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Sample records for metal organic chemical

  1. Toxic Industrial Chemical Removal by Isostructural Metal-Organic Frameworks

    DTIC Science & Technology

    2011-01-01

    distance between the MOF -74 metal and the adsorbed hydrogen molecule. In addition, the authors studied the methane storage capabilities of these MOFs and...industrial processes such as gas storage , separations, and catalysis [1-4]. MOFs self-assemble using combinations of metal clusters and organic linking...and organic linkers to achieve better selectivity and activity towards chemicals such as, hydrogen , carbon dioxide, and methane, for gas storage

  2. Metal Organic-Chemical Vapor Deposition fabrication of semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Thomas, C.

    1980-08-01

    The metal organic chemical vapor deposition (MO-CVD) process was studied and implemented in detail. Single crystal GaAs, and Ga(x)Al(1-x)As films were grown on GaAs by depositing metal organic alkyl gallium compounds in the presence of an arsine mixture. The metal organic chemical vapor deposition process allowed formation of the semiconductor compound directly on the heated substrate in only one hot temperature zone. With MO-CVD, semiconductor films can be efficiently produced by a more economical, less complicated process which will lend itself more easily than past fabrication procedures, to high quantity, high quality reproduction techniques of semiconductor lasers. Clearly MO-CVD is of interest to the communication industry where semiconductor lasers are used extensively in fiber optic communication systems, and similarly to the solar energy business where GaAs substrates are used as photoelectric cells.

  3. 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.

  4. Metal-Organic Frameworks for CO2 Chemical Transformations.

    PubMed

    He, Hongming; Perman, Jason A; Zhu, Guangshan; Ma, Shengqian

    2016-12-01

    Carbon dioxide (CO2 ), as the primary greenhouse gas in the atmosphere, triggers a series of environmental and energy related problems in the world. Therefore, there is an urgent need to develop multiple methods to capture and convert CO2 into useful chemical products, which can significantly improve the environment and promote sustainable development. Over the past several decades, metal-organic frameworks (MOFs) have shown outstanding heterogeneous catalytic activity due in part to their high internal surface area and chemical functionalities. These properties and the ability to synthesize MOF platforms allow experiments to test structure-function relationships for transforming CO2 into useful chemicals. Herein, recent developments are highlighted for MOFs participating as catalysts for the chemical fixation and photochemical reduction of CO2 . Finally, opportunities and challenges facing MOF catalysts are discussed in this ongoing research area.

  5. 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.

  6. 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.

  7. Metal-organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents.

    PubMed

    Bobbitt, N Scott; Mendonca, Matthew L; Howarth, Ashlee J; Islamoglu, Timur; Hupp, Joseph T; Farha, Omar K; Snurr, Randall Q

    2017-06-06

    Owing to the vast diversity of linkers, nodes, and topologies, metal-organic frameworks can be tailored for specific tasks, such as chemical separations or catalysis. Accordingly, these materials have attracted significant interest for capture and/or detoxification of toxic industrial chemicals and chemical warfare agents. In this paper, we review recent experimental and computational work pertaining to the capture of several industrially-relevant toxic chemicals, including NH3, SO2, NO2, H2S, and some volatile organic compounds, with particular emphasis on the challenging issue of designing materials that selectively adsorb these chemicals in the presence of water. We also examine recent research on the capture and catalytic degradation of chemical warfare agents such as sarin and sulfur mustard using metal-organic frameworks.

  8. Metal organic frameworks for the catalytic detoxification of chemical warfare nerve agents

    DOEpatents

    Hupp, Joseph T.; Farha, Omar K.; Katz, Michael J.; Mondloch, Joseph E.

    2017-04-18

    A method of using a metal organic framework (MOF) comprising a metal ion and an at least bidendate organic ligand to catalytically detoxify chemical warfare nerve agents including exposing the metal-organic-framework (MOF) to the chemical warfare nerve agent and catalytically decomposing the nerve agent with the MOF.

  9. 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.

  10. Comparison of InGaAs(100) Grown by Chemical Beam Epitaxy and Metal Organic Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Greene, A. L.; Daniels-Race, T.; Lum, R. M.

    2000-01-01

    Secondary ion mass spectrometry is used to study the effects of substrate temperature on the composition and growth rate of InGaAs/InP(100) multilayers grown by chemical beam epitaxy, metal-organic chemical vapor deposition and solid source molecular beam epitaxy. The growth kinetics of the material grown by the different techniques are analyzed and compared.

  11. Comparison of InGaAs(100) Grown by Chemical Beam Epitaxy and Metal Organic Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Greene, A. L.; Daniels-Race, T.; Lum, R. M.

    2000-01-01

    Secondary ion mass spectrometry is used to study the effects of substrate temperature on the composition and growth rate of InGaAs/InP(100) multilayers grown by chemical beam epitaxy, metal-organic chemical vapor deposition and solid source molecular beam epitaxy. The growth kinetics of the material grown by the different techniques are analyzed and compared.

  12. 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.

  13. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    SciTech Connect

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

  14. Catalyst accessibility to chemical reductants in metal-organic frameworks.

    PubMed

    Roy, Souvik; Pascanu, Vlad; Pullen, Sonja; González Miera, Greco; Martín-Matute, Belén; Ott, Sascha

    2017-03-18

    A molecular H2-evolving catalyst, [Fe2(cbdt)(CO)6] ([FeFe], cbdt = 3-carboxybenzene-1,2-dithiolate), has been attached covalently to an amino-functionalized MIL-101(Cr) through an amide bond. Chemical reduction experiments reveal that the MOF channels can be clogged by ion pairs that are formed between the oxidized reductant and the reduced catalyst. This effect is lessened in MIL-101-NH-[FeFe] with lower [FeFe] loadings. On longer timescales, it is shown that large proportions of the [FeFe] catalysts within the MOF engage in photochemical hydrogen production and the amount of produced hydrogen is proportional to the catalyst loading.

  15. 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.

  16. Impregnated Metal-Organic Frameworks for the Removal of Toxic Industrial Chemicals

    DTIC Science & Technology

    2008-11-01

    on a nanotechnology approach to sorbent development for air purification applications. Metal-organic frameworks ( MOFs ) are a novel class of materials...that allow for specific functionalities to be designed directly into a porous framework. This report summarizes the evaluation of MOFs impregnated...with various chemicals for enhanced reactivity. Specifically, MOF -5 (IRMOF-l) was impregnated with citric acid, copper acetate, copper oxide, and

  17. 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.

  18. 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.

  19. A chemically stable europium metal-organic framework for bifunctional chemical sensor and recyclable on-off-on vapor response

    NASA Astrophysics Data System (ADS)

    Wang, Dongbo; Liu, Jingjuan; Liu, Zhiliang

    2017-07-01

    A ratiometric luminescence sensing method is developed and makes the chemically stable Eu metal-organic framework to be the first bifunctional chemical sensor for Cd2+ and F- ions with naked-eye observation in the field of sensing applications utilizing luminescent Ln-MOFs. This is the first example of luminescent colorimetric sensor caused by the direct dual emissions of a single Ln-MOF. A recyclable vapoluminescent sensor for HCl and NH3 by the naked eye has also been realized.

  20. Quantitative assessment of the effects of metals on microbial degradation of organic chemicals

    SciTech Connect

    Said, W.A. ) Lewis, D.L. Georgia State Univ., Atlanta )

    1991-05-01

    Biodegradation inhibition of a benchmark chemical, 2,4-dichloro-phenozyacetic acid methyl ester (2,4-DME), was used to quantify the inhibitory effects of heavy metals on aerobic microbial degradation rates of organic chemicals. This procedure used lake sediments and aufwuchs (floating mats) collected in the field or from laboratory microcosms. Effects of CuCl{sub 2}, HgCl{sub 2}, ZnCl{sub 2}, Cd(NO{sub 3}){sub 2}, and Cr(NO{sub 3}){sub 3} at initial concentrations ranging from 0.3 {mu}M to 73 mM (approximately 0.1 to 10,000 mg liter{sup {minus}1}) were investigated. In general, such metallic compounds appeared to be considerably more inhibitory to the biodegradation of an organic chemical than high concentrations of microbially toxic organics studied previously. Effects of various metal concentrations were evaluated based on the following: (1) estimated MICs, (2) concentrations that caused a significant effect on biodegradation parameters (both a {gt}10% decrease in V{sub max} and a {gt}10% increase in t{sub 1/2} for 2,4-DME degradation), and (3) concentrations that caused biodegradation half-life doublings (HLDs).

  1. 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.

  2. 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.

  3. 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.

  4. 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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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.

  6. 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.

  7. 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.

  8. Quantitative assessment of the effects of metals on microbial degradation of organic chemicals.

    PubMed

    Said, W A; Lewis, D L

    1991-05-01

    Biodegradation inhibition of a benchmark chemical, 2,4-dichloro-phenoxyacetic acid methyl ester (2,4-DME), was used to quantify the inhibitory effects of heavy metals on aerobic microbial degradation rates of organic chemicals. This procedure used lake sediments and aufwuchs (floating mats) collected in the field or from laboratory microcosms. Effects of CuCl2, HgCl2, ZnCl2, Cd(NO3)2, and Cr(NO3)3 at initial concentrations ranging from 0.3 microM to 73 mM (approximately 0.1 to 10,000 mg liter-1) were investigated. In general, such metallic compounds appeared to be considerably more inhibitory to the biodegradation of an organic chemical than high concentrations of microbially toxic organics studied previously. Effects of various metal concentrations were evaluated based on the following: (i) estimated MICs, (ii) concentrations that caused a significant effect on biodegradation parameters (both a greater than 10% decrease in Vmax and a greater than 10% increase in t1/2 for 2,4-DME degradation), and (iii) concentrations that caused biodegradation half-life doublings (HLDs). The MICs of metals in sediment were lowest for Zn2+ (0.10 microM) and highest for Cd2+ and Cu2+ (0.9 and 1.2 microM, respectively). The MICs of metals in aufwuchs were lowest for Hg2+ (0.01 microM), intermediate for Cu2+ and Zn2+ (0.42 and 0.62 microM, respectively), and highest for Cr3+ and Cd2+ (3.4 and 5.6 microM, respectively). Compared with Cu2+ on aufwuchs, 70 times more Zn2+, 250 times more Cr3+, and 1,000 times more Cd2+ was required to significantly affect aufwuchs biodegradation rate parameters and coefficients (Vmax and t1/2). Aufwuchs was significantly affected by the lowest Hg2+ concentration tested (5 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Quantitative assessment of the effects of metals on microbial degradation of organic chemicals.

    PubMed Central

    Said, W A; Lewis, D L

    1991-01-01

    Biodegradation inhibition of a benchmark chemical, 2,4-dichloro-phenoxyacetic acid methyl ester (2,4-DME), was used to quantify the inhibitory effects of heavy metals on aerobic microbial degradation rates of organic chemicals. This procedure used lake sediments and aufwuchs (floating mats) collected in the field or from laboratory microcosms. Effects of CuCl2, HgCl2, ZnCl2, Cd(NO3)2, and Cr(NO3)3 at initial concentrations ranging from 0.3 microM to 73 mM (approximately 0.1 to 10,000 mg liter-1) were investigated. In general, such metallic compounds appeared to be considerably more inhibitory to the biodegradation of an organic chemical than high concentrations of microbially toxic organics studied previously. Effects of various metal concentrations were evaluated based on the following: (i) estimated MICs, (ii) concentrations that caused a significant effect on biodegradation parameters (both a greater than 10% decrease in Vmax and a greater than 10% increase in t1/2 for 2,4-DME degradation), and (iii) concentrations that caused biodegradation half-life doublings (HLDs). The MICs of metals in sediment were lowest for Zn2+ (0.10 microM) and highest for Cd2+ and Cu2+ (0.9 and 1.2 microM, respectively). The MICs of metals in aufwuchs were lowest for Hg2+ (0.01 microM), intermediate for Cu2+ and Zn2+ (0.42 and 0.62 microM, respectively), and highest for Cr3+ and Cd2+ (3.4 and 5.6 microM, respectively). Compared with Cu2+ on aufwuchs, 70 times more Zn2+, 250 times more Cr3+, and 1,000 times more Cd2+ was required to significantly affect aufwuchs biodegradation rate parameters and coefficients (Vmax and t1/2). Aufwuchs was significantly affected by the lowest Hg2+ concentration tested (5 microM).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1854203

  10. 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.

  11. Structural and chemical control in assembly of multicomponent metal-organic coordination networks on a surface.

    PubMed

    Shi, Ziliang; Lin, Nian

    2010-08-11

    Surface-supported supramolecular self-assembly has been used to generate multicomponent two-dimensional metal-organic coordination networks on a Au(111) surface. The networks consist of linker ligands of 4',4''''-(1,4-phenylene)bis(2,2':6',2''-terpyridine) and nodal ligands of 5,10,15,20-tetra(4-pyridyl)porphyrin that are connected by pyridine-Fe-terpyridine motifs. Scanning tunneling microscopy revealed the coexistence of two polymorphic types of network structures (rhombus and Kagome). Through control of the dosage of the constituent ligands, homogeneous structural phases were obtained selectively. In particular, the rhombus structure could be converted into the more complex and more open Kagome structure by inclusion of guest molecules. Finally, coordination networks providing structural and chemical homogeneity were realized by judiciously choosing the dosages of the constituent ligands and the chemical substitution of the porphyrin ligands.

  12. 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

  13. Exploiting Diffusion Barrier and Chemical Affinity of Metal-Organic Frameworks for Efficient Hydrogen Isotope Separation.

    PubMed

    Kim, Jin Yeong; Balderas-Xicohténcatl, Rafael; Zhang, Linda; Kang, Sung Gu; Hirscher, Michael; Oh, Hyunchul; Moon, Hoi Ri

    2017-09-29

    Deuterium plays a pivotal role in industrial and scientific research, and is irreplaceable for various applications such as isotope tracing, neutron moderation, and neutron scattering. In addition, deuterium is a key energy source for fusion reactions. Thus, the isolation of deuterium from a physico-chemically almost identical isotopic mixture is a seminal challenge in modern separation technology. However, current commercial approaches suffer from extremely low separation efficiency (i.e., cryogenic distillation, selectivity of 1.5 at 24 K), requiring a cost-effective and large-scale separation technique. Herein, we report a highly effective hydrogen isotope separation system based on metal-organic frameworks (MOFs) having the highest reported separation factor as high as ∼26 at 77 K by maximizing synergistic effects of the chemical affinity quantum sieving (CAQS) and kinetic quantum sieving (KQS). For this purpose, the MOF-74 system having high hydrogen adsorption enthalpies due to strong open metal sites is chosen for CAQS functionality, and imidazole molecules (IM) are employed to the system for enhancing the KQS effect. To the best of our knowledge, this work is not only the first attempt to implement two quantum sieving effects, KQS and CAQS, in one system, but also provides experimental validation of the utility of this system for practical industrial usage by isolating high-purity D2 through direct selective separation studies using 1:1 D2/H2 mixtures.

  14. Optical properties of InP doping superlattices grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gal, M.; Viner, J. M.; Taylor, P. C.; Yaun, J. S.; Stringfellow, G. B.

    1987-04-01

    Photoluminescence (PL), time-resolved PL, and photoreflectance spectroscopy are applied to InP doping superlattices grown by metal organic chemical vapor deposition. It is observed that the emission peak and line shape depend on the optical excitation intensity; the peak of the CW PL spectrum increases in energy with the intensity of the pumping light; the highest energy peak is at 888 nm; and the time-resolved PL exhibits long decay times. The energy separation of the quantized subbands is studied by measuring the PR spectra of two samples. The measurements reveal that PR line shapes are explained by photomodulation of the subbands in the conduction band; these line shapes account for the dependence of the spectrum on the power of the exciting light and on the layer thickness.

  15. 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.

  16. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition.

    PubMed

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-02-21

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers.

  17. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-02-01

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers.

  18. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition

    PubMed Central

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-01-01

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers. PMID:28220829

  19. III-nitride quantum cascade detector grown by metal organic chemical vapor deposition

    SciTech Connect

    Song, Yu Huang, Tzu-Yung; Badami, Pranav; Gmachl, Claire; Bhat, Rajaram; Zah, Chung-En

    2014-11-03

    Quantum cascade (QC) detectors in the GaN/Al{sub x}Ga{sub 1−x}N material system grown by metal organic chemical vapor deposition are designed, fabricated, and characterized. Only two material compositions, i.e., GaN as wells and Al{sub 0.5}Ga{sub 0.5}N as barriers are used in the active layers. The QC detectors operates around 4 μm, with a peak responsivity of up to ∼100 μA/W and a detectivity of up to 10{sup 8} Jones at the background limited infrared performance temperature around 140 K.

  20. Metallated metal-organic frameworks

    DOEpatents

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-08-22

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  1. Metallated metal-organic frameworks

    DOEpatents

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-02-07

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  2. Adsorptive removal and separation of chemicals with metal-organic frameworks: Contribution of π-complexation.

    PubMed

    Khan, Nazmul Abedin; Jhung, Sung Hwa

    2017-03-05

    Efficient removal and separation of chemicals from the environment has become a vital issue from a biological and environmental point of view. Currently, adsorptive removal/separation is one of the most promising approaches for cleaning purposes. Selective adsorption/removal of various sulfur- and nitrogen-containing compounds, olefins, and π-electron-rich gases via π-complex formation between an adsorbent and adsorbate molecules is very competitive. Porous metal-organic framework (MOF) materials are very promising in the adsorption/separation of various liquids and gases owing to their distinct characteristics. This review summarizes the literature on the adsorptive removal/separation of various π-electron-rich compounds mainly from fuel and gases using MOF materials containing metal ions that are active for π-complexation. Details of the π-complexation, including mechanism, pros/cons, applications, and efficient ways to form the complex, are discussed systematically. For in-depth understanding, molecular orbital calculations regarding charge transfer between the π-complexing species are also explained in a separate section. From this review, readers will gain an understanding of π-complexation for adsorption and separation, especially with MOFs, to develop new insight for future research.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Highly scalable, atomically thin WSe2 grown via metal-organic chemical vapor deposition.

    PubMed

    Eichfeld, Sarah M; Hossain, Lorraine; Lin, Yu-Chuan; Piasecki, Aleksander F; Kupp, Benjamin; Birdwell, A Glen; Burke, Robert A; Lu, Ning; Peng, Xin; Li, Jie; Azcatl, Angelica; McDonnell, Stephen; Wallace, Robert M; Kim, Moon J; Mayer, Theresa S; Redwing, Joan M; Robinson, Joshua A

    2015-02-24

    Tungsten diselenide (WSe2) is a two-dimensional material that is of interest for next-generation electronic and optoelectronic devices due to its direct bandgap of 1.65 eV in the monolayer form and excellent transport properties. However, technologies based on this 2D material cannot be realized without a scalable synthesis process. Here, we demonstrate the first scalable synthesis of large-area, mono and few-layer WSe2 via metal-organic chemical vapor deposition using tungsten hexacarbonyl (W(CO)6) and dimethylselenium ((CH3)2Se). In addition to being intrinsically scalable, this technique allows for the precise control of the vapor-phase chemistry, which is unobtainable using more traditional oxide vaporization routes. We show that temperature, pressure, Se:W ratio, and substrate choice have a strong impact on the ensuing atomic layer structure, with optimized conditions yielding >8 μm size domains. Raman spectroscopy, atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (TEM) confirm crystalline monoto-multilayer WSe2 is achievable. Finally, TEM and vertical current/voltage transport provide evidence that a pristine van der Waals gap exists in WSe2/graphene heterostructures.

  9. Metal-Organic Frameworks as Potential Platforms for Carbon Dioxide Capture and Chemical Transformation

    NASA Astrophysics Data System (ADS)

    Gao, Wenyang

    The anthropogenic carbon dioxide (CO2) emission into the atmosphere, mainly through the combustion of fossil fuels, has resulted in a balance disturbance of the carbon cycle. Overwhelming scientific evidence proves that the escalating level of atmospheric CO2 is deemed as the main culprit for global warming and climate change. It is thus imperative to develop viable CO2 capture and sequestration (CCS) technologies to reduce CO2 emissions, which is also essential to avoid the potential devastating effects in future. The drawbacks of energy-cost, corrosion and inefficiency for amine-based wet-scrubbing systems which are currently used in industry, have prompted the exploration of alternative approaches for CCS. Extensive efforts have been dedicated to the development of functional porous materials, such as activated carbons, zeolites, porous organic polymers, and metal-organic frameworks (MOFs) to capture CO2. However, these adsorbents are limited by either poor selectivity for CO2 separation from gas mixtures or low CO2 adsorption capacity. Therefore, it is still highly demanding to design next-generation adsorbent materials fulfilling the requirements of high CO2 selectivity and enough CO2 capacity, as well as high water/moisture stability under practical conditions. Metal-organic frameworks (MOFs) have been positioned at the forefront of this area as a promising type of candidate amongst various porous materials. This is triggered by the modularity and functionality of pore size, pore walls and inner surface of MOFs by use of crystal engineering approaches. In this work, several effective strategies, such as incorporating 1,2,3-triazole groups as moderate Lewis base centers into MOFs and employing flexible azamacrocycle-based ligands to build MOFs, demonstrate to be promising ways to enhance CO 2 uptake capacity and CO2 separation ability of porous MOFs. It is revealed through in-depth studies on counter-intuitive experimental observations that the local electric

  10. 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.

  11. 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.

  12. The growth and doping of Al(As)Sb by metal-organic chemical vapor deposition

    SciTech Connect

    Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R.

    1996-05-01

    AlSb and AlAs{sub x}Sb{sub 1{minus}x} epitaxial films grown by metal-organic chemical vapor deposition were successfully doped p- or n-type using diethylzinc or tetraethyltin, respectively. AlSb films were grown at 500 C and 76 torr using trimethylamine or ethyldimethylamine alane and triethylantimony. The authors examined the growth of AlAsSb using temperature of 500 to 600 C, pressures of 65 to 630 torr, V/III ratios of 1--17, and growth rates of 0.3 to 2.7 {micro}m/hour in a horizontal quartz reactor. SIMS showed C and O levels below 2 {times} 10{sup 18} cm{sup {minus}3} and 6 {times} 10{sup 18} cm{sup {minus}3} respectively for undoped AlSb. Similar levels of O were found in AlAs{sub 0.16}Sb{sub 0.84} films but C levels were an order of magnitude less in undoped and Sn-doped AlAs{sub 0.16}Sb{sub 0.84} films. Hall measurements of AlAs{sub 0.16}Sb{sub 0.84} showed hole concentrations between 1 {times} 10{sup 17} cm{sup {minus}3} to 5 {times} 10{sup 18} cm{sup {minus}3} for Zn-doped material and electron concentrations in the low to mid 10{sup 18} cm{sup {minus}3} for Sn-doped material. They have grown pseudomorphic InAs/InAsSb quantum well active regions on AlAsSb cladding layers. Photoluminescence of these layers has been observed up to 300 K.

  13. 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. 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.

  15. A Metal Organic Framework with Spherical Protein Nodes: Rational Chemical Design of 3D Protein Crystals.

    PubMed

    Sontz, Pamela A; Bailey, Jake B; Ahn, Sunhyung; Tezcan, F Akif

    2015-09-16

    We describe here the construction of a three-dimensional, porous, crystalline framework formed by spherical protein nodes that assemble into a prescribed lattice arrangement through metal-organic linker-directed interactions. The octahedral iron storage enzyme, ferritin, was engineered in its C3 symmetric pores with tripodal Zn coordination sites. Dynamic light scattering and crystallographic studies established that this Zn-ferritin construct could robustly self-assemble into the desired bcc-type crystals upon coordination of a ditopic linker bearing hydroxamic acid functional groups. This system represents the first example of a ternary protein-metal-organic crystalline framework whose formation is fully dependent on each of its three components.

  16. Metal-organic chemical vapor deposition in silicon/zinc sulfide quantum confined structures

    NASA Astrophysics Data System (ADS)

    Bretschneider, Eric Colin

    A comprehensive study of low pressure metal-organic chemical vapor deposition growth of zinc sulfide and silicon has been performed. The parameter space for successful deposition of both materials has been investigated and found to overlap, allowing successful deposition of both zinc sulfide and silicon under similar conditions. Undoped and aluminum doped zinc sulfide and silicon films were grown on both (100) and (111) 4sp° off orientation silicon substrates. Diethyl zinc, hydrogen sulfide, triethyl aluminum and disilane where used as precursor materials. It was found that high quality epitaxial zinc sulfide films could be deposited over the temperature range of 300 to 650sp°C. Growth rate was found to be nearly independent of temperature over this temperature range indicating a mass transfer limited growth mechanism. Aluminum doping yielded low resistivity, n-type material. Key parameters affecting the surface roughness of zinc sulfide films were determined using a fractional factorial design. This method increases the efficiency of data collection and allows easy determination of the magnitude of multi-parameter interactions. The parameters studied included substrate orientation, deposition temperature, precursor concentrations, total hydrogen flow and the push flow ratio of the alkyl and hydride injectors. Silicon growth rates varied from 120 to 9000 A/hour at 450 and 600sp° C respectively. A strong temperature dependence of the growth rate was found indicating a reaction limited step with an activation energy of 153.6 ± 18.0 kJ/mol. This agrees well with the energy barrier of 144.3 ± 19.2 kJ/mol for surface diffusion of hydrogen. Quantum mechanical calculations that take into account the differences in effective masses for electrons and holes in silicon and zinc sulfide indicate that the band gap energy of a silicon quantum well shifts into the visible portion of the spectrum for well widths below 20A. Samples containing single and multiple quantum wells

  17. 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.

  18. A Sr2+-metal-organic framework with high chemical stability: synthesis, crystal structure and photoluminescence property.

    PubMed

    Jia, Yan-Yuan; Liu, Xiao-Ting; Wang, Wen-He; Zhang, Li-Zhu; Zhang, Ying-Hui; Bu, Xian-He

    2017-01-13

    Metal-organic frameworks (MOFs) are typically built by assembly of metal centres and organic linkers, and have emerged as promising crystalline materials in a variety of fields. However, the stability of MOFs is a key limitation for their practical applications. Herein, we report a novel Sr 2+: -MOF [Sr4(Tdada)2(H2O)3(DMF)2] (denoted as NKU- 105: , NKU = Nankai University; H4Tdada = 5,5'-((thiophene-2,5-dicar bonyl)bis(azanediyl))diisophthalic acid; DMF = N,N-dimethylformamide) featuring an open square channel of about 6 Å along the c-axis. Notably, NKU- 105: exhibits much outstanding chemical stability against common organic solvents, boiling water, acids and bases, relative to most MOF materials. Furthermore, NKU- 105: is an environment-friendly luminescent material with a bright cyan emission.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

  19. 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.

  20. 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

    2014-03-03

    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.

  1. Optical Properties of Novel GaN 3D Structures Grown by Metal-Organic Chemical Vapor Deposition (MOCVD)

    NASA Astrophysics Data System (ADS)

    Sacilotti, Marco; Imhoff, Luc; Dumas, Colette; Viste, Pierre; Vial, Jean-Claude; Baldeck, Patrice; Colombier, Isabelle; Donatini, Fabrice

    2004-06-01

    Optical properties of novel micrometer-size Ga and GaN three-dimensional structures obtained by the metal-organic chemical vapour deposition (MOCVD) technique are presented in this letter. These structures are obtained as metallic three dimensions (3D) micrometer-size objects on an appropriate substrate by metalorganic (TMGa) pyrolisis and then GaN transformed on annealing under NH3 atmosphere at 650-750°C. These 3D GaN structures are analysed by optical means, using two-photon excitation (800 nm) and by UV Hg lamp fluorescent spectroscopy techniques, adapted to two-optical-microscopes apparatus. Very intense and blue/yellow light emission is observed from these 3D structures under 800 nm two-photon laser excitation and under UV Hg lamp excitation.

  2. Luminescent lanthanide metal-organic frameworks for chemical sensing and toxic anion detection.

    PubMed

    Wu, Rui-Zhi; Yang, Xing; Zhang, Liang-Wei; Zhou, Pan-Pan

    2017-08-01

    Prototype lanthanide metal-organic frameworks (LnMOFs), Ln(BTC) (Ln = Eu and Tb; BTC = benzene-1,3,5-tricarboxylate), have been considered as luminescent sensors for detecting toxic anions, while their neutral pore structures have limited the entrance and encapsulation of anions to produce highly anion-responsive photoluminescence (PL). To facilitate anions to enter the pore space of Ln(BTC), a one-pot synthesis method was proposed in which BTC was partially replaced with its structural analogue L·BF4 (H3L·BF4 = 2,4,6-tricarboxy-1-methylpyridinium tetrafluoroborate) which consists of an anion affinity site of cationic methylpyridinium. Compared to the original Ln(BTC), the co-doped cationic framework Eu0.05Tb0.95-BTC0.9L0.1 is highly sensitive for detecting different toxic anions by tuning the energy absorption of organic chromophores, the energy transfer efficiency to Ln(3+) ions and the energy allocation between different Ln(3+) ions in the PL spectra. We demonstrated that the Eu0.05Tb0.95-BTC0.9L0.1 PL sensor has the capability of decoding various toxic anions with a clearly differentiable and unique emission intensity ratio of (5)D4 → (7)F5 (Tb(3+), 545 nm) to (5)D0 → (7)F2 (Eu(3+), 618 nm) transitions (ITb/IEu). Compared to Ln(BTC), the co-doped Eu0.05Tb0.95-BTC0.9L0.1 presents self-calibrating, high distinguishable and stable PL signals for detecting toxic anions.

  3. 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.

  4. 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.

  5. 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

  6. 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. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Improvement of charge injection efficiency in organic-inorganic hybrid solar cells by chemical modification of metal oxides with organic molecules

    SciTech Connect

    Kudo, Naomi; Honda, Satoshi; Shimazaki, Yuta; Ohkita, Hideo; Ito, Shinzaburo; Benten, Hiroaki

    2007-04-30

    The effect of chemical modification of metal oxide surface with dye molecules in organic-inorganic hybrid solid solar cells was studied by using double layered cells consisting of poly(3-hexylthiophene) (P3HT) and a flat layer of dense TiO{sub 2}. The external quantum efficiency of the chemically modified cell was nearly double that expected from the photosensitizing effect of the dye molecules. The additional increase shows that the chemical modification with dye molecules can serve not only as a photosensitizer but mainly as an energy funnel and/or an electronic mediator to significantly improve the electron injection efficiency from P3HT to TiO{sub 2}.

  8. 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

  9. 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.

  10. Metal organic chemical vapor deposition of core-shell InAs-Al nanowires for proximity-induced superconductivity

    NASA Astrophysics Data System (ADS)

    Hartke, T. R.; Stehlik, J.; Petta, J. R.

    The zero-bias conductance peaks observed in proximitized InSb nanowires have been interpreted as evidence of Majorana fermions. However, these observations are complicated by the presence of a non-zero conductance throughout the gap, which has been termed a ``soft-gap.'' The characteristics of the gap can be improved by using MBE to epitaxially grow a superconducting aluminum shell around an InAs core. Here we use metal organic chemical vapor deposition (MOCVD) to grow high quality InAs nanowires on predefined Au catalyst sites. An aluminum shell is deposited immediately after the InAs growth is terminated. The resulting core-shell nanowires are structurally and electrically characterized. Supported by the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant No. GBMF4535.

  11. Structural and electrical characterization of Bi₂Se₃ nanostructures grown by metal-organic chemical vapor deposition.

    PubMed

    Alegria, L D; Schroer, M D; Chatterjee, A; Poirier, G R; Pretko, M; Patel, S K; Petta, J R

    2012-09-12

    We characterize nanostructures of Bi(2)Se(3) that are grown via metal-organic chemical vapor deposition using the precursors diethyl selenium and trimethyl bismuth. By adjusting growth parameters, we obtain either single-crystalline ribbons up to 10 μm long or thin micrometer-sized platelets. Four-terminal resistance measurements yield a sample resistivity of 4 mΩ·cm. We observe weak antilocalization and extract a phase coherence length l(ϕ) = 178 nm and spin-orbit length l(so) = 93 nm at T = 0.29 K. Our results are consistent with previous measurements on exfoliated samples and samples grown via physical vapor deposition.

  12. Effect of doped substrates on the growth of GaAs nanowires via metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Peng, Yan; Guo, Jingwei; La, Dongsheng; Xu, Zhaopeng; Wang, Haiyan

    2017-08-01

    Vertical GaAs nanowires were grown on different doped substrates via Metal Organic Chemical Vapor Deposition by catalyst assisted vapor-liquid-solid mechanism. It is found that both n and p type doped substrates affect catalyst distribution during the formation of alloy catalysts. The catalyst density decreases with an increase in the doping concentration of the substrates. In the growth of GaAs nanowires, the growth rate, which is mostly determined by the atoms diffusion from the pyrolysis of precursors on the surface of nanowires and substrates, is proportional to the catalyst densities. Moreover, the structures of as-grown nanowires are all pure zinc blende without any defects. These results will be valuable for the applications of nanowire-based optical and electrical devices.

  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. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Dislocation analysis of InGaN/GaN quantum dots grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yang, Di; Wang, Lai; Hao, Zhi-Biao; Luo, Yi; Sun, Changzheng; Han, Yanjun; Xiong, Bing; Wang, Jian; Li, Hongtao

    2016-11-01

    The dislocations in InGaN/GaN quantum dots grown by metal organic chemical vapor deposition were studied by high-resolution transmission electron microscopy combining the Fourier filtering process. The misfit dislocations were observed in uncapped InGaN/GaN quantum dots. However, for the capped InGaN/GaN quantum dots, the GaN capping layer was found to suppress the generation of misfit dislocations and hence hindered the strain relaxation. Therefore, an overgrowth InGaN layer was used to relieve the strain in InGaN quantum dots and misfit dislocations were correspondingly found in these samples. In addition, defects were observed in low temperature GaN layers which suggested the existence of stacking faults.

  16. Electric, dielectric and optical properties of Ga2O3 grown by metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Paskaleva, A.; Spassov, D.; Terziyska, P.

    2017-01-01

    Thin film (15-130 nm) of gallium oxide were grown by the industry relevant metal organic chemical vapour deposition (MOCVD) technique on p-type Si to check the possibility for integration of newly rediscovered wide bandgap material with the Si technology. Electric, dielectric and optical properties were studied and analyzed. To perform electrical characterization, Ga2O3 films were integrated into Al/Ga2O3/p-Si metal–oxide–semiconductor (MOS) capacitors. Relative dielectric permittivity, flat-band voltage shift and effective oxide charge density were obtained from C-V measurements. Spectroscopic ellipsometry measurements reveal that Ga2O3 deposited by MOCVD is a direct bandgap material with a large optical bandgap of about 5.1 eV. Both ellipsometrical and electrical results show formation of a thick interfacial SiO2.

  17. A computational study of the effect of the metal organic framework environment on the release of chemically stored nitric oxide.

    PubMed

    Li, Tanping; Taylor-Edinbyrd, Kiara; Kumar, Revati

    2015-09-28

    The use of copper based metal organic frameworks as a vehicle for the storage and delivery of chemically stored nitric oxide has been proposed based on recent experiments [J. Am. Chem. Soc., 2012, 134, 3330-3333]. In these experiments copper based metal organic frameworks (MOFs) suspended in ethanol catalytically convert chemically stored nitric oxide (in the S-nitrosothiol or RSNO form) to free nitric oxide at a slow and sustained rate, as compared to a quick release in a solution of ethanol containing free copper ions. In order to gain insight on the effect of the MOF environment on the catalytic activity, a combination of electronic structure calculations on representative clusters and classical simulations using a force-field (partly parameterized on the above calculations) is used to study a simple RSNO species, S-nitrosomethane (CH3SNO) as well as the biologically compatible S-nitrosocysteine, both in the MOF and free copper solution. The free energy profiles of bringing the RSNO species to the catalytic centers have been compared and related to the different solvation environments of the copper catalyst in the complex solvated MOF and in free copper solution. Surprisingly, in the case of the simple CH3SNO moiety as well as the S-nitrosocysteine case, the free energy profile of bringing the first RSNO from the center of one of the pores to the catalytic site in the pore is very similar to the free solution case. On the other hand, bringing a second RSNO molecule to the same catalytic site or to the adjacent catalytic copper site show relatively higher barriers. These studies help shed light on the sustained nitric oxide release in the MOF environment.

  18. 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.

  19. Long-term environmental monitoring of persistent organic pollutants and metals in a chemical/petrochemical area: human health risks.

    PubMed

    Nadal, Martí; Schuhmacher, Marta; Domingo, José L

    2011-07-01

    Organic pollutants such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polycyclic aromatic hydrocarbons (PAHs), as well as some metals are periodically monitored in soil and vegetation samples collected in Tarragona County (Spain). We here report the temporal trends of the concentrations of the above pollutants between the initial survey (2002) and that recently (2009) performed. The area under evaluation was divided into 4 sections (chemical, petrochemical, urban/residential and unpolluted). In general terms, urban soils presented the highest concentrations of PCDD/Fs, PCNs and PAHs, confirming that traffic is a very important emission source of these pollutants. In addition, substantially higher levels of PAHs and some metals were found in vegetation samples from the petrochemical complex. The assessment of health risks of these contaminants indicated that the current concentrations of micropollutants did not mean additional non-carcinogenic or cancer risks for the population living in the zone. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Multistage Infrared Emitters Based on InAsSb Strained Layers Grown by Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Allerman, A.A.; Baucom, K.C.; Biefeld, R.M.; Kurtz, S.R.

    1999-01-04

    We report on the metal-organic chemical vapor deposition (MOCVD) of mid-infrared InAaSb multistage emitters using a high speed rotating disk reactor. The devices contain AlAsSb cladding and strained InAsSb active regions. These emitters have multistage, type I InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multistage injection lasers and AlAsSb is the electron confinement layer. These structures are the first MOCVD multistage devices. Broadband LED's produced 2 mW average power at 3.7 {micro}m and 80 K and 0.1 mW at 4.3 {micro}m and 300K. A multistage, 3.8-3.9 {micro}m laser structure operated up to T=180 K. At 80 K, peak-power > 100 mW/facet and a high slope-efficiency (48%) were observed in these gain guided lasers.

  1. Progress in the growth of mid-infrared InAsSb emitters by metal-organic chemical vapor deposition

    SciTech Connect

    Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R.; Baucom, K.C.

    1998-08-01

    The authors report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) of mid-infrared InAsSb emitters using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained InAsSb active regions. These emitters have multi-stage, type 1, InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multistage injection lasers and AlAsSb is the electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in a horizontal reactor. Broadband LED`s produced 2 mW average power at 3.7 {micro}m and 80 K and 0.1 mW at 4.3 {micro}m and 300 K. a multi-stage, 3.8--3.9 {micro}m laser structure operated up to T = 180 K. At 80 K, peak-power > 100 mW/facet and a high slope efficiency (48%) were observed in these gain guided lasers.

  2. Recent Progress in the Growth of Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R.; Baucom, K.C.

    1998-01-01

    We report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) growth of mid-infrared lasers and using a high speed rotating disk reactor (RDR). The devices contain AlAsSb active regions. These lasers have multi-stage, type I InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multi-stage injection lasers and AlAsSb is an electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in conventional horizontal reactors. A single stage, optically pumped laser yielded improved power (greater than 650 mW/facet) at 80K and 3.8um. A multi-stage 3.8-3.9um laser structure operated up to T=170K. At 80K, peak power greater than 100mW and a high slope- efficiency were observed in gain guided lasers.

  3. Novel materials and device design by metal-organic chemical vapor deposition for use in infrared emitters

    SciTech Connect

    Biefeld, R.M.; Kurtz, S.R.; Allerman, A.A.

    1996-12-01

    The authors have grown AlSb and AlAs{sub x}Sb{sub 1{minus}x} epitaxial layers by metal-organic chemical vapor deposition(MOCVD) using trimethylamine or ethyldimethylamine alane, triethylantimony and arsine. These layers were successfully doped p- or n-type using diethylzinc or tetraethyltin, respectively. They examined the growth of AlAs{sub x}Sb{sub 1{minus}x} using temperatures of 500 to 600 C, pressures of 65 to 630 torr, V/III ratios of 1--17, and growth rates of 0.3 to 2.7 {micro}m/hour in a horizontal quartz reactor. They have also grown gain-guided, injection lasers using AlAsSb for optical confinement and a strained InAsSb/InAs multi-quantum well active region using MOCVD. The semi-metal properties of a p-GaAsSb/n-InAs heterojunction were utilized as a source for injection of electrons into the active region of the laser. In pulsed mode, the laser operated up to 210 K with an emission wavelength of 3.8--3.9 {micro}m. The dependence of active region composition on wavelength was determined. They also report on the 2-color emission of a light-emitting diode with two different active regions to demonstrate multi-stage operation of these devices.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Chemically functionalized magnetic exchange interactions of hybrid organic-ferromagnetic metal interfaces

    NASA Astrophysics Data System (ADS)

    Friedrich, Rico; Caciuc, Vasile; Kiselev, Nikolai S.; Atodiresei, Nicolae; Blügel, Stefan

    2015-03-01

    We theoretically explore through systematic multiscale ab initio and Monte Carlo calculations how the surface magnetism of a ferromagnetic surface can be fine-tuned by nonmagnetic organic molecules containing a single π bond. We demonstrate that a magnetic hardening or softening can be induced depending on the electronegativity of the heteroatom or when the π -bond "bridges" the magnetic surface atoms. Finally, the Monte Carlo simulations revealed taylored macroscopic hysteresis loops corresponding to soft and hard molecule-surface magnets.

  9. 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 ...

  10. A porous metal-organic framework based on Zn6O2 clusters: chemical stability, gas adsorption properties and solvatochromic behavior.

    PubMed

    Cui, Jiehu; Li, Yizhi; Guo, Zijian; Zheng, Hegen

    2013-01-21

    A highly connected 3D metal-organic framework with tfz-d topology based on Zn(6)O(2) clusters and flexible carboxylate ligands has been synthesized. The obtained Zn-MOF shows solvatochromic behavior for fluorescence sensing of small molecules, gas adsorption properties and exceptional chemical stability and might have applications for separation and detection purposes.

  11. In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks

    SciTech Connect

    Plonka, Anna M.; Wang, Qi; Gordon, Wesley O.; Balboa, Alex; Troya, Diego; Guo, Weiwei; Sharp, Conor H.; Senanayake, Sanjaya D.; Morris, John R.; Hill, Craig L.; Frenkel, Anatoly I.

    2016-12-30

    Recently, Zr-based metal organic frameworks (MOFs) were shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. Here, we report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination of DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. Our experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.

  12. Selective epitaxial growth of Ge1-xSnx on Si by using metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Washizu, Tomoya; Ike, Shinichi; Inuzuka, Yuki; Takeuchi, Wakana; Nakatsuka, Osamu; Zaima, Shigeaki

    2017-06-01

    Selective epitaxial growth of Ge and Ge1-xSnx layers on Si substrates was performed by using metal-organic chemical vapor deposition (MOCVD) with precursors of tertiary-butyl-germane (t-BGe) and tri-butyl-vinyl-tin (TBVSn). We investigated the effects of growth temperature and total pressure during growth on the selectivity and the crystallinity of the Ge and Ge1-xSnx epitaxial layers. Under low total pressure growth conditions, the dominant mechanism of the selective growth of Ge epitaxial layers is the desorption of the Ge precursors. At a high total pressure case, it is needed to control the surface migration of precursors to realize the selectivity because the desorption of Ge precursors was suppressed. The selectivity of Ge growth was improved by diffusion of the Ge precursors on the SiO2 surfaces when patterned substrates were used at a high total pressure. The selective epitaxial growth of Ge1-xSnx layer was also realized using MOCVD. We found that the Sn precursors less likely to desorb from the SiO2 surfaces than the Ge precursors.

  13. Thermoelectric properties of lattice-matched AlInN alloy grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tong, Hua; Zhang, Jing; Liu, Guangyu; Herbsommer, Juan A.; Huang, G. S.; Tansu, Nelson

    2010-09-01

    Thermoelectric properties of lattice-matched AlInN grown by metal organic chemical vapor deposition were measured and analyzed. The n-type Al0.83In0.17N alloy exhibited thermal conductivity of 4.87 W/(m K) measured by 3ω differential method. The Seebeck coefficient of n-Al0.83In0.17N was measured as -6.012×10-4 V/K by thermal gradient method. The sheet resistivity of n-Al0.83In0.17N was measured by using Van der Pauw method, and the electrical conductivity was measured as 2.38×104/(Ω m). The thermoelectric figure of merit (Z∗T) of n-type Al0.83In0.17N was measured as 0.532 at room temperature (T =300 K). The finding indicates lattice-matched AlInN alloy on GaN as excellent material candidate for thermoelectric application.

  14. Influence of metal organic chemical vapour deposition growth conditions on vibrational and luminescent properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Montenegro, D. N.; Hortelano, V.; Martínez, O.; Martínez-Tomas, M. C.; Sallet, V.; Muñoz-Sanjosé, V.; Jiménez, J.

    2013-04-01

    A detailed optical characterization by means of micro Raman and cathodoluminescence spectroscopy of catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition has been carried out. This characterization has allowed correlating the growth conditions, in particular the precursors partial-pressures and growth time, with the optical properties of nanorods. It has been shown that a high Zn supersaturation can favor the incorporation of nonradiative recombination centers, which can tentatively be associated with ZnI-related defects. Characterization of individual nanorods has evidenced that ZnI-related defects have a tendency to accumulate in the tip part of the nanorods, which present dark cathodoluminescence contrast with respect to the nanorods bottom. The effect of a ZnO buffer layer on the properties of the nanorods has been also investigated, showing that the buffer layer improves the luminescence efficiency of the ZnO nanorods, revealing a significant reduction of the concentration of nonradiative recombination centers.

  15. In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks

    DOE PAGES

    Plonka, Anna M.; Wang, Qi; Gordon, Wesley O.; ...

    2016-12-30

    Recently, Zr-based metal organic frameworks (MOFs) were shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. Here, we report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination ofmore » DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. Our experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.« less

  16. Direct Growth of a-Plane GaN on r-Plane Sapphire by Metal Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Chiu; Su, Yan-Kuin; Huang, Shyh-Jer; Wang, Yu-Jen; Wu, Chun-Ying; Chou, Ming-Chieh

    2010-04-01

    In this study, we had demonstrated the direct growth of nonpolar a-plane GaN on an r-plane sapphire by metal organic chemical vapor deposition (MOCVD) without any buffer layer. First, in this experiment, we had determined the optimum temperature for two-step growth, including obtaining three-dimensional (3D) GaN islands in the nucleation layer and coalescing with a further two-dimensional (2D) growth mode. The result shows that the nucleation layer grown under high temperature (1150 °C) leads to large islands with few grain boundaries. Under the same temperature, the effect of the V/III ratio on the growth of the overlaying GaN layer to obtain a flat and void free a-plane GaN layer is also studied. The result indicates one can directly grow a smooth epitaxial layer on an r-plane sapphire by changing the V/III ratio. The rms roughness decreases from 13.61 to 2.02 nm. The GaN crystal quality is verified using a mixed acid to etch the film surface. The etch pit density (EPD) is 3.16 ×107 cm-2.

  17. Catalyst-free growth of ZnO nanowires by metal-organic chemical vapour deposition (MOCVD) and thermal evaporation

    SciTech Connect

    Lee, Woong; Jeong, Min-Chang; Myoung, Jae-Min

    2004-08-02

    ZnO nanowires were grown on GaAs(0 0 2) substrates using metal-organic chemical vapour deposition (MOCVD) and on Si(0 0 1) substrates using thermal evaporation of source powders, respectively. It was demonstrated that well-aligned single crystalline nanowires could be grown with controlled sizes using a typical thin film deposition technique without catalysts. Arsenic doping of the ZnO nanowires grown on GaAs substrate was possible using post-growth heat-treatment, proposing a possible way of producing p-type ZnO nanowires. It was also shown that simplified process of carrier-free thermal evaporation without catalyst could be employed to grow nanowires with high yield while maintaining good crystalline and optical properties. Application potential of the nanowires as probes of atomic force microscopes (AFMs) was discussed by predicting their structural compatibility with AFM cantilevers based on continuum elasticity. It was predicted that the nanowires fabricated herein are structurally compatible with typical AFM cantilevers suggesting that they are promising candidates for high aspect ratio probes.

  18. 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.

  19. 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

    2013-10-10

    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.

  20. Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

    PubMed Central

    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 m2/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

  1. 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.

  2. Boosting Chemical Stability, Catalytic Activity, and Enantioselectivity of Metal-Organic Frameworks for Batch and Flow Reactions.

    PubMed

    Chen, Xu; Jiang, Hong; Hou, Bang; Gong, Wei; Liu, Yan; Cui, Yong

    2017-09-27

    A key challenge in heterogeneous catalysis is the design and synthesis of heterogeneous catalysts featuring high catalytic activity, selectivity, and recyclability. Here we demonstrate that high-performance heterogeneous asymmetric catalysts can be engineered from a metal-organic framework (MOF) platform by using a ligand design strategy. Three porous chiral MOFs with the framework formula [Mn2L(H2O)2] are prepared from enantiopure phosphono-carboxylate ligands of 1,1'-biphenol that are functionalized with 3,5-bis(trifluoromethyl)-, bismethyl-, and bisfluoro-phenyl substituents at the 3,3'-position. For the first time, we show that not only chemical stability but also catalytic activity and stereoselectivity of the MOFs can be tuned by modifying the ligand structures. Particularly, the MOF incorporated with -CF3 groups on the pore walls exhibits enhanced tolerance to water, weak acid, and base compared with the MOFs with -F and -Me groups. Under both batch and flow reaction systems, the CF3-containing MOF demonstrated excellent reactivity, selectivity, and recyclability, affording high yields and enantioselectivities for alkylations of indoles and pyrrole with a range of ketoesters or nitroalkenes. In contrast, the corresponding homogeneous catalysts gave low enantioselectivity in catalyzing the tested reactions.

  3. In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks.

    PubMed

    Plonka, Anna M; Wang, Qi; Gordon, Wesley O; Balboa, Alex; Troya, Diego; Guo, Weiwei; Sharp, Conor H; Senanayake, Sanjaya D; Morris, John R; Hill, Craig L; Frenkel, Anatoly I

    2017-01-18

    Zr-based metal organic frameworks (MOFs) have been recently shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. We report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination of DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. These experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.

  4. 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.

  5. 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.

  6. Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Ledyaev, Oleg; Miller, Ross; Beletsky, Valeria; Osinsky, Andrei; Schoenfeld, Winston V.

    2016-02-01

    We report on the growth of high Mg content, high quality, wurtzite MgxZn1-xO (MgZnO) epitaxial films using a pulsed metal organic chemical vapor deposition (PMOCVD) method. Series of MgZnO films with variable Mg concentration were deposited on bare and AlN coated sapphire substrates. The band gap of the films estimated using UV-visible transmission spectra ranges from 3.24 eV to 4.49 eV, corresponding to fraction of Mg between x=0.0 and x=0.51, as determined by Rutherford backscattering spectroscopy. The cathodoluminescence (CL) measurement has shown a blue-shift in the peak position of MgZnO with an increasing Mg content. No multi-absorption edges and CL band splitting were observed, suggesting the absence of phase segregation in the as grown films. The crystal structure and phase purity of the films were also confirmed by XRD analysis. Hall effect measurement in van der Pauw configuration was employed to evaluate the electrical properties of the films. With a rise in Mg incorporation into the ZnO lattice, the films became very resistive, consistent with the widening of the band gap. The AFM measurement on the films has shown a decreasing surface roughness with an Mg content. To the best of our knowledge, the current result shows the highest Mg content (x=0.51), high quality, wurtzite MgZnO epitaxial film ever grown by MOCVD. The high Mg incorporation without phase separation is believed to be due to the non-equilibrium behavior of the PMOCVD in which the kinetic processes dominate the thermodynamic one.

  7. InP/InGaAlAs distributed Bragg reflectors grown by low-pressure metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lu, T. C.; Tsai, J. Y.; Chu, J. T.; Chang, Y. S.; Wang, S. C.

    2003-04-01

    Long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered the best candidate for the future low-cost reliable light sources in fiber communications. However, the absence of high refractive index contrast in InP-lattice-matched materials impeded the development of 1.3-1.5 μm VCSELs. Although wafer fusions provided the alternative approaches to integrate the InP-based gain materials with the GaAs/AlAs materials for their inherent high refractive index contrast, the monolithic InP-based lattice-matched distributed Bragg reflectors (DBRs) are still highly attractive and desirable. In this report, we demonstrate InP/InGaAlAs DBRs with larger refractive index contrast than InP/InGaAsP and InAlAs/InGaAlAs DBRs. The switching between InP and InGaAlAs layers and growth rate control have been done by careful growth interruption technique and accurate in situ optical monitoring in low-pressure metal organic chemical vapor deposition. A 35 pairs 1.55 μm centered InP/InGaAlAs DBRs has the stopband of more than 100 nm and the highest reflectivity of more than 99%. A VCSEL structure incorporating 35 pairs InP/InGaAlAs DBR as the bottom mirror combined with a 2 λ thick periodic gain cavity and 10 pairs SiO 2/TiO 2 top dielectric mirrors was fabricated. The VCSELs lased at 1.56 μm by optical pumping at room temperature with the threshold pumping power of 30 mW.

  8. Growth of superconducting NdFe0.88Co0.12AsO films by metal-organic chemical vapor deposition and post arsenic diffusion

    NASA Astrophysics Data System (ADS)

    Corrales-Mendoza, I.; Bartolo-Pèrez, P.; Sánchez-Reséndiz, V. M.; Gallardo-Hernández, S.; Conde-Gallardo, A.

    2015-01-01

    Metal-organic chemical vapor deposition (MOCVD) and post-deposition arsenic diffusion processes were successfully employed to grow superconducting NdFe0.88Co0.12AsO thin films. First, by employing iron, cobalt and neodymium metal-organic precursors, a precursor film is grown by MOCVD on (001)-oriented LaAlO3 substrates. Subsequently, the arsenic is incorporated during an annealing of these precursor films in the presence of a NdFe0.9Co0.1AsO pellet. The chemical composition and crystallographic results indicate the formation of the cobalt-doped NdFeAsO polycrystalline phase. The secondary ion mass spectroscopy indicates a homogeneous arsenic diffusion process. The resistance and magnetization measurements as a function of temperature indicate a superconducting transition ˜15 \\text{K} .

  9. Real-time in-situ chemical sensing in aluminum gallium nitride/gallium nitride metal-organic chemical vapor deposition processes for advanced process control

    NASA Astrophysics Data System (ADS)

    Cho, Soon

    Gallium nitride and its alloys promise to be key materials for future semiconductor devices aimed at high frequency, high power electronic applications. However, manufacturing for such high performance products is challenged by reproducibility and material quality constraints that are notably more stringent than those required for optoelectronic applications. To meet this challenge, in-situ mass spectrometry was implemented as a real-time process- and wafer-state metrology tool in AlGaN/GaN/AlN metal-organic chemical vapor deposition processes on semi-insulating SiC substrate wafers. Dynamic chemical sensing through the process cycle, carried out downstream from the wafer, revealed generation of methane and ethane reaction byproducts, as well as other residual gas species. Real-time metrics were derived based on the chemical signals to predict/control material quality and thickness of critical layers within the heterostructure in real time during growth, and corresponding metrologies were used for real-time advanced process control. Using the methane/ethane ratio, GaN epilayer crystal quality was predicted in real time to 2--5% precision, which was verified by post-process x-ray diffraction. Moreover, the same real-time metric predicted material quality as indicated by post-process photoluminescence band-edge intensities to ˜5% precision. The methane/ethane ratio has a fundamental significance in terms of the intrinsic chemistry in that the two byproducts are believed to reflect two parallel reaction pathways leading to GaN-based material growth, namely the gas phase adduct formation route and the surface route for direct precursor decomposition, respectively. The fact that lower methane/ethane ratios consistently yield better material quality suggests that the surface pathway is preferred for high quality GaN growth. In addition, a metric based on methane and ethane signals integrated through the AlGaN growth period (˜1 min or less) enabled prediction of the cap

  10. The nature of catalyst particles and growth mechanisms of GaN nanowires grown by Ni-assisted metal-organic chemical vapor deposition.

    PubMed

    Weng, Xiaojun; Burke, Robert A; Redwing, Joan M

    2009-02-25

    The structure and chemistry of the catalyst particles that terminate GaN nanowires grown by Ni-assisted metal-organic chemical vapor deposition were investigated using a combination of electron diffraction, high-resolution transmission electron microscopy, and x-ray energy dispersive spectrometry. The crystal symmetry, lattice parameter, and chemical composition obtained reveal that the catalyst particles are Ni(3)Ga with an ordered L 1(2) structure. The results suggest that the catalyst is a solid particle during growth and therefore favor a vapor-solid-solid mechanism for the growth of GaN nanowires under these conditions.

  11. 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. © 2011 American Chemical Society

  12. Metal-organic framework thin films on a surface of optical fibre long period grating for chemical sensing

    NASA Astrophysics Data System (ADS)

    Hromadka, J.; Tokay, B.; James, S.; Korposh, S.

    2017-04-01

    An optical fibre long period grating (LPG) modified with a thin film of HKUST-1, a material from metal organic framework (MOF) family, was employed for the detection of carbon dioxide. The sensing mechanism is based on the measurement of the change of the refractive index (RI) of the coating that is induced by the penetration of CO2 molecules into the HKUST-1 pores. The responses of the resonance bands in the transmission spectrum of an LPG modified with 40 layers of HKUST-1 upon exposure to carbon dioxide in mixture with nitrogen were investigated.

  13. 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.

  14. Chemical characteristics of dissolved organic matter (DOM) in relation to heavy metal concentrations in soil water from boreal peatlands after clear-cut harvesting

    NASA Astrophysics Data System (ADS)

    Kiikkilä, O.; Nieminen, T.; Starr, M.; Ukonmaanaho, L.

    2012-04-01

    Boreal peatlands form an important terrestrial carbon reserve and are a major source of dissolved organic matter (DOM) to surface waters, particularly when disturbed through forestry practices such as draining or timber harvesting. Heavy metals show a strong affinity to organic matter and so, along with DOM, heavy metals can be mobilized and transported from the soil to surface waters and sediments where they may become toxic to aquatic organisms and pass up the food chain. The complexation of heavy metals with DOM can be expected to be related and determined by the chemical characteristics of DOM and oxidation/reducing conditions in the peat. We extracted interstitial water from peat samples and determined the concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and Al, Cu, Zn and Fe in various fractions of DOM isolated by adsorption properties (XAD-8 fractionation) and molecular-weight (ultrafiltration). The peat samples were taken from 0-30 and 30-50 cm depth in drained peatland catchments two years after whole-tree or stem-only clear-cut harvesting (Scots pine or Norway spruce) had been carried out. The samples from the upper layer had been subject to alternating saturation/aeration conditions while the deeper layer had been continuously under the water table. The fractionation of DOC and DON according to both adsorption properties and molecular-weight fractions clearly differed between the upper and lower peat layers. While the hydrophobic acid fraction contained proportionally more DOC and DON than the hydrophilic acid fraction in the upper peat layer the results were vice versa in the lower peat layer. High-molecular-weight compounds (> 100 kDa) were proportionally more abundant in the upper and low-molecular-weight compounds (< 1 kDa) in the lower peat layer. These differences are assumed to reflect differences in the aerobic/ anaerobic conditions and degree of decomposition between the two layers. The concentrations of Zn, Al

  15. Chemical contaminants (trace metals, persistent organic pollutants) in albacore tuna from western Indian and south-eastern Atlantic Oceans: Trophic influence and potential as tracers of populations.

    PubMed

    Chouvelon, Tiphaine; Brach-Papa, Christophe; Auger, Dominique; Bodin, Nathalie; Bruzac, Sandrine; Crochet, Sylvette; Degroote, Maxime; Hollanda, Stephanie J; Hubert, Clarisse; Knoery, Joël; Munschy, Catherine; Puech, Alexis; Rozuel, Emmanuelle; Thomas, Bastien; West, Wendy; Bourjea, Jérôme; Nikolic, Natacha

    2017-10-15

    Albacore tuna (Thunnus alalunga) is a highly commercial fish species harvested in the world's Oceans. Identifying the potential links between populations is one of the key tools that can improve the current management across fisheries areas. In addition to characterising populations' contamination state, chemical compounds can help refine foraging areas, individual flows and populations' structure, especially when combined with other intrinsic biogeochemical (trophic) markers such as carbon and nitrogen stable isotopes. This study investigated the bioaccumulation of seven selected trace metals - chromium, nickel, copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg) and lead - in the muscle of 443 albacore tunas, collected over two seasons and/or years in the western Indian Ocean (WIO: Reunion Island and Seychelles) and in the south-eastern Atlantic Ocean (SEAO: South Africa). The main factor that explained metal concentration variability was the geographic origin of fish, rather than the size and the sex of individuals, or the season/year of sampling. The elements Cu, Zn, Cd and Hg indicated a segregation of the geographic groups most clearly. For similar sized-individuals, tunas from SEAO had significantly higher concentrations in Cu, Zn and Cd, but lower Hg concentrations than those from WIO. Information inferred from the analysis of trophic markers (δ(13)C, δ(15)N) and selected persistent organic pollutants, as well as information on stomach contents, corroborated the geographical differences obtained by trace metals. It also highlighted the influence of trophic ecology on metal bioaccumulation. Finally, this study evidenced the potential of metals and chemical contaminants in general as tracers, by segregating groups of individuals using different food webs or habitats, to better understand spatial connectivity at the population scale. Limited flows of individuals between the SEAO and the WIO are suggested. Albacore as predatory fish also provided some

  16. 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.

  17. Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, Z. B.; Lei, W.; Chen, B.; Wang, Y. B.; Liao, X. Z.; Tan, H. H.; Zou, J.; Ringer, S. P.; Jagadish, C.

    2014-01-01

    Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.

  18. 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

  19. Growth of InN films by radical-enhanced metal organic chemical vapor deposition at a low temperature of 200 °C

    NASA Astrophysics Data System (ADS)

    Takai, Shinnosuke; Lu, Yi; Oda, Osamu; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

    2017-06-01

    The InN films were deposited on GaN surfaces at a low temperature of 200 °C by radical-enhanced metal organic chemical vapor deposition (REMOCVD). The REMOCVD system can provide N radicals from the plasma of a N2-H2 mixture gas without using ammonia. Two types of GaN substrate, bulk GaN and GaN on Si(111), were used. The growth mode was modeled as a step flow on the basis of surface morphology observation by atomic force microscopy.

  20. Recent progress in metal-organic chemical vapor deposition of \\left( 000\\bar{1} \\right) N-polar group-III nitrides

    NASA Astrophysics Data System (ADS)

    Keller, Stacia; Li, Haoran; Laurent, Matthew; Hu, Yanling; Pfaff, Nathan; Lu, Jing; Brown, David F.; Fichtenbaum, Nicholas A.; Speck, James S.; DenBaars, Steven P.; Mishra, Umesh K.

    2014-11-01

    Progress in metal-organic chemical vapor deposition of high quality \\left( 000\\bar{1} \\right) N-polar (Al, Ga, In)N films on sapphire, silicon carbide and silicon substrates is reviewed with focus on key process components such as utilization of vicinal substrates, conditions ensuring a high surface mobility of species participating in the growth process, and low impurity incorporation. The high quality of the fabricated films enabled the demonstration of N-polar (Al, Ga, In)N based devices with excellent performance for transistor applications. Challenges related to the growth of high quality N-polar InGaN films are also presented.

  1. Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition

    SciTech Connect

    Chen, Z. B.; Chen, B.; Wang, Y. B.; Liao, X. Z.; Lei, W.; Tan, H. H.; Jagadish, C.; Zou, J.; Ringer, S. P.

    2014-01-13

    Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.

  2. 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.

  3. The optimization of interfaces in InAsSb/InGaAs strained-layer superlattices grown by metal-organic chemical vapor deposition

    SciTech Connect

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

    1993-12-31

    We have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) under a variety of conditions. Presence of an InGaAsSb interface layer is indicated by x-ray diffraction patterns. Optimized growth conditions involved the use of low pressure, short purge times, and no reactant flow during the purges. MOCVD was used to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS/InPSb laser which emitted at 3.9 {mu}m with a maximum operating temperature of approximately 100 K.

  4. Nucleation of ReBa2Cu3Ox (Re = rare-earth) during high-rate metal-organic chemical vapor deposition growth

    NASA Astrophysics Data System (ADS)

    Solovyov, Vyacheslav F.; Li, Qiang; Chen, Y.; Guevara, A.; Shi, T.; Selvamanickam, V.

    2011-12-01

    Large-scale, high-rate epitaxial growth technology for the second-generation superconducting wire brings unique technological challenges for the thin-film coating industry. One of the most difficult steps of the process is controlling nucleation of a complex compound over a km-long low-cost oxide template. Here, we analyze early stages of industrial-scale epitaxial metal organic chemical vapor deposition (MOCVD) growth of ReBa2Cu3Ox (REBCO, Re = rare-earth) on buffered metal substrates. The nucleation event is detected by high-flux synchrotron X-ray diffraction and confirmed by atomic force microscopy. REBCO nuclei exhibit a strong preference for edges of the buffer grain, indicating that (001) steps of the buffer grains are preferred nucleation sites. It is concluded that random nucleation of REBCO is caused by agglomerates of small buffer grains.

  5. 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.

  6. 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.

  7. 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)

  8. 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)

  9. A study on the synthesis of Ni50Co50 alloy nanostructures with tuned morphology through metal-organic chemical routes.

    PubMed

    Mourdikoudis, Stefanos; Collière, Vincent; Fau, Pierre; Kahn, Myrtil L

    2014-06-14

    NiCo bimetallic nanostructures with various morphologies have been synthesized using a broad range of solvents, surfactants and precursors that are available in the metal-organic chemical toolbox. Polygonal particles, nanowires and isotropic nanospheres have been obtained, among others. We describe the chemical pathways to achieve anisotropic growth either by an 'in situ' seed-mediated approach or by simply selecting suitable reaction media and growth modifiers. We describe the role of a variety of synthetic factors that influence the final shape of such an alloy material at the nanoscale. The alloying between cobalt and nickel is evidenced by XRD and HRTEM techniques. Room-temperature ferromagnetic behavior is observed for NiCo nanoparticles and high values for saturation magnetization and coercivity are recorded by SQuID magnetometry. The saturation magnetization value for the NiCo nanostructures is typically set between the corresponding "bulk" ones of cobalt and nickel metals. It is always comparable to the suggested value of the Ni50Co50 bulk alloy. The synthetic protocols derived from our extensive study are quantitative and versatile, allowing high reaction yields. Although macroscopic characterization techniques evidence the presence of a stoichiometric NiCo alloy, we show that in certain cases nanoscale characterization analyses are also needed for a more accurate evaluation of the alloy composition at the atomic level.

  10. Effect of chemical structure of S-nitrosothiols on nitric oxide release mediated by the copper sites of a metal organic framework based environment.

    PubMed

    Taylor-Edinbyrd, Kiara; Li, Tanping; Kumar, Revati

    2017-05-17

    The effect of chemical structure of different biologically compatible S-nitrosothiols on the solvation environment at catalytic copper sites in a metal organic framework (MOF) suspended in a solution of ethanol is probed using computational methods. The use of a copper based MOF as a storage vehicle and catalyst (copper sites of the MOF) in the controlled and sustained release of chemically stored nitric oxide (NO) from S-nitrosocysteine has been shown to occur both experimentally and computationally [J. Am. Chem. Soc., 2012, 134, 3330-3333; Phys. Chem. Chem. Phys., 2015, 17, 23403]. Previous studies on a copper based MOF, namely HKUST-1, concluded that modifications in the R-group of s-nitrosothiols and/or organic linkers of MOFs led to a method capable of modulating NO release. In order to test the hypothesis that larger R-groups slow down NO release, four different RSNOs (R = cysteine, N-acetylcysteine, N-acetyl-d,l-penicillamine or glutathione) of varying size were investigated, which in turn required the use of a larger copper based MOF. Due to its desirable copper centers and more extensive framework, MOF-143, an analog of HKUST-1 was chosen to further explore both the effect of different RSNOs as well as MOF environments on NO release. Condensed phase classical molecular dynamics simulations are utilized to study the effect of the complex MOF environment as well as the chemical structure and size of the RSNO on the species on the catalytic reaction. The results indicate that in addition to the size of the RSNO species and the organic linkers within the MOF, the reaction rates can be modulated by the molecular structure of the RSNO and furthermore combining different RSNO species can also be used to tune the rate of NO release.

  11. Preparation of AlAsSb and mid-infrared (3-5 {mu}m) lasers by metal-organic chemical vapor deposition

    SciTech Connect

    Allerman, A.A.; Biefeld, R.M.; Kurtz, S.R.

    1996-12-31

    Mid-infrared (3-5 {mu}m) infrared lasers and LEDs are being developed for use in chemical sensor systems. As-rich, InAsSb heterostructures display unique electronic properties that are beneficial to the performance of these midwave infrared emitters. The authors have grown AlAs{sub 1{minus}x}Sb{sub x} epitaxial layers by metal-organic chemical vapor deposition using trimethylamine (TMAA) or ethyldimethylamine alane (EDMAA), triethylantimony (TESb) and arsine. They examined the growth of AlAs{sub 1{minus}x}Sb{sub x} using temperatures of 500 to 600 {degrees}C, pressures of 70 to 630 torr, V/III ratios of 1-27, and growth rates of 0.3 to 2.7 {mu}m/hour in a horizontal quartz reactor. The semi-metal properties of a p-GaAsSb/n-InAs heterojunction are utilized as a source for injection of electrons into the active region of lasers. A regrowth technique has been used to fabricate gain-guided lasers using AlAs{sub 1{minus}x}Sb{sub x} for optical confinement with either a strained InAsSb/InAs multi-quantum well (MQW) or an InAsSb/InAsP strained layer superlattice (SLS) as the active region. Under pulsed injection, the InAsSb/InAs MQW laser operated up to 210K with an emission wavelength of 3.8-3.9 {mu}m. Under pulsed optical pumping, the InAsSb/InAsP SLS operated to 240K with an emission wavelength of 3.5-3.7 {mu}m. LED emission has been observed with both active regions in both p-n junction and semi-metal injection structures.

  12. Optical study of a-plane InGaN/GaN multiple quantum wells with different well widths grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ko, T. S.; Lu, T. C.; Wang, T. C.; Chen, J. R.; Gao, R. C.; Lo, M. H.; Kuo, H. C.; Wang, S. C.; Shen, J. L.

    2008-11-01

    a-plane InGaN/GaN multiple quantum wells of different widths ranging from 3 to 12 nm grown on r-plane sapphire by metal-organic chemical vapor deposition were investigated. The peak emission intensity of the photoluminescence (PL) reveals a decreasing trend as the well width increases from 3 to 12 nm. Low temperature (9 K) time-resolved PL (TRPL) study shows that the sample with 3-nm-thick wells has the best optical property with a fastest exciton decay time of 0.57 ns. The results of cathodoluminescence and micro-PL scanning images for samples of different well widths further verify that the more uniform and stronger luminescence intensity distribution are observed for the samples of thinner quantum wells. In addition, more effective capturing of excitons due to larger localization energy Eloc and shorter radiative lifetime of localized excitons are observed in thinner well width samples in the temperature dependent TRPL.

  13. Epitaxial deposition of NiO film on a cube-textured Ni substrate by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, Hee-Gyoun; Lee, Young-Min; Shin, Hyung-Sik; Jung, Choong-Hwan; Hong, Gye-Won

    2000-12-01

    NiO films have been epitaxially grown by metal-organic chemical vapor deposition (MOCVD) on a bi-axially textured Ni substrate using Ni(thd)2 as a precursor. The NiO film was deposited at 470°C for 10 min at a deposition pressure of 10 Torr and oxygen partial pressure of 0.91 Torr. SEM and AFM observations for the deposited NiO film showed a smooth and dense morphology. X-ray rocking curve and φ-scan showed that the NiO film has a bi-axial texture with a (100)<001> orientation. The out-of-plane and the in-plane deviations were measured to be 4.2° and 6 7° from the FWHM of (200) and (111) planes, respectively.

  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. Morphological and optical study of thin films of CuAlS2 deposited by metal organic chemical vapour deposition technique

    NASA Astrophysics Data System (ADS)

    Damisa, J.; Olofinjana, B.; Ebomwonyi, O.; Bakare, F.; Azi, S. O.

    2017-08-01

    Single solid source precursor of Copper-Aluminium dithiocarbamate was prepared and characterized by infrared spectroscopy. Thin films of copper aluminium sulphide were deposited on the substrate (soda lime glass) using metal organic chemical vapour deposition (MOCVD) technique within temperature ranges of 420 and 450 °C through the pyrolysis of the prepared precursor. Morphological and optical characterizations were then carried out. Morphological study carried out using scanning electron microscopy (SEM) showed that the deposited films are dense and polycrystalline in nature, uniform with the particle size distribution of the grains decreasing with increase in temperature. A direct optical energy gap of 3.28 and 2.88 eV were obtained for films deposited at 420 and 450 °C respectively. Other optical constants were found to increase as temperature increased.

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

    SciTech Connect

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

    2016-04-21

    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.

  17. 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.

  18. Growth and characterization of a multi-dimensional ZnO hybrid structure on a glass substrate by using metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Sik; Lee, Dohan; Lee, Je-Haeng; Byun, Dongjin

    2014-05-01

    A multi-dimensional zinc oxide (ZnO) hybrid structure was successfully grown on a glass substrate by using metal organic chemical vapor deposition (MOCVD). The ZnO hybrid structure was composed of nanorods grown continuously on the ZnO film without any catalysts. The growth mode could be changed from a two-dimensional (2D) film to one-dimensional (1D) nanorods by simply controlling the substrate's temperature. The ZnO with a hybrid structure showed improved electrical and optical properties. The ZnO hybrid structure grown by using MOCVD has excellent potential for applications in opto-electronic devices and solar cells as anti-reflection coatings (ARCs), transparent conductive oxides (TCOs) and transparent thin-film transistors (TTFTs).

  19. Defects reduction in a-plane AlGaN epi-layers grown on r-plane sapphire substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Jianguo; Zhang, Xiong; Dai, Qian; Wang, Nan; Wu, Zili; Wang, Shuchang; Cui, Yiping

    2017-01-01

    Nonpolar a-plane AlGaN epi-layers were grown on a semi-polar r-plane sapphire substrate with an innovative two-way pulsed-flows metal organic chemical vapor deposition growth technology. A root-mean-square value of 1.79 nm was achieved, and the relative light transmittance of the a-plane AlGaN epi-layer was enhanced by 36.9%. These results reveal that the innovative growth method is able to improve the surface morphology and reduce the defect density in nonpolar a-plane Al x Ga1- x N epi-layers, particularly those with an Al composition greater than 0.5, which are key materials for the fabrication of nonpolar AlGaN-based high light emission efficiency deep-ultraviolet light-emitting diodes.

  20. Optimization of InAsSb/InGaAs strained-layer superlattice growth by metal-organic chemical vapor deposition for use in infrared emitters

    SciTech Connect

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

    1994-08-01

    We have prepared InAsSb/InGaAs strained-layer superlattices (SLSs) by metal-organic chemical vapor deposition using a variety of growth conditions. Presence of an InGaAsSb interface layer was indicated by x-ray diffraction. This interface effect was minimized by optimizing the purge times, reactant flows, and growth conditions. The optimized growth conditions involved the use of low pressure, short purge times between the growth of the layers, and no reactant flow during the purges. Electron diffraction indicates that CuPt-type compositional ordering occurs in InAs{sub 1{minus}x}Sb{sub x} alloys and SLSs which explains an observed bandgap reduction from previously accepted alloy values.

  1. 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.

  2. Gate-tunable electronic transport in topological insulator Bi2Te3 thin films synthesized by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cao, Helin; Venkatasubramanian, Rama; Pierce, Jonathan; Wu, Tai-Lung; Tian, Jifa; Childres, Isaac; Chen, Yong

    2012-02-01

    Topological insulator is a new state of matter with a nominally insulating gap in the bulk and non-trivial metallic states on the surface. One of the proto-type topological insulator materials, Bi2Te3, can be synthesized in the form of high quality, wafer scale thin films by metal-organic chemical vapor deposition (MOCVD). Here we present an experimental study of Bi2Te3 thin films with thickness ranging from a few nm's to 1 μm synthesized by MOCVD on semi-insulating GaAs (001) substrates. Hall bar shaped devices using atomic layer deposition (ALD) high-k Al2O3 or HfO2 as gate dielectric have been fabricated. We have measured the magneto-transport (including both Rxx, 4-terminal longitudinal resistance, and Rxy, the Hall resistance) at various temperatures and gate voltages to probe the possible transport signatures of the topological surface states. We have also studied gate-tunable weak anti-localization in Rxx(B) for ultra-thin films.

  3. 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

  4. 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

    NASA Astrophysics Data System (ADS)

    Cipro, R.; Baron, T.; Martin, M.; Moeyaert, J.; David, S.; Gorbenko, V.; 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.

    2014-06-01

    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 SiO2 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.

  5. 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...

  6. 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...

  7. New Metal-Organic Chemistry of Barium, AN Aqueous Synthesis for Volatile Alkaline Earth Complexes, and Synthesis and Characterization of Thallium-Barium - Thin Films by Metal-Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Schulz, Douglas Lloyd

    The synthesis and characterization of six fluorine -free barium MOCVD (metal-organic chemical vapor deposition) precursors based upon encapsulating beta -ketoiminate-polyether ligation and having the general formula Ba(RCOCHC(NR^')R ^{''})_2 (R^' = ^{rm t}butyl, R^ ' = polyether, and R^{ ''} = methyl or ^{rm t}butyl) is reported. The complexes were prepared by a nonaqueous approach which employs BaH_2 and the corresponding beta-ketoimine. These complexes have been characterized by ^1H and ^{13}C NMR spectroscopy, elemental analysis, mass spectroscopy, cryoscopic molecular weight determination, thermogravimetric analysis, and single crystal X-ray structural analysis. These complexes serve as volatile barium MOCVD precursors. Thus, BaPbO _3 films have been grown using the aforementioned barium beta-ketoiminate complexes and Pb(dipivaloylmethanate)_2 as the respective barium and lead sources, and have been characterized by X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, and variable-temperature resistivity measurements. Investigation of thermolytic decomposition of the barium beta -ketoiminate complexes led to identification of 2-methyl -4-^{rm t}butylpyridine (17), pinacolone, and 2,2-dimethyl-5-imino-3-hexanone as the major organic thermolysis products of 11, 12, and 13. The MOCVD synthesis of Tl-Ba-Ca-Cu-O thin films on novel substrates, a growth method and film configuration which is potentially applicable toward device technologies, has been investigated. These films were prepared in three steps: first, deposition of Ba-Ca-Cu-O-(F) thin films by MOCVD; next, defluorination via water/oxygen anneal; and finally, thallination using volatile thallium oxides. Films were characterized by X-ray diffraction (theta/2 theta, omega, and phi scans), variable temperature magnetization, variable temperature conductivity, and scanning and transmission electron microscopy. Attempts at preparing Tl-Ba-Ca-Cu -O thin films on Pt resulted in the

  8. Tuning the Morphology and Activity of Electrospun Polystyrene/UiO-66-NH2 Metal-Organic Framework Composites to Enhance Chemical Warfare Agent Removal.

    PubMed

    Peterson, Gregory W; Lu, Annie X; Epps, Thomas H

    2017-09-20

    This work investigates the processing-structure-activity relationships that ultimately facilitate the enhanced performance of UiO-66-NH2 metal-organic frameworks (MOFs) in electrospun polystyrene (PS) fibers for chemical warfare agent detoxification. Key electrospinning processing parameters including solvent type (dimethylformamide [DMF]) vs DMF/tetrahydrofuran [THF]), PS weight fraction in solution, and MOF weight fraction relative to PS were varied to optimize MOF incorporation into the fibers and ultimately improve composite performance. It was found that composites spun from pure DMF generally resulted in MOF crystal deposition on the surface of the fibers, while composites spun from DMF/THF typically led to MOF crystal deposition within the fibers. For cases in which the MOF was incorporated on the periphery of the fibers, the composites generally demonstrated better gas uptake (e.g., nitrogen, chlorine) because of enhanced access to the MOF pores. Additionally, increasing both the polymer and MOF weight percentages in the electrospun solutions resulted in larger diameter fibers, with polymer concentration having a more pronounced effect on fiber size; however, these larger fibers were generally less efficient at gas separations. Overall, exploring the electrospinning parameter space resulted in composites that outperformed previously reported materials for the detoxification of the chemical warfare agent, soman. The data and strategies herein thus provide guiding principles applicable to the design of future systems for protection and separations as well as a wide range of environmental remediation applications.

  9. 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)

  10. 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)

  11. Effectiveness of metal-metal and metal-organic compound combinations against Plutella xylostella: implications for plant elemental defense.

    PubMed

    Jhee, Edward M; Boyd, Robert S; Eubanks, Micky D

    2006-02-01

    Plants that contain elevated foliar metal concentrations can be categorized as accumulators or, if the accumulation is extreme, hyperaccumulators. The defense hypothesis suggests that these plants may be defended against folivore attack, and recent research has indicated that metal concentrations at or below the accumulator range may be defensively effective. This experiment explored the toxicity of four metals hyper-accumulated by plants (Cd, Ni, Pb, and Zn) and asked if combinations of metals, or metals and organic chemicals, might broaden the defensive effectiveness of metals. Metals were used alone and in certain metal + metal (Zn plus Ni, Pb, or Cd) and metal + organic defensive chemical (Ni plus tannic acid, atropine, or nicotine) combinations. Artificial diet amended with these treatments was fed to larvae of the crucifer specialist herbivore Plutella xylostella. Combinations of metals and metals + organic chemicals significantly decreased survival and pupation rates, compared to single treatments, for at least some concentrations in every experiment. Effects of combinations were additive rather than synergistic or antagonistic. Because Zn enhanced the toxicity of other metals and Ni enhanced the toxicity of organic defensive chemicals, our findings suggest that the defensive effects of metals are more widespread among plants than previously believed. They also support the hypothesis that herbivore defense may have led to the evolution of metal hyper-accumulation by increasing the preexisting defensive effects of metals at accumulator levels in plants.

  12. Coalesced nanomorphology, in situ, and ex situ applications of self assembled Gallium droplets grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lohani, J.; Bag, R. K.; Padmavati, M. V. G.; Sapra, S.; Tyagi, R.

    2017-08-01

    Self assembled Gallium droplets are used as catalyst for epitaxial growth of III-V semiconductor nanowires. Understanding the effect of droplets' nanostructure on in situ catalysed growth of nanowires is essential. Evolution of MOCVD grown Ga droplets' self-assembled structure under different growth conditions, therefore, has been studied. The droplet nanomorphology has been explained on the basis of Ostwald-ripening based coalescence growth model. Two major morphologies of Ga droplets have been observed, namely, Valved and Spherical. Where a partial coalescence leads to the formation of valved nanostructures, complete coalescence of droplets give rise to spherical nanomorphology. Droplet morphology has been observed to have significant effect on in situ catalysed growth of GaAs nanowires by MOCVD. Twin and singular nanowires have been grown using valved and spherical Ga droplets, respectively, as catalyst. In addition, Gallium droplets having spherical nanomorphology with average diameter of around 80 nm and surface density of about 4 × 109/cm2 have been subjected to ex situ chemical oxidation to examine their chemical and morphological stability. The scanning electron microscopy of the oxidized sample has confirmed the retention of spherical morphology. The detailed theoretical depth analysis of the photoemission spectrum of the oxidized droplets has revealed the formation of interesting Ga-Ga2O3 core-shell nanostructure within a spherical droplet with a shell thickness of more than 3 nm.

  13. Transmission electron microscopy, photoluminescence, and capacitance spectroscopy on GaAs/Si grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Bremond, Georges E.; Said, Hicham; Guillot, Gerard; Meddeb, Jaafar; Pitaval, M.; Draidia, Nasser; Azoulay, Rozette

    1991-03-01

    We present a complete characterization study of GaAs/Si heteroepitaxial layers grown by metalorganic chemical vapor deposition (MOCVD) at 750C using the two-step method. High resolution transmission electron microscopy secondary ion mass spectroscopy deep level transient spectroscopy (DLTS) and photoluminescence (PL) spectroscopy have been performed to study the initial stage of growth misfit and threading dislocations Si diffusion and the deep levels in the GaAs layer. We describe the influence of GaAs/AlAs superlattices in the buffer layer on the decrease of dislocation density and on Si diffusion from the substrate and the existence of deep electron traps induced by the heteroepitaxy. DLTS reveals hole traps attributed to Si incorporation on the basis of PL measurements which could contribute to the reduction of the minority carrier lifetime. We also show an improvement of the layer quality by the use of selective epitaxy.

  14. Variations of biomarkers response in mussels Mytilus galloprovincialis to low, moderate and high concentrations of organic chemicals and metals.

    PubMed

    Perić, Lorena; Nerlović, Vedrana; Žurga, Paula; Žilić, Luka; Ramšak, Andreja

    2017-05-01

    The changes of acetylcholinesterase activity (AChE), metallothioneins content (MTs), catalase activity (CAT) and lipid peroxidation (LPO) were assessed after 4 days exposure of mussels Mytilus galloprovincialis to a wide range of sublethal concentrations of chlorpyrifos (CHP, 0.03-100 μg/L), benzo(a)pyrene (B(a)P, 0.01-100 μg/L), cadmium (Cd, 0.2-200 μg/L) and copper (Cu, 0.2-100 μg/L). The activity of AChE in the gills decreased after exposure to CHP and Cu, whereas no change of activity was detected after exposure to B(a)P and Cd. Both induction and decrease of MTs content in digestive gland occurred after exposure to CHP and B(a)P, while a marked increase was evident at highest exposure concentrations of Cd. The content of MTs progressively decreased of MTs with increasing concentration of Cu. CAT activity and LPO in the gills did not change after exposure to any of the chemicals. The results demonstrate different response profile in relation to the type of chemical compound, and highlight the potential implications for evaluation of biological effect of contaminants in marine environment. Furthermore, the AChE activity in the gills and MTs content in the digestive gland could be modulated by CHP and Cu at environmentally relevant concentrations indicating the potential risks of short-term transient mussels exposure that may occur due to run-off from land or accidental releases.

  15. Emerging Multifunctional Metal-Organic Framework Materials.

    PubMed

    Li, Bin; Wen, Hui-Min; Cui, Yuanjing; Zhou, Wei; Qian, Guodong; Chen, Banglin

    2016-10-01

    Metal-organic frameworks (MOFs), also known as coordination polymers, represent an interesting type of solid crystalline materials that can be straightforwardly self-assembled through the coordination of metal ions/clusters with organic linkers. Owing to the modular nature and mild conditions of MOF synthesis, the porosities of MOF materials can be systematically tuned by judicious selection of molecular building blocks, and a variety of functional sites/groups can be introduced into metal ions/clusters, organic linkers, or pore spaces through pre-designing or post-synthetic approaches. These unique advantages enable MOFs to be used as a highly versatile and tunable platform for exploring multifunctional MOF materials. Here, the bright potential of MOF materials as emerging multifunctional materials is highlighted in some of the most important applications for gas storage and separation, optical, electric and magnetic materials, chemical sensing, catalysis, and biomedicine.

  16. 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.

  17. "Clickable" metal-organic framework.

    PubMed

    Goto, Yuta; Sato, Hiroki; Shinkai, Seiji; Sada, Kazuki

    2008-11-05

    We demonstrated the metal-organic framework bearing the azide group in the organic linkers and in situ click reactions with some small alkynes. The XRPD patterns indicated that the click reaction proceeded without any decomposition of the original MOF network. Controlling the organic linkers and incorporation of the azide groups should provide the designer-made MOFs that have controlled molecular cavities with the desired steric dimensions and functionality.

  18. 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

    2014-12-05

    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.

  19. Control of metamorphic buffer structure and device performance of InxGa1-xAs epitaxial layers fabricated by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    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 (˜106 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 × 1012 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.

  20. 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.

  1. 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.

  2. As-grown deep-level defects in n-GaN grown by metal-organic chemical vapor deposition on freestanding GaN

    SciTech Connect

    Chen Shang; Ishikawa, Kenji; Hori, Masaru; Honda, Unhi; Shibata, Tatsunari; Matsumura, Toshiya; Tokuda, Yutaka; Ueda, Hiroyuki; Uesugi, Tsutomu; Kachi, Tetsu

    2012-09-01

    Traps of energy levels E{sub c}-0.26 and E{sub c}-0.61 eV have been identified as as-grown traps in n-GaN grown by metal-organic chemical vapor deposition by using deep level transient spectroscopy of the Schottky contacts fabricated by resistive evaporation. The additional traps of E{sub c}-0.13 and E{sub c}-0.65 eV have been observed in samples whose contacts are deposited by electron-beam evaporation. An increase in concentration of the E{sub c}-0.13 and E{sub c}-0.65 eV traps when approaching the interface between the contact and the GaN film supports our argument that these traps are induced by electron-beam irradiation. Conversely, the depth profiles of as-grown traps show different profiles between several samples with increased or uniform distribution in the near surface below 50 nm. Similar profiles are observed in GaN grown on a sapphire substrate. We conclude that the growth process causes these large concentrations of as-grown traps in the near-surface region. It is speculated that the finishing step in the growth process should be an essential issue in the investigation of the surface state of GaN.

  3. 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

    2015-01-02

    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.

  4. 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.

  5. 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.

  6. 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

    SciTech Connect

    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.

  7. Cyclodextrin-based metal-organic frameworks particles as efficient carriers for lansoprazole: Study of morphology and chemical composition of individual particles.

    PubMed

    Li, Xue; Guo, Tao; Lachmanski, Laurent; Manoli, Francesco; Menendez-Miranda, Mario; Manet, Ilse; Guo, Zhen; Wu, Li; Zhang, Jiwen; Gref, Ruxandra

    2017-10-15

    Cyclodextrin-based metal-organic frameworks (CD-MOFs) represent an environment-friendly and biocompatible class of MOFs drawing increasing attention in drug delivery. Lansoprazole (LPZ) is a proton-pump inhibitor used to reduce the production of acid in the stomach and recently identified as an antitubercular prodrug. Herein, LPZ loaded CD-MOFs were successfully synthesized upon the assembly with γ-CD in the presence of K(+) ions using an optimized co-crystallization method. They were characterized in terms of morphology, size and crystallinity, showing almost perfect cubic morphologies with monodispersed size distributions. The crystalline particles, loaded or not with LPZ, have mean diameters of around 6μm. The payloads reached 23.2±2.1% (wt) which corresponds to a molar ratio of 1:1 between LPZ and γ-CD. It was demonstrated that even after two years storage, the incorporated drug inside the CD-MOFs maintained its spectroscopic characteristics. Molecular modelling provided a deeper insight into the interaction between the LPZ and CD-MOFs. Raman spectra of individual particles were recorded, confirming the formation of inclusion complexes within the tridimensional CD-MOF structures. Of note, it was found that each individual particle had the same chemical composition. The LPZ-loaded particles had remarkable homogeneity in terms of both drug loading and size. These results pave the way towards the use of CD-MOFs for drug delivery purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Magnetic porous carbon derived from Co-doped metal-organic frameworks for the magnetic solid-phase extraction of endocrine disrupting chemicals.

    PubMed

    Hao, Lin; Wei, Jiayi; Zheng, Ruixue; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2017-08-10

    Metal-organic frameworks-5 (MOF-5) was explored as a template to prepare porous carbon due to its high surface area, large pore volume, and permanent nanoscale porosity. Magnetic porous carbon, Co@MOF-5-C, was fabricated by the one-step direct carbonization of Co-doped MOF-5. After carbonization, the magnetic cobalt nanoparticles are well dispersed in the porous carbon matrix, and Co@MOF-5-C displays strong magnetism (with the saturation magnetization intensity of 70.17emu/g), high-specific surface area, and large pore volume. To evaluate its extraction performance, the Co@MOF-5-C was applied as an adsorbent for the magnetic solid-phase extraction of endocrine disrupting chemicals, followed by their analysis with high-performance liquid chromatography. The developed method exhibits a good linear response in the range of 0.5-100 ng/mL for pond water and 1.0-100 ng/mL for juice samples. The limits of detection (S/N = 3) for the analytes were in the range of 0.1-0.2 ng/mL. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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 Structural Evolution of (Gd, Y)Ba2Cu3Ox Tapes With Zr Addition Made by Metal Organic Chemical Vapor Deposition

    SciTech Connect

    Lei, CH; Galstyan, E; Chen, YM; Shi, T; Liu, YH; Khatri, N; Liu, JF; Xiong, XM; Majkic, G; Selvamanickam, V

    2013-06-01

    Structural analysis of (Gd, Y) Ba2Cu3Ox tapes with Zr addition made by metal organic chemical vapor deposition has been conducted with transmission electron microscopy and X-ray diffraction. Zr content in the films was varied from 0 to 25% in the precursor. In all Zr-doped films, self-assembled nanocolumnar structures of BaZrO3 (BZO) were observed along the c-axis. The amount of BaZrO3 was found to increase steadily with Zr content. Additionally, planar BZO plates were found on the (001) plane of (Gd, Y) Ba2Cu3Ox film. The size and thickness of BZO plates were seen to increase with Zr doping level. Rare-earth copper oxide phases were observed to begin to emerge in the 20% Zr-doped film. Cross-sectional study of the interface between (Gd, Y)Ba2Cu3Ox and LaMnO3 cap layer revealed a thin discrete BZO layer on the LaMnO3 in the 20% Zr doped film.

  11. Arsenic antisite defects in p-GaAs grown by metal-organic chemical-vapor deposition and the EL2 defect

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    Epitaxial layers of p-GaAs grown on p+-GaAs substrates by low-pressure metal organic chemical vapor deposition have been investigated using deep level transient spectroscopy (DLTS). One dominant peak and other relatively small peak, corresponding to deep levels at Ev+0.55 eV and Ev+0.96 (low field energies), respectively, have been observed in the lower half of the band gap. Investigation with double-correlation DLTS reveals that the measured thermal emission rate of holes from the dominant level is strongly dependent on the junction electric field. Detailed data on this field enhancement have been analyzed in terms of different available theoretical models. The hole capture cross section for the dominant deep level has been found to be temperature dependent. Detailed data on the temperature dependence of the hole capture cross section have been interpreted in terms of the multiphonon carrier capture mechanism, yielding a capture barrier of 0.11 eV. In order to get deeper insight into the nature and origin of these inadvertent (intrinsic) defects, thermal annealing behavior of these levels has also been studied. Analyses of field dependence and hole capture data, in combination with the annealing study, suggest that the dominant level is associated with an arsenic-antisite (AsGa) defect. Probable association of this dominant level with the doubly charged state of the well-known EL2 defect has been discussed in detail.

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

    SciTech Connect

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

    2016-04-15

    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]{sub sapp} direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]{sub 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.

  13. 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.

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

    SciTech Connect

    Xue, JunShuai Zhang, JinCheng; Hao, Yue

    2016-01-04

    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 cm{sup 2}/V s along with a sheet carrier density of 1.88 × 10{sup 13 }cm{sup −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.

  15. Phosphor-free white-light emitters using in-situ GaN nanostructures grown by metal organic chemical vapor deposition

    PubMed Central

    Min, Daehong; Park, Donghwy; Jang, Jongjin; Lee, Kyuseung; Nam, Okhyun

    2015-01-01

    Realization of phosphor-free white-light emitters is becoming an important milestone on the road to achieve high quality and reliability in high-power white-light-emitting diodes (LEDs). However, most of reported methods have not been applied to practical use because of their difficulties and complexity. In this study we demonstrated a novel and practical growth method for phosphor-free white-light emitters without any external processing, using only in-situ high-density GaN nanostructures that were formed by overgrowth on a silicon nitride (SiNx) interlayer deposited by metal organic chemical vapor deposition. The nano-sized facets produced variations in the InGaN thickness and the indium concentration when an InGaN/GaN double heterostructure was monolithically grown on them, leading to white-color light emission. It is important to note that the in-situ SiNx interlayer not only facilitated the GaN nano-facet structure, but also blocked the propagation of dislocations. PMID:26626890

  16. Low-temperature growth and orientational control in RuO{sub 2} thin films by metal-organic chemical vapor deposition

    SciTech Connect

    Bai, G.R.; Wang, A.; Foster, C.M.; Vetrone, J.; Patel, J.; Wu, X.

    1996-08-01

    For growth temperatures in the range of 275 C to 425 C, highly conductive RuO{sub 2} thin films with either (110)- or (101)-textured orientations have been grown by metal-organic chemical vapor deposition (MOCVD) on both SiO{sub 2}/Si(001) and Pt/Ti/SiO{sub 2}/Si(001) substrates. Both the growth temperature and growth rate were used to control the type and degree of orientational texture of the RuO{sub 2} films. In the upper part of this growth temperature range ({approximately} 350 C) and at a low growth rate (< 30 {angstrom}/min.), the RuO{sub 2} films favored a (110)-textured. In contrast, at the lower part of this growth temperature range ({approximately} 300 C) and at a high growth rate (> 30 {angstrom}/min.), the RuO{sub 2} films favored a (101)-textured. In contrast, a higher growth temperatures (> 425 C) always produced randomly-oriented polycrystalline films. For either of these low-temperature growth processes, the films produced were crack-free, well-adhered to the substrates, and had smooth, specular surfaces. Atomic force microscopy showed that the films had a dense microstructure with an average grain size of 50--80 nm and a rms. surface roughness of {approximately} 3--10 nm. Four-probe electrical transport measurements showed that the films were highly conductive with resistivities of 34--40 {micro}{Omega}-cm ({at} 25 C).

  17. 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.

  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. 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.

  20. Electrical properties of Ta-doped SnO2 thin films prepared by the metal-organic chemical-vapor deposition method

    NASA Astrophysics Data System (ADS)

    Lee, Sang woo; Kim, Young-Woon; Chen, Haydn

    2001-01-01

    Undoped and Ta-doped SnO2 (Sn1-xTaxO2) thin films were prepared on Corning 7059 glass substrates by the metal-organic chemical-vapor deposition method. The relative amount of Ta, CTa=XTa/(XTa+XSn), varied from 0 to 7.13 at. %. For the five compositions studied, the lowest resistivity at room temperature was 2.01×10-4 Ω cm at CTa=3.75% with charge carrier density and mobility of 1.27×1021cm-3 and 24.5 cm2/V s, respectively. In microstructural investigation, 3.75% Ta-doped film maintains a growth pattern of initial stage growth while 7.13% Ta-doped film has a high population of small grains at the interface, which results in large grains through competitive growth. The resistivity of the undoped film was 0.17 Ω cm with charge carrier density and mobility of 1.31×1018cm-3 and 28.1 cm2/V s obtained from Hall measurement. This study suggests that Ta is an excellent n-type dopant in SnO2.

  1. 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.

  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.

  3. Growth of self-aligned Ga2O3 nanostructures deposited on r-plane sapphire by using metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, Seoyoung; Lee, Seunghyun; Jo, Hyunjin; Bae, Sangki; Kim, Kimin; Song, Jiho; Cho, Younghwan; Kim, Jinsung; Ahn, Hyungsoo; Yang, Min

    2016-11-01

    The growth temperature dependence of self-aligned β-Ga2O3 nanostructures grown on an r-plane sapphire substrate by using metal-organic chemical vapor deposition is reported. Periodic self-alignment of the β-Ga2O3 grains was observed for certain growth temperature windows and the grain size of the β-Ga2O3 structure varied in response to the growth temperature. At temperatures under 800 °C, self-alignment of the β-Ga2O3 structures was not observed. The self-alignment tendency began to appear at 900 °C, and obvious self-alignment characteristics in a certain direction were observed at approximately 950 °C. However, as the growth temperature was increased to more than 900 °C the growth mode of the β-Ga2O3 structure gradually deviated from the self-alignment mode, finally exhibiting a two-dimensional thin film mode at 1100 °C. We surmise that the driving force of β-Ga2O3 grain self-alignment is the surface-potential difference between the planar and the step regions of the substrate on an atomic scale, which originates from misorientation occurring during the r-plane sapphire cutting process.

  4. The growth and characterization of GaInAsSb and AlGaAsSb on GaSb by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Biefeld, R. M.; Cederberg, J. G.; Peake, G. M.; Kurtz, S. R.

    2001-05-01

    The growth conditions for GaInAsSb and AlGaAsSb using metal-organic chemical vapor deposition in an high speed rotating disk reactor are described. Trimethylindium, triethylgallium, arsine, and trimethylantimony were used as precursors for the growth of GaInAsSb. Triethylgallium, ethyldimethylamine alane, triethylantimony, and arsine were the precursors used for the growth of AlGaAsSb. These materials were doped both n- and p-type using a mixture of diethyltellurium and diethylzinc as sources. An optimum growth temperature of 520°C was determined for the growth of GaInAsSb. Growth at this temperature yielded a root-mean-square (rms) surface roughness of 0.142 nm. AlGaAsSb could be grown over the range of 500-600°C with somewhat rougher surfaces (rms>0.7 nm). The photoluminescence was found to correlate with surface roughness, increasing with smoother surfaces. AlGaAsSb mesa isolated diodes were prepared and characterized. These diodes showed good current-voltage characteristics with breakdown voltages greater than -6 V.

  5. 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.

  6. Self-Catalyzed Growth of Vertical GaSb Nanowires on InAs Stems by Metal-Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Ji, Xianghai; Yang, Xiaoguang; Yang, Tao

    2017-06-01

    We report the first self-catalyzed growth of high-quality GaSb nanowires on InAs stems using metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates. To achieve the growth of vertical InAs/GaSb heterostructure nanowires, the two-step flow rates of the trimethylgallium (TMGa) and trimethylantimony (TMSb) are used. We first use relatively low TMGa and TMSb flow rates to preserve the Ga droplets on the thin InAs stems. Then, the flow rates of TMGa and TMSb are increased to enhance the axial growth rate. Because of the slower radial growth rate of GaSb at higher growth temperature, GaSb nanowires grown at 500 °C exhibit larger diameters than those grown at 520 °C. However, with respect to the axial growth, due to the Gibbs-Thomson effect and the reduction in the droplet supersaturation with increasing growth temperature, GaSb nanowires grown at 500 °C are longer than those grown at 520 °C. Detailed transmission electron microscopy (TEM) analyses reveal that the GaSb nanowires have a perfect zinc-blende (ZB) crystal structure. The growth method presented here may be suitable for other antimonide nanowire growth, and the axial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics.

  7. Preparation of MgO Films by Atmospheric Metal-Organic Chemical Vapor Deposition as a Protective Layer in AC Plasma Display Panels

    NASA Astrophysics Data System (ADS)

    Okada, Takeru; Komaki, Toshihiro

    2008-03-01

    MgO thin films were fabricated by atmospheric metal-organic chemical vapor deposition as a protective layer of AC plasma display panels. The deposition conditions and the discharge properties of the films were evaluated. Among four Mg precursors tested, Mg(C11H19O2)2 [Mg(DPM)2] was the most suitable source material in film growth properties and discharge characteristics. The deposition rate increased with increasing vaporizing temperature and substrate temperature, and the maximum deposition rate reached 3.3 nm/s (5.1 min/µm). The films had (200) main orientations, and highly crystalline square-pyramid structures were observed in high deposition-rate films. Under the high-rate deposition condition, the firing voltage and the discharge delay of the film were comparable to those of conventional vacuum-evaporated MgO film. The discharge delay was shorter when the crystal size was larger, the work function was smaller, and the concentrations of impurities were lower.

  8. Heavy metal pollutants and chemical ecology: exploring new frontiers.

    PubMed

    Boyd, Robert S

    2010-01-01

    Heavy metals are an important class of pollutants with both lethal and sublethal effects on organisms. The latter are receiving increased attention, as these may have harmful ecological outcomes. For example, recent explorations of heavy metals in freshwater habitats reveal that they can modify chemical communication between individuals, resulting in "info-disruption" that can impact ecological relationships within and between species. Info-disruption can affect animal behavior and social structure, which in turn can modify both intraspecies and interspecies interactions. In terrestrial habitats, info-disruption by metals is not well studied, but recent demonstrations of chemical signaling between plants via both roots and volatile organic molecules provide potential opportunities for info-disruption. Metals in terrestrial habitats also can form elemental plant defenses, in which they can defend a plant against natural enemies. For example, hyperaccumulation of metals by terrestrial plants has been shown to provide defensive benefits, although in almost all known cases the metals are not anthropogenic pollutants but are naturally present in soils inhabited by these plants. Info-disruption among microbes is another arena in which metal pollutants may have ecological effects, as recent discoveries regarding quorum sensing in bacteria provide an avenue for metals to affect interactions among bacteria or between bacteria and other organisms. Metal pollutants also may influence immune responses of organisms, and thus affect pathogen/host relationships. Immunomodulation (modification of immune system function) has been tied to some metal pollutants, although specific metals may boost or reduce immune system function depending on dose. Finally, the study of metal pollutants is complicated by their frequent occurrence as mixtures, either with other metals or with organic pollutants. Most studies of metal pollutants focus on single metals and therefore oversimplify complex

  9. 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.

  10. 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.

  11. 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

  12. New rht-Type Metal-Organic Frameworks Decorated with Acylamide Groups for Efficient Carbon Dioxide Capture and Chemical Fixation from Raw Power Plant Flue Gas.

    PubMed

    Guo, Xiangyang; Zhou, Zhen; Chen, Cong; Bai, Junfeng; He, Cheng; Duan, Chunying

    2016-11-23

    The combination of carbon dioxide capture and chemical fixation in a one-pot process is attractive for both chemists and governments. The cycloaddition of carbon dioxide with epoxides to produce cyclic carbonates is an atomic economical reaction without any side products. By incorporating acylamide to enhance the binding affinity toward CO2, new rht-type metal-organic frameworks (MOFs) with (3, 28) and (3, 24) connected units were constructed. Zn-NTTA with two types of dinuclear paddlewheel building blocks-{Zn2(OOC(-))4} and {Zn2(OOC(-))3}. The high uptake of CO2 (115.6 cm(3)·g(-1)) and selectivity over N2 (30:1) at 273 K indicated that these MOFs are excellent candidates for postcombustion CO2 isolation and capture. The MOFs feature high catalytic activity, rapid dynamics of transformation and excellent stability with turnover number (TON) values up to 110 000 per paddlewheel unit after 5 × 6 rounds of recyclability, demonstrating that they are promising heterogeneous catalysts for CO2 cyclo-addition to value-added cyclic carbonates. The cycloaddition of epoxides with wet gases demonstrated that the catalyst activity was not affected by moisture, and the indices of the PXRD patterns of the bulk samples filtered from the catalytic reaction revealed that the crystallinities were maintained. The combination of the selective capture and catalytic transformation in one-pot enables the use of a negative-cost feedstock-raw power plant flue gas without any separation and purification-revealing the broad prospects of such MOFs for practical CO2 fixation in industry.

  13. 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.

  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. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Nanostructured surface morphology of ZnO grown on p-type GaN and Si by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hung, S. C.; Huang, P. J.; Chan, C. E.; Uen, W. Y.; Ren, F.; Pearton, S. J.; Yang, T. N.; Chiang, C. C.; Lan, S. M.; Chi, G. C.

    2008-12-01

    The surface morphology of ZnO grown on p-GaN templates and p-Si (1 1 1) substrates at various temperatures by metal organic chemical vapor deposition (MOCVD) in a vertical reactor at atmospheric pressure is reported. A low temperature ZnO buffer was deposited initially at 200 °C for 15 min as a nucleation layer. Epitaxial ZnO was grown at 500 °C, 550 °C, 600 °C for 40 min, respectively. Uniformly distributed and well-aligned ZnO nanorods with diameter in the range 80-120 nm and length ˜0.7 μm were observed for deposition on p-GaN template. By contrast, the morphology of ZnO epilayers grown on p-Si (1 1 1) transitioned from 2D to 3D with increasing growth temperature. X-ray diffraction (XRD) spectra showed all the ZnO epilayers had the hexagonal wurtzite structure but different preferred orientation. PL spectra showed only free-exciton emission at 378 nm (˜3.28 eV) with a full width at half maximum of 13 nm without defect-related green emission in the epitaxial ZnO grown at 550 °C and 600 °C. The epitaxial ZnO layers grown on p-GaN and p-Si at the same temperature have similar PL spectra. The PL measurement also exhibits strong exciton-related emission without defect peak, which showed that the ZnO nanostructures grown at 550 °C and 600 °C have good optical properties with excellent crystal quality.

  16. 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.

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

    SciTech Connect

    Wu, Dan; Tang, Xiaohong E-mail: wangk@sustc.edu.cn; Li, Xianqiang; Wang, Kai E-mail: wangk@sustc.edu.cn; Olivier, Aurelien

    2016-03-07

    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.

  18. 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.

  19. Metal reduction at bulk chemical filtration

    NASA Astrophysics Data System (ADS)

    Umeda, Toru; Daikoku, Shusaku; Tsuzuki, Shuichi; Murakami, Tetsuya

    2017-03-01

    OK73 thinner and cyclohexanone, both of which were spiked with metals were passed through Nylon 6,6 filter, varying flow rate, which include the conditions of both point-of-use and bulk filtrations. The influent and effluent metal concentrations were measured using ICP-MS for metal removal efficiency of the filtration. As a result, removal efficiency for some metals descended depending on the flow rate, while others maintained. Slower flow rate is recommended to maintain low metal concentration in bulk filtration based on the result. Metals in cyclohexanone were reduced at higher efficiency than in OK73 thinner, agrees with a metal removal model of hydrophilic adsorbent in organic solvent, evidenced in our previous paper. Further, metal reduction on 300 mm φ Si wafer after coating organic solvents with Nylon 6,6 filtration was evidenced with TREX analysis.

  20. 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.

  1. 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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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.

  3. 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

    2016-08-30

    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.

  4. 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.

  5. 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

    2008-02-07

    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.

  6. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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

    PubMed Central

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

    2014-01-01

    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. PMID:25135307

  15. 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.

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

    SciTech Connect

    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 {alpha}-induced defects H{alpha}1, H{alpha}2, and H{alpha}3 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 {approx}150 K and the other at {approx}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 {sigma}({infinity}) = 2.3 x 10{sup -14} cm{sup 2}. The results of irradiation and isochronal thermal annealing study, in combination with the theoretical

  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. Consequences of cavity size and chemical environment on the adsorption properties of isoreticular metal-organic frameworks: an inverse gas chromatography study.

    PubMed

    Gutiérrez, Inés; Díaz, Eva; Vega, Aurelio; Ordóñez, Salvador

    2013-01-25

    The role of the structure of three isoreticular metal-organic frameworks (IRMOFs) on their adsorption behavior has been studied in this work, selecting different kinds of volatile organic compounds (VOCs) as adsorbates (alkanes, alkenes, cycloalkanes, aromatics and chlorinated). For this purpose, three samples (IRMOF-1, IRMOF-8 and IRMOF-10) with cubic structure and without functionalities on the organic linkers were synthesized. Adsorption capacities at infinite dilution were derived from the adsorption isotherms, whereas thermodynamic properties have been determined from chromatographic retention volume. The capacity and the strength of adsorption were strongly influenced by the adsorbate size. This effect is especially relevant for n-alkanes adsorption, indicating the key role of the cavity size on this phenomenon, and hence the importance of the IRMOF structural properties. A different behavior has been observed for the polar compounds, where an enhancement on the specificity of the adsorption with the π-electron rich regions was observed. This fact suggests the specific interaction of these molecules with the organic linkers of the IRMOFs.

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

    SciTech Connect

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

    2010-11-01

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

  20. Gas adsorption on metal-organic frameworks

    DOEpatents

    Willis, Richard R [Cary, IL; Low, John J. , Faheem, Syed A.; Benin, Annabelle I [Oak Forest, IL; Snurr, Randall Q [Evanston, IL; Yazaydin, Ahmet Ozgur [Evanston, IL

    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. Quantum chemical treatments of metal clusters.

    PubMed

    Weigend, Florian; Ahlrichs, Reinhart

    2010-03-28

    This work focuses on finding and rationalizing the building principles of clusters with approximately 300 atoms of different types of metals: main group elements (Al, Sn), alkaline earth metals (Mg), transition metals (Pd) and clusters consisting of two different elements (Ir and Pt). Two tools are inevitable for this purpose: (i) quantum chemical methods that are able to treat a given cluster with both sufficient accuracy and efficiency and (ii) algorithms that are able to systematically scan the (3n-6)-dimensional potential surface of an n-atomic cluster for promising isomers. Currently, the only quantum chemical method that can be applied to metal clusters is density functional theory (DFT). Other methods either do not account for the multi-reference character of metal clusters or are too expensive and thus can be applied only to clusters of very few atoms, which usually is not sufficient for studying the building principles. The accuracy of DFT is not known a priori, but extrapolations to bulk values from calculated series of data show satisfying agreement with experimental data. For scans of the potential surface, simulated annealing techniques or genetic algorithms were used for the smaller clusters (approx. 20-30 atoms), and for the larger clusters considerations were restricted to selected packings and shapes. For the mixed-metallic clusters, perturbation theory turned out to be efficient and successful for finding the most promising distributions of the two atom types at the different sites.

  2. Metal Organic Framework Research: High Throughput Discovery of Robust Metal Organic Framework for CO2 Capture

    SciTech Connect

    2010-08-01

    IMPACCT Project: LBNL is developing a method for identifying the best metal organic frameworks for use in capturing CO2 from the flue gas of coal-fired power plants. Metal organic frameworks are porous, crystalline compounds that, based on their chemical structure, vary considerably in terms of their capacity to grab hold of passing CO2 molecules and their ability to withstand the harsh conditions found in the gas exhaust of coal-fired power plants. Owing primarily to their high tunability, metal organic frameworks can have an incredibly wide range of different chemical and physical properties, so identifying the best to use for CO2 capture and storage can be a difficult task. LBNL uses high-throughput instrumentation to analyze nearly 100 materials at a time, screening them for the characteristics that optimize their ability to selectively adsorb CO2 from coal exhaust. Their work will identify the most promising frameworks and accelerate their large-scale commercial development to benefit further research into reducing the cost of CO2 capture and storage.

  3. 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.

  4. 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.

  5. 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.

  6. Color Coding Organic Chemicals for Inventory Control.

    ERIC Educational Resources Information Center

    Wystrach, V. P.; George, Babu

    1985-01-01

    Describes a system in which organic chemicals are recoded for inventory control and reshelving purposes. The system works well in undergraduate organic chemistry or biology laboratories but can be expanded to handle a larger and more complicated inventory. (JN)

  7. Color Coding Organic Chemicals for Inventory Control.

    ERIC Educational Resources Information Center

    Wystrach, V. P.; George, Babu

    1985-01-01

    Describes a system in which organic chemicals are recoded for inventory control and reshelving purposes. The system works well in undergraduate organic chemistry or biology laboratories but can be expanded to handle a larger and more complicated inventory. (JN)

  8. (111)-oriented Pb(Zr ,Ti)O3 films deposited on SrRuO3/Pt electrodes: Reproducible preparation by metal organic chemical vapor deposition, top electrode influence, and reliability

    NASA Astrophysics Data System (ADS)

    Menou, Nicolas; Funakubo, Hiroshi

    2007-12-01

    (111)-textured Pb(Zr0.4Ti0.6)O3 films (thickness of ˜120nm) were deposited on (111)-oriented SrRuO3 bottom electrodes by pulse metal organic chemical vapor deposition (MOCVD). PZT single phase was evidenced over a large range of Pb precursor input rate into the MOCVD chamber. In this process window, the good control of the (111) texture of PZT films was confirmed. It is shown that the control of both the composition and orientation of PZT films leads to reproducible electric properties (Pr, Vc, resistance to fatigue) across the process window. Furthermore, the impact of the top electrode chemical nature, elaboration process, and annealing process upon the electric properties was studied systematically.

  9. Multiaxis sensing using metal organic frameworks

    DOEpatents

    Talin, Albert Alec; Allendorf, Mark D.; Leonard, Francois; Stavila, Vitalie

    2017-01-17

    A sensor device including a sensor substrate; and a thin film comprising a porous metal organic framework (MOF) on the substrate that presents more than one transduction mechanism when exposed to an analyte. A method including exposing a porous metal organic framework (MOF) on a substrate to an analyte; and identifying more than one transduction mechanism in response to the exposure to the analyte.

  10. Electrically Conductive Porous Metal-Organic Frameworks.

    PubMed

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

    2016-03-07

    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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Stimulus-responsive metal-organic frameworks.

    PubMed

    Nagarkar, Sanjog S; Desai, Aamod V; Ghosh, Sujit K

    2014-09-01

    Materials that can recognize the changes in their local environment and respond by altering their inherent physical and/or chemical properties are strong candidates for future "smart" technology materials. Metal-organic frameworks (MOFs) have attracted a great deal of attention in recent years owing to their designable architecture, host-guest chemistry, and softness as porous materials. Despite this fact, studies on the tuning of the properties of MOFs by external stimuli are still rare. This review highlights the recent developments in the field of stimulus-responsive MOFs or so-called smart MOFs. In particular, the various stimuli used and the utility of stimulus-responsive smart MOFs for various applications such as gas storage and separation, sensing, clean energy, catalysis, molecular motors, and biomedical applications are highlighted by using representative examples. Future directions in the developments of stimulus-responsive smart MOFs and their applications are proposed from a personal perspective.

  12. Nanoporous carbohydrate metal-organic frameworks.

    PubMed

    Forgan, Ross S; Smaldone, Ronald A; Gassensmith, Jeremiah J; Furukawa, Hiroyasu; Cordes, David B; Li, Qiaowei; Wilmer, Christopher E; Botros, Youssry Y; Snurr, Randall Q; Slawin, Alexandra M Z; Stoddart, J Fraser

    2012-01-11

    The binding of alkali and alkaline earth metal cations by macrocyclic and diazamacrobicyclic polyethers, composed of ordered arrays of hard oxygen (and nitrogen) donor atoms, underpinned the development of host-guest supramolecular chemistry in the 1970s and 1980s. The arrangement of -OCCO- and -OCCN- chelating units in these preorganized receptors, including, but not limited to, crown ethers and cryptands, is responsible for the very high binding constants observed for their complexes with Group IA and IIA cations. The cyclodextrins (CDs), cyclic oligosaccharides derived microbiologically from starch, also display this -OCCO- bidentate motif on both their primary and secondary faces. The self-assembly, in aqueous alcohol, of infinite networks of extended structures, which have been termed CD-MOFs, wherein γ-cyclodextrin (γ-CD) is linked by coordination to Group IA and IIA metal cations to form metal-organic frameworks (MOFs), is reported. CD-MOF-1 and CD-MOF-2, prepared on the gram-scale from KOH and RbOH, respectively, form body-centered cubic arrangements of (γ-CD)(6) cubes linked by eight-coordinate alkali metal cations. These cubic CD-MOFs are (i) stable to the removal of solvents, (ii) permanently porous, with surface areas of ~1200 m(2) g(-1), and (iii) capable of storing gases and small molecules within their pores. The fact that the -OCCO- moieties of γ-CD are not prearranged in a manner conducive to encapsulating single metal cations has led to our isolating other infinite frameworks, with different topologies, from salts of Na(+), Cs(+), and Sr(2+). This lack of preorganization is expressed emphatically in the case of Cs(+), where two polymorphs assemble under identical conditions. CD-MOF-3 has the cubic topology observed for CD-MOFs 1 and 2, while CD-MOF-4 displays a channel structure wherein γ-CD tori are perfectly stacked in one dimension in a manner reminiscent of the structures of some γ-CD solvates, but with added crystal stability imparted

  13. 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.

  14. 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.

  15. 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. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. 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.

  17. 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.

  18. 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.

  19. Metal-loaded organic scintillators for neutrino physics

    SciTech Connect

    Buck, Christian; Yeh, Minfang

    2016-08-03

    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. Lastly, we review applications of metal loaded scintillators in neutrino experiments and compare the performance as well as the prospects of different scintillator types.

  20. Metal-loaded organic scintillators for neutrino physics

    DOE PAGES

    Buck, Christian; Yeh, Minfang

    2016-08-03

    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 bemore » used under stable conditions for many years even in ton scale experiments. Lastly, we review applications of metal loaded scintillators in neutrino experiments and compare the performance as well as the prospects of different scintillator types.« less

  1. Metal-loaded organic scintillators for neutrino physics

    SciTech Connect

    Buck, Christian; Yeh, Minfang

    2016-08-03

    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. Lastly, we review applications of metal loaded scintillators in neutrino experiments and compare the performance as well as the prospects of different scintillator types.

  2. 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.

  3. 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

  4. Exploring biologically relevant chemical space with metal complexes.

    PubMed

    Meggers, Eric

    2007-06-01

    Altering biological processes with small synthetic molecules is a general approach for the design of drugs and molecular probes. Medicinal chemistry and chemical biology are focused predominately on the design of organic molecules, whereas inorganic compounds find applications mainly for their reactivity (e.g. cisplatin as a DNA-reactive therapeutic) or imaging properties (e.g. gadolinium complexes as MRI diagnostics). In such inorganic pharmaceuticals or probes, coordination chemistry in the biological environment or at the target site lies at the heart of their modes of action. However, past and very recent results suggest that it is also worth exploring a different aspect of metal complexes: their ability to form structures with unique and defined shapes for the design of 'organic-like' small-molecule probes and drugs. In such metal-organic compounds, the metal has the main purpose to organize the organic ligands in three-dimensional space. It is likely that such an approach will complement the molecular diversity of organic chemistry in the quest for the discovery of compounds with superior biological activities.

  5. Direct photocatalysis of supported metal nanostructures for organic synthesis

    NASA Astrophysics Data System (ADS)

    Wu, Xiayan; Jaatinen, Esa; Sarina, Sarina; Zhu, Huai Yong

    2017-07-01

    Many organic synthesis systems use thermal catalysis to achieve higher product efficiency, and it is of interest to drive reactions by light irradiation at moderate reaction conditions. Other than semiconductors, recent reports have shown that metal nanostructures can be used as direct photocatalysts to drive chemical reactions. In this review, we summarize recent progress in direct photocatalysis in organic synthesis using plasmonic and non-plasmonic metal nanostructures. It starts with a comprehensive introduction to surface plasmons and the role of interband transitions in non-plasmonic metal nanostructures. The application of metal nanostructures in organic synthesis is systematically reviewed, followed by the reaction mechanisms; the role of light-excited energetic electrons, enhanced electromagnetic fields and the photothermal effect are detailed. The influence of light intensity and wavelength is discussed, as well as the critical parameters of photocatalyst design. Finally, the outlook and future opportunities of this new exciting field will be discussed.

  6. Ligand design for functional metal-organic frameworks.

    PubMed

    Paz, Filipe A Almeida; Klinowski, Jacek; Vilela, Sérgio M F; Tomé, João P C; Cavaleiro, José A S; Rocha, João

    2012-02-07

    Metal-organic frameworks (MOFs), also known as coordination polymers, are formed by the self-assembly of metallic centres and bridging organic linkers. In this critical review, we review the key advances in the field and discuss the relationship between the nature and structure of specifically designed organic linkers and the properties of the products. Practical examples demonstrate that the physical and chemical properties of the linkers play a decisive role in the properties of novel functional MOFs. We focus on target materials suitable for the storage of hydrogen and methane, sequestration of carbon dioxide, gas separation, heterogeneous catalysis and as magnetic and photoluminescent materials capable of both metal- and ligand-centred emission, ion exchangers and molecular sieves. The advantages of highly active discrete complexes as metal-bearing ligands in the construction of MOFs are also briefly reviewed (128 references). This journal is © The Royal Society of Chemistry 2012

  7. 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.

    2015-01-01

    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.

  8. Chemical and biological assessment of metal organic frameworks (MOFs) in pulmonary cells and in an acute in vivo model: relevance to pulmonary arterial hypertension therapy.

    PubMed

    Mohamed, Nura A; Davies, Robert P; Lickiss, Paul D; Ahmetaj-Shala, Blerina; Reed, Daniel M; Gashaw, Hime H; Saleem, Hira; Freeman, Gemma R; George, Peter M; Wort, Stephen J; Morales-Cano, Daniel; Barreira, Bianca; Tetley, Teresa D; Chester, Adrian H; Yacoub, Magdi H; Kirkby, Nicholas S; Moreno, Laura; Mitchell, Jane A

    2017-01-01

    Pulmonary arterial hypertension (PAH) is a progressive and debilitating condition. Despite promoting vasodilation, current drugs have a therapeutic window within which they are limited by systemic side effects. Nanomedicine uses nanoparticles to improve drug delivery and/or reduce side effects. We hypothesize that this approach could be used to deliver PAH drugs avoiding the systemic circulation. Here we report the use of iron metal organic framework (MOF) MIL-89 and PEGylated MIL-89 (MIL-89 PEG) as suitable carriers for PAH drugs. We assessed their effects on viability and inflammatory responses in a wide range of lung cells including endothelial cells grown from blood of donors with/without PAH. Both MOFs conformed to the predicted structures with MIL-89 PEG being more stable at room temperature. At concentrations up to 10 or 30 µg/mL, toxicity was only seen in pulmonary artery smooth muscle cells where both MOFs reduced cell viability and CXCL8 release. In endothelial cells from both control donors and PAH patients, both preparations inhibited the release of CXCL8 and endothelin-1 and in macrophages inhibited inducible nitric oxide synthase activity. Finally, MIL-89 was well-tolerated and accumulated in the rat lungs when given in vivo. Thus, the prototypes MIL-89 and MIL-89 PEG with core capacity suitable to accommodate PAH drugs are relatively non-toxic and may have the added advantage of being anti-inflammatory and reducing the release of endothelin-1. These data are consistent with the idea that these materials may not only be useful as drug carriers in PAH but also offer some therapeutic benefit in their own right.

  9. 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...

  10. 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...

  11. Melt-Quenched Hybrid Glasses from Metal-Organic Frameworks.

    PubMed

    Tao, Haizheng; Bennett, Thomas D; Yue, Yuanzheng

    2017-05-01

    While glasses formed by quenching the molten states of inorganic non-metallic, organic, and metallic species are known, those containing both inorganic and organic moieties are far less prevalent. Network materials consisting of inorganic nodes linked by organic ligands do however exist in the crystalline or amorphous domain. This large family of open framework compounds, called metal-organic frameworks (MOFs) or coordination polymers, has been investigated intensively in the past two decades for a variety of applications, almost all of which stem from their high internal surface areas and chemical versatility. Recently, a selection of MOFs has been demonstrated to undergo melting and vitrification upon cooling. Here, these recent discoveries and the connections between the fields of MOF chemistry and glass science are summarized. Possible advantages and applications for MOF glasses produced by utilizing the tunable chemistry of the crystalline state are also highlighted. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. 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

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

    DOE PAGES

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

    2015-01-01

    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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Metal-organic framework nanofibers via electrospinning.

    PubMed

    Ostermann, Rainer; Cravillon, Janosch; Weidmann, Christoph; Wiebcke, Michael; Smarsly, Bernd M

    2011-01-07

    A hierarchical system of highly porous nanofibers has been prepared by electrospinning MOF (metal-organic framework) nanoparticles with suitable carrier polymers. Nitrogen adsorption proved the MOF nanoparticles to be fully accessible inside the polymeric fibers.

  19. Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction grown by metal-organic chemical vapor deposition on sapphire substrate

    PubMed Central

    Zhang, Kexiong; Liang, Hongwei; Liu, Yang; Shen, Rensheng; Guo, Wenping; Wang, Dongsheng; Xia, Xiaochuan; Tao, Pengcheng; Yang, Chao; Luo, Yingmin; Du, Guotong

    2014-01-01

    Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction (PIBTJ) was grown by metal-organic chemical vapor deposition on sapphire substrate. A self-consistent solution of Poisson-Schrödinger equations combined with polarization-induced theory was used to model PIBTJ structure, energy band diagrams and free carrier concentrations distribution. The PIBTJ displays reliable and reproducible backward tunneling with a current density of 3 A/cm2 at the reverse bias of −1 V. The absence of negative differential resistance behavior of PIBTJ at forward bias can mainly be attributed to the hole compensation centers, including C, H and O impurities, accumulated at the p-GaN/Mg-doped AlGaN heterointerface. PMID:25205042

  20. Enhanced output power of near-ultraviolet LEDs with AlGaN/GaN distributed Bragg reflectors on 6H-SiC by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tao, Pengcheng; Liang, Hongwei; Xia, Xiaochuan; Liu, Yang; Jiang, Jianhua; Huang, Huishi; Feng, Qiuju; Shen, Rensheng; Luo, Yingmin; Du, Guotong

    2015-09-01

    Near-ultraviolet (UV) InGaN/AlGaN multiple quantum well (MQW) LEDs with 30 pairs AlGaN/GaN distributed Bragg reflectors (DBRs) were grown on 6H-SiC substrate by metal-organic chemical vapor deposition. A thin SiNx interlayer was introduced between the DBRs and n-GaN layer of the LED to reduce the threading dislocation density and result in enhancement the internal quantum efficiency (ηint) of the InGaN/AlGaN LED. The result indicates that the light output power for the LED with DBRs and SiNx interlayer was approximately 56% higher (at 350 mA) than the LED without DBRs and SiNx interlayer on 6H-SiC substrate, and this significant improvement in performance is attributed not only to the light extraction enhancement via the DBRs but also due to improve epilayer crystalline quality.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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...

  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. POLAR ORGANIC CHEMICAL INTEGRATIVE SAMPLING ...

    EPA Pesticide Factsheets

    The purpose of the research presented in this paper is two-fold: (1) to demonstrate the 4 coupling of two state-of-the-art techniques: a time-weighted polar organic integrative sampler (POCIS) and micro-liquid chromatography-electrospray/ion trap mass spectrometry (u-LC-6 ES/ITMS); and (2) the assessment of these methodologies in a real-world environment -wastewater effluent - for detecting six drugs (four prescription and two illicit). In the effluent from three wastewater treatment plants (WWTP), azithromycin was detected at concentrations ranging from 15ng/L to 66ng/L, equivalent to the total annual release of 0.4 -4 kg into the receiving waters. Detected and confirmed in the effluent from two WWTPs were two illicit drugs methamphetamine and methylenedioxymethamphetamine (MDMA), at 2ng/L and 0.5ng/L, respectively. While the ecotoxicological significance of drugs in environmental matrices, particularly water, has not been closely examined, it can only be surmised that these substances have the potential to adversely affect biota that are continuously exposed to them even at very low levels. The potential for chronic affects on human health is also unknown, but of increasing concern due to the multi use character of water, particularly in densely populated arid areas. The research focused on in the subtasks is the development and application of state-of the-art technologies to meet the needs of the public, Office of Water, and ORD in the area of Water Quality

  12. 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

  13. Degradation of Paraoxon and the Chemical Warfare Agents VX, Tabun, and Soman by the Metal-Organic Frameworks UiO-66-NH2, MOF-808, NU-1000, and PCN-777.

    PubMed

    de Koning, Martijn C; van Grol, Marco; Breijaert, Troy

    2017-10-02

    In recent years, Zr-based metal-organic frameworks (MOFs) have been developed that facilitate catalytic degradation of toxic organophosphate agents, such as chemical warfare agents (CWAs). Because of strict regulations, experiments using live agents are not possible for most laboratories and, as a result, simulants are used in the majority of cases. Reports that employ real CWAs are scarce and do not cover the whole spectrum of agents. We here present a comparative study in which UiO-66-NH2, NU-1000, MOF-808, and PCN-777 are evaluated for their effectiveness in the degradation of paraoxon and the chemical warfare agents tabun, VX, and soman, in N-ethylmorpholine buffer (pH 10) as well as in pure water. All MOFs showed excellent ability to degrade the agents under basic conditions. It was further disclosed that tabun is degraded by different mechanisms depending on the conditions. The presence of an amine, either as part of the MOF structure (UiO-66-NH2) or in the agent itself (VX, tabun), is the most important factor governing degradation rates in water. The results show that MOFs have great potential in future protective applications. Although the use of simulants provides valuable information for initial screening and selection of new MOFs, the use of live agents revealed additional mechanisms that should aid the future development of even better catalysts.

  14. 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.

  15. Transparent Conducting ZnO:B Thin Films Grown by Ultraviolet Light Assisted Metal Organic Chemical Vapor Deposition Using Triethylboron for Cu(In,Ga)Se2 Solar Cells

    NASA Astrophysics Data System (ADS)

    Kobayashi, Taizo; Yamauchi, Kotaro; Mise, Takahiro; Nakada, Tokio

    2012-10-01

    High-efficiency cadmium-free Cu(In,Ga)Se2 (CIGS) thin-film solar cells have been fabricated using a zinc compound buffer layer deposited by the chemical bath deposition (CBD) process. However, the zinc compound buffer layers such as ZnS(O,OH) are prone to plasma-induced damage during the subsequent ZnO sputtering process. A process causing less damage such as metal-organic chemical vapor deposition (MOCVD) is thus required for ZnO-based transparent conducting oxide (TCO) layers. In the present work, the boron-doped zinc oxide (ZnO:B) films were grown by MOCVD using diethyl zinc (DEZ), H2O, and low-toxicity triethylboron (TEB). An UV-assisted MOCVD process was developed in order to reduce the resistivity of ZnO:B films. As a result, the resisitivity significantly decreased together with the increased electron mobility and carrier concentration. The comparison of performance was also carried out for the ZnS(O,OH)/CIGS solar cells with MOCVD-deposited ZnO:B and sputter-deposited ZnO:Al window layers.

  16. Effect of metal spiking on different chemical pools and chemically extractable fractions of heavy metals in sewage sludge.

    PubMed

    Kandpal, Geeta; Ram, Bali; Srivastava, P C; Singh, S K

    2004-01-30

    A laboratory experiment was conducted to study the effect of metal spiking and incubation on some properties and sequentially extractable chemical pools of some heavy metals (F1, two extractions with 0.1 M Sr(NO3)2; F2, one extraction with 1 M NaOAc (pH 5.0); F3, three extractions with 5% NaOCl (pH 8.5) at 90-95 degrees C; F4, three extractions with 0.2 M oxalic acid + 0.2 M ammonium oxalate + 0.1 M ascorbic acid (pH 3.0); and F5, dissolution of sample residue in HF-HClO4 (residual fraction,) and also 1 M CaCl2 and 0.005 M DTPA extractable heavy metals in sewage sludge. Metal spiking and incubation decreased pH and easily oxidizable organic C content of sludge but increased electrical conductivity. Metal spiking and incubation increased F1 fraction of all heavy metals, F2 fraction of Ni, Pb, Cu, and Cd, F3 fraction of Pb, Cu, and Cd, F4 or reducible fraction of Ni, Cu, and Cd and residual fraction of Zn and Pb, but decreased F2 fraction of Zn, F3 of Zn and Ni, F4 fraction of Zn and F5 fraction of Ni, Cu, and Cd. Metal spiking and incubation increased 1 M CaCl2 and 0.005 M DTPA extractable amounts of all heavy metals in sludge except for 0.005 M DTPA extractable Zn, which registered only very marginal decrease.

  17. Optimization of Strontium Titanate (SrTiO3) Thin Films Fabricated by Metal Organic Chemical Vapor Deposition (MOCVD) for Microwave-Tunable Devices

    DTIC Science & Technology

    2015-12-01

    target materials are flash evaporated by an incident laser radiation source. It is carried out in a low- pressure environment and is the most popular...process variables than those required by RF sputtering and chemical deposition techniques. Because of the nature of evaporation and low- pressure ...growth of oxide materials provides great challenges for MBE. Oxide thin films grown in such low- pressure environments have suffered from oxygen

  18. Self-exfoliated metal organic nanosheets via hydrolytic unfolding of metal organic polyhedra.

    PubMed

    Banerjee, Rahul; Garai, Bikash; Mallick, Arjit; Das, Anuja; Mukherjee, Rabibrata

    2017-04-04

    Few layer thick metal-organic nanosheets have been synthesized using water-assisted solid state transformation through a combined top-down and bottom-up approach. The metal-organic polyhedra (MOPs) convert into metal-organic frameworks (MOFs) which subsequently self-exfoliate into few layered metal-organic nanosheets. These MOP crystals experience a hydrophobicity gradient with the inner surface during contact with water because of the existence of hydrophobic spikes on their outer surface. When the amount of water available for interaction is higher, the resultant layers are not stacked to form bulk materials; instead few layered nanosheets with high uniformity were obtained in high yield. The phenomenon has resulted high yield production of uniformly distributed layered metal-organic nanosheets from three different MOPs, showing its general adaptability.

  19. Study on plasma assisted metal-organic chemical vapor deposition of Zr(C,N) and Ti(C,N) thin films and in situ plasma diagnostics with optical emission spectroscopy

    SciTech Connect

    Cho, S. J.; Nam, S.-H.; Jung, C.-K.; Jee, H.-G.; Boo, J.-H.; Kim, S.; Han, J. G.

    2008-07-15

    Zr(C,N) and Ti(C,N) films were synthesized by pulsed dc plasma assisted metal-organic chemical vapor deposition method using metal-organic compounds of tetrakis diethylamido titanium and tetrakis diethylamido zirconium at 200-300 deg. C. To change the plasma characteristics, different carrier gases such as H{sub 2} and He/H{sub 2} were used and, as the reactive gas, N{sub 2} and NH{sub 3} were added to the gas mixture. The effect of N{sub 2} and NH{sub 3} gases was also evaluated in the reduction of C content of the films. Radical formation and ionization behaviors in plasma were analyzed by optical emission spectroscopy and mass spectrometry at various pulsed biases and gas conditions. The gas mixture of He and H{sub 2} as the carrier gas was very effective in enhancing the dissociation of molecular gases. In the case of N{sub 2} addition, N{sub 2} as reactive gas resulted in higher hardness. However, NH{sub 3} as reactive gas highly reduced the formation of CN radical, thereby greatly decreasing the C content of Zr(C,N) and Ti(C,N) films. The hardness of the film is 1400-1700 HK depending on gas species and bias voltage. Higher hardness can be obtained for a H{sub 2} and N{sub 2} gas atmosphere and bias voltage of -600 V. Plasma surface cleaning using N{sub 2} gas prior to deposition appeared to increase the adhesion of films on steel. The changes of plasmas including radicals and film properties are illustrated in terms of carrier and reactive gases, as well as pulsed power variation.

  20. Effects of Pelletization Pressure on the Physical and Chemical Properties of the Metal-Organic Frameworks Cu3(BTC)2 and UiO-66

    DTIC Science & Technology

    2013-02-26

    testing was conducted with CuBTC against ammonia , which probes the reactive sites, and UiO-66 against octane, which probes physical adsorption capacity...Even with the decrease in surface area, the CuBTC materials had consistent ammonia removal capacities, while the UiO-66 pressed materials showed a...21010, USA cGeorgia Institute of Technology, School of Chemical & Biomolecular Engineering, Atlanta, GA 30332, USA a r t i c l e i n f o Article history

  1. Methane storage in metal-organic frameworks.

    PubMed

    He, Yabing; Zhou, Wei; Qian, Guodong; Chen, Banglin

    2014-08-21

    Natural gas (NG), whose main component is methane, is an attractive fuel for vehicular applications. Realization of safe, cheap and convenient means and materials for high-capacity methane storage can significantly facilitate the implementation of natural gas fuelled vehicles. The physisorption based process involving porous materials offers an efficient storage methodology and the emerging porous metal-organic frameworks have been explored as potential candidates because of their extraordinarily high porosities, tunable pore/cage sizes and easily immobilized functional sites. In this view, we provide an overview of the current status of metal-organic frameworks for methane storage.

  2. Plant uptake of non ionic organic chemicals.

    PubMed

    Collins, Chris; Fryer, Mike; Grosso, Albania

    2006-01-01

    Plant uptake of organic chemicals is an important process when considering the risks associated with land contamination, the role of vegetation in the global cycling of persistent organic pollutants, and the potential for industrial discharges to contaminate the food chain. There have been some significant advances in our understanding of the processes of plant uptake of organic chemicals in recent years; most notably there is now a better understanding of the air to plant transfer pathway, which may be significant for a number of industrial chemicals. This review identifies the key processes involved in the plant uptake of organic chemicals including those for which there is currently little information, e.g., plant lipid content and plant metabolism. One of the principal findings is that although a number of predictive models exist using established relationships, these require further validation if they are to be considered sufficiently robust for the purposes of contaminated land risk assessment or for prediction of the global cycling of persistent organic pollutants. Finally, a number of processes are identified which should be the focus of future research.

  3. Preparation of AlGaN/GaN Heterostructures on Sapphire Using Light Radiation Heating Metal-Organic Chemical Vapor Deposition at Low Pressure

    NASA Astrophysics Data System (ADS)

    Zhou, Yu-Gang; Shen, Bo; Zhang, Rong; Li, Wei-Ping; Chen, Peng; Chen, Zhi-Zhong; Gu, Shu-Lin; Shi, Yi; Z, Huang C.; Zheng, You-Dou

    2000-08-01

    AlGaN/GaN heterostructures on sapphire substrate were fabricated by using light radiation heating metalorganic chemical vapor deposition. Photoluminescence excitation spectra show that there are two abrupt slopes corresponding to the absorption edges of AlGaN and GaN, respectively. X-ray diffraction spectra clearly exhibit the GaN (0002), (0004), and AlGaN (0002), (0004) diffraction peaks, and no diffraction peak other than those from the GaN {0001} and AlGaN {0001} planes is found. Reciprocal space mapping indicates that there is no tilt between the AlGaN layer and the GaN layer. All results also indicate that the sample is of sound quality and the Al composition in the AlGaN layer is of high uniformity.

  4. Phase-change InSbTe nanowires grown in situ at low temperature by metal-organic chemical vapor deposition.

    PubMed

    Ahn, Jun-Ku; Park, Kyoung-Woo; Jung, Hyun-June; Yoon, Soon-Gil

    2010-02-10

    Phase-change InSbTe (IST) single crystalline nanowires were successfully synthesized at a low temperature of 250 degrees C by metalorganic chemical vapor deposition (MOCVD). The growth of IST nanowires by MOCVD, at very high working pressure, was governed by supersaturation. The growth mechanism of the IST nanowires by MOCVD is addressed in this paper. Under high working pressure, the InTe phase was preferentially formed on the TiAlN electrode, and the InTe protrusions were nucleated on the InTe films under high supersaturation. The Sb was continuously incorporated into the InTe protrusions, which was grown as an IST nanowire. Phase-change-induced memory switching was realized in IST nanowires with a threshold voltage of about 1.6 V. The ability to grow IST nanowires at low temperature by MOCVD should open opportunities for investigation of the nanoscale phase-transition phenomena.

  5. Chemical metallization of KMPR photoresist polymer in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zeb, Gul; Duong, Xuan Truong; Vu, Ngoc Pi; Phan, Quang The; Nguyen, Duc Tuong; Ly, Viet Anh; Salimy, Siamak; Le, Xuan Tuan

    2017-06-01

    While conventional methods for preparing thin films of metals and metallic alloys on insulating substrates in the field of microelectromechanical systems (MEMS) include vapor deposition techniques, we demonstrate here that electroless deposition can be considered as an alternate efficient approach to metallize the surface of insulating substrates, such as KMPR epoxy photoresist polymer. In comparison with the physical and chemical vapor deposition methods, which are well-established for metallization of photoresist polymers, our electroless nickel plating requires only immersing the substrates into aqueous solutions in open air at low temperatures. Thin films of nickel alloy have been deposited electrolessly on KMPR surface, through a cost-effective and environmental chromium-free process, mediated through direct grafting of amine palladium complexes in aqueous medium. This covalent organic coating provides excellent adhesion between KMPR and the nickel film and allows better control of the palladium catalyst content. Covalent grafting and characterization of the deposited nickel film have been carried out by means of Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy techniques.

  6. Postsynthetic Tuning of Metal-Organic Frameworks for Targeted Applications.

    PubMed

    Islamoglu, Timur; Goswami, Subhadip; Li, Zhanyong; Howarth, Ashlee J; Farha, Omar K; Hupp, Joseph T

    2017-04-18

    Metal-organic frameworks (MOFs) are periodic, hybrid, atomically well-defined porous materials that typically form by self-assembly and consist of inorganic nodes (metal ions or clusters) and multitopic organic linkers. MOFs as a whole offer many intriguing properties, including ultrahigh porosity, tunable chemical functionality, and low density. These properties point to numerous potential applications, including gas storage, chemical separations, catalysis, light harvesting, and chemical sensing, to name a few. Reticular chemistry, or the linking of molecular building blocks into predetermined network structures, has been employed to synthesize thousands of MOFs. Given the vast library of candidate nodes and linkers, the number of potentially synthetically accessible MOFs is enormous. Nevertheless, a powerful complementary approach to obtain specific structures with desired chemical functionality is to modify known MOFs after synthesis. This approach is particularly useful when incorporation of particular chemical functionalities via direct synthesis is challenging or impossible. The challenges may stem from limited stability or solubility of precursors, unwanted secondary reactivity of precursors, or incompatibility of functional groups with the conditions needed for direct synthesis. MOFs can be postsynthetically modified by replacing the metal nodes and/or organic linkers or via functionalization of the metal nodes and/or organic linkers. Here we describe some of our efforts toward the development and application of postsynthetic strategies for imparting desired chemical functionalities in MOFs of known topology. The techniques include methods for functionalizing MOF nodes, i.e., solvent-assisted ligand incorporation (SALI) and atomic layer deposition in MOFs (AIM) as well as a method to replace structural linkers, termed solvent-assisted linker exchange (SALE), also known as postsynthethic exchange (PSE). For each functionalization strategy, we first describe

  7. Metal-organic chemical vapor deposition of high quality, high indium composition N-polar InGaN layers for tunnel devices

    NASA Astrophysics Data System (ADS)

    Lund, Cory; Romanczyk, Brian; Catalano, Massimo; Wang, Qingxiao; Li, Wenjun; DiGiovanni, Domenic; Kim, Moon J.; Fay, Patrick; Nakamura, Shuji; DenBaars, Steven P.; Mishra, Umesh K.; Keller, Stacia

    2017-05-01

    In this study, the growth of high quality N-polar InGaN films by metalorganic chemical vapor deposition is presented with a focus on growth process optimization for high indium compositions and the structural and tunneling properties of such films. Uniform InGaN/GaN multiple quantum well stacks with indium compositions up to 0.46 were grown with local compositional analysis performed by energy-dispersive X-ray spectroscopy within a scanning transmission electron microscope. Bright room-temperature photoluminescence up to 600 nm was observed for films with indium compositions up to 0.35. To study the tunneling behavior of the InGaN layers, N-polar GaN/In0.35Ga0.65N/GaN tunnel diodes were fabricated which reached a maximum current density of 1.7 kA/cm2 at 5 V reverse bias. Temperature-dependent measurements are presented and confirm tunneling behavior under reverse bias.

  8. Organically modified silicas on metal nanowires.

    PubMed

    Dean, Stacey L; Stapleton, Joshua J; Keating, Christine D

    2010-09-21

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling.

  9. Organically Modified Silicas on Metal Nanowires

    PubMed Central

    2010-01-01

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

  10. Mechanism of metal cationization in organic SIMS

    NASA Astrophysics Data System (ADS)

    Wojciechowski, I.; Delcorte, A.; Gonze, X.; Bertrand, P.

    2001-09-01

    A mechanism for metal cationization of phenyl group containing hydrocarbons is discussed. Intact molecules and their fragments are emitted from a thin organic layer covering a metal surface bombarded by fast ions. It is shown that the process of associative ionization of a neutral hydrocarbon molecule and a neutral excited metal atom, occurring above the surface, may contribute to the yield of cationized molecules. To demonstrate this we have calculated the potential energy curves for the model system C 6H 6+Me (Me=Ag, Cu, Au) making use of the density functional theory. The initial states of the metal atoms approaching the benzene ring along the C 6 symmetry axis were set as the ground, ionic, and excited in ( n-1)d 9ns 2 electronic configuration.

  11. Superhydrophobic perfluorinated metal-organic frameworks.

    PubMed

    Chen, Teng-Hao; Popov, Ilya; Zenasni, Oussama; Daugulis, Olafs; Miljanić, Ognjen Š

    2013-08-07

    Three perfluorinated Cu-based metal-organic frameworks (MOFs) were prepared starting from extensively fluorinated biphenyl-based ligands accessed via C-H functionalization. These new materials are highly hydrophobic: with water contact angles of up to 151 ± 1°, they are among the most water-repellent MOFs ever reported.

  12. TSCA Chemical Data Reporting Fact Sheet: Reporting Manufactured Chemical Substances from Metal Mining and Related Activities

    EPA Pesticide Factsheets

    This fact sheet provides guidance on the Chemical Data Reporting (CDR) rule requirements related to the reporting of mined metals, intermediates, and byproducts manufactured during metal mining and related activities.

  13. Metal and metal oxide nanoparticle synthesis from metal organic frameworks (MOFs): finding the border of metal and metal oxides

    NASA Astrophysics Data System (ADS)

    Das, Raja; Pachfule, Pradip; Banerjee, Rahul; Poddar, Pankaj

    2012-01-01

    Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co3O4, ZnO, Mn2O3, MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N2, whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N2. Another point of interest is the fact that we have found a unique relationship between the nanoparticle size and the distance between the secondary building units inside the MOF precursors. Interestingly, the crystallinity of the carbon matrix was also found to be greatly influenced by the environment (N2 and air) during thermolysis. Moreover, these nanoparticles dispersed in a carbon matrix showed promising H2 and CO2 adsorption properties depending on the environment used for the thermolysis of MOFs.Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co3O4, ZnO, Mn2O3, MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N2, whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N2. Another point of interest is the fact that we have

  14. Effect of fly ash, organic wastes and chemical fertilizers on yield, nutrient uptake, heavy metal content and residual fertility in a rice-mustard cropping sequence under acid lateritic soils.

    PubMed

    Rautaray, S K; Ghosh, B C; Mittra, B N

    2003-12-01

    A field experiment was conducted for two years in sandy loam acid lateritic soil to study the direct effect of fly ash, organic wastes and chemical fertilizers on rice (Oryza sativa) and their residual effect on mustard (Brassica napus var glauca) grown in sequence. Rice yields were higher when fly ash, organic wastes and chemical fertilizers were used in an integrated manner as compared to sole application of chemical fertilizers. Yields of mustard were also higher under the residual effect of the former rather than the latter. However, this beneficial residual effect under integrated nutrient sources was inadequate for the mustard crop in the low fertility test soil. Hence, direct application of fertilizers was needed, in addition to residual fertility. The effect of fly ash on mean rice equivalent yield of the rice-mustard cropping sequence was highest (up to 14%) when it was used in combination with organic wastes and chemical fertilizers. While the yield increase was 10% when it was used in combination with only chemical fertilizers. The minimum yield advantage, 3%, occurred when fly ash was applied alone. The equivalent yield of the rice-mustard cropping sequence was equally influenced by either of the organic wastes. Cadmium and Ni content in rice grain and straw were less under the direct effect of fly ash. The residual effect on mustard was similar for Ni content in seed and stover; however, Cd content was increased. Beneficial residual soil chemical properties in terms of pH, organic carbon and available N, P and K were noted for integrated nutrient treatments involved fly ash, organic wastes and chemical fertilizers as compared to continuous use of only chemical fertilizers. Application of fly ash alone was effective in raising soil available P. Thus, integrated use of fly ash, organic wastes and chemical fertilizers was beneficial in improving crop yield, soil pH, organic carbon and available N, P and K in sandy loam acid lateritic soil.

  15. Metal-assisted chemical etching of silicon: a review.

    PubMed

    Huang, Zhipeng; Geyer, Nadine; Werner, Peter; de Boor, Johannes; Gösele, Ulrich

    2011-01-11

    This article presents an overview of the essential aspects in the fabrication of silicon and some silicon/germanium nanostructures by metal-assisted chemical etching. First, the basic process and mechanism of metal-assisted chemical etching is introduced. Then, the various influences of the noble metal, the etchant, temperature, illumination, and intrinsic properties of the silicon substrate (e.g., orientation, doping type, doping level) are presented. The anisotropic and the isotropic etching behaviors of silicon under various conditions are presented. Template-based metal-assisted chemical etching methods are introduced, including templates based on nanosphere lithography, anodic aluminum oxide masks, interference lithography, and block-copolymer masks. The metal-assisted chemical etching of other semiconductors is also introduced. A brief introduction to the application of Si nanostructures obtained by metal-assisted chemical etching is given, demonstrating the promising potential applications of metal-assisted chemical etching. Finally, some open questions in the understanding of metal-assisted chemical etching are compiled.

  16. ESTIMATING DISSOLVED ORGANIC CARBON PARTITION COEFFICIENTS FOR NONIONIC ORGANIC CHEMICALS

    EPA Science Inventory

    A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic chemicals (Kdoc) and Kdoc data was taken from more than sixty references. The Kdoc data were evaluated as a function of the n-octanol/water partition coefficients (Kow). A pre...

  17. ESTIMATING DISSOLVED ORGANIC CARBON PARTITION COEFFICIENTS FOR NONIONIC ORGANIC CHEMICALS

    EPA Science Inventory

    A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic chemicals (Kdoc) and Kdoc data was taken from more than sixty references. The Kdoc data were evaluated as a function of the n-octanol/water partition coefficients (Kow). A pre...

  18. 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

  19. 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

  20. Nanoporous metal organic frameworks as hybrid polymer-metal composites for drug delivery and biomedical applications.

    PubMed

    Beg, Sarwar; Rahman, Mahfoozur; Jain, Atul; Saini, Sumant; Midoux, Patrick; Pichon, Chantal; Ahmad, Farhan Jalees; Akhter, Sohail

    2017-04-01

    Metal organic frameworks (MOFs), porous hybrid polymer-metal composites at the nanoscale, are recent innovations in the field of chemistry; they are novel polymeric materials with diverse biomedical applications. MOFs are nanoporous materials, consisting of metal ions linked together by organic bridging ligands. The unique physical and chemical characteristics of MOFs have attracted wider attention from the scientific community, exploring their utility in the field of material science, biology, nanotechnology and drug delivery. The practical feasibility of MOFs is possible owing to their abilities for biodegradability, excellent porosity, high loading capacity, ease of surface modification, among others. In this regard, this review provides an account of various types of MOFs, their physiochemical characteristics and use in diverse disciplines of biomedical sciences - with special emphasis on drug delivery and theranostics. Moreover, this review also highlights the stability and toxicity issues of MOFs, along with their market potential for biomedical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Effect of a Ti capping layer on thermal stability of NiSi formed from Ni thin films deposited by metal-organic chemical vapor deposition using a Ni(iPr-DAD)2 precursor

    NASA Astrophysics Data System (ADS)

    Park, Jingyu; Jeon, Heeyoung; Kim, Hyunjung; Jang, Woochool; Kang, Chunho; Yuh, Junhan; Jeon, Hyeongtag

    2015-02-01

    Ni films were deposited by metal-organic chemical vapor deposition (MOCVD) using a novel Ni precursor, bis(1,4-di-isopropyl-1,3-diazabutadienyl)nickel [Ni(iPr-DAD)2], and NH3 gas. To optimize process conditions, the deposition temperature and reactant partial pressure were varied from 200 to 350 °C and from 0.2 to 0.99 Torr, respectively. Ni films deposited at 300 °C with a reactant pressure of 0.8 Torr exhibited excellent quality, and had a low carbon impurity concentration of around 4%. In addition, a sacrificial Ti capping layer was deposited by an in situ e-beam evaporator on top of the Ni films to enhance the thermal stability of the subsequently formed NiSi films. Both the Ti-capped and uncapped Ni films were annealed by a two-step method, with a first annealing conducted at 500 °C, followed by wet etching and then a second annealing carried out from 500 to 900 °C. The Ti capping layer did not affect the silicidation kinetic process, but by acting as an oxygen scavenger, it did enhance the morphological stability of the NiSi films and thus improve their electrical properties.

  2. Enhanced optical properties of InAs/InAlGaAs/InP quantum dots grown by metal-organic chemical vapor deposition using a double-cap technique

    NASA Astrophysics Data System (ADS)

    Shi, Bei; Lau, Kei May

    2016-01-01

    The effects of a double-cap procedure on the optical properties of an InAs/InAlGaAs quantum dots (QDs) system grown by metal-organic chemical vapor deposition (MOCVD) have been investigated by atomic force microscopy (AFM) and room temperature photoluminescence (RT-PL) spectroscopy. An optimized QD growth condition has been achieved, with an areal density of 4.6×1010 cm-2. It was found that the thickness and lattice constant of the high temperature second cap layer (SCL) were crucial for improving the integrated PL intensity and line-width of the 1.55 μm emission from the InAs/InAlGaAs QD system grown on a semi-insulating InP (100) substrate. With fine-tuned SCL thickness and lattice constant, the optical performance of the five-stack QDs was enhanced. The improvements can be attributed to the smooth growth front, observed from the AFM images, and the well-balanced stress engineering.

  3. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: A Simple Route of Morphology Control and Structural and Optical Properties of ZnO Grown by Metal-Organic Chemical Vapour Deposition

    NASA Astrophysics Data System (ADS)

    Fan, Hai-Bo; Yang, Shao-Yan; Zhang, Pan-Feng; Wei, Hong-Yuan; Liu, Xiang-Lin; Jiao, Chun-Mei; Zhu, Qin-Sheng; Chen, Yong-Hai; Wang, Zhan-Guo

    2008-08-01

    Employing the metal-organic chemical vapour deposition (MOCVD) technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux (BDF) and the carrier gas flux of oxygen (OCGF). The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction (XRD) and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 2θ locations of ZnO (002) face in the XRD patterns and the E2 (high) locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopy results show all the samples have a sharp ultraviolet luminescent band without any defects-related emission. Upon the experiments a possible growth mechanism is proposed.

  4. Pilot-scale electron cyclotron resonance-metal organic chemical vapor deposition system for the preparation of large-area fluorine-doped SnO{sub 2} thin films

    SciTech Connect

    Jeon, Bup Ju; Hudaya, Chairul; Lee, Joong Kee

    2016-05-15

    The authors report the surface morphology, optical, electrical, thermal and humidity impacts, and electromagnetic interference properties of fluorine-doped tin oxide (SnO{sub 2}:F or “FTO”) thin films on a flexible polyethylene terephthalate (PET) substrate fabricated by a pilot-scale electron cyclotron resonance–metal organic chemical vapor deposition (PS ECR-MOCVD). The characteristics of large area FTO thin films were compared with a commercially available transparent conductive electrode made of tin-doped indium oxide (ITO), prepared with an identical film and PET thickness of 125 nm and 188 μm, respectively. The results revealed that the as-prepared FTO thin films exhibited comparable performances with the incumbent ITO films, including a high optical transmittance of 97% (substrate-subtracted), low electrical resistivity of about 5 × 10{sup −3} Ω cm, improved electrical and optical performances due to the external thermal and humidity impact, and an excellent shielding effectiveness of electromagnetic interference of nearly 2.3 dB. These excellent performances of the FTO thin films were strongly attributed to the design of the PS ECR-MOCVD, which enabled a uniform plasma environment resulting from a proper mixture of electromagnetic profiles and microwave power.

  5. Impact of (111)-Oriented SrRuO3/Pt Tailored Electrode for Highly Reproducible Preparation of Metal Organic Chemical Vapour Deposited Pb(Zr,Ti)O3 Films for High Density Ferroelectric Random Access Memory Applications

    NASA Astrophysics Data System (ADS)

    Menou, Nicolas; Kuwabara, Hiroki; Funakubo, Hiroshi

    2007-04-01

    In the present paper we report a comparative study of the structural, morphologic, and electric properties of Pb(Zr,Ti)O3 films, deposited by pulsed metal-organic chemical vapour deposition (MOCVD), on different (111)-oriented bottom-electrode stacks (SrRuO3/Pt, Pt, and Ir substrates). The Pb input ratio in the MOCVD chamber was systematically modified for each deposition run to obtain PZT films with various compositions within the Pb process window. Our results clearly demonstrate that only PZT films deposited on SrRuO3 show high quality and reproducible properties throughout the process window, i.e., high (111) texture, low roughness (<5 nm), high Pr (˜40 μC/cm2), low Vc (<1 V), as well as a relatively low leakage current (˜ 10-5 A/cm2 at 1.5 V). This study provides further evidence that SrRuO3/Pt substrates are good candidates for integration in next-generation high-density ferroelectric random access memories (FeRAM).

  6. Strain and in-plane orientation effects on the ferroelectricity of (111)-oriented tetragonal Pb(Zr0.35Ti0.65)O3 thin films prepared by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kuwabara, Hiroki; Menou, Nicolas; Funakubo, Hiroshi

    2007-05-01

    The growth and characterization of epitaxial (111)-oriented Pb(Zr0.35Ti0.65)O3 films deposited by metal organic chemical vapor deposition on (100)-oriented silicon substrates [(111)SrRuO3‖(111)Pt ‖(100)yttria-stabilizedzirconia‖(100)Si] are reported. The orientation, microstructure, and electric properties of these films are compared to those of fiber-textured highly (111)-oriented lead zirconate titanate (PZT) films deposited on (111)SrRuO3/(111)Pt/TiOx/SiO2/(100)Si substrates and epitaxial (111)-oriented PZT films deposited on (111)SrRuO3‖(111)SrTiO3 substrates. The ferroelectric properties of these films are not drastically influenced by the in-plane orientation of the film and by the strain state imposed by the underlying substrate. These results support the use of fiber-textured highly (111)-oriented films in highly stable ferroelectric capacitors.

  7. {ital In situ} growth of highly oriented Pb(Zr{sub 0.5}Ti{sub 0.5})O{sub 3} thin films by low-temperature metal{endash}organic chemical vapor deposition

    SciTech Connect

    Bai, G.; Tsu, I.; Wang, A.; Foster, C.M.; Murray, C.E.; Dravid, V.P.

    1998-03-01

    Highly oriented, polycrystalline Pb(Zr{sub 0.5}Ti{sub 0.5})O{sub 3} (PZT) thin films were successfully grown on RuO{sub 2}/SiO{sub 2}/(001)Si using metal{endash}organic chemical vapor deposition (MOCVD) at 525{degree}C. The orientation of the PZT film was controlled by using MOCVD-deposited highly textured RuO{sub 2} bottom electrodes. A (001)-oriented PZT film was observed for growth on (101)-textured RuO{sub 2}. In contrast, for (110) RuO{sub 2}, the growth of (001) PZT was greatly suppressed while the growth of both (110) and (111) were enhanced, resulting in a poorly (001)-textured polycrystalline film. The as-grown PZT films exhibited a dense columnar microstructure with an average grain size of 150{endash}250 nm. Both PZT films showed excellent ferroelectric properties without any postgrowth annealing. The (001) highly oriented PZT films showed significantly higher values of remnant polarization (P{sub r}=49.7{mu}C/cm{sup 2}) and saturation polarization (P{sub s}=82.5{mu}C/cm{sup 2}). In comparison, for the PZT films grown on (110) RuO{sub 2}, P{sub r} and P{sub s} were 21.5 and 35.4{mu}C/cm{sup 2}, respectively. {copyright} {ital 1998 American Institute of Physics.}

  8. Grain morphology and cation composition heterogeneity of Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} thin films deposited by metal-organic chemical vapor deposition

    SciTech Connect

    Tsu, I.; Bai, G.; Foster, C.M.; Merkle, K.L.; Liu, K.C.

    1998-06-01

    The preferred orientation, grain morphology, and composition heterogeneity of the polycrystalline Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and x-ray energy dispersive spectroscopy (EDS). PZT thin films with nominal x=0.5 were grown by metal-organic chemical vapor deposition (MOCVD) on (110)- and (101)-textured RuO{sub 2} bottom electrodes at temperatures {le}525thinsp{degree}C. Columnar grain microstructure with strongly faceted surface morphology was observed in both films. The grain morphology and surface roughness of the PZT films were observed to depend on those of the underlying RuO{sub 2} layers. TEM-EDS analysis shows notable cation composition heterogeneity in length scales of 0.2-2 {mu}m. Pronounced Pb composition deficiency and heterogeneity were also observed in PZT/(110)RuO{sub 2} in length scales above 40 {mu}m. The grain morphology and cation heterogeneity of the PZT films are discussed on the basis of diffusion-limited columnar growth mechanism. {copyright} {ital 1998 Materials Research Society.}

  9. β-Ga2O3 versus ε-Ga2O3: Control of the crystal phase composition of gallium oxide thin film prepared by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhuo, Yi; Chen, Zimin; Tu, Wenbin; Ma, Xuejin; Pei, Yanli; Wang, Gang

    2017-10-01

    Gallium oxide thin films of β and ε phase were grown on c-plane sapphire using metal-organic chemical vapor deposition and the phase compositions were analyzed using X-ray diffraction. The epitaxial phase diagram was constructed as a function of the growth temperature and VI/III ratio. A low growth temperature and low VI/III ratio were beneficial for the formation of hexagonal-type ε-Ga2O3. Further structure analysis revealed that the epitaxial relationship between ε-Ga2O3 and c-plane sapphire is ε-Ga2O3 (0001) || Al2O3 (0001) and ε-Ga2O3 || Al2O3 . The structural evolution of the mixed-phase sample during film thickening was investigated. By reducing the growth rate, the film evolved from a mixed phase to the energetically favored ε phase. Based on these results, a Ga2O3 thin film with a phase-pure ε-Ga2O3 upper layer was successfully obtained.

  10. 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.

  11. 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.

  12. Mechanical Alloying of Metal-Organic Frameworks.

    PubMed

    Panda, Tamas; Horike, Satoshi; Hagi, Keisuke; Ogiwara, Naoki; Kadota, Kentaro; Itakura, Tomoya; Tsujimoto, Masahiko; Kitagawa, Susumu

    2017-02-20

    The solvent-free mechanical milling process for two distinct metal-organic framework (MOF) crystals induced the formation of a solid solution, which is not feasible by conventional solution-based syntheses. X-ray and STEM-EDX studies revealed that performing mechanical milling under an Ar atmosphere promotes the high diffusivity of each metal ion in an amorphous solid matrix; the amorphous state turns into the porous crystalline structure by vapor exposure treatment to form a new phase of a MOF solid solution.

  13. Metal and metal oxide nanoparticle synthesis from metal organic frameworks (MOFs): finding the border of metal and metal oxides.

    PubMed

    Das, Raja; Pachfule, Pradip; Banerjee, Rahul; Poddar, Pankaj

    2012-01-21

    Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co(3)O(4), ZnO, Mn(2)O(3), MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N(2), whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N(2). Another point of interest is the fact that we have found a unique relationship between the nanoparticle size and the distance between the secondary building units inside the MOF precursors. Interestingly, the crystallinity of the carbon matrix was also found to be greatly influenced by the environment (N(2) and air) during thermolysis. Moreover, these nanoparticles dispersed in a carbon matrix showed promising H(2) and CO(2) adsorption properties depending on the environment used for the thermolysis of MOFs.

  14. Impacts of metal and metal oxide nanoparticles on marine organisms.

    PubMed

    Baker, Tony J; Tyler, Charles R; Galloway, Tamara S

    2014-03-01

    Increasing use of metal and metal oxide nanoparticles [Me(O)NPs] in products means many will inevitably find their way into marine systems. Their likely fate here is sedimentation following hetero-aggregation with natural organic matter and/or free anions, putting benthic, sediment-dwelling and filter feeding organisms most at risk. In marine systems, Me(O)NPs can absorb to micro-organisms with potential for trophic transfer following consumption. Filter feeders, especially bivalves, accumulate Me(O)NPs through trapping them in mucus prior to ingestion. Benthic in-fauna may directly ingest sedimented Me(O)NPs. In fish, uptake is principally via the gut following drinking, whilst Me(O)NPs caught in gill mucus may affect respiratory processes and ion transport. Currently, environmentally-realistic Me(O)NP concentrations are unlikely to cause significant adverse acute health problems, however sub-lethal effects e.g. oxidative stresses have been noted in many organisms, often deriving from dissolution of Ag, Cu or Zn ions, and this could result in chronic health impacts. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  15. Metal-organic frameworks: versatile heterogeneous catalysts for efficient catalytic organic transformations.

    PubMed

    Chughtai, Adeel H; Ahmad, Nazir; Younus, Hussein A; Laypkov, A; Verpoort, Francis

    2015-10-07

    Novel catalytic materials are highly demanded to perform a variety of catalytic organic reactions. MOFs combine the benefits of heterogeneous catalysis like easy post reaction separation, catalyst reusability, high stability and homogeneous catalysis such as high efficiency, selectivity, controllability and mild reaction conditions. The possible organization of active centers like metallic nodes, organic linkers, and their chemical synthetic functionalization on the nanoscale shows potential to build up MOFs particularly modified for catalytic challenges. In this review, we have summarized the recent research progress in heterogeneous catalysis by MOFs and their catalytic behavior in various organic reactions, highlighting the key features of MOFs as catalysts based on the active sites in the framework. Examples of their post functionalization, inclusion of active guest species and metal nanoparticles have been discussed. Finally, the use of MOFs as catalysts for asymmetric heterogeneous catalysis and stability of MOFs has been presented as separate sections.

  16. Increasing the reliability and quality of important cast products made of chemically active metals and alloys

    NASA Astrophysics Data System (ADS)

    Varfolomeev, M. S.; Moiseev, V. S.; Shcherbakova, G. I.

    2017-01-01

    A technology is developed to produce highly thermoresistant ceramic monoxide corundum molds using investment casting and an aluminum-organic binder. This technology is a promising trend in creating ceramic molds for precision complex-shape casting of important ingots made of high-alloy steels, high-temperature and titanium alloys, and refractory metals. The use of the casting molds that have a high thermal and chemical resistance to chemically active metals and alloys under high-temperature casting minimizes the physicochemical interaction and substantially decreases the depth of the hard-to-remove metal oxide layer on important products, which increases their service properties.

  17. Capture of organic iodides from nuclear waste by metal-organic framework-based molecular traps.

    PubMed

    Li, Baiyan; Dong, Xinglong; Wang, Hao; Ma, Dingxuan; Tan, Kui; Jensen, Stephanie; Deibert, Benjamin J; Butler, Joseph; Cure, Jeremy; Shi, Zhan; Thonhauser, Timo; Chabal, Yves J; Han, Yu; Li, Jing

    2017-09-07

    Effective capture of radioactive organic iodides from nuclear waste remains a significant challenge due to the drawbacks of current adsorbents such as low uptake capacity, high cost, and non-recyclability. We report here a general approach to overcome this challenge by creating radioactive organic iodide molecular traps through functionalization of metal-organic framework materials with tertiary amine-binding sites. The molecular trap exhibits a high CH3I saturation uptake capacity of 71 wt% at 150 °C, which is more than 340% higher than the industrial adsorbent Ag(0)@MOR under identical conditions. These functionalized metal-organic frameworks also serve as good adsorbents at low temperatures. Furthermore, the resulting adsorbent can be recycled multiple times without loss of capacity, making recyclability a reality. In combination with its chemical and thermal stability, high capture efficiency and low cost, the adsorbent demonstrates promise for industrial radioactive organic iodides capture from nuclear waste. The capture mechanism was investigated by experimental and theoretical methods.Capturing radioactive organic iodides from nuclear waste is important for safe nuclear energy usage, but remains a significant challenge. Here, Li and co-workers fabricate a stable metal-organic framework functionalized with tertiary amine groups that exhibits high capacities for radioactive organic iodides uptake.

  18. Non-essential metals in chemical biology.

    PubMed

    Dyson, Paul J

    2011-01-01

    Metal ions and compounds are essential to life and many people routinely take them as food supplements in the form of vitamin and mineral pills. Most non-essential metals are considered to be toxic, nevertheless, many are widely used in imaging, diagnostics and medicine. This short review provides an overview from selected examples of the on-going research within my laboratory that uses metal compounds to either understand biological processes or that exhibit therapeutic properties overcoming the limitations of existing chemotherapies.

  19. Metallic Taste from Electrical and Chemical Stimulation

    PubMed Central

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

    2005-01-01

    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. 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.

  1. Purification of metal-organic framework materials

    DOEpatents

    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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Spectroscopical properties of organic/metal nanohybrids.

    PubMed

    Dellepiane, Giovanna; Cuniberti, Carla; Alloisio, Marina; Demartini, Anna

    2010-03-28

    The aim of our work was to prepare stable nanohybrids of controlled size and shape consisting of a noble metal core decorated with polydiacetylenes (PDAs). Due to the combination of the outstanding linear and nonlinear optical properties of the polydiacetylenic chains with the electromagnetic field-enhancing capability of metal nanostructures, these novel composites can find potential application in different fields. In particular, the different colours exhibited by PDAs in relation to the chemical nature of the monomer and the polymerization procedure, as well as in response to environmental perturbations, make them excellent materials for the fabrication of sensing devices. On the basis of our previous work on PDA self-assembled monolayers on flat metal surfaces, the results of which are briefly reported, we prepared differently-shaped gold and silver nanocores (spheres, cages) coated with various diacetylenic monomers having end-groups able to firmly anchor to the metal surface. These nanohybrids exhibit in aqueous colloidal solution an enhanced photochemical polymerization monitored step by step with UV-Vis and SERS techniques. It is shown that in these stable assemblies an intra-particle polymerization takes place and that the dominant PDA form is conditioned by the core size and geometry. While the nanoparticles are SERS active in the visible, the nanocages should be excellent SERS substrates from the visible to the near infrared regions.

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

    SciTech Connect

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

    2016-08-30

    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.

  8. Capturing snapshots of post-synthetic metallation chemistry in metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Bloch, Witold M.; Burgun, Alexandre; Coghlan, Campbell J.; Lee, Richmond; Coote, Michelle L.; Doonan, Christian J.; Sumby, Christopher J.

    2014-10-01

    Post-synthetic metallation is employed strategically to imbue metal-organic frameworks (MOFs) with enhanced performance characteristics. However, obtaining precise structural information for metal-centred reactions that take place within the pores of these materials has remained an elusive goal, because of issues with high symmetry in certain MOFs, lower initial crystallinity for some chemically robust MOFs, and the reduction in crystallinity that can result from carrying out post-synthetic reactions on parent crystals. Here, we report a new three-dimensional MOF possessing pore cavities that are lined with vacant di-pyrazole groups poised for post-synthetic metallation. These metallations occur quantitatively without appreciable loss of crystallinity, thereby enabling examination of the products by single-crystal X-ray diffraction. To illustrate the potential of this platform to garner fundamental insight into metal-catalysed reactions in porous solids we use single-crystal X-ray diffraction studies to structurally elucidate the reaction products of consecutive oxidative addition and methyl migration steps that occur within the pores of the Rh-metallated MOF, 1·[Rh(CO)2][Rh(CO)2Cl2].

  9. 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

  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. 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.

  12. 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.

  13. The compositional, structural, and magnetic properties of a Fe3O4/Ga2O3/GaN spin injecting hetero-structure grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xu, Zhonghua; Huang, Shimin; Tang, Kun; Gu, Shulin; Zhu, Shunming; Ye, Jiandong; Xu, Mingxiang; Wang, Wei; Zheng, Youdou

    2016-12-01

    In this article, the authors have designed and fabricated a Fe3O4/Ga2O3/GaN spin injecting hetero-structure by metal-organic chemical vapor deposition. The compositional, structural, and magnetic properties of the hetero-structure have been characterized and discussed. From the characterizations, the hetero-structure has been successfully grown generally. However, due to the unintentional diffusion of Ga ions from Ga2O3/GaN layers, the most part of the nominal Fe3O4 layer is actually in the form of GaxFe3-xO4 with gradually decreased x values from the Fe3O4/Ga2O3 interface to the Fe3O4 surface. Post-annealing process can further aggravate the diffusion. Due to the similar ionic radius of Ga and Fe, the structural configuration of the GaxFe3-xO4 does not differ from that of pure Fe3O4. However, the ferromagnetism has been reduced with the incorporation of Ga into Fe3O4, which has been explained by the increased Yafet-Kittel angles in presence of considerable amount of Ga incorporation. A different behavior of the magnetoresistance has been found on the as-grown and annealed samples, which could be modelled and explained by the competition between the spin-dependent and spin-independent conduction channels. This work has provided detailed information on the interfacial properties of the Fe3O4/Ga2O3/GaN spin injecting hetero-structure, which is the solid basis for further improvement and application of the structure.

  14. Structural and optical properties of AlxGa1-xN (0.33 ≤ x ≤ 0.79) layers on high-temperature AlN interlayer grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xu, Qingjun; Liu, Bin; Zhang, Shiying; Tao, Tao; Dai, Jiangping; He, Guotang; Xie, Zili; Xiu, Xiangqian; Chen, Dunjun; Chen, Peng; Han, Ping; Zhang, Rong

    2017-01-01

    High-Al-content AlxGa1-xN films with x varying from 0.33 to 0.79 were grown on GaN templates with the high temperature AlN (HT-AlN) interlayer by metal organic chemical vapor deposition (MOCVD). The best crystalline quality, among these AlxGa1-xN alloys, can be obtained for an AlN mole fraction x = 0.55, where the full-width at half-maximum of the Al0.55Ga0.45N (0002) diffraction peak was measured to be 259 arcsec by high resolution X-ray diffraction (HRXRD). The screw threading dislocation (TDs) density was 2 × 108 cm-2 evaluated by transmission electron microscope (TEM), which agreed with the calculations from Williamson-Hall plots. Moreover, cross-sectional TEM indicated that the HT-AlN interlayer could sufficiently reduce the threading dislocations (TDs) through generation of V trenches in the HT-AlN interlayer, since the TDs propagated along the V trenches, then bent into basal planes and annihilated with other dislocations. The study of optical properties indicated that obvious S-shape of temperature dependence on emission energy was observed for Al0.55Ga0.45N layers, which was attributed to exciton localization with energy (Eloc) ∼14.95 meV at 10 K resulting from potential fluctuation and band tail states. The time-resolved photoluminescence (TRPL) curves showed a bi-exponential decay at low temperature. The fast decay time implied the presence of the localized excitons enhancing radiative recombination, while the quite slow one was due to the dominance of trapping mechanisms originating from cation vacancy complexes and the VIII-related complexes.

  15. 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.

  16. 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.

  17. Three-dimensional metal-intercalated covalent organic frameworks for near-ambient energy storage

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Ding, Zijing; Meng, Sheng

    2013-05-01

    A new form of nanoporous material, metal intercalated covalent organic framework (MCOF) is proposed and its energy storage property revealed. Employing density functional and thermodynamical analysis, we find that stable, chemically active, porous materials could form by stacking covalent organic framework (COF) layers with metals as a gluing agent. Metal acts as active sites, while its aggregation is suppressed by a binding energy significantly larger than the corresponding cohesive energy of bulk metals. Two important parameters, metal binding and metal-metal separation, are tuned by selecting suitable building blocks and linkers when constructing COF layers. Systematic searches among a variety of elements and organic molecules identify Ca-intercalated COF with diphenylethyne units as optimal material for H2 storage, reaching a striking gravimetric density ~ 5 wt% at near-ambient conditions (300 K, 20 bar), in comparison to < 0.1 wt% for bare COF-1 under the same condition.

  18. Three-dimensional metal-intercalated covalent organic frameworks for near-ambient energy storage

    PubMed Central

    Gao, Fei; Ding, Zijing; Meng, Sheng

    2013-01-01

    A new form of nanoporous material, metal intercalated covalent organic framework (MCOF) is proposed and its energy storage property revealed. Employing density functional and thermodynamical analysis, we find that stable, chemically active, porous materials could form by stacking covalent organic framework (COF) layers with metals as a gluing agent. Metal acts as active sites, while its aggregation is suppressed by a binding energy significantly larger than the corresponding cohesive energy of bulk metals. Two important parameters, metal binding and metal-metal separation, are tuned by selecting suitable building blocks and linkers when constructing COF layers. Systematic searches among a variety of elements and organic molecules identify Ca-intercalated COF with diphenylethyne units as optimal material for H2 storage, reaching a striking gravimetric density ~ 5 wt% at near-ambient conditions (300 K, 20 bar), in comparison to < 0.1 wt% for bare COF-1 under the same condition. PMID:23698018

  19. Site characteristics in metal organic frameworks for gas adsorption

    NASA Astrophysics Data System (ADS)

    Uzun, Alper; Keskin, Seda

    2014-02-01

    Metal organic frameworks (MOFs) are a new class of nanoporous materials that have many potential advantages over traditional nanoporous materials for several chemical technologies including gas adsorption, catalysis, membrane-based gas separation, sensing, and biomedical devices. Knowledge on the interaction of guest molecules with the MOF surface is required to design and develop these MOF-based processes. In this review, we examine the importance of identification of gas adsorption sites in MOFs using the current state-of-the-art in experiments and computational modeling. This review provides guidelines to design new MOFs with useful surface properties that exhibit desired performances, such as high gas storage capacity, and high gas selectivity.

  20. Advanced Organic Ligands for Protecting Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Jonathan Ka-Wing

    Organic monolayer protected metal nanoparticles have been utilized in many different fields such as catalysis, drug delivery, and sensor chemistry. However, these nanomaterials are prone to increase in size consequently losing its function at the nanoscale. The stability these nanoparticles have been a great interest of research. This thesis focuses on the synthesis of a novel cross-linkable ligand for the protection of metal nanoparticles. Chapter 1 reviews key concepts of nanoparticles, its usefulness in applications, some of the stabilizing strategies employed, and the scope of the thesis project. Chapter 2 describes the synthetic attempts and optimization of the novel cross-linkable ligand. In addition, its characterization data is also included. Section 2.8 also highlights another fully synthesized novel hydrophobic ligand. Chapter 3 contains the summary of the work and closing remarks. Future works is also included to describe the prospects of the synthesis of the novel ligand. Chapter 4 entails the experimental data and supplementary information.

  1. Increasing the Stability of Metal-Organic Frameworks

    DOE PAGES

    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

  2. Lanthanide Metal-Organic Framework Materials

    NASA Astrophysics Data System (ADS)

    Hsieh, Ping-Yen; Green, Mark A.; Briber, Robert M.

    2009-03-01

    A series of lanthanide metal-organic framework materials (MOF) with variable organic linkages including benzene-dicarboxylic acid (BDC); 1,3,5-benzene-tricarboxylic acid (BTC); and 1,3,5-tris(4-carboxyphenyl)benzene (BTB) have been synthesized. The low density and high porosity of MOFs make them candidates molecular sieve or hydrogen storage materials. The crystal structures have been determined using a combination of single crystal X-ray diffractometer and synchrotron powder X-ray diffraction work. Holmium with the BDC ligand material (Ho-BDC) crystallizes in a monoclinic C2/c space group, with lattice parameters of a = 17.06 å, b = 10.67 å, c = 10.57 å, b = 96.12^o. The crystal structure of Ho-BTC is in tetragonal P 41 2 2 space group and Ho-BTB is in a triclinic P-1 space group. A comprehensive examination of Ho-MOF with different ligands by x-ray and thermogravimetric analysis shows that there is a stable nanoporous structure for dehydrated Ho-BTC up to 250^oC. The same phenomenon is not observed in the Ho-BDC and Ho-BTB materials. The collapsed structure with BDC and BTB indicates the stability of dehydrated samples is strongly related to the interactions between the metal and the organic linkers.

  3. 40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Manufacturing Industry Chemicals 1 Table 1 to Subpart F of Part 63 Protection of Environment ENVIRONMENTAL... Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table 1 Table 1 to Subpart F of Part 63—Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical name a CAS No. b Group...

  4. 40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Manufacturing Industry Chemicals 1 Table 1 to Subpart F of Part 63 Protection of Environment ENVIRONMENTAL... Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table 1 Table 1 to Subpart F of Part 63—Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical name a CAS No. b Group...

  5. 40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Manufacturing Industry Chemicals 1 Table 1 to Subpart F of Part 63 Protection of Environment ENVIRONMENTAL... Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table 1 Table 1 to Subpart F of Part 63—Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical name a CAS No. b Group...

  6. 40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Manufacturing Industry Chemicals 1 Table 1 to Subpart F of Part 63 Protection of Environment ENVIRONMENTAL... Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table 1 Table 1 to Subpart F of Part 63—Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical name a CAS No. b Group...

  7. 40 CFR Table 1 to Subpart F of... - Synthetic Organic Chemical Manufacturing Industry Chemicals

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Manufacturing Industry Chemicals 1 Table 1 to Subpart F of Part 63 Protection of Environment ENVIRONMENTAL... Synthetic Organic Chemical Manufacturing Industry Pt. 63, Subpt. F, Table 1 Table 1 to Subpart F of Part 63—Synthetic Organic Chemical Manufacturing Industry Chemicals Chemical name a CAS No. b Group...

  8. 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.

  9. 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.

  10. Hydrogen storage in metal-organic frameworks.

    PubMed

    Hu, Yun Hang; Zhang, Lei

    2010-05-25

    Metal-organic frameworks (MOFs) are highly attractive materials because of their ultra-high surface areas, simple preparation approaches, designable structures, and potential applications. In the past several years, MOFs have attracted worldwide attention in the area of hydrogen energy, particularly for hydrogen storage. In this review, the recent progress of hydrogen storage in MOFs is presented. The relationships between hydrogen capacities and structures of MOFs are evaluated, with emphasis on the roles of surface area and pore size. The interaction mechanism between H(2) and MOFs is discussed. The challenges to obtain a high hydrogen capacity at ambient temperature are explored.

  11. 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.

  12. Chemically diverse and multifunctional hybrid organic-inorganic perovskites

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Zheming; Deschler, Felix; Gao, Song; Friend, Richard H.; Cheetham, Anthony K.

    2017-02-01

    Hybrid organic-inorganic perovskites (HOIPs) can have a diverse range of compositions including halides, azides, formates, dicyanamides, cyanides and dicyanometallates. These materials have several common features, including their classical ABX3 perovskite architecture and the presence of organic amine cations that occupy the A-sites. Current research in HOIPs tends to focus on metal halide HOIPs, which show promise for use in solar cells and optoelectronic devices; however, the other subclasses also exhibit a diverse range of physical properties. In this Review, we summarize the chemical variability and structural diversity of all known HOIP subclasses. We also present a comprehensive account of their intriguing physical properties, including photovoltaic and optoelectronic properties, dielectricity, magnetism, ferroelectricity, ferroelasticity and multiferroicity. Moreover, we discuss the current challenges and future opportunities in this exciting field.

  13. Chemical alteration of extraterrestrial organics during atmospheric entry of micrometeorites

    NASA Astrophysics Data System (ADS)

    Kress, M.; Brownlee, D.

    Most of the extraterrestrial carbon accreted by Earth is carried by the 40,000 tons of ~0.2 mm micrometeorites that enter the atmosphere every year. Particles in this size range would have supplied an enormous amount of carbon to the inchoate biosphere since the exogenous influx at ~4 Ga would have been much higher than today. However, these particles undergo strong drag heating to ~1500 K for several seconds upon atmospheric entry, ostensibly burning away all the organics as CO. Ironically, particles of this size seemed to contribute no organic carbon to Earth despite the fact that they constitute the bulk of the total incoming mass. Conventional wisdom has thus held that organics survive only in smaller cosmic dust grains and in >~cm-sized meteorites, which account for only a tiny fraction of the total exogenous mass flux. However, carbon has been found in several smaller, yet still strongly-heated particles in the form of a refractory, char-like material imbedded with tiny FeNi metal beads, motivating us to study the pyrolysis of complex organic matter. We will present results from experiments and chemical models of the transient drag heating of micrometeorites. We predict that small aromatics, light hydrocarbons, and other organics, as well as CO and char, are formed, indicating that strongly-heated micrometeorites may have indeed been a significant source of organic carbon during the origin of life on Earth.

  14. Contamination and galvanic corrosion in metal chemical-mechanical planarization

    NASA Astrophysics Data System (ADS)

    Zhang, Liming

    Chemical mechanical planarization (CMP) of metals is a critical process in the manufacturing of ultra-large scale integrated (ULSI) circuit devices. The overall success of a CMP process requires minimal particulate and metallic contamination of the structures subjected to CMP. The objective of this study was to investigate alumina particle contamination during tungsten CMP, copper contamination in copper CMP, and galvanic corrosion between metal films and adhesion layers during the final stages of tungsten and copper CMP. Particular attention was paid to the use of short chain organic carboxylic acids in reducing the contamination. Both electrokinetic and uptake measurements showed that citric acid and malonic acid interact with alumina particles by electrostatic as well as specific adsorption forces. Systematic immersion contamination and polishing experiments were carried out to demonstrate the effectiveness of the acids in controlling alumina particulate contamination on wafer surfaces. The difference in the surface cleanliness was interpreted using the electrokinetic data and the calculated interaction energy between alumina particles and the wafer surface. Electrochemical tests showed no severe attack on tungsten films by the acids. Copper ions were found to adsorb onto the silicon dioxide surface, leading to copper contamination levels of upto 1013 atoms/cm 2. The extent of copper contamination was found to depend on the solution pH and the presence of additives such as hydrogen peroxide. Both electrokinetic measurements and immersion contamination experiments showed that citric acid can reduce the copper contamination on the silicon dioxide surface. TiN is more noble than tungsten in the solutions containing oxidants used in tungsten CMP slurries. The most significant corrosion of tungsten was found in the presence of hydrogen peroxide. Copper was found to be more noble than tantalum in acidic solutions. However, in alkaline ammonium hydroxide solutions, the

  15. 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

  16. Stepwise Synthesis of Metal-Organic Frameworks.

    PubMed

    Bosch, Mathieu; Yuan, Shuai; Rutledge, William; Zhou, Hong-Cai

    2017-03-28

    Metal-organic frameworks (MOFs) are a category of porous materials that offer unparalleled control over their surface areas (demonstrated as higher than for any other material), pore characteristics, and functionalization. This allows them to be customized for exceptional performance in a wide variety of applications, most commonly including gas storage and separation, drug delivery, luminescence, or heterogeneous catalysis. In order to optimize biomimicry, controlled separations and storage of small molecules, and detailed testing of structure-property relationships, one major goal of MOF research is "rational design" or "pore engineering", or precise control of the placement of multiple functional groups in pores of chosen sizes and shapes. MOF crystal growth can be controlled through judicious design of stepwise synthetic routes, which can also allow functionalization of MOFs in ways that were previously synthetically inaccessible. Organic chemists have developed a library of powerful techniques over the last century, allowing the total synthesis and detailed customization of complex molecules. Our hypothesis is that total synthesis is also possible for customized porous materials, through the development of similar multistep techniques. This will enable the rational design of MOFs, which is a major goal of many researchers in the field. We have begun developing a library of stepwise synthetic techniques for MOFs, allowing the synthesis of ultrastable MOFs with multiple crystallographically ordered and customizable functional groups at controlled locations within the pores. In order to design MOFs with precise control over pore size and shape, stability, and the placement of multiple different functional groups within the pores at tunable distances from one another, we have concentrated on methods which allow us to circumvent the lack of control inherent to one-pot MOF crystallization. Kinetically tuned dimensional augmentation (KTDA) is an approach using

  17. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.

    2017-02-07

    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

  18. 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.

  19. 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.

  20. Metal nano-film resistivity chemical sensor.

    PubMed

    Podešva, Pavel; Foret, František

    2016-02-01

    In this work, we present a study on reusable thin metal film resistivity-based sensor for direct measurement of binding of thiol containing molecules in liquid samples. While in bulk conductors the DC current is not influenced by the surface events to a measureable degree in a thin metal layer the electrons close to the surface conduct a significant part of electricity and are influenced by the surface interactions. In this study, the thickness of the gold layer was kept below 100 nm resulting in easily measureable resistivity changes of the metal element upon a surface SH-groups binding. No further surface modifications were necessary. Thin film gold layers deposited on a glass substrate by vacuum sputtering were photolithographically structured into four sensing elements arranged in a Wheatstone bridge to compensate for resistance fluctuations due to the temperature changes. Concentrations as low 100 pM provided measureable signals. The surface after the measurement could be electrolytically regenerated for next measurements. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

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

    PubMed

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

    2013-09-03

    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

  3. 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.

  4. Controlling the magnetism of adsorbed metal-organic molecules

    NASA Astrophysics Data System (ADS)

    Kuch, Wolfgang; Bernien, Matthias

    2017-01-01

    Gaining control on the size or the direction of the magnetic moment of adsorbed metal-organic molecules constitutes an important step towards the realization of a surface-mounted molecular spin electronics. Such control can be gained by taking advantage of interactions of the molecule’s magnetic moment with the environment. The paramagnetic moments of adsorbed metal-organic molecules, for example, can be controlled by the interaction with magnetically ordered substrates. Metalloporphyrins and -phthalocyanines display a quasi-planar geometry, allowing the central metal ion to interact with substrate electronic states. This can lead to magnetic coupling with a ferromagnetic or even antiferromagnetic substrate. The molecule-substrate coupling can be mediated and controlled by insertion layers such as oxygen atoms, graphene, or nonmagnetic metal layers. Control on the magnetic properties of adsorbed metalloporphyrins or -phthalocyanines can also be gained by on-surface chemical modification of the molecules. The magnetic moment or the magnetic coupling to ferromagnetic substrates can be changed by adsorption and thermal desorption of small molecules that interact with the fourfold-coordinated metal center via the remaining axial coordination site. Spin-crossover molecules, which possess a metastable spin state that can be switched by external stimuli such as temperature or light, are another promising class of candidates for control of magnetic properties. However, the immobilization of such molecules on a solid surface often results in a quench of the spin transition due to the interaction with the substrate. We present examples of Fe(II) spin-crossover complexes in direct contact with a solid surface that undergo a reversible spin-crossover transition as a function of temperature, by illumination with visible light, or can be switched by the tip of a scanning tunneling microscope.

  5. Controlling the magnetism of adsorbed metal-organic molecules.

    PubMed

    Kuch, Wolfgang; Bernien, Matthias

    2017-01-18

    Gaining control on the size or the direction of the magnetic moment of adsorbed metal-organic molecules constitutes an important step towards the realization of a surface-mounted molecular spin electronics. Such control can be gained by taking advantage of interactions of the molecule's magnetic moment with the environment. The paramagnetic moments of adsorbed metal-organic molecules, for example, can be controlled by the interaction with magnetically ordered substrates. Metalloporphyrins and -phthalocyanines display a quasi-planar geometry, allowing the central metal ion to interact with substrate electronic states. This can lead to magnetic coupling with a ferromagnetic or even antiferromagnetic substrate. The molecule-substrate coupling can be mediated and controlled by insertion layers such as oxygen atoms, graphene, or nonmagnetic metal layers. Control on the magnetic properties of adsorbed metalloporphyrins or -phthalocyanines can also be gained by on-surface chemical modification of the molecules. The magnetic moment or the magnetic coupling to ferromagnetic substrates can be changed by adsorption and thermal desorption of small molecules that interact with the fourfold-coordinated metal center via the remaining axial coordination site. Spin-crossover molecules, which possess a metastable spin state that can be switched by external stimuli such as temperature or light, are another promising class of candidates for control of magnetic properties. However, the immobilization of such molecules on a solid surface often results in a quench of the spin transition due to the interaction with the substrate. We present examples of Fe(II) spin-crossover complexes in direct contact with a solid surface that undergo a reversible spin-crossover transition as a function of temperature, by illumination with visible light, or can be switched by the tip of a scanning tunneling microscope.

  6. Hydrogen Storage in Metal-Organic Frameworks

    SciTech Connect

    Long, Jeffrey R.

    2016-04-28

    The design and characterization of new materials for hydrogen storage is an important area of research, as the ability to store hydrogen at lower pressures and higher temperatures than currently feasible would lower operating costs for small hydrogen fuel cell vehicles. In particular, metal-organic frameworks (MOFs) represent promising materials for use in storing hydrogen in this capacity. MOFs are highly porous, three-dimensional crystalline solids that are formed via linkages between metal ions (e.g., iron, nickel, and zinc) and organic molecules. MOFs can store hydrogen via strong adsorptive interactions between the gas molecules and the pores of the framework, providing a high surface area for gas adsorption and thus the opportunity to store hydrogen at significantly lower pressures than with current technologies. By lowering the energy required for hydrogen storage, these materials hold promise in rendering hydrogen a more viable fuel for motor vehicles, which is a highly desirable outcome given the clean nature of hydrogen fuel cells (water is the only byproduct of combustion) and the current state of global climate change resulting from the combustion of fossil fuels. The work presented in this report is the result of collaborative efforts between researchers at Lawrence Berkeley National Lab (LBNL), the National Institute of Standards and Technology (NIST), and General Motors Corporation (GM) to discover novel MOFs promising for H2 storage and characterize their properties. Described herein are several new framework systems with improved gravimetric and volumetric capacity to strongly bind H2 at temperatures relevant for vehicle storage. These materials were rigorously characterized using neutron diffraction, to determine the precise binding locations of hydrogen within the frameworks, and high-pressure H2 adsorption measurements, to provide a comprehensive picture of H2 adsorption at all relevant pressures. A

  7. 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.

  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. 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.

  10. 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.

  11. Chemical abundances in metal-poor stars in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim; Norris, John; Shetrone, Matthew

    2015-08-01

    Stars in low-mass dwarf galaxies show a larger range in their chemical properties than those in the Milky Way halo. Not only are alpha-poor stars found at lower metallicities, but also r-process challenged stars, and a disparate fraction of carbon-enhanced metal-poor stars. A more pristine and chemically inhomogeneous interstellar medium, combined with stoichastic star formation in a metal-poor environment, is thought to cause these detectable differences in the early SN II contributions. We are also now finding stars in dwarf galaxies that appear to be iron-enhanced, i.e., stars that have formed in pockets of SN Ia enriched gas. A comparison of their chemical abundances with individual SN Ia models can provide unique constraints on the SN Ia progenitors.

  12. Redox-promoted associative assembly of metal-organic materials.

    PubMed

    Glavinović, Martin; Qi, Feng; Katsenis, Athanassios D; Friščić, Tomislav; Lumb, Jean-Philip

    2016-01-01

    We develop an associative synthesis of metal-organic materials that combines solid-state metal oxidation and coordination-driven self-assembly into a one-step, waste-free transformation. The methodology hinges on the unique reactivity of ortho-quinones, which we introduce as versatile oxidants for mechanochemical synthesis. Our strategy opens a previously unexplored route to paramagnetic metal-organic materials from elementary metals.

  13. 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)).

  14. Metal-Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal-Organic Framework.

    PubMed

    Cliffe, Matthew J; Castillo-Martínez, Elizabeth; Wu, Yue; Lee, Jeongjae; Forse, Alexander C; Firth, Francesca C N; Moghadam, Peyman Z; Fairen-Jimenez, David; Gaultois, Michael W; Hill, Joshua A; Magdysyuk, Oxana V; Slater, Ben; Goodwin, Andrew L; Grey, Clare P

    2017-04-19

    We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed "double cluster" (Hf12O8(OH)14), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal-organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal-organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials.

  15. 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.

  16. Proton-Conducting Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Ford, Jamie; Simmons, Jason; Yildirim, Taner

    2010-03-01

    Vehicles powered by polymer electrolyte membrane (PEM) fuel cells are an exciting alternative to current fossil fuel technology. The membranes in these cells serve as both charge transporter, ferrying protons from the anode to the cathode, and gas diffusion barrier, preventing the backflow of oxygen to the anode. Currently, hydrated sulfonated polymers are the preferred material for these membranes. The presence of water, however, limits the operating temperature to 100 C, reducing the electrode kinetics and CO tolerance of the entire system. In an effort to increase the efficiency and operating temperature of these fuel cells, we are investigating the proton conductivity of new host/guest materials based on metal-organic frameworks (MOFs) loaded with imidazole. These thermally stable frameworks provide well-defined pores that accommodate imidazole networks and form proton-conducting pathways. Here, we will present the structure and proton dynamics of these materials as elucidated by elastic and inelastic neutron scattering measurements.

  17. 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.

  18. 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.

  19. Heterogeneous processes affecting metal ion transport in the presence of organic ligands: Reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Kantar, Cetin

    2007-04-01

    The development of models to accurately simulate metal ion transport through saturated systems under variable chemical conditions, e.g., in systems containing organic ligands (L) such as natural organic matter (NOM), has two essential aspects: (1) establishing the ability to simulate metal ion sorption to aquifer solids over a range of metal/ligand ratios; and (2) to incorporate this ability to simulate metal speciation over a range in chemical conditions (e.g., pH, ligand activity) into mass transport models. Modeling approaches to evaluate metal ion sorption and transport in the presence of NOM include: (1) isotherm-based transport models, and (2) multicomponent (MC) transport models. The accuracy of transport models depends on how well the chemical interactions affecting metal ion transport in the presence of organic ligands (e.g., metal/ligand complexation) are described in transport equations. The isotherm-based transport models often fail to accurately describe metal ion transport in the presence of NOM since these models treat NOM as a single solute despite the fact that NOM is a multicomponent mixture of subcomponents with different chemical and polyfunctional behavior. On the other hand, the calculations presented in this study suggest that a multicomponent reactive transport model, in conjunction with a mechanistic modeling approach for the description of metal ion binding by NOM in a manner conducive to the application of surface complexation modeling (SCM), can effectively be used as an important predictive tool in simulating metal ion sorption and transport under variable chemical conditions in the presence of NOM.

  20. Recent applications of metal-organic frameworks in sample pretreatment.

    PubMed

    Wang, Yonghua; Rui, Min; Lu, Guanghua

    2017-06-19

    Metal-organic frameworks are promising materials in diverse analytical applications especially in sample pretreatment by virtue of their diverse structure topology, tunable pore size, permanent nanoscale porosity, high surface area, and good thermostability. According to hydrostability, metal-organic frameworks are divided into moisture-sensitive and water-stable types. In the actual applications, both kinds of metal-organic frameworks are usually engineered into hybrid composites containing magnetite, silicon dioxide, graphene, or directly carbonized to metal-organic frameworks derived carbon. These metal-organic frameworks based materials show good extraction performance to environmental pollutants. This review provides a critical overview of the applications of metal-organic frameworks and their composites in sample pretreatment modes, that is, solid-phase extraction, magnetic solid-phase extraction, micro-solid-phase extraction, solid-phase microextraction, and stir bar solid extraction. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

  2. 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.

  3. Metal-Organic Frameworks as Micromotors with Tunable Engines and Brakes.

    PubMed

    Li, Jinxing; Yu, Xiao; Xu, Mingli; Liu, Wenjuan; Sandraz, Elodie; Lan, Hsin; Wang, Joseph; Cohen, Seth M

    2017-01-18

    Herein, we report that UiO-type (UiO = University of Oslo) metal-organic frameworks (MOFs) can be transformed into self-propelled micromotors by employing several different metal-based propulsion systems. Incorporation of a bipyridine ligand into the UiO-67 lattice transforms the crystallites, upon metalation, into single-site, metal-based catalytic "engines" to power the micromotors with chemical fuel. The "engine performance" (i.e., propulsion) of the single-site powered micromotors has been tuned by the choice of the metal ion utilized. In addition, a chemical "braking" system was achieved by adding chelating agents capable of sequestering the metal ion engines and thereby suppressing the catalytic activity, with different chelators displaying different deceleration capacities. These results demonstrate that MOFs can be powered by various engines and halted by different brakes, resulting in a high degree of motion design and control at the nanoscale.

  4. 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…

  5. 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…

  6. 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.

  7. 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.

  8. Metal ion sorption by untreated and chemically treated biomass

    SciTech Connect

    Kilbane, J.J.; Xie, J.

    1992-12-31

    The metal-binding ability of biosorbents is well known; however, in comparison with commercial ion-exchange resins the capacity of biosorbents is low. The purpose of this research was to examine chemically modified biosorbents and biosorbents prepared from microorganisms isolated from extreme environments to determine if significant improvements in metal-binding capacity or biosorbents with unique capabilities could be produced. Chemical treatments examined included acid, alkali, carbon disulfide, phosphorus oxychloride, anhydrous formamide, sodium thiosulfate, sodium chloroacetic acid, and phenylsulfonate. Biosorbents were prepared from microorganisms isolated from pristine and acid mine drainage impacted sites and included heterotrophs, methanotrophs, algae, and sulfate reducers. Chemical modification with carbon disulfide, phosphorous oxychloride, and sodium thiosulfate yielded biosorbents with such as much as 74%, 133%, and 155% improvements, respectively, in metal-binding capacity, but the performance of these chemically modified biosorbents deteriorated upon repeated use. A culture isolated from an acid mine drainage impacted site, IGTM17, exhibits about 3-fold higher metal-binding capacity in comparison with other biosorbents examined in this study. IGTM17 also exhibits superior metal-binding ability at decreased pH or in the presence of interfering common cations in comparison with other biosorbents or some commercially available cation exchange resins. Some biosorbents, such as IGTM5, can bind anions. To our knowledge this is the first demonstration of the ability of biosorbents to bind anions. Moreover, preliminary data indicate that the chemical modification of biosorbents may be capable of imparting the ability to selectively bind certain anions. Further research is needed to optimize conditions for the chemical modification and stabilization of biosorbents.

  9. Catalytic activity of noble metals for metal-assisted chemical etching of silicon

    PubMed Central

    2012-01-01

    Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias. We have been studying the metal-assisted hydrofluoric acid etching of silicon using dissolved oxygen as an oxidizing agent. Three major factors control the etching reaction and the porous silicon structure: photoillumination during etching, oxidizing agents, and metal particles. In this study, the influence of noble metal particles, silver, gold, platinum, and rhodium, on this etching is investigated under dark conditions: the absence of photogenerated charges in the silicon. The silicon dissolution is localized under the particles, and nanopores are formed whose diameters resemble the size of the metal nanoparticles. The etching rate of the silicon and the catalytic activity of the metals for the cathodic reduction of oxygen in the hydrofluoric acid solution increase in the order of silver, gold, platinum, and rhodium. PMID:22738277

  10. 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.

  11. A generalized physiologically-based toxicokinetic modeling system for chemical mixtures containing metals

    PubMed Central

    2010-01-01

    Background Humans are routinely and concurrently exposed to multiple toxic chemicals, including various metals and organics, often at levels that can cause adverse and potentially synergistic effects. However, toxicokinetic modeling studies of exposures to these chemicals are typically performed on a single chemical basis. Furthermore, the attributes of available models for individual chemicals are commonly estimated specifically for the compound studied. As a result, the available models usually have parameters and even structures that are not consistent or compatible across the range of chemicals of concern. This fact precludes the systematic consideration of synergistic effects, and may also lead to inconsistencies in calculations of co-occurring exposures and corresponding risks. There is a need, therefore, for a consistent modeling framework that would allow the systematic study of cumulative risks from complex mixtures of contaminants. Methods A Generalized Toxicokinetic Modeling system for Mixtures (GTMM) was developed and evaluated with case studies. The GTMM is physiologically-based and uses a consistent, chemical-independent physiological description for integrating widely varying toxicokinetic models. It is modular and can be directly "mapped" to individual toxicokinetic models, while maintaining physiological consistency across different chemicals. Interaction effects of complex mixtures can be directly incorporated into the GTMM. Conclusions The application of GTMM to different individual metals and metal compounds showed that it explains available observational data as well as replicates the results from models that have been optimized for individual chemicals. The GTMM also made it feasible to model toxicokinetics of complex, interacting mixtures of multiple metals and nonmetals in humans, based on available literature information. The GTMM provides a central component in the development of a "source-to-dose-to-effect" framework for modeling

  12. 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...

  13. 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

    2014-01-09

    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

  14. 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

  15. 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

  16. The chemical form of metallic debris in tissues surrounding metal-on-metal hips with unexplained failure.

    PubMed

    Hart, Alister J; Quinn, Paul D; Sampson, Barry; Sandison, Ann; Atkinson, Kirk D; Skinner, John A; Powell, Jonathan J; Mosselmans, J Fred W

    2010-11-01

    Implant-derived material from metal-on-metal (MOM) hip arthroplasties may be responsible for an unexplained tissue inflammatory response. The chemical form of the metal species in the tissues is predominantly chromium (Cr), but the currently used techniques have not been able to determine whether this is Cr(III) phosphate or Cr(III) oxide. The analytical challenge must overcome the fact that the metal in the tissues is at a relatively low concentration and tissue preparation or the microscopy beam used can affect the results. Microfocus X-ray spectroscopy using a synchrotron beam is useful in addressing both these issues. Using this technique we compared tissue from failed MOM hips with: (1) tissue from metal-on-polyethylene (MOP) hips; (2) chemical standards; (3) metal discs cut from MOM hips. The most abundant implant-related species in all MOM hip tissues contained Cr. Comparison with standards revealed the chemical form was Cr(III) phosphate, which did not vary with manufacturer type (four types analysed) or level of blood metal ions. Cobalt (Co) and molybdenum (Mo) were occasionally present in areas of high Cr. Co was normally found in a metallic state in the tissue, while Mo was found in an oxidized state. The variety of metallic species may have arisen from corrosion, wear or a combination of both. No evidence of Cr(VI) was seen in the tissues examined.

  17. Highly mesoporous metal-organic framework assembled in a switchable solvent.

    PubMed

    Peng, Li; Zhang, Jianling; Xue, Zhimin; Han, Buxing; Sang, Xinxin; Liu, Chengcheng; Yang, Guanying

    2014-07-22

    The mesoporous metal-organic frameworks are a family of materials that have pore sizes ranging from 2 to 50 nm, which have shown promising applications in catalysis, adsorption, chemical sensing and so on. The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy. Here we report the template-free assembly of mesoporous metal-organic frameworks by using CO2-expanded liquids as switchable solvents. The mesocellular metal-organic frameworks with large mesopores (13-23 nm) are formed, and their porosity properties can be easily adjusted by controlling CO2 pressure. Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction. The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

  18. Highly mesoporous metal-organic framework assembled in a switchable solvent

    NASA Astrophysics Data System (ADS)

    Peng, Li; Zhang, Jianling; Xue, Zhimin; Han, Buxing; Sang, Xinxin; Liu, Chengcheng; Yang, Guanying

    2014-07-01

    The mesoporous metal-organic frameworks are a family of materials that have pore sizes ranging from 2 to 50 nm, which have shown promising applications in catalysis, adsorption, chemical sensing and so on. The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy. Here we report the template-free assembly of mesoporous metal-organic frameworks by using CO2-expanded liquids as switchable solvents. The mesocellular metal-organic frameworks with large mesopores (13-23 nm) are formed, and their porosity properties can be easily adjusted by controlling CO2 pressure. Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction. The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

  19. Metal-organic chemical vapor deposition of indium oxide based transparent conducting oxide thin films: Precursor synthesis, film growth and characterization, and their application in polymer light-emitting diode devices

    NASA Astrophysics Data System (ADS)

    Ni, Jun

    2005-07-01

    Four novel diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)2·(diamine)] can be synthesized in a single step reaction. Single crystal x-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these complexes are considerably greater than those of conventional solid/liquid zinc metal-organic chemical vapor deposition (MOCVD) precursors. Of the four complexes, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N '-diethylethylenediamine)zinc [Zn(hfa)2 ( N,N'-DEA)], is particularly effective in the growth of thin films of the transparent conducting oxide Zn- and Sn-doped In2O3 (ZITO) due to its superior volatility and low melting point of 64°C. ZITO (ZnInxSnyOz, 1.5 < x < 4.0, 0.5 < y < 2.5) thin films with In contents ranging from 40--70 cation % (a metastable phase) were grown by low pressure MOCVD using volatile precursors tris(2,2,6,6-tetramethyl-3,5-heptanedionato)indium [In(dpm) 3], bis(2,4-pentanedionato)tin [Sn(acac)2], and Zn(hfa) 2(N,N'-DEA). These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial ITO (Sn-doped indium oxide) films. They are more stable under acidic conditions than commercial ITO films as evidenced by XPS studies. Polymer light emitting diode (PLED) devices based on ZnIn 2.00Sn1.50Oz anode exhibit maximum light output of 4500 cd/m2 and current efficiency of 0.85 cd/A, which are 70% and 80% higher than those of PLED devices based on commercial ITO anode, respectively. The increased performance of ZITO based devices is attributed to the decreased reactivity of ZITO anode towards the acidic PEDOT-PSS hole injection layer compared to ITO anode. MITO (MgInxSnyOz, 6.0 < x < 16.0; 3.0 < y < 8.0, a metastable phase) thin films were grown by low-pressure MOCVD using volatile precursors In(dpm)3, Sn(acac)2, and bis(2,2,6,6-tetramethyl-3,5-heptanedionato)(tetramethylmethylenediamine)magnesium [Mg

  20. Metal-organic framework composites: from fundamentals to applications

    NASA Astrophysics Data System (ADS)

    Li, Shaozhou; Huo, Fengwei

    2015-04-01

    Metal-organic frameworks (MOFs) are a class of crystallized porous polymeric materials consisting of metal ions or clusters linked together by organic bridging ligands. Due to their permanent porosity, rich surface chemistry and tuneable pore sizes, MOFs have emerged as one type of important porous solid and have attracted intensive interests in catalysis, gas adsorption, separation and storage over the past two decades. When compared with pure MOFs, the combination of MOFs with functional species or matrix materials not only shows enhanced properties, but also broadens the applications of MOFs in new fields, such as bio-imaging, drug delivery and electrical catalysis, owing to the interactions of the functional species/matrix with the MOF structures. Although the synthesis, chemical modification and potential applications of MOFs have been reviewed previously, there is an increasing awareness on the synthesis and applications of their composites, which have rarely been reviewed. This review aims to fill this gap and discuss the fabrication, properties, and applications of MOF composites. The remaining challenges and future opportunities in this field, in terms of processing techniques, maximizing composite properties, and prospects for applications, have also been indicated.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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 ˜10 nm. A significant interface-derived signal showing a strong chemical interaction is observed for Au deposited onto a C60 film, while there is no such additional feature for copper phthalocyanine deposited onto a C60 film reflecting the weak interaction between the molecules in the latter case. A depth analysis with HAXPES reveals that a Au-C60 intermixed layer with a thickness of 5.1 nm is formed at the interface.

  3. Metal-organic frameworks for membrane-based separations

    NASA Astrophysics Data System (ADS)

    Denny, Michael S.; Moreton, Jessica C.; Benz, Lauren; Cohen, Seth M.

    2016-12-01

    As research into metal-organic frameworks (MOFs) enters its third decade, efforts are naturally shifting from fundamental studies to applications, utilizing the unique features of these materials. Engineered forms of MOFs, such as membranes and films, are being investigated to transform laboratory-synthesized MOF powders to industrially viable products for separations, chemical sensors and catalysts. Following encouraging demonstrations of gas separations using MOF-based membranes, liquid-phase separations are now being explored in an effort to build effective membranes for these settings. In this Review, we highlight MOF applications that are in their nascent stages, specifically liquid-phase separations using MOF-based mixed-matrix membranes. We also highlight the analytical techniques that provide important insights into these materials, particularly at surfaces and interfaces, to better understand MOFs and their interactions with other materials, which will ultimately lead to their use in advanced technologies.

  4. Structure and properties of an amorphous metal-organic framework.

    PubMed

    Bennett, Thomas D; Goodwin, Andrew L; Dove, Martin T; Keen, David A; Tucker, Matthew G; Barney, Emma R; Soper, Alan K; Bithell, Erica G; Tan, Jin-Chong; Cheetham, Anthony K

    2010-03-19

    ZIF-4, a metal-organic framework (MOF) with a zeolitic structure, undergoes a crystal-amorphous transition on heating to 300 degrees C. The amorphous form, which we term a-ZIF, is recoverable to ambient conditions or may be converted to a dense crystalline phase of the same composition by heating to 400 degrees C. Neutron and x-ray total scattering data collected during the amorphization process are used as a basis for reverse Monte Carlo refinement of an atomistic model of the structure of a-ZIF. The structure is best understood in terms of a continuous random network analogous to that of a-SiO2. Optical microscopy, electron diffraction and nanoindentation measurements reveal a-ZIF to be an isotropic glasslike phase capable of plastic flow on its formation. Our results suggest an avenue for designing broad new families of amorphous and glasslike materials that exploit the chemical and structural diversity of MOFs.

  5. Structure and Properties of an Amorphous Metal-Organic Framework

    NASA Astrophysics Data System (ADS)

    Bennett, Thomas D.; Goodwin, Andrew L.; Dove, Martin T.; Keen, David A.; Tucker, Matthew G.; Barney, Emma R.; Soper, Alan K.; Bithell, Erica G.; Tan, Jin-Chong; Cheetham, Anthony K.

    2010-03-01

    ZIF-4, a metal-organic framework (MOF) with a zeolitic structure, undergoes a crystal-amorphous transition on heating to 300°C. The amorphous form, which we term a-ZIF, is recoverable to ambient conditions or may be converted to a dense crystalline phase of the same composition by heating to 400°C. Neutron and x-ray total scattering data collected during the amorphization process are used as a basis for reverse Monte Carlo refinement of an atomistic model of the structure of a-ZIF. The structure is best understood in terms of a continuous random network analogous to that of a-SiO2. Optical microscopy, electron diffraction and nanoindentation measurements reveal a-ZIF to be an isotropic glasslike phase capable of plastic flow on its formation. Our results suggest an avenue for designing broad new families of amorphous and glasslike materials that exploit the chemical and structural diversity of MOFs.

  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. 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.

  8. Natural Organic Matter-Promoted Metal Inhibition of Hematite Bioreduction

    NASA Astrophysics Data System (ADS)

    Stone, J. J.; Burgos, W. D.

    2003-12-01

    A developing technology for the in situ treatment of metal and radionuclide contaminants is the stimulation of dissimilatory metal-reducing bacteria (DMRB) to reduce solid phase iron oxides which promote Fe(II) induced chemical reduction of contaminants. Natural organic matter (NOM) can stimulate the biological reduction of solid-phase iron oxides by serving as an electron shuttle and by complexing biogenic Fe(II). The addition of NOM to contaminated zones has been proposed to further stimulate iron reduction and the fortuitous reduction and immobilization of contaminants. However, little research has been conducted on quarternary systems that contain DMRB, ferric oxides, NOM, and metals or radionuclides. The effect of zinc on the biological reduction of hematite and nitrate by the DMRB Shewanella putrefaciens strain CN32 was studied in the absence and presence of NOM. Nitrate was used to compare results between solid-phase and soluble electron acceptors. Previous work has demonstrated that, in the absence of zinc, NOM significantly enhanced hematite bioreduction but slightly inhibited nitrate reduction. In the absence of NOM, zinc was shown to significantly inhibit both hematite and nitrate bioreduction. In the presence of NOM, zinc inhibition of nitrate bioreduction was completely eliminated, presumably due to the NOMs' ability to complex Zn(II) and decrease Zn2+ activity. It was assumed that the presence of NOM would also decrease zinc inhibition of hematite reduction. Contrary to this hypothesis, NOM significantly increased the inhibitory effect of zinc during hematite bioreduction. In addition, non-toxic Mn(II) became inhibitory in the presence of NOM during hematite bioreduction. These results suggest that ternary Me(II)-NOM-oxide surface complexes may specifically inhibit solid-phase bioreduction. Thus, interactions between NOM and metal/radionuclide contaminants may effect the overall efficacy of the biostimulation remediation strategy.

  9. 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.

  10. 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.

  11. Zeolite-like metal-organic frameworks (ZMOFs) based on the directed assembly of finite metal-organic cubes (MOCs).

    PubMed

    Alkordi, Mohamed H; Brant, Jacilynn A; Wojtas, Lukasz; Kravtsov, Victor Ch; Cairns, Amy J; Eddaoudi, Mohamed

    2009-12-16

    Two zeolite-like metal-organic frameworks (ZMOFs) with lta- and ast- topologies, zeolitic nets that can be interpreted as augmented edge-transitive 8-connected nets, are targeted through directed self-assembly of metal-organic cubes (MOCs) as supermolecular building blocks (SBBs).

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

    PubMed

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

    2015-02-28

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

  13. 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

  14. 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…

  15. 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 ...

  16. 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…

  17. Uptake, Metabolism, and Tissue Distribution of Chemicals in Organisms

    EPA Science Inventory

    This talk will explain how chemicals get into aquatic species, what tissues and organs the chemicals move into, and what can happen to the chemicals once they get there. This will be presented using examples from recent studies conducted using state-of-the-art microscopy with em...

  18. Uptake, Metabolism, and Tissue Distribution of Chemicals in Organisms

    EPA Science Inventory

    This talk will explain how chemicals get into aquatic species, what tissues and organs the chemicals move into, and what can happen to the chemicals once they get there. This will be presented using examples from recent studies conducted using state-of-the-art microscopy with em...

  19. 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...

  20. 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...

  1. 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).

  2. 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

  3. Electrochemical study on metal corrosion in chemical mechanical planarization process

    NASA Astrophysics Data System (ADS)

    Kondo, Seiichi; Ichige, Yasuhiro; Otsuka, Yuya

    2017-07-01

    Typical metal corrosions caused by the chemical mechanical planarization (CMP) process are discussed in this review paper. By categorizing them into seven kinds of corrosion, namely, chemical corrosion, crevice corrosion, crystal-orientation-dependent corrosion, narrow trench corrosion, photocorrosion, galvanic corrosion, and electrostatic-charge induced corrosion, we discuss their mechanisms and how to suppress them on the basis of electrochemical studies. Moreover, we demonstrate the usefulness of three-dimensional pH-potential diagrams for predicting corrosion issues in an actual CMP process.

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

    DOEpatents

    Boatner, Lynn A [Oak Ridge, TN; Kolopus, James A [Clinton, TN; Neal, John S [Knoxville, TN; Ramey, Joanne Oxendine [Knoxville, TN; Wisniewski, Dariusz J [Torun, PL

    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.

  5. Alternative treatment of organic solvents and sludges from metal finishing operations. Final report

    SciTech Connect

    Hedley, W.H.; Cheng, S.C.; Desai, B.O.; Smith, C.S.; Toy, H.D. Jr.

    1983-09-01

    A description of the metal finishing industry and its use of organic chemicals, i.e. solvents, oils, and coatings, is given. The quantities and composition of wastes from these processes is estimated, as well as current technologies used to recover or dispose of them. Recommendations for improvements in techniques for recovery/reuse and disposal of these wastes are included.

  6. 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

    2015-01-02

    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.

  7. Metal-organic framework catalysts for selective cleavage of aryl-ether bonds

    DOEpatents

    Allendorf, Mark D.; Stavila, Vitalie

    2017-08-01

    The present invention relates to methods of employing a metal-organic framework (MOF) as a catalyst for cleaving chemical bonds. In particular instances, the MOF results in selective bond cleavage that results in hydrogenolyzis. Furthermore, the MOF catalyst can be reused in multiple cycles. Such MOF-based catalysts can be useful, e.g., to convert biomass components.

  8. Silicon nanowire photodetectors made by metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Xu, Ying; Ni, Chuan; Sarangan, Andrew

    2016-09-01

    Silicon nanowires have unique optical effects, and have potential applications in photodetectors. They can exhibit simple optical effects such as anti-reflection, but can also produce quantum confined effects. In this work, we have fabricated silicon photodetectors, and then post-processed them by etching nanowires on the incident surface. These nanowires were produced by a wet-chemical etching process known as the metal-assisted-chemical etching, abbreviated as MACE. N-type silicon substrates were doped by thermal diffusion from a solid ceramic source, followed by etching, patterning and contact metallization. The detectors were first tested for functionality and optical performance. The nanowires were then made by depositing an ultra-thin film of gold below its percolation thickness to produce an interconnected porous film. This was then used as a template to etch high aspect ratio nanowires into the face of the detectors with a HF:H2O2 mixture.

  9. 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.

  10. Chemically Reversible Reactions of Hydrogen Sulfide with Metal Phthalocyanines

    PubMed Central

    2015-01-01

    Hydrogen sulfide (H2S) is an important signaling molecule that exerts action on various bioinorganic targets. Despite this importance, few studies have investigated the differential reactivity of the physiologically relevant H2S and HS– protonation states with metal complexes. Here we report the distinct reactivity of H2S and HS– with zinc(II) and cobalt(II) phthalocyanine (Pc) complexes and highlight the chemical reversibility and cyclability of each metal. ZnPc reacts with HS–, but not H2S, to generate [ZnPc-SH]−, which can be converted back to ZnPc by protonation. CoPc reacts with HS–, but not H2S, to form [CoIPc]−, which can be reoxidized to CoPc by air. Taken together, these results demonstrate the chemically reversible reaction of HS– with metal phthalocyanine complexes and highlight the importance of H2S protonation state in understanding the reactivity profile of H2S with biologically relevant metal scaffolds. PMID:24785654

  11. 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.

  12. A pH-responsive cleavage route based on a metal-organic coordination bond.

    PubMed

    Xing, Lei; Zheng, Haoquan; Che, Shunai

    2011-06-20

    The physical or chemical event that generally causes stimuli responses is limited to the formation or destruction of secondary forces, such as hydrogen bonding, hydrophobic effects, electrostatic interactions, and simple reactions. Here, pH-responsive behavior of metal-organic coordination bonding, which is intrinsic to natural systems (e.g., transferrin recycling in cells), is becoming a strong candidate for a new stimulus-responsive route. We have designed a simple pH-responsive release system by integrating a metal ion and ligand or self-assembling these species with biodegradable host molecules to form nanoparticles with "metal-ligand" or "host-metal-ligand" architectures. The cleavage of either or both the "metal-ligand" or the "host-metal" coordination bond in response to pH variations causes significant damage to the nanoparticles and the subsequent release of ligand molecules under designated pH conditions.

  13. Electrocatalytic Metal-Organic Frameworks for Energy Applications.

    PubMed

    Downes, Courtney A; Marinescu, Smaranda C

    2017-10-02

    With global energy demand expected to rise drastically over the next several decades, the development of a sustainable energy system to meet this rise is paramount. Renewable energy sources can be coupled with electrochemical conversion processes to store energy in chemical bonds. To promote these difficult transformations, electrocatalysts that operate at high conversion rates and efficiency are required. Metal-organic frameworks (MOFs) have emerged as a promising class of materials, however, the insulating nature of MOFs has limited their application as electrocatalysts. The recent development of conductive MOFs has led to several electrocatalytic MOFs that display activity comparable to the best performing heterogeneous catalysts. Although many electrocatalytic MOFs exhibit low activity and stability, the few successful examples highlight the possibility of MOF electrocatalysts as replacements for noble-metal based catalysts in commercial energy converting devices. We review here the use of pristine MOFs as electrocatalysts to facilitate important energy-related reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Heavy metal content in sediments along the Calore river: relationships with physical-chemical characteristics.

    PubMed

    Bartoli, G; Papa, S; Sagnella, E; Fioretto, A

    2012-03-01

    In the present study, trace metals contents (V, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb) and physico-chemical parameters (nitrogen, organic and inorganic carbon, pH and particle size) in sediments samples along the Calore river were analyzed in two seasons. Sediment samples were collected in ten sites upstream and downstream of the city of Benevento and its industrial area, the confluence of Sabato and Tammaro tributaries, and the confluence of Calore and Volturno rivers. The highest contents of trace metals were found, generally, in the sites immediately downstream of industrial area and of Benevento city. The sites on the Tammaro and Sabato also showed relatively high contents of Ni and, only for Sabato sites, of Cr, and Fe. With the exception of Cd, the heavy metal contents were highest in the last site of Calore river, which therefore is a source of pollution to the Volturno river. Besides the sites downstream of Benevento city showed the higher pH values and also the highest contents of fine particles size and organic matter. Positive correlations among trace metals, organic substance, particle size sediments were found. The data obtained in this study were analyzed with reference to Interim Sediment Quality Guidelines and indicated moderate-to-high pollution by some trace metals (V, Cr, Mn, Fe, Ni, Cu).

  15. [Chemical hazards induced by heavy metals refining processes].

    PubMed

    Gaweda, Ewa

    2003-01-01

    Processes of refining heavy metals consist in removing impurities, which can be found in metals produced on industrial scale. People involved in heavy metals refining processes are primarily exposed to metals (Pb, Cd, Cu), metalloids (As, Se) and metal compounds. Exposure to dusts (from 2 to 50% SiO2) and sulfuric acid is an additional hazard. The air concentrations of harmful chemical agents at heavy metals refining stations in two Polish Plants are presented. Several tens of workers employed in the processes of copper, lead, nickel sulfate, zinc, cadmium and silver production were examined. Concentrations of Cd, Ni, Se, Cu, Pb, Ag, As and Sb were determined by atomic absorption spectrometry (AAS) with a graphite tube, whereas Fe, ZnO oxide (as Zn), MgO (as Mg) and CaO (as Ca) by AAS with air-acetylene flame, and sulfuric acid by method described in PN-91/Z-04056/02. Lead concentrations in the samples collected in both Plants were often high (significantly exceeding Polish MAC values at some workstations). Arsenic concentrations ranged from very low in all processes in one Plant to very high, exceeding Polish MAC values, at some workstations in the other. In general, air concentrations of other agents were not high (fraction of MAC). The occurrence of antimony and magnesium oxide was not determined. The risk created by metals and metalloids at the workstations in two Plants was diversified. There is no need to determine Sb and MgO in further studies. Lead should be determined at all workstations, other agents can be determined at workstations with concentrations exceeding the determinability of relevant methods.

  16. Metal mobilization from metallurgical wastes by soil organic acids.

    PubMed

    Potysz, Anna; Grybos, Malgorzata; Kierczak, Jakub; Guibaud, Gilles; Fondaneche, Patrice; Lens, Piet N L; van Hullebusch, Eric D

    2017-07-01

    Three types of Cu-slags differing in chemical and mineralogical composition (historical, shaft furnace, and granulated slags) and a matte from a lead recovery process were studied with respect to their susceptibility to release Cu, Zn and Pb upon exposure to organic acids commonly encountered in soil environments. Leaching experiments (24-960 h) were conducted with: i) humic acid (20 mg/L) at pH t0 = 4.4, ii) fulvic acid (20 mg/L) at pH t0 = 4.4, iii) an artificial root exudates (ARE) (17.4 g/L) solution at pH t0 = 4.4, iv) ARE solution at pH t0 = 2.9 and v) ultrapure water (pH t0 = 5.6). The results demonstrated that the ARE contribute the most to the mobilization of metals from all the wastes analyzed, regardless of the initial pH of the solution. For example, up to 14%, 30%, 24% and 5% of Cu is released within 960 h from historical, shaft furnace, granulated slags and lead matte, respectively, when exposed to the artificial root exudates solution (pH 2.9). Humic and fulvic acids were found to have a higher impact on granulated and shaft furnace slags as compared to the ultrapure water control and increased the release of metals by a factor up to 37.5 (Pb) and 20.5 (Cu) for granulated and shaft furnace slags, respectively. Humic and fulvic acids amplified the mobilization of metals by a maximal factor of 13.6 (Pb) and 12.1 (Pb) for historical slag and lead matte, respectively. The studied organic compounds contributed to different release rates of metallic contaminants from individual metallurgical wastes under the conditions tested. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Adsorption mechanisms of organic chemicals on carbon nanotubes.

    PubMed

    Pan, Bo; Xing, Baoshan

    2008-12-15

    Carbon nanotubes (CNTs) have drawn special research attention because of their unique properties and potential applications. This review summarizes the research progress of organic chemical adsorption on CNTs, and will provide useful information for CNT application and risk assessment. Adsorption heterogeneity and hysteresis are two widely recognized features of organic chemical-CNT interactions. However, because different mechanisms may act simultaneously, mainly hydrophobic interactions, pi-pi bonds, electrostatic interactions, and hydrogen bonds, the prediction of organic chemical adsorption on CNTs is not straightforward. The dominant adsorption mechanism is different for different types of organic chemicals (such as polar and nonpolar), thus different models may be needed to predict organic chemical-CNT interaction. Adsorption mechanisms will be better understood by investigating the effects of properties of both CNTs and organic chemicals along with environmental conditions. Another majorfactor affecting adsorption by CNTs is their suspendability, which also strongly affects their mobility, exposure, and risk in the environment. Therefore, organic chemical-CNT interactions as affected by CNT dispersion and suspending merit further experimental research. In addition, CNTs have potential applications in water treatment due to their adsorption characteristics. Thus column and pilot studies are needed to evaluate their performance and operational cost.

  18. Site-specific metal and ligand substitutions in a microporous Mn(2+)-based metal-organic framework.

    PubMed

    Huxley, Michael; Coghlan, Campbell J; Burgun, Alexandre; Tarzia, Andrew; Sumida, Kenji; Sumby, Christopher J; Doonan, Christian J

    2016-03-14

    The precise tuning of the structural and chemical features of microporous metal-organic frameworks (MOFs) is a crucial endeavour for developing materials with properties that are suitable for specific applications. In recent times, techniques for preparing frameworks consisting of mixed-metal or ligand compositions have emerged. However, controlled spatial organisation of the components within these structures at the molecular scale is a difficult challenge, particularly when species possessing similar geometries or chemical properties are used. Here, we describe the synthesis of mixed-metal and ligand variants possessing the Mn3L3 (Mn-MOF-1; H2L = bis(4-(4'-carboxyphenyl)-3,5-dimethylpyrazolyl)methane) structure type. In the case of mixed-ligand synthesis using a mixture of L and its trifluoromethyl-functionalised derivative (H2L' = bis(4-(4'-carboxyphenyl)-3,5-di(trifluoromethyl)pyrazolyl)methane), a mixed-ligand product in which the L' species predominanantly occupies the pillar sites lining the pores is obtained. Meanwhile, post-synthetic metal exchange of the parent Mn3L3 compound using Fe(2+) or Fe(3+) ions results in a degree of cation exchange at the trinuclear carboxylate-based clusters and metalation at the pillar bispyrazolate sites. The results demonstrate the versatility of the Mn3L3 structure type toward both metal and ligand substitutions, and the potential utility of site-specific functionalisations in achieving even greater precision in the tuning of MOFs.

  19. Metal-specific interactions of H2 adsorbed within isostructural metal-organic frameworks.

    PubMed

    FitzGerald, Stephen A; Burkholder, Brian; Friedman, Michael; Hopkins, Jesse B; Pierce, Christopher J; Schloss, Jennifer M; Thompson, Benjamin; Rowsell, Jesse L C

    2011-12-21

    Diffuse reflectance infrared (IR) spectroscopy performed over a wide temperature range (35-298 K) is used to study the dynamics of H(2) adsorbed within the isostructural metal-organic frameworks M(2)L (M = Mg, Mn, Co, Ni and Zn; L = 2,5-dioxidobenzene-1,4-dicarboxylate) referred to as MOF-74 and CPO-27. Spectra collected at H(2) concentrations ranging from 0.1 to 3.0 H(2) per metal cation reveal that strongly red-shifted vibrational modes arise from isolated H(2) bound to the available metal coordination site. The red shift of the bands associated with this site correlate with reported isosteric enthalpies of adsorption (at small surface coverage), which in turn depend on the identity of M. In contrast, the bands assigned to H(2) adsorbed at positions >3 Å from the metal site exhibit only minor differences among the five materials. Our results are consistent with previous models based on neutron diffraction data and independent IR studies, but they do not support a recently proposed adsorption mechanism that invokes strong H(2)···H(2) interactions (Nijem et al. J. Am. Chem. Soc.2010, 132, 14834-14848). Room temperature IR spectra comparable to those on which the recently proposed adsorption mechanism was based were only reproduced after contaminating the adsorbent with ambient air. Our interpretation that the uncontaminated spectral features result from stepwise adsorption at discrete framework sites is reinforced by systematic red shifts of adsorbed H(2) isotopologues and consistencies among overtone bands that are well-described by the Buckingham model of molecular interactions in vibrational spectroscopy. © 2011 American Chemical Society

  20. Quantification of Stereochemical Communication in Metal-Organic Assemblies.

    PubMed

    Castilla, Ana M; Miller, Mark A; Nitschke, Jonathan R; Smulders, Maarten M J

    2016-08-26

    The derivation and application of a statistical mechanical model to quantify stereochemical communication in metal-organic assemblies is reported. The factors affecting the stereochemical communication within and between the metal stereocenters of the assemblies were experimentally studied by optical spectroscopy and analyzed in terms of a free energy penalty per "incorrect" amine enantiomer incorporated, and a free energy of coupling between stereocenters. These intra- and inter-vertex coupling constants are used to track the degree of stereochemical communication across a range of metal-organic assemblies (employing different ligands, peripheral amines, and metals); temperature-dependent equilibria between diastereomeric cages are also quantified. The model thus provides a unified understanding of the factors that shape the chirotopic void spaces enclosed by metal-organic container molecules.

  1. Organic matter in hydrothermal metal ores and hydrothermal fluids

    USGS Publications Warehouse

    Orem, W.H.; Spiker, E. C.; Kotra, R.K.

    1990-01-01

    Massive polymetallic sulfides are currently being deposited around active submarine hydrothermal vents associated with spreading centers. Chemoautolithotrophic bacteria are responsible for the high production of organic matter also associated with modern submarine hydrothermal activity. Thus, there is a significant potential for organic matter/metal interactions in these systems. We have studied modern and ancient hydrothermal metal ores and modern hydrothermal fluids in order to establish the amounts and origin of the organic matter associated with the metal ores. Twenty-six samples from modern and ancient hydrothermal systems were surveyed for their total organic C contents. Organic C values ranged from 0.01% to nearly 4.0% in these samples. Metal ores from modern and ancient sediment-covered hydrothermal systems had higher organic C values than those from modern and ancient hydrothermal systems lacking appreciable sedimentary cover. One massive pyrite sample from the Galapagos spreading center (3% organic C) had stable isotope values of -27.4% (??13C) and 2.1% (??15N), similar to those in benthic siphonophors from active vents and distinct from seep sea sedimentary organic matter. This result coupled with other analyses (e.g. 13C NMR, pyrolysis/GC, SEM) of this and other samples suggests that much of the organic matter may originate from chemoautolithotrophic bacteria at the vents. However, the organic matter in hydrothermal metal ores from sediment covered vents probably arises from complex sedimentary organic matter by hydrothermal pyrolysis. The dissolved organic C concentrations of hydrothermal fluids from one site (Juan de Fuca Ridge) were found to be the same as that of background seawater. This result may indicate that dissolved organic C is effectively scavenged from hydrothermal fluids by biological activity or by co-precipitation with metal ores. ?? 1990.

  2. 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)

  3. 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)

  4. 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.

  5. 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...

  6. From metal-organic framework to intrinsically fluorescent carbon nanodots.

    PubMed

    Amali, Arlin Jose; Hoshino, Hideto; Wu, Chun; Ando, Masanori; Xu, Qiang

    2014-07-01

    Highly photoluminescent carbon nanodots (CNDs) were synthesized for the first time from metal-organic framework (MOF, ZIF-8) nanoparticles. Coupled with fluorescence and non-toxic characteristics, these carbon nanodots could potentially be used in biosafe color patterning.

  7. 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.

  8. 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...

  9. Porous materials: Lining up metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Champness, Neil R.

    2017-02-01

    A new report demonstrates an innovative approach to aligning crystallites of metal-organic frameworks such that thin films are created with oriented channels -- potentially overcoming one of the major barriers to application of these highly topical materials.

  10. Bulk micromachining of Si by metal-assisted chemical etching.

    PubMed

    Kim, Sang-Mi; Khang, Dahl-Young

    2014-09-24

    Bulk micromachining of Si is demonstrated by the well-known metal-assisted chemical etching (MaCE). Si microstructures, having lateral dimension from 5 μm up to millimeters, are successfully sculpted deeply into Si substrate, as deep as >100 μm. The key ingredient of this success is found to be the optimizations of catalyst metal type and its morphology. Combining the respective advantages of Ag and Au in the MaCE as a Ag/Au bilayer configuration leads to quite stable etch reaction upon a prolonged etch duration up to >5 h. Further, the permeable nature of the optimized Ag/Au bilayer metal catalyst enables the etching of pattern features having very large lateral dimension. Problems such as the generation of micro/nanostructures and chemical attacks on the top of pattern surface are successfully overcome by process optimizations such as post-partum sonication treatment and etchant formulation control. The method can also be successful to vertical micromachining of Si substrate having other crystal orientations than Si(100), such as Si(110) and Si(111). The simple, easy, and low-cost nature of present approach may be a great help in bulk micromachining of Si for various applications such as microelectromechanical system (MEMS), micro total analysis system (μTAS), and so forth. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. 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.

  12. 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.

  13. Metal-organic framework for the separation of alkane isomers

    DOEpatents

    Long, Jeffrey R.; Herm, Zoey R.; Wiers, Brian M.; Krishna, Rajamani

    2017-01-10

    A metal organic framework Fe.sub.2(bdp).sub.3 (BDP.sup.2-=1,4-benzenedipyrazolate) with triangular channels is particularly suited for C5-C7 separations of alkanes according to the number of branches in the molecule rather than by carbon number. The metal-organic framework can offer pore geometries that is unavailable in zeolites or other porous media, facilitating distinct types of shape-based molecular separations.

  14. 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

  15. Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

    DOEpatents

    Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

    2017-01-10

    A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

  16. Photoluminescence emission from Alq3 organic layer in metal-Alq3-metal plasmonic structure

    NASA Astrophysics Data System (ADS)

    Huang, Bohr-Ran; Liao, Chung-Chi; Fan, Wan-Ting; Wu, Jin-Han; Chen, Cheng-Chang; Lin, Yi-Ping; Li, Jung-Yu; Chen, Shih-Pu; Ke, Wen-Cheng; Chen, Nai-Chuan

    2014-06-01

    The emission properties of an organic layer embedded in a metal-organic-metal (MOM) structure were investigated. A partially radiative odd-SPW as well as a non-radiative even-SPW modes are supported by hybridization of the SPW modes on the opposite organic/metal interface in the structure. Because of the competition by this radiative SPW, the population of excitons that recombine to form non-radiative SPW should be reduced. This may account for why the photoluminescence intensity of the MOM sample is higher than that of an organic-metal sample even though the MOM sample has an additional metal layer that should intuitively act as a filter.

  17. 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...

  18. 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...

  19. Residual metallic contamination of transferred chemical vapor deposited graphene.

    PubMed

    Lupina, Grzegorz; Kitzmann, Julia; Costina, Ioan; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Vaziri, Sam; Östling, Mikael; Pasternak, Iwona; Krajewska, Aleksandra; Strupinski, Wlodek; Kataria, Satender; Gahoi, Amit; Lemme, Max C; Ruhl, Guenther; Zoth, Guenther; Luxenhofer, Oliver; Mehr, Wolfgang

    2015-05-26

    Integration of graphene with Si microelectronics is very appealing by offering a potentially broad range of new functionalities. New materials to be integrated with the Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etching and electrochemical delamination methods with respect to residual submonolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection X-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 10(13) atoms/cm(2). These metal impurities appear to be partially mobile upon thermal treatment, as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter electronic and electrochemical properties of graphene and can severely impede the process of integration with silicon microelectronics, these results reveal that further progress in synthesis, handling, and cleaning of graphene is required to advance electronic and optoelectronic applications.

  20. 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).

  1. BASIC CHEMICAL RESEARCH PROGRAM. ELECTRICAL PROPERTIES OF ORGANIC COMPOUNDS

    DTIC Science & Technology

    BENZENE, *CYANIDES, *HYDROXIDES, *ORGANIC COMPOUNDS, ACETYLENES, ALKYL RADICALS, AMIDES, ANILINES , BENZALDEHYDES, CHEMICAL REACTIONS , CONDENSATION... REACTIONS , ELECTRICAL CONDUCTIVITY, MATERIALS, MEASUREMENT, MONOCYCLIC COMPOUNDS, PHENOLS, PHENYL RADICALS, QUINONES, SOLID STATE PHYSICS, SYNTHESIS.

  2. Chemical and spectroscopic studies of metal oxide surfaces

    SciTech Connect

    Goodman, D.W.

    1996-05-01

    Thin oxide films (e.g., 5{endash}10 nm of SiO{sub 2}, Al{sub 2}O{sub 3}, NiO, MgO) supported on a refractory metal substrate (e.g., Mo, W, Ta, Re) have been prepared by deposition of the oxide metal precursor in a background of oxygen. The thin-film nature of these samples facilitates investigation by an array of surface techniques, many of which cannot be effectively utilized on the corresponding bulk oxide. The structural, electronic, and chemical properties of these films have been studied with temperature programmed desorption, Auger electron spectroscopy, X-ray photoelectron spectroscopy, ion scattering spectroscopy, high resolution electron energy loss spectroscopy, and infrared reflection absorption spectroscopy. The results of these studies demonstrate the viability of using thin oxide films as models for the corresponding bulk oxide. {copyright} {ital 1996 American Vacuum Society}

  3. Chemical composition variations in shielded metal arc welds

    SciTech Connect

    Bracarense, A.Q.; Liu, S. . Center for Welding and Joining Research)

    1993-12-01

    The use of shielded metal arc (SMA) welding can result in chemical composition variations along the weld length. Manganese and silicon, commonly found in low-carbon steel welds, change in composition with weld position. This research was performed to better characterize the composition variations observed in structural steel welds and to understand the controlling factors that determine the extent of these composition changes. Single bead-on-plate and multipass welds were performed and analyzed. Manganese, silicon, and oxygen contents showed significant variation along the weld length. To determine the cause of such composition variations, additional experiments were carried out with the welding arc established between the electrode and a water-cooled copper pipe. The individual metal droplets were collected in water and processed using standard particulate materials processing techniques to remove the slag covering. The droplet size distribution was determined and related to the composition variation and position along the weld length.

  4. Chemical and electrochemical interactions on corroding metal surfaces

    SciTech Connect

    Isaacs, H.S.; Aldykiewicz, A.J. Jr.

    1994-10-01

    The corrosion resistance of many metals and alloys depend on their ability to repassivate after breakdown of the passive film. Following breakdown localized corrosion takes place. The consequences of initiation events depends on many factors leading to a dissolution rate of the metal which may be continuous, intermittent or transitory. Major changes in the solution chemistry at the breakdown site must take place to enable active dissolution to take place and prevent repassivation. However, mass transfer of the dissolution products to the bulk environment often plays a decisive role. The composition of the environment is important. Some species inhibit while others stimulate the anodic dissolution. In the presence of particular cations, deposition slowly takes place on cathodic sites. Current density mapping measurements have been used to study pitting processes on iron and aluminum alloys. The effects of phosphate as an anodic inhibitor for steel and cerium as a cathodic inhibitor for aluminum are discussed in conjunction with related chemical processes.

  5. Reconfigurable electronics using conducting metal-organic frameworks

    DOEpatents

    Allendorf, Mark D.; Talin, Albert Alec; Leonard, Francois; Stavila, Vitalie

    2017-07-18

    A device including a porous metal organic framework (MOF) disposed between two terminals, the device including a first state wherein the MOF is infiltrated by a guest species to form an electrical path between the terminals and a second state wherein the electrical conductivity of the MOF is less than the electrical conductivity in the first state. A method including switching a porous metal organic framework (MOF) between two terminals from a first state wherein a metal site in the MOF is infiltrated by a guest species that is capable of charge transfer to a second state wherein the MOF is less electrically conductive than in the first state.

  6. 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

  7. 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.

  8. 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.

  9. Chemical speciation of sulfur and metals in biogas reactors - Implications for cobalt and nickel bio-uptake processes.

    PubMed

    Yekta, Sepehr Shakeri; Skyllberg, Ulf; Danielsson, Åsa; Björn, Annika; Svensson, Bo H

    2017-02-15

    This article deals with the interrelationship between overall chemical speciation of S, Fe, Co, and Ni in relation to metals bio-uptake processes in continuous stirred tank biogas reactors (CSTBR). To address this topic, laboratory CSTBRs digesting sulfur(S)-rich stillage, as well as full-scale CSTBRs treating sewage sludge and various combinations of organic wastes, termed co-digestion, were targeted. Sulfur speciation was evaluated using acid volatile sulfide extraction and X-ray absorption spectroscopy. Metal speciation was evaluated by chemical fractionation, kinetic and thermodynamic analyses. Relative Fe to S content is identified as a critical factor for chemical speciation and bio-uptake of metals. In reactors treating sewage sludge, quantity of Fe exceeds that of S, inducing Fe-dominated conditions, while sulfide dominates in laboratory and co-digestion reactors due to an excess of S over Fe. Under sulfide-dominated conditions, metals availability for microorganisms is restricted due to formation of metal-sulfide precipitates. However, aqueous concentrations of different Co and Ni species were shown to be sufficient to support metal acquisition by microorganisms under sulfidic conditions. Concentrations of free metal ions and labile metal complexes in aqueous phase, which directly participate in bio-uptake processes, are higher under Fe-dominated conditions. This in turn enhances metal adsorption on cell surfaces and bio-uptake rates.

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

    SciTech Connect

    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. 15 refs., 8 figs., 1 tab.

  11. 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...

  12. 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...

  13. Thin films of metal oxides grown by chemical vapor deposition from volatile transition metal and lanthanide metal complexes

    NASA Astrophysics Data System (ADS)

    Pollard, Kimberly Dona

    1998-08-01

    This thesis describes the synthesis and characterization of novel volatile metal-organic complexes for the chemical vapor deposition (CVD) of metal oxides. Monomeric tantalum complexes, lbrack Ta(OEt)sb4(beta-diketonate)) are prepared by the acid-base reaction of lbrack Tasb2(OEt)sb{10}rbrack with a beta-diketone, (RC(O)CHsb2C(O)Rsp' for R = CHsb3, Rsp' = CFsb3; R = Rsp'=C(CHsb3)sb3; R = Csb3Fsb7,\\ Rsp'=C(CHsb3)sb3;\\ R=Rsp'=CFsb3; and R = Rsp' = CHsb3). The products are characterized spectroscopically. Thermal CVD using these complexes as precursors gave good quality Tasb2Osb5 thin films which are characterized by XPS, SEM, electrical measurements, and XRD. Factors affecting the film deposition such as the type of carrier gas and the temperature of the substrate were considered. Catalyst-enhanced CVD reactions with each of the precursors and a palladium catalyst, ((2-methylallyl)Pd(acac)), were studied as a lower temperature route to good quality Tasb2Osb5 films. The decomposition mechanism at the hot substrate surface was studied. Precursors for the formation of yttria by CVD were examined. New complexes of the form (Y(hfac)sb3(glyme)), (hfac = \\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3 for n = 1-4) were synthesized and characterized spectroscopically. X-ray structural determinations of three new complexes were obtained. CVD reaction conditions were determined which give YOF films and, with catalyst-enhanced CVD, reaction conditions which give selective formation of Ysb2Osb3, YOF, or YFsb3. The films were studied by XPS, SEM, and XRD. Decomposition mechanisms which lead to film formation, together with a possible route for fluorine atom transfer from the ligand to the metal resulting in fluorine incorporation, were studied by analysis of exhaust products using GC-MS. Novel precursors of the form lbrack Ce(hfac)sb3(glyme)rbrack,\\ (hfac=\\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3, n = 1-4) for CVD of ceria were

  14. 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

  15. 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.

  16. Molecular Properties and Fate of Organic Chemicals

    DTIC Science & Technology

    1990-08-14

    Monsen, R.M. Water Sci. Technol. 1989, 21, ?????-????? (7) Haber, F .; Weiss, J.J. Proc. Roy. Soc. London, Ser. A 1934, 147, 332-???? (8) Lindsay Smith...366. (30) Tejedor , I., personal comm. Table 1: Products from oxidation of chlorobenzene with Fenton’s Reagent Concentrations, (mM) atmosphere Fe÷3...Complete mineralization of organic compounds was not observed dluring the oxidation o) f 4-chhorophenol is most observed because some of the ring-cleavage

  17. 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.

  18. 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

  19. Gravimetric chemical sensors based on silica-based mesoporous organic-inorganic hybrids.

    PubMed

    Xu, Jiaqiang; Zheng, Qi; Zhu, Yongheng; Lou, Huihui; Xiang, Qun; Cheng, Zhixuan

    2014-09-01

    Silica-based mesoporous organic-inorganic hybrid material modified quartz crystal microbalance (QCM) sensors have been examined for their ability to achieve highly sensitive and selective detection. Mesoporous silica SBA-15 serves as an inorganic host with large specific surface area, facilitating gas adsorption, and thus leads to highly sensitive response; while the presence of organic functional groups contributes to the greatly improved specific sensing property. In this work, we summarize our efforts in the rational design and synthesis of novel sensing materials for the detection of hazardous substances, including simulant nerve agent, organic vapor, and heavy metal ion, and develop high-performance QCM-based chemical sensors.

  20. 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.

  1. 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.

  2. 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. ...

  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. 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.

  5. Chemical methods and phytoremediation of soil contaminated with heavy metals.

    PubMed

    Chen, H M; Zheng, C R; Tu, C; Shen, Z G

    2000-07-01

    The effects of chemical amendments (calcium carbonate (CC), steel sludge (SS) and furnace slag (FS)) on the growth and uptake of cadmium (Cd) by wetland rice, Chinese cabbage and wheat grown in a red soil contaminated with Cd were investigated using a pot experiment. The phytoremediation of heavy metal contaminated soil with vetiver grass was also studied in a field plot experiment. Results showed that treatments with CC, SS and FS decreased Cd uptake by wetland rice, Chinese cabbage and wheat by 23-95% compared with the unamended control. Among the three amendments, FS was the most efficient at suppressing Cd uptake by the plants, probably due to its higher content of available silicon (Si). The concentrations of zinc (Zn), lead (Pb) and Cd in the shoots of vetiver grass were 42-67%, 500-1200% and 120-260% higher in contaminated plots than in control, respectively. Cadmium accumulation by vetiver shoots was 218 g Cd/ha at a soil Cd concentration of 0.33 mg Cd/kg. It is suggested that heavy metal-contaminated soil could be remediated with a combination of chemical treatments and plants.

  6. Design and synthesis of metal-organic frameworks using metal-organic polyhedra as supermolecular building blocks.

    PubMed

    Perry, John J; Perman, Jason A; Zaworotko, Michael J

    2009-05-01

    This critical review highlights supermolecular building blocks (SBBs) in the context of their impact upon the design, synthesis, and structure of metal-organic materials (MOMs). MOMs, also known as coordination polymers, hybrid inorganic-organic materials, and metal-organic frameworks, represent an emerging class of materials that have attracted the imagination of solid-state chemists because MOMs combine unprecedented levels of porosity with a range of other functional properties that occur through the metal moiety and/or the organic ligand. First generation MOMs exploited the geometry of metal ions or secondary building units (SBUs), small metal clusters that mimic polygons, for the generation of MOMs. In this critical review we examine the recent (<5 years) adoption of much larger scale metal-organic polyhedra (MOPs) as SBBs for the construction of MOMs by highlighting how the large size and high symmetry of such SBBs can afford improved control over the topology of the resulting MOM and a new level of scale to the resulting framework (204 references).

  7. 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.

  8. 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.

  9. The chemical evolution of globular clusters - II. Metals and fluorine

    NASA Astrophysics Data System (ADS)

    Sánchez-Blázquez, P.; Marcolini, A.; Gibson, B. K.; Karakas, A. I.; Pilkington, K.; Calura, F.

    2012-01-01

    In the first paper of this series, we proposed a new framework in which to model the chemical evolution of globular clusters. This model is predicated upon the assumption that clusters form within an interstellar medium enriched locally by the ejecta of a single Type Ia supernova and varying numbers of asymptotic giant branch stars, superimposed on an ambient medium pre-enriched by low-metallicity Type II supernovae. Paper I was concerned with the application of this model to the observed abundances of several reactive elements and so-called non-metals for three classical intermediate-metallicity clusters, with the hallmark of the work being the successful recovery of many of their well-known elemental and isotopic abundance anomalies. Here, we expand upon our initial analysis by (i) applying the model to a much broader range of metallicities (from the factor of 3 explored in Paper I, to now a factor of ˜50; i.e. essentially, the full range of Galactic globular cluster abundances; and (ii) incorporating a broader suite of chemical species, including a number of iron-peak isotopes, heavier α-elements and fluorine. While allowing for an appropriate fine-tuning of the model input parameters, most empirical globular cluster abundance trends are reproduced; our model would suggest the need for a higher production of calcium, silicon and copper in low-metallicity (or so-called 'prompt') Type Ia supernovae than predicted in current stellar models in order to reproduce the observed trends in NGC 6752, and a factor of 2 reduction in carbon production from asymptotic giant branch stars to explain the observed trends between carbon and nitrogen. Observations of heavy-element isotopes produced primarily by Type Ia supernovae, including those of titanium, iron and nickel, could support/refute unequivocally our proposed framework, although currently the feasibility of the proposed observations is well beyond current instrumental capabilities. Hydrodynamical simulations would

  10. In-plane orientation and composition dependences of crystal structure and electrical properties of {100}-oriented Pb(Zr,Ti)O3 films grown on (100) Si substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Okamoto, Shoji; Sankara Rama Krishnan, P. S.; Okamoto, Satoshi; Yokoyama, Shintaro; Akiyama, Kensuke; Funakubo, Hiroshi

    2017-10-01

    In-plane orientation-controlled Pb(Zr x ,Ti1‑ x )O3 (PZT) films with a thickness of approximately 2 µm and a Zr/(Zr + Ti) ratio of 0.39–0.65 were grown on (100) Si substrates by pulsed metal–organic chemical vapor deposition (MOCVD). In-plane-oriented epitaxial PZT films and in-plane random fiber-textured PZT films with {100} out-of-plane orientation were grown on (100)c SrRuO3//(100)c LaNiO3//(100) CeO2//(100) YSZ//(100) Si and (100)c SrRuO3/(100)c LaNiO3/(111) Pt/TiO2/SiO2/(100) Si substrates, respectively. The effects of Zr/(Zr + Ti) ratio and in-plane orientation on the crystal structure, dielectric, ferroelectric, and piezoelectric properties of the films were systematically investigated. The X-ray diffraction measurement showed that the epitaxial PZT films had a higher volume fraction of (100) orientation than the fiber-textured PZT films in the tetragonal Zr/(Zr + Ti) ratio region. A large difference was not detected between the epitaxial films and the fiber-textured films for Zr/(Zr + Ti) ratio dependence of the dielectric constant, and remanent polarization. However, in the rhombohedral phase region [Zr/(Zr + Ti) = 0.65], coercive field was found to be 1.5-fold different between the epitaxial and fiber-textured PZT films. The maximum field-induced strains measured at 0–100 kV/cm by scanning atomic force microscopy were obtained at approximately Zr/(Zr + Ti) = 0.50 and were about 0.5 and 0.3% for the epitaxial and fiber-textured PZT films, respectively.

  11. Baade's window and APOGEE. Metallicities, ages, and chemical abundances

    NASA Astrophysics Data System (ADS)

    Schultheis, M.; Rojas-Arriagada, A.; García Pérez, A. E.; Jönsson, H.; Hayden, M.; Nandakumar, G.; Cunha, K.; Allende Prieto, C.; Holtzman, J. A.; Beers, T. C.; Bizyaev, D.; Brinkmann, J.; Carrera, R.; Cohen, R. E.; Geisler, D.; Hearty, F. R.; Fernandez-Tricado, J. G.; Maraston, C.; Minnitti, D.; Nitschelm, C.; Roman-Lopes, A.; Schneider, D. P.; Tang, B.; Villanova, S.; Zasowski, G.; Majewski, S. R.

    2017-03-01

    Context. Baade's window (BW) is one of the most observed Galactic bulge fields in terms of chemical abundances. Owing to its low and homogeneous interstellar absorption it is considered the perfect calibration field for Galactic bulge studies. Aims: In the era of large spectroscopic surveys, calibration fields such as BW are necessary for cross calibrating the stellar parameters and individual abundances of the APOGEE survey. Methods: We use the APOGEE BW stars to derive the metallicity distribution function (MDF) and individual abundances for α- and iron-peak elements of the APOGEE ASPCAP pipeline (DR13), as well as the age distribution for stars in BW. Results: We determine the MDF of APOGEE stars in BW and find a remarkable agreement with that of the Gaia-ESO survey (GES). Both exhibit a clear bimodal distribution. We also find that the Mg-metallicity planes of the two surveys agree well, except for the metal-rich part ([Fe/H] > 0.1), where APOGEE finds systematically higher Mg abundances with respect to the GES. The ages based on the [C/N] ratio reveal a bimodal age distribution, with a major old population at 10 Gyr, with a decreasing tail towards younger stars. A comparison of stellar parameters determined by APOGEE and those determined by other sources reveals detectable systematic offsets, in particular for spectroscopic surface gravity estimates. In general, we find a good agreement between individual abundances of O, Na, Mg, Al, Si, K, Ca, Cr, Mn, Co, and Ni from APOGEE with that of literature values. Conclusions: We have shown that in general APOGEE data show a good agreement in terms of MDF and individual chemical abundances with respect to literature works. Using the [C/N] ratio we found a significant fraction of young stars in BW.

  12. 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.

  13. Multi-shelled Hollow Metal-Organic Frameworks.

    PubMed

    Liu, Wenxian; Huang, Jijiang; Yang, Qiu; Wang, Shiji; Sun, Xiaoming; Zhang, Weina; Liu, Junfeng; Huo, Fengwei

    2017-05-08

    Hollow metal-organic frameworks (MOFs) are promising materials with sophisticated structures, such as multiple shells, that cannot only enhance the properties of MOFs but also endow them with new functions. Herein, we show a rational strategy to fabricate multi-shelled hollow chromium (III) terephthalate MOFs (MIL-101) with single-crystalline shells through step-by-step crystal growth and subsequent etching processes. This strategy relies on the creation of inhomogeneous MOF crystals in which the outer layer is chemically more robust than the inner layer and can be selectively etched by acetic acid. The regulation of MOF nucleation and crystallization allows the tailoring of the cavity size and shell thickness of each layer. The resultant multi-shelled hollow MIL-101 crystals show significantly enhanced catalytic activity during styrene oxidation. The insight gained from this systematic study will aid in the rational design and synthesis of other multi-shelled hollow structures and the further expansion of their applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. 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

  15. Unusual adsorption behavior on metal-organic frameworks.

    PubMed

    Fairen-Jimenez, David; Seaton, Nigel A; Düren, Tina

    2010-09-21

    Metal-organic frameworks (MOFs) have shown adsorption behavior that is not observed in other microporous materials such as zeolites or activated carbons. This study used grand canonical Monte Carlo simulation to evaluate a particular form of behavior, which corresponds to the presence of unusual type V adsorption isotherms. Study of a series of MOFs in the IRMOF family, containing chemically similar linkers of different length, showed that the presence of type V adsorption depends on a fine balance between the strength of the fluid-fluid and fluid-solid interactions, which in turn is a strong function of the length of the linker and therefore the pore size. A transition from type V behavior to the more common type I behavior is observed as the temperature increases. The temperature at which this transition occurs increases, and the transition becomes more diffuse, as the length of the linker increases. This type V behavior leads to an interesting possibility in the design of MOF adsorbents for use in gas separation and gas storage applications.

  16. Synthesis and characterization of functionalized metal-organic frameworks.

    PubMed

    Karagiaridi, Olga; Bury, Wojciech; Sarjeant, Amy A; Hupp, Joseph T; Farha, Omar K

    2014-09-05

    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.

  17. Organic thin-film transistors for chemical and biological sensing.

    PubMed

    Lin, Peng; Yan, Feng

    2012-01-03

    Organic thin-film transistors (OTFTs) show promising applications in various chemical and biological sensors. The advantages of OTFT-based sensors include high sensitivity, low cost, easy fabrication, flexibility and biocompatibility. In this paper, we review the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistors (OECTs), mainly focusing on the papers published in the past 10 years. Various types of OTFT-based sensors, including pH, ion, glucose, DNA, enzyme, antibody-antigen, cell-based sensors, dopamine sensor, etc., are classified and described in the paper in sequence. The sensing mechanisms and the detection limits of the devices are described in details. It is expected that OTFTs may have more important applications in chemical and biological sensing with the development of organic electronics.

  18. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-09

    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.

  19. Highly Efficient Luminescent Metal-Organic Framework for the Simultaneous Detection and Removal of Heavy Metals from Water.

    PubMed

    Rudd, Nathan D; Wang, Hao; Fuentes-Fernandez, Erika M A; Teat, Simon J; Chen, Feng; Hall, Gene; Chabal, Yves J; Li, Jing

    2016-11-09

    We have designed and synthesized an isoreticular series of luminescent metal-organic frameworks (LMOFs) by incorporating a strongly emissive molecular fluorophore and functionally diverse colinkers into Zn-based structures. The three-dimensional porous networks of LMOF-261, -262, and -263 represent a unique/new type of nets, classified as a 2-nodal, (4,4)-c net (mot-e type) with 4-fold, class IIIa interpenetration. All compounds crystallize in a body-centered tetragonal crystal system (space group I41/a). A systematic study has been implemented to analyze their interactions with heavy metals. LMOF-263 exhibits impressive water stability, high porosity, and strong luminescence, making it an excellent candidate as a fluorescent chemical sensor and adsorbent for aqueous contaminants. It is extremely responsive to toxic heavy metals at a parts per billion level (3.3 ppb Hg(2+), 19.7 ppb Pb(2+)) and demonstrates high selectivity for heavy metals over light metals, with detection ratios of 167.4 and 209.5 for Hg(2+)/Ca(2+) and Hg(2+)/Mg(2+), respectively. Mixed-metal adsorption experiments also show that LMOF-263 selectively adsorbs Hg(2+) over other heavy metal ions in addition to light metals. The Pb(2+) KSV value for LMOF-263 (55,017 M(-1)) is the highest among LMOFs reported to date, and the Hg(2+) KSV value is the second highest (459,446 M(-1)). LMOF-263 exhibits a maximum adsorption capacity of 380 mg Hg(2+)/g. The Hg(2+) adsorption process follows pseudo-second-order kinetics, removing 99.1% of the metal within 30 min. An in situ XPS study provides insight to help understand the interaction mechanism between Hg(2+) and LMOF-263. No other MOFs have demonstrated such a high performance in both the detection and the capture of Hg(2+) from aqueous solution.

  20. Metallacarboranes: Towards promising hydrogen storage metal organic framework

    NASA Astrophysics Data System (ADS)

    Singh, Abhishek; Sadrzadeh, Arta; Yakobson, Boris

    2011-03-01

    Using first principles calculations we show the high hydrogen storage capacity of metallacarboranes, where the transition metal (TM) atoms bind hydrogen via Kubas interaction. The average binding energy of ~ 0.3 eV/H favorably lies within the reversible adsorption range The Sc and Ti are found to be the optimum metal atoms maximizing the number of stored H2 molecules. Depending upon the structure, metallacarboranes can adsorb up to 8 wt% of hydrogen, which exceeds DOE goal for 2015. Being integral part of the cage, TMs do not suffer from the aggregation problem. Furthermore, the presence of carbon atom in the cages permits linking the metallacarboranes to form metal organic frameworks (MOF), thus able to adsorb hydrogen via Kubas interaction, in addition to van der Waals physisorption. A. K. Singh, A. Sadrzadeh, and B. I. Yakobson, Metallacarboranes: Toward Promising Hydrogen Storage Metal Organic Frameworks, JACS 132,14126 (2010).