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Sample records for metal alkoxides templates

  1. Metal alkoxides: templates for organometallic chemistry and catalysis. Final technical report on DE FG 02-86ER13570

    SciTech Connect

    Chisholm, Malcolm H.

    2002-11-01

    The physical properties and chemical reactivities of a series of alkoxide, fluoroalkoxide and thiolate compounds of molybdenum and tungsten having M{triple_bond}M or M{triple_bond}N bonds have been examined which reveal the influence of the pi-donor properties of the ligands: RO > R{sub f}O{approx}RS. Single-site metal alkoxide catalysts for the ring-opening polymerization of lactides have been prepared for the metals magnesium, zinc, and aluminum.

  2. Metal alkoxides and methods of making same

    DOEpatents

    Hentges, Patrick J.; Greene, Laura H.; Pafford, Margaret Mary; Westwood, Glenn; Klemperer, Walter G.

    2005-01-04

    A method of making a superconducting structure includes depositing a metal alkoxide on a surface of a metal and hydrolyzing the metal alkoxide on the surface to form a pinhole-free film. The metal is a superconductor. The metal alkoxide may be a compound of formula (I): where M is zirconium or hafnium, and the purity of the compound is at least 97% as measured by NMR spectroscopy.

  3. All-alkoxide synthesis of strontium-containing metal oxides

    DOEpatents

    Boyle, Timothy J.

    2001-01-01

    A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

  4. Metal Alkoxides - Models for Metal Oxides.

    DTIC Science & Technology

    1982-07-29

    metal bonded adaptations of the well known hollandite structure and closely -elated to the cluster found for CsNbCi1 1 . Triangulo Mo3 and W3 units are... triangulo complex- es as is shown in Figure 2. In both cases, the molybdenum atoms are surrounded by six oxygen ligands in a distorted octahedral manner

  5. Preparation of oxide glasses from metal alkoxides by sol-gel method

    NASA Technical Reports Server (NTRS)

    Kamiya, K.; Yoko, T.; Sakka, S.

    1987-01-01

    An investigation is carried out on the types of siloxane polymers produced in the course of the hydrolysis of silicon tetraethoxide, as well as the preparation of oxide glasses from metal alkoxides by the sol-gel method.

  6. Virus templated metallic nanoparticles.

    PubMed

    Aljabali, Alaa A A; Barclay, J Elaine; Lomonossoff, George P; Evans, David J

    2010-12-01

    Plant viruses are considered as nanobuilding blocks that can be used as synthons or templates for novel materials. Cowpea mosaic virus (CPMV) particles have been shown to template the fabrication of metallic nanoparticles by an electroless deposition metallization process. Palladium ions were electrostatically bound to the virus capsid and, when reduced, acted as nucleation sites for the subsequent metal deposition from solution. The method, although simple, produced highly monodisperse metallic nanoparticles with a diameter of ca. ≤35 nm. CPMV-templated particles were prepared with cobalt, nickel, iron, platinum, cobalt-platinum and nickel-iron.

  7. Impact of metal-alkoxide functionalized linkers on H2 binding: A density functional study

    NASA Astrophysics Data System (ADS)

    Banu, Tahamida; Ghosh, Avik; Das, Abhijit K.

    2016-08-01

    The effect of metal-alkoxide functionalization of different organic linkers on the H2 binding is investigated employing DFT approach. While analyzing the H2 binding interaction of magnesium-alkoxide modified benzene, naphthalene, anthracene and pyrene linkers, we find their comparable affinity toward H2 molecules. Six-member alkoxide ring containing naphthalene and pyrene systems interact with the H2 molecules in a comparatively better way than their five-member analogues. AIM, NBO and LMO-EDA analyses have been performed to comprehend the bonding nature between Mg center and the H2 molecules. Polarization along with the charge transfer interactions play significant role in stabilizing the systems.

  8. Virus templated metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Aljabali, Alaa A. A.; Barclay, J. Elaine; Lomonossoff, George P.; Evans, David J.

    2010-12-01

    Plant viruses are considered as nanobuilding blocks that can be used as synthons or templates for novel materials. Cowpea mosaic virus (CPMV) particles have been shown to template the fabrication of metallic nanoparticles by an electroless deposition metallization process. Palladium ions were electrostatically bound to the virus capsid and, when reduced, acted as nucleation sites for the subsequent metal deposition from solution. The method, although simple, produced highly monodisperse metallic nanoparticles with a diameter of ca. <=35 nm. CPMV-templated particles were prepared with cobalt, nickel, iron, platinum, cobalt-platinum and nickel-iron.Plant viruses are considered as nanobuilding blocks that can be used as synthons or templates for novel materials. Cowpea mosaic virus (CPMV) particles have been shown to template the fabrication of metallic nanoparticles by an electroless deposition metallization process. Palladium ions were electrostatically bound to the virus capsid and, when reduced, acted as nucleation sites for the subsequent metal deposition from solution. The method, although simple, produced highly monodisperse metallic nanoparticles with a diameter of ca. <=35 nm. CPMV-templated particles were prepared with cobalt, nickel, iron, platinum, cobalt-platinum and nickel-iron. Electronic supplementary information (ESI) available: Additional experimental detail, agarose gel electrophoresis results, energy dispersive X-ray spectra, ζ-potential measurements, dynamic light scattering data, nanoparticle tracking analysis and an atomic force microscopy image of Ni-CPMV. See DOI: 10.1039/c0nr00525h

  9. Complexation of alkoxides of trivalent iron. Alkoxyaluminates of transition metals

    SciTech Connect

    Rogova, T.V.; Turova, N.Ya.; Kozlova, N.I.

    1987-04-01

    An investigation of the solubility in the Y(OR)3-Fe(OR)3-ROH system (where R = i-Pr) has established the existence in solution of the two complexes YFe2(OR)9 and YFe3(OR)12, between whose compositions there is a region where glasses which are amorphous to x-rays form. A preparative, IR-spectroscopic, and mass-spectrometric study of the glasses has provided evidence of the absence of bimetallic alkoxides of Fe and Y of definite composition in the solid and gaseous phases. The polymeric compounds Ni(OR)2 do not react with Fe(OR)3. The literature data concerning the formation of volatile Fe(Al(OR)4)3 upon the reaction of FeCl3 with NaAl(OR)4 have been refuted. As a result of the investigation of the solubility in the M(OAlk)/sub n/-Fe(OAlk)3-AlkOH ternary systems (M = Li, Na, K, Ba, Y, Ni; Alk = Me, Et, i-Pr), it has been established that the formation of complexes in solution takes place only when the oligomeric compounds Fe(OPr-i)3 and Fe10 (OEt)22O4 x nEtOH (I) or the products of the partial hydrolysis and pyrolysis of the polymeric compounds Fe(OAlk)3 react with oligomeric (M = Y) or ionic (M = Li-Ba) alkoxides. Polymeric Fe(OMe)3 x MeOH and Fe(OEt)3 do not undergo complexation reactions. When I was reacted with alcoholic solutions of Ti(OEt)4 or Nb(OEt)5, the dehydration of I gave true Fe(OEt)3 for the first time in the form of a light yellow powder (T/sub m/ = 185C with decomposition) having a polymeric structure similar to the gibbsite form of Al(OH)3 (space group P21/n), a = 9.28, b = 5.43, c = 17.96 A, US = 94.54 d/sub x-ray/ = 2.80, and Z = 8. The absence of the complexation of Al(OR)3 with Ni(OR)3 or Cr(OR)3 has been established as a result of a preparative and mass-spectrometric investigation. Literature data on the existence of volatile alkoxy aluminates of Fe(III), Cr(III), and Ni have been refuted.

  10. Basic character of rare earth metal alkoxides. Utilization in catalytic C-C bond-forming reactions and catalytic asymmetric nitroaldol reactions

    SciTech Connect

    Sasai, H.; Suzuki, T.; Arai, S.

    1992-05-20

    In a recent paper, the authors reported that Zr(O-t-Bu){sub 4} was an efficient and convenient basic reagent in organic synthesis. However, all reactions examined were performed with stoichiometric quantities of the reagent. The authors envisioned that rare earth metal alkoxides would be stronger bases than group 4 metal alkoxides due to the lower ionization potential (ca. 5.4-6.4 eV) and the lower electronegativity (1.1-1.3) of rare earth elements; thus, the catalytic use of rare earth metal alkoxides in organic synthesis was expected. Although a variety of rare earth metal alkoxides have been prepared for the last three decades, to the authors knowledge, there have been few reports concerning the basicity of rare earth metal alkoxides. Herein, the authors report several carbon-carbon bond-forming reactions catalyzed by rare earth metal alkoxides and their application to a catalytic asymmetric nitroaldol reaction.

  11. Metal nanodisks using bicellar templates

    SciTech Connect

    Song, Yujiang; Shelnutt, John A

    2013-12-03

    Metallic nanodisks and a method of making them. The metallic nanodisks are wheel-shaped structures that that provide large surface areas for catalytic applications. The metallic nanodisks are grown within bicelles (disk-like micelles) that template the growth of the metal in the form of approximately circular dendritic sheets. The zero-valent metal forming the nanodisks is formed by reduction of a metal ion using a suitable electron donor species.

  12. Synthesis of inorganic-organic hybrids from metal alkoxides and silanol-terminated polydimethylsiloxane

    SciTech Connect

    Katayama, Shingo; Yoshinaga, Ikuko; Yamada, Noriko

    1996-12-31

    Inorganic-organic hybrids have been synthesized by reaction of Ti(OC{sub 2}H{sub 5}){sub 4} and Ta(OC{sub 2}H{sub 5}){sub 5} with silanol-terminated polydimethylsiloxane (PDMS). The chemical modification of the metal alkoxides with ethyl acetoacetate (EAcAc) was carried out in order to obtain a transparent and uniform hybrid. The hydrolysis behavior of Ti(OC{sub 2}H{sub 5}){sub 4} modified with EAcAc in the presence of PDMS and the formation of the Ti-O-Si bond in a Ti-O-PDMS hybrid were revealed by FT-IR experiments. Dynamic mechanical measurements showed that a Ta-O-PDMS hybrid was harder than a Ti-O-PDMS hybrid, indicating the effect of metal on the storage modulus of hybrids.

  13. Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

    PubMed Central

    Tätte, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Mändar, Hugo; Põhako, Kaija; Pehk, Tõnis; Reivelt, Kaido; Natali, Marco; Gurauskis, Jonas; Lõhmus, Ants; Mäeorg, Uno

    2011-01-01

    The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol–gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems. PMID:27877403

  14. Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

    NASA Astrophysics Data System (ADS)

    Tätte, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Mändar, Hugo; Põhako, Kaija; Pehk, Tõnis; Reivelt, Kaido; Natali, Marco; Gurauskis, Jonas; Lõhmus, Ants; Mäeorg, Uno

    2011-06-01

    The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

  15. Hard template synthesis of metal nanowires

    PubMed Central

    Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

    2014-01-01

    Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance, and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed. PMID:25453031

  16. Reactions of Metal-Metal Multiple Bonds. 14. Synthesis and Characterization of Triangulo-W3 and Mo2W-oxo Capped Alkoxide Clusters. Comproportionation of M-M Triple Bonds, sigma(2)pi(4) and d(o) Metal-oxo Groups: M Triple Bond M + M Triple Bond O Yields M3(micron 3-O).

    DTIC Science & Technology

    1984-05-02

    INDU/DC/TR-84/1-MC REACTIONS OF METAL-METAL MULTIPLE BONDS. 14. SYNTHESIS AND CHARACTERIZATION OF TRIANGULO -W 3 AND Mo2W-oxo CAPPED ALKOXIDE CLUSTERS...Mtal-Metal Multiple Bonds. 14. Syn- Technical Report 1984 thesis and Characterization of Triangulo -W 3 and 0Mo2W-oxo Capped Alkoxide Clusters...block number) triangulo metal atom clusters, molybdenum, tungsten, alkoxide, oxo, electronic structure, electrochemistry, UV-visible spectroscopy 20

  17. Soluble Metal Oxo Alkoxide Inks with Advanced Rheological Properties for Inkjet-Printed Thin-Film Transistors.

    PubMed

    Meyer, Sebastian; Pham, Duy Vu; Merkulov, Sonja; Weber, Dennis; Merkulov, Alexey; Benson, Niels; Schmechel, Roland

    2017-01-25

    Semiconductor inks containing an indium-based oxo alkoxide precursor material were optimized regarding rheology requirements for a commercial 10 pL inkjet printhead. The rheological stability is evaluated by measuring the dynamic viscosity of the formulations for 12 h with a constant shear rate stress under ambient conditions. It is believed that the observed superior stability of the inks is the result of effectively suppressing the hydrolysis and condensation reaction between the metal oxo alkoxide precursor complex and atmospheric water. This can be attributed to a strong precursor coordination and the resulting reduction in ligand exchange dynamics of the solvent tetrahydrofurfuryl alcohol which is used as the main solvent in the formulations. It is also shown that with a proper selection of cosolvents, having high polar Hansen solubility parameter values, the inks drop formation properties and wettability can be fine-tuned by maintaining the inks rheological stability. Good drop jetting performance without satellite formation and high drop velocities of 8.25 m/s were found with the support of dimensionless numbers and printability windows. By printing single 10 pL ink dots onto short channel indium-tin-oxide electrodes, In2O3 calcination at 350 °C and a solution-processed back-channel protection, high average saturation mobility of approximately 10 cm(2)/(V s) are demonstrated in a bottom-contact coplanar thin-film transistor device structure.

  18. Growth of highly oriented LiNbO 3 thin films through structure controlled metal alkoxide precursor solution

    NASA Astrophysics Data System (ADS)

    Hirano, Shin-ichi; Takeichi, Yoshikuni; Sakamoto, Wataru; Yogo, Toshinobu

    2002-04-01

    Highly oriented LiNbO 3 thin films have been successfully synthesized by chemical solution deposition through a structure controlled metal-organic precursor. The homogeneous LiNbO 3 precursor solution was prepared by controlling the reaction of metal alkoxides and selecting the ligand for modification. LiNbO 3 thin films with c-axis preferred orientation were directly crystallized on sapphire C substrates from chemical solutions synthesized in this study. The epitaxial relation of LiNbO 3 film to sapphire substrate was found to depend strongly upon the precursor structure modified with β-diketone. 1-Phenyl-1,3-butanedione (PBD) was found to be superior to acetylacetone (acacH) and dibenzoylmethane (DBM) for the crystallization of epitaxial LiNbO 3 films. The results suggested that the existence of a benzene ring in the ligand strongly influenced the degree of orientation of synthesized films.

  19. Low temperature synthesis of monolithic transparent Ta2O5 gels from hydrolysis of metal alkoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1993-01-01

    Tantalum oxide gels in the form of transparent monoliths and powder were prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)5:C2H50H:H20:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, time of gel formation increased with the alcohol to alkoxide mole ratio. Thermal evolution of the physical and structural changes in the gel was monitored by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. On heating to approximately 400 C, the amorphous gel crystallized into the low temperature orthorhombic phase Beta-Ta2O5, which transformed into the high temperature tetragonal phase Alpha-Ta2O5 when further heated to approximately 1450 C. The volume fraction of the crystalline phase increased with the firing temperature. The Alpha-Ta205 converted back into the low temperature phase, Beta-Ta2O5, on slow cooling through the transformation temperature of 1360 C indicating a slow but reversible transformation.

  20. Alkali metal yttrium neo-pentoxide double alkoxide precursors to alkali metal yttrium oxide nanomaterials

    DOE PAGES

    Boyle, Timothy J.; Neville, Michael L.; Sears, Jeremiah Matthew; ...

    2016-03-15

    In this study, a series of alkali metal yttrium neo-pentoxide ([AY(ONep)4]) compounds were developed as precursors to alkali yttrium oxide (AYO2) nanomaterials. The reaction of yttrium amide ([Y(NR2)3] where R=Si(CH3)3) with four equivalents of H-ONep followed by addition of [A(NR2)] (A=Li, Na, K) or Ao (Ao=Rb, Cs) led to the formation of a complex series of AnY(ONep)3+n species, crystallographically identified as [Y2Li3(μ3-ONep)(μ3-HONep)(μ-ONep)5(ONep)3(HONep)2] (1), [YNa2(μ3-ONep)4(ONep)]2 (2), {[Y2K3(μ3-ONep)3(μ-ONep)4(ONep)2(ηξ-tol)2][Y4K2(μ4-O)(μ3-ONep)8(ONep)4]•ηx-tol]} (3), [Y4K2(μ4-O)(μ3-ONep)8(ONep)4] (3a), [Y2Rb3(μ4-ONep)3(μ-ONep)6] (4), and [Y2Cs4(μ6-O)(μ3-ONep)6(μ3-HONep)2(ONep)2(ηx-tol)4]•tol (5). Compounds 1–5 were investigated as single source precursors to AYOx nanomaterials following solvothermal routes (pyridine, 185 °C for 24h). The final products after thermal processing weremore » found by powder X-ray diffraction experiments to be Y2O3 with variable sized particles based on transmission electron diffraction. Energy dispersive X-ray spectroscopy studies indicated that the heavier alkali metal species were present in the isolated nanomaterials.« less

  1. Metal templated design of protein interfaces.

    PubMed

    Salgado, Eric N; Ambroggio, Xavier I; Brodin, Jeffrey D; Lewis, Richard A; Kuhlman, Brian; Tezcan, F Akif

    2010-02-02

    Metal coordination is a key structural and functional component of a large fraction of proteins. Given this dual role we considered the possibility that metal coordination may have played a templating role in the early evolution of protein folds and complexes. We describe here a rational design approach, Metal Templated Interface Redesign (MeTIR), that mimics the time course of a hypothetical evolutionary pathway for the formation of stable protein assemblies through an initial metal coordination event. Using a folded monomeric protein, cytochrome cb(562), as a building block we show that its non-self-associating surface can be made self-associating through a minimal number of mutations that enable Zn coordination. The protein interfaces in the resulting Zn-directed, D(2)-symmetrical tetramer are subsequently redesigned, yielding unique protein architectures that self-assemble in the presence or absence of metals. Aside from its evolutionary implications, MeTIR provides a route to engineer de novo protein interfaces and metal coordination environments that can be tuned through the extensive noncovalent bonding interactions in these interfaces.

  2. Recent advances in tailoring the aggregation of heavier alkaline earth metal halides, alkoxides and aryloxides from non-aqueous solvents.

    PubMed

    Fromm, Katharina M

    2006-11-21

    This overview on one of the subjects treated in our group deals with the synthesis and study of low-dimensional polymer and molecular solid state structures formed with alkaline earth metal ions in non-aqueous solvents. We have chosen several synthetic approaches in order to obtain such compounds. The first concept deals with the "cutting out" of structural fragments from a solid state structure of a binary compound, which will be explained with reference to BaI2. Depending on the size and concentration of oxygen donor ligands, used as chemical scissors on BaI2, three-, two-, one- and zero-dimensional derived adducts of BaI2 are obtained, comparable to a structural genealogy tree for BaI2. A second part deals with the supramolecular approach for the synthesis of low dimensional polymeric compounds based on alkaline earth metal iodides, obtained by the combination of metal ion coordination with hydrogen bonding between the cationic complexes and their anions. Certain circumstances allow rules to be established for the prediction of the dimensionality of a given compound, contributing to the fundamental problem of structure prediction in crystal engineering. A third section describes a synthetic approach for generating pure alkaline earth metal cage compounds as well as alkali and alkaline earth mixed metal clusters. A first step deals with different molecular solvated alkaline earth metal iodides which are investigated as a function of the ligand size in non-aqueous solvents. These are then reacted with some alkali metal compound in order to partially or totally eliminate alkali iodide and to form the targeted clusters. These unique structures of ligand stabilized metal halide, hydroxide and/or alkoxide and aryloxide aggregates are of interest as potential precursors for oxide materials and as catalysts. Approaches to two synthetic methods of the latter, sol-gel and (MO)CVD (metal-organic chemical vapour deposition), are investigated with some of our compounds. (D

  3. Surfactant-Templated Mesoporous Metal Oxide Nanowires

    DOE PAGES

    Luo, Hongmei; Lin, Qianglu; Baber, Stacy; ...

    2010-01-01

    We demore » monstrate two approaches to prepare mesoporous metal oxide nanowires by surfactant assembly and nanoconfinement via sol-gel or electrochemical deposition. For example, mesoporous Ta 2 O 5 and zeolite nanowires are prepared by block copolymer Pluronic 123-templated sol-gel method, and mesoporous ZnO nanowires are prepared by electrodeposition in presence of anionic surfactant sodium dodecyl sulfate (SDS) surfactant, in porous membranes. The morphologies of porous nanowires are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses.« less

  4. Cycloaddition of phosphaalkynes to high-oxidation-state metal alkylidenes: Synthesis and characterization of a unique phosphametallacyclobutene via an alkoxide ligand shift

    SciTech Connect

    Jamison, G.M.; Saunders, R.S.; Wheeler, D.R.; McClain, M.D.; Loy, D.A.; Ziller, J.W.

    1996-01-09

    The phosphametallacycle 3, [ArN][RO]Mo=C(t-Bu)P(OR)C(H)(t-Bu) (Ar = 2, 6-(i-Pr){sub 2}-C{sub 6}H{sub 3}, R = CMe(CF{sub 3}){sub 2}), is formed from the cycloaddition of tert-butylphosphaacetylene to the high-oxidation-state molybdenum alkylidene [ArN][RO]{sub 2} Mo=C(H)(t-Bu), accompanied by an alkoxide metal-to-ligand shift. The 1-phospha-3-molybdacyclobut-2-ene has been characterized by multinuclear NMR spectroscopy and its molecular structure determined by X-ray crystallographic analysis. 20 refs., 2 figs.

  5. Heteroleptic metal alkoxide "oxoclusters" as molecular models for the sol-gel synthesis of perovskite nanoparticles for bio-imaging applications.

    PubMed

    Seisenbaeva, Gulaim A; Kessler, Vadim G; Pazik, Robert; Strek, Wieslaw

    2008-07-14

    Systematic structural study of the molecules, resulting from microhydrolysis of heterometallic beta-diketonate alkoxides of barium and strontium (single-source precursors of perovskite oxide materials), demonstrates that the structures of these products result from a thermodynamically driven self-assembly of metal cations and ligands directed towards the most densely packed cores. The ratio between metal cations, and of the cations to bidentate heteroligands, is easily changed to enable the highest packing density. The key to the application of single-source precursors appears to be the use of stoichiometric or superstoichiometric water amounts together with solvents preventing diffusion of possible homometallic intermediates. Eu-doped BaTiO3 nanoparticles have been successfully obtained and characterized.

  6. Templated Dry Printing of Conductive Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Rolfe, David Alexander

    Printed electronics can lower the cost and increase the ubiquity of electrical components such as batteries, sensors, and telemetry systems. Unfortunately, the advance of printed electronics has been held back by the limited minimum resolution, aspect ratio, and feature fidelity of present printing techniques such as gravure, screen printing and inkjet printing. Templated dry printing offers a solution to these problems by patterning nanoparticle inks into templates before drying. This dissertation shows advancements in two varieties of templated dry nanoprinting. The first, advective micromolding in vapor-permeable templates (AMPT) is a microfluidic approach that uses evaporation-driven mold filling to create submicron features with a 1:1 aspect ratio. We will discuss submicron surface acoustic wave (SAW) resonators made through this process, and the refinement process in the template manufacturing process necessary to make these devices. We also present modeling techniques that can be applied to future AMPT templates. We conclude with a modified templated dry printing that improves throughput and isolated feature patterning by transferring dry-templated features with laser ablation. This method utilizes surface energy-defined templates to pattern features via doctor blade coating. Patterned and dried features can be transferred to a polymer substrate with an Nd:YAG MOPA fiber laser, and printed features can be smaller than the laser beam width.

  7. Investigation of metal hydride nanoparticles templated in metal organic frameworks.

    SciTech Connect

    Jacobs, Benjamin W.; Herberg, Julie L.; Highley, Aaron M.; Grossman, Jeffrey; Wagner, Lucas; Bhakta, Raghu; Peaslee, D.; Allendorf, Mark D.; Liu, X.; Behrens, Richard, Jr.; Majzoub, Eric H.

    2010-11-01

    Hydrogen is proposed as an ideal carrier for storage, transport, and conversion of energy. However, its storage is a key problem in the development of hydrogen economy. Metal hydrides hold promise in effectively storing hydrogen. For this reason, metal hydrides have been the focus of intensive research. The chemical bonds in light metal hydrides are predominantly covalent, polar covalent or ionic. These bonds are often strong, resulting in high thermodynamic stability and low equilibrium hydrogen pressures. In addition, the directionality of the covalent/ionic bonds in these systems leads to large activation barriers for atomic motion, resulting in slow hydrogen sorption kinetics and limited reversibility. One method for enhancing reaction kinetics is to reduce the size of the metal hydrides to nano scale. This method exploits the short diffusion distances and constrained environment that exist in nanoscale hydride materials. In order to reduce the particle size of metal hydrides, mechanical ball milling is widely used. However, microscopic mechanisms responsible for the changes in kinetics resulting from ball milling are still being investigated. The objective of this work is to use metal organic frameworks (MOFs) as templates for the synthesis of nano-scale NaAlH4 particles, to measure the H2 desorption kinetics and thermodynamics, and to determine quantitative differences from corresponding bulk properties. Metal-organic frameworks (MOFs) offer an attractive alternative to traditional scaffolds because their ordered crystalline lattice provides a highly controlled and understandable environment. The present work demonstrates that MOFs are stable hosts for metal hydrides and their reactive precursors and that they can be used as templates to form metal hydride nanoclusters on the scale of their pores (1-2 nm). We find that using the MOF HKUST-1 as template, NaAlH4 nanoclusters as small as 8 formula units can be synthesized inside the pores. A detailed picture of

  8. Self-Assembling Protein Materials for Metal Nanoparticle Templation

    DTIC Science & Technology

    2015-05-01

    form nanoporous , durable frameworks upon which cells can be conditioned to grow.8,99,100 The remarkable feature of synthetic protein materials is... Materials for Metal Nanoparticle Templation The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued...Polytechnic Institute of New York University Brooklyn, NY 11201 -3840 ABSTRACT Self-assembling Protein Materials for Metal Nanoparticle Templation Report Title

  9. Peptide-templated noble metal catalysts: syntheses and applications.

    PubMed

    Wang, Wei; Anderson, Caleb F; Wang, Zongyuan; Wu, Wei; Cui, Honggang; Liu, Chang-Jun

    2017-05-01

    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches.

  10. Peptide-templated noble metal catalysts: syntheses and applications

    PubMed Central

    Wang, Wei; Anderson, Caleb F.; Wang, Zongyuan; Wu, Wei

    2017-01-01

    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches. PMID:28507701

  11. Templated synthesis of metal nanorods in silica nanotubes.

    PubMed

    Gao, Chuanbo; Zhang, Qiao; Lu, Zhenda; Yin, Yadong

    2011-12-14

    We report a general method for the synthesis of noble metal nanorods, including Au, Ag, Pt, and Pd, based on their seeded growth in silica nanotube templates. The controlled growth of the metals occurs exclusively on the seeds inside the silica nanotubes, which act as hard templates to confine the one-dimensional growth of the metal nanorods and define their aspect ratios. This method affords large quantities of noble metal nanorods with well-controlled aspect ratios and high yield, which may find wide use in the fields of nanophotonics, catalysis, sensing, imaging, and biomedicine.

  12. Alkali metal yttrium neo-pentoxide double alkoxide precursors to alkali metal yttrium oxide nanomaterials

    SciTech Connect

    Boyle, Timothy J.; Neville, Michael L.; Sears, Jeremiah Matthew; Cramer, Roger

    2016-03-15

    In this study, a series of alkali metal yttrium neo-pentoxide ([AY(ONep)4]) compounds were developed as precursors to alkali yttrium oxide (AYO2) nanomaterials. The reaction of yttrium amide ([Y(NR2)3] where R=Si(CH3)3) with four equivalents of H-ONep followed by addition of [A(NR2)] (A=Li, Na, K) or Ao (Ao=Rb, Cs) led to the formation of a complex series of AnY(ONep)3+n species, crystallographically identified as [Y2Li33-ONep)(μ3-HONep)(μ-ONep)5(ONep)3(HONep)2] (1), [YNa23-ONep)4(ONep)]2 (2), {[Y2K33-ONep)3(μ-ONep)4(ONep)2(ηξ-tol)2][Y4K24-O)(μ3-ONep)8(ONep)4]•ηx-tol]} (3), [Y4K24-O)(μ3-ONep)8(ONep)4] (3a), [Y2Rb34-ONep)3(μ-ONep)6] (4), and [Y2Cs46-O)(μ3-ONep)63-HONep)2(ONep)2x-tol)4]•tol (5). Compounds 1–5 were investigated as single source precursors to AYOx nanomaterials following solvothermal routes (pyridine, 185 °C for 24h). The final products after thermal processing were found by powder X-ray diffraction experiments to be Y2O3 with variable sized particles based on transmission electron diffraction. Energy dispersive X-ray spectroscopy studies indicated that the heavier alkali metal species were present in the isolated nanomaterials.

  13. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    NASA Astrophysics Data System (ADS)

    Patel, Malkeshkumar; Kim, Hong-Sik; Park, Hyeong-Ho; Kim, Joondong

    2016-04-01

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W-1) and detectivity (2.75 × 1015 Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  14. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    SciTech Connect

    Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong; Park, Hyeong-Ho

    2016-04-04

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W{sup −1}) and detectivity (2.75 × 10{sup 15} Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  15. Evolution of Metal Selectivity in Templated Protein Interfaces

    PubMed Central

    Brodin, Jeffrey D.; Medina-Morales, Annette; Ni, Thomas; Salgado, Eric N.; Ambroggio, Xavier I.; Tezcan, F. Akif

    2010-01-01

    Selective binding by metalloproteins to their cognate metal ions is essential to cellular survival. How proteins originally acquired the ability to selectively bind metals and evolved a diverse array of metal-centered functions despite the availability of only a few metal-coordinating functionalities remains an open question. Using a rational design approach (Metal-Templated Interface Redesign), we describe the transformation of a monomeric electron transfer protein, cytochrome cb562, into a tetrameric assembly (C96RIDC-1) that stably and selectively binds Zn2+, and displays a metal-dependent conformational change reminiscent of a signaling protein. A thorough analysis of the metal binding properties of C96RIDC-14 reveals that it can also stably harbor other divalent metals with affinities that rival (Ni2+) or even exceed (Cu2+) those of Zn2+ on a per site basis. Nevertheless, this analysis suggests that our templating strategy also introduces an increased bias towards binding a higher number of Zn2+ ions (4 high affinity sites) versus Cu2+ or Ni2+ (2 high affinity sites), ultimately leading to the exclusive selectivity of C96RIDC-14 for Zn2 over those ions. More generally, our results indicate that an initial metal-driven nucleation event followed by the formation of a stable protein architecture around the metal provides a straightforward path for generating structural and functional diversity. PMID:20515031

  16. Alkoxide routes to Inorganic Materials

    SciTech Connect

    Thomas, George H

    2007-12-01

    An all alkoxide solution chemistry utilizing metal 2-methoxyethoxide complexes in 2-methoxyethanol was used to deposit thin-films of metal oxides on single-crystal metal oxide substrates and on biaxially textured metal substrates. This same chemistry was used to synthesize complex metal oxide nanoparticles. Nuclear Magnetic Resonance spectroscopy was used to study precursor solutions of the alkaline niobates and tantalates. Film crystallization temperatures were determined from x-ray diffraction patterns of powders derived from the metal oxide precursor solutions. Film structure was determined via x-ray diffraction. Film morphology was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Epitaxial thin-films of strontium bismuth tantalate (SrBi{sub 2}Ta{sub 2}O{sub 9}, SBT) and strontium bismuth niobate (SrBi{sub 2}Nb{sub 2}O{sub 9}, SBN) were deposited on single crystal [1 0 0] magnesium oxide (MgO) buffered with lanthanum manganate (LaMnO{sub 3}, LMO). Epitaxial thin films of LMO were deposited on single crystal [100] MgO via Rf-magnetron sputtering and on single crysal [100] lanthanum aluminate (LaAlO{sub 3}) via the chemical solution deposition technique. Epitaxial thin-films of sodium potassium tantalate (na{sub 0.5}K{sub 0.5}TaO{sub 3}, NKT), sodium potassium niobate (Na{sub 0.5}K{sub 0.5}NbO{sub 3}, NKN) and sodium potassium tantalum niobate (Na{sub 0.5}K{sub 0.5}Ta{sub 0.5}O{sub 3}, NKTN) were deposited on single crystal [1 0 0] lanthanum aluminate and [1 0 0] MgO substrates (NKT and NKN) and biaxially textured metal substrates via the chemical solution deposition technique. Epitaxial growth of thin-films of NKT, NKN and NKTN was observed on LAO and Ni-5% W. Epitaxial growth of thin-films of NKN and the growth of c-axis aligned thin-films of NKT was observed on MgO. Nanoparticles of SBT, SBN, NKT and NKN were synthesized in reverse micelles from alkoxide precursor solutions. X-ray diffraction and transmission electron

  17. Coordination chemistry of N,N,N',N'-tetrakis(3,5-substituted benzyl-2-oxide)-2,2'-(ethylenedioxy)diethanamine modified Group 4 metal alkoxides.

    PubMed

    Boyle, Timothy J; Yonemoto, Daniel T; Steele, Leigh Anna; Farrell, Joshua; Renehan, Peter; Huhta, Taylor

    2012-11-05

    The coordination behavior of a set of (ethylenedioxy)diethanamine-based tetraphenol ligands with a series of Group 4 metal alkoxides ([M(OR)(4)]) was determined. The ligands were synthesized from a modified Mannich reaction and fully characterized as N,N,N',N'-tetrakis(3,5-tert-butyl-benzyl-2-hydroxy)-2,2'-(ethylenedioxy)diethanamine, termed H(4)-OEA-DBP(4) (1), and N,N,N',N'-tetrakis(3,5-chloro-benzyl-2-hydroxy)-2,2'-(ethylenedioxy)diethanamine, termed H(4)-OEA-DCP(4) (2). The reaction of 1 with a set of [M(OR)(4)] [M = Ti, Zr, or Hf; OR = iso-propoxide (OPr(i)), neo-pentoxide (ONep), or tert-butoxide (OBu(t))] precursors led to the isolation of [(OPr(i))(2)Ti](2)(μ-OEA-DBP(4)) (3), [(ONep)(2)Ti](2)(μ-OEA-DBP(4)) (4), and [(OBu(t))(2)M](2)(μ-OEA-DBP(4)) where M = Ti (5), Zr (6), or Hf (7). In addition, the [(ONep)(2)Ti](2)(μ-OEA-DCP(4)) (4a) derivative was isolated from the reaction of 2 and [Ti(ONep)(4)], demonstrating the similarity of coordination behavior between the two OEA-R(4) ligands. For 3-7, the metal center adopts a slightly distorted octahedral geometry by binding the two O atoms of the phenoxide moiety, as well as one N and one O atom from the OEA moieties, while retaining two of the original OR ligands. Solution NMR demonstrates inequivalent protons for the majority of the bound OEA ligands, which argues for retention of structure in solution. The synthesis and characterization of these compounds are presented in detail.

  18. Titanium alkoxide compound

    DOEpatents

    Boyle, Timothy J.

    2007-08-14

    A titanium alkoxide composition is provided, as represented by the chemical formula (OC.sub.6H.sub.5N).sub.2Ti(OC.sub.6H.sub.5NH.sub.2).sub.2. As prepared, the compound is a crystalline substance with a hexavalent titanium atom bonded to two OC.sub.6H.sub.5NH.sub.2 groups and two OC.sub.6H.sub.5N groups with a theoretical molecular weight of 480.38, comprising 60.01% C, 5.04% H and 11.66% N.

  19. The fabrication of short metallic nanotubes by templated electrodeposition.

    PubMed

    Huang, Chienwen; Hao, Yaowu

    2009-11-04

    Template-based electrochemical synthesis has widely been used to produce metal nanowires and nanorods. Commercially available filtration membranes, such as anodic aluminum oxide (AAO) and polycarbonate track etch membranes, have commonly been utilized as hard templates for this purpose. In this process, a thick metal film is usually sputtered or vacuum evaporated onto one side of the membrane to block the pores and serve as the working electrode for the subsequent electrodeposition. Here, we show that during the deposition of the metal electrode for AAO membranes, the electrode metal diffuses into the pores and is deposited on the pore walls which leads to preferential electrodeposition of metal on the walls and therefore forms metal tubes. This phenomenon has been utilized to fabricate short nanotubes by carefully controlling the electrodeposition conditions. The process is a straightforward method for any electroplatable materials to form nanoscale tubular structures. The effects of working electrodes and electrodeposition conditions on the formation of tubular structures are discussed in detail. A new mechanism based on this simple fact is proposed to explain the formation of Ni tubes by Ni-Cu co-deposition. Also, we demonstrate how to distinguish magnetic nanotubes from nanorods by a simple magnetic measurement.

  20. Mechanistic studies aimed at the development of single site metal alkoxide catalysts for the production of polyoxygenates from renewable resources.

    SciTech Connect

    Chisholm, Malcolm H.

    2015-12-15

    The work proposed herein follows on directly from the existing 3 year grant and the request for funding is for 12 months to allow completion of this work and graduation of current students supported by DOE. The three primary projects are as follows. 1.) A comparative study of the reactivity of LMg(OR) (solvent), where L= a β-diiminate or pyrromethene ligand, in the ring-opening of cyclic esters. 2.) The homopolymerization of expoxides, particularly propylene oxide and styrene oxide, and their copolymerizations with carbon dioxide or organic anhydrides to yield polycarbonates or polyesters, respectively. 3.) The development of well-defined bismuth (III) complexes for ring-opening polymerizations that are tolerant of both air and water. In each of these topics special emphasis is placed on developing a detailed mechanistic understanding of the ring-opening event and how this is modified by the employment of specific metal and ligand combinations. This document also provides a report on findings of the past grant period that are not yet in the public domain/published and shows how the proposed work will bring the original project to conclusion.

  1. Apoferritin-Templated Synthesis of Encoded Metallic Phosphate Nanoparticle Tags

    SciTech Connect

    Liu, Guodong; Wu, Hong; Dohnalkova, Alice; Lin, Yuehe

    2007-07-31

    Encoded metallic-phosphate nanoparticle tags, with distinct encoding patterns, have been prepared using an apoferritin template. A center-cavity structure as well as the disassociation and reconstructive characteristics of apoferritin at different pH environments provide a facile route for preparing such encoded nanoparticle tags. Encapsulation and diffusion approaches have been investigated during the preparation. The encapsulation approach, which is based on the dissociation and reconstruction of apoferritin at different pHs, exhibits an effective route to prepare such encoded metallic-phosphate nanoparticle tags. The compositionally encoded nanoparticle tag leads to a high coding capacity with a large number of distinguishable voltammetric signals, reflecting the predetermined composition of the metal mixture solution (and hence the nanoparticle composition). Releasing the metal components from the nanoparticle tags at pH 4.6 acetate buffer avoids harsh dissolution conditions, such as strong acids. Such a synthesis of encoded nanoparticle tags, including single-component and compositionally encoded nanoparticle tags, is substantially simple, fast, and convenient compared to that of encoded metal nanowires and semiconductor nanoparticle (CdS, PbS, and ZnS) incorporated polystyrene beads. The encoded metallic-phosphate nanoparticle tags thus show great promise for bioanalytical or product-tracking/identification/protection applications.

  2. Structure of fluorescent metal clusters on a DNA template.

    NASA Astrophysics Data System (ADS)

    Vdovichev, A. A.; Sych, T. S.; Reveguk, Z. V.; Smirnova, A. A.; Maksimov, D. A.; Ramazanov, R. R.; Kononov, A. I.

    2016-08-01

    Luminescent metal clusters are a subject of growing interest in recent years due to their bright emission from visible to near infrared range. Detailed structure of the fluorescent complexes of Ag and other metal clusters with ligands still remains a challenging task. In this joint experimental and theoretical study we synthesized Ag-DNA complexes on a DNA oligonucleotide emitting in violet- green spectral range. The structure of DNA template was determined by means of various spectral measurements (CD, MS, XPS). Comparison of the experimental fluorescent excitation spectra and calculated absorption spectra for different QM/MM optimized structures allowed us to determine the detailed structure of the green cluster containing three silver atoms in the stem of the DNA hairpin structure stabilized by cytosine-Ag+-cytosine bonds.

  3. Template-directed synthesis of oligoguanylic acids - Metal ion catalysis

    NASA Technical Reports Server (NTRS)

    Bridson, P. K.; Fakhrai, H.; Lohrmann, R.; Orgel, L. E.; Van Roode, M.

    1981-01-01

    The effects of Zn(2+), Pb(2+) and other metal ions on the efficiency and stereo-selectivity of the template-directed oligomerization of guanosine 5'-phosphorimidazolide are investigated. Reactions were run in the presence of a polyC template in a 2,6-lutidine buffer, and products analyzed by high-performance liquid chromatography on an RPC-5 column. The presence of the Pb(2+) ion is found to lead to the formation of 2'-5' linked oligomers up to the 40-mer, while Zn(2+) favors the formation of predominantly 3'-5' linked oligomers up to the 35-mer. When amounts of uracil, cytidine or adenosine 5'-phosphorimidazole equal to those of the guanosine derivative are included in the reaction mixture, the incorrect base is incorporated into the oligomer about 10% of the time with a Pb(2+) catalyst, but less than 0.5% of the time with Zn(2+). The Sn(2+), Sb(3+) and Bi(3+) ions are also found to promote the formation of 2'-5' oligomers, although not as effectively as Pb(2+), while no metal ions other than Zn(2+) promote the formation of the 3'-5' oligomers. The results may be important for the understanding of the evolution of nucleic acid replication in the absence of enzymes.

  4. Template-directed synthesis of oligoguanylic acids - Metal ion catalysis

    NASA Technical Reports Server (NTRS)

    Bridson, P. K.; Fakhrai, H.; Lohrmann, R.; Orgel, L. E.; Van Roode, M.

    1981-01-01

    The effects of Zn(2+), Pb(2+) and other metal ions on the efficiency and stereo-selectivity of the template-directed oligomerization of guanosine 5'-phosphorimidazolide are investigated. Reactions were run in the presence of a polyC template in a 2,6-lutidine buffer, and products analyzed by high-performance liquid chromatography on an RPC-5 column. The presence of the Pb(2+) ion is found to lead to the formation of 2'-5' linked oligomers up to the 40-mer, while Zn(2+) favors the formation of predominantly 3'-5' linked oligomers up to the 35-mer. When amounts of uracil, cytidine or adenosine 5'-phosphorimidazole equal to those of the guanosine derivative are included in the reaction mixture, the incorrect base is incorporated into the oligomer about 10% of the time with a Pb(2+) catalyst, but less than 0.5% of the time with Zn(2+). The Sn(2+), Sb(3+) and Bi(3+) ions are also found to promote the formation of 2'-5' oligomers, although not as effectively as Pb(2+), while no metal ions other than Zn(2+) promote the formation of the 3'-5' oligomers. The results may be important for the understanding of the evolution of nucleic acid replication in the absence of enzymes.

  5. Fabrication and characterization of metal-semiconductor-metal nanorod using template synthesis

    SciTech Connect

    Kim, Kyohyeok; Kwon, Namyong; Hong, Junki; Chung, Ilsub

    2009-07-15

    The authors attempted to fabricate and characterize one dimensional metal-semiconductor-metal (MSM) nanorod using a template. Cadmium selenide (CdSe) and polypyrrole (Ppy) were chosen as n-type and p-type semiconductor materials, respectively, whereas Au was chosen as a metal electrode. The fabrication of the nanorod was achieved by ''template synthesis'' method using polycarbonate membrane. The structure of the fabricated nanorod was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In addition, the electrical properties of MSM nanorods were characterized using scanning probe microscopy (Seiko Instruments, SPA 300 HV) by probing with a conductive cantilever. I-V characteristics as a function of the temperature give the activation energy, as well as the barrier height of a metal-semiconductor contact, which is useful to understand the conduction mechanism of MSM nanorods.

  6. Metal-organic framework templated inorganic sorbents for rapid and efficient extraction of heavy metals.

    PubMed

    Abney, C W; Gilhula, J C; Lu, K; Lin, W

    2014-12-17

    An innovative wet-treatment with Na2 S transforms two indium metal-organic frameworks (MOFs) into a series of porous inorganic sorbents. These MOF-templated materials display remarkable affinity for heavy metals with saturation occurring in less than 1 h. The saturation capacity for Hg(II) exceeds 2 g g(-1) , more than doubling the best thiol-functionalized sorbents in the literature.

  7. Silica needle template fabrication of metal hollow microneedle arrays

    NASA Astrophysics Data System (ADS)

    Zhu, M. W.; Li, H. W.; Chen, X. L.; Tang, Y. F.; Lu, M. H.; Chen, Y. F.

    2009-11-01

    Drug delivery through hollow microneedle (HMN) arrays has now been recognized as one of the most promising techniques because it minimizes the shortcomings of the traditional drug delivery methods and has many exciting advantages—pain free and tunable release rates, for example. However, this drug delivery method has been hindered greatly from mass clinical application because of the high fabrication cost of HMN arrays. Hence, we developed a simple and cost-effective procedure using silica needles as templates to massively fabricate HMN arrays by using popular materials and industrially applicable processes of micro- imprint, hot embossing, electroplating and polishing. Metal HMN arrays with high quality are prepared with great flexibility with tunable parameters of area, length of needle, size of hollow and array dimension. This efficient and cost-effective fabrication method can also be applied to other applications after minor alterations, such as preparation of optic, acoustic and solar harvesting materials and devices.

  8. Template-stripped asymmetric metallic pyramids for tunable plasmonic nanofocusing.

    PubMed

    Cherukulappurath, Sudhir; Johnson, Timothy W; Lindquist, Nathan C; Oh, Sang-Hyun

    2013-01-01

    We demonstrate a novel scheme for plasmonic nanofocusing with internally illuminated asymmetric metallic pyramidal tips using linearly polarized light. A wafer-scale array of sharp metallic pyramids is fabricated via template stripping with films of different thicknesses on opposing pyramid facets. This structural asymmetry is achieved through a one-step angled metal deposition that does not require any additional lithography processing and when internally illuminated enables the generation of plasmons using a Kretschmann-like coupling method on only one side of the pyramids. Plasmons traveling toward the tip on one side will converge at the apex, forming a nanoscale "hotspot." The asymmetry is necessary for these focusing effects since symmetric pyramids display destructive plasmon interference at the tip. Computer simulations confirm that internal illumination with linearly polarized light at normal incidence on these asymmetric pyramids will focus optical energy into nanoscale volumes. Far-field optical experiments demonstrate large field enhancements as well as angle-dependent spectral tuning of the reradiated light. Because of the low background light levels, wafer-scale fabrication, and a straightforward excitation scheme, these asymmetric pyramidal tips will find applications in near-field optical microscopy and array-based optical trapping.

  9. Metal-organic framework templated synthesis of ultrathin, well-aligned metallic nanowires.

    PubMed

    Volosskiy, Boris; Niwa, Kenta; Chen, Yu; Zhao, Zipeng; Weiss, Nathan O; Zhong, Xing; Ding, Mengning; Lee, Chain; Huang, Yu; Duan, Xiangfeng

    2015-03-24

    With well-defined porous structures and dimensions, metal-organic frameworks (MOFs) can function as versatile templates for the growth of metallic nanostructures with precisely controlled shapes and sizes. Using MOFs as templates, metallic nanostructures can be grown without the need of bulky surfactants and thus preserve their intrinsic surface. Additionally, the high surface area of MOFs can also ensure that the surface of the template metallic nanostructures is readily accessible, which is critical for the proper function of catalysts or sensors. The hybrid metal@MOF structures have been demonstrated to exhibit useful properties not found in either component separately. Here we report the growth of ultrafine metallic nanowires inside one-dimensional MOF pores with well-controlled shape and size. Our study shows that solvent selection plays an important role in controlling precursor loading and the reduction rate inside the MOF pores for the formation of the nanowires. The growth of the well-aligned, ultrathin nanowires was monitored and characterized by transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, fluorescence studies, and Brunauer-Emmet-Teller surface area analysis.

  10. Tridentate ligated heteronuclear tin(II) alkoxides for use as base catalysts

    DOEpatents

    Boyle, Timothy J.

    2001-01-01

    Tin alkoxide compounds are provided with accessible electrons. The tin alkoxide compound have the general formula (THME).sub.2 Sn.sub.3 (M(L).sub.x).sub.y, where THME is (O--CH.sub.2).sub.3 C(CH.sub.3), M is a metal atom selected from Sn and Ti, L is an organic/inorganic ligand selected from an alkoxide, a phenoxide or an amide, x is selected from 2 and 4 and y is selected from 0 and 1. These compounds have applicability as base catalysts in reactions and in metal-organic chemical vapor depositions processes.

  11. Mesoporous silicates prepared using preorganized templates in supercritical fluids.

    PubMed

    Pai, Rajaram A; Humayun, Raashina; Schulberg, Michelle T; Sengupta, Archita; Sun, Jia-Ning; Watkins, James J

    2004-01-23

    Well-ordered mesoporous silicate films were prepared by infusion and selective condensation of silicon alkoxides within microphase-separated block copolymer templates dilated with supercritical carbon dioxide. Confinement of metal oxide deposition to specific subdomains of the preorganized template yields high-fidelity, three-dimensional replication of the copolymer morphology, enabling the preparation of structures with multiscale order in a process that closely resembles biomineralization. Ordered mesoporous silicate films were synthesized with dielectric constants as low as 1.8 and excellent mechanical properties. The films survive the chemical-mechanical polishing step required for device manufacturing.

  12. Mesoporous Silicates Prepared Using Preorganized Templates in Supercritical Fluids

    NASA Astrophysics Data System (ADS)

    Pai, Rajaram A.; Humayun, Raashina; Schulberg, Michelle T.; Sengupta, Archita; Sun, Jia-Ning; Watkins, James J.

    2004-01-01

    Well-ordered mesoporous silicate films were prepared by infusion and selective condensation of silicon alkoxides within microphase-separated block copolymer templates dilated with supercritical carbon dioxide. Confinement of metal oxide deposition to specific subdomains of the preorganized template yields high-fidelity, three-dimensional replication of the copolymer morphology, enabling the preparation of structures with multiscale order in a process that closely resembles biomineralization. Ordered mesoporous silicate films were synthesized with dielectric constants as low as 1.8 and excellent mechanical properties. The films survive the chemical-mechanical polishing step required for device manufacturing.

  13. Preparation of silica stabilized Tobacco mosaic virus templates for the production of metal and layered nanoparticles.

    PubMed

    Royston, Elizabeth S; Brown, Adam D; Harris, Michael T; Culver, James N

    2009-04-15

    The use of biological molecules as templates for the production of metal nanoparticles and wires is often limited by the stability of the bio-template and its affinity for nucleating metal deposition. In this study, Tobacco mosaic virus (TMV) was used as a model bio-template to investigate the use of silica coatings as a means to both enhance template stability and increase its affinity for metal ions. Results indicate that the unmodified TMV particle can function as a template for the growth of thin (<1 nm) silica layers. However, this thin silica shell did not enhance the stability of the template during metal deposition. To increase silica growth on the TMV template, a pretreatment with aniline was used to produce a uniform silica attractive surface. Aniline pretreated templates yielded significant silica layers of >20 nm in thickness. These silica shells conferred a high degree of stability to the TMV particle and promoted the deposition of various metal nanoparticles through conventional silica mineralization chemistries. This process provides a simple and robust method for the layering of inorganics onto a biological template.

  14. Dextran templating for the synthesis of metallic and metal oxide sponges

    NASA Astrophysics Data System (ADS)

    Walsh, Dominic; Arcelli, Laura; Ikoma, Toshiyuki; Tanaka, Junzo; Mann, Stephen

    2003-06-01

    Silver or gold-containing porous frameworks have been used extensively in catalysis, electrochemistry, heat dissipation and biofiltration. These materials are often prepared by thermal reduction of metal-ion-impregnated porous insoluble supports (such as alumina and pumice), and have surface areas of about 1 m2 g-1, which is typically higher than that obtained for pure metal powders or foils prepared electrolytically or by infiltration and thermal decomposition of insoluble cellulose supports. Starch gels have been used in association with zeolite nanoparticles to produce porous inorganic materials with structural hierarchy, but the use of soft sacrificial templates in the synthesis of metallic sponges has not been investigated. Here we demonstrate that self-supporting macroporous frameworks of silver, gold and copper oxide, as well as composites of silver/copper oxide or silver/titania can be routinely prepared by heating metal-salt-containing pastes of the polysaccharide, dextran, to temperatures between 500 and 900 °C. Magnetic sponges were similarly prepared by replacing the metal salt precursor with preformed iron oxide (magnetite) nanoparticles. The use of dextran as a sacrificial template for the fabrication of metallic and metal oxide sponges should have significant benefits over existing technologies because the method is facile, inexpensive, environmentally benign, and amenable to scale-up and processing.

  15. Templated synthesis for highly ordered metal/support nanocomposite materials with catalytic applications

    NASA Astrophysics Data System (ADS)

    Sarkar, Jayashri

    Template synthesis is a powerful method of synthesizing materials with tunable properties. Tailorability of the templates makes it a viable method for high performance material synthesis. Surfactant, polymers and semiconductors have been used as templating tools for a long time. In the present work, we demonstrate the ability to synthesize hexagonally organized porous titania, zirconia and zirconia/titania mixed oxide supports and their respective nanocomposites of Pt from their alkoxide precursors using a highly viscous mixed surfactant template, separating nanoscopic bicontinuous channels of water and isooctane. Oil soluble precursor that eventually forms the support, precipitates at the oil-water interface mimicking the microstructure of the template. Subsequent reduction of Pt precursor in the aqueous nanochannels decorates the surface of the macropore walls with well-separated platinum (Pt) nanoparticles. This technique enables us to synthesize two components in a single template system by utilizing both oil and water phases. The composite formed possess a bimodal pore size distribution with one mean pore size ˜3.5nm (nanopores) and the other in the larger mean pore diameter regions ˜100nm-2mum (macropores), depending on the oxide support. Because of the decreased mass transfer resistance provided by the ordered and interconnected macropores in the support, the Pt/TiO2 nanocomposite exhibits a significantly higher carbon monoxide oxidation efficiency than that obtained with a commercial support that has a 4-fold larger specific surface area (at equivalent Pt loadings). We further demonstrate that simple changes in the post-synthesis processing can improve the properties of the material. Altering the drying technique and calcination temperature result in a substantial improvement in the specific surface area of the support material making them better than or comparable to the commercial support materials. We are able to synthesize materials with very low Pt

  16. Improved metal cluster deposition on a genetically engineered tobacco mosaic virus template

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yup; Royston, Elizabeth; Culver, James N.; Harris, Michael T.

    2005-07-01

    Improved depositions of various metal clusters onto a biomolecular template were achieved using a genetically engineered tobacco mosaic virus (TMV). Wild-type TMV was genetically altered to display multiple solid metal binding sites through the insertion of two cysteine residues within the amino-terminus of the virus coat protein. Gold, silver, and palladium clusters synthesized through in situ chemical reductions could be readily deposited onto the genetically modified template via the exposed cysteine-derived thiol groups. Metal cluster coatings on the cysteine-modified template were more densely deposited and stable than similar coatings on the unmodified wild-type template. Combined, these results confirm that the introduction of cysteine residues onto the outer surface of the TMV coat protein enhances the usefulness of this virus as a biotemplate for the deposition of metal clusters.

  17. Preparation of Mesoporous Silica Templated Metal Nanowire Films on Foamed Nickel Substrates

    SciTech Connect

    Campbell, Roger; Kenik, Edward A; Bakker, Martin; Havrilla, George; Montoya, Velma; Shamsuzzoha, Mohammed

    2006-01-01

    A method has been developed for the formation of high surface area nanowire films on planar and three-dimensional metal electrodes. These nanowire films are formed via electrodeposition into a mesoporous silica film. The mesoporous silica films are formed by a sol-gel process using Pluronic tri-block copolymers to template mesopore formation on both planar and three-dimensional metal electrodes. Surface area increases of up to 120-fold have been observed in electrodes containing a templated film when compared to the same types of electrodes without the templated film.

  18. Two-stage evaporated ordered nanoporous ultrathin metal films using reusable template

    NASA Astrophysics Data System (ADS)

    Li, Zeping; Xu, Zhimou; Qu, Xiaopeng; Mei, Lihong

    2017-02-01

    In this work, we present a versatile procedure for the formation of ordered nanoporous ultrathin metal film using reusable anodic aluminum oxide (AAO) template. Firstly, the Ag and Au films were evaporated on the bottom surface of AAO template sequentially, followed by selective removal of a sacrificial Ag film. This process results in an ultrathin nanoporous Au film was prepared without causing significant damage of the AAO replication template. The characterizations of SEM images indicate that obtained metal films have the hexagonal morphology similar to AAO template. The EDS analyses of the present Au film on the Si substrate indicate that Ag film was completely etched away. This novel fabrication method not only simplifies the preparation of ordered nanoporous ultrathin metal film, but also can be readily extended to other materials systems.

  19. Mechanisms of metal mineralization on virus templates for nanorod synthesis

    NASA Astrophysics Data System (ADS)

    Adigun, Oluwamayowa O.

    Solution synthesis of nanorods is currently an important area of study due to the precision required to engender advantages in a wide range of fields. Viruses provide a template for synthesis in order to form uniform metal nanorods at mild operating conditions, without the use of expensive technology. In recent years, many materials involving the Tobacco mosaic virus (TMV) and its variants have been synthesized in attempts to produce high quality nanomaterials. However, the underlying processes involved in virion mineralization have not been sufficiently studied to allow for directed synthesis. The fundamental study of the hydrothermal synthesis of palladium on biotemplates, which produces uniform, controllable, monodisperse palladium nanorods, is of interest in this thesis. Three different experimental studies are outlined in this thesis. In situ X-ray absorption spectroscopy (XAS) was employed in order to characterize the reduction and growth mechanisms of palladium (Pd) on the surface of genetically engineered TMV. XAS, via XANES and EXAFS analysis was combined with TEM to confirm an autocatalytic reduction, mediated by the TMV1Cys surface. This reduction interestingly proceeds via two first order regimes, which result in two linear growth regimes as spherical palladium nanoparticles are formed. Results in this project served as an entryway into fundamentally understanding virus-mediated reduction and the relationship between the underlying reduction and growth processes governing mineralization. Pd biomineralization was further elucidated by reframing it within commonly known molecular processes. These included the individual adsorption, reduction, and nanocrystal growth processes, which simultaneously occur during the hydrothermal synthesis on TMV. The adsorption of precursor and reduction of palladium were decoupled through UV-Vis Spectroscopy and in situ XAS studies. The role of additional cysteine (Cys) residues, ionic strength, and coating density on the

  20. Template-Directed Approach Towards the Realization of Ordered Heterogeneity in Bimetallic Metal-Organic Frameworks.

    PubMed

    Kim, Daeok; Coskun, Ali

    2017-03-29

    Controlling the arrangement of different metal ions to achieve ordered heterogeneity in metal-organic frameworks (MOFs) has been a great challenge. Herein, we introduce a template-directed approach, in which a 1D metal-organic polymer incorporating well-defined binding pockets for the secondary metal ions used as a structural template and starting material for the preparation of well-ordered bimetallic MOF-74s under heterogeneous-phase hydrothermal reaction conditions in the presence of secondary metal ions such as Ni(2+) and Mg(2+) in 3 h. The resulting bimetallic MOF-74s were found to possess a nearly 1:1 metal ratio regardless of their initial stoichiometry in the reaction mixture, thus demonstrating the possibility of controlling the arrangement of metal ions within the secondary building blocks in MOFs to tune their intrinsic properties such as gas affinity.

  1. Fabrication of Smooth Patterned Structures of Refractory Metals, Semiconductors, and Oxides via Template Stripping

    PubMed Central

    2013-01-01

    The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics. PMID:24001174

  2. Fabrication of smooth patterned structures of refractory metals, semiconductors, and oxides via template stripping.

    PubMed

    Park, Jong Hyuk; Nagpal, Prashant; McPeak, Kevin M; Lindquist, Nathan C; Oh, Sang-Hyun; Norris, David J

    2013-10-09

    The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics.

  3. Determination of rare earth elements in seawater by inductively coupled plasma mass spectrometry with on-line column pre-concentration using 8-quinolinole-immobilized fluorinated metal alkoxide glass

    NASA Astrophysics Data System (ADS)

    Kajiya, Tasuku; Aihara, Masato; Hirata, Shizuko

    2004-04-01

    The on-line column pre-concentration technique with inductively coupled plasma mass spectrometry (ICP-MS) has been developed using micro-column of 8-quinolinole-immobilized fluorinated metal alkoxide glass (MAF-8HQ). The aim of method was to determine rare earth elements (REEs) (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in seawater. A 6.4 ml of seawater sample was passed through the column for 2 min, after washing the column with ultrapure water, the adsorbed REEs were subsequently eluted into the plasma with 1.4 M nitric acid. Sample pH, sampling and eluting flow rates and acidity of eluent were optimized. Detection limits (3 σ) based on three times standard deviations of water by 8 replicates were in the range from 0.11 pg ml -1 for Y to 0.30 pg ml -1 for Tb, and the precisions by a 10 pg ml -1 REEs standard solution ( n=8) were in the range from 4.7% for Tm to 8.7% for Tb and Yb. Analysis of one sample could be processed in 7 min. The proposed method was verified by determination of REEs in the two certified reference materials (CRMs) of seawater, CASS-4 and NASS-5, and the method was also applied to determine REEs in the costal seawater of Hiroshima Bay, the Seto Inland Sea, Japan.

  4. Single crystalline hollow metal-organic frameworks: a metal-organic polyhedron single crystal as a sacrificial template.

    PubMed

    Kim, Hyehyun; Oh, Minhak; Kim, Dongwook; Park, Jeongin; Seong, Junmo; Kwak, Sang Kyu; Lah, Myoung Soo

    2015-02-28

    Single crystalline hollow metal-organic frameworks (MOFs) with cavity dimensions on the order of several micrometers and hundreds of micrometers were prepared using a metal-organic polyhedron single crystal as a sacrificial hard template. The hollow nature of the MOF crystal was confirmed by scanning electron microscopy of the crystal sliced using a focused ion beam.

  5. Replicative generation of metal microstructures by template-directed electrometallization

    SciTech Connect

    Thom, I.; Haehner, G.; Buck, M.

    2005-07-11

    Copper structures were produced by electrochemical deposition onto patterned self-assembled monolayers (SAMS) of thiols adsorbed on polycrystalline gold substrates and subsequent transfer to an insulating substrate. Selective metal deposition was achieved by use of thiols which differ in their electrochemical blocking properties, namely hexadecane thiol [CH{sub 3}(CH{sub 2}){sub 15}SH] and {omega}-(4{sup '}-methyl-biphenyl-4-yl)-methanethiol (CH{sub 3}-C{sub 6}H{sub 4}-C{sub 6}H{sub 4}-CH{sub 2}-SH). Besides control of the blocking properties, the SAM served to minimize adhesion between the metal deposit and the substrate, thus, allowing the transfer of the metal pattern. Since the process is replicative, it represents a very simple and fast route to generating metal patterns.

  6. Replicative generation of metal microstructures by template-directed electrometallization

    NASA Astrophysics Data System (ADS)

    Thom, I.; Hähner, G.; Buck, M.

    2005-07-01

    Copper structures were produced by electrochemical deposition onto patterned self-assembled monolayers (SAMS) of thiols adsorbed on polycrystalline gold substrates and subsequent transfer to an insulating substrate. Selective metal deposition was achieved by use of thiols which differ in their electrochemical blocking properties, namely hexadecane thiol [CH3(CH2)15SH] and ω-(4'-methyl-biphenyl-4-yl)-methanethiol (CH3-C6H4-C6H4-CH2-SH). Besides control of the blocking properties, the SAM served to minimize adhesion between the metal deposit and the substrate, thus, allowing the transfer of the metal pattern. Since the process is replicative, it represents a very simple and fast route to generating metal patterns.

  7. Synthesis and characterization of GaPO{sub 4} molecular sieves using metal complexes as templates

    SciTech Connect

    Balkus, K.J. Jr.; Kim, S.J.; Sargeson, A.M.

    1997-12-31

    Work on the preparations of zeolite ship-in-a-bottle complexes, which involves the encapsulation of metal complexes during zeolite synthesis, encouraged the authors to explore the relatively unknown structure directing properties of metal complexes. In particular, the authors have shown that bis(pentamethylcyclopentadienyl) cobalt(III) hydroxide, Cp*{sub 2}CoOH was a template for the novel high silica zeolite UTD-1 which is the first zeolite having greater than a 12 membered ring pore structure. The authors have extended this strategy to other oxide compositions and metal complexes. In this paper the authors describe the preparation and characterization (XRD, SEM) of the gallophosphates Cloverite and UTD-10 using the metal complex [Co(NMe{sub 3}){sub 2}sar]{sup 5+} (where (NMe{sub 3}){sub 2}sar = 1,8-bis(trimethylammonio)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]-icosane) as the template.

  8. Oxidation sharpening, template stripping, and passivation of ultra-sharp metallic pyramids and wedges.

    PubMed

    Im, Hyungsoon; Oh, Sang-Hyun

    2014-02-26

    Ultra-sharp metallic pyramids and wedges with tunable tip angles and 5-nm tip radii are replicated from oxidation-sharpened silicon templates with high throughput (80 million pyramids per wafer). Atomic layer deposition of Al2 O3 shells can protect these sharp pyramidal tips for subsequent usage in near-field imaging.

  9. Enantiopure anion templated synthesis of a zeolitic metal-organic framework.

    PubMed

    Xu, Zhong-Xuan; Ma, Yu-Lu; Zhang, Jian

    2016-01-31

    Utilizing (R)-H3CIA as a chiral template, an unprecedented homochiral metal-organic framework (MOF) with zeotype GIS topology is obtained from achiral 1.4-DIB ligands and Zn(II) ions, which opens up a feasible approach to create zeolitic MOFs with homochirality.

  10. Metal-organic framework templated synthesis of porous inorganic materials as novel sorbents

    DOEpatents

    Taylor-Pashow, Kathryn M. L.; Lin, Wenbin; Abney, Carter W.

    2017-03-21

    A novel metal-organic framework (MOF) templated process for the synthesis of highly porous inorganic sorbents for removing radionuclides, actinides, and heavy metals is disclosed. The highly porous nature of the MOFs leads to highly porous inorganic sorbents (such as oxides, phosphates, sulfides, etc) with accessible surface binding sites that are suitable for removing radionuclides from high level nuclear wastes, extracting uranium from acid mine drainage and seawater, and sequestering heavy metals from waste streams. In some cases, MOFs can be directly used for removing these metal ions as MOFs are converted to highly porous inorganic sorbents in situ.

  11. Thermally Stable Metal-Organic Framework-Templated Synthesis of Hierarchically Porous Metal Sulfides: Enhanced Photocatalytic Hydrogen Production.

    PubMed

    Xiao, Juan-Ding; Jiang, Hai-Long

    2017-07-01

    Porous nanostructured materials are demonstrated to be very promising in catalysis due to their well accessible active sites. Thermally stable metal-organic frameworks (MOFs) as hard templates are successfully utilized to afford porous metal oxides and subsequently metal sulfides by a nanocasting method. The resultant metal oxides/sulfides show considerable Brunauer-Emmett-Teller (BET) surface areas, by partially inheriting the pore character of MOF templates. Preliminary investigation on the obtained hierarchically porous CdS for water splitting, as a proof of concept, demonstrates its much higher activity than both corresponding bulk and nanosized counterparts, under visible light irradiation. Given the structural diversity and tailorability of MOFs, such synthetic approach may open an avenue to the synthesis of advanced porous materials for functional applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Metal-silicate catalysts: Single site, mesoporous systems without templates

    SciTech Connect

    Barnes, Craig E.; Sharp, Katherine; Albert, Austin A; Abbott, Joshua; Peretich, Michael E; Fulvio, Pasquale; Ciesielski, Peter N.; Donohoe, Bryon S.

    2015-06-01

    The textural properties of a family of silicate and mixed metal-silicate materials prepared by a nonaqueous sol-gel reaction involving the cubic silicate Si8O20(SnMe3)8 and metal chlorides MCl4 (M = Si, Ti, Zr) cross-linking reagents are described. Nitrogen adsorption isotherm data is presented and surface area and pore size distribution analyses for several examples of these materials are developed and correlated with the ratio of cross-linking reagent and the cubic silicate building block at the time of synthesis. Significant surface area and pore size distributions that shift to higher pore diameters are observed as the ratio of cross-linking reagent-to-cubic building block increases. A simple strategy for simultaneously controlling the porosity of these matrices while homogeneously dispersing identical metal centers on their surfaces for next generation catalysts is described.

  13. Template synthesis of metal nanowires containing monolayer molecular junctions.

    PubMed

    Mbindyo, Jeremiah K N; Mallouk, Thomas E; Mattzela, James B; Kratochvilova, Irena; Razavi, Baharak; Jackson, Thomas N; Mayer, Theresa S

    2002-04-17

    Metal nanowires containing in-wire monolayer junctions of 16-mercaptohexanoic acid were made by replication of the pores of 70 nm diameter polycarbonate track etch membranes. Au was electrochemically deposited halfway through the 6 microm long pores and a self-assembled monolayer (SAM) of 16-mercaptohexadecanoic acid was adsorbed on top. A thin layer of Au was then electrolessly grown to form a metal cap separated from the bottom part of the wire by the SAM. Electron micrographs showed that the bottom and top metal segments were separated by an approximately 2 nm thick organic monolayer. Current-voltage measurements of individual nanowires confirmed that the organic monolayer could be contacted electrically on the top and bottom by the metal nanowire segments without introducing electrical short circuits that penetrate the monolayer. The values of the electrical properties for zero-bias resistance, current density, and breakdown field strength were within the ranges expected for a well-ordered alkanethiol SAM of this thickness.

  14. Reactive template synthesis of polypyrrole nanotubes for fabricating metal/conducting polymer nanocomposites.

    PubMed

    Zhang, Jun; Liu, Xianghong; Zhang, Lixue; Cao, Bingqiang; Wu, Shihua

    2013-03-25

    Unique nanocomposites of polypyrrole/Au and polypyrrole/Pt hybrid nanotubes are synthesized employing polypyrrole (PPy) nanotubes as an advanced support by solution reduction. The conducting polymer PPy nanotubes are fabricated by using pre-prepared MnO2 nanowires as the reactive templates. MnO2 nanowires induce the 1D polymerization of pyrrole monomers and the simultaneous dissolution of the templates affords the hollow tube-like structure. The loading content of metal nanoparticles in the nanocomposites could be adjusted by simply changing the amount of metal precursors. This work provides an efficient approach to fabricate an important kind of metal/conducting polymer hybrid nanotubes that are potentially useful for electrocatalyst and sensor materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Engineering Hybrid Metallic Nanostructures Using a Single Domain of Block Copolymer Templates.

    PubMed

    Liu, Zhicheng; Chang, Tongxin; Huang, Haiying; He, Tianbai

    2015-11-25

    Building complex nanostructures using a simple patterned template is challenging in material science and nanotechnology. In the present work, three different strategies have been exploited for the successful fabrication of hybrid dots-on-wire metallic nanostructures through combining an in-situ method with an ex-situ method. Basically, plasma etching was applied to generate a metallic wire-like nanostructure, and preformed nanoparticles could be placed through multiple means before or after the formation of the wire-like nanostructure. Various monometallic and bimetallic nanostructures have been obtained by utilizing only one functional domain of block copolymer templates. In these cases, full utilization of the functional domain or introduction of the molecular linker is critical to engineering hybrid metallic nanostructures. Other complex and multifunctional hybrid nanostructures can be developed via these strategies similarly, and these nanostructures are promising for useful applications such as optics and surface-enhanced Raman spectroscopy (SERS).

  16. Formation of 3D graphene foams on soft templated metal monoliths

    NASA Astrophysics Data System (ADS)

    Tynan, Michael K.; Johnson, David W.; Dobson, Ben P.; Coleman, Karl S.

    2016-07-01

    Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy.Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy. Electronic supplementary information (ESI) available: Raman, EDX, PXRD, TGA, electrical conductivity data and SEM. See DOI: 10.1039/c6nr02455f

  17. Unifying the templating effects of porous anodic alumina on metallic nanoparticles for carbon nanotube synthesis

    NASA Astrophysics Data System (ADS)

    Haase, Mark R.; Alvarez, Noe T.; Malik, Rachit; Schulz, Mark; Shanov, Vesselin

    2015-09-01

    Carbon nanotubes (CNTs) are a promising material for many applications, due to their extraordinary properties. Some of these properties vary in relation to the diameter of the nanotubes; thus, precise control of CNT diameter can be critical. Porous anodic alumina (PAA) membranes have been successfully used to template electrodeposited catalyst. However, the catalysts used in CNT synthesis are frequently deposited with more precise techniques, such as electron beam deposition. We test the efficacy of PAA as a template for electron beam-deposited catalyst by studying the diameter distribution of CNTs grown catalyst of various thicknesses supported by PAA. These are then compared by ANOVA to the diameter distributions of CNTs grown on metal catalyst supported by a conventional alumina film. These results also allow a unified description of two templating effects, the more common particles-in-pores model, and the recently described particles-between-pores.

  18. Peptide template effects on the synthesis and reactivity of metal nanoparticle networks

    NASA Astrophysics Data System (ADS)

    Bhandari, Rohit

    A bio-templated approach for the synthesis of multiple inorganic materials has been presented that correlates with the role of a 3-dimensional peptide template in controlling the overall reactivity of the fabricated materials for a variety of chemical reactions. The role of self-assembling R5 peptide for the formation of metallic nanoparticles including Pd, Au and Pt has been described. The materials were fully characterized using UV-vis spectroscopy, dynamic light scattering analysis, transmission electron microscopy and powder-X ray diffraction analysis. Also, the materials were employed as efficient catalysts for the Stille coupling reaction, 4-nitrophenol reduction as well as olefin hydrogenation reactions. These results are important as these template-based materials could potentially serve as candidates for a variety of applications ranging from bio- sensing tocatalysis to energy production.

  19. Synthesis of ternary metal nitride nanoparticles using mesoporous carbon nitride as reactive template.

    PubMed

    Fischer, Anna; Müller, Jens Oliver; Antonietti, Markus; Thomas, Arne

    2008-12-23

    Mesoporous graphitic carbon nitride was used as both a nanoreactor and a reactant for the synthesis of ternary metal nitride nanoparticles. By infiltration of a mixture of two metal precursors into mesoporous carbon nitride, the pores act first as a nanoconfinement, generating amorphous mixed oxide nanoparticles. During heating and decomposition, the carbon nitride second acts as reactant or, more precisely, as a nitrogen source, which converts the preformed mixed oxide nanoparticles into the corresponding nitride (reactive templating). Using this approach, ternary metal nitride particles with diameters smaller 10 nm composed of aluminum gallium nitride (Al-Ga-N) and titanium vanadium nitride (Ti-V-N) were synthesized. Due to the confinement effect of the carbon nitride matrix, the composition of the resulting metal nitride can be easily adjusted by changing the concentration of the preceding precursor solution. Thus, ternary metal nitride nanoparticles with continuously adjustable metal composition can be produced.

  20. Hierarchical Metal Oxide Topographies Replicated from Highly Textured Graphene Oxide by Intercalation Templating.

    PubMed

    Chen, Po-Yen; Liu, Muchun; Valentin, Thomas M; Wang, Zhongying; Spitz Steinberg, Ruben; Sodhi, Jaskiranjeet; Wong, Ian Y; Hurt, Robert H

    2016-12-27

    Confined assembly in the intersheet gallery spaces of two-dimensional (2D) materials is an emerging templating route for creation of ultrathin material architectures. Here, we demonstrate a general synthetic route for transcribing complex wrinkled and crumpled topographies in graphene oxide (GO) films into textured metal oxides. Intercalation of hydrated metal ions into textured GO multilayer films followed by dehydration, thermal decomposition, and air oxidation produces Zn, Al, Mn, and Cu oxide films with high-fidelity replication of the original GO textures, including "multi-generational", multiscale textures that have been recently achieved through extreme graphene compression. The textured metal oxides are shown to consist of nanosheet-like aggregates of interconnected particles, whose mobility, attachment, and sintering are guided by the 2D template. This intercalation templating approach has broad applicability for the creation of complex, textured films and provides a bridging technology that can transcribe the wide variety of textures already realized in graphene into insulating and semiconducting materials. These textured metal oxide films exhibit enhanced electrochemical and photocatalytic performance over planar films and show potential as high-activity electrodes for energy storage, catalysis, and biosensing.

  1. Plate, wire, mesh, microsphere, and microtube composed of sodium titanate nanotubes on a titanium metal template.

    PubMed

    Yada, Mitsunori; Inoue, Yuko; Uota, Masafumi; Torikai, Toshio; Watari, Takanori; Noda, Iwao; Hotokebuchi, Takao

    2007-02-27

    Sodium titanate nanotube/titanium metal composites were synthesized by hydrothermal treatment of titanium metals with various morphologies such as plate, wire, mesh, microsphere, and microtube at 160 degrees C in aqueous NaOH solution and by the subsequent fixation treatment by calcination at 300 degrees C. The surface of the composite was covered with sodium titanate nanotubes with a diameter of approximately 7 nm, and the core part of the composite was titanium metal phase. The raw titanium metal acts as a template or a morphology-directing agent of micrometer size or more to arrange the nanotubes as well as a titanium source for the formation of nanotubes. The concentration of titanium species increases in the reaction solution as the dissolution of titanium metal is accelerated by the reaction between titanium and OH-. Furthermore, with an increase in concentration of titanium species in the reaction solution, the titanium species are re-precipitated as sodium titanate nanotubes onto the titanium metal. Titanium metal with a large surface area and volume can form sodium titanate nanotubes on the surface of the titanium metal, though titanium metal with a small volume and surface area tends to dissolve with the hydrothermal treatment. Even in the synthesis using titanium metal with a small volume and surface area, sodium titanate nanotubes are formed and cover the surface of the titanium metal by adding another titanium metal as a source of titanium species in the reaction solution.

  2. Structure of reverse microemulsion-templated metal hexacyanoferrate nanoparticles

    PubMed Central

    2012-01-01

    The droplet phase of a reverse microemulsion formed by the surfactant cetyltrimethylammonium ferrocyanide was used as a matrix to synthesize nanoparticles of nickel hexacyanoferrate by adding just a solution of NiCl2 to the microemulsion media. Dynamic light scattering and small-angle neutron scattering measurements show that the reverse microemulsion droplets employed have a globular structure, with sizes that depend on water content. Transmission electron microscopy and electron diffraction are used to obtain information about the structure of the synthesized nanoparticles. The results show that the size and shape of the coordination compound nanoparticles correspond with the size and shape of the droplets, suggesting that the presented system constitutes an alternative method of the synthesis of metal hexacyanoferrate nanoparticles. PMID:22264404

  3. Template-directed assembly of metal-chalcogenide nanocrystals into ordered mesoporous networks.

    SciTech Connect

    Vamvasakis, Ioannis; Subrahmanyam, Kota S.; Kanatzidis, Mercouri G.; Armatas, Gerasimos S.

    2015-04-01

    Although great progress in the synthesis of porous networks of metal and metal oxide nanoparticles with highly accessible pore surface and ordered mesoscale pores has been achieved, synthesis of assembled 3D mesostructures of metal-chalcogenide nanocrystals is still challenging. In this work we demonstrate that ordered mesoporous networks, which comprise well-defined interconnected metal sulfide nanocrystals, can be prepared through a polymer-templated oxidative polymerization process. The resulting self-assembled mesostructures that were obtained after solvent extraction of the polymer template impart the unique combination of light-emitting metal chalcogenide nanocrystals, three-dimensional open-pore structure, high surface area, and uniform pores. We show that the pore surface of these materials is active and accessible to incoming molecules, exhibiting high photocatalytic activity and stability, for instance, in oxidation of 1-phenylethanol into acetophenone. We demonstrate through appropriate selection of the synthetic components that this method is general to prepare ordered mesoporous materials from metal chalcogenide nanocrystals with various sizes and compositions.

  4. Use of carbonaceous polysaccharide microspheres as templates for fabricating metal oxide hollow spheres.

    PubMed

    Sun, Xiaoming; Liu, Junfeng; Li, Yadong

    2006-02-20

    A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.

  5. Template Synthesis of Noble Metal Nanocrystals with Unusual Crystal Structures and Their Catalytic Applications.

    PubMed

    Fan, Zhanxi; Zhang, Hua

    2016-12-20

    Noble metal nanocrystals own high chemical stability, unique plasmonic and distinctive catalytic properties, making them outstanding in many applications. However, their practical applications are limited by their high cost and scarcity on the earth. One promising strategy to solve these problems is to boost their catalytic performance in order to reduce their usage amount. To realize this target, great research efforts have been devoted to the size-, composition-, shape- and/or architecture-controlled syntheses of noble metal nanocrystals during the past two decades. Impressively, recent experimental studies have revealed that the crystal structure of noble metal nanocrystals can also significantly affect their physicochemical properties, such as optical, magnetic, catalytic, mechanical, electrical and electronic properties. Therefore, besides the well-established size, composition, shape, and architecture control, the rise of crystal structure-controlled synthesis of noble metal nanocrystals will open up new opportunities to further improve their functional properties, and thus promote their potential applications in energy conversion, catalysis, biosensing, information storage, surface enhanced Raman scattering, waveguide, near-infrared photothermal therapy, controlled release, bioimaging, biomedicine, and so on. In this Account, we review the recent research progress on the crystal structure control of noble metal nanocrystals with a template synthetic approach and their crystal structure-dependent catalytic properties. We first describe the template synthetic methods, such as epitaxial growth and galvanic replacement reaction methods, in which a presynthesized noble metal nanocrystal with either new or common crystal structure is used as the template to direct the growth of unusual crystal structures of other noble metals. Significantly, the template synthetic strategy described here provides an efficient, simple and straightforward way to synthesize unusual

  6. Self-ordering of small-diameter metal nanoparticles by dewetting on hexagonal mesh templates.

    PubMed

    Meshot, Eric R; Zhao, Zhouzhou; Lu, Wei; Hart, A John

    2014-09-07

    Arrays of small-diameter nanoparticles with high spatial order are useful for chemical and biological sensors, data storage, synthesis of nanowires and nanotubes, and many other applications. We show that self-ordered metal nanoparticle arrays can be formed by dewetting of thin films on hexagonal mesh substrates made of anodic aluminum oxide (AAO). Upon heating, the metal (Fe) film dewets onto the interstitial sites (i.e., the node points) between pores on the top surface of the AAO. We investigated the particle morphology and dynamics of dewetting using a combination of atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), and numerical simulations. Templated metal particles are more monodisperse and have higher local order than those formed by the same dewetting process on flat, nonporous alumina. The degree of order depends on the initial film thickness, and for the optimal thickness tested (nominally 2 nm), we achieved uniform coverage and high order of the particles, comparable to that of the AAO template itself. Computational modeling of dewetting on templates with various pore order and size shows that the order of AAO pores is primarily influential in determining particle position and spacing, while the variance in pore size is less impactful. Potential uses of these ordered nanoparticle arrays on porous materials include plasmonic sensors and spatially controlled catalysts.

  7. Alcohol-free alkoxide process for containing nuclear waste

    DOEpatents

    Pope, James M.; Lahoda, Edward J.

    1984-01-01

    Disclosed is a method of containing nuclear waste. A composition is first prepared of about 25 to about 80%, calculated as SiO.sub.2, of a partially hydrolyzed silicon compound, up to about 30%, calculated as metal oxide, of a partially hydrolyzed aluminum or calcium compound, about 5 to about 20%, calculated as metal oxide, of a partially hydrolyzed boron or calcium compound, about 3 to about 25%, calculated as metal oxide, of a partially hydrolyzed sodium, potassium or lithium compound, an alcohol in a weight ratio to hydrolyzed alkoxide of about 1.5 to about 3% and sufficient water to remove at least 99% of the alcohol as an azeotrope. The azeotrope is boiled off and up to about 40%, based on solids in the product, of the nuclear waste, is mixed into the composition. The mixture is evaporated to about 25 to about 45% solids and is melted and cooled.

  8. Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography.

    PubMed

    Klemme, Daniel J; Johnson, Timothy W; Mohr, Daniel A; Oh, Sang-Hyun

    2016-05-23

    We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magnetic recording.

  9. Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography

    SciTech Connect

    Klemme, Daniel J.; Johnson, Timothy W.; Mohr, Daniel A.; Oh, Sang-Hyun

    2016-05-23

    We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magnetic recording.

  10. Synthesis and photocatalytic property of porous metal oxides nanowires based on carbon nanofiber template

    NASA Astrophysics Data System (ADS)

    Fan, Weiqiang; Li, Meng; Xu, Jinfu; Bai, Hongye; Zhang, Rongxian; Chen, Chao

    2015-11-01

    A series of porous metal oxides nanowires (Fe2O3, Co3O4, NiO and CuO) have been successfully synthesized, where commercial carbon nanofibers were used as the template. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance (UV-Vis DR) spectra and transmission electron microscope (TEM). According to the photodegradation data, the porous metal oxides nanowires exhibit significantly photocatalytic activity for degrading tetracycline (TC). Furthermore, the porous Fe2O3 nanowires show the best photocatalytic performance among all the samples.

  11. Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography

    NASA Astrophysics Data System (ADS)

    Klemme, Daniel J.; Johnson, Timothy W.; Mohr, Daniel A.; Oh, Sang-Hyun

    2016-05-01

    We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magnetic recording.

  12. AlGaN Metal-Semiconductor-Metal Photodetectors on Planar and Epitaxial Laterally Overgrown AlN/Sapphire Templates for the Ultraviolet C Spectral Region

    NASA Astrophysics Data System (ADS)

    Knigge, Andrea; Brendel, Moritz; Brunner, Frank; Einfeldt, Sven; Knauer, Arne; Kueller, Viola; Zeimer, Ute; Weyers, Markus

    2013-08-01

    Schottky type metal-semiconductor-metal (MSM) Al0.4Ga0.6N photodetectors (PDs) for the ultraviolet C spectral region on conventional planar AlN templates are compared with epitaxial laterally overgrown (ELO) AlN templates. On planar templates solar blind MSM PDs with state-of-the-art dark current in the pA range and a power independent responsivity are obtained. PDs on ELO templates with fingers parallel to the etched stripes have properties similar to those on planar templates. PDs on ELO templates with contact fingers oriented perpendicular to the etched stripe pattern exhibit photoconductive gain leading to external quantum efficiencies of up to 77 at 30 V applied bias surpassing that of the planar grown PDs by a factor of 100. In spite of the high gain these PDs also show low dark currents, short switching times and two operating regimes with power independent responsivity.

  13. Preparation of metallic pivot-based imprinted monolith for polar template.

    PubMed

    Zhong, Dan-Dan; Huang, Yan-Ping; Xin, Xue-Lei; Liu, Zhao-Sheng; Aisa, Haji Akber

    2013-09-01

    One of the main challenges in MIPs preparation is the proper MIP monolith design for water-soluble compounds due to the difficulty in satisfying the demands of both good column permeability and affinity to polar template. A new strategy of metallic pivot in a ternary porogenic system of dimethyl sulfoxide (DMSO)-dimethylformamide (DMF)-1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) was suggested to solve this problem. An imprinted monolithic column with high porosity and good permeability was synthesized using a mixture of methyl gallate (template), 4-vinylpyridine, ethylene glycol dimethacrylate, and cobalt acetate. Some polymerization factors, such as template-monomer molar ratio and the composition of the ionic liquid, on the imprinting effect of the resulting MIPs monoliths were systematically investigated. In a mobile phase of acetonitrile-buffer, the greatest imprinting factor of 10.9 was obtained on the MIPs monolith with the optimized polymerization parameters. Thermodynamic analysis for separation demonstrated that the separation between the template and its analogs on the ion-mediated MIPs monolith is an enthalpy-controlled process.

  14. Synthesis of Hierarchical Porous Metals Using Ionic-Liquid-Based Media as Solvent and Template.

    PubMed

    Kang, Xinchen; Sun, Xiaofu; Ma, Xiaoxue; Zhang, Pei; Zhang, Zhanrong; Meng, Qinglei; Han, Buxing

    2017-10-02

    It was found that nanodomains existed in the ionic liquid (IL)-based ternary system containing IL 1-ethyl-3-methylimidazole tetrafluoroborate (EmimBF4 ), IL 1-decyl-3-methylimidazole nitrate (DmimNO3 ) and water, and the size distribution of the domains varied continuously with the composition of the solution. A strategy to synthesize hierarchical porous metals using IL-based media as solvent and template is proposed, and the hierarchical porous Ru and Pt metals were prepared by the assembly of metal clusters of about 1.5 nm using this new method. It is demonstrated that the metals have micropores and mesopores, and the size distribution is tuned by controlling the composition of the solution. Porous Ru was used for a series of hydrogenation reactions. It has an outstanding catalytic performance owing to its special morphology and structure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Simultaneous deposition of Ni nanoparticles and wires on a tubular halloysite template: A novel metallized ceramic microstructure

    SciTech Connect

    Fu Yubin . E-mail: ffyybb725@vip.sina.com; Zhang Lide

    2005-11-15

    Tubular halloysite can be used as a template to fabricate a novel metallized ceramic microstructure through electroless plating. Reduction of Pd ions by methanol is conducted to initiate Ni plating. There is a simultaneous deposition of Ni nanoparticles on the outer surface and discontinuous wires in the lumen site of the halloysite template obtained. The different deposition could be caused by the different composition distribution of ferric oxide impurity in the wall due to the isomorphic substitution during the formation of halloysite template. Its magnetic property is mainly attributed to the Ni nanoparticles, not the wires. The metallized ceramic microstructure has the potential to be utilized as a novel magnetic material.

  16. Spectrophotometric titration of bimetallic metal cation binding in polyamido(amine) dendrimer templates.

    PubMed

    Marvin, Katherine A; Johnson, Justin A; Rodenbusch, Stacia E; Gong, Lucy; Vanden Bout, David A; Stevenson, Keith J

    2012-06-05

    Spectrophotometric titration and a binding isotherm were used to accurately assess the loading capacity of generation four polyamido(amine) (PAMAM) dendrimer templates with terminal alcohol groups (G4-OH). Preparation of bimetallic G4-OH dendrimer-encapsulated metal nanoclusters (DENs) necessitates knowledge of the precise metal-ion binding capacity. The binding of metal ions such as Pt(2+) and Pd(2+) has proven difficult to assess via UV-vis spectroscopy because the absorbance shifts associated with metal-ion binding within the dendrimer template are masked by the absorbance of the PAMAM dendrimer itself. In contrast, the binding of Cu(2+) to G4-OH PAMAM dendrimer results in a strong, distinct absorption band at 300 nm, making UV-vis spectrophotometric titration with copper straightforward. Here we use copper binding as a means to assess the number of binding sites remaining within the PAMAM G4-OH dendrimer after the complexation of a specified molar excess of Pd(2+) or Pt(2+). In addition, we use a binding isotherm to mathematically estimate the loading capacity of the dendrimer in each case. The loading capacities for M(2+) in the G4-OH dendrimer were found to be ∼16 for copper alone, ∼21 for copper combined with palladium, and ∼25 for copper combined with platinum.

  17. Mesoporous mixed metal oxides derived from P123-templated Mg-Al layered double hydroxides

    SciTech Connect

    Wang Jun; Zhou Jideng; Li Zhanshuang; He Yang; Lin Shuangshuang; Liu Qi; Zhang Milin; Jiang Zhaohua

    2010-11-15

    We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg-Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 {sup o}C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg-Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m{sup 2}/g, and wide distribution of pore size (2-18 nm). An investigation of the 'memory effect' of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers. - Graphical abstract: Ordered mesoporous Mg-Al MMOs can be obtained through the calcination of P123-templated Mg-Al-CO{sub 3} LDHs. The pore diameter is 2.2 nm. At the presence of ibuprofen, the Mg-Al MMOs can recover to Mg-Al-IBU LDHs, based on its 'remember effect'. Display Omitted

  18. In-situ deposition of Pd nanoparticles on tubular halloysite template for initiation of metallization.

    PubMed

    Fu, Yubin; Zhang, Lide; Zheng, Jiyong

    2005-04-01

    Halloysite template has a tubular microstructure; its wall has a multi-layer aluminosilicate structure. A new catalytic method is adopted here, through the in-situ reduction of Pd ions on the surface of tubular halloysite by methanol to initiate electroless plating; the detailed deposition features of Pd nanoparticles are investigated for the first time. The results indicate that an in-situ reduction and deposition of Pd occurs at room temperature, in which the halloysite template plays an important role. Impurities in halloysite (such as ferric oxide) influence the formation and distribution of the Pd nanoparticles. The Pd nanoparticles are of a non-spherical shape in most cases, which would be caused by the irregular appearance of halloysite. No intercalation of the nanoparticles occurs between the aluminosilicate layers in the halloysite. The diameter of Pd nanoparticles increases with time; the average diameter ranges from 1 nm to 4 nm. Pd nanoparticles on a halloysite template can catalyze electroless deposition of Ni to prepare a novel nano-sized cermet at low cost. This practicable catalytic method could also be used on other clay substrates for the initiation of metallization.

  19. Alkoxide activation of aminoboranes towards selective amination.

    PubMed

    Solé, Cristina; Fernández, Elena

    2013-10-18

    Piece of the (inter)action: The interaction of alkoxides with the sp(2) Bpin (pin=pinacol) moiety in aminoboranes forms the in situ Lewis acid-base adduct [RO(-) →B(OR)2 N(R')2 ] which enables the amino moiety to react as a strong nucleophile with several electrophiles, thus providing amino alcohols, β-enamino esters, and β-hydroxy amides in a direct and remarkably selective way.

  20. Effects of metal composition and ratio on peptide-templated multimetallic PdPt nanomaterials

    DOE PAGES

    Merrill, Nicholas A.; Nitka, Tadeusz T.; McKee, Erik M.; ...

    2017-02-03

    It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bioinspired approaches have become increasingly popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a three-dimensional template for formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive toward a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratiomore » to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted, which indicated a slight catalytic enhancement for the multicomponent materials. Finally, these results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.« less

  1. Effects of Metal Composition and Ratio on Peptide-Templated Multimetallic PdPt Nanomaterials.

    PubMed

    Merrill, Nicholas A; Nitka, Tadeusz T; McKee, Erik M; Merino, Kyle C; Drummy, Lawrence F; Lee, Sungsik; Reinhart, Benjamin; Ren, Yang; Munro, Catherine J; Pylypenko, Svitlana; Frenkel, Anatoly I; Bedford, Nicholas M; Knecht, Marc R

    2017-03-08

    It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bioinspired approaches have become increasingly popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a three-dimensional template for formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive toward a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratio to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted, which indicated a slight catalytic enhancement for the multicomponent materials. These results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.

  2. A cracked polymer templated metal network as a transparent conducting electrode for ITO-free organic solar cells.

    PubMed

    Rao, K D M; Hunger, Christoph; Gupta, Ritu; Kulkarni, Giridhar U; Thelakkat, Mukundan

    2014-08-07

    We report a highly transparent, low resistance Ag metal network templated by a cracked polymer thin film and its incorporation in an organic solar cell. The performance of this scalable metallic network is comparable to that of conventional ITO electrodes. This is a general approach to replace ITO in diverse thin film devices.

  3. Fabrication of Porous Matrix Membrane (PMM) Using Metal-Organic Framework as Green Template for Water Treatment

    PubMed Central

    Lee, Jian-Yuan; Tang, Chuyang Y.; Huo, Fengwei

    2014-01-01

    Pressure-driven membranes with high porosity can potentially be fabricated by removing template, such as low water stability metal-organic frameworks (MOFs) or other nanoparticles, in polymeric matrix. We report on the use of benign MOFs as green template to enhance porosity and interconnectivity of the water treatment membranes. Significantly enhanced separation performance was observed which might be attributed to the mass transfer coefficient of the substrate layer increased in ultrafiltration (UF) application. PMID:24435326

  4. Spirulina-Templated Metal Microcoils with Controlled Helical Structures for THz Electromagnetic Responses

    NASA Astrophysics Data System (ADS)

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-05-01

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

  5. Spirulina-Templated Metal Microcoils with Controlled Helical Structures for THz Electromagnetic Responses

    PubMed Central

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-01-01

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region. PMID:24815190

  6. Spirulina-templated metal microcoils with controlled helical structures for THz electromagnetic responses.

    PubMed

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-05-12

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

  7. Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography

    PubMed Central

    Klemme, Daniel J.; Mohr, Daniel A.; Oh, Sang-Hyun

    2016-01-01

    We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magnetic recording. PMID:27375296

  8. Fabrication of block copolymer templated mesoporous metal oxide composites for energy storage applications

    NASA Astrophysics Data System (ADS)

    Bhaway, Sarang M.

    Block copolymer templated mesoporous (2 nm-50 nm) metal oxides are considered promising electrode materials for energy storage devices such as electrochemical capacitors or lithium/sodium ion batteries. The mesoporous electrode morphology offers several advantages: (1) high surface area and porosity facilitate charge transfer across the electrolyte-electrode interface, (2) nanoscale-dimension of the oxide framework minimizes the solid state ion diffusion paths, and (3) interconnected porous morphology enables rapid electrolyte transport through the electrodes, leading to overall enhancement in charge storage capabilities. This research attempts to study the effect of mesoporosity and mesopore geometry on charge storage capabilities and cycling stability of ordered mesoporous metal oxide electrodes in energy storage devices. The first part of this dissertation focuses on fabrication of ordered mesoporous metal oxide composites utilizing the Evaporation Induced Self-Assembly (EISA) and the Block Copolymer Micelle Templating (BCMT) strategy. Firstly, we demonstrate fabrication of ordered mesoporous carbon-vanadium oxide composites utilizing EISA of phenolic resin oligomer (resol), VOCl3 and an amphiphilic triblock. We illustrate that carbon yield from resol carbonization can prevent break-out crystallization of vanadia during calcination and help maintain an ordered mesostructure. The mesoporous carbon-vanadia mesostructured thin films exhibit specific capacitance 7 times higher than their non-porous analog at high scan rates when tested as electrode in aqueous supercapacitor. The second part of this thesis focuses on BCMT technique to fabricate ordered mesoporous mixed-metal oxide electrodes for battery applications. Ordered mesoporous NixCo(3-x)O4 thin films with varying chemical composition are fabricated using a metal nitrate-citric acid complex and an amphiphilic PEGMA-b-PBA block copolymer template. This templating strategy is further extended to fabricate

  9. Five discrete multinuclear metal-organic assemblies from one ligand: deciphering the effects of different templates.

    PubMed

    Riddell, Imogen A; Hristova, Yana R; Clegg, Jack K; Wood, Christopher S; Breiner, Boris; Nitschke, Jonathan R

    2013-02-20

    A rigid organic ligand, formed through the subcomponent self-assembly of p-toluidine and 6,6'-diformyl-3,3'-bipyridine, was employed in a systematic investigation into the synergistic and competing effects of metal and anion templation. A range of discrete and polymeric metal-organic complexes were formed, many of which represent structure types that have not previously been observed and whose formation would not be predicted on taking into account solely geometric considerations. These complex structures, capable of binding multiple guests within individual binding pockets, were characterized by NMR, ESI-MS, and single-crystal X-ray diffraction. The factors that stabilize individual complexes and lead to the formation of one over another are discussed.

  10. Formation of Periodic 2D Metallic Nanostructures by Template-Assisted Electrodeposition

    NASA Astrophysics Data System (ADS)

    Wang, Mu; Zhang, Bo; Weng, Yuyan; Peng, Ruwen; Ming, Naiben

    2008-03-01

    Two-dimensional ordered metallic nanostructures on solid surface with specific patterns may have potential applications in photonics and optoelectronics. Yet it remains a challenge to produce regular nanostructures over a large area with low cost and with a simple method. Here we report a novel method to fabricate well-aligned copper nanowire array on silicon surface by template-assisted electrodeposition. The template is introduced onto silicon surface by nanoimprinting. With our previously reported unique electrodeposition system [1-2], we find that the array of straight copper wires with their width varying from 400 nm to 20 nm can be fabricated. The wire width can be tuned by the control parameters in electrodeposition. It is shown that this method is not limited to straight wires only. It can be used to form more complicated patterns. The physical properties of the metallic nanostructures are also discussed. [1] M. Zhang, S. Lenhert, M. Wang, L. Chi, et al., Adv. Mater. 16, 409 (2004) [2] M. Wang, S. Zhong, X. Yin, J. Zhu, et al., Phys. Rev. Lett., 86, 3827 (2001)

  11. Metal-organic frameworks as templates for nanoscale NaAlH4.

    PubMed

    Bhakta, Raghunandan K; Herberg, Julie L; Jacobs, Benjamin; Highley, Aaron; Behrens, Richard; Ockwig, Nathan W; Greathouse, Jeffery A; Allendorf, Mark D

    2009-09-23

    Metal-organic frameworks (MOFs) offer an attractive alternative to traditional hard and soft templates for nanocluster synthesis because their ordered crystalline lattice provides a highly controlled and inherently understandable environment. We demonstrate that MOFs are stable hosts for metal hydrides proposed for hydrogen storage and their reactive precursors, providing platform to test recent theoretical predictions that some of these materials can be destabilized with respect to hydrogen desorption by reducing their critical dimension to the nanoscale. With the MOF HKUST-1 as template, we show that NaAlH(4) nanoclusters as small as eight formula units can be synthesized. The confinement of these clusters within the MOF pores dramatically accelerates the desorption kinetics, causing decomposition to occur at approximately 100 degrees C lower than bulk NaAlH(4). However, using simultaneous thermogravimetric modulated beam mass spectrometry, we also show that the thermal decomposition mechanism of NaAlH(4) is complex and may involve processes such as nucleation and growth in addition to the normally assumed two-step chemical decomposition reactions.

  12. Metal-Organic Frameworks As Templates for Nanoscale NaAlH 4

    SciTech Connect

    Bhakta, Raghunandan K.; Herberg, Julie L.; Jacobs, Benjamin; Highley, Aaron; Behrens, Richard; Ockwig, Nathan W.; Greathouse, Jeffery A.; Allendorf, Mark D.

    2009-09-01

    Metal-organic frameworks (MOFs) offer an attractive alternative to traditional hard and soft templates for nanocluster synthesis because their ordered crystalline lattice provides a highly controlled and inherently understandable environment. We demonstrate that MOFs are stable hosts for metal hydrides proposed for hydrogen storage and their reactive precursors, providing platform to test recent theoretical predictions that some of these materials can be destabilized with respect to hydrogen desorption by reducing their critical dimension to the nanoscale. With the MOF HKUST-1 as template, we show that NaAlH4 nanoclusters as small as eight formula units can be synthesized. The confinement of these clusters within the MOF pores dramatically accelerates the desorption kinetics, causing decomposition to occur at ~100 °C lower than bulk NaAlH4. However, using simultaneous thermogravimetric modulated beam mass spectrometry, we also show that the thermal decomposition mechanism of NaAlH4 is complex and may involve processes such as nucleation and growth in addition to the normally assumed two-step chemical decomposition reactions.

  13. Controlled DNA-templated metal deposition: towards ultra-thin nanowires.

    PubMed

    Berti, Lorenzo; Alessandrini, Andrea; Menozzi, Claudia; Facci, Paolo

    2006-08-01

    In this paper, we report the metallization of a dsDNA template using a novel photography-derived two-step strategy in which dsDNA is first complexed with Ag(I) ions and then irradiated with UV light at 254 nm. The nucleobases act as light harvesters and sensitizers, triggering the photoreduction of the complexed silver ions. This process yields a silver nanoparticles blueprint along the DNA strand. The silver latent image is then developed by depositing metallic nickel through an electroless plating process. This photography-derived procedure generates very homogeneous and evenly distributed strings of silver-core/nickel-shell nanoparticles. Although still discontinuous, we believe that such chains can serve as the base for obtaining continuous metal nanowires. Furthermore, this process can most likely be extended to other plating metals, resulting in a broadly general procedure for metallizing DNA with a variety of different materials. Because of the intrinsic simplicity in using light as the key step, this methodology might be amenable to large-scale development, eventually leading to a very efficient molecular-photolithography process.

  14. Manufacturing carbon nanofiber electrodes with embedded metallic nanoparticles using block copolymers templates

    NASA Astrophysics Data System (ADS)

    Ghazinejad, Maziar; Holmberg, Sunshine; Madou, Marc

    2016-09-01

    Owing to its superb thermal and electrical attributes, as well as electrochemical stability, carbon is emerging as an attractive material for fabrication of many bioelectrochemical devices such as biosensors and biofuel cells. However, carbon's inert nature makes it difficult to functionalize with biocatalysts; often requiring harsh chemical treatment, such as nitric acid oxidation, to attach reactive amines and carboxylic acids to its surface. Recent studies, however, points toward a self-assembly approach for fabricating well organized layers of carbon loaded with arrays of metallic nanoparticles patterned by block-copolymers (BCP) templates. Herein, we demonstrate an effective method for developing carbon nanofibers meshes embedded with metal nanoparticles, by incorporating a BCP self-assembly approach into our C-MEMS fabrication technique. The main phase of this hybrid method includes electrospinning metal salt-loaded BCP into nanofiber meshes, and subsequently reducing the metal salts into metal nanoparticles prior to pyrolysis. This cost-effective process will pave the way for fabricating scalable advanced 3-D carbon electrodes that can be applied to biosensors and biofuel cells devices.

  15. Synthesis, structure and characterization of five new organically templated metal sulfates with 2-aminopyridinium.

    PubMed

    Bednarchuk, Tamara J; Kinzhybalo, Vasyl; Pietraszko, Adam

    2016-05-01

    The chemistry of organically templated metal sulfates has attracted interest from the materials science community and the development of synthetic strategies for the preparation of organic-inorganic hybrid materials with novel structures and special properties is of current interest. Sulfur-oxygen-metal linkages provide the possibility of using sulfate tetrahedra as building units to form new solid-state materials. A series of novel organically templated metal sulfates of 2-aminopyridinium (2ap) with aluminium(III), cobalt(II), magnesium(II), nickel(II) and zinc(II) were obtained from the respective aqueous solutions and studied by single-crystal X-ray diffraction. The compounds crystallize in centrosymmetric triclinic unit cells in three structure types: type 1 for 2-aminopyridinium hexaaquaaluminium(III) bis(sulfate) tetrahydrate, (C5H7N2)[Al(H2O)6](SO4)2·4H2O, (I); type 2 for bis(2-aminopyridinium) tris[hexaaquacobalt(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Co(H2O)6]3(SO4)4·2H2O, (II), and bis(2-aminopyridinium) tris[hexaaquamagnesium(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Mg(H2O)6]3(SO4)4·2H2O, (III); and type 3 for bis(2-aminopyridinium) hexaaquanickel(II) bis(sulfate), (C5H7N2)2[Ni(H2O)6](SO4)2, (IV), and bis(2-aminopyridinium) hexaaquazinc(II) bis(sulfate), (C5H7N2)2[Zn(H2O)6](SO4)2, (V). The templating role of the 2ap cation in all of the reported crystalline substances is governed by the formation of characteristic charge-assisted hydrogen-bonded pairs with sulfate anions and the presence of π-π interactions between the cations. Additionally, both coordinated and uncoordinated water molecules are involved in hydrogen-bond formation. As a consequence, extensive three-dimensional hydrogen-bonding patterns are formed in the reported crystal structures.

  16. Water-soluble titanium alkoxide material

    DOEpatents

    Boyle, Timothy J.

    2010-06-22

    A water soluble, water stable, titanium alkoxide composition represented by the chemical formula (OC.sub.6H.sub.6N).sub.2Ti(OC.sub.6H.sub.2(CH.sub.2N(CH.sub.3).sub.2).sub- .3-2,4,6).sub.2 with a theoretical molecular weight of 792.8 and an elemental composition of 63.6% C, 8.1% H, 14.1% N, 8.1% O and 6.0% Ti.

  17. Replication of ordered block copolymer templates for the preparation of porous metal oxides in supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Pai, Rajaram Achut

    Ordered nanostructured materials are of enormous interest in photonics, sensing and detection arrays, catalysis, separations, microfluidics and low dielectric constant (low k) thin films. The traditional approach to preparation of these nanostructured films involves cooperative self-assembly of organic templates (including surfactants) and precursor molecules in solution. The approach has been successful in controlling the pore order at the local length scale, but has limited promise for controlling long-range pore order and orientation over the length scales of the device. We have developed a novel technique for the preparation of nanostructured metal oxide films by a rapid replication procedure of structured organic templates in supercritical carbon dioxide. The technique enables us to separate the self-assembly of the ordered template film from the formation of the metal oxide network. The structure of the pre-formed template on both the local and device levels can be achieved in three dimensions using established techniques prior to infusion of the inorganic phase. This approach also offers flexibility with regard to framework chemistry and the nature of the copolymer template, which can now be chosen independently without regard to compatibility in solution or concerns about disrupting the coordinated self-assembly process. The application of the technique to preparation of ordered mesostructured silicate/organosilicate films with dielectric constants below 2.2 and desirable mechanical properties is discussed. Post-synthesis treatments of mesostructured silicate and organosilicate films were also investigated with the aim of reducing the shrinkage associated with the template removal by calcination. In addition, blends of semicrystalline amphiphilic block copolymers and amorphous homopolymers was also studied to improve the wetting properties and reduce the crystallinity. Mesostructured silicate and organosilicate films that were templated with the blends

  18. The Obtaining of Nano Oxide Systems SiO2-REE with Alkoxide Technology

    NASA Astrophysics Data System (ADS)

    Amelina, Anna; Grinberg, Evgenii

    A lot of oxides systems with REE as dopants are used in catalytic processes in organic synthesis. They are very perspectives as thermostable coating in aerospace technics. These systems are usually based on silicon or aluminium oxides and doped with rare-earth elements. This systems can be produced by different methods. One of the most perspective of them is “sol-gel”-method with silicium, aluminium and rare-earth alkoxides as a precursor of doped silica and alumina, or their derivatives. Thus the obtaining of composite SiO _{2} - REE oxide materials by the hydrolysis doped with rare-earth elements was suggested. Some of alcoholate derivatives such as El(OR)n were used in this processes. The SiO _{2}- REE oxides were precipitated during the sol-gel process, where tetraethoxysilane (TEOS) as used as SiO _{2} sources. Also it is known that alkoxides of alkali metals, including lithium alkoxides, are widely used in industry and synthetic chemistry, as well as a source of lithium in various mixed oxide compositions, such as lithium niobate, lithium tantalate or lithium silicate. Therefore, we attempted to obtain the lithium silicate, which is also doped with rare-earth elements. Lithium silicate was obtained by alkaline hydrolysis of tetraethoxysilane with lithium alkoxide. Lithium alkoxide were synthesized by dissolving at metal in the corresponding alcohol are examined. The dependence of the rate of dissolving of the metal on the method of mixing of the reaction mixture and the degree of metal dispersion was investigated. The mathematical model of the process was composed and also optimization of process was carried out. Some oxide SiO _{2}, Al _{2}O _{3} and rare-earth nanostructured systems were obtained by sol-gel-method. The size of particle was determined by electron and X-ray spectroscopy and was in the range of 5 - 15 nm. Purity of this oxide examples for contaminating of heavy metals consists n.(1E-4...1E-5) wt%. Sols obtained by this method may be used

  19. Dual template effect of supercritical CO2 in ionic liquid to fabricate a highly mesoporous cobalt metal-organic framework.

    PubMed

    Yu, Huanan; Xu, Dongdong; Xu, Qun

    2015-08-28

    A hierarchical meso- and microporous metal-organic framework (MOF) was facilely fabricated in an ionic liquid (IL)/supercritical CO2 (SC CO2)/surfactant emulsion system. Notably, CO2 exerts a dual effect during the synthesis; that is, CO2 droplets act as a template for the cores of nanospheres while CO2-swollen micelles induce mesopores on nanospheres.

  20. Metal-organic framework templated synthesis of Fe2O3/TiO2 nanocomposite for hydrogen production.

    PubMed

    deKrafft, Kathryn E; Wang, Cheng; Lin, Wenbin

    2012-04-17

    A new metal-organic framework (MOF)-templated method has been developed for the synthesis of a metal oxide nanocomposite with interesting photophysical properties. Fe-containing nanoscale MOFs are coated with amorphous titania, then calcined to produce crystalline Fe(2)O(3)/TiO(2) composite nanoparticles. This material enables photocatalytic hydrogen production from water using visible light, which cannot be achieved by either Fe(2)O(3) or TiO(2) alone or a mixture of the two.

  1. Directly Patterned Mesoporous Carbon and Metal-Doped Carbon Films Prepared using Block Copolymer Templates in Supercritical CO2

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Gaurav; Watkins, James

    2006-03-01

    Porous carbon and metal-doped porous carbon films have wide applications in separations, sensors, catalysis and magnetic storage applications. Conventionally prepared carbon films have micropores in the size range of 2 nm. Recent techniques for the synthesize of mesoporous carbon with 10-50 nm pores using sacrificial silica templates have limitations with respect to pore connectivity and the preparation of patterned and metal-doped carbon films. Here we report supercritical fluid-assisted infusion and phase selective reaction within pre-organized block copolymer and block copolymer/homopolymer templates to synthesize mesoporous carbon and metal doped carbon films. Well-defined mesoporous carbon films patterned at the device level with good mechanical properties and metal doped carbon films by pre-infusion of block copolymer templates with metal precursors in supercritical carbon dioxide were synthesized. Platinum doped carbon films for applications in fuel cells having good electrochemical response were produced. The preparation of cobalt containing carbon films with potential use in magnetic storage applications demonstrates the general applicability of supercritical infusion technique to produce metal cluster containing films.

  2. Bicontinuous ceramics with high surface area from block copolymer templates.

    PubMed

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-05

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established.

  3. Graphene-Templated Synthesis of Magnetic Metal Organic Framework Nanocomposites for Selective Enrichment of Biomolecules.

    PubMed

    Cheng, Gong; Wang, Zhi-Gang; Denagamage, Sachira; Zheng, Si-Yang

    2016-04-27

    Successful control of homogeneous and complete coating of graphene or graphene-based composites with well-defined metal organic framework (MOF) layers is a great challenge. Herein, novel magnetic graphene MOF composites were constructed via a simple strategy for self-assembly of well-distributed, dense, and highly porous MOFs on both sides of graphene nanosheets. Graphene functionalized with magnetic nanoparticles and carboxylic groups on both sides was explored as the backbone and template to direct the controllable self-assembly of MOFs. The prepared composite materials have a relatively high specific surface area (345.4 m(2) g(-1)), and their average pore size is measured to be 3.2 nm. Their relatively high saturation magnetization (23.8 emu g(-1)) indicates their strong magnetism at room temperature. Moreover, the multifunctional composite was demonstrated to be a highly effective affinity material in selective extraction and separation of low-concentration biomolecules from biological samples, in virtue of the size-selection property of the unique porous structure and the excellent affinity of the composite materials. Besides providing a solution for the construction of well-defined functional graphene-based MOFs, this work could also contribute to selective extraction of biomolecules, in virtue of the universal affinity between immobilized metal ions and biomolecules.

  4. Scalable salt-templated synthesis of two-dimensional transition metal oxides

    PubMed Central

    Xiao, Xu; Song, Huaibing; Lin, Shizhe; Zhou, Ying; Zhan, Xiaojun; Hu, Zhimi; Zhang, Qi; Sun, Jiyu; Yang, Bo; Li, Tianqi; Jiao, Liying; Zhou, Jun; Tang, Jiang; Gogotsi, Yury

    2016-01-01

    Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm−3 in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications. PMID:27103200

  5. Simultaneous immunoassay of phosphorylated proteins based on apoferritin templated metallic phosphates as voltammetrically distinguishable signal reporters.

    PubMed

    Ge, Xiaoxiao; Zhang, Aidong; Lin, Yuehe; Du, Dan

    2016-06-15

    A novel electrochemical immunosensor has been developed to detect phosphorylated proteins, phospho-p53(15) and phospho-p53(392), simultaneously. Different apoferritin templated metal phosphates were used as distinguishable signal reporters (apoferritin templated cadmium phosphates (ATCP) and apoferritin templated lead phosphates (ATLP)) to enhance the detection sensitivity. Here, magnetic Fe3O4 nanoparticles functionalized phospho-p53(15) capture antibody (MP-p53(15)c-Ab) and phospho-p53(392) capture antibody (MP-p53(392)c-Ab), respectively, were used to specifically capture phospho-p53(15) and phospho-p53(392) antigens, followed by immunorecognition with p53(15) detection antibody (p53(15)d-Ab) and p53(392) detection antibody (p53(392)d-Ab) to form sandwich-like immunocomplexes. SiO2@Au nanocomposites served as nanocarriers for co-immobilization of both d-Ab and signal reporters (ATCP/SiO2@Au/p53(15)d-Ab, ATLP/SiO2@Au/p53(392)d-Ab), which greatly amplified the detection signal. The distinguished current responses were achieved by electrochemical detection of cadmium ions and lead ions with square wave voltammetry (SWV) after dissolution with acid. The proposed immunoassay exhibited high sensitivity and selectivity for the detection of phospho-p53(15) and phospho-p53(392) simultaneously. The linear relationships between electrochemical responses and the concentrations of phospho-p53(15) and phospho-p53(392) were obtained in the range of 0.1-20 ng/mL and 0.05-20 ng/mL, respectively. The detection limits were 0.05 and 0.02 ng/mL (S/N=3), respectively. This strategy provides a new platform for simultaneous immunoassay of multiple protein biomarkers.

  6. Correlation of photobleaching, oxidation and metal induced fluorescence quenching of DNA-templated silver nanoclusters

    NASA Astrophysics Data System (ADS)

    Morishita, Kiyoshi; Maclean, James L.; Liu, Biwu; Jiang, Hui; Liu, Juewen

    2013-03-01

    Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg2+, where d10-d10 metallophilic interaction has often been proposed for associating Hg2+ with nanoclusters. However, it cannot explain the lack of response to other d10 ions such as Zn2+ and Cd2+. In our effort to elucidate the quenching mechanism, we studied a total of eight AgNCs prepared by different hairpin DNA sequences; they showed different sensitivity to Hg2+, and DNA with a larger cytosine loop size produced more sensitive AgNCs. In all the cases, samples strongly quenched by Hg2+ were also more easily photobleached. Light of shorter wavelengths bleached AgNCs more potently, and photobleached samples can be recovered by NaBH4. Strong fluorescence quenching was also observed with high redox potential metal ions such as Ag+, Au3+, Cu2+ and Hg2+, but not with low redox potential ions. Such metal induced quenching cannot be recovered by NaBH4. Electronic absorption and mass spectrometry studies offered further insights into the oxidation reaction. Our results correlate many important experimental observations and will fuel the further growth of this field.Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg2+, where d10-d10 metallophilic interaction has often been proposed for associating Hg2+ with nanoclusters. However, it cannot explain the lack of response to other d10 ions such as Zn2+ and Cd2+. In

  7. Directing Colloidal Assembly and a Metal-Insulator Transition Using a Quench-Disordered Porous Rod Template

    NASA Astrophysics Data System (ADS)

    Jadrich, Ryan B.; Schweizer, Kenneth S.

    2014-11-01

    Replica and effective-medium theory methods are employed to elucidate how to massively reconfigure a colloidal assembly to achieve globally homogeneous, strongly clustered, and percolated equilibrium states of high electrical conductivity at low physical volume fractions. A key idea is to employ a quench-disordered, large-mesh rigid-rod network as a templating internal field. By exploiting bulk phase separation frustration and the tunable competing processes of colloid adsorption on the low-dimensional network and fluctuation-driven colloid clustering in the pore spaces, two distinct spatial organizations of greatly enhanced particle contacts can be achieved. As a result, a continuous, but very abrupt, transition from an insulating to metallic-like state can be realized via a small change of either the colloid-template or colloid-colloid attraction strength. The approach is generalizable to more complicated template or colloidal architectures.

  8. Preparation of silica stabilized biological templates for the production of metal and layered nanoparticles

    DOEpatents

    Culver, James N; Royston, Elizabeth; Brown, Adam; Harris, Michael

    2013-02-26

    The present invention relates to a system and method providing for increased silica growth on a bio-template, wherein the bio-template is pretreated with aniline to produce a uniform silica attractive surface and yielding a significant silica layers of at least 10 nm, and more preferably at least 20 nm in thickness, thereby providing for a high degree of stability to the bio-template.

  9. Metal-organic framework nanocrystals as sacrificial templates for hollow and exceptionally porous titania and composite materials.

    PubMed

    Yang, Hui; Kruger, Paul E; Telfer, Shane G

    2015-10-05

    We report a strategy that employs metal-organic framework (MOF) crystals in two roles for the fabrication of hollow nanomaterials. In the first role the MOF crystals provide a template on which a shell of material can be deposited. Etching of the MOF produces a hollow structure with a predetermined size and morphology. In combination with this strategy, the MOF crystals, including guest molecules in their pores, can provide the components of a secondary material that is deposited inside the initially formed shell. We used this approach to develop a straightforward and reproducible method for constructing well-defined, nonspherical hollow and exceptionally porous titania and titania-based composite nanomaterials. Uniform hollow nanostructures of amorphous titania, which assume the cubic or polyhedral shape of the original template, are delivered using nano- and microsized ZIF-8 and ZIF-67 crystal templates. These materials exhibit outstanding textural properties including hierarchical pore structures and BET surface areas of up to 800 m(2)/g. As a proof of principle, we further demonstrate that metal nanoparticles such as Pt nanoparticles, can be encapsulated into the TiO2 shell during the digestion process and used for subsequent heterogeneous catalysis. In addition, we show that the core components of the ZIF nanocrystals, along with their adsorbed guests, can be used as precursors for the formation of secondary materials, following their thermal decomposition, to produce hollow and porous metal sulfide/titania or metal oxide/titania composite nanostructures.

  10. Self-assembled bifunctional surface mimics an enzymatic and templating protein for the synthesis of a metal oxide semiconductor

    PubMed Central

    Kisailus, David; Truong, Quyen; Amemiya, Yosuke; Weaver, James C.; Morse, Daniel E.

    2006-01-01

    The recent discovery and characterization of silicatein, a mineral-synthesizing enzyme that assembles to form the filamentous organic core of the glassy skeletal elements (spicules) of a marine sponge, has led to the development of new low-temperature synthetic routes to metastable semiconducting metal oxides. These protein filaments were shown in vitro to catalyze the hydrolysis and structurally direct the polycondensation of metal oxides at neutral pH and low temperature. Based on the confirmation of the catalytic mechanism and the essential participation of specific serine and histidine residues (presenting a nucleophilic hydroxyl and a nucleophilicity-enhancing hydrogen-bonding imidazole nitrogen) in silicatein’s catalytic active site, we therefore sought to develop a synthetic mimic that provides both catalysis and the surface determinants necessary to template and structurally direct heterogeneous nucleation through condensation. Using lithographically patterned poly(dimethylsiloxane) stamps, bifunctional self-assembled monolayer surfaces containing the essential catalytic and templating elements were fabricated by using alkane thiols microcontact-printed on gold substrates. The interface between chemically distinct self-assembled monolayer domains provided the necessary juxtaposition of nucleophilic (hydroxyl) and hydrogen-bonding (imidazole) agents to catalyze the hydrolysis of a gallium oxide precursor and template the condensed product to form gallium oxohydroxide (GaOOH) and the defect spinel, gamma-gallium oxide (γ-Ga2O3). Using this approach, the production of patterned substrates for catalytic synthesis and templating of semiconductors for device applications can be envisioned. PMID:16585518

  11. Structural Engineering of Metal-Mesh Structure Applicable for Transparent Electrodes Fabricated by Self-Formable Cracked Template.

    PubMed

    Kim, Yeong-Gyu; Tak, Young Jun; Park, Sung Pyo; Kim, Hee Jun; Kim, Hyun Jae

    2017-08-05

    Flexible and transparent conducting electrodes are essential for future electronic devices. In this study, we successfully fabricated a highly-interconnected metal-mesh structure (MMS) using a self-formable cracked template. The template-fabricated from colloidal silica-can be easily formed and removed, presenting a simple and cost-effective way to construct a randomly and uniformly networked MMS. The structure of the MMS can be controlled by varying the spin-coating speed during the coating of the template solution or by stacking of metal-mesh layers. Through these techniques, the optical transparency and sheet resistance of the MMS can be designed for a specific purpose. A double-layered Al MMS showed high optical transparency (~80%) in the visible region, low sheet resistance (~20 Ω/sq), and good flexibility under bending test compared with a single-layered MMS, because of its highly-interconnected wire structure. Additionally, we identified the applicability of the MMS in the case of practical devices by applying it to electrodes of thin-film transistors (TFTs). The TFTs with MMS electrodes showed comparable electrical characteristics to those with conventional film-type electrodes. The cracked template can be used for the fabrication of a mesh structure consisting of any material, so it can be used for not only transparent electrodes, but also various applications such as solar cells, sensors, etc.

  12. Metal-mediated diradical tuning for DNA replication arrest via template strand scission.

    PubMed

    Porter, Meghan R; Lindahl, Sarah E; Lietzke, Anne; Metzger, Erin M; Wang, Quan; Henck, Erik; Chen, Chun-Hsing; Niu, Hengyao; Zaleski, Jeffrey M

    2017-09-05

    A series of M(PyED)·X (X = 2Cl(-), SO4(2-)) pyridine-metalloenediyne complexes [M = Cu(II), Fe(II), or Zn(II)] and their independently synthesized, cyclized analogs have been prepared to investigate their potential as radical-generating DNA-damaging agents. All complexes possess a 1:1 metal-to-ligand stoichiometry as determined by electronic absorption spectroscopy and X-ray diffraction. Solution structural analysis reveals a pπ Cl [Formula: see text] Cu(II) LMCT (22,026 cm(-1)) for Cu(PyED)·2Cl, indicating three nitrogens and a chloride in the psuedo-equatorial plane with the remaining pyridine nitrogen and solvent in axial positions. EPR spectra of the Cu(II) complexes exhibit an axially elongated octahedron. This spectroscopic evidence, together with density functional theory computed geometries, suggest six-coordinate structures for Cu(II) and Fe(II) complexes and a five-coordinate environment for Zn(II) analogs. Bergman cyclization via thermal activation of these constructs yields benzannulated product indicative of diradical generation in all complexes within 3 h at 37 °C. A significant metal dependence on the rate of the reaction is observed [Cu(II) > Fe(II) > Zn(II)], which is mirrored in in vitro DNA-damaging outcomes. Whereas in situ chelation of PyED leads to considerable degradation in the presence of all metals within 1 h under hyperthermia conditions, Cu(II) activation produces >50% compromised DNA within 5 min. Additionally, Cu(II) chelated PyED outcompetes DNA polymerase I to successfully inhibit template strand extension. Exposure of HeLa cells to Cu(PyBD)·SO4 (IC50 = 10 μM) results in a G2/M arrest compared with untreated samples, indicating significant DNA damage. These results demonstrate metal-controlled radical generation for degradation of biopolymers under physiologically relevant temperatures on short timescales.

  13. Assembly of new polyoxometalate-templated metal-organic frameworks based on flexible ligands

    NASA Astrophysics Data System (ADS)

    Li, Na; Mu, Bao; Lv, Lei; Huang, Rudan

    2015-03-01

    Four new polyoxometalate(POM)-templated metal-organic frameworks based on flexible ligands, namely, [Cu6(bip)12(PMoVI12O40)2(PMoVMoVI11O40O2)]·8H2O(1), [CuI3CuII3(bip)12(PMoVI12O40)2(PMoV12O34)]·8H2O(2), [Ni6(bip)12(PMoVI12O40)(PMoVI11MoVO40)2]Cl·6H2O(3), [CoII3CoIII2(H2bib)2(Hbib)2(PW9O34)2(H2O)6]·6H2O(4) (bip=1,3-bis(imidazolyl)propane, bib=1,4-bis(imidazolyl)butane) have been obtained under hydrothermal condition and characterized by single-crystal X-ray diffraction analyses, elemental analyses, and thermogravimetric (TG) analyses. The studies of single crystal X-ray indicate that compounds 1-3 crystallize in the trigonal space group P-3, and compound 4 crystallizes in the triclinic space group P-1. Compounds 1 and 3 represent 3D frameworks, and POMs as the guest molecules are incorporated into the cages which are composed of the ligands and metals, while compounds 2 and 4 show 3D frameworks by hydrogen bonds. This compounds provide new examples of host-guest compounds based on flexible bis(imidazole) ligands. In addition, the electrochemical property and the catalytic property of compound 1 have also been investigated.

  14. A template-free method for stable CuO hollow microspheres fabricated from a metal organic framework (HKUST-1)

    NASA Astrophysics Data System (ADS)

    Zhang, Suoying; Liu, Hong; Liu, Pengfei; Yang, Zhuhong; Feng, Xin; Huo, Fengwei; Lu, Xiaohua

    2015-05-01

    Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs.Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs. Electronic supplementary information (ESI) available: The experiment details, auxiliary FESEM, XRD, BET and TG results of synthesized products. See DOI: 10.1039/c5nr01443c

  15. Self-etching of metal-organic framework templates during polydopamine coating: Non-spherical polydopamine capsules and potential intracellular trafficking of metal ions.

    PubMed

    Ye, Zihan; Wu, Songhai; Zheng, Chunxiong; Yang, Lu; Zhang, Pengjiao; Zhang, Zhenkun

    2017-09-01

    Traditionally, containers made from steels or other metals are not good for making tea, probably due to the fact that polyphenol components in tea can chelate with metal ions. Similar reason might stand behind the observations as reported herein. During coating well-defined metal-organic framework (MOF) crystalline particles with polydopamine (PDA) via pH induced self-polymerization of dopamine, we found that the MOF templates automatically etch off during the coating, giving rise to non-spherical PDA capsules that inherit the morphologies of the templates. Such self-etching of MOF templates is ascribed to the chelation of the metal nodes of the MOFs by the catechol moieties in the PDA layer. In addition, the self-etching of the zeolitic imidazolate framework-8 (ZIF-8) with a truncated cubic shape probably follows a crystalline facet-dependent fashion, resulting in intermediate york-shell structures with ZIF-8 cargos of various shapes inside a highly biocompatible PDA shell. Incubation of such intermediate hybrid particles with the cancerous Hela cell line leads to pronounced cytotoxicity, which is tentatively connected with the cellular internalization of the ZIF@PDA nanoparticles due to the cell affinity of the PDA layer. Subsequently, continuous release of Zn2+ by the self-etching of the encapsulated ZIF-8 inside the cell increases intracellular Zn(2+) to a harmful level. Therefore, intracellular delivery of metal ions is probably realized which might offer a novel way for cancer therapy.

  16. An in situ self-assembly template strategy for the preparation of hierarchical-pore metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Huang, Hongliang; Li, Jian-Rong; Wang, Keke; Han, Tongtong; Tong, Minman; Li, Liangsha; Xie, Yabo; Yang, Qingyuan; Liu, Dahuan; Zhong, Chongli

    2015-11-01

    Metal-organic frameworks (MOFs) have recently emerged as a new type of nanoporous materials with tailorable structures and functions. Usually, MOFs have uniform pores smaller than 2 nm in size, limiting their practical applications in some cases. Although a few approaches have been adopted to prepare MOFs with larger pores, it is still challenging to synthesize hierarchical-pore MOFs (H-MOFs) with high structural controllability and good stability. Here we demonstrate a facile and versatile method, an in situ self-assembly template strategy for fabricating stable H-MOFs, in which multi-scale soluble and/or acid-sensitive metal-organic assembly (MOA) fragments form during the reactions between metal ions and organic ligands (to construct MOFs), and act as removable dynamic chemical templates. This general strategy was successfully used to prepare various H-MOFs that show rich porous properties and potential applications, such as in large molecule adsorption. Notably, the mesopore sizes of the H-MOFs can be tuned by varying the amount of templates.

  17. An in situ self-assembly template strategy for the preparation of hierarchical-pore metal-organic frameworks

    PubMed Central

    Huang, Hongliang; Li, Jian-Rong; Wang, Keke; Han, Tongtong; Tong, Minman; Li, Liangsha; Xie, Yabo; Yang, Qingyuan; Liu, Dahuan; Zhong, Chongli

    2015-01-01

    Metal-organic frameworks (MOFs) have recently emerged as a new type of nanoporous materials with tailorable structures and functions. Usually, MOFs have uniform pores smaller than 2 nm in size, limiting their practical applications in some cases. Although a few approaches have been adopted to prepare MOFs with larger pores, it is still challenging to synthesize hierarchical-pore MOFs (H-MOFs) with high structural controllability and good stability. Here we demonstrate a facile and versatile method, an in situ self-assembly template strategy for fabricating stable H-MOFs, in which multi-scale soluble and/or acid-sensitive metal-organic assembly (MOA) fragments form during the reactions between metal ions and organic ligands (to construct MOFs), and act as removable dynamic chemical templates. This general strategy was successfully used to prepare various H-MOFs that show rich porous properties and potential applications, such as in large molecule adsorption. Notably, the mesopore sizes of the H-MOFs can be tuned by varying the amount of templates. PMID:26548441

  18. A new route toward ultrasensitive, flexible chemical sensors: metal nanotubes by wet-chemical synthesis along sacrificial nanowire templates.

    PubMed

    Lim, Mi Ae; Kim, Dong Hwan; Park, Chong-Ook; Lee, Young Wook; Han, Sang Woo; Li, Zhiyong; Williams, R Stan; Park, Inkyu

    2012-01-24

    We developed a novel low-temperature, wet-chemical process for the facile synthesis of metal nanotube arrays through the reduction of metal precursors along sacrificial metal oxide nanowire templates and demonstrated its applications to the ultrasensitive, low-power, mechanically robust, and flexible chemical sensors. The in situ dissolution of ZnO nanowire templates, which were hydrothermally grown on electrode surfaces, during the reaction allows the direct formation of tubular Pd nanostructures on the sensor devices without the need of complex processes for device integration or template removal. Moreover, this simple synthesis was carried out at low-temperature with mild chemical conditions; therefore we could make Pd nanotube devices not only on silicon substrates but also on flexible polymer substrates. The H(2) sensing of such Pd nanotube devices was investigated under various mechanical loading and showed excellent reliability and robustness. The sensitivity of our devices was found to be at least 2 orders of magnitude higher than literature values for H(2) sensors, which can be attributed to the high surface area and the well-formed interconnect of Pd tubular nanostructures in our devices.

  19. Zirconium alkoxide interfaces for adhesion enhancement and electrocatalysis

    NASA Astrophysics Data System (ADS)

    Vanderkam, Susan Killian

    Tetra(tert-butoxy)zirconium was chemisorbed onto the native oxide layers of aluminum, iron, copper, and porous silicon, forming surface bound di- or tri-alkoxy zirconium species. Poly(ethylene- co-acrylic acid) was subsequently reacted with the surface forming chemically bound copolymer through carboxyzirconium linkages. Copolymer bound through the zirconium complex adhered to the metal oxide surfaces better than without the zirconium alkoxide intermediate, as determined by FTIR spectroscopy. Copper substrates were subjected to a variety of stability tests, including exposure to ambient conditions, base washing, and chronocoulometry. The copper-zirconium-copolymer ensemble was shown to be very stable in all of these tests. Indium tin oxide (ITO) powder was titrated to determine surface hydroxyl content per unit area. ITO-coated glass slides were reacted with tetra( tert-butoxy)zirconium, and subsequently with both carboxylic acid and phenol derivatives. Ferrocene-carboxyzirconium-coated ITO was characterized electrochemically, and the surface loading of ferrocene was found to be approximately one monolayer. Phenoxyzirconium-coated ITO was also characterized electrochemically and tested for electrocatalytic properties for the oxidation of several compounds in solution. Phenoxyzirconium-coated ITO was found to improve the oxidation kinetics for ferrocene and tetramethylphenylenediamine in acetonitrile.

  20. Soft-Templating Synthesis and Properties of Mesoporous Alumina-Titania

    SciTech Connect

    Morris, Stacy M; Horton, Jr, Joe A; Jaroniec, Mietek

    2010-01-01

    Mesoporous alumina-titania materials, having various molar compositions of aluminum and titanium, were synthesized via cooperative self-assembly of the corresponding metal alkoxides and Pluronic P123 triblock copolymer (soft template) in ethanolic solution under acidic conditions. The resulting mixed metal oxides possess ordered mesopores at low to equal molar compositions of titanium in relation to aluminum (up to 50%) and worm-like mesostructures at higher molar compositions of titanium (50-75%). In addition, these mesoporous oxides exhibit high BET surface areas (up to 438 m2/g), large pore widths (from 7.37 to 18.55 nm) and pore volumes (from 0.16 to 0.64 cm3/g), narrow pore size distributions, crystalline pore walls and high thermal stability.

  1. Syntheses and crystal structures of three new borates templated by transition-metal complexes in situ

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Ming; Sun, Yan-Qiong; Yang, Guo-Yu

    2006-05-01

    Three new cobalt borate compounds, [Co(DIEN) 2][B 5O 6(OH) 4] 2 (DIEN=diethylenetriamine) ( 1), [B 5O 7(OH) 3Co(TREN)] (TREN= tris(2-aminoethyl)amine) ( 2), and [Co 2(TETA) 3][B 5O 6(OH) 4] 4 (TETA=triethylenetetramine) ( 3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR, elemental analysis and thermogravimetry. The structures exhibit interesting 3D supramolecular hydrogen-bonded architectures, involving the similar borate polyanion [B 5O 6+n(OH) 4-n] ( n+1)- ( n=0 for 1 and 3, and n=1 for 2) and the templating transition metal complexes which are generated in situ under mild solvothermal conditions. Crystal data: 1, monoclinic, space group C2/ m (No. 12), a=15.2372(3) Å, b=11.5987(2) Å, c=8.4163(3) Å, β=93.601(4)°, V=1484.49(7) Å3, Z=2; 2, monoclinic, P2 1/ c (No. 14), a=8.9881(3) Å, b=20.7648(5) Å, c=9.3681(2) Å, β=99.926(4)°, V=1722.25(8) Å3, Z=4; 3, triclinic, space group P-1 (No. 2), a=12.3717(4) Å, b=12.9653(8) Å, c=19.0925(3) Å, α=77.009(5)°, β=80.095(2)°, γ=82.334(3)°, V=2925.3(2) Å3, Z=2.

  2. Solvent templates induced porous metal-organic materials: conformational isomerism and catalytic activity.

    PubMed

    Ding, Ran; Huang, Chao; Lu, Jingjing; Wang, Junning; Song, Chuanjun; Wu, Jie; Hou, Hongwei; Fan, Yaoting

    2015-02-16

    Solvent templates induced Co-based metal-organic materials; conformational isomers {[Co2(pdpa)(CH3CN)(H2O)3]·CH3OH·H2O}n (1) and {[Co2(pdpa)(CH3CN)(H2O)3]}n (2) and {[Co5(pdpa)2(μ3-OH)2(H2O)6]·2H2O}n (3) [H4pdpa = 5,5'-(pentane-1,2-diyl)-bis(oxy)diisophthalic acid] were synthesized under the same solvothermal conditions except with different concentrations of cyclic ethers (1,4-dioxane or tetrahydrofuran) as structure-directing agents. Structural transformations from a three-dimensional (3D) framework of 1 containing channels with dimensions of ∼6 Å × 6 Å to a two-dimensional layer structure of 2 consisting of large open channels with a size of ∼15 Å × 8 Å and then to a 3D nonporous framework of 3, resulting from the different concentrations of cyclic ethers, were observed. The anion-π interactions between electron-efficient oxygen atoms of cyclic ethers and electron-deficient dicarboxylic acid aromatic cores in H4pdpa imported into the synthetic process accounted for the conformational change of the ligand H4pdpa and the following structural variations. A systematic investigation was conducted to explore how different concentrations of structure-directing agents affected the frameworks of resultant metal-organic frameworks. Furthermore, 1-3 were shown to be available heterogeneous catalysts for the synthesis of 2-imidazoline and 1,4,5,6-tetrahydropyrimidine derivatives by the cascade cycloaddition reactions of aromatic nitriles with diamines. The results showed that the catalytic activity of 2 was much higher than that of 1 and 3, because of its unique structural features, including accessible catalytic sites and suitable channel size and shape. In addition, a plausible mechanism for these catalytic reactions was proposed, and the reactivity-structure relationship was further clarified.

  3. Synthesis of metal nanowires using nanocracks and DNA-templates and their characterization

    NASA Astrophysics Data System (ADS)

    Mani, Sathyanarayanan

    A major challenge in the field of nanotechnology is the synthesis and testing of nanostructures, such as nanowires, in a cost effective manner. Currently, there are two general approaches for fabricating nanowires, namely top-down and bottom-up. While the top-down approach that uses nano-lithography is controlled but expensive, the bottom-up approach that uses self-assembly is inexpensive but uncontrolled. This research, describes the mechanism behind an innovative and inexpensive method that combines both the top-down and bottom-up approaches to produce metal nanowires. The method uses cracks in PECVD silicon dioxide thin films on silicon substrate as molds to produce electroless deposited nickel nanowires. The cracks are initiated from voids formed due to nonconformal deposition of oxide on RIE etched trenches in silicon substrate. A model was developed to characterize void formation and the stress response of these oxide films during a thermal ramp, and identify the operating conditions such as film deposit thickness, trench dimensions and annealing temperature for controlled crack pattern formation. The nickel nanowires (50-250 nm wide) are polycrystalline with grain size ranging between 10 to 50 nm. Electrical characterization revealed that the resistivity of these wires decreased 10 times on sintering. However, this resistivity was still twice that of their bulk counterpart. This higher resistivity can be explained by the enhanced scattering of conductive electrons by grain boundaries and phosphorous impurities. An alternate nanowire fabrication technique that simplifies their testing by enabling their direct integration with MEMS test-beds has also been presented. In this approach, commercially available lambda DNA's (16.1 microns long and 2 nm wide) are used as templates to form nanowires of various metals through sputter deposition or evaporation. The test-bed is compatible with commercially available TEM stages for conducting in situ nanostructural

  4. Template-induced diverse metal-organic materials as catalysts for the tandem acylation-Nazarov cyclization.

    PubMed

    Huang, Chao; Ding, Ran; Song, Chuanjun; Lu, Jingjing; Liu, Lu; Han, Xiao; Wu, Jie; Hou, Hongwei; Fan, Yaoting

    2014-12-01

    In our continuing quest to develop a metal-organic framework (MOF)-catalyzed tandem pyrrole acylation-Nazarov cyclization reaction with α,β-unsaturated carboxylic acids for the synthesis of cyclopentenone[b]pyrroles, which are key intermediates in the synthesis of natural product (±)-roseophilin, a series of template-induced Zn-based (1-3) metal-organic frameworks (MOFs) have been solvothermally synthesized and characterized. Structural conversions from non-porous MOF 1 to porous MOF 2, and back to non-porous MOF 3 arising from the different concentrations of template guest have been observed. The anion-π interactions between the template guests and ligands could affect the configuration of ligands and further tailor the frameworks of 1-3. Futhermore, MOFs 1-3 have shown to be effective heterogeneous catalysts for the tandem acylation-Nazarov cyclization reaction. In particular, the unique structural features of 2, including accessible catalytic sites and suitable channel size and shape, endow 2 with all of the desired features for the MOF-catalyzed tandem acylation-Nazarov cyclization reaction, including heterogeneous catalyst, high catalytic activity, robustness, and excellent selectivity. A plausible mechanism for the catalytic reaction has been proposed and the structure-reactivity relationship has been further clarified. Making use of 2 as a heterogeneous catalyst for the reaction could greatly increase the yield of total synthesis of (±)-roseophilin. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Lithium bromide-induced structural changes in a nickel bis-alkoxide complex.

    PubMed

    Ichiokai, Hiromi; Vicic, David A

    2013-01-01

    The bis-alkoxide [(DEAMP)2Ni] (1, DEAMP = 1-(diethylamino)-2-methylpropan-2-olate) was found to react with trace amounts of lithium bromide to afford the bis-LiBr adduct 2, in which the oxygens of the DEAMP ligand coordinate to lithium to form a chiral-at-metal complex. This new complex is five-coordinate at nickel, and contains nickel and oxygen atoms which are all chiral. One diastereomer precipitates from pentane solution. The two lithium ions rigidify the new structure in the solid state by coordinating to the oxygen and bromide atoms.

  6. Catalytic reactions of titanium alkoxides with Grignard reagents and imines: a mechanistic study.

    PubMed

    Kumar, Akshai; Samuelson, Ashoka G

    2010-08-02

    The reactivity of Grignard reagents towards imines in the presence of catalytic and stoichiometric amounts of titanium alkoxides is reported. Alkylation, reduction, and coupling of imines take place. Whereas reductive coupling is the major reaction in stoichiometric reactions, alkylation is favored in catalytic reactions. Mechanistic studies clearly indicate that intermediates involved in the two reactions are different. Catalytic reactions involve a metal-alkyl complex. This has been confirmed by reactions of deuterium-labeled substrates and different alkylating agents. Under the stoichiometric conditions, however, titanium olefin complexes are formed through reductive elimination, probably through a multinuclear intermediate.

  7. Crackle template based metallic mesh with highly homogeneous light transmission for high-performance transparent EMI shielding

    NASA Astrophysics Data System (ADS)

    Han, Yu; Lin, Jie; Liu, Yuxuan; Fu, Hao; Ma, Yuan; Jin, Peng; Tan, Jiubin

    2016-05-01

    Our daily electromagnetic environment is becoming increasingly complex with the rapid development of consumer electronics and wireless communication technologies, which in turn necessitates the development of electromagnetic interference (EMI) shielding, especially for transparent components. We engineered a transparent EMI shielding film with crack-template based metallic mesh (CT-MM) that shows highly homogeneous light transmission and strong microwave shielding efficacy. The CT-MM film is fabricated using a cost-effective lift-off method based on a crackle template. It achieves a shielding effectiveness of ~26 dB, optical transmittance of ~91% and negligible impact on optical imaging performance. Moreover, high–quality CT-MM film is demonstrated on a large–calibre spherical surface. These excellent properties of CT-MM film, together with its advantages of facile large-area fabrication and scalability in processing on multi-shaped substrates, make CT-MM a powerful technology for transparent EMI shielding in practical applications.

  8. Micelle-Template Synthesis of Nitrogen-Doped Mesoporous Graphene as an Efficient Metal-Free Electrocatalyst for Hydrogen Production

    PubMed Central

    Huang, Xiaodan; Zhao, Yufei; Ao, Zhimin; Wang, Guoxiu

    2014-01-01

    Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications. PMID:25523276

  9. Micelle-Template Synthesis of Nitrogen-Doped Mesoporous Graphene as an Efficient Metal-Free Electrocatalyst for Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Huang, Xiaodan; Zhao, Yufei; Ao, Zhimin; Wang, Guoxiu

    2014-12-01

    Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications.

  10. Metal Organic Framework-Templated Chemiresistor: Sensing Type Transition from P-to-N Using Hollow Metal Oxide Polyhedron via Galvanic Replacement.

    PubMed

    Jang, Ji-Soo; Koo, Won-Tae; Choi, Seon-Jin; Kim, Il-Doo

    2017-08-30

    Facile synthesis of porous nanobuilding blocks with high surface area and uniform catalyst functionalization has always been regarded as an essential requirement for the development of highly sensitive and selective chemical sensors. Metal-organic frameworks (MOFs) are considered as one of the most ideal templates due to their ability to encapsulate ultrasmall catalytic nanoparticles (NPs) in microporous MOF structures in addition to easy removal of the sacrificial MOF scaffold by calcination. Here, we introduce a MOFs derived n-type SnO2 (n-SnO2) sensing layer with hollow polyhedron structures, obtained from p-n transition of MOF-templated p-type Co3O4 (p-Co3O4) hollow cubes during galvanic replacement reaction (GRR). In addition, the Pd NPs encapsulated in MOF and residual Co3O4 clusters partially remained after GRR led to uniform functionalization of efficient cocatalysts (PdO NPs and p-Co3O4 islands) on the porous and hollow polyhedron SnO2 structures. Due to high gas accessibility through the meso- and macrosized pores in MOF-templated oxides and effective modulation of electron depletion layer assisted by the creation of numerous p-n junctions, the GRR-treated SnO2 structures exhibited 21.9-fold higher acetone response (Rair/Rgas = 22.8 @ 5 ppm acetone, 90%RH) compared to MOF-templated p-Co3O4 hollow structures. To the best of our knowledge, the selectivity and response amplitudes reported here for the detection of acetone are superior to those MOF derived metal oxide sensing layers reported so far. Our results demonstrate that highly active MOF-derived sensing layers can be achieved via p-n semiconducting phase transition, driven by a simple and versatile GRR process combined with MOF templating route.

  11. Influence of lead(II) lone pairs on the serpentine structures for heterometallic alkoxides

    SciTech Connect

    Teff, D.J.; Huffman, J.C.; Caulton, K.G.

    1995-05-10

    Heterometallic alkoxides, M{sub a}M{sub b}{prime}(OR){sub m}, most often adopts closed polyhedral structures, in part to give suitably high coordination numbers to all metals. In general, the ratio m/(a + b) is typically low (because one or more of M and M{prime} are low valent) so that {mu}{sub 2}- and {mu}{sub 3}-OR functionalities are required, and a closed polyhedron best accommodates such demands. Thus the metals of KZr{sub 2}(O{sup i}Pr){sub 9}{sup 2} and [BaZr{sub 2}(O{sup i}Pr){sub 10}]{sub 2}{sup 3} form triangles, those of K{sub 2}Zr{sub 2}(O{sup t}Bu){sub 10}{sup 4} form a diamond, and those of K{sub 4}Zr{sub 2}O(O{sup i}Pr){sub 10}{sup 2} form an octahedron. The authors report here the very different outcome of combining Zr(IV) with the soft divalent metal Pb(II). These results demonstrate that rational synthetic control of two different stoichiometries can be effected in heterometallic alkoxide chemistry.

  12. A Qualitative Analysis of a "Bora-Brook Rearrangement": The Ambident Reactivity of Boryl-Substituted Alkoxide Including the Carbon-to-Oxygen Migration of a Boryl Group.

    PubMed

    Kisu, Haruki; Sakaino, Hirotoshi; Ito, Fumihiro; Yamashita, Makoto; Nozaki, Kyoko

    2016-03-16

    A bora-Brook rearrangement, i.e., the migration of boryl group from a carbon to an oxygen atom in an isolated α-boryl-substituted alkoxide, was examined, and decisive factors for the acceleration of this reaction are disclosed. In this rearrangement, the boryl-substituted alkoxide exhibited ambiphilic reactivity toward electrophiles to afford two types of products, which are electrophiles bound either at the oxygen or at the carbon atom. Using polar solvents, a saturated backbone of the boron-containing heterocycle, or larger alkali metal cations resulted in a significantly increased reaction rate of base-catalyzed isomerization of α-borylbenzyl alcohol including the bora-Brook rearrangement.

  13. Poly(cyclohexylethylene)-block-poly(ethylene oxide) block polymers for metal oxide templating

    SciTech Connect

    Schulze, Morgan W.; Sinturel, Christophe

    2015-09-01

    A series of poly(cyclohexylethylene)-block-poly(ethylene oxide) (CEO) diblock copolymers were synthesized through tandem anionic polymerizations and heterogeneous catalytic hydrogenation. Solvent-annealed CEO diblock films were used to template dense arrays of inorganic oxide nanodots via simple spin coating of an inorganic precursor solution atop the ordered film. The substantial chemical dissimilarity of the two blocks enables (i) selective inclusion of the inorganic precursor within the PEO domain and (ii) the formation of exceptionally small feature sizes due to a relatively large interaction parameter estimated from mean-field analysis of the order–disorder transition temperatures of compositionally symmetric samples. UV/ozone treatment following incorporation produces an ordered arrangement of oxide nanodots and simultaneously removes the block polymer template. However, we report the smallest particles (6 ± 1 nm) templated from a selective precursor insertion method to date using a block polymer scaffold.

  14. Poly(cyclohexylethylene)-block-poly(ethylene oxide) block polymers for metal oxide templating

    DOE PAGES

    Schulze, Morgan W.; Sinturel, Christophe; Hillmyer, Marc A.

    2015-09-01

    A series of poly(cyclohexylethylene)-block-poly(ethylene oxide) (CEO) diblock copolymers were synthesized through tandem anionic polymerizations and heterogeneous catalytic hydrogenation. Solvent-annealed CEO diblock films were used to template dense arrays of inorganic oxide nanodots via simple spin coating of an inorganic precursor solution atop the ordered film. The substantial chemical dissimilarity of the two blocks enables (i) selective inclusion of the inorganic precursor within the PEO domain and (ii) the formation of exceptionally small feature sizes due to a relatively large interaction parameter estimated from mean-field analysis of the order–disorder transition temperatures of compositionally symmetric samples. UV/ozone treatment following incorporation produces anmore » ordered arrangement of oxide nanodots and simultaneously removes the block polymer template. However, we report the smallest particles (6 ± 1 nm) templated from a selective precursor insertion method to date using a block polymer scaffold.« less

  15. A meta-analysis of the mechanical properties of ice-templated ceramics and metals

    PubMed Central

    Deville, Sylvain; Meille, Sylvain; Seuba, Jordi

    2015-01-01

    Ice templating, also known as freeze casting, is a popular shaping route for macroporous materials. Over the past 15 years, it has been widely applied to various classes of materials, and in particular ceramics. Many formulation and process parameters, often interdependent, affect the outcome. It is thus difficult to understand the various relationships between these parameters from isolated studies where only a few of these parameters have been investigated. We report here the results of a meta analysis of the structural and mechanical properties of ice templated materials from an exhaustive collection of records. We use these results to identify which parameters are the most critical to control the structure and properties, and to derive guidelines for optimizing the mechanical response of ice templated materials. We hope these results will be a helpful guide to anyone interested in such materials. PMID:27877817

  16. Metal complexes as templates: syntheses, structures, and luminescent properties of two zinc phosphonocarboxylates with ABW-zeolite topology.

    PubMed

    Chen, Zhenxia; Yang, Haiyang; Deng, Mingli; Ling, Yun; Weng, Linhong; Zhou, Yaming

    2012-04-14

    Two novel zinc phosphonocarboxylates, Zn(3)(pbc)(2)(bpy)(H(2)O)·H(2)O (1) and Zn(2)(pbc)(2)·Zn(bpy)(H(2)O)(4)·2H(2)O (2) (pbc = 4-phosphono-benzoic acid, bpy = 2,2'-bipyridine), were hydrothermally synthesized and structurally characterized. Both of them exhibit zeolitic ABW topology in which double-zigzag inorganic chains are cross-linked by the organic parts. It is notable that the metal complex Zn(bpy)(H(2)O)(x) plays different roles in the two compounds. In 1, the Zn(bpy)(H(2)O) units coordinate with the phosphonate and carboxylate oxygen atoms and participate in the construction of the three-dimensional framework. In 2, the in situ generated [Zn(bpy)(H(2)O)(4)](2+) cation acts as a template, which directs the ABW-type open-framework by strong hydrogen bonds. It is the first example where a metal complex is used as a template in the synthesis of metal phosphonates. The luminescent properties of 1 and 2 are also investigated.

  17. A sodalite-type porous metal-organic framework with polyoxometalate templates: adsorption and decomposition of dimethyl methylphosphonate.

    PubMed

    Ma, Feng-Ji; Liu, Shu-Xia; Sun, Chun-Yan; Liang, Da-Dong; Ren, Guo-Jian; Wei, Feng; Chen, Ya-Guang; Su, Zhong-Min

    2011-03-30

    A sodalite-type porous metal-organic framework with polyoxometalate templates, H(3)[(Cu(4)Cl)(3)(BTC)(8)](2)[PW(12)O(40)]·(C(4)H(12)N)(6)·3H(2)O (NENU-11; BTC = 1,3,5-benzenetricarboxylate), was obtained by a hydrothermal reaction. As a reasonable candidate for eliminating nerve gas, NENU-11 displays good adsorption behavior for dimethyl methylphosphonate (15.5 molecules per formula unit). In virtue of the catalytic activity of polyoxometalate guests, this nerve gas mimic could be facilely decomposed by a hydrolysis reaction.

  18. A facile precursor route to highly loaded metal/ceramic nanofibers as a robust surface-enhanced Raman template

    NASA Astrophysics Data System (ADS)

    Park, Jay Hoon; Joo, Yong Lak

    2017-09-01

    We report silver (Ag)/ceramic nanofibers with highly robust and sensitive optical sensory capabilities that can withstand harsh conditions. These nanofibers are fabricated by first electrospinning solutions of poly vinyl alcohol (PVA) and metal precursor polymers, followed by subsequent series of heat treatment. The reported fabrication method demonstrate the effects of (i) the location of Ag crystals, (ii) crystal size and shape, and (iii) constituents of the ceramic matrix as surface-enhanced Raman spectroscopy (SERS) templates with 10-6 M 4-mercaptobenzoic acid (4-MBA). Notably, these silver/ceramic nanofibers preserved most of their highly sensitive localized surface plasmon resonance (LSPR) even under high temperature of 400 °C, in contrast to preformed Ag nanoparticles (NPs) in PVA nanofibers which lost most of its optical property presumably due to (i) Ag oxidation and (ii) loss of the matrix material. Among the ceramic substrates of ZrO2, Al2O3, and ZnO with silver crystals, we discovered that the ZnO substrate showed the most consistent and the strongest signal strength owing to the synergistic chemical and optical properties of the ZnO substrate. Moreover, the pure Ag nanofiber proved to be the best heat-resistant SERS template, owing to its (i) anisotropic morphology and (ii) thicker diameter when compared with other conventional Ag nanomaterials. These results demonstrated simple yet highly controllable fabrication of robust SERS templates, with potential applications in a catalytic sensory which is often exposed to harsh conditions.

  19. Synthesis of robust mesoporous metal oxide films by the rapid replication of block copolymer templates in supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Pai, Rajaram; Agarwal, Sumit; Hess, David; Watkins, James

    2004-03-01

    Ordered nanostructured materials are of great interest for applications in sensor and detection arrays, catalysis, separations and as low dielectric constant films in microelectronics. The optimization of electrical and mechanical properties requires strict control over porosity, pore structure, matrix composition and ultimately over long range order and patterning at the device level. Here we discuss a new approach to mesoporous solids that involves the infusion and selective condensation of metal oxide precursors within one phase domain of highly ordered, preformed block copolymer templates using supercritical carbon dioxide as the reaction medium. The template is then removed to produce the mesoporous oxide. To date we have replicated ordered spherical and cylindrical morphologies to yield silica, organosilicate and mixed silica/organosilicate mesostructures in films over 1 micron thick while maintaining all the structural details of the sacrificial copolymer template. The elimination of excess alcohol from the reaction media enables rapid and high degrees of network condensation. The implications of this process for the design and fabrication of ultra-low dielectric constant thin films are discussed. After post-processing, these films exhibit dielectric constants as low as 1.8.

  20. DEXTROSE-TEMPLATED MICROWAVE-ASSISTED COMBUSTION SYNTHESIS OF SPONGY METAL OXIDES

    EPA Science Inventory

    Microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania is reported using dextrose as template and the product was compared with the one obtained using conventional heating furnace. Out of three compositions viz., 1:1, 1:3, and 1:5 (met...

  1. DEXTROSE-TEMPLATED MICROWAVE-ASSISTED COMBUSTION SYNTHESIS OF SPONGY METAL OXIDES

    EPA Science Inventory

    Microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania is reported using dextrose as template and the product was compared with the one obtained using conventional heating furnace. Out of three compositions viz., 1:1, 1:3, and 1:5 (met...

  2. Rapid (<3 min) microwave synthesis of block copolymer templated ordered mesoporous metal oxide and carbonate films using nitrate-citric acid systems.

    PubMed

    Zhang, Yuanzhong; Bhaway, Sarang M; Wang, Yi; Cavicchi, Kevin A; Becker, Matthew L; Vogt, Bryan D

    2015-03-25

    Rapid chemical transformation from micelle templated precursors (metal nitrate and citric acid) to ordered mesoporous metal carbonates and oxides is demonstrated using microwave heating for cobalt, copper, manganese and zinc. Without aging requirements, <3 min of microwave processing yields highly ordered mesoporous films.

  3. Template copolymerization to control site structure around metal ions: Applications towards sensing and gas storage and release

    NASA Astrophysics Data System (ADS)

    Mitchell-Koch, Jeremy T.

    The development of functional materials for sensing and gas storage and release is useful in a number of chemical and biological applications. Investigating function of molecularly imprinted polymers (MIP), often used for these purposes, has relied on circumstantial evidence because direct examination of immobilized sites is not possible. Described in this dissertation is the design, synthesis, characterization and function studies of materials synthesized by template copolymerization methods. Metal ions exhibit unique spectroscopic properties and their utilization makes site examination more feasible. Ligand binding modulates these properties such that the event can be measured by spectroscopy. The metal ion's secondary coordination environment can also be tuned to increase or decrease function of the material. In Chapter Two the utilization of template copolymerization to immobilize a europium-containing compound for the detection of volatile organic compounds is described. Luminescence of the immobilized complex is quenched in the presence of volatile organic compounds (VOC). The quenching effect is dependent on concentration of VOC and the nature of polymeric host. Chapters Three and Four describe the development of materials for the photolytic release of nitric oxide (NO). In Chapter Three, a novel manipulation of the immobilized complex is employed to produce binding sites that contain ligands covalently embedded into the host in a position to bind the metal ion upon NO release in order to block rebinding. Incompatible binding affinities of the iron-containing templates made it impossible to study NO photo-release from this material. Second-row transition metals are more compatible with NO binding, and Chapter Four describes a ruthenium salen-containing polymer that releases NO in response to light. Additionally, transfer of NO to a metalloporphyrin and myoglobin has been achieved. This is the first report of photolytic heterogeneous NO transfer by a material

  4. Stress modulation in desiccating crack networks for producing effective templates for patterning metal network based transparent conductors

    NASA Astrophysics Data System (ADS)

    Kumar, Ankush; Pujar, Rajashekhar; Gupta, Nikita; Tarafdar, Sujata; Kulkarni, Giridhar U.

    2017-07-01

    A drying layer of a colloidal dispersion tends to produce cracks, often in a network, due to internal stress arising from the rearrangement of particles while the substrate adhesion resists such movements. The stress can be modulated using experimental agents such as electric field, humidity, and surface structuring. In this work, repeated wet-drying cycles of the cracking layer have been used as stress modulating agents taking an aqueous dispersion of acrylic resin nanoparticles as the colloidal layer, offering cracks with widths in the sub-ten micrometer range. With increasing wet-drying cycles, the colloidal layer is seen to develop higher crack density and connectivity, as well as a well-defined hierarchy of formation. Thus developed crack layers have been used as templates for depositing metals (Cu and Au) to realize fine metal wire meshes. The latter serve as transparent conductors with excellent optoelectronic properties.

  5. Preparation and characterization of two-dimensional metallic nanoparticle and void films derived from a colloidal template layer.

    PubMed

    Sepsi, Örs; Pothorszky, Szilárd; Nguyen, Tuan Máté; Zámbó, Dániel; Ujhelyi, Ferenc; Lenk, Sándor; Koppa, Pál; Deák, András

    2016-01-25

    A novel and simple bottom-up fabrication method for the realization of metallic nanovoid and metallic film on nanoparticle (dome) array is presented and their optical performance assessed based on experimental and theoretical investigations. The structures are created by a simple, annealing induced replica formation of a template monolayer, which is composed of submicron particles deposited on top of a thin polymer film. Angle and wavelength dependent reflection measurements indicate the possibility to excite Bragg plasmons at the prepared structures. We found an excellent agreement between the measured and simulated reflection curves, but only when the simulated reflection was averaged over several possible azimuthal lattice orientations of the hexagonal unit cell with respect to the plane of incidence.

  6. Coordination polymer nanocapsules prepared using metal-organic framework templates for pH-responsive drug delivery

    NASA Astrophysics Data System (ADS)

    Tang, Lei; Shi, Jiafu; Wang, Xiaoli; Zhang, Shaohua; Wu, Hong; Sun, Hongfan; Jiang, Zhongyi

    2017-07-01

    A facile, efficient, and versatile approach is presented to synthesize pH-responsive nanocapsules (˜120 nm) by combining the advantages of metal-organic frameworks (MOFs) and metal-organic thin films. ZIF-8 nanoparticles are used as templates on which a thin film coating of iron(III)-catechol complexes is derived from the coordination between dopamine-modified alginate (AlgDA) and iron(III) ions. After the template removal, nanocapsules with a pH-responsive wall are obtained. Doxorubicin (Dox), a typical anticancer drug, is first immobilized in ZIF-8 frameworks through coprecipitation and then encapsulated in nanocapsules after the removal of ZIF-8. The structure of the iron(III)-catechol complex varies with pH value, thus conferring the Dox@Nanocapsules with tailored release behavior in vitro. Cytotoxicity tests illustrate the highly effective cytotoxicity of Dox@Nanocapsules towards cancer cells. This study provides a new method for preparing smart nanocapsules and offers more opportunities for the controlled delivery of drugs.

  7. Low-temperature oriented growth of vanadium dioxide films on CoCrTa metal template on Si and vertical metal-insulator transition

    SciTech Connect

    Okimura, Kunio; Mian, Md.Suruz

    2012-09-15

    The authors achieved oriented growth of vanadium dioxide (VO{sub 2}) films on CoCrTa metal template grown on an Si substrate. Low-temperature ({approx}250 Degree-Sign C) deposition of VO{sub 2} films using inductively coupled-plasma-assisted sputtering technique realized an abrupt interface between VO{sub 2} and CoCrTa layers, suppressing the oxidation and diffusion of metal components. The films revealed a metal-insulator transition with resistance change of over 2 orders of magnitude. The CoCrTa film, in which Co hexagonal crystalline grains with c-axis orientation were surrounded by segregated Cr and Ta, serves for the oriented growth of VO{sub 2} crystalline film, enabling higher orders of transition in resistance and low voltage switching, even for the vertical (out-of-plane) direction.

  8. Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

    PubMed Central

    Dumée, Ludovic F.; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

    2015-01-01

    The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation. PMID:28347094

  9. Surprisingly facile CO2 insertion into cobalt alkoxide bonds: A theoretical investigation

    PubMed Central

    Offermans, Willem K; Bizzarri, Claudia; Leitner, Walter

    2015-01-01

    Summary Exploiting carbon dioxide as co-monomer with epoxides in the production of polycarbonates is economically highly attractive. More effective catalysts for this reaction are intensively being sought. To promote better understanding of the catalytic pathways, this study uses density functional theory calculations to elucidate the reaction step of CO2 insertion into cobalt(III)–alkoxide bonds, which is also the central step of metal catalysed carboxylation reactions. It was found that CO2 insertion into the cobalt(III)–alkoxide bond of [(2-hydroxyethoxy)CoIII(salen)(L)] complexes (salen = N,N”-bis(salicyliden-1,6-diaminophenyl)) is exothermic, whereby the exothermicity depends on the trans-ligand L. The more electron-donating this ligand is, the more exothermic the insertion step is. Interestingly, we found that the activation barrier decreases with increasing exothermicity of the CO2 insertion. Hereby, a linear Brønsted–Evans–Polanyi relationship was found between the activation energy and the reaction energy. PMID:26425188

  10. Improving halide-containing magnesium-ion electrolyte performance via sterically hindered alkoxide ligands

    NASA Astrophysics Data System (ADS)

    Nist-Lund, Carl A.; Herb, Jake T.; Arnold, Craig B.

    2017-09-01

    While homoleptic magnesium dialkoxides (MgR2, R = alkoxide) have shown promise as precursors for magnesium-ion electrolytes, the effect of ligand steric bulk on the performance of electrolytes based on these compounds is not fully understood. Increasing steric hindrance, studied via R groups with additional phenyl moieties, produces electrolytes with sequentially lower deposition overpotentials (less than -90 mV), higher purity Mg deposits (ca. 100% Mg), and lower overall cell impedances. The two largest alkoxide ligands show consistent cycling behavior and low stripping and plating overpotentials over 200 constant-current plating/stripping cycles. A deep-red visual change and the presence of large solubilized magnesium particulates above 450 nm in size is observed in an electrolyte containing magnesium bis(triphenylmethoxide) and aluminum chloride in contact with an abraded magnesium anode. Further morphological and impedance characterization show that this electrolyte system rapidly activates the magnesium metal anode surface to produce low overpotentials and, as such, is a candidate for further investigation.

  11. Fast and reversible insertion of carbon dioxide into zirconocene-alkoxide bonds. A mechanistic study.

    PubMed

    Brink, Alice; Truedsson, Ida; Fleckhaus, André; Johnson, Magnus T; Norrby, Per Ola; Roodt, Andreas; Wendt, Ola F

    2014-06-21

    In two consecutive equilibria the compound (Cp*)2Zr(OMe)2 undergoes insertion of CO2 to form the mono- and bis-hemicarbonates. Both equilibria are exothermic but entropically disfavoured. Magnetisation transfer experiments gave kinetic data for the first equilibrium showing that the rate of insertion is overall second order with a rate constant of 3.20 ± 0.12 M(-1) s(-1), which is substantially higher than those reported for other early transition metal alkoxides, which are currently the best homogeneous catalysts for dimethyl carbonate formation from methanol and CO2. Activation parameters for the insertion reaction point to a highly ordered transition state and we interpret that as there being a substantial interaction between the CO2 and the metal during the C-O bond formation. This is supported by DFT calculations showing the lateral attack by CO2 to have the lowest energy transition state.

  12. Synthesis and characterization of cerium and yttrium alkoxide complexes supported by ferrocene-based chelating ligands.

    PubMed

    Broderick, Erin M; Thuy-Boun, Peter S; Guo, Neng; Vogel, Carola S; Sutter, Jörg; Miller, Jeffrey T; Meyer, Karsten; Diaconescu, Paula L

    2011-04-04

    Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mössbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.

  13. "Dual-template" synthesis of one-dimensional conductive nanoparticle superstructures from coordination metal-peptide polymer crystals.

    PubMed

    Rubio-Martínez, Marta; Puigmartí-Luis, Josep; Imaz, Inhar; Dittrich, Petra S; Maspoch, Daniel

    2013-12-20

    Bottom-up fabrication of self-assembled structures made of nanoparticles may lead to new materials, arrays and devices with great promise for myriad applications. Here a new class of metal-peptide scaffolds is reported: coordination polymer Ag(I)-DLL belt-like crystals, which enable the dual-template synthesis of more sophisticated nanoparticle superstructures. In these biorelated scaffolds, the self-assembly and recognition capacities of peptides and the selective reduction of Ag(I) ions to Ag are simultaneously exploited to control the growth and assembly of inorganic nanoparticles: first on their surfaces, and then inside the structures themselves. The templated internal Ag nanoparticles are well confined and closely packed, conditions that favour electrical conductivity in the superstructures. It is anticipated that these Ag(I)-DLL belts could be applied to create long (>100 μm) conductive Ag@Ag nanoparticle superstructures and polymetallic, multifunctional Fe3 O4 @Ag nanoparticle composites that marry the magnetic and conductive properties of the two nanoparticle types.

  14. Crackle template based metallic mesh with highly homogeneous light transmission for high-performance transparent EMI shielding

    PubMed Central

    Han, Yu; Lin, Jie; Liu, Yuxuan; Fu, Hao; Ma, Yuan; Jin, Peng; Tan, Jiubin

    2016-01-01

    Our daily electromagnetic environment is becoming increasingly complex with the rapid development of consumer electronics and wireless communication technologies, which in turn necessitates the development of electromagnetic interference (EMI) shielding, especially for transparent components. We engineered a transparent EMI shielding film with crack-template based metallic mesh (CT-MM) that shows highly homogeneous light transmission and strong microwave shielding efficacy. The CT-MM film is fabricated using a cost-effective lift-off method based on a crackle template. It achieves a shielding effectiveness of ~26 dB, optical transmittance of ~91% and negligible impact on optical imaging performance. Moreover, high–quality CT-MM film is demonstrated on a large–calibre spherical surface. These excellent properties of CT-MM film, together with its advantages of facile large-area fabrication and scalability in processing on multi-shaped substrates, make CT-MM a powerful technology for transparent EMI shielding in practical applications. PMID:27151578

  15. Syntheses of rare-earth metal oxide nanotubes by the sol gel method assisted with porous anodic aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Kuang, Qin; Lin, Zhi-Wei; Lian, Wei; Jiang, Zhi-Yuan; Xie, Zhao-Xiong; Huang, Rong-Bin; Zheng, Lan-Sun

    2007-04-01

    In this paper, we report a versatile synthetic method of ordered rare-earth metal (RE) oxide nanotubes. RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction (XRD) have been employed to characterize the morphology and composition of the as-prepared nanotubes. It is found that as-prepared RE oxides evolve into bamboo-like nanotubes and entirely hollow nanotubes. A new possible formation mechanism of RE oxide nanotubes in the AAO channels is proposed. These high-quantity RE oxide nanotubes are expected to have promising applications in many areas such as luminescent materials, catalysts, magnets, etc.

  16. Templated assembly of Co-Pt nanoparticles via thermal and laser-induced dewetting of bilayer metal films.

    PubMed

    Oh, Yong-Jun; Kim, Jung-Hwan; Thompson, Carl V; Ross, Caroline A

    2013-01-07

    Templated dewetting of a Co/Pt metal bilayer film on a topographic substrate was used to assemble arrays of Co-Pt alloy nanoparticles, with highly uniform particle size, shape and notably composition compared to nanoparticles formed on an untemplated substrate. Solid-state and liquid-state dewetting processes, using furnace annealing and laser irradiation respectively, were compared. Liquid state dewetting produced more uniform, conformal nanoparticles but they had a polycrystalline disordered fcc structure and relatively low magnetic coercivity. In contrast, solid state dewetting enabled formation of magnetically hard, ordered L1(0) Co-Pt single-crystal particles with coercivity >12 kOe. Furnace annealing converted the nanoparticles formed by liquid state dewetting into the L1(0) phase.

  17. Fabrication of Meso-Porous Sintered Metal Thin Films by Selective Etching of Silica Based Sacrificial Template

    PubMed Central

    Dumée, Ludovic F.; She, Fenghua; Duke, Mikel; Gray, Stephen; Hodgson, Peter; Kong, Lingxue

    2014-01-01

    Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm) as well as the sintering pressure (5–20 ton·m−2) and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested.

  18. Template-directed covalent conjugation of DNA to native antibodies, transferrin and other metal-binding proteins

    NASA Astrophysics Data System (ADS)

    Rosen, Christian B.; Kodal, Anne L. B.; Nielsen, Jesper S.; Schaffert, David H.; Scavenius, Carsten; Okholm, Anders H.; Voigt, Niels V.; Enghild, Jan J.; Kjems, Jørgen; Tørring, Thomas; Gothelf, Kurt V.

    2014-09-01

    DNA-protein conjugates are important in bioanalytical chemistry, molecular diagnostics and bionanotechnology, as the DNA provides a unique handle to identify, functionalize or otherwise manipulate proteins. To maintain protein activity, conjugation of a single DNA handle to a specific location on the protein is often needed. However, preparing such high-quality site-specific conjugates often requires genetically engineered proteins, which is a laborious and technically challenging approach. Here we demonstrate a simpler method to create site-selective DNA-protein conjugates. Using a guiding DNA strand modified with a metal-binding functionality, we directed a second DNA strand to the vicinity of a metal-binding site of His6-tagged or wild-type metal-binding proteins, such as serotransferrin, where it subsequently reacted with lysine residues at that site. This method, DNA-templated protein conjugation, facilitates the production of site-selective protein conjugates, and also conjugation to IgG1 antibodies via a histidine cluster in the constant domain.

  19. Graphene/MoS2 heterostructures as templates for growing two-dimensional metals: Predictions from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Šljivančanin, Željko; Belić, Milivoj

    2017-09-01

    Preparation of single-atom-thick layers of ordinary metals has been a challenging task since their closely packed atoms lack layered structure with highly anisotropic bonding. Using computational modeling based on density functional theory we showed that graphene/MoS2 heterostructures can be used as suitable templates to grow stable two-dimensional (2D) clusters, as well as extended monoatomic layers of metals with nonlayered structure in the bulk. Considering gold and lithium as two metals with markedly different properties, we found that Li intercalants strengthen coupling between graphene (G) and MoS2, mainly due to electrostatic attraction of 2D materials with positively charged Li atoms. However, intercalation with large Au atoms gives rise to a significant increase in the distance between G and MoS2 and thus, weakens their interaction. In addition to strong preference for 2D growth, we demonstrated that Au intercalants weakly interact with both G and MoS2, and hence G /MoS2 vertical heterostructures could be a promising framework to prepare gold 2D structures with electronic properties closely resembling those of the hypothetical free-standing hexagonal gold monolayer.

  20. Genetically Modified Collagen-like Triple helix Protein as Biomimetic Template to Fabricate Metal/Semiconductor Nanowires

    NASA Astrophysics Data System (ADS)

    Bai, Hanying

    Various metal and semiconductor nanowires have been developed as building blocks for electronics, optics, and sensors devices. Among these, new nanowires developed on biomolecular templates got more attention since the molecular recognition functions of these biomolecules with specific ligands can be employed to immobilize nanowires onto specific locations to establish desired device geometries. In order for their application in electronics, optics, and sensors device fabrications, after configuring device geometries with nanowires by the biomolecular recognition, we focused upon the biomineralization function of peptides on the nanotemplate sidewall to develop various material coatings such as metals and semiconductors for electronics and sensor applications. It should be noted that the coating morphology such as particle-domain size and inter-particle distance on the nanotemplates could be tuned by peptide sequences and conformations. We launched the genetically modified recombinant collagen-like triple helix proteins as a biorecognition, size-controlling and rigid biotemplate. This collagen-like triple helix is the genetically engineered polypeptide assembly that contains a fragment from the natural collagen sequence and has attractive features in hybrid nanomaterials. The length of the protein nanowire is uniform since it is determined by the number of amino acids. The length can be flexible if we genetically modify the sequence, which can also add chemical functionality by the genetic engineering procedure. Genetic engineering is more advantageous than the chemical synthesis for the functionalization /deritivization of peptide nanowire because only the desired specific residue of the peptide is functionalized by the genetic approach. The specific sequence can also increase stability so that the mechanical property can be tuned to be suitable for device application in harsh environment. By using the recombinant technology, it is possible to design and amplify a

  1. Alkoxide-based precursors for direct electrospinning of alumina fibers

    NASA Astrophysics Data System (ADS)

    Maneeratana, Vasana

    The vision for space exploration in 2004 reinvigorated excitement that was engendered during the 1960's space race. Looking to assist NASA's agency wide mission to develop new technologies to enhance space travel, it is the ultimate goal of this work to support future missions with a hand-held electrospinning apparatus to instantaneously repair existing crucial ceramic fiber structures, such as spacesuits, insulative foams, and tiles. In this research, a new type of precursor is designed based from aluminum alkoxide-based precursors, since alumina serves as a base material for a majority of high-temperature applications. The structure-processing behavior of these precursors is subsequently studied. New precursors of aluminum alkoxides were prepared by modifying solutions; as a result various types of structures were produced, ranging from continuous hollow fibers, continuous solid fibers, or hollow particles. Direct electrospinning with these alkoxide-based precursors yielded an average of 1.9 g/hr of Al2O3, compared to literature with the highest theoretical yield calculated to be 0.68 g/hr. Further exploration of electrospinning parameters found that flow rate directly related to exposure times; therefore fibers were produced in the atmosphere through hydrolysis/condensation with simultaneous solvent evaporation. Furthermore other processing parameters, including the effect of the microstructure due to processing in an electric field were studied. It was found that electrospinning promotes the reaction of the alkoxide, which thereby reduces trapped solvents. As a result of firing schedules, the fibers' hollow features were preserved, and precursors with volatile species resulted in near net shaped fibers. At low firing temperatures, specific surface areas in the range of 330-345 m 2/g were found electrospun fibers. Additionally modified precursors lowered alpha transitions of fibers down to ˜900°C.

  2. Highly Soluble Alkoxide Magnesium Salts for Rechargeable Magnesium Batteries

    SciTech Connect

    Liao, Chen; Guo, Bingkun; Jiang, Deen; Custelcean, Radu; Mahurin, Shannon Mark; Sun, Xiao-Guang; Dai, Sheng

    2014-01-01

    A unique class of air-stable and non-pyrophoric magnesium electrolytes has been developed based on alkoxide magnesium compounds. The crystals obtained from this class of electrolytes exhibit a unique structure of tri-magnesium cluster, [Mg3Cl3(OR)2(THF)6]+ [(THF)MgCl3] . High reversible capacities and good rate capabilities were obtained in Mg-Mo6S8 batteries using these new electrolytes at both 20 and 50 oC.

  3. A metal-organic framework-templated synthesis of γ-Fe2O3 nanoparticles encapsulated in porous carbon for efficient and chemoselective hydrogenation of nitro compounds.

    PubMed

    Li, Yang; Zhou, Yu-Xiao; Ma, Xiao; Jiang, Hai-Long

    2016-03-18

    The γ-Fe2O3 nanoparticles well dispersed in porous carbon were fabricated via a Fe-based metal-organic framework-templated pyrolysis. The resultant product exhibits excellent catalytic activity, chemoselectivity and magnetic recyclability for the hydrogenation of diverse nitro compounds under mild conditions.

  4. Ammonium-crown ether supramolecular cation-templated assembly of an unprecedented heterobicluster-metal coordination polymer with enhanced NLO properties.

    PubMed

    Zhang, Jinfang; Jia, Ding; Humphrey, Mark G; Meng, Suci; Zaworotko, Michael J; Cifuentes, Marie P; Zhang, Chi

    2016-03-07

    An ammonium-crown ether host-guest supramolecular cation-templated synthetic methodology has been developed to construct a structurally unprecedented heterobicluster-metal coordination polymer (HCM-CP 1) based on tetranuclear clusters [WS4Cu3](+) with different connection environments, pentanuclear clusters [WS4Cu4](2+), and Cu(+) building metal ions. HCM-CP 1 exhibits enhanced NLO properties, which may be ascribed to the incorporation of diverse building cluster components.

  5. Fabrication of Anisotropic Metal Nanostructures Using Innovations in Template-Assisted Lithography

    PubMed Central

    Tang, Zhao; Wei, Alexander

    2012-01-01

    Advances in the burgeoning field of plasmonics are increasingly dependent on the ability to fabricate metal nanostructures with precisely defined shapes and orientations, on a scale suitable for technological developments. Recent innovations in top-down lithography have created new windows of opportunity to produce anisotropic metal nanostructures en masse, with near-term applications in photonics, biosensing, and other nanotechnology-enabled pursuits. We focus specifically on C-shaped nanostructures (nanocrescents and split-ring resonators), which can be fabricated by using novel variants of shadow mask lithography, substrate etching, or microcontact printing. PMID:22324475

  6. Method to synthesize metal chalcogenide monolayer nanomaterials

    SciTech Connect

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  7. Polymer grafting surface as templates for the site-selective metallization

    NASA Astrophysics Data System (ADS)

    Yang, Fang; Li, Peiyuan; Li, Xiangcheng; Huo, Lini; Chen, Jinhao; Chen, Rui; Na, Wei; Tang, Wanning; Liang, Lifang; Su, Wei

    2013-06-01

    We report a simple, low-cost and universal method for the fabrication of copper circuit patterns on a wide range of flexible polymeric substrates. This method relies on procedures to modify the polymeric substrates with grafted polymer template to form surface-bound N-containing groups, which can bind palladium catalysts that subsequently initiate the site-selective deposition of copper granular layer patterns. The fabrications of patterned copper films were demonstrated on three kinds of flexible polymeric films including poly(imide) (PI), poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) with minimum feature sizes of 200 μm. The films were characterized by ATR FT-IR, contact angle, XPS, XRD, TEM, SEM. Furthermore, the copper layered structure shows good adhesion with polymeric film. This method, which provides a promising strategy for the fabrication of copper circuit patterns on flexible polymeric substrates, has the potential in manufacturing conductive features adopted in various fields including modern electronics, opto-electronics and photovoltaic applications.

  8. Metal-organic gel templated synthesis of magnetic porous carbon for highly efficient removal of organic dyes.

    PubMed

    Wang, Luhuan; Ke, Fei; Zhu, Junfa

    2016-03-21

    Magnetic porous carbon composites are promising materials in various applications, such as adsorbents, supercapacitors and catalyst supports, due to their high surface area, thermal and chemical stability, and easy separation. However, despite the increasing number of reports of magnetic porous carbon composites, the preparation of these materials with environmentally friendly procedures still remains a great challenge. Herein, we report a facile method to prepare a magnetic porous carbon composite with high surface area from a Fe-based metal-organic gel (MOG) template, an extended structure of a metal-organic framework (MOF). The obtained magnetic porous carbon composite was applied to remove organic dyes from an aqueous solution by selecting methyl orange (MO) as a model molecule. It exhibits excellent adsorption capacity (182.82 mg g(-1)), fast adsorption kinetics (8.13 × 10(-3) g mg(-1) min(-1)), and a perfect magnetic separation performance for the MO removal. This study demonstrates a new way to achieve clean synthesis of magnetic porous carbon materials, and opens a new door for the application of MOGs in organic dye removal.

  9. Metallotropic liquid crystals formed by surfactant templating of molten metal halides

    NASA Astrophysics Data System (ADS)

    Martin, James D.; Keary, Cristin L.; Thornton, Todd A.; Novotnak, Mark P.; Knutson, Jeremey W.; Folmer, Jacob C. W.

    2006-04-01

    Liquid crystals consist of anisotropic molecular units, and most are organic molecules. Materials incorporating metals into anisotropic molecules, described as metallomesogens, have been prepared. Anisotropic structures such as one-dimensional chains and two-dimensional layers are frequently observed in solid-state inorganic materials, however, little is understood about structural organization in melts of such materials. Achieving liquid-crystalline behaviour in inorganic fluids should be possible if the anisotropic structure can be retained or designed into the molten phase. We demonstrated the ability to engineer zeolite-type structures into metal halide glasses and liquids. In this work we have engineered lamellar, cubic and hexagonal liquid-crystalline structure in metal-halide melts by controlling the volume fraction and nature of the inorganic block (up to 80 mol%) with respect to alkylammonium surfactants. The high metal content of these liquid-crystalline systems significantly advances the field of metallomesogens, which seeks to combine magnetic, electronic, optical, redox and catalytic properties common to inorganic materials with the fluid properties of liquid crystals.

  10. Salt-Templated Synthesis of 2D Metallic MoN and Other Nitrides.

    PubMed

    Xiao, Xu; Yu, Huimin; Jin, Huanyu; Wu, Menghao; Fang, Yunsheng; Sun, Jiyu; Hu, Zhimi; Li, Tianqi; Wu, Jiabin; Huang, Liang; Gogotsi, Yury; Zhou, Jun

    2017-02-28

    Two-dimensional (2D) transition-metal nitrides just recently entered the research arena, but already offer a potential for high-rate energy storage, which is needed for portable/wearable electronics and many other applications. However, a lack of efficient and high-yield synthesis methods for 2D metal nitrides has been a major bottleneck for the manufacturing of those potentially very important materials, and only MoN, Ti4N3, and GaN have been reported so far. Here we report a scalable method that uses reduction of 2D hexagonal oxides in ammonia to produce 2D nitrides, such as MoN. MoN nanosheets with subnanometer thickness have been studied in depth. Both theoretical calculation and experiments demonstrate the metallic nature of 2D MoN. The hydrophilic restacked 2D MoN film exhibits a very high volumetric capacitance of 928 F cm(-3) in sulfuric acid electrolyte with an excellent rate performance. We expect that the synthesis of metallic 2D MoN and two other nitrides (W2N and V2N) demonstrated here will provide an efficient way to expand the family of 2D materials and add many members with attractive properties.

  11. Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

    NASA Astrophysics Data System (ADS)

    Li, Min; Yang, Da-Peng; Wang, Xiansong; Lu, Jianxin; Cui, Daxiang

    2013-04-01

    A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H2O2.

  12. Metal complexes of chiral pentaazacrowns as conformational templates for β-turn recognition

    NASA Astrophysics Data System (ADS)

    Reaka, Andrea J. H.; Ho, Chris M. W.; Marshall, Garland R.

    2002-08-01

    Examples of reverse turns as recognition motifs in biological systems can be found in high-resolution crystal structures of antibody-peptide complexes. Development of peptidomimetics is often based on replacing the amide backbone of peptides by sugar rings, steroids, benzodiazepines, or other hetero- and carbocycles. In this approach, the chemical scaffold of the peptide backbone can be replaced while retaining activity as long as the pharmacophoric groups of the peptide side chains stay in relatively the same place; in other words, similar functional groups must overlap in space for interaction with critical receptor sites. This study evaluates the potential of metal complexes of chiral pentaazacrowns (PAC) derived by reduction of cyclic pentapeptides as β-turn mimetics. Due to the limited flexibility of the pendant chiral side groups in these metal complexes, one can potentially elicit information about the receptor-bound conformation from their binding affinities. 11 PAC crystal structures with different substitution patterns complexed with 3 different metals (Mn, Fe, Cd) as a prototypical database of potential side-chain orientations. Complexation with different metals induces subtle differences in the conformations of a particular azacrown scaffold. The lack of parameterization of transition metals for force field calculations precludes a thorough theoretical study. Thus, this study utilizes a simple geometrical comparison between the experimental data for crystalline PAC complexes and the side-chain orientations seen in classic β-turns. The FOUNDATION program was used to overlap the Cα-Cβ vectors of the corresponding ideal β-turn side-chains to all possible leaving groups of the PAC complexes. When comparing the relative orientations of the chiral side chains, a strong overlap of the bonds (between about 0.1 Å to about 0.5 Å RMS for 3 residues and up to about 1 Å RMS for 4 residues) was observed for many of the molecules. Such metal complexes may lack

  13. Metal complexes of chiral pentaazacrowns as conformational templates for beta-turn recognition.

    PubMed

    Reaka, Andrea J H; Ho, Chris M W; Marshall, Garland R

    2002-01-01

    Examples of reverse turns as recognition motifs in biological systems can be found in high-resolution crystal structures of antibody-peptide complexes. Development of peptidomimetics is often based on replacing the amide backbone of peptides by sugar rings, steroids, benzodiazepines, or other hetero- and carbocycles. In this approach, the chemical scaffold of the peptide backbone can be replaced while retaining activity as long as the pharmacophoric groups of the peptide side chains stay in relatively the same place; in other words, similar functional groups must overlap in space for interaction with critical receptor sites. This study evaluates the potential of metal complexes of chiral pentaazacrowns (PAC) derived by reduction of cyclic pentapeptides as beta-turn mimetics. Due to the limited flexibility of the pendant chiral side groups in these metal complexes, one can potentially elicit information about the receptor-bound conformation from their binding affinities. 11 PAC crystal structures with different substitution patterns complexed with 3 different metals (Mn, Fe, Cd) as a prototypical database of potential side-chain orientations. Complexation with different metals induces subtle differences in the conformations of a particular azacrown scaffold. The lack of parameterization of transition metals for force field calculations precludes a thorough theoretical study. Thus, this study utilizes a simple geometrical comparison between the experimental data for crystalline PAC complexes and the side-chain orientations seen in classic beta-turns. The FOUNDATION program was used to overlap the Calpha-Cbeta vectors of the corresponding ideal beta-turn side-chains to all possible leaving groups of the PAC complexes. When comparing the relative orientations of the chiral side chains, a strong overlap of the bonds (between about 0.1 A to about 0.5 A RMS for 3 residues and up to about 1 A RMS for 4 residues) was observed for many of the molecules. Such metal complexes

  14. Conformal sol-gel coatings on three-dimensional nanostructured templates

    NASA Astrophysics Data System (ADS)

    Weatherspoon, Michael R.

    Sol-gel processing techniques, such as spin coating and dip coating, have successfully been utilized over the past several decades to apply conformal coatings on planar substrates; however, controlled film growth on three-dimensional (3-D) nanostructured templates using the sol-gel process remains a significant challenge. Obstacles such as, uncontrolled hydrolyzation and condensation of metal alkoxide precursors on nanostructured surfaces are a few of the obstacles which lead to coatings with undesirable thicknesses and excess inorganic particles. A little over a decade ago, a surface sol-gel process was developed which utilizes stepwise film growth of anhydrous metal alkoxide precursors with hydroxylated surfaces. The surface sol-gel process provides control over the applied coating thickness and is viewed as a wet chemical analog to atomic layer deposition (ALD). The work presented in this dissertation has focused on applying conformal sol-gel derived coatings with controlled thicknesses on 3-D nanostructured templates. The templates utilized in this work were derived from biological species, such as diatoms and butterflies, as well as a synthetic photoresist polymer (SU-8). Coatings were applied on the templates using a conventional reflux/evaporation deposition process and a custom-built computer controlled surface sol-gel pumping system. The coatings applied using the reflux/evaporation process yielded conformal coatings with uncontrolled film thicknesses whereas the coatings applied using the surface sol-gel process yielded conformal coatings with controlled thicknesses. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using the reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate

  15. General one-pot template-free hydrothermal method to metal oxide hollow spheres and their photocatalytic activities and lithium storage properties.

    PubMed

    Li, Di; Qin, Qing; Duan, Xiaochuan; Yang, Jiaqin; Guo, Wei; Zheng, Wenjun

    2013-09-25

    A general and facile one-pot template-free hydrothermal strategy has been developed to synthesize various metal oxide (TiO2, SnO2 and α-Fe2O3) hollow spheres with unified morphologies. The formation of hollow structure involves a trifluoroacetic acid (TFA)-assisted Ostwald ripening process. Photocatalytic activities of the as-prepared TiO2 product are evaluated by the photodegradation of Rhodamine B (RhB), which the TiO2 hollow spheres obtained from 450 °C thermal treatment exhibit higher photocatalytic activity than Degussa P25. In addition, electrochemical measurements demonstrate that all of the as-prepared metal oxides hollow spheres have the potential applications in lithium-ion battery. We have a great expectation that this synthesis strategy can afford a new universal route for functional metal oxide hollow materials preparation without using template.

  16. Photochemical Fabrication of Transition Metal Nanoparticles Using CdS Template and Their Co-Catalysis Effects for TiO2 Photocatalysis

    NASA Astrophysics Data System (ADS)

    Badhwar, Nidhi; Gupta, Nidhi; Pal, Bonamali

    2013-09-01

    Transition metal nanoparticles were prepared by chemical dissolution of CdS template from metal photodeposited CdS nanorod (length = 70-85 nm and width = 5-6 nm) heterocomposites. Size (9-10 nm) of metal nanoparticles obtained after CdS removal was larger than the size (4-6 nm) of metal nanodeposits over CdS template. The obtained Au nanoparticles displayed a broad red shifted absorption band at 660 nm, whereas Pt, Pd and Rh nanoparticles exhibit featureless absorption spectra. Elemental analysis confirms the complete removal of CdS template from Au-CdS (Au — 2.65 at.%) and Ag-CdS (Ag — 2.06 at.%) composites showing no Cd peak. These metal nanoparticles imparted dissimilar co-catalytic activity of TiO2 for photocatalytic degradation of salicylic acid in the order Au > Pt > Pd > Ag > Rh as a function of their nature, electronegativity, redox potential and work function.

  17. Graphene as a flexible template for controlling magnetic interactions between metal atoms.

    PubMed

    Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H; Lee, Gun-Do

    2017-03-01

    Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.

  18. Graphene as a flexible template for controlling magnetic interactions between metal atoms

    NASA Astrophysics Data System (ADS)

    Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W.; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H.; Lee, Gun-Do

    2017-03-01

    Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.

  19. Mix and match: templating chiral Schiff base ligands to suit the needs of the metal ion.

    PubMed

    Constable, Edwin C; Zhang, Guoqi; Housecroft, Catherine E; Zampese, Jennifer A

    2010-06-14

    One-pot reactions of 2,2'-bipyridine-6-carbaldehyde, (1S,2S)-(-)-1,2-diphenyl-1,2-diaminoethane and FeCl(2).4H(2)O or Zn(OAc)(2).2H(2)O (2 : 1 : 1) at room temperature in MeOH lead to [Fe{(S,S)-5}(2)][PF(6)]Cl or [Zn{(S,S)-5}(2)][PF(6)](2) in which (S,S)-5 contains an imidazolidine ring, produced by intramolecular cyclization. This has been confirmed with the single-crystal structure of 2{P-[Fe{(S,S)-5}(2)][PF(6)]Cl}.H(2)O. The diastereoselectivity observed in the solid state has been confirmed by NMR spectroscopy for solutions of [Fe{(S,S)-5}(2)][PF(6)]Cl and [Zn{(S,S)-5}(2)][PF(6)](2). At room temperature, a minor product competes with the formation of [Fe{(S,S)-5}(2)][PF(6)]Cl, and the preference for these complexes is switched by carrying out the reaction in MeOH at reflux. In this case the major product is M-[Fe(2){(S,S)-4}(2)][PF(6)](4) in which (S,S)-4 is the hexadentate Schiff base ligand formed by condensation of two equivalents of 2,2'-bipyridine-6-carbaldehyde with (1S,2S)-(-)-1,2-diphenyl-1,2-diaminoethane; the single-crystal structure of 4{M-[Fe(2){(S,S)-4}(2)][PF(6)](4)}.8Me(2)CO.5MeCN.3H(2)O confirms the assembly of a double helicate. When pyridine-6-carbaldehyde replaces 2,2'-bipyridine-6-carbaldehyde in the iron(II)-templated reaction with (1S,2S)-(-)-1,2-diphenyl-1,2-diaminoethane, the product is [Fe{(S,S)-7}(2)][PF(6)](2) (3 : 2 mixture of diastereoisomers in solution) in which (S,S)-7 is an asymmetrical Schiff base, formed by reaction of only one of the amine groups in (1S,2S)-(-)-1,2-diphenyl-1,2-diaminoethane. The solid state structure of P-[Fe{(S,S)-7}(2)][PF(6)](2).MeCN is presented.

  20. Nanoparticle-based immunosensor with apoferritin templated metallic phosphate label for quantification of phosphorylated acetylcholinesterase

    SciTech Connect

    Du, Dan; Chen, Aiqiong; Xie, Yunying; Zhang, Aidong; Lin, Yuehe

    2011-05-15

    A new sandwich-like electrochemical immunosensor has been developed for quantification of organophosphorylated acetylcholinesterase (OP-AChE), an exposure biomarker of organophosphate pesticides and nerve agents. Zirconia nanoparticles (ZrO2 NPs) were anchored on a screen printed electrode (SPE) to preferably capture OP-AChE adducts by metal chelation with phospho-moieties, which was selectively recognized by lead phosphate-apoferritin labeled anti-AChE antibody (LPA-anti-AChE). The sandwich-like immunoreactions were performed among ZrO2 NPs, OP-AChE and LPA-anti-AChE to form ZrO2/OP-AChE/LPA-anti-AChE complex and the released lead ions were detected on a disposable SPE. The binding affinity was investigated by both square wave voltammetry (SWV) and quartz crystal microbalance (QCM) measurements. The proposed immunosensor yielded a linear response current over a broad OP-AChE concentrations range from 0.05 nM to 10 nM, with detection limit of 0.02 nM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This method avoids the drawback of unavailability of commercial OP-specific antibody as well as amplifies detection signal by using apoferritin encoded metallic phosphate nanoparticle tags. This nanoparticle-based immunosensor offers a new method for rapid, sensitive, selective and inexpensive quantification of phosphorylated adducts for monitoring of OP pesticides and nerve agents exposures.

  1. Ligand design for alkali-metal-templated self-assembly of unique high-nuclearity CuII aggregates with diverse coordination cage units: crystal structures and properties.

    PubMed

    Du, Miao; Bu, Xian-He; Guo, Ya-Mei; Ribas, Joan

    2004-03-19

    The construction of two unique, high-nuclearity Cu(II) supramolecular aggregates with tetrahedral or octahedral cage units, [(mu(3)-Cl)[Li subset Cu(4)(mu-L(1))(3)](3)](ClO(4))(8)(H(2)O)(4.5) (1) and [[Na(2) subset Cu(12)(mu-L(2))(8)(mu-Cl)(4)](ClO(4))(8)(H(2)O)(10)(H(3)O(+))(2)](infinity) (2) by alkali-metal-templated (Li(+) or Na(+)) self-assembly, was achieved by the use of two newly designed carboxylic-functionalized diazamesocyclic ligands, N,N'-bis(3-propionyloxy)-1,4-diazacycloheptane (H(2)L(1)) or 1,5-diazacyclooctane-N,N'-diacetate acid (H(2)L(2)). Complex 1 crystallizes in the trigonal R3c space group (a = b = 20.866(3), c = 126.26(4) A and Z = 12), and 2 in the triclinic P1 space group (a = 13.632(4), b = 14.754(4), c = 19.517(6) A, alpha = 99.836(6), beta = 95.793(5), gamma = 116.124(5) degrees and Z = 1). By subtle variation of the ligand structures and the alkali-metal templates, different polymeric motifs were obtained: a dodecanuclear architecture 1 consisting of three Cu(4) tetrahedral cage units with a Li(+) template, and a supramolecular chain 2 consisting of two crystallographically nonequivalent octahedral Cu(6) polyhedra with a Na(+) template. The effects of ligand functionality and alkali metal template ions on the self-assembly processes of both coordination supramolecular aggregates, and their magnetic behaviors are discussed in detail.

  2. Anodized Aluminum Oxide Templated Synthesis of Metal-Organic Frameworks Used as Membrane Reactors.

    PubMed

    Yu, Yifu; Wu, Xue-Jun; Zhao, Meiting; Ma, Qinglang; Chen, Junze; Chen, Bo; Sindoro, Melinda; Yang, Jian; Han, Shikui; Lu, Qipeng; Zhang, Hua

    2017-01-09

    The incorporation of metal-organic frameworks (MOFs) into membrane-shaped architectures is of great importance for practical applications. The currently synthesized MOF-based membranes show many disadvantages, such as poor compatibility, low dispersity, and instability, which severely limit their utility. Herein, we present a general, facile, and robust approach for the synthesis of MOF-based composite membranes through the in situ growth of MOF plates in the channels of anodized aluminum oxide (AAO) membranes. After being used as catalysis reactors, they exhibit high catalytic performance and stability in the Knoevenagel condensation reaction. The high catalytic performance might be attributed to the intrinsic structure of MOF-based composite membranes, which can remove the products from the reaction zone quickly, and prevent the aggregation and loss of catalysts during reaction and recycling process.

  3. The new metal complex templated polyoxoborate(s) (POB(s)) structures. Synthesis, structural characterization, and hydrogen storage capacities

    NASA Astrophysics Data System (ADS)

    Ali Köse, Dursun; Yurdakul, Ömer; Şahin, Onur; Öztürk, Zeynel

    2017-04-01

    The polyoxoborate(s) (POB(s)) structures, including a neutral ligand-metal complex compound as a template, were synthesized and the structural characterizations were performed via single crystal X-ray diffraction, FTIR, 11B-NMR, solid state UV-Vis spectroscopy, SEM and elemental analysis methods. Moreover, the stabilization features were determined via TGA/DTA method. In addition, nitrogen and hydrogen adsorption measurements provided the realization to determine the pore size distribution, BET surface area, and hydrogen storage capacities. The molecular formulas of compounds were estimated as [Cu(C12H8N2)2(C2H3O2)][B5O6(OH)4]·2H3BO3·H2O (I) and [Ni(C12H8N2)2(H2O)2]·(B7O9(OH)5)·5H2O (II) and the existence of two different POB(s) structures as pentaborate (B5O6(OH)4) and heptaborate (B7O9(OH)5) within the compounds were observed. At last, it was found that the both structures have micro and mesoporosity with 0.407 and 1.480 m2/g BET surface areas, for the compound I and II, respectively. Moreover, within the same conditions, compound II could uptake 0.19 wt% hydrogen at 77 K and at the relative pressure of 1 while compound II uptakes 0.035 wt% hydrogen.

  4. Efficient removal of heavy metal ions with biopolymer template synthesized mesoporous titania beads of hundreds of micrometers size.

    PubMed

    Wu, Na; Wei, Huanhuan; Zhang, Lizhi

    2012-01-03

    We demonstrated that mesoporous titania beads of uniform size (about 450 μm) and high surface area could be synthesized via an alginate biopolymer template method. These mesoporous titania beads could efficiently remove Cr(VI), Cd(II), Cr(III), Cu(II), and Co(II) ions from simulated wastewater with a facile subsequent solid-liquid separation because of their large sizes. We chose Cr(VI) removal as the case study and found that each gram of these titania beads could remove 6.7 mg of Cr(VI) from simulated wastewater containing 8.0 mg·L(-1) of Cr(VI) at pH = 2.0. The Cr(VI) removal process was found to obey the Langmuir adsorption model and its kinetics followed pseudo-second-order rate equation. The Cr(VI) removal mechanism of titania beads might be attributed to the electrostatic adsorption of Cr(VI) ions in the form of negatively charged HCrO(4)(-) by positively charged TiO(2) beads, accompanying partial reduction of Cr(VI) to Cr(III) by the reductive surface hydroxyl groups on the titania beads. The used titania beads could be recovered with 0.1 mol·L(-1) of NaOH solution. This study provides a promising micro/nanostructured adsorbent with easy solid-liquid separation property for heavy metal ions removal.

  5. Thermal stability of gold nanoparticles embedded within metal oxide frameworks fabricated by hybrid modifications onto sacrificial textile templates.

    PubMed

    Padbury, Richard P; Halbur, Jonathan C; Krommenhoek, Peter J; Tracy, Joseph B; Jur, Jesse S

    2015-01-27

    The stability and spatial separation of nanoparticles (NP's) is essential for employing their advantageous nanoscale properties. This work demonstrates the entrapment of gold NP's embedded in a porous inorganic matrix. Initially, gold NP's are decorated on fibrous nylon-6, which is used as an inexpensive sacrificial template. This is followed by inorganic modification using a novel single exposure cycle vapor phase technique resulting in distributed NP's embedded within a hybrid organic-inorganic matrix. The processing is extended to the synthesis of porous nanoflakes after calcination of the modified nylon-6 yielding a porous metal oxide framework surrounding the disconnected NP's with a surface area of 250 m(2)/g. A unique feature of this work is the use of a transmission electron microscope (TEM) equipped with an in situ annealing sample holder. The apparatus affords the opportunity to explore the underlying nanoscopic stability of NP's embedded in these frameworks in a single step. TEM analysis indicates thermal stability up to 670 °C and agglomeration characteristics thereafter. The vapor phase processes developed in this work will facilitate new complex NP/oxide materials useful for catalytic platforms.

  6. The rhodium catalyzed three-component reaction of diazoacetates, titanium(IV) alkoxides and aldehydes.

    PubMed

    Lu, Chong-Dao; Liu, Hui; Chen, Zhi-Yong; Hu, Wen-Hao; Mi, Ai-Qiao

    2005-05-28

    The rhodium(II)-catalyzed three-component reaction of diazoacetates, titanium alkoxides and aldehydes is shown to give alpha-alkoxyl-beta-hydroxyl acid derivatives; the novel C-C bond formation reaction is proposed to occur through oxonium ylides derived from diazo compounds and titanium alkoxides, and followed by intermolecular trapping by aldehydes.

  7. Benzene-templated hydrothermal synthesis of metal-organic frameworks with selective sorption properties.

    PubMed

    Choi, Eun-Young; Park, Kyungsoo; Yang, Cheol-Min; Kim, Hyejin; Son, Jung-Ho; Lee, Soon W; Lee, Young Hee; Min, Dongwon; Kwon, Young-Uk

    2004-10-25

    In this paper, we report two metal-organic frameworks [Co3(ndc)3(bipyen)(1.5)]H2O (1) and [Co2(ndc)2bipyen)]C6H6.H2O (2) (bipyen=trans-1,2-bis(4-pyridyl)ethylene, H2ndc=2,6-naphthalenedicarboxylic acid). These compounds were both synthesized from identical hydrothermal reaction conditions except that benzene was added to the reaction for 2. Crystal structures show that the two compounds have triply interpenetrated three-dimensional frameworks and these frameworks have the same primary structure of a two-dimensional network of interconnected [Co2(O2CR)(4/2)] (R=naphthalene group) paddle-wheels and bridging bipyen ligands. Both compounds have guest water molecules and, in addition, 2 has guest benzene molecules. Structural transformations of the host accompanied guest removal, which can be monitored by powder X-ray diffraction. N2 adsorption data of 2 show that there are two different types of pores corresponding to the benzene and water pores. Upon exposure to vapors of several organic molecules, the heat-treated sample of 2 adsorbs benzene and cyclohexene, but does not adsorb toluene, (o-, m-, and p-)xylenes, cycloheptatriene, or cyclohexane.

  8. Method for making monolithic metal oxide aerogels

    DOEpatents

    Coronado, Paul R.

    1999-01-01

    Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The containment vessel is enclosed within an aqueous atmosphere that is above the supercritical temperature and pressure of the solvent of the metal alkoxide solution.

  9. Accelerated subcritical drying of large alkoxide silica gels

    NASA Astrophysics Data System (ADS)

    Wang, Shiho; Kirkbir, Fikret; Chaudhuri, S. R.; Sarkar, Arnab

    1992-12-01

    Fracture during drying has been the key hurdle in fabrication of large monolithic silica glass from alkoxide gels. Although existing literature suggests pore enlargement, aging, chemical additives, supercritical drying and freeze drying as helpful in avoiding fracture during drying, successful accelerated sub-critical drying of large silica monoliths from alkoxide gels has not yet been reported. In the present approach, acid catalyzed sols of TEOS, ethanol and water (pH equals 2) were cast as cylindrical rods in plastic molds of 8.0 and 10.0 cm diameter with volumes of 2000 cc and 3000 cc respectively. The resultant gels were aged for about 7 days and dried in a specially designed chamber under sub-critical conditions of the pore field. We have obtained monolithic dry gels in drying times of 3 - 7 days for sizes of 2000 - 3000 cc. The dry gels have narrow unimodal pore size distributions, with average pore radius of about 20 angstroms as measured by BET. Although capillary stress during drying increases with reduction of pore size, it was found that in this approach it is easier to dry gels of smaller pore size.

  10. Epimerization of secondary alcohols by new homogeneous, low oxidation state metal catalysts: Carbon-hydrogen bond activation in rhenium alkoxide complexes ({eta}{sup 5}-C{sub 5}R{sub 5})Re(NO)(PPh{sub 3})(OCHRR{prime})

    SciTech Connect

    Saura-Llamas, I.; Gladysz, J.A.

    1992-03-11

    Diastereomerically pure secondary alcohols epimerize to mixtures of diasteromers in C{sub 6}H{sub 5}R at 65-90 {degrees}C in the presence of 10 mol% ({eta}{sup 5}C{sub 5}R{sub 5})Re(NO)(PPh{sub 3})(OCH{sub 3}) (1; R = H, Me). The methoxide ligand of 1 first exchanges with the alcohol substrate to give alkoxide complexes {eta}{sup 5}-C{sub 5}R{sub 5})Re(NO)(PPh{sub 3})(OCHR{prime}R{double_prime} is derived from (+)- and (-)-, exo- and endo-borneol. NMR data show that epimerization occurs first at rhenium (ca. 35 {degrees}C) and then at carbon (ca. 65 {degrees}C). Substitution reactions and rate experiments show that PPh{sub 3} initially dissociates from 2 with anchimeric assistance by alkoxide oxygen lone pairs. An intermediate with a trigonal-planar rhenium which can either return to 2 (with epimerization at rhenium) or undergo {beta}-hydride elimination to a ketone hydride complex (leading to epimerization at carbon), is proposed. Accordingly, rates of epimerization at carbon (but not rhenium) are strongly inhibited by added PPh{sub 3}, and show a significant k{sub H}/k{sub D}. 38 refs., 7 figs., 3 tabs.

  11. Mesoporous Silicon Hollow Nanocubes Derived from Metal-Organic Framework Template for Advanced Lithium-Ion Battery Anode.

    PubMed

    Yoon, Taeseung; Bok, Taesoo; Kim, Chulhyun; Na, Younghoon; Park, Soojin; Kim, Kwang S

    2017-05-23

    Controlling the morphology of nanostructured silicon is critical to improving the structural stability and electrochemical performance in lithium-ion batteries. The use of removable or sacrificial templates is an effective and easy route to synthesize hollow materials. Herein, we demonstrate the synthesis of mesoporous silicon hollow nanocubes (m-Si HCs) derived from a metal-organic framework (MOF) as an anode material with outstanding electrochemical properties. The m-Si HC architecture with the mesoporous external shell (∼15 nm) and internal void (∼60 nm) can effectively accommodate volume variations and relieve diffusion-induced stress/strain during repeated cycling. In addition, this cube architecture provides a high electrolyte contact area because of the exposed active site, which can promote the transportation of Li ions. The well-designed m-Si HC with carbon coating delivers a high reversible capacity of 1728 mAhg(-1) with an initial Coulombic efficiency of 80.1% after the first cycle and an excellent rate capability of >1050 mAhg(-1) even at a 15 C-rate. In particular, the m-Si HC anode effectively suppresses electrode swelling to ∼47% after 100 cycles and exhibits outstanding cycle stability of 850 mAhg(-1) after 800 cycles at a 1 C-rate. Moreover, a full cell (2.9 mAhcm(-2)) comprising a m-Si HC-graphite anode and LiCoO2 cathode exhibits remarkable cycle retention of 72% after 100 cycles at a 0.2 C-rate.

  12. Synthesis, structural characterization, IR- and Raman spectroscopy, magnetic properties of new organically templated metal sulfates with 4-aminopyridinium

    NASA Astrophysics Data System (ADS)

    Bednarchuk, Tamara J.; Kinzhybalo, Vasyl; Bednarchuk, Oleksandr; Pietraszko, Adam

    2016-09-01

    Crystal structures of the series of twelve 4-aminopyridinium templated metal sulfates: (C5H7N2)2[MeII(H2O)6](SO4)2 (MeII = Cu (1), Co (2), Mg (3), Zn (4), Fe (5), Mn (6a)), (C5H7N2)2[MeII(H2O)4(SO4)2]·4H2O (MeII = Mn (6b), Cd (7a)), (C5H7N2)2[MnII(H2O)4(SO4)2] (6c), (C5H7N2)2[Cd(H2O)4(SO4)2] (7b), (C5H7N2)[Al(H2O)6](SO4)2·4H2O (low (8lt) and room temperature (8rt) phases) and (C5H7N2)[FeIII(H2O)4(SO4)2] (9) were determined by single-crystal X-ray diffraction. Compounds 1-6a are isostructural, crystal structure consists of [Me(H2O)6]2+ octahedra, 4-aminopyridinium cations (4ap) and sulfate anions. Crystal packing in 1-6a series is characterized by alternating 4ap and inorganic layers. In the structure of 1 Cu2+ coordination environment is axially deformed due to Jahn-Teller effect to tetragonal bipyramidal. Compounds 6 (a, b) and 7a at ambient conditions dehydrate to produce isostructural complexes 6c and 7b, respectively. In structures of 6c, 7b and 9 sulfate anions are involved in slightly distorted octahedral metal coordination composed of six O atoms from four water molecules and two sulfate anions. Room temperature phase of 8 is characterized by disorder of 4ap around center of inversion. Continuous phase transition at ≈185 K leads to the cell doubling and ordering of 4ap. All of the structures are governed by an extensive three-dimensional hydrogen bond networks, as well as π-π interactions visualized by Hirshfeld surface analysis. Moreover, selected compounds were characterized by the IR and Raman spectroscopy and magnetic measurement studies.

  13. Assembly of a Metal-Organic Framework into 3 D Hierarchical Porous Monoliths Using a Pickering High Internal Phase Emulsion Template.

    PubMed

    Zhu, He; Zhang, Qi; Zhu, Shiping

    2016-06-20

    3D Hierarchical porous metal-organic framework (MOF) monoliths are prepared by using Pickering high internal phase emulsion (HIPE) template. Pickering HIPEs were stabilized solely by UiO-66 MOF particles with internal phase up to 90 % of the volume. The effects of internal phase type and volume, as well as MOF particle concentration on the stability of resulting Pickering HIPEs were investigated. Furthermore, by adding small amount of polyvinyl alcohol (PVA) as binder or polymerization in the continuous aqueous phase, followed by freeze-drying, two types of MOF-based 3D hierarchical porous monoliths with ultralow density (as low as 12 mg cm(-3) ) were successfully prepared. This Pickering HIPE template approach provides a facile and practical way for assembling of MOFs into complex structures.

  14. Templating Water Stains for Nanolithography

    PubMed Central

    Liao, Wei-Ssu; Chen, Xin; Chen, Jixin; Cremer, Paul S.

    2008-01-01

    Herein, a nanoscale patterning technique is demonstrated for creating twin features in polymers and metals. The process works by combining evaporative staining with a templating process. Well-ordered hexagonally arrayed double rings were fabricated using hydrophobic spherical templates. The diameter of the rings, the width of individual rings, and the spacing between concentric and adjacent rings could be tuned by varying the solution conditions. Arrays could be made without the outer ring by employing hydrophilic templates. PMID:17637019

  15. Cubic nitride templates

    DOEpatents

    Burrell, Anthony K; McCleskey, Thomas Mark; Jia, Quanxi; Mueller, Alexander H; Luo, Hongmei

    2013-04-30

    A polymer-assisted deposition process for deposition of epitaxial cubic metal nitride films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures under a suitable atmosphere to yield metal nitride films and the like. Such films can be used as templates for the development of high quality cubic GaN based electronic devices.

  16. Reactions of Metal-Metal Multiple Bonds. 10. Reactions of Mo2(OR)6 (M Triple Bond M) and (M(OR)4)x Compounds with Molecular Oxygen. Preparation and Characterization of Oxo-Alkoxides of Formula MoO2(OR)2, MoO2(OR)2(bpy), MoO(OR)4, Mo3O(OR)10, Mo4O8(OR)4(py)4 and Mo6O10(OR)12.

    DTIC Science & Technology

    1983-06-06

    the Mo2 (OR)6 compounds are used. Mo3 O(OR)IO (R = i-Pr and CH2 -t-Bu). These compounds contain a triangulo Mo3 (12+) unit capped by an oxo and an...i In reaction 9, the triangulo Mo3 (12+) complex acts as a reducing agent and a similar sequence shown in 11 can be envisaged to give rise to Mo 60 (0...members of a now fairly extensive class of triangulo Mo3-containing compounds with 32 either one or two capping ligands. The geometry of the oxo-alkoxide

  17. Synthesis and thermolytic behavior of mixed-valence homo- and heterometallic group 14 alkoxides

    SciTech Connect

    Teff, D.J.; Minear, C.D.; Baxter, D.V.; Caulton, K.G.

    1998-05-18

    The mixed-valence molecule Sn{sup II}Sn{sup IV} (OPr){sub 6} is conveniently synthesized and is shown to exchange bridging and terminal alkoxides in solution in its Sn({micro}-OPr){sub 3}Sn(OPr){sub 3} structure. Pb{sub 3}SnO(POr){sub 8} is synthesized and shown to undergo an intramolecular fluxional process in solution. Both molecules are sufficiently volatile for CVD study, and comparison of CVD behaviors of these and of M(OPr){sub 2} (M = Sn, Pb), Sn(POr){sub 4}, SnZr(OPr){sub 6}, and Pb{sub 3}-ZrO(OPr){sub 8} shows the reducing capacity of the isopropoxide moiety dominates the thermolytic behavior of all these species, giving metallic Sn or Pb in all cases. Only Zr, when it is present, forms ZrO{sub 2}. The oxide in Pb{sub 3}SnO(POr){sub 8}yields PbO (and 2 Pb{sup 0} and 1 Sn{sup 0}), in contrast to the relative electropositivity of Sn and Pb, a fact attributed to kinetic control of CVD behavior.

  18. Formation of Gold(III) Alkyls from Gold Alkoxide Complexes

    PubMed Central

    2017-01-01

    The gold(III) methoxide complex (C∧N∧C)AuOMe (1) reacts with tris(p-tolyl)phosphine in benzene at room temperature under O abstraction to give the methylgold product (C∧N∧C)AuMe (2) together with O=P(p-tol)3 ((C∧N∧C) = [2,6-(C6H3tBu-4)2pyridine]2–). Calculations show that this reaction is energetically favorable (ΔG = −32.3 kcal mol–1). The side products in this reaction, the Au(II) complex [Au(C∧N∧C)]2 (3) and the phosphorane (p-tol)3P(OMe)2, suggest that at least two reaction pathways may operate, including one involving (C∧N∧C)Au• radicals. Attempts to model the reaction by DFT methods showed that PPh3 can approach 1 to give a near-linear Au–O–P arrangement, without phosphine coordination to gold. The analogous reaction of (C∧N∧C)AuOEt, on the other hand, gives exclusively a mixture of 3 and (p-tol)3P(OEt)2. Whereas the reaction of (C∧N∧C)AuOR (R = But, p-C6H4F) with P(p-tol)3 proceeds over a period of hours, compounds with R = CH2CF3, CH(CF3)2 react almost instantaneously, to give 3 and O=P(p-tol)3. In chlorinated solvents, treatment of the alkoxides (C∧N∧C)AuOR with phosphines generates [(C∧N∧C)Au(PR3)]Cl, via Cl abstraction from the solvent. Attempts to extend the synthesis of gold(III) alkoxides to allyl alcohols were unsuccessful; the reaction of (C∧N∧C)AuOH with an excess of CH2=CHCH2OH in toluene led instead to allyl alcohol isomerization to give a mixture of gold alkyls, (C∧N∧C)AuR′ (R′ = −CH2CH2CHO (10), −CH2CH(CH2OH)OCH2CH=CH2 (11)), while 2-methallyl alcohol affords R′ = CH2CH(Me)CHO (12). The crystal structure of 11 was determined. The formation of Au–C instead of the expected Au–O products is in line with the trend in metal–ligand bond dissociation energies for Au(III): M–H > M–C > M–O.

  19. A general salt-templating method to fabricate vertically aligned graphitic carbon nanosheets and their metal carbide hybrids for superior lithium ion batteries and water splitting.

    PubMed

    Zhu, Jixin; Sakaushi, Ken; Clavel, Guylhaine; Shalom, Menny; Antonietti, Markus; Fellinger, Tim-Patrick

    2015-04-29

    The synthesis of vertically aligned functional graphitic carbon nanosheets (CNS) is challenging. Herein, we demonstrate a general approach for the fabrication of vertically aligned CNS and metal carbide@CNS composites via a facile salt templating induced self-assembly. The resulting vertically aligned CNS and metal carbide@CNS structures possess ultrathin walls, good electrical conductivity, strong adhesion, excellent structural robustness, and small particle size. In electrochemical energy conversion and storage such unique features are favorable for providing efficient mass transport as well as a large and accessible electroactive surface. The materials were tested as electrodes in a lithium ion battery and in electrochemical water splitting. The vertically aligned nanosheets exhibit remarkable lithium ion storage properties and, concurrently, excellent properties as electrocatalysts for hydrogen evolution.

  20. Simultaneous electrochemical immunoassay using graphene-Au grafted recombinant apoferritin-encoded metallic labels as signal tags and dual-template magnetic molecular imprinted polymer as capture probes.

    PubMed

    Wang, De; Gan, Ning; Zhang, Huairong; Li, Tianhua; Qiao, Li; Cao, Yuting; Su, Xiurong; Jiang, Shan

    2015-03-15

    A novel electrochemical multiplexed immunoassay was designed for simultaneous determination of alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) using recombinant apoferritin-encoded metallic nanoparticles (rApo-M) as labels and dual-template magnetic molecularly imprinted polymers (MMIPs) as capture probes. The labels were prepared by loading recombinant apoferritin (r-Apo) and separately immobilize primary antibodies (anti-AFP and anti-CEA) via Au nanoparticles of in site growth on graphene (G). The capture probes were synthesized by self-polymerization of dopamine (DA) on the Fe3O4 nanoparticles (Fe3O4 NPs) and using AFP and CEA as the template proteins, which were used to enrich the targets simultaneously. After a sandwich-type immunoreaction, the labels were captured to the surface of MMIPs. The subsequent electrochemical stripping analysis of the metal components from the immunocomplex provide a means for quantification of targets based on the peak currents of Cd and Pb. Experimental results showed the immunoassay enabled the simultaneous determination of AFP and CEA in a single run with wide dynamic ranges of 0.001-5ngmL(-1). And the detection limits of AFP and CEA were 0.3 and 0.35pgmL(-1) (S/N=3), respectively. These results suggested that the proposed multiplexed immunoassay would be applied for clinical screening of other biomarkers.

  1. The first organically templated open-framework metal-sulfites with layered and three-dimensional diamondoid structures.

    PubMed

    Tiwari, Ranjay K; Kumar, Jitendra; Behera, J N

    2016-01-21

    The crystallographic signatures and characterization data of two novel organically templated open-framework zinc-sulfites (NH3CH2CH2NH3)[Zn3(SO3)4], 1, and (CN3H6)2[Zn(SO3)2], 2, are reported for the first time, synthesized under hydrothermal conditions using different amines, namely, ethylenediamine and guanidine, to generate 2D (for 1) and 3D (for 2) assemblies with 4-, 6-, 8- and 12-membered rings.

  2. Metal-Metal Bonds and Metal Carbon Bonds in the Chemistry of Molybdenum and Tungsten Alkoxides.

    DTIC Science & Technology

    1983-02-07

    appear trimeric in solution, it is interesting to speculate that triangulo Mo3 structures might be found for certain [Mo(OR)4]n compounds. The six...large group of triangulo Mo3- and W3-containlng complexes with capping 14 (P3-) oxo, sulfido and carbyne ligands.2 8 In solution, the IH NMR spectra...to green solutions containing the triangulo Mo 30(OR)to compounds (see Figure 5). A clean, direct synthesis of these compounds is by the addition of

  3. Small angle x-ray scattering: Instrument development and studies of protein aggregation, cellulose hydrolysis, and the production of nanoporous metals using surfactact templates

    NASA Astrophysics Data System (ADS)

    Banuelos, Jose Leobardo

    explored using surfactant-templated metal systems. In this, as with many materials for possible energy storage applications, chemically stable systems with good mechanical strength, high temperature resistance, and high surface areas are desirable. Time- dependent SAXS measurements were used to study the templating of Pt and Pd metals onto a surfactant structure. The reduction of these metals was carried out using two methods, reduction with ascorbate and using hydrogen-nitrogen gas mixtures.

  4. Syntheses of rare-earth metal oxide nanotubes by the sol-gel method assisted with porous anodic aluminum oxide templates

    SciTech Connect

    Kuang Qin; Lin Zhiwei; Lian Wei; Jiang Zhiyuan; Xie Zhaoxiong Huang Rongbin; Zheng Lansun

    2007-04-15

    In this paper, we report a versatile synthetic method of ordered rare-earth metal (RE) oxide nanotubes. RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction (XRD) have been employed to characterize the morphology and composition of the as-prepared nanotubes. It is found that as-prepared RE oxides evolve into bamboo-like nanotubes and entirely hollow nanotubes. A new possible formation mechanism of RE oxide nanotubes in the AAO channels is proposed. These high-quantity RE oxide nanotubes are expected to have promising applications in many areas such as luminescent materials, catalysts, magnets, etc. - Graphical abstract: A versatile synthetic method for the preparation of ordered rare-earth (RE) oxide nanotubes is reported, by which RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates.

  5. Tin(II) alkoxide hydrolysis products for use as base catalysts

    DOEpatents

    Boyle, Timothy J.

    2002-01-01

    Tin alkoxide compounds are provided with accessible electrons. The compounds are a polymeric tin alkoxide, [Sn(OCH.sub.2 C(CH.sub.3).sub.3).sub.2 ].sub.n, and the hydrolysis products Sn.sub.6 O.sub.4 (OCH.sub.2 C(CH.sub.3).sub.3).sub.4 and Sn.sub.5 O.sub.2 (OCH.sub.2 C(CH.sub.3).sub.3).sub.6. The hydrolysis products are formed by hydrolyzing the [Sn(OCH.sub.2 C(CH.sub.3).sub.3).sub.2 ].sub.n in a solvent with controlled amounts of water, between 0.1 and 2 moles of water per mole of the polymeric tin alkoxide.

  6. Dioximate- and Bis(salicylaldiminate)-Bridged Titanium and Zirconium Alkoxides: Structure Elucidation by Mass Spectrometry

    PubMed Central

    Maurer, Christian; Pittenauer, Ernst; Puchberger, Michael; Allmaier, Günter; Schubert, Ulrich

    2013-01-01

    The treatment of titanium alkoxides with 1,5-pentanedioxime or 2,5-hexanedioxime resulted in the formation of complexes [{TiL(OR)2}2] in which the dioximate ligands (L) bridge a dimeric Ti2(μ2-OR)2 unit. The structures of the complexes were determined by single-crystal structure analysis, ESI mass spectrometry, and 1D and 2D solution NMR spectroscopy. In contrast, the treatment of titanium alkoxides with dioximes bearing cyclic linkers, such as cyclohexyl or aryl groups, resulted in insoluble polymeric compounds. The treatment of various bis(salicylaldiminates) with titanium and zirconium alkoxides resulted in compounds with the same composition [{TiL(OR)2}2], in which, however, two monomeric Ti(OR)2 units are bridged by the ligands L. The two structural possibilities can be distinguished by low-energy collision-induced dissociation owing to their different fragmentation patterns. PMID:23795338

  7. The amplitude reduction factor and the cumulant expansion method: crucial factors in the structural analysis of alkoxide precursors in solution.

    PubMed

    Bauer, Matthias; Bertagnolli, Helmut

    2007-12-13

    The transition-metal alkoxide yttrium 2-methoxyethoxide Y(OEtOMe)(3) in solution is studied as a model system of the large class of alkoxide precursors used in the sol-gel process by means of EXAFS spectroscopy. The discussion is focused on the amplitude reduction factor S (2)(0) and the cumulant expansion method. If asymmetry is present in the radial distribution function, the determination of the correct structural model can only be achieved by balancing multiple Gaussian shell fits against only one shell fit with a third cumulant C3. A method to identify the best model, based on statistical parameters of the EXAFS fit, is proposed and checked with two well-known reference compounds, Y(5)O(O(i)Pr)(13) and Y(acac)(3).3H(2)O, and applied to the structurally unknown solution of Y(OEtOMe)(3) in 2-methoxyethanol. The two references are also used to discuss the transferability of S(2)(0) values, determined from reference compounds to unknown samples. A model-free procedure to identify the correct amplitude reduction factor S(2)(0) by making use of fits with different k-weighting schemes is critically investigated. This procedure, which does not require any crystallographic data, is used for the case of Y(OEtOMe)(3) in solution, where significant differences of the amplitude reducing factor of both the oxygen and yttrium shell in comparison to the reference Y(5)O(O(i)Pr)(13) were found. With such a detailed analysis of EXAFS data, a reliable characterization of Y(OEtOMe)3 in 2-methoxyethanol by means of EXAFS spectroscopy is possible. The decameric structure unit found in solid Y(OEtOMe)(3) is not preserved, but rather, a pentameric framework similar to that in Y5O(O(i)Pr)(13) is formed.

  8. High temperature operation of n-AlGaN channel metal semiconductor field effect transistors on low-defect AlN templates

    NASA Astrophysics Data System (ADS)

    Muhtadi, S.; Hwang, S.; Coleman, A.; Asif, F.; Lunev, A.; Chandrashekhar, M. V. S.; Khan, A.

    2017-05-01

    We report room-temperature to 200 °C operation of n-Al0.65Ga0.35N channel metal semiconductor field effect transistors (MESFET) grown over high-quality AlN/sapphire templates. For this temperature range, the source-drain currents, threshold voltages, and dc-transconductance values remain nearly unchanged with an estimated field-effect mobility of ˜90 cm2/V-s at 200 °C and currents of >100 mA/mm. The analysis of the temperature dependent current-voltage characteristics of the gate-source Schottky barrier diode reveals that the leakage currents arise from Frenkel-Poole emission. The capacitance-voltage data show no hysteresis, indicating a high quality Schottky barrier interface. These MESFET's have excellent potential for use as a high temperature power electronic or a solar-blind ultraviolet sensing device.

  9. Self-formation of highly aligned metallic, semiconducting and single chiral single-walled carbon nanotubes assemblies via a crystal template method

    SciTech Connect

    Kawai, Hideki; Hasegawa, Kai; Yanagi, Kazuhiro; Oyane, Ayako; Naitoh, Yasuhisa

    2014-09-01

    The fabrication of an aligned array of single-walled carbon nanotubes (SWCNTs) with a single chiral state has been a significant challenge for SWCNT applications as well as for basic science research. Here, we developed a simple, unique technique to produce assemblies in which metallic, semiconducting, and single chiral state SWCNTs were densely and highly aligned. We utilized a crystal of surfactant as a template on which mono-dispersed SWCNTs in solution self-assembled. Micro-Raman measurements and scanning electron microscopy measurements clearly showed that the SWCNTs were highly and densely aligned parallel to the crystal axis, indicating that approximately 70% of the SWCNTs were within 7° of being parallel. Moreover, the assemblies exhibited good field effect transistor characteristics with an on/off ratio of 1.3 × 10{sup 5}.

  10. Dinuclear uranium alkoxides. Preparation and structures of KU/sub 2/(OCMe/sub 3/)/sub 9/, U/sub 2/(OCMe/sub 3/)/sub 9/, and U/sub 2/(OCHMe/sub 2/)/sub 10/, containing (U(IV),U(IV)), (U(IV),U(V)), and (U(V), U(V)), respectively

    SciTech Connect

    Cotton, F.A.; Marler, D.O.; Schwotzer, W.

    1984-12-05

    The structural results by x-ray crystallography are reported for three uranium alkoxides, two of which are new compounds. All three are dinuclear in the solid state, and they contain the following combinations of oxidation states; (U(IV), U(VI)), (U(V), U(IV)), and (U(V), U(V)). The crystal parameters and U...U bond distances are given for all three compounds. The terminal alkoxide groups in all three compounds display nearly linear U-O-C arrangements, with U-O-C bond angles between 160 and 176/sup 0/. This appears to be a general feature of uranium alkoxides and suggests a high degree of O..pi.. ..-->.. U contributions to the metal-oxygen bonds.

  11. Room temperature perovskite production from bimetallic alkoxides by ketone assisted oxo supplementation (KAOS)

    SciTech Connect

    Gaskins, B.C.; Lannutti, J.J.

    1996-08-01

    Barium titanate has been prepared at room temperature from a well-characterized crystalline barium titanium oxo alkoxide by reaction with acetone. An aldol condensation apparently supplies oxygen to condensing oxo alkoxide clusters. Transmission electron microscopy confirms that the crystallites so formed are dense and perfect with an average size of approximately 85 A. Characterization of reactants and products provides a tentative understanding of structural evolution and the intermediates of the transformation. Crystalline SrTiO{sub 3} and BaZrO{sub 3} were also formed at room temperature by this same method. {copyright} {ital 1996 Materials Research Society.}

  12. Carbonaceous spheres—an unusual template for solid metal oxide mesoscale spheres: Application to ZnO spheres

    SciTech Connect

    Patrinoiu, Greta; Calderón-Moreno, Jose Maria; Culita, Daniela C.; Birjega, Ruxandra; Ene, Ramona; Carp, Oana

    2013-06-15

    A green template route for the synthesis of mesoscale solid ZnO spheres was ascertained. The protocol involves a double coating of the carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. The composites were characterized by FTIR spectroscopy, thermal analysis, scanning electron microscopy while the obtained ZnO spheres by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, N{sub 2} adsorption–desorption isotherms and photoluminescence investigations. A growth mechanism of the solid spheres is advanced based on these results. While the spheres' diameters and the mean size values of ZnO are independent on deposition order, the surface area and the external porosity are fairly dependent. The photoluminescence measurements showed interesting emission features, with emission bands in the violet to orange region. The spheres present high photocatalytical activity towards the degradation of phenol under UV irradiation, the main reaction being its mineralization. - Graphical abstract: A novel and eco-friendly methodology for the synthesis of mesoscale solid ZnO spheres was developed. The protocol involves a double coating of the starch-derived carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. - Highlights: • ZnO solid spheres are obtained via a template route using carbonaceous spheres. • Two-step coatings of interchangeable order are used as deposition procedure. • The coating procedure influences the porosity and surface area. • ZnO spheres exhibited interesting visible photoluminescence properties. • Solid spheres showed photocatalytical activity in degradation of phenol.

  13. In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates

    SciTech Connect

    Parent, Lucas R.; Robinson, David B.; Cappillino, Patrick J.; Hartnett, Ryan J.; Abellan Baeza, Patricia; Evans, James E.; Browning, Nigel D.; Arslan, Ilke

    2014-02-11

    The prevalent approach to developing new nanomaterials is a trial and error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can only be inferred from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution, and facilitates a mechanistic approach to nanomaterial development. Here we use in situ liquid stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and ultimately determine a refined synthesis procedure that yields ordered pores. We find that at low organic solvent (tetrahydrofuran, THF) content, the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order, but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order is greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround the micelles, forming an ordered mesoporous structure. The microscope observations revealed that template disorder can be addressed prior to reaction, and is not invariably induced by the growth process itself, allowing us to more quickly optimize the synthetic method. This work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830. This research

  14. Electrochemistry at nanoscale electrodes: individual single-walled carbon nanotubes (SWNTs) and SWNT-templated metal nanowires.

    PubMed

    Dudin, Petr V; Snowden, Michael E; Macpherson, Julie V; Unwin, Patrick R

    2011-12-27

    Individual nanowires (NWs) and native single-walled carbon nanotubes (SWNTs) can be readily used as well-defined nanoscale electrodes (NSEs) for voltammetric analysis. Here, the simple photolithography-free fabrication of submillimeter long Au, Pt, and Pd NWs, with sub-100 nm heights, by templated electrodeposition onto ultralong flow-aligned SWNTs is demonstrated. Both individual Au NWs and SWNTs are employed as NSEs for electron-transfer (ET) kinetic quantification, using cyclic voltammetry (CV), in conjunction with a microcapillary-based electrochemical method. A small capillary with internal diameter in the range 30-70 μm, filled with solution containing a redox-active mediator (FcTMA(+) ((trimethylammonium)methylferrocene), Fe(CN)(6)(4-), or hydrazine) is positioned above the NSE, so that the solution meniscus completes an electrochemical cell. A 3D finite-element model, faithfully reproducing the experimental geometry, is used to both analyze the experimental CVs and derive the rate of heterogeneous ET, using Butler-Volmer kinetics. For a 70 nm height Au NW, intrinsic rate constants, k(0), up to ca. 1 cm s(-1) can be resolved. Using the same experimental configuration the electrochemistry of individual SWNTs can also be accessed. For FcTMA(+/2+) electrolysis the simulated ET kinetic parameters yield very fast ET kinetics (k(0) > 2 ± 1 cm s(-1)). Some deviation between the experimental voltammetry and the idealized model is noted, suggesting that double-layer effects may influence ET at the nanoscale.

  15. Metal-Organic Framework Templated Synthesis of Ultrasmall Catalyst Loaded ZnO/ZnCo2O4 Hollow Spheres for Enhanced Gas Sensing Properties

    PubMed Central

    Koo, Won-Tae; Choi, Seon-Jin; Jang, Ji-Soo; Kim, Il-Doo

    2017-01-01

    To achieve the rational design of nanostructures for superior gas sensors, the ultrasmall nanoparticles (NPs) loaded on ternary metal oxide (TMO) hollow spheres (HS) were synthesized by using the polystyrene (PS) sphere template and bimetallic metal-organic framework (BM-MOFs) mold. The zinc and cobalt based zeolite imidazole frameworks (BM-ZIFs) encapsulating ultrasmall Pd NPs (2–3 nm) were assembled on PS spheres at room temperature. After calcination at 450 °C, these nanoscale Pd particles were effectively infiltrated on the surface of ZnO/ZnCo2O4 HSs. In addition, the heterojunctions of Pd-ZnO, Pd-ZnCo2O4, and ZnO-ZnCo2O4 were formed on each phase. The synthesized Pd-ZnO/ZnCo2O4 HSs exhibited extremely high selectivity toward acetone gas with notable sensitivity (S = 69% to 5 ppm at 250 °C). The results demonstrate that MOF driven ultrasmall catalyst loaded TMO HSs were highly effective platform for high performance chemical gas sensors. PMID:28327599

  16. Non-noble metal Bi deposition by utilizing Bi2WO6 as the self-sacrificing template for enhancing visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yu, Shixin; Zhang, Yihe; Li, Min; Du, Xin; Huang, Hongwei

    2017-01-01

    Bi metal deposited on Bi2WO6 composite photocatalysts have been successfully synthesized via a simple in-situ reduction method at room temperature with using Bi2WO6 as self-sacrificing template and NaBH4 as reducing agent. The reduction extent can be easily modulated by controlling the concentration of NaBH4 solution. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectra, N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), diffuse reflection spectroscopy (DRS) and photoelectrochemical measurements were carried out to analyze the phase, morphology, optical property and photoelectrochemical property of the as-prepared samples. The photocatalytic activity is surveyed by degradation of phenol under visible light (λ > 420 nm), which showed that the BWO-0.2 photocatalyst exhibited the highest efficiency, which was over 3 times as high as pure Bi2WO6. The enhanced photocatalytic activity should be attributed to strengthened photoabsorption and charge separation efficiency derived from the surface plasmon resonance (SPR) of Bi metal.

  17. Laser-ignited frontal polymerization of shape-controllable poly(VI-co-AM) hydrogels based on 3D templates toward adsorption of heavy metal ions

    NASA Astrophysics Data System (ADS)

    Fan, Suzhen; Liu, Sisi; Wang, Xiao-Qiao; Wang, Cai-Feng; Chen, Su

    2016-06-01

    Given the increasing heavy metal pollution issue, fast preparation of polymeric hydrogels with excellent adsorption property toward heavy metal ions is very attractive. In this work, a series of poly( N-vinylimidazole-co-acrylamide) (poly(VI-co-AM)) hydrogels were synthesized via laser-ignited frontal polymerization (LIFP) for the first time. The dependence of frontal velocity and temperature on two factors monomer ratios and initiator concentrations was systematically investigated. Poly(VI-co-AM) hydrogels with any self-supporting shapes can be synthesized by a one-step LIFP in seconds through the application of 3D templates. These shape-persistent hydrogels are pH-responsive and exhibit excellent adsorption/desorption characteristics toward Mn(II), Zn(II), Cd(II), Ni(II), Cu(II) and Co(II) ions, and the adsorption conformed to the pseudo-second-order kinetic model. The reusability of the hydrogels toward mental ions adsorption was further researched, which suggested that the hydrogels can be reused without serious decrease in adsorption capacity. This work might open a promising strategy to facilely prepare shape-controllable hydrogels and expand the application of LIFP.

  18. Mono- and Bis-Terpyridine-Based Dimer and Metallo-Organic Polymers as Ionic Templates for Preparation of Multi-Metallic Au Nanocluster and Nanowires.

    PubMed

    Liu, Die; Cao, Hongda; Jiang, Zhilong; Wu, Tun; Sun, Xiaoyi; Wang, Pingshan; Moorefield, Charles N; Dai, Liming; Newkome, George R

    2016-03-01

    The preparation of multi-metallic Au nanocluster and nanowires has been achieved using terpyridine-based metallo-organic polymers as multi-ionic templates through a straightforward counterion exchange with aqueous NaAuCl4 followed by a mild reduction in-situ with sodium citrate. The mild reduction of the [TpyFeTpy]2+ x 2[AuCl4]- complex, derived from [TpyFeTpy]2+ x 2Cl- 1 (tpy = 2,2':6',2"-terpyridine), led to the formation of Au nanoclusters (Au NC) with diameters ranging from 7.5-88 nm. Each Au NC alone contained multiple nanoparticles, with diameters ranging from 2.5-4.5 nm. 1,4-bis-terpyridine based metallo-oraganic polymer [-TpyFeTpy-TpyFeTpy-]n(2n+) x [Cl]2n- 2 was found to generate a multi-ionic metallo-polymer with AuCl4- as the counterion, after mild reduction with sodium citrate, resulting in irregular zigzag shaped Au nanowires (Au NW). The prepared Au NW from the di-metallic complex 3 should find applications within electronic devices. Both Au NC and NW were also found to possess excellent catalytic properties.

  19. Metal-Organic Framework Templated Synthesis of Ultrasmall Catalyst Loaded ZnO/ZnCo2O4 Hollow Spheres for Enhanced Gas Sensing Properties

    NASA Astrophysics Data System (ADS)

    Koo, Won-Tae; Choi, Seon-Jin; Jang, Ji-Soo; Kim, Il-Doo

    2017-03-01

    To achieve the rational design of nanostructures for superior gas sensors, the ultrasmall nanoparticles (NPs) loaded on ternary metal oxide (TMO) hollow spheres (HS) were synthesized by using the polystyrene (PS) sphere template and bimetallic metal-organic framework (BM-MOFs) mold. The zinc and cobalt based zeolite imidazole frameworks (BM-ZIFs) encapsulating ultrasmall Pd NPs (2–3 nm) were assembled on PS spheres at room temperature. After calcination at 450 °C, these nanoscale Pd particles were effectively infiltrated on the surface of ZnO/ZnCo2O4 HSs. In addition, the heterojunctions of Pd-ZnO, Pd-ZnCo2O4, and ZnO-ZnCo2O4 were formed on each phase. The synthesized Pd-ZnO/ZnCo2O4 HSs exhibited extremely high selectivity toward acetone gas with notable sensitivity (S = 69% to 5 ppm at 250 °C). The results demonstrate that MOF driven ultrasmall catalyst loaded TMO HSs were highly effective platform for high performance chemical gas sensors.

  20. Giant increase in the metal-enhanced fluorescence of organic molecules in nanoporous alumina templates and large molecule-specific red/blue-shift of the fluorescence peak.

    PubMed

    Sarkar, S; Kanchibotla, B; Nelson, J D; Edwards, J D; Anderson, J; Tepper, G C; Bandyopadhyay, S

    2014-10-08

    The fluorescence of organic fluorophore molecules is enhanced when they are placed in contact with certain metals (Al, Ag, Cu, Au, etc.) whose surface plasmon waves couple into the radiative modes of the molecules and increase the radiative efficiency. Here, we report a hitherto unknown size dependence of this metal-enhanced fluorescence (MEF) effect in the nanoscale. When the molecules are deposited in nanoporous anodic alumina films with exposed aluminum at the bottom of the pores, they form organic nanowires standing on aluminum nanoparticles whose plasmon waves have much larger amplitudes. This increases the MEF strongly, resulting in several orders of magnitude increase in the fluorescence intensity of the organic fluorophores. The increase in intensity shows an inverse superlinear dependence on nanowire diameter because the nanowires also act as plasmonic "waveguides" that concentrate the plasmons and increase the coupling of the plasmons with the radiative modes of the molecules. Furthermore, if the nanoporous template housing the nanowires has built-in electric fields due to space charges, a strong molecule-specific red- or blue-shift is induced in the fluorescence peak owing to a renormalization of the dipole moment of the molecule. This can be exploited to detect minute amounts of target molecules in a mixture using their optical signature (fluorescence) despite the presence of confounding background signals. It can result in a unique new technology for biosensing and chemical sensing.

  1. Metal-assisted exfoliation (MAE): green process for transferring graphene to flexible substrates and templating of sub-nanometer plasmonic gaps (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Zaretski, Aliaksandr V.; Marin, Brandon C.; Moetazedi, Herad; Dill, Tyler J.; Jibril, Liban; Kong, Casey; Tao, Andrea R.; Lipomi, Darren J.

    2015-09-01

    This paper describes a new technique, termed "metal-assisted exfoliation," for the scalable transfer of graphene from catalytic copper foils to flexible polymeric supports. The process is amenable to roll-to-roll manufacturing, and the copper substrate can be recycled. We then demonstrate the use of single-layer graphene as a template for the formation of sub-nanometer plasmonic gaps using a scalable fabrication process called "nanoskiving." These gaps are formed between parallel gold nanowires in a process that first produces three-layer thin films with the architecture gold/single-layer graphene/gold, and then sections the composite films with an ultramicrotome. The structures produced can be treated as two gold nanowires separated along their entire lengths by an atomically thin graphene nanoribbon. Oxygen plasma etches the sandwiched graphene to a finite depth; this action produces a sub-nanometer gap near the top surface of the junction between the wires that is capable of supporting highly confined optical fields. The confinement of light is confirmed by surface-enhanced Raman spectroscopy measurements, which indicate that the enhancement of the electric field arises from the junction between the gold nanowires. These experiments demonstrate nanoskiving as a unique and easy-to-implement fabrication technique that is capable of forming sub-nanometer plasmonic gaps between parallel metallic nanostructures over long, macroscopic distances. These structures could be valuable for fundamental investigations as well as applications in plasmonics and molecular electronics.

  2. Hydroxyapatite Nanowires@Metal-Organic Framework Core/Shell Nanofibers: Templated Synthesis, Peroxidase-Like Activity, and Derived Flexible Recyclable Test Paper.

    PubMed

    Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Sun, Tuan-Wei

    2017-03-08

    The templated synthesis of hydroxyapatite (HAP) nanowires@metal-organic framework (MOF) core/shell nanofibers (named HAP@MIL-100(Fe) nanofibers) is demonstrated. The ultralong hydroxyapatite nanowires are adopted as a hard template for the nucleation and growth of MIL-100(Fe) (a typical MOF) through the layer-by-layer method. The Coulombic and chelation interactions between Ca(2+) ions on the surface of the HAP nanowires and the COO(-) organic linkers of MIL-100(Fe) play key roles in the formation process. The as-prepared, water-stable HAP@MIL-100(Fe) nanofibers exhibit peroxidase-like activity toward the oxidation of different peroxidase substrates in the presence of H2 O2 , accompanied by a clear color change of the solution. Furthermore, a flexible, recyclable HAP@MIL-100(Fe) test paper is prepared successfully by using HAP@MIL-100(Fe) nanofibers as building blocks. A simple, low-cost, and sensitive colorimetric method for the detection of H2 O2 and glucose is established based on the as-prepared, flexible, recyclable HAP@MIL-100(Fe) test paper. More importantly, the HAP@MIL-100(Fe) test paper can be recovered easily for reuse by simply dipping in absolute ethanol for just 30 min, thus showing excellent recyclability. With its combination of advantages such as easy transportation, easy storage and use, rapid recyclability, light weight, and high flexibility, this HAP@MIL-100(Fe) test paper is promising for wide applications in various fields. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Biomimetic Templating of Porous Lamellar Silicas by Vesicular Surfactant Assemblies

    NASA Astrophysics Data System (ADS)

    Tanev, Peter T.; Pinnavaia, Thomas J.

    1996-03-01

    A biomimetic templating approach to the synthesis of lamellar silicas is demonstrated. The procedure is based on the hydrolysis and cross-linking of a neutral silicon alkoxide precursor in the interlayered regions of multilamellar vesicles formed from a neutral diamine bola-amphiphile. Unlike earlier surfactant-templating approaches, this method produces porous lamellar silicas (designated MSU-V) with vesicular particle morphology, exceptional thermal stability, a high degree of framework cross-linking, unusually high specific surface area and pore volume, and sorption properties that are typical of pillared lamellar materials. This approach circumvents the need for a separate pillaring step in building porosity into a lamellar host structure and offers new opportunities for the direct fabrication of adsorbents, catalysts, and nanoscale devices.

  4. Vertical Carbon Nanotube Device in Nanoporous Templates

    NASA Technical Reports Server (NTRS)

    Maschmann, Matthew Ralph (Inventor); Fisher, Timothy Scott (Inventor); Sands, Timothy (Inventor); Bashir, Rashid (Inventor)

    2014-01-01

    A modified porous anodic alumina template (PAA) containing a thin CNT catalyst layer directly embedded into the pore walls. CNT synthesis using the template selectively catalyzes SWNTs and DWNTs from the embedded catalyst layer to the top PAA surface, creating a vertical CNT channel within the pores. Subsequent processing allows for easy contact metallization and adaptable functionalization of the CNTs and template for a myriad of applications.

  5. Template-assisted synthesis of III-nitride and metal-oxide nano-heterostructures using low-temperature atomic layer deposition for energy, sensing, and catalysis applications (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Biyikli, Necmi; Ozgit-Akgun, Cagla; Eren, Hamit; Haider, Ali; Uyar, Tamer; Kayaci, Fatma; Guler, Mustafa Ozgur; Garifullin, Ruslan; Okyay, Ali K.; Ulusoy, Gamze M.; Goldenberg, Eda

    2015-08-01

    Recent experimental research efforts on developing functional nanostructured III-nitride and metal-oxide materials via low-temperature atomic layer deposition (ALD) will be reviewed. Ultimate conformality, a unique propoerty of ALD process, is utilized to fabricate core-shell and hollow tubular nanostructures on various nano-templates including electrospun nanofibrous polymers, self-assembled peptide nanofibers, metallic nanowires, and multi-wall carbon nanotubes (MWCNTs). III-nitride and metal-oxide coatings were deposited on these nano-templates via thermal and plasma-enhanced ALD processes with thickness values ranging from a few mono-layers to 40 nm. Metal-oxide materials studied include ZnO, TiO2, HfO2, ZrO2, and Al2O3. Standard ALD growth recipes were modified so that precursor molecules have enough time to diffuse and penetrate within the layers/pores of the nano-template material. As a result, uniform and conformal coatings on high-surface area nano-templates were demonstrated. Substrate temperatures were kept below 200C and within the self-limiting ALD window, so that temperature-sensitive template materials preserved their integrity III-nitride coatings were applied to similar nano-templates via plasma-enhanced ALD (PEALD) technique. AlN, GaN, and InN thin-film coating recipes were optimized to achieve self-limiting growth with deposition temperatures as low as 100C. BN growth took place only for >350C, in which precursor decomposition occured and therefore growth proceeded in CVD regime. III-nitride core-shell and hollow tubular single and multi-layered nanostructures were fabricated. The resulting metal-oxide and III-nitride core-shell and hollow nano-tubular structures were used for photocatalysis, dye sensitized solar cell (DSSC), energy storage and chemical sensing applications. Significantly enhanced catalysis, solar efficiency, charge capacity and sensitivity performance are reported. Moreover, core-shell metal-oxide and III-nitride materials

  6. Porphyrins as Templates for Site-Selective Atomic Layer Deposition: Vapor Metalation and in Situ Monitoring of Island Growth

    SciTech Connect

    Avila, Jason R.; Emery, Jonathan D.; Pellin, Michael J.; Martinson, Alex B. F.; Farha, Omar K.; Hupp, Joseph T.

    2016-08-10

    Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth. Analytical fitting of in situ QCM mass uptake reveals island growth to be hemispherical with a convergence radius of 1.74 nm. This growth mode is confirmed with synchrotron grazing-incidence small-angle X-ray scattering (GISAXS) measurements. Finally, we extend this approach to other ALD chemistries to demonstrate the generality of this route to discrete metallo island materials.

  7. Spontaneous, Solvent-Free, Polymer-Templated, Solid-Solid Transformation of Thin Metal Films into Nanoparticles.

    PubMed

    Hernández-Cruz, Olivia; Avila-Gutierrez, Lizeth; Zolotukhin, Mikhail G; Gonzalez, Gonzalo; Monroy, B Marel; Montiel, Raúl; Vera-Graziano, Ricardo; Romero-Ibarra, Josue E; Novelo-Peralta, Omar; Massó Rojas, Felipe Alonso

    2016-09-14

    Metal nanoparticles have unusual optical, electronic, sensing, recognition, catalytic, and therapeutic properties. They are expected to form the basis of many of the technological and biological innovations of this century. A prerequisite for future applications using nanoparticles as functional entities is control of the shape, size, and homogeneity of these nanoparticles and of their interparticle spacing and arrangement on surfaces, between electrodes, or in devices. Here, we demonstrate that thin films of gold, silver, and copper sputter-deposited onto the surface of an organic polymer poly[[1,1':4',1″-terphenyl]-4,4″-diyl(2-bromo-1-carboxyethylidene)] (PTBC) undergo spontaneous solid-solid transformation into nanoparticles. Furthermore, we show that, by varying the thickness of the films, the volume-to-surface ratio of the polymer substrate, and the amount of plasticizer, it is possible to control the rate of transformation and the morphology of the nanoparticles formed. PTBC containing Au nanoparticles was found to enhance the cell adhesion and proliferation. To the best of our knowledge, our findings constitute the first experimental evidence of spontaneous, room-temperature, solid-solid transformation of metal films sputtered onto the surface of an organic polymeric substrate into nanoparticles (crystals).

  8. Noble metal alloy clusters in the gas phase derived from protein templates: unusual recognition of palladium by gold

    NASA Astrophysics Data System (ADS)

    Baksi, Ananya; Pradeep, T.

    2013-11-01

    Matrix assisted laser desorption ionization of a mixture of gold and palladium adducts of the protein lysozyme (Lyz) produces naked alloy clusters of the type Au24Pd+ in the gas phase. While a lysozyme-Au adduct forms Au18+, Au25+, Au38+ and Au102+ ions in the gas phase, lysozyme-Pd alone does not form any analogous cluster. Addition of various transition metal ions (Ag+, Pt2+, Pd2+, Cu2+, Fe2+, Ni2+ and Cr3+) in the adducts contributes to drastic changes in the mass spectrum, but only palladium forms alloys in the gas phase. Besides alloy formation, palladium enhances the formation of specific single component clusters such as Au38+. While other metal ions like Cu2+ help forming Au25+ selectively, Fe2+ catalyzes the formation of Au25+ over all other clusters. Gas phase cluster formation occurs from protein adducts where Au is in the 1+ state while Pd is in the 2+ state. The creation of alloys in the gas phase is not affected whether a physical mixture of Au and Pd adducts or a Au and Pd co-adduct is used as the precursor. The formation of Au cores and AuPd alloy cores of the kind comparable to monolayer protected clusters implies that naked clusters themselves may be nucleated in solution.Matrix assisted laser desorption ionization of a mixture of gold and palladium adducts of the protein lysozyme (Lyz) produces naked alloy clusters of the type Au24Pd+ in the gas phase. While a lysozyme-Au adduct forms Au18+, Au25+, Au38+ and Au102+ ions in the gas phase, lysozyme-Pd alone does not form any analogous cluster. Addition of various transition metal ions (Ag+, Pt2+, Pd2+, Cu2+, Fe2+, Ni2+ and Cr3+) in the adducts contributes to drastic changes in the mass spectrum, but only palladium forms alloys in the gas phase. Besides alloy formation, palladium enhances the formation of specific single component clusters such as Au38+. While other metal ions like Cu2+ help forming Au25+ selectively, Fe2+ catalyzes the formation of Au25+ over all other clusters. Gas phase cluster

  9. Nitrogen-doped graphene quantum dots-labeled epitope imprinted polymer with double templates via the metal chelation for specific recognition of cytochrome c.

    PubMed

    Yan, Yun-Jing; He, Xi-Wen; Li, Wen-You; Zhang, Yu-Kui

    2017-05-15

    A novel fluorescent sensor nitrogen-doped graphene quantum dots (N-GQDs)/SiO2/molecular imprinting polymer(N-GQDs/SiO2/MIP)was fabricated by surface imprinting and epitope imprinting to recognize and detect the target protein cytochrome c (Cyt C) with fluorescence quenching. In the polymerization process, the C- and N-terminal nonapeptides of Cyt C were selected as the double templates which were fixed by functional monomer (zinc acrylate) through metal chelation and steady six-membered ring. The linear range of fluorescence quenching for this receptor towards Cyt C was 0.20-60μM, and the detection limit was 0.11μM. The precision for six times replicate determination of Cyt C at 30μM was 1.20%, and the imprinting factor (IF) was 3.06. The recoveries of the material to Cyt C in urine were 99.3-114.0%. In brief, this work proposed a strategy to prepare a new type fluorescent imprinting polymer based on N-GQDs and provided an attractive perspective for the detection of protein by using the combination of N-GQDs and molecular imprinting technique. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Incorporation of a Metal Oxide Interlayer using a Virus-Templated Assembly for Synthesis of Graphene-Electrode-Based Organic Photovoltaics.

    PubMed

    Lee, Yong Man; Kim, Wanjung; Kim, Young Hun; Kim, Jung Kyu; Jang, Ji-Ryang; Choe, Woo-Seok; Park, Jong Hyeok; Yoo, Pil J

    2015-07-20

    Transition metal oxide (TMO) thin films have been exploited as interlayers for charge extraction between electrodes and active layers in organic photovoltaic (OPV) devices. Additionally, graphene-electrode-based OPVs have received considerable attention as a means to enhance device stability. However, the film deposition process of a TMO thin-film layer onto the graphene electrode is highly restricted owing to the hydrophobic nature of the graphene surface; thus, the preparation of the device should rely on a vacuum process that is incompatible with solution processing. In this study, we present a novel means for creating a thin tungsten oxide (WO3 ) interlayer on a graphene electrode by employing an engineered biotemplate of M13 viruses, whereby nondestructive functionalization of the graphene and uniform synthesis of a WO3 thin interlayer are concurrently achieved. As a result, the incorporated virus-templated WO3 interlayer exhibited solar-conversion efficiency that was 20 % higher than that of conventional OPVs based on the use of a (3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) interlayer. Notably, bilayer-structured OPVs with synergistically integrated WO3 /PEDOT:PSS achieved >60 % enhancement in device performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Gum Arabic Microgels As Template for In Situ Metal-Sulfide Based Quantum Dots Preparation and Their Thermal, Spectroscopic, Optical, and Magnetic Characterization

    NASA Astrophysics Data System (ADS)

    Farooq, Muhammad; Sagbas, Selin; Yildiz, Mustafa; Meral, Kadem; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin

    2017-03-01

    Here, gum arabic (GA) microgel in 5-50 μm size range was used as a template for in situ quantum dot (QD) preparation. The in situ synthesis of metal sulfide quantum dots (QDs) such as CdS, PbS, CuS, ZnS, CoS, and MnS was accomplished by the absorption of the corresponding metal ions from aqueous solutions and then in situ precipitation with S2- treatments within GA microgels. Transmission electron microscopy (TEM) confirmed the existence of the evenly distributed QDs within GA microgel matrices for each of the prepared QDs. All the fabricated GA-QD composites have shown excellent semiconducting behaviors with relatively larger band gap values of 4.87 eV, 4.60 eV, 6.71 eV, 4.81 eV, 3.68 eV, 5.2 eV, and 4.0 eV for CdS, PbS, ZnS, CuS, CoS, MoS, and MnS, respectively. The results revealed that CdS and ZnS are found to be the most efficient florescence materials amongst the all QDs with 630 and 70 cd/cm2 fluorescence intensities, respectively. Moreover, the magnetic susceptibility study suggests that Mn(IV), Co(III), and Mo(IV), have mononuclear octahedral geometries whereas Zn(II), Cd(II), and Pb(II) show binuclear geometries.

  12. Gum Arabic Microgels As Template for In Situ Metal-Sulfide Based Quantum Dots Preparation and Their Thermal, Spectroscopic, Optical, and Magnetic Characterization

    NASA Astrophysics Data System (ADS)

    Farooq, Muhammad; Sagbas, Selin; Yildiz, Mustafa; Meral, Kadem; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin

    2017-07-01

    Here, gum arabic (GA) microgel in 5-50 μm size range was used as a template for in situ quantum dot (QD) preparation. The in situ synthesis of metal sulfide quantum dots (QDs) such as CdS, PbS, CuS, ZnS, CoS, and MnS was accomplished by the absorption of the corresponding metal ions from aqueous solutions and then in situ precipitation with S2- treatments within GA microgels. Transmission electron microscopy (TEM) confirmed the existence of the evenly distributed QDs within GA microgel matrices for each of the prepared QDs. All the fabricated GA-QD composites have shown excellent semiconducting behaviors with relatively larger band gap values of 4.87 eV, 4.60 eV, 6.71 eV, 4.81 eV, 3.68 eV, 5.2 eV, and 4.0 eV for CdS, PbS, ZnS, CuS, CoS, MoS, and MnS, respectively. The results revealed that CdS and ZnS are found to be the most efficient florescence materials amongst the all QDs with 630 and 70 cd/cm2 fluorescence intensities, respectively. Moreover, the magnetic susceptibility study suggests that Mn(IV), Co(III), and Mo(IV), have mononuclear octahedral geometries whereas Zn(II), Cd(II), and Pb(II) show binuclear geometries.

  13. Syntheses, Structures and Thermal Studies of Fluorinated and Non-Fluorinated Homo and Heterometallic Alkoxides

    NASA Astrophysics Data System (ADS)

    Samuels, John Andrew

    The following studies probe the effects of ligand structure and modification on the conversion of metal species to solid-state products. 1. The synthesis, characterization, thermal decomposition, and full hydrolysis of rm Cu^{I }_2 Zr_2(O^{i}Pr) _{10} (1), Cu^ {rm I}_4Zr_4 O(O^{rm i}Pr) _{18} (2), and Cu ^{rm II}_4Zr _4O_3(O^ {rm i}Pr)_{18 } (3) are reported. The structure of 1 contains a Zr_2(O^{rm i}Pr)_9^- face -sharing bioctahedron bound to a Cu^{ rm I}_2(mu_2-OR) ^+ fragment via two mu _2 -alkoxides. The structure for 2 contains two (C_2(mu_2-OR) _2Zr_2(mu_2 -OR)_3(OR)_4] ^{1-} fragments connected via a pseudo-tetrahedral mu_4-O ^{2-} ligand. The structure of 3 contains a planar Cu_4O(O ^{rm i}Pr)_2 ^{4+} fragment capped by two Zr _2O(O^{rm i}Pr)_8^{2-} face-sharing bioctahedral units. The central oxo of the copper fragment is square-planar. TGA studies of ClCuZr_2(O^{ rm i}Pr)_9, 1, 2, and 3 show that internal redox occurs, producing copper metal, acetone, and isopropanol. The final products contain an increasing amount of zirconia with increasing number of oxo ligands in the precursor species. Full hydrolysis of 1 and 3, followed by thermolysis, produces Cu ^0, Cu_2O, and CuO with zirconia, depending on thermolysis conditions. 2. The compounds Na(HFIP) (HFIP = OCH(CF _3)_2), 1a, Na(TFTB) (TFTB = OC(CH _3)_2(CF_3 )), 1b, Na(HFTB) (HFTB = OC(CH_3 )(CF_3)_2), 1c, Na(PFTB) (PFTB = OC(CF_3)_3), 1d, Zr(HFIP)_4, 2a, Zr(TFTB) _4, 2b, Zr(HFTB)_4, 2c, Zr(PFTB)_4, 2d, Na_2 Zr(OR_{rm f})_6 (C_6H_6)_ {rm n} (3a when n = 1 and 3b when n = 2), and Tl_2Zr(OR_ {rm f})_6, 4, have been synthesized and characterized by mass spectrometry, multinuclear NMR and (for 1a, 2c, 3a, 3b and 4) X-ray diffraction structure determinations. Intramolecular bonding interactions between organofluorines and sodium or thallium are seen in all structures and are supported by Tl/F coupling in ^{205}Tl and ^{19 }F NMR spectra. Chemical vapor depositions of 1a-d, 2b-d and 3 produce metal fluoride

  14. Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess.

    PubMed

    Matsumoto, Arimasa; Abe, Takaaki; Hara, Atsushi; Tobita, Takayuki; Sasagawa, Taisuke; Kawasaki, Tsuneomi; Soai, Kenso

    2015-12-07

    Asymmetric amplification during self-replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine-5-carbaldehyde is a unique example of this phenomenon. Crystallization of zinc alkoxides of this 5-pyrimidyl alkanol and single-crystal X-ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.

  15. Metal-organic framework-templated synthesis of magnetic nanoporous carbon as an efficient absorbent for enrichment of phenylurea herbicides.

    PubMed

    Liu, Xingli; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2015-04-22

    Nanoporous carbon with a high specific surface area and unique porous structure represents an attractive material as an adsorbent in analytical chemistry. In this study, a magnetic nanoporous carbon (MNC) was fabricated by direct carbonization of Co-based metal-organic framework in nitrogen atmosphere without using any additional carbon precursors. The MNC was used as an effective magnetic adsorbent for the extraction and enrichment of some phenylurea herbicides (monuron, isoproturon, diuron and buturon) in grape and bitter gourd samples prior to their determination by high performance liquid chromatography with ultraviolet detection. Several important experimental parameters that could influence the extraction efficiency were investigated and optimized. Under the optimum conditions, a good linearity was achieved in the concentration range of 1.0-100.0 ng g(-1) for monuron, diuron and buturon and 1.5-100.0 ng g(-1) for isoproturon with the correlation coefficients (r) larger than 0.9964. The limits of detection (S/N=3) of the method were in the range from 0.17 to 0.46 ng g(-1). The results indicated that the MNC material was stable and efficient adsorbent for the magnetic solid-phase extraction of phenylurea herbicides and would have a great application potential for the extraction and preconcentration of more organic pollutants from real samples.

  16. Rapid enrichment of rare-earth metals by carboxymethyl cellulose-based open-cellular hydrogel adsorbent from HIPEs template.

    PubMed

    Zhu, Yongfeng; Wang, Wenbo; Zheng, Yian; Wang, Feng; Wang, Aiqin

    2016-04-20

    A series of monolithic open-cellular hydrogel adsorbents based on carboxymethylcellulose (CMC) were prepared through high internal phase emulsions (HIPEs) and used to enrich the rare-earth metals La(3+) and Ce(3+). The changes of pore structure, and the effects of pH, contact time, initial concentration on the adsorption performance were systematically studied. The results show that the as-prepared monolithic hydrogel adsorbents possess good open-cellular framework structure and have fast adsorption kinetics and high adsorption capacity for La(3+) and Ce(3+). The involved adsorption system can reach equilibrium within 30min and the maximal adsorption capacity is determined to be 384.62mg/g for La(3+) and 333.33mg/g for Ce(3+). Moreover, these porous hydrogel adsorbents show an excellent adsorptive reusability for La(3+) and Ce(3+) through five adsorption-desorption cycles. Such a pore hierarchy structure makes this monolithic open-cellular hydrogel adsorbent be an effective adsorbent for effective enrichment of La(3+) and Ce(3+) from aqueous solution.

  17. Identifying the Atomic-Level Effects of Metal Composition on the Structure and Catalytic Activity of Peptide-Templated Materials.

    PubMed

    Merrill, Nicholas A; McKee, Erik M; Merino, Kyle C; Drummy, Lawrence F; Lee, Sungsik; Reinhart, Benjamin; Ren, Yang; Frenkel, Anatoly I; Naik, Rajesh R; Bedford, Nicholas M; Knecht, Marc R

    2015-12-22

    Bioinspired approaches for the formation of metallic nanomaterials have been extensively employed for a diverse range of applications including diagnostics and catalysis. These materials can often be used under sustainable conditions; however, it is challenging to control the material size, morphology, and composition simultaneously. Here we have employed the R5 peptide, which forms a 3D scaffold to direct the size and linear shape of bimetallic PdAu nanomaterials for catalysis. The materials were prepared at varying Pd:Au ratios to probe optimal compositions to achieve maximal catalytic efficiency. These materials were extensively characterized at the atomic level using transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, and atomic pair distribution function analysis derived from high-energy X-ray diffraction patterns to provide highly resolved structural information. The results confirmed PdAu alloy formation, but also demonstrated that significant surface structural disorder was present. The catalytic activity of the materials was studied for olefin hydrogenation, which demonstrated enhanced reactivity from the bimetallic structures. These results present a pathway to the bioinspired production of multimetallic materials with enhanced properties, which can be assessed via a suite of characterization methods to fully ascertain structure/function relationships.

  18. Systematic Investigation of Controlled Nanostructuring of Mn12 Single-Molecule Magnets Templated by Metal-Organic Frameworks.

    PubMed

    Aulakh, Darpandeep; Xie, Haomiao; Shen, Zhe; Harley, Alexander; Zhang, Xuan; Yakovenko, Andrey A; Dunbar, Kim R; Wriedt, Mario

    2017-06-19

    This is the first systematic study exploring metal-organic frameworks (MOFs) as platforms for the controlled nanostructuring of molecular magnets. We report the incorporation of seven single-molecule magnets (SMMs) of general composition [Mn12O12(O2CR)16(OH2)4], with R = CF3 (1), (CH3)CCH2 (2), CH2Cl (3), CH2Br (4), CHCl2 (5), CH2Bu(t) (6), and C6H5 (7), into the hexagonal channel pores of a mesoporous MOF host. The resulting nanostructured composites combine the key SMM properties with the functional properties of the MOF. Synchrotron-based powder diffraction with difference envelope density analysis, physisorption analysis (surface area and pore size distribution), and thermal analyses reveal that the well-ordered hexagonal structure of the host framework is preserved, and magnetic measurements indicate that slow relaxation of the magnetization, characteristic of the corresponding Mn12 derivative guests, occurs inside the MOF pores. Structural host-guest correlations including the bulkiness and polarity of peripheral SMM ligands are discussed as fundamental parameters influencing the global SMM@MOF loading capacities. These results demonstrate that employing MOFs as platforms for the nanostructuration of SMMs is not limited to a particular host-guest system but potentially applicable to a multitude of other molecular magnets. Such fundamental findings will assist in paving the way for the development of novel advanced spintronic devices.

  19. Method for extracting metals from aqueous waste streams for long term storage

    DOEpatents

    Chaiko, D.J.

    1993-01-01

    A liquid-liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average. individual particle sizes of approximately 40 manometers.

  20. Method for extracting metals from aqueous waste streams for long term storage

    DOEpatents

    Chaiko, D.J.

    1995-03-07

    A liquid-liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average individual particle sizes of approximately 40 nanometers. 2 figs.

  1. Method for extracting metals from aqueous waste streams for long term storage

    DOEpatents

    Chaiko, David J.

    1995-01-01

    A liquid--liquid extraction method for removing metals and hydrous metal colloids from waste streams is provided wherein said waste streams are contacted with a solvent system containing a water-in-oil microemulsion wherein the inverted micelles contain the extracted metal. A silicon alkoxide, either alone or in combination with other metal alkoxide compounds is added to the water-in-oil microemulsion, thereby allowing encapsulation of the extracted metal within a silicon oxide network. Lastly, the now-encapsulated metal is precipitated from the water-in-oil microemulsion phase to yield aggregates of metal-silicate particles having average individual particle sizes of approximately 40 nanometers.

  2. Redox-controlled polymerization of lactide catalyzed by bis(imino)pyridine iron bis(alkoxide) complexes.

    PubMed

    Biernesser, Ashley B; Li, Bo; Byers, Jeffery A

    2013-11-06

    Bis(imino)pyridine iron bis(alkoxide) complexes have been synthesized and utilized in the polymerization of (rac)-lactide. The activities of the catalysts were particularly sensitive to the identity of the initiating alkoxide with more electron-donating alkoxides resulting in faster polymerization rates. The reaction displayed characteristics of a living polymerization with production of polymers that exhibited low molecular weight distributions, linear relationships between molecular weight and conversion, and polymer growth observed for up to fifteen sequential additions of lactide monomer to the polymerization reaction. Mechanistic experiments revealed that iron bis(aryloxide) catalysts initiate polymerization with one alkoxide ligand, while iron bis(alkylalkoxide) catalysts initiate polymerization with both alkoxide ligands. Oxidation of an iron(II) catalyst precursor lead to a cationic iron(III) bis-alkoxide complex that was completely inactive toward lactide polymerization. When redox reactions were carried out during lactide polymerization, catalysis could be switched off and turned back on upon oxidation and reduction of the iron catalyst, respectively.

  3. Steric vs electronic effects in binary uranyl alkoxides: A spectroscopic perspective

    NASA Astrophysics Data System (ADS)

    Morris, David E.; Wilkerson, Marianne P.; Burns, Carol J.; Scott, Brian L.; Wilkerson, Marianne P.; Paine, Robert T.

    2000-07-01

    Recent advances in the non-aqueous alkoxide chemistry of UO22+ have provided the wherewithal to prepare and isolate a broad range of discrete molecular uranyl entities both as solids and in aprotic solvents in which it is possible to tune the ligand basicity and steric encumbrance. Uranyl complexes have been isolated as monomers, dimers, and higher order oligomers. These complexes afford an opportunity to examine in some detail the relative importance of ligand basicity and steric demand in directing structural preferences (monomer vs. dimer, cis vs. trans isomers) and in determining electronic structural properties and relative bond strengths in the "yl" and equatorial bonds. In the present report the electronic and vibrational spectroscopic data for a series of uranyl alkoxides are correlated with molecular structural data to examine trends in electronic structure and bonding and compare these results with existing models based on the more classical uranyl coordination compounds.

  4. Isomerization of methyl linoleate on ruthenium(III) alkoxide complex; Mathematical modeling

    SciTech Connect

    Mukesh, D.; Narasimhan, C.S.; Ramnarayan, K.; Deshpande, V.M

    1989-08-01

    The isomerization of methyl linoleate using ruthenium alkoxide complexes is described. With alcohols, such as isopropyl alcohol (IPA), 1-butanol, 1-hexanol, and 1-octanol, isomerization of double bonds to produce a conjugated system is the main reaction, with hydrogenation being the side reaction. The latter is formed via the conjugated product. Based on kinetic and infrared spectroscopic data, it is concluded that the active catalytic species is a ruthenium hydride complex formed by the decomposition of the unstable alkoxide. The reaction is mathematically modeled, and the rate parameters are obtained by fitting the simulation to experimental data. These values are compared with data obtained from reactions carried out with supported ruthenium-nickel heterogeneous catalyst.

  5. Photoinduced Formation of Colloidal Silver in Nitrocellulose Solutions Containing Titanium Alkoxides

    NASA Astrophysics Data System (ADS)

    Kulak, A. I.; Branitsky, G. A.

    2016-07-01

    The study shows the possibility of photo-induced reduction of silver nitrate and formation of stable colloidal silver particles in an isopropanol-N,N-dimethylacetamide solution of titanium alkoxide (polybutyl titanate) stabilized by nitrocellulose. It is established that titanium alkoxide and the products of its partial hydrolysis in the liquid composition play the role of a photocatalyst for the reduction of silver ions; the introduction of nitric or acetic acid additives to the composition significantly increases its photosensitivity. The films deposited from the liquid composition, previously irradiated with visible or UV light, consist of hydrated titanium dioxide and nitrocellulose with incorporated colloidal silver. Thermal treatment of the films at 150-245°C leads to the decomposition of nitrocellulose and an increase in the absorption by silver particles.

  6. Well-defined cationic alkyl- and alkoxide-aluminum complexes and their reactivity with epsilon-caprolactone and lactides.

    PubMed

    Dagorne, Samuel; Le Bideau, Franck; Welter, Richard; Bellemin-Laponnaz, Stéphane; Maisse-François, Aline

    2007-01-01

    -alkyl cations form robust four-coordinate adducts in the presence of cyclic esters such as epsilon-caprolactone and (D,L)-lactide, but no insertion chemistry occurs, illustrating the poor ability of the Al-R+ moiety to ring-open. In contrast, the Al-alkoxide cation 10+ polymerizes epsilon-caprolactone in a controlled manner with excellent activity, but is inactive in the polymerization of (D,L)-lactide and L-lactide. Control experiments with L-lactide show that cation 10+ ring-opens L-lactide to yield a robust five-coordinated Al--lactate cation [(N,O)Al(eta2-L-lactate-OiPr)(thf)]+ (13+), derived from a monoinsertion of L-lactide into the Al--OiPr bond of 10+, that does not further react. Cation 13+ may be regarded as a structurally characterized close mimic of the initial intermediate in the ring opening polymerization (ROP), of lactides by [{LX}M(OR)(L)] (where LX-=bidentate monoanionic ligand and L=labile ligand) metal complex initiators.

  7. Synthesis, crystal structure and two-dimensional infrared correlation spectroscopy of a layer-like transition metal (TM)-oxalate templated polyoxovanadium borate

    NASA Astrophysics Data System (ADS)

    Cao, Yanning; Zhang, Hanhui; Huang, Changcang; Yang, Qiyu; Chen, Yiping; Sun, Ruiqing; Zhang, Fengli; Guo, Wenjun

    2005-11-01

    A novel polyoxometalate (POM) Na 2(H 2en) 2{(VO) 10[B 14O 30(OH) 2] 2}{Mn 4(C 2O 4) [B 2O 4(OH) 2] 2}Mn(H 2O) 2·(H 3O) 12(H 2O) 191 (en=ethylenediamine), which is a layer-like transition metal (TM) oxalate templated polyoxovanadium borate, has been synthesized under hydrothermal conditions and characterized by EPR, elemental analysis, thermal analysis, single crystal X-ray diffraction and 2D IR correlation spectroscopy studies, respectively. This compound crystallized in the triclinic space group P1¯ with a=14.3842(4) Å, b=14.6837(3) Å, c=15.8681(4) Å, α=64.48(1)°, β=64.68(1)°, γ=63.93(1)°, V=2596.80(11) Å3 and Z=2. The cluster anion with an open central cavity has a central band of ten edge-sharing VO 5 square pyramids, which is capped top and bottom by two crown-like polyborate ligands of formula [B 14O 30(OH) 2] 20-. There is a fragment of {Mn 4(C 2O 4)[B 2O 4(OH) 2] 2} 2- fixed in the central cavity as a guest part. The cluster units are connected to form a two-dimensional (2D) framework by octahedral Mn(II) and Na + sites. In addition, we first introduce the generalized 2D correlation spectroscopy to explore the POMs and obtain the dynamic information about structural changes of POMs.

  8. Synthesis and characterization of amine-bridged bis(phenolate)lanthanide alkoxides and their application in the controlled polymerization of rac-lactide and rac-β-butyrolactone.

    PubMed

    Nie, Kun; Fang, Lei; Yao, Yingming; Zhang, Yong; Shen, Qi; Wang, Yaorong

    2012-10-15

    A series of neutral lanthanide alkoxides supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were explored. The reactions of (C(5)H(5))(3)Ln(THF) with amine-bridged bis(phenol) LH(2) [L = Me(2)NCH(2)CH(2)N{CH(2)-(2-OC(6)H(2)Bu(t)(2)-3,5)}(2)] in a 1:1 molar ratio in THF for 1 h and then with 1 equiv each of 2,2,2-trifluoroethanol, benzyl alcohol, and 2-propanol gave the neutral lanthanide alkoxides LLn(OCH(2)CF(3))(THF) [Ln = Y (1), Yb (2), Er (3), Sm (4)], LY(OCH(2)Ph)(THF) (5), and LY(OPr(i))(THF) (6), respectively. These lanthanide alkoxides are sensitive to moisture, and the yttrium complex [(LY)(2)(μ-OPr(i))(μ-OH)] (7) was also isolated as a byproduct during the synthesis of complex 6. Complexes 1-6 were well characterized by elemental analyses and IR and NMR spectroscopy in the cases of complexes 1 and 4-6. The definitive molecular structures of all of these complexes were determined by single-crystal X-ray analysis. It was found that complexes 1-6 can initiate efficiently the ring-opening polymerization of rac-LA and rac-BBL in a controlled manner. For rac-LA, polymerization gave polymers with very narrow molecular weight distributions (PDI ≤ 1.12) and very high heterotacticity (P(r) up to 0.99). The observed activity-increasing order is in agreement with the order of the ionic radii, whereas the order for stereoselectivity is in the reverse order. For rac-BBL polymerization, the resultant polymers have narrow molecular distributions (PDI ≤ 1.26) and high syndiotacticity (P(r) up to 0.83). It is worth noting that the activity-decreasing order Yb > Er > Y > Sm is observed for rac-BBL polymerization, which is opposite to the order of ionic radii and to the order of activity for rac-LA polymerization. The ionic radii of lanthanide metals have no obvious effect on the stereoselectivity for rac-BBL polymerization, which is quite

  9. A silica sol-gel design strategy for nanostructured metallic materials.

    PubMed

    Warren, Scott C; Perkins, Matthew R; Adams, Ashley M; Kamperman, Marleen; Burns, Andrew A; Arora, Hitesh; Herz, Erik; Suteewong, Teeraporn; Sai, Hiroaki; Li, Zihui; Werner, Jörg; Song, Juho; Werner-Zwanziger, Ulrike; Zwanziger, Josef W; Grätzel, Michael; DiSalvo, Francis J; Wiesner, Ulrich

    2012-03-18

    Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals--including noble metals--to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm(-1). This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

  10. Synthesis, crystal structure and two-dimensional infrared correlation spectroscopy of a layer-like transition metal (TM)-oxalate templated polyoxovanadium borate

    SciTech Connect

    Cao Yanning; Zhang Hanhui . E-mail: zhanghh1840@hotmail.com; Huang Changcang; Yang Qiyu; Chen Yiping; Sun Ruiqing; Zhang Fengli; Guo Wenjun

    2005-11-15

    A novel polyoxometalate (POM) Na{sub 2}(H{sub 2}en){sub 2}{l_brace}(VO){sub 10}[B{sub 14}O{sub 30}(OH){sub 2}]{sub 2}{r_brace}{l_brace}Mn{sub 4}(C{sub 2}O{sub 4}) [B{sub 2}O{sub 4}(OH){sub 2}]{sub 2}{r_brace}Mn(H{sub 2}O){sub 2}.(H{sub 3}O){sub 12}(H{sub 2}O){sub 19}1 (en=ethylenediamine), which is a layer-like transition metal (TM) oxalate templated polyoxovanadium borate, has been synthesized under hydrothermal conditions and characterized by EPR, elemental analysis, thermal analysis, single crystal X-ray diffraction and 2D IR correlation spectroscopy studies, respectively. This compound crystallized in the triclinic space group P1-bar with a=14.3842(4)A, b=14.6837(3)A, c=15.8681(4)A, {alpha}=64.48(1){sup o}, {beta}=64.68(1){sup o}, {gamma}=63.93(1){sup o}, V=2596.80(11)A{sup 3} and Z=2. The cluster anion with an open central cavity has a central band of ten edge-sharing VO{sub 5} square pyramids, which is capped top and bottom by two crown-like polyborate ligands of formula [B{sub 14}O{sub 30}(OH){sub 2}]{sup 20-}. There is a fragment of {l_brace}Mn{sub 4}(C{sub 2}O{sub 4})[B{sub 2}O{sub 4}(OH){sub 2}]{sub 2}{r_brace}{sup 2-} fixed in the central cavity as a guest part. The cluster units are connected to form a two-dimensional (2D) framework by octahedral Mn(II) and Na{sup +} sites. In addition, we first introduce the generalized 2D correlation spectroscopy to explore the POMs and obtain the dynamic information about structural changes of POMs.

  11. Spin crossover behavior in a series of iron(III) alkoxide complexes.

    PubMed

    Ortega-Villar, Norma; Guerrero-Estrada, Areli Yesareth; Piñeiro-López, Lucía; Muñoz, M Carmen; Flores-Álamo, Marcos; Moreno-Esparza, Rafael; Real, José A; Ugalde-Saldívar, Víctor M

    2015-04-06

    The synthesis, crystal structures, magnetic behavior, and electron paramagnetic resonance studies of five new Fe(III) spin crossover (SCO) complexes are reported. The [Fe(III)N5O] coordination core is constituted of the pentadentate ligand bztpen (N5) and a series of alkoxide anions (ethoxide, propoxide, n-butoxide, isobutoxide, and ethylene glycoxide). The methoxide derivative previously reported by us is also reinvestigated. The six complexes crystallize in the orthorhombic Pbca space group and show similar molecular structures and crystal packing. The coordination octahedron is strongly distorted in both the high- and low-temperature structures. The structural changes upon spin conversion are consistent with those previously observed for [Fe(III)N4O2] SCO complexes of the Schiff base type, except for the Fe-O(alkoxide) bond distance, which shortens significantly in the high-spin state. Application of the Slichter-Drickamer thermodynamic model to the experimental SCO curves afforded reasonably good simulations with typical enthalpy and entropy variations ranging in the intervals ΔH = 6-13 kJ mol(-1) and ΔS = 40-50 J mol(-1) K(-1), respectively. The estimated values of the cooperativity parameter Γ, found in the interval 0-2.2 kJ mol(-1), were consistent with the nature of the SCO. Electron paramagnetic resonance spectroscopy confirmed the transformation between the high-spin and low-spin states, characterized by signals at g ≈ 4.47 and 2.10, respectively. Electrochemical analysis demonstrated the instability of the Fe(II) alkoxide derivatives in solution.

  12. Synthesis and characterization of 2-hydroxy-pyridine modified Group 4 alkoxides

    SciTech Connect

    Boyle, Timothy J.; Sivonxay, Eric

    2016-05-19

    Here, the reaction of Group 4 metal alkoxides ([M(OR)4]) with the potentially bidentate ligand, 2-hydroxy-pyridine (2-HO-(NC5H4) or H-PyO), led to the isolation of a family of compounds. The products isolated from the reaction of [M(OR)4] [where M = Ti, Zr, or Hf; OR = OPri (OCH(CH3)2), OBut (OC(CH3)3), or ONep (OCH2C(CH3)3] under a variety of stoichiometries with H-PyO were identified by single crystal X-ray diffraction as [(OPri)2(PyO-κ2(O,N))Ti(μ-OPri)]2, [(ONep)2Ti(μ(O)-PyO-κ2(O,N))2(μ-ONep)Ti(ONep)3], [(ONep)2Ti(μ(O)-PyO-κ2(O,N))(η1(N),μ(O)-PyO)(μ-O)Ti(ONep)2]2, [H][(PyO-κ2(O,N))(η1(O)-PyO)Ti(ONep)3], [(OR)2Zr(μ(O)-PyO-κ2(O,N))2(μ-OR)Zr(OR)3] (OR = OBut, ONep), [(OR)2Zr(μ(O,N)-PyO-κ2(O,N))2(μ(O,N)-PyO)Zr(OR)3] (OR = OBut, ONep), [[(OBut)2Zr(μ(O)-PyO-(κ2(N,O))(μ(O,N)-PyO)2Zr(OBut)](μ3-O)]2, [[(ONep)(PyO-κ2(N,O))Zr(μ(O,N)-PyO-κ2(N,O))2(μ(O)-PyO-κ2(N,O))Zr(ONep)](μ3-O)]2, [(OBut)(PyO-κ2(O,N))Zr(μ(O)-PyO-κ2(O,N))2((μ(O,N)-PyO)Zr(OBut)3], [(OBut)2Hf(μ(O)-PyO-κ2(N,O))2(μ-OBut)Hf(OBut)3], [(OR)2 M(μ(O)-PyO-κ2(N,O))2(μ(O,N)-PyO)M(OR)3] (OR = OBut, ONep), and [(ONep)3Hf(μ-ONep)(η1(N),μ(O)-PyO)]2Hf(ONep)2·tol. The structural diversity of the binding modes of the PyO led to a number of novel structure types in comparison to other pyridine alkoxy derivatives. The majority of

  13. Synthesis and characterization of 2-hydroxy-pyridine modified Group 4 alkoxides

    DOE PAGES

    Boyle, Timothy J.; Sivonxay, Eric

    2016-05-19

    Here, the reaction of Group 4 metal alkoxides ([M(OR)4]) with the potentially bidentate ligand, 2-hydroxy-pyridine (2-HO-(NC5H4) or H-PyO), led to the isolation of a family of compounds. The products isolated from the reaction of [M(OR)4] [where M = Ti, Zr, or Hf; OR = OPri (OCH(CH3)2), OBut (OC(CH3)3), or ONep (OCH2C(CH3)3] under a variety of stoichiometries with H-PyO were identified by single crystal X-ray diffraction as [(OPri)2(PyO-κ2(O,N))Ti(μ-OPri)]2, [(ONep)2Ti(μ(O)-PyO-κ2(O,N))2(μ-ONep)Ti(ONep)3], [(ONep)2Ti(μ(O)-PyO-κ2(O,N))(η1(N),μ(O)-PyO)(μ-O)Ti(ONep)2]2, [H][(PyO-κ2(O,N))(η1(O)-PyO)Ti(ONep)3], [(OR)2Zr(μ(O)-PyO-κ2(O,N))2(μ-OR)Zr(OR)3] (OR = OBut, ONep), [(OR)2Zr(μ(O,N)-PyO-κ2(O,N))2(μ(O,N)-PyO)Zr(OR)3] (OR = OBut, ONep), [[(OBut)2Zr(μ(O)-PyO-(κ2(N,O))(μ(O,N)-PyO)2Zr(OBut)](μ3-O)]2, [[(ONep)(PyO-κ2(N,O))Zr(μ(O,N)-PyO-κ2(N,O))2(μ(O)-PyO-κ2(N,O))Zr(ONep)](μ3-O)]2, [(OBut)(PyO-κ2(O,N))Zr(μ(O)-PyO-κ2(O,N))2((μ(O,N)-PyO)Zr(OBut)3], [(OBut)2Hf(μ(O)-PyO-κ2(N,O))2(μ-OBut)Hf(OBut)3], [(OR)2 M(μ(O)-PyO-κ2(N,O))2(μ(O,N)-PyO)M(OR)3] (OR = OBut, ONep), and [(ONep)3Hf(μ-ONep)(η1(N),μ(O)-PyO)]2Hf(ONep)2·tol. The structural diversity of the binding modes ofmore » the PyO led to a number of novel structure types in comparison to other pyridine alkoxy derivatives. The majority of compounds adopt a dinuclear arrangement but oxo-based tetra-, tri-, and monomers were observed as well. Compounds 1–12 were further characterized using a variety of analytical techniques including Fourier Transform Infrared Spectroscopy, elemental analysis, and multinuclear NMR spectroscopy.« less

  14. Synthesis and characterization of 2-hydroxy-pyridine modified Group 4 alkoxides

    SciTech Connect

    Boyle, Timothy J.; Sivonxay, Eric

    2016-05-19

    Here, the reaction of Group 4 metal alkoxides ([M(OR)4]) with the potentially bidentate ligand, 2-hydroxy-pyridine (2-HO-(NC5H4) or H-PyO), led to the isolation of a family of compounds. The products isolated from the reaction of [M(OR)4] [where M = Ti, Zr, or Hf; OR = OPri (OCH(CH3)2), OBut (OC(CH3)3), or ONep (OCH2C(CH3)3] under a variety of stoichiometries with H-PyO were identified by single crystal X-ray diffraction as [(OPri)2(PyO-κ2(O,N))Ti(μ-OPri)]2, [(ONep)2Ti(μ(O)-PyO-κ2(O,N))2(μ-ONep)Ti(ONep)3], [(ONep)2Ti(μ(O)-PyO-κ2(O,N))(η1(N),μ(O)-PyO)(μ-O)Ti(ONep)2]2, [H][(PyO-κ2(O,N))(η1(O)-PyO)Ti(ONep)3], [(OR)2Zr(μ(O)-PyO-κ2(O,N))2(μ-OR)Zr(OR)3] (OR = OBut, ONep), [(OR)2Zr(μ(O,N)-PyO-κ2(O,N))2(μ(O,N)-PyO)Zr(OR)3] (OR = OBut, ONep), [[(OBut)2Zr(μ(O)-PyO-(κ2(N,O))(μ(O,N)-PyO)2Zr(OBut)](μ3-O)]2, [[(ONep)(PyO-κ2(N,O))Zr(μ(O,N)-PyO-κ2(N,O))2(μ(O)-PyO-κ2(N,O))Zr(ONep)](μ3-O)]2, [(OBut)(PyO-κ2(O,N))Zr(μ(O)-PyO-κ2(O,N))2((μ(O,N)-PyO)Zr(OBut)3], [(OBut)2Hf(μ(O)-PyO-κ2(N,O))2(μ-OBut)Hf(OBut)3], [(OR)2 M(μ(O)-PyO-κ2(N,O))2(μ(O,N)-PyO)M(OR)3] (OR = OBut, ONep), and [(ONep)3Hf(μ-ONep)(η1(N),μ(O)-PyO)]2Hf(ONep)2·tol. The structural diversity of the binding modes of the PyO led to a number of novel structure types in comparison to other pyridine alkoxy derivatives. The majority of

  15. Synthesis and characterization of titanium oxo-alkoxides through solvatothermal process

    SciTech Connect

    Steunou, N.; Dromzee, Y.; Robert, F.; Sanchez, C.

    1996-12-31

    The non hydrolytic synthesis of several titanium oxo-alkoxo clusters Ti{sub 3}O(OPr{sup i}){sub 8}(OR){sub 2}, Ti{sub 11}O{sub 13}(OPr{sup i}){sub 18}, Ti{sub 7}O{sub 4}(OEt){sub 20} and Ti{sub 16}O{sub 16}(OEt){sub 32} have been performed via thermolysis of different titanium alkoxides (Ti(OEt){sub 4}, Ti(OPr{sup i}){sub 4}). The structures of these clusters were mainly determined by X-ray diffraction, {sup 17}O NMR and {sup 13}C NMR.

  16. Templated and template-free fabrication strategies for zero-dimensional hollow MOF superstructures.

    PubMed

    Kim, Hyehyun; Lah, Myoung Soo

    2017-05-16

    Various fabrication strategies for hollow metal-organic framework (MOF) superstructures are reviewed and classified using various types of external templates and their properties. Hollow MOF superstructures have also been prepared without external templates, wherein unstable intermediates obtained during reactions convert to the final hollow MOF superstructures. Many hollow MOF superstructures have been fabricated using hard templates. After the core-shell core@MOF structure was prepared using a hard template, the core was selectively etched to generate a hollow MOF superstructure. Another approach for generating hollow superstructures is to use a solid reactant as a sacrificial template; this method requires no additional etching process. Soft templates such as discontinuous liquid/emulsion droplets and gas bubbles in a continuous soft phase have also been employed to prepare hollow MOF superstructures.

  17. Fast and selective ring-opening polymerizations by alkoxides and thioureas

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangyi; Jones, Gavin O.; Hedrick, James L.; Waymouth, Robert M.

    2016-11-01

    Ring-opening polymerization of lactones is a versatile approach to generate well-defined functional polyesters. Typical ring-opening catalysts are subject to a trade-off between rate and selectivity. Here we describe an effective catalytic system combining alkoxides with thioureas that catalyses rapid and selective ring-opening polymerizations. Deprotonation of thioureas by sodium, potassium or imidazolium alkoxides generates a hydrogen-bonded alcohol adduct of the thiourea anion (thioimidate). The ring-opening polymerization of L-lactide mediated by these alcohol-bonded thioimidates yields highly isotactic polylactide with fast kinetics and living polymerization behaviour, as evidenced by narrow molecular weight distributions (Mw/Mn < 1.1), chain extension experiments and minimal transesterifications. Computational studies indicate a bifunctional catalytic mechanism whereby the thioimidate activates the carbonyl of the monomer and the alcohol initiator/chain end to effect the selective ring-opening of lactones and carbonates. The high selectivity of the catalyst towards monomer propagation over transesterification is attributed to a selective activation of monomer over polymer chains.

  18. Elemental Metals or Oxides Distributed on a Carbon Substrate or Self-Supported and the Manufacturing Process Using Graphite Oxide as Template

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Chen (Inventor)

    1999-01-01

    A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a percursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon, metal, chloride, and oxygen. This intermediary product can be further processed by direct exposure to carbonate solutions to form a second intermediary product comprising carbon, metal carbonate, and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide; b) in an inert environment to produce metal oxide on carbon substrate; c) in a reducing environment to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

  19. Elemental Metals or Oxides Distributed on a Carbon Substrate or Self-Supported and the Manufacturing Process Using Graphite Oxide as Template

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh (Inventor)

    1999-01-01

    A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a precursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon, metal, chloride, and oxygen. This intermediary product can be further processed by direct exposure to carbonate-solutions to form a second intermediary product comprising carbon, metal carbonate, and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide; b) in an inert environment to produce metal oxide on carbon substrate; c) in a reducing environment to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

  20. Method for making monolithic metal oxide aerogels

    DOEpatents

    Droege, M.W.; Coronado, P.R.; Hair, L.M.

    1995-03-07

    Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels. 6 figs.

  1. Method for making monolithic metal oxide aerogels

    DOEpatents

    Droege, Michael W.; Coronado, Paul R.; Hair, Lucy M.

    1995-01-01

    Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels.

  2. Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

    PubMed

    Rodriguez-Navarro, Carlos; Vettori, Irene; Ruiz-Agudo, Encarnacion

    2016-05-24

    Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol(-1) for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preserving the external hexagonal (platelike) morphology of the parent phase. Textural and kinetic results reveal that this pseudomorphic replacement involves a 3D diffusion-controlled deceleratory advancement of the reaction front. The results are consistent with an interface-coupled dissolution-precipitation replacement mechanism. Analysis of the carbonation of Ca(OH)2 particles with different degree of conversion into Ca-ethoxide (α up to 0.08) and Ca-isopropoxide (α up to 0.04) exposed to air (20 °C, 80% relative humidity) reveals that Ca-alkoxides significantly reduce the rate of transformation into cementing CaCO3 and induce the formation of metastable vaterite, as opposed to stable calcite which forms in untransformed Ca(OH)2 samples. Similar effects are obtained when a commercial nanolime partially transformed into Ca-ethoxide is subjected to carbonation. Such effects may hamper/delay the strengthening or consolidation effects of nanolimes, thus having

  3. Programmable imprint lithography template

    DOEpatents

    Cardinale, Gregory F.; Talin, Albert A.

    2006-10-31

    A template for imprint lithography (IL) that reduces significantly template production costs by allowing the same template to be re-used for several technology generations. The template is composed of an array of spaced-apart moveable and individually addressable rods or plungers. Thus, the template can be configured to provide a desired pattern by programming the array of plungers such that certain of the plungers are in an "up" or actuated configuration. This arrangement of "up" and "down" plungers forms a pattern composed of protruding and recessed features which can then be impressed onto a polymer film coated substrate by applying a pressure to the template impressing the programmed configuration into the polymer film. The pattern impressed into the polymer film will be reproduced on the substrate by subsequent processing.

  4. Sonographic stroke templates.

    PubMed

    Govaert, Paul

    2009-10-01

    This chapter provides arterial and venous stroke templates, designed with neonatal brain ultrasound as the viewpoint and adult stroke templates as the basis. Images change with maturation of the stages of infarction: swelling, necrosis, organisation and tissue loss. Adult templates permit recognition of well-delineated stroke types observed in the newborn brain. All circle of Willis arteries can be involved, as can their perforator branches. Middle cerebral artery (MCA) truncal stroke (anterior or posterior) is an important entity, with different prognosis than complete MCA stroke. Knowledge of these templates also aids in the definition of combinations of infarction (e.g. internal carotid artery stroke or pial plus perforator stroke) and of interarterial watershed injury. Venous templates, even if still under development around the time of birth, permit us to understand brain injury associated with sinus or deep vein thrombosis, especially several types of intracranial haemorrhage. Hindbrain stroke templates are scarcely applied to perinatal lesions.

  5. Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base difunctional catalysts for transesterification.

    PubMed

    Zeng, Ruijie; Sheng, Hongting; Zhang, Yongcang; Feng, Yan; Chen, Zhi; Wang, Junfeng; Chen, Man; Zhu, Manzhou; Guo, Qingxiang

    2014-10-03

    A practical lanthanide(III)-catalyzed transesterification of carboxylic esters, weakly reactive carbonates, and much less-reactive ethyl silicate with primary and secondary alcohols was developed. Heterobimetallic dinuclear lanthanide alkoxide complexes [Ln2Na8{(OCH2CH2NMe2)}12(OH)2] (Ln = Nd (I), Sm (II), and Yb (III)) were used as highly active catalysts for this reaction. The mild reaction conditions enabled the transesterification of various substrates to proceed in good to high yield. Efficient activation of transesterification may be endowed by the above complexes as cooperative acid-base difunctional catalysts, which is proposed to be responsible for the higher reactivity in comparison with simple acid/base catalysts.

  6. Living polymerization of (o-(trimethylsilyl)phenyl)acetylene using `small alkoxide` molybdenum(VI) initiators

    SciTech Connect

    Schrock, R.R.; Luo, S.; Zanetti, N.C.; Fox, H.H.

    1994-09-01

    (o-(Trimethylsily)phenyl)acetylene (o-TM-SPA) is polymerized in a living manner by the new `small alkoxide` initiators Mo(CHCMe{sub 2}Ph)(N-1-adamantyl) [OCH(CF{sub 3}){sub 2}]{sub 2}(2,4-lutidine) (1b) and Mo(CHCMe{sub 2}-Ph)(NAr{prime})(OC{sub 6}F{sub 5}){sub 2}(quinulidine) (2; Ar{prime} = 2,6-C{sub 6}H{sub 3}Me{sub 2}) to give low-polydispersity polyenes containing up to 100 equiv of o-TMSPA. The thermodynamically most stable form of poly(o-TMSPA) that contains <25 double bonds is air-sensitive and has a significantly red-shifted {lambda}{sub max}. 29 refs., 1 fig., 1 tab.

  7. Synthesis of Industrially Relevant Carbamates towards Isocyanates using Carbon Dioxide and Organotin(IV) Alkoxides.

    PubMed

    Germain, Nicolas; Müller, Imke; Hanauer, Matthias; Paciello, Rocco A; Baumann, Robert; Trapp, Oliver; Schaub, Thomas

    2016-07-07

    A straightforward phosgene-free synthesis of aromatic isocyanates and diisocyanates is disclosed. Theoretical investigations suggested that the insertion of carbon dioxide (CO2 ) by dialkyltin(IV) dialkoxides could be used to convert aromatic amines into aromatic mono- and dicarbamates. Here we show, that methyl phenylcarbamate (MPC) from aniline using organotin(IV) dimethoxide and CO2 can be formed in high yield of up to 92 %, experimentally corroborating the predictions of density functional theory (DFT) calculations. MPC was then separated from the tin oxide residues and converted into phenyl isocyanate. Furthermore, organotin(IV) alkoxides could be regenerated from the tin oxide residues and reused, paving the way for a continuous industrial process. Extension of the scope to the synthesis of diurethanes from toluene 2,4-diamine and 4,4'-methylenedianiline could potentially allow the efficient production of industrially relevant diisocyanates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Radiophase development in hot-pressed alkoxide-derived titanate ceramics for nuclear waste stabilization

    SciTech Connect

    Dickson, F.J. ); Mitamura, H. ); White, T.J. )

    1989-06-01

    This paper reports phase development as a function of hot-pressing temperature studied in alkoxide-derived titanate-based ceramics doped with a 10 wt% loading of a sodium-rich (NAR) and a sodium-poor (NAP) simulated high-level waste. Pyrochlore was found to be the most abundant phase in both calcine powders. A pseudobrookite phase existed metastably at hot-pressing temperatures between 890{degrees} and 920{degrees} C. After hot-pressing at 1100{degrees} C, the final phase assemblage for the NAP material consisted of zirconolite, hollandite-type, perovskite, alloy, and reduced rutile (Magneli phases). In addition, NAR samples contained hibonite, freudenbergite, and loveringite. Phase development was driven to completion over a very narrow temperature range ({le}50{degrees} C), beginning at 870{degrees} and 850{degrees} C for NAP and NAR, respectively, although full densification was not achieved below 1100{degrees} C. Both waste forms exhibited comparable microstructure and aqueous durability.

  9. Role of tetraalkyl(benzyl)ammonium alkoxides in the catalysis of the alkaline dehydrochlorination reaction

    SciTech Connect

    Shavanov, S.S.; Tolstikov, G.A.; Shutenkova, T.V.; Viktorov, G.A.

    1988-01-10

    The reaction was conducted by the action of aqueous NaOH taken as a 50% solution at a molar ratio to dichloroethane of 2:1 at 50-55 C in the 1% of catalyst on the dichloroethane. The results of the experiments indicated the rising activity of the tetra-alkyl(benzyl) ammonium alkoxides as the lipophilicity of the anion increased, which proceeds in the organic phase. Reaction was effected through a complex formed by the association of quaternary ammonium salts with a hydroxyl-containing compound, the solvation of the associated species with the organochlorine substrate, and coordination with NaOH. The reaction goes in the organic phase and on the interphase surface.

  10. Direct Access to Functional (Meth)acrylate Copolymers through Transesterification with Lithium Alkoxides.

    PubMed

    Fleischmann, Carolin; Anastasaki, Athina; Gutekunst, Will R; McGrath, Alaina J; Hustad, Phillip D; Clark, Paul G; Laitar, David S; Hawker, Craig J

    2017-05-01

    A straightforward and efficient synthetic method that transforms poly(methyl methacrylate) (PMMA) into value-added materials is presented. Specifically, PMMA is modified by transesterification to produce a variety of functional copolymers from a single starting material. Key to the reaction is the use of lithium alkoxides, prepared by treatment of primary alcohols with LDA, to displace the methyl esters. Under optimized conditions, up to 65% functionalization was achieved and copolymers containing alkyl, alkene, alkyne, benzyl, and (poly)ether side groups could be prepared. The versatility of this protocol was further demonstrated through the functionalization of both PMMA homo and block copolymers obtained through either radical polymerization (traditional and controlled) or anionic procedures. The scope of this strategy was illustrated by extension to a range of architectures and polymer backbones.

  11. Templates, Numbers & Watercolors.

    ERIC Educational Resources Information Center

    Clemesha, David J.

    1990-01-01

    Describes how a second-grade class used large templates to draw and paint five-digit numbers. The lesson integrated artistic knowledge and vocabulary with their mathematics lesson in place value. Students learned how draftspeople use templates, and they studied number paintings by Charles Demuth and Jasper Johns. (KM)

  12. Templates, Numbers & Watercolors.

    ERIC Educational Resources Information Center

    Clemesha, David J.

    1990-01-01

    Describes how a second-grade class used large templates to draw and paint five-digit numbers. The lesson integrated artistic knowledge and vocabulary with their mathematics lesson in place value. Students learned how draftspeople use templates, and they studied number paintings by Charles Demuth and Jasper Johns. (KM)

  13. Three dimensional mesoporous silica strucutres with templated macropores

    NASA Astrophysics Data System (ADS)

    Kothari, Rohit; Hendricks, Nicholas R.; Watkins, James J.

    2013-03-01

    A novel approach to fabricate three dimensional macroporous structures comprised of mesoporous silica is demonstrated. Well-ordered mesoporous silica structures with macroporosity were obtained by using humidified supercritical carbon dioxide as a carrier medium to infuse and domain selectively condense silica alkoxide precursor in a microphase separated block copolymer/small molecule additive blend solution casted on macroporous supports such as cellulose filter paper and sponge. Subsequent calcination was used to remove both the block copolymer template and the macroporous support. Transition electron microscopy (TEM) and small angle x-ray diffraction (SAXD) confirmed the presence of well-ordered mesopores. Scanning electron microscopy confirmed faithful replication of the features of the macroporous supports. Physisorption showed BET surface areas as high as 400m2/g and the BJH pore size distributions obtained are in close agreement with the TEM and SAXD results. This dual scale porosity within the silica template will enhance overall transport and diffusion, which is appropriate for many applications including catalysis and sensing.

  14. Different mechanisms at different temperatures for the ring-opening polymerization of lactide catalyzed by binuclear magnesium and zinc alkoxides.

    PubMed

    Sun, Yangyang; Cui, Yaqin; Xiong, Jiao; Dai, Zhongran; Tang, Ning; Wu, Jincai

    2015-10-07

    Two binuclear magnesium and zinc alkoxides supported by a bis-salalen type dinucleating heptadentate Schiff base ligand were synthesized and fully characterized. The two complexes are efficient initiators for the ring-opening polymerization (ROP) of L-lactide, affording polymers with narrow polydispersities and desirable molecular weights. Interestingly, the mechanisms for the ROP of lactide are different at different temperatures. At a high temperature of 130 °C, a coordination-insertion mechanism is reasonable for the bulk melt polymerization of lactide. At a low temperature, the alkoxide cannot initiate the ROP reaction; however, upon the addition of external benzyl alcohol into the system, the ROP of lactide can smoothly proceed via an "activated monomer" mechanism. In addition, these complexes display slight stereo-selectivity for the ring-opening polymerization of rac-lactide, affording partially isotactic polylactide in toluene with a Pm value of 0.59.

  15. Using bacterial cell growth to template catalytic asymmetry.

    PubMed

    Kaehr, Bryan; Brinker, C Jeffrey

    2010-08-07

    We report an approach to position gold nanoparticle catalysts for metal reduction asymmetrically on a biological template (E. coli) by exploiting the polarity of the bacterial cell envelope undergoing growth and division.

  16. Molecular Level Coating of Metal Oxide Particles

    NASA Technical Reports Server (NTRS)

    McDaniel, Patricia R. (Inventor); St.Clair, Terry L. (Inventor)

    2002-01-01

    Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar osmotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing, synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper. making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

  17. Molecular Level Coating for Metal Oxide Particles

    NASA Technical Reports Server (NTRS)

    McDaniel, Patricia R. (Inventor); Saint Clair, Terry L. (Inventor)

    2000-01-01

    Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar aprotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper, making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

  18. Molecular Level Coating of Metal Oxide Particles

    NASA Technical Reports Server (NTRS)

    McDaniel, Patricia R. (Inventor); St.Clair, Terry L. (Inventor)

    2002-01-01

    Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar osmotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing, synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper. making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

  19. Strong influence of polymer architecture on the microstructural evolution of hafnium-alkoxide-modified silazanes upon ceramization.

    PubMed

    Papendorf, Benjamin; Nonnenmacher, Katharina; Ionescu, Emanuel; Kleebe, Hans-Joachim; Riedel, Ralf

    2011-04-04

    The present study focuses on the synthesis and ceramization of novel hafnium-alkoxide-modified silazanes as well as on their microstructure evolution at high temperatures. The synthesis of hafnia-modified polymer-derived SiCN ceramic nanocomposites is performed via chemical modification of a polysilazane and of a cyclotrisilazane, followed by cross-linking and pyrolysis in argon atmosphere. Spectroscopic investigation (i.e., NMR, FTIR, and Raman) shows that the hafnium alkoxide reacts with the N-H groups of the cyclotrisilazane; in the case of polysilazane, reactions of N-H as well as Si-H groups with the alkoxide are observed. Consequently, scanning and transmission electron microscopy studies reveal that the ceramic nanocomposites obtained from cyclotrisilazane and polysilazane exhibited markedly different microstructures, which is a result of the different reaction pathways of the hafnium alkoxide with cyclotrisilazane and with polysilazane. Furthermore, the two prepared ceramic nanocomposites are unexpectedly found to exhibit extremely different high-temperature behavior with respect to decomposition and crystallization; this essential difference is found to be related to the different distribution of hafnium throughout the ceramic network in the two samples. Thus, the homogeneous distribution of hafnium observed in the polysilazane-derived ceramic leads to an enhanced thermal stability with respect to decomposition, whereas the local enrichment of hafnium within the matrix of the cyclotrisilazane-based sample induces a pronounced decomposition upon annealing at high temperatures. The results indicate that the chemistry and architecture of the precursor has a crucial effect on the microstructure of the resulting ceramic material and consequently on its high-temperature behavior. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Bridged bis(amidinate) ytterbium alkoxide and phenoxide: syntheses, structures, and their high activity for controlled polymerization of L-lactide and epsilon-caprolactone.

    PubMed

    Wang, Junfeng; Yao, Yingming; Zhang, Yong; Shen, Qi

    2009-01-19

    Bridged bis(amidinate) ytterbium alkoxide and phenoxide with diverse molecular structures were synthesized in high yields and confirmed by X-ray crystal structural analysis. The reaction of LYbCl(THF)(2) (L = Me(3)SiNC(Ph)N(CH(2))(3)NC(Ph)NSiMe(3)) with 1 equiv of NaOAr (ArO = 2,6-diisopropylphenoxo) afforded the mononuclear complex LYb(OAr)DME 1 with a seven-coordinated ytterbium atom surrounded by one chelating bis(amidinate) ligand, one phenoxo group, and one DME (dimethoxyethane) molecule. The same reaction with 1 equiv of NaO(i)Pr yielded the binuclear complex Yb(mu(2)-L)(2)(mu(2)-O(i)Pr)(2)Yb, 2, with two equivalent six-coordinate metal centers connected by two linked bis(amidinate)s and two O(i)Pr bridges formed via a ligand redistribution reaction that occurred during the metathesis reaction. Both 1 and 2 initiated the ring-opening polymerization of L-lactide, as well as epsilon-caprolactone (epsilon-CL), in a controlled manner with high reactivity, as indicated by a linear relationship between M(n) and conversion and by narrow molecular weight distributions (PDI = 1.15-1.25) up to 100% conversion. The differences in catalytic performance between complexes 1 and 2 are discussed.

  1. Electrochemical synthesis, structural characterization, and decomposition of rhenium oxoethoxide, Re4O4(OEt)12. Ligand influence on the structure and bonding in the high-valent tetranuclear planar rhenium alkoxide clusters.

    PubMed

    Nikonova, Olesya A; Jansson, Kjell; Kessler, Vadim G; Sundberg, Margareta; Baranov, Alexei I; Shevelkov, Andrei V; Drobot, Dmitrii V; Seisenbaeva, Gulaim A

    2008-02-18

    Anodic oxidation of rhenium in ethanol in the presence of LiCl as a conductive additive results with high yield in formation of a new oxoethoxide cluster, Re(4)O(4)(OEt)(12). The structure of the planar centrosymmetric metal-oxygen core of this molecule is composed of four edge-sharing Re(V)O(6) octahedra. Eight electrons are available for the formation of metal-metal bonds indicated by five relatively short Re-Re distances within the Re 4-rhombus, a "planar butterfly" type cluster. The theoretical calculations are indicating relatively low contribution of metal-metal bonding in the stability of the core. The stability of the +V-oxidation state, unusual for rhenium alkoxides can be at least partially attributed to the size effects in the packing of ligands. The X-ray powder study indicates that treatment of Re(4)O(4)(OEt)(12). in ambient atmosphere rapidly transforms it into a mixed-valence derivative Re(4)O(6)(OEt)(10) with a structure related to the earlier investigated cluster Re(4)O(6)(O(i)Pr)(10). Thermal decomposition of the latter rhenium oxoethoxide results in reduction to rhenium metal at as low temperatures as 380 degrees C, producing aggregates of metal nanoparticles with the average size of 3 nm.

  2. Ice-templated synthesis of multifunctional three dimensional graphene/noble metal nanocomposites and their mechanical, electrical, catalytic, and electromagnetic shielding properties

    PubMed Central

    Sahoo, P. K.; Aepuru, Radhamanohar; Panda, Himanshu Sekhar; Bahadur, D.

    2015-01-01

    In-situ homogeneous dispersion of noble metals in three-dimensional graphene sheets is a key tactic for producing macroscopic architecture, which is desirable for practical applications, such as electromagnetic interference shielding and catalyst. We report a one-step greener approach for developing porous architecture of 3D-graphene/noble metal (Pt and Ag) nanocomposite monoliths. The resulting graphene/noble metal nanocomposites exhibit a combination of ultralow density, excellent elasticity, and good electrical conductivity. Moreover, in order to illuminate the advantages of the 3D-graphene/noble metal nanocomposites, their electromagnetic interference (EMI) shielding and electrocatalytic performance are further investigated. The as-synthesized 3D-graphene/noble metal nanocomposites exhibit excellent EMI shielding effectiveness when compared to bare graphene; the effectiveness has an average of 28 dB in the 8.2–12.4 GHz X-band range. In the electro-oxidation of methanol, the 3D-graphene/Pt nanocomposite also exhibits significantly enhanced electrocatalytic performance and stability than compared to reduced graphene oxide/Pt and commercial Pt/C. PMID:26638827

  3. DNA-templated nickel nanostructures and protein assemblies.

    PubMed

    Becerril, Hector A; Ludtke, Paul; Willardson, Barry M; Woolley, Adam T

    2006-11-21

    We report a straightforward method for the fabrication of DNA-templated nickel nanostructures on surfaces. These nickel nanomaterials have potential to be applied as nanowires, as templated catalyst lines, as nanoscale magnetic domains, or in directed protein localization. Indeed, we show here that histidine-tagged phosducin-like protein (His-PhLP) binds with high selectivity to both Ni2+-treated surface DNA and DNA-templated nickel metal to create linear protein assemblies on surfaces. The association of His-PhLP with DNA-templated nickel ions or metal is reversible under appropriate rinsing conditions. Nanoscale DNA-templated protein assemblies might be useful in the construction of high-density protein lines for proteomic analysis, for example. Importantly, these nanofabrication procedures are not limited to linear DNA and can be applied readily to other self-assembled DNA topologies.

  4. Templates for Deposition of Microscopic Pointed Structures

    NASA Technical Reports Server (NTRS)

    Pugel, Diane E.

    2008-01-01

    Templates for fabricating sharply pointed microscopic peaks arranged in nearly regular planar arrays can be fabricated by a relatively inexpensive technique that has recently been demonstrated. Depending on the intended application, a semiconducting, insulating, or metallic film could be deposited on such a template by sputtering, thermal evaporation, pulsed laser deposition, or any other suitable conventional deposition technique. Pointed structures fabricated by use of these techniques may prove useful as photocathodes or field emitters in plasma television screens. Selected peaks could be removed from such structures and used individually as scanning tips in atomic force microscopy or mechanical surface profiling.

  5. E3 Charter Template

    EPA Pesticide Factsheets

    This is a charter template which includes decisions made during the project planning phase, as well as local project goals, a communication strategy, an outreach strategy, distribution of responsibilities and a schedule.

  6. A fast template periodogram

    NASA Astrophysics Data System (ADS)

    Hoffman, John; VanderPlas, Jake; Hartman, Joel; Bakos, Gáspár

    2017-09-01

    This proceedings contribution presents a novel, non-linear extension to the Lomb-Scargle periodogram that allows periodograms to be generated for arbitrary signal shapes. Such periodograms are already known as "template periodograms" or "periodic matched filters," but current implementations are computationally inefficient. The "fast template periodogram" presented here improves existing techniques by a factor of ˜a few for small test cases (O(10) observations), and over three orders of magnitude for lightcurves containing O(104) observations. The fast template periodogram scales asymptotically as O(HNf log HNf + H4Nf), where H denotes the number of harmonics required to adequately approximate the template and Nf is the number of trial frequencies. Existing implementations scale as O(NobsNf), where Nobs is the number of observations in the lightcurve. An open source Python implementation is available on GitHub.

  7. Optimizing ultrathin Ag films for high performance oxide-metal-oxide flexible transparent electrodes through surface energy modulation and template-stripping procedures

    NASA Astrophysics Data System (ADS)

    Yang, Xi; Gao, Pingqi; Yang, Zhenhai; Zhu, Juye; Huang, Feng; Ye, Jichun

    2017-03-01

    Among new flexible transparent conductive electrode (TCE) candidates, ultrathin Ag film (UTAF) is attractive for its extremely low resistance and relatively high transparency. However, the performances of UTAF based TCEs critically depend on the threshold thickness for growth of continuous Ag films and the film morphologies. Here, we demonstrate that these two parameters could be strongly altered through the modulation of substrate surface energy. By minimizing the surface energy difference between the Ag film and substrate, a 9 nm UTAF with a sheet resistance down to 6.9 Ω sq‑1 can be obtained using an electron-beam evaporation process. The resultant UTAF is completely continuous and exhibits smoother morphologies and smaller optical absorbances in comparison to the counterpart of granular-type Ag film at the same thickness without surface modulation. Template-stripping procedure is further developed to transfer the UTAFs to flexible polymer matrixes and construct Al2O3/Ag/MoOx (AAM) electrodes with excellent surface morphology as well as optical and electronic characteristics, including a root-mean-square roughness below 0.21 nm, a transparency up to 93.85% at 550 nm and a sheet resistance as low as 7.39 Ω sq‑1. These AAM based electrodes also show superiority in mechanical robustness, thermal oxidation stability and shape memory property.

  8. Optimizing ultrathin Ag films for high performance oxide-metal-oxide flexible transparent electrodes through surface energy modulation and template-stripping procedures.

    PubMed

    Yang, Xi; Gao, Pingqi; Yang, Zhenhai; Zhu, Juye; Huang, Feng; Ye, Jichun

    2017-03-14

    Among new flexible transparent conductive electrode (TCE) candidates, ultrathin Ag film (UTAF) is attractive for its extremely low resistance and relatively high transparency. However, the performances of UTAF based TCEs critically depend on the threshold thickness for growth of continuous Ag films and the film morphologies. Here, we demonstrate that these two parameters could be strongly altered through the modulation of substrate surface energy. By minimizing the surface energy difference between the Ag film and substrate, a 9 nm UTAF with a sheet resistance down to 6.9 Ω sq(-1) can be obtained using an electron-beam evaporation process. The resultant UTAF is completely continuous and exhibits smoother morphologies and smaller optical absorbances in comparison to the counterpart of granular-type Ag film at the same thickness without surface modulation. Template-stripping procedure is further developed to transfer the UTAFs to flexible polymer matrixes and construct Al2O3/Ag/MoOx (AAM) electrodes with excellent surface morphology as well as optical and electronic characteristics, including a root-mean-square roughness below 0.21 nm, a transparency up to 93.85% at 550 nm and a sheet resistance as low as 7.39 Ω sq(-1). These AAM based electrodes also show superiority in mechanical robustness, thermal oxidation stability and shape memory property.

  9. Optimizing ultrathin Ag films for high performance oxide-metal-oxide flexible transparent electrodes through surface energy modulation and template-stripping procedures

    PubMed Central

    Yang, Xi; Gao, Pingqi; Yang, Zhenhai; Zhu, Juye; Huang, Feng; Ye, Jichun

    2017-01-01

    Among new flexible transparent conductive electrode (TCE) candidates, ultrathin Ag film (UTAF) is attractive for its extremely low resistance and relatively high transparency. However, the performances of UTAF based TCEs critically depend on the threshold thickness for growth of continuous Ag films and the film morphologies. Here, we demonstrate that these two parameters could be strongly altered through the modulation of substrate surface energy. By minimizing the surface energy difference between the Ag film and substrate, a 9 nm UTAF with a sheet resistance down to 6.9 Ω sq−1 can be obtained using an electron-beam evaporation process. The resultant UTAF is completely continuous and exhibits smoother morphologies and smaller optical absorbances in comparison to the counterpart of granular-type Ag film at the same thickness without surface modulation. Template-stripping procedure is further developed to transfer the UTAFs to flexible polymer matrixes and construct Al2O3/Ag/MoOx (AAM) electrodes with excellent surface morphology as well as optical and electronic characteristics, including a root-mean-square roughness below 0.21 nm, a transparency up to 93.85% at 550 nm and a sheet resistance as low as 7.39 Ω sq−1. These AAM based electrodes also show superiority in mechanical robustness, thermal oxidation stability and shape memory property. PMID:28291229

  10. A Pyridine Alkoxide Chelate Ligand That Promotes Both Unusually High Oxidation States and Water-Oxidation Catalysis.

    PubMed

    Michaelos, Thoe K; Shopov, Dimitar Y; Sinha, Shashi Bhushan; Sharninghausen, Liam S; Fisher, Katherine J; Lant, Hannah M C; Crabtree, Robert H; Brudvig, Gary W

    2017-03-08

    Water-oxidation catalysis is a critical bottleneck in the direct generation of solar fuels by artificial photosynthesis. Catalytic oxidation of difficult substrates such as water requires harsh conditions, so the ligand must be designed both to stabilize high oxidation states of the metal center and to strenuously resist ligand degradation. Typical ligand choices either lack sufficient electron donor power or fail to stand up to the oxidizing conditions. Our research on Ir-based water-oxidation catalysts (WOCs) has led us to identify a ligand, 2-(2'-pyridyl)-2-propanoate or "pyalk", that fulfills these requirements. Work with a family of Cp*Ir(chelate)Cl complexes had indicated that the pyalk-containing precursor gave the most robust WOC, which was still molecular in nature but lost the Cp* fragment by oxidative degradation. In trying to characterize the resulting active "blue solution" WOC, we were able to identify a diiridium(IV)-mono-μ-oxo core but were stymied by the extensive geometrical isomerism and coordinative variability. By moving to a family of monomeric complexes [Ir(III/IV)(pyalk)3] and [Ir(III/IV)(pyalk)2Cl2], we were able to better understand the original WOC and identify the special properties of the ligand. In this Account, we cover some results using the pyalk ligand and indicate the main features that make it particularly suitable as a ligand for oxidation catalysis. The alkoxide group of pyalk allows for proton-coupled electron transfer (PCET) and its strong σ- and π-donor power strongly favors attainment of exceptionally high oxidation states. The aromatic pyridine ring with its methyl-protected benzylic position provides strong binding and degradation resistance during catalytic turnover. Furthermore, the ligand has two additional benefits: broad solubility in aqueous and nonaqueous solvents and an anisotropic ligand field that enhances the geometry-dependent redox properties of its complexes. After discussion of the general properties, we

  11. Synthesis of metal oxide nanoparticles (CuO and ZnO NPs) via biological template and their optical sensor applications

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthuchamy; Zuo, Yong; Chen, Jing-Shuai; Song, Ji-Ming; Niu, He-Lin; Mao, Chang-Jie; Zhang, Sheng-Yi; Shen, Yu-Hua

    2017-03-01

    The present study is focused on employing Camellia japonica leaf extract as inductive and stabilizing agent to synthesis CuO and ZnO nanoparticles (NPs). The chemicals, such as (Cu(NO3)2·3H2O) and (Zn(NO3)2·6H2O) were converted into copper and zinc ions, respectively because of the different natural products present in the C. japonica leaf extract. The UV-vis spectra of CuO and ZnO NPs showed absorption peak at 290 nm and 301 nm, respectively. The XRD result revealed crystalline nature of the metal oxide NPs and the TEM images indicated that average sizes of the synthesized CuO and ZnO NPs were ∼17 nm and ∼20 nm, respectively. The FTIR spectra of C. japonica leaf extract showed the presence of organic groups, such as, sbnd OH, sbnd Csbnd N, and N-H, which would be responsible for forming CuO and ZnO NPs. The synthesized CuO and ZnO NPs were tested for the optical sensing of metal ions, viz. Li+ and Ag+ that illustrated excellent outcome and hence this method offers a novel lane for the synthesis of metal oxide NPs, which can be used as optical sensor for the detection of metal ions.

  12. Synthesis and thermal evolution of structure in alkoxide-derived niobium pentoxide gels

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1993-01-01

    Niobium pentoxide gels in the form of transparent monoliths and powder have been synthesized from the controlled hydrolysis and polycondensation of niobium pentaethoxide under different experimental conditions using various mole ratios of Nb(OC2H5)5:H2O:C2H5OH:HCl. Alcohol acted as the mutual solvent and HCl as the deflocculating agent. In the absence of HCl, precipitation of colloidal particles was encountered on the addition of any water to the alkoxide. The gels were subjected to various thermal treatments and characterized by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. After drying at 400 C, the gels were amorphous to x-rays. The amorphous powder crystallized into the low-temperature orthorhombic form of Nb2O5 at approximately 500 C, which transformed irreversibly into the high-temperature monoclinic alpha-Nb2O5 between 900 to 1000 C. The kinetics of crystallization of the amorphous niobium pentoxide have been investigated by non-isothermal differential scanning calorimetry. The crystallization activation energy was determined to be 399 kJ/mol.

  13. A core-shell templated approach to the nanocomposites of silver sulfide and noble metal nanoparticles with hollow/cage-bell structures

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Ye, Feng; Cao, Hongbin; Ji, Ge; Lee, Jim Yang; Yang, Jun

    2013-07-01

    The integration of semiconductor and noble metal nanoparticles with controlled structures into a nanosystem can effectively couple various effects specific to the different domains of the nanocomposite for greater application versatility. Herein, we demonstrate the general synthesis of nanocomposites of Ag2S and noble metal nanoparticles with a hollow or cage-bell structure. The synthesis is based on the inside-out diffusion of Ag in core-shell nanoparticles. It begins with the preparation of core-shell Ag-M or core-shell-shell MA-Ag-MB nanoparticles in an organic solvent. The Ag is then removed from the core or from the internal shell and converted into Ag2S by elemental sulfur or sodium sulfide. The Ag2S forms the semiconductor domain in the nanocomposite and shares solid-state interfaces with the resultant hollow or cage-bell structured metal nanoparticle. The structural transformation from core-shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting physicochemical properties.The integration of semiconductor and noble metal nanoparticles with controlled structures into a nanosystem can effectively couple various effects specific to the different domains of the nanocomposite for greater application versatility. Herein, we demonstrate the general synthesis of nanocomposites of Ag2S and noble metal nanoparticles with a hollow or cage-bell structure. The synthesis is based on the inside-out diffusion of Ag in core-shell nanoparticles. It begins with the preparation of core-shell Ag-M or core-shell-shell MA-Ag-MB nanoparticles in an organic solvent. The Ag is then removed from the core or from the internal shell and converted into Ag2S by elemental sulfur or sodium sulfide. The Ag2S forms the semiconductor domain in the nanocomposite and shares solid-state interfaces with the resultant hollow or cage-bell structured metal nanoparticle. The structural transformation from core-shell to

  14. Are computer numerical control (CNC)-manufactured patient-specific metal templates available for posterior thoracic pedicle screw insertion? Feasibility and accuracy evaluation.

    PubMed

    Kong, Xiangxue; Tang, Lei; Ye, Qiang; Huang, Wenhua; Li, Jianyi

    2017-07-17

    Accurate and safe posterior thoracic pedicle insertion (PTPI) remains a challenge. Patient-specific drill templates (PDTs) created by rapid prototyping (RP) can assist in posterior thoracic pedicle insertion, but pose biocompatibility risks. The aims of this study were to develop alternative PDTs with computer numerical control (CNC) and assess their feasibility and accuracy in assisting PTPI. Preoperative CT images of 31 cadaveric thoracic vertebras were obtained and then the optimal pedicle screw trajectories were planned. The PDTs with optimal screw trajectories were randomly assigned to be designed and manufactured by CNC or RP in each vertebra. With the guide of the CNC- or RP-manufactured PDTs, the appropriate screws were inserted into the pedicles. Postoperative CT scans were performed to analyze any deviations at entry point and midpoint of the pedicles. The CNC group was found to be significant manufacture-time-shortening, and cost-decreasing, when compared with the RP group (P < 0.01). The PDTs fitted the vertebral laminates well while all screws were being inserted into the pedicles. There were no significant differences in absolute deviations at entry point and midpoint of the pedicle on either axial or sagittal planes (P > 0.05). The screw positions were grade 0 in 90.3% and grade 1 in 9.7% of the cases in the CNC group and grade 0 in 93.5% and grade 1 in 6.5% of the cases in the RP group (P = 0.641). CNC-manufactured PDTs are viable for assisting in PTPI with good feasibility and accuracy.

  15. Templated blue phases.

    PubMed

    Ravnik, Miha; Fukuda, Jun-ichi

    2015-11-21

    Cholesteric blue phases of a chiral liquid crystal are interesting examples of self-organised three-dimensional nanostructures formed by soft matter. Recently it was demonstrated that a polymer matrix introduced by photopolymerization inside a bulk blue phase not only stabilises the host blue phase significantly, but also serves as a template for blue phase ordering. We show with numerical modelling that the transfer of the orientational order of the blue phase to the surfaces of the polymer matrix, together with the resulting surface anchoring, can account for the templating behaviour of the polymer matrix inducing the blue phase ordering of an achiral nematic liquid crystal. Furthermore, tailoring the anchoring conditions of the polymer matrix surfaces can bring about orientational ordering different from those of bulk blue phases, including an intertwined complex of the polymer matrix and topological line defects of orientational order. Optical Kerr response of templated blue phases is explored, finding large Kerr constants in the range of K = 2-10 × 10(-9) m V(-2) and notable dependence on the surface anchoring strength. More generally, the presented numerical approach is aimed to clarify the role and actions of templating polymer matrices in complex chiral nematic fluids, and further to help design novel template-based materials from chiral liquid crystals.

  16. Heterometallic alkoxides of zirconium with tin(II) or lead(II)

    SciTech Connect

    Teff, D.J.; Huffman, J.C.; Caulton, K.G.

    1996-05-08

    Syntheses of SnZr(OR){sub 6} (R = {sup i}Pr, {sup t}Bu) and PbZr(O{sup t}Bu){sub 6} are described. With Pb and the smaller ligand O{sup i}Pr, no 1:1 compound forms, but instead Pb{sub 4}Zr{sub 2}(O{sup i}Pr){sub 16} and Pb{sub 2}Zr{sub 4}(O{sup i}Pr){sub 20} are isolated. The latter two compounds are shown to have serpentine (not closo) structures with six-coordinate Zr and three- and four-coordinate Pb. Spectroscopic studies show fluxionality (including Pb site exchange) and retention of structure in aromatic solvents. Synthetic interconversions are effected with addition of the appropriate alkoxide (Pb(O{sup i}Pr){sub 2} or Zr(O{sup i}Pr){sub 4}) with the correct stoichiometry. Titanium forms no analogous compounds. Crystallographic data (both P2{sub 1}/c at {minus}174{degrees}C) for Pb{sub 4}Zr{sub 2}(O{sup i}Pr){sub 16}, a = 12.190(6) {angstrom}, b = 14.701(7) {angstrom}, c = 19.978(13) {angstrom}, and {beta} = 105.57(3){degrees} with Z = 2; for Pb{sub 2}Zr{sub 4}(O{sup i}Pr){sub 20}, {alpha} = 16.996(6) {angstrom}, b = 10.014(3) {angstrom}, c = 24.924(9) {angstrom}, and {beta} = 105.86(1){degrees} with Z = 2.

  17. Preparation of zirconia coatings by hydrolysis of zirconium alkoxide with hydrogen peroxide

    SciTech Connect

    Sakurai, Chihiro; Fukui, Toshimi; Okuyama, Masahiko )

    1993-04-01

    Zirconia has gained a great deal of attention because of its superior properties of mechanical strength, chemical resistance, and ionic conductivity. Zirconia coatings and thin films are receiving attention as tribological and thermal barrier coatings for engines, high-reflective coatings, solid electrolytes for fuel cells, oxygen sensors, etc. The sol-gel coating method has several advantages, such as low processing temperatures, homogeneity, control of micro-structure, and good productivity compared to chemical vapor deposition and physical vapor deposition. However, there are few reports concerning the preparation of zirconia coatings and thin films by the sol-gel method. Up to the present, zirconia coatings have been prepared from zirconium propoxide (not heated), zirconium tetrabutoxide modified by acetylacetone and ethyl acetoacetate, zirconium diethoxydichloride (ZrCl[sub 2](OC[sub 2]H[sub 5])[sub 2]), and a hydrosol prepared from a zirconium oxychloride solution. Coatings of 8.8-mol%-yttria-doped zirconia were fabricated using a transparent and spinnable sol prepared by hydrolysis of zirconium alkoxide with hydrogen peroxide and nitric acid. The sol gave a crack-free coating film consisting of fine grains. The crystalline phase was cubic after heating of 1,000 and 1,200 C and cubic and tetragonal at 1,350 C, with the coating being highly oriented in the (111) plane, especially at 1,000 C. Activation energy of the coating films was higher than that of the bulk. Transmittance through a film thickness of about 0.3 [mu]m on each side was 75%.

  18. Synthesis of High Surface Area Alumina Aerogels without the Use of Alkoxide Precursors

    SciTech Connect

    Baumann, T F; Gash, A E; Chinn, S C; Sawvel, A M; Maxwell, R S; Satcher Jr., J H

    2004-06-25

    Alumina aerogels were prepared through the addition of propylene oxide to aqueous or ethanolic solutions of hydrated aluminum salts, AlCl{sub 3} {center_dot} 6H{sub 2}O or Al(NO{sub 3}){sub 3} {center_dot} 9H{sub 2}O, followed by drying with supercritical CO{sub 2}. This technique affords low-density (60-130 kg/m{sup 3}), high surface area (600-700 m{sup 2}/g) alumina aerogel monoliths without the use of alkoxide precursors. The dried alumina aerogels were characterized using elemental analysis, high-resolution transmission electron microscopy, powder X-ray diffraction, solid state NMR, acoustic measurements and nitrogen adsorption/desorption analysis. Powder X-ray diffraction and TEM analysis indicated that the aerogel prepared from hydrated AlCl{sub 3} in water or ethanol possessed microstructures containing highly reticulated networks of pseudoboehmite fibers, 2-5 nm in diameter and of varying lengths, while the aerogels prepared from hydrated Al(NO{sub 3}){sub 3} in ethanol were amorphous with microstructures comprised of interconnected spherical particles with diameters in the 5-15 nm range. The difference in microstructure resulted in each type of aerogel displaying distinct physical and mechanical properties. In particular, the alumina aerogels with the weblike microstructure were far more mechanically robust than those with the colloidal network, based on acoustic measurements. Both types of alumina aerogels can be transformed to {gamma}-Al{sub 2}O{sub 3} through calcination at 800 C without a significant loss in surface area or monolithicity.

  19. Synthesis, Radical Reactivity, and Thermochemistry of Monomeric Cu(II) Alkoxide Complexes Relevant to Cu/Radical Alcohol Oxidation Catalysis.

    PubMed

    Porter, Thomas R; Capitao, Dany; Kaminsky, Werner; Qian, Zhaoshen; Mayer, James M

    2016-06-06

    Two new monomeric Cu(II) alkoxide complexes were prepared and fully characterized as models for intermediates in copper/radical mediated alcohol oxidation catalysis: Tp(tBuR)Cu(II)OCH2CF3 with Tp(tBu) = hydro-tris(3-tert-butyl-pyrazol-1-yl)borate 1 or Tp(tBuMe) = hydro-tris(3-tert-butyl-5-methyl-pyrazol-1-yl)borate 2. These complexes were made as models for potential intermediates in enzymatic and synthetic catalytic cycles for alcohol oxidation. However, the alkoxide ligands are not readily oxidized by loss of H; instead, these complexes were found to be hydrogen atom acceptors. They oxidize the hydroxylamine TEMPOH, 2,4,6-tri-t-butylphenol, and 1,4-cyclohexadiene to the nitroxyl radical, phenoxyl radical, and benzene, with formation of HOCH2CF3 (TFE) and the Cu(I) complexes Tp(tBuR)Cu(I)-MeCN in dichloromethane/1% MeCN or 1/2 [Tp(tBuR)Cu(I)]2 in toluene. On the basis of thermodynamics and kinetics arguments, these reactions likely proceed through concerted proton-electron transfer mechanisms. Thermochemical analyses give lower limits for the "effective bond dissociation free energies (BDFE)" of the O-H bonds in 1/2[Tp(tBuR)Cu(I)]2 + TFE and upper limits for the free energies associated with alkoxide oxidations via hydrogen atom transfer (effective alkoxide α-C-H BDFEs). These values are summations of the free energies of multiple chemical steps, which include the energetically favorable formation of 1/2[Tp(tBuR)Cu(I)]2. The effective alkoxide α-C-H bonds are very weak, BDFE ≤ 38 ± 4 kcal mol(-1) for 1 and ≤44 ± 5 kcal mol(-1) for 2 (gas-phase estimates), because C-H homolysis is thermodynamically coupled to one electron transfer to Cu(II) as well as the favorable formation of the 1/2[Tp(tBuR)Cu(I)]2 dimer. Treating 1 with the H atom acceptor (t)Bu3ArO(•) did not result in the expected alkoxide oxidation to an aldehyde, but rather net 2,2,2-trifluoroethoxyl radical transfer occurred to generate an unusual 2-substituted dienone-ether product. Treating 2

  20. Large Area Nano-transfer Printing of Sub-50-nm Metal Nanostructures Using Low-cost Semi-flexible Hybrid Templates.

    PubMed

    Nagel, Robin D; Haeberle, Tobias; Schmidt, Morten; Lugli, Paolo; Scarpa, Giuseppe

    2016-12-01

    In this work, we present a method for printing metal micro- and nanopatterns down to sub-50-nm feature sizes using replicated, defect-tolerant stamps made out of OrmoStamp®; material. The relevant parameters for a successful transfer over large areas were investigated and yields above 99 % have been achieved. Comparing our results to conventional nano-transfer printing using PDMS stamps, we find that the more rigid hybrid polymer used here prevents unintended transfer from interspaces between structures of large distance due to roof collapse and deformation of nano-sized structures due to lateral collapse. Yet, our stamps are flexible enough to ensure intimate contact with the underlying substrate over large areas even in the presence of defect particles. Additionally, the presented patterning technique is resist-, solvent-, and chemical-free and is therefore ideally suited for applications in organic nanoelectronics where standard nanostructuring methods can harm or destroy the organic material.

  1. The Investigation of Intermediate Stage of Template Etching with Metal Droplets by Wetting Angle Analysis on (001) GaAs Surface.

    PubMed

    Lyamkina, A A; Dmitriev, D V; Galitsyn, Yu G; Kesler, V G; Moshchenko, S P; Toropov, A I

    2011-12-01

    In this work, we study metal droplets on a semiconductor surface that are the initial stage for both droplet epitaxy and local droplet etching. The distributions of droplet geometrical parameters such as height, radius and volume help to understand the droplet formation that strongly influences subsequent nanohole etching. To investigate the etching and intermixing processes, we offer a new method of wetting angle analysis. The aspect ratio that is defined as the ratio of the height to radius was used as an estimation of wetting angle which depends on the droplet material. The investigation of the wetting angle and the estimation of indium content revealed significant materials intermixing during the deposition time. AFM measurements reveal the presence of two droplet groups that is in agreement with nanohole investigations. To explain this observation, we consider arsenic evaporation and consequent change in the initial substrate. On the basis of our analysis, we suggest the model of droplet evolution and the formation of two droplet groups.

  2. Bis(phosphinic)diamido yttrium amide, alkoxide, and aryloxide complexes: an evaluation of lactide ring-opening polymerization initiator efficiency.

    PubMed

    Platel, Rachel H; White, Andrew J P; Williams, Charlotte K

    2011-08-15

    The synthesis and characterization of a series of bis(phosphinic)diamido yttrium alkoxide, amide, and aryloxide initiators are reported. The new complexes are characterized using multinuclear nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and, in some cases, X-ray crystallography. The alkoxide complexes are all dimeric in both the solid state and in solution, as are the amide complexes substituted with iso-propyl or phenyl groups on the phosphorus atoms. On the other hand, increasing the steric hindrance of the phosphorus substituents (tert-butyl), enables isolation of mononuclear yttrium amide complexes with either 2,2-dimethylpropylene or ethylene diamido ligand backbones. The complex of 2,6-di-tert-butyl-4-methylphenoxide is also mononuclear. All the new complexes are efficient initiators for rac-lactide ring-opening polymerization. The polymerization kinetics are compared and pseudo first order rate constants, k(obs), determined. The polymerization control is also discussed, by monitoring the number-averaged molecular weight, M(n), and polydispersity index, PDI, obtained using gel permeation chromatography (GPC). The alkoxide complexes are the most efficient initiators, showing very high rates and good polymerization control, behavior consistent with rapid rates of initiation. The phenoxide and amide complexes are less efficient as manifest by nonlinear regions in the kinetic plots, lower values for k(obs), and reduced polymerization control. One of the mononuclear yttrium amide complexes shows heteroselectivity in the polymerization of rac-lactide; however, this effect is reduced on changing the initiating group to phenoxide or on changing the ancillary ligand diamido backbone group.

  3. Effects of alkoxide addition on the electrochemical deposition and dissolution in triglyme-based solution dissolving magnesium bis(trifluoromethanesulfonyl)amide

    NASA Astrophysics Data System (ADS)

    Kim, In-Tae; Yamabuki, Kazuhiro; Morita, Masayuki; Tsutsumi, Hiromori; Yoshimoto, Nobuko

    2015-03-01

    Electrochemical deposition and dissolution of magnesium (Mg) has been examined in triethylene glycol dimethyl ether (triglyme, G3) dissolving magnesium bis(triflouromethanesulfonyl)amide, Mg(TFSA)2. The voltammetric current responses at platinum (Pt) electrode in the G3-based electrolytes revealed that the Mg deposition/dissolution process depends on the Mg species in the solution phase. The addition of alkoxides, Mg(OCnH2n+1)2, was effective on the reversibility of the process in Mg(TFSA)2/G3. Higher anodic current corresponding to the electrochemical dissolution was observed in the electrolyte solution containing Mg(OC2H5)2 as the additive. The morphology of the Mg deposition at the Pt substrate also depended on the additive Mg-alkoxides. The resulting Mg(TFSA)2/G3 solutions containing Mg-alkoxides were found to be a possible electrolyte system for rechargeable Mg battery operating at ambient temperature.

  4. Biometric template revocation

    NASA Astrophysics Data System (ADS)

    Arndt, Craig M.

    2004-08-01

    Biometric are a powerful technology for identifying humans both locally and at a distance. In order to perform identification or verification biometric systems capture an image of some biometric of a user or subject. The image is then converted mathematical to representation of the person call a template. Since we know that every human in the world is different each human will have different biometric images (different fingerprints, or faces, etc.). This is what makes biometrics useful for identification. However unlike a credit card number or a password to can be given to a person and later revoked if it is compromised and biometric is with the person for life. The problem then is to develop biometric templates witch can be easily revoked and reissued which are also unique to the user and can be easily used for identification and verification. In this paper we develop and present a method to generate a set of templates which are fully unique to the individual and also revocable. By using bases set compression algorithms in an n-dimensional orthogonal space we can represent a give biometric image in an infinite number of equally valued and unique ways. The verification and biometric matching system would be presented with a given template and revocation code. The code will then representing where in the sequence of n-dimensional vectors to start the recognition.

  5. Design and Fabrication of a Precision Template for Spine Surgery Using Selective Laser Melting (SLM).

    PubMed

    Wang, Di; Wang, Yimeng; Wang, Jianhua; Song, Changhui; Yang, Yongqiang; Zhang, Zimian; Lin, Hui; Zhen, Yongqiang; Liao, Suixiang

    2016-07-22

    In order to meet the clinical requirements of spine surgery, this paper proposes the fabrication of the customized template for spine surgery through computer-aided design. A 3D metal printing-selective laser melting (SLM) technique was employed to directly fabricate the 316L stainless steel template, and the metal template with tiny locating holes was used as an auxiliary tool to insert spinal screws inside the patient's body. To guarantee accurate fabrication of the template for cervical vertebra operation, the contact face was placed upwards to improve the joint quality between the template and the cervical vertebra. The joint surface of the printed template had a roughness of Ra = 13 ± 2 μm. After abrasive blasting, the surface roughness was Ra = 7 ± 0.5 μm. The surgical metal template was bound with the 3D-printed Acrylonitrile Butadiene Styrene (ABS) plastic model. The micro-hardness values determined at the cross-sections of SLM-processed samples varied from HV0.3 250 to HV0.3 280, and the measured tensile strength was in the range of 450 MPa to 560 MPa, which showed that the template had requisite strength. Finally, the metal template was clinically used in the patient's surgical operation, and the screws were inserted precisely as the result of using the auxiliary template. The geometrical parameters of the template hole (e.g., diameter and wall thickness) were optimized, and measures were taken to optimize the key geometrical units (e.g., hole units) in metal 3D printing. Compared to the traditional technology of screw insertion, the use of the surgical metal template enabled the screws to be inserted more easily and accurately during spinal surgery. However, the design of the high-quality template should fully take into account the clinical demands of surgeons, as well as the advice of the designing engineers and operating technicians.

  6. Design and Fabrication of a Precision Template for Spine Surgery Using Selective Laser Melting (SLM)

    PubMed Central

    Wang, Di; Wang, Yimeng; Wang, Jianhua; Song, Changhui; Yang, Yongqiang; Zhang, Zimian; Lin, Hui; Zhen, Yongqiang; Liao, Suixiang

    2016-01-01

    In order to meet the clinical requirements of spine surgery, this paper proposes the fabrication of the customized template for spine surgery through computer-aided design. A 3D metal printing-selective laser melting (SLM) technique was employed to directly fabricate the 316L stainless steel template, and the metal template with tiny locating holes was used as an auxiliary tool to insert spinal screws inside the patient’s body. To guarantee accurate fabrication of the template for cervical vertebra operation, the contact face was placed upwards to improve the joint quality between the template and the cervical vertebra. The joint surface of the printed template had a roughness of Ra = 13 ± 2 μm. After abrasive blasting, the surface roughness was Ra = 7 ± 0.5 μm. The surgical metal template was bound with the 3D-printed Acrylonitrile Butadiene Styrene (ABS) plastic model. The micro-hardness values determined at the cross-sections of SLM-processed samples varied from HV0.3 250 to HV0.3 280, and the measured tensile strength was in the range of 450 MPa to 560 MPa, which showed that the template had requisite strength. Finally, the metal template was clinically used in the patient’s surgical operation, and the screws were inserted precisely as the result of using the auxiliary template. The geometrical parameters of the template hole (e.g., diameter and wall thickness) were optimized, and measures were taken to optimize the key geometrical units (e.g., hole units) in metal 3D printing. Compared to the traditional technology of screw insertion, the use of the surgical metal template enabled the screws to be inserted more easily and accurately during spinal surgery. However, the design of the high-quality template should fully take into account the clinical demands of surgeons, as well as the advice of the designing engineers and operating technicians. PMID:28773730

  7. Synthesis and chemistry of yttrium and lanthanide metal complexes

    SciTech Connect

    Evans, W.J.

    1991-09-01

    The objective of this research project is to determine the special features of complexes of yttrium and the lanthanide metals which will allow the design and synthesis of materials with unique chemical, physical, and catalytic properties. Past studies of yttrium and lanthanide metal alkyl and hydride complexes stabilized by cyclopentadienyl co-ligands have shown that a substantial, often singular, organometallic chemistry is available via these metals. More extensive utilization of the chemical opportunities available through yttrium and the lanthanides would be possible, however, if stabilizing ancillary ligand systems less sensitive to oxidation and protonolysis than cyclopentadienides could be developed. Alkoxide ligands are attractive in this regard and our recent research had focused on alkoxides and the special opportunities they can provide to these metals. 6 refs., 10 figs.

  8. Macroscopically Oriented Porous Materials with Periodic Ordered Structures: From Zeolites and Metal-Organic Frameworks to Liquid-Crystal-Templated Mesoporous Materials.

    PubMed

    Cho, Joonil; Ishida, Yasuhiro

    2017-07-01

    Porous materials with molecular-sized periodic structures, as exemplified by zeolites, metal-organic frameworks, or mesoporous silica, have attracted increasing attention due to their range of applications in storage, sensing, separation, and transformation of small molecules. Although the components of such porous materials have a tendency to pack in unidirectionally oriented periodic structures, such ideal types of packing cannot continue indefinitely, generally ceasing when they reach a micrometer scale. Consequently, most porous materials are composed of multiple randomly oriented domains, and overall behave as isotropic materials from a macroscopic viewpoint. However, if their channels could be unidirectionally oriented over a macroscopic scale, the resultant porous materials might serve as powerful tools for manipulating molecules. Guest molecules captured in macroscopically oriented channels would have their positions and directions well-defined, so that molecular events in the channels would proceed in a highly controlled manner. To realize such an ideal situation, numerous efforts have been made to develop various porous materials with macroscopically oriented channels. An overview of recent studies on the synthesis, properties, and applications of macroscopically oriented porous materials is presented. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Template engaged synthesis of hollow ceria-based composites

    NASA Astrophysics Data System (ADS)

    Chen, Guozhu; Rosei, Federico; Ma, Dongling

    2015-03-01

    Hollow ceria-based composites, which consist of noble metal nanoparticles or metal oxides as a secondary component, are being studied extensively for potential applications in heterogeneous catalysis. This is due to their unique features, which exhibit the advantages of a hollow structure (e.g. high surface area and low weight), and also integrate the properties of ceria and noble metals/metal oxides. More importantly, the synergistic effect between constituents in hollow ceria-based composites has been demonstrated in various catalytic reactions. In this feature article, we summarize the state-of-the-art in the synthesis of hollow ceria-based composites, including traditional hard-templates and more recently, sacrificial-template engaged strategies, highlighting the key role of selected templates in the formation of hollow composites. In addition, the catalytic applications of hollow ceria-based composites are briefly surveyed. Finally, challenges and perspectives on future advances of hollow ceria-based composites are outlined.

  10. Template engaged synthesis of hollow ceria-based composites.

    PubMed

    Chen, Guozhu; Rosei, Federico; Ma, Dongling

    2015-03-19

    Hollow ceria-based composites, which consist of noble metal nanoparticles or metal oxides as a secondary component, are being studied extensively for potential applications in heterogeneous catalysis. This is due to their unique features, which exhibit the advantages of a hollow structure (e.g. high surface area and low weight), and also integrate the properties of ceria and noble metals/metal oxides. More importantly, the synergistic effect between constituents in hollow ceria-based composites has been demonstrated in various catalytic reactions. In this feature article, we summarize the state-of-the-art in the synthesis of hollow ceria-based composites, including traditional hard-templates and more recently, sacrificial-template engaged strategies, highlighting the key role of selected templates in the formation of hollow composites. In addition, the catalytic applications of hollow ceria-based composites are briefly surveyed. Finally, challenges and perspectives on future advances of hollow ceria-based composites are outlined.

  11. Forward and reverse (retro) iron(III) or gallium(III) desferrioxamine E and ring-expanded analogues prepared using metal-templated synthesis from endo-hydroxamic acid monomers.

    PubMed

    Lifa, Tulip; Tieu, William; Hocking, Rosalie K; Codd, Rachel

    2015-04-06

    A metal-templated synthesis (MTS) approach was used to preorganize the forward endo-hydroxamic acid monomer 4-[(5-aminopentyl)(hydroxy)amino]-4-oxobutanoic acid (for-PBH) about iron(III) in a 1:3 metal/ligand ratio to furnish the iron(III) siderophore for-[Fe(DFOE)] (ferrioxamine E) following peptide coupling. Substitution of for-PBH with the reverse (retro) hydroxamic acid analogue 3-(6-amino-N-hydroxyhexanamido)propanoic acid (ret-PBH) furnished ret-[Fe(DFOE)] (ret-ferrioxamine E). As isomers, for-[Fe(DFOE)] and ret-[Fe(DFOE)] gave identical mass spectrometry signals ([M + H(+)](+), m/zcalc 654.3, m/zobs 654.3), yet for-[Fe(DFOE)] eluted in a more polar window (tR = 23.44 min) than ret-[Fe(DFOE)] (tR = 28.13 min) on a C18 reverse-phase high-performance liquid chromatography (RP-HPLC) column. for-[Ga(DFOE)] (tR = 22.99 min) and ret-[Ga(DFOE)] (tR = 28.11 min) were prepared using gallium(III) as the metal-ion template and showed the same trend for the retention time. Ring-expanded analogues of for-[Fe(DFOE)] and ret-[Fe(DFOE)] were prepared from endo-hydroxamic acid monomers with one additional methylene unit in the amine-containing region, 4-[(6-aminohexyl)(hydroxy)amino]-4-oxobutanoic acid (for-HBH) or 3-(7-amino-N-hydroxyheptanamido)propanoic acid (ret-HBH), to give the corresponding tris(homoferrioxamine E) macrocycles, for-[Fe(HHDFOE)] or ret-[Fe(HHDFOE)] ([M + H(+)](+), m/zcalc 696.3, m/zobs 696.4). The MTS reaction using a constitutional isomer of for-HBH that transposed the methylene unit to the carboxylic acid containing region, 5-[(5-aminopentyl)(hydroxy)amino]-5-oxopentanoic acid (for-PPH), gave the macrocycle for-[Fe(HPDFOE)] in a yield significantly less than that for for-[Fe(HHDFOE)], with the gallium(III) analogue for-[Ga(HPDFOE)] unable to be detected. The work demonstrates the utility and limits of MTS for the assembly of macrocyclic siderophores from endo-hydroxamic acid monomers. Indirect measures (RP-HPLC order of elution, c log P values

  12. Regioselective, Transition Metal-Free C-O Coupling Reactions Involving Aryne Intermediates.

    PubMed

    Dong, Yuyang; Lipschutz, Michael I; Tilley, T Don

    2016-04-01

    A new transition-metal-free synthetic method for C-O coupling between various aryl halides and alkoxides is described. This type of transformation is typically accomplished using palladium catalysts containing a specialized phosphine ligand. The reactions reported here can be performed under mild, ambient conditions using certain potassium alkoxides and a range of aryl halides, with iodide and bromide derivatives giving the best results. A likely mechanistic pathway involves the in situ generation of an aryne intermediate, and directing groups on the aryl ring inductively control regioselectivity.

  13. Mesostructured Metal Germanium Sulfide and Selenide Materials Based on the Tetrahedral [Ge 4S 10] 4- and [Ge 4Se 10] 4- Units: Surfactant Templated Three-Dimensional Disordered Frameworks Perforated with Worm Holes

    NASA Astrophysics Data System (ADS)

    Wachhold, Michael; Kasthuri Rangan, K.; Lei, Ming; Thorpe, M. F.; Billinge, Simon J. L.; Petkov, Valeri; Heising, Joy; Kanatzidis, Mercouri G.

    2000-06-01

    The polymerization of [Ge4S10]4- and [Ge4Se10]4- unit clusters with the divalent metal ions Zn2+, Cd2+, Hg2+, Ni2+, and Co2+ in the presence of various surfactant cations leads to novel mesostructured phases. The surfactants are the quaternary ammonium salts C12H25NMe3Br, C14H29NMe3Br, C16H33NMe3Br, and C18H37NMe3Br, which play the role of templates, helping to assemble a three-dimensional mesostructured metal-germanium chalcogenide framework. These materials are stoichiometric in nature and have the formula of (R-NMe3)2[MGe4Q10] (Q=S, Se). The local atomic structure was probed by X-ray diffuse scattering and pair distribution function analysis methods and indicates that the adamantane clusters stay intact while the linking metal atoms possess a tetrahedral coordination environment. A model can be derived, from the comparison of measured and simulated X-ray powder diffraction patterns, describing the structure as an amorphous three-dimensional framework consisting of adamantane [Ge4Q10]4- units that are bridged by tetrahedral coordinated M2+ cations. The network structures used in the simulations were derived from corresponding disordered structures developed for amorphous silicon. The frameworks in (R-NMe3)2[MGe4Q10] are perforated with worm hole-like tunnels, occupied by the surfactant cations, which show no long-range order. This motif is supported by transmission electron microscopy images of these materials. The pore sizes of these channels were estimated to lie in the range of 20-30 Å, depending on the appointed surfactant cation length. The framework wall thickness of ca. 10 Å is thereby independent from the surfactant molecules used. Up to 80% of the surfactant molecules can be removed by thermal degradation under vacuum without loss of mesostructural integrity. Physical, chemical, and spectroscopic properties of these materials are discussed.

  14. Environmental Learning Centers: A Template.

    ERIC Educational Resources Information Center

    Vozick, Eric

    1999-01-01

    Provides a working model, or template, for community-based environmental learning centers (ELCs). The template presents a philosophy as well as a plan for staff and administration operations, educational programming, and financial support. The template also addresses "green" construction and maintenance of buildings and grounds and…

  15. Organically modified silicas on metal nanowires.

    PubMed

    Dean, Stacey L; Stapleton, Joshua J; Keating, Christine D

    2010-09-21

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling.

  16. Organically Modified Silicas on Metal Nanowires

    PubMed Central

    2010-01-01

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

  17. Gallium hydride complexes stabilised by multidentate alkoxide ligands: precursors to thin films of Ga2O3 at low temperatures.

    PubMed

    Pugh, David; Bloor, Leanne G; Parkin, Ivan P; Carmalt, Claire J

    2012-05-07

    The donor-functionalised alkoxides {Me(3-x)N(CH(2)CH(2)O)(x)} (L(x); x = 1, 2) have been used to form gallium hydride complexes [{GaH(2)(L(1))}(2)] and [{GaH(L(2))}(2)] that are stable and isolable at room temperature. Along with a heteroleptic gallium tris(alkoxide) complex [Ga(L(1))(3)] and the dimeric complex [{GaMe(L(2))}(2)], these compounds have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted chemical vapour deposition (AACVD) with toluene as solvent. The resulting films were mostly transparent, indicating low levels of carbon contamination, and they were also mainly amorphous. However, [Ga(L(1))(3)] did contain visibly crystalline material deposited at a substrate temperature of 450 °C, by far the lowest ever observed for the CVD of gallium oxide. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Fabrication and characterization of Sb-doped Sn02 thin films derived from methacrylic acid modified tin(IV)alkoxides

    NASA Astrophysics Data System (ADS)

    Kololuoma, Terho K.; Tolonen, Ari; Johansson, Leena-Sisko; Campbell, Joseph M.; Karkkainen, Ari H. O.; Hiltunen, Marianne; Haatainen, Tomi; Rantala, Juha T.

    2002-10-01

    We report on the fabrication of transparent, conductive and directly photopatternable, pure and Sb-doped tin dioxide thin films. Precursors used were antimony(III)isopropoxide and a photo-reactive tin alkoxide synthesized from tin(IV)isopropoxide and methacrylic acid. The synthesis of methacrylic acid modified tin alkoxide was monitored in-situ using IR- and ESI-TOF mass spectroscopic techniques. Sb-doped organo-tin films were deposited via single layer spin coating. After deposition the films were patterned via photopolymerization, using a mercury I-line UV-lamp. All investigated materials could be patterned with 3 μm features. After development in isopropanol, the films were annealed in air, in order to obtain crystalline and conductive films. The electrical conductivities of the annealed thin films with, and without, UV-irradiation were determined using a linear four-point method. The direct photopatterning process was found to increase the film conductivity for all the Sb-doping levels tested. The mechanisms for the increased conductivity were characterized using AFM, XPS and XRD techniques.

  19. Effect of CaTiO(3)-CaCO(3) prepared by alkoxide method on cell response.

    PubMed

    Rodriguez, Andrea P; Inoue, Miho; Tanaka, Toshiyuki; Miyake, Michihiro; Sfer, Ana M; Kishimoto, Etsuo; Tsujigiwa, Hidetsugu; Rivera, Rosario S; Nagatsuka, Hitoshi

    2010-04-01

    In recent years, calcium titanate (CaTiO(3)) and carbon-containing materials have gained much attention in a number of biomedical material researches. To maximize the advantages of both materials, we developed a novel alkoxide method to get "calcium titanate with calcium carbonate" (CaTiO(3)-CaCO(3)). The objective was to evaluate the crystallinity and elemental composition of CaTiO(3)-CaCO(3) prepared by alkoxide method, CaTiO(3)-aC elaborated by modified thermal decomposition method, commercially-prepared CaTiO(3), and the effect of these materials on the bone marrow stromal cell. Hydroxyapatite was used as positive control material. We examined the cellular proliferation, osteoblastic differentiation, and mineralization of KUSA/A1 cells cultured with the materials. The results showed that CaTiO(3)-CaCO(3) and CaTiO(3)-aC contained evidence of calcium carbonate enhancing cell proliferation, osteoblastic differentiation, and mineralization. On the contrary, the commercially-prepared CaTiO(3) revealed absence of calcium carbonate with lower cell response than the other groups. The results indicated that calcium carbonate could play a key role in the cell response of CaTiO(3) material. In conclusion, our findings suggest that CaTiO(3)-CaCO(3) could be considered an important candidate as a biomaterial for medical and dental applications.

  20. Organic or organometallic template mediated clay synthesis

    SciTech Connect

    Gregar, K.C.; Winans, R.E.; Botto, R.E.

    1992-12-31

    A method is given for incorporating diverse varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and LiF for 2 days with an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by US patent No. 3,887,454 issued to Hickson, June 13, 1975; however, a variety of intercalants or templates may be introduced. The intercalants or templates should have water-solubility, positive charge, and thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays.

  1. Organic or organometallic template mediated clay synthesis

    DOEpatents

    Gregar, Kathleen C.; Winans, Randall E.; Botto, Robert E.

    1994-01-01

    A method for incorporating diverse Varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalants or templates may be introduced. The intercalants or templates should have (i) water-solubility, (ii) positive charge, and (iii) thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays.

  2. Organic or organometallic template mediated clay synthesis

    DOEpatents

    Gregar, K.C.; Winans, R.E.; Botto, R.E.

    1994-05-03

    A method is described for incorporating diverse varieties of intercalates or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalate or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalates or templates may be introduced. The intercalates or templates should have (i) water-solubility, (ii) positive charge, and (iii) thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays. 22 figures.

  3. Templated Electrodeposition of Highly Porous Nanostructured Materials

    NASA Astrophysics Data System (ADS)

    Yang, Han-Chang; Lim, Stephanie; Liu, Jiabin; Wu, Qian; Cheng, X. M.

    2011-03-01

    The fabrication of nanoporous materials has been of great interest for applications such as biosensors, photonic materials and energy storage. Compared to many other methods, the templated electrodeposition method is low cost, fast, and compatible with large-scale production. In this work, we developed a templated electrochemical deposition technique for fabricating highly ordered and highly porous nanostructured materials. The fabrication involves the following steps: self-assembly of monodispersed polystyrene spheres, electrochemical deposition of the desired materials, and sphere removal by a dissolution process. Deposition of Au and Ni layered metallic nanoporous structures were studied using different electrolytes at appropriate potentials. The pore size of the materials was tuned by using different sizes of template polystyrene spheres ranging from 50nm to 1000nm. Scanning electron microscopy images confirmed the highly ordered 3-dimensional hexagonal closed pack (hcp) structures in the samples. The templated electrochemical deposition technique provides a promising alternative approach to preparing highly porous anode materials for battery applications. Work supported by Bryn Mawr K/G fund for faculty research.

  4. Biologically Inspired Flagella-Templated Silica Nanotubes

    NASA Astrophysics Data System (ADS)

    Jo, Wonjin

    The desire and need for various types of nanostructures have been met with challenges of feasibility, reproducibility, and long fabrication time. To work towards improved bottom-up methods of nanofabrication, bacterial flagella are particularly attractive bio-templates for nanotubes due to their tubular structures and small inner and outer diameters. In this work, flagella isolated from Salmonella typhimurium are used as bio-templates to fabricate silica mineralized nanotubes. The process involves as well-controlled hydrolysis and condensation reaction with aminopropyltriethoxysilane (APTES), followed by the addition of tetraethoxysilane (TEOS). By controlling the concentration of TEOS and the reaction time, a simple and precise method is developed for creating silica-mineralized flagella nanotubes (SMFNs) with various thicknesses of the silica layer. In addition, the SMFNs are further modified to multifunctional nanotubes by coating metal nanoparticles (NPs) or metal oxide NPs such as gold, palladium, and iron oxide. The metallized SMFNs are achieved through reactions including reductive metallization or oxidative hydrolysis. The results from these studies provide evidence for the complete coating of SMFNs with uniform metal NP sizes and high surface area coverage. The metallized SMFNs are found to be electrically conductive along their network structures. The current-voltage characteristics show remarkably improved electrical conductivities depending on the types of metal NPs loading and SMFN networks concentration. The biologically inspired SMFNs with metal loading will allow have controlled electrical properties that can lead to the potential of creating unique and precise nanoelectronic materials. Lastly, the randomly entangled SMFNs are characterized to demonstrate their capabilities for hydrophilic and hydrophobic surface applications.

  5. Template-Stripped Tunable Plasmonic Devices on Stretchable and Rollable Substrates

    PubMed Central

    2015-01-01

    We use template stripping to integrate metallic nanostructures onto flexible, stretchable, and rollable substrates. Using this approach, high-quality patterned metals that are replicated from reusable silicon templates can be directly transferred to polydimethylsiloxane (PDMS) substrates. First we produce stretchable gold nanohole arrays and show that their optical transmission spectra can be modulated by mechanical stretching. Next we fabricate stretchable arrays of gold pyramids and demonstrate a modulation of the wavelength of light resonantly scattered from the tip of the pyramid by stretching the underlying PDMS film. The use of a flexible transfer layer also enables template stripping using a cylindrical roller as a substrate. As an example, we demonstrate roller template stripping of metallic nanoholes, nanodisks, wires, and pyramids onto the cylindrical surface of a glass rod lens. These nonplanar metallic structures produced via template stripping with flexible and stretchable films can facilitate many applications in sensing, display, plasmonics, metasurfaces, and roll-to-roll fabrication. PMID:26402066

  6. Highly active and stereoselective zirconium and hafnium alkoxide initiators for solvent-free ring-opening polymerization of rac-lactide.

    PubMed

    Chmura, Amanda J; Davidson, Matthew G; Frankis, Catherine J; Jones, Matthew D; Lunn, Matthew D

    2008-03-21

    Under solvent-free conditions (at 130 degrees C), zirconium and hafnium amine tris(phenolate) alkoxides are extremely active, well-controlled, single-site initiators for the ring-opening polymerization of rac-lactide, yielding highly heterotactic polylactide.

  7. Templated biomimetic multifunctional coatings

    NASA Astrophysics Data System (ADS)

    Sun, Chih-Hung; Gonzalez, Adriel; Linn, Nicholas C.; Jiang, Peng; Jiang, Bin

    2008-02-01

    We report a bioinspired templating technique for fabricating multifunctional optical coatings that mimic both unique functionalities of antireflective moth eyes and superhydrophobic cicada wings. Subwavelength-structured fluoropolymer nipple arrays are created by a soft-lithography-like process. The utilization of fluoropolymers simultaneously enhances the antireflective performance and the hydrophobicity of the replicated films. The specular reflectivity matches the optical simulation using a thin-film multilayer model. The dependence of the size and the crystalline ordering of the replicated nipples on the resulting antireflective properties have also been investigated by experiment and modeling. These biomimetic materials may find important technological application in self-cleaning antireflection coatings.

  8. Synthesis of oligoguanylates on oligocytidylate templates. [on primitive earth

    NASA Technical Reports Server (NTRS)

    Fakhrai, H.; Van Roode, J. H. G.; Orgel, L. E.

    1981-01-01

    The influence of template length in the self-condensation of guanosine 5'-phosphorimidazole in the presence of oligocytidylate templates is investigated. Reactions were carried out with cyclic cytidine 2',3'-phosphate, oligo- or polyC, and radioactively labeled guanosine 5'-phosphorimidazolide in the presence of Zn(+2) or Pb(+2) catalyst; product yields were determined by paper chromatography, thin-layer chromatography, and high-performance liquid chromatography. In the absence of a catalytic metal or in the presence of Pb(+2), a significant template effect is observed starting with the cytidine dimer and increasing in yield up to the hexamer template. Oligomers longer than the template are observed, and are predominantly 2'-5' linked in the presence of Pb(+2) and of mixed linkages in the uncatalyzed reaction. With the zinc ion as the catalyst, the template effect is first observed with the pentamer and is maximal with the heptamer. Products are predominantly 3'-5', and only a small proportion of them are longer than the template. The importance of the demonstrated formation of molecules with up to 10 guanosine units from oligocytidines as short as the dimer on the primitive earth is noted.

  9. Homoepitaxial growth of MOD-YBCO thick films on evaporated and MOD templates

    NASA Astrophysics Data System (ADS)

    Tanabe, D.; Yamaguchi, I.; Sohma, M.; Tsukada, K.; Matsui, M.; Kumagai, T.; Manabe, T.

    2011-11-01

    We have prepared metal organic deposition (MOD)-YBCO thick films by repeating the coating-pyrolysis-crystallization procedure onto ∼100-nm-thick evaporated and MOD templates. Surface morphology of the template was found to strongly affect the homoepitaxial growth of MOD-YBCO layers on the template; namely, the epitaxial growth of MOD-YBCO on the evaporated template was much easier than that on the MOD template. A 220-nm-thick epitaxial MOD-YBCO film was successfully prepared on the 100-nm-thick evaporated-YBCO template to obtain a 320-nm-thick YBCO film, which exhibited Jc = 2.44 MA/cm2 and Ic = 78 A/cm. The Ic value has significantly increased from 37 A/cm for the evaporated-template.

  10. Understanding the nucleophilic character and stability of the carbanions and alkoxides of 1-(9-anthryl)ethanol and derivatives.

    PubMed

    Ramírez, Ramsés E; García-Martínez, Cirilo; Méndez, Francisco

    2013-08-22

    The nucleophilic character and stability of the carbanions vs. alkoxides derived from 2,2,2-trifluoro-1-(9-anthryl)ethanol and 1-(9-anthryl)ethanol containing X electron-releasing and X electron-acceptor substituents attached to C-10, have been studied at the B3LYP/6-31+G(d,p) level of theory. Results analyzed in terms of the absolute gas-phase acidity, Fukui function, the local hard and soft acids and bases principle, and the molecular electrostatic potential, show that the central ring of the 9-anthryl group confers an ambident nucleophilic character and stabilizes the conjugated carbanion by electron-acceptor delocalization.

  11. Ordered Nanomaterials Thin Films via Supported Anodized Alumina Templates

    NASA Astrophysics Data System (ADS)

    Es-Souni, Mohammed; Habouti, Salah

    2014-10-01

    Supported anodized alumina template films with highly ordered porosity are best suited for fabricating large area ordered nanostructures with tunable dimensions and aspect ratios. In this paper we first discuss important issues for the generation of such templates, including required properties of the Al/Ti/Au/Ti thin film heterostructure on a substrate for high quality templates. We then show examples of anisotropic nanostructure films consisting of noble metals using these templates, discuss briefly their optical properties and their applications to molecular detection using surface enhanced Raman spectroscopy. Finally we briefly address the possibility to make nanocomposite films, exemplary shown on a plasmonic-thermochromic nanocomposite of VO2-capped Au-nanorods.

  12. Synthesis, characterization and magnetic properties of four new organically templated metal sulfates [C5H14N2][M(II)(H2O)6](SO4)2, (M(II) = Mn, Fe, Co, Ni).

    PubMed

    Hajlaoui, Fadhel; Naïli, Houcine; Yahyaoui, Samia; Turnbull, Mark M; Mhiri, Tahar; Bataille, Thierry

    2011-11-21

    A series of novel organically templated metal sulfates, [C(5)H(14)N(2)][M(II)(H(2)O)(6)](SO(4))(2) with (M(II) = Mn (1), Fe (2), Co (3) and Ni (4)), have been successfully synthesized by slow evaporation and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, thermogravimetric analysis and magnetic measurements. All compounds were prepared using a racemic source of the 2-methylpiperazine and they crystallized in the monoclinic systems, P2(1)/n for (1, 3) and P2(1)/c for (2,4). Crystal data are as follows: [C(5)H(14)N(2)][Mn(H(2)O)(6)](SO(4))(2), a = 6.6385(10) Å, b = 11.0448(2) Å, c = 12.6418(2) Å, β = 101.903(10)°, V = 906.98(3) Å(3), Z = 2; [C(5)H(14)N(2)][Fe(H(2)O)(6)](SO(4))(2), a = 10.9273(2) Å, b = 7.8620(10) Å, c = 11.7845(3) Å, β = 116.733(10)°, V = 904.20(3) Å(3), Z = 2; [C(5)H(14)N(2)][Co(H(2)O)(6)](SO(4))(2), a = 6.5710(2) Å, b = 10.9078(3) Å, c = 12.5518(3) Å, β = 101.547(2)°, V = 881.44(4) Å(3), Z = 2; [C(5)H(14)N(2)][Ni(H(2)O)(6)](SO(4))(2), a = 10.8328(2) Å, b = 7.8443(10) Å, c = 11.6790(2) Å, β = 116.826(10)°, V = 885.63(2) Å(3), Z = 2. The three-dimensional structure networks for these compounds consist of isolated [M(II)(H(2)O)(6)](2+) and [C(5)H(14)N(2)](2+) cations and (SO(4))(2-) anions linked by hydrogen-bonds only. The use of racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion centers. The magnetic measurements indicate that the Mn complex (1) is paramagnetic, while compounds 2, 3 and 4, (M(II) = Fe, Co, Ni respectively) exhibit single ion anisotropy. This journal is © The Royal Society of Chemistry 2011

  13. Digital templating in primary total hip and knee arthroplasty.

    PubMed

    Levine, Brett; Fabi, David; Deirmengian, Carl

    2010-11-02

    The use of digital radiography is becoming more prevalent in orthopedics. This transition impacts the ability to preoperatively plan for implants in total hip arthroplasty (THA) and total knee arthroplasty (TKA). This article reports on the clinical success of digital templating using the Advanced Case Plan (Stryker Imaging, Flower Mound, Texas) system in primary THA and TKA. Digital radiographs of 269 consecutive patients undergoing primary THA (93 cases) or TKA (176 cases) were templated using the Advanced Case Plan digital software package. A 25.4-mm metallic sphere was used as a calibrating marker. Anteroposterior hip and lateral knee radiographs were digitally templated preoperatively and compared to the actual size of the implants at the time of surgery. The accuracy of calibrating images using the metallic sphere was validated by measuring the diameter of femoral heads on 25 postoperative hip radiographs. Digital templating was accurate in predicting the correct implant size in 58.5% of THAs and 66% of TKAs. In 93% of THAs and 98.5% of TKAs, preoperative templating was within 1 size of the final implant. There were no cases in which the predicted implant size varied from the final components by >2 sizes. Calibrating the image using the metallic sphere marker was found to be highly accurate, predicting the correct femoral head size within 1.5 mm in all 25 cases (7 hemiarthroplasties and 18 THAs). Digital templating is an effective means for predicting the size of THA and TKA components, thus remaining a viable option as we transition into the modern era of digital radiography. Future studies will evaluate interobserver reliability and the impact of level of training on templating accuracy. Copyright 2010, SLACK Incorporated.

  14. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).

  15. Silver nanowires--unique templates for functional nanostructures.

    PubMed

    Sun, Yugang

    2010-09-01

    This feature article reviews the synthesis and application of silver nanowires with the focus on a polyol process that is capable of producing high quality silver nanowires with high yield. The as-synthesized silver nanowires can be used as both physical templates for the synthesis of metal/dielectric core/shell nanowires and chemical templates for the synthesis of metal nanotubes as well as semiconductor nanowires. Typical examples including Ag/SiO(2) coaxial nanocables, single- and multiple-walled nanotubes made of Au-Ag alloy, AgCl nanowires and AgCl/Au core/shell nanowires are discussed in detail to illustrate the versatility of nanostructures derived from silver nanowire templates. Novel properties associated with these one-dimensional nanostructures are also briefly discussed to shed the light on their potential applications in electronics, photonics, optoelectronics, catalysis, and medicine.

  16. Probing the Effects of Templating on the UV and Visible Light Photocatalytic Activity of Porous Nitrogen-Modified Titania Monoliths for Dye Removal.

    PubMed

    Nursam, Natalita M; Wang, Xingdong; Tan, Jeannie Z Y; Caruso, Rachel A

    2016-07-13

    Porous nitrogen-modified titania (N-titania) monoliths with tailored morphologies were prepared using phase separation and agarose gel templating techniques. The doping and templating process were simultaneously carried out in a one-pot step using alcohol amine-assisted sol-gel chemistry. The amount of polymer used in the monoliths that were prepared using phase separation was shown to affect both the physical and optical properties: higher poly(ethylene glycol) content increased the specific surface area, porosity, and visible light absorption of the final materials. For the agarose-templated monoliths, the infiltration conditions affected the monolith morphology. A porous monolith with high surface area and the least shrinkage was obtained when the N containing alkoxide precursor was infiltrated into the agarose scaffolds at 60 °C. The effect of the diverse porous morphologies on the photocatalytic activity of N-titania was studied for the decomposition of methylene blue (MB) under visible and UV light irradiation. The highest visible light activity was achieved by the agarose-templated N-titania monolith, in part due to higher N incorporation. This sample also showed better UV activity, partly because of the higher specific surface area (up to 112 m(2) g(-1)) compared to the phase separation-induced monoliths (up to 103 m(2) g(-1)). Overall, agarose-templated, porous N-titania monoliths provided better features for effectively removing the MB contaminant.

  17. DNA-templated nanofabrication.

    PubMed

    Becerril, Héctor A; Woolley, Adam T

    2009-02-01

    Nanofabrication, or the organizational control over matter at the nanometre scale, is an intriguing scientific challenge requiring multidisciplinary tools for its solution. DNA is a biomolecule that can be combined with other nanometre-scale entities through chemical self-assembly to form a broad variety of nanomaterials. In this tutorial review we present the principles that allow DNA to interact with other chemical species, and describe the challenges and potential applications of DNA as a template for making both biological and inorganic features with nanometre resolution. As such, this report should be of interest to chemists, surface and materials scientists, biologists, and nanotechnologists, as well as others who seek to use DNA in nanofabrication.

  18. Templated quasicrystalline molecular layers

    NASA Astrophysics Data System (ADS)

    Smerdon, Joe; Young, Kirsty; Lowe, Michael; Hars, Sanger; Yadav, Thakur; Hesp, David; Dhanak, Vinod; Tsai, An-Pang; Sharma, Hem Raj; McGrath, Ronan

    2014-03-01

    Quasicrystals are materials with long range ordering but no periodicity. We report scanning tunneling microscopy (STM) observations of quasicrystalline molecular layers on five-fold quasicrystal surfaces. The molecules adopt positions and orientations on the surface consistent with the quasicrystalline ordering of the substrate. Carbon-60 adsorbs atop sufficiently-separated Fe atoms on icosahedral Al-Cu-Fe to form a unique quasicrystalline lattice whereas further C60 molecules decorate remaining surface Fe atoms in a quasi-degenerate fashion. Pentacene (Pn) adsorbs at tenfold-symmetric points around surface-bisected rhombic triacontahedral clusters in icosahedral Ag-In-Yb. These systems constitute the first demonstrations of quasicrystalline molecular ordering on a template. EPSRC EP/D05253X/1, EP/D071828/1, UK BIS.

  19. A Template for Insect Cryopreservation

    USDA-ARS?s Scientific Manuscript database

    This article is intended to update the reader on the progress made on insect embryo cryopreservation in the past 20 years and gives information for developing a protocol for cryopreserving insects by using a 2001 study as a template. The study used for the template is the cryopreservation of the Old...

  20. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1991-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  1. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  2. Controlled nucleation and growth studies in metal oxide and alkoxide systems by dynamic laser-light-scattering methods

    NASA Astrophysics Data System (ADS)

    Byers, C. H.; Brunson, R. R.; Harris, M. T.; Williams, D. F.

    1987-04-01

    A method for studying the dynamics of crystallization by using an in situ crystallizer in a dynamic laser-light-scattering system has been developed. Results for growing systems in the size range of 0.005 to 1 micron may be monitored nondestructively using this method. In a series of tests, homogeneous precipitation techniques provide reproducible, controlled nucleation and growth of oxides such as hematite and silica. The effects of driving force and homogeneous and heterogeneous seeding were compared with a theoretical treatment of crystal formation and growth. The hydrolysis of tetraethoxysilicate (TEOS) in ethanol, n-butanol, and tert-butyl alcohol was investigated as a function of initial water and ammonia contents. Ethanol concentration, particle size, and number concentration were studied as a function of time. Preliminary results indicate that in the presence of excess water the growth rate of silica particles has a first-order dependence on TEOS concentration.

  3. Processing of Nanosensors Using a Sacrificial Template Approach

    NASA Technical Reports Server (NTRS)

    Biaggi-Labiosa, Azlin M.; Hunter, Gary W.

    2012-01-01

    A new microsensor fabrication approach has been demonstrated based upon the use of nanostructures as templates. The fundamental idea is that existing nanostructures, such as carbon nano tubes or biological structures, have a material structure that can be used advantageously in order to provide new sensor systems but lack the advantages of some materials to, for example, operate at high temperatures. The approach is to start with a template using nanostructures such as a carbon nanotube. This template can then be coated by an oxide material with higher temperature capabilities. Upon heating in air, the carbon nanotube template is burned off, leaving only the metal oxide nanostructure. The resulting structure has a combination of the crystal structure and surface morphology of the carbon nanotube, combined with the material durability and hightemperature- sensing properties of the metal oxide. Further, since the metal oxide nanocrystals are deposited on the carbon nanotube, after burn-off what is left is a metal oxide porous nanostructure. This makes both the interior and the exterior of this nano structured sensor available for gas species detection. This, in effect, increases the surface area available for sensing, which has been shown in the past to significantly increase sensor performance.

  4. Brain templates and atlases.

    PubMed

    Evans, Alan C; Janke, Andrew L; Collins, D Louis; Baillet, Sylvain

    2012-08-15

    The core concept within the field of brain mapping is the use of a standardized, or "stereotaxic", 3D coordinate frame for data analysis and reporting of findings from neuroimaging experiments. This simple construct allows brain researchers to combine data from many subjects such that group-averaged signals, be they structural or functional, can be detected above the background noise that would swamp subtle signals from any single subject. Where the signal is robust enough to be detected in individuals, it allows for the exploration of inter-individual variance in the location of that signal. From a larger perspective, it provides a powerful medium for comparison and/or combination of brain mapping findings from different imaging modalities and laboratories around the world. Finally, it provides a framework for the creation of large-scale neuroimaging databases or "atlases" that capture the population mean and variance in anatomical or physiological metrics as a function of age or disease. However, while the above benefits are not in question at first order, there are a number of conceptual and practical challenges that introduce second-order incompatibilities among experimental data. Stereotaxic mapping requires two basic components: (i) the specification of the 3D stereotaxic coordinate space, and (ii) a mapping function that transforms a 3D brain image from "native" space, i.e. the coordinate frame of the scanner at data acquisition, to that stereotaxic space. The first component is usually expressed by the choice of a representative 3D MR image that serves as target "template" or atlas. The native image is re-sampled from native to stereotaxic space under the mapping function that may have few or many degrees of freedom, depending upon the experimental design. The optimal choice of atlas template and mapping function depend upon considerations of age, gender, hemispheric asymmetry, anatomical correspondence, spatial normalization methodology and disease

  5. DNA-templated nanowires as sacrificial materials for creating nanocapillaries

    NASA Astrophysics Data System (ADS)

    Stewart, Jacob T.; Becerril, Hector A.; Yang, Weichun; Larsen, Megan G.; Woolley, Adam T.

    2008-08-01

    DNA has shown great promise as a template for the controlled localization of various materials and the construction of wires with nanometer-dimension cross sections. We have recently developed a strategy for fabrication of nanocapillaries, using DNA-templated nanowires as a sacrificial material. We first form metal nanowires through the selective electrochemical deposition of nickel atop a surface-aligned DNA molecule. We then deposit a thin layer of silicon dioxide on top of the DNA nanostructures. Next, we photolithographically pattern openings over the ends of the wires and etch through the silicon dioxide layer to expose the metal nanowires. Finally, we etch out the DNA-templated nickel nanowires. This process results in the formation of nanocapillaries having the same dimensions as the originally formed DNA-templated nanowires. We have characterized these DNA-templated nanocapillaries using atomic force microscopy, optical microscopy and scanning electron microscopy. These constructs have potential for application in nanofluidics, power generation, sample preconcentration, and chemical sensing.

  6. Templated nanocarbons for energy storage.

    PubMed

    Nishihara, Hirotomo; Kyotani, Takashi

    2012-08-28

    The template carbonization method is a powerful tool for producing carbon materials with precisely controlled structures at the nanometer level. The resulting templated nanocarbons exhibit extraordinarily unique (often ordered) structures that could never be produced by any of the conventional methods for carbon production. This review summarizes recent publications about templated nanocarbons and their composites used for energy storage applications, including hydrogen storage, electrochemical capacitors, and lithium-ion batteries. The main objective of this review is to clarify the true significance of the templated nanocarbons for each application. For this purpose, the performance characteristics of almost all templated nanocarbons reported thus far are listed and compared with those of conventional materials, so that the advantages/disadvantages of the templated nanocarbons are elucidated. From the practical point of view, the high production cost and poor mass-producibility of the templated nanocarbons make them rather difficult to utilize; however, the study of their unique, specific, and ordered structures enables a deeper insight into energy storage mechanisms and the guidelines for developing energy storage materials. Thus, another important purpose of this work is to establish such general guidelines and to propose future strategies for the production of carbon materials with improved performance for energy storage applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Cloning nanocrystal morphology with soft templates

    NASA Astrophysics Data System (ADS)

    Thapa, Dev Kumar; Pandey, Anshu

    2016-08-01

    In most template directed preparative methods, while the template decides the nanostructure morphology, the structure of the template itself is a non-general outcome of its peculiar chemistry. Here we demonstrate a template mediated synthesis that overcomes this deficiency. This synthesis involves overgrowth of silica template onto a sacrificial nanocrystal. Such templates are used to copy the morphologies of gold nanorods. After template overgrowth, gold is removed and silver is regrown in the template cavity to produce a single crystal silver nanorod. This technique allows for duplicating existing nanocrystals, while also providing a quantifiable breakdown of the structure - shape interdependence.

  8. An alkoxide cluster with 18 Li+ ions encapsulating two borate anions, [((t)BuO)12Li18(BO3)2].

    PubMed

    Tombul, Mustafa; Errington, R John; Coxall, Robert A; Clegg, William

    2003-06-01

    The title compound, bis(borato)dodeca(tert-butoxo)octadecalithium, [Li(18)(BO(3))(2)(C(4)H(9)O)(12)], is formulated conveniently as [(((t)BuOLi)(3)(Li(3)BO(3)))(2)((t)BuOLi)(6)]. A central 12-membered ring and two outer six-membered rings are formed by alternating Li(+) cations and alkoxide O atoms. Sandwiched between the central ring and each of the outer rings is a planar array of three further Li(+) cations surrounding a [BO(3)](3-) anion. Thus, the molecule consists of a cationic [Li(18)(O(t)Bu)(12)](6+) cage encapsulating two borate anions. This compound is the first example of a structurally characterized polynuclear lithium borate, and a rare case of a lithium alkoxide cage with nuclearity greater than eight. All the alkoxide ligands are triply bridging, and the lithium ions have trigonal-planar, trigonal-pyramidal and fourfold coordination, all with major distortions from regular coordination geometry.

  9. Morphology Control for Fully Printable Organic-Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer.

    PubMed

    Kato, Takehito; Oinuma, Chihiro; Otsuka, Munechika; Hagiwara, Naoki

    2017-01-10

    The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

  10. Nanowire-templated lateral epitaxial growth of non-polar group III nitrides

    DOEpatents

    Wang, George T.; Li, Qiming; Creighton, J. Randall

    2010-03-02

    A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.

  11. Controlling Pore Geometries and Interpore Distances of Anodic Aluminum Oxide Templates via Three-Step Anodization.

    PubMed

    Lim, Jin-Hee; Wiley, John B

    2015-01-01

    Porous alumina membranes have attracted much attention because they are very useful templates for the fabrication of various nanostructures important to nanotechnology. However, there are challenges in controlling pore geometries and interpore distances in alumina templates while maintaining highly ordered hexagonal pore structures. Herein, a three-step anodization method is utilized to prepare anodic alumina templates with various pore morphologies (e.g., arched-shape, tree-like, branched-shape) and tunable interpore distances. Such structures are not found within the more traditional alumina templates fabricated by a two-step anodization of aluminum films. The range of interpore distances and pore diameters within the modified templates increases with increasing voltages. In contrast, under decreasing voltages, hexagonally ordered pores can also branch into several pores with smaller sizes and reduced interpore distances. Electrochemical growth of metal nanowires in the modified templates helps to highlight details of the pore structures and which pore channels are active.

  12. Asymmetric Image-Template Registration

    PubMed Central

    Sabuncu, Mert R.; Yeo, B.T. Thomas; Van Leemput, Koen; Vercauteren, Tom; Golland, Polina

    2010-01-01

    A natural requirement in pairwise image registration is that the resulting deformation is independent of the order of the images. This constraint is typically achieved via a symmetric cost function and has been shown to reduce the effects of local optima. Consequently, symmetric registration has been successfully applied to pairwise image registration as well as the spatial alignment of individual images with a template. However, recent work has shown that the relationship between an image and a template is fundamentally asymmetric. In this paper, we develop a method that reconciles the practical advantages of symmetric registration with the asymmetric nature of image-template registration by adding a simple correction factor to the symmetric cost function. We instantiate our model within a log-domain diffeomorphic registration framework. Our experiments show exploiting the asymmetry in image-template registration improves alignment in the image coordinates. PMID:20426033

  13. Template Synthesis of Carbon Nanotubules

    NASA Astrophysics Data System (ADS)

    Tee, J. C.; Sanip, S. M.; Aziz, M.; Ismail, A. F.

    2010-03-01

    The template synthesis of carbon nanostructures formed in porous anodic aluminium oxide (AAO) template with a pore size of 200 nm by a liquid phase impregnation of the template with a polymer, polyfurfuryl alcohol, followed by carbonization is studied. The temperatures of exposure to furfuryl alcohol vapour were varied between 50 and 70° C. The resultant carbon nanotubules formed were hollow with open ends having diameter ranging from 220-300 nm which is in agreement with the pore size of the template used. The BET surface area was found to increase from 11.64 m2/g before pyrolysis to 90.19 m2/g after pyrolysis as a result of the formation of carbon nanotubules.

  14. Magnetic and conductive magnetite nanowires by DNA-templating.

    PubMed

    Mohamed, Hasan Daw A; Watson, Scott M D; Horrocks, Benjamin R; Houlton, Andrew

    2012-09-28

    The synthesis of nanowires made of magnetite (Fe(3)O(4)) phase iron oxide was achieved using DNA as a template to direct formation of the metal oxide and confine its growth in two dimensions. This simple solution-based approach involves initial association of Fe(2+) and Fe(3+) to the DNA "template" molecules, and subsequent co-precipitation of the Fe(3)O(4) material, upon increasing the solution pH, to give the final metal oxide nanowires. Analysis of the DNA-templated material, using a combination of FTIR, XRD, XPS, and Raman spectroscopy, confirmed the iron oxide formed to be the Fe(3)O(4) crystal phase. Investigation of the structural character of the nanowires, carried out by AFM, revealed the metal oxide to form regular coatings of nanometre-scale thickness around the DNA templates. Statistical analysis showed the size distribution of the nanowires to follow a trimodal model, with the modal diameter values identified as 5-6 nm, 14-15 nm, and 23-24 nm. Additional scanning probe microscopy techniques (SCM, MFM) were also used to verify that the nanowire structures are electrically conducting and exhibit magnetic behaviour. Such properties, coupled with the small dimensions of these materials, make them potentially good candidates for application in a host of future nanoscale device technologies.

  15. Templated Growth of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Siochik Emilie J. (Inventor)

    2007-01-01

    A method of growing carbon nanotubes uses a synthesized mesoporous si lica template with approximately cylindrical pores being formed there in. The surfaces of the pores are coated with a carbon nanotube precu rsor, and the template with the surfaces of the pores so-coated is th en heated until the carbon nanotube precursor in each pore is convert ed to a carbon nanotube.

  16. Synthesis of platinum nanowheels using a bicellar template.

    PubMed

    Song, Yujiang; Dorin, Rachel M; Garcia, Robert M; Jiang, Ying-Bing; Wang, Haorong; Li, Peng; Qiu, Yan; van Swol, Frank; Miller, James E; Shelnutt, John A

    2008-09-24

    Disk-like surfactant bicelles provide a unique meso-structured reaction environment for templating the wet-chemical reduction of platinum(II) salt by ascorbic acid to produce platinum nanowheels. The Pt wheels are 496 +/-55 nm in diameter and possess thickened centers and radial dendritic nanosheets (about 2-nm in thickness) culminating in flared dendritic rims. The structural features of the platinum wheels arise from confined growth of platinum within the bilayer that is also limited at edges of the bicelles. The size of CTAB/FC7 bicelles is observed to evolve with the addition of Pt(II) complex and ascorbic acid. Synthetic control is demonstrated by varying the reaction parameters including metal salt concentration, temperature, and total surfactant concentration. This study opens up opportunities for the use of other inhomogeneous soft templates for synthesizing metals, metal alloys, and possibly semiconductors with complex nanostructures.

  17. Quantifying the Sigma and Pi interactions between U(V) f orbitals and halide, alkyl, alkoxide, amide and ketimide ligands

    SciTech Connect

    University of California, Berkeley; Lukens, Wayne W.; Edelstein, Norman M.; Magnani, Nicola; Hayton, Trevor W.; Fortier, Skye; Seaman, Lani A.

    2013-06-20

    f Orbital bonding in actinide and lanthanide complexes is critical to their behavior in a variety of areas from separations to magnetic properties. Octahedral f1 hexahalide complexes have been extensively used to study f orbital bonding due to their simple electronic structure and extensive spectroscopic characterization. The recent expansion of this family to include alkyl, alkoxide, amide, and ketimide ligands presents the opportunity to extend this study to a wider variety of ligands. To better understand f orbital bonding in these complexes, the existing molecular orbital (MO) model was refined to include the effect of covalency on spin orbit coupling in addition to its effect on orbital angular momentum (orbital reduction). The new MO model as well as the existing MO model and the crystal field (CF) model were applied to the octahedral f1 complexes to determine the covalency and strengths of the ? and ? bonds formed by the f orbitals. When covalency is significant, MO models more precisely determined the strengths of the bonds derived from the f orbitals; however, when covalency was small, the CF model was better than either MO model. The covalency determined using the new MO model is in better agreement with both experiment and theory than that predicted by the existing MO model. The results emphasize the role played by the orbital energy in determining the strength and covalency of bonds formed by the f orbitals.

  18. Effect of Ligand Field Tuning on the SMM Behavior for Three Related Alkoxide-Bridged Dysprosium Dimers.

    PubMed

    Peng, Yan; Mereacre, Valeriu; Baniodeh, Amer; Lan, Yanhua; Schlageter, Martin; Kostakis, George E; Powell, Annie K

    2016-01-04

    The synthesis and characterization of three Dy2 compounds, [Dy2(HL1)2(NO3)4] (1), [Dy2(L2)2(NO3)4] (2), and [Dy2(HL3)2(NO3)4] (3), formed using related tripodal ligands with a central tertiary amine bearing picolyl and alkoxy arms, 2-[(2-hydroxy-ethyl)-pyridin-2-ylmethylamino]-ethanol (H2L1), 2-(bis-pyridin-2-ylmethylamino)-ethanol (HL2), and 2-(bis-pyridin-2-ylmethylamino)-propane-1,3-diol (H2L3), are reported. The compounds are rare examples of alkoxide-bridged {Dy2} complexes and display capped square antiprism coordination geometry around each Dy(III) ion. Changes in the ligand field environment around the Dy(III) ions brought about through variations in the ligand donors can be gauged from the magnetic properties, with compounds 1 and 2 showing antiparallel coupling between the Dy(III) ions and 3 showing parallel coupling. Furthermore, slow relaxation of the magnetization typical of SMM behavior could be observed for compounds 2 and 3, suggesting that small variations in the ligand field can have a significant influence on the slow relaxation processes responsible for SMM behavior of Dy(III)-based systems.

  19. Influence of water/alkoxide ratio in the synthesis of nanosized sol-gel titania on the release of phenytoin.

    PubMed

    López, T; Espinoza, K A; Kozina, A; Castillo, P; Silvestre-Albero, A; Rodriguez-Reinoso, F; Alexander-Katz, R

    2011-04-05

    The sol-gel method was used to synthesize inorganic reservoirs with encapsulated antiepileptic drug phenytoin. The drug release profile was shown to depend on the morphology and surface properties of the matrix. A parameter of the synthesis such as water/alkoxide ratio r(w) was varied in order to investigate its influence on the matrix properties and as a result on the drug release profile. It was found that the specific surface area and crystallization degree decrease with an increase of r(w), whereas the hydroxyl group coverage increases with an increase of r(w). Drug release kinetics studies revealed that the initial release rate increases with an increase of water content in the reaction, whereas the long time release rate first slightly increases with an increase of water content from 4 to 8 and then decreases for r(w) = 16. The interplay of different parameters of the matrix is shown to be responsible for such a dependence and is discussed in the Article.

  20. The effect of refluxing on the alkoxide-based sodium potassium niobate sol-gel system: Thermal and spectroscopic studies

    SciTech Connect

    Chowdhury, Anirban; Bould, Jonathan; Londesborough, Michael G.S.; Milne, Steven J.

    2011-02-15

    A study on the effects of prolonged heating under reflux conditions of up to 70 h on alkoxides of sodium, potassium and niobium dissolved in 2-methoxyethanol for the synthesis of sols of composition Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) has been carried out using combined thermogravimetric-Fourier transform infrared spectroscopic analyses. Extended refluxing increases the homogeneity of the Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) system. Spectroscopic analyses on the non-refluxed and 70 h refluxed NKN gels reveal the existence of inorganic hydrated carbonates and bicarbonates, which we propose arise from the hydration and carbonation of the samples on standing in air. The X-ray diffraction patterns of these two types of gels show orthorhombic NKN phase evolutions at higher temperatures. -- Graphical abstract: Total organic evolution plots over time for NKN dried gels obtained under different refluxing times show different thermochemical behaviours and these were investigated by thermal and spectroscopic analysis tools to find a correlation between the extent of -M-O-M- chain link formation and the amount of solvent vapour (methoxyethanol) evolution. Display Omitted Research highlights: > Prolonged refluxing of sol-gel NKN precursor solutions improves final properties of an NKN system. > An NKN process thermo-chemistry with thermal and spectroscopic analysis tools was explored. > An FTIR of NKN gels reveals tendency of NKN systems for rehydration and recarbonation on standing.

  1. Synthesis and chemistry of yttrium and lanthanide metal complexes. Progress report, March 15, 1991--March 14, 1992

    SciTech Connect

    Evans, W.J.

    1991-09-01

    The objective of this research project is to determine the special features of complexes of yttrium and the lanthanide metals which will allow the design and synthesis of materials with unique chemical, physical, and catalytic properties. Past studies of yttrium and lanthanide metal alkyl and hydride complexes stabilized by cyclopentadienyl co-ligands have shown that a substantial, often singular, organometallic chemistry is available via these metals. More extensive utilization of the chemical opportunities available through yttrium and the lanthanides would be possible, however, if stabilizing ancillary ligand systems less sensitive to oxidation and protonolysis than cyclopentadienides could be developed. Alkoxide ligands are attractive in this regard and our recent research had focused on alkoxides and the special opportunities they can provide to these metals. 6 refs., 10 figs.

  2. Chitin Liquid-Crystal-Templated Oxide Semiconductor Aerogels.

    PubMed

    Chau, Trang The Lieu; Le, Dung Quang Tien; Le, Hoa Thi; Nguyen, Cuong Duc; Nguyen, Long Viet; Nguyen, Thanh-Dinh

    2017-09-13

    Chitin nanocrystals have been used as a liquid crystalline template to fabricate layered oxide semiconductor aerogels. Anisotropic chitin liquid crystals are transformed to sponge-like aerogels by hydrothermally cross-linked gelation and lyophilization-induced solidification. The hydrothermal gelation of chitin aqueous suspensions then proceeds with peroxotitanate to form hydrogel composites that recover to form aerogels after freeze-drying. The homogeneous peroxotitanate/chitin composites are calcined to generate freestanding titania aerogels that exhibit the nanostructural integrity of layered chitin template. Our extended investigations show that coassembling chitin nanocrystals with other metal-based precursors also yielded semiconductor aerogels of perovskite BaTiO3 and CuOx nanocrystals. The potential of these materials is great to investigate these chitin sponges for biomedicine and these semiconductor aerogels for photocatalysis, gas sensing, and other applications. Our results present a new aerogel templating method of highly porous, ultralight materials with chitin liquid crystals.

  3. Fabrication of DNA-templated Te and Bi2Te3 nanowires by galvanic displacement.

    PubMed

    Liu, Jianfei; Uprety, Bibek; Gyawali, Shailendra; Woolley, Adam T; Myung, Nosang V; Harb, John N

    2013-09-03

    This paper demonstrates the use of galvanic displacement to form continuous tellurium-based nanowires on DNA templates, enabling the conversion of metals, which can be deposited site-specifically, into other materials needed for device fabrication. Specifically, galvanic displacement reaction of copper and nickel nanowires is used to fabricate tellurium and bismuth telluride nanowires on λ-DNA templates. The method is simple, rapid, highly selective, and applicable to a number of different materials. In this study, continuous Ni and Cu nanowires are formed on DNA templates by seeding with Ag followed by electroless plating of the desired metal. These wires are then displaced by a galvanic displacement reaction where either Te or Bi2Te3 is deposited from an acidic solution containing HTeO2(+) ions or a combination of HTeO2(+) and Bi(3+) ions, and the metal wire is simultaneously dissolved due to oxidation. Both tellurium and bismuth telluride wires can be formed from nickel templates. In contrast, copper templates only form tellurium nanowires under the conditions considered. Therefore, the composition of the metal being displaced can be used to influence the chemistry of the resulting nanowire. Galvanic displacement of metals deposited on DNA templates has the potential to enable site-specific fabrication of a variety of materials and, thereby, make an important contribution to the advancement of useful devices via self-assembled nanotemplates.

  4. Large-scale ultraflat nanopatterned surfaces without template residues.

    PubMed

    Jung, Bongsu; Frey, Wolfgang

    2008-04-09

    Ultraflat surfaces are required for many studies of single molecules, and the need for both a wide choice of surface materials and the ability to pattern these surfaces has led to the development of different template-stripping approaches. The fabrication of nanopatterned ultraflat surfaces is particularly challenging, because more than one material is present in the surface. We demonstrate a new template-stripping strategy that allows us to fabricate large-area nanopatterned surfaces, solving the problem of incomplete template removal by introducing a sacrificial carbon layer and a sandwich structure for the template. The thin residual carbon film transferred from the template is removed from the nanopatterned surface by dry etching, as demonstrated by x-ray photoelectron spectroscopy and, for metal nanoparticles embedded in a glass surface, by a shift in the absorption of the localized surface plasmon resonance. We show that gold nanoparticles in a glass surface can be selectively functionalized with thiols yielding about 2 nm height increase. Atomic force microscopy and localized surface plasmon resonance spectroscopy both indicate that the nanoparticle shape is preserved well.

  5. e-Stars Template Builder

    NASA Technical Reports Server (NTRS)

    Cox, Brian

    2003-01-01

    e-Stars Template Builder is a computer program that implements a concept of enabling users to rapidly gain access to information on projects of NASA's Jet Propulsion Laboratory. The information about a given project is not stored in a data base, but rather, in a network that follows the project as it develops. e-Stars Template Builder resides on a server computer, using Practical Extraction and Reporting Language (PERL) scripts to create what are called "e-STARS node templates," which are software constructs that allow for project-specific configurations. The software resides on the server and does not require specific software on the user machine except for an Internet browser. A user's computer need not be equipped with special software (other than an Internet-browser program). e-Stars Template Builder is compatible with Windows, Macintosh, and UNIX operating systems. A user invokes e-Stars Template Builder from a browser window. Operations that can be performed by the user include the creation of child processes and the addition of links and descriptions of documentation to existing pages or nodes. By means of this addition of "child processes" of nodes, a network that reflects the development of a project is generated.

  6. Metal-oxide-based energetic materials and synthesis thereof

    DOEpatents

    Tillotson, Thomas M. , Simpson; Randall L.; Hrubesh, Lawrence W.

    2006-01-17

    A method of preparing energetic metal-oxide-based energetic materials using sol-gel chemistry has been invented. The wet chemical sol-gel processing provides an improvement in both safety and performance. Essentially, a metal-oxide oxidizer skeletal structure is prepared from hydrolyzable metals (metal salts or metal alkoxides) with fuel added to the sol prior to gelation or synthesized within the porosity metal-oxide gel matrix. With metal salt precursors a proton scavenger is used to destabilize the sol and induce gelation. With metal alkoxide precursors standard well-known sol-gel hydrolysis and condensation reactions are used. Drying is done by standard sol-gel practices, either by a slow evaporation of the liquid residing within the pores to produce a high density solid nanocomposite, or by supercritical extraction to produce a lower density, high porous nanocomposite. Other ingredients may be added to this basic nanostructure to change physical and chemical properties, which include organic constituents for binders or gas generators during reactions, burn rate modifiers, or spectral emitters.

  7. Effect of Body Mass Index on Digital Templating for Total Hip Arthroplasty.

    PubMed

    Sershon, Robert A; Diaz, Alejandro; Bohl, Daniel D; Levine, Brett R

    2017-03-01

    Digital templating is becoming more prevalent in orthopedics. Recent investigations report high accuracy using digital templating in total hip arthroplasty (THA); however, the effect of body mass index (BMI) on templating accuracy is not well described. Digital radiographs of 603 consecutive patients (645 hips) undergoing primary THA by a single surgeon were digitally templated using OrthoView (Jacksonville, FL). A 25-mm metallic sphere was used as a calibration marker. Preoperative digital hip templates were compared with the final implant size. Hips were stratified into groups based on BMI: BMI <30 (315), BMI 30-35 (132), BMI 35-40 (97), and BMI >40 (101). Accuracy between templating and final size did not vary by BMI for acetabular or femoral components. Digital templating was within 2 sizes of the final acetabular and femoral implants in 99.1% and 97.1% of cases, respectively. Digital templating is an effective means of predicting the final size of THA components. BMI does not appear to play a major role in altering THA digital templating accuracy. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. CAD/CAM surface templates as an alternative to the intermediate wafer in orthognathic surgery.

    PubMed

    Bai, Shizhu; Bo, Bin; Bi, Yunpeng; Wang, Bo; Zhao, Jinlong; Liu, Yanpu; Feng, Zhihong; Shang, Hongtao; Zhao, Yimin

    2010-11-01

    A new simple technique using a pair of surface templates fabricated by CAD/CAM technique as an alternative to the use of intermediate surgical wafer is presented. A patient with transverse maxillary cant and maxillary midline deviation was scanned using computed tomography (CT) to create a 3D model of the maxillofacial bone. Eight virtual cylindrical markers were placed on the selected locations of maxilla. Subsequently, the locations of these cylinders were expressed as drill holes in the preosteotomy templates. The maxillary segment was separated and repositioned in the computer according to preoperative plans. Postosteotomy surface templates were then designed and resin templates were fabricated by a rapid prototyping machine. After investing and casting, metal templates were fabricated. At the beginning of operation, surgical fixation holes on the maxilla were drilled with the preosteotomy templates. Once maxillary osteotomy and segmentation were finished, screws were placed through the holes in the postosteotomy templates into the predrilled holes on the bone correspondingly, and maxillary segments were fixed with the titanium plates. After the postosteotomy templates were positioned and fixed, the maxillary segment was placed to the desired position. Maxillary transverse cant and midline deviation were corrected as the preoperative plan and simulation. The use of the surface templates before and after osteotomy as an alternative to intermediate wafer in orthognathic surgery can minimize labor and errors contained in the traditional way, reducing preoperative work as well as a reduction in operation time. Copyright © 2010 Mosby, Inc. All rights reserved.

  9. Cooperation of catalysts and templates

    NASA Technical Reports Server (NTRS)

    White, D. H.; Kanavarioti, A.; Nibley, C. W.; Macklin, J. W.

    1986-01-01

    In order to understand how self-reproducing molecules could have originated on the primitive Earth or extraterrestrial bodies, it would be useful to find laboratory models of simple molecules which are able to carry out processes of catalysis and templating. Furthermore, it may be anticipated that systems in which several components are acting cooperatively to catalyze each other's synthesis will have different behavior with respect to natural selection than those of purely replicating systems. As the major focus of this work, laboratory models are devised to study the influence of short peptide catalysts on template reactions which produce oligonucleotides or additional peptides. Such catalysts could have been the earliest protoenzymes of selective advantage produced by replicating oligonucleotides. Since this is a complex problem, simpler systems are also studied which embody only one aspect at a time, such as peptide formation with and without a template, peptide catalysis of nontemplated peptide synthesis, and model reactions for replication of the type pioneered by Orgel.

  10. Cooperation of catalysts and templates

    NASA Technical Reports Server (NTRS)

    White, D. H.; Kanavarioti, A.; Nibley, C. W.; Macklin, J. W.

    1986-01-01

    In order to understand how self-reproducing molecules could have originated on the primitive Earth or extraterrestrial bodies, it would be useful to find laboratory models of simple molecules which are able to carry out processes of catalysis and templating. Furthermore, it may be anticipated that systems in which several components are acting cooperatively to catalyze each other's synthesis will have different behavior with respect to natural selection than those of purely replicating systems. As the major focus of this work, laboratory models are devised to study the influence of short peptide catalysts on template reactions which produce oligonucleotides or additional peptides. Such catalysts could have been the earliest protoenzymes of selective advantage produced by replicating oligonucleotides. Since this is a complex problem, simpler systems are also studied which embody only one aspect at a time, such as peptide formation with and without a template, peptide catalysis of nontemplated peptide synthesis, and model reactions for replication of the type pioneered by Orgel.

  11. Biometric template transformation: a security analysis

    NASA Astrophysics Data System (ADS)

    Nagar, Abhishek; Nandakumar, Karthik; Jain, Anil K.

    2010-01-01

    One of the critical steps in designing a secure biometric system is protecting the templates of the users that are stored either in a central database or on smart cards. If a biometric template is compromised, it leads to serious security and privacy threats because unlike passwords, it is not possible for a legitimate user to revoke his biometric identifiers and switch to another set of uncompromised identifiers. One methodology for biometric template protection is the template transformation approach, where the template, consisting of the features extracted from the biometric trait, is transformed using parameters derived from a user specific password or key. Only the transformed template is stored and matching is performed directly in the transformed domain. In this paper, we formally investigate the security strength of template transformation techniques and define six metrics that facilitate a holistic security evaluation. Furthermore, we analyze the security of two wellknown template transformation techniques, namely, Biohashing and cancelable fingerprint templates based on the proposed metrics. Our analysis indicates that both these schemes are vulnerable to intrusion and linkage attacks because it is relatively easy to obtain either a close approximation of the original template (Biohashing) or a pre-image of the transformed template (cancelable fingerprints). We argue that the security strength of template transformation techniques must consider also consider the computational complexity of obtaining a complete pre-image of the transformed template in addition to the complexity of recovering the original biometric template.

  12. Characteristics of tetrahydrofuran-based electrolytes with magnesium alkoxide additives for rechargeable magnesium batteries

    NASA Astrophysics Data System (ADS)

    Kim, In-Tae; Yamabuki, Kazuhiro; Sumimoto, Michinori; Tsutsumi, Hiromori; Morita, Masayuki; Yoshimoto, Nobuko

    2016-08-01

    The electrochemical behavior of magnesium (Mg) metal was investigated in tetrahydrofuran (THF)-based solutions containing magnesium bromide (MgBr2) and/or magnesium ethoxide (Mg(OEt)2). THF solutions containing a single solute, MgBr2 or Mg(OEt)2, show no visible faradaic current based on Mg deposition and/or dissolution. However, the electrolyte system containing both solutes, MgBr2 + Mg(OEt)2/THF, gives a reversible current response of Mg deposition and dissolution. The ionic structure of the electrolyte system containing the binary solute was examined by infrared (IR) spectroscopy and density functional theory (DFT) calculations. It was confirmed that MgBr2 and Mg(OEt)2 are coordinated (solvated) with THF molecules to form an EtOsbnd Mgsbnd Br·4THF complex. The DFT calculations also suggest the possible formation of μ-complexes for the MgBr2/Mg(OEt)2 binary system in THF. The voltammetric responses at the Pt electrode indicate low overpotential and high coulombic efficiency for Mg deposition and dissolution in THF-based solutions containing suitable molar ratios of MgBr2 and Mg(OEt)2. The constant-current charge-discharge cycling of Mg in MgBr2 + Mg(OEt)2/THF electrolyte also shows low overpotential and good cyclability over 300 cycles.

  13. Electronic Structure of a CuII-Alkoxide Complex Modeling Intermediates in Copper-Catalyzed Alcohol Oxidations

    PubMed Central

    Hayes, Ellen C.; Porter, Thomas R.; Barrows, Charles J.; Kaminsky, Werner; Mayer, James M.; Stoll, Stefan

    2016-01-01

    In the copper-catalyzed oxidation of alcohols to aldehydes, a CuII-alkoxide (CuII-OR) intermediate is believed to modulate the αC-H bond strength of the deprotonated substrate to facilitate the oxidation. As a structural model for these intermediates, we characterized the electronic structure of the stable compound TptBuCuII(OCH2CF3) (TptBu = (hydro-tris (3-tert-butyl-pyrazolyl) borate) and investigated the influence of the trifluoroethoxide ligand on the electronic structure of the complex. The compound exhibits an electron paramagnetic resonance (EPR) spectrum with an unusually large gzz value of 2.44 and a small copper hyperfine coupling Azz of 40·10−4 cm−1 (120 MHz). Single-crystal electron nuclear double resonance (ENDOR) spectra show that the unpaired spin population is highly localized on the copper ion (≈ 68 %), with no more than 15 % on the ethoxide oxygen. Electronic absorption and magnetic circular dichroism (MCD) spectra show weak ligand-field transitions between 5000 and 12000 cm−1 and an intense ethoxide-to-copper charge transfer (LMCT) transition at 24000 cm−1, resulting in the red color of this complex. Resonance Raman (rR) spectroscopy reveals a Cu-O stretch mode at 592 cm−1. Quantum chemical calculations support the interpretation and assignment of the experimental data. Compared to known CuII-thiolate and CuII-alkylperoxo complexes from the literature, we found an increased σ interaction in the CuII-OR bond that results in the spectroscopic features. These insights lay the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations. PMID:26907976

  14. Electronic Structure of a Cu(II)-Alkoxide Complex Modeling Intermediates in Copper-Catalyzed Alcohol Oxidations.

    PubMed

    Hayes, Ellen C; Porter, Thomas R; Barrows, Charles J; Kaminsky, Werner; Mayer, James M; Stoll, Stefan

    2016-03-30

    In the copper-catalyzed oxidation of alcohols to aldehydes, a Cu(II)-alkoxide (Cu(II)-OR) intermediate is believed to modulate the αC-H bond strength of the deprotonated substrate to facilitate the oxidation. As a structural model for these intermediates, we characterized the electronic structure of the stable compound Tp(tBu)Cu(II)(OCH2CF3) (Tp(tBu) = hydro-tris(3-tert-butyl-pyrazolyl)borate) and investigated the influence of the trifluoroethoxide ligand on the electronic structure of the complex. The compound exhibits an electron paramagnetic resonance (EPR) spectrum with an unusually large gzz value of 2.44 and a small copper hyperfine coupling Azz of 40 × 10(-4) cm(-1) (120 MHz). Single-crystal electron nuclear double resonance (ENDOR) spectra show that the unpaired spin population is highly localized on the copper ion (≈68%), with no more than 15% on the ethoxide oxygen. Electronic absorption and magnetic circular dichroism (MCD) spectra show weak ligand-field transitions between 5000 and 12,000 cm(-1) and an intense ethoxide-to-copper charge transfer (LMCT) transition at 24,000 cm(-1), resulting in the red color of this complex. Resonance Raman (rR) spectroscopy reveals a Cu-O stretch mode at 592 cm(-1). Quantum chemical calculations support the interpretation and assignment of the experimental data. Compared to known Cu(II)-thiolate and Cu(II)-alkylperoxo complexes from the literature, we found an increased σ interaction in the Cu(II)-OR bond that results in the spectroscopic features. These insights lay the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations.

  15. Template polymerization of nucleotide analogues

    NASA Technical Reports Server (NTRS)

    Orgel, L. E.

    1991-01-01

    Recent work on the template-directed reactions of the natural D-nucleotides has made it clear that l-nucleotides and nucleotide-like derivatives of other sugars would strongly inhibit the formation of long oligonucleotides. Consequently, attention is focusing on molecules simpler than nucleotides that might have acted as monomers of an information transfer system. We have begun a general exploration of the template directed reactions of diverse peptide analogues. I will present work by Dr. Taifeng Wu on oxidative oligomerization of phosphorothioates and of Dr. Mary Tohidi on the cyclic polymerization of nucleoside and related cyclic pyrophosphates.

  16. Wide band gap semiconductor templates

    DOEpatents

    Arendt, Paul N.; Stan, Liliana; Jia, Quanxi; DePaula, Raymond F.; Usov, Igor O.

    2010-12-14

    The present invention relates to a thin film structure based on an epitaxial (111)-oriented rare earth-Group IVB oxide on the cubic (001) MgO terminated surface and the ion-beam-assisted deposition ("IBAD") techniques that are amendable to be over coated by semiconductors with hexagonal crystal structures. The IBAD magnesium oxide ("MgO") technology, in conjunction with certain template materials, is used to fabricate the desired thin film array. Similarly, IBAD MgO with appropriate template layers can be used for semiconductors with cubic type crystal structures.

  17. Virus Assemblies as Templates for Nanocircuits

    SciTech Connect

    James N Culver; Michael T Harris

    2011-08-31

    The goals of this project were directed at the identification and characterization of bio-mineralization processes and patterning methods for the development of nano scale materials and structures with novel energy and conductive traits. This project utilized a simple plant virus as a model template to investigate methods to attach and coat metals and other inorganic compounds onto biologically based nanotemplates. Accomplishments include: the development of robust biological nanotemplates with enhanced inorganic coating activities; novel coating strategies that allow for the deposition of a continuous inorganic layer onto a bio-nanotemplate even in the absence of a reducing agent; three-dimensional patterning methods for the assemble of nano-featured high aspect ratio surfaces and the demonstrated use of these surfaces in enhancing battery and energy storage applications. Combined results from this project have significantly advanced our understanding and ability to utilize the unique self-assembly properties of biologically based molecules to produce novel materials at the nanoscale level.

  18. (Ligand intermediates in metal-catalyzed reactions)

    SciTech Connect

    Not Available

    1992-01-01

    This report consists of sections on sigma bond complexes of alkenes, a new carbon-hydrogen bond activation reaction of alkene complexes, carbon-hydrogen bond migrations in alkylidene complexes, carbon- hydrogen bond migrations in alkyne complexes, synthesis, structure and reactivity of C{sub x} complexes, synthesis and reactivity of alcohol and ether complexes, new catalysts for the epimerization of secondary alcohols; carbon-hydrogen bond activation in alkoxide complexes, pi/sigma equilibria in metal/O=CXX' complexes, and other hydrocarbon ligands; miscellaneous.(WET)

  19. Templated dewetting: designing entirely self-organized platforms for photocatalysis

    PubMed Central

    Altomare, Marco; Nguyen, Nhat Truong

    2016-01-01

    Formation and dispersion of metal nanoparticles on oxide surfaces in site-specific or even arrayed configuration are key in various technological processes such as catalysis, photonics, electrochemistry and for fabricating electrodes, sensors, memory devices, and magnetic, optical, and plasmonic platforms. A crucial aspect towards an efficient performance of many of these metal/metal oxide arrangements is a reliable fabrication approach. Since the early works on graphoepitaxy in the 70s, solid state dewetting of metal films on patterned surfaces has been much explored and regarded as a most effective tool to form defined arrays of ordered metal particles on a desired substrate. While templated dewetting has been studied in detail, particularly from a mechanistic perspective on lithographically patterned Si surfaces, the resulting outstanding potential of its applications on metal oxide semiconductors, such as titania, has received only limited attention. In this perspective we illustrate how dewetting and particularly templated dewetting can be used to fabricate highly efficient metal/TiO2 photocatalyst assemblies e.g. for green hydrogen evolution. A remarkable advantage is that the synthesis of such photocatalysts is completely based on self-ordering principles: anodic self-organized TiO2 nanotube arrays that self-align to a highest degree of hexagonal ordering are an ideal topographical substrate for a second self-ordering process, that is, templated-dewetting of sputter-deposited metal thin films. The controllable metal/semiconductor coupling delivers intriguing features and functionalities. We review concepts inherent to dewetting and particularly templated dewetting, and outline a series of effective tools that can be synergistically interlaced to reach fine control with nanoscopic precision over the resulting metal/TiO2 structures (in terms of e.g. high ordering, size distribution, site specific placement, alloy formation) to maximize their photocatalytic

  20. Cyclic polyvanadates incorporating template transition metal cationic species: synthesis and structures of hexavanadate [PdV6O18]4-, octavanadate [Cu2V8O24]4-, and decavanadate [Ni4V10O30(OH)2(H2O)6]4-.

    PubMed

    Kurata, Taisei; Uehara, Akira; Hayashi, Yoshihito; Isobe, Kiyoshi

    2005-04-04

    Three types of heteropolyvanadates, [(C2H5)4N]4[PdV6O18] (1), [(C2H5)4N]4[Cu2V8O24] (2), and [(C6H5)4P]4[Ni4V10O30(OH)2(H2O)6] (3), were synthesized through the reaction between the [VO3]- anion and metal template cations of Pd(II), Cu(II), and Ni(II). The X-ray crystal structures of 1 (a = 29.952(4) A, b = 12.911(2) A, and c = 13.678(2) A, orthorhombic, space group Pca2(1) with Z = 4), 2 (a = 13.740(1) A, b = 22.488(2) A, c = 18.505(2) A, and beta= 94.058(2) degrees , monoclinic, space group P2(1)/n with Z = 4), and 3 (a = 12.333(2) A, b = 16.208(4) A, c = 16.516(3) A, alpha = 112.438(3) degrees , beta = 94.735(3) degrees , and gamma = 104.749(3) degrees , triclinic, space group P with Z = 1) demonstrate that the metal cationic species induced cyclic [VO3](n-)n (n = 6, 8, 10) ring formation and the cations are incorporated in the rings themselves. In the metal inclusion products, the cyclic vanadates act as macrocyclic ligands, in which the metal cationic species act as the templates. The cyclic vanadate is composed of tetrahedral VO4 units that share corners and incorporates a metal cationic species in the center of the molecules. The bowl-shaped complex 1 includes a Pd2+ cation that is coordinated by the oxygen donors of a boatlike hexavanadate ring. The diamagnetic complex 1 was characterized via 51V and 17O NMR spectroscopy. Complex 2 involves an octavanadate ring and two Cu2+, which are located on both sides of the mean plane as defined by the eight oxygen atoms that bridge the vanadium atoms. In the case of complex 3, the di-mu-hydroxo-bridged Ni2+ dimer with capped Ni2+ aqua ions is formed by hydrolysis to form the decavanadate ring, in which two of the tetrahedral vanadate units are not bonded to the Ni2+ core but supported by hydrogen bonds through the aqua-ligand in the capped Ni2+ cation. Complexes 1-3 in solution were clearly identified by their characteristic isotope patterns using ESI-MS studies.

  1. Preparation, structural, and calorimetric characterization of bicomponent metallic photonic crystals

    NASA Astrophysics Data System (ADS)

    Kozlov, M. E.; Murthy, N. S.; Udod, I.; Khayrullin, I. I.; Baughman, R. H.; Zakhidov, A. A.

    2007-03-01

    We report preparation and characterization of novel bicomponent metal-based photonic crystals having submicron three-dimensional (3D) periodicity. Fabricated photonic crystals include SiO2 sphere lattices infiltrated interstitially with metals, carbon inverse lattices filled with metal or metal alloy spheres, Sb inverse lattices, and Sb inverse lattices filled with Bi spheres. Starting from a face centered SiO2 lattice template, these materials were obtained by sequences of either templating and template extraction or templating, template extraction, and retemplating. Surprising high fidelity was obtained for all templating and template extraction steps. Scanning electron microscopy (SEM), small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize the structure and the effects of the structure on calorimetric properties. To the best of our knowledge, SAXS data on metallic photonic crystals were collected for first time.

  2. Method of making metal oxide ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method for the production of metal oxide ceramic membranes is composed of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  3. Oxide formation upon thermolysis of a Pb(II)/Zr(IV) alkoxide

    SciTech Connect

    Teff, D.J.; Huffman, J.C.; Caulton, K.G.

    1996-05-01

    While Pb({mu}-O{sup t}Bu){sub 3}Zr(O{sup t}Bu){sub 3} is stable for days in refluxing toluene, addition of stoichiometric [Pb(O{sup t}Bu){sub 2}]{sub 3} prior to reflux yields {sup t}BuOH, H{sub 2}C=CMe{sub 2}, and Pb{sub 3}ZrO(O{sup t}Bu){sub 8}, which was characterized by multinuclear NMR and X-ray diffraction. Highly pure [Pb(O{sup t}Bu){sub 2}]{sub 3} itself is unchanged in refluxing toluene, although it is slowly converted to Pb{sub 4}O(O{sup t}Bu){sub 6} by catalytic quantities of {sup t}BuOH, LiNme{sub 2}, or HN(SiMe{sub 3}){sub 2}, but not by Pb metal. Stoichiometric water converts [Pb(O{sup t}Bu){sub 2}]{sub 3} completely to Pb{sub 4}O(O{sup t}Bu){sub 6}, which reacts at 25{degree}C with Zr(O{sup t}Bu){sub 4} to give Pb{sub 3}ZrO(O{sup t}Bu){sub 8}. The mechanism of the formation of Pb{sub 3}ZrO(O{sup t}Bu){sub 8} is suggested to involve O/C heterolysis and C-H bond scission as the rate determining step during thermolysis. Convenient syntheses of Pb{sub 4}O(O{sup t}Bu){sub 6} and Pb{sub 6}O{sub 4}(O{sup t}Bu){sub 4} are described, and {sup 207}Pb and {sup 17}O NMR spectra of all species are described. Crystallographic data for Pb{sub 3}ZrO(O{sup t}Bu){sub 8} (at -174{degree}C) include a = 16.663(2) A, b = 12.608(1), c = 21.117(2), and Z = 4 in space group Pbc2{sub 1}. 27 refs., 2 figs., 2 tabs.

  4. Robust Cluster Building Unit: Icosanuclear Heteropolyoxocopperate Templated by Carbonate.

    PubMed

    Liu, Fu-Ling; Kozlevčar, Bojan; Strauch, Peter; Zhuang, Gui-Lin; Guo, Ling-Yu; Wang, Zhi; Sun, Di

    2015-12-14

    The encapsulation of carbonate derived from atmospheric CO2 has resulted in an icosanuclear heteropolyoxocopperate, isolated as a metal-organic 1D chain, 2D sheet, or 3D framework, in which the Cu20 nanocluster represents the first eight-capped α-Keggin polyoxometalate with the late-transition-metal Cu(II) as the polyatom, CO3(2-) as the heteroanion, and OH(-) and suc(2-) or glu(2-) (H2suc=succinic acid; H2glu=glutaric acid) as the terminal ligands, which suggests a conceptual similarity to classical polyoxometalates. Even in the presence of competitive SO4(2-) in the assembly system, the CO3(2-) anion is still captured as a template to direct the formation of the Cu20 nanocluster, which indicates the stronger templation ability of CO3(2-) compared with SO4(2-). When other aliphatic dicarboxylates, such as glutaric acid, were used as ligands, the CO3(2-)-templated Cu20 nanocluster was maintained and acted as a cluster building unit (CBU) to be linked by two glutarate bridges to generate a distinct 1D metal-organic chain. This report presents not only a rare example of a huge anion-templated transition-metal cluster, but also its use as a robust CBU to construct novel coordination architectures. Variable-temperature magnetic susceptibility studies revealed that an antiferromagnetic interaction exists within the Cu20 nanocluster. The correlation between the coordination structure and the electron paramagnetic resonance spectra recorded of both powder and single-crystal samples are discussed in detail. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Supply-Chain Optimization Template

    NASA Technical Reports Server (NTRS)

    Quiett, William F.; Sealing, Scott L.

    2009-01-01

    The Supply-Chain Optimization Template (SCOT) is an instructional guide for identifying, evaluating, and optimizing (including re-engineering) aerospace- oriented supply chains. The SCOT was derived from the Supply Chain Council s Supply-Chain Operations Reference (SCC SCOR) Model, which is more generic and more oriented toward achieving a competitive advantage in business.

  6. Progress of NIL template making

    NASA Astrophysics Data System (ADS)

    Yusa, Satoshi; Hiraka, Takaaki; Kobiki, Ayumi; Sasaki, Shiho; Itoh, Kimio; Toyama, Nobuhito; Kurihara, Masaaki; Mohri, Hiroshi; Hayashi, Naoya

    2007-05-01

    Nano-imprint lithography (NIL) has been counted as one of the lithography solutions for hp32nm node and beyond. Recently, the small line edge roughness (LER) as well as the potentially high resolution that will ensure no-OPC mask feature is attracting many researchers. The template making is one of the most critical issues for the realization of NIL. Especially when we think of a practical template fabrication process on a 65mm square format that is going to be the industry standard, the resolution of the template making process showed a limitation. We have achieved for the first time an hp22nm resolution on the 65nm template format. Both line and space patterns and hole patterns were well resolved. Regarding dot patterns, we still need improvement, but we have achieved resolution down to hp28nm. Although so far we cannot achieve these resolution limits of various pattern category at the same time on one substrate, an intermediate process condition showed sufficient uniformity both in lateral CD and in vertical depth. Global pattern image placement also showed sufficient numbers at this stage of lithography development. A 20nm feature (with a pitch of 80nm) showed sufficient imprint result.

  7. Viral-templated Palladium Nanocatalysts

    NASA Astrophysics Data System (ADS)

    Yang, Cuixian

    Despite recent progress on nanocatalysis, there exist several critical challenges in simple and readily controllable nanocatalyst synthesis including the unpredictable particle growth, deactivation of catalytic activity, cumbersome catalyst recovery and lack of in-situ reaction monitoring. In this dissertation, two novel approaches are presented for the fabrication of viral-templated palladium (Pd) nanocatalysts, and their catalytic activities for dichromate reduction reaction and Suzuki Coupling reaction were thoroughly studied. In the first approach, viral template based bottom-up assembly is employed for the Pd nanocatalyst synthesis in a chip-based format. Specifically, genetically displayed cysteine residues on each coat protein of Tobacco Mosaic Virus (TMV) templates provide precisely spaced thiol functionalities for readily controllable surface assembly and enhanced formation of catalytically active Pd nanoparticles. Catalysts with the chip-based format allow for simple separation and in-situ monitoring of the reaction extent. Thorough examination of synthesis-structure-activity relationship of Pd nanoparticles formed on surface-assembled viral templates shows that Pd nanoparticle size, catalyst loading density and catalytic activity of viral-templated Pd nanocatalysts can be readily controlled simply by tuning the synthesis conditions. The viral-templated Pd nanocatalysts with optimized synthesis conditions are shown to have higher catalytic activity per unit Pd mass than the commercial Pd/C catalysts. Furthermore, tunable and selective surface assembly of TMV biotemplates is exploited to control the loading density and location of Pd nanocatalysts on solid substrates via preferential electroless deposition. In addition, the catalytic activities of surface-assembled TMV-templated Pd nanocatalysts were also investigated for the ligand-free Suzuki Coupling reaction under mild reaction conditions. The chip-based format enables simple catalyst separation and

  8. An alkali-metal ion extracted layered compound as a template for a metastable phase synthesis in a low-temperature solid-state reaction: preparation of brookite from K0.8Ti1.73Li0.27O4.

    PubMed

    Ozawa, Tadashi C; Sasaki, Takayoshi

    2010-03-15

    We have designed a new approach to synthesize brookite, i.e., to extract alkali-metal ions from K(0.8)Ti(1.73)Li(0.27)O(4) (KTLO) and to apply simultaneous heat treatment to the remaining lepidocrocite-type layers of TiO(6) octahedra. For the alkali-metal ion extraction and the simultaneous heat treatment, KTLO was heated at 400 degrees C with polytetrafluoroethylene (PTFE) in flowing Ar. PTFE has been found to be an effective agent to extract strongly electropositive alkali-metal ions from KTLO because of the strong electronegativity of F as its component. The product of this reaction consists of a mixture of brookite, K(2)CO(3), LiF, and PTFE derivatives, indicating the complete extraction of K(+) and Li(+) from KTLO and formation of brookite from the lepidocrocite-type layer of TiO(6) octahedra as a template. This brookite has a partial replacement of O(2-) with F(-) and/or slight oxygen deficiency; thus, its color is light-bluish gray. Fully oxidized brookite formation and complete decomposition of PTFE derivatives have been achieved by further heating in flowing air, and coproduced alkali-metal salts have been removed by washing in water. Powder X-ray diffraction, Raman spectroscopy, and chemical analysis results have confirmed that the final brookite product treated at 600 degrees C is single phase, and it is white. The method to extract alkali-metal ions from a crystalline material using PTFE is drastically different from the common methods such as soft-chemical and electrochemical reactions. It is likely that this new synthetic approach is applicable to other layered systems to prepare a diverse family of compounds, including novel metastable ones.

  9. Plasmonic nanodot array optimization on organic thin film solar cells using anodic aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Bae, Kyuyoung; Kim, Kyoungsik

    2013-09-01

    The fabrication method of plasmonic nanodots on ITO or nc-ZnO substrate has been developed to improve the efficiency of organic thin film solar cells. Nanoscale metallic nanodots arrays are fabricated by anodic aluminum oxide (AAO) template mask which can have different structural parameters by varying anodization conditions. In this paper, the structural parameters of metallic nanodots, which can be controlled by the diverse structures of AAO template mask, are investigated to enhance the optical properties of organic thin film solar cells. It is found that optical properties of the organic thin film solar cells are improved by finding optimization values of the structural parameters of the metallic nanodot array.

  10. Synthesis and characterization of the first organically templated metal oxalatophosphonate: (C3H12N2)0.5[Ga3(C2O4)(CH3PO3)4].0.5H2O.

    PubMed

    Lin, Chia-Hui; Lii, Kwang-Hwa

    2004-10-04

    The first organically templated gallium oxalatophosphonate has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The structure consists of GaO(6) octahedra and GaO(4) tetrahedra connected by methylphosphonate and bis-bidentate oxalate anions to form anionic sheets in the ab plane with the charge-compensating propylenediammonium cations and water molecules between the sheets. The methyl groups of the phosphonate ligands extend from both sides of the layers into the interlamellar region. Crystal data: monoclinic, space group P2(1)/n (No. 14), a = 8.8514(4) A, b = 16.3030(7) A, c = 15.0816(7) A, beta = 97.539(1) degrees, and Z = 4.

  11. Spreadsheet Templates for Chemical Equilibrium Calculations.

    ERIC Educational Resources Information Center

    Joshi, Bhairav D.

    1993-01-01

    Describes two general spreadsheet templates to carry out all types of one-equation chemical equilibrium calculations encountered by students in undergraduate chemistry courses. Algorithms, templates, macros, and representative examples are presented to illustrate the approach. (PR)

  12. Fumigant Management Plan - Phase 1 Templates

    EPA Pesticide Factsheets

    FMPs are required by pesticide labels, so EPA provides chemical-specific soil fumigant templates and samples in PDF and Word formats. Choose the appropriate template for products containing chloropicrin, dazomet, metam sodium/potassium, or methyl bromide.

  13. Transforming surgery through biomaterial template technology.

    PubMed

    Hodde, Jason; Hiles, Michael

    2016-03-01

    Templates inserted into surgical wounds strongly influence the healing responses in humans. The science of these templates, in the form of extracellular matrix biomaterials, is rapidly evolving and improving as the natural interactions with the body become better understood.

  14. Rigid templating of high surface-area, mesoporous, nanocrystalline rutile using a polyether block amide copolymer template.

    PubMed

    Jiang, Xingmao; Brinker, C Jeffrey

    2010-09-07

    Highly crystalline rutile with a specific surface area as high as 280 m(2) g(-1) and well-connected uniform mesoporosity has been synthesized by rigid templating using commercial, low-cost polyether block amide. This general, simple synthesis route for high surface-area mesoporous nanocrystalline oxides and nanocomposite membranes is important for catalysis, sensors, energy storage, solar cells, heavy metal removal and separations.

  15. Large Area Nanolithographic Templates by Selective Etching of Chemically Stained Block Copolymer Thin Films

    NASA Astrophysics Data System (ADS)

    Olayo-Valles, Roberto; Lund, Michael S.; Leighton, C.; Hillmyer, Marc A.

    2004-03-01

    Block copolymer thin films have been employed as effective template precursors for the preparation of inorganic nanostructure arrays. We have prepared nanoscopic templates from polystyrene-polylactide (PS-PLA) diblock copolymer thin films where the minor PLA component forms cylinders in a matrix of PS. Controlled thickness, large area PS-PLA films were spin coated on a variety of substrates (MgO, Al_2O_3, GaAs, Al, Cu, SiO_2). In all cases, annealing the films above the glass transition temperature of both blocks induced spontaneous perpendicular orientation of the cylinders. Selectively staining the PS phase with RuO4 followed by oxygen reactive ion etching produced a corresponding nanoporous template. Metal nanodot arrays were then prepared by deposition of a metal layer on the template followed by liftoff of the polymer mask. The generic nature of this methodology allows for the growth of magnetic nanostructures on single crystal substrates.

  16. Fabrication of metal nanoshells

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, Jr., James R. (Inventor)

    2012-01-01

    Metal nanoshells are fabricated by admixing an aqueous solution of metal ions with an aqueous solution of apoferritin protein molecules, followed by admixing an aqueous solution containing an excess of an oxidizing agent for the metal ions. The apoferritin molecules serve as bio-templates for the formation of metal nanoshells, which form on and are bonded to the inside walls of the hollow cores of the individual apoferritin molecules. Control of the number of metal atoms which enter the hollow core of each individual apoferritin molecule provides a hollow metal nonparticle, or nanoshell, instead of a solid spherical metal nanoparticle.

  17. AN EXPRESSION TEMPLATE AWARE LAMBDA FUNCTION

    SciTech Connect

    S. A. SMITH; J. STRIEGNITZ

    2000-09-19

    The authors show how the paradigms of lambda functions and expression templates fit together in order to provide a means to increase the expressiveness of existing STL algorithms. They demonstrate how the expression templates approach could be extended in order to work with built-in types. To be portable, their solution is based on the Portable Expression Template Engine (PETE), which is a framework that enables the development of expression template aware classes.

  18. Metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong; Song, Yujiang; Shelnutt, John A; Medforth, Craig J

    2013-10-29

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  19. DNA-templated three-branched nanostructures for nanoelectronic devices.

    PubMed

    Becerril, Héctor A; Stoltenberg, Randall M; Wheeler, Dean R; Davis, Robert C; Harb, John N; Woolley, Adam T

    2005-03-09

    Three-branched DNA molecules have been designed and assembled from oligonucleotide components. These nucleic acid constructs contain double- and single-stranded regions that control the hybridization behavior of the assembly. Specific localization of a single streptavidin molecule at the center of the DNA complex has been investigated as a model system for the directed placement of nanostructures. Highly selective silver and copper metallization of the DNA template has also been characterized. Specific hybridization of these DNA complexes to oligonucleotide-coupled nanostructures followed by metallization should provide a bottom-up self-assembly route for the fabrication and characterization of discrete three-terminal nanodevices.

  20. Templated electrodeposition of silver nanowires in a nanoporous polycarbonate membrane from a nonaqueous ionic liquid electrolyte

    NASA Astrophysics Data System (ADS)

    Kazeminezhad, I.; Barnes, A. C.; Holbrey, J. D.; Seddon, K. R.; Schwarzacher, W.

    2007-03-01

    Template electrodeposition has been used to prepare a wide range of nanostructures but has generally been restricted to aqueous electrolytes. We report the deposition of silver nanowires in a commercial nuclear track-etched polycarbonate template from the nonaqueous ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) using silver electrochemically dissolved from the anode. Transmission electron microscopy (TEM) shows that the nanowires have a very high aspect ratio with an average diameter of 80 nm and length of 5 μm. Ionic liquid electrolytes should greatly extend the range of metals that can be electrodeposited as nanowires using templates.

  1. Alkoxide coordination of iron(III) protoporphyrin IX by antimalarial quinoline methanols: a key interaction observed in the solid-state and solution.

    PubMed

    Gildenhuys, Johandie; Sammy, Chandre J; Müller, Ronel; Streltsov, Victor A; le Roex, Tanya; Kuter, David; de Villiers, Katherine A

    2015-10-14

    The quinoline methanol antimalarial drug mefloquine is a structural analogue of the Cinchona alkaloids, quinine and quinidine. We have elucidated the single crystal X-ray diffraction structure of the complexes formed between racemic erythro mefloquine and ferriprotoporphyrin IX (Fe(iii)PPIX) and show that alkoxide coordination is a key interaction in the solid-state. Mass spectrometry confirms the existence of coordination complexes of quinine, quinidine and mefloquine to Fe(iii)PPIX in acetonitrile. The length of the iron(iii)-O bond in the quinine and quinidine complexes as determined by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy unequivocally confirms that coordination of the quinoline methanol compounds to Fe(iii)PPIX occurs in non-aqueous aprotic solution via their benzylic alkoxide functional group. UV-visible spectrophotometric titrations of the low-spin bis-pyridyl-Fe(iii)PPIX complex with each of the quinoline methanol compounds results in the displacement of a single pyridine molecule and subsequent formation of a six-coordinate pyridine-Fe(iii)PPIX-drug complex. We propose that formation of the drug-Fe(iii)PPIX coordination complexes is favoured in a non-aqueous environment, such as that found in lipid bodies or membranes in the malaria parasite, and that their existence may contribute to the mechanism of haemozoin inhibition or other toxicity effects that lead ultimately to parasite death. In either case, coordination is a key interaction to be considered in the design of novel antimalarial drug candidates.

  2. Metallic nanowire networks

    DOEpatents

    Song, Yujiang; Shelnutt, John A.

    2012-11-06

    A metallic nanowire network synthesized using chemical reduction of a metal ion source by a reducing agent in the presence of a soft template comprising a tubular inverse micellar network. The network of interconnected polycrystalline nanowires has a very high surface-area/volume ratio, which makes it highly suitable for use in catalytic applications.

  3. Three-Dimensional Bicontinuous Graphene Monolith from Polymer Templates.

    PubMed

    Liu, Kewei; Chen, Yu-Ming; Policastro, Gina M; Becker, Matthew L; Zhu, Yu

    2015-06-23

    The two-dimensional single-layer and few-layered graphene exhibit many attractive properties such as large specific surface area and high charge carrier mobility. However, graphene sheets tend to stack together and form aggregates, which do not possess the desirable properties associated with graphene. Herein, we report a method to fabricate three-dimensional (3D), bicontinuous graphene monolith through a versatile hollow nickel (Ni) template derived from polymer blends. The poly(styrene)/poly(ethylene oxide) were used to fabricate a bicontinuous gyroid template using controlled phase separation. The Ni template was formed by electroless metal depositing on the polymer followed by removing the polymer phase. The resulting hollow Ni structure was highly porous (95.2%). Graphene was then synthesized from this hollow Ni template using chemical vapor deposition and the free-standing bicontinuous graphene monolith was obtained in high-throughput process. Finally, the bicontinuous graphene monolith was used directly as binder-free electrode in supercapacitor applications. The supercapacitor devices exhibited excellent stability.

  4. Ordered nanoparticle arrays formed on engineered chaperonin protein templates

    NASA Technical Reports Server (NTRS)

    McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

    2002-01-01

    Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

  5. Ordered nanoparticle arrays formed on engineered chaperonin protein templates

    NASA Technical Reports Server (NTRS)

    McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

    2002-01-01

    Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

  6. How to protect biometric templates

    NASA Astrophysics Data System (ADS)

    Sutcu, Yagiz; Li, Qiming; Memon, Nasir

    2007-02-01

    In addition to the inherent qualities that biometrics posses, powerful signal processing tools enabled widespread deployment of the biometric-based identification/verification systems. However, due to the nature of biometric data, well-established cryptographic tools (such as hashing, encryption, etc.) are not sufficient for solving one of the most important problems related to biometric systems, namely, template security. In this paper, we examine and show how to apply a recently proposed secure sketch scheme in order to protect the biometric templates. We consider face biometrics and study how the performance of the authentication scheme would be affected after the application of the secure sketch. We further study the trade-off between the performance of the scheme and the bound of the entropy loss from the secure sketch.

  7. Porous Networks Through Colloidal Templates

    NASA Astrophysics Data System (ADS)

    Li, Qin; Retsch, Markus; Wang, Jianjun; Knoll, Wolfgang; Jonas, Ulrich

    Porous networks represent a class of materials with interconnected voids with specific properties concerning adsorption, mass and heat transport, and spatial confinement, which lead to a wide range of applications ranging from oil recovery and water purification to tissue engineering. Porous networks with well-defined, highly ordered structure and periodicities around the wavelength of light can furthermore show very sophisticated optical properties. Such networks can be fabricated from a very large range of materials by infiltration of a sacrificial colloidal crystal template and subsequent removal of the template. The preparation procedures reported in the literature are discussed in this review and the resulting porous networks are presented with respect to the underlying material class. Furthermore, methods for hierarchical superstructure formation and functionalization of the network walls are discussed.

  8. Template boundary definition in mammalian telomerase.

    PubMed

    Chen, Jiunn-Liang; Greider, Carol W

    2003-11-15

    Telomerase uses a short template sequence in its intrinsic RNA component to synthesize telomere repeats. Disruption of the helix P1b in human telomerase RNA or alteration of its distance from the template resulted in telomerase copying residues past the normal template boundary both in vivo and in vitro. Therefore, helix P1b is important for template boundary definition in human telomerase. Mouse telomerase RNA lacks helix P1b, and the boundary is established at 2 nt downstream of the 5'-end. The divergent structure of boundary definition elements in mammals, yeast, and ciliates suggests diverse mechanisms for template boundary definition in telomerase.

  9. RNA-templated DNA repair

    PubMed Central

    Storici, Francesca; Bebenek, Katarzyna; Kunkel, Thomas A.; Gordenin, Dmitry A.; Resnick, Michael A.

    2007-01-01

    RNA can act as a template for DNA synthesis in the reverse transcription of retroviruses and retrotransposons1 and in the elongation of telomeres2. Despite its abundance in the nucleus, there has been no evidence for a direct role of RNA as a template in the repair of any chromosomal DNA lesions, including DNA double-strand breaks (DSBs), which are repaired in most organisms by homologous recombination or by non-homologous end joining3. An indirect role for RNA in DNA repair, following reverse transcription and formation of a complementary DNA, has been observed in the non-homologous joining of DSB ends4,5. In the yeast Saccharomyces cerevisiae, in which homologous recombination is efficient3, RNA was shown to mediate recombination, but only indirectly through a cDNA intermediate6,7 generated by the reverse transcriptase function of Ty retrotransposons in Ty particles in the cytoplasm8. Although pairing between duplex DNA and single-strand (ss)RNA can occur in vitro9,10 and in vivo11, direct homologous exchange of genetic information between RNA and DNA molecules has not been observed. We show here that RNA can serve as a template for DNA synthesis during repair of a chromosomal DSB in yeast. The repair was accomplished with RNA oligonucleotides complementary to the broken ends. This and the observation that even yeast replicative DNA polymerases such as α and δ can copy short RNA template tracts in vitro demonstrate that RNA can transfer genetic information in vivo through direct homologous interaction with chromosomal DNA. PMID:17429354

  10. FUZZY SUPERNOVA TEMPLATES. I. CLASSIFICATION

    SciTech Connect

    Rodney, Steven A.; Tonry, John L. E-mail: jt@ifa.hawaii.ed

    2009-12-20

    Modern supernova (SN) surveys are now uncovering stellar explosions at rates that far surpass what the world's spectroscopic resources can handle. In order to make full use of these SN data sets, it is necessary to use analysis methods that depend only on the survey photometry. This paper presents two methods for utilizing a set of SN light-curve templates to classify SN objects. In the first case, we present an updated version of the Bayesian Adaptive Template Matching program (BATM). To address some shortcomings of that strictly Bayesian approach, we introduce a method for Supernova Ontology with Fuzzy Templates (SOFT), which utilizes fuzzy set theory for the definition and combination of SN light-curve models. For well-sampled light curves with a modest signal-to-noise ratio (S/N >10), the SOFT method can correctly separate thermonuclear (Type Ia) SNe from core collapse SNe with >=98% accuracy. In addition, the SOFT method has the potential to classify SNe into sub-types, providing photometric identification of very rare or peculiar explosions. The accuracy and precision of the SOFT method are verified using Monte Carlo simulations as well as real SN light curves from the Sloan Digital Sky Survey and the SuperNova Legacy Survey. In a subsequent paper, the SOFT method is extended to address the problem of parameter estimation, providing estimates of redshift, distance, and host galaxy extinction without any spectroscopy.

  11. Titanium template for scaphoid reconstruction.

    PubMed

    Haefeli, M; Schaefer, D J; Schumacher, R; Müller-Gerbl, M; Honigmann, P

    2015-06-01

    Reconstruction of a non-united scaphoid with a humpback deformity involves resection of the non-union followed by bone grafting and fixation of the fragments. Intraoperative control of the reconstruction is difficult owing to the complex three-dimensional shape of the scaphoid and the other carpal bones overlying the scaphoid on lateral radiographs. We developed a titanium template that fits exactly to the surfaces of the proximal and distal scaphoid poles to define their position relative to each other after resection of the non-union. The templates were designed on three-dimensional computed tomography reconstructions and manufactured using selective laser melting technology. Ten conserved human wrists were used to simulate the reconstruction. The achieved precision measured as the deviation of the surface of the reconstructed scaphoid from its virtual counterpart was good in five cases (maximal difference 1.5 mm), moderate in one case (maximal difference 3 mm) and inadequate in four cases (difference more than 3 mm). The main problems were attributed to the template design and can be avoided by improved pre-operative planning, as shown in a clinical case. © The Author(s) 2014.

  12. Template synthesis of nanophase mesocarbon.

    PubMed

    Yang, Nancy Y; Jian, Kengqing; Külaots, Indrek; Crawford, Gregory P; Hurt, Robert H

    2003-10-01

    Templating techniques are used increasingly to create carbon materials with precisely engineered pore systems. This article presents a new templating technique that achieves simultaneous control of pore structure and molecular (crystal) structure in a single synthesis step. With the use of discotic liquid crystalline precursors, unique carbon structures can be engineered by selecting the size and geometry of the confining spaces and selecting the template material to induce edge-on or face-on orientation of the discotic precursor. Here mesophase pitch is infiltrated by capillary forces into a nanoporous glass followed by slow carbonization and NaOH etching. The resulting porous carbon material exhibits interconnected solid grains about 100 nm in size, a monodisperse pore size of 60 nm, 42% total porosity, and an abundance of edge-plane inner surfaces that reflect the favored edge-on anchoring of the mesophase precursor on glass. This new carbon form is potentially interesting for a number of important applications in which uniform large pores, active-site-rich surfaces, and easy access to interlayer spaces in nanometric grains are advantageous.

  13. LTL - The Little Template Library

    NASA Astrophysics Data System (ADS)

    Gössl, C. A.; Drory, N.; Snigula, J.

    2004-07-01

    The Little Template Library is an expression templates based C++ library for array processing, image processing, FITS and ASCII I/O, and linear algebra. It is released under the GNU Public License (GPL). Although the library is developed with application to astronomical image and data processing in mind, it is by no means restricted to these fields of application. In fact, it qualifies as a fully general array processing package. Focus is laid on a high abstraction level regarding the handling of expressions involving arrays or parts thereof and linear algebra related operations without the usually involved negative impact on performance. The price to pay is dependence on a compiler implementing enough of the current ANSI C++ specification, as well as significantly higher demand on resources at compile time. The LTL provides dynamic arrays of up to 5 dimensions, sub-arrays and slicing, support for fixed size vectors and matrices including basic linear algebra operations, expression templates based evaluation, and I/O facilities for columnar ASCII and FITS format files. In addition it supplies utility classes for statistics, linear and non-linear least squares fitting, and command line and configuration file parsing. YODA (Drory 2002) and all elements of the WeCAPP reduction pipeline (Riffeser et al. 2001, Gössl & Riffeser 2002, 2003) were implemented using the LTL.

  14. Random template banks and relaxed lattice coverings

    NASA Astrophysics Data System (ADS)

    Messenger, C.; Prix, R.; Papa, M. A.

    2009-05-01

    Template-based searches for gravitational waves are often limited by the computational cost associated with searching large parameter spaces. The study of efficient template banks, in the sense of using the smallest number of templates, is therefore of great practical interest. The traditional approach to template-bank construction requires every point in parameter space to be covered by at least one template, which rapidly becomes inefficient at higher dimensions. Here we study an alternative approach, where any point in parameter space is covered only with a given probability η<1. We find that by giving up complete coverage in this way, large reductions in the number of templates are possible, especially at higher dimensions. The prime examples studied here are random template banks in which templates are placed randomly with uniform probability over the parameter space. In addition to its obvious simplicity, this method turns out to be surprisingly efficient. We analyze the statistical properties of such random template banks, and compare their efficiency to traditional lattice coverings. We further study relaxed lattice coverings (using Zn and An* lattices), which similarly cover any signal location only with probability η. The relaxed An* lattice is found to yield the most efficient template banks at low dimensions (n≲10), while random template banks increasingly outperform any other method at higher dimensions.

  15. Random template banks and relaxed lattice coverings

    SciTech Connect

    Messenger, C.; Prix, R.; Papa, M. A.

    2009-05-15

    Template-based searches for gravitational waves are often limited by the computational cost associated with searching large parameter spaces. The study of efficient template banks, in the sense of using the smallest number of templates, is therefore of great practical interest. The traditional approach to template-bank construction requires every point in parameter space to be covered by at least one template, which rapidly becomes inefficient at higher dimensions. Here we study an alternative approach, where any point in parameter space is covered only with a given probability {eta}<1. We find that by giving up complete coverage in this way, large reductions in the number of templates are possible, especially at higher dimensions. The prime examples studied here are random template banks in which templates are placed randomly with uniform probability over the parameter space. In addition to its obvious simplicity, this method turns out to be surprisingly efficient. We analyze the statistical properties of such random template banks, and compare their efficiency to traditional lattice coverings. We further study relaxed lattice coverings (using Z{sub n} and A{sub n}* lattices), which similarly cover any signal location only with probability {eta}. The relaxed A{sub n}* lattice is found to yield the most efficient template banks at low dimensions (n < or approx. 10), while random template banks increasingly outperform any other method at higher dimensions.

  16. Distorted colloidal arrays as designed template

    NASA Astrophysics Data System (ADS)

    Yu, Ye; Zhou, Ziwei; Möhwald, Helmuth; Ai, Bin; Zhao, Zhiyuan; Ye, Shunsheng; Zhang, Gang

    2015-01-01

    In this paper, a novel type of colloidal template with broken symmetry was generated using commercial, inductively coupled plasma reactive ion etching (ICP-RIE). With proper but simple treatment, the traditional symmetric non-close-packed colloidal template evolves into an elliptical profile with high uniformity. This unique feature can add flexibility to colloidal lithography and/or other lithography techniques using colloidal particles as building blocks to fabricate nano-/micro-structures with broken symmetry. Beyond that the novel colloidal template we developed possesses on-site tunability, i.e. the transformability from a symmetric into an asymmetric template. Sandwich-type particles with eccentric features were fabricated utilizing this tunable template. This distinguishing feature will provide the possibility to fabricate structures with unique asymmetric features using one set of colloidal template, providing flexibility and broad tunability to enable nano-/micro-structure fabrication with colloidal templates.

  17. Distorted colloidal arrays as designed template.

    PubMed

    Yu, Ye; Zhou, Ziwei; Möhwald, Helmuth; Ai, Bin; Zhao, Zhiyuan; Ye, Shunsheng; Zhang, Gang

    2015-01-21

    In this paper, a novel type of colloidal template with broken symmetry was generated using commercial, inductively coupled plasma reactive ion etching (ICP-RIE). With proper but simple treatment, the traditional symmetric non-close-packed colloidal template evolves into an elliptical profile with high uniformity. This unique feature can add flexibility to colloidal lithography and/or other lithography techniques using colloidal particles as building blocks to fabricate nano-/micro-structures with broken symmetry. Beyond that the novel colloidal template we developed possesses on-site tunability, i.e. the transformability from a symmetric into an asymmetric template. Sandwich-type particles with eccentric features were fabricated utilizing this tunable template. This distinguishing feature will provide the possibility to fabricate structures with unique asymmetric features using one set of colloidal template, providing flexibility and broad tunability to enable nano-/micro-structure fabrication with colloidal templates.

  18. Template Electrosynthesis of High-Performance Graphene Microengines.

    PubMed

    Martín, Aída; Jurado-Sánchez, Beatriz; Escarpa, Alberto; Wang, Joseph

    2015-08-05

    Template-prepared graphene/Pt and graphene/Au tubular microengines, with extremely high electrocatalytic activity and propulsion efficiency, are described. The new bubble-propelled graphene/metal micromotors are synthesized rapidly and inexpensively by the direct electrodeposition of graphene oxide (GO) within the conical pores of a polycarbonate template membrane followed by deposition of the inner metal layer. The presence of high number of edges and defects in the graphene layer results in highly reactive microporous Pt or Au catalytic structures. The high catalytic activity leads to an ultrafast bubble propulsion (as high as 170 body lengths/sec) and operation at extremely low levels (0.1%) of the peroxide fuel. The effect of such dramatically enhanced catalytic surface area on the bubble growth and motor speed has been theoretically modeled. The template-prepared graphene-based microengines display distinct moving trajectories, along with long microbubble tails. The fast catalytic locomotion and attractive performance of the new graphene/Pt micromotors hold considerable promise for diverse applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cryogenic Gellant and Fuel Formulation for Metallized Gelled Propellants: Hydrocarbons and Hydrogen with Aluminum

    NASA Technical Reports Server (NTRS)

    Wong, Wing; Starkovich, John; Adams, Scott; Palaszewski, Bryan; Davison, William; Burt, William; Thridandam, Hareesh; Hu-Peng, Hsiao; Santy, Myrrl J.

    1994-01-01

    An experimental program to determine the viability of nanoparticulate gellant materials for gelled hydrocarbons and gelled liquid hydrogen was conducted. The gellants included alkoxides (BTMSE and BTMSH) and silica-based materials. Hexane, ethane, propane and hydrogen were gelled with the newly-formulated materials and their rheological properties were determined: shear stress versus shear rate and their attendant viscosities. Metallized hexane with aluminum particles was also rheologically characterized. The propellant and gellant formulations were selected for the very high surface area and relatively-high energy content of the gellants. These new gellants can therefore improve rocket engine specific impulse over that obtained with traditional cryogenic-fuel gellant materials silicon dioxide, frozen methane, or frozen ethane particles. Significant reductions in the total mass of the gellant were enabled in the fuels. In gelled liquid hydrogen, the total mass of gellant was reduced from 10-40 wt percent of frozen hydrocarbon particles to less that 8 wt percent with the alkoxide.

  20. Method for producing metal oxide aerogels

    DOEpatents

    Tillotson, Thomas M.; Poco, John F.; Hrubesh, Lawrence W.; Thomas, Ian M.

    1995-01-01

    A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm.sup.3 and greater than 0.27g/cm.sup.3. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods.

  1. Method for producing metal oxide aerogels

    DOEpatents

    Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

    1995-04-25

    A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm{sup 3} and greater than 0.27g/cm{sup 3}. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods. 8 figs.

  2. Functional Programming with C++ Template Metaprograms

    NASA Astrophysics Data System (ADS)

    Porkoláb, Zoltán

    Template metaprogramming is an emerging new direction of generative programming. With the clever definitions of templates we can force the C++ compiler to execute algorithms at compilation time. Among the application areas of template metaprograms are the expression templates, static interface checking, code optimization with adaption, language embedding and active libraries. However, as template metaprogramming was not an original design goal, the C++ language is not capable of elegant expression of metaprograms. The complicated syntax leads to the creation of code that is hard to write, understand and maintain. Although template metaprogramming has a strong relationship with functional programming, this is not reflected in the language syntax and existing libraries. In this paper we give a short and incomplete introduction to C++ templates and the basics of template metaprogramming. We will enlight the role of template metaprograms, and some important and widely used idioms. We give an overview of the possible application areas as well as debugging and profiling techniques. We suggest a pure functional style programming interface for C++ template metaprograms in the form of embedded Haskell code which is transformed to standard compliant C++ source.

  3. Amine templated zinc phosphates phases for membrane separations

    SciTech Connect

    Nenoff, T.M.; Chavez, A.V.; Thoma, S.G.; Provencio, P.; Harrison, W.T.A.; Phillips, M.L.F.

    1998-08-01

    This research is focused on developing inorganic molecular sieve membranes for light gas separations such as hydrogen recovery and natural gas purification, and organic molecular separations, such as chiral enantiomers. The authors focus on zinc phosphates because of the ease in crystallization of new phases and the wide range of pore sizes and shapes obtained. With hybrid systems of zinc phosphate crystalline phases templated by amine molecules, the authors are interested in better understanding the association of the template molecules to the inorganic phase, and how the organic transfers its size, shape, and (in some cases) chirality to the bulk. Furthermore, the new porous phases can also be synthesized as thin films on metal oxide substrates. These films allow one to make membranes from organic/inorganic hybrid systems, suitable for diffusion experiments. Characterization techniques for both the bulk phases and the thin films include powder X-ray diffraction, TGA, Scanning Electron Micrograph (SEM) and Electron Dispersive Spectrometry (EDS).

  4. Radial growth of plasmon coupled gold nanowires on colloidal templates.

    PubMed

    Farrokhtakin, Elmira; Rodríguez-Fernández, Denis; Mattoli, Virgilio; Solís, Diego M; Taboada, José M; Obelleiro, Fernando; Grzelczak, Marek; Liz-Marzán, Luis M

    2015-07-01

    The library of plasmonic nanosystems keeps expanding with novel structures with the potential to provide new solutions to old problems in science and technology. We report the synthesis of a novel plasmonic system based on the growth of gold nanowires radially branching from the surface of silica particles. The nanowires length could be controlled by tuning the molar ratio between metal salt and surface-grafted seeds. Electron microscopy characterization revealed that the obtained one-dimensional nanoparticles are polycrystalline but uniformly distributed on the spherical template. The length of the nanowires in turn determines the optical response of the metallodielectric particles, so that longer wires display red-shifted longitudinal plasmon bands. Accurate theoretical modeling of these complex objects revealed that the densely organized nanowires display intrinsically coupled plasmon modes that can be selectively decoupled upon detachment of the nanowires from the surface of the colloidal silica template. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Nitrile hydration by thiolate- and alkoxide-ligated Co-NHase analogues. Isolation of Co(III)-amidate and Co(III)-iminol intermediates.

    PubMed

    Swartz, Rodney D; Coggins, Michael K; Kaminsky, Werner; Kovacs, Julie A

    2011-03-23

    Nitrile hydratases (NHases) are thiolate-ligated Fe(III)- or Co(III)-containing enzymes, which convert nitriles to the corresponding amide under mild conditions. Proposed NHase mechanisms involve M(III)-NCR, M(III)-OH, M(III)-iminol, and M(III)-amide intermediates. There have been no reported crystallographically characterized examples of these key intermediates. Spectroscopic and kinetic data support the involvement of a M(III)-NCR intermediate. A H-bonding network facilitates this enzymatic reaction. Herein we describe two biomimetic Co(III)-NHase analogues that hydrate MeCN, and four crystallographically characterized NHase intermediate analogues, [Co(III)(S(Me2)N(4)(tren))(MeCN)](2+) (1), [Co(III)(S(Me2)N(4)(tren))(OH)](+) (3), [Co(III)(S(Me2)N(4)(tren))(NHC(O)CH(3))](+) (2), and [Co(III)(O(Me2)N(4)(tren))(NHC(OH)CH(3))](2+) (5). Iminol-bound 5 represents the first example of a Co(III)-iminol compound in any ligand environment. Kinetic parameters (k(1)(298 K) = 2.98(5) M(-1) s(-1), ΔH(‡) = 12.65(3) kcal/mol, ΔS(‡) = -14(7) e.u.) for nitrile hydration by 1 are reported, and the activation energy E(a) = 13.2 kcal/mol is compared with that (E(a) = 5.5 kcal/mol) of the NHase enzyme. A mechanism involving initial exchange of the bound MeCN for OH- is ruled out by the fact that nitrile exchange from 1 (k(ex)(300 K) = 7.3(1) × 10(-3) s(-1)) is 2 orders of magnitude slower than nitrile hydration, and that hydroxide bound 3 does not promote nitrile hydration. Reactivity of an analogue that incorporates an alkoxide as a mimic of the highly conserved NHase serine residue shows that this moiety facilitates nitrile hydration under milder conditions. Hydrogen-bonding to the alkoxide stabilizes a Co(III)-iminol intermediate. Comparison of the thiolate versus alkoxide intermediate structures shows that C≡N bond activation and C═O bond formation proceed further along the reaction coordinate when a thiolate is incorporated into the coordination sphere.

  6. Nanoporous carbon supported metal particles: their synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Yang, Yunxia; Tang, Liangguang; Burke, Nick; Chiang, Ken

    2012-08-01

    In the current work, a simplified hard templating approach is used to synthesise metal (Ag, Rh, Ir and Pt) containing structured carbon. The target metals are first introduced into the NaY zeolite template by wetness impregnation. The metals are carried in the super cages of the zeolite and subsequently embedded in the final structures after the steps of carbonisation and the template removal. Scanning electron microscopy images have confirmed that the carbon structures produced by this method retain the morphology of the original template. Transmission electron microscopy reveals the presence of dispersed metal particles in all the carbon structures produced. The metal loadings in these templated structures can reach 35 wt% without significant losses of surface areas and pore volumes. Selected carbon supported metals are tested for their catalytic activity for the methanation of carbon monoxide. The finding suggested that this method is effective in preparing metal nanoparticles for use as catalysts.

  7. Template-assisted GLAD: approach to single and multipatch patchy particles with controlled patch shape.

    PubMed

    He, Zhenping; Kretzschmar, Ilona

    2013-12-23

    Template-assisted glancing angle deposition (GLAD) is explored for the fabrication of single and multipatch patchy particles with one or more patches of controlled but asymmetric shape. The template is used to ensure the formation of uniform patchy particles, whereas rotation of the template gives access to a large number of asymmetric patch shapes caused by the shadowing effect of the templating groove and/or the neighboring particle. Careful analysis with a straightforward geometric model reveals the effect of the angle of incidence, rotational angle, groove size, and particle size on the patch shape. Initial magnetic field assembly results are presented to illustrate the removal of patchy particles from their template and accessibility to a large number of patchy particles. Two-patch particles with overlapping patches are also accessible by means of secondary metal vapor deposition. The connectivity of these two patches on each particle and the predictable size of the overlapping section provide access to functional patchy particles. The combination of the template-assisted GLAD method with rotation of the template and secondary evaporation is demonstrated to be a good method for fabricating patchy particles with a variety of asymmetric patch shapes, sizes, and multipatches where every particle of a batch carries exactly the same patch pattern and thereby provides valuable input on experimentally accessible patch shapes for future experimental and computational studies of patchy particles.

  8. Learning templates for artistic portrait lighting analysis.

    PubMed

    Chen, Xiaowu; Jin, Xin; Wu, Hongyu; Zhao, Qinping

    2015-02-01

    Lighting is a key factor in creating impressive artistic portraits. In this paper, we propose to analyze portrait lighting by learning templates of lighting styles. Inspired by the experience of artists, we first define several novel features that describe the local contrasts in various face regions. The most informative features are then selected with a stepwise feature pursuit algorithm to derive the templates of various lighting styles. After that, the matching scores that measure the similarity between a testing portrait and those templates are calculated for lighting style classification. Furthermore, we train a regression model by the subjective scores and the feature responses of a template to predict the score of a portrait lighting quality. Based on the templates, a novel face illumination descriptor is defined to measure the difference between two portrait lightings. Experimental results show that the learned templates can well describe the lighting styles, whereas the proposed approach can assess the lighting quality of artistic portraits as human being does.

  9. Alternating Sequence Controlled Copolymer Synthesis of α-Hydroxy Acids via Syndioselective Ring-Opening Polymerization of O-Carboxyanhydrides Using Zirconium/Hafnium Alkoxide Initiators.

    PubMed

    Sun, Yangyang; Jia, Zhaowei; Chen, Changjuan; Cong, Yong; Mao, Xiaoyang; Wu, Jincai

    2017-08-09

    The ring-opening polymerization (ROP) of O-carboxyanhydrides (OCAs) can give diverse poly(α-hydroxy acid)s (PAHAs) with different functional groups because of easy modification of the side group of OCAs, which can extend applications of PAHAs widely. The stereoselective polymerization of O-carboxyanhydrides and further sequence controlled alternating copolymerization of OCAs were still big challenges until now for lack of suitable catalysts/initiators. In this work, a highly syndioselective ROP of OCAs system as the first stereoselective example in this area is reported using zirconium/hafnium alkoxides as initiators with the highest Pr value up to 0.95. Furthermore, these initiators were successfully applied in the precisely alternating sequence controlled copolymerization of PheOCA and Tyr(Bn)OCA, and alternating copolymerization of LacOCA and PheOCA was also achieved.

  10. Fluorinated Alkoxide-Based Magnesium-Ion Battery Electrolytes that Demonstrate Li-Ion-Battery-Like High Anodic Stability and Solution Conductivity.

    PubMed

    Crowe, Adam J; Stringham, Kyle K; Bartlett, Bart M

    2016-09-07

    Based on DFT predictions, a series of highly soluble fluorinated alkoxide-based electrolytes were prepared, examined electrochemically, and reversibly cycled. The alcohols react with ethylmagnesium chloride to generate a fluoroalkoxy-magnesium chloride intermediate, which subsequently reacts with aluminum chloride to generate the electrolyte. Solutions starting from a 1,1,1,3,3,3-hexafluoro-2-methylpropan-2-ol precursor exhibit high anodic stability, 3.2 V vs Mg(2+/0), and a record 3.5 mS/cm solution conductivity. Excellent galvanostatic cycling and capacity retention (94%) is observed with more than 300 h of cycle time while employing the standard Chevrel phase-Mo6S8 cathode material.

  11. DNA-templated gold nanowires

    NASA Astrophysics Data System (ADS)

    Mohammadzadegan, Reza; Mohabatkar, Hassan; Sheikhi, Mohammad Hossein; Safavi, Afsaneh; Khajouee, Mahmood Barati

    2008-10-01

    We have developed simple methods of reproducibly creating deoxyribonucleic acid (DNA)-templated gold nanowires on silicon. First DNA nanowires were aligned on silicon surfaces. Briefly, modified silicon wafer was soaked in the DNA solution, and then the solution was removed using micropipettes; the surface tension at the moving air-solution interface is sufficient to align the DNA nanowires on the silicon wafer. In another attempt, an aqueous dispersion of sodium azide-stabilized gold nanoparticles was prepared. The nanoparticles aligned double-stranded λ-DNA to form a linear nanoparticle array. Continuous gold nanowires were obtained. The above nanowires were structurally characterized using scanning electron microscopy. The results of the characterizations show the wires to be 57-323 nm wide, to be continuous with a length of 2.8-9.5 μm. The use of DNA as a template for the self-assembly of conducting nanowires represents a potentially important approach in the fabrication of nanoscale interconnects.

  12. Ferroelectric nanotubes fabricated using nanowires as positive templates

    SciTech Connect

    Alexe, M.; Hesse, D.; Schmidt, V.; Senz, S.; Fan, H. J.; Zacharias, M.; Goesele, U.

    2006-10-23

    The authors report on fabrication and electrical characterization of ferroelectric nanotubes and metal-ferroelectric-metal composite nanotubes using silicon and ZnO nanowires as positive templates. Nanotubes of high aspect ratio with a minimum inner diameter of about 100 nm and a length ranging from 0.5 {mu}m to a few microns have been obtained by magnetron sputtering and/or pulsed laser deposition. Metal-ferroelectric one-dimensional structures were characterized by piezoelectric scanning probe microscopy, showing piezoelectric hysteresis loops and ferroelectric switching. The presented fabrication approach can be used to fabricate three-dimensional capacitors for ferroelectric nonvolatile memories as well as nanosize piezoelectric scanners and actuators.

  13. Method of installing sub-sea templates

    SciTech Connect

    Hampton, J.E.

    1984-03-06

    A subsea template is installed by a method which includes the steps of securing the template in a position beneath the deck of a semi-submersible drilling vessel, moving the semi-submersible drilling vessel to an appropriate offshore site and subsequently lowering the template from the semi-submersible to the sea bed. In addition, at least three anchorage templates may be loaded onto one or both of the pontoons of the semi-submersible drilling vessel at its original position and are subsequently lowered from the pontoons to their respective locations on the sea bed after the semi-submersible has moved to the offshore site.

  14. Template overlap method for massive jets

    NASA Astrophysics Data System (ADS)

    Almeida, Leandro G.; Lee, Seung J.; Perez, Gilad; Sterman, George; Sung, Ilmo

    2010-09-01

    We introduce a new class of infrared safe jet observables, which we refer to as template overlaps, designed to filter targeted highly-boosted particle decays from QCD jets and other background. Template overlaps are functional measures that quantify how well the energy flow of a physical jet matches the flow of a boosted partonic decay. Any region of the partonic phase space for the boosted decays defines a template. We will refer to the maximum functional overlap found this way as the template overlap. To illustrate the method, we test lowest-order templates designed to distinguish highly-boosted top and Higgs decays from backgrounds produced by event generators. For the functional overlap, we find good results with a simple construction based on a Gaussian in energy differences within angular regions surrounding the template partons. Although different event generators give different averages for our template overlaps, we find in each case excellent rejection power, especially when combined with cuts based on jet shapes. The template overlaps are capable of systematic improvement by including higher-order corrections in the template phase space.

  15. Optimized periocular template selection for human recognition.

    PubMed

    Bakshi, Sambit; Sa, Pankaj K; Majhi, Banshidhar

    2013-01-01

    A novel approach for selecting a rectangular template around periocular region optimally potential for human recognition is proposed. A comparatively larger template of periocular image than the optimal one can be slightly more potent for recognition, but the larger template heavily slows down the biometric system by making feature extraction computationally intensive and increasing the database size. A smaller template, on the contrary, cannot yield desirable recognition though the smaller template performs faster due to low computation for feature extraction. These two contradictory objectives (namely, (a) to minimize the size of periocular template and (b) to maximize the recognition through the template) are aimed to be optimized through the proposed research. This paper proposes four different approaches for dynamic optimal template selection from periocular region. The proposed methods are tested on publicly available unconstrained UBIRISv2 and FERET databases and satisfactory results have been achieved. Thus obtained template can be used for recognition of individuals in an organization and can be generalized to recognize every citizen of a nation.

  16. A hybrid approach for face template protection

    NASA Astrophysics Data System (ADS)

    Feng, Y. C.; Yuen, Pong C.; Jain, Anil K.

    2008-03-01

    Biometric template protection is one of the important issues in deploying a practical biometric system. To tackle this problem, many algorithms have been reported in recent years, most of them being applicable to fingerprint biometric. Since the content and representation of fingerprint template is different from templates of other modalities such as face, the fingerprint template protection algorithms cannot be directly applied to face template. Moreover, we believe that no single template protection method is capable of satisfying the diversity, revocability, security and performance requirements. We propose a three-step cancelable framework which is a hybrid approach for face template protection. This hybrid algorithm is based on the random projection, class distribution preserving transform and hash function. Two publicly available face databases, namely FERET and CMU-PIE, are used for evaluating the template protection scheme. Experimental results show that the proposed method maintains good template discriminability, resulting in good recognition performance. A comparison with the recently developed random multispace quantization (RMQ) biohashing algorithm shows that our method outperforms the RMQ algorithm.

  17. Influence of template fill in graphoepitaxy DSA

    NASA Astrophysics Data System (ADS)

    Doise, Jan; Bekaert, Joost; Chan, Boon Teik; Hong, SungEun; Lin, Guanyang; Gronheid, Roel

    2016-03-01

    Directed self-assembly (DSA) of block copolymers (BCP) is considered a promising patterning approach for the 7 nm node and beyond. Specifically, a grapho-epitaxy process using a cylindrical phase BCP may offer an efficient solution for patterning randomly distributed contact holes with sub-resolution pitches, such as found in via and cut mask levels. In any grapho-epitaxy process, the pattern density impacts the template fill (local BCP thickness inside the template) and may cause defects due to respectively over- or underfilling of the template. In order to tackle this issue thoroughly, the parameters that determine template fill and the influence of template fill on the resulting pattern should be investigated. In this work, using three process flow variations (with different template surface energy), template fill is experimentally characterized as a function of pattern density and film thickness. The impact of these parameters on template fill is highly dependent on the process flow, and thus pre-pattern surface energy. Template fill has a considerable effect on the pattern transfer of the DSA contact holes into the underlying layer. Higher fill levels give rise to smaller contact holes and worse critical dimension uniformity. These results are important towards DSA-aware design and show that fill is a crucial parameter in grapho-epitaxy DSA.

  18. Anisotropic Electroless Deposition on DNA Origami Templates To Form Small Diameter Conductive Nanowires.

    PubMed

    Uprety, Bibek; Westover, Tyler; Stoddard, Michael; Brinkerhoff, Kamron; Jensen, John; Davis, Robert C; Woolley, Adam T; Harb, John N

    2017-01-24

    An improved method for the metallization of DNA origami is examined in this work. DNA origami, a simple and robust method for creating a wide variety of nanostructured shapes and patterns, provides an enabling template for bottom-up fabrication of next-generation nanodevices. Selective metallization of these DNA templates is needed to make nanoelectronic devices. Here, we demonstrate a metallization process that uses gold nanorod seeds followed by anisotropic plating to provide improved morphology and greater control of the final metallized width of the structure. In our approach, gold nanorods are attached to an origami template to create a seed layer. Electroless gold deposition is then used to fill the gaps between seeds in order to create continuous, conductive nanowires. Importantly, growth during electroless deposition occurs preferentially in the length direction at a rate that is approximately 4 times the growth rate in the width direction, which enables fabrication of narrow, continuous wires. The electrical properties of 49 nanowires with widths ranging from 13 to 29 nm were characterized, and resistivity values as low as 8.9 × 10(-7) Ω·m were measured. The anisotropic metallization process presented here represents important progress toward the creation of nanoelectronic devices by molecularly directed placement of functional components onto self-assembled biological templates.

  19. Ordered macroporous materials by emulsion templating

    NASA Astrophysics Data System (ADS)

    Imhof, A.; Pine, D. J.

    1997-10-01

    Ordered macroporous materials with pore diameters comparable to optical wavelengths are predicted to have unique and highly useful optical properties such as photonic bandgaps and optical stop-bands. Tight control over the pore size distribution might also lead to improved macroporous materials (those with pores greater than approximately 50nm) for application as catalytic surfaces and supports, adsorbents, chromatographic materials, filters, light-weight structural materials, and thermal, acoustic and electrical insulators. Although methods exist for producing ordered porous materials with pore diameters less than 10nm (refs 10, 11), there is no general method for producing such materials with uniform pore sizes at larger length scales. Here we report a new method for producing highly monodisperse macroporous materials with pore sizes ranging from 50nm to several micrometres. Starting with an emulsion of equally sized droplets (produced through a repeated fractionation procedure), we form macroporous materials of titania, silica and zirconia by using the emulsion droplets as templates around which material is deposited through a sol-gel process. Subsequent drying and heat treatment yields solid materials with spherical pores left behind by the emulsion droplets. These pores are highly ordered, reflecting the self-assembly of the original monodisperse emulsion droplets into a nearly crystalline array. We show that the pore size can be accurately controlled, and that the technique should be applicable to a wide variety of metal oxides and even organic polymer gels.

  20. DNA-Templated Introduction of an Aldehyde Handle in Proteins.

    PubMed

    Kodal, Anne Louise B; Rosen, Christian B; Mortensen, Michael R; Tørring, Thomas; Gothelf, Kurt V

    2016-07-15

    Many medical and biotechnological applications rely on protein labeling, but a key challenge is the production of homogeneous and site-specific conjugates. This can rarely be achieved by simple residue-specific random labeling, but generally requires genetic engineering. Using site-selective DNA-templated reductive amination, we created DNA-protein conjugates with control over labeling stoichiometry and without genetic engineering. A guiding DNA strand with a metal-binding functionality facilitates site-selectivity by directing the coupling of a second reactive DNA strand in the vicinity of a protein metal-binding site. We demonstrate DNA-templated reductive amination for His6 -tagged proteins and metal-binding proteins, including IgG1 antibodies. We also used a cleavable linker between the DNA and the protein to remove the DNA and introduce a single aldehyde on the protein. This functions as a handle for further modifications with desired labels. In addition to directing the aldehyde positioning, the DNA provides a straightforward route for purification between reaction steps. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Zinc finger proteins as templates for metal ion exchange: Substitution effects on the C-finger of HIV nucleocapsid NCp7 using M(chelate) species (M=Pt, Pd, Au).

    PubMed

    de Paula, Queite A; Mangrum, John B; Farrell, Nicholas P

    2009-10-01

    The interactions of monofunctional [MCl(chelate)] compounds (M=Pt(II), Pd(II) or Au(III) and chelate=diethylenetriamine, dien or 2,2',2''-terpyridine, terpy) with the C-terminal finger of the HIV nucleocapsid NCp7 zinc finger (ZF) were studied by mass spectrometry and circular dichroism spectroscopy. In the case of [M(dien)] species, Pt(II) and Pd(II) behaved in a similar fashion with evidence of adducts caused by displacement of Pt-Cl or Pd-Cl by zinc-bound thiolate. Labilization, presumably under the influence of the strong trans influence of thiolate, resulted in loss of ligand (dien) as well as zinc ejection and formation of species with only Pd(II) or Pt(II) bound to the finger. For both Au(III) compounds the reactions were very fast and only "gold fingers" with no ancillary ligands were observed. For all terpyridine compounds ligand scrambling and metal exchange occurred with formation of [Zn(terpy)](2+). The results conform well to those proposed from the study of model Zn compounds such as N,N'-bis(2-mercapto-ethyl)-1,4-diazacycloheptanezinc(II), [Zn(bme-dach)](2). The possible structures of the adducts formed are discussed and, for Pt(II) and Pd(II), the evidence for possible expansion of the zinc coordination sphere from four- to five-coordinate is discussed. This observation reinforces the possibility of change in geometry for zinc in biology, even in common "structural" sites in metalloenzymes. The results further show that the extent and rate of zinc displacement by inorganic compounds can be modulated by the nature (metal, ligands) of the reacting compound.

  2. Facile synthetic route to nanosized ferrites by using mesoporous silica as a hard template

    NASA Astrophysics Data System (ADS)

    Valdés-Solís, T.; Tartaj, P.; Marbán, G.; Fuertes, A. B.

    2007-04-01

    Spinel ferrite nanoparticles (AFe2O4; A = Mn, Ni, Cu, Co) of around 10-20 nm have been successfully synthesized via a simple nanocasting route using metal nitrates as precursors and mesoporous silica gel as a hard template. Spinel nanoparticles were formed under a nitrogen atmosphere by the high-temperature decomposition of a mixture of metal nitrates that fill the silica pores. The decomposition reactions occurred in the confined space provided by the mesopores of the silica template. Under these conditions, the silica walls restricted the growth of the oxide particles formed and so nanosized particles were obtained. The incorporation of different cations into the spinel ferrite enabled us to easily modulate the magnetic properties of the nanomaterials prepared by the template method. Depending on the chemical composition and temperature, we were able to obtain samples that display reversible magnetic behaviour (zero coercivity field) and samples with coercivity values as high as 1.3 T (13 000 Oe).

  3. Air Sampling System Evaluation Template

    SciTech Connect

    Blunt, Brent

    2000-05-09

    The ASSET1.0 software provides a template with which a user can evaluate an Air Sampling System against the latest version of ANSI N13.1 "Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stacks and Ducts of Nuclear Facilities". The software uses the ANSI N13.1 PIC levels to establish basic design criteria for the existing or proposed sampling system. The software looks at such criteria as PIC level, type of radionuclide emissions, physical state of the radionuclide, nozzle entrance effects, particulate transmission effects, system and component accuracy and precision evaluations, and basic system operations to provide a detailed look at the subsystems of a monitoring and sampling system/program. A GAP evaluation can then be completed which leads to identification of design and operational flaws in the proposed systems. Corrective measures can then be limited to the GAPs.

  4. Mesoporous silica templated zirconia nanoparticles

    NASA Astrophysics Data System (ADS)

    Ballem, Mohamed A.; Córdoba, José M.; Odén, Magnus

    2011-07-01

    Nanoparticles of zirconium oxide (ZrO2) were synthesized by infiltration of a zirconia precursor (ZrOCl2·8H2O) into a SBA-15 mesoporous silica mold using a wet-impregnation technique. X-ray diffractometry and high-resolution transmission electron microscopy show formation of stable ZrO2 nanoparticles inside the silica pores after a thermal treatment at 550 °C. Subsequent leaching out of the silica template by NaOH resulted in well-dispersed ZrO2 nanoparticles with an average diameter of 4 nm. The formed single crystal nanoparticles are faceted with 110 surfaces termination suggesting it to be the preferred growth orientation. A growth model of these nanoparticles is also suggested.

  5. Design of block copolymer templated solid state batteries

    NASA Astrophysics Data System (ADS)

    Bullock, Steven Edward

    The advent of portable electronics has placed a great demand on the power requirements of battery systems. High power batteries for small devices, such as cell phones, laptop computers, and personal data assistants (PDA's) have focused primarily on lithium ion batteries. With the introduction of large flexible panel displays, the need for a flexible battery system is apparent. Ring Opening Metathesis Polymerization (ROMP) is a facile method for synthesizing block copolymers with polar functional groups. These functional groups allow the formation of metal oxide clusters via a template of the microphase separated block copolymer domains. In this thesis, the synthesis of a flexible polymer battery system is described. Diblock copolymers of an ionically conductive unsaturated polyethylene oxide block with a carboxylic acid functionalized block were synthesized and characterized with NMR, IR and Gel Permeation Chromatography (GPC). Characterization of polymer templated LiMn2O 4 clusters and nanocomposites synthesized for the study have a distributed cluster morphology within the polymer matrix. The nanocomposites were analyzed with transmission electron microscopy to determine the morphology of the nanocomposites. Battery performance was characterized with cyclic voltammetry and galvanostatic charge/discharge cycling for power capacity. The ionic conductivity was measured with impedance spectroscopy. The novel room temperature templating strategy used for the synthesis of these ionically conductive nanocomposites requires no thermal cycling steps. This makes it attractive for processing of sheet structures to power flexible displays.

  6. Visual Templates in Pattern Generalization Activity

    ERIC Educational Resources Information Center

    Rivera, F. D.

    2010-01-01

    In this research article, I present evidence of the existence of visual templates in pattern generalization activity. Such templates initially emerged from a 3-week design-driven classroom teaching experiment on pattern generalization involving linear figural patterns and were assessed for existence in a clinical interview that was conducted four…

  7. Visual Templates in Pattern Generalization Activity

    ERIC Educational Resources Information Center

    Rivera, F. D.

    2010-01-01

    In this research article, I present evidence of the existence of visual templates in pattern generalization activity. Such templates initially emerged from a 3-week design-driven classroom teaching experiment on pattern generalization involving linear figural patterns and were assessed for existence in a clinical interview that was conducted four…

  8. Template synthesis of ordered macroporous hydroxyapatite bioceramics.

    PubMed

    Ji, Lijun; Jell, Gavin; Dong, Yixiang; Jones, Julian R; Stevens, Molly M

    2011-08-28

    Hydroxyapatite has found wide application in bone tissue engineering. Here we use a macroporous carbon template to generate highly ordered macroporous hydroxyapatite bioceramics composed of close-packed hollow spherical pores with interconnected channels. The template has advantages for the preparation of ordered materials.

  9. Subject Matter Expert's Training Module Template.

    ERIC Educational Resources Information Center

    Beaudin, Bart P.; Quick, Don

    This template was designed to assist subject matter experts in developing presentations. The template is for a training session plan (lesson plan, presentation plan, evaluation suggestions) that can be used to determine the sequence of what the presenter will say and do. Subject matter experts can easily copy the pages for use during the design…

  10. Self-Templated Formation of Hollow Structures for Electrochemical Energy Applications.

    PubMed

    Yu, Le; Wu, Hao Bin; Lou, Xiong Wen David

    2017-02-21

    in virtue of their exceptional composition-/structure-induced merits. As electrode materials for lithium-ion batteries, hybrid or multishelled metal oxides exhibit high cyclability because of their capability to well accommodate the lithium insertion strain. Also the rate capability is effectively improved by the fast lithium insertion/deinsertion in multishelled or hierarchical hollow structures. These exceptional structural merits also significantly enhance the reaction kinetics and prolong the cycling lifetime of metal-sulfides-based electrodes, which enables the assembly of hybrid supercapacitors with high energy and power densities. On the other hand, multicompositional hollow structures with large exposed surface area and rich open pore channels offer abundant robust active sites and fast charge/mass transport for electrocatalytic reactions. These studies demonstrate that the versatility and superiority of self-templated methods for hollow structured functional materials have greatly promoted their applications for electrochemical energy storage and conversion. With continued research efforts, we are expecting greater and broader impacts brought by the rapidly growing family of hollow structures formed by self-templated methods.

  11. Self-Templated Synthesis of Co- and N-Doped Carbon Microtubes Composed of Hollow Nanospheres and Nanotubes for Efficient Oxygen Reduction Reaction.

    PubMed

    Ahn, Sung Hoon; Manthiram, Arumugam

    2017-03-01

    A facile, self-templated strategy for the synthesis of Co- and N-doped carbon microtubular structures composed of nanoscale hollow spheres and nanotubes is proposed. Cobalt oxalate microtubes serve simultaneously as the solid cobalt precursor for the in situ conversion reaction to metal-organic framework and self-templates for the 1D tubular structure.

  12. Nanoimprint lithography using disposable biomass template

    NASA Astrophysics Data System (ADS)

    Hanabata, Makoto; Takei, Satoshi; Sugahara, Kigen; Nakajima, Shinya; Sugino, Naoto; Kameda, Takao; Fukushima, Jiro; Matsumoto, Yoko; Sekiguchi, Atsushi

    2016-04-01

    A novel nanoimprint lithography process using disposable biomass template having gas permeability was investigated. It was found that a disposable biomass template derived from cellulose materials shows an excellent gas permeability and decreases transcriptional defects in conventional templates such as quartz, PMDS, DLC that have no gas permeability. We believe that outgasses from imprinted materials are easily removed through the template. The approach to use a cellulose for template material is suitable as the next generation of clean separation technology. It is expected to be one of the defect-less thermal nanoimprint lithographic technologies. It is also expected that volatile materials and solvent including materials become available that often create defects and peelings in conventional temples that have no gas permeability.

  13. Poly(ethylene imine)-based granular sorbents by a new process of templated gel-filling. High capacity and selectivity of copper sorption in acidic and alkaline media

    SciTech Connect

    Chanda, M.; Rempel, G.L.

    1995-08-01

    A new process has been developed for making granular gel-type sorbents from chelating resins using metal ion as template. Named as templated gel-filling, the process uses the chosen metal as templating host ion on high-surface-area silica to build a templated gel layer from a solution of the chelating resin in a suitable solvent in which the resin is soluble but its metal complex is insoluble. After cross-linking the templated gel layer, the silica support is removed by alkali to produce a hollow shell of the templated gel. The shells are then soaked in a concentrated aqueous solution of the same metal ion and suspended in the same resin solution to afford gel-filling. The shells thus filled with metal-templated gel are treated with cross-linking agent, followed by acid to remove the template ion and activate the resin for metal sorption. Poly(ethyleneimine) and its partially ethylated derivative have been used to produce granular gel-type sorbents by this process, with Cu(II) as the template ion. These sorbents are found to offer high capacity and selectivity for copper over nickel, cobalt, and zinc in both acidic and alkaline media. Containing a relatively high fraction of imbibed water, the sorbents exhibit markedly enhanced rate behavior, in both sorption and stripping.

  14. Attributes and templates from active measurements with {sup 252}Cf

    SciTech Connect

    Mihalczo, J.T.; Mattingly, J.K.

    2000-02-01

    Active neutron interrogation is useful for the detection of shielded HEU and could also be used for Pu. In an active technique, fissile material is stimulated by an external neutron source to produce fission with the emanation of neutrons and gamma rays. The time distribution of particles leaving the fissile material is measured with respect to the source emission in a variety of ways. A variety of accelerator and radioactive sources can be used. Active interrogation of nuclear weapons/components can be used in two ways: template matching or attribute estimation. Template matching compares radiation signatures with known reference signatures and for treaty applications has the problem of authentication of the reference signatures along with storage and retrieval of templates. Attribute estimation determines, for example, the fissile mass from various features of the radiation signatures and does not require storage of radiation signatures but does require calibration, which can be repeated as necessary. A nuclear materials identification system (NMIS) has been in use at the Oak Ridge Y-12 Plant for verification of weapons components being received and in storage by template matching and has been used with calibrations for attribute (fissile mass) estimation for HEU metal. NMIS employs a {sup 252}Cf source of low intensity (< 2 x 10{sup 6} n/sec) such that the dose at 1 m is approximately twice that on a commercial airline at altitude. The use of such a source presents no significant safety concerns either for personnel or nuclear explosive safety, and has been approved for use at the Pantex Plant on fully assembled weapons systems.

  15. Nanofibrillated cellulose from appalachian hardwoods logging residues as template for antimicrobial copper

    Treesearch

    Masoumeh Hassanzadeh; Ronald Sabo; Alan Rudie; Richard Reiner; Roland Gleisner; Gloria S. Oporto

    2017-01-01

    TEMPO nanofibrillated cellulose (TNFC) fromtwo underutilized Appalachian hardwoods, Northern red oak (Quercus rubra) and yellow poplar (Liriodendron tulipifera), was prepared to determine its feasibility to be used as template for antimicrobial metallic copper particles. In addition, a comparison of the TNFC from the two...

  16. Synthesis of nanostructured/macroscopic low-density copper foams based on metal-coated polymer core–shell particles [Templated synthesis of nanowalled low-density copper foams

    DOE PAGES

    Kim, Sung Ho; Bazin, Nick; Shaw, Jessica I.; ...

    2016-12-06

    A robust, millimeter-sized low-density Cu foam with ~90% (v/v) porosity, ~30 nm thick walls, and ~1 μm diameter spherical pores is prepared by the slip-casting of metal-coated polymer core–shell particles followed by a thermal removal of the polymer. In this paper, we report our key findings that enable the development of the low-density Cu foams. First, we need to synthesize polystyrene (PS) particles coated with a very thin Cu layer (in the range of tens of nanometers). A simple reduction in the amount of Cu deposited onto the PS was not sufficient to form such a low-density Cu foams duemore » to issues related to foam collapse and densification upon the subsequent polymer removal step. Precise control over the morphology of the Cu coating on the particles is essential for the synthesis of a lower density of foams. Second, improving the dispersion of PS–Cu particles in a suspension used for the casting as well as careful optimization of a baking condition minimize the formation of irregular large voids, leading to Cu foams with a more uniform packing and a better connectivity of neighboring Cu hollow shells. Finally, we analyzed mechanical properties of the Cu foams with a depth-sensing indentation test. The uniform Cu foams show a significant improvement in mechanical properties (~1.5× modulus and ~3× hardness) compared to those of uncontrolled foam samples with a similar foam density but irregular large voids. As a result, higher surface areas and a good electric conductivity of the Cu foams present a great potential to future applications.« less

  17. Synthesis of nanostructured/macroscopic low-density copper foams based on metal-coated polymer core–shell particles [Templated synthesis of nanowalled low-density copper foams

    SciTech Connect

    Kim, Sung Ho; Bazin, Nick; Shaw, Jessica I.; Yoo, Jae -Hyuck; Worsley, Marcus A.; Satcher, Jr., Joe H.; Sain, John D.; Kuntz, Joshua D.; Kucheyev, Sergei O.; Baumann, Theodore F.; Hamza, Alex V.

    2016-12-06

    A robust, millimeter-sized low-density Cu foam with ~90% (v/v) porosity, ~30 nm thick walls, and ~1 μm diameter spherical pores is prepared by the slip-casting of metal-coated polymer core–shell particles followed by a thermal removal of the polymer. In this paper, we report our key findings that enable the development of the low-density Cu foams. First, we need to synthesize polystyrene (PS) particles coated with a very thin Cu layer (in the range of tens of nanometers). A simple reduction in the amount of Cu deposited onto the PS was not sufficient to form such a low-density Cu foams due to issues related to foam collapse and densification upon the subsequent polymer removal step. Precise control over the morphology of the Cu coating on the particles is essential for the synthesis of a lower density of foams. Second, improving the dispersion of PS–Cu particles in a suspension used for the casting as well as careful optimization of a baking condition minimize the formation of irregular large voids, leading to Cu foams with a more uniform packing and a better connectivity of neighboring Cu hollow shells. Finally, we analyzed mechanical properties of the Cu foams with a depth-sensing indentation test. The uniform Cu foams show a significant improvement in mechanical properties (~1.5× modulus and ~3× hardness) compared to those of uncontrolled foam samples with a similar foam density but irregular large voids. As a result, higher surface areas and a good electric conductivity of the Cu foams present a great potential to future applications.

  18. Synthesis of metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong; Song, Yujiang; Shelnutt, John A.; Medforth, Craig J.

    2011-12-13

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  19. Assembly of a bacteriophage-based template for the organization of materials into nanoporous networks.

    PubMed

    Courchesne, Noémie-Manuelle Dorval; Klug, Matthew T; Chen, Po-Yen; Kooi, Steven E; Yun, Dong Soo; Hong, Nina; Fang, Nicholas X; Belcher, Angela M; Hammond, Paula T

    2014-06-04

    M13 bacteriophages are assembled via a covalent layer-by-layer process to form a highly nanoporous network capable of organizing nanoparticles and acting as a scaffold for templating metal-oxides. The morphological and optical properties of the film itself are presented as well as its ability to organize and disperse metal nanoparticles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. First Synthesis of Continuous Mesoporous Copper Films with Uniformly Sized Pores by Electrochemical Soft Templating.

    PubMed

    Li, Cuiling; Jiang, Bo; Wang, Zhongli; Li, Yunqi; Hossain, Md Shahriar A; Kim, Jung Ho; Takei, Toshiaki; Henzie, Joel; Dag, Ömer; Bando, Yoshio; Yamauchi, Yusuke

    2016-10-04

    Although mesoporous metals have been synthesized by electrochemical methods, the possible compositions have been limited to noble metals (e.g., palladium, platinum, gold) and their alloys. Herein we describe the first fabrication of continuously mesoporous Cu films using polymeric micelles as soft templates to control the growth of Cu under sophisticated electrochemical conditions. Uniformly sized mesopores are evenly distributed over the entire film, and the pore walls are composed of highly crystalized Cu.

  1. A Finger Vein Identification Method Based on Template Matching

    NASA Astrophysics Data System (ADS)

    Zou, Hui; Zhang, Bing; Tao, Zhigang; Wang, Xiaoping

    2016-01-01

    New methods for extracting vein features from finger vein image and generating templates for matching are proposed. In the algorithm for generating templates, we proposed a parameter-templates quality factor (TQF) - to measure the quality of generated templates. So that we can use fewer finger vein samples to generate templates that meet the quality requirement of identification. The recognition accuracy of using proposed methods of finger vein feature extraction and template generation strategy for identification is 97.14%.

  2. [Covalent immobilization of urease on polysiloxane templates containing 3-aminopropyl and 3-mercaptopropyl groups].

    PubMed

    Pogorilyĭ, R P; Goncharik, V P; Kozhara, L I; Zub, Iu L

    2008-01-01

    A technique of covalent immobilization of urease on polysiloxane templates, involving the sol-gel method, based on the use of crosslinking reagents (such as glutaraldehyde and Ellman's reagent) has been proposed. Urease, covalently grafted onto the surface of a poly(3-mercaptopropyl)siloxane template, was shown to retain its activity (67-84%) and stability (a decrease of 10% was observed over a period of 300 days). Urease adsorbed onto the poly(3-mercaptopropyl)siloxane template exhibited a higher activity than the native enzyme. The 3-mercaptopropyl groups of the polysiloxane template could be brought into the vicinity of the active metal center of the adsorbed urease and start acting as proton donors, thereby increasing the rate of the reaction catalyzed by the enzyme. Covalent immobilization of urease onto a 3-aminopropyl-containing polysiloxane template was shown to be less efficient, because it resulted in considerable losses of the activity of the enzyme. Conversely, urease adsorbed onto this template exhibited a high activity (60-86%).

  3. Dislocations limited electronic transport in hydride vapour phase epitaxy grown GaN templates: A word of caution for the epitaxial growers

    SciTech Connect

    Chatterjee, Abhishek Khamari, Shailesh K.; Kumar, R.; Dixit, V. K.; Oak, S. M.; Sharma, T. K.

    2015-01-12

    GaN templates grown by hydride vapour phase epitaxy (HVPE) and metal organic vapour phase epitaxy (MOVPE) techniques are compared through electronic transport measurements. Carrier concentration measured by Hall technique is about two orders larger than the values estimated by capacitance voltage method for HVPE templates. It is learnt that there exists a critical thickness of HVPE templates below which the transport properties of epitaxial layers grown on top of them are going to be severely limited by the density of charged dislocations lying at layer-substrate interface. On the contrary MOVPE grown templates are found to be free from such limitations.

  4. Tunable hierarchical macro/mesoporous gold microwires fabricated by dual-templating and dealloying processes.

    PubMed

    Sattayasamitsathit, Sirilak; Gu, Yonge; Kaufmann, Kevin; Minteer, Shelley; Polsky, Ronen; Wang, Joseph

    2013-09-07

    Tailor-made highly ordered macro/mesoporous hierarchical metal architectures have been created by combining sphere lithography, membrane template electrodeposition and alloy-etching processes. The new double-template preparation route involves the electrodeposition of Au/Ag alloy within the interstitial (void) spaces of polystyrene (PS) microspheres which are closely packed within the micropores of a polycarbonate membrane (PC), followed by dealloying of the Ag component and dissolution of the microsphere and membrane templates. The net results of combining such sphere lithography and silver etching is the creation of highly regular three-dimensional macro/mesoporous gold architecture with well-controlled sizes and shapes. The morphology and porosity of the new hierarchical porous structures can be tailored by controlling the preparation conditions, such as the composition of the metal mixture plating solution, the size of the microspheres template, or the dealloying time. Such tunable macro/mesoporous hierarchical structures offer control of the electrochemical reactivity and of the fuel mass transport, as illustrated for the enhanced oxygen reduction reaction (ORR) and hydrogen-peroxide detection. The new double templated electrodeposition method provides an attractive route for preparing highly controllable multiscale porous materials and diverse morphologies based on different materials and hence holds considerable promise for designing electrocatalytic or bioelectrocatalytic surfaces for a variety sensing and energy applications.

  5. Template optimization and transfer in perceptual learning.

    PubMed

    Kurki, Ilmari; Hyvärinen, Aapo; Saarinen, Jussi

    2016-08-01

    We studied how learning changes the processing of a low-level Gabor stimulus, using a classification-image method (psychophysical reverse correlation) and a task where observers discriminated between slight differences in the phase (relative alignment) of a target Gabor in visual noise. The method estimates the internal "template" that describes how the visual system weights the input information for decisions. One popular idea has been that learning makes the template more like an ideal Bayesian weighting; however, the evidence has been indirect. We used a new regression technique to directly estimate the template weight change and to test whether the direction of reweighting is significantly different from an optimal learning strategy. The subjects trained the task for six daily sessions, and we tested the transfer of training to a target in an orthogonal orientation. Strong learning and partial transfer were observed. We tested whether task precision (difficulty) had an effect on template change and transfer: Observers trained in either a high-precision (small, 60° phase difference) or a low-precision task (180°). Task precision did not have an effect on the amount of template change or transfer, suggesting that task precision per se does not determine whether learning generalizes. Classification images show that training made observers use more task-relevant features and unlearn some irrelevant features. The transfer templates resembled partially optimized versions of templates in training sessions. The template change direction resembles ideal learning significantly but not completely. The amount of template change was highly correlated with the amount of learning.

  6. Templated Growth of Magnetic Recording Media

    NASA Astrophysics Data System (ADS)

    Sundar, Vignesh

    Current and potential next-generation magnetic recording technologies are based on the writing and reading of bits on a magnetic thin film with a granular microstructure, with grains of the magnetic material surrounded by an amorphous segregant. In order to realize the highest achievable data storage capabilities, there is a need for better control of the magnetic media microstructure, particularly in terms of minimizing grain size and grain boundary thickness distributions. In this work, a guided magnetic media growth is attempted by creating a pre-fabricated template with a specific material and morphology. The template is designed in such a way that, when magnetic media consisting of the magnetic alloy and segregant are sputtered, the sites on the template result in a controlled two-phase growth of magnetic media. The template is fabricated using self-assembling block copolymers, which can be used to fabricate nanostructures with a regular hexagonal lattice of spheres of one block in the other's matrix. These are then used as etch-masks to fabricate the template. In this thesis, we describe the approach used to fabricate these templates and demonstrate the two-phase growth of magnetic recording media. In such an approach, the magnetic grain size is defined by the uniform pitch of the block copolymer pattern, resulting in a uniform microstructure with much better grain size distribution than can be obtained with conventional un-templated media growth. The templated growth technique is also a suitable additive technique for the fabrication of Bit Patterned Media, another potential next-generation technology wherein the magnetic bits are isolated patterned islands. Combining nanoimprint lithography with templated growth, we can generate a long range spatially ordered array of magnetic islands with no etching of the magnetic material.

  7. Lanthanide Template Synthesis of Trefoil Knots of Single Handedness.

    PubMed

    Zhang, Gen; Gil-Ramírez, Guzmán; Markevicius, Augustinas; Browne, Colm; Vitorica-Yrezabal, Iñigo J; Leigh, David A

    2015-08-19

    We report on the assembly of 2,6-pyridinedicarboxamide ligands (1) with point chirality about lanthanide metal ion (Ln(3+)) templates, in which the helical chirality of the resulting entwined 3:1 ligand:metal complexes is covalently captured by ring-closing olefin metathesis to form topologically chiral molecular trefoil knots of single handedness. The ligands do not self-sort (racemic ligands form a near-statistical mixture of homoleptic and heteroleptic lanthanide complexes), but the use of only (R,R)-1 leads solely to a trefoil knot of Λ-handedness, whereas (S,S)-1 forms the Δ-trefoil knot with complete stereoselectivity. The knots and their isomeric unknot macrocycles were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography and the expression of the chirality that results from the topology of the knots studied by circular dichroism.

  8. Universal soft matter template: from photonic to metamaterial applications

    NASA Astrophysics Data System (ADS)

    Umeton, Cesare; De Sio, Luciano; Caputo, Roberto; Ferjani, Sameh; Strangi, Giuseppe; Bartolino, Roberto

    2011-10-01

    We report on the realization and characterization of a polymeric template sculptured in photosensitive material, on a chemical inert surface. The structure is devoted to micro/nanoconfinement and stabilization of a wide range of organic and nano-particle components with selfarrangement properties at the nanoscale [1]. High quality morphology of a polymeric, micropatterned, array is obtained by combining a, nano-precision level, optical holographic setup and a multi-step chemico-physical process. The "universal" template represents the basic platform to be filled with different organic materials, which can also include metallic nano-particles. The long range self-organization is induced without making use of any kind of surface chemistry. Due to their capability of exhibiting self organization, light responsive Liquid Crystals (LC) [2] and short pitch Cholesterics LC [3] have been exploited, and experimental studies have been carried out in order to investigate the photo-optical and elecro-optical response of obtained composite structures for the realization of photonic devices. Finally, the possibility of including metallic nano-particles has been also investigated, with the aim of inducing a "metamaterial" behavior of the realized structure.

  9. Condensation of activated diguanylates on a poly(C) template.

    PubMed

    Lohrmann, R; Bridson, P K; Orgel, L E

    1981-01-01

    We have studied the metal-ion catalysis of a number of reactions of the isomers of ImpGpG on a poly(C) template. In the absence of a catalytic metal ion, oligomers at least up to (pG)20 are obtained from the ImpGpG isomers in a 1-methylimidazole buffer. The Pb2+ ion improves the yield of longer oligomers and changes substantially the distribution of linkage isomers. The Pb2+ ion greatly improves the yield of longer oligomers obtained from G and ImpGpG on a poly(C) template. The self-condensation of ImpGpG in a 2, 6-lutidine buffer is much less efficient than in a 1-methylimidazole buffer. The Zn2+ greatly increases the yield of products from the [3'-5']-linked dimer, but fails to catalyze the formation of long oligomers from the [2'-5']-linked dimer. The bonds formed in the Zn2+-catalyzed self-condensation of ImpG3pG on poly(C) are mainly [3'-5']-linked.

  10. Templated Native Silk Smectic Gels

    NASA Technical Reports Server (NTRS)

    Jin, Hyoung-Joon (Inventor); Park, Jae-Hyung (Inventor); Valluzzi, Regina (Inventor)

    2016-01-01

    One aspect of the present invention relates to a method of preparing a fibrous protein smectic hydrogel by way of a solvent templating process, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; and collecting the resulting fibrous protein smectic hydrogel and allowing it to dry. Another aspect of the present invention relates to a method of obtaining predominantly one enantiomer from a racemic mixture, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; allowing the enantiomers of racemic mixture to diffuse selectively into the smectic hydrogel in solution; removing the smectic hydrogel from the solution; rinsing predominantly one enantiomer from the surface of the smectic hydrogel; and extracting predominantly one enantiomer from the interior of the smectic hydrogel. The present invention also relates to a smectic hydrogel prepared according to an aforementioned method.

  11. Templated Native Silk Smectic Gels

    NASA Technical Reports Server (NTRS)

    Jin, Hyoung-Joon (Inventor); Park, Jae-Hyung (Inventor); Valluzzi, Regina (Inventor)

    2013-01-01

    One aspect of the present invention relates to a method of preparing a fibrous protein smectic hydrogel by way of a solvent templating process, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; and collecting the resulting fibrous protein smectic hydrogel and allowing it to dry. Another aspect of the present invention relates to a method of obtaining predominantly one enantiomer from a racemic mixture, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; allowing the enantiomers of racemic mixture to diffuse selectively into the smectic hydrogel in solution; removing the smectic hydrogel from the solution; rinsing predominantly one enantiomer from the surface of the smectic hydrogel; and extracting predominantly one enantiomer from the interior of the smectic hydrogel. The present invention also relates to a smectic hydrogel prepared according to an aforementioned method.

  12. Biomineralization Guided by Paper Templates

    PubMed Central

    Camci-Unal, Gulden; Laromaine, Anna; Hong, Estrella; Derda, Ratmir; Whitesides, George M.

    2016-01-01

    This work demonstrates the fabrication of partially mineralized scaffolds fabricated in 3D shapes using paper by folding, and by supporting deposition of calcium phosphate by osteoblasts cultured in these scaffolds. This process generates centimeter-scale free-standing structures composed of paper supporting regions of calcium phosphate deposited by osteoblasts. This work is the first demonstration that paper can be used as a scaffold to induce template-guided mineralization by osteoblasts. Because paper has a porous structure, it allows transport of O2 and nutrients across its entire thickness. Paper supports a uniform distribution of cells upon seeding in hydrogel matrices, and allows growth, remodelling, and proliferation of cells. Scaffolds made of paper make it possible to construct 3D tissue models easily by tuning material properties such as thickness, porosity, and density of chemical functional groups. Paper offers a new approach to study mechanisms of biomineralization, and perhaps ultimately new techniques to guide or accelerate the repair of bone. PMID:27277575

  13. Templated native silk smectic gels

    NASA Technical Reports Server (NTRS)

    Jin, Hyoung-Joon (Inventor); Park, Jae-Hyung (Inventor); Valluzzi, Regina (Inventor)

    2009-01-01

    One aspect of the present invention relates to a method of preparing a fibrous protein smectic hydrogel by way of a solvent templating process, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; and collecting the resulting fibrous protein smectic hydrogel and allowing it to dry. Another aspect of the present invention relates to a method of obtaining predominantly one enantiomer from a racemic mixture, comprising the steps of pouring an aqueous fibrous protein solution into a container comprising a solvent that is not miscible with water; sealing the container and allowing it to age at about room temperature; allowing the enantiomers of racemic mixture to diffuse selectively into the smectic hydrogel in solution; removing the smectic hydrogel from the solution; rinsing predominantly one enantiomer from the surface of the smectic hydrogel; and extracting predominantly one enantiomer from the interior of the smectic hydrogel. The present invention also relates to a smectic hydrogel prepared according to an aforementioned method.

  14. Templating irreversible covalent macrocyclization by using anions.

    PubMed

    Kataev, Evgeny A; Kolesnikov, Grigory V; Arnold, Rene; Lavrov, Herman V; Khrustalev, Victor N

    2013-03-11

    Inorganic anions were used as templates in the reaction between a diamine and an activated diacid to form macrocyclic amides. The reaction conditions were found to perform the macrocyclization sufficiently slow to observe a template effect. A number of analytical methods were used to clarify the reaction mechanisms and to show that the structure of the intermediate plays a decisive role in determining the product distribution. For the macrocyclization under kinetic control, it was shown that the amount of a template, the conformational rigidity of building blocks, and the anion affinities of reaction components and intermediates are important parameters that one should take into consideration to achieve high yields.

  15. NPTFit: Non-Poissonian Template Fitting

    NASA Astrophysics Data System (ADS)

    Safdi, Benjamin R.; Rodd, Nicholas L.; Mishra-Sharma, Siddharth

    2017-05-01

    NPTFit is a specialized Python/Cython package that implements Non-Poissonian Template Fitting (NPTF), originally developed for characterizing populations of unresolved point sources. It offers fast evaluation of likelihoods for NPTF analyses and has an easy-to-use interface for performing non-Poissonian (as well as standard Poissonian) template fits using MultiNest (ascl:1109.006) or other inference tools. It allows inclusion of an arbitrary number of point source templates, with an arbitrary number of degrees of freedom in the modeled flux distribution, and has modules for analyzing and plotting the results of an NPTF.

  16. A PANOPLY OF CEPHEID LIGHT CURVE TEMPLATES

    SciTech Connect

    Yoachim, Peter; McCommas, Les P.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2009-06-15

    We have generated accurate V and I template light curves using a combination of Fourier decomposition and principal component analysis for a large sample of Cepheid light curves. Unlike previous studies, we include short-period Cepheids and stars pulsating in the first overtone mode in our analysis. Extensive Monte Carlo simulations show that our templates can be used to precisely measure Cepheid magnitudes and periods, even in cases where there are few observational epochs. These templates are ideal for characterizing serendipitously discovered Cepheids and can be used in conjunction with surveys such as Pan-Starrs and LSST where the observational sampling may not be optimized for Cepheids.

  17. Template boundary definition in Tetrahymena telomerase.

    PubMed

    Lai, Cary K; Miller, Michael C; Collins, Kathleen

    2002-02-15

    Telomerase elongates chromosome ends by addition of telomeric DNA repeats. The telomerase ribonucleoprotein can copy only a short template sequence within the telomerase RNA subunit. Here, we identify a region of telomerase RNA that is necessary for both correct 5' template boundary definition and high affinity telomerase reverse transcriptase (TERT) interaction. We also demonstrate that TERT mutants in the RNA binding domain compromise both 5' boundary definition and RNA binding. Our results indicate that sequence-specific interaction of a telomerase RNA element with the TERT RNA binding domain, not the active site motifs, defines the template boundary.

  18. Integration of molecular-layer-deposited aluminum alkoxide interlayers into inorganic nanolaminate barriers for encapsulation of organic electronics with improved stress resistance

    SciTech Connect

    Hossbach, Christoph Fischer, Dustin; Albert, Matthias; Bartha, Johann W.; Nehm, Frederik Klumbies, Hannes; Müller-Meskamp, Lars; Leo, Karl; Singh, Aarti; Richter, Claudia; Schroeder, Uwe; Mikolajick, Thomas

    2015-01-15

    Diffusion barrier stacks for the encapsulation of organic electronics made from inorganic nanolaminates of Al{sub 2}O{sub 3} and TiO{sub 2} with aluminum alkoxide interlayers have been deposited by atomic layer deposition (ALD) and molecular layer deposition (MLD). As a part of the MLD process development, the deposition of aluminum alkoxide with low a density of about 1.7 g/cm{sup 3} was verified. The ALD/MLD diffusion barrier stack is meant to be deposited either on a polymer film, creating a flexible barrier substrate, or on top of a device on glass, creating a thin-film encapsulation. In order to measure the water vapor transmission rate (WVTR) through the barrier, the device is replaced by a calcium layer acting as a water sensor in an electrical calcium test. For the barrier stack applied as thin-film encapsulation on glass substrates, high resolution scanning electron microscopy investigations indicate that the inorganic nanolaminates without MLD interlayers are brittle as they crack easily upon the stress induced by the corroding calcium below. The introduction of up to three MLD interlayers of 12 nm each into the 48 nm barrier film laminate successfully mitigates stress issues and prevents the barrier from cracking. Using the three MLD interlayer configurations on glass, WVTRs of as low as 10{sup −5} g/m{sup 2}/d are measured at 38 °C and 32% relative humidity. On polymer barrier substrates, the calcium is evaporated onto the barrier stack and encapsulated with a cavity glass. In this configuration, the corroding calcium has space for expansion and gas release without affecting the underlying barrier film. In consequence, a WVTR of about 3 × 10{sup −3} g/m{sup 2}/d is measured for all samples independently of the number of MLD interlayers. In conclusion, a stabilization and preservation of the ALD barrier film against mechanical stress is achieved by the introduction of MLD interlayers into the inorganic nanolaminate.

  19. Nanoparticle Array Assembly Using Chemical Templates

    NASA Astrophysics Data System (ADS)

    Adams, Sarah Marie

    This dissertation demonstrates chemically-driven self-assembly techniques to produce assemblies of closely-spaced metal nanoparticles from colloidal nanoparticle solution in order to engineer enhanced optical fields. Planar nanoparticle assemblies provide a platform for a multitude of applications and material architectures. With nanoscale inter-particle spacing, metallic nanoparticles enable increased efficiency of photovoltaic devices due to light focusing and enhancement of electromagnetic fields useful for optical sensing of molecules due to coupling of the plasmon resonance in nanoparticle gaps. For molecular sensors, development of self-assembled two-dimensional assemblies of closely-spaced nanoparticles is useful for producing surface plasmon resonance sensors and surface-enhanced Raman spectroscopy (SERS) based sensing. Using chemical self-assembly, monodisperse, colloidal gold nanoparticles were attached on self-organized polymer templates in order to pattern assemblies of nanoparticle clusters with sub-10 nanometer inter-particle spacing. First citrate-stabilized Au nanoparticles were functionalized with thioctic acid ligands in solution. Then poly(methyl methacrylate) domains in phase-separated poly(styrene-block-methyl methacrylate) (PS-b-PMMA) thin films were chemically modified with surface amine functional groups. Au nanoparticles were preferentially attached to the functionalized PMMA surface domains using cross-linking chemistry. This method allows for versatility of size, shape, and composition. In this dissertation, we demonstrated attachment of 5, 10, and 20 nm Au and 20 nm Ag nanoparticles. PS-b-PMMA thin films also exhibit versatility of domain size and morphology by varying polymer molecular weights. The nanoparticle diameter to PMMA domain size ratio influenced the cluster size. As the ratio decreased, larger clusters were observed on PMMA domains with increased frequency. SERS measurement of nanoparticle assemblies showed uniform signal

  20. Template synthesis and characterization of nanostructured lithium insertion electrodes and nanogold/porous aluminum oxide composite membranes

    NASA Astrophysics Data System (ADS)

    Patrissi, Charles John

    A membrane-based template synthesis method was used to prepare nanostructured Li-ion battery electrodes and nanogold/porous aluminum oxide composite membranes. Membrane-based template synthesis is a general method for the preparation of nanomaterials which entails deposition of the material of interest, or a suitable precursor, within the nanometer-diameter pores in a porous template membrane. This method allows for control of nanoparticle size and shape and is compatible with many methods of synthesis for bulk materials. The template membranes used in this work were commercially available porous polycarbonate filtration membranes and nanoporous aluminum oxide membranes that were prepared in-house. Nanostructured electrodes of orthorhombic V2O5, prepared using membrane-based template synthesis, were used to investigate the effects of Li-ion diffusion distance and V2O5 surface area on electrode rate capability. Nanowires of V2O5 were prepared by depositing a precursor in the pores of microporous polycarbonate filtration membranes. The result was an ensemble of 115 nm diameter, 2 mum long nanowires of V2O5 which protruded from a V 2O5 surface layer like the bristles of a brush. The Li + storage capacity of the nanostructured electrode was compared to a thin film control electrode at high discharge rates. Results show that the nanostructured electrode delivered three to four times the capacity of the thin film electrode at discharge rates above 500 C. A membrane based template synthesis method was also used to prepare crystalline V2O5 electrodes which have high volumetric charge capacities, at high discharge rates, compared to a thin-film control electrode. In order to obtain high volumetric rate capability, the as-received polycarbonate template membranes were chemically etched to increase membrane porosity. Nanofibrous electrodes of crystalline V2O5 were then prepared by depositing an alkoxide precursor in the pores of the etched membranes. Electrode volumetric