistribution processes are present throughout the synthetic work, as has often been observed in uranium cyclopentadienyl chemistry. The effects of covalent M-L bonding on the solution and solid state properties of U(III) coordination complexes are considered. In particular, the nature of the more subtle interaction between the metal and the neutral ligand are examined. Using relative basicity data obtained in solution, and solid state structural data (and supplemented by gas phase photoelectron measurements), it is demonstrated that the more electron rich U(III) centers engage in significant U → L π-donation. Trivalent uranium is shown to be capable of acting either as a one- or two-electron reducing agent toward a wide variety of unsaturated organic and inorganic molecules, generating molecular classes unobtainable via traditional synthetic approaches, as well as offering an alternative synthetic approach to molecules accessible via metathesis reactions. Ligand redistribution processes are again observed, but given the information concerning ligand lability, this reactivity pattern is applied to the synthesis of pure materials inaccessible from redox chemistry. 214 refs., 33 figs., 10 tabs

Development of a Probabilistic Dynamic Synthesis Method for the Analysis of Nondeterministic Structures

Science.gov (United States)

Brown, A. M.

1998-01-01

Accounting for the statistical geometric and material variability of structures in analysis has been a topic of considerable research for the last 30 years. The determination of quantifiable measures of statistical probability of a desired response variable, such as natural frequency, maximum displacement, or stress, to replace experience-based "safety factors" has been a primary goal of these studies. There are, however, several problems associated with their satisfactory application to realistic structures, such as bladed disks in turbomachinery. These include the accurate definition of the input random variables (rv's), the large size of the finite element models frequently used to simulate these structures, which makes even a single deterministic analysis expensive, and accurate generation of the cumulative distribution function (CDF) necessary to obtain the probability of the desired response variables. The research presented here applies a methodology called probabilistic dynamic synthesis (PDS) to solve these problems. The PDS method uses dynamic characteristics of substructures measured from modal test as the input rv's, rather than "primitive" rv's such as material or geometric uncertainties. These dynamic characteristics, which are the free-free eigenvalues, eigenvectors, and residual flexibility (RF), are readily measured and for many substructures, a reasonable sample set of these measurements can be obtained. The statistics for these rv's accurately account for the entire random character of the substructure. Using the RF method of component mode synthesis, these dynamic characteristics are used to generate reduced-size sample models of the substructures, which are then coupled to form system models. These sample models are used to obtain the CDF of the response variable by either applying Monte Carlo simulation or by generating data points for use in the response surface reliability method, which can perform the probabilistic analysis with an order of

Structure-Based Design and Synthesis of Potent and Selective Matrix Metalloproteinase 13 Inhibitors.

Science.gov (United States)

Choi, Jun Yong; Fuerst, Rita; Knapinska, Anna M; Taylor, Alexander B; Smith, Lyndsay; Cao, Xiaohang; Hart, P John; Fields, Gregg B; Roush, William R

2017-07-13

We describe the use of comparative structural analysis and structure-guided molecular design to develop potent and selective inhibitors (10d and (S)-17b) of matrix metalloproteinase 13 (MMP-13). We applied a three-step process, starting with a comparative analysis of the X-ray crystallographic structure of compound 5 in complex with MMP-13 with published structures of known MMP-13·inhibitor complexes followed by molecular design and synthesis of potent but nonselective zinc-chelating MMP inhibitors (e.g., 10a and 10b). After demonstrating that the pharmacophores of the chelating inhibitors (S)-10a, (R)-10a, and 10b were binding within the MMP-13 active site, the Zn 2+ chelating unit was replaced with nonchelating polar residues that bridged over the Zn 2+ binding site and reached into a solvent accessible area. After two rounds of structural optimization, these design approaches led to small molecule MMP-13 inhibitors 10d and (S)-17b, which bind within the substrate-binding site of MMP-13 and surround the catalytically active Zn 2+ ion without chelating to the metal. These compounds exhibit at least 500-fold selectivity versus other MMPs.

Synthesis and characterization of bimetallic metal-organic framework Cu-Ru-BTC with HKUST-1 structure.

Science.gov (United States)

Gotthardt, Meike A; Schoch, Roland; Wolf, Silke; Bauer, Matthias; Kleist, Wolfgang

2015-02-07

The bimetallic metal-organic framework Cu-Ru-BTC with the stoichiometric formula Cu2.75Ru0.25(BTC)2·xH2O, which is isoreticular to HKUST-1, was successfully prepared in a direct synthesis using mild reaction conditions. The partial substitution of Cu(2+) by Ru(3+) centers in the paddlewheel structure and the absence of other Ru-containing phases was proven using X-ray absorption spectroscopy.

Stereodivergent Synthesis of 1,3-Syn-Polyol Natural Product for Stereochemical-Based Structure Activity Relationship Studies

Science.gov (United States)

Zheng, Jiamin

The 1,3-syn-diol functionality is very common in many natural products. An important class containing this moiety are the 1,3-syn-polyol/pyranone natural products, which have been isolated from a variety of plant sources, and possess biological activities like plant growth inhibition as well as antifeedant, antifungal, antibacterial, and antitumor properties. The feature of this class is a 6-membered lactone where the lactoe oxygen is part of a 1,3-syn-diol motif. To pursue the 1,3-syn-polyol/pyranone natural products, an iterative hydration of polyene strategy was utilized to provide the 1,3- syn-diol functionality, and asymmetric synthetic strategies were explored to form the requisite stereochemistry. The versatility of the asymmetric approach was demonstrated in the synthesis of eupatorium pyranone and also in an ongoing project aimed at the synthesis of SIA7248. As an outgrowth of our work on the total syntheses of 1,3-syn -polyol natural products inspired a stereo-divergent synthesis of 1,3-syn-polyol natural products and their analogs for stereochemical-based structure-activity relationship (SSAR) studies. To identify the key structural factors important for the anticancer activity of the 1,3-syn-polyol/pyranones, a stereo-divergent 16-member library of pyranone/polyol congeners was designed, synthesized and tested with variations in both stereochemistry and numbers of polyol repeat units. Having access to stereochemical isomers of the biologically active natural products allowed us to design experiments that help illustrate their mechanisms of action.

Synthesis, characterization and structural refinement of polycrystalline uranium substituted zirconolite

International Nuclear Information System (INIS)

Shrivastava, O.P.; Narendra Kumar; Sharma, I.B.

2005-01-01

Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution Zr 4+ cationic sites. This makes them potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr 0.95 U 0.5 Ti 2 O 7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 degC. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (15). The following unit cell parameters have been calculated: a =12.4883(15), b =7.2448(5), c 11.3973(10) and β = 100.615(9)0. The structure was refined to satisfactory completion. The Rp and Rwp are found to be 7.48% and 9.74% respectively. (author)

Remote Stereoinductive Intramolecular Nitrile Oxide Cycloaddition: Asymmetric Total Synthesis and Structure Revision of (-)-11β-Hydroxycurvularin.

Science.gov (United States)

Choe, Hyeonjeong; Pham, Thuy Trang; Lee, Joo Yun; Latif, Muhammad; Park, Haeil; Kang, Young Kee; Lee, Jongkook

2016-03-18

The first total synthesis and structure revision of (-)-11β-hydroxycurvularin (1b), a macrolide possessing a β-hydroxyketone moiety, were accomplished. The β-hydroxyketone moiety in this natural product was introduced by cleavage of the N-O bond in an isoxazoline ring that was formed diastereoselectively in a 1,5-remote stereocontrolled fashion by employing intramolecular nitrile oxide cycloaddition.

Nanoparticles of the superconductor MgB2: structural characterization and in situ study of synthesis kinetics

International Nuclear Information System (INIS)

Cui Chunxiang; Liu Debao; Shen Yutian; Sun Jinbin; Meng Fanbin; Wang Ru; Liu Shuangjin; Greer, A.L.; Chen, S.K.; Glowacki, B.A.

2004-01-01

Single-crystal MgB 2 nanoparticles, with diameters in the range 20-100 nm, have been synthesized in situ in the sample chamber of an X-ray diffractometer. The reaction kinetics are analyzed and related to the atomic-level structure of the particles as observed by high-resolution electron microscopy. Synthesis conditions may have a significant influence on microstructure and superconducting properties

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Directory of Open Access Journals (Sweden)

Nam-Hee Park

2015-07-01

Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

Trends in computerized structural analysis and synthesis; Proceedings of the Symposium, Washington, D.C., October 30-November 1, 1978

Science.gov (United States)

Noor, A. K. (Editor); Mccomb, H. G., Jr.

1978-01-01

The subjects considered are related to future directions of structural applications and potential of new computing systems, advances and trends in data management and engineering software development, advances in applied mathematics and symbolic computing, computer-aided instruction and interactive computer graphics, nonlinear analysis, dynamic analysis and transient response, structural synthesis, structural analysis and design systems, advanced structural applications, supercomputers, numerical analysis, and trends in software systems. Attention is given to the reliability and optimality of the finite element method, computerized symbolic manipulation in structural mechanics, a standard computer graphics subroutine package, and a drag method as a finite element mesh generation scheme.

Synthesis of Copper-Based Transparent Conductive Oxides with Delafossite Structure via Sol-Gel Processing

OpenAIRE

Götzendörfer, Stefan

2011-01-01

Starting off with solubility experiments of possible precursors, the present study reveals the whole development of a sol gel processing route for transparent p type semiconductive thin films with delafossite structure right to the fabrication of functional p-n junctions. The versatile sol formulation could successfully be modified for several oxide compositions, enabling the synthesis of CuAlO2, CuCrO2, CuMnO2, CuFeO2 and more. Although several differences in the sintering behaviour of powde...

Quick synthesis of highly aligned or randomly oriented nanofibrous structures composed of C60 molecules via self-assembly

International Nuclear Information System (INIS)

Kurosu, Shunji; Fukuda, Takahiro; Maekawa, Toru

2013-01-01

Assemblies, which are composed of nanoparticles such as nanofibres, have been intensively studied in recent years. This has particularly been the case in the field of biomedicine, where the aim is to develop efficient methodologies for capturing and separating target biomolecules and cells and/or encouraging bio-chemical reactions, utilizing the extremely high surface area to volume ratio of assemblies. There is an urgent need for the development of a quick synthesis method of forming nanofibrous structures on the surface of biomedical microchips and devices for the investigation of the interactions between biomolecules/cells and the nanostructures. Here, we produce nanofibrous structures composed of C 60 molecules, which are aligned in one direction or randomly oriented, by dissolving C 60 molecules and sulphur in benzene and evaporating a droplet of the solution on a glass substrate under appropriate conditions. The synthesis time is as short as 30 s. Sulphur is extracted and nanofibres are crystallized by leaving them in supercritical carbon dioxide. (paper)

Nanoparticle synthesis of zinc peroxide: structural and morphological characterization for bactericidal applications

International Nuclear Information System (INIS)

Colonia, Roberto; Martinez, Vanessa C.; Solis, Jose L.; Gomez, Monica M.

2013-01-01

Zinc peroxide (ZnO 2 ) nanoparticles were synthesized by sol-gel technique. The chemicals used for the synthesis were zinc acetate di-hydrate (Zn(CH 3 COO) 2. 2H 2 O) and hydrogen peroxide (H 2 O 2 ) at 30 % in an aqueous solution with sonication. The structure of the ZnO 2 nanoparticles was characterized by X-ray diffraction. While the morphology and the cluster size were determined using scanning and transmission electron microscopy. For a preliminary evaluation of the bactericidal properties of the ZnO 2 , the material was exposed to Staphylococcus aureus, Escherichia coli y Bacillus subtili, and the nanoparticles presented good bactericidal properties. (author)

The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis.

Science.gov (United States)

Yang, Hua-feng; Xie, Peng-yang; Yu, Hui-you; Li, Xiao-nian; Wang, Jian-guo

2012-12-28

The structures and catalytic properties of AuPd clusters supported on carbon nanotubes (CNTs) for H(2)O(2) synthesis have been investigated by means of density functional theory calculations. Firstly, the structures of AuPd clusters are strongly influenced by CNTs, in which the bottom layers are mainly composed of Pd and the top layers are a mix of Au and Pd due to the stronger binding of Pd than Au on CNTs. Especially, it is found that O(2) adsorption on the Pd/CNTs interfacial sites is much weaker than that on the only Pd sites, which is in contrast to transition metal oxide (for example TiO(2), Al(2)O(3), CeO(2)) supported metal clusters. Furthermore, Pd ensembles on the interfacial sites have far superior catalytic properties for H(2)O(2) formation than those away from CNT supports due to the changes in electronic structures caused by the CNTs. Therefore, our study provides a physical insight into the enhanced role of carbon supports in H(2)O(2) synthesis over supported AuPd catalysts.

The formation mechanism of a textured ceramic of thermoelectric [Ca2CoO3](0.62)[CoO2] on beta-Co(OH)2 templates through in situ topotactic conversion.

Science.gov (United States)

Itahara, Hiroshi; Seo, Won-Seon; Lee, Sujeong; Nozaki, Hiroshi; Tani, Toshihiko; Koumoto, Kunihito

2005-05-04

We investigated the formation mechanism of thermoelectric [Ca(2)CoO(3)](0.62)[CoO(2)] (CCO) on beta-Co(OH)(2) templates with maintained orientations by identifying the intermediate phases and specifying the relationship between their crystallographic orientations. We mixed beta-Co(OH)(2) templates with the complementary reactant CaCO(3) and prepared a compact by tape casting, with the developed (001) plane of the templates aligned along the casting plane. High-temperature XRD of the compact revealed that beta-Co(OH)(2) decomposed into Co(3)O(4) by 873 K, and Co(3)O(4) reacted with CaO to form CCO by 1193 K via the formation of the newly detected intermediate phase beta-Na(x)()CoO(2)-type Ca(x)()CoO(2) at 913-973 K. Pole figure measurements and SEM and TEM observations revealed that the relationship between the crystallographic planes was (001) beta-Co(OH)(2)//{111} Co(3)O(4)//(001) Ca(x)()CoO(2)//(001) CCO. The crystal structures of the four materials possess the common CoO(2) layer (or similar), which is composed of edge-sharing CoO(6) octahedra, parallel to the planes. The cross-sectional HRTEM analysis of an incompletely reacted specimen showed transient lattice images from Ca(x)()CoO(2) into CCO, in which every other CoO(2) layer of Ca(x)()CoO(2) was preserved. Thus, it was demonstrated that a textured CCO ceramic is produced through a series of in situ topotactic conversion reactions with a preserved CoO(2) layer of its template.

Solid State Structure-Reactivity Studies on Bixbyites, Fluorites and Perovskites Belonging to the Vanadate, Titanate and Cerate Families

Science.gov (United States)

Shafi, Shahid P.

This thesis primarily focuses on the systematic understanding of structure-reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in-situ techniques including powder x-ray diffraction and thermogravimetric-differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure-reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite-type oxide ion conductor Ce1-xInxO2-delta (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO 3-delta perovskites and the subsequent CO2-capture reaction

Templated Atom-Precise Galvanic Synthesis and Structure Elucidation of a [Ag 24 Au(SR) 18 ] − Nanocluster

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2015-11-27

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18]- cluster (SR: thiolate) using a pure [Ag25(SR)18]- cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag25-xAux(SR)18]-, x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)18]- reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level.

Controlled synthesis of Zn0 nanoparticles by bioreduction

International Nuclear Information System (INIS)

Canizal, G.; Schabes-Retchkiman, P.S.; Pal, U.; Liu, Hong Bo; Ascencio, J.A.

2006-01-01

Synthesis of metallic Zn nanoparticles through bio-reduction methods is reported for the first time. The structure, shape and size of the nanoparticles are critically controlled through the pH used in the sample preparation. High resolution electron microscopy was used in order to determine the structure of individual nanoparticles. Formation of quantum dots and the efficiency of ion reduction in the synthesis process are studied through the optical absorption in colloids. The structure and stability of the Zn clusters (up to 4000 atoms) were determined through the calculation of minimum energy configurations using molecular and quantum mechanics approximations and image simulation. The structure of the obtained nanoparticles was preferentially hexagonal, although multiple twinned and fcc-like structures were identified. The size controlled synthesis of small nanoparticles in the quantum-dot range was demonstrated successfully

Crystal Engineering: Synthesis and Structural Analysis of Coordination Polymers with Wavelike Properties

Directory of Open Access Journals (Sweden)

Matasebia T. Munie

2011-10-01

Full Text Available Supramolecular coordination polymers with wavelike structures have been synthesized by self-assembly and their structures analyzed using the sine trigonometric function. Slow evaporation of a methylene chloride-methanol solution of a 1:1 molar mixture of [M(tmhd2], where M = Co or Ni, and quinoxaline; a 1:2:1 molar mixture of [M(acac2], where M = Co or Ni, 2,2,6,6-tetramethyl-3,5-heptadione and quinoxaline; or a 1:2:1 molar mixture of [Co(acac2], dibenzoylmethane, and quinoxaline, yielded the crystalline coordination polymers. In the presence of the nitrogenous base, ligand scrambling occurs yielding the most insoluble product. The synthesis and structures of the following wavelike polymers are reported: trans-[Co(DBM2(qox]n·nH2O (2, trans-[Co(tmhd2(qox]n (3, trans-[Ni(tmhd2(qox]n (4, where DBM− = dibenzoylmethanate, tmhd− = 2,2,6,6-tetramethyl-3,5-heptadionate, and qox = quinoxaline. The wavelike structures are generated by intramolecular steric interactions and crystal packing forces between the chains. Some of the tert-butyl groups show a two-fold disorder. The sine function, φ = A sin 2πx/λ, where φ = distance (Ǻ along the polymer backbone, λ = wavelength (Ǻ, A = amplitude (Ǻ, x = distance (Ǻ along the polymer axis, provides a method to approximate and visualize the polymer structures.

Pressure response of vacancy ordered maghemite (γ-Fe2O3) and high pressure transformed hematite (α-Fe2O3)

International Nuclear Information System (INIS)

Hearne, Giovanni; Pischedda, Vittoria

2012-01-01

Combined XRD and Mössbauer effect spectroscopy studies to high pressures of ∼30 GPa of vacancy ordered maghemite are presented. The vacancy ordered superstructure is robust and remains intact up to the pressure-induced onset transition to hematite at 13–16 GPa. The pressure transformed hematite is shown to be crystallographically textured, unlike the randomised low pressure maghemite phase. This arises out of a pressure or stress instigated topotactic transformation of the cubic-spinel to hexagonal-corundum structure. The textured sample permits us to obtain information on the spin reorientation behavior of the pressure transformed hematite in compression and decompression sequences. Spin reorientation is restricted to ∼15° over wide pressure ranges, attributable to the effect of entrapped vacancies in the high pressure structure. Thus there are structural and magnetic peculiarities specific to pressure transformed hematite not evident in pressurized hematite starting material. These are triggered by the maghemite→hematite transformation. - Graphical abstract: Pressure instigated topotactic transformation of vacancy ordered γ-Fe 2 O 3 →α-Fe 2 O 3 . There is restricted spin (B hf ) reorientation in the new pressure transformed hematite due to entrapped vacancies. The change in direction of V zz signifies a distortion of the FeO 6 octahedral local environment. Highlights: ► Robust vacancy ordered superstructure in maghemite to high pressures. ► Pressure instigated topotactic transformation to hematite and subsequent texture. ► Defect trapping in the pressure transformed hematite. ► Entrapped defects restricts spin reorientation in pressure transformed hematite. ► Contrasting behavior with pressurized hematite starting material.

Synthesis and structure of the unligated carbene of chromium

Energy Technology Data Exchange (ETDEWEB)

Billups, W.E.; Souchan Chang; Hauge, R.H.; Margrave, J.L. (Rice Univ., Houston, TX (United States))

1993-04-14

Complexes with metal-carbon double bonds have found applications as intermediates in many important catalytic reactions including cyclopropanation of alkenes by diazoalkanes, Fischer-Tropsch synthesis, olefin metathesis, Ziegler-Natta polymerization, alkane activation, and in the decomposition of transition metal alkyl complexes. However, complexes with the simplest carbene, CH[sub 2], coordinated to the metal center are relatively rare. In this paper the authors report the synthesis and characterization of the simple unligated carbene of chromium by FTIR matrix isolation spectroscopy. 7 refs., 3 figs., 4 tabs.

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazolines

Directory of Open Access Journals (Sweden)

Richard Hoogenboom

2010-09-01

Full Text Available The synthesis of well-defined polymer architectures is of major importance for the development of complex functional materials. In this contribution, we discuss the synthesis of a range of multifunctional star-shaped tosylates as potential initiators for the living cationic ring-opening polymerization (CROP of 2-oxazolines resulting in star-shaped polymers. The synthesis of the tosylates was performed by esterification of the corresponding alcohols with tosyl chloride. Recrystallization of these tosylate compounds afforded single crystals, and the X-ray crystal structures of di-, tetra- and hexa-tosylates are reported. The use of tetra- and hexa-tosylates, based on (dipentaerythritol as initiators for the CROP of 2-ethyl-2-oxazoline, resulted in very slow initiation and ill-defined polymers, which is most likely caused by steric hindrance in these initiators. As a consequence, a porphyrin-cored tetra-tosylate initiator was prepared, which yielded a well-defined star-shaped poly(2-ethyl-2-oxazoline by CROP as demonstrated by SEC with RI, UV and diode-array detectors, as well as by 1H NMR spectroscopy.

Controlled synthesis of multi-shelled transition metal oxide hollow structures through one-pot solution route

Institute of Scientific and Technical Information of China (English)

Xi Wang; Yi-Jun Yang; Ying Ma; Jian-Nian Yao

2013-01-01

As one type of promising candidates fot environmental and energy-related systems,multi-shelled transition metal oxide hollow structures (MS-TMOHSs) have drawn great scientific and technical interest in the past few years.This article highlights recent advances in one-pot solution synthesis of MS-TMOHSs.We begin it with an overview of synthetic strategies that have been exploited to achieve these peculiar structures.We then focus on one-pot solution approaches in the following four sections:i) soft templates directed growth; ii) Ostwald ripening; iii) controlled etching; and iv) gas bubble assisted growth.After giving a brief discussion on the unique properties and applications of these multi-shelled hollow structures,we conclude this review with the general challenges and the potential future directions of this exciting area of research.

Green synthesis and structural control of metal and mineral nanostructures

DEFF Research Database (Denmark)

Engelbrekt, Christian

of nanoparticle formation which, however, entails the development of new methods. Two approaches to the advancement of solution synthesis of gold nanomaterials for energy technology were exploited, namely the development of techniques to study nanoparticle formation and the synthesis of active, composite...... nanomaterials. In the first approach, time-resolved chronopotentiometry, pH, conductivity and turbidity, and ultraviolet-visible light spectroscopy were employed to follow the green synthesis of gold nanoparticles. Several distinct phases were observed with all techniques providing a broad picture...... of the complex processes. Strong indications of sequential reduction were found and details about ligands and surface immobilized molecules disclosed. This platform is a widely available alternative to traditionally used synchrotron techniques. In the second approach, systematic efforts toward size and shape...

The Synthesis of Peculiar Structure of Springlike Multiwall Carbon Nanofibers/Nanotubes via Mechanothermal Method

Directory of Open Access Journals (Sweden)

Sahebali Manafi

2012-01-01

Full Text Available Mechanothermal (MT method is one of the methods used for large-scale production of carbon nanotubes/nanofibers. The different peculiar morphologies of carbon allotropes are introduced with an extraordinary structure for the first time by MT method. In this paper, the influence of milling time and annealing temperature on the crystallinity and morphology of the synthesized nanopowders was investigated. Surprisingly, in this investigation, we report the synthesis of springlike multiwalled carbon nanofibers (S-MWCNFs by a two-step annealing of milled graphite in an Ar atmosphere. On the other hand, the MT method could be used for the preparation of suitable structures with applications in nanocomposite materials, which is an important task in the era of nanotechnology.

Ligand-protected gold clusters: the structure, synthesis and applications

International Nuclear Information System (INIS)

Pichugina, D A; Kuz'menko, N E; Shestakov, A F

2015-01-01

Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Au n with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au 15 and Au 25 ) and on anchorage to a support surface (Au 25 /SiO 2 , Au 20 /C, Au 10 /FeO x ) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR) n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters M x Au n L m (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR) x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active

Synthesis of CdS hollow/solid nanospheres and their chain-structures by membrane technique

International Nuclear Information System (INIS)

Duan Shumin; Wu Qingsheng; Jia Runping; Liu Xinbo

2008-01-01

CdS hollow/solid nanospheres and their chain-structures were successfully synthesized through supporting liquid membrane (SLM) system with bio-membrane. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy, and photoluminescence (PL) spectroscopy have been used for the characterization of the products. The average diameters of CdS solid/hollow spheres are about 10, 40 nm, respectively. The wall of the hollow spheres is about 5 nm. CdS products are all cubic face-centered structure with the cell constant a = 5.830 A. We also explore the morphology, structure and possible synthesis mechanism. A possible template mechanism has been proposed for the production of the hollow CdS nanocrystals, that is, CdS nanoparticles grow along the non-soakage interface between CHCl3 and reactant solution. During this process, the organic functional groups were crucial to the control of crystal morphologies

Total synthesis of bryostatins: the development of methodology for the atom-economic and stereoselective synthesis of the ring C subunit.

Science.gov (United States)

Trost, Barry M; Frontier, Alison J; Thiel, Oliver R; Yang, Hanbiao; Dong, Guangbin

2011-08-22

Bryostatins, a family of structurally complicated macrolides, exhibit an exceptional range of biological activities. The limited availability and structural complexity of these molecules makes development of an efficient total synthesis particularly important. This article describes our initial efforts towards the total synthesis of bryostatins, in which chemoselective and atom-economical methods for the stereoselective assembly of the ring C subunit were developed. A Pd-catalyzed tandem alkyne-alkyne coupling/6-endo-dig cyclization sequence was explored and successfully pursued in the synthesis of a dihydropyran ring system. Elaboration of this methodology ultimately led to a concise synthesis of the ring C subunit of bryostatins. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gadolinium (III) 2-benzoyl-1,1,3,3-tetracyanopropenide diacetate. Synthesis and crystal structure

Energy Technology Data Exchange (ETDEWEB)

Karpov, Sergey V.; Kayukov, Yakov S.; Grigor' ev, Arthur A. [Department of Chemistry and Pharmaceutics, I.N. Ul' yanov Chuvash State University, Cheboksary (Russian Federation); Tafeenko, Victor A. [Department of Chemistry, Lomonosov Moscow State University (Russian Federation)

2018-02-15

2-Acyl-1,1,3,3-tetracyanopropenides (ATCN) is a stable organic salts, containing the carbonyl group in addition to the tetracyanoallyl (TCA) fragment in the anion. TCA anions are known as bridging ligands with variable denticity with potential application in organic electronics and as a ionic liquids components. In this communication we reporting the synthesis and crystal structure of gadolinium(III) 2-benzoyl-1,1,3,3-tetracyanopropenide diacetate - the first lanthanide ATCN. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Simple synthesis, structure and ab initio study of 1,4-benzodiazepine-2,5-diones

Science.gov (United States)

Jadidi, Khosrow; Aryan, Reza; Mehrdad, Morteza; Lügger, Thomas; Ekkehardt Hahn, F.; Ng, Seik Weng

2004-04-01

A simple procedure for the synthesis of pyrido[2,1-c][1,4] benzodiazepine-6,12-dione ( 1) and 1,4-benzodiazepine-2,5-diones ( 2a- 2d), using microwave irradiation and/or conventional heating is reported. The configuration of 1 was determined by single-crystal X-ray diffraction. A detailed ab initio B3LYP/6-31G* calculation of structural parameters and substituent effects on ring inversion barriers (Δ G#) and also free energy differences (Δ G0) for benzodiazepines are reported.

Solution based approaches for the morphology control of BaTiO3 particulates

Directory of Open Access Journals (Sweden)

Florentina Maxim

2010-09-01

Full Text Available Within the action COST 539 - ELENA our contribution was aimed at studying solution based approaches for the morphology control of BaTiO3 particulates. Initially, our kinetic analysis and systematic structural and morphological studies, demonstrated that during hydrothermal synthesis from layered titanate nanotubes (TiNTS, BaTiO3 forms via two mechanisms depending on the temperature and time. At low temperatures (90°C, “wild” type BaTiO3 dendritic particles with cubic structure were formed through a phase boundary topotactic reaction. At higher temperatures and/or for longer times time, the reaction is controlled by a dissolution precipitation mechanism and “seaweed” type BaTiO3 dendrites are formed. Our results unambiguously elucidated why TiNTs do not routinely act as templates for the formation of 1D BaTiO3.In our subsequent investigations, the effect of additives on the aqueous and hydrothermal synthesis of BaTiO3 was assessed. We reported that although the tested additives influenced the growth of BaTiO3, their behaviour varied; poly(acrylic acid (PAA adsorbed on specific crystallographic faces changing the growth kinetics and inducing the oriented attachment of the particles; poly(vinyl pyrrolidone (PVP, sodium dodecylsulfate (SDS and hydroxypropylmethylcellulose (HPMC act as growth inhibitors rather than crystal habit modifiers; and DFructose appeared to increase the activation energy for nucleation, resulting in small crystals (26 nm. Our work clearly indicates that the synthesis of 1D nanostructures of complex oxides by chemical methods is non trivial.

Enhancing photocatalytic activity by using TiO2-MgO core-shell-structured nanoparticles

International Nuclear Information System (INIS)

Jung, Hyun Suk; Lee, Jung-Kun; Nastasi, Michael; Kim, Jeong-Ryeol; Lee, Sang-Wook; Kim, Jin Young; Park, Jong-Sung; Hong, Kug Sun; Shin, Hyunho

2006-01-01

Hygroscopic Mg(OH) 2 gel was topotactically decomposed on TiO 2 particle surfaces, resulting in highly nanoporous MgO-coated TiO 2 particles. The highly hygroscopic and nanoporous MgO shell absorbed more water molecules and hydroxyl groups from the environment to yield an improved photocatalytic property of the core-shell particles as compared to the uncoated TiO 2 counterpart

Synthesis and structural characterization of amorphous alloys of the Fe-Ni-B type

International Nuclear Information System (INIS)

Cabral P, A.; Jimenez B, J.; Garcia S, I.

2004-01-01

It was prepared the alloy FeNiB for chemical reduction, using four p H values (5, 6, 7 and 7.5). To p H=6 partially oxidized particles were obtained, between 16 and 20%. In the synthesis to other p H values, the obtained particles were highly oxidized (65-90%) according to the X-ray diffraction results, in all the preparations the particles were partially crystallized, with crystal size that varied between 4 and 10 nm. The structure of these particles can be consider that they are formed by a nucleus due to the alloy and an oxide armor recovering it. (Author)

Phase formation of V2O5.xNb2O5 compounds via gels and freeze-dried precursors

International Nuclear Information System (INIS)

Langbein, Hubert; Mayer-Uhma, Tobias

2009-01-01

An X-ray powder diffraction study of the phase formation in the system V 2 O 5 /Nb 2 O 5 is performed. Freeze-dried ammonium vanadate and ammonium oxalato niobate, alkoxide-derived xerogels and a mixture of active oxides are used as precursors to compare the resulting phase composition. Thermal decomposition of the freeze-dried precursor is monitored with DTA/TG and mass spectrometry. In the quasi-binary system V 2 O 5 -Nb 2 O 5 metastable VNbO 5 , V 4 Nb 18 O 55 , VNb 9 O 25 and solid solutions of V 2 O 5 in TT-Nb 2 O 5 as also thermodynamically stable VNb 9 O 25 exist. The thermal decomposition of freeze-dried vanadate-oxalatoniobate solution allows the synthesis of all these phases in a relative simple manner. Structural relationships between an intermediate phase and the product, or, in the case of solid-state reactions, between one of the starting oxide and the product, favour the desired reaction. Therefore, the structure of a former phase influences or directs the structure of the product similar to a topotactic reaction

Synthesis and computer-aided structural investigation of potentially photochromic spirooxazines

International Nuclear Information System (INIS)

Chi, L.

2000-03-01

Quantum mechanical methods, PPP-MO and ZINDO, were used to predict the electronic spectra of the ring-opened forms and ring-closed forms respectively of a series of spirooxazines. Molecular mechanics was used to optimise the molecular geometry and to calculate the molecular final energy (steric energy) using the MM2 force field method. An all-valence-electron quantum mechanical method was employed to calculate the heats of formation using AM1 parameters, and the data were used to provide a measure of the stability of the molecules. This computer-aided structural investigation has provided an enhanced understanding of the spirooxazine system and methods with the potential to predict photochromic behaviour have emerged. The synthesis of a series of heterocyclic analogues of the well-known spironaphthoxazines based on quinolines, coumarin and pyrazolones were attempted. The properties of the compounds obtained were correlated with the results of the calculations. (author)

SIZE OF BOEHMITE NANOPARTICLES BY TEM IMAGES ANALYSIS

Directory of Open Access Journals (Sweden)

Maxime Moreaud

2011-05-01

Full Text Available Transition aluminas, and especially the gamma type, are largely used as catalyst supports in refining and petrochemicals. Most studies focus on properties resulting from material texture and casting (specific surface, porous volume, pore shape and diameter. However, surface properties of alumina should be considered as well, as the catalytic activity is tightly related to the structure of exposed crystalline faces. As γ alumina results from controlled thermal treatment of boehmite γ-AlOOH by a topotactic transformation, the nature of exposed crystalline planes is related to the starting material. Therefore, the synthesis of the oxihydroxide γ-AlOOH, and especially size and shape of these particles, is critical in determining the relevant surface properties. Unlike often aggregated alumina, boehmite nanoparticles can be observed by TEM. Analysis of these TEM images can be performed to estimate the size of the boehmite nanoparticles. Information about morphology of the nanoparticles is obtained by the analysis of the covariance, modeling micrographs by a dilution model.

Design, synthesis, and characterization of new phosphazene related materials, and study the structure property correlations

Science.gov (United States)

Tian, Zhicheng

The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships. Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described. Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing alpha-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in

Synthesis, extraction and electronic structure of Ce@C2n

Science.gov (United States)

Liu, Bing-Bing; Zou, Guang-Tian; Yang, Hai-Bin; Yu, San; Lu, Jin-Shan; Liu, Zi-Yang; Liu, Shu-Ying; Xu, Wen-Guo

1997-11-01

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical+ 4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce @ C2n are investigated. Soot containing Ce@C2n was synthesized in high yield by carbonizing CeO2-containing graphite rods and are back-burning the CeC2-enriched cathode deposit in a DC arc plasma apparatus. Ce@C2n dominated by Ce@C82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C2n(2n = 82, 80, 78, 76) and 35% Ce@C82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C2n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to+ 3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C82 is formally described as Ce+3@C3-82.

Synthesis of Carbon nano structures by plasma discharge; Sintesis de nanoestructuras de carbono por descarga de plasmaa

Energy Technology Data Exchange (ETDEWEB)

Jimenez L, M L

2007-07-01

Due to the great quantity of applications of the carbon nano structures (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, it has seen the necessity to generate new processes of synthesis of this materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither sludges. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arch discharge, in a gas mixture of He-CH{sub 4} with 34% at. Ni/10.32% at.Y like catalyst; at a frequency of 42 kHz and low power (300 W). This method benefits the amass of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the NEC type obtained and by X-ray diffraction analysis and Raman spectroscopy for determining the purity of the samples. The NFC is relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of plasma using the Swan band for determining the temperature. (Author)

Tunable synthesis of copper nanotubes

International Nuclear Information System (INIS)

Kaniukov, E; Yakimchuk, D; Kozlovsky, A; Shlimas, D; Zdorovets, M; Kadyrzhanov, K

2016-01-01

Simple method of tunable synthesis of copper nanotubes based on template synthesis was developed. A comprehensive study of the structural, morphological and electrical characteristics of the obtained nanostructures was carried out. Characterization of structural features was made by methods of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry analysis. Evaluation of wall thickness is made by methods of gas permeability. Electrical conductivity of nanotubes was define in the study of their current-voltage characteristics. The possibility to control of copper nanotubes physical properties by variation of the deposition parameters was shown. (paper)

Structured mesoporous Mn, Fe, and Co oxides: Synthesis, physicochemical, and catalytic properties

Science.gov (United States)

Maerle, A. A.; Karakulina, A. A.; Rodionova, L. I.; Moskovskaya, I. F.; Dobryakova, I. V.; Egorov, A. V.; Romanovskii, B. V.

2014-02-01

Structured mesoporous Mn, Fe, and Co oxides are synthesized using "soft" and "hard" templates; the resulting materials are characterized by XRD, SEM, TEM, BET, and TG. It is shown that in the first case, the oxides have high surface areas of up to 450 m2/g that are preserved after calcination of the material up to 300°C. Even though, the surface area of the oxides prepared by the "hard-template" method does not exceed 100 m2/g; it is, however, thermally stable up to 500°C. Catalytic activity of mesoporous oxides in methanol conversion was found to depend on both the nature of the transition metal and the type of template used in synthesis.

Formation of rod type structures of CaSO4: Ce,P,Dy TLD phosphor using different synthesis routes

International Nuclear Information System (INIS)

Atone, M.S.; Wani, J.A.; Dhoble, S.J.

2011-01-01

Effect of Ce and P co-activation in CaSO 4 : Dy, standard TLD phosphor prepared by different synthesis root techniques and it's structural morphology is reported first time in this paper. We have already reported the sensitization of luminescence in CaSO 4 : Dy with phosphorous (P) and cerium (Ce) ions separately via acid distillation route. In the current investigation, we have doped these impurities (Ce, P, Dy) simultaneously in CaSO 4 host lattice. We have employed a well known chemical precipitation method and modified acid distillation method and have attempted to analyse the surface morphology resulted from these two synthesis routes. Chemical precipitation usually takes place at room temperature and in this way allows the reaction to take place silently. In case of acid distillation method we have reduced the synthesis temperature to 493K which is considerably less than 653K employed in previously reported literature. In case of precipitation method particle shape seems to be spherical and particle size is around one micro range or in the neighbourhood of nanorange. However, in the case of modified acid distillation method particles have shaped in to rod like structures and particle size again falls in the micro range. The photoluminescence intensity of the phosphor prepared by chemical precipitation method is weak as compared to the phosphor prepared by modified acid distillation method. Both the phosphors prepared by different methods have shown characteristic transitions of dopants. The emission spectra of prepared phosphors at 309 nm and 329 nm of Ce 3+ ions overlap well with excitation of Dy 3+ ions. Thermoluminescence (TL) property of both phosphors is again good though certain variation is observed in case of phosphor prepared by modified acid distillation method which shows rod like structure of phosphor. This variation in TL may be attributed to change in surface morphology (formation of rod type structure of particles) of the phosphor. (author)

Using a precursor in lamellar structure for the synthesis of uniform ZnS nanocrystals

KAUST Repository

Xu, Xinjiang

2011-11-12

Uniform ZnS nanocrystals of about 15 nm were prepared through a low temperature hydrothermal approach by treating Zn-PhPO nanosheets with Na 2S aqueous solution. Both the precursor and the final product were studied by the means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photo-luminescent spectrum of the synthesized ZnS nanocrystals showed their good crystalline nature. Based on this study, the precursor structure-controlling effect was discussed, and in addition, the relevant factors possibly affecting the particle formation and the growth possessed were applied in the discussion to interpret the transformation mechanism. Further research showed that both the structure characters of the precursors and the mass transportation which occurred during the synthesis greatly affected the morphology and organization state of the final products. This research may provide some facts on the structure-controlling approaches along with a general method for the preparation of uniform sulfide nanocrystals. © Springer Science+Business Media B.V. 2011.

Aperture synthesis observations of NH3 in OMC-1 - Filamentary structures around Orion-KL

International Nuclear Information System (INIS)

Murata, Yasuhiro; Kawabe, Ryohei; Ishiguro, Masato; Morita, Kohichiro; Kasuga, Takashi

1990-01-01

Aperture synthesis observations of the Orion molecular cloud 1 (OMC-1) have been made in NH 3 (1, 1) and (2, 2) emission at 23.7 GHz, using the Nobeyama Millimeter Array (NMA), and obtained 16 arcsec resolution maps for OMC-1 and 8 arcsec resolution maps for the Orion-KL region. Filamentary structures extending over 0.5 pc from the Orion-KL region to the north and northwest directions were found. These structures are associated with the H2 finger structures and Herbig-Haro objects which are located at the blue-shifted side of the bipolar molecular outflow. The results suggest that these filaments are ambient molecular cloudlets with shocked surfaces caused by the strong stellar wind from the Orion-KL region. The 8 arcsec resolution NH 3 (2, 2) maps show the extended features around the hot core of Orion-KL. These extended features correspond to the rotating disk and shocked shell associated with the bipolar molecular outflow. 37 refs

Synthesis and properties of ZnFe2O4 replica with biological hierarchical structure

International Nuclear Information System (INIS)

Liu, Hongyan; Guo, Yiping; Zhang, Yangyang; Wu, Fen; Liu, Yun; Zhang, Di

2013-01-01

Highlights: • ZFO replica with hierarchical structure was synthesized from butterfly wings. • Biotemplate has a significant impact on the properties of ZFO material. • Our method opens up new avenues for the synthesis of spinel ferrites. -- Abstract: ZnFe 2 O 4 replica with biological hierarchical structure was synthesized from Papilio paris by a sol–gel method followed by calcination. The crystallographic structure and morphology of the obtained samples were characterized by X-ray diffraction, field-emission scanning electron microscope, and transmittance electron microscope. The results showed that the hierarchical structures were retained in the ZFO replica of spinel structure. The magnetic behavior of such novel products was measured by a vibrating sample magnetometer. A superparamagnetism-like behavior was observed due to nanostructuration size effects. In addition, the ZFO replica with “quasi-honeycomb-like structure” showed a much higher specific capacitance of 279.4 F g −1 at 10 mV s −1 in comparison with ZFO powder of 137.3 F g −1 , attributing to the significantly increased surface area. These results demonstrated that ZFO replica is a promising candidate for novel magnetic devices and supercapacitors

Synthesis of TiO 2 nanostructured reservoir with temozolomide: Structural evolution of the occluded drug

Science.gov (United States)

López, T.; Sotelo, J.; Navarrete, J.; Ascencio, J. A.

2006-10-01

Sol-gel synthesized nanostructured TiO 2 matrix were produced with different channel sizes, where drug are immersed, producing a reservoir with Temozolomide (TMZ). This drug is particularly important for the treatment of cancer tumors, which are fundamentally a consequence of the uncontrolled reproduction of human cell. In this way the chemotherapy plays an important role in the treatment of both recurrent and newly diagnosed patients. In the handling of brain tumors TMZ has been discovered as a recent and efficient second generation drug employed in the control of advanced brain gliomas, and it is a welcome addition. Its active component binds to the cancerous DNA cells, thus preventing their disordered growth, destroying them. In this work, we report the synthesis of TiO 2 nanostructured reservoir with TMZ, focusing the effort to the understanding of structural effects on the TMZ configuration by using nuclear magnetic resonance, Raman and IR spectroscopy methods. Our results establish that TMZ molecules are quite sensible to chemical processes and it produces the activation of the molecule, which is followed and understood with help of quantum molecular simulation methods. The study of the molecules allows determining the conditions that produce the activation and chemical selectivity of the molecules, which determines the conditions of synthesis. This information gives parameters for the reservoir structural and chemical optimization.

Improved conductivity of infinite-layer LaNiO2 thin films by metal organic decomposition

Science.gov (United States)

Ikeda, Ai; Manabe, Takaaki; Naito, Michio

2013-12-01

Infinite-layer LaNiO2 thin films were synthesized by metal organic decomposition and subsequent topotactic reduction in hydrogen, and their transport properties were investigated. LaNiO2 is isostructural to SrCuO2, the parent compound of high-Tc Sr0.9La0.1CuO2 with Tc = 44 K, and has 3d9 configuration, which is very rare in oxides but common to high-Tc copper oxides. The bulk synthesis of LaNiO2 is not easy, but we demonstrate in this article that the thin-film synthesis of LaNiO2 is rather easy, thanks to a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Our refined synthesis conditions produced highly conducting films of LaNiO2. The resistivity of the best film is as low as 640 μΩ cm at 295 K and decreases with temperature down to 230 K but it shows a gradual upturn at lower temperatures.

Hybrid composites of monodisperse pi-conjugated rodlike organic compounds and semiconductor quantum particles

DEFF Research Database (Denmark)

Hensel, V.; Godt, A.; Popovitz-Biro, R.

2002-01-01

Composite materials of quantum particles (Q-particles) arranged in layers within crystalline powders of pi-conjugated, rodlike dicarboxylic acids are reported. The synthesis of the composites, either as three-dimensional crystals or as thin films at the air-water interface, comprises a two...... analysis of the solids and grazing incidence X-ray diffraction analysis of the films on water. 2) Topotactic solid/gas reaction of these salts with H2S to convert the metal ions into Q-particles of CdS or PbS embedded in the organic matrix that consists of the acids 6(H) and 8(H). These hybrid materials...

VHDL for logic synthesis

CERN Document Server

Rushton, Andrew

2011-01-01

Many engineers encountering VHDL (very high speed integrated circuits hardware description language) for the first time can feel overwhelmed by it. This book bridges the gap between the VHDL language and the hardware that results from logic synthesis with clear organisation, progressing from the basics of combinational logic, types, and operators; through special structures such as tristate buses, register banks and memories, to advanced themes such as developing your own packages, writing test benches and using the full range of synthesis types. This third edition has been substantially rewritten to include the new VHDL-2008 features that enable synthesis of fixed-point and floating-point hardware. Extensively updated throughout to reflect modern logic synthesis usage, it also contains a complete case study to demonstrate the updated features. Features to this edition include: * a common VHDL subset which will work across a range of different synthesis systems, targeting a very wide range of technologies...

Controlled synthesis of Zn{sup 0} nanoparticles by bioreduction

Energy Technology Data Exchange (ETDEWEB)

Canizal, G. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, Apartado Postal 14-805, C.P. 07730, Mexico D.F. (Mexico); Schabes-Retchkiman, P.S. [Instituto de Fisica, Universidad Nal. Autonoma de Mexico, A.P. 20-364, C.P. 01000, Mexico D.F. (Mexico); Pal, U. [Instituto de Fisica, Universidad Autonoma de Puebla, Apdo. Postal J-48, Puebla, Pue. 72570 (Mexico); Liu, Hong Bo [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, Apartado Postal 14-805, C.P. 07730, Mexico D.F. (Mexico); Ascencio, J.A. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, Apartado Postal 14-805, C.P. 07730, Mexico D.F. (Mexico)]. E-mail: ascencio@imp.mx

2006-06-10

Synthesis of metallic Zn nanoparticles through bio-reduction methods is reported for the first time. The structure, shape and size of the nanoparticles are critically controlled through the pH used in the sample preparation. High resolution electron microscopy was used in order to determine the structure of individual nanoparticles. Formation of quantum dots and the efficiency of ion reduction in the synthesis process are studied through the optical absorption in colloids. The structure and stability of the Zn clusters (up to 4000 atoms) were determined through the calculation of minimum energy configurations using molecular and quantum mechanics approximations and image simulation. The structure of the obtained nanoparticles was preferentially hexagonal, although multiple twinned and fcc-like structures were identified. The size controlled synthesis of small nanoparticles in the quantum-dot range was demonstrated successfully.

Epothilones as lead structures for the synthesis-based discovery of new chemotypes for microtubule stabilization.

Science.gov (United States)

Feyen, Fabian; Cachoux, Frédéric; Gertsch, Jürg; Wartmann, Markus; Altmann, Karl-Heinz

2008-01-01

Epothilones are macrocyclic bacterial natural products with potent microtubule-stabilizing and antiproliferative activity. They have served as successful lead structures for the development of several clinical candidates for anticancer therapy. However, the structural diversity of this group of clinical compounds is rather limited, as their structures show little divergence from the original natural product leads. Our own research has explored the question of whether epothilones can serve as a basis for the development of new structural scaffolds, or chemotypes, for microtubule stabilization that might serve as a basis for the discovery of new generations of anticancer drugs. We have elaborated a series of epothilone-derived macrolactones whose overall structural features significantly deviate from those of the natural epothilone scaffold and thus define new structural families of microtubule-stabilizing agents. Key elements of our hypermodification strategy are the change of the natural epoxide geometry from cis to trans, the incorporation of a conformationally constrained side chain, the removal of the C3-hydroxyl group, and the replacement of C12 with nitrogen. So far, this approach has yielded analogs 30 and 40 that are the most advanced, the most rigorously modified, structures, both of which are potent antiproliferative agents with low nanomolar activity against several human cancer cell lines in vitro. The synthesis was achieved through a macrolactone-based strategy or a high-yielding RCM reaction. The 12-aza-epothilone ("azathilone" 40) may be considered a "non-natural" natural product that still retains most of the overall structural characteristics of a true natural product but is structurally unique, because it lies outside of the general scope of Nature's biosynthetic machinery for polyketide synthesis. Like natural epothilones, both 30 and 40 promote tubulin polymerization in vitro and at the cellular level induce cell cycle arrest in mitosis. These

Synthesis of hydroxyapatite and structural refinement by X-ray diffraction

International Nuclear Information System (INIS)

Araujo, Jorge Correa de

2007-01-01

A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effects with an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals. (author)

Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

Energy Technology Data Exchange (ETDEWEB)

Arslan, Ilke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dixon, David A. [Univ. of Alabama, Tuscaloosa, AL (United States); Gates, Bruce C. [Univ. of California, Davis, CA (United States); Katz, Alexander [Univ. of California, Berkeley, CA (United States)

2015-09-30

To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures.

Science.gov (United States)

Bigdeli, Fahime; Ghasempour, Hosein; Azhdari Tehrani, Alireza; Morsali, Ali; Hosseini-Monfared, Hassan

2017-07-01

A 3D, porous Zn(II)-based metal-organic framework {[Zn 2 (oba) 2 (4-bpmn)]·(DMF) 1.5 } n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H 2 oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn 2 (oba) 2 (4-bpmn)] (TMU-21) and {[Zn 2 (oba) 2 (4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

Pressure response of vacancy ordered maghemite ({gamma}-Fe{sub 2}O{sub 3}) and high pressure transformed hematite ({alpha}-Fe{sub 2}O{sub 3})

Energy Technology Data Exchange (ETDEWEB)

Hearne, Giovanni, E-mail: grhearne@uj.ac.za [Department of Physics, University of Johannesburg, PO Box 524, Auckland Park, 2006 Johannesburg (South Africa); Pischedda, Vittoria, E-mail: Vittoria.Pischedda@univ-lyon1.fr [Laboratoire de Physique de la Matiere Condensee et Nanostructures, University Lyon 1 and CNRS, 69622 Villeurbanne Cedex (France)

2012-03-15

Combined XRD and Moessbauer effect spectroscopy studies to high pressures of {approx}30 GPa of vacancy ordered maghemite are presented. The vacancy ordered superstructure is robust and remains intact up to the pressure-induced onset transition to hematite at 13-16 GPa. The pressure transformed hematite is shown to be crystallographically textured, unlike the randomised low pressure maghemite phase. This arises out of a pressure or stress instigated topotactic transformation of the cubic-spinel to hexagonal-corundum structure. The textured sample permits us to obtain information on the spin reorientation behavior of the pressure transformed hematite in compression and decompression sequences. Spin reorientation is restricted to {approx}15 Degree-Sign over wide pressure ranges, attributable to the effect of entrapped vacancies in the high pressure structure. Thus there are structural and magnetic peculiarities specific to pressure transformed hematite not evident in pressurized hematite starting material. These are triggered by the maghemite{yields}hematite transformation. - Graphical abstract: Pressure instigated topotactic transformation of vacancy ordered {gamma}-Fe{sub 2}O{sub 3}{yields}{alpha}-Fe{sub 2}O{sub 3}. There is restricted spin (B{sub hf}) reorientation in the new pressure transformed hematite due to entrapped vacancies. The change in direction of V{sub zz} signifies a distortion of the FeO{sub 6} octahedral local environment. Highlights: Black-Right-Pointing-Pointer Robust vacancy ordered superstructure in maghemite to high pressures. Black-Right-Pointing-Pointer Pressure instigated topotactic transformation to hematite and subsequent texture. Black-Right-Pointing-Pointer Defect trapping in the pressure transformed hematite. Black-Right-Pointing-Pointer Entrapped defects restricts spin reorientation in pressure transformed hematite. Black-Right-Pointing-Pointer Contrasting behavior with pressurized hematite starting material.

Two-dimensional tantalum disulfide: controlling structure and properties via synthesis

Science.gov (United States)

Zhao, Rui; Grisafe, Benjamin; Krishna Ghosh, Ram; Holoviak, Stephen; Wang, Baoming; Wang, Ke; Briggs, Natalie; Haque, Aman; Datta, Suman; Robinson, Joshua

2018-04-01

Tantalum disulfide (TaS2) is a transition metal dichalcogenide (TMD) that exhibits phase transition induced electronic property modulation at low temperature. However, the appropriate phase must be grown to enable the semiconductor/metal transition that is of interest for next generation electronic applications. In this work, we demonstrate direct and controllable synthesis of ultra-thin 1T-TaS2 and 2H-TaS2 on a variety of substrates (sapphire, SiO2/Si, and graphene) via powder vapor deposition. The synthesis process leads to single crystal domains ranging from 20 to 200 nm thick and 1-10 µm on a side. The TaS2 phase (1T or 2H) is controlled by synthesis temperature, which subsequently is shown to control the electronic properties. Furthermore, this work constitutes the first demonstration of a metal-insulator phase transition in directly synthesized 1T-TaS2 films and domains by electronic means.

Growth and structure of carbide nanorods

International Nuclear Information System (INIS)

Lieber, C.M.; Wong, E.W.; Dai, H.; Maynor, B.W.; Burns, L.D.

1996-01-01

Recent research on the growth and structure of carbide nanorods is reviewed. Carbide nanorods have been prepared by reacting carbon nanotubes with volatile transition metal and main group oxides and halides. Using this approach it has been possible to obtain solid carbide nanorods of TiC, SiC, NbC, Fe 3 C, and BC x having diameters between 2 and 30 nm and lengths up to 20 microm. Structural studies of single crystal TiC nanorods obtained through reactions of TiO with carbon nanotubes show that the nanorods grow along both [110] and [111] directions, and that the rods can exhibit either smooth or saw-tooth morphologies. Crystalline SiC nanorods have been produced from reactions of carbon nanotubes with SiO and Si-iodine reactants. The preferred growth direction of these nanorods is [111], although at low reaction temperatures rods with [100] growth axes are also observed. The growth mechanisms leading to these novel nanomaterials have also been addressed. Temperature dependent growth studies of TiC nanorods produced using a Ti-iodine reactant have provided definitive proof for a template or topotactic growth mechanism, and furthermore, have yielded new TiC nanotube materials. Investigations of the growth of SiC nanorods show that in some cases a catalytic mechanism may also be operable. Future research directions and applications of these new carbide nanorod materials are discussed

Synthesis and Crystal Structures of Ni(II)/(III) and Zn(II) Complexes with Schiff Base Ligands

International Nuclear Information System (INIS)

Koo, Bon Kweon

2013-01-01

Coordination polymers are of great interest due to their intriguing structural motifs and potential applications in optical, electronic, magnetic, and porous materials. The most commonly used strategy for designing such materials relies on the utilization of multidentate N- or Odonor ligands which have the capacity to bridge between metal centers to form polymeric structures. The Schiff bases with N,O,S donor atoms are an useful source as they are readily available and easily form stable complexes with most transition metal ions. Schiff bases are also important intermediates in synthesis of some bioactive compounds and are potent anti-bacterial, anti-fungal, anticancer and antiviral compounds. In this work, the Schiff bases, Hapb and Hbpb, derived from 2-acetylpyridene or 2-benzoylpyridine and benzhydrazide were taken as trifunctional (N,N,O) monobasic ligand (Scheme 1). This ligand is of important because the π-delocalization of charge and the configurational flexibility of their molecular chain can give rise to a great variety of coordination modes. Although many metal.Schiff base complexes have been reported, the 1D, 2D, and 3D networks of coordination polymers linked through the bridging of ligands such as dicyanamide, N(CN) 2 - as coligand have been little published. In the process of working to extend the dimensionality of the metal-Schiff base complexes using benzilic acid as a bridging ligand, we obtained three simple metal (II)/(III) complexes of acetylpyridine/2-benzoyl pyridine based benzhydrazide ligand. Therefore, we report here the synthesis and crystal structures of the complexes

Synthesis of arborescent model polymer structures by living carbocationic polymerization for structure-property studies

Science.gov (United States)

Dos Santos Freire, Lucas

Polyisobutylene is fully saturated, therefore exhibits outstanding chemical, oxidative and thermal stability,1 which makes it ideally suitable as a model to study mechanical and viscoelastic properties of elastomers, and to correlate properties with structure. The main objective of this dissertation was to develop a fundamental understanding of the mechanism of the synthesis of arborescent (hyperbranched) polyisobutylene (arbPIB) by inimer-type (initiator-monomer) living carbocationic polymerization. The strategy for the effective synthesis of arbPIBs consists of copolymerizing the 4-(2-methoxyisopropyl)styrene (IUPAC name: p-vinylcumyl methyl ether) (IB) via controlled/living carbocationic polymerization using TiCl4 coinitiator. In situ FTIR monitoring showed that the self-condensing vinyl polymerization (SCVP) of MeOIM is possible, and that when copolymerizing MeOIM and IB, a nearly alternating structure and multiple end groups are obtained. arbPIB was synthesized and the repeatability of the polymerization was demonstrated. It was found that higher branching was obtained with increasing [MeOIM] and that branching did not further increase if additional IB was added after the MeOIM had reacted completely. No evident changes were observed when switching solvents from Hx/MeCl to a MeCHx/MeCl mixture. Branching parameters showed that arbPIBs have a behavior between polydisperse stars and polycondensates with the number of branches increasing linearly with molecular weight. Novel arbPIB-based block copolymers (TPEs) were synthesized and it was found that copolymers with low Tg short end blocks and less than 5 mol% of a second monomer exhibit thermoplastic elastomeric properties. The materials were strongly reinforced when compounded with carbon black. arbPIB-b-PS are prospective biomaterials and the establishment of reliable methods for evaluating their short and long term properties is a subject of great importance. A dynamic fatigue testing methodology was developed

Synthesis and characterization of MoO3 films by acid hydrolysis of K2Mo4O13

International Nuclear Information System (INIS)

Hernan, L.; Morales, J.

1989-01-01

The behaviour of K 2 Mo 4 O 13 heated under reflux in an acid medium has been studied. A metastable polymorphic MoO 3 phase crystallizing in the hexagonal system was obtained. Lengthy treatment led to the formation of orthorhombic MoO 3 with the (010) planes perfectly oriented parallel to the substrate. SEM images do not support a topotactic mechanism for the successive transformations. The reactions involved probably take place through the polymerization of discrete units formed in the bulk solution

Structural characterization of birnessite: influence of the way of synthesis; Caracterisation structurale de la birnessite: influence du protocole de synthese

Energy Technology Data Exchange (ETDEWEB)

Gaillot, A.C.

2002-01-15

Birnessite is a lamellar manganese oxide whose layers are built up of edge sharing MnO{sub 6} octahedra. The presence of hetero-valent Mn cations and/or of vacant sites in these layers leads to a charge deficit compensated for by the presence of hydrated cations in the interlayer space. Because of their high specific area and of their strong oxidative character, these ubiquitous manganese oxides play a fundamental role in the fate of organic and metallic pollutants in the environment, but our imperfect knowledge of their structure limits the understanding and the modeling of this impact. This study aimed at classifying all different kinds of birnessite obtained using existing synthesis protocols according to two relevant criteria: layer symmetry and layer stacking mode, and at determining the structure of several essential varieties using X-ray and electron diffraction. Layers of hydrothermal birnessite contain vacant sites and, as a result, possess an hexagonal symmetry. Their stacking mode is 3R. In high-temperature birnessites, adjacent layers have an opposite orientation, which results in a two-layer polytype. The symmetry of these layers, linked to the origin of the layer charge deficit, depends on the temperature of synthesis. At 800 C the presence of vacant sites results in an hexagonal symmetry (2H polytype). At 1000 C, the layer charge deficit originates from the presence of Mn{sup 3+} cations in the layer lowering the layer symmetry (2O polytype). A variety of chemical and structural heterogeneities was also described in these samples, along with the occurrence of a new type of structural disorder. Finally we proved both the fundamental link between the origin of the layer charge and the layer symmetry, and the influence of physico-chemical parameters during synthesis (temperature, average manganese oxidation degree, nature of the interlayer cation) on the structure of the obtained compound. The chemical and thermal stabilities of these birnessites are

Epitope-Targeting of Tertiary Protein Structure Enables Target-Guided Synthesis of a Potent in Cell Inhibitor of Botulinum Neurotoxin**

OpenAIRE

Farrow, Blake; Wong, Michelle; Malette, Jacquie; Lai, Bert; Deyle, Kaycie M.; Das, Samir; Nag, Arundhati; Agnew, Heather D.; Heath, James R.

2015-01-01

Botulinum neurotoxin (BoNT) serotype A is the most lethal known toxin and has an occluded structure, which prevents direct inhibition of its active site before it enters the cytosol. Target-guided synthesis by in situ click chemistry is combined with synthetic epitope targeting to exploit the tertiary structure of the BoNT protein as a landscape for assembling a competitive inhibitor. A substrate-mimicking peptide macrocycle is used as a direct inhibitor of BoNT. An epitope-targeting in situ ...

Synthesis of derivatives of tetronic acid and pulvinic acid. Total synthesis of norbadione A

International Nuclear Information System (INIS)

Mallinger, A.

2008-11-01

When vegetables like mushrooms are contaminated by radioactive caesium 137, this radioactive caesium is associated to norbadione A, a natural pigment present in two mushroom species and which can be used as a caesium decorporation agent or maybe as protection agent against ionizing radiations. Within this perspective, this research report describes the biosynthesis and the structure and properties of the norbadione A and of pulvinic acids (physicochemical properties, anti-oxidizing properties). Then, it presents the various tetronic acids (3-acyl-, 3-alkyl-, 3-alkoxy-, 3-aryl-tetronic acids and non 3-substituted tetronic acids), their synthesis path as they are described in the literature, and presents a new synthesis approach using a tandem reaction (with different esters or hydroxy esters) and the synthesis of tetronic acids. The author also proposes a new synthesis way for methyl pulvinates, and finally reports the work on the development of a total synthesis of the norbadione A

Sustainable processes synthesis for renewable resources

International Nuclear Information System (INIS)

Halasz, L.; Povoden, G.; Narodoslawsky, M.

2005-01-01

Renewable resources pose special challenges to process synthesis. Due to decentral raw material generation, usually low transport densities and the perishable character of most renewable raw materials in combination with their time dependent availability, logistical questions as well as adaptation to regional agricultural structures are necessary. This calls for synthesis of structures not only of single processes but of the whole value chain attached to the utilisation of a certain resource. As most of the innovative technologies proposed to build on a renewable raw material base face stiff economic competition from fossil based processes, economic optimality of the value chain is crucial to their implementation. On top of this widening of the process definition for synthesis, many processes on the base of renewable resources apply technologies (like membrane separations, chromatographic purification steps, etc.) for which the heuristic knowledge is still slim. This reduces the choice of methods for process synthesis, mainly to methods based on combinatorial principles. The paper investigates applicability as well as impact on technology development of process synthesis for renewable raw material utilisation. It takes logistic considerations into account and applies process synthesis to the case study of the green biorefinery concept. The results show the great potential of process synthesis for technology development of renewable resource utilisation. Applied early in the development phase, it can point towards the most promising utilisation pathways, thus guiding the engineering work. On top of that, and even more important, it can help avoid costly development flops as it also clearly indicates 'blind alleys' that have to be avoided

Raman scattering in La1-xSrxFeO3-δ thin films: annealing-induced reduction and phase transformation

Science.gov (United States)

Islam, Mohammad A.; Xie, Yujun; Scafetta, Mark D.; May, Steven J.; Spanier, Jonathan E.

2015-04-01

Raman scattering in thin film La0.2Sr0.8FeO3-δ on MgO(0 0 1) collected at 300 K after different stages of annealing at selected temperatures T (300 K topotactic transformation of the crystal structure from that of the rhombohedral ABO3 perovskites to that of Brownmillerite-like structure consisting of octahedrally and tetrahedrally coordinated Fe atoms.

Structure, reactivity and synthesis of piramidines and their derivates (dihidroperimidines and perimidinones); Estructura, reactividad y sintesis de perimidinas y de sus derivados (dihidroperimidinas y perimifinonas)

Energy Technology Data Exchange (ETDEWEB)

Claramunt, R.M.; Dotor, J.; Elguero, J. [Departamento de Quimica Organica, Facultad de Ciencias, UNED, Madrid (Spain)

1995-12-01

This review reports 346 references dealing with structure, reactivity and synthesis of pyrimidines and their derivatives (mainly 2,3-dihidroperimidines, 2-perimidinones and perimidinium salts). Special emphasis has been made on spectroscopy and structural properties as well as on reactivity. 346 refs.

Structure and synthesis of a new library of N,N-Bis-[1,2,4]triazol-1-ylmethyl-amino compounds

Czech Academy of Sciences Publication Activity Database

Al Bay, H.; Touzani, R.; Taleb, M.; Benchat, N.-e.; El Bali, B.; Dušek, Michal; Fejfarová, Karla; El Kadiri, S.

2010-01-01

Roč. 40, č. 18 (2010), s. 2767-2779 ISSN 0039-7911 Grant - others:AV ČR(CZ) AP0701 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : amines * crystal structure * chemical synthesis Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.937, year: 2010

Facile Synthesis of Yolk/Core-Shell Structured TS-1@Mesosilica Composites for Enhanced Hydroxylation of Phenol

KAUST Repository

Zou, Houbing

2015-12-14

© 2015 by the authors. In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, while the yolk-shell TS-1@mesosilica composite was prepared using a resorcinol-formaldehyde resin (RF) middle-layer as the sacrificial template. The obtained materials were characterized by X-ray diffraction (XRD), N2 sorption, Fourier transform infrared spectoscopy (FT-IR) UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results showed that these samples possessed highly uniform yolk/core-shell structures, high surface area (560–700 m2 g−1) and hierarchical pore structures from oriented mesochannels to zeolite micropores. Importantly, owing to their unique structural properties, these composites exhibited enhanced activity, and also selectivity in the phenol hydroxylation reaction.

Synthesis and crystal structure of the quaternary compound AgFe{sub 2}GaTe{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Delgado, Gerzon E., E-mail: gerzon@ula.ve [Laboratorio de Cristalografía, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101 (Venezuela, Bolivarian Republic of); Quintero, Eugenio; Tovar, Rafael; Grima-Gallardo, Pedro; Quintero, Miguel [Centro de Estudio de Semiconductores, Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101 (Venezuela, Bolivarian Republic of)

2014-11-15

Highlights: • New quaternary compound. • Synthesis from solid state reaction. • Crystal structure. • Rietveld refinement. - Abstract: The crystal structure of the quaternary compound AgFe{sub 2}GaTe{sub 4}, belonging to the system I–II{sub 2}–III–VI{sub 4}, was characterized by Rietveld refinement using X-ray powder diffraction data. The powder pattern was composed by 84.5% of the principal phase AgFe{sub 2}GaTe{sub 4} and 15.5% of the secondary phase FeTe. This material crystallizes with stannite structure in the tetragonal space group I-42m (N° 121), Z = 2, unit cell parameters a = 6.3409(2) Å, c = 12.0233(4) Å, V = 483.42(3) Å{sup 3}, and is isostructural with CuFe{sub 2}InSe{sub 4}.

Robust control synthesis for uncertain dynamical systems

Science.gov (United States)

Byun, Kuk-Whan; Wie, Bong; Sunkel, John

1989-01-01

This paper presents robust control synthesis techniques for uncertain dynamical systems subject to structured parameter perturbation. Both QFT (quantitative feedback theory) and H-infinity control synthesis techniques are investigated. Although most H-infinity-related control techniques are not concerned with the structured parameter perturbation, a new way of incorporating the parameter uncertainty in the robust H-infinity control design is presented. A generic model of uncertain dynamical systems is used to illustrate the design methodologies investigated in this paper. It is shown that, for a certain noncolocated structural control problem, use of both techniques results in nonminimum phase compensation.

Synthesis of magnesium- and manganese-doped hydroxyapatite structures assisted by the simultaneous incorporation of strontium

Energy Technology Data Exchange (ETDEWEB)

Moreira, Mirna Pereira [Laboratório de Biomateriais, P" 2CEM/UFS, Av. Marechal Rondon, s/n, São Cristóvão 49100-000, Sergipe (Brazil); Dulce de Almeida Soares, Gloria [Dep. de Eng. Metal. e de Materiais, COPPE/UFRJ, CP 68505, Rio de Janeiro 21941-972 (Brazil); Dentzer, Joseph; Anselme, Karine [Institut de Science des Matériaux de Mulhouse (IS2M), CNRS UMR7361, Université de Haute-Alsace, 15, rue Jean Starcky, BP 2488, 68057 Mulhouse (France); Sena, Lídia Ágata de; Kuznetsov, Alexei [Divisão de Metrologia de Materiais, Inmetro, Av. N. Sra. das Graças, 50, Duque de Caxias 25250-020, Rio de Janeiro (Brazil); Santos, Euler Araujo dos, E-mail: euler@ufs.br [Laboratório de Biomateriais, P" 2CEM/UFS, Av. Marechal Rondon, s/n, São Cristóvão 49100-000, Sergipe (Brazil)

2016-04-01

Samples of crystalline hydroxyapatite (HA) with and without the addition of individual Mg{sup 2+}, Mn{sup 2+} and Sr{sup 2+} ions and samples with the addition of all three ions simultaneously were prepared using the precipitation method in an aqueous medium. Chemical, structural, spectroscopic and thermophysical analyses of the synthesized samples were conducted. The obtained results indicate that Sr{sup 2+} ions were easily incorporated into the HA crystal structure, whereas it was difficult to incorporate Mg{sup 2+} and Mn{sup 2+} ions into the HA lattice when these ions were individually introduced into the samples. The synthesis of HA with Mg{sup 2+} or Mn{sup 2+} ions is characterized by the formation of HA with a low concentration of doping elements that is outweighed by the amount of these atoms present in less biocompatible phases that formed simultaneously. However, the incorporation of Sr{sup 2+} along with Mg{sup 2+} and Mn{sup 2+} ions into the samples allowed for the synthesis of HA with considerably higher concentrations of Mg{sup 2+} and Mn{sup 2+} in the crystal lattice. - Graphical abstract: Sr{sup 2+} ions were easily incorporated into the HA lattice, whereas Mg{sup 2+} and Mn{sup 2+} ions were hardly retained in the HA structure after heating to 1000 °C when they were individually incorporated in the samples. Nevertheless, co-substitution with Sr{sup 2+} ions allowed for better fixation of the Mg{sup 2+} and Mn{sup 2+} ions into the HA lattice. - Highlights: • Mg{sup 2+} and Mn{sup 2+} ions have a great difficulty being stabilized in the apatite lattice. • Sr{sup 2+} ions can stabilize Mg{sup 2+} and Mn{sup 2+} in the hydroxyapatite structure. • Except for Mn{sup 2+}, Sr{sup 2+} and Mg{sup 2+} obstruct the release of CO{sub 2}.

Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

Energy Technology Data Exchange (ETDEWEB)

Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D., E-mail: jdfv2009@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Grupo de Ressonância Magnética Nuclear e Química Medicinal

2017-07-01

This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

International Nuclear Information System (INIS)

Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D.

2017-01-01

This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

Polymorphism of the iron doped strontium aluminate SrAl1.5Fe0.5O4

International Nuclear Information System (INIS)

Desmoulins, H.; Malo, S.; Boudin, S.; Caignaert, V.; Hervieu, M.

2009-01-01

The partial substitution of Al by Fe atoms in SrAl 2 O 4 allowed to stabilize four stuffed tridymite derivative structures SrAl 1.5 Fe 0.5 O 4 . The different phases have been characterized by TEM and XRPD techniques. Two are isotypes of those observed for the undoped oxides, namely the hexagonal phase with √(3)Ax√(3)AxC (with A and C being the tridymite unit cell parameters) and space group P6 3 and the monoclinic one with Ax√(3)AxC, β∼93 o and space group P2 1 , with a synthesis temperature lower than the one required for SrAl 2 O 4 . By annealing, two original phases, denoted O 1 and O 2 , are obtained; they are metrically similar (3Ax√(3)AxC and β∼90 o ) and only differ by their space groups. The TEM study showed that the transitions between the different phases follow topotactic mechanisms, through the formation of twinning boundaries, antiphase boundaries and planar defects. The annealed sample exhibits a mesomorph state and a reversible transition from this semi-ordered state to a crystalline phase. This dynamic transition takes place over a very wide temperature range from 620 to 1120 deg. C. The reversibility of the transition has been studied by DSC measurements. The crystallization energy of the orthorhombic phases is of the order of 10 J/g, at T∼622 deg. C as T decreases. The variation of the peak height observed as the annealing temperature increases is explained by the complex microstructures, which create an ill-defined energy barrier. Structural models related to the stuffed tridymite derivative structures are proposed for the new forms of the ferri-aluminate. - Graphical abstract: Four tridymite derivative structures SrAl 1.5 Fe 0.5 O 4 have been characterized. Two phases are isotypes of those observed for SrAl 2 O 4 . Two 'orthorhombic' original phases are characterized by superstructures. The transitions between the different phases follow topotactic mechanisms. The transition LT→HT takes place from 620 to 1120 deg. C, explained

Methodology in structural determination and synthesis of insect pheromone

Directory of Open Access Journals (Sweden)

Guo-Qiang Lin

1991-01-01

Full Text Available By means of ethereal washing of insect pheromone glands of female moths, GC-MS detection along with microchemical reactions and electroantennogram (EAG survey, six economically important insect species were targeted for pheromone identification. The discovery of a natural pheromone inhibitor, chemo-selectivity and species isolation by pheromone will be described. The modified triple bond migration and triethylamine liganded vinyl cuprate were applied for achiral pheromone synthesis in double bond formation. Some optically active pheromones and their stereoisomers were synthesized through chiral pool or asymmetric synthesis. Some examples of chiral recognition of insects towards their chiral pheromones will be discussed. A CaH2 and silica gel catalyzed Sharpless Expoxidation Reaction was found in shortening the reaction time.

Low-temperature synthesis and structural properties of ferroelectric K 3WO 3F 3 elpasolite

Science.gov (United States)

Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.

2010-06-01

Low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO 3F 3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3) Å, b = 8.6808(5) Å, c = 6.1581(3) Å, β = 135.124(3) Å, V = 329.46(3) Å 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A 2BMO 3F 3 oxyfluorides is discussed.

Hydrothermal synthesis and crystal structure of CsFe23(HPO4)2(PO4)(H2O)

International Nuclear Information System (INIS)

Anisimova, N.Yu.; Ilyukhin, A.B.; Chudinova, N.N.; Serafin, M.

2001-01-01

The double acid iron-cesium orthophosphate CsFe 2 3 (HPO 4 ) 2 (PO 4 )(H 2 O) was prepared by hydrothermal synthesis (from the Fe 2 O 3 , Cs 2 CO 3 and H 3 PO 4 mixture at 290 Deg C during 1 h following by cooling to 25 Deg C). Its crystal structure (a = 5.021(3), b = 15.80(1), c = 13.646(8), β 94.49(4) Deg, sp. gr. P2 1 /n, Z = 4) was analyzed by X-ray diffraction. The structure is formed by the orthophosphate tetrahedrons and the FeO 6 octahedrons, the water molecule is coordinated by the iron atom [ru

6-Pyruvoyltetrahydropterin synthase orthologs of either a single or dual domain structure are responsible for tetrahydrobiopterin synthesis in bacteria.

Science.gov (United States)

Kong, Jin Sun; Kang, Ji-Youn; Kim, Hye Lim; Kwon, O-Seob; Lee, Kon Ho; Park, Young Shik

2006-09-04

6-Pyruvoyltetrahydropterin synthase (PTPS) catalyzes the second step of tetrahydrobiopterin (BH4) synthesis. We previously identified PTPS orthologs (bPTPS-Is) in bacteria which do not produce BH4. In this study we disrupted the gene encoding bPTPS-I in Synechococcus sp. PCC 7942, which produces BH4-glucoside. The mutant was normal in BH4-glucoside production, demonstrating that bPTPS-I does not participate in BH4 synthesis in vivo and bringing us a new PTPS ortholog (bPTPS-II) of a bimodular polypeptide. The recombinant Synechococcus bPTPS-II was assayed in vitro to show PTPS activity higher than human enzyme. Further computational analysis revealed the presence of mono and bimodular bPTPS-II orthologs mostly in green sulfur bacteria and cyanobacteria, respectively, which are well known for BH4-glycoside production. In summary we found new bacterial PTPS orthologs, having either a single or dual domain structure and being responsible for BH4 synthesis in vivo, thereby disclosing all the bacterial PTPS homologs.

Combinatorial Synthesis of Structurally Diverse Triazole-Bridged Flavonoid Dimers and Trimers

Directory of Open Access Journals (Sweden)

Tze Han Sum

2016-09-01

Full Text Available Flavonoids are a large family of compounds associated with a broad range of biologically useful properties. In recent years, synthetic compounds that contain two flavonoid units linked together have attracted attention in drug discovery and development projects. Numerous flavonoid dimer systems, incorporating a range of monomers attached via different linkers, have been reported to exhibit interesting bioactivities. From a medicinal chemistry perspective, the 1,2,3-triazole ring system has been identified as a particularly attractive linker moiety in dimeric derivatives (owing to several favourable attributes including proven biological relevance and metabolic stability and triazole-bridged flavonoid dimers possessing anticancer and antimalarial activities have recently been reported. However, there are relatively few examples of libraries of triazole-bridged flavonoid dimers and the diversity of flavonoid subunits present within these is typically limited. Thus, this compound type arguably remains underexplored within drug discovery. Herein, we report a modular strategy for the synthesis of novel and biologically interesting triazole-bridged flavonoid heterodimers and also very rare heterotrimers from readily available starting materials. Application of this strategy has enabled step-efficient and systematic access to a library of structurally diverse compounds of this sort, with a variety of monomer units belonging to six different structural subclasses of flavonoid successfully incorporated.

Synthesis, structure-activity relationship, and pharmacological profile of analogs of the ASIC-3 inhibitor A-317567.

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Kuduk, Scott D; Di Marco, Christina N; Bodmer-Narkevitch, Vera; Cook, Sean P; Cato, Matthew J; Jovanovska, Aneta; Urban, Mark O; Leitl, Michael; Sain, Nova; Liang, Annie; Spencer, Robert H; Kane, Stefanie A; Hartman, George D; Bilodeau, Mark T

2010-01-20

The synthesis, structure-activity relationship (SAR), and pharmacological evaluation of analogs of the acid-sensing ion channel (ASIC) inhibitor A-317567 are reported. It was found that the compound with an acetylenic linkage was the most potent ASIC-3 channel blocker. This compound reversed mechanical hypersensitivity in the rat iodoacetate model of osteoarthritis pain, although sedation was noted. Sedation was also observed in ASIC-3 knockout mice, questioning whether sedation and antinociception are mediated via a non-ASIC-3 specific mechanism.

Synthesis and structure of nanomaterials in the system K2O-Nb2O5-SiO2

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Georgi Chernev

2009-06-01

Full Text Available The aim of the present work is synthesis of ferroelectric nanomaterials, in the K2O-Nb2O5-SiO2 system via solgel method and studying the processes of formation and structure of the synthesized ferroelectric nanomaterials. The structure of synthesized materials has been studied by means of the following methods: EDS, XRD, FT-IR, SEM and AFM. The results obtained showed that the structure of the investigated compositions does not depend on the niobium content and all the samples keep their amorphous nature at room temperature. The surface structure shows random distribution of different kinds of aggregates with dimensions about 200–500 nm. The presence of a hybrid nanostructure with well-defi ned nanounits having special geometry is clearly observed.

Synthesis of MoS{sub 2} ribbons and their branched structures by chemical vapor deposition in sulfur-enriched environment

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Mahyavanshi, Rakesh D., E-mail: rmahyavanshi@gmail.com [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Sharma, Kamal P. [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kondo, Masuharu; Dewa, Takeshita [Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kawahara, Toshio [Department of Electronics and Information Engineering, Chubu University, 1200 Matsumoto-cho, Kasugai 487-8501 (Japan); Tanemura, Masaki [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2017-07-01

Highlights: • We demonstrate synthesis of monolayer MoS{sub 2} ribbons and their branched structures. • Unidirectional, bi and tri-directional growth of ribbons from the nucleation point are obtained. • Unidirectional and other branched structures can be synthesized controlling the composition of MoO{sub 3} and sulfur vapor. • The ribbons possess uneven edge structures with angles of 60° and 120°, indicating molybdenum and sulfur terminations. - Abstract: Here, we demonstrate the synthesis of monolayer molybdenum disulfide (MoS{sub 2}) ribbons and their branched structures by chemical vapor deposition (CVD) in sulfur-enriched environment. The growth of the MoS{sub 2} ribbons, triangular and other crystals significantly depends on the exposure of sulfur and concentration of molybdenum oxide (MoO{sub 3}) vapor on the substrate surface. The width and length of the synthesized ribbons is around 5–10 and 50–100 μm, respectively, where the width reduces from the nucleation point toward the end of the ribbon. Unidirectional, bi and tri-directional growth of ribbons from the nucleation point with an angle of 60° and 120° were obtained attributing to crystallographic growth orientation of MoS{sub 2} crystals. The directional growth of dichalcogenides ribbons is a significant challenge, our process shows that such unidirectional and other branched structures can be achieved by controlling the stoichiometric composition of MoO{sub 3} and sulfur exposure on the substrate surface. Interestingly, all the individual and branched ribbons possess uneven abundant edge structures, where the edges are formed with angles of 60° and 120°, indicating variation in molybdenum and sulfur edge terminations. The directional growth of MoS{sub 2} ribbons with defined edge structures in particular CVD condition can open up new possibilities for electronic and electrochemical applications.

Synthesis, structural characterization and quantum chemical studies of silicon-containing benzoic acid derivatives

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Zaltariov, Mirela-Fernanda; Cojocaru, Corneliu; Shova, Sergiu; Sacarescu, Liviu; Cazacu, Maria

2016-09-01

The present paper is concerned with the synthesis and molecular structure investigation of two new benzoic acid derivatives having trimethylsilyl tails, 4-((trimethylsilyl)methoxy) and 4-(3-(trimethylsilyl)propoxy)benzoic acids. The structures of the novel compounds have been confirmed by X-ray crystallography, Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H and 13C NMR). The theoretical studies of molecules were conducted by using the quantum chemical methods, such as Density Functional Theory (DFT B3LYP/6-31 + G**), Hartree-Fock (HF/6-31 + G**) and semiempirical computations (PM3, PM6 and PM7). The optimized molecular geometries have been found to be in good agreement with experimental structures resulted from the X-ray diffraction. The maximum electronic absorption bands observed at 272-287 nm (UV-vis spectra) have been assigned to π → π* transitions, which were in reasonable agreement with the time dependent density functional theory (TD-DFT) calculations. The computed vibrational frequencies by DFT method were assigned and compared with the experimental FTIR spectra. The mapped electrostatic potentials revealed the reactive sites, which corroborated the observation of the dimer supramolecular structures formed in the crystals by hydrogen-bonding. The energies of frontier molecular orbitals (HOMO and LUMO), energy gap, dipole moment and molecular descriptors for the new compounds were calculated and discussed.

Rhombohedral polytypes of the layered honeycomb delafossites with optical brilliance in the visible.

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Roudebush, John H; Sahasrabudhe, Girija; Bergman, Susanna L; Cava, R J

2015-04-06

We report the synthesis of the Delafossite honeycomb compounds Cu3Ni2SbO6 and Cu3Co2SbO6 via a copper topotactic reaction from the layered α-NaFeO2-like precursors Na3Ni2SbO6 and Na3Co2SbO6. The low-temperature exchange reaction exclusively produces the rhombahedral 3R polytype subcell, whereas only the hexagonal 2H polytype subcell has been made by conventional synthesis. The thus-synthesized 3R variants are visually striking; they are bright lime-green (Ni variant) and terracotta-orange (Co variant), while both of the conventionally synthesized 2H variants have a burnt-red color. The new structures are characterized by powder X-ray diffraction and Rietveld analysis as well as magnetic susceptibility, X-ray photoelectron spectroscopy (XPS), and diffuse-reflectance optical spectroscopy. Using thermogravimetric analysis, we identify a second order 3R → 2H phase transition as well as a first-order structural transition associated with rearrangement of the honeycomb stacking layers. The optical absorbance spectra of the samples show discrete edges that correlate well to their visual colors. Exposing Cu3Ni2SbO6 to O2 and heat causes the sample to change color. XPS confirms the presence of Cu(2+) in these samples, which implies that the difference in color between the polytypes is due to oxygen intercalation resulting from their different synthetic routes.

Crystal structure and thermal expansion of the low- and high-temperature forms of Ba MIV(PO 4) 2 compounds ( M=Ti, Zr, Hf and Sn)

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Bregiroux, D.; Popa, K.; Jardin, R.; Raison, P. E.; Wallez, G.; Quarton, M.; Brunelli, M.; Ferrero, C.; Caciuffo, R.

2009-05-01

The crystal structure of β-BaZr(PO 4) 2, archetype of the high-temperature forms of Ba M(PO 4) 2 phosphates (with M=Ti, Zr, Hf and Sn), has been solved ab initio by Rietveld analysis from synchrotron X-ray powder diffraction data. The phase transition appears as a topotactic modification of the monoclinic (S.G. C2/m) lamellar α-structure into a trigonal one (S.G. P3¯m1) through a simple mechanism involving the unfolding of the [Zr)]n2- layers. The thermal expansion is very anisotropic (e.g., -4.1< α i<34.0×10 -6 K -1 in the case of α-BaZr(PO 4) 2) and quite different in the two forms, as a consequence of symmetry. It stems from a complex combination of several mechanisms, involving bridging oxygen rocking in M-O-P linkages, and "bond thermal expansion".