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Sample records for chemistry biocatalytic oxidation

  1. Bioorganometallic chemistry: biocatalytic oxidation reactions with biomimetic nad+/nadh co-factors and [cp*rh(bpy)h]+ for selective organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Lutz, Jochen; Hollman, Frank; Ho, The Vinh; Schnyder, Adrian; Fish, Richard H.; Schmid, Andreas

    2004-03-09

    The biocatalytic, regioselective hydroxylation of 2-hydroxybiphenyl to the corresponding catechol was accomplished utilizing the monooxygenase 2-hydroxybiphenyl 3-monooxygenase (HbpA). The necessary natural nicotinamide adenine dinucleotide (NAD{sup +}) co-factor for this biocatalytic process was replaced by a biomimetic co-factor, N-benzylnicotinamide bromide, 1a. The interaction between the flavin (FAD) containing HbpA enzyme and the corresponding biomimetic NADH compound, N-benzyl-1,4-dihdronicotinamide, 1b, for hydride transfers, was shown to readily occur. The in situ recycling of the reduced NADH biomimic 1b from 1a was accomplished with [Cp*Rh(bpy)H](Cl); however, productive coupling of this regeneration reaction to the enzymatic hydroxylation reaction was not totally successful, due to a deactivation process concerning the HbpA enzyme peripheral groups; i.e., -SH or -NH{sub 2} possibly reacting with the precatalyst, [Cp*Rh(bpy)(H{sub 2}O)](Cl){sub 2}, and thus inhibiting the co-factor regeneration process. The deactivation mechanism was studied, and a promising strategy of derivatizing these peripheral -SH or -NH{sub 2} groups with a polymer containing epoxide was successful in circumventing the undesired interaction between HbpA and the precatalyst. This latter strategy allowed tandem co-factor regeneration using 1a or 2a, [Cp*Rh(bpy)(H2O)](Cl){sub 2}, and formate ion, in conjunction with the polymer bound, FAD containing HbpA enzyme to provide the catechol product.

  2. Biocatalytic Resolution of para-Nitrostyrene Oxide by Resting Cells of Different Aspergillus niger Strains

    Institute of Scientific and Technical Information of China (English)

    金浩; 李祖义; 王清

    2001-01-01

    Biocatalytic resolution of racemic para-nitrostyrene oxide was accomplished by employing the epoxide hydrolases from the whole cells of several Aspergillus niger (A. niger) strains. In the cases investigated, excellent selectivity was achieved with such strains as A, niger 5450, A. niger 5320.

  3. Biocatalytic anode for glucose oxidation utilizing carbon nanotubes for direct electron transfer with glucose oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Vaze, Abhay; Hussain, Nighat; Tang, Chi [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Leech, Donal [School of Chemistry, National University of Ireland, Galway (Ireland); Rusling, James [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06032 (United States); School of Chemistry, National University of Ireland, Galway (Ireland)

    2009-10-15

    Covalently linked layers of glucose oxidase, single-wall carbon nanotubes and poly-L-lysine on pyrolytic graphite resulted in a stable biofuel cell anode featuring direct electron transfer from the enzyme. Catalytic response observed upon addition of glucose was due to electrochemical oxidation of FADH{sub 2} under aerobic conditions. The electrode potential depended on glucose concentration. This system has essential attributes of an anode in a mediator-free biocatalytic fuel cell. (author)

  4. Biocatalytic oxidation of benzyl alcohol to benzaldehyde via hydrogen transfer

    NARCIS (Netherlands)

    Orbegozo, Thomas; Lavandera, Iván; Fabian, Walter M.F.; Mautner, Barbara; Vries, Johannes G. de; Kroutil, Wolfgang

    2009-01-01

    Various types of biocatalysts like oxidases, alcohol dehydrogenases, and microbial cells were tested for the oxidation of benzyl alcohol. Oxidases in combination with molecular oxygen led to low conversion. Alcohol dehydrogenases and microbial cells were tested in a hydrogen transfer reaction employ

  5. Oxidase-based biocatalytic processes

    DEFF Research Database (Denmark)

    Ramesh, Hemalata; Woodley, John; Krühne, Ulrich

    solvent-resistant oxygen sensors as supporting technology for oxidase-basedreactions using a glucose oxidase reaction system as an example.iiImplementation of biocatalytic oxidation at scale still requires process knowledge which includes thelimitations of the system and the knowledge about the potential......Biocatalytic processes are gaining significant focus in frontiers where they offer unique advantages(selectivity and mild operating conditions) over chemical catalysts. It is therefore not surprising that therehave been many industrial biocatalytic processes implemented.Despite past successes......, the implementation of a new biocatalytic process still presents some challenges (demands placed on the biocatalyst) in terms of the requirements to make a viable industrial process. Inorder for a biocatalytic process to be economically successful, it is necessary that certain a set of targetmetrics (product titre...

  6. Branched zinc oxide nanorods arrays modified paper electrode for electrochemical immunosensing by combining biocatalytic precipitation reaction and competitive immunoassay mode.

    Science.gov (United States)

    Sun, Guoqiang; Yang, Hongmei; Zhang, Yan; Yu, Jinghua; Ge, Shenguang; Yan, Mei; Song, Xianrang

    2015-12-15

    Branched zinc oxide nanorods (BZR) arrays, an array with high charge carries collection efficiency and specific surface area, are grown on the reduced graphene oxide-paper working electrode for the first time to construct a paper-based electrochemical (EC) immunosensor. Typically, the BZR are fabricated via a simple hydrothermal process, which can provide abundant sites for antibodies loading. By combining the large surface area of porous zinc oxide (PZS) and good biocompatibility of gold nanoparticles (AuNPs), PZS-AuNPs (PZS@Au) nanocomposites are designed to label horseradish peroxide (HRP) and antigens. After a competitive reaction between antigens and PZS@Au nanocomposites labeled antigens, the signal labels are introduced into the immunosensor, in which, HRP participate in biocatalytic precipitation process. The produced precipitate reduces the electrode surface area and hinders the electron transfer. With the increase of concentration of antigens, the signal labels introduced into the sensor decrease, thus, a signal-on immunoassay for α-fetoprotein detection is constructed. The proposed paper-based EC immunosensor combines enzymatic biocatalytic precipitation reaction and competitive immunoassay mode for the first time, and possesses a wide linear range from 0.2 pg mL(-1) to 500 ng mL(-1) with a detection limit of 0.08 pg mL(-1). In addition, the proposed method is simple, sensitive and specific and can be a promising platform for other protein detection.

  7. The chemistry of graphene oxide.

    Science.gov (United States)

    Dreyer, Daniel R; Park, Sungjin; Bielawski, Christopher W; Ruoff, Rodney S

    2010-01-01

    The chemistry of graphene oxide is discussed in this critical review. Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure. Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed. This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references).

  8. The Oxidation of Thiols by Flavoprotein Oxidases : a Biocatalytic Route to Reactive Thiocarbonyls

    NARCIS (Netherlands)

    Ewing, Tom A.; Dijkman, Willem P.; Vervoort, Jacques M.; Fraaije, Marco W.; van Berkel, Willem J. H.

    2014-01-01

    Flavoprotein oxidases are a diverse class of biocatalysts, most of which catalyze the oxidation of C-O, C-N, or C-C bonds. Flavoprotein oxidases that are known to catalyze the oxidation of C-S bonds are rare, being limited to enzymes that catalyze the oxidative cleavage of thioethers. Herein, we rep

  9. The Oxidation of Thiols by Flavoprotein Oxidases: a Biocatalytic Route to Reactive Thiocarbonyls.

    NARCIS (Netherlands)

    Ewing, T.A.; Dijkman, W.P.; Vervoort, J.J.M.; Fraaije, M.W.; Berkel, van W.J.H.

    2014-01-01

    Flavoprotein oxidases are a diverse class of biocatalysts, most of which catalyze the oxidation of C[BOND]O, C[BOND]N, or C[BOND]C bonds. Flavoprotein oxidases that are known to catalyze the oxidation of C[BOND]S bonds are rare, being limited to enzymes that catalyze the oxidative cleavage of thioet

  10. Biocatalytic conversion of ethylene to ethylene oxide using an engineered toluene monooxygenase

    Energy Technology Data Exchange (ETDEWEB)

    Carlin, DA; Bertolani, SJ; Siegel, JB

    2015-01-01

    Mutants of toluene o-xylene monooxygenase are demonstrated to oxidize ethylene to ethylene oxide in vivo at yields of >99%. The best mutant increases ethylene oxidation activity by >5500-fold relative to the native enzyme. This is the first report of a recombinant enzyme capable of carrying out this industrially significant chemical conversion.

  11. Catalytic Chemistry on Oxide Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Asthagiri, Aravind; Dixon, David A.; Dohnalek, Zdenek; Kay, Bruce D.; Rodriquez, Jose A.; Rousseau, Roger J.; Stacchiola, Dario; Weaver, Jason F.

    2016-05-29

    Metal oxides represent one of the most important and widely employed materials in catalysis. Extreme variability of their chemistry provides a unique opportunity to tune their properties and to utilize them for the design of highly active and selective catalysts. For bulk oxides, this can be achieved by varying their stoichiometry, phase, exposed surface facets, defect, dopant densities and numerous other ways. Further, distinct properties from those of bulk oxides can be attained by restricting the oxide dimensionality and preparing them in the form of ultrathin films and nanoclusters as discussed throughout this book. In this chapter we focus on demonstrating such unique catalytic properties brought by the oxide nanoscaling. In the highlighted studies planar models are carefully designed to achieve minimal dispersion of structural motifs and to attain detailed mechanistic understanding of targeted chemical transformations. Detailed level of morphological and structural characterization necessary to achieve this goal is accomplished by employing both high-resolution imaging via scanning probe methods and ensemble-averaged surface sensitive spectroscopic methods. Three prototypical examples illustrating different properties of nanoscaled oxides in different classes of reactions are selected.

  12. Enhanced biocatalytic esterification with lipase-immobilized chitosan/graphene oxide beads.

    Directory of Open Access Journals (Sweden)

    Siaw Cheng Lau

    Full Text Available In this work, lipase from Candida rugosa was immobilized onto chitosan/graphene oxide beads. This was to provide an enzyme-immobilizing carrier with excellent enzyme immobilization activity for an enzyme group requiring hydrophilicity on the immobilizing carrier. In addition, this work involved a process for the preparation of an enzymatically active product insoluble in a reaction medium consisting of lauric acid and oleyl alcohol as reactants and hexane as a solvent. This product enabled the stability of the enzyme under the working conditions and allowed the enzyme to be readily isolated from the support. In particular, this meant that an enzymatic reaction could be stopped by the simple mechanical separation of the "insoluble" enzyme from the reaction medium. Chitosan was incorporated with graphene oxide because the latter was able to enhance the physical strength of the chitosan beads by its superior mechanical integrity and low thermal conductivity. The X-ray diffraction pattern showed that the graphene oxide was successfully embedded within the structure of the chitosan. Further, the lipase incorporation on the beads was confirmed by a thermo-gravimetric analysis. The lipase immobilization on the beads involved the functionalization with coupling agents, N-hydroxysulfosuccinimide sodium (NHS and 1-ethyl-(3-dimethylaminopropyl carbodiimide (EDC, and it possessed a high enzyme activity of 64 U. The overall esterification conversion of the prepared product was 78% at 60 °C, and it attained conversions of 98% and 88% with commercially available lipozyme and novozyme, respectively, under similar experimental conditions.

  13. Biocatalytic conversion of epoxides

    NARCIS (Netherlands)

    de Vries, Erik; Janssen, DB

    2003-01-01

    Epoxides are attractive intermediates for producing chiral compounds. Important biocatalytic reactions involving epoxides include epoxide hydrolase mediated kinetic resolution, leading to the formation of diols and enantiopure remaining substrates, and enantioconvergent enzymatic hydrolysis, which g

  14. Inorganic chemistry: Deconstructing water oxidation

    Science.gov (United States)

    Cook, Sarah A.; Borovik, A. S.

    2013-04-01

    During photosynthesis, the oxygen-evolving complex oxidizes water to produce molecular oxygen. Now, a possible role for the calcium ion in this complex has been proposed based on the electrochemical properties of a series of synthetic heterometallic clusters.

  15. Aromatic-radical oxidation chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Glassman, I.; Brezinsky, K. [Princeton Univ., NJ (United States)

    1993-12-01

    The research effort has focussed on discovering an explanation for the anomalously high CO{sub 2} concentrations observed early in the reaction sequence of the oxidation of cyclopentadiene. To explain this observation, a number of plausible mechanisms have been developed which now await experimental verification. One experimental technique for verifying mechanisms is to probe the reacting system by perturbing the radical concentrations. Two forms of chemical perturbation of the oxidation of cyclopentadiene were begun during this past year--the addition of NO{sub 2} and CO to the reacting mixture.

  16. Biocatalytic Refining of Soybean Oil into Cosmeceutical Ingredients

    Science.gov (United States)

    Our mission is to develop new, value-added uses for commodity crops and oils. We chose to fulfill this mission while adhering as closely as possible to the tenants of “green” chemistry. We have developed patented, all-natural oils called Feruloyl Soy Glycerols (FSG) from the biocatalytic transester...

  17. Biocatalytic portfolio of Basidiomycota.

    Science.gov (United States)

    Schmidt-Dannert, Claudia

    2016-04-01

    Basidiomycota fungi have received little attention for applications in biocatalysis and biotechnology and remain greatly understudied despite their importance for carbon recycling, ecosystem functioning and medicinal properties. The steady influx of genome data has facilitated detailed studies aimed at understanding the evolution and function of fungal lignocellulose degradation. These studies and recent explorations into the secondary metabolomes have uncovered large portfolios of enzymes useful for biocatalysis and biosynthesis. This review will provide an overview of the biocatalytic repertoires of Basidiomycota characterized to date with the hope of motivation more research into the chemical toolkits of this diverse group of fungi.

  18. Biocatalytic material comprising multilayer enzyme coated fiber

    Science.gov (United States)

    Kim, Jungbae [Richland, WA; Kwak, Ja Hun [Richland, WA; Grate, Jay W [West Richland, WA

    2009-11-03

    The present invention relates generally to high stability, high activity biocatalytic materials and processes for using the same. The materials comprise enzyme aggregate coatings having high biocatalytic activity and stability useful in heterogeneous environment. These new materials provide a new biocatalytic immobilized enzyme system with applications in bioconversion, bioremediation, biosensors, and biofuel cells.

  19. Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.; Schoonheydt, R.A.

    1996-01-01

    Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

  20. Analytical chemistry methods for mixed oxide fuel, March 1985

    Energy Technology Data Exchange (ETDEWEB)

    1985-03-01

    This standard provides analytical chemistry methods for the analysis of materials used to produce mixed oxide fuel. These materials are ceramic fuel and insulator pellets and the plutonium and uranium oxides and nitrates used to fabricate these pellets.

  1. Fenton Redox Chemistry: Arsenite Oxidation by Metallic Surfaces

    NARCIS (Netherlands)

    Borges Freitas, S.C.; Van Halem, D.; Badruzzaman, A.B.M.; Van der Meer, W.G.J.

    2014-01-01

    Pre-oxidation of As(III) is necessary in arsenic removal processes in order to increase its efficiency. Therefore, the Fenton Redox Chemistry is defined by catalytic activation of H2O2 and currently common used for its redox oxidative properties. In this study the effect of H2O2 production catalysed

  2. Oxidation and Reduction Reactions in Organic Chemistry

    Science.gov (United States)

    Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.

    2010-01-01

    A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what type…

  3. Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry.

    Science.gov (United States)

    Guo, Zhen; Liu, Bin; Zhang, Qinghong; Deng, Weiping; Wang, Ye; Yang, Yanhui

    2014-05-21

    Oxidation catalysis not only plays a crucial role in the current chemical industry for the production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to the establishment of novel green and sustainable chemical processes. This review is devoted to dealing with selective oxidation reactions, which are important from the viewpoint of green and sustainable chemistry and still remain challenging. Actually, some well-known highly challenging chemical reactions involve selective oxidation reactions, such as the selective oxidation of methane by oxygen. On the other hand some important oxidation reactions, such as the aerobic oxidation of alcohols in the liquid phase and the preferential oxidation of carbon monoxide in hydrogen, have attracted much attention in recent years because of their high significance in green or energy chemistry. This article summarizes recent advances in the development of new catalytic materials or novel catalytic systems for these challenging oxidation reactions. A deep scientific understanding of the mechanisms, active species and active structures for these systems are also discussed. Furthermore, connections among these distinct catalytic oxidation systems are highlighted, to gain insight for the breakthrough in rational design of efficient catalytic systems for challenging oxidation reactions.

  4. The Biocatalytic Desulfurization Project

    Energy Technology Data Exchange (ETDEWEB)

    David Nunn; James Boltz; Philip M. DiGrazia; Larry Nace

    2006-03-03

    The material in this report summarizes the Diversa technical effort in development of a biocatalyst for the biodesulfurization of Petro Star diesel as well as an economic report of standalone and combined desulfurization options, prepared by Pelorus and Anvil, to support and inform the development of a commercially viable process. We will discuss goals of the projected as originally stated and their modification as guided by parallel efforts to evaluate commercialization economics and process parameters. We describe efforts to identify novel genes and hosts for the generation of an optimal biocatalyst, analysis of diesel fuels (untreated, chemically oxidized and hydrotreated) for organosulfur compound composition and directed evolution of enzymes central to the biodesulfurization pathway to optimize properties important for their use in a biocatalyst. Finally we will summarize the challenges and issues that are central to successful development of a viable biodesulfurization process.

  5. THE BIOCATALYTIC DESULFURIZATION PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Steven E. Bonde; David Nunn

    2003-01-01

    During the first quarter of the Biological Desulfurization project several activities were pursued. A project kickoff meeting was held at the Diversa facility in San Diego, CA. Activities that were in process before the meeting and begun afterwards by Diversa Corporation and Petro Star Inc. include: Technology transfer in the form of information generated by Enchira to Diversa, the purchase and installation of equipment by Diversa, development of synthetic methods and preparation of organo-sulfur substrates for use in determining enzyme activities, production of extract via Petro Star's CED process, detailed analysis of Petro Star Inc. diesel and CED extract, and several activities in molecular biology. Diversa Corporation, in the area of molecular biology, engaged in several activities in support of the task list of the contract. These included: construction of a genomic library; development and utilization of a sequence-based gene discovery effort; a parallel discovery approach based on functional expression of enzymes with the ability to oxidize organosulfur compounds. Biodesulfurization genes have already been identified and are being sequenced and subcloned for expression in heterologous biological hosts. Diversa has evaluated and adapted assays developed by Enchira used to assess the activities of DBT and DBTO{sub 2} monooxygenases. Finally, Diversa personnel have developed two novel selection/screen strategies for the improvement of biocatalyst strains by directed evolution.

  6. THE BIOCATALYTIC DESULFURIZATION PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Steven E. Bonde; David Nunn

    2003-04-01

    Research activities in the second quarter have largely been a continuation of efforts previously described in the first quarterly report as well as a degree of redirection of effort as a result of discussions during the first quarterly meeting held in San Diego. Chemical synthesis efforts have been refined and are currently being used to support generation of substrates for evaluation and evolution of enzymes for their oxidation. Analysis of the sulfur species in Petro Star diesel, CED extract and refinement of the speciation data is nearly complete. Molecular biology efforts continue with the cloning, expression and characterization of the DszA and DszC proteins as well as the flavin reductases to support regeneration of the essential FMN cofactors. In addition, we have initiated an evolution effort for the extension and improvement of DszA enzyme activity using Diversa's Gene Site Saturation Mutagenesis (GSSM{trademark}) technology. To support the evolution effort as well as of characterization of enzyme activities on a variety of substrates, a high-throughput mass spectroscopy-based assay has been developed. Two selection/screen strategies for the discovery and evolution of biocatalyst enzyme have been developed and are being evaluated for performance using gene libraries constructed from known biodesulfurization strains and environmental libraries.

  7. Oxidation Kinetics of Copper: An Experiment in Solid State Chemistry.

    Science.gov (United States)

    Ebisuzaki, Y.; Sanborn, W. B.

    1985-01-01

    Oxidation kinetics in metals and the role defects play in diffusion-controlled reactions are discussed as background for a junior/senior-level experiment in the physical or inorganic chemistry laboratory. Procedures used and typical data obtained are provided for the experiment. (JN)

  8. Surface Chemistry and Properties of Oxides as Catalyst Supports

    Energy Technology Data Exchange (ETDEWEB)

    DeBusk, Melanie Moses [ORNL; Narula, Chaitanya Kumar [ORNL; Contescu, Cristian I [ORNL

    2015-01-01

    Heterogeneous catalysis relies on metal-oxides as supports for the catalysts. Catalyst supports are an indispensable component of most heterogeneous catalysts, but the role of the support is often minimized in light of the one played by the catalytically active species it supports. The active species of supported catalysts are located on the surface of the support where their contact with liquid or gas phase reactants will be greatest. Considering that support plays a major role in distribution and stability of active species, the absorption and retention of reactive species, and in some cases in catalytic reaction, the properties and chemistry that can occur at the surface of an oxide support are important for understanding their impact on the activity of a supported catalyst. This chapter examines this rich surface chemistry and properties of oxides used as catalyst supports, and explores the influence of their interaction with the active species.

  9. Oxidation Chemistry of Inorganic Benzene Complexes.

    Science.gov (United States)

    Fleischmann, Martin; Dielmann, Fabian; Balázs, Gábor; Scheer, Manfred

    2016-10-17

    The oxidation of the 28 VE cyclo-E6 triple-decker complexes [(Cp(R) Mo)2 (μ,η(6) :η(6) -E6 )] (E=P, Cp(R) =Cp(2 a), Cp*(2 b), Cp(Bn) (2 c)=C5 (CH2 Ph)5 ; E=As, Cp(R) =Cp*(3)) by Cu(+) or Ag(+) leads to cationic 27 VE complexes that retain their general triple-decker geometry in the solid state. The obtained products have been characterized by cyclic voltammetry (CV), EPR, Evans NMR, multinuclear NMR spectroscopy, MS, and structural analysis by single-crystal X-ray diffraction. The cyclo-E6 middle decks of the oxidized complexes are distorted to a quinoid (2 a) or bisallylic (2 b, 2 c, 3) geometry. DFT calculations of 2 a, 2 b, and 3 persistently result in the bisallylic distortion as the minimum geometry and show that the oxidation leads to a depopulation of the σ-system of the cyclo-E6 ligands in 2 a-3. Among the starting complexes, 2 c is reported for the first time including its preparation and full characterization.

  10. Computational Chemistry of Cyclopentane Low Temperature Oxidation

    KAUST Repository

    El Rachidi, Mariam

    2015-03-30

    Cycloalkanes are significant constituents of conventional fossil fuels, but little is known concerning their combustion chemistry and kinetics, particularly at low temperatures. This study investigates the pressure dependent kinetics of several reactions occurring during low-temperature cyclopentane combustion using theoretical chemical kinetics. The reaction pathways of the cyclopentyl + O2 adduct is traced to alkylhydroperoxide, cyclic ether, β-scission and HO2 elimination products. The calculations are carried out at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The barrierless entrance channel is treated using variable-reaction-coordinate transition state theory (VRC-TST) at the CASPT2(7e,6o) level of theory, including basis set, geometry relaxation and ZPE corrections. 1-D time-dependent multiwell master equation analysis is used to determine pressure-and temperature-dependent rate parameters of all investigated reactions. Tunneling corrections are included using Eckart barriers. Comparison with cyclohexane is used to elucidate the effect of ring size on the low temperature reactivity of naphthenes. The rate coefficients reported herein are suitable for use in cyclopentane and methylcyclopentane combustion models, even below ~900 K, where ignition is particularly sensitive to these pressure-dependent values.

  11. Initiation Chemistries in Hydrocarbon (Aut)Oxidation.

    Science.gov (United States)

    Sandhiya, Lakshmanan; Zipse, Hendrik

    2015-09-28

    For the (aut)oxidation of toluene to benzyl hydroperoxide, benzyl alcohol, benzaldehyde, and benzoic acid, the thermochemical profiles for various radical-generating reactions have been compared. A key intermediate in all of these reactions is benzyl hydroperoxide, the heat of formation of which has been estimated by using results from CBS-QB3, G4, and G3B3 calculations. Homolytic O-O bond cleavage in this hydroperoxide is strongly endothermic and thus unlikely to contribute significantly to initiation processes. In terms of reaction enthalpies the most favorable initiation process involves bimolecular reaction of benzyl hydroperoxide to yield hydroxy and benzyloxy radicals along with water and benzaldehyde. The reaction enthalpy and free energy of this process is significantly more favorable than those for the unimolecular dissociation of known radical initiators, such as dibenzoylperoxide or dibenzylhyponitrite.

  12. Pentavalent Uranium Chemistry - Synthetic Pursuit Of A Rare Oxidation State

    Energy Technology Data Exchange (ETDEWEB)

    Graves, Christopher R [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

    2009-01-01

    This feature article presents a comprehensive overview of pentavalent uranium systems in non-aqueous solution with a focus on the various synthetic avenues employed to access this unusual and very important oxidation state. Selected characterization data and theoretical aspects are also included. The purpose is to provide a perspective on this rapidly evolving field and identify new possibilities for future developments in pentavalent uranium chemistry.

  13. E factors, green chemistry and catalysis: an odyssey.

    Science.gov (United States)

    Sheldon, Roger A

    2008-08-07

    The development of green chemistry is traced from the introduction of the concepts of atom economy (atom utilisation) and E factors in the early 1990s. The important role of catalysis in reducing or eliminating waste is emphasised and illustrated with examples from heterogeneous catalytic oxidations with hydrogen peroxide, homogeneous catalytic oxidations and carbonylations and organocatalytic oxidations with stable N-oxy radicals. Catalytic reactions in non-conventional media, e.g. aqueous biphasic, supercritical carbon dioxide and ionic liquids, are presented. Biotransformations involving non-natural reactions of enzymes, e.g. ester ammoniolysis, and the rational design of semi-synthetic enzymes, such as vanadate phytase, are discussed. The optimisation of enzyme properties using in vitro evolution and improvement of their operational stability by immobilisation as cross-linked enzyme aggregates (CLEA) are presented. The ultimate in green chemistry is the integration of catalytic steps into a one-pot, catalytic cascade process. An example of a chemoenzymatic synthesis of an enantiomerically pure amino acid in water and a trienzymatic cascade process using a triple-decker oxynitrilase/nitrilase/amidase CLEA are discussed. Finally, catalytic conversions of renewable raw materials are examined and the biocatalytic aerobic oxidation of starch to carboxy starch is presented as an example of green chemistry in optima forma i.e. a biocompatible product from a renewable raw material using a biocatalytic air oxidation.

  14. Application of environmental and economic metrics to guide the development of biocatalytic processes

    DEFF Research Database (Denmark)

    Lima Ramos, Joana; Tufvesson, Pär; Woodley, John

    2014-01-01

    The increasing industrial interest in biocatalytic processes is predominantly driven by the need for selective chemistry, with high reaction yield (Y-reaction) and few side reactions, as well as the need for optically pure chiral molecules (in particularly in the pharmaceutical industry). Interes......The increasing industrial interest in biocatalytic processes is predominantly driven by the need for selective chemistry, with high reaction yield (Y-reaction) and few side reactions, as well as the need for optically pure chiral molecules (in particularly in the pharmaceutical industry...... processes are not yet fully optimized. Hence, in this paper we propose the use of a range of tools which can be used to guide process development, research tasks and support decision-making. Three sets of metrics are identified, each for use at different stages of process development (route selection, early...

  15. Impact of environmental chemistry on mycogenic Mn oxide minerals

    Science.gov (United States)

    Santelli, C. M.; Farfan, G. A.; Post, A.; Post, J. E.

    2012-12-01

    Manganese (Mn) oxide minerals are ubiquitous in aquatic and terrestrial environments and their presence can have broad environmental consequences. In particular, Mn oxides scavenge nutrients and metals, degrade complex organics, and oxidize a variety of inorganic contaminants. The "reactivity" of Mn oxides, however, is highly dependent upon crystallite size, composition, and structure, which are largely determined by environmental factors such as solution chemistry. It is has been suggested that most Mn oxides in terrestrial and aquatic environments are formed by microbial activity; indeed, a diversity of Mn(II)-oxidizing bacteria and fungi have been isolated and their mineral byproducts are consistent with those observed in natural systems. Previous studies showed that Mn(II)-oxidizing Ascomycete fungi produce highly-disordered, nanocrystalline Mn oxides that are structurally similar to synthetic δ-MnO2 or natural vernadite. Unlike related studies with Mn-oxidizing bacteria, Mn oxides produced by these fungi did not "age" or transform to more crystalline mineral phases with time. We hypothesize that fungal growth conditions, in particular the low concentration of cations, are inhibiting secondary mineral formation. The overall goal of this research is to examine the structure and speciation of fungally-precipitated Mn oxides with respect to fungal species, time, and concentration of soluble Mn(II), Na, and Ca - three environmentally relevant cations that promote the transformation of δ-MnO2 to more crystalline mineral phases such as feitknechtite, birnessite, or ranciéite. For this study, we examined the Mn oxides formed by different species of Mn(II)-oxidizing fungi (Pyrenochaeta sp., Stagonospora sp., Plectosphaerella cucumerina., and Acremonium strictum). Isolates were grown for 8 or 16 days in a nutrient lean media consisting of yeast extract, trace elements and 0.2 mM MnCl2 supplemented with varying concentrations of Na, Ca, or Mn(II) compounds. The

  16. Grafting of Polycaprolactone on Oxidized Nanocelluloses by Click Chemistry

    Directory of Open Access Journals (Sweden)

    Claude Daneault

    2013-03-01

    Full Text Available The main objective of this work is the grafting of polycaprolactone diol (PCL on the surface of oxidized nanocelluloses (ONC in order to enhance the compatibility between the hydrophilic cellulose nanofibres and the hydrophobic polymer matrix. This grafting was successfully realized with a new strategy known as click chemistry. In this context, the oxidized nanocelluloses bearing alkyl groups (ONC-PR were prepared by reacting amino groups of propargylamine (PR with carboxyl groups of ONC. In parallel, PCL was converted into azido-polycaprolactone (PCL-N3 in two steps: (i tosylation of polycaprolactone (PCL-OTs and (ii conversion of PCL-OTs into PCL-N3 by nucleophilic displacement using sodium azide. Finally, ONC-PR was reacted with PCL-N3 in heterogeneous conditions through click chemistry in order to prepare polycaprolactone grafted oxidized nanocellulose (ONC-g-PCL, which could be suitable for improving the interfacial adhesion in the composite materials. The grafted samples were characterized by transmission electron microscopy and by Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS and Carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR spectroscopic techniques.

  17. Green chemistry synthesis of nano-cuprous oxide.

    Science.gov (United States)

    Ceja-Romero, L R; Ortega-Arroyo, L; Ortega Rueda de León, J M; López-Andrade, X; Narayanan, J; Aguilar-Méndez, M A; Castaño, V M

    2016-04-01

    Green chemistry and a central composite design, to evaluate the effect of reducing agent, temperature and pH of the reaction, were employed to produce controlled cuprous oxide (Cu2O) nanoparticles. Response surface method of the ultraviolet-visible spectroscopy is allowed to determine the most relevant factors for the size distribution of the nanoCu2O. X-ray diffraction reflections correspond to a cubic structure, with sizes from 31.9 to 104.3 nm. High-resolution transmission electron microscopy reveals that the different shapes depend strongly on the conditions of the green synthesis.

  18. Biocatalytic oxidation of phenolic compounds by bovine methemoglobin in the presence of H{sub 2}O{sub 2}: Quantitative structure-activity relationships

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Prior, M. Teresa, E-mail: MariaTeresa.Perez@uclm.es [Department of Physical Chemistry, University of Castilla-La Mancha, Campus Universitario, E-02071 Albacete (Spain); Gomez-Bombarelli, Rafael, E-mail: R.GomezBombarelli@hw.ac.uk [Department of Physics, Heriot-Watt University, David Brewster Building G.45, Edinburgh (United Kingdom); Gonzalez-Sanchez, M. Isabel, E-mail: MIsabel.Gonzalez@uclm.es [Department of Physical Chemistry, University of Castilla-La Mancha, Campus Universitario, E-02071 Albacete (Spain); Valero, Edelmira, E-mail: Edelmira.Valero@uclm.es [Department of Physical Chemistry, University of Castilla-La Mancha, Campus Universitario, E-02071 Albacete (Spain)

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer The kinetics of metHb-catalyzed oxidation of a group of phenols were analyzed. Black-Right-Pointing-Pointer Unusual kinetic behaviour was observed for the phenols here tested. Black-Right-Pointing-Pointer QSAR equations for a number of physicochemical parameters were established. Black-Right-Pointing-Pointer A relationship between the peroxidase and catalase activities of metHb was found. Black-Right-Pointing-Pointer Bovine metHb might represent a good economical alternative to other peroxidases. - Abstract: In the present work, 13 p-substituted phenols with different functional groups have been systematically evaluated as metHb substrates by means of HPLC analysis. Non-hyperbolic kinetics were observed and Hill coefficients in the 0.37-1.00 range were obtained. The catalytic constants and the Hill coefficients were found to be quantitatively correlated with two independent variables: the energy level of the highest-occupied molecular orbital (E{sub HOMO}), which describes the intrinsic redox activity of the substrates and the pK{sub a}-values, which are related to substrate ionization. Oxygen evolution in the presence of each phenol derivative was also measured, and good correlation between peroxidase-like and catalase-like activities of the protein was observed. It is also shown that bovine metHb, although less active than other peroxidases, may represent a good alternative from an economical point of view for phenol removal processes. The equations here obtained may serve as a basis to further explore the potential use of metHb-mediated reactions in the treatment of phenols in wastewaters and to predict which phenol will be removed most efficiently under this treatment with satisfactory reliability.

  19. Model visualization for evaluation of biocatalytic processes

    DEFF Research Database (Denmark)

    Law, HEM; Lewis, DJ; McRobbie, I

    2008-01-01

    Biocatalysis offers great potential as an additional, and in some cases as an alternative, synthetic tool for organic chemists, especially as a route to introduce chirality. However, the implementation of scalable biocatalytic processes nearly always requires the introduction of process and/or bi...

  20. Engineering of Biocatalysts and Biocatalytic Processes

    DEFF Research Database (Denmark)

    Lima Ramos, Joana; Lima Afonso Neto, Watson; Woodley, John

    2014-01-01

    Discovering and developing new biocatalytic reactions and biocatalysts has been the major focus of the activities in the EC FP7 BIOTRAINS network. However, industrial implementation of these new reactions requires engineering of both the biocatalysts and the associated processes, to achieve the n...

  1. Ethylene oxidation chemistry in a well-stirred reactor

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, N. [Lawrence Livermore National Lab., CA (United States); Malte, P. [Univ. of Washington, Seattle, WA (United States). Dept. of Mechanical Engineering

    1994-09-01

    Ethylene is an important intermediate in the combustion of methane, larger aliphatic hydrocarbons, and aromatics. Detailed fuel-lean C{sub 2}H{sub 4}H{sub 2}O/air well-stirred reactor data by Thornton were used to analyze reported combustion chemistry mechanisms and the development of this study`s ethylene oxidation mechanism. The data set had been obtained for the temperature range 1,003 to 1,253 K and ethylene-oxygen equivalence ratio range 0.086 to 0.103, at atmospheric pressure. Mechanisms were derived from reaction sets of Westbrook and Pitz, and Dagaut, Cathonnet and Boettner. Examination of each reported mechanism indicated unusually large kinetic rates for the vinyl decomposition reaction were used in order to obtain agreement with the Thornton data set. An ethylene oxidation model was developed in order to address the mechanistic problems of the previous models. This study`s mechanism well simulated the overall rate of ethylene oxidation and concentration profiles of CO, CO{sub 2}, H{sub 2}, CH{sub 2}O, C{sub 2}H{sub 2}, CH{sub 3}OH, CH{sub 4}, and C{sub 2}H{sub 6}. Successful predictions by the model were dependent on a new high temperature vinyl oxidation reaction route, C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}CHO + O with a branching ratio of 1.19--1.21 at 1,053 K to 1.63--2.47 at 1,253 K. The branching ratio values were dependent upon the extent of fall-off for the C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}O + HCO reaction. 132 refs.

  2. Photosynthetic water oxidation: insights from manganese model chemistry.

    Science.gov (United States)

    Young, Karin J; Brennan, Bradley J; Tagore, Ranitendranath; Brudvig, Gary W

    2015-03-17

    Catalysts for light-driven water oxidation are a critical component for development of solar fuels technology. The multielectron redox chemistry required for this process has been successfully deployed on a global scale in natural photosynthesis by green plants and cyanobacteria using photosystem II (PSII). PSII employs a conserved, cuboidal Mn4CaOX cluster called the O2-evolving complex (OEC) that offers inspiration for artificial O2-evolution catalysts. In this Account, we describe our work on manganese model chemistry relevant to PSII, particularly the functional model [Mn(III/IV)2(terpy)2(μ-O)2(OH2)2](NO3)3 complex (terpy = 2,2';6',2″-terpyridine), a mixed-valent di-μ-oxo Mn dimer with two terminal aqua ligands. In the presence of oxo-donor oxidants such as HSO5(-), this complex evolves O2 by two pathways, one of which incorporates solvent water in an O-O bond-forming reaction. Deactivation pathways of this catalyst include comproportionation to form an inactive Mn(IV)Mn(IV) dimer and also degradation to MnO2, a consequence of ligand loss when the oxidation state of the complex is reduced to labile Mn(II) upon release of O2. The catalyst's versatility has been shown by its continued catalytic activity after direct binding to the semiconductor titanium dioxide. In addition, after binding to the surface of TiO2 via a chromophoric linker, the catalyst can be oxidized by a photoinduced electron-transfer mechanism, mimicking the natural PSII process. Model oxomanganese complexes have also aided in interpreting biophysical and computational studies on PSII. In particular, the μ-oxo exchange rates of the Mn-terpy dimer have been instrumental in establishing that the time scale for μ-oxo exchange of high-valent oxomanganese complexes with terminal water ligands is slower than O2 evolution in the natural photosynthetic system. Furthermore, computational studies on the Mn-terpy dimer and the OEC point to similar Mn(IV)-oxyl intermediates in the O-O bond

  3. Metalloporphyrins as Oxidation Catalysts: Moving toward "Greener" Chemistry in the Inorganic Chemistry Laboratory

    Science.gov (United States)

    Clark, Rose A.; Stock, Anne E.; Zovinka, Edward P.

    2012-01-01

    Training future chemists to be aware of the environmental impact of their work is of fundamental importance to global society. To convince chemists to embrace sustainability, the integration of green chemistry across the entire chemistry curriculum is a necessary step. This experiment expands the reach of green chemistry techniques into the…

  4. Biocatalytic trifluoromethylation of unprotected phenols

    Science.gov (United States)

    Simon, Robert C.; Busto, Eduardo; Richter, Nina; Resch, Verena; Houk, Kendall N.; Kroutil, Wolfgang

    2016-11-01

    Organofluorine compounds have become important building blocks for a broad range of advanced materials, polymers, agrochemicals, and increasingly for pharmaceuticals. Despite tremendous progress within the area of fluorination chemistry, methods for the direct introduction of fluoroalkyl-groups into organic molecules without prefunctionalization are still highly desired. Here we present a concept for the introduction of the trifluoromethyl group into unprotected phenols by employing a biocatalyst (laccase), tBuOOH, and either the Langlois' reagent or Baran's zinc sulfinate. The method relies on the recombination of two radical species, namely, the phenol radical cation generated directly by the laccase and the CF3-radical. Various functional groups such as ketone, ester, aldehyde, ether and nitrile are tolerated. This laccase-catalysed trifluoromethylation proceeds under mild conditions and allows accessing trifluoromethyl-substituted phenols that were not available by classical methods.

  5. Steam assisted oxide growth on aluminium alloys using oxidative chemistries: Part II corrosion performance

    Science.gov (United States)

    Din, Rameez Ud; Jellesen, Morten Stendahl; Ambat, Rajan

    2015-11-01

    Surface treatment of aluminium alloys using steam with oxidative chemistries, namely KMnO4 and HNO3 resulted in accelerated growth of oxide on aluminium alloys. Detailed investigation of the corrosion performance of the treated surfaces was carried out using potentiodynamic polarisation and standard industrial test methods such as acetic acid salt spray (AASS) and filiform corrosion on commercial AA6060 alloy. Barrier properties of the film including adhesion were evaluated using tape test under wet and dry conditions. Electrochemical results showed reduced cathodic and anodic activity, while the protection provided by steam treatment with HNO3 was a function of the concentration of NO3- ions. The coating generated by inclusion of KMnO4 showed highest resistance to filiform corrosion. Overall, the performance of the steam treated surfaces under filiform corrosion and AASS test was a result of the local coverage of the alloy microstructure resulting from steam containing with KMnO4 and HNO3.

  6. Biocatalytic process development using microfluidic miniaturized systems

    DEFF Research Database (Denmark)

    Krühne, Ulrich; Heintz, Søren; Ringborg, Rolf Hoffmeyer

    2014-01-01

    The increasing interest in biocatalytic processes means there is a clear need for a new systematic development paradigm which encompasses both protein engineering and process engineering. This paper argues that through the use of a new microfluidic platform, data can be collected more rapidly...... and integrated with process modeling, can provide the basis for validating a reduced number of potential processes. The miniaturized platform should use a smaller reagent inventory and make better use of precious biocatalysts. The EC funded BIOINTENSE project will use ω-transaminase based synthesis of chiral...

  7. Tin Oxide Chemistry from Macquer (1758) to Mendeleeff (1891) as Revealed in the Textbooks and Other Literature of the Era

    Science.gov (United States)

    de Berg, Kevin C.

    2008-01-01

    Eight chemistry textbooks written from 1758 to 1891 have been analyzed for the way they present the chemistry of the oxides of tin. This analysis gives insight into the foundation of a number of chemical ideas such as nomenclature and composition used in modern chemistry. Four major preparation techniques for the production of tin oxides emerge…

  8. PSE opportunities in biocatalytic process design and development

    DEFF Research Database (Denmark)

    Tufvesson, Pär; Krühne, Ulrich; Gernaey, Krist

    2012-01-01

    to pharmaceuticals and other chemical products, since enzymes usually work in an aqueous solution and under mild conditions. Nevertheless the implementation of a biocatalytic reaction and the integration of a biocatalytic reaction into an otherwise chemical catalytic sequence is a complex task where PSE tools have...... a particularly important role to play. In this paper we will present a variety of PSE tools including computational fluid dynamics (CFD), operating windows, kinetic modelling, economic analysis and environmental assessment to support the development of economically viable biocatalytic processes....

  9. The oxidation of hydrogen cyanide and related chemistry

    DEFF Research Database (Denmark)

    Dagaut, Philippe; Glarborg, Peter; Alzueta, Maria U.

    2008-01-01

    For modeling the formation of nitrogen oxides in combustion via both the prompt-NO and the fuel-NO mechanisms, as well as for modeling the reduction of nitrogen oxides via reburning, a good knowledge of the kinetics of oxidation of hydrogen cyanide (HCN) is required. The formation routes to HCN a...... and the thermochemistry of HCN-related species are reviewed. The available kinetic data for the oxidation of HCN are presented and a comprehensive detailed chemical kinetic reaction mechanism for the oxidation of HCN is proposed and discussed....

  10. Exploring the biocatalytic potential of a DyP-type peroxidase by profiling the substrate acceptance of Thermobifida fusca DyP peroxidase

    NARCIS (Netherlands)

    Loncar, Nikola; Colpa, Dana I.; Fraaije, Marco W.

    2016-01-01

    Dye-decolorizing peroxidases (DyPs) represent a new class of oxidative enzymes for which the natural substrates are largely unknown. To explore the biocatalytic potential of a DyP, we have studied the substrate acceptance profile of a robust DyP peroxidase, a DyP from Thermobifida fusca (TfuDyP). Wh

  11. Surface chemistry of black phosphorus under a controlled oxidative environment

    Science.gov (United States)

    Luo, Wei; Zemlyanov, Dmitry Y.; Milligan, Cory A.; Du, Yuchen; Yang, Lingming; Wu, Yanqing; Ye, Peide D.

    2016-10-01

    Black phosphorus (BP), the bulk counterpart of monolayer phosphorene, is a relatively stable phosphorus allotrope at room temperature. However, monolayer phosphorene and ultra-thin BP layers degrade in ambient atmosphere. In this paper, we report the investigation of BP oxidation and discuss the reaction mechanism based on the x-ray photoelectron spectroscopy (XPS) data. The kinetics of BP oxidation was examined under various well-controlled conditions, namely in 5% O2/Ar, 2.3% H2O/Ar, and 5% O2 and 2.3% H2O/Ar. At room temperature, the BP surface is demonstrated not to be oxidized at a high oxidation rate in 5% O2/Ar nor in 2.3% H2O/Ar, according to XPS, with the thickness of the oxidized phosphorus layer <5 Å for 5 h. On the other hand, in the O2/H2O mixture, a 30 Å thickness oxide layer was detected already after 2 h of the treatment. This result points to a synergetic effect of water and oxygen in the BP oxidation. The oxidation effect was also studied in applications to the electrical measurements of BP field-effect transistors (FETs) with or without passivation. The electrical performance of BP FETs with atomic layer deposition (ALD) dielectric passivation or h-BN passivation formed in a glove-box environment are also presented.

  12. Surface Chemistry of Nano-Structured Mixed Metal Oxide Films

    Science.gov (United States)

    2012-12-11

    Low Temperature Synthesis and Characterization of Nanocrystalline Titanium Carbide with Tunable Porous Architectures, Chemistry of Materials, (01...of the C–H bond to form carboxyl, both of which decompose via a COd 2 intermediate to evolve CO2 and H2. High surface area, porous titanium carbide films...characterization of nanocrystalline titanium carbide with tunable porous architectures” Chem. Mater. 22, 319-329 (2010). http://dx.doi.org/10.1021/cm902184m 3

  13. Structure, Bonding and Surface Chemistry of Metal Oxide Nanoclusters

    Science.gov (United States)

    2015-06-23

    spectroscopy, complemented by computational quantum chemistry. Recent experiments have investigated the carbonyl complexes of Ti, Zr, Hf , Sc, Y and...16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT unlimited 18. NUMBER OF PAGES 9 19a. NAME OF RESPONSIBLE PERSON Michael A. Duncan a...information. 15. SUBJECT TERMS. Key words or phrases identifying major concepts in the report. 16. SECURITY CLASSIFICATION. Enter security classification in

  14. Aerobic Alcohol Oxidation Using a Copper(I)/TEMPO Catalyst System: A Green, Catalytic Oxidation Reaction for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Hill, Nicholas J.; Hoover, Jessica M.; Stahl, Shannon S.

    2013-01-01

    Modern undergraduate organic chemistry textbooks provide detailed discussion of stoichiometric Cr- and Mn-based reagents for the oxidation of alcohols, yet the use of such oxidants in instructional and research laboratories, as well as industrial chemistry, is increasingly avoided. This work describes a laboratory exercise that uses ambient air as…

  15. Biocatalytic carbon capture via reversible reaction cycle catalyzed by isocitrate dehydrogenase.

    Science.gov (United States)

    Xia, Shunxiang; Frigo-Vaz, Benjamin; Zhao, Xueyan; Kim, Jungbae; Wang, Ping

    2014-09-12

    The practice of carbon capture and storage (CCS) requires efficient capture and separation of carbon dioxide from its gaseous mixtures such as flue gas, followed by releasing it as a pure gas which can be subsequently compressed and injected into underground storage sites. This has been mostly achieved via reversible thermochemical reactions which are generally energy-intensive. The current work examines a biocatalytic approach for carbon capture using an NADP(H)-dependent isocitrate dehydrogenase (ICDH) which catalyzes reversibly carboxylation and decarboxylation reactions. Different from chemical carbon capture processes that rely on thermal energy to realize purification of carbon dioxide, the biocatalytic strategy utilizes pH to leverage the reaction equilibrium, thereby realizing energy-efficient carbon capture under ambient conditions. Results showed that over 25 mol of carbon dioxide could be captured and purified from its gas mixture for each gram of ICDH applied for each carboxylation/decarboxylation reaction cycle by varying pH between 6 and 9. This work demonstrates the promising potentials of pH-sensitive biocatalysis as a green-chemistry route for carbon capture.

  16. Significance of membrane bioreactor design on the biocatalytic performance of glucose oxidase and catalase: Free vs. immobilized enzyme systems

    DEFF Research Database (Denmark)

    Morthensen, Sofie Thage; Meyer, Anne S.; Jørgensen, Henning;

    2017-01-01

    Membrane separation of xylose and glucose can be accomplished via oxidation of glucose to gluconic acid by enzymatic glucose oxidase catalysis. Oxygen for this reaction can be supplied via decomposition of hydrogen peroxide by enzymatic catalase catalysis. In order to maximize the biocatalytic...... productivity of glucose oxidase and catalase (gluconic acid yield per total amount of enzyme) the following system set-ups were compared: immobilization of glucose oxidase alone; co-immobilization of glucose oxidase and catalase; glucose oxidase and catalase free in the membrane bioreactor. Fouling......-induced enzyme immobilization in the porous support of an ultrafiltration membrane was used as strategy for entrapment of glucose oxidase and catalase. The biocatalytic productivity of the membrane reactor was found to be highly related to the oxygen availability, which in turn depended on the reactor...

  17. Functional monolayers on oxide-free silicon surfaces via thiol–ene click chemistry

    NARCIS (Netherlands)

    Caipa Campos, Mabel A.; Paulusse, Jos M.J.; Zuilhof, Han

    2010-01-01

    Thiol–ene click chemistry was used for the attachment of a variety of functional molecules onto oxide-free Si(111) surfaces using very mild conditions; the efficient nature of this coupling strategy allowed for successful light-induced micropatterning and thus provides a novel route towards biofunct

  18. Circular Dichroism Investigation of Dess-Martin Periodinane Oxidation in the Organic Chemistry Laboratory

    Science.gov (United States)

    Reed, Nicole A.; Rapp, Robert D.; Hamann, Christian S.; Artz, Pamela G.

    2005-01-01

    Dess-Martin periodinane oxidation is an experiment that provides an avenue to the introduction of Circular Dichroism (CD) spectroscopy in organic chemistry curriculum as a diagnostic tool for examination of the results of a familiar reaction, and absolute configuration. From the experiment, students increased their understanding of CD theory and…

  19. The impact of oxidation on spore and pollen chemistry: an experimental study

    Science.gov (United States)

    Jardine, Phillip; Fraser, Wesley; Lomax, Barry; Gosling, William

    2016-04-01

    Sporomorphs (pollen and spores) form a major component of the land plant fossil record. Sporomorphs have an outer wall composed of sporopollenin, a highly durable biopolymer, the chemistry of which contains both a signature of ambient ultraviolet-B flux and taxonomic information. Despite the high preservation potential of sporopollenin in the geological record, it is currently unknown how sensitive its chemical signature is to standard palynological processing techniques. Oxidation in particular is known to cause physical degradation to sporomorphs, and it is expected that this should have a concordant impact on sporopollenin chemistry. Here, we test this by experimentally oxidizing Lycopodium (clubmoss) spores using two common oxidation techniques: acetolysis and nitric acid. We also carry out acetolysis on eight angiosperm (flowering plant) taxa to test the generality of our results. Using Fourier Transform infrared (FTIR) spectroscopy, we find that acetolysis removes labile, non-fossilizable components of sporomorphs, but has a limited impact upon the chemistry of sporopollenin under normal processing durations. Nitric acid is more aggressive and does break down sporopollenin and reorganize its chemical structure, but when limited to short treatments (i.e. ≤10 min) at room temperature sporomorphs still contain most of the original chemical signal. These findings suggest that when used carefully oxidation does not adversely affect sporopollenin chemistry, and that palaeoclimatic and taxonomic signatures contained within the sporomorph wall are recoverable from standard palynological preparations.

  20. CHEMISTRY OF SO2 AND DESOX PROCESSES ON OXIDE NANOPARTICLES.

    Energy Technology Data Exchange (ETDEWEB)

    RODRIGUEZ, J.A.

    2006-06-30

    On bulk stoichiometric oxides, SO{sub 2} mainly reacts with the O centers to form SO{sub 3} or SO{sub 4} species that decompose at elevated temperatures. Adsorption on the metal cations occurs below 300 K and does not lead to cleavage of the S-O bonds. In bulk oxides, the occupied cation bands are too stable for effective bonding interactions with the LUMO of SO{sub 2}. The effects of quantum confinement on the electronic properties of oxide nanoparticles and the structural defects that usually accompany these systems in general favor the bonding and dissociation of SO{sub 2}. Thus, nanoparticles of MgO, CaO, SrO, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3} and CeO{sub 2} are all more efficient for sequestering SO{sub 2} than the corresponding bulk oxides. Structural imperfections in pure or metal-doped ceria nanoparticles accelerate the reduction of SO{sub 2} by CO by facilitating the formation and migration of O vacancies in the oxide surface.

  1. Biocatalytic removal of organic sulfur from coal

    Energy Technology Data Exchange (ETDEWEB)

    Webster, D.A. [Illinois Inst. of Tech., Chicago, IL (United States); Kilbane, J.J. II [Institute of Gas Technology, Chicadgo, IL (United States)

    1994-09-09

    The objective is to characterize more completely the biochemical ability of the bacterium, Rhodococcus rhodochrous IGTS8, to cleave carbon-sulfur bonds with emphasis on data that will allow the development of a practical coal biodesulfurization process. Another approach for increasing the desulfurization activity of the IGTS8 cultures is to produce strains genetically that have higher activity. The goal of this part of research is to achieve strain improvement by introducing a stronger promoter using genetic engineering techniques. The promoter regulates the transcription of the genes for the desulfurization enzymes, and a stronger promoter, would up-regulate the expression of these genes, resulting in cells with higher desulfurization activity. Promoter probe vectors are used to identify and isolate promoters from a DNA library of the experimental organism. The major accomplishments have been to obtain high biodesulfurization activity in nonaqueous, media, especially using freeze-dried cells, and to have isolated strong promoters from R. rhodochrous IGTS8 which will be used to engineer the organism to produce strains with higher biocatalytic activity.

  2. Nanopropulsion by biocatalytic self-assembly.

    Science.gov (United States)

    Leckie, Joy; Hope, Alexander; Hughes, Meghan; Debnath, Sisir; Fleming, Scott; Wark, Alastair W; Ulijn, Rein V; Haw, Mark D

    2014-09-23

    A number of organisms and organelles are capable of self-propulsion at the micro- and nanoscales. Production of simple man-made mimics of biological transportation systems may prove relevant to achieving movement in artificial cells and nano/micronscale robotics that may be of biological and nanotechnological importance. We demonstrate the propulsion of particles based on catalytically controlled molecular self-assembly and fiber formation at the particle surface. Specifically, phosphatase enzymes (acting as the engine) are conjugated to a quantum dot (the vehicle), and are subsequently exposed to micellar aggregates (fuel) that upon biocatalytic dephosphorylation undergo fibrillar self-assembly, which in turn causes propulsion. The motion of individual enzyme/quantum dot conjugates is followed directly using fluorescence microscopy. While overall movement remains random, the enzyme-conjugates exhibit significantly faster transport in the presence of the fiber forming system, compared to controls without fuel, a non-self-assembling substrate, or a substrate which assembles into spherical, rather than fibrous structures upon enzymatic dephosphorylation. When increasing the concentration of the fiber-forming fuel, the speed of the conjugates increases compared to non-self-assembling substrate, although directionality remains random.

  3. Biocatalytic desulfurization (BDS) of petrodiesel fuels.

    Science.gov (United States)

    Mohebali, Ghasemali; Ball, Andrew S

    2008-08-01

    Oil refineries are facing many challenges, including heavier crude oils, increased fuel quality standards, and a need to reduce air pollution emissions. Global society is stepping on the road to zero-sulfur fuel, with only differences in the starting point of sulfur level and rate reduction of sulfur content between different countries. Hydrodesulfurization (HDS) is the most common technology used by refineries to remove sulfur from intermediate streams. However, HDS has several disadvantages, in that it is energy intensive, costly to install and to operate, and does not work well on refractory organosulfur compounds. Recent research has therefore focused on improving HDS catalysts and processes and also on the development of alternative technologies. Among the new technologies one possible approach is biocatalytic desulfurization (BDS). The advantage of BDS is that it can be operated in conditions that require less energy and hydrogen. BDS operates at ambient temperature and pressure with high selectivity, resulting in decreased energy costs, low emission, and no generation of undesirable side products. Over the last two decades several research groups have attempted to isolate bacteria capable of efficient desulfurization of oil fractions. This review examines the developments in our knowledge of the application of bacteria in BDS processes, assesses the technical viability of this technology and examines its future challenges.

  4. Biocatalytic potential of laccase-like multicopper oxidases from Aspergillus niger

    Directory of Open Access Journals (Sweden)

    Tamayo-Ramos Juan Antonio

    2012-12-01

    Full Text Available Abstract Background Laccase-like multicopper oxidases have been reported in several Aspergillus species but they remain uncharacterized. The biocatalytic potential of the Aspergillus niger fungal pigment multicopper oxidases McoA and McoB and ascomycete laccase McoG was investigated. Results The laccase-like multicopper oxidases McoA, McoB and McoG from the commonly used cell factory Aspergillus niger were homologously expressed, purified and analyzed for their biocatalytic potential. All three recombinant enzymes were monomers with apparent molecular masses ranging from 80 to 110 kDa. McoA and McoG resulted to be blue, whereas McoB was yellow. The newly obtained oxidases displayed strongly different activities towards aromatic compounds and synthetic dyes. McoB exhibited high catalytic efficiency with N,N-dimethyl-p-phenylenediamine (DMPPDA and 2,2-azino-di(3-ethylbenzthiazoline sulfonic acid (ABTS, and appeared to be a promising biocatalyst. Besides oxidizing a variety of phenolic compounds, McoB catalyzed successfully the decolorization and detoxification of the widely used textile dye malachite green. Conclusions The A. niger McoA, McoB, and McoG enzymes showed clearly different catalytic properties. Yellow McoB showed broad substrate specificity, catalyzing the oxidation of several phenolic compounds commonly present in different industrial effluents. It also harbored high decolorization and detoxification activity with the synthetic dye malachite green, showing to have an interesting potential as a new industrial biocatalyst.

  5. Chemistry and liquid chromatography methods for the analyses of primary oxidation products of triacylglycerols.

    Science.gov (United States)

    Zeb, A

    2015-05-01

    Triacylglycerols (TAGs) are one of the major components of the cells in higher biological systems, which can act as an energy reservoir in the living cells. The unsaturated fatty acid moiety is the key site of oxidation and formation of oxidation compounds. The TAG free radical generates several primary oxidation compounds. These include hydroperoxides, hydroxides, epidioxides, hydroperoxy epidioxides, hydroxyl epidioxides, and epoxides. The presence of these oxidized TAGs in the cell increases the chances of several detrimental processes. For this purpose, several liquid chromatography (LC) methods were reported in their analyses. This review is therefore focused on the chemistry, oxidation, extraction, and the LC methods reported in the analyses of oxidized TAGs. The studies on thin-layer chromatography were mostly focused on the total oxidized TAGs separation and employ hexane as major solvent. High-performance LC (HPLC) methods were discussed in details along with their merits and demerits. It was found that most of the HPLC methods employed isocratic elution with methanol and acetonitrile as major solvents with an ultraviolet detector. The coupling of HPLC with mass spectrometry (MS) highly increases the efficiency of analysis as well as enables reliable structural elucidation. The use of MS was found to be helpful in studying the oxidation chemistry of TAGs and needs to be extended to the complex biological systems.

  6. Click chemistry approach to functionalize two-dimensional macromolecules of graphene oxide nanosheets

    Institute of Scientific and Technical Information of China (English)

    Liang Kou; Hongkun He; Chao Gao

    2010-01-01

    A facile “click chemistry” approach to functionalize 2D macromolecules of graphene oxide nanosheets with poly (ethylene glycol) of different molecular weights, polystyrene, palmitic acid and various amino acids was presented. FTIR, TGA, Raman spectroscopy, XPS, XRD, TEM, AFM and SEM were utilized to characterize the products. High degree of functionalization was achieved on the flat surfaces of graphene oxide, affording polymer-grafted 2D brushes and amino acids-immobilized nanosheets, which show improved solubility in organic solvents. The click chemistry strategy reported herein provides a facile and general method for functionalization of graphene oxide with macromolecules and desired biomolecules.

  7. Three-Carbon Planetary Chemistry - Propylene and Propylene Oxide

    Science.gov (United States)

    Hudson, Reggie L.; Yocum, Katarina; Loeffler, Mark

    2016-10-01

    We recently have published new studies of solid CO2, CH4, C2H2, C2H4, and C2H6, recording new, and in some cases the first, infrared (IR) spectra of the amorphous phases of these compounds and correcting multiple problems and contradictions in the literature that have persisted for several decades and influenced both planetary and interstellar studies (e.g., Hudson et al. 2014, 2015). We now extend this work by examining two three-carbon molecules, the acyclic propylene (C3H6) and the cyclic molecule propylene oxide (OC3H6). Both molecules have been detected in low-temperature astronomical environments (Titan, interstellar medium (ISM)) and are suspected in others. However, in contrast to the astronomical relevance of these compounds, there are almost no laboratory measurements of spectra and other properties for either of them at low temperatures. Here we report new results on ices containing propylene and propylene oxide including IR spectra of multiple solid phases and measurements of phase transition temperatures, IR band strengths, refractive indices, vapor pressures, and sublimation energies. Radiation-chemical reactions connecting propylene and propylene oxide have been investigated for possible applications to the moon, Europa, TNOs, comets, and the ISM, and first results will be presented. Propylene oxide is of particular interest as it recently was announced (McGuire et al. 2016) as the first chiral molecule identified in the ISM. [Our work was supported by NASA Goddard's DREAM2 center, funded by NASA's SSERVI program, and by the NASA Astrobiology Institute's Goddard Center for Astrobiology.

  8. Sustainable biocatalytic biodiesel production : A thermodynamic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Guezel, G.

    2012-09-15

    In the present thesis it was aimed at achieving thermodynamic analysis of reactions involved in enzymatic biodiesel production with specific focus on chemical and phase equilibria of reactive systems. Lipase-catalyzed biodiesel production (biocatalytic ethanolysis) presents significant advantages: Easy recovery of glycerol, no complex down-processing operations for elimination of catalyst and salt, and requires less organic solvent and lower energy consumption compared with conventional chemical methods. In overall, the major aims of this thesis were evaluating and subsequently finding feasible solutions to the questions emerged during the corresponding studies that have been performed worldwide. Some of the questions that were answered as appropriate as possible can be listed as follows: 1) What is the solubility of EtOH in vegetable oils and in FAEE blends and how does it change with temperature? 2) Is it possible to prevent denaturing impact of EtOH on biocatalysts? 3) What are the feedstock content (water and FFA) impacts on glycerol and EtOH miscibility with ester species? 4) Is it necessary removing glycerol by-product simultaneously? 5) Is it feasible providing monophasic or homogeneous reaction media that procure lower external mass transfer resistance? 6) What are the moisture absorption limits of FAAE species? 7) How are the interactions of reactive species in terms of miscibility/immiscibility phenomena? 8) Is it thermodynamically feasible providing monophasic reaction media? 9) How can LLE and VLE phase behaviors help to determine optimum reaction conditions? 10) How can the results of LLE and VLE studies be used so as to determine appropriate refining operations? (LN)

  9. Flotation and flocculation chemistry of coal and oxidized coals

    Energy Technology Data Exchange (ETDEWEB)

    Somasundaran, P.

    1990-01-01

    The objective of this research project is to understand the fundamentals involved in the flotation and flocculation of coal and oxidized coals and elucidate mechanisms by which surface interactions between coal and various reagents enhance coal beneficiation. An understanding of the nature of the heterogeneity of coal surfaces arising from the intrinsic distribution of chemical moieties is fundamental to the elucidation of mechanism of coal surface modification and its role in interfacial processes such as flotation, flocculation and agglomeration. A new approach for determining the distribution in surface properties of coal particles was developed in this study and various techniques capable of providing such information were identified. Distributions in surface energy, contact angle and wettability were obtained using novel techniques such as centrifugal immersion and film flotation. Changes in these distributions upon oxidation and surface modifications were monitored and discussed. An approach to the modelling of coal surface site distributions based on thermodynamic information obtained from gas adsorption and immersion calorimetry is proposed. Polyacrylamide and dodecane was used to alter the coal surface. Methanol adsorption was also studied. 62 figs.

  10. Coated-wall microreactor for continuous biocatalytic transformations using immobilized enzymes.

    Science.gov (United States)

    Thomsen, Malene S; Nidetzky, Bernd

    2009-01-01

    Microstructured flow reactors are emerging tools for biocatalytic process development. A compelling design is that of the coated-wall reactor where enzyme is present as a surface layer attached to microchannel walls. However, preparation of a highly active wall biocatalyst remains a problem. Here, a stainless steel microreactor was developed where covalent immobilization of the enzyme in multiple linear flow channels of the reaction plate was supported by a macroporous wash-coat layer of gamma-aluminum oxide. Using surface functionalization with aminopropyl triethoxysilane followed by activation with glutardialdehyde, the thermophilic beta-glycosidase CelB from Pyrococcus furiosus was bound with retention of half of the specific activity of the free enzyme (800 U/mg), yielding a high catalyst loading of about 500 U/mL. This microreactor was employed for the continuous hydrolysis of lactose (100 mM) at 80 degrees C, providing a space-time yield of 500 mg glucose/(mL h) at a stable conversion of > or =70%. The immobilized enzyme displayed a half-life of 15 days under the operational conditions. Due to the absence of hydrophobic solute-material interactions, which limit the scope of microstructures fabricated from poly(dimethylsiloxane) for biocatalytic applications, the new microreactor was fully compatible with the alternate enzyme substrate 2-nitro-phenyl-beta-D-galactoside and the 2-nitro-phenol product resulting from its hydrolysis catalyzed by CelB.

  11. Experimental determination of thermodynamic equilibrium in biocatalytic transamination

    DEFF Research Database (Denmark)

    Tufvesson, Pär; Jensen, Jacob Skibsted; Kroutil, Wolfgang;

    2012-01-01

    The equilibrium constant is a critical parameter for making rational design choices in biocatalytic transamination for the synthesis of chiral amines. However, very few reports are available in the scientific literature determining the equilibrium constant (K) for the transamination of ketones...

  12. Multistep soft chemistry method for valence reduction in transition metal oxides with triangular (CdI2-type) layers.

    Science.gov (United States)

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

    2014-03-14

    Transition metal (M) oxides with MO2 triangular layers demonstrate a variety of physical properties depending on the metal oxidation states. In the known compounds, metal oxidation states are limited to either 3+ or mixed-valent 3+/4+. A multistep soft chemistry synthetic route for novel phases with M(2+/3+)O2 triangular layers is reported.

  13. Non-OH chemistry in oxidation flow reactors for the study of atmospheric chemistry systematically examined by modeling

    Directory of Open Access Journals (Sweden)

    Z. Peng

    2015-09-01

    Full Text Available Oxidation flow reactors (OFRs using low-pressure Hg lamp emission at 185 and 254 nm produce OH radicals efficiently and are widely used in atmospheric chemistry and other fields. However, knowledge of detailed OFR chemistry is limited, allowing speculation in the literature about whether some non-OH reactants, including several not relevant for tropospheric chemistry, may play an important role in these OFRs. These non-OH reactants are UV radiation, O(1D, O(3P, and O3. In this study, we investigate the relative importance of other reactants to OH for the fate of reactant species in OFR under a wide range of conditions via box modeling. The relative importance of non-OH species is less sensitive to UV light intensity than to relative humidity (RH and external OH reactivity (OHRext, as both non-OH reactants and OH scale roughly proportional to UV intensity. We show that for field studies in forested regions and also the urban area of Los Angeles, reactants of atmospheric interest are predominantly consumed by OH. We find that O(1D, O(3P, and O3 have relative contributions to VOC consumption that are similar or lower than in the troposphere. The impact of O atoms can be neglected under most conditions in both OFR and troposphere. Under "pathological OFR conditions" of low RH and/or high OHRext, the importance of non-OH reactants is enhanced because OH is suppressed. Some biogenics can have substantial destructions by O3, and photolysis at non-tropospheric wavelengths (185 and 254 nm may also play a significant role in the degradation of some aromatics under pathological conditions. Working under low O2 with the OFR185 mode allows OH to completely dominate over O3 reactions even for the biogenic species most reactive with O3. Non-tropospheric VOC photolysis may have been a problem in some laboratory and source studies, but can be avoided or lessened in future studies by diluting source emissions and working at lower precursor concentrations in lab

  14. Biocatalytic Characterization of Human FMO5: Unearthing Baeyer-Villiger Reactions in Humans.

    Science.gov (United States)

    Fiorentini, Filippo; Geier, Martina; Binda, Claudia; Winkler, Margit; Faber, Kurt; Hall, Mélanie; Mattevi, Andrea

    2016-04-15

    Flavin-containing mono-oxygenases are known as potent drug-metabolizing enzymes, providing complementary functions to the well-investigated cytochrome P450 mono-oxygenases. While human FMO isoforms are typically involved in the oxidation of soft nucleophiles, the biocatalytic activity of human FMO5 (along its physiological role) has long remained unexplored. In this study, we demonstrate the atypical in vitro activity of human FMO5 as a Baeyer-Villiger mono-oxygenase on a broad range of substrates, revealing the first example to date of a human protein catalyzing such reactions. The isolated and purified protein was active on diverse carbonyl compounds, whereas soft nucleophiles were mostly non- or poorly reactive. The absence of the typical characteristic sequence motifs sets human FMO5 apart from all characterized Baeyer-Villiger mono-oxygenases so far. These findings open new perspectives in human oxidative metabolism.

  15. Kinetic and photochemical data for atmospheric chemistry reactions of the nitrogen oxides

    Science.gov (United States)

    Hampson, R. F., Jr.

    1980-01-01

    Data sheets for thermal and photochemical reactions of importance in the atmospheric chemistry of the nitrogen oxides are presented. For each reaction the available experimental data are summarized and critically evaluated, and a preferred value of the rate coefficient is given. The selection of the preferred value is discussed and an estimate of its accuracy is given. For the photochemical process, the data are summarized, and preferred for the photoabsorption cross section and primary quantum yields are given.

  16. Efficient Functionalization of Oxide-Free Silicon(111) Surfaces: Thiol–yne versus Thiol–ene Click Chemistry

    NARCIS (Netherlands)

    Bhairamadgi, N.S.; Gangarapu, S.; Caipa Campos, M.A.; Paulusse, J.M.J.; Rijn, van C.J.M.; Zuilhof, H.

    2013-01-01

    Thiol-yne click (TYC) chemistry was utilized as a copper-free click reaction for the modification of alkyne-terminated monolayers on oxide-free Si(111) surfaces, and the results were compared with the analogous thiol–ene click (TEC) chemistry. A wide range of thiols such as 9-fluorenylmethoxy-carbon

  17. Efficient Functionalization of Oxide-Free Silicon(111) Surfaces: Thiol-yne versus Thiol-ene Click Chemistry

    NARCIS (Netherlands)

    Bhairamadgi, N.S.; Gangarapu, S.; Caipa Campos, M.A.; Paulusse, J.M.J.; Rijn, van C.J.M.; Zuilhof, H.

    2013-01-01

    Thiol-yne click (TYC) chemistry was utilized as a copper-free click reaction for the modification of alkyne-terminated monolayers on oxide-free Si(111) surfaces, and the results were compared with the analogous thiol–ene click (TEC) chemistry. A wide range of thiols such as 9-fluorenylmethoxy-carbon

  18. Selection of crucible oxides in molten titanium and titanium aluminum alloys by thermo-chemistry calculations

    Directory of Open Access Journals (Sweden)

    Kostov A.

    2005-01-01

    Full Text Available Titanium and its alloys interstitially dissolve a large amount of impurities such as oxygen and nitrogen, which degrade the mechanical and physical properties of alloys. On the other hand crucible oxides based on CaO, ZrO2 Y2O3, etc., and their spinels (combination of two or more oxides can be used for melting titanium and its alloys. However, the thermodynamic behavior of calcium, zirconium, yttrium on the one side, and oxygen on the other side, in molten Ti and Ti-Al alloys have not been made clear and because of that, it is very interesting for research. Owing of literature data, as well as these crucibles are cheaper than standard crucibles for melting titanium and titanium alloys, in this paper will be presented the results of selection of thermo-chemistry analysis with the aim to determine the crucible oxide stability in contact with molten titanium and titanium-aluminum alloys.

  19. Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces.

    Science.gov (United States)

    Chapleski, Robert C; Zhang, Yafen; Troya, Diego; Morris, John R

    2016-07-01

    Heterogeneous chemistry of the most important atmospheric oxidants, O3, NO3, and OH, plays a central role in regulating atmospheric gas concentrations, processing aerosols, and aging materials. Recent experimental and computational studies have begun to reveal the detailed reaction mechanisms and kinetics for gas-phase O3, NO3, and OH when they impinge on organic surfaces. Through new research approaches that merge the fields of traditional surface science with atmospheric chemistry, researchers are developing an understanding for how surface structure and functionality affect interfacial chemistry with this class of highly oxidizing pollutants. Together with future research initiatives, these studies will provide a more complete description of atmospheric chemistry and help others more accurately predict the properties of aerosols, the environmental impact of interfacial oxidation, and the concentrations of tropospheric gases.

  20. Steam assisted oxide growth on aluminium alloys using oxidative chemistries: Part I Microstructural investigation

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Piotrowska, Kamila; Gudla, Visweswara Chakravarthy;

    2015-01-01

    The surface treatment of aluminium alloys under steam containing KMnO4 and HNO3resulted in the formation of an oxide layer having a thickness of up to 825 nm. The use of KMnO4 and HNO3 in the steam resulted in incorporation of the respective chemical species into the oxide layer. Steam treatment ...

  1. Non-OH chemistry in oxidation flow reactors for the study of atmospheric chemistry systematically examined by modeling

    Science.gov (United States)

    Peng, Zhe; Day, Douglas A.; Ortega, Amber M.; Palm, Brett B.; Hu, Weiwei; Stark, Harald; Li, Rui; Tsigaridis, Kostas; Brune, William H.; Jimenez, Jose L.

    2016-04-01

    Oxidation flow reactors (OFRs) using low-pressure Hg lamp emission at 185 and 254 nm produce OH radicals efficiently and are widely used in atmospheric chemistry and other fields. However, knowledge of detailed OFR chemistry is limited, allowing speculation in the literature about whether some non-OH reactants, including several not relevant for tropospheric chemistry, may play an important role in these OFRs. These non-OH reactants are UV radiation, O(1D), O(3P), and O3. In this study, we investigate the relative importance of other reactants to OH for the fate of reactant species in OFR under a wide range of conditions via box modeling. The relative importance of non-OH species is less sensitive to UV light intensity than to water vapor mixing ratio (H2O) and external OH reactivity (OHRext), as both non-OH reactants and OH scale roughly proportionally to UV intensity. We show that for field studies in forested regions and also the urban area of Los Angeles, reactants of atmospheric interest are predominantly consumed by OH. We find that O(1D), O(3P), and O3 have relative contributions to volatile organic compound (VOC) consumption that are similar or lower than in the troposphere. The impact of O atoms can be neglected under most conditions in both OFR and troposphere. We define "riskier OFR conditions" as those with either low H2O ( 200 s-1 in OFR254). We strongly suggest avoiding such conditions as the importance of non-OH reactants can be substantial for the most sensitive species, although OH may still dominate under some riskier conditions, depending on the species present. Photolysis at non-tropospheric wavelengths (185 and 254 nm) may play a significant (> 20 %) role in the degradation of some aromatics, as well as some oxidation intermediates, under riskier reactor conditions, if the quantum yields are high. Under riskier conditions, some biogenics can have substantial destructions by O3, similarly to the troposphere. Working under low O2 (volume mixing

  2. Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab

    Science.gov (United States)

    Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

    2006-01-01

    A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

  3. The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

    Science.gov (United States)

    Černý, Radovan; Schouwink, Pascal

    2015-12-01

    The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

  4. Green chemistry perspectives of methane conversion via oxidative methylation of aromatics over zeolite catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Adebajo, M.O. [University of Queensland, St Lucia, Qld. (Australia)

    2007-06-15

    This paper provides a general overview of the recent work that we and other researchers have done on the utilisation of methane for catalytic methylation of aromatic compounds and for direct coal liquefaction for the production of liquid hydrocarbons. In particular, the paper presents a detailed description of more recent substantial experimental evidence that we have provided for the requirement of oxygen as a stoichiometry reactant for benzene methylation with methane over moderately acidic zeolite catalysts. The reaction, which has been termed 'oxidative methylation', was thus postulated to involve a two-step mechanism involving intermediate methanol formation by methane partial oxidation, followed by benzene methylation with methanol in the second step. However, strongly acidic zeolites can cause cracking of benzene to yield methylated products in the absence of oxygen. The participation of methane and oxygen, and the effective use of zeolite catalysts in this methylation reaction definitely have some positive green chemistry implications. Thus, the results of these previous studies are also discussed in this review in light of the principles and tools of green chemistry. Various metrics were used to evaluate the greenness, cost-effectiveness, and material and energy efficiency of the oxidative methylation reaction.

  5. Microscale technology and biocatalytic processes: Opportunities and challenges for synthesis

    DEFF Research Database (Denmark)

    Wohlgemuth, Roland; Plazl, Igor; Žnidaršič-Plazl, Polona

    2015-01-01

    Despite the expanding presence of microscale technology in chemical synthesis and energy production as well as in biomedical devices and analytical and diagnostic tools, its potential in biocatalytic processes for pharmaceutical and fine chemicals, as well as related industries, has not yet been ......, and the future outlook for the implementation of these key green engineering methods and the role of supporting tools such as mathematical models to establish sustainable production processes are discussed....

  6. Steam assisted oxide growth on aluminium alloys using oxidative chemistries: Part I Microstructural investigation

    Science.gov (United States)

    Din, Rameez Ud; Piotrowska, Kamila; Gudla, Visweswara Chakravarthy; Jellesen, Morten Stendahl; Ambat, Rajan

    2015-11-01

    The surface treatment of aluminium alloys under steam containing KMnO4 and HNO3 resulted in the formation of an oxide layer having a thickness of up to 825 nm. The use of KMnO4 and HNO3 in the steam resulted in incorporation of the respective chemical species into the oxide layer. Steam treatment with solution containing HNO3 caused dissolution of Cu and Si from the intermetallic particles in the aluminium substrate. The growth rate of oxide layer was observed to be a function of MnO4- and NO3- ions present in the aqueous solution. The NO3- ions exhibit higher affinity towards the intermetallic particles resulting in poor coverage by the steam generated oxide layer compared to the coating formed using MnO4- ions. Further, increase in the concentration of NO3- ions in the solution retards precipitation of the steam generated aluminium hydroxide layer.

  7. Oxide/Water Interfaces: How the Surface Chemistry Modifies the Electronic Energy Alignment

    Science.gov (United States)

    Sprik, Michiel

    2014-03-01

    The minimum of the d-electron conduction band of an aqueous transition metal oxide electrode is typically no more than a few 100 mV away from the standard hydrogen electrode (SHE). Because of this favourable alignment of the electronic energy levels (near) metallic transition metal oxides with partly filled d bands can be used as electrocatalysts while the compounds with finite electronic gap can be used as photocatalysts. However, because of their ionic character, transition metal-oxide surfaces also show amphiphilic acid-base activity. At low pH the basic sites are protonated and at high pH the acidic sites deprotonated creating an electrical double layer with corresponding surface potential. The alignment of the electronic energy levels, and by implication their redox activity, is therefore pH dependent. In fact, even in absence of protonic surface charge, the coordination with water molecules is already capable of shifting the electronic energy levels of the oxide by 1 eV or more. Computation of the electronic energies in transition metal oxide electrodes requires therefore a detailed modeling of their aqueous surface chemistry. The solvation energy of the proton is the common energy reference for both redox potentials on the SHE scale and acidity constants (pKa). Computation of the H+ solvation energy is therefore a key component in a unified treatment of redox and acid-base chemistry. In this talk we outline the Density Functional Theory based Molecular Dynamics (DFTMD) method we have developed for this purpose. The central tool of our approach is a method for reversible insertion of protons in the aqueous part of the DFTMD model system. As an illustration we discuss the application to the rutile TiO2/water and MnO2/water interface.

  8. A methodology for development of biocatalytic processes

    DEFF Research Database (Denmark)

    Lima Ramos, Joana

    -enzymatic process, chiral amine production using Z-transaminase and finally long-chain chiral aliphatic Abstract ii alcohol production by a bi-enzymatic system. For each case study presented, a different tool is used to guide development and evaluate the process when different levels of underlying process knowledge...... are available. The first case study presents a rational approach for defining a development strategy for multi-enzymatic processes. The proposed methodology requires a profound and structured knowledge of the multi-enzyme systems, integrating chemistry, biological and process engineering. In order to suggest......). These process metrics can often be attained by improvements in the reaction chemistry, the biocatalyst, and/or by process engineering, which often requires a complex process development strategy. Interestingly this complexity, which arises from the need for integration of biological and process technologies...

  9. Oxygen transfer rates and requirements in oxidative biocatalysis

    DEFF Research Database (Denmark)

    Pedersen, Asbjørn Toftgaard; Rehn, Gustav; Woodley, John

    Biocatalytic oxidation reactions offer several important benefits such as regio- and stereoselectivity, avoiding the use of toxic metal based catalysts and replacing oxidizing reagents by allowing the use of oxygen. However, the development of biocatalytic oxidation processes is a complex task wh......-up is relatively straight forward (Gabelman and Hwang, 1999), and membrane contactors are implemented for various industrial applications (Klaassen et al., 2005)....

  10. Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

    Science.gov (United States)

    Külah, Elçin; Marot, Laurent; Steiner, Roland; Romanyuk, Andriy; Jung, Thomas A.; Wäckerlin, Aneliia; Meyer, Ernst

    2017-01-01

    Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect – oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level. PMID:28327642

  11. Fluorescent detection of copper(II) based on DNA-templated click chemistry and graphene oxide.

    Science.gov (United States)

    Zhou, Lifen; Shen, Qinpeng; Zhao, Peng; Xiang, Bingbing; Nie, Zhou; Huang, Yan; Yao, Shouzhuo

    2013-12-15

    A novel DNA-templated click chemistry strategy for homogenous fluorescent detection of Cu(2+) has been developed based on click ligation-dependent DNA structure switch and the selective quenching ability of graphene oxide (GO) nanosheet. The clickable duplex probe consists of two DNA strands with alkyne and azide group, respectively, and Cu(+)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction can chemically ligate these two strands. Toehold sequence displacement was consequently exploited to achieve DNA structure transformation bearing fluorescent tag FAM. Cu(2+)-induced chemical ligation caused the probe transfer to hybrid structure with single stranded DNA (ssDNA) tail, while only duplex structure was obtained without Cu(2+). This structural difference can be probed by GO-based fluorescence detection due to the preferential binding of GO to ssDNA. Under the optimum conditions, this sensor can sensitively and specifically detect Cu(2+) with a low detection limit of 58 nM and a linear range of 0.1-10 μM. This new strategy is highly sensitive and selective for Cu(2+) detection because of the great specificity of click chemistry and super-quenching ability of GO. Moreover, with the aid of high efficient DNA templated synthesis, the detection process requires only about half an hour which is much quicker than previous click-chemistry-based Cu(2+) sensors.

  12. Thermal chemistry of copper acetamidinate atomic layer deposition precursors on silicon oxide surfaces studied by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Yunxi; Zaera, Francisco, E-mail: zaera@ucr.edu [Department of Chemistry, University of California, Riverside, California 92521 (United States)

    2016-01-15

    The thermal surface chemistry of copper(I)-N,N′-di-sec-butylacetamidinate, [Cu({sup s}Bu-amd)]{sub 2}, a metalorganic complex recently proposed for the chemical-based deposition of copper films, has been characterized on SiO{sub 2} films under ultrahigh vacuum conditions by x-ray photoelectron spectroscopy (XPS). Initial adsorption at cryogenic temperatures results in the oxidation of the copper centers with Cu 2p{sub 3/2} XPS binding energies close to those seen for a +2 oxidation state, an observation that the authors interpret as the result of the additional coordination of oxygen atoms from the surface to the Cu atoms of the molecular acetamidinate dimer. Either heating to 300 K or dosing the precursor directly at that temperature leads to the loss of one of its two ligands, presumably via hydrogenation/protonation with a hydrogen/proton from a silanol group, or following a similar reaction on a defect site. By approximately 500 K the Cu 2p{sub 3/2}, C 1s, and N 1s XPS data suggest that the remaining acetamidinate ligand is displaced from the copper center and bonds to the silicon oxide directly, after which temperatures above 900 K need to be reached to promote further (and only partial) decomposition of those organic moieties. It was also shown that the uptake of the Cu precursor is self-limiting at either 300 or 500 K, although the initial chemistry is somewhat different at the two temperatures, and that the nature of the substrate also defines reactivity, with the thin native silicon oxide layer always present on Si(100) surfaces being less reactive than thicker films grown by evaporation, presumably because of the lower density of surface nucleation sites.

  13. Surface chemistry and cytotoxicity of reactively sputtered tantalum oxide films on NiTi plates

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, K. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Kolaj-Robin, O.; Belochapkine, S.; Laffir, F. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Gandhi, A.A. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Tofail, S.A.M., E-mail: tofail.syed@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland)

    2015-08-31

    NiTi, an equiatomic alloy containing nickel and titanium, exhibits unique properties such as shape memory effect and superelasticity. NiTi also forms a spontaneous protective titanium dioxide (TiO{sub 2}) layer that allows its use in biomedical applications. Despite the widely perceived biocompatibility there remain some concerns about the sustainability of the alloy's biocompatibility due to the defects in the TiO{sub 2} protective layer and the presence of high amount of sub-surface Ni, which can give allergic reactions. Many surface treatments have been investigated to try to improve both the corrosion resistance and biocompatibility of this layer. For such purposes, we have sputter deposited tantalum (Ta) oxide thin films onto the surface of the NiTi alloy. Despite being one of the promising metals for biomedical applications, Ta, and its various oxides and their interactions with cells have received relatively less attention. The oxidation chemistry, crystal structure, morphology and biocompatibility of these films have been investigated. In general, reactive sputtering especially in the presence of a low oxygen mixture yields a thicker film with better control of the film quality. The sputtering power influenced the surface oxidation states of Ta. Both microscopic and quantitative cytotoxicity measurements show that Ta films on NiTi are biocompatible with little to no variation in cytotoxic response when the surface oxidation state of Ta changes. - Highlights: • Reactive sputtering in low oxygen mixture yields thicker better quality films. • Sputtering power influenced surface oxidation states of Ta. • Cytotoxicity measurements show Ta films on NiTi are biocompatible. • Little to no variation in cytotoxic response when oxidation state changes.

  14. Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces

    OpenAIRE

    Chapleski, Robert C.; Zhang, Yafen; Troya, Diego; Morris, John R.

    2015-01-01

    Heterogeneous chemistry of the most important atmospheric oxidants, O3, NO3, and OH, plays a central role in regulating atmospheric gas concentrations, processing aerosols, and aging materials. Recent experimental and computational studies have begun to reveal the detailed reaction mechanisms and kinetics for gas-phase O3, NO3, and OH when they impinge on organic surfaces. Through new research approaches that merge the fields of traditional surface science with atmospheric chemistry, research...

  15. CHEMISTRY OF SO{sub 2} ON MODEL METAL AND OXIDE CATALYSTS: PHOTOEMISSION AND XANES STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    RODRIGUEZ,J.A.; JIRSAK,T.; CHATURVEDI,S.; HRBEK,J.; FREITAG,A.; LARESE,J.Z.

    2000-07-09

    High-resolution synchrotron based photoemission and x-ray absorption spectroscopy have been used to study the interaction of SO{sub 2} with a series of metals and oxides. The chemistry of SO{sub 2} on metal surfaces is rich. At low coverages, the molecule fully decomposes into atomic S and O. At large coverages, the formation of SO{sub 3} and SO{sub 4} takes place. The following sequence was found for the reactivity of the metals towards SO{sub 2}: Pt {approx} Rh < Ru < Mo << Zn, Sn, Cs. Alloying can be useful for reducing the chemical affinity of a metal for SO{sub 2} and controlling S poisoning. Pd atoms bonded to Rh and Pt atoms bonded to Sn interact weakly with SO{sub 2}. In general, SO{sub 2} mainly reacts with the O centers of metal oxides. SO{sub 4} is formed on CeO{sub 2} and SO{sub 3} on ZnO. On these systems there is no decomposition of SO{sub 2}. Dissociation of the molecule is observed after introducing a large amount of Ce{sup 3+} sites in ceria, or after depositing Cu or alkali metals on the oxide surfaces. These promote the catalytic activity of the oxides during the destruction of SO{sub 2}.

  16. Radical Chemistry and Cytotoxicity of Bioreductive 3-Substituted Quinoxaline Di-N-Oxides.

    Science.gov (United States)

    Anderson, Robert F; Yadav, Pooja; Shinde, Sujata S; Hong, Cho R; Pullen, Susan M; Reynisson, Jóhannes; Wilson, William R; Hay, Michael P

    2016-08-15

    The radical chemistry and cytotoxicity of a series of quinoxaline di-N-oxide (QDO) compounds has been investigated to explore the mechanism of action of this class of bioreductive drugs. A series of water-soluble 3-trifluoromethyl (4-10), 3-phenyl (11-19), and 3-methyl (20-21) substituted QDO compounds were designed to span a range of electron affinities consistent with bioreduction. The stoichiometry of loss of QDOs by steady-state radiolysis of anaerobic aqueous formate buffer indicated that one-electron reduction of QDOs generates radicals able to initiate chain reactions by oxidation of formate. The 3-trifluoromethyl analogues exhibited long chain reactions consistent with the release of the HO(•), as identified in EPR spin trapping experiments. Several carbon-centered radical intermediates, produced by anaerobic incubation of the QDO compounds with N-terminal truncated cytochrome P450 reductase (POR), were characterized using N-tert-butyl-α-phenylnitrone (PBN) and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps and were observed by EPR. Experimental data were well simulated for the production of strongly oxidizing radicals, capable of H atom abstraction from methyl groups. The kinetics of formation and decay of the radicals produced following one-electron reduction of the parent compounds, both in oxic and anoxic solutions, were determined using pulse radiolysis. Back oxidation of the initially formed radical anions by molecular oxygen did not compete effectively with the breakdown of the radical anions to form oxidizing radicals. The QDO compounds displayed low hypoxic selectivity when tested against oxic and hypoxic cancer cell lines in vitro. The results from this study form a kinetic description and explanation of the low hypoxia-selective cytotoxicity of QDOs against cancer cells compared to the related benzotriazine 1,4-dioxide (BTO) class of compounds.

  17. The basic chemistry of exercise-induced DNA oxidation: oxidative damage, redox signalling and their interplay

    Directory of Open Access Journals (Sweden)

    James Nathan Cobley

    2015-06-01

    Full Text Available Acute exercise increases reactive oxygen and nitrogen species generation. This phenomenon is associated with two major outcomes: (1 redox signalling and (2 macromolecule damage. Mechanistic knowledge of how exercise-induced redox signalling and macromolecule damage are interlinked is limited. This review focuses on the interplay between exercise-induced redox signalling and DNA damage, using hydroxyl radical (·OH and hydrogen peroxide (H2O2 as exemplars. It is postulated that the biological fate of H2O2 links the two processes and thus represents a bifurcation point between redox signalling and damage. Indeed, H2O2 can participate in two electron signalling reactions but its diffusion and chemical properties permit DNA oxidation following reaction with transition metals and ·OH generation. It is also considered that the sensing of DNA oxidation by repair proteins constitutes a non-canonical redox signalling mechanism. Further layers of interaction are provided by the redox regulation of DNA repair proteins and their capacity to modulate intracellular H2O2 levels. Overall, exercise-induced redox signalling and DNA damage may be interlinked to a greater extent than was previously thought but this requires further investigation.

  18. Tuning microstructure and surface chemistry of reduced graphene oxide by mild reduction

    Institute of Scientific and Technical Information of China (English)

    冷娴; 刘如铁; 邹俭鹏; 熊翔; 何捍卫

    2016-01-01

    Reduced graphene oxide (RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with larged spacing (0.852 nm) of graphene oxide (GO), the (002) plane distance decreases to 0.358−0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. TheID/IG ratio of RGOs is about 1.0−1.15, indicating that reconstructed sp2 domains have smaller sizes and larger quantity. The content of sp2 bonded C in GO (36.93%, molar fraction) increases to 45.48%−72.92% (molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.

  19. Modeling chemistry in and above snow at Summit, Greenland − Part 2: Impact of snowpack chemistry on the oxidation capacity of the boundary layer

    Directory of Open Access Journals (Sweden)

    B. Lefer

    2012-02-01

    Full Text Available The chemical composition of the boundary layer in snow covered regions is impacted by chemistry in the snowpack via uptake, processing, and emission of atmospheric trace gases. We use the coupled one-dimensional (1-D snow chemistry and atmospheric boundary layer model MISTRA-SNOW to study the impact of snowpack chemistry on the oxidation capacity of the boundary layer. The model includes gas phase photochemistry and chemical reactions both in the interstitial air and the atmosphere. Chemistry on snow grains is simulated assuming a liquid-like layer (LLL, treated as an aqueous layer on the snow grain surface. The model has been recently compared with BrO and NO data taken on 10 June–13 June 2008 as part of the Greenland Summit Halogen-HOx experiment (GSHOX. In the present study, we use the same focus period to investigate the influence of snowpack derived chemistry on OH and HOx + RO2 in the boundary layer. We compare model results with chemical ionization mass spectrometry (CIMS measurements of the hydroxyl radical (OH and of the hydroperoxyl radical (HO2 plus the sum of all organic peroxy radicals (RO2 taken at Summit during summer 2008. Using sensitivity runs we show that snowpack influenced nitrogen cycling and bromine chemistry both increase the oxidation capacity of the boundary layer and that together they increase the mid-day OH concentrations by approximately a factor of 2. We show for the first time, using an unconstrained coupled one-dimensional snowpack-boundary layer model, that air-snow interactions impact the oxidation capacity of the boundary layer and that it is not possible to match measured OH levels without snowpack NOx and halogen emissions. Model predicted HONO compared with mistchamber measurements suggests there may be an unknown HONO source at Summit. Other model predicted HOx precursors, H2O2 and HCHO, compare well with measurements taken in summer 2000. Over 3 days, snow sourced NOx contributes an additional 2 ppb to

  20. Measurement and modelling of the defect chemistry and transport properties of ceramic oxide mixed ionic and electronic conductors

    NARCIS (Netherlands)

    Dalslet, Bjarke Thomas

    2008-01-01

    The mixed ionic and electronic conducting fluorite and perovskite materials examined in this thesis are all oxide ion conducting materials. The defect chemistry and transport properties of a number of these materials are measured using: 1) a measurement technique using an oxygen pump and an electrol

  1. Influence of pH on the redox chemistry of metal (hydr)oxides and organic matter in paddy soils

    NARCIS (Netherlands)

    Pan, Y.; Koopmans, G.F.; Bonten, L.T.C.; Song, J.; Luo, Y.; Temminghoff, E.J.M.; Comans, R.N.J.

    2014-01-01

    The primary purpose of this study was to determine how flooding and draining cycles affect the redox chemistry of metal (hydr)oxides and organic matter in paddy soils and how the pH influences these processes. Our secondary purpose was to determine to what extent a geochemical thermodynamic equilibr

  2. Chemistry and oxidation capacity of the nitrate radical in the continental boundary layer near Berlin

    Science.gov (United States)

    Geyer, Andreas; Alicke, BjöRn; Konrad, Stephan; Schmitz, Thomas; Stutz, Jochen; Platt, Ulrich

    2001-04-01

    The nitrate radical is in many situations the most important nighttime oxidizing species, removing, for example, hydrocarbons, which would otherwise be available to daytime ozone formation. In spite of its importance in the night and probably also under certain conditions during the day, our understanding of the NO3 chemistry and its impact on the oxidation capacity of the atmosphere is still incomplete. Here we present measurements of NO3 by differential optical absorption spectroscopy (DOAS) and a number of other atmospheric trace gases performed during the Berliner Ozonexperiment (BERLIOZ) campaign at Pabstthum near Berlin, Germany, to quantify the contribution of NO3 to the atmospheric oxidation rate of volatile organic compounds (VOCs) and NOx removal. The measurements show that only two NO3 sinks were of importance: (1) About 50-30% (depending on the distance (0.1-3 km) to a near forest) of the NO3 was lost due to reaction with biogenic hydrocarbons. (2) The major part of the remaining loss probably can be attributed to the indirect loss via the reaction of N2O5 on aerosol surfaces. Assuming that heterogeneous hydrolysis of N2O5 is occurring, the nonphotolytical conversion of NOx to HNO3 via N2O5 was found to be comparable with daytime conversion by the reaction of OH with NO2. In combination with measurements of the OH concentration, it was possible for the first time to derive a relative contribution of 28% (24-hour average) for the NO3-initiated oxidation to the total VOC degradation.

  3. A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere

    Energy Technology Data Exchange (ETDEWEB)

    Francisco, Joseph S.; Kathmann, Shawn M.; Schenter, Gregory K.; Dang, Liem X.; Xantheas, Sotiris S.; Garrett, Bruce C.; Du, Shiyu; Dixon, David A.; Bianco, Roberto; Wang, Shuzhi; Hynes, James T.; Morita, Akihiro; Peterson, Kirk A.

    2006-04-18

    An understanding of the mechanisms and kinetics of aerosol formation and ozone production in the troposphere is currently a high priority because these phenomena are recognized as two major effects of energy-related air pollution. Atmospheric aerosols are of concern because of their effect on visibility, climate, and human health. Equally important, aerosols can change the chemistry of the atmosphere, in dramatic fashion, by providing new chemical pathways (in the condensed phase) unavailable in the gas phase. The oxidation of volatile organic compounds (VOCs) and inorganic compounds (e.g., sulfuric acid, ammonia, nitric acid, ions, and mineral) can produce precursor molecules that act as nucleation seeds. The U.S. Department of Energy (DOE) Atmospheric Chemistry Program (ACP) has identified the need to evaluate the causes of variations in tropospheric aerosol chemical composition and concentrations, including determining the sources of aerosol particles and the fraction of such that are of primary and secondary origin. In particular, the ACP has called for a deeper understanding into aerosol formation because nucleation creates substantial concentrations of fresh particles that, via growth and coagulation, influence the Earth's radiation budget. Tropospheric ozone is also of concern primarily because of its impact on human health. Ozone levels are controlled by NOx and by VOCs in the lower troposphere. The VOCs can be either from natural emissions from such sources as vegetation and phytoplankton or from anthropogenic sources such as automobiles and oil-fueled power production plants. The major oxidant for VOCs in the atmosphere is the OH radical. With the increase in VOC emissions, there is rising concern regarding the available abundance of HOx species needed to initiate oxidation. Over the last five years, there have been four field studies aimed at initial measurements of HOx species (OH and HO? radicals). These measurements revealed HOx levels that are

  4. Research in Physical Chemistry and Chemical Education: Part A--Water Mediated Chemistry of Oxidized Atmospheric Compounds Part B--The Development of Surveying Tools to Determine How Effective Laboratory Experiments Contribute to Student Conceptual Understanding

    Science.gov (United States)

    Maron, Marta Katarzyna

    2011-01-01

    This dissertation is a combination of two research areas, experimental physical chemistry, Chapters I to V, and chemical education, Chapters VI to VII. Chapters I to V describe research on the water-mediated chemistry of oxidized atmospheric molecules and the impact that water has on the spectra of these environmental systems. The role of water…

  5. Quantum Diffusion-Controlled Chemistry: Reactions of Atomic Hydrogen with Nitric Oxide in Solid Parahydrogen.

    Science.gov (United States)

    Ruzi, Mahmut; Anderson, David T

    2015-12-17

    Our group has been working to develop parahydrogen (pH2) matrix isolation spectroscopy as a method to study low-temperature condensed-phase reactions of atomic hydrogen with various reaction partners. Guided by the well-defined studies of cold atom chemistry in rare-gas solids, the special properties of quantum hosts such as solid pH2 afford new opportunities to study the analogous chemical reactions under quantum diffusion conditions in hopes of discovering new types of chemical reaction mechanisms. In this study, we present Fourier transform infrared spectroscopic studies of the 193 nm photoinduced chemistry of nitric oxide (NO) isolated in solid pH2 over the 1.8 to 4.3 K temperature range. Upon short-term in situ irradiation the NO readily undergoes photolysis to yield HNO, NOH, NH, NH3, H2O, and H atoms. We map the postphotolysis reactions of mobile H atoms with NO and document first-order growth in HNO and NOH reaction products for up to 5 h after photolysis. We perform three experiments at 4.3 K and one at 1.8 K to permit the temperature dependence of the reaction kinetics to be quantified. We observe Arrhenius-type behavior with a pre-exponential factor of A = 0.036(2) min(-1) and Ea = 2.39(1) cm(-1). This is in sharp contrast to previous H atom reactions we have studied in solid pH2 that display definitively non-Arrhenius behavior. The contrasting temperature dependence measured for the H + NO reaction is likely related to the details of H atom quantum diffusion in solid pH2 and deserves further study.

  6. A robust methodology for kinetic model parameter estimation for biocatalytic reactions

    DEFF Research Database (Denmark)

    Al-Haque, Naweed; Andrade Santacoloma, Paloma de Gracia; Lima Afonso Neto, Watson;

    2012-01-01

    Effective estimation of parameters in biocatalytic reaction kinetic expressions are very important when building process models to enable evaluation of process technology options and alternative biocatalysts. The kinetic models used to describe enzyme-catalyzed reactions generally include several...

  7. Nonmethane hydrocarbons at Pico Mountain, Azores: 1. Oxidation chemistry in the North Atlantic region

    Science.gov (United States)

    Helmig, D.; Tanner, D. M.; Honrath, R. E.; Owen, R. C.; Parrish, D. D.

    2008-10-01

    Measurements of nonmethane hydrocarbons (NMHC) at the Pico Mountain observatory at 2225 m asl on Pico Island, Azores, Portugal, from August 2004 to August 2005 (in part overlapping with the field campaign of the International Consortium on Atmospheric Research on Transport and Transformation study) were used to investigate NMHC sources and seasonal oxidation chemistry in the central North Atlantic region. Levels of anthropogenic NMHC were characteristic of the marine free troposphere. Their concentrations were low compared to continental sites at higher northern latitudes, but higher than data reported from a similarly located Pacific mountain site at Mauna Loa Observatory, Hawaii. These higher NMHC levels are indicative of a greater influence of the adjacent continents on air composition at Pico. Substantially enhanced NMHC concentrations during the summers of 2004 and 2005 were attributed to long-range transport of biomass burning plumes originating from fires in northern Canada, Alaska, and Siberia. This finding exemplifies the continuing impact of biomass burning plumes on atmospheric composition and chemistry many days downwind of these emission sources. Seasonal cycles with lower NMHC concentrations and lower ratios of more reactive to less reactive NMHC during summer reflect the higher degree of photochemical processing occurring during transport. The NMHC concentrations indicate no significant role of chlorine atom oxidation on NMHC. Ozone above 35 ppbv was measured at Pico Mountain throughout all seasons. Enhanced ozone levels were observed in air that had relatively "fresh" photochemical signatures (e.g., ln [propane]/[ethane] > -2.5). During spring-summer air that was more processed ("older" air with ln [propane]/[ethane] < -2.5) on average had lower ozone levels (down to <20 ppbv). This relationship indicates that conditions in the lower free troposphere over the mid-North Atlantic during the spring and summer lead to net photochemical ozone destruction

  8. Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

    Directory of Open Access Journals (Sweden)

    S. Coburn

    2015-10-01

    Full Text Available The elevated deposition of atmospheric mercury over the Southeastern United States is currently not well understood. Here we measure partial columns and vertical profiles of bromine monoxide (BrO radicals, a key component of mercury oxidation chemistry, to better understand the processes and altitudes at which mercury is being oxidized in the atmosphere. We use the data from a ground-based MAX-DOAS instrument located at a coastal site ~ 1 km from the Gulf of Mexico in Gulf Breeze, FL, where we had previously detected tropospheric BrO (Coburn et al., 2011. Our profile retrieval assimilates information about stratospheric BrO from the WACCM chemical transport model, and uses only measurements at moderately low solar zenith angles (SZA to estimate the BrO slant column density contained in the reference spectrum (SCDRef. The approach has 2.6 degrees of freedom, and avoids spectroscopic complications that arise at high SZA; knowledge about SCDRef helps to maximize sensitivity in the free troposphere (FT. A cloud-free case study day with low aerosol load (9 April 2010 provided optimal conditions for distinguishing marine boundary layer (MBL: 0–1 km and free tropospheric (FT: 1–15 km BrO from the ground. The average daytime tropospheric BrO vertical column density (VCD of ~ 2.3 × 1013 molec cm−2 (SZA 5 molec cm−2 s−1 for bromine, while contributions from ozone (O3 and chlorine (Cl were 0.9 × 105 and 0.2 × 105 molec cm−2 s−1, respectively. The GOM formation rate is sensitive to recently proposed atmospheric scavenging reactions of the HgBr adduct by nitrogen dioxide (NO2, and to a lesser extent also HO2 radicals. Using a 3-D chemical transport model, we find that surface GOM variations are typical also of other days, and are mainly derived from the free troposphere. Bromine chemistry is active in the FT over Gulf Breeze, where it forms water-soluble GOM that is subsequently available for wet scavenging by thunderstorms or transport to

  9. Lipase-immobilized biocatalytic membranes for biodiesel production.

    Science.gov (United States)

    Kuo, Chia-Hung; Peng, Li-Ting; Kan, Shu-Chen; Liu, Yung-Chuan; Shieh, Chwen-Jen

    2013-10-01

    Microbial lipase from Candida rugosa (Amano AY-30) has good transesterification activity and can be used for biodiesel production. In this study, polyvinylidene fluoride (PVDF) membrane was grafted with 1,4-diaminobutane and activated by glutaraldehyde for C. rugosa lipase immobilization. After immobilization, the biocatalytic membrane was used for producing biodiesel from soybean oil and methanol via transesterification. Response Surface Methodology (RSM) in combination with a 5-level-5-factor central composite rotatable design (CCRD) was employed to evaluate the effects of reaction time, reaction temperature, enzyme amount, substrate molar ratio and water content on the yield of soybean oil methyl ester. By ridge max analysis, the predicted and experimental yields under the optimum synthesis conditions were 97% and 95%, respectively. The lipase-immobilized PVDF membrane showed good reuse ability for biodiesel production, enabling operation for at least 165 h during five reuses of the batch, without significant loss of activity.

  10. Microfluidic multi-input reactor for biocatalytic synthesis using transketolase☆

    Science.gov (United States)

    Lawrence, James; O'Sullivan, Brian; Lye, Gary J.; Wohlgemuth, Roland; Szita, Nicolas

    2013-01-01

    Biocatalytic synthesis in continuous-flow microreactors is of increasing interest for the production of specialty chemicals. However, the yield of production achievable in these reactors can be limited by the adverse effects of high substrate concentration on the biocatalyst, including inhibition and denaturation. Fed-batch reactors have been developed in order to overcome this problem, but no continuous-flow solution exists. We present the design of a novel multi-input microfluidic reactor, capable of substrate feeding at multiple points, as a first step towards overcoming these problems in a continuous-flow setting. Using the transketolase-(TK) catalysed reaction of lithium hydroxypyruvate (HPA) and glycolaldehyde (GA) to l-erythrulose (ERY), we demonstrate the transposition of a fed-batch substrate feeding strategy to our microfluidic reactor. We obtained a 4.5-fold increase in output concentration and a 5-fold increase in throughput compared with a single input reactor. PMID:24187515

  11. Simple coupling chemistry linking carboxyl-containing organic molecules to silicon oxide surfaces under acidic conditions.

    Science.gov (United States)

    Schmidt, Sebastian W; Christ, Timo; Glockner, Christian; Beyer, Martin K; Clausen-Schaumann, Hauke

    2010-10-05

    The coupling chemistry of carboxymethylated amylose with organo-silanized silicon oxide surfaces at pH 7.4 and 2.0 was investigated using atomic force microscopy (AFM) based single-molecule force spectroscopy. At close to neutral pH, carbodiimide activation of a carboxylic acid affords formation of an amide bond with an amino surface linker. At pH 2.0, no activation with carbodiimide was required to anchor carboxymethylated amylose between an AFM tip and a glass substrate. At the same time, the mean bond rupture force f(r) dropped from 1.65 ± 0.37 nN at pH 7.4 to 1.39 ± 0.30 nN at pH 2.0 without carbodiimide, indicating that a different link to the surface can be formed at low pH. The coupling mechanism at pH 2.0 was elucidated by a series of experiments, in which the surface was functionalized with four different organosilanes, each containing characteristic functional groups. The results are rationalized with an acid-catalyzed ester condensation between a carboxyl group and a free, unreacted silanol group in the surface anchor or on the surface.

  12. Mentha suaveolens Ehrh. (Lamiaceae Essential Oil and Its Main Constituent Piperitenone Oxide: Biological Activities and Chemistry

    Directory of Open Access Journals (Sweden)

    Mijat Božović

    2015-05-01

    Full Text Available Since herbal medicines play an important role in the treatment of a wide range of diseases, there is a growing need for their quality control and standardization. Mentha suaveolens Ehrh. (MS is an aromatic herb with fruit and a spearmint flavor, used in the Mediterranean areas as a traditional medicine. It has an extensive range of biological activities, including cytotoxic, antimicrobial, antioxidant, anti-inflammatory, hypotensive and insecticidal properties, among others. This study aims to review the scientific findings and research reported to date on MS that prove many of the remarkable various biological actions, effects and some uses of this species as a source of bioactive natural compounds. On the other hand, piperitenone oxide (PO, the major chemical constituent of the carvone pathway MS essential oil, has been reported to exhibit numerous bioactivities in cells and animals. Thus, this integrated overview also surveys and interprets the present knowledge of chemistry and analysis of this oxygenated monoterpene, as well as its beneficial bioactivities. Areas for future research are suggested.

  13. Al-doped and undoped zinc oxide films obtained by soft chemistry

    Directory of Open Access Journals (Sweden)

    Suzana M. Mihaiu

    2009-06-01

    Full Text Available Zinc oxide with a hexagonal wurzite type structure is an unique material that exhibits semiconducting, piezoelectric and pyroelectric properties. These properties play a key role for applications in optoelectronic devices. In the present work Al-doped and undoped ZnO films were obtained by soft chemistry starting with zinc acetate dihydrate and Al(III isopropoxide in absolute ethyl alcohol. Trietanolamine was used as chelating agent. The fi lms were deposited by dip coating technique on the silicon substrate and thermally treated at 500°C for one hour. The morphological characteristics of the films were investigated by Atomic Force Microscopy (AFM. Optical constants, such as refractive index (n and extinction coeffi cient (k, were established by Spectroellipsometry measurements. Electrical conductivity of the studied fi lms was determined in the 20–500°C temperature range by “the four point method”. The morphology of the fi lms is infl uenced by the starting sol composition, as found from AFM. According to the ellipsometric spectral data, more porous and thinner films, with smaller refractive index were obtained in the case of Al-doped ZnO fi lms as compared with ZnO films. Both ZnO and Al-doped ZnO fi lms presented high electrical resistivity.

  14. On the relevance of the methane oxidation cycle to ozone hole chemistry

    Science.gov (United States)

    Mueller, Rolf; Crutzen, Paul J.

    1994-01-01

    High concentrations of active chlorine are clearly responsible for the observed ozone depletion during the Antarctic polar spring. However, the mechanism behind the activation of chlorine from the reservoirs species HCl and ClONO2 and the maintenance of extremely high levels of active chlorine after polar sunrise is less well understood. Here, we focus on the influence of the methane oxidation cycle on 'ozone hole' chemistry through its effect on HOx and ClOx radicals. We demonstrate the great potential importance of the heterogeneous reaction HCl + HOCl yields Cl2 + H2O and the gasphase reaction ClO + CH3O2 yields ClOO + CH3O under sunlight conditions in polar spring. Under these conditions, the heterogeneous reaction is the main sink for HOx radicals. Through this channel, the HCl reservoir may be almost completely depleted. The gas phase reaction may control the levels of the CH3O2 radical, provided that high levels of ClO exist. Otherwise this radical initiates a sequence of reactions leading to a considerable loss of active chlorine. Moreover, the production of HOx radicals is reduced, and thereby the efficiency of the heterogeneous reaction limited. The two reactions together may accomplish the complete conversion of HCl into active chlorine, thereby leading to a rapid destruction of ozone.

  15. Mentha suaveolens Ehrh. (Lamiaceae) Essential Oil and Its Main Constituent Piperitenone Oxide: Biological Activities and Chemistry.

    Science.gov (United States)

    Božović, Mijat; Pirolli, Adele; Ragno, Rino

    2015-05-13

    Since herbal medicines play an important role in the treatment of a wide range of diseases, there is a growing need for their quality control and standardization. Mentha suaveolens Ehrh. (MS) is an aromatic herb with fruit and a spearmint flavor, used in the Mediterranean areas as a traditional medicine. It has an extensive range of biological activities, including cytotoxic, antimicrobial, antioxidant, anti-inflammatory, hypotensive and insecticidal properties, among others. This study aims to review the scientific findings and research reported to date on MS that prove many of the remarkable various biological actions, effects and some uses of this species as a source of bioactive natural compounds. On the other hand, piperitenone oxide (PO), the major chemical constituent of the carvone pathway MS essential oil, has been reported to exhibit numerous bioactivities in cells and animals. Thus, this integrated overview also surveys and interprets the present knowledge of chemistry and analysis of this oxygenated monoterpene, as well as its beneficial bioactivities. Areas for future research are suggested.

  16. Surface chemistry of the atomic layer deposition of metals and group III oxides

    Science.gov (United States)

    Goldstein, David Nathan

    Atomic Layer Deposition (ALD) is a thin-film growth technique offering precise control of film thickness and the ability to coat high-aspect-ratio features such as trenches and nanopowders. Unlike other film growth techniques, ALD does not require harsh processing conditions and is not limited by line-of-sight deposition. Emerging applications for ALD materials include semiconductor devices, gas sensors, and water-diffusion barriers. The chemistry behind ALD involves understanding how the precursors interact with surfaces to deposit the desired material. All ALD precursors need to be stable on the substrate to ensure self-limiting behavior yet reactive enough to be easily removed with the second reagent. Recent precursor development has provided many volatile organometallic compounds for most of the periodic table. As the number of precursors increases, proper precursor choice becomes crucial. This is because the film properties, growth rates, and growth temperature vary widely between the precursors. Many of the above traits can be predicted with knowledge of the precursor reaction mechanisms. This thesis aims to link surface reaction mechanisms to observed growth and nucleation trends in metal and oxide ALD systems. The first portion of this thesis explores the mechanisms of two ALD oxide systems. First, I examine the mechanism of ALD alumina with ozone. Ozone is used as an oxidant in the semiconductor industry because the deposited Al 2O3 films possess better insulating properties and ozone is easier to purge from a vacuum system. FT-IR analysis reveals a complicated array of surface intermediates such as formate, carbonate, and methoxy groups that form during Al2O3 growth with ozone. Next, a new method to deposit thin films of Ga2O3 is introduced. Gallium oxide is a transparent conducting oxide that needs expensive solid precursors to be deposited by ALD. I show that trimethylgallium is a good high-temperature ALD precursor that deposits films of Ga2O 3 with

  17. Ionic Liquid-assisted Synthesis of Polyaniline/Gold Nanocomposite and Its Biocatalytic Application

    Directory of Open Access Journals (Sweden)

    Liu Jingquan

    2008-01-01

    Full Text Available Abstract In this report, a novel chemical synthesis of polyaniline/gold nanocomposite is explored using ionic liquid (IL 1-Butyl-3-methylimidazolium hexafluorophosphate. The direct chemical synthesis of polyaniline/gold nanocomposite was initiated via the spontaneous oxidation of aniline by AuCl4 −in IL. A nearly uniform dispersion of polyaniline/Au particles with a diameter of 450 ± 80 nm was produced by this method, which indicates that this method is more suitable for controlling particle dimensions. It was also found that the electrical conductivity of the polyaniline/gold nanocomposite was more than 100 times higher than that of the pure polyaniline nanoparticles. The polyaniline/gold nanocomposite displays superior function in the biocatalytic activation of microperoxidase-11 because of the high surface area of the assembly and the enhanced charge transport properties of the composite material. We also report the possible application of polyaniline/gold nanocomposite as a H2O2biosensor.

  18. Two-Input Enzymatic Logic Gates Made Sigmoid by Modifications of the Biocatalytic Reaction Cascades

    CERN Document Server

    Zavalov, Oleksandr; Halamek, Jan; Halamkova, Lenka; Korkmaz, Sevim; Arugula, Mary A; Chinnapareddy, Soujanya; Katz, Evgeny; Privman, Vladimir

    2013-01-01

    Computing based on biochemical processes is a newest rapidly developing field of unconventional information and signal processing. In this paper we present results of our research in the field of biochemical computing and summarize the obtained numerical and experimental data for implementations of the standard two-input OR and AND gates with double-sigmoid shape of the output signal. This form of response was obtained as a function of the two inputs in each of the realized biochemical systems. The enzymatic gate processes in the first system were activated with two chemical inputs and resulted in optically detected chromogen oxidation, which happens when either one or both of the inputs are present. In this case, the biochemical system is functioning as the OR gate. We demonstrate that the addition of a "filtering" biocatalytic process leads to a considerable reduction of the noise transmission factor and the resulting gate response has sigmoid shape in both inputs. The second system was developed for functi...

  19. Exploring Atmospheric Aqueous Chemistry (and Secondary Organic Aerosol Formation) through OH Radical Oxidation Experiments, Droplet Evaporation and Chemical Modeling

    Science.gov (United States)

    Turpin, B. J.; Kirkland, J. R.; Lim, Y. B.; Ortiz-Montalvo, D. L.; Sullivan, A.; Häkkinen, S.; Schwier, A. N.; Tan, Y.; McNeill, V. F.; Collett, J. L.; Skog, K.; Keutsch, F. N.; Sareen, N.; Carlton, A. G.; Decesari, S.; Facchini, C.

    2013-12-01

    Gas phase photochemistry fragments and oxidizes organic emissions, making water-soluble organics ubiquitous in the atmosphere. My group and others have found that several water-soluble compounds react further in the aqueous phase forming low volatility products under atmospherically-relevant conditions (i.e., in clouds, fogs and wet aerosols). Thus, secondary organic aerosol can form as a result of gas followed by aqueous chemistry (aqSOA). We have used aqueous OH radical oxidation experiments coupled with product analysis and chemical modeling to validate and refine the aqueous chemistry of glyoxal, methylglyoxal, glycolaldehyde, and acetic acid. The resulting chemical model has provided insights into the differences between oxidation chemistry in clouds and in wet aerosols. Further, we conducted droplet evaporation experiments to characterize the volatility of the products. Most recently, we have conducted aqueous OH radical oxidation experiments with ambient mixtures of water-soluble gases to identify additional atmospherically-important precursors and products. Specifically, we scrubbed water-soluble gases from the ambient air in the Po Valley, Italy using four mist chambers in parallel, operating at 25-30 L min-1. Aqueous OH radical oxidation experiments and control experiments were conducted with these mixtures (total organic carbon ≈ 100 μM-C). OH radicals (3.5E-2 μM [OH] s-1) were generated by photolyzing H2O2. Precursors and products were characterized using electrospray ionization mass spectrometry (ESI-MS), ion chromatography (IC), IC-ESI-MS, and ultra high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Chemical modeling suggests that organic acids (e.g., oxalate, pyruvate, glycolate) are major products of OH radical oxidation at cloud-relevant concentrations, whereas organic radical - radical reactions result in the formation of oligomers in wet aerosols. Products of cloud chemistry and droplet evaporation have

  20. Glyoxal as a tracer of VOC oxidation chemistry: Comparison of measurements with model results for Blodgett Forest, California

    Science.gov (United States)

    Huisman, Andrew; Carlton, Annmarie; Keutsch, Frank

    2010-05-01

    We present a study investigating Volatile Organic Compound (VOC) oxidation chemistry in the context of regional ozone (O3) production during the BEARPEX 2007 and 2009 campaigns at Blodgett Forest Research Station (BFRS) in the Sierra Nevada mountains, CA. Measurements are compared with results from a regional model (US EPA CMAQ) and a zero dimensional (0-D) box model based on the Master Chemical Mechanism (MCM). We use glyoxal (CHOCHO) and formaldehyde (HCHO) as tracers for generalized oxidation processes and employ ratios of compounds (e.g. CHOCHO / HCHO, CHOCHO / MPAN) to study plume evolution as doing so attenuates the influence of meteorology. One of the goals of this study is to investigate the utility of glyoxal as a tracer of VOC oxidation chemistry for measurement/model comparisons, for which formaldehyde has served in the past. In this context, we investigate the discrepancies between models and measurements, and the degree to which these can be attributed to the representation of glyoxal chemistry (e.g. yields) or whether these discrepancies reflect VOC-HOx-NOx oxidation more generally, which has implications for ozone and secondary organic aerosol formation. Model results from CMAQ and the 0-D box model substantially overestimate the absolute measured concentration of CHOCHO at BFRS, and the CMAQ model also shows poor agreement with the diurnal profile. The 0-D box model also overestimates CHOCHO in data taken at the Caltech Indoor Air Chambers, suggesting that 2nd- and/or higher-generation yields of CHOCHO from isoprene are substantially overestimated in the MCM. 0-D model results that use attenuated 2nd- and higher-generation production of CHOCHO from isoprene show enhanced agreement with chamber results. We will present model results of the 0-D Box Model from BFRS employing these reduced yields that show improved agreement with measurements and also compare these results with the other models. We also present results obtained with two modifications of

  1. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    Directory of Open Access Journals (Sweden)

    Nicola H. Perry

    2016-10-01

    Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

  2. Modeling aerosol surface chemistry and gas-particle interaction kinetics with K2-SURF: PAH oxidation

    Science.gov (United States)

    Shiraiwa, M.; Garland, R.; Pöschl, U.

    2009-04-01

    Atmospheric aerosols are ubiquitous in the atmosphere. They have the ability to impact cloud properties, radiative balance and provide surfaces for heterogeneous reactions. The uptake of gaseous species on aerosol surfaces impacts both the aerosol particles and the atmospheric budget of trace gases. These subsequent changes to the aerosol can in turn impact the aerosol chemical and physical properties. However, this uptake, as well as the impact on the aerosol, is not fully understood. This uncertainty is due not only to limited measurement data, but also a dearth of comprehensive and applicable modeling formalizations used for the analysis, interpretation and description of these heterogeneous processes. Without a common model framework, comparing and extrapolating experimental data is difficult. In this study, a novel kinetic surface model (K2-SURF) [Ammann & Pöschl, 2007; Pöschl et al., 2007] was used to describe the oxidation of a variety of polycyclic aromatic hydrocarbons (PAHs). Integrated into this consistent and universally applicable kinetic and thermodynamic process model are the concepts, terminologies and mathematical formalizations essential to the description of atmospherically relevant physicochemical processes involving organic and mixed organic-inorganic aerosols. Within this process model framework, a detailed master mechanism, simplified mechanism and parameterizations of atmospheric aerosol chemistry are being developed and integrated in analogy to existing mechanisms and parameterizations of atmospheric gas-phase chemistry. One of the key aspects to this model is the defining of a clear distinction between various layers of the particle and surrounding gas phase. The processes occurring at each layer can be fully described using known fluxes and kinetic parameters. Using this system there is a clear separation of gas phase, gas-surface and surface bulk transport and reactions. The partitioning of compounds can be calculated using the flux

  3. Low-temperature combustion chemistry of n-butanol: principal oxidation pathways of hydroxybutyl radicals.

    Science.gov (United States)

    Welz, Oliver; Zádor, Judit; Savee, John D; Sheps, Leonid; Osborn, David L; Taatjes, Craig A

    2013-11-21

    Reactions of hydroxybutyl radicals with O2 were investigated by a combination of quantum-chemical calculations and experimental measurements of product formation. In pulsed-photolytic Cl-initiated oxidation of n-butanol, the time-resolved and isomer-specific product concentrations were probed using multiplexed tunable synchrotron photoionization mass spectrometry (MPIMS). The interpretation of the experimental data is underpinned by potential energy surfaces for the reactions of O2 with the four hydroxybutyl isomers (1-hydroxybut-1-yl, 1-hydroxybut-2-yl, 4-hydroxybut-2-yl, and 4-hydroxybut-1-yl) calculated at the CBS-QB3 and RQCISD(T)/cc-pV∞Z//B3LYP/6-311++G(d,p) levels of theory. The observed product yields display substantial temperature dependence, arising from a competition among three fundamental pathways: (1) stabilization of hydroxybutylperoxy radicals, (2) bimolecular product formation in the hydroxybutyl + O2 reactions, and (3) decomposition of hydroxybutyl radicals. The 1-hydroxybut-1-yl + O2 reaction is dominated by direct HO2 elimination from the corresponding peroxy radical forming butanal as the stable coproduct. The chemistry of the other three hydroxybutylperoxy radical isomers mainly proceeds via alcohol-specific internal H-atom abstractions involving the H atom from either the -OH group or from the carbon attached to the -OH group. We observe evidence of the recently reported water elimination pathway (Welz et al. J. Phys. Chem. Lett. 2013, 4 (3), 350-354) from the 4-hydroxybut-2-yl + O2 reaction, supporting its importance in γ-hydroxyalkyl + O2 reactions. Experiments using the 1,1-d2 and 4,4,4-d3 isotopologues of n-butanol suggest the presence of yet unexplored pathways to acetaldehyde.

  4. Dominance of interface chemistry over the bulk properties in determining the electronic structure of epitaxial metal/perovskite oxide heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, Scott A.; Du, Yingge; Gu, Meng; Droubay, Timothy C.; Hepplestone, Steven; Sushko, Petr

    2015-06-09

    We show that despite very similar crystallographic properties and work function values in the bulk, epitaxial Fe and Cr metallizations on Nb:SrTiO3(001) generate completely different heterojunction electronic properties. Cr is Ohmic whereas Fe forms a Schottky barrier with a barrier height of 0.50 eV. This contrast arises because of differences in interface chemistry. In contrast to Cr [Chambers, S. A. et al., Adv. Mater. 2013, 25, 4001.], Fe exhibits a +2 oxidation state and occupies Ti sites in the perovskite lattice, resulting in negligible charge transfer to Ti, upward band bending, and Schottky barrier formation. The differences between Cr and Fe are understood by performing first-principles calculations of the energetics of defect formation which corroborate the observed interface chemistry and structure.

  5. Biocatalytic nerve agent detoxification in fire fighting foams.

    Science.gov (United States)

    LeJeune, K E; Russell, A J

    1999-03-20

    Current events across the globe necessitate rapid technological advances to combat the epidemic of nerve agent chemical weapons. Biocatalysis has emerged as a viable tool in the detoxification of organophosphorus neurotoxins, such as the chemical weapons VX and sarin. Efficient detoxification of contaminated equipment, machinery, and soils are of principal concern. This study describes the incorporation of a biocatalyst (organophosphorus hydrolase, E.C. 3.1.8.1) into conventional formulations of fire fighting foam. The capacity of fire fighting foams to decrease volatilization of contained contaminants, increase surface wettability, and control the rate of enzyme delivery to large areas makes them useful vehicles for enzyme application at surfaces. The performance of enzyme containing foams has been shown to be not only reproducible but also predictable. An empirical model provides reasonable estimations for the amounts of achievable surface decontamination as a function of the important parameters of the system. Theoretical modeling illustrates that the enzyme-containing foam is capable of extracting agent from the surface and is catalytically active at the foam-surface interface and throughout the foam itself. Biocatalytic foam has proven to be an effective, "environmentally friendly" means of surface and soil decontamination.

  6. Improved simulation of isoprene oxidation chemistry with the ECHAM5/MESSy chemistry-climate model: lessons from the GABRIEL airborne field campaign

    Directory of Open Access Journals (Sweden)

    T. M. Butler

    2008-03-01

    Full Text Available The GABRIEL airborne field measurement campaign, conducted over the Guyanas in October 2005, produced measurements of hydroxyl radical (OH concentration which are significantly higher than can be simulated using current generation models of atmospheric chemistry. Based on the hypothesis that this "missing OH" is due to an as-yet undiscovered mechanism for recycling OH during the oxidation chain of isoprene, we determine that an OH recycling of about 40–50% (compared with 5–10% in current generation isoprene oxidation mechanisms is necessary in order for our modelled OH to approach the lower error bounds of the OH observed during GABRIEL. Such a large amount of OH in our model leads to unrealistically low mixing ratios of isoprene. In order for our modelled isoprene mixing ratios to match those observed during the campaign, we also require that the effective rate constant for the reaction of isoprene with OH be reduced by about 50% compared with the lower bound of the range recommended by IUPAC. We show that a reasonable explanation for this lower effective rate constant could be the segregation of isoprene and OH in the mixed layer. Our modelling results are consistent with a global, annual isoprene source of about 500 Tg(C yr−1, allowing experimentally derived and established isoprene flux rates to be reconciled with global models.

  7. Improved simulation of isoprene oxidation chemistry with the ECHAM5/MESSy chemistry-climate model: lessons from the GABRIEL airborne field campaign

    Directory of Open Access Journals (Sweden)

    T. M. Butler

    2008-08-01

    Full Text Available The GABRIEL airborne field measurement campaign, conducted over the Guyanas in October 2005, produced measurements of hydroxyl radical (OH concentration which are significantly higher than can be simulated using current generation models of atmospheric chemistry. Based on the hypothesis that this "missing OH" is due to an as-yet undiscovered mechanism for recycling OH during the oxidation chain of isoprene, we determine that an OH recycling of about 40–50% (compared with 5–10% in current generation isoprene oxidation mechanisms is necessary in order for our modelled OH to approach the lower error bounds of the OH observed during GABRIEL. Such a large amount of OH in our model leads to unrealistically low mixing ratios of isoprene. In order for our modelled isoprene mixing ratios to match those observed during the campaign, we also require that the effective rate constant for the reaction of isoprene with OH be reduced by about 50% compared with the lower bound of the range recommended by IUPAC. We show that a reasonable explanation for this lower effective rate constant could be the segregation of isoprene and OH in the mixed layer. Our modelling results are consistent with a global, annual isoprene source of about 500 Tg(C yr−1, allowing experimentally derived and established isoprene flux rates to be reconciled with global models.

  8. Using Demonstrations Involving Combustion and Acid-Base Chemistry to Show Hydration of Carbon Dioxide, Sulfur Dioxide, and Magnesium Oxide and Their Relevance for Environmental Climate Science

    Science.gov (United States)

    Shaw, C. Frank, III; Webb, James W.; Rothenberger, Otis

    2016-01-01

    The nature of acidic and basic (alkaline) oxides can be easily illustrated via a series of three straightforward classroom demonstrations for high school and general chemistry courses. Properties of carbon dioxide, sulfur dioxide, and magnesium oxide are revealed inexpensively and safely. Additionally, the very different kinetics of hydration of…

  9. A First Principles Investigation of Proton Chemistry in Perovskite-Type Oxides

    Science.gov (United States)

    Tauer, Tania Allison

    Certain acceptor-doped perovskite-type oxides show significant promise for deployment into a number of electrochemical device applications, including fuel cells, batteries, and electrolyzers, owing to their rapid proton conductivities at high temperatures. However, limitations in bulk material hydration and slow grain boundary conductivities have reduced the viability of these materials in intermediate temperatures applications. This thesis work uses density functional theory to gain a fundamental understanding of proton and defect chemistry within various perovskite environments in order to identify strategies to increase proton concentration and improve overall proton conductivity. First, material hydration was probed within yttrium-doped barium cerate (BCY) to examine how the thermodynamics of material hydration are influenced by dopant concentration. A model was derived from solely first principle techniques to describe hydration within BCY as a function of dopant concentration, temperature, and partial pressure of water. The resulting model can be used to screen for favorable perovskite-dopant combinations with enhanced hydration capabilities. Next, defect segregation was investigated in the more complex interfacial environment to probe the origin of low proton conductivity across perovskite grain boundaries (GB). The results of this study suggest that screening for perovskite-dopant combinations with strong dopant-oxygen bond strengths may reduce the segregation of dopant ions and oxygen vacancies to the GB interface, mitigating the development of a positive GB core and enhancing proton conduction across the GB. Finally, proton stability was assessed at various interfacial regions within the perovskite material. An examination of proton adsorption at the BaZrO3-vacuum interface reveals a destabilization of protons in the first subsurface layer of the perovskite, yielding a potential barrier for proton diffusion into and out of the perovskite membrane. An

  10. Crystal chemistry of volcanic allanites indicative of naturally induced oxidation-dehydrogenation

    Science.gov (United States)

    Hoshino, Mihoko; Kimata, Mitsuyoshi; Chesner, Craig A.; Nishida, Norimasa; Shimizu, Masahiro; Akasaka, Takeshi

    2010-05-01

    The crystal chemistry of volcanic allanites from both the Youngest Toba Tuff (YTT), Sumatra, Indonesia and SK100 volcanic ash beds (SK100-VAB), Niigata, Japan has been examined by electron microprobe analysis (EMPA), Fourier-transform infrared spectroscopic analysis (FTIR), and single-crystal structure analysis. In the FTIR study, based on the Diamond ATR accessory, YTT and SK100- VAB allanites were observed to have different OH contents, respectively: the former has 0.64 wt% H2O (OH: 0.40 apfu.), while the latter has 1.65 wt% H2O (OH: 1.00 apfu.). The crystal structures of these two allanites have been refined to individual R indices (3.64 and 4.25) based on 1350 observed reflections (|Fo| > 4sig|Fo|) measured using a single-crystal diffractometer with MoKα X-radiation. The OH-poor YTT allanite has a shorter b axis, a longer c axis, and larger β value than the relatively OH-rich SK100-VAB one. The bond valence sums of O4 (accepter oxygen for H atom) and O10 (donor oxygen for H atom) are 1.962 and 1.709 v.u. for YTT allanite (valence sum: 3.671 v.u.) and 1.754 and 1.271 v.u. for SK100-VAB one (valence sum: 3.025 v.u.). The difference from the ideal total bond valence value (4.00 v.u.) of O4 and O10 in YTT allanite (0.33 v.u.) is smaller than that in SK100-VAB (0.98 v.u.). These difference values are also broadly consistent with the corresponding differences in OH content between the YTT (OH: 0.40 apfu.) and SK100-VAB allanites (OH: 1.00 apfu.) determined by FTIR- ATR. Chemical analyses, FTIR-ATR and crystal structure refinement of YTT and SK100-VAB allanites yielded the following crystal chemical formula: YTT: (Ca0.83Mn2+ 0.06Fe2+ 0.11)(La0.24Ce0.32Pr0.04Nd0.11Sm0.02Th0.04Ca0.21)(Al0.73Fe3+ 0.19Ti0.08)(Al0.89Fe3+ 0.11)(Fe2+ 0.22Fe3+ 0.62Mg0.16)(SiO4)Si2O7O1.6(OH)0.4, SK100-VAB: (Ca0.81Fe2+ 0.13Mn2+ 0.06)(La0.22Ce0.34Pr0.05Nd0.13Sm0.02Th0.02Ca0.22)(Al0.76Fe3+ 0.19Ti0.05)Al1.00(Fe2+ 0.73Fe3+ 0.17Mg0.10)(Si0.96Al0.04O4)Si2O7O(OH). Therefore, it is concluded that

  11. Design of Highly Selective Platinum Nanoparticle Catalysts for the Aerobic Oxidation of KA-Oil using Continuous-Flow Chemistry.

    Science.gov (United States)

    Gill, Arran M; Hinde, Christopher S; Leary, Rowan K; Potter, Matthew E; Jouve, Andrea; Wells, Peter P; Midgley, Paul A; Thomas, John M; Raja, Robert

    2016-03-01

    Highly active and selective aerobic oxidation of KA-oil to cyclohexanone (precursor for adipic acid and ɛ-caprolactam) has been achieved in high yields using continuous-flow chemistry by utilizing uncapped noble-metal (Au, Pt & Pd) nanoparticle catalysts. These are prepared using a one-step in situ methodology, within three-dimensional porous molecular architectures, to afford robust heterogeneous catalysts. Detailed spectroscopic characterization of the nature of the active sites at the molecular level, coupled with aberration-corrected scanning transmission electron microscopy, reveals that the synthetic methodology and associated activation procedures play a vital role in regulating the morphology, shape and size of the metal nanoparticles. These active centers have a profound influence on the activation of molecular oxygen for selective catalytic oxidations.

  12. Measurement and control of in-plane surface chemistry during the oxidation of H-terminated (111) Si.

    Science.gov (United States)

    Gokce, Bilal; Adles, Eric J; Aspnes, David E; Gundogdu, Kenan

    2010-10-12

    In-plane directional control of surface chemistry during interface formation can lead to new opportunities regarding device structures and applications. Control of this type requires techniques that can probe and hence provide feedback on the chemical reactivity of bonds not only in specific directions but also in real time. Here, we demonstrate both control and measurement of the oxidation of H-terminated (111) Si. Control is achieved by externally applying uniaxial strain, and measurement by second-harmonic generation (SHG) together with the anisotropic-bond model of nonlinear optics. In this system anisotropy results because bonds in the strain direction oxidize faster than those perpendicular to it, leading in addition to transient structural changes that can also be detected at the bond level by SHG.

  13. Influence of corrosive solutions on microhardness and chemistry of magnesium oxide /001/ surfaces

    Science.gov (United States)

    Ishigaki, H.; Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analyses and hardness experiments were conducted on cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved to specimen size along the /001/ surface, and indentations were made on the cleaved surface in corrosive solutions containing HCl, NaOH, or HNO3 and in water without exposing the specimen to any other environment. The results indicated that chloride (such as MgCl2) and sodium films are formed on the magnesium oxide surface as a result of interactions between an HCl-containing solution and a cleaved magnesium oxide surface. The chloride films soften the magnesium oxide surface. In this case microhardness is strongly influenced by the pH value of the solution. The lower the pH, the lower the microhardness. Sodium films, which are formed on the magnesium oxide surface exposed to an NaOH containing solution, do not soften the magnesium oxide surface.

  14. Efficient functionalization of oxide-free silicon(111) surfaces: thiol-yne versus thiol-ene click chemistry.

    Science.gov (United States)

    Bhairamadgi, Nagendra S; Gangarapu, Satesh; Caipa Campos, Mabel A; Paulusse, Jos M J; van Rijn, Cees J M; Zuilhof, Han

    2013-04-09

    Thiol-yne click (TYC) chemistry was utilized as a copper-free click reaction for the modification of alkyne-terminated monolayers on oxide-free Si(111) surfaces, and the results were compared with the analogous thiol-ene click (TEC) chemistry. A wide range of thiols such as 9-fluorenylmethoxy-carbonyl cysteine, thio-β-d-glucose tetraacetate, thioacetic acid, thioglycerol, thioglycolic acid, and 1H,1H,2H,2H-perfluorodecanethiol was immobilized using TYC under photochemical conditions, and all modified surfaces were characterized by static water contact angle measurements, X-ray photoelectron spectroscopy (including a simulation thereof by density functional calculations), and infrared absorption reflection spectroscopy. Surface-bound TYC proceeds with an efficiency of up to 1.5 thiols per alkyne group. This high surface coverage proceeds without oxidizing the Si surface. TYC yielded consistently higher surface coverages than TEC, due to double addition of thiols to alkyne-terminated monolayers. This also allows for the sequential and highly efficient attachment of two different thiols onto an alkyne-terminated monolayer.

  15. Study on technetium-99m labeling of graphene oxide nanosheets through click chemistry-99mTc labeling of graphene oxide nanosheets

    Institute of Scientific and Technical Information of China (English)

    江大卫; 彭程; 孙艳红; 贾丽娜; 李剑波; 张岚

    2015-01-01

    Graphene oxide (GO) nanosheets possess several advantages, such as a large surface, outstanding bio-compatibility, and straightforward chemical modification capability. They also have great potential as a drug-carrier. In this article, we radiolabeled GO nanosheets with 99mTc, which satisfies the potential needs of micro-SPECT imaging probes in pre-clinical and clinical research. GO nanosheets were synthesized through the modified Hummers’ method, then GO nanosheets with azide group covalently functionalized in two steps were conjugated to DOTA (1,4,7,10-tetraazacyclododecane-N,N0,N00,N000-tetraacetic acid) and functionalized with an alkynyl group by means of click chemistry. Then through the addition and reduction of technetium-99m, the 99mTc-DOTA-GO were attained. DOTA-conjugated GOs with lateral dimensions of 500–600 nm were synthe-sized. Both atomic force microscopy (AFM) and FT-IR were performed to characterize the GO-DOTA. Labeling efficiency of GO-DOTA with 99mTc was>90%and radiochemical purities were>96%with purification. We successfully synthesized graphene oxide derivatives, DOTA-conjugated GOs, via Click Chemistry, and it was labeled with 99mTc for SPECT imaging. High radiolabeling efficiency makes GO nanosheets suitable platforms for future molecular imaging research.

  16. Genotoxicity of copper oxide nanoparticles with different surface chemistry on rat bone marrow mesenchymal stem cells

    DEFF Research Database (Denmark)

    Zhang, Wenjing; Jiang, Pengfei; Chen, Wei

    2016-01-01

    chemistry had influence on the toxicity to some extent too. The intracellular reactive oxygen species (ROS) level of MSCs was then quantified. Finally, the genotoxicity of the CuO NPs was studied by comet assay. The results suggest that the genotoxicity of CuO NPs was mainly dependent on NPs concentration...... impact on the differentiation potential of the MSCs....

  17. Dry deposition parameterization of sulfur oxides in a chemistry and general circulation

    NARCIS (Netherlands)

    Ganzeveld, L.N.; Lelieveld, J.; Roelofs, G.J.

    1998-01-01

    A dry deposition scheme, originally developed to calculate the deposition velocities for the trace gases O3, NO2, NO, and HNO3 in the chemistry and general circulation European Centre Hamburg Model (ECHAM), is extended to sulfur dioxide (SO2) and sulfate (SO42-). In order to reduce some of the short

  18. Green Oxidation of Menthol Enantiomers and Analysis by Circular Dichroism Spectroscopy: An Advanced Organic Chemistry Laboratory

    Science.gov (United States)

    Geiger, H. Cristina; Donohoe, James S.

    2012-01-01

    Green chemistry addresses environmental concerns associated with chemical processes and increases awareness of possible harmful effects of chemical reagents. Efficient reactions that eliminate or reduce the use of organic solvents or toxic reagents are increasingly available. A two-week experiment is reported that entails the calcium hypochlorite…

  19. Study of Heterogeneouse Processes Related to the Chemistry of Tropospheric Oxidants and Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Davidovits, Paul; Worsnop, D R; Jayne, J T; Colb, C E

    2013-02-13

    The objective of the studies was to elucidate the heterogeneous chemistry of tropospheric aerosols. Experiments were designed to measure both specifically needed parameters, and to obtain systematic data required to build a fundamental understanding of the nature of gas-surface physical and chemical interactions

  20. Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.

    Science.gov (United States)

    Yang, Jin; Bitter, Julie L; Smith, Billy A; Fairbrother, D Howard; Ball, William P

    2013-12-17

    This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.

  1. Biocatalytic potential of laccase-like multicopper oxidases from Aspergillus niger

    NARCIS (Netherlands)

    Tamayo Ramos, J.A.; Berkel, van W.J.H.; Graaff, de L.H.

    2012-01-01

    BACKGROUND: Laccase-like multicopper oxidases have been reported in several Aspergillus species but they remain uncharacterized. The biocatalytic potential of the Aspergillus niger fungal pigment multicopper oxidases McoA and McoB and ascomycete laccase McoG was investigated. RESULTS: The laccase-li

  2. Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Keller, D.E.

    2003-01-01

    Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular str

  3. Understanding the Chemistry of Uncommon Americium Oxidation States for Application to Actinide/Lanthanide Separations

    Energy Technology Data Exchange (ETDEWEB)

    Leigh Martin; Bruce J. Mincher; Nicholas C. Schmitt

    2007-09-01

    A spectroscopic study of the stability of Am(V) and Am(VI) produced by oxidizing Am(III) with sodium bismuthate is presented, varying the initial americium concentration, temperature and length of the oxidation was seen to have profound effects on the resultant solutions.

  4. Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

    2015-09-14

    Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co3O4 or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

  5. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol.

    Science.gov (United States)

    Kroll, Jesse H; Donahue, Neil M; Jimenez, Jose L; Kessler, Sean H; Canagaratna, Manjula R; Wilson, Kevin R; Altieri, Katye E; Mazzoleni, Lynn R; Wozniak, Andrew S; Bluhm, Hendrik; Mysak, Erin R; Smith, Jared D; Kolb, Charles E; Worsnop, Douglas R

    2011-02-01

    A detailed understanding of the sources, transformations and fates of organic species in the environment is crucial because of the central roles that they play in human health, biogeochemical cycles and the Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here, we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state, a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of the average carbon oxidation state, using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number.

  6. A computational chemistry investigation of the mechanism of the water-assisted decomposition of trichloroethylene oxide.

    Science.gov (United States)

    Huang, Jinqing; Yeung, Chi Shun; Ma, Jiani; Gayner, Emma R; Phillips, David Lee

    2014-03-06

    Trichloroethylene oxide is a downstream product in the oxidative metabolism of trichloroethylene (TCE) and it may be involved in cytochrome P450 inactivation, protein function destruction, and nucleic acid base alkalization. To explore the hydrolysis mechanism of the decomposition of TCE oxide, an investigation using Second-order Møller-Plesset perturbation theory in conjunction with density functional theory has been conducted to analyze the effect of the water solvation shell on probable reaction steps. The decomposition of TCE oxide is accelerated by coordinated water molecules (up to seven), which reveals that water molecules can help to solvate the TCE oxide molecule and activate the release of the Cl(-) leaving group. After the opening of the epoxide ring, several pathways are proposed to account for the dehalogenation step along with the formation of CO as well as three carboxylic acids (formic acid, glyoxylic acid, and dichloroacetic acid). The predominant pathways were examined by comparing the computed activation energies for the formation of the products to each other for the possible reaction steps examined in this work. After rationally analyzing the computational results, the ring-opening reaction has been identified as the rate-determining step. The rate constant estimated for the TCE oxide decomposition from the calculations performed here was found to be reasonably consistent with previous experimental observations reported in the literature.

  7. Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents.

    Science.gov (United States)

    Mutti, Francesco G; Orthaber, Andreas; Schrittwieser, Joerg H; de Vries, Johannes G; Pietschnig, Rudolf; Kroutil, Wolfgang

    2010-11-14

    An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to enantioenriched chlorohydrins via an oxidation-asymmetric reduction sequence.

  8. Dynamics of ozone and nitrogen oxides at Summit, Greenland. II. Simulating snowpack chemistry during a spring high ozone event with a 1-D process-scale model

    NARCIS (Netherlands)

    Murray, K.A.; Kramer, L.J.; Doskey, P.V.; Ganzeveld, L.N.; Seok, B.; Dam, van B.; Helmig, D.

    2015-01-01

    Observed depth profiles of nitric oxide (NO), nitrogen dioxide (NO2), and ozone (O3) in snowpack interstitial air at Summit, Greenland were best replicated by a 1-D process-scale model, which included (1) geometrical representation of snow grains as spheres, (2) aqueous-phase chemistry confined to a

  9. Oxidation of methionine residues in polypeptide ions via gas-phase ion/ion chemistry.

    Science.gov (United States)

    Pilo, Alice L; McLuckey, Scott A

    2014-06-01

    The gas-phase oxidation of methionine residues is demonstrated here using ion/ion reactions with periodate anions. Periodate anions are observed to attach in varying degrees to all polypeptide ions irrespective of amino acid composition. Direct proton transfer yielding a charge-reduced peptide ion is also observed. In the case of methionine and, to a much lesser degree, tryptophan-containing peptide ions, collisional activation of the complex ion generated by periodate attachment yields an oxidized peptide product (i.e., [M + H + O](+)), in addition to periodic acid detachment. Detachment of periodic acid takes place exclusively for peptides that do not contain either a methionine or tryptophan side chain. In the case of methionine-containing peptides, the [M + H + O](+) product is observed at a much greater abundance than the proton transfer product (viz., [M + H](+)). Collisional activation of oxidized Met-containing peptides yields a signature loss of 64 Da from the precursor and/or product ions. This unique loss corresponds to the ejection of methanesulfenic acid from the oxidized methionine side chain and is commonly used in solution-phase proteomics studies to determine the presence of oxidized methionine residues. The present work shows that periodate anions can be used to 'label' methionine residues in polypeptides in the gas phase. The selectivity of the periodate anion for the methionine side chain suggests several applications including identification and location of methionine residues in sequencing applications.

  10. Study of the Stereochemistry and Oxidation Mechanism of Plant Polyphenols, Assisted by Computational Chemistry.

    Science.gov (United States)

    Matsuo, Yosuke

    2017-01-01

     In recent years, plant polyphenols have attracted great attention due to their wide range of biological activities. Certain kinds of polyphenols have complex structures; therefore, it is difficult to elucidate their total structure, including stereochemistry. In this study, we reinvestigated the stereostructures of two major C-glycosidic ellagitannins contained in Quercus plants, vescalagin and castalagin, and revised their stereostructures based on theoretical calculations of spectroscopic data. We also determined the structures of quercusnins A and B, isolated from the sapwood of Quercus crispula, based on theoretical calculations of NMR data. The oxidation mechanism of polyphenols has not been entirely elucidated. Therefore, we have also studied the oxidation mechanism of tea catechins during black tea production. Our investigation of the oxidation mechanism of black tea pigment theaflavins revealed that the difference in the position of the galloyl ester affords different oxidation products of theaflavins. In addition, oxidation products of pyrogallol-type catechins could be classified into three types-dehydrotheasinensins, theacitrins, and proepitheaflagallins; their detailed production and degradation mechanisms were also examined.

  11. Iron(III) Fluorinated Porphyrins: Greener Chemistry from Synthesis to Oxidative Catalysis Reactions.

    Science.gov (United States)

    Rebelo, Susana L H; Silva, André M N; Medforth, Craig J; Freire, Cristina

    2016-04-12

    Iron(III) fluorinated porphyrins play a central role in the biomimetics of heme enzymes and enable cleaner routes to the oxidation of organic compounds. The present work reports significant improvements in the eco-compatibility of the synthesis of 5,10,15,20-tetrakis-pentafluorophenylporphyrin (H₂TPFPP) and the corresponding iron complex [Fe(TPFPP)Cl], and the use of [Fe(TPFPP)Cl] as an oxidation catalyst in green conditions. The preparations of H₂TPFPP and [Fe(TPFPP)Cl] typically use toxic solvents and can be made significantly greener and simpler using microwave heating and optimization of the reaction conditions. In the optimized procedure it was possible to eliminate nitrobenzene from the porphyrin synthesis and replace DMF by acetonitrile in the metalation reaction, concomitant with a significant reduction of reaction time and simplification of the purification procedure. The Fe(III)porphyrin is then tested as catalyst in the selective oxidation of aromatics at room temperature using a green oxidant (hydrogen peroxide) and green solvent (ethanol). Efficient epoxidation of indene and selective oxidation of 3,5-dimethylphenol and naphthalene to the corresponding quinones is observed.

  12. Iron(III Fluorinated Porphyrins: Greener Chemistry from Synthesis to Oxidative Catalysis Reactions

    Directory of Open Access Journals (Sweden)

    Susana L. H. Rebelo

    2016-04-01

    Full Text Available Iron(III fluorinated porphyrins play a central role in the biomimetics of heme enzymes and enable cleaner routes to the oxidation of organic compounds. The present work reports significant improvements in the eco-compatibility of the synthesis of 5,10,15,20-tetrakis-pentafluorophenylporphyrin (H2TPFPP and the corresponding iron complex [Fe(TPFPPCl], and the use of [Fe(TPFPPCl] as an oxidation catalyst in green conditions. The preparations of H2TPFPP and [Fe(TPFPPCl] typically use toxic solvents and can be made significantly greener and simpler using microwave heating and optimization of the reaction conditions. In the optimized procedure it was possible to eliminate nitrobenzene from the porphyrin synthesis and replace DMF by acetonitrile in the metalation reaction, concomitant with a significant reduction of reaction time and simplification of the purification procedure. The Fe(IIIporphyrin is then tested as catalyst in the selective oxidation of aromatics at room temperature using a green oxidant (hydrogen peroxide and green solvent (ethanol. Efficient epoxidation of indene and selective oxidation of 3,5-dimethylphenol and naphthalene to the corresponding quinones is observed.

  13. Oligomerization of Glycine and Alanine Catalyzed by Iron Oxides: Implications for Prebiotic Chemistry

    Science.gov (United States)

    Shanker, Uma; Bhushan, Brij; Bhattacharjee, G.; Kamaluddin

    2012-02-01

    Iron oxide minerals are probable constituents of the sediments present in geothermal regions of the primitive earth. They might have adsorbed different organic monomers (amino acids, nucleotides etc.) and catalyzed polymerization processes leading to the formation of the first living cell. In the present work we tested the catalytic activity of three forms of iron oxides (Goethite, Akaganeite and Hematite) in the intermolecular condensation of each of the amino acids glycine and L-alanine. The effect of zinc oxide and titanium dioxide on the oligomerization has also been studied. Oligomerization studies were performed for 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The products formed were characterized by HPLC and ESI-MS techniques. All three forms of iron oxides catalyzed peptide bond formation (23.2% of gly2 and 10.65% of ala2). The reaction was monitored every 7 days. Formation of peptides was observed to start after 7 days at 50°C. Maximum yield of peptides was found after 35 days at 90°C. Reaction at 120°C favors formation of diketopiperazine derivatives. It is also important to note that after 35 days of reaction, goethite produced dimer and trimer with the highest yield among the oxides tested. We suggest that the activity of goethite could probably be due to its high surface area and surface acidity.

  14. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Massachusetts Institute of Technology; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R.; Wilson, Kevin R.; Altieri, Katye E.; Mazzoleni, Lynn R.; Wozniak, Andrew S.; Bluhm, Hendrik; Mysak, Erin R.; Smith, Jared D.; Kolb, Charles E.; Worsnop, Douglas R.

    2010-11-05

    A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).

  15. Influence of mineral oil and additives on microhardness and surface chemistry of magnesium oxide (001) surface

    Science.gov (United States)

    Miyoshi, K.; Shigaki, H.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analyses and hardness experiments were conducted with cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved into specimens along the /001/ surface, and indentations were made on the cleaved surface in laboratory air, in nitrogen gas, or in degassed mineral oil with and without an additive while not exposing specimen surface to any other environment. The various additives examined contained sulfur, phosphorus, chlorine, or oleic acid. The sulfur-containing additive exhibited the highest hardness and smallest dislocation patterns evidencing plastic deformation; the chlorine-containing additive exhibited the lowest hardness and largest dislocation patterns evidencing plastic deformation. Hydrocarbon and chloride (MgCl2) films formed on the magnesium oxide surface. A chloride film was responsible for the lowest measured hardness.

  16. The Oxidation of Iron: Experiment, Simulation, and Analysis in Introductory Chemistry

    Science.gov (United States)

    Schubert, Frederic E.

    2015-01-01

    In this exercise, an actual chemical reaction, oxidation of iron in air, is studied along with a related analogue simulation of that reaction. The rusting of steel wool is carried out as a class effort. The parallel simulation is performed by students working in small groups. The analogue for the reacting gas is a countable set of discrete marble…

  17. Photo-oxidation of pinonaldehyde at low NOx: from chemistry to organic aerosol formation

    Directory of Open Access Journals (Sweden)

    N. M. Donahue

    2012-03-01

    Full Text Available Pinonaldehyde oxidation by OH radicals under low-NOx conditions produces significant secondary organic aerosol (SOA mass yields. Under concurrent UV illumination, mass yields are lower than high-NOx yields published earlier by our group. However, when OH radicals are produced via dark ozonolysis the SOA mass yields are comparable at high and low NOx. Because pinonaldehyde is a major first-generation gas-phase product of α-pinene oxidation by either ozone or OH radicals, its potential to form SOA serves as a molecular counterpoint to bulk SOA aging experiments involving SOA formed from α-pinene. Both the general tendency for aging reactions to produce more SOA and the sensitivity of the low-NOx products to UV photolysis observed in the bulk clearly occur for this single species as well. Photochemical oxidation of pinonaldehye and analogous first-generation terpene oxidation products are potentially a significant source of additional SOA in biogenically influenced air masses.

  18. The Solubility of metal oxides in molten carbonates - why the acid-basic chemistry fails?

    DEFF Research Database (Denmark)

    Bjerrum, Niels; Qingfeng, Li; Borup, Flemming

    1999-01-01

    Solubilities of various metal oxides in molten Li/K carbonates have been measured at 650°C under carbon dioxide atmosphere. It is found that the solubility of NiO and PbO decreases with increasing lithium mole fraction and decreasing CO2 partial pressure. On the other hand, the emf measurement...

  19. Role of surface chemistry in modified ACF (activated carbon fiber)-catalyzed peroxymonosulfate oxidation

    Science.gov (United States)

    Yang, Shiying; Li, Lei; Xiao, Tuo; Zheng, Di; Zhang, Yitao

    2016-10-01

    A commercial activated carbon fiber (ACF-0) was modified by three different methods: nitration treatment (ACF-N), heat treatment (ACF-H) and heat treatment after nitration (ACF-NH), and the effects of textural and chemical properties on the ability of the metal-free ACF-catalyzed peroxymonosulfate (PMS) oxidation of Reactive Black 5 (RB5), an azo dye being difficultly adsorbed onto ACF, in aqueous solution were investigated in this work. Surface density of functional groups, surface area changes, surface morphology and the chemical state inside ACF samples were characterized by Boehm titration, N2 adsorption, scanning electron microscopy in couple with energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), respectively. XPS spectra deconvolution was applied to figure out the importance of surface nitrogen-containing function groups. We found that π-π, pyridine and amine have promoting effect on the catalytic oxidation while the -NO2 has inhibitory effect on the ACF/PMS systems for RB5 destroy. Sustainability and renewability of the typical ACF-NH for catalytic oxidation of RB5 were also discussed in detail. Information about our conclusions are useful to control and improve the performance of ACF-catalyzed PMS oxidation for organic pollutants in wastewater treatment.

  20. Tris(pyrazolyl)phosphine Oxides. Synthesis and Coordination Chemistry with Copper(I)

    NARCIS (Netherlands)

    Tazelaar, C.G.J.; Lyaskovskyy, V.; van Dijk, T.; Broere, D.L.J.; Kolfschoten, L.A.; Khiar, R.O.H.; Lutz, M.; Slootweg, J.C.; Lammertsma, K.

    2012-01-01

    A set of substituted tris(pyrazolyl)phosphine oxides (OP(pzx)3) has been prepared in high yield and applied as neutral scorpion-type ligands. The P apex provides a convenient spectroscopic handle. Substitution at the 3-position of the pyrazolyl ring influences the steric demands of the ligand, while

  1. Catalyst design in oxidation chemistry; from KMnO4 to artificial metalloenzymes

    NARCIS (Netherlands)

    Doble, Megan V.; Ward, Andrew C. C.; Deuss, Peter J.; Jarvis, Amanda G.; Kamer, Paul C. J.

    2014-01-01

    Oxidation reactions are an important part of the synthetic organic chemist's toolkit and continued advancements have, in many cases, resulted in high yields and selectivities. This review aims to give an overview of the current state-of-the-art in oxygenation reactions using both chemical and enzyma

  2. The pro-oxidant chemistry of the natural antioxidants vitamin C, vitamin E, carotenoids and flavonoids

    NARCIS (Netherlands)

    Rietjens, I.M.C.M.; Boersma, M.G.; Haan, L. de; Spenkelink, B.; Awad, H.M.; Cnubben, N.H.P.; Zanden, J.J. van; Woude, H. van der; Alink, G.M.; Koeman, J.H.

    2002-01-01

    Natural antioxidants like vitamin C, vitamin E, carotenoids, and polyphenols like flavonoids, are at present generally considered to be beneficial components from fruit and vegetables. The anti-oxidative properties of these compounds are often claimed to be responsible for various beneficial health

  3. Reaction Chemistry of W-Mn/SiO2 Catalyst for the Oxidative Coupling of Methane

    Institute of Scientific and Technical Information of China (English)

    Shuben Li

    2003-01-01

    Reaction chemistry of the OCM reaction on W-Mn/SiO2 catalyst has been reviewed in thisaccount. Initial activity and selectivity, stability in a long-term reaction, reaction at elevated pressures anda modelling test in a stainless-steel fluidized-bed reactor show that W-Mn/SiO2 has promising performancefor the development of an OCM process that directly produces ethylene from natural gas. A study onsurface catalytic reaction kinetics and used catalyst structure characterization revealed a possible reasonwhy C2 and COx selectivity changed during the long-term reaction. Further improvement of the catalystcomposition and preparation method should be a future direction of study on OCM reaction over W-Mn/SiO2 catalyst.

  4. Versatile Redox Chemistry Complicates Antioxidant Capacity Assessment: Flavonoids as Milieu-Dependent Anti- and Pro-Oxidants

    Directory of Open Access Journals (Sweden)

    Gert Bachmann

    2013-06-01

    Full Text Available Some antioxidants have been shown to possess additional pro-oxidant effects. Diverse methodologies exist for studying redox properties of synthetic and natural chemicals. The latter are substantial components of our diet. Exploration of their contribution to life-extending or -compromising effects is mandatory. Among reactive oxygen species (ROS, hydroxyl radical (•OH is the most damaging species. Due to its short half-life, the assay has to contain a specific generation system. Plants synthesize flavonoids, phenolic compounds recognized as counter-agents to coronary heart disease. Their antioxidant activities are affected by their hydroxylation patterns. Moreover, in the plant, they mainly occur as glycosides. We chose three derivatives, quercetin, luteolin, and rutin, in attempts to explore their redox chemistry in contrasting hydrogen peroxide environments. Initial addition of hydrogen peroxide in high concentration or gradual development constituted a main factor affecting their redox chemical properties, especially in case of quercetin. Our study exemplifies that a combination of a chemical assay (deoxyribose degradation with an electrochemical method (square-wave voltammetry provides insightful data. The ambiguity of the tested flavonoids to act either as anti- or pro-oxidant may complicate categorization, but probably contributed to their evolution as components of a successful metabolic system that benefits both producer and consumer.

  5. Versatile redox chemistry complicates antioxidant capacity assessment: flavonoids as milieu-dependent anti- and pro-oxidants.

    Science.gov (United States)

    Chobot, Vladimir; Kubicova, Lenka; Bachmann, Gert; Hadacek, Franz

    2013-06-04

    Some antioxidants have been shown to possess additional pro-oxidant effects. Diverse methodologies exist for studying redox properties of synthetic and natural chemicals. The latter are substantial components of our diet. Exploration of their contribution to life-extending or -compromising effects is mandatory. Among reactive oxygen species (ROS), hydroxyl radical (•OH) is the most damaging species. Due to its short half-life, the assay has to contain a specific generation system. Plants synthesize flavonoids, phenolic compounds recognized as counter-agents to coronary heart disease. Their antioxidant activities are affected by their hydroxylation patterns. Moreover, in the plant, they mainly occur as glycosides. We chose three derivatives, quercetin, luteolin, and rutin, in attempts to explore their redox chemistry in contrasting hydrogen peroxide environments. Initial addition of hydrogen peroxide in high concentration or gradual development constituted a main factor affecting their redox chemical properties, especially in case of quercetin. Our study exemplifies that a combination of a chemical assay (deoxyribose degradation) with an electrochemical method (square-wave voltammetry) provides insightful data. The ambiguity of the tested flavonoids to act either as anti- or pro-oxidant may complicate categorization, but probably contributed to their evolution as components of a successful metabolic system that benefits both producer and consumer.

  6. Role of surface chemistry in modified ACF (activated carbon fiber)-catalyzed peroxymonosulfate oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shiying, E-mail: ysy@ouc.edu.cn [Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao 266100 (China); College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China); Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (MEGE), Qingdao 266100 (China); Li, Lei [College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China); Xiao, Tuo [College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China); China City Environment Protection Engineering Limited Company, Wuhan 430071 (China); Zheng, Di; Zhang, Yitao [College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China)

    2016-10-15

    Highlights: • ACF can efficiently activate peroxymonosulfate to degrade organic pollutants. • Basic functional groups may mainly increase the adsorption capacity of ACF. • C1, N1, N2 have promoting effect on the ACF catalyzed PMS oxidation. • Modification by heat after nitric acid is also a way of ACF regeneration. - Abstract: A commercial activated carbon fiber (ACF-0) was modified by three different methods: nitration treatment (ACF-N), heat treatment (ACF-H) and heat treatment after nitration (ACF-NH), and the effects of textural and chemical properties on the ability of the metal-free ACF-catalyzed peroxymonosulfate (PMS) oxidation of Reactive Black 5 (RB5), an azo dye being difficultly adsorbed onto ACF, in aqueous solution were investigated in this work. Surface density of functional groups, surface area changes, surface morphology and the chemical state inside ACF samples were characterized by Boehm titration, N{sub 2} adsorption, scanning electron microscopy in couple with energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), respectively. XPS spectra deconvolution was applied to figure out the importance of surface nitrogen-containing function groups. We found that π-π, pyridine and amine have promoting effect on the catalytic oxidation while the −NO{sub 2} has inhibitory effect on the ACF/PMS systems for RB5 destroy. Sustainability and renewability of the typical ACF-NH for catalytic oxidation of RB5 were also discussed in detail. Information about our conclusions are useful to control and improve the performance of ACF-catalyzed PMS oxidation for organic pollutants in wastewater treatment.

  7. Water oxidation chemistry of a synthetic dinuclear ruthenium complex containing redox-active quinone ligands.

    Science.gov (United States)

    Isobe, Hiroshi; Tanaka, Koji; Shen, Jian-Ren; Yamaguchi, Kizashi

    2014-04-21

    We investigated theoretically the catalytic mechanism of electrochemical water oxidation in aqueous solution by a dinuclear ruthenium complex containing redox-active quinone ligands, [Ru2(X)(Y)(3,6-tBu2Q)2(btpyan)](m+) [X, Y = H2O, OH, O, O2; 3,6-tBu2Q = 3,6-di-tert-butyl-1,2-benzoquinone; btpyan =1,8-bis(2,2':6',2″-terpyrid-4'-yl)anthracene] (m = 2, 3, 4) (1). The reaction involves a series of electron and proton transfers to achieve redox leveling, with intervening chemical transformations in a mesh scheme, and the entire molecular structure and motion of the catalyst 1 work together to drive the catalytic cycle for water oxidation. Two substrate water molecules can bind to 1 with simultaneous loss of one or two proton(s), which allows pH-dependent variability in the proportion of substrate-bound structures and following pathways for oxidative activation of the aqua/hydroxo ligands at low thermodynamic and kinetic costs. The resulting bis-oxo intermediates then undergo endothermic O-O radical coupling between two Ru(III)-O(•) units in an anti-coplanar conformation leading to bridged μ-peroxo or μ-superoxo intermediates. The μ-superoxo species can liberate oxygen with the necessity for the preceding binding of a water molecule, which is possible only after four-electron oxidation is completed. The magnitude of catalytic current would be limited by the inherent sluggishness of the hinge-like bending motion of the bridged μ-superoxo complex that opens up the compact, hydrophobic active site of the catalyst and thereby allows water entry under dynamic conditions. On the basis of a newly proposed mechanism, we rationalize the experimentally observed behavior of electrode kinetics with respect to potential and discuss what causes a high overpotential for water oxidation by 1.

  8. A global model of tropospheric chlorine chemistry: Organic versus inorganic sources and impact on methane oxidation

    Science.gov (United States)

    Hossaini, Ryan; Chipperfield, Martyn P.; Saiz-Lopez, Alfonso; Fernandez, Rafael; Monks, Sarah; Feng, Wuhu; Brauer, Peter; Glasow, Roland

    2016-12-01

    Chlorine atoms (Cl) are highly reactive toward hydrocarbons in the Earth's troposphere, including the greenhouse gas methane (CH4). However, the regional and global CH4 sink from Cl is poorly quantified as tropospheric Cl concentrations ([Cl]) are uncertain by 2 orders of magnitude. Here we describe the addition of a detailed tropospheric chlorine scheme to the TOMCAT chemical transport model. The model includes several sources of tropospheric inorganic chlorine (Cly), including (i) the oxidation of chlorocarbons of natural (CH3Cl, CHBr2Cl, CH2BrCl, and CHBrCl2) and anthropogenic (CH2Cl2, CHCl3, C2Cl4, C2HCl3, and CH2ClCH2Cl) origin and (ii) sea-salt aerosol dechlorination. Simulations were performed to quantify tropospheric [Cl], with a focus on the marine boundary layer, and quantify the global significance of Cl atom CH4 oxidation. In agreement with observations, simulated surface levels of hydrogen chloride (HCl), the most abundant Cly reservoir, reach several parts per billion (ppb) over polluted coastal/continental regions, with sub-ppb levels typical in more remote regions. Modeled annual mean surface [Cl] exhibits large spatial variability with the largest levels, typically in the range of 1-5 × 104 atoms cm-3, in the polluted northern hemisphere. Chlorocarbon oxidation provides a tropospheric Cly source of up to 4320 Gg Cl/yr, sustaining a background surface [Cl] of methane sink of 12-13 Tg CH4/yr due the CH4 + Cl reaction ( 2.5% of total CH4 oxidation). Larger regional effects are predicted, with Cl accounting for 10 to >20% of total boundary layer CH4 oxidation in some locations.

  9. OH and HO2 chemistry during NAMBLEX: roles of oxygenates, halogen oxides and heterogeneous uptake

    Directory of Open Access Journals (Sweden)

    R. Sommariva

    2006-01-01

    Full Text Available Several zero-dimensional box-models with different levels of chemical complexity, based on the Master Chemical Mechanism (MCM, have been used to study the chemistry of OH and HO2 in a coastal environment in the Northern Hemisphere. The models were constrained to and compared with measurements made during the NAMBLEX campaign (Mace Head, Ireland in summer 2002. The base models, which were constrained to measured CO, CH4 and NMHCs, were able to reproduce [OH] within 25%, but overestimated [HO2] by about a factor of 2. Agreement was improved when the models were constrained to oxygenated compounds (acetaldehyde, methanol and acetone, highlighting their importance for the radical budget. When the models were constrained to measured halogen monoxides (IO, BrO and used a more detailed, measurements-based, treatment to describe the heterogeneous uptake, modelled [OH] increased by up to 15% and [HO2] decreased by up to 30%. The actual impact of halogen monoxides on the modelled concentrations of HOx was dependant on the uptake coefficients used for HOI, HOBr and HO2. Better agreement, within the combined uncertainties of the measurements and of the model, was achieved when using high uptake coefficients for HO2 and HOI (γHO2=1, γHOI=0.6. A rate of production and destruction analysis of the models allowed a detailed study of OH and HO2 chemistry under the conditions encountered during NAMBLEX, showing the importance of oxygenates and of XO (where X=I, Br as co-reactants for OH and HO2 and of HOX photolysis as a source for OH.

  10. Ultrasensitive photoelectrochemical immunoassay of antibody against tumor-associated carbohydrate antigen amplified by functionalized graphene derivates and enzymatic biocatalytic precipitation.

    Science.gov (United States)

    Zhang, Xiaoru; Liu, Mingshuai; Mao, Yaning; Xu, Yunpeng; Niu, Shuyan

    2014-09-15

    Tumor-associated carbohydrate antigens (TACAs) are often found on the surface of cancer cells. The determination of the carbohydrate components of glycoconjugates is challenging because of the chemical complexity of glycan chains. Through monitoring corresponding antibody, we can get a good solution for clinical diagnosis. Here breast tumor-associated carbohydrate antigens Tn were used as a model and a new photoelectrochemical biosensor for ultrasensitive detection of antibody against Tn was developed. To enhance the sensitivity, both graphene oxide and graphene were used during the construction of biosensor. Through the formation of immunocomplex and the insoluble biocatalytic precipitation (BCP) product, photocurrent intensity was decreased greatly and the antibody could be detected from 0.5 to 500 pg/mL with a detection limit of 1.0×10(-13) g/mL. At the same time, the developed biosensor showed acceptable selectivity and could be used in the complex matrix. Compared with the traditional glycoarray method, this PEC method is more sensitive (5 orders of magnitude), and thus provides another platform to monitor the immune response to carbohydrate epitopes at different stages during differentiation, metastasis, or treatment.

  11. Modeling and experimental validation of CO heterogeneous chemistry and electrochemistry in solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Yurkiv, Vitaly

    2010-12-17

    In the present work experimental and numerical modeling studies of the heterogeneously catalyzed and electrochemical oxidation of CO at Nickel/yttria-stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) anode systems were performed to evaluate elementary charge-transfer reaction mechanisms taking place at the three-phase boundary of CO/CO{sub 2} gas-phase, Ni electrode, and YSZ electrolyte. Temperature-programmed desorption and reaction experiments along with density functional theory calculations were performed to determine adsorption/desorption and surface diffusion kinetics as well as thermodynamic data for the CO/CO{sub 2}/Ni and CO/CO{sub 2}/YSZ systems. Based on these data elementary reaction based models with four different charge transfer mechanisms for the electrochemical CO oxidation were developed and applied in numerical simulations of literature experimental electrochemical data such as polarization curves and impedance spectra. Comparison between simulation and experiment demonstrated that only one of the four charge transfer mechanisms can consistently reproduce the electrochemical data over a wide range of operating temperatures and CO/CO{sub 2} gas compositions. (orig.) [German] In der vorliegenden Arbeit wurden experimentelle und numerische Untersuchungen zur heterogen katalysierten und elektrochemischen Oxidation von CO an Anodensystemen (bestehend aus Nickel und yttriumdotiertem Zirkoniumdioxid, YSZ) von Festoxidbrennstoffzellen (engl. Solid Oxide Fuel Cells, SOFCs) ausgefuehrt, um den mikroskopischen Mechanismus der an der CO/CO{sub 2}-Gasphase/Ni-Elektrode/YSZ-Elektrolyt- Dreiphasen-Grenzflaeche ablaufenden Ladungsuebertragungsreaktion aufzuklaeren. Temperaturprogrammierte Desorptionsmessungen (TPD) und Temperaturprogrammierte Reaktionsmessungen (TPR) sowie Dichtefunktionaltheorierechnungen wurden ausgefuehrt, um adsorptions-, desorptions- und reaktionskinetische sowie thermodynamische Daten fuer die CO/CO{sub 2}/Ni- und CO/CO{sub 2}/YSZ

  12. Modeling the oxidative coupling of methane:Heterogeneous chemistry coupled with 3D flow field simulation

    Institute of Scientific and Technical Information of China (English)

    Yaghobi Nakisa; Ghoreishy Mir Hamid Reza

    2009-01-01

    The oxidative coupling of methane (OCM) over titanate perovskite catalyst has been developed by three-dimensional numerical simulations of flow field coupled with heat transfer as well as heterogeneous kinetic model.The reaction was assumed to take place both in the gas phase and on the catalytic surface.Kinetic rate constants were experimentally obtained using a ten step kinetic model.The simulation results agree quite well with the data of OCM experiments,which were used to investigate the effect of temperature on the selectivity and conversion obtained in the methane oxidative coupling process.The conversion of methane linearly increased with temperature and the selectivity of C2 was practically constant in the temperature range of 973-1073 K.The study shows that CFD tools make it possible to implement the heterogeneous kinetic model even for high exothermic reaction such as OCM.

  13. Mechanochemistry of magnesium oxide revisited: facile derivatisation of pharmaceuticals using coordination and supramolecular chemistry.

    Science.gov (United States)

    Chow, Ernest H H; Strobridge, Fiona C; Friscić, Tomislav

    2010-09-14

    Liquid-assisted grinding allows the rapid, waste-free and one-pot synthesis of a variety of magnesium drug derivatives directly from the excipient MgO; such reactivity is relevant for the behaviour of ibuprofen formulations involving MgO and can be used for oxide-based mechanosynthesis of metal-organic salts, discrete complexes and carboxylate clusters involving magnesium and pharmaceutically active ingredients.

  14. Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gopalan, Srikanth [Boston Univ., MA (United States)

    2013-03-31

    In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

  15. Photo-oxidants and precursors at Schauinsland, Black Forest: chemistry and transport

    Energy Technology Data Exchange (ETDEWEB)

    Volz-Thomas, A.; Buers, H.J.; Flocke, F.; Geiss, H.; Heil, T.; Heitlinger, M.; Houben, N.; Jansen, S.; Klemp, D.; Kramp, F.; Mihelcic, D.; Muesgen, P.; Paetz, H.W.; Schultz, M.; Su, Y.; Kley, D. [Forschungszentrum Juelich (Germany). Inst. fuer Chemie and Dynamik der Geosphaere (ICG-2)

    1997-12-31

    The main goal of this contribution was to contribute to a better understanding of the processes that control the budget of ozone and other photo-oxidants over Europe. Besides establishing a climatology of ozone and precursors in the context of TOR, particular emphasis was given to the role that meteorological and chemical processes play in controlling the concentrations observed at Schauinsland, an elevated rural site situated about three hours downwind of an urban settlement. (orig.)

  16. Formaldehyde and Glyoxal Measurements as Tracers of Oxidation Chemistry in the Amazon Basin

    Science.gov (United States)

    Thayer, M. P.; Dorris, M. R.; Keutsch, F. N.; Springston, S. R.; Jimenez, J. L.; Palm, B. B.; Seco, R.; Kim, S.; Yee, L.; Wernis, R. A.; Goldstein, A. H.; Isaacman-VanWertz, G. A.; Liu, Y.; Martin, S. T.

    2015-12-01

    Formaldehyde (HCHO) and glyoxal (CHOCHO) are important tracers for oxidative processes in the atmosphere such as oxidation of volatile organic compounds (VOCs) and production of HO2 radicals by photolysis or reaction with OH. Products of VOC oxidation and radical cycling, such as aerosols and tropospheric ozone, have direct impacts on human health. During the Green Ocean Amazon campaign (GoAmazon2014/5), HCHO and CHOCHO measurements were obtained together with OH, RO2+HO2, CO, CO2, O3, NOx, (o)VOCs, and aerosol particle size distribution. HCHO concentration was measured by the Madison FIber Laser-Induced Fluorescence (FILIF) instrument, while CHOCHO concentrations were collected by the Madison Laser-Induced Phosphorescence (Mad-LIP) instrument. Here we present data collected during 2014 at the T3 field site, 60 km to the west of Manaus, Brazil (3°12'47.82"S, 60°35'55.32"W). The T3 GoAmazon site varies between sampling strictly pristine (biogenic) emissions and influence from anthropogenic emissions from Manaus, depending on meteorological conditions. Here we present overall trends and regimes observed during the campaign, with a focus on HCHO, CHOCHO, and related species within the context of VOC oxidation and secondary pollutant production. We acknowledge the support from the Central Office of the Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA), the Instituto Nacional de Pesquisas da Amazonia (INPA), and the Universidade do Estado do Amazonia (UEA). The work was conducted under 001030/2012-4 of the Brazilian National Council for Scientific and Technological Development (CNPq). Data were collected from the Atmospheric Radiation Measurement (ARM) Climate Research Facility, a U.S. Department of Energy Office of Science user facility sponsored by the Office of Biological and Environmental Research. Additionally, we acknowledge logistical support from the ARM Climate Research Facility. Additional funding from: NSF GRFP DGE-1256259, and NSF AGS-1051338

  17. The complex interface chemistry of thin-film silicon/zinc oxide solar cell structures.

    Science.gov (United States)

    Gerlach, D; Wimmer, M; Wilks, R G; Félix, R; Kronast, F; Ruske, F; Bär, M

    2014-12-21

    The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.

  18. Heterocycles 38. Biocatalytic Synthesis of New Heterocyclic Mannich Bases and Derivatives

    Directory of Open Access Journals (Sweden)

    Denisa Leonte

    2015-07-01

    Full Text Available This paper describes the biocatalytic synthesis of new Mannich bases containing various heterocyclic rings (thiazole, furane, thiophene, pyridine by applying the lipase catalyzed trimolecular condensation of the corresponding heterocyclic aldehydes with acetone and primary aromatic amines, in mild and eco-friendly reaction conditions. The obtained Mannich bases were acylated to their corresponding N-acetyl derivatives. All compounds were characterized by 1H-NMR, 13C-NMR and MS spectrometry.

  19. Nitrogen Oxides in the Nocturnal Boundary Layer: Chemistry of Nitrous Acid (HONO) and the Nitrate Radical (N03)

    Energy Technology Data Exchange (ETDEWEB)

    Jochen Stutz

    2005-05-24

    Summary Chemical processes occurring at night in the lowest part of the urban atmosphere, the so called nocturnal boundary layer (NBL), can influence the composition of the atmosphere during the night as well as the following day. They may impact the budgets of some of the most important pollutants, such as ozone and nitrogen oxides, as well as influence size and composition of particular matter. Few studies have thus far concentrated on the nocturnal chemistry of the urban NBL, most likely due to the strong influence of vertical transport and mixing, which requires the measurement of trace gas profiles instead of simple point observations. Motivated by our lack of observations and understanding of nocturnal chemistry, the focus of this project was the study of the vertical distribution of trace gases and the altitude dependence of nocturnal chemistry under polluted conditions through field observations and modeling studies. The analysis of three field experiments (TEXAQS, Houston, 2000; Phoenix Sunrise Ozone Experiment, 2001; NAPOX, Boston, 2002), two of which were performed in this project, showed that ozone concentrations typically increase with height in the lowest 150m, while NO2 typically decreases. NO3, the dominant nocturnal radical species, showed much higher concentrations in the upper part of the NBL, and was often not present at the ground. With the help of a one-dimensional chemical transport model, developed in this project, we found that the interaction of ground emissions of NOx and hydrocarbons, together with their vertical transport, is responsible for the vertical profiles. The dominant chemical reactions influencing ozone, NO2 and NO3 are the reaction of ozone and NO3 with freshly emitted NO. Sensitivity studies with our model showed that the magnitude of the trace gas gradients depend both on the emission rates and the vertical stability of the NBL. Observations and model analysis clearly show that nocturnal chemistry in urban areas is altitude

  20. Short-term inactivation rates of selected Gram-positive and Gram-negative bacteria attached to metal oxide mineral surfaces: role of solution and surface chemistry.

    Science.gov (United States)

    Asadishad, Bahareh; Ghoshal, Subhasis; Tufenkji, Nathalie

    2013-06-04

    Metal oxides such as ferric or aluminum oxides can play an important role in the retention of bacteria in granular aquatic environments; however, their role in bacterial inactivation is not well understood. Herein, we examined the role of water chemistry and surface chemistry on the short-term inactivation rates of three bacteria when adhered to surfaces. To evaluate the role of water chemistry on the inactivation of attached bacteria, the loss in membrane integrity of bacteria attached to an iron oxide (Fe2O3) surface was measured over a range of water ionic strengths of either monovalent or divalent salts in the absence of a growth substrate. The influence of surface chemistry on the inactivation of attached bacteria was examined by measuring the loss in membrane integrity of cells attached to three surfaces (SiO2, Fe2O3, and Al2O3) at a specific water chemistry (10 mM KCl). Bacteria were allowed to attach onto the SiO2 or metal oxide coated slides mounted in a parallel-plate flow cell, and their inactivation rate (loss in membrane integrity) was measured directly without removing the cells from the surface and without disturbing the system. X-ray photoelectron spectroscopy analysis revealed a high correlation between the amounts of C-metal or O-metal bonds and the corresponding bacterial inactivation rates for each surface. Finally, for all three surfaces, a consistent increase in inactivation rate was observed with the type of bacterium in the order: Enterococcus faecalis, Escherichia coli O157:H7, and Escherichia coli D21f2.

  1. Tungsten Incorporation into Gallium Oxide: Crystal Structure, Surface and Interface Chemistry, Thermal Stability and Interdiffusion

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, E. J.; Mates, T. E.; Manandhar, S.; Nandasiri, M.; Shutthanandan, V.; Ramana, C. V.

    2016-12-01

    Tungsten (W) incorporated gallium oxide (Ga2O3) (GWO) thin films were deposited by radio-frequency magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying sputtering power applied to the W-target in order to achieve variable W-content (0-12 at%) into Ga2O3 while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-deposited and annealed GWO films were evaluated as a function of W-content. The structural and chemical analyses indicate that the samples deposited without any W-incorporation are stoichiometric, nanocrystalline Ga2O3 films, which crystallize in β-phase monoclinic structure. While GWO films also crystallize in monoclinic β-Ga2O3 phase, W-incorporation induces surface amorphization as revealed by structural studies. The chemical valence state of Ga ions probed by X-ray photoelectron spectroscopic (XPS) analyses is characterized by the highest oxidation state i.e., Ga3+. No changes in Ga chemical state are noted for variable W-incorporation in the range of 0-12 at%. Rutherford backscattering spectrometry (RBS) analyses indicate the uniform distribution of W-content in the GWO films. However, XPS analyses indicate the formation of mixed valence states for W ions, which may be responsible for surface amorphization in GWO films. GWO films were stable up to 900 oC, at which point thermally induced secondary phase (W-oxide) formation was observed. A transition to mesoporous structure coupled with W interdiffusion occurs due to thermal annealing as derived from the chemical analyses at the GWO films’ surface as well as depth-profiling towards the GWO-Si interface. A model has been formulated to account for the mechanism of W-incorporation, thermal stability and interdiffusion via pore formation in GWO films.

  2. Mechanistic Aspects of Aryl-Halide Oxidative Addition, Coordination Chemistry, and Ring-Walking by Palladium.

    Science.gov (United States)

    Zenkina, Olena V; Gidron, Ori; Shimon, Linda J W; Iron, Mark A; van der Boom, Milko E

    2015-11-01

    This contribution describes the reactivity of a zero-valent palladium phosphine complex with substrates that contain both an aryl halide moiety and an unsaturated carbon-carbon bond. Although η(2) -coordination of the metal center to a C=C or C≡C unit is kinetically favored, aryl halide bond activation is favored thermodynamically. These quantitative transformations proceed under mild reaction conditions in solution or in the solid state. Kinetic measurements indicate that formation of η(2) -coordination complexes are not nonproductive side-equilibria, but observable (and in several cases even isolated) intermediates en route to aryl halide bond cleavage. At the same time, DFT calculations show that the reaction with palladium may proceed through a dissociation-oxidative addition mechanism rather than through a haptotropic intramolecular process (i.e., ring walking). Furthermore, the transition state involves coordination of a third phosphine to the palladium center, which is lost during the oxidative addition as the C-halide bond is being broken. Interestingly, selective activation of aryl halides has been demonstrated by adding reactive aryl halides to the η(2) -coordination complexes. The product distribution can be controlled by the concentration of the reactants and/or the presence of excess phosphine.

  3. Crystal-chemistry guidelines for noncentrosymmetric A2BO4 Ruddlesden-Popper oxides.

    Science.gov (United States)

    Balachandran, Prasanna V; Puggioni, Danilo; Rondinelli, James M

    2014-01-01

    Noncentrosymmetric (NCS) phases are seldom seen in layered A2BO4 Ruddlesden-Popper (214 RP) oxides. In this work, we uncover the underlying crystallographic symmetry restrictions that enforce the spatial parity operation of inversion and then subsequently show how to lift them to achieve NCS structures. Simple octahedral distortions alone, while impacting the electronic and magnetic properties, are insufficient. We show using group theory that the condensation of two distortion modes, which describe suitable symmetry unique octahedral distortions or a combination of a single octahedral distortion with a "compositional" A or B cation ordering mode, is able to transform the centrosymmetric aristotype into a NCS structure. With these symmetry guidelines, we formulate a data-driven model founded on Bayesian inference that allows us to rationally search for combinations of A- and B-site elements satisfying the inversion symmetry lifting criterion. We describe the general methodology and apply it to 214 iridates with A(2+) cations, identifying RP-structured Ca2IrO4 as a potential NCS oxide, which we evaluate with density functional theory. We find a strong energetic competition between two closely related polar and nonpolar low-energy crystal structures in Ca2IrO4 and suggest pathways to stabilize the NCS structure.

  4. Recent advances in surface chemistry strategies for the fabrication of functional iron oxide based magnetic nanoparticles

    Science.gov (United States)

    Turcheniuk, Kostiantyn; Tarasevych, Arkadii V.; Kukhar, Valeriy P.; Boukherroub, Rabah; Szunerits, Sabine

    2013-10-01

    The synthesis of superparamagnetic nanostructures, especially iron-oxide based nanoparticles (IONPs), with appropriate surface functional groups has been intensively researched for many high-technological applications, including high density data storage, biosensing and biomedicine. In medicine, IONPs are nowadays widely used as contrast agents for magnetic resonance imaging (MRI), in hyperthermia therapy, but are also exploited for drug and gene delivery, detoxification of biological fluids or immunoassays, as they are relatively non-toxic. The use of magnetic particles in vivo requires IONPs to have high magnetization values, diameters below 100 nm with overall narrow size distribution and long time stability in biological fluids. Due to the high surface energies of IONPs agglomeration over time is often encountered. It is thus of prime importance to modify their surface to prevent aggregation and to limit non-specific adsorption of biomolecules onto their surface. Such chemical modifications result in IONPs being well-dispersed and biocompatible, and allow for targeted delivery and specific interactions. The chemical nature of IONPs thus determines not only the overall size of the colloid, but also plays a significant role for in vivo and in vitro applications. This review discusses the different concepts currently used for the surface functionalization and coating of iron oxide nanoparticles. The diverse strategies for the covalent linking of drugs, proteins, enzymes, antibodies, and nucleotides will be discussed and the chemically relevant steps will be explained in detail.

  5. Peroxy radical chemistry and OH radical production during the NO3-initiated oxidation of isoprene

    Directory of Open Access Journals (Sweden)

    P. O. Wennberg

    2012-01-01

    Full Text Available Peroxy radical reactions (RO2 + RO2 from the NO3-initiated oxidation of isoprene are studied with both gas chromatography and a chemical ionization mass spectrometry technique that allows for more specific speciation of products than in previous studies of this system. We find high nitrate yields (>~80%, consistent with other studies. We further see evidence of significant hydroxyl radical (OH formation in this system, which we propose comes from RO2 + HO2 reactions with a yield of ~42–62%. An additional OH source is the second generation oxidation of the nitrooxyhydroperoxide, which produces OH and a dinitrooxyepoxide with a yield of ~35%. The branching ratio of the radical propagating, carbonyl- and alcohol-forming, and dimer-forming channels of the RO2 + RO2 reaction are found to be ~18–38%, ~59–77%, and ~3–4%, respectively. HO2 formation in this system is lower than has been previously assumed. Addition of RO2 to isoprene is suggested as a possible route to the formation of several isoprene dimer compounds (ROOR. The nitrooxy, allylic, and C5 peroxy radicals present in this system exhibit different behavior than the limited suite of peroxy radicals that have been studied to date.

  6. Chemistry of hydrogen oxide radicals (HOx in the Arctic troposphere in spring

    Directory of Open Access Journals (Sweden)

    L. Jaeglé

    2010-07-01

    Full Text Available We use observations from the April 2008 NASA ARCTAS aircraft campaign to the North American Arctic, interpreted with a global 3-D chemical transport model (GEOS-Chem, to better understand the sources and cycling of hydrogen oxide radicals (HOx≡H+OH+peroxy radicals and their reservoirs (HOy≡HOx+peroxides in the springtime Arctic atmosphere. We find that a standard gas-phase chemical mechanism overestimates the observed HO2 and H2O2 concentrations. Computation of HOx and HOy gas-phase chemical budgets on the basis of the aircraft observations also indicates a large missing sink for both. We hypothesize that this could reflect HO2 uptake by aerosols, favored by low temperatures and relatively high aerosol loadings, through a mechanism that does not produce H2O2. We implemented such an uptake of HO2 by aerosol in the model using a standard reactive uptake coefficient parameterization with γ(HO2 values ranging from 0.02 at 275 K to 0.5 at 220 K. This successfully reproduces the concentrations and vertical distributions of the different HOx species and HOy reservoirs. HO2 uptake by aerosol is then a major HOx and HOy sink, decreasing mean OH and HO2 concentrations in the Arctic troposphere by 32% and 31% respectively. Better rate and product data for HO2 uptake by aerosol are needed to understand this role of aerosols in limiting the oxidizing power of the Arctic atmosphere.

  7. Peroxy radical chemistry and OH radical production during the NO3-initiated oxidation of isoprene

    Directory of Open Access Journals (Sweden)

    J. H. Seinfeld

    2012-08-01

    Full Text Available Peroxy radical reactions (RO2 + RO2 from the NO3-initiated oxidation of isoprene are studied with both gas chromatography and a chemical ionization mass spectrometry technique that allows for more specific speciation of products than in previous studies of this system. We find high nitrate yields (~ 80%, consistent with other studies. We further see evidence of significant hydroxyl radical (OH formation in this system, which we propose comes from RO2 + HO2 reactions with a yield of ~38–58%. An additional OH source is the second generation oxidation of the nitrooxyhydroperoxide, which produces OH and a dinitrooxyepoxide with a yield of ~35%. The branching ratio of the radical propagating, carbonyl- and alcohol-forming, and organic peroxide-forming channels of the RO2 + RO2 reaction are found to be ~18–38%, ~59–77%, and ~3–4%, respectively. HO2 formation in this system is lower than has been previously assumed. Addition of RO2 to isoprene is suggested as a possible route to the formation of several isoprene C10-organic peroxide compounds (ROOR. The nitrooxy, allylic, and C5 peroxy radicals present in this system exhibit different behavior than the limited suite of peroxy radicals that have been studied to date.

  8. Microbial reduction of graphene oxide by Escherichia coli: a green chemistry approach.

    Science.gov (United States)

    Gurunathan, Sangiliyandi; Han, Jae Woong; Eppakayala, Vasuki; Kim, Jin-Hoi

    2013-02-01

    Graphene and graphene related materials are an important area of research in recent years due to their unique properties. The extensive industrial application of graphene and related compounds has led researchers to devise novel and simple methods for the synthesis of high quality graphene. In this paper, we developed an environment friendly, cost effective, simple method and green approaches for the reduction of graphene oxide (GO) using Escherichia coli biomass. In biological method, we can avoid use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The biomass of E. coli reduces exfoliated GO to graphene at 37°C in an aqueous medium. The E. coli reduced graphene oxide (ERGO) was characterized with UV-visible absorption spectroscopy, particle analyzer, high resolution X-ray diffractometer, scanning electron microscopy and Raman spectroscopy. Besides the reduction potential, the biomass could also play an important role as stabilizing agent, in which synthesized graphene exhibited good stability in water. This method can open up the new avenue for preparing graphene in cost effective and large scale production. Our findings suggest that GO can be reduced by simple eco-friendly method by using E. coli biomass to produce water dispersible graphene.

  9. Solid state chemistry of nitrogen oxides--part II: surface consumption of NO2.

    Science.gov (United States)

    Ioppolo, S; Fedoseev, G; Minissale, M; Congiu, E; Dulieu, F; Linnartz, H

    2014-05-14

    Nitrogen oxides are considered to be important astrochemical precursors of complex species and prebiotics. However, apart from the hydrogenation of solid NO that leads to the surface formation of hydroxylamine, little is known about the full solid state reaction network involving both nitrogen and oxygen. Our study is divided into two papers, hereby called Part I and Part II. In the accompanying paper, we investigate the surface reactions NO + O/O2/O3 and NO + N with a focus on the formation of NO2 ice. Here, we complement this study by measurements of the surface destruction of solid NO2, e.g., NO2 + H/O/N. Experiments are performed in two separate ultra-high vacuum setups and therefore under different experimental conditions to better constrain the experimental results. Surface reaction products are monitored by means of Fourier Transform Reflection Absorption Infrared Spectroscopy (FT-RAIRS) and Temperature Programmed Desorption (TPD) techniques using mass spectrometry. The surface destruction of solid NO2 leads to the formation of a series of nitrogen oxides such as NO, N2O, N2O3, and N2O4 as well as HNO, NH2OH, and H2O. When NO2 is mixed with an interstellar more relevant apolar (i.e., CO) ice, solid CO2 and HCOOH are also formed due to interactions between different reaction routes. The astrophysical implications of the full nitrogen and oxygen reaction network derived from Parts I and II are discussed.

  10. High-Temperature Chemistry in Solid Oxide Fuel Cells: In Situ Optical Studies.

    Science.gov (United States)

    Pomfret, Michael B; Walker, Robert A; Owrutsky, Jeffrey C

    2012-10-18

    Solid oxide fuels cells (SOFCs) are promising devices for versatile and efficient power generation with fuel flexibility, but their viability is contingent upon understanding chemical and material processes to improve their performance and durability. Newly developed in situ optical methods provide new insight into how carbon deposition varies with different hydrocarbon and alcohol fuels and depends on operating conditions. Some findings, such as heavier hydrocarbon fuels forming more carbon than lighter fuels, are expected, but other discoveries are surprising. For example, methanol shows a greater tendency to form carbon deposits than methane at temperatures below 800 °C, and kinetically controlled steam reforming with ethanol at high temperatures (∼800 °C) is less detrimental to SOFC performance than operating the device with dry methanol as the fuel. In situ optical techniques will continue to provide the chemical information and mechanistic insight that is critical for SOFCs to become a viable energy conversion technology.

  11. Large scale computational chemistry modeling of the oxidation of highly oriented pyrolytic graphite.

    Science.gov (United States)

    Poovathingal, Savio; Schwartzentruber, Thomas E; Srinivasan, Sriram Goverapet; van Duin, Adri C T

    2013-04-04

    Large scale molecular dynamics (MD) simulations are performed to study the oxidation of highly oriented pyrolytic graphite (HOPG) by hyperthermal atomic oxygen beam (5 eV). Simulations are performed using the ReaxFF classical reactive force field. We present here additional evidence that this method accurately reproduces ab initio derived energies relevant to HOPG oxidation. HOPG is modeled as multilayer graphene and etch-pit formation and evolution is directly simulated through a large number of sequential atomic oxygen collisions. The simulations predict that an oxygen coverage is first established that acts as a precursor to carbon-removal reactions, which ultimately etch wide but shallow pits, as observed in experiments. In quantitative agreement with experiment, the simulations predict the most abundant product species to be O2 (via recombination reactions), followed by CO2, with CO as the least abundant product species. Although recombination occurs all over the graphene sheet, the carbon-removal reactions occur only about the edges of the etch pit. Through isolated defect analysis on small graphene models as well as trajectory analysis performed directly on the predicted etch pit, the activation energies for the dominant reaction mechanisms leading to O2, CO2, and CO product species are determined to be 0.3, 0.52, and 0.67 eV, respectively. Overall, the qualitative and quantitative agreement between MD simulation and experiment is very promising. Thus, the MD simulation approach and C/H/O ReaxFF parametrization may be useful for simulating high-temperature gas interactions with graphitic materials where the microstructure is more complex than HOPG.

  12. Soft chemistry routes for synthesis of rare earth oxide nanoparticles with well defined morphological and structural characteristics

    Science.gov (United States)

    Mancic, L.; Marinkovic, B. A.; Marinkovic, K.; Dramicanin, M.; Milosevic, O.

    2011-11-01

    Phosphors of (Y0.75Gd0.25)2O3:Eu3+ (5 at.%) have been prepared through soft chemistry routes. Conversion of the starting nitrates mixture into oxide is performed through two approaches: (a) hydrothermal treatment (HT) at 200 °C/3 h of an ammonium hydrogen carbonate precipitated mixture and (b) by thermally decomposition of pure nitrate precursor solution at 900 °C in dispersed phase (aerosol) within a tubular flow reactor by spray pyrolysis process (SP). The powders are additionally thermally treated at different temperatures: 600, 1000, and 1100 °C for either 3 or 12 h. HT—derived particles present exclusively one-dimensional morphology (nanorods) up to the temperatures of 600 °C, while the leaf-like particles start to grow afterward. SP—derived particles maintain their spherical shape up to the temperatures of 1100 °C. These submicron sized spheres were actually composed of randomly aggregated nanoparticles. All powders exhibits cubic Ia- 3 structure (Y0.75Gd0.25)2O3:Eu and have improved optical characteristics due to their nanocrystalline nature. The detailed study of the influence of structural and morphological powder characteristics on their emission properties is performed based on the results of X-ray powder diffractometry, scanning electron microscopy, X-ray energy dispersive spectroscopy, transmission electron microscopy, and photoluminescence measurements.

  13. Removal of graphene oxide nanomaterials from aqueous media via coagulation: Effects of water chemistry and natural organic matter.

    Science.gov (United States)

    Duan, Lin; Hao, Rongjie; Xu, Zhu; He, Xizhen; Adeleye, Adeyemi S; Li, Yao

    2017-02-01

    With the increasing use of graphene oxide (GO) nanomaterials, its possible environmental release and human effects have received much attention. As GO may enter drinking or wastewater treatment systems like other carbonaceous nanomaterials, and have potential impact on human and/or environmental health, its removal efficiency during water treatment is important and requires investigation. In this study, the removal efficiency of GO during water treatment procedure via coagulation was evaluated, and the effects of solution chemistry and natural organic matter on the coagulation-based removal of GO nanomaterials were investigated. The results indicate that the removal efficiency of GO with alum coagulation can reach 80% with 20 mg/L alum dosage at neutral pH, and will not change significantly with higher concentration of alum. The coagulation mechanism and efficiency were strongly affected by the Al species in aqueous phase, which are controlled by pH. Co-existing cations (e.g. Na) may have minimal effect on GO removal efficiency, and the presence of humic acid (HA) suppresses coagulation remarkably at alum concentrations below 40 mg/L. The results from this study provide critical information for predicting the removal efficiency of GO nanomaterials during alum coagulation phase of water treatment procedure.

  14. Physical chemistry of the interface between oxide and aqueous solution; Quelques aspects de la chimie a l'interface oxyde - solution

    Energy Technology Data Exchange (ETDEWEB)

    Jolivet, J.P. [Universite Pierre et Marie Curie, Chimie de la Matiere Condensee, URA CNRS 1466, 75 - Paris (France)

    1997-07-01

    The behavior and properties of small oxide particles in aqueous suspension are dominated by the physico-chemistry of their surface. It is electrostatically charged and strongly solvated. The origin of the surface charge is discussed through the MUSIC model [Hiemstra 1996], allowing to estimate the acid-base behavior of surface oxygen atoms. The stability of aqueous dispersions of particles is analysed following the DLVO model, with a special attention on the hydration layers allowing the peptization of flocs. Different adsorption mechanisms of metal cations are presented in terms of coordination chemistry (outer- and inner-sphere complexes) emphasizing the coordinating ability of the surface towards metal complexes in solution. The anion adsorption is also studied in relation with some interesting consequences on spinel iron oxide nano-particles. (author)

  15. Assessing the Protective Activity of a Recently Discovered Phenolic Compound against Oxidative Stress Using Computational Chemistry.

    Science.gov (United States)

    Villuendas-Rey, Yenny; Alvarez-Idaboy, Juan Raul; Galano, Annia

    2015-12-28

    The protection exerted by 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), a phenolic compound recently isolated from the Pacific oyster, against oxidative stress (OS) is investigated using the density functional theory. Our results indicate that DHMBA is an outstanding peroxyl radical scavenger, being about 15 times and 4 orders of magnitude better than Trolox for that purpose in lipid and aqueous media, respectively. It was also found to react faster with HOO(•) than other known antioxidants such as resveratrol and ascorbic acid. DHMBA is also predicted to be able to sequester Cu(II) ions, consequently inhibiting the OS induced by Cu(II)-ascorbate mixtures and downgrading the (•)OH production via the Haber-Weiss reaction. However, it is proposed that DHMBA is more efficient as a primary antioxidant (free radical scavenger), than as a secondary antioxidant (metal ion chelator). In addition, it was found that DHMBA can be efficiently regenerated in aqueous solution, at physiological pH. Such regeneration is expected to contribute to increase the antioxidant protection exerted by DHMBA. These results suggest that probably synthetic routes for this compound should be pursued, because albeit its abundance in nature is rather low, its antioxidant activity is exceptional.

  16. Detonation chemistry: an investigation of fluorine as an oxidizing moiety in explosives

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, R.R.; Ornellas, D.L.; Helm, F.H.; Coon, C.L.; Finger, M.

    1982-07-07

    We have investigated the use of fluorine in the form of the difluoramino (NF/sub 2/) group as an oxidizing moiety. Bis- and tris-difluoramino perfluorobutane, previously unknown, were especially synthesized for this study. We performed detonation calorimetry to determine the exact detonation product composition and the heat of detonation of a series of NF/sub 2/ compounds and mixtures. We then performed cylinder tests to determine their detonation performance. Similar tests on NO/sub 2/ compounds were used for comparison. For reasons of toxicity and safety, we designed and built remote mixing and loading apparati for certain of the materials. Materials were chosen to highlight certain of the detonation products. Hydrogen fluoride was found to be a favorable detonation product compared with H/sub 2/O; CO/sub 2/ outperforms CF/sub 4/ at all cylinder expansion ratios; and Al/sub 2/O/sub 3/ was a favorable detonation product compared to AlF/sub 3/. The most important result is better understanding of the mechanism of reaction of small-particle aluminum in a detonation.

  17. Research in physical chemistry and chemical education: Part A: Water Mediated Chemistry of Oxidized Atmospheric Compounds Part B: The Development of Surveying Tools to Determine How Effective Laboratory Experiments Contribute to Student Conceptual Understanding

    Science.gov (United States)

    Maron, Marta Katarzyna

    This dissertation is a combination of two research areas, experimental physical chemistry, Chapters I to V, and chemical education, Chapters VI to VII. Chapters I to V describe research on the water-mediated chemistry of oxidized atmospheric molecules and the impact that water has on the spectra of these environmental systems. The role of water in the Earth's atmosphere has been of considerable interest due to its ability to impact chemistry and climate. Oxidized atmospheric molecules in the presence of water have the ability to form hydrogen bonded water complexes. The spectroscopic investigation of nitric acid-water complexes, outlined in Chapter III, was undertaken to characterize intermolecular hydrogen bonds in a water-restricted environment at ambient temperatures. Additionally, this characterization of nitric acid-water complexes allowed for the comparison of calculated overtone OH-stretching vibrational band frequencies, intensities, and anharmonicities of intermolecular hydrogen-bonded water complexes with experimental observations. Oxidized organic molecules, such as aldehydes and ketones, in addition to forming hydrogen-bonded water complexes can undergo a hydration reaction of the carbonyl group and form germinal diols in the presence of water. This chemistry has been studied extensively in bulk aqueous media, however little is known about this process in the gas-phase at low water concentrations. The focus of the studies outlined in Chapters IV and V is motivated by the ability of pyruvic acid and formaldehyde to form germinal diols and water complexes in water-restricted environment. This water-mediated chemistry changes the physical and chemical properties of these organic molecules, therefore, impacting the partitioning between gas and particle phase, as well as the chemistry and photochemistry of oxidized organic molecules in the Earth's atmosphere. The results presented in this dissertation may help resolve the significant discrepancy between

  18. Visualization of custom-tailored iron oxide nanoparticles chemistry, uptake, and toxicity

    Science.gov (United States)

    Wilkinson, Kai; Ekstrand-Hammarström, Barbro; Ahlinder, Linnea; Guldevall, Karolin; Pazik, Robert; Kępiński, Leszek; Kvashnina, Kristina O.; Butorin, Sergei M.; Brismar, Hjalmar; Önfelt, Björn; Österlund, Lars; Seisenbaeva, Gulaim A.; Kessler, Vadim G.

    2012-11-01

    Nanoparticles of iron oxide generated by wearing of vehicles have been modelled with a tailored solution of size-uniform engineered magnetite particles produced by the Bradley reaction, a solvothermal metal-organic approach rendering hydrophilic particles. The latter does not bear any pronounced surface charge in analogy with that originating from anthropogenic sources in the environment. Physicochemical properties of the nanoparticles were thoroughly characterized by a wide range of methods, including XPD, TEM, SEM, DLS and spectroscopic techniques. The magnetite nanoparticles were found to be sensitive for transformation into maghemite under ambient conditions. This process was clearly revealed by Raman spectroscopy for high surface energy magnetite particles containing minor impurities of the hydromaghemite phase and was followed by quantitative measurements with EXAFS spectroscopy. In order to assess the toxicological effects of the produced nanoparticles in humans, with and without surface modification with ATP (a model of bio-corona formed in alveolar liquid), a pathway of potential uptake and clearance was modelled with a sequence of in vitro studies using A549 lung epithelial cells, lymphocyte 221-B cells, and 293T embryonal kidney cells, respectively. Raman microscopy unambiguously showed that magnetite nanoparticles are internalized within the A549 cells after 24 h co-incubation, and that the ATP ligand is retained on the nanoparticles throughout the uptake process. The toxicity of the nanoparticles was estimated using confocal fluorescence microscopy and indicated no principal difference for unmodified and modified particles, but revealed considerably different biochemical responses. The IL-8 cytokine response was found to be significantly lower for the magnetite nanoparticles compared to TiO2, while an enhancement of ROS was observed, which was further increased for the ATP-modified nanoparticles, implicating involvement of the ATP signalling pathway in

  19. Effects of solution chemistry on the transport of graphene oxide in saturated porous media.

    Science.gov (United States)

    Lanphere, Jacob D; Luth, Corey J; Walker, Sharon L

    2013-05-07

    A transport study was performed in saturated porous media through a packed bed column to simulate fate of graphene oxide nanoparticles (GONPs) in the subsurface environment. Transport experiments, along with mass balances and column dissections, were conducted as a function of ionic strength (IS, 10(-3)-10(-1) M). Additionally, an extensive evaluation of the electrokinetic properties and hydrodynamic diameters of GONPs were determined as a function of IS and pH. The measured hydrodynamic diameter and the electrophoretic mobility (EPM) of GONPs indicated an insensitivity to pH, although IS did play a role. Results from a stability study indicated that the hydrodynamic diameter of GONPs was stable and unchanging at the lower range of IS (10(-3) and 10(-2) M) then became unstable when IS ≥ 10(-1.5) M KCl was achieved. Specifically, for IS ≥ 10(-1.5) M KCl, the hydrodynamic diameter became greater and showed a larger size range of particles than at the lower IS range (10(-3) and 10(-2) M). In addition, the EPM of GONPs became less negative over the IS range of 10(-3) and 10(-2) M KCl. Furthermore, GONPs were found to be increasingly mobile for IS ≤ 10(-2) M KCl. When GONPs were passed through the packed bed column at 10(-2) and 10(-1) M KCl, 5% and 100% of the GONPs were retained in the column, respectively. Finally, mass balances and column dissections revealed that in the first cm of the column 7% and 95% of the GONPs were deposited at 10(-2) and 10(-1) M KCl, respectively, confirming that the transport of GONPs is a function of IS. The fraction of GONPs eluted during the transport experiments provides insight into the contribution of aggregation and reversibly bound fraction of GONPs in saturated porous media.

  20. Allosteric inhibitors of inducible nitric oxide synthase dimerization discovered via combinatorial chemistry

    Science.gov (United States)

    McMillan, Kirk; Adler, Marc; Auld, Douglas S.; Baldwin, John J.; Blasko, Eric; Browne, Leslie J.; Chelsky, Daniel; Davey, David; Dolle, Ronald E.; Eagen, Keith A.; Erickson, Shawn; Feldman, Richard I.; Glaser, Charles B.; Mallari, Cornell; Morrissey, Michael M.; Ohlmeyer, Michael H. J.; Pan, Gonghua; Parkinson, John F.; Phillips, Gary B.; Polokoff, Mark A.; Sigal, Nolan H.; Vergona, Ronald; Whitlow, Marc; Young, Tish A.; Devlin, James J.

    2000-01-01

    Potent and selective inhibitors of inducible nitric oxide synthase (iNOS) (EC 1.14.13.39) were identified in an encoded combinatorial chemical library that blocked human iNOS dimerization, and thereby NO production. In a cell-based iNOS assay (A-172 astrocytoma cells) the inhibitors had low-nanomolar IC50 values and thus were >1,000-fold more potent than the substrate-based direct iNOS inhibitors 1400W and N-methyl-l-arginine. Biochemical studies confirmed that inhibitors caused accumulation of iNOS monomers in mouse macrophage RAW 264.7 cells. High affinity (Kd ≈ 3 nM) of inhibitors for isolated iNOS monomers was confirmed by using a radioligand binding assay. Inhibitors were >1,000-fold selective for iNOS versus endothelial NOS dimerization in a cell-based assay. The crystal structure of inhibitor bound to the monomeric iNOS oxygenase domain revealed inhibitor–heme coordination and substantial perturbation of the substrate binding site and the dimerization interface, indicating that this small molecule acts by allosterically disrupting protein–protein interactions at the dimer interface. These results provide a mechanism-based approach to highly selective iNOS inhibition. Inhibitors were active in vivo, with ED50 values of <2 mg/kg in a rat model of endotoxin-induced systemic iNOS induction. Thus, this class of dimerization inhibitors has broad therapeutic potential in iNOS-mediated pathologies. PMID:10677491

  1. Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents

    NARCIS (Netherlands)

    Mutti, Francesco G.; Orthaber, Andreas; Schrittwieser, Joerg H.; Vries, Johannes G. de; Pietschnig, Rudolf; Kroutil, Wolfgang

    2010-01-01

    An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to enantioenrich

  2. Optimizing the biocatalytic productivity of an engineered sialidase from Trypanosoma rangeli for 3′-sialyllactose production

    DEFF Research Database (Denmark)

    Zeuner, Birgitte; Luo, Jianquan; Nyffenegger, Christian

    2014-01-01

    -use methods were compared to optimize the biocatalytic productivity, i.e. 3′-sialyllactose formation per amount of Tr6 employed: (i) His-tag immobilization on magnetic Cu2+-iminodiacetic acid-functionalized nanoparticles (MNPs), (ii) membrane immobilization, (iii) calcium alginate encapsulation of cross......-linked Tr6, and (iv) Tr6 catalysis in a membrane reactor. Tr6 immobilized on MNPs gave a biocatalytic productivity of 84mg 3′-sialyllactose/mg Tr6 after seven consecutive reaction runs. Calcium-alginate and membrane immobilization were inefficient. Using free Tr6 in a 10kDa membrane reactor produced a 9...

  3. The influence of modified water chemistries on metal oxide films, activity build-up and stress corrosion cracking of structural materials in nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Maekelae, K.; Laitinen, T.; Bojinov, M. [VTT Manufacturing Technology, Espoo (Finland)

    1999-03-01

    The primary coolant oxidises the surfaces of construction materials in nuclear power plants. The properties of the oxide films influence significantly the extent of incorporation of actuated corrosion products into the primary circuit surfaces, which may cause additional occupational doses for the maintenance personnel. The physical and chemical properties of the oxide films play also an important role in different forms of corrosion observed in power plants. This report gives a short overview of the factors influencing activity build-up and corrosion phenomena in nuclear power plants. Furthermore, the most recent modifications in the water chemistry to decrease these risks are discussed. A special focus is put on zinc water chemistry, and a preliminary discussion on the mechanism via which zinc influences activity build-up is presented. Even though the exact mechanisms by which zinc acts are not yet known, it is assumed that Zn may block the diffusion paths within the oxide film. This reduces ion transport through the oxide films leading to a reduced rate of oxide growth. Simultaneously the number of available adsorption sites for {sup 60}Co is also reduced. The current models for stress corrosion cracking assume that the anodic and the respective cathodic reactions contributing to crack growth occur partly on or in the oxide films. The rates of these reactions may control the crack propagation rate and therefore, the properties of the oxide films play a crucial role in determining the susceptibility of the material to stress corrosion cracking. Finally, attention is paid also on the novel techniques which can be used to mitigate the susceptibility of construction materials to stress corrosion cracking. (orig.) 127 refs.

  4. Electrochemical behavior of biocatalytical composite based on heme-proteins, didodecyldimethylammonium bromide and room-temperature ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Xu Yanxia, E-mail: xuyanxiatv@yahoo.com.cn [Department of Chemistry and Environmental Engineering, Wuhan Bioengineering Institute, Wuhan 430415 (China); College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 100080 (China); Hu Chengguo [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 100080 (China); Hu Shengshui, E-mail: sshu@whu.edu.cn [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 100080 (China)

    2010-03-17

    A novel biocompatible composite film based on a water-insoluble surfactant, didodecyldimethylammonium bromide (DDAB), and a hydrophobic room-temperature ionic liquid (RTIL), 1-hexyl-3-methyl-imidazolium hexafluorophosphate (HIMIMPF{sub 6}), for the immobilization of biocatalytical proteins was reported. Differential scanning calorimetry (DSC) showed that the DDAB-HIMIMPF{sub 6} composite film has higher thermal stability than the DDAB film alone. SEM images indicated that different microstructures existed between the DDAB film and the composite film, indicating the interaction between DDAB and RTILs. This composite can be used as the immobilization matrix of proteins and other biomacromolecules. Heme-proteins, including hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP), were used as model proteins for studying the electrochemical behaviors of the resulting biocatalytical composite films. In the case of Hb, a pair of well-defined quasi-reversible redox peaks was obtained when the composite film containing Hb was modified on a glassy carbon electrode. The formal potential (E{sup o}'), the surface coverage ({Gamma}{sup *}) and the electron transfer rate constant (k{sub s}) were calculated as -0.308 V, 1.32 x 10{sup -11} mol cm{sup -2} and 11.642 s{sup -1}, respectively. While, these parameters for Hb on DDAB films alone were -0.309 V, 7.20 x 10{sup -12} mol cm{sup -2} and 2.748 s{sup -1}, respectively. Therefore, the composite are more suitable for the direct electron transfer between Hb than DDAB alone. The native conformation and bioactivity of Hb adsorbed on the composite film was proved to be maintained, reflected by the unchanged ultraviolet-visible (UV-vis) as well as the catalytic activity toward hydrogen peroxide (H{sub 2}O{sub 2}) and nitric oxide (NO) compared with the free Hb molecules. Furthermore, Hb on the composite film are more sensitive for the detection of hydrogen peroxide (H{sub 2}O{sub 2}) and nitric oxide (NO) than that on

  5. Introduction to Homogenous Catalysis with Ruthenium-Catalyzed Oxidation of Alcohols: An Experiment for Undergraduate Advanced Inorganic Chemistry Students

    Science.gov (United States)

    Miecznikowski, John R.; Caradonna, John P.; Foley, Kathleen M.; Kwiecien, Daniel J.; Lisi, George P.; Martinez, Anthony M.

    2011-01-01

    A three-week laboratory experiment, which introduces students in an advanced inorganic chemistry course to air-sensitive chemistry and catalysis, is described. During the first week, the students synthesize RuCl[subscript 2](PPh[subscript 3])[subscript 3]. During the second and third weeks, the students characterize the formed coordination…

  6. Biocatalytic Synthesis of Chiral Alcohols and Amino Acids for Development of Pharmaceuticals

    Directory of Open Access Journals (Sweden)

    Ramesh N. Patel

    2013-10-01

    Full Text Available Chirality is a key factor in the safety and efficacy of many drug products and thus the production of single enantiomers of drug intermediates and drugs has become increasingly important in the pharmaceutical industry. There has been an increasing awareness of the enormous potential of microorganisms and enzymes derived there from for the transformation of synthetic chemicals with high chemo-, regio- and enatioselectivities. In this article, biocatalytic processes are described for the synthesis of chiral alcohols and unntural aminoacids for pharmaceuticals.

  7. Towards biochemical filters with a sigmoidal response to pH changes: buffered biocatalytic signal transduction.

    Science.gov (United States)

    Pita, Marcos; Privman, Vladimir; Arugula, Mary A; Melnikov, Dmitriy; Bocharova, Vera; Katz, Evgeny

    2011-03-14

    We realize a biochemical filtering process by introducing a buffer in a biocatalytic signal-transduction logic system based on the function of an enzyme, esterase. The input, ethyl butyrate, is converted into butyric acid--the output signal, which in turn is measured by the drop in the pH value. The developed approach offers a versatile "network element" for increasing the complexity of biochemical information processing systems. Evaluation of an optimal regime for quality filtering is accomplished in the framework of a kinetic rate-equation model.

  8. Towards biochemical filters with a sigmoidal response to pH changes: buffered biocatalytic signal transduction

    Science.gov (United States)

    Pita, Marcos; Privman, Vladimir; Arugula, Mary A.; Melnikov, Dmitriy; Bocharova, Vera; Katz, Evgeny

    We realize a biochemical filtering process by introducing a buffer in a biocatalytic signal-transduction logic system based on the function of an enzyme, esterase. The input, ethyl butyrate, is converted into butyric acid-the output signal, which in turn is measured by the drop in the pH value. The developed approach offers a versatile "network element" for increasing the complexity of biochemical information processing systems. Evaluation of an optimal regime for quality filtering is accomplished in the framework of a kinetic rate-equation model.

  9. Evaluation of new oxidation methods for the measurement of bilirubin on the aeroset clinical chemistry analyzer and comparison with methods on the Hitachi 717.

    Science.gov (United States)

    Sturm, Ernhard; Albrecht-Groos, Ragnhild; Seyfarth, Michael

    2002-01-01

    We evaluated analytical and performance quality of the new oxidation methods for direct and total bilirubin on the Abbott Aeroset clinical chemistry analyzer. Within-day imprecisions for Abbott Aeroset assays ranged from 0.7 to 2.9% and between-day imprecisions from 2.1 to 7.3%. Inaccuracies as compared with the control "target values" for the Jendrassik-Gróf method showed deviations of -18.2 to +4.2%. Limits of detection were determined and showed very low values of 300 micromol/l. A method comparison for 100 patient samples with established Jendrassik-Gróf and DPD methods on the Roche Hitachi 717 showed good linearities between the investigated methods (r > or = 0.995). Due to slopes that ranged from 0.829 to 0.950, reference ranges for the oxidation methods differ slightly from those of established Roche Jendrassik-Gróf methods, but results can be adapted by the introduction of converting factors. In conclusion, the oxidation bilirubin assays revealed convincing analytical and performance qualities for medical needs that were similar or even better than for established methods. Application of the oxidation methods on the Aeroset clinical chemistry analyzer also improves laboratory efficiency by increasing throughput, speed of obtaining results and lowered sample and reagent volumes compared to established methods.

  10. Tyramine-based enzymatic conjugate repeats for ultrasensitive immunoassay accompanying tyramine signal amplification with enzymatic biocatalytic precipitation.

    Science.gov (United States)

    Hou, Li; Tang, Yun; Xu, Mingdi; Gao, Zhuangqiang; Tang, Dianping

    2014-08-19

    A new impedimetric immunoassay protocol based on enzyme-triggered formation of tyramine-enzyme repeats on gold nanoparticle (AuNP) was designed for highly sensitive detection of carcinoembryonic antigen (CEA, as a model) by virtue of utilizing enzymatic biocatalytic precipitation toward 4-chloro-1-naphthol (4-CN) on anti-CEA antibody (Ab1)-modified immunosensor. Initially, AuNP was functionalized with horseradish peroxidase and detection antibody (HRP-AuNP-Ab2), and then HRP-tyramine conjugate was utilized for the formation of tyramine-HRP repeats through the triggering of the immobilized HRP on the AuNP with the aid of H2O2. In the presence of target CEA, the carried HRP-tyramine repeats accompanying the sandwiched immunocomplex catalyzed the 4-CN oxidation to produce an insoluble precipitation on the immunosensor, thus causing a local alteration of the conductivity. Three signal-transduction tags including HRP-Ab2, HRP-AuNP-Ab2, and HRP-AuNP-Ab2 with HRP-tyramine repeats were employed for target CEA evaluation, and improved analytical properties were achieved by HRP-AuNP-Ab2 with HRP-tyramine repeats. Using the unique signal-transduction tag, the analytical performance of the impedimetric immunoassay was studied in detail. Under the optimal conditions, the impedimetric immunosensor displayed a wide dynamic working range of between 0.5 pg mL(-1) and 40 ng mL(-1) with a detection limit (LOD) of 0.38 pg mL(-1) relative to target CEA. The coefficients of variation (CVs) were ≤9.3% and 13.3% for the intra-assay and interassay, respectively. The levels of CEA in eight clinical serum specimens were measured by using the developed impedimetric immunosensor. The obtained results correlated well with those from the electrochemiluminescent (ECL)-based immunoassay with a correlation coefficient of 0.998.

  11. Oxidative capacity and radical chemistry in the polluted atmosphere of Hong Kong and Pearl River Delta region: analysis of a severe photochemical smog episode

    Science.gov (United States)

    Xue, Likun; Gu, Rongrong; Wang, Tao; Wang, Xinfeng; Saunders, Sandra; Blake, Donald; Louie, Peter K. K.; Luk, Connie W. Y.; Simpson, Isobel; Xu, Zheng; Wang, Zhe; Gao, Yuan; Lee, Shuncheng; Mellouki, Abdelwahid; Wang, Wenxing

    2016-08-01

    We analyze a photochemical smog episode to understand the oxidative capacity and radical chemistry of the polluted atmosphere in Hong Kong and the Pearl River Delta (PRD) region. A photochemical box model based on the Master Chemical Mechanism (MCM v3.2) is constrained by an intensive set of field observations to elucidate the budgets of ROx (ROx = OH+HO2+RO2) and NO3 radicals. Highly abundant radical precursors (i.e. O3, HONO and carbonyls), nitrogen oxides (NOx) and volatile organic compounds (VOCs) facilitate strong production and efficient recycling of ROx radicals. The OH reactivity is dominated by oxygenated VOCs (OVOCs), followed by aromatics, alkenes and alkanes. Photolysis of OVOCs (except for formaldehyde) is the dominant primary source of ROx with average daytime contributions of 34-47 %. HONO photolysis is the largest contributor to OH and the second-most significant source (19-22 %) of ROx. Other considerable ROx sources include O3 photolysis (11-20 %), formaldehyde photolysis (10-16 %), and ozonolysis reactions of unsaturated VOCs (3.9-6.2 %). In one case when solar irradiation was attenuated, possibly by the high aerosol loadings, NO3 became an important oxidant and the NO3-initiated VOC oxidation presented another significant ROx source (6.2 %) even during daytime. This study suggests the possible impacts of daytime NO3 chemistry in the polluted atmospheres under conditions with the co-existence of abundant O3, NO2, VOCs and aerosols, and also provides new insights into the radical chemistry that essentially drives the formation of photochemical smog in the high-NOx environment of Hong Kong and the PRD region.

  12. HOx radical chemistry in oxidation flow reactors with low-pressure mercury lamps systematically examined by modeling

    Science.gov (United States)

    Peng, Z.; Day, D. A.; Stark, H.; Li, R.; Lee-Taylor, J.; Palm, B. B.; Brune, W. H.; Jimenez, J. L.

    2015-11-01

    Oxidation flow reactors (OFRs) using OH produced from low-pressure Hg lamps at 254 nm (OFR254) or both 185 and 254 nm (OFR185) are commonly used in atmospheric chemistry and other fields. OFR254 requires the addition of externally formed O3 since OH is formed from O3 photolysis, while OFR185 does not since O2 can be photolyzed to produce O3, and OH can also be formed from H2O photolysis. In this study, we use a plug-flow kinetic model to investigate OFR properties under a very wide range of conditions applicable to both field and laboratory studies. We show that the radical chemistry in OFRs can be characterized as a function of UV light intensity, H2O concentration, and total external OH reactivity (OHRext, e.g., from volatile organic compounds (VOCs), NOx, and SO2). OH exposure is decreased by added external OH reactivity. OFR185 is especially sensitive to this effect at low UV intensity due to low primary OH production. OFR254 can be more resilient against OH suppression at high injected O3 (e.g., 70 ppm), as a larger primary OH source from O3, as well as enhanced recycling of HO2 to OH, make external perturbations to the radical chemistry less significant. However if the external OH reactivity in OFR254 is much larger than OH reactivity from injected O3, OH suppression can reach 2 orders of magnitude. For a typical input of 7 ppm O3 (OHRO3 = 10 s-1), 10-fold OH suppression is observed at OHRext ~ 100 s-1, which is similar or lower than used in many laboratory studies. The range of modeled OH suppression for literature experiments is consistent with the measured values except for those with isoprene. The finding on OH suppression may have important implications for the interpretation of past laboratory studies, as applying OHexp measurements acquired under different conditions could lead to over a 1-order-of-magnitude error in the estimated OHexp. The uncertainties of key model outputs due to uncertainty in all rate constants and absorption cross-sections in the

  13. Surface Chemistry and Interface Evolution during the Atomic Layer Deposition of High-k Metal Oxides on InAs(100) and GaAs(100) Surfaces

    Science.gov (United States)

    Henegar, Alex J.

    Device scaling has been key for creating faster and more powerful electronic devices. Integral circuit components like the metal-oxide semiconductor field-effect transistor (MOSFET) now rely on material deposition techniques, like atomic layer deposition (ALD), that possess atomic-scale thickness precision. At the heart of the archetypal MOSFET is a SiO2/Si interface which can be formed to near perfection. However when the thickness of the SiO 2 layer is shrunk down to a few nanometers several complications arise like unacceptably high leakage current and power consumption. Replacing Si with III-V semiconductors and SiO2 with high-k dielectric materials is appealing but comes with its own set of challenges. While SiO2 is practically defect-free, the native oxides of III-Vs are poor dielectrics. In this dissertation, the surface chemistry and interface evolution during the ALD of high-k metal oxides on Si(100), GaAs(100) and InAs(100) was studied. In particular, the surface chemistry and crystallization of TiO2 films grown on Si(100) was investigated using transmission Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Large, stable, and highly reactive anatase TiO2 grains were found to form during a post-deposition heat treatment after the ALD at 100 °C. The remainder of this work was focused on the evolution of the interfacial oxides during the deposition of TiO2 and Al2O3 on InAs(100) and GaAs(100) and during the deposition of Ta2O 5 on InAs(100). In summary the ALD precursor type, deposited film, and substrate had an influence in the evolution of the native oxides. Alkyl amine precursors fared better at removing the native oxides but the deposited films (TiO2 and Ta2O5) were susceptible to significant native oxide diffusion. The alkyl precursor used for the growth of Al 2O3 was relatively ineffective at removing the oxides but was

  14. Effects of heavy-ion irradiation on the grain boundary chemistry of an oxide-dispersion strengthened Fe-12 wt.% Cr alloy

    Science.gov (United States)

    Marquis, Emmanuelle A.; Lozano-Perez, Sergio; Castro, Vanessa de

    2011-10-01

    Understanding the behaviour of oxide-dispersion strengthened (ODS) ferritic martensitic steels under irradiation is of prime importance in the design of future fusion reactors. Although changes in grain boundary chemistry during irradiation can significantly affect fracture strength, little is known on the behaviour of grain boundaries in ODS steels. Here, the effect of heavy-ion implantation at 500 °C on grain boundary chemistry in a model ODS Fe-12 wt.% Cr alloy was investigated using atom-probe tomography (APT) and analytical scanning-transmission electron microscopy ((S)TEM) techniques. While chromium and carbon segregation at grain boundaries is found in annealed alloys before irradiation, the three-dimensional APT reconstructions and TEM observations after irradiation reveal a complex distribution of Cr segregation and depletion at grain boundaries of varying character.

  15. Oxygen Point Defect Chemistry in Ruddlesden-Popper Oxides (La1-xSrx)2MO4±δ (M = Co, Ni, Cu).

    Science.gov (United States)

    Xie, Wei; Lee, Yueh-Lin; Shao-Horn, Yang; Morgan, Dane

    2016-05-19

    Stability of oxygen point defects in Ruddlesden-Popper oxides (La1-xSrx)2MO4±δ (M = Co, Ni, Cu) is studied with density functional theory calculations to determine their stable sites, charge states, and energetics as functions of Sr content (x), transition metal (M), and defect concentration (δ). We demonstrate that the dominant O point defects can change between oxide interstitials, peroxide interstitials, and vacancies. In general, increasing x and atomic number of M stabilizes peroxide over oxide interstitials as well as vacancies over both peroxide and oxide interstitials; increasing δ destabilizes both oxide interstitials and vacancies but barely affects peroxide interstitials. We also demonstrate that the O 2p-band center is a powerful descriptor for these materials and correlates linearly with the formation energy of all defects. The trends of formation energy versus x, M, and δ and the correlation with O 2p-band center are explained in terms of oxidation chemistry and electronic structure.

  16. Recent advances on halohydrin dehalogenases-from enzyme identification to novel biocatalytic applications.

    Science.gov (United States)

    Schallmey, Anett; Schallmey, Marcus

    2016-09-01

    Halohydrin dehalogenases are industrially relevant enzymes that catalyze the reversible dehalogenation of vicinal haloalcohols with formation of the corresponding epoxides. In the reverse reaction, also other negatively charged nucleophiles such as azide, cyanide, or nitrite are accepted besides halides to open the epoxide ring. Thus, novel C-N, C-C, or C-O bonds can be formed by halohydrin dehalogenases, which makes them attractive biocatalysts for the production of various β-substituted alcohols. Despite the fact that only five individual halohydrin dehalogenase enzyme sequences have been known until recently enabling their heterologous production, a large number of different biocatalytic applications have been reported using these enzymes. The recent characterization of specific sequence motifs has facilitated the identification of novel halohydrin dehalogenase sequences available in public databases and has largely increased the number of recombinantly available enzymes. These will help to extend the biocatalytic repertoire of this enzyme family and to foster novel biotechnological applications and developments in the future. This review gives a general overview on the halohydrin dehalogenase enzyme family and their biochemical properties and further focuses on recent developments in halohydrin dehalogenase biocatalysis and protein engineering.

  17. From waste to value - direct utilization of limonene from orange peel in a biocatalytic cascade reaction towards chiral carvolactone

    NARCIS (Netherlands)

    Oberleitner, N.; Ressmann, A. K.; Bica, K.; Gaertner, P.; Fraaije, M. W.; Bornscheuer, U. T.; Rudroff, F.; Mihovilovic, M. D.

    2017-01-01

    In this proof of concept study we demonstrate direct utilization of limonene containing waste product orange peel as starting material for a biocatalytic cascade reaction. The product of this cascade is chiral carvolactone, a promising building block for thermoplastic polymers. Four different concep

  18. Atmospheric chemistry of 3-pentanol: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOX.

    Science.gov (United States)

    Hurley, M D; Wallington, T J; Bjarrum, M; Javadi, M S; Nielsen, O J

    2008-09-04

    Smog chamber/FTIR techniques were used to study the atmospheric chemistry of 3-pentanol and determine rate constants of k(Cl+3-pentanol) = (2.03 +/- 0.23) x 10 (-10) and k(OH+3-pentanol) = (1.32 +/- 0.15) x 10 (-11) cm (3) molecule (-1) s (-1) in 700 Torr of N 2/O 2 diluent at 296 +/- 2 K. The primary products of the Cl atom initiated oxidation of 3-pentanol in the absence of NO were (with molar yields) 3-pentanone (26 +/- 2%), propionaldehyde (12 +/- 2%), acetaldehyde (13 +/- 2%) and formaldehyde (2 +/- 1%). The primary products of the Cl atom initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (51 +/- 4%), propionaldehyde (39 +/- 2%), acetaldehyde (44 +/- 4%) and formaldehyde (4 +/- 1%). The primary products of the OH radical initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (58 +/- 3%), propionaldehyde (28 +/- 2%), and acetaldehyde (37 +/- 2%). In all cases the product yields were independent of oxygen concentration over the partial pressure range 10-700 Torr. The reactions of Cl atoms and OH radicals with 3-pentanol proceed 26 +/- 2 and 58 +/- 3%, respectively, via attack on the 3-position to give an alpha-hydroxyalkyl radical, which reacts with O 2 to give 3-pentanone. The results are discussed with respect to the literature data and atmospheric chemistry of 3-pentanol.

  19. Chemistry of α-pinene and naphthalene oxidation products generated in a Potential Aerosol Mass (PAM chamber as measured by acetate chemical ionization mass spectrometry

    Directory of Open Access Journals (Sweden)

    P. S. Chhabra

    2014-07-01

    Full Text Available Recent developments in high resolution, time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS have made possible the direct detection of atmospheric organic compounds in real-time with high sensitivity and with little or no fragmentation, including low volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, for the first time, we examine gas-phase O3 and OH oxidation products of α-pinene and naphthalene formed in the PAM flow reactor with an HR-ToF-CIMS using acetate reagent ion chemistry. Integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec cm−3 s, corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition and fragmentation (carbon loss as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. We present a method that estimates vapor pressures of organic molecules using the measured O/C ratio, H/C ratio, and carbon number for each compound detected by the CIMS. The predicted condensed-phase SOA average acid yields and O/C and H/C ratios agree within uncertainties with previous AMS measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.

  20. Chemistry of α-pinene and naphthalene oxidation products generated in a Potential Aerosol Mass (PAM) chamber as measured by acetate chemical ionization mass spectrometry

    Science.gov (United States)

    Chhabra, P. S.; Lambe, A. T.; Canagaratna, M. R.; Stark, H.; Jayne, J. T.; Onasch, T. B.; Davidovits, P.; Kimmel, J. R.; Worsnop, D. R.

    2014-07-01

    Recent developments in high resolution, time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made possible the direct detection of atmospheric organic compounds in real-time with high sensitivity and with little or no fragmentation, including low volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, for the first time, we examine gas-phase O3 and OH oxidation products of α-pinene and naphthalene formed in the PAM flow reactor with an HR-ToF-CIMS using acetate reagent ion chemistry. Integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec cm-3 s, corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. We present a method that estimates vapor pressures of organic molecules using the measured O/C ratio, H/C ratio, and carbon number for each compound detected by the CIMS. The predicted condensed-phase SOA average acid yields and O/C and H/C ratios agree within uncertainties with previous AMS measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.

  1. Understanding the Atomic-Level Chemistry and Structure of Oxide Deposits on Fuel Rods in Light Water Nuclear Reactors Using First Principles Methods

    Science.gov (United States)

    Rak, Zs.; O'Brien, C. J.; Brenner, D. W.; Andersson, D. A.; Stanek, C. R.

    2016-09-01

    The results of recent studies are discussed in which first principles calculations at the atomic level have been used to expand the thermodynamic database for science-based predictive modeling of the chemistry, composition and structure of unwanted oxides that deposit on the fuel rods in pressurized light water nuclear reactors. Issues discussed include the origin of the particles that make up deposits, the structure and properties of the deposits, and the forms by which boron uptake into the deposits can occur. These first principles approaches have implications for other research areas, such as hydrothermal synthesis and the stability and corrosion resistance of other materials under other extreme conditions.

  2. TOPICAL REVIEW Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

    Directory of Open Access Journals (Sweden)

    Tadashi C Ozawa et al

    2008-01-01

    Full Text Available Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.

  3. Nitrogen oxide chemistry in an urban plume: investigation of the chemistry of peroxy and multifunctional organic nitrates with a Lagrangian model

    Directory of Open Access Journals (Sweden)

    I. M. Pérez

    2009-12-01

    Full Text Available Air quality in the outflow from urban centers affects millions of people, as well as, natural and managed ecosystems downwind. In locations where there are large sources of biogenic VOCs downwind of urban centers, the outflow is characterized by a high VOC reactivity due to biogenic emissions and low NOx. However most field and chamber studies have focused on limiting cases of high NOx or of near zero NOx. Recent measurements of a wide suite of VOCs, O3 and meteorological parameters at several locations within the Sacramento urban plume have provided a detailed benchmark for testing our understanding of chemistry in a plume transitioning from high NOx to low NOx and high VOC reactivity. As an additional simplification, the strong mountain valley circulation in the region makes this urban plume a physical realization of a nearly idealized Lagrangian plume. Here, we describe a model of this plume. We use a Lagrangian model representing chemistry based on the Master Chemical Mechanism (MCM v3.1 along with mixing and deposition. We discuss the effects of entrainment of background air, the branching ratio for the production of isoprene nitrates and the effects of soil NOx emissions on the composition of the evolving plume. The model predicts that after 2–3 h of chemical processing only 45% of the peroxynitrates (ΣPNs are PAN and that most (69% RONO2 are secondary alkyl nitrate products of the reaction of OH with RONO2. We find the model is more consistent with the observations if: a the yield of ΣPNs from large and multi-functional aldehydes is close to zero; and b the reaction between OH and RONO2 produces multifunctional nitrates as opposed to either HNO3 or NO2 as is typical in most currently adopted reaction mechanisms. Model results also show that adding NOx emissions throughout the transect increases

  4. Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag(+) /X2 (X=Cl, Br, I) System.

    Science.gov (United States)

    Malinowski, Przemysław J; Himmel, Daniel; Krossing, Ingo

    2016-08-01

    The synergistic Ag(+) /X2 system (X=Cl, Br, I) is a very strong, but ill-defined oxidant-more powerful than X2 or Ag(+) alone. Intermediates for its action may include [Agm (X2 )n ](m+) complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: (A)Ag-I2 -Ag(A), [Ag2 (I2 )4 ](2+) (A(-) )2 and [Ag2 (I2 )6 ](2+) (A(-) )2 ⋅(I2 )x≈0.65 form by reaction of Ag(A) (A=Al(OR(F) )4 ; R(F) =C(CF3 )3 ) with diiodine (single crystal/powder XRD, Raman spectra and quantum-mechanical calculations). The molecular (A)Ag-I2 -Ag(A) is ideally set up to act as a 2 e(-) oxidant with stoichiometric formation of 2 AgI and 2 A(-) . Preliminary reactivity tests proved this (A)Ag-I2 -Ag(A) starting material to oxidize n-C5 H12 , C3 H8 , CH2 Cl2 , P4 or S8 at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF6 (M=4d metals). This suggests that (A)Ag-I2 -Ag(A) will serve as an easily in bulk accessible, well-defined, and very potent oxidant with multiple applications.

  5. Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhen-Bei, E-mail: 1021453457@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Wu, Jing-Jing, E-mail: 957522275@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Su, Yu, E-mail: 819388710@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Zhou, Jin, E-mail: zhoujin_ah@163.com [Department of Materials and Chemical Engineering, Chizhou University, Muzhi Rd. 199, Chizhou, Anhui 247000 (China); Gao, Yong, E-mail: 154682180@qq.com [School of Chemistry and Environmental Engineering, Jiangsu University of Technology, Changzhou 213001 (China); Yu, Hai-Yin, E-mail: yhy456@mail.ahnu.edu.cn [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Gu, Jia-Shan, E-mail: jiashanG@mail.ahnu.edu.cn [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China)

    2015-03-30

    Graphical abstract: - Highlights: • Clickable membrane prepared by photo bromination and S{sub N}2 nucleophilic substitution. • Azide graphene oxide prepared by ring-opening reaction. • Alkyne graphene oxide was prepared via esterification reaction. • Layer-by-layer assembly of graphene oxide on membrane by click chemistry. • Antibacterial and antifouling characteristics were enhanced greatly. - Abstract: Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane. Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface.

  6. Immobilized biocatalytic process development and potential application in membrane separation: a review.

    Science.gov (United States)

    Chakraborty, Sudip; Rusli, Handajaya; Nath, Arijit; Sikder, Jaya; Bhattacharjee, Chiranjib; Curcio, Stefano; Drioli, Enrico

    2016-01-01

    Biocatalytic membrane reactors have been widely used in different industries including food, fine chemicals, biological, biomedical, pharmaceuticals, environmental treatment and so on. This article gives an overview of the different immobilized enzymatic processes and their advantages over the conventional chemical catalysts. The application of a membrane bioreactor (MBR) reduces the energy consumption, and system size, in line with process intensification. The performances of MBR are considerably influenced by substrate concentration, immobilized matrix material, types of immobilization and the type of reactor. Advantages of a membrane associated bioreactor over a free-enzyme biochemical reaction, and a packed bed reactor are, large surface area of immobilization matrix, reuse of enzymes, better product recovery along with heterogeneous reactions, and continuous operation of the reactor. The present research work highlights immobilization techniques, reactor setup, enzyme stability under immobilized conditions, the hydrodynamics of MBR, and its application, particularly, in the field of sugar, starch, drinks, milk, pharmaceutical industries and energy generation.

  7. Application of Enzyme Coupling Reactions to Shift Thermodynamically Limited Biocatalytic Reactions

    DEFF Research Database (Denmark)

    Abu, Rohana; Woodley, John M.

    2015-01-01

    shift the equilibrium of otherwise thermodynamically unfavourable reactions to give a higher conversion of the target product. By coupling an energetically unfavourable reaction with a more favourable one, the multi-enzyme cascade mimics the approach taken in nature in metabolic pathways. Nevertheless......, it can be challenging to combine several engineered enzymes in vitro for the conversion of non-natural substrates. In this mini-review we focus on enzyme coupling reactions as a tool to alleviate thermodynamic constraints in synthetically useful biocatalytic reactions. The implications of thermodynamic...... parameters such as the equilibrium constant on the multienzyme cascades and the conventional methods of equilibrium shifting are also discussed in addition to methods used to estimate such values....

  8. On the Defect Chemistry, Electrical Properties and Electrochemical Performances As Solid Oxide Fuel Cell Cathode Materials of New La-(Sr/Vac)-Co-Ti-O Perovskites

    DEFF Research Database (Denmark)

    García-Alvarado, Flaviano; Gómez-Pérez, Alejandro; Pérez-Flores, Juan Carlos

    2015-01-01

    Perovskite-type oxides are well known materials that have been proposed as electrodes and electrolytes for solid oxide fuel cells (SOFCs). The structure, which is referred to the ABO3 stoichiometry, can accommodate many different transition metal ions in the B-site; its electronic conductivity...... materials with valuable properties for SOFCs. We have analysed the effect of La3+ by Sr2+ substitution and vacancies creation in several double perovskites, La2MTiO6 (M = Co, Ni, Cu). Defect chemistry and electrical behavior have been investigated in order to unveil the nature of charge carriers....... Electrochemical performances have been assessed through polarization resistance measurements. In this communication we present the results regarding La2SrTiO6 perovskites. La/Sr substitution in La2-xSrxCoTiO6-δ produces Co2+ to Co3+ oxidation while vacancies in La2-xCoTiO6-δ yield Co2+ oxidation for low A...

  9. Single-Site VO x Moieties Generated on Silica by Surface Organometallic Chemistry: A Way To Enhance the Catalytic Activity in the Oxidative Dehydrogenation of Propane

    KAUST Repository

    Barman, Samir

    2016-07-26

    We report here an accurate surface organometallic chemistry (SOMC) approach to propane oxidative dehydrogenation (ODH) using a μ2-oxo-bridged, bimetallic [V2O4(acac)2] (1) (acac = acetylacetonate anion) complex as a precursor. The identity and the nuclearity of the product of grafting and of the subsequent oxidative treatment have been systematically studied by means of FT-IR, Raman, solid-state (SS) NMR, UV-vis DRS, EPR and EXAFS spectroscopies. We show that the grafting of 1 on the silica surface under a rigorous SOMC protocol and the subsequent oxidative thermal treatment lead exclusively to well-defined and isolated monovanadate species. The resulting material has been tested for the oxidative dehydrogenation of propane in a moderate temperature range (400-525 °C) and compared with that of silica-supported vanadium catalysts prepared by the standard impregnation technique. The experimental results show that the catalytic activity in propane ODH is strongly upgraded by the degree of isolation of the VOx species that can be achieved by employing the SOMC protocol. © 2016 American Chemical Society.

  10. Calculated ionisation potentials to determine the oxidation of vanillin precursors by lignin peroxidase.

    NARCIS (Netherlands)

    ten Have, R.; Rietjens, I.M.C.M.; Hartmans, S.; Swarts, H.J.; Field, J.A.

    1998-01-01

    In view of the biocatalytic production of vanillin, this research focused on the lignin peroxidase (LiP) catalysed oxidation of naturally occurring phenolic derivatives: O-methyl ethers, O-acetyl esters, and O-glucosyl ethers. The ionisation potential (IP) of a series of model compounds was calculat

  11. Conceptual chemistry approach towards the support effect in supported vanadium oxides : Valence bond calculations on the ionicity of vanadium catalysts

    NARCIS (Netherlands)

    Fievez, Tim; De Proft, Frank; Geerlings, Paul; Weckhuysen, Bert M.; Havenith, Remco W. A.

    2011-01-01

    The concept of bond ionicity, obtained via a valence bond analysis, is invoked in the interpretation of the catalytic activity of supported vanadium oxides, in analogy with previous work conducted within the framework of conceptual DFT. For a set of model clusters representing the vanadium oxide sup

  12. Mechanistic chemistry of oxidation of balsalazide with acidic chloramine-T and bromamine-T: A comparative spectrophotometric kinetic study

    Indian Academy of Sciences (India)

    Puttaswamy; S Dakshayani

    2014-11-01

    Balsalazide (BSZ) belongs to a class of non-steroidal anti-inflammatory drugs. Kinetics and mechanism of oxidation of BSZ with sodium N-halo-p-toluenesulfonamides viz., chloramine-T(CAT) and bromamine-T(BAT) in HClO4 medium have been spectrophotometrically investigated (max =357nm) at 303 K. Under comparable experimental conditions, reactions with both the oxidants follow a first-order dependence of rate on [BSZ] and fractional-order dependence on each [oxidant] and [HClO4]. Activation parameters and reaction constants have been computed. 2-hydroxy-5-nitroso-benzoic acid and 3-(4-nitroso-benzoylamino)-propionic acid are identified as the oxidation products of BSZ with both CAT and BAT. The rate of oxidation of BSZ is about five-fold faster with BAT than with CAT. Plausible mechanism and related rate law have been deduced for the observed kinetics.

  13. Life Cycle Assessment as a tool for green Chemistry: Application to different advanced oxidation processes for wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Munoz Ortiz, I.; Domenech Antunez, X.; Malato Rodriguez, S.

    2006-07-01

    The development of chemistry during the twentieth century has changed our lives. In fact, chemistry and chemicals surrounds US in our daily activities, due to the huge supply of products aimed at improving our quality of life. Chemistry has resulted in the medical revolution of the past century, in which drugs as antibiotics have been used to cure diseases that affected mankind for centuries. These advances have led to the rise in the average life expectancy from 47 in 1900, to 75 years in the 1990s (Breslow 1997). On the other hand, the world's food supply has seen an explosive expansion because of the development of pesticides as well as fertilisers that protect crops and improve their productivity. Other common chemicals are those related to hygiene, such as soaps, detergents, disinfectants, toothpaste, etc. Therefore, there is practically no facet in material life-transportation communication, clothing, shelter, office- in which chemistry does not play an important role, either to supply consumer products or to improve services addressed to society in general (Domenech 2005). In spite of all these clear benefits, the chemical industry is often viewed by the general public as causing more harm than good (Lancaster 2002). A major reason for this is that the industry is perceived as being polluting and causing significant environmental damage. Indeed, the manufacture, use and disposal of chemicals consume large amounts of resources, and originates emissions of pollutants to all environmental compartments, not to mention the numerous accidents and disasters in which the chemical industry has been involved in the recent past. (Author)

  14. Preparation of Biocatalytic Microparticles by Interfacial Self-Assembly of Enzyme-Nanoparticle Conjugates Around a Cross-Linkable Core.

    Science.gov (United States)

    Andler, S M; Wang, L-S; Goddard, J M; Rotello, V M

    2016-01-01

    Rational design of hierarchical interfacial assembly of reusable biocatalytic microparticles is described in this chapter. Specifically, purified enzymes and functionalized nanoparticles are electrostatically assembled at the interface of cross-linked microparticles which are formed through ring opening metathesis polymerization. The diameters of microparticle assemblies average 10μm, and they show enhanced kinetic efficiency as well as improved stability against heat, pH, and solvent denaturation when compared to stabilities of the corresponding native enzymes.

  15. Efficiency Analysis and Mechanism Insight of that Whole-Cell Biocatalytic Production of Melibiose from Raffinose with Saccharomyces cerevisiae.

    Science.gov (United States)

    Zhou, Yingbiao; Zhu, Yueming; Dai, Longhai; Men, Yan; Wu, Jinhai; Zhang, Juankun; Sun, Yuanxia

    2017-01-01

    Melibiose is widely used as a functional carbohydrate. Whole-cell biocatalytic production of melibiose from raffinose could reduce its cost. However, characteristics of strains for whole-cell biocatalysis and mechanism of such process are unclear. We compared three different Saccharomyces cerevisiae strains (liquor, wine, and baker's yeasts) in terms of concentration variations of substrate (raffinose), target product (melibiose), and by-products (fructose and galactose) in whole-cell biocatalysis process. Distinct difference was observed in whole-cell catalytic efficiency among three strains. Furthermore, activities of key enzymes (invertase, α-galactosidase, and fructose transporter) involved in process and expression levels of their coding genes (suc2, mel1, and fsy1) were investigated. Conservation of key genes in S. cerevisiae strains was also evaluated. Results show that whole-cell catalytic efficiency of S. cerevisiae in the raffinose substrate was closely related to activity of key enzymes and expression of their coding genes. Finally, we summarized characteristics of producing strain that offered advantages, as well as contributions of key genes to excellent strains. Furthermore, we presented a dynamic mechanism model to achieve some mechanism insight for this whole-cell biocatalytic process. This pioneering study should contribute to improvement of whole-cell biocatalytic production of melibiose from raffinose.

  16. Use of a Ceramic Membrane to Improve the Performance of Two-Separate-Phase Biocatalytic Membrane Reactor.

    Science.gov (United States)

    Ranieri, Giuseppe; Mazzei, Rosalinda; Wu, Zhentao; Li, Kang; Giorno, Lidietta

    2016-03-14

    Biocatalytic membrane reactors (BMR) combining reaction and separation within the same unit have many advantages over conventional reactor designs. Ceramic membranes are an attractive alternative to polymeric membranes in membrane biotechnology due to their high chemical, thermal and mechanical resistance. Another important use is their potential application in a biphasic membrane system, where support solvent resistance is highly needed. In this work, the preparation of asymmetric ceramic hollow fibre membranes and their use in a two-separate-phase biocatalytic membrane reactor will be described. The asymmetric ceramic hollow fibre membranes were prepared using a combined phase inversion and sintering technique. The prepared fibres were then used as support for lipase covalent immobilization in order to develop a two-separate-phase biocatalytic membrane reactor. A functionalization method was proposed in order to increase the density of the reactive hydroxyl groups on the surface of ceramic membranes, which were then amino-activated and treated with a crosslinker. The performance and the stability of the immobilized lipase were investigated as a function of the amount of the immobilized biocatalytst. Results showed that it is possible to immobilize lipase on a ceramic membrane without altering its catalytic performance (initial residual specific activity 93%), which remains constant after 6 reaction cycles.

  17. Use of a Ceramic Membrane to Improve the Performance of Two-Separate-Phase Biocatalytic Membrane Reactor

    Directory of Open Access Journals (Sweden)

    Giuseppe Ranieri

    2016-03-01

    Full Text Available Biocatalytic membrane reactors (BMR combining reaction and separation within the same unit have many advantages over conventional reactor designs. Ceramic membranes are an attractive alternative to polymeric membranes in membrane biotechnology due to their high chemical, thermal and mechanical resistance. Another important use is their potential application in a biphasic membrane system, where support solvent resistance is highly needed. In this work, the preparation of asymmetric ceramic hollow fibre membranes and their use in a two-separate-phase biocatalytic membrane reactor will be described. The asymmetric ceramic hollow fibre membranes were prepared using a combined phase inversion and sintering technique. The prepared fibres were then used as support for lipase covalent immobilization in order to develop a two-separate-phase biocatalytic membrane reactor. A functionalization method was proposed in order to increase the density of the reactive hydroxyl groups on the surface of ceramic membranes, which were then amino-activated and treated with a crosslinker. The performance and the stability of the immobilized lipase were investigated as a function of the amount of the immobilized biocatalytst. Results showed that it is possible to immobilize lipase on a ceramic membrane without altering its catalytic performance (initial residual specific activity 93%, which remains constant after 6 reaction cycles.

  18. Chemical insights, explicit chemistry, and yields of secondary organic aerosol from OH radical oxidation of methylglyoxal and glyoxal in the aqueous phase

    Directory of Open Access Journals (Sweden)

    Y. B. Lim

    2013-09-01

    Full Text Available Atmospherically abundant, volatile water-soluble organic compounds formed through gas-phase chemistry (e.g., glyoxal (C2, methylglyoxal (C3, and acetic acid have great potential to form secondary organic aerosol (SOA via aqueous chemistry in clouds, fogs, and wet aerosols. This paper (1 provides chemical insights into aqueous-phase OH-radical-initiated reactions leading to SOA formation from methylglyoxal and (2 uses this and a previously published glyoxal mechanism (Lim et al., 2010 to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012. This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010, and is used to simulate the profiles of products and to estimate SOA yields. At cloud-relevant concentrations (~ 10−6 − ~ 10−3 M; Munger et al., 1995 of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass are ~ 120% for glyoxal and ~ 80% for methylglyoxal. During droplet evaporation oligomerization of unreacted methylglyoxal/glyoxal that did not undergo aqueous photooxidation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (~ 10 M, the major oxidation products are oligomers formed via organic radical–radical reactions, and simulated SOA yields (by mass are ~ 90% for both glyoxal and methylglyoxal. Non-radical reactions (e.g., with ammonium could enhance yields.

  19. Chemical insights, explicit chemistry, and yields of secondary organic aerosol from OH radical oxidation of methylglyoxal and glyoxal in the aqueous phase

    Science.gov (United States)

    Lim, Y. B.; Tan, Y.; Turpin, B. J.

    2013-09-01

    Atmospherically abundant, volatile water-soluble organic compounds formed through gas-phase chemistry (e.g., glyoxal (C2), methylglyoxal (C3), and acetic acid) have great potential to form secondary organic aerosol (SOA) via aqueous chemistry in clouds, fogs, and wet aerosols. This paper (1) provides chemical insights into aqueous-phase OH-radical-initiated reactions leading to SOA formation from methylglyoxal and (2) uses this and a previously published glyoxal mechanism (Lim et al., 2010) to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012). This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010), and is used to simulate the profiles of products and to estimate SOA yields. At cloud-relevant concentrations (~ 10-6 - ~ 10-3 M; Munger et al., 1995) of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass) are ~ 120% for glyoxal and ~ 80% for methylglyoxal. During droplet evaporation oligomerization of unreacted methylglyoxal/glyoxal that did not undergo aqueous photooxidation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (~ 10 M), the major oxidation products are oligomers formed via organic radical-radical reactions, and simulated SOA yields (by mass) are ~ 90% for both glyoxal and methylglyoxal. Non-radical reactions (e.g., with ammonium) could enhance yields.

  20. Role of solution chemistry in the retention and release of graphene oxide nanomaterials in uncoated and iron oxide-coated sand

    Science.gov (United States)

    Upon increasing production and use of graphene oxide nanoparticles (GONPs), concerns agitate over their potential impacts and risks to the environment, ecosystem, and human health. An improved understanding of the fate and transport including remobilization of GONPs in the subsur...

  1. Role of solution chemistry on the deposition and release of graphene oxide nanoparticles in uncoated and iron oxide-coated sand

    Science.gov (United States)

    Upon increasing production and use of graphene oxide nanoparticles (GONPs), concerns agitate over their potential impacts and risks to the environment, ecosystem, and human health. An improved understanding of the fate and transport including remobilization of GONPs in the subsur...

  2. Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

    Directory of Open Access Journals (Sweden)

    Abdelhaq Benkaddour

    2013-12-01

    Full Text Available Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC using Polycaprolactone-diol (PCL as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM, Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, and Thermogravimetry analysis (TGA. Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification.

  3. Iron Oxide Surface Chemistry: The Effect of Chemical Structure on Binding in Benzoic Acid and Catechol Derivatives.

    Science.gov (United States)

    Korpany, Katalin V; Majewski, Dorothy D; Chiu, Cindy T; Cross, Shoronia N; Blum, Amy Szuchmacher

    2017-02-18

    Excellent performance of functionalized iron oxide nanoparticles in nanomaterial and biomedical applications often relies on achieving attachment of ligands to the iron oxide surface both in sufficient number and with proper orientation. Towards this end, we determine relationships between ligand chemical structure and surface binding on magnetic iron oxide nanoparticles for a series of related benzoic acid and catechol derivatives. Ligand exchange was used to introduce the model ligands, and the resulting nanoparticles were characterized by FTIR-ATR, transmission electron microscopy (TEM), and nanoparticle solubility behavior. An in-depth analysis of ligand electronic effects and reaction conditions reveals that the nature of ligand binding does not solely depend on the presence of functional groups known to bind to iron oxide nanoparticles. The structure of the resulting ligand-surface complex was primarily influenced by the relative positioning of hydroxyl and carboxylic acid groups within the ligand as well as whether or not HCl(aq) was added to the ligand exchange reaction. Overall, this study will help guide future ligand design and ligand exchange strategies towards realizing truly custom-built iron oxide nanoparticles.

  4. Oxidizing dissolution of spent MOX47 fuel subjected to water radiolysis: Solution chemistry and surface characterization by Raman spectroscopy

    Science.gov (United States)

    Jégou, C.; Caraballo, R.; De Bonfils, J.; Broudic, V.; Peuget, S.; Vercouter, T.; Roudil, D.

    2010-04-01

    The mechanisms of oxidizing dissolution of spent MOX fuel (MIMAS TU2®) subjected to water radiolysis were investigated experimentally by leaching spent MOX47 fuel samples in pure water at 25 °C under different oxidizing conditions (with and without external gamma irradiation); the leached surfaces were characterized by Raman spectroscopy. The highly oxidizing conditions resulting from external gamma irradiation significantly increased the concentration of plutonium (Pu(V)) and uranium (U(VI)) compared with a benchmark experiment (without external irradiation). The oxidation behavior of the plutonium-enriched aggregates differed significantly from that of the UO 2 matrix after several months of leaching in water under gamma irradiation. The plutonium in the aggregates appears to limit fuel oxidation. The only secondary phases formed and identified to date by Raman spectroscopy are uranium peroxides that generally precipitate on the surface of the UO 2 grains. Concerning the behavior of plutonium, solution analysis results appear to be compatible with a conventional explanation based on an equilibrium with a Pu(OH) 4(am) phase. The fission product release - considered as a general indicator of matrix alteration - from MOX47 fuel also increases under external gamma irradiation and a change in the leaching mode is observed. Diffusive leaching was clearly identified, coinciding with the rapid onset of steady-state actinide concentrations in the bulk solution.

  5. Minor components in food oils: a critical review of their roles on lipid oxidation chemistry in bulk oils and emulsions.

    Science.gov (United States)

    Chen, Bingcan; McClements, David Julian; Decker, Eric Andrew

    2011-12-01

    Food oils are primarily composed of triacylglycerols (TAG), but they may also contain a variety of other minor constituents that influence their physical and chemical properties, including diacylglycerols (DAG), monoacylglycerols (MAG), free fatty acids (FFA), phospholipids (PLs), water, and minerals. This article reviews recent research on the impact of these minor components on lipid oxidation in bulk oils and oil-in-water emulsions. In particular, it highlights the origin of these minor components, the influence of oil refining on the type and concentration of minor components present, and potential physicochemical mechanisms by which these minor components impact lipid oxidation in bulk oils and emulsions. This knowledge is crucial for designing food, pharmaceutical, personal care, and other products with improved stability to lipid oxidation.

  6. Solar thermal energy storage via exploitation and rational combination of porous ceramic structures and redox oxides chemistry

    OpenAIRE

    Agrafiotis, Christos; Becker, Andreas; Roeb, Martin; Sattler, Christian

    2015-01-01

    The current state-of-the-art solar heat storage concept in air-operated Solar Tower Power Plants is to store the solar energy provided during on-sun operation as sensible heat in porous solid materials that operate as recuperators during off-sun operation. This storage concept can be rendered from “purely” sensible to “hybrid” sensible/thermochemical one, via coating the chemically inert porous heat exchange modules with oxides of multivalent metals for which their reduction/oxidation reactio...

  7. Measurement and modelling of the defect chemistry and transport properties of ceramic oxide mixed ionic and electronic conductors

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas

    2008-01-01

    The subject of this thesis is ceramic mixed ionic and electronic conductors (MIECs). MIECs have potential uses, such as solid oxygen permeation membranes, as catalysts, and as components in fuel cells. The MIECs examined in this thesis are all oxide ion conducting materials. This thesis describes...

  8. Oxidation of Borneol to Camphor Using Oxone and Catalytic Sodium Chloride: A Green Experiment for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Lang, Patrick T.; Harned, Andrew M.; Wissinger, Jane E.

    2011-01-01

    A new green oxidation procedure was developed for the undergraduate organic teaching laboratories using Oxone and a catalytic quantity of sodium chloride for the conversion of borneol to camphor. This simple 1 h, room temperature reaction afforded high quality and yield of product, was environmentally friendly, and produced negligible quantities…

  9. Apollo 14 - Oxide, metal, and olivine mineral chemistries in 14072 with a bearing on the temporal relationships of subsolidus reduction

    Science.gov (United States)

    Haggerty, S. E.

    1977-01-01

    One of three primary objectives of the reported study is related to the definition of the distribution of troilite and Fe and the evaluation of the role of FeS in subsolidus reduction assemblages. Another objective was concerned with the definition of the lower limit of stabilizing elements such as Mg, Al, and Cr in ulvospinel to determine the terminal compositions at which reduction is inhibited. The third objective involves a comparison of the mineral chemistries of decomposed olivine with unaltered olivine in an attempt to determine the temperature limits. The sample was selected because it is one of the most intensely reduced samples returned from the moon. The model invoked for reduction is a magmatic-deuteric process which requires an environment approximating that of a closed system in which the volatile constituents are contained and in which reduction proceeds continuously with crystallization.

  10. Green-chemistry Compatible Approach to TiO2-supported PdAu Bimetallic Nanoparticles for Solvent-free 1-Phenylethanol Oxidation under Mild Conditions

    Institute of Scientific and Technical Information of China (English)

    Jian-Bing Chang; Chang-Hai Liu; Jie Liu; Yu-Yan Zhou; Xu Gao; Sui-Dong Wang

    2015-01-01

    TiO2-supported PdAu bimetallic nanoparticles (NPs) with small size and good dispersity were prepared by the room-temperature ionic liquid-assisted bimetal sputtering, which is simple, environmentally friendly, and free of additives and byproducts. Pd/Au atomic ratio can be tuned by controlling the sputtering conditions simply. High catalytic activity was found in PdAu–NPs–TiO2 hybrids for solvent-free selective oxidation of 1-phenylethanol using O2 as the oxidant at the low temperature of 50 °C and low pressure of 1 atm. It was found that Pd/Au ratio strongly affected the catalytical activity, and the highest conversion of about 35%and turnover frequency of about 421 h-1 were achieved at 1:1 of Pd/Au atomic ratio. The synergistic effect in PdAu NPs was also discussed based on the comprehensive characterization results. The present approach may offer an alternative platform for future development of green-chemistry compatible bimetallic nanocatalysts.

  11. A microwave molecular solution based approach towards high-κ-tantalum(V)oxide nanoparticles: synthesis, dielectric properties and electron paramagnetic resonance spectroscopic studies of their defect chemistry.

    Science.gov (United States)

    Hoffmann, R C; Kaloumenos, M; Spiehl, D; Erdem, E; Repp, S; Weber, S; Schneider, J J

    2015-12-21

    Stable dispersions of tantalum oxide nanoparticles are accessible from solutions of tantalum(V) complexes with a mixed malonato and alkanolato ligand sphere in ethoxyethanol by microwave processing. The malonato ligand is cleaved during decomposition and acetic acid or acetic acid esters are formed as derived from in situ spectroscopic studies. The solubility of the tantalum precursor and the obtained particle size therefrom depend strongly on the type of alkanolato ligand moiety. Dispersions of the molecular complexes possess good film forming properties. Films with low surface roughness can be obtained by spincoating. These exhibited a dielectric constant of about 15 and disruptive strengths above 1.5 MV cm(-1). The electrical measurements indicate that the presence of moisture is detrimental with respect to the dielectric performance of the films. After removal of the solvent from the suspensions of the nanoparticles, the residue can be redispersed in aprotic solvents. The particles can be isolated therefrom by precipitation with pentane. XRD and HRTEM indicate that the material remains amorphous up to temperatures of 750 °C. XPS proved that only Ta2O5 is formed as lower oxidation states of Ta cannot be detected. A detailed EPR study allows us to gain insight into the surface defect chemistry. Multiple types of oxygen vacancies exist at the surface of the Ta2O5 particles which are influenced by additional calcination and annealing in a vacuum.

  12. Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides.

    Science.gov (United States)

    Puszko, Aniela; Brzuszkiewicz, Anna; Jezierska, Julia; Adach, Anna; Wietrzyk, Joanna; Filip, Beata; Pełczynska, Marzena; Cieslak-Golonka, Maria

    2011-08-01

    Three new nitrato copper(II) complexes of dimethyl substituted 4-nitropyridine N-oxide were synthesized and characterized by elemental analysis, magnetic, spectroscopic, thermal and X-ray methods, respectively. They were isolated as trans isomers, mononuclear (μ=1.70-1.88 BM), five (1-2) and four (3) coordinate species of general formula [Cu(NO3)2(H2O)L2] where L=2,3-dimethyl-, 2,5-dimethyl-4-nitropyridine N-oxide and [Cu (NO3)2L2], L=3,5-dimethyl-4-nitropyridine N-oxide, respectively. The X-ray crystal structure of (1) (L=2,3-dimethyl-4-nitropyridine N-oxide) was determined. The organic ligands, the complexes and copper hexaqua ion as a reference were tested in vitro on the cytotoxic activity against human cancer cell lines: MCF-7 (breast), SW-707 (colon) and P-388 (murine leukemia). The complexes are relatively strong cytotoxic agents towards P-388 cell line. Comparative analysis was performed for all known copper(II) complexes containing methyl derivatives of the 4-nitropyridine N-oxide on the basis of their composition, structure and cytotoxic activities. To obtain the typical structure for these species (i.e., 4-coordinate mononuclear of the type trans-[Cu(inorganic anion)2L2]), two methyl groups must be situated on both sides of nitrogen atom(s) (i.e., NO and NO2) in the ligand. The biological activity was found to be strongly dependent upon the number of the methyl groups and the type of cell line. The best cytotoxic results were found for the complexes without substituents or with one methyl group. Generally, for all cell lines, the complexation increased cytotoxicity when compared with the free ligands.

  13. Green chemistry at work

    Energy Technology Data Exchange (ETDEWEB)

    Frost, J. [Michigan State Univ., East Lansing, MI (United States)

    1994-12-31

    The 1.7 billion pounds of benzene produced each year in the US provide one measure of its utility. At the same time, there are a number of environmental reasons for avoiding the use of benzene in chemical manufacture. Perhaps most compelling: benzene is a potent carcinogen. Scrutiny of many of the chemicals derived from benzene reveals that each molecule contains at least one oxygen atom while benzene completely lacks oxygen atoms. Introduction of oxygen to make up for this lack can require processes that are environmentally problematic. One of the steps used to introduce oxygen atoms during manufacture of adipic acid, a component of Nylon 66, is responsible for 10% of the annual global increase in atmospheric nitrous oxide. This by-product is a causative agent of atmospheric ozone depletion and has been implicated in global warming. With support from EPA and the National Science Foundation, alternative manufacturing processes are being explored. By these new methods, chemicals usually created from benzene are made instead from nontoxic glucose, a component of table sugar. Unlike benzene, glucose is obtained from such renewable resources as plant starch and cellulose. ``Green`` manufacturing routes ideally should lead to chemicals that are economically competitive with chemicals produced by traditional methods. For two chemicals of roughly comparable cost, the consumer or producer can then be realistically expected to choose in favor of the chemical produced by a ``green`` process. Projections indicate that catechol and hydroquinone can be biocatalytically produced from glucose at a cost competitive with current market prices. Synthesis of chemicals from glucose using biocatalysis offers the premise of achieving fundamental environmental improvement while increasing the demand for agricultural products. In the final analysis, what is good for the environment can also be good for American agriculture.

  14. Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

    Science.gov (United States)

    Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

    2015-02-16

    The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology.

  15. Building carbon-carbon bonds using a biocatalytic methanol condensation cycle.

    Science.gov (United States)

    Bogorad, Igor W; Chen, Chang-Ting; Theisen, Matthew K; Wu, Tung-Yun; Schlenz, Alicia R; Lam, Albert T; Liao, James C

    2014-11-11

    Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C-C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through (13)C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives.

  16. Building Bridges: Biocatalytic C-C-Bond Formation toward Multifunctional Products.

    Science.gov (United States)

    Schmidt, Nina G; Eger, Elisabeth; Kroutil, Wolfgang

    2016-07-01

    Carbon-carbon bond formation is the key reaction for organic synthesis to construct the carbon framework of organic molecules. The review gives a selection of biocatalytic C-C-bond-forming reactions which have been investigated during the last 5 years and which have already been proven to be applicable for organic synthesis. In most cases, the reactions lead to products functionalized at the site of C-C-bond formation (e.g., α-hydroxy ketones, aminoalcohols, diols, 1,4-diketones, etc.) or allow to decorate aromatic and heteroaromatic molecules. Furthermore, examples for cyclization of (non)natural precursors leading to saturated carbocycles are given as well as the stereoselective cyclopropanation of olefins affording cyclopropanes. Although many tools are already available, recent research also makes it clear that nature provides an even broader set of enzymes to perform specific C-C coupling reactions. The possibilities are without limit; however, a big library of variants for different types of reactions is required to have the specific enzyme for a desired specific (stereoselective) reaction at hand.

  17. Building Bridges: Biocatalytic C–C-Bond Formation toward Multifunctional Products

    Science.gov (United States)

    2016-01-01

    Carbon–carbon bond formation is the key reaction for organic synthesis to construct the carbon framework of organic molecules. The review gives a selection of biocatalytic C–C-bond-forming reactions which have been investigated during the last 5 years and which have already been proven to be applicable for organic synthesis. In most cases, the reactions lead to products functionalized at the site of C–C-bond formation (e.g., α-hydroxy ketones, aminoalcohols, diols, 1,4-diketones, etc.) or allow to decorate aromatic and heteroaromatic molecules. Furthermore, examples for cyclization of (non)natural precursors leading to saturated carbocycles are given as well as the stereoselective cyclopropanation of olefins affording cyclopropanes. Although many tools are already available, recent research also makes it clear that nature provides an even broader set of enzymes to perform specific C–C coupling reactions. The possibilities are without limit; however, a big library of variants for different types of reactions is required to have the specific enzyme for a desired specific (stereoselective) reaction at hand. PMID:27398261

  18. Biocatalytic methanation of hydrogen and carbon dioxide in an anaerobic three-phase system.

    Science.gov (United States)

    Burkhardt, M; Koschack, T; Busch, G

    2015-02-01

    A new type of anaerobic trickle-bed reactor was used for biocatalytic methanation of hydrogen and carbon dioxide under mesophilic temperatures and ambient pressure in a continuous process. The conversion of gaseous substrates through immobilized hydrogenotrophic methanogenic archaea in a biofilm is a unique feature of this type of reactor. Due to the formation of a three-phase system on the carrier surface and operation as a plug flow reactor without gas recirculation, a complete reaction could be observed. With a methane concentration higher than c(CH4) = 98%, the product gas exhibits a very high quality. A specific methane production of P(CH4) = 1.49 Nm(3)/(m(3)(SV) d) was achieved at a hydraulic loading rate of LR(H2) = 6.0 Nm(3)/(m(3)(SV) d). The relation between trickle flow through the reactor and productivity could be shown. An application for methane enrichment in combination with biogas facilities as a source of carbon dioxide has also been positively proven.

  19. Characterisation of a Recombinant Patchoulol Synthase Variant for Biocatalytic Production of Terpenes.

    Science.gov (United States)

    Frister, Thore; Hartwig, Steffen; Alemdar, Semra; Schnatz, Katharina; Thöns, Laura; Scheper, Thomas; Beutel, Sascha

    2015-08-01

    The patchoulol synthase (PTS) is a multi-product sesquiterpene synthases which is the central enzyme for biosynthesis of patchouli essential oil in the patchouli plant. Sesquiterpene synthases catalyse the formation of various complex carbon backbones difficult to approach by organic synthesis. Here, we report the characterisation of a recombinant patchoulol synthase complementary DNA (cDNA) variant (PTS var. 1), exhibiting significant amino acid exchanges compared to the native PTS. The product spectrum using the natural substrate E,E-farnesyl diphosphate (FDP) as well as terpenoid products resulting from conversions employing alternative substrates was analysed by GC-MS. In respect to a potential use as a biocatalyst, important enzymatic parameters such as the optimal reaction conditions, kinetic behaviour and the product selectivity were studied as well. Adjusting the reaction conditions, an increased patchoulol ratio in the recombinant essential oil was achieved. Nevertheless, the ratio remained lower than in plant-derived patchouli oil. As alternative substrates, several prenyl diposphates were accepted and converted in numerous compounds by the PTS var. 1, revealing its great biocatalytic potential.

  20. Bioinorganic Chemistry in Thyroid Gland: Effect of Antithyroid Drugs on Peroxidase-Catalyzed Oxidation and Iodination Reactions

    Directory of Open Access Journals (Sweden)

    G. Mugesh

    2006-11-01

    Full Text Available Propylthiouracil (PTU and methimazole (MMI are the most commonly used antithyroid drugs. The available data suggest that these drugs may block the thyroid hormone synthesis by inhibiting the thyroid peroxidase (TPO or diverting oxidized iodides away from thyroglobulin. It is also known that PTU inhibits the selenocysteine-containing enzyme ID-1 by reacting with the selenenyl iodide intermediate (E-SeI. In view of the current interest in antithyroid drugs, we have recently carried out biomimetic studies to understand the mechanism by which the antithyroid drugs inhibit the thyroid hormone synthesis and found that the replacement of sulfur with selenium in MMI leads to an interesting compound that may reversibly block the thyroid hormone synthesis. Our recent results on the inhibition of lactoperoxidase (LPO-catalyzed oxidation and iodination reactions by antithyroid drugs are described.

  1. Complex Roles of Solution Chemistry on Graphene Oxide Coagulation onto Titanium Dioxide: Batch Experiments, Spectroscopy Analysis and Theoretical Calculation

    OpenAIRE

    Shujun Yu; Xiangxue Wang; Rui Zhang; Tongtong Yang; Yuejie Ai; Tao Wen; Wei Huang; Tasawar Hayat; Ahmed Alsaedi; Xiangke Wang

    2017-01-01

    Although graphene oxide (GO) has been used in multidisciplinary areas due to its excellent physicochemical properties, its environmental behavior and fate are still largely unclear. In this study, batch experiments, spectroscopy analysis and theoretical calculations were addressed to promote a more comprehensive understanding toward the coagulation behavior of GO onto TiO2 under various environmental conditions (pH, co-existing ions, temperature, etc.). The results indicated that neutral pH w...

  2. Effects of prenatal and postnatal exposure to GSM-like radiofrequency on blood chemistry and oxidative stress in infant rabbits, an experimental study.

    Science.gov (United States)

    Ozgur, Elcin; Kismali, Gorkem; Guler, Goknur; Akcay, Aytac; Ozkurt, Guzin; Sel, Tevhide; Seyhan, Nesrin

    2013-11-01

    We aimed to investigate the potential hazardous effects of prenatal and/or postnatal exposure to 1800 MHz GSM-like radiofrequency radiation (RFR) on the blood chemistry and lipid peroxidation levels of infant rabbits. A total of 72 New Zealand female and male white rabbits aged 1-month were used. Thirty-six female and 36 male were divided into four groups which were composed of nine infants: (i) Group 1 were the sham exposure (control), (ii) Group 2 were exposed to RFR, 15 min daily for 7 days in the prenatal period (between 15th and 22nd days of the gestational period) (prenatal exposure group). (iii) Group 3 were exposed to RFR 15 min/day (14 days for male, whereas 7 days for female) after they reached 1-month of age (postnatal exposure group). (iv) Group 4 were exposed to RFR for 15 min daily during 7 days in the prenatal period (between 15th and 22nd days of the gestational period) and 15 min/day (14 days for male, whereas 7 days for female) after they reached 1-month of age (prenatal and postnatal exposure group). Results showed that serum lipid peroxidation level in both female and male rabbits changed due to the RFR exposure. However, different parameters of the blood biochemistry were affected by exposure in male and female infants. Consequently, the whole-body 1800 MHz GSM-like RFR exposure may lead to oxidative stress and changes on some blood chemistry parameters. Studies on RFR exposure during prenatal and postnatal periods will help to establish international standards for the protection of pregnants and newborns from environmental RFR.

  3. Sulphate chemistry under pressurized oxidizing, reducing and fluctuating conditions; Sulfatkemi under trycksatta oxiderande, reducerande och fluktuerande foerhaallanden

    Energy Technology Data Exchange (ETDEWEB)

    Hupa, M.; Yrjas, P.; Backman, P. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

    1997-10-01

    In the literature it has been reported that sulfur capture with limestone (CaCO{sub 3}) under atmospheric fluidized bed combustion conditions reaches a maximum at about 850 deg C. Previously, the maximum has been attributed to the sintering of sorbent particles which decreases the reactive surface area. Lately, also another explanation has been reported. In this case the sulfur capture decrease at higher temperatures was concluded to be due to fluctuating oxidizing/reducing conditions in the atmospheric combustor. In this work the influence of alternating oxidizing/reducing conditions on SO{sub 2} capture at atmospheric and elevated pressure (15 bar) has been studied. In the pressurized case, the CO{sub 2} partial pressure was kept high enough to prevent CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} under reducing conditions. The experiments were done with a pressurized TGA by periodically changing the gas environment between oxidizing (O{sub 2}. SO{sub 2}, CO{sub 2} and N{sub 2}) and slightly reducing (CO, SO{sub 2}, CO{sub 2} and N{sub 2}) gas mixtures at different temperatures. The results from the experiments showed that under normal pressure and slightly reducing conditions CaO formation from CaSO{sub 4} increased with temperature as expected. However, no significant amounts of CaCO{sub 3} were formed from CaSO{sub 4} at elevated pressure. It was also concluded that since the formation of CaO from CaSO{sub 4} was relatively slow it could not explain the sharp sulfur capture maximum at about 850 deg C. Therefore, it was assumed that the strongly reducing zones, where CaS thermodynamically is the stable compound, play a more important role concerning the sulfur capture in fluidized bed combustors. (orig.)

  4. Prediction of hydrodynamics and chemistry of confined turbulent methane-air flames with attention to formation of oxides of nitrogen

    Science.gov (United States)

    Elghobashi, S.; Spalding, D. B.; Srivatsa, S. K.

    1977-01-01

    A formulation of the governing partial differential equations for fluid flow and reacting chemical species in a tubular combustor is presented. A numerical procedure for the solution of the governing differential equations is described, and models for chemical equilibrium and chemical kinetics calculations are presented. The chemical equilibrium model is used to characterize the hydrocarbon reactions. The chemical kinetics model is used to predict the concentrations of the oxides of nitrogen. The combustor consists of a cylindrical duct of varying cross sections with concentric streams of gaseous fuel and air entering the duct at one end. Four sample cases with specified inlet and boundary conditions are considered, and the results are discussed

  5. The Effect of Oxidation on the Surface Chemistry of Sulfur-Containing Carbons and their Arsine Adsorption Capacity

    Science.gov (United States)

    2010-01-01

    hydrogen sulfide . Carbon 2004;42(3):469–76. Fig. 6 – Water adsorption isotherms of the samples studied. 1786 C A R B O N 4 8 ( 2 0 1 0 ) 1 7 7 9 –1 7 8...that oxygen- and sulfur-containing groups participate in arsine oxida- tion to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides ...technological difficulties, arsine is also a powerful toxin susceptible to oxidation with a strong exothermic effect. Of all the methods to separate

  6. In-Situ Investigation of Gas Phase Radical Chemistry in the Catalytic Partial Oxidation of Methane on Pt

    OpenAIRE

    Geske, M.; Pelzer, K.; Horn, R.; Jentoft, F.; R. Schlögl

    2009-01-01

    The catalytic partial oxidation of methane on platinum was studied in situ under atmospheric pressure and temperatures between 1000 and 1300 °C. By combining radical measurements using a molecular beam mass spectrometer and threshold ionization with GC, GC-MS and temperature profile measurements it was demonstrated that a homogeneous reaction pathway is opened at temperatures above 1100 °C, in parallel to hetero-geneous reactions which start already at 600 °C. Before ignition of gas phase che...

  7. A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation

    Directory of Open Access Journals (Sweden)

    Jamie Hawkes

    2013-02-01

    Full Text Available This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles confirm the existence of secondary amines in hair dyes (and their intermediates, the possibility of nitrosation by atmospheric NOx of secondary amines to give the N-nitrosamines, and the significant safety risks on N-nitrosamines. It is believed that such nitrosamine derivatives should be investigated more fully in the interests of consumer safety.

  8. Colour Chemistry

    Science.gov (United States)

    Griffiths, J.; Rattee, I. D.

    1973-01-01

    Discusses the course offerings in pure color chemistry at two universities and the three main aspects of study: dyestuff chemistry, color measurement, and color application. Indicates that there exists a constant challenge to ingenuity in the subject discipline. (CC)

  9. Chemistry Dashboard

    Science.gov (United States)

    The Chemistry Dashboard is part of a suite of dashboards developed by EPA to help evaluate the safety of chemicals. The Chemistry Dashboard provides access to a variety of information on over 700,000 chemicals currently in use.

  10. Chemistry Notes

    Science.gov (United States)

    School Science Review, 1976

    1976-01-01

    Described are eight chemistry experiments and demonstrations applicable to introductory chemistry courses. Activities include: measure of lattice enthalpy, Le Chatelier's principle, decarboxylation of soap, use of pocket calculators in pH measurement, and making nylon. (SL)

  11. Biophysical chemistry.

    Science.gov (United States)

    Häussinger, Daniel; Pfohl, Thomas

    2010-01-01

    Biophysical chemistry at the Department of Chemistry, University of Basel, covers the NMR analysis of protein-protein interaction using paramagnetic tags and sophisticated microscopy techniques investigating the dynamics of biological matter.

  12. Heterocyclic chemistry

    OpenAIRE

    Hemming, Karl

    2011-01-01

    Recent progress in the synthesis of heterocyclic compounds is presented\\ud 2010 offered highlights in pericyclic chemistry, particularly 1,3-dipolar cycloaddition chemistry, asymmetric synthesis, gold catalysis, organocatalysis, hydroamination, C–H activation and multicomponent reactions.

  13. Microfluidics in inorganic chemistry.

    Science.gov (United States)

    Abou-Hassan, Ali; Sandre, Olivier; Cabuil, Valérie

    2010-08-23

    The application of microfluidics in chemistry has gained significant importance in the recent years. Miniaturized chemistry platforms provide controlled fluid transport, rapid chemical reactions, and cost-saving advantages over conventional reactors. The advantages of microfluidics have been clearly established in the field of analytical and bioanalytical sciences and in the field of organic synthesis. It is less true in the field of inorganic chemistry and materials science; however in inorganic chemistry it has mostly been used for the separation and selective extraction of metal ions. Microfluidics has been used in materials science mainly for the improvement of nanoparticle synthesis, namely metal, metal oxide, and semiconductor nanoparticles. Microfluidic devices can also be used for the formulation of more advanced and sophisticated inorganic materials or hybrids.

  14. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land-use change in response to growing food needs

    Directory of Open Access Journals (Sweden)

    C. J. Hardacre

    2013-06-01

    Full Text Available We quantify the impact of land-use change, determined by our growing demand for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000 of land-use change realizations from 1990–2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land-use change required to address projected biofuel usage using two scenarios: (1 assuming that world governments make no changes to biofuel policy after 2009, and (2 assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR statistics of the ensemble and show that land-use change between −1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of −3.5 to +2.8 Tg yr−1 in 2015 and −7.7 to +6.4 Tg yr−1 in 2030. We use land-use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2, and the atmospheric concentration and deposition of ozone (O3. We show that across subcontinental regions the monthly surface O3 increases by 0.1–0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases in surface isoprene in high (low NOx environments. At the local scale (4° × 5° we find that surface O3 increases by 5–12 ppb over temperate North America, China and boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel production.

  15. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land use change in response to growing food needs

    Directory of Open Access Journals (Sweden)

    C. J. Hardacre

    2012-12-01

    Full Text Available We quantify the impact of land use change, determined by our growing need for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000 of land use change realizations from 1990–2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land use change required to address projected biofuel usage using two scenarios: (1 assuming that world governments make no changes to biofuel policy after 2009, and (2 assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR statistics of the ensemble and show that land use change between −1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of −3.5 to +2.8 Tg yr−1 in 2015 and −7.7 to +6.4 Tg yr−1 in 2030. We use land use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2, and the atmospheric concentration and deposition of ozone (O3. We show that across sub-continental regions the monthly surface O3 increases by 0.1–0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases in surface isoprene in high (low NOx environments. At the local scale (4° × 5° we find that surface O3 increases by 5–12 ppb over temperate North America, China and Boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel

  16. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land use change in response to growing food needs

    Science.gov (United States)

    Hardacre, C. J.; Palmer, P. I.; Baumanns, K.; Rounsevell, M.; Murray-Rust, D.

    2012-12-01

    We quantify the impact of land use change, determined by our growing need for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000) of land use change realizations from 1990-2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land use change required to address projected biofuel usage using two scenarios: (1) assuming that world governments make no changes to biofuel policy after 2009, and (2) assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR) statistics of the ensemble and show that land use change between -1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of -3.5 to +2.8 Tg yr-1 in 2015 and -7.7 to +6.4 Tg yr-1 in 2030. We use land use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2), and the atmospheric concentration and deposition of ozone (O3). We show that across sub-continental regions the monthly surface O3 increases by 0.1-0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases) in surface isoprene in high (low) NOx environments. At the local scale (4° × 5°) we find that surface O3 increases by 5-12 ppb over temperate North America, China and Boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel production.

  17. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land-use change in response to growing food needs

    Science.gov (United States)

    Hardacre, C. J.; Palmer, P. I.; Baumanns, K.; Rounsevell, M.; Murray-Rust, D.

    2013-06-01

    We quantify the impact of land-use change, determined by our growing demand for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000) of land-use change realizations from 1990-2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land-use change required to address projected biofuel usage using two scenarios: (1) assuming that world governments make no changes to biofuel policy after 2009, and (2) assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR) statistics of the ensemble and show that land-use change between -1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of -3.5 to +2.8 Tg yr-1 in 2015 and -7.7 to +6.4 Tg yr-1 in 2030. We use land-use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2), and the atmospheric concentration and deposition of ozone (O3). We show that across subcontinental regions the monthly surface O3 increases by 0.1-0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases) in surface isoprene in high (low) NOx environments. At the local scale (4° × 5°) we find that surface O3 increases by 5-12 ppb over temperate North America, China and boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel production.

  18. Combinatorial chemistry

    DEFF Research Database (Denmark)

    Nielsen, John

    1994-01-01

    An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

  19. Positronium chemistry

    CERN Document Server

    Green, James

    1964-01-01

    Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

  20. Selective Gas-Phase Oxidation and Localization of Alkylated Cysteine Residues in Polypeptide Ions via Ion/Ion Chemistry.

    Science.gov (United States)

    Pilo, Alice L; Zhao, Feifei; McLuckey, Scott A

    2016-09-01

    The thiol group in cysteine residues is susceptible to several post-translational modifications (PTMs), including prenylation, nitrosylation, palmitoylation, and the formation of disulfide bonds. Additionally, cysteine residues involved in disulfide bonds are commonly reduced and alkylated prior to mass spectrometric analysis. Several of these cysteine modifications, specifically S-alkyl modifications, are susceptible to gas-phase oxidation via selective ion/ion reactions with periodate anions. Multiply protonated peptides containing modified cysteine residues undergo complex formation upon ion/ion reaction with periodate anions. Activation of the ion/ion complexes results in oxygen transfer from the reagent to the modified sulfur residue to create a sulfoxide functionality. Further activation of the sulfoxide derivative yields abundant losses of the modification with the oxidized sulfur as a sulfenic acid (namely, XSOH) to generate a dehydroalanine residue. This loss immediately indicates the presence of an S-alkyl cysteine residue, and the mass of the loss can be used to easily deduce the type of modification. An additional step of activation can be used to localize the modification to a specific residue within the peptide. Selective cleavage to create c- and z-ions N-terminal to the dehydroalanine residue is often noted. As these types of ions are not typically observed upon collision-induced dissociation (CID), they can be used to immediately indicate where in the peptide the PTM was originally located.

  1. The Discovery-Oriented Approach to Organic Chemistry. 7. Rearrangement of "trans"-Stilbene Oxide with Bismuth Trifluoromethanesulfonate and Other Metal Triflates: A Microscale Green Organic Chemistry Laboratory Experiment

    Science.gov (United States)

    Christensen, James E.; Huddle, Matthew G.; Rogers, Jamie L.; Yung, Herbie; Mohan, Ram S.

    2008-01-01

    Although green chemistry principles are increasingly stressed in the undergraduate curriculum, there are only a few lab experiments wherein the toxicity of reagents is taken into consideration in the design of the experiment. We report a microscale green organic chemistry laboratory experiment that illustrates the utility of metal triflates,…

  2. Biocatalytic Synthesis of Novel Partial Esters of a Bioactive Dihydroxy 4-Methylcoumarin by Rhizopus oryzae Lipase (ROL

    Directory of Open Access Journals (Sweden)

    Vinod Kumar

    2016-11-01

    Full Text Available Highly regioselective acylation has been observed in 7,8-dihydroxy-4-methylcoumarin (DHMC by the lipase from Rhizopus oryzae suspended in tetrahydrofuran (THF at 45 °C using six different acid anhydrides as acylating agents. The acylation occurred regioselectively at one of the two hydroxy groups of the coumarin moiety resulting in the formation of 8-acyloxy-7-hydroxy-4-methylcoumarins, which are important bioactive molecules for studying biotansformations in animals, and are otherwise very difficult to obtain by only chemical steps. Six monoacylated, monohydroxy 4-methylcoumarins have been biocatalytically synthesised and identified on the basis of their spectral data and X-ray crystal analysis.

  3. Utility of a redox-active pyridine(diimine) chelate in facilitating two electron oxidative addition chemistry at uranium.

    Science.gov (United States)

    Kiernicki, John J; Fanwick, Phillip E; Bart, Suzanne C

    2014-08-01

    Exposure of the uranium(IV) complex, Cp(P)U((Mes)PDI(Me)) (1) ((Mes)PDI(Me) = 2,6-((Mes)N=CMe)2–C5H3N; Mes = 2,4,6-trimethylphenyl; Cp(P) = 1-(7,7-dimethylbenzyl)cyclopentadienyl), which contains a [(Mes)PDI(Me)](3−) chelate, to I2, Cl2, PhSeCl, and PhEEPh (E = S, Se, Te) results in oxidative addition to form the uranium(IV) family, Cp(P)U(XX′)((Mes)PDI(Me)) (X = X′ = I, Cl, EPh; X = SePh, X′ = Cl). Spectroscopic and structural studies support products with [(Mes)PDI(Me)](1−), indicating the reducing equivalents derive from this redox-active chelate.

  4. Forensic chemistry.

    Science.gov (United States)

    Bell, Suzanne

    2009-01-01

    Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

  5. Biocatalytic desulfurization of thiophenic compounds and crude oil by newly isolated bacteria

    Directory of Open Access Journals (Sweden)

    Magdy El-Said Mohamed

    2015-02-01

    Full Text Available Microorganisms possess enormous highly specific metabolic activities, which enable them to utilize and transform nearly every known chemical class present in crude oil. In this context, one of the most studied biocatalytic processes is the biodesulfurization (BDS of thiophenic sulfur-containing compounds such as benzothiophene (BT and dibenzothiophene (DBT in crude oils and refinery streams. Three newly isolated bacterial strains, which were affiliated as Rhodococcus sp. strain SA11, Stenotrophomonas sp. strain SA21, and Rhodococcus sp. strain SA31, were enriched from oil contaminated soil in the presence of DBT as the sole S source. GC-FID analysis of DBT-grown cultures showed consumption of DBT, transient formation of DBT sulfone (DBTO2 and accumulation of 2-hydroxybiphenyl (2-HBP. Molecular detection of the plasmid-borne dsz operon, which codes for the DBT desulfurization activity, revealed the presence of dszA, dszB, and dszC genes. These results point to the operation of the known 4S pathway in the BDS of DBT. The maximum consumption rate of DBT was 11 µmol/g Dry Cell Weight (DCW/h and the maximum formation rate of 2-HBP formation was 4 µmol/g DCW/h. Inhibition of both cell growth and DBT consumption by 2-HBP was observed for all isolates but SA11 isolate was the least affected. The isolated biocatalysts desulfurized other model DBT alkylated homologs. SA11 isolate was capable of desulfurizing BT as well. Resting cells of SA11 exhibited 10% reduction in total sulfur present in heavy crude oil and 18% reduction in total sulfur present in the hexane-soluble fraction of the heavy crude oil. The capabilities of the isolated bacteria to survive and desulfurize a wide range of S compounds present in crude oil are desirable traits for the development of a robust BDS biocatalyst to upgrade crude oils and refinery streams.

  6. Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

    Science.gov (United States)

    Zhang, Zhen-Bei; Wu, Jing-Jing; Su, Yu; Zhou, Jin; Gao, Yong; Yu, Hai-Yin; Gu, Jia-Shan

    2015-03-01

    Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane. Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface.

  7. Chemistry, phase formation, and catalytic activity of thin palladium-containing oxide films synthesized by plasma-assisted physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2010-11-26

    The chemistry, microstructure, and catalytic activity of thin films incorporating palladium were studied using scanning and transmission electron microscopies, X-ray diffraction, spectrophotometry, 4-point probe and catalytic tests. The films were synthesized using pulsed filtered cathodic arc and magnetron sputter deposition, i.e. techniques far from thermodynamic equilibrium. Catalytic particles were formed by thermally cycling thin films of the Pd-Pt-O system. The evolution and phase formation in such films as a function of temperature were discussed in terms of the stability of PdO and PtO2 in air. The catalytic efficiency was found to be strongly affected by the chemical composition, with oxidized palladium definitely playing a major role in the combustion of methane. Reactive sputter deposition of thin films in the Pd-Zr-Y-O system allowed us forming microstructures ranging from nanocrystalline zirconia to palladium nanoparticles embedded in a (Zr,Y)4Pd2O matrix. The sequence of phase formation is put in relation to simple thermodynamic considerations.

  8. Morphological effects of single-layer graphene oxide in the formation of covalently bonded polypyrrole composites using intermediate diisocyanate chemistry

    Science.gov (United States)

    Whitby, Raymond L. D.; Korobeinyk, Alina; Mikhalovsky, Sergey V.; Fukuda, Takahiro; Maekawa, Toru

    2011-10-01

    Single-layer graphene oxide (SLGO) possesses carboxylic and hydroxyl groups suitable for reactions with aliphatic or aromatic diisocyanate molecules. TEM analysis reveals that aliphatic diisocyanate molecules caused SLGO to scroll into star-like formations, whereas aromatic diisocyanate molecules retained SGLO in a flat-sheet morphology. TGA confirms the stabilisation of the formed urea and urethane groups on SLGO, but the onset of sheet pyrolysis occurs at a lower temperature due to isocyanate reactions with anhydride and epoxide groups embedded in the sheet. Pendant isocyanate groups act as bridging units to facilitate the attachment of pyrrole molecules, which are then used as anchor sites for the covalent polymerisation of pyrrole to polypyrrole (PPy). The use of FeCl3 as the polymerisation catalyst generated both covalent and free PPy, but also iron hydroxide nanoparticles were observed decorating the SLGO surface. When using ammonium persulfate as a catalyst and dodecylbenzenesulfonate as a dopant, free PPy could be removed under treatment with solvents to leave a purely covalent system. Discrete regions of SLGO were observed decorated with nanoparticles of PPy along the edge or across the surface of individual sheets. It was found that the flexibility of the SLGO sheet and the type of diisocyanate used directly affected the electrical resistance of the final composite.

  9. Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells

    Directory of Open Access Journals (Sweden)

    Camille C. Hanot

    2015-12-01

    Full Text Available Superparamagnetic iron-oxide nanoparticles (SPIONs show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells. We evaluated the effect of particle diameter (50 and 100 nm and polyethylene glycol (PEG chain length (2k, 5k and 20k Da on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and sulforhodamine B (SRB assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS. Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications.

  10. Complex Roles of Solution Chemistry on Graphene Oxide Coagulation onto Titanium Dioxide: Batch Experiments, Spectroscopy Analysis and Theoretical Calculation

    Science.gov (United States)

    Yu, Shujun; Wang, Xiangxue; Zhang, Rui; Yang, Tongtong; Ai, Yuejie; Wen, Tao; Huang, Wei; Hayat, Tasawar; Alsaedi, Ahmed; Wang, Xiangke

    2017-01-01

    Although graphene oxide (GO) has been used in multidisciplinary areas due to its excellent physicochemical properties, its environmental behavior and fate are still largely unclear. In this study, batch experiments, spectroscopy analysis and theoretical calculations were addressed to promote a more comprehensive understanding toward the coagulation behavior of GO onto TiO2 under various environmental conditions (pH, co-existing ions, temperature, etc.). The results indicated that neutral pH was beneficial to the removal of GO due to the electrostatic interaction. The presence of cations accelerated GO coagulation significantly owing to the influence of electrical double layer compression. On the contrary, the presence of anions improved the stability of GO primarily because of electrostatic repulsion and steric hindrance. Results of XRD, FTIR and XPS analysis indicated that the coagulation of GO on TiO2 was mainly dominated by electrostatic interactions and hydrogen bonds, which were further evidenced by DFT calculations. The high binding energy further indicated the stability of GO + TiO2 system, suggesting that TiO2 can be used as an effective coagulant for the efficient elimination and coagulation of GO from aqueous solutions. These findings might likely lead to a better understanding of the migration and transformation of carbon nanomaterials in the natural environment.

  11. Computational chemistry

    OpenAIRE

    2000-01-01

    Computational chemistry has come of age. With significant strides in computer hardware and software over the last few decades, computational chemistry has achieved full partnership with theory and experiment as a tool for understanding and predicting the behavior of a broad range of chemical, physical, and biological phenomena. The Nobel Prize award to John Pople and Walter Kohn in 1998 highlighted the importance of these advances in computational chemistry. With massively parallel computers ...

  12. Organic chemistry

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-08-15

    This book with sixteen chapter explains organic chemistry on linkage isomerism such as alkane, cycloalkane, alkene, aromatic compounds, stereo selective isomerization, aromatic compounds, stereo selective isomerization, organic compounds, stereo selective isomerization, organic halogen compound, alcohol, ether, aldehyde and ketone, carboxylic acid, dicarboxylic acid, fat and detergent, amino, carbohydrate, amino acid and protein, nucleotide and nucleic acid and spectroscopy, a polymer and medical chemistry. Each chapter has introduction structure and characteristic and using of organic chemistry.

  13. Bioinorganic Chemistry

    OpenAIRE

    Bertini, Ivano; Gray, Harry B.; Lippard, Stephen J.; Valentine, Joan Selverstone

    1994-01-01

    This book covers material that could be included in a one-quarter or one-semester course in bioinorganic chemistry for graduate students and advanced undergraduate students in chemistry or biochemistry. We believe that such a course should provide students with the background required to follow the research literature in the field. The topics were chosen to represent those areas of bioinorganic chemistry that are mature enough for textbook presentation. Although each chapter presents material...

  14. Chemistry Technology

    Data.gov (United States)

    Federal Laboratory Consortium — Chemistry technology experts at NCATS engage in a variety of innovative translational research activities, including:Design of bioactive small molecules.Development...

  15. Selective recovery of pure copper nanopowder from indium-tin-oxide etching wastewater by various wet chemical reduction process: Understanding their chemistry and comparisons of sustainable valorization processes.

    Science.gov (United States)

    Swain, Basudev; Mishra, Chinmayee; Hong, Hyun Seon; Cho, Sung-Soo

    2016-05-01

    Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11kg/m(3) of copper and 1.35kg/m(3) of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered using various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100-500nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process.

  16. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  17. Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

    Directory of Open Access Journals (Sweden)

    Verena Weidmann

    2013-10-01

    Full Text Available Allylic oxidations of olefins to enones allow the efficient synthesis of value-added products from simple olefinic precursors like terpenes or terpenoids. Biocatalytic variants have a large potential for industrial applications, particularly in the pharmaceutical and food industry. Herein we report efficient biocatalytic allylic oxidations of spirocyclic terpenoids by a lyophilisate of the edible fungus Pleurotus sapidus. This ‘’mushroom catalysis’’ is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio- and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been developed. The oxidations follow a radical mechanism and the regioselectivity of the reaction is mainly determined by bond-dissociation energies of the available allylic CH-bonds and steric accessibility of the oxidation site.

  18. A biocatalytic approach to capuramycin analogues by exploiting a substrate permissive N-transacylase CapW.

    Science.gov (United States)

    Liu, Xiaodong; Jin, Yuanyuan; Cai, Wenlong; Green, Keith D; Goswami, Anwesha; Garneau-Tsodikova, Sylvie; Nonaka, Koichi; Baba, Satoshi; Funabashi, Masanori; Yang, Zhaoyong; Van Lanen, Steven G

    2016-04-28

    Using the ATP-independent transacylase CapW required for the biosynthesis of capuramycin-type antibiotics, we developed a biocatalytic approach for the synthesis of 43 analogues via a one-step aminolysis reaction from a methyl ester precursor as an acyl donor and various nonnative amines as acyl acceptors. Further examination of the donor substrate scope for CapW revealed that this enzyme can also catalyze a direct transamidation reaction using the major capuramycin congener as a semisynthetic precursor. Biological activity tests revealed that a few of the new capuramycin analogues have significantly improved antibiotic activity against Mycobacterium smegmatis MC2 155 and Mycobacterium tuberculosis H37Rv. Furthermore, most of the analogues are able to be covalently modified by the phosphotransferase CapP/Cpr17 involved in self resistance, providing critical insight for future studies regarding clinical development of the capuramycin antimycobacterial antibiotics.

  19. Quantum chemistry

    CERN Document Server

    Lowe, John P

    1993-01-01

    Praised for its appealing writing style and clear pedagogy, Lowe's Quantum Chemistry is now available in its Second Edition as a text for senior undergraduate- and graduate-level chemistry students. The book assumes little mathematical or physical sophistication and emphasizes an understanding of the techniques and results of quantum chemistry, thus enabling students to comprehend much of the current chemical literature in which quantum chemical methods or concepts are used as tools. The book begins with a six-chapter introduction of standard one-dimensional systems, the hydrogen atom,

  20. Enhancing the biocatalytic manufacture of the key intermediate of atorvastatin by focused directed evolution of halohydrin dehalogenase

    Science.gov (United States)

    Luo, Yu; Chen, Yangzi; Ma, Hongmin; Tian, ZhenHua; Zhang, Yeqi; Zhang, Jian

    2017-01-01

    Halohydrin dehalogenases (HHDHs) are biocatalytically interesting enzymes due to their ability to form C-C, C-N, C-O, and C-S bonds. One of most important application of HHDH was the protein engineering of HheC (halohydrin dehalogenase from Agrobacterium radiobacter AD1) for the industrial manufacturing of ethyl (R)-4-cyano-3-hydroxybutanoate (HN), a key chiral synthon of a cholesterol-lowering drug of atorvastatin. During our development of an alternative, more efficient and economic route for chemo-enzymatic preparation of the intermediate of atorvastatin, we found that the HheC2360 previously reported for HN manufacture, had insufficient activity for the cyanolysis production of tert-butyl (3 R,5 S)-6-cyano-3,5-dihydroxyhexanoate (A7). Herein, we present the focused directed evolution of HheC2360 with higher activity and enhanced biocatalytic performance using active site mutagenesis. Through docking of the product, A7, into the crystal structure of HheC2360, 6 residues was selected for combined active sites testing (CASTing). After library screening, the variant V84G/W86F was identified to have a 15- fold increase in activity. Time course analysis of the cyanolysis reaction catalyzed by this variant, showed 2- fold increase in space time productivity compared with HheC2360. These results demonstrate the applicability of the variant V84G/W86F as a biocatalyst for the efficient and practical production of atorvastatin intermediate. PMID:28165015

  1. The radiation chemistry of macromolecules

    CERN Document Server

    1973-01-01

    The Radiation Chemistry of Macromolecules, Volume II is a collection of papers that discusses radiation chemistry of specific systems. Part 1 deals with radiation chemistry of substituted vinyl polymers, particularly polypropylene (PP) as its structure is intermediate between polyethylene and polyisobutylene. This part also discusses polypropylene oxide (PPOx) for it can be prepared in the atactic, isotactic, and optically active forms. One paper focuses on the fundamental chemical processes and the changes in physical properties that give rise to many different applications of polystyrene. An

  2. Assessment of the reduction methods used to develop chemical schemes: building of a new chemical scheme for VOC oxidation suited to three-dimensional multiscale HOx-NOx-VOC chemistry simulations

    Science.gov (United States)

    Szopa, S.; Aumont, B.; Madronich, S.

    2005-02-01

    The objective of this work was to develop and assess an automatic procedure to write reduced chemical schemes for modeling gaseous photooxidant pollution at different scales. The method is based on (i) the development of a tool for writing the fully explicit schemes 5 for VOC oxidation and (ii) the assessment of reduced schemes using the fully explicit scheme as a reference. The reference scheme contained ca. seventy emitted VOCs chosen to be representative of both anthropogenic and biogenic emissions, and their atmospheric degradation chemistry involving more than two million reactions and 350 000 species was written using an expert system generator approach. 10 Three methods were applied to reduce the size of chemical schemes: (i) use of operators, based on the redundancy of the reaction sequences involved in the VOC oxidation, (ii) lumping of primary species having similar reactivities and (iii) lumping of secondary products into surrogate species. The number of species in the final reduced scheme is 150, i.e. low enough for 3-D modeling purposes using CTMs. Comparisons 15 between the fully explicit and reduced schemes, carried out with a box model for several typical tropospheric conditions, showed that the reduced chemical scheme accurately predicts ozone concentrations and some other aspects of oxidant chemistry for both polluted and clean tropospheric conditions.

  3. Assessment of the reduction methods used to develop chemical schemes: building of a new chemical scheme for VOC oxidation suited to three-dimensional multiscale HOx-NOx-VOC chemistry simulations

    Directory of Open Access Journals (Sweden)

    B. Aumont

    2005-02-01

    Full Text Available The objective of this work was to develop and assess an automatic procedure to write reduced chemical schemes for modeling gaseous photooxidant pollution at different scales. The method is based on (i the development of a tool for writing the fully explicit schemes 5 for VOC oxidation and (ii the assessment of reduced schemes using the fully explicit scheme as a reference. The reference scheme contained ca. seventy emitted VOCs chosen to be representative of both anthropogenic and biogenic emissions, and their atmospheric degradation chemistry involving more than two million reactions and 350 000 species was written using an expert system generator approach. 10 Three methods were applied to reduce the size of chemical schemes: (i use of operators, based on the redundancy of the reaction sequences involved in the VOC oxidation, (ii lumping of primary species having similar reactivities and (iii lumping of secondary products into surrogate species. The number of species in the final reduced scheme is 150, i.e. low enough for 3-D modeling purposes using CTMs. Comparisons 15 between the fully explicit and reduced schemes, carried out with a box model for several typical tropospheric conditions, showed that the reduced chemical scheme accurately predicts ozone concentrations and some other aspects of oxidant chemistry for both polluted and clean tropospheric conditions.

  4. Assessment of the reduction methods used to develop chemical schemes: building of a new chemical scheme for VOC oxidation suited to three-dimensional multiscale HOx-NOx-VOC chemistry simulations

    Directory of Open Access Journals (Sweden)

    S. Szopa

    2005-01-01

    Full Text Available The objective of this work was to develop and assess an automatic procedure to generate reduced chemical schemes for the atmospheric photooxidation of volatile organic carbon (VOC compounds. The procedure is based on (i the development of a tool for writing the fully explicit schemes for VOC oxidation (see companion paper Aumont et al., 2005, (ii the application of several commonly used reduction methods to the fully explicit scheme, and (iii the assessment of resulting errors based on direct comparison between the reduced and full schemes. The reference scheme included seventy emitted VOCs chosen to be representative of both anthropogenic and biogenic emissions, and their atmospheric degradation chemistry required more than two million reactions among 350000 species. Three methods were applied to reduce the size of the reference chemical scheme: (i use of operators, based on the redundancy of the reaction sequences involved in the VOC oxidation, (ii grouping of primary species having similar reactivities into surrogate species and (iii grouping of some secondary products into surrogate species. The number of species in the final reduced scheme is 147, this being small enough for practical inclusion in current three-dimensional models. Comparisons between the fully explicit and reduced schemes, carried out with a box model for several typical tropospheric conditions, showed that the reduced chemical scheme accurately predicts ozone concentrations and some other aspects of oxidant chemistry for both polluted and clean tropospheric conditions.

  5. Introductory Chemistry

    OpenAIRE

    Baron, Mark; Gonzalez-Rodriguez, Jose; Stevens, Gary; Gray, Nathan; Atherton, Thomas; Winn, Joss

    2010-01-01

    Teaching and Learning resources for the 1st Year Introductory Chemistry course (Forensic Science). 30 credits. These are Open Educational Resources (OER), made available for re-use under a Creative Commons license.

  6. Nuclear Chemistry.

    Science.gov (United States)

    Chemical and Engineering News, 1979

    1979-01-01

    Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

  7. Materials Chemistry

    CERN Document Server

    Fahlman, Bradley D

    2011-01-01

    The 2nd edition of Materials Chemistry builds on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field. The 2nd edition continues to offer innovative coverage and practical perspective throughout. After briefly defining materials chemistry and its history, seven chapters discuss solid-state chemistry, metals, semiconducting materials, organic "soft" materials, nanomaterials, and materials characterization. All chapters have been thoroughly updated and expanded with, for example, new sections on ‘soft lithographic’ patterning, ‘click chemistry’ polymerization, nanotoxicity, graphene, as well as many biomaterials applications. The polymer and ‘soft’ materials chapter represents the largest expansion for the 2nd edition. Each ch...

  8. Atmospheric Chemistry and Air Pollution

    Directory of Open Access Journals (Sweden)

    Jeffrey S. Gaffney

    2003-01-01

    Full Text Available Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an overview of some of the basic photochemistry involved in the production of ozone and other oxidants in the atmosphere. Urban air quality issues are reviewed with a specific focus on ozone and other oxidants, primary and secondary aerosols, alternative fuels, and the potential for chlorine releases to amplify oxidant chemistry in industrial areas. Regional air pollution issues such as acid rain, long-range transport of aerosols and visibility loss, and the connections of aerosols to ozone and peroxyacetyl nitrate chemistry are examined. Finally, the potential impacts of air pollutants on the global-scale radiative balances of gases and aerosols are discussed briefly.

  9. Green Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Collison, Melanie

    2011-05-15

    Green chemistry is the science of chemistry used in a way that will not use or create hazardous substances. Dr. Rui Resendes is working in this field at GreenCentre Canada, an offshoot of PARTEQ Innovations in Kingston, Ontario. GreenCentre's preliminary findings suggest their licensed product {sup S}witchable Solutions{sup ,} featuring 3 classes of solvents and a surfactant, may be useful in bitumen oil sands extraction.

  10. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  11. Synthesis and characterization of biocatalytic γ-Fe2O3@SiO2 particles as recoverable bioreactors.

    Science.gov (United States)

    Vaz, A M; Serrano-Ruiz, D; Laurenti, M; Alonso-Cristobal, P; Lopez-Cabarcos, E; Rubio-Retama, J

    2014-02-01

    In this work, we present a suitable methodology to produce magnetically recoverable bioreactors based on enzymes, which are covalently attached on the surface of iron oxide@silica nanoparticles. In order to produce this system, iron oxide clusters with a mean diameter of 68 nm were covered with silica. This strategy yields spherical γ-Fe2O3@SiO2 cluster@shell nanoparticles with a mean diameter of 200 nm which present magnetic responsiveness and enhanced stability. The surface of these nanoparticles was modified into two steps with the aim to obtain carboxylic functional groups, which were activated to react with the enzyme glucose oxidase (GOx) that was thus immobilized on the surface of the nanoparticles. The objective of this chemistry at the nanoparticles interface is to produce magnetic-responsive bioreactors. The enzymatic activity was evaluated by using the recoverable bioreactors as part of an amperometric biosensor. These measurements allowed determining the stability, catalytic activity and the amount of enzyme immobilized on the surface of the nanoparticles. Furthermore, the functionalized nanoparticles can be recovered by applying an external magnetic field, which allows them to be employed in chemical processes where the recovery of the biocatalyst is important.

  12. Ni-doped (CeO{sub 2−δ})–YSZ mesoarchitectured with nanocrystalline framework: the effect of thermal treatment on structure, surface chemistry and catalytic properties in the partial oxidation of methane (CPOM)

    Energy Technology Data Exchange (ETDEWEB)

    Somacescu, Simona, E-mail: ssimona@icf.ro [Romanian Academy, “Ilie Murgulescu” Institute of Physical Chemistry (Romania); Florea, Mihaela [University of Bucharest, Department of Organic Chemistry, Biochemistry and Catalysis, Faculty of Chemistry (Romania); Osiceanu, Petre; Calderon-Moreno, Jose Maria [Romanian Academy, “Ilie Murgulescu” Institute of Physical Chemistry (Romania); Ghica, Corneliu [National Institute of Materials Physics (Romania); Serra, Jose Manuel [Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Científicas, Instituto de Tecnología Química (Spain)

    2015-11-15

    Ni-doped (CeO{sub 2−δ})–YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been synthesized by an original, facile and cheap approach based on Triton X100 nonionic surfactant as template and water as solvent at a strong basic pH value. Following the hydrothermal treatment under autogenous pressure (∼18 bars), Ni, Ce, Y, and Zr were well ordered as MA with nanocrystalline framework, assuring thermal stability. A comprehensive investigation of structure, texture, morphology, and surface chemistry was performed by means of a variety of complementary techniques (X-Ray Diffraction, XRD; Raman Spectroscopy, RS; Brunauer—Emmett—Teller, BET; Temperature—Programmed Reduction, TPR; Transmission Electron Microscopy, TEM and DF-STEM; X-ray Photoelectron Spectroscopy, XPS; Catalytic activity and selectivity). N{sub 2} sorption measurements highlighted that the mesoporous structure is formed at 600 °C and remains stable at 800 °C. At 900 °C, the MA collapses, favoring the formation of macropores. The XRD and Raman Spectroscopy of all samples showed the presence of a pure, single phase with fluorite-type structure. At 900 °C, an increased tetragonal distortion of the cubic lattice was observed. The surface chemistry probed by XPS exhibits a mixture of oxidation states (Ce{sup 3+} + Ce{sup 4+}) with high percentage of Ce{sup 3+} valence state ∼35 % and (Ni{sup 3+} and Ni{sup 2+}) oxidation states induced by the thermal treatment. These nanoparticles assembled into MA show high stability and selectivity over time in catalytic partial oxidation of methane (CPOM). These promising performances suggest an interesting prospect for introduction as anode within IT-SOFC assemblies.Graphical Abstract.

  13. Polymer Chemistry

    Science.gov (United States)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  14. An introduction to serious nuclear accident chemistry

    OpenAIRE

    Mark Russell St. John Foreman

    2015-01-01

    A review of the chemistry occurring inside a nuclear power plant during a serious reactor accident is presented. This includes some aspects of the behavior of nuclear fuel, its cladding, cesium and iodine. This review concentrates on the chemistry of an accident in a water-cooled reactor loaded with uranium dioxide or mixed metal oxide fuel.

  15. Visualizing Chemistry: Investigations for Teachers.

    Science.gov (United States)

    Ealy, Julie B.; Ealy, James L., Jr.

    This book contains 101 investigations for chemistry classrooms. Topics include: (1) Physical Properties; (2) Reactions of Some Elements; (3) Reactions Involving Gases; (4) Energy Changes; (5) Solutions and Solubility; (6) Transition Metals and Complex Ions; (7) Kinetics and Equilibrium; (8) Acids and Bases; (9) Oxidation-Reduction; (10)…

  16. Chemistry of high temperature superconductors

    CERN Document Server

    1991-01-01

    This review volume contains the most up-to-date articles on the chemical aspects of high temperature oxide superconductors. These articles are written by some of the leading scientists in the field and includes a comprehensive list of references. This is an essential volume for researchers working in the fields of ceramics, materials science and chemistry.

  17. Understanding the molecular-level chemistry of water plasmas and the effects of surface modification and deposition on a selection of oxide substrates

    Science.gov (United States)

    Trevino, Kristina J.

    2011-12-01

    This dissertation first examines electrical discharges used to study wastewater samples for contaminant detection and abatement. Two different water samples contaminated with differing concentrations of either methanol (MeOH) or methyl tert-butyl ether (MTBE) were used to follow breakdown mechanisms. Emission from CO* was used to monitor the contaminant and for molecular breakdown confirmation through actinometric OES as it can only arise from the carbon-based contaminant in either system. Detection was achieved at concentrations as low as 0.01 ppm, and molecular decomposition was seen at a variety of plasma parameters. This dissertation also explores the vibrational (thetaV), rotational (thetaR) and translational (thetaT) temperatures for a range of diatomic species in different plasma systems. For the majority of the plasma species studied, thetaV are much higher than thetaR and thetaT. This suggests that more energy is partitioned into the vibrational degrees of freedom in our plasmas. The thetaR reported are significantly lower in all the plasma systems studied and this is a result of radical equilibration to the plasma gas temperature. thetaT values show two characteristics; (1) they are less than the thetaV and higher than the theta R and (2) show varying trends with plasma parameters. Radical energetics were examined through comparison of thetaR, thetaT, and thetaV, yielding significant insight on the partitioning of internal and kinetic energies in plasmas. Correlations between energy partitioning results and corresponding radical surface scattering coefficients obtained using our imaging of radicals interacting with surfaces (IRIS) technique are also presented. Another aspect of plasma process chemistry, namely surface modification via plasma treatment, was investigated through characterization of metal oxides (SiOxNy, nat-SiO2, and dep-SiO2) following their exposure to a range of plasma discharges. Here, emphasis was placed on the surface wettability

  18. Systematic methodology for the development of biocatalytic hydrogen-borrowing cascades: application to the synthesis of chiral α-substituted carboxylic acids from α-substituted α,β-unsaturated aldehydes.

    Science.gov (United States)

    Knaus, Tanja; Mutti, Francesco G; Humphreys, Luke D; Turner, Nicholas J; Scrutton, Nigel S

    2015-01-07

    Ene-reductases (ERs) are flavin dependent enzymes that catalyze the asymmetric reduction of activated carbon-carbon double bonds. In particular, α,β-unsaturated carbonyl compounds (e.g. enals and enones) as well as nitroalkenes are rapidly reduced. Conversely, α,β-unsaturated esters are poorly accepted substrates whereas free carboxylic acids are not converted at all. The only exceptions are α,β-unsaturated diacids, diesters as well as esters bearing an electron-withdrawing group in α- or β-position. Here, we present an alternative approach that has a general applicability for directly obtaining diverse chiral α-substituted carboxylic acids. This approach combines two enzyme classes, namely ERs and aldehyde dehydrogenases (Ald-DHs), in a concurrent reductive-oxidative biocatalytic cascade. This strategy has several advantages as the starting material is an α-substituted α,β-unsaturated aldehyde, a class of compounds extremely reactive for the reduction of the alkene moiety. Furthermore no external hydride source from a sacrificial substrate (e.g. glucose, formate) is required since the hydride for the first reductive step is liberated in the second oxidative step. Such a process is defined as a hydrogen-borrowing cascade. This methodology has wide applicability as it was successfully applied to the synthesis of chiral substituted hydrocinnamic acids, aliphatic acids, heterocycles and even acetylated amino acids with elevated yield, chemo- and stereo-selectivity. A systematic methodology for optimizing the hydrogen-borrowing two-enzyme synthesis of α-chiral substituted carboxylic acids was developed. This systematic methodology has general applicability for the development of diverse hydrogen-borrowing processes that possess the highest atom efficiency and the lowest environmental impact.

  19. Biotechnological production of fucosylated human milk oligosaccharides: Prokaryotic fucosyltransferases and their use in biocatalytic cascades or whole cell conversion systems.

    Science.gov (United States)

    Petschacher, Barbara; Nidetzky, Bernd

    2016-10-10

    Human milk oligosaccharides (HMOs) constitute a class of complex carbohydrates unique to mother's milk and are strongly correlated to the health benefits of breastfeeding in infants. HMOs are important as functional ingredients of advanced infant formula and have attracted broad interest for use in health-related human nutrition. About 50% of the HMOs structures contain l-fucosyl residues, which are introduced into nascent oligosaccharides by enzymatic transfer from GDP-l-fucose. To overcome limitation in the current availability of fucosylated HMOs, biotechnological approaches for their production have been developed. Functional expression of the fucosyltransferase(s) and effective supply of GDP-l-fucose, respectively, are both bottlenecks of the biocatalytic routes of synthesis. Strategies of in vitro and in vivo production of fucosylated HMOs are reviewed here. Besides metabolic engineering for enhanced HMO production in whole cells, the focus is on the characteristics and the heterologous overexpression of prokaryotic α1,2- and α1,3/4-fucosyltransferases. Up to 20g/L of fucosylated HMOs were obtained in optimized production systems. Optimized expression enabled recovery of purified fucosyltransferases in a yield of up to 45mg/L culture for α1,2-fucosyltransferases and of up to 200mg protein/L culture for α1,3/4-fucosyltransferases.

  20. Separation of electron-transfer and coupled chemical reaction components of biocatalytic processes using Fourier transform ac voltammetry.

    Science.gov (United States)

    Fleming, Barry D; Zhang, Jie; Bond, Alan M; Bell, Stephen G; Wong, Luet-Lok

    2005-06-01

    The underlying electron-transfer and coupled chemical processes associated with biologically important catalytic reactions can be resolved using a combination of Fourier transform ac voltammetry with an analysis of the separated dc and ac components. This outcome can be achieved because the response associated with generation of the catalytic current is essentially confined to the steady-state dc component, whereas the electron-transfer step is dominant in the fundamental and higher harmonics. For the mediated oxidation of glucose with glucose oxidase, it was found that the underlying reversible redox chemistry of the mediator, ferrocenemonocarboxylic acid, as detected in the third and higher harmonics, was totally unaffected by introduction of the catalytic process. In contrast, for the catalytic reduction of molecular oxygen by cytochrome P450, slight changes in the P450 redox process were detected when the catalytic reaction was present. Simulations of a simple catalytic reaction scheme support the fidelity of this novel FT ac voltammetric approach for examining mechanistic nuances of catalytic forms of electrochemical reaction schemes.

  1. Computational chemistry

    Science.gov (United States)

    Arnold, J. O.

    1987-01-01

    With the advent of supercomputers, modern computational chemistry algorithms and codes, a powerful tool was created to help fill NASA's continuing need for information on the properties of matter in hostile or unusual environments. Computational resources provided under the National Aerodynamics Simulator (NAS) program were a cornerstone for recent advancements in this field. Properties of gases, materials, and their interactions can be determined from solutions of the governing equations. In the case of gases, for example, radiative transition probabilites per particle, bond-dissociation energies, and rates of simple chemical reactions can be determined computationally as reliably as from experiment. The data are proving to be quite valuable in providing inputs to real-gas flow simulation codes used to compute aerothermodynamic loads on NASA's aeroassist orbital transfer vehicles and a host of problems related to the National Aerospace Plane Program. Although more approximate, similar solutions can be obtained for ensembles of atoms simulating small particles of materials with and without the presence of gases. Computational chemistry has application in studying catalysis, properties of polymers, all of interest to various NASA missions, including those previously mentioned. In addition to discussing these applications of computational chemistry within NASA, the governing equations and the need for supercomputers for their solution is outlined.

  2. Plasma chemistry for inorganic materials

    Science.gov (United States)

    Matsumoto, O.

    1980-01-01

    Practical application of plasma chemistry to the development of inorganic materials using both low temperature and warm plasmas are summarized. Topics cover: the surface nitrification and oxidation of metals; chemical vapor deposition; formation of minute oxide particles; the composition of oxides from chloride vapor; the composition of carbides and nitrides; freezing high temperature phases by plasma arc welding and plasma jet; use of plasma in the development of a substitute for petroleum; the production of silicon for use in solar cell batteries; and insulating the inner surface of nuclear fusion reactor walls.

  3. BIOCATALYTIC METHODS IN THE SUNFLOWER BIODIESEL PRODUCTION BY Candida antarctica LIPASE

    Directory of Open Access Journals (Sweden)

    Maiara Priscilla de Souza

    2010-12-01

    Full Text Available The use of lipases in reactions of transformation of vegetable oil is against the principles of green chemistry, mainly because they are renewable and have a high efficiency and specificity in oleochemical reactions. Among the lipases studied stands out mainly Candida antarctica B (Novozym ® 435 and being marketed already immobilized in support of acrylic resin, has the advantage of being reused in the reactions. It was possible to optimize a system of transesterification by a continuous process, with which it was possible maximum conversion of substrate (sunflower oil in ethyl esters, and perform 87 cycles with the same enzyme without reducing the activity and 224 cycles, after the reduction of the activity. The system obtained are adequate to objectives and can be used in absence of organic solvent, it is only need the alcohol excess.

  4. Reaction Engineering of Biocatalytic Enantioselective Reduction: A Case Study for Aliphatic Ketones

    DEFF Research Database (Denmark)

    Leuchs, Susanne; Lima-Ramos, Joana; Greiner, Lasse

    2013-01-01

    Previously, it could be demonstrated, that the monophasic, enzymatic reduction of aliphatic 2-ketones into the corresponding (R)-2-alcohols is an adequate and viable method as carried out in a cascade of two enzyme–membrane reactors (Leuchs, S.; Na’amnieh, S. N.; Greiner, L. Green Chemistry 2013......, 15, 167–176.). In the present work, the process metrics of the ketone reduction were calculated. A cost analysis revealed that the enzyme costs are negligible, but the cost for nicotinamide cofactor NADP+ is dominating the overall cost of the chemical raw material followed by the ionic liquid (TEGO...... IL K5) used as solubiliser and the buffer. The overall cost of chemicals was €148/kgproduct. To assess the environmental impact of the process, the E-factor (kgwaste/kgproduct) 132 and the process mass intensity 133 (PMI, kgsubstrate/kgproduct) were calculated. A process model based on initial rate...

  5. The heterogeneous OH oxidation of palmitic acid in single component and internally mixed aerosol particles: vaporization, secondary chemistry, and the role of particle phase

    Directory of Open Access Journals (Sweden)

    V. F. McNeill

    2008-03-01

    Full Text Available We studied the OH oxidation of submicron aerosol particles consisting of pure palmitic acid (PA or thin (near monolayer coatings of PA on aqueous and effloresced inorganic salt particles. Experiments were performed as a function of particle size and OH exposure using a continuous-flow photochemical reaction chamber coupled to a chemical ionization mass spectrometer (CIMS system, for detection of gas and particle-bound organics, and a DMA/CPC for monitoring particle size distributions. The loss rate of PA observed for pure PA aerosols and PA on crystalline NaCl aerosols indicates that the OH oxidation of PA at the gas-aerosol interface is efficient. The pure PA oxidation data are well represented by a model consisting of four main processes: 1 surface-only reactions between OH and palmitic acid, 2 secondary reactions between palmitic acid and OH oxidation products, 3 volatilization of condensed-phase mass, and 4 a surface renewal process. Using this model we infer a value of γOH between 0.8 and 1. The oxidation of palmitic acid in thin film coatings of salt particles is also efficient, though the inferred γOH is lower, ranging from ~0.3 (+0.1/−0.05 for coatings on solid NaCl and ~0.05 (±0.01 on aqueous NaCl particles. These results, together with simultaneous data on particle size change and volatilized oxidation products, provide support for the ideas that oxidative aging of aliphatic organic aerosol is a source of small oxidized volatile organic compounds (OVOCs, and that OH oxidation may initiate secondary condensed-phase reactions.

  6. Beryllium chemistry and processing

    CERN Document Server

    Walsh, Kenneth A

    2009-01-01

    This book introduces beryllium; its history, its chemical, mechanical, and physical properties including nuclear properties. The 29 chapters include the mineralogy of beryllium and the preferred global sources of ore bodies. The identification and specifics of the industrial metallurgical processes used to form oxide from the ore and then metal from the oxide are thoroughly described. The special features of beryllium chemistry are introduced, including analytical chemical practices. Beryllium compounds of industrial interest are identified and discussed. Alloying, casting, powder processing, forming, metal removal, joining and other manufacturing processes are covered. The effect of composition and process on the mechanical and physical properties of beryllium alloys assists the reader in material selection. The physical metallurgy chapter brings conformity between chemical and physical metallurgical processing of beryllium, metal, alloys, and compounds. The environmental degradation of beryllium and its all...

  7. Atmospheric chemistry of 4 : 2 fluorotelomer alcohol (CF3(CF2)(3)CH2CH2OH): Products and mechanism of Cl atom initiated oxidation

    DEFF Research Database (Denmark)

    Hurley, MD; Ball, JC; Wallington, TJ;

    2004-01-01

    Smog chamber/FTIR techniques were used to study the products and mechanism of the Cl atom initiated oxidation of 4:2 fluorotelomer alcohol (CF3(CF2)(3)CH2CH2OH) in 700 Torr of N-2/O-2 diluent at 296 K. CF3(CF2)(3)CH2CHO is the sole primary oxidation product. CF3(CF2)(3)CHO, CF3(CF2)(3)CH2COOH, an...

  8. Accelerated growth of oxide film on aluminium alloys under steam: Part II: Effects of alloy chemistry and steam vapour pressure on corrosion and adhesion performance

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Bordo, Kirill; Jellesen, Morten Stendahl;

    2015-01-01

    The steam treatment of aluminium alloys with varying vapour pressure of steamresulted in the growth of aluminium oxyhydroxide films of thickness range between 450 - 825nm. The surface composition, corrosion resistance, and adhesion of the produced films was characterised by XPS, potentiodynamic...... of the vapour pressure of the steam. The accelerated corrosion and adhesion tests on steam generated oxide films with commercial powder coating verified that the performance of the oxide coating is highly dependent on the vapour pressure of the steam....

  9. Accelerated growth of oxide film on aluminium alloys under steam: Part I: Effects of alloy chemistry and steam vapour pressure on microstructure

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Gudla, Visweswara C.; Jellesen, Morten S.;

    2015-01-01

    at the top. The kinetics of formation of film understeamwas rapid; approx. 350nm thick layers were generated within 5 s of steam treatment, however increase in thickness of the oxide retarded further growth. The enrichment or depletion of different alloying elements at the surface of aluminium as a result...... of alkaline etching pre-treatment influenced the thickness and growth of theoxide. Moreover the steam treatment resulted in the partial oxidation of second phase intermetallic particles present in the aluminium alloy microstructure....

  10. Theoretical chemistry periodicities in chemistry and biology

    CERN Document Server

    Eyring, Henry

    1978-01-01

    Theoretical Chemistry: Periodicities in Chemistry and Biology, Volume 4 covers the aspects of theoretical chemistry. The book discusses the stably rotating patterns of reaction and diffusion; the chemistry of inorganic systems exhibiting nonmonotonic behavior; and population cycles. The text also describes the mathematical modeling of excitable media in neurobiology and chemistry; oscillating enzyme reactions; and oscillatory properties and excitability of the heart cell membrane. Selected topics from the theory of physico-chemical instabilities are also encompassed. Chemists, mechanical engin

  11. Alkene cleavage catalysed by heme and nonheme enzymes: reaction mechanisms and biocatalytic applications.

    Science.gov (United States)

    Mutti, Francesco G

    2012-01-01

    The oxidative cleavage of alkenes is classically performed by chemical methods, although they display several drawbacks. Ozonolysis requires harsh conditions (-78°C, for a safe process) and reducing reagents in a molar amount, whereas the use of poisonous heavy metals such as Cr, Os, or Ru as catalysts is additionally plagued by low yield and selectivity. Conversely, heme and nonheme enzymes can catalyse the oxidative alkene cleavage at ambient temperature and atmospheric pressure in an aqueous buffer, showing excellent chemo- and regioselectivities in certain cases. This paper focuses on the alkene cleavage catalysed by iron cofactor-dependent enzymes encompassing the reaction mechanisms (in case where it is known) and the application of these enzymes in biocatalysis.

  12. Oxidação do borneol à cânfora com água sanitária - um experimento simples, de baixo custo e limpo Oxidation of borneol to camphor with bleach: a simple, green chemistry and inexpensive experiment

    Directory of Open Access Journals (Sweden)

    Ana Paula Bernardo dos Santos

    2009-01-01

    Full Text Available Regulatory pressure is increasingly focusing on the use and disposal of substances hazardous to human health and environment. In the last years efforts have also been made to introduce green chemistry concepts in undergraduate courses. In this paper we present an experiment on the oxidation reaction of borneol to camphor with bleach in acetone. This experiment is important to show undergraduate students that a cheap and non hazardous commercial product can be a useful oxidation agent of alcohols.

  13. Biocatalytic route to chiral acyloins: P450-catalyzed regio- and enantioselective α-hydroxylation of ketones.

    Science.gov (United States)

    Agudo, Rubén; Roiban, Gheorghe-Doru; Lonsdale, Richard; Ilie, Adriana; Reetz, Manfred T

    2015-01-16

    P450-BM3 and mutants of this monooxygenase generated by directed evolution are excellent catalysts for the oxidative α-hydroxylation of ketones with formation of chiral acyloins with high regioselectivity (up to 99%) and enantioselectivity (up to 99% ee). This constitutes a new route to a class of chiral compounds that are useful intermediates in the synthesis of many kinds of biologically active compounds.

  14. Drastic changes of electronic structure and crystal chemistry upon oxidation of SnII2TiO4E2 into SnIV2TiO6: An ab initio study

    Science.gov (United States)

    Matar, Samir F.; Maglione, Mario; Nakhl, Michel; Kfoury, Charbel N.; Etourneau, Jean

    2016-09-01

    From DFT based calculations establishing energy-volume equations of state and electron localization mapping, the electronic structure and crystal chemistry changes from Sn2TiO4 to Sn2TiO6 by oxidation are rationalized; the key effect being the destabilization of divalent tin SnII towards tetravalent state SnIV leading to rutile Sn2TiO6 as experimentally observed. The subsequent electronic structure change is highlighted in the relative change of the electronic band gap which increases from ∼1 eV up to 2.2 eV and the 1.5 times increase of the bulk modulus assigned to the change from covalently SnII based compound to the more ionic SnIV one. Such trends are also confronted with the relevant properties of black SnIIO.

  15. PEROXYNITRITE CHEMISTRY

    Energy Technology Data Exchange (ETDEWEB)

    Lymar, S.V.

    2000-11-29

    This century old area of research has been experiencing a renaissance during the last decade, with the annual number of publications on the subject increasing from only one in 1990 to nearly 200 in the late-1990s. This renewed interest is stimulated by the discovery of biological roles of nitric oxide, distinguished by the 1998 Nobel prize, and the recognition that the conversion of nitric oxide into peroxynitrite may play major roles in human diseases associated with oxidative stress and in cellular defense against invading pathogens. Peroxynitrite (ONOO{sup {minus}})is a structural isomer of nitrate (NO{sub 3}{sup {minus}}) that contains a peroxo bond. The physiological route to ONOO{sup {minus}} is provided by the combination of nitric oxide ({center_dot}NO) with superoxide ({center_dot}O{sub 2}{sup {minus}}), an extremely rapid reaction occurring upon every encounter of these radicals (the upper dot denotes radical species). Both {center_dot}NO and {center_dot}O{sub 2}{sup {minus}} are the oxygen metabolic products simultaneously generated in a number of cell types within a human body. Compared to its precursors, peroxynitrite is a much stronger oxidant capable of oxidizing proteins, nucleic acids, and lipids.

  16. A coordination chemistry study of hydrated and solvated cationic vanadium ions in oxidation states +III, +IV, and +V in solution and solid state

    OpenAIRE

    Krakowiak, Joanna; Lundberg, Daniel; Persson, Ingmar

    2012-01-01

    The coordination chemistry of hydrated and solvated vanadium(III), oxovanadium(IV), and dioxovanadium(V) ions in the oxygen donor solvents water, dimethylsulfoxide (dmso) and N,N′-dimethylpropyleneurea (dmpu) has been studied in solution by EXAFS and large angle X-ray scattering (LAXS) and in solid state by single crystal X-ray diffraction and EXAFS. The hydrated vanadium(III) ion has a regular octahedral configuration with a mean V-O bond distance of 1.99 Å. In the hydrated and dimethylsulfo...

  17. Effect of the chemistry and structure of the native oxide surface film on the corrosion properties of commercial AZ31 and AZ61 alloys

    Energy Technology Data Exchange (ETDEWEB)

    Feliu, Sebastian, E-mail: sfeliu@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Maffiotte, C. [CIEMAT-DT edificio 30, Avda. Complutense, 22, 28040 Madrid (Spain); Samaniego, A.; Galvan, Juan Carlos [Centro Nacional de Investigaciones Metalurgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Barranco, Violeta [Centro Nacional de Investigaciones Metalurgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Instituto de Ciencias de Materiales de Madrid, ICMM, Consejo Superior de Investigaciones Cientificas, CSIC, Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain)

    2011-08-01

    The purpose of this study has been to advance in knowledge of the chemical composition, structure and thickness of the thin native oxide film formed spontaneously in contact with the laboratory atmosphere on the surface of freshly polished commercial AZ31 and AZ61 alloys with a view to furthering the understanding of protection mechanisms. For comparative purposes, and to more fully describe the behaviour of the native oxide film, the external oxide films formed as a result of the manufacturing process (as-received condition) have been characterised. The technique applied in this research to study the thin oxide films (thickness of just a few nanometres) present on the surface of the alloys has basically been XPS (X-ray photoelectron spectroscopy) in combination with ion sputtering. Corrosion properties of the alloys were studied in 0.6 M NaCl by measuring charge transfer resistance values, which are deduced from EIS (electrochemical impedance spectroscopy) measurements after 1 h of exposure. Alloy AZ61 generally showed better corrosion resistance than AZ31, and the freshly polished alloys showed better corrosion resistance than the alloys in as-received condition. This is attributed to a combination of (1) higher thickness of the native oxide film on the AZ61 alloy and (2) greater uniformity of the oxide film in the polished condition. The formation of an additional oxide layer composed by a mixture of spinel (MgAl{sub 2}O{sub 4}) and MgO seems to diminish the protective properties of the passive layer on the surface of the alloys in as-received condition.

  18. Surface chemistry

    CERN Document Server

    Desai, KR

    2008-01-01

    The surface Chemistry of a material as a whole is crucially dependent upon the Nature and type of surfaces exposed on crystallites. It is therefore vitally important to independently Study different, well - defined surfaces through surface analytical techniques. In addition to composition and structure of surface, the subject also provides information on dynamic light scattering, micro emulsions, colloid Stability control and nanostructures. The present book endeavour to bring before the reader that the understanding and exploitation of Solid state phenomena depended largely on the ability to

  19. Energy, atmospheric chemistry, and global climate

    Science.gov (United States)

    Levine, Joel S.

    1991-01-01

    Global atmospheric changes due to ozone destruction and the greenhouse effect are discussed. The work of the Intergovernmental Panel on Climate Change is reviewed, including its judgements regarding global warming and its recommendations for improving predictive capability. The chemistry of ozone destruction and the global atmospheric budget of nitrous oxide are reviewed, and the global sources of nitrous oxide are described.

  20. Layer by layer assembly of a biocatalytic packaging film: lactase covalently bound to low-density polyethylene.

    Science.gov (United States)

    Wong, Dana E; Talbert, Joey N; Goddard, Julie M

    2013-06-01

    Active packaging is utilized to overcome limitations of traditional processing to enhance the health, safety, economics, and shelf life of foods. Active packaging employs active components to interact with food constituents to give a desired effect. Herein we describe the development of an active package in which lactase is covalently attached to low-density polyethylene (LDPE) for in-package production of lactose-free dairy products. The specific goal of this work is to increase the total protein content loading onto LDPE using layer by layer (LbL) deposition, alternating polyethylenimine, glutaraldehyde (GL), and lactase, to enhance the overall activity of covalently attached lactase. The films were successfully oxidized via ultraviolet light, functionalized with polyethylenimine and glutaraldehyde, and layered with immobilized purified lactase. The total protein content increased with each additional layer of conjugated lactase, the 5-layer sample reaching up to 1.3 μg/cm2 . However, the increase in total protein did not lend to an increase in overall lactase activity. Calculated apparent Km indicated the affinity of immobilized lactase to substrate remains unchanged when compared to free lactase. Calculated apparent turnover numbers (kcat ) showed with each layer of attached lactase, a decrease in substrate turnover was experienced when compared to free lactase; with a decrease from 128.43 to 4.76 s(-1) for a 5-layer conjugation. Our results indicate that while LbL attachment of lactase to LDPE successfully increases total protein mass of the bulk material, the adverse impact in enzyme efficiency may limit the application of LbL immobilization chemistry for bioactive packaging use.

  1. A coordination chemistry study of hydrated and solvated cationic vanadium ions in oxidation states +III, +IV, and +V in solution and solid state.

    Science.gov (United States)

    Krakowiak, Joanna; Lundberg, Daniel; Persson, Ingmar

    2012-09-17

    The coordination chemistry of hydrated and solvated vanadium(III), oxovanadium(IV), and dioxovanadium(V) ions in the oxygen-donor solvents water, dimethyl sulfoxide (DMSO), and N,N'-dimethylpropyleneurea (DMPU) has been studied in solution by extended X-ray absorption fine structure (EXAFS) and large-angle X-ray scattering (LAXS) and in the solid state by single-crystal X-ray diffraction and EXAFS. The hydrated vanadium(III) ion has a regular octahedral configuration with a mean V-O bond distance of 1.99 Å. In the hydrated and DMSO-solvated oxovanadium(IV) ions, vanadium binds strongly to an oxo group at ca. 1.6 Å. The solvent molecule trans to the oxo group is very weakly bound, at ca. 2.2 Å, while the remaining four solvent molecules, with a mean V-O bond distance of 2.0 Å, form a plane slightly below the vanadium atom; the mean O═V-O(perp) bond angle is ca. 98°. In the DMPU-solvated oxovanadium(IV) ion, the space-demanding properties of the DMPU molecule leave no solvent molecule in the trans position to the oxo group, which reduces the coordination number to 5. The O═V-O bond angle is consequently much larger, 107°, and the mean V═O and V-O bond distances decrease to 1.58 and 1.97 Å, respectively. The hydrated and DMSO-solvated dioxovanadium(V) ions display a very distorted octahedral configuration with the oxo groups in the cis position with a mean V═O bond distance of 1.6 Å and a O═V═O bond angle of ca. 105°. The solvent molecules trans to the oxo groups are weakly bound, at ca. 2.2 Å, while the remaining two have bond distances of 2.02 Å. The experimental studies of the coordination chemistry of hydrated and solvated vanadium(III,IV,V) ions are complemented by summarizing previously reported crystal structures to yield a comprehensive description of the coordination chemistry of vanadium with oxygen-donor ligands.

  2. Chemistry of 4-membered cyclic nitrones (2, 3-dihydroazete 1-oxides); a novel one-step synthesis of N-acetoxy β-latams

    NARCIS (Netherlands)

    Pennings, M.L.M.; Reinhoudt, D.N.

    1981-01-01

    2,3-dihydroazete 1-oxide 1 reacts at room temperature with base, acid and lead tetraacetate to give the 5-hydroxyisoxazolidines 4a and 4b , the 6H-1,2-oxazin-6-one 7 and the N-acetoxy β-lactam 8, respectively; the reaction with lead tetraacetate represents a simple one-step conversion of a 4-membere

  3. Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB: oxidation of oleic acid by ozone

    Directory of Open Access Journals (Sweden)

    C. Pfrang

    2010-05-01

    Full Text Available We present a kinetic double layer model coupling aerosol surface and bulk chemistry (K2-SUB based on the PRA framework of gas-particle interactions (Pöschl-Rudich-Ammann, 2007. K2-SUB is applied to a popular model system of atmospheric heterogeneous chemistry: the interaction of ozone with oleic acid. We show that our modelling approach allows de-convoluting surface and bulk processes, which has been a controversial topic and remains an important challenge for the understanding and description of atmospheric aerosol transformation. In particular, we demonstrate how a detailed treatment of adsorption and reaction at the surface can be coupled to a description of bulk reaction and transport that is consistent with traditional resistor model formulations.

    From literature data we have derived a consistent set of kinetic parameters that characterise mass transport and chemical reaction of ozone at the surface and in the bulk of oleic acid droplets. Due to the wide range of rate coefficients reported from different experimental studies, the exact proportions between surface and bulk reaction rates remain uncertain. Nevertheless, the model results suggest an important role of chemical reaction in the bulk and an approximate upper limit of ~10−11 cm2 s−1 for the surface reaction rate coefficient. Sensitivity studies show that the surface accommodation coefficient of the gas-phase reactant has a strong non-linear influence on both surface and bulk chemical reactions. We suggest that K2-SUB may be used to design, interpret and analyse future experiments for better discrimination between surface and bulk processes in the oleic acid-ozone system as well as in other heterogeneous reaction systems of atmospheric relevance.

  4. Science Update: Inorganic Chemistry

    Science.gov (United States)

    Rawls, Rebecca

    1978-01-01

    This first in a series of articles describing the state of the art of various branches of chemistry reviews inorganic chemistry, including bioinorganic, photochemistry, organometallic, and solid state chemistries. (SL)

  5. Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids.

    Science.gov (United States)

    Schrittwieser, Joerg H; Resch, Verena; Wallner, Silvia; Lienhart, Wolf-Dieter; Sattler, Johann H; Resch, Jasmin; Macheroux, Peter; Kroutil, Wolfgang

    2011-08-19

    A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.

  6. Biocatalytic Organic Synthesis of Optically Pure (S)-Scoulerine and Berbine and Benzylisoquinoline Alkaloids

    Science.gov (United States)

    2011-01-01

    A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C–C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4–8 linear steps using either a Bischler–Napieralski cyclization or a C1–Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5–9 linear steps. PMID:21739961

  7. Astronomical chemistry.

    Science.gov (United States)

    Klemperer, William

    2011-01-01

    The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

  8. Combustion chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

  9. Environmental chemistry. Seventh edition

    Energy Technology Data Exchange (ETDEWEB)

    Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

    1999-11-01

    This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

  10. Purification of CYP2B-like protein from feral leaping mullet (Liza saliens) liver microsomes and its biocatalytic, molecular, and immunological characterization.

    Science.gov (United States)

    Bozcaarmutlu, Azra; Arinç, Emel

    2008-01-01

    In this study, CYP2B-immunoreactive protein was purified to electrophoretic homogeneity from the liver microsomes of leaping mullet. The purified cytochrome P450 (CYP) gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis having a M(r) of 49,300 Da. Absolute absorption spectrum of the purified CYP showed a maximum at 417 nm and CO-difference spectrum of dithionite-reduced cytochrome P450 gave a peak at 450 nm. The purified CYP was found to be active in N-demethylation of benzphetamine, erythromycin, and ethylmorphine, and O-dealkylation of pentoxyresorufin in the reconstituted system. However, it was unable to catalyze O-dealkylation of ethoxyresorufin, methoxyresorufin, benzyloxyresorufin, and hydroxylation of lauric acid and aniline. The purified CYP showed strong cross-reactivity with anti-sheep lung CYP2B, a homologue of CYP2B4. N-terminal amino acid sequence of the mullet P450 had the highest degree of homology with CYP2Bs among the known CYPs. Spectral, electrophoretic, immunochemical, N-terminal amino acid sequence, and biocatalytic properties of the purified CYP are most similar to those of mammalian cytochrome P4502B. All these data indicate that the purified CYP is certainly 2B-like. In this study, we not only purified biocatalytically active CYP2B-like protein from fish, but also demonstrated detailed functional properties of CYP2B-like protein for the first time.

  11. Advanced Chemistry Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Description/History: Chemistry laboratory The Advanced Chemistry Laboratory (ACL) is a unique facility designed for working with the most super toxic compounds known...

  12. Science Update: Inorganic Chemistry.

    Science.gov (United States)

    Rawls, Rebecca

    1981-01-01

    Describes areas of inorganic chemistry which have changed dramatically in the past year or two, including photochemistry, electrochemistry, organometallic complexes, inorganic reaction theory, and solid state chemistry. (DS)

  13. Organic chemistry on solid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhen; Zaera, Francisco [Department of Chemistry, University of California, Riverside, CA 92521 (United States)

    2006-07-15

    Chemistry on solid surfaces is central to many areas of practical interest such as heterogeneous catalysis, tribology, electrochemistry, and materials processing. With the development of many surface-sensitive analytical techniques in the past decades, great advances have been possible in our understanding of such surface chemistry at the molecular level. Earlier studies with model systems, single crystals in particular, have provided rich information about the adsorption and reaction kinetics of simple inorganic molecules. More recently, the same approach has been expanded to the study of the surface chemistry of relatively complex organic molecules, in large measure in connection with the selective synthesis of fine chemicals and pharmaceuticals. In this report, the chemical reactions of organic molecules and fragments on solid surfaces, mainly on single crystals of metals but also on crystals of metal oxides, carbides, nitrides, phosphides, sulfides and semiconductors as well as on more complex models such as bimetallics, alloys, and supported particles, are reviewed. A scheme borrowed from the organometallic and organic chemistry literature is followed in which key examples of representative reactions are cited first, and general reactivity trends in terms of both the reactants and the nature of the surface are then identified to highlight important mechanistic details. An attempt has been made to emphasize recent advances, but key earlier examples are cited as needed. Finally, correlations between surface and organometallic and organic chemistry, the relevance of surface reactions to applied catalysis and materials functionalization, and some promising future directions in this area are briefly discussed. (author)

  14. Development and Parametric Evaluation of a Tabulated Chemistry Tool for the Simulation of n-Heptane Low-Temperature Oxidation and Autoignition Phenomena

    OpenAIRE

    George Vourliotakis; Dionysios I. Kolaitis; Founti, Maria A.

    2014-01-01

    Accurate modelling of preignition chemical phenomena requires a detailed description of the respective low-temperature oxidative reactions. Motivated by the need to simulate a diesel oil spray evaporation device operating in the “stabilized” cool flame regime, a “tabulated chemistry” tool is formulated and evaluated. The tool is constructed by performing a large number of kinetic simulations, using the perfectly stirred reactor assumption. n-Heptane is used as a surrogate fuel for diesel oil ...

  15. Structure and chemistry of the heteronuclear oxo-cluster [VPO4]•+: a model system for the gas-phase oxidation of small hydrocarbons.

    Science.gov (United States)

    Dietl, Nicolas; Wende, Torsten; Chen, Kai; Jiang, Ling; Schlangen, Maria; Zhang, Xinhao; Asmis, Knut R; Schwarz, Helmut

    2013-03-06

    The heteronuclear oxo-cluster [VPO4](•+) is generated via electrospray ionization and investigated with respect to both its electronic structure as well as its gas-phase reactivity toward small hydrocarbons, thus permitting a comparison to the well-known vanadium-oxide cation [V2O4](•+). As described in previous studies, the latter oxide exhibits no or just minor reactivity toward small hydrocarbons, such as CH4, C2H6, C3H8, n-C4H10, and C2H4, while substitution of one vanadium by a phosphorus atom yields the reactive [VPO4](•+) ion; the latter brings about oxidative dehydrogenation (ODH) of saturated hydrocarbons, e.g., propane and butane as well as oxygen-atom transfer (OAT) to unsaturated hydrocarbons, e.g. ethene, at thermal conditions. Further, the gas-phase structure of [VPO4](•+) is determined by IR photodissociation spectroscopy and compared to that of [V2O4](•+). DFT calculations help to elucidate the reaction mechanism. The results underline the crucial role of phosphorus in terms of C-H bond activation of hydrocarbons by mixed VPO clusters.

  16. Thimerosal-Derived Ethylmercury Is a Mitochondrial Toxin in Human Astrocytes: Possible Role of Fenton Chemistry in the Oxidation and Breakage of mtDNA

    Directory of Open Access Journals (Sweden)

    Martyn A. Sharpe

    2012-01-01

    Full Text Available Thimerosal generates ethylmercury in aqueous solution and is widely used as preservative. We have investigated the toxicology of Thimerosal in normal human astrocytes, paying particular attention to mitochondrial function and the generation of specific oxidants. We find that ethylmercury not only inhibits mitochondrial respiration leading to a drop in the steady state membrane potential, but also concurrent with these phenomena increases the formation of superoxide, hydrogen peroxide, and Fenton/Haber-Weiss generated hydroxyl radical. These oxidants increase the levels of cellular aldehyde/ketones. Additionally, we find a five-fold increase in the levels of oxidant damaged mitochondrial DNA bases and increases in the levels of mtDNA nicks and blunt-ended breaks. Highly damaged mitochondria are characterized by having very low membrane potentials, increased superoxide/hydrogen peroxide production, and extensively damaged mtDNA and proteins. These mitochondria appear to have undergone a permeability transition, an observation supported by the five-fold increase in Caspase-3 activity observed after Thimerosal treatment.

  17. Isotope modeling of nitric acid formation in the atmosphere using ISO-RACM: testing the importance of NO oxidation, heterogeneous reactions, and trace gas chemistry

    Directory of Open Access Journals (Sweden)

    G. Michalski

    2010-03-01

    Full Text Available Here we present ISO-RACM, an isotope mass balance model that utilizes the Regional Atmospheric Chemistry Mechanism to predict Δ17O values in atmospheric nitrate. A large number of simulations were carried out that varied atmospheric parameters that are important in altering the magnitude and range of Δ17O values generated in photochemically produce nitrate. These parameters included temperature, relative humidity, actinic flux, aerosol surface area and chemical speciation, and three different N2O5 uptake parameterizations. Trace gas mixing ratios were also varied including CH4, CO, NOx, O3, volatile organic compounds and biogenic organic compounds. The model predicts that there are seasonal, latitudinal and diurnal variations in Δ17O values due to changes in actinic flux with lower values corresponding to higher actinic fluxes. There was also a minor positive correlation between higher Δ17O values and increased temperature. There were distinct differences in Δ17O depending on which N2O5 parameterization was used, mostly the result of changing relative humidity being a factor in two of the parameterization schemes. Changing CO and CH4 mixing ratios had negligible impact on Δ17O values but significant variation in magnitude and range were predicted with NOx, O3, and organic loading. High NOx and O3 generated high Δ17O with a narrow (10 ‰ range, while high organics led to low Δ17O values and a wider range of possible values. Implications for using Δ17O to evaluate NOx-NOy chemistry and aerosol formation processes are discussed, as is needed future research.

  18. Biocatalytically Oligomerized Epicatechin with Potent and Specific Anti-proliferative Activity for Human Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Ramaswamy Nagarajan

    2008-11-01

    Full Text Available Catechins, naturally occurring flavonoids derived from wine and green tea, are known to exhibit multiple health benefits. Epigallocatechin gallate (EGCG is one of the most widely investigated catechins, but its efficacy in cancer therapy is still inconsistent and limited. The poor stability of EGCG has contributed to the disparity in the reported anti-cancer activity and other beneficial properties. Here we report an innovative enzymatic strategy for the oligomerization of catechins (specifically epicatechin that yields stable, water-soluble oligomerized epicatechins with enhanced and highly specific anti-proliferative activity for human breast cancer cells. This one-pot oxidative oligomerization is carried out in ambient conditions using Horseradish Peroxidase (HRP as a catalyst yielding water-soluble oligo(epicatechins. The oligomerized epicatechins obtained exhibit excellent growth inhibitory effects against human breast cancer cells with greater specificity towards growth-inhibiting cancer cells as opposed to normal cells, achieving a high therapeutic differential. Our studies indicate that water-soluble oligomeric epicatechins surpass EGCG in stability, selectivity and efficacy at lower doses.

  19. Biocatalytic carboxylation of phenol derivatives: kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis.

    Science.gov (United States)

    Pesci, Lorenzo; Glueck, Silvia M; Gurikov, Pavel; Smirnova, Irina; Faber, Kurt; Liese, Andreas

    2015-04-01

    Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (K(m), V(max)) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes.

  20. Biocatalysis--key to sustainable industrial chemistry.

    Science.gov (United States)

    Wohlgemuth, Roland

    2010-12-01

    The ongoing trends to process improvements, cost reductions and increasing quality, safety, health and environment requirements of industrial chemical transformations have strengthened the translation of global biocatalysis research work into industrial applications. One focus has been on biocatalytic single-step reactions with one or two substrates, the identification of bottlenecks and molecular as well as engineering approaches to overcome these bottlenecks. Robust industrial procedures have been established along classes of biocatalytic single-step reactions. Multi-step reactions and multi-component reactions (MCRs) enable a bottom-up approach with biocatalytic reactions working together in one compartment and recations hindering each other within different compartments or steps. The understanding of the catalytic functions of known and new enzymes is key for the development of new sustainable chemical transformations.

  1. Prebiotic phosphorus chemistry reconsidered

    Science.gov (United States)

    Schwartz, A. W.; Orgel, L. E. (Principal Investigator)

    1997-01-01

    The available evidence indicates that the origin of life on Earth certainly occurred earlier than 3.5 billion years ago and perhaps substantially earlier. The time available for the chemical evolution which must have preceded this event is more difficult to estimate. Both endogenic and exogenic contributions to chemical evolution have been considered; i.e., from chemical reactions in a primitive atmosphere, or by introduction in the interiors of comets and/or meteorites. It is argued, however, that the phosphorus chemistry of Earth's earliest hydrosphere, whether primarily exogenic or endogenic in origin, was most likely dominated by compounds less oxidized than phosphoric acid and its esters. A scenario is presented for the early production of a suite of reactive phosphonic acid derivatives, the properties of which may have foreshadowed the later appearance of biophosphates.

  2. Reactive oxygen species at the oxide/water interface: Formation mechanisms and implications for prebiotic chemistry and the origin of life

    Science.gov (United States)

    Xu, Jie; Sahai, Nita; Eggleston, Carrick M.; Schoonen, Martin A. A.

    2013-02-01

    The goal of our study is to identify free radical formation pathways on mineral surfaces. Organic molecules on early Earth might have been modified or decomposed by such pathways, thus affecting the total organic inventory for prebiotic synthesis reactions. Specifically, we evaluated several common oxide minerals under a range of environmental conditions and combinations of conditions (pH, O2 level, UV-wavelength, and particle loading), for formation of highly reactive oxygen species (ROS) at the oxide surfaces by quantifying the generated [OHrad ] and [H2O2]. We identified anatase/rutile (β-TiO2/α-TiO2) and hematite (α-Fe2O3) as active in ROS production and, importantly, found different dominant pathways for ROS formation on anatase/rutile versus hematite. Hydroxyl radicals (OHrad ) in anatase and rutile suspensions were generated mainly through the oxidation of OH- by photo-generated holes and H2O2 was generated through the combination of an OHrad radical with an OH- and a hole. This pathway for the TiO2 phases did not require the presence of O2, and was not shut down under anaerobic conditions. In contrast, formation of H2O2 and OHrad in hematite suspensions involved reduction of O2 by electrons, which was inhibited under anaerobic conditions. The surface ROS as well as free radicals formed by reactions with other gases on early Earth atmosphere were capable of destroying molecules such as lipids and pre-RNA or RNA essential to assembly of protocells and survival of the earliest cells. At the same time, surface associated ROS and other free radicals may also have promoted aminoamide formation. Thus, the surface ROS would have affected prebiotic organic compound inventory and protocell/early life evolution.

  3. Degradation of the beta-blocker propranolol by electrochemical advanced oxidation processes based on Fenton's reaction chemistry using a boron-doped diamond anode

    Energy Technology Data Exchange (ETDEWEB)

    Isarain-Chavez, Eloy; Rodriguez, Rosa Maria; Garrido, Jose Antonio; Arias, Conchita; Centellas, Francesc; Cabot, Pere Lluis [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Brillas, Enric, E-mail: brillas@ub.ed [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

    2010-12-15

    The electro-Fenton (EF) and photoelectro-Fenton (PEF) degradation of solutions of the beta-blocker propranolol hydrochloride with 0.5 mmol dm{sup -3} Fe{sup 2+} at pH 3.0 has been studied using a single cell with a boron-doped diamond (BDD) anode and an air diffusion cathode (ADE) for H{sub 2}O{sub 2} electrogeneration and a combined cell containing the above BDD/ADE pair coupled in parallel to a Pt/carbon felt (CF) cell. This naphthalene derivative can be mineralized by both methods with a BDD anode. Almost overall mineralization is attained for the PEF treatments, more rapidly with the combined system due to the generation of higher amounts of hydroxyl radical from Fenton's reaction by the continuous Fe{sup 2+} regeneration at the CF cathode, accelerating the oxidation of organics to Fe(III)-carboxylate complexes that are more quickly photolyzed by UVA light. The homologous EF processes are less potent giving partial mineralization. The effect of current density, pH and Fe{sup 2+} and drug concentrations on the oxidation power of PEF process in combined cell is examined. Propranolol decay follows a pseudo first-order reaction in most cases. Aromatic intermediates such as 1-naphthol and phthalic acid and generated carboxylic acids such as maleic, formic, oxalic and oxamic are detected and quantified by high-performance liquid chromatography. The chloride ions present in the starting solution are slowly oxidized at the BDD anode. In PEF treatments, all initial N of propranolol is completely transformed into inorganic ions, with predominance of NH{sub 4}{sup +} over NO{sub 3}{sup -} ion.

  4. Alcohol Selectivity in a Synthetic Thermophilic n-Butanol Pathway Is Driven by Biocatalytic and Thermostability Characteristics of Constituent Enzymes

    Science.gov (United States)

    Loder, Andrew J.; Zeldes, Benjamin M.; Garrison, G. Dale; Lipscomb, Gina L.; Adams, Michael W. W.

    2015-01-01

    n-Butanol is generated as a natural product of metabolism by several microorganisms, but almost all grow at mesophilic temperatures. A synthetic pathway for n-butanol production from acetyl coenzyme A (acetyl-CoA) that functioned at 70°C was assembled in vitro from enzymes recruited from thermophilic bacteria to inform efforts for engineering butanol production into thermophilic hosts. Recombinant versions of eight thermophilic enzymes (β-ketothiolase [Thl], 3-hydroxybutyryl-CoA dehydrogenase [Hbd], and 3-hydroxybutyryl-CoA dehydratase [Crt] from Caldanaerobacter subterraneus subsp. tengcongensis; trans-2-enoyl-CoA reductase [Ter] from Spirochaeta thermophila; bifunctional acetaldehyde dehydrogenase/alcohol dehydrogenase [AdhE] from Clostridium thermocellum; and AdhE, aldehyde dehydrogenase [Bad], and butanol dehydrogenase [Bdh] from Thermoanaerobacter sp. strain X514) were utilized to examine three possible pathways for n-butanol. These pathways differed in the two steps required to convert butyryl-CoA to n-butanol: Thl-Hbd-Crt-Ter-AdhE (C. thermocellum), Thl-Hbd-Crt-Ter-AdhE (Thermoanaerobacter X514), and Thl-Hbd-Crt-Ter-Bad-Bdh. n-Butanol was produced at 70°C, but with different amounts of ethanol as a coproduct, because of the broad substrate specificities of AdhE, Bad, and Bdh. A reaction kinetics model, validated via comparison to in vitro experiments, was used to determine relative enzyme ratios needed to maximize n-butanol production. By using large relative amounts of Thl and Hbd and small amounts of Bad and Bdh, >70% conversion to n-butanol was observed in vitro, but with a 60% decrease in the predicted pathway flux. With more-selective hypothetical versions of Bad and Bdh, >70% conversion to n-butanol is predicted, with a 19% increase in pathway flux. Thus, more-selective thermophilic versions of Bad, Bdh, and AdhE are needed to fully exploit biocatalytic n-butanol production at elevated temperatures. PMID:26253677

  5. The combustion chemistry of a fuel tracer: Measured flame speeds and ignition delays and a detailed chemical kinetic model for the oxidation of acetone

    Energy Technology Data Exchange (ETDEWEB)

    Pichon, S.; Black, G.; Simmie, J.M.; Curran, H.J. [Combustion Chemistry Centre, National University of Ireland, Galway (Ireland); Chaumeix, N.; Yahyaoui, M. [Institut de Combustion Aerothermique Reactivite et Environnement, CNRS, Orleans (France); Donohue, R. [Information Technology, National University of Ireland, Galway (Ireland)

    2009-02-15

    Acetone ignition delay and stretch-free laminar flame speed measurements have been carried out and a kinetic model has been developed to simulate these and literature data for acetone and for ketene, which was found to be an important intermediate in its oxidation. The mechanism has been based on one originally devised for dimethyl ether and modified through validation of the hydrogen, carbon monoxide and methane sub-mechanisms. Acetone oxidation in argon was studied behind reflected shock waves in the temperature range 1340-1930 K, at 1 atm and at equivalence ratios of 0.5, 1 and 2; it is also shown that the addition of up to 15% acetone to a stoichiometric n-heptane mixture has no effect on the measured ignition delay times. Flame speeds at 298 K and 1 atm of pure acetone in air were measured in a spherical bomb; a maximum flame speed of {proportional_to}35 cm s{sup -1} at {phi}=1.15 is indicated. (author)

  6. Effect of ethylene glycol bis (propionitrile) ether (EGBE) on the performance and interfacial chemistry of lithium-rich layered oxide cathode

    Science.gov (United States)

    Hong, Pengbo; Xu, Mengqing; Zheng, Xiongwen; Zhu, Yunmin; Liao, Youhao; Xing, Lidan; Huang, Qiming; Wan, Huaping; Yang, Yongjun; Li, Weishan

    2016-10-01

    Ethylene glycol bis (propionitrile) ether (EGBE) is used as an electrolyte additive to improve the cycling stability and rate capability of Li/Li1.2Mn0.54Ni0.13Co0.13O2 cells at high operating voltage (4.8 V). After 150 cycles, cells with 1.0 wt% of EGBE containing electrolyte have remarkable cycling performance, 89.0% capacity retention; while the cells with baseline electrolyte only remain 67.4% capacity retention. Linear sweep voltammetry (LSV) and computation results demonstrate that EGBE preferably oxidizes on the cathode surface compared to the LiPF6/carbonate electrolyte. In order to further understand the effects of EGBE on Li1.2Mn0.54Ni0.13Co0.13O2 cathode upon cycling at high voltage, electrochemical behaviors and ex-situ surface analysis of Li1.2Mn0.54Ni0.13Co0.13O2 are investigated via electrochemical impedance spectroscopy (EIS), scanning electron spectroscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and inductive coupled plasma spectroscopy (ICP-MS). The improved cycling performance can be attributed to more stable and robust surface layer yield via incorporation of EGBE, which mitigates the oxidation of electrolyte on the cathode electrode, and also inhibits the dissolution of bulk transition metal ions as well upon cycling at high voltage.

  7. Atmospheric Chemistry of cis-CF3CH=CHF: Kinetics of reactions with OH radicals and O3 and products of OH radical initiated oxidation

    DEFF Research Database (Denmark)

    Nilsson, Elna Johanna Kristina; Nielsen, Ole John; Johnson, Matthew Stanley

    2009-01-01

    Long path length FTIR-smog chamber techniques were used to measure k(OH + cis-CF3CH@CHF) = (1.20 ± 0.14) 1012 and k(O3 + cis-CF3CH@CHF) = (1.65 ± 0.16) 1021 cm3 molecule 1 s1 in 700 Torr of N2/O2 diluent at 296 K. The OH initiated oxidation of cis-CF3CH@CHF gives CF3CHO and HCOF in molar yields...... which are indistinguishable from 100%. The atmospheric lifetime of cis-CF3CH@CHF is determined by its reaction with OH and is approximately 10 days. cis-CF3CH@CHF has an integrated IR absorption cross section (600–2000 cm1) of (1.71 ± 0.09) 1016 cm molecule1 and a global warming potential...

  8. Modifications to the surface chemistry of low-rank coal-based carbon catalysts to improve flue gas nitric oxide removal

    Energy Technology Data Exchange (ETDEWEB)

    Izquierdo, M.T.; Rubio, B. [Departamento de Energia y Medio Ambiente, Instituto de Carboquimica (CSIC), C/Maria de Luna, 12, 50015 Zaragoza (Spain); Mayoral, C.; Andres, J.M. [Departamento de Procesos Quimicos, Instituto de Carboquimica (CSIC), C/Maria de Luna, 12, 50015 Zaragoza (Spain)

    2001-10-25

    The effectiveness of carbons as low-temperature selective catalytic reduction (SCR) catalysts will depend upon their physical and chemical properties. Surface functional groups containing oxygen are closely related to the catalytic activity of carbons. These groups are expected to change the interaction between the carbon surface and the reactants through a variation in adsorption and reaction characteristics. This paper presents a more detailed study of the effects of either gas-phase sulfuric acid or oxygen oxidation treatments on the catalytic NO reduction by low-rank coal-based carbon catalysts. Raw and treated carbons were characterized by N{sub 2} and CO{sub 2} surface areas, TPD and ash content. NO removal capacity of carbons was determined by passing a flow containing NO, H{sub 2}O, O{sub 2}, NH{sub 3} and N{sub 2} through a fixed bed of carbon at 150C and 4s of residence time, the effluent concentration being monitored continuously during the reaction. The effects of varying the type and conditions of the treatment on the physicochemical features of carbons were studied. The gas-phase sulfuric acid treatment (corresponding to a first step SO{sub 2} removal) markedly enhanced carbon activities for NO removal. On the contrary, oxygen oxidation enhanced NO removal capacity of chars to a lower extent. Therefore, the carbons studied could be used in a combined SO{sub 2}/NO removal process, because the use and regeneration of the carbon in the first step is beneficial for the performance in the second one.

  9. Computational Chemistry and Lubrication

    Science.gov (United States)

    Zehe, Michael J.

    1998-01-01

    Members of NASA Lewis Research Center's Tribology and Surface Science Branch are applying high-level computational chemistry techniques to the development of new lubrication systems for space applications and for future advanced aircraft engines. The next generation of gas turbine engines will require a liquid lubricant to function at temperatures in excess of 350 C in oxidizing environments. Conventional hydrocarbon-based lubricants are incapable of operating in these extreme environments, but a class of compounds known as the perfluoropolyether (PFAE) liquids (see the preceding illustration) shows promise for such applications. These commercially available products are already being used as lubricants in conditions where low vapor pressure and chemical stability are crucial, such as in satellite bearings and composite disk platters. At higher temperatures, however, these compounds undergo a decomposition process that is assisted (catalyzed) by metal and metal oxide bearing surfaces. This decomposition process severely limits the applicability of PFAE's at higher temperatures. A great deal of laboratory experimentation has revealed that the extent of fluid degradation depends on the chemical properties of the bearing surface materials. Lubrication engineers would like to understand the chemical breakdown mechanism to design a less vulnerable PFAE or to develop a chemical additive to block this degradation.

  10. Green chemistry: A tool in Pharmaceutical Chemistry

    OpenAIRE

    Smita Talaviya; Falguni Majumdar

    2012-01-01

    Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceut...

  11. From Matter to Life:Chemistry?Chemistry!

    Institute of Scientific and Technical Information of China (English)

    Jean-Marie; LEHN

    2007-01-01

    1 Results Animate as well as inanimate matter,living organisms as well as materials,are formed of molecules and of the organized entities resulting from the interaction of molecules with each other.Chemistry provides the bridge between the molecules of inanimate matter and the highly complex molecular architectures and systems which make up living organisms. Synthetic chemistry has developed a very powerful set of methods for constructing ever more complex molecules.Supramolecular chemistry seeks to con...

  12. Atmospheric chemistry in volcanic plumes.

    Science.gov (United States)

    von Glasow, Roland

    2010-04-13

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis.

  13. Influence of the surfactant and temperature on the morphology and physical-chemistry properties of hydrothermal synthesized composite oxide BiVO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Yang, T.; Wang, Z.; Yu, C.; Xia, D. [Beijing Univ. of Technology, Beijing (China)

    2007-07-01

    During the past two decades, great advances have been made in photocatalytic field, such as the photocatalytic splitting of water into oxygen and the photocatalytic degradation of organic pollution. The visible light responsive photocatalyst bismuth vanadate (BiVO{sub 4}) exhibits activity toward oxygen separation and 4-alkylphenols oxidation, and is increasingly attractive because approximately half of the solar spectrum is visible light. However, in its three structure systems, tetragonal zircon, monoclinic scheelite and tetragonal scheelite, only the monoclinic scheelite type BiVO{sub 4} has the best photocatalytic ability under visible light irradiation. This paper presented the results of a study that prepared BiVO{sub 4} with monoclinic scheelite structure by adding sodium dodecyl sulfate (SDS) in the solution using hydrothermal methods and examined the factors affecting the particle's grain size, specific area, microstructure, local structure, morphology and its photocatalytic ability. The BiVO{sub 4} samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and Raman spectroscopy. The photocatalytic activity of the decahedron BiVO{sub 4} was then evaluated under UV and visible light sources. It was concluded that the BiVO{sub 4} prepared in this experiment is a promising photocatalyst to split water into oxygen in the visible light zone. 15 refs., 2 tabs., 6 figs.

  14. Solid-state transition metal chemistry with quinolin-4-yl-methyl-[N-(n-butyl)amino]-diphenylphosphine oxide (4-qmape): Crystal structure of the 4-qmape ligand

    Science.gov (United States)

    Żurowska, Bogumiła; Brzuszkiewicz, Anna; Boduszek, Bogdan

    2012-11-01

    A series of three perchlorate coordination compounds of bioactive diethyl quinolin-4-yl-methyl(N-butylamino)diphenylphosphine oxide (4-qmape) ligand, with the following stoichiometries [M(2-qmape)2](ClO4)2 Mdbnd Cu and Ni and [Co(2-qmape)2](ClO4)2, were obtained and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic studies as well as by elemental analyses. In particular, the crystal structure of the free ligand was determined. The 4-qmape ligand has a potential capacity to coordinate to metal ions by following atoms: phosphoryl oxygen, amino nitrogen and quinolyl nitrogen. In studied compounds, 4-qmape adopts the didentate N,O-coordination mode, bonding metal centers through the phosphoryl oxygen and amino nitrogen. Quinoline nitrogen atom does not participate in coordination. The all complexes are monomeric with tetrahedral environment of metal ions. Magnetic studies (1.8-300 K) indicate existence of a very weak exchange coupling between metal centers in crystal lattice.

  15. Biocatalytic preparation and absolute configuration of enantiomerically pure fungistatic anti-2-benzylindane derivatives. Study of the detoxification mechanism by Botrytis cinerea.

    Science.gov (United States)

    Pinedo-Rivilla, Cristina; Aleu, Josefina; Grande Benito, Manuel; Collado, Isidro G

    2010-08-21

    Enantiomerically pure 2-benzylindane derivatives were prepared using biocatalytic methods and their absolute configuration determined. (1R,2S)-2-Benzylindan-1-ol ((1R,2S)-2) and (S)-2-benzylindan-1-one ((S)-3) were produced by fermenting baker's yeast. Lipase-mediated esterifications and hydrolysis of the corresponding racemic substrates gave rise to the enantiopure compounds (1S,2R)-2-benzylindan-1-ol ((1S,2R)-2) and (1R,2S)-2-benzylindan-1-ol ((1R,2S)-2), respectively. The antifungal activity of these products against two strains of the plant pathogen Botrytis cinerea was tested. The metabolism of anti-(+/-)-2-benzylindan-1-ol (anti-(+/-)-2) by B. cinerea as part of the fungal detoxification mechanism is also described and revealed interesting differences in the genome of both strains.

  16. Combustion chemistry - activities in the CHEK research programme

    Energy Technology Data Exchange (ETDEWEB)

    Dam-Johansen, K.; Johnsson, J.E.; Glarborg, P.; Frandsen, F.; Jensen, A.; Oestberg, M. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemical Engineering

    1997-10-01

    The combustion chemistry in the oxidation of fossil fuels and biofuels determines together with mixing and heat transfer the required size of a furnace, the emission of gaseous pollutants, and the formation of ash and deposits on surfaces. This presentation describes technologies for solid fuels combustion and gives a summary of the fuels, the pollutant chemistry and the inorganic chemistry in combustion processes. Emphasis is put on the work carried out in the CHEC (Combustion and Harmful Emission Control) Research Programme. (orig.)

  17. Highly regioselective hydride transfer, oxidative dehydrogenation, and hydrogen-atom abstraction in the thermal gas-phase chemistry of [Zn(OH)](+)/C3H8.

    Science.gov (United States)

    Wu, Xiao-Nan; Zhao, Hai-Tao; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2014-12-28

    The thermal reactions of [Zn(OH)](+) with C3H8 have been studied by means of gas-phase experiments and computational investigation. Two types of C-H bond activation are observed in the experiment, and pertinent mechanistic features include inter alia: (i) the metal center of [Zn(OH)](+) serves as active site in the hydride transfer to generate [i-C3H7](+) as major product, (ii) generally, a high regioselectivity is accompanied by remarkable chemoselectivity: for example, the activation of a methyl C-H bond results mainly in the formation of water and [Zn(C3,H7)](+). According to computational work, this ionic product corresponds to [HZn(CH3CH=CH2)](+). Attack of the zinc center at a secondary C-H bond leads preferentially to hydride transfer, thus giving rise to the generation of [i-C3H7](+); (iii) upon oxidative dehydrogenation (ODH), liberation of CH3CH2=CH2 occurs to produce [HZn(H2O)](+). Both, ODH as well as H2O loss proceed through the same intermediate which is characterized by the fact that a methylene hydrogen atom from the substrate is transferred to the zinc and one hydrogen atom from the methyl group to the OH group of [Zn(OH)](+). The combined experimental/computational gas-phase study of C-H bond activation by zinc hydroxide provides mechanistic insight into related zinc-catalyzed large-scale processes and identifies the crucial role that the Lewis-acid character of zinc plays.

  18. Constitutional dynamic chemistry: bridge from supramolecular chemistry to adaptive chemistry.

    Science.gov (United States)

    Lehn, Jean-Marie

    2012-01-01

    Supramolecular chemistry aims at implementing highly complex chemical systems from molecular components held together by non-covalent intermolecular forces and effecting molecular recognition, catalysis and transport processes. A further step consists in the investigation of chemical systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, thus behaving as programmed chemical systems. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous change in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.CDC introduces a paradigm shift with respect to constitutionally static chemistry. The latter relies on design for the generation of a target entity, whereas CDC takes advantage of dynamic diversity to allow variation and selection. The implementation of selection in chemistry introduces a fundamental change in outlook. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization with selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation.The merging of the features: -information and programmability, -dynamics and reversibility, -constitution and structural diversity, points to the emergence of adaptive and evolutive chemistry, towards a chemistry of complex matter.

  19. Chemistry of high-oxidation-state groups V and VI complexes: Novel silyl and imido complexes and the reactions of silyl and alkyl alkylidyne complexes with oxygen

    Science.gov (United States)

    Chen, Tianniu

    This dissertation describes the synthesis and characterization of the novel early transition metal (especially group VI metals) complexes free of anionic pi-ligands such as cyclopentadienyl (Cp) and studies of their reactions with oxygen and silanes. Our study of Cp-free tungsten silyl chemistry is reported. A novel d 0 tungsten silyl complex 2 [(ButCH 2)W(=CHBut)2(SiButPh2 ) (2a) ⇌ (ButCH2)2W(≡CBu t)(SiButPh2) (2b)] and an equilibrium between 2a and 2b are described in Chapter 2. The thermodynamics of this equilibrium [DeltaH° = -0.9(0.2) kcal/mol, DeltaS° = -0.6(0.8) eu] was investigated by 1H NMR. The studies of the alpha-hydrogen exchange between 2a and 2b by 2-D EXSY experiments gave kinetic parameters of the exchange: DeltaH≠ = 17.9(1.1) kcal/mol, DeltaS≠ = 1.9(5.7) eu for the forward reaction (2a → 2b) and Delta H≠ = 18.6 (1.1) kcal/mol, DeltaS ≠ = 1.9(5.7) eu for the back reaction (2b → 2a). The reaction of O2 with silyl alkylidyne 2b [(Bu tCH2)W(=CHBut)2(SiBut Ph2) (2a) ⇌ (ButCH2)2W(≡CBu t)(SiButPh2) (2b)] is described in Chapter 3. A silyl migration product (ButCH2) 2W(=O)[=C(But)(SiButPh2)] ( 5) was characterized. A siloxy analog of 2b, (Bu tCH2)2W≡CBut(OSiBu tPh2) (6), was prepared and excluded as a possible intermediate in the formation of 5. Ab initio calculations suggested a pathway involving silyl migration in 2b to give a tungsten (IV) intermediate (ButCH 2)2W=C(But)(SiButPh2) (7) prior to the reaction with O2. A crystal structure of (Me3SiCH2)2W(=O)(=CHSiMe3)(O=PMe 3)•(Me3SiCH2)3W≡CSiMe 3 (12) was obtained from the reaction of alkyl alkylidyne (Me3SiCH2)3W≡CSiMe3 with O2 in the presence of PMe3. In Chapter 4, preparation and characterization of bis(2,6-diisopropylphenylimido)molybdenum(VI) amide and silyl complexes (ArN=)2Mo(NMe2)2 (14), (ArN=)2Mo(NMe2)[Si(SiMe3) 3] (15), (ArN=)2MoCl[N(SiMe3) 2] (16), (ArN=)2Mo(NMe2)[N(SiMe 3)2] (17), and (ArN=)2Mo(NHAr) 2 (18) are reported. In addition, new bis

  20. Green chemistry: A tool in Pharmaceutical Chemistry

    Directory of Open Access Journals (Sweden)

    Smita Talaviya

    2012-07-01

    Full Text Available Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceuticals is to utilize eco-friendly, non-hazardous, reproducible and efficient solvents and catalysts in synthesis of drug molecules, drug intermediates and in researches involving synthetic chemistry. Microwave synthesis is also an important tool of green chemistry by being an energy efficient process.

  1. Environmental chemistry: Volume A

    Energy Technology Data Exchange (ETDEWEB)

    Yen, T.F.

    1999-08-01

    This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume A include a brief review of basic chemistry prior to coverage of litho, atmo, hydro, pedo, and biospheres.

  2. Advanced Chemistry Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Description/History: Chemistry laboratoryThe Advanced Chemistry Laboratory (ACL) is a unique facility designed for working with the most super toxic compounds known...

  3. Organometallic Chemistry of Molybdenum.

    Science.gov (United States)

    Lucas, C. Robert; Walsh, Kelly A.

    1987-01-01

    Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

  4. Chemistry for Potters.

    Science.gov (United States)

    Denio, Allen A.

    1980-01-01

    Relates pottery making to chemistry by providing chemical information about clay, its origin, composition, properties, and changes that occur during firing; also describes glaze compositions, examples of redox chemistry, salt glazing, crystalline glazes, and problems in toxicity. (CS)

  5. CHINESE JOURNAL OF CHEMISTRY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Chinese Journal of Chemistry is an international journal published in English by the Chinese Chemical Society with its editorial office hosted by Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.

  6. THE BIOCATALYTIC DESULFURIZATION PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Scott Collins; David Nunn

    2003-10-01

    The analysis of Petro Star diesel sulfur species is complete and a report is attached. Further analytical efforts will concentrate on characterization of diesel fuel, hydrodesulfurized to varying degrees, in order to determine sulfur species that may be problematic to hydrogen treatment and represent potential target substrates for biodesulfurization in a combined HDS-BDS process. Quotes have been received and are being considered for the partial treatment of Petro Star Inc. marine diesel fuel. Direction of research is changing slightly; economic analysis of the hyphenated--BDSHDS, BDS-CED--has shown the highest probability of success to be with a BDS-HDS process where the biodesulfurization precedes hydrodesulfurization. Thus, the microorganisms will be tailored to focus on those compounds that tend to be recalcitrant to hydrodesulfurization and decrease the severity of the hydrodesulfurization step. A separate, detailed justification for this change is being prepared. Research activities have continued in the characterization of the desulfurization enzymes from multiple sources. Genes for all DszA, -B, -C and -D enzymes (and homologs) have been cloned and expressed. Activity determinations, on a variety of substituted benzothiophene and dibenzothiophene substrates, have been carried out and continue. In addition, chemical synthesis efforts have been carried out to generate additional substrates for analytical standards and activity determinations. The generation of a GSSM mutant library of the ''Rhodococcus IGTS8 dszA'' gene has been completed and development of protocols for a high throughput screen to expand substrate specificity are nearing completion. In an effort to obtain improved hosts as biocatalyst, one hundred-thirty ''Rhodococcus'' and related strains are being evaluated for growth characteristics and other criteria deemed important for an optimal biocatalyst strain. We have also begun an effort to generate derivatives of the entire IGTS8 BDS plasmid that will allow for its easy transfer and manipulation into a variety of hosts. To support this activity and to gain an understanding of additional genes that may potentially affect BDS activity, the nucleotide sequence of the entire complement of plasmids in IGTS8 is being determined. Lastly, we continue to develop genetic screens and selections for the discovery and improvement of the biodesulfurization genes and strains.

  7. Sustainable Biocatalytic Biodiesel Production

    DEFF Research Database (Denmark)

    Güzel, Günduz

    and chemical equilibria as part of his main sustainable biodiesel project. The transesterification reaction of vegetable oils or fats with an aliphatic alcohol – in most cases methanol or ethanol – yields biodiesel (long-chain fatty acid alkyl esters – FAAE) as the main product in the presence of alkaline....../acid catalysts or biocatalysts (free or immobilised lipase enzymes). The reaction by-product glycerol is immiscible with the ester products (FAAE and oils/fats) in addition to the partial miscibility problem of methanol or ethanol with oils/fats. The insoluble parts of alcohol feeds or by-products form emulsion...... droplets within the reaction media, where continuous stirring operations are applied to improve mass transfer and thus reaction rates. In all other cases, there is a heterogeneous alcohol phase in equilibrium with the ester phase under equilibrium conditions. The immiscibility and/or miscibility drawbacks...

  8. Organic chemistry experiment

    Energy Technology Data Exchange (ETDEWEB)

    Mun, Seok Sik

    2005-02-15

    This book deals with organic chemistry experiments, it is divided five chapters, which have introduction, the way to write the experiment report and safety in the laboratory, basic experiment technic like recrystallization and extraction, a lot of organic chemistry experiments such as fischer esterification, ester hydrolysis, electrophilic aromatic substitution, aldol reaction, benzoin condensation, wittig reaction grignard reaction, epoxidation reaction and selective reduction. The last chapter introduces chemistry site on the internet and way to find out reference on chemistry.

  9. Nitrogen Compounds in Radiation Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Sims, H.E. [NNL Sellafield (United Kingdom); Dey, G.R. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Vaudey, C.E.; Peaucelle, C. [Institut de Physique Nucleaire de Lyon - IPNL, 69 - Lyon (France); Boucher, J.L. [Lab. de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS 45 rue des Saints Peres, 75270 Paris cedex 06, Univ Paris 5, 75 (France); Toulhoat, N. [Institut de Physique Nucleaire de Lyon (France); Commissariat a l' Energie Atomique CEA/DEN, Centre de Saclay (France); Bererd, N. [Institut de Physique Nucleaire de Lyon (France); IUT Departement Chimie, Universite Claude Bernard Lyon 1 (France); Koppenol, W.H. [Department of Chemistry and Applied Biosciences, ETH Zurich (Switzerland); Janata, E. [Helmholtz-Zentrum fuer Materialien und Energie, Solar Energy Research, Berlin (Germany); Dauvois, V.; Durand, D.; Legand, S.; Roujou, J.L.; Doizi, D.; Dannoux, A.; Lamouroux, C. [Laboratoire de Speciation des Radionucleides et des Molecules, DEN/DPC/Service d' Etude du Comportement des Radionucleides, CEA Saclay, 91 - Gif sur yvette (France)

    2009-07-01

    Water radiolysis in presence of N{sub 2} is probably the topic the most controversy in the field of water radiolysis. It still exists a strong discrepancy between the different reports of ammonia formation by water radiolysis in presence of N{sub 2} and moreover in absence of oxygen there is no agreement on the formation or not of nitrogen oxide like NO{sub 2}- and NO{sub 3}-. These discrepancies come from multiple sources: - the complexity of the reaction mechanisms where nitrogen is involved - the experimental difficulties - and, the irradiation conditions. The aim of the workshop is to capitalize the knowledge needed to go further in simulations and understanding the problems caused (or not) by the presence of nitrogen / water in the environment of radioactive materials. Implications are evident in terms of corrosion, understanding of biological systems and atmospheric chemistry under radiation. Topics covered include experimental and theoretical approaches, application and fundamental researches: - Nitrate and Ammonia in radiation chemistry in nuclear cycle; - NOx in biological systems and atmospheric chemistry; - Formation of Nitrogen compounds in Nuclear installations; - Nitrogen in future power plant projects (Gen4, ITER...) and large particle accelerators. This document gathers the transparencies available for 7 of the presentations given at this workshop. These are: - H.E SIMS: 'Radiation Chemistry of Nitrogen Compounds in Nuclear Power Plant'; - G.R. DEY: 'Nitrogen Compounds Formation in the Radiolysis of Aqueous Solutions'; - C.E. VAUDEY et al.: 'Radiolytic corrosion of nuclear graphite studied with the dedicated gas irradiation cell of IPNL'; - J.L. BOUCHER: 'Roles and biosynthesis of NO in eukaryotes and prokaryotes'; - W.H. KOPPENOL: 'Chemistry of NOx'; - E. JANATA: 'Yield of OH in N{sub 2}O saturated aqueous solution'; - V. DAUVOIS: 'Analytical strategy for the study of radiolysis gases'

  10. Elucidation of mechanisms in manganese and iron based oxidation catalysis : Mechanistic insights and development of novel approaches applied to transition metal catalyzed oxidations catalysis

    NARCIS (Netherlands)

    Angelone, Davide

    2016-01-01

    Oxidation chemistry is central to life and to the modern chemical industry and hence understanding chemical oxidation is essential to developing new processes and elucidating biological oxidation mechanisms. Elucidating mechanisms in inorganic oxidation catalysis and simultaneously developing new to

  11. Alcohol combustion chemistry

    KAUST Repository

    Sarathy, Mani

    2014-10-01

    Alternative transportation fuels, preferably from renewable sources, include alcohols with up to five or even more carbon atoms. They are considered promising because they can be derived from biological matter via established and new processes. In addition, many of their physical-chemical properties are compatible with the requirements of modern engines, which make them attractive either as replacements for fossil fuels or as fuel additives. Indeed, alcohol fuels have been used since the early years of automobile production, particularly in Brazil, where ethanol has a long history of use as an automobile fuel. Recently, increasing attention has been paid to the use of non-petroleum-based fuels made from biological sources, including alcohols (predominantly ethanol), as important liquid biofuels. Today, the ethanol fuel that is offered in the market is mainly made from sugar cane or corn. Its production as a first-generation biofuel, especially in North America, has been associated with publicly discussed drawbacks, such as reduction in the food supply, need for fertilization, extensive water usage, and other ecological concerns. More environmentally friendly processes are being considered to produce alcohols from inedible plants or plant parts on wasteland. While biofuel production and its use (especially ethanol and biodiesel) in internal combustion engines have been the focus of several recent reviews, a dedicated overview and summary of research on alcohol combustion chemistry is still lacking. Besides ethanol, many linear and branched members of the alcohol family, from methanol to hexanols, have been studied, with a particular emphasis on butanols. These fuels and their combustion properties, including their ignition, flame propagation, and extinction characteristics, their pyrolysis and oxidation reactions, and their potential to produce pollutant emissions have been intensively investigated in dedicated experiments on the laboratory and the engine scale

  12. Green Chemistry and Education.

    Science.gov (United States)

    Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

    2000-01-01

    Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

  13. Sulfur Chemistry in Combustion I

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Glarborg, Peter

    2000-01-01

    Most fossil fuels contain sulphur and also biofuels and household waste have a sulphur content. As a consequence sulphur species will often be present in combustion processes. In this paper the fate and influence of fuel sulphur species in combustion will be treated. First a description...... of the sulphur compounds in fossil fuels and the possibilities to remove them will be given. Then the combustion of sulphur species and their influence on the combustion chemistry and especially on the CO oxidation and the NOx formation will be described. Finally the in-situ removal of sulphur in the combustion...

  14. Surface chemistry essentials

    CERN Document Server

    Birdi, K S

    2013-01-01

    Surface chemistry plays an important role in everyday life, as the basis for many phenomena as well as technological applications. Common examples range from soap bubbles, foam, and raindrops to cosmetics, paint, adhesives, and pharmaceuticals. Additional areas that rely on surface chemistry include modern nanotechnology, medical diagnostics, and drug delivery. There is extensive literature on this subject, but most chemistry books only devote one or two chapters to it. Surface Chemistry Essentials fills a need for a reference that brings together the fundamental aspects of surface chemistry w

  15. The New Color of Chemistry: Green Chemistry

    Directory of Open Access Journals (Sweden)

    Zuhal GERÇEK

    2012-01-01

    Full Text Available Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provide a solution for this requirement, green chemistry rules and under standings should be primarily taken in the university curriculum and at all educational levels.

  16. N-Heterocyclic carbene chemistry of iron: fundamentals and applications.

    Science.gov (United States)

    Ingleson, Michael J; Layfield, Richard A

    2012-04-14

    The use of N-heterocyclic carbenes (NHCs) in the chemistry of iron is stimulating important new applications of one of the most ubiquitous ligand types in modern organometallic chemistry. A series of reports has shown how the flexible and modifiable stereo-electronic properties of NHC ligands can be combined with iron in a range of oxidation states to create opportunities for studying unique structures, bonding and reactivity. Of particular interest are the roles of iron NHC complexes in: the stabilization of unusual oxidation states and coordination environments; the activation of small molecules; homogeneous catalysis; and bio-mimetic chemistry. Our feature article summarizes the key developments in the field.

  17. Atmospheric and aerosol chemistry

    Energy Technology Data Exchange (ETDEWEB)

    McNeill, V. Faye [Columbia Univ., New York, NY (United States). Dept. of Chemical Engineering; Ariya, Parisa A. (ed.) [McGill Univ. Montreal, QC (Canada). Dept. of Chemistry; McGill Univ. Montreal, QC (Canada). Dept. of Atmospheric and Oceanic Sciences

    2014-09-01

    This series presents critical reviews of the present position and future trends in modern chemical research. Short and concise reports on chemistry, each written by the world renowned experts. Still valid and useful after 5 or 10 years. More information as well as the electronic version of the whole content available at: springerlink.com. Christian George, Barbara D'Anna, Hartmut Herrmann, Christian Weller, Veronica Vaida, D. J. Donaldson, Thorsten Bartels-Rausch, Markus Ammann Emerging Areas in Atmospheric Photochemistry. Lisa Whalley, Daniel Stone, Dwayne Heard New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Neil M. Donahue, Allen L. Robinson, Erica R. Trump, Ilona Riipinen, Jesse H. Kroll Volatility and Aging of Atmospheric Organic Aerosol. P. A. Ariya, G. Kos, R. Mortazavi, E. D. Hudson, V. Kanthasamy, N. Eltouny, J. Sun, C. Wilde Bio-Organic Materials in the Atmosphere and Snow: Measurement and Characterization V. Faye McNeill, Neha Sareen, Allison N. Schwier Surface-Active Organics in Atmospheric Aerosols.

  18. The New Color of Chemistry: Green Chemistry

    OpenAIRE

    Zuhal GERÇEK

    2012-01-01

    Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provid...

  19. Oxidation and Reduction: Too Many Definitions?

    Science.gov (United States)

    Silverstein, Todd P.

    2011-01-01

    IUPAC gives several different definitions of oxidation: loss of electrons, increase in oxidation state, loss of hydrogen, or gain of oxygen. Most introductory or general chemistry textbooks use all of these definitions at one time or another, which can lead to some confusion in the minds of first-year chemistry students. Some paradoxical…

  20. Encapsulated Laccases for the Room-Temperature Oxidation of Aromatics: Towards Synthetic Low-Molecular-Weight Lignins.

    Science.gov (United States)

    Pistone, Lucia; Ottolina, Gianluca; De, Sudipta; Romero, Antonio A; Martins, Lígia O; Luque, Rafael

    2016-04-01

    A new approach for the encapsulation of laccases with enhanced activity and stability by biomimetic silica mineralisation is reported. A range of lignin model compounds, which includes syringol, syringyl acid, 4-vinylphenol, gallic acid, vanillic acid and guaiacol, was oxidised to lignin-type polymers by the silica-immobilised laccase systems at room temperature. The oxidation rate of the immobilised systems was lower than that of the free enzyme counterparts, but interesting products were observed with the new bio-catalytic materials, which showed reusability and good stability.

  1. Switching surface chemistry with supramolecular machines.

    Energy Technology Data Exchange (ETDEWEB)

    Dunbar, Timothy D.; Kelly, Michael James; Jeppesen, Jan O. (University of California, Los Angeles, CA); Bunker, Bruce Conrad; Matzke, Carolyn M.; Stoddart, J. Fraser; Huber, Dale L.; Kushmerick, James G.; Flood, Amar H. (University of California, Los Angeles, CA); Perkins, Julie (University of California, Los Angeles, CA); Cao, Jianguo (University of California, Los Angeles, CA)

    2005-07-01

    Tethered supramolecular machines represent a new class of active self-assembled monolayers in which molecular configurations can be reversibly programmed using electrochemical stimuli. We are using these machines to address the chemistry of substrate surfaces for integrated microfluidic systems. Interactions between the tethered tetracationic cyclophane host cyclobis(paraquat-p-phenylene) and dissolved {pi}-electron-rich guest molecules, such as tetrathiafulvalene, have been reversibly switched by oxidative electrochemistry. The results demonstrate that surface-bound supramolecular machines can be programmed to adsorb or release appropriately designed solution species for manipulating surface chemistry.

  2. Environmentally Friendly Zirconium Oxide Pretreatment

    Science.gov (United States)

    2013-05-01

    chemistries and is intended to coat interstitial spaces between crystals, and to provide a more insoluble layer at the crystal surface.12 Because...distinct layers (metal/metal oxide and organic coatings), it must have functional groups that interact with both layers. In general, organometallic ...fluorides. In sol-gel chemistry , the applied coating must progress through condensation reactions to transform from a mixed oxide/hydroxide state to

  3. Orbital interactions in chemistry

    CERN Document Server

    Albright, Thomas A; Whangbo, Myung-Hwan

    2013-01-01

    Explains the underlying structure that unites all disciplines in chemistry Now in its second edition, this book explores organic, organometallic, inorganic, solid state, and materials chemistry, demonstrating how common molecular orbital situations arise throughout the whole chemical spectrum. The authors explore the relationships that enable readers to grasp the theory that underlies and connects traditional fields of study within chemistry, thereby providing a conceptual framework with which to think about chemical structure and reactivity problems. Orbital Interactions

  4. Group theory and chemistry

    CERN Document Server

    Bishop, David M

    1993-01-01

    Group theoretical principles are an integral part of modern chemistry. Not only do they help account for a wide variety of chemical phenomena, they simplify quantum chemical calculations. Indeed, knowledge of their application to chemical problems is essential for students of chemistry. This complete, self-contained study, written for advanced undergraduate-level and graduate-level chemistry students, clearly and concisely introduces the subject of group theory and demonstrates its application to chemical problems.To assist chemistry students with the mathematics involved, Professor Bishop ha

  5. Green Chemistry Pedagogy

    Science.gov (United States)

    Kolopajlo, Larry

    2017-02-01

    This chapter attempts to show how the practice of chemistry teaching and learning is enriched by the incorporation of green chemistry (GC) into lectures and labs. To support this viewpoint, evidence from a wide range of published papers serve as a cogent argument that GC attracts and engages both science and nonscience students, enhances chemistry content knowledge, and improves the image of the field, while preparing the world for a sustainable future. Published pedagogy associated with green and sustainable chemistry is critically reviewed and discussed.

  6. Advances in quantum chemistry

    CERN Document Server

    Sabin, John R

    2013-01-01

    Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. This volume focuses on the theory of heavy ion physics in medicine.Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features

  7. Science Update: Analytical Chemistry.

    Science.gov (United States)

    Worthy, Ward

    1980-01-01

    Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)

  8. Combination of deep eutectic solvent and ionic liquid to improve biocatalytic reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cell

    Science.gov (United States)

    Xu, Pei; Du, Peng-Xuan; Zong, Min-Hua; Li, Ning; Lou, Wen-Yong

    2016-05-01

    The efficient anti-Prelog asymmetric reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cells was successfully performed in a biphasic system consisting of deep eutectic solvent (DES) and water-immiscible ionic liquid (IL). Various DESs exerted different effects on the synthesis of (R)-2-octanol. Choline chloride/ethylene glycol (ChCl/EG) exhibited good biocompatibility and could moderately increase the cell membrane permeability thus leading to the better results. Adding ChCl/EG increased the optimal substrate concentration from 40 mM to 60 mM and the product e.e. kept above 99.9%. To further improve the reaction efficiency, water-immiscible ILs were introduced to the reaction system and an enhanced substrate concentration (1.5 M) was observed with C4MIM·PF6. Additionally, the cells manifested good operational stability in the reaction system. Thus, the efficient biocatalytic process with ChCl/EG and C4MIM·PF6 was promising for efficient synthesis of (R)-2-octanol.

  9. Steam gasification of wood biomass in a fluidized biocatalytic system bed gasifier: A model development and validation using experiment and Boubaker Polynomials Expansion Scheme BPES

    Directory of Open Access Journals (Sweden)

    Luigi Vecchione

    2015-07-01

    Full Text Available One of the most important issues in biomass biocatalytic gasification is the correct prediction of gasification products, with particular attention to the Topping Atmosphere Residues (TARs. In this work, performedwithin the European 7FP UNIfHY project, we develops and validate experimentally a model which is able of predicting the outputs,including TARs, of a steam-fluidized bed biomass gasifier. Pine wood was chosen as biomass feedstock: the products obtained in pyrolysis tests are the relevant model input. Hydrodynamics and chemical properties of the reacting system are considered: the hydrodynamic approach is based on the two phase theory of fluidization, meanwhile the chemical model is based on the kinetic equations for the heterogeneous and homogenous reactions. The derived differentials equations for the gasifier at steady state were implemented MATLAB. Solution was consecutively carried out using the Boubaker Polynomials Expansion Scheme by varying steam/biomass ratio (0.5-1 and operating temperature (750-850°C.The comparison between models and experimental results showed that the model is able of predicting gas mole fractions and production rate including most of the representative TARs compounds

  10. Biocatalytic Behaviour of Immobilized Rhizopus oryzae Lipase in the 1,3-Selective Ethanolysis of Sunflower Oil to Obtain a Biofuel Similar to Biodiesel

    Directory of Open Access Journals (Sweden)

    Carlos Luna

    2014-08-01

    Full Text Available A new biofuel similar to biodiesel was obtained in the 1,3-selective transesterification reaction of sunflower oil with ethanol using as biocatalyst a Rhizopus oryzae lipase (ROL immobilized on Sepiolite, an inorganic support. The studied lipase was a low cost powdered enzyme preparation, Biolipase-R, from Biocon-Spain, a multipurpose additive used in food industry. In this respect, it is developed a study to optimize the immobilization procedure of these lipases on Sepiolite. Covalent immobilization was achieved by the development of an inorganic-organic hybrid linker formed by a functionalized hydrocarbon chain with a pendant benzaldehyde, bonded to the AlPO4 support surface. Thus, the covalent immobilization of lipases on amorphous AlPO4/sepiolite (20/80 wt % support was evaluated by using two different linkers (p-hydroxybenzaldehyde and benzylamine-terephthalic aldehyde, respectively. Besides, the catalytic behavior of lipases after physical adsorption on the demineralized sepiolite  was also evaluated. Obtained results indicated that covalent immobilization with the p-hydroxybenzaldehyde linker gave the best biocatalytic behavior. Thus, this covalently immobilized lipase showed a remarkable stability as well as an excellent capacity of reutilization (more than five successive reuses without a significant loss of its initial catalytic activity. This could allow a more efficient fabrication of biodiesel minimizing the glycerol waste production.

  11. Biocatalytic behaviour of immobilized Rhizopus oryzae lipase in the 1,3-selective ethanolysis of sunflower oil to obtain a biofuel similar to biodiesel.

    Science.gov (United States)

    Luna, Carlos; Verdugo, Cristóbal; Sancho, Enrique D; Luna, Diego; Calero, Juan; Posadillo, Alejandro; Bautista, Felipa M; Romero, Antonio A

    2014-08-04

    A new biofuel similar to biodiesel was obtained in the 1,3-selective transesterification reaction of sunflower oil with ethanol using as biocatalyst a Rhizopus oryzae lipase (ROL) immobilized on Sepiolite, an inorganic support. The studied lipase was a low cost powdered enzyme preparation, Biolipase-R, from Biocon-Spain, a multipurpose additive used in food industry. In this respect, it is developed a study to optimize the immobilization procedure of these lipases on Sepiolite. Covalent immobilization was achieved by the development of an inorganic-organic hybrid linker formed by a functionalized hydrocarbon chain with a pendant benzaldehyde, bonded to the AlPO4 support surface. Thus, the covalent immobilization of lipases on amorphous AlPO4/sepiolite (20/80 wt %) support was evaluated by using two different linkers (p-hydroxybenzaldehyde and benzylamine-terephthalic aldehyde, respectively). Besides, the catalytic behavior of lipases after physical adsorption on the demineralized sepiolite  was also evaluated. Obtained results indicated that covalent immobilization with the p-hydroxybenzaldehyde linker gave the best biocatalytic behavior. Thus, this covalently immobilized lipase showed a remarkable stability as well as an excellent capacity of reutilization (more than five successive reuses) without a significant loss of its initial catalytic activity. This could allow a more efficient fabrication of biodiesel minimizing the glycerol waste production.

  12. Biocatalytic Synthesis of Flavor Ester “Pentyl Valerate” Using Candida rugosa Lipase Immobilized in Microemulsion Based Organogels: Effect of Parameters and Reusability

    Science.gov (United States)

    Raghavendra, Tripti; Panchal, Nilam; Divecha, Jyoti; Shah, Amita; Madamwar, Datta

    2014-01-01

    Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL) immobilized in microemulsion based organogels (MBGs). The optimum conditions were found to be pH 7.0, temperature of 37°C, ratio of concentration of water to surfactant (Wo) of 60, and the surfactant sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (Km = 23.2 mM for pentanol and 76.92 mM for valeric acid) whereas, after immobilization, the Km values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid) resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99%) as compared to free enzyme (~19%). Simultaneous effects of important parameters were studied using response surface methodology (RSM) conjugated with Box-Behnken design (BBD) with five variables (process parameters), namely, enzyme concentration, initial water content (Wo), solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%). The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction. PMID:25093166

  13. Immobilization of the α-amylase of Bacillus amyloliquifaciens TSWK1-1 for the improved biocatalytic properties and solvent tolerance.

    Science.gov (United States)

    Kikani, B A; Pandey, S; Singh, S P

    2013-05-01

    The α-amylase of Bacillus amyloliquifaciens TSWK1-1 (GenBank Number, GQ121033) was immobilized by various methods, including ionic binding with DEAE cellulose, covalent coupling with gelatin and entrapment in polyacrylamide and agar. The immobilization of the purified enzyme was most effective with the DEAE cellulose followed by gelatin, agar and polyacrylamide. The K m increased, while V max decreased upon immobilization on various supports. The temperature and pH profiles broadened, while thermostability and pH stability enhanced after immobilization. The immobilized enzyme exhibited greater activity in various non-ionic surfactants, such as Tween-20, Tween-80 and Triton X-100 and ionic surfactant, SDS. Similarly, the enhanced stability of the immobilized α-amylase in various organic solvents was among the attractive features of the study. The reusability of the immobilized enzyme in terms of operational stability was assessed. The DEAE cellulose immobilized α-amylase retained its initial activity even after 20 consequent cycles. The DEAE cellulose immobilized enzyme hydrolyzed starch with 27 % of efficiency. In summary, the immobilization of B. amyloliquifaciens TSWK1-1 α-amylase with DEAE cellulose appeared most suitable for the improved biocatalytic properties and stability.

  14. Combination of deep eutectic solvent and ionic liquid to improve biocatalytic reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cell.

    Science.gov (United States)

    Xu, Pei; Du, Peng-Xuan; Zong, Min-Hua; Li, Ning; Lou, Wen-Yong

    2016-01-01

    The efficient anti-Prelog asymmetric reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cells was successfully performed in a biphasic system consisting of deep eutectic solvent (DES) and water-immiscible ionic liquid (IL). Various DESs exerted different effects on the synthesis of (R)-2-octanol. Choline chloride/ethylene glycol (ChCl/EG) exhibited good biocompatibility and could moderately increase the cell membrane permeability thus leading to the better results. Adding ChCl/EG increased the optimal substrate concentration from 40 mM to 60 mM and the product e.e. kept above 99.9%. To further improve the reaction efficiency, water-immiscible ILs were introduced to the reaction system and an enhanced substrate concentration (1.5 M) was observed with C4MIM·PF6. Additionally, the cells manifested good operational stability in the reaction system. Thus, the efficient biocatalytic process with ChCl/EG and C4MIM·PF6 was promising for efficient synthesis of (R)-2-octanol.

  15. Biocatalytic Synthesis of Flavor Ester “Pentyl Valerate” Using Candida rugosa Lipase Immobilized in Microemulsion Based Organogels: Effect of Parameters and Reusability

    Directory of Open Access Journals (Sweden)

    Tripti Raghavendra

    2014-01-01

    Full Text Available Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL immobilized in microemulsion based organogels (MBGs. The optimum conditions were found to be pH 7.0, temperature of 37°C, ratio of concentration of water to surfactant (Wo of 60, and the surfactant sodium bis-2-(ethylhexylsulfosuccinate (AOT for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (Km = 23.2 mM for pentanol and 76.92 mM for valeric acid whereas, after immobilization, the Km values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99% as compared to free enzyme (~19%. Simultaneous effects of important parameters were studied using response surface methodology (RSM conjugated with Box-Behnken design (BBD with five variables (process parameters, namely, enzyme concentration, initial water content (Wo, solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%. The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction.

  16. Advanced fuel chemistry for advanced engines.

    Energy Technology Data Exchange (ETDEWEB)

    Taatjes, Craig A.; Jusinski, Leonard E.; Zador, Judit; Fernandes, Ravi X.; Miller, James A.

    2009-09-01

    Autoignition chemistry is central to predictive modeling of many advanced engine designs that combine high efficiency and low inherent pollutant emissions. This chemistry, and especially its pressure dependence, is poorly known for fuels derived from heavy petroleum and for biofuels, both of which are becoming increasingly prominent in the nation's fuel stream. We have investigated the pressure dependence of key ignition reactions for a series of molecules representative of non-traditional and alternative fuels. These investigations combined experimental characterization of hydroxyl radical production in well-controlled photolytically initiated oxidation and a hybrid modeling strategy that linked detailed quantum chemistry and computational kinetics of critical reactions with rate-equation models of the global chemical system. Comprehensive mechanisms for autoignition generally ignore the pressure dependence of branching fractions in the important alkyl + O{sub 2} reaction systems; however we have demonstrated that pressure-dependent 'formally direct' pathways persist at in-cylinder pressures.

  17. Chemistry in Microfluidic Channels

    Science.gov (United States)

    Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

    2011-01-01

    General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

  18. Exercises in Computational Chemistry

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2016-01-01

    A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16).......A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16)....

  19. Physical Chemistry of Molecular

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Established in 2009, the group consists of six researchers and more than 70 research assistants and graduate students from the CAS Key Laboratory of Molecular Nanostructures and Nanotechnologies at the CAS Institute of Chemistry.Its research focuses on the physical chemistry involved in molecular assembly, molecular nanostructures, functional nanomaterials and conceptual nano-devices.

  20. The Breath of Chemistry

    DEFF Research Database (Denmark)

    Josephsen, Jens

    The present preliminary text is a short thematic presentation in biological inorganic chemistry meant to illustrate general and inorganic (especially coordination) chemistry in biochemistry. The emphasis is on molecular models to explain features of the complicated mechanisms essential to breathing...

  1. Bioorganic and bioinorganic chemistry.

    Science.gov (United States)

    Constable, Edwin C; Housecroft, Catherine E; Creus, Marc; Gademann, Karl; Giese, Bernd; Ward, Thomas R; Woggon, Wolf D; Chougnet, Antoinette

    2010-01-01

    The interdisciplinary projects in bioinorganic and bioorganic chemistry of the Department of Chemistry, University of Basel led to the preparation of new systems that mimic biologically important processes and to the discovery of compounds from natural sources which are very promising with respect to medical applications. The advances in these areas are reported here.

  2. Mathematics and Chemistry

    Science.gov (United States)

    Henson, R.; Stumbles, A.

    1977-01-01

    The relationship between mathematics and chemistry has been changing rapidly in recent years. Some chemistry teachers have experienced difficulties in their teaching with the introduction of modern mathematics in the schools. Some suggestions for reinforcing the concepts and language of modern mathematics are put forth. (Author/MA)

  3. Chemistry of americium

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, W.W.

    1976-01-01

    Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, separation, purification. Author and subject indexes are included. (JCB)

  4. Biosynthetic inorganic chemistry.

    Science.gov (United States)

    Lu, Yi

    2006-08-25

    Inorganic chemistry and biology can benefit greatly from each other. Although synthetic and physical inorganic chemistry have been greatly successful in clarifying the role of metal ions in biological systems, the time may now be right to utilize biological systems to advance coordination chemistry. One such example is the use of small, stable, easy-to-make, and well-characterized proteins as ligands to synthesize novel inorganic compounds. This biosynthetic inorganic chemistry is possible thanks to a number of developments in biology. This review summarizes the progress in the synthesis of close models of complex metalloproteins, followed by a description of recent advances in using the approach for making novel compounds that are unprecedented in either inorganic chemistry or biology. The focus is mainly on synthetic "tricks" learned from biology, as well as novel structures and insights obtained. The advantages and disadvantages of this biosynthetic approach are discussed.

  5. Commentary: Reforming the General Chemistry Textbook

    Science.gov (United States)

    Gillespie, Ronald G.

    1997-05-01

    Most of use who teach chemistry want students to understand what we teach them. But many students, perhaps most, do not try to understand. Even if they set out trying to understand they usually soon conclude that it is too difficult, at least in the time they have available, and they resort, like the others, to learning the material. By learning they mean memorizingnames of substances, formulas, definitions of oxidation and reduction, shapes of orbitals, recipes for assigning oxidation numbers and doing pH calculations, etc., etc. Most students do not particularly object to doing this because it is what they did in high school and is what it means to study. Many will object to being expected to understand, as they find it easier to memorize and most of them have little understanding of what it means to understand. Surprising as it may seem to us, they see chemistry as very abstract, very difficult, and unrelated to real life. But this is perhaps not so surprising if we remember that for these students, chemistry consists of a large amount of apparently unrelated, irrelevant, and useless material that they have memorized rather than understood! Their main objective is to pass the course and get on to something they consider more interesting and more useful. They take from the course very little of value in other courses or in later life and little, if any, understanding of what chemistry is really aboutmerely a conviction that they will never understand it. Over many years I have noticed that when I meet people socially and reveal that I am a professor of chemistry, they are amazed. How could an otherwise normal-appearing sort of guy possibly understand that stuff? They often admit, somewhat apologetically, that chemistry was their worst subject at high school or university or that it was the most difficult of all the subjects they took. Why do I rarely meet anyone who tells me chemistry was fascinating or exciting, or at least interesting? Why do most students find

  6. Advances in computational actinide chemistry in China

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dongqi; Wu, Jingyi; Chai, Zhifang [Chinese Academy of Sciences, Beijing (China). Multidisciplinary Initiative Center; Su, Jing [Chinese Academy of Sciences, Shanghai (China). Div. of Nuclear Materials Science and Engineering; Li, Jun [Tsinghua Univ., Beijing (China). Dept. of Chemistry and Laboratory of Organic Optoelectronics and Molecular Engineering

    2014-04-01

    The advances in computational actinide chemistry made in China are reviewed. Several areas relevant to chemistry of actinides in gas, liquid, and solid phases have been explored. However, we limit the scope to selected contributions in the chemistry of molecular actinide systems in gas and liquid phases. These studies may be classified into two categories: treatment of relativistic effects, which cover the development of two- and four-component Hamiltonians and the optimization of relativistic pseudopotentials, and the applications of theoretical methods in actinide chemistry. The applications include (1) the electronic structures of actinocene, noble gas complexes, An-C multiple bonding compounds, uranyl and its isoelectronic species, fluorides and oxides, molecular systems with metal-metal bonding in their isolated forms (U{sub 2}, Pu{sub 2}) and in fullerene (U{sub 2} rate at C{sub 60}), and the excited states of actinide complexes; (2) chemical reactions, including oxidation, hydrolysis of UF{sub 6}, ligand exchange, reactivities of thorium oxo and sulfido metallocenes, CO{sub 2}/CS{sub 2} functionalization promoted by trivalent uranium complex; and (3) migration of actinides in the environment. A future outlook is discussed. (orig.)

  7. Annual Report 1984. Chemistry Department

    DEFF Research Database (Denmark)

    Funck, Jytte; Nielsen, Ole John

    This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1984 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, an......, analytical- and organic chemistry, environmental chemistry, polymer chemistry, geochemistry and waste disposal, radical chemistry, positron annihilation, mineral processing, and general.......This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1984 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry...

  8. Kinetics and Product Channels in Combustion Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Hershberger, John F. [North Dakota State Univ., Fargo, ND (United States)

    2017-02-28

    We report study of the chemical kinetics and/or photochemistry of several chemical reactions of potential interest in understanding the gas phase combustion chemistry of nitrogen-containing molecules. Studies completed during the final grant period include determination of quantum yields of the photolysis of HCNO, fulminic acid, a kinetics and product channel study of the reaction of CN radicals with methyl bromide, and study of the products of the reaction of hydroxymethyl radical with nitric oxide.

  9. Green chemistry of carbon nanomaterials.

    Science.gov (United States)

    Basiuk, Elena V; Basiuk, Vladimir A

    2014-01-01

    The global trend of looking for more ecologically friendly, "green" techniques manifested itself in the chemistry of carbon nanomaterials. The main principles of green chemistry emphasize how important it is to avoid the use, or at least to reduce the consumption, of organic solvents for a chemical process. And it is precisely this aspect that was systematically addressed and emphasized by our research group since the very beginning of our work on the chemistry of carbon nanomaterials in early 2000s. The present review focuses on the results obtained to date on solvent-free techniques for (mainly covalent) functionalization of fullerene C60, single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively), as well as nanodiamonds (NDs). We designed a series of simple and fast functionalization protocols based on thermally activated reactions with chemical compounds stable and volatile at 150-200 degrees C under reduced pressure, when not only the reactions take place at a high rate, but also excess reagents are spontaneously removed from the functionalized material, thus making its purification unnecessary. The main two classes of reagents are organic amines and thiols, including bifunctional ones, which can be used in conjunction with different forms of nanocarbons. The resulting chemical processes comprise nucleophilic addition of amines and thiols to fullerene C60 and to defect sites of pristine MWNTs, as well as direct amidation of carboxylic groups of oxidized nanotubes (mainly SWNTs) and ND. In the case of bifunctional amines and thiols, reactions of the second functional group can give rise to cross-linking effects, or be employed for further derivatization steps.

  10. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 1 covers papers on the advances of gas phase ion chemistry. The book discusses the advances in flow tubes and the measurement of ion-molecule rate coefficients and product distributions; the ion chemistry of the earth's atmosphere; and the classical ion-molecule collision theory. The text also describes statistical methods in reaction dynamics; the state selection by photoion-photoelectron coincidence; and the effects of temperature and pressure in the kinetics of ion-molecule reactions. The energy distribution in the unimolecular decomposition of ions, as well

  11. Mathematics for physical chemistry

    CERN Document Server

    Mortimer, Robert G

    2013-01-01

    Mathematics for Physical Chemistry is the ideal supplementary text for practicing chemists and students who want to sharpen their mathematics skills while enrolled in general through physical chemistry courses. This book specifically emphasizes the use of mathematics in the context of physical chemistry, as opposed to being simply a mathematics text. This 4e includes new exercises in each chapter that provide practice in a technique immediately after discussion or example and encourage self-study. The early chapters are constructed around a sequence of mathematical topics, wit

  12. Experiments in physical chemistry

    CERN Document Server

    Wilson, J M; Denaro, A R

    1968-01-01

    Experiments in Physical Chemistry, Second Edition provides a compilation of experiments concerning physical chemistry. This book illustrates the link between the theory and practice of physical chemistry. Organized into three parts, this edition begins with an overview of those experiments that generally have a simple theoretical background. Part II contains experiments that are associated with more advanced theory or more developed techniques, or which require a greater degree of experimental skill. Part III consists of experiments that are in the nature of investigations wherein these invest

  13. Spatially Resolved Artificial Chemistry

    DEFF Research Database (Denmark)

    Fellermann, Harold

    2009-01-01

    Although spatial structures can play a crucial role in chemical systems and can drastically alter the outcome of reactions, the traditional framework of artificial chemistry is a well-stirred tank reactor with no spatial representation in mind. Advanced method development in physical chemistry has...... made a class of models accessible to the realms of artificial chemistry that represent reacting molecules in a coarse-grained fashion in continuous space. This chapter introduces the mathematical models of Brownian dynamics (BD) and dissipative particle dynamics (DPD) for molecular motion and reaction...

  14. Fluorine in medicinal chemistry.

    Science.gov (United States)

    Swallow, Steven

    2015-01-01

    Since its first use in the steroid field in the late 1950s, the use of fluorine in medicinal chemistry has become commonplace, with the small electronegative fluorine atom being a key part of the medicinal chemist's repertoire of substitutions used to modulate all aspects of molecular properties including potency, physical chemistry and pharmacokinetics. This review will highlight the special nature of fluorine, drawing from a survey of marketed fluorinated pharmaceuticals and the medicinal chemistry literature, to illustrate key concepts exploited by medicinal chemists in their attempts to optimize drug molecules. Some of the potential pitfalls in the use of fluorine will also be highlighted.

  15. Research for the advancement of green chemistry practice: Studies in atmospheric and educational chemistry

    Science.gov (United States)

    Cullipher, Steven Gene

    Green chemistry is a philosophy of chemistry that emphasizes a decreasing dependence on limited non-renewable resources and an increasing focus on preventing pollution byproducts of the chemical industry. In short, it is the discipline of chemistry practiced through the lens of environmental stewardship. In an effort to advance the practice of green chemistry, three studies will be described that have ramifications for the practice. The first study examines the atmospheric oxidation of a hydrofluorinated ether, a third-generation CFC replacement compound with primarily unknown atmospheric degradation products. Determination of these products has the potential to impact decisions on refrigerant usage in the future. The second study examines chemistry students' development of understanding benefits-costs-risks analysis when presented with two real-world scenarios: refrigerant choice and fuel choice. By studying how benefits-costs-risks thinking develops, curricular materials and instructional approaches can be designed to better foster the development of an ability that is both necessary for green chemists and important in daily decision-making for non-chemists. The final study uses eye tracking technology to examine students' abilities to interpret molecular properties from structural information in the context of global warming. Such abilities are fundamental if chemists are to appropriately assess risks and hazards of chemistry practice.

  16. Heterogeneous catalytic materials solid state chemistry, surface chemistry and catalytic behaviour

    CERN Document Server

    Busca, Guido

    2014-01-01

    Heterogeneous Catalytic Materials discusses experimental methods and the latest developments in three areas of research: heterogeneous catalysis; surface chemistry; and the chemistry of catalysts. Catalytic materials are those solids that allow the chemical reaction to occur efficiently and cost-effectively. This book provides you with all necessary information to synthesize, characterize, and relate the properties of a catalyst to its behavior, enabling you to select the appropriate catalyst for the process and reactor system. Oxides (used both as catalysts and as supports for cata

  17. Biological Chemistry of Hydrogen Selenide.

    Science.gov (United States)

    Cupp-Sutton, Kellye A; Ashby, Michael T

    2016-11-22

    There are no two main-group elements that exhibit more similar physical and chemical properties than sulfur and selenium. Nonetheless, Nature has deemed both essential for life and has found a way to exploit the subtle unique properties of selenium to include it in biochemistry despite its congener sulfur being 10,000 times more abundant. Selenium is more easily oxidized and it is kinetically more labile, so all selenium compounds could be considered to be "Reactive Selenium Compounds" relative to their sulfur analogues. What is furthermore remarkable is that one of the most reactive forms of selenium, hydrogen selenide (HSe(-) at physiologic pH), is proposed to be the starting point for the biosynthesis of selenium-containing molecules. This review contrasts the chemical properties of sulfur and selenium and critically assesses the role of hydrogen selenide in biological chemistry.

  18. Biological Chemistry of Hydrogen Selenide

    Directory of Open Access Journals (Sweden)

    Kellye A. Cupp-Sutton

    2016-11-01

    Full Text Available There are no two main-group elements that exhibit more similar physical and chemical properties than sulfur and selenium. Nonetheless, Nature has deemed both essential for life and has found a way to exploit the subtle unique properties of selenium to include it in biochemistry despite its congener sulfur being 10,000 times more abundant. Selenium is more easily oxidized and it is kinetically more labile, so all selenium compounds could be considered to be “Reactive Selenium Compounds” relative to their sulfur analogues. What is furthermore remarkable is that one of the most reactive forms of selenium, hydrogen selenide (HSe− at physiologic pH, is proposed to be the starting point for the biosynthesis of selenium-containing molecules. This review contrasts the chemical properties of sulfur and selenium and critically assesses the role of hydrogen selenide in biological chemistry.

  19. Origins of life systems chemistry

    Science.gov (United States)

    Sutherland, J.

    2015-10-01

    By reconciling previously conflicting views about the origin of life - in which one or other cellular subsystem emerges first, and then 'invents' the others - a new modus operandi for its study is suggested. Guided by this, a cyanosulfidic protometabolism is uncovered which uses UV light and the stoichiometric reducing power of hydrogen sulfide to convert hydrogen cyanide, and a couple of other prebiotic feedstock molecules which can be derived therefrom, into nucleic acid, peptide and lipid building blocks. Copper plays several key roles in this chemistry, thus, for example, copper(I) catalysed cross coupling and copper(II) driven oxidative crosscoupling reactions generate key feedstock molecules. Geochemical scenarios consistent with this protometabolism are outlined. Finally, the transition of a system from the inanimate to the animate state is considered in the context of there being intermediate stages of partial 'aliveness'.

  20. Combustion chemistry. Activities in the CHEC research programme

    Energy Technology Data Exchange (ETDEWEB)

    Dam-Johansen, K.; Johnsson, J.E.; Glarborg, P.; Frandsen, F.; Jensen, A.; Oestberg, M. [Technical Univ. of Denmark, Dept. of Chemical Engineering, Lyngby (Denmark)

    1996-12-01

    The combustion chemistry in the oxidation of fossil fuels and biofuels determines together with mixing and heat transfer the required size of a furnace, the emission of gaseous pollutants, and the formation of ash and deposits on surfaces. This paper describes technologies for solid fuels combustion and gives a summary of the fuels, the pollutant chemistry and the inorganic chemistry in combustion processes. Emphasis is put on the work carried out in the CHEC (Combustion and Harmful Emission Control Research Programme). (au) 173 refs.

  1. Indicators: Soil Chemistry

    Science.gov (United States)

    The chemical makeup of the soil can provide information on wetland condition, wetland water quality and services being provided by the wetland ecosystem. Analyzing soil chemistry reveals if the soil is contaminated with a toxic chemical or heavy metal.

  2. Chemistry for Kids.

    Science.gov (United States)

    Sato, Sanae; Majoros, Bela

    1988-01-01

    Reports two methods for interesting children in chemistry. Describes a method for producing large soap bubbles and films for study. Examines the use of simple stories to explain common chemical concepts with example given. Lists titles of available stories. (ML)

  3. Beauty in chemistry

    Directory of Open Access Journals (Sweden)

    Peter Atkins

    2006-03-01

    Full Text Available Though hard going for the general reader and highly personal in its selectivity, Elegant Solutions: Ten Beautiful Experiments in Chemistry provides reflections of a thoughtful author that will delight chemists

  4. Uncertainty in chemistry.

    Science.gov (United States)

    Menger, Fredric M

    2010-09-01

    It might come as a disappointment to some chemists, but just as there are uncertainties in physics and mathematics, there are some chemistry questions we may never know the answer to either, suggests Fredric M. Menger.

  5. Chemistry at large

    Directory of Open Access Journals (Sweden)

    Jeremy. K.M. Sanders

    2007-06-01

    Full Text Available A new book introduces young researchers to supramolecular chemistry, starting from the basics and working up to the more complicated aspects of the topic. While the text is inspiring for new graduates, it lacks a critical view.

  6. Enzymes in Analytical Chemistry.

    Science.gov (United States)

    Fishman, Myer M.

    1980-01-01

    Presents tabular information concerning recent research in the field of enzymes in analytic chemistry, with methods, substrate or reaction catalyzed, assay, comments and references listed. The table refers to 128 references. Also listed are 13 general citations. (CS)

  7. Water Chemistry: Seeking Information

    Science.gov (United States)

    Delfino, Joseph J.

    1977-01-01

    A survey of the available literature in water chemistry is presented. Materials surveyed include: texts, reference books, bibliographic resources, journals, American Chemical Society publications, proceedings, unpublished articles, and reports. (BT)

  8. Forensic Chemistry Training

    OpenAIRE

    GERÇEK, Zuhal

    2012-01-01

    Increasing the types of terrorism and crime nowadays, the importance of the forensic sciences can be bett er understood. Forensic science is the application of the wide spectrum of science to answer the question of legal system. It contains the application of the principles, techniques and methods of basic sciences and its main aim is the determination of the physical facts which are important in legal situations. Forensic chemistry is the branch of chemistry which performs the chemical analy...

  9. Click chemistry with DNA

    OpenAIRE

    El-Sagheer, Afaf H.; Brown, Tom

    2010-01-01

    The advent of click chemistry has led to an influx of new ideas in the nucleic acids field. The copper catalysed alkyne–azide cycloaddition (CuAAC) reaction is the method of choice for DNA click chemistry due to its remarkable efficiency. It has been used to label oligonucleotides with fluorescent dyes, sugars, peptides and other reporter groups, to cyclise DNA, to synthesise DNA catenanes, to join oligonucleotides to PNA, and to produce analogues of DNA with modified nucleobases and backbone...

  10. Impact of surface chemistry

    OpenAIRE

    2010-01-01

    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized.

  11. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 2 covers the advances in gas phase ion chemistry. The book discusses the stabilities of positive ions from equilibrium gas-phase basicity measurements; the experimental methods used to determine molecular electron affinities, specifically photoelectron spectroscopy, photodetachment spectroscopy, charge transfer, and collisional ionization; and the gas-phase acidity scale. The text also describes the basis of the technique of chemical ionization mass spectrometry; the energetics and mechanisms of unimolecular reactions of positive ions; and the photodissociation

  12. Fundamentals of quantum chemistry

    CERN Document Server

    House, J E

    2004-01-01

    An introduction to the principles of quantum mechanics needed in physical chemistry. Mathematical tools are presented and developed as needed and only basic calculus, chemistry, and physics is assumed. Applications include atomic and molecular structure, spectroscopy, alpha decay, tunneling, and superconductivity. New edition includes sections on perturbation theory, orbital symmetry of diatomic molecules, the Huckel MO method and Woodward/Hoffman rules as well as a new chapter on SCF and Hartree-Fock methods. * This revised text clearly presents basic q

  13. Applications of supramolecular chemistry

    CERN Document Server

    Schneider, Hans-Jörg

    2012-01-01

    ""The time is ripe for the present volume, which gathers thorough presentations of the numerous actually realized or potentially accessible applications of supramolecular chemistry by a number of the leading figures in the field. The variety of topics covered is witness to the diversity of the approaches and the areas of implementation…a broad and timely panorama of the field assembling an eminent roster of contributors.""-Jean-Marie Lehn, 1987 Noble Prize Winner in Chemistry

  14. Biocatalytic synthesis of flavones and hydroxyl-small molecules by recombinant Escherichia coli cells expressing the cyanobacterial CYP110E1 gene

    Directory of Open Access Journals (Sweden)

    Makino Takuya

    2012-07-01

    Full Text Available Abstract Background Cyanobacteria possess several cytochrome P450s, but very little is known about their catalytic functions. CYP110 genes unique to cyanaobacteria are widely distributed in heterocyst-forming cyanobacteria including nitrogen-fixing genera Nostoc and Anabaena. We screened the biocatalytic functions of all P450s from three cyanobacterial strains of genus Nostoc or Anabaena using a series of small molecules that contain flavonoids, sesquiterpenes, low-molecular-weight drugs, and other aromatic compounds. Results Escherichia coli cells carrying each P450 gene that was inserted into the pRED vector, containing the RhFRed reductase domain sequence from Rhodococcus sp. NCIMB 9784 P450RhF (CYP116B2, were co-cultured with substrates and products were identified when bioconversion reactions proceeded. Consequently, CYP110E1 of Nostoc sp. strain PCC 7120, located in close proximity to the first branch point in the phylogenetic tree of the CYP110 family, was found to be promiscuous for the substrate range mediating the biotransformation of various small molecules. Naringenin and (hydroxyl flavanones were respectively converted to apigenin and (hydroxyl flavones, by functioning as a flavone synthase. Such an activity is reported for the first time in prokaryotic P450s. Additionally, CYP110E1 biotransformed the notable sesquiterpene zerumbone, anti-inflammatory drugs ibuprofen and flurbiprofen (methylester forms, and some aryl compounds such as 1-methoxy and 1-ethoxy naphthalene to produce hydroxylated compounds that are difficult to synthesize chemically, including novel compounds. Conclusion We elucidated that the CYP110E1 gene, C-terminally fused to the P450RhF RhFRed reductase domain sequence, is functionally expressed in E. coli to synthesize a robust monooxygenase, which shows promiscuous substrate specificity (affinity for various small molecules, allowing the biosynthesis of not only flavones (from flavanones but also a variety of

  15. Immobilisation and characterisation of biocatalytic co-factor recycling enzymes, glucose dehydrogenase and NADH oxidase, on aldehyde functional ReSyn™ polymer microspheres.

    Science.gov (United States)

    Twala, Busisiwe V; Sewell, B Trevor; Jordaan, Justin

    2012-05-10

    The use of enzymes in industrial applications is limited by their instability, cost and difficulty in their recovery and re-use. Immobilisation is a technique which has been shown to alleviate these limitations in biocatalysis. Here we describe the immobilisation of two biocatalytically relevant co-factor recycling enzymes, glucose dehydrogenase (GDH) and NADH oxidase (NOD) on aldehyde functional ReSyn™ polymer microspheres with varying functional group densities. The successful immobilisation of the enzymes on this new high capacity microsphere technology resulted in the maintenance of activity of ∼40% for GDH and a maximum of 15.4% for NOD. The microsphere variant with highest functional group density of ∼3500 μmol g⁻¹ displayed the highest specific activity for the immobilisation of both enzymes at 33.22 U mg⁻¹ and 6.75 U mg⁻¹ for GDH and NOD with respective loading capacities of 51% (0.51 mg mg⁻¹) and 129% (1.29 mg mg⁻¹). The immobilised GDH further displayed improved activity in the acidic pH range. Both enzymes displayed improved pH and thermal stability with the most pronounced thermal stability for GDH displayed on ReSyn™ A during temperature incubation at 65 °C with a 13.59 fold increase, and NOD with a 2.25-fold improvement at 45 °C on the same microsphere variant. An important finding is the suitability of the microspheres for stabilisation of the multimeric protein GDH.

  16. Leloir Glycosyltransferases and Natural Product Glycosylation: Biocatalytic Synthesis of the C-Glucoside Nothofagin, a Major Antioxidant of Redbush Herbal Tea.

    Science.gov (United States)

    Bungaruang, Linda; Gutmann, Alexander; Nidetzky, Bernd

    2013-10-11

    Nothofagin is a major antioxidant of redbush herbal tea and represents a class of bioactive flavonoid-like C-glycosidic natural products. We developed an efficient enzymatic synthesis of nothofagin based on a one-pot coupled glycosyltransferase-catalyzed transformation that involves perfectly selective 3'-C-β-d-glucosylation of naturally abundant phloretin and applies sucrose as expedient glucosyl donor. C-Glucosyltransferase from Oryza sativa (rice) was used for phloretin C-glucosylation from uridine 5'-diphosphate (UDP)-glucose, which was supplied continuously in situ through conversion of sucrose and UDP catalyzed by sucrose synthase from Glycine max (soybean). In an evaluation of thermodynamic, kinetic, and stability parameters of the coupled enzymatic reactions, poor water solubility of the phloretin acceptor substrate was revealed as a major bottleneck of conversion efficiency. Using periodic feed of phloretin controlled by reaction progress, nothofagin concentrations (45 mM; 20 g l(-1)) were obtained that vastly exceed the phloretin solubility limit (5-10 mM). The intermediate UDP-glucose was produced from catalytic amounts of UDP (1.0 mM) and was thus recycled 45 times in the process. Benchmarked against comparable glycosyltransferase-catalyzed transformations (e.g., on quercetin), the synthesis of nothofagin has achieved intensification in glycosidic product formation by up to three orders of magnitude (μM→mM range). It thus makes a strong case for the application of Leloir glycosyltransferases in biocatalytic syntheses of glycosylated natural products as fine chemicals.

  17. Evidence for strong, widespread chlorine radical chemistry associated with pollution outflow from continental Asia

    Science.gov (United States)

    Baker, Angela K.; Sauvage, Carina; Thorenz, Ute R.; van Velthoven, Peter; Oram, David E.; Zahn, Andreas; Brenninkmeijer, Carl A. M.; Williams, Jonathan

    2016-11-01

    The chlorine radical is a potent atmospheric oxidant, capable of perturbing tropospheric oxidative cycles normally controlled by the hydroxyl radical. Significantly faster reaction rates allow chlorine radicals to expedite oxidation of hydrocarbons, including methane, and in polluted environments, to enhance ozone production. Here we present evidence, from the CARIBIC airborne dataset, for extensive chlorine radical chemistry associated with Asian pollution outflow, from airborne observations made over the Malaysian Peninsula in winter. This region is known for persistent convection that regularly delivers surface air to higher altitudes and serves as a major transport pathway into the stratosphere. Oxidant ratios inferred from hydrocarbon relationships show that chlorine radicals were regionally more important than hydroxyl radicals for alkane oxidation and were also important for methane and alkene oxidation (>10%). Our observations reveal pollution-related chlorine chemistry that is both widespread and recurrent, and has implications for tropospheric oxidizing capacity, stratospheric composition and ozone chemistry.

  18. Role of acidic chemistries in steam treatment of aluminium alloys

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Jellesen, Morten Stendahl; Ambat, Rajan

    2015-01-01

    The effect of acidic chemistry on the accelerated growth of oxide on aluminium alloys Peraluman 706TM and AA6060 under exposure to high temperature steam was investigated. Studied chemistries were based on citrates and phosphates. Results showed that the presence of citrate and phosphate anions...... initiate doxide growth at the intermetallic particles while growth and corrosion performance of oxide was found tobe a function of anions type and their concentration. Further, steam treatment with phosphates exhibited better performance under acetic acid salt spray and filiform corrosion test whereas...

  19. Titan: a laboratory for prebiological organic chemistry

    Science.gov (United States)

    Sagan, C.; Thompson, W. R.; Khare, B. N.

    1992-01-01

    When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

  20. Processes regulating nitric oxide emissions from soils

    DEFF Research Database (Denmark)

    Pilegaard, Kim

    2013-01-01

    Nitric oxide (NO) is a reactive gas that plays an important role in atmospheric chemistry by influencing the production and destruction of ozone and thereby the oxidizing capacity of the atmosphere. NO also contributes by its oxidation products to the formation of acid rain. The major sources...

  1. Copper Nanoparticles in Click Chemistry.

    Science.gov (United States)

    Alonso, Francisco; Moglie, Yanina; Radivoy, Gabriel

    2015-09-15

    The challenges of the 21st century demand scientific and technological achievements that must be developed under sustainable and environmentally benign practices. In this vein, click chemistry and green chemistry walk hand in hand on a pathway of rigorous principles that help to safeguard the health of our planet against negligent and uncontrolled production. Copper-catalyzed azide-alkyne cycloaddition (CuAAC), the paradigm of a click reaction, is one of the most reliable and widespread synthetic transformations in organic chemistry, with multidisciplinary applications. Nanocatalysis is a green chemistry tool that can increase the inherent effectiveness of CuAAC because of the enhanced catalytic activity of nanostructured metals and their plausible reutilization capability as heterogeneous catalysts. This Account describes our contribution to click chemistry using unsupported and supported copper nanoparticles (CuNPs) as catalysts prepared by chemical reduction. Cu(0)NPs (3.0 ± 1.5 nm) in tetrahydrofuran were found to catalyze the reaction of terminal alkynes and organic azides in the presence of triethylamine at rates comparable to those achieved under microwave heating (10-30 min in most cases). Unfortunately, the CuNPs underwent dissolution under the reaction conditions and consequently could not be recovered. Compelling experimental evidence on the in situ generation of highly reactive copper(I) chloride and the participation of copper(I) acetylides was provided. The supported CuNPs were found to be more robust and efficient catalyst than the unsupported counterpart in the following terms: (a) the multicomponent variant of CuAAC could be applied; (b) the metal loading could be substantially decreased; (c) reactions could be conducted in neat water; and (d) the catalyst could be recovered easily and reutilized. In particular, the catalyst composed of oxidized CuNPs (Cu2O/CuO, 6.0 ± 2.0 nm) supported on carbon (CuNPs/C) was shown to be highly versatile and very

  2. Stimulus Responsive Poly(ferrocenylsilanes): Redox Chemistry of Iron in the Main Chain

    NARCIS (Netherlands)

    Giannotti, M.; Lv, H.; Ma, Y.; Steenvoorden, M.P.; Overweg, A.R.; Roerdink, M.; Hempenius, M.A.; Vancso, G.J.

    2006-01-01

    Redox chemistry of organometallic poly(ferrocenylsilane) polymers (soluble in organic or aqueous environment) is discussed. Poly(ferrocenyldimethylsilane) (PFDMS) was oxidized in CH2Cl2 solution with different oxidants. Oxidation was accomplished with stepwise increasing amounts of ferric chloride (

  3. Principles of Chemistry (by Michael Munowitz)

    Science.gov (United States)

    Kovac, Reviewed By Jeffrey

    2000-05-01

    principles. This is a very conceptual book. Each chapter has two parts, which are distinguished by having different-colored pages: white and gray. The first part of every chapter is a lovely conceptual development of the "big picture". In these white pages, there are no sample problems, no tables of data, just elegant prose liberally illustrated with graphs and diagrams. Mathematical and chemical equations and chemical structures are presented as needed, but the goal is to provide the reader with a conceptual understanding. I found these introductory "lectures", as Munowitz terms them, to be enchanting. The second part of each chapter is a review and guide to problems, what Munowitz calls the "recitation" section. These pages are gray. This second section gives a brief summary of the material, which is followed by a series of worked examples that apply the concepts to practical problems. This structure reflects the author's pedagogical philosophy--begin with the general and move to the specific--and his view of chemistry as a combination of "lofty principles and gritty practicality". Following the worked examples, of course, are exercises for the student, ranging from simple drill problems to more sophisticated applications of the principles. I was a little disappointed, however, that there were so few conceptual exercises. Although Munowitz describes the second part of each chapter as a review and applications, he does put new material into the sample problems. For example, in Chapter 3 the concept of oxidation numbers is introduced and sample problems on the assignment of oxidation numbers are presented. Then, in example 3-3, the concept of formal charge is presented as a contrast to the oxidation number even though this idea had not been previously introduced. The dual structure of white and gray pages makes this book unique but also very long. The combined length of the white sections is about 800 pages, but an approximately 25-page conceptual section is always followed

  4. Influences of operating conditions on biocatalytic activity and reusability of Novozym 435 for esterification of free fatty acids with short-chain alcohols:A case study of palm fatty acid distillate

    Institute of Scientific and Technical Information of China (English)

    Sawittree Mulalee; Pongrumpa Srisuwan; Muenduen Phisalaphong

    2015-01-01

    In the present study, the effects of operating conditions on biocatalytic activity and stability of Novozym 435 for repeated-batch biodiesel production from free fatty acid (FFA) were investigated. Thermal deactivation caused by increased operating temperature from 45 to 50 °C could seriously affect the reusability of Novozym 435. The deactivation of Novozym 435 during the esterification of oleic acid with ethanol tended to be stronger than that in the system with methanol. Under the optimal conditions, considering both biocatalytic activity and stability of the enzyme, Novozym 435 could be reused for 13 cycles for biodiesel productions from oleic acid and absolute alcohols (methanol and ethanol) with FFA conversions of at least 90%. The presence of 4%–5%water in ethanol significantly affected the reusability of Novozym 435. Changes in the surface morphology of Novozym 435 during the esterification with various conditions were observed. It was revealed that the reduc-tion in catalytic activity was related to the swel ing degree of the catalyst surface. Additionally, biodiesel produc-tion from low cost renewable feedstocks, such as palm fatty acid distillate (PFAD) and 95%ethanol was examined. The esterification of PFAD with 95%ethanol catalyzed by Novozym 435 in 10-repeated batch operation showed the similar results in FFA conversion as compared to those using oleic acid. Novozym 435 remained active and could maintain 97.6%of its initial conversion after being used for 10 batches.

  5. Clay-protein ultrathin films: Design and bio-catalytic performance study%粘土矿物-蛋白质超薄膜的设计与生物催化性能

    Institute of Scientific and Technical Information of China (English)

    苗世顶; 邱治国; 崔鹏

    2012-01-01

    In recent years, immense interest has been paid to the biomolecular architecture with the aim of protein assembly in 2-dimensions on solid substrates, and the constructions of clay-protein ultrathin films (CPUFs) are particularly concerned. This paper gives an overview of the recent research concerning the protein molecules (lysozyme, papain, protamine, bovine serum albumin) immobilized on clay mineral (Na-saponite) platelets and assembled in monolayered or multilayered hybrid ultrafilms or nanofilms. Two techniques including alternate layer-by-layer (LbL) assembly and the Langmuir-Blodgett (LB) are described in detail. A variety of means, including UV-vis absorption, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, XRD, AFM and surface chemistry techniques, have been described for characterization of the films in terms of quantification of protein and clay. The result reveals that electrostatic interaction is a prominent but not the only driving force in CPUF construction. In the case of LB technique, we managed to manipulate the elementary clay mineral platelets (1.3 nm in thickness) and assemble proteins into CPUFs with the aid of surfactants, and the formation of CPUFs was monitored via surface pressure vs. Time (π-t) kinetics curves and surface pressure vs. Area (π-A) isotherms. The factors that influence protein adsorption on the clay layer, such as surfactants, the concentration of clay, equilibrium time, categories of protein, and injection methods, were investigated. The parameters such as protein amount (ns), packing density (0), and average surface area per molecule (Ω) of deposited CPUFs were measured via method of surface chemistry and spectroscopy. By comparing the results of surface chemistry with those of adsorption experiments, we demonstrate that the surface chemistry method is a useful tool in investigating CPUFs. We also found that the water soluble protein molecules could form protein-clay hybrid monolayer

  6. Chemistry beyond positivism.

    Science.gov (United States)

    Brandt, Werner W

    2003-05-01

    Chemistry is often thought to be quite factual, and therefore might be considered close to the "positivist" ideal of a value-free science. A closer look, however, reveals that the field is coupled to the invisible realm of values, meanings, and purpose in various ways, and chemists interact with that realm loosely and unevenly. Tacit knowledge is one important locus of such interactions. We are concerned in this essay with two questions. What is the nature of the knowledge when we are in the early stages of discovery? and In what ways does the hidden reality we are seeking affect our search for an understanding of it? The first question is partly answered by Polanyi's theory of tacit knowledge, while the second one leads us to realize the limitations of our language when discussing "reality"-or certain chemical experimental results. A strictly positivist approach is of little use, but so is the opposite, the complete disregard of facts. The contrast between positivism and non-formulable aspects of scientific reasoning amounts to a paradox that needs to be analyzed and can lead to a "connected" chemistry. This in turn resembles networks described by Schweber and is more concerned than the chemistry "as it is" with aspects such as the image of chemistry, the challenges chemists face as citizens, and chemistry in liberal education.

  7. Δ9-Tetrahydrocannabinolic acid synthase: The application of a plant secondary metabolite enzyme in biocatalytic chemical synthesis.

    Science.gov (United States)

    Lange, Kerstin; Schmid, Andreas; Julsing, Mattijs K

    2016-09-10

    Δ(9)-Tetrahydrocannabinolic acid synthase (THCAS) from the secondary metabolism of Cannabis sativa L. catalyzes the oxidative formation of an intramolecular CC bond in cannabigerolic acid (CBGA) to synthesize Δ(9)-tetrahydrocannabinolic acid (THCA), which is the direct precursor of Δ(9)-tetrahydrocannabinol (Δ(9)-THC). Aiming on a biotechnological production of cannabinoids, we investigated the potential of the heterologously produced plant oxidase in a cell-free system on preparative scale. THCAS was characterized in an aqueous/organic two-liquid phase setup in order to solubilize the hydrophobic substrate and to allow in situ product removal. Compared to the single phase aqueous setup the specific activity decreased by a factor of approximately 2 pointing to a substrate limitation of CBGA in the two-liquid phase system. However, the specific activity remained stable for at least 3h illustrating the benefit of the two-liquid phase setup. In a repeated-batch setup, THCAS showed only a minor loss of specific activity in the third batch pointing to a high intrinsic stability and high solvent tolerance of the enzyme. Maximal space-time-yields of 0.121gL(-1)h(-1) were reached proving the two-liquid phase concept suitable for biotechnological production of cannabinoids.

  8. Uranium triamidoamine chemistry.

    Science.gov (United States)

    Gardner, Benedict M; Liddle, Stephen T

    2015-07-01

    Triamidoamine (Tren) complexes of the p- and d-block elements have been well-studied, and they display a diverse array of chemistry of academic, industrial and biological significance. Such in-depth investigations are not as widespread for Tren complexes of uranium, despite the general drive to better understand the chemical behaviour of uranium by virtue of its fundamental position within the nuclear sector. However, the chemistry of Tren-uranium complexes is characterised by the ability to stabilise otherwise reactive, multiply bonded main group donor atom ligands, construct uranium-metal bonds, promote small molecule activation, and support single molecule magnetism, all of which exploit the steric, electronic, thermodynamic and kinetic features of the Tren ligand system. This Feature Article presents a current account of the chemistry of Tren-uranium complexes.

  9. Mathematics for physical chemistry

    CERN Document Server

    Mortimer, Robert G

    2005-01-01

    Mathematics for Physical Chemistry, Third Edition, is the ideal text for students and physical chemists who want to sharpen their mathematics skills. It can help prepare the reader for an undergraduate course, serve as a supplementary text for use during a course, or serve as a reference for graduate students and practicing chemists. The text concentrates on applications instead of theory, and, although the emphasis is on physical chemistry, it can also be useful in general chemistry courses. The Third Edition includes new exercises in each chapter that provide practice in a technique immediately after discussion or example and encourage self-study. The first ten chapters are constructed around a sequence of mathematical topics, with a gradual progression into more advanced material. The final chapter discusses mathematical topics needed in the analysis of experimental data.* Numerous examples and problems interspersed throughout the presentations * Each extensive chapter contains a preview, objectives, and ...

  10. Air Composition and Chemistry

    Science.gov (United States)

    Brimblecombe, Peter

    1996-01-01

    This book is about the atmosphere and humanity's influence on it. For this new edition, Brimblecombe has rewritten and updated much of the book. In the early chapters, he discusses the geochemical, biological and maritime sources of the trace gases. Next, he examines the chemistry of atmospheric gases, suspended particles, and rainfall. After dealing with the natural atmosphere, he examines the sources of air pollution and its effects, with all scenarios updated from the last edition. Scenarios include decline in health, damage to plants and animals, indoor pollution, and acid rain. The final chapters, also revised, are concerned with the chemistry and evolution of the atmospheres of the planets of the solar system. Students with an interest in chemistry and the environmental sciences will find this book highly valuable.

  11. Chemistry and lithography

    CERN Document Server

    Okoroanyanwu, Uzodinma

    2011-01-01

    This is a unique book, combining chemistry and physics with technology and history in a way that is both enlightening and lively. No other book in the field of lithography has as much breadth. Highly recommended for anyone interested in the broad application of chemistry to lithography. --Chris Mack, Gentleman Scientist. This book provides a comprehensive treatment of the chemical phenomena in lithography in a manner that is accessible to a wide readership. The book presents topics on the optical and charged particle physics practiced in lithography, with a broader view of how the marriage bet

  12. Chemistry in microelectronics

    CERN Document Server

    Le Tiec, Yannick

    2013-01-01

    Microelectronics is a complex world where many sciences need to collaborate to create nano-objects: we need expertise in electronics, microelectronics, physics, optics and mechanics also crossing into chemistry, electrochemistry, as well as biology, biochemistry and medicine. Chemistry is involved in many fields from materials, chemicals, gases, liquids or salts, the basics of reactions and equilibrium, to the optimized cleaning of surfaces and selective etching of specific layers. In addition, over recent decades, the size of the transistors has been drastically reduced while the functionalit

  13. Dynamic Combinatorial Chemistry

    DEFF Research Database (Denmark)

    Lisbjerg, Micke

    This thesis is divided into seven chapters, which can all be read individually. The first chapter, however, contains a general introduction to the chemistry used in the remaining six chapters, and it is therefore recommended to read chapter one before reading the other chapters. Chapter 1...... is a general introductory chapter for the whole thesis. The history and concepts of dynamic combinatorial chemistry are described, as are some of the new and intriguing results recently obtained. Finally, the properties of a broad range of hexameric macrocycles are described in detail. Chapter 2 gives...

  14. Chemistry WebBook

    Science.gov (United States)

    SRD 69 NIST Chemistry WebBook (Web, free access)   The NIST Chemistry WebBook contains: Thermochemical data for over 7000 organic and small inorganic compounds; thermochemistry data for over 8000 reactions; IR spectra for over 16,000 compounds; mass spectra for over 33,000 compounds; UV/Vis spectra for over 1600 compounds; electronic and vibrational spectra for over 5000 compounds; constants of diatomic molecules(spectroscopic data) for over 600 compounds; ion energetics data for over 16,000 compounds; thermophysical property data for 74 fluids.

  15. Solvent effects in chemistry

    CERN Document Server

    Buncel, Erwin

    2015-01-01

    This book introduces the concepts, theory and experimental knowledge concerning solvent effects on the rate and equilibrium of chemical reactions of all kinds.  It begins with basic thermodynamics and kinetics, building on this foundation to demonstrate how a more detailed understanding of these effects may be used to aid in determination of reaction mechanisms, and to aid in planning syntheses. Consideration is given to theoretical calculations (quantum chemistry, molecular dynamics, etc.), to statistical methods (chemometrics), and to modern day concerns such as ""green"" chemistry, where ut

  16. Progress in physical chemistry

    CERN Document Server

    Hempelmann, Rolf

    2008-01-01

    Progress in Physical Chemistry is a collection of recent ""Review Articles"" published in the ""Zeitschrift für Physikalische Chemie"". The second volume of Progress in Physical Chemistry is a collection of thematically closely related minireview articles written by the members of the Collaborative Research Centre (SFB) 277 of the German Research Foundation (DFG). These articles are based on twelve years of intense coordinated research efforts. Central topics are the synthesis and the characterization of interface-dominated, i.e. nanostructured materials, mainly in the solid state but also as

  17. The chemistry of silicon

    CERN Document Server

    Rochow, E G; Emeléus, H J; Nyholm, Ronald

    1975-01-01

    Pergamon Texts in Organic Chemistry, Volume 9: The Chemistry of Silicon presents information essential in understanding the chemical properties of silicon. The book first covers the fundamental aspects of silicon, such as its nuclear, physical, and chemical properties. The text also details the history of silicon, its occurrence and distribution, and applications. Next, the selection enumerates the compounds and complexes of silicon, along with organosilicon compounds. The text will be of great interest to chemists and chemical engineers. Other researchers working on research study involving s

  18. Spins in chemistry

    CERN Document Server

    McWeeny, Roy

    2004-01-01

    Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp

  19. Quest for new materials: Inorganic chemistry plays a crucial role

    Indian Academy of Sciences (India)

    J Gopalakrishnan; Rohini Mani

    2009-05-01

    There is an endless quest for new materials to meet the demands of advancing technology. Thus, we need new magnetic and metallic/semiconducting materials for spintronics, new low-loss dielectrics for telecommunication, new multi-ferroic materials that combine both ferroelectricity and ferromagnetism for memory devices, new piezoelectrics that do not contain lead, new lithium containing solids for application as cathode/anode/electrolyte in lithium batteries, hydrogen storage materials for mobile/transport applications and catalyst materials that can convert, for example, methane to higher hydrocarbons, and the list is endless! Fortunately for us, chemistry - inorganic chemistry in particular - plays a crucial role in this quest. Most of the functional materials mentioned above are inorganic non-molecular solids, while much of the conventional inorganic chemistry deals with isolated molecules or molecular solids. Even so, the basic concepts that we learn in inorganic chemistry, for example, acidity/basicity, oxidation/reduction (potentials), crystal field theory, low spin-high spin/inner sphere-outer sphere complexes, role of -electrons in transition metal chemistry, electron-transfer reactions, coordination geometries around metal atoms, Jahn-Teller distortion, metal-metal bonds, cation-anion (metal-nonmetal) redox competition in the stabilization of oxidation states - all find crucial application in the design and synthesis of inorganic solids possessing technologically important properties. An attempt has been made here to illustrate the role of inorganic chemistry in this endeavour, drawing examples from the literature as well as from the research work of my group.

  20. Impact of turbulent mixing on isoprene chemistry

    Science.gov (United States)

    Kim, S.-W.; Barth, M. C.; Trainer, M.

    2016-07-01

    Isoprene, a volatile organic compound that is mainly emitted from trees, rapidly reacts with hydroxyl radical (OH) during daytime and subsequently forms ozone and aerosols in the troposphere. The isoprene-OH reaction can be affected by the interplay between chemistry and mixing because the two processes occur at a similar time scale. We investigate the impact of turbulent mixing on isoprene-OH reactivity with large eddy simulations (LES) coupled with comprehensive chemistry. Our results show that the covariance of isoprene and OH causes ~20% decrease to ~10% increase of the horizontal average reaction rate, depending on nitrogen oxides (NOx = NO + NO2) abundances, compared to the rate that neglects the covariance. This wide range of effects on reaction rates is caused by the primary production and loss reactions of OH in each NOx regime. Our research promotes the use of LES for better understanding the role of turbulence in isoprene-OH reaction and parameterizations in large-scale models.

  1. Is Chemistry Attractive for Pupils? Czech Pupils' Perception of Chemistry

    Science.gov (United States)

    Kubiatko, Milan

    2015-01-01

    Chemistry is an important subject due to understanding the composition and structure of the things around us. The main aim of the study was to find out the perception of chemistry by lower secondary school pupils. The partial aims were to find out the influence of gender, year of study and favorite subject on the perception of chemistry. The…

  2. Turkish Prospective Chemistry Teachers' Beliefs about Chemistry Teaching

    Science.gov (United States)

    Boz, Yezdan; Uzuntiryaki, Esen

    2006-01-01

    In order to study the beliefs of Turkish prospective chemistry teachers about teaching chemistry, semi-structured interviews were conducted with 12 prospective teachers. Analysis of the interviews revealed that most of the prospective teachers held intermediate (transition between constructivist and traditional) beliefs about chemistry teaching.…

  3. Top Down Chemistry Versus Bottom up Chemistry

    Science.gov (United States)

    Oka, Takeshi; Witt, Adolf N.

    2016-06-01

    The idea of interstellar top down chemistry (TDC), in which molecules are produced from decomposition of larger molecules and dust in contrast to ordinary bottom up chemistry (BUC) in which molecules are produced synthetically from smaller molecules and atoms in the ISM, has been proposed in the chemistry of PAH and carbon chain molecules both for diffusea,c and dense cloudsb,d. A simple and natural idea, it must have occurred to many people and has been in the air for sometime. The validity of this hypothesis is apparent for diffuse clouds in view of the observed low abundance of small molecules and its rapid decrease with molecular size on the one hand and the high column densities of large carbon molecules demonstrated by the many intense diffuse interstellar bands (DIBs) on the other. Recent identification of C60^+ as the carrier of 5 near infrared DIBs with a high column density of 2×1013 cm-2 by Maier and others confirms the TDC. This means that the large molecules and dust produced in the high density high temperature environment of circumstellar envelopes are sufficiently stable to survive decompositions due to stellar UV radiaiton, cosmic rays, C-shocks etc. for a long time (≥ 10^7 year) of their migration to diffuse clouds and seems to disagree with the consensus in the field of interstellar grains. The stability of molecules and aggregates in the diffuse interstellar medium will be discussed. Duley, W. W. 2006, Faraday Discuss. 133, 415 Zhen,J., Castellanos, P., Paardekooper, D. M., Linnartz, H., Tielens, A. G. G. M. 2014, ApJL, 797, L30 Huang, J., Oka, T. 2015, Mol. Phys. 113, 2159 Guzmán, V. V., Pety, J., Goicoechea, J. R., Gerin, M., Roueff, E., Gratier, P., Öberg, K. I. 2015, ApJL, 800, L33 L. Ziurys has sent us many papers beginning Ziurys, L. M. 2006, PNAS 103, 12274 indicating she had long been a proponent of the idea. Campbell, E. K., Holz, M., Maier, J. P., Gerlich, D., Walker, G. A. H., Bohlender, D, 2016, ApJ, in press Draine, B. T. 2003

  4. Overview of actinide chemistry in the WIPP

    Energy Technology Data Exchange (ETDEWEB)

    Borkowski, Marian [Los Alamos National Laboratory; Lucchini, Jean - Francois [Los Alamos National Laboratory; Richmann, Michael K [Los Alamos National Laboratory; Reed, Donald T [Los Alamos National Laboratory; Khaing, Hnin [Los Alamos National Laboratory; Swanson, Juliet [Los Alamos National Laboratory

    2009-01-01

    The year 2009 celebrates 10 years of safe operations at the Waste Isolation Pilot Plant (WIPP), the only nuclear waste repository designated to dispose defense-related transuranic (TRU) waste in the United States. Many elements contributed to the success of this one-of-the-kind facility. One of the most important of these is the chemistry of the actinides under WIPP repository conditions. A reliable understanding of the potential release of actinides from the site to the accessible environment is important to the WIPP performance assessment (PA). The environmental chemistry of the major actinides disposed at the WIPP continues to be investigated as part of the ongoing recertification efforts of the WIPP project. This presentation provides an overview of the actinide chemistry for the WIPP repository conditions. The WIPP is a salt-based repository; therefore, the inflow of brine into the repository is minimized, due to the natural tendency of excavated salt to re-seal. Reducing anoxic conditions are expected in WIPP because of microbial activity and metal corrosion processes that consume the oxygen initially present. Should brine be introduced through an intrusion scenario, these same processes will re-establish reducing conditions. In the case of an intrusion scenario involving brine, the solubilization of actinides in brine is considered as a potential source of release to the accessible environment. The following key factors establish the concentrations of dissolved actinides under subsurface conditions: (1) Redox chemistry - The solubility of reduced actinides (III and IV oxidation states) is known to be significantly lower than the oxidized forms (V and/or VI oxidation states). In this context, the reducing conditions in the WIPP and the strong coupling of the chemistry for reduced metals and microbiological processes with actinides are important. (2) Complexation - For the anoxic, reducing and mildly basic brine systems in the WIPP, the most important

  5. Polymer Chemistry in High School.

    Science.gov (United States)

    Stucki, Roger

    1984-01-01

    Discusses why polymer chemistry should be added to the general chemistry curriculum and what topics are appropriate (listing traditional with related polymer topics). Also discusses when and how these topics should be taught. (JN)

  6. The Chemistry of Curcumin: From Extraction to Therapeutic Agent

    Directory of Open Access Journals (Sweden)

    Kavirayani Indira Priyadarsini

    2014-12-01

    Full Text Available Curcumin, a pigment from turmeric, is one of the very few promising natural products that has been extensively investigated by researchers from both the biological and chemical point of view. While there are several reviews on the biological and pharmacological effects of curcumin, chemistry reviews are comparatively scarcer. In this article, an overview of different aspects of the unique chemistry research on curcumin will be discussed. These include methods for the extraction from turmeric, laboratory synthesis methods, chemical and photochemical degradation and the chemistry behind its metabolism. Additionally other chemical reactions that have biological relevance like nucleophilic addition reactions, and metal chelation will be discussed. Recent advances in the preparation of new curcumin nanoconjugates with metal and metal oxide nanoparticles will also be mentioned. Directions for future investigations to be undertaken in the chemistry of curcumin have also been suggested.

  7. The chemistry of curcumin: from extraction to therapeutic agent.

    Science.gov (United States)

    Priyadarsini, Kavirayani Indira

    2014-12-01

    Curcumin, a pigment from turmeric, is one of the very few promising natural products that has been extensively investigated by researchers from both the biological and chemical point of view. While there are several reviews on the biological and pharmacological effects of curcumin, chemistry reviews are comparatively scarcer. In this article, an overview of different aspects of the unique chemistry research on curcumin will be discussed. These include methods for the extraction from turmeric, laboratory synthesis methods, chemical and photochemical degradation and the chemistry behind its metabolism. Additionally other chemical reactions that have biological relevance like nucleophilic addition reactions, and metal chelation will be discussed. Recent advances in the preparation of new curcumin nanoconjugates with metal and metal oxide nanoparticles will also be mentioned. Directions for future investigations to be undertaken in the chemistry of curcumin have also been suggested.

  8. Water Chemistry Laboratory Manual.

    Science.gov (United States)

    Jenkins, David; And Others

    This manual of laboratory experiments in water chemistry serves a dual function of illustrating fundamental chemical principles of dilute aqueous systems and of providing the student with some familiarity with the chemical measurements commonly used in water and wastewater analysis. Experiments are grouped in categories on the basis of similar…

  9. Chemistry and Popperism.

    Science.gov (United States)

    Akeroyd, F. Michael

    1984-01-01

    Discusses the relationship of Karl Popper's theories to chemistry, examining scientific statements and verisimilitude (which indicates that newer theories should have a higher degree of truth content compared with older theories). Also provides examples illustrating the use of Agassi's criteria for assessing currently fashionable theories. (JN)

  10. Supramolecular Chemistry in Water

    NARCIS (Netherlands)

    Oshovsky, Gennady V.; Reinhoudt, David N.; Verboom, Willem

    2007-01-01

    Supramolecular chemistry in water is a constantly growing research area because noncovalent interactions in aqueous media are important for obtaining a better understanding and control of the major processes in nature. This Review offers an overview of recent advances in the area of water-soluble sy

  11. Forensic Chemistry Training

    Directory of Open Access Journals (Sweden)

    Zuhal GERÇEK

    2012-01-01

    Full Text Available Increasing the types of terrorism and crime nowadays, the importance of the forensic sciences can be bett er understood. Forensic science is the application of the wide spectrum of science to answer the question of legal system. It contains the application of the principles, techniques and methods of basic sciences and its main aim is the determination of the physical facts which are important in legal situations. Forensic chemistry is the branch of chemistry which performs the chemical analysis of evidences that used in the courts. Forensic chemist is the professional chemist who analyzes the evidences from crime scene and reaches a result by application of tests. Th us, they have to have a special education. In forensic laboratories candidates who have chemistry/biochemistry undergraduate degree and took biology and forensic chemistry lectures are preferred. It is necessary to design graduate and undergraduate education to train a forensic chemist. Science education should be at the core of the undergraduate education. In addition to this strong laboratory education on both science and forensic science should be given. Th e graduate program of forensic science example should contain forensic science subjects, strong academic lectures on special subjects and research and laboratory components.

  12. Online organic chemistry

    Science.gov (United States)

    Janowicz, Philip A.

    This is a comprehensive study of the many facets of an entirely online organic chemistry course. Online homework with structure-drawing capabilities was found to be more effective than written homework. Online lecture was found to be just as effective as in-person lecture, and students prefer an online lecture format with shorter Webcasts. Online office hours were found to be effective, and discussion sessions can be placed online as well. A model was created that explains 36.1% of student performance based on GPA, ACT Math score, grade in previous chemistry course, and attendance at various forms of discussion. Online exams have been created which test problem-solving skills and is instantly gradable. In these exams, students can submit answers until time runs out for different numbers of points. These facets were combined effectively to create an entirely online organic chemistry course which students prefer over the in-person alternative. Lastly, there is a vision for where online organic chemistry is going and what can be done to improve education for all.

  13. Array processors in chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ostlund, N.S.

    1980-01-01

    The field of attached scientific processors (''array processors'') is surveyed, and an attempt is made to indicate their present and possible future use in computational chemistry. The current commercial products from Floating Point Systems, Inc., Datawest Corporation, and CSP, Inc. are discussed.

  14. Analytical Chemistry Laboratory

    Science.gov (United States)

    Anderson, Mark

    2013-01-01

    The Analytical Chemistry and Material Development Group maintains a capability in chemical analysis, materials R&D failure analysis and contamination control. The uniquely qualified staff and facility support the needs of flight projects, science instrument development and various technical tasks, as well as Cal Tech.

  15. Supramolecular analytical chemistry.

    Science.gov (United States)

    Anslyn, Eric V

    2007-02-02

    A large fraction of the field of supramolecular chemistry has focused in previous decades upon the study and use of synthetic receptors as a means of mimicking natural receptors. Recently, the demand for synthetic receptors is rapidly increasing within the analytical sciences. These classes of receptors are finding uses in simple indicator chemistry, cellular imaging, and enantiomeric excess analysis, while also being involved in various truly practical assays of bodily fluids. Moreover, one of the most promising areas for the use of synthetic receptors is in the arena of differential sensing. Although many synthetic receptors have been shown to yield exquisite selectivities, in general, this class of receptor suffers from cross-reactivities. Yet, cross-reactivity is an attribute that is crucial to the success of differential sensing schemes. Therefore, both selective and nonselective synthetic receptors are finding uses in analytical applications. Hence, a field of chemistry that herein is entitled "Supramolecular Analytical Chemistry" is emerging, and is predicted to undergo increasingly rapid growth in the near future.

  16. Computational chemistry at Janssen.

    Science.gov (United States)

    van Vlijmen, Herman; Desjarlais, Renee L; Mirzadegan, Tara

    2016-12-19

    Computer-aided drug discovery activities at Janssen are carried out by scientists in the Computational Chemistry group of the Discovery Sciences organization. This perspective gives an overview of the organizational and operational structure, the science, internal and external collaborations, and the impact of the group on Drug Discovery at Janssen.

  17. Online Organic Chemistry

    Science.gov (United States)

    Janowicz, Philip A.

    2010-01-01

    This is a comprehensive study of the many facets of an entirely online organic chemistry course. Online homework with structure-drawing capabilities was found to be more effective than written homework. Online lecture was found to be just as effective as in-person lecture, and students prefer an online lecture format with shorter Webcasts. Online…

  18. Evaluating Environmental Chemistry Textbooks.

    Science.gov (United States)

    Hites, Ronald A.

    2001-01-01

    A director of the Indiana University Center for Environmental Science Research reviews textbooks on environmental chemistry. Highlights clear writing, intellectual depth, presence of problem sets covering both the qualitative and quantitative aspects of the material, and full coverage of the topics of concern. Discusses the director's own approach…

  19. Chemistry in Protoplanetary Disks

    CERN Document Server

    Henning, Thomas

    2013-01-01

    This comprehensive review summarizes our current understanding of the evolution of gas, solids and molecular ices in protoplanetary disks. Key findings related to disk physics and chemistry, both observationally and theoretically, are highlighted. We discuss which molecular probes are used to derive gas temperature, density, ionization state, kinematics, deuterium fractionation, and study organic matter in protoplanetary disks.

  20. Chemistry and Heritage

    Science.gov (United States)

    Vittoria Barbarulo, Maria

    2014-05-01

    Chemistry is the central science, as it touches every aspect of the society we live in and it is intertwined with many aspects of our culture; in particular, the strong link between Chemistry and Archaeology and Art History is being explored, offering a penetrating insight into an area of growing interest from an educational point of view. A series of vital and vibrant examples (i.e., ancient bronzes composition, colour changes due to natural pigment decomposition, marble degradation) has been proposed, on one hand, to improve student understanding of the relationship between cultural and scientific issues arising from the examination, the conservation, and the maintenance of cultural Heritage, on the other, to illustrate the role of the underlying Chemistry. In some case studies, a survey of the most relevant atmospheric factors, which are involved in the deterioration mechanisms, has also been presented to the students. First-hand laboratory experiences have been providing an invaluable means of discovering the full and varied world of Chemistry. Furthermore, the promotion of an interdisciplinary investigation of a famous painting or fresco, involving the study of its nature and significance, the definition of its historical context, any related literature, the chemical knowledge of the materials used, may be an excellent occasion to experiment the Content and Language Integrated Learning (CLIL). The aim of this approach is to convey the important message that everyone has the responsibility to care for and preserve Heritage for the benefit of present and future generations.