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Sample records for metal organic chemical

  1. Chemically crosslinked isoreticular metal-organic frameworks.

    PubMed

    Allen, Corinne A; Boissonnault, Jake A; Cirera, Jordi; Gulland, Ryan; Paesani, Francesco; Cohen, Seth M

    2013-04-21

    Herein we report the synthesis of canonical isoreticular metal-organic frameworks (IRMOFs) containing interligand crosslinks. Chemically crosslinking two molecules of 2-amino-1,4-benzene dicarboxylic acid (NH2-BDC) gives ligands that readily form IRMOF-1 analogs, producing crosslinked MOFs that may be designed to have novel properties.

  2. Chemical, thermal and mechanical stabilities of metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Howarth, Ashlee J.; Liu, Yangyang; Li, Peng; Li, Zhanyong; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.

    2016-03-01

    The construction of thousands of well-defined, porous, metal-organic framework (MOF) structures, spanning a broad range of topologies and an even broader range of pore sizes and chemical functionalities, has fuelled the exploration of many applications. Accompanying this applied focus has been a recognition of the need to engender MOFs with mechanical, thermal and/or chemical stability. Chemical stability in acidic, basic and neutral aqueous solutions is important. Advances over recent years have made it possible to design MOFs that possess different combinations of mechanical, thermal and chemical stability. Here, we review these advances and the associated design principles and synthesis strategies. We focus on how these advances may render MOFs effective as heterogeneous catalysts, both in chemically harsh condensed phases and in thermally challenging conditions relevant to gas-phase reactions. Finally, we briefly discuss future directions of study for the production of highly stable MOFs.

  3. Destruction of chemical warfare agents using metal-organic frameworks.

    PubMed

    Mondloch, Joseph E; Katz, Michael J; Isley, William C; Ghosh, Pritha; Liao, Peilin; Bury, Wojciech; Wagner, George W; Hall, Morgan G; DeCoste, Jared B; Peterson, Gregory W; Snurr, Randall Q; Cramer, Christopher J; Hupp, Joseph T; Farha, Omar K

    2015-05-01

    Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic Zr(IV) ions as the active sites and to their superb accessibility as a defining element of their efficacy. PMID:25774952

  4. Destruction of chemical warfare agents using metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Mondloch, Joseph E.; Katz, Michael J.; Isley, William C., III; Ghosh, Pritha; Liao, Peilin; Bury, Wojciech; Wagner, George W.; Hall, Morgan G.; Decoste, Jared B.; Peterson, Gregory W.; Snurr, Randall Q.; Cramer, Christopher J.; Hupp, Joseph T.; Farha, Omar K.

    2015-05-01

    Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic ZrIV ions as the active sites and to their superb accessibility as a defining element of their efficacy.

  5. Destruction of chemical warfare agents using metal-organic frameworks.

    PubMed

    Mondloch, Joseph E; Katz, Michael J; Isley, William C; Ghosh, Pritha; Liao, Peilin; Bury, Wojciech; Wagner, George W; Hall, Morgan G; DeCoste, Jared B; Peterson, Gregory W; Snurr, Randall Q; Cramer, Christopher J; Hupp, Joseph T; Farha, Omar K

    2015-05-01

    Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic Zr(IV) ions as the active sites and to their superb accessibility as a defining element of their efficacy.

  6. Natural and active chemical remediation of toxic metals, organics, and radionuclides in the aquatic environment

    SciTech Connect

    McPherson, G.; Pintauro, P.; O`Connor, S.

    1996-05-02

    This project focuses on the chemical aspects of remediation, with the underlying theme that chemical remediation does occur naturally. Included are studies on the fate of heavy metal and organic contaminants discharged into aquatic environments; accurate assay metal contaminants partitioned into soils, water and tissue; development of novel polymeric membranes and microporous solids for the entrapment of heavy metals; and the development of hybrid chemo-enzymatic oxidative schemes for aromatics decontamination. 49 refs.

  7. Separation of chemical reaction intermediates by metal-organic frameworks.

    PubMed

    Centrone, Andrea; Santiso, Erik E; Hatton, T Alan

    2011-08-22

    HPLC columns custom-packed with metal-organic framework (MOF) materials are used for the separation of four small intermediates and byproducts found in the commercial synthesis of an important active pharmaceutical ingredient in methanol. In particular, two closely related amines can be separated in the methanol reaction medium using MOFs, but not with traditional C18 columns using an optimized aqueous mobile phase. Infrared spectroscopy, UV-vis spectroscopy, X-ray diffraction, and thermogravimetric analysis are used in combination with molecular dynamic simulations to study the separation mechanism for the best-performing MOF materials. It is found that separation with ZIF-8 is the result of an interplay between the thermodynamic driving force for solute adsorption within the framework pores and the kinetics of solute diffusion into the material pores, while the separation with Basolite F300 is achieved because of the specific interactions between the solutes and Fe(3+) sites. This work, and the exceptional ability to tailor the porous properties of MOF materials, points to prospects for using MOF materials for the continuous separation and synthesis of pharmaceutical compounds.

  8. Direct conversion of radioactive and chemical waste containing metals, ceramics, amorphous solids, and organics to glass

    SciTech Connect

    Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

    1994-05-02

    The Glass Material Oxidation and Dissolution System (CMODS) is a new process for direct conversion of radioactive, mixed, and chemical wastes to glass. The wastes can be in the chemical forms of metals, ceramics, amorphous solids, and organics. GMODS destroys organics and it incorporates heavy metals and radionuclides into a glass. Processable wastes may include miscellaneous spent fuels (SF), SF hulls and hardware, plutonium wastes in different forms, high-efficiency particulate air (HEPA) filters, ion-exchange resins, failed equipment, and laboratory wastes. Thermodynamic calculations indicate theoretical feasibility. Small-scale laboratory experiments (< 100 g per test) have demonstrated chemical laboratory feasibility for several metals. Additional work is needed to demonstrate engineering feasibility.

  9. GaN Stress Evolution During Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Amano, H.; Chason, E.; Figiel, J.; Floro, J.A.; Han, J.; Hearne, S.; Hunter, J.; Tsong, I.

    1998-10-14

    The evolution of stress in gallium nitride films on sapphire has been measured in real- time during metal organic chemical vapor deposition. In spite of the 161%0 compressive lattice mismatch of GaN to sapphire, we find that GaN consistently grows in tension at 1050"C. Furthermore, in-situ stress monitoring indicates that there is no measurable relaxation of the tensile growth stress during annealing or thermal cycling.

  10. Metal organic chemical vapor deposition of phase change Ge1Sb2Te4 nanowires.

    PubMed

    Longo, Massimo; Fallica, Roberto; Wiemer, Claudia; Salicio, Olivier; Fanciulli, Marco; Rotunno, Enzo; Lazzarini, Laura

    2012-03-14

    The self-assembly of Ge(1)Sb(2)Te(4) nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, catalyzed by Au nanoislands in a narrow range of temperatures and deposition pressures. In the optimized conditions of 400 °C, 50 mbar, the NWs are Ge(1)Sb(2)Te(4) single hexagonal crystals. Phase change memory switching was reversibly induced by nanosecond current pulses through metal-contacted NWs with threshold voltage of about 1.35 V.

  11. Y-Ba-Cu-O film deposition by metal organic chemical vapor deposition on buffered metal substrates.

    SciTech Connect

    Selvamanickam, V.; Galinski, G.; DeFrank, J.; Trautwein, C.; Haldar, P.; Balachandran, U.; Lanagan, M.; Chudzik, M.

    1999-10-12

    YBa{sub 2}Cu{sub 3}O{sub 2} (YBCO) films have been deposited on buffered metal substrates by Metal Organic Chemical Vapor Deposition (MOCVD). Cube-textured nickel substrates were fabricated by a thermomechanical process. Epitaxial CeO{sub 2}films were deposited on these substrates by thermal evaporation. Nickel alloy substrates with biaxially-textured Yttria-Stabilized Zirconia (YSZ) buffer layers deposited by Ion Beam Assisted Deposition were also prepared. Highly biaxially-textured YBCO films were deposited by MOCVD on both types of metal substrates. A critical current density greater than 10{sup 5} A/cm{sup 2} at 77 K has been achieved in YBCO films on metal substrates.

  12. Micro- and Nanostructured Metal Oxide Chemical Sensors for Volatile Organic Compounds

    NASA Technical Reports Server (NTRS)

    Alim, M. A.; Penn, B. G.; Currie, J. R., Jr.; Batra, A. K.; Aggarwal, M. D.

    2008-01-01

    Aeronautic and space applications warrant the development of chemical sensors which operate in a variety of environments. This technical memorandum incorporates various kinds of chemical sensors and ways to improve their performance. The results of exploratory investigation of the binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. A short review of the present status of the new types of nanostructured sensors such as nanobelts, nanorods, nanotube, etc. based on metal oxides is presented.

  13. Assessment of tissue concentrations of metals and volatile organic chemicals in farm animal products

    SciTech Connect

    Stone, P.R. III; Shortelle, A.B.; Charna, R.; Maxwell, J.

    1995-12-31

    An Army site in Pennsylvania is included on the National Priorities List. Site-related chemicals such as volatile organic chemicals (VOCs) and metals have been released to the groundwater from the industrial sewer which have now been repaired. VOCs are also present in groundwater in off post residential wells. The purpose of this study was to address the possible effects of groundwater and surface water chemicals to livestock and humans via the food chain pathway in the off post areas. Sampling of off post farm animal tissues was performed to confirm or revise the conclusion (based on modeled results) that this exposure pathway does not pose significant risk to human or animal health. Objectives of this study were to: (1) determine the potential presence of study constituents in the components of the food chain, and (2) develop data for use in the future risk assessment. Samples collected from the study area and reference (background) areas include beef (4 cuts), poultry, eggs, pork (5 cuts), and cow`s milk. The analyses were performed using published EPA methodologies modified as appropriate for sample (tissue) preparation. VOCs were analyzed using the EPA GC/MS purge and trap method SW846-8240. Metals were analyzed using the EPA inductively coupled/mass spectrometer (ICP/MS) method SW846-6020. Metals were found ubiquitously in samples from both areas. VOCs were only sporadically found. Statistical analyses were performed to identify chemicals in specific tissues where concentrations differed significantly between study area and reference areas.

  14. Life cycle cost study for coated conductor manufacture by metal organic chemical vapor deposition

    SciTech Connect

    Chapman, J.N.

    1999-07-13

    The purpose of this report is to calculate the cost of producing high temperature superconducting wire by the Metal Organic Chemical Vapor Deposition (MOCVD) process. The technology status is reviewed from the literature and a plant conceptual design is assumed for the cost calculation. The critical issues discussed are the high cost of the metal organic precursors, the material utilization efficiency and the capability of the final product as measured by the critical current density achieved. Capital, operating and material costs are estimated and summed as the basis for calculating the cost per unit length of wire. Sensitivity analyses of key assumptions are examined to determine their effects on the final wire cost. Additionally, the cost of wire on the basis of cost per kiloampere per meter is calculated for operation at lower temperatures than the liquid nitrogen boiling temperature. It is concluded that this process should not be ruled out on the basis of high cost of precursors alone.

  15. Textile/metal-organic-framework composites as self-detoxifying filters for chemical-warfare agents.

    PubMed

    López-Maya, Elena; Montoro, Carmen; Rodríguez-Albelo, L Marleny; Aznar Cervantes, Salvador D; Lozano-Pérez, A Abel; Cenís, José Luis; Barea, Elisa; Navarro, Jorge A R

    2015-06-01

    The current technology of air-filtration materials for protection against highly toxic chemicals, that is, chemical-warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self-cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal-organic framework (MOF) materials to develop advanced self-detoxifying adsorbents of chemical-warfare agents containing hydrolysable P-F, P-O, and C-Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air-permeation properties of the textiles with the self-detoxifying properties of the MOF material.

  16. Pulsed supersonic molecular beam for characterization of chemically active metal-organic complexes at surfaces

    NASA Astrophysics Data System (ADS)

    Lear, Amanda M.

    Metal-organic coordination networks (MOCNs) at surfaces consist of a complex of organic ligands bound to an atomic metal center. The MOCNs, when chosen appropriately, can form highly-ordered arrays at surfaces. Ultra-high vacuum surface studies allow control of surface composition and provide 2D growth restrictions, which lead to under-coordinated metal centers. These systems provide an opportunity to tailor the chemical function of the metal centers due to the steric restrictions imposed by the surface. Tuning the adsorption/desorption energy at a metal center and developing a cooperative environment for catalysis are the key scientific questions that motivate the construction of a molecular beam surface analysis system. Characterization of the created systems can be performed utilizing a pulsed supersonic molecular beam (PSMB) in unison with a quadrupole mass spectrometer. A PSMB allows for the highly controlled delivery of reactants with well-defined energy to a given platform making it possible to elucidate detailed chemical tuning information. In this thesis, a summary of prior theoretical molecular beam derivations is provided. Design considerations and an overview of the construction procedure for the current molecular beam apparatus, including initial characterization experiments, are presented. By impinging an Ar beam on a Ag(111) surface, the location of the specular angle (˜65°) and rough sample perimeter coordinates were determined. Additionally, surface analysis experiments, mainly Auger Electron Spectroscopy (AES), were performed to investigate the oxidation of epitaxial graphene on the SiC(0001) surface utilizing an oxygen cracking method. The AES experiments are described in detail and highlight the challenges that were faced when several different graphene samples were used for the oxygen adsorption/desorption experiments.

  17. Peptide-Metal Organic Framework Swimmers that Direct the Motion toward Chemical Targets.

    PubMed

    Ikezoe, Yasuhiro; Fang, Justin; Wasik, Tomasz L; Shi, Menglu; Uemura, Takashi; Kitagawa, Susumu; Matsui, Hiroshi

    2015-06-10

    Highly efficient and robust chemical motors are expected for the application in microbots that can selectively swim toward targets and accomplish their tasks in sensing, labeling, and delivering. However, one of major issues for such development is that current artificial swimmers have difficulty controlling their directional motion toward targets like bacterial chemotaxis. To program synthetic motors with sensing capability for the target-directed motion, we need to develop swimmers whose motions are sensitive to chemical gradients in environments. Here we create a new intelligent biochemical swimmer by integrating metal organic frameworks (MOFs) and peptides that can sense toxic heavy metals in solution and swim toward the targets. With the aid of Pb-binding enzymes, the peptide-MOF motor can directionally swim toward PbSe quantum dots (QD) by sensing pH gradient and eventually complete the motion as the swimmer reaches the highest gradient point at the target position in solution. This type of technology could be evolved to miniaturize chemical robotic systems that sense target chemicals and swim toward target locations. PMID:26010172

  18. Method of making AlInSb by metal-organic chemical vapor deposition

    DOEpatents

    Biefeld, Robert M.; Allerman, Andrew A.; Baucom, Kevin C.

    2000-01-01

    A method for producing aluminum-indium-antimony materials by metal-organic chemical vapor deposition (MOCVD). This invention provides a method of producing Al.sub.X In.sub.1-x Sb crystalline materials by MOCVD wherein an Al source material, an In source material and an Sb source material are supplied as a gas to a heated substrate in a chamber, said Al source material, In source material, and Sb source material decomposing at least partially below 525.degree. C. to produce Al.sub.x In.sub.1-x Sb crystalline materials wherein x is greater than 0.002 and less than one.

  19. Chemical reactions catalyzed by metalloporphyrin-based metal-organic frameworks.

    PubMed

    Nakagaki, Shirley; Ferreira, Gabriel Kaetan Baio; Ucoski, Geani Maria; Dias de Freitas Castro, Kelly Aparecida

    2013-06-21

    The synthetic versatility and the potential application of metalloporphyrins (MP) in different fields have aroused researchers' interest in studying these complexes, in an attempt to mimic biological systems such as cytochrome P-450. Over the last 40 years, synthetic MPs have been mainly used as catalysts for homogeneous or heterogeneous chemical reactions. To employ them in heterogeneous catalysis, chemists have prepared new MP-based solids by immobilizing MP onto rigid inorganic supports, a strategy that affords hybrid inorganic-organic materials. More recently, materials obtained by supramolecular assembly processes and containing MPs as building blocks have been applied in a variety of areas, like gas storage, photonic devices, separation, molecular sensing, magnets, and heterogeneous catalysis, among others. These coordination polymers, known as metal-organic frameworks (MOFs), contain organic ligands or complexes connected by metal ions or clusters, which give rise to a 1-, 2- or 3-D network. These kinds of materials presents large surface areas, Brønsted or redox sites, and high porosity, all of which are desirable features in catalysts with potential use in heterogeneous phases. Building MOFs based on MP is a good way to obtain solid catalysts that offer the advantages of bioinspired systems and zeolitic materials. In this mini review, we will adopt a historical approach to present the most relevant MP-based MOFs applicable to catalytic reactions such as oxidation, reduction, insertion of functional groups, and exchange of organic functions.

  20. [Toxicology of chemical substances (metals and organic solvents): management as an occupational physician].

    PubMed

    Ueno, Susumu

    2013-10-01

    Even in Japan, there was a time when cases of occupational poisoning had frequently occurred, which led to the enactment of the Industrial Safety and Health Act in 1972. Currently, the use of only a part of chemical substances utilized in the workplace is regulated according to their designated hazardous level, but there are many other substances whose toxicities have not been elucidated. Risk assessment is now required of entrepreneurs in all categories of industry by the recently-revised Industrial Safety and Health Act. This article will focus on the toxicology of metals and organic solvents, and it will discuss how occupational physicians should manage chemicals, including the ones whose toxicities have not been clarified. PMID:24107340

  1. Cobalt(I) Olefin Complexes: Precursors for Metal-Organic Chemical Vapor Deposition of High Purity Cobalt Metal Thin Films.

    PubMed

    Hamilton, Jeff A; Pugh, Thomas; Johnson, Andrew L; Kingsley, Andrew J; Richards, Stephen P

    2016-07-18

    We report the synthesis and characterization of a family of organometallic cobalt(I) metal precursors based around cyclopentadienyl and diene ligands. The molecular structures of the complexes cyclopentadienyl-cobalt(I) diolefin complexes are described, as determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis and thermal stability studies of the complexes highlighted the isoprene, dimethyl butadiene, and cyclohexadiene derivatives [(C5H5)Co(η(4)-CH2CHC(Me)CH2)] (1), [(C5H5)Co(η(4)-CH2C(Me)C(Me)CH2)] (2), and [(C5H5)Co(η(4)-C6H8)] (4) as possible cobalt metal organic chemical vapor deposition (MOCVD) precursors. Atmospheric pressure MOCVD was employed using precursor 1, to synthesize thin films of metallic cobalt on silicon substrates under an atmosphere (760 torr) of hydrogen (H2). Analysis of the thin films deposited at substrate temperatures of 325, 350, 375, and 400 °C, respectively, by scanning electron microscopy and atomic force microscopy reveal temperature-dependent growth features. Films grown at these temperatures are continuous, pinhole-free, and can be seen to be composed of hexagonal particles clearly visible in the electron micrograph. Powder X-ray diffraction and X-ray photoelectron spectroscopy all show the films to be highly crystalline, high-purity metallic cobalt. Raman spectroscopy was unable to detect the presence of cobalt silicides at the substrate/thin film interface. PMID:27348614

  2. Computational Investigations of Potential Energy Function Development for Metal--Organic Framework Simulations, Metal Carbenes, and Chemical Warfare Agents

    NASA Astrophysics Data System (ADS)

    Cioce, Christian R.

    Metal-Organic Frameworks (MOFs) are three-dimensional porous nanomaterials with a variety of applications, including catalysis, gas storage and separation, and sustainable energy. Their potential as air filtration systems is of interest for designer carbon capture materials. The chemical constituents (i.e. organic ligands) can be functionalized to create rationally designed CO2 sequestration platforms, for example. Hardware and software alike at the bleeding edge of supercomputing are utilized for designing first principles-based molecular models for the simulation of gas sorption in these frameworks. The classical potentials developed herein are named PHAST --- Potentials with High Accuracy, Speed, and Transferability, and thus are designed via a "bottom-up" approach. Specifically, models for N2 and CH4 are constructed and presented. Extensive verification and validation leads to insights and range of applicability. Through this experience, the PHAST models are improved upon further to be more applicable in heterogeneous environments. Given this, the models are applied to reproducing high level ab initio energies for gas sorption trajectories of helium atoms in a variety of rare-gas clusters, the geometries of which being representative of sorption-like environments commonly encountered in a porous nanomaterial. This work seeks to push forward the state of classical and first principles materials modeling. Additionally, the characterization of a new type of tunable radical metal---carbene is presented. Here, a cobalt(II)---porphyrin complex, [Co(Por)], was investigated to understand its role as an effective catalyst in stereoselective cyclopropanation of a diazoacetate reagent. Density functional theory along with natural bond order analysis and charge decomposition analysis gave insight into the electronics of the catalytic intermediate. The bonding pattern unveiled a new class of radical metal---carbene complex, with a doublet cobalt into which a triplet carbene

  3. Controlling nucleation of monolayer WSe2 during metal-organic chemical vapor deposition growth

    NASA Astrophysics Data System (ADS)

    Eichfeld, Sarah M.; Oliveros Colon, Víctor; Nie, Yifan; Cho, Kyeongjae; Robinson, Joshua A.

    2016-06-01

    Tungsten diselenide (WSe2) is a semiconducting, two-dimensional (2D) material that has gained interest in the device community recently due to its electronic properties. The synthesis of atomically thin WSe2, however, is still in its infancy. In this work we elucidate the requirements for large selenium/tungsten precursor ratios and explain the effect of nucleation temperature on the synthesis of WSe2 via metal-organic chemical vapor deposition (MOCVD). The introduction of a nucleation-step prior to growth demonstrates that increasing nucleation temperature leads to a transition from a Volmer–Weber to Frank–van der Merwe growth mode. Additionally, the nucleation step prior to growth leads to an improvement of WSe2 layer coverage on the substrate. Finally, we note that the development of this two-step technique may allow for improved control and quality of 2D layers grown via CVD and MOCVD processes.

  4. Controlling nucleation of monolayer WSe2 during metal-organic chemical vapor deposition growth

    NASA Astrophysics Data System (ADS)

    Eichfeld, Sarah M.; Oliveros Colon, Víctor; Nie, Yifan; Cho, Kyeongjae; Robinson, Joshua A.

    2016-06-01

    Tungsten diselenide (WSe2) is a semiconducting, two-dimensional (2D) material that has gained interest in the device community recently due to its electronic properties. The synthesis of atomically thin WSe2, however, is still in its infancy. In this work we elucidate the requirements for large selenium/tungsten precursor ratios and explain the effect of nucleation temperature on the synthesis of WSe2 via metal-organic chemical vapor deposition (MOCVD). The introduction of a nucleation-step prior to growth demonstrates that increasing nucleation temperature leads to a transition from a Volmer-Weber to Frank-van der Merwe growth mode. Additionally, the nucleation step prior to growth leads to an improvement of WSe2 layer coverage on the substrate. Finally, we note that the development of this two-step technique may allow for improved control and quality of 2D layers grown via CVD and MOCVD processes.

  5. Chromophore-immobilized luminescent metal-organic frameworks as potential lighting phosphors and chemical sensors.

    PubMed

    Wang, Fangming; Liu, Wei; Teat, Simon J; Xu, Feng; Wang, Hao; Wang, Xinlong; An, Litao; Li, Jing

    2016-08-11

    An organic chromophore H4tcbpe-F was synthesized and immobilized into metal-organic frameworks along with two bipyridine derivatives as co-ligands to generate two strongly luminescent materials [Zn2(tcbpe-F)(4,4'-bpy)·xDMA] (1) and [Zn2(tcbpe-F)(bpee)·xDMA] (2) [4,4'-bpy = 4,4'-bipyridine, bpee = 4,4'-bipyridyl-ethylene, tcbpe-F = 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(3-fluoro-[1,1'-biphenyl]-4-carboxylic acid), DMA = N,N-dimethylacetamide]. Compounds 1 and 2 are isoreticular and feature a 2-fold interpenetrated three-dimensional porous structure. Both compounds give green-yellow emission under blue light excitation. Compound 1 has a high internal quantum yield of ∼51% when excited at 455 nm and shows selective luminescence signal change (e.g. emission energy and/or intensity) towards different solvents, including both aromatic and nonaromatic volatile organic species. These properties make it potentially useful as a lighting phosphor and a chemical sensor. PMID:27465685

  6. Research Update: Mechanical properties of metal-organic frameworks - Influence of structure and chemical bonding

    NASA Astrophysics Data System (ADS)

    Li, Wei; Henke, Sebastian; Cheetham, Anthony K.

    2014-12-01

    Metal-organic frameworks (MOFs), a young family of functional materials, have been attracting considerable attention from the chemistry, materials science, and physics communities. In the light of their potential applications in industry and technology, the fundamental mechanical properties of MOFs, which are of critical importance for manufacturing, processing, and performance, need to be addressed and understood. It has been widely accepted that the framework topology, which describes the overall connectivity pattern of the MOF building units, is of vital importance for the mechanical properties. However, recent advances in the area of MOF mechanics reveal that chemistry plays a major role as well. From the viewpoint of materials science, a deep understanding of the influence of chemical effects on MOF mechanics is not only highly desirable for the development of novel functional materials with targeted mechanical response, but also for a better understanding of important properties such as structural flexibility and framework breathing. The present work discusses the intrinsic connection between chemical effects and the mechanical behavior of MOFs through a number of prototypical examples.

  7. Diagenesis of Metals Chemically Complexed to Bacteria: Laboratory Formation of Metal Phosphates, Sulfides, and Organic Condensates in Artificial Sediments

    PubMed Central

    Beveridge, T. J.; Meloche, J. D.; Fyfe, W. S.; Murray, R. G. E.

    1983-01-01

    Cells of Bacillus subtilis, when suspended in a 5mM metal solution, bind metals tenaciously to their cell walls. These metal-loaded cells, when mixed with a synthetic sediment and put under laboratory conditions to simulate low-temperature sediment diagenesis, nucleate the formation of a mixed assemblage of crystalline metal phosphates, metal sulfides, and polymeric, metal-complexed, organic residues. The sequential series of diagenetic events leading to the formation of authigenic mineral phases was followed by transmission electron microscopy and energy-dispersive X-ray analysis. The minerals quartz (SiO2) and calcite (CaCO3) were employed in the synthetic sediment. Crystalline magnetite (Fe2O3) and elemental sulfur were added as redox buffering agents to ensure anoxic conditions. Quartz and magnetite appeared unreactive throughout the experimental conditions. Elemental sulfur interacted with the metal-loaded cells, affected both the eventual chemistry and crystal habit of the metal phosphates, and formed a variety of crystalline metal sulfides. Calcite raised the pH of the fluid phase of the sediment, which influenced phosphate mineralization and inhibited metal sulfide genesis. Images PMID:16346230

  8. Improving source efficiency for aluminum nitride grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Foronda, Humberto M.; Laurent, Matthew A.; Yonkee, Benjanim; Keller, Stacia; DenBaars, Steven P.; Speck, James S.

    2016-08-01

    Parasitic pre-reactions are known to play a role in the growth of aluminum nitride (AlN) via metal organic chemical vapor deposition, where they can deplete precursor molecules before reaching the substrate, leading to poor growth efficiency. Studies have shown that reducing the growth pressure and growth temperature results in improved growth efficiency of AlN; however, superior crystal quality and reduced impurity incorporation are generally best obtained when growing at high temperatures. This study shows that, with proper alkyl source dilution, parasitic pre-reactions can be suppressed while maintaining high growth temperatures. The results show an 18× increase in growth rate and efficiency of AlN films: from 0.04 μm h-1 to 0.73 μm h-1, and 26 μm mol-1 to 502 μm mol-1, respectively; under constant TMAl flow and a small change in total gas flow. This results in 6.8% of Al atoms from the injected TMAl being utilized for AlN layer growth for this reactor configuration. This is better than the standard GaN growth, where 6.0% of the Ga atoms injected from TMGa are utilized for GaN growth.

  9. Topological insulator Bi2Te3 films synthesized by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cao, Helin; Venkatasubramanian, Rama; Liu, Chang; Pierce, Jonathan; Yang, Haoran; Zahid Hasan, M.; Wu, Yue; Chen, Yong P.

    2012-10-01

    Topological insulator (TI) materials such as Bi2Te3 and Bi2Se3 have attracted strong recent interests. Large scale, high quality TI thin films are important for developing TI-based device applications. In this work, structural and electronic properties of Bi2Te3 thin films deposited by metal organic chemical vapor deposition (MOCVD) on GaAs (001) substrates were characterized via x-ray diffraction (XRD), Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and electronic transport measurements. The characteristic topological surface states with a single Dirac cone have been clearly revealed in the electronic band structure measured by ARPES, confirming the TI nature of the MOCVD Bi2Te3 films. Resistivity and Hall effect measurements have demonstrated relatively high bulk carrier mobility of ˜350 cm2/Vs at 300 K and ˜7400 cm2/Vs at 15 K. We have also measured the Seebeck coefficient of the films. Our demonstration of high quality topological insulator films grown by a simple and scalable method is of interests for both fundamental research and practical applications of thermoelectric and TI materials.

  10. Nano sized bismuth oxy chloride by metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Jagdale, Pravin; Castellino, Micaela; Marrec, Françoise; Rodil, Sandra E.; Tagliaferro, Alberto

    2014-06-01

    Metal organic chemical vapour deposition (MOCVD) method was used to prepare thin films of bismuth based nano particles starting from bismuth salts. Nano sized bismuth oxy chloride (BiOCl) crystals were synthesized from solution containing bismuth chloride (BiCl3) in acetone (CH3sbnd COsbnd CH3). Self-assembly of nano sized BiOCl crystals were observed on the surface of silicon, fused silica, copper, carbon nanotubes and aluminium substrates. Various synthesis parameters and their significant impact onto the formation of self-assembled nano-crystalline BiOCl were investigated. BiOCl nano particles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Micro-Raman spectroscopy. These analyses confirm that bismuth nanometer-sized crystal structures showing a single tetragonal phase were indeed bismuth oxy chloride (BiOCl) square platelets 18-250 nm thick and a few micrometres wide.

  11. Improving source efficiency for aluminum nitride grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Foronda, Humberto M.; Laurent, Matthew A.; Yonkee, Benjanim; Keller, Stacia; DenBaars, Steven P.; Speck, James S.

    2016-08-01

    Parasitic pre-reactions are known to play a role in the growth of aluminum nitride (AlN) via metal organic chemical vapor deposition, where they can deplete precursor molecules before reaching the substrate, leading to poor growth efficiency. Studies have shown that reducing the growth pressure and growth temperature results in improved growth efficiency of AlN; however, superior crystal quality and reduced impurity incorporation are generally best obtained when growing at high temperatures. This study shows that, with proper alkyl source dilution, parasitic pre-reactions can be suppressed while maintaining high growth temperatures. The results show an 18× increase in growth rate and efficiency of AlN films: from 0.04 μm h‑1 to 0.73 μm h‑1, and 26 μm mol‑1 to 502 μm mol‑1, respectively; under constant TMAl flow and a small change in total gas flow. This results in 6.8% of Al atoms from the injected TMAl being utilized for AlN layer growth for this reactor configuration. This is better than the standard GaN growth, where 6.0% of the Ga atoms injected from TMGa are utilized for GaN growth.

  12. Opportunities and challenges in GaN metal organic chemical vapor deposition for electron devices

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koh; Yamaoka, Yuya; Ubukata, Akinori; Arimura, Tadanobu; Piao, Guanxi; Yano, Yoshiki; Tokunaga, Hiroki; Tabuchi, Toshiya

    2016-05-01

    The current situation and next challenge in GaN metal organic chemical vapor deposition (MOCVD) for electron devices of both GaN on Si and GaN on GaN are presented. We have examined the possibility of increasing the growth rate of GaN on 200-mm-diameter Si by using a multiwafer production MOCVD machine, in which the vapor phase parasitic reaction is well controlled. The impact of a high-growth-rate strained-layer-superlattice (SLS) buffer layer is presented in terms of material properties. An SLS growth rate of as high as 3.46 µm/h, which was 73% higher than the current optimum, was demonstrated. As a result, comparable material properties were obtained. Next, a typical result of GaN doped with Si of 1 × 1016 cm-3 grown at the growth rate of 3.7 µm/h is shown. For high-voltage application, we need a thick high-purity GaN drift layer with a low carbon concentration, of less than 1016 cm-3. It is shown that achieving a high growth rate by precise control of the vapor phase reaction is still challenge in GaN MOCVD.

  13. Stress-induced chemical detection using flexible metal-organic frameworks.

    SciTech Connect

    Allendorf, Mark D.; Hesketh, Peter J.; Gall, Kenneth A.; Choudhury, A.; Pikarsky, J.; Andruszkiewicz, Leanne; Houk, Ronald J. T.; Talin, Albert Alec

    2009-09-01

    In this work we demonstrate the concept of stress-induced chemical detection using metal-organic frameworks (MOFs) by integrating a thin film of the MOF HKUST-1 with a microcantilever surface. The results show that the energy of molecular adsorption, which causes slight distortions in the MOF crystal structure, can be efficiently converted to mechanical energy to create a highly responsive, reversible, and selective sensor. This sensor responds to water, methanol, and ethanol vapors, but yields no response to either N{sub 2} or O{sub 2}. The magnitude of the signal, which is measured by a built-in piezoresistor, is correlated with the concentration and can be fitted to a Langmuir isotherm. Furthermore, we show that the hydration state of the MOF layer can be used to impart selectivity to CO{sub 2}. We also report the first use of surface-enhanced Raman spectroscopy to characterize the structure of a MOF film. We conclude that the synthetic versatility of these nanoporous materials holds great promise for creating recognition chemistries to enable selective detection of a wide range of analytes. A force field model is described that successfully predicts changes in MOF properties and the uptake of gases. This model is used to predict adsorption isotherms for a number of representative compounds, including explosives, nerve agents, volatile organic compounds, and polyaromatic hydrocarbons. The results show that, as a result of relatively large heats of adsorption (> 20 kcal mol{sup -1}) in most cases, we expect an onset of adsorption by MOF as low as 10{sup -6} kPa, suggesting the potential to detect compounds such as RDX at levels as low as 10 ppb at atmospheric pressure.

  14. Method for the preparation of protective coatings by low-temperature metal--organic chemical vapor deposition (MOCVD)

    SciTech Connect

    Kaloyeros, A.E.; Williams, W.S.; Constant, G.

    1988-07-01

    A simple and effective method is reported for the deposition of protective coatings of titanium carbide using low-temperature (as low as 150 /sup 0/C) metal--organic chemical vapor deposition. This method is based on the thermolysis of metal--organic molecules containing titanium and does not require the high temperature (<1100 /sup 0/C) involved in the standard TiC--CVD technique. Furthermore, the structure of the films produced (crystalline or amorphous) and their purity (inclusion of organic clusters or hydrogen) can be tailored easily by simple variations in the deposition parameters. This technique permits the coating of polymers and low-melting metals that are thermally too fragile for other deposition techniques. The process could be applied to produce films of other materials, e.g., niobium carbide, silicon carbide, titanium diboride, and gallium arsenide.

  15. Alumina coating on dense tungsten powder by fluidized bed metal organic chemical vapour deposition.

    PubMed

    Rodriguez, Philippe; Caussat, Brigitte; Ablitzer, Carine; Iltis, Xavière; Brothier, Meryl

    2011-09-01

    In order to study the feasibility of coating very dense powders by alumina using Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD), experiments were performed on a commercial tungsten powder, 75 microm in median volume diameter and 19,300 kg/m3 in grain density. The first part of the work was dedicated to the experimental study of the tungsten powder fluidization using argon as carrier gas at room temperature and at 400 degrees C. Due to the very high density of the tungsten powder, leading to low initial fixed bed heights and low bed expansions, different weights of powder were tested in order to reach satisfactory temperature profiles along the fluidized bed. Then, using argon as a fluidized bed former and aluminium acetylacetonate Al(C5O2H7)3 as a single source precursor, alumina thin films were deposited on tungsten particles at a low temperature range (e.g., 370-420 degrees C) by FB-MOCVD. The influence of the weight of powder, bed temperature and run duration was studied. Characterizations of the obtained samples were performed by various techniques including scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) analyses, Field Emission Gun SEM (FEG-SEM) and Fourier Transform InfraRed (FT-IR) spectroscopy. The different analyses indicated that tungsten particles were uniformly coated by a continuous alumina thin film. The thickness of the film ranged between 25 and 80 nm, depending on the coating conditions. The alumina thin films were amorphous and contained carbon contamination. This latter may correspond to the adsorption of species resulting from incomplete decomposition of the precursor at so low deposition temperature. PMID:22097534

  16. Atomic MoS2 monolayers synthesized from a metal-organic complex by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Qiu, Hailong; Wang, Jingyi; Xu, Guanchen; Jiao, Liying

    2016-02-01

    The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs).The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs). Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09089j

  17. Soluble organic carbon and pH of organic amendments affect metal mobility and chemical speciation in mine soils.

    PubMed

    Pérez-Esteban, Javier; Escolástico, Consuelo; Masaguer, Alberto; Vargas, Carmen; Moliner, Ana

    2014-05-01

    We evaluated the effects of pH and soluble organic carbon affected by organic amendments on metal mobility to find out the optimal conditions for their application in the stabilization of metals in mine soils. Soil samples (pH 5.5-6.2) were mixed with 0, 30 and 60 th a(-1) of sheep-horse manure (pH 9.4) and pine bark compost (pH 5.7). A single-step extraction procedure was performed using 0.005 M CaCl2 adjusted to pH 4.0-7.0 and metal speciation in soil solution was simulated using NICA-Donnan model. Sheep-horse manure reduced exchangeable metal concentrations (up to 71% Cu, 75% Zn) due to its high pH and degree of maturity, whereas pine bark increased them (32% Cu, 33% Zn). However, at increasing dose and hence pH, sheep-horse manure increased soluble Cu because of higher soluble organic carbon, whereas soluble Cu and organic carbon increased at increasing dose and correspondingly decreasing pH in pine bark and non-amended treatments. Near the native pH of these soils (at pH 5.8-6.3), with small doses of amendments, there was minimum soluble Cu and organic carbon. Pine bark also increased Zn solubility, whereas sheep-horse manure reduced it as soluble Zn always decreased with increasing pH. Sheep-horse manure also reduced the proportion of free metals in soil solution (from 41% to 4% Cu, from 97% to 94% Zn), which are considered to be more bioavailable than organic species. Sheep-horse manure amendment could be efficiently used for the stabilization of metals with low risk of leaching to groundwater at low doses and at relatively low pH, such as the native pH of mine soils.

  18. Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

    NASA Technical Reports Server (NTRS)

    Collis, Ward J.; Abul-Fadl, Ali

    1988-01-01

    The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

  19. Chemical reactions of metal powders with organic and inorganic liquids during ball milling

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1975-01-01

    Chromium and/or nickel powders were milled in metal chlorides and in organic liquids representative of various functional groups. The powders always reacted with the liquid and became contaminated with elements from them. The milled powders had specific surface areas ranging from 0.14 to 37 sq m/g, and the total contamination with elements from the milling liquid ranged from 0.01 to 56 weight percent. Compounds resulting from substitution, addition, or elimination reactions formed in or from the milling liquid.

  20. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Dutta, P.; Rathi, M.; Zheng, N.; Gao, Y.; Yao, Y.; Martinez, J.; Ahrenkiel, P.; Selvamanickam, V.

    2014-09-01

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ˜107 cm-2. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm2/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  1. Groundwater and organic chemicals

    SciTech Connect

    Dawson, H.E.

    1995-12-01

    Groundwater is a major source of drinking water for many communities. Unfortunately, organic chemicals such as dry cleaning fluids, solvent, fuels, and pesticides have contaminated groundwater in many areas, rendering the groundwater useless as a drinking water resource. In many cases, the groundwater cannot be cleaned up with current technologies, particularly if the groundwater has been contaminated with immiscible (low solubility) organic liquids. In this talk, I will describe the path I have followed from geologist to geochemist and finally to environmental engineer. As a geologist, I studied the chemistry of rock metamorphosis. As a geochemist, I explored for gold and other metals. Now as an environmental engineer, I investigate the behavior of organic liquids in the subsurface. While these fields all appear very different, in reality I have always focused on the interaction of rocks or sediments with the fluids with which they come in contact.

  2. Crystal engineering of an nbo topology metal-organic framework for chemical fixation of CO2 under ambient conditions.

    PubMed

    Gao, Wen-Yang; Chen, Yao; Niu, Youhong; Williams, Kia; Cash, Lindsay; Perez, Pastor J; Wojtas, Lukasz; Cai, Jianfeng; Chen, Yu-Sheng; Ma, Shengqian

    2014-03-01

    Crystal engineering of the nbo metal-organic framework (MOF) platform MOF-505 with a custom-designed azamacrocycle ligand (1,4,7,10-tetrazazcyclododecane-N,N',N'',N'''-tetra-p-methylbenzoic acid) leads to a high density of well-oriented Lewis active sites within the cuboctahedral cage in MMCF-2, [Cu2(Cu-tactmb)(H2O)3(NO3)2]. This MOF demonstrates high catalytic activity for the chemical fixation of CO2 into cyclic carbonates at room temperature under 1 atm pressure.

  3. Organic semiconductor/gold interface interactions: from physisorption on planar surfaces to chemical reactions with metal nanoparticles.

    PubMed

    Ligorio, Giovanni; Nardi, Marco Vittorio; Christodoulou, Christos; Koch, Norbert

    2015-08-24

    The interaction of gold nanoparticles (AuNPs) with prototypical organic semiconductors used in optoelectronics, namely, tris(8-hydroxyquinoline)aluminium (Alq3 ) and 4,4-bis[N-(1-naphthyl)-N-phenylamino]diphenyl (α-NPD), is investigated in situ by X-ray photoelectron spectroscopy (XPS). These AuNPs-on-molecule experiments are compared with the reversed molecule-on-Au cases. The molecules-on-Au systems show only weak interactions, and the evolution of the XP spectra is dominated by final-state effects. In contrast, in the AuNPs-on-molecules cases, both initial-state effects and final-state effects occur. Spectral features arising for both molecules and metal indicate charge transfer and the formation of organometallic complexes (initial-state effects). The energy shift in the metal emission underlines the size-induced nanometric nature of the molecule/Au interaction (final-state effects). Consequently, the chemical interaction between metals and organic semiconductors likely depends strongly on the deposition sequence in general.

  4. Production of strontium sulfide coatings by metal organic chemical vapor deposition

    SciTech Connect

    Moss, T.S.; Dye, R.C.; Tuenge, R.T.

    1998-11-01

    This work was focused on the MOCVD of the cerium-doped strontium sulfide (SrS:Ce) phosphor for use in thin film electroluminescent displays (TFELs). Following previous research on a small scale reactor, a feasibility scale-up using a commercially available reactor enlarged the size of the deposition area to a 4`` diameter wafer or a 2`` by 2`` glass slide. Films were deposited from the reaction of Sr(thd){sub 2}, Ce(thd){sub 4}, and H{sub 2}S at 450{degrees}C and 5 torr. This system employed a liquid delivery system for the accurate and repeatable delivery of the metal organic reagents. The deposition from this reactor was shown to be crystalline-as-deposited SrS with a (200) orientation, possibly a result of the thin nature of the coating and the involvement of (200) grains in the initial nucleation process. The wafers showed good uniformity, but had some thickness variation near the outer radius of the wafer resulting from the addition of H{sub 2}S from the outer edge. There were eighteen total deposition experiments, of which nine were characterized for EL performance. The highest brightness observed was 5 fL.. The samples were exceedingly thin as a result of the fifteen fold increase in the surface area between the deposition reactors. Increasing the sample thickness to 7,000{angstrom} or higher will dramatically increase the brightness of the emission.

  5. Organic polymer-metal nano-composites for opto-electronic sensing of chemicals in agriculture

    NASA Astrophysics Data System (ADS)

    Sarkisov, Sergey S.; Czarick, Michael; Fairchild, Brian D.; Liang, Yi; Kukhtareva, Tatiana; Curley, Michael J.

    2013-03-01

    Recent research findings led the team to conclude that a long lasting and inexpensive colorimetric sensor for monitoring ammonia emission from manure in confined animal feeding operations could eventually become feasible. The sensor uses robust method of opto-electronic spectroscopic measurement of the reversible change of the color of a sensitive nano-composite reagent film in response to ammonia. The film is made of a metal (gold, platinum, or palladium) nano-colloid in a polymer matrix with an ammonia-sensitive indicator dye additive. The response of the indicator dye (increase of the optical absorption in the region 550 to 650 nm) is enhanced by the nano-particles (~10 nm in size) in two ways: (a) concentration of the optical field near the nano-particle due to the plasmon resonance; and (b) catalytic acceleration of the chemical reaction of deprotonization of the indicator dye in the presence of ammonia and water vapor. This enhancement helps to make a miniature and rugged sensing element without compromising its sensitivity of less than 1 ppm for the range 0 to 100 ppm. The sensor underwent field tests in commercial broiler farms in Georgia, Alabama, and Arkansas and was compared against a commercial photoacoustic gas analyzer. The sensor output correlated well with the data from the photoacoustic analyzer (correlation coefficient not less than 0.9 and the linear regression slope after calibration close to 1.0) for several weeks of continuous operation. The sources of errors were analyzed and the conclusions on the necessary improvements and the potential use of the proposed device were made.

  6. Encapsulation of redox polysulphides via chemical interaction with nitrogen atoms in the organic linkers of metal-organic framework nanocrystals

    PubMed Central

    Park, Jung Hyo; Choi, Kyung Min; Lee, Dong Ki; Moon, Byeong Cheul; Shin, Sang Rim; Song, Min-Kyu; Kang, Jeung Ku

    2016-01-01

    Lithium polysulphides generated during discharge in the cathode of a lithium-sulphur redox cell are important, but their dissolution into the electrolyte from the cathode during each redox cycle leads to a shortened cycle life. Herein, we use in situ spectroelectrochemical measurements to demonstrate that sp2 nitrogen atoms in the organic linkers of nanocrystalline metal-organic framework-867 (nMOF-867) are able to encapsulate lithium polysulphides inside the microcages of nMOF-867, thus helping to prevent their dissolution into the electrolyte during discharge/charge cycles. This encapsulation mechanism of lithiated/delithiated polysulphides was further confirmed by observations of shifted FTIR spectra for the C = N and C-N bonds, the XPS spectra for the Li-N bonds from nMOF-867, and a visualization method, demonstrating that nMOF-867 prevents lithium polysulphides from being dissolved in the electrolyte. Indeed, a cathode fabricated using nMOF-867 exhibited excellent capacity retention over a long cycle life of 500 discharge/charge cycles, with a capacity loss of approximately 0.027% per cycle from a discharge capacity of 788 mAh/g at a high current rate of 835 mA/g. PMID:27149405

  7. Encapsulation of redox polysulphides via chemical interaction with nitrogen atoms in the organic linkers of metal-organic framework nanocrystals

    NASA Astrophysics Data System (ADS)

    Park, Jung Hyo; Choi, Kyung Min; Lee, Dong Ki; Moon, Byeong Cheul; Shin, Sang Rim; Song, Min-Kyu; Kang, Jeung Ku

    2016-05-01

    Lithium polysulphides generated during discharge in the cathode of a lithium-sulphur redox cell are important, but their dissolution into the electrolyte from the cathode during each redox cycle leads to a shortened cycle life. Herein, we use in situ spectroelectrochemical measurements to demonstrate that sp2 nitrogen atoms in the organic linkers of nanocrystalline metal-organic framework-867 (nMOF-867) are able to encapsulate lithium polysulphides inside the microcages of nMOF-867, thus helping to prevent their dissolution into the electrolyte during discharge/charge cycles. This encapsulation mechanism of lithiated/delithiated polysulphides was further confirmed by observations of shifted FTIR spectra for the C = N and C-N bonds, the XPS spectra for the Li-N bonds from nMOF-867, and a visualization method, demonstrating that nMOF-867 prevents lithium polysulphides from being dissolved in the electrolyte. Indeed, a cathode fabricated using nMOF-867 exhibited excellent capacity retention over a long cycle life of 500 discharge/charge cycles, with a capacity loss of approximately 0.027% per cycle from a discharge capacity of 788 mAh/g at a high current rate of 835 mA/g.

  8. Encapsulation of redox polysulphides via chemical interaction with nitrogen atoms in the organic linkers of metal-organic framework nanocrystals.

    PubMed

    Park, Jung Hyo; Choi, Kyung Min; Lee, Dong Ki; Moon, Byeong Cheul; Shin, Sang Rim; Song, Min-Kyu; Kang, Jeung Ku

    2016-01-01

    Lithium polysulphides generated during discharge in the cathode of a lithium-sulphur redox cell are important, but their dissolution into the electrolyte from the cathode during each redox cycle leads to a shortened cycle life. Herein, we use in situ spectroelectrochemical measurements to demonstrate that sp(2) nitrogen atoms in the organic linkers of nanocrystalline metal-organic framework-867 (nMOF-867) are able to encapsulate lithium polysulphides inside the microcages of nMOF-867, thus helping to prevent their dissolution into the electrolyte during discharge/charge cycles. This encapsulation mechanism of lithiated/delithiated polysulphides was further confirmed by observations of shifted FTIR spectra for the C = N and C-N bonds, the XPS spectra for the Li-N bonds from nMOF-867, and a visualization method, demonstrating that nMOF-867 prevents lithium polysulphides from being dissolved in the electrolyte. Indeed, a cathode fabricated using nMOF-867 exhibited excellent capacity retention over a long cycle life of 500 discharge/charge cycles, with a capacity loss of approximately 0.027% per cycle from a discharge capacity of 788 mAh/g at a high current rate of 835 mA/g. PMID:27149405

  9. Natural radioactivity levels and heavy metals in chemical and organic fertilizers used in Kingdom of Saudi Arabia.

    PubMed

    El-Taher, A; Althoyaib, S S

    2012-01-01

    The present work deals with identifying and determining the activity levels of natural occuring radionuclides, (226)Ra and (232)Th series, their decay products and (40)K, in chemical and organic fertilizers used in Kingdom of Saudi Arabia. A total of 30 samples: 20 phosphatic fertilizers (single super-phosphate SSP and triple super-phosphate,TSP) and 10 organic fertilizers (cow, sheep and chicken) collected from markets and farms. The gamma-ray spectrometer consists of NaI(Tl) detector and its electronic circuit was used for measuring γ-ray spectra. The ranges of radioactivity levels of (226)Ra, (232)Th and (40)K in chemical fertilizers are 51.5±5.2-106.3±7.5, 5.1±1.6-9.9±3.2. and 462.6±21-607.3±14Bqkg(-1), respectively. The activities of (226)Ra, (232)Th and (40)K in natural fertilizers (cow, sheep and chicken) are lower than the activities in chemical fertilizers. The obtained data are compared with available reported data from other countries in literature. The Ra(eq) in chemical fertilizer ranges from 100.37 to 161.43Bqkg(-1) and in organic fertilizer ranges from 34.07 to 102.19Bqkg(-1), which are lower than the limit of 370Bqkg(-1) adopted from NEA-OECD (1979). The average heavy metal (Pb, Cd, Ni, Co and Cr) contents of the fertilizers marketed in the Kingdom of Saudi Arabia are also determined and within the limits of those used worldwide.

  10. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    NASA Astrophysics Data System (ADS)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  11. Catalytic hydrothermal conversion of carboxymethyl cellulose to value-added chemicals over metal-organic framework MIL-53(Al).

    PubMed

    Zi, Guoli; Yan, Zhiying; Wang, Yangxia; Chen, Yongjuan; Guo, Yunlong; Yuan, Fagui; Gao, Wenyu; Wang, Yanmei; Wang, Jiaqiang

    2015-01-22

    Catalytic hydrolysis of biomass over solid catalysts can be one of the most efficient pathways for a future sustainable society dependent on cellulose biomass. In this work metal-organic framework MIL-53(Al) without any functionalization was directly employed as an efficient heterogeneous catalyst for the hydrolysis of carboxymethyl cellulose (CMC) to 5-hydroxymethyl-furaldehyde (5-HMF) in aqueous phase. A 5-HMF molar yield of 40.3% and total reducing sugar (TRS) molar yield of 54.2% were obtained with water as single solvent at 473 K for 4 h. The catalyst could be reused three times without losing activity to a greater extent. With the remarkable advantages such as the use of water as single solvent and MIL-53(Al) as a novel heterogeneous green catalyst, the work provides a new platform for the production of value added chemicals and liquid fuels from biomass. PMID:25439879

  12. Magnetic Properties of Fe-Implanted ZnO Nanotips Grown by Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Wu,P.; Saraf, G.; Lu, Y.; Hill, D.; Arena, D.; Bartynski, R.; Cosandey, F.; Al-Sharab, J.; Wielunski, L.; et al.

    2007-01-01

    Fe ions were implanted into well-aligned single-crystal ZnO nanotips grown on SiO{sub 2}/quartz substrates using metal-organic chemical vapor deposition (MOCVD). The Fe ion concentration distribution within a single nanotip is mapped by electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) and the nanotips imaged by high-resolution transmission electron microscopy (TEM). X-ray absorption spectroscopy (XAS) identified the presence of Fe{sup 2+} and Fe{sup 3+} ions in both as-implanted and annealed samples. However, Fe{sup 3+} ion concentration increased during postannealing. Superconducting quantum interference device (SQUID) measurements show that the as-implanted and postannealed ZnO nanotips are ferromagnetic at room temperature. The observed ferromagnetism in the as-implanted nanotips is primarily attributed to the near surface 10-nm region that has high Fe concentration. The saturation magnetization reduces after annealing.

  13. Dual-Function Metal-Organic Framework as a Versatile Catalyst for Detoxifying Chemical Warfare Agent Simulants.

    PubMed

    Liu, Yangyang; Moon, Su-Young; Hupp, Joseph T; Farha, Omar K

    2015-12-22

    The nanocrystals of a porphyrin-based zirconium(IV) metal-organic framework (MOF) are used as a dual-function catalyst for the simultaneous detoxification of two chemical warfare agent simulants at room temperature. Simulants of nerve agent (such as GD, VX) and mustard gas, dimethyl 4-nitrophenyl phosphate and 2-chloroethyl ethyl sulfide, have been hydrolyzed and oxidized, respectively, to nontoxic products via a pair of pathways catalyzed by the same MOF. Phosphotriesterase-like activity of the Zr6-containing node combined with photoactivity of the porphyrin linker gives rise to a versatile MOF catalyst. In addition, bringing the MOF crystals down to the nanoregime leads to acceleration of the catalysis.

  14. InAs/GaSb core-shell nanowires grown on Si substrates by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Luo, Shuai; Ji, Haiming; Xu, H. Q.; Yang, Tao

    2016-07-01

    We report the growth of InAs/GaSb core-shell heterostructure nanowires with smooth sidewalls on Si substrates using metal-organic chemical vapor deposition with no assistance from foreign catalysts. Sb adatoms were observed to strongly influence the morphology of the GaSb shell. In particular, Ga droplets form on the nanowire tips when a relatively low TMSb flow rate is used, whereas the droplets are missing and the radial growth of the GaSb is enhanced due to a reduction in the diffusion length of the Ga adatoms when the TMSb flow rate is increased. Moreover, transmission electron microscopy measurements revealed that the GaSb shell coherently grew on the InAs core. The results obtained here show that the InAs/GaSb core-shell nanowires grown using the Si platform have strong potential in the fabrication of future nanometer-scale devices and in the study of fundamental quantum physics.

  15. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    SciTech Connect

    Dutta, P. Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V.; Zheng, N.; Ahrenkiel, P.; Martinez, J.

    2014-09-01

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ∼10{sup 7 }cm{sup −2}. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm{sup 2}/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  16. The interplay between interface structure, energy level alignment and chemical bonding strength at organic-metal interfaces.

    PubMed

    Willenbockel, M; Lüftner, D; Stadtmüller, B; Koller, G; Kumpf, C; Soubatch, S; Puschnig, P; Ramsey, M G; Tautz, F S

    2015-01-21

    What do energy level alignments at metal-organic interfaces reveal about the metal-molecule bonding strength? Is it permissible to take vertical adsorption heights as indicators of bonding strengths? In this paper we analyse 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on the three canonical low index Ag surfaces to provide exemplary answers to these questions. Specifically, we employ angular resolved photoemission spectroscopy for a systematic study of the energy level alignments of the two uppermost frontier states in ordered monolayer phases of PTCDA. Data are analysed using the orbital tomography approach. This allows the unambiguous identification of the orbital character of these states, and also the discrimination between inequivalent species. Combining this experimental information with DFT calculations and the generic Newns-Anderson chemisorption model, we analyse the alignments of highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) with respect to the vacuum levels of bare and molecule-covered surfaces. This reveals clear differences between the two frontier states. In particular, on all surfaces the LUMO is subject to considerable bond stabilization through the interaction between the molecular π-electron system and the metal, as a consequence of which it also becomes occupied. Moreover, we observe a larger bond stabilization for the more open surfaces. Most importantly, our analysis shows that both the orbital binding energies of the LUMO and the overall adsorption heights of the molecule are linked to the strength of the chemical interaction between the molecular π-electron system and the metal, in the sense that stronger bonding leads to shorter adsorption heights and larger orbital binding energies. PMID:25475998

  17. Metal organic chemical vapor deposition of 111-v compounds on silicon

    DOEpatents

    Vernon, Stanley M.

    1986-01-01

    Expitaxial composite comprising thin films of a Group III-V compound semiconductor such as gallium arsenide (GaAs) or gallium aluminum arsenide (GaAlAs) on single crystal silicon substrates are disclosed. Also disclosed is a process for manufacturing, by chemical deposition from the vapor phase, epitaxial composites as above described, and to semiconductor devices based on such epitaxial composites. The composites have particular utility for use in making light sensitive solid state solar cells.

  18. A novel three-jet microreactor for localized metal-organic chemical vapour deposition of gallium arsenide: design and simulation

    NASA Astrophysics Data System (ADS)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2016-08-01

    We present a novel three-jet microreactor design for localized deposition of gallium arsenide (GaAs) by low-pressure Metal-Organic Chemical Vapour Deposition (MOCVD) for semiconductor devices, microelectronics and solar cells. Our approach is advantageous compared to the standard lithography and etching technology, since it preserves the nanostructure of the deposited material, it is less time-consuming and less expensive. We designed two versions of reactor geometry with a 10-micron central microchannel for precursor supply and with two side jets of a dilutant to control the deposition area. To aid future experiments, we performed computational modeling of a simplified-geometry (twodimensional axisymmetric) microreactor, based on Navier-Stokes equations for a laminar flow of chemically reacting gas mixture of Ga(CH3)3-AsH3-H2. Simulation results show that we can achieve a high-rate deposition (over 0.3 μm/min) on a small area (less than 30 μm diameter). This technology can be used in material production for microelectronics, optoelectronics, photovoltaics, solar cells, etc.

  19. Growth mechanism of Co:TiO2 thin film deposited by metal organic chemical vapor deposition technique

    NASA Astrophysics Data System (ADS)

    Saripudin, A.; Arifin, P.

    2016-04-01

    In this research, we investigated the growth mechanism of cobalt-doped titanium dioxide (Co:TiO2) films. Thi Co:TiO2 thin films were grown on the n-type silicon substrate. The films were grown by metal organic chemical vapor deposition method. The growth temperature was varied of 325°C - 450°C. The films were characterized by SEM. Using Arheniu’s equation, it is known that the activation energy value of film growth is positive in the range of temperature of 325°C - 400°C and negative in the range of temperature of 400°C - 450°C. These results show that the decomposition rate in the range of temperature of 325°C - 400°C is due to diffusion phase of precursor gas. On the other hand, the decomposition rate decreased in the range of temperature of 400°C - 450°C because the precursor gas decreased, and the surface chemical reaction was high.

  20. Modified dislocation filter method: toward growth of GaAs on Si by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hu, Haiyang; Wang, Jun; He, Yunrui; Liu, Kai; Liu, Yuanyuan; Wang, Qi; Duan, Xiaofeng; Huang, Yongqing; Ren, Xiaomin

    2016-06-01

    In this paper, metamorphic growth of GaAs on (001) oriented Si substrate, with a combination method of applying dislocation filter layer (DFL) and three-step growth process, was conducted by metal organic chemical vapor deposition. The effectiveness of the multiple InAs/GaAs self-organized quantum dot (QD) layers acting as a dislocation filter was researched in detail. And the growth conditions of the InAs QDs were optimized by theoretical calculations and experiments. A 2-μm-thick buffer layer was grown on the Si substrate with the three-step growth method according to the optimized growth conditions. Then, a 114-nm-thick DFL and a 1-μm-thick GaAs epilayer were grown. The results we obtained demonstrated that the DFL can effectively bend dislocation direction via the strain field around the QDs. The optimal structure of the DFL is composed of three-layer InAs QDs with a growth time of 55 s. The method could reduce the etch pit density from about 3 × 106 cm-2 to 9 × 105 cm-2 and improve the crystalline quality of the GaAs epilayers on Si.

  1. Isoreticular zirconium-based metal-organic frameworks: discovering mechanical trends and elastic anomalies controlling chemical structure stability.

    PubMed

    Ryder, Matthew R; Civalleri, Bartolomeo; Tan, Jin-Chong

    2016-04-01

    Understanding the mechanical properties of metal-organic frameworks (MOFs) is crucial not only to yield robust practical applications, but also to advance fundamental research underpinning the flexibility of a myriad of open-framework chemical compounds. Herein we present one of the most comprehensive structural analyses yet on MOF-mechanics: elucidating the complex elastic response of an isoreticular series of topical Zr-based MOFs, explaining all the important mechanical properties, and identifying major trends arising from systematic organic linker exchange. Ab initio density functional theory (DFT) was employed to establish the single-crystal elastic constants of the nanoporous MIL-140(A-D) structures, generating a complete 3-D representation of the principal mechanical properties, encompassing the Young's modulus, shear modulus, linear compressibility and Poisson's ratio. Of particular interest, we discovered significantly high values of both positive and negative linear compressibility and Poisson's ratio, whose framework molecular mechanisms responsible for such elastic anomalies have been fully revealed. In addition to pinpointing large elastic anisotropy and unusual physical properties, we analyzed the bulk modulus of isoreticular Zr-MOF compounds to understand the framework structural resistance against the hydrostatic pressure, and determined the averaged mechanical behaviour of bulk (polycrystalline) MOF materials important for the design of emergent applications.

  2. A Chemical Route to Activation of Open Metal Sites in the Copper-Based Metal-Organic Framework Materials HKUST-1 and Cu-MOF-2.

    PubMed

    Kim, Hong Ki; Yun, Won Seok; Kim, Min-Bum; Kim, Jeung Yoon; Bae, Youn-Sang; Lee, JaeDong; Jeong, Nak Cheon

    2015-08-12

    Open coordination sites (OCSs) in metal-organic frameworks (MOFs) often function as key factors in the potential applications of MOFs, such as gas separation, gas sorption, and catalysis. For these applications, the activation process to remove the solvent molecules coordinated at the OCSs is an essential step that must be performed prior to use of the MOFs. To date, the thermal method performed by applying heat and vacuum has been the only method for such activation. In this report, we demonstrate that methylene chloride (MC) itself can perform the activation role: this process can serve as an alternative "chemical route" for the activation that does not require applying heat. To the best of our knowledge, no previous study has demonstrated this function of MC, although MC has been popularly used in the pretreatment step prior to the thermal activation process. On the basis of a Raman study, we propose a plausible mechanism for the chemical activation, in which the function of MC is possibly due to its coordination with the Cu(2+) center and subsequent spontaneous decoordination. Using HKUST-1 film, we further demonstrate that this chemical activation route is highly suitable for activating large-area MOF films. PMID:26197386

  3. AN ASSESSMENT OF THE DATA QUALITY FOR NHEXAS--PART I: EXPOSURE TO METALS AND VOLATILE ORGANIC CHEMICALS IN REGION 5

    EPA Science Inventory

    A National Human Exposure Assessment Survey (NHEXAS) was performed in U.S. Environmental Protection Agency (U.S. EPA) Region V, providing population-based exposure distribution data for metals and volatile organic chemicals (VOCs) in personal, indoor, and outdoor air, drinking ...

  4. Liquid source metal-organic chemical-vapor deposition of high-quality YBa2Cu3O7-x films on polycrystalline silver substrates

    NASA Astrophysics Data System (ADS)

    Studebaker, D. B.; Zhang, J.; Marks, T. J.; Wang, Y. Y.; Dravid, V. P.; Schindler, J. L.; Kannewurf, C. R.

    1998-03-01

    High-temperature superconducting YBa2Cu3O7-x films were grown by liquid delivery metal-organic chemical-vapor deposition on silver-coated stainless-steel substrates. The films are highly c-axis oriented, have a Tc above 90 K, and exhibit a surface resistance of 110 μΩ at 77 K and 3 GHz.

  5. Effective, Facile, and Selective Hydrolysis of the Chemical Warfare Agent VX Using Zr6-Based Metal-Organic Frameworks.

    PubMed

    Moon, Su-Young; Wagner, George W; Mondloch, Joseph E; Peterson, Gregory W; DeCoste, Jared B; Hupp, Joseph T; Farha, Omar K

    2015-11-16

    The nerve agent VX is among the most toxic chemicals known to mankind, and robust solutions are needed to rapidly and selectively deactivate it. Herein, we demonstrate that three Zr6-based metal-organic frameworks (MOFs), namely, UiO-67, UiO-67-NH2, and UiO-67-N(Me)2, are selective and highly active catalysts for the hydrolysis of VX. Utilizing UiO-67, UiO-67-NH2, and UiO-67-N(Me)2 in a pH 10 buffered solution of N-ethylmorpholine, selective hydrolysis of the P-S bond in VX was observed. In addition, UiO-67-N(Me)2 was found to catalyze VX hydrolysis with an initial half-life of 1.8 min. This half-life is nearly 3 orders of magnitude shorter than that of the only other MOF tested to date for hydrolysis of VX and rivals the activity of the best nonenzymatic materials. Hydrolysis utilizing Zr-based MOFs is also selective and facile in the absence of pH 10 buffer (just water) and for the destruction of the toxic byproduct EA-2192.

  6. Preparation of hydrophobic metal-organic frameworks via plasma enhanced chemical vapor deposition of perfluoroalkanes for the removal of ammonia.

    PubMed

    DeCoste, Jared B; Peterson, Gregory W

    2013-01-01

    Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m(2)/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials. PMID:24145623

  7. Growth mechanism of single-crystalline NiO thin films grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Roffi, Teuku Muhammad; Nozaki, Shinji; Uchida, Kazuo

    2016-10-01

    Nickel oxide (NiO) thin films were grown by atmospheric-pressure metal organic chemical vapor deposition (APMOCVD). Growth was carried out using various growth parameters, including the growth temperature, the input precursor (O2/Ni) ratio, and the type of substrate material. Effects of the growth parameters on the structural and electrical properties of the films were investigated. X-ray diffraction analysis revealed that the crystal structure and quality were strongly affected by the growth temperature and the type of substrate material. At an optimized growth temperature, single-crystalline NiO films were grown on MgO(100) and MgO(111) substrates in a cube-on-cube orientation relationship, while on an Al2O3(001) substrate, the film was grown in the NiO[111] direction. The use of MgO substrates successfully suppressed the formation of twin defects, which have been frequently reported in the growth of NiO. The difference in the formation of the twin defects on MgO and Al2O3 substrates was discussed. It was observed that the resistivity dependence on crystal quality was affected by the choice of substrate material. The effects of the precursor ratio on the transmittance and resistivity of the films were also investigated. Improved transparency in the visible wavelength region and higher conductivity were found in films grown with higher O2/Ni ratios.

  8. Parameters influencing interfacial morphology in GaAs/Ge superlattices grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jia, Roger; Fitzgerald, Eugene A.

    2016-02-01

    We investigated the epitaxy and morphology of GaAs/Ge superlattices grown by metal organic chemical vapor deposition (MOCVD) under a range of conditions. The surfaces of Ge layers deposited on GaAs at 650 °C and 100 Torr are observed to be rough in cross-sectional transmission electron microscopy. When either the temperature is lowered to 500 °C or the pressure is increased to 250 Torr, the surface of the first deposited Ge layer is observed to be smooth. This behavior suggests that Ge roughening is a thermodynamically favorable process that can be kinetically limited with appropriate growth conditions. At 500 °C, GaAs islands on Ge do not completely coalesce into one film. This may result from poor surface coverage; the short depositions would not be sufficient to coarsen and completely coalesce the islands. At 650 °C, growth on offcut substrates did not suppress antiphase boundaries, likely due to the unique conditions for GaAs/Ge superlattice growth. A wide-range of two- and three- dimensional nanostructures are formed and should allow insight in structure-property correlations in semiconducting thermoelectric materials.

  9. Effective, Facile, and Selective Hydrolysis of the Chemical Warfare Agent VX Using Zr6-Based Metal-Organic Frameworks.

    PubMed

    Moon, Su-Young; Wagner, George W; Mondloch, Joseph E; Peterson, Gregory W; DeCoste, Jared B; Hupp, Joseph T; Farha, Omar K

    2015-11-16

    The nerve agent VX is among the most toxic chemicals known to mankind, and robust solutions are needed to rapidly and selectively deactivate it. Herein, we demonstrate that three Zr6-based metal-organic frameworks (MOFs), namely, UiO-67, UiO-67-NH2, and UiO-67-N(Me)2, are selective and highly active catalysts for the hydrolysis of VX. Utilizing UiO-67, UiO-67-NH2, and UiO-67-N(Me)2 in a pH 10 buffered solution of N-ethylmorpholine, selective hydrolysis of the P-S bond in VX was observed. In addition, UiO-67-N(Me)2 was found to catalyze VX hydrolysis with an initial half-life of 1.8 min. This half-life is nearly 3 orders of magnitude shorter than that of the only other MOF tested to date for hydrolysis of VX and rivals the activity of the best nonenzymatic materials. Hydrolysis utilizing Zr-based MOFs is also selective and facile in the absence of pH 10 buffer (just water) and for the destruction of the toxic byproduct EA-2192. PMID:26505999

  10. Low resistivity aluminum nitride: Carbon (AlN:C) films grown by metal organic chemical vapor deposition

    SciTech Connect

    Wongchotiqul, K.; Chen, N.; Zhang, D.P.; Tang, X.; Spencer, M.G.

    1996-11-01

    Low resistivity single crystal aluminum nitride-carbon (AlN:C) films were grown by metal organic chemical vapor deposition (MOCVD). The growth system used ammonia (NH{sub 3}), trimethylaluminum (TMA), hydrogen (H{sub 2}), and propane (C{sub 3}H{sub 8}) precursors. Films produced with high partial pressure of propane during growth exhibited high conductivity. Van der Paw measurements indicated that the resistivity of the as grown films changed dramatically from 10{sup 8} ohm-cm for unintentionally doped samples to less than .2 ohm-cm for partial pressures of propane greater than 0.5 {times} 10{sup {minus}3} torr. Reflection electron diffraction (RHEED) measurements performed in situ just after film growth indicated that the material is single crystal up to a propane partial pressure of 2.5 {times} 10{sup {minus}3} torr. P-n junctions of n-type 6H-SiC and p-type AlN:C were fabricated, blue emission (centered at 490 nm) was observed from the heterojunction under forward bias.

  11. InAs/GaSb core-shell nanowires grown on Si substrates by metal-organic chemical vapor deposition.

    PubMed

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Luo, Shuai; Ji, Haiming; Xu, H Q; Yang, Tao

    2016-07-01

    We report the growth of InAs/GaSb core-shell heterostructure nanowires with smooth sidewalls on Si substrates using metal-organic chemical vapor deposition with no assistance from foreign catalysts. Sb adatoms were observed to strongly influence the morphology of the GaSb shell. In particular, Ga droplets form on the nanowire tips when a relatively low TMSb flow rate is used, whereas the droplets are missing and the radial growth of the GaSb is enhanced due to a reduction in the diffusion length of the Ga adatoms when the TMSb flow rate is increased. Moreover, transmission electron microscopy measurements revealed that the GaSb shell coherently grew on the InAs core. The results obtained here show that the InAs/GaSb core-shell nanowires grown using the Si platform have strong potential in the fabrication of future nanometer-scale devices and in the study of fundamental quantum physics. PMID:27232079

  12. Properties of shallow donors in ZnMgO epilayers grown by metal organic chemical vapor deposition

    SciTech Connect

    Zhao, Q. X.; Liu, X. J.; Holtz, P. O.

    2014-11-14

    High quality Zn{sub 1−x}Mg{sub x}O epilayers have been grown by means of metal organic chemical vapor deposition technique on top of ZnO templates. The grown samples were investigated by x-ray photoelectron spectroscopy and photoluminescence. The magnesium (Mg) concentration was varied between 0% and 3% in order to study the properties of shallow donors. The free and donor bound excitons could be observed simultaneously in our high quality Zn{sub 1−x}Mg{sub x}O epilayers in the photoluminescence spectra. The results indicate that both built-in strain and Mg-concentration influence the donor exciton binding energy. It clearly shows that the donor exciton binding energy decreases with increasing Mg-concentration and with increasing built-in strain. Furthermore, the results indicate that the donor bound exciton transition energy increases with decreasing strength of the built-in strain if the Mg-concentration is kept the same in the Zn{sub 1−x}Mg{sub x}O epilayers.

  13. Synthesis of novel barium precursors and their use to deposit thin films by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Studebaker, Daniel Bliss

    A new class of volatile compounds of barium were synthesized. These 'capsule' compounds were prepared to saturate the coordination sphere of barium with one ligand. The covalent bonding of the polyglyme ligand to the 2,2,6,6-tetramethyl-3,5-heptanedione or similar ligand also increased the chelate effect, making loss of the glyme ligand on sublimation less likely. Single crystal X-ray crystal diffraction studies were done on these complexes. One of the complexes was used to grow BaTiO3 thin films to display the ability for these complexes to be used as metal organic chemical vapor deposition (MOCVD) precursors. Thin films of the superconducting material YBa2Cu3O 7-x were deposited on silver substrates by MOCVD. These films were analyzed by microscopy, and the electrical properties are discussed. The first reported growth of beta-BaBLO4 thin films by MOCVD is given. These films were grown on platinum, fused silica, sapphire, and silicon. Second harmonic generation of light from a Nd:YAG laser is observed in optical measurements.

  14. Organic chemical evolution

    NASA Technical Reports Server (NTRS)

    Chang, S.

    1981-01-01

    The course of organic chemical evolution preceding the emergence of life on earth is discussed based on evidence of processes occurring in interstellar space, the solar system and the primitive earth. Following a brief review of the equilibrium condensation model for the origin and evolution of the solar system, consideration is given to the nature and organic chemistry of interstellar clouds, comets, Jupiter, meteorites, Venus and Mars, and the prebiotic earth. Major issues to be resolved in the study of organic chemical evolution on earth are identified regarding condensation and accretion in the solar nebula, early geological evolution, the origin and evolution of the atmosphere, organic production rates, organic-inorganic interactions, environmental fluctuations, phase separation and molecular selectivity.

  15. Synergistic catalysis of metal-organic framework-immobilized Au-Pd nanoparticles in dehydrogenation of formic acid for chemical hydrogen storage.

    PubMed

    Gu, Xiaojun; Lu, Zhang-Hui; Jiang, Hai-Long; Akita, Tomoki; Xu, Qiang

    2011-08-10

    Bimetallic Au-Pd nanoparticles (NPs) were successfully immobilized in the metal-organic frameworks (MOFs) MIL-101 and ethylenediamine (ED)-grafted MIL-101 (ED-MIL-101) using a simple liquid impregnation method. The resulting composites, Au-Pd/MIL-101 and Au-Pd/ED-MIL-101, represent the first highly active MOF-immobilized metal catalysts for the complete conversion of formic acid to high-quality hydrogen at a convenient temperature for chemical hydrogen storage. Au-Pd NPs with strong bimetallic synergistic effects have a much higher catalytic activity and a higher tolerance with respect to CO poisoning than monometallic Au and Pd counterparts. PMID:21761819

  16. a Study of Volatile Precursors for the Growth of Cadmium Sulphide and Cadmium Selenide by Metal Organic Chemical Vapour Deposition.

    NASA Astrophysics Data System (ADS)

    Beer, Michael P.

    Available from UMI in association with The British Library. The wide-band-gap semiconductors, cadmium sulphide and cadmium selenide, may be grown by Metal Organic Chemical Vapour Deposition (MOCVD). This method typically involves the reaction of gaseous streams of Me_2 Cd and H_2Y (Y = S, Se) over a heated substrate (usually gallium arsenide) on which the desired compound is grown as an epitaxial layer. Unfortunately, the precursors start to react in the cold zone of the reactor, that is before they reach the heated substrate. This problem is known as prereaction. The problem of prereaction is partially reduced by the use of adducts of dimethyl cadmium in place of the free dialkyl compound although the mechanism by which such adducts block prereaction is unknown. Accordingly, a study of adducts of dimethyl cadmium was undertaken with a view to determining their properties in all phases. The adduct of Me_2Cd with 2,2^ '-bipyridyl was found to be monomeric in the solid state while that with 1,4-dioxane, a volatile compound used for prereaction reduction, was found to be polymeric. A study of adducts in the gas phase using mass spectrometry and gas phase Fourier transform infrared spectroscopy gave no evidence to suggest there is any gas phase association between 1,4-dioxane and dimethyl cadmium. With the 2,2 ^'-bipyridyl adduct some evidence for partial retention of coordinate bonds upon sublimation was obtained. The solid adduct of Me _2Cd with N,N,N^' ,N^'-tetramethylethylenediamine (TMEDA) was prepared as it was hoped that the flexibility of the aliphatic Lewis base would permit the formation of an adduct containing strong co-ordinate bonds which would remain intact upon sublimation. Using gas phase electron diffraction, the structure of the adduct of Me_2Cd and TMEDA was determined. It was shown to exist in the gas phase purely as the associated monomeric species. The adduct was then employed for the growth of CdS and CdSe in an industrial MOCVD apparatus. The

  17. Dual Exchange in PCN-333: A Facile Strategy to Chemically Robust Mesoporous Chromium Metal-Organic Framework with Functional Groups.

    PubMed

    Park, Jihye; Feng, Dawei; Zhou, Hong-Cai

    2015-09-16

    A facile preparation of a mesoporous Cr-MOF, PCN-333(Cr) with functional group, has been demonstrated through a dual exchange strategy, involving a sequential ligand exchange and metal metathesis process. After optimization of the exchange system, the functionalized PCN-333(Cr), N3-PCN-333(Cr) shows well maintained crystallinity, porosity, as well as much improved chemical stability. Because of the exceptionally large pores (∼5.5 nm) in PCN-333(Cr), a secondary functional moiety, Zn-TEPP with a size of 18 Å × 18 Å, has been successfully clicked into the framework. In this article, we have also analyzed kinetics and thermodynamics during dual exchange process, showing our attempts to interpret the exchange event in the PCN-333. Our findings not only provide a highly stable mesoporous Cr-MOF platform for expanding MOF-based applications, but also suggest a route to functionalized Cr-MOF which may have not been achievable through conventional approaches.

  18. Crystal Engineering of an nbo Topology Metal-Organic Framework for Chemical Fixation of CO₂ under Ambient Conditions

    SciTech Connect

    Gao, Wen-Yang; Chen, Yao; Niu, Youhong; Williams, Kia; Cash, Lindsay; Perez, Pastor J.; Wojtas, Lukasz; Cai, Jianfeng; Chen, Yu-Sheng; Ma, Shengqian

    2015-02-20

    Crystal engineering of the nbo metal–organic framework (MOF) platform MOF-505 with a custom-designed azamacrocycle ligand (1,4,7,10-tetrazazcyclododecane-N,N',N'',N'''-tetra-p-methylbenzoic acid) leads to a high density of well-oriented Lewis active sites within the cuboctahedral cage in MMCF-2, [Cu₂(Cu-tactmb)(H₂O)₃(NO₃)₂]. This MOF demonstrates high catalytic activity for the chemical fixation of CO₂ into cyclic carbonates at room temperature under 1 atm pressure.

  19. High hole concentration Li-doped NiZnO thin films grown by photo-assisted metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Y. D.; Dong, X.; Ma, Z. Z.; Zhang, Y. T.; Wu, B.; Zhuang, S. W.; Zhang, B. L.; Li, W. C.; Du, G. T.

    2016-11-01

    High hole concentration Li-doped NiZnO thin films were grown by metal-organic chemical vapor deposition (MOCVD). The crystalline, optical, electrical, and morphological characteristics of the NiZnO films were studied as a function of lithium content. The resistance of the films decreased and the hole concentration greatly increased with increasing lithium content. However, the crystalline and optical properties were observed to degrade as the lithium content was increased. To relieve the degradation, a photo-assisted MOCVD method was used in order to restrict this degradation and this represents a new way to obtain stable high hole concentration NiZnO films.

  20. Structural properties of Al-rich AlInN grown on c-plane GaN substrate by metal-organic chemical vapor deposition

    PubMed Central

    2014-01-01

    The attractive prospect for AlInN/GaN-based devices for high electron mobility transistors with advanced structure relies on high-quality AlInN epilayer. In this work, we demonstrate the growth of high-quality Al-rich AlInN films deposited on c-plane GaN substrate by metal-organic chemical vapor deposition. X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy show that the films lattice-matched with GaN can have a very smooth surface with good crystallinity and uniform distribution of Al and In in AlInN. PMID:25489282

  1. Influence of vicinal sapphire substrate on the properties of N-polar GaN films grown by metal-organic chemical vapor deposition

    SciTech Connect

    Lin, Zhiyu; Zhang, Jincheng Xu, Shengrui; Chen, Zhibin; Yang, Shuangyong; Tian, Kun; Hao, Yue; Su, Xujun; Shi, Xuefang

    2014-08-25

    The influence of vicinal sapphire substrates on the growth of N-polar GaN films by metal-organic chemical vapor deposition is investigated. Smooth GaN films without hexagonal surface feature are obtained on vicinal substrate. Transmission electron microscope results reveal that basal-plane stacking faults are formed in GaN on vicinal substrate, leading to a reduction in threading dislocation density. Furthermore, it has been found that there is a weaker yellow luminescence in GaN on vicinal substrate than that on (0001) substrate, which might be explained by the different trends of the carbon impurity incorporation.

  2. Recycling of metal-organic chemical vapor deposition waste of GaN based power device and LED industry by acidic leaching: Process optimization and kinetics study

    NASA Astrophysics Data System (ADS)

    Swain, Basudev; Mishra, Chinmayee; Kang, Leeseung; Park, Kyung-Soo; Lee, Chan Gi; Hong, Hyun Seon; Park, Jeung-Jin

    2015-05-01

    Recovery of metal values from GaN, a metal-organic chemical vapor deposition (MOCVD) waste of GaN based power device and LED industry is investigated by acidic leaching. Leaching kinetics of gallium rich MOCVD waste is studied and the process is optimized. The gallium rich waste MOCVD dust is characterized by XRD and ICP-AES analysis followed by aqua regia digestion. Different mineral acids are used to find out the best lixiviant for selective leaching of the gallium and indium. Concentrated HCl is relatively better lixiviant having reasonably faster kinetic and better leaching efficiency. Various leaching process parameters like effect of acidity, pulp density, temperature and concentration of catalyst on the leaching efficiency of gallium and indium are investigated. Reasonably, 4 M HCl, a pulp density of 50 g/L, 100 °C and stirring rate of 400 rpm are the effective optimum condition for quantitative leaching of gallium and indium.

  3. Growth of TiO2 anti-reflection layer on textured Si (100) wafer substrate by metal-organic chemical vapor deposition method.

    PubMed

    Nam, Sang-Hun; Choi, Jin-Woo; Cho, Sang-Jin; Kimt, Keun Soo; Boo, Jin-Hyo

    2011-08-01

    Recently anti-reflective films (AR) have been intensely studied. Particularly for textured silicon solar cells, the AR films can further reduce the reflection of the incident light through trapping the incident light into the cells. In this work, TiO2 anti-reflection films have been grown on the textured Si (100) substrate which is processed in two steps, and the films are deposited using metal-organic chemical vapor deposition (MOCVD) with a precursor of titanium tetra-isopropoxide (TTIP). The effect of the substrate texture and the growth conditions of TiO2 films on the reflectance has been investigated. Pyramid size of textured silicon had approximately 2-9 microm. A well-textured silicon surface can lower the reflectance to 10%. For more reduced reflection, TiO2 anti-reflection films on the textured silicon were deposited at 600 degrees C using titanium tetra-isopropoxide (TTIP) as a precursor by metal-organic chemical vapor deposition (MOCVD), and the deposited TiO2 layers were then treated by annealing for 2 h in air at 600 and 1000 degrees C, respectively. In this process, the treated samples by annealing showed anatase and rutile phases, respectively. The thickness of TiO2 films was about 75 +/- 5 nm. The reflectance at specific wavelength can be reduced to 3% in optimum layer. PMID:22103185

  4. A state-wide survey in Oregon (USA) of trace metals and organic chemicals in municipal effluent.

    PubMed

    Hope, Bruce K; Pillsbury, Lori; Boling, Brian

    2012-02-15

    Oregon's Senate Bill 737, enacted in 2007, required the state's 52 largest municipal wastewater treatment plants (WWTP) and water pollution control facilities (WPCF) to collect effluent samples in 2010 and analyze them for persistent organic pollutants. These facilities are located state-wide and represent a variety of treatment types, service population sizes, geographic areas, and flow conditions. Of the 406 chemicals ultimately analyzed, 114 were detected above the level of quantification (LOQ) in at least one sample. Few persistent pollutants were found possibly because of their diversion from effluent via sorption to sludge (solids phase) or high LOQs for certain chemicals. Several pesticides, as well as benzene and phenol degradation products, all previously unreported in effluent, were detected. Ten polychlorinated biphenyls (PCB) congeners were present at low concentrations in ≤ 10 samples, while polychlorinated naphthalenes and dioxins/furans were not detected at all. Twenty-one polybrominated diphenyl ether (PBDE) congeners were found, nine of which have been reported in Osprey eggs in Oregon and Washington. Methylmercury was present in 65% of samples, with average and maximum concentrations of 0.18 and 1.36 ng/L, respectively. Although they are generally assumed to be innocuous by-products of sewage treatment, additional research is needed on potential impacts to aquatic ecosystems of high loadings of coprostanol and cholesterol. These results suggest that effluent, rather than just receiving waters, should itself be analyzed for a wide range of contaminants in order to understand how upstream sources, conveyed through WWTPs and WPCFs, could be impacting aquatic ecosystems.

  5. Low trap states in in situ SiN{sub x}/AlN/GaN metal-insulator-semiconductor structures grown by metal-organic chemical vapor deposition

    SciTech Connect

    Lu, Xing; Ma, Jun; Jiang, Huaxing; Liu, Chao; Lau, Kei May

    2014-09-08

    We report the use of SiN{sub x} grown in situ by metal-organic chemical vapor deposition as the gate dielectric for AlN/GaN metal-insulator-semiconductor (MIS) structures. Two kinds of trap states with different time constants were identified and characterized. In particular, the SiN{sub x}/AlN interface exhibits remarkably low trap state densities in the range of 10{sup 11}–10{sup 12 }cm{sup −2}eV{sup −1}. Transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the in situ SiN{sub x} layer can provide excellent passivation without causing chemical degradation to the AlN surface. These results imply the great potential of in situ SiN{sub x} as an effective gate dielectric for AlN/GaN MIS devices.

  6. Organic Superconductor, Made without Metals.

    ERIC Educational Resources Information Center

    Science News, 1980

    1980-01-01

    The discovery of a superconducting organic compound is reported. The compound, (TMTSF)-2, has no metal in its composition, and the author believes that it is the precursor of a family of superconducting organics. (Author/SA)

  7. Electroluminescence at 1.3 µm from InAs/GaAs quantum dots monolithically grown on Ge/Si substrate by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Rajesh, Mohan; Nishioka, Masao; Arakawa, Yasuhiko

    2016-10-01

    We report the first demonstration of electroluminescence at 1.3 µm from InAs/GaAs quantum dots (QDs) monolithically grown on a Ge/Si substrate by metal organic chemical vapor deposition (MOCVD). High-density coalescence-free InAs/Sb:GaAs QDs emitting at 1.3 µm were obtained on a GaAs/Ge/Si wafer. The post-growth annealing of the GaAs buffer layer shows a significant improvement in the room-temperature (RT) photoluminescence (PL) intensity of QDs grown on a GaAs/Ge/Si wafer, comparable to those QDs grown on a reference GaAs substrate. Together, these results are promising for the realization of a QD laser on a Si substrate by MOCVD for silicon photonics application.

  8. Nearly lattice-matched InAlN/GaN high electron mobility transistors grown on SiC substrate by pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xue, JunShuai; Hao, Yue; Zhang, JinCheng; Zhou, XiaoWei; Liu, ZiYang; Ma, JunCai; Lin, ZhiYu

    2011-03-01

    We report on a growth of nearly lattice-matched InAlN/GaN heterostructures on 4H-SiC substrates by pulsed metal organic chemical vapor deposition, and an excellent device characteristic of high electron mobility transistors (HEMTs) fabricated on these InAlN/GaN heterostructures. The electron mobility is 1032 cm2/V s together with a high two-dimensional-electron-gas density of 1.59×1013 cm-2 for the In0.17Al0.83N/AlN heterostructures. HEMTs with gate dimensions of 0.5×50 μm2 and 3 μm source-drain distance exhibits a maximum drain current of 1 A/mm, a maximum extrinsic transconductance of 310 mS/mm, and current gain and maximum oscillation cutoff frequencies of 18 GHz and 39 GHz, respectively.

  9. Terahertz-frequency photoconductive detectors fabricated from metal-organic chemical vapor deposition-grown Fe-doped InGaAs

    NASA Astrophysics Data System (ADS)

    Hatem, O.; Cunningham, J.; Linfield, E. H.; Wood, C. D.; Davies, A. G.; Cannard, P. J.; Robertson, M. J.; Moodie, D. G.

    2011-03-01

    We report the detection of terahertz frequency radiation using photoconductive antennas fabricated from Fe-doped InGaAs, grown by metal-organic chemical vapor deposition. Coherent photoconductive detection is demonstrated using femtosecond laser pulses centered at either an 800 or a 1550 nm wavelength. The InGaAs resistivity and the sensitivity of photoconductive detection are both found to depend on the Fe-doping level. We investigate a wide range of probe laser powers, finding a peak in detected signal for ˜5 mW probe power, followed by a reduction at larger powers, attributed to screening of the detected THz field by photo-generated carriers in the material. The measured signal from Fe:InGaAs photoconductive detectors excited at 800 nm is four times greater than that from a low-temperature-grown GaAs photodetector with identical antenna design, despite the use of a ten times smaller probe power.

  10. Growth of ultrathin GaSb layer on GaAs using metal-organic chemical vapor deposition with Sb interfacial treatment

    NASA Astrophysics Data System (ADS)

    Hsiao, Chih-Jen; Ha, Minh-Thien-Huu; Hsu, Ching-Yi; Lin, Yueh-Chin; Chang, Sheng-Po; Chang, Shoou-Jinn; Chang, Edward Yi

    2016-09-01

    GaSb epitaxial layers were directly grown on GaAs substrates by metal-organic chemical vapor deposition involving Sb interfacial treatment with optimized growth temperature and V/III ratio. The interfacial treatment effectively reduces the surface energy and strain energy difference, resulting in a quasi-2D growth mode. When the GaSb layer was grown at 520 °C, the strain induced by lattice mismatch was accommodated by 90° dislocations with a period of 5.67 nm. By optimizing the V/III ratio, the surface roughness of the ultrathin GaSb/GaAs heterostructure was reduced, resulting in a reduced carrier scattering and improved electronic properties.

  11. Metal-organic chemical vapor deposition growth of β-FeSi2/Si composite powder via vapor-liquid-solid method and its photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Akiyama, Kensuke; Motoizumi, Yuu; Funakubo, Hiroshi; Irie, Hiroshi; Matsumoto, Yoshihisa

    2016-06-01

    Semiconducting iron disilicide (β-FeSi2) island grains of a few hundred nanometers in diameter were formed on the surface of Si powder by metal-organic chemical vapor deposition. On Au-coated Si powder, the Au-Si liquidus phase was obtained by melting the Si surface via the Au-Si eutectic reaction, which contributed to the formation of island grains. The dramatic decrease in the defect density in β-FeSi2, which was due to this growth mechanism, was confirmed by the photoluminescence properties. The β-FeSi2/Si composite powder could evolve hydrogen from formaldehyde aqueous solution under irradiation of visible light with wavelengths of 420-650 nm.

  12. Structural and optical properties of InAs/InAsSb superlattices grown by metal organic chemical vapor deposition for mid-wavelength infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Ning, Zhen-Dong; Liu, Shu-Man; Luo, Shuai; Ren, Fei; Wang, Feng-Jiao; Yang, Tao; Liu, Feng-Qi; Wang, Zhan-Guo; Zhao, Lian-Cheng

    2016-04-01

    InAs/InAsSb superlattices were grown on (0 0 1) GaSb substrates by metal organic chemical vapor deposition for potential applications as mid-infrared optoelectronic devices. X-ray diffraction, transmission electron microscopy, photoluminescence emission and spectral photoconductivity were used to characterize the grown structures. Generally, photoluminescence emission measurements of InAs/InAsSb superlattices were performed over the temperature range from 11 K to 300 K. The Varshni and Bose-Einstein parameters were determined. Low-temperature photoluminescence measurements showed peaks at 3-5 μm, while photoconductance results showed strong spectral response up to room temperature, when the photoresponse onset was extended to 5.5 μm. The photoluminescence emission band covers the CO2 absorption peak making it suitable for application in CO2 detection.

  13. Generation of continuous wave terahertz frequency radiation from metal-organic chemical vapour deposition grown Fe-doped InGaAs and InGaAsP

    NASA Astrophysics Data System (ADS)

    Mohandas, Reshma A.; Freeman, Joshua R.; Rosamond, Mark C.; Hatem, Osama; Chowdhury, Siddhant; Ponnampalam, Lalitha; Fice, Martyn; Seeds, Alwyn J.; Cannard, Paul J.; Robertson, Michael J.; Moodie, David G.; Cunningham, John E.; Davies, A. Giles; Linfield, Edmund H.; Dean, Paul

    2016-04-01

    We demonstrate the generation of continuous wave terahertz (THz) frequency radiation from photomixers fabricated on both Fe-doped InGaAs and Fe-doped InGaAsP, grown by metal-organic chemical vapor deposition. The photomixers were excited using a pair of distributed Bragg reflector lasers with emission around 1550 nm, and THz radiation was emitted over a bandwidth of greater than 2.4 THz. Two InGaAs and four InGaAsP wafers with different Fe doping concentrations were investigated, with the InGaAs material found to outperform the InGaAsP in terms of emitted THz power. The dependencies of the emitted power on the photomixer applied bias, incident laser power, and material doping level were also studied.

  14. In situ and real-time characterization of metal-organic chemical vapor deposition growth by high resolution x-ray diffraction

    SciTech Connect

    Kharchenko, A.; Lischka, K.; Schmidegg, K.; Sitter, H.; Bethke, J.; Woitok, J.

    2005-03-01

    We present an x-ray diffractometer for the analysis of epitaxial layers during (in situ) metal-organic chemical vapor deposition (MOCVD). Our diffractometer has a conventional x-ray source, does not need a goniometer stage, and is not sensitive to precise adjustment of the samples before measurement. It allows us to perform measurements within a few seconds even from rotating and wobbling samples. The first results of laboratory tests performed with our x-ray diffraction system show that it is well suited for in situ and real-time monitoring of the MOCVD growth process. We were able to measure the growth rate of a cubic GaN layer and the intensity and peak position of Bragg reflections of the growing layer in less than 20 s only.

  15. Multifunctional Metal-Organic Frameworks for Photocatalysis.

    PubMed

    Wang, Sibo; Wang, Xinchen

    2015-07-01

    Metal-organic frameworks (MOFs) have attracted significant research attention in diverse areas due to their unique physical and chemical characteristics that allow their innovative application in various research fields. Recently, the application of MOFs in heterogeneous photocatalysis for water splitting, CO2 reduction, and organic transformation have emerged, aiming at providing alternative solutions to address the world-wide energy and environmental problems by taking advantage of the unique porous structure together with ample physicochemical properties of the metal centers and organic ligands in MOFs. In this review, the latest progress in MOF-involved solar-to-chemical energy conversion reactions are summarized according to their different roles in the photoredox chemical systems, e.g., photocatalysts, co-catalysts, and hosts. The achieved progress and existing problems are evaluated and proposed, and the opportunities and challenges of MOFs and their related materials for their advanced development in photocatalysis are discussed and anticipated.

  16. Role of metal oxides in chemical evolution

    NASA Astrophysics Data System (ADS)

    Kamaluddin

    2013-06-01

    Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Formation of small molecules like amino acids, organic bases, sugar etc. could have occurred in the reducing atmosphere of the primitive Earth. Polymerization of these small molecules could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

  17. CHEMICAL STABILIZATION OF MIXED ORGANIC AND METAL COMPOUNDS - EPA SITE PROGRAM DEMONSTRATION OF THE SILICATE TECHNOLOGY CORPORATION PROCESS

    EPA Science Inventory

    In November 1990, the Silicate Technology Corporation`s (STC) proprietary process for treating soil contaminated with toxic semivolatile organic and inorganic contaminants was evaluated in a Superfund Innovative Technology Evaluation (SITE) field demonstration at the Selma Pressu...

  18. Ultraviolet photoconductive devices with an n-GaN nanorod-graphene hybrid structure synthesized by metal-organic chemical vapor deposition

    PubMed Central

    Kang, San; Mandal, Arjun; Chu, Jae Hwan; Park, Ji-Hyeon; Kwon, Soon-Yong; Lee, Cheul-Ro

    2015-01-01

    The superior photoconductive behavior of a simple, cost-effective n-GaN nanorod (NR)-graphene hybrid device structure is demonstrated for the first time. The proposed hybrid structure was synthesized on a Si (111) substrate using the high-quality graphene transfer method and the relatively low-temperature metal-organic chemical vapor deposition (MOCVD) process with a high V/III ratio to protect the graphene layer from thermal damage during the growth of n-GaN nanorods. Defect-free n-GaN NRs were grown on a highly ordered graphene monolayer on Si without forming any metal-catalyst or droplet seeds. The prominent existence of the undamaged monolayer graphene even after the growth of highly dense n-GaN NRs, as determined using Raman spectroscopy and high-resolution transmission electron microscopy (HR-TEM), facilitated the excellent transport of the generated charge carriers through the photoconductive channel. The highly matched n-GaN NR-graphene hybrid structure exhibited enhancement in the photocurrent along with increased sensitivity and photoresponsivity, which were attributed to the extremely low carrier trap density in the photoconductive channel. PMID:26028318

  19. Ultraviolet photoconductive devices with an n-GaN nanorod-graphene hybrid structure synthesized by metal-organic chemical vapor deposition.

    PubMed

    Kang, San; Mandal, Arjun; Chu, Jae Hwan; Park, Ji-Hyeon; Kwon, Soon-Yong; Lee, Cheul-Ro

    2015-06-01

    The superior photoconductive behavior of a simple, cost-effective n-GaN nanorod (NR)-graphene hybrid device structure is demonstrated for the first time. The proposed hybrid structure was synthesized on a Si (111) substrate using the high-quality graphene transfer method and the relatively low-temperature metal-organic chemical vapor deposition (MOCVD) process with a high V/III ratio to protect the graphene layer from thermal damage during the growth of n-GaN nanorods. Defect-free n-GaN NRs were grown on a highly ordered graphene monolayer on Si without forming any metal-catalyst or droplet seeds. The prominent existence of the undamaged monolayer graphene even after the growth of highly dense n-GaN NRs, as determined using Raman spectroscopy and high-resolution transmission electron microscopy (HR-TEM), facilitated the excellent transport of the generated charge carriers through the photoconductive channel. The highly matched n-GaN NR-graphene hybrid structure exhibited enhancement in the photocurrent along with increased sensitivity and photoresponsivity, which were attributed to the extremely low carrier trap density in the photoconductive channel.

  20. Organic Chemicals: Angels or Goblins?

    ERIC Educational Resources Information Center

    Ferguson, Lloyd N.

    1978-01-01

    Discusses some of the controversial organic chemical substances such as DDT, Red Dye No. 2, DES, Tris, Laetrile, cyclamate, and saccharin. Concludes that the use of some has to be considered on a benefit/risk ratio. (GA)

  1. Metal-organic frameworks for photocatalysis.

    PubMed

    Li, Ying; Xu, Hua; Ouyang, Shuxin; Ye, Jinhua

    2016-03-21

    Photocatalysis is a promising technology to convert solar energy into chemical energy. Recently, metal-organic frameworks (MOFs) have emerged as novel photocatalysts owing to their inherent structural characteristics of a large surface area and a well-ordered porous structure. Most importantly, via modulation of the organic linker/metal clusters or incorporation with metal/complex catalysts, not only the reactant adsorption and light absorption but also the charge separation and reactant activation will be largely promoted, leading to superior photocatalytic performance. In this article, we will first introduce the photophysical/chemical properties of MOFs; then various strategies of modification of MOFs towards better photocatalytic activity will be presented; finally, we will address the challenge and further perspective in MOF-based photocatalysis.

  2. Structural and Electrical Characterization of SrTiO3 Thin Films Prepared by Metal Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiromu; Lesaicherre, Pierre-Yves; Sakuma, Toshiyuki; Miyasaka, Yoichi; Ishitani, Akihiko; Yoshida, Masaji

    1993-09-01

    SrTiO3 thin films were prepared on Si and Pt/TaOx/Si substrates by Sr(DPM)2/Ti(i-OC3H7)4/O2/Ar chemical vapor deposition (CVD), using a simple vaporizing-and-transport source delivery system. A thickness uniformity of ± 5.6% and a composition uniformity of ± 2.7% were obtained. The dielectric constant was 210 for 110 nm thick SrTiO3 films (Sr/(Sr+Ti)=0.5) annealed at 600°C for 2 hours. An SiO2 equivalent thickness of 1.1 nm was obtained for 40 nm thick SrTiO3 films, and leakage current densities were 6× 10-8 A/cm2 at 1.0 V and 5× 10-7 A/cm2 at 1.65 V. The structural and electrical properties were affected by the film composition.

  3. Nanoscale metal-organic materials.

    PubMed

    Carné, Arnau; Carbonell, Carlos; Imaz, Inhar; Maspoch, Daniel

    2011-01-01

    Metal-organic materials are found to be a fascinating novel class of functional nanomaterials. The limitless combinations between inorganic and organic building blocks enable researchers to synthesize 0- and 1-D metal-organic discrete nanostructures with varied compositions, morphologies and sizes, fabricate 2-D metal-organic thin films and membranes, and even structure them on surfaces at the nanometre length scale. In this tutorial review, the synthetic methodologies for preparing these miniaturized materials as well as their potential properties and future applications are discussed. This review wants to offer a panoramic view of this embryonic class of nanoscale materials that will be of interest to a cross-section of researchers working in chemistry, physics, medicine, nanotechnology, materials chemistry, etc., in the next years.

  4. Organic metal neutron detector

    DOEpatents

    Butler, M.A.; Ginley, D.S.

    1984-11-21

    A device for detection of neutrons comprises: as an active neutron sensing element, a conductive organic polymer having an electrical conductivity and a cross-section for said neutrons whereby a detectable change in said conductivity is caused by impingement of said neutrons on the conductive organic polymer which is responsive to a property of said polymer which is altered by impingement of said neutrons on the polymer; and means for associating a change in said alterable property with the presence of neutrons at the location of said device.

  5. Control of metamorphic buffer structure and device performance of In(x)Ga(1-x)As epitaxial layers fabricated by metal organic chemical vapor deposition.

    PubMed

    Nguyen, H Q; Yu, H W; Luc, Q H; Tang, Y Z; Phan, V T H; Hsu, C H; Chang, E Y; Tseng, Y C

    2014-12-01

    Using a step-graded (SG) buffer structure via metal-organic chemical vapor deposition, we demonstrate a high suitability of In0.5Ga0.5As epitaxial layers on a GaAs substrate for electronic device application. Taking advantage of the technique's precise control, we were able to increase the number of SG layers to achieve a fairly low dislocation density (∼10(6) cm(-2)), while keeping each individual SG layer slightly exceeding the critical thickness (∼80 nm) for strain relaxation. This met the demanded but contradictory requirements, and even offered excellent scalability by lowering the whole buffer structure down to 2.3 μm. This scalability overwhelmingly excels the forefront studies. The effects of the SG misfit strain on the crystal quality and surface morphology of In0.5Ga0.5As epitaxial layers were carefully investigated, and were correlated to threading dislocation (TD) blocking mechanisms. From microstructural analyses, TDs can be blocked effectively through self-annihilation reactions, or hindered randomly by misfit dislocation mechanisms. Growth conditions for avoiding phase separation were also explored and identified. The buffer-improved, high-quality In0.5Ga0.5As epitaxial layers enabled a high-performance, metal-oxide-semiconductor capacitor on a GaAs substrate. The devices displayed remarkable capacitance-voltage responses with small frequency dispersion. A promising interface trap density of 3 × 10(12) eV(-1) cm(-2) in a conductance test was also obtained. These electrical performances are competitive to those using lattice-coherent but pricey InGaAs/InP systems.

  6. Organic metal neutron detector

    DOEpatents

    Butler, Michael A.; Ginley, David S.

    1987-01-01

    A device for detecting neutrons comprises a layer of conductive polymer sandwiched between electrodes, which may be covered on each face with a neutron transmissive insulating material layer. Conventional electrodes are used for a non-imaging integrating total neutron fluence-measuring embodiment, while wire grids are used in an imaging version of the device. The change in conductivity of the polymer after exposure to a neutron flux is determined in either case to provide the desired data. Alternatively, the exposed conductive polymer layer may be treated with a chemical reagent which selectively binds to the sites altered by neutrons to produce an image of the flux detected.

  7. Preparation of photocatalytic Fe 2O 3-TiO 2 coatings in one step by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Xingwang; Lei, Lecheng

    2008-02-01

    There are two major difficulties in the TiO 2 liquid-solid photocatalytic system: effective immobilization of the TiO 2 particles; and improving the catalytic activity under visible light. To simultaneously solve these two problems, Fe 2O 3-TiO 2 coatings supported on activated carbon fiber (ACF), have been prepared in one step by a convenient and efficient method—metal organic chemical vapor deposition (MOCVD). XRD results revealed that Fe 2O 3-TiO 2 coatings mainly composed of anatase TiO 2, α-Fe 2O 3 phases and little Fe 2Ti 3O 9. The pore structure of ACF was preserved well after loading with Fe 2O 3-TiO 2 coatings. UV-vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an enhancement of the absorption in the visible region for Fe 2O 3-TiO 2 coatings, compared to the pure TiO 2 sample. A moderate Fe 2O 3-TiO 2 loading (13.7 wt%) was beneficial to mineralizing wastewater because the intermediates could be adsorbed onto the surface of photocatalyst following decomposition. The stable performance revealed that the Fe 2O 3-TiO 2 coatings were strongly adhered to the ACF surface, and the as prepared catalysts could be reused showing potential application for wastewater treatment.

  8. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    PubMed

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra. PMID:19198399

  9. Ultrathin barrier AlN/GaN high electron mobility transistors grown at a dramatically reduced growth temperature by pulsed metal organic chemical vapor deposition

    SciTech Connect

    Xue, JunShuai Zhang, JinCheng Hao, Yue

    2015-07-27

    Ultrathin-barrier AlN/GaN heterostructures were grown on sapphire substrates by pulsed metal organic chemical vapor deposition (PMOCVD) using indium as a surfactant at a dramatically reduced growth temperature of 830 °C. Upon optimization of growth parameters, an electron mobility of 1398 cm{sup 2}/V s together with a two-dimensional-electron-gas density of 1.3 × 10{sup 13 }cm{sup −2} was obtained for a 4 nm thick AlN barrier. The grown structures featured well-ordered parallel atomic steps with a root-mean-square roughness of 0.15 nm in a 5 × 5 μm{sup 2} area revealed by atomic-force-microscopic image. Finally, the potential of such structures for device application was demonstrated by fabricating and testing under dc operation AlN/GaN high-electron-mobility transistors. These results indicate that this low temperature PMOCVD growth technique is promising for the fabrication of GaN-based electronic devices.

  10. The growth of InAsSb/InGaAs strained-layer superlattices by metal-organic chemical vapor deposition

    SciTech Connect

    Biefeld, R.M.; Baucom, K.C.; Kurtz, S.R.; Follstaedt, D.M.

    1993-12-31

    We have grown InAs{sub l-x}Sb{sub x}/In{sub 1-y}Ga{sub y}As strained-layer superlattice (SLS) semiconductors lattice matched to InAs using a variety of conditions by metal-organic chemical vapor deposition. The V/III ratio was varied from 2.5 to 10 at 475 C, at pressures of 200 to 660 torr and growth rates of 3 {minus} 5 {angstrom}/s and layer thicknesses ranging from 55 to 152 {angstrom}. Composition of InAsSb ternary can be predicted from the input gas molar flow rates using a thermodynamic model. At lower temperatures, the thermodynamic model must be modified to take account of the incomplete decomposition of arsine and trimethylantimony. Diodes have been prepared using Zn as the p-type dopant and undoped SLS as the n-type material. The diode was found to emit at 3.56 {mu}m. These layers have been characterized by optical microscopy, SIMS, x-ray diffraction, and transmission electron diffraction. The optical properties of these SLS`s were determined by infrared photoluminescence and absorption measurements.

  11. Demonstration of InAlN/AlGaN high electron mobility transistors with an enhanced breakdown voltage by pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xue, JunShuai; Zhang, JinCheng; Hao, Yue

    2016-01-01

    In this work, InAlN/AlGaN heterostructures employing wider bandgap AlGaN instead of conventional GaN channel were grown on sapphire substrate by pulsed metal organic chemical vapor deposition, where the nominal Al composition in InAlN barrier and AlGaN channel were chosen to be 83% and 5%, respectively, to achieve close lattice-matched condition. An electron mobility of 511 cm2/V s along with a sheet carrier density of 1.88 × 1013 cm-2 were revealed in the prepared heterostructures, both of which were lower compared with lattice-matched InAlN/GaN due to increased intrinsic alloy disorder scattering resulting from AlGaN channel and compressively piezoelectric polarization in barrier, respectively. While the high electron mobility transistor (HEMT) processed on these structures not only exhibited a sufficiently high drain output current density of 854 mA/mm but also demonstrated a significantly enhanced breakdown voltage of 87 V, which is twice higher than that of reported InAlN/GaN HEMT with the same device dimension, potential characteristics for high-voltage operation of GaN-based electronic devices.

  12. Thermal stability of an InAlN/GaN heterostructure grown on silicon by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Watanabe, Arata; Freedsman, Joseph J.; Urayama, Yuya; Christy, Dennis; Egawa, Takashi

    2015-12-01

    The thermal stabilities of metal-organic chemical vapor deposition-grown lattice-matched InAlN/GaN/Si heterostructures have been reported by using slower and faster growth rates for the InAlN barrier layer in particular. The temperature-dependent surface and two-dimensional electron gas (2-DEG) properties of these heterostructures were investigated by means of atomic force microscopy, photoluminescence excitation spectroscopy, and electrical characterization. Even at the annealing temperature of 850 °C, the InAlN layer grown with a slower growth rate exhibited a smooth surface morphology that resulted in excellent 2-DEG properties for the InAlN/GaN heterostructure. As a result, maximum values for the drain current density (IDS,max) and transconductance (gm,max) of 1.5 A/mm and 346 mS/mm, respectively, were achieved for the high-electron-mobility transistor (HEMT) fabricated on this heterostructure. The InAlN layer grown with a faster growth rate, however, exhibited degradation of the surface morphology at an annealing temperature of 850 °C, which caused compositional in-homogeneities and impacted the 2-DEG properties of the InAlN/GaN heterostructure. Additionally, an HEMT fabricated on this heterostructure yielded lower IDS,max and gm,max values of 1 A/mm and 210 mS/mm, respectively.

  13. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition.

    PubMed

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P D; Chung, Choong-Heui

    2016-12-01

    We report the growth of vertical <111>-oriented InAs x P1-x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1-x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix. PMID:27094822

  14. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition.

    PubMed

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P D; Chung, Choong-Heui

    2016-12-01

    We report the growth of vertical <111>-oriented InAs x P1-x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1-x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix.

  15. Growth and characterization of well-aligned densely-packed rutile TiO(2) nanocrystals on sapphire substrates via metal-organic chemical vapor deposition.

    PubMed

    Chen, C A; Chen, Y M; Korotcov, A; Huang, Y S; Tsai, D S; Tiong, K K

    2008-02-20

    Well-aligned densely-packed rutile TiO(2) nanocrystals (NCs) have been grown on sapphire (SA) (100) and (012) substrates via metal-organic chemical vapor deposition (MOCVD), using titanium-tetraisopropoxide (TTIP, Ti(OC(3)H(7))(4)) as a source reagent. The surface morphology as well as structural and spectroscopic properties of the as-deposited NCs were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffractometry (SAED), x-ray diffraction (XRD) and micro-Raman spectroscopy. FESEM micrographs reveal that vertically aligned NCs were grown on SA(100), whereas the NCs on the SA(012) were grown with a tilt angle of ∼33° from the normal to substrates. TEM and SAED measurements showed that the TiO(2) NCs on SA(100) with square cross section have their long axis directed along the [001] direction. The XRD results reveal TiO(2) NCs with either (002) orientation on SA(100) substrate or (101) orientation on SA(012) substrate. A strong substrate effect on the alignment of the growth of TiO(2) NCs has been demonstrated and the probable mechanism for the formation of these NCs has been discussed. PMID:21817648

  16. Growth and characterization of well-aligned densely-packed rutile TiO2 nanocrystals on sapphire substrates via metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, C. A.; Chen, Y. M.; Korotcov, A.; Huang, Y. S.; Tsai, D. S.; Tiong, K. K.

    2008-02-01

    Well-aligned densely-packed rutile TiO2 nanocrystals (NCs) have been grown on sapphire (SA) (100) and (012) substrates via metal-organic chemical vapor deposition (MOCVD), using titanium-tetraisopropoxide (TTIP, Ti(OC3H7)4) as a source reagent. The surface morphology as well as structural and spectroscopic properties of the as-deposited NCs were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffractometry (SAED), x-ray diffraction (XRD) and micro-Raman spectroscopy. FESEM micrographs reveal that vertically aligned NCs were grown on SA(100), whereas the NCs on the SA(012) were grown with a tilt angle of ~33° from the normal to substrates. TEM and SAED measurements showed that the TiO2 NCs on SA(100) with square cross section have their long axis directed along the [001] direction. The XRD results reveal TiO2 NCs with either (002) orientation on SA(100) substrate or (101) orientation on SA(012) substrate. A strong substrate effect on the alignment of the growth of TiO2 NCs has been demonstrated and the probable mechanism for the formation of these NCs has been discussed.

  17. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    PubMed

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra.

  18. Ground state lasing at 1.30 microm from InAs/GaAs quantum dot lasers grown by metal-organic chemical vapor deposition.

    PubMed

    Guimard, Denis; Ishida, Mitsuru; Bordel, Damien; Li, Lin; Nishioka, Masao; Tanaka, Yu; Ekawa, Mitsuru; Sudo, Hisao; Yamamoto, Tsuyoshi; Kondo, Hayato; Sugawara, Mitsuru; Arakawa, Yasuhiko

    2010-03-12

    We investigated the effects of post-growth annealing on the photoluminescence (PL) characteristics of InAs/GaAs quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD). The onset temperature at which both the peak linewidth and the PL intensity degraded and the blueshift of the ground state emission wavelength occurred was found to depend on both the QD density and the In composition of the capping layer. This behavior is particularly important in view of QD integration in photonic devices. From the knowledge of the dependences of the PL characteristics after annealing on the QD and capping growth conditions, ground state lasing at 1.30 microm could be demonstrated from InAs/GaAs QDs grown by MOCVD. Finally, we compared the laser characteristics of InAs/GaAs QDs with those of InAs/Sb:GaAs QDs, grown according to the antimony-mediated growth technique, and showed that InAs/Sb:GaAs QDs are more appropriate for laser fabrication at 1.3 microm by MOCVD.

  19. Chemical and structural stability of zirconium-based metal-organic frameworks with large three-dimensional pores by linker engineering.

    PubMed

    Kalidindi, Suresh B; Nayak, Sanjit; Briggs, Michael E; Jansat, Susanna; Katsoulidis, Alexandros P; Miller, Gary J; Warren, John E; Antypov, Dmytro; Corà, Furio; Slater, Ben; Prestly, Mark R; Martí-Gastaldo, Carlos; Rosseinsky, Matthew J

    2015-01-01

    The synthesis of metal-organic frameworks with large three-dimensional channels that are permanently porous and chemically stable offers new opportunities in areas such as catalysis and separation. Two linkers (L1=4,4',4'',4'''-([1,1'-biphenyl]-3,3',5,5'-tetrayltetrakis(ethyne-2,1-diyl)) tetrabenzoic acid, L2=4,4',4'',4'''-(pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid) were used that have equivalent connectivity and dimensions but quite distinct torsional flexibility. With these, a solid solution material, [Zr6 O4 (OH)4 (L1)2.6 (L2)0.4 ]⋅(solvent)x , was formed that has three-dimensional crystalline permanent porosity with a surface area of over 4000 m(2)  g(-1) that persists after immersion in water. These properties are not accessible for the isostructural phases made from the separate single linkers.

  20. Effects of growth temperature on the properties of InGaN channel heterostructures grown by pulsed metal organic chemical vapor deposition

    SciTech Connect

    Zhang, Yachao; Zhou, Xiaowei; Xu, Shengrui; Wang, Zhizhe; Chen, Zhibin; Zhang, Jinfeng; Zhang, Jincheng E-mail: xd-zhangyachao@163.com; Hao, Yue E-mail: xd-zhangyachao@163.com

    2015-12-15

    Pulsed metal organic chemical vapor deposition (P-MOCVD) is introduced into the growth of high quality InGaN channel heterostructures. The effects of InGaN channel growth temperature on the structural and transport properties of the heterostructures are investigated in detail. High resolution x-ray diffraction (HRXRD) and Photoluminescence (PL) spectra indicate that the quality of InGaN channel strongly depends on the growth temperature. Meanwhile, the atomic force microscopy (AFM) results show that the interface morphology between the InGaN channel and the barrier layer also relies on the growth temperature. Since the variation of material properties of InGaN channel has a significant influence on the electrical properties of InAlN/InGaN heterostructures, the optimal transport properties can be achieved by adjusting the growth temperature. A very high two dimension electron gas (2DEG) density of 1.92 × 10{sup 13} cm{sup −2} and Hall electron mobility of 1025 cm{sup 2}/(V⋅s) at room temperature are obtained at the optimal growth temperature around 740 °C. The excellent transport properties in our work indicate that the heterostructure with InGaN channel is a promising candidate for the microwave power devices, and the results in this paper will be instructive for further study of the InGaN channel heterostructures.

  1. Small-Area, Resistive Volatile Organic Compound (VOC) Sensors Using Metal-Polymer Hybrid Film Based on Oxidative Chemical Vapor Deposition (oCVD).

    PubMed

    Wang, Xiaoxue; Hou, Sichao; Goktas, Hilal; Kovacik, Peter; Yaul, Frank; Paidimarri, Arun; Ickes, Nathan; Chandrakasan, Anantha; Gleason, Karen

    2015-08-01

    We report a novel room temperature methanol sensor comprised of gold nanoparticles covalently attached to the surface of conducting copolymer films. The copolymer films are synthesized by oxidative chemical vapor deposition (oCVD), allowing substrate-independent deposition, good polymer conductivity and stability. Two different oCVD copolymers are examined: poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid)[poly(EDOT-co-TAA)] and poly(3,4-ehylenedioxythiophene-co-thiophene-3-ethanol)[poly(EDOT-co-3-TE)]. Covalent attachment of gold nanoparticles to the functional groups of the oCVD films results in a hybrid system with efficient sensing response to methanol. The response of the poly(EDOT-co-TAA)/Au devices is found to be superior to that of the other copolymer, confirming the importance of the linker molecules (4-aminothiophenol) in the sensing behavior. Selectivity of the sensor to methanol over n-pentane, acetone, and toluene is demonstrated. Direct fabrication on a printed circuit board (PCB) is achieved, resulting in an improved electrical contact of the organic resistor to the metal circuitry and thus enhanced sensing properties. The simplicity and low fabrication cost of the resistive element, mild working temperature, together with its compatibility with PCB substrates pave the way for its straightforward integration into electronic devices, such as wireless sensor networks. PMID:26176840

  2. InGaAs/InP Avalanche Photodiode for Single Photon Detection with Zinc Diffusion Process Using Metal Organic Chemical Vapor Deposition.

    PubMed

    Lee, In Joon; Lee, Min Soo; Kim, Min Su; Jun, Dong-Hwan; Jeong, Hae Yong; Kim, Sangin; Han, Sang-wook; Moon, Sung

    2016-05-01

    In this paper, we describe a design, simulation, and fabrication of an InGaAs/InP single photon avalanche photodiode (SPAD), which requires a much higher gain, compared to APD's for conventional optical communications. To achieve a higher gain, an efficient multiplication width control is essential because it significantly affects the overall performance including not only gain but also noise characteristics. Normally, the multiplication layer width is controlled by the Zinc diffusion process. For the reliable and controllable diffusion process, we used metal organic chemical vapor deposition (MOCVD). The controllability of the proposed diffusion process is proved by the diffusion depth measurement of the fabricated devices which show the proportional dependence on the square root of the diffusion time. As a result, we successfully implemented the SPAD that exhibits a high gain enough to detect single photons and a very low dark current level of about 0.1 nA with 0.95 breakdown voltage. The single photon detection efficiency of 15% was measured at the 100 kHz gate pulse rate and the temperature of 230 K. PMID:27483891

  3. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P. D.; Chung, Choong-Heui

    2016-04-01

    We report the growth of vertical <111>-oriented InAs x P1- x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1- x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix.

  4. Hexagonal phase-pure wide band gap ɛ-Ga2O3 films grown on 6H-SiC substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xia, Xiaochuan; Chen, Yuanpeng; Feng, Qiuju; Liang, Hongwei; Tao, Pengcheng; Xu, Mengxiang; Du, Guotong

    2016-05-01

    In this paper, hexagonal structure phase-pure wide-band gap ɛ-Ga2O3 films were grown by metal organic chemical vapor deposition on 6H-SiC substrates. The ɛ-Ga2O3 films with good crystal quality were verified by high-resolution X-ray diffraction. The out-of-plane epitaxial relationship between ɛ-Ga2O3 films and 6H-SiC substrates is confirmed to be ɛ-Ga2O3 (0001)//6H-SiC (0001), and the in-plane epitaxial relationship is also confirmed to be ɛ-Ga2O3 ⟨ 11 2 ¯ 0 ⟩//6H-SiC ⟨ 11 2 ¯ 0 ⟩. The SEM and AFM images show that the ɛ-Ga2O3 films are uniform and flat. The ɛ-Ga2O3 films are thermally stable up to approximately 800 °C and begin to transform into β-phase Ga2O3 at 850 °C. Then, they are completely converted to β-Ga2O3 films under 900 °C. The high-quality ɛ-Ga2O3 films with hexagonal structure have potential application in the optoelectronic field.

  5. Optical and structural properties of microcrystalline GaN on an amorphous substrate prepared by a combination of molecular beam epitaxy and metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Min, Jung-Wook; Hwang, Hyeong-Yong; Kang, Eun-Kyu; Park, Kwangwook; Kim, Ci-Hyun; Lee, Dong-Seon; Jho, Young-Dahl; Bae, Si-Young; Lee, Yong-Tak

    2016-05-01

    Microscale platelet-shaped GaN grains were grown on amorphous substrates by a combined epitaxial growth method of molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). First, MBE GaN was grown on an amorphous substrate as a pre-orienting layer and its structural properties were investigated. Second, MOCVD grown GaN samples using the different growth techniques of planar and selective area growth (SAG) were comparatively investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). In MOCVD planar GaN, strong bound exciton peaks dominated despite the high density of the threading dislocations (TDs). In MOCVD SAG GaN, on the other hand, TDs were clearly reduced with bending, but basal stacking fault (BSF) PL peaks were observed at 3.42 eV. The combined epitaxial method not only provides a deep understanding of the growth behavior but also suggests an alternative approach for the growth of GaN on amorphous substances.

  6. Self-assembled growth and structural analysis of inclined GaN nanorods on nanoimprinted m-sapphire using catalyst-free metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, Kyuseung; Chae, Sooryong; Jang, Jongjin; Min, Daehong; Kim, Jaehwan; Nam, Okhyun

    2016-04-01

    In this study, self-assembled inclined (1-10-3)-oriented GaN nanorods (NRs) were grown on nanoimprinted (10-10) m-sapphire substrates using catalyst-free metal-organic chemical vapor deposition. According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ˜57.5° to the [10-10]sapp direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]sapp. Uni-directionally inclined NRs were formed through the one-sided (10-11)-faceted growth of the interfacial a-GaN plane layer. It was confirmed that a thin layer of a-GaN was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation. The interfacial a-GaN nucleation affected both the inclined angle and the growth direction of the inclined GaN NRs. Using X-ray diffraction and selective area electron diffraction, the epitaxial relationship between the inclined (1-10-3) GaN NRs and interfacial a-GaN layer on m-sapphire substrates was systematically investigated. Moreover, the inclined GaN NRs were observed to be mostly free of stacking fault-related defects using high-resolution transmission electron microscopy.

  7. High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Lian-Kai; Liu, Ren-Jun; Lü, You; Yang, Hao-Yu; Li, Guo-Xing; Zhang, Yuan-Tao; Zhang, Bao-Lin

    2015-01-01

    Orthogonal experiments of GaSb films growth on GaAs(001) substrates have been designed and performed by using a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters. It was demonstrated that the optimized GaSb thin film has a narrow full width at half maximum (358 arc sec) of the (004) ω-rocking curve, and a smooth surface with a low root-mean-square roughness of about 6 nm, which is typical in the case of the heteroepitaxial single-crystal films. In addition, we studied the effects of layer thickness of GaSb thin film on the density of dislocations by Raman spectra. It is believed that our research can provide valuable information for the fabrication of high-crystalline GaSb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices. Project supported by the National Natural Science Foundation of China (Grant No. 61076010) and the International Science and Technology Cooperation Program of Science and Technology Bureau of Changchun, China (Grant No. 12ZX68).

  8. Metal-organic chemical vapor deposition of cerium oxide, gallium-indium-oxide, and magnesium oxide thin films: Precursor design, film growth, and film characterization

    NASA Astrophysics Data System (ADS)

    Edleman, Nikki Lynn

    A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric cerium, neodymium, gadolinium, and erbium complexes are coordinatively saturated by a versatile, multidentate, ether-functionalized beta-ketoiminate ligand, and complex melting point and volatility characteristics can be tuned by altering the alkyl substituents on the ligand periphery. Direct comparison with lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO 2 buffer layer films have been grown on (001) YSZ substrates by MOCVD at significantly lower temperatures than previously reported using one of the newly developed cerium precursors. High-quality YBCO films grown on these CeO2 buffer layers by POMBE exhibit very good electrical transport properties. The cerium complex has therefore been explicitly demonstrated to be a stable and volatile precursor and is attractive for low-temperature growth of coated conductor multilayer structures by MOCVD. Gallium-indium-oxide thin films (GaxIn2-xO 3), x = 0.0˜1.1, have been grown by MOCVD using the volatile metal-organic precursors In(dpm)3 and Ga(dpm)3. The films have a homogeneously Ga-substituted, cubic In2O3 microstructure randomly oriented on quartz or heteroepitaxial on (100) YSZ single-crystal substrates. The highest conductivity of the as-grown films is found at x = 0.12. The optical transmission window and absolute transparency of the films rivals or exceeds that of the most transparent conductive oxides known. Reductive annealing results in improved charge transport characteristics with little loss of optical transparency. No significant difference in electrical properties is observed between randomly oriented and heteroepitaxial films, thus arguing that carrier scattering effects at high-angle grain boundaries play a minor role in the film conductivity mechanism

  9. Substitution reactions in metal-organic frameworks and metal-organic polyhedra.

    PubMed

    Han, Yi; Li, Jian-Rong; Xie, Yabo; Guo, Guangsheng

    2014-08-21

    Substitution reaction, as one of the most powerful and efficient chemical reactions, has been widely used in various syntheses, including those for the design and preparation of functional molecules or materials. In the past decade, a class of newly developed inorganic-organic hybrid materials, namely metal-organic materials (MOMs), has experienced a rapid development. MOMs are composed of metal-containing nodes connected by organic linkers through strong chemical bonds, and can be divided into metal-organic frameworks (MOFs) and metal-organic polygons/polyhedra (MOPs) with infinite and discrete structural features, respectively. Recent research has shown that the substitution reaction can be used as a new strategy in the synthesis and modification of MOFs and MOPs, particularly for pre-designed ones with desired structures and functions, which are usually difficult to access by a direct one-pot self-assembly synthetic approach. This review highlights the implementation of the substitution reaction in MOFs and MOPs. Examples of substitution reactions at metal ions, organic ligands, and free guest molecules of MOFs and MOPs are listed and analyzed. The changes or modifications in the structures and/or properties of these materials induced by the substitutions, as well as the nature of the associated reaction, are discussed, with the conclusion that the substitution reaction is really feasible and powerful in synthesizing and tailoring MOMs.

  10. Metal-doped organic foam

    DOEpatents

    Rinde, James A.

    1982-01-01

    Organic foams having a low density and very small cell size and method for producing same in either a metal-loaded or unloaded (nonmetal loaded) form are described. Metal-doped foams are produced by soaking a polymer gel in an aqueous solution of desired metal salt, soaking the gel successively in a solvent series of decreasing polarity to remove water from the gel and replace it with a solvent of lower polarity with each successive solvent in the series being miscible with the solvents on each side and being saturated with the desired metal salt, and removing the last of the solvents from the gel to produce the desired metal-doped foam having desired density cell size, and metal loading. The unloaded or metal-doped foams can be utilized in a variety of applications requiring low density, small cell size foam. For example, rubidium-doped foam made in accordance with the invention has utility in special applications, such as in x-ray lasers.

  11. Nitride passivation reduces interfacial traps in atomic-layer-deposited Al{sub 2}O{sub 3}/GaAs (001) metal-oxide-semiconductor capacitors using atmospheric metal-organic chemical vapor deposition

    SciTech Connect

    Aoki, T. Fukuhara, N.; Osada, T.; Sazawa, H.; Hata, M.; Inoue, T.

    2014-07-21

    Using an atmospheric metal-organic chemical vapor deposition system, we passivated GaAs with AlN prior to atomic layer deposition of Al{sub 2}O{sub 3}. This AlN passivation incorporated nitrogen at the Al{sub 2}O{sub 3}/GaAs interface, improving the capacitance-voltage (C–V) characteristics of the resultant metal-oxide-semiconductor capacitors (MOSCAPs). The C–V curves of these devices showed a remarkable reduction in the frequency dispersion of the accumulation capacitance. Using the conductance method at various temperatures, we extracted the interfacial density of states (D{sub it}). The D{sub it} was reduced over the entire GaAs band gap. In particular, these devices exhibited D{sub it} around the midgap of less than 4 × 10{sup 12} cm{sup −2}eV{sup −1}, showing that AlN passivation effectively reduced interfacial traps in the MOS structure.

  12. Performance of metal-organic framework MIL-101 after surfactant modification in the extraction of endocrine disrupting chemicals from environmental water samples.

    PubMed

    Huang, Zhenzhen; Lee, Hian Kee

    2015-10-01

    The research presented in this paper explored the modification and application of a metal-organic framework, MIL-101, with nonionic surfactant-Triton X-114 in dispersive solid-phase extraction for the preconcentration of four endocrine disrupting chemicals (estrone, 17α-ethynylestradiol, estriol and diethylstilbestrol) from environmental water samples. Triton X-114 molecules could be adsorbed by the hydrophobic surface of the MIL-101 crystals, and thus improved the dispersibility of MIL-101 in aqueous solution by serving as a hydrophilic coating. Cloud point phase separation from Triton X-114 accelerated the separation of extracts from the aqueous matrix. The proposed method combines the favorable attributes of strong adsorption capacity resulting from the porous structure of MIL-101 and self-assembly of Triton X-114 molecules. Post-extraction derivatization using N-methyl-N-(trimethylsilyl)trifluoroacetamide was employed to facilitate the quantitative determination of the extracts by gas chromatography-mass spectrometry. The main factors affecting the preparation of modified MIL-101, and extraction of the analytes, such as the amount of surfactant, the ultrasonic and vortex durations, solution pH and desorption conditions, were investigated in detail. Under the optimized conditions, the present method yielded low limits of detection (0.006-0.023 ng/mL), good linearity from 0.09 to 45 ng/mL (coefficients of determination higher than 0.9980) and acceptable precision (relative standard deviations of 2.2-13%). The surface modified MIL-101 was demonstrated to be effective for the extraction of the selected estrogens from aqueous samples, giving rise to markedly improved extraction performance compared to the unmodified MIL-101. PMID:26078172

  13. Thermal stability of an InAlN/GaN heterostructure grown on silicon by metal-organic chemical vapor deposition

    SciTech Connect

    Watanabe, Arata Freedsman, Joseph J.; Urayama, Yuya; Christy, Dennis; Egawa, Takashi

    2015-12-21

    The thermal stabilities of metal-organic chemical vapor deposition-grown lattice-matched InAlN/GaN/Si heterostructures have been reported by using slower and faster growth rates for the InAlN barrier layer in particular. The temperature-dependent surface and two-dimensional electron gas (2-DEG) properties of these heterostructures were investigated by means of atomic force microscopy, photoluminescence excitation spectroscopy, and electrical characterization. Even at the annealing temperature of 850 °C, the InAlN layer grown with a slower growth rate exhibited a smooth surface morphology that resulted in excellent 2-DEG properties for the InAlN/GaN heterostructure. As a result, maximum values for the drain current density (I{sub DS,max}) and transconductance (g{sub m,max}) of 1.5 A/mm and 346 mS/mm, respectively, were achieved for the high-electron-mobility transistor (HEMT) fabricated on this heterostructure. The InAlN layer grown with a faster growth rate, however, exhibited degradation of the surface morphology at an annealing temperature of 850 °C, which caused compositional in-homogeneities and impacted the 2-DEG properties of the InAlN/GaN heterostructure. Additionally, an HEMT fabricated on this heterostructure yielded lower I{sub DS,max} and g{sub m,max} values of 1 A/mm and 210 mS/mm, respectively.

  14. Performance of metal-organic framework MIL-101 after surfactant modification in the extraction of endocrine disrupting chemicals from environmental water samples.

    PubMed

    Huang, Zhenzhen; Lee, Hian Kee

    2015-10-01

    The research presented in this paper explored the modification and application of a metal-organic framework, MIL-101, with nonionic surfactant-Triton X-114 in dispersive solid-phase extraction for the preconcentration of four endocrine disrupting chemicals (estrone, 17α-ethynylestradiol, estriol and diethylstilbestrol) from environmental water samples. Triton X-114 molecules could be adsorbed by the hydrophobic surface of the MIL-101 crystals, and thus improved the dispersibility of MIL-101 in aqueous solution by serving as a hydrophilic coating. Cloud point phase separation from Triton X-114 accelerated the separation of extracts from the aqueous matrix. The proposed method combines the favorable attributes of strong adsorption capacity resulting from the porous structure of MIL-101 and self-assembly of Triton X-114 molecules. Post-extraction derivatization using N-methyl-N-(trimethylsilyl)trifluoroacetamide was employed to facilitate the quantitative determination of the extracts by gas chromatography-mass spectrometry. The main factors affecting the preparation of modified MIL-101, and extraction of the analytes, such as the amount of surfactant, the ultrasonic and vortex durations, solution pH and desorption conditions, were investigated in detail. Under the optimized conditions, the present method yielded low limits of detection (0.006-0.023 ng/mL), good linearity from 0.09 to 45 ng/mL (coefficients of determination higher than 0.9980) and acceptable precision (relative standard deviations of 2.2-13%). The surface modified MIL-101 was demonstrated to be effective for the extraction of the selected estrogens from aqueous samples, giving rise to markedly improved extraction performance compared to the unmodified MIL-101.

  15. Cubic SiC nano-thin films and nano-wires: high vacuum metal-organic chemical vapor deposition, surface characterization, and application tests.

    PubMed

    Hyun, J S; Nam, S H; Kang, B C; Park, J H; Boo, J H

    2008-10-01

    Single-crystalline and epitaxial cubic silicon carbide (beta-SiC) nano-thin films have been deposited on Si(100) substrates at a sample temperature of approximately 900 degrees C using single source precursors by the thermal metal-organic chemical vapor deposition (MOCVD) method. Diethylmethylsilane and 1,3-disilabutane, which contain Si and C atoms in the same molecule, were used as precursors without any carrier or bubbler gas. Upon increasing the deposition temperature from 900 to 950 degrees C, beta-SiC nano-thin films with relatively small crystals and smoother surfaces were created on Si(100) substrates. Moreover, beta-SiC nano-wires with 40 approximately 100 nm in diameter have also been grown selectively on nickel catalyzed Si(100) substrates with dichloromethylvinylsilane by the MOCVD method. The deposition temperature in this case was as low as 800 degrees C under the pressure of 5.0 x 10(-2) Torr. It is worth noting that the initial growth rates of deposited beta-SiC nano-thin films and nano-wires strongly depend on the deposition temperature rather than the time. In order to test the possibility of applications of these materials for electronic components such as field emitter, MEMS, and high-power transistor, we fabricated the nanoelectronic devices using both beta-SiC nano-wires and nano-thin films. With these preliminary application tests, it is expected that SiC nanowires can be used as field emitter and nanoelectronic high-power transistor, and application of the SiC nano-thin films to MEMS is promising as well.

  16. In-situ wafer bowing measurements of GaN grown on Si (111) substrate by reflectivity mapping in metal organic chemical vapor deposition system

    NASA Astrophysics Data System (ADS)

    Yang, Yi-Bin; Liu, Ming-Gang; Chen, Wei-Jie; Han, Xiao-Biao; Chen, Jie; Lin, Xiu-Qi; Lin, Jia-Li; Luo, Hui; Liao, Qiang; Zang, Wen-Jie; Chen, Yin-Song; Qiu, Yun-Ling; Wu, Zhi-Sheng; Liu, Yang; Zhang, Bai-Jun

    2015-09-01

    In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2″ Thomas Swan close coupled showerhead metal organic chemical vapor deposition (MOCVD) system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses (tensile and compressive) during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, GaN grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded AlGaN buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274039 and 51177175), the National Basic Research Program of China (Grant No. 2011CB301903), the Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20110171110021), the International Science and Technology Collaboration Program of China (Grant No. 2012DFG52260), the International Science and Technology Collaboration Program of Guangdong Province, China (Grant No. 2013B051000041), the Science and Technology Plan of Guangdong Province, China (Grant No. 2013B010401013), the National High Technology Research and Development Program of China (Grant No. 2014AA032606), and the Opened Fund of the State Key Laboratory on Integrated Optoelectronics, China (Grant No. IOSKL2014KF17).

  17. Inclined angle-controlled growth of GaN nanorods on m-sapphire by metal organic chemical vapor deposition without a catalyst.

    PubMed

    Lee, Kyuseung; Chae, Sooryong; Jang, Jongjin; Min, Daehong; Kim, Jaehwan; Eom, Daeyong; Yoo, Yang-Seok; Cho, Yong-Hoon; Nam, Okhyun

    2015-08-21

    In this study, we have intentionally grown novel types of (11-22)- and (1-10-3)-oriented(3) and self-assembled inclined GaN nanorods (NRs) on (10-10) m-sapphire substrates using metal organic chemical vapor deposition without catalysts and ex situ patterning. Nitridation of the m-sapphire surface was observed to be crucial to the inclined angle as well as the growth direction of the GaN NRs. Polarity-selective KOH etching confirmed that both (11-22) and (1-10-3) GaN NRs are nitrogen-polar. Using pole figure measurements and selective area electron diffraction patterns, the epitaxial relationship between the inclined (11-22) and (1-10-3) GaN NRs and m-sapphire substrates was systematically demonstrated. Furthermore, it was verified that the GaN NRs were single-crystalline wurtzite structures. We observed that stacking fault-related defects were generated during the initial growth stage using high-resolution transmission electron microscopy. The blue-shift of the near band edge (NBE) peak in the inclined angle-controlled GaN NRs can be explained by a band filling effect through carrier saturation of the conduction band, resulting from a high Si-doping concentration; in addition, the decay time of NBE emission in (11-22)- and (1-10-3)-oriented NRs was much shorter than that of stacking fault-related emission. These results suggest that defect-free inclined GaN NRs can be grown on m-sapphire without ex situ treatment.

  18. Nanodots and microwires of ZrO2 grown on LaAlO3 by photo-assisted metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Feng, Guo; Xin-Sheng, Wang; Shi-Wei, Zhuang; Guo-Xing, Li; Bao-Lin, Zhang; Pen-Chu, Chou

    2016-02-01

    ZrO2 nanodots are successfully prepared on LaAlO3 (LAO) (100) substrates by photo-assisted metal-organic chemical vapor deposition (MOCVD). It is indicated that the sizes and densities of ZrO2 nanodots are controllable by modulating the growth temperature, oxygen partial pressure, and growth time. Meanwhile, the microwires are observed on the surfaces of substrates. It is found that there is an obvious competitive relationship between the nanodots and the microwires. In a growth temperature range from 500 °C to 660 °C, the microwires turn longest and widest at 600 °C, but in contrast, the nanodots grow into the smallest diameter at 600 °C. This phenomenon could be illustrated by the energy barrier, decomposition rate of Zr(tmhd)4, and mobility of atoms. In addition, growth time or oxygen partial pressure also affects the competitive relationship between the nanodots and the microwires. With increasing oxygen partial pressure from 451 Pa to 752 Pa, the microwires gradually grow larger while the nanodots become smaller. To further achieve the controllable growth, the coarsening effect of ZrO2 is modified by varying the growth time, and the experimental results show that the coarsening effect of microwires is higher than that of nanodots by increasing the growth time to quickly minimize ZrO2 energy density. Project supported by the National Natural Science Foundation of China (Grant No. 51002063) and the International Science and Technology Cooperation Program of Science and Technology Bureau of Changchun City, China (Grant No. 12ZX68).

  19. Resonant and nonresonant vibrational excitation of ammonia molecules in the growth of gallium nitride using laser-assisted metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Golgir, Hossein Rabiee; Zhou, Yun Shen; Li, Dawei; Keramatnejad, Kamran; Xiong, Wei; Wang, Mengmeng; Jiang, Li Jia; Huang, Xi; Jiang, Lan; Silvain, Jean Francois; Lu, Yong Feng

    2016-09-01

    The influence of exciting ammonia (NH3) molecular vibration in the growth of gallium nitride (GaN) was investigated by using an infrared laser-assisted metal organic chemical vapor deposition method. A wavelength tunable CO2 laser was used to selectively excite the individual vibrational modes. Resonantly exciting the NH-wagging mode (v2) of NH3 molecules at 9.219 μm led to a GaN growth rate of 84 μm/h, which is much higher than the reported results. The difference between the resonantly excited and conventional thermally populated vibrational states was studied via resonant and nonresonant vibrational excitations of NH3 molecules. Resonant excitation of various vibrational modes was achieved at 9.219, 10.35, and 10.719 μm, respectively. Nonresonant excitation was conducted at 9.201 and 10.591 μm, similar to conventional thermal heating. Compared to nonresonant excitation, resonant excitation noticeably promotes the GaN growth rate and crystalline quality. The full width at half maximum value of the XRD rocking curves of the GaN (0002) and GaN (10-12) diffraction peaks decreased at resonant depositions and reached its minimum value of 45 and 53 arcmin, respectively, at the laser wavelength of 9.219 μm. According to the optical emission spectroscopic studies, resonantly exciting the NH3 v2 mode leads to NH3 decomposition at room temperature, reduces the formation of the TMGa:NH3 adduct, promotes the supply of active species in GaN formation, and, therefore, results in the increased GaN growth rate.

  20. Parameters study on the growth of GaAs nanowires on indium tin oxide by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wu, Dan; Tang, Xiaohong; Wang, Kai; Olivier, Aurelien; Li, Xianqiang

    2016-03-01

    After successful demonstration of GaAs nanowire (NW) epitaxial growth on indium tin oxide (ITO) by metal organic chemical vapor deposition, we systematically investigate the effect of growth parameters' effect on the GaAs NW, including temperature, precursor molar flow rates, growth time, and Au catalyst size. 40 nm induced GaAs NWs are observed with zinc-blende structure. Based on vapor-liquid-solid mechanism, a kinetic model is used to deepen our understanding of the incorporation of growth species and the role of various growth parameters in tuning the GaAs NW growth rate. Thermally activated behavior has been investigated by variation of growth temperature. Activation energies of 40 nm Au catalyst induced NWs are calculated at different trimethylgallium (TMGa) molar flow rates about 65 kJ/mol. The GaAs NWs growth rates increase with TMGa molar flow rates whereas the growth rates are almost independent of growth time. Due to Gibbs-Thomson effect, the GaAs NW growth rates increase with Au nanoparticle size at different temperatures. Critical radius is calculated as 2.14 nm at the growth condition of 430 °C and 1.36 μmol/s TMGa flow rate. It is also proved experimentally that Au nanoparticle below the critical radius such as 2 nm cannot initiate the growth of NWs on ITO. This theoretical and experimental growth parameters investigation enables great controllability over GaAs NWs grown on transparent conductive substrate where the methodology can be expanded to other III-V material NWs and is critical for potential hybrid solar cell application.

  1. An assessment of the data quality for NHEXAS--Part I: Exposure to metals and volatile organic chemicals in Region 5.

    PubMed

    Pellizzari, E D; Smith, D J; Clayton, C A; Michael, L C; Quackenboss, J J

    2001-01-01

    A National Human Exposure Assessment Survey (NHEXAS) was performed in U.S. Environmental Protection Agency (U.S. EPA) Region V, providing population-based exposure distribution data for metals and volatile organic chemicals (VOCs) in personal, indoor, and outdoor air, drinking water, beverages, food, dust, soil, blood, and urine. One of the principal objectives of NHEXAS was the testing of protocols for acquiring multimedia exposure measurements and developing databases for use in exposure models and assessments. Analysis of the data quality is one element in assessing the performance of the collection and analysis protocols used in NHEXAS. In addition, investigators must have data quality information available to guide their analyses of the study data. At the beginning of the program quality assurance (QA) goals were established for precision, accuracy, and method quantification limits. The assessment of data quality was complicated. First, quality control (QC) data were not available for all analytes and media sampled, because some of the QC data, e.g., precision of duplicate sample analysis, could be derived only if the analyte was present in the media sampled in at least four pairs of sample duplicates. Furthermore, several laboratories were responsible for the analysis of the collected samples. Each laboratory provided QC data according to their protocols and standard operating procedures (SOPs). Detection limits were established for each analyte in each sample type. The calculation of the method detection limits (MDLs) was different for each analytical method. The analytical methods for metals had adequate sensitivity for arsenic, lead, and cadmium in most media but not for chromium. The QA goals for arsenic and lead were met for all media except arsenic in dust and lead in air. The analytical methods for VOCs in air, water, and blood were sufficiently sensitive and met the QA goals, with very few exceptions. Accuracy was assessed as recovery from field

  2. Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate.

    PubMed

    Wijesekara, S S R M D H R; Basnayake, B F A; Vithanage, Meththika

    2014-01-01

    The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process.

  3. Heavy metals in Antarctic organisms

    SciTech Connect

    Moreno, J.E.A. de; Moreno, V.J.; Gerpe, M.S.; Vodopivez, C.

    1997-02-01

    To evaluate levels of essential (zinc and copper) and non-essential (mercury and cadmium) heavy metals, 34 species of organisms from different areas close to the Antarctic Peninsula were analysed. These included algae, filter-feeders, omnivorous invertebrates and vertebrates. Mercury was not detected, while cadmium was found in the majority of organisms analysed (detection limit was 0.05 ppm for both metals). The highest cadmium concentration was observed in the starfish Odontaster validus. Anthozoans, sipunculids and nudibranchs showed maximum levels of zinc, while the highest copper level was found in the gastropod Trophon brevispira. Mercury and cadmium levels in fishes were below the detection limit. Concentrations of essential and non-essential metals in birds were highest in liver followed by muscle and eggs. Cadmium and mercury levels in muscle of southern elephant seals were above the detection limit, whereas in Antarctic fur seals they were below it. The objective of the study was to gather baseline information for metals in Antarctic Ocean biota that may be needed to detect, measure and monitor future environmental changes. 46 refs., 7 figs., 8 tabs.

  4. Reclaiming metals and organics from industrial wastewaters

    SciTech Connect

    Kilambi, S.

    1996-08-01

    The liquid membrane transport process is an emerging new technology where specific material species are transported selectively and rapidly across a liquid membrane. Supported liquid membranes (SLMs) can be used in metal ion separations, gas transfer, volatile organic compounds (VOCs) removal, solvent extraction, biotechnology and reverse osmosis (RO)/ultrafiltration (UF). Although SLMs were invented in the early 1970s, the bulk of experimental studies involving SLMs for metal removal have been carried out in the last 10 years. Some of these experimental studies included work that surveyed the liquid membrane applications in general, including those for metal ion removal; discussed the theoretical and experimental aspects of general, facilitated transport systems; reviewed the work being carried out at Argonne National Laboratory on separation of metal species by SLMs and also the development of /simple equations to describe the metal ions transport by SLMs; and presented the basic principles involved in applying SLM transport processes for recovery and separation of metals from aqueous solutions that include passive and active transport, aqueous and membrane diffusion and chemical reactions. This article will describe the economic feasibility for using an SLM for recovery of nickel and chromium from plating rise waters and compare the economics with alternate technologies.

  5. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    PubMed

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  6. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes

    NASA Astrophysics Data System (ADS)

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X.; Urban, Ania; Thacker, Nathan C.; Lin, Wenbin

    2016-08-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  7. Chemical sensing and imaging with metallic nanorods.

    PubMed

    Murphy, Catherine J; Gole, Anand M; Hunyadi, Simona E; Stone, John W; Sisco, Patrick N; Alkilany, Alaaldin; Kinard, Brian E; Hankins, Patrick

    2008-02-01

    In this Feature Article, we examine recent advances in chemical analyte detection and optical imaging applications using gold and silver nanoparticles, with a primary focus on our own work. Noble metal nanoparticles have exciting physical and chemical properties that are entirely different from the bulk. For chemical sensing and imaging, the optical properties of metallic nanoparticles provide a wide range of opportunities, all of which ultimately arise from the collective oscillations of conduction band electrons ("plasmons") in response to external electromagnetic radiation. Nanorods have multiple plasmon bands compared to nanospheres. We identify four optical sensing and imaging modalities for metallic nanoparticles: (1) aggregation-dependent shifts in plasmon frequency; (2) local refractive index-dependent shifts in plasmon frequency; (3) inelastic (surface-enhanced Raman) light scattering; and (4) elastic (Rayleigh) light scattering. The surface chemistry of the nanoparticles must be tunable to create chemical specificity, and is a key requirement for successful sensing and imaging platforms. PMID:18209787

  8. Metal-organic frameworks in chromatography.

    PubMed

    Yusuf, Kareem; Aqel, Ahmad; ALOthman, Zeid

    2014-06-27

    Metal-organic frameworks (MOFs) emerged approximately two decades ago and are the youngest class of porous materials. Despite their short existence, MOFs are finding applications in a variety of fields because of their outstanding chemical and physical properties. This review article focuses on the applications of MOFs in chromatography, including high-performance liquid chromatography (HPLC), gas chromatography (GC), and other chromatographic techniques. The use of MOFs in chromatography has already had a significant impact; however, the utilisation of MOFs in chromatography is still less common than other applications, and the number of MOF materials explored in chromatography applications is limited.

  9. Cascade reactions catalyzed by metal organic frameworks.

    PubMed

    Dhakshinamoorthy, Amarajothi; Garcia, Hermenegildo

    2014-09-01

    Cascade or tandem reactions where two or more individual reactions are carried out in one pot constitute a clear example of process intensification, targeting the maximization of spatial and temporal productivity with mobilization of minimum resources. In the case of catalytic reactions, cascade processes require bi-/multifunctional catalysts that contain different classes of active sites. Herein, we show that the features and properties of metal-organic frameworks (MOFs) make these solids very appropriate materials for the development of catalysts for cascade reactions. Due to composition and structure, MOFs can incorporate different types of sites at the metal nodes, organic linkers, or at the empty internal pores, allowing the flexible design and synthesis of multifunctional catalysts. After some introductory sections on the relevance of cascade reactions from the point of view of competitiveness, sustainability, and environmental friendliness, the main part of the text provides a comprehensive review of the literature reporting the use of MOFs as heterogeneous catalysts for cascade reactions including those that combine in different ways acid/base, oxidation/reduction, and metal-organic centers. The final section summarizes the current state of the art, indicating that the development of a first commercial synthesis of a high-added-value fine chemical will be a crucial milestone in this area.

  10. Chemical and biological properties of toxic metals and use of chelating agents for the pharmacological treatment of metal poisoning.

    PubMed

    Sinicropi, Maria Stefania; Amantea, Diana; Caruso, Anna; Saturnino, Carmela

    2010-07-01

    Exposure to toxic metals is a well-known problem in industrialized countries. Metals interfere with a number of physiological processes, including central nervous system (CNS), haematopoietic, hepatic and renal functions. In the evaluation of the toxicity of a particular metal it is crucial to consider many parameters: chemical forms (elemental, organic or inorganic), binding capability, presence of specific proteins that selectively bind metals, etc. Medical treatment of acute and chronic metal toxicity is provided by chelating agents, namely organic compounds capable of interacting with metal ions to form structures called chelates. The present review attempts to provide updated information about the mechanisms, the cellular targets and the effects of toxic metals.

  11. Thermodynamics of metal-organic frameworks

    SciTech Connect

    Wu, Di; Navrotsky, Alexandra

    2015-03-15

    Although there have been extensive studies over the past decade in the synthesis and application of metal-organic frameworks (MOFs), investigation of their thermodynamic stability and of the energetics of guest–host interactions has been much more limited. This review summarizes recent progress in experimental (calorimetric) determination of the thermodynamics of MOF materials. The enthalpies of MOFs relative to dense phase assemblages suggest only modest metastability, with a general increase of enthalpy with increasing molar volume, which becomes less pronounced at higher porosity. The energy landscape of nanoporous materials (inorganic and hybrid) consists of a pair of parallel patterns within a fairly narrow range of metastability of 5–30 kJ per mole of tetrahedra in zeolites and mesoporous silicas or per mole of metal in MOFs. Thus strong thermodynamic instability does not seem to limit framework formation. There are strong interactions within the chemisorption range for small molecule–MOF interactions with defined chemical binding at the metal centers or other specific locations. Coexistence of surface binding and confinement can lead to much stronger guest–host interactions. - Graphical abstract: Energy landscape of inorganic and hybrid porous materials. - Highlights: • Thermochemical data on various MOF structures were experimentally determined. • MOFs are moderately unstable relative to their dense phase assemblage. • Overall energetic landscape of porous materials was revealed. • Guest–host interactions in MOFs were evaluated directly using calorimetry. • Confinement effect and defined chemical binding lead to strong interactions.

  12. Method of stripping metals from organic solvents

    DOEpatents

    Todd, Terry A.; Law, Jack D.; Herbst, R. Scott; Romanovskiy, Valeriy N.; Smirnov, Igor V.; Babain, Vasily A.; Esimantovski, Vyatcheslav M.

    2009-02-24

    A new method to strip metals from organic solvents in a manner that allows for the recycle of the stripping agent. The method utilizes carbonate solutions of organic amines with complexants, in low concentrations, to strip metals from organic solvents. The method allows for the distillation and reuse of organic amines. The concentrated metal/complexant fraction from distillation is more amenable to immobilization than solutions resulting from current practice.

  13. An Electrically Switchable Metal-Organic Framework

    SciTech Connect

    Fernandez, CA; Martin, PC; Schaef, T; Bowden, ME; Thallapally, PK; Dang, L; Xu, W; Chen, XL; McGrail, BP

    2014-08-19

    Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ = 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in a reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.

  14. An Electrically Switchable Metal-Organic Framework

    SciTech Connect

    Fernandez, Carlos A.; Martin, Paul F.; Schaef, Herbert T.; Bowden, Mark E.; Thallapally, Praveen K.; Dang, Liem X.; Xu, Wu; Chen, Xilin; McGrail, B. Peter

    2014-08-19

    Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ 5 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in a reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.

  15. An Electrically Switchable Metal-Organic Framework

    NASA Astrophysics Data System (ADS)

    Fernandez, Carlos A.; Martin, Paul C.; Schaef, Todd; Bowden, Mark E.; Thallapally, Praveen K.; Dang, Liem; Xu, Wu; Chen, Xilin; McGrail, B. Peter

    2014-08-01

    Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ = 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in a reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.

  16. Chemical vapor deposition and atomic layer deposition of Ta-based diffusion barriers using tert-butylimido tris(diethylamido) tantalum metal organic precursor

    NASA Astrophysics Data System (ADS)

    Kim, Keechan

    Ta-N and Ta-Al-N Cu diffusion barriers were deposited by chemical vapor deposition (CVD) and atomic layer deposition (ALD) using tert-butylimido tris(diethylamido) tantalum (TBTDET)/tri-ethyl aluminum (TEA) metal organic precursors. The effect of NH3 addition on film properties during TaN CVD from TBTDET was examined. As the NH3 flow was increased at constant TBTDET flow, the film density, nitrogen content, and grain size increased, while resistivity and carbon content decreased as compared to films deposited with TBTDET alone. These property changes are attributed, in part, to transamination reaction between the diethylamido ligands in TBTDET and NH3. The higher film density and nitrogen content produced TaN films that exhibited superior diffusion barrier performance compared to those deposited without NH3 addition. TaN was also successfully deposited by ALD with alternating exposure to TBTDET and NH3. TBTDET adsorption was shown to be self-limiting with a single monolayer growth rate of 2.6 A/cycle over the process temperature window of 200 to 300°C. An incubation period exists during the initial cycles as evidenced by a non-linear relationship between film thickness and cycle number. Ultra-thin ALD-TaN layers, as thin as 38 A, effectively blocked Cu diffusion during a 30 min anneal at 500°C. Ternary Ta-Al-N films were deposited from TBTDET and TEA to promote formation of an amorphous film and increasing the recrystallization temperature. The Al mole fraction was linearly dependent on the TEA exposure time suggesting growth was self-limiting. Although Al insertion into TaN promoted an amorphous structure, it also lowered the overall film density. A comparative study of the diffusion barrier performance showed that failure occurred for both TaN and Ta-Al-N films at the same thickness, suggesting the increased amorphous content by adding Al was offset by the lower film density. Selecting a different reactant exposure sequence produced different film properties. A

  17. Effects of irradiation and annealing on deep levels in rhodium-doped p-GaAs grown by metal-organic chemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Naz, Nazir A.; Qurashi, Umar S.; Iqbal, M. Zafar

    2011-06-01

    This paper reports a detailed study of the effects of irradiation and thermal annealing on deep levels in Rh-doped p-type GaAs grown by low-pressure metal-organic chemical-vapor deposition, using deep level transient spectroscopy (DLTS) technique. It is found upon irradiation with alpha particles that, in addition to the radiation-induced defect peaks, all the Rh-related peaks observed in majority, as well as minority-carrier emission DLTS scans show an increase in their respective concentrations. The usually observed α-induced defects Hα1, Hα2, and Hα3 are found to have lower introduction rates in Rh-doped samples, as compared to reference samples (not doped with Rh). Alpha-irradiation has been found to decompose the two minority carrier emitting bands (one at low temperature ˜150 K and the other at ˜380 K) observed prior to irradiation into distinct peaks corresponding to deep levels Rh1 and Rh2 and EL2 and Rh3, respectively. A similar effect is also observed for the majority-carrier emitting band composed of hole emission from deep levels RhA and RhB, which separate out well upon irradiation. Further, from the double-correlation DLTS measurements, the emission rates of carriers from the radiation-enhanced peaks corresponding to deep levels Rh1, Rh2, Rh3, and RhC were found to be dependent on junction electric field. For RhC, the field dependence data have been analyzed in terms of the Poole-Frenkel model employing a 3-dimensional Coulomb potential with q = 2e (electronic charge). Temperature dependence of the hole capture cross-sections of the levels RhA and RhC was also studied quantitatively. The observed dependence of the hole capture cross-section of RhC on temperature can be interpreted in terms of multiphonon capture model, yielding a capture barrier of 0.2 eV and σ(∞) = 2.3 × 10-14 cm2. The results of irradiation and isochronal thermal annealing study, in combination with the theoretical analysis of the field dependence of hole emission data

  18. Chemical resistance guide for metals and alloys

    SciTech Connect

    1998-12-31

    This guide contains data for 29,000 combinations of corrodents vs. metals, metal alloys, and carbon. Features and specifications include: (1) 963 liquid or dry chemicals, gases, lubricants, household fluids, foods, atmospheres, and other environments are covered; (2) 70 chemical trade names are covered; (3) 500 synonyms of covered chemicals, gases, etc. are indexed to page numbers; (4) corrodents are listed in alphabetical order; (5) data are presented in symbolic format (A, B, C, NR); (6) where known chemical resistance varies with concentration and temperature, data are presented in descending order of concentration and temperature; (7) mechanical, physical, and electrical properties data for each metal are provided; (8) a flex thumb index is provided at the right-hand margin of the right-hand pages to facilitate quick access to the desired data; (9) an electromotive or galvanic series list covering 120 metals, alloys, and carbon is included; (10) machinability ratings for most metals, including some specific S.F.M. rates, is included; (11) creep or stress relaxation rates at various levels of stress, temperature, and time are included; and (12) printed on semigloss, 70 pound, plastic-coated bond paper that last through years of reference.

  19. New pathways for organic synthesis. Practical applications of transition metals

    SciTech Connect

    Colquhoun, H.M.; Holton, J.; Thompson, D.J.; Twigg, M.V.

    1984-01-01

    This book contains a considerable number of transition-metal-based procedures that have genuine applications in synthesis, and which are arranged according to the nature of the organic product or synthetic transformation being carried out. The objective is to provide those engaged in the preparation of pharmaceuticals, natural products, herbicides, dyestuffs, and other organic chemicals with a practical guide to the application of transition metals in organic synthesis. Topics considered include the formation of carbon-carbon bonds, the formation of carbocyclic compounds, the formation of heterocyclic compounds, the isomerization of alkenes, the direct introduction and removal of carbonyl groups, reduction, oxidation, and preparing and handling transition metal catalysts.

  20. Gas adsorption on metal-organic frameworks

    DOEpatents

    Willis, Richard R.; Low, John J. , Faheem, Syed A.; Benin, Annabelle I.; Snurr, Randall Q.; Yazaydin, Ahmet Ozgur

    2012-07-24

    The present invention involves the use of certain metal organic frameworks that have been treated with water or another metal titrant in the storage of carbon dioxide. The capacity of these frameworks is significantly increased through this treatment.

  1. A chemical equilibrium model for metal adsorption onto bacterial surfaces

    NASA Astrophysics Data System (ADS)

    Fein, Jeremy B.; Daughney, Christopher J.; Yee, Nathan; Davis, Thomas A.

    1997-08-01

    This study quantifies metal adsorption onto cell wall surfaces of Bacillus subtilis by applying equilibrium thermodynamics to the specific chemical reactions that occur at the water-bacteria interface. We use acid/base titrations to determine deprotonation constants for the important surface functional groups, and we perform metal-bacteria adsorption experiments, using Cd, Cu, Pb, and Al, to yield site-specific stability constants for the important metal-bacteria surface complexes. The acid/base properties of the cell wall of B. subtilis can best be characterized by invoking three distinct types of surface organic acid functional groups, with pK a values of 4.82 ± 0.14, 6.9 ± 0.5, and 9.4 ± 0.6. These functional groups likely correspond to carboxyl, phosphate, and hydroxyl sites, respectively, that are displayed on the cell wall surface. The results of the metal adsorption experiments indicate that both the carboxyl sites and the phosphate sites contribute to metal uptake. The values of the log stability constants for metal-carboxyl surface complexes range from 3.4 for Cd, 4.2 for Pb, 4.3 for Cu, to 5.0 for Al. These results suggest that the stabilities of the metal-surface complexes are high enough for metal-bacterial interactions to affect metal mobilities in many aqueous systems, and this approach enables quantitative assessment of the effects of bacteria on metal mobilities.

  2. Photochemical deterioration of the organic/metal contacts in organic optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Williams, Graeme; Tsui, Ting; Aziz, Hany

    2012-09-01

    We study the effect of exposure to light on a wide range of organic/metal contacts that are commonly used in organic optoelectronic devices and found that irradiation by light in the visible and UV range results in a gradual deterioration in their electrical properties. This photo-induced contact degradation reduces both charge injection (i.e., from the metal to the organic layer) and charge extraction (i.e., from the organic layer to the metal). X-ray photoelectron spectroscopy (XPS) measurements reveal detectable changes in the interface characteristics after irradiation, indicating that the photo-degradation is chemical in nature. Changes in XPS characteristics after irradiation suggests a possible reduction in bonds associated with organic-metal complexes. Measurements of interfacial adhesion strength using the four-point flexure technique reveal a decrease in organic/metal adhesion in irradiated samples, consistent with a decrease in metal-organic bond density. The results shed the light on a new material degradation mechanism that appears to have a wide presence in organic/metal interfaces in general, and which likely plays a key role in limiting the stability of various organic optoelectronic devices such as organic light emitting devices, organic solar cells, and organic photo-detectors.

  3. Thermodynamics of metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Wu, Di; Navrotsky, Alexandra

    2015-03-01

    Although there have been extensive studies over the past decade in the synthesis and application of metal-organic frameworks (MOFs), investigation of their thermodynamic stability and of the energetics of guest-host interactions has been much more limited. This review summarizes recent progress in experimental (calorimetric) determination of the thermodynamics of MOF materials. The enthalpies of MOFs relative to dense phase assemblages suggest only modest metastability, with a general increase of enthalpy with increasing molar volume, which becomes less pronounced at higher porosity. The energy landscape of nanoporous materials (inorganic and hybrid) consists of a pair of parallel patterns within a fairly narrow range of metastability of 5-30 kJ per mole of tetrahedra in zeolites and mesoporous silicas or per mole of metal in MOFs. Thus strong thermodynamic instability does not seem to limit framework formation. There are strong interactions within the chemisorption range for small molecule-MOF interactions with defined chemical binding at the metal centers or other specific locations. Coexistence of surface binding and confinement can lead to much stronger guest-host interactions.

  4. Chemical segregation in metallic glass nanowires

    SciTech Connect

    Zhang, Qi; Li, Mo; Li, Qi-Kai

    2014-11-21

    Nanowires made of metallic glass have been actively pursued recently due to the superb and unique properties over those of the crystalline materials. The amorphous nanowires are synthesized either at high temperature or via mechanical disruption using focused ion beam. These processes have potential to cause significant changes in structure and chemical concentration, as well as formation of defect or imperfection, but little is known to date about the possibilities and mechanisms. Here, we report chemical segregation to surfaces and its mechanisms in metallic glass nanowires made of binary Cu and Zr elements from molecular dynamics simulation. Strong concentration deviation are found in the nanowires under the conditions similar to these in experiment via focused ion beam processing, hot imprinting, and casting by rapid cooling from liquid state. Our analysis indicates that non-uniform internal stress distribution is a major cause for the chemical segregation, especially at low temperatures. Extension is discussed for this observation to multicomponent metallic glass nanowires as well as the potential applications and side effects of the composition modulation. The finding also points to the possibility of the mechanical-chemical process that may occur in different settings such as fracture, cavitation, and foams where strong internal stress is present in small length scales.

  5. Electrically Conductive Porous Metal-Organic Frameworks.

    PubMed

    Sun, Lei; Campbell, Michael G; Dincă, Mircea

    2016-03-01

    Owing to their outstanding structural, chemical, and functional diversity, metal-organic frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy-related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility. Herein we review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long-range charge transport properties. In addition, key experiments that have been employed to demonstrate electrical transport, as well as selected applications for this subclass of MOFs, will be discussed.

  6. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process.

    PubMed

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-01

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga0.97N0.9O0.09 is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga0.97N0.9O0.09 of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4M HCl, 100°C and pulp density of 100 kg/m(3,) respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition.

  7. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, Ahmet

    1989-01-01

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula (I) ##STR1## where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula I is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula I and a heat decomposable tellurium compound under nonoxidizing conditions.

  8. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, A.

    1989-11-21

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula given in the patent where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula 1 is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula 1 and a heat decomposable tellurium compound under nonoxidizing conditions.

  9. Adsorption of organic chemicals in soils.

    PubMed Central

    Calvet, R

    1989-01-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described. PMID:2695323

  10. Adsorption of organic chemicals in soils.

    PubMed

    Calvet, R

    1989-11-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described.

  11. Benchmarking density functional theory predictions of framework structures and properties in a chemically diverse test set of metal-organic frameworks

    SciTech Connect

    Nazarian, Dalar; Ganesh, P.; Sholl, David S.

    2015-09-30

    We compiled a test set of chemically and topologically diverse Metal–Organic Frameworks (MOFs) with high accuracy experimentally derived crystallographic structure data. The test set was used to benchmark the performance of Density Functional Theory (DFT) functionals (M06L, PBE, PW91, PBE-D2, PBE-D3, and vdW-DF2) for predicting lattice parameters, unit cell volume, bonded parameters and pore descriptors. On average PBE-D2, PBE-D3, and vdW-DF2 predict more accurate structures, but all functionals predicted pore diameters within 0.5 Å of the experimental diameter for every MOF in the test set. The test set was also used to assess the variance in performance of DFT functionals for elastic properties and atomic partial charges. The DFT predicted elastic properties such as minimum shear modulus and Young's modulus can differ by an average of 3 and 9 GPa for rigid MOFs such as those in the test set. Moreover, we calculated the partial charges by vdW-DF2 deviate the most from other functionals while there is no significant difference between the partial charges calculated by M06L, PBE, PW91, PBE-D2 and PBE-D3 for the MOFs in the test set. We find that while there are differences in the magnitude of the properties predicted by the various functionals, these discrepancies are small compared to the accuracy necessary for most practical applications.

  12. Chemical enhancement of metallized zinc anode performance

    SciTech Connect

    Bennett, J.

    1998-12-31

    Galvanic current delivered to reinforced concrete by a metallized zinc anode was studied relative to the humidity of its environment and periodic direct wetting. Current decreased quickly at low humidity to values unlikely to meet accepted cathodic protection criteria, but could be easily restored by direct wetting of the anode. Thirteen chemicals were screened for their ability to enhance galvanic current. Such chemicals, when applied to the exterior surface of the anode, are easily transported by capillary action to the anode-concrete interface where they serve to maintain the interface conductive and the zinc electrochemically active. The most effective chemicals were potassium and lithium bromide, acetate, chloride and nitrate, which increased galvanic current by a factor of 2--15, depending on relative humidity and chloride contamination of the concrete. This new technique is expected to greatly expand the number of concrete structures which can be protected by simple galvanic cathodic protection, The use of lithium-based chemicals together with metallized zinc anode is also proposed for mitigation of existing problems due to ASR. In this case, lithium which prevents or inhibits expansion due to ASR can be readily injected into the concrete. A new process, electrochemical maintenance of concrete (EMC), is also proposed to benefit reinforced concrete structures suffering from chloride-induced corrosion.

  13. Metal-loaded organic scintillators for neutrino physics

    NASA Astrophysics Data System (ADS)

    Buck, Christian; Yeh, Minfang

    2016-09-01

    Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can be used under stable conditions for many years even in ton scale experiments. Applications of metal loaded scintillators in neutrino experiments are reviewed and the performance as well as the prospects of different scintillator types are compared.

  14. A metal-organic framework-derived bifunctional oxygen electrocatalyst

    NASA Astrophysics Data System (ADS)

    Xia, Bao Yu; Yan, Ya; Li, Nan; Wu, Hao Bin; Lou, Xiong Wen (David); Wang, Xin

    2016-01-01

    Oxygen electrocatalysis is of great importance for many energy storage and conversion technologies, including fuel cells, metal-air batteries and water electrolysis. Replacing noble metal-based electrocatalysts with highly efficient and inexpensive non-noble metal-based oxygen electrocatalysts is critical for the practical applications of these technologies. Here we report a general approach for the synthesis of hollow frameworks of nitrogen-doped carbon nanotubes derived from metal-organic frameworks, which exhibit higher electrocatalytic activity and stability for oxygen reduction and evolution than commercial Pt/C electrocatalysts. The remarkable electrochemical properties are mainly attributed to the synergistic effect from chemical compositions and the robust hollow structure composed of interconnected crystalline nitrogen-doped carbon nanotubes. The presented strategy for controlled design and synthesis of metal-organic framework-derived functional nanomaterials offers prospects in developing highly active electrocatalysts in electrochemical energy devices.

  15. COSOLVENCY AND SOPRTION OF HYDROPHOBIC ORGANIC CHEMICALS

    EPA Science Inventory

    Sorption of hydrophobic organic chemicals (HOCs) by two soils was measured from mixed solvents containing water plus completely miscible organic solvents (CMOSs) and partially miscible organic solvents (PMOSs). The utility of the log-linear cosolvency model for predicting HOC sor...

  16. Benchmarking density functional theory predictions of framework structures and properties in a chemically diverse test set of metal-organic frameworks

    DOE PAGESBeta

    Nazarian, Dalar; Ganesh, P.; Sholl, David S.

    2015-09-30

    We compiled a test set of chemically and topologically diverse Metal–Organic Frameworks (MOFs) with high accuracy experimentally derived crystallographic structure data. The test set was used to benchmark the performance of Density Functional Theory (DFT) functionals (M06L, PBE, PW91, PBE-D2, PBE-D3, and vdW-DF2) for predicting lattice parameters, unit cell volume, bonded parameters and pore descriptors. On average PBE-D2, PBE-D3, and vdW-DF2 predict more accurate structures, but all functionals predicted pore diameters within 0.5 Å of the experimental diameter for every MOF in the test set. The test set was also used to assess the variance in performance of DFT functionalsmore » for elastic properties and atomic partial charges. The DFT predicted elastic properties such as minimum shear modulus and Young's modulus can differ by an average of 3 and 9 GPa for rigid MOFs such as those in the test set. Moreover, we calculated the partial charges by vdW-DF2 deviate the most from other functionals while there is no significant difference between the partial charges calculated by M06L, PBE, PW91, PBE-D2 and PBE-D3 for the MOFs in the test set. We find that while there are differences in the magnitude of the properties predicted by the various functionals, these discrepancies are small compared to the accuracy necessary for most practical applications.« less

  17. Thermodynamics of Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Hughes, James Thomas

    Metal-Organic Frameworks (MOF) are crystalline nanoporous lattices constructed from the combination of cation and multi-dentate organic molecules. MOFs can display both chemical and thermal robustness while having large surface areas and pore volumes. In addition the modular composition of MOFs allows a degree of design and control of MOF structures. These unique physical properties have attracted wide interest and position MOFs to make meaningful contributions towards many applications, such as adsorption, catalysis, separation, and sensing. Despite the extensive investigative work over the last decade on MOF materials, the initial synthesis is still done by trial and error. Of the identified structures some MOFs are robust while others are fragile. It is unclear what role thermodynamics plays in the formation energies of MOFs and guest molecules interactions within the pores. Better understanding of thermochemical properties of MOFs is critical if MOF synthesis is to obtain true predictive design. To address these questions aqueous solution calorimetry was performed on ten different frameworks in both the as-synthesized and activated state. To understand the structural energetics of MOFs, the heat of formation from dense states (metal oxide and protonated organic linkers) to the open MOF framework was measured. Chapter 2 discusses the new aqueous calorimetry methodology developed to measure the enthalpy of solution for hybrid materials. Chapters 3, 4 and 5 detail the enthalpies of formation from their dense states of the frameworks: (MOF-5, ZIF-zni, ZIF-1, ZIF-3, ZIF-4, ZIF-7, ZIF-8, ZIF-9 and Cu-HKUST-1). These chapters also compare the MOF heat of formation energetics to those of zeolites, zeotypes and mesoporous silica materials. Finding that MOFs are metastable with respect to their dense states (metal oxide and protonated organic), following the current destabilization trend of the main group porous materials. The thermochemical effect of solvent on the MOF

  18. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process

    SciTech Connect

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-15

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga{sub 0.97}N{sub 0.9}O{sub 0.09} is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga{sub 0.97}N{sub 0.9}O{sub 0.09} of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4 M HCl, 100 °C and pulp density of 100 kg/m{sup 3,} respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition. - Highlights: • Waste MOCVD dust is treated through mechanochemical leaching. • GaN is hardly leached, and converted to NaGaO{sub 2} through ball milling and annealing. • Process for gallium recovery from waste MOCVD dust has been developed. • Thermal analysis and phase properties of GaN to Ga{sub 2}O{sub 3} and GaN to NaGaO{sub 2} is revealed. • Solid-state chemistry involved in this process is reported.

  19. Magnetism in metal-organic capsules

    SciTech Connect

    Atwood, Jerry L.; Brechin, Euan K; Dalgarno, Scott J.; Inglis, Ross; Jones, Leigh F.; Mossine, Andrew; Paterson, Martin J.; Power, Nicholas P.; Teat, Simon J.

    2010-01-07

    Nickel and cobalt seamed metal-organic capsules have been isolated and studied using structural, magnetic and computational approaches. Antiferromagnetic exchange in the Ni capsule results from coordination environments enforced by the capsule framework.

  20. Melt-Quenched Glasses of Metal-Organic Frameworks.

    PubMed

    Bennett, Thomas D; Yue, Yuanzheng; Li, Peng; Qiao, Ang; Tao, Haizheng; Greaves, Neville G; Richards, Tom; Lampronti, Giulio I; Redfern, Simon A T; Blanc, Frédéric; Farha, Omar K; Hupp, Joseph T; Cheetham, Anthony K; Keen, David A

    2016-03-16

    Crystalline solids dominate the field of metal-organic frameworks (MOFs), with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration to framework chemistry and topology to expand the phenomenon of the melting of 3D MOFs, linking crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to facilitate the melting of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic nonmetallic, organic, and metallic), and retain the basic metal-ligand connectivity of crystalline MOFs, which connects their mechanical properties to their starting chemical composition. The transfer of functionality from crystal to glass points toward new routes to tunable, functional hybrid glasses.

  1. Decontamination of metals using chemical etching

    DOEpatents

    Lerch, Ronald E.; Partridge, Jerry A.

    1980-01-01

    The invention relates to chemical etching process for reclaiming contaminated equipment wherein a reduction-oxidation system is included in a solution of nitric acid to contact the metal to be decontaminated and effect reduction of the reduction-oxidation system, and includes disposing a pair of electrodes in the reduced solution to permit passage of an electrical current between said electrodes and effect oxidation of the reduction-oxidation system to thereby regenerate the solution and provide decontaminated equipment that is essentially radioactive contamination-free.

  2. Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents.

    PubMed

    Štengl, Václav; Henych, Jiří; Janoš, Pavel; Skoumal, Miroslav

    2016-01-01

    Metal oxides have very important applications in many areas of chemistry, physics and materials science; their properties are dependent on the method of preparation, the morphology and texture. Nanostructured metal oxides can exhibit unique characteristics unlike those of the bulk form depending on their morphology, with a high density of edges, corners and defect surfaces. In recent years, methods have been developed for the preparation of metal oxide powders with tunable control of the primary particle size as well as of a secondary particle size: the size of agglomerates of crystallites. One of the many ways to take advantage of unique properties of nanostructured oxide materials is stoichiometric degradation of chemical warfare agents (CWAs) and volatile organic compounds (VOC) pollutants on their surfaces.

  3. InAlN/InGaN/GaN double heterostructure with improved carrier confinement and high-temperature transport performance grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Shuai Xue, Jun; Zhang, Jin Cheng; Zhou, Xiao Wei; Chao Zhang, Ya; Hao, Yue

    2015-07-01

    A nearly lattice-matched InAlN/InGaN/GaN double heterostructure (DH) and traditional InAlN/GaN single heterostructure (SH) were grown by metal-organic chemical vapor deposition. The InN mole fraction of InGaN channel was deduced by XRD and photoluminescence. The electrical properties were characterized by capacitance-voltage and temperature-dependent Hall measurements. Both results revealed that the InAlN/InGaN/GaN DH possessed superior carrier confinement over traditional InAlN/GaN SH owing to the back barrier formed at the InGaN/GaN interface, which prevents the spilling over of carriers and thus remarkably improves the transport performance at high temperature. Furthermore, a thin InGaN layer was preferable for carrier channel applications to a thick one.

  4. Metal-organic frameworks for artificial photosynthesis and photocatalysis.

    PubMed

    Zhang, Teng; Lin, Wenbin

    2014-08-21

    Solar energy is an alternative, sustainable energy source for mankind. Finding a convenient way to convert sunlight energy into chemical energy is a key step towards realizing large-scale solar energy utilization. Owing to their structural regularity and synthetic tunability, metal-organic frameworks (MOFs) provide an interesting platform to hierarchically organize light-harvesting antennae and catalytic centers to achieve solar energy conversion. Such photo-driven catalytic processes not only play a critical role in the solar to chemical energy conversion scheme, but also provide a novel methodology for the synthesis of fine chemicals. In this review, we summarize the fundamental principles of energy transfer and photocatalysis and provide an overview of the latest progress in energy transfer, light-harvesting, photocatalytic proton and CO2 reduction, and water oxidation using MOFs. The applications of MOFs in organic photocatalysis and degradation of model organic pollutants are also discussed.

  5. A Novel Permeable Reactive Barrier (PRB) for Simultaneous and Rapid Removal of Heavy Metal and Organic Matter - A Systematic Chemical Speciation Approach on Sustainable Technique for Pallikarani Marshland Remediation

    NASA Astrophysics Data System (ADS)

    Selvaraj, A.; Nambi, I. M.

    2014-12-01

    In this study, an innovative technique of ZVI mediated 'coupling of Fenton like oxidation of phenol and Cr(VI) reduction technique' was attempted. The hypothesis is that Fe3+ generated from Cr(VI) reduction process acts as electron acceptor and catalyst for Fenton's Phenol oxidation process. The Fe2+ formed from Fenton reactions can be reused for Cr(VI) reduction. Thus iron can be made to recycle between two reactions, changing back and forth between Fe2+ and Fe3+ forms, makes treatment sustainable.(Fig 1) This approach advances current Fenton like oxidation process by (i)single system removal of heavy metal and organic matter (ii)recycling of iron species; hence no additional iron required (iii)more contaminant removal to ZVI ratio (iv)eliminating sludge related issues. Preliminary batch studies were conducted at different modes i) concurrent removal ii) sequential removal. The sequential removal was found better for in-situ PRB applications. PRB was designed based on kinetic rate slope and half-life time, obtained from primary column study. This PRB has two segments (i)ZVI segment[Cr(VI)] (ii)iron species segment[phenol]. This makes treatment sustainable by (i) having no iron ions in outlet stream (ii)meeting hypothesis and elongates the life span of PRB. Sequential removal of contaminates were tested in pilot scale PRB(Fig 2) and its life span was calculated based on the exhaustion of filling material. Aqueous, sand and iron aliquots were collected at various segments of PRB and analyzed for precipitation and chemical speciation thoroughly (UV spectrometer, XRD, FTIR, electron microscope). Chemical speciation profile eliminates the uncertainties over in-situ PRB's long term performance. Based on the pilot scale PRB study, 'field level PRB wall construction' was suggested to remove heavy metal and organic compounds from Pallikaranai marshland(Fig 3)., which is contaminated with leachate coming from nearby Perungudi dumpsite. This research provides (i

  6. Asymmetric organic/metal(oxide) hybrid nanoparticles: synthesis and applications

    NASA Astrophysics Data System (ADS)

    He, Jie; Liu, Yijing; Hood, Taylor C.; Zhang, Peng; Gong, Jinlong; Nie, Zhihong

    2013-05-01

    Asymmetric particles (APs) with broken centrosymmetry are of great interest, due to the asymmetric surface properties and diverse functionalities. In particular, organic/metal(oxide) APs naturally combine the significantly different and complementary properties of organic and inorganic species, leading to their unique applications in various fields. In this review article, we highlighted recent advances in the synthesis and applications of organic/metal(oxide) APs. This type of APs is grounded on chemical or physical interactions between metal(oxide) NPs and organic small molecular or polymeric ligands. The synthetic methodologies were summarized in three categories, including the selective surface modifications, phase separation of mixed ligands on the surface of metal(oxide) NPs, and direct synthesis of APs. We further discussed the unique applications of organic/metal(oxide) APs in self-assembly, sensors, catalysis, and biomedicine, as a result of the distinctions between asymmetrically distributed organic and inorganic components. Finally, challenges and future directions are discussed in an outlook section.

  7. Asymmetric organic/metal(oxide) hybrid nanoparticles: synthesis and applications.

    PubMed

    He, Jie; Liu, Yijing; Hood, Taylor C; Zhang, Peng; Gong, Jinlong; Nie, Zhihong

    2013-06-21

    Asymmetric particles (APs) with broken centrosymmetry are of great interest, due to the asymmetric surface properties and diverse functionalities. In particular, organic/metal(oxide) APs naturally combine the significantly different and complementary properties of organic and inorganic species, leading to their unique applications in various fields. In this review article, we highlighted recent advances in the synthesis and applications of organic/metal(oxide) APs. This type of APs is grounded on chemical or physical interactions between metal(oxide) NPs and organic small molecular or polymeric ligands. The synthetic methodologies were summarized in three categories, including the selective surface modifications, phase separation of mixed ligands on the surface of metal(oxide) NPs, and direct synthesis of APs. We further discussed the unique applications of organic/metal(oxide) APs in self-assembly, sensors, catalysis, and biomedicine, as a result of the distinctions between asymmetrically distributed organic and inorganic components. Finally, challenges and future directions are discussed in an outlook section.

  8. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    PubMed

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals. PMID:27574182

  9. Quantum chemical simulations of atomic layer deposition of metal oxides and metal nitrides

    NASA Astrophysics Data System (ADS)

    Xu, Ye

    Scaling of SiO2 gate dielectrics to extend the miniaturization of complementary metal oxide semiconductor (CMOS) devices in accordance with Moore's Law has resulted in unacceptable tunneling current leakage levels. The projection that this challenge could significantly limit CMOS performance has prompted the intense search for alternative gate dielectric materials that can achieve high capacitances with physically thicker films which minimize tunneling leakage current. Atomic layer deposition is an ideal deposition method for high-k films because it controls the film thickness with atomic layer precision and can achieve high film conformality and uniformity. We use density functional theory (DFT) to explore chemical reactions involved in ALD processes at the atomic level. We have investigated different metal precursors for ALD process. Compared to halides, metal alkylamides are more favorable on nitrided silicon surfaces and subsequent film growth. Likewise, hafnium alkylamide is more favorable than water to initiate the nucleation on hydrogen terminated silicon surfaces. For deposition on organic self-assembled monolayers, different end groups significantly affect the selectivity towards ALD reactions. The chemical mechanisms involved in ALD of hafnium nitride, aluminum nitride are developed which provide an understanding to the difficulty in producing oxygen free metal nitrides by ALD. By combining ALD of metal oxide and metal nitride, a new method for incorporating nitrogen into oxide films is proposed. In TMA and ozone reaction, it's found that by-product water can be a catalyzer for this reaction.

  10. EFFECT OF NON-TARGET ORGANICS ON ORGANIC CHEMICAL TRANSPORT

    EPA Science Inventory

    To improve our standard of living, man has synthesized organic compounds for use in products considered essential for life. These compounds are having and will continue to have a significant impact on the terrestrial environment. Understanding organic chemical transport through s...

  11. Minerals with metal-organic framework structures.

    PubMed

    Huskić, Igor; Pekov, Igor V; Krivovichev, Sergey V; Friščić, Tomislav

    2016-08-01

    Metal-organic frameworks (MOFs) are an increasingly important family of advanced materials based on open, nanometer-scale metal-organic architectures, whose design and synthesis are based on the directed assembly of carefully designed subunits. We now demonstrate an unexpected link between mineralogy and MOF chemistry by discovering that the rare organic minerals stepanovite and zhemchuzhnikovite exhibit structures found in well-established magnetic and proton-conducting metal oxalate MOFs. Structures of stepanovite and zhemchuzhnikovite, exhibiting almost nanometer-wide and guest-filled apertures and channels, respectively, change the perspective of MOFs as exclusively artificial materials and represent, so far, unique examples of open framework architectures in organic minerals. PMID:27532051

  12. Minerals with metal-organic framework structures

    PubMed Central

    Huskić, Igor; Pekov, Igor V.; Krivovichev, Sergey V.; Friščić, Tomislav

    2016-01-01

    Metal-organic frameworks (MOFs) are an increasingly important family of advanced materials based on open, nanometer-scale metal-organic architectures, whose design and synthesis are based on the directed assembly of carefully designed subunits. We now demonstrate an unexpected link between mineralogy and MOF chemistry by discovering that the rare organic minerals stepanovite and zhemchuzhnikovite exhibit structures found in well-established magnetic and proton-conducting metal oxalate MOFs. Structures of stepanovite and zhemchuzhnikovite, exhibiting almost nanometer-wide and guest-filled apertures and channels, respectively, change the perspective of MOFs as exclusively artificial materials and represent, so far, unique examples of open framework architectures in organic minerals. PMID:27532051

  13. Metal-Organic Frameworks as Platforms for Functional Materials.

    PubMed

    Cui, Yuanjing; Li, Bin; He, Huajun; Zhou, Wei; Chen, Banglin; Qian, Guodong

    2016-03-15

    Discoveries of novel functional materials have played very important roles to the development of science and technologies and thus to benefit our daily life. Among the diverse materials, metal-organic framework (MOF) materials are rapidly emerging as a unique type of porous and organic/inorganic hybrid materials which can be simply self-assembled from their corresponding inorganic metal ions/clusters with organic linkers, and can be straightforwardly characterized by various analytical methods. In terms of porosity, they are superior to other well-known porous materials such as zeolites and carbon materials; exhibiting extremely high porosity with surface area up to 7000 m(2)/g, tunable pore sizes, and metrics through the interplay of both organic and inorganic components with the pore sizes ranging from 3 to 100 Å, and lowest framework density down to 0.13 g/cm(3). Such unique features have enabled metal-organic frameworks to exhibit great potentials for a broad range of applications in gas storage, gas separations, enantioselective separations, heterogeneous catalysis, chemical sensing and drug delivery. On the other hand, metal-organic frameworks can be also considered as organic/inorganic self-assembled hybrid materials, we can take advantages of the physical and chemical properties of both organic and inorganic components to develop their functional optical, photonic, and magnetic materials. Furthermore, the pores within MOFs can also be utilized to encapsulate a large number of different species of diverse functions, so a variety of functional MOF/composite materials can be readily synthesized. In this Account, we describe our recent research progress on pore and function engineering to develop functional MOF materials. We have been able to tune and optimize pore spaces, immobilize specific functional groups, and introduce chiral pore environments to target MOF materials for methane storage, light hydrocarbon separations, enantioselective recognitions

  14. Metal-Organic Frameworks as Platforms for Functional Materials.

    PubMed

    Cui, Yuanjing; Li, Bin; He, Huajun; Zhou, Wei; Chen, Banglin; Qian, Guodong

    2016-03-15

    Discoveries of novel functional materials have played very important roles to the development of science and technologies and thus to benefit our daily life. Among the diverse materials, metal-organic framework (MOF) materials are rapidly emerging as a unique type of porous and organic/inorganic hybrid materials which can be simply self-assembled from their corresponding inorganic metal ions/clusters with organic linkers, and can be straightforwardly characterized by various analytical methods. In terms of porosity, they are superior to other well-known porous materials such as zeolites and carbon materials; exhibiting extremely high porosity with surface area up to 7000 m(2)/g, tunable pore sizes, and metrics through the interplay of both organic and inorganic components with the pore sizes ranging from 3 to 100 Å, and lowest framework density down to 0.13 g/cm(3). Such unique features have enabled metal-organic frameworks to exhibit great potentials for a broad range of applications in gas storage, gas separations, enantioselective separations, heterogeneous catalysis, chemical sensing and drug delivery. On the other hand, metal-organic frameworks can be also considered as organic/inorganic self-assembled hybrid materials, we can take advantages of the physical and chemical properties of both organic and inorganic components to develop their functional optical, photonic, and magnetic materials. Furthermore, the pores within MOFs can also be utilized to encapsulate a large number of different species of diverse functions, so a variety of functional MOF/composite materials can be readily synthesized. In this Account, we describe our recent research progress on pore and function engineering to develop functional MOF materials. We have been able to tune and optimize pore spaces, immobilize specific functional groups, and introduce chiral pore environments to target MOF materials for methane storage, light hydrocarbon separations, enantioselective recognitions

  15. Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

    SciTech Connect

    Cipro, R.; Gorbenko, V.; Baron, T. Martin, M.; Moeyaert, J.; David, S.; Bassani, F.; Bogumilowicz, Y.; Barnes, J. P.; Rochat, N.; Loup, V.; Vizioz, C.; Allouti, N.; Chauvin, N.; Bao, X. Y.; Ye, Z.; Pin, J. B.; Sanchez, E.

    2014-06-30

    Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO{sub 2} cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

  16. An analysis of the growth of silver catalyzed InxGa1-xAs nanowires on Si (100) by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sarkar, K.; Palit, M.; Chattopadhyay, S.; Banerji, P.

    2016-08-01

    A model is proposed here to understand the nucleation of III-V semiconductor nanowires (NW). Whereas the classical nucleation theory is not adequately sufficient in explaining the evolution of the shape of the NWs under different chemical environment such as flow rate or partial pressure of the precursors, the effect of adsorption and desorption mediated growth, and diffusion limited growth are taken into account to explain the morphology and the crystal structure of InxGa1-xAs nanowires (NW) on Silicon (100) substrates grown by a metalorganic chemical vapor deposition technique. It is found that the monolayer nucleus that originates at the triple phase line covers the entire nucleus-substrate (NS) region at a specific level of supersaturation and there are cases when the monolayer covers a certain fraction of the NS interface. When the monolayer covers the total NS interface, NWs grow with perfect cylindrical morphology and whenever a fraction of the interface is covered by the nucleus, the NWs become curved as observed from high resolution transmission electron microscopy images. The supersaturation, i.e., the chemical potential is found to be governed by the concentration of precursors into the molten silver which in the present case is taken as a catalyst. Our study provides new insights into the growth of ternary NWs which will be helpful in understanding the behavior of growth of different semiconducting NWs.

  17. Metal-Organic Frameworks as Sensory Materials and Imaging Agents

    PubMed Central

    Liu, Demin; Lu, Kuangda; Poon, Christopher

    2014-01-01

    Metal-organic frameworks (MOFs) are a class of hybrid materials self-assembled from organic bridging ligands and metal ion/cluster connecting points. The combination of a variety of organic linkers, metal ions/clusters, and structural motifs can lead to an infinite array of new materials with interesting properties for many applications. In this Forum article, we discuss the design and applications of MOFs in chemical sensing and biological imaging. The first half of this article focuses on the development of MOFs as chemical sensors by highlighting how unique attributes of MOFs can be utilized to enhance sensitivity and selectivity. We also discuss some of the issues that need to be addressed in order to develop practically useful MOF sensors. The second half of this article focuses on the design and applications of nanoscale metal-organic frameworks (NMOFs) as imaging contrast agents. NMOFs possess several interesting attributes, such as high cargo loading capacity, ease of post-modification, tunable size and shape, and intrinsic biodegradability, to make them excellent candidates as imaging contrast agents. We discuss the use of representative NMOFs in magnetic resonance imaging (MRI), X-ray computed tomography (CT), and optical imaging (OI). Although still in their infancy, we believe that the compositional tunability and mild synthetic conditions of NMOF imaging agents should greatly facilitate their further development for clinical translation. PMID:24251853

  18. Chemical Sensors Based on Metal Oxide Nanostructures

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  19. Influences of group-III source preflow on the polarity, optical, and structural properties of GaN grown on nitridated sapphire substrates by metal-organic chemical vapor deposition

    SciTech Connect

    Li, Chengguo; Liu, Hongfei; Chua, Soo Jin

    2015-03-28

    We report the influences of group-III source preflow, which were introduced prior to the growth of the low temperature GaN on the polarity, photoluminescence (PL), and crystallographic properties of GaN epilayers grown on nitridated c-plane sapphire substrates by metal-organic chemical vapor deposition. By studying the surface morphology evolutions under chemical etching in KOH, we found that with increasing the trimethyl-gallium (TMGa) preflow duration (t), the polarity of the GaN film can be changed from a complete N-polarity to a mixture of N- and Ga-polarity and further to a complete Ga-polarity. PL and high-resolution X-ray diffraction studies revealed that the impurity incorporation and the edge- and screw-type threading dislocations are strongly polarity dependent. A further study at the optimized t (i.e., 30 s for TMGa) shows that the polarity inversion of GaN can be realized not only by TMGa preflow but also by trimethyl-aluminium preflow and by trimethyl-indium preflow. A two-monolayer model was employed to explain the polarity inversion mechanism.

  20. Metal-Organic Chemical Vapor Deposition (MOCVD) Synthesis of Heteroepitaxial Pr0.7Ca0.3MnO3 Films: Effects of Processing Conditions on Structural/Morphological and Functional Properties

    PubMed Central

    Catalano, Maria R; Cucinotta, Giuseppe; Schilirò, Emanuela; Mannini, Matteo; Caneschi, Andrea; Lo Nigro, Raffaella; Smecca, Emanuele; Condorelli, Guglielmo G; Malandrino, Graziella

    2015-01-01

    Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices. PMID:26478849

  1. Metal-Organic Chemical Vapor Deposition (MOCVD) Synthesis of Heteroepitaxial Pr0.7Ca0.3MnO3 Films: Effects of Processing Conditions on Structural/Morphological and Functional Properties.

    PubMed

    Catalano, Maria R; Cucinotta, Giuseppe; Schilirò, Emanuela; Mannini, Matteo; Caneschi, Andrea; Lo Nigro, Raffaella; Smecca, Emanuele; Condorelli, Guglielmo G; Malandrino, Graziella

    2015-08-01

    Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices. PMID:26478849

  2. Chemiresistive sensing with chemically modified metal and alloy nanoparticles.

    PubMed

    Ibañez, Francisco J; Zamborini, Francis P

    2012-01-23

    This review describes the use of chemically modified pure and alloyed metal nanoparticles for chemiresistive sensing applications. Chemically modified metal nanoparticles consist of a pure or alloyed metallic core with some type of chemical coating. Researchers have studied the electronic properties of 1D, 2D, and 3D assemblies of chemically modified metal nanoparticles, and even single individual nanoparticles. The interaction with the analyte alters the conductivity of the sensitive material, providing a signal to measure the analyte concentration. This review focuses on chemiresistive sensing of a wide variety of gas- and liquid-phase analytes with metal nanoparticles coated with organothiols, ions, polymers, surfactants, and biomolecules. Different strategies used to incorporate chemically modified nanoparticles into chemiresistive sensing devices are reviewed, focusing on the different types of metal and alloy compositions, coatings, methods of assembly, and analytes (vapors, gases, liquids, biological materials), along with other important factors.

  3. Healable supramolecular polymers as organic metals.

    PubMed

    Armao, Joseph J; Maaloum, Mounir; Ellis, Thomas; Fuks, Gad; Rawiso, Michel; Moulin, Emilie; Giuseppone, Nicolas

    2014-08-13

    Organic materials exhibiting metallic behavior are promising for numerous applications ranging from printed nanocircuits to large area electronics. However, the optimization of electronic conduction in organic metals such as charge-transfer salts or doped conjugated polymers requires high crystallinity, which is detrimental to their processability. To overcome this problem, the combination of the electronic properties of metal-like materials with the mechanical properties of soft self-assembled systems is attractive but necessitates the absence of structural defects in a regular lattice. Here we describe a one-dimensional supramolecular polymer in which photoinduced through-space charge-transfer complexes lead to highly coherent domains with delocalized electronic states displaying metallic behavior. We also reveal that diffusion of supramolecular polarons in the nanowires repairs structural defects thereby improving their conduction. The ability to access metallic properties from mendable self-assemblies extends the current understanding of both fields and opens a wide range of processing techniques for applications in organic electronics. PMID:25053238

  4. Chemical Evolution of Presolar Organics in Astromaterials

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Clemett, S. J.; Messenger, Scott; Keller, L. P.

    2010-01-01

    Sub-micron, hollow organic globules reported from several carbonaceous chondrites, interplanetary dust particles, and comet Wild-2 samples returned by NASA?s Stardust mission are enriched in N-15/N-14 and D/H compared with terrestrial materials and the parent materials [1-4]. These anomalies are ascribed to the preservation of presolar cold molecular cloud material from where H, C, and N isotopic constraints point to chemical fractionation near 10 K [5]. An origin well beyond the planet forming region and their survival in meteorites suggests submicrometer organic globules were once prevalent throughout the solar nebula. The survival of the membrane structures indicates primitive meteorites and cometary dust particles would have delivered these organic precursors to the early Earth as well as other planets and satellites. The physical, chemical, and isotopic properties of the organic globules varies to its meteorite types and its lithologies. For example, organic globules in the Tagish Lake meteorite are always embedded in fined grained (poorly crystallized) saponite, and hardly encapsulated in coarse grained serpentine, even though saponite and serpentine are both main components of phyllosilicate matrix of the Tagish Lake meteorite. The organic globules are commonly observed in the carbonate-poor lithology but not in the carbonate-rich one. In Tagish Lake, isolated single globules are common, but in the Bells (CM2) meteorite, globules are mostly aggregated. We will review the evolutions of the organic globules from its birth to alteration in the parent bodies in terms of its own physical and chemical properties as well as its associated minerals.

  5. [Progress in metal-organic frameworks].

    PubMed

    Zhai, Rui; Jiao, Fenglong; Lin, Hongjun; Hao, Feiran; Li, Jiabin; Yan, Hui; Li, Nannan; Wang, Huanhuan; Jin, Zuyao; Zhang, Yangjun; Qian, Xiaohong

    2014-02-01

    Metal-organic frameworks (MOFs) are a class of crystalline materials built from organic binding ligands and metal ions through self-assembly. Currently, MOFs have drawn a growing interest among the scientific teams of various fields. Compared with conventional inorganic porous materials, MOFs possess larger specific surface areas, higher porosity and diversity of structures and functions, thus many potential applications have been proposed in the domains of gas adsorption and separation, sensors, drug delivery, catalysis or others. The combinations of MOFs and other materials such as graphene oxide, magnetic nanoparticles have obvious advantages in adsorption and separation. The appearance of novel materials greatly promotes interdisciplinary developments such as organic chemistry, inorganic chemistry, coordination chemistry, materials chemistry, life science and computer science. This article reviews the progress of MOFs in recent years, including the characteristics of MOFs, advances at home and abroad, applications, central issues of compound MOFs and the prospects in the future.

  6. Self-organized nanoporous materials for chemical separations and chemical sensing

    NASA Astrophysics Data System (ADS)

    Pandey, Bipin

    Self-organized nanoporous materials have drawn a lot of attention because the uniform, highly dense, and ordered cylindrical nanopores in these materials provide a unique platform for chemical separations and chemical sensing applications. Here, we explore self-organized nanopores of PS-b-PMMA diblock copolymer thin films and anodic gallium oxide for chemical separations and sensing applications. In the first study, cyclic voltammograms of cytochrome c on recessed nanodisk-array electrodes (RNEs) based on nanoporous films (11, 14 or 24 nm in average pore diameter; 30 nm thick) derived from polystyrene-poly(methylmethacrylate) diblock copolymers were measured. The faradic current of cytochrome c was observed on RNEs, indicating the penetration of cytochrome c (hydrodynamic diameter ≈ 4 nm) through the nanopores to the underlying electrodes. Compared to the 24-nm pores, the diffusion of cytochrome c molecules through the 11- and 14-nm pores suffered significantly larger hindrance. The results reported in this study will provide guidance in designing RNEs for size-based chemical sensing and also for controlled immobilization of biomolecules within nanoporous media for biosensors and bioreactors. In another study, conditions for the formation of self-organized nanopores of a metal oxide film were investigated. Self-organized nanopores aligned perpendicular to the film surface were obtained upon anodization of gallium films in ice-cooled 4 and 6 M aqueous H2SO4 at 10 V and 15 V. The average pore diameter was in the range of 18 ~ 40 nm, and the anodic gallium oxide was ca. 2 microm thick. In addition, anodic formation of self-organized nanopores was demonstrated for a solid gallium monolith incorporated at the end of a glass capillary. Nanoporous anodic oxide monoliths formed from a fusible metal will lead to future development of unique devices for chemical sensing and catalysis. In the final study, surface chemical property of self-organized nanoporous anodic gallium

  7. Metal-Organic Coordination Number Determined Charge Transfer Magnitude

    NASA Astrophysics Data System (ADS)

    Yang, Hung-Hsiang; Chu, Yu-Hsun; Lu, Chun-I.; Yang, Tsung-Han; Yang, Kai-Jheng; Kaun, Chao-Cheng; Hoffmann, Germar; Lin, Minn-Tsong

    2014-03-01

    By the appropriate choice of head groups and molecular ligands, various metal-organic coordination geometries can be engineered. Such metal-organic structures provide different chemical environments for molecules and give us templates to study the charge redistribution within the metal-organic interface. We created various metal-organic bonding environment by growing self-assembly nanostructures of Fe-PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) chains and networks on a Au(111) surface. Bonding environment dependent frontier molecular orbital energies are acquired by low temperature scanning tunneling microscopy and scanning tunneling spectroscopy. By comparing the frontier energies with the molecular coordination environments, we conclude that the specific coordination affects the magnitude of charge transfer onto each PTCDA in the Fe-PTCDA hybridization system. H.-H. Yang, Y.-H. Chu, C.-I Lu, T.-H. Yang, K.-J. Yang, C.-C. Kaun, G. Hoffmann, and M.-T. Lin, ACS Nano 7, 2814 (2013).

  8. Effects of AlN interlayer on the transport properties of nearly lattice-matched InAlN/GaN heterostructures grown on sapphire by pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xue, JunShuai; Zhang, JinCheng; Zhang, Wei; Li, Liang; Meng, FanNa; Lu, Ming; Ning, Jing; Hao, Yue

    2012-03-01

    The effects of AlN interlayer thickness on the transport properties of nearly lattice-matched InAlN/GaN heterostructures grown on sapphire substrates by pulsed metal organic chemical vapor deposition have been studied in detail. A very high electron mobility of approximately 1425 cm2/V s at room temperature and 5308 cm2/V s at 77 K together with a two dimensional electron gas (2DEG) density of 1.75×1013 cm-2 were obtained for nearly lattice-matched InAlN/GaN heterostructures with an optimum ˜1.2 nm thick AlN interlayer. For comparison, InAlN/GaN heterostructure without AlN interlayer exhibited a 2DEG density of 1.61×1013 cm-2 with low electron mobility of 949 and 2032 cm2/V s at room temperature and 77 K, respectively. This significant enhancement of electron mobility is mainly attributed to an optimized AlN interlayer, which provides a smooth interface between InAlN barrier layer and GaN buffer layer and hence remarkably reduces the alloy disorder scattering by suppressing carrier penetration from the GaN channel into the InAlN barrier layer. Simultaneously, a best surface morphology with a root mean square roughness value of 0.24 nm is obtained with the optimized AlN interlayer.

  9. Pulsed metal organic chemical vapor deposition of nearly latticed-matched InAlN/GaN/InAlN/GaN double-channel high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Xue, JunShuai; Zhang, JinCheng; Hou, YaoWei; Zhou, Hao; Zhang, JinFeng; Hao, Yue

    2012-01-01

    High quality, nearly lattice-matched InAlN/GaN/InAlN/GaN double-channel heterostructures were grown on sapphire by pulsed-metal-organic-chemical-vapor-deposition (PMOCVD). High electron mobility of 1414 cm2/Vs was achieved along with a two-dimensional-electron-gas density of 2.55 × 1013 cm-2. We attribute it to the high quality PMOCVD-grown InAlN barriers and, additionally, to the novel GaN layer growth between two InAlN barriers, which consists of a thin GaN spacer to prevent indium-redistribution and indium-cluster formation during the subsequent growth and a relatively thick GaN channel to enhance electron mobility. High-electron-mobility-transistors fabricated on these heterostructures with 0.8-μm-length gate exhibit a maximum drain current of 906 mA/mm and a transconductance of 186 mS/mm.

  10. Effects of Growth Temperature on Structural and Electrical Properties of InAlN/GaN Heterostructures Grown by Pulsed Metal Organic Chemical Vapor Deposition on c-Plane Sapphire

    NASA Astrophysics Data System (ADS)

    Xue, JunShuai; Zhang, JinCheng; Hao, Yue

    2013-08-01

    The authors report the effects of growth temperature on the structural and electrical properties of InAlN/GaN heterostructures, which were grown on c-plane sapphire substrates by pulsed metal organic chemical vapor deposition (PMOCVD). High resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) measurements indicate that the quality of InAlN barrier is strongly dependent on the growth temperature. It is observed that the indium composition and surface root-mean-square (rms) roughness value of InAlN barrier decrease with increasing the growth temperature, and a nearly lattice-matched InAlN/GaN heterostructure with a smooth surface is obtained at 710 °C. As a consequence, the variation of structural properties of InAlN barrier influences the electrical properties of InAlN/GaN heterostructures, and high electron mobility in excess of 1400 cm2 V-1 s-1 is achieved at an optimized growth temperature window of InAlN barrier layer between 710 and 730 °C.

  11. Intersubband absorption properties of high Al content AlxGa1−xN/GaN multiple quantum wells grown with different interlayers by metal organic chemical vapor deposition

    PubMed Central

    2012-01-01

    High Al content AlxGa1−xN/GaN multiple quantum well (MQW) films with different interlayers were grown by metal organic chemical vapor deposition. These MQWs were designed to achieve intersubband (ISB) absorption in the mid-infrared spectral range. We have considered two growth conditions, with AlGaN interlayer and GaN/AlN superlattice (SL) interlayer, both deposited on GaN-on-sapphire templates. Atomic force microscopy images show a relatively rough surface with atomic-step terraces and surface depression, mainly dominated by dislocations. High-resolution X-ray diffraction and transmission electron microscopy analyses indicate that good crystalline quality of the AlGaN/GaN MQW layer could be achieved when the AlGaN interlayer is inserted. The ISB absorption with a peak at 3.7 μm was demonstrated in MQW films with AlGaN interlayer. However, we have not observed the infrared absorption in MQW films with GaN/AlN SL interlayer. It is believed that the high dislocation density and weaker polarization that resulted from the rough interface are determinant factors of vanished ISB absorption for MQW films with the GaN/AlN SL interlayer. PMID:23181766

  12. Comparison of electrical properties and deep traps in p-Al{sub x}Ga{sub 1-x}N grown by molecular beam epitaxy and metal organic chemical vapor deposition

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Dabiran, A. M.; Chow, P. P.; Wowchak, A. M.; Lee, In-Hwan; Ju, Jin-Woo; Pearton, S. J.

    2009-10-01

    The electrical properties, admittance spectra, microcathodoluminescence, and deep trap spectra of p-AlGaN films with an Al mole fraction up to 45% grown by both metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were compared. The ionization energy of Mg increases from 0.15 to 0.17 eV in p-GaN to 0.3 eV in 45% Al p-AlGaN. In p-GaN films grown by MBE and MOCVD and in MOCVD grown p-AlGaN, we observed additional acceptors with a concentration an order lower than that of Mg acceptors, with a higher hole capture cross section and an ionization energy close to that of Mg. For some of the MBE grown p-AlGaN, we also detected the presence of additional acceptor centers, but in that case the centers were located near the p-AlGaN layer interface with the semi-insulating AlGaN buffer and showed activation energies considerably lower than those of Mg.

  13. Double-sided reel-to-reel metal-organic chemical vapor deposition system of YBa{sub 2}Cu{sub 3}O{sub 7-δ} thin films

    SciTech Connect

    Zhang, Fei; Xiong, Jie Liu, Xin; Zhao, Ruipeng; Zhao, Xiaohui; Tao, Bowan; Li, Yanrong

    2014-07-01

    Two-micrometer thick YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) films have been successfully deposited on both sides of LaAlO{sub 3} single crystalline substrates by using a home-made reel-to-reel metal-organic chemical vapor deposition (MOCVD) system, which has two opposite symmetrical shower heads and a special-designed heater. This technique can simultaneously fabricate double-sided films with high deposition rate up to 500 nm/min, and lead to doubling current carrying capability of YBCO, especially for coated conductors (CCs). X-ray diffraction analysis showed that YBCO films were well crystallized and highly epitaxial with the full width at half maximum values of 0.2° ∼ 0.3° for the rocking curves of (005) YBCO and 1.0° for Φ-scans of (103) YBCO. Scanning electron microscope revealed dense, crack-free, slightly rough surface with Ba-Cu-O precipitates. The films showed critical current density (J{sub c}, 77 K, 0 T) of about 1 MA/cm{sup 2}, and overall critical current of 400 A/cm, ascribed to the double-sided structure. Our results also demonstrated that the temperature and composition in the deposition zone were uniform, which made MOCVD preparation of low cost and high performance double-sided YBCO CCs more promising for industrialization.

  14. Defects and disorder in metal organic frameworks.

    PubMed

    Cheetham, Anthony K; Bennett, Thomas D; Coudert, François-Xavier; Goodwin, Andrew L

    2016-03-14

    The wide-ranging properties of metal organic frameworks (MOFs) rely in many cases on the presence of defects within their structures and the disorder that is inevitably associated with such defects. In the present work we review several aspects of defects in MOFs, ranging from simple substitutional defects at metal cation or ligand positions, to correlated defects on a larger length scale and the extreme case of disorder associated with amorphous MOFs. We consider both porous and dense MOFs, and focus particularly on the way in which defects and disorder can be used to tune physical properties such as gas adsorption, catalysis, photoluminescence, and electronic and mechanical properties.

  15. Defects and disorder in metal organic frameworks.

    PubMed

    Cheetham, Anthony K; Bennett, Thomas D; Coudert, François-Xavier; Goodwin, Andrew L

    2016-03-14

    The wide-ranging properties of metal organic frameworks (MOFs) rely in many cases on the presence of defects within their structures and the disorder that is inevitably associated with such defects. In the present work we review several aspects of defects in MOFs, ranging from simple substitutional defects at metal cation or ligand positions, to correlated defects on a larger length scale and the extreme case of disorder associated with amorphous MOFs. We consider both porous and dense MOFs, and focus particularly on the way in which defects and disorder can be used to tune physical properties such as gas adsorption, catalysis, photoluminescence, and electronic and mechanical properties. PMID:26836459

  16. Metal hybrid nanoparticles for catalytic organic and photochemical transformations.

    PubMed

    Song, Hyunjoon

    2015-03-17

    In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly have multiple components including active metal nanoparticles and metal oxide supports. On the other hand, as nanochemistry has rapidly been developed and been applied to various fields, many researchers have begun to discuss the impact of nanochemistry on heterogeneous catalysis. Metal hybrid nanoparticles bearing multiple components are structurally very close to the actual catalysts, and their uniform and controllable morphology is suitable for investigating the relationship between the structure and the catalytic properties in detail. In this Account, we introduce four typical structures of metal hybrid nanoparticles that can be used to conduct catalytic organic and photochemical reactions. Metal@silica (or metal oxide) yolk-shell nanoparticles, in which metal cores exist in internal voids surrounded by thin silica (or metal oxide) shells, exhibited extremely high thermal and chemical stability due to the geometrical protection of the silica layers against the metal cores. The morphology of the metal cores and the pore density of the hollow shells were precisely adjusted to optimize the reaction activity and diffusion rates of the reactants. Metal@metal oxide core-shell nanoparticles and inverted structures, where the cores supported the shells serving an active surface, exhibited high activity with no diffusion barriers for the reactants and products. These nanostructures were used as effective catalysts for various organic and gas-phase reactions, including hydrogen transfer, Suzuki coupling, and steam methane reforming. In contrast to the yolk- and core-shell structures, an asymmetric arrangement of distinct domains generated acentric dumbbells and tipped rods. A large domain of each component added multiple

  17. Metal-organic frameworks as sensory materials and imaging agents.

    PubMed

    Liu, Demin; Lu, Kuangda; Poon, Christopher; Lin, Wenbin

    2014-02-17

    Metal-organic frameworks (MOFs) are a class of hybrid materials self-assembled from organic bridging ligands and metal ion/cluster connecting points. The combination of a variety of organic linkers, metal ions/clusters, and structural motifs can lead to an infinite array of new materials with interesting properties for many applications. In this Forum Article, we discuss the design and applications of MOFs in chemical sensing and biological imaging. The first half of this article focuses on the development of MOFs as chemical sensors by highlighting how unique attributes of MOFs can be utilized to enhance sensitivity and selectivity. We also discuss some of the issues that need to be addressed in order to develop practically useful MOF sensors. The second half of this article focuses on the design and applications of nanoscale MOFs (NMOFs) as imaging contrast agents. NMOFs possess several interesting attributes, such as high cargo loading capacity, ease of postmodification, tunable size and shape, and intrinsic biodegradability, to make them excellent candidates as imaging contrast agents. We discuss the use of representative NMOFs in magnetic resonance imaging (MRI), X-ray computed tomography (CT), and optical imaging. Although still in their infancy, we believe that the compositional tunability and mild synthetic conditions of NMOF imaging agents should greatly facilitate their further development for clinical translation.

  18. Metal-organic framework@microporous organic network: hydrophobic adsorbents with a crystalline inner porosity.

    PubMed

    Chun, Jiseul; Kang, Sungah; Park, Nojin; Park, Eun Ji; Jin, Xing; Kim, Kwang-Dae; Seo, Hyun Ook; Lee, Sang Moon; Kim, Hae Jin; Kwon, Woo Hyun; Park, Young-Kwon; Kim, Ji Man; Kim, Young Dok; Son, Seung Uk

    2014-05-14

    This work reports the synthesis and application of metal-organic framework (MOF)@microporous organic network (MON) hybrid materials. Coating a MOF, UiO-66-NH2, with MONs forms hybrid microporous materials with hydrophobic surfaces. The original UiO-66-NH2 shows good wettability in water. In comparison, the MOF@MON hybrid materials float on water and show excellent performance for adsorption of a model organic compound, toluene, in water. Chemical etching of the MOF results in the formation of hollow MON materials. PMID:24786337

  19. Metallic taste from electrical and chemical stimulation.

    PubMed

    Lawless, Harry T; Stevens, David A; Chapman, Kathryn W; Kurtz, Anne

    2005-03-01

    A series of three experiments investigated the nature of metallic taste reports after stimulation with solutions of metal salts and after stimulation with metals and electric currents. To stimulate with electricity, a device was fabricated consisting of a small battery affixed to a plastic handle with the anode side exposed for placement on the tongue or oral tissues. Intensity of taste from metals and batteries was dependent upon the voltage and was more robust in areas dense in fungiform papillae. Metallic taste was reported from stimulation with ferrous sulfate solutions, from metals and from electric stimuli. However, reports of metallic taste were more frequent when the word 'metallic' was presented embedded in a list of choices, as opposed to simple free-choice labeling. Intensity decreased for ferrous sulfate when the nose was occluded, consistent with a decrease in retronasal smell, as previously reported. Intensity of taste evoked by copper metal, bimetallic stimuli (zinc/copper) or small batteries (1.5-3 V) was not affected by nasal occlusion. This difference suggests two distinct mechanisms for evocation of metallic taste reports, one dependent upon retronasal smell and a second mediated by oral chemoreceptors. PMID:15741603

  20. Metallization with generic metallo-organic inks

    NASA Technical Reports Server (NTRS)

    Vest, G. M.

    1983-01-01

    The use and fabrication of metallo-organic films are discussed. Metallo-organic compounds are ones in which a metal is linked to a long chain carbon ligand through a hetero atom such as O, S, N, P or As. Films formed by the thermal decomposition of these metallo-organics are called MOD films. In order that the products of decomposition contain only CO2, H2O, and in rare cases nitrogen compounds, and to avoid S containing products, the use of a set of metallo-organic compounds for ink fabrication where the linking hetero atom was oxygen was pioneered. These links were made from commercially available carboxylates, or synthesized from commonly available reagents. The processing is described and the molecular design criteria are given. The particular carboxylates or amine carboxylates selected were the octoates or neodecanoates, and they are described.

  1. Porosity in metal-organic framework glasses.

    PubMed

    Thornton, A W; Jelfs, K E; Konstas, K; Doherty, C M; Hill, A J; Cheetham, A K; Bennett, T D

    2016-03-01

    The porosity of a glass formed by melt-quenching a metal-organic framework, has been characterized by positron annihilation lifetime spectroscopy. The results reveal porosity intermediate between the related open and dense crystalline frameworks ZIF-4 and ZIF-zni. A structural model for the glass was constructed using an amorphous polymerization algorithm, providing additional insight into the gas-inaccessible nature of porosity and the possible applications of hybrid glasses.

  2. Purification of metal-organic framework materials

    SciTech Connect

    Farha, Omar K.; Hupp, Joseph T.

    2015-06-30

    A method of purification of a solid mixture of a metal-organic framework (MOF) material and an unwanted second material by disposing the solid mixture in a liquid separation medium having a density that lies between those of the wanted MOF material and the unwanted material, whereby the solid mixture separates by density differences into a fraction of wanted MOF material and another fraction of unwanted material.

  3. Purification of metal-organic framework materials

    SciTech Connect

    Farha, Omar K.; Hupp, Joseph T.

    2012-12-04

    A method of purification of a solid mixture of a metal-organic framework (MOF) material and an unwanted second material by disposing the solid mixture in a liquid separation medium having a density that lies between those of the wanted MOF material and the unwanted material, whereby the solid mixture separates by density differences into a fraction of wanted MOF material and another fraction of unwanted material.

  4. Multiferroic materials based on organic transition-metal molecular nanowires.

    PubMed

    Wu, Menghao; Burton, J D; Tsymbal, Evgeny Y; Zeng, Xiao Cheng; Jena, Puru

    2012-09-01

    We report on the density functional theory aided design of a variety of organic ferroelectric and multiferroic materials by functionalizing crystallized transition-metal molecular sandwich nanowires with chemical groups such as -F, -Cl, -CN, -NO(2), ═O, and -OH. Such functionalized polar wires exhibit molecular reorientation in response to an electric field. Ferroelectric polarizations as large as 23.0 μC/cm(2) are predicted in crystals based on fully hydroxylized sandwich nanowires. Furthermore, we find that organic nanowires formed by sandwiching transition-metal atoms in croconic and rhodizonic acids, dihydroxybenzoquinone, dichloro-dihydroxy-p-benzoquinone, or benzene decorated by -COOH groups exhibit ordered magnetic moments, leading to a multiferroic organometallic crystal. When crystallized through hydrogen bonds, the microscopic molecular reorientation translates into a switchable polarization through proton transfer. A giant interface magnetoelectric response that is orders of magnitude greater than previously reported for conventional oxide heterostructure interfaces is predicted. PMID:22881120

  5. Multiphoton harvesting metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Quah, Hong Sheng; Chen, Weiqiang; Schreyer, Martin K.; Yang, Hui; Wong, Ming Wah; Ji, Wei; Vittal, Jagadese J.

    2015-08-01

    Multiphoton upconversion is a process where two or more photons are absorbed simultaneously to excite an electron to an excited state and, subsequently, the relaxation of electron gives rise to the emission of a photon with frequency greater than those of the absorbed photons. Materials possessing such property attracted attention due to applications in biological imaging, photodynamic therapy, three-dimensional optical data storage, frequency-upconverted lasing and optical power limiting. Here we report four-photon upconversion in metal-organic frameworks containing the ligand, trans, trans-9,10-bis(4-pyridylethenyl)anthracene. The ligand has a symmetrical acceptor-π-donor-π-acceptor structure and a singlet biradical electronic ground state, which boosted its multiphoton absorption cross-sections. We demonstrate that the upconversion efficiency can be enhanced by Förster resonance energy transfer within host-guest metal-organic frameworks consisting of encapsulated high quantum yielding guest molecules. Using these strategies, metal-organic framework materials, which can exhibit frequency-upconverted photoluminescence excited by simultaneous multiphoton absorption, can be rationally designed and synthesized.

  6. Metal Vinylidenes as Catalytic Species in Organic Reactions

    PubMed Central

    McClory, Andrew

    2008-01-01

    Organic vinylidene species have found limited use in organic synthesis due to their inaccessibility. In contrast, metal vinylidenes are much more stable, and may be readily accessed through transition metal activation of terminal alkynes. These electrophilic species may be trapped by a number of nucleophiles. Additionally, metal vinylidenes can participate in pericyclic reactions and processes involving migration of a metal ligand to the vinylidene species. This review addresses the reactions and applications of metal vinylidenes in organic synthesis. PMID:18172846

  7. Chemical characterization and metal abundance in Sri Lankan serpentine soils

    NASA Astrophysics Data System (ADS)

    Vithanage, M. S.; Rajapaksha, A. U.; Ok, Y. S.; Oze, C.

    2012-12-01

    Chemical weathering of ultramafic rocks and their related soils provide localized sources of metal contamination. In Sri Lanka, rural communities live in close proximity to these rocks and soils and utilize associated groundwaters where human intake of these high metal sources may have adverse human health effects. This study investigates metal abundances and variations in Sri Lankan serpentine soils to begin evaluating potential human health hazards. Specifically, we examine serpentinite occurrences at Ussangoda, Wasgamuwa, Ginigalpelessa, and Indikolapelessa located at the geological boundary between the Highland and Vijayan Complexes. The pH of the soils are near neutral (6.26 to 7.69) with soil electrical conductivities (EC) ranging from 33.5 to 129.9 μS cm-1, a range indicative of relatively few dissolved salts and/or major dissolved inorganic solutes. The highest EC is from the Ussangoda soil which may be due to the atmospheric deposition of salt spray from the sea. Organic carbon contents of the soils range from 1.09% to 2.58%. The highest organic carbon percentage is from the Wasgamuwa soil which is located in a protected preserve. X-ray fluorescence (XRF) spectrometry and total metal digestion results show that all serpentine soils are Fe-, Cr-, and Ni-rich with abundant aluminosilicate minerals. Nickel is highest in the Ussangoda soil (6,459 mg kg-1), while Cr (>10,000 mg kg-1), Co (441 mg kg-1) and Mn (2,263 mg kg-1) are highest in the Wasgamuwa serpentine soil. Additionally, Mn (2,200 mg kg-1) and Co (400 mg kg-1) are present at high concentrations in the Wasgamuwa and Ginigalpelessa soils respectively. Electron microprobe mapping demonstrates that these heavy metals are not homogeneously distributed where Cr is specifically associated with Al and Fe phases. Metal speciation of these serpentine soils are currently being investigated using X-ray absorption spectroscopy (XAS) to provide better constraints with regards to their mobility and toxicity.

  8. Effects of metals on chromosomes of higher organisms.

    PubMed

    Sharma, A; Talukder, G

    1987-01-01

    An analysis of the available data on the clastogenic effects of metals and their compounds on higher organisms indicates some general trends. Following chronic exposure to subtoxic doses, a decrease in mitotic frequency and an increase in the number of chromosomal abnormalities are observed. These effects are usually directly proportional to the dose applied and the duration of treatment within the threshold limits. Recovery after acute treatment is inversely related to the dosage. The ultimate expression of the effects depends on certain factors, including the mode and vehicle of administration; the form administered; the test system used; the rate of detoxification, distribution, and retention in the different tissues; and interaction with foreign and endogenous substances as well as the mode of action with the biological macromolecules. In mammals, the clastogenic activity of the metals within each vertical group of the periodic table is directly proportional to the increase in atomic weight, electropositivity, and solubility of the metallic cations in water and lipids, except for Li and Ba. This pattern of inherent cytotoxicity increases with successive periods in the horizontal level. It is enhanced by the formation of covalent and coordinate covalent complexes by heavy metals with the biological macromolecules. In plants, the solubility of the metals in water is of much greater importance. The degree of dissociation of metallic salts and the rate of absorption affect significantly the frequency of chromosomal aberrations. In assessing the effects of environmental metal pollution, the presence of other metals and toxic chemicals and the level of nutrition should be taken into account, since in nature, metals occur in combination and these factors modify the cytotoxic effects to a significant extent. PMID:3545801

  9. TMVOC, simulator for multiple volatile organic chemicals

    SciTech Connect

    Pruess, Karsten; Battistelli, Alfredo

    2003-03-25

    TMVOC is a numerical simulator for three-phase non-isothermal flow of water, soil gas, and a multicomponent mixture of volatile organic chemicals (VOCs) in multidimensional heterogeneous porous media. It is an extension of the TOUGH2 general-purpose simulation program developed at the Lawrence Berkeley National Laboratory. TMVOC is designed for applications to contamination problems that involve hydrocarbon fuel or organic solvent spills in saturated and unsaturated zones. It can model contaminant behavior under ''natural'' environmental conditions, as well as for engineered systems, such as soil vapor extraction, groundwater pumping, or steam-assisted source remediation. TMVOC is upwards compatible with T2VOC (Falta et al., 1995) and can be initialized from T2VOC-style initial conditions. The main enhancements in TMVOC relative to T2VOC are as follows: a multicomponent mixture of volatile organic chemicals can be modeled; any and all combinations of the three phases water-oil-gas are treated; several non-condensible gases may be present; diffusion is treated in all phases in a manner that is fully coupled with phase partitioning. This paper gives a brief summary of the methodology used in TMVOC as well as highlighting some implementation issues. Simulation of a NAPL spill and subsequent remediation is discussed for a 2-D vertical section of a saturated-unsaturated flow problem.

  10. Microporous Metal Organic Materials for Hydrogen Storage

    SciTech Connect

    S. G. Sankar; Jing Li; Karl Johnson

    2008-11-30

    We have examined a number of Metal Organic Framework Materials for their potential in hydrogen storage applications. Results obtained in this study may, in general, be summarized as follows: (1) We have identified a new family of porous metal organic framework materials with the compositions M (bdc) (ted){sub 0.5}, {l_brace}M = Zn or Co, bdc = biphenyl dicarboxylate and ted = triethylene diamine{r_brace} that adsorb large quantities of hydrogen ({approx}4.6 wt%) at 77 K and a hydrogen pressure of 50 atm. The modeling performed on these materials agree reasonably well with the experimental results. (2) In some instances, such as in Y{sub 2}(sdba){sub 3}, even though the modeling predicted the possibility of hydrogen adsorption (although only small quantities, {approx}1.2 wt%, 77 K, 50 atm. hydrogen), our experiments indicate that the sample does not adsorb any hydrogen. This may be related to the fact that the pores are extremely small or may be attributed to the lack of proper activation process. (3) Some samples such as Zn (tbip) (tbip = 5-tert butyl isophthalate) exhibit hysteresis characteristics in hydrogen sorption between adsorption and desorption runs. Modeling studies on this sample show good agreement with the desorption behavior. It is necessary to conduct additional studies to fully understand this behavior. (4) Molecular simulations have demonstrated the need to enhance the solid-fluid potential of interaction in order to achieve much higher adsorption amounts at room temperature. We speculate that this may be accomplished through incorporation of light transition metals, such as titanium and scandium, into the metal organic framework materials.

  11. Impact of metals on the biodegradation of organic pollutants.

    PubMed Central

    Sandrin, Todd R; Maier, Raina M

    2003-01-01

    Forty percent of hazardous waste sites in the United States are co-contaminated with organic and metal pollutants. Data from both aerobic and anaerobic systems demonstrate that biodegradation of the organic component can be reduced by metal toxicity. Metal bioavailability, determined primarily by medium composition/soil type and pH, governs the extent to which metals affect biodegradation. Failure to consider bioavailability rather than total metal likely accounts for much of the enormous variability among reports of inhibitory concentrations of metals. Metals appear to affect organic biodegradation through impacting both the physiology and ecology of organic degrading microorganisms. Recent approaches to increasing organic biodegradation in the presence of metals involve reduction of metal bioavailability and include the use of metal-resistant bacteria, treatment additives, and clay minerals. The addition of divalent cations and adjustment of pH are additional strategies currently under investigation. PMID:12826480

  12. Melt-Quenched Glasses of Metal-Organic Frameworks.

    PubMed

    Bennett, Thomas D; Yue, Yuanzheng; Li, Peng; Qiao, Ang; Tao, Haizheng; Greaves, Neville G; Richards, Tom; Lampronti, Giulio I; Redfern, Simon A T; Blanc, Frédéric; Farha, Omar K; Hupp, Joseph T; Cheetham, Anthony K; Keen, David A

    2016-03-16

    Crystalline solids dominate the field of metal-organic frameworks (MOFs), with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration to framework chemistry and topology to expand the phenomenon of the melting of 3D MOFs, linking crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to facilitate the melting of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic nonmetallic, organic, and metallic), and retain the basic metal-ligand connectivity of crystalline MOFs, which connects their mechanical properties to their starting chemical composition. The transfer of functionality from crystal to glass points toward new routes to tunable, functional hybrid glasses. PMID:26885940

  13. Governing metal-organic frameworks towards high stability.

    PubMed

    Li, Na; Xu, Jian; Feng, Rui; Hu, Tong-Liang; Bu, Xian-He

    2016-06-30

    Metal-organic frameworks (MOFs) constructed with metal ions/clusters and organic ligands have emerged as an important family of porous materials for various applications. However, the stability of this class of materials is crucial for their practical applications, which might be improved by varying their chemical composition and/or structurally tuning them. To fabricate MOFs with high stability, several strategies for enhancing the stability of MOFs have been developed, in which the strength of metal-ligand bonds is especially considered: the use of highly charged cations and higher pKa ligands, and varying the chemical functionality of linkers. On the other hand, the regulation of their structural architectures is also investigated: interpenetrated frameworks, multi-walled frameworks, and self-strengthening of the frameworks. In addition, the surface modification can also improve the stability of the materials. In this review, we introduce and summarize these strategies from the viewpoint of structural tuning and component choosing, providing useful instructions for the further design and synthesis of MOFs with high-level stability.

  14. High-quality uniaxial In(x)Ga(1-x)N/GaN multiple quantum well (MQW) nanowires (NWs) on Si(111) grown by metal-organic chemical vapor deposition (MOCVD) and light-emitting diode (LED) fabrication.

    PubMed

    Ra, Yong-Ho; Navamathavan, R; Park, Ji-Hyeon; Lee, Cheul-Ro

    2013-03-01

    This article describes the growth and device characteristics of vertically aligned high-quality uniaxial p-GaN/InxGa1-xN/GaN multiple quantum wells (MQW)/n-GaN nanowires (NWs) on Si(111) substrates grown by metal-organic chemical vapor deposition (MOCVD) technique. The resultant nanowires (NWs), with a diameter of 200-250 nm, have an average length of 2 μm. The feasibility of growing high-quality NWs with well-controlled indium composition MQW structure is demonstrated. These resultant NWs grown on Si(111) substrates were utilized for fabricating vertical-type light-emitting diodes (LEDs). The steep and intense photoluminescence (PL) and cathodoluminescence (CL) spectra are observed, based on the strain-free NWs on Si(111) substrates. High-resolution transmission electron microscopy (HR-TEM) analysis revealed that the MQW NWs are grown along the c-plane with uniform thickness. The current-voltage (I-V) characteristics of these NWs exhibited typical p-n junction LEDs and showed a sharp onset voltage at 2.75 V in the forward bias. The output power is linearly increased with increasing current. The result indicates that the pulsed MOCVD technique is an effective method to grow uniaxial p-GaN/InxGa1-xN/GaN MQW/n-GaN NWs on Si(111), which is more advantageous than other growth techniques, such as molecular beam epitaxy. These results suggest the uniaxial NWs are promising to allow flat-band quantum structures, which can enhance the efficiency of LEDs.

  15. Using chemical organization theory for model checking

    PubMed Central

    Kaleta, Christoph; Richter, Stephan; Dittrich, Peter

    2009-01-01

    Motivation: The increasing number and complexity of biomodels makes automatic procedures for checking the models' properties and quality necessary. Approaches like elementary mode analysis, flux balance analysis, deficiency analysis and chemical organization theory (OT) require only the stoichiometric structure of the reaction network for derivation of valuable information. In formalisms like Systems Biology Markup Language (SBML), however, information about the stoichiometric coefficients required for an analysis of chemical organizations can be hidden in kinetic laws. Results: First, we introduce an algorithm that uncovers stoichiometric information that might be hidden in the kinetic laws of a reaction network. This allows us to apply OT to SBML models using modifiers. Second, using the new algorithm, we performed a large-scale analysis of the 185 models contained in the manually curated BioModels Database. We found that for 41 models (22%) the set of organizations changes when modifiers are considered correctly. We discuss one of these models in detail (BIOMD149, a combined model of the ERK- and Wnt-signaling pathways), whose set of organizations drastically changes when modifiers are considered. Third, we found inconsistencies in 5 models (3%) and identified their characteristics. Compared with flux-based methods, OT is able to identify those species and reactions more accurately [in 26 cases (14%)] that can be present in a long-term simulation of the model. We conclude that our approach is a valuable tool that helps to improve the consistency of biomodels and their repositories. Availability: All data and a JAVA applet to check SBML-models is available from http://www.minet.uni-jena.de/csb/prj/ot/tools Contact: dittrich@minet.uni-jena.de Supplementary information: Supplementary data are available at Bioinformatics online. PMID:19468053

  16. Complexed metals in hazardous waste: Limitations of conventional chemical oxidation

    SciTech Connect

    Diel, B.N.; Kuchynka, D.J.; Borchert, J.

    1994-12-31

    In the management of hazardous waste, more is known regarding the treatment of metals than about the fixation, destruction and/or immobilization of any other hazardous constituent group. Metals are the only hazardous constituents which cannot be destroyed, and so must be converted to their least soluble and/or reactive form to prevent reentry into the environment. The occurrence of complexed metals, e.g., metallocyanides, and/or chelated metals, e.g., M{center_dot}EDTA in hazardous waste streams presents formidable challenges to conventional waste treatment practices. This paper presents the results of extensive research into the destruction (chemical oxidation) of metallocyanides and metal-chelates, defines the utility and limitations of conventional chemical oxidation approaches, illustrates some of the waste management difficulties presented by such species, and presents preliminary data on the UV/H{sub 2}O{sub 2} photodecomposition of chelated metals.

  17. Electronic and chemical structure of metal-silicon interfaces

    NASA Technical Reports Server (NTRS)

    Grunthaner, P. J.; Grunthaner, F. J.

    1984-01-01

    This paper reviews our current understanding of the near-noble metal silicides and the interfaces formed with Si(100). Using X-ray photoemission spectroscopy, we compare the chemical composition and electronic structure of the room temperature metal-silicon and reacted silicide-silicon interfaces. The relationship between the interfacial chemistry and the Schottky barrier heights for this class of metals on silicon is explored.

  18. Increasing the Stability of Metal-Organic Frameworks

    DOE PAGESBeta

    Bosch, Mathieu; Zhang, Muwei; Zhou, Hong-Cai

    2014-01-01

    Metal-organic frameworks (MOFs) are a new category of advanced porous materials undergoing study by many researchers for their vast variety of both novel structures and potentially useful properties arising from them. Their high porosities, tunable structures, and convenient process of introducing both customizable functional groups and unsaturated metal centers have afforded excellent gas sorption and separation ability, catalytic activity, luminescent properties, and more. However, the robustness and reactivity of a given framework are largely dependent on its metal-ligand interactions, where the metal-containing clusters are often vulnerable to ligand substitution by water or other nucleophiles, meaning that the frameworks may collapsemore » upon exposure even to moist air. Other frameworks may collapse upon thermal or vacuum treatment or simply over time. This instability limits the practical uses of many MOFs. In order to further enhance the stability of the framework, many different approaches, such as the utilization of high-valence metal ions or nitrogen-donor ligands, were recently investigated. This review details the efforts of both our research group and others to synthesize MOFs possessing drastically increased chemical and thermal stability, in addition to exemplary performance for catalysis, gas sorption, and separation.« less

  19. Heterogeneity within a Mesoporous Metal-Organic Framework with Three Distinct Metal-Containing Building Units.

    PubMed

    Tu, Binbin; Pang, Qingqing; Ning, Erlong; Yan, Wenqing; Qi, Yi; Wu, Doufeng; Li, Qiaowei

    2015-10-28

    Materials built from multiple constituents have revealed emerging properties that are beyond linear integration of those from single components. We report a mesoporous metal-organic framework made from three geometrically distinct metal-containing secondary building units (SBUs) as a result of topological induction. The combinations of the Cu-based triangular, Zn-based octahedral, and Zn-based square pyramidal SBUs have created four types of cages in the network, despite that only one organic linker pyrazolecarboxylate was used. The longest distance for molecules maneuvering inside the largest cage is 5.2 nm. Furthermore, the complex and diversified pore environments allow the installation of various new functionalities in the framework as well as the expedited Ag nanoparticle formation in the pores. As presented in the molecule movement diagram, the crystal has provided specific arrangements of cages and apertures with distinct chemical features for guests transporting between the pores. PMID:26335899

  20. Heterogeneity within a Mesoporous Metal-Organic Framework with Three Distinct Metal-Containing Building Units.

    PubMed

    Tu, Binbin; Pang, Qingqing; Ning, Erlong; Yan, Wenqing; Qi, Yi; Wu, Doufeng; Li, Qiaowei

    2015-10-28

    Materials built from multiple constituents have revealed emerging properties that are beyond linear integration of those from single components. We report a mesoporous metal-organic framework made from three geometrically distinct metal-containing secondary building units (SBUs) as a result of topological induction. The combinations of the Cu-based triangular, Zn-based octahedral, and Zn-based square pyramidal SBUs have created four types of cages in the network, despite that only one organic linker pyrazolecarboxylate was used. The longest distance for molecules maneuvering inside the largest cage is 5.2 nm. Furthermore, the complex and diversified pore environments allow the installation of various new functionalities in the framework as well as the expedited Ag nanoparticle formation in the pores. As presented in the molecule movement diagram, the crystal has provided specific arrangements of cages and apertures with distinct chemical features for guests transporting between the pores.

  1. Biomimicry in metal-organic materials

    SciTech Connect

    Zhang, MW; Gu, ZY; Bosch, M; Perry, Z; Zhou, HC

    2015-06-15

    Nature has evolved a great number of biological molecules which serve as excellent constructional or functional units for metal-organic materials (MOMs). Even though the study of biomimetic MOMs is still at its embryonic stage, considerable progress has been made in the past few years. In this critical review, we will highlight the recent advances in the design, development and application of biomimetic MOMs, and illustrate how the incorporation of biological components into MOMs could further enrich their structural and functional diversity. More importantly, this review will provide a systematic overview of different methods for rational design of MOMs with biomimetic features. Published by Elsevier B.V.

  2. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H.; Baumann, Theodore F.

    2007-10-23

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  3. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H.; Baumann, Theodore F.

    2003-09-02

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  4. Hydrogen Storage in Metal-Organic Frameworks

    SciTech Connect

    Omar M. Yaghi

    2012-04-26

    Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up

  5. Comparison of rapid screening assays using organic chemicals

    SciTech Connect

    Beach, S.A.; Robideau, R.R.

    1994-12-31

    In a continuation of a study presented last year using metals, the sensitivity of short term toxicity tests is examined using common organic chemicals. In toxicity testing, the focus has shifted from the traditional long-term studies utilizing the mortality of complex, multicellular eukaryotic organisms as the endpoint towards short-term studies in which transformation of biochemical pathways are monitored. The relative sensitivity of aquatic screening techniques are compared to the standardized 48-hr Daphnia magna and Ceriodaphnia dubia, 96-hr fathead minnow and 96-hr algal acute assays. The short-term test procedures investigated are: dehydrogenase enzyme activity assays utilizing triphenyltetrazolium chloride (TTC) and resazurin as the calorimetric indicators; TOXI-Chromotest, inhibition of {beta}-galactosidase; reduction in bioluminescence output utilizing the Microtox{reg_sign} test; nitrification inhibition assays with a commercial preparation of nitrifying bacteria (Nitroseed{trademark}) and municipal activated sludge; respiration inhibition assays with a commercial preparation of heterotrophic bacteria (Polytox{reg_sign}) and activated sludge; inhibition of root growth in terrestrial plants; and galactosidase inhibition through the use of a fluorometrically tagged substrate with the Daphnia magna IQ{trademark} test. Toxicity values generated by this laboratory on commonly used organic chemicals are compared.

  6. Organic Chemicals from Bioprocesses in China

    NASA Astrophysics Data System (ADS)

    Huang, Jin; Huang, Lei; Lin, Jianping; Xu, Zhinan; Cen, Peilin

    Over the last 20 years, China has successfully established a modern biotechnology industry from almost nothing. Presently, China is a major producer of a vast array of products involving bioprocesses, for some China is even the world's top producer. The ever-increasing list of products includes organic acids, amino acids, antibiotics, solvents, chiral chemicals, biopesticides, and biopolymers. Herein, the research and development of bioprocesses in China will be reviewed briefly. We will concentrate on three categories of products: small molecules produced via fermentation, biopolymers produced via fermentation and small chemicals produced by enzyme-catalyzed reactions. In comparison with the traditional chemical process, in which, nonrenewable mineral resources are generally used, products in the first and second categories noted above can use renewable bioresources as raw materials. The bioprocesses are generally energy saving and environmentally benign. For products developed via the third category, although the raw materials still need to be obtained from mineral resources, the biocatalysts are more effective with higher selectivity and productivity, and the bioprocesses occur under ambient temperature and pressure, therefore, these are "green processes." Most of the products such as citric acid, xanthan and acrylamide etc., discussed in this paper have been in large-scale commercial production in China. Also introduced herein are three scientists, Prof. Shen Yinchu, Prof. Ouyang Pingkai and Prof. Chen Guoqiang, and six enterprises, Anhui Fengyuan Biochemical Co. Ltd., Shandong Hiland Biotechnology Co. Ltd., Shandong Fufeng Fermentation Co. Ltd., Shandong Bausch & Lomb-Freda Pharmaceutical Co. Ltd., Zhejiang Hangzhou Xinfu Pharmaceutical Co. Ltd., and Changzhou Changmao Biochemical Engineering Co. Ltd.; they have all contributed a great deal to research and development in the commercialization of bioprocesses.

  7. Organic chemicals from bioprocesses in China.

    PubMed

    Huang, Jin; Huang, Lei; Lin, Jianping; Xu, Zhinan; Cen, Peilin

    2010-01-01

    Over the last 20 years, China has successfully established a modern biotechnology industry from almost nothing. Presently, China is a major producer of a vast array of products involving bioprocesses, for some China is even the world's top producer. The ever-increasing list of products includes organic acids, amino acids, antibiotics, solvents, chiral chemicals, biopesticides, and biopolymers. Herein, the research and development of bioprocesses in China will be reviewed briefly. We will concentrate on three categories of products: small molecules produced via fermentation, biopolymers produced via fermentation and small chemicals produced by enzyme-catalyzed reactions. In comparison with the traditional chemical process, in which, nonrenewable mineral resources are generally used, products in the first and second categories noted above can use renewable bioresources as raw materials. The bioprocesses are generally energy saving and environmentally benign. For products developed via the third category, although the raw materials still need to be obtained from mineral resources, the biocatalysts are more effective with higher selectivity and productivity, and the bioprocesses occur under ambient temperature and pressure, therefore, these are "green processes." Most of the products such as citric acid, xanthan and acrylamide etc., discussed in this paper have been in large-scale commercial production in China. Also introduced herein are three scientists, Prof. Shen Yinchu, Prof. Ouyang Pingkai and Prof. Chen Guoqiang, and six enterprises, Anhui Fengyuan Biochemical Co. Ltd., Shandong Hiland Biotechnology Co. Ltd., Shandong Fufeng Fermentation Co. Ltd., Shandong Bausch & Lomb-Freda Pharmaceutical Co. Ltd., Zhejiang Hangzhou Xinfu Pharmaceutical Co. Ltd., and Changzhou Changmao Biochemical Engineering Co. Ltd.; they have all contributed a great deal to research and development in the commercialization of bioprocesses. PMID:20549466

  8. Organic chemicals from bioprocesses in China.

    PubMed

    Huang, Jin; Huang, Lei; Lin, Jianping; Xu, Zhinan; Cen, Peilin

    2010-01-01

    Over the last 20 years, China has successfully established a modern biotechnology industry from almost nothing. Presently, China is a major producer of a vast array of products involving bioprocesses, for some China is even the world's top producer. The ever-increasing list of products includes organic acids, amino acids, antibiotics, solvents, chiral chemicals, biopesticides, and biopolymers. Herein, the research and development of bioprocesses in China will be reviewed briefly. We will concentrate on three categories of products: small molecules produced via fermentation, biopolymers produced via fermentation and small chemicals produced by enzyme-catalyzed reactions. In comparison with the traditional chemical process, in which, nonrenewable mineral resources are generally used, products in the first and second categories noted above can use renewable bioresources as raw materials. The bioprocesses are generally energy saving and environmentally benign. For products developed via the third category, although the raw materials still need to be obtained from mineral resources, the biocatalysts are more effective with higher selectivity and productivity, and the bioprocesses occur under ambient temperature and pressure, therefore, these are "green processes." Most of the products such as citric acid, xanthan and acrylamide etc., discussed in this paper have been in large-scale commercial production in China. Also introduced herein are three scientists, Prof. Shen Yinchu, Prof. Ouyang Pingkai and Prof. Chen Guoqiang, and six enterprises, Anhui Fengyuan Biochemical Co. Ltd., Shandong Hiland Biotechnology Co. Ltd., Shandong Fufeng Fermentation Co. Ltd., Shandong Bausch & Lomb-Freda Pharmaceutical Co. Ltd., Zhejiang Hangzhou Xinfu Pharmaceutical Co. Ltd., and Changzhou Changmao Biochemical Engineering Co. Ltd.; they have all contributed a great deal to research and development in the commercialization of bioprocesses.

  9. Transcutaneous metal absorption following chemical burn injury.

    PubMed

    Neligan, P C

    1996-05-01

    A 33-year-old metal refinery worker sustained a 40 per cent TBSA burn injury from a mixture containing acids and salts of nickel and cobalt. High levels of both nickel and cobalt were detected in both serum and urine, necessitating treatment with EDTA, a chelating agent. No detrimental effects of either nickel or cobalt have so far been detected, though the patient is being followed in the long term. PMID:8726265

  10. Metal-organic framework materials with ultrahigh surface areas

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Wilmer, Christopher E.; Eryazici, Ibrahim; Snurr, Randall Q.; Gomez-Gualdron, Diego A.; Borah, Bhaskarjyoti

    2015-12-22

    A metal organic framework (MOF) material including a Brunauer-Emmett-Teller (BET) surface area greater than 7,010 m.sup.2/g. Also a metal organic framework (MOF) material including hexa-carboxylated linkers including alkyne bond. Also a metal organic framework (MOF) material including three types of cuboctahedron cages fused to provide continuous channels. Also a method of making a metal organic framework (MOF) material including saponifying hexaester precursors having alkyne bonds to form a plurality of hexa-carboxylated linkers including alkyne bonds and performing a solvothermal reaction with the plurality of hexa-carboxylated linkers and one or more metal containing compounds to form the MOF material.

  11. Single-crystal Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} thin films prepared by metal-organic chemical vapor deposition: Systematic compositional variation of electronic and optical properties

    SciTech Connect

    Foster, C.M.; Bai, G.; Csencsits, R.; Vetrone, J.; Jammy, R.; Wills, L.A.; Carr, E.; Amano, J.

    1997-03-01

    Single-crystal thin films of Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) covering the full compositional range (0{le}{ital x}{le}1) were deposited by metal-organic chemical vapor deposition. Epitaxial SrRuO{sub 3}(001) thin films grown on SrTiO{sub 3}(001) substrates by rf-magnetron sputter deposition served as template electrode layers. X-ray diffraction, energy-dispersive x-ray spectroscopy, atomic force microscopy, transmission electron microscopy, and optical waveguiding were used to characterize the crystalline structure, composition, surface morphology, microstructure, refractive index, and film thickness of the deposited films. The PZT films were single crystalline for all compositions exhibiting cube-on-cube growth epitaxy with the substrate and showed very high degrees of crystallinity and orientation. The films exhibited typical root mean square surface roughness of {approximately}1.0{endash}2.5 nm. For tetragonal films, the surface morphology was dominated by grain tilting resulting from ferroelectric domain formation. We report the systematic compositional variation of the optical, dielectric, polarization, and electronic transport properties of these single-crystalline PZT thin films. The solid-solution phase diagram of the PZT system for thin films differs from the bulk due to epitaxy-induced strains and interfacial defect formation. High values of remanant polarization (30{endash}55 {mu}C/cm{sup 2}) were observed for ferroelectric compositions in the range of 0.8{le}{ital x}{le}0.2. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225 to 650. The coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm for {ital x}=0.8. The undoped films exhibited both high resistivity and dielectric-breakdown strength (10{sup 13}{endash}10{sup 14} {Omega}cm at 100 kV/cm and 300{endash}700 kV/cm, respectively). {copyright} {ital 1997 American Institute of Physics.}

  12. Homochiral helical metal-organic frameworks of group 1 metals.

    PubMed

    Reger, Daniel L; Leitner, Andrew; Smith, Mark D; Tran, T Thao; Halasyamani, P Shiv

    2013-09-01

    The reactions of (S)-2-(1,8-naphthalimido)propanoic acid (HL(ala)) and (S)-2-(1,8-naphthalimido)-3-hydroxypropanoic acid (HL(ser)), protonated forms of ligands that contain a carboxylate donor group, an enantiopure chiral center, and a 1,8-naphthalimide π···π stacking supramolecular tecton and in the case of HL(ser) an alcohol functional group, with the appropriate alkali metal hydroxide followed by a variety of crystallization methods leads to the formation of crystalline K(L(ala))(MeOH) (1), K(L(ala))(H2O) (2), Na(L(ala))(H2O) (3), KL(ser) (4), CsL(ser) (5), and CsL(ala) (6). Each of these new complexes has a solid state structure based on six-coordinate metals linked into homochiral helical rod secondary building unit (SBU) central cores. In addition to the bonding of the carboxylate and solvent (in the case of L(ser) the ligand alcohol) to the metals, both oxygens on the 1,8-naphthalimide act as donor groups. One naphthalimide oxygen bonds to the same helical rod SBU as the carboxylate group of that ligand forming a chelate ring. The other naphthalimide oxygen bonds to adjacent SBUs. In complexes 1-3, this inter-rod link has a square arrangement bonding four other rods forming a three-dimensional enantiopure metal-organic framework (MOF) structure, whereas in 4-6 this link has a linear arrangement bonding two other rods forming a two-dimensional, sheet structure. In the latter case, the third dimension is supported exclusively by interdigitated π···π stacking interactions of the naphthalimide supramolecular tecton, forming enantiopure supramolecular MOF solids. Compounds 1-3 lose the coordinated solvent when heating above 100 °C. For 1, the polycrystalline powder reverts to 1 only by recrystallization from methanol, whereas compounds 2 and 3 undergo gas/solid, single-crystal to single-crystal transformations to form dehydrated compounds 2* and 3*, and rehydration occurs when crystals of these new complexes are left out in air. The reversible single

  13. A critical review and evaluation of bioproduction of organic chemicals

    SciTech Connect

    Leeper, S.A.; Andrews, G.F.

    1991-12-31

    Dependence on petroleum as the primary feedstock for production of chemicals cannot continue indefinitely. Bioconversion could provide an alternate route to production of organic chemicals. A wide range of commodity chemicals and potentially new chemicals can be produced via bioconversion of biomass. However, before large-scale bioproduction of organic chemicals become a reality issues related to economics, feedstock availability, environment, and energy requirements must be addressed. In this paper, these issues are discussed, and promising potential candidates for bioproduction are identified.

  14. Chemical Reactivity Perspective into the Group 2B Metals Halides.

    PubMed

    Özen, Alimet Sema; Akdeniz, Zehra

    2016-06-30

    Chemical reactivity descriptors within the conceptual density functional theory can be used to understand the nature of the interactions between two monomers of the Group 2B metal halides. This information might be valuable in the development of adequate force law parameters for simulations in the liquid state. In this study, MX2 monomers and dimers, where M = Zn, Cd, Hg and X = F, Cl, Br, I, were investigated in terms of chemical reactivity descriptors. Relativistic effects were taken into account using the effective core potential (ECP) approach. Correlations were produced between global and local reactivity descriptors and dimerization energies. Results presented in this work represent the first systematic investigation of Group 2B metal halides in the literature from a combined point of view of both relativistic effects and chemical reactivity descriptors. Steric effects were found to be responsible for the deviation from the chemical reactivity principles. They were introduced into the chemical reactivity descriptors such as local softness.

  15. Metal-contaminated soil remediation by means of paper mill sludges addition: chemical and ecotoxicological evaluation.

    PubMed

    Calace, N; Campisi, T; Iacondini, A; Leoni, M; Petronio, B M; Pietroletti, M

    2005-08-01

    Metal pollution of soils is a great environmental problem. The major risks due to metal pollution of soil consist of leaching to groundwater and potential toxicity to plants and/or animals. The objective of this study is to evaluate by means of chemical and ecotoxicological approach the effects of paper mill sludge addition on the mobile metal fraction of polluted metal soils. The study was carried out on acidic soil derived from mining activities and thus polluted with heavy metals, and on two paper mill sludges having different chemical features. The results obtained by leaching experiments showed that the addition of a paper mill sludge, consisting mainly of carbonates, silicates and organic matter, to a heavy-metal polluted soil produces a decrease of available metal forms. The carbonate content seems to play a key role in the chemical stabilisation of metals and consequently in a decrease of toxicity of soil. The leached solutions have a non-toxic effect. The mild remediation by addition of sludge has moreover a lasting effect.

  16. Heavy metals fractionation and organic matter mineralisation in contaminated calcareous soil amended with organic materials.

    PubMed

    Clemente, Rafael; Escolar, Angeles; Bernal, M Pilar

    2006-10-01

    Degradation of organic matter (OM) from organic amendments used in the remediation of metal contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of two differing organic amendments on OM mineralisation and fractionation of heavy metals in a contaminated soil were investigated in an incubation experiment. The treatments were: control unamended soil, soil amended with fresh cow manure, and soil amended with a compost having a high maturity degree. The soil used was characteristic of the mining area at La Unión (Murcia, Spain) with 28% CaCO(3) and sandy-loam texture (pH 7.7; 2602 mg kg(-1)Zn; 1572 mg kg(-1)Pb). Manure and compost C-mineralisation after 56 days (24% and 3.8%, respectively) were below values reported previously for uncontaminated soils. Both amendments favoured Zn and Pb fixation, particularly the manure. Mn solubility increased at the beginning of the experiment due to a pH effect, and only Cu solubility increased through organic matter chelation in both amended soils.

  17. Kinetically tuned dimensional augmentation as a versatile synthetic route towards robust metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Feng, Dawei; Wang, Kecheng; Wei, Zhangwen; Chen, Ying-Pin; Simon, Cory M.; Arvapally, Ravi K.; Martin, Richard L.; Bosch, Mathieu; Liu, Tian-Fu; Fordham, Stephen; Yuan, Daqiang; Omary, Mohammad A.; Haranczyk, Maciej; Smit, Berend; Zhou, Hong-Cai

    2014-12-01

    Metal-organic frameworks with high stability have been pursued for many years due to the sustainability requirement for practical applications. However, researchers have had great difficulty synthesizing chemically ultra-stable, highly porous metal-organic frameworks in the form of crystalline solids, especially as single crystals. Here we present a kinetically tuned dimensional augmentation synthetic route for the preparation of highly crystalline and extremely robust metal-organic frameworks with a preserved metal cluster core. Through this versatile synthetic route, we obtain large single crystals of 34 different iron-containing metal-organic frameworks. Among them, PCN-250(Fe2Co) exhibits high volumetric uptake of hydrogen and methane, and is also stable in water and aqueous solutions with a wide range of pH values.

  18. Kinetically tuned dimensional augmentation as a versatile synthetic route towards robust metal-organic frameworks.

    PubMed

    Feng, Dawei; Wang, Kecheng; Wei, Zhangwen; Chen, Ying-Pin; Simon, Cory M; Arvapally, Ravi K; Martin, Richard L; Bosch, Mathieu; Liu, Tian-Fu; Fordham, Stephen; Yuan, Daqiang; Omary, Mohammad A; Haranczyk, Maciej; Smit, Berend; Zhou, Hong-Cai

    2014-12-04

    Metal-organic frameworks with high stability have been pursued for many years due to the sustainability requirement for practical applications. However, researchers have had great difficulty synthesizing chemically ultra-stable, highly porous metal-organic frameworks in the form of crystalline solids, especially as single crystals. Here we present a kinetically tuned dimensional augmentation synthetic route for the preparation of highly crystalline and extremely robust metal-organic frameworks with a preserved metal cluster core. Through this versatile synthetic route, we obtain large single crystals of 34 different iron-containing metal-organic frameworks. Among them, PCN-250(Fe2Co) exhibits high volumetric uptake of hydrogen and methane, and is also stable in water and aqueous solutions with a wide range of pH values.

  19. Metal-Organic Heat Carrier Nanofluids

    SciTech Connect

    McGrail, B. Peter; Thallapally, Praveen K.; Blanchard, Jeremy; Nune, Satish K.; Jenks, Jeromy WJ; Dang, Liem X.

    2013-09-01

    Nanofluids, dispersions of metal or oxide nanoparticles in a base working fluid, are being intensively studied due to improvements they offer in thermal properties of the working fluid. However, these benefits have been erratically demonstrated and proven impacts on thermal conductivity are modest and well described from long-established effective medium theory. In this paper, we describe a new class of metal-organic heat carrier (MOHC) nanofluid that offers potential for a larger performance boost in thermal vapor-liquid compression cycles. MOHCs are nanophase porous coordination solids designed to reversibly uptake the working fluid molecules in which the MOHCs are suspended. Additional heat can be extracted in a heat exchanger or solar collector from the endothermic enthalpy of desorption, which is then released as the nanofluid transits through a power generating device such as a turboexpander. Calculations for an R123 MOHC nanofluid indicated potential for up to 15% increase in power output. Capillary tube experiments show that liquid-vapor transitions occur without nanoparticle deposition on the tube walls provided entrance Reynolds number exceeds approximately 100.

  20. High-temperature metal-organic magnets.

    PubMed

    Jain, Rajsapan; Kabir, Khayrul; Gilroy, Joe B; Mitchell, Keith A R; Wong, Kin-chung; Hicks, Robin G

    2007-01-18

    For over two decades there have been intense efforts aimed at the development of alternatives to conventional magnets, particularly materials comprised in part or wholly of molecular components. Such alternatives offer the prospect of realizing magnets fabricated through controlled, low-temperature, solution-based chemistry, as opposed to high-temperature metallurgical routes, and also the possibility of tuning magnetic properties through synthesis. However, examples of magnetically ordered molecular materials at or near room temperature are extremely rare, and the properties of these materials are often capricious and difficult to reproduce. Here we present a versatile solution-based route to a new class of metal-organic materials exhibiting magnetic order well above room temperature. Reactions of the metal (M) precursor complex bis(1,5-cyclooctadiene)nickel with three different organics A-TCNE (tetracyanoethylene), TCNQ (7,7,8,8-tetracyanoquinodimethane) or DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone)--proceed via electron transfer from nickel to A and lead to materials containing Ni(II) ions and reduced forms of A in a 2:1 Ni:A ratio--that is, opposite to that of conventional (low Curie temperature) MA(2)-type magnets. These materials also contain oxygen-based species within their architectures. Magnetic characterization of the three compounds reveals spontaneous field-dependent magnetization and hysteresis at room temperature, with ordering temperatures well above ambient. The unusual stoichiometry and striking magnetic properties highlight these three compounds as members of a class of stable magnets that are at the interface between conventional inorganic magnets and genuine molecule-based magnets.

  1. Metal-adeninate vertices for the construction of an exceptionally porous metal-organic framework.

    PubMed

    An, Jihyun; Farha, Omar K; Hupp, Joseph T; Pohl, Ehmke; Yeh, Joanne I; Rosi, Nathaniel L

    2012-01-03

    Metal-organic frameworks comprising metal-carboxylate cluster vertices and long, branched organic linkers are the most porous materials known, and therefore have attracted tremendous attention for many applications, including gas storage, separations, catalysis and drug delivery. To increase metal-organic framework porosity, the size and complexity of linkers has increased. Here we present a promising alternative strategy for constructing mesoporous metal-organic frameworks that addresses the size of the vertex rather than the length of the organic linker. This approach uses large metal-biomolecule clusters, in particular zinc-adeninate building units, as vertices to construct bio-MOF-100, an exclusively mesoporous metal-organic framework. Bio-MOF-100 exhibits a high surface area (4,300 m(2) g(-1)), one of the lowest crystal densities (0.302 g cm(-3)) and the largest metal-organic framework pore volume reported to date (4.3 cm(3) g(-1)).

  2. Effects of toxic metals and chemicals on biofilm and biocorrosion.

    PubMed

    Fang, Herbert H P; Xu, Li-Chong; Chan, Kwong-Yu

    2002-11-01

    Microbes in marine biofilms aggregated into clusters and increased the production of extracellular polymeric substances (EPS), by over 100% in some cases, when the seawater media containing toxic metals and chemicals, such as Cd(II), Cu(II), Pb(II), Zn(II), AI(III), Cr(III), glutaraldehyde, and phenol. The formation of microbial cluster and the increased production of EPS, which contained 84-92% proteins and 8-16% polysaccharides, accelerated the corrosion of the mild steel. However, there was no quantitative relationship between the degree of increased corrosion and the toxicity of metals/chemicals towards sulfate-reducing bacteria, or the increased EPS production.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  4. Ultrahigh porosity in metal-organic frameworks.

    PubMed

    Furukawa, Hiroyasu; Ko, Nakeun; Go, Yong Bok; Aratani, Naoki; Choi, Sang Beom; Choi, Eunwoo; Yazaydin, A Ozgür; Snurr, Randall Q; O'Keeffe, Michael; Kim, Jaheon; Yaghi, Omar M

    2010-07-23

    Crystalline solids with extended non-interpenetrating three-dimensional crystal structures were synthesized that support well-defined pores with internal diameters of up to 48 angstroms. The Zn4O(CO2)6 unit was joined with either one or two kinds of organic link, 4,4',4''-[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate (BTE), 4,4',44''-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate (BBC), 4,4',44''-benzene-1,3,5-triyl-tribenzoate (BTB)/2,6-naphthalenedicarboxylate (NDC), and BTE/biphenyl-4,4'-dicarboxylate (BPDC), to give four metal-organic frameworks (MOFs), MOF-180, -200, -205, and -210, respectively. Members of this series of MOFs show exceptional porosities and gas (hydrogen, methane, and carbon dioxide) uptake capacities. For example, MOF-210 has Brunauer-Emmett-Teller and Langmuir surface areas of 6240 and 10,400 square meters per gram, respectively, and a total carbon dioxide storage capacity of 2870 milligrams per gram. The volume-specific internal surface area of MOF-210 (2060 square meters per cubic centimeter) is equivalent to the outer surface of nanoparticles (3-nanometer cubes) and near the ultimate adsorption limit for solid materials. PMID:20595583

  5. Chemical compatibility of structural materials in alkali metals

    SciTech Connect

    Natesan, K.; Rink, D.L.; Haglund, R.

    1995-04-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments.

  6. Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: a review.

    PubMed

    Wan Ngah, W S; Hanafiah, M A K M

    2008-07-01

    The application of low-cost adsorbents obtained from plant wastes as a replacement for costly conventional methods of removing heavy metal ions from wastewater has been reviewed. It is well known that cellulosic waste materials can be obtained and employed as cheap adsorbents and their performance to remove heavy metal ions can be affected upon chemical treatment. In general, chemically modified plant wastes exhibit higher adsorption capacities than unmodified forms. Numerous chemicals have been used for modifications which include mineral and organic acids, bases, oxidizing agent, organic compounds, etc. In this review, an extensive list of plant wastes as adsorbents including rice husks, spent grain, sawdust, sugarcane bagasse, fruit wastes, weeds and others has been compiled. Some of the treated adsorbents show good adsorption capacities for Cd, Cu, Pb, Zn and Ni.

  7. Metal accumulation by stream bryophytes, related to chemical speciation.

    PubMed

    Tipping, E; Vincent, C D; Lawlor, A J; Lofts, S

    2008-12-01

    Metal accumulation by aquatic bryophytes was investigated using data for headwater streams of differing chemistry. The Windermere Humic Aqueous Model (WHAM) was applied to calculate chemical speciation, including competitive proton and metal interactions with external binding sites on the plants. The speciation modelling approach gives smaller deviations between observed and predicted bryophyte contents of Cu, Zn, Cd and Pb than regressions based on total filtered metal concentrations. If all four metals, and Ni, are considered together, the WHAM predictions are superior at the 1% level. Optimised constants for bryophyte binding by the trace metals are similar to those for humic substances and simple carboxylate ligands. Bryophyte contents of Na, Mg and Ca are approximately explained by binding at external sites, while most of the K is intracellular. Oxide phases account for some of the Al, and most of the Mn, Fe and Co.

  8. Role of transition metal ferrocyanides (II) in chemical evolution

    NASA Astrophysics Data System (ADS)

    Kamaluddin; Nath, Mala; Deopujari, Sushama W.; Sharma, Archana

    1990-05-01

    Due to ease of formation of cyanide under prebiotic conditions, cyanide ion might have formed stable complexes with transition metal ions on the primitive earth. In the course of chemical evolution insoluble metal cyano complexes, which settled at the bottom of primeval sea could have formed peptide and metal amino acid complexes through adsorption processes of amino acids onto these metal cyano complexes. Adsorption of amino acids such as glycine, aspartic acid, and histidine on copper ferrocyanide and zinc ferrocyanide have been studied over a wide pH range of 3.6 8.5. Amino acids were adsorbed on the metal ferrocyanide complexes for different time periods. The progress of the adsorption was followed spectro-photometrically using ninhydrin reagent. Histidine was found to show maximum adsorption on both the adsorbents at neutral pH. Zinc ferrocyanide exhibits good sorption behaviour for all the three amino acids used in these investigations.

  9. The Generation of an Organic Inverted Chemical Garden.

    PubMed

    Pampalakis, Georgios

    2016-05-10

    A chemical garden based on iron salt that grows in organic solvents and ions is demonstrated for the first time. This prototype chemical garden develops in an inverted orientation, thus providing evidence that downward growth is feasible.

  10. CHEMICAL DYNAMICS OF HYDROPHOBIC ORGANIC CONTAMINANTS DURING RESUSPENSION

    EPA Science Inventory

    Laboratory experiments were designed to study the chemical-particle dynamics of toxic hydrophobic organics during resuspension episodes using a particle entrainment simulator (PES). The purpose was to obtain insight into chemical transport mechanisms during resuspension. Informat...

  11. Selective Metal-vapor Deposition on Organic Surfaces.

    PubMed

    Tsujioka, Tsuyoshi

    2016-02-01

    Selective metal-vapor deposition signifies that metal-vapor atoms are deposited on a hard organic surface, but not on a soft (low glass transition temperature, low Tg ) surface. In this paper, we introduce the origin, extension, and applications of selective metal-vapor deposition. An amorphous photochromic diarylethene film shows light-controlled selective metal-vapor deposition, which is caused by a large Tg change based on photoisomerization, but various organic surfaces, including organic crystal and polymers, can be utilized for achieving selective metal-vapor deposition. Various applications of selective metal-vapor deposition, including cathode patterning of organic light-emitting devices, micro-thin-film fuses, multifunctional diffraction gratings, in-plane electrical bistability for memory devices, and metal-vapor integration, have been demonstrated.

  12. Preparation, Characterization, and Postsynthetic Modification of Metal-Organic Frameworks: Synthetic Experiments for an Undergraduate Laboratory Course in Inorganic Chemistry

    ERIC Educational Resources Information Center

    Sumida, Kenji; Arnold, John

    2011-01-01

    Metal-organic frameworks (MOFs) are crystalline materials that are composed of an infinite array of metal nodes (single ions or clusters) linked to one another by polyfunctional organic compounds. Because of their extraordinary surface areas and high degree of control over the physical and chemical properties, these materials have received much…

  13. Metal-Organic Frameworks: Bimetallic Metal-Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion (Small 17/2016).

    PubMed

    Zou, Ruyi; Li, Pei-Zhou; Zeng, Yong-Fei; Liu, Jia; Zhao, Ruo; Duan, Hui; Luo, Zhong; Wang, Jin-Gui; Zou, Ruqiang; Zhao, Yanli

    2016-05-01

    On page 2334, R. Q. Zou, Y. L. Zhao, and co-workers present a porous metal-organic framework (MOF) that serves as a platform for studying the metal exchange effect on both CO2 adsorption and catalytic fixation. The effect is demonstrated by catalytic CO2 cycloaddition with propylene oxide to produce propylene carbonate. Molecular dynamic simulations are carried out to further confirm the catalytic performance of these MOFs on chemical fixation of CO2 to carbonates. This research sheds light on how metal exchange could influence the intrinsic properties of MOFs.

  14. A homochiral metal-organic porous material for enantioselective separation and catalysis

    NASA Astrophysics Data System (ADS)

    Seo, Jung Soo; Whang, Dongmok; Lee, Hyoyoung; Jun, Sung Im; Oh, Jinho; Jeon, Young Jin; Kim, Kimoon

    2000-04-01

    Inorganic zeolites are used for many practical applications that exploit the microporosity intrinsic to their crystal structures. Organic analogues, which are assembled from modular organic building blocks linked through non-covalent interactions, are of interest for similar applications. These range from catalysis, separation and sensor technology to optoelectronics, with enantioselective separation and catalysis being especially important for the chemical and pharmaceutical industries. The modular construction of these analogues allows flexible and rational design, as both the architecture and chemical functionality of the micropores can, in principle, be precisely controlled. Porous organic solids with large voids and high framework stability have been produced, and investigations into the range of accessible pore functionalities have been initiated. For example, catalytically active organic zeolite analogues are known, as are chiral metal-organic open-framework materials. However, the latter are only available as racemic mixtures, or lack the degree of framework stability or void space that is required for practical applications. Here we report the synthesis of a homochiral metal-organic porous material that allows the enantioselective inclusion of metal complexes in its pores and catalyses a transesterification reaction in an enantioselective manner. Our synthesis strategy, which uses enantiopure metal-organic clusters as secondary building blocks, should be readily applicable to chemically modified cluster components and thus provide access to a wide range of porous organic materials suitable for enantioselective separation and catalysis.

  15. Ethanol-mediated metal transfer printing on organic films.

    PubMed

    Aldakov, Dmitry; Tondelier, Denis; Palacin, Serge; Bonnassieux, Yvan

    2011-03-01

    Ethanol-mediated metal transfer printing (mTP) is a soft method, which allows to efficiently deposit metals onto various organic surfaces for applications in organic electronics. This simple approach in based on the stronger adhesion of the metals to the organic materials in the presence of thin ethanol layer between the metallized PDMS and the substrate due to the capillary action. Patterns with a resolution of at least 20 μm have been obtained on organic polymeric materials and photoresists without heating or applied pressure. Compared to other methods ethanol mediated mTP is considerably faster and has smaller limitations on the stamp depth. Residual silicone layer detected on the metal surface after the transfer by XPS studies has been mostly removed by UV/ozone treatment. Organic field-effect transistors (OTFTs) based on the metal electrodes deposited by mTP have been successfully fabricated and tested.

  16. A metal-free organic-inorganic aqueous flow battery

    SciTech Connect

    Huskinson, B; Marshak, MP; Suh, C; Er, S; Gerhardt, MR; Galvin, CJ; Chen, XD; Aspuru-Guzik, A; Gordon, RG; Aziz, MJ

    2014-01-08

    As the fraction of electricity generation from intermittent renewable sources-such as solar or wind-grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output(1,2). In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form(3-5). Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts(6,7). Here we describe a class of energy storage materials that exploits the favourable chemical and electro-chemical properties of a family of molecules known as quinones. The example we demonstrate is ametal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br-2/Br- redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals(8). This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of p-aromatic redox-active organic molecules instead of redox-active metals

  17. A metal-free organic-inorganic aqueous flow battery.

    PubMed

    Huskinson, Brian; Marshak, Michael P; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R; Galvin, Cooper J; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G; Aziz, Michael J

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br(-) redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals

  18. A metal-free organic-inorganic aqueous flow battery.

    PubMed

    Huskinson, Brian; Marshak, Michael P; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R; Galvin, Cooper J; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G; Aziz, Michael J

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br(-) redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals

  19. A metal-free organic-inorganic aqueous flow battery

    NASA Astrophysics Data System (ADS)

    Huskinson, Brian; Marshak, Michael P.; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R.; Galvin, Cooper J.; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G.; Aziz, Michael J.

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br- redox couple, yields a peak galvanic power density exceeding 0.6Wcm-2 at 1.3Acm-2. Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals represents a new and

  20. Effect of plants on the bioavailability of metals and other chemical properties of biosolids in a column study.

    PubMed

    Huynh, Trang T; Laidlaw, W Scott; Singh, Balwant; Zhang, Hao; Baker, Alan J M

    2012-10-01

    The effects of metal-accumulating plants (Salix x reichardtii and Populus balsamifera) on the chemical properties and dynamics of metals in biosolids were investigated using different techniques including diffusive gradients in thin films (DGT), sequential extraction procedures and partitioning coefficient (K(d)). Plants could effectively extract Cd, Ni, and Zn and decreased dissolved organic carbon (DOC). The presence of plants increased the potential bioavailability of these metals, as assessed by an increase in the ratio of metal measured by DGT and metals in the solution. The plants affected the Cd, Ni, and Zn pools (soluble/exchangeable; Fe/Mn oxide and organic matter bound) characterised by sequential extraction and K(d) but did not reduce the total metals in either substrate. However, plants had no effect on Cu, presumably because of the effective buffering of available Cu by organic matter in both solution and solid phases. A high density of plant roots was associated with increased leaching of metals.

  1. GaN nanowire arrays by a patterned metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Wang, K. C.; Yuan, G. D.; Wu, R. W.; Lu, H. X.; Liu, Z. Q.; Wei, T. B.; Wang, J. X.; Li, J. M.; Zhang, W. J.

    2016-04-01

    We developed an one-step and two-step metal-assisted chemical etching method to produce self-organized GaN nanowire arrays. In one-step approach, GaN nanowire arrays are synthesized uniformly on GaN thin film surface. However, in a two-step etching processes, GaN nanowires are formed only in metal uncovered regions, and GaN regions with metal-covering show nano-porous sidewalls. We propose that nanowires and porous nanostructures are tuned by sufficient and limited etch rate, respectively. PL spectra shows a red-shift of band edge emission in GaN nanostructures. The formation mechanism of nanowires was illustrated by two separated electrochemical reactions occur simultaneously. The function of metals and UV light was illustrated by the scheme of potential relationship between energy bands in Si, GaN and standard hydrogen electrode potential of solution and metals.

  2. Pyrolysis of pine and gasification of pine chars--influence of organically bound metals.

    PubMed

    Aho, A; DeMartini, N; Pranovich, A; Krogell, J; Kumar, N; Eränen, K; Holmbom, B; Salmi, T; Hupa, M; Murzin, D Yu

    2013-01-01

    Pyrolysis of pine and gasification of pine chars was studied in this work, focusing on the influence of organically bound metals. Selective leaching of the major ash-forming elements in pine wood was performed with different acids, namely, nitric, sulfuric, hydrochloric and oxalic acids. No other major changes in the chemical composition of the biomass were observed except the removal of the metals. The effect of organically bound sodium, potassium, magnesium and calcium was studied in both pyrolysis and gasification. Removal of the metals had a positive effect on the pyrolysis, resulting in higher bio-oil, lower char and gas yields. PMID:23196217

  3. Large-scale screening of hypothetical metal-organic frameworks.

    PubMed

    Wilmer, Christopher E; Leaf, Michael; Lee, Chang Yeon; Farha, Omar K; Hauser, Brad G; Hupp, Joseph T; Snurr, Randall Q

    2011-11-06

    Metal-organic frameworks (MOFs) are porous materials constructed from modular molecular building blocks, typically metal clusters and organic linkers. These can, in principle, be assembled to form an almost unlimited number of MOFs, yet materials reported to date represent only a tiny fraction of the possible combinations. Here, we demonstrate a computational approach to generate all conceivable MOFs from a given chemical library of building blocks (based on the structures of known MOFs) and rapidly screen them to find the best candidates for a specific application. From a library of 102 building blocks we generated 137,953 hypothetical MOFs and for each one calculated the pore-size distribution, surface area and methane-storage capacity. We identified over 300 MOFs with a predicted methane-storage capacity better than that of any known material, and this approach also revealed structure-property relationships. Methyl-functionalized MOFs were frequently top performers, so we selected one such promising MOF and experimentally confirmed its predicted capacity.

  4. Elimination kinetic model for organic chemicals in earthworms.

    PubMed

    Dimitrova, N; Dimitrov, S; Georgieva, D; Van Gestel, C A M; Hankard, P; Spurgeon, D; Li, H; Mekenyan, O

    2010-08-15

    Mechanistic understanding of bioaccumulation in different organisms and environments should take into account the influence of organism and chemical depending factors on the uptake and elimination kinetics of chemicals. Lipophilicity, metabolism, sorption (bioavailability) and biodegradation of chemicals are among the important factors that may significantly affect the bioaccumulation process in soil organisms. This study attempts to model elimination kinetics of organic chemicals in earthworms by accounting for the effects of both chemical and biological properties, including metabolism. The modeling approach that has been developed is based on the concept for simulating metabolism used in the BCF base-line model developed for predicting bioaccumulation in fish. Metabolism was explicitly accounted for by making use of the TIMES engine for simulation of metabolism and a set of principal transformations. Kinetic characteristics of transformations were estimated on the basis of observed kinetics data for the elimination of organic chemicals from earthworms. PMID:20185163

  5. Probing buried organic-organic and metal-organic heterointerfaces by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Shibuta, Masahiro; Eguchi, Toyoaki; Watanabe, Yoshio; Nakajima, Atsushi; Son, Jin-Young; Oji, Hiroshi

    2012-11-26

    We present a nondestructive characterization method for buried hetero-interfaces for organic/organic and metal/organic systems using hard x-ray photoelectron spectroscopy (HAXPES) which can probe electronic states at depths deeper than {approx}10 nm. A significant interface-derived signal showing a strong chemical interaction is observed for Au deposited onto a C{sub 60} film, while there is no such additional feature for copper phthalocyanine deposited onto a C{sub 60} film reflecting the weak interaction between the molecules in the latter case. A depth analysis with HAXPES reveals that a Au-C{sub 60} intermixed layer with a thickness of 5.1 nm is formed at the interface.

  6. Metal oxide charge transport material doped with organic molecules

    DOEpatents

    Forrest, Stephen R.; Lassiter, Brian E.

    2016-08-30

    Doping metal oxide charge transport material with an organic molecule lowers electrical resistance while maintaining transparency and thus is optimal for use as charge transport materials in various organic optoelectronic devices such as organic photovoltaic devices and organic light emitting devices.

  7. Chemical reactions of organic compounds on clay surfaces

    SciTech Connect

    Soma, Yuko; Soma, Mitsuyuki )

    1989-11-01

    Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Broensted or Lewis acidity of clay minerals.

  8. LOSS OF ORGANIC CHEMICALS IN SOIL: PURE COMPOUND TREATABILITY STUDIES

    EPA Science Inventory

    Comprehensive screening data on the treatability of 32 organic chemicals in soil were developed. Of the evaluated chemicals, 22 were phenolic compounds. Aerobic batch laboratory microcosm experiments were conducted using two soils: an acidic clay soil with <1% organic matter and ...

  9. Synthetic Organic Chemicals: United States Production and Sales, 1976.

    ERIC Educational Resources Information Center

    Adams, Roger; And Others

    This is the sixth annual report of the U.S. Trade Commission on domestic production and sales of synthetic organic chemicals and the raw materials from which they are made. The report consists of 15 sections, each covering a specified group (based primarily on use) of organic chemicals as follows: tar and tar crudes; primary products from…

  10. COSOLVENCY OF PARTIALLY MISCIBLE ORGANIC SOLVENTS ON THE SOLUBILITY OF HYDROPHOBIC ORGANIC CHEMICALS

    EPA Science Inventory

    The cosolvency of completely miscible organic solvents (CMOSs) and partially miscible organic solvents (PMOSs) on the solubility of hydrophobic organic chemicals (HOCs) was examined, with an emphasis on PMOSs. Measured solubilities were compared with predictions from the log- lin...

  11. Acute toxicity handbook of chemicals to estuarine organisms

    SciTech Connect

    Mayer, F.L.

    1987-04-01

    All acute toxicity data developed by the Gulf Breeze Environmental Research Laboratory, U.S. Environmental Protection Agency, since 1961 were evaluated for quality. A data base was established for 1175 tests with 197 chemicals and 52 species of estuarine organisms. The chemicals represent all major groups of pesticides, as well as numerous industrial and inorganic chemicals.

  12. Metal transport and chemical heterogeneity in early star forming systems

    NASA Astrophysics Data System (ADS)

    Ritter, Jeremy S.; Sluder, Alan; Safranek-Shrader, Chalence; Milosavljević, Miloš; Bromm, Volker

    2015-08-01

    To constrain the properties of the first stars with the chemical abundance patterns observed in metal-poor stars, one must identify any non-trivial effects that the hydrodynamics of metal dispersal can imprint on the abundances. We use realistic cosmological hydrodynamic simulations to quantify the distribution of metals resulting from one Population III supernova and from a small number of such supernovae exploding in close succession. Overall, supernova ejecta are highly inhomogeneously dispersed throughout the simulations. When the supernova bubbles collapse, quasi-virialized metal-enriched clouds, fed by fallback from the bubbles and by streaming of metal-free gas from the cosmic web, grow in the centres of the dark matter haloes. Partial turbulent homogenization on scales resolved in the simulation is observed only in the densest clouds where the vortical time-scales are short enough to ensure true homogenization on subgrid scales. However, the abundances in the clouds differ from the gross yields of the supernovae. Continuing the simulations until the cloud have gone into gravitational collapse, we predict that the abundances in second-generation stars will be deficient in the innermost mass shells of the supernova (if only one has exploded) or in the ejecta of the latest supernovae (when multiple have exploded). This indicates that hydrodynamics gives rise to biases complicating the identification of nucleosynthetic sources in the chemical abundance spaces of the surviving stars.

  13. Metal-assisted chemical etch porous silicon formation method

    DOEpatents

    Li, Xiuling; Bohn, Paul W.; Sweedler, Jonathan V.

    2004-09-14

    A thin discontinuous layer of metal such as Au, Pt, or Au/Pd is deposited on a silicon surface. The surface is then etched in a solution including HF and an oxidant for a brief period, as little as a couple seconds to one hour. A preferred oxidant is H.sub.2 O.sub.2. Morphology and light emitting properties of porous silicon can be selectively controlled as a function of the type of metal deposited, Si doping type, silicon doping level, and/or etch time. Electrical assistance is unnecessary during the chemical etching of the invention, which may be conducted in the presence or absence of illumination.

  14. Chemically engineered graphene-based 2D organic molecular magnet.

    PubMed

    Hong, Jeongmin; Bekyarova, Elena; de Heer, Walt A; Haddon, Robert C; Khizroev, Sakhrat

    2013-11-26

    Carbon-based magnetic materials and structures of mesoscopic dimensions may offer unique opportunities for future nanomagnetoelectronic/spintronic devices. To achieve their potential, carbon nanosystems must have controllable magnetic properties. We demonstrate that nitrophenyl functionalized graphene can act as a room-temperature 2D magnet. We report a comprehensive study of low-temperature magnetotransport, vibrating sample magnetometry (VSM), and superconducting quantum interference (SQUID) measurements before and after radical functionalization. Following nitrophenyl (NP) functionalization, epitaxially grown graphene systems can become organic molecular magnets with ferromagnetic and antiferromagnetic ordering that persists at temperatures above 400 K. The field-dependent, surface magnetoelectric properties were studied using scanning probe microscopy (SPM) techniques. The results indicate that the NP-functionalization orientation and degree of coverage directly affect the magnetic properties of the graphene surface. In addition, graphene-based organic magnetic nanostructures were found to demonstrate a pronounced magneto-optical Kerr effect (MOKE). The results were consistent across different characterization techniques and indicate room-temperature magnetic ordering along preferred graphene orientations in the NP-functionalized samples. Chemically isolated graphene nanoribbons (CINs) were observed along the preferred functionality directions. These results pave the way for future magnetoelectronic/spintronic applications based on promising concepts such as current-induced magnetization switching, magnetoelectricity, half-metallicity, and quantum tunneling of magnetization.

  15. Porous metal-organic frameworks for heterogeneous biomimetic catalysis.

    PubMed

    Zhao, Min; Ou, Sha; Wu, Chuan-De

    2014-04-15

    Metalloporphyrins are the active sites in monooxygenases that oxidize a variety of substrates efficiently and under mild conditions. Researchers have developed artificial metalloporphyrins, but these structures have had limited catalytic applications. Homogeneous artificial metalloporphyrins can undergo catalytic deactivation via suicidal self-oxidation, which lowers their catalytic activity and sustainability relative to their counterparts in Nature. Heme molecules in protein scaffolds can maintain high efficiency over numerous catalytic cycles. Therefore, we wondered if immobilizing metalloporphyrin moieties within porous metal-organic frameworks (MOFs) could stabilize these structures and facilitate the molecular recognition of substrates and produce highly efficient biomimetic catalysis. In this Account, we describe our research to develop multifunctional porphyrinic frameworks as highly efficient heterogeneous biomimetic catalysts. Our studies indicate that porous porphyrinic frameworks provide an excellent platform for mimicking the activity of biocatalysts and developing new heterogeneous catalysts that effect new chemical transformations under mild conditions. The porous structures and framework topologies of the porphyrinic frameworks depend on the configurations, coordination donors, and porphyrin metal ions of the metalloporphyrin moieties. To improve the activity of porous porphyrinic frameworks, we have developed a two-step synthesis that introduces the functional polyoxometalates (POMs) into POM-porphyrin hybrid materials. To tune the pore structures and the catalytic properties of porphyrinic frameworks, we have designed metalloporphyrin M-H8OCPP ligands with four m-benzenedicarboxylate moieties, and introduced the secondary auxiliary ligands. The porphyrin metal ions and the secondary functional moieties that are incorporated into porous metal-organic frameworks greatly influence the catalytic properties and activities of porphyrinic frameworks in

  16. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    SciTech Connect

    Lichtenberger, D.L.

    1992-01-01

    Purpose of this research program is to obtain experimental information on the different fundamental ways metals bond and activate organic molecules. Our approach has been to directly probe the electronic interactions between metals and molecules through a wide variety of ionization spectroscopies and other techniques, and to investigate the relationships with bonding modes, structures, and chemical behavior. During this period, we have (1) characterized the electronic features of diphosphines and monophosphines in their coordination to metals, (2) carried out theoretical and experimental investigations of the bonding capabilities of C[sub 60] to transition metals, (3) developed techniques for the imaging of single molecules on gold substrates that emphasizes the electronic backbonding from the metal to the molecule, (4) obtained the high resolution photoelectron spectrum of pure C[sub 70] in the gas phase, (5) compared the bonding of [eta][sup 3]- acetylide ligands to the bonding of other small organic molecules with metals, and (6) reported the photoelectron spectra and bonding of [eta][sup 3]-cyclopropenyl groups to metals.

  17. Aerosol chemical vapor deposition of metal oxide films

    DOEpatents

    Ott, Kevin C.; Kodas, Toivo T.

    1994-01-01

    A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

  18. Metal-organic scintillator crystals for X-ray, gamma ray, and neutron detection

    DOEpatents

    Boatner, Lynn A; Kolopus, James A.; Neal, John S; Ramey, Joanne Oxendine; Wisniewski, Dariusz J

    2012-01-03

    New metal-organic materials are useful as scintillators and have the chemical formula LX.sub.3(CH.sub.3OH).sub.4 where L is Y, Sc, or a lanthanide element, and X is a halogen element. An example of the scintillator materials is CeCl.sub.3(CH.sub.3OH).sub.4.

  19. Lipase-supported metal-organic framework bioreactor catalyzes warfarin synthesis.

    PubMed

    Liu, Wan-Ling; Yang, Ni-Shin; Chen, Ya-Ting; Lirio, Stephen; Wu, Cheng-You; Lin, Chia-Her; Huang, Hsi-Ya

    2015-01-01

    A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase-supported metal-organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors.

  20. Controlling embedment and surface chemistry of nanoclusters in metal-organic frameworks.

    PubMed

    Coupry, D E; Butson, J; Petkov, P S; Saunders, M; O'Donnell, K; Kim, H; Buckley, C; Addicoat, M; Heine, T; Szilágyi, P Á

    2016-04-14

    A combined theoretical and experimental approach demonstrates that nanocluster embedment into the pores of metal-organic frameworks (MOF) may be influenced by the chemical functionalisation of the MOF. Furthermore, this results in the surface functionalisation of the embedded nanoclusters, highlighting the potential of MOF scaffolds for the design and synthesis of novel functional materials.

  1. Modelling of trace metal uptake by roots taking into account complexation by exogenous organic ligands

    NASA Astrophysics Data System (ADS)

    Jean-Marc, Custos; Christian, Moyne; Sterckeman, Thibault

    2010-05-01

    The context of this study is phytoextraction of soil trace metals such as Cd, Pb or Zn. Trace metal transfer from soil to plant depends on physical and chemical processes such as minerals alteration, transport, adsorption/desorption, reactions in solution and biological processes including the action of plant roots and of associated micro-flora. Complexation of metal ions by organic ligands is considered to play a role on the availability of trace metals for roots in particular in the event that synthetic ligands (EDTA, NTA, etc.) are added to the soil to increase the solubility of the contaminants. As this role is not clearly understood, we wanted to simulate it in order to quantify the effect of organic ligands on root uptake of trace metals and produce a tool which could help in optimizing the conditions of phytoextraction.We studied the effect of an aminocarboxilate ligand on the absorption of the metal ion by roots, both in hydroponic solution and in soil solution, for which we had to formalize the buffer power for the metal. We assumed that the hydrated metal ion is the only form which can be absorbed by the plants. Transport and reaction processes were modelled for a system made up of the metal M, a ligand L and the metal complex ML. The Tinker-Nye-Barber model was adapted to describe the transport of solutes M, L and ML in the soil and absorption of M by the roots. This allowed to represent the interactions between transport, chelating reactions, absorption of the solutes at the root surface, root growth with time, in order to simulate metal uptake by a whole root system.Several assumptions were tested such as i) absorption of the metal by an infinite sink and according to a Michaelis-Menten kinetics, solutes transport by diffusion with and without ii) mass flow and iii) soil buffer power for the ligand L. In hydroponic solution (without soil buffer power), ligands decreased the trace metal flux towards roots, as they reduced the concentration of hydrated

  2. Chemical Abundances of Metal-poor stars in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.; Jablonka, Pascale; Hill, Vanessa; Starkenburg, Else; Lemasle, Bertrand; Shetrone, Matthew; Irwin, Mike; Norris, John; Yong, David; Gilmore, Gerry; Salvadori, Stephania; Skuladottir, Asa; Tolstoy, Eline

    2016-08-01

    Stars in low-mass dwarf galaxies show a larger range in their chemical properties than those in the Milky Way halo. The slower star formation efficiency make dwarf galaxies ideal systems for testing nucleosynthetic yields. Not only are alpha-poor stars found at lower metallicities, and a higher fraction of carbon-enhanced stars, but we are also finding stars in dwarf galaxies that appear to be iron-rich. These are compared with yields from a variety of supernova predictions.

  3. Influence of Filler Metals in Welding Wires on the Phase and Chemical Composition of Weld Metal

    NASA Astrophysics Data System (ADS)

    Kozyrev, N. A.; Osetkovskiy, I. V.; Kozyreva, O. A.; Zernin, E. A.; Kartsev, D. S.

    2016-04-01

    The influence of filler metals used in welding wires on the phase and chemical composition of the metal, which is surfaced to mining equipment exposed to abrasive wear, has been investigated. Under a laboratory environment, samples of Mo-V-B and Cr-Mn-Mo-V wires were made. The performed experiments have revealed that fillers of the Cr-Mn-Mo-V system used in powder wire show better wear resistance of the weld metal than that of the Mn-Mo-V-B system; the absence of boron, which promotes grain refinement in the Mn-Mo-V-B system, significantly reduces wear resistance; the Mn-Mo-V-B weld metal has a finer structure than the Cr-Mn-Mo-V weld metal.

  4. New hybrid organic-zincophosphate frameworks: single-crystal-to-single-crystal structural transformation and remarkable thermal and chemical stabilities.

    PubMed

    Chang, Tsung-Yuan; Yan, Zhao-Nan; Wang, Chun-Chi; Li, Hsing-Chun; Lin, Hsiu-Mei; Wang, Chih-Min

    2016-05-01

    This research is the first example of a hybrid metal phosphate that undergoes an SCSC structural transformation and provides a new route for the synthesis of organic-inorganic hybrid materials with high stabilities via the introduction of nitrogen-donor ligands into a metal-phosphate system. The synthesis, structural diversity, and thermal and chemical stabilities are also discussed.

  5. Tattoo inks: legislation, pigments, metals and chemical analysis.

    PubMed

    Prior, Gerald

    2015-01-01

    Legal limits for chemical substances require that they are linked to clearly defined analytical methods. Present limits for certain chemicals in tattoo and permanent make-up inks do not mention analytical methods for the detection of metals, polycyclic aromatic hydrocarbons or forbidden colourants. There is, therefore, no established method for the determination of the quantities of these chemicals in tattoo and permanent make-up inks. Failing to provide an appropriate method may lead to unqualified and questionable results which often cause legal disputes that are ultimately resolved by a judge with regard to the method that should have been applied. Analytical methods are tuned to exactly what is to be found and what causes the health problems. They are extremely specific. Irrespective of which is the correct method for detecting metals in tattoo inks, the focus should be on the actual amounts of ink in the skin. CTL® has conducted experiments to determine these amounts and these experiments are crucial for toxicological evaluations and for setting legal limits. When setting legal limits, it is essential to also incorporate factors such as daily consumption, total uptake and frequency of use. A tattoo lasts for several decades; therefore, the limits that have been established for heavy metals used in drinking water or soap are not relevant. Drinking water is consumed on a daily basis and soap is used several times per week, while tattooing only occurs once. PMID:25833637

  6. Safety in the Chemical Laboratory. Organic Peroxides.

    ERIC Educational Resources Information Center

    Shanley, Edward S.

    1990-01-01

    Discussed is the thermodynamic instability of organic peroxides. The process of autoxidation which results in peroxide formation is described. Precautions necessary to prevent autoxidation hazards associated with these reagents are suggested. (CW)

  7. COSOLVENT EFFECTS ON ORGANIC CHEMICAL PARTITIONING TO SEDIMENT ORGANIC CARBON

    EPA Science Inventory

    Sorption-desorption hysteresis, slow desorption kinetics and resultant bioavailability, and other nonideal phenomena have been attributed to the differing sorptive characteristics of the natural organic polymers associated with soils and sediments. The objectives of this study we...

  8. Cadmium and Zinc Thiolate and Selenolate Metal-Organic Frameworks

    SciTech Connect

    Turner, D.; Stone, K; Stephens, P; Vaid, T

    2010-01-01

    Metal-organic frameworks based on metal-sulfur or metal-selenium bonds are relatively rare; herein we describe the synthesis and structural characterization of several examples, including, for example, [Cd(en){sub 3}][Cd(SC{sub 6}H{sub 4}S){sub 2}], which contains the anionic two-dimensional square-grid network [Cd(SC{sub 6}H{sub 4}S){sub 2}]{sub n}{sup 2n-}.

  9. USING ZERO-VALENT METAL NANOPARTICLES TO REMEDIATE ORGANIC CONTAMINANTS

    EPA Science Inventory

    The transport of organic contaminants down the soil profile constitutes a serious threat to the quality of ground water. Zero-valent metals are considered innocuous abiotic agents capable of mediating decontamination processes in terrestrial systems. In this investigation, ze...

  10. Applications of metal-organic frameworks in heterogeneous supramolecular catalysis.

    PubMed

    Liu, Jiewei; Chen, Lianfen; Cui, Hao; Zhang, Jianyong; Zhang, Li; Su, Cheng-Yong

    2014-08-21

    This review summarizes the use of metal-organic frameworks (MOFs) as a versatile supramolecular platform to develop heterogeneous catalysts for a variety of organic reactions, especially for liquid-phase reactions. Following a background introduction about catalytic relevance to various metal-organic materials, crystal engineering of MOFs, characterization and evaluation methods of MOF catalysis, we categorize catalytic MOFs based on the types of active sites, including coordinatively unsaturated metal sites (CUMs), metalloligands, functional organic sites (FOS), as well as metal nanoparticles (MNPs) embedded in the cavities. Throughout the review, we emphasize the incidental or deliberate formation of active sites, the stability, heterogeneity and shape/size selectivity for MOF catalysis. Finally, we briefly introduce their relevance into photo- and biomimetic catalysis, and compare MOFs with other typical porous solids such as zeolites and mesoporous silica with regard to their different attributes, and provide our view on future trends and developments in MOF-based catalysis.

  11. Multi-responsive metal-organic lantern cages in solution.

    PubMed

    Brega, Valentina; Zeller, Matthias; He, Yufan; Lu, H Peter; Klosterman, Jeremy K

    2015-03-25

    Soluble copper-based M4L4 lantern-type metal-organic cages bearing internal amines were synthesized. The solution state integrity of the paramagnetic metal-organic cages was demonstrated using NMR, DLS, MS, and AFM spectroscopy. 1D supramolecular pillars of pre-formed cages or covalent host-guest complexes selectively formed upon treatment with 4,4'-bipyridine and acetic anhydride, respectively.

  12. Effect of metal films on the photostabilities of emissive organic layers as probed by fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Abbas, Sikandar; Peteanu, Linda A.

    2015-09-01

    Realization of energy efficient and cost effective electroluminescence applications of conjugated polymers, like organic light emitting diodes (OLEDs), requires a complete understanding of photo-chemical processes at metal-polymer interfaces. Therefore it is useful to study the effects of metal films on the photoluminescence of emissive organic layer fabricated on it. While investigating these processes we observed an interesting and unexpected phenomenon that, when conjugated polymer is deposited on thin gold film substrates, it exhibits remarkable photo-stability relative to that deposited on glass, even in the presence of molecular oxygen. This paper addresses the photo-stability enhancement by thin Au films and explores the photochemical mechanism behind it.

  13. Chemiluminescent chemical sensors for inorganic and organic vapors

    SciTech Connect

    Collins, G.E.; Rose-Pehrsson, S.L.

    1995-12-31

    Chemiluminescent, chemical sensors for inorganic and organic vapors are being investigated via the immobilization of 3-aminophthalhydrazide (luminol) within hydrogels and polymeric, sorbent coatings. The films are supported behind a teflon membrane and positioned in front of a photomultiplier tube, permitting the sensitive detection of numerous toxic vapors. Some selectivity has been tailored into these devices by careful selection of the polymer type, pH and metal catalyst incorporated within the film. The incorporation of luminol and Fe(3) within a polyvinylalcohol hydrogel gave a film with superior sensitivity toward NO{sub 2} (detection limit of 0.46 ppb and a response time on the order of seconds). The use of the hydrogel matrix helped eliminate humidity problems associated with other polymeric films. Other chemiluminescent thin films prepared have demonstrated the detection of ppb levels of SO{sub 2}(g) and hydrazine, N{sub 2}H{sub 4}(g). Recently, the authors have begun investigating the incorporation of a heated Pt filament into the inlet line as a pre-oxidative step prior to passage of the gas stream across the teflon membrane. This has permitted the sensitive detection of ppm levels of CCl{sub 4}(g), CHCl{sub 3}(g) and CH{sub 2}Cl{sub 2}(g).

  14. Chemical vapor deposition of ceramic coatings on metals and ceramic fibers

    NASA Astrophysics Data System (ADS)

    Nable, Jun Co

    2005-07-01

    The research presented in this study consists of two major parts. The first part is about the development of ceramic coatings on metals by chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD). Ceramics such as Al2O3 and Cr2O3, are used as protective coatings for materials used at elevated temperatures (>700°C). These metal oxides either exhibit oxidation resistance or have been used as environmental bond coats. Conventional methods of coating by chemical vapor deposition requires deposition temperatures of >950°C which could damage the substrate material during the coating process. Lower deposition temperatures (400 to 600°C) by MOCVD of these metal oxides were successful on Ni metal substrates. Surface modification such as pre-oxidation and etching were also investigated. In addition, a novel approach for the CVD of TiN on metals was developed. This new approach utilizes ambient pressure conditions which lead to deposition temperatures of 800°C or lower compared to conventional CVD of TiN at 1000°C. Titanium nitride can be used as an abrasive and wear coating on cutting and grinding tools. This nitride can also serve as a diffusion coating in metals. The second major part of this research involves the synthesis of interfacial coatings on ceramic reinforcing fibers for ceramic matrix composites. Aluminum and chromium oxides were deposited onto SiC, and Al2O3-SiO 2 fibers by MOCVD. The effects of the interface coatings on the tensile strength of ceramic fibers are also discussed. New duplex interface coatings consisting of BN or TiN together with Al2O3 or ZrO 2 were also successfully deposited and evaluated on SiC fibers.

  15. Chemical reactions of organic compounds on clay surfaces.

    PubMed Central

    Soma, Y; Soma, M

    1989-01-01

    Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Brönsted or Lewis acidity of clay minerals. PMID:2533556

  16. Distribution of volatile organic chemicals in outdoor and indoor air

    NASA Technical Reports Server (NTRS)

    Shah, Jitendra J.; Singh, Hanwant B.

    1988-01-01

    The EPA volatile organic chemistry (VOC) national ambient data base (Shah, 1988) is discussed. The 320 chemicals included in the VOC data base are listed. The methods used to obtain the data are reviewed and the availability, accessibility, and operation of the data base are examined. Tables of the daily outdoor concentrations for 66 chemicals and the daily indoor concentrations for 35 chemicals are presented.

  17. Metal-organic frameworks as biosensors for luminescence-based detection and imaging.

    PubMed

    Miller, Sophie E; Teplensky, Michelle H; Moghadam, Peyman Z; Fairen-Jimenez, David

    2016-08-01

    Metal-organic frameworks (MOFs), formed by the self-assembly of metal centres or clusters and organic linkers, possess many key structural and chemical features that have enabled them to be used in sensing platforms for a variety of environmentally, chemically and biomedically relevant compounds. In particular, their high porosity, large surface area, tuneable chemical composition, high degree of crystallinity, and potential for post-synthetic modification for molecular recognition make MOFs promising candidates for biosensing applications. In this review, we separate our discussion of MOF biosensors into two categories: quantitative sensing, focusing specifically on luminescence-based sensors for the direct measurement of a specific analyte, and qualitative sensing, where we describe MOFs used for fluorescence microscopy and as magnetic resonance imaging contrast agents. We highlight several key publications in each of these areas, concluding that MOFs present an exciting, versatile new platform for biosensing applications and imaging, and we expect to see their usage grow as the field progresses.

  18. CTEPP NC DATA ANALYTICAL RESULTS ORGANIZED BY CHEMICAL AND MEDIA

    EPA Science Inventory

    This data set contains the field sample data by chemical and matrix. The data are organized at the sample, chemical level.

    The Children’s Total Exposure to Persistent Pesticides and Other Persistent Pollutant (CTEPP) study was one of the largest aggregate exposure studies of y...

  19. Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

    PubMed Central

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X.; Urban, Ania; Thacker, Nathan C.; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals. PMID:27574182

  20. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING

    SciTech Connect

    LICHTENBERGER, DENNIS L.

    2002-03-26

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems.

  1. Modeling organic chemical fate in aquatic systems: significance of bioaccumulation and relevant time-space scales.

    PubMed

    Thomann, R V

    1995-06-01

    The importance of aquatic food chain bioaccumulation of organic chemicals in contributing to human dose is derived. It is shown that for chemicals with log octanol water partition coefficients greater than about 3, the role of food chain transfer to fish consumed by humans becomes the more dominant route over drinking water. Modeling of aquatic food chain bioaccumulation then becomes necessary to accurately estimate dose of such chemicals to humans. The relevant time and space scales for groundwater and surface water also indicate a division of organic chemicals at a log octanol water partition coefficient of about 3. For chemicals greater than that level, groundwater transport is minimal, while for chemicals with log octanol water coefficients of less than about 3, detention times are long relative to surface water and biodegradation processes become more significant. An illustration is given of modeling the groundwater transport of two organic chemicals (BCEE and benzene) and a metal (chromium) at a Superfund site. The model indicates that after 10 years only a relatively small fraction of the chemicals had traveled in the groundwater about 300 m to the point of release from the site to surface water. On the other hand, steady state in the adjacent stream and lake is reached rapidly over a distance of 2000 m, illustrating the difference in spatial and temporal scales for the groundwater and surface water.

  2. Separating of organic and inorganic forms of metals in sediments

    SciTech Connect

    Hsieh, Yuch Ping

    1995-12-31

    Separating organic forms of trace metals from their pyritic forms is a difficult problem one constantly faced when studying trace metals in a reduced soil. It is known that pyritic forms and organic forms of metals can be separated by solubilizing pyritic forms in a reducing agent while leaving the organic forms intact. The problem is that the reducing agents used in those procedures are also metals such as Cr or Sn that makes the study of trace metals impossible. If oxidation procedure is used, both pyritic anorganic forms oxidize almost at the same rate which resulted in hardly any separation. Reported here is a new procedure that oxidizes > 95% of pyritic forms and < 5% of organic forms of heavy metal using a modified hydrogen peroxide solution. The procedure is examined using mixtures of standards and salt marsh sediments. Using this procedure, we prove that rarely any added Cu retained in salt marshes is in organic form, a result has been repeatedly mistakenly reported.

  3. CHEMICAL TRANSPORT FACILITATED BY COLLOIDAL-SIZED ORGANIC MOLECULES

    EPA Science Inventory

    The fluid passing through the pores of soils and geologic materials is not just water with dissolved inorganic chemicals, but a complex mixture of organic and inorganic molecules. Large organic molecules such as humic and fulvic materials may impact the movement of contaminants. ...

  4. Membrane-Organized Chemical Photoredox Systems

    SciTech Connect

    Hurst, James K.

    2014-09-18

    This project has three interrelated goals relevant to solar water photolysis, which are to develop: (1) vesicle-organized assemblies for H2 photoproduction that utilize pyrylium and structurally related compounds as combined photosensitizers and cyclic electroneutral transmembrane electron carriers; (2) transmembrane redox systems whose reaction rates can be modulated by light; and (3) homogeneous catalysts for water oxidation. . In area (1), initial efforts to photogenerate H2 from vectorially-organized vesicles containing occluded colloidal Pt and commonly available pyrylium ions as transmembrane redox mediators were unsuccessful. New pyrylium compounds with significantly lower reduction potentials have been synthesized to address this problem, their apparent redox potentials in functioning systems have been now evaluated by using a series of occluded viologens, and H2 photoproduction has been demonstrated in continuous illumination experiments. In area (2), spirooxazine-quinone dyads have been synthesized and their capacity to function as redox mediators across bilayer membranes has been evaluated through continuous photolysis and transient spectrophotometric measurements. Photoisomerization of the spiro moiety to the ring-open mero form caused net quantum yields to decrease significantly, providing a basis for photoregulation of transmembrane redox. Research on water oxidation (area 3) has been directed at understanding mechanisms of catalysis by cis,cis-[(bpy)2Ru(OH2)]2O4+ and related polyimine complexes. Using a variety of physical techniques, we have: (i) identified the redox state of the complex ion that is catalytically active; (ii) shown using 18O isotopic labeling that there are two reaction pathways, both of which involve participation of solvent H2O; and (iii) detected and characterized by EPR and resonance Raman spectroscopies new species which may be key intermediates in the catalytic cycle.

  5. Biomimetic mineralization of metal-organic frameworks as protective coatings for biomacromolecules

    NASA Astrophysics Data System (ADS)

    Liang, Kang; Ricco, Raffaele; Doherty, Cara M.; Styles, Mark J.; Bell, Stephen; Kirby, Nigel; Mudie, Stephen; Haylock, David; Hill, Anita J.; Doonan, Christian J.; Falcaro, Paolo

    2015-06-01

    Enhancing the robustness of functional biomacromolecules is a critical challenge in biotechnology, which if addressed would enhance their use in pharmaceuticals, chemical processing and biostorage. Here we report a novel method, inspired by natural biomineralization processes, which provides unprecedented protection of biomacromolecules by encapsulating them within a class of porous materials termed metal-organic frameworks. We show that proteins, enzymes and DNA rapidly induce the formation of protective metal-organic framework coatings under physiological conditions by concentrating the framework building blocks and facilitating crystallization around the biomacromolecules. The resulting biocomposite is stable under conditions that would normally decompose many biological macromolecules. For example, urease and horseradish peroxidase protected within a metal-organic framework shell are found to retain bioactivity after being treated at 80 °C and boiled in dimethylformamide (153 °C), respectively. This rapid, low-cost biomimetic mineralization process gives rise to new possibilities for the exploitation of biomacromolecules.

  6. Biomimetic mineralization of metal-organic frameworks as protective coatings for biomacromolecules

    PubMed Central

    Liang, Kang; Ricco, Raffaele; Doherty, Cara M.; Styles, Mark J.; Bell, Stephen; Kirby, Nigel; Mudie, Stephen; Haylock, David; Hill, Anita J.; Doonan, Christian J.; Falcaro, Paolo

    2015-01-01

    Enhancing the robustness of functional biomacromolecules is a critical challenge in biotechnology, which if addressed would enhance their use in pharmaceuticals, chemical processing and biostorage. Here we report a novel method, inspired by natural biomineralization processes, which provides unprecedented protection of biomacromolecules by encapsulating them within a class of porous materials termed metal-organic frameworks. We show that proteins, enzymes and DNA rapidly induce the formation of protective metal-organic framework coatings under physiological conditions by concentrating the framework building blocks and facilitating crystallization around the biomacromolecules. The resulting biocomposite is stable under conditions that would normally decompose many biological macromolecules. For example, urease and horseradish peroxidase protected within a metal-organic framework shell are found to retain bioactivity after being treated at 80 °C and boiled in dimethylformamide (153 °C), respectively. This rapid, low-cost biomimetic mineralization process gives rise to new possibilities for the exploitation of biomacromolecules. PMID:26041070

  7. A new metalation complex for organic synthesis and polymerization reactions

    NASA Technical Reports Server (NTRS)

    Hirshfield, S. M.

    1971-01-01

    Organometallic complex of N,N,N',N' tetramethyl ethylene diamine /TMEDA/ and lithium acts as metalation intermediate for controlled systhesis of aromatic organic compounds and polymer formation. Complex of TMEDA and lithium aids in preparation of various organic lithium compounds.

  8. Chemically Modified Metal Oxide Nanostructure for Photoelectrochemical Water Splitting

    NASA Astrophysics Data System (ADS)

    Wang, Gongming

    Hydrogen gas is chemical fuel with high energy density, and represents a clean, renewable and carbon-free burning fuel, which has the potential to solve the more and more urgent energy crisis in today's society. Inspired by natural photosynthesis, artificial photosynthesis to generate hydrogen energy has attracted a lot of attentions in the field of chemistry, physics and material. Photoelectrochemical water splitting based on semiconductors represents a green and low cost method to generate hydrogen fuel. However, the current overall efficiency of solar to hydrogen is quite low, due to some intrinsic limitations such as bandgap, diffusion distance, carrier lifetime and photostability of semiconductors. Although nanostructured semiconductors can improve their photoelectrochemical water splitting performance to some extent, by increasing electrolyte accessible area and shortening minority carrier diffusion distance, nanostructure engineering cannot change their intrinsic electronic properties. Recent development in chemically modified nanostructures such as surface catalyst decoration, element doping, plasmonic modification and interfacial hetero-junction design have led to significant advancement in the photoelectrochemical water splitting, by improving surface reaction kinetics and charge separation, transportation and collection efficiency. In this thesis, I will give a detailed discussion on the chemically modified metal oxide nanostructures for photoelectrocemical hydrogen generation, with a focus on the element doping, hydrogen treatment and catalyst modification. I have demonstrated nitrogen doping on ZnO and Ti doping on hematite can improve their photoelectrochemical performance. In addition, we found hydrogen treatment is a general and effective method to improve the photocatalytic performance, by increasing their carrier desities. Hydrogen treatment has been demonstrated on TiO2, WO3 and BiVO4. In the end, we also used electrochemical catalyt to modify

  9. Combined chemical and microbiological removal of organic sulfur from coal

    SciTech Connect

    Raphaelian, L.A.

    1991-01-01

    The objective of this work is to investigate techniques for chemically converting the sulfur containing organic compounds in coal to compounds that can be treated microbiologically to remove the organically bound sulfur. The goal is to achieve an economically feasible mild chemical oxidation of the organic sulfur in a representative Illinois Basin coal by converting the sulfur to sulfoxides and sulfones; the carbon sulfur bond in the sulfoxides and sulfones would then be broken microbiologically and the sulfur removed from the coal as sulfate.

  10. Ohmic current in organic metal-insulator-metal diodes revisited

    NASA Astrophysics Data System (ADS)

    Wetzelaer, G. A. H.; Blom, P. W. M.

    2014-06-01

    In the classical analysis of charge transport in solids by Lampert in 1956 an Ohmic current is attributed to the presence of a background carrier density due to (unintentional) doping. We demonstrate that Ohmic currents are also observed in undoped semiconductors as a result of diffusion of charge carriers from the contacts into the semiconductor. This Ohmic diffusion current shows an enhanced thickness scaling and is governed by the charge-carrier mobility. Specific for organic semiconductors the charge-carrier density dependence of the mobility at zero electric field can be accurately determined from the Ohmic diffusion current.

  11. Metal-Organic Frameworks for Highly Selective Separations

    SciTech Connect

    Omar M. Yaghi

    2009-09-28

    This grant was focused on the study of metal-organic frameworks with these specific objectives. (1) To examine the use of MOFs with well-defined open metal sites for binding of gases and small organics. (2) To develop a strategy for producing MOFs that combine large pore size with high surface area for their use in gas adsorption and separation of polycyclic organic compounds. (3) To functionalize MOFs for the storage of inert gases such as methane. A brief outline of our progress towards these objectives is presented here as it forms part of the basis for the ideas to be developed under the present proposal.

  12. In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

    DOEpatents

    Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

    2004-03-23

    A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

  13. In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

    DOEpatents

    Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

    2007-07-17

    A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

  14. Controls on metal exposure to aquatic organisms in urban streams.

    PubMed

    Turpin-Nagel, Katelyn; Vadas, Timothy M

    2016-08-10

    Streams in urban ecosystems receive metal inputs primarily from stormwater runoff and wastewater effluent. The relative contribution of these metal sources to stream impairment is difficult to discern based on simple water characteristics and biological surveys. Stream impairment in these systems is often indicated by reduced abundance and diversity of aquatic insects, which tend to be more sensitive to chronic metal exposures. Metal species and controls on metal species in both the waterborne and dietborne exposure pathways to aquatic organisms are reviewed here. In addition, ecological changes that can control dietborne species are discussed. A main focus is on how organic matter from different anthropogenic sources may control both aqueous metal speciation as well as interaction with various inorganic or microbiological surfaces in streams. Most of the reviewed research focuses on Cu, Zn or Pb as those are the primary metals of concern in developed systems and Cu and Pb have unique and strong interactions with organic matter. Recommendations for further research are described in the context of exposure species, dynamics of exposure, stoichiometry, or advanced analytical tools, and regulatory implications are discussed. PMID:27170052

  15. Active-Site-Accessible, Porphyrinic Metal;#8722;Organic Framework Materials

    SciTech Connect

    Farha, Omar K.; Shultz, Abraham M.; Sarjeant, Amy A.; Nguyen, SonBinh T.; Hupp, Joseph T.

    2012-02-06

    On account of their structural similarity to cofactors found in many metallo-enzymes, metalloporphyrins are obvious potential building blocks for catalytically active, metal-organic framework (MOF) materials. While numerous porphyrin-based MOFs have already been described, versions featuring highly accessible active sites and permanent microporosity are remarkably scarce. Indeed, of the more than 70 previously reported porphyrinic MOFs, only one has been shown to be both permanently microporous and contain internally accessible active sites for chemical catalysis. Attempts to generalize the design approach used in this single successful case have failed. Reported here, however, is the synthesis of an extended family of MOFs that directly incorporate a variety of metalloporphyrins (specifically Al{sup 3+}, Zn{sup 2+}, Pd{sup 2+}, Mn{sup 3+}, and Fe{sup 3+} complexes). These robust porphyrinic materials (RPMs) feature large channels and readily accessible active sites. As an illustrative example, one of the manganese-containing RPMs is shown to be catalytically competent for the oxidation of alkenes and alkanes.

  16. Synthesis and Characterization of Functionalized Metal-organic Frameworks

    PubMed Central

    Karagiaridi, Olga; Bury, Wojciech; Sarjeant, Amy A.; Hupp, Joseph T.; Farha, Omar K.

    2014-01-01

    Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy. PMID:25225784

  17. Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

    PubMed

    Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

    2016-04-13

    Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.

  18. Hydrophobic and moisture-stable metal-organic frameworks.

    PubMed

    Fernandez, Carlos A; Nune, Satish K; Annapureddy, Harsha V; Dang, Liem X; McGrail, B Peter; Zheng, Feng; Polikarpov, Evgueni; King, David L; Freeman, Charles; Brooks, Kriston P

    2015-08-14

    Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO(2) separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behaviour and chemical stability against moisture without compromising CO(2) sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. We herein report preliminary results on routinely studied MOF materials [MIL-101(Cr) and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO(2) sorption capacity while reducing the water adsorption up to three times, with respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF performance and recyclability. PMID:25970023

  19. Effect of Ocean Acidification on Organic and Inorganic Speciation of Trace Metals.

    PubMed

    Stockdale, Anthony; Tipping, Edward; Lofts, Stephen; Mortimer, Robert J G

    2016-02-16

    Rising concentrations of atmospheric carbon dioxide are causing acidification of the oceans. This results in changes to the concentrations of key chemical species such as hydroxide, carbonate and bicarbonate ions. These changes will affect the distribution of different forms of trace metals. Using IPCC data for pCO2 and pH under four future emissions scenarios (to the year 2100) we use a chemical speciation model to predict changes in the distribution of organic and inorganic forms of trace metals. Under a scenario where emissions peak after the year 2100, predicted free ion Al, Fe, Cu, and Pb concentrations increase by factors of up to approximately 21, 2.4, 1.5, and 2.0 respectively. Concentrations of organically complexed metal typically have a lower sensitivity to ocean acidification induced changes. Concentrations of organically complexed Mn, Cu, Zn, and Cd fall by up to 10%, while those of organically complexed Fe, Co, and Ni rise by up to 14%. Although modest, these changes may have significance for the biological availability of metals given the close adaptation of marine microorganisms to their environment.

  20. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-01

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  1. Mechanochemical synthesis of an yttrium based metal-organic framework.

    PubMed

    Singh, Niraj K; Hardi, Meenakshi; Balema, Viktor P

    2013-02-01

    For the first time a metal hydride has been used for the preparation of a metal-organic framework. MIL-78 has been synthesized by the solid-state mechanochemical reaction between yttrium hydride and trimesic acid. The process does not involve solvents and does not generate liquid by-products, thus proving the viability of the solid-state approach to the synthesis of MOFs.

  2. Inorganic Metal Oxide/Organic Polymer Nanocomposites And Method Thereof

    DOEpatents

    Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

    2004-11-16

    A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal in organic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophilic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the material, providing superb mixing of the component phases in the energetic nanocomposite.

  3. From Bioavailability Science to Regulation of Organic Chemicals.

    PubMed

    Ortega-Calvo, Jose-J; Harmsen, Joop; Parsons, John R; Semple, Kirk T; Aitken, Michael D; Ajao, Charmaine; Eadsforth, Charles; Galay-Burgos, Malyka; Naidu, Ravi; Oliver, Robin; Peijnenburg, Willie J G M; Römbke, Jörg; Streck, Georg; Versonnen, Bram

    2015-09-01

    The bioavailability of organic chemicals in soil and sediment is an important area of scientific investigation for environmental scientists, although this area of study remains only partially recognized by regulators and industries working in the environmental sector. Regulators have recently started to consider bioavailability within retrospective risk assessment frameworks for organic chemicals; by doing so, realistic decision-making with regard to polluted environments can be achieved, rather than relying on the traditional approach of using total-extractable concentrations. However, implementation remains difficult because scientific developments on bioavailability are not always translated into ready-to-use approaches for regulators. Similarly, bioavailability remains largely unexplored within prospective regulatory frameworks that address the approval and regulation of organic chemicals. This article discusses bioavailability concepts and methods, as well as possible pathways for the implementation of bioavailability into risk assessment and regulation; in addition, this article offers a simple, pragmatic and justifiable approach for use within retrospective and prospective risk assessment.

  4. From Bioavailability Science to Regulation of Organic Chemicals.

    PubMed

    Ortega-Calvo, Jose-J; Harmsen, Joop; Parsons, John R; Semple, Kirk T; Aitken, Michael D; Ajao, Charmaine; Eadsforth, Charles; Galay-Burgos, Malyka; Naidu, Ravi; Oliver, Robin; Peijnenburg, Willie J G M; Römbke, Jörg; Streck, Georg; Versonnen, Bram

    2015-09-01

    The bioavailability of organic chemicals in soil and sediment is an important area of scientific investigation for environmental scientists, although this area of study remains only partially recognized by regulators and industries working in the environmental sector. Regulators have recently started to consider bioavailability within retrospective risk assessment frameworks for organic chemicals; by doing so, realistic decision-making with regard to polluted environments can be achieved, rather than relying on the traditional approach of using total-extractable concentrations. However, implementation remains difficult because scientific developments on bioavailability are not always translated into ready-to-use approaches for regulators. Similarly, bioavailability remains largely unexplored within prospective regulatory frameworks that address the approval and regulation of organic chemicals. This article discusses bioavailability concepts and methods, as well as possible pathways for the implementation of bioavailability into risk assessment and regulation; in addition, this article offers a simple, pragmatic and justifiable approach for use within retrospective and prospective risk assessment. PMID:26230485

  5. Dielectric properties of metal-organic chemical vapor deposited highly textured Pb(ScTa){sub 1{minus}x}Ti{sub x}O{sub 3} (x=0{endash}0.3) relaxor ferroelectric thin films on LaNiO{sub 3} electrode buffered Si

    SciTech Connect

    Lin, C.H.; Lee, S.W.; Chen, H.; Wu, T.B.

    1999-10-01

    Highly (100) textured Pb(ScTa){sub 1{minus}x}Ti{sub x}O{sub 3} (x=0{endash}0.3) thin films were grown on LaNiO{sub 3}/Pt/Ti electrode-coated Si substrate using metal-organic chemical vapor deposition at 685thinsp{degree}C. Ti addition was introduced to modify the dielectric properties. Diffuse phase transition, typical of relaxor ferroelectrics was noticed. As Ti content increased from 0{percent} to 30{percent}, the phase transition temperature (T{sub max}) gradually shifted from {minus}10 to 120thinsp{degree}C with the dielectric constant at T{sub max} increased from 1397 to 1992 (1 kHz). Loss tangent values are generally below 0.025. {copyright} {ital 1999 American Institute of Physics.}

  6. Metal speciation in landfill leachates with a focus on the influence of organic matter

    SciTech Connect

    Claret, Francis; Tournassat, Christophe; Crouzet, Catherine; Gaucher, Eric C.; Schaefer, Thorsten; Braibant, Gilles; Guyonnet, Dominique

    2011-09-15

    Highlights: > This study characterises the heavy-metal content in leachates collected from eight landfills in France. > Most of the metals are concentrated in the <30 kDa fraction, while Pb, Cu and Cd are associated with larger particles. > Metal complexation with OM is not sufficient to explain apparent supersaturation of metals with sulphide minerals. - Abstract: This study characterises the heavy-metal content in leachates collected from eight landfills in France. In order to identify heavy metal occurrence in the different size fractions of leachates, a cascade filtration protocol was applied directly in the field, under a nitrogen gas atmosphere to avoid metal oxidation. The results of analyses performed on the leachates suggest that most of the metals are concentrated in the <30 kDa fraction, while lead, copper and cadmium show an association with larger particles. Initial speciation calculations, without considering metal association with organic matter, suggest that leachate concentrations in lead, copper, nickel and zinc are super-saturated with respect to sulphur phases. Speciation calculations that account for metal complexation with organic matter, considered as fulvic acids based on C1(s) NEXAFS spectroscopy, show that this mechanism is not sufficient to explain such deviation from equilibrium conditions. It is therefore hypothesized that the deviation results also from the influence of biological activity on the kinetics of mineral phase precipitation and dissolution, thus providing a dynamic system. The results of chemical analyses of sampled fluids are compared with speciation calculations and some implications for the assessment of metal mobility and natural attenuation in a context of landfill risk assessment are discussed.

  7. Bioavailability of Heavy Metals in Soil: Impact on Microbial Biodegradation of Organic Compounds and Possible Improvement Strategies

    PubMed Central

    Olaniran, Ademola O.; Balgobind, Adhika; Pillay, Balakrishna

    2013-01-01

    Co-contamination of the environment with toxic chlorinated organic and heavy metal pollutants is one of the major problems facing industrialized nations today. Heavy metals may inhibit biodegradation of chlorinated organics by interacting with enzymes directly involved in biodegradation or those involved in general metabolism. Predictions of metal toxicity effects on organic pollutant biodegradation in co-contaminated soil and water environments is difficult since heavy metals may be present in a variety of chemical and physical forms. Recent advances in bioremediation of co-contaminated environments have focussed on the use of metal-resistant bacteria (cell and gene bioaugmentation), treatment amendments, clay minerals and chelating agents to reduce bioavailable heavy metal concentrations. Phytoremediation has also shown promise as an emerging alternative clean-up technology for co-contaminated environments. However, despite various investigations, in both aerobic and anaerobic systems, demonstrating that metal toxicity hampers the biodegradation of the organic component, a paucity of information exists in this area of research. Therefore, in this review, we discuss the problems associated with the degradation of chlorinated organics in co-contaminated environments, owing to metal toxicity and shed light on possible improvement strategies for effective bioremediation of sites co-contaminated with chlorinated organic compounds and heavy metals. PMID:23676353

  8. Bioavailability of heavy metals in soil: impact on microbial biodegradation of organic compounds and possible improvement strategies.

    PubMed

    Olaniran, Ademola O; Balgobind, Adhika; Pillay, Balakrishna

    2013-05-15

    Co-contamination of the environment with toxic chlorinated organic and heavy metal pollutants is one of the major problems facing industrialized nations today. Heavy metals may inhibit biodegradation of chlorinated organics by interacting with enzymes directly involved in biodegradation or those involved in general metabolism. Predictions of metal toxicity effects on organic pollutant biodegradation in co-contaminated soil and water environments is difficult since heavy metals may be present in a variety of chemical and physical forms. Recent advances in bioremediation of co-contaminated environments have focussed on the use of metal-resistant bacteria (cell and gene bioaugmentation), treatment amendments, clay minerals and chelating agents to reduce bioavailable heavy metal concentrations. Phytoremediation has also shown promise as an emerging alternative clean-up technology for co-contaminated environments. However, despite various investigations, in both aerobic and anaerobic systems, demonstrating that metal toxicity hampers the biodegradation of the organic component, a paucity of information exists in this area of research. Therefore, in this review, we discuss the problems associated with the degradation of chlorinated organics in co-contaminated environments, owing to metal toxicity and shed light on possible improvement strategies for effective bioremediation of sites co-contaminated with chlorinated organic compounds and heavy metals.

  9. Metal Speciation in Landfill Leachates with a Focus on the Influence of Organic Matter

    SciTech Connect

    F Claret; C Tournassat; C Crouzet; E Gaucher; T Schäfer; G Braibant; D Guyonnet

    2011-12-31

    This study characterizes the heavy-metal content in leachates collected from eight landfills in France. In order to identify heavy metal occurrence in the different size fractions of leachates, a cascade filtration protocol was applied directly in the field, under a nitrogen gas atmosphere to avoid metal oxidation. The results of analyses performed on the leachates suggest that most of the metals are concentrated in the <30 kDa fraction, while lead, copper and cadmium show an association with larger particles. Initial speciation calculations, without considering metal association with organic matter, suggest that leachate concentrations in lead, copper, nickel and zinc are super-saturated with respect to sulphur phases. Speciation calculations that account for metal complexation with organic matter, considered as fulvic acids based on C1(s) NEXAFS spectroscopy, show that this mechanism is not sufficient to explain such deviation from equilibrium conditions. It is therefore hypothesized that the deviation results also from the influence of biological activity on the kinetics of mineral phase precipitation and dissolution, thus providing a dynamic system. The results of chemical analyses of sampled fluids are compared with speciation calculations and some implications for the assessment of metal mobility and natural attenuation in a context of landfill risk assessment are discussed.

  10. Encoding of Fundamental Chemical Entities of Organic Reactivity Interest using chemical ontology and XML.

    PubMed

    Durairaj, Vijayasarathi; Punnaivanam, Sankar

    2015-09-01

    Fundamental chemical entities are identified in the context of organic reactivity and classified as appropriate concept classes namely ElectronEntity, AtomEntity, AtomGroupEntity, FunctionalGroupEntity and MolecularEntity. The entity classes and their subclasses are organized into a chemical ontology named "ChemEnt" for the purpose of assertion, restriction and modification of properties through entity relations. Individual instances of entity classes are defined and encoded as a library of chemical entities in XML. The instances of entity classes are distinguished with a unique notation and identification values in order to map them with the ontology definitions. A model GUI named Entity Table is created to view graphical representations of all the entity instances. The detection of chemical entities in chemical structures is achieved through suitable algorithms. The possibility of asserting properties to the entities at different levels and the mechanism of property flow within the hierarchical entity levels is outlined. PMID:26188793

  11. Encoding of Fundamental Chemical Entities of Organic Reactivity Interest using chemical ontology and XML.

    PubMed

    Durairaj, Vijayasarathi; Punnaivanam, Sankar

    2015-09-01

    Fundamental chemical entities are identified in the context of organic reactivity and classified as appropriate concept classes namely ElectronEntity, AtomEntity, AtomGroupEntity, FunctionalGroupEntity and MolecularEntity. The entity classes and their subclasses are organized into a chemical ontology named "ChemEnt" for the purpose of assertion, restriction and modification of properties through entity relations. Individual instances of entity classes are defined and encoded as a library of chemical entities in XML. The instances of entity classes are distinguished with a unique notation and identification values in order to map them with the ontology definitions. A model GUI named Entity Table is created to view graphical representations of all the entity instances. The detection of chemical entities in chemical structures is achieved through suitable algorithms. The possibility of asserting properties to the entities at different levels and the mechanism of property flow within the hierarchical entity levels is outlined.

  12. Charge injection and recombination at the metal organic interface

    NASA Astrophysics Data System (ADS)

    Scott, J. Campbell; Malliaras, George G.

    1999-01-01

    We consider the mechanism of charge injection from metals into amorphous organic semiconductors. By first treating charge recombination at the interface as a hopping process in the image potential, we obtain an expression for the surface recombination rate. The principle of detailed balance is then used to determine the injection current. This simple approach yields the effective Richardson constant for injection from metal to organic, and provides a means to derive the electric field dependence of thermionic injection. The result for the net current, injected minus recombination, is in agreement with a more exact treatment of the drift-diffusion equation.

  13. Predicting the bioconcentration factor of highly hydrophobic organic chemicals.

    PubMed

    Garg, Rajni; Smith, Carr J

    2014-07-01

    Bioconcentration refers to the process of uptake and buildup of chemicals in living organisms. Experimental measurement of bioconcentration factor (BCF) is time-consuming and expensive, and is not feasible for a large number of chemicals of regulatory concern. Quantitative structure-activity relationship (QSAR) models are used for estimating BCF values to help in risk assessment of a chemical. This paper presents the results of a QSAR study conducted to address an important problem encountered in the prediction of the BCF of highly hydrophobic chemicals. A new QSAR model is derived using a dataset of diverse organic chemicals previously tested in a United States Environmental Protection Agency laboratory. It is noted that the linear relationship between the BCF and hydrophobic parameter, i.e., calculated octanol-water partition coefficient (ClogP), breaks down for highly hydrophobic chemicals. The parabolic QSAR equation, log BCF=3.036 ClogP-0.197 ClogP(2)-0.808 MgVol (n=28, r(2)=0.817, q(2)=0.761, s=0.558) (experimental log BCF range=0.44-5.29, ClogP range=3.16-11.27), suggests that a non-linear relationship between BCF and the hydrophobic parameter, along with inclusion of additional molecular size, weight and/or volume parameters, should be considered while developing a QSAR model for more reliable prediction of the BCF of highly hydrophobic chemicals.

  14. Synthesis of magnetic metal-organic framework (MOF) for efficient removal of organic dyes from water.

    PubMed

    Zhao, Xiaoli; Liu, Shuangliu; Tang, Zhi; Niu, Hongyun; Cai, Yaqi; Meng, Wei; Wu, Fengchang; Giesy, John P

    2015-01-01

    A novel, simple and efficient strategy for fabricating a magnetic metal-organic framework (MOF) as sorbent to remove organic compounds from simulated water samples is presented and tested for removal of methylene blue (MB) as an example. The novel adsorbents combine advantages of MOFs and magnetic nanoparticles and possess large capacity, low cost, rapid removal and easy separation of the solid phase, which makes it an excellent sorbent for treatment of wastewaters. The resulting magnetic MOFs composites (also known as MFCs) have large surface areas (79.52 m(2) g(-1)), excellent magnetic response (14.89 emu g(-1)), and large mesopore volume (0.09 cm(3) g(-1)), as well as good chemical inertness and mechanical stability. Adsorption was not drastically affected by pH, suggesting π-π stacking interaction and/or hydrophobic interactions between MB and MFCs. Kinetic parameters followed pseudo-second-order kinetics and adsorption was described by the Freundlich isotherm. Adsorption capacity was 84 mg MB g(-1) at an initial MB concentration of 30 mg L(-1), which increased to 245 mg g(-1) when the initial MB concentration was 300 mg L(-1). This capacity was much greater than most other adsorbents reported in the literature. In addition, MFC adsorbents possess excellent reusability, being effective after at least five consecutive cycles. PMID:26149818

  15. Synthesis of magnetic metal-organic framework (MOF) for efficient removal of organic dyes from water

    PubMed Central

    Zhao, Xiaoli; Liu, Shuangliu; Tang, Zhi; Niu, Hongyun; Cai, Yaqi; Meng, Wei; Wu, Fengchang; Giesy, John P.

    2015-01-01

    A novel, simple and efficient strategy for fabricating a magnetic metal-organic framework (MOF) as sorbent to remove organic compounds from simulated water samples is presented and tested for removal of methylene blue (MB) as an example. The novel adsorbents combine advantages of MOFs and magnetic nanoparticles and possess large capacity, low cost, rapid removal and easy separation of the solid phase, which makes it an excellent sorbent for treatment of wastewaters. The resulting magnetic MOFs composites (also known as MFCs) have large surface areas (79.52 m2 g−1), excellent magnetic response (14.89 emu g−1), and large mesopore volume (0.09 cm3 g−1), as well as good chemical inertness and mechanical stability. Adsorption was not drastically affected by pH, suggesting π–π stacking interaction and/or hydrophobic interactions between MB and MFCs. Kinetic parameters followed pseudo-second-order kinetics and adsorption was described by the Freundlich isotherm. Adsorption capacity was 84 mg MB g−1 at an initial MB concentration of 30 mg L−1, which increased to 245 mg g−1 when the initial MB concentration was 300 mg L−1. This capacity was much greater than most other adsorbents reported in the literature. In addition, MFC adsorbents possess excellent reusability, being effective after at least five consecutive cycles. PMID:26149818

  16. Synthesis of magnetic metal-organic framework (MOF) for efficient removal of organic dyes from water

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaoli; Liu, Shuangliu; Tang, Zhi; Niu, Hongyun; Cai, Yaqi; Meng, Wei; Wu, Fengchang; Giesy, John P.

    2015-07-01

    A novel, simple and efficient strategy for fabricating a magnetic metal-organic framework (MOF) as sorbent to remove organic compounds from simulated water samples is presented and tested for removal of methylene blue (MB) as an example. The novel adsorbents combine advantages of MOFs and magnetic nanoparticles and possess large capacity, low cost, rapid removal and easy separation of the solid phase, which makes it an excellent sorbent for treatment of wastewaters. The resulting magnetic MOFs composites (also known as MFCs) have large surface areas (79.52 m2 g-1), excellent magnetic response (14.89 emu g-1), and large mesopore volume (0.09 cm3 g-1), as well as good chemical inertness and mechanical stability. Adsorption was not drastically affected by pH, suggesting π-π stacking interaction and/or hydrophobic interactions between MB and MFCs. Kinetic parameters followed pseudo-second-order kinetics and adsorption was described by the Freundlich isotherm. Adsorption capacity was 84 mg MB g-1 at an initial MB concentration of 30 mg L-1, which increased to 245 mg g-1 when the initial MB concentration was 300 mg L-1. This capacity was much greater than most other adsorbents reported in the literature. In addition, MFC adsorbents possess excellent reusability, being effective after at least five consecutive cycles.

  17. Chemical changes in heavy metals in the leachates from Technosols.

    PubMed

    Yao, F X; Macías, F; Virgel, S; Blanco, F; Jiang, X; Camps Arbestain, M

    2009-09-01

    A 2 month long column study was conducted to evaluate the mobility of heavy metals eluting from Technosols constituted from sewage sludges (aerobic or anaerobic) (as controls) or a mixture of different types of sewage sludges with green foundry sand (FS) or/and Linz-Donowitz slag (LD). The organic and inorganic wastes were mixed at a ratio of 56:44 (w/w). The mixtures and the controls were moistened to field capacity before adding them to the polypropylene columns (4.5 cm wide and 14 cm long). During the 8-week experimental period, the columns were watered, twice a week, with 100 mL of deionised water. The concentrations of heavy metals (Cu, Zn, Ni, Pb, Cd, and Cr) in the leachates were determined periodically. The concentrations of all the heavy metals were generally higher in the leachates from the Technosols containing anaerobic sewage sludge as a component. The concentration of Cu was strongly dependent on pH and was significantly higher (P<0.05) in the most alkaline leachates (pH>10) than in the other leachates. More Zn was mobilized in the most acidic leachates (pH<6) than in other leachates. The concentration of Ni in 80% of the leachates exceeded the EU drinking water limit for Ni (0.02 mgL(-1)). The concentrations of Pb were lower in the Technosols containing FS. The concentrations of Cd in the leachates from Technosols containing the conditioners were relatively high, while concentrations of Cr were higher in the controls. As far as the potential toxicity of heavy metals is concerned, the combination of aerobic sludge, inorganic conditioners able to buffer the pH to around neutrality, and reactive aluminosilicates, can be regarded as suitable choice for formulating Technosols from wastes. PMID:19580987

  18. Micro- and nano-structured metal oxides based chemical sensors: an overview.

    PubMed

    Batra, Ashok K; Chilvery, A K; Guggilla, Padmaja; Aggarwal, Mohan; Currie, James R

    2014-02-01

    This article examines various kinds of chemical sensors, their mechanism of operation and the ways to improve their performance. It reports the results of exploratory investigation of binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, and SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. It also contains an overview on the status of the new types of metal oxide based nanostructured sensors, such as nano belts, nanorods, nanotubes, nanofibers, nanocomposites, etc.

  19. Metals in sediments and benthic organisms in the Mersey estuary

    NASA Astrophysics Data System (ADS)

    Langston, W. J.

    1986-08-01

    Concentrations of twelve metals were determined in sediments, seaweed ( Fucus vesiculosus), winkles ( Littorina littorea), polychaetes ( Nereis diversicolor), suspension feeding bivalves ( Mytilus edulis, Cerastoderma edule) and deposit feeding bivalves ( Macoma balthica, Scrobicularia plana) collected from the Mersey estuary between April 1980 and June 1984. Sediments and organisms in the Mersey are moderately contaminated with most of the metals measured, but mercury concentrations are consistently higher than in other United Kingdom estuaries. Comparisons with other sites in the North West of England indicate that mercury residues in organisms, though primarily dependent on sediment concentrations, are also influenced by complexation with particulate organic matter which reduces the availability of mercury. The biological availability of arsenic in Mersey sediments is similarly influenced by complexation with iron oxyhydroxides. Nereis diversicolor and Macoma balthica are the most suitable indicator species in terms of abundance and widespread distribution along the estuary, and, for the majority of metals, tissue concentrations increase upstream, reflecting corresponding gradients in sediment contamination. However mid-estuarine peaks for tin, chromium copper and nickel in Nereis indicate more localised inputs to the estuary. Correlations between lead in sediments and organisms are poor; it is suggested that hydrophilic alkyl lead compounds may be the predominant biologically available forms. Progressive reductions in mercury contamination in sediments and mercury and lead in organisms have occurred in recent years, which coincide with efforts to reduce inputs of these metals to teh Mersey estuary.

  20. Investigation into the chemical, thermal and radiological changes of organic chemicals added to the underground storage tanks at Hanford

    SciTech Connect

    Samuels, W.D.; Camaioni, D.M.; Clauss, S.A.; Linehan, J.C.

    1996-10-01

    Uranium and plutonium production at the Hanford site produced large quantities of radioactive by-products and contaminated process chemicals that are presently stored in underground tanks awaiting treatment and disposal. Having been made strongly alkaline and then subjected to successive water evaporation campaigns to increase storage capacity, the wastes now exist in the physical forms of salt cakes, metal oxide sludges, and saturated aqueous brine solutions. Those waste storage tanks containing organic process chemicals mixed with nitrate/nitrite salt wastes are thought to be at risk for fuel-nitrate combustion accidents. To support resolution of this potential hazard, we are studying how organic chemicals added to the tanks may have {open_quotes}aged{close_quotes} or changed under storage conditions. Simulated wastes have been irradiated with gamma rays at temperatures between ambient and 90{degrees}C and subsequently analyzed quantitatively. The presentation will report findings on the rates and products of organic degradation. Reaction mechanisms and implications of the findings will be discussed.

  1. Species sensitivity analysis of heavy metals to freshwater organisms.

    PubMed

    Xin, Zheng; Wenchao, Zang; Zhenguang, Yan; Yiguo, Hong; Zhengtao, Liu; Xianliang, Yi; Xiaonan, Wang; Tingting, Liu; Liming, Zhou

    2015-10-01

    Acute toxicity data of six heavy metals [Cu, Hg, Cd, Cr(VI), Pb, Zn] to aquatic organisms were collected and screened. Species sensitivity distributions (SSD) curves of vertebrate and invertebrate were constructed by log-logistic model separately. The comprehensive comparisons of the sensitivities of different trophic species to six typical heavy metals were performed. The results indicated invertebrate taxa to each heavy metal exhibited higher sensitivity than vertebrates. However, with respect to the same taxa species, Cu had the most adverse effect on vertebrate, followed by Hg, Cd, Zn and Cr. When datasets from all species were included, Cu and Hg were still more toxic than the others. In particular, the toxicities of Pb to vertebrate and fish were complicated as the SSD curves of Pb intersected with those of other heavy metals, while the SSD curves of Pb constructed by total species no longer crossed with others. The hazardous concentrations for 5 % of the species (HC5) affected were derived to determine the concentration protecting 95 % of species. The HC5 values of the six heavy metals were in the descending order: Zn > Pb > Cr > Cd > Hg > Cu, indicating toxicities in opposite order. Moreover, potential affected fractions were calculated to assess the ecological risks of different heavy metals at certain concentrations of the selected heavy metals. Evaluations of sensitivities of the species at various trophic levels and toxicity analysis of heavy metals are necessary prior to derivation of water quality criteria and the further environmental protection.

  2. Chemical and Biological Sensors Based on Organic Electrochemical Transistors

    NASA Astrophysics Data System (ADS)

    Lin, Peng

    Organic thin film transistors (OTFTs) have been explored for sensing applications for several decades due to their many advantages like easy fabrication, low cost, flexibility, and biocompatibility. Among these OTFTs, organic electrochemical transistors (OECTs) have attracted a great deal of interest in recent years since the devices can operate stably in aqueous environment with relatively low working voltages and are suitable for applications in chemical and biological sensing. In this thesis, ion-sensitive properties of OECTs based on poly(3,4- ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) have been systematically studied. It was found that the gate electrode played an important role on the ion-sensitive properties of OECTs. For the devices with Ag/AgCl gate electrode, Nernstian relationships between the shift of gate voltage and the concentrations of cations were obtained. For the devices with Pt and Au gate electrodes, the ion sensitivities were higher than that given by Nernst equation, which could be attributed to the interface between the metal gate electrode and the electrolyte. Moreover, OECTs based on PEDOT:PSS were integrated into flexible microfluidic systems. Then a novel label-free DNA sensor was developed, in which single-stranded DNA probes were immobilized on the surface of Au gate electrode. These devices successfully detected complementary DNA targets at concentrations as low as 1 nM. The detection limit was also extended to 10 pM by pulse-enhanced hybridization process of DNA. OECTs based on PEDOT:PSS were also exploited as cell-based biosensors. Human esophageal squamous epithelial cancer cell lines (KYSE30) and fibroblast cell lines (HFFI) were successfully grown on the surface of PEDOT:PSS film. Then the devices were used for in-vitro monitoring cell activities when the living cells were treated by trypsin and an anti-cancer drug, retinoic acid. It was found that the devices were sensitive to the change of surface charge

  3. Textbook Errors: 137. Physical and Chemical Properties and Bonding of Metallic Elements.

    ERIC Educational Resources Information Center

    Myers, R. Thomas

    1979-01-01

    Focuses attention on the almost universal practice of discussing all metals as malleable. The author points out that some are brittle and then he presents the variation in chemical properties of metals. (SA)

  4. The Development of Metal Oxide Chemical Sensing Nanostructures

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; VanderWal,R. L.; Xu, J. C.; Evans, L. J.; Berger, G. M.; Kulis, M. J.

    2008-01-01

    This paper discusses sensor development based on metal oxide nanostructures and microsystems technology. While nanostructures such as nanowires show significant potential as enabling materials for chemical sensors, a number of significant technical challenges remain. This paper discusses development to address each of these technical barriers: 1) Improved contact and integration of the nanostructured materials with microsystems in a sensor structure; 2) Control of nanostructure crystallinity to allow control of the detection mechanism; and 3) Widening the range of gases that can be detected by fabricating multiple nanostructured materials. A sensor structure composed of three nanostructured oxides aligned on a single microsensor has been fabricated and tested. Results of this testing are discussed and future development approaches are suggested. It is concluded that while this work lays the foundation for further development, these are the beginning steps towards realization of repeatable, controlled sensor systems using oxide based nanostructures.

  5. Rational design of metal-organic electronic devices: A computational perspective

    NASA Astrophysics Data System (ADS)

    Chilukuri, Bhaskar

    Organic and organometallic electronic materials continue to attract considerable attention among researchers due to their cost effectiveness, high flexibility, low temperature processing conditions and the continuous emergence of new semiconducting materials with tailored electronic properties. In addition, organic semiconductors can be used in a variety of important technological devices such as solar cells, field-effect transistors (FETs), flash memory, radio frequency identification (RFID) tags, light emitting diodes (LEDs), etc. However, organic materials have thus far not achieved the reliability and carrier mobility obtainable with inorganic silicon-based devices. Hence, there is a need for finding alternative electronic materials other than organic semiconductors to overcome the problems of inferior stability and performance. In this dissertation, I research the development of new transition metal based electronic materials which due to the presence of metal-metal, metal-pi, and pi-pi interactions may give rise to superior electronic and chemical properties versus their organic counterparts. Specifically, I performed computational modeling studies on platinum based charge transfer complexes and d 10 cyclo-[M(mu-L)]3 trimers (M = Ag, Au and L = monoanionic bidentate bridging (C/N~C/N) ligand). The research done is aimed to guide experimental chemists to make rational choices of metals, ligands, substituents in synthesizing novel organometallic electronic materials. Furthermore, the calculations presented here propose novel ways to tune the geometric, electronic, spectroscopic, and conduction properties in semiconducting materials. In addition to novel material development, electronic device performance can be improved by making a judicious choice of device components. I have studied the interfaces of a p-type metal-organic semiconductor viz cyclo-[Au(mu-Pz)] 3 trimer with metal electrodes at atomic and surface levels. This work was aimed to guide the device

  6. High and Reversible Ammonia Uptake in Mesoporous Azolate Metal-Organic Frameworks with Open Mn, Co, and Ni Sites.

    PubMed

    Rieth, Adam J; Tulchinsky, Yuri; Dincă, Mircea

    2016-08-01

    A series of new mesoporous metal-organic frameworks (MOFs) made from extended bisbenzenetriazolate linkers exhibit coordinatively unsaturated metal sites that are responsible for high and reversible uptake of ammonia. Isostructural Mn, Co, and Ni materials adsorb 15.47, 12.00, and 12.02 mmol of NH3/g, respectively, at STP. Importantly, these near-record capacities are reversible for at least three cycles. These results demonstrate that azolate MOFs are sufficiently thermally and chemically stable to find uses in recyclable sorption, storage, and potentially separation of chemically challenging and/or corrosive gases, especially when designed to exhibit a high density of open metal sites.

  7. Inorganic metal oxide/organic polymer nanocomposites and method thereof

    DOEpatents

    Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

    2004-03-30

    A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal inorganic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophillic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the composite material, providing superb mixing of the component phases in the energetic nanocomposite.

  8. Chemical Trends for Transition Metal Compound Bonding to Graphene

    NASA Astrophysics Data System (ADS)

    Lange, Bjoern; Blum, Volker

    2015-03-01

    Transition metal compounds are of interest as catalysts for the hydrogen evolution reaction (HER). However, a perfect candidate to replace expensive platinum has not yet been identified. To tailor a specific compound, several properties come into play. One is the bonding to the underlying substrate, for which π-bonded carbon nanostructures are promising candidates. Here we analyze the bonding of small transition metal compound nanoclusters to a graphene layer for a range of chemical compositions: MxAy (M = Mo, Ti; A = S, O, B, N, C). The clusters are generated by an unbiased random search algorithm. We perform total energy calculations based on density functional theory to identify lowest energy clusters. We calculate binding energies using the PBE and HSE functionals with explicit van der Waals treatment and benchmark those against RPA cluster calculations. Our results indicate that molybdenum-carbides and -nitrides tend to bond tightly to graphene. Mo-oxides and -sulfides show small binding energies, indicating van der Waals bonding.

  9. The vomeronasal organ and chemical sensitivity: a hypothesis.

    PubMed

    Greene, Glenn J; Kipen, Howard M

    2002-08-01

    Environmental exposures to very low levels of airborne chemicals are associated with adverse symptoms, often affecting multiple organ systems, in the phenomenon of chemical sensitivity (CS). Recent surveys suggest a significant prevalence of chemically sensitive subjects in the United States, but the mechanism linking exposure to symptoms remains unclear, despite the advancement of a variety of theoretical models. In many of these models, exposure of the nasal respiratory system to an airborne agent is the first step in the pathway leading to symptoms. In this article, we advance the hypothesis that interactions between environmental chemicals and the vomeronasal organ (VNO) may play a role in the etiology of CS. The VNO, a bilateral, tubular organ located in the nose, serves in animals as part of a sensitive chemosensory system; however, evidence suggesting that the VNO retains a functional role in the adult human is controversial. Reported characteristics of the human VNO relevant to CS, including location, prevalence, selective sensitivity to airborne chemical exposure, and capacity to produce systemic effects, are discussed within the context of this ongoing debate. Beyond relevance to CS, the demonstration of an active, adult VNO could have significant impact on environmental toxicology.

  10. The vomeronasal organ and chemical sensitivity: a hypothesis.

    PubMed Central

    Greene, Glenn J; Kipen, Howard M

    2002-01-01

    Environmental exposures to very low levels of airborne chemicals are associated with adverse symptoms, often affecting multiple organ systems, in the phenomenon of chemical sensitivity (CS). Recent surveys suggest a significant prevalence of chemically sensitive subjects in the United States, but the mechanism linking exposure to symptoms remains unclear, despite the advancement of a variety of theoretical models. In many of these models, exposure of the nasal respiratory system to an airborne agent is the first step in the pathway leading to symptoms. In this article, we advance the hypothesis that interactions between environmental chemicals and the vomeronasal organ (VNO) may play a role in the etiology of CS. The VNO, a bilateral, tubular organ located in the nose, serves in animals as part of a sensitive chemosensory system; however, evidence suggesting that the VNO retains a functional role in the adult human is controversial. Reported characteristics of the human VNO relevant to CS, including location, prevalence, selective sensitivity to airborne chemical exposure, and capacity to produce systemic effects, are discussed within the context of this ongoing debate. Beyond relevance to CS, the demonstration of an active, adult VNO could have significant impact on environmental toxicology. PMID:12194902

  11. Relationship between metal levels in the vent mussel Bathymodiolus azoricus and local microhabitat chemical characteristics of Eiffel Tower (Lucky Strike)

    NASA Astrophysics Data System (ADS)

    Martins, Inês; Cosson, Richard P.; Riou, Virginie; Sarradin, Pierre-Marie; Sarrazin, Jozée; Santos, Ricardo S.; Colaço, Ana

    2011-03-01

    The turbulent mixing of hydrothermal hot fluid with cold seawater creates large chemical gradients at a small spatial scale that may induce variable physiological and biochemical adaptations within the vent fauna. The adaptation to such a variable environment by the vent mussel Bathymodiolus azoricus relies on a dual symbiosis hosted in the gills, and digestion of particulate organic matter. The surrounding environment not only provides the necessary energy sources and suspended organic particles for the vent mussel nutrition, but also potentially toxic compounds such as metals. Our main goal was to see if there is a relation between metal accumulation in mussel organs and the chemical characteristics of their close environment. Mussels were collected at six locations in a cold part of the Eiffel Tower fluid-seawater mixing zone, characterized by distinct chemical compositions. Metals (Cd, Cu, Fe and Zn) and metallothioneins were quantified in the gills and digestive gland. The physiological condition of the sampled mussels was also evaluated using tissues and gill indices. Our study indicates that the accumulation of metals in B. azoricus is related to their spatial distribution and linked to fine scale environmental conditions that influence the physiological status of the organism.

  12. UPTAKE OF IONIZABLE ORGANIC CHEMICALS AT FISH GILLS

    EPA Science Inventory

    Uptake of organic acids by fish, and their toxicity, generally decrease with increasing pH above the pK, presumably due to neutral forms of such chemicals being more readily adsorbed than their ionized forms. However, uptake usually exceeds that expected based just on the concent...

  13. Salt-water organisms may yield chemicals. [Dunalilla

    SciTech Connect

    Not Available

    1981-01-28

    The harvesting of suspended cyanobacteria and algae that grow in saline water is being studied by Ecoenergetics. The organisms are promising sources of lipids, glycerol, polysaccharides and carotenoids. Israel already has a pilot plant in operation which harvests the green alga, Dunalilla, by centrifuging and chemical treatments.

  14. Fate of synthetic organic chemicals in soil-groundwater systems.

    PubMed

    Pancorbo, O C; Varney, T C

    1986-04-01

    Land disposal of municipal, industrial and agricultural wastes often leads to soil and groundwater contamination with synthetic organic chemicals. In this review, the fate of such organics in soils and the subsurface environment is discussed. In particular, the biodegradation of organic compounds in soils and the subsurface region, as well as the sorption of these compounds to soils is emphasized. Due to the disastrous impact of groundwater contamination on a community and the great cost of restoring a contaminated aquifer, a case is made for concentrating future efforts on isolating potential sources of groundwater contamination and instituting appropriate control measures.

  15. Intrinsic electrical conductivity of nanostructured metal-organic polymer chains.

    PubMed

    Hermosa, Cristina; Vicente Álvarez, Jose; Azani, Mohammad-Reza; Gómez-García, Carlos J; Fritz, Michelle; Soler, Jose M; Gómez-Herrero, Julio; Gómez-Navarro, Cristina; Zamora, Félix

    2013-01-01

    One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 10(4) S m(-1), three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices.

  16. Omar Yaghi on Chemistry and Metal Organic Frameworks

    ScienceCinema

    Omar Yaghi

    2016-07-12

    In this edited version of the hour long talk, Omar Yaghi, director of the Molecular Foundry, sat down in conversation with Jeff Miller, head of Public Affairs, on July 11th, 2012 to discuss his fascination with the hidden world of chemistry and his work on Metal Organic Frameworks.

  17. SEQUESTERING AGENTS FOR ACTIVE CAPS - REMEDIATION OF METALS AND ORGANICS

    SciTech Connect

    Knox, A; Michael Paller, M; Danny D. Reible, D; Xingmao Ma, X; Ioana G. Petrisor, I

    2007-05-10

    This research evaluated organoclays, zeolites, phosphates, and a biopolymer as sequestering agents for inorganic and organic contaminants. Batch experiments were conducted to identify amendments and mixtures of amendments for metal and organic contaminants removal and retention. Contaminant removal was evaluated by calculating partitioning coefficients. Metal retention was evaluated by desorption studies in which residue from the removal studies was extracted with 1 M MgCl{sub 2} solution. The results indicated that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective sequestering agents for metals in fresh and salt water. Organoclays were very effective sorbents for phenanthrene, pyrene, and benzo(a)pyrene. Partitioning coefficients for the organoclays were 3000-3500 ml g{sup -1} for benzo(a)pyrene, 400-450 ml g{sup -1} for pyrene, and 50-70 ml g{sup -1} for phenanthrene. Remediation of sites with a mixture of contaminants is more difficult than sites with a single contaminant because metals and organic contaminants have different fate and transport mechanisms in sediment and water. Mixtures of amendments (e.g., organoclay and rock phosphate) have high potential for remediating both organic and inorganic contaminants under a broad range of environmental conditions, and have promise as components in active caps for sediment remediation.

  18. Omar Yaghi on Chemistry and Metal Organic Frameworks

    SciTech Connect

    Omar Yaghi

    2012-07-23

    In this edited version of the hour long talk, Omar Yaghi, director of the Molecular Foundry, sat down in conversation with Jeff Miller, head of Public Affairs, on July 11th, 2012 to discuss his fascination with the hidden world of chemistry and his work on Metal Organic Frameworks.

  19. Metal-organic frameworks: Shuttling in the solid state

    NASA Astrophysics Data System (ADS)

    Olson, Mark A.

    2015-06-01

    Incorporating mechanically interlocked molecular shuttles within a metal-organic framework that has enough free space in the crystal lattice to permit volume-conserving translational motion sets the stage for defect-free molecular-electronic device fabrication and more.

  20. Adsorption of volatile organic compounds in porous metal-organic frameworks functionalized by polyoxometalates

    SciTech Connect

    Ma Fengji; Liu Shuxia; Liang Dadong; Ren Guojian; Wei Feng; Chen Yaguang; Su Zhongmin

    2011-11-15

    The functionalization of porous metal-organic frameworks (Cu{sub 3}(BTC){sub 2}) was achieved by incorporating Keggin-type polyoxometalates (POMs), and further optimized via alkali metal ion-exchange. In addition to thermal gravimetric analysis, IR, single-crystal X-ray diffraction, and powder X-ray diffraction, the adsorption properties were characterized by N{sub 2} and volatile organic compounds (VOCs) adsorption measurements, including short-chain alcohols (C<4), cyclohexane, benzene, and toluene. The adsorption enthalpies estimated by the modified Clausius-Clapeyron equation provided insight into the impact of POMs and alkali metal cations on the adsorption of VOCs. The introduction of POMs not only improved the stability, but also brought the increase of adsorption capacity by strengthening the interaction with gas molecules. Furthermore, the exchanged alkali metal cations acted as active sites to interact with adsorbates and enhanced the adsorption of VOCs. - Graphical Abstract: The adsorption behavior of volatile organic compounds in porous metal-organic frameworks functionalized by polyoxometalates has been systematically evaluated. Highlights: > Functionalization of MOFs was achieved by incorporating Keggin-type POMs. > Introduction of POMs improved the thermal stability and adsorption capacity. > Alkali metal ion-exchange modified the inclusion state and also enhanced the adsorption. > Adsorption enthalpies were estimated to study the impact of POMs and alkali metal cations.

  1. Method of making metal-doped organic foam products

    DOEpatents

    Rinde, James A.

    1981-01-01

    Organic foams having a low density and very small cell size and method for roducing same in either a metal-loaded or unloaded (nonmetal loaded) form are described. Metal-doped foams are produced by soaking a polymer gel in an aqueous solution of desired metal salt, soaking the gel successively in a solvent series of decreasing polarity to remove water from the gel and replace it with a solvent of lower polarity with each successive solvent in the series being miscible with the solvents on each side and being saturated with the desired metal salt, and removing the last of the solvents from the gel to produce the desired metal-doped foam having desired density cell size, and metal loading. The unloaded or metal-doped foams can be utilized in a variety of applications requiring low density, small cell size foam. For example, rubidium-doped foam made in accordance with the invention has utility in special applications, such as in x-ray lasers.

  2. Adsorptive desulfurization and denitrogenation using metal-organic frameworks.

    PubMed

    Ahmed, Imteaz; Jhung, Sung Hwa

    2016-01-15

    With the increasing worldwide demand for energy, utilization of fossil fuels is increasing proportionally. Additionally, new and unconventional energy sources are also being utilized at an increasing rate day-by-day. These sources, along with some industrial processes, result in the exposal of several sulfur- and nitrogen-containing compounds (SCCs and NCCs, respectively) to the environment, and the exposure is one of the greatest environmental threats in the recent years. Although, several methods were established for the removal of these pollutants during the last few decades, recent advancements in adsorptive desulfurization and denitrogenation (ADS and ADN, respectively) with metal-organic frameworks (MOFs) make this the most promising and remarkable method. Therefore, many research groups are currently involved with ADS and ADN with MOFs, and the results are improving gradually by modifying the MOF adsorbents according to several specific adsorption mechanisms. In this review, ADS and ADN studies are thoroughly discussed for both liquid-phase and gas-phase adsorption. The MOF modification procedures, which are important for improved adsorption, are also described. To improve the knowledge among the scientific community, it is very important to understand the detailed chemistry and mechanism involved in a chemical process, which also creates the possibility and pathway for further developments in research and applications. Therefore, the mechanisms related to the adsorption procedures are also discussed in detail. From this review, it can be expected that the scientific community will obtain an understanding of the current state of ADS and ADN, their importance, and some encouragement and insight to take the research knowledge base to a higher level. PMID:26368800

  3. Adsorptive desulfurization and denitrogenation using metal-organic frameworks.

    PubMed

    Ahmed, Imteaz; Jhung, Sung Hwa

    2016-01-15

    With the increasing worldwide demand for energy, utilization of fossil fuels is increasing proportionally. Additionally, new and unconventional energy sources are also being utilized at an increasing rate day-by-day. These sources, along with some industrial processes, result in the exposal of several sulfur- and nitrogen-containing compounds (SCCs and NCCs, respectively) to the environment, and the exposure is one of the greatest environmental threats in the recent years. Although, several methods were established for the removal of these pollutants during the last few decades, recent advancements in adsorptive desulfurization and denitrogenation (ADS and ADN, respectively) with metal-organic frameworks (MOFs) make this the most promising and remarkable method. Therefore, many research groups are currently involved with ADS and ADN with MOFs, and the results are improving gradually by modifying the MOF adsorbents according to several specific adsorption mechanisms. In this review, ADS and ADN studies are thoroughly discussed for both liquid-phase and gas-phase adsorption. The MOF modification procedures, which are important for improved adsorption, are also described. To improve the knowledge among the scientific community, it is very important to understand the detailed chemistry and mechanism involved in a chemical process, which also creates the possibility and pathway for further developments in research and applications. Therefore, the mechanisms related to the adsorption procedures are also discussed in detail. From this review, it can be expected that the scientific community will obtain an understanding of the current state of ADS and ADN, their importance, and some encouragement and insight to take the research knowledge base to a higher level.

  4. Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Cacha, Brian Joseph Gonda

    Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

  5. Physico-chemical changes in dissolved organic matters in the rhizosphere of plants grown in soil amended with organic wastes: an in-situ investigation.

    NASA Astrophysics Data System (ADS)

    Djae, Tanalou; Bravin, Matthieu; Garnier, Cédric; Mayen, Jean-Fabien; Doelsch, Emmanuel

    2014-05-01

    In agricultural context, prerequisite condition to forecast trace metal phytodisponibility is to evaluate trace metal speciation in the rhizosphere solution, especially in soil amended with organic wastes. The most advanced trace metal speciation models (e.g. WHAM, NICA-DONNAN) take into account dissolved organic matter (DOM) reactivity toward trace metals. Generally, the scientific community uses, a fixed percentage of DOM reactivity, usually of 40 % to 80 %, to predict trace metal speciation. However, recent studies have demonstrated that the binding capacity of DOM towards trace metals is much larger than expected. The aim of our study was to investigate the mechanisms supporting the variability in DOM reactivity by assessing the physico-chemical changes of DOM in the bulk-soil and rhizosphere in context of agricultural recycling of organic wastes. An in-situ experiment was conducted in Reunion Island (Indian Ocean). Two plant species, i.e. a graminaceous species the fescue (Festuca rubra) and a dicotyledonous species the tomato (Lycopersicon esculentum), were grown on a soil where we applied two types of organic wastes (pig manure compost and poultry manure compost) at three rates and a mineral fertilizer. Following this experiment, the soil either adhering to the roots (i.e. rhizosphere) or not (i.e. bulk-soil) was sampled and the soil solution was recovered by chemical extraction. DOM concentration, total acidity and DOM fluorescence were measured. Root activities and organic wastes induced variations in the physico-chemical parameters of DOM. DOM concentration tended to increase in bulk-soil with increasing organic waste application rate. DOM concentrations measured in rhizosphere are significantly greater than those in the bulk-soil especially when organic wastes were applied to soil. Preliminary results allow us to observe a decrease in the density of carboxylic-like (pKa

  6. Approaches to Establishing the Chemical Structure of Extraterrestrial Organic Solids

    NASA Technical Reports Server (NTRS)

    Cody, G. D.; Alexander, C. M. OD.; Wirick, Susan

    2003-01-01

    The majority of extraterrestrial organic matter in carbonaceous chondrites resides in a chemically complex, insoluble and perhaps macromolecular phase. We have been applying a series of independent solid state NMR experiments that are designed to provide a self consistent chemical characterization of this complex material. To date we have thoroughly analyzed 8 organic residues from different meteorites, including a CR2 (EET92042), CIl(Orgueil), CM2 (Murchison), Tagish Lake, CM2 (AlH83100), CM2 (Cold Bokkefeld), CM2 (Mighei), CM3 (Y86720). In fig 1. (1)H to (13)C cross polarization NMR spectra of four of these are shown. Note that there exists an enormous range in chemistry exhibited in organic solid [evident by the breadth of the spectral features both in the aliphatic region (sp(sup 3)) and the aromatic region (sp(sup 2))]. There is also considerable differences in the carbon chemistry across the meteorite groups.

  7. Optical Detection of Organic Chemical Biosignatures at Hydrothermal Vents

    NASA Technical Reports Server (NTRS)

    Conrad, P. G.; Lane, A. L.; Bhartia, R.; Hug, W. H.

    2004-01-01

    We have developed a non-contact, optical life detection instrument that can detect organic chemical biosignatures in a number of different environments, including dry land, shallow aqueous, deep marine or in ice. Hence, the instrument is appropriate as a biosignature survey tool both for Mars exploration or in situ experiments in an ice-covered ocean such as one might wish to explore on Europa. Here, we report the results we obtained on an expedition aboard the Russian oceanographic vessel Akademik Mstislav Keldysh to hydrothermal vent sites in the Pacific Ocean using our life detection instrument MCDUVE, a multichannel, deep ultraviolet excitation fluorescence detector. MCDUVE detected organic material distribution on rocks near the vent, as well as direct detection of organisms, both microbial and microscopic. We also were able to detect organic material issuing directly from vent chimneys, measure the organic signature of the water column as we ascended, and passively observe the emission of light directly from some vents.

  8. In Situ Synthesis of Metal Sulfide Nanoparticles Based on 2D Metal-Organic Framework Nanosheets.

    PubMed

    Lu, Qipeng; Zhao, Meiting; Chen, Junze; Chen, Bo; Tan, Chaoliang; Zhang, Xiao; Huang, Ying; Yang, Jian; Cao, Feifei; Yu, Yifu; Ping, Jianfeng; Zhang, Zhicheng; Wu, Xue-Jun; Zhang, Hua

    2016-09-01

    A facile in situ synthetic method is developed to synthesize metal sulfide nanoparticles based on 2D M-TCPP (M = Cu, Cd, or Co, TCPP = tetrakis(4-carboxyphenyl)porphyrin)) metal-organic framework nanosheets. The obtained CuS/Cu-TCPP composite nanosheet is used as the active material in photoelectrochemical cells, showing notably increased photocurrent due to the improved exciton separation and charge carrier transport.

  9. 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.

  10. 40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... organic chemicals subcategory. 414.70 Section 414.70 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Bulk Organic Chemicals § 414.70 Applicability; description of the bulk organic chemicals...

  11. 40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... organic chemicals subcategory. 414.70 Section 414.70 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Bulk Organic Chemicals § 414.70 Applicability; description of the bulk organic chemicals...

  12. 40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... organic chemicals subcategory. 414.70 Section 414.70 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Bulk Organic Chemicals § 414.70 Applicability; description of the bulk organic chemicals...

  13. 40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... organic chemicals subcategory. 414.70 Section 414.70 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Bulk Organic Chemicals § 414.70 Applicability; description of the bulk organic chemicals...

  14. 40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... organic chemicals subcategory. 414.70 Section 414.70 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Bulk Organic Chemicals § 414.70 Applicability; description of the bulk organic chemicals...

  15. Sedimentary Trace Metal-Organic Interactions as Proxies for Oceanic Redox Conditions

    NASA Astrophysics Data System (ADS)

    Cruse, A. M.; Lyons, T. W.; Hannigan, R.

    2007-12-01

    Knowledge of trace-metal partitioning in oceanic sediments (e.g., Fe, Mo, U, Zn) are requisite to the construction of accurate models of geochemical cycling in modern and ancient waters. Factors such as oxygen penetration depth and bottom-water redox; sedimentation rate; and supply of reactants, such as dissolved sulfide, are known to affect metal sequestration in and remobilization from coastal sediments. In addition to these factors, the flux of organic carbon (OC) and the composition of this carbon are also a key in the sequestration of these metals. Currently, however, there is an absence of quantitative information on the mass balance of metals fixed in coastal sediments through direct interactions with OC, how OC remineralization affects this mass balance, and the specific nature of the metal-OC relationship. To address these issues, we have undertaken a field-based study to test the hypothesis that porewater redox conditions are recorded in the concentrations of trace metals bound in the sedimentary OC pool. We have collected sediments from several modern anoxic/euxinic basins: the central Black Sea, the Orca Basin, the Cariaco Basin, and Effingham Inlet (Vancouver Island). These environments vary in terms of dissolved sulfide concentrations and sedimentary iron sulfide geochemistry. Additionally, the sediments are characterized by a range in OC concentrations, and proximity to terrestrial sources. Extractable organic carbon was characterized with gas chromatography, and OC-bound metals are quantified using high-performance liquid chromatography- inductively coupled mass spectrometry. The preliminary results suggest that variations in the ratios of aromatic to saturate hydrocarbons may control the speciation of metals in the organic carbon pool. Bottomwater redox may be one factor controlling this relationship, although it is currently unclear if this is due to variations in metal speciation or the direct involvement of S in the OC-metal reaction mechanism

  16. Characterization of magnetite-organic complex nanoparticles by metal-reducing bacteria.

    PubMed

    Kim, Yumi; Jang, Heedong; Suh, Yongjae; Roh, Yul

    2011-08-01

    Magnetite nanoparticles exhibit clear technological potential for biomedical applications. The objectives of this study were to synthesize magnetite-organic complex nanoparticles through the use of metal-reducing bacteria and characterize the mineralogical and surface chemical properties of these nanoparticles as well as to test their potential applications in biomedical technology with regards to their protein immobilization capacity. The microbially formed magnetite nanoparticles had a size of around 10 nm with a spherical shape and were coated with organics containing an abundance of reactive carboxyl groups without any chemical process for functionalizing them. These microbial processes may lead to a simple preparation of functional magnetite-organic complex nanoparticles which have benefits for biomedical applications.

  17. INFLUENCE OF ORGANIC COSOLVENTS ON THE SORPTION KINETICS OF HYDROPHOBIC ORGANIC CHEMICALS

    EPA Science Inventory

    A quantitative examination of the kinetics of sorption of hydrophobic organic chemicals by soils from mixed solvents reveals that the reverse sorption rate constant (k2) increases log-linearly with increasing volume fraction of organic cosolvent (fc). This relationship was expec...

  18. A Green Strategy to Prepare Metal Oxide Superstructure from Metal-Organic Frameworks

    PubMed Central

    Song, Yonghai; Li, Xia; Wei, Changting; Fu, Jinying; Xu, Fugang; Tan, Hongliang; Tang, Juan; Wang, Li

    2015-01-01

    Metal or metal oxides with diverse superstructures have become one of the most promising functional materials in sensor, catalysis, energy conversion, etc. In this work, a novel metal-organic frameworks (MOFs)-directed method to prepare metal or metal oxide superstructure was proposed. In this strategy, nodes (metal ions) in MOFs as precursors to form ordered building blocks which are spatially separated by organic linkers were transformed into metal oxide micro/nanostructure by a green method. Two kinds of Cu-MOFs which could reciprocally transform by changing solvent were prepared as a model to test the method. Two kinds of novel CuO with three-dimensional (3D) urchin-like and 3D rods-like superstructures composed of nanoparticles, nanowires and nanosheets were both obtained by immersing the corresponding Cu-MOFs into a NaOH solution. Based on the as-formed CuO superstructures, a novel and sensitive nonenzymatic glucose sensor was developed. The small size, hierarchical superstructures and large surface area of the resulted CuO superstructures eventually contribute to good electrocatalytic activity of the prepared sensor towards the oxidation of glucose. The proposed method of hierarchical superstructures preparation is simple, efficient, cheap and easy to mass production, which is obviously superior to pyrolysis. It might open up a new way for hierarchical superstructures preparation. PMID:25669731

  19. Role of chemical and ecological factors in trophic transfer of organic chemicals in aquatic food webs

    SciTech Connect

    Russell, R.W.; Gobas, F.A.P.C. . School of Resource and Environmental Management); Haffner, G.D. )

    1999-06-01

    Trophic transfer of chlorinated organic contaminants was investigated in an aquatic community composed of zooplankton, benthic invertebrates, and fish. Biomagnification, measured as the increase in lipid-based chemical concentrations in predator over that in prey, was observed for high-K[sub OW] chemicals (log K[sub OW] > 6.3). Low-K[sub OW] chemicals (log K[sub OW] < 5.5) did not biomagnify in the food web, and chemicals with log K[sub OW] between 5.5 and 6.3 showed some evidence of biomagnification. Trophic level differences in chemical accumulation in the food web could not be attributed to bioconcentration into increasing trophic levels with increasing lipid levels, as no relationship was observed between trophic position and lipid content of organisms. Plots of contaminant-ordinated principal component scores in component space predicted the detailed diets of the species examined. It is concluded that (1) trophic interactions play a crucial role in the distribution of high-K[sub OW] chemicals but not for low-K[sub OW] chemicals and that (2) contaminant distributions provide a means to determine structure in aquatic communities.

  20. Metal Nanoparticles Protected with Monolayers: Applications for Chemical Vapor Sensing and Gas Chromatography

    SciTech Connect

    Grate, Jay W.; Nelson, David A.; Skaggs, Rhonda L.; Synovec, Robert E.; Gross, Gwen M.

    2004-03-31

    Nanoparticles and nanoparticle-based materials are of considerable interest for their unique properties and their potential for use in a variety of applications. Metal nanoparticles, in which each particle’s surface is coated with a protective organic monolayer, are of particular interest because the surface monolayer stabilizes them relative to aggregation and they can be taken up into solutions.(1-4) As a result they can be processed into thin films for device applications. We will refer to these materials as monolayer-protected nanoparticles, or MPNs. Typically the metal is gold, the organic layer is a self-assembled thiol layer, and this composition will be assumed throughout the remainder of this chapter. A diversity of materials and properties is readily accessible by straightforward synthetic procedures, either by the structures of the monolayer-forming thiols used in the synthesis or by post-synthetic modifications of the monolayers. A particularly promising application for these materials is as selective layers on chemical vapor sensors. In this role, the thin film of MPNs on the device surface serves to collect and concentrate gas molecules at the sensor’s surface. Their sorptive properties also lend them to use as new nanostructured gas chromatographic stationary phases. This chapter will focus on the sorptive properties of MPNs as they relate to chemical sensors and gas chromatography.

  1. Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response

    NASA Astrophysics Data System (ADS)

    Herderick, Edward D.; Polomoff, Nicholas A.; Huey, Bryan D.; Padture, Nitin P.

    2010-08-01

    A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO3-Au and Au-PbTiO3-Au. This method entails electrodeposition of segmented nanowires of Au-TiO2-Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO2 segments into BaTiO3 or PbTiO3 segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics.

  2. Chemical evolution and the preservation of organic compounds on Mars

    NASA Technical Reports Server (NTRS)

    Kanavarioti, Anastassia; Mancinelli, Rocco L.

    1989-01-01

    Several lines of evidence suggest that the environment on early Mars and early Earth were very similar. Since life is abundant on Earth, it seems likely that conditions on early Earth were conducive to chemical evolution and the origin of life. The similarity between early Mars and early Earth encourages the hypothesis that chemical evolution might have also occurred on Mars, but that decreasing temperatures and the loss of its atmosphere brought the evolution to a halt. The possibility of finding on Mars remnants of organic material dating back to this early clement period is addressed.

  3. Reactions of metal cluster anions with inorganic and organic molecules in the gas phase.

    PubMed

    Zhao, Yan-Xia; Liu, Qing-Yu; Zhang, Mei-Qi; He, Sheng-Gui

    2016-07-28

    The study of gas phase ion-molecule reactions by state-of-the-art mass spectrometric experiments in conjunction with quantum chemistry calculations offers an opportunity to clarify the elementary steps and mechanistic details of bond activation and conversion processes. In the past few decades, a considerable number of publications have been devoted to the ion-molecule reactions of metal clusters, the experimentally and theoretically tractable models for the active phase of condensed phase systems. The focus of this perspective concerns progress on activation and transformation of important inorganic and organic molecules by negatively charged metal clusters. The metal cluster anions cover bare metal clusters as well as ligated systems with oxygen, carbon, and nitrogen, among others. The following important issues have been summarized and discussed: (i) dependence of chemical reactivity and selectivity on cluster structures and sizes, metals and metal oxidation states, odd-even electron numbers, etc. and (ii) effects of doping, ligation, and pre-adsorption on the reactivity of metal clusters toward rather inert molecules. PMID:27346242

  4. Designing Metal-Organic Frameworks for Catalytic Applications

    NASA Astrophysics Data System (ADS)

    Ma, Liqing; Lin, Wenbin

    Metal-organic frameworks (MOFs) are constructed by linking organic bridging ligands with metal-connecting points to form infinite network structures. Fine tuning the porosities of and functionalities within MOFs through judicious choices of bridging ligands and metal centers has allowed their use as efficient heterogeneous catalysts. This chapter reviews recent developments in designing porous MOFs for a variety of catalytic reactions. Following a brief introduction to MOFs and a comparison between porous MOFs and zeolites, we categorize catalytically active achiral MOFs based on the types of catalytic sites and organic transformations. The unsaturated metal-connecting points in MOFs can act as catalytic sites, so can the functional groups that are built into the framework of a porous MOF. Noble metal nanoparticles can also be entrapped inside porous MOFs for catalytic reactions. Furthermore, the channels of porous MOFs have been used as reaction hosts for photochemical and polymerization reactions. We also summarize the latest results of heterogeneous asymmetric catalysis using homochiral MOFs. Three distinct strategies have been utilized to develop homochiral MOFs for catalyzing enantioselective reactions, namely the synthesis of homochiral MOFs from achiral building blocks by seeding or by statistically manipulating the crystal growth, directing achiral ligands to form homochiral MOFs in chiral environments, and incorporating chiral linker ligands with functionalized groups. The applications of homochiral MOFs in several heterogeneous asymmetric catalytic reactions are also discussed. The ability to synthesize value-added chiral molecules using homochiral MOF catalysts differentiates them from traditional zeolite catalysis, and we believe that in the future many more homochiral MOFs will be designed for catalyzing numerous asymmetric organic transformations.

  5. Metal-Organic and Organic TADF-Materials: Status, Challenges and Characterization.

    PubMed

    Bergmann, Larissa; Zink, Daniel M; Bräse, Stefan; Baumann, Thomas; Volz, Daniel

    2016-06-01

    This section covers both metal-organic and organic materials that feature thermally activated delayed fluorescence (TADF). Such materials are especially useful for organic light-emitting diodes (OLEDs), a technology that was introduced in commercial displays only recently. We compare both material classes to show commonalities and differences, highlighting current issues and challenges. Advanced spectroscopic techniques as valuable tools to develop solutions to those issues are introduced. Finally, we provide an outlook over the field and highlight future trends. PMID:27573262

  6. Chemical Control of Plasmons in Metal Chalcogenide and Metal Oxide Nanostructures.

    PubMed

    Mattox, Tracy M; Ye, Xingchen; Manthiram, Karthish; Schuck, P James; Alivisatos, A Paul; Urban, Jeffrey J

    2015-10-14

    The field of plasmonics has grown to impact a diverse set of scientific disciplines ranging from quantum optics and photovoltaics to metamaterials and medicine. Plasmonics research has traditionally focused on noble metals; however, any material with a sufficiently high carrier density can support surface plasmon modes. Recently, researchers have made great gains in the synthetic (both intrinsic and extrinsic) control over the morphology and doping of nanoscale oxides, pnictides, sulfides, and selenides. These synthetic advances have, collectively, blossomed into a new, emerging class of plasmonic metal chalcogenides that complement traditional metallic materials. Chalcogenide and oxide nanostructures expand plasmonic properties into new spectral domains and also provide a rich suite of chemical controls available to manipulate plasmons, such as particle doping, shape, and composition. New opportunities in plasmonic chalcogenide nanomaterials are highlighted in this article, showing how they may be used to fundamentally tune the interaction and localization of electromagnetic fields on semiconductor surfaces in a way that enables new horizons in basic research and energy-relevant applications.

  7. Tracing the migration history of metal catalysts in metal-assisted chemically etched silicon.

    PubMed

    Güder, Firat; Yang, Yang; Küçükbayrak, Umut M; Zacharias, Margit

    2013-02-26

    Three-dimensional (3D) visualization of complex embedded nanopore networks in silicon requires expensive machinery and tedious sample preparation procedures such as electron tomography, also known as 3D transmission electron microscopy. In this article, we report a new, fast, powerful, and low-cost three-dimensional imaging technique with sub-5 nm resolution. This new imaging method is applied to metal-assisted chemically etched monocrystalline Si to demonstrate its capabilities. The AFEI (atomic layer deposition-fill-etch-imaging) technique consists of three simple process steps that are available in most material research settings. First the porous substrate is conformally coated with an atomic layer deposition (ALD) metal oxide layer. ALD is able to penetrate deep into complex, high aspect ratio pores, as it is a sequential gas-phase deposition process. Next, the cross-section of the ALD-filled porous Si substrate is etched with high-density fluorine-based plasma processing, which yields very high selectivity toward Si (e.g., >400:1 for Si:ZnO). This step removes the bulk Si and exposes the metal oxide structures grown inside the pores. In the last step, the sample cross-section is examined using a standard scanning electron microscope at various angles, which allows precise imaging of hidden features and reconstruction of a 3D model of the embedded pore network. PMID:23368781

  8. Chemical and Magnetic Order in Vapor-Deposited Metal Films

    NASA Astrophysics Data System (ADS)

    Rooney, Peter Wiliam

    1995-01-01

    A stochastic Monte Carlo model of vapor deposition and growth of a crystalline, binary, A_3 B metallic alloy with a negative energy of mixing has been developed which incorporates deposition and surface diffusion in a physically correct manner and allows the simulation of deposition rates that are experimentally realizable. The effects of deposition rate and growth temperature on the development of short range order (SRO) in vapor-deposited films have been examined using this model. SRO in the simulated films increases with growth temperature up to the point at which the temperature corresponds to the energy of mixing, but we see no corresponding development of anisotropic SRO (preferential ordering of A-B pairs along the growth direction). Epitaxial (100) and (111) CoPt_3 films have been deposited over a range of growth temperatures from -50^circ C to 800^circC. Curie temperature (T_{rm c}) and saturation magnetization are dramatically enhanced in those films grown near 400^circ C over the values expected for the chemically homogeneous alloy. Magnetization data indicates that the high T _{rm c} films are inhomogeneous. These phenomena are interpreted as evidence of a previously unobserved magnetically driven miscibility gap in the Co-Pt phase diagram. Films grown near 400^circ C exhibit large uniaxial perpendicular magnetic anisotropy that cannot be accounted for by strain. The observed anisotropy coincides with the chemical phase separation and it seems likely that these two phenomena are related. Long range order (LRO) in the as-deposited films peaks at a growth temperature of 630^circC and then decreases with decreasing growth temperature. The decrease in LRO is either due to kinetic frustration or to competition from magnetically induced Co clustering. Theoretical phase diagrams based on the appropriate Blume-Emery-Griffiths Hamiltonian suggest the latter.

  9. When hole extraction determines charge transfer across metal-organic-metal structure

    NASA Astrophysics Data System (ADS)

    Govor, L. V.; Reiter, G.; Parisi, J.

    2016-03-01

    We examined the charge transfer in metal-organic-metal structure, where the contact resistance of the extracting interface is larger than the resistance of the organic crystalline material and the resistance of the injecting interface. If direct tunneling (low voltage) and Fowler-Nordheim tunnelling (high voltage) across both interfaces take place, part of the injected holes remains located in the organic crystal because of the blocking action of the extracting interface, but not because of traps within the organic crystalline material (which was negligible). If Fowler-Nordheim tunneling across the injecting interface and direct tunneling across the extracting interface take place for high voltages, the latter leads to the deviation of the total current-voltage characteristic from the power law I∼ Vγ with γ>2 to Ohm's law with γ≃1.0 .

  10. Seamless metal-clad fiber-reinforced organic matrix composite structures and process for their manufacture

    NASA Technical Reports Server (NTRS)

    Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

    1990-01-01

    A metallic outer sleeve is provided which is capable of enveloping a hollow metallic inner member having continuous reinforcing fibers attached to the distal end thereof. The inner member is then introduced into outer sleeve until inner member is completely enveloped by outer sleeve. A liquid matrix member is then injected into space between inner member and outer sleeve. A pressurized heat transfer medium is flowed through the inside of inner member, thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. The novelty of this invention resides in the development of a efficient method of producing seamless metal clad fiber reinforced organic matrix composite structures.

  11. Gas uptake and chemical aging of semisolid organic aerosol particles.

    PubMed

    Shiraiwa, Manabu; Ammann, Markus; Koop, Thomas; Pöschl, Ulrich

    2011-07-01

    Organic substances can adopt an amorphous solid or semisolid state, influencing the rate of heterogeneous reactions and multiphase processes in atmospheric aerosols. Here we demonstrate how molecular diffusion in the condensed phase affects the gas uptake and chemical transformation of semisolid organic particles. Flow tube experiments show that the ozone uptake and oxidative aging of amorphous protein is kinetically limited by bulk diffusion. The reactive gas uptake exhibits a pronounced increase with relative humidity, which can be explained by a decrease of viscosity and increase of diffusivity due to hygroscopic water uptake transforming the amorphous organic matrix from a glassy to a semisolid state (moisture-induced phase transition). The reaction rate depends on the condensed phase diffusion coefficients of both the oxidant and the organic reactant molecules, which can be described by a kinetic multilayer flux model but not by the traditional resistor model approach of multiphase chemistry. The chemical lifetime of reactive compounds in atmospheric particles can increase from seconds to days as the rate of diffusion in semisolid phases can decrease by multiple orders of magnitude in response to low temperature or low relative humidity. The findings demonstrate that the occurrence and properties of amorphous semisolid phases challenge traditional views and require advanced formalisms for the description of organic particle formation and transformation in atmospheric models of aerosol effects on air quality, public health, and climate.

  12. Modelling the chemical speciation of trace metals in the surface waters of the Humber system

    PubMed

    Tipping; Lofts; Lawlor

    1998-03-24

    Calculations have been performed to estimate the chemical speciation at equilibrium of six divalent trace metals (Co, Ni, Cu, Zn, Cd, Pb) in riverine, estuarine and marine surface waters of the Humber system. The Windermere Humic Aqueous Model (WHAM) was used to compute distributions of dissolved metals. In the rivers, the free aquo ion (M2+) is a major part of dissolved Co, Ni, Zn and Cd, but accounts for less than 1% of Cu and Pb. The main complexes are formed with carbonate ligands and dissolved natural organic matter, represented by fulvic acid. In the low-salinity region of the estuary and in seawater, complexation with fulvic acid is less significant, although most of the Cu is still in this form, while the speciation of Cd is dominated by chloride complexes. Adsorption of metals by suspended particulate matter was calculated with a simple model involving the concentrations of the free aquo ions (M2+) and H+, together with a constant for each metal estimated from laboratory adsorption data. Calculated adsorbed concentrations were used to predict the partition coefficient (KD) for each metal under different circumstances. The values can vary by an order of magnitude or more, depending upon solution conditions. Typical values for rivers, low-salinity water and seawater are within one order of magnitude of observations. However, there is a general tendency to underestimate KD, possible reasons being (1) neglect of electrostatic enhancement of adsorption at low ionic strengths; and (2) analytical overestimation of particulate metal in equilibrium with the solution phase. There is a strong case for the development of a more sophisticated adsorption model.

  13. Changes in soil chemical and microbiological properties during 4 years of application of various organic residues.

    PubMed

    Odlare, M; Pell, M; Svensson, K

    2008-01-01

    A 4-year field trial was established in eastern Sweden to evaluate the effects of organic waste on soil chemical and microbiological variables. A simple crop rotation with barley and oats was treated with either compost from household waste, biogas residue from household waste, anaerobically treated sewage sludge, pig manure, cow manure or mineral fertilizer. All fertilizers were amended in rates corresponding to 100kgNha(-1)year(-1). The effects of the different types of organic waste were evaluated by subjecting soil samples, taken each autumn 4 weeks after harvest, to an extensive set of soil chemical (pH, Org-C, Tot-N, Tot-P, Tot-S, P-AL, P-Olsen, K-AL, and some metals) and microbiological (B-resp, SIR, microSIR active and dormant microorganisms, PDA, microPDA, PAO, Alk-P and N-min) analyses. Results show that compost increased pH, and that compost as well as sewage sludge increased plant available phosphorus; however, the chemical analysis showed few clear trends over the 4 years and few clear relations to plant yield or soil quality. Biogas residues increased substrate induced respiration (SIR) and, compared to the untreated control amendment of biogas residues as well as compost, led to a higher proportion of active microorganisms. In addition, biogas residues increased potential ammonia oxidation rate (PAO), nitrogen mineralization capacity (N-min) as well as the specific growth rate constant of denitrifiers (microPDA). Despite rather large concentrations of heavy metals in some of the waste products, no negative effects could be seen on either chemical or microbiological soil properties. Changes in soil microbial properties appeared to occur more rapidly than most chemical properties. This suggests that soil microbial processes can function as more sensitive indicators of short-term changes in soil properties due to amendment of organic wastes. PMID:17697770

  14. Electronic Chemical Potentials of Porous Metal–Organic Frameworks

    PubMed Central

    2014-01-01

    The binding energy of an electron in a material is a fundamental characteristic, which determines a wealth of important chemical and physical properties. For metal–organic frameworks this quantity is hitherto unknown. We present a general approach for determining the vacuum level of porous metal–organic frameworks and apply it to obtain the first ionization energy for six prototype materials including zeolitic, covalent, and ionic frameworks. This approach for valence band alignment can explain observations relating to the electrochemical, optical, and electrical properties of porous frameworks. PMID:24447027

  15. Unraveling the chemical space of terrestrial and meteoritic organic matter

    NASA Astrophysics Data System (ADS)

    Schmitt-Kopplin, Philippe; Harir, Mourad; Hertkorn, Norbert; Kanawati, Basem; Ruf, Alexander; Quirico, Eric; Bonal, Lydie; Beck, Pierre; Gabelica, Zelimir

    2015-04-01

    In terrestrial environments natural organic matter (NOM) occurs in soils, freshwater and marine environments, in the atmosphere and represents an exceedingly complex mixture of organic compounds that collectively exhibits a nearly continuous range of properties (size-reactivity continuum). In these materials, the "classical" biogeosignatures of the (biogenic and geogenic) precursor molecules, like lipids, lignins, proteins and natural products have been attenuated, often beyond recognition, during a succession of biotic and abiotic (e.g. photo- and redox chemistry) reactions. Because of this loss of biochemical signature, these materials can be designated non-repetitive complex systems. The access to extra-terrestrial organic matter is given i.e. in the analysis of meteoritic materials. Numerous descriptions of organic molecules present in organic chondrites have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, many molecular analyses are so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a non-targeted ultrahigh-resolution molecular analysis of the solvent-accessible organic fraction of meteorite extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. The description of the molecular complexity provides hints on heteroatoms chronological assembly, shock and thermal events and revealed recently new classes of thousands of novel organic, organometallic compounds uniquely found in extra-terrestrial materials and never described in terrestrial systems. This high polymolecularity suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological and biogeochemical-driven chemical space. (ultra

  16. GaN Epitaxial Layer Grown with Conductive Al(x)Ga(1-x)N Buffer Layer on SiC Substrate Using Metal Organic Chemical Vapor Deposition.

    PubMed

    So, Byeongchan; Lee, Kyungbae; Lee, Kyungjae; Heo, Cheon; Pyeon, Jaedo; Ko, Kwangse; Jang, Jongjin; Nam, Okhyun

    2016-05-01

    This study investigated GaN epitaxial layer growth with a conductive Al(x)Ga(1-x)N buffer layer on n-type 4H-SiC by high-temperature metalorganic chemical vapor deposition (HT-MOCVD). The Al composition of the Al(x)Ga(1-x)N buffer was varied from 0% to 100%. In terms of the crystal quality of the GaN layer, 79% Al was the optimal composition of the Al(x)Ga(1-x)N buffer layer in our experiment. A vertical conductive structure was fabricated to measure the current voltage (I-V) characteristics as a function of Al composition, and the I-V curves showed that the resistance increased with increasing Al concentration of the Al(x)Ga(1-x)N buffer layer. PMID:27483845

  17. Synthesis Single Layer Transition Metal Dichalcogenides with Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Li, Yi-Hsien; Wang, Han; Yu, Lili; Fang, Wenjing; Palacios, Tomas; Li, Lain-Jong; Kong, Jing

    2013-03-01

    Recently, monolayers of layered transition metal dichalcogenides (LTMD), such as MX2 (M =Mo, W and X =S, Se), have been reported to exhibit significant spin-valley coupling and optoelectronic performances because of the unique structural symmetry and band structures. Monolayers in this class of materials offered a burgeoning field in fundamental physics, energy harvesting, electronics and optoelectronics. However, most studies to date are hindered with great challenges on the synthesis and transfer of high quality LTMD monolayers. Hence, a feasible synthetic process to overcome the challenges is essential. Here, we demonstrate the growth of high-quality MS2 (M =Mo, W) monolayers using ambient-pressure-chemical-vapor-deposition (APCVD) with the seeding of aromatic molecules. Electronic transport and optical performances of the as-grown MS2 monolayers are comparable to those of exfoliated MS2 monolayers. The growth of MS2 monolayer is achieved on various surfaces. Growth mechanism on the novel synthetic process is investigated. Understanding and better control of seeds for the novel growth on the class of materials may stimulate the progress in the emerging filed.

  18. Apparatus for sensing volatile organic chemicals in fluids

    DOEpatents

    Hughes, Robert C.; Manginell, Ronald P.; Jenkins, Mark W.; Kottenstette, Richard; Patel, Sanjay V.

    2005-06-07

    A chemical-sensing apparatus is formed from the combination of a chemical preconcentrator which sorbs and concentrates particular volatile organic chemicals (VOCs) and one or more chemiresistors that sense the VOCs after the preconcentrator has been triggered to release them in concentrated form. Use of the preconcentrator and chemiresistor(s) in combination allows the VOCs to be detected at lower concentration than would be possible using the chemiresistor(s) alone and further allows measurements to be made in a variety of fluids, including liquids (e.g. groundwater). Additionally, the apparatus provides a new mode of operation for sensing VOCs based on the measurement of decay time constants, and a method for background correction to improve measurement precision.

  19. Negative ion photoelectron spectroscopy of metal clusters, metal-organic clusters, metal oxides, and metal-doped silicon clusters

    NASA Astrophysics Data System (ADS)

    Zheng, Weijun

    The techniques of time-of-flight mass spectrometry and negative ion photoelectron spectroscopy were utilized to study metal clusters (Mgn -, Znn-, Can -, Mnn-, CuAln -, LiAln-, and NmSn n-), metal-organic complexes (Tin(benzene) m-, Fn(benzene)m- , Nin(benzene)m-), metal oxides(AuO-, PtO-, TaOn -, HfO2-, and MnnO -), and metal-doped semiconductor clusters (CrSin -, GdmSin- and HoSi n-). The study of magnesium and zinc cluster anions shows that they have magic numbers at size 9, 19 and 34, and the closures and reopenings of the s-p band gap are related to the mass spectra magic numbers. The evolution of electronic structure in Can clusters resembles that of Mgn - and Znn- with band gap closure and reopening. However, the electronic structures Can- clusters are more complicated and the magic numbers are different from those of Mgn- and Znn -. That might due to the involvement of calcium's empty d orbitals. In Mn clusters, a dramatic change of electronic structure was observed at Mn5-. The transition of metallic and magnetic properties is strongly related to the s-d hybridization. The photoelectron study of LiAln- is consistent with theoretical predictions, which described LiAl13 as alkali-halide-like ionic entity, Li+(Al13)-. The results of CuAln- show that copper atom might occupy interior position in these clusters. The results of Nam Snn- implied that Na4Sn 4 and NaSn5- could be described as (Na +)4Sn44- and (Na +)Sn52-, respectively. The formation of these species indicates the existence of Zintl phase structure in the gas phase. Tin(Bz)n+1- clusters have multiple-decker sandwich structures with each titanium atom located between two parallel benzene rings. The structures of Fen(Bz)m - and Nin(Bz)m- are characterized with a metal cluster core caged by benzene molecules. The information for the electronic states of PtO, AuO, and TaOn (n = 1--3) were obtained from the photoelectron spectra of their corresponding negative ions. The coincidence between electron

  20. Size-controlled synthesis of transition metal nanoparticles through chemical and photo-chemical routes

    NASA Astrophysics Data System (ADS)

    Tangeysh, Behzad

    The central objective of this work is developing convenient general procedures for controlling the formation and stabilization of nanoscale transition metal particles. Contemporary interest in developing alternative synthetic approaches for producing nanoparticles arises in large part from expanding applications of the nanomaterials in areas such as catalysis, electronics and medicine. This research focuses on advancing the existing nanoparticle synthetic routes by using a new class of polymer colloid materials as a chemical approach, and the laser irradiation of metal salt solution as a photo-chemical method to attain size and shape selectivity. Controlled synthesis of small metal nanoparticles with sizes ranging from 1 to 5nm is still a continuing challenge in nanomaterial synthesis. This research utilizes a new class of polymer colloid materials as nano-reactors and protective agents for controlling the formation of small transition metal nanoparticles. The polymer colloid particles were formed from cross-linking of dinegatively charged metal precursors with partially protonated poly dimethylaminoethylmethacrylate (PDMAEMA). Incorporation of [PtCl6]2- species into the colloidal particles prior to the chemical reduction was effectively employed as a new strategy for synthesis of unusually small platinum nanoparticles with narrow size distributions (1.12 +/-0.25nm). To explore the generality of this approach, in a series of proof-of-concept studies, this method was successfully employed for the synthesis of small palladium (1.4 +/-0.2nm) and copper nanoparticles (1.5 +/-0.6nm). The polymer colloid materials developed in this research are pH responsive, and are designed to self-assemble and/or disassemble by varying the levels of protonation of the polymer chains. This unique feature was used to tune the size of palladium nanoparticles in a small range from 1nm to 5nm. The procedure presented in this work is a new convenient room temperature route for synthesis of

  1. Metal-Organic Frameworks as Catalysts for Oxidation Reactions.

    PubMed

    Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Garcia, Hermenegildo

    2016-06-01

    This Concept is aimed at describing the current state of the art in metal-organic frameworks (MOFs) as heterogeneous catalysts for liquid-phase oxidations, focusing on three important substrates, namely, alkenes, alkanes and alcohols. Emphases are on the nature of active sites that have been incorporated within MOFs and on future targets to be set in this area. Thus, selective alkene epoxidation with peroxides or oxygen catalyzed by constitutional metal nodes of MOFs as active sites are still to be developed. Moreover, no noble metal-free MOF has been reported to date that can act as a general catalyst for the aerobic oxidation of primary and secondary aliphatic alcohols. In contrast, in the case of alkanes, a target should be to tune the polarity of MOF internal pores to control the outcome of the autooxidation process, resulting in the selective formation of alcohol/ketone mixtures at high conversion.

  2. Comparison of characteristics of fluorine doped zinc and gallium tin oxide composite thin films deposited on stainless steel 316 bipolar plate by electron cyclotron resonance-metal organic chemical vapor deposition for proton exchange membrane fuel cells.

    PubMed

    Park, Jihun; Hudaya, Chairul; Lee, Joong Kee

    2011-09-01

    In order to replace the brittle graphite bipolar plates currently used for the PEMFC stack, coated SUS 316 was employed. As a metallic bipolar plate, coated SUS 316 can provide higher mechanical strength, better durability to shocks and vibration, less permeability, improved thermal and bulk electrical conductivity, as well as being thinner and lighter. To enhance the interfacial contact resistance and corrosion resistance of SUS 316, the deposition of GTO:F and ZTO:F composite films was carried out by ECR-MOCVD. The surface morphology of the films consisted of tiny elliptically shaped grains with a thickness of 1 microm. The corrosion current for GTO:F was 0.13 Acm(-2) which was much lower than that of bare SUS 316 (50.16 Acm(-2)). The GTO:F coated film had the smallest corrosion current due to the formation of a tight surface morphology with very few pin-holes. The GTO:F coated film exhibited the highest cell voltage and power density due to its lower ICR values. PMID:22097519

  3. Bhasmas: unique ayurvedic metallic-herbal preparations, chemical characterization.

    PubMed

    Kumar, A; Nair, A G C; Reddy, A V R; Garg, A N

    2006-03-01

    Bhasmas are unique Ayurvedic metallic preparations with herbal juices/fruits, known in the Indian subcontinent since the seventh century BC and widely recommended for treatment of a variety of chronic ailments. Twenty bhasmas based on calcium, iron, zinc, mercury, silver, potassium, arsenic, copper, tin, and gemstones were analyzed for up to 18 elements by instrumental neutron activation analysis, including their C, H, N, and S contents. In addition to the major constituent element found at % level, several other essential elements such as Na, K, Ca, Mg, V, Mn, Fe, Cu, and Zn have also been found in microg/g amounts and ultratrace (ng/g) amounts of Au and Co. These seem to remain chelated with organic ligands derived from medicinal herbs. The bhasmas are biologically produced nanoparticles and are taken along with milk, butter, honey, or ghee (a preparation from milk); thus, this makes these elements easily assimilable, eliminating their harmful effects and enhancing their biocompatibility. Siddha Makaradhwaja, a mercury preparation is found to be stoichiometrically HgS without any traces of any other element. Similarly, Swet Parpati is stoichiometrically KNO3 but is found to have Mn, Cu, Zn, Na, P, and Cl as well. An attempt has been made to correlate the metallic contents with their medicinal importance. Na and K, the two electrolytic elements, seem to be well correlated, although K/Na varies in a wide range from 0.06 to 95, with specifically low values for Ca-, Fe-, and Zn-based bhasmas. K/P also varies in a wide range from 0.23 to 12, although for most bhasmas (n = 12), it is 2.3 +/- 1.2. Further, Fe/Mn is linearly correlated (r = 0.96) with Fe in nine noniron bhasmas.

  4. Bhasmas: unique ayurvedic metallic-herbal preparations, chemical characterization.

    PubMed

    Kumar, A; Nair, A G C; Reddy, A V R; Garg, A N

    2006-03-01

    Bhasmas are unique Ayurvedic metallic preparations with herbal juices/fruits, known in the Indian subcontinent since the seventh century BC and widely recommended for treatment of a variety of chronic ailments. Twenty bhasmas based on calcium, iron, zinc, mercury, silver, potassium, arsenic, copper, tin, and gemstones were analyzed for up to 18 elements by instrumental neutron activation analysis, including their C, H, N, and S contents. In addition to the major constituent element found at % level, several other essential elements such as Na, K, Ca, Mg, V, Mn, Fe, Cu, and Zn have also been found in microg/g amounts and ultratrace (ng/g) amounts of Au and Co. These seem to remain chelated with organic ligands derived from medicinal herbs. The bhasmas are biologically produced nanoparticles and are taken along with milk, butter, honey, or ghee (a preparation from milk); thus, this makes these elements easily assimilable, eliminating their harmful effects and enhancing their biocompatibility. Siddha Makaradhwaja, a mercury preparation is found to be stoichiometrically HgS without any traces of any other element. Similarly, Swet Parpati is stoichiometrically KNO3 but is found to have Mn, Cu, Zn, Na, P, and Cl as well. An attempt has been made to correlate the metallic contents with their medicinal importance. Na and K, the two electrolytic elements, seem to be well correlated, although K/Na varies in a wide range from 0.06 to 95, with specifically low values for Ca-, Fe-, and Zn-based bhasmas. K/P also varies in a wide range from 0.23 to 12, although for most bhasmas (n = 12), it is 2.3 +/- 1.2. Further, Fe/Mn is linearly correlated (r = 0.96) with Fe in nine noniron bhasmas. PMID:16632893

  5. Organic molecules on silicon surface: A way to tune metal dependent Schottky barrier

    NASA Astrophysics Data System (ADS)

    Rabinal, M. K.

    2016-09-01

    Effect of covalently bonded organic molecules on p-type Si surfaces, in controlling the performance of metal-silicon Schottky junctions, is studied. Monolayers of 1-dodecyne were formed on hydrated surfaces of p-type Si ((100) orientation) using weak Lewis acid. The chemical modification results in highly homogeneous surfaces. Gold-Si and Aluminum-Si junctions were prepared, both, on modified and unmodified Si surfaces, and I-V characteristics were studied. The results have been interpreted in terms of energy band diagrams. It is demonstrated that the molecular monolayer of 1-dodecyne is effective in controlling the surface states leading to unpinning of the Fermi level and junction responding to the work function of the metal, as expected from theoretical considerations. The simple method presented provides a unique technique to tune the electrical properties of devices with metal-semiconductor interfaces.

  6. Using blood samples to estimate persistent organic pollutants and metals in green sea turtles (Chelonia mydas).

    PubMed

    van de Merwe, Jason P; Hodge, Mary; Olszowy, Henry A; Whittier, Joan M; Lee, Shing Y

    2010-04-01

    Persistent organic pollutants (POPs) and heavy metals have been reported in a number of green turtle (Chelonia mydas) populations worldwide. However, due to ethical considerations, these studies have generally been on tissues from deceased and stranded animals. The purpose of this study was to investigate the use of blood samples to estimate the tissue contamination of live C. mydas populations. This study analysed 125 POP compounds and eight heavy metals in the blood, liver, kidney and muscle of 16 C. mydas from the Sea World Sea Turtle Rehabilitation Program, Gold Coast, Australia. Strong correlations were observed between blood and tissue concentrations for a number of POPs and metals. Furthermore, these correlations were observed over large ranges of turtle size, sex and condition. These results indicate that blood samples are a reliable non-lethal method for predicting chemical contamination in C. mydas.

  7. REMOVAL OF ORGANIC CHEMICALS FROM WASTEWATER BY SURFACTANT SEPARATION

    SciTech Connect

    Unknown

    2002-01-01

    This research presents a novel hybrid process for removing organic chemicals from contaminated water. The process uses surfactant to carry out two unit operations (1) Extraction; (2) Foam flotation. In the first step, surfactant is used to extract most of the amounts of organic contaminants in the stream. In the second step, foam flotation is used to further reduce organic contaminants and recover surfactant from the stream. The process combines the advantages of extraction and foam flotation, which allows the process not only to handle a wide range of organic contaminants, but also to effectively treat a wide range of the concentration of organic contaminants in the stream and reduce it to a very low level. Surfactant regeneration can be done by conventional methods. This process is simple and low cost. The wastes are recoverable. The objective of this research is to develop an environmentally innocuous process for the wastewater or reclaimed water treatment with the ability to handle a wide range of organic contaminants, also to effectively treat a wide range of the concentration of organic contaminants in contaminated water and reduce it to a very low level, finally, provides simpler, less energy cost and economically-practical process design. Another purpose is to promote the environmental concern in minority students and encourage minority students to become more involved in environmental engineering research.

  8. Recent progress in the synthesis of metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Sun, Yujia; Zhou, Hong-Cai

    2015-10-01

    Metal-organic frameworks (MOFs) have attracted considerable attention for various applications due to their tunable structure, porosity and functionality. In general, MOFs have been synthesized from isolated metal ions and organic linkers under hydrothermal or solvothermal conditions via one-spot reactions. The emerging precursor approach and kinetically tuned dimensional augmentation strategy add more diversity to this field. In addition, to speed up the crystallization process and create uniform crystals with reduced size, many alternative synthesis routes have been explored. Recent advances in microwave-assisted synthesis and electrochemical synthesis are presented in this review. In recent years, post-synthetic approaches have been shown to be powerful tools to synthesize MOFs with modified functionality, which cannot be attained via de novo synthesis. In this review, some current accomplishments of post-synthetic modification (PSM) based on covalent transformations and coordinative interactions as well as post-synthetic exchange (PSE) in robust MOFs are provided.

  9. Increased Thermal Conductivity in Metal-Organic Heat Carrier Nanofluids.

    PubMed

    Nandasiri, Manjula I; Liu, Jian; McGrail, B Peter; Jenks, Jeromy; Schaef, Herbert T; Shutthanandan, Vaithiyalingam; Nie, Zimin; Martin, Paul F; Nune, Satish K

    2016-01-01

    Metal-organic heat carriers (MOHCs) are recently developed nanofluids containing metal-organic framework (MOF) nanoparticles dispersed in various base fluids including refrigerants (R245Fa) and methanol. Here, we report the synthesis and characterization of MOHCs containing nanoMIL-101(Cr) and graphene oxide (GO) in an effort to improve the thermo-physical properties of various base fluids. MOHC/GO nanocomposites showed enhanced surface area, porosity, and nitrogen adsorption compared with the intrinsic nanoMIL-101(Cr) and the properties depended on the amount of GO added. MIL-101(Cr)/GO in methanol exhibited a significant increase in the thermal conductivity (by approximately 50%) relative to that of the intrinsic nanoMIL-101(Cr) in methanol. The thermal conductivity of the base fluid (methanol) was increased by about 20%. The increase in the thermal conductivity of nanoMIL-101(Cr) MOHCs due to GO functionalization is explained using a classical Maxwell model. PMID:27302196

  10. Increased Thermal Conductivity in Metal-Organic Heat Carrier Nanofluids

    NASA Astrophysics Data System (ADS)

    Nandasiri, Manjula I.; Liu, Jian; McGrail, B. Peter; Jenks, Jeromy; Schaef, Herbert T.; Shutthanandan, Vaithiyalingam; Nie, Zimin; Martin, Paul F.; Nune, Satish K.

    2016-06-01

    Metal-organic heat carriers (MOHCs) are recently developed nanofluids containing metal-organic framework (MOF) nanoparticles dispersed in various base fluids including refrigerants (R245Fa) and methanol. Here, we report the synthesis and characterization of MOHCs containing nanoMIL-101(Cr) and graphene oxide (GO) in an effort to improve the thermo-physical properties of various base fluids. MOHC/GO nanocomposites showed enhanced surface area, porosity, and nitrogen adsorption compared with the intrinsic nanoMIL-101(Cr) and the properties depended on the amount of GO added. MIL-101(Cr)/GO in methanol exhibited a significant increase in the thermal conductivity (by approximately 50%) relative to that of the intrinsic nanoMIL-101(Cr) in methanol. The thermal conductivity of the base fluid (methanol) was increased by about 20%. The increase in the thermal conductivity of nanoMIL-101(Cr) MOHCs due to GO functionalization is explained using a classical Maxwell model.

  11. Increased Thermal Conductivity in Metal-Organic Heat Carrier Nanofluids

    PubMed Central

    Nandasiri, Manjula I.; Liu, Jian; McGrail, B. Peter; Jenks, Jeromy; Schaef, Herbert T.; Shutthanandan, Vaithiyalingam; Nie, Zimin; Martin, Paul F.; Nune, Satish K.

    2016-01-01

    Metal-organic heat carriers (MOHCs) are recently developed nanofluids containing metal-organic framework (MOF) nanoparticles dispersed in various base fluids including refrigerants (R245Fa) and methanol. Here, we report the synthesis and characterization of MOHCs containing nanoMIL-101(Cr) and graphene oxide (GO) in an effort to improve the thermo-physical properties of various base fluids. MOHC/GO nanocomposites showed enhanced surface area, porosity, and nitrogen adsorption compared with the intrinsic nanoMIL-101(Cr) and the properties depended on the amount of GO added. MIL-101(Cr)/GO in methanol exhibited a significant increase in the thermal conductivity (by approximately 50%) relative to that of the intrinsic nanoMIL-101(Cr) in methanol. The thermal conductivity of the base fluid (methanol) was increased by about 20%. The increase in the thermal conductivity of nanoMIL-101(Cr) MOHCs due to GO functionalization is explained using a classical Maxwell model. PMID:27302196

  12. Seed-Mediated Synthesis of Metal-Organic Frameworks.

    PubMed

    Xu, Hai-Qun; Wang, Kecheng; Ding, Meili; Feng, Dawei; Jiang, Hai-Long; Zhou, Hong-Cai

    2016-04-27

    The synthesis of phase-pure metal-organic frameworks (MOFs) is of prime importance but remains a significant challenge because of the flexible and diversified coordination modes between metal ions and organic linkers. In this work, we report the synthesis of phase-pure MOFs via a facile seed-mediated approach. For several "accompanying" pairs of Zr-porphyrinic MOFs that are prone to yield mixtures, by fixing all reaction parameters except introducing seed crystals, MOFs in phase-pure forms have been obtained because the stage of MOF nucleation, which generates mixed nuclei, is bypassed. In addition, phase-pure MOF isomers with distinct pore structures have also been prepared through such an approach, revealing its versatility. To the best of our knowledge, this is an initial report on seed-assisted synthesis of phase-pure MOFs.

  13. Defects in Metal-Organic Frameworks: Challenge or Opportunity?

    PubMed

    Sholl, David S; Lively, Ryan P

    2015-09-01

    Metal-organic framework (MOF) materials are nanoporous materials whose crystalline character has made them attractive targets for synthesis of new materials and potential use in a diverse set of applications. The vast majority of studies of MOFs envision these materials as having ideal crystal structures. This Perspective gives an overview of the current understanding of defects in MOFs. Compared to related materials such as zeolites, the ability to detect and control defects in MOFs is nascent. Nevertheless, it is likely that defects will play a vital role in a number of contexts where MOFs are of widespread interest, so advancing our understanding of these structural features will be important in coming years. Potential origins of point defects, plane defects, and surface defects are discussed. The difficulty of defect detection in metal-organic frameworks is discussed and useful paths for future work are provided. PMID:26268796

  14. Lanthanides: new metallic cathode materials for organic photovoltaic cells.

    PubMed

    Nikiforov, Maxim P; Strzalka, Joseph; Jiang, Zhang; Darling, Seth B

    2013-08-21

    Organic photovoltaics (OPVs) are compliant with inexpensive, scalable, and environmentally benign manufacturing technologies. While substantial attention has been focused on optimization of active layer chemistry, morphology, and processing, far less research has been directed to understanding charge transport at the interfaces between the electrodes and the active layer. Electrical properties of these interfaces not only impact efficiency, but also play a central role in stability of organic solar cells. Low work function metals are the most widely used materials for the electron transport layer with Ca being the most common material. In bulk heterojunction OPV devices, low work function metals are believed to mirror the role they play in OLEDs, where such metals are used to control carrier selectivity, transport, extraction, and blocking, as well as interface band bending. Despite their advantages, low work function materials are generally prone to reactions with water, oxygen, nitrogen, and carbon dioxide from air leading to rapid device degradation. Here we discuss the search for a new metallic cathode interlayer material that increases device stability and still provides device efficiency similar to that achieved with a Ca interlayer.

  15. Hydrogen storage in microporous metal-organic frameworks with exposed metal sites.

    PubMed

    Dincă, Mircea; Long, Jeffrey R

    2008-01-01

    Owing to their high uptake capacity at low temperature and excellent reversibility kinetics, metal-organic frameworks have attracted considerable attention as potential solid-state hydrogen storage materials. In the last few years, researchers have also identified several strategies for increasing the affinity of these materials towards hydrogen, among which the binding of H(2) to unsaturated metal centers is one of the most promising. Herein, we review the synthetic approaches employed thus far for producing frameworks with exposed metal sites, and summarize the hydrogen uptake capacities and binding energies in these materials. In addition, results from experiments that were used to probe independently the metal-hydrogen interaction in selected materials will be discussed.

  16. Using risk-ranking of metals to identify which poses the greatest threat to freshwater organisms in the UK.

    PubMed

    Donnachie, Rachel L; Johnson, Andrew C; Moeckel, Claudia; Pereira, M Glória; Sumpter, John P

    2014-11-01

    Freshwater aquatic organisms face the challenge of being exposed to a multitude of chemicals discharged by the human population. The objective of this study was to rank metals according to the threat they pose to aquatic organisms. This will contribute to a wider Chemical Strategy for freshwater which will risk-rank all chemicals based on their potential risk to wildlife in a UK setting. The method involved comparing information on ecotoxicological thresholds with measured concentrations in rivers. The bioconcentration factor was also considered as a ranking method. The metals; Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn, were analysed using this approach. Triclosan and lindane were used as comparative organic pollutants. Using a range of ranking techniques, Cu, Al and Zn came top of the list of concern, with Cu coming first.

  17. Solvent-dependent cation exchange in metal-organic frameworks.

    PubMed

    Brozek, Carl K; Bellarosa, Luca; Soejima, Tomohiro; Clark, Talia V; López, Núria; Dincă, Mircea

    2014-06-01

    We investigated which factors govern the critical steps of cation exchange in metal-organic frameworks by studying the effect of various solvents on the insertion of Ni(2+) into MOF-5 and Co(2+) into MFU-4l. After plotting the extent of cation insertion versus different solvent parameters, trends emerge that offer insight into the exchange processes for both systems. This approach establishes a method for understanding critical aspects of cation exchange in different MOFs and other materials.

  18. Environmental availability of chlorinated organics, explosives, and metals in soils

    SciTech Connect

    Anderson, W.C.; Loehr, R.C.; Smith, B.P.

    1999-08-01

    Environmental availability is key to defining the extent of remediation required. Nationally recognized experts summarize what is known about the environmental availability of chlorinated organics (Perry McCarty), explosives (Judith Pennington), and metals (Rufus Chaney). It also summarizes the current use of environmental availability to set cleanup goals for petroleum hydrocarbons and identifies essential research needed to expand the knowledge base for environmental availability.

  19. Crystalline capsules: metal-organic frameworks locked by size-matching ligand bolts.

    PubMed

    Wang, Hao; Xu, Jian; Zhang, Da-Shuai; Chen, Qiang; Wen, Rong-Mei; Chang, Ze; Bu, Xian-He

    2015-05-11

    Metal-organic frameworks (MOFs) are shown to be good examples of a new class of crystalline porous materials for guest encapsulation. Since the encapsulation/release of guest molecules in MOF hosts is a reversible process in nature, how to prevent the leaching of guests from the open pores with minimal and nondestructive modifications of the structure is a critical issue. To address this issue, we herein propose a novel strategy of encapsulating guests by introducing size-matching organic ligands as bolts to lock the pores of the MOFs through deliberately anchoring onto the open metal sites in the pores. Our proposed strategy provides a mechanical way to prevent the leaching of guests and thereby has less dependence on the specific chemical environment of the hosts, thus making it applicable for a wide variety of existing MOFs once the size-matching ligands are employed.

  20. Heavy metal and organic contaminants in mangrove ecosystems of China: a review.

    PubMed

    Zhang, Zai-Wang; Xu, Xiang-Rong; Sun, Yu-Xin; Yu, Shen; Chen, Yong-Shan; Peng, Jia-Xi

    2014-10-01

    China's rapid economic growth has been accompanied by increasing environmental pollution. Mangrove ecosystems are now facing greater pollution pressures due to elevated chemical discharges from various land-based sources. Data on the levels of heavy metals and organic pollutants in mangrove compartments (sediments, plants, zoobenthos, and fish) in China over the past 20 years have been summarized to evaluate the current pollution status of the mangrove ecosystem. Overall, the Pearl River and Jiulong River estuaries were severely polluted spots. Concentrations of Cu, Zn, Cd, and Pb in mangrove sediments of Guangdong, Fujian, and Hong Kong were higher than those from Guangxi and Hainan. The pollution status was closely linked to industrialization and urbanization. The highest concentrations of polycyclic aromatic hydrocarbons (PAHs) were found in mangrove sediments from Hong Kong, followed by Fujian and Guangdong. Mangrove plants tend to have low-enriched ability for heavy metals and organic pollutants. Much higher levels of Pb, Cd, and Hg were observed in mollusks.

  1. Complex organic molecules at metal surfaces: bonding, organisation and chirality [review article

    NASA Astrophysics Data System (ADS)

    Barlow, S. M.; Raval, R.

    2003-08-01

    Surface science techniques have now reached a stage of maturity that has enabled their successful deployment in the study of complex adsorption systems. A particular example of this success has been the understanding that has been gained regarding the behaviour of multi-functional organic molecules at metal surfaces. These organic-metal systems show enormous diversity, starting from their local description which can vary in terms of chemical structure, orientation and bonding. Additionally, in many cases, these complex organic molecules self-organise into beautiful, ordered superstructures held together by networks of intermolecular bonds. Both these aspects enable a single organic molecule-metal system to exhibit a wide-ranging and flexible approach to its environment, leading to a variety of adsorption phases, according to the prevailing temperature and coverage conditions. In this review we have attempted to capture this complexity by constructing adsorption phase diagrams from the available literature for complex carboxylic acids, amino acids, anhydrides and ring systems, all deposited under controlled conditions onto defined metal surfaces. These provide an accessible, pictorial basis of the adsorption phases which are then discussed further in the text of the review. Finally, interest has recently focused on the property of chirality that can be bestowed at an achiral metal surface by the adsorption of these complex organic molecules. The creation of such architectures offers the opportunity for ultimate stereocontrol of reactions and responses at surfaces. We have, therefore, specifically examined the various ways in which chirality can be expressed at a surface and provide a framework for classifying chiral hierarchies that are manifested at surfaces, with particular attention being paid to the progression of chirality from a local to a global level.

  2. On the occurrence of metallic character in the periodic table of the chemical elements.

    PubMed

    Hensel, Friedrich; Slocombe, Daniel R; Edwards, Peter P

    2015-03-13

    The classification of a chemical element as either 'metal' or 'non-metal' continues to form the basis of an instantly recognizable, universal representation of the periodic table (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23; Poliakoff M. & Tang S. 2015 Phil. Trans. R. Soc. A 373: , 20140211). Here, we review major, pre-quantum-mechanical innovations (Goldhammer DA. 1913 Dispersion und Absorption des Lichtes; Herzfeld KF. 1927 Phys. Rev. 29: , 701-705) that allow an understanding of the metallic or non-metallic status of the chemical elements under both ambient and extreme conditions. A special emphasis will be placed on recent experimental advances that investigate how the electronic properties of chemical elements vary with temperature and density, and how this invariably relates to a changing status of the chemical elements. Thus, the prototypical non-metals, hydrogen and helium, becomes metallic at high densities; and the acknowledged metals, mercury, rubidium and caesium, transform into their non-metallic forms at low elemental densities. This reflects the fundamental fact that, at temperatures above the absolute zero of temperature, there is therefore no clear dividing line between metals and non-metals. Our conventional demarcation of chemical elements as metals or non-metals within the periodic table is of course governed by our experience of the nature of the elements under ambient conditions. Examination of these other situations helps us to examine the exact divisions of the chemical elements into metals and non-metals (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23). PMID:25666074

  3. On the occurrence of metallic character in the periodic table of the chemical elements.

    PubMed

    Hensel, Friedrich; Slocombe, Daniel R; Edwards, Peter P

    2015-03-13

    The classification of a chemical element as either 'metal' or 'non-metal' continues to form the basis of an instantly recognizable, universal representation of the periodic table (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23; Poliakoff M. & Tang S. 2015 Phil. Trans. R. Soc. A 373: , 20140211). Here, we review major, pre-quantum-mechanical innovations (Goldhammer DA. 1913 Dispersion und Absorption des Lichtes; Herzfeld KF. 1927 Phys. Rev. 29: , 701-705) that allow an understanding of the metallic or non-metallic status of the chemical elements under both ambient and extreme conditions. A special emphasis will be placed on recent experimental advances that investigate how the electronic properties of chemical elements vary with temperature and density, and how this invariably relates to a changing status of the chemical elements. Thus, the prototypical non-metals, hydrogen and helium, becomes metallic at high densities; and the acknowledged metals, mercury, rubidium and caesium, transform into their non-metallic forms at low elemental densities. This reflects the fundamental fact that, at temperatures above the absolute zero of temperature, there is therefore no clear dividing line between metals and non-metals. Our conventional demarcation of chemical elements as metals or non-metals within the periodic table is of course governed by our experience of the nature of the elements under ambient conditions. Examination of these other situations helps us to examine the exact divisions of the chemical elements into metals and non-metals (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23).

  4. Constructing Chemical Concepts through a Study of Metals and Metal Ions: Guided Inquiry Experiments for General Chemistry

    NASA Astrophysics Data System (ADS)

    Lamba, Ram S.; Sharma, Shiva; Lloyd, Baird W.

    1997-09-01

    This paper describes a set of inquiry-based experiments designed to help students develop an understanding of basic chemical concepts within the framework of studying the properties and reactivity of metals and metal ions. The students perform these experiments before the concepts are discussed in class, with the emphasize on the construction of meaning from observation, measurement, and data analysis. The set includes: Are All Pennies the Same?, which introduces students to the differences between extensive and intensive quantities. How Much is Enough?, examines the quantitative aspects of the reaction between metals and hydrogen ions leading to the concept of the mole and stoichiometric calculations. How Much is Too Much?, which identifies and distinguishes between limiting reagents, excess reagents, spectator ions and reactant ions. What is an Active Metal?, provides the observations needed to sort common metals into an activity series and How Active are the Active Metals?, allows students to develop a quantitative model of metal activity.

  5. Evaluating metal-organic frameworks for natural gas storage

    SciTech Connect

    Mason, JA; Veenstra, M; Long, JR

    2014-01-01

    Metal-organic frameworks have received significant attention as a new class of adsorbents for natural gas storage; however, inconsistencies in reporting high-pressure adsorption data and a lack of comparative studies have made it challenging to evaluate both new and existing materials. Here, we briefly discuss high-pressure adsorption measurements and review efforts to develop metal-organic frameworks with high methane storage capacities. To illustrate the most important properties for evaluating adsorbents for natural gas storage and for designing a next generation of improved materials, six metal-organic frameworks and an activated carbon, with a range of surface areas, pore structures, and surface chemistries representative of the most promising adsorbents for methane storage, are evaluated in detail. High-pressure methane adsorption isotherms are used to compare gravimetric and volumetric capacities, isosteric heats of adsorption, and usable storage capacities. Additionally, the relative importance of increasing volumetric capacity, rather than gravimetric capacity, for extending the driving range of natural gas vehicles is highlighted. Other important systems-level factors, such as thermal management, mechanical properties, and the effects of impurities, are also considered, and potential materials synthesis contributions to improving performance in a complete adsorbed natural gas system are discussed.

  6. 40 CFR 455.30 - Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... metallo-organic pesticide chemicals manufacturing subcategory. 455.30 Section 455.30 Protection of...) PESTICIDE CHEMICALS Metallo-Organic Pesticide Chemicals Manufacturing Subcategory § 455.30 Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory. The provisions of...

  7. 40 CFR 455.30 - Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... metallo-organic pesticide chemicals manufacturing subcategory. 455.30 Section 455.30 Protection of...) PESTICIDE CHEMICALS Metallo-Organic Pesticide Chemicals Manufacturing Subcategory § 455.30 Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory. The provisions of...

  8. 40 CFR 455.30 - Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... metallo-organic pesticide chemicals manufacturing subcategory. 455.30 Section 455.30 Protection of...) PESTICIDE CHEMICALS Metallo-Organic Pesticide Chemicals Manufacturing Subcategory § 455.30 Applicability; description of the metallo-organic pesticide chemicals manufacturing subcategory. The provisions of...

  9. 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.

  10. Mechanisms of Heavy Metal Sequestration in Soils: Plant-Microbe Interactions and Organic Matter Aging

    SciTech Connect

    Fan, Teresa W. M.; Higashi, Richard M.; Crowley

    2001-06-25

    The myriad of human activities including strategic and energy development at various DOE installations have resulted in the contamination of soils and waterways that can seriously threaten human and ecosystem health. Development of efficacious and economical remediation technologies is needed to ameliorate these immensely costly problems. Bioremediation (both plant and microbe-based) has promising potential to meet this demand but still requires advances in fundamental knowledge. For bioremediation of heavy metals, the three-way interaction of plant root, microbial community, and soil organic matter (SOM)1 in the rhizosphere is critically important for long-term sustainability but often underconsidered. Particularly urgent is the need to understand processes that lead to metal ion stabilization in soils, which is crucial to all of the goals of bioremediation: removal, stabilization, and transformation. This project will build on the knowledge that we have generated on the role of root exudation and metabolism for metal mobilization and accumulation, to address the following objectives: (1) Identify molecular markers and characterize the chemical nature of recalcitrant SOM pools that are involved in below ground metal ion interactions, which are likely to be markers for sustainable sequestration; (2) Utilize (1) to determine plant and microbial factors that contribute to sustainable metal sequestration or mobility, as well as bioavailability; (3) Utilize information from (1) and (2) to explore efficacious means for enhancing sustainable phytostabilization of heavy metals in the subsurface zone.

  11. ELECTRONIC AND CHEMICAL PROPERTIES OF PD IN BIMETALLIC SYSTEMS: HOW MUCH DO WE KNOW ABOUT HETERONUCLEAR METAL-METAL BONDING?

    SciTech Connect

    RODRIGUEZ,J.A.

    2001-09-27

    The experimental and theoretical studies described above illustrate the complex nature of the heteronuclear metal-metal bond. In many cases, bimetallic bonding induces a significant redistribution of charge around the bonded metals. This redistribution of charge is usually linked to the strength of the bimetallic bond, affects the position of the core and valence levels of the metals, and can determine the chemical reactivity of the system under study. New concepts are emerging [22,23,34,36] and eventually the coupling of experiment and theory can be useful for designing more efficient bimetallic catalysts [98,106,107].

  12. 40 CFR 414.60 - Applicability; description of the commodity organic chemicals subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... commodity organic chemicals subcategory. 414.60 Section 414.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Commodity Organic Chemicals § 414.60 Applicability; description of the commodity organic...

  13. 40 CFR 414.80 - Applicability; description of the specialty organic chemicals subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... specialty organic chemicals subcategory. 414.80 Section 414.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Specialty Organic Chemicals § 414.80 Applicability; description of the specialty organic...

  14. 40 CFR 414.60 - Applicability; description of the commodity organic chemicals subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... commodity organic chemicals subcategory. 414.60 Section 414.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Commodity Organic Chemicals § 414.60 Applicability; description of the commodity organic...

  15. 40 CFR 414.80 - Applicability; description of the specialty organic chemicals subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... specialty organic chemicals subcategory. 414.80 Section 414.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Specialty Organic Chemicals § 414.80 Applicability; description of the specialty organic...

  16. 40 CFR 414.60 - Applicability; description of the commodity organic chemicals subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... commodity organic chemicals subcategory. 414.60 Section 414.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Commodity Organic Chemicals § 414.60 Applicability; description of the commodity organic...

  17. 40 CFR 414.80 - Applicability; description of the specialty organic chemicals subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... specialty organic chemicals subcategory. 414.80 Section 414.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Specialty Organic Chemicals § 414.80 Applicability; description of the specialty organic...

  18. 40 CFR 414.80 - Applicability; description of the specialty organic chemicals subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... specialty organic chemicals subcategory. 414.80 Section 414.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Specialty Organic Chemicals § 414.80 Applicability; description of the specialty organic...

  19. 40 CFR 414.80 - Applicability; description of the specialty organic chemicals subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... specialty organic chemicals subcategory. 414.80 Section 414.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Specialty Organic Chemicals § 414.80 Applicability; description of the specialty organic...

  20. 40 CFR 414.60 - Applicability; description of the commodity organic chemicals subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... commodity organic chemicals subcategory. 414.60 Section 414.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Commodity Organic Chemicals § 414.60 Applicability; description of the commodity organic...

  1. 40 CFR 414.60 - Applicability; description of the commodity organic chemicals subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... commodity organic chemicals subcategory. 414.60 Section 414.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Commodity Organic Chemicals § 414.60 Applicability; description of the commodity organic...

  2. High-internal-phase emulsions stabilized by metal-organic frameworks and derivation of ultralight metal-organic aerogels.

    PubMed

    Zhang, Bingxing; Zhang, Jianling; Liu, Chengcheng; Peng, Li; Sang, Xinxin; Han, Buxing; Ma, Xue; Luo, Tian; Tan, Xiuniang; Yang, Guanying

    2016-01-01

    To design high-internal-phase emulsion (HIPE) systems is of great interest from the viewpoints of both fundamental researches and practical applications. Here we demonstrate for the first time the utilization of metal-organic framework (MOF) for HIPE formation. By stirring the mixture of water, oil and MOF at room temperature, the HIPE stabilized by the assembly of MOF nanocrystals at oil-water interface could be formed. The MOF-stabilized HIPE provides a novel route to produce highly porous metal-organic aerogel (MOA) monolith. After removing the liquids from the MOF-stabilized HIPE, the ultralight MOA with density as low as 0.01 g·cm(-3) was obtained. The HIPE approach for MOA formation has unique advantages and is versatile in producing different kinds of ultralight MOAs with tunable porosities and structures. PMID:26892258

  3. High-internal-phase emulsions stabilized by metal-organic frameworks and derivation of ultralight metal-organic aerogels

    PubMed Central

    Zhang, Bingxing; Zhang, Jianling; Liu, Chengcheng; Peng, Li; Sang, Xinxin; Han, Buxing; Ma, Xue; Luo, Tian; Tan, Xiuniang; Yang, Guanying

    2016-01-01

    To design high-internal-phase emulsion (HIPE) systems is of great interest from the viewpoints of both fundamental researches and practical applications. Here we demonstrate for the first time the utilization of metal-organic framework (MOF) for HIPE formation. By stirring the mixture of water, oil and MOF at room temperature, the HIPE stabilized by the assembly of MOF nanocrystals at oil-water interface could be formed. The MOF-stabilized HIPE provides a novel route to produce highly porous metal-organic aerogel (MOA) monolith. After removing the liquids from the MOF-stabilized HIPE, the ultralight MOA with density as low as 0.01 g·cm−3 was obtained. The HIPE approach for MOA formation has unique advantages and is versatile in producing different kinds of ultralight MOAs with tunable porosities and structures. PMID:26892258

  4. Sediment Surface Areas, Organic Content, and Metal Fractionation of Point Mugu Sediments

    NASA Astrophysics Data System (ADS)

    Becerra, C. A.; Wong, N.; Khachikian, C. S.

    2002-12-01

    Point Mugu contains one of the largest coastal wetlands ecosystems in California, which includes a Naval Air station, several sewage oxidation ponds and a partly dredged lagoon. Remediation efforts include investigating the feasibility of using the present sewage pond sludge to restore a dredged area in the lagoon. A problem with this approach is the potential release and subsequent environmental impact of the toxic substances from the sludge. Contaminants may become unavailable once sorbed onto particles. In general, this process is a direct function of surface area and organic carbon sorbed onto the sediment. The goal of the current investigation is to provide insight into the biological availability of a suite of metal contaminants in Pt. Mugu marsh sediments by studying changes in the physical and chemical properties of the sediments at horizontal and vertical spatial scales. The surface area and organic carbon for eight cores were measured as well as the first three sequential extraction of a host of metals. We have found that a direct correlation exists between surface area and the organic content of sediments as a function of depth. Surface area and the amount of organic carbon decreases with depth, which could result in higher availability of metals with increasing depth into the sediments.

  5. Defining the Proton Topology of the Zr6-Based Metal-Organic Framework NU-1000.

    PubMed

    Planas, Nora; Mondloch, Joseph E; Tussupbayev, Samat; Borycz, Joshua; Gagliardi, Laura; Hupp, Joseph T; Farha, Omar K; Cramer, Christopher J

    2014-11-01

    Metal-organic frameworks (MOFs) constructed from Zr6-based nodes have recently received considerable attention given their exceptional thermal, chemical, and mechanical stability. Because of this, the structural diversity of Zr6-based MOFs has expanded considerably and in turn given rise to difficulty in their precise characterization. In particular it has been difficult to assign where protons (needed for charge balance) reside on some Zr6-based nodes. Elucidating the precise proton topologies in Zr6-based MOFs will have wide ranging implications in defining their chemical reactivity, acid/base characteristics, conductivity, and chemical catalysis. Here we have used a combined quantum mechanical and experimental approach to elucidate the precise proton topology of the Zr6-based framework NU-1000. Our data indicate that a mixed node topology, [Zr6(μ3-O)4(μ3-OH)4(OH)4 (OH2)4](8+), is preferred and simultaneously rule out five alternative node topologies. PMID:26278741

  6. Defining the Proton Topology of the Zr6-Based Metal-Organic Framework NU-1000.

    PubMed

    Planas, Nora; Mondloch, Joseph E; Tussupbayev, Samat; Borycz, Joshua; Gagliardi, Laura; Hupp, Joseph T; Farha, Omar K; Cramer, Christopher J

    2014-11-01

    Metal-organic frameworks (MOFs) constructed from Zr6-based nodes have recently received considerable attention given their exceptional thermal, chemical, and mechanical stability. Because of this, the structural diversity of Zr6-based MOFs has expanded considerably and in turn given rise to difficulty in their precise characterization. In particular it has been difficult to assign where protons (needed for charge balance) reside on some Zr6-based nodes. Elucidating the precise proton topologies in Zr6-based MOFs will have wide ranging implications in defining their chemical reactivity, acid/base characteristics, conductivity, and chemical catalysis. Here we have used a combined quantum mechanical and experimental approach to elucidate the precise proton topology of the Zr6-based framework NU-1000. Our data indicate that a mixed node topology, [Zr6(μ3-O)4(μ3-OH)4(OH)4 (OH2)4](8+), is preferred and simultaneously rule out five alternative node topologies.

  7. Adsorption characteristics of metal ions on chitosan chemically modified by D-galactose

    SciTech Connect

    Kondo, Kazuo; Sumi, Hisaharu; Matsumoto, Michiaki

    1996-07-01

    The adsorption characteristics of metal ions on chitosan chemically modified by D-galactose were examined. The pH dependency on the distribution ratio was found to be affected by the valency of the metal ion, and the apparent adsorption equilibrium constants of the metal ions were determined. The order of adsorption of the metal ions is Ga > In > Nd > Eu for the trivalent metal ions and Cu > Ni > Co for the divalent metal ions. It is believed that amino and hydroxyl groups in the chitosan act as a chelating ligand.

  8. Hazardous organic chemicals in rubber recycled tire playgrounds and pavers.

    PubMed

    Llompart, Maria; Sanchez-Prado, Lucia; Pablo Lamas, J; Garcia-Jares, Carmen; Roca, Enrique; Dagnac, Thierry

    2013-01-01

    In this study, the presence of hazardous organic chemicals in surfaces containing recycled rubber tires is investigated. Direct material analyses using solvent extraction, as well as SPME analysis of the vapour phase above the sample, were carried out. Twenty-one rubber mulch samples were collected from nine different playgrounds. In addition, seven commercial samples of recycled rubber pavers were acquired in a local store of a multinational company. All samples were extracted by ultrasound energy, followed by analysis of the extract by GC-MS. The analysis confirmed the presence of a large number of hazardous substances including PAHs, phthalates, antioxidants (e.g. BHT, phenols), benzothiazole and derivatives, among other chemicals. The study evidences the high content of toxic chemicals in these recycled materials. The concentration of PAHs in the commercial pavers was extremely high, reaching values up to 1%. In addition, SPME studies of the vapour phase above the samples confirm the volatilisation of many of those organic compounds. Uses of recycled rubber tires, especially those targeting play areas and other facilities for children, should be a matter of regulatory concern.

  9. 3D porous metal-organic framework exhibiting selective adsorption of water over organic solvents.

    PubMed

    Gu, Jin-Zhong; Lu, Wen-Guan; Jiang, Long; Zhou, Hong-Cai; Lu, Tong-Bu

    2007-07-23

    A 3D porous metal-organic framework (MOF) with 1D open channels has been constructed hydrothermally using Zn(II) and a rigid planar ligand IDC(3)- (imidazole-4,5-dicarboxylate). This MOF can adsorb water selectively over organic solvents and can be regenerated and reused. It also represents a rare example of a MOF with open channels that form/collapse reversibly upon hydration/dehydration.

  10. Chemical reactions at metallic and metal/semiconductor interfaces stimulated by pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Petit, E. J.; Caudano, R.

    1992-01-01

    Multilayer Al/Sb thin films have been evaporated on GaSb single crystals in ultra-high vacuum and pulsed-laser irradiated in-situ above the energy density threshold for surface melting. Superficial and interfacial chemical reactions have been characterized in-situ by Auger electron spectroscopy; and later, by X-ray photoelectron spectroscopy profiling, Rutherford backscattering spectrometry and scanning electron microscopy. The chemical reaction between the Al and Sb films is considered as a model reaction for laser-assisted synthesis of high-purity intermetallic compounds. The observation of a strong interfacial reaction between the melted film and the substrate is also a subject of great concern for optical data recording and laser alloying of ohmic contacts on semiconductors. We show that a suitable choice of the substrate and adding a low surface tension element into the metallic film can improve its stability during melting, and prevent inhomogeneous reaction and formation of holes, cracks and particles. Finally, other solutions are suggested to improve the control of these reactions.

  11. Metal-induced gap states in epitaxial organic-insulator/metal interfaces

    NASA Astrophysics Data System (ADS)

    Kiguchi, Manabu; Arita, Ryotaro; Yoshikawa, Genki; Tanida, Yoshiaki; Ikeda, Susumu; Entani, Shiro; Nakai, Ikuyo; Kondoh, Hiroshi; Ohta, Toshiaki; Saiki, Koichiro; Aoki, Hideo

    2005-08-01

    We have shown, both experimentally and theoretically, that the metal-induced gap states (MIGS) can exist in epitaxially grown organic insulator/metal interfaces. The experiment is done for alkane/Cu(001) with an element-selective near edge x-ray absorption fine structure (NEXAFS), which exhibits a prepeak indicative of MIGS. An ab initio electronic structure calculation supports the existence of the MIGS. When the Cu substrate is replaced with Ni, an interface magnetism may be possible with a carrier doping.

  12. Nanoporous metal oxides with tunable and nanocrystalline frameworks via conversion of metal-organic frameworks.

    PubMed

    Kim, Tae Kyung; Lee, Kyung Joo; Cheon, Jae Yeong; Lee, Jae Hwa; Joo, Sang Hoon; Moon, Hoi Ri

    2013-06-19

    Nanoporous metal oxide materials are ubiquitous in the material sciences because of their numerous potential applications in various areas, including adsorption, catalysis, energy conversion and storage, optoelectronics, and drug delivery. While synthetic strategies for the preparation of siliceous nanoporous materials are well-established, nonsiliceous metal oxide-based nanoporous materials still present challenges. Herein, we report a novel synthetic strategy that exploits a metal-organic framework (MOF)-driven, self-templated route toward nanoporous metal oxides via thermolysis under inert atmosphere. In this approach, an aliphatic ligand-based MOF is thermally converted to nanoporous metal oxides with highly nanocrystalline frameworks, in which aliphatic ligands act as the self-templates that are afterward evaporated to generate nanopores. We demonstrate this concept with hierarchically nanoporous magnesia (MgO) and ceria (CeO2), which have potential applicability for adsorption, catalysis, and energy storage. The pore size of these nanoporous metal oxides can be readily tuned by simple control of experimental parameters. Significantly, nanoporous MgO exhibits exceptional CO2 adsorption capacity (9.2 wt %) under conditions mimicking flue gas. This MOF-driven strategy can be expanded to other nanoporous monometallic and multimetallic oxides with a multitude of potential applications.

  13. General Deposition of Metal-Organic Frameworks on Highly Adaptive Organic-Inorganic Hybrid Electrospun Fibrous Substrates.

    PubMed

    Liu, Chang; Wu, Yi-Nan; Morlay, Catherine; Gu, Yifan; Gebremariam, Binyam; Yuan, Xiao; Li, Fengting

    2016-02-01

    Electrospun nanofibrous mats are ideal substrates for metal-organic frameworks (MOFs) crystal deposition because of their specific structural parameters and chemical tenability. In this work, we utilized organic-inorganic hybrid electrospun fibrous mats as support material to study the deposition of various MOF particles. HKUST-1 and MIL-53(Al) were produced through solvothermal method, while ZIF-8 and MIL-88B(Fe) were prepared using microwave-induced heating method. The synthesis procedure for both methods were simple and effective because the hybrid nanofibrous mats showed considerable affinity to MOF particles and could be used without additional modifications. The obtained MOF composites exhibited effective incorporation between MOF particles and the porous substrates. MIL-53(Al) composite was applied as fibrous sorbent and showed enhanced adsorption capacity and removal rate, as well as easier operation, compared with thepowdered sample. Moreover, MIL-53(Al) composite was easier to be regenerated compared with powder form.

  14. Trophic magnification of organic chemicals: A global synthesis

    USGS Publications Warehouse

    Walters, David; Jardine, T.D.; Cade, Brian S.; Kidd, K.A.; Muir, D.C.G.; Leipzig-Scott, Peter C.

    2016-01-01

    Production of organic chemicals (OCs) is increasing exponentially, and some OCs biomagnify through food webs to potentially toxic levels. Biomagnification under field conditions is best described by trophic magnification factors (TMFs; per trophic level change in log-concentration of a chemical) which have been measured for more than two decades. Syntheses of TMF behavior relative to chemical traits and ecosystem properties are lacking. We analyzed >1500 TMFs to identify OCs predisposed to biomagnify and to assess ecosystem vulnerability. The highest TMFs were for OCs that are slowly metabolized by animals (metabolic rate kM < 0.01 day–1) and are moderately hydrophobic (log KOW 6–8). TMFs were more variable in marine than freshwaters, unrelated to latitude, and highest in food webs containing endotherms. We modeled the probability that any OC would biomagnify as a combined function of KOW and kM. Probability is greatest (∼100%) for slowly metabolized compounds, regardless of KOW, and lowest for chemicals with rapid transformation rates (kM > 0.2 day–1). This probabilistic model provides a new global tool for screening existing and new OCs for their biomagnification potential.

  15. Trophic Magnification of Organic Chemicals: A Global Synthesis.

    PubMed

    Walters, D M; Jardine, T D; Cade, B S; Kidd, K A; Muir, D C G; Leipzig-Scott, P

    2016-05-01

    Production of organic chemicals (OCs) is increasing exponentially, and some OCs biomagnify through food webs to potentially toxic levels. Biomagnification under field conditions is best described by trophic magnification factors (TMFs; per trophic level change in log-concentration of a chemical) which have been measured for more than two decades. Syntheses of TMF behavior relative to chemical traits and ecosystem properties are lacking. We analyzed >1500 TMFs to identify OCs predisposed to biomagnify and to assess ecosystem vulnerability. The highest TMFs were for OCs that are slowly metabolized by animals (metabolic rate kM < 0.01 day(-1)) and are moderately hydrophobic (log KOW 6-8). TMFs were more variable in marine than freshwaters, unrelated to latitude, and highest in food webs containing endotherms. We modeled the probability that any OC would biomagnify as a combined function of KOW and kM. Probability is greatest (∼100%) for slowly metabolized compounds, regardless of KOW, and lowest for chemicals with rapid transformation rates (kM > 0.2 day(-1)). This probabilistic model provides a new global tool for screening existing and new OCs for their biomagnification potential. PMID:27014905

  16. Force-induced chemical reactions on the metal centre in a single metalloprotein molecule.

    PubMed

    Zheng, Peng; Arantes, Guilherme M; Field, Martin J; Li, Hongbin

    2015-06-25

    Metalloproteins play indispensable roles in biology owing to the versatile chemical reactivity of metal centres. However, studying their reactivity in many metalloproteins is challenging, as protein three-dimensional structure encloses labile metal centres, thus limiting their access to reactants and impeding direct measurements. Here we demonstrate the use of single-molecule atomic force microscopy to induce partial unfolding to expose metal centres in metalloproteins to aqueous solution, thus allowing for studying their chemical reactivity in aqueous solution for the first time. As a proof-of-principle, we demonstrate two chemical reactions for the FeS4 centre in rubredoxin: electrophilic protonation and nucleophilic ligand substitution. Our results show that protonation and ligand substitution result in mechanical destabilization of the FeS4 centre. Quantum chemical calculations corroborated experimental results and revealed detailed reaction mechanisms. We anticipate that this novel approach will provide insights into chemical reactivity of metal centres in metalloproteins under biologically more relevant conditions.

  17. Force-induced chemical reactions on the metal centre in a single metalloprotein molecule

    NASA Astrophysics Data System (ADS)

    Zheng, Peng; Arantes, Guilherme M.; Field, Martin J.; Li, Hongbin

    2015-06-01

    Metalloproteins play indispensable roles in biology owing to the versatile chemical reactivity of metal centres. However, studying their reactivity in many metalloproteins is challenging, as protein three-dimensional structure encloses labile metal centres, thus limiting their access to reactants and impeding direct measurements. Here we demonstrate the use of single-molecule atomic force microscopy to induce partial unfolding to expose metal centres in metalloproteins to aqueous solution, thus allowing for studying their chemical reactivity in aqueous solution for the first time. As a proof-of-principle, we demonstrate two chemical reactions for the FeS4 centre in rubredoxin: electrophilic protonation and nucleophilic ligand substitution. Our results show that protonation and ligand substitution result in mechanical destabilization of the FeS4 centre. Quantum chemical calculations corroborated experimental results and revealed detailed reaction mechanisms. We anticipate that this novel approach will provide insights into chemical reactivity of metal centres in metalloproteins under biologically more relevant conditions.

  18. Force-induced chemical reactions on the metal centre in a single metalloprotein molecule

    PubMed Central

    Zheng, Peng; Arantes, Guilherme M.; Field, Martin J.; Li, Hongbin

    2015-01-01

    Metalloproteins play indispensable roles in biology owing to the versatile chemical reactivity of metal centres. However, studying their reactivity in many metalloproteins is challenging, as protein three-dimensional structure encloses labile metal centres, thus limiting their access to reactants and impeding direct measurements. Here we demonstrate the use of single-molecule atomic force microscopy to induce partial unfolding to expose metal centres in metalloproteins to aqueous solution, thus allowing for studying their chemical reactivity in aqueous solution for the first time. As a proof-of-principle, we demonstrate two chemical reactions for the FeS4 centre in rubredoxin: electrophilic protonation and nucleophilic ligand substitution. Our results show that protonation and ligand substitution result in mechanical destabilization of the FeS4 centre. Quantum chemical calculations corroborated experimental results and revealed detailed reaction mechanisms. We anticipate that this novel approach will provide insights into chemical reactivity of metal centres in metalloproteins under biologically more relevant conditions. PMID:26108369

  19. Photonic confinement in laterally structured metal-organic microcavities

    SciTech Connect

    Mischok, Andreas Brückner, Robert; Sudzius, Markas; Reinhardt, Christoph; Lyssenko, Vadim G.; Fröb, Hartmut; Leo, Karl

    2014-08-04

    We investigate the formation of optical modes in organic microcavities with an incorporated perforated silver layer. The metal leads to a formation of Tamm-plasmon-polaritons and thus separates the sample into metal-free or metal-containing areas, supporting different resonances. This mode splitting is exploited to confine photons in elliptic holes and triangular cuts, forming distinctive standing wave patterns showing the strong lateral confinement. A comparison with a Maxwell-Bloch based rate equation model clearly shows the nonlinear transition into the lasing regime. The concentration of the electric field density and inhibition of lateral loss channels in turn decreases the lasing threshold by up to one order of magnitude, to 0.1 nJ. By spectroscopic investigation of such a triangular wedge, we observe the transition from the unperturbed cavity state to a strongly confined complex transversal mode. Such a structured silver layer can be utilized in future for charge carrier injection in an electrically driven organic solid state laser.

  20. Measurement of volatile organic chemicals at selected sites in California

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.; Salas, L.; Viezee, W.; Sitton, B.; Ferek, R.

    1992-01-01

    Urban air concentrations of 24 selected volatile organic chemicals that may be potentially hazardous to human health and environment were measured during field experiments conducted at two California locations, at Houston, and at Denver. Chemicals measured included chlorofluorocarbons, halomethanes, haloethanes, halopropanes, chloroethylenes, and aromatic hydrocarbons. With emphasis on California sites, data from these studies are analyzed and interpreted with respect to variabilities in ambient air concentrations, diurnal changes, relation to prevailing meteorology, sources and trends. Except in a few instances, mean concentrations are typically between 0 and 5 ppb. Significant variabilities in atmospheric concentrations associated with intense sources and adverse meteorological conditions are shown to exist. In addition to short-term variability, there is evidence of systematic diurnal and seasonal trends. In some instances it is possible to detect declining trends resulting from the effectiveness of control strategies.

  1. Evaluation of volatile organic compound reduction technologies for metal coatings

    SciTech Connect

    Wang, Y.; Huang, E.W.

    1997-12-31

    Under the sponsorship of California Air Resources Board, AeroVironment Environmental Services, Inc. (AVES) is currently conducting a study to demonstrate a new zero-VOC Industrial Maintenance Metal Coating. This new technology can help the coating industry reduce emissions of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). In a previous study conducted by AVES, current VOCs technologies available on the market for metal parts and product coatings were evaluated for compliance with the South Coast Air Quality Management District (SCAQMD) proposed Rule 1107 (Metal Parts and Product Coatings). There are low-VOC coating products available for industries of interest. For general metal coating applications, certain coating products can comply with current SCAQMD Rule 1107 VOC limits. Some of the low-VOC products that are considered as a substitute or an alternative to high-VOC petroleum-based products are summarized. The current available emerging technologies offer a great opportunity for emission reduction through a gradual shift from high to low/no VOC coatings. By phasing in low/no VOC coatings, industries will be able to reduce energy use and air emissions without installation of add-on controls.

  2. Chemically active organically doped sol-gel materials: enzymatic sensors, chemical sensors, and photoactive materials

    NASA Astrophysics Data System (ADS)

    Avnir, David; Braun, S.; Lev, Ovadia; Ottolenghi, M.

    1992-12-01

    Organically-doped porous sol-gel matrices of optical grade have evolved in recent years into a wide class of materials with diverse applications. We review recent progress made in our laboratories in three domains of applications: the trapping of enzymes with the consequent design of (e.g. glucose) sensors; the development of chemical sensors; and the design of photoactive material for (solar) light energy conversion.

  3. Metal-organic frameworks as biosensors for luminescence-based detection and imaging

    PubMed Central

    Miller, Sophie E.; Teplensky, Michelle H.; Moghadam, Peyman Z.; Fairen-Jimenez, David

    2016-01-01

    Metal-organic frameworks (MOFs), formed by the self-assembly of metal centres or clusters and organic linkers, possess many key structural and chemical features that have enabled them to be used in sensing platforms for a variety of environmentally, chemically and biomedically relevant compounds. In particular, their high porosity, large surface area, tuneable chemical composition, high degree of crystallinity, and potential for post-synthetic modification for molecular recognition make MOFs promising candidates for biosensing applications. In this review, we separate our discussion of MOF biosensors into two categories: quantitative sensing, focusing specifically on luminescence-based sensors for the direct measurement of a specific analyte, and qualitative sensing, where we describe MOFs used for fluorescence microscopy and as magnetic resonance imaging contrast agents. We highlight several key publications in each of these areas, concluding that MOFs present an exciting, versatile new platform for biosensing applications and imaging, and we expect to see their usage grow as the field progresses. PMID:27499847

  4. Metal-organic frameworks as biosensors for luminescence-based detection and imaging.

    PubMed

    Miller, Sophie E; Teplensky, Michelle H; Moghadam, Peyman Z; Fairen-Jimenez, David

    2016-08-01

    Metal-organic frameworks (MOFs), formed by the self-assembly of metal centres or clusters and organic linkers, possess many key structural and chemical features that have enabled them to be used in sensing platforms for a variety of environmentally, chemically and biomedically relevant compounds. In particular, their high porosity, large surface area, tuneable chemical composition, high degree of crystallinity, and potential for post-synthetic modification for molecular recognition make MOFs promising candidates for biosensing applications. In this review, we separate our discussion of MOF biosensors into two categories: quantitative sensing, focusing specifically on luminescence-based sensors for the direct measurement of a specific analyte, and qualitative sensing, where we describe MOFs used for fluorescence microscopy and as magnetic resonance imaging contrast agents. We highlight several key publications in each of these areas, concluding that MOFs present an exciting, versatile new platform for biosensing applications and imaging, and we expect to see their usage grow as the field progresses. PMID:27499847

  5. Distribution and phytoavailability of heavy metal chemical fractions in artificial soil on rock cut slopes alongside railways.

    PubMed

    Chen, Zhaoqiong; Ai, Yingwei; Fang, Chen; Wang, Kexiu; Li, Wei; Liu, Shui; Li, Chunlin; Xiao, Jingyao; Huang, Zhiyu

    2014-05-30

    Artificial soil is often sprayed onto cut slopes alongside railroad tracks to promote revegetation. This study evaluated the heavy metal content and the distribution of heavy metal chemical fractions in the soil, as well as the uptake of heavy metals by plants. The soil at four sites was determined to be considerably contaminated with Cd and Pb. The concentrations of Cd and Pb increased with the length of time the railway had been in use and decreased further away from the railway tracks. Pb primarily existed in reducible form but as residual fractions, whereas Cd was predominantly in exchangeable form. A correlation analysis indicated that pH, organic matter, and total phosphorus levels were important factors affecting the distribution of the heavy metal chemical fractions. The amounts of exchangeable Pb and Cd in the soil were highly correlated with their amounts in the plants sampled, indicating that the exchangeable fraction is a better indication of heavy metal phytoavailability than the total amount of heavy metals in the soil. Bioaccumulation and translocation factors indicated that Indigofera amblyantha had moderate tolerance and bioaccumulation capability for Pb, as did Leucaena leucocephala for Cd. These two plant species can serve as ideal slope remediation plants. PMID:24727018

  6. Direct Visualization of Etching Trajectories in Metal-Assisted Chemical Etching of Si by the Chemical Oxidation of Porous Sidewalls.

    PubMed

    Yoon, Sung-Soo; Khang, Dahl-Young

    2015-09-29

    We demonstrate a simple method for the visualization of trajectories traced by noble metal nanoparticles during metal-assisted chemical etching (MaCE) of Si. The nanoporous Si layer formed around drilled pores is converted into SiO2 by simple chemical oxidation. Etch removal of the remaining Si using alkali hydroxide leaves SiO2 nanostructures that are the exact replica of those drilled pores or etching trajectories. The differences in etching characteristics between Ag and Au have been investigated using the proposed visualization method. The shape and chemical stability of metal nanoparticles used for MaCE have been found to be critical in determining etching paths. The proposed method would be very helpful in studying the fundamental mechanism of MaCE as well as in micro/nanostructuring of the Si surface for various applications. This approach can also be used for the generation of straight or helical SiO2 nanotubes.

  7. Research in the Field of Organic Photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences

    NASA Astrophysics Data System (ADS)

    Troshin, Pavel A.

    2015-08-01

    In the present review we highlight the main research activities in the field of organic photonics and photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences (IPCP RAS). Extensive investigation of optical and electrical properties of π-conjugated organic compounds performed at IPCP RAS since 1960's resulted in design of many exciting materials representing organic semiconductors, metals and superconductors. Organic Schottky barrier and p/n junction photovoltaic devices constructed at IPCP RAS in 1960's and 1970's were among the first examples of reasonably efficient organic solar cells at that time. These early discoveries inspired younger generations of the researchers to continue the work of their mentors and explore the world of organic materials and photonic devices such as molecular photonic switches, organic light emitting diodes, solar cells, photodetectors, photoswitchable organic field-effect transistors and memory elements.

  8. Predicting microbial toxicity of nonuniform multicomponent mixtures of organic chemicals

    SciTech Connect

    Peace, J.; Daniel, D.; Nirmalakhandan, N.; Egemen, E.

    1997-04-01

    Three schemes proposed in the literature for analyzing joint toxic effects of multicomponent mixtures on fish, namely the additivity index (AI), the mixture toxicity index (MTI), and the similarity parameter ({lambda}) are evaluated in this study for microbial toxicity. A new approach is proposed to establish acceptance limits for the similarity parameter, {lambda}, based on experimental errors and uncertainties. Quantitative structure activity relationship (QSAR) techniques are then used to develop a model to predict the concentrations of components in mixtures that would jointly cause 50% inhibition of microbial respiration. The application of this approach is demonstrated on the experimental toxicity data of six eight-component organic chemical mixtures on microorganisms.

  9. Chemical probing of glycans in cells and organisms.

    PubMed

    Rouhanifard, Sara H; Nordstrøm, Lars Ulrik; Zheng, Tianqing; Wu, Peng

    2013-05-21

    Among the four major building blocks of life, glycans play essential roles in numerous physiological and pathological processes. Due to their non-templated biosynthesis, advances towards elucidating the molecular details of glycan functions are relatively slow compared with the pace of protein and nucleic acid research. Over the past 30 years, chemical tools have emerged as powerful allies to genetics and molecular biology in the study of glycans in their native environment. This tutorial review will provide an overview of the recent technological developments in the field, as well as the progress in the application of these techniques to probe glycans in cells and organisms.

  10. Electron beam synthesis of metal and semiconductor nanoparticles using metal-organic frameworks as ordered precursors

    NASA Astrophysics Data System (ADS)

    Jacobs, Benjamin W.; Houk, Ronald J. T.; Wong, Bryan M.; Talin, A. Alec; Allendorf, Mark D.

    2011-09-01

    We demonstrate a versatile, bottom-up method of forming metal and semiconducting nanoparticles by exposing precursor metal-organic frameworks (MOFs) to an electron beam. Using a transmission electron microscope to initiate and observe growth, we show that the composition, size, and morphology of the nanoparticles are determined by the chemistry and structure of the MOF, as well as the electron beam properties. Zinc oxide, metallic indium and copper particles were produced with narrow and tunable size distributions comparable to those obtained from state-of-the-art methods. This method represents a first step toward the fabrication of nanoscale heterostructures using the highly controlled environment of the MOF pores as a scaffold or template.

  11. Transformation of metal-organic frameworks for molecular sieving membranes.

    PubMed

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-04-19

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively.

  12. Boosting Responsivity of Organic-Metal Oxynitride Hybrid Heterointerface Phototransistor.

    PubMed

    Rim, You Seung; Ok, Kyung-Chul; Yang, Yang Michael; Chen, Huajun; Bae, Sang-Hoon; Wang, Chen; Huang, Yu; Park, Jin-Seong; Yang, Yang

    2016-06-15

    Amorphous metal oxides are attractive materials for various sensor applications, because of high electrical performance and easy processing. However, low absorption coefficient, slow photoresponse, and persistent photoconductivity of amorphous metal oxide films from the origin of deep-level defects are obstacles to their use as photonic applications. Here, we demonstrate ultrahigh photoresponsivity of organic-inorganic hybrid phototransistors featuring bulk heterojunction polymers and low-bandgap zinc oxynitride. Spontaneous formation of ultrathin zinc oxide on the surface of zinc oxynitride films could make an effective band-alignment for electron transfer from the dissociation of excitons in the bulk heterojunction, while holes were blocked by the deep highest occupied molecular orbital level of zinc oxide. These hybrid structure-based phototransistors are ultrasensitive to broad-bandwidth photons in ultraviolet to near-infrared regions. The detectivity and a linear dynamic range exceeded 10(12) Jones and 122.3 dB, respectively. PMID:27193237

  13. Transformation of metal-organic frameworks for molecular sieving membranes

    NASA Astrophysics Data System (ADS)

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-04-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively.

  14. Transformation of metal-organic frameworks for molecular sieving membranes

    PubMed Central

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-01-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

  15. Ab initio carbon capture in open-site metal-organic frameworks

    SciTech Connect

    Dzubak, AL; Lin, LC; Kim, J; Swisher, JA; Poloni, R; Maximoff, SN; Smit, B; Gagliardi, L

    2012-08-19

    During the formation of metal-organic frameworks (MOFs), metal centres can coordinate with the intended organic linkers, but also with solvent molecules. In this case, subsequent activation by removal of the solvent molecules creates unsaturated 'open' metal sites known to have a strong affinity for CO2 molecules, but their interactions are still poorly understood. Common force fields typically underestimate by as much as two orders of magnitude the adsorption of CO2 in open-site Mg-MOF-74, which has emerged as a promising MOF for CO2 capture. Here we present a systematic procedure to generate force fields using high-level quantum chemical calculations. Monte Carlo simulations based on an ab initio force field generated for CO2 in Mg-MOF-74 shed some light on the interpretation of thermodynamic data from flue gas in this material. The force field describes accurately the chemistry of the open metal sites, and is transferable to other structures. This approach may serve in molecular simulations in general and in the study of fluid-solid interactions.

  16. Ab initio carbon capture in open-site metal-organic frameworks.

    PubMed

    Dzubak, Allison L; Lin, Li-Chiang; Kim, Jihan; Swisher, Joseph A; Poloni, Roberta; Maximoff, Sergey N; Smit, Berend; Gagliardi, Laura

    2012-10-01

    During the formation of metal-organic frameworks (MOFs), metal centres can coordinate with the intended organic linkers, but also with solvent molecules. In this case, subsequent activation by removal of the solvent molecules creates unsaturated 'open' metal sites known to have a strong affinity for CO(2) molecules, but their interactions are still poorly understood. Common force fields typically underestimate by as much as two orders of magnitude the adsorption of CO(2) in open-site Mg-MOF-74, which has emerged as a promising MOF for CO(2) capture. Here we present a systematic procedure to generate force fields using high-level quantum chemical calculations. Monte Carlo simulations based on an ab initio force field generated for CO(2) in Mg-MOF-74 shed some light on the interpretation of thermodynamic data from flue gas in this material. The force field describes accurately the chemistry of the open metal sites, and is transferable to other structures. This approach may serve in molecular simulations in general and in the study of fluid-solid interactions.

  17. Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

    PubMed

    Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

    2014-01-28

    Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content. PMID:24359584

  18. Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

    PubMed

    Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

    2014-01-28

    Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content.

  19. Chemical ions affect survival of avian cholera organisms in pondwater

    USGS Publications Warehouse

    Price, J.I.; Yandell, B.S.; Porter, W.P.

    1992-01-01

    Avian cholera (Pasteurella multocida) is a major disease of wild waterfowl, but its epizootiology remains little understood. Consequently, we examined whether chemical ions affected survival of avian cholera organisms in water collected from the Nebraska Rainwater Basin where avian cholera is enzootic. We tested the response of P. multocida to ammonium (NH4), calcium (Ca), magnesium (Mg), nitrate (NO3), and ortho-phosphate (PO4) ions individually and in combination using a fractional factorial design divided into 4 blocks. High concentrations of Ca and Mg, singly or in combination, increased survival of P. multocida organisms (P < 0.001). We developed a survival index to predict whether or not specific ponds could be "problem" or "nonproblem" avian cholera sites based on concentrations of these ions in the water.

  20. Hydrogen storage by physisorption on Metal Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Dailly, Anne

    2008-03-01

    Cryo-adsorption systems based on materials with high specific surface areas have the main advantage that they can store and release hydrogen with fast kinetics and high reversibility over multiples cycles. Recently Metal Organic Frameworks (MOFs) have been proposed as promising adsorbents for hydrogen. These crystallographically well organized hybrid solids resulting from the three dimensional connection of inorganic clusters using organic linkers show the largest specific surface areas of all known crystalline solids. The determination of the relationships between physical properties (chemistry, structure, surface area ) of the MOFs and their hydrogen storage behavior is a key step in the characterization of these materials, if they are to be designed for hydrogen storage applications. Excess hydrogen sorption measurements for different MOFs will be presented. We show that maximum hydrogen uptake at high pressure and 77K does not always scale with the specific surface area. A linear correlation trend only apply within a class of specific materials and breaks down when the surface area measurement does not represent the surface sites that are available to H2. The influence of pore size and shape will also be discussed by comparing several MOFs with different structure types. The hydrogen adsorption and binding energy at low pressure are strongly dependent on the metal ions and the pore size.