ORGANOMETALLIC IRON(II) COMPLEXES CONTAINING P-SUBSTITUTED ACETOPHENONE-ARYLHYDRAZONE LIGANDS

OpenAIRE

Manzur, Carolina; Millán, Lorena; Figueroa, Walter; Hamon, Jean-René; Mata, Jose A.; Carrillo, David

2002-01-01

A series of twelve new organometallic acetophenone-hydrazone complexes of general formula [(h 5-Cp)Fe(h 6-o-RC6H4)-NHN=CMe-C6H4-p-R’]+PF6- (Cp= C5H5; R,R’=H,Me, [5]+PF6-; H,MeO, [6]+PF6-; H,NMe2, [7]+PF6-; Me,Me, [8]+PF6-; Me,MeO, [9]+PF6-; Me,NMe2, [10]+PF6-; MeO,Me, [11]+PF6-; MeO,MeO, [12]+PF6-; MeO,NMe2, [13]+PF6-; Cl,Me, [14]+PF6-; Cl,MeO, [15]+PF6-; Cl,NMe2, [16]+PF6-) has been prepared by reaction between their corresponding organometallic hydrazine precursors [(h 5-Cp)Fe(h 6-o-RC6H4)-...

Organometallic compounds in the environment

National Research Council Canada - National Science Library

Craig, P. J

2003-01-01

... of Organometallic Species in the Environment 20 1.10 Stability of Organometallic Compounds in Biological Systems 1.11 G eneral Comments on the Toxicities of Organometallic Compounds 22 1.12 General Considerations on Environmental R eactivity of Organometallic Compounds 24 1.13 Microbial Biotransformation of Metals and M etalloids 25 1.13.1 Introduction 25 1...

Methods for forming particles from single source precursors

Science.gov (United States)

Fox, Robert V [Idaho Falls, ID; Rodriguez, Rene G [Pocatello, ID; Pak, Joshua [Pocatello, ID

2011-08-23

Single source precursors are subjected to carbon dioxide to form particles of material. The carbon dioxide may be in a supercritical state. Single source precursors also may be subjected to supercritical fluids other than supercritical carbon dioxide to form particles of material. The methods may be used to form nanoparticles. In some embodiments, the methods are used to form chalcopyrite materials. Devices such as, for example, semiconductor devices may be fabricated that include such particles. Methods of forming semiconductor devices include subjecting single source precursors to carbon dioxide to form particles of semiconductor material, and establishing electrical contact between the particles and an electrode.

Peroxide organometallic compounds and their transformations

International Nuclear Information System (INIS)

Razuvaev, G.A.; Brilkina, T.G.

1976-01-01

A survey is given experimental works on synthesis and reactions of peroxide organometallic compounds. Reactions have been considered of organometallic compounds with oxygen and organic peroxides which result in formation of both peroxide and non-peroxide products. Possible routes and mechanisms of chemical transformations of peroxide organometallic compounds have been discussed. Reactions of organometallic compounds with oxygen and peroxides have been considered

Two-Photon Absorption in Organometallic Bromide Perovskites

KAUST Repository

Walters, Grant

2015-07-21

Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

Two-Photon Absorption in Organometallic Bromide Perovskites

KAUST Repository

Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P.; Bakr, Osman; Sargent, Edward H.

2015-01-01

Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

Organometallic-inorganic hybrid electrodes for lithium-ion batteries

Science.gov (United States)

Huang, Qian; Lemmon, John P.; Choi, Daiwon; Cosimbescu, Lelia

2016-09-13

Disclosed are embodiments of active materials for organometallic and organometallic-inorganic hybrid electrodes and particularly active materials for organometallic and organometallic-inorganic hybrid cathodes for lithium-ion batteries. In certain embodiments the organometallic material comprises a ferrocene polymer.

Zigzag-shaped nickel nanowires via organometallic template-free route

Energy Technology Data Exchange (ETDEWEB)

Shviro, Meital; Paszternak, Andras [Bar Ilan Institute of Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Department of Chemistry (Israel); Chelly, Avraham [Bar Ilan Institute of Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Department of Engineering (Israel); Zitoun, David, E-mail: david.zitoun@biu.ac.il [Bar Ilan Institute of Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Department of Chemistry (Israel)

2013-08-15

In this manuscript, the formation of nickel nanowires of 10-20 nm in diameter (average size: several tens to hundreds of {mu}m long and 1.0-1.5 {mu}m wide) at low temperature is found to be driven by dewetting of liquid organometallic precursors during spin-coating process and by self-assembly of Ni clusters. Elaboration of metallic thin films by low-temperature deposition technique makes the preparation process compatible with most of the substrates. The use of iron and cobalt precursor shows that the process could be extended to other metallic systems. In this work, AFM and SEM are used to follow the assembly of Ni clusters into straight or zigzag lines. The formation of zigzag structure is specific to the Ni precursor at appropriate preparation parameters. This template-free process allows a control of anisotropic structures with homogeneous sizes and angles on the standard Si/SiO{sub 2} surface.

Synthesis and characterization of a liquid Eu precursor (EuCppm2) allowing for valence control of Eu ions doped into GaN by organometallic vapor phase epitaxy

International Nuclear Information System (INIS)

Mitchell, Brandon; Koizumi, Atsushi; Nunokawa, Takumi; Wakamatsu, Ryuta; Lee, Dong-gun; Saitoh, Yasuhisa; Timmerman, Dolf; Kuboshima, Yoshinori; Mogi, Takayuki; Higashi, Shintaro; Kikukawa, Kaoru; Ofuchi, Hironori; Honma, Tetsuo; Fujiwara, Yasufumi

2017-01-01

A liquid Eu precursor, bis(normal-propyl-tetramethylcyclopentadienyl)europium has been synthesized. This precursor exists as a liquid at temperatures higher than 49 °C, has a moderately high vapor pressure, contains no oxygen in its molecular structure, and can be distilled to high purity. These properties make it ideal for doping using a chemical vapor or atomic layer deposition method, and provide a degree of control previously unavailable. As a precursor the Eu exists in the divalent valance state, however, once doped into GaN by organometallic vapor phase epitaxy, the room-temperature photoluminescence of the Eu-doped GaN exhibited the typical red emission due to the intra-4f shell transition of trivalent Eu. After variation of the growth temperature, it was found that divalent Eu could be stabilized in the GaN matrix. By tuning the Fermi level through donor doping, the ratio of Eu 2+ to Eu 3+ could be controlled. The change in valence state of the Eu ions was confirmed using X-ray absorption near-edge structure. - Highlights: • A liquid Eu precursor was synthesized and its properties were characterized. • Precursor has a low melting point and a moderately high vapor pressure. • Does not contain oxygen in its molecular structure. • Eu can changed its valance state when incorporated into GaN. • Valence state of Eu in GaN can be controlled by donor doping.

Energy and chemicals from the selective electrooxidation of renewable diols by organometallic fuel cells.

Science.gov (United States)

Bellini, Marco; Bevilacqua, Manuela; Filippi, Jonathan; Lavacchi, Alessandro; Marchionni, Andrea; Miller, Hamish A; Oberhauser, Werner; Vizza, Francesco; Annen, Samuel P; Grützmacher, H

2014-09-01

Organometallic fuel cells catalyze the selective electrooxidation of renewable diols, simultaneously providing high power densities and chemicals of industrial importance. It is shown that the unique organometallic complex [Rh(OTf)(trop2NH)(PPh3)] employed as molecular active site in an anode of an OMFC selectively oxidizes a number of renewable diols, such as ethylene glycol , 1,2-propanediol (1,2-P), 1,3-propanediol (1,3-P), and 1,4-butanediol (1,4-B) to their corresponding mono-carboxylates. The electrochemical performance of this molecular catalyst is discussed, with the aim to achieve cogeneration of electricity and valuable chemicals in a highly selective electrooxidation from diol precursors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Labeling of thymidine analog with an organometallic complex of technetium-99m for diagnostic of cancer: radiochemical and biological evaluation

International Nuclear Information System (INIS)

Santos, Rodrigo Luis Silva Ribeiro

2007-01-01

Thymidine analogs have been labeled with different radioisotopes due to their potential in monitoring the uncontrollable cell proliferation. Considering that the radioisotopes technetium-99m still keep a privileged position as a marker due to its chemical and nuclear properties, this dissertation was constituted by the developed of a new technique of labeling of thymidine analog with 99m Tc, by means of the organometallic complex. The aims of this research were: synthesis of the organometallic complex technetium-99m-carbonyl, thymidine labeling with this precursor, evaluation of stability, and radiochemical e biological evaluation with healthy and tumor-bearing animals. The preparation of the organometallic precursor, using the CO gas, was easily achieved, as well as the labeling of thymidine with this precursor, resulting itself a radiochemical pureness of ≥ 97% and ≥ 94%, respectively. Chromatography systems with good levels of trustworthiness were used, ensuring the qualification and quantification of the radiochemical samples. The result of in vitro testing of lipophilicity disclosed that the radiolabeled complex is hydrophilic, with a partition coefficient (log P) of -1.48. The precursor complex and the radiolabeled have good radiochemical stability up to 6 h in room temperature. The cysteine and histidine challenge indicated losses between 8 and 1 1 % for concentrations until 300 mM. The biodistribution assay in healthy mice revealed rapid blood clearance and low uptake by general organs with renal and hepatobiliary excretion. The tumor concentration was low with values of 0.28 and 0.18 %ID/g for lung and breast cancer, respectively. The results imply more studies in other tumor models or the modification of the structure of the organic molecule that act like ligand. (author)

Local structure of Iridium organometallic catalysts covalently bonded to carbon nanotubes.

Science.gov (United States)

Blasco, J.; Cuartero, V.; Subías, G.; Jiménez, M. V.; Pérez-Torrente, J. J.; Oro, L. A.; Blanco, M.; Álvarez, P.; Blanco, C.; Menéndez, R.

2016-05-01

Hybrid catalysts based on Iridium N-heterocyclic carbenes anchored to carbon nanotubes (CNT) have been studied by XAFS spectroscopy. Oxidation of CNT yields a large amount of functional groups, mainly hydroxyl groups at the walls and carboxylic groups at the tips, defects and edges. Different kinds of esterification reactions were performed to functionalize oxidized CNT with imidazolium salts. Then, the resulting products were reacted with an Ir organometallic compound to form hybrid catalysts efficient in hydrogen transfer processes. XANES spectroscopy agree with the presence of Ir(I) in these catalysts and the EXAFS spectra detected differences in the local structure of Ir atoms between the initial Ir organometallic compound and the Ir complexes anchored to the CNT. Our results confirm that the halide atom, present in the Ir precursor, was replaced by oxygen from -OH groups at the CNT wall in the first coordination shell of Ir. The lability of this group accounts for the good recyclability and the good efficiency shown by these hybrid catalysts.

A [4Fe-4S]-Fe(CO)(CN)-l-cysteine intermediate is the first organometallic precursor in [FeFe] hydrogenase H-cluster bioassembly

Science.gov (United States)

Rao, Guodong; Tao, Lizhi; Suess, Daniel L. M.; Britt, R. David

2018-05-01

Biosynthesis of the [FeFe] hydrogenase active site (the 'H-cluster') requires the interplay of multiple proteins and small molecules. Among them, the radical S-adenosylmethionine enzyme HydG, a tyrosine lyase, has been proposed to generate a complex that contains an Fe(CO)2(CN) moiety that is eventually incorporated into the H-cluster. Here we describe the characterization of an intermediate in the HydG reaction: a [4Fe-4S][(Cys)Fe(CO)(CN)] species, 'Complex A', in which a CO, a CN- and a cysteine (Cys) molecule bind to the unique 'dangler' Fe site of the auxiliary [5Fe-4S] cluster of HydG. The identification of this intermediate—the first organometallic precursor to the H-cluster—validates the previously hypothesized HydG reaction cycle and provides a basis for elucidating the biosynthetic origin of other moieties of the H-cluster.

Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

Science.gov (United States)

Chadwick, F Mark; McKay, Alasdair I; Martinez-Martinez, Antonio J; Rees, Nicholas H; Krämer, Tobias; Macgregor, Stuart A; Weller, Andrew S

2017-08-01

Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(η 2 η 2 -NBA)][BAr F 4 ] (NBA = norbornane; Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(alkene) x ][BAr F 4 ] are formed. The ethene ( x = 2) complex, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Oct , has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Hex , that has a hexagonal microporous structure ( P 6 3 22). The propene complex ( x = 1) [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(propene)][BAr F 4 ] is characterized as having a π-bound alkene with a supporting γ-agostic Rh···H 3 C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d 3 -propene, H 2 C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111

Synthesis and characterization of a liquid Eu precursor (EuCp{sup pm}{sub 2}) allowing for valence control of Eu ions doped into GaN by organometallic vapor phase epitaxy

Energy Technology Data Exchange (ETDEWEB)

Mitchell, Brandon, E-mail: bmitchell@wcupa.edu [Department of Physics, West Chester University, West Chester, PA, 19383 (United States); Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871 (Japan); Koizumi, Atsushi; Nunokawa, Takumi; Wakamatsu, Ryuta; Lee, Dong-gun; Saitoh, Yasuhisa; Timmerman, Dolf [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871 (Japan); Kuboshima, Yoshinori; Mogi, Takayuki; Higashi, Shintaro; Kikukawa, Kaoru [Kojundo Chemical Laboratory Co., Ltd., 5-1-28 Chiyoda, Sakado, Saitama, 350-0284 (Japan); Ofuchi, Hironori; Honma, Tetsuo [Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198 (Japan); Fujiwara, Yasufumi, E-mail: fujiwara@mat.eng.osaka-u.ac.jp [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871 (Japan)

2017-06-01

A liquid Eu precursor, bis(normal-propyl-tetramethylcyclopentadienyl)europium has been synthesized. This precursor exists as a liquid at temperatures higher than 49 °C, has a moderately high vapor pressure, contains no oxygen in its molecular structure, and can be distilled to high purity. These properties make it ideal for doping using a chemical vapor or atomic layer deposition method, and provide a degree of control previously unavailable. As a precursor the Eu exists in the divalent valance state, however, once doped into GaN by organometallic vapor phase epitaxy, the room-temperature photoluminescence of the Eu-doped GaN exhibited the typical red emission due to the intra-4f shell transition of trivalent Eu. After variation of the growth temperature, it was found that divalent Eu could be stabilized in the GaN matrix. By tuning the Fermi level through donor doping, the ratio of Eu{sup 2+} to Eu{sup 3+} could be controlled. The change in valence state of the Eu ions was confirmed using X-ray absorption near-edge structure. - Highlights: • A liquid Eu precursor was synthesized and its properties were characterized. • Precursor has a low melting point and a moderately high vapor pressure. • Does not contain oxygen in its molecular structure. • Eu can changed its valance state when incorporated into GaN. • Valence state of Eu in GaN can be controlled by donor doping.

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

Directory of Open Access Journals (Sweden)

Rachel M. Thorman

2015-09-01

Full Text Available Focused electron beam induced deposition (FEBID is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (3, Pt(PF34, Co(CO3NO, and W(CO6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

New Route to Synthesize Surface Organometallic Complexes (SOMC): An Approach by Alkylating Halogenated Surface Organometallic Fragments

KAUST Repository

Hamieh, Ali Imad Ali

2017-01-01

The aim of this thesis is to explore new simpler and efficient routes for the preparation of surface organometallic complexes (SOMC) for the transformation of small organic molecules to valuable products. The key element in this new route relies on surface alkylation of various halogenated surface coordination complexes or organometallic fragments (SOMF).

New Route to Synthesize Surface Organometallic Complexes (SOMC): An Approach by Alkylating Halogenated Surface Organometallic Fragments

KAUST Repository

Hamieh, Ali Imad

2017-02-01

The aim of this thesis is to explore new simpler and efficient routes for the preparation of surface organometallic complexes (SOMC) for the transformation of small organic molecules to valuable products. The key element in this new route relies on surface alkylation of various halogenated surface coordination complexes or organometallic fragments (SOMF).

Catalytic Hydrodechlorination of Trichlorobenzenes with Pd(PhenCl2 as Catalyst Precursor

Directory of Open Access Journals (Sweden)

Guanlin Zhang

2015-01-01

Full Text Available We reported the catalytic hydrodechlorination (HDC of trichlorobenzenes by an organometallic compound Pd(PhenCl2 as a catalyst precursor. The catalyst precursor was prepared by chemical coordination reaction and characterized by FTIR and 1H NMR techniques. The HDC performance of Pd(PhenCl2 as catalyst precursor was evaluated on 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes (TCBs. All TCBs could be converted to dechlorination products with high conversion. Products distribution was closely related with the substrate structures and C-Cl bond energies. A reasonable reaction mechanism was also proposed.

Mew organometallic complexes of technetium in different oxidation states

International Nuclear Information System (INIS)

Joachim, J.E.

1993-09-01

New organometallic compounds of Tc(I), Tc(III) and Tc(VII) were synthesized and their properties examined. These compounds were correlated with their homologous compounds of manganese and rhenium, which were also synthesized by the same route. The molecular and crystal structures of most technetium complexes and of the homologous complexes of manganese and rhenium were determined by single crystal X-ray diffraction. (orig.) [de

Precursors-Derived Ceramic Membranes for High-Temperature Separation of Hydrogen

OpenAIRE

Yuji, Iwamoto

2007-01-01

This review describes recent progress in the development of hydrogen-permselective ceramic membranes derived from organometallic precursors. Microstructure and gas transport property of microporous amorphous silica-based membranes are briefly described. Then, high-temperature hydrogen permselectivity, hydrothermal stability as well as hydrogen/steam selectivity of the amorphous silica-based membranes are discussed from a viewpoint of application to membrane reactors for conversion enhancement...

Half-metallicity in 2D organometallic honeycomb frameworks

Science.gov (United States)

Sun, Hao; Li, Bin; Zhao, Jin

2016-10-01

Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule—CN—noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology.

Half-metallicity in 2D organometallic honeycomb frameworks

International Nuclear Information System (INIS)

Sun, Hao; Li, Bin; Zhao, Jin

2016-01-01

Half-metallic materials with a high Curie temperature (T C ) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d – p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule—CN—noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology. (paper)

A computational glance at organometallic cyclizations and coupling reactions

OpenAIRE

Fiser, Béla

2016-01-01

210 p. Organometallic chemistry is one of the main research topics in chemical science.Nowadays, organometallic reactions are the subject of intensive theoretical investigations.However, in many cases, only joint experimental and theoretical effortscould reveal the answers what we are looking for.The fruits of such experimental and theoretical co-operations will be presentedhere. In this work, we are going to deal with homogeneous organometallic catalysisusing computational chemical tools....

Structure of organometallic compounds obtained by plasma of titanium isopropoxide

International Nuclear Information System (INIS)

Arreola R, M. L.

2012-01-01

This work presents a study on the synthesis and characterization of organometallic compounds of titanium oxide obtained from glow discharges of titanium tetraisopropoxide (TTIP) and water on glass and polyethylene. The objective is the synthesis of titanium oxide particles which can be fixed on different supports for use in further studies of contaminants degradation in effluent streams. The synthesis was carried out by plasma in a glass tubular reactor of 750 cm 3 and 15 cm length at 10 -1 mbar with power between 100 and 150 W during 2, 3 and 4 h. The precursors were TTIP and water vapor. TTIP is an organometallic compound composed of a central atom of Ti surrounded by 4 O atoms, which in turn are connected with chains of 3 C (propane s). The objective is the use of plasma collisions to separate the organic and inorganic phases of TTIP, so that both structure independently in a single material. The result was the formation of white titanium oxide powder composed with agglomerates of spherical particles with average diameter between 160 and 452 nm adhered to small films. The agglomerates have a tendency to change from film to particles with the energy applied to the synthesis. The study of the chemical structure showed a great presence of O 2 -Ti-O 2 (Ti surrounded by O) which can be found in most titanium oxides. Other chemical groups belonging to the organic phase were C=C=C, C=C=O and C 2 -C-Ch appearing from the dehydrogenation of TTIP, which can be a possible precursor of this reactions kind. The structural superficial analyses showed that the atomic composition varies according to type of substrate used. The greatest content of Ti was obtained on glass substrates. However, the synthesis conditions had not evident effect in the participation of chemical states found in the inorganic phase. The crystalline studies indicated that the material is amorphous, although the de convoluted X-ray spectra showed that the synthesized titanium oxides on glass tend to

Electro-oxidation of methanol in alkaline conditions using Pd–Ni nanoparticles prepared from organometallic precursors and supported on carbon vulcan

Energy Technology Data Exchange (ETDEWEB)

Manzo-Robledo, A., E-mail: amanzor@ipn.mx [UPALM, Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Extractivas-IPN (Mexico); Costa, Natália J. S. [Universidade de São Paulo, Instituto de Química (Brazil); Philippot, K. [CNRS, LCC, Laboratoire de Chimie de Coordination (France); Rossi, Liane M. [Universidade de São Paulo, Instituto de Química (Brazil); Ramírez-Meneses, E. [Universidad Iberoamericana, Departamento de Ingeniería y Ciencias Químicas (Mexico); Guerrero-Ortega, L. P. A. [UPALM, Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Extractivas-IPN (Mexico); Ezquerra-Quiroga, S. [Universidad Iberoamericana, Departamento de Ingeniería y Ciencias Químicas (Mexico)

2015-12-15

Oxidation of low-molecular weight alcohols as energy sources using metal nanoparticles has attracted considerable interest for use as a power source in portable electronic devices. In this work, a series of mono- and bimetallic nanoparticles based on palladium and nickel (Pd, Pd{sub 90}Ni{sub 10}, Pd{sub 50}Ni{sub 50}, Pd{sub 10}Ni{sub 90}, and Ni) have been synthesized from organometallic precursors, namely tris(dibenzylideneacetone) dipalladium(0), Pd{sub 2}(dba){sub 3}, and bis(1,5-cyclooctadiene)nickel(0), Ni(cod){sub 2}. Well-defined metal particles in the nanometric scale from 4.2 to 6.3 nm were observed by transmission electron microscopy. The as-prepared nanoparticles were mixed with a carbon Vulcan matrix (10 % wt. of the catalyst in turn) for investigation as electrocatalysts in methanol oxidation reaction (MOR) in alkaline conditions. The i–E profiles from cyclic voltammetry for the monometallic systems indicated a redox process attributed only to palladium or nickel, as expected. With the bimetallic nanomaterials, the redox process and the i–E characteristics are functions of the amount of nickel associated to palladium. From a fundamental point of view, it has been established that the OH ions’ interfacial interaction and the MOR kinetics are affected by the presence of nickel (decreasing the faradic current) as supported by the current versus potential profiles obtained as a function of methanol concentration and with temperature variation.

Modules for Introducing Organometallic Reactions: A Bridge between Organic and Inorganic Chemistry

Science.gov (United States)

Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.

2015-01-01

Transition metal organometallic reactions have become increasingly important in the synthesis of organic molecules. A new approach has been developed to introduce organometallic chemistry, along with organic and inorganic chemistry, at the foundational level. This change highlights applications of organometallic chemistry that have dramatically…

Hydrotelluration of alkynes: a unique route to Z-vinyl organometallics

Directory of Open Access Journals (Sweden)

Vieira Maurício L.

2001-01-01

Full Text Available The hydrotelluration reaction of alkynes is reviewed. The transformation of vinylic tellurides into reactive vinyl organometallics and the coupling reactions of vinylic tellurides with alkynes and organometallics are presented.

Supramolecular Dendriphores: Anionic Organometallic Phosphors Embedded in Polycationic Dendritic Species

NARCIS (Netherlands)

McDonald, A.R.; Mores, D.; de Mello-Donega, C.; van Walree, C.A.; Klein Gebbink, R.J.M.; Lutz, M.; Spek, A.L.; Meijerink, A.; van Klink, G.P.M.; van Koten, G.

2009-01-01

Heteroleptic iridium(III) organometallic complexes have been functionalized with sulfate tethers. These systems have been thoroughly characterized spectroscopically. Subsequently these iridium(III) complexes were reacted with polyionic dendritic materials yielding iridium(III) organometallic

2012 Gordon Research Conference, Organometallic Chemistry, 8-13 2012

Energy Technology Data Exchange (ETDEWEB)

Hillhouse, Gregory [Univ. of Chicago, IL (United States)

2012-07-13

The 2012 Organometallic Chemistry Gordon Research Conference will highlight new basic science and fundamental applications of organometallic chemistry in industrial, academic, and national lab settings. Scientific themes of the conference will include chemical synthesis, reactivity, catalysis, polymer chemistry, bonding, and theory that involve transition-metal (and main-group) interactions with organic moieties.

Organometallic and Bioorganometallic Chemistry - Ferrocene and Metal Carbonyls

Directory of Open Access Journals (Sweden)

Čakić Semenčić, M.

2011-02-01

Full Text Available Organometallic chemistry deals with compounds containing metal-carbon bonds. Basic organometallics derived from the s- and p-block metals (containing solely σ-bonds were understood earlier, while organometallic chemistry of the d- and f-block has developed much more recently. These compounds are characterized by three types of M-C bonds (σ, π and δand their structures are impossible to deduce by chemical means alone; fundamental advances had to await the development of X-ray diffraction, as well as IR- and NMR-spectroscopy. On the other hand, elucidation of the structure of e. g. vitamin B12 and ferrocene (discovered in 1951 contributed to progress in these instrumental analytical methods, influencing further phenomenal success of transition-metal organometallic chemistry in the second half of the twentieth century. The most thoroughly explored fields of application of organometallics were in the area of catalysis, asymmetric synthesis, olefin metathesis, as well as organic synthesis and access to new materials and polymers.The most usual ligands bound to d- and f-metals are carbon monoxide, phosphines, alkyls, carbenes and arenes, and in this review the bonding patterns in the metal carbonyls and ferrocene are elaborated. The common characteristics of these two classes are two-component bonds. The CO-M bonds include (i donation from ligand HOMO to vacant M d-orbitals (σ-bond, and (ii back-donation from the filled M d-orbitals in the ligand LUMO (π-bond. Similar (but much more complicated ferrocene contains delocalized bonds consisting of electron donation from Cp to Fe (σ-bonds- and π-bonding and δ-back-bonding from metal to Cp. In such a way ferrocene, i. e. (η5-Cp2Fe contains 18 bonding electrons giving to this compound "superaromatic" properties in the sense of stability and electrophilic substitution. In contrast to benzenoid aromatic compounds reactions in two Cp-rings can occur giving homo- and heteroannularly mono-, two-… per

Organometallic Chemistry. Final Progress Report

Energy Technology Data Exchange (ETDEWEB)

Wolczanski, Peter [Cornell Univ., Ithaca, NY (United States)

2003-07-14

The Gordon Research Conference (GRC) on Organometallic Chemistry was held at Salve Regina, Newport, Rhode Island, 7/21-26/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

New Concept of C–H and C–C Bond Activation via Surface Organometallic Chemistry

KAUST Repository

Samantaray, Manoja

2015-08-18

In this chapter we describe the recent applications of well-defined oxidesupported metal alkyls/alkylidenes/alkylidynes and hydrides of group IV, V, and VI transition metals in the field of C–H and C–C bond activation. The activation of ubiquitous C–H and C–C bonds of paraffin is a long-standing challenge because of intrinsic low reactivity. There are many concepts derived from surface organometallic chemistry (SOMC): surface organometallic fragments are always intermediates in heterogeneous catalysis. The study of their synthesis and reactivity is a way to rationalize mechanism of heterogeneous catalysis and to achieve structure activity relationship. By surface organometallic chemistry one can enter any catalytic center by a reaction intermediate leading in fine to single site catalysts. With surface organometallic chemistry one can coordinate to the metal which can play a role in different elementary steps leading for example to C–H activation and Olefin metathesis. Because of the development of SOMC there is a lot of space for the improvement of homogeneous catalysis. After the 1997 discovery of alkane metathesis using silica-supported tantalum hydride by Basset et al. at low temperature (150ºC) the focus in this area was shifted to the discovery of more and more challenging surface complexes active in the application of C–H and C–C bond activation. Here we describe the evolution of well-defined metathesis catalyst with time as well as the effect of support on catalysis. We also describe here which metal–ligand combinations are responsible for a variety of C–H and C–C bond activation.

Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

KAUST Repository

Bakr, Osman M.

2017-03-02

Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making organometallic halide perovskite monocrystalline film, and the like.

Growth and physicochemical properties of organometallic (DL)-trithioureatartrato-O1,O2,O3-cadmium(II) single crystals

Science.gov (United States)

Sathyamoorthy, K.; Vinothkumar, P.; Irshad Ahamed, J.; Murali Manohar, P.; Priya, M.; Liu, Jinghe

2018-04-01

Single crystals of organometallic (DL)-trithioureatartrato-O1,O2,O3-cadmium(II) (TUDLC) have been grown from methanol solution by using the slow evaporation of solvent growth technique. The lattice structure and crystalline perfection have been determined by carrying out single crystal X-ray diffraction and high resolution X-ray diffraction measurements. The grown crystal was characterized thermally and mechanically by carrying out thermo-gravimetric and micro hardness measurements. The linear and nonlinear optical characterizations were made by carrying out optical transmittance, surface laser damage threshold, particle size-dependent second harmonic generation (SHG) efficiency and photo conductivity measurements. The grown crystal was electrically characterized by carrying out frequency-dependent dielectric measurements. Chemical etching study was also carried out and the dislocation density was estimated. Results obtained in the present study indicate that the grown TUDLC crystal is optically transparent with lower cut-off wavelength 304 nm, mechanically soft, thermally stable up to 101 °C and NLO active with SHG efficiency 2.13 (in KDP unit). The grown crystal is found to have considerably large size, good crystalline perfection, large specific heat capacity, higher surface laser damage threshold and negative photoconductivity.

Organometallic chemistry of metal surfaces

International Nuclear Information System (INIS)

Muetterties, E.L.

1981-06-01

The organometallic chemistry of metal surfaces is defined as a function of surface crystallography and of surface composition for a set of cyclic hydrocarbons that include benzene, toluene, cyclohexadienes, cyclohexene, cyclohexane, cyclooctatetraene, cyclooctadienes, cyclooctadiene, cycloheptatriene and cyclobutane. 12 figures

Atomically precise graphene nanoribbon heterojunctions from a single molecular precursor

Science.gov (United States)

Nguyen, Giang D.; Tsai, Hsin-Zon; Omrani, Arash A.; Marangoni, Tomas; Wu, Meng; Rizzo, Daniel J.; Rodgers, Griffin F.; Cloke, Ryan R.; Durr, Rebecca A.; Sakai, Yuki; Liou, Franklin; Aikawa, Andrew S.; Chelikowsky, James R.; Louie, Steven G.; Fischer, Felix R.; Crommie, Michael F.

2017-11-01

The rational bottom-up synthesis of atomically defined graphene nanoribbon (GNR) heterojunctions represents an enabling technology for the design of nanoscale electronic devices. Synthetic strategies used thus far have relied on the random copolymerization of two electronically distinct molecular precursors to yield GNR heterojunctions. Here we report the fabrication and electronic characterization of atomically precise GNR heterojunctions prepared through late-stage functionalization of chevron GNRs obtained from a single precursor. Post-growth excitation of fully cyclized GNRs induces cleavage of sacrificial carbonyl groups, resulting in atomically well-defined heterojunctions within a single GNR. The GNR heterojunction structure was characterized using bond-resolved scanning tunnelling microscopy, which enables chemical bond imaging at T = 4.5 K. Scanning tunnelling spectroscopy reveals that band alignment across the heterojunction interface yields a type II heterojunction, in agreement with first-principles calculations. GNR heterojunction band realignment proceeds over a distance less than 1 nm, leading to extremely large effective fields.

Electrically Conductive Silver Paste Obtained by Use of Silver Neodecanoate as Precursor

Science.gov (United States)

Shen, Longguang; Liu, Jianguo; Zeng, Xiaoyan; Ren, Zhao

2015-02-01

An electrically conductive silver paste has been prepared from an organometallic compound, silver neodecanoate, as silver precursor. The precursor was highly soluble in organic solvents and decomposed into metallic silver at low sintering temperatures (writing process, enabling production of silver lines on a substrate. The electrical resistivity of the silver lines was 9 × 10-6 Ω cm after sintering at 115°C for 60 min, 5.8 × 10-6 Ω cm when sintered at 150°C for 60 min, and 3 × 10-6 Ω cm when sintered above 300°C, values which are similar to those of bulk silver. Hence, the prepared paste can be successfully used on flexible substrates such as polymers.

Methods of forming single source precursors, methods of forming polymeric single source precursors, and single source precursors formed by such methods

Science.gov (United States)

Fox, Robert V.; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin; Margulieux, Kelsey R.; Holland, Andrew W.

2014-09-09

Methods of forming single source precursors (SSPs) include forming intermediate products having the empirical formula 1/2{L.sub.2N(.mu.-X).sub.2M'X.sub.2}.sub.2, and reacting MER with the intermediate products to form SSPs of the formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2, wherein L is a Lewis base, M is a Group IA atom, N is a Group IB atom, M' is a Group IIIB atom, each E is a Group VIB atom, each X is a Group VIIA atom or a nitrate group, and each R group is an alkyl, aryl, vinyl, (per)fluoro alkyl, (per)fluoro aryl, silane, or carbamato group. Methods of forming polymeric or copolymeric SSPs include reacting at least one of HE.sup.1R.sup.1E.sup.1H and MER with one or more substances having the empirical formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2 or L.sub.2N(.mu.-X).sub.2M'(X).sub.2 to form a polymeric or copolymeric SSP. New SSPs and intermediate products are formed by such methods.

The preparation of highly active antimicrobial silver nanoparticles by an organometallic approach

International Nuclear Information System (INIS)

Fernandez, Eduardo J; Garcia-Barrasa, Jorge; Lopez-de-Luzuriaga, Jose M; Monge, Miguel; Laguna, Antonio; Torres, Carmen

2008-01-01

Silver nanoparticles of small size with a high surface to volume ratio have been prepared using an organometallic approach. For this, the complex NBu 4 [Ag(C 6 F 5 ) 2 ] has been treated with AgClO 4 in a 1:1 molar ratio, giving rise to the nanoparticle precursor [Ag(C 6 F 5 )] in solution. Addition of one equivalent of hexadecylamine (HDA) and 5 h of reflux in toluene leads to a deep yellow solution containing monodisperse silver nanoparticles (Ag NPs) of ca. 10 nm. This approach leads to nanoparticles with almost uncontaminated surfaces which make them very reactive. Antimicrobial studies show that these nanoparticles are very active as antimicrobial agents. Very low concentrations between 12 and 25 μg ml -1 of Ag NPs are enough to produce bacteriostatic and bactericidal effectiveness

Organometallic B12-DNA conjugate

DEFF Research Database (Denmark)

Hunger, Miriam; Mutti, Elena; Rieder, Alexander

2014-01-01

Design, synthesis, and structural characterization of a B12-octadecanucleotide are presented herein, a new organometallic B12-DNA conjugate. In such covalent conjugates, the natural B12 moiety may be a versatile vector for controlled in vivo delivery of oligonucleotides to cellular targets in hum...

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

International Nuclear Information System (INIS)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving η 5 -to η 1 -cyclopentadienyl ring slippage in catalysis was completed

Catalysis by Design: Well-Defined Single-Site Heterogeneous Catalysts

KAUST Repository

Pelletier, Jeremie

2016-03-09

support taken as a X, L ligands in the Green formalism, the catalyst can be designed and generated by grafting the organometallic precursor containing the functional group(s) suitable to target a given transformation (surface organometallic fragments (SOMF)). The choice of these SOMF is based on the elementary steps known in molecular chemistry applied to the desired reaction. The coordination sphere necessary for any catalytic reaction involving paraffins, olefins, and alkynes also can thus be predicted. Only their most complete understanding can allow development of catalytic reactions with the highest possible selectivity, activity, and lifetime. This Account will examine the results of SOMC for hydrocarbon transformations on oxide surfaces bearing metals of group 4-6. The silica-supported catalysts are exhibiting remarkable performances for Ziegler-Natta polymerization and depolymerization, low temperature hydrogenolysis of alkanes and waxes, metathesis of alkanes and cycloalkanes, olefins metathesis, and related reactions. In the case of reactions involving molecules that do not contain carbon (water-gas shift, NH3 synthesis, etc.) this single site approach is also valid but will be considered in a later review. © 2016 American Chemical Society.

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

Energy Technology Data Exchange (ETDEWEB)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving {eta}{sup 5}-to {eta}{sup 1}-cyclopentadienyl ring slippage in catalysis was completed.

Organometallic approach to polymer-protected antibacterial silver nanoparticles: optimal nanoparticle size-selection for bacteria interaction

Energy Technology Data Exchange (ETDEWEB)

Crespo, Julian; Garcia-Barrasa, Jorge; Lopez-de-Luzuriaga, Jose M.; Monge, Miguel, E-mail: miguel.monge@unirioja.es; Olmos, M. Elena [Universidad de La Rioja, Centro de Investigacion en Sintesis Quimica (CISQ), Departamento de Quimica (Spain); Saenz, Yolanda; Torres, Carmen [Centro de Investigacion Biomedica de La Rioja, Area de Microbiologia Molecular (Spain)

2012-12-15

The optimal size-specific affinity of silver nanoparticles (Ag NPs) towards E. coli bacteria has been studied. For this purpose, Ag NPs coated with polyvinylpyrrolidone (PVP) and cellulose acetate (CA) have been prepared using an organometallic approach. The complex NBu{sub 4}[Ag(C{sub 6}F{sub 5}){sub 2}] has been treated with AgClO{sub 4} in a 1:1 molar ratio giving rise to the nanoparticle precursor [Ag(C{sub 6}F{sub 5})] in solution. Addition of an excess of PVP (1) or CA (2) and 5 h of reflux in tetrahydrofuran (THF) at 66 Degree-Sign C leads to Ag NPs of small size (4.8 {+-} 3.0 nm for PVP-Ag NPs and 3.0 {+-} 1.2 nm for CA-Ag NPs) that coexist in both cases with larger nanoparticles between 7 and 25 nm. Both nanomaterials display a high antibacterial effectiveness against E. coli. The TEM analysis of the nanoparticle-bacterial cell membrane interaction shows an optimal size-specific affinity for PVP-Ag NPs of 5.4 {+-} 0.7 nm in the presence of larger size silver nanoparticles.Graphical AbstractAn organometallic approach permits the synthesis of small size silver nanoparticles (ca 5 nm) as a main population in the presence of larger size nanoparticles. Optimal silver nanoparticle size-selection (5.4 nm) for the interaction with the bacterial membrane is achieved.

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.

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; Maity, Niladri; Bhatte, Kushal; Ould-Chikh, Samy; Dachwald, Oliver; Haeß ner, Carmen; Saih, Youssef; Abou-Hamad, Edy; Llorens, Isabelle; Hazemann, Jean-Louis; Kö hler, Klaus; D’ Elia, Valerio; Basset, Jean-Marie

2016-01-01

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.

The preparation of highly active antimicrobial silver nanoparticles by an organometallic approach

Energy Technology Data Exchange (ETDEWEB)

Fernandez, Eduardo J; Garcia-Barrasa, Jorge; Lopez-de-Luzuriaga, Jose M; Monge, Miguel [Departamento de Quimica Grupo de SIntesis Quimica de La Rioja, UA-CSIC, Universidad de La Rioja, Complejo CientIfico-Tecnologico, E-26004 Logrono (Spain); Laguna, Antonio [Departamento de Quimica Inorganica, Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC, E-50009 Zaragoza (Spain); Torres, Carmen [Departamento de Agricultura y Alimentacion, Universidad de La Rioja, Complejo Cientifico-Tecnologico, E-26004 Logrono (Spain)], E-mail: eduardo.fernandez@unirioja.es

2008-05-07

Silver nanoparticles of small size with a high surface to volume ratio have been prepared using an organometallic approach. For this, the complex NBu{sub 4}[Ag(C{sub 6}F{sub 5}){sub 2}] has been treated with AgClO{sub 4} in a 1:1 molar ratio, giving rise to the nanoparticle precursor [Ag(C{sub 6}F{sub 5})] in solution. Addition of one equivalent of hexadecylamine (HDA) and 5 h of reflux in toluene leads to a deep yellow solution containing monodisperse silver nanoparticles (Ag NPs) of ca. 10 nm. This approach leads to nanoparticles with almost uncontaminated surfaces which make them very reactive. Antimicrobial studies show that these nanoparticles are very active as antimicrobial agents. Very low concentrations between 12 and 25 {mu}g ml{sup -1} of Ag NPs are enough to produce bacteriostatic and bactericidal effectiveness.

Demonstrating the utility of boron based precursor molecules for selective area deposition in a scanning tunneling microscope

International Nuclear Information System (INIS)

Perkins, F.K.; Onellion, M.; Lee, S.; Bowben, T.A.

1992-01-01

The scanning tunneling microscope (STM) can be used to selectively deposit material from a gaseous precursor compound. Ultrasmall (less than a 100 nm across) spatial dimensions for selective area deposition may be achieved by this means. In this paper the authors outline a scheme foreselecting and designing main group cluster compounds and organometallics for this type of selective area deposition using nido-decaborane(14) as an example

Single-particle spectra and magnetic field effects within precursor superconductivity

International Nuclear Information System (INIS)

Pieri, P.; Pisani, L.; Strinati, G.C.; Perali, A.

2004-01-01

We study the single-particle spectra below the superconducting critical temperature from weak to strong coupling within a precursor superconductivity scenario. The spectral-weight function is obtained from a self-energy that includes pairing-fluctuations within a continuum model representing the hot spots of the Brillouin zone. The effects of strong magnetic fields on the pseudogap temperature are also discussed within the same scenario

Reduction of precursor decay anomaly in single crystal lithium fluoride

Science.gov (United States)

Sano, Yukio

2000-08-01

The purpose of this study is to reveal that the precursor decay anomaly in single crystal lithium fluoride is reduced by Sano's decay curve [Y. Sano, J. Appl. Phys. 85, 7616 (1999)], which is much smaller in slope than Asay's decay curve [J. R. Asay, G. R. Fowles, G. E. Duvall, M. H. Miles, and R. F. Tinder, J. Appl. Phys. 43, 2132 (1972)]. To this end, strain, particle, velocity, and stress in a precursor and near the leading edge of the follower changing with time along Sano's decay curve are first analyzed quantitatively. The analysis verified the existence of degenerate contraction waves I and II and a subrarefaction wave R', and the decay process [Y. Sano, J. Appl. Phys. 77, 3746 (1995)] caused in sequence by evolving followers C, I, II, R', Rb. Next, inequalities relating decay rates qualitatively to plastic strain rates at the leading edge of the follower, which are derived using the properties of the followers, are incorporated into the analysis. Calculation results showed that the plastic strain rates were reduced by low decay rates. This indicates that the precursor decay anomaly might be greatly reduced by Sano's decay curve.

Application of imaging spectroscopic reflectometry for characterization of gold reduction from organometallic compound by means of plasma jet technology

Energy Technology Data Exchange (ETDEWEB)

Vodák, Jiří, E-mail: jiri.vodak@yahoo.com [Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); Nečas, David [RG Plasma Technologies, CEITEC Masaryk University, Kamenice 5, 625 00 Brno (Czech Republic); Pavliňák, David [Department of Physical Electronics, Masaryk University, Kotlářská 2, 611 37 Brno (Czech Republic); Macak, Jan M [Center of Materials and Nanotechnologies, Faculty of Chemical Technology, University of Pardubice, Nám. Čs. Legií 565, 530 02 Pardubice (Czech Republic); Řičica, Tomáš; Jambor, Roman [Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice (Czech Republic); Ohlídal, Miloslav [Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); Institute of Physics, Faculty of Mining and Geology, VŠB – Technical University of Ostrava (Czech Republic)

2017-02-28

Highlights: • Metallic gold is reduced from an organometallic compound layer using a plasma jet. • Imaging spectroscopic reflectometry is used to locate areas with metallic gold. • The results are completed with XPS and optical microscopy observations. - Abstract: This work presents a new application of imaging spectroscopic reflectometry to determine a distribution of metallic gold in a layer of an organogold precursor which was treated by a plasma jet. Gold layers were prepared by spin coating from a solution of the precursor containing a small amount of polyvinylpyrrolidone on a microscopy glass, then they were vacuum dried. A difference between reflectivity of metallic gold and the precursor was utilized by imaging spectroscopic reflectometry to create a map of metallic gold distribution using a newly developed model of the studied sample. The basic principle of the imaging spectroscopic reflectometry is also shown together with the data acquisition principles. XPS measurements and microscopy observations were made to complete the imaging spectroscopic reflectometry results. It is proved that the imaging spectroscopic reflectometry represents a new method for quantitative evaluation of local reduction of metallic components from metaloorganic compounds.

Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

KAUST Repository

Bakr, Osman; Peng, Wei; Wang, Lingfei

2017-01-01

Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making

Methods of forming single source precursors, methods of forming polymeric single source precursors, and single source precursors and intermediate products formed by such methods

Science.gov (United States)

Fox, Robert V.; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin; Margulieux, Kelsey R.; Holland, Andrew W.

2012-12-04

Methods of forming single source precursors (SSPs) include forming intermediate products having the empirical formula 1/2{L.sub.2N(.mu.-X).sub.2M'X.sub.2}.sub.2, and reacting MER with the intermediate products to form SSPs of the formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2, wherein L is a Lewis base, M is a Group IA atom, N is a Group IB atom, M' is a Group IIIB atom, each E is a Group VIB atom, each X is a Group VIIA atom or a nitrate group, and each R group is an alkyl, aryl, vinyl, (per)fluoro alkyl, (per)fluoro aryl, silane, or carbamato group. Methods of forming polymeric or copolymeric SSPs include reacting at least one of HE.sup.1R.sup.1E.sup.1H and MER with one or more substances having the empirical formula L.sub.2N(.mu.-ER).sub.2M'(ER).sub.2 or L.sub.2N(.mu.-X).sub.2M'(X).sub.2 to form a polymeric or copolymeric SSP. New SSPs and intermediate products are formed by such methods.

Photocatalytic applications of Cr{sub 2}S{sub 3} synthesized from single and multi-source precursors

Energy Technology Data Exchange (ETDEWEB)

Hussain, Wajid [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Badshah, Amin, E-mail: aminbadshah@qau.edu.pk [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Hussain, Raja Azadar; Imtiaz-ud-Din [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Aleem, Muhammad Adeel [The Pakistan Institute of Engineering and Applied Sciences (PIEAS) (Pakistan); Bahadur, Ali [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan); Iqbal, Shahid [School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing, 100049 (China); Farooq, Muhammad Umar; Ali, Hassan [Department of Chemistry, Quaid-i-Azam University, 45320, Islamabad (Pakistan)

2017-06-15

Most of the material research work is pertinent to the synthesis of transition-metal sulfides nanoparticles but here the studies are limited to the synthesis of chromium sulfide. However, the preparation method, presented in this work, may be extended to other metal chalcogenides nanoparticles for various potential applications. The ligand (precursor), 1-(2-chloro-4-nitrophenyl)-3,3-chlorobenzoyl and Cr{sub 2}S{sub 3} have been synthesized initially from single source precursor and then from multi source precursors. The target was to alter the morphologies of nanomaterial while altering the synthetic route and that was successfully achieved. Chromium sulfide nano-rods were synthesized using single source precursors while nanoparticles were fabricated using multi source precursors. Characterization were carried out through {sup 1}H and {sup 13}C NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction microscopy (PXRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). Our objective is to change the morphologies by changing the synthetic route so that is why further applications were done only for multi-source product, denying single source product. The metal sulfides nanoparticles exhibit higher activity than their bulk material for the photocatalytic degradation of organic dyes under visible-light irradiation. So, photocatalytic activity was successfully achieved under direct sunlight against five different cationic and anionic organic dyes including malachite green (MG), methylene blue (MB), rhodamine B (RhB), methyl violet (MV) and methyl orange (MO). These organic dyes MV, MG, MB, and RB were almost diminished or decolorized by Cr{sub 2}S{sub 3} within 110, 90, 100, and 130, minutes, respectively expect MO. - Highlights: • Synthesis of Cr{sub 2}S{sub 3} from single and multisource precursors is

DNA-based asymmetric organometallic catalysis in water

NARCIS (Netherlands)

Oelerich, Jens; Roelfes, Gerard

2013-01-01

Here, the first examples of DNA-based organometallic catalysis in water that give rise to high enantioselectivities are described. Copper complexes of strongly intercalating ligands were found to enable the asymmetric intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones in water. Up to

Molecular metal catalysts on supports: organometallic chemistry meets surface science.

Science.gov (United States)

Serna, Pedro; Gates, Bruce C

2014-08-19

Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

Surface characterization of III-V MOCVD films from heterocyclic single-source precursors; Oberflaechencharakterisierung von III-V MOCVD-Filmen aus heterozyklischen Single Source Precursoren

Energy Technology Data Exchange (ETDEWEB)

Seemayer, Andreas

2009-07-13

In the present thesis the sublimation and evaporation properties of heterocyclic gallium and antimony containing single-source precursors as well as the chemical composition and morphology of the films fabricated from this were studied. The single-source precursors available by a new synthesis route were characterized concerning their evaporation properties and the obtained films studied surface-physically. By this way the process parameters were optimized and the applicability of the single-source precursors in HV-MOCVD processes studied. By evaporation experiments in the UHV it could be shown that thereby lighter ligands like ethyl- and methyl-groups lead to a lower contamination of the reaction space with carbon containing molecules. Furthermore it was expected that the 6-rings synthetized with short ligands exhibit a high stability. This however could not be confirmed. By unwanted parasitary reactions in the gaseous phase respectively dissociative sublimation in the gaseous phase a deposition of GaSb with these precursors was not possible. The 4-ring stabilized with tertiary-butyl and ethyl-groups caused in the evaporation the largest contamination of the gaseous phase, becauselonger-chain hydrocarbons exhibil only a bad pump cross section. By parasitary reactions originating elementary antimony is detectable in the gaseous phase. The films were studied concerning their chemical composition and their transport- respectively storage-conditioned surface contamination. Furthermore it has become clear that not only a purely synthetized precursor substance but also the reactor design is deciding for a successful deposition and a high film quality. First by successive optimization of the evaporation geometry it was possible to reduce the roughness of the produced GaSb films down to about 10 nm-30 nm.

Ligand Rearrangements of Organometallic Complexes inSolution

Energy Technology Data Exchange (ETDEWEB)

Shanoski, Jennifer E. [Univ. of California, Berkeley, CA (United States)

2006-01-01

Many chemical reactions utilize organometallic complexes as catalysts. These complexes find use in reactions as varied as bond activation, polymerization, and isomerization. This thesis outlines the construction of a new ultrafast laser system with an emphasis on the generation of tunable mid-infrared pulses, data collection, and data analysis.

New twists and turns for actinide chemistry. Organometallic infinite coordination polymers of thorium diazide

Energy Technology Data Exchange (ETDEWEB)

Monreal, Marisa J.; Seaman, Lani A.; Goff, George S.; Michalczyk, Ryszard; Morris, David E.; Scott, Brian L.; Kiplinger, Jaqueline L. [Los Alamos National Laboratory, Los Alamos, NM (United States)

2016-03-07

Two organometallic 1D infinite coordination polymers and two organometallic monometallic complexes of thorium diazide have been synthesized and characterized. Steric control of these self-assembled arrays, which are dense in thorium and nitrogen, has also been demonstrated: infinite chains can be circumvented by using steric bulk either at the metallocene or with a donor ligand in the wedge.

Enthalpies of vaporization of organometallic compounds

International Nuclear Information System (INIS)

Kuznetsov, N.T.; Sevast'yanov, V.G.; Mitin, V.A.; Krasnodubskaya, S.V.; Zakharov, L.N.; Domrachev, G.A.; AN SSSR, Gor'kij. Inst. Khimii)

1987-01-01

A possibility to use the method of additive schemes for the calculation of vaporizaton enthalpies of uranium organometallic compounds is discussed while comparing the values obtained using the method with experimental data. The possibility of apriori evaluation of evaporation enthalpy values of different uranium compounds using the method of additive schemes and structural characteristics of molecules, such as the sum of ligand solid angles, is shown

Homogeneous photocatalytic reactions with organometallic and coordination compounds--perspectives for sustainable chemistry.

Science.gov (United States)

Hoffmann, Norbert

2012-02-13

Since the time of Giacomo Ciamician at the beginning of the 20th century, photochemical transformations have been recognized as contributing to sustainable chemistry. Electronic excitation significantly changes the reactivity of chemical compounds. Thus, the application of activation reagents is frequently avoided and transformations can be performed under mild conditions. Catalysis plays a central role in sustainable chemistry. Stoichiometric amounts of activation reagents are often avoided. This fact and the milder catalytic reaction conditions diminish the formation of byproducts. In the case of homogeneous catalysis, organometallic compounds are often applied. The combination of both techniques develops synergistic effects in the sense of "Green Chemistry". Herein, metal carbonyl-mediated reactions are reported. These transformations are of considerable interest for the synthesis of complex polyfunctionalized compounds. Copper(I)-catalyzed [2+2] photocycloaddition gives access to a large variety of cyclobutane derivatives. Currently, a large number of publications deal with photochemical electron-transfer-induced reactions with organometallic and coordination compounds, particularly with ruthenium complexes. Several photochemically induced oxidations can easily be performed with air or molecular oxygen when they are catalyzed with organometallic complexes. Photochemical reaction conditions also play a certain role in C-H activation with organometallic catalysts, for instance, with alkanes, although such transformations are conveniently performed with a variety of other photochemical reactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silicone Resin Applications for Ceramic Precursors and Composites

Directory of Open Access Journals (Sweden)

Masaki Narisawa

2010-06-01

Full Text Available This article reviews the applications of silicone resins as ceramic precursors. The historical background of silicone synthesis chemistry is introduced to explain the production costs and supply availability of various silicones. Thermal degradation processes of silicones are classified in terms of the main chain structure and cyclic oligomer expulsion process, which determine the resulting ceramic yield and the chemical composition. The high temperature decomposition of Si-O-C beyond 1,400 °C in an inert atmosphere and formation of a protective silica layer on material surfaces beyond 1,200 °C in an oxidative atmosphere are discussed from the viewpoints of the wide chemical composition of the Si-O-C materials. Applications of the resins for binding agents, as starting materials for porous ceramics, matrix sources with impregnation, fiber spinning and ceramic adhesions are introduced. The recent development of the process of filler or cross-linking agent additions to resin compounds is also introduced. Such resin compounds are useful for obtaining thick coatings, MEMS parts and bulk ceramics, which are difficult to obtain by pyrolysis of simple organometallic precursors without additives.

Correlation of precursor and product ions in single-stage high resolution mass spectrometry. A tool for detecting diagnostic ions and improving the precursor elemental composition elucidation

Energy Technology Data Exchange (ETDEWEB)

Borràs, S. [Departament de Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain); Kaufmann, A., E-mail: anton.kaufmann@klzh.ch [Official Food Control Authority, Fehrenstrasse 15, 8032 Zürich (Switzerland); Companyó, R. [Departament de Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain)

2013-04-15

Highlights: ► We are describing a technique to spot ions which are derived from each other. ► Single stage high resolution data is used. ► This “in silicon” technique is compared to conventional precursor scan. ► Some applications for this technique are presented. -- Abstract: Monitoring of common diagnostic fragments is essential for recognizing molecules which are members of a particular compound class. Up to now, unit resolving tandem quadrupole mass spectrometers, operating in the precursor ion scan mode, have been typically used to perform such analysis. By means of high-resolution mass spectrometry (HRMS) a much more sensitive and selective detection can be achieved. However, using a single-stage HRMS instrument, there is no unequivocal link to the corresponding precursor ion, since such instrumentation does not permit a previous precursor selection. Thus, to address this limitation, an in silico approach to locate precursor ions, based on diagnostic fragments, was developed. Implemented as an Excel macro, the algorithm rapidly assembles and surveys exact mass data to provide a list of feasible precursor candidates according to the correlation of the chromatographic peak shape profile and other additional filtering criteria (e.g. neutral losses and isotopes). The macro was tested with two families of veterinary drugs, sulfonamides and penicillins, which are known to yield diagnostic product ions when fragmented. Data sets obtained from different food matrices (fish and liver), both at high and low concentration of the target compounds, were investigated in order to evaluate the capabilities and limitations of the reported approach. Finally, other possible applications of this technique, such as the elucidation of elemental compositions based on product ions and corresponding neutral losses, were also presented and discussed.

Correlation of precursor and product ions in single-stage high resolution mass spectrometry. A tool for detecting diagnostic ions and improving the precursor elemental composition elucidation

International Nuclear Information System (INIS)

Borràs, S.; Kaufmann, A.; Companyó, R.

2013-01-01

Highlights: ► We are describing a technique to spot ions which are derived from each other. ► Single stage high resolution data is used. ► This “in silicon” technique is compared to conventional precursor scan. ► Some applications for this technique are presented. -- Abstract: Monitoring of common diagnostic fragments is essential for recognizing molecules which are members of a particular compound class. Up to now, unit resolving tandem quadrupole mass spectrometers, operating in the precursor ion scan mode, have been typically used to perform such analysis. By means of high-resolution mass spectrometry (HRMS) a much more sensitive and selective detection can be achieved. However, using a single-stage HRMS instrument, there is no unequivocal link to the corresponding precursor ion, since such instrumentation does not permit a previous precursor selection. Thus, to address this limitation, an in silico approach to locate precursor ions, based on diagnostic fragments, was developed. Implemented as an Excel macro, the algorithm rapidly assembles and surveys exact mass data to provide a list of feasible precursor candidates according to the correlation of the chromatographic peak shape profile and other additional filtering criteria (e.g. neutral losses and isotopes). The macro was tested with two families of veterinary drugs, sulfonamides and penicillins, which are known to yield diagnostic product ions when fragmented. Data sets obtained from different food matrices (fish and liver), both at high and low concentration of the target compounds, were investigated in order to evaluate the capabilities and limitations of the reported approach. Finally, other possible applications of this technique, such as the elucidation of elemental compositions based on product ions and corresponding neutral losses, were also presented and discussed

Organometallics Roundtable 2011

Energy Technology Data Exchange (ETDEWEB)

Gladysz, John A.; Ball, Zachary T.; Bertrand, Guy; Blum, Suzanne A.; Dong, Vy M.; Dorta, Reto; Hahn, F. Ekkehardt; Humphrey, Mark; Jones, William D.; Klosin, Jerzy; Manners, Ian; Marks, Tobin J.; Mayer, James M.; Rieger, Bernhard; Ritter, Joachim C.; Sattelberger, Alfred P.; Schomaker, Jennifer M.; Wing-Wah Yam, Vivian

2012-01-09

We are living in an era of unprecedented change in academic, industrial, and government-based research worldwide, and navigating these rough waters requires "all hands on deck". Toward this end, Organometallics has assembled a panel of seventeen experts who share their thoughts on a variety of matters of importance to our field. In constituting this panel, an attempt was made to secure representation from a number of countries and career stages, as well as from industry. We were fortunate that so many busy experts could take the time to spend with us. The following pages constitute an edited transcript of the panel discussion held on August 29, 2011, which was structured around the 10 questions summarized in the side bar and repeated below.

CORROSION RESISTANCE OF ORGANOMETALLIC COATING APLICATED IN FUEL TANKS USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY IN BIOFUEL – PART I

Directory of Open Access Journals (Sweden)

Milene Adriane Luciano

2014-10-01

Full Text Available Nowadays, the industry has opted for more sustainable production processes, and the planet has also opted for new energy sources. From this perspective, automotive tanks with organometallic coatings as well as a partial substitution of fossil fuels by biofuels have been developed. These organometallic coated tanks have a zinc layer, deposited by a galvanizing process, formed between the steel and the organometallic coating. This work aims to characterize the organometallic coating used in metal automotive tanks and evaluate their corrosion resistance in contact with hydrated ethyl alcohol fuel (AEHC. For this purpose, the resistance of all layers formed between Zinc and EEP steel and also the tin coated steel, which has been used for over thirty years, were evaluated. The technique chosen was the Electrochemical Impedance Spectroscopy. The results indicated an increase on the corrosion resistance when organometallic coatings are used in AEHC medium. In addition to that, these coatings allow an estimated 25% reduction in tanks production costs.

Synthesis of organometallic hydroxides of titanium, vanadium, cobalt and chromium as precursors of thin films type MaOb

International Nuclear Information System (INIS)

Montero Villalobos, Mavis

2001-01-01

This study shows the results obtained from a general objective that was the synthesis and characterization of precursors of thin films of metallic oxides, two different routes of synthesis have been practiced: route molecular precursors and route Sol-Gel technic. In the first route one of the objectives of the investigation is to obtain a molecular precursor of material type M a O b a route of synthesis have been tried proved that involves anhydrous chlorides of the transition metals and linked R that are alcoxides of metal such as silicon, titanium and zirconium. In the second route the general objective to create thin films of metallic oxide has been maintained but the way to resolve the problem has changed, not giving so much emphasis to the molecular precursors as it was originally presented (this due mainly to its instability and difficulty of synthesis), but being supported in the sun-gel chemistry. It was started a new synthesis line through the sun-gel chemistry that is more versatile and simplifies the process in the film formation [es

Basic organometallic chemistry: containing comprehensive bibliography

National Research Council Canada - National Science Library

Haiduc, Ionel; Zuckerman, Jerry J

1985-01-01

.... Organometallic chemistry is the discipline dealing with compounds containing at least one direct metal-carbon bond. This bond can be simple covalent [as in lead tetraethyl, Pb(C H )J or π-dative [as in ferrocene, Fe(i/ 5 2 5 -C 5 H 5 ) 2 ] or even predominantly ionic [as in ethylsodium, N a + C 2 Hs ]. On this basis, compounds like metal alkoxides, [for example, alu...

Synthesis and X-ray crystal structure of a novel organometallic (µ(3)-oxido)(µ(3)-imido) trinuclear iridium complex

DEFF Research Database (Denmark)

Schau-Magnussen, Magnus; Malcho, Phillip; Herbst, Konrad

2011-01-01

Reaction of the organometallic aqua ion [Cp*Ir(H(2)O)(3)](2+) with tert-butyl(trimethylsilyl)amine in acetone yielded a novel trinuclear (µ(3)-oxido)(µ(3)-imido)pentamethylcyclopentadienyliridium(iii) complex, [(Cp*Ir)(3)(O)(N(t)Bu)](2+). Single crystal structure analyses show the complex can be ...... that a trinuclear (µ(3)-oxido)(µ(3)-imido) transition metal complex has been structurally characterized....

Removal of both N-nitrosodimethylamine and trihalomethanes precursors in a single treatment using ion exchange resins.

Science.gov (United States)

Beita-Sandí, Wilson; Karanfil, Tanju

2017-11-01

Drinking water utilities are relying more than ever on water sources impacted by wastewater effluents. Disinfection/oxidation of these waters during water treatment may lead to the formation of several disinfection by-products, including the probable human carcinogen N-nitrosodimethylamine (NDMA) and the regulated trihalomethanes (THMs). In this study, the potential of ion exchange resins to control both NDMA and THMs precursors in a single treatment is presented. Two ion exchange resins were examined, a cation exchange resin (Plus) to target NDMA precursors and an anion exchange resin (MIEX) for THMs precursors control. We applied the resins, individually and combined, in the treatment of surface and wastewater effluent samples. The treatment with both resins removed simultaneously NDMA (43-85%) and THMs (39-65%) precursors. However, no removal of NDMA precursors was observed in the surface water with low initial NDMA FP (14 ng/L). The removals of NDMA FP and THMs FP with Plus and MIEX resins applied alone were (49-90%) and (41-69%), respectively. These results suggest no interaction between the resins, and thus the feasibility of effectively controlling NDMA and THMs precursors concomitantly. Additionally, the effects of the wastewater impact and the natural attenuation of precursors were studied. The results showed that neither the wastewater content nor the attenuation of the precursor affected the removals of NDMA and THMs precursors. Finally, experiments using a wastewater effluent sample showed that an increase in the calcium concentration resulted in a reduction in the removal of NDMA precursors of about 50%. Copyright © 2017 Elsevier Ltd. All rights reserved.

ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

OpenAIRE

Onwudiwe, Damian C.; Ajibade, Peter A.

2011-01-01

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescen...

New twists and turns for actinide chemistry: organometallic infinite coordination polymers of thorium diazide

Energy Technology Data Exchange (ETDEWEB)

Monreal, Marisa J.; Seaman, Lani A.; Goff, George S.; Michalczyk, Ryszard; Morris, David E.; Scott, Brian L.; Kiplinger, Jaqueline L. [Los Alamos National Laboratory, Los Alamos, NM (United States)

2016-03-07

Two organometallic 1D infinite coordination polymers and two organometallic monometallic complexes of thorium diazide have been synthesized and characterized. Steric control of these self-assembled arrays, which are dense in thorium and nitrogen, has also been demonstrated: infinite chains can be circumvented by using steric bulk either at the metallocene or with a donor ligand in the wedge. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Organometallic copper I, II or III species in an intramolecular dechlorination reaction

KAUST Repository

Poater, Albert

2013-03-15

The present paper gives insight into an intramolecular dechlorination reaction involving Copper (I) and an ArCH2Cl moiety. The discussion of the presence of a CuIII organometallic intermediate becomes a challenge, and because of the lack of clear experimental detection of this proposed intermediate, and due to the computational evidence that it is less stable than other isomeric species, it can be ruled out for the complex studied here. Our calculations are completely consistent with the key hypothesis of Karlin et al. that TMPA-CuI is the substrate of intramolecular dechlorination reactions as well as the source to generate organometallic species. However the organometallic character of some intermediates has been refused because computationally these species are less stable than other isomers. Thus this study constitutes an additional piece towards the full understanding of a class of reaction of biological relevance. Further, the lack of high energy barriers and deep energy wells along the reaction pathway explains the experimental difficulties to trap other intermediates. © Springer-Verlag Berlin Heidelberg 2013.

Structure of organometallic compounds obtained by plasma of titanium isopropoxide; Estructura de compuestos organometalicos obtenidos por plasma de isopropoxido de titanio

Energy Technology Data Exchange (ETDEWEB)

Arreola R, M. L.

2012-07-01

This work presents a study on the synthesis and characterization of organometallic compounds of titanium oxide obtained from glow discharges of titanium tetraisopropoxide (TTIP) and water on glass and polyethylene. The objective is the synthesis of titanium oxide particles which can be fixed on different supports for use in further studies of contaminants degradation in effluent streams. The synthesis was carried out by plasma in a glass tubular reactor of 750 cm{sup 3} and 15 cm length at 10{sup -1} mbar with power between 100 and 150 W during 2, 3 and 4 h. The precursors were TTIP and water vapor. TTIP is an organometallic compound composed of a central atom of Ti surrounded by 4 O atoms, which in turn are connected with chains of 3 C (propane s). The objective is the use of plasma collisions to separate the organic and inorganic phases of TTIP, so that both structure independently in a single material. The result was the formation of white titanium oxide powder composed with agglomerates of spherical particles with average diameter between 160 and 452 nm adhered to small films. The agglomerates have a tendency to change from film to particles with the energy applied to the synthesis. The study of the chemical structure showed a great presence of O{sub 2}-Ti-O{sub 2} (Ti surrounded by O) which can be found in most titanium oxides. Other chemical groups belonging to the organic phase were C=C=C, C=C=O and C{sub 2}-C-Ch appearing from the dehydrogenation of TTIP, which can be a possible precursor of this reactions kind. The structural superficial analyses showed that the atomic composition varies according to type of substrate used. The greatest content of Ti was obtained on glass substrates. However, the synthesis conditions had not evident effect in the participation of chemical states found in the inorganic phase. The crystalline studies indicated that the material is amorphous, although the de convoluted X-ray spectra showed that the synthesized titanium oxides

Platinum-195 nuclear magnetic resonance of organometallic compounds

OpenAIRE

Ursini, Cleber Vinicius

1997-01-01

A brief review of 195Pt NMR is presented, focusing organometallic compounds. This article gives initially basic information of NMR processes involving 195Pt nucleus. It is followed by a discussion of the factors which affect the chemical shifts and coupling constants. Finally, some aspects of 195Pt NMR of solids are commented.

Systems and methods for solar energy storage, transportation, and conversion utilizing photochemically active organometallic isomeric compounds and solid-state catalysts

Science.gov (United States)

Vollhardt, K. Peter C.; Segalman, Rachel A; Majumdar, Arunava; Meier, Steven

2015-02-10

A system for converting solar energy to chemical energy, and, subsequently, to thermal energy includes a light-harvesting station, a storage station, and a thermal energy release station. The system may include additional stations for converting the released thermal energy to other energy forms, e.g., to electrical energy and mechanical work. At the light-harvesting station, a photochemically active first organometallic compound, e.g., a fulvalenyl diruthenium complex, is exposed to light and is photochemically converted to a second, higher-energy organometallic compound, which is then transported to a storage station. At the storage station, the high-energy organometallic compound is stored for a desired time and/or is transported to a desired location for thermal energy release. At the thermal energy release station, the high-energy organometallic compound is catalytically converted back to the photochemically active organometallic compound by an exothermic process, while the released thermal energy is captured for subsequent use.

A review of the inorganic and organometallic chemistry of zirconium

International Nuclear Information System (INIS)

Kalvins, A.K.

1985-01-01

The results of a literature review of the inorganic and organometallic chemistry of zirconium are presented. Compounds with physical and chemical properties compatible with the requirements of an ir laser zirconium isotope separation process have been identified

Automated building of organometallic complexes from 3D fragments.

Science.gov (United States)

Foscato, Marco; Venkatraman, Vishwesh; Occhipinti, Giovanni; Alsberg, Bjørn K; Jensen, Vidar R

2014-07-28

A method for the automated construction of three-dimensional (3D) molecular models of organometallic species in design studies is described. Molecular structure fragments derived from crystallographic structures and accurate molecular-level calculations are used as 3D building blocks in the construction of multiple molecular models of analogous compounds. The method allows for precise control of stereochemistry and geometrical features that may otherwise be very challenging, or even impossible, to achieve with commonly available generators of 3D chemical structures. The new method was tested in the construction of three sets of active or metastable organometallic species of catalytic reactions in the homogeneous phase. The performance of the method was compared with those of commonly available methods for automated generation of 3D models, demonstrating higher accuracy of the prepared 3D models in general, and, in particular, a much wider range with respect to the kind of chemical structures that can be built automatically, with capabilities far beyond standard organic and main-group chemistry.

Horizons of organic and organoelemental chemistry. 7. All-Russian conference on organometallic chemistry. Summaries of reports. V. 2

International Nuclear Information System (INIS)

1999-01-01

Abstracts of the seventh All-Russian conference on organometallic chemistry are presented. The main part of reports are devoted to the synthesis of organometallic compounds with assigned properties of rare earths, transition elements and other metals. Data on molecular structure, chemical and electrochemical properties of these compounds are presented

A Rhodium(III) Complex as an Inhibitor of Neural Precursor Cell Expressed, Developmentally Down-Regulated 8-Activating Enzyme with in Vivo Activity against Inflammatory Bowel Disease.

Science.gov (United States)

Zhong, Hai-Jing; Wang, Wanhe; Kang, Tian-Shu; Yan, Hui; Yang, Yali; Xu, Lipeng; Wang, Yuqiang; Ma, Dik-Lung; Leung, Chung-Hang

2017-01-12

We report herein the identification of the rhodium(III) complex [Rh(phq) 2 (MOPIP)] + (1) as a potent and selective ATP-competitive neural precursor cell expressed, developmentally down-regulated 8 (NEDD8)-activating enzyme (NAE) inhibitor. Structure-activity relationship analysis indicated that the overall organometallic design of complex 1 was important for anti-inflammatory activity. Complex 1 showed promising anti-inflammatory activity in vivo for the potential treatment of inflammatory bowel disease.

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Cahoon, James Francis [Univ. of California, Berkeley, CA (United States)

2008-12-01

One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO)₃ and CpFe(CO)₂ have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO)₅[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO)₅ have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

MOCVD of hexagonal boron nitride thin films on Si(100) using new single source precursors

CERN Document Server

Boo, J H; Yu, K S; Kim, Y S; Kim, Y S; Park, J T

1999-01-01

We have been carried out the growth of hexagonal boron nitride (h-BN) thin films on Si(100) substrates by low pressure metal-organic chemical vapor deposition (LPMOCVD) method using triethylborane tert-butylamine complex (TEBTBA), Et sub 3 BNH sub 2 ( sup t Bu), and triethylborane isopropylamine complex (TEBIPA), Et sub 3 BNH sub 2 ( sup t Pr) as a new single molecular precursors in the temperature range of 850 approx 1000 .deg. C. polycrystalline, crack-free h-BN film was successfully grown on Si(100) substrate at 850 .deg. C using TEBTBA. This growth temperature is very lower than those in previous reports. Carbon-rich polycrystalline BN was also obtained at 900 .deg. C from TEBIPA. With increasing substrate temperature to 1000 .deg. C, however, BC sub 4 N-like species are strongly formed along with h-BN and the BN films obtained from both TEBTBA and TEBIPA but almost polycrystalline. To our best knowledge, this is the first report of the growth of h-BN films formed with the new single source precursors of ...

Organometallic benzene-vanadium wire: A one-dimensional half-metallic ferromagnet

DEFF Research Database (Denmark)

Maslyuk, V.; Bagrets, A.; Meded, V.

2006-01-01

Using density functional theory we perform theoretical investigations of the electronic properties of a freestanding one-dimensional organometallic vanadium-benzene wire. This system represents the limiting case of multidecker V-n(C6H6)(n+1) clusters which can be synthesized with established meth...

Homologation chemistry with nucleophilic α-substituted organometallic reagents: chemocontrol, new concepts and (solved) challenges.

Science.gov (United States)

Castoldi, Laura; Monticelli, Serena; Senatore, Raffaele; Ielo, Laura; Pace, Vittorio

2018-05-31

The transfer of a reactive nucleophilic CH2X unit into a preformed bond enables the introduction of a fragment featuring the exact and desired degree of functionalization through a single synthetic operation. The instability of metallated α-organometallic species often poses serious questions regarding the practicability of using this conceptually intuitive and simple approach for forming C-C or C-heteroatom bonds. A deep understanding of processes regulating the formation of these nucleophiles is a precious source of inspiration not only for successfully applying theoretically feasible transformations (i.e. determining how to employ a given reagent), but also for designing new reactions which ultimately lead to the introduction of molecular complexity via short experimental sequences.

Sol-gel precursors and products thereof

Science.gov (United States)

Warren, Scott C.; DiSalvo, Jr., Francis J.; Weisner, Ulrich B.

2017-02-14

The present invention provides a generalizable single-source sol-gel precursor capable of introducing a wide range of functionalities to metal oxides such as silica. The sol-gel precursor facilitates a one-molecule, one-step approach to the synthesis of metal-silica hybrids with combinations of biological, catalytic, magnetic, and optical functionalities. The single-source precursor also provides a flexible route for simultaneously incorporating functional species of many different types. The ligands employed for functionalizing the metal oxides are derived from a library of amino acids, hydroxy acids, or peptides and a silicon alkoxide, allowing many biological functionalities to be built into silica hybrids. The ligands can coordinate with a wide range of metals via a carboxylic acid, thereby allowing direct incorporation of inorganic functionalities from across the periodic table. Using the single-source precursor a wide range of functionalized nanostructures such as monolith structures, mesostructures, multiple metal gradient mesostructures and Stober-type nanoparticles can be synthesized. ##STR00001##

Design and synthesis of single-source molecular precursors to homogeneous multi-component oxide materials

Science.gov (United States)

Fujdala, Kyle Lee

This dissertation describes the syntheses of single-source molecular precursors to multi-component oxide materials. These molecules possess a core metal or element with various combinations of -OSi(O tBu)3, -O2P(OtBu) 2, and -OB[OSi(OtBu)3] 2 ligands. Such molecules decompose under mild thermolytic conditions (models for oxide-supported metal species and multi-component oxides. Significantly, the first complexes to contain three or more heteroelements suitable for use in the TMP method have been synthesized. Compounds for use as single-source molecular precursors have been synthesized containing Al, B, Cr, Hf, Mo, V, W, and Zr, and their thermal transformations have been examined. Heterogeneous catalytic reactions have been examined for selected materials. Also, cothermolyses of molecular precursors and additional molecules (i.e., metal alkoxides) have been utilized to provide materials with several components for potential use as catalysts or catalyst supports. Reactions of one and two equivs of HOSi(OtBu) 3 with Cr(OtBu)4 afforded the first Cr(IV) alkoxysiloxy complexes (tBuO) 3CrOSi(OtBu)3 and ( tBuO)2Cr[OSi(OtBu) 3]2, respectively. The high-yielding, convenient synthesis of (tBuO)3CrOSi(O tBu)3 make this complex a useful single-source molecular precursor, via the TMP method, to Cr/Si/O materials. The thermal transformations of (tBuO)3CrOSi(O tBu)3 and (tBuO) 2Cr[OSi(OtBu)3]2 to chromia-silica materials occurr at low temperatures (≤180°C), to give isobutene as the major carbon-containing product. The material generated from the solid-state conversion of (tBuO) 3CrOSi(OtBu)3 (CrOS ss) has an unexpectedly high surface area of 315 m2 g-1 that is slightly reduced to 275 m2 g-1 after calcination at 500°C in O2. The xerogel obtained by the thermolysis of an n-octane solution of (tBuO)3CrOSi(O tBu)3 (CrOSixg) has a surface area of 315 m2 g-1 that is reduced to 205 m2 g-1 upon calcination at 500°C. Powder X-ray diffraction (PXRD) analysis revealed that Cr2O 3 is

Analysis of several irdoid and indole precursors of terpenoid indole alkaloids with a single HPLC run

DEFF Research Database (Denmark)

Dagnino, Denise; Schripsema, Jan; Verpoorte, Robert

1996-01-01

An isocratic HPLC system is described which allows the separation of the iridoid and indole precursors of terpenoid indole alkaloids, which are present in a single crude extract. The system consists of a column of LiChrospher 60 RP select B 5 my, 250x4 mm (Merck) with an eluent of 1 % formic acid...

Highvalent and organometallic technetium and rhenium compounds

International Nuclear Information System (INIS)

Oehlke, Elisabeth

2010-01-01

Diagnostic methods in nuclear medicine allow a detailed description of morphological organ structures and their function. The beta emitting isotope Tc-99 has optimal physical properties (140 keV gamma rays, half-life 6 h) and is therefore used for radiopharmaceuticals. The thesis is concerned with the search for new technetium complexes and their reproducible production. The (TcO3) core is of main interest. The second part of the thesis deals with organometallic technetium and rhenium complexes with carbonyl ligands and N-heterocyclic carbenes that show stability in aerobic aqueous solutions.

Organometallics and related molecules for energy conversion

CERN Document Server

Wong, Wai-Yeung

2015-01-01

This book presents a critical perspective of the applications of organometallic compounds (including those with metal or metalloid elements) and other related metal complexes as versatile functional materials in the transformation of light into electricity (solar energy conversion) and electricity into light (light generation in light emitting diode), in the reduction of carbon dioxide to useful chemicals, as well as in the safe and efficient production and utilization of hydrogen, which serves as an energy storage medium (i.e. energy carrier). This book focuses on recent research developmen

Writing nanopatterns with electrochemical oxidation on redox responsive organometallic multilayers by AFM

NARCIS (Netherlands)

Song, Jing; Hempenius, Mark A.; Chung, H.J.; Vancso, Gyula J.

2015-01-01

Nanoelectrochemical patterning of redox responsive organometallic poly(ferrocenylsilane) (PFS) multilayers is demonstrated by electrochemical dip pen lithography (EDPN). Local electrochemical oxidation and Joule heating of PFS multilayers from the tip are considered as relevant mechanisms related to

Theory of Hydrogen Storage: A New Strategy within Organometallic Chemistry

Science.gov (United States)

Zhao, Yufeng

2006-03-01

As one of the most vigorous fields in modern chemistry, organometallic chemistry has made vast contributions to a broad variety of technological fields including catalysis, light emitters, molecular devices, liquid crystals, and even superconductivity. Here we show that organometallic chemistry in nanoscale could be the frontier in hydrogen storage. Our study is based on the notion that the 3d transition metal (TM) atoms are superb absorbers for H storage, as their empty d orbital can bind dihydrogen ligands (elongated but non-dissociated H2) with high capacity at nearly ideal binding energy for reversible hydrogen storage. By embedding the TM atoms into a carbon-based nanostructures, high H capacity can be maintained. This presentation contains four parts. First, by comparing the conventional hydrogen storage media, e.g., metal hydrides and carbon-based materials, the general principles for designing hydrogen storage materials are outlined. Second, organometallic buckyballs are studied to demonstrate the novel strategy. The amount of H2 adsorbed on a Sc-coated fullerene, C48B12 [ScH]12, could approach 9 wt%, with binding energies of 30-40 kJ/mol. Third, the method is applied to the transition-metal carbide nanoparticles that have been synthesized experimentally. The similar non-dissociative H2 binding is revealed in our calculation, thereby demonstrating the resilience of the overall mechanism. Moreover, a novel self-catalysis process is identified. In the fourth part, transition-metal functionalization of highly porous carbon-based materials is discussed heuristically to foresee macroscopic media for hydrogen storage. Finally follows the summary and discussion of the remaining challenges to practical hydrogen storage. Work in collaboration with A. C. Dillon, Y.-H. Kim, M. Heben & S. B. Zhang and supported by the U.S. DOE/EERE under contract No. DE-AC36-99GO10337.

2011 Organometallic Chemistry (July 10-15, 2011, Salve Regina University, Newport, RI)

Energy Technology Data Exchange (ETDEWEB)

Dr. Emilio Bunel

2011-07-15

Organometallic chemistry has played and will continue to play a significant role in helping us understand the way bonds are made or broken in the presence of a transition metal complex. Current challenges range from the efficient exploitation of energy resources to the creative use of natural and artificial enzymes. Most of the new advances in the area are due to our extended understanding of processes at a molecular level due to new mechanistic studies, techniques to detect reaction intermediates and theory. The conference will bring the most recent advances in the field including nanocatalysis, surface organometallic chemistry, characterization techniques, new chemical reactivity and theoretical approaches along with applications to organic synthesis and the discovery of new materials. The Conference will bring together a collection of investigators who are at the forefront of their field, and will provide opportunities for junior scientists and graduate students to present their work in poster format and exchange ideas with leaders in the field. Six outstanding posters will be selected for short talks. The collegial atmosphere of this Conference, with programmed discussion sessions as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to brainstorm and promotes cross-disciplinary collaborations in the various research areas represented. Graduate students and postdoctoral fellows should also consider participating in the Gordon Research Seminar on Organometallic Chemistry (July 9-10, same location) which is specially designed to promote interaction and discussion between junior scientists.

Toxicology of organic-inorganic hybrid molecules: bio-organometallics and its toxicology.

Science.gov (United States)

Fujie, Tomoya; Hara, Takato; Kaji, Toshiyuki

2016-01-01

Bio-organometallics is a research strategy of biology that uses organic-inorganic hybrid molecules. The molecules are expected to exhibit useful bioactivities based on the unique structure formed by interaction between the organic structure and intramolecular metal(s). However, studies on both biology and toxicology of organic-inorganic hybrid molecules have been incompletely performed. There can be two types of toxicological studies of bio-organometallics; one is evaluation of organic-inorganic hybrid molecules and the other is analysis of biological systems from the viewpoint of toxicology using organic-inorganic hybrid molecules. Our recent studies indicate that cytotoxicity of hybrid molecules containing a metal that is nontoxic in inorganic forms can be more toxic than that of hybrid molecules containing a metal that is toxic in inorganic forms when the structure of the ligand is the same. Additionally, it was revealed that organic-inorganic hybrid molecules are useful for analysis of biological systems important for understanding the toxicity of chemical compounds including heavy metals.

Volatile organometallic and semiconductor materials

International Nuclear Information System (INIS)

Dickson, R.S.

1991-01-01

This article reports on a project concerned with the metal organic chemical vapour deposition (MOCVD) of mercury-cadmium telluride (MCT) undertaken by a research consortium based in the Clayton area involving Monash University Chemistry Department, Telecom Research Laboratories, and CSIRO Division of Material Sciences and Technology. An M.R. Semicon 226 MOCVD reactor, operating near atmospheric presure with hydrogen carrier gas has been used. Most applications of MCT are direct consequence of its responsiveness to radiation in infrared region spectrum. The main aims of the project were to prepare and assess a range of volatile organometallics that might find use as a dopant sources for MCT, to prepare and study the properties of a range of different lanthanide complexes for MOCVD applications and to fully characterize the semiconductor wafers after growth. 19 refs., 3 figs

Control and Characterization of Titanium Dioxide Morphology: Applications in Surface Organometallic Chemistry

KAUST Repository

Jeantelot, Gabriel

2014-05-01

Surface Organometallic Chemistry leads to the combination of the high activity and specificity of homogeneous catalysts with the recoverability and practicality of heterogeneous catalysts. Most metal complexes used in this chemistry are grafted on metal oxide supports such as amorphous silica (SiO2) and γ-alumina (Al2O3). In this thesis, we sought to enable the use of titania (TiO2) as a new support for single-site well-defined grafting of metal complexes. This was achieved by synthesizing a special type of anatase-TiO2, bearing a high density of identical hydroxyl groups, through hydrothermal synthesis then post-treatment under high vacuum followed by oxygen flow, and characterized by several analytical techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and nuclear magnetic resonance. Finally, as a proof of concept, the grafting of vanadium oxychloride (VOCl3) was successfully attempted.

Recent Applications of Polymer Supported Organometallic Catalysts in Organic Synthesis

Directory of Open Access Journals (Sweden)

Nina Kann

2010-09-01

Full Text Available Recent developments concerning the application of polymer supported organometallic reagents in solid phase synthesis are reviewed, with a special focus on methodology for carbon-carbon formation. Examples of reactions that are covered include the classical Suzuki, Sonogashira and Heck coupings, but also aryl amination, epoxide opening, rearrangements, metathesis and cyclopropanation. Applications in the field of asymmetric synthesis are also discussed.

Molecular orbital studies of the bonding in heavy element organometallics

International Nuclear Information System (INIS)

Bursten, B.E.

1990-01-01

This progress report contains highlights of research projects in actinide chemistry. Projects covered are bonding in Np, Pu, and transplutonium organometallic compounds, applications of the discrete variational Xα method to actinide chemistry, ab initio calculations on actinide molecules, and experimental comparisons of organoactinide and organotransition metal chemistry. Also included is brief discussions on budgets, funding, invited papers and invited presentations. (JL)

Synthesis, Optical and Structural Properties of Copper Sulfide Nanocrystals from Single Molecule Precursors

Directory of Open Access Journals (Sweden)

Peter A. Ajibade

2017-02-01

Full Text Available We report the synthesis and structural studies of copper sulfide nanocrystals from copper (II dithiocarbamate single molecule precursors. The precursors were thermolysed in hexadecylamine (HDA to prepare HDA-capped CuS nanocrystals. The optical properties of the nanocrystals studied using UV–visible and photoluminescence spectroscopy showed absorption band edges at 287 nm that are blue shifted, and the photoluminescence spectra show emission curves that are red-shifted with respect to the absorption band edges. These shifts are as a result of the small crystallite sizes of the nanoparticles leading to quantum size effects. The structural studies were carried out using powder X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, energy dispersive X-ray spectroscopy (EDS, and atomic force microscopy. The XRD patterns indicates that the CuS nanocrystals are in hexagonal covellite crystalline phases with estimated particles sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes, with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microspheres on the surfaces, and EDS spectra confirmed the presence of CuS nanoparticles.

ZnO THIN FILMS PREPARED BY SPRAY-PYROLYSIS TECHNIQUE FROM ORGANO-METALLIC PRECURSOR

Directory of Open Access Journals (Sweden)

Martin Mikulics

2012-07-01

Full Text Available Presented experiments utilize methanolic solution of zinc acetyl-acetonate as a precursor and sapphire (001 as a substrate for deposition of thin films of ZnO. The X-ray diffraction analysis revealed polycrystalline character of prepared films with preferential growth orientation along c-axis. The roughness of prepared films was assessed by AFM microscopy and represented by roughness root mean square (RMS value in range of 1.8 - 433 nm. The surface morphology was mapped by scanning electron microscopy showing periodical structure with several local defects. The optical transmittance spectrum of ZnO films was measured in wavelength range of 200-1000 nm. Prepared films are transparent in visible range with sharp ultra-violet cut-off at approximately 370 nm. Raman spectroscopy confirmed wurtzite structure and the presence of compressive stress within its structure as well as the occurrence of oxygen vacancies. The four-point Van der Pauw method was used to study the transport prosperities. The resistivity of presented ZnO films was found 8 × 10–2 Ω cm with carrier density of 1.3 × 1018 cm–3 and electron mobility of 40 cm2 V–1 s–1.

Horizons of organic and organoelemental chemistry. 7. All-Russian conference on organometallic chemistry. Program and summaries of communications. V. 1

International Nuclear Information System (INIS)

1999-01-01

Abstracts of the seventh All-Russian conference on organometallic chemistry are presented. The synthesis of organometallic compounds of rare earth, transition elements, the synthesis of organic boron compounds are played an important role in modern organic chemistry and the main part of reports are devoted to these problems. Methods of labelling by radioactive isotopes of organic compounds used in medicine are discussed

A silica-supported double-decker silsesquioxane provides a second skin for the selective generation of bipodal surface organometallic complexes

KAUST Repository

Espinas, Jeff

2012-11-12

A well-defined silica-based material with a homogeneous nanolayer presenting identical pairs of vicinal silanols has been prepared by reaction of the surface organometallic species [≡SiOZr(CH 2CMe 3) 3], obtained on a silica dehydroxylated at 900 °C, with the double-decker-shaped silsesquioxane (OH) 2DD(OH) 2. The surface structure has been established using extensive NMR characterization ( 1H, 13C, 29Si, HETCOR, double-quantum, triple-quantum). Treatment with Zr(CH 2CMe 3) 4 leads to the first well-defined single-site bipodal grafted bis-neopentyl zirconium complex. © 2012 American Chemical Society.

A silica-supported double-decker silsesquioxane provides a second skin for the selective generation of bipodal surface organometallic complexes

KAUST Repository

Espinas, Jeff; Pelletier, Jeremie; Abou-Hamad, Edy; Emsley, Lyndon; Basset, Jean-Marie

2012-01-01

A well-defined silica-based material with a homogeneous nanolayer presenting identical pairs of vicinal silanols has been prepared by reaction of the surface organometallic species [≡SiOZr(CH 2CMe 3) 3], obtained on a silica dehydroxylated at 900 °C, with the double-decker-shaped silsesquioxane (OH) 2DD(OH) 2. The surface structure has been established using extensive NMR characterization ( 1H, 13C, 29Si, HETCOR, double-quantum, triple-quantum). Treatment with Zr(CH 2CMe 3) 4 leads to the first well-defined single-site bipodal grafted bis-neopentyl zirconium complex. © 2012 American Chemical Society.

Interplay between experiments and calculations for organometallic clusters and caged clusters

International Nuclear Information System (INIS)

Nakajima, Atsushi

2015-01-01

Clusters consisting of 10-1000 atoms exhibit size-dependent electronic and geometric properties. In particular, composite clusters consisting of several elements and/or components provide a promising way for a bottom-up approach for designing functional advanced materials, because the functionality of the composite clusters can be optimized not only by the cluster size but also by their compositions. In the formation of composite clusters, their geometric symmetry and dimensionality are emphasized to control the physical and chemical properties, because selective and anisotropic enhancements for optical, chemical, and magnetic properties can be expected. Organometallic clusters and caged clusters are demonstrated as a representative example of designing the functionality of the composite clusters. Organometallic vanadium-benzene forms a one dimensional sandwich structure showing ferromagnetic behaviors and anomalously large HOMO-LUMO gap differences of two spin orbitals, which can be regarded as spin-filter components for cluster-based spintronic devices. Caged clusters of aluminum (Al) are well stabilized both geometrically and electronically at Al 12 X, behaving as a “superatom”

Redox responsive nanotubes from organometallic polymers by template assisted layer by layer fabrication

NARCIS (Netherlands)

Song, Jing; Janczewski, D.J.; Guo, Y.Y.; Guo, Yuanyuan; Xu, Jianwei; Vancso, Gyula J.

2013-01-01

Redox responsive nanotubes were fabricated by the template assisted layer-by-layer (LbL) assembly method and employed as platforms for molecular payload release. Positively and negatively charged organometallic poly(ferrocenylsilane)s (PFS) were used to construct the nanotubes, in combination with

Advanced polymer chemistry of organometallic anions

International Nuclear Information System (INIS)

Chamberlin, R.M.; Abney, K.D.; Balaich, G.J.; Fino, S.A.

1997-01-01

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to prepare and characterize new polymers incorporating cobalt dicarbollide. Specific goals were to prepare polymerizable cobalt dicarbollide monomers using the nucleophilic substitution route discovered in laboratories and to establish the reaction conditions required to form polymers from these complexes. This one-year project resulted in two publications (in press), and provided the foundation for further investigations into polymer synthesis and characterization using cobalt dicarbollide and other metallocarboranes. Interest in synthesizing organometallic polymers containing the cobalt bis(dicarbollide) anion is motivated by their possible application as cation exchange materials for the remediation of cesium-137 and strontium-90 from nuclear wastes

Synthesis, characterization and reactivity of some lanthanide organometallics

International Nuclear Information System (INIS)

Marchal, N.

1991-12-01

Organo lanthanides with reactive metal-carbon bonds are obtained by direct synthesis of the metal (powder) and a hydrocarbon in ether medium, like with alkali metals. Two types of synthesis are envisaged: formation of covalent bonds by opening cycles, only biphenylene is reactive enough in regard to ytterbium and samarium, these organometallic compounds can also be prepared by the classical way, i.e. reaction of 2.2'-dilithio biphenyl on rare earth halogenides and coupling of 6.6-dimethylfulvene leading to dicyclopentadienyl compounds with Sm and Yb. The reactivity of these complexes is studied by catalysis of ethylene polymerization

Rapid synthesis of macrocycles from diol precursors

DEFF Research Database (Denmark)

Wingstrand, Magnus; Madsen, Charlotte Marie; Clausen, Mads Hartvig

2009-01-01

A method for the formation of synthetic macrocycles with different ring sizes from diols is presented. Reacting a simple diol precursor with electrophilic reagents leads to a cyclic carbonate, sulfite or phosphate in a single step in 25-60% yield. Converting the cyclization precursor to a bis-ele...

Binding CO2 from Air by a Bulky Organometallic Cation Containing Primary Amines.

Science.gov (United States)

Luo, Yang-Hui; Chen, Chen; Hong, Dan-Li; He, Xiao-Tong; Wang, Jing-Wen; Ding, Ting; Wang, Bo-Jun; Sun, Bai-Wang

2018-03-21

The organometallic cation 1 (Fe(bipy-NH 2 ) 3 2+ , bipy-NH 2 = 4,4'-diamino-2,2'-bipyridine), which was constructed in situ in solution, can bind CO 2 from air effectively with a stoichiometric ratio of 1:4 (1/CO 2 ), through the formation of "H-bonded CO 2 " species: [CO 2 -OH-CO 2 ] - and [CO 2 -CO 2 -OH] - . These two species, along with the captured individual CO 2 molecules, connected 1 into a novel 3D (three-dimensional) architecture, that was crystal 1·2(OH - )·4(CO 2 ). The adsorption isotherms, recycling investigations, and the heat capacity of 1 have been investigated; the results revealed that the organometallic cation 1 can be recycled at least 10 times for the real-world CO 2 capture applications. The strategies presented here may provide new hints for the development of new alkanolamine-related absorbents or technologies for CO 2 capture and sequestration.

The Future of Polar Organometallic Chemistry Written in Bio-Based Solvents and Water.

Science.gov (United States)

García-Álvarez, Joaquín; Hevia, Eva; Capriati, Vito

2018-06-19

There is a strong imperative to reduce the release of volatile organic compounds (VOCs) into the environment, and many efforts are currently being made to replace conventional hazardous VOCs in favour of safe, green and bio-renewable reaction media that are not based on crude petroleum. Recent ground-breaking studies from a few laboratories worldwide have shown that both Grignard and (functionalised) organolithium reagents, traditionally handled under strict exclusion of air and humidity and in anhydrous VOCs, can smoothly promote both nucleophilic additions to unsaturated substrates and nucleophilic substitutions in water and other bio-based solvents (glycerol, deep eutectic solvents), competitively with protonolysis, at room temperature and under air. The chemistry of polar organometallics in the above protic media is a complex phenomenon influenced by several factors, and understanding its foundational character is surely stimulating in the perspective of the development of a sustainable organometallic chemistry. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kinetic and Surface Study of Single-Walled Aluminosilicate Nanotubes and Their Precursors

Directory of Open Access Journals (Sweden)

Mauricio Molina

2013-03-01

Full Text Available The structural and surface changes undergone by the different precursors that are produced during the synthesis of imogolite are reported. The surface changes that occur during the synthesis of imogolite were determined by electrophoretic migration (EM measurements, which enabled the identification of the time at which the critical precursor of the nanoparticles was generated. A critical parameter for understanding the evolution of these precursors is the isoelectric point (IEP, of which variation revealed that the precursors modify the number of active ≡Al-OH and ≡Si-OH sites during the formation of imogolite. We also found that the IEP is displaced to a higher pH level as a consequence of the surface differentiation that occurs during the synthesis. At the same time, we established that the pH of the reaction (pHrx decreases with the evolution and condensation of the precursors during aging. Integration of all of the obtained results related to the structural and surface properties allows an overall understanding of the different processes that occur and the products that are formed during the synthesis of imogolite.

Induced-fit recognition of DNA by organometallic complexes with dynamic stereogenic centers

Czech Academy of Sciences Publication Activity Database

Chen, H.; Parkinson, J. A.; Nováková, Olga; Bella, J.; Wang, F.; Dawson, A.; Gould, R.; Parsons, S.; Brabec, Viktor; Sadler, P. J.

2003-01-01

Roč. 100, č. 25 (2003), s. 14623-14628 ISSN 0027-8424 R&D Projects: GA ČR GA305/02/1552; GA ČR GA305/01/0418; GA AV ČR IAA5004101 Institutional research plan: CEZ:AV0Z5004920 Keywords : organometallic complexes * platinum * DNA Subject RIV: BO - Biophysics Impact factor: 10.272, year: 2003

Organometallic compounds of the lanthanides, actinides and early transition metals

Energy Technology Data Exchange (ETDEWEB)

Cardin, D J [Trinity Coll., Dublin (Ireland); Cotton, S A [Stanground School, Peterborough (UK); Green, M [Bristol Univ. (UK); Labinger, J A [Atlantic Richfield Co., Los Angeles, CA (USA); eds.

1985-01-01

This book provides a reference compilation of physical and biographical data on over 1500 of the most important and useful organometallic compounds of the lanthanides, actinides and early transition metals representing 38 different elements. The compounds are listed in molecular formula order in a series of entries in dictionary format. Details of structure, physical and chemical properties, reactions and key references are clearly set out. All the data is fully indexed and a structural index is provided.

Formation of Micro and Mesoporous Amorphous Silica-Based Materials from Single Source Precursors

Directory of Open Access Journals (Sweden)

Mohd Nazri Mohd Sokri

2016-03-01

Full Text Available Polysilazanes functionalized with alkoxy groups were designed and synthesized as single source precursors for fabrication of micro and mesoporous amorphous silica-based materials. The pyrolytic behaviors during the polymer to ceramic conversion were studied by the simultaneous thermogravimetry-mass spectrometry (TG-MS analysis. The porosity of the resulting ceramics was characterized by the N2 adsorption/desorption isotherm measurements. The Fourier transform infrared spectroscopy (FT-IR and Raman spectroscopic analyses as well as elemental composition analysis were performed on the polymer-derived amorphous silica-based materials, and the role of the alkoxy group as a sacrificial template for the micro and mesopore formations was discussed from a viewpoint to establish novel micro and mesoporous structure controlling technologies through the polymer-derived ceramics (PDCs route.

A golden future in medicinal inorganic chemistry : The promise of anticancer gold organometallic compounds

NARCIS (Netherlands)

Bertrand, B.; Casini, A.

2014-01-01

From wedding rings on fingers to stained glass windows, by way of Olympic medals, gold has been highly prized for millennia. Nowadays, organometallic gold compounds occupy an important place in the field of medicinal inorganic chemistry due to their unique chemical properties with respect to gold

Integrated rotating-compensator polarimeter for real-time measurements and analysis of organometallic chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Flock, K.; Kim, S.-J.; Asar, M.; Kim, I.K.; Aspnes, D.E

2004-05-01

We describe a single-beam rotating-compensator rotating-sample spectroscopic polarimeter (RCSSP) integrated with an organometallic chemical vapor deposition (OMCVD) reactor for in-situ diagnostics and control of epitaxial growth, and report representative results. The rotating compensator generates Fourier coefficients that provide information about layer thicknesses and compositions, while sample rotation provides information about optical anisotropy and therefore surface chemistry. We illustrate capabilities with various examples, including the simultaneous determination of <{epsilon}> and {alpha}{sub 10} during exposure of (001)GaAs to TMG, the heteroepitaxial growth of GaP on GaAs, and the growth of (001)GaSb with TMG and TMSb. Using a recently developed approach for quantitatively determining thickness and dielectric function of depositing layers, we find the presence of metallic Ga on TMG-exposed (001)GaAs. The (001)GaSb data show that Sb deposition is self-limiting, in contrast to expectations.

Microchip electrophoresis-single wall carbon nanotube press-transferred electrodes for fast and reliable electrochemical sensing of melatonin and its precursors.

Science.gov (United States)

Gomez, Federico José Vicente; Martín, Aída; Silva, María Fernanda; Escarpa, Alberto

2015-08-01

In the current work, single-wall carbon nanotube press-transferred electrodes (SW-PTEs) were used for detection of melatonin (MT) and its precursors tryptophan (Trp) and serotonin (5-HT) on microchip electrophoresis (ME). SW-PTEs were simply fabricated by press transferring a filtered dispersion of single-wall carbon nanotubes on a nonconductive PMMA substrate, where single-wall carbon nanotubes act as exclusive transducers. The coupling of ME-SW-PTEs allowed the fast detection of MT, Trp, and 5-HT in less than 150 s with excellent analytical features. It exhibited an impressive antifouling performance with RSD values of ≤2 and ≤4% for migration times and peak heights, respectively (n = 12). In addition, sample analysis was also investigated by analysis of 5-HT, MT, and Trp in commercial samples obtaining excellent quantitative and reproducible recoveries with values of 96.2 ± 1.8%, 101.3 ± 0.2%, and 95.6 ± 1.2% for 5-HT, MT, and Trp, respectively. The current novel application reveals the analytical power of the press-transfer technology where the fast and reliable determination of MT and its precursors were performed directly on the nanoscale carbon nanotube detectors without the help of any other electrochemical transducer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Beyond organometallic flow chemistry : the principles behind the use of continuous-flow reactors for synthesis

NARCIS (Netherlands)

Noel, T.; Su, Y.; Hessel, V.; Noël, T.

2015-01-01

Flow chemistry is typically used to enable challenging reactions which are difficult to carry out in conventional batch equipment. Consequently, the use of continuous-flow reactors for applications in organometallic and organic chemistry has witnessed a spectacular increase in interest from the

The electromagnetic Brillouin precursor in one-dimensional photonic crystals

NARCIS (Netherlands)

Uitham, R.; Hoenders, B. J.

2008-01-01

We have calculated the electromagnetic Brillouin precursor that arises in a one-dimensional photonic crystal that consists of two homogeneous slabs which each have a single electron resonance. This forerunner is compared with the Brillouin precursor that arises in a homogeneous double-electron

Cluster-derived Ir-Sn/SiO2 catalysts for the catalytic dehydrogenation of propane: A spectroscopic study

KAUST Repository

Gallo, Alessandro; Psaro, Rinaldo; Guidotti, Matteo; Dal Santo, Vladimiro; Pergola, Roberto Della; Masih, Dilshad; Izumi, Yasuo

2013-01-01

Ir-Sn bimetallic silica-based materials have been prepared via deposition of the molecular organometallic clusters (NEt4)2[Ir 4(CO)10(SnCl3)2] and NEt 4[Ir6(CO)15(SnCl3)] or via deposition of Sn organometallic precursor Sn(n-C4H9) 4 onto pre

Use of ionic liquids as coordination ligands for organometallic catalysts

Science.gov (United States)

Li, Zaiwei [Moreno Valley, CA; Tang, Yongchun [Walnut, CA; Cheng,; Jihong, [Arcadia, CA

2009-11-10

Aspects of the present invention relate to compositions and methods for the use of ionic liquids with dissolved metal compounds as catalysts for a variety of chemical reactions. Ionic liquids are salts that generally are liquids at room temperature, and are capable of dissolving a many types of compounds that are relatively insoluble in aqueous or organic solvent systems. Specifically, ionic liquids may dissolve metal compounds to produce homogeneous and heterogeneous organometallic catalysts. One industrially-important chemical reaction that may be catalyzed by metal-containing ionic liquid catalysts is the conversion of methane to methanol.

Mechanisms of inorganic and organometallic reactions

CERN Document Server

The purpose of this series is to provide a continuing critical review of the literature concerned with mechanistic aspects of inorganic and organo­ metallic reactions in solution, with coverage being complete in each volume. The papers discussed are selected on the basis of relevance to the elucidation of reaction mechanisms and many include results of a nonkinetic nature when useful mechanistic information can be deduced. The period of literature covered by this volume is July 1982 through December 1983, and in some instances papers not available for inclusion in the previous volume are also included. Numerical results are usually reported in the units used by the original authors, except where data from different papers are com­ pared and conversion to common units is necessary. As in previous volumes material included covers the major areas of redox processes, reactions of the nonmetallic elements, reaction of inert and labile metal complexes and the reactions of organometallic compounds. While m...

Well-defined mono(η3-allyl)nickel complex MONi(η3-C3H5) (M = Si or Al) grafted onto silica or alumina: A molecularly dispersed nickel precursor for syntheses of supported small size nickel nanoparticles

KAUST Repository

Li, Lidong; Abou-Hamad, Edy; Anjum, Dalaver H.; Zhou, Lu; Laveille, Paco; Emsley, Lyndon; Basset, Jean-Marie

2014-01-01

Preparing evenly-dispersed small size nickel nanoparticles over inert oxides remains a challenge today. In this context, a versatile method to prepare supported small size nickel nanoparticles (ca. 1-3 nm) with narrow size distribution via a surface organometallic chemistry (SOMC) route is described. The grafted mono(η3-allyl)nickel complexes MONi(η 3-C3H5) (M = Si or Al) as precursors are synthesized and fully characterized by elemental analysis, FTIR spectroscopy and paramagnetic solid-state NMR. © 2014 the Partner Organisations.

Single source precursors for fabrication of I-III-VI{sub 2} thin-film solar cells via spray CVD

Energy Technology Data Exchange (ETDEWEB)

Hollingsworth, J.A.; Banger, K.K.; Jin, M.H.-C.; Harris, J.D.; Cowen, J.E.; Bohannan, E.W.; Switzer, J.A.; Buhro, W.E.; Hepp, A.F

2003-05-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power (W/kg). Thin-film fabrication studies demonstrate that ternary single source precursors can be used in either a hot, or cold-wall spray chemical vapour deposition reactor, for depositing CuInS{sub 2}, CuGaS{sub 2} and CuGaInS{sub 2} at reduced temperatures (400-450 sign C), which display good electrical and optical properties suitable for photovoltaic devices. X-ray diffraction studies, energy dispersive spectroscopy and scanning electron microscopy confirmed the formation of the single phase CIS, CGS, CIGS thin-films on various substrates at reduced temperatures.

Use of one delayed-neutron precursor group in transient analysis

International Nuclear Information System (INIS)

Diamond, D.J.

1983-01-01

In most reactor dynamics calculations six groups of delayed-neutron precursors are usually accounted for. However, under certain circumstances it may be advantageous to simplify the calculation and utilize a single delayed-neutron group. The motivation for going to one precursor group is economy. For LWR transient codes that use point kinetics the equations are solved very rapidly and six precursor groups should always be used. However, codes with spatially dependent neutron kinetics are very long running and the use of one precursor group may save computer costs and not impair the accuracy of the results significantly. Furthermore, in some codes, the elimation of five presursor groups makes additional memory available which may be used to give a net increase in the accuracy of the calculations, e.g., by allowing for an increase in mesh density. In order to use one delayed neutron precursor group it is necessary to derive a single decay constant, 6 lambda-, which, along with the total (or one group) delayed neutron fraction β = Σ/sub i = 1/β/sub i/, will adequately describe the transeint precursor behavior. The present summary explains how a recommendation for lambda- was derived

Organometallic Gold(III) Complexes Similar to Tetrahydroisoquinoline Induce ER-Stress-Mediated Apoptosis and Pro-Death Autophagy in A549 Cancer Cells.

Science.gov (United States)

Huang, Ke-Bin; Wang, Feng-Yang; Tang, Xiao-Ming; Feng, Hai-Wen; Chen, Zhen-Feng; Liu, Yan-Cheng; Liu, You-Nian; Liang, Hong

2018-04-26

Agents inducing both apoptosis and autophagic death can be effective chemotherapeutic drugs. In our present work, we synthesized two organometallic gold(III) complexes harboring C^N ligands that structurally resemble tetrahydroisoquinoline (THIQ): Cyc-Au-1 (AuL 1 Cl 2 , L 1 = 3,4-dimethoxyphenethylamine) and Cyc-Au-2 (AuL 2 Cl 2 , L 2 = methylenedioxyphenethylamine). In screening their in vitro activity, we found both gold complexes exhibited lower toxicity, lower resistance factors, and better anticancer activity than those of cisplatin. The organometallic gold(III) complexes accumulate in mitochondria and induce elevated ROS and an ER stress response through mitochondrial dysfunction. These effects ultimately result in simultaneous apoptosis and autophagy. Importantly, compared to cisplatin, Cyc-Au-2 exhibits lower toxicity and better anticancer activity in a murine tumor model. To the best of our knowledge, Cyc-Au-2 is the first organometallic Au(III) compound that induces apoptosis and autophagic death. On the basis of our results, we believe Cyc-Au-2 to be a promising anticancer agent or lead compound for further anticancer drug development.

A versatile single molecular precursor for the synthesis of layered oxide cathode materials for Li-ion batteries.

Science.gov (United States)

Li, Maofan; Liu, Jiajie; Liu, Tongchao; Zhang, Mingjian; Pan, Feng

2018-02-01

A carbonyl-bridged single molecular precursor LiTM(acac) 3 [transition metal (TM) = cobalt/manganese/nickel (Co/Mn/Ni), acac = acetylacetone], featuring a one-dimensional chain structure, was designed and applied to achieve the layered oxide cathode materials: LiTMO 2 (TM = Ni/Mn/Co, NMC). As examples, layered oxides, primary LiCoO 2 , binary LiNi 0.8 Co 0.2 O 2 and ternary LiNi 0.5 Mn 0.3 Co 0.2 O 2 were successfully prepared to be used as cathode materials. When they are applied to lithium-ion batteries (LIBs), all exhibit good electrochemical performance because of their unique morphology and great uniformity of element distribution. This versatile precursor is predicted to accommodate many other metal cations, such as aluminum (Al 3+ ), iron (Fe 2+ ), and sodium (Na + ), because of the flexibility of organic ligand, which not only facilitates the doping-modification of the NMC system, but also enables synthesis of Na-ion layered oxides. This opens a new direction of research for the synthesis of high-performance layered oxide cathode materials for LIBs.

Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

Science.gov (United States)

Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

1995-01-01

Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

A single-source solid-precursor method for making eco-friendly doped semiconductor nanoparticles emitting multi-color luminescence.

Science.gov (United States)

Manzoor, K; Aditya, V; Vadera, S R; Kumar, N; Kutty, T R N

2007-02-01

A novel synthesis method is presented for the preparation of eco-friendly, doped semiconductor nanocrystals encapsulated within oxide-shells, both formed sequentially from a single-source solid-precursor. Highly luminescent ZnS nanoparticles, in situ doped with Cu(+)-Al3+ pairs and encapsulated with ZnO shells are prepared by the thermal decomposition of a solid-precursor compound, zinc sulfato-thiourea-oxyhydroxide, showing layered crystal structure. The precursor compound is prepared by an aqueous wet-chemical reaction involving necessary chemical reagents required for the precipitation, doping and inorganic surface capping of the nanoparticles. The elemental analysis (C, H, N, S, O, Zn), quantitative estimation of different chemical groups (SO4(2-) and NH4(-)) and infrared studies suggested that the precursor compound is formed by the intercalation of thiourea, and/or its derivatives thiocarbamate (CSNH2(-)), dithiocarbamate (CS2NH2(-)), etc., and ammonia into the gallery space of zinc-sulfato-oxyhydroxide corbel where the Zn(II) ions are both in the octahedral as well as tetrahedral coordination in the ratio 3 : 2 and the dopant ions are incorporated within octahedral voids. The powder X-ray diffraction of precursor compound shows high intensity basal reflection corresponding to the large lattice-plane spacing of d = 11.23 angstroms and the Rietveld analysis suggested orthorhombic structure with a = 9.71 angstroms, b = 12.48 angstroms, c = 26.43 angstroms, and beta = 90 degrees. Transmission electron microscopy studies show the presence of micrometer sized acicular monocrystallites with prismatic platy morphology. Controlled thermolysis of the solid-precursor at 70-110 degrees C leads to the collapse of layered structure due to the hydrolysis of interlayer thiourea molecules or its derivatives and the S2- ions liberated thereby reacts with the tetrahedral Zn(II) atoms leading to the precipitation of ZnS nanoparticles at the gallery space. During this process

DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

Energy Technology Data Exchange (ETDEWEB)

Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

2008-04-30

The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

Design of supported bi-metallic nanoparticles based on Platinum and Palladium using Surface Organometallic Chemistry (SOMC)

KAUST Repository

Al-Shareef, Reem A.

2017-01-01

Well-defined silica supported bimetallic catalysts Pt100-x Pdx (where x is the molar ratio of Pd) are prepared by Surface Organometallic Chemistry (SOMC) via controlled decomposition of Pd2(allyl)2Cl2 on Pt/SiO2. For comparison purposes, Pt100-x Pdx

A paradigm shift for radical SAM reactions: The organometallic intermediate Ω is central to catalysis.

Science.gov (United States)

Byer, Amanda S; Yang, Hao; McDaniel, Elizabeth C; Kathiresan, Venkatesan; Impano, Stella; Pagnier, Adrien; Watts, Hope; Denler, Carly; Vagstad, Anna; Piel, Jörn; Duschene, Kaitlin S; Shepard, Eric M; Shields, Thomas P; Scott, Lincoln G; Lilla, Edward A; Yokoyama, Kenichi; Broderick, William E; Hoffman, Brian M; Broderick, Joan B

2018-06-28

Radical S-adenosyl-L-methionine (SAM) en-zymes comprise a vast superfamily catalyzing diverse reactions essential to all life through ho-molytic SAM cleavage to liberate the highly-reactive 5-deoxyadenosyl radical (5-dAdo•). Our recent observation of a catalytically compe-tent organometallic intermediate Ω that forms dur-ing reaction of the radical SAM (RS) enzyme py-ruvate formate-lyase activating-enzyme (PFL-AE) was therefore quite surprising, and led to the question of its broad relevance in the superfamily. We now show that Ω in PFL-AE forms as an in-termediate under a variety of mixing order condi-tions, suggesting it is central to catalysis in this enzyme. We further demonstrate that Ω forms in a suite of RS enzymes chosen to span the totality of superfamily reaction types, implicating Ω as essential in catalysis across the RS superfamily. Finally, EPR and electron nuclear double reso-nance spectroscopy establish that Ω involves an Fe-C5 bond between 5-dAdo• and the [4Fe-4S] cluster. An analogous organometallic bond is found in the well-known adenosylcobalamin (co-enzyme B12) cofactor used to initiate radical reac-tions via a 5'-dAdo• intermediate. Generation of a 5'-dAdo• intermediate via homolytic metal-carbon bond cleavage thus appears to be similar for Ω and coenzyme B12. However coenzyme B12 is involved in enzymes catalyzing of only a small number (~12) of distinct reactions, while the RS superfamily has more than 100,000 distinct se-quences and over 80 reaction types character-ized to date. The appearance of Ω across the RS superfamily therefore dramatically enlarges the sphere of bio-organometallic chemistry in Nature.

Using Molecular Modeling in Teaching Group Theory Analysis of the Infrared Spectra of Organometallic Compounds

Science.gov (United States)

Wang, Lihua

2012-01-01

A new method is introduced for teaching group theory analysis of the infrared spectra of organometallic compounds using molecular modeling. The main focus of this method is to enhance student understanding of the symmetry properties of vibrational modes and of the group theory analysis of infrared (IR) spectra by using visual aids provided by…

Effect of temperature on the optical and structural properties of hexadecylamine capped ZnS nanoparticles using Zinc(II) N-ethyl-N-phenyldithiocarbamate as single source precursor

Energy Technology Data Exchange (ETDEWEB)

Onwudiwe, Damian C., E-mail: dconwudiwe@webmail.co.za [Chemical Resource Beneficiation, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Strydom, Christien [Chemical Resource Beneficiation, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Oluwafemi, Oluwatobi S., E-mail: oluwafemi.oluwatobi@gmail.com [Department of Chemistry and Chemical Technology, Walter Sisulu University, Mthatha Campus, Private Bag X1, Mthatha (South Africa); Songca, Sandile P. [Faculty of Science, Engineering and Technology, Walter Sisulu University, P.O. Box 19712, Tecoma, East London (South Africa)

2012-12-15

Graphical abstract: Display Omitted Highlights: ► HDA-capped ZnS nanoparticles were synthesized via thermolysis of a single source precursor. ► Zinc(II) N-ethyl-N-phenyldithiocarbamate was used as the single source precursor. ► The growth temperature was varied to study the optical properties of the nanocrystals. ► Change in growth temperature affects the structural properties of the ZnS nanoparticles. ► Hexagonal wurtzite phase was obtained at lower temperatures while cubic sphalerite phase was obtained at higher growth temperatures. -- Abstract: Reported in this work is the synthesis of HDA (hexadecylamine)-capped ZnS nanoparticles by a single source route using Zinc(II) N-ethyl-N-phenyldithiocarbamate as a precursor. By varying the growth temperature, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated. The as-synthesized nanoparticles were characterized using UV–vis absorption and photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). All the particles exhibited quantum confinement in their optical properties with band edge emission at the early stage of the reaction. The XRD showed transition from hexagonal wurtzite phase to cubic sphalerite phase as the growth temperature increases. The TEM image showed that the particles are small and spherical in shape while the HRTEM image confirmed the crystalline nature of the material.

The organometallic chemistry of neptunium

International Nuclear Information System (INIS)

Bohlander, R.

1986-09-01

Organometallic compounds of neptunium with carbocyclic ligands (C 5 H 5 - =cp, C 8 H 8 2- =cot) have been prepared and investigated. Starting from tetrakis(cyclopentadienyle)neptunium(IV) (cp 4 Np) and tris(cyclopentadienyle)neptunium(IV) chloride (cp 3 NpCl) a lot of other Np(IV)-compounds can be obtained by ligand-exchange reactions. These have the general formula cp 3 NpL with either inorganic ionic (L=Br - , I - , 1/2SO 4 2- , NCS - , AlCl 4 - ) or organic ligands (L=NC 4 H 4 - , N 2 C 3 H 3 - , C=CH - , 1/2C= 2- , CH 3 - , C 2 H 5 - , C 6 H 5 - ). Produced by reduction, tris(cyclopentadienyle)neptunium(III), cp 3 Np) gives similar structured 1:1-adduct complexes, cp 3 Np * B, with Lewis-bases like THF, diethylether, acetonitrile. Physico-chemical properties and changes in the molecular structure of the complexes have been studied using IR-, FTIR- and optical spectroscopy (in the NIR, VIS and UV region) as well as by magnetic and EPR measurements and Moessbauer spectrometry. The results are discussed as to their classification within the actinide complex chemistry and to the comparison with lanthanide complexes. (orig./RB) [de

BFCA for labeling with the M(CO)3 precursor (M = Re, 99mTc) : cysteine toward a tridentate complex

International Nuclear Information System (INIS)

Hong, Young Don; Choi, Ok Ja; Gwon, Hui Jeong; Choi, Sang Mu; Park, Sang Hyun; Park, Kyung Bae; Choi, Sun Ju

2004-01-01

Organometallic complexes of techneutium in its low oxidation states received little attention till the development of very stable water-soluble organometallic Tc(I) complexes using monodentate isonitrile ligands. The Tc(I) oxidation state is pratically advantegeous because of the kinetic inertness inherent in its low-spin d 6 configuration and good stability in aqueous media. That is, Tc(I) or Re(I) tricarbonyl complexes are ideal candidates for the radiolabeling of biomolecules which M(CO) 3 core allows the high efficient labelling with the retention of the biological affinity. To be used as a BFCA, it should possess not only both a strong metal-binding moiety and a group that binds to a biomolecules, but also the metal complex should maintain the high stability in vitro and in vivo. In this investigation, to estimate the usefulness of thiol modified L-cysteine as a new BFCA with M(CO)3 precursor for the conjugation to biomolecules while maintaining high stability, their non-carrier added and macroscopic level complexes of L-cycteine (L 1 ), S-methyl L-cysteine (L 2 ), L-methionine (L 3 ), and S-carboxymethyl-L-cysteine (L 4 ) were prepared for the evaluation of radiolabelling efficiency with 99m Tc(CO) 3 and macroscopic characteristics. Furthermore, in order to study in vivo pharmacokinetics, scintigraphic imaging scans using gamma camera were acquired after intravenous administration of each 99m Tc(CO) 3 complex and biodistribution study on 99m Tc(CO) 3 -L 4 was implemented using ICR mice

Indium Sulfide and Indium Oxide Thin Films Spin-Coated from Triethylammonium Indium Thioacetate Precursor for n-Channel Thin Film Transistor

Energy Technology Data Exchange (ETDEWEB)

Tung, Duy Dao; Jeong, Hyun Dam [Chonnam Natioal University, Gwangju (Korea, Republic of)

2014-09-15

The In{sub 2}S{sub 3} thin films of tetragonal structure and In{sub 2}O{sub 3} films of cubic structure were synthesized by a spin coating method from the organometallic compound precursor triethylammonium indium thioacetate ([(Et){sub 3}NH]+ [In(SCOCH{sub 3}){sub 4}]''-; TEA-InTAA). In order to determine the electron mobility of the spin-coated TEA-InTAA films, thin film transistors (TFTs) with an inverted structure using a gate dielectric of thermal oxide (SiO{sub 2}) was fabricated. These devices exhibited n-channel TFT characteristics with a field-effect electron mobility of 10.1 cm''2 V''-1s''-1 at a curing temperature of 500 o C, indicating that the semiconducting thin film material is applicable for use in low-cost, solution-processed printable electronics.

Fast-grown CdS quantum dots: Single-source precursor approach vs microwave route

Energy Technology Data Exchange (ETDEWEB)

Fregnaux, Mathieu [Laboratoire de Chimie et Physique: Approche Multi-échelles des Milieux Complexes, Institut Jean Barriol, Université de Lorraine, 1 Boulevard Arago, 57070 Metz (France); Dalmasso, Stéphane, E-mail: stephane.dalmasso@univ-lorraine.fr [Laboratoire de Chimie et Physique: Approche Multi-échelles des Milieux Complexes, Institut Jean Barriol, Université de Lorraine, 1 Boulevard Arago, 57070 Metz (France); Durand, Pierrick [Laboratoire de Cristallographie, Résonance Magnétique et Modélisations, Institut Jean Barriol, Université de Lorraine, UMR CNRS 7036, Faculté des Sciences, BP 70239, 54506 Vandoeuvre lès Nancy (France); Zhang, Yudong [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux, Université de Lorraine, UMR CNRS 7239, Ile du Saulcy, 57045 Metz cedex 01 (France); Gaumet, Jean-Jacques; Laurenti, Jean-Pierre [Laboratoire de Chimie et Physique: Approche Multi-échelles des Milieux Complexes, Institut Jean Barriol, Université de Lorraine, 1 Boulevard Arago, 57070 Metz (France)

2013-10-01

A cross-disciplinary protocol of characterization by joint techniques enables one to closely compare chemical and physical properties of CdS quantum dots (QDs) grown by single source precursor methodology (SSPM) or by microwave synthetic route (MWSR). The results are discussed in relation with the synthesis protocols. The QD average sizes, reproducible as a function of the temperatures involved in the growth processes, range complementarily in 2.8–4.5 nm and 4.5–5.2 nm for SSPM and MWSR, respectively. Hexagonal and cubic structures after X-ray diffraction on SSPM and MWSR grown CdS QDs, respectively, are tentatively correlated to a better crystalline quality of the latter with respect to the further ones, suggested by (i) a remarkable stability of the MWSR grown QDs after exposure to air during several days and (ii) no evidence of their fragmentation during mass spectrometry (MS) analyses, after a fair agreement between size dispersities obtained by transmission electron microscopy (TEM) and MS, in contrast with the discrepancy found for the SSPM grown QDs. Correlatively, a better optical quality is suggested for the MWSR grown QDs by the resolution of n > 1 excitonic transitions in their absorption spectra. The QD average sizes obtained by TEM and deduced from MS are in overall agreement. This agreement is improved for the MWSR grown QDs, taking into account a prolate shape of the QDs also observed in the TEM images. For both series of samples, the excitonic responses vs the average sizes are consistent with the commonly admitted empirical energy-size correspondence. A low energy PL band is observed in the case of the SSPM grown QDs. Its decrease in intensity with QD size increase suggests a surface origin tentatively attributed to S vacancies. In the case of the MWSR grown QDs, the absence of this PL is tentatively correlated to an absence of S vacancies and therefore to the stable behavior observed when the QDs are exposed to air. - Highlights: • Single

Synthesis of zinc sulfide by chemical vapor deposition using an organometallic precursor: Di-tertiary-butyl-disulfide

International Nuclear Information System (INIS)

Vasekar, Parag; Dhakal, Tara; Ganta, Lakshmikanth; Vanhart, Daniel; Desu, Seshu

2012-01-01

Zinc sulfide has gained popularity in the last few years as a cadmium-free heterojunction partner for thin film solar cells and is seen as a good replacement for cadmium sulfide due to better blue photon response and non-toxicity. In this work, zinc sulfide films are prepared using an organic sulfur source. We report a simple and repeatable process for development of zinc sulfide using a cost-effective and less hazardous organic sulfur source. The development of zinc sulfide has been studied on zinc oxide-coated glass where the zinc oxide is converted into zinc sulfide. Zinc oxide grown by atomic layer deposition as well as commercially available zinc oxide-coated glass was used. The zinc sulfide synthesis has been studied and the films are characterized using scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and a UV–VIS spectrophotometer. XRD, XPS and optical characterization confirm the zinc sulfide phase formation. - Highlights: ► Synthesis of ZnS using a less-hazardous precursor, di-tertiary-butyl-disulfide. ► ZnS process optimized for two types of ZnO films. ► Preliminary results for a solar cell show an efficiency of 1.09%.

Spectroscopic studies of organometallic compounds on single crystal metal surfaces: Surface acetylides of silver (110)

Science.gov (United States)

Madix, Robert J.

The nature of compounds formed by the reaction of organic molecules with metal surfaces can be studied with a battery of analytical methods based on both physicals and chemical understanding. In this paper the application of UPS, XPS, LEED and EELS as well as temperature programmed reaction spectroscopy (TPRS) and chemical titration methods to the characterization of surface complexes is discussed. Particular emphasis is given to the reaction of acetylene with a single crystal surface of silver, Ag(110). Previous work has shown that this surface, when clean, is unreactive to hydrocarbons, alcohols and carboxylic acids under ultra high vacuum conditions. Preadsorption of oxygen, however, renders the surface reactive, and a wide variety of organometallic surface compounds can be formed. As expected then, no stable adsorption state and no reaction was observed with clean Ag(110) following room temperature exposure to acetylene. Following exposure at 150 K, however, a weekly bound chemisorption state was observed to desorb at 195 K, indicating a binding energy to the surface of approximately 12 kcal/gmole. Reaction with preadsorbed oxygen gave water formulation upon dosing and produced surface intermediates which yeilded two acetylene desorption states at 195 and 175 K. Heating above 300 K to completely desorb the higher temperature state produced new, well-defined LEED Features due to residual surface carbon which disappeared when the surface was heated above 550 K. Clearly, there were distinc changes in the nature of the absorbed layer at 195, 300 and 550 K. These changes were reflected in XPS. For the weakly chemisorbed acetylene a large C(ls) peak at 285.6 eV with a small, broad, indistinc shoulder at higher binding energy (288.2) was observed. The spectrum of the species following acetylene desorption at 275 K, however, showed the formulation of a large C(ls) peak at 283.6 eV in addition to peaks characteristics of the weakly chemisorbed state. This result

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1993

Energy Technology Data Exchange (ETDEWEB)

Schmidt, E.; Kirby, S.; Song, Chunshan; Schobert, H.H.

1994-04-01

Development of new catalysts is a promising approach to more, efficient coal liquefaction. It has been recognized that dispersed catalysts can be superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires infinite contact between the catalyst and coal. The primary objective of this research is to explore the potential of bimetallic dispersed catalysts from heterometallic molecular precursors in their use in model compound liquefaction reactions. This quarterly report describes the use of three precursors in model compound reactions. The first catalyst is a heterometallic complex consisting of two transition metals, Mo and Ni, and sulfur in a single molecule. The second is a thiocubane type complex consisting of cobalt, molybdenum and sulfur. The third is a thiocubane type cluster consisting of iron and sulfur and the fourth, the pure inorganic salt ammonium tetrathiomolybdate (ATM). It was found that the structure and the ligands in the model complexes affect the activity of the resulting catalyst significantly. The optimum reaction at a pressure of 6.9 MPa hydrogen gas varied for different catalysts. The bimetallic catalysts generated in situ from the organometallic precursor are more active than monometallic catalysts like ATTM and the thiocubane type cluster Fe{sub 4}. Main products are hydrogenated phenanthrene derivatives, like DBP, THP, sym-OHP, cis- and trans-unsym-OHP with minor isomerization products such as sym-OHA. Our results indicate that other transition metal and ligand combinations in the organometallic precursors and the use of another model compound could result in substantially higher conversion activity.

ZnS, CdS and HgS nanoparticles via alkyl-phenyl dithiocarbamate complexes as single source precursors.

Science.gov (United States)

Onwudiwe, Damian C; Ajibade, Peter A

2011-01-01

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively.

ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

Directory of Open Access Journals (Sweden)

Peter A. Ajibade

2011-08-01

Full Text Available The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm, 2.91 eV (426 nm and 4.27 eV (290 nm for the ZnS, CdS and HgS samples respectively.

Generation of Well-Defined Pairs of Silylamine on Highly Dehydroxylated SBA-15: Application to the Surface Organometallic Chemistry of Zirconium

KAUST Repository

Azzi, Joachim

2012-11-01

Design of a new well-defined surface organometallic species [O-(=Si–NH)2Zr(IV)Np2] has been obtained by reaction of tetraneopentyl zirconium (ZrNp4) on SBA-15 surface displaying mainly silylamine pairs [O-(=Si–NH2)2]. These surface species have been achieved by an ammonia treatment of a highly dehydroxylated SBA-15 at 1000°C (SBA-151000). This support is known to contain mainly strained reactive siloxane bridges (≡Si-O-Si≡)[1] along with a small amount of isolated plus germinal silanols =Si(OH)2. Chemisorption of ammonia occurs primarily by opening these siloxane bridges[2] to generate silanol/silylamine pairs [O-(=Si–NH2)(=SiOH)] followed by substitution of the remaining silanol. Further treatment using hexamethyldisilazane (HMDS) results in the protection of the isolated remaining silanol groups by formation of ≡Si-O-SiMe3 and =Si(OSiMe3)2 but leaves ≡SiNH2 untouched. After reaction of this functionalized surface with ZrNp4, this latter displays mainly a bi-podal zirconium neopentyl organometallic complex [O-(=Si–NH)2Zr(IV)Np2] which has been fully characterized by diverse methods such as infrared transmission spectroscopy, magic angle spinning solid state nuclear magnetic resonance, surface elemental analysis, small angle X-ray powder diffraction (XRD), nitrogen adsorption and energy filtered transmission electron microscopy (EFTEM). These different characterization tools unambiguously prove that the zirconium organometallic complex reacts mostly with silylamine pairs to give a bi-podal zirconium bis-neopentyl complex, uniformly distributed into the channels of SBA-151000. Therefore this new material opens a new promising research area in Surface Organometallic Chemistry which, so far, was dealing mainly with O containing surface. It is expected that vicinal amine functions may play a very different role as compared with classical inorganic supports. Given the importance in the last decades of N containing ligands in catalysis, one may expect

Homogeneity of single phase Cu(In,Ga)Se2 produced by selenisation of metal precursors: An optical investigation

International Nuclear Information System (INIS)

Botha, J.R.; Schumacher, S.A.; Leitch, A.W.R.; Alberts, V.

2006-01-01

Two-stage processes involving the selenisation of metallic precursor layers are among the most promising techniques for the formation of chalcopyrite-based solar cell absorber layers on a commercial scale. In this paper, the homogeneity of Cu(In 0.75 Ga 0.25 )Se 2 prepared by a new two-stage technique [V. Alberts, Semicond. Sci. Technol., 19 (2004) 65.], which involves the selenisation of sputtered CuIn 0.75 Ga 0.25 precursor films in steps designed to control the reaction rates of the binary selenide phases and to prevent the formation of the more stable CuGaSe 2 phase, is studied. Photoluminescence spectroscopy, optical absorption measurements and X-ray diffraction measurements confirm that layers grown by a traditional process, which involves a single selenisation step, contain separate quaternary phases: gallium-rich phases are found closer to the substrate, while gallium-poor phases reside near the front surface. Layers produced by the novel process do not show this grading. A line appearing at ∼ 0.8 eV is ascribed to Na III , which results from the out-diffusion of Na from the glass substrate

Catalysis by Design: Well-Defined Single-Site Heterogeneous Catalysts

KAUST Repository

Pelletier, Jeremie; Basset, Jean-Marie

2016-01-01

concepts and tools of surface organometallic chemistry (SOMC). This approach operates by reacting organometallic compounds with surfaces of highly divided oxides (or of metal nanoparticles). This strategy has a solid track record to reveal structure

Organic or organometallic template mediated clay synthesis

Science.gov (United States)

Gregar, Kathleen C.; Winans, Randall E.; Botto, Robert E.

1994-01-01

A method for incorporating diverse Varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalants or templates may be introduced. The intercalants or templates should have (i) water-solubility, (ii) positive charge, and (iii) thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays.

Electroluminescence Properties of IrQ(ppy)2 Dual-Emitter Organometallic Compound in Organic Light-Emitting Devices

Science.gov (United States)

Ciobotaru, Constantin Claudiu; Polosan, Silviu; Ciobotaru, Iulia Corina

2018-02-01

This paper reports the influence of the charge carrier mobility on the electroluminescent properties of a dual-emitter organometallic compound dispersed in two conjugated organic small-molecule host materials and embedded in organic light-emitting devices (OLEDs). The electroluminescent processes in OLEDs are strongly influenced by the host-guest interaction. The charge carrier mobility in the host material plays an important role in the electroluminescent processes but also depends on the triplet-triplet interaction with the organometallic compound. The low charge carrier mobility in 4,4'-bis( N-carbazolyl)-1,1'-biphenyl (CBP) host material reduces the electroluminescent processes, but they are slightly enhanced by the triplet-triplet exothermic charge transfer. The higher charge carrier mobility in the case of N, N'-bis(3-methylphenyl)- N, N'-diphenylbenzidine (TPD) host material influences the electroluminescent processes by the endothermic energy transfer at room temperature, which facilitates the triplet-triplet harvesting in the host-guest system. The excitation is transferred to the guest molecules by triplet-triplet interaction as a Dexter transfer, which occurs by endothermic transfer from the triplet exciton in the host to the triplet exciton in the guest.

Spray Chemical Vapor Deposition of Single-Source Precursors for Chalcopyrite I-III-VI2 Thin-Film Materials

Science.gov (United States)

Hepp, Aloysius F.; Banger, Kulbinder K.; Jin, Michael H.-C.; Harris, Jerry D.; McNatt, Jeremiah S.; Dickman, John E.

2008-01-01

Thin-film solar cells on flexible, lightweight, space-qualified substrates provide an attractive approach to fabricating solar arrays with high mass-specific power. A polycrystalline chalcopyrite absorber layer is among the new generation of photovoltaic device technologies for thin film solar cells. At NASA Glenn Research Center we have focused on the development of new single-source precursors (SSPs) for deposition of semiconducting chalcopyrite materials onto lightweight, flexible substrates. We describe the syntheses and thermal modulation of SSPs via molecular engineering. Copper indium disulfide and related thin-film materials were deposited via aerosol-assisted chemical vapor deposition using SSPs. Processing and post-processing parameters were varied in order to modify morphology, stoichiometry, crystallography, electrical properties, and optical properties to optimize device quality. Growth at atmospheric pressure in a horizontal hotwall reactor at 395 C yielded the best device films. Placing the susceptor closer to the evaporation zone and flowing a more precursor-rich carrier gas through the reactor yielded shinier-, smoother-, and denser-looking films. Growth of (112)-oriented films yielded more Cu-rich films with fewer secondary phases than growth of (204)/(220)-oriented films. Post-deposition sulfur-vapor annealing enhanced stoichiometry and crystallinity of the films. Photoluminescence studies revealed four major emission bands and a broad band associated with deep defects. The highest device efficiency for an aerosol-assisted chemical vapor deposited cell was one percent.

The optical characterization of organometallic complex thin films by spectroscopic ellipsometry and photovoltaic diode application

International Nuclear Information System (INIS)

Özaydın, C.; Güllü, Ö.; Pakma, O.; Ilhan, S.; Akkılıç, K.

2016-01-01

Highlights: • Optical properties and thickness of the A novel organometallic complex (OMC) film were investigated by spectroscopic ellipsometry (SE). • Au/OMC/n-Si metal/interlayer/semiconductor (MIS) diode has been fabricated • This paper presents the I–V analysis of Au/OMC/n-Si MIS diode. • Current–voltage and photovoltaic properties of the diode were investigated. - Abstract: In this work, organometallic complex (OMC) films have been deposited onto glass or silicon substrates by spin coating technique and their photovoltaic application potential has been investigated. Optical properties and thickness of the film have been investigated by spectroscopic ellipsometry (SE). Also, transmittance spectrum has been taken by UV/vis spectrophotometer. The optical method has been used to determine the band gap value of the films. Also, Au/OMC/n-Si metal/interlayer/semiconductor (MIS) diode has been fabricated. Current–voltage and photovoltaic properties of the structure were investigated. The ideality factor (n) and barrier height (Φ_b) values of the diode were found to be 2.89 and 0.79 eV, respectively. The device shows photovoltaic behavior with a maximum open-circuit voltage of 396 mV and a short circuit current of 33.8 μA under 300 W light.

The optical characterization of organometallic complex thin films by spectroscopic ellipsometry and photovoltaic diode application

Energy Technology Data Exchange (ETDEWEB)

Özaydın, C. [Batman University, Engineering Faculty, Department of Computer Eng., Batman (Turkey); Güllü, Ö., E-mail: omergullu@gmail.com [Batman University, Science and Art Faculty, Department of Physics, Batman (Turkey); Pakma, O. [Batman University, Science and Art Faculty, Department of Physics, Batman (Turkey); Ilhan, S. [Siirt University, Science and Art Faculty, Department of Chemistry, Siirt (Turkey); Akkılıç, K. [Dicle University, Education Faculty, Department of Physics Education, Diyarbakır (Turkey)

2016-05-15

Highlights: • Optical properties and thickness of the A novel organometallic complex (OMC) film were investigated by spectroscopic ellipsometry (SE). • Au/OMC/n-Si metal/interlayer/semiconductor (MIS) diode has been fabricated • This paper presents the I–V analysis of Au/OMC/n-Si MIS diode. • Current–voltage and photovoltaic properties of the diode were investigated. - Abstract: In this work, organometallic complex (OMC) films have been deposited onto glass or silicon substrates by spin coating technique and their photovoltaic application potential has been investigated. Optical properties and thickness of the film have been investigated by spectroscopic ellipsometry (SE). Also, transmittance spectrum has been taken by UV/vis spectrophotometer. The optical method has been used to determine the band gap value of the films. Also, Au/OMC/n-Si metal/interlayer/semiconductor (MIS) diode has been fabricated. Current–voltage and photovoltaic properties of the structure were investigated. The ideality factor (n) and barrier height (Φ{sub b}) values of the diode were found to be 2.89 and 0.79 eV, respectively. The device shows photovoltaic behavior with a maximum open-circuit voltage of 396 mV and a short circuit current of 33.8 μA under 300 W light.

The synthesis and properties of some organometallic compounds containing group IV (Ge, Sn)-group II (Zn, Cd) metal---metal bonds

NARCIS (Netherlands)

Des Tombe, F.J.A.; Kerk, G.J.M. van der; Creemers, H.M.J.C.; Carey, N.A.D.; Noltes, J.G.

1972-01-01

The reactions of triphenylgermane and triphenyltin hydride with coordinatively saturated organozinc or organocadmium compounds give organometallic complexes containing Group IV (Ge, Sn)-Group II(Zn, Cd) metal---metal bonds. The 2,2′-bipyridine complexes show solvent-dependent charge-transfer

Organometallic compounds of the 2-6 group elements of periodic system as perspective substances for microelectrnics

International Nuclear Information System (INIS)

Fedorov, V.A.

1986-01-01

Results of investigating methods of preparation and analysis of organometallic compounds (OMC) of the 2B-6B group elements, behaviour of microimpurities in the process of their complete purification, physical-chemical properties for developing rational flowsheets of OMC purification are presented. Results of microimpurities quantitative transition from OMC to gallium arsenide epitaxial layers are presented. Prospects for OMC application in microelectronics are discussed

Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment.

Science.gov (United States)

Brog, Jean-Pierre; Crochet, Aurélien; Seydoux, Joël; Clift, Martin J D; Baichette, Benoît; Maharajan, Sivarajakumar; Barosova, Hana; Brodard, Pierre; Spodaryk, Mariana; Züttel, Andreas; Rothen-Rutishauser, Barbara; Kwon, Nam Hee; Fromm, Katharina M

2017-08-22

LiCoO 2 is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO 2 (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li + ) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated. Several new single source precursors containing lithium (Li + ) and cobalt (Co 2+ ) ions, based on alkoxides and aryloxides have been structurally characterized and were thermally transformed into nanoscale HT-LCO at 450 °C within few hours. The size of the nanoparticles depends on the precursor, determining the electrochemical performance. The Li-ion diffusion coefficients of our LiCoO 2 nanoparticles improved at least by a factor of 10 compared to commercial one, while showing good reversibility upon charging and discharging. The hazard of occupational exposure to nanoparticles during battery recycling was investigated with an in vitro multicellular lung model. Our heterobimetallic single source precursors allow to dramatically reduce the production temperature and time for HT-LCO. The obtained nanoparticles of LiCoO 2 have faster kinetics for Li + insertion/extraction compared to microparticles. Overall, nano-sized LiCoO 2 particles indicate a lower cytotoxic and (pro-)inflammogenic potential in vitro compared to their micron-sized counterparts. However, nanoparticles aggregate in air and behave partially like microparticles.

Particulate Sol-Gel Synthesis and Characterization of LiMO2 (M=Ni, Ni(0.75)Co(0.25) Using the Thermal and Mass Spectrometry Analyses Work-Station

National Research Council Canada - National Science Library

Chang, Chun-Chieh

2000-01-01

.... Four different processes: (a)rotary evaporation (b)gelation (c)spray drying and (d)spray decomposition have been developed and studied using inorganic and organometallic precursors other than metal alkoxides...

Annealing of RF-magnetron sputtered SnS{sub 2} precursors as a new route for single phase SnS thin films

Energy Technology Data Exchange (ETDEWEB)

Sousa, M.G., E-mail: martasousa@ua.pt [AIN, I3N and Departamento de Física, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Cunha, A.F. da, E-mail: antonio.cunha@ua.pt [AIN, I3N and Departamento de Física, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Fernandes, P.A., E-mail: pafernandes@ua.pt [AIN, I3N and Departamento de Física, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Departamento de Física, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072 Porto (Portugal)

2014-04-01

Tin sulphide thin films have been grown on soda-lime glass substrates through the annealing of RF-magnetron sputtered SnS{sub 2} precursors. Three different approaches to the annealing were compared and the resulting films thoroughly studied. One series of precursors was annealed in a tubular furnace directly exposed to a flux of sulphur vapour plus forming gas, N{sub 2} + 5%H{sub 2}, and at a constant pressure of 500 mbar. The other two series of identical precursors were annealed in the same furnace but inside a graphite box with and without elemental sulphur evaporation again in the presence of N{sub 2} + 5%H{sub 2} and at the same pressure as for the sulphur flux experiments. Different maximum annealing temperatures for each set of samples, in the range of 300–570 °C, were tested to study their effects on the properties of the final films. The resulting phases were structurally investigated by X-Ray Diffraction (XRD) and Raman spectroscopy. Annealing of SnS{sub 2} precursors in sulphur flux produced films where SnS{sub 2} was dominant for temperatures up to 480 °C. Increasing the temperature to 530 °C and 570 °C led to films where the dominant phase became Sn{sub 2}S{sub 3}. Annealing of SnS{sub 2} precursors in a graphite box with sulphur vapour at temperatures in the range between 300 °C and 480 °C the films are multi-phase, containing Sn{sub 2}S{sub 3}, SnS{sub 2} and SnS. For high annealing temperatures of 530 °C and 570 °C the films have SnS as the dominant phase. Annealing of SnS{sub 2} precursors in a graphite box without sulphur vapour at 300 °C and 360 °C the films are essentially amorphous, at 420 °C SnS{sub 2} is the dominant phase. For temperatures of 480 °C and 530 °C SnS is the dominant phase but also same residual SnS{sub 2} and Sn{sub 2}S{sub 3} phases are observed. For annealing at 570 °C, according to the XRD results the films appear to be single phase SnS. The composition was studied using energy dispersive spectroscopy being

Understanding organometallic reaction mechanisms and catalysis experimental and computational tools computational and experimental tools

CERN Document Server

Ananikov, Valentin P

2014-01-01

Exploring and highlighting the new horizons in the studies of reaction mechanisms that open joint application of experimental studies and theoretical calculations is the goal of this book. The latest insights and developments in the mechanistic studies of organometallic reactions and catalytic processes are presented and reviewed. The book adopts a unique approach, exemplifying how to use experiments, spectroscopy measurements, and computational methods to reveal reaction pathways and molecular structures of catalysts, rather than concentrating solely on one discipline. The result is a deeper

Improved synthesis of carbon nanotubes with junctions and of single ...

Indian Academy of Sciences (India)

Unknown

Abstract. Pyrolysis of thiophene over nickel nanoparticles dispersed on silica is shown to yield Y- junction carbon nanotubes with smaller diameters than those obtained by the pyrolysis of organometallic- thiophene mixtures. In the presence of water vapour, the pyrolysis of organometallic-hydrocarbon mixtures.

Single molecule analysis of c-myb alternative splicing reveals novel classifiers for precursor B-ALL.

Directory of Open Access Journals (Sweden)

Ye E Zhou

Full Text Available The c-Myb transcription factor, a key regulator of proliferation and differentiation in hematopoietic and other cell types, has an N-terminal DNA binding domain and a large C-terminal domain responsible for transcriptional activation, negative regulation and determining target gene specificity. Overexpression and rearrangement of the c-myb gene (MYB has been reported in some patients with leukemias and other types of cancers, implicating activated alleles of c-myb in the development of human tumors. Alternative RNA splicing can produce variants of c-myb with qualitatively distinct transcriptional activities that may be involved in transformation and leukemogenesis. Here, by performing a detailed, single molecule assay we found that c-myb alternative RNA splicing was elevated and much more complex in leukemia samples than in cell lines or CD34+ hematopoietic progenitor cells from normal donors. The results revealed that leukemia samples express more than 60 different c-myb splice variants, most of which have multiple alternative splicing events and were not detectable by conventional microarray or PCR approaches. For example, the single molecule assay detected 21 and 22 splice variants containing the 9B and 9S exons, respectively, most of which encoded unexpected variant forms of c-Myb protein. Furthermore, the detailed analysis identified some splice variants whose expression correlated with poor survival in a small cohort of precursor B-ALL samples. Our findings indicate that single molecule assays can reveal complexities in c-myb alternative splicing that have potential as novel biomarkers and could help explain the role of c-Myb variants in the development of human leukemia.

Thermal lens and all optical switching of new organometallic compound doped polyacrylamide gel

Science.gov (United States)

Badran, Hussain Ali

In this work thermal lens spectrometry (TLS) is applied to investigate the thermo-optical properties of new organometallic compound containing azomethine group, Dichloro bis [2-(2-hydroxybenzylideneamino)-5-methylphenyl] telluride platinum(II), doped polyacrylamide gel using transistor-transistor logic (TTL) modulated cw 532 nm laser beam as an excitation beam modulated at 10 Hz frequency and probe beam wavelength 635 nm at 14 mW. The technique is applied to determine the thermal diffusivities, ds/dT and the linear thermal expansion coefficient of the sample. All-optical switching effects with low background and high stability are demonstrated.

A single amino acid difference between the intracellular domains of amyloid precursor protein and amyloid-like precursor protein 2 enables induction of synaptic depression and block of long-term potentiation.

Science.gov (United States)

Trillaud-Doppia, Emilie; Paradis-Isler, Nicolas; Boehm, Jannic

2016-07-01

Alzheimer disease (AD) is initially characterized as a disease of the synapse that affects synaptic transmission and synaptic plasticity. While amyloid-beta and tau have been traditionally implicated in causing AD, recent studies suggest that other factors, such as the intracellular domain of the amyloid-precursor protein (APP-ICD), can also play a role in the development of AD. Here, we show that the expression of APP-ICD induces synaptic depression, while the intracellular domain of its homolog amyloid-like precursor protein 2 (APLP2-ICD) does not. We are able to show that this effect by APP-ICD is due to a single alanine vs. proline difference between APP-ICD and APLP2-ICD. The alanine in APP-ICD and the proline in APLP2-ICD lie directly behind a conserved caspase cleavage site. Inhibition of caspase cleavage of APP-ICD prevents the induction of synaptic depression. Finally, we show that the expression of APP-ICD increases and facilitates long-term depression and blocks induction of long-term potentiation. The block in long-term potentiation can be overcome by mutating the aforementioned alanine in APP-ICD to the proline of APLP2. Based on our results, we propose the emergence of a new APP critical domain for the regulation of synaptic plasticity and in consequence for the development of AD. Copyright © 2016 Elsevier Inc. All rights reserved.

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

International Nuclear Information System (INIS)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Tanemura, Masaki

2016-01-01

The synthesis of large-area monolayer tungsten disulphide (WS 2 ) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS 2 crystals using tungsten hexachloride (WCl 6 ) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl 6 in ethanol was drop-casted on SiO 2 /Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS 2 crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS 2 single crystalline monolayer can be grown using the WCl 6 precursor. Our finding shows an easier and effective approach to grow WS 2 monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1 - C10

Science.gov (United States)

Acree, William; Chickos, James S.

2016-09-01

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880-2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Single-source-precursor synthesis of dense SiC/HfCxN1-x-based ultrahigh-temperature ceramic nanocomposites

Science.gov (United States)

Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; Guillon, Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

2014-10-01

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1-x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1-x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1-x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm-1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm-1.A novel single-source precursor was synthesized by the reaction of an allyl hydrido

Ionospheric earthquake precursors

International Nuclear Information System (INIS)

Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

1996-01-01

Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

Large-scale preparation of CdS quantum dots by direct thermolysis of a single-source precursor

Energy Technology Data Exchange (ETDEWEB)

Li Zhiguo; Cai Wei; Sui Jiehe [School of Material Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)

2008-01-23

CdS quantum dots (QDs) have been synthesized on a large scale, based on the direct thermolysis of one single-source precursor (Me{sub 4}N){sub 4}[S{sub 4}Cd{sub 10}(SPh){sub 16}], in hexadecylamine (HDA). Transmission electron microscopy (TEM) observations show that the CdS QDs are well-defined, nearly spherical particles. The clear lattice fringes in high-resolution TEM (HRTEM) images confirm the crystalline nature of the QDs. The broad diffraction in the x-ray diffraction (XRD) pattern and diffuse diffraction rings of the selected-area electron diffraction (SAED) pattern are typical of nanomeric-size particles and indicative of the hexagonal phase of CdS QDs. The absorption spectra confirm quantum confinement of CdS QDs. The synthesis process for CdS QDs was investigated by ultraviolet-visible (UV-vis) absorption spectroscopy. The results demonstrate that the nucleation and growth stages were separated automatically in a homogeneous system.

Low-voltage organic field-effect transistors based on novel high-κ organometallic lanthanide complex for gate insulating materials

Directory of Open Access Journals (Sweden)

Qi Liu

2014-08-01

Full Text Available A novel high-κ organometallic lanthanide complex, Eu(tta3L (tta=2-thenoyltrifluoroacetonate, L = 4,5-pinene bipyridine, is used as gate insulating material to fabricate low-voltage pentacene field-effect transistors (FETs. The optimized gate insulator exhibits the excellent properties such as low leakage current density, low surface roughness, and high dielectric constant. When operated under a low voltage of −5 V, the pentacene FET devices show the attractive electrical performance, e.g. carrier mobility (μFET of 0.17 cm2 V−1 s−1, threshold voltage (Vth of −0.9 V, on/off current ratio of 5 × 103, and subthreshold slope (SS of 1.0 V dec−1, which is much better than that of devices obtained on conventional 300 nm SiO2 substrate (0.13 cm2 V−1 s−1, −7.3 V and 3.1 V dec−1 for μFET, Vth and SS value when operated at −30 V. These results indicate that this kind of high-κ organometallic lanthanide complex becomes a promising candidate as gate insulator for low-voltage organic FETs.

Organometallic complexes of thiocarbanilides and substituted thiocarbanilides using manganese (II) chloride

International Nuclear Information System (INIS)

Babiker, Musa Elaballa Mohamed

2000-01-01

Organo-metallic complexes of substituted thiocarbanilide using manganese (II) chloride were prepared, these are: (VIII) 3:3'-Dichloro thiocarbanilide. Manganese (II) chloride. (IX) 3:3'-Dimethyl thiocarbanilide. Manganese (II) chloride. (X) 2:2'-dimethyl thiocarbanilide. Manganese (II) chloride. These compounds are coloured, soluble in most organic solvents, insoluble in water, decomposed by hot solvents. The physical properties of compounds (IX) and (X) were studied by UV and IR spectra, and the physical properties of compound (VIII) were studied by UV, IR, mass spectra and NMR. The molecular weight of the compound (VIII) was determined by three different methods; Rast's camphor method, mass spectra and the nitrogen contents. The stoichiometry of the reaction was found to be 2:1, and the coordination is from sulphur atom more than nitrogen.(Author)

Insights into the deactivation mechanism of supported tungsten hydride on alumina (W-H/Al2O3) catalyst for the direct conversion of ethylene to propylene

KAUST Repository

Mazoyer, Etienne; Szeto, Kaï Chung; Merle, Nicolas; Thivolle-Cazat, Jean; Boyron, Olivier; Basset, Jean-Marie; Nicholas, Christopher P.; Taoufik, Mostafa

2014-01-01

Tungsten hydride supported on alumina prepared by the surface organometallic chemistry method is an active precursor for the direct conversion of ethylene to propylene at low temperature and pressure. An extensive contact time study revealed

p-type Mesoscopic nickel oxide/organometallic perovskite heterojunction solar cells.

Science.gov (United States)

Wang, Kuo-Chin; Jeng, Jun-Yuan; Shen, Po-Shen; Chang, Yu-Cheng; Diau, Eric Wei-Guang; Tsai, Cheng-Hung; Chao, Tzu-Yang; Hsu, Hsu-Cheng; Lin, Pei-Ying; Chen, Peter; Guo, Tzung-Fang; Wen, Ten-Chin

2014-04-23

In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics.

Synthesis and studies of some organometallic compounds of uranium IV

International Nuclear Information System (INIS)

Marquet-Ellis, Hubert; Folcher, Gerard.

1975-06-01

The organometallic compounds of uranium IV have been well known for a long-time but some difficulties in the synthese subsist. The procedures and the apparatus allowing to obtain these compounds with good yields are described. The cyclopenta dienyl compounds U(C 5 H 5 ) 3 Cl, U(C 5 H 5 ) 4 are prepared by reaction of UCl 4 with Na(C 5 H 5 ) in tetrahydrofurane. The cyclooctatetraene compound U(C 8 H 8 ) 2 ''Uranocene'' is obtained by reaction of K 2 (C 8 H 8 ) on UCl 4 in tetrahydrofurane. The NMR spectrum of the solution during the reaction shows the appearance of the product. These compounds have been identified by chemical analysis and X rays. The visible spectra of U(C 5 H 5 ) 2 Cl and U(C 8 H 8 ) 2 in gaseous phase have been obtained [fr

Naturally Efficient Emitters: Luminescent Organometallic Complexes Derived from Natural Products

Science.gov (United States)

Zhang, Wen-Hua; Young, David J.

2013-08-01

Naturally occurring molecules offer intricate structures and functionality that are the basis of modern medicinal chemistry, but are under-represented in materials science. Herein, we review recent literature describing the use of abundant and relatively inexpensive, natural products for the synthesis of ligands for luminescent organometallic complexes used for organic light emitting diodes (OLEDs) and related technologies. These ligands are prepared from the renewable starting materials caffeine, camphor, pinene and cinchonine and, with the exception of caffeine, impart performance improvements to the emissive metal complexes and resulting OLED devices, with emission wavelengths that span the visible spectrum from blue to red. The advantages of these biologically-derived molecules include improved solution processibility and phase homogeneity, brighter luminescence, higher quantum efficiencies and lower turn-on voltages. While nature has evolved these carbon-skeletons for specific purposes, they also offer some intriguing benefits in materials science and technology.

Distribution of PCDD/Fs and organometallic compounds in sewage sludge of wastewater treatment plants in China

International Nuclear Information System (INIS)

Lu Mang; Wu Xuejiao; Zeng Decai; Liao Yong

2012-01-01

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), organotin and organolead compounds were measured in sewage sludge samples collected from 24 wastewater treatment plants from 18 cities of 13 provinces in China. Total international toxicity equivalent (I-TEQ) values were evaluated for PCDD/Fs. The total concentration of PCDD/Fs ranged from 104.0 to 1661 pg/g dry weight (d.w.) and 2.51–75.21 pg I-TEQ/g d.w., indicating that all I-TEQs were below Chinese legislation limit value regulated for land application. The concentrations ranged from 258 to 3886, 126 to 1129, and 84–2133 ng/g as Sn d.w., for tributyltin (TBT), dibutyltin (DBT), and diphenyltin (DPhT), respectively. On the other side, organolead concentrations ranged from 85 to 668 with an average of 279 ng/g as lead. High concentrations of organolead compounds in sewage sludge indicated that the environmental impact of organolead compounds remains in China. - Highlights: ► The first study on PCDD/F distribution in sewage sludge in China on a national scale. ► The first study on organometallic compounds distribution in sewage sludge on a national scale. ► The persistence of tetraethyllead deserves attention. - This is the first study on the survey of the distributions of POPs and organometallic compounds in sewage sludge in China on a national scale.

Analysis of mechanical properties of N2in situ doped polycrystalline 3C-SiC thin films by chemical vapor deposition using single-precursor hexamethyildisilane

International Nuclear Information System (INIS)

Kim, Kang-San; Han, Ki-Bong; Chung, Gwiy-Sang

2010-01-01

This paper describes the mechanical properties of poly (polycrystalline) 3C-SiC thin films with N 2 in situ doping. In this work, in situ doped poly 3C-SiC film was deposited by using the atmospheric pressure chemical vapor deposition (APCVD) method at 1200 deg. C using single-precursor hexamethyildisilane: Si 2 (CH 3 ) 6 (HMDS) as Si and C precursors, and 0∼100 sccm N 2 as the dopant source gas. The mechanical properties of doped poly 3C-SiC thin films were measured by nano-indentation. Young's modulus and hardness were measured to be 285 and 35 GPa at 0 sccm N 2 , respectively. Young's modulus and hardness decreased with increasing N 2 flow rate. Surface morphology was evaluated by atomic force microscopy (AFM) according to N 2 flow rate.

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

Energy Technology Data Exchange (ETDEWEB)

Chunshan, Song; Kirby, S.; Schmidt, E. [Pennsylvania State Univ., University Park, PA (United States)] [and others

1995-12-31

The objective of this project is to explore bimetallic dispersed catalysts for more efficient coal liquefaction. Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting various aromatic units and the reactions of various oxygen functional groups. This paper describes recent results on (1) hydrodeoxygenation of O-containing polycyclic model compounds using novel organometallic catalyst precursors; and (2) activity and selectivity of dispersed Fe catalysts from organometallic and inorganic precursors for hydrocracking of 4-(1-naphthylmethyl) bibenzyl. The results showed that some iron containing catalysts have higher activity in the sulfur-free form, contrary to conventional wisdom. Adding sulfur to Fe precursors with Cp-ligands decreased the activity of the resulting catalyst. This is in distinct contrast to the cases with iron pentacarbonyl and superfine Fe{sub 2}O{sub 3}, where S addition increased their catalytic activity substantially. A positive correlation between sulfur addition and increased activity can be seen, but a reversed trend between Fe cluster size and hydrocracking conversion could be observed, for carbonyl-type Fe precursors. It is apparent that the activity and selectivity of Fe catalysts for NMBB conversion depends strongly on both the type of ligand environment, the oxidation state and the number of intermetal bonds in the molecular precursor.

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

Energy Technology Data Exchange (ETDEWEB)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2016-02-01

The synthesis of large-area monolayer tungsten disulphide (WS{sub 2}) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS{sub 2} crystals using tungsten hexachloride (WCl{sub 6}) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl{sub 6} in ethanol was drop-casted on SiO{sub 2}/Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS{sub 2} crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS{sub 2} single crystalline monolayer can be grown using the WCl{sub 6} precursor. Our finding shows an easier and effective approach to grow WS{sub 2} monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction.

Synthesis and structure determination of a stable organometallic uranium(V) imine complex and its isolobal anionic U(IV)-ate complex

Energy Technology Data Exchange (ETDEWEB)

Sharma, M.; Botoshanskii, M.; Eisen, M.S. [Schulich Faculty of Chemistry, and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology, Haifa (Israel); Bannenberg, Th.; Tamm, M. [Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig (Germany)

2010-06-15

The reaction of one equivalent of Cp*{sub 2}UCl{sub 2} with 2-(trimethylsilyl-imino)-1,3-di-tert-butyl-imidazoline in boiling toluene afforded a one electron oxidation of the uranium metal and the opening of the N-heterocyclic ring, resulting in the formation of an organometallic uranium(V) imine complex. This complex crystallized with one molecule of toluene in the unit cell, and its solid-state structure was determined by X-ray diffraction analysis. When the same reaction was performed in perdeuterated toluene, a myriad of organometallic complexes were obtained, however, when equimolar amounts of water were used in toluene, the same complex was obtained, and its solid state characterization shows two independent molecules in the unit cell with an additional water molecule. For comparison of the geometric parameters, the corresponding isolobal anionic uranium(IV) complex [Cp*{sub 2}UCl{sub 3}]{sup -} was synthesized by the reaction of Cp*{sub 2}UCl{sub 2} with 1,3-di-tert-butyl-imidazolium chloride, and the resulting U(IV)-ate complex was characterized by X-ray diffraction analysis. (authors)

Preparation of highly dispersed Ru-Sn bimetallic supported catalysts from the single source precursors Cp(PPh32Ru-SnX3 (X = Cl or Br

Directory of Open Access Journals (Sweden)

Ana Cláudia Bernardes Silva

2003-06-01

Full Text Available In this work highly dispersed Ru-Sn bimetallic catalysts have been prepared from organobimetallic Cp(PPh32Ru-SnX3 (X = Cl or Br complexes. These single source precursors can be easily impregnated in high surface area supports, such as activated carbon and sol-gel SiO2, and upon controlled thermal treatment the ligands are released as volatile products resulting in the formation of the bimetallic system Ru-Sn. Catalytic reactions, such as hydrodechlorination of CCl4 and chlorobenzene and TPR (Temperature Programmed Reduction experiments carried out with these RuSn catalysts suggested a strong interaction between Ruthenium and Tin. Mössbauer measurements showed that these materials when exposed to air are immediately oxidized to form Sn (IV. It was shown that upon controlled reduction conditions with H2 it is possible to reduce selectively Sn to different oxidation states and different phases. The Sn oxidation state showed significant effect on the catalytic hydrogenation of 1,5-cyclooctadiene. The use of these single source precursors with a controlled decomposition/reduction procedure allows the preparation of unique catalysts with an intimate interaction between the components ruthenium and tin and the possibility of varying the Sn oxidation state around the Ru metal.

Metal-doped single-walled carbon nanotubes and production thereof

Science.gov (United States)

Dillon, Anne C.; Heben, Michael J.; Gennett, Thomas; Parilla, Philip A.

2007-01-09

Metal-doped single-walled carbon nanotubes and production thereof. The metal-doped single-walled carbon nanotubes may be produced according to one embodiment of the invention by combining single-walled carbon nanotube precursor material and metal in a solution, and mixing the solution to incorporate at least a portion of the metal with the single-walled carbon nanotube precursor material. Other embodiments may comprise sputter deposition, evaporation, and other mixing techniques.

Four residues of propeptide are essential for precursor folding of nattokinase.

Science.gov (United States)

Jia, Yan; Cao, Xinhua; Deng, Yu; Bao, Wei; Tang, Changyan; Ding, Hanjing; Zheng, Zhongliang; Zou, Guolin

2014-11-01

Subtilisin propeptide functions as an intramolecular chaperone that guides precursor folding. Nattokinase, a member of subtilisin family, is synthesized as a precursor consisting of a signal peptide, a propeptide, and a subtilisin domain, and the mechanism of its folding remains to be understood. In this study, the essential residues of nattokinase propeptide which contribute to precursor folding were determined. Deletion analysis showed that the conserved regions in propeptide were important for precursor folding. Single-site and multi-site mutagenesis studies confirmed the role of Tyr10, Gly13, Gly34, and Gly35. During stage (i) and (ii) of precursor folding, Tyr10 and Gly13 would form the part of interface with subtilisin domain. While Gly34 and Gly35 connected with an α-helix that would stabilize the structure of propeptide. The quadruple Ala mutation, Y10A/G13A/G34A/G35A, resulted in a loss of the chaperone function for the propeptide. This work showed the essential residues of propeptide for precursor folding via secondary structure and kinetic parameter analyses. © The Author 2014. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

Synthesis and evaluation of germanic organometallic compounds as precursors for chemical vapor deposition (CVD) and for obtaining nanoparticles of elemental germanium

International Nuclear Information System (INIS)

Ballestero Martinez, Ernesto

2014-01-01

The interest in the development of materials that have applications in areas such as electronics or biomarkers has affected the synthesis of new compounds based on germanium. This element has two states of common oxidation, +4 and +2, of them, the +2 oxidation state is the least studied and more reactive. Additionally, compounds of germanium (II) have similarities to carbenes in terms Lewis'acid base chemistry. The preparation of compounds of germanium (II) with ligands β-diketiminates has made possible the stabilization of new chemical functionalities and, simultaneously, it has provided interesting thermal properties to develop new methods of preparation of materials with novel properties. The preparation of amides germanium (II) L'Ge (NHPh) [1, L'= {HC (CMeN-2,4,6-Me 3 C 6 H 2 ) 2 } - ], L'Ge (4-NHPy) [2], L'Ge (2-NHPy) [3] and LGe(2-NHPy) [4, L = {HC (CMeN-2,6- i Pr 2 C 6 H 3 ) 2 ] - ] are presented, the chemical and structural composition was determined by using techniques such as nuclear magnetic resonance ( 1 H, 13 C), elemental analysis, melting point, infrared spectroscopy, X-ray diffraction of single crystal and thermogravimetric analysis (TGA). The TGA has demonstrated that 1-4 experience a thermal decomposition, therefore, these compounds could be considered as potential starting materials for the obtaining of germanium nitride (GeN x ). Certainly, the availability of coordinating nitrogen atoms in the chemical composition in 2-4 have been interesting given that it could act as ligands in reactions with transition metal complexes. Thus, relevant information to molecular level could be obtained for some reactions and interactions that have used similar link sites in surface chemistry, for example, the chemical functionalization of silicon and germanium substrate. Additionally, the synthesis and structural characterization of germanium chloride compound (II) L G eCl [5, L' = HC{(CMe) (N-2,6-Me 2 C 6 H 3 )} 2 - ] is reported

Synthesis and evaluation of germanium organometallic compounds as precursors for chemical vapor deposition (CVD) and for obtaining nanoparticles of elemental germanium

International Nuclear Information System (INIS)

Ballestero Martinez, Ernesto

2014-01-01

The interest in the development of materials having applications such as electronics areas or biomarkers has affected the synthesis of new compounds based on germanium. This element has had two common oxidation states, +4 and +2, of them, +2 oxidation state has been the least studied and more reactive. Additionally, compounds of germanium (II) have had similarities with carbenes regarding the chemical acid-base Lewis. The preparation of compounds of germanium (II) with ligands β-decimations has enabled stabilization of new chemical functionalities and, simultaneously, provided interesting thermal properties to develop new preparation methodologies of materials with novel properties. The preparation of amides germanium(II) L'Ge(NHPh) [1, L' = {HC (CMeN-2,4,6-Me 3 C 6 H 2 ) 2 }], L'Ge(4-NHPy) [2] L'Ge(2-NHPy) [3] and LGe(2-NHPy) [4, L = {HC(CMeN-2,6- i Pr 2 C 6 H 3 ) 2 }]; the structural chemical composition were determined using techniques such as nuclear magnetic resonance ( 1 H, 13 C), other techniques are treated: elemental analysis, melting point, infrared spectroscopy, X-ray diffraction of single crystal and thermal gravimetric analysis (TGA). The TGA has showed that 4-1 have experimented a thermal decomposition; therefore, these compounds could be considered as potential starting materials for obtaining germanium nitride (GeN x ). Certainly, the availability of nitrogen coordinating atoms in the chemical composition in 2-4 have been interesting because it could act as ligands in reactions with transition metal complexes. That way, information could be obtained at the molecular level for some reactions and interactions that in surface chemistry have used similar link sites, for example, chemical functionalization of silicon and germanium substrates. The synthesis and structural characterization of germanium chloride compound(II) L''GeCl [5, L'' = HC{(CMe) (N-2,6-Me 2 C 6 H 3 )} 2 ], which could be used later for the

Micro-sized organometallic compound of ferrocene as high-performance anode material for advanced lithium-ion batteries

Science.gov (United States)

Liu, Zhen; Feng, Li; Su, Xiaoru; Qin, Chenyang; Zhao, Kun; Hu, Fang; Zhou, Mingjiong; Xia, Yongyao

2018-01-01

An organometallic compound of ferrocene is first investigated as a promising anode for lithium-ion batteries. The electrochemical properties of ferrocene are conducted by galvanostatic charge and discharge. The ferrocene anode exhibits a high reversible capacity and great cycling stability, as well as superior rate capability. The electrochemical reaction of ferrocene is semi-reversible and some metallic Fe remains in the electrode even after delithiation. The metallic Fe formed in electrode and the stable solid electrolyte interphase should be responsible for its excellent electrochemical performance.

Primary structure of the human follistatin precursor and its genomic organization

International Nuclear Information System (INIS)

Shimasaki, Shunichi; Koga, Makoto; Esch, F.

1988-01-01

Follistatin is a single-chain gonadal protein that specifically inhibits follicle-stimulating hormone release. By use of the recently characterized porcine follistatin cDNA as a probe to screen a human testis cDNA library and a genomic library, the structure of the complete human follistatin precursor as well as its genomic organization have been determined. Three of eight cDNA clones that were sequenced predicted a precursor with 344 amino acids, whereas the remaining five cDNA clones encoded a 317 amino acid precursor, resulting from alternative splicing of the precursor mRNA. Mature follistatins contain four contiguous domains that are encoded by precisely separated exons; three of the domains are highly similar to each other, as well as to human epidermal growth factor and human pancreatic secretory trypsin inhibitor. The genomic organization of the human follistatin is similar to that of the human epidermal growth factor gene and thus supports the notion of exon shuffling during evolution

OMVPE growth of GaInAsSb in the 2 to 2.4 microm range

International Nuclear Information System (INIS)

Charache, G.W.; Wang, C.A.

1997-12-01

Ga 1-x In x As y Sb 1-y epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy using all organometallic precursors, which include triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony. Layers were grown over a temperature range between 525 and 575 C, a V/III ratio range between 0.9 and 1.7, x 15 cm -3 and hole mobility of ∼ 430 to 560 cm 2 /V-s. The n- and p-type doping of GaInAsSb with diethyltellurium and dimethylzinc, respectively, are also reported

Cluster-derived Ir-Sn/SiO2 catalysts for the catalytic dehydrogenation of propane: A spectroscopic study

KAUST Repository

Gallo, Alessandro

2013-01-01

Ir-Sn bimetallic silica-based materials have been prepared via deposition of the molecular organometallic clusters (NEt4)2[Ir 4(CO)10(SnCl3)2] and NEt 4[Ir6(CO)15(SnCl3)] or via deposition of Sn organometallic precursor Sn(n-C4H9) 4 onto pre-formed Ir metal particles. These solids possess promising properties, in terms of selectivity, as catalysts for propane dehydrogenation to propene. Detailed CO-adsorption DRIFTS, XANES and EXAFS characterization studies have been performed on these systems in order to compare the structural and electronic evolution of systems in relation to the nature of the Ir-Sn bonds present in the precursor compounds and to propose a structural model of the Ir-Sn species present at the silica surface of the final catalyst. © 2013 The Royal Society of Chemistry.

Low-voltage organic field-effect transistors based on novel high-κ organometallic lanthanide complex for gate insulating materials

Energy Technology Data Exchange (ETDEWEB)

Liu, Qi; Li, Yi; Zhang, Yang; Song, You, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Wang, Xizhang, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Hu, Zheng [Key Laboratory of Mesoscopic Chemistry of MOE, Jiangsu Provincial Lab for Nanotechnology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China. High-Tech Research Institute of Nanjing University (Suzhou), Suzhou 215123 (China); Sun, Huabin; Li, Yun, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Shi, Yi [School of Electronic Science and Engineering and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials, Nanjing University, Nanjing 210093 (China)

2014-08-15

A novel high-κ organometallic lanthanide complex, Eu(tta){sub 3}L (tta=2-thenoyltrifluoroacetonate, L = 4,5-pinene bipyridine), is used as gate insulating material to fabricate low-voltage pentacene field-effect transistors (FETs). The optimized gate insulator exhibits the excellent properties such as low leakage current density, low surface roughness, and high dielectric constant. When operated under a low voltage of −5 V, the pentacene FET devices show the attractive electrical performance, e.g. carrier mobility (μ{sub FET}) of 0.17 cm{sup 2} V{sup −1} s{sup −1}, threshold voltage (V{sub th}) of −0.9 V, on/off current ratio of 5 × 10{sup 3}, and subthreshold slope (SS) of 1.0 V dec{sup −1}, which is much better than that of devices obtained on conventional 300 nm SiO{sub 2} substrate (0.13 cm{sup 2} V{sup −1} s{sup −1}, −7.3 V and 3.1 V dec{sup −1} for μ{sub FET}, V{sub th} and SS value when operated at −30 V). These results indicate that this kind of high-κ organometallic lanthanide complex becomes a promising candidate as gate insulator for low-voltage organic FETs.

Single-source-precursor synthesis of dense SiC/HfC(x)N(1-x)-based ultrahigh-temperature ceramic nanocomposites.

Science.gov (United States)

Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; Guillon, Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

2014-11-21

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfC(x)N(1-x)-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfC(x)N(1-x)-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfC(x)N(1-x)-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm(-1), the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm(-1).

Developmental Dyslexia: Early Precursors, Neurobehavioral Markers, and Biological Substrates

Science.gov (United States)

Benasich, April A., Ed.; Fitch, R. Holly, Ed.

2012-01-01

Understanding the precursors and early indicators of dyslexia is key to early identification and effective intervention. Now there's a single research volume that brings together the very latest knowledge on the earliest stages of dyslexia and the diverse genetic, neurobiological, and cognitive factors that may contribute to it. Based on findings…

Chemically deposed layer sytems for the realization of YBa2Cu3O7-δ band conductors

International Nuclear Information System (INIS)

Engel, Sebastian

2009-01-01

The aim of this thesis was to produce new buffer-layer systems for biaxially texturated Ni5at%W substrates by means of chemical processes. As very promising materials for the buffer layers CaTiO 3 and SrTiO 3 were chosen. The production of the single layers pursued from the organometallic prestage by means of dip coating and subsequent head treatment. During the work first the single precursor solutions were to be developed. A main component of the theses forms the understanding of the texture development during the heat treatment of precursor layers on biaxially texturated metallic substrates. Based on this the growth of thick buffer layers is studied and by means of YBCO layers, which were deposed by beans of a pulsed laser, the functionality of the synthesized buffer layers proved. A further component of this thesis formes the influence of nanoscaling precipitations in thew YBCO on its superconducting properties. The YBCO deposition pursued via a variation of the TFA process, as substrate (001)-oriented SrTiO 3 monocrystals were applied

Chemically deposed layer sytems for the realization of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} band conductors; Chemisch deponierte Schichtsysteme zur Realisierung von YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}-Bandleitern

Energy Technology Data Exchange (ETDEWEB)

Engel, Sebastian

2009-04-30

The aim of this thesis was to produce new buffer-layer systems for biaxially texturated Ni5at%W substrates by means of chemical processes. As very promising materials for the buffer layers CaTiO{sub 3} and SrTiO{sub 3} were chosen. The production of the single layers pursued from the organometallic prestage by means of dip coating and subsequent head treatment. During the work first the single precursor solutions were to be developed. A main component of the theses forms the understanding of the texture development during the heat treatment of precursor layers on biaxially texturated metallic substrates. Based on this the growth of thick buffer layers is studied and by means of YBCO layers, which were deposed by beans of a pulsed laser, the functionality of the synthesized buffer layers proved. A further component of this thesis formes the influence of nanoscaling precipitations in thew YBCO on its superconducting properties. The YBCO deposition pursued via a variation of the TFA process, as substrate (001)-oriented SrTiO{sub 3} monocrystals were applied.

Synthesis and Characterization of Hexadecylamine Capped ZnS, CdS, and HgS Nanoparticles Using Heteroleptic Single Molecular Precursors

Directory of Open Access Journals (Sweden)

Peter A. Ajibade

2014-01-01

Full Text Available Zn(II, Cd(II, and Hg(II complexes of tetramethyl thiuram disulfides and 1-ethoxylcarbonyl-1-ethylenecarbonyl-2-dithiolate were synthesized and characterized by elemental analysis, FTIR, and 1H- and 13C-NMR spectroscopy. The complexes were thermolysed in hexadecylamine as single molecule precursors to prepare HDA capped ZnS, CdS, and HgS nanoparticles. The optical and structural properties of the nanoparticles are reported. ZnS nanoparticles existed in the hexagonal phase with particle sizes of 8–15 nm; the CdS nanoparticles in the cubic phase have particle sizes in the range 4–7 nm and the HgS nanoparticles indexed to face-centered cubic phase have an average particle size of 7–12 nm.

CNA Seminar

Energy Technology Data Exchange (ETDEWEB)

Browne, Kevin Patrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-10-16

Presentation that covers: an introduction to the field of high-nitrogen chemistry; aqueous chemistry of Th with the high-nitrogen ligand bis(tetrazolylamine) and BTA; and water-free, oxygen-free chemistry of Th, U with high-nitrogen ligands using organometallic actinide precursors

The synthesis and filling of single-walled carbon nanotubes

International Nuclear Information System (INIS)

Friedrichs, Steffi

2002-01-01

This thesis is concerned with the synthesis, properties and application of single-walled carbon nanotubes (SWNTs). The two main objectives of the work were the development of a continuous-flow synthesis of SWNTs, using chemical vapour deposition (CVD) techniques, and the application of the hollow SWNTs as moulds for the study of the crystallisation behaviour of inorganic materials in the confined space of their inner cavity. The latter study was mainly performed by interpreting high-resolution transmission electron microscopy (HRTEM) images of the filled SWNTs. A so-called focal series restoration approach, which enhances the resolution of the images and thereby increases the information content, was employed where possible. Chapter I reviews the previous work in the field of SWNTs and introduces their basic structure, symmetry, physical and mechanical properties and the common methods of SWNT synthesis. The chapter ends with an overview of the techniques used in the present work for the characterisation of carbon nanotube samples by giving a description of the high-resolution transmission electron microscopy (HRTEM) techniques and the digital image processing method. Other physical measurement techniques used, such as Raman spectroscopy and thermogravimetric analysis (TGA), are discussed with reference to their application for the characterisation of carbon nanotubes. Chapter II describes the development of an improved synthesis strategy for SWNTs. A continuous-flow chemical vapour deposition (CVD) method was explored using carbon monoxide or mixtures of methane and hydrogen as the carbon feedstock gas and introducing various volatile organometallic compounds to catalyse the formation of SWNTs. In this study, a special water-cooled copper nozzle was designed and built so as to prevent the premature decompositiont (disproportionation) of the reactants (the carbon monoxide gas) and to allow their direct introduction into the centre of the hot reaction zone. A

Layered niobate KNb3O8 synthesized by the polymeric precursor method

International Nuclear Information System (INIS)

Souza, J.K.D. de; Honório, L.M.C.; Torres, S.M.; Santos, I.M.G.; Maia, A.S.; Ferreira, J.M.

2018-01-01

The polymeric precursor method was used for the synthesis of KNb 3 O 8 and compared to the solid-state method. The materials were characterized by X-ray diffraction (XRD), infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and determination of surface area and total pore volume by nitrogen isotherms at 77 K. The material prepared by the polymeric precursor method was single-phase while K 2 Nb 4 O 11 was obtained as secondary phase when the solid state method was used, as evidenced by the XRD patterns and the Raman spectra. The morphology of the materials was significantly altered by the synthesis method, as the KNb 3 O 8 prepared by the polymeric precursor method presented a more porous morphology leading to a higher surface area and pore volume. (author)

Ceramic matrix and resin matrix composites - A comparison

Science.gov (United States)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Ceramic matrix and resin matrix composites: A comparison

Science.gov (United States)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Precursors prior to type IIn supernova explosions are common: Precursor rates, properties, and correlations

Energy Technology Data Exchange (ETDEWEB)

Ofek, Eran O.; Steinbok, Aviram; Arcavi, Iair; Gal-Yam, Avishay; Tal, David; Ben-Ami, Sagi; Yaron, Ofer [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Sullivan, Mark [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Shaviv, Nir J. [Racah Institute of Physics, The Hebrew University, 91904 Jerusalem (Israel); Kulkarni, Shrinivas R. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Nugent, Peter E. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kasliwal, Mansi M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Cenko, S. Bradley [Astrophysics Science Division, NASA/Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Bloom, Joshua S.; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Silverman, Jeffrey M. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

2014-07-10

There is a growing number of Type IIn supernovae (SNe) which present an outburst prior to their presumably final explosion. These precursors may affect the SN display, and are likely related to poorly charted phenomena in the final stages of stellar evolution. By coadding Palomar Transient Factory (PTF) images taken prior to the explosion, here we present a search for precursors in a sample of 16 Type IIn SNe. We find five SNe IIn that likely have at least one possible precursor event (PTF 10bjb, SN 2010mc, PTF 10weh, SN 2011ht, and PTF 12cxj), three of which are reported here for the first time. For each SN we calculate the control time. We find that precursor events among SNe IIn are common: at the one-sided 99% confidence level, >50% of SNe IIn have at least one pre-explosion outburst that is brighter than 3 × 10{sup 7} L{sub ☉} taking place up to 1/3 yr prior to the SN explosion. The average rate of such precursor events during the year prior to the SN explosion is likely ≳ 1 yr{sup –1}, and fainter precursors are possibly even more common. Ignoring the two weakest precursors in our sample, the precursors rate we find is still on the order of one per year. We also find possible correlations between the integrated luminosity of the precursor and the SN total radiated energy, peak luminosity, and rise time. These correlations are expected if the precursors are mass-ejection events, and the early-time light curve of these SNe is powered by interaction of the SN shock and ejecta with optically thick circumstellar material.

Synthetic strategies for efficient conjugation of organometallic complexes with pendant protein reactive markers

KAUST Repository

Jantke, Dominik; Marziale, Alexander N.; Reiner, Thomas; Kraus, Florian; Herdtweck, Eberhardt; Raba, Andreas; Eppinger, Jö rg

2013-01-01

Site-directed conjugation of metal centers to proteins is fundamental for biological and bioinorganic applications of transition metals. However, methods for the site-selective introduction of metal centers remain scarce. Herein, we present broadly applicable synthetic strategies for the conjugation of bioactive molecules with a range of organometallic complexes. Following three different synthetic strategies, we were able to synthesize a small library of metal conjugated protein markers featuring different types of protein reactive sites (epoxides, phenylphosphonates, fluorosulfonates and fluorophosphonate groups) as well as different late transition metals (iron, ruthenium, rhodium, palladium and platinum). The products were isolated in moderate to excellent yields and high purity. Furthermore, X-ray diffraction of the metalated protein markers corroborates structural integrity of the metal complex and the protein reactive site. © 2013 Elsevier B.V. All rights reserved.

Synthetic strategies for efficient conjugation of organometallic complexes with pendant protein reactive markers

KAUST Repository

Jantke, Dominik

2013-11-01

Site-directed conjugation of metal centers to proteins is fundamental for biological and bioinorganic applications of transition metals. However, methods for the site-selective introduction of metal centers remain scarce. Herein, we present broadly applicable synthetic strategies for the conjugation of bioactive molecules with a range of organometallic complexes. Following three different synthetic strategies, we were able to synthesize a small library of metal conjugated protein markers featuring different types of protein reactive sites (epoxides, phenylphosphonates, fluorosulfonates and fluorophosphonate groups) as well as different late transition metals (iron, ruthenium, rhodium, palladium and platinum). The products were isolated in moderate to excellent yields and high purity. Furthermore, X-ray diffraction of the metalated protein markers corroborates structural integrity of the metal complex and the protein reactive site. © 2013 Elsevier B.V. All rights reserved.

Structural phase transition and precursor phenomena in V3Si

International Nuclear Information System (INIS)

Kobayashi, T.; Fukase, T.; Toyota, N.; Muto, Y.

1982-01-01

Thermal dilation experiments on the transforming single crystals V 3 Si indicated that the precursor of the structural transformation at Tsub(m) of about 21 K starts at anomalously high temperatures (proportional70 K) and grows drastically near Tsub(m). This anomaly is also accompanied by the critical increment of electrical resistivity showing a sharp peak at Tsub(m). The application of the uniaxial stress suppresses the resistivity anomaly and makes the superconducting transition width narrower. We propose a model for the precursor phenomena in terms of (1) the directional strain fields (non-cubic) pinned near the defects and (2) the memory effect of orientation of the tetragonal domains born by the defects such as dislocations. (orig.)

Fluid Mechanics of Lean Blowout Precursors in Gas Turbine Combustors

Directory of Open Access Journals (Sweden)

T. M. Muruganandam

2012-03-01

Full Text Available Understanding of lean blowout (LBO phenomenon, along with the sensing and control strategies could enable the gas turbine combustor designers to design combustors with wider operability regimes. Sensing of precursor events (temporary extinction-reignition events based on chemiluminescence emissions from the combustor, assessing the proximity to LBO and using that data for control of LBO has already been achieved. This work describes the fluid mechanic details of the precursor dynamics and the blowout process based on detailed analysis of near blowout flame behavior, using simultaneous chemiluminescence and droplet scatter observations. The droplet scatter method represents the regions of cold reactants and thus help track unburnt mixtures. During a precursor event, it was observed that the flow pattern changes significantly with a large region of unburnt mixture in the combustor, which subsequently vanishes when a double/single helical vortex structure brings back the hot products back to the inlet of the combustor. This helical pattern is shown to be the characteristic of the next stable mode of flame in the longer combustor, stabilized by double helical vortex breakdown (VBD mode. It is proposed that random heat release fluctuations near blowout causes VBD based stabilization to shift VBD modes, causing the observed precursor dynamics in the combustor. A complete description of the evolution of flame near the blowout limit is presented. The description is consistent with all the earlier observations by the authors about precursor and blowout events.

Primary structure of the precursor for the anthozoan neuropeptide Antho-RFamide from Renilla köllikeri: Evidence for unusual processing enzymes

DEFF Research Database (Denmark)

Reinscheid, R K; Grimmelikhuijzen, C J

1994-01-01

distributed over the precursor protein. Of the 36 Antho-RFamide sequences, 29 copies are separated by the five amino acid spacer sequence Arg-Glu/Gly-Asn/Ser/Asp-Glu/Lys-Glu. This implicates processing at single Arg and single Glu residues. Endoproteolytic cleavage at the C-terminal side of paired or single......, and possibly also at other residues, and thus liberate all Antho-RFamide sequences. The processing of one precursor molecule probably yields 38 neuropeptides.(ABSTRACT TRUNCATED AT 250 WORDS)...... basic residues is a well known initial step in the maturation of precursor proteins. Cleavage at the C-terminal side of acidic residues, however, is unusual and must be catalyzed by a new type of processing enzyme. This processing enzyme is most likely to be an endoprotease, because the simplest way...

Patterned YBa2Cu3O7-x thin films from photopolymerizable precursors

International Nuclear Information System (INIS)

Hung, Y.; Agostinelli, J.A.

1990-01-01

A technique which combines the fabrication and patterning of thin films of the high T c superconductor YBa 2 Cu 3 O 7-x has been developed. The technique possesses the essential features of the metalorganic decomposition method with the additional attribute that the metalorganic precursor is photopolymerizable. Patterns are generated directly in the precursor film using optical exposure through a mask followed by development in a solvent. A subsequent thermal treatment transforms the patterned precursor film to the oriented superconducting phase with c axis perpendicular to the substrate surface. Resistivity measurements for such a patterned film on a single crystal (100)MgO substrate show an onset to the superconducting state occurring at 85 K with zero resistivity below 67 K

Identification of isomers of organometallic compounds

Energy Technology Data Exchange (ETDEWEB)

Mbue, Sona Peter; Cho, Kwang Hwi [Dept. of Bioinformatics and Life Science, School of Systems Biomedical Science, Soongsil University,Seoul (Korea, Republic of)

2015-06-15

The yaChI is a newly suggested chemical naming system. However, yaChI is a derivative of the IUPAC InChI with a modified algorithm that includes additional layers of chemical structure information. Consequently, yaChI string contains more structure details while preserving the original structure file information and can distinctively identify very closely related compounds reducing the chances of ambiguity in chemical compound databases as opposed to the general SMILES, InChI, and InChIKey. This study examines the relative performances of yaChI, SMILES, InChI, and InChIKey in duplication check for isomers. For simplicity, a small data set of 28 organometallic compounds (structural isomers of Rh-containing compounds) subdivided into three major groups (A, B, and C) based on the number and the type of ligands attached to the center atom was used to study the performances of each encoding scheme in describing chemical structures. SMILES, InChI, and InChIKey were generated using Openbabel and RDkit, whereas yaChI strings were generated with in-house program. Strings generated from SMILES, InChI, and InChIKey though different, resulted to only three unique chemical identifiers, with each belonging to one group indicating the presence of only three unique compounds in the study data. However, yaChI results depicted that all structures in each group are indeed unique and differ among themselves as well as those from other groups, mapping each structure with a unique identifier given a total number of 28 unique structures in the study data. This high perception of yaChI probe justifies its accuracy and reliability in duplication check among closely related compounds especially structures exhibiting stereo properties.

Coupling of carbon monoxide molecules over oxygen-defected UO2(111) single crystal and thin film surfaces.

Science.gov (United States)

Senanayake, S D; Waterhouse, G I N; Idriss, H; Madey, Theodore E

2005-11-22

While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO2(111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene.

Coupling of Carbon Monoxide Molecules over Oxygen Defected UO2 (111) Single Crystal and Thin Film Surfaces

International Nuclear Information System (INIS)

Senanayake, S.; Waterhouse, G.; Idriss, H.; Madey, T.

2005-01-01

While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C 2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO 2 (111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U 4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene

Tricyanomethane and Its Ketenimine Tautomer: Generation from Different Precursors and Analysis in Solution, Argon Matrix, and as a Single Crystal.

Science.gov (United States)

Banert, Klaus; Chityala, Madhu; Hagedorn, Manfred; Beckers, Helmut; Stüker, Tony; Riedel, Sebastian; Rüffer, Tobias; Lang, Heinrich

2017-08-01

Solutions of azidomethylidenemalononitrile were photolyzed at low temperatures to produce the corresponding 2H-azirine and tricyanomethane, which were analyzed by low-temperature NMR spectroscopy. The latter product was also observed after short thermolysis of the azide precursor in solution whereas irradiation of the azide isolated in an argon matrix did not lead to tricyanomethane, but to unequivocal detection of the tautomeric ketenimine by IR spectroscopy for the first time. When the long-known "aquoethereal" greenish phase generated from potassium tricyanomethanide, dilute sulfuric acid, and diethyl ether was rapidly evaporated and sublimed, a mixture of hydronium tricyanomethanide and tricyanomethane was formed instead of the previously claimed ketenimine tautomer. Under special conditions of sublimation, single crystals of tricyanomethane could be isolated, which enabled the analysis of the molecular structure by X-ray diffraction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying

International Nuclear Information System (INIS)

Dom, Rekha; Sivakumar, G.; Hebalkar, Neha Y.; Joshi, Shrikant V.; Borse, Pramod H.

2012-01-01

Highlights: ► Highly economic solution precursor route capable of producing films/coating even for mass scale production. ► Pure spinel phase ZnFe 2 O 4 porous, immobilized films deposited in single step. ► Parameter optimization yields access to nanostructuring in SPPS method. ► The ecofriendly immobilized ferrite films were active under solar radiation. ► Such magnetic system display advantage w.r.t. recyclability after photocatalyst extraction. -- Abstract: Deposition of pure spinel phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor conditions (7 2 O 4 film. Very high/low precursor concentrations yielded mixed phase, less adherent, and highly inhomogeneous thin films. Desired spinel phase was achieved in as-deposited condition under appropriately controlled spray conditions and exhibited a band gap of ∼1.9 eV. The highly porous nature of the films favored its photocatalytic performance as indicated by methylene blue de-coloration under solar radiation. These immobilized films display good potential for visible light photocatalytic applications.

Study of two examples of non linear interaction of a laser wave with matter: laser-induced damage of dielectrics and non linear optical properties of organometallic molecules in solution

International Nuclear Information System (INIS)

Gaudry, Jean-Baptiste

2000-01-01

This research thesis reports the study of two mechanisms of non linear interaction of a laser wave with matter. More particularly, it reports the experimental investigation of non linear optical properties of organometallic molecules in solution, as well as the damage of perfect silica under laser irradiation by using simulation codes. As far as optical properties are concerned, the author highlights the influence of the electronic configuration of the metal present in the organometallic compound, and the influence of the ligand on the second-order non-linear response. As far as the simulation is concerned, some experimental results have been reproduced. This work can be useful for the investigation of the extrinsic damage of imperfect materials, and for the design of experiments of transient measurements of excited silica [fr

Reactive surface organometallic complexes observed using dynamic nuclear polarization surface enhanced NMR spectroscopy

KAUST Repository

Pump, Eva; Viger-Gravel, Jasmine; Abou-Hamad, Edy; Samantaray, Manoja; Hamzaoui, Bilel; Gurinov, Andrei; Anjum, Dalaver H.; Gajan, David; Lesage, Anne; Bendjeriou-Sedjerari, Anissa; Emsley, Lyndon; Basset, Jean-Marie

2016-01-01

Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) is an emerging technique that allows access to high-sensitivity NMR spectra from surfaces. However, DNP SENS usually requires the use of radicals as an exogenous source of polarization, which has so far limited applications for organometallic surface species to those that do not react with the radicals. Here we show that reactive surface species can be studied if they are immobilized inside porous materials with suitably small windows, and if bulky nitroxide bi-radicals (here TEKPol) are used as the polarization source and which cannot enter the pores. The method is demonstrated by obtaining significant DNP enhancements from highly reactive complelxes [(equivalent to Si-O-)W(Me)(5)] supported on MCM-41, and effects of pore size (6.0, 3.0 and 2.5 nm) on the performance are discussed.

Reactive surface organometallic complexes observed using dynamic nuclear polarization surface enhanced NMR spectroscopy

KAUST Repository

Pump, Eva

2016-08-15

Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) is an emerging technique that allows access to high-sensitivity NMR spectra from surfaces. However, DNP SENS usually requires the use of radicals as an exogenous source of polarization, which has so far limited applications for organometallic surface species to those that do not react with the radicals. Here we show that reactive surface species can be studied if they are immobilized inside porous materials with suitably small windows, and if bulky nitroxide bi-radicals (here TEKPol) are used as the polarization source and which cannot enter the pores. The method is demonstrated by obtaining significant DNP enhancements from highly reactive complelxes [(equivalent to Si-O-)W(Me)(5)] supported on MCM-41, and effects of pore size (6.0, 3.0 and 2.5 nm) on the performance are discussed.

Silicon oxynitride films deposited by reactive high power impulse magnetron sputtering using nitrous oxide as a single-source precursor

Energy Technology Data Exchange (ETDEWEB)

Hänninen, Tuomas, E-mail: tuoha@ifm.liu.se; Schmidt, Susann; Jensen, Jens; Hultman, Lars; Högberg, Hans [Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping SE-581 83 (Sweden)

2015-09-15

Silicon oxynitride thin films were synthesized by reactive high power impulse magnetron sputtering of silicon in argon/nitrous oxide plasmas. Nitrous oxide was employed as a single-source precursor supplying oxygen and nitrogen for the film growth. The films were characterized by elastic recoil detection analysis, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray reflectivity, scanning electron microscopy, and spectroscopic ellipsometry. Results show that the films are silicon rich, amorphous, and exhibit a random chemical bonding structure. The optical properties with the refractive index and the extinction coefficient correlate with the film elemental composition, showing decreasing values with increasing film oxygen and nitrogen content. The total percentage of oxygen and nitrogen in the films is controlled by adjusting the gas flow ratio in the deposition processes. Furthermore, it is shown that the film oxygen-to-nitrogen ratio can be tailored by the high power impulse magnetron sputtering-specific parameters pulse frequency and energy per pulse.

Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore

KAUST Repository

Goswami, Subhadip; Winkel, Russell W.; Alarousu, Erkki; Ghiviriga, Ion; Mohammed, Omar F.; Schanze, Kirk S.

2014-01-01

A pair of diketopyrrolopyrrole (DPP) chromophores that are end-functionalized with platinum containing "auxochromes" were subjected to electrochemical and photophysical study. The chromophores contain either platinum acetylide or ortho-metalated 2-thienylpyridinyl(platinum) end-groups (DPP-Pt(CC) and DPP-Pt(acac), respectively). The ground state redox potentials of the chromophores were determined by solution electrochemistry, and the HOMO and LUMO levels were estimated. The chromophores' photophysical properties were characterized by absorption, photoluminescence, and time-resolved absorption spectroscopy on time scales from sub-picoseconds to microseconds. Density functional theory (DFT) computations were performed to understand the molecular orbitals involved in both the singlet and triplet excited state photophysics. The results reveal that in both platinum DPP derivatives the organometallic auxochromes have a significant effect on the chromophores' photophysics. The most profound effect is a reduction in the fluorescence yields accompanied by enhanced triplet yields due to spin-orbit coupling induced by the metal centers. The effects are most pronounced in DPP-Pt(acac), indicating that the orthometalated platinum auxochrome is able to induce spin-orbital coupling to a greater extent compared to the platinum acetylide units. (Figure Presented).

Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore

KAUST Repository

Goswami, Subhadip

2014-12-18

A pair of diketopyrrolopyrrole (DPP) chromophores that are end-functionalized with platinum containing "auxochromes" were subjected to electrochemical and photophysical study. The chromophores contain either platinum acetylide or ortho-metalated 2-thienylpyridinyl(platinum) end-groups (DPP-Pt(CC) and DPP-Pt(acac), respectively). The ground state redox potentials of the chromophores were determined by solution electrochemistry, and the HOMO and LUMO levels were estimated. The chromophores\\' photophysical properties were characterized by absorption, photoluminescence, and time-resolved absorption spectroscopy on time scales from sub-picoseconds to microseconds. Density functional theory (DFT) computations were performed to understand the molecular orbitals involved in both the singlet and triplet excited state photophysics. The results reveal that in both platinum DPP derivatives the organometallic auxochromes have a significant effect on the chromophores\\' photophysics. The most profound effect is a reduction in the fluorescence yields accompanied by enhanced triplet yields due to spin-orbit coupling induced by the metal centers. The effects are most pronounced in DPP-Pt(acac), indicating that the orthometalated platinum auxochrome is able to induce spin-orbital coupling to a greater extent compared to the platinum acetylide units. (Figure Presented).

A single source precursor route to group 13 homo- and heterometallic oxides as highly active supports for gold-catalyzed aerobic epoxidation of trans-stilbene

KAUST Repository

Mishra, Shashank K.; Mendez, Violaine; Jeanneau, Erwann; Caps, Valerie; Daniè le, Sté phane

2012-01-01

A new Mitsubishi-type of star-shaped homoleptic derivative of indium(III), In4(mdea)6 (2, mdeaH2 = N-methyldiethanolamine) , was synthesized by the chloro-aminoalkoxo exchange reaction of a heteroleptic complex In6Cl6(mdea)6 (1) and used as a facile single source molecular precursor for the sol-gel preparation of high surface area indium oxide. Successful deposition of gold nanoparticles (1 wt.-%) of average size 3.3 nm on the above metal oxide by using HAuCl4· 3H2O afforded a highly efficient Au/In2O3 catalyst for the aerobic epoxidation of trans-stilbene at low temperature. The above single source precursor approach was further extended to obtain other group 13 homo- and heterometallic oxides, namely, α-Ga2O 3, β-Ga2O3 and Al4Ga 2O9, as highly active supports for gold catalysts. The obtained Au/M2O3 (M = Ga, In) and Au/Al4Ga 2O9 catalysts were thoroughly characterized by using several physicochemical techniques such as XRD, high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A comparative study of the above catalysts for the model aerobic oxidation of stilbene in methylcyclohexane was undertaken. Highly efficient catalysts for aerobic oxidation reactions were obtained by depositing gold nanoparticles on group 13 mono- or mixed metal oxides prepared from the hydrolysis of well-characterized homo- and heterometallic N-methyldiethanolaminate derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A single source precursor route to group 13 homo- and heterometallic oxides as highly active supports for gold-catalyzed aerobic epoxidation of trans-stilbene

KAUST Repository

Mishra, Shashank K.

2012-12-14

A new Mitsubishi-type of star-shaped homoleptic derivative of indium(III), In4(mdea)6 (2, mdeaH2 = N-methyldiethanolamine) , was synthesized by the chloro-aminoalkoxo exchange reaction of a heteroleptic complex In6Cl6(mdea)6 (1) and used as a facile single source molecular precursor for the sol-gel preparation of high surface area indium oxide. Successful deposition of gold nanoparticles (1 wt.-%) of average size 3.3 nm on the above metal oxide by using HAuCl4· 3H2O afforded a highly efficient Au/In2O3 catalyst for the aerobic epoxidation of trans-stilbene at low temperature. The above single source precursor approach was further extended to obtain other group 13 homo- and heterometallic oxides, namely, α-Ga2O 3, β-Ga2O3 and Al4Ga 2O9, as highly active supports for gold catalysts. The obtained Au/M2O3 (M = Ga, In) and Au/Al4Ga 2O9 catalysts were thoroughly characterized by using several physicochemical techniques such as XRD, high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A comparative study of the above catalysts for the model aerobic oxidation of stilbene in methylcyclohexane was undertaken. Highly efficient catalysts for aerobic oxidation reactions were obtained by depositing gold nanoparticles on group 13 mono- or mixed metal oxides prepared from the hydrolysis of well-characterized homo- and heterometallic N-methyldiethanolaminate derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dissolved oxygen sensing using organometallic dyes deposited within a microfluidic environment

Science.gov (United States)

Chen, Q. L.; Ho, H. P.; Jin, L.; Chu, B. W.-K.; Li, M. J.; Yam, V. W.-W.

2008-02-01

This work primarily aims to integrate dissolved oxygen sensing capability with a microfluidic platform containing arrays of micro bio-reactors or bio-activity indicators. The measurement of oxygen concentration is of significance for a variety of bio-related applications such as cell culture and gene expression. Optical oxygen sensors based on luminescence quenching are gaining much interest in light of their low power consumption, quick response and high analyte sensitivity in comparison to similar oxygen sensing devices. In our microfluidic oxygen sensor device, a thin layer of oxygen-sensitive luminescent organometallic dye is covalently bonded to a glass slide. Micro flow channels are formed on the glass slide using patterned PDMS (Polydimethylsiloxane). Dissolved oxygen sensing is then performed by directing an optical excitation probe beam to the area of interest within the microfluidic channel. The covalent bonding approach for sensor layer formation offers many distinct advantages over the physical entrapment method including minimizing dye leaching, ensuring good stability and fabrication simplicity. Experimental results confirm the feasibility of the device.

Conversion of actual flue gas CO 2 via cycloaddition to propylene oxide catalyzed by a single-site, recyclable zirconium catalyst

KAUST Repository

Kelly, Michael J.

2017-06-12

A reusable zirconium-based catalyst for the cycloaddition of CO2 to propylene oxide (PO) was prepared by the surface organometallic chemistry (SOMC) methodology. Accordingly, well-defined amounts of the ZrCl4·(OEt2)2 precursor were grafted on the surface of silica dehydroxylated at 700°C (SiO2-700) and at 200°C (SiO2-200) in order to afford surface coordination compounds with different podality and chemical environment. The identity of the surface complexes was thoroughly investigated by FT-IR, elemental microanalysis and solid state NMR and applied as a recoverable and reusable heterogeneous catalyst for the title reaction using pure CO2 and flue gas samples from a cement factory. The observed catalytic activity for the isolated zirconium complexes is rationalized by means of systematic DFT calculations.

Conversion of actual flue gas CO 2 via cycloaddition to propylene oxide catalyzed by a single-site, recyclable zirconium catalyst

KAUST Repository

Kelly, Michael J.; Barthel, Alexander; Maheu, Clement; Sodpiban, Ounjit; Dega, Frank-Blondel; Vummaleti, Sai V.C.; Abou-Hamad, Edy; Pelletier, Jeremie; Cavallo, Luigi; D'Elia, Valerio; Basset, Jean-Marie

2017-01-01

A reusable zirconium-based catalyst for the cycloaddition of CO2 to propylene oxide (PO) was prepared by the surface organometallic chemistry (SOMC) methodology. Accordingly, well-defined amounts of the ZrCl4·(OEt2)2 precursor were grafted on the surface of silica dehydroxylated at 700°C (SiO2-700) and at 200°C (SiO2-200) in order to afford surface coordination compounds with different podality and chemical environment. The identity of the surface complexes was thoroughly investigated by FT-IR, elemental microanalysis and solid state NMR and applied as a recoverable and reusable heterogeneous catalyst for the title reaction using pure CO2 and flue gas samples from a cement factory. The observed catalytic activity for the isolated zirconium complexes is rationalized by means of systematic DFT calculations.

Organometallic Polymeric Conductors

Science.gov (United States)

Youngs, Wiley J.

1997-01-01

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for

Iron filled carbon nanostructures from different precursors

International Nuclear Information System (INIS)

Costa, S.; Borowiak-Palen, E.; Bachmatiuk, A.; Ruemmeli, M.H.; Gemming, T.; Kalenczuk, R.J.

2008-01-01

Here, we present a study on the synthesis of different nanostructures with one single-step in situ filling (encapsulation) via carbon vapor deposition (CVD). Ferrocene, acetylferrocene and iron (II) nitrate as iron precursors were explored. The application of each of these compounds resulted in different carbon nanomaterials such as: iron filled multiwalled carbon nanotubes with a low filling ratio (Fe-MWCNT), iron filled nanocapsules and unfilled MWCNT. The as-produced samples were purified by high temperature annealing and acid treatment. The purified materials were characterised using transmission electron microscopy (TEM) and Raman spectroscopy

Novel routes to nanodispersed semiconductors

International Nuclear Information System (INIS)

Green, M.A.

1999-01-01

Novel synthetic routes to nanodispersed compound semiconductors using organometallic precursors have been developed. The quantum dots have been studied by optical absorption spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, infra red spectroscopy and nuclear magnetic resonance. Polar Lewis base solvents such as tri-n-octylphosphine oxide and 4-ethylpyridine were utilized as both passivating agent and dispersing medium. In the the search for new solvent systems and passivating agents, and investigation was also made into the use of dimethyl sulfoxide as a reaction solvent and capping agent in the preparation of nanocrystalline CdS. Existing routes using metal alkyls and silylated precursors in hot TOPO were improved by substituting the metal alkyl with an metal alkyl adduct. Cadmium monothiocarbamate and a related precursor, cadmium thioacetate were investigated as possible single source precursors to nanometer sized CdS. The thermolysis of diorganophosphides in the Lewis bases coordinating solvent (4-ethylpridine) has been investigated, including studies of decompositon mechanisms, and quantum dots of Cd 3 P 2 , Zn 3 P 2 , Inp and GaP have been prepared. The synthesis of InAs using the metal chloride and an aminoarsenide precursor in 4-ethylpridine has also been developed. A simple method for the organization of III-V materials into glass like aggregates has been described. (author)

Solution precursor plasma deposition of nanostructured ZnO coatings

International Nuclear Information System (INIS)

Tummala, Raghavender; Guduru, Ramesh K.; Mohanty, Pravansu S.

2011-01-01

Highlights: → The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. → It is highly capable of developing tailorable nanostructures. → This technique can be employed to spray the coatings on any kind of substrates including polymers. → The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance (∼65-80%) and reflectivity (∼65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 mΩ cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

Solution precursor plasma deposition of nanostructured ZnO coatings

Energy Technology Data Exchange (ETDEWEB)

Tummala, Raghavender [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Guduru, Ramesh K., E-mail: rkguduru@umich.edu [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Mohanty, Pravansu S. [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States)

2011-08-15

Highlights: {yields} The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. {yields} It is highly capable of developing tailorable nanostructures. {yields} This technique can be employed to spray the coatings on any kind of substrates including polymers. {yields} The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance ({approx}65-80%) and reflectivity ({approx}65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 m{Omega} cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

Synthesis and characterization of organosilicon compounds as novel precursors for CVD processes

Energy Technology Data Exchange (ETDEWEB)

Ermakova, E.N.; Sysoev, S.V.; Nikulina, L.D. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Acad. Lavrentiev Ave. 3, Novosibirsk 630090 (Russian Federation); Tsyrendorzhieva, I.P.; Rakhlin, V.I. [Favorskii Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorskii Str. 1, Irkutsk 664033 (Russian Federation); Kosinova, M.L., E-mail: marina@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Acad. Lavrentiev Ave. 3, Novosibirsk 630090 (Russian Federation)

2015-12-20

Highlights: • The temperature dependences of vapor pressure of four precursors have been measured. • The experimental data were used to calculate standard thermodynamic functions. • The thermodynamic modelling of SiC{sub x}N{sub y} films formation has been performed. - Abstract: Chemical vapor deposition using single-source organosilicon precursors is one of the most effective ways to produce multifunctional SiC{sub x}N{sub y} films. It is worth mentioning that the precursor molecule design affects both the composition and properties of films. Four organosilicon compounds containing a phenyl substituent (namely, trimethylphenylsilane, trimethyl(phenylamino) silane, trimethyl(benzylamino)silane and bis(trimethylsilyl)phenylamine) have been synthesized and characterized as potential CVD precursors for SiC{sub x}N{sub y} films synthesis. The compounds have been shown to be volatile and stable enough to be used in chemical vapor deposition of SiC{sub x}N{sub y} films. Thermodynamic modeling of the film deposition from the gaseous mixture of trimethylphenylsilane and ammonia in Si–C–N–H system has demonstrated that SiC{sub x}N{sub y} films can be deposited, and there is an opportunity to determine the area of appropriate deposition conditions.

Sweetening ruthenium and osmium: organometallic arene complexes containing aspartame.

Science.gov (United States)

Gray, Jennifer C; Habtemariam, Abraha; Winnig, Marcel; Meyerhof, Wolfgang; Sadler, Peter J

2008-09-01

The novel organometallic sandwich complexes [(eta(6)-p-cymene)Ru(eta(6)-aspartame)](OTf)(2) (1) (OTf = trifluoromethanesulfonate) and [(eta(6)-p-cymene)Os(eta(6)-aspartame)](OTf)(2) (2) incorporating the artificial sweetener aspartame have been synthesised and characterised. A number of properties of aspartame were found to be altered on binding to either metal. The pK(a) values of both the carboxyl and the amino groups of aspartame are lowered by between 0.35 and 0.57 pH units, causing partial deprotonation of the amino group at pH 7.4 (physiological pH). The rate of degradation of aspartame to 3,6-dioxo-5-phenylmethylpiperazine acetic acid (diketopiperazine) increased over threefold from 0.12 to 0.36 h(-1) for 1, and to 0.43 h(-1) for 2. Furthermore, the reduction potential of the ligand shifted from -1.133 to -0.619 V for 2. For the ruthenium complex 1 the process occurred in two steps, the first (at -0.38 V) within a biologically accessible range. This facilitates reactions with biological reductants such as ascorbate. Binding to and activation of the sweet taste receptor was not observed for these metal complexes up to concentrations of 1 mM. The factors which affect the ability of metal-bound aspartame to interact with the receptor site are discussed.

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

Energy Technology Data Exchange (ETDEWEB)

Taette, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Maendar, Hugo; Pohako, Kaija; Reivelt, Kaido; Lohmus, Ants [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Pehk, Tonis [National Institute of Chemical and Biological Physics, Akadeemia tee 23, Tallinn 12618 (Estonia); Natali, Marco [ICIS-CNR, Corso Stati Uniti 4, Padova 35127 (Italy); Gurauskis, Jonas [Instituto de Ciencia de Materiales de Aragon C.S.I.C., University of Zaragoza Fac. De Ciencias, c/Pedro Cerbuna 12, Zaragoza 50009 (Spain); Maeeorg, Uno, E-mail: tanelt@fi.tartu.ee [Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411 (Estonia)

2011-06-15

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO{sub 2}, TiO{sub 2}, ZrO{sub 2}, HfO{sub 2} and CeO{sub 2}) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

Single-Source Molecular Precursor for Synthesis of CdS Nanoparticles and Nanoflowers

Science.gov (United States)

Salavati-Niasari, Masoud; Sobhani, Azam

2012-04-01

CdS Semiconductor nanostructures were synthesized by using two different methods. Using triphenylphosphine (C18H15P) and oleylamine (C18H37N) as surfactant, CdS semiconductor nanocrystals with a size ranging from 30 to 90 nm can be synthesized by thermal decomposition of precursor [bis(thiosemicarbazide)cadmium(II)]. CdS nanoflowers were synthesized via hydrothermal decomposition of [bis(thiosemicarbazide) cadmium(II)] without any surfactant. X-ray diffraction (XRD) patterns confirm that the resulting samples were a pure hexagonal phase of CdS. The optical property test indicates that the absorption peak of the samples shifts towards short wavelength, and the blue shift phenomenon might be ascribed to the quantum effect.

[(≢SiO)TaVCl2Me2]: A well-defined silica-supported tantalum(V) surface complex as catalyst precursor for the selective cocatalyst-free trimerization of ethylene

KAUST Repository

Chen, Yin; Callens, Emmanuel; Abou-Hamad, Edy; Merle, Nicolas; White, Andrew J P; Taoufik, Mostafa; Copé ret, Christophe; Le Roux, Erwan; Basset, Jean-Marie

2012-01-01

On the surface of it: In the absence of co-catalyst, a well-defined silica-supported surface organometallic complex [(≢SiO)Ta VCl2Me2] selectively catalyzes the oligomerization of ethylene. The use of surface organometallic species allows three different pathways to be determined for the reduction of TaV to TaIII species under pressure of ethylene. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[(≢SiO)TaVCl2Me2]: A well-defined silica-supported tantalum(V) surface complex as catalyst precursor for the selective cocatalyst-free trimerization of ethylene

KAUST Repository

Chen, Yin

2012-10-22

On the surface of it: In the absence of co-catalyst, a well-defined silica-supported surface organometallic complex [(≢SiO)Ta VCl2Me2] selectively catalyzes the oligomerization of ethylene. The use of surface organometallic species allows three different pathways to be determined for the reduction of TaV to TaIII species under pressure of ethylene. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid Organometallic-Inorganic Nanomaterial: Acetyl Ferrocene Schiff base Immobilized on Silica Coated Magnetite Nanoparticles

Directory of Open Access Journals (Sweden)

M. Masteri-Farahani

2015-10-01

Full Text Available In  this  work,  a  new  hybrid  organometallic-inorganic  hybrid nanomaterial was prepared by immobilization of acetyl ferrocene on the  surface  of magnetite  nanoparticles. Covalent  grafting of silica coated magnetite nanoparticles (SCMNPs with 3-aminopropyl triethoxysilane gave aminopropyl-modified magnetite nanoparticles (AmpSCMNPs. Then, Schiff base condensation  of AmpSCMNPs with acetyl  ferrocene resulted in the preparation of acferro-SCMNPs hybrid nanomaterial. Characterization of the prepared nanomaterial was performed with different physicochemical methods such as Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD, vibrating sample magnetometry (VSM, thermogravimetric analysis (TGA, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. VSM analysis showed superparamagnetic properties of the prepared nanomaterial and TEM and SEM analyses indicated the relatively spherical nanoparticles with 15 nm average size.

Theoretical study of the structure and reactivity of lanthanide and actinide based organometallic complexes

International Nuclear Information System (INIS)

Barros, N.

2007-06-01

In this PhD thesis, lanthanide and actinide based organometallic complexes are studied using quantum chemistry methods. In a first part, the catalytic properties of organo-lanthanide compounds are evaluated by studying two types of reactions: the catalytic hydro-functionalization of olefins and the polymerisation of polar monomers. The reaction mechanisms are theoretically determined and validated, and the influence of possible secondary non productive reactions is envisaged. A second part focuses on uranium-based complexes. Firstly, the electronic structure of uranium metallocenes is analysed. An analogy with the uranyl compounds is proposed. In a second chapter, two isoelectronic complexes of uranium IV are studied. After validating the use of DFT methods for describing the electronic structure and the reactivity of these compounds, it is shown that their reactivity difference can be related to a different nature of chemical bonding in these complexes. (author)

Meat flavor precursors and factors influencing flavor precursors--A systematic review.

Science.gov (United States)

Khan, Muhammad Issa; Jo, Cheorun; Tariq, Muhammad Rizwan

2015-12-01

Flavor is the sensory impression sensed by taste and smell buds and is a leading factor determining the meat quality and purchasing decision of the consumer. Meat flavor is characteristic of volatiles produced as a result of reactions of non-volatile components that are induced thermally. The water soluble compounds having low molecular weight and meat lipids are important precursors of cooked meat flavor. The Maillard reaction, lipid oxidation, and vitamin degradation are leading reactions during cooking which develop meat flavor from uncooked meat with little aroma and bloody taste. The pre-slaughter and postmortem factors like animal breed, sex, age, feed, aging and cooking conditions contribute to flavor development of cooked meat. The objective of this review is to highlight the flavor chemistry, meat flavor precursors and factors affecting meat flavor precursors. Copyright © 2015 Elsevier Ltd. All rights reserved.

Boron nitride ceramics from molecular precursors: synthesis, properties and applications.

Science.gov (United States)

Bernard, Samuel; Salameh, Chrystelle; Miele, Philippe

2016-01-21

Hexagonal boron nitride (h-BN) attracts considerable interest because its structure is similar to that of carbon graphite while it displays different properties which are of interest for environmental and green technologies. The polar nature of the B-N bond in sp(2)-bonded BN makes it a wide band gap insulator with different chemistry on its surface and particular physical and chemical properties such as a high thermal conductivity, a high temperature stability, a high resistance to corrosion and oxidation and a strong UV emission. It is chemically inert and nontoxic and has good environmental compatibility. h-BN also has enhanced physisorption properties due to the dipolar fields near its surface. Such properties are closely dependent on the processing method. Bottom-up approaches consist of transforming molecular precursors into non-oxide ceramics with retention of the structural units inherent to the precursor molecule. The purpose of the present review is to give an up-to-date overview on the most recent achievements in the preparation of h-BN from borazine-based molecular single-source precursors including borazine and 2,4,6-trichloroborazine through both vapor phase syntheses and methods in the liquid/solid state involving polymeric intermediates, called the Polymer-Derived Ceramics (PDCs) route. In particular, the effect of the chemistry, composition and architecture of the borazine-based precursors and derived polymers on the shaping ability as well as the properties of h-BN is particularly highlighted.

Organometallic Routes into the Nanorealms of Binary Fe-Si Phases

Directory of Open Access Journals (Sweden)

Teddy M. Keller

2010-02-01

Full Text Available The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, a-FeSi2 and b-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR. The silicon-rich b-FeSi2 is a direct band gap material usable in light emitting diode (LED applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions.

Single-Site Palladium(II) Catalyst for Oxidative Heck Reaction: Catalytic Performance and Kinetic Investigations

Energy Technology Data Exchange (ETDEWEB)

Duan, Hui; Li, Mengyang; Zhang, Guanghui; Gallagher, James R.; Huang, Zhiliang; Sun, Yu; Luo, Zhong; Chen, Hongzhong; Miller, Jeffrey T.; Zou, Ruqiang; Lei, Aiwen; Zhao, Yanli

2015-01-01

ABSTRACT: The development of organometallic single-site catalysts (SSCs) has inspired the designs of new heterogeneous catalysts with high efficiency. Nevertheless, the application of SSCs in certain modern organic reactions, such as C-C bond formation reactions, has still been less investigated. In this study, a single-site Pd(II) catalyst was developed, where 2,2'-bipyridine-grafted periodic mesoporous organosilica (PMO) was employed as the support of a Pd(II) complex. The overall performance of the single-site Pd(II) catalyst in the oxidative Heck reaction was then investigated. The investigation results show that the catalyst displays over 99% selectivity for the product formation with high reaction yield. Kinetic profiles further confirm its high catalytic efficiency, showing that the rate constant is nearly 40 times higher than that for the free Pd(II) salt. X-ray absorption spectroscopy reveals that the catalyst has remarkable lifetime and recyclability.

BET inhibition as a single or combined therapeutic approach in primary paediatric B-precursor acute lymphoblastic leukaemia

International Nuclear Information System (INIS)

Da Costa, D; Agathanggelou, A; Perry, T; Weston, V; Petermann, E; Zlatanou, A; Oldreive, C; Wei, W; Stewart, G; Longman, J; Smith, E; Kearns, P; Knapp, S; Stankovic, T

2013-01-01

Paediatric B-precursor ALL is a highly curable disease, however, treatment resistance in some patients and the long-term toxic effects of current therapies pose the need for more targeted therapeutic approaches. We addressed the cytotoxic effect of JQ1, a highly selective inhibitor against the transcriptional regulators, bromodomain and extra-terminal (BET) family of proteins, in paediatric ALL. We showed a potent in vitro cytotoxic response of a panel of primary ALL to JQ1, independent of their prognostic features but dependent on high MYC expression and coupled with transcriptional downregulation of multiple pro-survival pathways. In agreement with earlier studies, JQ1 induced cell cycle arrest. Here we show that BET inhibition also reduced c-Myc protein stability and suppressed progression of DNA replication forks in ALL cells. Consistent with c-Myc depletion and downregulation of pro-survival pathways JQ1 sensitised primary ALL samples to the classic ALL therapeutic agent dexamethasone. Finally, we demonstrated that JQ1 reduces ALL growth in ALL xenograft models, both as a single agent and in combination with dexamethasone. We conclude that targeting BET proteins should be considered as a new therapeutic strategy for the treatment of paediatric ALL and particularly those cases that exhibit suboptimal responses to standard treatment

Air-tolerant C–C bond formation via organometallic ruthenium catalysis: diverse catalytic pathways involving (C5Me5)Ru or (C5H5)Ru are robust to molecular oxygen

Czech Academy of Sciences Publication Activity Database

Severa, Lukáš; Vávra, Jan; Kohoutová, Anna; Čížková, Martina; Šálová, Tereza; Hývl, Jakub; Šaman, David; Pohl, Radek; Adriaenssens, Louis; Teplý, Filip

2009-01-01

Roč. 50, č. 31 (2009), s. 4526-4528 ISSN 0040-4039 Institutional research plan: CEZ:AV0Z40550506 Keywords : ruthenium * organometallic catalysis * [2+2+2] cycloaddition * terminal alkynes Subject RIV: CC - Organic Chemistry Impact factor: 2.660, year: 2009

Organometallics and quaternary ammonium salts affect calcium ion desorption from lecithin liposome membranes

International Nuclear Information System (INIS)

Kral, T.E.; Kuczera, J.; Przestalski, S.

2001-01-01

The objective of the present work was to compare the effects of groups of tin and lead organometallic compounds and their mixtures with amphiphilic quaternary ammonium salts (QAS) on the process of calcium ion desorption from lecithin liposome membranes, as dependent on the properties of the hydrophilic and hydrophobic parts of QAS. In the investigations the method of radioactive labels was applied. Synergism and antagonism in the action of both groups of compounds were found. The effectiveness of the cooperation depended more on chain length of QAS compounds than on the size and polarity of their hydrophobic parts. The most effective of all compounds studied was a the mixture of benzyldimethylammonium chloride in a mixture with tripropyltin. Since the rate of calcium desorption proved to be a good measure of efficacy of biologically active surfactants, it seems that the conclusions reached in this paper may be useful for choosing compounds which are able to decontaminate the environment polluted with heavy metals. (orig.)

Single-step production of the simvastatin precursor monacolin J by engineering of an industrial strain of Aspergillus terreus.

Science.gov (United States)

Huang, Xuenian; Liang, Yajing; Yang, Yong; Lu, Xuefeng

2017-07-01

Monacolin J is a key precursor for the synthesis of simvastatin (Zocor), an important drug for treating hypercholesterolemia. Industrially, monacolin J is manufactured through alkaline hydrolysis of lovastatin, a fungal polyketide produced by Aspergillus terreus. Multistep chemical processes for the conversion of lovastatin to simvastatin are laborious, cost expensive and environmentally unfriendly. A biocatalysis process for monacolin J conversion to simvastatin has been developed. However, direct bioproduction of monacolin J has not yet been achieved. Here, we identified a lovastatin hydrolase from Penicillium chrysogenum, which displays a 232-fold higher catalytic efficiency for the in vitro hydrolysis of lovastatin compared to a previously patented hydrolase, but no activity for simvastatin. Furthermore, we showed that an industrial A. terreus strain heterologously expressing this lovastatin hydrolase can produce monacolin J through single-step fermentation with high efficiency, approximately 95% of the biosynthesized lovastatin was hydrolyzed to monacolin J. Our results demonstrate a simple and green technical route for the production of monacolin J, which makes complete bioproduction of the cholesterol-lowering drug simvastatin feasible and promising. Copyright © 2017 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Effect of temperature, precursor concentration and capping group on the shape of Cds nanoparticles

CSIR Research Space (South Africa)

Moloto, N

2009-01-01

Full Text Available A novel ligand to the synthesis of nanoparticles has been employed in this study. A Tetramethylthiuram disulphide cadmium complex (abundant in sulphur atoms) was used as a single-source precursor for the synthesis of CdS nanoparticles. The CdS...

The stream of precursors that colonizes the thymus proceeds selectively through the early T lineage precursor stage of T cell development

Science.gov (United States)

Benz, Claudia; Martins, Vera C.; Radtke, Freddy; Bleul, Conrad C.

2008-01-01

T cell development in the thymus depends on continuous colonization by hematopoietic precursors. Several distinct T cell precursors have been identified, but whether one or several independent precursor cell types maintain thymopoiesis is unclear. We have used thymus transplantation and an inducible lineage-tracing system to identify the intrathymic precursor cells among previously described thymus-homing progenitors that give rise to the T cell lineage in the thymus. Extrathymic precursors were not investigated in these studies. Both approaches show that the stream of T cell lineage precursor cells, when entering the thymus, selectively passes through the early T lineage precursor (ETP) stage. Immigrating precursor cells do not exhibit characteristics of double-negative (DN) 1c, DN1d, or DN1e stages, or of populations containing the common lymphoid precursor 2 (CLP-2) or the thymic equivalent of circulating T cell progenitors (CTPs). It remains possible that an unknown hematopoietic precursor cell or previously described extrathymic precursors with a CLP, CLP-2, or CTP phenotype feed into T cell development by circumventing known intrathymic T cell lineage progenitor cells. However, it is clear that of the known intrathymic precursors, only the ETP population contributes significant numbers of T lineage precursors to T cell development. PMID:18458114

Protective Actions of 17β-Estradiol and Progesterone on Oxidative Neuronal Injury Induced by Organometallic Compounds

Directory of Open Access Journals (Sweden)

Yasuhiro Ishihara

2015-01-01

Full Text Available Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.

Single-phase ceramics with La{sub 1-x}Sr{sub x}Ga{sub 1-y}Mg{sub y}O{sub 3-{delta}} composition from precursors obtained by mechanosynthesis

Energy Technology Data Exchange (ETDEWEB)

Moure, A.; Tartaj, J.; Moure, C. [Instituto de Ceramica y Vidrio, CSIC, C/Kelsen 5, 28049 Madrid (Spain); Castro, A. [Instituto de Ciencia de Materiales de Madrid, CSIC, c/Sor Juana Ines de la Cruz, 3 Cantoblanco, 28049 Madrid (Spain)

2009-03-15

Dense ceramics with La{sub 0.80}Sr{sub 0.20}Ga{sub 0.85}Mg{sub 0.15}O{sub 2.825} and La{sub 0.80}Sr{sub 0.15}Ga{sub 0.85}Mg{sub 0.20}O{sub 2.825} compositions have been prepared by sintering of mechanosynthesized precursors. The perovskite is synthesized after 85 h of milling in a planetary mill. Single phases have been obtained at conditions that are not possible if traditional solid-state reaction (SSR) method is used. The influence of milling time and composition in the reactivity of the precursors is studied. Highest purity is obtained in Sr = 0.15 and Mg = 0.20 composition, with relative density higher than 97%. The total elimination of typical secondary phases for these compositions, as SrLaGaO{sub 4} and SrLaGa{sub 3}O{sub 7}, allows the total conductivity of the ceramics to be improved. The influence of the grain size and the nature of the grain boundaries on the electrical characteristic of the ceramics are also discussed. (author)

Observation and Characterization of Fragile Organometallic Molecules Encapsulated in Single-Wall Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Daisuke Ogawa

2014-01-01

Full Text Available Thermally fragile tris(η5-cyclopentadienylerbium (ErCp3 molecules are encapsulated in single-wall carbon nanotubes (SWCNTs with high yield. We realized the encapsulation of ErCp3 with high filling ratio by using high quality SWCNTs at an optimized temperature under higher vacuum. Structure determination based on high-resolution transmission electron microscope observations together with the image simulations reveals the presence of almost free rotation of each ErCp3 molecule in SWCNTs. The encapsulation is also confirmed by X-ray diffraction. Trivalent character of Er ions (i.e., Er3+ is confirmed by X-ray absorption spectrum.

A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

Directory of Open Access Journals (Sweden)

Daniela Lehr

2015-11-01

Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.

Synthesis and optical properties of Mg-Al layered double hydroxides precursor powders

Directory of Open Access Journals (Sweden)

Chia-Hsuan Lin

2017-12-01

Full Text Available The synthesis and optical properties of Mg-Al layered double hydroxide (LDH precursor powders were investigated using X-ray diffraction (XRD, Fourier transform-infrared (FT-IR spectroscopy, transmission electron microscopy (TEM, selected area electron diffraction (SAED, high-resolution TEM (HRTEM, UV-transmission spectrometer, and fluorescence spectrophotometer. The FT-IR results show that the intense absorption at around 1363–1377 cm-1 can be assigned to the antisymmetric ν3 mode of interlayer carbonate anions because the LDH phase contains some CO32-. The XRD results show that all of the Mg-Al LDH precursor powders contain only a single phase of [Mg0.833Al0.167(OH2](CO30.083·(H2O0.75 but have broad and weak intensities of peaks. All of Mg-Al LDHs precursor powders before calcination have the same photoluminescence (PL spectra. Moreover, these spectra were excited at λex = 235 nm, and the broad emission band was in the range 325-650 nm. In the range, there were relatively strong intensity at around 360, 407 and 510 nm, respectively.

Effect of precursor concentration, temperature and capping group on the morphology of CdS nanoparticles

CSIR Research Space (South Africa)

Moloto, N

2008-01-01

Full Text Available A novel ligand to the synthesis of nanoparticles has been employed in this study. A Tetramethylthiuram disulphide cadmium complex (abundant in sulphur atoms) was used as a single-source precursor for the synthesis of CdS nanoparticles. The CdS...

Some peculiarities of zirconium tungstate synthesis by thermal decomposition of hydrothermal precursors

International Nuclear Information System (INIS)

Gubanov, Alexander I.; Dedova, Elena S.; Plyusnin, Pavel E.; Filatov, Eugeny Y.; Kardash, Tatyana Y.; Korenev, Sergey V.; Kulkov, Sergey N.

2014-01-01

Highlights: • Synthesis of ZrW 2 O 8 using hydrothermal method. • On hydrothermal synthesis optimal conc. of HCl in the reaction mixture is 2.3 M. • Thermal decomposition of ZrW 2 O 7 ((OH) 1.5 ,Cl 0.5 )·2H 2 O begins are 200 °S. • Amorphous intermediate crystallizes into cubic single-phase ZrW 2 O 8 above 550 °S. • ZrW 2 O 8 destructed at temperatures above 700 °S. - Abstract: This article discusses some peculiarities of the synthesis of ZrW 2 O 8 (1) using thermal decomposition of the precursor ZrW 2 O 7 ((OH) 1.5 ,Cl 0.5 )·2H 2 O (2) prepared by hydrothermal method. On hydrothermal synthesis of 2 the optimal concentration of hydrochloric acid in the reaction mixture is about 2.3 M. TG approach to determine the chemical composition of the precursor was suggested. It has been found that the precursor for the synthesis of zirconium tungstate has chemical formula 2. Thermal decomposition of the precursor 2 begins at 200 °S and affords an amorphous intermediate, which crystallizes as a cubic phase 1 above 550 °S with an exoeffect. The temperature of the beginning of the transition from amorphous to the crystalline state is 350 ± 25 °S

Synthesis and Use of [Cd(Detu2(OOCCH32]·H2O as Single Molecule Precursor for Cds Nanoparticles

Directory of Open Access Journals (Sweden)

Peter A. Ajibade

2013-01-01

Full Text Available Substituted thiourea ligands are of interest because they possess various donor sites for metal ions and their application in separation of metal ions and as antimicrobial agents. The coordination of the sulfur donor atom led to interest in them as precursor for semiconductor nanoparticles. In this study, cadmium(II complex of diethylthiourea was synthesized and characterized by elemental analysis, FTIR, and X-ray crystallography. Single crystal X-ray structure of the complex showed that the octahedral geometry around the Cd ion consists of two molecules of diethylthiourea acting as monodentate ligands and two chelating acetate ions. The thermal decomposition of the compound showed that it decomposed to give CdS. The compound was thermolysed in hexadecylamine (HDA to prepare HDA-capped CdS nanoparticles. The absorption spectrum showed blue shifts in its absorption band edges which clearly indicated quantum confinement effect, and the emission spectrum showed characteristic band edge luminescence. The broad diffraction peaks of the XRD pattern showed the materials to be of the nanometric size.

NATO Advanced Research Workshop on the Mechanisms of Reactions of Organometallic Compounds with Surfaces

CERN Document Server

Williams, J

1989-01-01

A NATO Advanced Research Workshop on the "Mechanisms of Reactions of Organometallic Compounds with Surfaces" was held in St. Andrews, Scotland in June 1988. Many of the leading international researchers in this area were present at the workshop and all made oral presentations of their results. In addition, significant amounts of time were set aside for Round Table discussions, in which smaller groups considered the current status of mechanistic knowledge, identified areas of dispute or disagreement, and proposed experiments that need to be carried out to resolve such disputes so as to advance our understanding of this important research area. All the papers presented at the workshop are collected in this volume, together with summaries of the conclusions reached at the Round Table discussions. The workshop could not have taken place without financial support from NATO, and donations were also received from Associated Octel, Ltd., STC Ltd., and Epichem Ltd., for which the organisers are very grateful. The orga...

Precision design of ethylene- and polar-monomer-based copolymers by organometallic-mediated radical polymerization

Science.gov (United States)

Kermagoret, Anthony; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

2014-03-01

The copolymerization of ethylene with polar monomers is a major challenge when it comes to the manufacture of materials with potential for a wide range of commercial applications. In the chemical industry, free-radical polymerization is used to make a large proportion of such copolymers, but the forcing conditions result in a lack of fine control over the architecture of the products. Herein we introduce a synthetic tool, effective under mild experimental conditions, for the precision design of unprecedented ethylene- and polar-monomer-based copolymers. We demonstrate how an organocobalt species can control the growth of the copolymer chains, their composition and the monomer distribution throughout the chain. By fine tuning the ethylene pressure during polymerization and by exploiting a unique reactive mode of the end of the organometallic chain, novel block-like copolymer structures can be prepared. This highly versatile synthetic platform provides access to a diverse range of polymer materials.

A pyrazolyl-based thiolato single-source precursor for the selective synthesis of isotropic copper-deficient copper(I) sulfide nanocrystals: synthesis, optical and photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Mondal, Gopinath; Santra, Ananyakumari; Bera, Pradip; Acharjya, Moumita [Vidyasagar University, Post Graduate Department of Chemistry, Panskura Banamali College (India); Jana, Sumanta [Indian Institute of Engineering Science and Technology (IIEST), Department of Chemistry (India); Chattopadhyay, Dipankar [University of Calcutta, Department of Polymer Science and Technology (India); Mondal, Anup [Indian Institute of Engineering Science and Technology (IIEST), Department of Chemistry (India); Seok, Sang Il [Korea Research Institute of Chemical Technology, KRICT-EPFL Global Research Laboratory, Division of Advanced Materials (Korea, Republic of); Bera, Pulakesh, E-mail: pbera.pbc.chem@gmail.com [Vidyasagar University, Post Graduate Department of Chemistry, Panskura Banamali College (India)

2016-10-15

Hexagonal copper-deficient copper(I) sulfide (Cu{sub 2-x}S, x = 0.03, 0.2) nanocrystals (NCs) are synthesized from a newly prepared single-source precursor (SP), [Cu(bdpa){sub 2}][CuCl{sub 2}], where bdpa is benzyl 3,5-dimethyl-pyrazole-1-carbodithioate. The SP is crystallized with space group Pī and possesses a distorted tetrahedron structure with a CuN{sub 2}S{sub 2} chromophore where the central copper is in +1 oxidation state. Distortion in copper(I) structure and the low decomposition temperature of SP make it favorable for the low-temperature solvent-assisted selective growth of high-copper content sulfides. The nucleation and growth of Cu{sub 2-x}S (x = 0.03, 0.2) are effectively controlled by the SP and the solvent in the solvothermal decomposition process. During decomposition, fragment benzyl thiol (PhCH{sub 2}SH) from SP effectively passivates the nucleus leading to spherical nanocrystals. Further, solvent plays an important role in the selective thermochemical transformation of Cu{sup I}-complex to Cu{sub 2-x}S (x = 0.03, 0.2) NCs. The chelating binders (solvent) like ethylene diamine (EN) and ethylene glycol (EG) prefer to form spherical Cu{sub 1.97}S nanoparticles (djurleite), whereas nonchelating hydrazine hydrate (HH) shows the tendency to furnish hexagonal platelets of copper-deficient Cu{sub 1.8}S. The optical band gap values (2.25–2.50 eV) show quantum confinement effect in the structure. The synthesized NCs display excellent catalytic activity (~87 %) toward photodegradation of organic dyes like Congo Red (CR) and Methylene Blue (MB).Graphical abstractA pyrazolyl-based thiolato single-source precursor for the selective synthesis of isotropic copper-deficient copper(I) sulfide nanocrystals: Synthesis, optical and photocatalytic activity.Gopinath Mondal, Ananyakumari Santra, Pradip Bera, Moumita Acharjya, Sumanta Jana, Dipankar Chattopadhyay, Anup Mondal, Sang Il Seok, Pulakesh Bera.

Preparation of superconductor precursor powders

Science.gov (United States)

Bhattacharya, Raghunath

1998-01-01

A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products.

Toward a theory of precursors

International Nuclear Information System (INIS)

Freivogel, Ben; Giddings, Steven B.; Lippert, Matthew

2002-01-01

To better understand the possible breakdown of locality in quantum gravitational systems, we pursue the identity of precursors in the context of the anti-de Sitter/conformal field theory correspondence. Holography implies a breakdown of standard bulk locality which we expect to occur only at extremely high energy. We consider precursors that encode bulk information causally disconnected from the boundary and whose measurement involves nonlocal bulk processes. We construct a toy model of holography which encapsulates the expected properties of precursors and compare it with previous such discussions. If these precursors can be identified in the gauge theory, they are almost certainly Wilson loops, perhaps with decorations, but the relevant information is encoded in the high-energy sector of the theory and should not be observable by low energy measurements. This would be in accord with the locality bound, which serves as a criterion for situations where breakdown of bulk locality is expected

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas; Le Qué mé ner, Fré dé ric; Bouhoute, Yassine; Szeto, Kai C.; De Mallmann, Aimery; Barman, Samir; Samantaray, Manoja; Delevoye, Laurent; Gauvin, Ré gis M.; Taoufik, Mostafa; Basset, Jean-Marie

2016-01-01

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas

2016-12-05

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

Chromocene in porous polystyrene: an example of organometallic chemistry in confined spaces.

Science.gov (United States)

Estephane, Jane; Groppo, Elena; Vitillo, Jenny G; Damin, Alessandro; Lamberti, Carlo; Bordiga, Silvia; Zecchina, Adriano

2009-04-07

In this work, we present an innovative approach to investigate the structure and the reactivity of a molecularly dispersed organometallic compound. The poly(4-ethylstyrene-co-divinylbenzene) microporous system (PS) is used as "solid solvent" able to molecularly disperse CrCp2, allowing: (i) its full characterization by means of spectroscopic techniques; (ii) the pressure and temperature dependent study of its interaction towards simple molecules like CO freely diffusing through the pores; (iii) the accurate determination of the reaction enthalpies by both direct microcalorimetric measurements and by an indirect spectroscopic approach. The experimental results are compared with quantum-mechanical calculations adopting the DFT approximation with two different functionals (namely BP86 and B3-LYP), showing the limitations and the potentialities of DFT methods in predicting the properties of open shell systems. It is concluded that modern DFT methods are able to give a coherent view of the vibrational properties of the CrCp2 molecule (and of the complex formed upon CO adsorption) that well match the experimental results, while the energetic predictions should be taken with care as they are significantly dependent on the functionals used.

The use of a well-defined surface organometallic complex as a probe molecule: [(≡SiO)TaVCl2Me2] shows different isolated silanol sites on the silica surface

KAUST Repository

Chen, Yin

2014-01-01

TaVCl2Me3 reacts with silica(700) and produces two different [(≡SiO)TaVCl2Me2] surface organometallic species, suggesting a heterogeneity of the highly dehydroxylated silica surface, which was studied with a combined experimental and theoretical approach. This journal is © the Partner Organisations 2014.

Expedient multi-step synthesis of organometallic complexes of Tc and Re in high effective specific activity. A new platform for the production of molecular imaging and therapy agents.

Science.gov (United States)

Causey, Patrick W; Besanger, Travis R; Schaffer, Paul; Valliant, John F

2008-09-15

For over thirty years, instant labeling kits which involve no purification steps have been the only method used to prepare (99m)Tc radiopharmaceuticals for clinical studies. To address the limitations imposed by instant kits, which is hindering the development of molecularly targeted Tc- and Re-based imaging and therapy agents, a new strategy for the rapid multistep synthesis and purification of organometallic technetium-based molecular probes and corresponding rhenium-based therapeutic analogues was developed. Beginning with MO4(-) (M = (99m)Tc, (186/188)Re), the carbonyl precursor [M(CO)3(H2O)3](+) was synthesized in 3 min in quantitative yield in a microwave reactor. A dipicolyl ligand was added and the chelate complex was formed in high yield in 2 min using microwave heating at 150 degrees C. This was followed by a new purification strategy to remove unlabeled ligand which entailed using a copper resin/C18 solid phase extraction protocol giving the desired product in greater than 78% decay corrected yield (dcy). Conversion to the corresponding succinimidyl active ester was achieved following a 5 min microwave irradiation at 120 degrees C and C18 solid phase extraction purification in 60% dcy. A series of amides were prepared subsequently by microwave heating at 120 degrees C for 5 min producing the desired targets in greater than 86% dcy. The reported method represents a move away from traditional instant kits toward more versatile platform synthesis and purification technologies that are better suited for producing modern molecular imaging and therapy agents.

Magnetic Properties of Ni-Zn Ferrite Prepared with the Layered Precursor Method

International Nuclear Information System (INIS)

Zhou Xin; Hou Zhi-Ling; Li Feng; Qi Xin

2010-01-01

We prepare NiZnFe 2 O 4 soft magnetic ferrites with different molar ratios with the layered precursor method and investigate their magnetic properties. In the layered precursor, metal ions are scattered on the layer plate in a certain way on account of the effect of lowest lattice energy and lattice orientation. After high temperature calcinations, spinel ferrites with uniform structural component and single magnetic domain can be obtained, and the magnetic property is improved greatly. NiZnFe 2 O 4 ferrites prepared have the best specific saturation magnetization of 79.15 emu·g −1 , higher than that of 68 emu·g −1 prepared by the chemical co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. Meanwhile the coercivity of NiZnFe 2 O 4 ferrites prepared by layered precursor method is 14 kA·m −1 , lower than that of 50 emu·g −1 prepared by the co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Precursors, gauge invariance, and quantum error correction in AdS/CFT

Energy Technology Data Exchange (ETDEWEB)

Freivogel, Ben; Jefferson, Robert A.; Kabir, Laurens [ITFA and GRAPPA, Universiteit van Amsterdam,Science Park 904, Amsterdam (Netherlands)

2016-04-19

A puzzling aspect of the AdS/CFT correspondence is that a single bulk operator can be mapped to multiple different boundary operators, or precursors. By improving upon a recent model of Mintun, Polchinski, and Rosenhaus, we demonstrate explicitly how this ambiguity arises in a simple model of the field theory. In particular, we show how gauge invariance in the boundary theory manifests as a freedom in the smearing function used in the bulk-boundary mapping, and explicitly show how this freedom can be used to localize the precursor in different spatial regions. We also show how the ambiguity can be understood in terms of quantum error correction, by appealing to the entanglement present in the CFT. The concordance of these two approaches suggests that gauge invariance and entanglement in the boundary field theory are intimately connected to the reconstruction of local operators in the dual spacetime.

Development of molecular precursors for deposition of indium sulphide thin film electrodes for photoelectrochemical applications.

Science.gov (United States)

Ehsan, Muhammad Ali; Peiris, T A Nirmal; Wijayantha, K G Upul; Olmstead, Marilyn M; Arifin, Zainudin; Mazhar, Muhammad; Lo, K M; McKee, Vickie

2013-08-14

Symmetrical and unsymmetrical dithiocarbamato pyridine solvated and non-solvated complexes of indium(III) with the general formula [In(S2CNRR')3]·n(py) [where py = pyridine; R,R' = Cy, n = 2 (1); R,R' = (i)Pr, n = 1.5 (2); NRR' = Pip, n = 0.5 (3) and R = Bz, R' = Me, n = 0 (4)] have been synthesized. The compositions, structures and properties of these complexes have been studied by means of microanalysis, IR and (1)H-NMR spectroscopy, X-ray single crystal and thermogravimetric (TG/DTG) analyses. The applicability of these complexes as single source precursors (SSPs) for the deposition of β-In2S3 thin films on fluorine-doped SnO2 (FTO) coated conducting glass substrates by aerosol-assisted chemical vapour deposition (AACVD) at temperatures of 300, 350 and 400 °C is studied. All films have been characterized by powder X-ray diffraction (PXRD) and energy dispersive X-ray analysis (EDX) for the detection of phase and stoichiometry of the deposit. Scanning electron microscopy (SEM) studies reveal that precursors (1)-(4), irrespective of different metal ligand design, generate comparable morphologies of β-In2S3 thin films at different temperatures. Direct band gap energies of 2.2 eV have been estimated from the UV-vis spectroscopy for the β-In2S3 films fabricated from precursors (1) and (4). The photoelectrochemical (PEC) properties of β-In2S3 were confirmed by recording the current-voltage plots under light and dark conditions. The plots showed anodic photocurrent densities of 1.25 and 0.65 mA cm(-2) at 0.23 V vs. Ag/AgCl for the β-In2S3 films made at 400 and 350 °C from the precursors (1) and (4), respectively. The photoelectrochemical performance indicates that the newly synthesised precursors are highly useful in fabricating β-In2S3 electrodes for solar energy harvesting and optoelectronic application.

H and C NMR investigations of Pb(Zr,Ti)O3 thin-film precursor solutions

International Nuclear Information System (INIS)

Assink, R.A.; Schwartz, R.W.

1993-01-01

Solvent reactions, ligand substitutions, and the oligomer/polymer backbone structure are important factors in the solution preparation of ceramic films. In this study the authors have used H and C NMR spectroscopy to characterize solvent and ligand effects in precursor solutions used for the deposition of ferroelectric PZT (lead zirconate titanate) thin films. Solutions were prepared by a sequential precursor addition method from carboxylate and alkoxide precursors of the three cations, and the solvent, acetic acid, methanol, and water. The results indicate that acetic acid was a key component in the solution preparation process. As observed previously for single metallic component systems, its presence resulted in esterification reactions, leading in the present case to the formation of methyl, isopropyl, and n-butyl acetates. Second, acetic acid functioned as a chemical modifier, or chelating agent, replacing essentially all of the alkoxy ligands of the original precursors. Since alkoxy replacement appeared to be complete, we may describe the PZT species formed in solution as oxo acetate in nature. Finally, the solvent and ligand behavior of a solution prepared by an inverted mixing order was compared to the behavior of the solution prepared by a sequential precursor addition. The spectra for the two solutions were similar, and only differences in the relative intensities of the ester and alcoholic resonances were observed. 29 refs., 5 figs., 3 tabs

The interrelationships of mathematical precursors in kindergarten.

Science.gov (United States)

Cirino, Paul T

2011-04-01

This study evaluated the interrelations among cognitive precursors across quantitative, linguistic, and spatial attention domains that have been implicated for math achievement in young children. The dimensionality of the quantity precursors was evaluated in 286 kindergarteners via latent variable techniques, and the contribution of precursors from each domain was established for small sums addition. Results showed a five-factor structure for the quantity precursors, with the major distinction being between nonsymbolic and symbolic tasks. The overall model demonstrated good fit and strong predictive power (R(2)=55%) for addition number combinations. Linguistic and spatial attention domains showed indirect relationships with outcomes, with their effects mediated by symbolic quantity measures. These results have implications for the measurement of mathematical precursors and yield promise for predicting future math performance. Copyright © 2010 Elsevier Inc. All rights reserved.

Some peculiarities of zirconium tungstate synthesis by thermal decomposition of hydrothermal precursors

Energy Technology Data Exchange (ETDEWEB)

Gubanov, Alexander I., E-mail: gubanov@niic.nsc.su [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Dedova, Elena S. [Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, pr. Akademicheskii 2/4, 634021 Tomsk (Russian Federation); Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk (Russian Federation); Plyusnin, Pavel E.; Filatov, Eugeny Y. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Kardash, Tatyana Y. [Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 5, 630090 Novosibirsk (Russian Federation); Korenev, Sergey V. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Kulkov, Sergey N. [Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, pr. Akademicheskii 2/4, 634021 Tomsk (Russian Federation); Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk (Russian Federation)

2014-12-10

Highlights: • Synthesis of ZrW{sub 2}O{sub 8} using hydrothermal method. • On hydrothermal synthesis optimal conc. of HCl in the reaction mixture is 2.3 M. • Thermal decomposition of ZrW{sub 2}O{sub 7}((OH){sub 1.5},Cl{sub 0.5})·2H{sub 2}O begins are 200 °S. • Amorphous intermediate crystallizes into cubic single-phase ZrW{sub 2}O{sub 8} above 550 °S. • ZrW{sub 2}O{sub 8} destructed at temperatures above 700 °S. - Abstract: This article discusses some peculiarities of the synthesis of ZrW{sub 2}O{sub 8} (1) using thermal decomposition of the precursor ZrW{sub 2}O{sub 7}((OH){sub 1.5},Cl{sub 0.5})·2H{sub 2}O (2) prepared by hydrothermal method. On hydrothermal synthesis of 2 the optimal concentration of hydrochloric acid in the reaction mixture is about 2.3 M. TG approach to determine the chemical composition of the precursor was suggested. It has been found that the precursor for the synthesis of zirconium tungstate has chemical formula 2. Thermal decomposition of the precursor 2 begins at 200 °S and affords an amorphous intermediate, which crystallizes as a cubic phase 1 above 550 °S with an exoeffect. The temperature of the beginning of the transition from amorphous to the crystalline state is 350 ± 25 °S.

One-pot synthesis of highly luminescent InP/ZnS nanocrystals without precursor injection.

Science.gov (United States)

Li, Liang; Reiss, Peter

2008-09-03

InP/ZnS core/shell nanocrystals are prepared using a single-step heating-up method relying on the difference in reactivity of the applied InP and ZnS precursors. The obtained particles exhibit size-dependent emission in the range of 480-590 nm, a fluorescence quantum yield of 50-70%, and high photostability.

Influence of aminosilane precursor concentration on physicochemical properties of composite Nafion membranes for vanadium redox flow battery applications

Science.gov (United States)

Kondratenko, Mikhail S.; Karpushkin, Evgeny A.; Gvozdik, Nataliya A.; Gallyamov, Marat O.; Stevenson, Keith J.; Sergeyev, Vladimir G.

2017-02-01

A series of composite proton-exchange membranes have been prepared via sol-gel modification of commercial Nafion membranes with [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane. The structure and physico-chemical properties (water uptake, ion-exchange capacity, vanadyl ion permeability, and proton conductivity) of the prepared composite membranes have been studied as a function of the precursor loading (degree of the membrane modification). If the amount of the precursor is below 0.4/1 M ratio of the amino groups of the precursor to the sulfonic groups of Nafion, the composite membranes exhibit decreased vanadium ion permeability while having relatively high proton conductivity. With respect to the use of a non-modified Nafion membrane, the performance of the composite membrane with an optimum precursor loading in a single-cell vanadium redox flow battery demonstrates enhanced energy efficiency in 20-80 mA cm-2 current density range. The maximum efficiency increase of 8% is observed at low current densities.

Different processing of CAPA and pyrokinin precursors in the giant mealworm beetle Zophobas atratus (Tenebrionidae) and the boll weevil Anthonomus grandis grandis (Curculionidae).

Science.gov (United States)

Neupert, Susanne; Marciniak, Pawel; Köhler, Rene; Nachman, Ronald J; Suh, Charles P-C; Predel, Reinhard

2018-03-01

Capa and pyrokinin (pk) genes in hexapods share a common evolutionary origin. Using transcriptomics and peptidomics, we analyzed products of these genes in two beetles, the giant mealworm beetle (Zophobas atratus; Tenebrionidae) and the boll weevil (Anthonomus grandis grandis; Curculionidae). Our data revealed that even within Coleoptera, which represents a very well-defined group of insects, highly different evolutionary developments occurred in the neuropeptidergic system. These differences, however, primarily affect the general structure of the precursors and differential processing of mature peptides and, to a lesser degree, the sequences of the active core motifs. With the differential processing of the CAPA-precursor in Z. atratus we found a perfect example of completely different products cleaved from a single neuropeptide precursor in different cells. The CAPA precursor in abdominal ganglia of this species yields primarily periviscerokinins (PVKs) whereas processing of the same precursor in neurosecretory cells of the subesophageal ganglion results in CAPA-tryptoPK and a novel CAPA-PK. Particularly important was the detection of that CAPA-PK which has never been observed in the CNS of insects before. The three different types of CAPA peptides (CAPA-tryptoPK, CAPA-PK, PVK) each represent potential ligands which activate different receptors. In contrast to the processing of the CAPA precursor from Z. atratus, no indications of a differential processing of the CAPA precursor were found in A. g. grandis. These data suggest that rapid evolutionary changes regarding the processing of CAPA precursors were still going on when the different beetle lineages diverged. The sequence of the single known PVK of A. g. grandis occupies a special position within the known PVKs of insects and might serve asa basis to develop lineage-specific peptidomimetics capable of disrupting physiological processes regulated by PVKs. Copyright © 2017 Elsevier Inc. All rights reserved.

Precursors of vertebrate peptide antibiotics dermaseptin b and adenoregulin have extensive sequence identities with precursors of opioid peptides dermorphin, dermenkephalin, and deltorphins.

Science.gov (United States)

Amiche, M; Ducancel, F; Mor, A; Boulain, J C; Menez, A; Nicolas, P

1994-07-08

The dermaseptins are a family of broad spectrum antimicrobial peptides, 27-34 amino acids long, involved in the defense of the naked skin of frogs against microbial invasion. They are the first vertebrate peptides to show lethal effects against the filamentous fungi responsible for severe opportunistic infections accompanying immunodeficiency syndrome and the use of immunosuppressive agents. A cDNA library was constructed from skin poly(A+) RNA of the arboreal frog Phyllomedusa bicolor and screened with an oligonucleotide probe complementary to the COOH terminus of dermaseptin b. Several clones contained a full-length DNA copy of a 443-nucleotide mRNA that encoded a 78-residue dermaseptin b precursor protein. The deduced precursor contained a putative signal sequence at the NH2 terminus, a 20-residue spacer sequence extremely rich (60%) in glutamic and aspartic acids, and a single copy of a dermaseptin b progenitor sequence at the COOH terminus. One clone contained a complete copy of adenoregulin, a 33-residue peptide reported to enhance the binding of agonists to the A1 adenosine receptor. The mRNAs encoding adenoregulin and dermaseptin b were very similar: 70 and 75% nucleotide identities between the 5'- and 3'-untranslated regions, respectively; 91% amino acid identity between the signal peptides; 82% identity between the acidic spacer sequences; and 38% identity between adenoregulin and dermaseptin b. Because adenoregulin and dermaseptin b have similar precursor designs and antimicrobial spectra, adenoregulin should be considered as a new member of the dermaseptin family and alternatively named dermaseptin b II. Preprodermaseptin b and preproadenoregulin have considerable sequence identities to the precursors encoding the opioid heptapeptides dermorphin, dermenkephalin, and deltorphins. This similarity extended into the 5'-untranslated regions of the mRNAs. These findings suggest that the genes encoding the four preproproteins are all members of the same family

Synthesis of a sugar-organometallic compound 1,1′-difurfurylferrocene and its microwave preparation of carbon/iron oxide nanocomposite

International Nuclear Information System (INIS)

Zhao Shanyu; Cooper, Daniel C.; Xu, Haixun; Zhu Pinghua; Suggs, J. William

2013-01-01

Graphical abstract: In order to synthesize a carbon–metal or metal oxide combination sphere, carbonaceous resource furfural was introduced, which was nucleophilic treated with 1,1′-dilithioferrocene to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1′-difurfurylferrocene, which can be hydrothermally treated in a microwave reactor to give 300–500 nm microspheres with the α-Fe 2 O 3 or Fe 3 O 4 formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses. Highlights: ► We synthesized 1,1′-difurfurylferrocene by nucleophilic treating furfural with 1,1′-dilithioferrocene. ► 1,1′-Difurfurylferrocene can be hydrothermally treated by microwave to give microspheres with iron oxides on the surface. ► 1,1′-Difurfurylferrocene has 2 reactive furanose units, which form carbonspheres and ferrocenyl can give iron oxides. ► REDOX atmosphere influences the coating structures. - Abstract: In order to synthesize a carbon–metal or metal oxide combination sphere, carbonaceous resource furfural 1 was introduced, which was nucleophilic treated with 1,1′-dilithioferrocene 2 to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1′-difurfurylferrocene 3. 1,1′-Difurfurylferrocene 3 can be hydrothermally treated in a microwave reactor to give 300–500 nm microspheres with the α-Fe 2 O 3 or Fe 3 O 4 nanocrystals formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses.

Synthesis of a sugar-organometallic compound 1,1 Prime -difurfurylferrocene and its microwave preparation of carbon/iron oxide nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Zhao Shanyu, E-mail: syzhao65@gmail.com [School of Environmental and Safty Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Department of Chemistry, Brown University, Providence, RI 02912-9108 (United States); Cooper, Daniel C. [Department of Chemistry, Brown University, Providence, RI 02912-9108 (United States); Xu, Haixun [Institute of Building Materials, Dalian University of Technology, Dalian, Liaoning 116024 (China); Zhu Pinghua [School of Environmental and Safty Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Suggs, J. William, E-mail: j_suggs@brown.edu [Department of Chemistry, Brown University, Providence, RI 02912-9108 (United States)

2013-01-01

Graphical abstract: In order to synthesize a carbon-metal or metal oxide combination sphere, carbonaceous resource furfural was introduced, which was nucleophilic treated with 1,1 Prime -dilithioferrocene to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1 Prime -difurfurylferrocene, which can be hydrothermally treated in a microwave reactor to give 300-500 nm microspheres with the {alpha}-Fe{sub 2}O{sub 3} or Fe{sub 3}O{sub 4} formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses. Highlights: Black-Right-Pointing-Pointer We synthesized 1,1 Prime -difurfurylferrocene by nucleophilic treating furfural with 1,1 Prime -dilithioferrocene. Black-Right-Pointing-Pointer 1,1 Prime -Difurfurylferrocene can be hydrothermally treated by microwave to give microspheres with iron oxides on the surface. Black-Right-Pointing-Pointer 1,1 Prime -Difurfurylferrocene has 2 reactive furanose units, which form carbonspheres and ferrocenyl can give iron oxides. Black-Right-Pointing-Pointer REDOX atmosphere influences the coating structures. - Abstract: In order to synthesize a carbon-metal or metal oxide combination sphere, carbonaceous resource furfural 1 was introduced, which was nucleophilic treated with 1,1 Prime -dilithioferrocene 2 to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1 Prime -difurfurylferrocene 3. 1,1 Prime -Difurfurylferrocene 3 can be hydrothermally treated in a microwave reactor to give 300-500 nm microspheres with the {alpha}-Fe{sub 2}O{sub 3} or Fe{sub 3}O{sub 4} nanocrystals formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses.

Investigation of Spectral Characteristics of Pulsed Xenon Lamps for Combined Photochemical Degradation of Organometallic Compounds in Liquid Radioactive Waste

Directory of Open Access Journals (Sweden)

M. A. Mishakov

2017-01-01

Full Text Available The paper considers the composition of liquid radioactive wastes from the nuclear plants. Using traditional ways to extract organometallic compounds formed, when using the deactivation solutions to clean the surfaces of nuclear plant rooms, are complicated. The paper studies the edge-cutting methods of solving this problem. Its proposal is to use a combined ultraviolet treatment for organometallic compounds degradation based on ethylenediaminetetraacetic acid (EDTA via pulsed xenon lamps. A potential use of the tubular and spherical geometry lamps is examined and advantages, disadvantages and features of these lamps are described. Instead of the pure EDTA the experiments used its disodium salt (Na2-EDTA. The hydrogen peroxide was used as an extra oxidizer. Absorption spectrums of solutions with various Na2-EDTA - hydrogen peroxide ratio were measured. It is found that the absorbance curve maximum is in the shortwave spectrum region (λ < 210 nm. The use of amalgam lamps of monochromatic radiation at wavelength λ = 254 nm will result only in formation of hydroxyl radicals but direct destruction processes of EDTA molecules due to radiation will be rare, and this decreases efficiency of their use.The spectral radiation characteristics of various continuum spectrum pulsed xenon lamps was measured. The experimental data expressed in relative units were compared with the emission spectrum of an absolutely black body. The paper shows that in spherical lamps high brightness temperature can be reached. Thus, in spherical lamps it is possible to obtain a spectrum, which is in maximum correlation with the absorption spectrum of the solutions under study, thereby making them a prospective radiation source for photo-degradation of EDTA compounds. For drawing a final conclusion it is necessary to conduct researches in order to compare Na2-EDTA degradation via tubular and spherical xenon lamps.

Lattice site location of optical centers in GaN:Eu light emitting diode material grown by organometallic vapor phase epitaxy

KAUST Repository

Lorenz, K.; Alves, E.; Roqan, Iman S.; O’ Donnell, K. P.; Nishikawa, A.; Fujiwara, Y.; Boćkowski, M.

2010-01-01

Eu-doped GaN was grown by organometallic vapor phase epitaxy at temperatures from 900 to 1100 °C. Eu incorporation is influenced by temperature with the highest concentration found for growth at 1000 °C. In all samples, Eu is incorporated entirely on substitutional Ga sites with a slight displacement which is highest (∼0.2 Å) in the sample grown at 900 °C and mainly directed along the c-axis. The major optical Eu3+ centers are identical for in situdoped and ion-implanted samples after high temperature and pressure annealing. The dominant Eu3+luminescence lines are attributed to isolated, substitutional Eu.

Lattice site location of optical centers in GaN:Eu light emitting diode material grown by organometallic vapor phase epitaxy

KAUST Repository

Lorenz, K.

2010-09-16

Eu-doped GaN was grown by organometallic vapor phase epitaxy at temperatures from 900 to 1100 °C. Eu incorporation is influenced by temperature with the highest concentration found for growth at 1000 °C. In all samples, Eu is incorporated entirely on substitutional Ga sites with a slight displacement which is highest (∼0.2 Å) in the sample grown at 900 °C and mainly directed along the c-axis. The major optical Eu3+ centers are identical for in situdoped and ion-implanted samples after high temperature and pressure annealing. The dominant Eu3+luminescence lines are attributed to isolated, substitutional Eu.

Silica-supported, single-site titanium catalysts for olefin epoxidation. A molecular precursor strategy for control of catalyst structure.

Science.gov (United States)

Jarupatrakorn, Jonggol; Don Tilley, T

2002-07-17

A molecular precursor approach involving simple grafting procedures was used to produce site-isolated titanium-supported epoxidation catalysts of high activity and selectivity. The tris(tert-butoxy)siloxy titanium complexes Ti[OSi(O(t)Bu)(3)](4) (TiSi4), ((i)PrO)Ti[OSi(O(t)Bu)(3)](3) (TiSi3), and ((t)BuO)(3)TiOSi(O(t)Bu)(3) (TiSi) react with the hydroxyl groups of amorphous Aerosil, mesoporous MCM-41, and SBA-15 via loss of HO(t)Bu and/or HOSi(O(t)Bu)(3) and introduction of titanium species onto the silica surface. Powder X-ray diffraction, nitrogen adsorption/desorption, infrared, and diffuse reflectance ultraviolet spectroscopies were used to investigate the structures and chemical natures of the surface-bound titanium species. The titanium species exist mainly in isolated, tetrahedral coordination environments. Increasing the number of siloxide ligands in the molecular precursor decreases the amount of titanium that can be introduced this way, but also enhances the catalytic activity and selectivity for the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. In addition, the high surface area mesoporous silicas (MCM-41 and SBA-15) are more effective than amorphous silica as supports for these catalysts. Supporting TiSi3 on the SBA-15 affords highly active cyclohexene epoxidation catalysts (0.25-1.77 wt % Ti loading) that provide turnover frequencies (TOFs) of 500-1500 h(-1) after 1 h (TOFs are reduced by about half after calcination). These results demonstrate that oxygen-rich siloxide complexes of titanium are useful as precursors to supported epoxidation catalysts.

Thermally activated, single component epoxy systems

KAUST Repository

Unruh, David A.; Pastine, Stefan J.; Moreton, Jessica C.; Frechet, Jean

2011-01-01

A single component epoxy system in which the resin and hardener components found in many two-component epoxies are combined onto the same molecule is described. The single molecule precursor to the epoxy resin contains both multiple epoxide moieties and a diamine held latent by thermally degradable carbamate linkages. These bis-carbamate "single molecule epoxies" have an essentially infinite shelf life and access a significant range in curing temperatures related to the structure of the carbamate linkages used. © 2011 American Chemical Society.

Thermally activated, single component epoxy systems

KAUST Repository

Unruh, David A.

2011-08-23

A single component epoxy system in which the resin and hardener components found in many two-component epoxies are combined onto the same molecule is described. The single molecule precursor to the epoxy resin contains both multiple epoxide moieties and a diamine held latent by thermally degradable carbamate linkages. These bis-carbamate "single molecule epoxies" have an essentially infinite shelf life and access a significant range in curing temperatures related to the structure of the carbamate linkages used. © 2011 American Chemical Society.

Synthesis and characterization of graphene layers prepared by low-pressure chemical vapor deposition using triphenylphosphine as precursor

Energy Technology Data Exchange (ETDEWEB)

Mastrapa, G.C.; Maia da Costa, M.E.H. Maia [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Larrude, D.G., E-mail: dunigl@vdg.fis.puc-rio.br [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Freire, F.L. [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Brazilian Center for Physical Research, 22290-180, Rio de Janeiro, RJ (Brazil)

2015-09-15

The synthesis of a single-layer graphene using a low-pressure Chemical Vapor Deposition (CVD) system with triphenylphosphine as precursor is reported. The amount of triphenylphosphine used as precursor was in the range of 10–40 mg. Raman spectroscopy was employed to analyze samples prepared with 10 mg of the precursor, and these spectra were found typical of graphene. The Raman measurements indicate that the progressive degradation of graphene occurs as the amount of triphenylphosphine increases. X-ray photoelectron spectroscopy measurements were performed to investigate the different chemical environments involving carbon and phosphorous atoms. Scanning electron microscopy and transmission electron microscopy were also employed and the results reveal the formation of dispersed nanostructures on top of the graphene layer, In addition, the number of these nanostructures is directly related to the amount of precursor used for sample growth. - Highlights: • We grow graphene using the solid precursor triphenylphosphine. • Raman analysis confirms the presence of monolayer graphene. • SEM images show the presence of small dark areas dispersed on the graphene surface. • Raman I{sub D}/I{sub G} ratio increases in the dark region of the graphene surface.

Effect of Precursor Concentration on Structural Optical and Electrical Properties of NiO Thin Films Prepared by Spray Pyrolysis

Directory of Open Access Journals (Sweden)

Rafia Barir

2017-01-01

Full Text Available Undoped nickel oxide (NiO thin films were deposited on 500°C heated glass substrates using spray pyrolysis method at (0.015–0.1 M range of precursor. The latter was obtained by decomposition of nickel nitrate hexahydrate in double distilled water. Effect of precursor concentration on structural, optical, and electrical properties of NiO thin films was investigated. X-ray diffraction (XRD shows the formation of NiO under cubic structure with single diffraction peak along (111 plane at 2θ=37.24°. When precursor concentration reaches 0.1 M, an increment in NiO crystallite size over 37.04 nm was obtained indicating the product nano structure. SEM images reveal that beyond 0.04 M as precursor concentration the substrate becomes completely covered with NiO and thin films exhibit formation of nano agglomerations at the top of the sample surface. Ni-O bonds vibrations modes in the product of films were confirmed by FT-IR analysis. Transparency of the films ranged from 57 to 88% and band gap energy of the films decreases from 3.68 to 3.60 eV with increasing precursor concentration. Electrical properties of the elaborated NiO thin films were correlated to the precursor concentration.

High quality long-wavelength lasers grown by atmospheric organometallic vapor phase epitaxy using tertiarybutylarsine

International Nuclear Information System (INIS)

Miller, B.I.; Young, M.G.; Oron, M.; Koren, U.; Kisker, D.

1990-01-01

High quality long-wavelength InGaAsP/InP lasers were grown by atmospheric organometallic vapor phase epitaxy using tertiarybutylarsine (TBA) as a substitute for AsH 3 . Electrical and photoluminescence measurements on InGaAs and InGaAsP showed that TBA-grown material was at least as good as AsH 3 material in terms of suitability for lasers. From two wafers grown by TBA, current thresholds I th as low as 11 mA were obtained for a 2-μm-wide semi-insulating blocking planar buried heterostructure laser lasing near 1.3 μm wavelength. The differential quantum efficiencies η D were as high as 21%/facet with a low internal loss α=21 cm -1 . In addition I th as low as 18 mA and η D as high as 18% have been obtained for multiplequantum well lasers at 1.54 μm wavelength. These results show that TBA might be used to replace AsH 3 without compromising on laser performance

The Sommerfeld precursor in photonic crystals

NARCIS (Netherlands)

Uitham, R; Hoenders, BJ

2006-01-01

We calculate the Sommerfeld precursor that results after transmission of a generic electromagnetic plane wave pulse with transverse electric polarization, through a one-dimensional rectangular N-layer photonic crystal with two slabs per layer. The shape of this precursor equals the shape of the

Silicon structuring by etching with liquid chlorine and fluorine precursors using femtosecond laser pulses

International Nuclear Information System (INIS)

Radu, C.; Simion, S.; Zamfirescu, M.; Ulmeanu, M.; Enculescu, M.; Radoiu, M.

2011-01-01

The aim of this study is to investigate the micrometer and submicrometer scale structuring of silicon by liquid chlorine and fluorine precursors with 200 fs laser pulses working at both fundamental (775 nm) and frequency doubled (387 nm) wavelengths. The silicon surface was irradiated at normal incidence by immersing the Si (111) substrates in a glass container filled with liquid chlorine (CCl 4 ) and fluorine (C 2 Cl 3 F 3 ) precursors. We report that silicon surfaces develop an array of spikes with single step irradiation processes at 775 nm and equally at 387 nm. When irradiating the Si surface with 400 pulses at 330 mJ/cm 2 laser fluence and a 775 nm wavelength, the average height of the formed Si spikes in the case of fluorine precursors is 4.2 μm, with a full width at half maximum of 890 nm. At the same irradiation wavelength chlorine precursors develop Si spikes 4 μm in height and with a full width at half maximum of 2.3 μm with irradiation of 700 pulses at 560 mJ/cm 2 laser fluence. Well ordered areas of submicrometer spikes with an average height of about 500 nm and a width of 300 nm have been created by irradiation at 387 nm by chlorine precursors, whereas the fluorine precursors fabricate spikes with an average height of 700 nm and a width of about 200 nm. Atomic force microscopy and scanning electron microscopy of the surface show that the formation of the micrometer and sub-micrometer spikes involves a combination of capillary waves on the molten silicon surface and laser-induced etching of silicon, at both 775 nm and 387 nm wavelength irradiation. The energy-dispersive x-ray measurements indicate the presence of chlorine and fluorine precursors on the structured surface. The fluorine precursors create a more ordered area of Si spikes at both micrometer and sub-micrometer scales. The potential use of patterned Si substrates with gradient topography as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell

The preparation of HfC/C ceramics via molecular design.

Science.gov (United States)

Inzenhofer, Kathrin; Schmalz, Thomas; Wrackmeyer, Bernd; Motz, Günter

2011-05-07

Polymer derived ceramics have received lots of attention throughout the last few decades. Unfortunately, only a few precursor systems have been developed, focusing on silicon based polymers and ceramics, respectively. Herein, the synthesis of novel hafnium containing organometallic polymers by two different approaches is reported. Dialkenyl substituted hafnocene monomers were synthesized and subsequently polymerized via a free radical mechanism. Salt metathesis reactions of hafnocene dichloride with bifunctional linkers led to the formation of polymeric materials. NMR spectroscopic methods--in solution as well as in the solid state--were used to characterize the organometallic polymers. Ceramics were finally obtained after cross-linking and thermal treatment under argon (T(max) = 1800 °C). SEM investigations, elemental analyses, Raman spectroscopy and XRD investigations identified the pyrolyzed products as partially crystalline HfC/C mixed phases.

Progress in molecular precursors for electronic materials

Energy Technology Data Exchange (ETDEWEB)

Buhro, W.E. [Washington Univ., St. Louis, MO (United States)

1996-09-01

Molecular-precursor chemistry provides an essential underpinning to all electronic-materials technologies, including photovoltaics and related areas of direct interest to the DOE. Materials synthesis and processing is a rapidly developing field in which advances in molecular precursors are playing a major role. This article surveys selected recent research examples that define the exciting current directions in molecular-precursor science. These directions include growth of increasingly complex structures and stoichiometries, surface-selective growth, kinetic growth of metastable materials, growth of size-controlled quantum dots and quantum-dot arrays, and growth at progressively lower temperatures. Continued progress in molecular-precursor chemistry will afford precise control over the crystal structures, nanostructures, and microstructures of electronic materials.

Efficient singlet exciton fission in pentacene prepared from a soluble precursor

Directory of Open Access Journals (Sweden)

Maxim Tabachnyk

2016-11-01

Full Text Available Carrier multiplication using singlet exciton fission (SF to generate a pair of spin-triplet excitons from a single optical excitation has been highlighted as a promising approach to boost the photocurrent in photovoltaics (PVs thereby allowing PV operation beyond the Shockley-Queisser limit. The applicability of many efficient fission materials, however, is limited due to their poor solubility. For instance, while acene-based organics such as pentacene (Pc show high SF yields (up to200%, the plain acene backbone renders the organic molecule insoluble in common organic solvents. Previous approaches adding solubilizing side groups such as bis(tri-iso-propylsilylethynyl to the Pc core resulted in low vertical carrier mobilities due to reduction of the transfer integrals via steric hindrance, which prevented high efficiencies in PVs. Here we show how to achieve good solubility while retaining the advantages of molecular Pc by using a soluble precursor route. The precursor fully converts into molecular Pc through thermal removal of the solubilizing side groups upon annealing above 150 °C in the solid state. The annealed precursor shows small differences in the crystallinity compared to evaporated thin films of Pc, indicating that the Pc adopts the bulk rather than surface polytype. Furthermore, we identify identical SF properties such as sub-100 fs fission time and equally long triplet lifetimes in both samples.

Current Progress in Solution Precursor Plasma Spraying of Cermets: A Review

Directory of Open Access Journals (Sweden)

Romnick Unabia

2018-06-01

Full Text Available Ceramic and metal composites, known also as cermets, may considerably improve many material properties with regards to that of initial components. Hence, cermets are frequently applied in many technological fields. Among many processes which can be employed for cermet manufacturing, thermal spraying is one of the most frequently used. Conventional plasma spraying of powders is a popular and cost-effective manufacturing process. One of its most recent innovations, called solution precursor plasma spraying (SPPS, is an emerging coating deposition method which uses homogeneously mixed solution precursors as a feedstock. The technique enables a single-step deposition avoiding the powder preparation procedures. The nanostructured coatings developed by SPPS increasingly find a place in the field of surface engineering. The present review shows the recent progress in the fabrication of cermets using SPPS. The influence of starting solution precursors, such as their chemistry, concentration, and solvents used, to the micro-structural characteristics of cermet coatings is discussed. The effect of the operational plasma spray process parameters such as solution injection mode to the deposition process and coatings’ microstructure is also presented. Moreover, the advantages of the SPPS process and its drawbacks compared to the conventional powder plasma spraying process are discussed. Finally, some applications of SPPS cermet coatings are presented to understand the potential of the process.

Lessons learned on probabilistic methodology for precursor analyses

Energy Technology Data Exchange (ETDEWEB)

Babst, Siegfried [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Berlin (Germany); Wielenberg, Andreas; Gaenssmantel, Gerhard [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Garching (Germany)

2016-11-15

Based on its experience in precursor assessment of operating experience from German NPP and related international activities in the field, GRS has identified areas for enhancing probabilistic methodology. These are related to improving the completeness of PSA models, to insufficiencies in probabilistic assessment approaches, and to enhancements of precursor assessment methods. Three examples from the recent practice in precursor assessments illustrating relevant methodological insights are provided and discussed in more detail. Our experience reinforces the importance of having full scope, current PSA models up to Level 2 PSA and including hazard scenarios for precursor analysis. Our lessons learned include that PSA models should be regularly updated regarding CCF data and inclusion of newly discovered CCF mechanisms or groups. Moreover, precursor classification schemes should be extended to degradations and unavailabilities of the containment function. Finally, PSA and precursor assessments should put more emphasis on the consideration of passive provisions for safety, e. g. by sensitivity cases.

Lessons learned on probabilistic methodology for precursor analyses

International Nuclear Information System (INIS)

Babst, Siegfried; Wielenberg, Andreas; Gaenssmantel, Gerhard

2016-01-01

Based on its experience in precursor assessment of operating experience from German NPP and related international activities in the field, GRS has identified areas for enhancing probabilistic methodology. These are related to improving the completeness of PSA models, to insufficiencies in probabilistic assessment approaches, and to enhancements of precursor assessment methods. Three examples from the recent practice in precursor assessments illustrating relevant methodological insights are provided and discussed in more detail. Our experience reinforces the importance of having full scope, current PSA models up to Level 2 PSA and including hazard scenarios for precursor analysis. Our lessons learned include that PSA models should be regularly updated regarding CCF data and inclusion of newly discovered CCF mechanisms or groups. Moreover, precursor classification schemes should be extended to degradations and unavailabilities of the containment function. Finally, PSA and precursor assessments should put more emphasis on the consideration of passive provisions for safety, e. g. by sensitivity cases.

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

Science.gov (United States)

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

2014-04-11

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

Earthquakes: hydrogeochemical precursors

Science.gov (United States)

Ingebritsen, Steven E.; Manga, Michael

2014-01-01

Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

Magnetic reconnection and precursor effect in coaxial discharge

International Nuclear Information System (INIS)

Masoud, M.M.; Soliman, H.M.; El-Khalafawy, T.A.

1988-01-01

A precursor pulse was observed ahead of the plasma sheath produced by a coaxial electrode discharge system. The velocity of the precursor pulse was 4x10 7 cmS -1 and the velocity of the plasma sheath was 6x10 6 cmS -1 . The precursor pulse was unaffected when an axial magnetic field of 6 K.G. was applied to the propagation chamber, while the plasma sheath velocity increased and downstream structure were changed. The precursor pulse was split, sometimes, into two or more peaks, had the same shape and structure of the original one. The rest gas was heated up to 20 e.V. when the precursor pulse was destructed. The precursor pulse propagation mechanism and parameters showed that it had a solitary wave structure and behaviour. A reversed magnetic field was detected, when the plasma sheath had diamagnetic properties, where magnetic reconnection took place. Magnetic reconnection was responsible for energy transfiguration and wave generation. This was due to acceleration mechanism of charged particles occurred by the induced electric field at the moment of magnetic reconnection. The detected induced electric field had a high field intensity and fast rise time pulse. Several instabilities were referred to magnetic reconnection and the precursor pulse observed was a result of such instabilities

Identified EM Earthquake Precursors

Science.gov (United States)

Jones, Kenneth, II; Saxton, Patrick

2014-05-01

Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for

Simultaneous removal of ammonia and N-nitrosamine precursors from high ammonia water by zeolite and powdered activated carbon.

Science.gov (United States)

Xue, Runmiao; Donovan, Ariel; Zhang, Haiting; Ma, Yinfa; Adams, Craig; Yang, John; Hua, Bin; Inniss, Enos; Eichholz, Todd; Shi, Honglan

2018-02-01

When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products (DBPs) may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine (NDMA), may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes. The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon (PAC) sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than 67% ammonia and 70%-100% N-nitrosamine precursors were removed by Mordenite zeolite (except 3-(dimethylaminomethyl)indole (DMAI) and 4-dimethylaminoantipyrine (DMAP)). PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors (dimethylamine (DMA), ethylmethylamine (EMA), diethylamine (DEA), dipropylamine (DPA), trimethylamine (TMA), DMAP, and DMAI) during the alum coagulation process. Copyright © 2017. Published by Elsevier B.V.

Bleogens: Cactus-Derived Anti-Candida Cysteine-Rich Peptides with Three Different Precursor Arrangements

Directory of Open Access Journals (Sweden)

Shining Loo

2017-12-01

Full Text Available Cysteine-rich peptides (CRPs play important host-defense roles in plants. However, information concerning CRPs in the Cactaceae (cactus family is limited, with only a single cactus-derived CRP described to date. Here, we report the identification of 15 novel CRPs with three different precursor architectures, bleogens pB1-15 from Pereskia bleo of the Cactaceae family. By combining proteomic and transcriptomic methods, we showed that the prototype, bleogen pB1, contained 36 amino acid residues, a six-cysteine motif typical of the six-cysteine-hevein-like peptide (6C-HLP family, and a type I two-domain precursor consisting of an endoplasmic reticulum (ER and a mature domain. In contrast, the precursors of the other 14 bleogens contained a type II three-domain architecture with a propeptide domain inserted between the ER and the mature bleogen domain. Four of these 14 bleogens display a third type of architecture with a tandemly repeating bleogen domain. A search of the Onekp database revealed that <1% plant species possess three different precursor architectures for the biosynthesis of 6C-HLPs, including Lophophora williamsii, Pereskia aculeate, Portulaca cryptopetala, Portulaca oleracea, Portulaca suffruticosa, and Talinum sp. NMR analysis confirmed that bleogen pB1 has cystine-knot disulfide connectivity as well as a two-beta-sheet and a four-loop structural fold that is similar to other 6C-HLPs. Sequence analysis, structural studies, and in silico modeling revealed that bleogen pB1 has a cation-polar-cation motif, a signature heparin-binding motif that was confirmed by heparin affinity chromatography. Cell-based assays showed that bleogen pB1 is non-toxic to mammalian cells but functions as an anti-Candida peptide. Taken together, our findings provide insight into the occurrence, functions and precursor architectures of CRPs in the cactus family.

Organometallic model complexes elucidate the active gallium species in alkane dehydrogenation catalysts based on ligand effects in Ga K-edge XANES

Energy Technology Data Exchange (ETDEWEB)

Getsoian, Andrew “Bean”; Das, Ujjal; Camacho-Bunquin, Jeffrey; Zhang, Guanghui; Gallagher, James R.; Hu, Bo; Cheah, Singfoong; Schaidle, Joshua A.; Ruddy, Daniel A.; Hensley, Jesse E.; Krause, Theodore R.; Curtiss, Larry A.; Miller, Jeffrey T.; Hock, Adam S.

2016-01-01

Gallium-modified zeolites are known catalysts for the dehydrogenation of alkanes, reactivity that finds industrial application in the aromatization of light alkanes by Ga-ZSM5. While the role of gallium cations in alkane activation is well known, the oxidation state and coordination environment of gallium under reaction conditions has been the subject of debate. Edge shifts in Ga K-edge XANES spectra acquired under reaction conditions have long been interpreted as evidence for reduction of Ga(III) to Ga(I). However, a change in oxidation state is not the only factor that can give rise to a change in the XANES spectrum. In order to better understand the XANES spectra of working catalysts, we have synthesized a series of molecular model compounds and grafted surface organometallic Ga species and compared their XANES spectra to those of gallium-based catalysts acquired under reducing conditions. We demonstrate that changes in the identity and number of gallium nearest neighbors can give rise to changes in XANES spectra similar to those attributed in literature to changes in oxidation state. Specifically, spectral features previously attributed to Ga(I) may be equally well interpreted as evidence for low-coordinate Ga(III) alkyl or hydride species. These findings apply both to gallium-impregnated zeolite catalysts and to silica-supported single site gallium catalysts, the latter of which is found to be active and selective for dehydrogenation of propane and hydrogenation of propylene.

Enumeration of minimal stoichiometric precursor sets in metabolic networks.

Science.gov (United States)

Andrade, Ricardo; Wannagat, Martin; Klein, Cecilia C; Acuña, Vicente; Marchetti-Spaccamela, Alberto; Milreu, Paulo V; Stougie, Leen; Sagot, Marie-France

2016-01-01

What an organism needs at least from its environment to produce a set of metabolites, e.g. target(s) of interest and/or biomass, has been called a minimal precursor set. Early approaches to enumerate all minimal precursor sets took into account only the topology of the metabolic network (topological precursor sets). Due to cycles and the stoichiometric values of the reactions, it is often not possible to produce the target(s) from a topological precursor set in the sense that there is no feasible flux. Although considering the stoichiometry makes the problem harder, it enables to obtain biologically reasonable precursor sets that we call stoichiometric. Recently a method to enumerate all minimal stoichiometric precursor sets was proposed in the literature. The relationship between topological and stoichiometric precursor sets had however not yet been studied. Such relationship between topological and stoichiometric precursor sets is highlighted. We also present two algorithms that enumerate all minimal stoichiometric precursor sets. The first one is of theoretical interest only and is based on the above mentioned relationship. The second approach solves a series of mixed integer linear programming problems. We compared the computed minimal precursor sets to experimentally obtained growth media of several Escherichia coli strains using genome-scale metabolic networks. The results show that the second approach efficiently enumerates minimal precursor sets taking stoichiometry into account, and allows for broad in silico studies of strains or species interactions that may help to understand e.g. pathotype and niche-specific metabolic capabilities. sasita is written in Java, uses cplex as LP solver and can be downloaded together with all networks and input files used in this paper at http://www.sasita.gforge.inria.fr.

Controllable architecture of CdS and CuS by single-source precursor-mediated approach and their photocatalytic activity

International Nuclear Information System (INIS)

Sahoo, Ashish K.; Srivastava, Suneel K.

2013-01-01

The present work deals with the preparation of hexagonal CdS and CuS by solvothermal decomposition of the morpholine-4-carbdithioate (MCDT) complexes of Cd and Cu in a water/THF mixture at 140–180 °C for 24 h and characterization. Scanning electron microscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy show that CdS exhibits a hierarchical star- and lotus flower-like morphology in the presence of disodium salt of ethylenediamine tetraaceticacid and sodium dodecyl benzene sulphonate as soft templates at 140 and 160 °C, respectively. However, Cu complex of MCDT forms CuS nanoparticles in the temperature range of 140–180 °C. On the contrary, CdS nanoparticles and CuS microparticles are formed in the absence of any template under the identical experimental conditions. Raman studies show the characteristic peak of CdS and CuS, irrespective of their size and morphology. Finally, CdS and CuS of varying morphology have successfully been used as catalysts in UV photocatalytic decomposition of methylene blue dye. These findings show that CdS lotus-like microflowers are more effective catalysts than hierarchical stars, though the latter is found to have better reusability.Graphical AbstractA simple soft template-assisted and single complex source precursor-mediated solvothermal synthesis of CdS and CuS with a diverse set of morphology has been reported. In addition, the morphology and application in photocatalysis are also discussed.

Controllable architecture of CdS and CuS by single-source precursor-mediated approach and their photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Sahoo, Ashish K.; Srivastava, Suneel K., E-mail: sunil111954@yahoo.co.uk [Indian Institute of Technology Kharagpur, Department of Chemistry (India)

2013-04-15

The present work deals with the preparation of hexagonal CdS and CuS by solvothermal decomposition of the morpholine-4-carbdithioate (MCDT) complexes of Cd and Cu in a water/THF mixture at 140-180 Degree-Sign C for 24 h and characterization. Scanning electron microscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy show that CdS exhibits a hierarchical star- and lotus flower-like morphology in the presence of disodium salt of ethylenediamine tetraaceticacid and sodium dodecyl benzene sulphonate as soft templates at 140 and 160 Degree-Sign C, respectively. However, Cu complex of MCDT forms CuS nanoparticles in the temperature range of 140-180 Degree-Sign C. On the contrary, CdS nanoparticles and CuS microparticles are formed in the absence of any template under the identical experimental conditions. Raman studies show the characteristic peak of CdS and CuS, irrespective of their size and morphology. Finally, CdS and CuS of varying morphology have successfully been used as catalysts in UV photocatalytic decomposition of methylene blue dye. These findings show that CdS lotus-like microflowers are more effective catalysts than hierarchical stars, though the latter is found to have better reusability.Graphical AbstractA simple soft template-assisted and single complex source precursor-mediated solvothermal synthesis of CdS and CuS with a diverse set of morphology has been reported. In addition, the morphology and application in photocatalysis are also discussed.

Are any public-reported earthquake precursors valid?

Directory of Open Access Journals (Sweden)

N. E. Whitehead

2004-01-01

Full Text Available This article examines retrospective public-supplied precursor reports statistically, and confirms published hypotheses that some alleged precursors within 100km and within a day prior to the large 1995 Kobe and 1999 Izmit earthquakes, may be valid. The confirmations are mostly at the p<0.001 level of significance. Most significant were alleged meteorological and geophysical precursors, and less often, animal reports. The chi-squared test used, for the first time eliminates the distorting effects of psychological factors on the reports. However it also shows that correct reports are diluted with about the same number which are merely wishful thinking, and obtaining more reliable data would be logistically difficult. Some support is found for another published hypothesis in which other precursors occurred within the ten days prior to the earthquake.

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

Directory of Open Access Journals (Sweden)

Peter Hesemann

2014-04-01

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

Perfluoroalkyl Acids (PFAAs) and Selected Precursors in the Baltic Sea Environment: Do Precursors Play a Role in Food Web Accumulation of PFAAs?

Science.gov (United States)

Gebbink, Wouter A; Bignert, Anders; Berger, Urs

2016-06-21

The present study examined the presence of perfluoroalkyl acids (PFAAs) and selected precursors in the Baltic Sea abiotic environment and guillemot food web, and investigated the relative importance of precursors in food web accumulation of PFAAs. Sediment, water, zooplankton, herring, sprat, and guillemot eggs were analyzed for perfluoroalkane sulfonic acids (PFSAs; C4,6,8,10) and perfluoroalkyl carboxylic acids (PFCAs; C6-15) along with six perfluoro-octane sulfonic acid (PFOS) precursors and 11 polyfluoroalkyl phosphoric acid diesters (diPAPs). FOSA, FOSAA and its methyl and ethyl derivatives (Me- and EtFOSAA), and 6:2/6:2 diPAP were detected in sediment and water. While FOSA and the three FOSAAs were detected in all biota, a total of nine diPAPs were only detected in zooplankton. Concentrations of PFOS precursors and diPAPs exceeded PFOS and PFCA concentrations, respectively, in zooplankton, but not in fish and guillemot eggs. Although PFOS precursors were present at all trophic levels, they appear to play a minor role in food web accumulation of PFOS based on PFOS precursor/PFOS ratios and PFOS and FOSA isomer patterns. The PFCA pattern in fish could not be explained by the intake pattern based on PFCAs and analyzed precursors, that is, diPAPs. Exposure to additional precursors might therefore be a dominant exposure pathway compared to direct PFCA exposure for fish.

Effects of Precursor-Substrate Distances on the Growth of GaN Nanowires

Directory of Open Access Journals (Sweden)

Hongbin Cheng

2015-01-01

Full Text Available GaN nanowires were synthesized through the Ni-catalyzed chemical vapor deposition (CVD method using Ga2O3/GaN mixtures as gallium sources, and precursor-substrate distances were investigated as the important factor for the growth of GaN nanowires. The microstructure, composition, and photoluminescence property were characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra. The results showed that single crystalline GaN nanowires with the diameter of about 90 nm and the length up to tens of micrometers had been grown thickly across Si (100 substrates with uniform density. Moreover, the variations of the GaN nanowire morphology, density, and size were largely attributed to substrate positions which would influence Ga precursor density in the carrier gas, the saturation degree of gaseous reactants, and the catalyst activity, respectively, in the fabrication of GaN nanowires by the vapour liquid solid mechanism.

Trending analysis of precursor events

International Nuclear Information System (INIS)

Watanabe, Norio

1998-01-01

The Accident Sequence Precursor (ASP) Program of United States Nuclear Regulatory Commission (U.S.NRC) identifies and categorizes operational events at nuclear power plants in terms of the potential for core damage. The ASP analysis has been performed on yearly basis and the results have been published in the annual reports. This paper describes the trends in initiating events and dominant sequences for 459 precursors identified in the ASP Program during the 1969-94 period and also discusses a comparison with dominant sequences predicted in the past Probabilistic Risk Assessment (PRA) studies. These trends were examined for three time periods, 1969-81, 1984-87 and 1988-94. Although the different models had been used in the ASP analyses for these three periods, the distribution of precursors by dominant sequences show similar trends to each other. For example, the sequences involving loss of both main and auxiliary feedwater were identified in many PWR events and those involving loss of both high and low coolant injection were found in many BWR events. Also, it was found that these dominant sequences were comparable to those determined to be dominant in the predictions by the past PRAs. As well, a list of the 459 precursors identified are provided in Appendix, indicating initiating event types, unavailable systems, dominant sequences, conditional core damage probabilities, and so on. (author)

Accident Precursor Analysis and Management: Reducing Technological Risk Through Diligence

Science.gov (United States)

Phimister, James R. (Editor); Bier, Vicki M. (Editor); Kunreuther, Howard C. (Editor)

2004-01-01

Almost every year there is at least one technological disaster that highlights the challenge of managing technological risk. On February 1, 2003, the space shuttle Columbia and her crew were lost during reentry into the atmosphere. In the summer of 2003, there was a blackout that left millions of people in the northeast United States without electricity. Forensic analyses, congressional hearings, investigations by scientific boards and panels, and journalistic and academic research have yielded a wealth of information about the events that led up to each disaster, and questions have arisen. Why were the events that led to the accident not recognized as harbingers? Why were risk-reducing steps not taken? This line of questioning is based on the assumption that signals before an accident can and should be recognized. To examine the validity of this assumption, the National Academy of Engineering (NAE) undertook the Accident Precursors Project in February 2003. The project was overseen by a committee of experts from the safety and risk-sciences communities. Rather than examining a single accident or incident, the committee decided to investigate how different organizations anticipate and assess the likelihood of accidents from accident precursors. The project culminated in a workshop held in Washington, D.C., in July 2003. This report includes the papers presented at the workshop, as well as findings and recommendations based on the workshop results and committee discussions. The papers describe precursor strategies in aviation, the chemical industry, health care, nuclear power and security operations. In addition to current practices, they also address some areas for future research.

Report on Fukushima Daiichi NPP precursor events

International Nuclear Information System (INIS)

2014-01-01

The main questions to be answered by this report were: The Fukushima Daiichi NPP accident, could it have been prevented? If there is a next severe accident, may it be prevented? To answer the first question, the report addressed several aspects. First, the report investigated whether precursors to the Fukushima Daiichi NPP accident existed in the operating experience; second, the reasons why these precursors did not evolve into a severe accident. Third, whether lessons learned from these precursor events were adequately considered by member countries; and finally, if the operating experience feedback system needs to be improved, based on the previous analysis. To address the second question which is much more challenging, the report considered precursor events identified through a search and analysis of the IRS database and also precursors events based on risk significance. Both methods can point out areas where further work may be needed, even if it depends heavily on design and site-specific factors. From the operating experience side, more efforts are needed to ensure timely and full implementation of lessons learnt from precursor events. Concerning risk considerations, a combined use of risk precursors and operating experience may drive to effective changes to plants to reduce risk. The report also contains a short description and evaluation of selected precursors that are related to the course of the Fukushima Daiichi NPP accident. The report addresses the question whether operating experience feedback can be effectively used to identify plant vulnerabilities and minimize potential for severe core damage accidents. Based on several of the precursor events national or international in-depth evaluations were started. The vulnerability of NPPs due to external and internal flooding has clearly been addressed. In addition to the IRS based investigation, the WGRISK was asked to identify important precursor events based on risk significance. These precursors have

Split2 Protein-Ligation Generates Active IL-6-Type Hyper-Cytokines from Inactive Precursors.

Science.gov (United States)

Moll, Jens M; Wehmöller, Melanie; Frank, Nils C; Homey, Lisa; Baran, Paul; Garbers, Christoph; Lamertz, Larissa; Axelrod, Jonathan H; Galun, Eithan; Mootz, Henning D; Scheller, Jürgen

2017-12-15

Trans-signaling of the major pro- and anti-inflammatory cytokines Interleukin (IL)-6 and IL-11 has the unique feature to virtually activate all cells of the body and is critically involved in chronic inflammation and regeneration. Hyper-IL-6 and Hyper-IL-11 are single chain designer trans-signaling cytokines, in which the cytokine and soluble receptor units are trapped in one complex via a flexible peptide linker. Albeit, Hyper-cytokines are essential tools to study trans-signaling in vitro and in vivo, the superior potency of these designer cytokines are accompanied by undesirable stress responses. To enable tailor-made generation of Hyper-cytokines, we developed inactive split-cytokine-precursors adapted for posttranslational reassembly by split-intein mediated protein trans-splicing (PTS). We identified cutting sites within IL-6 (E 134 /S 135 ) and IL-11 (G 116 /S 117 ) and obtained inactive split-Hyper-IL-6 and split-Hyper-IL-11 cytokine precursors. After fusion with split-inteins, PTS resulted in reconstitution of active Hyper-cytokines, which were efficiently secreted from transfected cells. Our strategy comprises the development of a background-free cytokine signaling system from reversibly inactivated precursor cytokines.

Biochemical Removal of HAP Precursors From Coal

Energy Technology Data Exchange (ETDEWEB)

Olson, G.; Tucker, L.; Richards, J.

1997-07-01

This project addresses DOE`s interest in advanced concepts for controlling emissions of air toxics from coal-fired utility boilers. We are determining the feasibility of developing a biochemical process for the precombustion removal of substantial percentages of 13 inorganic hazardous air pollutant (HAP) precursors from coal. These HAP precursors are Sb, As, Be, Cd, Cr, Cl, Co, F, Pb, Hg, Mn, Ni, and Se. Although rapid physical coal cleaning is done routinely in preparation plants, biochemical processes for removal of HAP precursors from coal potentially offer advantages of deeper cleaning, more specificity, and less coal loss. Compared to chemical processes for coal cleaning, biochemical processes potentially offer lower costs and milder process conditions. Pyrite oxidizing bacteria, most notably Thiobacillusferrooxidans, are being evaluated in this project for their ability to remove HAP precursors from U.S. coals.

Biochemical Removal of HAP Precursors From Coal

International Nuclear Information System (INIS)

Olson, G.; Tucker, L.; Richards, J.

1997-07-01

This project addresses DOE's interest in advanced concepts for controlling emissions of air toxics from coal-fired utility boilers. We are determining the feasibility of developing a biochemical process for the precombustion removal of substantial percentages of 13 inorganic hazardous air pollutant (HAP) precursors from coal. These HAP precursors are Sb, As, Be, Cd, Cr, Cl, Co, F, Pb, Hg, Mn, Ni, and Se. Although rapid physical coal cleaning is done routinely in preparation plants, biochemical processes for removal of HAP precursors from coal potentially offer advantages of deeper cleaning, more specificity, and less coal loss. Compared to chemical processes for coal cleaning, biochemical processes potentially offer lower costs and milder process conditions. Pyrite oxidizing bacteria, most notably Thiobacillusferrooxidans, are being evaluated in this project for their ability to remove HAP precursors from U.S. coals

SEARCH FOR PRECURSOR ERUPTIONS AMONG TYPE IIB SUPERNOVAE

Energy Technology Data Exchange (ETDEWEB)

Strotjohann, Nora L.; Ofek, Eran O.; Gal-Yam, Avishay; Yaron, Ofer [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Sullivan, Mark [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Kulkarni, Shrinivas R.; Cao, Yi [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Shaviv, Nir J. [School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540 (United States); Fremling, Christoffer; Sollerman, Jesper [The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm (Sweden); Kasliwal, Mansi M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Nugent, Peter E. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Arcavi, Iair [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93111 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States)

2015-10-01

The progenitor stars of several Type IIb supernovae (SNe) show indications of extended hydrogen envelopes. These envelopes might be the outcome of luminous energetic pre-explosion events, so-called precursor eruptions. We use the Palomar Transient Factory (PTF) pre-explosion observations of a sample of 27 nearby SNe IIb to look for such precursors during the final years prior to the SN explosion. No precursors are found when combining the observations in 15-day bins, and we calculate the absolute-magnitude-dependent upper limit on the precursor rate. At the 90% confidence level, SNe IIb have on average <0.86 precursors as bright as an absolute R-band magnitude of −14 in the final 3.5 years before the explosion and <0.56 events over the final year. In contrast, precursors among SNe IIn have a ≳5 times higher rate. The kinetic energy required to unbind a low-mass stellar envelope is comparable to the radiated energy of a few-weeks-long precursor that would be detectable for the closest SNe in our sample. Therefore, mass ejections, if they are common in such SNe, are radiatively inefficient or have durations longer than months. Indeed, when using 60-day bins, a faint precursor candidate is detected prior to SN 2012cs (∼2% false-alarm probability). We also report the detection of the progenitor of SN 2011dh that does not show detectable variability over the final two years before the explosion. The suggested progenitor of SN 2012P is still present, and hence is likely a compact star cluster or an unrelated object.

Production and application of synthetic precursors labeled with carbon-11 and fluorine-18

Energy Technology Data Exchange (ETDEWEB)

Ferrieri, R.A.

2001-04-02

It is evident from this chapter that there is enormous flexibility both in the selection of the nature of the radioisotope and ways to generate it, as well as in the selection of the labeling precursor to appropriately attach that radioisotope to some larger biomolecule of interest. The arsenal of radiolabeling precursors now available to the chemist is quite extensive, and without a doubt will continue to grow as chemists develop new ones. However, the upcoming years will perhaps reflect a greater effort in refining existing methods for preparing some of those precursors that are already available to us. For example, the use of solid-phase reactions to accomplish in a single step what would normally take several using conventional solvent-based reactions has already been shown to work in many occasions. The obvious advantage here is that processes become more amenable to system automation thus affording greater reliability in day-to-day operations. There are perhaps other technologies in science that have yet to be realized by the chemist in the PET laboratory that could provide a similar or even a greater benefit. One only needs to be open to new ideas, and imaginative enough to apply them to the problems at hand.

Production and application of synthetic precursors labeled with carbon-11 and fluorine-18

International Nuclear Information System (INIS)

Ferrieri, R.A.

2001-01-01

It is evident from this chapter that there is enormous flexibility both in the selection of the nature of the radioisotope and ways to generate it, as well as in the selection of the labeling precursor to appropriately attach that radioisotope to some larger biomolecule of interest. The arsenal of radiolabeling precursors now available to the chemist is quite extensive, and without a doubt will continue to grow as chemists develop new ones. However, the upcoming years will perhaps reflect a greater effort in refining existing methods for preparing some of those precursors that are already available to us. For example, the use of solid-phase reactions to accomplish in a single step what would normally take several using conventional solvent-based reactions has already been shown to work in many occasions. The obvious advantage here is that processes become more amenable to system automation thus affording greater reliability in day-to-day operations. There are perhaps other technologies in science that have yet to be realized by the chemist in the PET laboratory that could provide a similar or even a greater benefit. One only needs to be open to new ideas, and imaginative enough to apply them to the problems at hand

Bioinspired magnetite synthesis via solid precursor phases

NARCIS (Netherlands)

Lenders, J.J.M.; Mirabello, G.; Sommerdijk, N.A.J.M.

2016-01-01

Living organisms often exploit solid but poorly ordered mineral phases as precursors in the biomineralization of their inorganic body parts. Generally speaking, such precursor-based approaches allow the organisms-without the need of high supersaturation levels-to accumulate significant quantities of

Effect of precursor solutions on ZnO film via solution precursor plasma spray and corresponding gas sensing performances

Science.gov (United States)

Yu, Z. X.; Ma, Y. Z.; Zhao, Y. L.; Huang, J. B.; Wang, W. Z.; Moliere, M.; Liao, H. L.

2017-08-01

Solution precursor plasma spraying (SPPS) as a novel thermal spray method was employed to deposit nano-structured ZnO thin film using different formulations of the precursor solution. This article focuses on the influence of the solution composition on the preferential orientation of crystal growth, on crystal size and surface morphology of the resulting ZnO films. The trend of preferential growth along (002) lattice plane of ZnO film was studied by slow scanning X-ray diffraction using a specific coefficient P(002). It appears that the thermal spray process promotes the buildup of ZnO films preferentially oriented along the c-axis. The shape of single particle tends to change from round shaped beads to hexagonal plates by increasing the volume ratio of ethanol in the solvent. Both cauliflower and honeycomb-like surface morphologies featuring high specific surface area and roughness were obtained through the SPPS process by varying solution composition. These ZnO films are hydrophobic with contact angle as high as 136°, which is seemingly associated with micro reliefs developing high surface specific area. Then the gas sensing performances of ZnO films preferentially oriented along (002) face were tentatively predicted using the "first principle calculation method" and were compared with those of conventional films that are mainly oriented along the (101) face. The (002) face displays better hydrogen adsorption capability than the (101) face with much larger resulting changes in electrical resistance. In conclusion, the c-axis oriented ZnO films obtained through SSPS have favorable performances to be used as sensitive layer in gas sensing applications.

Chromospheric Response during the Precursor and the Main Phase of a B6.4 Flare on 2005 August 20

Science.gov (United States)

Awasthi, Arun Kumar; Rudawy, Pawel; Falewicz, Robert; Berlicki, Arkadiusz; Liu, Rui

2018-05-01

Solar flare precursors depict a constrained rate of energy release, in contrast to the imminent rapid energy release, which calls for a different regime of plasma processes to be at play. Due to the subtle emission during the precursor phase, its diagnostics remain delusive, revealing either nonthermal electrons (NTEs) or thermal conduction to be the driver. In this regard, we investigate the chromospheric response during various phases of a B6.4 flare on 2005 August 20. Spatiotemporal investigation of flare ribbon enhancement during the precursor phase, carried out using spectra images recorded in several wavelength positions on the Hα line profile, revealed its delayed response (180 s) compared to the X-ray emission, as well as a sequential increment in the width of the line profile, which are indicative of a slow heating process. However, the energy contained in the Hα emission during the precursor phase can reach as high as 80% of that estimated during the main phase. Additionally, the plasma hydrodynamics during the precursor phase, resulting from the application of a single-loop one-dimensional model, revealed the presence of a power-law extension in the model-generated X-ray spectra, with a flux lower than the RHESSI background. Therefore, our multiwavelength diagnostics and hydrodynamical modeling of the precursor emission indicates the role of a two-stage process. First, reconnection-triggered NTEs, although too small in flux to overcome the observational constraints, thermalize in the upper chromosphere. This leads to the generation of a slow conduction front, which causes plasma heating during the precursor phase.

Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis

Energy Technology Data Exchange (ETDEWEB)

Casey, Charles P

2012-11-14

Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis Charles P. Casey, Principal Investigator Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706 Phone 608-262-0584 FAX: 608-262-7144 Email: casey@chem.wisc.edu http://www.chem.wisc.edu/main/people/faculty/casey.html Executive Summary. Our goal was to learn the intimate mechanistic details of reactions involved in homogeneous catalysis and to use the insight we gain to develop new and improved catalysts. Our work centered on the hydrogenation of polar functional groups such as aldehydes and ketones and on hydroformylation. Specifically, we concentrated on catalysts capable of simultaneously transferring hydride from a metal center and a proton from an acidic oxygen or nitrogen center to an aldehyde or ketone. An economical iron based catalyst was developed and patented. Better understanding of fundamental organometallic reactions and catalytic processes enabled design of energy and material efficient chemical processes. Our work contributed to the development of catalysts for the selective and mild hydrogenation of ketones and aldehydes; this will provide a modern green alternative to reductions by LiAlH4 and NaBH4, which require extensive work-up procedures and produce waste streams. (C5R4OH)Ru(CO)2H Hydrogenation Catalysts. Youval Shvo described a remarkable catalytic system in which the key intermediate (C5R4OH)Ru(CO)2H (1) has an electronically coupled acidic OH unit and a hydridic RuH unit. Our efforts centered on understanding and improving upon this important catalyst for reduction of aldehydes and ketones. Our mechanistic studies established that the reduction of aldehydes by 1 to produce alcohols and a diruthenium bridging hydride species occurs much more rapidly than regeneration of the ruthenium hydride from the diruthenium bridging hydride species. Our mechanistic studies require simultaneous transfer of hydride from ruthenium to

Growth, optical, electrical and photoconductivity studies of a novel nonlinear optical single crystal: Mercury cadmium chloride thiocyanate

Science.gov (United States)

Kumar, S. M. Ravi; Selvakumar, S.; Sagayaraj, P.; Anbarasi, A.

2015-02-01

SCN- ligand based organometallic non-linear optical mercury cadmium chloride thiocyanate (MCCTC) crystals are grown from water plus methanol mixed solvent by slow evaporation technique. The grown crystals are confirmed by single crystal X-ray diffraction analysis which reveals that the MCCTC belongs to rhombohedral system with R3c space group. MCCTC exhibits a SHG efficiency which is nearly 17 times more than that of KDP. The dielectric constant, dielectric loss measurements of the sample have been carried out for different frequencies (100 Hz to 5 MHz) and, temperatures (308 to 388 K) and the results are discussed. Photoconductivity study confirms that the title compound possesses negative photoconducting nature. The surface morphology of MCCTC was also investigated

Phosphane-Based Cyclodextrins as Mass Transfer Agents and Ligands for Aqueous Organometallic Catalysis

Directory of Open Access Journals (Sweden)

Eric Monflier

2012-11-01

Full Text Available The replacement of hazardous solvents and the utilization of catalytic processes are two key points of the green chemistry movement, so aqueous organometallic catalytic processes are of great interest in this context. Nevertheless, these processes require not only the use of water-soluble ligands such as phosphanes to solubilise the transition metals in water, but also the use of mass transfer agents to increase the solubility of organic substrates in water. In this context, phosphanes based on a cyclodextrin skeleton are an interesting alternative since these compounds can simultaneously act as mass transfer agents and as coordinating species towards transition metals. For twenty years, various cyclodextrin-functionalized phosphanes have been described in the literature. Nevertheless, while their coordinating properties towards transition metals and their catalytic properties were fully detailed, their mass transfer agent properties were much less discussed. As these mass transfer agent properties are directly linked to the availability of the cyclodextrin cavity, the aim of this review is to demonstrate that the nature of the reaction solvent and the nature of the linker between cyclodextrin and phosphorous moieties can deeply influence the recognition properties. In addition, the impact on the catalytic activity will be also discussed.

Probabilistic precursor analysis - an application of PSA

International Nuclear Information System (INIS)

Hari Prasad, M.; Gopika, V.; Sanyasi Rao, V.V.S.; Vaze, K.K.

2011-01-01

Incidents are inevitably part of the operational life of any complex industrial facility, and it is hard to predict how various contributing factors combine to cause the outcome. However, it should be possible to detect the existence of latent conditions that, together with the triggering failure(s), result in abnormal events. These incidents are called precursors. Precursor study, by definition, focuses on how a particular event might have adversely developed. This paper focuses on the events which can be analyzed to assess their potential to develop into core damage situation and looks into extending Probabilistic Safety Assessment techniques to precursor studies and explains the benefits through a typical case study. A preliminary probabilistic precursor analysis has been carried out for a typical NPP. The major advantages of this approach are the strong potential for augmenting event analysis which is currently carried out purely on deterministic basis. (author)

Investigating the synthesis of ligated metal clusters in solution using a flow reactor and electrospray ionization mass spectrometry.

Science.gov (United States)

Olivares, Astrid; Laskin, Julia; Johnson, Grant E

2014-09-18

The scalable synthesis of ligated subnanometer metal clusters containing an exact number of atoms is of interest due to the highly size-dependent catalytic, electronic, and optical properties of these species. While significant research has been conducted on the batch preparation of clusters through reduction synthesis in solution, the processes of metal complex reduction as well as cluster nucleation, growth, and postreduction etching are still not well understood. Herein, we demonstrate a prototype temperature-controlled flow reactor for qualitatively studying cluster formation in solution at steady-state conditions. Employing this technique, methanol solutions of a chloro(triphenylphosphine)gold precursor, 1,4-bis(diphenylphosphino)butane capping ligand, and borane-tert-butylamine reducing agent were combined in a mixing tee and introduced into a heated capillary with a known length. In this manner, the temperature dependence of the relative abundance of different ionic reactants, intermediates, and products synthesized in real time was characterized qualitatively using online mass spectrometry. A wide distribution of doubly and triply charged cationic gold clusters was observed as well as smaller singly charged organometallic complexes. The results demonstrate that temperature plays a crucial role in determining the relative population of cationic gold clusters and, in general, that higher temperature promotes the formation of doubly charged clusters and singly charged organometallic complexes while reducing the abundance of triply charged species. Moreover, the distribution of clusters observed at elevated temperatures is found to be consistent with that obtained at longer reaction times at room temperature, thereby demonstrating that heating may be used to access cluster distributions characteristic of different stages of batch reduction synthesis in solution.

Thermodynamic approach to the synthesis of silicon carbide using tetramethylsilane as the precursor at high temperature

Science.gov (United States)

Jeong, Seong-Min; Kim, Kyung-Hun; Yoon, Young Joon; Lee, Myung-Hyun; Seo, Won-Seon

2012-10-01

Tetramethylsilane (TMS) is commonly used as a precursor in the production of SiC(β) films at relatively low temperatures. However, because TMS contains much more C than Si, it is difficult to produce solid phase SiC at high temperatures. In an attempt to develop a more efficient TMS-based SiC(α) process, computational thermodynamic simulations were performed under various temperatures, working pressures and TMS/H2 ratios. The findings indicate that each solid phase has a different dependency on the H2 concentration. Consequently, a high H2 concentration results in the formation of a single, solid phase SiC region at high temperatures. Finally, TMS appears to be useful as a precursor for the high temperature production of SiC(α).

The relationship between elastic constants and structure of shock waves in a zinc single crystal

Science.gov (United States)

Krivosheina, M. N.; Kobenko, S. V.; Tuch, E. V.

2017-12-01

The paper provides a 3D finite element simulation of shock-loaded anisotropic single crystals on the example of a Zn plate under impact using a mathematical model, which allows for anisotropy in hydrostatic stress and wave velocities in elastic and plastic ranges. The simulation results agree with experimental data, showing the absence of shock wave splitting into an elastic precursor and a plastic wave in Zn single crystals impacted in the [0001] direction. It is assumed that the absence of an elastic precursor under impact loading of a zinc single crystal along the [0001] direction is determined by the anomalously large ratio of the c/a-axes and close values of the propagation velocities of longitudinal and bulk elastic waves. It is shown that an increase in only one elastic constant along the [0001] direction results in shock wave splitting into an elastic precursor and a shock wave of "plastic" compression.

Planar half-cell shaped precursor body

DEFF Research Database (Denmark)

2015-01-01

The invention relates to a half-cell shaped precursor body of either anode type or cathode type, the half-cell shaped precursor body being prepared to be free sintered to form a sintered or pre-sintered half-cell being adapted to be stacked in a solid oxide fuel cell stack. The obtained half......-cell has an improved planar shape, which remains planar also after a sintering process and during temperature fluctuations....

Precursors in photonic crystals - art. no. 618218

NARCIS (Netherlands)

Uitham, R.; Hoenders, B. J.; DeLaRue, RM; Viktorovitch, P; Lopez, C; Midrio, M

2006-01-01

We derive the Sommerfeld precursor and present the first calculations for the Brillouin precursor that result from the transmission of a pulse through a photonic crystal. The photonic crystal is modelled by a one-dimensional N-layer medium and the pulse is a generic electromagnetic plane wave packet

Synthesis of (Cr,V){sub 2}(C,N) solid solution powders by thermal processing precursors

Energy Technology Data Exchange (ETDEWEB)

Liu, Anrui [School of Materials Science & Engineering, Sichuan University, Chengdu, 610065 (China); Liu, Ying [School of Materials Science & Engineering, Sichuan University, Chengdu, 610065 (China); Key Laboratory of Advanced Special Material & Technology, Ministry of Education, Chengdu, 610065 (China); Ma, Shiqing; Qiu, Yuchong; Rong, Pengcheng; Ye, Jinwen [School of Materials Science & Engineering, Sichuan University, Chengdu, 610065 (China)

2017-06-01

The single-phase (Cr,V){sub 2}(C,N) solid solution powders were fabricated via carbothermal reduction-nitridation (CRN) processing technique. The effects of heat treatment temperature, nitrogen pressure and carbon proportion were experimentally studied in detail by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and thermal analysis. The chemical transformations of vanadium and chromium compounds were as follows: precursors → V{sub 2}O{sub 3}, Cr{sub 2}O{sub 3} → Cr{sub 3}C{sub 2}, Cr{sub 2}O{sub 3}, (Cr,V){sub 2}(C,N) → (Cr,V){sub 2}(C,N). When the heat-treated temperature was below 1200 °C, chromium oxides didn’t completely react. However, higher temperature ∼1300 °C could not only lead to the segregation of some nitrides and carbon black, but also to the occurrence of fiber-bridged particles. The system nitrogen pressure over 0.03 MPa would cause a subtle transformation of (Cr,V){sub 2}(C,N) to VCrN{sub 2}. When the carbon proportion was below 15 wt%, the oxides could not be completely reduced, while when the carbon proportion was above 15.5 wt%, some undesired carbides, like Cr{sub 23}C{sub 6} and Cr{sub 3}C{sub 2}, would form. Ultimately, the homogeneously distributed pure-phase (Cr,V){sub 2}(C,N) spherical particles with the average size of ∼1.5 μm were obtained at the optimal conditions of the treatment of precursors at 1200 °C for 1 h with the nitrogen pressure of 0.03 MPa and carbon content of 15.5 wt%. The chemical composition of the solid solution with the optimal process could be drawn as (Cr{sub 0.85}V{sub 0.15}){sub 2}(C{sub 0.57}N{sub 0.43}). Thermal processing precursors method shows the advantages of lower synthesis temperature, shorter period and finer particles when comparing with the conventional preparations. - Highlights: • Single phase of (Cr,V){sub 2}(C,N) powders were synthesized for the first time. • Precursors were used to prepared the powders by carbothermal

Synthesis, spectral and thermal studies of pyridyl adducts of Zn(II) and Cd(II) dithiocarbamates, and their use as single source precursors for ZnS and CdS nanoparticles.

Science.gov (United States)

Onwudiwe, Damian C; Strydom, Christien A; Oluwafemi, Oluwatobi S; Hosten, Eric; Jordaan, Anine

2014-06-21

The synthesis, spectroscopic characterisation, and thermal studies of pyridyl adducts of Zn(II) and Cd(II) complexes of N-ethyl-N-phenyl dithiocarbamate, represented as [ZnL2py] and [CdL2py2], are reported. Single-crystal X-ray structural analysis of the Zn compound showed that it is five-coordinate with four sulphurs from dithiocarbamate and one nitrogen from pyridine in a distorted square pyramidal geometry. The thermogravimetric studies indicate that the zinc and cadmium compounds undergo fast weight loss, and the temperature at maximum rate of decomposition is at 277 °C and 265 °C respectively, to give the metal (Zn or Cd) sulphide residues. These compounds were used as single molecule precursors to produce nanocrystalline MS (M = Zn, Cd) after thermolysis in hexadecylamine. The morphological and optical properties of the resulting MS nanocrystallites were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis absorption and photoluminescence (PL) spectroscopy, and powdered X-ray diffraction (XRD). By varying the growth time, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated.

Synthesis, characterization and biological assay of Salicylaldehyde Schiff base Cu(II) complexes and their precursors

Science.gov (United States)

Iftikhar, Bushra; Javed, Kanwal; Khan, Muhammad Saif Ullah; Akhter, Zareen; Mirza, Bushra; Mckee, Vickie

2018-03-01

Three new Schiff base ligands were synthesized by the reaction of Salicylaldehyde with semi-aromatic diamines, prepared by the reduction of corresponding dinitro-compounds, and were further used for the formation of complexes with Cu(II) metal ion. The structural features of the synthesized compounds were confirmed by their physical properties and infrared, electronic and NMR spectroscopic techniques. The studies revealed that the synthesized Schiff bases existed as tetradentate ligands and bonded to the metal ion through the phenolic oxygen and azomethine nitrogen. One of the dinitro precursors was also analyzed by single crystal X-ray crystallography, which showed that it crystallizes in monoclinic system with space group P2/n. The thermal behavior of the Cu(II) complexes was determined by thermogravimetric analysis (TGA) and kinetic parameters were evaluated from the data. Schiff base ligands, their precursors and metal complexes were also screened for antibacterial, antifungal, antitumor, Brine shrimp lethality, DPPH free radical scavenging and DNA damage assays. The results of these analyses indicated the substantial potential of the synthesized Schiff bases, their precursors and Cu(II) complexes in biological field as future drugs.

Adenine nucleotide translocator transports haem precursors into mitochondria.

Directory of Open Access Journals (Sweden)

Motoki Azuma

2008-08-01

Full Text Available Haem is a prosthetic group for haem proteins, which play an essential role in oxygen transport, respiration, signal transduction, and detoxification. In haem biosynthesis, the haem precursor protoporphyrin IX (PP IX must be accumulated into the mitochondrial matrix across the inner membrane, but its mechanism is largely unclear. Here we show that adenine nucleotide translocator (ANT, the inner membrane transporter, contributes to haem biosynthesis by facilitating mitochondrial accumulation of its precursors. We identified that haem and PP IX specifically bind to ANT. Mitochondrial uptake of PP IX was inhibited by ADP, a known substrate of ANT. Conversely, ADP uptake into mitochondria was competitively inhibited by haem and its precursors, suggesting that haem-related porphyrins are accumulated into mitochondria via ANT. Furthermore, disruption of the ANT genes in yeast resulted in a reduction of haem biosynthesis by blocking the translocation of haem precursors into the matrix. Our results represent a new model that ANT plays a crucial role in haem biosynthesis by facilitating accumulation of its precursors into the mitochondrial matrix.

Synthesis and thermal behavior of new organometallic poly ketones and co-poly ketones based on diferrocenylidene piperidone

International Nuclear Information System (INIS)

Aly, K.I.

2005-01-01

A new interesting category of organometallic poly ketones and copolyketones were synthesized via Friedel - Crafts reaction through the polymerization of 2,6-[Bis (2-ferrocenyl )methylene] N-methylpiperidone (II) with different diacid chlorides. The model compound was synthesized by reacting the monomer (II) with benzoyl chloride and characterized by HNMR, IR and elemental analyses. The poly ketones and copolyketones were insoluble in most organic solvents but soluble easily in protic solvents. The thermal properties of these poly ketones and copolyketones were evaluated and correlated to their structural units by TGA and DSC measurements, and had inherent viscosity 0.34-0.52 dl g-1. Moreover, the electrical conductivity of one of the poly ketones, as selected example, Va and copolyketone VI were investigated above the temperature range (300-500 K) and showed that it followed an Arrhenius equation with activation energy 2.09 eV, also the morphological properties of selected examples of poly-and copolyketones were detected by SEM

Formation of crystalline InGaO₃(ZnO)n nanowires via the solid-phase diffusion process using a solution-based precursor.

Science.gov (United States)

Guo, Yujie; Van Bilzen, Bart; Locquet, Jean Pierre; Seo, Jin Won

2015-12-11

One-dimensional single crystalline InGaO3(ZnO)n (IGZO) nanostructures have great potential for various electrical and optical applications. This paper demonstrates for the first time, to our knowledge, a non-vacuum route for the synthesis of IGZO nanowires by annealing ZnO nanowires covered with solution-based IGZO precursor. This method results in nanowires with highly periodic IGZO superlattice structure. The phase transition of IGZO precursor during thermal treatment was systematically studied. Transmission electron microscopy studies reveal that the formation of the IGZO structure is driven by anisotropic inter-diffusion of In, Ga, and Zn atoms, and also by the crystallization of the IGZO precursor. Optical measurements using cathodoluminescence and UV-vis spectroscopy confirm that the nanowires consist of the IGZO compound with wide optical band gap and suppressed luminescence.

Synthesis, solubilization, and surface functionalization of highly fluorescent quantum dots for cellular targeting through a small molecule

Science.gov (United States)

Galloway, Justin F.

To achieve long-term fluorescence imaging with quantum dots (QDs), a CdSe core/shell must first be synthesized. The synthesis of bright CdSe QDs is not trivial and as a consequence, the role of surfactant in nucleation and growth was investigated. It was found that the type of surfactant used, either phosphonic or fatty acid, played a pivotal role in the size of the CdSe core. The study of surfactant on CdSe synthesis, ultimately led to an electrical passivation method that utilized a short-chained phosphonic acid and highly reactive organometallic precursors to achieve high quantum yield (QY) as has been previously described. The synthesis of QDs using organometallic precursors and a phosphonic acid for passivation resulted in 4 out of 9 batches of QDs achieving QYs greater than 50% and 8 out of 9 batches with QYs greater than 35%. The synthesis of CdSe QDs was done in organic solutions rendering the surface of the particle hydrophobic. To perform cell-targeting experiments, QDs must be transferred to water. The transfer of QDs to water was successfully accomplished by using single acyl chain lipids. A systematic study of different lipid combinations and coatings demonstrated that 20-40 mol% single acyl chained lipids were able to transfer QDs to water resulting in monodispersed, stable QDs without adversely affecting the QY. The advantage to water solubilization using single acyl chain lipids is that the QD have a hydrodynamic radius less than 15 nm, QYs that can exceed 50% and additional surface functionalization can be down using the reactive sites incorporated into the lipid bilayer. QDs that are bright and stable in water were studied for the purpose of targeting G protein-coupled Receptors (GPCR). GPCRs are transmembrane receptors that internalize extracellular cues, and thus mediate signal transduction. The cyclic Adenosine Monophosphate Receptor 1 of the model organism Dictyostelium disodium was the receptor of interest. The Halo protein, a genetically

Precursors of chicken flavor. II. Identification of key flavor precursors using sensory methods.

Science.gov (United States)

Aliani, Michel; Farmer, Linda J

2005-08-10

Sensory evaluation was used to identify flavor precursors that are critical for flavor development in cooked chicken. Among the potential flavor precursors studied (thiamin, inosine 5'-monophosphate, ribose, ribose-5-phosphate, glucose, and glucose-6-phosphate), ribose appears most important for chicken aroma. An elevated concentration (added or natural) of only 2-4-fold the natural concentration gives an increase in the selected aroma and flavor attributes of cooked chicken meat. Assessment of the volatile odor compounds by gas chromatography-odor assessment and gas chromatography-mass spectrometry showed that ribose increased odors described as "roasted" and "chicken" and that the changes in odor due to additional ribose are probably caused by elevated concentrations of compounds such as 2-furanmethanethiol, 2-methyl-3-furanthiol, and 3-methylthiopropanal.

CHEMICAL VAPOUR DEPOSITION FROM A RADIATION-SENSITIVE PRECURSOR

DEFF Research Database (Denmark)

2017-01-01

The present invention relates in one aspect to a method of depositing a thin film on a substrate by chemical vapour deposition (CVD) from a radiation-sensitive precursor substance. The method comprises the steps of: (i) placing the substrate in a reaction chamber of a CVD system; (ii) heating...... heating pulse followed by an idle period; (iii) during at least one of the idle periods, providing a pressure pulse of precursor substance inside the reaction chamber by feeding at least one precursor substance to the reaction chamber so as to establish a reaction partial pressure for thin film deposition...... is formed. According to a further aspect, the invention relates to a chemical vapour deposition (CVD) system for depositing a thin film onto a substrate using precursor substances containing at least one radiation sensitive species....

Effect of fiber coatings on room and elevated temperature mechanical properties of Nicalon trademark fiber reinforced Blackglas trademark ceramic matrix composites (CMCs)

International Nuclear Information System (INIS)

Aly, E.I.; Freitag, D.W.; Littlefield, J.E.

1993-01-01

With the development of silicon organometallic preceramic polymers as precursors for producing oxidation resistant ceramic matrices, through the polymer pyrolysis route, the fabrication of lightweight, complex advanced aircraft and missile structures from fiber reinforced composites is increasingly becoming more feasible. Besides refinement of processing techniques, the potential for achieving this objective depends upon identifying and developing the proper debond barrier coating layer, between the fiber and the matrix, for optimization of strength, toughness, and durability properties. Blackglas trademark based CMC's reinforced with Nicalon trademark SiC fibers with different types of coatings were fabricated. Coating schemes evaluated include CVD applied single layer boron nitride (BN) composition, dual-layer coatings of BN/SiC, and triple-layer coatings of SiC BN/SiC. Results of tensile and flexural property tests, scanning electron microscopy (SEM) of fracture surfaces, and auger electron spectroscopy (AES) microanalysis of the fiber/matrix interface have been discussed

Growth and scintillation properties of 3 in. diameter Ce doped Gd.sub.3./sub.Ga.sub.3./sub.Al.sub.2./sub.O.sub.12./sub. scintillation single crystal

Czech Academy of Sciences Publication Activity Database

Kamada, K.; Shoji, Y.; Kochurikhin, V.V.; Okumura, S.; Yamamoto, S.; Nagura, A.; Yeom, J.Y.; Kurosawa, S.; Yokota, Y.; Ohashi, Y.; Nikl, Martin; Yoshikawa, A.

2016-01-01

Roč. 452, Oct (2016), s. 81-84 ISSN 0022-0248. [American Conference on Crystal Growth and Epitaxy /20./ (ACCGE) / 17th Biennial Workshop on Organometallic Vapor Phase Epitaxy (OMVPE) / 2nd 2D Electronic Materials Symposium. Big Sky, MT, 02.08.2015-07.08.2015] R&D Projects: GA MŠk(CZ) LH14266; GA ČR GJ15-18300Y EU Projects: European Commission(XE) 644260 - INTELUM Institutional support: RVO:68378271 Keywords : single crystal growth * oxides * scintillator materials * scintillators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.751, year: 2016

Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

Energy Technology Data Exchange (ETDEWEB)

Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

2008-02-16

Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

Theoretical Study of Indium Compounds of Interest for Organometallic Chemical Vapor Deposition

Science.gov (United States)

Cardelino, B. H.; Moore, C. E.; Cardelino, C. A.; Frazier, D. O.; Backmann, K. J.

2000-01-01

The structural. electronic and therinochemical properties of indium compounds which are of interest in halide transport and organometallic chemical vapor deposition processes have been studied by ab initio and statistical mechanics methods. The compounds reported include: indium halides and hydrides (InF, InCl, InCl3, InH, InH2, InH3); indium clusters (In2, In3); methylindium, dimethylindium, and their hydrogen derivatives [In(CH3), In(CH3)H, In(CH3)H2, In(CH3)2, In(CH3)2H]; dimethyl-indium dimer [In2(CH3)4], trimethyl-indium [In(CH3)3]; dehydrogenated methyl, dimethyl and trimethylindium [In(CH3)2CH2, In(CH3)CH2, In(CH2)], trimethylindium adducts with ammonia, trimethylamine and hydrazine [(CH3)3In:NH3, (CH3)3In:N(CH3)3, (CH3)3In:N(H2)N(H2)]; dimethylamino-indium and methylimino-indium [In(CH3)2(NH2), In(CH3)(NH)]; indium nitride and indium nitride dimer (InN, In2N2), indium phosphide, arsenide and antimonide ([InP, InAs, InSb). The predicted electronic properties are based on density functional theory calculations; the calculated thermodynamic properties are reported following the format of the JANAF (Joint Army, Navy, NASA, Air Force) Tables. Equilibrium compositions at two temperatures (298 and 1000 K) have been analyzed for groups of competing simultaneous reactions.

Synthesis of nanocrystalline Gd{sub 2}O{sub 2}NCN from a versatile single-source precursor

Energy Technology Data Exchange (ETDEWEB)

Ionescu, Emanuel; Wiehl, Leonore; Mera, Gabriela; Riedel, Ralf [Fachbereich Material- und Geowissenschaften, Technische Universitaet Darmstadt (Germany); Li, Wenjie [Fachbereich Material- und Geowissenschaften, Technische Universitaet Darmstadt (Germany); Center for Energy Harvesting Materials and Systems, Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA (United States)

2017-11-17

Nanocrystalline Gd{sub 2}O{sub 2}NCN (P anti 3m1, crystallite size 30-40 nm) was synthesized upon ammonolysis of bis[[(N-carboxymethyl,N-carboxy-κO-methyl)amino-κN-ethyl]-glycinato( 3-)-κN,κO]gadolinium(III) (diethylenetriamine pentaacetic acid gadolinium(III) dihydrogen salt or gadopentetic acid, Gd-H{sub 2}DTPA hereafter) at 900 C. The conversion of Gd-H{sub 2}DTPA into Gd{sub 2}O{sub 2}NCN takes place in several steps, probably via transient formation of iminodiacetate-, glycinate-, and carbamate-containing complexes of Gd. Thermal treatment in air of Gd-H{sub 2}DTPA at 750 and 1300 C delivers nanocrystalline bixbyite-type Gd{sub 2}O{sub 3} (Ia anti 3, crystallite size 30-70 nm); in an argon or nitrogen atmosphere the formation of monoclinic Gd{sub 2}O{sub 3} (C2/m) was observed at 1300 C. The synthesized Gd{sub 2}O{sub 2}NCN converts upon thermal treatment in air, nitrogen, or argon atmosphere into monoclinic Gd{sub 2}O{sub 3} (C2/m). In ammonia atmosphere, Gd{sub 2}O{sub 2}NCN seems to be stable against decomposition, even upon prolonged exposure to 1000 C. This study indicates that Gd-H{sub 2}DTPA may be a robust, low-cost, and flexible precursor for nanoscaled Gd-based nanopowders. Moreover, precursor approaches based on metal complexes using H{sub 5}DTPA as a ligand are suggested as promising access pathways towards nanocrystalline materials in the M/O/C/N system. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Adult subependymal neural precursors, but not differentiated cells, undergo rapid cathodal migration in the presence of direct current electric fields.

Directory of Open Access Journals (Sweden)

Robart Babona-Pilipos

Full Text Available BACKGROUND: The existence of neural stem and progenitor cells (together termed neural precursor cells in the adult mammalian brain has sparked great interest in utilizing these cells for regenerative medicine strategies. Endogenous neural precursors within the adult forebrain subependyma can be activated following injury, resulting in their proliferation and migration toward lesion sites where they differentiate into neural cells. The administration of growth factors and immunomodulatory agents following injury augments this activation and has been shown to result in behavioural functional recovery following stroke. METHODS AND FINDINGS: With the goal of enhancing neural precursor migration to facilitate the repair process we report that externally applied direct current electric fields induce rapid and directed cathodal migration of pure populations of undifferentiated adult subependyma-derived neural precursors. Using time-lapse imaging microscopy in vitro we performed an extensive single-cell kinematic analysis demonstrating that this galvanotactic phenomenon is a feature of undifferentiated precursors, and not differentiated phenotypes. Moreover, we have shown that the migratory response of the neural precursors is a direct effect of the electric field and not due to chemotactic gradients. We also identified that epidermal growth factor receptor (EGFR signaling plays a role in the galvanotactic response as blocking EGFR significantly attenuates the migratory behaviour. CONCLUSIONS: These findings suggest direct current electric fields may be implemented in endogenous repair paradigms to promote migration and tissue repair following neurotrauma.

The proliferative human monocyte subpopulation contains osteoclast precursors

Science.gov (United States)

Lari, Roya; Kitchener, Peter D; Hamilton, John A

2009-01-01

Introduction Immediate precursors of bone-resorbing osteoclasts are cells of the monocyte/macrophage lineage. Particularly during clinical conditions showing bone loss, it would appear that osteoclast precursors are mobilized from bone marrow into the circulation prior to entering tissues undergoing such loss. The observed heterogeneity of peripheral blood monocytes has led to the notion that different monocyte subpopulations may have special or restricted functions, including as osteoclast precursors. Methods Human peripheral blood monocytes were sorted based upon their degree of proliferation and cultured in macrophage colony-stimulating factor (M-CSF or CSF-1) and receptor activator of nuclear factor-kappa-B ligand (RANKL). Results The monocyte subpopulation that is capable of proliferation gave rise to significantly more multinucleated, bone-resorbing osteoclasts than the bulk of the monocytes. Conclusions Human peripheral blood osteoclast precursors reside in the proliferative monocyte subpopulation. PMID:19222861

Organometallic DNA-B12 Conjugates as Potential Oligonucleotide Vectors: Synthesis and Structural and Binding Studies with Human Cobalamin-Transport Proteins.

Science.gov (United States)

Mutti, Elena; Hunger, Miriam; Fedosov, Sergey; Nexo, Ebba; Kräutler, Bernhard

2017-11-16

The synthesis and structural characterization of Co-(dN) 25 -Cbl (Cbl: cobalamin; dN: deoxynucleotide) and Co-(dN) 39 -Cbl, which are organometallic DNA-B 12 conjugates with single DNA strands consisting of 25 and 39 deoxynucleotides, respectively, and binding studies of these two DNA-Cbl conjugates to three homologous human Cbl transporting proteins, transcobalamin (TC), intrinsic factor (IF), and haptocorrin (HC), are reported. This investigation tests the suitability of such DNA-Cbls for the task of eventual in vivo oligonucleotide delivery. The binding of DNA-Cbl to TC, IF, and HC was investigated in competition with either a fluorescent Cbl derivative and Co-(dN) 25 -Cbl, or radiolabeled vitamin B 12 ( 57 Co-CNCbl) and Co-(dN) 25 -Cbl or Co-(dN) 39 -Cbl. Binding of the new DNA-Cbl conjugates was fast and tight with TC, but poorer with HC and IF, which extends a similar original finding with the simpler DNA-Cbl, Co-(dN) 18 -Cbl. The contrasting affinities of TC versus IF and HC for the DNA-Cbl conjugates are rationalized herein by a stepwise mechanism of Cbl binding. Critical contributions to overall affinity result from gradual conformational adaptations of the Cbl-binding proteins to the DNA-Cbl, which is first bound to the respective β domains. This transition is fast with TC, but slow with IF and HC, with which weaker binding results. The invariably tight interaction of the DNA-Cbl conjugates with TC makes the Cbl moiety a potential natural vector for the specific delivery of oligonucleotide loads from the blood into cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effects of Annealing Parameters on the Crystallization and Morphology of Cu(In,GaSe2 Absorber Layers Prepared by Annealing Stacked Metallic Precursors

Directory of Open Access Journals (Sweden)

Chia-Ho Huang

2014-01-01

Full Text Available CIGS films are prepared by single-stage annealing of the solid Se-coated In/Cu-Ga bilayer precursor. The annealing processes were performed using various Ar pressures, heating rates, and soaking times. A higher Ar pressure is needed to fabricate highly crystalline CIGS films, as no extra Se-vapor source is supplied. As the heating rate increases, the surface morphologies of the CIGS films become looser and some cracks are observed. However, the influence of soaking time is insignificant and the selenization process only requires a short time when the precursors are selenized at a higher temperature with a lower heating rate and a higher Ar pressure. In this study, a dense chalcopyrite CIGS film with a thickness of about 1.5-1.6 μm, with large grains (~1.2 μm and no cracking or peeling is obtained after selenizing at a temperature of 550°C, an Ar pressure of 300 Torr, a heating rate of 60°C/min, and a soaking time of 20 min. By adequate design of the stacked precursor and controlling the annealing parameters, single-stage annealing of the solid Se-coated In/Cu-Ga bilayer precursor is simplified for the fabrication of a fully crystallized chalcopyrite CIGS absorber layers with good crystallization and large grains.

The use of a well-defined surface organometallic complex as a probe molecule: [(≡SiO)Ta^VCl₂Me₂] shows different isolated silanol sites on the silica surface

KAUST Repository

Chen, Yin; Zheng, Bin; Abou-Hamad, Edy; Hamieh, Ali Imad Ali; Hamzaoui, Bilel; Huang, Kuo-Wei; Basset, Jean-Marie

2014-01-01

TaVCl2Me3 reacts with silica(700) and produces two different [(≡SiO)TaVCl2Me2] surface organometallic species, suggesting a heterogeneity of the highly dehydroxylated silica surface, which was studied with a combined experimental and theoretical approach. This journal is © the Partner Organisations 2014.

Formation of crystalline InGaO_3(ZnO)_n nanowires via the solid-phase diffusion process using a solution-based precursor

International Nuclear Information System (INIS)

Guo, Yujie; Seo, Jin Won; Bilzen, Bart Van; Locquet, Jean Pierre

2015-01-01

One-dimensional single crystalline InGaO_3(ZnO)_n (IGZO) nanostructures have great potential for various electrical and optical applications. This paper demonstrates for the first time, to our knowledge, a non-vacuum route for the synthesis of IGZO nanowires by annealing ZnO nanowires covered with solution-based IGZO precursor. This method results in nanowires with highly periodic IGZO superlattice structure. The phase transition of IGZO precursor during thermal treatment was systematically studied. Transmission electron microscopy studies reveal that the formation of the IGZO structure is driven by anisotropic inter-diffusion of In, Ga, and Zn atoms, and also by the crystallization of the IGZO precursor. Optical measurements using cathodoluminescence and UV-vis spectroscopy confirm that the nanowires consist of the IGZO compound with wide optical band gap and suppressed luminescence. (paper)

Radiochemical Means of Investigating Delayed Neutron Precursors

International Nuclear Information System (INIS)

Marmol, P. del

1968-01-01

Fast radiochemical methods used now for the determination of delayed neutron precursors are classified and reviewed: precipitations, solvent extractions, range experiments, milking, gas sweeping, isotopic and ion exchange, hot atom reactions and diffusion loss. Advantages and limitations of irradiation systems with respect to fast separations are discussed: external beams which allow faster separations only have low neutron fluxes, internal beams which are mostly fit for gaseous reactions; and rabbits for solution irradiations. Future prospects of radiochemical procedures are presented; among these, studies should be mostly oriented towards gaseous reactions which offer possibilities of isolating very short-lived delayed neutron precursors. Chemical procedures for delayed neutron precursor detection are compared with mass spectrometric and isotope separator techniques; it is concluded that the methods are complementary. (author)

Radiochemical Means of Investigating Delayed Neutron Precursors

International Nuclear Information System (INIS)

Marmol, P. del

1968-01-01

Fast radiochemical methods used now for the determination of delayed neutron precursors are classified and reviewed: precipitations, solvent extractions, range experiments, milking, gas sweeping, isotopic and ion exchange, hot-atom reactions and diffusion loss. Advantages and limitations of irradiation systems with respect to fast separations are discussed: external beams which allow faster separations only have low neutron fluxes, internal beams which are mostly fit for gaseous reactions; and rabbits for solution irradiations. Future prospects of radiochemical procedures are presented; among these, studies should be mostly oriented towards gaseous reactions which offer possibilities of isolating very short-lived delayed neutron precursors. Chemical procedures for delayed neutron precursor detection are compared with mass spectrometric and isotope-separator techniques; it is concluded that the methods are complementary. (author)

Thin HTSC films produced by a polymer metal precursor technique

Science.gov (United States)

Lampe, L. v.; Zygalsky, F.; Hinrichsen, G.

In precursors the metal ions are combined with acid groups of polymethacrylic acid (PMAA), polyacrylic acid (PAA) or novolac. Compared to thermal degradation temperature of pure polymers those of precursors are low. Precursors films were patterned by UV lithography. Diffractometric investigations showed that the c-axis oriented epitaxial films of YBa 2Cu 3O x and Bi 2Sr 2CaCu 2O x originated from amorphous metal oxide films, which were received after thermal degradation of the precursor. Transition temperatures and current densities were determined by electric resistivity measurements.

The EM Earthquake Precursor

Science.gov (United States)

Jones, K. B., II; Saxton, P. T.

2013-12-01

Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After the 1989 Loma Prieta Earthquake, American earthquake investigators predetermined magnetometer use and a minimum earthquake magnitude necessary for EM detection. This action was set in motion, due to the extensive damage incurred and public outrage concerning earthquake forecasting; however, the magnetometers employed, grounded or buried, are completely subject to static and electric fields and have yet to correlate to an identifiable precursor. Secondly, there is neither a networked array for finding any epicentral locations, nor have there been any attempts to find even one. This methodology needs dismissal, because it is overly complicated, subject to continuous change, and provides no response time. As for the minimum magnitude threshold, which was set at M5, this is simply higher than what modern technological advances have gained. Detection can now be achieved at approximately M1, which greatly improves forecasting chances. A propagating precursor has now been detected in both the field and laboratory. Field antenna testing conducted outside the NE Texas town of Timpson in February, 2013, detected three strong EM sources along with numerous weaker signals. The antenna had mobility, and observations were noted for recurrence, duration, and frequency response. Next, two

Bimetallic oxamato complexes synthesized into mesoporous matrix as precursor to tunable nanosized oxide

Energy Technology Data Exchange (ETDEWEB)

Kalinke, Lucas H.G. [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil); Instituto Federal de Goiás—IFG, Anápolis, GO (Brazil); Stumpf, Humberto O. [Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG (Brazil); Mazali, Italo O. [Instituto de Química, Universidade Estadual de Campinas—UNICAMP, Campinas, SP (Brazil); Cangussu, Danielle, E-mail: danielle_cangussu@ufg.br [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil)

2015-10-15

Highlights: • The bimetallic oxamato complexes as single-source precursor. • We prepared into a porous silica glass tunable nanosized oxide powders. • X-ray diffraction shows the formation of CeO{sub 2}/CuO and spinel cobaltite. • The different number of IDC allows control of the nanoparticle size. - Abstract: The bimetallic complexes were employed to prepare into a porous silica glass tunable nanosized oxide powders through the single source precursor (SSP) method. These materials were prepared by first anchoring of [Cu(opba)]{sup 2−} [opba = ortho-phenylenebis(oxamato)], second by reaction in situ with second metal [Co(II) or Ce(III)] and followed by a thermal treatment. The different number of impregnation–decomposition cycles (IDC) allows control of the nanoparticle size. X-ray diffraction shows the formation of mixture CeO{sub 2}–CuO and spinel copper cobaltite. Raman spectroscopy confirmed the formation of such phases. Transmission electron microscopy images revealed that spinel cobaltite particles (8 IDC) present a mean size of about 9 nm, whereas for the CeO{sub 2}–CuO phase the particle diameters are 4 nm (2 IDC) and 8 nm (6 IDC). For CeO{sub 2}–CuO the diffuse reflectance spectroscopy indicates a consistent red shift in band gap from 3.41 to 2.87 eV with increasing of particle size due to quantum confinement effect.

Proteolytic processing of the vitellogenin precursor in the boll weevil, Anthonomus grandis.

Science.gov (United States)

Heilmann, L J; Trewitt, P M; Kumaran, A K

1993-01-01

The soluble proteins of the eggs of the coleopteran insect Anthonomus grandis Boheman, the cotton boll weevil, consist almost entirely of two vitellin types with M(r)s of 160,000 and 47,000. We sequenced their N-terminal ends and one internal cyanogen bromide fragment of the large vitellin and compared these sequences with the deduced amino acid sequence from the vitellogenin gene. The results suggest that both the boll weevil vitellin proteins are products of the proteolytic cleavage of a single precursor protein. The smaller 47,000 M(r) vitellin protein is derived from the N-terminal portion of the precursor adjacent to an 18 amino acid signal peptide. The cleavage site between the large and small vitellins at amino acid 362 is adjacent to a pentapeptide sequence containing two pairs of arginine residues. Comparison of the boll weevil sequences with limited known sequences from the single 180,000 M(r) honey bee protein show that the honey bee vitellin N-terminal exhibits sequence homology to the N-terminal of the 47,000 M(r) boll weevil vitellin. Treatment of the vitellins with an N-glycosidase results in a decrease in molecular weight of both proteins, from 47,000 to 39,000 and from 160,000 to 145,000, indicating that about 10-15% of the molecular weight of each vitellin consists of N-linked carbohydrate. The molecular weight of the deglycosylated large vitellin is smaller than that predicted from the gene sequence, indicating possible further proteolytic processing at the C-terminal of that protein.

The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces.

Science.gov (United States)

Barry, Seán T; Teplyakov, Andrew V; Zaera, Francisco

2018-03-20

viewed from the point of view of the metalorganic complexes used as precursors: they are bulky and rigid, can provide multiple binding sites for a single reaction, and can promote unique bonding modes, especially on metals, which have delocalized electronic structures. The differences between the molecular and surface chemistry of CVD and ALD precursors can result in significant variations in their reactivity, ultimately leading to unpredictable properties in the newly grown films. In this Account, we discuss some of the main similarities and differences in chemistry that CVD/ALD precursors follow on surfaces when contrasted against their known behavior in solution, with emphasis on our own work but also referencing other key contributions. Our approach is unique in that it combines expertise from the inorganic, surface science, and quantum-mechanics fields to better understand the mechanistic details of the chemistry of CVD and ALD processes and to identify new criteria to consider when designing CVD/ALD precursors.

Development of novel strategy for the synthesis of organometallic compounds usable as protein ligands: application to the human cyclophilin hCyp-18

International Nuclear Information System (INIS)

Clavaud, C.

2006-02-01

This thesis describes a new strategy for the development of bioactive organometallic compounds, basing on the combinatorial assembly of sub-chemical libraries (A and B) independent but complementary and able to coordinate a metallic heart M to form A-M-B complex potential ligands of biomolecules. The coordination of metals, well adapted to the production of molecular variety is usually used in medicinal chemistry, in diagnostic and therapeutic nuclear medicine. Among the useful elements, the rhenium and the technetium are metals of choice for the development of the assembly strategy because of their chemical and radiochemical properties and of the structure analogy of their complexes. This strategy was validated in vitro. The protein chosen for this purpose was the cyclophilin hCyp-18. (N.C.)

A facile synthesis of ZnS nanocrystallites by pyrolysis of single

Indian Academy of Sciences (India)

)2 and ZnCl2 (cinnamtsczH)2 (cinnamtsczH = cinnamaldehyde thiosemicarbazone) as single source precursors. The prepared ZnS nanocrystallites were characterized by powder X-ray diffraction (XRD), transmission electron microscopy ...

Natural attenuation of NDMA precursors in an urban, wastewater-dominated wash.

Science.gov (United States)

Woods, Gwen C; Dickenson, Eric R V

2016-02-01

N-Nitrosodimethylamine (NDMA) is a disinfection by-product (DBP) that is potentially carcinogenic and has been found to occur in drinking water treatment systems impacted with treated wastewater. A major gap in NDMA research is an understanding of the persistence of wastewater-derived precursors within the natural environment. This research sought to fill this knowledge gap by surveying NDMA precursors across the length of a wastewater effluent-dominated wash. Significant precursor reduction (17%) was found to occur from introduction into the wash to a point 9 h downstream. This reduction translates into a half-life of roughly 32 h for bulk NDMA precursors. Further laboratory experiments examining rates of photolysis, biodegradation and loss to sediments, illustrated that both photolytic and biological degradation were effective removal mechanisms for NDMA precursors. Loss to sediments that were acquired from the wash did not appear to reduce NDMA precursors in the water column, although a control conducted with DI water provided evidence that significant NDMA precursors could be released from autoclaved sediments (suggesting that sorption does occur). Microbial experiments revealed that microbes associated with sediments were much more effective at degrading precursors than microbes within the water column. Overall, this study demonstrated that natural processes are capable of attenuating NDMA precursors relatively quickly within the environment, and that utilities might benefit from maximizing source water residency time in the environment, prior to introduction into treatment plants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Analysis of Precursor Properties of mixed Al/Alumel Cylindrical Wire Arrays*

Science.gov (United States)

Stafford, A.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Weller, M. E.; Shrestha, I.; Osborne, G. C.; Shlyaptseva, V. V.; Keim, S. F.; Coverdale, C. A.; Chuvatin, A. S.

2012-10-01

Previous studies of mid-Z (Cu and Ni) cylindrical wire arrays (CWAs) on Zebra have found precursors with high electron temperatures of >300 eV. However, past experiments with Al CWAs did not find the same high temperature precursors. New precursor experiments using mixed Al/Alumel (Ni 95%, Si 2%, and Al 2%) cylindrical wire arrays have been performed to understand how the properties of L-shell Ni precursor will change and whether Al precursor will be observed. Time gated spectra and pinholes are used to determine precursor plasma conditions for comparison with previous Alumel precursor experiments. A full diagnostic set which included more than ten different beam-lines was implemented. Future work in this direction is discussed. [4pt] *This work was supported by NNSA under DOE Cooperative Agreements DE-FC52-06NA27588, and in part by DE-FC52-06NA27586, and DE-FC52-06NA27616. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane

KAUST Repository

Samantaray, Manoja; Kavitake, Santosh Giridhar; Morlanes, Natalia Sanchez; Abou-Hamad, Edy; Hamieh, Ali Imad Ali; Dey, Raju; Basset, Jean-Marie

2017-01-01

Two compatible organometallic complexes, W(Me)(6) (1) and TiNp4 (2), were successively anchored on a highly dehydroxylated single silica support (SiO2-700) to synthesize the well-defined bimetallic precatalyst [(equivalent to Si-O-)W(Me)(5)(equivalent to Si-O-)Ti(Np)(3)] (4). Precatalyst 4 was characterized at the molecular level using advanced surface organometallic chemistry (SOMC) characterization techniques. The strong autocorrelation observed between methyl of W and Ti in H-1-H-1 multiple-quantum NMR spectra demonstrates that W and Ti species are in close proximity to each other. The bimetallic precatalyst 4, with a turnover number (TON) of 9784, proved to be significantly more efficient than the silica-supported monometallic catalyst [(equivalent to Si-O-)W(Me)(5)] (3), with a TON of 98, for propane metathesis at 150 degrees C in a flow reactor. The dramatic improvement in the activity signifies the cooperativity between Ti and W and indicates that the key step of alkane metathesis (C-H bond activation followed by beta-H elimination) occurs on Ti, followed by olefin metathesis, which occurs on W. We have demonstrated the influence and importance of proximity of Ti to W for achieving such a significantly high activity. This is the first report demonstrating the considerably high activity (TON = 9784) in propane metathesis at moderate temperature (150 degrees C) using a well-defined bimetallic system prepared via the SOMC approach.

Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane

KAUST Repository

Samantaray, Manoja

2017-02-10

Two compatible organometallic complexes, W(Me)(6) (1) and TiNp4 (2), were successively anchored on a highly dehydroxylated single silica support (SiO2-700) to synthesize the well-defined bimetallic precatalyst [(equivalent to Si-O-)W(Me)(5)(equivalent to Si-O-)Ti(Np)(3)] (4). Precatalyst 4 was characterized at the molecular level using advanced surface organometallic chemistry (SOMC) characterization techniques. The strong autocorrelation observed between methyl of W and Ti in H-1-H-1 multiple-quantum NMR spectra demonstrates that W and Ti species are in close proximity to each other. The bimetallic precatalyst 4, with a turnover number (TON) of 9784, proved to be significantly more efficient than the silica-supported monometallic catalyst [(equivalent to Si-O-)W(Me)(5)] (3), with a TON of 98, for propane metathesis at 150 degrees C in a flow reactor. The dramatic improvement in the activity signifies the cooperativity between Ti and W and indicates that the key step of alkane metathesis (C-H bond activation followed by beta-H elimination) occurs on Ti, followed by olefin metathesis, which occurs on W. We have demonstrated the influence and importance of proximity of Ti to W for achieving such a significantly high activity. This is the first report demonstrating the considerably high activity (TON = 9784) in propane metathesis at moderate temperature (150 degrees C) using a well-defined bimetallic system prepared via the SOMC approach.

Role of Precursor-Conversion Chemistry in the Crystal-Phase Control of Catalytically Grown Colloidal Semiconductor Quantum Wires.

Science.gov (United States)

Wang, Fudong; Buhro, William E

2017-12-26

Crystal-phase control is one of the most challenging problems in nanowire growth. We demonstrate that, in the solution-phase catalyzed growth of colloidal cadmium telluride (CdTe) quantum wires (QWs), the crystal phase can be controlled by manipulating the reaction chemistry of the Cd precursors and tri-n-octylphosphine telluride (TOPTe) to favor the production of either a CdTe solute or Te, which consequently determines the composition and (liquid or solid) state of the Bi x Cd y Te z catalyst nanoparticles. Growth of single-phase (e.g., wurtzite) QWs is achieved only from solid catalysts (y ≪ z) that enable the solution-solid-solid growth of the QWs, whereas the liquid catalysts (y ≈ z) fulfill the solution-liquid-solid growth of the polytypic QWs. Factors that affect the precursor-conversion chemistry are systematically accounted for, which are correlated with a kinetic study of the composition and state of the catalyst nanoparticles to understand the mechanism. This work reveals the role of the precursor-reaction chemistry in the crystal-phase control of catalytically grown colloidal QWs, opening the possibility of growing phase-pure QWs of other compositions.

On-Surface Pseudo-High-Dilution Synthesis of Macrocycles: Principle and Mechanism.

Science.gov (United States)

Fan, Qitang; Wang, Tao; Dai, Jingya; Kuttner, Julian; Hilt, Gerhard; Gottfried, J Michael; Zhu, Junfa

2017-05-23

Macrocycles have attracted much attention due to their specific "endless" topology, which results in extraordinary properties compared to related linear (open-chain) molecules. However, challenges still remain in their controlled synthesis with well-defined constitution and geometry. Here, we report the successful application of the (pseudo-)high-dilution method to the conditions of on-surface synthesis in ultrahigh vacuum. This approach leads to high yields (up to 84%) of cyclic hyperbenzene ([18]-honeycombene) via an Ullmann-type reaction from 4,4″-dibromo-meta-terphenyl (DMTP) as precursor on a Ag(111) surface. The mechanism of macrocycle formation was explored in detail using scanning tunneling microscopy and X-ray photoemission spectroscopy. We propose that the dominant pathway for hyperbenzene (MTP) 6 formation is the stepwise desilverization of an organometallic (MTP-Ag) 6 macrocycle, which forms via cyclization of (MTP-Ag) 6 chains under pseudo-high-dilution conditions. The high probability of cyclization on the stage of the organometallic phase results from the reversibility of the C-Ag bond. The case is different from that in solution, in which cyclization typically occurs on the stage of a covalently bonded open-chain precursor. This difference in the cyclization mechanism on a surface compared to that in solution stems mainly from the 2D confinement exerted by the surface template, which hinders the flipping of chain segments necessary for cyclization.

Precursor conditions related to Zimbabwe's summer droughts

Science.gov (United States)

Nangombe, Shingirai; Madyiwa, Simon; Wang, Jianhong

2018-01-01

Despite the increasing severity of droughts and their effects on Zimbabwe's agriculture, there are few tools available for predicting these droughts in advance. Consequently, communities and farmers are more exposed, and policy makers are always ill prepared for such. This study sought to investigate possible cycles and precursor meteorological conditions prior to drought seasons that could be used to predict impending droughts in Zimbabwe. The Single Z-Index was used to identify and grade drought years between 1951 and 2010 according to rainfall severity. Spectral analysis was used to reveal the cycles of droughts for possible use of these cycles for drought prediction. Composite analysis was used to investigate circulation and temperature anomalies associated with severe and extreme drought years. Results indicate that severe droughts are more highly correlated with circulation patterns and embedded weather systems in the Indian Ocean and equatorial Pacific Ocean than any other area. This study identified sea surface temperatures in the average period June to August, geopotential height and wind vector in July to September period, and air temperature in September to November period as precursors that can be used to predict a drought occurrence several months in advance. Therefore, in addition to sea surface temperature, which was identified through previous research for predicting Zimbabwean droughts, the other parameters identified in this study can aid in drought prediction. Drought cycles were established at 20-, 12.5-, 3.2-, and 2.7-year cycles. The spectral peaks, 12.5, 3.2, and 2.7, had a similar timescale with the luni-solar tide, El Niño Southern Oscillation and Quasi Biennial Oscillation, respectively, and hence, occurrence of these phenomena have a possibility of indicating when the next drought might be.

Probing the chemistry, electronic structure and redox energetics in pentavalent organometallic actinide complexes

Energy Technology Data Exchange (ETDEWEB)

Graves, Christopher R [Los Alamos National Laboratory; Vaughn, Anthony E [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

2008-01-01

Complexes of the early actinides (Th-Pu) have gained considerable prominence in organometallic chemistry as they have been shown to undergo chemistries not observed with their transition- or lanthanide metal counterparts. Further, while bonding in f-element complexes has historically been considered to be ionic, the issue of covalence remains a subject of debate in the area of actinide science, and studies aimed at elucidating key bonding interactions with 5f-orbitals continue to garner attention. Towards this end, our interests have focused on the role that metal oxidation state plays in the structure, reactivity and spectral properties of organouranium complexes. We report our progress in the synthesis of substituted U{sup V}-imido complexes using various routes: (1) Direct oxidation of U{sup IV}-imido complexes with copper(I) salts; (2) Salt metathesis with U{sup V}-imido halides; (3) Protonolysis and insertion of an U{sup V}-imido alkyl or aryl complex with H-N{double_bond}CPh{sub 2} or N{triple_bond}C-Ph, respectively, to form a U{sup V}-imido ketimide complex. Further, we report and compare the crystallographic, electrochemical, spectroscopic and magnetic characterization of the pentavalent uranium (C{sub 5}Me{sub 5}){sub 2}U({double_bond}N-Ar)(Y) series (Y = OTf, SPh, C{triple_bond}C-Ph, NPh{sub 2}, OPh, N{double_bond}CPh{sub 2}) to further interrogate the molecular, electronic, and magnetic structures of this new class of uranium complexes.

Functional Analysis of Precursors for Serious Problem Behavior and Related Intervention

Science.gov (United States)

Langdon, Nancy A.; Carr, Edward G.; Owen-DeSchryver, Jamie S.

2008-01-01

Precursor behaviors are innocuous behaviors that reliably precede the occurrence of problem behavior. Intervention efforts applied to precursors might prevent the occurrence of severe problem behavior. We examined the relationship between precursor behavior and problem behavior in three individuals with developmental disabilities. First, a…

Geometrizing configurations. Heinrich Hertz and his mathematical precursors

DEFF Research Database (Denmark)

Lützen, Jesper

1999-01-01

A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics......A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics...

Anti-HIV-1 B cell responses are dependent on B cell precursor frequency and antigen-binding affinity.

Science.gov (United States)

Dosenovic, Pia; Kara, Ervin E; Pettersson, Anna-Klara; McGuire, Andrew T; Gray, Matthew; Hartweger, Harald; Thientosapol, Eddy S; Stamatatos, Leonidas; Nussenzweig, Michel C

2018-04-16

The discovery that humans can produce potent broadly neutralizing antibodies (bNAbs) to several different epitopes on the HIV-1 spike has reinvigorated efforts to develop an antibody-based HIV-1 vaccine. Antibody cloning from single cells revealed that nearly all bNAbs show unusual features that could help explain why it has not been possible to elicit them by traditional vaccination and instead would require a sequence of different immunogens. This idea is supported by experiments with genetically modified immunoglobulin (Ig) knock-in mice. Sequential immunization with a series of specifically designed immunogens was required to shepherd the development of bNAbs. However, knock-in mice contain superphysiologic numbers of bNAb precursor-expressing B cells, and therefore how these results can be translated to a more physiologic setting remains to be determined. Here we make use of adoptive transfer experiments using knock-in B cells that carry a synthetic intermediate in the pathway to anti-HIV-1 bNAb development to examine how the relationship between B cell receptor affinity and precursor frequency affects germinal center (GC) B cell recruitment and clonal expansion. Immunization with soluble HIV-1 antigens can recruit bNAb precursor B cells to the GC when there are as few as 10 such cells per mouse. However, at low precursor frequencies, the extent of clonal expansion is directly proportional to the affinity of the antigen for the B cell receptor, and recruitment to GCs is variable and dependent on recirculation.

Precursors to potential severe core damage accidents: 1995 A status report

International Nuclear Information System (INIS)

Belles, R.J.; Cletcher, J.W.; Copinger, D.A.

1997-04-01

Ten operational events that affected 10 commercial light-water reactors during 1995 and that are considered to be precursors to potential severe core damage are described. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10 -6 . These events were identified by first computer-screening the 1995 licensee event reports from commercial light-water reactors to identify those events that could potentially be precursors. Candidate precursors were selected and evaluated in a process similar to that used in previous assessments. Selected events underwent engineering evaluation that identified, analyzed, and documented the precursors. Other events designated by the Nuclear Regulatory Commission (NRC) also underwent a similar evaluation. Finally, documented precursors were submitted for review by licensees and NRC headquarters and regional offices to ensure the plant design and its response to the precursor were correctly characterized. This study is a continuation of earlier work, which evaluated 1969-1981 and 1984-1994 events. The report discusses the general rationale for this study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events

Precursors to potential severe core damage accidents: 1995 A status report

Energy Technology Data Exchange (ETDEWEB)

Belles, R.J.; Cletcher, J.W.; Copinger, D.A. [and others

1997-04-01

Ten operational events that affected 10 commercial light-water reactors during 1995 and that are considered to be precursors to potential severe core damage are described. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10{sup {minus}6}. These events were identified by first computer-screening the 1995 licensee event reports from commercial light-water reactors to identify those events that could potentially be precursors. Candidate precursors were selected and evaluated in a process similar to that used in previous assessments. Selected events underwent engineering evaluation that identified, analyzed, and documented the precursors. Other events designated by the Nuclear Regulatory Commission (NRC) also underwent a similar evaluation. Finally, documented precursors were submitted for review by licensees and NRC headquarters and regional offices to ensure the plant design and its response to the precursor were correctly characterized. This study is a continuation of earlier work, which evaluated 1969-1981 and 1984-1994 events. The report discusses the general rationale for this study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events.

Hydrokinetic simulations of nanoscopic precursor films in rough channels

International Nuclear Information System (INIS)

Chibbaro, S; Biferale, L; Binder, K; Milchev, A; Dimitrov, D; Diotallevi, F; Succi, S

2009-01-01

We report on simulations of capillary filling of highly wetting fluids in nanochannels with and without obstacles. We use atomistic (molecular dynamics) and hydrokinetic (lattice Boltzmann; LB) approaches which indicate clear evidence of the formation of thin precursor films, moving ahead of the main capillary front. The dynamics of the precursor films is found to obey a square-root law like that obeyed by the main capillary front, z 2 (t)∝t, although with a larger prefactor, which we find to take the same value for the different geometries (2D–3D) under inspection. The two methods show a quantitative agreement which indicates that the formation and propagation of thin precursors can be handled at a mesoscopic/hydrokinetic level. This can be considered as a validation of the LB method and opens the possibility of using hydrokinetic methods to explore space–time scales and complex geometries of direct experimental relevance. Then, the LB approach is used to study the fluid behaviour in a nanochannel when the precursor film encounters a square obstacle. A complete parametric analysis is performed which suggests that thin-film precursors may have an important influence on the efficiency of nanochannel-coating strategies

Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

Science.gov (United States)

Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

2014-12-21

Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

Development of an accident sequence precursor methodology and its application to significant accident precursors

Energy Technology Data Exchange (ETDEWEB)

Jang, Seung Hyun; Park, Sung Hyun; Jae, Moo Sung [Dept. of of Nuclear Engineering, Hanyang University, Seoul (Korea, Republic of)

2017-03-15

The systematic management of plant risk is crucial for enhancing the safety of nuclear power plants and for designing new nuclear power plants. Accident sequence precursor (ASP) analysis may be able to provide risk significance of operational experience by using probabilistic risk assessment to evaluate an operational event quantitatively in terms of its impact on core damage. In this study, an ASP methodology for two operation mode, full power and low power/shutdown operation, has been developed and applied to significant accident precursors that may occur during the operation of nuclear power plants. Two operational events, loss of feedwater and steam generator tube rupture, are identified as ASPs. Therefore, the ASP methodology developed in this study may contribute to identifying plant risk significance as well as to enhancing the safety of nuclear power plants by applying this methodology systematically.

Synthesis and Characterization of Fluoro- and Chlorobimetallic Alkoxides as Precursors for Luminescent Metal Oxide Materials via Sol-Gel Technique

Institute of Scientific and Technical Information of China (English)

ATHAR, Taimur; SEOK, Sang II; KWON, Jeong Oh

2007-01-01

Heterobimetallic alkoxides are broadly recognized as versatile precursors for luminescence materials, and efforts are being made to develop novel routes by applying the concept of geometrical molecular design, for their synthesis and to design a single source precursor suited to photoluminescent materials. Novel and new series of bimetallic alkoxides has been prepared by metathesis route. They exhibit a lower sensitivity towards hydrolysis and so they are easier to handle as compared to other alkoxides. All the compounds were characterized by elemental analysis, FT-IR and multinuclear NMR spectroscopies. FT-IR revealed that the molecular structure of these metal spectroscopy provided useful information about chemical shifts for better understanding the likely structure based on interactions with their coordinate metals. The mass spectra show similar types of fragmentation pattern.SEM-EDS analyses showed consistency with the formulation. XRD patterns show an enhanced homogeneity at high temperature. TGA measurements show that thermal decomposition occured in steps that depended entirely on the chemical compositions and the synthesis routes. SEM observation reveals that the morphology and particle size strongly depend on synthesis routes for their precursors.

Advances in organometallic and protein chemistry

OpenAIRE

Ryan, C. P.

2010-01-01

This thesis describes two areas of scientific investigation. The first contains a description of a study on the synthesis of biotinylated and fluoresceinylated bromomaleimide based reagents. Upon synthesis, the ability of these reagents to add reversibly to cysteine containing proteins is investigated by a series of LCMS experiments. A single point mutant (L111C) of the SH2 domain of the Grb2 adaptor protein, containing a single cysteine residue, is chosen as an ideal protein for study. Thus ...

Synthesis of anisotropic CdS nanostructures via a single-source route

CSIR Research Space (South Africa)

Rajasekhar Pullabhotla, VSR

2011-02-01

Full Text Available A cadmium tetrahydroisoquinoline dithiocarbamate (DTC) complex has been used as single-source precursor for the synthesis of highly faceted hexadecylamine (HDA) capped CdS nanoparticles. Hexagonal and close to cubic shaped particles with distinct...

Molten carbonate fuel cell cathode with mixed oxide coating

Science.gov (United States)

Hilmi, Abdelkader; Yuh, Chao-Yi

2013-05-07

A molten carbonate fuel cell cathode having a cathode body and a coating of a mixed oxygen ion conductor materials. The mixed oxygen ion conductor materials are formed from ceria or doped ceria, such as gadolinium doped ceria or yttrium doped ceria. The coating is deposited on the cathode body using a sol-gel process, which utilizes as precursors organometallic compounds, organic and inorganic salts, hydroxides or alkoxides and which uses as the solvent water, organic solvent or a mixture of same.

Methods of making copper selenium precursor compositions with a targeted copper selenide content and precursor compositions and thin films resulting therefrom

Science.gov (United States)

Curtis, Calvin J [Lakewood, CO; Miedaner, Alexander [Boulder, CO; van Hest, Marinus Franciscus Antonius Maria; Ginley, David S [Evergreen, CO; Leisch, Jennifer [Denver, CO; Taylor, Matthew [West Simsbury, CT; Stanbery, Billy J [Austin, TX

2011-09-20

Precursor compositions containing copper and selenium suitable for deposition on a substrate to form thin films suitable for semi-conductor applications. Methods of forming the precursor compositions using primary amine solvents and methods of forming the thin films wherein the selection of temperature and duration of heating controls the formation of a targeted species of copper selenide.

The Innate Lymphoid Cell Precursor.

Science.gov (United States)

Ishizuka, Isabel E; Constantinides, Michael G; Gudjonson, Herman; Bendelac, Albert

2016-05-20

The discovery of tissue-resident innate lymphoid cell populations effecting different forms of type 1, 2, and 3 immunity; tissue repair; and immune regulation has transformed our understanding of mucosal immunity and allergy. The emerging complexity of these populations along with compounding issues of redundancy and plasticity raise intriguing questions about their precise lineage relationship. Here we review advances in mapping the emergence of these lineages from early lymphoid precursors. We discuss the identification of a common innate lymphoid cell precursor characterized by transient expression of the transcription factor PLZF, and the lineage relationships of innate lymphoid cells with conventional natural killer cells and lymphoid tissue inducer cells. We also review the rapidly growing understanding of the network of transcription factors that direct the development of these lineages.

The presence of modifiable residues in the core peptide part of precursor nisin is not crucial for precursor nisin interactions with NisB- and NisC.

Directory of Open Access Journals (Sweden)

Rustem Khusainov

Full Text Available Precursor nisin is a model posttranslationally modified precursor lantibiotic that can be structurally divided into a leader peptide sequence and a modifiable core peptide part. The nisin core peptide clearly plays an important role in the precursor nisin-nisin modification enzymes interactions, since it has previously been shown that the construct containing only the nisin leader sequence is not sufficient to pull-down the nisin modification enzymes NisB and NisC. Serines and threonines in the core peptide part are the residues that NisB specifically dehydrates, and cysteines are the residues that NisC stereospecifically couples to the dehydrated amino acids. Here, we demonstrate that increasing the number of negatively charged residues in the core peptide part of precursor nisin, which are absent in wild-type nisin, does not abolish binding of precursor nisin to the modification enzymes NisB and NisC, but dramatically decreases the antimicrobial potency of these nisin mutants. An unnatural precursor nisin variant lacking all serines and threonines in the core peptide part and an unnatural precursor nisin variant lacking all cysteines in the core peptide part still bind the nisin modification enzymes NisB and NisC, suggesting that these residues are not essential for direct interactions with the nisin modification enzymes NisB and NisC. These results are important for lantibiotic engineering studies.

An optimized In–CuGa metallic precursors for chalcopyrite thin films

Energy Technology Data Exchange (ETDEWEB)

Han, Jun-feng, E-mail: junfeng.han@cnrs-imn.fr [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Department of Physics, Peking University, Beijing 100871 (China); Liao, Cheng [Department of Physics, Peking University, Beijing 100871 (China); Chengdu Green Energy and Green Manufacturing Technology R and D Center, Chengdu, Sichuan Province 601207 (China); Jiang, Tao; Xie, Hua-mu; Zhao, Kui [Department of Physics, Peking University, Beijing 100871 (China); Besland, M.-P. [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France)

2013-10-31

We report a study of CuGa–In metallic precursors for chalcopyrite thin film. CuGa and In thin films were prepared by DC sputtering at room temperature. Due to low melting point of indium, the sputtering power on indium target was optimized. Then, CuGa and In multilayers were annealed at low temperature. At 120 °C, the annealing treatment could enhance diffusion and alloying of CuGa and In layers; however, at 160 °C, it caused a cohesion and crystalline of indium from the alloy which consequently formed irregular nodules on the film surface. The precursors were selenized to form copper indium gallium selenide (CIGS) thin films. The morphological and structural properties were investigated by scanning electron microscopy, X-ray diffraction and Raman spectra. The relationships between metallic precursors and CIGS films were discussed in the paper. A smooth precursor layer was the key factor to obtain a homogeneous and compact CIGS film. - Highlights: • An optimized sputtered indium film • An optimized alloying process of metallic precursor • An observation of nodules forming on the indium film and precursor surface • An observation of cauliflower structure in copper indium gallium selenide film • The relationship between precursor and CIGS film surface morphology.

Fabrication of a Cu(InGaSe2 Thin Film Photovoltaic Absorber by Rapid Thermal Annealing of CuGa/In Precursors Coated with a Se Layer

Directory of Open Access Journals (Sweden)

Chun-Yao Hsu

2013-01-01

Full Text Available Cu(InGaSe2 (CIGS thin film absorbers are prepared using sputtering and selenization processes. The CuGa/In precursors are selenized during rapid thermal annealing (RTA, by the deposition of a Se layer on them. This work investigates the effect of the Cu content in precursors on the structural and electrical properties of the absorber. Using X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, and Hall effect measurement, it is found that the CIGS thin films produced exhibit facetted grains and a single chalcopyrite phase with a preferred orientation along the (1 1 2 plane. A Cu-poor precursor with a Cu/( ratio of 0.75 demonstrates a higher resistance, due to an increase in the grain boundary scattering and a reduced carrier lifetime. A Cu-rich precursor with a Cu/( ratio of 1.15 exhibits an inappropriate second phase ( in the absorber. However, the precursor with a Cu/( ratio of 0.95 exhibits larger grains and lower resistance, which is suitable for its application to solar cells. The deposition of this precursor on Mo-coated soda lime glass substrate and further RTA causes the formation of a MoSe2 layer at the interface of the Mo and CIGS.

Cryopreservation of GABAergic Neuronal Precursors for Cell-Based Therapy.

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Daniel Rodríguez-Martínez

Full Text Available Cryopreservation protocols are essential for stem cells storage in order to apply them in the clinic. Here we describe a new standardized cryopreservation protocol for GABAergic neural precursors derived from the medial glanglionic eminence (MGE, a promising source of GABAergic neuronal progenitors for cell therapy against interneuron-related pathologies. We used 10% Me2SO as cryoprotectant and assessed the effects of cell culture amplification and cellular organization, as in toto explants, neurospheres, or individualized cells, on post-thaw cell viability and retrieval. We confirmed that in toto cryopreservation of MGE explants is an optimal preservation system to keep intact the interneuron precursor properties for cell transplantation, together with a high cell viability (>80% and yield (>70%. Post-thaw proliferation and self-renewal of the cryopreserved precursors were tested in vitro. In addition, their migration capacity, acquisition of mature neuronal morphology, and potency to differentiate into multiple interneuron subtypes were also confirmed in vivo after transplantation. The results show that the cryopreserved precursor features remained intact and were similar to those immediately transplanted after their dissection from the MGE. We hope this protocol will facilitate the generation of biobanks to obtain a permanent and reliable source of GABAergic precursors for clinical application in cell-based therapies against interneuronopathies.

Using superoxide dismutase/catalase mimetics to manipulate the redox environment of neural precursor cells

International Nuclear Information System (INIS)

Limoli, C. L.; Giedzinski, E.; Baure, J.; Doctrow, S. R.; Rola, R.; Fike, J. R.

2006-01-01

Past work has shown that neural precursor cells are predisposed to redox sensitive changes, and that oxidative stress plays a critical role in the acute and persistent changes that occur within the irradiated CNS. Irradiation leads to a marked rise in reactive oxygen species (ROS) that correlates with oxidative endpoints in vivo and reductions in neuro-genesis. To better understand the impact of oxidative stress on neural precursor cells, and to determine if radiation-induced oxidative damage and precursor cell loss after irradiation could be reduced, a series of antioxidant compounds (EUK-134, EUK-163, EUK-172, EUK-189) were tested, three of which possess both superoxide dismutase (SOD) and catalase activities and one (EUK-163) whose only significant activity is SOD. Our results show that these SOD/catalase mimetics apparently increase the oxidation of a ROS-sensitive fluorescent indicator dye, particularly after short (12 h) treatments, but that longer treatments (24 h) decrease oxidation attributable to radiation-induced ROS. Similarly, other studies found that cells incubated with CuZnSOD showed some increase in intracellular ROS levels. Subsequent data suggested that the dye-oxidising capabilities of the EUK compounds were linked to differences in their catalase activity and, most likely, their ability to catalyse per-oxidative pathways. In unirradiated mice, the EUK-134 analogue induced some decrease of proliferating precursor cells and immature neurons 48 h after radiation, an effect that may be attributable to cytotoxicity and/or inhibition of precursor proliferation. In irradiated mice, a single injection of EUK-134 was not found to be an effective radioprotector at acute times (48 h). The present results support continued development of our in vitro model as a tool for predicting certain in vivo responses, and suggest that in some biological systems the capability to scavenge superoxide but produce excess H 2 O 2 , as is known for CuZnSOD, may be

Manganite perovskite ceramics, their precursors and methods for forming

Science.gov (United States)

Payne, David Alan; Clothier, Brent Allen

2015-03-10

Disclosed are a variety of ceramics having the formula Ln.sub.1-xM.sub.xMnO.sub.3, where 0.Itoreq.x.Itoreq.1 and where Ln is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; M is Ca, Sr, Ba, Cd, or Pb; manganite precursors for preparing the ceramics; a method for preparing the precursors; and a method for transforming the precursors into uniform, defect-free ceramics having magnetoresistance properties. The manganite precursors contain a sol and are derived from the metal alkoxides: Ln(OR).sub.3, M(OR).sub.2 and Mn(OR).sub.2, where R is C.sub.2 to C.sub.6 alkyl or C.sub.3 to C.sub.9 alkoxyalkyl, or C.sub.6 to C.sub.9 aryl. The preferred ceramics are films prepared by a spin coating method and are particularly suited for incorporation into a device such as an integrated circuit device.

Whole-cell fungal transformation of precursors into dyes

Directory of Open Access Journals (Sweden)

Jarosz-Wilkołazka Anna

2010-07-01

Full Text Available Abstract Background Chemical methods of producing dyes involve extreme temperatures and unsafe toxic compounds. Application of oxidizing enzymes obtained from fungal species, for example laccase, is an alternative to chemical synthesis of dyes. Laccase can be replaced by fungal biomass acting as a whole-cell biocatalyst with properties comparable to the isolated form of the enzyme. The application of the whole-cell system simplifies the transformation process and reduces the time required for its completion. In the present work, four fungal strains with a well-known ability to produce laccase were tested for oxidation of 17 phenolic and non-phenolic precursors into stable and non-toxic dyes. Results An agar-plate screening test of the organic precursors was carried out using four fungal strains: Trametes versicolor, Fomes fomentarius, Abortiporus biennis, and Cerrena unicolor. Out of 17 precursors, nine were transformed into coloured substances in the presence of actively growing fungal mycelium. The immobilized fungal biomass catalyzed the transformation of 1 mM benzene and naphthalene derivatives in liquid cultures yielding stable and non-toxic products with good dyeing properties. The type of fungal strain had a large influence on the absorbance of the coloured products obtained after 48-hour transformation of the selected precursors, and the most effective was Fomes fomentarius (FF25. Whole-cell transformation of AHBS (3-amino-4-hydroxybenzenesulfonic acid into a phenoxazinone dye was carried out in four different systems: in aqueous media comprising low amounts of carbon and nitrogen source, in buffer, and in distilled water. Conclusions This study demonstrated the ability of four fungal strains belonging to the ecological type of white rot fungi to transform precursors into dyes. This paper highlights the potential of fungal biomass for replacing isolated enzymes as a cheaper industrial-grade biocatalyst for the synthesis of dyes and other

Biochemical Removal of HAP Precursors from Coal

Energy Technology Data Exchange (ETDEWEB)

Olson, Gregory J

1997-05-12

Column biooxidation tests with Kentucky coal confirmed results of earlier shake flask tests showing significant removal from the coal of arsenic, selenium, cobalt, manganese, nickel and cadmium. Rates of pyrite biooxidation in Kentucky coal were only slightly more than half the rates found previously for Indiana and Pittsburgh coals. Removal of pyrite from Pittsburgh coal by ferric ion oxidation slows markedly as ferrous ions accumulate in solution, requiring maintenance of high redox potentials in processes designed for removal of pyrite and hazardous air pollutant (HAP) precursors by circulation of ferric solutions through coal. The pyrite oxidation rates obtained in these tests were used by Unifield Engineering to support the conceptual designs for alternative pyrite and HAP precursor bioleaching processes for the phase 2 pilot plant. Thermophilic microorganisms were tested to determine if mercury could be mobilized from coal under elevated growth temperatures. There was no evidence for mercury removal from coal under these conditions. However, the activity of the organisms may have liberated mercury physically. It is also possible that the organisms dissolved mercury and it readsorbed to the clay preferentially. Both of these possibilities are undergoing further testing. The Idaho National Engineering and Environmental Laboratory's (INEEL) slurry column reactor was operated and several batches of feed coal, product coal, waste solids and leach solutions were submitted to LBL for HAP precursor analysis. Results to date indicate significant removal of mercury, arsenic and other HAP precursors in the combined physical-biological process.

Non-invasive method for in vivo detection of chlorophyll precursors

DEFF Research Database (Denmark)

Kristiansen, Kim Anker; Khrouchtchova, Anastassia; Stenbæk, Anne

2009-01-01

Traditionally chlorophyll (Chl) and Chl precursors have been studied in vitro or in leaf tissue at low temperature. These methods are destructive and make it impossible to work with the same individual plant later on. In this paper we present a method for in vivo detection of Chl and its precursors...... is compared to current methods. Furthermore, we report on optimization of the spectral scanning method with the aim to minimize the excitation light-evoked photo-conversion of the chlorophyll precursors....

A karyometric note on nucleoli in human early granulocytic precursors.

Science.gov (United States)

Smetana, K; Mikulenková, D; Jirásková, I; Klamová, H

2006-01-01

The diameter of nucleoli was measured in human bone marrow early granulocytic precursors after visualization by a simple cytochemical method for demonstration of RNA. Such method facilitated to clearly see nucleolar bodies without perinucleolar chromatin, including those of micronucleoli. The bone marrow of patients suffering from chronic myeloid leukaemia (untreated with cytostatics) provided a satisfactory number of both myeloblasts and promyelocytes for nucleolar measurements because of prevailing granulopoiesis. The direct nucleolar measurement was carried out on digitized and processed images on the screen at magnification 4,300x. It seems to be likely that the nucleolar size is directly related to the number of nucleoli per cell. The largest nucleoli were present in both myeloblasts and promyelocytes that possessed a single nucleolus. In contrast, the nucleolar diameter was significantly smaller in cells with multiple nucleoli. However, in cells with small multiple nucleoli, one of them was always larger and dominant with a large number of AgNORs. Such large nucleoli are possibly visible in specimens stained with panoptic procedures or methods staining nuclear chromatin or DNA. It should also be mentioned that both myeloblasts and promyelocytes mostly possessed two nucleoli with the mean diameter close to 1.5 microm. The incidence of early granulocytic precursors classified according to the nucleolar number and size strongly suggested that the various nucleolar number and nucleolar size in these cells might be related to the different stage of the cell cycle and might also explain their heterogeneity.

Unconsumed precursors and couplers after formation of oxidative hair dyes

DEFF Research Database (Denmark)

Rastogi, Suresh Chandra; Søsted, Heidi; Johansen, Jeanne Duus

2006-01-01

Contact allergy to hair dye ingredients, especially precursors and couplers, is a well-known entity among consumers having hair colouring done at home or at a hairdresser. The aim of the present investigation was to estimate consumer exposure to some selected precursors (p-phenylenediamine, toluene......-2,5-diamine) and couplers (3-aminophenol, 4-aminophenol, resorcinol) of oxidative hair dyes during and after hair dyeing. Concentrations of unconsumed precursors and couplers in 8 hair dye formulations for non-professional use were investigated, under the conditions reflecting hair dyeing. Oxidative...... hair dye formation in the absence of hair was investigated using 6 products, and 2 products were used for experimental hair dyeing. In both presence and absence of hair, significant amounts of unconsumed precursors and couplers remained in the hair dye formulations after final colour development. Thus...

Sythesis of metal sulfide nanomaerials via thermal decomposition of single-source percursors

Energy Technology Data Exchange (ETDEWEB)

Jen-La Plante, Ilan; Zeid, Tahani W.; Yang, Peidong; Mokari, Taleb

2010-06-03

In this report, we present a synthetic method for the formation of cuprous sulfide (Cu2S) and lead sulfide (PbS) nanomaterials directly on substrates from the thermolysis of single-source precursors. We find that the final morphology and arrangement of the nanomaterials may be controlled through the concentration of the dissolved precursors and choice of solvent. One-dimensional (1-D) morphologies may also be grown onto substrates with the addition of a metal catalyst layer through solution-liquid-solid (SLS) growth. These synthetic techniques may be expanded to other metal sulfide materials.

Capability of cation exchange technology to remove proven N-nitrosodimethylamine precursors.

Science.gov (United States)

Li, Shixiang; Zhang, Xulan; Bei, Er; Yue, Huihui; Lin, Pengfei; Wang, Jun; Zhang, Xiaojian; Chen, Chao

2017-08-01

N-nitrosodimethylamine (NDMA) precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA precursors. In this study, we tested the removal of two representative NDMA precursors, dimethylamine (DMA) and ranitidine (RNTD), by strong acidic cation exchange resin. The results showed that pH greatly affected the exchange efficiency, with high removal (DMA>78% and RNTD>94%) observed at pHMg 2+ >RNTD + >K + >DMA + >NH 4 + >Na + . The partition coefficient of DMA + to Na + was 1.41±0.26, while that of RNTD + to Na + was 12.1±1.9. The pseudo second-order equation fitted the cation exchange kinetics well. Bivalent inorganic cations such as Ca 2+ were found to have a notable effect on NA precursor removal in softening column test. Besides DMA and RNTD, cation exchange process also worked well for removing other 7 model NDMA precursors. Overall, NDMA precursor removal can be an added benefit of making use of cation exchange water softening processes. Copyright © 2017. Published by Elsevier B.V.

Effect of precursor solutions on ZnO film via solution precursor plasma spray and corresponding gas sensing performances

International Nuclear Information System (INIS)

Yu, Z.X.; Ma, Y.Z.; Zhao, Y.L.; Huang, J.B.; Wang, W.Z.; Moliere, M.; Liao, H.L.

2017-01-01

Highlights: • C-axis preferential oriented grown ZnO films were firstly deposited via SPPS with different solutions. • ZnO films were hydrophobic due to cauliflower and honeycomb-like surface morphologies with high surface specific area. • Gas detecting performance of (002) plane oriented ZnO was predicted and compared by “first principle calculation method”. - Abstract: Solution precursor plasma spraying (SPPS) as a novel thermal spray method was employed to deposit nano-structured ZnO thin film using different formulations of the precursor solution. This article focuses on the influence of the solution composition on the preferential orientation of crystal growth, on crystal size and surface morphology of the resulting ZnO films. The trend of preferential growth along (002) lattice plane of ZnO film was studied by slow scanning X-ray diffraction using a specific coefficient P_(_0_0_2_)_. It appears that the thermal spray process promotes the buildup of ZnO films preferentially oriented along the c-axis. The shape of single particle tends to change from round shaped beads to hexagonal plates by increasing the volume ratio of ethanol in the solvent. Both cauliflower and honeycomb-like surface morphologies featuring high specific surface area and roughness were obtained through the SPPS process by varying solution composition. These ZnO films are hydrophobic with contact angle as high as 136°, which is seemingly associated with micro reliefs developing high surface specific area. Then the gas sensing performances of ZnO films preferentially oriented along (002) face were tentatively predicted using the “first principle calculation method” and were compared with those of conventional films that are mainly oriented along the (101) face. The (002) face displays better hydrogen adsorption capability than the (101) face with much larger resulting changes in electrical resistance. In conclusion, the c-axis oriented ZnO films obtained through SSPS have

Effect of precursor solutions on ZnO film via solution precursor plasma spray and corresponding gas sensing performances

Energy Technology Data Exchange (ETDEWEB)

Yu, Z.X., E-mail: zexin.yu@utbm.fr [Univ Bourgogne Franche Comte, CNRS, Lab ICB, UMR 6303, Site UTBM, F-90010 Belfort (France); Ma, Y.Z., E-mail: yangzhou.ma@outlook.com [School of Materials Science and Engineering, Anhui University of Technology, Ma’anshan 243002 (China); Zhao, Y.L. [Univ Bourgogne Franche Comte, CNRS, Lab ICB, UMR 6303, Site UTBM, F-90010 Belfort (France); Huang, J.B.; Wang, W.Z. [Key Lab of Safety Science of Pressurized System, Ministry of Education, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China); Moliere, M.; Liao, H.L. [Univ Bourgogne Franche Comte, CNRS, Lab ICB, UMR 6303, Site UTBM, F-90010 Belfort (France)

2017-08-01

Highlights: • C-axis preferential oriented grown ZnO films were firstly deposited via SPPS with different solutions. • ZnO films were hydrophobic due to cauliflower and honeycomb-like surface morphologies with high surface specific area. • Gas detecting performance of (002) plane oriented ZnO was predicted and compared by “first principle calculation method”. - Abstract: Solution precursor plasma spraying (SPPS) as a novel thermal spray method was employed to deposit nano-structured ZnO thin film using different formulations of the precursor solution. This article focuses on the influence of the solution composition on the preferential orientation of crystal growth, on crystal size and surface morphology of the resulting ZnO films. The trend of preferential growth along (002) lattice plane of ZnO film was studied by slow scanning X-ray diffraction using a specific coefficient P{sub (002).} It appears that the thermal spray process promotes the buildup of ZnO films preferentially oriented along the c-axis. The shape of single particle tends to change from round shaped beads to hexagonal plates by increasing the volume ratio of ethanol in the solvent. Both cauliflower and honeycomb-like surface morphologies featuring high specific surface area and roughness were obtained through the SPPS process by varying solution composition. These ZnO films are hydrophobic with contact angle as high as 136°, which is seemingly associated with micro reliefs developing high surface specific area. Then the gas sensing performances of ZnO films preferentially oriented along (002) face were tentatively predicted using the “first principle calculation method” and were compared with those of conventional films that are mainly oriented along the (101) face. The (002) face displays better hydrogen adsorption capability than the (101) face with much larger resulting changes in electrical resistance. In conclusion, the c-axis oriented ZnO films obtained through SSPS have

Cellular Kinetics of Perivascular MSC Precursors

Directory of Open Access Journals (Sweden)

William C. W. Chen

2013-01-01

Full Text Available Mesenchymal stem/stromal cells (MSCs and MSC-like multipotent stem/progenitor cells have been widely investigated for regenerative medicine and deemed promising in clinical applications. In order to further improve MSC-based stem cell therapeutics, it is important to understand the cellular kinetics and functional roles of MSCs in the dynamic regenerative processes. However, due to the heterogeneous nature of typical MSC cultures, their native identity and anatomical localization in the body have remained unclear, making it difficult to decipher the existence of distinct cell subsets within the MSC entity. Recent studies have shown that several blood-vessel-derived precursor cell populations, purified by flow cytometry from multiple human organs, give rise to bona fide MSCs, suggesting that the vasculature serves as a systemic reservoir of MSC-like stem/progenitor cells. Using individually purified MSC-like precursor cell subsets, we and other researchers have been able to investigate the differential phenotypes and regenerative capacities of these contributing cellular constituents in the MSC pool. In this review, we will discuss the identification and characterization of perivascular MSC precursors, including pericytes and adventitial cells, and focus on their cellular kinetics: cell adhesion, migration, engraftment, homing, and intercellular cross-talk during tissue repair and regeneration.

Associations between musical abilities and precursors of reading in preschool aged children.

Science.gov (United States)

Degé, Franziska; Kubicek, Claudia; Schwarzer, Gudrun

2015-01-01

The association between music and language, in particular, the overlap in their processing results in the possibility to use one domain for the enhancement of the other. Especially in the preschool years music may be a valuable tool to train language abilities (e.g., precursors of reading). Therefore, detailed knowledge about associations between musical abilities and precursors of reading can be of great use for designing future music intervention studies that target language-related abilities. Hence, the present study investigated the association between music perception as well as music production and precursors of reading. Thereby, not only phonological awareness, the mostly studied precursor of reading, was investigated, but also other precursors were examined. We assessed musical abilities (production and perception) and precursors of reading (phonological awareness, working memory, and rapid retrieval from long-term memory) in 55 preschoolers (27 boys). Fluid intelligence was measured and controlled in the analyses. Results showed that phonological awareness, working memory, and rapid retrieval from long-term memory were related to music perception as well as to music production. Our data suggest that several precursors of reading were associated with music perception as well as music production.

Associations between musical abilities and precursors of reading in preschool aged children

Directory of Open Access Journals (Sweden)

Franziska eDegé

2015-08-01

Full Text Available The association between music and language, in particular, the overlap in their processing results in the possibility to use one domain for the enhancement of the other. Especially in the preschool years music may be a valuable tool to train language abilities (e.g., precursors of reading. Therefore, detailed knowledge about associations between musical abilities and precursors of reading can be of great use for designing future music intervention studies that target language-related abilities. Hence, the present study investigated the association between music perception as well as music production and precursors of reading. Thereby, not only phonological awareness, the mostly studied precursor of reading, was investigated, but also other precursors were examined. We assessed musical abilities (production and perception and precursors of reading (phonological awareness, working memory, and rapid retrieval from long-term memory in 55 preschoolers (27 boys. Fluid intelligence was measured and controlled in the analyses. Results showed that phonological awareness, working memory, and rapid retrieval from long-term memory were related to music perception as well as to music production. Our data suggest that several precursors of reading were associated with music perception as well as music production.

Process research of non-CZ silicon material

Science.gov (United States)

Campbell, R. B.

1984-01-01

Advanced processing techniques for non-CZ silicon sheet material that might improve the cost effectiveness of photovoltaic module production were investigated. Specifically, the simultaneous diffusion of liquid boron and liquid phosphorus organometallic precursors into n-type dendritic silicon web was examined. The simultaneous junction formation method for solar cells was compared with the sequential junction formation method. The electrical resistivity of the n-n and p-n junctions was discussed. Further research activities for this program along with a program documentation schedule are given.

Precursor polymer compositions comprising polybenzimidazole

Science.gov (United States)

Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

2015-07-14

Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

Ionospheric precursors for crustal earthquakes in Italy

Directory of Open Access Journals (Sweden)

L. Perrone

2010-04-01

Full Text Available Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979–2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8–5.9 tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

Aroma Precursors in Grapes and Wine: Flavor Release during Wine Production and Consumption.

Science.gov (United States)

Parker, Mango; Capone, Dimitra L; Francis, I Leigh; Herderich, Markus J

2018-03-14

Pioneering investigations into precursors of fruity and floral flavors established the importance of terpenoid and C 13 -norisoprenoid glycosides to the flavor of aromatic wines. Nowadays flavor precursors in grapes and wine are known to be structurally diverse, encompassing glycosides, amino acid conjugates, odorless volatiles, hydroxycinnamic acids, and many others. Flavor precursors mainly originate in the grape berry but also from oak or other materials involved in winemaking. Flavors are released from precursors during crushing and subsequent production steps by enzymatic and nonenzymatic transformations, via microbial glycosidases, esterases, C-S lyases, and decarboxylases, and through acid-catalyzed hydrolysis and chemical rearrangements. Flavors can also be liberated from glycosides and amino acid conjugates by oral microbiota. Hence, it is increasingly likely that flavor precursors contribute to retronasal aroma formation through in-mouth release during consumption, prompting a shift in focus from identifying aroma precursors in grapes to understanding aroma precursors present in bottled wine.

Ternary Precursors for Depositing I-III-VI2 Thin Films for Solar Cells via Spray CVD

Science.gov (United States)

Banger, K. K.; Hollingsworth, J. A.; Jin, M. H.-C.; Harris, J. D.; Duraj, S. A.; Smith, M.; Scheiman, D.; Bohannan, E. W.; Switzer, J. A.; Buhro, W. E.

2002-01-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power (W/kg). Thin-film fabrication studies demonstrate that ternary single source precursors (SSP's) can be used in either a hot or cold-wall spray chemical vapour deposition (CVD) reactor, for depositing CuInS2, CuGaS2, and CuGaInS2 at reduced temperatures (400 to 450 C), which display good electrical and optical properties suitable for photovoltaic (PV) devices. X-ray diffraction studies, energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) confirmed the formation of the single phase CIS, CGS, CIGS thin-films on various substrates at reduced temperatures.

TUT7 controls the fate of precursor microRNAs by using three different uridylation mechanisms

OpenAIRE

Kim, Boseon; Ha, Minju; Loeff, Luuk; Chang, Hyeshik; Simanshu, Dhirendra K; Li, Sisi; Fareh, Mohamed; Patel, Dinshaw J; Joo, Chirlmin; Kim, V Narry

2015-01-01

Terminal uridylyl transferases (TUTs) function as integral regulators of microRNA (miRNA) biogenesis. Using biochemistry, single-molecule, and deep sequencing techniques, we here investigate the mechanism by which human TUT7 (also known as ZCCHC6) recognizes and uridylates precursor miRNAs (pre-miRNAs) in the absence of Lin28. We find that the overhang of a pre-miRNA is the key structural element that is recognized by TUT7 and its paralogues, TUT4 (ZCCHC11) and TUT2 (GLD2/PAPD4). For group II...

MOVPE growth and characterization of heteroepitaxial germanium on silicon using iBuGe as precursor

Energy Technology Data Exchange (ETDEWEB)

Attolini, G. [IMEM-CNR, Parco Area delle Scienze, 37 A, 43124 Parma (Italy); Ponraj, J.S. [University of Information Science and Technology, St Paul the Apostle, Ohrid 6000 (Macedonia, The Former Yugoslav Republic of); Frigeri, C.; Buffagni, E.; Ferrari, C. [IMEM-CNR, Parco Area delle Scienze, 37 A, 43124 Parma (Italy); Musayeva, N.; Jabbarov, R. [Research and Development Center for Hi-Technologies, MCIT, Inshaatchilar ave., 2, AZ1073, Baku (Azerbaijan); Institute of Physics, ANAS, H. Javid ave., 33, AZ1143, Baku (Azerbaijan); Bosi, M., E-mail: bosi@imem.cnr.it [IMEM-CNR, Parco Area delle Scienze, 37 A, 43124 Parma (Italy)

2016-01-01

Graphical abstract: - Highlights: • Germanium layer were deposited on silicon substrates. • A novel metal organic precursor (isobutyl germane) was used. • MOVPE growth process was optimized. • Layers were characterized by TEM, XRD; SEM and AFM. - Abstract: Being an attractive and demanding candidate in the field of energy conversion, germanium has attained widespread applications. The present work is aimed at the study of metal organic vapour phase epitaxy of germanium thin films on (0 0 1) silicon at different growth temperatures using isobutyl germane as a precursor. The epilayers were characterized by X-ray diffraction, high resolution transmission electron microscopy, atomic force microscopy and scanning electron microscopy in order to understand the structural and morphological properties. The films were found to be epitaxially grown and single crystalline with slight misorientation (below 0.1 degrees). The interface between the film and substrate was analyzed in depth and different temperature dependent growth behaviours were evidenced. The major relevant lattice imperfections observed were attributed to planar defects and threading dislocations.

[The role of endothelial cells and endothelial precursor cells in angiogenesis].

Science.gov (United States)

Poreba, Małgorzata; Usnarska-Zubkiewicz, Lidia; Kuliczkowski, Kazimierz

2006-01-01

Endothelium plays a key role in maintenance of vascular homeostasis in human organism. According to new data endothelial cells and hematopoietic cells have a common precursor in prenatal life--a hemangioblast, which explains the fact of sharing the same determinants on the surface of both type of cells. Circulating endothelial precursors were identified in adults and this suggests that hemangioblasts may be present not only during embriogenesis. In some clinical situations the increased numbers of endothelial cells and endothelial precursors were noted, and especially in patients with neoplastic diseases, which is probably the result of increased angiogenesis. Endothelial precursors are thought to be the promice for therapeutic purposes in future--to increase local angiogenesis.

Deposition of metal Islands, metal clusters and metal containing single molecules on self-assembled monolayers

NARCIS (Netherlands)

Speets, Emiel Adrianus

2005-01-01

The central topic of this thesis is the deposition of metals on Self-Assembled Monolayers (SAMs). Metals are deposited in the form of submicron scale islands, nanometer scale clusters, and as supramolecular, organometallic coordination cages. Several SAMs on various substrates were prepared and

Molecular cloning of a cDNA encoding the precursor of adenoregulin from frog skin. Relationships with the vertebrate defensive peptides, dermaseptins.

Science.gov (United States)

Amiche, M; Ducancel, F; Lajeunesse, E; Boulain, J C; Ménez, A; Nicolas, P

1993-03-31

Adenoregulin has recently been isolated from Phyllomedusa skin as a 33 amino acid residues peptide which enhanced binding of agonists to the A1 adenosine receptor. In order to study the structure of the precursor of adenoregulin we constructed a cDNA library from mRNAs extracted from the skin of Phyllomedusa bicolor. We detected the complete nucleotide sequence of a cDNA encoding the adenoregulin biosynthetic precursor. The deduced sequence of the precursor is 81 amino acids long, exhibits a putative signal sequence at the NH2 terminus and contains a single copy of the biologically active peptide at the COOH terminus. Structural and conformational homologies that are observed between adenoregulin and the dermaseptins, antimicrobial peptides exhibiting strong membranolytic activities against various pathogenic agents, suggest that adenoregulin is an additional member of the growing family of cytotropic antimicrobial peptides that allow vertebrate animals to defend themselves against microorganisms. As such, the adenosine receptor regulating activity of adenoregulin could be due to its ability to interact with and disrupt membranes lipid bilayers.

The fate of wastewater-derived NDMA precursors in the aquatic environment.

Science.gov (United States)

Pehlivanoglu-Mantas, Elif; Sedlak, David L

2006-03-01

To assess the stability of precursors of the chloramine disinfection byproduct N-nitrosodimethylamine (NDMA) under conditions expected in effluent-dominated surface waters, effluent samples from four municipal wastewater treatment plants were subjected to chlorination and chloramination followed by incubation in the presence of inocula derived from activated sludge. Samples subjected to free chlorine disinfection showed lower initial concentrations of NDMA precursors than those that were not chlorinated or were disinfected with pre-formed chloramines. For chloraminated and control (unchlorinated) treatments, the concentration of NDMA precursors decreased by an average of 24% over the 30-day incubation in samples from three of the four facilities. At the fourth facility, where samples were collected on three different days, NDMA precursor concentrations decreased by approximately 80% in one sample and decreased by less than 20% in the other two samples. In contrast to the low reactivity of the NDMA precursors, NDMA disappeared within 30 days under the conditions employed in these experiments. These results and measurements made in an effluent-dominated river suggest that although NDMA may be removed after wastewater effluent is discharged, wastewater-derived NDMA precursors could persist long enough to form significant concentrations of NDMA in drinking water treatment plants that use water originating from sources that are subjected to wastewater effluent discharges.

nanoparticles synthesized by citrate precursor m

African Journals Online (AJOL)

user

(M=Co, Cu) nanoparticles synthesized by citrate precursor method ... The structural characterization was carried out using an X-ray Diffractometer (Rikagu Miniflex, Japan) ..... His current area of interest includes magnetic nanomaterials.

Low-temperature CVD of iron, cobalt, and nickel nitride thin films from bis[di(tert-butyl)amido]metal(II) precursors and ammonia

International Nuclear Information System (INIS)

Cloud, Andrew N.; Abelson, John R.; Davis, Luke M.; Girolami, Gregory S.

2014-01-01

Thin films of late transition metal nitrides (where the metal is iron, cobalt, or nickel) are grown by low-pressure metalorganic chemical vapor deposition from bis[di(tert-butyl)amido]metal(II) precursors and ammonia. These metal nitrides are known to have useful mechanical and magnetic properties, but there are few thin film growth techniques to produce them based on a single precursor family. The authors report the deposition of metal nitride thin films below 300 °C from three recently synthesized M[N(t-Bu) 2 ] 2 precursors, where M = Fe, Co, and Ni, with growth onset as low as room temperature. Metal-rich phases are obtained with constant nitrogen content from growth onset to 200 °C over a range of feedstock partial pressures. Carbon contamination in the films is minimal for iron and cobalt nitride, but similar to the nitrogen concentration for nickel nitride. X-ray photoelectron spectroscopy indicates that the incorporated nitrogen is present as metal nitride, even for films grown at the reaction onset temperature. Deposition rates of up to 18 nm/min are observed. The film morphologies, growth rates, and compositions are consistent with a gas-phase transamination reaction that produces precursor species with high sticking coefficients and low surface mobilities

Influence of aging time of oleate precursor on the magnetic relaxation of cobalt ferrite nanoparticles synthesized by the thermal decomposition method

International Nuclear Information System (INIS)

Herrera, Adriana P.; Polo-Corrales, Liliana; Chavez, Ermides; Cabarcas-Bolivar, Jari; Uwakweh, Oswald N.C.; Rinaldi, Carlos

2013-01-01

that relax through a single relaxation mechanism. The resulting nanoparticles would be suitable for sensors based on the Brownian relaxation mechanism and in determining mechanical properties of complex fluids at the size scale of the nanoparticles. - Graphical Abstract: The aging time of the oleate precursor influenced the crystal structure, size, magnetic properties, and AC susceptibility of cobalt ferrite nanoparticles synthesized by the thermal decomposition method, resulting in crossing of the in-phase χ′ and out-of-phase χ″ components of the complex susceptibility, an attribute of a collection of nanoparticles with a single dominant magnetic relaxation mechanism. Highlights: ► Effect of aging of an iron–cobalt oleate precursor on properties of CoFe 2 O 4 nanoparticles was evaluated. ► Aging of the iron–cobalt oleate resulted in changes in its thermo physical properties. ► Nanoparticles obtained with precursor aged for 2 days showed evidence of an impurity phase. ► Aging for 15–30 days resulted in nanoparticles with predominantly Brownian magnetic relaxation.

MatureBayes: a probabilistic algorithm for identifying the mature miRNA within novel precursors.

Directory of Open Access Journals (Sweden)

Katerina Gkirtzou

Full Text Available BACKGROUND: MicroRNAs (miRNAs are small, single stranded RNAs with a key role in post-transcriptional regulation of thousands of genes across numerous species. While several computational methods are currently available for identifying miRNA genes, accurate prediction of the mature miRNA remains a challenge. Existing approaches fall short in predicting the location of mature miRNAs but also in finding the functional strand(s of miRNA precursors. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present a computational tool that incorporates a Naive Bayes classifier to identify mature miRNA candidates based on sequence and secondary structure information of their miRNA precursors. We take into account both positive (true mature miRNAs and negative (same-size non-mature miRNA sequences examples to optimize sensitivity as well as specificity. Our method can accurately predict the start position of experimentally verified mature miRNAs for both human and mouse, achieving a significantly larger (often double performance accuracy compared with two existing methods. Moreover, the method exhibits a very high generalization performance on miRNAs from two other organisms. More importantly, our method provides direct evidence about the features of miRNA precursors which may determine the location of the mature miRNA. We find that the triplet of positions 7, 8 and 9 from the mature miRNA end towards the closest hairpin have the largest discriminatory power, are relatively conserved in terms of sequence composition (mostly contain a Uracil and are located within or in very close proximity to the hairpin loop, suggesting the existence of a possible recognition site for Dicer and associated proteins. CONCLUSIONS: This work describes a novel algorithm for identifying the start position of mature miRNA(s produced by miRNA precursors. Our tool has significantly better (often double performance than two existing approaches and provides new insights about the potential use

Precursor incident program at EDF

International Nuclear Information System (INIS)

Fourest, B.; Maliverney, B.; Rozenholc, M.; Piovesan, C.

1998-01-01

The precursor program was started by EDF in 1994, after an investigation of the US NRC's Accident Sequence Precursor Program. Since then, reported operational events identified as Safety Outstanding Events have been analyzed whenever possible using probabilistic methods based on PSAs. Analysis provides an estimate of the remaining protection against core damage at the time the incident occurred. Measuring the incidents' severity enables to detect incidents important regarding safety. Moreover, the most efficient feedback actions can be derived from the main accident sequences identified through the analysis. Therefore, incident probabilistic analysis provides a way to assess priorities in terms of treatment and resource allocation, and so, to implement countermeasures preventing further occurrence and development of the most significant incidents. As some incidents cannot be analyzed using this method, probabilistic analysis can only be one among the methods used to assess the nuclear power plants' safety level. Nevertheless, it provides an interesting complement to classical methods of deterministic studies. (author)

GH mediates exercise-dependent activation of SVZ neural precursor cells in aged mice.

Directory of Open Access Journals (Sweden)

Daniel G Blackmore

Full Text Available Here we demonstrate, both in vivo and in vitro, that growth hormone (GH mediates precursor cell activation in the subventricular zone (SVZ of the aged (12-month-old brain following exercise, and that GH signaling stimulates precursor activation to a similar extent to exercise. Our results reveal that both addition of GH in culture and direct intracerebroventricular infusion of GH stimulate neural precursor cells in the aged brain. In contrast, no increase in neurosphere numbers was observed in GH receptor null animals following exercise. Continuous infusion of a GH antagonist into the lateral ventricle of wild-type animals completely abolished the exercise-induced increase in neural precursor cell number. Given that the aged brain does not recover well after injury, we investigated the direct effect of exercise and GH on neural precursor cell activation following irradiation. This revealed that physical exercise as well as infusion of GH promoted repopulation of neural precursor cells in irradiated aged animals. Conversely, infusion of a GH antagonist during exercise prevented recovery of precursor cells in the SVZ following irradiation.

GH Mediates Exercise-Dependent Activation of SVZ Neural Precursor Cells in Aged Mice

Science.gov (United States)

Blackmore, Daniel G.; Vukovic, Jana; Waters, Michael J.; Bartlett, Perry F.

2012-01-01

Here we demonstrate, both in vivo and in vitro, that growth hormone (GH) mediates precursor cell activation in the subventricular zone (SVZ) of the aged (12-month-old) brain following exercise, and that GH signaling stimulates precursor activation to a similar extent to exercise. Our results reveal that both addition of GH in culture and direct intracerebroventricular infusion of GH stimulate neural precursor cells in the aged brain. In contrast, no increase in neurosphere numbers was observed in GH receptor null animals following exercise. Continuous infusion of a GH antagonist into the lateral ventricle of wild-type animals completely abolished the exercise-induced increase in neural precursor cell number. Given that the aged brain does not recover well after injury, we investigated the direct effect of exercise and GH on neural precursor cell activation following irradiation. This revealed that physical exercise as well as infusion of GH promoted repopulation of neural precursor cells in irradiated aged animals. Conversely, infusion of a GH antagonist during exercise prevented recovery of precursor cells in the SVZ following irradiation. PMID:23209615

Coercivities of hot-deformed magnets processed from amorphous and nanocrystalline precursors

International Nuclear Information System (INIS)

Tang, Xin; Sepehri-Amin, H.; Ohkubo, T.; Hioki, K.; Hattori, A.; Hono, K.

2017-01-01

Hot-deformed magnets have been processed from amorphous and nanocrystalline precursors and their hard magnetic properties and microstructures have been investigated in order to explore the optimum process route. The hot-deformed magnets processed from an amorphous precursor exhibited the coercivity of 1.40 T that is higher than that processed from nanocrystalline powder, ∼1.28 T. The average grain size was larger in the magnets processed from amorphous precursor. Detailed microstructure analyses by aberration corrected scanning transmission electron microscopy revealed that the Nd + Pr concentrations in the intergranular phases were higher in the hot-deformed magnet processed from the amorphous precursor, which is considered to lead to the enhanced coercivity due to a stronger pinning force against magnetic domain wall motion.

Increased KPI containing amyloid precursor protein in experimental autoimmune encephalomyelitis brains.

Science.gov (United States)

Beilin, Orit; Karussis, Dimitrios M; Korczyn, Amos D; Gurwitz, David; Aronovich, Ramona; Mizrachi-Kol, Rachel; Chapman, Joab

2007-04-16

Amyloid precursor protein can be translated from three alternatively spliced mRNAs. We measured levels of amyloid precursor protein isoforms containing the Kunitz protease inhibitor domain (KPIAPP), and amyloid precursor protein without the Kunitz protease inhibitor domain (KPIAPP) in brain homogenates of acute experimental autoimmune encephalomyelitis mice. At the preclinical phase of the disease, both KPIAPP and KPIAPP levels were significantly higher in homogenates from brains of autoimmune encephalomyelitis mice, whereas at the acute phase of the disease only KPIAPP remained significantly elevated compared with controls. At the recovery phase, no differences were observed between the groups. The early and isoform-specific elevation of KPIAPP in autoimmune encephalomyelitis mice suggests a possible role for amyloid precursor protein in the immune response mediating the disease.

Characterization of electrochemically deposited films from aqueous and ionic liquid cobalt precursors toward hydrogen evolution reactions

Energy Technology Data Exchange (ETDEWEB)

Dushatinski, Thomas; Huff, Clay; Abdel-Fattah, Tarek M., E-mail: fattah@cnu.edu

2016-11-01

Highlights: • Co films deposition via aqueous and ionic liquid Precursors. • Hydrogen evolution produced from reactive surfaces. • Co deposited films characterized by SEM, AFM, EDX and XRD techniques. - Abstract: Electrodepositions of cobalt films were achieved using an aqueous or an ethylene glycol based non-aqueous solution containing choline chloride (vitamin B4) with cobalt chloride hexahydrate precursor toward hydrogen evolution reactions from sodium borohydride (NaBH{sub 4}) as solid hydrogen feedstock (SHF). The resulting cobalt films had reflectivity at 550 nm of 2.2% for aqueously deposited films (ACoF) and 1.3% for non-aqueously deposited films (NCoF). Surface morphology studied by scanning electron microscopy showed a positive correlation between particle size and thickness. The film thicknesses were tunable between >100 μm and <300 μm for each film. The roughness (Ra) value measurements by Dektak surface profiling showed that the NCoF (Ra = 165 nm) was smoother than the ACoF (Ra = 418 nm). The NCoFs and ACoFs contained only α phase (FCC) crystallites. The NCoFs were crystalline while the ACoFs were largely amorphous from X-ray diffraction analysis. The NCoF had an average Vickers hardness value of 84 MPa as compared to 176 MPa for ACoF. The aqueous precursor has a single absorption maximum at 510 nm and the non-aqueous precursor had three absorption maxima at 630, 670, and 695 nm. The hydrogen evolution reactions over a 1 cm{sup 2} catalytic surface with aqueous NaBH{sub 4} solutions generated rate constants (K) = equal to 4.9 × 10{sup −3} min{sup −1}, 4.6 × 10{sup −3} min{sup −1}, and 3.3 × 10{sup −3} min{sup −1} for ACoF, NCoF, and copper substrate respectively.

Controlled synthesis of single-crystalline graphene

Directory of Open Access Journals (Sweden)

Wang Xueshen

2014-02-01

Full Text Available This paper reports the controlled synthesis of single-crystalline graphene on the back side of copper foil using CH4 as the precursor. The influence of growth time and the pressure ratio of CH4/H2 on the structure of graphene are examined. An optimized polymer-assisted method is used to transfer the synthesized graphene onto a SiO2/Si substrate. Scanning electron microscopy and Raman spectroscopy are used to characterize the graphene.

Identification of an indigo precursor from leaves of Isatis tinctoria (Woad).

Science.gov (United States)

Maugard, T; Enaud, E; Choisy, P; Legoy, M D

2001-11-01

Indole is presumably a product of indole-3-glycerol phosphate catabolism in Isatis tinctoria. It is oxidized into indoxyl and stored in young leaves as indigo precursor. Further oxidation and dimerization of indoxyl produces indigoid pigments. In this work, we describe an HPLC method dedicated to the identification and quantification of indigoid pigments (indigo, indirubin, isoindigo and isoindirubin) and indigo precursors produced in I. tinctoria (Woad). This work, carried out with two cultivars of I. tinctoria, has confirmed that the quantity of indigo precursors is dependent on the species and the harvest period. In addition we have shown for the first time that young leaves of I. tinctoria, harvested in June contained a new indigo precursor in addition to isatan B (indoxyl-5-ketogluconate) and indican (indoxyl-beta-D-glucoside). We suggest the name "isatan C" for this new indigo precursor in I. tinctoria. Its chemical characteristics point to an dioxindole ester with PM of 395. We have shown that isatan C reacts with isatan B increasing the red pigment production.

Application of precursor methodology in initiating frequency estimates

International Nuclear Information System (INIS)

Kohut, P.; Fitzpatrick, R.G.

1991-01-01

The precursor methodology developed in recent years provides a consistent technique to identify important accident sequence precursors. It relies on operational events (extracting information from actual experience) and infers core damage scenarios based on expected safety system responses. The ranking or categorization of each precursor is determined by considering the full spectrum of potential core damage sequences. The methodology estimates the frequency of severe core damage based on the approach suggested by Apostolakis and Mosleh, which may lead to a potential overestimation of the severe-accident sequence frequency due to the inherent dependencies between the safety systems and the initiating events. The methodology is an encompassing attempt to incorporate most of the operating information available from nuclear power plants and is an attractive tool from the point of view of risk management. In this paper, a further extension of this methodology is discussed with regard to the treatment of initiating frequency of the accident sequences

Accident sequence precursor events with age-related contributors

Energy Technology Data Exchange (ETDEWEB)

Murphy, G.A.; Kohn, W.E.

1995-12-31

The Accident Sequence Precursor (ASP) Program at ORNL analyzed about 14.000 Licensee Event Reports (LERs) filed by US nuclear power plants 1987--1993. There were 193 events identified as precursors to potential severe core accident sequences. These are reported in G/CR-4674. Volumes 7 through 20. Under the NRC Nuclear Plant Aging Research program, the authors evaluated these events to determine the extent to which component aging played a role. Events were selected that involved age-related equipment degradation that initiated an event or contributed to an event sequence. For the 7-year period, ORNL identified 36 events that involved aging degradation as a contributor to an ASP event. Except for 1992, the percentage of age-related events within the total number of ASP events over the 7-year period ({approximately}19%) appears fairly consistent up to 1991. No correlation between plant ape and number of precursor events was found. A summary list of the age-related events is presented in the report.

Controlled Growth of ZnSe Nanocrystals by Tuning Reactivity and Amount of Zinc Precursor

Directory of Open Access Journals (Sweden)

Lai-Jun Zhang

2013-01-01

Full Text Available Zinc selenide (ZnSe nanocrystals were synthesized via a phosphine-free route using the highly reactive alkylamine-H2Se complex as selenium precursor and zinc precursors with different reactivity. The reactivity of zinc precursor was tuned by using three kinds of zinc carboxylates with different alkyl chain lengths, including zinc acetate, zinc nonanoate, and zinc stearate. The effect of the reactivity and the amount of zinc precursor on nucleation and growth of ZnSe nanocrystals were investigated by ultraviolet-visible absorption and photoluminescence spectra. Result indicates that the growth and optical property of the resulting ZnSe nanocrystals are strongly dependent on the alkyl chain length and the amount of the zinc carboxylates and both shorter alkyl chain length, and more amount of zinc carboxylate will lead to faster growth of ZnSe nanocrystals. This allows that the controlled growth and excellent optical property of high-quality ZnSe nanocrystals can be achieved by combining the different reactivity and the used amount of zinc precursor, such as by using stoichiometric and reactive Zn precursor and Se precursor or by using larger amount of more unreactive Zn precursor relative to the highly reactive alkylamine-H2Se complex precursor.

Nonlinear magnetohydrodynamics of edge localized mode precursors

Energy Technology Data Exchange (ETDEWEB)

Guo, Z. B., E-mail: guozhipku@gmail.com [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing (China); WCI Center for Fusion Theory, NFRI, Gwahangno 113, Yusung-gu, Daejeon 305-333 (Korea, Republic of); Wang, Lu [SEEE, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang, X. G. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing (China)

2015-02-15

A possible origin of edge-localized-mode (ELM) precursors based on nonlinear ideal peeling-ballooning mode is reported. Via nonlinear variational principle, a nonlinear evolution equation of the radial displacement is derived and solved, analytically. Besides an explosive growth in the initial nonlinear phase, it is found that the local displacement evolves into an oscillating state in the developed nonlinear phase. The nonlinear frequency of the ELM precursors scales as ω{sub pre}∼x{sup 1/3}ξ{sup ^}{sub ψ,in}{sup 2/3}n, with x position in radial direction, ξ{sup ^}{sub ψ,in} strength of initial perturbation, and n toroidal mode number.

Synthesis of Monodisperse CdSe QDs using Controlled Growth Temperatures

International Nuclear Information System (INIS)

Noor Razinah Rahmat; Akrajas Ali Umar; Muhammad Yahya; Muhamad Mat Salleh; Mohammad Hafizuddin Jumali

2011-01-01

The effect of growth temperatures on size of CdSe quantum dots (QDs) has been investigated. CdSe QDs were synthesized using thermolysis of organometallics precursor route using wet chemical method. The growth temperature was varied from 260-310 degree Celsius with growth period fixed at 60 s. As the growth temperature increased, the monodispersed CdSe QDs with diameter in the range 3-7 nm were obtained. Both absorption and PL spectra of the QDs revealed a strong red-shift supporting the increment size of QDs with the rise of growth temperature. (author)

Silica-Supported Catalyst for Enantioselective Arylation of Aldehydes under Batch and Continuous-Flow Conditions.

Science.gov (United States)

Watanabe, Satoshi; Nakaya, Naoyuki; Akai, Junichiro; Kanaori, Kenji; Harada, Toshiro

2018-05-04

A silica-supported 3-aryl H 8 -BINOL-derived titanium catalyst exhibited high performance in the enantioselective arylation of aromatic aldehydes using Grignard and organolithium reagents not only under batch conditions but also under continuous-flow conditions. Even with a simple pipet reactor packed with the heterogeneous catalyst, the enantioselective production of chiral diarylmethanols could be achieved through a continuous introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The pipet reactor could be used repeatedly in different reactions without appreciable deterioration of the activity.

Molecule-by-Molecule Writing Using a Focused Electron Beam

DEFF Research Database (Denmark)

Van Dorp, Willem F.; Zhang, Xiaoyan; Feringa, Ben L.

2012-01-01

atoms also be written with an electron beam? We verify this with focused electron-beam-induced deposition (FEBID), a direct-write technique that has the current record for the smallest feature written by (electron) optical lithography. We show that the deposition of an organometallic precursor...... on graphene can be followed molecule-by-molecule with FEBID. The results show that mechanisms that are inherent to the process inhibit a further increase in control over the process. Hence, our results present the resolution limit of (electron) optical lithography techniques. The writing of isolated...

Synthesis of labelled ecdysone precursors

International Nuclear Information System (INIS)

Haag, T.; Hetru, C.; Nakatani, Y.; Luu, B.; Meister, M.; Pichat, L.; Audinot, M.

1985-01-01

High specific activity tritiated 3β,14α-dihydroxy-5β-cholest-7-en-6-one, has been prepared using a precursor which permits rapid and easy labelling. This compound is converted to ecdysone under in vitro conditions by insect prothoracic glands, a well known site of ecdysone biosynthesis. (author)

Toroidally asymmetric ELM precursor oscillations in the TCV tokamak

International Nuclear Information System (INIS)

Reimerdes, H.; Pochelon, A.; Guittienne, P.; Weisen, H.; Suttrop, W.

1997-01-01

In TCV ohmic H-modes have been obtained in diverted single-null (SND), double-null (DND), and elongated limited plasma configurations. In ELM-free H-modes the particle density rises continuously until the discharge usually terminates with a high density disruption. Quasi-stationary H-modes have been obtained in the presence of ELMs. The observed ELM spectrum is continuous and ranges from clearly identifiable type III ELMs to low frequency, large ELMs. The necessity of ELMs for particle control of H-mode plasmas while causing high peak-power loads on strike points makes the control of their level and nature desirable and motivates the study of the underlying MHD-instability. Prior to ELMs in TCV coherent magnetic oscillations, that indicate a rapidly growing MHD instability, have been observed. The structure of these precursor oscillation is investigated with TCV's Mirnov probe arrays. In particular an observed toroidal asymmetry in the growth of the instability has to be explained. (author) 2 figs., 6 refs

Precursors to potential severe core damage accidents: 1996. A status report. Volume 25

International Nuclear Information System (INIS)

Belles, R.J.; Cletcher, J.W.; Copinger, D.A.; Muhlheim, M.D.; Dolan, B.W.; Minarick, J.W.

1997-12-01

This report describes the 14 operational events in 1996 that affected 13 commercial light-water reactors and that are considered to be precursors to potential severe core damage accidents. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10 -6 . These events were identified by first computer-screening the 1996 licensee event reports from commercial light-water reactors to identify those events that could potentially be precursors. Candidate precursors were selected and evaluated in a process similar to that used in previous assessments. Selected events underwent engineering evaluation that identified, analyzed, and documented the precursors. Other events designated by the Nuclear Regulatory Commission (NRC) also underwent a similar evaluation. Finally, documented precursors were submitted for review by licensees and NRC headquarters and regional offices to ensure the plant design and its response to the precursor were correctly characterized. This study is a continuation of earlier work, which evaluated 1969--1995 events. The report discusses the general rationale for this study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events

Precursors to potential severe core damage accidents: 1997 - A status report. Volume 26

International Nuclear Information System (INIS)

Belles, R.J.; Cletcher, J.W.; Copinger, D.A.; Muhlheim, M.D.; Dolan, B.W.; Minarick, J.W.

1998-11-01

This report describes the five operational events in 1997 that affected five commercial light-water reactors (LWRs) and that are considered to be precursors to potential severe core damage accidents. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10 -6 . These events were identified by first computer-screening the 1997 licensee event reports from commercial LWRs to identify those events that could be precursors. Candidate precursors were selected and evaluated in a process similar to that used in previous assessments. Selected events underwent engineering evaluation that identified, analyzed, and documented the precursors. Other events designated by the Nuclear Regulatory Commission (NRC) also underwent a similar evaluation. Finally, documented precursors were submitted for review by licensees and NRC headquarters to ensure that the plant design and its response to the precursor were correctly characterized. This study is a continuation of earlier work, which evaluated 1969--1996 events. The report discusses the general rationale for this study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events

Thin film solar cells by selenization sulfurization using diethyl selenium as a selenium precursor

Science.gov (United States)

Dhere, Neelkanth G.; Kadam, Ankur A.

2009-12-15

A method of forming a CIGSS absorber layer includes the steps of providing a metal precursor, and selenizing the metal precursor using diethyl selenium to form a selenized metal precursor layer (CIGSS absorber layer). A high efficiency solar cell includes a CIGSS absorber layer formed by a process including selenizing a metal precursor using diethyl selenium to form the CIGSS absorber layer.

Organometallic synthesis of ZnO nanoparticles for gas sensing: towards selectivity through nanoparticles morphology

Energy Technology Data Exchange (ETDEWEB)

Ryzhikov, Andrey; Jońca, Justyna; Kahn, Myrtil; Fajerwerg, Katia [Laboratoire de Chimie de Coordination (LCC), CNRS (France); Chaudret, Bruno [Laboratoire de Physique et de Chimie de Nano-objets (LPCNO), INSA, UPS, CNRS (France); Chapelle, Audrey [Laboratoire d’Analyse et d’Architecture des Systèmes (LAAS), CNRS (France); Ménini, Philippe [Université Toulouse III, Paul Sabatier (France); Shim, Chang Hyun [Laboratoire d’Analyse et d’Architecture des Systèmes (LAAS), CNRS (France); Gaudon, Alain [Alpha M.O.S. SA (France); Fau, Pierre, E-mail: pierre.fau@lcc-toulouse.fr [Laboratoire de Chimie de Coordination (LCC), CNRS (France)

2015-07-15

ZnO nanoparticles (NP) with different morphologies such as nanorods (NR), isotropic NP, and cloud-like (CL) structures have been synthesized by an organometallic route. The prepared ZnO nanostructures have been deposited on miniaturized silicon gas sensor substrates by an inkjet method, and their responses to CO, C{sub 3}H{sub 8}, and NH{sub 3} gases have been studied at different operating temperatures (340–500 °C) and relative humidity of 50 %. It is noteworthy that the morphology of the nanostructure of the sensitive layer is maintained after thermal treatment. The morphology of ZnO NP significantly influences the sensor response level and their selectivity properties to reducing gases. Among the three different ZnO types, sensors prepared with NR show the highest response to both CO and C{sub 3}H{sub 8}. Sensors made of isotropic NP and CL structures show a lower but similar response to CO. From all investigated nanostructures, sensors made of CL structures show the weakest response to C{sub 3}H{sub 8}. With NH{sub 3} gas, no effect of the morphology of the ZnO sensitive layer has been evidenced. These different responses highlight the important role of the nanostructure of the ZnO sensitive layer and the nature of the target gas on the detection properties of the sensors. Graphical Abstract: Three different ZnO nanoparticles morphologies (cloud-like, dots, rods) have been employed as sensitive layers in chemoresistive sensors for the selective detection of CO, C{sub 3}H{sub 8} and NH{sub 3}.

Mechanistic Insights on the Reductive Dehydroxylation Pathway for the Biosynthesis of Isoprenoids Promoted by the IspH Enzyme

KAUST Repository

Abdel-Azeim, Safwat

2015-06-22

Here, we report an integrated quantum mechanics/molecular mechanics (QM/MM) study of the bio-organometallic reaction pathway of the 2H+/2e- reduction of (E)-4-hydroxy-3-methylbut-2-enyl pyrophosphate (HMBPP) into the so called universal terpenoids precursors isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), promoted by the IspH enzyme. Our results support the viability of the bio-organometallic pathway from rotation of the OH group of HMBPP away from the [Fe4S4] cluster at the core of the catalytic site, to be engaged in a H-bond with Glu126. This rotation is synchronous with π-coordination of the C2=C3 double bond of HMBPP to the apical Fe atom of the [Fe4S4] cluster. Dehydroxylation of HMBPP is triggered by a proton transfer from Glu126 to the OH group of HMBPP. The reaction pathway is completed by competitive proton transfer from the terminal phosphate group to the C2 or C4 atom of HMBPP.

Dichloro (bis[diphenylthiourea]) cadmium complex as a precursor for HDA-capped CdS nanoparticles and their solubility in water

OpenAIRE

Tshinyadzo R. Tshikhudo; Manuel Fernandes; Makwena J. Moloto; Poslet M. Shumbula

2010-01-01

A single-source precursor route has been explored by using the diphenylthiourea cadmium complex as the source of cadmium sulphide (CdS) nanoparticles. The reaction was carried out using hexadecylamine (HDA) as the solvent and stabilising agent for the particles. The phenylthiourea complex was synthesised and characterised by means of a combination of spectroscopic techniques, microanalysis and X-ray crystal structural analysis. The diphenylthiourea complex was thermolysed in HDA at 120 ºC for...

From bismuth oxide/hydroxide precursor clusters towards stable oxides: Proton transfer reactions and structural reorganization govern the stability of [Bi18O13(OH)10]-nitrate clusters

Science.gov (United States)

Walther, M.; Zahn, D.

2018-01-01

Structural relaxation and stability of a Bi18-cluster as obtained from association of [Bi6O4(OH)4](NO3)6 precursor clusters in DMSO solution is investigated from a combination of quantum chemical calculations and μs-scale molecular dynamics simulations using empirical interaction potentials. The Bi18-cluster undergoes a OH⋯OH proton transfer reaction, followed by considerable structural relaxation. While the aggregation of the Bi18-cluster is induced by the dissociation of a single nitrate ion leading to [Bi6O4(OH)4](NO3)5+ as an activated precursor species that can bind two more Bi6-clusters, we find the [Bi18O13(OH)10](NO3)18-x+x species (explored for x = 1-6) rather inert against either nitrate dissociation, collision with Bi6-precursors or combinations thereof.

Growth and optical characteristics of Tm-doped AlGaN layer grown by organometallic vapor phase epitaxy

Science.gov (United States)

Takatsu, J.; Fuji, R.; Tatebayashi, J.; Timmerman, D.; Lesage, A.; Gregorkiewicz, T.; Fujiwara, Y.

2018-04-01

We report on the growth and optical properties of Tm-doped AlGaN layers by organometallic vapor phase epitaxy (OMVPE). The morphological and optical properties of Tm-doped GaN (GaN:Tm) and Tm-doped AlGaN (AlGaN:Tm) were investigated by Nomarski differential interference contrast microscopy and photoluminescence (PL) characterization. Nomarski images reveal an increase of surface roughness upon doping Tm into both GaN and AlGaN layers. The PL characterization of GaN:Tm shows emission in the near-infrared range originating from intra-4f shell transitions of Tm3+ ions. In contrast, AlGaN:Tm also exhibits blue light emission from Tm3+ ions. In that case, the wider band gap of the AlGaN host allows energy transfer to higher states of the Tm3+ ions. With time-resolved PL measurements, we could distinguish three types of luminescent sites of Tm3+ in the AlGaN:Tm layer, having different decay times. Our results confirm that Tm ions can be doped into GaN and AlGaN by OMVPE, and show potential for the fabrication of novel high-color-purity blue light emitting diodes.

Do glycine-extended hormone precursors have clinical significance?

DEFF Research Database (Denmark)

Rehfeld, Jens Frederik

2014-01-01

Half of the known peptide hormones are C-terminally amidated. Subsequent biogenesis studies have shown that the immediate precursor is a glycine-extended peptide. The clinical interest in glycine-extended hormones began in 1994, when it was suggested that glycine-extended gastrin stimulated cancer...... and clinical effects of glycine-extended precursors for most other amidated hormones than gastrin and cholecystokinin (CCK). The idea of glycine-extended peptides as independent messengers was interesting. But clinical science has to move ahead from ideas that cannot be supported at key points after decades...

Development of Advanced Materials for Electro-Ceramic Application Final Report CRADA No. TC-1331-96

Energy Technology Data Exchange (ETDEWEB)

Caplan, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Olstad, R. [General Atomics, San Diego, CA (United States); McMillan, L. [Symetrix International, Inc., Colorado Springs, CO (United States); Tulupov, A. [Soliton-NTT, Moscow (Russia)

2017-10-19

The goal of this project was to further develop and characterize the electrochemical methods originating in Russia for producing ultra high purity organometallic compounds utilized as precursors in the production of high quality electro-ceramic materials. Symetrix planned to use electro-ceramic materials with high dielectric constant for microelectronic memory circuit applications. General Atomics planned to use the barium titanate type ceramics with low loss tangent for producing a high power ferroelectric tuner used to match radio frequency power into their Dill-D fusion machine. Phase I of the project was scheduled to have a large number of organometallic (alkoxides) chemical samples produced using various methods. These would be analyzed by LLNL, Soliton and Symetrix independently to determine the level of chemical impurities thus verifying each other's analysis. The goal was to demonstrate a cost-effective production method, which could be implemented in a large commercial facility to produce high purity organometallic compounds. In addition, various compositions of barium-strontium-titanate ceramics were to be produced and analyzed in order to develop an electroceramic capacitor material having the desired characteristics with respect to dielectric constant, loss tangent, temperature characteristics and non-linear behavior under applied voltage. Upon optimizing the barium titanate material, 50 capacitor preforms would be produced from this material demonstrating the ability to produce, in quantity, the pills ultimately required for the ferroelectric tuner (approx 2000-3000 ceramic pills).

Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n -Butane

KAUST Repository

Bendjeriou-Sedjerari, Anissa

2013-11-27

We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(Sî - Si-NH 2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu) 2 (3) and [(≡Si-NH-)2]Zr(CH2tBu) 2 (4) have been obtained by reaction with Zr(CH2tBu) 4. The surfaces were characterized with 2D multiple-quantum 1H-1H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H) 2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an 1H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-Nî)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)] Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]. © 2013 American Chemical Society.

Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n -Butane

KAUST Repository

Bendjeriou-Sedjerari, Anissa; Azzi, Joachim; Abou-Hamad, Edy; Anjum, Dalaver H.; Pasha, Fahran A.; Huang, Kuo-Wei; Emsley, Lyndon; Basset, Jean-Marie

2013-01-01

We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(Sî - Si-NH 2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu) 2 (3) and [(≡Si-NH-)2]Zr(CH2tBu) 2 (4) have been obtained by reaction with Zr(CH2tBu) 4. The surfaces were characterized with 2D multiple-quantum 1H-1H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H) 2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an 1H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-Nî)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)] Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]. © 2013 American Chemical Society.

Catalytic Organometallic Reactions of Ammonia

Science.gov (United States)

Klinkenberg, Jessica L.

2012-01-01

Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466

Evolution of elastic precursor and plastic shock wave in copper via molecular dynamics simulations

International Nuclear Information System (INIS)

Perriot, Romain; Zhakhovsky, Vasily V; Oleynik, Ivan I; Inogamov, Nail A

2014-01-01

Large-scale molecular dynamics (MD) simulations are performed to investigate shock propagation in single crystal copper. It is shown that the P-V plastic Hugoniot is unique regardless of the sample's orientation, its microstructure, or its length. However, the P-V pathway to the final state is not, and depends on many factors. Specifically, it is shown that the pressure in the elastic precursor (the Hugoniot elastic limit (HEL)) decreases as the shock wave propagates in a micron-sized sample. The attenuation of the HEL in sufficiently-long samples is the main source of disagreement between previous MD simulations and experiment: while single crystal experiments showed that the plastic shock speed is orientation-independent, the simulated plastic shock speed was observed to be orientation-dependent in relatively short single-crystal samples. Such orientation dependence gradually disappears for relatively long, micrometer-sized, samples for all three low-index crystallographic directions (100), (110), and (111), and the plastic shock velocities for all three directions approach the one measured in experiment. The MD simulations also demonstrate the existence of subsonic plastic shock waves generated by relatively weak supporting pressures.

The biosynthesis and processing of high molecular weight precursors of soybean glycinin subunits.

Science.gov (United States)

Barton, K A; Thompson, J F; Madison, J T; Rosenthal, R; Jarvis, N P; Beachy, R N

1982-06-10

The predominant storage protein of soybean seed, glycinin, is composed of two heterogeneous classes of related subunits, the acidics (Mr approximately 38,000) and the basics (Mr approximately 22,000). Immunoreaction of polypeptides translated in vitro from isolated seed mRNA using antibodies prepared against either purified acidic or basic subunit groups precipitated precursor polypeptides of Mr = 60,000 to Mr = 63,000. High pressure liquid chromatography fingerprinting of trypsin-generated fragments from in vitro synthesized precursors showed fragments specific to both acidic and basic subunits. No mature acidic or basic subunits were detected in vitro translation reactions by either immunoprecipitation or high pressure liquid chromatography fingerprinting. Pulse-labeling of cotyledons growing in culture with [3H]glycine showed rapid accumulation of label in glycinin precursors of Mr = 59,000 to Mr = 62,000. Although in vivo synthesized precursors had slightly greater electrophoretic mobility than in vitro synthesized precursors, little label initially appeared in mature glycinin subunits. After several hours of continued cotyledon growth in absence of label, precursors were processed and label accumulated in both acidic and basic subunit groups. Recombinant plasmids were prepared by reverse transcription of soybean seed mRNA, and clones which encode glycinin precursors were identified by heteroduplex-hybridization of translatable messages. Northern blot analysis of seed mRNA shows the mRNA-encoding glycinin precursors to migrate at Mr = 0.71 X 10(6) on agarose gels, corresponding to approximately 2050 nucleotides. This is sufficiently large to encode a polypeptide consisting of both a glycinin acidic and basic subunit.

Exploiting nanospace for asymmetric catalysis: confinement of immobilized, single-site chiral catalysts enhances enantioselectivity.

Science.gov (United States)

Thomas, John Meurig; Raja, Robert

2008-06-01

In the mid-1990s, it became possible to prepare high-area silicas having pore diameters controllably adjustable in the range ca. 20-200 Å. Moreover, the inner walls of these nanoporous solids could be functionalized to yield single-site, chiral, catalytically active organometallic centers, the precise structures of which could be determined using in situ X-ray absorption and FTIR and multinuclear magic angle spinning (MAS) NMR spectroscopy. This approach opened up the prospect of performing heterogeneous enantioselective conversions in a novel manner, under the spatial restrictions imposed by the nanocavities within which the reactions occur. In particular, it suggested an alternative method for preparing pharmaceutically and agrochemically useful asymmetric products by capitalizing on the notion, initially tentatively perceived, that spatial confinement of prochiral reactants (and transition states formed at the chiral active center) would provide an altogether new method of boosting the enantioselectivity of the anchored chiral catalyst. Initially, we anchored chiral single-site heterogeneous catalysts to nanopores covalently via a ligand attached to Pd(II) or Rh(I) centers. Later, we employed a more convenient and cheaper electrostatic method, relying in part on strong hydrogen bonding. This Account provides many examples of these processes, encompassing hydrogenations, oxidations, and aminations. Of particular note is the facile synthesis from methyl benzoylformate of methyl mandelate, which is a precursor in the synthesis of pemoline, a stimulant of the central nervous system; our procedure offers several viable methods for reducing ketocarboxylic acids. In addition to relying on earlier (synchrotron-based) in situ techniques for characterizing catalysts, we have constructed experimental procedures involving robotically controlled catalytic reactors that allow the kinetics of conversion and enantioselectivity to be monitored continually, and we have access to

Metabolic Precursors to Amphetamine and Methamphetamine.

Science.gov (United States)

Cody, J D

1993-12-01

Analysis and interpretation of amphetamine results is a challenging process made difficult by a number of factors. One of the complications comes from determination of the origin of amphetamine or methamphetamine in a sample. Given the relatively rare occasions that either of these two drugs are prescribed, legal prescription of one of these drugs is seldom a reason for positive findings. A number of other precursor compounds are metabolized by the body to amphetamine or methamphetamine, many of which could be used for legitimate reasons. Fourteen different metabolic precursors of amphetamine or methamphetamine are included in this review. They are amphetaminil, benzphetamine, clobenzorex, deprenyl, dimethylamphetamine, ethylamphetamine, famprofazone, fencamine, fenethylline, fenproporex, furfenorex, mefenorex, mesocarb, and prenylamine. Medical use, metabolism, analysis, and interpretation are described to afford sufficient information to evaluate the possible involvement of these drugs in positive amphetamine or methamphetamine results. Copyright © 1993 Central Police University.

Comparison exercise of probabilistic precursor analysis

International Nuclear Information System (INIS)

Fauchille, V.; Babst, S.

2004-01-01

From 2000 up to 2003, a comparison exercise concerning accident precursor programs was performed by IRSN, GRS, and NUPEC (Japan). The objective of this exercise was to compare the methodologies used to quantify conditional core damage probability related to incidents which can be considered as accident precursors. This exercise provided interesting results concerning the interpretation of such events. Generally, the participants identified similar scenarios of potential degradation. However, for several dominant sequences, differences in the results were noticed. The differences can be attributed to variations in the plant design, the strategy of management and in the methodological approach. For many reasons, comparison of human reliability analysis was difficult and perhaps another exercise in the future could provide more information about this subject. On the other hand, interesting outcomes have been obtained from the quantification of both common cause failures and potential common cause failures. (orig.)

Preparation of single-crystal copper ferrite nanorods and nanodisks

International Nuclear Information System (INIS)

Du Jimin; Liu Zhimin; Wu Weize; Li Zhonghao; Han Buxing; Huang Ying

2005-01-01

This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

A methodology for analyzing precursors to earthquake-initiated and fire-initiated accident sequences

International Nuclear Information System (INIS)

Budnitz, R.J.; Lambert, H.E.; Apostolakis, G.

1998-04-01

This report covers work to develop a methodology for analyzing precursors to both earthquake-initiated and fire-initiated accidents at commercial nuclear power plants. Currently, the U.S. Nuclear Regulatory Commission sponsors a large ongoing project, the Accident Sequence Precursor project, to analyze the safety significance of other types of accident precursors, such as those arising from internally-initiated transients and pipe breaks, but earthquakes and fires are not within the current scope. The results of this project are that: (1) an overall step-by-step methodology has been developed for precursors to both fire-initiated and seismic-initiated potential accidents; (2) some stylized case-study examples are provided to demonstrate how the fully-developed methodology works in practice, and (3) a generic seismic-fragility date base for equipment is provided for use in seismic-precursors analyses. 44 refs., 23 figs., 16 tabs

Precursors to potential severe core damage accidents: 1992, A status report

International Nuclear Information System (INIS)

Cox, D.F.; Cletcher, J.W.; Copinger, D.A.; Cross-Dial, A.E.; Morris, R.H.; Vanden Heuvel, L.N.; Dolan, B.W.; Jansen, J.M.; Minarick, J.W.; Lau, W.; Salyer, W.D.

1993-12-01

Twenty-seven operational events with conditional probabilities of subsequent severe core damage of 1.0 x 10E-06 or higher occurring at commercial light-water reactors during 1992 are considered to be precursors to potential core damage. These are described along with associated significance estimates, categorization, and subsequent analyses. The report discusses (1) the general rationale for this study, (2) the selection and documentation of events as precursors, (3) the estimation and use of conditional probabilities of subsequent severe core damage to rank precursor events, and (4) the plant models used in the analysis process

New labeling methods via organometallic species: new synthesis of a chiral methyl group

International Nuclear Information System (INIS)

Faucher, Nicolas

2000-01-01

Chapter 1: New labeling methods via organometallic species. In the first part of this work, we have developed a new labeling strategy based on the hydrogenolysis of organolithium compounds with tritium gas or deuterium gas. This reaction is catalyzed with palladium on charcoal and leads to the labelled compounds with direct replacement of the proton by its isotopes ("2H or "3H) without further chemical modification of the target molecule. Using this strategy, tritium or deuterium atoms can be introduced in a region but also in a stereoselective fashion with more than 90% ee. The former result was obtained using (-)-sparteine during the lithiation step. Chapter II: New synthesis of a chiral methyl group. In the second part of this work, we have developed a new synthetic method to prepare chiral ditosyl-methylamine using 4,5-disubstituted oxazolidines. Dia-stereoselective substitution of the methoxy group of a 2-alkoxy-oxazolidine by a deuteride in the presence of a Lewis acid leads to the 2-deutero-oxazolidine in a highly stereoselective fashion (de = 100%). Still using a lewis acid, a tritiated hydride open the former 2-deutero-oxazolidine to afford chiral methyl group borne by the nitrogen. Further de-protection and re-protection steps lead to the ditosyl-methylamine with an ee of 65% (RIS= 83/17). Nowadays, this is the best known synthetic method, not only in terms of enantioselectivity but also in terms of chemical yield and number of radioactive steps. As NTs_2 is a fairly good leaving group, the ditosyl-methylamine offers the possibility of introducing chiral methyl group in many substrates using a S_N2 reaction with various nucleophiles. This last point leads to many potential applications in the field of biochemistry or for mechanical studies. (author) [fr

Survey of perfluoroalkyl acids (PFAAs) and their precursors present in Japanese consumer products.

Science.gov (United States)

Ye, Feng; Zushi, Yasuyuki; Masunaga, Shigeki

2015-05-01

Perfluoroalkyl acids (PFAAs) and their precursors have been used in various consumer products. However, limited information regarding their occurrence and concentration levels in products is available. In this study, we investigated 18 PFAAs and 14 PFAA precursors in various categories of consumer products purchased in Japan. Relatively high total concentrations of PFAAs and their precursors were found in sprays for fabrics and textiles (car wash/coating products (precursor of perfluorooctane sulfonic acid (PFOS), N-methyl perfluorooctane sulfonamidoethanol (MeFOSE) was detected in a higher frequency (8%) and in greater concentrations (precursors in consumer products is required. Furthermore, the amount of PFAAs emitted from consumer products may be underestimated if the occurrence of PFAA precursors is not considered. In addition to PFAA precursors, long chain perfluoroalkyl carboxylic acids (PFCAs) (carbon chain length⩾7) were also detected in greater concentrations than short chain PFCAs (⩽6). This result suggests that consumer products are one of the important sources of long-chain PFCAs in the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Non radioactive precursor import into chloroplasts

International Nuclear Information System (INIS)

Lombardo, V.A.; Ottado, J.

2003-01-01

Full text: Eukaryotic cells have a subcellular organization based on organelles. Protein transport to these organelles is quantitatively important because the majority of cellular proteins are codified in nuclear genes and then delivered to their final destination. Most of the chloroplast proteins are translated on cytoplasmic ribosomes as larger precursors with an amino terminal transit peptide that is necessary and sufficient to direct the precursor to the chloroplast. Once inside the organelle the transit peptide is cleaved and the mature protein adopts its folded form. In this work we developed a system for the expression and purification of the pea ferredoxin-NADP + reductase precursor (preFNR) for its import into chloroplasts in non radioactive conditions. We constructed a preFNR fused in its carboxy terminus to a 6 histidines peptide (preFNR-6xHis) that allows its identification using a commercial specific antibody. The construction was expressed, purified, processed and precipitated, rendering a soluble and active preFNR-6xHis that was used in binding and import into chloroplasts experiments. The reisolated chloroplasts were analyzed by SDS-PAGE, electro-blotting and revealed by immuno-detection using either colorimetric or chemiluminescent reactive. We performed also import experiments labeling preFNR and preFNR-6xHis with radioactive methionine as controls. We conclude that preFNR-6xHis is bound and imported into chloroplasts as the wild type preFNR and that both colorimetric or chemiluminescent detection methods are useful to avoid the manipulation of radioactive material. (author)

Electron heating, magnetic field amplification, and cosmic-ray precursor length at supernova remnant shocks

Energy Technology Data Exchange (ETDEWEB)

Laming, J. Martin [Space Science Division, Naval Research Laboratory, Code 7684, Washington, DC 20375 (United States); Hwang, Una [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Ghavamian, Parviz [Department of Physics, Astronomy and Geosciences, Towson University, Towson, MD 21252 (United States); Rakowski, Cara, E-mail: laming@nrl.navy.mil, E-mail: Una.Hwang-1@nasa.gov, E-mail: pghavamian@towson.edu

2014-07-20

We investigate the observability, by direct and indirect means, of a shock precursor arising from magnetic field amplification by cosmic rays. We estimate the depth of such a precursor under conditions of nonresonant amplification, which can provide magnetic field strengths comparable to those inferred for supernova remnants. Magnetic field generation occurs as the streaming cosmic rays induce a plasma return current, and it may be quenched by either nonresonant or resonant channels. In the case of nonresonant saturation, the cosmic rays become magnetized and amplification saturates at higher magnetic fields. The precursor can extend out to 10{sup 17}-10{sup 18} cm and is potentially detectable. If resonant saturation occurs, the cosmic rays are scattered by turbulence and the precursor length will likely be much smaller. The dependence of precursor length on shock velocity has implications for electron heating. In the case of resonant saturation, this dependence is similar to that in the more familiar resonantly generated shock precursor, which when expressed in terms of the cosmic-ray diffusion coefficient kappav and shock velocity v{sub s} is kappav/v{sub s} . In the nonresonantly saturated case, the precursor length declines less quickly with increasing v{sub s} . Where precursor length proportional to 1/v{sub s} gives constant electron heating, this increased precursor length could be expected to lead to higher electron temperatures for nonresonant amplification. This should be expected at faster supernova remnant shocks than studied by previous works. Existing results and new data analysis of SN 1006 and Cas A suggest some observational support for this idea.

De novo and salvage pathway precursor incorporation during DNA replication at the nuclear matrix

International Nuclear Information System (INIS)

Panzeter, P.L.

1988-01-01

Total nuclear DNA can be empirically subdivided into low salt-soluble (LS) DNA (75-80%), high salt-soluble (HS) DNA (18-23%), and nuclear matrix-associated (NM) DNA which remains tightly bound to the nuclear matrix (∼2%). The most-newly replicated DNA is that associated with the nuclear matrix in regenerating rat liver. Analyses of the DNA fractions after various pulse times revealed that the salvage and de novo pathway DNA precursors investigated were incorporated preferentially into NM-DNA at early pulse times, after which the radioactivity became progressively incorporated into HS- and LS-DNA, respectively. These results support two models of nuclear matrix-associated DNA replication, proposed previously, and a third model presented in this dissertation. In addition, the incorporation of de novo pathway precursors lagged significantly (> 10 minutes) behind the incorporation of precursors entering through the salvage pathway. Channeling of salvage pathway precursors to DNA replication sites would explain the more rapid uptake of salvage precursors into NM-DNA than de novo precursors. To investigate the possibility of this heretofore in vitro phenomenon, the incorporation of the salvage precursor, ( 3 H)deoxythymidine, and the de novo precursor, ( 14 C)orotic acid, into NM-DNA and dTTP was examined in regenerating rat liver. There was no significant difference between the incorporation pattern of ( 14 C)orotic acid into NM-DNA thymine and that of ( 14 C)orotic acid into soluble dTTP. Contrastingly, the salvage pathway precursor, ( 3 H)deoxythymidine, labeled NM-DNA before labeling the dTTP pool

Optical precursors with tunneling-induced transparency in asymmetric quantum wells

International Nuclear Information System (INIS)

Peng Yandong; Qi Yihong; Yao Haifeng; Niu Yueping; Gong Shangqing

2011-01-01

A scheme for separating optical precursors from a square-modulated laser pulse through an asymmetric double Al x Ga 1-x As/GaAs quantum-well structure via resonant tunneling is proposed. Destructive interference inhibits linear absorption, and a tunneling-induced transparency (TIT) window appears with normal dispersion, which delays the main pulse; then optical precursors are obtained. Due to resonant tunneling, constructive interference for nonlinear susceptibility is created. The enhanced dispersion in a narrow TIT window is about one order of magnitude larger than that of the linear case. In this case, the main pulse is much delayed and the precursor signals are easier to obtain. Moreover, the main pulse builds up due to the gain introduced by the enhanced cross-nonlinearity.

Replicable Expansion and Differentiation of Neural Precursors from Adult Canine Skin

Directory of Open Access Journals (Sweden)

Thomas Duncan

2017-08-01

Full Text Available Repopulation of brain circuits by neural precursors is a potential therapeutic strategy for neurodegenerative disorders; however, choice of cell is critical. Previously, we introduced a two-step culture system that generates a high yield of neural precursors from small samples of adult canine skin. Here, we probe their gene and protein expression profiles in comparison with dermal fibroblasts and brain-derived neural stem cells and characterize their neuronal potential. To date, we have produced >50 skin-derived neural precursor (SKN lines. SKNs can be cultured in a highly replicable fashion and uniformly express a panel of identifying markers. Upon differentiation, they self-upregulate neural specification genes, generating neurons with basic electrophysiological functionality. This unique population of neural precursors, derived from mature skin, overcomes many of the practical issues that have limited clinical translation of alternative cell types. Easily accessible, neuronally committed, and patient specific, SKNs may have potential for the treatment of brain disorders.

Marine bacterial transparent exopolymer particles (TEP) and TEP precursors: Characterization and RO fouling potential

KAUST Repository

Li, Sheng

2015-10-31

This paper investigated the characteristics and membrane fouling potential of bacterial transparent exopolymer particles (TEP)/TEP precursors released from two marine bacteria, Pseudidiomarina homiensis (P. homiensis) and Pseudoalteromonas atlantica (P. atlantica), isolated from the Red Sea. Results showed that both bacteria grew at the similar rate, but the production of TEP/TEP precursors from P. atlantica was higher than that from P. homiensis. During the 168. h of incubation time, production rates of TEP/TEP precursors from P. atlantica and P. homiensis were 0.30 and 0.08 xanthan gum eq. mg/L-h, respectively. Isolated bacterial TEP precursors were mainly biopolymer, and P. atlantica produced a significantly higher concentration of biopolymer than that produced by P. homiensis. TEP/TEP precursors from both marine bacteria possessed protein-like material and were very similar in composition to previously reported foulants isolated from a fouled reverse osmosis (RO) membrane. Bacterial TEP/TEP precursors mostly consisted of aliphatic hydrocarbon from amino acids and amide group carbon of proteins (around 55%). Bacterial TEP precursors caused obvious fouling on RO membranes, which may create an ideal environment for bacteria attachment and promote to biofouling.

Electrical properties of a novel lead alkoxide precursor: Lead glycolate

International Nuclear Information System (INIS)

Tangboriboon, Nuchnapa; Pakdeewanishsukho, Kittikhun; Jamieson, Alexander; Sirivat, Anuvat; Wongkasemjit, Sujitra

2006-01-01

The reaction of lead acetate trihydrate Pb(CH 3 COO) 2 .3H 2 O and ethylene glycol, using triethylenetetramine (TETA) as a catalyst, provides in one step access to a polymer-like precursor of lead glycolate [-PbOCH 2 CH 2 O-]. On the basis of high-resolution mass spectroscopy, chemical analysis composition, FTIR, 13 C-solid state NMR and TGA, the lead glycolate precursor can be identified as a trimer structure. The FTIR spectrum demonstrates the characteristics of lead glycolate; the peaks at 1086 and 1042 cm -1 can be assigned to the C-O-Pb stretchings. The 13 C-solid state NMR spectrum gives notably only one peak at 68.639 ppm belonging to the ethylene glycol ligand. The phase transformations of lead glycolate and lead acetate trihydrate to lead oxide, their microstructures, and electrical properties were found to vary with increasing temperature. The lead glycolate precursor has superior electrical properties relative to those of lead acetate trihydrate, suggesting that the lead glycolate precursor can possibly be used as a starting material for producing electrical and semiconducting ceramics, viz. ferroelectric, anti-ferroelectric, and piezoelectric materials

Surface and Interface Engineering of Organometallic and Two Dimensional Semiconductor

Science.gov (United States)

Park, Jun Hong

For over half a century, inorganic Si and III-V materials have led the modern semiconductor industry, expanding to logic transistor and optoelectronic applications. However, these inorganic materials have faced two different fundamental limitations, flexibility for wearable applications and scaling limitation as logic transistors. As a result, the organic and two dimensional have been studied intentionally for various fields. In the present dissertation, three different studies will be presented with followed order; (1) the chemical response of organic semiconductor in NO2 exposure. (2) The surface and stability of WSe2 in ambient air. (3) Deposition of dielectric on two dimensional materials using organometallic seeding layer. The organic molecules rely on the van der Waals interaction during growth of thin films, contrast to covalent bond inorganic semiconductors. Therefore, the morphology and electronic property at surface of organic semiconductor in micro scale is more sensitive to change in gaseous conditions. In addition, metal phthalocyanine, which is one of organic semiconductor materials, change their electronic property as reaction with gaseous analytes, suggesting as potential chemical sensing platforms. In the present part, the growth behavior of metal phthalocyanine and surface response to gaseous condition will be elucidated using scanning tunneling microscopy (STM). In second part, the surface of layered transition metal dichalcogenides and their chemical response to exposure ambient air will be investigated, using STM. Layered transition metal dichalcogenides (TMDs) have attracted widespread attention in the scientific community for electronic device applications because improved electrostatic gate control and suppression of short channel leakage resulted from their atomic thin body. To fabricate the transistor based on TMDs, TMDs should be exposed to ambient conditions, while the effect of air exposure has not been understood fully. In this part

Synthesis and characterization of a boron-containing precursor for ZrB{sub 2} ceramic

Energy Technology Data Exchange (ETDEWEB)

Tao, X.Y.; Xiang, Z.; Zhou, S.; Zhu, Y. [China Univ. of Mining and Technology, Xuzhou (China). School of Materials Science and Engineering; Qiu, W.; Zhao, T. [Chinese Academy of Sciences, Beijing (China). Lab. of Advanced Polymer Materials

2016-07-01

A precursor for ZrB{sub 2} ceramic was successfully synthesized in a chemical reaction between polyzirconoxanesal (PZS) and boric acid. The molecular structure of the precursor, thermal properties and the pyrolysis behavior of the precursor were investigated. The results showed that the as-synthesized precursor was a polymer based on Zr-O-C-B bonds. The precursor was stable in air atmosphere and soluble in common organic solvents. The ceramic yield of the precursor at 1200 C was around 65.5 % under N{sub 2} atmosphere. The derived ceramics obtained at 1200 C were composed of B{sub 2}O{sub 3}, ZrO{sub 2} and carbon. When the temperature was increased up to 1300 C, peaks of ZrC emerged owing to carbothermal reduction. m-ZrO{sub 2} and t-ZrO{sub 2} disappeared when the pyrolysis temperature was increased to above 1400 C. ZrB{sub 2} became the predominant phase when the pyrolysis temperature was increased up to 1500 C.

IL-9-Producing Mast Cell Precursors and Food Allergy

Science.gov (United States)

2017-10-01

AWARD NUMBER: W81XWH-15-1-0517 TITLE: IL-9-Producing Mast Cell Precursors and Food Allergy PRINCIPAL INVESTIGATOR: Dr. Simon P. Hogan PhD...IL-9-Producing Mast Cell Precursors and Food Allergy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Yui Hsi Wang, Sunil...threatening anaphylaxis. We have identified a novel multi-functional IL-9-producing mucosal mast cells (MMC9s) that produce large amounts of IL-9, IL

XANES- and EXAFS-Investigations on Chromium-Doped Mullite Precursors

OpenAIRE

Arzberger , I.; Küper , G.; Pantelouris , A.; Peitz , B.; Hormes , J.; Schneider , H.; Saruhan , B.

1997-01-01

Chromium-doped non-crystalline mullite precursors for ceramics were investigated with x-ray absorption spectroscopy at the Cr K edge. They were prepared using a sol-gel-route. 3 wt% Cr2O3 were added to partially substitute aluminium by chromium in the aluminosilicate network. The aim of the study was to characterize the development of the electronic and geometric structure of the precursor at different temperatures prior to its crystallization to mullite. The x-ray absorption spectra of the p...

Adsorption of N-nitrosodimethylamine precursors by powdered and granular activated carbon.

Science.gov (United States)

Hanigan, David; Zhang, Jinwei; Herckes, Pierre; Krasner, Stuart W; Chen, Chao; Westerhoff, Paul

2012-11-20

Activated carbon (AC) has been shown to remove precursors of halogenated disinfection byproducts. Granular and powdered activated carbon (GAC, PAC) were investigated for their potential to adsorb N-nitrosodimethylamine (NDMA) precursors from blends of river water and effluent from a wastewater treatment plant (WWTP). At bench scale, waters were exposed to lignite or bituminous AC, either as PAC in bottle point experiments or as GAC in rapid small-scale column tests (RSSCTs). NDMA formation potential (FP) was used as a surrogate for precursor removal. NDMA FP was reduced by 37, 59, and 91% with 3, 8, and 75 mg/L of one PAC, respectively, with a 4-h contact time. In RSSCTs and in full-scale GAC contactors, NDMA FP removal always exceeded that of the bulk dissolved organic carbon (DOC) and UV absorbance at 254 nm. For example, whereas DOC breakthrough exceeded 90% of its influent concentration after 10,000 bed volumes of operation in an RSSCT, NDMA FP was less than 40% of influent concentration after the same bed life of the GAC. At full or pilot scale, high NDMA FP reduction ranging from >60 to >90% was achieved across GAC contactors, dependent upon the GAC bed life and/or use of a preoxidant (chlorine or ozone). In all experiments, NDMA formation was not reduced to zero, which suggests that although some precursors are strongly sorbed, others are not. This is among the first studies to show that AC is capable of adsorbing NDMA precursors, but further research is needed to better understand NDMA precursor chemical properties (e.g., hydrophobicity, molecular size) and evaluate how best to incorporate this finding into full-scale designs and practice.

Thermoset precursor

International Nuclear Information System (INIS)

Yamamoto, Y.

1983-04-01

This invention pertains to a distinctive thermoset precursor which is prepared by mixing a resin composition (A) which can be hardened by ionizing radiation, and a resin composition (B) which can be hardened by heat but cannot be hardened by, or is resistant to, ionizing radiation, and by coating or impregnating a molding or other substrate with a sheet or film of this mixture and irradiating this with an ionizing radiation. The principal components of composition (A) and (B) can be the following: (1) an acrylate or methacrylate and an epoxy resin and an epoxy resin hardener; (2) an unsaturated polyester resin and epoxy resin and an epoxy resin hardener; (3) a diacrylate or dimethacrylate or polyethylene glycol and an epoxy resin; (4) an epoxy acrylates or epoxy methacrylate obtained by the addition reaction of epoxy resin and acrylic or methacrylic acid

Single step radiolytic synthesis of iridium nanoparticles onto graphene oxide

International Nuclear Information System (INIS)

Rojas, J.V.; Molina Higgins, M.C.; Toro Gonzalez, M.; Castano, C.E.

2015-01-01

Graphical abstract: - Highlights: • Ir nanoparticles were synthesized through a single step gamma irradiation process. • Homogeneously distributed Ir nanoparticles on graphene oxide are ∼2.3 nm in size. • Ir−O bonds evidenced the interaction of the nanoparticles with the support. - Abstract: In this work a new approach to synthesize iridium nanoparticles on reduced graphene oxide is presented. The nanoparticles were directly deposited and grown on the surface of the carbon-based support using a single step reduction method through gamma irradiation. In this process, an aqueous isopropanol solution containing the iridium precursor, graphene oxide, and sodium dodecyl sulfate was initially prepared and sonicated thoroughly to obtain a homogeneous dispersion. The samples were irradiated with gamma rays with energies of 1.17 and 1.33 MeV emitted from the spontaneous decay of the 60 Co irradiator. The interaction of gamma rays with water in the presence of isopropanol generates highly reducing species homogeneously distributed in the solution that can reduce the Ir precursor down to a zero valence state. An absorbed dose of 60 kGy was used, which according to the yield of reducing species is sufficient to reduce the total amount of precursor present in the solution. This novel approach leads to the formation of 2.3 ± 0.5 nm Ir nanoparticles distributed along the surface of the support. The oxygenated functionalities of graphene oxide served as nucleation sites for the formation of Ir nuclei and their subsequent growth. XPS results revealed that the interaction of Ir with the support occurs through Ir−O bonds.

Molecular pathogenesis of precursor lesions of pancreatic ductal adenocarcinoma.

Science.gov (United States)

Biankin, Andrew V; Kench, James G; Dijkman, Floriaan P; Biankin, Sandra A; Henshall, Susan M

2003-02-01

Precursor lesions are assuming greater importance in the study of pancreatic ductal adenocarcinoma. As pancreatic cancer is almost universally fatal due to late clinical presentation and biological aggressiveness, characterisation of its precursor lesions may create scope for early diagnosis and improved outcome with conventional therapies as well as the development of novel therapeutic and preventative strategies. Pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous tumours (IPMTs) are thought to be precursor lesions of ductal adenocarcinoma of the pancreas. Recent work has focused on the molecular aberrations associated with these lesions leading to the formulation of a progression model for pancreatic cancer. Progressive histopathological changes along the progression model are associated with aberrations of cell cycle regulatory and growth factor signalling molecules that occur in pancreatic cancer at high frequency and are common to many cancers. Characterisation of these molecular aberrations provides scope for the development of novel diagnostic and treatment strategies that will ultimately impact on the outcome for people who develop pancreatic cancer.

Early postradiation recovery of precursor cells of hemopoietic stroma

International Nuclear Information System (INIS)

Todriya, T.V.

1984-01-01

Ability of stroma precursor cells to early postradiation recovery was studied in male mices using the method of fraction irradiation of bone marrow. Donor mices of bone marrow were irradiated in vivo once by the total dose (nonfraction irradiation) and fractionally with 6 h interval between two irradiation doses. The cumulative irradiation doses equal to 10, 12, 14, 16 Gr were investigated. Irradiation was carried out using gamma facility. Bone marrow of the femur was implanted immediately after irradiation under kidney capsule of nonirradiated syngeneic recipient. The ability of stroma precursor cells to intracellular repair (repair index) was evaluated according to the ratio of the number of hemopoietic cells formed in heterotropic transplants in groups with fraction irradiation to the same one in groups with nonfraction irradiation. The obtained results testify to the fact that slowly regenerated highly radioresistant population of precursor cells of hemopoietic stroma is capable to early postradiation recovery

Fluorinated Phenylalanine Precursor Resistance in Yeast

Directory of Open Access Journals (Sweden)

Ian S. Murdoch

2018-06-01

Full Text Available Development of a counter-selection method for phenylalanine auxotrophy could be a useful tool in the repertoire of yeast genetics. Fluorinated and sulfurated precursors of phenylalanine were tested for toxicity in Saccharomyces cerevisiae. One such precursor, 4-fluorophenylpyruvate (FPP, was found to be toxic to several strains from the Saccharomyces and Candida genera. Toxicity was partially dependent on ARO8 and ARO9, and correlated with a strain’s ability to convert FPP into 4-fluorophenylalanine (FPA. Thus, strains with deletions in ARO8 and ARO9, having a mild phenylalanine auxotrophy, could be separated from a culture of wild-type strains using FPP. Tetrad analysis suggests FPP resistance in one strain is due to two genes. Strains resistant to FPA have previously been shown to exhibit increased phenylethanol production. However, FPP resistant isolates did not follow this trend. These results suggest that FPP could effectively be used for counter-selection but not for enhanced phenylethanol production.

Precursors of nitrogenous disinfection by-products in drinking water--A critical review and analysis

Energy Technology Data Exchange (ETDEWEB)

Bond, Tom [Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Templeton, Michael R.; Graham, Nigel [Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

2012-10-15

Highlights: Black-Right-Pointing-Pointer The proportion of N-DBP formation attributable to specific precursors was calculated. Black-Right-Pointing-Pointer Precursor concentrations are typically insufficient to account for observed N-DBP formation, except CNX and NDMA. Black-Right-Pointing-Pointer Amino acid precursors are easier to remove during water treatment than suggested by laboratory studies. - Abstract: In recent years research into the formation of nitrogenous disinfection by-products (N-DBPs) in drinking water - including N-nitrosodimethylamine (NDMA), the haloacetonitriles (HANs), haloacetamides (HAcAms), cyanogen halides (CNX) and halonitromethanes (HNMs) - has proliferated. This is partly due to their high reported toxicity of N-DBPs. In this review paper information about the formation yields of N-DBPs from model precursors, and about environmental precursor occurrence, has been employed to assess the amount of N-DBP formation that is attributable to known precursors. It was calculated that for HANs and HAcAms, the concentrations of known precursors - mainly free amino acids are insufficient to account for the observed concentrations of these N-DBP groups. However, at least in some waters, a significant proportion of CNX and NDMA formation can be explained by known precursors. Identified N-DBP precursors tend to be of low molecular weight and low electrostatic charge relative to bulk natural organic matter (NOM). This makes them recalcitrant to removal by water treatment processes, notably coagulation, as confirmed by a number of bench-scale studies. However, amino acids have been found to be easier to remove during water treatment than would be suggested by the known molecular properties of the individual free amino acids.

Nano structured TiO2 thin films by polymeric precursor method

International Nuclear Information System (INIS)

Stroppa, Daniel Grando; Giraldi, Tania Regina; Leite, Edson Roberto; Varela, Jose Arana; Longo, Elson

2008-01-01

This work focuses in optimizing setup for obtaining TiO 2 thin films by polymeric precursor route due to its advantages on stoichiometric and morphological control. Precursor stoichiometry, synthesis pH, solids concentration and rotation speed at deposition were optimized evaluating thin films morphology and thickness. Thermogravimetry and NMR were applied for precursor's characterization and AFM, XRD and ellipsometry for thin films evaluation. Results showed successful attainment of homogeneous nanocrystalline anatase TiO 2 thin films with outstanding control over morphological characteristics, mean grain size of 17 nm, packing densities between 57 and 75%, estimated surface areas of 90 m 2 /g and monolayers thickness within 20 and 128 nm. (author)

CH3 NH3 PbI3 and HC(NH2 )2 PbI3 Powders Synthesized from Low-Grade PbI2 : Single Precursor for High-Efficiency Perovskite Solar Cells.

Science.gov (United States)

Zhang, Yong; Kim, Seul-Gi; Lee, Do-Kyoung; Park, Nam-Gyu

2018-05-09

High-efficiency perovskite solar cells are generally fabricated by using highly pure (>99.99 %) PbI 2 mixed with an organic iodide in polar aprotic solvents. However, the use of such an expensive chemical may impede progress toward large-scale industrial applications. Here, we report on the synthesis of perovskite powders by using inexpensive low-grade (99 %) PbI 2 and on the photovoltaic performance of perovskite solar cells prepared from a powder-based single precursor. Pure APbI 3 [A=methylammonium (MA) or formamidinium (FA)] perovskite powders were synthesized by treating low-grade PbI 2 with MAI or FAI in acetonitrile at ambient temperature. The structural phase purity was confirmed by X-ray diffraction. The solar cell with a MAPbI 3 film prepared from the synthesized perovskite powder demonstrated a power conversion efficiency (PCE) of 17.14 %, which is higher than the PCE of MAPbI 3 films prepared by using both MAI and PbI 2 as precursors (PCE=13.09 % for 99 % pure PbI 2 and PCE=16.39 % for 99.9985 % pure PbI 2 ). The synthesized powder showed better absorption and photoluminescence, which were responsible for the better photovoltaic performance. For the FAPbI 3 powder, a solution with a yellow non-perovskite δ-FAPbI 3 powder synthesized at room temperature was found to lead to a black perovskite film, whereas a solution with the black perovskite α-FAPbI 3 powder synthesized at 150 °C was not transformed into a black perovskite film. The α↔δ transition between the powder and film was assumed to correlate with the difference in the iodoplumbates in the powder-dissolved solution. An average PCE of 17.21 % along with a smaller hysteresis [ΔPCE=PCE reverse -PCE forward )=1.53 %] was demonstrated from the perovskite solar cell prepared by using δ-FAPbI 3 powder; this PCE is higher than the average PCE of 17.05 % with a larger hysteresis (ΔPCE=2.71 %) for a device based on a conventional precursor solution dissolving MAI with high

Investigation of electronic quality of electrodeposited cadmium sulphide layers from thiourea precursor for use in large area electronics

Energy Technology Data Exchange (ETDEWEB)

Ojo, A.A., E-mail: chartell2006@yahoo.com; Dharmadasa, I.M.

2016-09-01

CdS layers used in thin film solar cells and other electronic devices are usually grown by wet chemical methods using CdCl{sub 2} as the Cadmium source and either Na{sub 2}S{sub 2}O{sub 3}, NH{sub 4}S{sub 2}O{sub 3} or NH{sub 2}CSNH{sub 2} as Sulphur sources. Obviously, one of the sulphur precursors should produce more suitable CdS layers required to give the highest performing devices. This can only be achieved by comprehensive experimental work on growth and characterisation of CdS layers from the above mentioned sulphur sources. This paper presents the results observed on CdS layers grown by electrodepositing using two electrode configuration and thiourea as the sulphur precursor. X-ray diffraction (XRD), Raman spectroscopy, optical absorption, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and photoelectrochemical (PEC) cell methods have been used to characterise the material properties. In order to test and study the electronic device quality of the layers, ohmic and rectifying contacts were fabricated on the electroplated layers. Schottky barriers, formed on the layers were also compared with previously reported work on Chemical Bath Deposited CBD-CdS layers and bulk single crystals of CdS. Comparatively, Schottky diodes fabricated on electroplated CdS layers using two-electrode system and thiourea precursor exhibit excellent electronic properties suitable for electronic devices such as thin film solar panels and large area display devices. - Highlights: • Precipitate-free electrodeposition of CdS is achievable using Thiourea precursor. • Electrodeposition of CdS using 2-electrode configuration. • The electrodeposited CdS shows excellent electronic properties. • Exploration of the effect of heat treatment temperature and heat treatment duration.

Laser synthesis of nanostructured ceramics from liquid precursors

International Nuclear Information System (INIS)

Wilden, Johannes; Fischer, Georg

2007-01-01

The free-form net shape laser synthesis of nanostructured ceramics from liquid precursors enables a residual stress-free production of high temperature resistant ceramic units and components for the use in microsystem engineering. Due to the use of molecular compounded liquid, ceramic precursors the resulting ceramic components show outstanding properties, for example high purity and a nanostructured material design. The use of pulsed lasers enables a defined input of energy required to pyrolyse the precursor material into a crystalline ceramic, so the active volume can be reduced significantly compared to other processes, for example pyrolysis by furnace. In this paper several methods for a further minimization of the active volume are presented. The investigations determined different factors affecting the process. Realizing selective experiments allows a determination of their influencing level and the definition of a working area to produce three-dimensional components with high aspect ratio. By several studies, e.g., scanning electron microscopy, transmission electron microscopy as well as X-ray diffraction analysis, the atomic structure and composition of the created components were analyzed and valued, so the different reaction processes can be described extensively

Immature MEF2C-dysregulated T-cell leukemia patients have an early T-cell precursor acute lymphoblastic leukemia gene signature and typically have non-rearranged T-cell receptors

Science.gov (United States)

Zuurbier, Linda; Gutierrez, Alejandro; Mullighan, Charles G.; Canté-Barrett, Kirsten; Gevaert, A. Olivier; de Rooi, Johan; Li, Yunlei; Smits, Willem K.; Buijs-Gladdines, Jessica G.C.A.M.; Sonneveld, Edwin; Look, A. Thomas; Horstmann, Martin; Pieters, Rob; Meijerink, Jules P.P.

2014-01-01

Three distinct immature T-cell acute lymphoblastic leukemia entities have been described including cases that express an early T-cell precursor immunophenotype or expression profile, immature MEF2C-dysregulated T-cell acute lymphoblastic leukemia cluster cases based on gene expression analysis (immature cluster) and cases that retain non-rearranged TRG@ loci. Early T-cell precursor acute lymphoblastic leukemia cases exclusively overlap with immature cluster samples based on the expression of early T-cell precursor acute lymphoblastic leukemia signature genes, indicating that both are featuring a single disease entity. Patients lacking TRG@ rearrangements represent only 40% of immature cluster cases, but no further evidence was found to suggest that cases with absence of bi-allelic TRG@ deletions reflect a distinct and even more immature disease entity. Immature cluster/early T-cell precursor acute lymphoblastic leukemia cases are strongly enriched for genes expressed in hematopoietic stem cells as well as genes expressed in normal early thymocyte progenitor or double negative-2A T-cell subsets. Identification of early T-cell precursor acute lymphoblastic leukemia cases solely by defined immunophenotypic criteria strongly underestimates the number of cases that have a corresponding gene signature. However, early T-cell precursor acute lymphoblastic leukemia samples correlate best with a CD1 negative, CD4 and CD8 double negative immunophenotype with expression of CD34 and/or myeloid markers CD13 or CD33. Unlike various other studies, immature cluster/early T-cell precursor acute lymphoblastic leukemia patients treated on the COALL-97 protocol did not have an overall inferior outcome, and demonstrated equal sensitivity levels to most conventional therapeutic drugs compared to other pediatric T-cell acute lymphoblastic leukemia patients. PMID:23975177

Understanding Animal Detection of Precursor Earthquake Sounds.

Science.gov (United States)

Garstang, Michael; Kelley, Michael C

2017-08-31

We use recent research to provide an explanation of how animals might detect earthquakes before they occur. While the intrinsic value of such warnings is immense, we show that the complexity of the process may result in inconsistent responses of animals to the possible precursor signal. Using the results of our research, we describe a logical but complex sequence of geophysical events triggered by precursor earthquake crustal movements that ultimately result in a sound signal detectable by animals. The sound heard by animals occurs only when metal or other surfaces (glass) respond to vibrations produced by electric currents induced by distortions of the earth's electric fields caused by the crustal movements. A combination of existing measurement systems combined with more careful monitoring of animal response could nevertheless be of value, particularly in remote locations.

Functional Nanoporous Polymers from Block Copolymer Precursors

DEFF Research Database (Denmark)

Guo, Fengxiao

Abstract Self-assembly of block copolymers provides well-defined morphologies with characteristic length scales in the nanometer range. Nanoporous polymers prepared by selective removal of one block from self-assembled block copolymers offer great technological promise due to their many potential...... functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed......, where living anionic polymerization and atom transfer radical polymerization (ATRP) are combined to synthesize a polydimethylsiloxane-b-poly(tert-butyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer precursor. By using either anhydrous hydrogen fluoride or trifluoroacetic acid, PtBA block...

A possible island of beta-delayed neutron precursors in heavy nucleus region

International Nuclear Information System (INIS)

Zhang Li

1991-01-01

The possible Beta-Delayed neutron precursors in the elements Tl, Hg, and Au were predicted following a systematic research on the known Beta-Delayed neutron precursors. The masses of the unknown nuclei and neutron emission probabilities were calculated

Precursors to potential severe core damage accidents. A status report, 1982--1983

Energy Technology Data Exchange (ETDEWEB)

Forester, J.A.; Mitchell, D.B.; Whitehead, D.W. [and others

1997-04-01

This study is a continuation of earlier work that evaluated 1969-1981 and 1984-1994 events affecting commercial light-water reactors. One-hundred nine operational events that affected 51 reactors during 1982 and 1983 and that are considered to be precursors to potential severe core damage are described. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10{sup {minus}6}. These events were identified by first computer screening the 1982-83 licensee event reports from commercial light-water reactors to select events that could be precursors to core damage. Candidates underwent engineering evaluation that identified, analyzed, and documented the precursors. This report discusses the general rationale for the study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events.

Precursors to potential severe core damage accidents. A status report, 1982--1983

International Nuclear Information System (INIS)

Forester, J.A.; Mitchell, D.B.; Whitehead, D.W.

1997-04-01

This study is a continuation of earlier work that evaluated 1969-1981 and 1984-1994 events affecting commercial light-water reactors. One-hundred nine operational events that affected 51 reactors during 1982 and 1983 and that are considered to be precursors to potential severe core damage are described. All these events had conditional probabilities of subsequent severe core damage greater than or equal to 1.0 x 10 -6 . These events were identified by first computer screening the 1982-83 licensee event reports from commercial light-water reactors to select events that could be precursors to core damage. Candidates underwent engineering evaluation that identified, analyzed, and documented the precursors. This report discusses the general rationale for the study, the selection and documentation of events as precursors, and the estimation of conditional probabilities of subsequent severe core damage for the events

Influence of Pd-precursor on the acetoxylation activity of Pd-Sb/TiO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Ben-homeid, A. [Benghazi Univ. (Libyan Arab Jamahiriya). Chemistry Dept.; Kalevaru, V.N.; Radnik, J.; Luecke, B.; Martin, A. [Leibniz-Institut fuer Katalyse e.V. an der Universitaet Rostock (Germany)

2013-11-01

The impact of palladium precursors (e.g. chloride-PdCl{sub 2}; acetate-Pd(OAc){sub 2}; nitrate-Pd(NO{sub 3}){sub 2}) on the catalytic properties of Pd-Sb/TiO{sub 2} catalysts used for acetoxylation of toluene has been investigated. The catalysts were characterized by different techniques such as N{sub 2}-adsorption (BET-surface area and pore volume), XRD, TEM, CO-Chemisorption and XPS for better understanding of the catalytic properties of the catalysts. The acetate and nitrate-type precursors exhibited higher surface areas, pore volumes and higher dispersion of Pd, but displayed poor performance compared to chloride precursor. TEM analysis indicated that the size of Pd particles depended upon the nature of Pd-precursor. Among the three, chloride precursor exhibited bigger Pd particles. XPS results revealed that all the fresh catalysts irrespective of Pd-precursor contained Pd in oxidized state (i.e. Pd{sup +2}), while in the spent catalysts such oxidized Pd species were reduced. The catalytic performance was found to depend strongly on the nature of precursor used. Among the three, the catalysts prepared from chloride-type precursor showed much higher overall catalytic activity (68%) than those of nitrate and/or acetate type precursors. Moreover, these two precursors (acetate and nitrate) gave higher total oxidation products due to oxidative decomposition of mainly acetic acid. Furthermore, the catalyst prepared from Cl-precursor revealed easy deactivation due to coke deposition and also due to loss of Pd in the near-surface-region. (orig.)

Mechanistic insights on the cycloisomerization of polyunsaturated precursors catalyzed by platinum and gold complexes.

Science.gov (United States)

Soriano, Elena; Marco-Contelles, José

2009-08-18

Organometallic chemistry provides powerful tools for the stereocontrolled synthesis of heterocycles and carbocycles. The electrophilic transition metals Pt(II) and Au(I, III) are efficient catalysts in these transitions and promote a variety of organic transformations of unsaturated precursors. These reactions produce functionalized cyclic and acyclic scaffolds for the synthesis of natural and non-natural products efficiently, under mild conditions, and with excellent chemoselectivity. Because these transformations are strongly substrate-dependent, they are versatile and may yield diverse molecular scaffolds. Therefore, synthetic chemists need a mechanistic interpretation to optimize this reaction process and design a new generation of catalysts. However, so far, no intermediate species has been isolated or characterized, so the formulated mechanistic hypotheses have been primarily based on labeling studies or trapping reactions. Recently, theoretical DFT studies have become a useful tool in our research, giving us insights into the key intermediates and into a variety of plausible reaction pathways. In this Account, we present a comprehensive mechanistic overview of transformations promoted by Pt and Au in a non-nucleophilic medium based on quantum-mechanical studies. The calculations are consistent with the experimental observations and provide fundamental insights into the versatility of these reaction processes. The reactivity of these metals results from their peculiar Lewis acid properties: the alkynophilic character of these soft metals and the pi-acid activation of unsaturated groups promotes the intra- or intermolecular attack of a nucleophile. 1,n-Enynes (n = 3-8) are particularly important precursors, and their transformation may yield a variety of cycloadducts depending on the molecular structure. However, the calculations suggest that these different cyclizations would have closely related reaction mechanisms, and we propose a unified mechanistic

From chelating precursors to La0.05Sr0.95CoO3-y oxide

International Nuclear Information System (INIS)

Hong, L.; Guo, F.; Lin, J.

1999-01-01

Several La 0.05 Sr 0.95 CoO 3-y (LSCO-95) powders were synthesized by means of a chelated complex-based precursor approach, which involved pyrolysis of chelating precursors and subsequent calcination of the resulting oxides. This paper focuses on the coordination effects of the precursors on the formation of the crystalline phases of the LSCO-95 oxide, showing that when the precursor is composed of EDTA-metal complexes, the perovskite-type oxide LSCO-95, an electronic-ionic mixed conducting ceramic material, can be achieved. In contrast, those LSCO-95 powders obtained initially from the pyrolysis of the precursors containing other coordination ligands possess only the undesirable hexagonal structure